Hepatic steatosis and plasma dyslipidemia induced by a high-sucrose diet are corrected by an acute leptin infusion

Abstract

High sucrose (HS) feeding in rats induces hepatic steatosis and plasma dyslipidemia. In previous reports (Huang W, Dedousis N, Bhatt BA, O'Doherty RM. J Biol Chem 279: 21695–21700, 2004; and Huang W, Dedousis N, Bandi A, Lopaschuk GD, O'Doherty RM. Endocrinology 147: 1480–1487, 2006), our laboratory demonstrated a rapid (∼100 min) leptin-induced decrease in liver and plasma VLDL triglycerides (TG) in lean rats, effects that were abolished in obese rats fed a high-fat diet, a model that also presents with hepatic steatosis and plasma dyslipidemia. To further examine the capacity of acute leptin treatment to improve metabolic abnormalities induced by nutrient excess, hepatic leptin action was studied in rats after 5 wk of HS feeding. HS feeding induced hepatic steatosis (TG +80 ± 8%; P = 0.001), plasma hyperlipidemia (VLDL-TG +102 ± 14%; P = 0.001), hyperinsulinemia (plasma insulin +67 ± 12%; P = 0.04), and insulin resistance as measured by homeostasis model assessment (+125 ± 20%; P = 0.02), without increases in adiposity or plasma leptin concentration compared with standard chow-fed controls. A 120-min infusion of leptin (plasma leptin 13.6 ± 0.7 ng/ml) corrected hepatic steatosis (liver TG −29 ± 3%; P = 0.003) and plasma hyperlipidemia in HS (VLDL-TG −42 ± 4%; P = 0.001) and increased plasma ketones (+45 ± 3%; P = 0.006), without altering plasma glucose, insulin, or homeostasis model assessment compared with saline-infused HS controls. In addition, leptin activated liver phosphatidylinositol 3-kinase (+70 ± 18%; P = 0.01) and protein kinase B (Akt; +90 ± 29%; P = 0.02), and inhibited acetyl-CoA carboxylase (40 ± 7%; P = 0.04) in HS, further demonstrating that hepatic leptin action was intact in these animals. We conclude that 1) leptin action on hepatic lipid metabolism remains intact in HS-fed rats, 2) leptin rapidly reverses hepatic steatosis and plasma dyslipidemia induced by sucrose, and 3) the preservation of hepatic leptin action after a HS diet is associated with the maintenance of low adiposity and plasma leptin concentrations.