EFFECTS OF PROTEIN, LIPID, OR CARBOHYDRATE SUPPLEMENTATION ON HEPATICLIPID-ACCUMULATION DURING RAPID WEIGHT-LOSS IN OBESE CATS

Effects of restricted tube-feeding (25% of energy requirements) of pro tein, lipid, or carbohydrates on body weight loss; hematologic and cli nical chemical variables; plasma lipid and amino acid concentrations; nitrogen balance; and hepatic histologic features and lipid concentrat ions 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 we re also tube-fed isocaloric amounts (88 kcal of metabolizable energy) of a casein-soybean protein mixture, corn oil, or a dextrin-dextrose m ixture, respectively, during the 4 weeks. AU cats fasted, rather than eat the low-palatability purified diet. Cats of the PRO group lost wei ght at a lower rate (P < 0.05) than did cats of other groups. After 4 weeks of fasting, serum alkaline phosphatase activities were higher th an reference values in all cats of the CON and LIP groups and in 2 cat s of the CHO group. At that time, 1 cat of the LIP group had lethargy, hepatomegaly, and hyperbilirubinemia. Total hepatic lipid and triglyc eride 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 gr oup, compared with those of the LIP group. Hepatic total lipid and tri glyceride concentrations correlated well with lipid score for liver bi opsy specimens when lipidosis was mild or severe, but not as well in a ssociation 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 gro up. Plasma aminograms indicated that methionine and arginine might bec ome limiting for protein synthesis during fasting in cats. Results ind icate that dietary protein reduces hepatic lipid accumulation and nitr ogen balance is maintained during rapid weight loss in obese cats. Ing estion of only lipids increases the risk of inducing hepatic lipidosis . Ingestion of carbohydrates reduces hepatic lipid accumulation, but i s not as effective as protein in preventing all the clinical manifesta tions of hepatic lipidosis.