Mitochondrial function, morphology and metabolic parameters improve after switching from stavudine to a tenofovir-containing regimen

Dolutegravir-containing HIV therapy reversibly alters mitochondrial health and morphology in cultured human fibroblasts and peripheral blood mononuclear cells

OBJECTIVES

Given the success of combination antiretroviral therapy (cART) in treating HIV viremia, drug toxicity remains an area of interest in HIV research. Despite newer integrase strand transfer inhibitors (InSTIs), such as dolutegravir (DTG) and raltegravir (RAL), having excellent clinical tolerance, there is emerging evidence of off-target effects and toxicities. Although limited in number, recent reports have highlighted the vulnerability of mitochondria to these toxicities. The aim of the present study is to quantify changes in cellular and mitochondrial health following exposure to current cART regimens at pharmacological concentrations. A secondary objective is to determine whether any cART-associated toxicities would be modulated by human telomerase reverse transcriptase (hTERT).

METHODS

We longitudinally evaluated markers of cellular (cell count, apoptosis), and mitochondrial health [mitochondrial reactive oxygen species (mtROS), membrane potential (MMP) and mass (mtMass)] by flow cytometry in WI-38 human fibroblast with differing hTERT expression/localization and peripheral blood mononuclear cells. This was done after 9 days of exposure to, and 6 days following the removal of, seven current cART regimens, including three that contained DTG. Mitochondrial morphology was assessed by florescence microscopy and quantified using a recently developed deep learning-based pipeline.

RESULTS

Exposure to DTG-containing regimens increased apoptosis, mtROS, mtMass, induced fragmented mitochondrial networks compared with non-DTG-containing regimens, including a RAL-based combination. These effects were unmodulated by telomerase expression. All effects were fully reversible following removal of drug pressure.

CONCLUSION

Taken together, our observations indicate that DTG-containing regimens negatively impact cellular and mitochondrial health and may be more toxic to mitochondria, even among the generally well tolerated InSTI-based cART.

A Critical Review of the Biochemical Mechanisms and Epigenetic Modifications in HIV- and Antiretroviral-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a non-communicable disease characterised by a cluster of metabolic irregularities. Alarmingly, the prevalence of MetS in people living with Human Immunodeficiency Virus (HIV) and antiretroviral (ARV) usage is increasing rapidly. This study aimed to look at biochemical mechanisms and epigenetic modifications associated with HIV, ARVs, and MetS. More specifically, emphasis was placed on mitochondrial dysfunction, insulin resistance, inflammation, lipodystrophy, and dyslipidaemia. We found that mitochondrial dysfunction was the most common mechanism that induced metabolic complications. Our findings suggest that protease inhibitors (PIs) are more commonly implicated in MetS-related effects than other classes of ARVs. Furthermore, we highlight epigenetic studies linking HIV and ARV usage to MetS and stress the need for more studies, as the current literature remains limited despite the advancement in and popularity of epigenetics.

Mitochondrial oxidative phosphorylation in peripheral blood mononuclear cells is decreased in chronic HIV and correlates with immune dysregulation

Background

Cellular immunometabolism among people living with HIV (PLWH) on antiretroviral therapy (ART) remains under investigated. We assessed the relationships between mitochondrial oxidative phosphorylation (OXPHOS) in peripheral blood mononuclear cells (PBMCs) and blood parameters associated with HIV immune dysregulation.

Methods

PLWH ≥40 years old and on stable ART ≥3 months were enrolled (N = 149). OXPHOS complex I (CI, NADH dehydrogenase) and complex IV (CIV, cytochrome c oxidase) protein levels in PBMCs were quantified using immunoassays. Monocyte subsets and markers of T-cell activation, senescence, and exhaustion were measured on PBMC by flow cytometry. Plasma inflammatory mediators were quantified using a multiplex assay. HIV-uninfected group (N = 44) of similar age, gender, and ethnicity had available OXPHOS levels.

Results

PLWH had a median age of 51 years. Majority were male (88.6%), Caucasian (57.7%), and with undetectable plasma HIV RNA <50 copies/mL (84.6%). Median CI level was lower in PLWH compared with the HIV-seronegative group (65.5 vs 155.0 optical density/μg protein x 10³, p <0.0001). There was no significant difference in median CIV levels. Lower OXPHOS levels correlated with lower CD4% and CD4/CD8 ratio. On multivariable linear regression adjusted for age, current use of zidovudine/didanosine, and HIV RNA (detectable versus undetectable), lower OXPHOS levels were significantly associated with higher MPO, SAA, SAP, and sVCAM, and higher frequencies of intermediate (CD14⁺⁺CD16⁺) monocytes and TIGIT+TIM3+ CD4 T-cell (p<0.01).

Conclusion

CI PBMC protein levels were decreased in PLWH on ART. Decreased OXPHOS correlated with disease severity and inflammation. Further studies on the relationship between immunometabolism and immune dysregulation in HIV are warranted.

Viral Vector-Mediated Gene Transfer of Glutamic Acid Decarboxylase for Chronic Pain Treatment: A Literature Review

Chronic pain is long-lasting nociceptive state, impairing the patient's quality of life. Existing analgesics are generally not effective in the treatment of chronic pain, some of which such as opioids have the risk of tolerance/dependence and overdose death with higher daily opioid doses for increasing analgesic effect. Opioid use disorders have already reached an epidemic level in the United States; therefore, nonopioid analgesic approach and/or use of nonpharmacologic interventions will be employed with increasing frequency. Viral vector-mediated gene therapy is promising in clinical trials in the nervous system diseases. Glutamic acid decarboxylase (GAD) enzyme, a key enzyme in biosynthesis of γ-aminobutyric acid (GABA), plays an important role in analgesic mechanism. In the literature review, we used PubMed and bioRxiv to search the studies, and the eligible criteria include (1) article written in English, (2) use of viral vectors expressing GAD67 or GAD65, and (3) preclinical pain models. We identified 13 eligible original research articles, in which the pain models include nerve injury, HIV-related pain, painful diabetic neuropathy, and formalin test. GAD expressed by the viral vectors from all the reports produced antinociceptive effects. Restoring GABA systems is a promising therapeutic strategy for chronic pain, which provides evidence for the clinical trial of gene therapy for pain in the near future.

Bone metabolism dysfunction mediated by the increase of proinflammatory cytokines in chronic HIV infection

Despite the efficacy of antiretroviral therapy (ART) on the control of viral replication, the current challenge is to decrease the chronic inflammatory status and toxicity of the antiretroviral drugs that contribute to increase the risk of metabolic complications. To verify the influence of proinflammatory cytokines on bone metabolism mediated by chronic HIV infection, a cross-sectional study was conducted with 50 HIV-infected adult men treated or not treated with ART. Dual energy X-ray absorptiometry (DXA) was performed to assess bone mineral density. Biochemical analysis were performed of IL-6, TNF-α, osteocalcin, PTH, 25-OH-D, total calcium, albumin, 24 h urinary calcium, and urinary deoxypyridinoline. The participants not treated with ART exhibited higher values of IL-6 and TNF-α than the participants treated with ART for more than 2 years. The TNF-α values were higher in the participants treated with ART for <2 years than in participants treated with ART for more than 2 years (p < 0.05). The increased values of urinary deoxypyridinoline indicated a high reabsorptive activity of bone tissue in all groups, with a significant difference between the participants not treated with ART and the participants treated with ART for <2 years. Through the DXA we found a bone mass reduction in all bone sites in each group. The increase in production of proinflammatory cytokines, most notably in the viremic group, demonstrated the ability to stimulate osteoclast activity and subsequently affect bone mass. The reduction of bone mineral density was observed in all bone sites, principally for the groups receiving antiretroviral treatment.

Oxidative mitochondrial DNA damage in peripheral blood mononuclear cells is associated with reduced volumes of hippocampus and subcortical gray matter in chronically HIV-infected patients

Cross-sectional relationships were examined between regional brain volumes and mitochondrial DNA (mtDNA) 8-hydroxy-2-deoxyguanosine (8-oxo-dG) in peripheral blood mononuclear cells (PBMCs) of 47 HIV patients [mean age 51years; 81% with HIV RNA ≤50copies/mL] on combination antiretroviral therapy. The gene-specific DNA damage and repair assay measured mtDNA 8-oxo-dG break frequency. Magnetic resonance imaging was performed at 3T. Higher mtDNA 8-oxo-dG was associated with lateral ventricular enlargement and with decreased volumes of hippocampus, pallidum, and total subcortical gray matter, suggesting the involvement of systemic mitochondrial-specific oxidative stress in chronic HIV-related structural brain changes and cognitive difficulties. Clarification of the mechanism may provide potential therapeutic targets.

Clinical management of dyslipidaemia associated with combination antiretroviral therapy in HIV-infected patients

The introduction of potent combination antiretroviral therapy (cART) has had a remarkable impact on the natural history of HIV infection, leading to a dramatic decline in the mortality rate and a considerable increase in the life expectancy of HIV-positive people. However, cART use is frequently associated with several metabolic complications, mostly represented by lipid metabolism alterations, which are reported very frequently among persons treated with antiretroviral agents. In particular, hyperlipidaemia occurs in up to 70%-80% of HIV-positive subjects receiving cART and is mainly associated with specific antiretroviral drugs belonging to three classes of antiretroviral agents: NRTIs, NNRTIs and PIs. The potential long-term consequences of cART-associated dyslipidaemia are not completely understood, but an increased risk of premature coronary heart disease has been reported in HIV-infected patients on cART, so prompt correction of lipid metabolism abnormalities is mandatory in this population. Dietary changes, regular aerobic exercise and switching to a different antiretroviral regimen associated with a more favourable metabolic profile are the first steps in clinical management, but lipid-lowering therapy with fibrates or statins is often required. In this case, the choice of hypolipidaemic drugs should take into account the potential pharmacokinetic interactions with many antiretroviral agents.

The purine analogues abacavir and didanosine increase acetaminophen-induced hepatotoxicity by enhancing mitochondrial dysfunction

BACKGROUND

NRTIs are essential components of HIV therapy with well-documented, long-term mitochondrial toxicity in hepatic cells, but whose acute effects on mitochondria are unclear. As acetaminophen-induced hepatotoxicity also involves mitochondrial interference, we hypothesized that it would be exacerbated in the context of ART.

METHODS

We evaluated the acute effects of clinically relevant concentrations of the most widely used NRTIs, alone or combined with acetaminophen, on mitochondrial function and cellular viability.

RESULTS

The purine analogues abacavir and didanosine produced an immediate and concentration-dependent inhibition of oxygen consumption and complex I and III activity. This inhibition was accompanied by an undermining of mitochondrial function, with increased production of reactive oxygen species and reduction of mitochondrial membrane potential and intracellular ATP levels. However, this interference did not compromise cell survival. Co-administration with concentrations of acetaminophen below those considered hepatotoxic exacerbated the deleterious effects of both compounds on mitochondrial function and compromised cellular viability, showing a clear correlation with diminished glutathione levels.

CONCLUSIONS

The simultaneous presence of purine analogues and low concentrations of acetaminophen significantly potentiates mitochondrial dysfunction, increasing the risk of liver injury. This new mechanism is relevant given the liver's susceptibility to mitochondrial dysfunction-related toxicity and the tendency of the HIV infection to increase oxidative stress.

Distal leg epidermal nerve fiber density as a surrogate marker of HIV-associated sensory neuropathy risk: risk factors and change following initial antiretroviral therapy

Distal leg epidermal nerve fiber density (ENFD) is a validated predictor of HIV sensory neuropathy (SN) risk. We assessed how ENFD is impacted by initiation of first-time antiretroviral therapy (ART) in subjects free of neuropathy and how it is altered when mitochondrial toxic nucleoside medications are used as part of ART. Serial changes in proximal thigh and distal leg ENFD were examined over 72 weeks in 150 Thai subjects randomized to a regimen of stavudine (d4T) switching to zidovudine (ZDV) at 24 weeks vs ZDV vs tenofovir (TDF) for the entire duration of study, all given in combination with nevirapine. We found individual variations in ENFD change, with almost equal number of subjects who decreased or increased their distal leg ENFD over 72 weeks and no relationship to nucleoside backbone or to development of neuropathic signs or symptoms. Lower baseline distal leg ENFD and greater increases in mitochondrial oxidative phosphorylation complex I (CI) activity were associated with larger increases in distal leg ENFD over 72 weeks. Distal leg ENFD correlated with body composition parameters (body surface area, body mass index, height) as well as with blood pressure measurements. Assessed together with a companion cross-sectional study, we found that mean distal leg ENFD in all HIV+ subjects was lower than in HIV- subjects but similar among HIV+ groups whether ART-naïve or on d4T with/without neuropathy/neuropathic symptoms. The utility of ENFD as a useful predictor of small unmyelinated nerve fiber damage and neuropathy risk in HIV may be limited in certain populations.

Lipoprotein concentration, particle number, size and cholesterol efflux capacity are associated with mitochondrial oxidative stress and function in an HIV positive cohort

BACKGROUND

Association of lipoprotein particle size/number and HDL function with mitochondrial oxidative stress and function may underlie the excess cardiovascular (CVD) risk in HIV.

METHODS AND RESULTS

Among HIV infected individuals on stable highly active antiretroviral therapy, we related standard and novel lipid measures [plasma total cholesterol, triglycerides, HDL-C, LDL-C, lipoprotein particle (-P) subclass size and number and HDL function (via cholesterol-efflux capacity)] with oxidative stress [peripheral blood mononuclear cell's mitochondrial-specific 8-oxo-deoxyguanine (8-oxo-dG)] and function markers [oxidative phosphorylation (OXPHOS) NADH dehydrogenase (Complex I) and cytochrome c oxidase (Complex IV) enzyme activities]. Multivariable-adjusted logistic and linear regression analyses were employed adjusting for age, gender, CD4 nadir, viral load, smoking, diabetes, HOMA-IR, hypertension and lipid medications. Among 150 HIV-infected persons (mean age 52 years, 12% women, median CD4 count 524 cell/mm3), low HDL-C and high total cholesterol/HDL-C ratio were related to PBMC 8-oxo-deoxyguanine (p = 0.01 and 0.02 respectively). Large HDL-P and HDL-P size were inversely related to PBMC 8-oxo-deoxyguanine (p = 0.04). Small LDL-P (p = 0.01) and total LDL-P (p = 0.01) were related to decreased OXPHOS Complex I activity. LDL-P was related to decreased OXPHOS Complex IV activity (p = 0.02). Cholesterol efflux capacity was associated with increased OXPHOS Complex IV activity.

CONCLUSIONS

HDL concentration and particle size and number are related to decreased PBMC mitochondrial oxidative stress whereas HDL function is positively related to mitochondrial oxidative function. The association we find between atherogenic lipoprotein profile and increased oxidative stress and function suggests these pathways may be important in the pathogenesis of cardiometabolic disease in HIV disease.

HIV/AIDS and lipodystrophy: implications for clinical management in resource-limited settings

Introduction

Lipodystrophy is a term used to describe a metabolic complication of fat loss, fat gain, or a combination of fat loss and gain, which is associated with some antiretroviral (ARV) therapies given to HIV-infected individuals. There is limited research on lipodystrophy in low- and middle-income countries, despite accounting for more than 95% of the burden of HIV/AIDS. The objective of this review was to evaluate the prevalence, pathogenesis and prognosis of HIV-related lipoatrophy, lipohypertrophy and mixed syndrome, to inform clinical management in resource-limited settings.

Methods

We conducted a structured literature search using MEDLINE electronic databases. Relevant MeSH terms were used to identify published human studies on HIV and lipoatrophy, lipohypertrophy, or mixed syndrome in low-, low-middle- and upper-middle-income countries through 31 March 2014. The search resulted in 5296 articles; after 1599 studies were excluded (958 reviews, 641 non-human), 3697 studies were extracted for further review. After excluding studies conducted in high-income settings (n=2808), and studies that did not meet inclusion criteria (n=799), 90 studies were included in this review.

Results and Discussion

Of the 90 studies included in this review, only six were from low-income countries and eight were from lower middle-income economies. These studies focused on lipodystrophy prevalence, risk factors and side effects of antiretroviral therapy (ART). In most studies, lipodystrophy developed after the first six months of therapy, particularly with the use of stavudine. Lipodystrophy is associated with increased risk of cardiometabolic complications. This is disconcerting and anticipated to increase, given the rapid scale-up of ART worldwide, the increasing number and lifespan of HIV-infected patients on long-term therapy, and the emergence of obesity and non-communicable diseases in settings with extensive HIV burden.

Conclusions

Lipodystrophy is common in resource-limited settings, and has considerable implications for risk of metabolic diseases, quality of life and adherence. Comprehensive evidence-based interventions are urgently needed to reduce the burden of HIV and lipodystrophy, and inform clinical management in resource-limited settings.

Metabolic syndrome and the environmental pollutants from mitochondrial perspectives

The worldwide epidemic of diabetes and metabolic syndrome in the last few decades cannot be fully accounted for only by changes in the lifestyle factors, such as sedentary lifestyle and overeating. Besides genetic factors, there must be other causes to explain this rapid change. They could not be infectious in nature and induce insulin resistance as key biochemical abnormality. Mitochondrial dysfunction could be underlying mechanism behind the insulin resistance, thus metabolic syndrome. Then there have been increasing number of reports suggesting that chronic exposure to and accumulation of endocrine disrupting chemicals (EDCs), especially so-called the persistent organic pollutants (POPs) within the body might be associated with metabolic syndrome. Combining two concepts, we developed new "EDCs-induced mitochondrial dysfunction hypothesis of metabolic syndrome". In this review we suggest that classifying those chemicals into 5 groups might be clinically useful considering their removal or avoidance; POPs, non-persistent organic pollutants, heavy metals, air pollutants and drugs. We will also discuss briefly how those insights could be applied to clinical medicine.

Epidermal nerve fiber density, oxidative stress, and mitochondrial haplogroups in HIV-infected Thais initiating therapy

OBJECTIVE

We explored associations between mitochondrial DNA (mtDNA) haplogroups, epidermal nerve fiber density (ENFD), and HIV-associated sensory neuropathy (HIV-SN) in a randomized trial of Thai patients initiating antiretroviral therapy (ART).

DESIGN

The South East Asia Research Collaboration with Hawaii 003 study evaluated toxicity of nucleoside reverse transcriptase inhibitors (stavudine vs. zidovudine vs. tenofovir). We present secondary analyses of mtDNA haplogroups and ENFD changes.

METHODS

ENFD, peripheral blood mononuclear cell mitochondrial complex I and IV, and 8-oxo-deoxyguanine (8-oxo-dG) were quantified. Peripheral blood mononuclear cell mtDNA sequences were obtained for haplogroup determination. Multivariate regression of ENFD change was performed.

RESULTS

Paired ENFD was available from 118 patients. Median age, CD4 cell count, and height at entry were 34 years, 172 cells/μl, and 162 cm, respectively. Major haplogroups included M (42%), F (21%), and B (16%). Baseline ENFD, CD4 cell count, randomized ART, and biomarkers did not differ by haplogroup. Haplogroup B patients were older (P=0.02) at baseline, and had an increase in median ENFD (+1.5 vs. -2.9 fibers/mm; P=0.03) and 8-oxo-dG break frequency (+0.05 vs. 0.00; P=0.05) compared to other haplogroups. In a multivariate model, haplogroup B was associated with increased ENFD (β=3.5, P=0.009) at week 24, whereas older age (P=0.02), higher baseline CD4 cell count, (P=0.03), higher complex I level (P=0.03), and higher ENFD (P<0.001) at baseline were all associated with decreased ENFD. Three of the six HIV-SN cases were haplogroup B (P=0.05).

CONCLUSIONS

Thai persons belonging to mtDNA haplogroup B had increased ENFD and 8-oxo-dG on ART, and were more likely to develop HIV-SN. These results suggest that mtDNA variation influences early oxidative damage and ENFD changes.

Differentially altered molecular signature of visceral adipose tissue in HIV-1-associated lipodystrophy

OBJECTIVE

Lipodystrophy in HIV-1-infected antiretroviral-treated patients is often associated with opposite alterations in adipose tissue depots as follows: lipoatrophy of subcutaneous adipose tissue (SAT) versus lipohypertrophy of visceral adipose tissue (VAT). We determined the specific molecular alterations in VAT relative to SAT in patients.

DESIGN

We analyzed the expression of marker genes of mitochondrial function, adipogenesis, and inflammation in a unique collection of 8 biopsies of omental VAT from HIV-1-infected antiretroviral-treated patients with lipodystrophy. For comparison, we analyzed SAT from 10 patients, and SAT and VAT from 10 noninfected individuals.

METHODS

Quantitative real-time polymerase chain reaction of mitochondrial DNA and gene transcripts; immunoblot and multiplex for quantification of specific proteins.

RESULTS

Similar mitochondrial DNA depletion and abnormal increases in mitochondrial protein levels were found in VAT and SAT from patients. Transcript levels of adipogenesis and metabolism marker genes were unaltered in VAT but were decreased in SAT. Tumor necrosis factor α and CD68 were similarly induced in both adipose depots from patients, but other markers of inflammation-related pathways showed distinct alterations as follows: interleukin 18 and interleukin 1 receptor antagonist were induced only in SAT, whereas interleukin 6, interleukin 8, and monocyte chemoattractant protein 1 expression was reduced in VAT but not in SAT.

CONCLUSIONS

Mitochondrial alterations are similar in VAT and SAT from patients, whereas adipogenic gene expression is decreased in SAT but unaltered in VAT, highlighting the relevance of adipogenic processes in the differential alterations of fat depots. Specific disturbances in inflammatory status in VAT relative to SAT are present. Milder induction of proinflammatory signaling in VAT could be involved in preventing fat wasting in this depot.

Role of mitochondria in HIV infection and associated metabolic disorders: focus on nonalcoholic fatty liver disease and lipodystrophy syndrome

Highly active antiretroviral therapy (HAART) has considerably improved the prognosis of HIV-infected patients. However, prolonged use of HAART has been related to long-term adverse events that can compromise patient health such as HIV-associated lipodystrophy syndrome (HALS) and nonalcoholic fatty liver disease (NAFLD). There is consistent evidence for a central role of mitochondrial dysfunction in these pathologies. Nucleotide reverse transcriptase inhibitors (NRTIs) have been described to be mainly responsible for mitochondrial dysfunction in adipose tissue and liver although nonnucleoside transcriptase inhibitors (NNRTIs) or protease inhibitors (PIs) have also showed mitochondrial toxicity, which is a major concern for the selection and the long-term adherence to a particular therapy. Several mechanisms explain these deleterious effects of HAART on mitochondria, and evidence points to other mechanisms beyond the “Pol-γ hypothesis.” HIV infection has also direct effects on mitochondria. In addition to the negative effects described for HIV itself and/or HAART on mitochondria, HIV-infected patients are more prone to develop a premature aging and, therefore, to present an increased oxidative state that could lead to the development of these metabolic disturbances observed in HIV-infected patients.

NRTI backbone in HIV treatment: will it remain relevant?

Nucleoside reverse transcriptase inhibitors (NRTIs) remain a critical component of therapy for HIV-infected patients. The drugs are effective, relatively inexpensive and an important component of antiretroviral therapy (ART), particularly in areas where the introduction of effective therapy has been delayed. They are an essential part of initial therapy for HIV and for prevention of mother-to-child transmission; however, toxicities and resistance may limit their use. The role for pre-exposure prophylaxis (PrEP) to reduce sexual transmission of HIV is still undefined, but this use may have a significant impact on NRTI resistance worldwide, most particularly in areas where subtype C predominates. With increasing prevalence of resistant HIV, the approval of new agents that are effective against resistant virus, and those that use novel cellular targets, are essential. Large studies are now in progress examining the safety and efficacy of NRTI-sparing regimens, but results are not currently available. NRTIs may lose relevance in the not distant future unless steps are put in place to reduce the development and spread of NRTI-resistant viruses, and new NRTIs with minimal toxicity are developed that have a novel resistance profile. This article describes the principal NRTIs, their mechanism of action, and resistance and selected toxicities of the class and of the individual drugs.

Zidovudine/lamivudine but not nevirapine in combination with lopinavir/ritonavir decreases subcutaneous adipose tissue mitochondrial DNA

OBJECTIVE

No randomized study has prospectively followed subcutaneous adipose tissue mitochondrial DNA (mtDNA) changes when starting thymidine nucleoside reverse transcriptase inhibitors (tNRTIs).

DESIGN

The Metabolic Effects of DIfferent CLasses of AntiretroviralS study randomized HIV-positive, treatment-naive male participants to start lopinavir/ritonavir (LPVr) with either zidovudine/lamivudine (ZDV/3TC) or nevirapine (NVP).

METHODS

Regional body fat was assessed by dual energy x-ray absorptiometry and abdominal computed tomography at months 0, 3, 12, 24 and 36. In a molecular substudy, subcutaneous adipose tissue (SAT) biopsies were taken, with mtDNA quantified by quantitative PCR. Data were analyzed using repeated measures linear regression analyses.

RESULTS

Of 50 participants recruited (23 to LPVr/ZDV/3TC), 48 started therapy, and 37 participants (19 on LPVr/ZDV/3TC) enrolled in the substudy. At 36 months, the LPVr/ZDV/3TC group had significantly lower limb fat [6.4 kg (0.26) versus 7.3 kg (0.31), P = 0.017] and a trend toward lower abdominal SAT compared to the LPVr/NVP group [131 cm (6.86) versus 146 cm (6.33), P = 0.097]. Over 36 months, mtDNA declined in the LPVr/ZDV/3TC group [mtDNA region 1: -190 (95) copies/cell, P = 0.053, region 2: -269 (106) copies/cell, P = 0.016] but not within the LPVr/NVP group [region 1: +28 (99) copies/cell, P = 0.78, region 2: +51 (111) copies/cell, P = 0.65, between-group difference P < 0.01 for both measurements]. mtDNA was significantly lower in the LPVr/ZDV/3TC group at 36 months.

CONCLUSION

This is the first randomized study to prospectively demonstrate reductions in SAT mtDNA in patients initiating ZDV/3TC-containing antiretroviral therapy (ART) but not in those initiating nucleoside reverse transcriptase inhibitor-sparing ART containing NVP and protease inhibitor. That reductions in SAT mtDNA were also accompanied by lower limb fat suggests that use of ART not containing ZDV/3TC may help prevent development of peripheral lipoatrophy.

Quantification of mitochondrial toxicity in HIV-infected individuals by quantitative PCR compared to flow cytometry

BACKGROUND

Non-invasive diagnostic assays to evaluate mitochondrial toxicity could have significant clinical utility for HIV-infected individuals on antiretroviral therapy (ART).

METHODS

This study compared the ratio of mitochondrial to nuclear DNA determined by quantitative polymerase chain reaction (qPCR) to the ratio of mitochondrial to nuclear-encoded proteins by flow cytometry, in peripheral blood mononuclear cells from 73 HIV-infected individuals with and without risk factors for mitochondrial toxicity.

RESULTS

PCR detected similar mitochondrial/nuclear DNA in HIV-infected individuals without a history of ART, and those receiving ART with lipodystrophy, lipoatrophy, or a history of suspected lactic acidosis. However, the ratio was significantly greater in ART-untreated compared to those receiving either stavudine or didanosine. In contrast, flow cytometry did not detect any differences in mitochondrial/nuclear protein (Lin et al., Cytometry B 2009;76B:181-190). There was no correlation between the assays (rho = -0.05, P = 0.65).

CONCLUSIONS

Assessment of the mitochondrial/nuclear DNA ratio by qPCR performed better than the mitochondrial/nuclear-encoded protein ratio by flow cytometry to detect adverse effects of nucleoside analogs on mitochondria.

HIV-1 infection and first line ART induced differential responses in mitochondria from blood lymphocytes and monocytes: the ANRS EP45 "Aging" study

BACKGROUND

The ANRS EP45 "Aging" study investigates the cellular mechanisms involved in the accelerated aging of HIV-1 infected and treated patients. The data reported focus on mitochondria, organelles known to be involved in cell senescence.

METHODS

49 HIV-1 infected patients untreated with antiretroviral therapy, together with 49 seronegative age- and sex-matched control subjects and 81 HIV-1 infected and treated patients, were recruited by 3 AIDS centres (Marseille, Montpellier, Nice; France; http://clinicaltrials.gov/, NCT01038999). In more than 88% of treated patients, the viral load was <40 copies/ml and the CD4+ cell count was >500/mm(3). ROS (reactive oxygen species) production and ΔΨm (inner membrane potential) were measured by flow cytometry in blood lymphocytes and monocytes (functional parameters). Three mitochondrial network quantitative morphological parameters were computed using confocal microscopy and image analysis. Three PBMC mitochondrial proteins (porin and subunits 2 and 4 of cytochrome C oxidase encoded by mtDNA or nuclear DNA, respectively) were analysed by western blotting.

RESULTS

Quantitative changes in PBMC mitochondrial proteins were not induced by either HIV-1 infection or ART. Discriminant analysis integrating functional (ROS production and ΔΨm) or morphological (network volume density, fragmentation and branching) parameters revealed HIV-1 infection and ART differential effects according to cell type. First line ART tended to rescue lymphocyte mitochondrial parameters altered by viral infection, but induced slight changes in monocytes. No statistical difference was found between the effects of three ART regimens on mitochondrial parameters. Correlations between functional parameters and viral load confirmed the damaging effects of HIV-1 in lymphocyte mitochondria.

CONCLUSIONS

In patients considered to be clinically stable, mitochondria exhibited functional and morphological modifications in PBMCs resulting from either direct or indirect effects of HIV-1 infection (lymphocytes), or from first line ART (monocytes). Together with other tissue impairments, these changes may contribute to global aging.

Determinants of epidermal nerve fibre density in antiretroviral-naïve HIV-infected individuals

OBJECTIVES

Distal leg epidermal nerve fibre density (ENFD) is a validated predictor of small unmyelinated nerve fibre damage and neuropathy risk in HIV infection. As pre-existing damage may increase the risk of neuropathy following antiretroviral (ARV) therapy, particularly when the regimen contains stavudine (d4T), we assessed the relationship between ENFD and various parameters including mitochondrial factors in HIV-infected Thai individuals naïve to ARV therapy.

METHODS

Distal leg and proximal thigh ENFDs were quantified in HIV-infected Thai individuals without neuropathy prior to randomization to a HIV clinical trial that focused on mitochondrial toxicity issues. We assessed their association with various clinical and immunovirological parameters as well as with peripheral blood mononuclear cell (PBMC) mitochondrial (mt) DNA copies/cell, oxidative phosphorylation (OXPHOS) complex I (CI) and complex IV (CIV) enzyme activities, and mt 8-oxo-deoxyguanine (8-oxo-dG) break frequencies.

RESULTS

In 132 subjects, the median (interquartile range) ENFD (fibres/mm) values were 21.0 (16.2-26.6) for the distal leg and 31.7 (26.2-40.0) for the proximal thigh. By linear regression, lower CD4 count (P < 0.01), older age (P < 0.01), increased body mass index (BMI) (P = 0.04), increased height (P = 0.02), and higher PBMC OXPHOS activity as measured by CIV activity (P = 0.02) were associated with lower distal leg ENFD.

CONCLUSIONS

Older age, increased height, higher BMI, poorer immunological status and higher PBMC OXPHOS activity are associated with lower distal leg ENFD in HIV-infected subjects free of neuropathy prior to initiation of first-time ARV therapy.

Combination nucleoside/nucleotide reverse transcriptase inhibitors for treatment of HIV infection

INTRODUCTION

The combination of two nucleoside/nucleotide reverse transcriptase inhibitors (N(t)RTIs) and a third agent from another antiretroviral class is currently recommended for initial antiretroviral therapy. In general, N(t)RTIs remain relevant in subsequent regimens. There are currently six nucleoside reverse transcriptase inhibitors and one nucleotide reverse transcriptase inhibitor drug entities available, and several formulations that include two or more N(t)RTIs in a fixed-dose combination. These entities have heterogeneous pharmacological and clinical properties. Accordingly, toxicity, pill burden, dosing frequency, potential drug-drug interaction, preexisting antiretroviral drug resistance and comorbid conditions should be considered when constructing a regimen. This approach is critical in order to optimize virologic efficacy and clinical outcomes.

AREAS COVERED

This article reviews N(t)RTI combinations used in the treatment of HIV-infected adults. The pharmacological properties of each N(t)RTI, and the clinical trials that have influenced treatment guidelines are discussed.

EXPERT OPINION

It is likely that N(t)RTIs will continue to dominate the global landscape of HIV treatment and prevention, despite emerging interest in N(t)RTI-free combination therapy. Clinical domains where only few alternatives to N(t)RTIs exist include treatment of HIV/HBV coinfection and HIV-2. There is a need for novel N(t)RTIs with enhanced safety and resistance profiles compared with current N(t)RTIs.

Sex differences in urinary biomarkers of vascular and endothelial function in HIV-infected persons receiving antiretroviral therapy

BACKGROUND

Cardiovascular disease (CVD) risk can be underestimated in HIV-infected patients receiving antiretroviral therapy (ART). Novel CVD risk markers in this population are needed. We hypothesized that eicosanoid metabolite production is increased with metabolic complications of ART. Our objective was to determine relationships between urine eicosanoids and traditional CVD risk factors in a cohort of HIV-infected persons receiving ART.

METHODS

Cross-sectional analysis of 107 individuals from a prospective cohort study with urine eicosanoids (isoprostane [15-F(2t)-IsoP], prostaglandin-E metabolite [PGE-M], thromboxane metabolite [11dTxB(2)], prostacyclin metabolite [PGI-M]) determined by gas or liquid chromatography-mass spectrometry.

RESULTS

15-F(2t)-IsoP was higher (P=0.003), 11dTxB(2) tended to be higher (P=0.07) and PGE-M was lower (P=0.003) in females than in males. The overall median Framingham score was 4 (IQR 1-7). In multivariable analyses adjusting for age, CD4(+) T-cells, smoking status, non-steroidal anti-inflammatory drug use, aspirin use and body mass index (BMI), associations included: higher 15-F(2t)-IsoP with female sex (P=0.004) and current smoking (P=0.04), lower PGE-M with female sex (P=0.005) and higher BMI (P=0.03), higher 11dTxB(2) with increasing age (P=0.02) and current smoking (P=0.04), lower 11dTxB(2) with higher BMI (P=0.02), and higher PGI-M with current smoking (P=0.04).

CONCLUSIONS

In this pilot study of predominantly virologically suppressed HIV-infected individuals on ART, there were sex-specific differences in urinary eicosanoids, with females having more risk-associated parameters despite a low Framingham score. Eicosanoids might be useful CVD biomarkers in ART-treated, HIV-infected patients. Future studies should examine eicosanoids while assessing effects of specific ART regimens and targeted interventions on CVD outcomes.

Association of increased upper trunk and decreased leg fat with 2-h glucose in control and HIV-infected persons

OBJECTIVE

Changes in body fat distribution and abnormal glucose metabolism are common in HIV-infected patients. We hypothesized that HIV-infected participants would have a higher prevalence of impaired glucose tolerance (IGT) compared with control subjects.

RESEARCH DESIGN AND METHODS

A total of 491 HIV-infected and 187 control participants from the second examination of the Study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM) underwent glucose tolerance testing (GTT). Multivariable regression was used to identify factors associated with GTT parameters.

RESULTS

The prevalence of impaired fasting glucose (IFG) (>110 mg/dL) was similar in HIV-infected and control participants (21 vs. 25%, P = 0.23). In those without IFG, the prevalence of IGT was slightly higher in HIV-infected participants compared with control subjects (13.1 vs. 8.2%, P = 0.14) and in HIV+ participants with lipoatrophy versus without (18.1 vs. 11.5%, P = 0.084). Diabetes detected by GTT was rare (HIV subjects 1.3% and control subjects 0%, P = 0.65). Mean 2-h glucose levels were 7.6 mg/dL higher in the HIV-infected participants (P = 0.012). Increased upper trunk subcutaneous adipose tissue (SAT) and decreased leg SAT were associated with 2-h glucose and IGT in both HIV-infected and control participants. Adjusting for adipose tissue reduced the estimated effects of HIV. Exercise, alcohol use, and current tenofovir use were associated with lower 2-h glucose levels in HIV-infected participants.

CONCLUSIONS

In HIV infection, increased upper trunk SAT and decreased leg SAT are associated with higher 2-h glucose. These body fat characteristics may identify HIV-infected patients with normal fasting glucose but nonetheless at increased risk for diabetes.

Mitochondrial function, inflammation, fat and bone in HIV lipoatrophy: randomized study of uridine supplementation or switch to tenofovir

BACKGROUND

Lipoatrophy modestly improves when the thymidine analogue nucleoside reverse transcriptase inhibitor (tNRTI) is removed. In vitro, uridine (NucleomaxX(®); Pharma Nord, Vojens, Denmark) reversed tNRTI mitochondrial toxicity.

METHODS

All patients had lipoatrophy on a tNRTI-containing regimen with HIV RNA<400 copies/ml. A randomized 48-week study switched patients from tNRTI to tenofovir (TDF) or added uridine (continuing tNRTI). End points were changes in limb fat (DEXA), subcutaneous abdominal fat mitochondrial DNA (mtDNA) and mitochondrial RNA (mtRNA), inflammation markers (soluble tumour necrosis factor receptors, high-sensitivity C reactive protein [hsCRP], interleukin-6 [IL-6], soluble vascular cell adhesion molecule 1), bone mineral density (BMD) of the hip and spine, HIV-1 RNA, CD4(+) T-cells and fasting metabolic parameters.

RESULTS

Fifty patients were enrolled (n=24 TDF switch; n=26 uridine); median age 48 years; 54% white; 86% male; limb fat 4,494 g. Baseline characteristics were similar between groups. In the NucleomaxX(®) arm, mtRNA increased (all P<0.001), hsCRP and IL-6 increased (both P=0.02), whereas fat mtDNA decreased without changes in limb fat. In the TDF-switch arm, fat mtDNA and inflammation markers did not change; however, significant increases in mtRNAs (P<0.001), limb fat (409 g; IQR -59-1,155) and CD4(+) T-cell count (P=0.03), and decreases in total and hip BMD (median -3.3%; IQR -5.1-0; P=0.005) were observed. Between-group changes were significant for fat mtDNA, hsCRP, IL-6, limb fat and hip BMD. No correlation was found between changes in limb fat and those of fat mtRNA, inflammation markers or protease inhibitor duration.

CONCLUSIONS

In HIV lipoatrophy, NucleomaxX(®) improved mtRNA, but worsened inflammation markers and fat mtDNA without changes in limb fat. Switching from a tNRTI to TDF for 48 weeks increased limb fat and fat mtRNA. Large decreases in total and hip BMD were seen after TDF switch.
ClinicalTrials.gov identifier: NCT00119379.

Decreased mitochondrial DNA content in subcutaneous fat from HIV-infected women taking antiretroviral therapy as measured at delivery

BACKGROUND

Increasing numbers of pregnant HIV-positive women are receiving combination antiretroviral regimens for preventing mother-to-child virus transmission or for treating the infection itself. Several studies have demonstrated that nucleoside reverse transcriptase inhibitors (NRTIs) induce mitochondrial toxicity by several mechanisms, including depletion of mitochondrial DNA (mtDNA). By the quantification of mtDNA levels, we studied mitochondrial toxicity in HIV-positive women at delivery and the possible correlations with antiretroviral regimens, viroimmunological and metabolic parameters.

METHODS

We analysed 68 HIV-positive women enrolled in the Italian Prospective Cohort Study on Efficacy and Toxicity of Antiretroviral in Pregnancy (TARGET Study); all were taking ≥1 NRTI. We quantified mtDNA copies per cell in subcutaneous fat samples collected during delivery. At the 3rd, 6th and 9th month of pregnancy, we collected data concerning CD4(+) T-cell count, plasma HIV RNA, total and high-density lipoprotein (HDL) cholesterol, fasting plasma glucose and triglycerides. As a control, we analysed mtDNA levels in abdominal subcutaneous fat samples from 23 HIV-seronegative women at delivery.

RESULTS

mtDNA content was significantly lower in HIV-infected women when compared with HIV-negative controls. mtDNA content varied independently from viroimmunological, lipid and glucose parameters at the different months, with the exceptions of triglycerides at the 9th month and of HDL at the 6th month of pregnancy.

CONCLUSIONS

In subcutaneous tissue from women taking NRTI-based antiretroviral regimens, we observed a significant decrease of mtDNA content, compared with uninfected women not on antiviral treatment. Moreover, a significant correlation was noted between mtDNA content and HDL cholesterol and triglycerides.

Increased plasma levels of extracellular mitochondrial DNA during HIV infection: a new role for mitochondrial damage-associated molecular patterns during inflammation

HIV infection is characterized by a chronic inflammatory state. Recently, it has been shown that mitochondrial DNA (mtDNA) released from damaged or dead cells can bind Toll like receptor-9 (TLR9), an intracellular receptor that responds to bacterial or viral DNA molecules. The activation of TLR9 present within monocytes or neutrophils results in a potent inflammatory reaction, with the production of proinflammatory cytokines. We measured plasma levels of mtDNA in different groups of HIV(+) patients, i.e., those experiencing an acute HIV infection (AHI), long term non progressors (LTNP), late presenters (LP) taking antiretroviral therapy for the first time, and healthy controls. We found that in AHI and LP mtDNA plasma levels were significantly higher than in healthy individuals or in LTNP. Plasma mtDNA levels were not correlated to peripheral blood CD4(+) T cell count, nor to markers of immune activation, but had a significant correlation with plasma viral load, revealing a possible role for mtDNA in inflammation, or as a biomarker of virus-induced damage.

Insulin resistance in treated HIV infection

Insulin resistance (IR) was one of the first metabolic complications reported with highly active antiretroviral therapy for HIV infection. It continues to be of concern despite the introduction of newer antiretrovirals with safer metabolic profiles and is associated with inflammation and the development of diabetes mellitus. As the HIV-infected population ages, the prevalence of IR is likely to rise. Specific antiretrovirals can increase insulin resistance through two principal mechanisms, either directly by interfering with insulin signalling at the cellular level or indirectly as a consequence of defects in lipid metabolism (lipotoxocity) arising from antiretroviral toxicities such as the IR observed in those with HIV-associated lipodystrophy. There is considerable overlap between different antiretrovirals in their propensity to cause IR making it more difficult to attribute development of IR to a particular antiretroviral medication. In addition, in the setting of a generalised epidemic of obesity that exists in many populations worldwide, HIV-infected patients may be more prone to the consequences of antiretroviral-induced insulin resistance and diabetes mellitus. Optimal screening and treatment strategies for IR in treated HIV infection have not been established. In this article we review current opinion on insulin resistance in HIV and identify potential areas for future research.

Tenofovir-induced renal toxicity in 324 HIV-infected, antiretroviral-naïve patients

To better evaluate the renal safety profile of tenofovir, we performed a retrospective study of HIV-infected antiretroviral-naïve patients starting a first antiretroviral therapy between July 2004 and July 2008, and followed-up for 24 months. The glomerular filtration rate (GFR) was calculated using the MDRD formula, and tubular dysfunction was diagnosed with 2 or more of the following: proteinuria, glucosuria, hypouricemia, hypophosphatemia and hypokalemia. Overall, 324 patients were enrolled: 201 were tenofovir-exposed and were compared with 123 tenofovir-unexposed subjects. In both the unadjusted and adjusted analyses, tenofovir-exposed subjects had a significantly greater decline in GFR and a significantly higher incidence of proximal tubular dysfunction through 24 months. Reduced glomerular and tubular functions were significantly associated with older age, diabetes, hypertension and concomitant therapy with a protease inhibitor.

Impact of antiretroviral treatment on (13) C-methionine metabolism as a marker of hepatic mitochondrial function: a longitudinal study

OBJECTIVES

Uncontrolled viral replication and antiretroviral treatment (ART) may independently contribute to hepatic mitochondrial toxicity. The present study was designed to explore the longitudinal effects of treatment modifications on hepatic mitochondrial function by means of noninvasive (13) C-methionine breath test (MeBT) diagnostics.

METHODS

A total of 113 HIV-infected patients underwent two consecutive MeBTs over an interval of 11.8±3.5 months. Forty-nine patients remained on stable ART or no therapy; 28 participants switched ART; 27 patients (re)initiated ART, and nine individuals underwent a structured treatment interruption (STI) of ART between MeBTs 1 and 2. Breath test results were expressed as cumulative percentage dose of (13) CO(2) recovered after 1.5 h test time (cPDR(1.5h) ).

RESULTS

Initiation of ART in treatment-naïve individuals and patients on STI was associated with a significant improvement of hepatic mitochondrial function (P<0.05). Cessation of ART or a prolonged delay in initiating therapy in treatment-naïve patients in turn led to a significant decline of (13) C-exhalation compared with baseline (P<0.05). A marked increase in (13) C-exhalation was observed in individuals who switched from stavudine or ddI to tenofovir or abacavir (+170%; P<0.001), while no differences between MeBTs 1 and 2 were found in individuals on ART who had remained on stable regimens or in those who changed a protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor (NNRTI) component.

CONCLUSION

The present data suggest that hepatic mitochondrial function in HIV disease is a dynamic process with a high regenerative capacity and highlight the pathogenic relevance of HIV replication. Our findings suggest that modern ART per se does not negatively impact hepatic mitochondrial function.

Mitochondrial damage in adipose tissue of untreated HIV-infected patients

OBJECTIVE

antiretrovirals, especially thymidine-analogue nucleoside reverse transcriptase inhibitors (tNRTIs), may cause the mitochondrial damage in adipose tissue that has been associated with lipodystrophy development. HIV itself may damage blood cell mitochondria. However, the viral capacity to induce adipose tissue mitochondrial lesion is still a matter of doubt. We aimed to assess whether untreated HIV infection was associated with adipose tissue mitochondrial abnormalities.

DESIGN

: Single-site, cross-sectional, controlled observational and exploratory study without intervention.

METHODS

we included 24 uninfected controls and 18 HIV-infected patients with undetectable viral load and no clinical signs of lipodystrophy stratified as antiretroviral naive (n = 11) or at least 6-month antiviral-treated with a double NRTI combination, including lamivudine plus one tNRTI (n = 7). Subcutaneous adipose tissue was homogenated to determine mtDNA content by rtPCR and mitochondrial function per mitochondria through the spectrophotometric measurement of cytochrome c oxidase activity normalized by citrate synthase amount (COX/citrate synthase). Differences in mitochondrial parameters among groups were sought to determine the contribution of HIV and antiretrovirals to mitochondrial alterations.

RESULTS

compared with uninfected controls (arbitrarily assigned 100%), naive individuals presented a marked decrease in adipose tissue mtDNA content and COX/citrate synthase function (62 and 75% remaining content/activity, P < 0.001 and P < 0.05). Antiretrovirals did not increase this impairment (69 and 70% remaining content/activity, P < 0.05 compared to controls and P = not significant compared to naives). Additionally, molecular and functional mitochondrial parameters were positively correlated (P < 0.05).

CONCLUSION

in nonlipodystrophic HIV-infected naive patients, viral infection is associated with adipose tissue mtDNA decrease and mitochondrial dysfunction independently of antiretroviral treatment.

Impact of NRTIs on lipid levels among a large HIV-infected cohort initiating antiretroviral therapy in clinical care

OBJECTIVE

to assess the associations between nucleoside reverse transcriptase inhibitors (NRTIs) and change in lipid levels among a large cohort of HIV-infected patients in routine clinical care initiating their first potent antiretroviral regimen.

DESIGN

longitudinal observational cohort study from the Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort.

METHODS

we used generalized estimating equations to examine the association between NRTIs and lipids accounting for within-patient correlations between repeated measures and key clinical and demographic characteristics including other antiretroviral medications.

RESULTS

among 2267 individuals who started their first antiretroviral regimen, tenofovir with emtricitabine or lamivudine was associated with lower levels for total cholesterol, low-density lipoprotein (LDL), triglycerides, non-high-density lipoprotein (HDL), and HDL, compared with other NRTI pairs in adjusted analyses. LDL levels were highest among patients receiving didanosine/lamivudine. Triglyceride levels were highest in stavudine/lamivudine users. HDL levels were highest among patients receiving didanosine/stavudine. Hepatitis C infection and younger age were also associated with lower lipid levels.

CONCLUSION

we found clinically important heterogeneity within the NRTI class of antiretroviral medications regarding their effect on lipid levels over time. Although the lipid profile of tenofovir with emtricitabine or lamivudine appeared to be less pro-atherogenic in this large longitudinal study of HIV-infected patients in routine clinical care, there was no association with beneficial HDL levels. In general, the change in lipid levels associated with most antiretroviral agents, particularly those NRTI combinations currently in common use, are relatively modest. Additional studies are needed to understand the long-term implications of these findings on cardiovascular disease risk.

Aging, human immunodeficiency virus, and bone health

Highly active antiretroviral therapy (HAART) has had a profound impact on improving the long-term prognosis for individuals infected with human immunodeficiency virus (HIV). HAART has been available for close to two decades, and now a significant number of patients with access to HAART are over the age of 50 years. Many clinical studies have indicated that HIV infection, as well as components of HAART, can increase the risk in these individuals to a variety of noninfectious complications, including a risk to bone health. There is a significant need for detailed mechanistic analysis of the aging, HIV-infected population regarding the risk of HIV infection and therapy in order to maintain bone health. Insights from basic mechanistic studies will help to shed light on the role of HIV infection and the components of HAART that impact bone health, and will help in identifying preventative countermeasures, particularly for individuals 50 years of age and older.

Tenofovir-associated bone density loss

Clinical observations have revealed a strong correlation between loss of bone density in HIV-infected individuals, particularly in conjunction with the antiretroviral drug tenofovir, a nucleotide analog that inhibits HIV reverse transcriptase. The most compelling correlations have been observed in clinical studies involving young children and adolescents. These observations strongly suggest that bone density is being affected during active bone growth and development, implicating a role for tenofovir in bone loss. Here we discuss the literature and potential mechanisms for how tenofovir-associated bone loss may arise, which likely involves perturbation of cellular DNA synthesis and gene expression. Elucidation of the mechanism(s) involved in tenofovir-mediated bone loss will help in developing adjuvant therapies to reduce tenofovir-associated bone density loss.

Mitochondrial dysfunction and metabolic syndrome-looking for environmental factors

The centerpiece of the pathophysiologic mechanism of metabolic syndrome is insulin resistance. Recently, it is becoming evident that mitochondrial dysfunction is closely related to insulin resistance and metabolic syndrome. The underlying mechanism of mitochondrial dysfunction is very complex, which includes genetic factors from both nuclear and mitochondrial genome and numerous environmental factors. Several mitochondrial DNA polymorphisms are associated with the components of metabolic syndrome. Numerous chemicals and drugs may cause mitochondrial dysfunction and insulin resistance. Notably, it was recently reported that serum levels of several mitochondrial toxins, such as persistent organic pollutants are associated with metabolic syndrome, which necessitates further investigation to reveal its precise mechanism. Given that the health impact of metabolic syndrome is tremendous, it is necessary to develop therapeutic modalities to correct mitochondrial dysfunction or at least to halt its aggravation. In this regard, exercise can improve both mitochondrial function and insulin sensitivity, and some pharmaceutical agents were reported to improve mitochondrial function. However, further studies are warranted to find more effective therapeutic strategies to treat mitochondrial dysfunction. By doing so, we can also shed light on the path of research for other diseases related to mitochondrial dysfunction.