Effect of atazanavir and ritonavir on the differentiation and adipokine secretion of human subcutaneous and omental preadipocytes

Cellular Mechanism Underlying Highly-Active or Antiretroviral Therapy-Induced Lipodystrophy: Atazanavir, a Protease Inhibitor, Compromises Adipogenic Conversion of Adipose-Derived Stem/Progenitor Cells through Accelerating ER Stress-Mediated Cell Death in Differentiating Adipocytes

Lipodystrophy is a common complication in human immunodeficiency virus (HIV)-infected patients receiving highly active antiretroviral therapy (HAART) or antiretroviral therapy (ART). Previous studies demonstrated that endoplasmic reticulum (ER) stress-mediated unfolded protein response (UPR) is involved in lipodystrophy; however, the detailed mechanism has not been fully described in human adipogenic cell lineage. We utilized adipose tissue-derived stem cells (ADSCs) obtained from human subcutaneous adipose tissue, and atazanavir (ATV), a protease inhibitor (PI), was administered to ADSCs and ADSCs undergoing adipogenic conversion. Marked repression of adipogenic differentiation was observed when ATV was administered during 10 days of ADSC culture in adipogenic differentiation medium. Although ATV had no effect on ADSCs, it significantly induced apoptosis in differentiating adipocytes. ATV treatment also caused the punctate appearance of CCAAT-enhancer-binding (C/EBP) protein homologous protein (CHOP), and altered expression of CHOP and GRP78/Bip, which are the representation of ER stress, only in differentiating adipocytes. Administration of UPR inhibitors restored adipogenic differentiation, indicating that ER stress-mediated UPR was induced in differentiating adipocytes in the presence of ATV. We also observed autophagy, which was potentiated in differentiating adipocytes by ATV treatment. Thus, adipogenic cell atrophy leads to ATV-induced lipodystrophy, which is mediated by ER stress-mediated UPR and accelerated autophagy, both of which would cause adipogenic apoptosis. As our study demonstrated for the first time that ADSCs are unsusceptible to ATV and its deleterious effects are limited to the differentiating adipocytes, responsible target(s) for ATV-induced lipodystrophy may be protease(s) processing adipogenesis-specific protein(s).

HIV and antiretroviral therapy-related fat alterations

Early in the HIV epidemic, lipodystrophy, characterized by subcutaneous fat loss (lipoatrophy), with or without central fat accumulation (lipohypertrophy), was recognized as a frequent condition among people living with HIV (PLWH) receiving combination antiretroviral therapy. The subsequent identification of thymidine analogue nucleoside reverse transcriptase inhibitors as the cause of lipoatrophy led to the development of newer antiretroviral agents; however, studies have demonstrated continued abnormalities in fat and/or lipid storage in PLWH treated with newer drugs (including integrase inhibitor-based regimens), with fat gain due to restoration to health in antiretroviral therapy-naive PLWH, which is compounded by the rising rates of obesity. The mechanisms of fat alterations in PLWH are complex, multifactorial and not fully understood, although they are known to result in part from the direct effects of HIV proteins and antiretroviral agents on adipocyte health, genetic factors, increased microbial translocation, changes in the adaptive immune milieu after infection, increased tissue inflammation and accelerated fibrosis. Management includes classical lifestyle alterations with a role for pharmacological therapies and surgery in some patients. Continued fat alterations in PLWH will have an important effect on lifespan, healthspan and quality of life as patients age worldwide, highlighting the need to investigate the critical uncertainties regarding pathophysiology, risk factors and management.

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.

Correlation of Leptin, Adiponectin, and Resistin Levels in Different Types of Lipodystrophy in HIV/AIDS Patients

BACKGROUND

Leptin, adiponectin, and resistin may play an important role in the development of lipodystrophy (LD) in HIV/AIDS patients. The aim of this study was to correlate levels of leptin, adiponectin, and resistin between HIV/AIDS patients with LD and without lipodystrophy (non-LD), as well as between subgroups of LD [lipoatrophy (LA), lipohypertrophy (LH), and mixed fat redistribution (MFR)] and non-LD patients.

METHODS

Cross-sectional study of 66 HIV/AIDS patients. Serum levels of leptin, adiponectin, and resistin were measured. The associations between adipocytokine levels and metabolic variables were estimated by Spearman correlation. Analysis of covariance with bootstrapping method was used to examine the relationship between adiponectin and leptin and lipodystrophy categories.

RESULTS

The LD was observed in 29 (44%) patients, while 15 (52%) of them had LA, 4 (14%) had LH, and 10 (34%) patients had MFR. No significant differences regarding leptin, adiponectin, and resistin levels, between LD and non-LD patients, were observed. LH patients had significantly higher levels of leptin and adiponectin in comparison with non-LD patients (P = 0.039, P = 0.011, respectively). Within the LD group, LA patients had significantly lower levels of leptin (LA vs. LH, P = 0.020; LA vs. MFR, P = 0.027), while LH patients had significantly higher levels of adiponectin (LH vs. LA, P = 0.027; LH vs. MFR, P = 0.028). Correlation of adiponectin with LD remains significant in the LH subgroup after adjustment for age, body mass index, cystatin-C, plasminogen activator inhibitor-1 (PAI-1), and interferon gamma (IFN-γ) (P = 0.001).

CONCLUSIONS

Adiponectin and leptin levels differ significantly between LH patients and non-LD patients, as well as between the LD subgroups. Adiponectin may be a more useful marker of LD in HIV/AIDS patients.

[Wasting syndrome in HIV-infected patients]

The review of literature analyzes scientific data on wasting syndrome in HIV-infected patients. It considers its etiology, diagnosis,and therapeutic approaches.

HIV protease inhibitors disrupt lipid metabolism by activating endoplasmic reticulum stress and inhibiting autophagy activity in adipocytes

BACKGROUND

HIV protease inhibitors (PI) are core components of Highly Active Antiretroviral Therapy (HAART), the most effective treatment for HIV infection currently available. However, HIV PIs have now been linked to lipodystrophy and dyslipidemia, which are major risk factors for cardiovascular disease and metabolic syndrome. Our previous studies have shown that HIV PIs activate endoplasmic reticulum (ER) stress and disrupt lipid metabolism in hepatocytes and macrophages. Yet, little is known on how HIV PIs disrupt lipid metabolism in adipocytes, a major cell type involved in the pathogenesis of metabolic syndrome.

METHODOLOGY AND PRINCIPAL FINDINGS

Cultured and primary mouse adipocytes and human adipocytes were used to examine the effect of frequently used HIV PIs in the clinic, lopinavir/ritonavir, on adipocyte differentiation and further identify the underlying molecular mechanism of HIV PI-induced dysregulation of lipid metabolism in adipocytes. The results indicated that lopinavir alone or in combination with ritonavir, significantly activated the ER stress response, inhibited cell differentiation, and induced cell apoptosis in adipocytes. In addition, HIV PI-induced ER stress was closely linked to inhibition of autophagy activity. We also identified through the use of primary adipocytes of CHOP(-/-) mice that CHOP, the major transcriptional factor of the ER stress signaling pathway, is involved in lopinavir/ritonavir-induced inhibition of cell differentiation in adipocytes. In addition, lopinavir/ritonavir-induced ER stress appears to be associated with inhibition of autophagy activity in adipocytes.

CONCLUSION AND SIGNIFICANCE

Activation of ER stress and impairment of autophagy activity are involved in HIV PI-induced dysregulation of lipid metabolism in adipocytes. The key components of ER stress and autophagy signaling pathways are potential therapeutic targets for HIV PI-induced metabolic side effects in HIV patients.

The protease inhibitor atazanavir triggers autophagy and mitophagy in human preadipocytes

BACKGROUND

The association between HAART and lipodystrophy is well established, but lipodystrophy pathogenesis is still poorly understood. Drugs, and in particular protease inhibitors, accumulate in adipose tissue affecting adipocyte physiology and gene expression by several mechanisms. Recent studies have identified autophagy as another process affected by these classes of drugs, but no studies have been performed in adipose cells.

METHODS

SW872 preadipocytic human cell line was used to evaluate changes induced by amprenavir (APV), ritonavir (RTV), or atazanavir (ATV), all used at 10-200 μmol/l. A subline was stably transfected with murine stem cell virus (pMSCV)-enhanced green fluorescent protein (EGFP)-LC3 plasmid (to obtain a fluorescent LC3 protein) and treated with ATV at different doses. The distribution of LC3 and the colocalization of mitochondria, lysosome, and autophagosome were assessed by confocal microscopy. Transmission electron microscopy of ATV-treated cells was also performed. The cellular content of lysosomes was assessed using Lysotracker Green; apoptosis was evaluated by annexin V/propidium iodide staining, and mitochondrial superoxide anion (mtO2) was analyzed by mitoSOX red. Lysosomes, apoptosis, and mtO2 were studied by flow cytometry and multispectral imaging flow cytometry.

RESULTS

In SW872 cells, RTV caused massive apoptosis, more than autophagy, whereas APV was almost ineffective. ATV induced both apoptosis (high doses) and autophagy (low doses). ATV-treated cells displayed LC3-specific punctae, suggesting the formation of autophagosomes that enclosed mitochondria, as revealed by electron microscopy. At low doses, ATV promoted mitochondrial superoxide generation, whereas at high doses, it induced mitochondrial membrane depolarization.

CONCLUSION

Autophagy/mitophagy can be considered a mechanism triggered by ATV in SW872 preadipocytes.

Metabolic disorders and cardiovascular consequences of HIV infection and antiretroviral therapy

Metabolic disturbances associated with HIV disease have become an important factor in patient management and have important implications for long-term outcomes, both in regards to mortality and healthcare burden. Recent research has implicated both HIV infection itself and specific antiretroviral therapies in the development of these disorders. This review examines recent findings from research into insulin and glucose dysregulation, serum lipid abnormalities, adipose tissue and derangements in bone metabolism. This review then describes the cardiovascular consequences and management of these metabolic disorders, and summarizes current thinking on the pathogenesis and effects of antiretroviral therapy. Finally, the review raises some questions regarding ongoing challenges and unmet needs in this field of research.

Body composition and metabolic changes in HIV-infected patients

As antiretroviral therapy has decreased human immunodeficiency virus (HIV)-associated mortality, cardiometabolic abnormalities have become increasingly apparent in HIV-infected individuals. Many patients treated for HIV infection exhibit body composition changes, including peripheral fat atrophy and visceral lipohypertrophy. In addition, HIV-infected individuals demonstrate a higher prevalence of dyslipidemia, insulin resistance and diabetes, and cardiovascular risk, compared with the general population. Although antiretroviral therapy appears to contribute to some of the cardiometabolic abnormalities in HIV infection, HIV itself, immunologic factors, and lifestyle factors are also important mediators of cardiovascular risk. Treatment strategies for body composition changes and cardiometabolic abnormalities in HIV infection include lifestyle modification, lipid-lowering agents, insulin sensitizers, and treatments to reverse endocrine abnormalities in HIV, including growth hormone-releasing hormone. None of these strategies has comprehensively addressed the abnormalities experienced by this population, however, and further research is needed into combined strategies to improve body composition and ameliorate cardiovascular risk.

Ritonavir boosting dose reduction from 100 to 50 mg does not change the atazanavir steady-state exposure in healthy volunteers

OBJECTIVES

To evaluate the pharmacokinetics, tolerability and safety of 300 mg of atazanavir boosted with 100 or 50 mg of ritonavir, both once daily, at steady state.

METHODS

This was a single-blind, multiple-dose, crossover, sequence-randomized trial. Thirteen healthy HIV-1-negative men received witnessed once-daily doses of atazanavir (300 mg) and 100 or 50 mg of ritonavir for 10 days (15 day washout). Atazanavir and ritonavir plasma concentrations were determined for 24 h on day 10. Log-transformed individual pharmacokinetic parameters were compared between treatments (analysis of variance); the difference between treatments on the log scale and 95% CIs were calculated. Fasting cholesterol, triglycerides, glucose and bilirubin plasma levels were measured at the beginning and end of each period and compared (Wilcoxon signed rank test). Gastrointestinal symptoms and other events were recorded.

RESULTS

Ritonavir C(max) and the AUC₀₋₂₄ were lower after the 50 mg booster dose than after 100 mg [geometric mean ratio (GMR) (95% CI), 0.40 (0.31-0.51) and 0.35 (0.29-0.42), respectively]. No differences were observed in atazanavir exposure with 50 or 100 mg of ritonavir [GMR C(max) (95% CI), 1.00 (0.79-1.28); GMR AUC₀₋₂₄ (95% CI), 0.98 (0.79-1.21)]. Atazanavir trough concentration was >0.15 mg/L in all volunteers. Total and low-density lipoprotein cholesterol increased 0.40 mM (P = 0.01) and 0.37 mM (P = 0.003) from their corresponding baseline value during the 100 mg dosing period; there were no significant changes on 50 mg. Mild increases in bilirubin were detected on day 10 after both treatments without differences between treatments.

CONCLUSIONS

In spite of higher exposure to ritonavir with 100 mg, atazanavir exposure was equivalent; the lipid profile was better under the lower booster dose (50 mg).

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.

The effect of polymorphisms in candidate genes on the long-term risk of lipodystrophy and dyslipidemia in HIV-infected white patients starting antiretroviral therapy

We investigated whether polymorphisms in human candidate genes could be associated with a different risk of developing lipodystrophy and dyslipidemia in HIV-infected patients starting combination antiretroviral therapy (cART). Genomic DNA samples from white HIV-1-infected patients were analyzed for seven polymorphisms located in the MDR1, TNF-α, APM1, APOE, and LPL genes. Lipid data were retrospectively collected beginning with the initiation of cART. Lipodystrophy was assessed cross-sectionally and then prospectively. The association with lipodystrophy and National Cholesterol Evaluation Program Adult Treatment Panel III-defined lipid thresholds was analyzed using survival analysis and logistic regression. One-hundred and seventy-four patients were genotyped. In 151 patients assessed for lipodystrophy, MDR1 3435 T homozygosis was associated with a higher hazard (adjusted hazard ratio, aHR, versus CT 0.25; p=0.02) and tumor necrosis factor (TNF)-α 308 G homozygosis with a lower hazard (vs. AA aHR 2.14; p=0.04) of developing trunk fat accumulation after adjusting for gender and initial cART type. The TNF 238 GG genotype was associated with a higher risk of developing low HDL-cholesterol levels (adjusted odd ratio, aOR, 5.91; p=0.01) while patients carrying the LPL S477X mutation were at lower risk of reaching high non-HDL-cholesterol levels (aOR 0.39; p=0.05). The APOEe3/3 genotype patients were at lower risk (aOR 0.26, p=0.015), whereas the adiponectin 276 GT carriers were at higher risk of developing hypertriglyceremia (vs. GG aOR 3.10; p=0.04). Knowledge of the effect of genetic determinants on dyslipidemia and lipodystrophy may prompt the investigation of potential pathogenetic mechanisms and might eventually be used for guiding individualized treatment decisions.

Effects of ritonavir-boosted darunavir, atazanavir and lopinavir on adipose functions and insulin sensitivity in murine and human adipocytes

BACKGROUND

Ritonavir-boosted protease inhibitors (PIs) could adversely affect metabolism and adipose tissue to different extents, depending on the molecule. Using drugs with minimal adverse metabolic effects is an important consideration in at-risk HIV-infected patients. In vitro adipocyte models can be useful for comparing the effects of different PIs.

METHODS

We compared the effects of darunavir, darunavir/ritonavir, atazanavir/ritonavir and lopinavir/ritonavir in murine and human adipocytes on differentiation, mitochondrial function, reactive oxygen species (ROS) production and insulin sensitivity.

RESULTS

In human and murine adipocytes, differentiation evaluated by lipid content and protein expression of adipogenic markers, mitochondrial function evaluated by aggregation of the cationic dye JC-1 and by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide lysis, and mitochondrial mass evaluated by MitoTracker fluorescence and the expression of mitochondrial proteins were unaffected by darunavir, mildly affected by darunavir/ritonavir and further altered by atazanavir/ritonavir and lopinavir/ritonavir. ROS production was unaltered by darunavir and darunavir/ritonavir but was increased by lopinavir/ritonavir and atazanavir/ritonavir. Regarding insulin sensitivity, darunavir and darunavir/ritonavir had no significant effect on insulin activation of protein kinase B (Akt/PKB) and MAP kinase and of glucose transport, whereas lopinavir/ritonavir and atazanavir/ritonavir partly impaired the effect of insulin. The effect of atazanavir/ritonavir was generally milder than that of lopinavir/ritonavir.

CONCLUSIONS

The various PIs differentially modified adipocyte functions. Darunavir alone did not affect adipocyte functions and only modestly altered differentiation and mitochondrial function when associated with ritonavir. Lopinavir/ritonavir adversely affected differentiation and lipid content, mitochondrial function, ROS production and insulin sensitivity, and the effect of atazanavir/ritonavir was intermediate. Thus, in vitro, darunavir/ritonavir presented a safer metabolic profile on adipocytes than atazanavir/ritonavir and lopinavir/ritonavir.

Randomized comparison of metabolic and renal effects of saquinavir/r or atazanavir/r plus tenofovir/emtricitabine in treatment-naïve HIV-1-infected patients

OBJECTIVES

The aim of the study was to compare the effects on lipids, body composition and renal function of once-daily ritonavir-boosted saquinavir (SQV/r) or atazanavir (ATV/r) in combination with tenofovir/emtricitabine (TDF/FTC) over 48 weeks.

METHODS

An investigator-initiated, randomized, open-label, multinational trial comparing SQV/r 2000/100 mg and ATV/r 300/100 mg once daily, both in combination with TDF/FTC, in 123 treatment-naïve HIV-1-infected adults was carried out. The primary endpoint was to demonstrate noninferiority of SQV/r compared with ATV/r with respect to the change in fasting cholesterol after 24 weeks. Secondary outcome measures were changes in metabolic abnormalities, body composition, renal function, and virological and immunological efficacy over 48 weeks. Patients who had used at least one dose of trial drug were included in the analysis.

RESULTS

Data for 118 patients were analysed (57 patients on SQV/r and 61 on ATV/r). At week 24, changes in lipids were modest, without increases in triglycerides, including a significant rise in high-density lipoprotein (HDL) cholesterol and a nonsignificant decrease in the total:HDL cholesterol ratio in both arms with no significant difference between arms. Lipid changes at week 48 were similar to the changes observed up to week 24, with no significant change in the homeostasis model assessment (HOMA) index. Adipose tissue increased regardless of the regimen, particularly in the peripheral compartment and to a lesser extent in the central abdominal compartment, with an increase in adipose tissue reaching statistical significance in the ATV/r arm. A slight decline in the estimated glomerular filtration rate (eGFR) was observed in both arms during the first 24 weeks, with no progression thereafter. The immunological and virological responses were similar over the 48 weeks.

CONCLUSIONS

Combined with TDF/FTC, both SQV/r 2000/100 mg and ATV/r 300/100 mg had comparable modest effects on lipids, had little effect on glucose metabolism, conserved adipose tissue, and similarly reduced eGFR. The virological efficacy was similar.

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.

Effects of the HIV protease inhibitor ritonavir on GLUT4 knock-out mice

HIV protease inhibitors acutely block glucose transporters (GLUTs) in vitro, and this may contribute to altered glucose homeostasis in vivo. However, several GLUT-independent mechanisms have been postulated. To determine the contribution of GLUT blockade to protease inhibitor-mediated glucose dysregulation, the effects of ritonavir were investigated in mice lacking the insulin-sensitive glucose transporter GLUT4 (G4KO). G4KO and control C57BL/6J mice were administered ritonavir or vehicle at the start of an intraperitoneal glucose tolerance test and during hyperinsulinemic-euglycemic clamps. G4KO mice exhibited elevated fasting blood glucose compared with C57BL/6J mice. Ritonavir impaired glucose tolerance in control mice but did not exacerbate glucose intolerance in G4KO mice. Similarly, ritonavir reduced peripheral insulin sensitivity in control mice but not in G4KO mice. Serum insulin levels were reduced in vivo in ritonavir-treated mice. Ritonavir reduced serum leptin levels in C57BL/6J mice but had no effect on serum adiponectin. No change in these adipokines was observed following ritonavir treatment of G4KO mice. These data confirm that a primary effect of ritonavir on peripheral glucose disposal is mediated through direct inhibition of GLUT4 activity in vivo. The ability of GLUT4 blockade to contribute to derangements in the other molecular pathways that influence insulin sensitivity remains to be determined.

Antiretroviral therapy with heart

Antiretroviral therapy (ART) has resulted in a substantial improvement in the morbidity and mortality associated with human immunodeficiency virus (HIV) infection. As this population ages, cardiovascular disease is becoming an increasingly important health burden. It is clear that many factors are involved in the development of this problem, with traditional risk factors (smoking, dyslipidemia, diabetes, family history, hypertension) the main contributors. ART and HIV infection itself can modify the risk of cardiovascular disease. Not only does this increased risk seem to be mediated through effects on traditional cardiovascular risk factors, namely dyslipidemia and insulin resistance, but there is also some evidence that HIV and ART may be associated with accelerated atherosclerosis and endothelial dysfunction. Current data are conflicting and further investigation into this area is needed. Drugs from both nucleoside reverse transcriptase inhibitor and protease inhibitor classes have been demonstrated to increase cardiovascular risk; however these effects are variable not only between classes but also between drugs in the same class. As newer therapies become available (in existing and new drug classes), the cardiovascular impact of these will need careful evaluation. Currently published guidelines suggest regular monitoring of cardiovascular risks (both before and after commencing ART) and pre-emptive treatment. Existing risk assessment tools have not been fully validated in an HIV setting and need to be used with caution. Lifestyle modification, in the first instance, and pharmacological intervention to reduce traditional risk factors are important management strategies. Initiating, or switching to, ART with a lower potential for metabolic derangement should also be considered.

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.

Atazanavir: a review of its use in the management of HIV-1 infection

Atazanavir (Reyataz), a protease inhibitor (PI), is approved in many countries for use as a component of antiretroviral therapy (ART) regimens for the treatment of adult, and in some countries in paediatric, patients with HIV-1 infection. ART regimens containing ritonavir-boosted atazanavir improved virological and immunological markers in adult patients with HIV-1 infection, and had similar efficacy to regimens containing lopinavir/ritonavir in treatment-naive and treatment-experienced patients. In addition, unboosted atazanavir was noninferior to ritonavir-boosted atazanavir in treatment-naive patients. Atazanavir is administered once daily and has a low capsule burden. Atazanavir, whether unboosted or boosted, was generally well tolerated and appeared to be associated with less marked metabolic effects, including less alteration of lipid levels, than other PIs. These properties mean that boosted atazanavir, and unboosted atazanavir in patients unable to tolerate ritonavir, continues to have a role as a component of ART regimens in patients with HIV-1 infection.

Clinical management of HIV-associated lipodystrophy

PURPOSE OF REVIEW

Lipodystrophy or fat re-distribution, and its associated metabolic abnormalities, are common in HIV patients. The pathogenesis is multifactorial. This article provides an update on the latest findings of the different clinical management strategies that have been utilized in patients with lipodystrophy.

RECENT FINDINGS

Treatment strategies need to be different in those patients with lipoatrophy when compared with patients with central fat accumulation (lipohypertrophy). Most of the treatments studied have produced minimal or modest effects, which are not sustained when the therapy is discontinued. The treatment of associated metabolic abnormalities such as insulin resistance and hyperlipidemia should have similar goals to that in the non-HIV population, but is complicated by the fact that response may be worse and there is a need to consider drug-drug interactions with the antiretrovirals.

SUMMARY

Multiple complex strategies will need to be utilized in these patients to treat the different features seen in lipodystrophy in order to reduce their long-term cardiovascular risk. Further research is also needed to evaluate combination therapies and to identify the underlying mechanisms in order to develop novel therapies for the future.

Effects of switching from lopinavir/ritonavir to atazanavir/ritonavir on muscle glucose uptake and visceral fat in HIV-infected patients

OBJECTIVE

To determine the effects of switching from lopinavir/ritonavir (LPV/r) to atazanavir/ritonavir (ATV/r) on muscle glucose uptake, glucose homeostasis, lipids, and body composition.

METHODS

Fifteen HIV-infected men and women on a regimen containing LPV/r and with evidence of hyperinsulinemia and/or dyslipidemia were randomized to continue LPV/r or to switch to ATV/r (ATV 300 mg and ritonavir 100 mg daily) for 6 months. The primary endpoint was change in thigh muscle glucose uptake as measured by positron emission tomography. Secondary endpoints included abdominal visceral adipose tissue, fasting lipids, and safety parameters. The difference over time between treatment groups (treatment effect of ATV/r relative to LPV/r) was determined by repeated measures ANCOVA.

RESULTS

After 6 months, anterior thigh muscle glucose uptake increased significantly (treatment effect +18.2 +/- 5.9 micromol/kg per min, ATV/r vs. LPV/r, P = 0.035), and visceral adipose tissue area decreased significantly in individuals who switched to ATV/r (treatment effect -31 +/- 11 cm, ATV/r vs. LPV/r, P = 0.047). Switching to ATV/r significantly decreased triglyceride (treatment effect -182 +/- 64 mg/dl, ATV/r vs. LPV/r, P = 0.02) and total cholesterol (treatment effect -23 +/- 8 mg/dl, ATV/r vs. LPV/r, P = 0.01), whereas high-density lipoprotein and low-density lipoprotein did not change significantly. Fasting glucose also decreased significantly following switch to ATV/r (treatment effect -15 +/- 4 mg/dl, ATV/r vs. LPV/r, P = 0.002).

CONCLUSION

Switching from LPV/r to ATV/r significantly increases glucose uptake by muscle, decreases abdominal visceral adipose tissue, improves lipid parameters, and decreases fasting glucose over 6 months.

Depot-specific adipocyte cell lines reveal differential drug-induced responses of white adipocytes--relevance for partial lipodystrophy

Intra-abdominal (IA) fat functionally differs from subcutaneous (SC) adipose tissue, likely contributing to its stronger association with obesity-induced morbidity and to differential response to medications. Drug-induced partial lipodystrophy, like in response to antiretroviral agents, is an extreme manifestation of the different response of different fat depots, with loss of SC but not IA. Investigating depot-specific adipocyte differences is limited by the low accessibility to IA fat and by the heterogenous cell population comprising adipose tissue. Here, we aimed at utilizing immortalized preadipocyte cell lines from IA (epididymal) or SC (inguinal) fat to investigate whether they differentially respond to the HIV protease inhibitor nelfinavir. Preadipocytes were readily amenable to adipogenesis, as evidenced by lipid accumulation, expression of adipose-specific genes, measurable lipolysis, and insulin responsiveness. Leptin secretion was higher by the SC line, consistent with known differences between IA and SC fat. As previously reported, nelfinavir inhibited adipogenesis downstream of C/EBPbeta, but similarly in both cell lines. In contrast, nelfinavir's capacity to diminish insulin signaling, decrease leptin secretion, enhance basal lipolysis, and decrease expression of the lipid droplet-associated protein perilipin occurred more robustly and/or at lower nelfinavir concentrations in the SC line. This was despite similar intracellular concentrations of nelfinavir (23.8 +/- 5.6 and 33.6 +/- 12.2 microg/mg protein for inguinal and epididymal adipocytes, respectively, P = 0.46). The cell lines recapitulated depot-differential effects of nelfinavir observed in differentiated primary preadipocytes and with whole tissue explants. Thus, we report the use of fat depot-specific adipocyte cell lines for unraveling depot-differential responses to a drug causing partial lipodystrophy.