Effects of protein, lipid, or carbohydrate supplementation on hepatic lipid accumulation during rapid weight loss in obese cats

Abstract

Summary Effects of restricted tube-feeding (25% of energy requirements) of protein, lipid, or carbohydrates on body weight loss; hematologic and clinical chemical variables; plasma lipid and amino add concentrations; nitrogen balance; and hepatic histologic features and lipid concentrations were compared with values in voluntary-fasting cats (control, con). Twelve obese cats (6.1 ± 0.1 kg, > 40% above optimal body weight) were randomly assigned to 4 matched treatment groups (n = 3)—protein (pro), lipid (lip), carbohydrate (cho), and con—and were offered a low-palatability diet for 4 weeks. Cats of the pro, lip, and cho groups were also tube-fed isocaloric amounts (88 kcal of metabolizable energy) of a casein-soybean protein mixture, com oil, or a dextrin-dextrose mixture, respectively, during the 4 weeks. All cats fasted, rather than eat the low-palatability purified diet. Cats of the pro group lost weight at a lower rate (P < 0.05) than did cats of other groups. After 4 weeks of fasting, serum alkaline phosphatase activities were higher than reference values in all cats of the con and lip groups and in 2 cats of the cho group. At that time, 1 cat of the lip group had lethargy, hepatomegaly, and hyperbilirubinemia. Total hepatic lipid and triglyceride concentrations increased in all groups during the study, but the increase was significantly (P < 0.05) less in cats of the pro group, compared with those of the con and lip groups, and those of the cho group, compared with those of the lip group. Hepatic total lipid and triglyceride concentrations correlated well with lipid score for liver biopsy specimens when lipidosis was mild or severe, but not as well in association with the intermediate lipidosis. Cats of the PRO group were in nitrogen balance after 2 weeks of fasting. All other cats remained in negative nitrogen balance during the fast, although less nitrogen was lost by cats of the cho and lip groups than by cats of the con group. Plasma aminograms indicated that methionine and arginine might become limiting for protein synthesis during fasting in cats. Results indicate that dietary protein reduces hepatic lipid accumulation and nitrogen balance is maintained during rapid weight loss in obese cats. Ingestion of only lipids increases the risk of inducing hepatic lipidosis. Ingestion of carbohydrates reduces hepatic lipid accumulation, but is not as effective as protein in preventing all the clinical manifestations of hepatic lipidosis.