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Mitochondrial DNA depletion and morphologic changes in adipocytes associated with nucleoside reverse transcriptase
David Nolan1, Emma Hammond, Annalise Martin
1Centre for Clinical Immunology and Biomedical Statistics, Royal Perth Hospital and Murdoch University, Western Australia, Australia.
Background:
Nucleoside analogue reverse transcriptase inhibitor (NRTI) therapy provides sufficient conditions for progressive subcutaneous fat wasting in HIV-infected patients. As NRTI-induced host toxicity is proposed to involve cellular mitochondrial DNA (mtDNA) depletion, determinants of cellular mtDNA copy number and mitochondrial mass in adipocyte samples from NRTI-treated HIV-infected patients and antiretroviral-naive controls were investigated. Adipose tissue morphology was also assessed.
Methods:
Subcutaneous fat samples were obtained from NRTI-treated, HIV-infected patients (n = 21), antiretroviral therapy-naive HIV-infected controls (n = 11), and HIV-seronegative controls (n = 6). Non-adipocytes were removed by collagenase digestion. Adipocyte mtDNA copies/cell was measured using a real time PCR-based assay, and adipocyte mitochondrial protein content was also measured. Light and electron microscopy were performed on tissue samples.
Findings:
Adipocyte mtDNA copies/cell values were similar (P = 0.56) in HIV seronegative and HIV-infected control groups. NRTI treatment was associated with reduced adipocyte mtDNA copies/cell, representing mean mtDNA depletion in NRTI-treated individuals of 77.7% compared with the mean value for the HIV-infected control group (P < 0001). Additionally, significant differences were found in adipocyte mtDNA copies/cell between patients receiving stavudine (n = 12, mean mtDNA depletion 87.1%) and zidovudine (n = 9, mean mtDNA depletion 52.1%) (P < 0.001). Adipocyte mitochondrial mass was increased in the stavudine group only (mean increase 289%, P < 0.01).
Interpretation:
NRTI therapy is associated with mtDNA depletion and mitochondrial proliferation in adipocytes, consistent with the hypothesis that NRTI-induced mtDNA depletion contributes to the pathogenesis of subcutaneous fat wasting. Morphologic assessment also supports a role for NRTI therapy in inducing adipocyte metabolic dysfunction and cell death.
Insights
Nucleoside analogue reverse transcriptase inhibitor (NRTI) therapy causes mitochondrial DNA depletion in fat cells, leading to subcutaneous fat wasting in HIV patients. Stavudine showed greater depletion than zidovudine.
Area of Science:
- Cellular Biology
- HIV Pathogenesis
- Mitochondrial Medicine
Background:
- Nucleoside analogue reverse transcriptase inhibitor (NRTI) therapy is linked to subcutaneous fat wasting in HIV-infected individuals.
- Mitochondrial DNA (mtDNA) depletion is a proposed mechanism for NRTI-induced host toxicity.
Purpose of the Study:
- To investigate cellular mitochondrial DNA (mtDNA) copy number and mitochondrial mass in adipocytes from NRTI-treated HIV patients.
- To compare these parameters with antiretroviral-naive HIV-infected controls and HIV-seronegative controls.
- To assess adipose tissue morphology in relation to NRTI treatment.
Main Methods:
- Subcutaneous fat samples were collected from three groups: NRTI-treated HIV patients (n=21), antiretroviral therapy-naive HIV patients (n=11), and HIV-seronegative controls (n=6).
- Adipocyte mitochondrial DNA (mtDNA) copy number per cell was quantified using real-time PCR.
- Adipocyte mitochondrial protein content was measured, and tissue morphology was examined via light and electron microscopy.
Main Results:
- NRTI treatment significantly reduced adipocyte mtDNA copy number per cell by a mean of 77.7% compared to HIV-infected controls (P < 0.001).
- Stavudine treatment resulted in greater mtDNA depletion (87.1%) than zidovudine (52.1%) (P < 0.001).
- Adipocyte mitochondrial mass increased significantly (289%) in the stavudine group only (P < 0.01).
Conclusions:
- NRTI therapy is associated with significant mitochondrial DNA depletion in adipocytes.
- Mitochondrial proliferation in adipocytes, particularly with stavudine, suggests a compensatory or pathological response.
- Findings support the hypothesis that NRTI-induced mtDNA depletion contributes to subcutaneous fat wasting and adipocyte dysfunction.
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