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

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.

PPARγ Gene as a Possible Link between Acquired and Congenital Lipodystrophy and its Modulation by Dietary Fatty Acids

Lipodystrophy syndromes are rare diseases that could be of genetic or acquired origin. The main complication of lipodystrophy is the dysfunction of adipose tissue, which leads to an ectopic accumulation of triglycerides in tissues such as the liver, pancreas and skeletal muscle. This abnormal fat distribution is associated with hypertriglyceridemia, insulin resistance, liver steatosis, cardiomyopathies and chronic inflammation. Although the origin of acquired lipodystrophies remains unclear, patients show alterations in genes related to genetic lipodystrophy, suggesting that this disease could be improved or aggravated by orchestrating gene activity, for example by diet. Nowadays, the main reason for adipose tissue dysfunction is an imbalance in metabolism, caused in other pathologies associated with adipose tissue dysfunction by high-fat diets. However, not all dietary fats have the same health implications. Therefore, this article aims to summarize the main genes involved in the pathophysiology of lipodystrophy, identify connections between them and provide a systematic review of studies published between January 2017 and January 2022 of the dietary fats that can modulate the development of lipodystrophy through transcriptional regulation or the regulation of protein expression in adipocytes.

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.

Inflammation and Metabolic Complications in HIV

PURPOSE OF REVIEW

We aim to provide an in-depth review of recent literature highlighting the role of inflammation involving the adipose tissue, liver, skeletal muscles, and gastrointestinal tract in the development of metabolic complications among persons living with HIV (PLWH).

RECENT FINDINGS

Recent studies in PLWH have demonstrated a significant association between circulating inflammatory markers and development of insulin resistance and metabolic complications. In adipose tissue, pro-inflammatory cytokine expression inhibits adipocyte insulin signaling, which alters lipid and glucose homeostasis. Increased lipolysis and lipogenesis elevate levels of circulating free fatty acids and promote ectopic fat deposition in liver and skeletal muscles. This leads to lipotoxicity characterized by a pro-inflammatory response with worsening insulin resistance. Finally, HIV is associated with gastrointestinal tract inflammation and changes in the gut microbiome resulting in reduced diversity, which is an additional risk factor for diabetes. Metabolic complications in PLWH are in part due to chronic, multisite tissue inflammation resulting in dysregulation of glucose and lipid trafficking, utilization, and storage.

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.

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.

Differential adipose tissue gene expression profiles in abacavir treated patients that may contribute to the understanding of cardiovascular risk: a microarray study

OBJECTIVE

To compare changes in gene expression by microarray from subcutaneous adipose tissue from HIV treatment naïve patients treated with efavirenz based regimens containing abacavir (ABC), tenofovir (TDF) or zidovidine (AZT).

DESIGN

Subcutaneous fat biopsies were obtained before, at 6- and 18-24-months after treatment, and from HIV negative controls. Groups were age, ethnicity, weight, biochemical profile, and pre-treatment CD4 count matched. Microarray data was generated using the Agilent Whole Human Genome Microarray. Identification of differentially expressed genes and genomic response pathways was performed using limma and gene set enrichment analysis.

RESULTS

There were significant divergences between ABC and the other two groups 6 months after treatment in genes controlling cell adhesion and environmental information processing, with some convergence at 18-24 months. Compared to controls the ABC group, but not AZT or TDF showed enrichment of genes controlling adherence junction, at 6 months and 18-24 months (adjusted p<0.05) and focal adhesions and tight junction at 6 months (p<0.5). Genes controlling leukocyte transendothelial migration (p<0.05) and ECM-receptor interactions (p = 0.04) were over-expressed in ABC compared to TDF and AZT at 6 months but not at 18-24 months. Enrichment of pathways and individual genes controlling cell adhesion and environmental information processing were specifically dysregulated in the ABC group in comparison with other treatments. There was little difference between AZT and TDF.

CONCLUSION

After initiating treatment, there is divergence in the expression of genes controlling cell adhesion and environmental information processing between ABC and both TDF and AZT in subcutaneous adipose tissue. If similar changes are also taking place in other tissues including the coronary vasculature they may contribute to the increased risk of cardiovascular events reported in patients recently started on abacavir-containing regimens.

A pilot study of telmisartan for visceral adiposity in HIV infection: the metabolic abnormalities, telmisartan, and HIV infection (MATH) trial

Background

Visceral adiposity in the setting of HIV infection and antiretroviral therapy (ART) is not fully understood, and treatment options remain limited. Telmisartan, an angiotensin receptor blocker and partial PPAR-γ agonist, has been shown to decrease visceral fat and improve metabolic and inflammatory parameters in HIV-uninfected subjects.

Methods

HIV-infected subjects with HIV-1 RNA <50 copies/mL on ART and (women/men) waist circumference >94/95 cm or waist: hip ratio >0.88/0.94 received open-label telmisartan 40 mg po daily for 24 weeks. Adipose tissue (AT) volumes were quantified by L4–L5 single slice computed tomography. Metabolic and inflammatory markers were obtained fasting. Thirty-five subjects provided 80% power to detect a 10% 24-week decrease in visceral AT (VAT, two-sided α = 0.05).

Results

Thirty-five subjects enrolled and completed the protocol. At entry (median or %): age 49 years, 43% female, 77% non-white, 91% non-smokers, CD4+ T cell count 590 cells/mm³, BMI 31 kg/m². AT responses were heterogeneous, with statistically significant losses of median (IQR) total (TAT, 2.9% (−9.8, 0.7), p = 0.03) and subcutaneous (SAT, −2.7% (−9.8, 1.1), p = 0.03) AT, but not VAT (−2.7% (−20.5, 14.2), p = 0.53). Significant decreases in waist circumference and waist:hip ratio occurred (both p<0.001) without BMI or weight changes. In an exploratory analysis, significant increases in TNF-α occurred among female subjects without changes in other inflammatory or metabolic markers. No related adverse events occurred.

Conclusions

Telmisartan was well tolerated. Small losses of AT from all depots were observed after 24 weeks of telmisartan therapy. Further study is needed to determine whether HIV-infected patients can receive metabolic benefits from telmisartan.

Trial Registration

ClinicalTrials.gov NCT01088295

Peroxisome proliferator-activated receptor-γ mutations responsible for lipodystrophy with severe hypertension activate the cellular renin-angiotensin system

OBJECTIVE

Inactivating peroxisome proliferator-activated receptor-γ (PPARγ) mutations lead to a syndrome of familial partial lipodystrophy (FPLD3) associated with early-onset severe hypertension. PPARγ can repress the vascular renin-angiotensin system (RAS) and angiotensin II receptor 1 expression. We evaluated the relationships between PPARγ inactivation and cellular RAS using FPLD3 patients' cells and human vascular smooth muscle cells expressing mutant or wild-type PPARγ. Approach and Results- We identified 2 novel PPARG mutations, R165T and L339X, located in the DNA and ligand-binding domains of PPARγ, respectively in 4 patients from 2 FPLD3 families. In cultured skin fibroblasts and peripheral blood mononuclear cells from the 4 patients and healthy controls, we compared markers of RAS activation, oxidative stress, and inflammation, and tested the effect of modulators of PPARγ and angiotensin II receptor 1. We studied the impact of the 2 mutations on the transcriptional activity of PPARγ and on the vascular RAS in transfected human vascular smooth muscle cells. Systemic RAS was not altered in patients. However, RAS markers were overexpressed in patients' fibroblasts and peripheral blood mononuclear cells, as in vascular cells expressing mutant PPARγ. Angiotensin II-mediated mitogen-activated protein kinase activity increased in patients' fibroblasts, consistent with RAS constitutive activation. Patients' cells also displayed oxidative stress and inflammation. PPARγ activation and angiotensin II receptor 1 mRNA silencing reversed RAS overactivation, oxidative stress, and inflammation, arguing for a role of angiotensin II receptor 1 in these processes.

CONCLUSIONS

Two novel FPLD3-linked PPARG mutations are associated with a defective transrepression of cellular RAS leading to cellular dysfunction, which might contribute to the specific FPLD3-linked severe hypertension.

Nonreceptor tyrosine phosphatase Shp2 promotes adipogenesis through inhibition of p38 MAP kinase

The molecular mechanism underlying adipogenesis and the physiological functions of adipose tissue are not fully understood. We describe here a unique mouse model of severe lipodystrophy. Ablation of Ptpn11/Shp2 in adipocytes, mediated by aP2-Cre, led to premature death, lack of white fat, low blood pressure, compensatory erythrocytosis, and hepatic steatosis in Shp2(fat-/-) mice. Fat transplantation partially rescued the lifespan and blood pressure in Shp2(fat-/-) mice, and administration of leptin also restored partially the blood pressure of mutant animals with endogenous leptin deficiency. Consistently, homozygous deletion of Shp2 inhibited adipocyte differentiation from embryonic stem (ES) cells. Biochemical analyses suggest a Shp2-TAO2-p38-p300-PPARγ pathway in adipogenesis, in which Shp2 suppresses p38 activation, leading to stabilization of p300 and enhanced PPARγ expression. Inhibition of p38 restored adipocyte differentiation from Shp2(-/-) ES cells, and p38 signaling is also suppressed in obese patients and obese animals. These results illustrate an essential role of adipose tissue in mammalian survival and physiology and also suggest a common signaling mechanism involved in adipogenesis and obesity development.

Nelfinavir suppresses insulin signaling and nitric oxide production by human aortic endothelial cells: protective effects of thiazolidinediones

BACKGROUND

In human immunodeficiency virus 1 (HIV-1)-infected individuals, exposure to a protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) regimen increases cardiovascular disease and endothelial dysfunction. However, the mechanisms of PI-induced effects on endothelial cells (ECs) are not known. Furthermore, strategies to suppress these deleterious outcomes of PIs need to be developed. Insulin-induced PI3K/Akt signaling and endothelial nitric oxide (NO)-synthase (eNOS) phosphorylation regulates NO production by ECs that maintain vascular homeostasis. We evaluated whether nelfinavir (NEL), a potent HIV-1 PI that suppresses Akt phosphorylation, can alter insulin-induced NO production in human aortic endothelial cells (HAECs) and whether insulin sensitization of HAECs via the peroxisome proliferator-activated receptor-gamma agonists, thiazolidinediones, can ameliorate these side effects.

METHODS

Real-time NO production in HAECs was monitored by fluorimetric dyes DAF-FM DA and DAF-2 DA. Immunodetection studies were used to determine the phosphorylation of Akt, eNOS, insulin receptor-β (IR-β), insulin receptor substrate-1 (IRS-1), and PI3K/p85α. Expression of eNOS messenger RNA was measured by reverse transcription polymerase chain reaction.

RESULTS

In vitro exposure (72 hours) of HAECs to NEL (0.25-2 μg/mL) decreased both basal (2.5-fold) and insulin-induced NO production (4- to 5-fold). NEL suppressed insulin-induced phosphorylation of both Akt and eNOS at serine residues 473 and 1177, respectively. NEL decreased tyrosine phosphorylation of IR-β, IRS-1, and PI3K. Coexposure to troglitazone (TRO; 250 nM) ameliorated the suppressive effects of NEL on insulin signaling and NO production. Coexposure to TRO also increased eNOS expression in NEL-treated HAECs.

CONCLUSION

Our findings indicate that treatment with potent insulin sensitizers may protect against PI-mediated endothelial dysfunction during long-term HAART.

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.

Mitochondrial interference by anti-HIV drugs: mechanisms beyond Pol-γ inhibition

The combined pharmacological approach to the treatment of HIV infection, known as highly active antiretroviral therapy (HAART), has dramatically reduced AIDS-related morbidity and mortality. However, its use has been associated with serious adverse reactions, of which those resulting from mitochondrial dysfunction are particularly widespread. Nucleos(t)ide-reverse transcriptase inhibitors (NRTIs) have long been considered the main source of HAART-related mitochondrial toxicity due to their ability to inhibit Pol-γ, the DNA polymerase responsible for the synthesis of mitochondrial DNA. Nevertheless, accumulating evidence points to a more complex relationship between these organelles and NRTIs. Also, alternative pathways by which other groups of anti-HIV drugs (non-nucleoside reverse transcriptase inhibitors and protease inhibitors) interfere with mitochondria have been suggested, although their implications, both pharmacological and clinical, are open to debate. This review aims to provide a comprehensive overview of the mechanisms and factors which influence the mitochondrial involvement in the toxicity of all three major classes of anti-HIV drugs.

Central players in inherited lipodystrophies

Common obesity and inherited lipodystrophies, rare disorders characterized by a partial (familial partial lipodystrophy; FPLD) or complete (congenital generalized lipodystrophy; CGL) lack of adipose tissue, are both associated with metabolic complications such as insulin resistance and type 2 diabetes. Mutations in the transcription factor peroxisome proliferator activated receptor (PPAR)γ and a number of its downstream target genes result in lipodystrophy. We hypothesize that signalling by another transcription factor, sterol response element binding protein (SREBP)1c, also needs to be intact to prevent lipodystrophy. The future challenge is to understand how inactivation of such central players or of their upstream regulators or downstream effectors can affect adipose tissue in a depot-specific fashion.

New and emerging agents in the management of lipodystrophy in HIV-infected patients

Lipodystrophy remains a major long-term complication in human immunodeficiency virus-infected patients under antiretroviral (ARV) therapy. Patients may present with lipoatrophy or lipohypertrophy or both. The choice of treatments to improve fat redistribution depends on the form of lipodystrophy and its duration. Measures known to improve lipoatrophy are switches in ARV therapy (stavudine or zidovudine to abacavir or tenofovir) and filling interventions. Pioglitazone may be added to these measures, although any benefits appear small. Uridine and leptin were found to be disappointing so far. Regarding lipohypertrophy, diet and exercise, recombinant human growth hormone, and metformin may reduce visceral fat, but may worsen subcutaneous lipoatrophy. Surgical therapy may be required. Attractive pharmacologic treatments include growth hormone-releasing factor and leptin. Adiponectin and adiponectin receptors are promising therapeutic targets to explore.

Comparison of the influence of four classes of HIV antiretrovirals on adipogenic differentiation: the minimal effect of raltegravir and atazanavir

Antiretroviral therapy for HIV infection is associated with lipodystrophy. However, raltegravir (RAL), a new integrase inhibitor, and atazanavir (ATV), a new generation of protease inhibitor (PI), have not been reported to significantly induce metabolic abnormalities in some clinical studies. The aim of this study was to investigate the influence and molecular mechanisms of RAL and compared it with the other three classes of ARVs (nucleoside reverse-transcriptase inhibitors; NRTI, nonnucleoside reverse-transcriptase inhibitor; NNRTI, and PI) on adipogenesis using 3T3-L1 cells. RAL and ATV had minimal effects on the lipid metabolism of 3T3-L1 cells. NRTI induced a moderate change, and NNRTI and some PIs induced a severe reduction in cell lipid content. These ARVs induced a decrease in the expression of genes associated with lipogenic transcription factors (sterol regulatory-element-binding protein-1c, CAAT box enhancer-binding protein-α, and peroxisome proliferator-activated receptor-γ). The differentiated 3T3-L1 cells were less sensitive to ARV-induced metabolic disturbance than were predifferentiated cells. RAL and ATV did not significantly affect the lipid metabolism in our in vitro study. The other ARVs had a direct influence on adipocytes. Degree and underlying mechanisms of metabolic disturbance differed among different ARVs. These data suggest that the distinct metabolic side-effect profiles of ARVs are a consequences of their differential effects on the adipocyte physiology. A better understanding of the mechanism of ARV-induced metabolic abnormalities could lead to safer use of ARVs or selection of alternative agents for further clinical development.

Recent advances in antiretroviral drugs

IMPORTANCE OF THE FIELD

Acquired immunodeficiency syndrome (AIDS) is one of the leading causes of death worldwide. Although the combination therapies of highly active antiretroviral therapy (HAART) have significantly contributed to virological suppression, improved immune function and quality of life, issues such as tolerability, drug-drug interactions and cross-resistance amongst members of a particular drug class still pose a significant barrier to long-term successful treatment. There is a constant need for newer anti HIV drugs with increased potency and improved pharmacokinetic properties either in the existing classes or drugs from new classes that target several new steps in HIV replication cycle.

AREAS COVERED IN THIS REVIEW

The authors have discussed newer antiretroviral drugs belonging to second-generation nucleoside analog reverse transcriptase inhibitors (amdoxovir, elvucitabine, apricitabine, racivir), non-nucleoside analog reverse transcriptase inhibitors (etravirine, rilpivirine), protease inhibitors (darunavir, tipranavir) as well as emerging new classes, i.e., fusion inhibitors (enfuvirtide, sifuvirtide), CCR5 inhibitors (maraviroc, vicriviroc, PRO 140, PRO 542), CD4-receptor inhibitors (ibalizumab), integrase inhibitors (raltegravir, elvitegravir, GSK-1349572), maturation inhibitors (bevirimat), cobicistat (pharmacoenhancer), lens epithelium-derived growth factor inhibitors and capsid assembly inhibitors.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the mechanism of action, mechanism of resistance, stages of development and important clinical trials related to the newer antiretroviral drugs and future potential of these drugs.

TAKE HOME MESSAGE

The initial clinical trial data of these newer drugs are very encouraging for the long-term successful control of HIV in both treatment-naïve and treatment-experienced patients.

Effect of ritonavir and atazanavir on human subcutaneous preadipocyte proliferation and differentiation

Protease inhibitors (PIs) have been implicated in the development of HIV-associated lipodystrophy through a reduction in the differentiation of preadipocytes. While atazanavir (ATV) is associated with fewer clinical metabolic abnormalities in the short-term, the effects of long-term exposure are not known. ATV effects on preadipocyte replication or differentiation would indicate the potential for long-term problems. This study compared ritonavir (RTV) and ATV effects on preadipocyte replication and differentiation in human primary cultures. Preadipocytes from subcutaneous fat were studied in the presence of therapeutic concentrations of RTV and ATV for replication, differentiation, and adipokine secretion. The effects of the drugs on the expression of PPARgamma and related genes during differentiation were also assessed by real-time quantitative PCR. RTV induced a significant inhibition of preadipocyte proliferation, differentiation and adiponectin secretion. ATV at concentrations within the range of therapeutic levels did not affect differentiation or adiponectin secretion, but did have inhibitory effects on preadipocyte proliferation. Inhibition of differentiation by PIs was associated with decreased expression of PPARgamma, C/EBPalpha, and aP2 genes. In summary, although ATV at therapeutic levels has a smaller impact on adipogenesis, alterations in preadipocyte proliferation suggest the potential for adverse effects with long-term use.