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

HIV and adipose tissue: A long history linked to therapeutic classes of antiretrovirals

HIV infection has been controlled only since the introduction of triple therapy in 1996, combining, as antiretroviral agents, two nucleoside reverse transcriptase inhibitors (NRTIs) and one protease inhibitor (PI). However, among the NRTIs, the thymidine analogues stavudine and zidovudine led to lipoatrophy, either generalized or associated with visceral fat hypertrophy and buffalo hump. These molecules also increased insulin resistance and the prevalence of diabetes. They were replaced by other NRTIs or non-NRTIs (NNRTIs) that were considered to be free of adipose tissue (AT) toxicity. More recently, the NRTI tenofovir disoproxyfumarate (TDF) and the NNRTI efavirenz have been associated with inhibition of fat gain but not with clear lipoatrophy. Otherwise, the use of PIs led to a phenotype of trunk fat hypertrophy associated with cardiometabolic complications. To avoid their adverse effects, PIs have recently been replaced by a new class of antiretrovirals, the integrase inhibitors (INSTIs), which are well tolerated and effective in controlling HIV. However, this class has been associated with global weight gain, which may be important and concerning for some people living with HIV (PWH). Also, in the NRTI class, TDF has often been replaced by tenofovir alafenamide (TAF) due to bone and renal toxicities, and TAF has been associated with global fat gain. The cardiometabolic consequences of INTIs and TAF are primarily related to the associated weight gain. In the global obesogenic worldwide context, PWH are gaining weight as well in relation to poor health life conditions. Taking in charge obesity uses the same strategies as those used in the general population.

Pathophysiology and Clinical Management of Dyslipidemia in People Living with HIV: Sailing through Rough Seas

Infections with human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) represent one of the greatest health burdens worldwide. The complex pathophysiological pathways that link highly active antiretroviral therapy (HAART) and HIV infection per se with dyslipidemia make the management of lipid disorders and the subsequent increase in cardiovascular risk essential for the treatment of people living with HIV (PLHIV). Amongst HAART regimens, darunavir and atazanavir, tenofovir disoproxil fumarate, nevirapine, rilpivirine, and especially integrase inhibitors have demonstrated the most favorable lipid profile, emerging as sustainable options in HAART substitution. To this day, statins remain the cornerstone pharmacotherapy for dyslipidemia in PLHIV, although important drug-drug interactions with different HAART agents should be taken into account upon treatment initiation. For those intolerant or not meeting therapeutic goals, the addition of ezetimibe, PCSK9, bempedoic acid, fibrates, or fish oils should also be considered. This review summarizes the current literature on the multifactorial etiology and intricate pathophysiology of hyperlipidemia in PLHIV, with an emphasis on the role of different HAART agents, while also providing valuable insights into potential switching strategies and therapeutic options.

Prevalence and risk factors of metabolic syndrome in Ethiopia: describing an emerging outbreak in HIV clinics of the sub-Saharan Africa - a cross-sectional study

OBJECTIVES

HIV-induced chronic inflammation, immune activation and combination antiretroviral therapy (cART) are linked with adverse metabolic changes known to cause cardiovascular adversities. This study evaluates the prevalence of lipodystrophy, and metabolic syndrome (MetS), and analyses risk factors in HIV-infected Ethiopians taking cART.

METHODS

A multicentre cross-sectional study was conducted at tertiary-level hospitals. Eligible participants attending the HIV clinics were enrolled. Sociodemographic, anthropometric, clinical, HIV treatment variables, lipid profile, fasting blood glucose level, risk factors and components of MetS, also lipodystrophy, were studied. Data were analysed by SPSS statistical package V.25 with descriptive and analytical statistics. For multivariable analysis of risk factors, a logistic regression model was used. Results were presented in frequency and percentages, mean±SD, or median+IQR. Statistical significance was taken as p<0.05.

RESULTS

Among 518 studied participants, two-thirds were females, and the mean age of the study population was 45 years (SD=11). The mean duration of cART was 10 years (SD=4). Median CD4 count was 460 cells/mm3. The prevalence of MetS according to the Adult Treatment Panel III (2005) criteria was 37.6%. In multivariable analysis, independent risk factors for MetS were age >45 years (aHR 1.8, 95% CI 1.2 to 2.4), female sex (aHR 1.8, 95% CI 1.1 to 2.8), body mass index (BMI)>25 kg/m2 (aHR 2.7, 95% CI 1.8 to 4.1), efavirenz-based cART (aHR 2.8, 95% CI 1.6 to 4.8) and lopinavir/ritonavir-based cART (aHR 3.7, 95% CI 1.0 to 13.3). The prevalence of lipodystrophy was 23.6%. Prior exposure to a stavudine-containing regimen was independently associated with lipodystrophy (aHR 3.1, 95% CI 1.6 to 6.1).

CONCLUSION

Our study revealed 38% of the participants had MetS indicating considerable cardiovascular disease (CVD) risks. Independent risk factors for MetS were BMI≥25 kg/m2, efavirenz and lopinavir/ritonavir-based cART, female sex and age ≥45 years. In addition to prevention, CVD risk stratification and management will reduce morbidity and mortality in people with HIV infection.

The Influence of Nucleoside Reverse Transcriptase Inhibitors on Mitochondrial Activity, Lipid Content, and Fatty-Acid-Binding Protein Levels in Microglial HMC3 Cells

Despite the availability of a wide range of preventive measures and comprehensive treatment options following infection, the development of acquired immunodeficiency syndrome (AIDS) remains a persistent challenge. Nucleoside reverse transcriptase inhibitors (NRTIs) represent the most commonly utilized therapeutic approach, despite being on the pharmaceutical market for nearly four decades. During this time, a spectrum of side effects ranging from mild discomfort and hypersensitivity reactions to the more prevalent nephrotoxicity and hepatotoxicity has been documented. In light of these considerations, our study aimed to investigate the impacts of two NRTIs, lamivudine and zidovudine, on lipid metabolism in HMC3 microglial cells. Our findings revealed statistically significant reductions in the ATP levels (nearly 8%) and increased mitochondrial superoxide levels (around 10%) after 24 h of treatment with the maximum therapeutic concentration of zidovudine compared to the untreated microglial cells. Furthermore, the concentrations of fatty-acid-binding proteins 4 and 5 were significantly lower (approximately 40%) in the microglial cells that were exposed to NRTIs than in the untreated cells. Notably, the total lipid concentration within the microglial cells markedly increased following NRTI administration with a 13% rise after treatment with 10 µM lamivudine and a remarkable 70% surge following the administration of 6 µM zidovudine. These results suggest that the prolonged administration of NRTIs may potentially lead to lipid accumulation, posing a significant risk to the delicate homeostasis of the neuronal system and potentially triggering a pro-inflammatory response in microglial cells.

Azidothymidine Downregulates Insulin-Like Growth Factor-1 Induced Lipogenesis by Suppressing Mitochondrial Biogenesis and Mitophagy in Immortalized Human Sebocytes

Background

Increased sebum secretion is considered the main causative factor in the pathogenesis of acne. There is an unmet pharmacological need for a novel drug that can control sebum production with a favorable adverse effect profile.

Objective

To investigate the effect of azidothymidine on lipid synthesis in sebocytes and to identify the underlying mechanism of the inhibitory effect of azidothymidine on insulinlike growth factor (IGF)-1-induced lipid synthesis in sebocytes.

Methods

Immortalized human sebocytes were used for the analysis. Thin-layer chromatography (TLC) and Oil Red O staining were performed to evaluate lipid synthesis in the sebocytes. The differentiation, lipid synthesis, mitochondrial biogenesis, and mitophagy in sebocytes were investigated.

Results

TLC and Oil Red O staining revealed that azidothymidine reduced IGF-1 induced lipid synthesis in the immortalized human sebocytes. Azidothymidine also reduced IGF-1-induced expression of transcriptional factors and enzymes involved in sebocyte differentiation and lipid synthesis, respectively. Moreover, we found that IGF-1 upregulated the levels of peroxisome proliferator-activated receptorgamma coactivator-1α, LC-3B, p62, and Parkin, major regulators of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. In contrast, azidothymidine inhibited IGF-1 induced mitochondrial biogenesis and mitophagy in the sebocytes.

Conclusion

These results suggest that azidothymidine downregulates IGF-1-induced lipogenesis by dysregulating the quality of mitochondria through suppression of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. Our study provides early evidence that azidothymidine may be an effective candidate for a new pharmacological agent for controlling lipogenesis in sebocytes.

Chronic binge alcohol and ovariectomy dysregulate omental adipose tissue metaboproteome in simian immunodeficiency virus-infected female macaques

Effective antiretroviral therapy (ART) has significantly reduced mortality of people living with HIV (PLWH), and the prevalence of at-risk alcohol use is higher among PLWH. Increased survival and aging of PLWH is associated with increased prevalence of metabolic comorbidities especially among menopausal women, and adipose tissue metabolic dysregulation may be a significant contributing factor. We examined the differential effects of chronic binge alcohol (CBA) administration and ovariectomy (OVX) on the omental adipose tissue (OmAT) proteome in a subset of simian immunodeficiency virus (SIV)-infected macaques of a longitudinal parent study. Quantitative discovery-based proteomics identified 1,429 differentially expressed proteins. Ingenuity Pathway Analysis (IPA) was used to calculate z-scores, or activation predictions, for functional pathways and diseases. Results revealed that protein changes associated with functional pathways centered around the "OmAT metaboproteome profile." Based on z-scores, CBA did not affect functional pathways of metabolic disease but dysregulated proteins involved in adenosine monophosphate-activated protein kinase (AMPK) signaling and lipid metabolism. OVX-mediated proteome changes were predicted to promote pathways involved in glucose- and lipid-associated metabolic disease. Proteins involved in apoptosis, necrosis, and reactive oxygen species (ROS) pathways were also predicted to be activated by OVX and these were predicted to be inhibited by CBA. These results provide evidence for the role of ovarian hormone loss in mediating OmAT metaboproteome dysregulation in SIV and suggest that CBA modifies OVX-associated changes. In the context of OVX, CBA administration produced larger metabolic and cellular effects, which we speculate may reflect a protective role of estrogen against CBA-mediated adipose tissue injury in female SIV-infected macaques.

Hepatic Steatosis and Ectopic Fat Are Associated With Differences in Subcutaneous Adipose Tissue Gene Expression in People With HIV

Persons with human immunodeficiency virus (PWH) have subcutaneous adipose tissue (SAT) dysfunction related to antiretroviral therapy and direct viral effects, which may contribute to a higher risk of nonalcoholic fatty liver disease compared with human immunodeficiency virus-negative individuals. We assessed relationships between SAT expression of major adipocyte regulatory and lipid storage genes with hepatic and other ectopic lipid deposits in PWH. We enrolled 97 PWH on long-term antiretroviral therapy with suppressed plasma viremia and performed computed tomography measurements of liver attenuation, a measure of hepatic steatosis, skeletal muscle (SM) attenuation, and the volume of abdominal subcutaneous, visceral, and pericardial adipose tissue. Whole SAT gene expression was measured using the Nanostring platform, and relationships with computed tomography imaging and fasting lipids were assessed using multivariable linear regression and network mapping. The cohort had a mean age of 47 years, body mass index of 33.4 kg/m2, and CD4 count of 492 cells/mm3. Lower liver attenuation, a marker of greater steatosis, was associated with differences in SAT gene expression, including lower lipoprotein lipase and acyl-CoA dehydrogenase, and higher phospholipid transfer protein. Lower liver attenuation clustered with lower visceral adipose tissue (VAT) attenuation and greater VAT volume, pericardial fat volume and triglycerides, but no relationship was observed between liver attenuation and SAT volume, SM attenuation, or low-density lipoprotein. Conclusion: Liver attenuation was associated with altered SAT expression of genes regulating lipid metabolism and storage, suggesting that SAT dysfunction may contribute to nonalcoholic fatty liver disease in PWH. SAT gene-expression relationships were similar for VAT volume and attenuation, but not SM, indicating that ectopic lipid deposition may involve multiple pathways.

Contribution of Adipose Tissue to the Chronic Immune Activation and Inflammation Associated With HIV Infection and Its Treatment

White adipose tissue (AT) contributes significantly to inflammation – especially in the context of obesity. Several of AT’s intrinsic features favor its key role in local and systemic inflammation: (i) large distribution throughout the body, (ii) major endocrine activity, and (iii) presence of metabolic and immune cells in close proximity. In obesity, the concomitant pro-inflammatory signals produced by immune cells, adipocytes and adipose stem cells help to drive local inflammation in a vicious circle. Although the secretion of adipokines by AT is a prime contributor to systemic inflammation, the lipotoxicity associated with AT dysfunction might also be involved and could affect distant organs. In HIV-infected patients, the AT is targeted by both HIV infection and antiretroviral therapy (ART). During the primary phase of infection, the virus targets AT directly (by infecting AT CD4 T cells) and indirectly (via viral protein release, inflammatory signals, and gut disruption). The initiation of ART drastically changes the picture: ART reduces viral load, restores (at least partially) the CD4 T cell count, and dampens inflammatory processes on the whole-body level but also within the AT. However, ART induces AT dysfunction and metabolic side effects, which are highly dependent on the individual molecules and the combination used. First generation thymidine reverse transcriptase inhibitors predominantly target mitochondrial DNA and induce oxidative stress and adipocyte death. Protease inhibitors predominantly affect metabolic pathways (affecting adipogenesis and adipocyte homeostasis) resulting in insulin resistance. Recently marketed integrase strand transfer inhibitors induce both adipocyte adipogenesis, hypertrophy and fibrosis. It is challenging to distinguish between the respective effects of viral persistence, persistent immune defects and ART toxicity on the inflammatory profile present in ART-controlled HIV-infected patients. The host metabolic status, the size of the pre-established viral reservoir, the quality of the immune restoration, and the natural ageing with associated comorbidities may mitigate and/or reinforce the contribution of antiretrovirals (ARVs) toxicity to the development of low-grade inflammation in HIV-infected patients. Protecting AT functions appears highly relevant in ART-controlled HIV-infected patients. It requires lifestyle habits improvement in the absence of effective anti-inflammatory treatment. Besides, reducing ART toxicities remains a crucial therapeutic goal.

Association of Male Sex and Obesity With Residual Plasma Human Immunodeficiency Virus 1 Viremia in Persons on Long-Term Antiretroviral Therapy

BACKGROUND

Although adipose tissue has been proposed to harbor part of the human immunodeficiency virus 1 (HIV-1) reservoir, the influence of host characteristics, including sex and body mass index (BMI), on measures of HIV-1 persistence during antiretroviral therapy (ART) are incompletely understood.

METHODS

We evaluated age, sex, BMI, waist circumference, years on ART, pre-ART HIV-1 RNA, pre-ART CD4+ T-cell count, and initial ART regimen with measures of HIV-1 persistence in blood (residual viremia, cellular HIV-1 DNA and RNA) in a cohort of 295 individuals with well-documented long-term virologic suppression (HIV-1 RNA <50 copies/mL) on ART (AIDS Clinical Trials Group study A5321).

RESULTS

Men were more likely than women to have detectable plasma HIV-1 RNA by single-copy assay (52% vs 29%; P = .003), and the proportion of participants with detectable residual viremia increased in a stepwise fashion by BMI category (normal weight or underweight, 38%; overweight, 50%; and obese, 55%). ART regimen type was not associated with measures of HIV-1 persistence after controlling for ART duration.

CONCLUSIONS

Sex and obesity are independently associated with residual viremia in people on long-term ART. Additional studies to confirm these relationships and to define the mechanisms by which sex and obesity affect HIV-1 persistence are needed to inform HIV-1 cure strategies.

Antiretroviral Therapy-Associated Metabolic Complications: Review of the Recent Studies

The extensive utilization of antiretroviral therapy (ART) has successfully improved human immunodeficiency virus (HIV)-associated complications. The incidence of opportunistic infections is decreased by the viral load suppression and the CD4 count promotion. However, metabolic complications, commonly bone demineralization, lipodystrophy, and lactic acidosis, are arising following the adaptation of long-term ART. The events are not drug-specific, but the severity and incidence individually vary depending upon classes of drugs. Such concerning occurrences may lead to discontinuation of current therapy or switching to another regimen with fewer adverse effects. The purpose of this review is to demonstrate the common metabolic abnormalities associated with each class of widely used ART in people living with HIV (PLHIV). Electronic databases such as PubMed, ScienceDirect, Scopus, Google Scholar, SciFinder, and Web of Science were used for the literature search. A better understanding of ART-associated metabolic adverse effects is helpful in various clinical settings so that therapists may optimize treatments in this population.

Sex Differences in the Association of Fat and Inflammation Among People with Treated HIV Infection

INTRODUCTION

Ectopic fat deposition may contribute to chronic inflammation in people with HIV (PWH). To provide information for future mechanistic studies of metabolic risk in this population, we sought to determine which fat measures relate more strongly to inflammation and whether the fat-inflammation relationship is modified by sex or HIV status.

METHODS

We conducted a cross-sectional study of 105 PWH and 20 age- and sex-matched HIV-negative controls. Interleukin-6 (IL-6) and high-sensitivity C reactive protein (hs-CRP) levels were measured from plasma. Pericardial fat (PCF) and thoracic periaortic adipose tissue (TAT) volumes and peri-right coronary artery (RCA), left atrium (LA) roof, and liver densities were measured from cardiac CT scans. Unadjusted and multivariate adjusted linear regression models were used to determine the relationship between ectopic fat measures and inflammation biomarkers.

RESULTS

Forty participants had BMI < 25, 33 had BMI 25 to 30, and 52 had BMI > 30. Systolic blood pressure and insulin resistance increased with BMI. Participants with higher BMI had a higher CD4+ count. In models adjusted for demographics, HIV status, and metabolic risk factors, BMI was positively associated with IL-6 and hs-CRP. Ectopic PCF and TAT volumes were positively associated with IL-6 and hs-CRP; however, these relationships were somewhat attenuated in adjusted models. LA roof (but not peri-RCA) fat radiodensity was inversely associated with hs-CRP in fully adjusted models, and the association with IL-6 was borderline statistically signifi-cant (P = 0.054). IL-6 was more strongly associated with BMI and LA roof density in women than in men (P for interaction = 0.05).

CONCLUSIONS

Among PWH receiving antiretroviral therapy, higher BMI and excessive ectopic fat burden were associated with circulating markers of systemic inflammation. Because these measures appear to be more strongly related to inflammation among women than men, future clinical studies of metabolic risk and inflammation among PWH should include sex-stratified analyses.

Metabolic complications affecting adipose tissue, lipid and glucose metabolism associated with HIV antiretroviral treatment

Introduction: Efficient antiretroviral-treatment (ART) generally allows control of HIV infection. However, persons-living-with-HIV (PLWH), when aging, present a high prevalence of metabolic diseases. Area covered: Altered adiposity, dyslipidemias, insulin resistance, diabetes, and their consequences are prevalent in PLWH and could be partly related to ART. Expert opinion: At first, personal and lifestyle factors are involved in the onset of these complications. The persistence of HIV in tissue reservoirs could synergize with some ART and enhance metabolic disorders. Altered fat repartition, diagnosed as lipodystrophy, has been related to first-generation nucleoside-reverse-transcriptase-inhibitors (NRTIs) (stavudine zidovudine) and some protease inhibitors (PIs). Recently, use of some integrase-inhibitors (INSTI) resulted in weight/fat gain, which represents a worrisome unresolved situation. Lipid parameters were affected by some first-generation NRTIs, non-NRTIs (efavirenz) but also PIs boosted by ritonavir, with increased total and LDL-cholesterol and triglycerides. Insulin resistance is common associated with abdominal obesity. Diabetes incidence, high with first-generation-ART (zidovudine, stavudine, didanosine, indinavir) has declined with contemporary ART close to that of the general population. Metabolic syndrome, a dysmetabolic situation with central obesity and insulin resistance, and liver steatosis are common in PLWH and could indirectly result from ART-associated fat gain and insulin resistance. All these dysmetabolic situations increase the atherogenic cardiovascular risk.

Adipose Tissue is Enriched for Activated and Late-Differentiated CD8+ T Cells and Shows Distinct CD8+ Receptor Usage, Compared With Blood in HIV-Infected Persons

BACKGROUND

Adverse viral and medication effects on adipose tissue contribute to the development of metabolic disease in HIV-infected persons, but T cells also have a central role modulating local inflammation and adipocyte function. We sought to characterize potentially proinflammatory T-cell populations in adipose tissue among persons on long-term antiretroviral therapy and assess whether adipose tissue CD8 T cells represent an expanded, oligoclonal population.

METHODS

We recruited 10 HIV-infected, non-diabetic, overweight or obese adults on efavirenz, tenofovir, and emtricitabine for >4 years with consistent viral suppression. We collected fasting blood and subcutaneous abdominal adipose tissue to measure the percentage of CD4 and CD8 T cells expressing activation, exhaustion, late differentiation/senescence, and memory surface markers. We performed T-cell receptor (TCR) sequencing on sorted CD8 cells. We compared the proportion of each T-cell subset and the TCR repertoire diversity, in blood versus adipose tissue.

RESULTS

Adipose tissue had a higher percentage of CD3CD8 T cells compared with blood (61.0% vs. 51.7%, P < 0.01) and was enriched for both activated CD8HLA-DR T cells (5.5% vs. 0.9%, P < 0.01) and late-differentiated CD8CD57 T cells (37.4% vs. 22.7%, P < 0.01). Adipose tissue CD8 T cells displayed distinct TCRβ V and J gene usage, and the Shannon Entropy index, a measure of overall TCRβ repertoire diversity, was lower compared with blood (4.39 vs. 4.46; P = 0.05).

CONCLUSIONS

Adipose tissue is enriched for activated and late-differentiated CD8 T cells with distinct TCR usage. These cells may contribute to tissue inflammation and impaired adipocyte fitness in HIV-infected persons.

Evaluation of Oral Antiretroviral Drugs in Mice With Metabolic and Neurologic Complications

Antiretroviral (ART) drugs has previously been associated with lipodystrophic syndrome, metabolic consequences, and neuropsychiatric complications. ART drugs include three main classes of protease inhibitors (PIs), nucleoside analog reverse transcriptase inhibitors (NRTIs), and non-nucleoside reverse transcriptase inhibitors (NNRTIs). Our previous work demonstrated that a high risk of hyperlipidemia was observed in HIV-1-infected patients who received ART drugs in Taiwan. Patients receiving ART drugs containing either Abacavir/Lamivudine (Aba/Lam; NRTI/NRTI), Lamivudine/Zidovudine (Lam/Zido; NRTI/NRTI), or Lopinavir/Ritonavir (Lop/Rit; PI) have the highest risk of hyperlipidemia. The aim of this study was to investigate the effects of Aba/Lam (NRTI/NRTI), Lam/Zido (NRTI/NRTI), and Lop/Rit (PI) on metabolic and neurologic functions in mice. Groups of C57BL/6 mice were administered Aba/Lam, Lam/Zido, or Lop/Rit, orally, once daily for a period of 4 weeks. The mice were then extensively tested for metabolic and neurologic parameters. In addition, the effect of Aba/Lam, Lam/Zido, and Lop/Rit on lipid metabolism was assessed in HepG2 hepatocytes and during the 3T3-L1 preadipocyte differentiation. Administration with Aba/Lam caused cognitive and motor impairments in mice, as well as their metabolic imbalances, including alterations in leptin serum levels. Administration with Lop/Rit also caused cognitive and motor impairments in mice, as well as their metabolic imbalances, including alterations in serum levels of total cholesterol, and HDL-c. Treatment of mice with Aba/Lam and Lop/Rit enhanced the lipid accumulation in the liver, and the decrease in AMP-activated protein kinase (AMPK) phosphorylation and/or its downstream target acetyl-CoA carboxylase (ACC) protein expression. In HepG2 hepatocytes, Aba/Lam, Lam/Zido, and Lop/Rit also enhanced the lipid accumulation and decreased phosphorylated AMPK and ACC proteins. In 3T3-L1 pre-adipocyte differentiation, Aba/Lam and Lop/Rit reduced adipogenesis by decreasing expression of transcription factor CEBPb, implicating the lipodystrophic syndrome. Our results demonstrate that daily oral administration of Aba/Lam and Lop/Rit may produce cognitive, motor, and metabolic impairments in mice, regardless of HIV-1 infection.

Adipose Tissue in HIV Infection

HIV infection and antiretroviral therapy (ART) treatment exert diverse effects on adipocytes and stromal-vascular fraction cells, leading to changes in adipose tissue quantity, distribution, and energy storage. A HIV-associated lipodystrophic condition was recognized early in the epidemic, characterized by clinically apparent changes in subcutaneous, visceral, and dorsocervical adipose depots. Underlying these changes is altered adipose tissue morphology and expression of genes central to adipocyte maturation, regulation, metabolism, and cytokine signaling. HIV viral proteins persist in circulation and locally within adipose tissue despite suppression of plasma viremia on ART, and exposure to these proteins impairs preadipocyte maturation and reduces adipocyte expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) and other genes involved in cell regulation. Several early nucleoside reverse transcriptase inhibitor and protease inhibitor antiretroviral drugs demonstrated substantial adipocyte toxicity, including reduced mitochondrial DNA content and respiratory chain enzymes, reduced PPAR-γ and other regulatory gene expression, and increased proinflammatory cytokine production. Newer-generation agents, such as integrase inhibitors, appear to have fewer adverse effects. HIV infection also alters the balance of CD4+ and CD8+ T cells in adipose tissue, with effects on macrophage activation and local inflammation, while the presence of latently infected CD4+ T cells in adipose tissue may constitute a protected viral reservoir. This review provides a synthesis of the literature on how HIV virus, ART treatment, and host characteristics interact to affect adipose tissue distribution, immunology, and contribution to metabolic health, and adipocyte maturation, cellular regulation, and energy storage. © 2017 American Physiological Society. Compr Physiol 7:1339-1357, 2017.

Central nervous system-penetrating antiretrovirals impair energetic reserve in striatal nerve terminals

The use of antiretroviral (ARV) drugs with central nervous system (CNS) penetration effectiveness (CPE) may be useful in the treatment of HIV-associated neurocognitive disorder (HAND) as well as targeting a CNS reservoir in strategies to achieve a functional cure for HIV. However, increased cognitive deficits are linked to at least one of these drugs (efavirenz). As mitochondrial dysfunction has been found with a number of ARVs, and as such can affect neuronal function, the objective of this study was to assess the effects of ARV with high CPE for toxicological profiles on presynaptic nerve terminal energy metabolism. This subcellular region is especially vulnerable in that a constant supply of ATP is required for the proper maintenance of neurotransmitter release and uptake supporting proper neuronal function. We evaluated the effects of acute treatment with ten different high CPE ARVs from five different drug classes on rat cortical and striatal nerve terminal bioenergetic function. While cortical nerve terminal bioenergetics were not altered, striatal nerve terminals exposed to efavirenz, nevirapine, abacavir, emtricitabine, zidovudine, darunavir, lopinavir, raltegravir, or maraviroc (but not indinavir) exhibit reduced mitochondrial spare respiratory capacity (SRC). Further examination of efavirenz and maraviroc revealed a concentration-dependent impairment of striatal nerve terminal maximal mitochondrial respiration and SRC as well as a reduction of intraterminal ATP levels. Depletion of ATP at the synapse may underlie its dysfunction and contribute to neuronal dysfunction in treated HIV infection.

Anatomic Fat Depots and Coronary Plaque Among Human Immunodeficiency Virus-Infected and Uninfected Men in the Multicenter AIDS Cohort Study

Methods. In a cross-sectional substudy of the Multicenter AIDS Cohort Study, noncontrast cardiac computed tomography (CT) scanning for coronary artery calcium (CAC) scoring was performed on all men, and, for men with normal renal function, coronary CT angiography (CTA) was performed. Associations between fat depots (visceral adipose tissue [VAT], abdominal subcutaneous adipose tissue [aSAT], and thigh subcutaneous adipose tissue [tSAT]) with coronary plaque presence and extent were assessed with logistic and linear regression adjusted for age, race, cardiovascular disease (CVD) risk factors, body mass index (BMI), and human immunodeficiency virus (HIV) parameters.

Results. Among HIV-infected men (n = 597) but not HIV-uninfected men (n = 343), having greater VAT was positively associated with noncalcified plaque presence (odds ratio [OR] = 1.04, P < .05), with a significant interaction (P < .05) by HIV serostatus. Human immunodeficiency virus-infected men had lower median aSAT and tSAT and greater median VAT among men with BMI <25 and 25–29.9 kg/m². Among HIV-infected men, VAT was positively associated with presence of coronary plaque on CTA after adjustment for CVD risk factors (OR = 1.04, P < .05), but not after additional adjustment for BMI. There was an inverse association between aSAT and extent of total plaque among HIV-infected men, but not among HIV-uninfected men. Lower tSAT was associated with greater CAC and total plaque score extent regardless of HIV serostatus.

Conclusions. The presence of greater amounts of VAT and lower SAT may contribute to increased risk for coronary artery disease among HIV-infected persons.

Naringin Reverses Hepatocyte Apoptosis and Oxidative Stress Associated with HIV-1 Nucleotide Reverse Transcriptase Inhibitors-Induced Metabolic Complications

Nucleoside Reverse Transcriptase Inhibitors (NRTIs) have not only improved therapeutic outcomes in the treatment of HIV infection but have also led to an increase in associated metabolic complications of NRTIs. Naringin’s effects in mitigating NRTI-induced complications were investigated in this study. Wistar rats, randomly allotted into seven groups (n = 7) were orally treated daily for 56 days with 100 mg/kg zidovudine (AZT) (groups I, II III), 50 mg/kg stavudine (d4T) (groups IV, V, VI) and 3 mL/kg of distilled water (group VII). Additionally, rats in groups II and V were similarly treated with 50 mg/kg naringin, while groups III and VI were treated with 45 mg/kg vitamin E. AZT or d4T treatment significantly reduced body weight and plasma high density lipoprotein concentrations but increased liver weights, plasma triglycerides and total cholesterol compared to controls, respectively. Furthermore, AZT or d4T treatment significantly increased oxidative stress, adiposity index and expression of Bax protein, but reduced Bcl-2 protein expression compared to controls, respectively. However, either naringin or vitamin E significantly mitigated AZT- or d4T-induced weight loss, dyslipidemia, oxidative stress and hepatocyte apoptosis compared to AZT- or d4T-only treated rats. Our results suggest that naringin reverses metabolic complications associated with NRTIs by ameliorating oxidative stress and apoptosis. This implies that naringin supplements could mitigate lipodystrophy and dyslipidemia associated with NRTI therapy.

Xenobiotics that affect oxidative phosphorylation alter differentiation of human adipose-derived stem cells at concentrations that are found in human blood

Adipogenesis is accompanied by differentiation of adipose tissue-derived stem cells to adipocytes. As part of this differentiation, biogenesis of the oxidative phosphorylation system occurs. Many chemical compounds used in medicine, agriculture or other human activities affect oxidative phosphorylation function. Therefore, these xenobiotics could alter adipogenesis. We have analyzed the effects on adipocyte differentiation of some xenobiotics that act on the oxidative phosphorylation system. The tested concentrations have been previously reported in human blood. Our results show that pharmaceutical drugs that decrease mitochondrial DNA replication, such as nucleoside reverse transcriptase inhibitors, or inhibitors of mitochondrial protein synthesis, such as ribosomal antibiotics, diminish adipocyte differentiation and leptin secretion. By contrast, the environmental chemical pollutant tributyltin chloride, which inhibits the ATP synthase of the oxidative phosphorylation system, can promote adipocyte differentiation and leptin secretion, leading to obesity and metabolic syndrome as postulated by the obesogen hypothesis.

Summary: Some medical drugs and environmental chemical pollutants acting on the oxidative phosphorylation system can alter adipocyte differentiation and adipogenesis and, thus, have important consequences for human health.

Different origin of adipogenic stem cells influences the response to antiretroviral drugs

Lipodystrophy (LD) is a main side effect of antiretroviral therapy for HIV infection, and can be provoked by nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs). LD exists in different forms, characterized by fat loss, accumulation, or both, but its pathogenesis is still unclear. In particular, few data exist concerning the effects of antiretroviral drugs on adipocyte differentiation. Adipose tissue can arise either from mesenchymal stem cells (MSCs), that include bone marrow-derived MSCs (hBM-MSCs), or from ectodermal stem cells, that include dental pulp stem cells (hDPSCs). To analyze whether the embryonal origin of adipocytes might impact the occurrence of different phenotypes in LD, we quantified the effects of several antiretroviral drugs on the adipogenic differentiation of hBM-MSCs and hDPSCs. hBM-MSCs and hDPSCs were isolated from healthy donors. Cells were treated with 10 and 50 μM stavudine (d4T), efavirenz (EFV), atazanavir (ATV), ritonavir (RTV), and ATV-boosted RTV. Viability and adipogenesis were evaluated by staining with propidium iodide, oil red, and adipoRed; mRNA levels of genes involved in adipocyte differentiation, i.e. CCAAT/enhancer-binding protein alpha (CEBPα) and peroxisome proliferator-activated receptor gamma (PPARγ), and in adipocyte functions, i.e. fatty acid synthase (FASN), fatty acid binding protein-4 (FABP4), perilipin-1 (PLIN1) and 1-acylglycerol-3-phosphate O-acyltransferase-2 (AGPAT2), were quantified by real time PCR. We found that ATV, RTV, EFV, and ATV-boosted RTV, but not d4T, caused massive cell death in both cell types. EFV and d4T affected the accumulation of lipid droplets and induced changes in mRNA levels of genes involved in adipocyte functions in hBM-MSCs, while RTV and ATV had little effects. All drugs stimulated the accumulation of lipid droplets in hDPSCs. Thus, the adipogenic differentiation of human stem cells can be influenced by antiretroviral drugs, and depends, at least in part, on their embryonal origin.

Changes in Body Fat Measured by DEXA in Patients Taking Different Formulations of Stavudine

BACKGROUND

Lipoatrophy is a frequent complication of chronic stavudine therapy. Stavudine extended release formulation (stavudine ER) gives lower peak and higher trough levels than the immediate release formulation (stavudine IR), and we hypothesized that the lower peak might result in less lipoatrophy.

OBJECTIVE

To compare the rate of peripheral lipoatrophy between patients taking stavudine ER and stavudine IR.

METHOD

Body composition was measured by dual energy X-ray absorptiometry (DEXA) every 6 months for 18 months in 29 patients taking either stavudine ER or IR as part of a randomized controlled clinical trial.

RESULTS

DEXA fat measurements did not differ between the ER and IR groups at baseline, after a median of 32 months on stavudine-containing treatment. Over the 18 months of follow-up in the whole cohort limb fat decreased by a mean of 0.29 +/- 0.50 kg (p = .01) and leg fat percent decreased by a mean of 1.23% +/- 1.92% (p = .001), whereas trunk fat and trunk-to-limb fat percent ratio did not change significantly. There was no significant difference between the ER and IR groups in the rate of change of any of the fat parameters. At study completion, the proportion of patients with clinical lipodystrophy was similar in the stavudine ER and stavudine IR groups (67% and 64%, respectively; p = .893).

CONCLUSION

Stavudine ER does not appear to cause less peripheral lipoatrophy.

Adipose tissue mitochondrial dysfunction triggers a lipodystrophic syndrome with insulin resistance, hepatosteatosis, and cardiovascular complications

Mitochondrial dysfunction in adipose tissue occurs in obesity, type 2 diabetes, and some forms of lipodystrophy, but whether this dysfunction contributes to or is the result of these disorders is unknown. To investigate the physiological consequences of severe mitochondrial impairment in adipose tissue, we generated mice deficient in mitochondrial transcription factor A (TFAM) in adipocytes by using mice carrying adiponectin-Cre and TFAM floxed alleles. These adiponectin TFAM-knockout (adipo-TFAM-KO) mice had a 75-81% reduction in TFAM in the subcutaneous and intra-abdominal white adipose tissue (WAT) and interscapular brown adipose tissue (BAT), causing decreased expression and enzymatic activity of proteins in complexes I, III, and IV of the electron transport chain (ETC). This mitochondrial dysfunction led to adipocyte death and inflammation in WAT and a whitening of BAT. As a result, adipo-TFAM-KO mice were resistant to weight gain, but exhibited insulin resistance on both normal chow and high-fat diets. These lipodystrophic mice also developed hypertension, cardiac hypertrophy, and cardiac dysfunction. Thus, isolated mitochondrial dysfunction in adipose tissue can lead a syndrome of lipodystrophy with metabolic syndrome and cardiovascular complications.

Zidovudine induces visceral mitochondrial toxicity and intra-abdominal fat gain in a rodent model of lipodystrophy

BACKGROUND

The use of zidovudine is associated with a loss of subcutaneous adipose tissue (SAT). We assessed if zidovudine treatment also affects visceral adipose tissue (VAT) and if uridine supplementation abrogates the adverse effects of zidovudine on VAT.

METHODS

Rats were fed zidovudine for 21 weeks with or without simultaneous uridine supplementation. Control animals did not receive zidovudine, or were treated with uridine alone. Changes in SAT and VAT were monitored by magnetic resonance imaging. Adipose tissue was examined for structural and molecular signs of mitochondrial toxicity.

RESULTS

Zidovudine induced lipoatrophy in SAT and fat hypertrophy in VAT. Compared with controls zidovudine-exposed VAT adipocytes had increased diameters, microvesicular steatosis and enlarged mitochondria with disrupted crystal architecture on electron microscopy. VAT adipocyte mitochondrial DNA (mtDNA) copy numbers were diminished, as were mtDNA-encoded respiratory chain proteins. The 'common' mtDNA deletion was detected in high frequencies in zidovudine treated animals, but not in the controls. Although mtDNA depletion was more profound in SAT compared with VAT, the 'common' deletion tended to be more frequent in the VAT than in the SAT. Uridine coadministration abrogated all effects of zidovudine on VAT and SAT pathology.

CONCLUSIONS

Zidovudine induces a gain of intra-abdominal fat in association with quantitative and qualitative alterations of the mitochondrial genome and impaired expression of mtDNA-encoded respiratory chain components, indicating that zidovudine may contribute to abdominal fat hypertrophy in HIV-infected patients. In this rodent model, uridine supplementation abrogates both SAT and VAT pathology induced by zidovudine.

Effects of switching from stavudine to raltegravir on subcutaneous adipose tissue in HIV-infected patients with HIV/HAART-associated lipodystrophy syndrome (HALS). A clinical and molecular study

HIV-1/HAART-associated lipodystrophy syndrome (HALS) has been associated with exposure to stavudine (d4T) through mitochondrial dysfunction. We performed a 48-week study to assess the effects of switching from d4T to raltegravir (RAL) on metabolic and fat molecular parameters of patients with HALS. Forty-two patients with HALS and a median exposure to d4T > 7 years were switched to RAL and followed for 48 weeks. Fasting metabolic tests, HIV RNA, CD4 cell count, and fat measured by DEXA were obtained at baseline and week 48. mtDNA and gene transcripts for PPAR gamma, adiponectin, cytochrome b, Cox IV, TNF alpha, MCP-1 and CD68 were assessed in paired subcutaneous fat tissue biopsies. Lipid parameters, fasting glucose, insulin, and HOMA-IR did not change significantly. Whole body fat (P = 0.0027) and limb fat mass (P<0.0001) increased from baseline. Trunk/limb fat ratio (P = 0.0022), fat mass ratio (P = 0.0020), fat mass index (P = 0.0011) and percent leg fat normalized to BMI (P<0.0001) improved after 48 weeks. Relative abundance of mtDNA, expression of PPAR gamma, adiponectin, Cyt b, and MCP-1 genes increased, whereas Cox IV, TNF alpha, and CD68 did not change significantly from baseline. Switching from d4T to RAL in patients with HALS is associated with an increase in limb fat mass and an improvement in markers of adipocyte differentiation and mitochondrial function in SAT.

Targeting cancer stem cells expressing an embryonic signature with anti-proteases to decrease their tumor potential

Cancer stem cells (CSCs) are a specific subset of cancer cells that sustain tumor growth and dissemination. They might represent a significant treatment target to reduce malignant progression and prevent tumor recurrence. In solid tumors, several hierarchically organized CSC clones coexist, even within a single tumor. Among them, CSCs displaying an embryonic stem cell ‘stemness' signature, based on the expression of Oct-4, Nanog and Sox2, are present in distinct high-grade tumor types associated with poor prognosis. We previously designed a model to isolate pure populations of these CSCs from distinct solid tumors and used it to screen for molecules showing selective toxicity for this type of CSC. Here we show that human immunodeficiency virus (HIV)-protease inhibitors (HIV-PIs) specifically target CSCs expressing an embryonic signature derived from tumors with distinct origins. They reduced proliferation in a dose-dependent manner with a higher specificity as compared with the total population of cancer cells and/or healthy stem cells, and they were efficient in inducing cell death. Lopinavir was the most effective HIV-PI among those tested. It reduced self-renewal and induced apoptosis of CSCs, subsequently impairing in vivo CSC-induced allograft formation. Two key pharmacophores in the LPV structure were also identified. They are responsible for the specificity of CSC targeting and also for the overall antitumoral activity. These results contribute to the identification of molecules presenting selective toxicity for CSCs expressing an embryonic stemness signature. This paves the way to promising therapeutic opportunities for patients suffering from solid cancer tumors of poor prognosis.

Nutrition and the HIV-associated lipodystrophy syndrome

HIV-associated lipodystrophy syndrome (HALS), comprising metabolic and morphological alterations, is a known side effect of highly active antiretroviral therapy (HAART). Evidence for the role of nutrition in the management of the systemic parameters of HALS is currently limited. In the present paper we review the current knowledge base surrounding HALS, focusing particularly on the role of nutrition in mitigating the systemic parameters of the syndrome. Reported prevalence of HALS was found to vary from 9 to 83 % due to lack of a standardised definition, as well as variations in assessment methods and in the study population used. HALS is associated with both morphological (lipoatrophy, lipohypertrophy) and metabolic (dyslipidaemia, glucose intolerance, diabetes, hypertension, endothelial dysfunction and atherosclerosis) alterations, which may occur singly or in combination, and are associated with an increased risk of CVD. HAART-induced adipocyte inflammation, oxidative stress and macrophage infiltration, as well as altered adipocyte function and mitochondrial toxicity, have been shown to be central to the development of HALS. The adipocyte, therefore, represents a plausible target for treatment. Pharmacological and surgical treatment interventions have shown effect. However, their use is associated with numerous adverse effects and complications. Targeted lifestyle interventions may provide a useful alternative for managing HALS owing to their safety and tolerability. A Mediterranean-style diet has been found to be effective in improving the systemic parameters of HALS. Furthermore, the effects of n-3 PUFA supplementation are encouraging and future randomised controlled trials investigating the beneficial effects of n-3 PUFA in HALS are justified.

Thymidine analogues suppress autophagy and adipogenesis in cultured adipocytes

Lipoatrophy in HIV patients can result from prolonged exposure to thymidine analogues. Mitochondrial toxicity leading to dysregulated adipogenesis and increased cell death has been proposed as a leading factor in the etiology of peripheral fat loss. We hypothesized that thymidine analogues interfere with autophagy, a lysosomal degradation pathway, which is important for mitochondrial quality control, cellular survival, and adipogenesis. We assessed the effects of zidovudine (AZT), stavudine (d4T), and lamivudine (3TC) on autophagy in eukaryotic cells and adipocytes (3T3-F442A) by fluorescence microscopy and flow cytometry. The effects were compared to interventions with established genetic and pharmacological inhibitors of autophagy and correlated to assessments of cell viability, proliferation, and differentiation. AZT and d4T, but not 3TC, inhibited both constitutive and induced autophagic activity in adipocytes. This inhibition was associated with accumulation of dysfunctional mitochondria, increased reactive oxygen species (ROS) production, increased apoptosis, decreased proliferation, and impaired adipogenic conversion. Autophagy inhibition was dose and time dependent and detectable at therapeutic drug concentrations. Similar phenotypic changes were obtained when genetic or pharmacological inhibition of autophagy was employed. Our data suggest that thymidine analogues disturb adipocyte function through inhibition of autophagy. This novel mechanism potentially contributes to peripheral fat loss in HIV-infected patients.

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.

A new way of measuring apoptosis by absolute quantitation of inter-nucleosomally fragmented genomic DNA

Several critical events of apoptosis occur in the cell nucleus, including inter-nucleosomal DNA fragmentation (apoptotic DNA) and eventual chromatin condensation. The generation of apoptotic DNA has become a biochemical hallmark of apoptosis because it is a late ‘point of no return’ step in both the extrinsic (cell-death receptor) and intrinsic (mitochondrial) apoptotic pathways. Despite investigators observing apoptotic DNA and understanding its decisive role as a marker of apoptosis for over 20 years, measuring it has proved elusive. We have integrated ligation-mediated PCR and qPCR to design a new way of measuring apoptosis, termed ApoqPCR, which generates an absolute value for the amount (picogram) of apoptotic DNA per cell population. ApoqPCR’s advances over current methods include a 1000-fold linear dynamic range yet sensitivity to distinguish subtle low-level changes, measurement with a 3- to 4-log improvement in sample economy, and capacity for archival or longitudinal studies combined with high-throughput capability. We demonstrate ApoqPCR’s utility in both in vitro and in vivo contexts. Considering the fundamental role apoptosis has in vertebrate and invertebrate health, growth and disease, the reliable measurement of apoptotic nucleic acid by ApoqPCR will be of value in cell biology studies in basic and applied science.

Minimal effects of Darunavir on adipocyte differentiation and metabolism in 3T3-L1 cells

Darunavir (DRV) has been confirmed to be an effective option for antiretroviral-naïve and experienced patients. It results in a more favorable lipid and glucose profile than other antiretrovirals. The objective of this study was to investigate the molecular mechanisms that could underline the lack of toxicity of DRV to metabolism and the better profile observed in HIV-infected patients in comparison with other drugs. The effects of DRV on adipogenesis were evaluated by oil red O staining after 8 days of induction of differentiation in 3T3-L1 cells, a very adequate and convenient cell culture model for investigation of adipose function. Several adipogenic genes (C/EBPα, PPARγ, Pref-1, and AP2) were analyzed by real time-PCR. Fully differentiated adipocytes were also incubated with DRV for 24 h and glucose utilization and lactate and glycerol production were quantified by use of an autoanalyzer. No effects of DRV on murine adipocyte differentiation were observed. Significant decreases in lipolysis, glucose uptake, and lactate production were observed at the highest concentration used (50 μM:) (p < 0.01-p < 0.001). However, DRV treatment did not modify the percentage of glucose transformed into lactate. Co-treatment with RTV did not induce any further effects on lipolysis and glucose metabolism. This study suggests that the decrease in lipolysis observed after DRV treatment could explain, at least in part, the lower plasma lipids observed in patients under DRV/r treatment in comparison with other drugs. The lack of effects of RTV co-treatment on glucose and lipid metabolism emphasizes the safety of this treatment.

Adipose tissue biology and HIV-infection

HIV-1/highly active antiretroviral therapy-associated lipodystrophy syndrome (HALS) is an adipose tissue redistribution disorder characterized by subcutaneous adipose tissue lipoatrophy, sometimes including visceral adipose tissue hypertrophy and accumulation of dorsocervical fat ('buffalo hump'). The pathophysiology of HALS appears to be multifactorial and several key pathophysiological factors associated with HALS have been identified. These include mitochondrial dysfunction, adipocyte differentiation disturbances, high adipocyte lipolysis, and adipocyte apoptosis. These alterations in adipose tissue biology expand to involve systemic metabolism through alterations in endocrine functions of adipose tissue (via disturbed adipokine release), enhanced production of pro-inflammatory cytokines and excessive free fatty-acid release due to lipolysis. The deleterious action of some antiretroviral drugs is an important factor in eliciting these alterations in adipose tissue. However, HIV-1 infection-related events and HIV-1-encoded proteins also contribute directly to the complex development of HALS through effects on adipocyte biology, or indirectly through the promotion of local inflammation in adipose tissue.

HIV and HAART-Associated Dyslipidemia

Effective highly active antiretroviral therapy (HAART) for human immunodeficiency virus-1 (HIV) infection has led to marked improvement in life-expectancy for those infected with HIV. Despite reductions in the incidence of AIDS with effective treatment, patients continue to experience considerable morbidity and mortality from non-AIDS illness such as premature cardiovascular disease, liver failure and renal failure. These morbidities, particularly premature cardiovascular disease, are thought to be related to a combination of the effects of an ageing HIV-infected population coupled with long-term effects of HIV infection and antiretroviral therapy (ART). One of the principle drivers behind the well documented increase in the risk of cardiovascular disease in HIV-infected patients is dyslipidemia.

This review will focus on the clinical presentation of HIV and ART-associated dyslipidemia, what is known of its patho-physiology, including associations with use of specific antiretroviral medications, and suggest screening and management strategies.

Mesodermal developmental gene Tbx15 impairs adipocyte differentiation and mitochondrial respiration

Increased intraabdominal (visceral) fat is associated with a high risk of diabetes and metabolic syndrome. We have previously shown that the mesodermal developmental transcription factor Tbx15 is highly differentially expressed between visceral and subcutaneous (s.c.) fat in both humans and rodents, and in humans visceral fat Tbx15 expression is decreased in obesity. Here we show that, in mice, Tbx15 is 260-fold more highly expressed in s.c. preadipocytes than in epididymal preadipocytes. Overexpression of Tbx15 in 3T3-L1 preadipocytes impairs adipocyte differentiation and decreases triglyceride content. This defect in differentiation can be corrected by stimulating cells with the PPARγ agonist rosiglitazone (Rosi). However, triglyceride accumulation remains decreased by ∼50%, due to a decrease in basal lipogenic rate and increase in basal lipolytic rate. 3T3-L1 preadipocytes overexpressing Tbx15 also have a 15% reduction in mitochondrial mass and a 28% reduction in basal mitochondrial respiration (P = 0.004) and ATP turnover (P = 0.02), and a 45% (P = 0.003) reduction in mitochondrial respiratory capacity. Thus, differential expression of Tbx15 between fat depots plays an important role in the interdepot differences in adipocyte differentiation, triglyceride accumulation, and mitochondrial function that may contribute to the risk of diabetes and metabolic disease.

From old to new nucleoside reverse transcriptase inhibitors: changes in body fat composition, metabolic parameters and mitochondrial toxicity after the switch from thymidine analogs to tenofovir or abacavir

INTRODUCTION

Thymidine analogs zidovudine (AZT) and stavudine (d4T) have been widely used because of their antiviral activity against HIV, but at the expense of high toxicity, mainly related to mitochondrial damage. Many studies have been performed replacing AZT or d4T with newer nucleoside analogs reverse transcriptase inhibitors (NRTIs) with less toxicity, such as tenofovir (TDF) or abacavir (ABC), maintaining virological efficacy.

AREAS COVERED

Relevant literature was identified using a PubMed search of articles published up to June 2010. Search terms included: 'thymidine analogs', 'stavudine', 'zidovudine', 'd4T', 'AZT', 'ZDV', 'treatment switch'. Original articles in which d4T or AZT had been replaced by TDF or ABC as switch strategies (with undetectable viral load) were reviewed where information about body fat distribution, mitochondrial functionality and/or plasma lipid parameters were available. Relevant references from these articles were also considered. Only studies performed in adult patients (18 years or older) are included. The readers will gain a better understanding of the toxicity caused by thymidine analogs, the treatment alternatives and the benefits observed after treatment switch to newer NRTIs.

EXPERT OPINION

Thymidine analogs AZT and d4T yield considerable toxicity and proactive switch to newer NRTIs such as TDF or ABC is necessary in order to avoid or partially reverse such side effects.

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.

Adipocyte dysfunction in response to antiretroviral therapy: clinical, tissue and in-vitro studies

PURPOSE OF REVIEW

Lipodystrophy, a major complication of antiretroviral therapy, is an adipose tissue disease involving severe alterations of fat tissue distribution and metabolic functions. Protease inhibitors and nucleoside reverse transcriptase inhibitors (NRTIs) are implicated to different extents. We review recent findings on the toxicity of HIV antiretroviral drugs at the fat cell and tissue levels and point out the underlying pathophysiological mechanisms.

RECENT FINDINGS

Peripheral fat loss and central accumulation are distinct phenomena. Lipoatrophy is the dominant feature after prolonged treatment. Protease inhibitors and NRTIs promote fat tissue disease by separate mechanisms that converge and worsen adipocyte dysfunctions. The pathogenesis involves the mitochondrial toxicity of NRTIs and the adverse effects of protease inhibitors and NRTIs on adipocyte differentiation status, insulin sensitivity, survival and adipokine secretion. Oxidative stress and local inflammation induced by these drugs may participate in the setup of lipodystrophy. Partial and slow reversion can be obtained by switch strategies or drug therapy.

SUMMARY

Patients using antiviral therapy develop severe fat tissue damage. The toxicity of protease inhibitors and NRTIs remains an important issue for patients and clinicians. Since fat tissue regeneration is difficult, it is important to understand the mechanisms by which these drugs alter fat tissue depots.

Combined effect of C-reactive protein and stavudine on adipogenesis

BACKGROUND

Subcutaneous fat wasting in HIV therapy is primarily associated with the use of stavudine (d4T) and zidovudine (AZT). We hypothesized that C-reactive protein (CRP) might have an additive effect on nucleoside reverse transcriptase inhibitor (NRTI)-mediated peripheral fat loss.

METHODS

3T3-F442A cells were exposed to AZT (6 microM), d4T (3 microM) and/or CRP (0.5 microg/ml) during differentiation. Differentiation was assessed by real-time PCR measurement of peroxisome proliferator-activated receptor (PPAR)gamma and CCAAT/enhancer-binding protein (C/EBP)alpha, by quantification of triglyceride accumulation and by determination of adiponectin expression and secretion. In addition, parameters of lipid accumulation, lipolysis, cell viability and apoptosis were examined.

RESULTS

When preadipocytes were induced to differentiate in the presence of only AZT, d4T or CRP, only AZT significantly impaired adipogenic differentiation. When combined, d4T+CRP also led to reduced triacylglycerol accumulation, an effect not explained by CRP-induced apoptosis or cell death, but instead confirmed by reduced PPARgamma and C/EBPalpha expression and decreased expression of factors involved in lipogenesis, such as fatty acid synthase and acetyl-coenzyme A carboxylase. We observed further reduction in adiponectin expression and secretion when adipocytes were differentiated in the presence of AZT or d4T together with CRP. Addition of rosiglitazone (1 microM) had no effect on reduced adipogenesis, but partially rescued the effects of d4T and d4T+CRP on adiponectin production.

CONCLUSIONS

We conclude that CRP at levels circulating in patients with HIV infection might promote the anti-adipogenic potential of d4T, a cooperative effect that could account for the in vivo observed variability in the development of lipoatrophy.

The accumulation and metabolism of zidovudine in 3T3-F442A pre-adipocytes

BACKGROUND AND PURPOSE

Cultured pre-adipocytes accumulate and metabolize zidovudine (ZDV), but its mode of accumulation into these cells is unclear. We investigated the mode of accumulation of [(3)H]-ZDV, and the impact of changes in external pH and modulators of drug transporters on its accumulation and metabolism.

EXPERIMENTAL APPROACH

The initial rate and steady-state accumulation of [(3)H]-ZDV were measured in 3T3-F442A cells. P-glycoprotein (P-gp) expression was detected by Western blotting. External pH was varied, and modulators of intracellular pH and drug transporters were used to study the mode of accumulation of ZDV. Phosphorylated ZDV metabolites were detected by high-performance liquid chromatography.

KEY RESULTS

Intracellular accumulation of ZDV was rapid, reaching equilibrium within 20 min; nigericin increased accumulation by 1.9-fold, but this did not alter the generation of ZDV mono-, di- and triphosphate. The accumulation and metabolism were pH dependent, being maximal at pH 7.4 and least at pH 5.1. Monensin, carbonyl cyanide p-trifluoromethoxy) phenyl hydrazone, brefeldin A, bafilomycin A1 and concanamycin A increased accumulation; 2-deoxyglucose, dipyridamole, thymidine and tetraphenylphosphonium inhibited accumulation. The accumulation was saturable; the derived K(d) and capacity of binding were 250 nmol per 10(6) cells and 265 nM respectively. 3T3-F442A cells express P-gp; inhibitors of P-gp (XR9576 and verapamil), P-gp/BCRP (GF120918), multidrug resistance protein (MRP) (MK571) and MRP/OATP (probenecid) increased the accumulation of ZDV. Saquinavir, ritonavir, amprenavir and lopinavir increased accumulation.

CONCLUSIONS AND IMPLICATIONS

The accumulation of ZDV in 3T3-F442A cells was rapid, energy dependent, saturable and pH sensitive. Western blot analysis showed that 3T3-F442A cells express P-gp, and direct inhibition assays suggest that ZDV is a substrate of P-gp and MRP.

Mitochondrial DNA depletion and respiratory chain activity in primary human subcutaneous adipocytes treated with nucleoside analogue reverse transcriptase inhibitors

Mitochondrial dysfunction as a consequence of mitochondrial DNA (mtDNA) depletion due to therapy with nucleoside analogue reverse transcriptase inhibitors (NRTI) has been proposed as a pathogenic mechanism leading to lipoatrophy in HIV-infected patients. The aim of our study was to investigate the impact of NRTI treatment on mtDNA abundance and the activities of respiratory chain complexes in primary human subcutaneous preadipocytes (phsPA). We studied adipocyte phenotypes, viability, and differentiation (CCAAT/enhancer-binding protein alpha [C/EBPalpha] and peroxisome proliferator-activated receptor gamma [PPARgamma] expression) and adiponectin production, mtDNA content, mitochondrial membrane potential, mitochondrial mass, and respiratory chain enzyme and citrate synthase activities in both proliferating and differentiating phsPA. Cells were exposed to zidovudine (6 microM), stavudine (d4T; 3 microM), and zalcitabine (ddC; 0.1 microM) for 8 weeks. NRTI-induced mtDNA depletion occurred in proliferating and differentiating phsPA after exposure to therapeutic drug concentrations of d4T and ddC. At these concentrations, ddC and d4T led to an almost 50% decrease in the number of mtDNA copies per cell without major impact on adipocyte differentiation. Despite mtDNA depletion by NRTI, the activities of the respiratory chain complexes, the mitochondrial membrane potential, and the mitochondrial mass were found to be unaffected. Severe NRTI-mediated mtDNA depletion in phsPA is not inevitably associated with impaired respiratory chain activity or altered mitochondrial membrane potential.

Mitochondrial (dys)function in adipocyte (de)differentiation and systemic metabolic alterations

In mammals, adipose tissue, composed of BAT and WAT, collaborates in energy partitioning and performs metabolic regulatory functions. It is the most flexible tissue in the body, because it is remodeled in size and shape by modifications in adipocyte cell size and/or number, depending on developmental status and energy fluxes. Although numerous reviews have focused on the differentiation program of both brown and white adipocytes as well as on the pathophysiological role of white adipose tissues, the importance of mitochondrial activity in the differentiation or the dedifferentiation programs of adipose cells and in systemic metabolic alterations has not been extensively reviewed previously. Here, we address the crucial role of mitochondrial functions during adipogenesis and in mature adipocytes and discuss the cellular responses of white adipocytes to mitochondrial activity impairment. In addition, we discuss the increase in scientific knowledge regarding mitochondrial functions in the last 10 years and the recent suspicion of mitochondrial dysfunction in several 21st century epidemics (ie, obesity and diabetes), as well as in lipodystrophy found in HIV-treated patients, which can contribute to the development of new therapeutic strategies targeting adipocyte mitochondria.

Metabolic syndrome associated with HIV and highly active antiretroviral therapy

The introduction of highly active antiretroviral therapy (HAART) has significantly improved the clinical outcome of HIV disease with increased survival rates. However, some HAART regimens, especially those including protease inhibitors, have been shown to cause in a high proportion of HIV-infected patients metabolic (dyslipidemia, insulin resistance) and somatic (lipodystrophy/lipoatrophy) changes that are associated with an increased risk of cardiovascular disease (coronary artery disease and stroke). The pathogenesis of HAART-associated metabolic syndrome and of its atherogenic profile is complex, and several factors are involved, including direct effects of HAART on lipid metabolism, endothelial and adipocyte cell function, activation of proinflammatory cytokines, and mitochondrial dysfunction. A better understanding of the molecular mechanisms responsible for this syndrome will lead to the discovery of new drugs that will reduce the incidence of lipodystrophy and related metabolic complications in HIV-infected patients facing long-term HAART.

The role of protease inhibitors in the pathogenesis of HIV-associated lipodystrophy: cellular mechanisms and clinical implications

Metabolic complications associated with HIV infection and treatment frequently present as a relative lack of peripheral adipose tissue associated with dyslipidemia and insulin resistance. In this review we explain the connection between abnormalities of intermediary metabolism, observed either in vitro or in vivo, and this group of metabolic effects. We review molecular mechanisms by which the HIV protease inhibitor (PI) class of drugs may affect the normal stimulatory effect of insulin on glucose and fat storage. We then propose that both chronic inflammation from HIV infection and treatment with some drugs in this class trigger cellular homeostatic stress responses with adverse effects on intermediary metabolism. The physiologic outcome is such that total adipocyte storage capacity is decreased, and the remaining adipocytes resist further fat storage. The excess circulating and dietary lipid metabolites, normally "absorbed" by adipose tissue, are deposited ectopically in lean (muscle and liver) tissue, where they impair insulin action. This process leads to a pathologic cycle of lipotoxicity and lipoatrophy and a clinical phenotype of body fat distribution with elevated waist-to-hip ratio similar to the metabolic syndrome.

Antiretroviral-related adipocyte dysfunction and lipodystrophy in HIV-infected patients: Alteration of the PPARγ-dependent pathways

Lipodystrophy and metabolic alterations are major complications of antiretroviral therapy in HIV-infected patients. In vitro studies using cultured murine and human adipocytes revealed that some protease inhibitors (PIs) and nucleoside reverse transcriptase inhibitors (NRTIs) were implicated to a different extent in adipose cell dysfunction and that a chronic incubation with some PIs decreased mRNA and protein expression of PPARγ. Defective lamin A maturation linked to PI inhibitory activity could impede the nuclear translocation of SREBP1c, therefore, reducing PPARγ expression. Adipose cell function was partially restored by the PPARγ agonists, thiazolidinediones. Adverse effects of PIs and NRTIs have also been reported in macrophages, a cell type that coexists with, and modulates, adipocyte function in fat tissue. In HIV-infected patients under ART, a decreased expression of PPARγ and of PPARγ-related genes was observed in adipose tissue, these anomalies being more severe in patients with ART-induced lipoatrophy. Altered PPARγ expression was reversed in patients stopping PIs. Treatment of patients with agonists of PPARγ could improve, at least partially, the subcutaneous lipoatrophy. These data indicate that decreased PPARγ expression and PPARγ-related function, resulting from ART-induced adipose tissue toxicity, play a central role in HIV-related lipoatrophy and metabolic consequences.

Measuring and monitoring apoptosis and drug toxicity in HIV patients by ligation-mediated polymerase chain reaction

Apoptosis has a critical role in normal physiology while its dysregulation has causal links with certain pathologies. A biochemical hallmark of apoptosis, internucleosomal genomic DNA fragmentation, is detectable by ligation-mediated polymerase chain reaction (LM-PCR). Here we converted LM-PCR into a new apoptosis quantifier by dividing trace quantities of 600 bp apoptotic amplicons into those of a single copy house-keeping gene, generating the LM-PCR 'value'. Dynamic range was approximately 17-fold correlating with a approximately 200-fold difference in degree of apoptotic fragmentation. Inter- and intra-gel reliability were both excellent, supporting LM-PCR's utility with large sample sets. Validation experiments comprising cell exposure to staurosporine over time revealed LM-PCR is as sensitive as caspase-3/ELISA and more sensitive than terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling/flourescence-activated cell sorting (TUNEL/FACS) for distinguishing low degrees of apoptosis (the spectrum most relevant in vivo). The LM-PCR profile mirrored that of caspase-3/ELISA but not TUNEL/FACS. We then applied this molecular tool to clinical investigation. Increased apoptosis is implicated in lipoatrophy (subcutaneous fat wasting), a serious, persistent toxicity of some nucleoside analogue reverse transcriptase inhibitors (NRTIs) used in anti-HIV highly active antiretroviral therapy (HAART). We demonstrated in 105 peripheral blood mononuclear cell samples that elevated LM-PCR values are seen during therapy with stavudine (d4T), a particularly toxic NRTI (P< 0.0001 versus no HAART, unpaired t-test). Elevated values were also independently associated with clinical evidence of lipoatrophy (P= 0.007, multiple logistic regression modelling) but not with patient age, CD4 T-cell count nor HIV viral load (P> 0.8 for each). Together these data demonstrate that LM-PCR is a robust and reliable quantifier of apoptosis with potential for basic science and clinical investigation.

The effects of Thiazolidinediones on metabolic complications and Lipodystrophy in HIV-infected patients

Highly active antiretroviral therapy (HAART)-associated metabolic complications include lipoatrophy (loss of subcutaneous adipose tissue (SAT)) and insulin resistance. Thiazolidinediones are insulin-sensitizing antidiabetic agents which-as an untoward side effect in obese diabetic patients-increase SAT. Furthermore, troglitazone has improved lipoatrophy and glycemic control in non-HIV patients with various forms of lipodystrophy. These data have led to 14 clinical trials to examine whether thiazolidinediones could be useful in the treatment of HAART-associated metabolic complications. The results of these studies indicate very modest, if any, effect on lipoatrophic SAT, probably due to ongoing HAART negating the beneficial effect. The benefit might be more prominent in patients not taking thymidine analoges. Despite the poor effect on lipoatrophy, thiazolidin-ediones improved insulin sensitivity. However, especially rosiglitazone induced harmful effects on blood lipids. Current data do not provide evidence for the use of thiazolidinediones in the treatment of HAART-associated lipoatrophy, but treatment of lipoatrophy-associated diabetes may be warranted. The role of thiazolidinediones for novel indications, such as hepatosteatosis, should be studied in these patients.

Inhibition of cation channels and suicidal death of human erythrocytes by zidovudine

Zidovudine, a drug widely used in the treatment of AIDS, has been shown to influence cytosolic calcium activity in HIV-infected lymphocytes. Thus, zidovudine may modify the activity of Ca(2+)-permeable ion channels. In erythrocytes, activation of Ca(2+)-permeable cation channels stimulates eryptosis, the suicidal erythrocyte death. Eryptosis is characterized by cell shrinkage (apparent from a decrease of forward scatter) and phosphatidylserine (PS) exposure (apparent from annexin V-binding) at the erythrocyte surface. Triggers of eryptosis include isotonic cell shrinkage (Cl(-) replacement by gluconate), energy depletion (removal of glucose) or exposure to a variety of drugs including azathioprine. The present study explored, whether zidovudine influences the activity of erythrocytic Ca(2+)-permeable cation channels and eryptosis. Whole-cell patch-clamp recordings indeed revealed that zidovudine blocked the Ca(2+)-permeable cation channels activated by Cl(-) removal. In the presence of Cl(-) and glucose, the percentage of annexin V-binding cells was low and not significantly modified by the presence of zidovudine. Both, Cl(-) removal and glucose depletion increased annexin V-binding and decreased forward scatter, effects significantly blunted by zidovudine (2 microg/ml). According to Fluo3 fluorescence, zidovudine (2 microg/ml) did not significantly modify cytosolic Ca(2+) concentration under control conditions, but significantly blunted the increase in cytosolic Ca(2+) activity following glucose depletion. Furthermore, zidovudine significantly inhibited azathioprine-induced eryptosis. The present observations disclose a completely novel effect of zidovudine, i.e. its inhibitory influence on Ca(2+) entry and subsequent suicidal erythrocyte death during isotonic cell shrinkage or energy depletion.

Drug-specific effect of nelfinavir and stavudine on primary culture of human preadipocytes

Lipodystrophic syndrome is a major side effect of antiviral therapy leading to profound disturbances in adipose tissue. Human preadipocyte primary culture represents a model to understand mechanisms by which antiretroviral drugs alter adipocyte biology. The aim of this study was to evaluate the effects of various protease and nucleoside reverse transcriptase inhibitors in this model. We tested the effect of drugs on triglyceride accumulation and expression of specific genes by real-time polymerase chain reaction. To determine differential mechanisms by which the efficient drugs operate, we studied mitochondrial effects by evaluating oxygen consumption rates and nuclear lamina alteration by immunocytology. Only stavudine and nelfinavir, both at 10 microM, altered human adipose cell differentiation, as shown by reduced triglyceride accumulation. Our studies revealed that stavudine increased expression of genes such as PGC1 and LPL and affected mitochondrial respiration. Cells treated with nelfinavir had a lower expression of PPARgamma, LPL, and ap2 and presented disorganization of lamin A/C. Our data suggest for the first time in a model of human adipocytes differentiated in vitro that stavudine and nelfinavir interfere with the process of differentiation by 2 distinct mechanisms. This may be particularly relevant in understanding the physiopathologic mechanisms underlying the lipodystrophic syndrome.