Mitochondrial DNA decrease in subcutaneous adipose tissue of HIV-infected individuals with peripheral lipoatrophy

Mitochondrial Toxicity of Indinavir, Stavudine and Zidovudine Involves Multiple Cellular Targets in white and brown adipocytes

Objective

To evaluate the mechanisms of mitochondrial toxicity associated with antiretroviral treatment.

Methods

3T3–F442A white and T37i brown adipocytes were exposed to stavudine (10 μM), zidovudine (1 μM) and indinavir (10 μM), alone or in combination. Adipocyte fat content was measured with Oil Red O staining. Quantification of mRNA levels and of mitochondrial DNA content used PCR-based techniques. Mitochondrial activities were evaluated with respiration, ATP synthesis and spectrophotometric assays. Mitochondrial mass was assessed by the fluorescent probe MitoTracker Red.

Results

In both cell types, all the treatments induced a severe defect of adipogenesis (low lipid content and decreased markers of adipogenic maturation: peroxisome proliferator-activated receptor [PPAR]γ2 and aP2 but also uncoupling protein 1 in brown adipocytes) as well as altered mitochondrial function (decreased respiration rate and increased mitochondrial mass). Drug combination did not give additional toxicity. Brown adipocytes appeared more affected than white adipocytes (lower respiration rate and decreased ATP production). The mechanisms of mitochondrial toxicity differed with the drug and the cell type. Only stavudine induced severe mitochondrial DNA depletion in both cell types. With all the treatments, white adipocytes showed a decrease in the expression of mitochondrial and nuclear-DNA-encoded respiratory chain subunits (cytochrome c oxidase [CytOx]2 and CytOx4), whereas brown adipocytes maintained normal expression in accordance with their increase of the transcriptional factors of mitochondrial biogenesis nuclear respiratory factor 1 and PPARγ coactivator (PGC)1-related cofactor PRC, but not PGC1α.

Conclusion

Our results provide evidence for dissociation between mitochondrial activity, transcription and mitochondrial DNA content, highlighting the complexity of mitochondrial toxicity, which affects multiple cellular targets.

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.

The role of compartment penetration in PI-monotherapy: the Atazanavir-Ritonavir Monomaintenance (ATARITMO) Trial

OBJECTIVES

To limit exposure to anti-HIV drugs and minimize risk of long-term side effects, studies have looked at the possibility of simplified maintenance strategies. Ritonavir-boosted protease-inhibitor (PI)-monotherapies are an attractive alternative, but limited compartmental penetration of PI remains a concern.

DESIGN

Non-comparative 24-week pilot study.

METHOD

Ritonavir-boosted atazanavir (ATV/r) monotherapy administered to fully suppressed patients (>3 month HIV RNA < 50 copies/ml). Plasma was obtained every 4 weeks and cerebrospinal fluid (CSF) and semen at W24.

RESULTS

Two patients (7%) failed ATV/r monotherapy. One patient was subsequently identified as a protocol violator since he had a previous history of treatment failure under indinavir. The second patient deliberately decided to stop treatment after W20. Excluding failing patients, individual measurements of HIV RNA in patients having occasional viral 'blips' was found in five patients. At W24, 3/20 patients had elevated viral loads in CSF (HIV RNA > 100 copies/ml), and 2/15 in semen, despite viral suppression in plasma (< 50 copies/ml). Samples with elevated HIV RNA (> 500 copies/ml) in CSF were all wild type. The mean ATV drug concentration ratio (CSF/blood, n = 22) was 0.9%. Indicators of altered immune activation (CD8CD38 C-reactive protein) remained unchanged.

CONCLUSION

This study supports previous results indicating the potential use of PI-based mono-maintenance therapies. However, our results in CSF cautions against the uncontrolled use of PI-based monotherapies.

Dysregulated Energy Expenditure in HIV-Infected Patients: A Mechanistic Review

Metabolic abnormalities are common in patients with human immunodeficiency virus (HIV) infection and range from protein catabolism to lipodystrophy and dyslipidemia associated with the use of highly active antiretroviral therapy. One abnormality is increased resting energy expenditure, which even occurs in clinically stable HIV-infected patients. Increased resting energy expenditure may aggravate the tendency towards weight loss and wasting, which are independent predictors of mortality. Despite much investigation, the factors associated with altered resting energy expenditure remain unclear; viral load, CD4 cell count, use of antiretroviral drugs, body composition, hormones, and proinflammatory cytokines have been imputed. Mechanisms that could explain increased resting energy expenditure include the HIV accessory protein viral protein R, antiretroviral drugs that affect mitochondrial function, and futile cycling within adipocytes. Other components of energy expenditure are also important to overall energy balance and may also be affected. Identifying unifying mechanisms will be an important step to finding effective treatments for HIV-related alterations in energy expenditure and to reversing metabolic risks in patients with HIV infection.

The Impact of Reducing Stavudine dose versus switching to tenofovir on plasma lipids, body composition and mitochondrial function in HIV-infected patients

Background

Stavudine (d4T)-containing regimens are associated with a potential for lipoatrophy and dyslipidaemia. We assessed the safety and efficacy of reducing the dose of stavudine compared with switching to tenofovir or maintaining the standard dose of d4T.

Methods

Clinically stable HIV-infected patients receiving antiretroviral therapy containing stavudine 40 mg twice daily with a plasma HIV RNA <200 copies/ml for at least 6 months were randomized to maintain stavudine 40 mg twice daily (d4T40 arm), to reduce to 30 mg twice daily (d4T30 arm), or to switch from d4T to tenofovir (TDF arm).

Results

Fifty-eight (93% male) patients were included: 22 in the d4T40 arm, 19 in the d4T30 arm and 17 in TDF arm. At baseline, median time on d4T was 6 years (interquartile range [IQR] 2.6–7.1), median age 43 years (IQR 36–51) and median CD4+ T-cell count was 587/mm3 (IQR 329–892). At week 24, median limb fat changes (g) were as follows: d4T40=-182 (95% CI: -469—5); d4T30=527 (95% CI: -343–694); and TDF=402 (95% CI: 130–835; d4T40 versus TDF, P=0.0003). Significant differences between median values of laboratory parameters were detected: triglycerides (mg/dl): d4T40=19; d4T30=-23 and TDF=-79 (d4T40 versus TDF, P=0.03); and total cholesterol (mg/dl): d4t40=22, d4T30=-4, and TDF=-28 (d4T40 versus TDF, P=0.04). No significant difference was observed in mitochondrial function assessed in peripheral blood mononuclear cells.

Conclusions

Although both strategies were associated with a trend toward a decrease in plasma lipids and an increase in body fat, the only significant changes were observed among those who switched to tenofovir.

Exploratory study comparing the metabolic toxicities of a lopinavir/ritonavir plus saquinavir dual protease inhibitor regimen versus a lopinavir/ritonavir plus zidovudine/lamivudine nucleoside regimen

OBJECTIVES

To assess the safety, efficacy and metabolic toxicity of lopinavir/ritonavir + saquinavir or zidovudine/lamivudine and evaluate the pharmacokinetics of lopinavir/ritonavir + saquinavir.

METHODS

HIV-1-infected, antiretroviral-naive subjects were randomized to lopinavir/ritonavir (400/100 mg) twice daily + saquinavir (800 mg) or zidovudine/lamivudine (150/300 mg) in a Phase II, 48 week study. Subjects receiving lopinavir/ritonavir + zidovudine/lamivudine initiated escalating doses of saquinavir (400, 600 and 800 mg) weekly for 3 weeks.

RESULTS

By intent-to-treat (non-completer = failure) analysis, 10/16 (63%) lopinavir/ritonavir + saquinavir-treated and 7/14 (50%) lopinavir/ritonavir + zidovudine/lamivudine-treated subjects achieved plasma HIV-1 RNA <50 copies/mL (P=0.713) at week 48. Safety, tolerability, metabolic changes and truncal fat increases were similar between groups. Small decreases in the lower extremity fat in the zidovudine/lamivudine group (-6%) and a statistically significant increase in the lower extremity fat in the saquinavir group (+19%) were observed. Lopinavir/ritonavir co-administered with saquinavir 600 or 800 mg twice daily produced saquinavir concentrations similar to those previously reported for saquinavir/ritonavir 1000/100 mg twice daily.

CONCLUSIONS

Treatment regimens had similar efficacy and tolerability. Metabolic parameters suggested lipoatrophy in the zidovudine/lamivudine treatment group. Saquinavir 600 and 800 mg twice daily produced concentrations similar to those previously reported for saquinavir/ritonavir 1000/100 mg twice daily.

Increased resting energy expenditure, fat oxidation, and food intake in patients with highly active antiretroviral therapy-associated lipodystrophy

Highly active antiretroviral therapy (HAART) is associated with metabolic adverse events such as lipodystrophy in human immunodeficiency virus (HIV)-infected patients. The objective of the present study was to evaluate the effects of HAART-associated lipodystrophy on resting energy expenditure and caloric intake. In this cross-sectional study we compared resting energy expenditure (REE) and energy intake in 30 HAART-treated patients with lipodystrophy (HAART+LD+) with 13 HAART-treated patients without lipodystrophy (HAART+LD-). REE was measured using indirect calorimetry, and energy intake was recorded as a 3-day diary of food intake. REE (5,180+/-160 vs. 4,260+/-150 J/min, P<0.01) and also REE expressed per fat-free mass (86+/-1 vs. 78+/-2 J.kg fat-free mass-1.min-1, P<0.01) were significantly higher in the HAART+LD+ than the HAART+LD- group. Rate of lipid oxidation was significantly higher in the HAART+LD+ than the HAART+LD- group. Total energy and fat intakes were significantly increased in the HAART+LD+ compared with the HAART+LD- group. These results imply that HAART-associated lipodystrophy is associated with increased REE and lipid oxidation and with increased caloric and fat intake.

Micronutrients in HIV-positive persons receiving highly active antiretroviral therapy

In HIV-infected persons, low serum concentrations of vitamins and minerals, termed micronutrients, are associated with an increased risk of HIV disease progression and mortality. Micronutrient supplements can delay HIV disease progression and reduce mortality in HIV-positive persons not receiving highly active antiretroviral therapy (HAART). With the transition to more universal access to HAART, a better understanding of micronutrient deficiencies and the role of micronutrient supplements in HIV-positive persons receiving HAART has become a priority. The provision of simple, inexpensive micronutrient supplements as an adjunct to HAART may have several cellular and clinical benefits, such as a reduction in mitochondrial toxicity and oxidative stress and an improvement in immune reconstitution. We reviewed observational and trial evidence on micronutrients in HIV-positive persons receiving HAART to summarize the current literature and suggest future research priorities. A small number of observational studies have suggested that some, but not all, micronutrients may become replete after HAART initiation, and few intervention studies have found that certain micronutrients may be a beneficial adjunct to HAART. However, most of these studies had some major limitations, including a small sample size, a short duration of follow-up, a lack of adjustment for inflammatory markers, and an inadequate assessment of HIV-related outcomes. Therefore, few data are available to determine whether HAART ameliorates micronutrient deficiencies or to recommend or refute the benefit of providing micronutrient supplements to HIV-positive persons receiving HAART. Because micronutrient supplementation may cause harm, randomized placebo-controlled trials are needed. Future research should determine whether HAART initiation restores micronutrient concentrations, independent of inflammatory markers, and whether micronutrient supplements affect HIV-related outcomes in HIV-positive persons receiving HAART.

Changes in the peripheral blood mtDNA levels in naive patients treated by different nucleoside reverse transcriptase inhibitor combinations and their association with subsequent lipodystrophy

Nucleoside reverse transcriptase inhibitors (NRTIs) differ in the type and severity of adverse effects resulting from mitochondrial abnormalities. mtDNA in peripheral blood mononuclear cells (PBMCs) was measured during the first 12 months of different NRTIs combinations and its association with clinical lipodystrophy was estimated. Extended follow-up of a randomized trial, ALBI-ANRS 070, including antiretroviral naive patients was conducted. Total DNA was extracted from available cryopreserved PBMCs at baseline and months 6 and 12. Nuclear and mitochondrial genes were amplified using a real-time PCR assay. Clinical lipodystrophy was assessed 30 months after randomization using a standardized questionnaire. A logistic regression analysis assessed the value of mtDNA to predict lipodystrophy. Mean mtDNA level (copies/cell) significantly decreased from 5847 at baseline to 3176 at month 12 (p < 0.0001). In the zidovudine + lamivudine (ZDV + 3TC) arm (n = 37), the mean mtDNA was 6098, 6807, and 3725 copies/cell for baseline, month 6, and month 12, respectively. In the stavudine + didanosine (d4T + ddI) arm (n = 40), the mean values were 5616, 5731, and 2648 copies/cell, respectively. The proportion of patients in the lowest quartile of mtDNA (<1421 copies/cell) at month 12 was higher in 18 patients with lipodystrophy (44%) than in 28 without lipodystrophy (7%) (p = 0.008). At 12 months, a larger reduction of mtDNA from baseline was observed in those started on the d4T + ddI arm. Furthermore, a low mtDNA level at month 12 was associated with the subsequent development of lipodystrophy. This marker may be of value for the early prevention of lipodystrophy in treated HIV-infected patients.

Patogenia de la lipodistrofia y de las alteraciones metabólicas asociadas a la infección por el VIH

Lipodystrophy, and the metabolic alterations (dislipemia, insulin-resistance) associated with human immunodeficiency virus (HIV) infection, is a multifactorial syndrome due to the interaction of host related factors (cellular immune status, diet, gene mutations), viral factors (cytokine synthesis, polyunsaturated fatty acid or PUFA depletion), and pharmacological effects (mitochondrial DNA-polymerase inhibition, lipolysis inhibition, adiponectin synthesis reduction). HIV probably modifies the adipocyte differentiation and the lipid metabolism. This retroviral effect is mediated by proinflammatory cytokines (tumor necrosis factor) and the participation of other factors (drugs, diet), all in the context of a particular host genetic setting. The adipocyte (and several cellular receptors, fatty acids, membrane proteins, and cytokines) plays a central role in the pathogenesis of HIV-associated lipodystrophy.

Tissue-specific associations between mitochondrial DNA levels and current treatment status in HIV-infected individuals

BACKGROUND

Tissue mitochondrial DNA (mtDNA) levels have been proposed as a marker of nucleoside analouge reverse transcriptase inhibitor (NRTI) toxicity. However, clinical studies have yielded conflicting data regarding possible associations with mtDNA levels. This study examined mtDNA levels in matched samples of peripheral blood mononuclear cells (PBMCs) and subcutaneous fat from a large Australian cohort to examine treatment, clinical, and demographic associations with mtDNA depletion.

METHODS

mtDNA was quantified by real-time polymerase chain reaction. Results were compared across patient treatment and demographic details using linear mixed models.

RESULTS

One hundred sixty-three PBMCs and 161 fat samples were available from 61 individuals. Current NRTI exposure was the major determinant of mtDNA levels. Both ddI (didanosine) and d4T (stavudine) exposures were associated with mtDNA depletion in fat (P < or = 0.0001 vs. those not on NRTIs). DdI exposure (P = 0.003), but not d4T exposure (P = 0.5), was associated with mtDNA depletion in PBMCs. No association between patient demographics or time on current therapy and mtDNA was observed.

CONCLUSIONS

Current NRTI exposure is the major determinant of tissue mtDNA, but the precise determinants are tissue specific. Both ddI and d4T exposure are associated with fat mtDNA depletion, whereas ddI exposure was the only observed association with mtDNA depletion in PBMCs.

Adverse effects of antiretroviral drugs on HIV-1-infected and -uninfected human monocyte-derived macrophages

Antiretroviral drugs approved for treatment of HIV-1 infection include nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs). Use of these drugs in combinations (highly active antiretroviral therapy) has delayed disease progression. However, long-term therapy is associated with potentially serious adverse effects. NRTIs are thought to contribute to these adverse effects via depletion of mtDNA. Inasmuch as macrophages (major targets for HIV-1) are highly metabolically active with large numbers of mitochondria, we investigated the effects of NRTIs (didanosine, stavudine, lamivudine, and zidovudine) on the viability and function of HIV-1-infected and -uninfected human monocyte-derived macrophages (MDMs). We demonstrate that the combinations didanosine/stavudine and lamivudine/zidovudine decrease mtDNA content in MDMs, with HIV-1-infected MDMs displaying a greater reduction than uninfected cells. This decrease correlated with decreased complement-mediated phagocytosis (C'MP) by MDMs, a process dependent on mitochondrial function. Inasmuch as PIs have previously been reported to interact with cellular proteases and given that cellular proteases are involved in the phagocytic process, we investigated the effects of the PI indinavir on C'MP. We demonstrate that indinavir augments C'MP by uninfected MDMs, but not HIV-1-infected MDMs. This study provides additional understanding on the effects of commonly used antiretroviral drugs on cellular immune function.

Effects of discontinuing stavudine or protease inhibitor therapy on human immunodeficiency virus-related fat redistribution evaluated by dual-energy x-ray absorptiometry

STUDY OBJECTIVE

To determine whether discontinuation of stavudine or protease inhibitor therapy improves human immunodeficiency virus (HIV)-related fat distribution in men.

DESIGN

Observational, retrospective study consisting of a cross-sectional (part 1) and a longitudinal (part 2) study.

DATA SOURCE

Medical records from Purpan University Hospital and La Grave University Hospital, Toulouse, France. Subjects. Eighty men with HIV infection treated with antiretrovirals and 151 healthy male controls matched for age.

MEASUREMENTS AND MAIN RESULTS

In part 1, body composition and fat distribution of the HIV-infected men were compared by dual energy x-ray absorptiometry (DEXA) with those of the controls to determine whether body fat distribution is altered in HIV-infected men. In part 2, we analyzed modifications of body composition and fat distribution in 45 of the 80 patients. These 45 had been exposed to antiretroviral drugs, including stavudine and a protease inhibitor, for at least 5 months before the first of two DEXA assessments. They received three different treatment strategies for several months. In group 1, stavudine was withdrawn; in group 2, protease inhibitor was discontinued, and in group 3, stavudine plus protease inhibitor were continued. Group 1 showed a significant fat gain in the lower extremities 31.7 +/- 5.9 months after stavudine discontinuation (p<0.0001). Group 2 did not show any significant modification of total body, lower limb, or trunk fat despite protease inhibitor discontinuation for 35.2 +/- 6.6 months. Findings were similar for group 3, who continued receiving stavudine-protease inhibitor therapy for 21.2 +/- 12.8 months.

CONCLUSION

These data suggest that long-term withdrawal of stavudine from the antiretroviral therapy regimen may be associated with significant improvement in lipoatrophy in the lower extremities, whereas long-term protease inhibitor withdrawal did not modify fat distribution.

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.

[Antiretroviral treatments-related lipodystrophy syndrome: clinico-pathological findings]

Effective therapies are available that can stop or slow down the progression of HIV infection. Highly active antiretroviral therapy (HAART) is a combination of antiretroviral drugs such as viral protease inhibitors or nucleoside-analogue reverse-transcriptase inhibitors. Among the side effects due to these drugs, lipodystrophy is a pathology characterized by fat wasting in face and limbs, accumulation of visceral fat, breast adiposity, cervical fat-pads, hyperlipidemia (hypertriglyceridemia and hypercholesterolemia), insulin resistance, and lactic acidemia. The main clinical features include peripheral fat loss (presumed lipoatrophy in the face, limbs, and buttocks) and central fat accumulation (within the abdomen, breasts, and over the dorsocervical spine, so-called "buffalo hump"). Histopathological features disclose a peculiar type of involutional lipodystrophy. Skin biopsies generally show thinning of the subcutaneous fat, associated with fibrosis, lipogranuloma and sometimes vessel proliferation. There is still an open debate concerning the precise responsibility of HAART as well as the metabolic pathways and mechanisms that are involved in the onset of lipodystrophy. There is no proven therapy for any component of lipodystrophy syndrome.

Antiretroviral therapy and the kidney: balancing benefit and risk in patients with HIV infection

The widespread introduction of highly active antiretroviral therapy (HAART) has revolutionised the treatment and course of HIV infection, with complications of chronic HIV infection and HAART playing an increasingly important role in morbidity and mortality. Both HIV infection and HAART have been associated with the development of acute and chronic kidney disease. The incidence of HIV-associated nephropathy, the classic kidney disease of HIV, reached a plateau following the introduction of HAART, consistent with the pathogenic role of direct viral infection of the kidney. At the same time, antiretroviral agents and related therapies have demonstrated a range of nephrotoxic effects, including crystal-induced obstruction, lactic acidosis, tubular toxicity, interstitial nephritis and electrolyte abnormalities. This article reviews the impact of HAART on the epidemiology of HIV-related kidney disease, the potential nephrotoxicity of specific antiretroviral agents and related medications, and guidelines for monitoring kidney function in HAART-treated patients.

Depot-specific regulation of glucose uptake and insulin sensitivity in HIV-lipodystrophy

Altered fat distribution is associated with insulin resistance in HIV, but little is known about regional glucose metabolism in fat and muscle depots in this patient population. The aim of the present study was to quantify regional fat, muscle, and whole body glucose disposal in HIV-infected men with lipoatrophy. Whole body glucose disposal was determined by hyperinsulinemic clamp technique (80 mU x m(-2) x min(-1)) in 6 HIV-infected men and 5 age/weight-matched healthy volunteers. Regional glucose uptake in muscle and subcutaneous (SAT) and visceral adipose tissue (VAT) was quantified in fasting and insulin-stimulated states using 2-deoxy-[18F]fluoro-D-glucose positron emission tomography. HIV-infected subjects with lipoatrophy had significantly increased glucose uptake into SAT (3.8 +/- 0.4 vs. 2.3 +/- 0.5 micromol x kg tissue(-1) x min(-1), P < 0.05) in the fasted state. Glucose uptake into VAT did not differ between groups. VAT area was inversely related with whole body glucose disposal, insulin sensitivity, and muscle glucose uptake during insulin stimulation. VAT area was highly predictive of whole body glucose disposal (r2 = 0.94, P < 0.0001). This may be mediated by adiponectin, which was significantly associated with VAT area (r = -0.75, P = 0.008), and whole body glucose disposal (r = 0.80, P = 0.003). This is the first study to directly demonstrate increased glucose uptake in subcutaneous fat of lipoatrophic patients, which may partially compensate for loss of SAT. Furthermore, we demonstrate a clear relationship between VAT and glucose metabolism in multiple fat and muscle depots, suggesting the critical importance of this depot in the regulation of glucose and highlighting the significant potential role of adiponectin in this process.

[Mitochondrial cytopathies associated with HIV infection]

The tremendous progress achieved during the last few years with the use of highly active antiretroviral therapy in suppressing HIV replication together with improvements in immunity have been tempered by a growing number of new adverse effects. Mitochondrial toxicity is one aspect of these long-term toxicities of antiretroviral drugs, with the role of nucleoside analogs particularly underlined. Some cases of impaired mitochondrial function have been clearly identified, such as pancreatitis due to didanosine, neuropathy due to zalcitabine, myopathy due to zidovudine, and lactic acidosis due to stavudine. These mitochondrial toxicities can affect several organs, presenting different patterns of symptoms: from asymptomatic to states with few symptoms despite huge metabolic abnormalities whose prognosis is immediately life-threatening. Beyond the inhibition of DNA polymerase gamma using nucleoside analogs, responsible for decreasing mitochondrial DNA in certain targeted organs, it appears that several physiopathologic mechanisms interact to explain this observed toxicity, HIV itself plays a role, and the underlying genetic pool needs to be better identified. Such cases mean that, it is imperative to avoid cumulated toxicities caused by associated treatments. With serious cases, or persistent symptoms despite discontinuing the nucleoside analogs responsible for such toxicity, one must propose vitamins, mitochondrial co-factors, or anti-oxidants. However, the future lies in the use of potent, less toxic nucleoside analogs, and in developing compounds belonging to other classes of antiretrovirals.

Mitochondrial toxicity of nucleoside analogues: mechanism, monitoring and management

Nucleoside analogues (NRTIs) are potent antiretroviral medications and are central to effective highly active antiretroviral therapy (HAART). Their intended action is to inhibit HIV reverse transcriptase. Nucleoside analogues also inhibit replication of mitochondrial DNA, and the pathogenesis of many of the toxicities associated with HAART is thought to be NRTI-induced mitochondrial dysfunction. Individuals with HIV infection may be particularly susceptible to clinically significant mitochondrial toxicity due to possible effects of HIV itself on mitochondria. At present there is no reliable method of detecting subclinical mitochondrial toxicity in patients exposed to NRTIs. Clinical awareness of this problem is therefore important to ensure the early detection of significant side effects and to allow timely consideration of changing therapy in those affected. There is no proven, effective therapy for NRTI-associated mitochondrial toxicity other than ceasing the implicated agent, and even with this strategy, resolution of symptoms may be incomplete. Similarly, there are no established methods for preventing mitochondrial toxicity in those on therapy including NRTIs. Micronutrients may have a role, but further study is needed to clarify optimal prevention as well as monitoring strategies.

Depletion of mitochondrial DNA copies/cell in peripheral blood mononuclear cells in HIV-1-infected treatment-naive patients

OBJECTIVES

Mitochondrial toxicity is believed to be the main reason for adverse effects related to nucleoside reverse transcriptase inhibitors (NRTIs). The aim of the present study was to compare mitochondrial toxicity in NRTI-treated HIV-positive patients, HIV-positive treatment-naïve patients and HIV-negative controls by comparing mitochondrial DNA (mtDNA) copies/cell in peripheral blood mononuclear cells (PBMCs) and lactate/pyruvate (L/P) ratios in the different groups.

METHODS

We enrolled 60 participants in the study: 31 patients on combined antiretroviral therapy (CART), 14 HIV-positive treatment-naive patients and 15 HIV-negative controls. mtDNA (copies/cell) in peripheral blood was analysed using quantitative real-time polymerase chain reaction (PCR). Standard curves and serial dilutions of plasmid-cloned mitochondrion and retinoblastoma (RB1) PCR products with known concentrations were generated to estimate the mtDNA and nuclear DNA (nDNA) copy numbers in each sample. The L/P ratio was enzymatically and spectrophotometrically analysed in samples from individuals in a fasted, non-exercise state. Results The median mtDNA copy number was 63 copies/cell (interquartile range 33-94) in HIV-positive patients and 153 (132-283) in HIV-negative controls (P<0.001). No significant difference was seen between the HIV-positive NRTI-exposed patients and the HIV-positive treatment-naive patients. Current use of didanosine was negatively correlated with depletion of mtDNA (r=-0.36, P=0.046). HIV-positive patients also had a higher L/P ratio compared with HIV-negative controls (P=0.004).

CONCLUSIONS

The number of mtDNA copies/cell in PBMCs was depleted in HIV-positive treatment-naive patients as well as in HIV-positive NRTI-exposed patients. HIV-positive patients also had a higher L/P ratio compared with HIV-negative controls, which supports this conclusion. The study suggests that neither mtDNA in PBMCs nor L/P ratio is a good marker of NRTI-associated mitochondrial toxicity.

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.

Effect of nucleoside reverse transcriptase inhibitors on mitochondrial DNA synthesis in rats and humans

Nucleoside reverse transcriptase inhibitors (NRTIs) have been hypothesized to inhibit mitochondrial DNA polymerase gamma, resulting in decreased mtDNA synthesis and mitochondrial insufficiency in HIV-1-infected patients. mtDNA synthesis was measured directly using a stable isotope mass spectrometric method following NRTI treatment in rodents. 3'-Azido-3'-deoxythymidine (AZT) was added to water (1 mg/mL) and administered ad libitum to female Sprague-Dawley rats for 1-8 weeks (n = 4 or 5 animals/timepoint). Neither body weight nor food intake was affected by AZT intake. Untreated controls and AZT-treated rats were given 4% H2O as drinking water for 2 weeks. AZT (approximately 100 mg/kg/d) produced a significant (P < 0.05) decrease in cardiac and hindlimb muscle mtDNA fractional synthesis compared with control groups (from 13.8 +/- 4.2% to 7.0 +/- 4.8% and from 7.6 +/- 1.8% to 4.5 +/- 0.4%, respectively) after 4 weeks. Cytochrome c oxidase content in hindlimb muscle was also decreased by 50% compared with controls after 4 weeks of AZT treatment (P < 0.07) and a calculated index of absolute mitochondrial biogenesis rate was significantly reduced by week 2 of AZT (P < 0.05) in hindlimb muscle. In preliminary studies, platelet mtDNA enrichments were compared to monocyte nDNA enrichments (used as a marker of a fully turned over tissue) in healthy human subjects. Fractional synthesis of mtDNA in platelets reached 98 +/- 3% after 5 weeks of H2O labeling. It is concluded that NRTIs decrease mtDNA synthesis and oxidative enzyme content and thus mitochondrial biogenesis in rodents and that the effects of NRTIs on mitochondrial biogenesis in tissues of HIV-1- infected humans can in principle be measured using this approach.

Plasma leptin levels in men are not related to the development of lipoatrophy during antiretroviral therapy

OBJECTIVES

To assess the correlations between the hormone leptin and lipoatrophy in HIV-positive, treatment-naive patients on combination antiretroviral therapy (cART).

DESIGN

Case-control study nested in a multicentre cohort of HIV-infected adults. Cases were patients that developed lipoatrophy and controls those who did not.

PATIENTS AND METHODS

Clinical parameters and plasma leptin determinations were studied in 97 HIV-1-infected, treatment-naive Caucasian men (10 cases and 87 controls) on an unchanged and virologically successful drug regimen with a zidovudine/lamivudine backbone at baseline and after 2 years of cART. The association of plasma leptin levels and the development of lipoatrophy was investigated.

RESULTS

Two years of cART was not associated with a change in plasma leptin levels. Plasma leptin levels remained sensible to changes in body mass index. There was no difference in leptin levels between patients who developed lipoatrophy and controls, neither before nor after cART. The only predictor of development of lipoatrophy was a higher age (P = 0.02).

CONCLUSIONS

Leptin as measured in plasma is unlikely to play a major role in the genesis of lipoatrophy.

Effect of treatment interruption monitored by CD4 cell count on mitochondrial DNA content in HIV-infected patients: a prospective study

BACKGROUND

HIV infection per se and HAART can alter mitochondrial functionality, leading to a decrease in mitochondrial DNA content.

OBJECTIVE

To evaluate whether treatment interruption monitored by CD4 cell count can restore mitochondrial DNA content in peripheral blood lymphocytes.

METHODS

Mitochondrial DNA content was measured in platelet-free CD4 and CD8 T cells by real-time polymerase chain reaction; flow cytometry was used to identify and quantify activated CD4 and CD8 T lymphocytes.

RESULTS

The 30 patients had been treated for a mean of 107 months (range, 27-197). Median CD4 cell count at discontinuation was 702 cells/microl (range, 547-798). Median observational time from HAART discontinuation was 11.3 months (range, 4-26). Discontinuation of treatment provoked significant increases in mitochondrial DNA in CD8 T cells, which started only 6 months after therapy discontinuation [5.12 copies/cell per month from 0 to 6 months (P = 0.37) and 26.96 copies/cell per month from 6 to 12 months (P < 0.0001)].

CONCLUSIONS

This study is the first showing that mitochondrial DNA content can increase in peripheral blood lymphocytes during treatment interruption, but only after at least 6 months of interruption. Consequently, interruptions of shorter periods, whether by clinician or patient decision, are unlikely to allow restoration of mitochondrial DNA and so decrease HAART-related toxicity.

Oxygen consumption by cultured human cells is impaired by a nucleoside analogue cocktail that inhibits mitochondrial DNA synthesis

We evaluated oxygen consumption rates in human cells cultured in the presence of a nucleoside analog reverse transcriptase inhibitor (NRTI) cocktail that inhibits mitochondrial DNA synthesis. We treated a proliferating human lymphocyte cell line and a primary culture of human adipose cells with antiretroviral drugs (AZT+ddC+d4T). The effects of these drugs on mitochondrial DNA (mtDNA) levels and oxygen consumption rates were evaluated using semi-quantitative real-time PCR and an on-line monitoring Clark electrode system. We found that the NRTI treatment lowered oxygen consumption rates and inhibited mitochondrial DNA replication in human cell cultures. Inhibition of oxygen consumption was linearly proportional to inhibition of mtDNA replication. These results show for the first time that mitochondrial respiration is impaired in NRTI sensitive cells. The linear relationship between NRTI inhibition of respiration and NRTI inhibition of mtDNA replication indicates that small decreases in mtDNA levels can lead to respiratory deficits in the tissues of patients treated with anti-HIV drugs. We propose a model that takes into account the small differences in metabolic dynamics between peripheral and axial/visceral fat tissues. This model explains how NRTI-related respiratory deficits may lead to the presentation of opposing lipodystrophic syndromes in same patient.

Redefining Lipodystrophy Syndrome

Lipodystrophy syndrome comprises several conditions (lipoatrophy; lipohypertrophy; mixed syndrome, often associated with dyslipidemia; and insulin resistance). These conditions, though sometimes occurring together, may occur independently, suggesting a complex, multifactorial cause. To elucidate the relative contribution of risk factors of drug, disease, and host to fat redistribution, large epidemiologic studies using multivariate analysis were reviewed. In studies assessing lipoatrophy, the most common statistically significant risk factors were use of specific nucleoside analogues, increasing age, presence of markers of disease severity (CD4/HIV RNA), duration of therapy, and white race. In studies assessing lipohypertrophy, the most common statistically significant risk factors were duration of therapy, markers of disease severity, and protease inhibitor use. The pathogenesis of these disorders is complex, but recent hypotheses and evidence suggest that impairment to adipocyte differentiation, impairment of adipokine regulation, unopposed production of proinflammatory cytokines, dysregulation of 11-beta-hydroxysteroid dehydrogenase, and mitochondrial toxicity may play a role.

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.

Regional differences in oxidative capacity of rat white adipose tissue are linked to the mitochondrial content of mature adipocytes

Two metabolic pathways of the white adipocytes (i.e. de novo lipogenesis and lipolysis) require mitochondria functionality. In this report, the oxidative capacity of two white adipose tissues of rat and their respective isolated adipocytes were evaluated. Two major white fat pads, namely inguinal and epididymal tissues, were chosen as subcutaneous and visceral adipose tissues, respectively. The mitochondrial content of these tissues was estimated using cytological and biochemical analysis. Electron microscopy analysis showed higher mitochondrial density in epididymal than in inguinal adipocytes. The mitochondrial DNA content and mitochondrial enzymatic equipment were also higher in the former than in the latter tissue. A positive correlation between two mitochondrial enzymatic activities, namely cytochrome c oxidase and citrate synthase, and the mtDNA content of adipose tissue was reported. Moreover, NRF1 protein, which belongs to the transcriptional activator family and is thought to be involved in mitochondrial biogenesis regulation, was present in higher proportions in nuclei isolated from epididymal cells than in those from inguinal cells. Finally, greater abundance of mitochondria in epididymal tissue is in agreement with higher cytochrome c oxidase activity as well as increased respiration (i.e. basal and noradrenaline-stimulated) of adipocytes isolated from epididymal tissue as compared to adipocytes isolated from inguinal tissue. Therefore, white adipose tissue appears as a heterogeneous organ with marked variation in mitochondrial content depending on its anatomical location.

Mitochondrial DNA depletion in adipose tissue of HIV-infected patients with peripheral lipoatrophy

BACKGROUND

NRTI-induced host toxicity is proposed to involve cellular mitochondrial DNA (mtDNA) depletion. Determinants of cellular mtDNA copy number from HIV-infected patients receiving HAART and HIV-seronegative controls were investigated from subcutaneous fat samples, and relation with antiretroviral regimen was studied.

STUDY DESIGN

HIV-infected patients receiving HAART (n = 50), HIV-infected patients not currently under HAART regimen (n = 2) and HIV-seronegative controls (n = 9) of similar age and BMI were enrolled prospectively when undergoing Coleman's lipostructure for correction of facial lipoatrophy or plastic surgery, respectively. After centrifugation, abdominal fat tissue was collected and stored at -80 degrees C. MtDNA analysis was blindly performed after a total DNA extraction from adipose tissue, followed by a real-time PCR quantification. The log of mtDNA copies/cell in adipose tissue [log(DNA)] was compared between groups by means of analysis of variance.

RESULTS

The log(DNA) in adipose tissue of HIV-infected patients was significantly lower than in the HIV-seronegative control group (P < 0.0001). In HIV-infected patients, log(DNA) was significantly reduced in the 50 NRTI-treated patients (P < 0.01), but not when considering mtDNA level according to the use of PI or NNRTI in current HAART regimen. In NRTI-treated patients, only stavudine (n = 20) and didanosine (n=14) were significantly and independently associated with reduced mtDNA level (P < 0.0001 and <0.05, respectively). Currently stavudine or didanosine-treated patients had a significant reduced mtDNA level compared to past users (P < 0.0001 and <0.05, respectively). Other clinical, biological, and immuno-virological variables than NRTI did not correlate significantly to adipocyte mtDNA level.

CONCLUSION

This study supports that current treatment by NRTI is a main determinant of mtDNA depletion in adipose tissue of HIV-seropositive patients with peripheral fat wasting. Stavudine or didanosine current intake is significantly associated with mtDNA depletion in vivo, that could be reversible after the discontinuation of these molecules, when considering mtDNA level according to current use versus past use of these molecules.

Reverse Transcriptase Inhibitors Alter Uncoupling Protein-1 and Mitochondrial Biogenesis in Brown Adipocytes

Objective

Human adipose depots contain remnant brown adipocytes interspersed among white adipocytes, and disturbances of brown with respect to white adipocyte biology have been implicated in highly active antiretroviral therapy (HAART)-induced lipo matosis. Brown adipocytes express the uncoupling protein-1 (UCP1) and contain a large number of mitochondria, potential targets of HAART toxicity. The aim of this study was to evaluate the effects of reverse transcriptase inhibitors (RTIs) on primary brown adipocytes differentiated in culture.

Design and methods

We analysed the effects of RTIs, nucleoside analogues (NRTIs: stavudine, zidovudine, didanosine and lamivudine) and non-nucleoside analogues (NNRTIs: nevirapine and efavirenz), on differentiation, mitochondrial biogenesis and gene expression in brown adipocytes.

Results

None of the NRTIs altered brown adipocyte differentiation whereas NNTRIs had differing effects. Efavirenz blocked lipid deposition and expression of adipose marker genes but nevirapine induced lipid accumulation and adipose gene expression, promoted mitochondrial biogenesis and increased UCP1. Stavudine, zidovudine and didanosine reduced mitochondrial DNA (mtDNA) content. However, mitochondrial genome expression was only impaired in didanosine-treated adipocytes. Stavudine, but not zidovudine, induced expression of the mitochondrial transcription factors and this may explain compensatory mechanisms for the depletion of mtDNA by up-regulating mtDNA transcription. Stavudine caused a specific induction of UCP1 gene expression through direct interaction with a retinoic acid-dependent pathway.

Conclusions

Specific disturbances in brown adipocytes in adipose depots may contribute to HAART-induced lipomatosis. Mitochondrial depletion does not appear to be the only mechanism explaining adverse effects in brown adipocytes because there is evidence of compensatory mechanisms that maintain mtDNA expression, and the expression of the UCP1 gene is specifically altered.

Therapeutic approaches to combating lipoatrophy: do they work?

Therapeutic strategies for combating HIV-associated lipodystrophy, and lipoatrophy in particular, have been a major focus of HIV clinical research. The initial impetus focused on protease inhibitor withdrawal strategies, which resulted in improved lipid profiles and insulin resistance but no change in subcutaneous or visceral adipose tissue. Nucleoside reverse transcriptase inhibitor withdrawal strategies, specifically withdrawal of thymidine analogues, have achieved greater success in the reversal of lipoatrophy. In particular, the MITOX extension study demonstrated a 35% improvement in limb fat over a 2 year period after a switch from a thymidine analogue to abacavir. However, recovery from lipoatrophy is a slow process, and limited access to and potential toxicities introduced by alternative therapies can limit switch strategies. The use of thiazolidinediones as agents to reverse lipoatrophy has, unfortunately, been shown to be ineffective, as have alternative therapeutic approaches with agents such as metformin, lipid-lowering agents and growth hormones. Although prevention of lipodystrophy may be the only definitive approach to combat this syndrome, the role of intermittent highly active antiretroviral therapy as a means of reducing the incidence, or slowing the development, of lipodystrophy is currently under evaluation.

Methodological Considerations in Human Studies of Gene Expression in HIV-Associated Lipodystrophy

In the majority of cases, HIV-associated lipodystrophy, lipoatrophy in particular, becomes clinically apparent only after months or years of continuous exposure to antiretroviral medications and, once developed, is difficult to reverse. Many lipid-related side effects of antiretroviral medications result from drug-induced changes in gene expression. As our understanding of the pathogenic mechanisms underlying HIV-associated lipodystrophy improves, it is important to be able to explore changes at a molecular level in order to fully elucidate the mechanisms whereby antiretroviral drugs exert their toxicities. Monitoring changes in gene expression in vivo may enable physicians to identify, predict or prevent drug toxicities early, before irreversible changes in body composition occur. However, monitoring changes in gene expression at a population level presents many methodological challenges that need to be addressed, over and above the considerable intra- and inter-individual variability inherent in the cellular expression of any gene. Careful collection and processing of adequate biological samples, robust laboratory processes and assays, and appropriate study design can help overcome many of these difficulties.

Mitochondrial Dna Levels of Peripheral Blood Mononuclear Cells and Subcutaneous Adipose Tissue from Thigh, Fat and Abdomen of HIV-1 Seropositive and Negative Individuals

Mitochondrial dysfunction has been demonstrated in subcutaneous adipose tissue from lipoatrophic HIV-1-infected patients treated with nucleoside reverse transcriptase inhibitors (NRTIs). To further assess mitochondrial toxicity, mitochondrial DNA (mtDNA) copies/cell were measured in subcutaneous fat from various sites. Peripheral adipose tissues were obtained from the abdominal wall near the umbilicus, anterior lateral thigh, and dorsal cervical region of the neck of individuals from four cohorts: 1) seven lipoatrophic HIV-1-infected patients receiving a regimen with nucleoside reverse transcriptase inhibitors (NRTIs) as part of highly active antiretroviral therapy (HAART) for >6 months; 2) seven non-lipoatrophic HIV-1-infected patients receiving NRTIs-containing HAART; 3) five HIV-1-infected patients on antiretroviral therapy <2 weeks (naive); 4) and five HIV-1-negative participants. Along with the adipose tissue samples, peripheral blood mononuclear cells (PBMC) were also obtained from each patient for mtDNA depletion examination. Total DNA was isolated and mtDNA copies/cell quantitated by competitive and realtime PCR. MtDNA copies/cell in abdomen, thigh, and neck fat were depleted in lipoatrophic HIV-1 seropositive compared to the seropositive naive and seronegative cohorts. MtDNA copies/cell in thigh and neck fat were also decreased in non-lipoatrophic subjects exposed to NRTIs compared with NRTI-naive and HIV seronegative controls. PBMC values did not differ among the cohorts and there was no correlation with lipoatrophy state or HIV-1 serostatus. Additionally, differences in mtDNA copies/cell were observed in the fat depots from seronegative subjects. Thigh fat mtDNA levels were 45–55% lower than abdomen and neck. These studies help demonstrate that mtDNA levels can vary in different subcutaneous adipose depots suggesting possible metabolic differences.

Lipodystrophy associated with highly active anti-retroviral therapy for HIV infection: the adipocyte as a target of anti-retroviral-induced mitochondrial toxicity

The lipodystrophy syndrome and associated metabolic alterations are the most prevalent adverse effects in HIV-infected patients taking highly active anti-retroviral therapy (HAART). This syndrome involves profound disturbances in adipose tissue. The toxic effect of nucleoside reverse transcriptase inhibitors on mitochondrial function is a major contributor to the lipodystrophy syndrome. Although adipocytes were not expected to be preferential targets of mitochondrial toxicity, recent re-evaluation of the role of mitochondria in white adipocytes helps to explain the molecular basis of HAART-associated lipodystrophy. Adipocytes are a source of paracrine and endocrine signals that influence adipocyte biology and systemic metabolism. Mitochondrial disturbances elicited by HAART result in an abnormal perception of the bioenergetic status by adipocytes, thus leading to enhancement of catalytic pathways and apoptosis in peripheral adipose tissue, alterations in the differentiation of brown versus white adipocytes, and the release of hormonal signals that lead to systemic metabolic disturbances.

Altered Mitochondrial Rna Production in Adipocytes from HIV-Infected Individuals with Lipodystrophy

Background

Damage to mitochondria (mt) is a major side effect of highly active antiretroviral therapy (HAART) that includes a nucleoside reverse transcriptase inhibitor (NRTI). Such damage is associated with the onset of lipodystrophy in HAART-treated HIV+ patients. To further investigate mt changes during this syndrome, we analysed the expression of mtRNA in adipocytes from lipodystrophic HIV+ patients taking NRTI-containing HAART and compared it with similar cells from healthy individuals.

Materials and methods

Total RNA was extracted from adipocytes collected from different anatomical locations of 11 HIV+ lipodystrophic patients and seven healthy control individuals. RNA was reverse transcribed and Taqman-based real-time PCR was used to quantify three different mt transcripts (ND1, CYTB and ND6 gene products). mtRNA content was normalized versus the housekeeping transcript L13.

Results

ND1, CYTB and ND6 expression was significantly reduced in HIV+ lipodystrophic patients. HIV+ men and women did not differ in a statistically significant way regarding the levels of ND1 and ND6, whereas the opposite occurred for CYTB.

Conclusions

Lipodystrophy following treatment with NRTI-containing HAART is associated with a decrease in adipose tissue mtRNAs.

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.

Possible Ways Nucleoside Analogues Can Affect Mitochondrial Dna Content and Gene Expression during HIV Therapy

In recent years, research into nucleoside reverse transcriptase inhibitor (NRTI)-related mitochondrial (mt) toxicity in HIV therapy has led to conflicting results and many unanswered questions regarding the molecular mechanisms that lead to such toxicity. From the early hypothesis that inhibition of the human mt polymerase γ by NRTIs was responsible for the drugs’ mt toxicity, an increasingly complex picture is emerging that probably involves multiple mt pathways. Results have been presented suggesting that NRTIs affect not only mtDNA but also mtRNA, nucleotide phosphorylation and the mt respiratory chain. Based on the current level of knowledge, this overview addresses some of the potential mechanisms through which NRTIs could affect mitochondria and ultimately cause the toxicity symptoms observed in HIV patients receiving NRTI-containing antiretroviral therapy.

Improvements in lipoatrophy, mitochondrial DNA levels and fat apoptosis after replacing stavudine with abacavir or zidovudine

OBJECTIVE

To determine if stavudine (alpha4T)-associated mitochondrial toxicity could be reversed by substitution with another nucleoside reverse transcriptase inhibitor. As apoptosis and dysfunction of electron transport chain (ETC) activities may underlie mitochondrial toxicity, these parameters were also evaluated.

DESIGN

The 16 participants (on d4T for >3 years; with lipoatrophy and/or hyperlactatemia) substituted abacavir or zidovudine for stavudine in their antiretroviral regimen. Key parameters including dual-energy X-ray absorptiometry (DEXA) scans, fat apoptosis, mitochondrial DNA (mtDNA) content in peripheral blood mononuclear cells (PBMC), skeletal muscle and fat, as well as skeletal muscle mitochondrial ETC activities were evaluated at study entry and at 48 weeks after the substitution.

METHODS

Quantitative PCR was used to evaluate mtDNA levels and the presence of deletions/rearrangements; CLIA-validated methods for ETC activities; terminal deoxynucleotidyl transferase dUTP-digoxigenin nick-end labeling assays to evaluate adipocyte apoptosis; and DEXA scans to measure changes in body fat.

RESULTS

MtDNA was depleted at study entry in muscle, adipose tissue and PBMC but levels rebounded with respective mean increases of 141%, 146%, and 369% at week 48. Corresponding fat improvements were noted with DEXA increases of 21%, 11%, and 16% in arm, leg, and trunk, respectively. Quantitative adipocyte apoptosis were significantly increased at baseline (P < 0.01 versus HIV-negative controls), with a significant reduction at week 48 (P < 0.05 versus baseline). Mean values for seven mitochondrial enzyme activities assays at entry indicated substantial loss of function (48% to 85% of controls) with significant improvement of complex I activity by week 48.

CONCLUSIONS

Substitution of stavudine with abacavir or zidovudine improves mitochondrial indices and fat apoptosis in the setting of lipoatrophy.

The HIV-1 nucleoside reverse transcriptase inhibitors stavudine and zidovudine alter adipocyte functions in vitro

OBJECTIVES

Nucleoside analogues are suspected of playing a role in peripheral fat loss in patients during long-term treatment with antiretroviral drugs.

DESIGN AND METHODS

We compared the long-term effects of stavudine (10 microM), zidovudine (1 muM), didanosine (10 microM), abacavir (4 microM), lamivudine (10 microM), and tenofovir (1 microM), near their maximum concentration values, on the differentiation, lipid accumulation, survival and mitochondrial function of differentiating 3T3-F442A and differentiated 3T3-L1 adipocytes.

RESULTS

None of the nucleoside reverse transcriptase inhibitors (NRTI) markedly altered the differentiation of 3T3-F442A cells, as shown by the unmodified percentage of cells with lipid droplets on day 7 and the expression of the early differentiation markers CCAAT/enhancer binding protein (C/EBP) beta (on day 2) and sterol regulatory element-binding protein. However, stavudine and zidovudine altered the lipid phenotype, decreasing the lipid content and expression of markers involved in lipid metabolism, namely C/EBPalpha, peroxisome proliferator-activated receptor gamma, adipocyte lipid binding protein 2, fatty acid synthase and acetyl-coenzyme A carboxylase. Stavudine and zidovudine, contrary to the other NRTI, drove 5-10% of 3T3-F442A cells towards apoptosis, and reduced the lipid content and survival of differentiated 3T3-L1 adipocytes. Stavudine and zidovudine increased mitochondrial mass by two to fourfold, and lowered the mitochondrial membrane potential (JC-1 stain) as did zalcitabine (0.2 microM). Co-treatment with zidovudine plus lamivudine, or zidovudine plus lamivudine and abacavir, did not increase the effect of zidovudine on cell viability or apoptosis.

CONCLUSION

The thymidine analogues stavudine and zidovudine decreased lipid content, mitochondrial activity, and adipocyte survival in vitro.

Acetyl-l-carnitine for the Treatment of HIV Lipoatrophy

Lipodystrophy is an increasingly recognized complication of antiretroviral therapy for human immunodeficiency virus (HIV) infection. This syndrome encompasses both fat accumulation and wasting, which may be accompanied by metabolic derangements in glucose and lipid metabolism. While the precise mechanism of its development is not fully understood, lipodystrophy may represent chronic mitochondrial toxicity due to antiretroviral therapy and/or chronic HIV infection. Treatment of this condition has proven difficult, prompting research into agents that promote fat metabolism and mitochondrial function. L-carnitine is a nonessential micronutrient that regulates fatty acid transport into the mitochondrial matrix for metabolism via beta-oxidation. HIV-infected individuals on antiretroviral therapy may become deficient in this cofactor, limiting mitochondrial fat metabolism. While studies have shown some benefit for carnitine supplementation in cardiovascular disease, mitochondrial myopathies, and possibly male infertility, the data for its use in HIV-infected individuals are limited. Given its known physiologic function and the hypothesized mitochondrial basis for lipodystrophy, carnitine supplementation for this antiretroviral toxicity is reviewed. The available data from several small studies are inconclusive, although further research into this promising agent is warranted.

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.

Mitochondrial effects of HIV infection on the peripheral blood mononuclear cells of HIV-infected patients who were never treated with antiretrovirals

To investigate the effects of HIV infection on mitochondrial DNA (mtDNA) content and other mitochondrial parameters, we used peripheral blood mononuclear cells (PBMCs) from 25 asymptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected patients and from 25 healthy control subjects. HIV-infected patients had significant decreases in mtDNA content (decrease, 23%; P<.05) and in the activities of mitochondrial respiratory chain (MRC) complex II (decrease, 41%; P<.001), MRC complex III (decrease, 38%; P<.001), MRC complex IV (decrease, 19%; P=.001), and glycerol-3-phosphate dehydrogenase (decrease, 22%; P<.001), along with increased lipid peroxidation of PBMC membranes (P=.007). Therefore, HIV infection is associated not only with mtDNA depletion, but also with extensive MRC disturbances and increased oxidative damage.