Adipocyte differentiation, mitochondrial gene expression and fat distribution: differences between zidovudine and...

Abnormal lipid metabolism and cell oxidative mechanisms are reported in patients on antiretroviral treatment. We compared the expression of several key adipocyte genes in HIV-infected patients randomized to antiretroviral regimens containing zidovudine (AZT) or tenofovir disoproxil fumarate (TDF).

Subcutaneous fat was sampled from 32 HIV-positive treatment-naive patients before and 6 months after randomization to AZT/lamivudine/efavirenz (n=15) or TDF/emtricitabine/efavirenz (n=17) plus 15 HIV-negative matched controls. Expression of genes involved in adipocyte differentiation, lipid metabolism, mitochondrial function and glucocorticoid generation were profiled using real-time PCR. Lipoprotein lipase and hepatic lipase activity were assessed.

Before treatment, 11beta-hydroxysteroid dehydrogenase expression was down-regulated compared with controls. Following 6 months treatment with AZT, there was a significant increase in visceral adipose tissue (VAT; P=0.02) and the ratio of VAT to subcutaneous adipose tissue (P=0.008), down-regulation of cytochrome B (P=0.003) and cytochrome oxidase (COX)-3 gene expression (P=0.03), up-regulation of NADH dehydrogenase (P=0.008) and nuclear-encoded COX-4 (complex IV) gene expression (P=0.012). Genes involved with adipocyte cortisol generation, fatty acid metabolism and the tricarboxylic acid cycle were up-regulated. In the TDF-treated patients, there was no significant change in regional body fat or mitochondrial genes compared with pretreatment values. Changes in the expression of genes involved with cortisol and fatty acid metabolism were less marked with TDF.

Interference with the mitochondrial electron transport chain appears to occur early in an AZT-containing regimen and occurs at a time when there is increased visceral fat and up-regulation of genes involved with adipocyte differentiation and fatty acid flux.