Differential effect of HIV protease inhibitors on adipogenesis: intracellular ritonavir is not sufficient to inhibit differentiation

Adipose tissue aging partially accounts for fat alterations in HIV lipodystrophy

Lipodystrophy is a major disturbance in people living with HIV-1 (PLWH). Several systemic alterations in PLWH are reminiscent of those that occur in ageing. It is unknown whether the lipodystrophy in PLWH is the consequence of accelerated ageing in adipose tissue. We compared systemic and adipose tissue disturbances in PLWH with those in healthy elderly individuals (~80 y old). We observed similarly enhanced expression of inflammation-related genes and decreased autophagy in adipose tissues from elderly individuals and PLWH. Indications of repressed adipogenesis and mitochondrial dysfunction were found specifically in PLWH, whereas reduced telomere length and signs of senesce were specific to elderly individuals. We conclude that ageing of adipose tissue accounts only partially for the alterations in adipose tissues of PLWH.

Mitochondrial toxicity and body shape changes during nucleos(t)ide analogues administration in patients with chronic hepatitis B

Our study purpose was to evaluate mitochondrial (mt)DNA and RNA in peripheral blood mononuclear cells (PBMCs) and body shape changes (BSC) in HBV-infected patients. mtDNA and mtRNA were measured in PBMCs. The presence of BSC was evaluated through a questionnaire and clinical evaluation. A total of 157 subjects were enrolled, of these 107 were HBV-infected patients, 54 receiving nucleoside analogues (NAs, Group A), 53 naive to antivirals (Group B) and 50 age-sex matched controls (Group C). All HBV-treated patients had negative HBV–DNA. Twenty (37,0%) received lamivudine + adefovir, 20 (37.0%) tenofovir, 2 (3.7%) lamivudine and 12 (22.2%) entecavir. Therapy median duration was 38 months (IQR 20–60) in NA-treated patients. Group A showed significantly higher mtDNA/nuclear (n) DNA ratio (p = 0.000008) compared to Group C and Group B (p = 0.002). Group B showed significantly higher mtDNA/nDNA ratio compared to Group C (p = 0.017). Group A and B had significantly lower mtRNA/nRNA ratio compared to Group C (p = 0.00003 and p = 0.00006, respectively). Tenofovir and entecavir showed less impact compared to lamivudine + adefovir. mtDNA/nDNA ratio positively (Rho = 0.34, p < 0.05) and mtRNA/nRNA ratio negatively (Rho = −0.34, p < 0.05) correlated with therapy duration. BSC were significantly more frequent in Group A [10/54 (18.5%)] compared to Group B [3/53 (5.6%, p = 0.04)] and Group C [0/50, (p = 0.0009)]. In conclusion, long-term NA therapy was associated both to mitochondrial toxicity and BSC, showing significant differences in mtDNA and mtRNA levels. Tenofovir and entecavir showed lower impact on alterations, compared to 1^st generation NA.

Physical fitness in children infected with the human immunodeficiency virus: associations with highly active antiretroviral therapy

Obesity, sedentary lifestyles, and antiretroviral therapies may predispose HIV-infected children to poor physical fitness. Estimated peak oxygen consumption (VO(2) peak), maximal strength and endurance, and flexibility were measured in HIV-infected and uninfected children. Among HIV-infected children, anthropometric and HIV disease-specific factors were evaluated to determine their association with VO(2) peak. Forty-five HIV-infected children (mean age 16.1 years) and 36 uninfected children (mean age 13.5 years) participated in the study. In HIV-infected subjects, median viral load was 980 copies/ml (IQR 200-11,000 copies/ml), CD4% was 28% (IQR 15-35%), and 82% were on highly active antiretroviral therapy (HAART). Compared to uninfected children, after adjusting for age, sex, race, body fat, and siblingship, HIV-infected children had lower VO(2) peak (25.92 vs. 30.90 ml/kg/min, p<0.0001), flexibility (23.71% vs. 46.09%, p=0.0003), and lower-extremity strength-to-weight ratio (0.79 vs. 1.10 kg lifted/kg of body weight, p=0.002). Among the HIV-infected children, a multivariable analysis adjusting for age, sex, race, percent body fat, and viral load showed VO(2) peak was 0.30 ml/kg/min lower per unit increase in percent body fat (p<0.0001) and VO(2) peak (SE) decreased 29.45 (± 1 .62), 28.70 (± 1.87), and 24.09 (± 0.75) ml/kg/min across HAART exposure categories of no exposure, <60, and ≥ 60 months, respectively (p<0.0001). HIV-infected children had, in general, lower measures of fitness compared to uninfected children. Factors negatively associated with VO(2) peak in HIV-infected children include higher body fat and duration of HAART ≥ 60 months. Future studies that elucidate the understanding of these differences and mechanisms of decreased physical fitness should be pursued.

Pathophysiology of the HIV-Associated Lipodystrophy Syndrome

The widespread use of highly active antiretroviral therapy (HAART) has radically transformed the prognosis of HIV-infected patients in the developed countries. Unfortunately, a serious metabolic syndrome combining peripheral lipoatrohy, central adiposity, insulin resistance, and dyslipidemia has arisen in these individuals. The etiology of this heterogeneous syndrome named lipodystrophy syndrome (LDS) is multifactorial, but adipose tissue is very likely a key factor that contributes to several clinical or metabolic aspects of the syndrome. In peripheral adipose tissue, HAART may act on both preadipocytes and adipocytes to induce fat loss. Several components of the HAART regimen can inhibit preadipocyte differentiation, in particular through alterations in the expression and/or function of the transcription factor sterol responsive element binding protein-1c. In superficial mature adipocytes, HAART promotes insulin resistance and apoptosis. Insulin resistance of peripheral fat cells could be the consequence of increased lipolysis and adipocytokine dysregulation. In turn, the increased free fatty acid disposal and the disturbances in adipocytokine production may induce skeletal muscle and liver insulin resistance, dyslipidemia, and a fat redistribution toward deep depots, causing visceral lipohypertrophy. The metabolic profile observed in LDS is reminiscent of that observed in metabolic syndrome, raising potential implications for cardiovascular risk in these patients. The pathophysiological mechanisms at the basis of this syndrome represent a rational basis for the treatment or prevention of the metabolic complications.

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.

Body-fat abnormalities in patients with HIV: progress and challenges

The introduction of newer antiretroviral drugs has provided greater levels of HIV suppression with fewer of the metabolic effects, lipoatrophy, and body habitus changes associated with earlier therapies. Previously classified under the collective term, lipodystrophy, lipoatrophy and body-fat changes are now known to occur independently in some HIV-infected patients, depending on the type and duration of antiretroviral therapy and a myriad of factors including HIV infection alone that contribute significantly to these changes. This article reviews the current scientific literature and recent clinical trial results that distinguish lipoatrophy or dyslipidemia pathophysiologically from body-fat changes seen as central and peripheral lipohypertrophy and fat redistribution, as well as the nature and extent of changes associated with HIV infection alone and newer antiretroviral therapies. This information may assist physicians in identifying individual risk factors and choosing the type of antiretroviral therapy that may minimize these changes without loss of virologic suppression.

Insulin resistance, glucose intolerance and diabetes mellitus in HIV-infected patients

An increased prevalence of insulin resistance, glucose intolerance and diabetes has been reported in HIV infection in the highly active antiretroviral therapy (HAART) era. This development might be clinically significant because of its association with cardiovascular morbidity and mortality as well as the therapeutic challenges of managing polypharmacy. The development of insulin resistance, glucose intolerance and diabetes could be related to the underlying HIV infection, the contribution of different antiretroviral agents, treatment-associated weight gain, immune restoration, as well as the non-HIV related factors. Dissecting these factors in clinical practice might be difficult. Clinical studies include short-term treatments in healthy, non-HIV-infected individuals; randomized, controlled trials; comparative studies of different HAART regimens; and randomized studies of switching regimens in patients with viral suppression and stable immune function. This article reviews the latest knowledge regarding the epidemiology, pathogenesis, prevention and treatment of insulin resistance, glucose intolerance and diabetes mellitus in HIV-infected individuals.

Some HIV Antiretrovirals Increase Oxidative Stress and Alter Chemokine, Cytokine or Adiponectin Production in Human Adipocytes and Macrophages

Objectives

Adipose tissue from patients with HIV-related lipodystrophy presents a state of chronic inflammation. Altered expression of cytokines/adipokines and macrophage infiltration could be involved in patients’ insulin resistance and lipoatrophy. We tested whether antiretrovirals affected adipokine release by human subcutaneous adipocytes and cytokine/chemokine production by human macrophages and examined whether reactive oxygen species (ROS) hyperproduction was related to the effect of antiretrovirals.

Methods

Differentiated human adipocytes and PMA-THP-1 macrophages were treated with protease inhibitors (PIs: indinavir, nelfinavir, amprenavir, lopinavir, ritonavir and atazanavir) or nucleoside reverse transcriptase inhibitors (NRTIs: stavudine, zidovudine and abacavir) for 24–48 h without or with diphenylene iodonium (DPI), an inhibitor of oxidative stress. Lipid content was assessed by Oil Red O staining and ROS production by nitroblue tetrazolium (NBT) reduction. Cytokine/chemokines, adiponectin and leptin release was evaluated by ELISA or multiplex assays.

Results

In human adipocytes, PIs and NRTIs (except amprenavir, atazanavir and abacavir) reduced lipid content, adiponectin and leptin release and increased in parallel ROS production and monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-6 release. The effects of PIs, but not of NRTIs, were prevented by the addition of DPI. In PMA-THP-1 macrophages, all PIs, but no NRTI, increased macrophage inflammatory protein-1α and MCP-1 release. Lopinavir, nelfinavir, zidovudine and stavudine markedly increased ROS production and release of IL-1β and tumour necrosis factor-α.

Conclusions

Some PIs altered adipokine secretion and lipid content through ROS production in human subcutaneous adipocytes. Thymidine analogues altered adipocyte functions but their effect on adipokine secretion was not reverted by ROS production inhibition. Increased chemokine/cytokine production by adipocytes and macrophages could be involved in macrophage recruitment and participate in lipoatrophy and insulin resistance.

Cardiovascular risks of antiretroviral therapies

The use of highly active antiretroviral therapy (HAART) has resulted in sustained reductions in mortality from HIV infection. In recent years, HAART has also been associated with metabolic complications that may increase patients' cardiovascular disease risk. Recent studies have begun to support a more complex interaction between HAART, HIV infection itself, and other traditional social and immunologic factors that may predispose patients to premature cardiovascular disease. Substantial progress has been made in the development of newer antiretroviral therapies that have a better metabolic profile with respect to dyslipidemia, hyperglycemia, and lipodystrophy. Optimal selection of metabolically neutral antiretroviral therapies, together with aggressive management of other modifiable coronary risk factors, may improve cardiovascular disease risk in the long term.

HIV protease inhibitor-specific alterations in human adipocyte differentiation and metabolism

OBJECTIVE

Human immunodeficiency virus (HIV) patients on antiretroviral regimens frequently develop a syndrome of abnormal fat distribution, insulin resistance, and dyslipidemia. This lipodystrophic syndrome has been most closely linked to the use of HIV protease inhibitors (PIs). Several mechanisms have been postulated to explain these adverse effects of PIs, based largely on studies of rodent adipocytes. Intriguingly, atazanavir, a newer PI equally effective against HIV, is associated with fewer signs of lipodystrophy. We hypothesized that the less deleterious clinical effects of atazanavir would be reflected in physiological differences observed in PI-treated adipocytes.

RESEARCH METHODS AND PROCEDURES

We compared the effects of atazanavir and an older PI associated with lipodystrophy, ritonavir, on differentiation, gene expression, adipocytokine secretion, and insulin signaling in a human adipocyte cell line.

RESULTS

Ritonavir inhibited human adipocyte differentiation and induced apoptosis to a greater extent than atazanavir. Treatment of mature adipocytes with ritonavir, but not atazanavir, also selectively decreased insulin signaling. Moreover, ritonavir also selectively decreased expression of adiponectin, an insulin-sensitizing adipocytokine, while inducing interleukin-6, a proinflammatory cytokine implicated in insulin resistance.

DISCUSSION

These data suggest that the distinct metabolic side effect profiles of these PIs could be a consequence of their differential effects on adipocyte physiology.

Highly Active Antiretroviral Therapy–Associated Metabolic Syndrome: Pathogenesis and Cardiovascular Risk*

The introduction of highly active antiretroviral therapy (HAART) has significantly modified the course of HIV disease, with longer survival and improved quality of life of HIV-infected subjects. However, HAART regimens, especially those including protease inhibitors (PIs) have been shown to cause in a high proportion of HIV-infected patients a metabolic syndrome that may be associated with an increased risk of cardiovascular disease (about 1.4 cardiac events per 1,000 years of therapy according to the Framingham score). Metabolic features associated with somatic changes (lipodystrophy/lipoatrophy) include dyslipidemia (about 70% of patients), insulin resistance (elevated C-peptide and insulin), type 2 diabetes mellitus (8%-10% of the patients), hypertension (up to 75% of patients), coagulation abnormalities (25% of patients), lactic acidemia, and elevated hepatic transaminases (nonalcoholic steatohepatitis). HAART-associated metabolic syndrome is an increasingly recognized clinical entity. A better understanding of the molecular mechanisms responsible for this syndrome will lead to the discovery of new drugs that will reduce the cardiovascular risk in patients under HAART. A careful stratification of the cardiovascular risk and cardiovascular monitoring of patients under HAART is needed according to the most recent clinical guidelines.

Glucose metabolism, lipid, and body fat changes in antiretroviral-naive subjects randomized to nelfinavir or efavirenz plus dual nucleosides

OBJECTIVE

To determine if particular components of antiretroviral drug regimens are associated with greater insulin resistance, dyslipidemia, and peripheral lipoatrophy.

METHODS

Metabolic and body composition variables were measured prospectively over 64 weeks in 334 antiretroviral-naive, HIV-infected subjects who were randomized to receive nelfinavir, efavirenz, or both, combined with zidovudine/lamivudine or didanosine/stavudine in a factorial design, multicenter trial. Subjects assigned to efavirenz (n = 110) were compared with those assigned to nelfinavir (n = 99); subjects assigned to zidovudine/lamivudine (n = 154) were compared with those assigned to didanosine/stavudine (n = 180). A subset of 157 subjects had serial dual-energy X-ray absorptiometry (DEXA) scans.

RESULTS

Lipid measures increased in all groups. Greater increases in high density lipoprotein (HDL) cholesterol occurred with efavirenz than with nelfinavir. Greater increases in total cholesterol, non-HDL cholesterol and HDL cholesterol occurred with stavudine and didanosine than with zidovudine/lamivudine. There were no differences in insulin resistance in the comparisons. After initial increases in the first 16 weeks, median limb fat decreased. Greater changes in percentage changes in limb fat occurred with didanosine/stavudine (-16.8%) than with zidovudine/lamivudine (+4.0%; P < 0.001 for overall change from baseline) and with nelfinavir (-13.1%) compared with efavirenz (+1.8%; P = 0.003).

CONCLUSIONS

Over 64 weeks, all regimens were associated with increases in lipids but insulin resistance did not differ between groups. Regimens containing didanosine/stavudine and regimens containing nelfinavir were associated with greater loss of limb fat.

HIV antiretroviral treatment alters adipokine expression and insulin sensitivity of adipose tissue in vitro and in vivo

HIV-1-infected patients on antiretroviral therapy frequently develop a lipodystrophy syndrome, characterized by peripheral lipoatrophy and visceral fat redistribution associated with metabolic alterations including dyslipidemia and insulin resistance. Its pathophysiology remains unclear but the antiretroviral treatment, associating protease inhibitors (PIs) and nucleoside analogue inhibitors of the viral reverse transcriptase (NRTIs), plays a major role. Some antiretroviral molecules inhibit differentiation and induce insulin resistance and apoptosis in adipose cells both in vitro and in vivo. In vitro, PIs and NRTIs increase the expression and secretion of pro-inflammatory cytokines such as TNF alpha, IL-6 and L-1beta, which are involved in altered adipocyte functions and decrease that of adiponectin, a positive modulator of insulin sensitivity. Similar alterations are observed in fat and serum from HIV-1-infected lipodystrophic patients under antiviral treatment associating PIs and NRTIs. Altered adipokine secretion could result from patients' exposure to PIs and NRTIs and lead to altered adipocyte differentiation, insulin resistance and apoptosis, ultimately resulting in lipoatrophy. These disorders probably result in a decreased secretion of adiponectin and an increased release of free fatty acids by insulin-resistant adipose tissue. Therefore, they could be involved in whole body insulin resistance and metabolic alterations in lipodystrophic HIV-1-infected patients.

Effects of the human immunodeficiency virus-protease inhibitor, ritonavir, on basal and catecholamine-stimulated lipolysis

Several of the aspartic acid protease inhibitors used to treat HIV infection increase basal lipolysis in adipocytes, but the cellular mechanisms leading to this augmentation are not well understood. We therefore studied the effects of chronic exposure to the HIV protease inhibitor, ritonavir, on the lipolytic cascade in 3T3-L1 adipocytes. Treatment of 3T3-L1 adipocytes with ritonavir for 14 d (during and after differentiation) enhanced basal, isoproterenol (Iso)-stimulated, and cAMP analog-stimulated lipolysis. Enhancement of lipolysis was observed after Iso at concentrations between 0.1 and 10 mum. Despite a significant decrease in cyclic nucleotide phosphodiesterase (PDE)3B activity and protein levels, there were no changes in Iso-stimulated intracellular cAMP, protein kinase A (PKA) expression, or PKA activity. Ritonavir-augmented lipolysis was also observed under conditions that reversed the effect on PDE3B activity via preincubation with 1 mum (-)-N(6)-(2-phenylisopropyl)adenosine. In ritonavir-treated cells, protein expression of the lipid droplet-protective protein, perilipin, was significantly decreased, whereas there was no change in hormone-sensitive lipase. Activation of ERK1/2 by Iso did not play a role in the augmentation. We conclude that ritonavir decreases PDE3B and perilipin protein expression and affects both basal and catecholamine-stimulated lipolysis in 3T3-L1 adipocytes primarily through actions at sites downstream of PKA.

Human Immunodeficiency Virus Protease Inhibitors Accumulate into Cultured Human Adipocytes and Alter Expression of Adipocytokines

Lipodystrophic syndrome is a major side effect of highly active antiviral therapy. Fat tissue redistribution is associated with changes in adipocyte gene expression and in circulating levels of adipocytokines involved in the development of insulin resistance. However, the evidence that HIV drugs accumulate into human adipocytes and have a direct effect on the expression of adipocyte-specific genes is still lacking. To address these questions, we used adipocytes derived from adult stem (hMADS) cells isolated from human adipose tissue. We showed by ELISA that two inhibitors of the HIV protease, lopinavir and ritonavir, accumulated at similar levels during the development of hMADS cells in adipocytes, whereas a non-nucleoside reverse transcriptase inhibitor, the nevirapine, accumulated at lower levels. Two fluorescent protease inhibitors then have been generated to investigate their subcellular localization. The data showed that HIV drugs accumulated into adipocytes and displayed various effects on hMADS cell-derived adipocytes. Indinavir, amprenavir, and nevirapine did not alter differentiation of precursor cells. In contrast, lopinavir, saquinavir, and ritonavir inhibited the development of preadipocytes into adipocytes. In adipocytes, amprenavir increased leptin expression and ritonavir was able to up-regulate tumor necrosis factor-alpha, interleukin 6, and leptin expression and down-regulate the expression of peroxisome proliferator-activated receptor gamma and adiponectin. Intracellular accumulation and localization of HIV drugs into human adipocytes strongly suggest that adipose tissues store these drugs. Because ritonavir can alter the expression of insulin resistance-related cytokines in human adipocytes in a way parallel to the situation observed in vivo upon treatment of HIV-infected patients, we propose that protease inhibitors participate in insulin resistance through a direct effect on adipocytes.

Protease inhibitor treatments reveal specific involvement of matrix metalloproteinase-9 in human adipocyte differentiation

We previously showed that human and murine 3T3-F442A preadipocytes produced and released matrix metalloproteinases (MMPs) 2 and 9 and that a treatment by MMP inhibitors resulted in the blockade of murine fat cell adipose conversion. In parallel, investigators reported that other protease inhibitors, the human immunodeficiency virus (HIV) protease inhibitors (PIs) involved in lipodystrophy in humans, also reduced the adipocyte differentiation process of several murine cell lines. The present work was performed to define the effects of MMP inhibitors and HIV-PIs on the human adipocyte differentiation process, to clarify the involvement of MMPs in the control of human adipogenesis, and to determine whether HIV-PIs interact with MMPs in the control of this process. The effect of two MMP inhibitor and four HIV-PI treatments on the differentiation of primary culture human preadipocytes, as well as the putative relationships between HIV-PIs and MMP-2 and -9 expression, release, or activity were investigated. We showed that MMP inhibitors and HIV-PIs reduced the human adipocyte differentiation process as assessed by the decrease of cell protein and/or triglyceride contents and expression of fatty acid binding protein and hormone-sensitive lipase, two adipocyte markers. Unlike MMP inhibitors, HIV-PIs were devoid of any effect per se on recombinant MMP-2 and 9 activities but reduced the expression and release of MMP-9 by human preadipocytes. Thus, the present study indicates that the modulation of the extracellular matrix components through the production and/or activity of MMPs, and, more precisely, MMP-9 might be a key factor in the regulation of human adipose tissue development.

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

OBJECTIVES

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

DESIGN AND METHODS

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

RESULTS

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

CONCLUSION

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

Antiretroviral Drugs with Adverse Effects on Adipocyte Lipid Metabolism and Survival Alter the Expression and Secretion of Proinflammatory Cytokines and Adiponectin In Vitro

Objective

The lipodystrophy syndrome is a major adverse effect of highly active antiretroviral therapy (HAART), associated with altered circulating levels and adipose tissue mRNA expression of proinflammatory cytokines interleukin-6 (IL-6) and tumour necrosis factor (TNF)α, and adiponectin. Proinflammatory cytokines and adiponectin, which are secreted by adipose tissue, regulate fat metabolism, insulin sensitivity and adipose cell apoptosis. We examined the direct effects of individual antiretrovirals on lipid metabolism and cytokine and adiponectin production by cultured adipocytes.

Methods

Differentiating 3T3-F442A cells and differentiated 3T3-L1 adipocytes were treated for 12 or 4 days, respectively, with protease inhibitors (PIs) indinavir, nelfinavir, amprenavir, lopinavir and ritonavir, or nucleoside reverse transcriptase inhibitors (NRTIs) stavudine and zidovudine, at near-Cmax concentrations. Lipid metabolism was estimated by Oil Red O staining of intracellular lipids, mRNA expression of fatty acid synthase and adipocyte lipid binding protein 2, and insulin activation of lipogenesis. Apoptosis was estimated by flow cytometry. The expression and secretion of proinflammatory cytokines (IL-6, TNFα and IL-1β) and adiponectin were evaluated by real-time reverse transcription PCR and ELISA.

Results

Chronic treatment of 3T3-F442A differentiating adipocytes and differentiated 3T3-L1 adipocytes with PIs and NRTIs reduced lipid accumulation, mRNA expression of lipid markers and insulin-induced lipogenesis. IL-6, TNFα, IL-1β and adiponectin expression and secretion were markedly altered in differentiating 3T3-F442A adipocytes. PIs had either no effect on differentiated 3T3-L1 adipocytes (TNFα expression and secretion) or their effect was less marked than in 3T3-F442A cells. Indinavir and amprenavir did not alter cytokine secretion and expression by mature adipocytes. The effects of stavudine and zidovudine on differentiating and mature adipocytes were similar, despite the difference in treatment procedure. The drugs with the strongest effect on TNFα expression also increased adipocyte apoptosis, in contrast to the drugs that only moderately increased TNFα expression.

Conclusions

These results suggest that increased cytokine and decreased adiponectin secretion and expression induced by some PIs and NRTIs may contribute to the adipose tissue loss (via apoptosis and lipid leakage) and insulin resistance associated with the lipodystrophy syndrome.

In vitro suppression of the lipogenic pathway by the nonnucleoside reverse transcriptase inhibitor efavirenz in 3T3 and human preadipocytes or adipocytes

A serious metabolic syndrome combining insulin-resistance, dyslipidemia, central adiposity, and peripheral lipoatrophy has arisen in HIV-infected patients receiving highly active antiretroviral therapy. The aim of this work was to examine the effects of the nonnucleoside reverse transcriptase inhibitor (NNRTI) efavirenz on adipocyte differentiation and metabolism. When induced to differentiate in the presence of efavirenz (5-50 microm), 3T3-F442A preadipocytes failed to accumulate cytoplasmic triacylglycerol droplets. This phenomenon was rapidly reversible and was also readily detectable in the 3T3-L1 preadipose cell line and in primary cultures of human preadipocytes. When applied to mature 3T3-F442A adipocytes, efavirenz induced a delayed and moderate reduction in cell triglyceride content. Measurement of [(3)H]deoxyglucose uptake, basal and agonist-stimulated lipolysis, and cell viability indicated that these pathways are not involved in efavirenz effects on triacylglycerol accumulation. By contrast, we found that the NNRTI induced a dramatic dose- and time-dependent decrease in gene and protein expression of the lipogenic transcription factor sterol regulatory element-binding protein-1c (SREBP-1c). Adipose conversion was only altered at the highest efavirenz concentrations, as suggested by the mild reduction in peroxisome proliferator-activated receptor-gamma and CCAAT/enhancer-binding protein-alpha. CCAAT/enhancer-binding protein-beta remained unchanged. The inhibition of SREBP-1c expression was accompanied by a sharp reduction in the expression of SREBP-1c target genes and in the adipocyte lipogenic activity in efavirenz-treated cells. Finally, the inhibitory effect of efavirenz on cell triglyceride accumulation was prevented by directly providing free fatty acids to the cells and was reversed by overexpression of a dominant positive form of SREBP-1c, reinforcing the implication of this transcription factor in the antilipogenic effect of the drug. When considered together, these results demonstrate for the first time that the NNRTI efavirenz induces a strong inhibition of the SREBP-1c-dependent lipogenic pathway that might contribute to adipose tissue atrophy.