Mitochondrial DNA Content, an Inaccurate Biomarker of Mitochondrial Alteration in Human Immunodeficiency Virus-Related Lipodystrophy

Abstract

Lipoatrophy is a prevalent side effect of antiretroviral treatment of human immunodeficiency virus (HIV)infection. Its mechanisms are still disputed but include mitochondrial toxicity and, in particular, mitochondrial DNA (mtDNA) depletion induced by nucleoside reverse transcriptase inhibitors. To obtain an integrated evaluation of the mitochondrial alteration in lipoatrophy, we investigated the DNA, RNA, and protein levels in 15 samples of abdominal subcutaneous adipose tissue from HIV-infected patients with peripheral lipoatrophy and compared the results with those for 15 samples from age-and body mass index-matched controls. The DNA and RNA analyses used PCR-based techniques, while proteins were quantified with enzyme-linked immunosorbent assay and measurement of activities with spectrophotometric assays. Depletion of mtDNA and mtDNAencoded MT-CO2 mRNA was present, but normal levels of mtDNA-dependent activity (cytochrome c oxidase) and protein (MT-CO2p) showed that it was compensated for. An increase in nuclear-DNA-dependent mitochondrial activities (citrate synthase and malate dehydrogenase) and protein (COX4I1p), as well as transcriptional up-regulation of nuclear-DNA-encoded mitochondrial genes (COX4I1 and UCP2), demonstrated increased mitochondrial biogenesis. However, the expression of the known transcription factors of mitochondrial biogenesis (TFAM, NRF1, GABPA, PPARGC1A, PPARGC1B, and PPRC1) was normal or decreased. Increased amounts of activated caspase 3 and of DDIT3 mRNA showed the induction of apoptosis and oxidative stress, respectively. The mtDNA content did not correlate with any other mitochondrial parameter. In conclusion, mtDNA content does not appear to be an accurate biomarker of mitochondrial alteration in lipoatrophic adipose tissue. The preservation of mtDNA-dependent mitochondrial functions occurred despite severe mtDNA depletion. The presence of significant oxidative stress and apoptosis did not correlate with the mtDNA content.

Proteomic Profiling of Adipose Tissue from Zmpste24−/− Mice, a Model of Lipodystrophy and Premature Aging, Reveals Major Changes in Mitochondrial Function and Vimentin Processing

“…Remarkably, antiretroviral treatment of HIV patients which causes severe lipoatrophies, altered the expression of genes involved in FA oxidation, TCA cycle and oxidative phosphorylation in adipose tissue (47)(48)(49). These changes were associated to up-regulation of genes involved in oxidative stress (49,50). In particular, HIV antiretroviral protease inhibitors (PIs), which inhibit Zmpste24 activity and lead to prelamin A accumulation (51), induce the expression of oxidative stress markers in adipose tissue in a manner comparable to that observed in patients with LMNA mutations (52).…”

Mitochondrial dysfunction and human immunodeficiency virus infection

“…73 More recently, Garrabou et al found significant mtDNA depletion and reduced mitochondrial oxidative function in adipocytes of HIVinfected ART-naïve individuals compared to uninfected controls. 74 The value of tissue mtDNA measurement has been questioned by Kim et al, 75 who confirmed findings of depleted mtDNA in adipose tissue of lipoatrophic HAART-treated patients, but found no decrease in mtDNA-dependent mitochondrial function and an actual compensatory increase in nuclear-driven mitochondrial biogenesis, suggesting that mtDNA depletion was not a good marker for mitochondrial function. In another cross-sectional study by Magaard et al, 34 mitochondrial DNA was lower in muscle biopsies from 24 patients with HIV on HAART than 10 ART-naïve HIV patients, but both groups demonstrated decreased PBL mtDNA compared to 11 healthy controls.…”

Improved adipose tissue function with initiation of protease inhibitor-only ART

“…No accompanying changes were observed in the expression of the key regulator of mitochondrial biogenesis PPARG coactivator 1α ( PPARGC1A ) or in the mitochondrially associated uncoupling protein 2 ( UCP2 ) (Figure 1d), genes dysregulated in tNRTI-mediated SAT toxicity. 31,32 …”