Active anti-HIV therapy can induce hypertriglyceridemia, low high-density lipoprotein (HDL) and insulin resistance, eventually accompanied by clinical lipodystrophy, associated loss of subcutaneous ad Show more
Active anti-HIV therapy can induce hypertriglyceridemia, low high-density lipoprotein (HDL) and insulin resistance, eventually accompanied by clinical lipodystrophy, associated loss of subcutaneous adipose tissue and an increase in abdominal adiposity. The frequency of these metabolic disorders is approximately 50% and host genetic factors might confer particular susceptibility. Variants of apolipoproteins (apo) A5 and C3, interacting with APOE genotypes, have been associated with the severity of antiretroviral therapy-induced dyslipidemia and with occurrence of lipodystrophy, and for APOC3, with objective criteria of fat redistribution. Genetic polymorphisms of the nuclear transcription-factor sterol response element-binding proteins (SREBP1c) and of tumor necrosis factor-alpha (TNFalpha) have yielded contrasting results. Other candidate genes will be explored to define a pharmacogenomic strategy to identify patients at high risk of metabolic disorders upon antiretroviral therapy. Show less
The newly identified apolipoprotein A5 (APOA5), selectively expressed in the liver, is a crucial determinant of plasma triglyceride levels. Because elevated plasma triglyceride concentrations constitu Show more
The newly identified apolipoprotein A5 (APOA5), selectively expressed in the liver, is a crucial determinant of plasma triglyceride levels. Because elevated plasma triglyceride concentrations constitute an independent risk factor for cardiovascular diseases, it is important to understand how the expression of this gene is regulated. In the present study, we identified the retinoic acid receptor-related orphan receptor-alpha (RORalpha) as a regulator of human APOA5 gene expression. Using electromobility shift assays, we first demonstrated that RORalpha1 and RORalpha4 proteins can bind specifically to a direct repeat 1 site present at the position -272/-260 in the APOA5 gene promoter. In addition, using transient cotransfection experiments in HepG2 and HuH7 cells, we demonstrated that both RORalpha1 and RORalpha4 strongly increase APOA5 promoter transcriptional activity in a dose-dependent manner. Finally, adenoviral overexpression of hRORalpha in HepG2 cells led to enhanced hAPOA5 mRNA accumulation. We show that the homologous region in mouse apoa5 promoter is not functional. Moreover, we show that in staggerer mice, apoa5 gene is not affected by RORalpha. These findings identify RORalpha1 and RORalpha4 as transcriptional activators of human APOA5 gene expression. These data suggest an additional important physiological role for RORalpha in the regulation of genes involved in lipid homeostasis and probably in the development of atherosclerosis. Show less