Luminal fermentation and colonocyte metabolism in a rat model of enteral nutrition

Large intestinal fermentation and nutrient metabolism in colonocytes were investigated in a rat model of enteral feeding. Male Wistar rats (240-280 g) were submitted to 7 or 14 days of treatment: intragastric feeding (elemental formula) versus oral feeding (isocaloric and isonitrogenous diet, containing 5% purified cellulose) in the control group. Fermentation products and bacterial populations were analyzed in cecal contents. Colonic cells were isolated and tested for their capacities to metabolize [1-(14)C] butyrate and [U-(14)C]glutamine. After 7 days of enteral nutrition, short-chain fatty acid concentrations represented 52% of those measured in the control group, but colonocyte metabolism remained unchanged. After 14 days of enteral nutrition, short-chain fatty acid concentrations were still decreasing, although bacterial counts remained unchanged. In parallel, ammonia and lactate concentrations were significantly increased. The capacities to utilize butyrate and glutamine in colonocytes were only slightly affected. However, there was a dramatic increase in the ratio of beta-OH-butyrate to acetoacetate fluxes, suggesting a more reduced redox mitochondrial state associated with enteral feeding.