Inhibition of adipocyte differentiation by HIV protease inhibitors

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.

Serum Interleukin-6 and Weight Loss in Antiretroviral-naïve and Antiretroviral-treated Patients with HIV/AIDS: Relationships and Predictors

BACKGROUND

Cachexia is usually associated with elevated serum interleukin-6 (IL.6) as it stimulates the breakdown of muscle proteins and promotes wasting.

OBJECTIVE

A case-control study to evaluate the relationship between weight loss, facial fat loss, and IL-6 in antiretroviral-naïve and treated participants living with HIV/AIDS.

METHODS

IL-6 was assayed by High performance liquid chromatography (HPLC) in 97 in consecutive newly diagnosed antiretroviral-naive (ART-naïve) people living with HIV/AIDS (age ≥18 years); and 118 consecutive, age-matched participants currently on Highly Active Antiretroviral Therapy (HAART), using age as a criterion. In the treated group, 78 (66.7%) subjects were on zidovudine, lamivudine with nevirapine (Z+L+N); 27(23.1%) on tenofovir, lamivudine with emtricitabine (T+L+E); 5(4.3%) on zidovudine, lamivudine with emtricitabine (Z+L+E); 4(3.4%) on zidovudine, lamivudine with tenofovir (Z+L+T); 2(1.7%) on lamivudine, tenofovir with nevirapine (L+T+N); 1(0.9%) on tenofovir, zidovudine, emtricitabine (Z+T+E).

RESULTS

A total of 215 participants: 97 ART-naive and 118 HAART-treated, age-matched subjects (40.3±9.6 versus 42.7±10.20years, p=0.08). The mean IL-6 was significantly higher in naïve than treated (0.69±0.04 versus 0.66±0.04 pg/ml, p =0.002). In all, 73 subjects experienced weight loss, 56(76.7%) naive, 17(23.3%) treated, p <0.0001, with significantly higher IL-6 in those with weight loss (0.69±0.05 versus 0.67±0.05pg/ml, p= 0.047). Fifty-eight (27.0%) subjects experienced facial fat loss, 49 (84.5%) naïve, and 9 (15.5%) treated, p <0.0001, with significantly higher IL-6 in those with facial fat loss (0.7 ± 0.05 versus 0.67±0.05pg/ml, p= 0.0001). Negative correlation exists between IL-6 and CD4+ count (r=-0.141, p=0.041). In logistic regression, independent predictors of weight loss include: IL-6 (Adjusted Odds Ratio, aOR 1.3, 95%CI 0·1-2·6, p=0.047); HIV duration (aOR 11.6, p <0.0001); AIDS-defining illness (aOR 3.5, p <0.0001); CD4+ count (aOR 3.2, p=0.004); HAART status (aOR 2.7, p<0.0001).

CONCLUSION

HIV infection is associated with elevation of serum interleukin-6, which likely contributes to weight and facial fat loss among the treatment-naïve participants; while HAART is associated with suppressed IL-6 levels, thereby ameliorating weight and facial fat loss. Inverse relationship exists between serum IL-6 and CD4+ count; serum IL-6 could differentiate between mild- to moderate and severe immunosuppressive states.

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

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

Body composition in HIV-infected patients receiving highly active antiretroviral therapy

BACKGROUND

The development of combination antiretroviral therapies (cART) represents a significant advance in the treatment of (human immunodeficiency virus) HIV infection. However, several studies report that a large percentage of individuals with HIV, particularly those receiving cART, present body composition differences compared with the general population. The aim of this study was to explore body composition differences by dual-energy X-ray absorptiometry (DEXA), among HIV-positive patients receiving cART, in comparison to healthy controls.

METHODS

The cross-sectional study included 60 HIV-infected patients (all under 50 years old). We analyzed the association of antiretroviral medication use and different HIV-related factors, to the body composition parameters.

RESULTS

Our cohort had significantly lower fat mass and lower bone mass compared to non HIV-infected persons. Median time since HIV infection diagnosis was 5 years (interquartile range, [IQR], 2-10.25) and viral suppression was achieved in 49 (81.66%) patients. Treatment with protease inhibitors (PIs) was strongly correlated with low fat mass, reduced lean mass and loss of bone mineral density. Nucleoside reverse transcriptase inhibitors (NRTIs)-containing treatment was associated with decrease of lean tissue mass (LM). The prevalence of osteopenia was 41.67% at the lumbar spine (L1-L4) and 36.7% at the hip. We found osteoporosis in 10% of the patients at the lumbar spine. Reduced bone mass was associated, in the patient group, with the duration of PIs use and with smoking (in the males group).

CONCLUSION

In our research, HIV-infected individuals compared to healthy controls had body composition differences, including fat mass atrophy and reduced bone mineral content.

Adiponectin, Leptin and Inflammatory Markers in HIV-associated Metabolic Syndrome in Children and Adolescents

BACKGROUND

Metabolic syndrome (MetS) is more common in HIV-infected adults and children than in the general population. Adipocytokines and inflammatory markers may contribute to the pathophysiology of this condition and could be useful indices for monitoring MetS. The objective of this study was to provide information on the prevalence of MetS and investigate the role of adipocytokines and other biomarkers in this syndrome in HIV-infected pediatric patients.

METHODS

A cross-sectional study was conducted between October 2013 and March 2014 in the outpatient clinics of 2 tertiary pediatric referral hospitals. Fifty-four HIV-infected children and adolescents were included. MetS was defined according to the International Diabetes Federation and modified National Cholesterol Education Program Adult Treatment Panel III criteria. Measurements included anthropometry, waist circumference, blood pressure, fasting lipids, glucose and insulin, adiponectin, leptin, interleukin-6, vitamin D and C-reactive protein and clinical lipodystrophy assessment.

RESULTS

Among the total, 3.7% of patients met the International Diabetes Federation criteria for MetS and 7.4% met the National Cholesterol Education Program Adult Treatment Panel III criteria. C-reactive protein and leptin levels were significantly higher and adiponectin level significantly lower in patients with MetS, regardless of the criteria used. Insulin resistance was observed in 40.7% of patients; abnormal quantitative insulin sensitivity check index values were found in 88.9%. Eighteen patients (33.3%) had vitamin D deficiency.

CONCLUSIONS

The prevalence of MetS was similar to that observed in larger cohorts of HIV-infected patients in our setting. Adipocytokine dysregulation seems to be related to MetS in HIV-infected children. A high percentage of patients showed insulin resistance, which should be strictly monitored.

Using reverse docking to identify potential targets for ginsenosides

Background

Ginsenosides are the main ingredients of ginseng, which, in traditional Eastern medicine, has been claimed to have therapeutic values for many diseases. In order to verify the effects of ginseng that have been empirically observed, we utilized the reverse docking method to screen for target proteins that are linked to specific diseases.

Methods

We constructed a target protein database including 1,078 proteins associated with various kinds of diseases, based on the Potential Drug Target Database, with an added list of kinase proteins. We screened 26 kinds of ginsenosides of this target protein database using docking.

Results

We found four potential target proteins for ginsenosides, based on docking scores. Implications of these “hit” targets are discussed. From this screening, we also found four targets linked to possible side effects and toxicities, based on docking scores.

Conclusion

Our method and results can be helpful for finding new targets and developing new drugs from natural products.

Metabolic Syndrome in Children and Adolescents Living with HIV

BACKGROUND

Metabolic syndrome (MetS) is considered an independent risk factor for developing cardiovascular disease. It is well known that the prevalence of metabolic disorders have increased in pediatric HIV-infected children. The objective of this study is to assess the prevalence and characteristics of MetS in HIV-infected children and adolescents in Spain.

METHODS

A cross-sectional multicenter study in 152 patients from the pediatric cohort of the Spanish AIDS Research Network (CoRISpe) was performed. MetS was defined according to the new International Diabetes Federation (IDF) diagnostic criteria and the modified National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria. Measurements included anthropometry, waist circumference, blood pressure, fasting lipids, glucose and insulin and lipodystrophy assessment. Demographic, clinical, immunological, virological and antiretroviral therapy data were obtained from the Network database.

RESULTS

An abnormally low high-density lipoprotein-cholesterol level was the most prevalent disturbance (21.05%) found. Three patients met IDF criteria for MetS (1.97%), and MetS was significantly associated with lipohypertrophy (P=0.029) in the analysis. When the modified NCEP-ATP III criteria were used, the prevalence of MetS was 5.92% (9 patients), and MetS was significantly associated with Tanner stage ≥2 (P=0.041), lipohypertrophy (P=0.001) and higher Z scores for weight and body mass index (P=0.002 and P<0.001). Insulin resistance was observed in 17 patients (11.18%) and was associated with MetS (as per the modified NCEP-ATP III criteria) (P=0.03) and lower high-density lipoprotein-cholesterol values (P=0.036).

CONCLUSIONS

The prevalence of MetS in our cohort was 1.97% or 5.92%, depending on the diagnostic criteria used. MetS should be actively assessed, particularly in children who show lipohypertrophy.

Role of 3 lipoprotein lipase variants in triglycerides in children receiving highly active antiretroviral therapy

BACKGROUND

Lipoprotein lipase is a key enzyme in lipid metabolism, especially for plasma triglycerides (TGs). Genetic variants have been associated with lipid levels in healthy individuals, cardiovascular disease, obesity and diabetes. Our aim was to evaluate the influence of 3 polymorphisms: Hind III, Pvu II and S447X in plasma TG levels in human immunodeficiency virus-1-infected children under highly active antiretroviral therapy (HAART).

METHODS

Fifty-two children diagnosed with human immunodeficiency virus-1 between 2005 and 2009 were retrospectively selected with at least 1 plasma TG level assessment. TG levels were examined before and after 1 year of HAART. Hypertriglyceridemia was defined as TG > 150 mg/dL. Hind III (H+/H-), Pvu II (P+/P-) and S447X (S/X) were determined by polymerase chain reaction and restricted fragment length polymorphism. The Wilcoxon sum-rank test was used to compare median plasma TG among groups. Also, allelic frequencies were estimated for these variants in an Argentinean population.

RESULTS

Allelic frequencies for human immunodeficiency virus-1-infected children were: H-, 0.21; P-, 0.53; and X, 0.05 with no significant differences to controls. After 1 year of HAART, median TG levels were significantly lower in P-/P- (98.5 mg/dL) when compared with P+/P+ (180 mg/dL) (P = 0.039). The presence of the P- allele was associated with an 11-fold lower risk of hypertriglyceridemia. Hind III and S447X were not associated with TG at the selected time points.

CONCLUSIONS

Our findings suggest a protective effect of lipoprotein lipase polymorphisms against hypertriglyceridemia in children after 1 year of HAART. These results could endorse a prompt nutritional or pharmacological intervention in patients lacking the P- allele.

Inhibition of Preadipocyte Differentiation by Germacranolides fromCalea urticifoliain 3T3-L1 Cells

The effects of germacranolides isolated from Calea urticifolia on adipocytic differentiation of 3T3-L1 cells were examined. These germacranolides inhibited adipogenesis at a concentration of 1.25-5 microM. But no inhibitory activity against cell proliferation and no nonspecific binding activity to protein were observed. These results indicate that these germacranolides are the specific inhibitors of preadipocyte differentiation.

Lopinavir/Ritonavir Impairs Physical Strength in Association with Reduced Igf1 Expression in Skeletal Muscle of Older Mice

Background

Late-middle age HIV patients are prone to fatigue despite effective viral control by antiretroviral therapies. Rodent models to recapitulate this phenotype are still not available.

Hypothesis

Drug treatment may compromise muscle strength and physical performance more in older individuals with pre-existing metabolic disorders than normal young ones.

Methods

Kaletra was given to overweight male mice at late-middle age and normal young adults; both on a rodent diet containing 30% fat calorie. Body composition and grip strength were measured at baseline and after drug treatment. Rota-rod running, insulin and glucose tolerance were measured at the end of the experiment. Drug effect on metabolic activity and spontaneous movements were assessed using the metabolic cage system. Representative muscle and fat tissue were analyzed for protein and mRNA expression. Selected findings were tested using murine C2C12 myotubes.

Results

Kaletra reduced grip strength in both young and older mice but impaired rotarod performance only in the old. Spontaneous movements were also reduced in Kaletra-treated old mice. Kaletra reduced IGF-1 expression in all muscle groups tested for the old and in cultured myotubes but to a less extent in the muscle of young animals. Reduced IGF-1 expression correlated with increased expression of muscle-specific atrogene MAFbx and MuRF1. Kaletra also increased abdominal fat mass markedly in the old animals and to a less extend in the young.

Conclusion

Long-term Kaletra intake aggravated abdominal obesity and impaired muscle strength. This effect was worse in older animals than in normal young adults.

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.

Molecular mechanisms for insulin resistance in treated HIV-infection

Identification and characterization of the molecular mechanisms contributing to the high incidence of insulin resistance in HIV infected patients treated with combined antiretroviral therapy remains a critically important goal in the quest to improve the safety of antiretroviral treatment regimens. The use of in vitro model systems together with the investigation of drug-mediated effects on glucose homeostasis in animals and healthy human volunteers has provided important insight into the contribution of individual drugs to insulin resistance and affected cellular pathways. HIV protease inhibitor mediated blockade of glucose transport and nucleoside reverse transcriptase inhibitor mediated mitochondrial toxicity have been well characterized. Together with growing understanding of mediators of insulin resistance in non-HIV metabolic syndrome, additional cellular effects including the induction of endoplasmic reticulum and oxidative stress, altered adipocytokine secretion, and lipotoxicity have been integrated into this developing picture. Further elucidation of these mechanisms provides potential for the continued development of safer antiviral drugs and targeted treatment of insulin resistance in affected patients.

Insulin metabolism in human adipocytes from subcutaneous and visceral depots

Subjects with the metabolic syndrome (insulin resistance, glucose intolerance, dyslipidemia, hypertension, etc.) have a relative increase in abdominal fat tissue compared to normal individuals and obesity has also been shown to be associated with a decrease in insulin clearance. The majority of the clearance of insulin is due to the action of insulin-degrading enzyme (IDE) and IDE is present throughout all tissues. Since abdominal fat is increased in obesity we hypothesized that IDE may be altered in the different fat depots. Adipocytes were isolated from fat samples obtained from subjects during elective abdominal surgery. Fat samples were taken from subcutaneous (SQ) and visceral (VIS) sites. Insulin metabolism was compared in adipocytes isolated from SQ and VIS fat tissue. Adipocytes from the VIS site degraded more insulin that those from SQ fat tissue. Inhibitors of cathepsins B and D has no effect on the degradation of insulin, while bacitracin, an inhibitor of IDE, inhibited degradation by approx. 33% in both SQ and VIS adipocytes. These data show that insulin metabolism is relatively greater in VIS than in SQ fat tissue and potentially due to IDE.

Long-term ritonavir exposure increases fatty acid and glycerol recycling in 3T3-L1 adipocytes as compensatory mechanisms for increased triacylglycerol hydrolysis

Lipodystrophy with high nonesterified fatty acid (FA) efflux is reported in humans receiving highly active antiretroviral therapy (HAART) to treat HIV infection. Ritonavir, a common component of HAART, alters adipocyte FA efflux, but the mechanism for this effect is not established. To investigate ritonavir-induced changes in FA flux and recycling through acylglycerols, we exposed differentiated murine 3T3-L1 adipocytes to ritonavir for 14 d. FA efflux, uptake, and incorporation into acylglycerols were measured. To identify a mediator of FA efflux, we measured adipocyte triacylglycerol lipase (ATGL) transcript and protein. To determine whether ritonavir-treated adipocytes increased glycerol backbone synthesis for FA reesterification, we measured labeled glycerol and pyruvate incorporation into triacylglycerol (TAG). Ritonavir-treated cells had increased FA efflux, uptake, and incorporation into TAG (all P < 0.01). Ritonavir increased FA efflux without consistently increasing glycerol release or changing TAG mass, suggesting increased partial TAG hydrolysis. Ritonavir-treated adipocytes expressed significantly more ATGL mRNA (P < 0.05) and protein (P < 0.05). Ritonavir increased glycerol (P < 0.01) but not pyruvate (P = 0.41), utilization for TAG backbone synthesis. Consistent with this substrate utilization, glycerol kinase transcript (required for glycerol incorporation into TAG backbone) was up-regulated (P < 0.01), whereas phosphoenolpyruvate carboxykinase transcript (required for pyruvate utilization) was down-regulated (P < 0.001). In 3T3-L1 adipocytes, long-term ritonavir exposure perturbs FA metabolism by increasing ATGL-mediated partial TAG hydrolysis, thus increasing FA efflux, and leads to compensatory increases in FA reesterification with glycerol and acylglycerols. These changes in FA metabolism may, in part, explain the increased FA efflux observed in ritonavir-associated lipodystrophy.

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.

Role of protease inhibitors and acylation stimulating protein in the adipogenesis in 3T3-L1 cells

Treatment of AIDS (HIV) and hepatitis C virus needs protease inhibitors (PI) to prevent viral replication. Uses of PI in therapy are usually associated with a decrease in body weight and dyslipidemia. Acylation stimulating protein (ASP) is a protein synthesized in adipocytes to increase triglycerides biosynthesis, for that the relation of PI and ASP to adipogenesis is tested in this work. ASP expression was increased during 3T3-L1 differentiation and reached a peak at day 8 with cell maturation. Addition of PI during adipocytes differentiation dose dependently and significantly (p < 0.5) inhibited the degree of triglycerides (TG) accumulation. Moreover, presence of ASP (450 ng/mL) in media significantly (p < 0.5) stimulated the degree of TG accumulation and there was additive stimulation for ASP when added with insulin (10 µg/mL). Finally, when ASP in different doses (Low, 16.7; Medium, 45 and High, 450 ng/mL) incubated with a dose of ×150 PI, ASP partially inhibited the PI-inhibited adipogenesis and TG accumulation. The results in this study show that PI inhibit lipids accumulation and confirm role of ASP in TG biosynthesis and adipogenesis.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSIONS AND IMPLICATIONS

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

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.

Update on therapeutic strategies to increase adiponectin function and secretion in metabolic syndrome

Changes in diagnostic criteria have impacted on the definition of the metabolic syndrome. The central aetiological importance of insulin resistance has lessened, while the role of other cardiovascular risk factors has progressively increased. Inflammatory mediators have also been identified as crucial targets for more selective therapies in metabolic syndrome. Among several pro-inflammatory factors, adiponectin has been shown to be associated with reduced cardiovascular risk in metabolic syndrome patients. Here, we review new therapeutic approaches, which could potentially increase adiponectin levels in metabolic syndrome.

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

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

Repositioning HIV protease inhibitors as cancer therapeutics

PURPOSE OF REVIEW

Although designed to target only the HIV protease, HIV protease inhibitors induce toxicities in patients such as insulin resistance and lipodystrophy that suggest that protease inhibitors have other targets in mammalian cells. Akt controls insulin signaling and is an important target in cancer, but no Akt inhibitors are approved as cancer therapeutics. These observations have prompted the study of HIV protease inhibitors as inhibitors of Akt and possible cancer therapeutics. This review will highlight the latest advances in repositioning HIV protease inhibitors as cancer therapeutics.

RECENT FINDINGS

Although protease inhibitors can inhibit Akt activation and the proliferation of over 60 cancer cell lines, as well as improve sensitivity to radiation or chemotherapy, these effects do not always correlate with Akt inhibition. Other important processes, such as the induction of endoplasmic reticulum stress, appear critical to the biological activity of protease inhibitors. These impressive and surprising preclinical data have prompted clinical testing of nelfinavir as a lead HIV protease inhibitor in cancer patients.

SUMMARY

Although mechanisms of action for the antitumor effects of HIV protease inhibitors are complex, their broad spectrum of activity, minimal toxicity, and wide availability make protease inhibitors ideal candidates for repositioning as cancer therapeutics.

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

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

Association of hypercholesterolemia incidence with antiretroviral treatment, including protease inhibitors, among perinatally HIV-infected children

CONTEXT

Antiretroviral therapy has been associated with hypercholesterolemia in HIV-infected children. Few longitudinal studies have been conducted to examine this association, however.

OBJECTIVE

To evaluate the incidence of and risk factors for development of hypercholesterolemia in a large pediatric study.

DESIGN

Prospective cohort study (Pediatric AIDS Clinical Trials Group 219C).

PARTICIPANTS

A total of 2122 perinatally HIV-infected children free of hypercholesterolemia at entry.

OUTCOME

Development of hypercholesterolemia (total cholesterol >or=220 mg/dL at 2 consecutive visits). Cox proportional hazards models were used to evaluate risk factors.

RESULTS

Thirteen percent of children had hypercholesterolemia at entry, and an additional 13% developed hypercholesterolemia during follow-up for an incidence rate of 3.4 cases per 100 person-years (95% confidence interval [CI]: 3.0 to 3.9). After adjustment for age, boosted protease inhibitor (PI) use (hazard ratio [HR] = 13.9, 95% CI: 6.73 to 28.6), nonboosted PI use (HR = 8.65, 95% CI: 4.19 to 17.9), and nonnucleoside reverse transcriptase inhibitor use (HR = 1.33, 95% CI: 1.04 to 1.71) were associated with increased risk of hypercholesterolemia, and higher viral load was protective (>50,000 vs.

CONCLUSIONS

PIs were significant risk factors for hypercholesterolemia. Higher viral load was protective and may reflect nonadherence. Further follow-up is critical to evaluate long-term consequences of chronic PI exposure and hypercholesterolemia.

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Key Words

• hiv
• cholesterol
• pediatric
• protease inhibitors
• dyslipidemia

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MESH Headings

• Adolescent
• Antiretroviral Therapy, Highly Active/adverse effects
• Child
• Child, Preschool
• Cholesterol/blood
• Cohort Studies
• Female
• HIV/drug effects
• HIV/isolation & purification
• HIV Infections/drug therapy
• HIV Infections/virology
• HIV Protease Inhibitors/adverse effects
• HIV Protease Inhibitors/therapeutic use
• Humans
• Hypercholesterolemia/chemically induced
• Hypercholesterolemia/epidemiology
• Incidence
• Male
• Proportional Hazards Models
• Prospective Studies
• Risk Factors
• Viral Load

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Grants

• U01 AI068632 NIAID NIH HHS
• U01 AI068632-03 NIAID NIH HHS
• UM1 AI069415 NIAID NIH HHS
• U01 AI068616 NIAID NIH HHS
• U01 AI041110 NIAID NIH HHS
• M01 RR006192-120196 NCRR NIH HHS
• M01 RR006192 NCRR NIH HHS
• UM1 AI069477 NIAID NIH HHS
• 1 U01 AI068616 NIAID NIH HHS
• 5 U01 AI41110 NIAID NIH HHS

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Affiliation(s)

Katherine Tassiopoulos Center for Biostatistics in AIDS Research, Harvard School of Public Health, Boston, MA 02115, USA.
Paige L Williams
George R Seage
Marilyn Crain
James Oleske
John Farley

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Mitochondrial Toxicity of Indinavir, Stavudine and Zidovudine Involves Multiple Cellular Targets in white and brown adipocytes

Objective

To evaluate the mechanisms of mitochondrial toxicity associated with antiretroviral treatment.

Methods

3T3–F442A white and T37i brown adipocytes were exposed to stavudine (10 μM), zidovudine (1 μM) and indinavir (10 μM), alone or in combination. Adipocyte fat content was measured with Oil Red O staining. Quantification of mRNA levels and of mitochondrial DNA content used PCR-based techniques. Mitochondrial activities were evaluated with respiration, ATP synthesis and spectrophotometric assays. Mitochondrial mass was assessed by the fluorescent probe MitoTracker Red.

Results

In both cell types, all the treatments induced a severe defect of adipogenesis (low lipid content and decreased markers of adipogenic maturation: peroxisome proliferator-activated receptor [PPAR]γ2 and aP2 but also uncoupling protein 1 in brown adipocytes) as well as altered mitochondrial function (decreased respiration rate and increased mitochondrial mass). Drug combination did not give additional toxicity. Brown adipocytes appeared more affected than white adipocytes (lower respiration rate and decreased ATP production). The mechanisms of mitochondrial toxicity differed with the drug and the cell type. Only stavudine induced severe mitochondrial DNA depletion in both cell types. With all the treatments, white adipocytes showed a decrease in the expression of mitochondrial and nuclear-DNA-encoded respiratory chain subunits (cytochrome c oxidase [CytOx]2 and CytOx4), whereas brown adipocytes maintained normal expression in accordance with their increase of the transcriptional factors of mitochondrial biogenesis nuclear respiratory factor 1 and PPARγ coactivator (PGC)1-related cofactor PRC, but not PGC1α.

Conclusion

Our results provide evidence for dissociation between mitochondrial activity, transcription and mitochondrial DNA content, highlighting the complexity of mitochondrial toxicity, which affects multiple cellular targets.

Mycophenolic acid as a latent agonist of PPARgamma

Mycophenolic acid (MPA), known as an inhibitor of inosine monophosphate dehydrogenase (IMPDH), was found to inhibit the differentiation of 3T3-L1 pre-adipocytes into mature adipocytes. Although the effect of MPA was attributed to inhibition of IMPDH, we uncovered a hidden biological property of MPA as an agonist of peroxisome proliferator activated receptor gamma (PPARgamma).

Effects of transgenic expression of HIV-1 Vpr on lipid and energy metabolism in mice

HIV infection is associated with abnormal lipid metabolism, body fat redistribution, and altered energy expenditure. The pathogenesis of these complex abnormalities is unclear. Viral protein R (Vpr), an HIV-1 accessory protein, can regulate gene transcription mediated by the glucocorticoid receptor and peroxisome proliferator-activated receptor-gamma and affect mitochondrial function in vitro. To test the hypothesis that expression of Vpr in liver and adipocytes can alter lipid metabolism in vivo, we engineered mice to express Vpr under control of the phosphoenolpyruvate carboxykinase promoter in a tissue-specific and inducible manner and investigated the effects of dietary fat, indinavir, and dexamethasone on energy metabolism and body composition. The transgenic mice expressed Vpr mRNA in white and brown adipose tissues and liver and immunoaffinity capillary electrophoresis revealed that they had free Vpr protein in the plasma. Compared with wild-type (WT) animals, Vpr mice had lower plasma triglyceride levels after 6 wk (P < 0.05) but not after 10 wk of a high-fat diet and lower plasma cholesterol levels after 10 wk of high-fat diet (P < 0.05). Treatment with dexamethasone obviated group differences, whereas indinavir had no significant independent effect on lipids. In the fasted state, Vpr mice had a higher respiratory quotient than WT mice (P < 0.05). These data provide the first in vivo evidence that HIV-1 Vpr expressed at low levels in adipose tissues and liver can 1) circulate in the blood, 2) regulate lipid and fatty acid metabolism, and 3) alter fuel selection for oxidation in the fasted state.

Nelfinavir Induces Adipocyte Insulin Resistance through the Induction of Oxidative Stress: Differential Protective Effect of Antioxidant Agents

Background

Antiretroviral therapy is frequently associated with adverse metabolic effects and lipodystrophy, but the role of HIV protease inhibitors and the mechanisms involved are poorly understood. The HIV protease inhibitor nelfinavir (NFV) impairs insulin signal propagation by inducing similar signalling defects to those induced by exposure to oxidative stress.

Aim

We set out to determine if oxidative stress is involved in NFV-induced insulin resistance in 3T3-L1 adipocytes, and whether antioxidant agents with unique modes of action can prevent this effect.

Results

Cells exposed to NFV exhibited the following markers of increased oxidative stress: a decrease in both total and low molecular weight reduced thiols, a 20-fold increase in haem oxygenase 1 (HO-1) mRNA, an increase in intracellular reactive oxygen species production (determined by 2′,7′-dichlorofluorescein fluorescence), and increased markers of apoptosis. Enhancing cellular thiols with N-acetylcystein prevented the NFV-induced drop in reduced thiols and partially protected against the induction in HO-1, but failed to prevent insulin resistance or cleavage of poly ADP ribose polymerase (PARP), a process indicative of activation of pro-apoptotic caspases. Conversely, the superoxide dismutase-mimetic antioxidant MnTBAP had no effect on cellular thiols in response to NFV, but protected against HO-1 induction and against the impairment in insulin-stimulated Akt/protein kinase B activation and PARP cleavage.

Conclusions

Induction of oxidative stress plays a role in adipocyte insulin resistance and apoptosis induced by NFV through a radical-dependent but thiol-independent mechanism(s). The results may suggest a new mechanism for the adverse effects of NFV on fat cells, and offer potential new intervention approaches.

Long-term treatment with lopinavir-ritonavir induces a reduction in peripheral adipose depots in mice

Highly active antiretroviral therapy (HAART) of human immunodeficiency virus-infected patients is associated with adverse effects, such as lipodystrophy and hyperlipidemia. The lipodystrophic syndrome is characterized by a peripheral lipoatrophy and/or fat accumulation in the abdomen and neck. In order to get insights into the physiopathological mechanisms underlying this syndrome, we treated mice with protease inhibitors (PIs) over a long period of time. Although atazanavir-treated mice presented the same circulating triglyceride concentration as control mice, lopinavir-ritonavir-treated mice rapidly became hypertriglyceridemic, with triglyceride levels of 200 mg/dl, whereas control and atazanavir-treated animals had triglyceride levels of 80 mg/dl. These results obtained with mice reproduce the metabolic disorder observed in humans. White adipose tissue (WAT) was analyzed after 8 weeks of treatment. Compared to the control or atazanavir treatment, lopinavir-ritonavir treatment induced a significant 25% weight reduction in the peripheral inguinal WAT depot. By contrast, the profound epididymal WAT depot was not affected. This effect was associated with a 5.5-fold increase in SREBP-1c gene expression only in the inguinal depot. Our results demonstrate that the long-term treatment of mice with PIs constitutes an interesting experimental model with which some aspects of the lipoatrophy induced by HAART in humans may be studied.

Nelfinavir induces liposarcoma apoptosis and cell cycle arrest by upregulating sterol regulatory element binding protein-1

"HIV protease-induced lipodystrophy syndrome" is associated with the use of HIV protease inhibitors for treatment of HIV infection. In-vitro studies suggest that alteration of sterol regulatory element binding protein-1 levels underlie its pathogenesis. We postulated that HIV protease inhibitors may represent a novel class of antiliposarcoma agents. SW872, FU-DDLS-1 and LiSa-2 liposarcoma, and HT1080 and 293 nonliposarcoma cell lines were treated with HIV protease inhibitors (nelfinavir, ritonavir, saquinavir, indinavir and amprenavir), and clonogenic assays were performed. Nelfinavir exhibited the most potent inhibition of clonogenicity, and further assays for proliferation, cell cycle and apoptosis were performed with nelfinavir. Immunoblots were performed for sterol regulatory element binding protein-1, proapoptotic and cell cycle-related protein expression after nelfinavir treatment. Finally, a sterol regulatory element binding protein-1-inducible SW872 cell line was developed to examine the phenotype resulting from upregulated sterol regulatory element binding protein-1. Nelfinavir selectively inhibited clonogenicity and proliferation, and induced G1 cell cycle block and induced apoptosis in a dose-dependent manner in SW872 and LiSa-2 cells, whereas it had minimal or no effect on these parameters in FU-DDLS-1 or nonliposarcoma cells. Nelfinavir induced significant sterol regulatory element binding protein-1 expression in a dose-dependent and time-dependent fashion in sensitive SW872 and LiSa-2 cells, modestly in HT1080 cells, but not in nelfinavir-insensitive FU-DDLS-1 and 293 cells without inducing adipocytic differentiation. Forced expression of sterol regulatory element binding protein-1 in inducible-SW872 cells led to the induction of proapoptotic and antiproliferative proteins, and consequent reduction of cellular proliferation. Our data indicate that nelfinavir represents a novel class of antiliposarcoma agent that acts by selectively upregulating sterol regulatory element binding protein-1 expression in liposarcomas.

Adipose tissue lipin expression levels distinguish HIV patients with and without lipodystrophy

OBJECTIVE

Lipodystrophy is the major complication of antiretroviral therapy in HIV-infected patients. Its pathophysiology is not well understood, but has been linked to antiadipogenic effects of antiretroviral drugs. Lipin represents a newly characterized protein that is critical for adipocyte differentiation, and lipin deficiency leads to lipodystrophy in the mouse. The objective of this study was to determine whether altered lipin gene expression is associated with HIV lipodystrophy in humans.

DESIGN

We measured lipin mRNA levels in subcutaneous abdominal and femoral-gluteal adipose tissue biopsies from HIV-infected patients with or without lipodystrophy, and in healthy controls. Real-time reverse transcription-PCR was performed to quantitate total lipin expression levels, and expression of two lipin isoforms (lipin-alpha and -beta) that are generated by alternative mRNA splicing.

RESULTS

As predicted from studies with mice, lipin mRNA levels were correlated with limb fat mass in HIV patients, with lower lipin levels in patients with lipodystrophy than those without lipodystrophy. Unexpectedly, however, this was explained by an increase in lipin-beta expression in HIV patients without lipodystrophy compared to patients with lipodystrophy and control subjects. In addition, lipin expression levels were inversely correlated with adipose tissue expression of inflammatory cytokines interleukin (IL)-6, IL-8 and IL-18, which typically increase in HIV-associated lipoatrophy.

CONCLUSIONS

Elevated lipin expression levels are associated both with the maintenance of greater fat mass and lower cytokine expression in HIV-infected patients. Based on the demonstrated role for lipin in promoting lipogenic gene expression, these observations raise the possibility that variations in lipin levels may contribute to variations in adipose tissue mass and function that distinguish HIV patients with and without lipodystrophy.

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.

Leptin and Adiponectin in the HIV Associated Metabolic Syndrome: Physiologic and Therapeutic Implications

Leptin and adiponectin represent two newly discovered adipose tissue derived hormones with important roles in energy homeostasis and insulin resistance. Their interrelations with the manifestations of the HIV associated metabolic syndrome and specific somatomorphic changes i.e. fat redistribution is reviewed. A synopsis of published studies is presented and the potential role of leptin and adiponectin is discussed. We have described an association of the HIV metabolic syndrome with a state of reduced insulin sensitivity due to adiponectin deficiency. The metabolic syndrome is also accompanied by leptin deficiency in lipoatrophic subjects and possibly by a leptin resistance state in lipohypertrophic patients. Adiponectin and / or leptin therapy in a manner similar to other leptin deficiency states may assist in the future management of such patients.

In Combination, Nucleoside Reverse Transcriptase Inhibitors Have Significant Effects on 3T3–L1 Adipocyte Lipid Accumulation and Survival

The use of nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infection is clearly linked to the development of subcutaneous fat atrophy. Until recently, however, in vitro studies of adipocytes have shown no or only modest and inconsistent effects of these agents on adipocyte biology. This is in contrast to the protease inhibitors (PIs), which are also linked to the development of HIV lipodystrophy. These agents have relatively consistent inhibitory effects on the differentiation of cultured adipocytes, and have occasionally been found to have other effects on adipocyte biology as well. We aimed to explore more thoroughly the effects of NRTIs and combinations of antiretroviral agents commonly used in clinical practice on multiple aspects of adipocyte biology using the 3T3-L1 adipocyte cell line. We found that when used individually, NRTIs decrease cell survival but only lamivudine significantly alters lipid accumulation. However, NRTI and dual NRTI-PI combinations do significantly decrease lipid accumulation in 3T3-L1 adipocytes, have a much greater detrimental impact on cell survival and decrease adipocyte differentiation.

HIV protease inhibitors block adipocyte differentiation independently of lamin A/C

OBJECTIVES

To determine the importance of lamin A/C for fat cell differentiation in vitro and for the anti-adipogenic activity of HIV protease inhibitors such as indinavir.

METHODS

Lipodystrophy-associated and processing-defective mutants of lamin A were stably expressed at high levels in 3T3-L1 pre-adipocytes. Additionally, 3T3-L1 pre-adipocytes with stable reduction of lamin A/C or emerin were derived. The cells were differentiated for 8 days into mature adipocytes in the presence or absence of indinavir or nelfinavir.

RESULTS

3T3-L1 cells stably expressing high levels of lipodystrophy-associated or processing-defective mutants of lamin A differentiated with comparable efficiencies to control cells. Similarly, cells with dramatically reduced lamin A levels differentiated as efficiently as controls. Although indinavir stimulated the accumulation of unprocessed lamin A, cells with dramatically reduced lamin A/C levels and no detectable prelamin A remained responsive to an indinavir-induced inhibition of adipogenesis.

CONCLUSIONS

The ability of HIV protease inhibitor to stimulate the accumulation of unprocessed lamin A is neither necessary nor sufficient to explain their anti-adipogenic activity. Furthermore, lamin A/C plays a minimal role in the differentiation of 3T3-L1.

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.

Alterations in thigh subcutaneous adipose tissue gene expression in protease inhibitor-based highly active antiretroviral therapy

Use of protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) has been associated with altered regional fat distribution, insulin resistance, and dyslipidemias. To assess how PI-based HAART affects adipocyte gene expression in male HIV-1-infected patients, reverse transcription-polymerase chain reaction was used to quantify messenger RNA expression of adipocyte transcription factors and adipocytokines in thigh and abdominal subcutaneous adipose tissue from male (1) HIV-1 seronegative subjects (control, n = 9), (2) asymptomatic treatment-naive HIV-1-infected patients (naive, n = 6), (3) HIV-1-infected patients who were receiving antiretroviral agents but never received PIs (PI naive, n = 5), (4) HIV-1-infected patients who were receiving PI-based HAART (PI, n = 7), and (5) HIV-1-infected patients who discontinued the PI component of their antiviral therapy more than 6 months before enrollment (past PI, n =7). In the PI group, the messenger RNA expression levels of the CCAAT/enhancer-binding protein alpha , leptin, and adiponectin (18%, P < .01; 23%, P < .05; and 13%, P < .05, respectively) were significantly lower than the levels measured in the PI-naive group. These results are consistent with previous studies on the effects of PIs on cultured adipocytes. Prospective longitudinal studies of thigh fat adipose tissue gene expression could provide further insights on the pathogenesis of metabolic complications associated with PI-based HAART.

Chemical genetic identification of the histamine H1 receptor as a stimulator of insulin-induced adipogenesis

A large collection of bioactive compounds with diverse biological effects can be used as probes to elucidate new biological mechanisms that influence a particular cellular process. Here we analyze the effects of 880 well-known small-molecule bioactives or drugs on the insulin-induced adipogenesis of 3T3-L1 fibroblasts, a cell-culture model of fat cell differentiation. Our screen identified 86 compounds as modulators of the adipogenic differentiation of 3T3-L1 cells. Examination of their chemical and pharmacological information revealed that antihistamine drugs with distinct chemical scaffolds inhibit differentiation. Histamine H1 receptor is expressed in 3T3-L1 cells, and its knockdown by small interfering RNA impaired the insulin-induced adipogenic differentiation. Histamine receptors and histamine-like biogenic amines may play a role in inducing adipogenesis in response to insulin.

Interventions for managing antiretroviral therapy-associated lipoatrophy

PURPOSE OF REVIEW

The purpose of this review is to summarize recent data on treatment options for highly active antiretroviral therapy-associated lipoatrophy.

RECENT FINDINGS

Modification of antiretroviral therapy, especially replacing stavudine by abacavir, induces a slow but continuous increase in the subcutaneous fat mass in patients with highly active antiretroviral therapy-associated lipoatrophy. As part of an initial highly active antiretroviral therapy combination, tenofovir and emtricitabine cause less lipodystrophy than stavudine, but no data from controlled studies have yet assessed the effects of switching from older agents to tenofovir or emtricitabine. Novel antidiabetic drugs, glitazones, cause little improvement in highly active antiretroviral therapy-associated lipoatrophy, but increase blood cholesterol and triglyceride concentrations significantly, and thus cannot be recommended for the treatment of highly active antiretroviral therapy-associated lipoatrophy. Various reconstructive procedures have been used to correct facial lipoatrophy. Bioabsorbable fillers have been used successfully, but treatment with such fillers has to be repeated over time. Permanent fillers have a durable effect, but may be difficult or impossible to remove if complications occur. Furthermore, an optimal volume correction with a permanent filler now may prove to be an over-correction in the future, if the recovery process of adipose tissue continues after the modification of antiretroviral therapy.

SUMMARY

The optimal choice of antiretroviral combination is of crucial importance for the prevention and treatment of highly active antiretroviral therapy-associated lipoatrophy. Switching from stavudine to abacavir causes a slow but continuous increase in the subcutaneous fat mass. Bioabsorbable skin fillers are the safest option for the reconstructive treatment of facial lipoatrophy.

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.

Nelfinavir Induces Necrosis of 3T3F44-2A Adipocytes by Oxidative Stress

Protease inhibitor treatment strongly diminishes mortality in HIV-infected patients. This treatment has also been associated with lipodystrophy and has been shown to alter adipocyte differentiation. The protease inhibitor nelfinavir has been indirectly implicated in the appearance and development of lipodystrophic syndrome, as well as in adipocyte cell death. The aim of this study was to evaluate the effects of nelfinavir on the 3T3-F442A adipocyte cell line. Nelfinavir (30 microM) induced cell death of 3T3-F442A adipocytes by a necrotic process that was not mediated by TNF-alpha. Treatment of cells with this protease inhibitor led to a significant increase in expression of the heme oxygenase-1 gene that could be reduced by 100 microM of the antioxidant ascorbate. Moreover, ascorbate had a protective effect on nelfinavir-induced necrosis, decreasing the percentage of necrotic cells by 70%. Our results show that nelfinavir induces necrosis of adipocytes mediated by a cellular increase of reactive oxygen species. This deleterious effect could be counterbalanced by ascorbate.

New insights into inhibitors of adipogenesis

PURPOSE OF REVIEW

Adipose tissue is a dynamic organ that changes mass throughout life in response to the metabolic needs of the animal. In the past three decades, significant advances have been made in delineating key extracellular and intracellular stimulators of fat cell formation or adipogenesis. In this review, the author focuses on new findings of specific inhibitors of adipogenesis. Understanding the balance between positive and negative regulators of adipogenesis has important health-related implications for anti-obesity medical therapy and lipodystrophy.

RECENT FINDINGS

Adipogenesis is a highly regulated process requiring coordinated expression and activation of two main groups of adipogenic transcription factors, CCAAT/enhancer binding proteins and peroxisome proliferators activated receptor gamma. In response to hormonal and nutrient stimuli, the increased expression and activation of these transcription factors induce the expression of adipocyte-specific genes. More recently, several groups have identified extracellular inhibitors of adipocyte formation, including cytokines, lipid molecules, genistein, and protease inhibitors. Intracellular signaling molecules, which negatively regulate adipogenesis, include Pref-1, Foxo1, Foxa2, SMAD-3, WNT-10b, GATA-2 and GATA-3.

SUMMARY

The prevalence of obesity is increasing in the United States and in other westernized societies. Understanding the mechanisms of excessive energy storage in adipose tissue is necessary to develop a comprehensive strategy to prevent and treat obesity. One potential, but unrealized, approach to obesity treatment is to target excessive adipose tissue enlargement. A number of promising extra- and intracellular inhibitors of fat cell formation have been identified, but the modulation of adipose tissue mass may have both advantageous and deleterious health effects.

Nelfinavir-induced insulin resistance is associated with impaired plasma membrane recruitment of the PI 3-kinase effectors Akt/PKB and PKC-zeta

AIMS/HYPOTHESIS

Chronic exposure of 3T3-L1 adipocytes to the HIV protease inhibitor nelfinavir induces insulin resistance, recapitulating key metabolic alterations of adipose tissue in the lipodystrophy syndrome induced by these agents. Our goal was to identify the defect in the insulin signal transduction cascade leading to nelfinavir-induced insulin resistance.

METHODS

Fully differentiated 3T3-L1 adipocytes were exposed to 30 micro mol/l nelfinavir for 18 h, after which the amount, the phosphorylation and the localisation of key proteins in the insulin signalling cascade were evaluated.

RESULTS

Insulin-induced interaction of phosphatidylinositol 3'-kinase (PI 3-kinase) with IRS proteins was normal in cells treated with nelfinavir, as was IRS-1-associated PI 3-kinase activity. Yet insulin-induced phosphorylation of Akt/protein kinase B (PKB), p70S6 kinase and extracellular signal-regulated kinase 1/2 was significantly impaired. This could not be attributed to increased protein phosphatase 2A activity or to increased expression of phosphoinositide phosphatases (SHIP2 or PTEN). However, insulin failed to induce translocation of the PI 3-kinase effectors Akt/PKB and protein kinase C-zeta (PKC-zeta) to plasma membrane fractions of nelfinavir-treated adipocytes.

CONCLUSIONS/INTERPRETATION

We therefore conclude that nelfinavir induces a defect in the insulin signalling cascade downstream of the activation of PI 3-kinase. This defect manifests itself by impaired insulin-mediated recruitment of Akt/PKB and PKC-zeta to the plasma membrane.

Adipocytes Targets and Actors in the Pathogenesis of HIV-Associated Lipodystrophy and Metabolic Alterations

The recent clinical use of potent HIV-1 drugs, including nucleoside reverse transcriptase inhibitors (NRTIs) and non-peptidic viral protease inhibitors (PIs), and their combinations, termed highly active antiretroviral therapy (HAART), has dramatically reduced the infection-related mortality of AIDS patients, but it is associated with severe metabolic adverse events such as lipodystrophy syndrome, dyslipidaemia, insulin resistance and diabetes mellitus. The aetiology of this syndrome and metabolic alterations appear to be multifactorial, including HIV drug inhibitory effects on adipocyte differentiation, alteration of mitochondrial functions in adipocytes and altered leptin, adiponectin and cytokine expression in adipose tissue of patients. Adipose tissue may thus be a central regulator in disorganized lipid metabolism and insulin resistance associated with antiretroviral therapy, and we propose in this review to explore how adipose tissue may be a target, but also an actor, in the aetiopathogenesis of the lipodystrophy syndrome.

Adiponectin ameliorates dyslipidemia induced by the human immunodeficiency virus protease inhibitor ritonavir in mice

Although the clinical application of HIV protease inhibitors (PIs) has markedly reduced HIV-related morbidity and mortality, it is now recognized that PI-based therapy often causes serious metabolic disorders, including hyperlipidemia and premature atherosclerosis. The etiology of these adverse effects remains obscure. Here, we demonstrate that deficiency of the fat-derived hormone adiponectin might play a role. The steady-state mRNA levels of the adiponectin gene and secretion of this protein from 3T3-L1 adipocytes are significantly decreased after treatment with several PIs (indinavir, nelfinavir, and ritonavir), with ritonavir having the greatest effect. Intragastric administration of ritonavir into mice decreases plasma concentrations of adiponectin and concurrently increases the plasma levels of triglyceride, free fatty acids, and cholesterol. Adiponectin replacement therapy markedly ameliorates ritonavir-induced elevations of triglyceride and free fatty acids. These beneficial effects of adiponectin are partly due to its ability to decrease ritonavir-induced synthesis of fatty acids and triglyceride, and to increase fatty acid combustion in the liver tissue. In contrast, adiponectin has little effect on ritonavir-induced hypercholesterolemia and hepatic cholesterol synthesis. These results suggest that hypoadiponectinemia is partly responsible for the metabolic disorders induced by HIV PIs, and adiponectin or its agonists might be useful for the treatment of these disorders.

Increased systemic and adipose tissue cytokines in patients with HIV-associated lipodystrophy

The lipodystrophy syndrome (adipose tissue redistribution and metabolic abnormalities) observed with highly active antiretroviral therapy (HAART) during human immunodeficiency virus (HIV) infection may be related to increased proinflammatory cytokine activity. We measured acute cytokine (TNF-alpha, IL-6, leptin), glycerol, and lactate secretion from abdominal subcutaneous adipose tissue (SAT), and systemic cytokine levels, in HIV-infected subjects with and without lipodystrophy (HIVL+ and HIVL-, respectively) and healthy non-HIV controls. Lipodystrophy was confirmed and characterized as adipose tissue redistribution in HIVL+ compared with HIVL- and controls, by dual-energy X-ray absorptiometry and by whole body MRI. TNF-alpha secretion from abdominal SAT and circulating levels of IL-6, soluble TNF receptors I and II, and insulin were elevated in HIVL+ relative to HIVL- and/or controls, particularly in HIVL+ undergoing HAART. In the HIV-infected group as a whole, IL-6 secretion from abdominal SAT and serum IL-6 were positively associated with visceral fat and were negatively associated with the relative amount of lower limb adipose tissue (P < 0.01). Decreased leptin and increased lactate secretion from abdominal SAT were specifically associated with HAART. In conclusion, increased cytokine secretion from adipose tissue and increased systemic proinflammatory cytokine activity may play a significant role in the adipose tissue remodeling and/or the metabolic abnormalities associated with the HIV-lipodystrophy syndrome in patients undergoing HAART.

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.