Feeding Free Fatty Acids to Study Lipid Metabolism in Rats

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Abstract
A 12-week rat feeding study was conducted to test the feasibility of feeding dietary fat in the form of free fatty acids (FFA) in large quantities, over an extended period of time. Male weanling rats were fed 3 diets consisting of different forms and levels: diet 15CO contained corn oil at 15% by weight, diet 35CO contained 35% corn oil, and diet 35FA contained 35% FFA isolated from corn oil. At 4 and 12 weeks, body composition, food intake and body weight gain were not different among rats fed the different diets. Weights and percentage of fat in liver and epididymal fat pads, as well as lipid patterns of plasma and liver were similar between the 35FA and 35CO fed rats. The amount of fecal fat excreted differed significantly between levels (15CO versus 35CO) and forms (35CO versus 35FA) of dietary fat. Apparent fat absorbabilities for 15CO, 35CO and 35FA were 96.1, 94.2, and 90.5%, respectively, at the end of the 12 week feeding study. At both 4 and 12 weeks, specific activity of pancreatic lipase was similar in rats fed 35CO and 35FA suggesting that the activity of this enzyme does not depend on the presence of the unhydrolyzed substrate. Results from this study suggest that FFA in large quantities can be used by rats as the sole source of fat. Feeding FFA may be a useful approach to long term studies of 1) lipid metabolism as influenced by quantity and quality of dietary fatty acids, 2) the intestinal reesterification mechanism and 3) the dietary treatment of malabsorption syndromes due to diseases of the pancreas.