Effect of dietary protein quality and fatty acid composition on plasma lipoprotein concentrations and hepatic triglyceride fatty acid synthesis in obese cats undergoing rapid weight loss

Objective - To determine effects of dietary lipid and protein on plasma lipoprotein and free fatty acid concentrations and hepatic fatty acid synthesis during weight gain and rapid weight loss in cats. Animals - 24 ovariohysterectomized cats. Procedure - Cats were fed a high energy diet until they gained 30% of their ideal body weight and then randomly assigned to receive 1 of 4 weight reduction diets (6 cats/diet) at 25% of maintenance energy requirements. Diets contained a low or high quality protein source and a lipid source deficient or sufficient in long chain essential fatty acids. Plasma samples and liver biopsy specimens were obtained before and after weight gain and during and after weight loss for determination of free fatty acid, triglyceride, and lipoprotein concentrations. Synthesis of these substances was measured by use of isotope enrichment. Results - Plasma total cholesterol concentration and concentration of lipoprotein fractions increased after weight gain, compared with baseline values. Weight loss resulted in a significant decrease in concentrations of all lipoprotein fractions except high density lipoprotein. High density lipoprotein concentration was significantly greater in cats fed diets containing an oil blend, compared with cats fed diets containing corn oil. Fatty acid synthesis after weight loss was below the detection limit of the measurement technique. Conclusions and Clinical Relevance - In cats undergoing rapid weight loss there is neither increased triglyceride synthesis nor decreased transport of very low density lipoproteins from the liver, suggesting that their involvement in the development of hepatic lipidosis may be minimal.