Down-regulation of liver Galβ1, 4GlcNAc α2, 6-sialyltransferase gene by ethanol significantly correlates with alcoholic steatosis in humans Maokai Gong a,b , Leslie Castillo a,b , Robert S. Redman c , Mamatha Garige a,b , Kenneth Hirsch d , Magnus Azuine a,b , Richard L. Amdur e , Devanshi Seth f , Paul S. Haber f , M. Raj Lakshman a,b, ⁎ a The Lipid Research Laboratory, Veterans Affairs Medical Center, The George Washington University, Washington, DC 20422, USA b Department of Biochemistry, Molecular Biology and Medicine, The George Washington University, Washington, DC 20422, USA c Oral Pathology Research Laboratory, Veterans Affairs Medical Center, Washington, DC 20422, USA d Gastroenterology, Hepatology and Nutrition Section, Veterans Affairs Medical Center, Washington, DC 20422, USA e Research Service for Biostatistics, Veterans Affairs Medical Center, Washington, DC 20422, USA f Centenary Institute of Cancer Medicine and Cell Biology, The University of Sydney, Newton, New South Wales 2042, Australia Received 21 March 2008; accepted 23 July 2008 Abstract Hepatic steatosis and steatohepatitis are frequent results of long-term ethanol exposure. We have previously demonstrated that long-term ethanol down-regulates Galβl, 4GlcNAc α2, 6-sialyltransferase (ST6Gal1), leading to defective glycosylation of a number of proteins including apolipoprotein (apo) E and apo J and the appearance of asialoconjugates in the blood of continuously alcohol-fed animals as well as in human alcoholics. In the current study, we have explored the possibility of whether ethanol-induced down-regulation of ST6Gal1 could contribute toward alcoholic steatosis in human alcoholics presumably because of impaired lipid and lipoprotein transport caused by this down-regulation. Real-time quantitative polymerase chain reaction analyses of liver samples from nondrinkers, moderate drinkers, and heavy drinkers as well as from subjects with and without alcoholic liver disease revealed direct evidence that the down-regulation of ST6Gal1 may be due to ethanol per se. The ST6Gal1 messenger RNA level was reduced by as much as 70% in moderate and heavy drinkers as well as in patients with alcoholic liver disease, but was not changed in subjects with liver disease due to causes other than alcohol exposure. Biochemical and histopathologic analysis demonstrated that the liver total cholesterol was increased by more than 30% (P b .05) and 75% (P b .01), respectively, in moderate and heavy drinkers compared with nondrinkers, with even more dramatic changes in triglyceride levels. Significantly, there was a strong inverse correlation between ST6Gal1 messenger RNA level and liver lipid deposit (F = 8.68, P b .001) by statistical analysis. Thus, it is suggested that alcohol- mediated down-regulation of hepatic ST6Gal1 gene leads to defective glycosylation of lipid-carrying apolipoproteins such as apo E and apo J, resulting in defective intracellular lipid and lipoprotein transport, which in turn may contribute to alcoholic steatosis. © 2008 Published by Elsevier Inc. 1. Introduction Alcoholic steatosis (AS) is a liver disease characterized by hepatic accumulation of lipids (triacylglycerol and choles- terol). Alcoholic steatosis afflicts millions of subjects world- wide and is one of the major causes of death in developed countries [1]. Essentially, AS leads to inflammation, necrosis, fibrosis, and finally cirrhosis that eventually results in death [2]. The pathogenesis of AS is a complex multifactorial process that is manifested through several mechanisms [3] involving a number of fat-metabolizing genes such as the activation of fat-synthesizing genes via sterol regulatory element–binding proteins [4] and the down-regulation of fat- oxidizing genes via peroxisome proliferator–activated receptor α [5]. Apart from these abnormalities, we propose the following mechanism that may contribute to the pathogenesis of AS. Our ongoing studies have shown impairment in the glycosylation [6,7] and trafficking [8] of apolipoprotein (apo) E and apo J, the 2 important lipid- carrying apolipoproteins. As a result, high-density lipopro- teins (HDLs) are depleted of apo E, whereas very low-density lipoproteins (VLDLs) are enriched with asialo apo E [9], resulting in their impaired intracellular trafficking. This leads to a profound accumulation of lipids in the liver [10] and impairment in reverse cholesterol transport (RCT) function of Available online at www.sciencedirect.com Metabolism Clinical and Experimental 57 (2008) 1663 – 1668 www.metabolismjournal.com ⁎ Corresponding author. Lipid Research Laboratory (151-T), Veterans Affairs Medical Center, The George Washington University, Washington, DC 20422, USA. Tel.: +1 202 745 8330; fax: +1 202 462 2006. E-mail address: raj.lakshman@med.va.gov (M.R. Lakshman). 0026-0495/$ – see front matter © 2008 Published by Elsevier Inc. doi:10.1016/j.metabol.2008.07.021