Aging stimulates fatty acid oxidation in rat colonocytes but does not influence the response to dietary fiber.

Metabolism was studied in colonocytes isolated from young (4 mo) and aged (24 mo) Fischer 344 rats. Animals were fed fiber-free, low-fiber (5% cellulose), or high-fiber (oat bran or NIH 31 stock) diets. Colonocytes isolated from aged animals oxidized both short- and long-chain fatty acids at significantly higher rates than did colonocytes isolated from young animals. No differences between the young and aged were noted for the oxidation to CO2 of glucose and glutamine or for flux of glucose through glycolysis. Net adenosine triphosphate (ATP) production by colonocytes was calculated to be 20% higher for the aged than for the young, although the relative contribution of substrates to net ATP production from exogenous substrates was similar for the young and aged (45-50% from butyrate, 20-25% from glucose, and 30% from other substrates including acetate, propionate, palmitate, and glutamine). Substrate oxidation was generally higher in colonocytes from the oat bran (17% total dietary fiber, highly soluble fiber) versus fiber-free diet.