In Vivo Mitochondrial Function in HIV-Infected Persons Treated with Contemporary Anti-Retroviral Therapy: A Magnetic Resonance Spectroscopy Study Brendan A. I. Payne 1,2 *, Kieren G. Hollingsworth 3 , Joanne Baxter 4 , Edmund Wilkins 4 , Vincent Lee 5 , D. Ashley Price 2 , Michael Trenell 6 , Patrick F. Chinnery 1 1 Institute of Genetic Medicine, Newcastle University, Newcastle-upon-Tyne, United Kingdom, 2 Department of Infection and Tropical Medicine, Royal Victoria Infirmary, Newcastle-upon-Tyne, United Kingdom, 3 Newcastle Magnetic Resonance Centre, Newcastle University, Newcastle-upon-Tyne, United Kingdom, 4 Department of Infectious Diseases, North Manchester General Hospital, Manchester, United Kingdom, 5 Manchester Centre for Sexual Health, Manchester Royal Infirmary, Manchester, United Kingdom, 6 Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, United Kingdom Abstract Modern anti-retroviral therapy is highly effective at suppressing viral replication and restoring immune function in HIV- infected persons. However, such individuals show reduced physiological performance and increased frailty compared with age-matched uninfected persons. Contemporary anti-retroviral therapy is thought to be largely free from neuromuscular complications, whereas several anti-retroviral drugs previously in common usage have been associated with mitochondrial toxicity. It has recently been established that patients with prior exposure to such drugs exhibit irreversible cellular and molecular mitochondrial defects. However the functional significance of such damage remains unknown. Here we use phosphorus magnetic resonance spectroscopy ( 31 P-MRS) to measure in vivo muscle mitochondrial oxidative function, in patients treated with contemporary anti-retroviral therapy, and compare with biopsy findings (cytochrome c oxidase (COX) histochemistry). We show that dynamic oxidative function (post-exertional ATP (adenosine triphosphate) resynthesis) was largely maintained in the face of mild to moderate COX defects (affecting up to ,10% of fibers): t K ADP (half-life of adenosine diphosphate clearance), HIV-infected 22.169.9 s, HIV-uninfected 18.864.4 s, p = 0.09. In contrast, HIV-infected patients had a significant derangement of resting state ATP metabolism compared with controls: ADP/ATP ratio, HIV- infected 1.2460.08 6 10 23 , HIV-uninfected 1.1660.05 6 10 23 , p = 0.001. These observations are broadly reassuring in that they suggest that in vivo mitochondrial function in patients on contemporary anti-retroviral therapy is largely maintained at the whole organ level, despite histochemical (COX) defects within individual cells. Basal energy requirements may nevertheless be increased. Citation: Payne BAI, Hollingsworth KG, Baxter J, Wilkins E, Lee V, et al. (2014) In Vivo Mitochondrial Function in HIV-Infected Persons Treated with Contemporary Anti-Retroviral Therapy: A Magnetic Resonance Spectroscopy Study. PLoS ONE 9(1): e84678. doi:10.1371/journal.pone.0084678 Editor: Robert J. Wilkinson, Institute of Infectious Diseases and Molecular Medicine, South Africa Received September 29, 2013; Accepted November 18, 2013; Published January 7, 2014 Copyright: ß 2014 Payne et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work received financial support from: Medical Research Council (MRC, UK) (BP)(www.mrc.ac.uk); Newcastle National Institute for Health Research (NIHR) Biomedical Research Centre in Ageing and Age-Related Diseases (BP, PFC) (http://www.ncl.ac.uk/biomedicine/research/brc); Medical Research Council (MRC, UK) Centre for Translational Muscle Disease (PFC); Wellcome Trust (084980/Z/08/Z & 096919Z/11/Z, PFC) (www.wellcome.ac.uk); Medical Research Council (MRC, UK) (G1100160, KGH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: brendan.payne@ncl.ac.uk Introduction Combination anti-retroviral therapy (cART) has transformed the prognosis for HIV-infected persons since the late 1990s. However, patients are at risk of mitochondrial toxicity, thought to be mediated very largely through exposure to certain nucleoside analog reverse transcriptase inhibitor (NRTI) anti-retrovirals. NRTIs were the first class of licensed anti-retroviral drug, and several of the older members of this class, zidovudine, stavudine, zalcitabine and didanosine, are known to inhibit the sole mitochondrial DNA (mtDNA) polymerase, pol c, resulting in chain termination during mtDNA replication. During therapy, the molecular consequence of this inhibition is reduction in cellular mtDNA content (mtDNA depletion). A wealth of previous studies has demonstrated this phenomenon both in vitro, and in a variety of tissues in vivo [1–4]. These older NRTIs are no longer in common usage in industrialized countries owing to concerns over their toxicity profiles, although zidovudine and stavudine have been very extensively used in anti-retroviral therapy ‘roll-out’ programs in developing countries in recent years. Currently used NRTIs, such as tenofovir (a nucleotide RTI) and abacavir, have been shown to be essentially free from pol c inhibition in vitro and to cause no significant mtDNA depletion in vivo [5,6]. If a patient’s therapy is switched away from a pol c inhibiting NRTI, the impairment of mtDNA replication is removed and mtDNA content returns to normal [7]. Therefore, although most patients are no longer exposed to pol c inhibiting NRTIs, a significant cohort of long-term patients will have extensive prior exposure to such drugs. Although such patients do not have persistent mtDNA depletion, it has recently been established that they may have persistent histochemical mitochondrial defects evidenced by an increased proportion of COX (cytochrome c oxidase) deficient skeletal muscle fibers. These COX deficient fibers contain high levels of individual somatic (acquired) mtDNA mutations (princi- PLOS ONE | www.plosone.org 1 January 2014 | Volume 9 | Issue 1 | e84678