Nutritional and Pharmacological Enhancement of the Gut‐Associated Lymphoid Tissue

Abstract

There has been an explosion of research in the field of nutrition over the past quarter century. Clinical studies have demonstrated the effectiveness of providing nutrition by the enteral route in reducing septic morbidity in critically ill patients. These improved outcomes have been substantiated by animal models that show that enteral nutrition decreases gut permeability while maintaining the gut-associated lymphoid tissue (GALT) in mucosal immunity. Evidence points to the important immunological role of the gut in the maintenance of mucosal immunity at both intestinal and extraintestinal sites. The preservation of this mucosal immunity by enteral nutrition is consistent with the lower morbidity seen in severely injured patients who receive nutrition via the gastrointestinal tract. For patients who are unable to be fed by the enteral route and who require parenteral nutrition, several supplements show promise in enhancing the mucosal immune system defenses. The nutritional and pharmacological tactics that may enhance the GALT and thereby maintain mucosal immunity are examined.

Randomized trial of initial trophic versus full-energy enteral nutrition in mechanically ventilated patients with acute respiratory failure

“…Specifically, enteral nutrition stimulates epithelial cell growth and proliferation, maintains mucosal mass and microvilli height (22,23), preserves tight junctions between epithelial cells, and promotes blood flow (24). The intestine responds to intraluminal contents by producing and secreting a variety of endogenous agents which have a trophic effect on the intestinal epithelium (25,26). …”

N-Acetyl-l-Glutamine, A Liquid-Stable Source of Glutamine, Partially Prevents Changes in Body Weight and on Intestinal Immunity Induced by Protein Energy Malnutrition in Pigs

“…The hypothesis that enteral feeding prevents intestinal mucosal atrophy and bacterial translocation (when fasting or malnutrition is present) suggests that nutrition support by the enteral route should be preferred, unless clinically contraindicated [29]. Enteral nutrition decreases gut permeability while maintaining gut-associated lymphoid tissue (GALT), and the preservation of this mucosal immunity by enteral nutrition is consistent with lower morbidity seen in severely injured patients who receive nutrition via the gastrointestinal tract [30]. Moreover, a recent systematic review of the literature comparing enteral versus parenteral nutrition regarding their influence on outcomes in critically ill patients concludes that the use of enteral nutrition as opposed to parenteral nutrition results in an important decrease in the incidence of infectious complications and recommends enteral nutrition as the first choice for nutritional support in the critically ill [31].…”

Malnutrition in Intensive Care Units: An Important Risk Factor for Intensive Care Unit-Acquired Infections

“…Glutamine is predominantly important in the intestine as the favored fuel source of enterocytes and immune cells within gutassociated lymphoid tissue (GALT), where up to 50% of available glutamine is metabolized following enteral feeding. Activated immune cells, such as lymphocytes and macrophages, also use glutamine as a source of energy (35)(36)(37).…”