Background:  To evaluate the contribution of nucleoside-analogue reverse transcriptase inhibitor (NRTI) therapy to lipoatrophy and to investigate the effects of HIV protease inhibitor indinavir (IDV) on adipogenesis and adipocyte survival.

Methods:  Longitudinal effects (21 days) of 3 NRTI on different stages of adipocyte development and differentiation were inestigated. We assessed the relationship between adipocyte mitochondrial DNA (mtDNA) content, developmental stage of adipocytes, and adiponectin production using real-time PCR and ELISA. Effect of IDV on adipocyte differentiation was determined by measuring transcription profiles of lipoprotein lipase, the adipogenic transcription factors CCAAT/enhancer-binding protein α and β and peroxisome proliferator-activated receptor γ. Cytoplasmic triacylglycerol accumulation was measured using Oil Red O staining. Cell death apoptosis/necrosis was assessed with Hoechst/propidium iodide staining and trypan blue exclusion.

Results:  Stavudine (d4T) incubation was associated with more severe adipocyte mtDNA depletion, but heavily depending on adipocyte proliferation. Also, d4T directly leads to decreased adiponectin production. Zidovudine (AZT) incubation was associated with impaired differentiation and decrease in adiponectin production. Effects of zalcitabine (ddC) on adipocytes mtDNA were stronger in preadipocytes with almost no effect on differentiating cells and adiponectin production. We found no inhibitory effect of IDV to critical early events in preadipocyte differentiation or completion of the mitotic clonal expansion phase. Adipocyte function, however, was impaired by IDV as judged by the expression of adiponectin and loss of cell viability. In contrast, cell proliferation and viability of preadipocytes were unaffected by IDV treatment.

Conclusions:  Different NRTI affect adipose tissue mtDNA content and function through mechanisms depending on the developmental stage and individual drugs. We provide evidence that d4T-induced mitochondrial DNA depletion is associated with decrease in adiponectin production. Molecular or cellular changes that occur during acquisition of the adipocyte phenotype promote susceptibility to IDV-induced cell death and impaired adiponectin production. These results suggest that IDV may promote adipose tissue atrophy by directly compromising adipocyte function and not by inhibition of preadipocyte differentiation.

Keywords: lipodystrophy; mitochondrial toxicity; adipocytes