Factors associated with mitochondrial dysfunction in circulating peripheral blood lymphocytes from HIV-infected people

Neuroinflammatory profiles regulated by the redox environment predicted cognitive dysfunction in people living with HIV: A cross-sectional study

BACKGROUND

Despite effective combination antiretroviral therapy (cART), people living with HIV (PLWH) remain at risk for developing neurocognitive impairment primarily due to systemic inflammation that persists despite virologic suppression, albeit the mechanisms underlying such inflammation are poorly understood.

METHODS

Herein, we evaluate the predictive capacity of the mitochondrial redox environment on circulating neuro- and T-lymphocyte-related inflammation and concomitant cognitive function in 40 virally-suppressed PLWH and 40 demographically-matched controls using structural equation modeling. We used state-of-the-art systems biology approaches including Seahorse Analyzer of mitochondrial function, electron paramagnetic resonance (EPR) spectroscopy to measure superoxide levels, antioxidant activity assays, and Meso Scale multiplex technology to quantify inflammatory proteins in the periphery.

FINDINGS

We observed disturbances in mitochondrial function and the redox environment in PLWH compared to controls, which included reduced mitochondrial capacity (t(76) = -1.85, p = 0.034, 95% CI: -∞,-0.13), elevated levels of superoxide (t(75) = 1.70, p = 0.047, 95% CI: 8.01 E 3, ∞) and alterations in antioxidant defense mechanisms (t(74) = 1.76, p = 0.041, 95% CI: -710.92, ∞). Interestingly, alterations in both superoxide- and hydrogen peroxide-sensitive redox environments were differentially predictive of neuro-, but not T-lymphocyte-related inflammatory profiles in PLWH and controls, respectively (ps < 0.026). Finally, when accounting for superoxide-sensitive redox pathways, neuroinflammatory profiles significantly predicted domain-specific cognitive function across our sample (β = -0.24, p = 0.034, 95% CI: -0.09, -0.004 for attention; β = -0.26, p = 0.018, 95% CI: -0.10, -0.01 for premorbid function).

INTERPRETATION

Our results suggest that precursors to neuroinflammation apparent in PLWH (i.e., mitochondrial function and redox environments) predict overall functionality and cognitive dysfunction and importantly, may serve as a proxy for characterizing inflammation-related functional decline in the future.

FUNDING

National Institute of Mental Health, National Institute for Neurological Disorders and Stroke, National Institute on Drug Abuse, National Science Foundation.

Refining Current Scientific Priorities and Identifying New Scientific Gaps in HIV-Related Heart, Lung, Blood, and Sleep Research

The National Heart, Lung, and Blood Institute (NHLBI) AIDS Program's goal is to provide direction and support for research and training programs in areas of HIV-related heart, lung, blood, and sleep (HLBS) diseases. To better define NHLBI current HIV-related scientific priorities and with the goal of identifying new scientific priorities and gaps in HIV-related HLBS research, a wide group of investigators gathered for a scientific NHLBI HIV Working Group on December 14-15, 2015, in Bethesda, MD. The core objectives of the Working Group included discussions on: (1) HIV-related HLBS comorbidities in the antiretroviral era; (2) HIV cure; (3) HIV prevention; and (4) mechanisms to implement new scientific discoveries in an efficient and timely manner so as to have the most impact on people living with HIV. The 2015 Working Group represented an opportunity for the NHLBI to obtain expert advice on HIV/AIDS scientific priorities and approaches over the next decade.

Metabonomic analysis of HIV-infected biofluids

Monitoring the progression of HIV infection to full-blown acquired immune deficiency syndrome (AIDS) and assessing responses to treatment will benefit greatly from the identification of novel biological markers especially since existing clinical indicators of disease are not infallible. Nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) are powerful methodologies used in metabonomic analyses for an approximation of HIV-induced changes to the phenotype of an infected individual. Although early in its application to HIV/AIDS, (biofluid) metabonomics has already identified metabolic pathways influenced by both HIV and/or its treatment. To date, biofluid NMR and MS data show that the virus and highly active antiretroviral treatment (HAART) mainly influence carbohydrate and lipid metabolism, suggesting that infected individuals are susceptible to very specific metabolic complications. A number of well-defined biofluid metabonomic studies clearly distinguished HIV negative, positive and treatment experienced patient profiles from one another. While many of the virus or treatment affected metabolites have been identified, the metabonomics measurements were mostly qualitative. The identities of the molecules were not always validated neither were the statistical models used to distinguish between groups. Assigning particular metabolic changes to specific drug regimens using metabonomics also remains to be done. Studies exist where identified metabolites have been linked to various disease states suggesting great potential for the use of metabonomics in disease prognostics. This review therefore examines the field of metabonomics in the context of HIV/AIDS, comments on metabolites routinely detected as being affected by the pathogen or treatment, explains what existing data suggest and makes recommendations on future research.

Possible mitochondrial dysfunction and its association with antiretroviral therapy use in children perinatally infected with HIV

BACKGROUND

Mitochondrial dysfunction has been associated with both human immunodeficiency virus (HIV) infection and exposure to antiretroviral therapy. Mitochondrial dysfunction has not been widely studied in HIV-infected children. We estimated the incidence of clinically defined mitochondrial dysfunction among children with perinatal HIV infection.

METHODS

Children with perinatal HIV infection enrolled in a prospective cohort study (Pediatric AIDS Clinical Trials Group protocols 219 and 219C) from 1993 through 2004 were included. Two clinical case definitions of mitochondrial dysfunction, the Enquête Périnatale Française criteria and the Mitochondrial Disease Classification criteria, were used to classify signs and symptoms that were consistent with possible mitochondrial dysfunction. Adjusted odds ratios of the associations between single and dual nucleoside reverse-transcriptase inhibitor use and possible mitochondrial dysfunction were estimated using logistic regression.

RESULTS

Overall, 982 (33.5%) of 2931 children met 1 or both case definitions of possible mitochondrial dysfunction. Mortality was highest among the 96 children who met both case definitions (20%). After adjusting for confounders, there was a higher risk of possible mitochondrial dysfunction among children who received stavudine regardless of exposure to other medications (odds ratio, 3.44 [95% confidence interval, 1.91-6.20]) or who received stavudine-didanosine combination therapy (odds ratio, 2.23 [95% confidence interval, 1.19-4.21]). Exposure to lamivudine and to lamivudine-stavudine were also associated with an increased risk of mitochondrial dysfunction.

CONCLUSIONS

Receipt of nucleoside reverse-transcriptase inhibitors, especially stavudine and lamivudine, was associated with possible mitochondrial dysfunction in children with perinatal HIV infection. Further studies are warranted to elucidate potential mechanisms of nucleoside reverse-transcriptase inhibitor toxicities.

Modifications to the dNTP triphosphate moiety: from mechanistic probes for DNA polymerases to antiviral and anti-cancer drug design

Abnormal replication of DNA is associated with many important human diseases, most notably viral infections and neoplasms. Existing approaches to chemotherapeutics for diseases associated with dysfunctional DNA replication classically involve nucleoside analogues that inhibit polymerase activity due to modification in the nucleobase and/or ribose moieties. These compounds must undergo multiple phosphorylation steps in vivo, converting them into triphosphosphates, in order to inhibit their targeted DNA polymerase. Nucleotide monophosphonates enable bypassing the initial phosphorylation step at the cost of decreased bioavailability. Relatively little attention has been paid to higher nucleotides (corresponding to the natural di- and triphosphate DNA polymerase substrates) as drug platforms due to their expected poor deliverability. However, a better understanding of DNA polymerase mechanism and fidelity dependence on the triphosphate moiety is beginning to emerge, aided by systematic incorporation into this group of substituted methylenebisphosphonate probes. Meanwhile, other bridging, as well as non-bridging, modifications have revealed intriguing possibilities for new drug design. We briefly survey some of this recent work, and argue that the potential of nucleotide-based drugs, and intriguing preliminary progress in this area, warrant acceptance of the challenges that they present with respect to bioavailability and metabolic stability.

Mitochondrial membrane potential and apoptosis of blood mononuclear cells in untreated HIV-1 infected patients

OBJECTIVES

Infection with HIV leads to progressive CD4 T-cell loss, resulting in AIDS. Apoptosis is the main mechanism for the loss of infected and bystander cells, but the complex interacting factors inducing and inhibiting apoptosis are not fully understood. Mitochondrial dysfunction is a pivotal step of the apoptotic cascade and can result in reduced mitochondrial membrane potential.

METHODS

The mitochondrial membrane potential of peripheral blood mononuclear cells (PBMC) was measured by flow cytometry using the dye JC-1 (Molecular Probes Inc). Apoptotic cells were identified using the Annexin V assay (Becton Dickinson GmbH).

RESULTS

The mitochondrial membrane potential of PBMC was significantly decreased and apoptotic cell rate was increased in HIV-infected therapy-naïve patients compared with HIV-negative controls. There was a highly significant correlation between the mitochondrial membrane potential and the rate of apoptosis. CD4 cell count was correlated negatively to the apoptotic rate and positively to the mitochondrial membrane potential.

CONCLUSIONS

The JC-1 assay is a sensitive tool to detect changes of mitochondrial membrane potential associated with apoptosis in HIV-infected therapy-naïve patients. We could show in vivo that a reduction of mitochondrial membrane potential is correlated to apoptosis of PBMC, CD4 cell count and HIV viral load during HIV infection.

Severe Hyperlactataemia Complicating Stavudine First-Line Antiretroviral Therapy in South Africa

Background

In the public sector antiretroviral therapy (ART) programme in South Africa the standardized first-line regimen includes stavudine (d4T). Severe symptomatic hyperlactataemia (SHL) is a potentially life- threatening complication of d4T.

Methods

GF Jooste Hospital is a referral centre for six ART clinics. We retrospectively reviewed cases referred with lactate levels ≥5 mmol/l that were attributed to nucleoside reverse transcriptase inhibitors from August 2003 to November 2005. We calculated cumulative ART exposure in patients attending these clinics to derive a referral rate.

Results

In total, 75 patients were referred with severe SHL (71 female). All had been on d4T and on ART for a median of 10 months. The referral rate for severe SHL was 17.5 cases per 1,000 patient-years. In 53 patients (71%), lactic acidosis (standard bicarbonate [SHCO3]<20 mmol/l) was confirmed, resulting in a referral rate of 12.3 cases per 1,000 patient-years. Twelve patients (16%) died during acute admission (≤30 days). SHCO3<15 mmol/l and pH<7.2 were the only factors associated with acute mortality (odds ratio [OR] 22.5, 95% confidence interval [CI] 2.8–1,045.7 and OR 13.9, 95% CI 2.7–86.9, respectively). A total of 30 less severe cases were rechallenged with zidovudine without recurrence of SHL.

Conclusions

This study confirms a high incidence of severe SHL in Africa, which has been shown in previous studies. Rechallenge with zidovudine in less severe cases was found to be safe.

The Influence of HIV Infection and Antiretroviral Therapy on the Mitochondrial Membrane Potential of Peripheral Mononuclear Cells

Objectives

Clinical disorders occurring in HIV-infected patients on antiretroviral therapy (ART) have been linked to mitochondrial dysfunction, for example, lactic acidosis and lipodystrophy. Mitochondrial membrane potential (ΔΨm) is the most direct measure of the state of energization of the mitochondria. We analysed ΔΨm of peripheral blood mononuclear cells (PBMCs) in HIV-negative, healthy subjects ( n=8), HIV-infected, treatment-naive patients ( n=30), and HIV-infected patients on ART ( n=58). The influence of ART was analysed in six patients who started their first regimen.

Methods

The ΔΨm of PBMC was measured by flow cytometry using the dye JC-1.

Results

The ΔΨm was significantly lower in HIV-infected patients than in HIV-negative controls. This difference was detected in both treated ( P=0.0001) and untreated patients ( P=0.001). The ΔΨm of PBMCs was highly correlated with CD4+ T-cell count in therapy-naive patients ( P=0.002, r=0.546) and in treated patients ( P=0.028, r=0.288). The ΔΨm increased significantly in therapy-naive patients after starting ART ( P=0.001). Patients with lipoatrophy had significantly lower ΔΨm than patients without lipodystrophy or with lipohypertrophy ( P=0.023).

Conclusions

In HIV-infected persons ΔΨm is significantly reduced. Patients with lipoatrophy have significantly reduced ΔΨm. This is the first study showing that the ΔΨm of PBMCs is highly correlated with CD4+ T-cell count in HIV infection.

Glucose production, oxidation and disposal correlate with plasma lactate levels in HIV-infected patients on HAART

OBJECTIVES

Hyperlactatemia is prevalent in HIV-infected patients on highly active antiretroviral therapy (HAART) and may be associated with depletion of mitochondrial DNA. However, the correlation between fasting lactate and mitochondrial DNA may be weak or absent, implicating that other factors e.g. glucose turnover may contribute to hyperlactatemia.

METHODS

HIV-infected patients receiving HAART who had lipodystrophy (LIPO, n=18) or were without lipodystrophy (NONLIPO, n=18) were investigated. Insulin sensitivity (M-value), glucose oxidation rate (GOX) and fasting endogenous glucose production (EGP) were determined by hyperinsulinemic euglycemic clamp, indirect calorimetry and glucose tracer technique, respectively.

RESULTS

Fasting p-lactate (median 1.2 mmol/L; range 0.6-4.3, n=36) tended to be increased in LIPO (P=0.12); 6 patients (4 LIPO) had lactate > or =2.0 mmol/L. Fasting lactate correlated inversely with M-value (P<0.001) and positively with fasting EGP (P<0.05) and fasting GOX (P<0.05), together explaining 51% (R2, n=36) of the variation in fasting lactate. Lactate increased in NONLIPO (P<0.05) but not in LIPO (P>0.5) during clamp. Incremental (clamp minus fasting value) GOX (P<0.01) was decreased and incremental insulin (P<0.01) was increased in LIPO.

CONCLUSIONS

Fasting EGP, GOX and insulin resistance may be major determinants of fasting lactate levels in HIV-infected patients on HAART. Insulin levels per se may not determine plasma lactate in such patients.

Toxic metabolic syndrome associated with HAART

Acquired fat redistribution, that is, peripheral fat loss often accompanied by central fat accumulation in patients with HIV infection is the most common form of lipodystrophy in man. Approximately 30 - 50% of HIV-infected individuals after > or = 12 months on highly active antiretroviral therapy (HAART) may encounter the HIV-associated lipodystrophy syndrome (HALS), which attenuates patient compliance to this treatment. HALS is characterised by impaired glucose and lipid metabolism and other risk factors for cardiovascular disease. This review depicts the metabolic abnormalities associated with HAART by describing the key cell and organ systems that are involved, emphasising the role of insulin resistance. An opinion on the remedies available to treat the metabolic abnormalities and phenotype of HALS is provided.

Anti-HIV drugs and the mitochondria

Several drugs are currently used that can significantly prolong the course of the infection with the human immunodeficiency virus (HIV), the cause of the acquired immunodeficiency syndrome (AIDS). Among these drugs, the nucleosidic inhibitors of viral reverse transcriptase can alter mitochondrial (mt) function by inhibiting the mitochondrial DNA polymerase gamma (the enzyme responsible for the replication of mtDNA). Decreased mtDNA content provokes a diminished synthesis of respiratory chain enzymes, leading to alterations in mt function. These are in turn responsible for a variety of side effects frequently observed in HIV+ patients, that range from hyperlactatemia and lactic acidosis to lipodystrophy, a pathology characterized by accumulation of visceral fat, breast adiposity, cervical fat-pads, hyperlipidemia, insulin resistance and fat wasting in face and limbs. In this paper, data concerning the effects of different compounds on mitochondria, their role in the pathogenesis of lipodystrophy, and problems related to studies on the mt toxicity of antiviral drugs are reviewed and thoroughly discussed.

Upregulatory mechanisms compensate for mitochondrial DNA depletion in asymptomatic individuals receiving stavudine plus didanosine

Nucleoside analogue use is often related to mitochondrial DNA (mtDNA) depletion, but mitochondrial function is preserved in most asymptomatic patients. We determined whether homeostatic mechanisms are able to compensate for this mtDNA depletion in patients receiving stavudine plus didanosine (d4T + ddI), an antiretroviral combination with great in vitro and in vivo capacity to decrease mtDNA. We included 28 asymptomatic HIV-infected individuals: 17 subjects (cases) on a first-line antiretroviral regimen consisting of d4T + ddI as the nucleoside backbone plus nevirapine or nelfinavir for at least 6 months (mean: 16 +/- 8 months) and 11 naive subjects (controls). We assessed the following in peripheral blood mononuclear cells: mitochondrial mass by citrate synthase activity, mtDNA content by real-time polymerase chain reaction, cytochrome c oxidase subunit II (COX-II) expression by Western blot analysis, and COX activity by spectrophotometry. The mitochondrial mass and mtDNA content of cases decreased when compared with controls, whether normalized per cell or per mitochondrion. Conversely, COX-II expression and COX activity were similar in cases and controls. COX-II expression was constant and independent of the mtDNA content, whereas it was closely related to COX activity. We concluded that treatment with dd4T + ddI is associated with decreased mitochondrial mass and mtDNA content but that COX-II expression and COX activity remain unaltered. These data suggest that upregulatory transcriptional or posttranscriptional mechanisms compensate for mtDNA depletion caused by d4T + ddI before profound mtDNA depletion occurs.

Mitochondrial DNA depletion in liver tissue of patients infected with hepatitis C virus: contributing effect of HIV infection?

OBJECTIVES

It has been suggested that chronic hepatitis C virus (HCV) infection depletes mitochondrial DNA (mtDNA) in the liver. Because decreased mtDNA levels were also found in humans infected with HIV, we investigated whether HIV may have aggravated hepatic mtDNA depletion in individuals with HCV infection.

METHODS

In this cross-sectional study, liver biopsies were performed in a total of 40 individuals prior to any antiviral therapy. The individuals were recruited from the Hospital Clinic, Barcelona and the HIV Centre, Dusseldorf. Seventeen patients were negative for HIV and HCV and were biopsied for liver enzyme elevation of unknown cause (controls), 14 individuals had chronic HCV but no HIV infection, and nine subjects were coinfected with both viruses. mtDNA and liver histology were centrally assessed.

RESULTS

The groups did not differ with respect to age, gender, liver function tests and HCV viral load, where applicable. mtDNA levels were decreased by 19% in the HCV-monoinfected group (P=0.03) and by 27% in the HIV/HCV-coinfected subjects (P=0.02) compared to controls. The mtDNA content, however, did not differ between individuals with HCV monoinfection and HCV/HIV coinfection (P=0.75). The degrees of liver fibrosis, inflammatory activity or steatosis did not correlate with mtDNA content.

CONCLUSIONS

Liver mtDNA content is reduced in both HCV-monoinfected and HIV/HCV-coinfected patients. Under the limitations of our study, we could demonstrate only a slight trend towards more pronounced mtDNA depletion in HIV/HCV-coinfected subjects.

Mitochondrial (Mt)Dna Changes in Tissue May Not be Reflected by Depletion of Mtdna in Peripheral Blood Mononuclear Cells in HIV-Infected Patients

Objectives

Most data on mitochondrial toxicity have been derived from peripheral blood mononuclear cells (PBMCs). However, whether mitochondrial DNA (mtDNA) content in PBMCs reflects the mitochondrial state in tissues remains elusive. We report herein on mitochondrial toxicity in skeletal muscle in HIV-infected patients naive to antiretroviral treatment (ART [HIV+ART-naive]; n=10) patients exposed to nucleoside reverse transcriptase inhibitors (NRTIs [HIV+NRTI+]; n=24) and healthy controls ( n=11), and compare these tissue data with mtDNA in PBMCs.

Methods

Muscle biopsies were examined for (i) mtDNA and nuclear DNA (nDNA) content using TaqMan realtime PCR system, (ii) mtDNA deletions using long expand PCR with subsequent gel electrophoresis, and (iii) mitochondrial myopathy expressed as cytochrome c oxidase (COX)-deficient muscle fibres.

Results

The mt/n DNA ratio in muscle from HIV+NRTI+patients was reduced compared with HIV-negative controls ( P=0.028). Moreover, mtDNA deletions were more frequent in HIV+NRTI+ patients than in both HIV-negative controls ( P=0.009) and HIV+ART-naive patients ( P=0.005). HIV+NRTI+ also tended to have more COX-deficient fibres than HIV-negative controls ( P=0.076). COX-deficient fibres were positively correlated with mtDNA deletions in HIV+NRTI+ patients (r=0.83, P<0.001). Patients with current use of didanosine (ddI) had more frequent mtDNA deletions and COX-deficient fibres than HIV+NRTI+ not on current treatment with ddI. It should be noted that mitochondrial alterations were not correlated with mtDNA/cell in PBMCs in any group.

Conclusions

In skeletal muscle, HIV+NRTI+ had a reduced mt/n DNA ratio, more frequent mtDNA deletions and possibly more COX-deficient muscle fibres than HIV-negative controls. However, the mtDNA/cell in peripheral blood was decreased in both HIV+NRTI+ and HIV+ART-naive patients. Thus, mtDNA in peripheral blood may not be a relevant marker of mitochondrial toxicity in organ-specific tissue.

Incidence and Risk Factors for Mitochondrial Toxicity in Treated HIV/HCV-Coinfected Patients

Background

Coinfection with hepatitis C virus (HCV) and HIV is not uncommon and therapies for both infections are currently available. A major drawback, however, could be a potentially higher risk for mitochondrial toxicity (MT), defined as the elevation of pancreatic enzymes or lactate levels due to the nucleoside analogue reverse transcriptase inhibitors contained in both therapies.

Methods

Prospective analyses of clinical and laboratory data, including plasma lactate levels and pancreatic enzymes, of 113 consecutive HIV/HCV-coinfected patients were assigned to receive ribavirin (RBV) plus interferon (IFN)-α.

Results

Fourteen patients (12%) showed increased levels of amylase/lipase and/or hyperlactataemia. No patient developed clinical pancreatitis. Four patients with hyperlactataemia had clinical symptoms of lactic acidosis and recovered uneventfully by 2 weeks after treatment withdrawal. The variables significantly associated with MT in the univariate analysis were: therapy with didanosine (ddI), ddI plus stavudine (d4T), previous history of diabetes and the baseline lactate level. However, ddI use was the only independent risk factor for MT identified in the multivariate analysis. MT was not associated with gender, age, alcohol consumption, type of IFN, degree of steatosis and fibrosis in liver biopsy, presence of lipodystrophy, CD4+ cell count, HCV or HIV viral load, mitochondrial DNA and COXII-expression in liver tissue, or antiretroviral therapy containing d4T or protease inhibitors.

Conclusions

12% of HIV/HCV-coinfected patients receiving IFN plus RBV concomitantly with highly active antiretroviral therapy developed laboratory markers of MT. Although most of cases were asymptomatic, our study suggests that concomitant use of RBV plus ddI should be avoided, and that routine monitoring of lactate and pancreatic enzymes may be recommended.

Mitochondrial Studies in Haart-Related Lipodystrophy: From Experimental Hypothesis to Clinical Findings

Chronic use of antiretrovirals (ARVs) to treat HIV infection, along with more prolonged patient survival, has been associated with an increase in adverse drug effects in HIV-infected patients on treatment. It has been proposed that some of these adverse effects (including myopathy, cardiomyopathy, anaemia, hyperlactataemia/ lactic acidosis, pancreatitis, polyneuritis and lipodystrophy) could be mediated by mitochondrial (mt) toxicity. From the experimental data, it has been proposed that nucleoside analogue reverse transcriptase inhibitors (NRTIs) also inhibit γ-polymerase, the enzyme devoted to replicate (and, to a lesser extent, repair) mtDNA. It is now widely accepted that the use of most NRTIs in HIV-infected patients is associated with mtDNA depletion. Although cross-sectional studies suggest that certain ARVs, especially stavudine, are more toxic to mitochondria, the differences among different highly active ARV therapy (HAART) schedules detected in the analysis of longitudinal studies are not so clear. These types of study in previously untreated individuals suggest that the greatest mtDNA loss appears at the beginning of the treatment. Conversely, in ARV-experienced patients, the potential beneficial effects of HAART changes in terms of mtDNA content remain controversial and must be further investigated. Functional studies accompanying genetic investigations are needed for the correct pathogenic interpretation of the mtDNA abnormalities.

Uridine in the Prevention and Treatment of Nrti-Related Mitochondrial Toxicity

Long-term side effects of antiretroviral therapy are attributed to the mitochondrial (mt) toxicity of nucleoside analogue reverse transcriptase inhibitors (NRTIs) and their ability to deplete mtDNA. Studies in hepatocytes suggest that uridine is able to prevent and treat mtDNA depletion by pyrimidine NRTIs [zalcitabine (ddC) and stavudine (d4T)] and to fully abrogate hepatocyte death, elevated lactate production and intracellular steatosis. Uridine was also found to improve the liver and haematopoietic toxicities of zidovudine (AZT), which are unrelated to mtDNA depletion, and to prevent neuronal cell death induced by ddC. Most recently, uridine was found to prevent the onset of a lipoatrophic phenotype (reduced intracellular lipids, increased apoptosis, mtDNA depletion and mt depolarization) in adipocytes incubated long-term with d4T and AZT. Various steps of mt nucleoside utilization may be involved in the protective effect, but competition of uridine metabolites with NRTIs at polymerase y or other enzymes is a plausible explanation. Pharmacokinetic studies suggest that uridine serum levels can be safely increased in humans to achieve concentrations which are protective in vitro (50–200 μM). Uridine was not found to interfere with the antiretroviral activity of NRTIs. Mitocnol, a sugar cane extract which effectively increases uridine in human serum, was beneficial in individual HIV patients with mt toxicity and is now being tested in placebo-controlled randomized trials. Until these data become available, the risk-benefit calculation of using uridine should be individualized. The current safety data justify the closely monitored use of uridine in individuals who suffer from mt toxicity but who cannot be switched to less toxic NRTIs.

Depleted skeletal muscle mitochondrial DNA, hyperlactatemia, and decreased oxidative capacity in HIV-infected patients on highly active antiretroviral therapy

The nucleoside reverse transcriptase inhibitors (NRTIs), especially stavudine, may deplete mitochondrial (mt) DNA in human tissues by inhibiting the mitochondrial polymerase gamma, a setting, which is associated with hyperlactatemia. The aim of the present study was to examine whether hyperlactatemia is associated with depletion of skeletal muscle (sm)-mtDNA and decreased oxidative capacity in HIV-infected patients on NRTI based highly active antiretroviral therapy (HAART) and whether HIV infection itself is associated with sm-mtDNA depletion. Sm-mtDNA was determined in 42 HIV-infected patients (35 patients on HAART including at least one NRTI (HIV-NRTI) and 7 patients never treated with antiretroviral drugs (NAIVE)) and 14 healthy controls. Whole body oxidative capacity (DeltaGOX) was estimated in HIV-infected patients by indirect calorimetry. Hyperlactatemia (>or=2.0 mM) was detected in six HIV-NRTI, who all used Stavudine (P < 0.01), displayed depleted sm-mtDNA (P < 0.02) and decreased DeltaGOX (P < 0.01) compared with normolactatemic HIV-NRTI (n = 29). NAIVE displayed decreased sm-mtDNA (P < 0.05), increased HIV-RNA (P < 0.01) and increased plasma TNF-alpha (P < 0.05) compared to all HIV-NRTI (n = 35), in turn displaying decreased sm-mtDNA (P < 0.01) compared to healthy controls. Thus, hyperlactatemia in HIV-NRTI may be associated with pronounced depletion of sm-mtDNA, decreased oxidative capacity and current stavudine therapy. Further, HIV may deplete sm-mtDNA of NAIVE, which in part could be mediated through an enhanced pro-inflammatory response.

Mitochondrial DNA Levels in Fat and Blood Cells from Patients with Lipodystrophy or Peripheral Neuropathy and the Effect of 90 Days of High-Dose Coenzyme Q Treatment: A Randomized, Double-Blind, Placebo-Controlled Pilot Study

BACKGROUND

Mitochondrial toxicity can be induced by reverse-transcriptase inhibitors, and an association between levels of mitochondrial DNA (mtDNA) per cell and lipodystrophy, peripheral neuropathy, and HIV infection per se has been suggested. Studies aimed at increasing the oxidative capacity in HIV-infected patients have been sparse.

METHODS

Levels of mtDNA in fat and peripheral blood mononuclear cells (PBMCs) from 25 HIV infected patients and 10 healthy control subjects were studied with real-time PCR analysis. A placebo-controlled and double-blind design was used to assign individuals to receive either 100 mg of coenzyme Q twice daily for 3 months or a matching placebo regimen. Levels of mtDNA and other parameters were assessed before and after the intervention period.

RESULTS

The mean number of mtDNA copies per cell was lower in fat tissue obtained from patients with peripheral neuropathy (1547 mtDNA copies/cell; P=.045), patients with lipodystrophy (1732 mtDNA copies/cell; P=.003) and in HIV patients with no complications associated with highly active antiretroviral therapy (2935 mtDNA copies/cell; P=.078), compared with healthy control subjects (6198 mtDNA copies/cell). No clear difference was seen in mtDNA content in PBMCs. Coenzyme Q therapy improved the general condition of patients (P=.005) and caused a reversible increase in peripheral neuropathy pain (P=.048). Compared with placebo, treatment with coenzyme Q did not result in changes in mtDNA levels in fat cells or in PBMCs after the treatment period.

CONCLUSIONS

Levels of mtDNA in fat tissue, but not in PBMCs, were associated with peripheral neuropathy and lipodystrophy. High-dose coenzyme Q therapy increased well-being in asymptomatic HIV-infected patients and those with lipodystrophy, as well as in control subjects, but aggravated pain in patients with peripheral neuropathy.