Title: Impaired Gut Barrier Function

Key words: leaky bowel syndrome, impaired absorption, malnutrition, parenteral feeding, enteral feeding, gut motility, taurine, glutamine

Date: July 2000

Category: 8. The Gut

Type: Article

Author: Dr van Rhijn

 

Impaired Gut Barrier Function

Leaky Bowel Syndrome

 

Introduction

One of the major functions of the intestine is to form a barrier against lumenal micro-organisms and endotoxins. Critically ill patients, in a hyper metabolic state, requiring parenteral nutrition1, especially when combined with malnutrition and impaired immune function, are particularly at risk of developing impaired gut barrier function. Its consequences and nutritional support will be discussed below.

Consequences of an Impaired Gut Barrier

Impaired gut barrier function may lead to overgrowth of gut derived2,3 micro-organisms. The subsequent endotoxin-induced4 liver dysfunction (depressed Kupffer cell function5) is a risk factor for impaired systemic immunity (RES), leading to sepsis6 and multisystem organ failure7. Colonic enterocytes lose their protective barrier function and increased intestinal permeability8 allows microbial translocation (and endotoxins) from the epithelial mucosa into mesenteric lymph nodes9 and circulation. Low-level pathogens only cause morbidity, whilst potentially pathogenic microorganisms also cause mortality10.

However, systemic endotoxaemia (septicaemia) only occurs in those who already carry abnormal flora, indicating gut overgrowth, thus a carrier state is a marker for the severity of the underlying disease11. Sepsis may result in liver failure, multi perfusion injury, subsequent free radical damage and multisystem organ failure that pose a difficult nutritional challenge, especially because impaired absorption of essential nutrients (especially essential amino acids12 due to hypoplasia) further contributes to deterioration of the disease.

Nutritional Support Measures

The presence of gut lumen nutrients is the most important stimulus for intestinal growth and function13. Enteral feeding14 at the earliest15 opportunity is the best support for in maintaining mucosal structure and function16, strengthening local & systemic immune defences by re-establishing gut motility17 and gall bladder contractility18. It is safe and efficient19 and allows for providing specialized immune-modulating nutrition support20. Gut protection can be further enhanced by taurine & glutamine21, essential nutrients for the mucosal enterocyte22, having trophic23, 24 effects on the gut (increased villus height and decreased gut permeability25) and maintaining function of rapidly proliferating cells such as lymphocytes (immuno-enhancing26). Epidermal growth factor27 and short chain fatty acids28 exert a trophic effect on the small intestine and colonic mucosa respectively and cholecystokinin reduces cholestasis29. Other immuno-modulatory nutrients include arginine30, RNA31, n-3 essential fatty acids32, ornithine a -ketoglutarate33 and antioxidants to reduce septic complications, speed up recovery34 and increase survival35 in the critically ill. Branched chain amino acid-enriched enteral formula may aid liver recovery36.

 

Conclusion

Critical illness has a variety of effects on intestinal mucosa and the most practical approach for bowel protection is to maximize enteral37 immuno-enhancing nutritional38 supplements to stimulate mucosal growth and promote gut health. Nutritional pharmacology has come of age.

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