Short-chain fatty acid in the human colon. Relation to inflammatory bowel diseases and colon cancer

Abstract

Short chain fatty acids (SCFAs) are the end products of anaerobic bacteria break down of carbohydrates in the large bowel. This process, namely fermentation, is an important function of the large bowel; SCFAs, mainly acetate, propionate and butyrate account for approximately 80% of the colonic anion concentration and are produced in nearly constant molar ratio 60:25:15. Among their various properties, SCFAs are readily absorbed by intestinal mucosa, are relatively high in caloric content, are metabolized by colonocytes and epatocytes, stimulate sodium and water absorption in the colon and are trophic to the intestinal mucosa. While the fermentative production of SCFAs has been acknowledged as a principal mechanism of intestinal digestion in ruminants, the interest in the effects of SCFAs production on the human organism has been raising in the last ten years. SCFAs are of major importance in understanding the physiological function of dietary fibers and their possible role in intestinal neoplasia. SCFAs production and absorption are closely related to the nourishment of colonic mucosa, its production from dietary carbohydrates is a mechanism whereby considerable amounts of calories can be produced in short-bowel patients with remaining colonic function and kept on an appropriate dietary regimen. SCFAs enemas or oral probiotics are a new and promising treatment for ulcerative colitis. The effects have been attributed to the oxidation of SCFAs in the colonocytes and to the ability of butyrate to induce enzymes (i.e. transglutaminase) promoting mucosal restitution. Evidence is mounting regarding the effects of butyrate on various cell functions the significance of which needs further considerations. Up until now, attention has been related especially to cancer prophylaxis and treatment. This article briefly reviews the role of SCFAs, particularly butyrate, in intestinal mucosal growth and potential clinical applications in inflammatory and neoplastic processes of the large bowel.