L-arginine-enriched parenteral nutrition affects lymphocyte phenotypes of gut-associated lymphoid tissue

The immune modifying effects of amino acids on gut-associated lymphoid tissue

The intestine and the gut-associated lymphoid tissue (GALT) are essential components of whole body immune defense, protecting the body from foreign antigens and pathogens, while allowing tolerance to commensal bacteria and dietary antigens. The requirement for protein to support the immune system is well established. Less is known regarding the immune modifying properties of individual amino acids, particularly on the GALT. Both oral and parenteral feeding studies have established convincing evidence that not only the total protein intake, but the availability of specific dietary amino acids (in particular glutamine, glutamate, and arginine, and perhaps methionine, cysteine and threonine) are essential to optimizing the immune functions of the intestine and the proximal resident immune cells. These amino acids each have unique properties that include, maintaining the integrity, growth and function of the intestine, as well as normalizing inflammatory cytokine secretion and improving T-lymphocyte numbers, specific T cell functions, and the secretion of IgA by lamina propria cells. Our understanding of this area has come from studies that have supplemented single amino acids to a mixed protein diet and measuring the effect on specific immune parameters. Future studies should be designed using amino acid mixtures that target a number of specific functions of GALT in order to optimize immune function in domestic animals and humans during critical periods of development and various disease states.

Does pharmacological dose of parenteral arginine have beneficial effect in rats with sub-acute peritonitis?

PURPOSE

Peritonitis is a life-threatening condition that may occur as a sequela of intra-abdominal infection. The management of peritonitis includes surgical intervention, antimicrobial therapy, and nutritional support. Arginine has been reported to have beneficial and adverse effects in subjects with inflammation, which might be related to the dose, time, and route of supplementation and the disease severity. So far, the optimal doses of parenteral arginine are not known. In this study, we investigated dose effects of parenterally supplemented arginine on anabolism and arginine-derived metabolites in sub-acute inflammation.

METHODS AND MATERIALS

Male Wistar rats underwent modified cecal puncture procedure for induction of peritonitis were infused with total parenteral nutrition solutions for 7 days, which contained conventional, low, medium, and high doses of arginine, i.e., 1.61, 2.85, 4.08, and 6.54% of calories from arginine. Healthy, orally fed rats were included as references.

RESULTS

On day 7, peritonitic rats had significantly decreased body weight, declined serum albumin, and increased serum nitric oxide (NO) and tumor-necrosis factor-alpha compared to references (ANOVA, P < 0.05). There were no dose effects of parenteral arginine on body weight, nitrogen retention, and serum blood urea nitrogen and creatinine in peritonitic rats. In contrast, plasma arginine, proline, and ornithine, and urinary urea nitrogen were significantly increased, whereas serum NO and plasma glutamine were significantly decreased in dose-dependent manners with parenteral arginine. Pharmacological dose of parenteral arginine may increase the synthesis of ornithine, urea, and proline instead of citrulline and NO in peritonitic rats.

CONCLUSION

These results suggest that high dose of parenteral arginine may facilitate ureagenesis and proline conversion without causing augmentation of NO production in sub-acute inflammation. Therefore, pharmacological dose of parenteral arginine may not have benefits in anabolism but does not cause adverse effect in rats with sub-acute inflammation.

L-Arginine stimulates intestinal intraepithelial lymphocyte functions and immune response in chickens orally immunized with live intermediate plus strain of infectious bursal disease vaccine

Infectious bursal disease (IBD) continues to pose potential threat to poultry industry all over the world. The disease can spell disaster not only through its infection but also by break of immunity in chickens vaccinated for other diseases. l-Arginine, a ubiquitous, semi-essential amino acid has emerged as an imunostimulant from variety of human and animal studies. In the present study, we demonstrate the stimulatory effects of l-arginine on intestinal intraepithelial lymphocyte (iIELs) functions as well as on systemic immune response in chickens orally vaccinated with live intermediate plus (IP) strain of IBD vaccine. Challenge studies with virulent IBDV revealed complete (100%) protection in IP + l-arginine group compared with 80% protection recorded in IP strain vaccinated chickens. Functional activities of iIELs evaluated by cytotoxicity assay demonstrated significantly high percentage cytotoxicity in IP + l-arginine groups compared with IP group (P < 0.05). Proliferative response of iIELs against IBDV antigen and Con-A was also significantly higher in IP + l-arginine group. Similar results were obtained with peripheral blood mononuclear cell blastogenic response to IBDV and Con-A analyzed as an indicator of systemic cell-mediated immune response. Orally administered IP strain vaccine elicited good antibody titres in both the groups, IP and IP + l-arginine, however, the antibody titres were significantly higher in IP + l-arginine group compared with IP vaccinated group (P < 0.05). These results clearly demonstrate that l-arginine stimulates intestinal and systemic immune response against IBDV.