Abstract:
Background: Nucleoside-nucleotide mixture has been shown to improve gut morphology and reduce the incidence of bacterial translocation in protein deficient mice.
Aims: To compare the reparative effect of nucleoside-nucleotide mixture and their individual components on maintenance of gut integrity and bacterial translocation based on their differential metabolism and utilisation.
Methods: ICR (CD-1) mice were randomised into eight groups of 10 animals each and fed 20% casein diet (control), protein free diet, or protein free diet supplemented with 3 M cytidine, uridine, thymidine, inosine, guanosine monophosphate, or nucleoside-nucleotide mixture for four weeks. On the fourth week, each mouse was injected lipopolysaccharide intraperitoneally (50 micrograms/500 microliters) and the incidence of bacterial translocation, caecal bacterial populations, and the ileal histology, noted 48 hours later.
Results: The death rate in the control group was 40% compared with 10% in the nucleoside-nucleotide mixture and 20% each in the individual components groups, respectively. Bacterial translocation to the mesenteric lymph node did occur in 100% of the surviving mice fed the control diet in comparison with 44% (nucleoside-nucleotide), 50% (cytidine), 75% (thymidine), 75% (uridine), 63% (inosine), and 63% (guanosine monophosphate). Histologically, the damage to the gut was more distinct in the protein free diet group. Villous height, crypt depth, and wall thickness in the nucleoside-nucleotide mixture group mean (SEM) (5.01 (0.34); 0.87 (0.14); 0.33 (0.10)), were respectively, higher compared with the protein free diet (3.34 (0.34); 0.61 (0.03); 0.18 (0.04)) group. In the cytidine group, crypt depth (0.86) (0.08)), and wall thickness (0.30 (0.002)) were higher. The same measurements in the components groups tended to be higher than the protein free diet group. Caecal bacterial populations were, however, similar in all groups.
Conclusions: These results suggest that dietary nucleosides and nucleotides are essential nutrients for intestinal repair; nucleotides or cytidine provide a better response.

Abstract:
Background: Growing evidence suggests that intestinal recovery from injury induced by radiation, endotoxin, and protein deficiency is improved by the ingestion of nucleosides and nucleotides.
Aim: This study examined the effect of dietary nucleosides and nucleotides supplementation on trinitrobenzene sulphonic acid induced colonic damage in experimental colitis.
Methods: Sprague-Dawley rats were randomised into two groups and fed nucleic acid free 20% casein diet (control) or this diet supplemented with 0.5% nucleoside-nucleotide mixture for four weeks. On the second week, colonic inflammation was induced in rats by intracolonic administration of 0.25 ml of 50% ethanol containing 25 mg of trinitrobenzene sulphonic acid. Additionally, other sets of rats were treated with 0.25 ml of 50% ethanol, 25 mg of trinitrobenzene sulphonic acid in 0.25 ml saline, or 0.25 ml of 0.9% saline.
Results: After two weeks, colon weight, macroscopic and microscopic damage scores, were significantly greater (p < 0.05) in the nucleoside-nucleotide supplemented group compared with the non-supplemented control groups. The same variables seen in the trinitrobenzene sulphonic acid-ethanol group fed nucleoside-nucleotide free diet were greater (p < 0.05) than in the rest of the groups fed nucleoside-nucleotide free diet and treated with ethanol, trinitrobenzene sulphonic acid in saline, or saline. Histologically, segmental ulceration and inflammation associated with significantly increased infiltration of polymorphonuclear leucocytes, macrophages, lymphocytes, fibroblasts were observed in the supplemented group compared with the controls. In the nucleoside-nucleotide supplemented group the epithelial damage, mucosal erosion, oedema, and coagulative necrosis of the muscularis propria was more extensive in comparison to the non-supplemented control groups.
Conclusions: This study suggests that dietary nucleosides and nucleotides may aggravate colonic damage and inflammation in chemically induced experimental colitis in rats; and that nucleoside-nucleotide free diet combined with other pharmacological agents may offer a better response.

Abstract:
Background: Chronic diarrhea during early infancy is characterized by intestinal mucosal injury, and as a consequence, the mitochondrial system of oxidation and reduction and energy production is altered. Since dietary nucleotides have been associated with the process of intestinal mucosal repair in rats with chronic diarrhea, the aim of this study was to examine the effects of dietary nucleotides on the functioning of mucosal mitochondria.
Methods: Weanling rats were fed with a semipurified synthetic diet (C) or the same diet in which carbohydrates were substituted by lactose (L), resulting in chronic diarrhea. During recovery, rats were fed with the semipurified synthetic diet (LC) or the same diet supplemented with nucleotides (LN). The activities of adenosine triphosphate synthase (ATPase), cytochrome c oxidase, citrate synthase, and malate dehydrogenase were measured in mitochondria from ileum and colon mucosa.
Results: These enzymatic activities rose in rats with chronic diarrhea, possibly to compensate for the drastic decline in adenosine triphosphate (ATP) synthesis. Dietary nucleotide supplementation allowed normalizing of the activities of ATPase (C: 0.37 +/- 0.16 microg/min/mg protein; L: 0.68 +/- 0.25 microg/min/mg protein; LC: 0.60 +/- 0.20 microg/min/mg protein; LN: 0.42 +/- 0.22 microg/min/mg protein), citrate synthase (C: 0.12 +/- 0.05 mM/min/mg protein; L: 0.21 +/- 0.07 mM/min/mg protein; LC: 0.21 +/- 0.06 mM/min/mg protein; LN: 0.12 +/- 0.02 mM/min/mg protein), and malate dehydrogenase (C: 0.77 +/- 0.48 mM/min/mg protein; L: 3.08 +/- 0.85 mM/min/mg protein; LC: 2.11 +/- 0.44 mM/min/mg protein; LN: 1.13 +/- 0.51 mM/min/mg protein) in the ileum mitochondria of the diarrheic rats. In colonic mucosa, mitochondrial enzymatic activities were restored after eliminating lactose from the diet.
Conclusion: These results suggest that dietary nucleotides promote earlier restoration of the ileal mitochondrial function after chronic diarrhea.

Abstract:
Background: Nonsteroidal anti-inflammatory drug (NSAID) use is associated with an elevated risk of gastrointestinal damage. As adenosine 5'-triphosphate (ATP) may play a protective role in the small intestine, our objective was to determine the local effect of ATP on small intestinal permeability changes induced by short-term challenge of the NSAID indomethacin in healthy humans.
Methods: Mucosal permeability of the small intestine was assessed by the lactulose/rhamnose permeability test, that is, ingestion of a test drink containing 5 g lactulose and 0.5 g L-rhamnose followed by total urine collection for 5 h. Urinary excretion of lactulose and L-rhamnose was determined by fluorescent detection high-pressure liquid chromatography (HPLC). Basal small intestinal permeability was assessed as a control condition. As a model of increased small intestinal permeability, two doses of indomethacin were ingested before ingestion of the test drink (75 mg and 50 mg at 10 h and 1 h before the test drink, respectively). Concomitantly with indomethacin ingestion, placebo or 30 mg/kg ATP was administered through a naso-intestinal tube.
Results: Median urinary lactulose/rhamnose ratio (g/g) in the control condition was 0.023 (interquartile range: 0.013-0.041). Compared with the control condition, urinary lactulose/rhamnose ratio after ingestion of indomethacin and administration of placebo was significantly increased [0.042 (0.028-0.076); P<0.01]. In contrast, urinary lactulose/rhamnose ratio after indomethacin ingestion plus ATP administration [0.027 (0.020-0.046)] was significantly lower than the lactulose/rhamnose ratio in the placebo condition (P<0.01).
Conclusions: Topical ATP administration into the small intestine during short-term challenge of the NSAID indomethacin attenuates the NSAID-induced increase in small intestinal permeability in healthy humans.

Abstract: The effects of specific nutrients on intestinal maturation and repair after injury are practically unknown. The purpose of this work was to study the effects of dietary nucleotides on the repair of the intestinal mucosa after chronic diarrhoea induced by a lactose enriched diet in the weanling rat. One group of weanling rats was fed with a standard semipurified diet (control group), and another group was fed with the same diet containing lactose as the only soluble carbohydrate (lactose group). After 14 days the lactose group was allowed to recover for four weeks with the control diet (lactose-control group) or with the control diet supplemented with AMP, GMP, IMP, CMP, and UMP 50 mg/100 g each (lactose-nucleotide group). The control group was divided into two subgroups, which were fed with the control diet and the nucleotide supplemented diet for the same period (control-control group and control-nucleotide group). The lactose diet induced diarrhoea after 24 hours of feeding. Two weeks later there were changes in intestinal structure with loss of enterocyte microvillar surface, significant lymphocyte infiltration, supranuclear cytoplasmic vesiculation, decreased number of goblet cells, and enlarged mitochondria with low density and few cristae. After recovery from diarrhoea, animals fed the nucleotide enriched diet showed an intestinal histology and ultrastructure closer to that of the normal control group. Mitochondrial ultrastructure was closer to normal in comparison with the lactose-control diet group. In this second group the number of goblet cells as well as the villous height/crypt depth ratio was reduced and the number of intraepithelial lymphocytes increased compared with the nucleotide supplemented group. These results suggest that dietary nucleotides may be important nutrients for intestinal repair.

Abstract: Dietary nucleotides, found in normal diets, have been recently determined to be required for normal immune defences. Rejection of cardiac transplants, graft-vs, -host disease, and delayed cutaneous hypersensitivity in animal models area all suppressed by a diet deficient in nucleotides. T lymphocytes seem to require dietary nucleotides for normal maturation and function. Host resistance to bacterial and fungal infections is decreased in mice on nucleotide free diets; addition of RNA or uracil prevents this vulnerability to infection. Dietary RNA is required to restore lost immune function after protein deprivation.  Adequate calories and protein alone do not return immune function to normal. Dietary nucleotides can restore lost immune function even during protein starvation and weight loss. Because all parenteral and most enteral nutrient solutions are nucleotide free, clinical studies were undertaken comparing a new nucleotide containing diet (Impact) to a standard high protein enteral feeding. In two separate double blind clinical studies the patients fed the enteral diet containing nucleotides had improved immune function compared with patients receiving a nucleotide free diet. In addition, infectious complications and length of hospital stay were reduced in postoperative cancer patients fed Impact compared with a control group.

Abstract: No abstract available.

Abstract: Trials were carried out in Atlantic salmon to determine the effects on vaccine efficacy, vaccination and salt water transfer stress, growth performance and intestinal morphology of the inclusion in salmon diets of supplemental nucleotides. When added to normal salmon feeds at a combined inclusion level of 0.03%, these additional nucleotides were shown to significantly enhance the efficacy of vaccination as indicated by elevated antibody titres (1/144 with nucleotide diet vs.. 1/160 with control diet) and lower (although non-significant) mortality following challenge. Significantly reduced blood chloride levels following salt water transfer was indicative of a greatly enhanced capacity for osmoregulation. Increases were also observed in red blood cell levels. Furthermore, the checks in growth rates normally following these particular physical stressors were negated, with fish fed nucleotide-supplemented diets having a 15-22% weight advantage after 8 weeks (5 weeks following each of the two stress events). The growth benefits described following feeding with nucleotide-supplemented diets, ever after just 3 weeks, could be due in part to an increase in the mucosal surface area of the gut due to significantly enhanced intestinal fold morphology.

Abstract: Although the concept of purinergic signalling arose from experiments designed to find the identity of the non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmitter in the gut, it has taken many years for the more general importance of the various roles of ATP as a physiological messenger in the gut to be recognized. Firstly, vasoactive intestitial polypeptide (VIP) and later nitric oxide (NO) were considered the NANC transmitter and it was only later, after the concept of cotransmission was established, that ATP, NO and VIP were recognized as cotransmitters in NANC nerves, although the proportions vary in different gut regions. Recently, many purinoceptor subtypes have been identified on myenteric, submucosal motor, sensory and interneurons involved in synaptic neurotransmission and neuromodulation and reflex activity of several kinds, including ascending excitatory and descending inhibitory reflex pathways. Nucleotide receptors have been shown to be expressed on enteric glial cells and interstitial cells of Cajal. Purinergic mechanosensory transduction, involving release of ATP from mucosal epithelial cells during distension to stimulate subepithelial nerve endings of intrinsic and extrinsic sensory nerves to modulate peristalsis and initiate nociception respectively, is attracting current attention. Exciting new areas of interest about purinergic signalling in the gut include: involvement of purines in development, ageing and regeneration, including the role of stem cells; studies of the involvement of nucleotides in the activity of the gut of invertebrates and lower vertebrates; and the pathophysiology of enteric purinergic signalling in diseases including irritable bowel syndrome, postoperative ileus, oesophageal reflux, constipation, diarrhoea, diabetes, Chaga's and Hirschprung's disease.

Abstract: Nucleotides in the intestinal lumen may decrease the inflammatory response to ischemia-reperfusion. In a newborn-swine model, we showed that perfusion of the intestinal lumen with nucleotides in concentrations similar to those in human milk induced hyperemia. The levels of hypoxanthine (and xanthine) were not increased in the presence of nucleotides during ischemia-reperfusion, and the number of leukocytes accumulated in the intestine was reduced in the presence of nucleotides. Furthermore, nucleotides may have decreased protein leak and the production of nitric oxide during ischemia. These effects are not changed significantly in the presence of an adenosine antagonist. We interpreted our results to indicate that the protective effects of nucleotides in the intestinal lumen are not due to adenosine alone.

Abstract: Investigations with animals demonstrate that dietary nucleotides influence immune function. Restriction of dietary nucleotides in mice decreases several indices of cell-mediated immunity as well as resistance to challenge with Staphylococcus aureus or Candida albicans. Spleen cells of mice maintained on nucleotide free diet produce less interleukin-2 and have lower natural killer cell cytotoxicity and macrophage activation that those of animals fed nucleotide-supplemented diets. In vivo lymphoproliferative response, macrophage phagocytic activity and expression of interleukin-2 receptor and lyt1 surface marker are also lower in animals fed nucleotide-fee diets. At 2 mo of age, infants fed breast milk or nucleotide-supplemented infant formula exhibit increased natural killer cell activity compared with infants fed unsupplemented formula. Dietary nucleotide restriction in animals may also result in hepatic lipid accumulation and decreased mucosal height and gut wall thickness. Adenosine monophosphate, a mediator of hepatic and small bowel blood flow, may play a unique role among the nucleotides studied. In conclusion, de novo synthesis and salvage of nucleotides is a metabolically costly process. An exogenous source of nucleotides from diet may optimize the function of rapidly dividing tissues, particularly when growth is rapid and the diet is low in nucleotides. J. Nutr: 144S-148S, 1994.

Abstract: Nucleotides (NT) and their related metabolic products play key roles in many biological processes. NT can be synthesized endogenously and thus are not considered essential nutrients. Studies have demonstrated, however, that dietary NT can have beneficial effects; the term ‘conditionally essential’ has been used to describe their role in human nutrition. These nutrients may become essential when the endogenous supply is insufficient for normal function, even though their absence from the diet does not lead to a classic clinical deficiency syndrome. Most dietary NT are rapidly metabolized and excreted. However, some are incorporated into tissues, particularly at younger ages and with fasting. Under conditions of limited NT intake, rapid growth or certain disease states, dietary NT may spare the cost of de novo NT synthesis and optimize the function of rapidly dividing tissues such as those of the gastrointestinal and immune systems. Animals fed NT-supplemented versus non-NT supplemented diets have enhanced gastrointestinal growth and maturation, and improved recovery following small and large bowel injury. Indices of humoral and cellular immunity are enhanced, and survival rates are higher following infection with pathogens. Infants receive NT in human milk, where they are present as nucleic acids, nucleosides, nucleotides and related metabolic products. The NT content of human milk is significantly higher than most cow’s milk-based infant formulae. Dietary NT are reported to enhance the gastrointestinal and immune systems of formula-fed infants. Infants fed NT-supplemented versus non-supplemented formula have a lower incidence of diarrhea, higher antibody titers following Haemophilus influenza type b vaccination and higher natural killer cell activity. These data suggest that human milk NT may contribute to superior clinical performance of the breastfed infant.

Abstract: The current study aimed to determine whether dietary nucleotides supplementation could improve growth performance, intestinal development and immune function of intra-uterine growth restricted (IUGR) neonate using pig as animal model. A total of 14 pairs of normal birth weight (NBW) and IUGR piglets (7 days old) were randomly assigned to receive a milk-based control diet (CON diet) or diet supplemented with nucleotides (NT diet) for a period of 21 days. Blood samples, intestinal tissues and digesta were collected at necropsy and analyzed for morphology, digestive enzyme activities, microbial populations, peripheral immune cells, expression of intestinal innate immunity and barrier-related genes and proteins. Compared with NBW piglets, IUGR piglets had significantly lower average daily dry matter intake and body weight gain (P<0.05). Moreover, IUGR markedly decreased the villous height and villi: crypt ratio in duodenum (P<0.05), as well as the maltase activity in jejunum (P<0.05). In addition, IUGR significantly decreased the serum concentrations of IgA, IL-1beta and IL-10 (P<0.05), as well as the percentage of peripheral lymphocytes (P<0.05). Meanwhile, the down-regulation of innate immunity-related genes such as TOLLIP (P<0.05), TLR-9 (P = 0.08) and TLR-2 (P = 0.07) was observed in the ileum of IUGR relative to NBW piglets. Regardless of birth weight, however, feeding NT diet markedly decreased (P<0.05) feed conversion ratio, increased the villous height in duodenum (P<0.05), activities of lactase and maltase in jejunum (P<0.05), count of peripheral leukocytes (P<0.05), serum concentrations of IgA and IL-1beta as well as gene expressions of TLR-9, TLR-4 and TOLLIP in ileum (P<0.05). In addition, expressions of tight junction proteins (Claudin-1 and ZO-1) in ileum were markedly increased by feeding NT diet relative to CON diet (P<0.05). These results indicated that IUGR impaired growth performance, intestinal and immune function, but dietary nucleotides supplementation improved nutrients utilization, intestinal function and immunity.

Abstract: Secretomotor reflexes in the gastrointestinal (GI) tract are important in the lubrication and movement of digested products, absorption of nutrients, or the diarrhea that occurs in diseases to flush out unwanted microbes. Mechanical or chemical stimulation of mucosal sensory enterochromaffin (EC) cells triggers release of serotonin (5-HT) (among other mediators) and initiates local reflexes by activating intrinsic primary afferent neurons of the submucous plexus. Signals are conveyed to interneurons or secretomotor neurons to stimulate chloride and fluid secretion. Inputs from myenteric neurons modulate secretory rates and reflexes, and special neural circuits exist to coordinate secretion with motility. Cellular components of secretomotor reflexes variably express purinergic receptors for adenosine (A1, A2a, A2b, or A3 receptors) or the nucleotides adenosine 5'-triphosphate (ATP), adenosine diphosphate (ADP), uridine 5'-triphosphate (UTP), or uridine diphosphate (UDP) (P2X1-7, P2Y2, P2Y4, P2Y6, P2Y12 receptors). This review focuses on the emerging concepts in our understanding of purinergic regulation at these receptors, and in particular of mechanosensory reflexes. Purinergic inhibitory (A1, A3, P2Y12) or excitatory (A2, P2Y1) receptors modulate mechanosensitive 5-HT release. Excitatory (P2Y1, other P2Y, P2X) or inhibitory (A1, A3) receptors are involved in mechanically evoked secretory reflexes or “neurogenic diarrhea”. Distinct neural (pre- or postsynaptic) and non-neural distribution profiles of P2X2, P2X3, P2X5, P2Y1, P2Y2, P2Y4, P2Y6, or P2Y12 receptors, and for some their effects on neurotransmission, suggests their role in GI secretomotor function. Luminal A2b, P2Y2, P2Y4, and P2Y6 receptors are involved in fluid and Cl-, HCO3 -, K+, or mucin secretion. Abnormal receptor expression in GI diseases may be of clinical relevance. Adenosine A2a or A3 receptors are emerging as therapeutic targets in inflammatory bowel diseases (IBD) and gastroprotection; they can also prevent purinergic receptor abnormalities and diarrhea. Purines are emerging as fundamental regulators of enteric secretomotor reflexes in health and disease.

Abstract: Nucleotides are essential for the development of the gastrointestinal tract and immune function, but their intake with milk by piglets could be insufficient. The effect of nucleotides on growth and health was tested on 98 piglets divided into two groups: NU, orally administrated with 4 mL of a nucleotide-based product (SwineMOD^®) at 10, 15, 18, 21, 27 days, or not (CO). Blood and feces were sampled at weaning (26 d, T1), and at 38 d (T2). Per each group and time-point, eight piglets were slaughtered and jejunal Peyer's patches (JPPs) were collected. NU increased hemoglobin content and hematocrit, but not growth. At weaning, the NU fecal microbiota was characterized by the abundance of Campylobacteraceae, more typical of the growing phase, compared to CO, with a greater abundance of Streptococcaceae. For the blood transcriptome, an initial greater inflammatory activation was seen in CO, while at T2, NU enriched gene sets related to erythropoiesis. The activation of gene groups ranging from epigenetic response to transcriptional regulation evidenced an intense proliferative activity in NU JPPs. NU supplementation did not influence the growth performance of piglets but could have expressed a positive effect on pig microbiota anticipating its maturation at weaning. This immunostimulant activity in the JPPs could moderate the inflammation in the immediate pre-weaning.

Abstract:
Objective: The objective of this study was to evaluate long-term enteral nutrition support in postoperative cancer patients.
Background: Multimodality therapy for surgical patients with upper gastrointestinal malignancies may improve survival, but often results in substantial malnutrition, immunosuppression, and morbidity. The benefits of combined inpatient and outpatient enteral feeding with standard diets or diets supplemented with arginine, RNA + omega-3 fatty acids are unclear.
Methods: Sixty adult patients with esophageal (22), gastric (16), and pancreatic (22) lesions were stratified by disease site and percent usual weight and randomized to receive supplemental or standard diet via jejunostomy beginning on the first postoperative day (goal = 25 kcal/kg/day) until hospital discharge. Patients also were randomized to receive (n = 37) or not receive (n = 23) enteral jejunostomy feedings (1000 kcal/day overnight) for the 12- to 16-week recovery and radiation/chemotherapy periods. Plasma and peripheral white blood cells were obtained for fatty acid levels and PGE2 production measurements.
Results: Mean plasma and cellular omega 3/omega 6 fatty acid levels (percent composition) increased significantly (p < 0.05) in the arginine + omega-3 fatty acid group by postoperative day 7 (0.30 vs. 0.13) and (0.29 vs. 0.14) and continued to increase over time. Mean PGE2 production decreased significantly (p < 0.05) from 2760 to 1600 ng/10(6) cells/mL at day 7 in the arginine + omega-3 fatty acid group, whereas no significant change over time was noted in the standard group. Infectious/wound complications occurred in 10% of the supplemented group compared with 43% of the standard group (p < 0.05); mean length of hospital stay was 16 vs. 22 (p < 0.05) days, respectively. Of the patients who received postoperative chemoradiation therapy, only 1 (6%) of the 18 patients randomized to receive tube feeding did not continue, whereas 8 (61%) of the 13 patients not randomized to tube feedings required crossover to jejunostomy nutritional support.
Conclusions: Supplemental enteral feeding significantly increased plasma and peripheral white blood cell omega 3/omega 6 ratios and significantly decreased PGE2 production and postoperative infectious/wound complications compared with standard enteral feeding. For outpatients receiving adjuvant therapy, those initially randomized to oral feedings alone required rehospitalization more frequently, and 61% crossed over to supplemental enteral feedings.

Abstract:
Background: Dietary nucleotide supplementation has been shown to have important effects on the growth and development of cells which have a rapid turnover such as those in the immune system and the gastrointestinal tract. Work with infants has shown that the incidence and duration of diarrhoea is lower when nucleotide supplementation is given, and animal work show that villi height and crypt depth in the intestine is increased as a result of dietary nucleotides. Dietary nucleotides may be semi-essential under conditions of ill-health, poor diet or stress. Since people with Irritable Bowel Syndrome tend to fulfil these conditions, we tested the hypothesis that symptoms would be improved with dietary nucleotide supplementation.
Methods: Thirty-seven people with a diagnosis of Irritable Bowel gave daily symptom severity ratings for abdominal pain, diarrhoea, urgency to have a bowel movement, complete feeling of evacuation after a bowel movement, bloating, flatulence and constipation for 28 days (baseline). They were then assigned to either placebo (56 days) followed by experimental (56 days) or the reverse. There was a four week washout period before crossover. During the placebo and experimental conditions participants took one 500 mg capsule three times a day; in the experimental condition the capsule contained the nutroceutical substances. Symptom severity ratings and psychological measures (anxiety, depression, illness intrusiveness and general health) were obtained and analysed by repeated measures ANOVAs.
Results: Symptom severity for all symptoms (except constipation) were in the expected direction of baseline>placebo>experimental condition. Symptom improvement was in the range 4-6%. A feeling of incomplete evacuation and abdominal pain showed the most improvement. The differences between conditions for diarrhoea, bloating and flatulence were not significant at the p < .05 level. There were no significant differences between the conditions for any of the psychological measures.
Conclusion: Dietary nucleotide supplementation improves some of the symptoms of irritable bowel above baseline and placebo level. As expected, placebo effects were high. Apart from abdominal pain and urgency to have a bowel movement, the improvements, while consistent, are modest, and were not accompanied by improvements in any of the psychological measures. We suggest that the percentage improvement over and above the placebo effect is a physiological effect of the nucleotide supplement on the gut. The mechanisms by which these effects might improve symptoms are discussed.

Abstract: In the present study, we aimed to evaluate the effects of maternal yeast-based nucleotide (YN) supplementation on the intestinal immune response and barrier function in neonatal pigs, as well as the diarrhoea rate and growth performance in suckling piglets. Sixty-four late-gestation sows were assigned to the following groups: the CON (fed a basal diet) and YN groups (fed a basal diet with 4 g YN/kg diet). The experiment started on d 85 of gestation and ended on d 20 of lactation. Diarrhoea rate and average daily gain of the piglets were recorded, and samples of blood and intestines from neonatal piglets were collected before they consumed colostrum during farrowing. Compared with the CON group, maternal YN supplementation increased the weaning weight of litter and decreased the diarrhoea rate (P < 0.01). In addition, maternal YN supplementation promoted the ileal villus development in the neonates compared with that in the CON group (P < 0.01). Maternal YN supplementation also increased the ileal secretory immunoglobulin A (sIgA) level compared with that in the CON group (P < 0.05). The real-time PCR results showed that maternal dietary YN supplementation increased the jejunal and ileal expression of interleukin (IL)-17, IL-8, IL-1beta, IL-10 and tumor necrosis factor (TNF)-alpha in the neonates compared with that in the CON group (P < 0.05). Overall, maternal nucleotide supplementation improved the villus development and innate immunity of neonatal piglets during late pregnancy. This may be associated with the decrease in diarrhoea and the increase in weaning weight of the litter of suckling piglets. 

Abstract: Dietary nucleotides have been reportedly beneficial, especially for infants, since they positively influence lipid metabolism, immunity, and tissue growth, development and repair. Rapidly proliferating tissues, such as the immune system or the intestine are not able to fulfil the needs of cell nucleotides exclusively by de novo synthesis and they preferentially utilize the salvage pathway recovering nucleosides and nucleobases from blood and diet. In the present review we describe the modulatory effect of dietary nucleotides on the immune system together with some of their effects on gut-associated lymphoid tissue. Dietary nucleotides influence lymphocyte maturation, activation and proliferation. Likewise, they affect the lymphocyte subset populations in both the small intestine and blood. Moreover, they are involved in enhancing macrophage phagocytosis and delayed hypersensitivity as well as allograft and tumour responses. In addition, they contribute to the immunoglobulin response in early life, having a positive effect on infection. In fact the incidence and duration of acute diarrhoea is lower in infants fed supplemented-nucleotide formulas. The molecular mechanisms by which dietary nucleotides modulate the immune system are practically unknown. Dietary nucleotides have been shown to enhance the production and the genetic expression of IL-6 and IL-8 by foetal small intestinal explants. Dietary nucleotides may influence protein biosynthesis as well as signal membrane transduction mediated by the interaction of exogenous nucleosides and their receptors may also contribute to modulate the expression of a number of genes, some of which can directly affect the levels of intestinal cytokines.

Abstract: Nucleotides are low molecular weight biological molecules key to biochemical processes. Sources include de novo synthesis, recovery via salvage mechanisms, and dietary intakes. Although endogenous production serves as the main nucleotide source, evidence suggests that exogenous sources are essential to immune competence, intestinal development, and recovery. Dietary nucleotides serve a marked role in rapidly proliferating cells where they are necessary for optimal function. Accordingly, dietary nucleotides are deemed conditionally essential in the presence of various physiological stresses, including growth and development, recovery from injury, infection, and certain disease states. Clinical studies that evaluated nutrition formulations of nucleotides in combination with other specific nutrient substances demonstrated improved clinical outcomes in patients characterized as critically ill, injured, immune suppressed, or with chronic gastrointestinal conditions. However, conclusions regarding specific benefits of nucleotides are limited. Scientific substantiation of nucleotide supplementation in infant formula has been reported to improve the maturation and development of the intestinal tract as well as immune function. All medical nutrition products except for one immune-modulating formulation are devoid of nucleotides. In an effort to build on this, the current review presents the data to support potential clinical applications for nucleotides in enteral nutrition that may contribute to improved outcomes in physiologically stressed patients.

Abstract: Emerging evidence suggests that nucleotide-free diets induce immune suppression and may seriously influence intestinal growth, maturation, and function. Thus, DNA-Na+ salt from fish soft roe, used as a nucleotide source, was investigated in regard to its effect on intestinal growth under optimal and nutrition–depleted conditions. The effect of another dietary additive, RNA from bakers yeast (S. cervisiae) and various deoxy-mononucleotides have also been clarified. DNA-Na+, RNA, dAMP, dCMP, dGMP, and TMP were added to a human malignant intestinal cell line, CaCO-2 and a rat intestinal cell line of normal origin, IEC-6. Growth effects were ascertained by measuring the amount of tritium-labeled thymidine incorporated into the cell DNA. Our results show that DNA-Na+, RNA, and deoxy-mononucleotides have beneficial effects on growth, tying to compensate for the glutamine- and partially serum-deprived culture condition, depending on the intestinal cell line investigated. Especially the “normal” IEC-6 cell line seemed to benefit from the exogenous nucleotide supply. dAMP increased mostly CACo-2 growth under optimal conditions. Both dCMP and dGMP supported growth of both cell lines under most culture conditions. In contrast, TMP acted as a general growth inhibitor. Of interest also was the growth-suppressing ability of DNA-Na+ in particular, but also RNA, on vigorously proliferating CaCo-2 cells cultured under optimal nutrition supply. This activity should be investigated in regard to other hyperproliferating and malignant cell types.

Abstract: Total parenteral nutrition (TPN) is associated with atrophic changes in the structure and function of the intestinal mucosa. Because rapidly renewing intestinal mucosal cells may require an external source of purines and pyrimidines for their optimal growth, it can be assumed that supplementation of nucleosides and a nucleotide mixture (OG-VI) during TPN may prevent the progression of mucosal atrophy by compensating for a relatively insufficient delivery from liver. To test that hypothesis, male Wistar rats receiving TPN for 7 days were divided into four groups according to different TPN solutions. Group C (n = 10) received a standard solution, group O (n = 10) received OG-VI in addition to the standard solution, and group G (n = 10) received a glutamine-rich TPN solution containing almost the same amount of calories and nitrogen as the standard solution. Group O+G (n = 10) received OG-VI in addition to the glutamine-rich solution. Various parameters were examined on the eighth day in the jejunal and ileal segments. The following significant changes in comparison with group C were observed: total wet weight of the jejunal segment in group O was significantly greater, as was mucosal wet weight of the jejunal and ileal segments in groups O and O+G; protein contents of the ileal segment in group O as well as the DNA content of the jejunal segment in group O increased significantly; and maltase activity of the jejunal segment in group O+G increased, as did the villus height of the jejunal segment in groups O and O+G and the villus height of the ileal segment in group G.

Abstract: The effects of supplementing a total parenteral nutrition solution with a nucleoside and nucleotide mixture on mucosal adaptive processes after massive bowel resection were studied. Male Wistar rats (n=30) underwent 80% small intestine resection, were randomized into two groups and received either standard total parenteral nutrition (TPN) or TPN supplemented with a nucleoside and nucleotide mixture (2.5 mL.kg-1.d-1). An additional five rats, fed a nonpurified diet and not resected, were used as controls. After 4 or 7 d, rats were killed and samples were collected for mucosal indices and intestinal enzymatic activities (disaccharidases and diamine oxidase). After massive small bowel resection and TPN, residual jejunal mucosal wet weights, villus heights, protein and RNA contents on d 4 and 7, and total wet weights and DNA contents on d 7 were significantly lower than in the control group. Administration of the nucleoside and nucleotide mixture resulted in significantly higher residual jejunal total and mucosal weights, proteins, DNA, RNA contents, and the ratio of proliferating cell nuclear antigen positive cells per crypt than did the standard TPN solution on d 7. However, disaccharidase and diamine oxidase activities were not affected by supplementation with the nucleoside and nucleotide mixture. Our data suggest the supplementation of a nucleoside and nucleotide mixture to a TPN solution can attenuate the initial mucosal atrophy and improve intestinal cell turnover after massive bowel resection, but the supplementation has little effect on enterocyte enzymatic activities.

Abstract: Nucleotides are ubiquitous intracellular compounds of crucial importance to cellular function and metabolism. They have been demonstrated to have a wide variety of physiological effects such as antiviral, anti-proliferative, immunomodulatory and other such beneficial functions. Nucleotides can be synthesised endogenously and hence are not essential nutrients. However, their requirements go up in situations of stress like infection, surgery, tissue repair and/or when de novo synthesis may be inadequate. The need then arises for extraneous supplementation. Thus the nucleotides have come to be classified, in recent times, as ‘conditionally essential nutrient’ like the amino acid glutamine. The building blocks of nucleotides are purine and pyrimidine bases attached to a sugar (ribose or deoxyribose). When phosphate moiety is also added, it is termed a nucleotide. Table 1 gives the nucleotide nomenclature.

Abstract: Adenosine modulates the intestinal functions of secretion, motility, and immunity, yet little is known about the regulation of nutrient absorption. Therefore, we measured the carrier-mediated uptake of tracer D-[(14)C]glucose (2 microM) by everted sleeves of the mouse intestine after a lumenal exposure to adenosine and a disodium salt of AMP. Rates of glucose uptake by intact tissues increased almost twofold after a 7-min exposure to 5 mM adenosine (a physiological dose). The response was slightly more pronounced for AMP and could be induced by forskolin. The response to adenosine was blocked by theophylline and the A(2) receptor antagonist 3,7-dimethyl-1-proparglyxanthine but not by the A(1) receptor antagonist 8-phenyltheophylline. Glucose uptake by control and AMP-stimulated tissues was inhibited by phloridzin, implying that sodium-dependent glucose transporter 1 (SGLT1) is the responsive transporter, but the involvement of glucose transporter 2 (GLUT2) cannot be excluded. Of clinical relevance, AMP accelerated the systemic availability of 3-O-methylglucose after an oral administration to mice. Our results indicate that adenosine causes a rapid increase in carrier-mediated glucose uptake that is of clinical relevance and acts via receptors linked to a signaling pathway that involves intracellular cAMP production.

Abstract: Microgravity and its environment have adverse effects on the immune system. Abnormal immune responses observed in microgravity may pose serious consequences, especially for the recent directions of NASA for long-term space missions to Moon, Mars and deep Space exploration. The study of space flight immunology is limited due to relative inaccessibility, difficulty of performing experiments in space, and inadequate provisions in this area in the United States and Russian space programs (Taylor 1993). Microgravity and stress experienced during space flights results in immune system aberration (Taylor 1993). In ground-based mouse models for some of the microgravity effects on the human body, hind limb unloading (HU) has been reported to cause abnormal cell proliferation and cytokine production (Armstrong et al., 1993 Chapes et al. 1993). In this report, we document that a nutritional nucleotide supplementation as studied in ground-based mirogravity analogs, has potential to serve as a countermeasure for the immune dysfunction aboserved in space travel.

Abstract: Most alterations during weaning involve physiological changes in intestinal structure and function. Here, we evaluated the molecular mechanisms regulating the effects of nucleotides on weaning. Nucleotide treatment induced Trefoil factor 3 (TFF3) expression and IPEC-J2 cell growth and reduced wound width. Treatment with nucleosides and TFF3 in lipopolysaccharide-challenged IPEC-J2 cells increased intestinal transepithelial electrical resistance and decreased intestinal permeability. Additionally, nucleosides improved intestinal barrier function through induction of TFF3-mediated phosphatidylinositol 3-kinase/Akt, extracellular signal-regulated kinase 1/2, p38, and Janus kinase/signal transducer and activator of transcription signaling pathways. Among selected differentially expressed genes, SAM pointed domain containing ETS transcription factor (SPDEF) expression was elevated by nucleotides in a concentration-dependent manner. Moreover, SPDEF directly regulated TFF3 expression via binding to the promoter. In vivo, nucleotide supplementation improved growth performance, serum stress levels, and intestinal morphology. Our findings provide insights into the molecular mechanisms of intestinal development during weaning in pigs.

Abstract: The health benefits of specific nutrients in the diet are reviewed as they pertain to the pediatric population and its unique needs. Secretory immunoglobulins, lysozyme, interferon, and growth factors, among others, are known to confer immunological advantages to breast milk. Inhibition of bacterial pathogens, as well as permissive growth of a protective colonic ecoflora occur as a result of various cellular and biochemical mechanisms at play. The immunomodulatory properties of mineral such as iron, zinc, and selenium, are presented and the newly recognized protective role of vitamin A and its importance in developing countries and in conditions of compromised nutrition are discussed. The review also covers the role of arganine, glutamine, and nucleotides in adaptive responses of the developing gut and in pathologic states such as necrotizing enterocolitis, short bowel syndrome, and inflammatory bowel disease. Probiotics (specific microbial feeds with potential benefits to the host), and prebiotics (dietary components such as complex carbohydrates able to change the colonic microenvironment fostering colonization with non-enteropathogens) are areas of current interest because they offer alternatives for the management of the growing problem of multiple antibiotic resistance and overwhelming infections in the hospitalized patient.

Abstract: The objective of this study was to evaluate the influence of dietary nucleotide supplementation in preterm infants during the first month of life on the intestinal permeability to lactulose, mannitol and to beta-lactoglobulin and on the development of circulating antibodies to beta-lactoglobulin and alpha-casein. Twenty-seven preterm infants were enrolled in the study; 11 of them were fed a standard low-birth weight milk formula and 16 infants were fed the same formula supplemented with nucleotides at similar levels to those found in human milk. Blood and urine samples were obtained at 1, 7 and 30 days of age. Serum beta-lactoglobulin, serum IgG antibody to alpha-casein and serum IgG antibody to beta-lactoglobulin were measured by ELISA. The lactulose/mannitol urinary excretion rate was measured by gas liquid chromatography. Neither the intestinal permeability to saccharides nor the intestinal absorption of beta-lactoglobulin were affected by the nucleotide supplementation. However, serum concentrations of IgG antibody to beta-lactoglobulin were higher in preterm neonates fed the supplemented formula than in those fed the standard formula. According to these results, dietary nucleotides might influence the maturation of the humoral immune response in preterm newborn infants.

Abstract:
Background: Aim of this study is to evaluate the incidence of diarrhea in children fed with a nucleotide-supplemented formula (Similac FormulaPlus) in comparison with formula without nucleotide supplementation.
Methods: We investigated the effects of a nucleotide-supplemented formula on the incidence of diarrheal episodes in 3315 infants with a multicentre study conducted by 386 pediatricians since March 1998 until October 1999. The study population has been divided into 4 groups based on the type of feeding: group 1 (n=958)= exclusively nucleotide-supplemented formula, group 2 (n=824)=exclusively without nucleotide-supplementation, group 3 (n=920)=mixed breast-feeding and nucleotide-supplemented formula, group 4 (n=613)=mixed breastfeeding and formula without nucleotide supplementation. At the beginning of the study the 4 groups did not differ for body weight, length and mass index. The infants were enrolled since the first month up to the end of the third month of life and they were followed up to the end of the sixth month of life. During the period of observation the growth of length, weight and mass index was similar among the 4 groups.
Results: Monthly incidence of diarrhea was computed and the comparison between group 1 and group 2 using the summary odds-ration of Mantel-Haenszel showed that in group 1 the incidence of diarrhea was significantly lower that un group 2 (RR=0.567); CI 95%=0.440-0.732); similar results were obtained comparing the incidence of diarrhea between group 3 and group 4, having the former a RR=0.630 (CI 95%=0.476-0.834).
Conclusions: The conclusion drawn in that the supplementation with nucleotide of the formula milk decreases the risk of diarrhea episodes during the first six month of life in healthy infants. Such a positive effect is present both in exclusively nucleotide-supplemented formula and in mixed breast-feeding and nucleotide-supplemented formula fed infants. Interpretation of these results is that nucleotides, much more present in human milk than in formula milk, improve the immune defense of the infants stimulating particularly the cell-mediated immunity.

Abstract: The current study aimed to evaluate the efficiency of dietary nucleotides-supplementation on broiler chickens to alleviate the intestinal Clostridium perfringens (C. perfringens) levels and its adverse effect on gut and growth performance parameters. In this study, a total of 270 one-day-old mixed broiler chicks (Cobb 500) were randomly divided into six treatment groups with three replicates of 15 chicks/ replicate. Treatment 1 (CX), a negative control group was fed corn-soybean basal diet without added nucleotides. Treatment 2 (CN 0.05) and treatment 3 (CN 0.1), consisted of chicks were fed the basal diet with the addition of nucleotides on top at two levels (0.05 and 0.1%) respectively. Treatment 4 (PX), treatment 5 (PN 0.05), and treatment 6 (PN 0.1) consisted of chicks that were challenged with C. perfringens inoculum (~4 × 108 CFU/ml) on day 14, 15, 16 and 17 of the experiment and were fed diets similar to treatments 1, 2, and 3 respectively. The trial continued for 35 days. At the end of the experiment, the intestinal C. perfringens counts, microscopic lesion scores, intestinal histomorphology, intestinal barriers (occludin and mucin mRNA expression) and growth parameters were determined. The results showed that the pathogen challenge significantly (P<0.05) increased both C. perfringens levels and intestinal lesion scores. Which adversely affects intestinal barriers and intestinal histomorphology resulting in a significant decrease (P<0.05) in body weight gain (BWG) with an increase in feed conversion ratio (FCR). Whereas, nucleotides-supplementation, at 0.1%, significantly decreased both C. perfringens levels and intestinal lesion scores, and significantly improved intestinal barriers and intestinal histomorphology which consequently resulted in improved growth performance parameters to be nearly the same as that of the control un-supplemented group. In conclusion, nucleotides markedly ameliorated the negative effects of C. perfringens challenge by improving the intestinal barrier function and intestinal histomorphology which positively reflected on the growth performance of challenged birds.

Abstract: Our previous studies showed that dietary nucleotides fed to mice enhanced the secretion of interleukin 7 (IL-7) and transforming growth factor beta (TGF-beta) from intestinal epithelial cells (IECs). To explore whether nucleotides influence IECs directly to enhance the secretion of the cytokines or not, the effects of nucleotides added in vitro on the cytokine secretion from primary-cultured murine IECs were examined. When the mixture of nucleotide 5'-monophosphates (CMP, GMP, IMP, and UMP) or individual nucleotide 5'-monophosphates were added to the primary culture of IECs derived from BALB/c mice, the secretion of IL-7, but not that of TGF-beta, was increased significantly. Addition of nucleotides to the culture did not alter the number of the IECs. Secretion of IL-6 and granulocyte-macrophage colony-stimulating factor, which are known to be secreted from IECs, was not enhanced by the addition of nucleotides. These results demonstrate that nucleotides can affect IECs directly to enhance the secretion of IL-7, and suggest that the increased secretion of TGF-beta from IECs by dietary nucleotides was due to indirect effects of the nucleotides, which may affect intestinal microflora or cells other than IECs that in turn influence the cytokine secretion of IECs.

Abstract: We have investigated the effects of dietary nucleotides on intraepithelial lymphocytes (IEL) and intestinal epithelial cells (IEC) in weanling mice. The proportion of T-cell receptor (TCR) gamma delta+ IEL in BALB/c mice fed a diet supplemented with nucleotides (NT(+) diet) was significantly higher than that in mice fed the nucleotide-free diet, while the proportion of TCR alpha beta+ IEL in NT(+) diet-fed mice was significantly decreased. The change of the TCR alpha beta+/TCR gamma delta+ ratio was mainly observed in the CD8 alpha alpha+ subset of IEL. IEC from NT(+) diet-fed mice produced a higher level of IL-7, which is important in the development of TCR gamma delta+ IEL, than those from control diet-fed mice. The expression levels of IL-7 and IL-2 receptors on IEL were not different between the two dietary groups. Our findings suggest that the increased population of a TCR gamma delta+ IEL subset by feeding nucleotides may be caused by the increased production of IL-7 by IEC.

Abstract: Nucleic acid synthesis in tissues of rapid growth is preferentially done using dietary purines and pyrimidines via the salvage pathway. In the case of a low protein intake, dietary nucleotides may be semiessential for cell replication of gut, lymphocytes, and bone marrow, and especially in those intestinal diseases in which the mucosa is altered, dietary nucleotides may have a role in intestinal development. The effect of dietary nucleotides on intestinal weight and length, gut mucosal weight, intestinal protein and DNA contents, and lactase, maltase, and intestinal mucosal activities was assessed in a controlled way. Weanling (21-day-old) rats were separated into two groups of 36, each receiving blindly a basal diet containing glucose polymers (C) or a basal diet with lactose as the main carbohydrate (L) for 15 days. Those fed with L developed a syndrome of chronic diarrhea and malnutrition. Ten rats of each group were sacrificed at that time. The rest of the animals of each group were separated into two subgroups. The first was fed with the C diet and the second with the C diet supplemented with 50 mg/100 g of each of the following nucleotides: AMP, GMP, CMP, UMP, and IMP (CN). Thus the subgroups CC, CN, LC, and LN were formed. Rats were sacrificed after 4 weeks and gut separated into three segments corresponding to duodenum, jejunum, and ileum. Analysis of variance was used to compare the effect of diet or segments. DNA and lactase, maltase, and sucrase activities increased in the LN group with respect to LC especially in jejunum and ileum but there were not any differences between CC and CN.

Abstract: Immune cells and cells undergoing rapid turn-over can obtain exogenous nucleotides via salvage synthesis. We evaluated whether or not the balanced nucleoside and nucleotide mixture OG-VI, could rescue intestinal epithelial-like Caco-2 cells from the cytotoxic effects of several chemotherapeutic agents, in the presence and absence of glutamine (Gln). Cells were exposed to 5-fluorouracil (5FU), methotrexate (MTX) or 6-mercaptopurine (6MP), after which proliferation and cell cycle analyses were performed. Following exposure to the chemotherapeutic agents, we observed that cells treated with OG-VI proliferated well, whereas those without the supplement did not proliferate. Furthermore, following treatment with either 5FU or MTX, we observed that the number of cells in the G0/G1 phase decreased and those in the S phases increased. However, these cell cycle alterations were prevented by the addition of OG-VI. With the exception of 6MP-treated cells, we did not observe any effects on proliferation or cell cycle regulation that could be ascribed to the presence of Gln. Thus, we have demonstrated that OG-VI rescues cells from the cytotoxic effects of several chemotherapeutic agents.

Abstract: Previous studies in very young rats have shown that dietary nucleotides improve small intestine repair after injury or malnutrition. To investigate the potential effect of nucleotides in old rats, which have a diminished capability for intestinal repair, 17-mo-old rats were deprived of food for 5 d and then fed a nucleotide-free diet or a nucleotide-supplemented diet for 3 or 6 d. Intestinal jejunal and ileal mucosal weight, protein and DNA were evaluated as intestinal growth markers, and brush-border maltase, sucrase, lactase and aminopeptidase activities were evaluated as intestinal differentiation markers. The adenine nucleotide pool and the adenylate energy charge were also evaluated as indices of nucleotide availability. Food deprivation significantly decreased mucosal growth markers as well as differentiation markers in both jejunum and ileum. The ATP pool was also significantly depressed, but the adenylate energy charge was not significantly altered. To a certain extent, refeeding restored the losses, but in the rats that were fed the nucleotide-free diet, the restoration of the jejunum was significantly slower and the restoration of the ileum differentiation markers was incomplete compared with the rats fed the nucleotide-supplemented diet. The results suggest that dietary nucleotide intake in the elderly may accelerate the normal physiological intestinal response to refeeding after food deprivation.

Absytact: Defensins are antimicrobial peptides produced at a variety of epithelial surfaces. In the intestinal tract, they contribute to host immunity and assist in maintaining the balance between protection from pathogens and tolerance to normal flora. However, attenuated expression of defensins compromises host immunity and hence may alter the balance toward inflammation. Altered defensin production is suggested to be an integral element in the pathogenesis of inflammatory bowel disease (IBD). Evidence for this is shown in Crohn's disease where reduced alpha-defensin levels are seen in patients with ileal disease and reduced beta-defensin levels in those with colonic involvement. Further evidence is provided by research linking nucleotide oligomerization domain 2 (NOD2) mutations and deficient defensin expression. However, alternate studies suggest that NOD2 status and defensin expression are independent, and that defensin deficiency is due to mucosal surface destruction as a result of inflammatory changes, indicating that reduced defensin expression is a symptom of the disease and not the cause. Although it is clear that defensin expression is altered in IBD, it is less clear whether defensin deficiency is implicated in the pathogenesis of IBD or is a consequence of the disease process. The aim of this article is to review the current knowledge of defensins in IBD and discuss their potential role in IBD pathogenesis.

Abstract: Exogenous nucleotides are considered semiessential nutritional components that play an important role in intestinal development, maintenance, and recovery from tissue damage. Nucleosides (NS) are the best-absorbed chemical form of nucleotides in the intestinal epithelium. The aim of this work was to clarify, at the cellular level, the effects described in vivo. Under conditions of high intracellular availability of NS, we studied the effects of 2 NS mixtures on the NS uptake and intracellular distribution and on the proliferation, morphology, viability, and cell-cycle phase distribution of rat intestinal epithelial cell line 6. Purine and pyrimidine NS showed a similar uptake profile, but the intracellular incorporation of guanosine was greater than that of uridine, without differences in intracellular distribution. Proliferation assays demonstrated that IEC-6 cell proliferation is increased by a mixture containing thymidine but decreased by one containing uridine. In fact, the antiproliferative effect started at 75 micromol/L, which indicated that it may not be correct to consider concentrations of uridine >75 micromol/L as physiological. Interestingly, these effects were not related to increased cell necrosis or apoptosis or to changed cell morphology but rather to a reduced S-phase and increased G0/G1 phase of the cell cycle. In summary, our results suggest that NS molecules are well-absorbed by rat intestinal epithelial cell line 6 cells, whose proliferation can be promoted or inhibited (according to the NS mixtures used) by a mechanism that is not dependent on the toxicity of the mixtures.

Abstract:
Background: Dietary nucleotides are nonprotein nitrogenous compounds that are thought to be important for growth, repair, and differentiation of the gastrointestinal tract. A higher nucleotide intake may also have favorable effects on the fecal microbial composition and incidence of diarrhea in infancy. However, few studies have tested this hypothesis with an experimental study design.
Objective: We tested the hypothesis that nucleotide supplementation of infant formula has beneficial effects on fecal bacteriology.
Design: Oligonucleotide probes were used to measure bacterial genus-specific 16S ribosomal RNA in stools of a subset of infants (mean age: 20.4 wk) who were randomly assigned to nucleotide-supplemented (31 mg/L; n = 35) or control formula (n = 37) from birth until age 20 wk or were breastfed (reference group; n = 44). The microbial pattern was assessed as the ratio of Bacteroides-Porphyromonas-Prevotella group (BPP) to Bifidobacterium species.
Results: The ratio of BPP to Bifidobacterium spp. rRNA in infants randomly assigned to the nucleotide-supplemented formula was lower than in infants receiving the control formula (mean difference: -118%; 95% CI: -203%, -34%; P = 0.007), but it did not differ in infants who were breastfed. The difference between randomized formula-fed groups was independent of potential confounding factors (P = 0.003).
Conclusions: Our data support the hypothesis that nucleotide supplementation improves the composition of the gut microbiota in formula-fed infants. Because this effect could contribute to previously described benefits of nucleotide supplementation for gastrointestinal tract and immune function, these findings have important implications for optimizing the diet of formula-fed infants.

Abstract: Since dietary nucleotides play an important role in the growth and development of the intestine, supplementation of a nucleic acid solution (OG-VI) may support the optimal growth and integrity of the intestine under total parenteral nutrition (TPN). Supplementation of OG-VI to a TPN solution improved mucosal morphologic and functional changes, increased mucosal proliferation, and decreased mucosal permeability of the intestine. After 80% small bowel resection, OG-VI supplementation to a TPN solution attenuated the initial mucosal atrophy and improved intestinal cell turnover. Nucleic acid supplementation may be clinically beneficial in certain situations.

Abstract:
Background: Dietary nucleotides play an important role in the growth and development of the intestine. Parenteral supplementation of nucleic acids may be necessary to maintain the mucosal proliferation and barrier functions during parenteral nutrition (PN).
Methods: Male Wistar rats were divided into 3 groups: FED (food ad libitum with saline infusion); PN ( a standard PN solution); and OG(OG-6, a mixture of nucleotide and nucleosides, in addition to the PN solution). The mucosal wet weight, protein, and DNA contents, villous height and crypt depth, electronmicroscopic examination of the intercellular junctions, proliferating activity of the mucosal cells, mucosal permeability, bacterial translocation, and mucosal cathepsin activities were examined.
Results: The wet weight, protein, and DNA contents of the jejuna mucosa were significantly increased in the OG group, compared with those in the PN group. The morphometric examination revealed a significant increase in the villous height but not in the crypt depth in the OG group. The widths of both the tight and intermediate junctions were narrower in the OG group than those in the PN group. The activity of diamine oxidase was increased in the OG group, compared with that in the PN group. The ratio of proliferating cell nuclear antigen positive cells and the index of bromodeoxy uridine labelling index in the OG group were as high as in the FED group, and significantly higher than those in the PN group. The portal concentration of fluorescein isothiocyanate-dextran 70,000 after intragastric loading was significantly higher in the PN group than that in OG group. Likewise, the rate of urinary lactulose excretion after intragastric loading was higher in the PN group. The positive rate of bacteria cultured in mesenteric lymph nodes was higher in the PN group than in the OG group although the difference was not significant. The activities of mucosal cathepsins (B, H, and L), markers for phagocytic degradation of extrinsic substances and organisms, were higher in the PN group than those in the OG and FED groups.
Conclusions: Parenteral supplementation of nucleic acids supports the mucosal cell proliferation and functions.

Abstract: It is apparent from the number of symposia published in the last few years that the role of nucleotides in the diet is an extremely important issue. This roundtable, entitled Nucleotides and Nutrition, helped update our knowledge on the use of nucleotides as a supplement in newborns and in older children and adults. We were very fortunate to have many of the world’s authorities in the field available to discuss the salient issues surrounding this topic.
In session 1: Frederick B. Rudolph and Lewis A. Barness reviewed the current knowledge on the chemistry, physiology and composition of nucleotides in breast milk from parturition until weaning. Dr. Rudolph described the metabolism of nucleotides, underscoring their importance in cellular function and the consequences of dysfunction vis-à-vis various human disease states. He reviewed his studies with Charles T. Van Buren over the last several years examining the role of nucleotides in optimal host defense against infection and as a substrate for a normal immune response to noxious foreign stimuli. He pointed out, based on his research, that the absence of nucleotides tends to cause an arrest in the cell cycle between the G1-G2 and the S phases of T helper cells. It was apparent from this review that additional basic research is necessary to further define the importance of nucleotides within various metabolic pathways of specific cell types and under various conditions in which there may be higher requirements for them as substrates for normal host defense function. Dr. Barness reviewed data on the composition of the nonprotein nitrogen pool in breast milk and the contribution made by nucleotides. He also indicated that the total nucleotide pool, including the nucleotides in the soluble fraction and those released by the breakdown of cells in the breast milk, may be grossly underestimated and that any consideration of nucleotide supplementation of infant formula must include a re-examination of these fluids using such modern quantitative techniques as HPLC. Very little is now known about the capacity of the enterocytes in premature and full-term human infants to use nucleotides through the salvage pathway or the de nove synthesis pathway. Again, this presentation underscored the need for further molecular and cellular studies in human development, as well as for a reassessment of our knowledge of the composition and quantity of nucleotides, before recommendations for meaningful supplementation in premature infants and in posttraumatic stress can be made.
In session 2: Ian R.Sanderson and Harumi Jyonouchi reviewed molecular studies involving nucleotide uptake and metabolism in human intestinal cell lines and organ cultures from human foetuses, as well as in vivo and in vitro studies of specific mechanisms of lymphocyte function. Dr. Sanderson reviewed the data obtained in his laboratory using Caco-2 cells, a human cancer cell line that differentiates in a manner similar to that of the crypt villus differentiation pathway, and IEC-6 cells, a noncancer rodent crypt cell line that requires growth factors from an extracellular matrix for maturation to occur. In the neoplastic cells (Caco-2) the de novo synthetic pathway for nucleotides was active and, under conditions of normal growth, exogenous nucleotides were not required However, under conditions of nutritional stress, they became essential. With the non-neoplastic crypt cells (IEC-6) in the presence of an extracellular matrix (Matrigel), nucleotides provided an additive stimulus for the differentiation.

Abstract: Emerging evidence indicates the importance of nucleosides and nucleotides in the maintenance of functions of the bone marrow hematopoietic cells, intestinal mucosa, and the brain, which have limited de novo synthesis of purine and pyrimidine bases. We have found that nucleosides and nucleotides stimulate hemopoieses and increase peripheral neutrophil counts in mice treated with cyclophosphoamide. Intraperitoneal administration of nucleosides and nucleotides decreased bacterial translocation, the number of colony-forming units, and increased survival against methicillin-resistant Staphylococcus aureus. In vitro immune studies in mice showed that nucleosides and nucleotides increase the delayed-type cutaneous hypersensitivity and the popliteal lymph node blastogenic response to antigens, allogens, and mitogens. Both intraperitoneal and oral administration of nucleosides and nucleotides reduced endotoxin-induced bacterial translocation and improved injury to the gut in protein-deficient mice. However, oral administration of nucleosides and nucleotides in experimental colitis resulted in a worsening of colitic conditions and increased interleukin-8 and tumor necrosis factor-alpha concentrations in inflamed colonic portions, indicating the pro-inflammatory activities of nucleosides and nucleotides. Memory-deficient senescence-accelerated mice and mice with dementia showed improved memory with dietary nucleosides and nucleotides supplementation. These results indicate that supplementation with nucleosides and nucleotides is beneficial to the functions of the system and the brain. However, beneficial effects to the gut appear to depend on the type of damage sustained by the gut.

Abstract: The present review examines the role of dietary nucleotides in infants, and the scientific rationale and benefits of nucleotide supplementation of infant formula. The immunoprotective benefits of human milk, the biology of human milk nucleotides, and the immunological and gastrointestinal effects of dietary nucleotides in animal studies and in vitro experiments are examined. Clinical studies are reviewed, especially those examining the efficacy of nucleotide supplemented infant formula in enhancing immunity and reducing the risk of sepsis. The presence of human milk cells, and a variety of immunoactive and trophic components of human milk, can explain the reduced incidence of sepsis in breastfed term and preterm infants. Nucleotides, believed to play an immunomodulatory role, are found in lower concentrations in differentiation and repair of the gut. Several clinical studies have reported beneficial effects of nucleotide supplementation on gut microflora, diarrhoea and immune function, and one study has reported better catch-up growth in term infants with severe intrauterine growth retardation. More basic research studying the metabolism of nucleotides in neonates is encouraged. Additional randomized controlled trials are necessary to demonstrate the clinical benefits of nucleotide supplementation of infant formula, as it cannot be presumed that nucleotides produce the same benefits for the infant as human milk. Studies are especially necessary in high-risk neonatal situations, such as extreme prematurity, significant suboptimal nutrient intake before and after birth, and recovery from gut injury.

Abstract: Human milk has a higher concentration of nucleotides than bovine milk which is the source of most infant formulas. As the composition of human milk is considered the ‘gold standard’, an increasing number of infant formulas are supplemented with nucleotides. This review summarises the biology of human milk nucleotides and evaluates the studies which investigated the clinical benefits of feeding infants with nucleotide-supplemented formulas. Although dietary nucleotides have been suggested to have beneficial gastrointestinal and immunological effects, nucleotide-supplemented formula feeding has not been shown to confer the same benefits as breast feeding, and randomised controlled trials have yet to prove that healthy term infants fed nucleotide supplemented formulas compared to those fed nonsupplemented formulas, have accelerated physical growth and neurological development, better growth and development of their gastrointestinal tract resulting in improved digestive and absorptive functions, enhanced development of their immune system resulting in increased resistance to infection and lower bacterial and viral infection rates during infancy, and a more favourable intestinal microflora associated with a lower rate of infectious diarrhoea. However, a randomised controlled trial has reported that term infants with sever intrauterine growth retardation do have better catch-up growth with nucleotide supplementation. The hypothesis that nucleotides are semi-essential nutrients needs to be further studied, in particular in the presence of prematurity, fetal growth retardation, intestinal injury and limited nutrient intake. As no deleterious effects have been reported with the use of nucleotide supplemented formulas, the first of which was introduced over 30 years ago, such products are considered safe when nucleotides are supplemented to an amount equivalent to the free nucleotide concentration of human milk. More basic and clinical research studies are awaited to further define the biology and role of human milk nucleotides, and to critically assess the potential benefits and appropriate level of nucleotide supplementation of infant formula.

Abstract:
Background: Irritable bowel syndrome (IBS) is a disorder with unknown pathophysiology, although it would appear that stress of different types plays an important role in the onset and development of the disorder. It affects 10-15% of the general population. Currently, anticholinergics and prokinetics are the main therapies.
Objective: The objective of this study was to examine the effects of sildenafil in an animal model of IBS.
Methods: IBS was induced in rats using the wrap-restraint method and sildenafil was administered intragastrically by gavage at doses of 0.5, 1 and 5mg/kg. Gastric emptying, small bowel transit and fecal excretion (index of large intestine motility) as well as concentrations of cyclic nucleotides (cGMP and cAMP) and total antioxidant capacity in the large intestine were determined.
Results: Sildenafil at all doses used (0.5, 1 and 5mg/kg) significantly reduced gastric emptying up to 120min postdrug administration. All doses (0.5, 1 and 5mg/kg) of sildenafil dose-dependently reduced small bowel transit up to 60 and 90min after sildenafil administration. Treatment of rats using sildenafil (0.5, 1 and 5mg/kg) increased the concentration of cAMP 40min post administration. At 90min postdrug administration, only sildenafil (5mg/kg) increased cAMP concentration. At 40min postdrug administration, sildenafil (1 and 5mg/kg) and at 90min, all doses of sildenafil increased the concentration of cGMP. Sildenafil (5mg/kg) increased total antioxidantcapacity and reduced fecal excrements in IBS rats.
Conclusion: Sildenafil administration appears to have beneficial effects in the treatment of IBS in rats, which is in relation with the drugs potential to increase bowel total antioxidant capacity and cyclic nucleotides.

Abstract:
Background: The 5-hydroxytryptamine7 receptor (5-HT(7) receptor, 5-HT(7)R) plays an important role in the regulation of smooth muscle relaxation and visceral sensation and might be involved in the pathogenesis of the gastrointestinal dyskinesia, abdominal pain and visceral paresthesia in irritable bowel syndrome (IBS). The aim of this study was to investigate the role of the 5-HT(7) receptor in the pathogenesis of IBS.
Methods: A rat model of irritable bowel syndrome with diarrhea (IBS-D) was established by colonic instillation of acetic acid and restraint stress. A rat model with irritable bowel syndrome with constipation (IBS-C) was established by stomach irrigated with 0 - 4 degrees C cool water daily for 14 days. The content and distribution of 5-HT in the brain and gut were examined by immunohistochemistry and the mRNA expression of the 5-HT(7) receptor was determined by fluorescent quantitative reverse transcription polymerase chain reaction. The accumulation of cyclic adenosine monophosphate (cAMP) in all the same tissues was measured by radioimmunity.
Results: The models of IBS were reliable by identification. The immunohistochemistry results showed that there were significantly more 5-HT positive cells in the IBS-D group than in the control group in the hippocampus, hypothalamus, jejunum, ileum, proximate colon and distal colon (P < 0.05), as well as more than were found in the IBS-C group in jejunum and ileum (P < 0.05). There were more 5-HT positive cells in the IBS-C group than in the control hippocampus, hypothalamus, ileum, proximate colon, and distal colon (P < 0.05). Real time-PCR results showed that the expression level of the 5-HT(7) receptor in both the IBS-C and IBS-D groups were enhanced compared with the control group in the hippocampus and hypothalamus (P < 0.05). The expression level of 5-HT(7) receptors in the IBS-C group was notably greater when compared with the controls in the ileum and colon (P < 0.05). The cAMP accumulation in the hippocampus and hypothalamus in both the IBS-C and IBS-D groups was higher than that in the control group (P < 0.01 and P < 0.05). The cAMP accumulation in the IBS-C group was higher than that in the control group in the proximal and distal colon (P < 0.05).
Conclusions: The increased 5-HT content in the brain and intestine is related to the IBS pathogenesis. The up-regulated expression of the 5-HT(7) receptor in the brain and colon might play an important role in the pathogenesis of IBS-C.