Interaction between metformin and leucine in reducing hyperlipidemia and hepatic lipid accumulation in diet-induced obese mice ☆ Lizhi Fu a , Antje Bruckbauer b , Fenfen Li a , Qiang Cao a , Xin Cui a , Rui Wu a , Hang Shi a , Michael B. Zemel b , Bingzhong Xue a, ⁎ a Center for Obesity Reversal, Department of Biology, Georgia State University, 24 Peachtree Center Avenue, Atlanta, GA 30303, USA b NuSirt Biopharma Inc., 3835 Cleghorn Ave, Nashville, TN 37215, USA ARTICLE INFO ABSTRACT Article history: Received 29 March 2015 Accepted 13 July 2015 Background. Leucine stimulates Sirt1 and AMPK signaling in vitro and in vivo. Since metformin converges on the same pathway, we have tested the ability of leucine to amplify the effects of metformin on AMPK-mediated hepatic lipid metabolism in diet-induced-obese insulin-resistant mice. Methods. Mice were fed high leucine (24 g/kg diet) with or without sub-therapeutic levels of metformin (0.05–0.50 g/kg diet) or therapeutic levels of metformin (1.5 g/kg diet; ~300 mg/kg body weight). Results. High-fat diet produced a 10-fold increase in inguinal fat pad weight and 25% increase in liver weight, histologically confirmed as steatosis. The leucine-metformin combinations reduced fat pad mass, normalized liver weight, liver and plasma lipids and inflammatory markers (interleukin 6, interleukin 1 beta, tumor necrosis factor alpha, monocyte chemotactic protein-1, C-reactive protein) comparable to the effects of therapeutic metformin. Moreover, the highest sub-therapeutic levels of metformin with leucine exerted significantly greater effects than therapeutic levels of metformin and fully reversed hepatic steatosis. These effects were mediated by upregulation of hepatic AMPK and associated changes in lipogenic gene expression (fatty acid synthase, stearoyl CoA desaturase, acetyl CoA carboxylase) in the liver. Conclusion. A low-dose leucine-metformin combination exerts comparable effects on adiposity to therapeutic doses of metformin and fully reverses hepatic steatosis in diet- induced-obese mice. © 2015 Elsevier Inc. All rights reserved. Keywords: Diabetes AMPK Sirt1 Steatosis Obesity METABOLISM CLINICAL AND EXPERIMENTAL XX (2015) XXX – XXX Abbreviations: ACC, acetyl CoA carboxylase; ALT, alanine aminotransferase; AMPK, 5’ adenosine monophosphate-activated protein kinase; AST, aspartate transaminase; CRP, C-reactive protein; FAS, fatty acid synthase; HFD, high-fat diet; HMB, β-hydroxy-β-methyl- butyrate;IL6, interleukin 6; IL1β, interleukin 1 beta; Leu, leucine; LFD, low-fat diet; LKB1, liver kinase B1; MCP1, monocyte chemotactic protein 1; Met, metformin; NAD, nicotinamide adenine dinucleotide; NAFLD, non-alcoholic fatty liver disease; NASH, non-alcoholic steatohepatitis; Res, resveratrol; SCD1, Stearoyl-CoA carboxylase; Sirt1, sirtuin 1; TNFα, tumor necrosis factor 1 alpha. ☆ All authors have read and agree to the publication of the manuscript. ⁎ Corresponding author at: Center for Obesity Reversal, Department of Biology, Georgia State University, 24 Peachtree Center Avenue, Atlanta, GA 30303, USA. Tel.: + 1 404 413 5747. E-mail address: bxue@gsu.edu (B. Xue). http://dx.doi.org/10.1016/j.metabol.2015.07.006 0026-0495/© 2015 Elsevier Inc. All rights reserved. Available online at www.sciencedirect.com Metabolism www.metabolismjournal.com Please cite this article as: Fu L, et al, Interaction between metformin and leucine in reducing hyperlipidemia and hepatic lipid accumulation in diet-induced obese mice, Metabolism (2015), http://dx.doi.org/10.1016/j.metabol.2015.07.006