EFFECT OF FIBER AND ITS FERMENTATION ON COLONIC ADAPTATION AFTER CECAL RESECTION IN THE RAT

Background: The role of fiber in postresection adaptation is poorly un derstood. We examined the significance of short-chain fatty acids prod uced by intracolonic fiber fermentation during colonic adaptation. Met hods: Rats underwent one of three surgeries: control laparotomy, cecal resection, or cecal resection with placement of perfusion catheter. R ats of each surgical group were randomly assigned to receive treatment regimens of standard fiber diet (with or without fermentation-suppres sing antibiotics), fiber-free diet, or diet plus intracolonic perfusio n of short-chain fatty acids. Adaptation parameters of mucosal weight, mucosal DNA and protein content, water absorption, and butyrate absor ption were measured. Results: Compared with controls, postresection ra ts that were fed fiber had 65% greater basal and 112% greater butyrate -stimulated water absorption as well as 140% greater butyrate absorpti on. Fiber-fed rats exhibited significantly greater colonic weight and colonic mucosal protein after cecal resection. These changes were abse nt in postresection rats fed a fiber-free diet. Inhibition of fermenta tion by neomycin and metronidazole added to a standard fiber diet also prevented postresection adaptation. All adaptive changes were restore d when the cecal-resection rats that were fed the fiber diet with anti biotics received an intracolonic infusion of short-chain fatty acids. Adaptation did not occur when short-chain fatty acids were infused int o colons of postresection rats that were fed a fiber-free diet. Conclu sions: Cecal resection leads to significant functional and structural changes in the adapting residual colon. Fermentation of dietary fiber by colonic flora to short-chain fatty acids is necessary, but it alone is not sufficient to mediate adaptation.