NRTIs and Mitochondrial Toxicity

In my first report from the Lipodystrophy Workshop in Toronto, I explained briefly what is mitochondrial toxicity and the thinking that NRTIs' causing of mitochondrial toxicity may lead to body fat redistribution (lipodystrophy). Following are results from two studies reported at the Lipodystrophy Workshop finding a link between mitochondrial toxicity and body changes and suggesting a link with NRTI use.

Decrease in mitochondrial DNA content in adipose (fat) tissue of HIV infected patients treated with NRTIs  

Dr. Ulrich Walker (Albert-Ludwig University, Germany) reported his findings from a study evaluating if lipo-atrophy is associated with mitochondrial-DNA depletion in subcutaneous fat tissue. Fat cell biopsies from subcutaneous fat cells were taken from the buttocks of 24 HI+ patients (19 patients treated with NRTIs + a protease inhibitor, 4 patients treated with NNRTI + a protease inhibitor without NRTIs and 1 treatment-naÔve patient). Eleven patients receiving antiretrovitral therapy had clinical evidence of ;ipo-atrophy at the biopsy site and 12 patients did not. In addition, 8 HIV-negative patients were biopsied. Mitovhondrial-DNA-content in each fat biopsy sample was quantified using a Southern blot technique and normalized to the contant of nuclear DNA.

The age of the subjects was not different between all groups. Mitochondrial DNA content did not differ between the 8 HIV-negative controls and the 4 HIV-patients never exposed to NRTIs (p=0.9). However, mitochondrial DNA content was significantly decreased in HIV patients treated with NRTIs (n=19) compared to HIV positive patients never exposed to NRTIs (n=4) (p=0.009) Mitochondrial DNA content in patients under antiretroviral therapy with clinical evidence of lipoatrophy (n=11) was reduced by 44% compared with patients without lipo-atrophy (n=12) (p=0.04). Mitochondrial DNA loss was significantly associated with d4T but some caveats or limitations of the data were raised in the discussion. Half or more of the patients on d4T previously received AZT. This is often the case in these lipodystrophy studies. Mitochondrial DNA loss was associated with the duration of NRTI treatment. And, is a 44% decline in mitochondrial DNA content enough of a loss to cause lipo-atrphy? It is not known how much DNA loss is needed to cause lipo-atrophy, if this is indeed the cause. Dr Walker concluded this suggests a link between mitochondrial damage due to NRTIs and the presence of lipo-atrophy in HIV-infected patients.

Subcutaneous adipose (fat) tissue mitochondrial DNA analysis from individuals with HAART-associated lipodystrophy

Dr. Cecilia Shikuma (University of Hawaii at Manoa) presented similar findings in her preliminary data from an ongoing study. She is analyzing mitochondrial DNA from HIV-infected individuals on HAART with and without self-reported lipodystrophy. As well, she compared HIV infected to non-infected. She performed core-needle biopsies of subcutaneous fat from individual's neck, abdomen, and thigh. Mitochondrial DNA was extracted and long-distance PCR was used to amplify mitochondrial DNA and semiquantitate the mitochondrial DNA. She reported that the lipodystrophic patients (n=8) on HAART showed reduced or absent mitochondrial DNA in 87% versus 45% of the combined lipodystrophiv and non-lipodystrophic patients (n=7). By comparison, HAART naÔve (n=2), HIV-infected without lipodystrophy, and HIV-negative (n=7) individuals showed mitochondrial loss in 0%-30% of samples. Bear in mind, that mitochondrial loss can occur for other reasons than NRTI use--genetic, environmental, etc. Shikuma concluded that this preliminary data suggests absence or decreased amounts of mitochondrial DNA in subcutaneous fat tissue in HIV-infected persons with lipodystrophy is consistent with mitochondrial toxicity.

In other words, findings from both of these studies suggest that the mitochondrial toxicity caused by NRTIs may lead to lipodystrophy.

Evaluating mitochondrial damage in human sperm on HAART

Dr. Justin St. John (University of Birmingham, UK) reported findings from his small study of mitochondrial DNA deletions (damage or loss) in human male sperm who were taking HAART. Of those men who had taken HAART for >12 months (n=4) all had multiple deletions or damage to the mitochondrial DNA. While none of the men who had been on HAART for <12 months had deletions. This suggests a time relationship with mitochondrial DNA damage. In men who had never taken HIV antivirals, 4 presented with no deletions and one with multiple deletions. St. John suggested that sperm Mitochondria DNA analysis may provide a non-invasive method of monitoring treatment associated mitochondrial damage.