ABSTRACT
Objective To analyze the effects of acute depletion of liver-specific insulin signaling on secretion of apolipoprotein B (apoB) and triglyceride (TG).Methods Based on Cre-LoxP principle,a promoter of hepatic tissue specific albumin gene was inserted into upstream of the cre recombinase gene.Albumin-Cre adenovirus (Ad-CRE) and GFP adenovirus (Ad-GFP) were amplified in 293A cells and purified before intravenous administration to mice.After adenovirus infection for 2 days,4 days and 6 days,blood samples from mice were collected and hepatic tissues were frozen.The secretion rates of hepatic newly synthesized apoB and very low density lipoprotein (VLDL)-TG were determined by injection of Triton WR-1339.The levels of plasma cholesterol (TC) and TG were measured.The expressions of insulin receptor and other lipoprotein metabolism related proteins in hepatic tissues were analyzed by Western blot.Results After 2 d,4 d and 6 d of the Ad-CRE injection into mice,insulin receptor expression was reduced by 30.50％ (P＜0.05),60.12％ (P＜ 0.01) and 99.54％ (P＜0.001),and VLDL-TG secretion rate was decreased by 20.43％ (P＜0.05),33.63％ (P＜0.05) and 44.21％ (P＜0.01),respectively.Expressions of sterol regulatory binding proteins 1,fatty acid synthase,and the related proteins of VLDL-formation were decreased,but there were no changes in hepatic secretion of apoB100 and hepatic lipids.The hepatic secretion of apoB48 was increased by 35.07％ (P＜0.05) 6 d after Ad-CRE injection.Conclusions Acute depletion of hepatic insulin receptor might reduce VLDL-TG secretion in manner of time-dependent,and increase the assembly and secretion of smaller apoB-containing lipoproteins in mice liver,which is probably associated with decreased lipogenesis.