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Background:  HIV therapy include 3 class of drugs : nucleoside (NRTI) and non-nucleoside (NNRTI) reverse transcriptase inhibitors, and protease inhibitors (PI). Lipodystrophic syndrome is a major side effect of HIV antiretroviral therapy, and fat tissue redistribution is associated with the development of insulin resistance. Reports from clinical studies indicate several changes in circulating levels of cytokines (adiponectin decrease, IL6 and TNF-a increase) secreted from adipose tissue which are implicated in the outbreak of insulin resistance. Yet there is no evidence that HIV drugs accumulate in human adipocytes and affect secretion of adipocytokines.

Methods:  Accumulation of HIV drugs (3 PI and 1 NNRTI) was assessed by ELISA in cultured cells of a newly preadipocyte clonal line established from humans (hMADS cells). We have subsequently determined the expression of adipocyte markers (G3PDH activity, PPAR-g and aFABP mRNA) during adipogenesis of hMADS cells exposed to HIV drugs (PI:  ritonavir, lopinavir, amprenavir, indinavir, and saquinavir and 1 NNRTI, nevirapine). Furthermore, regulation by PI of the expression of various adipocytokines (adiponectin, IL6 and TNF-a) has been studied in differentiated cells by real-time PCR whereas leptin secretion modulated by PI was assayed by ELISA.

Results:  Lopinavir, ritonavir, and nevirapin enter human adipose cells and accumulate at different levels (respectively, 5.4±0.8 nmoles/10⁶ cells, 4.1±0.3 nmoles/10⁶ cells, and 0.7±0.03 nmoles/10⁶ cells) during adipogenesis. Chronic treatment with indinavir, amprenavir and nevirapine does not affect this process whereas lopinavir, saquinavir, and ritonavir reduce G3PDH activity and triglyceride accumulation. In adipocytes, lopinavir does not alter the expression of cytokines. In contrast, amprenavir increases leptin secretion. Ritonavir is able both to up-regulate TNF-a, IL6, and leptin expression and down-regulate PPAR-g, aFABP and adiponectin expression.

Conclusions:  HIV drugs accumulate into human adipocytes at different levels and PI display varying inhibitory effects on adipogenesis of human cells. Ritonavir can alter the expression of insulin resistance -related cytokines in human adipocytes in a way parallel to the situation observed in vivo upon treatment of HIV-infected patients developing insulin resistance. Thus it is proposed that, in adipose tissue, HIV drugs participate in the development of insulin resistance through a direct effect on adipocytes.

Keywords: lipodystrophy; Ritonavir; insuline-resistance related adipocytokines