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

Obesity-induced tissue alterations resist weight loss: A mechanistic review

Interventions aimed at weight control often have limited effectiveness in combating obesity. This review explores how obesity-induced dysfunction in white (WAT) and brown adipose tissue (BAT), skeletal muscle, and the brain blunt weight loss, leading to retention of stored fat. In obesity, increased adrenergic stimulation and inflammation downregulate β-adrenoreceptors and impair catecholaminergic signalling in adipocytes. This disrupts adrenergic-mediated lipolysis, diminishing lipid oxidation in both white and brown adipocytes, lowering thermogenesis and blunting fat loss. Emerging evidence suggests that WAT fibrosis is associated with worse weight loss outcomes; indeed, limiting collagen and laminin-α4 deposition mitigates WAT accumulation, enhances browning, and protects against high-fat-diet-induced obesity. Obesity compromises mitochondrial oxidative capacity and lipid oxidation in skeletal muscle, impairing its ability to switch between glucose and lipid metabolism in response to varying nutrient levels and exercise. This dysfunctional phenotype in muscle is exacerbated in the presence of obesity-associated sarcopenia. Additionally, obesity suppresses sarcolipin-induced sarcoplasmic reticulum calcium ATPase (SERCA) activation, resulting in reduced oxidative capacity, diminished energy expenditure, and increased adiposity. In the hypothalamus, obesity and overnutrition impair insulin and leptin signalling. This blunts central satiety signals, favouring a shift in energy balance toward energy conservation and body fat retention. Moreover, both obese animals and humans demonstrate impaired dopaminergic signalling and diminished responses to nutrient intake in the striatum, which tend to persist after weight loss. This may result in enduring inclinations toward overeating and a sedentary lifestyle. Collectively, the tissue adaptations described pose significant challenges to effectively achieving and sustaining weight loss in obesity.

Drug Reprofiling to Identify Potential HIV-1 Protease Inhibitors

The use of protease inhibitors in human immunodeficiency virus type 1 (HIV-1) treatment is limited by adverse effects, including metabolic complications. To address these challenges, efforts are underway in the pursuit of more potent and less toxic HIV-1 protease inhibitors. Repurposing existing drugs offers a promising avenue to expedite the drug discovery process, saving both time and costs compared to conventional de novo drug development. This study screened FDA-approved and investigational drugs in the DrugBank database for their potential as HIV-1 protease inhibitors. Molecular docking studies and cell-based assays, including anti-HIV-1 in vitro assays and XTT cell viability tests, were conducted to evaluate their efficacy. The study findings revealed that CBR003PS, an antibiotic currently in clinical use, and CBR013PS, an investigational drug for treating endometriosis and uterine fibroids, exhibited significant binding affinity to the HIV-1 protease with high stability. Their EC50 values, measured at 100% cell viability, were 9.4 nM and 36.6 nM, respectively. Furthermore, cell-based assays demonstrated that these two compounds showed promising results, with therapeutic indexes higher than 32. In summary, based on their favorable therapeutic indexes, CBR003PS and CBR013PS show potential for repurposing as HIV-1 protease inhibitors.

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.

Relationship between weight gain and insulin resistance in people living with HIV switching to integrase strand transfer inhibitors-based regimens

OBJECTIVE

The primary objective was to explore weight and BMI changes in people with HIV (PWH) undergoing integrase strand transfer inhibitors (INSTI)-based regimens (vs. non-INSTI) in a large cohort and in the subsets of individuals without diabetes and insulin resistance (IR) at the time of switch to INSTI. The secondary objective was to identify risk factors for IR and cut-off of weight or BMI increase associated with IR in PWH switching to INSTI.

DESIGN

A longitudinal matched-cohort study including PWH attending Modena HIV Metabolic Clinic, Italy.

METHODS

PWH were divided into two groups: non-INSTI and INSTI-switch. The effect of switching to INSTI on weight and BMI change was tested through a linear mixed model. A mediation analysis explored the mediation effect of weight and BMI change in the association between the switch to INSTI and IR.

RESULTS

We analyzed 2437 PWH (1025 INSTI-switch, 1412 non-INSTI), in 54 826 weight assessments. Trends for weight increase were significantly higher in early-INSTI-switch (vs. early-non-INSTI), but no difference was observed in the late period after the switch. In the subset of 634 PWH without IR, switching to INSTI (vs. non-INSTI) was associated with a lower risk of IR (hazard ratio = 0.70, 95% confidence interval: 0.51, 0.98). A weight increase by 1% reduced the total protective effect of INSTI by 21.1% over 1 year of follow-up, which identifies a 5% weight increase as a clinically meaningful weight gain definition.

CONCLUSION

A cut-off of 5% weight gain from the time of INSTI-switch is associated with IR, which may be a clinically meaningful endpoint that could be used in clinical and research settings.

Differential effects of dolutegravir, bictegravir and raltegravir in adipokines and inflammation markers on human adipocytes

AIMS

To assess the potential direct effects of the integrase strand-transfer inhibitors (INsTIs) dolutegravir, bictegravir, and raltegravir, drugs used as treatment for people living with human immunodeficiency virus (PLWH), on human adipose cells.

MAIN METHODS

Drugs were added to the differentiation medium of human Simpson-Golabi-Behmel syndrome (SGBS) adipose cells and morphological adipogenesis was monitored for 10 days. Also, adipocytes were exposed to drugs following differentiation (day 14). The gene expression levels of selected adipogenesis markers, adipocyte metabolism markers, adipokines, and cytokines were determined by quantitative-reverse transcription polymerase-chain reaction. The release of adiponectin and leptin into the culture medium was measured using specific enzyme-linked immunosorbent assay, and release of interleukin-6 and chemokine (CC motif) ligand-2 using Multiplex assays.

KEY FINDINGS

Overall morphological adipogenesis was unaltered by INsTIs. The expression of adipogenesis marker genes (peroxisome proliferator-activated receptor-Ɣ and lipoprotein lipase) was slightly reduced in dolutegravir-treated differentiating adipocytes. Bictegravir repressed gene expression and the release of pro-inflammatory cytokines in differentiating adipocytes. Dolutegravir and raltegravir increased interleukin-6 gene expression, but only dolutegravir increased interleukin-6 release. Dolutegravir repressed adiponectin expression and release in differentiating adipocytes and had a similar but milder effect on leptin. Drug treatment of mature adipocytes reduced adiponectin gene expression in response to dolutegravir.

SIGNIFICANCE

The INsTIs studied do not have a significant effect on human adipose cell differentiation but exert distinct effects on gene expression and secretion of adipokines and cytokines. These findings will help understand and manage the effects of INsTI-containing treatments on body weight and metabolic dysregulation in PLWH.

Non-Alcoholic Fatty Liver Disease in HIV/HBV Patients - a Metabolic Imbalance Aggravated by Antiretroviral Therapy and Perpetuated by the Hepatokine/Adipokine Axis Breakdown

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with the metabolic syndrome and is one of the most prevalent comorbidities in HIV and HBV infected patients. HIV plays an early and direct role in the development of metabolic syndrome by disrupting the mechanism of adipogenesis and synthesis of adipokines. Adipokines, molecules that regulate the lipid metabolism, also contribute to the progression of NAFLD either directly or via hepatic organokines (hepatokines). Most hepatokines play a direct role in lipid homeostasis and liver inflammation but their role in the evolution of NAFLD is not well defined. The role of HBV in the pathogenesis of NAFLD is controversial. HBV has been previously associated with a decreased level of triglycerides and with a protective role against the development of steatosis and metabolic syndrome. At the same time HBV displays a high fibrogenetic and oncogenetic potential. In the HIV/HBV co-infection, the metabolic changes are initiated by mitochondrial dysfunction as well as by the fatty overload of the liver, two interconnected mechanisms. The evolution of NAFLD is further perpetuated by the inflammatory response to these viral agents and by the variable toxicity of the antiretroviral therapy. The current article discusses the pathogenic changes and the contribution of the hepatokine/adipokine axis in the development of NAFLD as well as the implications of HIV and HBV infection in the breakdown of the hepatokine/adipokine axis and NAFLD progression.

Cardiovascular computed tomography and HIV: The evolving role of imaging biomarkers in enhanced risk prediction

The treatment of human immunodeficiency virus (HIV) with antiretroviral (ARV) medications has revolutionised the care for these patients. The dramatic increase in life expectancy has brought new challenges in treating diseases of aging in this cohort. Cardiovascular disease (CVD) is now a leading cause of morbidity and mortality with risk matched HIV-positive patients having double the risk of MI compared to HIV-negative patients. This enhanced risk is secondary to the interplay the virus (and accessory proteins), ARV medications and traditional risk factors. The culmination of these factors can lead to a hybrid metabolic syndrome characterised by heightened ectopic fat. Cardiovascular computed tomography (CT) is ideal for quantifying epicardial adipose tissue volumes, hepatosteatosis and cardiovascular disease burden. The CVD risk attributed to disease burden and plaque morphology is well established in general populations but is less clear in HIV populations. The purpose of this review article is to appraise the latest data on CVD development in HIV-positive patients and how the use of cardiovascular CT may be used to enhance risk prediction in this population. This may have important implications on individualised treatment decisions and risk reduction strategies which will improve the care of these patients.

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

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

Resveratrol and HIV-protease inhibitors control UCP1 expression through opposite effects on p38 MAPK phosphorylation in human adipocytes

Brown and brown-like adipocytes (BBAs) control thermogenesis and are detected in adult humans. They express UCP1, which transforms energy into heat. They appear as promising cells to fight obesity. Deciphering the molecular mechanisms leading to the browning of human white adipocytes or the whitening of BBAs represents a goal to properly and safely control the pathways involved in these processes. Here, we analyzed how drugs endowed with therapeutic potential affect the differentiation of human adipose progenitor-cells into BBAs and/or their phenotype. We showed that HIV-protease inhibitors (PI) reduced UCP1 expression in BBAs modifying their metabolic profile and the mitochondria functionality. Lopinavir (LPV) was more potent than darunavir (DRV), a last PI generation. PPARγ and PGC-1α were decreased in a PI or cell-specific manner, thus altering UCP1's constitutive expression. In addition, LPV altered p38 MAPK phosphorylation, blunting then the β-adrenergic responses. In contrast, low doses of resveratrol stimulated the activatable expression of UCP1 in a p38 MAPK-dependent manner and counteracted the LPV induced loss of UCP1. This effect was independent of the resveratrol-induced sirtuin-1 expression. Altogether our results uncover how drugs impact crucial components of the networks regulating the expression of the thermogenic signature. They provide important information to control the relevant pathways involved in energy expenditure.

Clinical outcome after lipectomy in the management of patients with human immunodeficiency virus-associated dorsocervical fat accumulation: An observational cohort study

Lipo-accumulation of the dorsocervical fat pad ("buffalo hump") is a complication observed in people living with human immunodeficiency virus (HIV). We described the clinical outcome of people living with HIV with "buffalo hump" treated by excisional lipectomy.From April 2013 to March 2018, medical records of people living with HIV, who received care in our hospital have been evaluated. Among them, patients with dorsocervical fat accumulation treated by excisional lipectomy have been retrospectively assessed.Nine patients with "buffalo hump" among 2886 people living with HIV (3.1‰, 9/2886) were included. Eight were women with a mean age of 47.9 ± 8.0 years old (range, 36-60). Most of them have been infected by blood transfusion (77%, 7/9) and the mean duration of HIV infection was 14.1 ± 5.5 years (range, 6-22). The mean duration for antiretroviral therapy was 8.8 ± 2.1 years (range, 6-11). The mean pre-ART CD4+ T cell count was 91.3 ± 76.5 cells/μL (range, 4-233) and 477.4 ± 271.8 cells/μL (range, 114-926) at the time of surgery. All 9 patients underwent excisional lipectomy of their hypertrophied dorsocervical fat pad. The mean size of the excised specimens was 14 × 11 × 6 cm. The median follow-up time was 24 months (range, 2-60), all 9 patients reported satisfaction with their results, with no recurrence has been observed.Corrective surgery used to treat localized fat accumulations in people living with HIV with "buffalo hump" showed a favorable effect and can therefore be considered when necessary. Whereas drugs such as integrase inhibitors may avoid lipo-accumulation related syndrome and should be given to people living with HIV in China.

Adipose Tissue in Persons With HIV Is Enriched for CD4+ T Effector Memory and T Effector Memory RA+ Cells, Which Show Higher CD69 Expression and CD57, CX3CR1, GPR56 Co-expression With Increasing Glucose Intolerance

Chronic T cell activation and accelerated immune senescence are hallmarks of HIV infection, which may contribute to the increased risk of cardiometabolic diseases in people living with HIV (PLWH). T lymphocytes play a central role in modulating adipose tissue inflammation and, by extension, adipocyte energy storage and release. Here, we assessed the CD4+ and CD8+ T cell profiles in the subcutaneous adipose tissue (SAT) and blood of non-diabetic (n = 9; fasting blood glucose [FBG] < 100 mg/dL), pre-diabetic (n = 8; FBG = 100-125 mg/dL) and diabetic (n = 9; FBG ≥ 126 mg/dL) PLWH, in addition to non- and pre-diabetic, HIV-negative controls (n = 8). SAT was collected by liposuction and T cells were extracted by collagenase digestion. The proportion of naïve (TNai) CD45RO-CCR7+, effector memory (TEM) CD45RO+CCR7-, central memory (TCM) CD45RO+CCR7+, and effector memory revertant RA+(TEMRA) CD45RO-CCR7- CD4+ and CD8+ T cells were measured by flow cytometry. CD4+ and CD8+ TEM and TEMRA were significantly enriched in SAT of PLWH compared to blood. The proportions of SAT CD4+ and CD8+ memory subsets were similar across metabolic status categories in the PLWH, but CD4+ T cell expression of the CD69 early-activation and tissue residence marker, particularly on TEM cells, increased with progressive glucose intolerance. Use of t-distributed Stochastic Neighbor Embedding (t-SNE) identified a separate group of predominantly CD69lo TEM and TEMRA cells co-expressing CD57, CX3CR1, and GPR56, which were significantly greater in diabetics compared to non-diabetics. Expression of the CX3CR1 and GPR56 markers indicate these TEM and TEMRA cells may have anti-viral specificity. Compared to HIV-negative controls, SAT from PLWH had an increased CD8:CD4 ratio, but the distribution of CD4+ and CD8+ memory subsets was similar irrespective of HIV status. Finally, whole adipose tissue from PLWH had significantly higher expression of TLR2, TLR8, and multiple chemokines potentially relevant to immune cell homing compared to HIV-negative controls with similar glucose tolerance.

Female sex hormones are necessary for the metabolic effects mediated by loss of Interleukin 18 signaling

OBJECTIVE

Interleukin (IL)-18 plays a crucial role in maintaining metabolic homeostasis and levels of this cytokine are influenced by gender, age, and sex hormones. The role of gender on IL-18 signaling, however, is unclear. We hypothesized that the presence of female sex hormone could preserve the metabolic phenotype of the IL-18R^-/- animals.

METHODS

We studied female mice with a global deletion of the α isoform of the IL-18 receptor (IL-18R^-/-) and littermates control. Three studies were done: 1) animals fed a high fat diet (HFD) for 16 weeks; 2) animals fed chow diet for 72 weeks and 3) animals (3 weeks-old) randomized to either bilateral ovariectomy (OVX) or control surgery (SHAM) and followed for 16 weeks.

RESULTS

Female IL-18R^-/- mice gained less weight and maintained glucose homeostasis on a chow diet compared with HFD, but no differences between genotypes were observed. The maintenance of body weight and glucose homeostasis in IL-18R^-/- mice was lost with aging. By 72 weeks of age, IL-18R^-/- mice became heavier compared with WT mice due to an increase in both visceral and subcutaneous adiposity and displayed glucose intolerance. OVX did not affect body weight in IL-18R^-/- mice but exacerbated glucose intolerance and impaired liver insulin signaling when compared with SHAM mice.

CONCLUSIONS

Female mice harboring a global deletion of the IL-18R, only present the same phenotype as reported in male IL-18R^-/- mice if they are aged or have undergone OVX, in which circulating estrogen is likely to be blunted. The role of estrogen signaling in the protection against altered metabolic homeostasis in IL-18R^-/- mice appears to be mediated by liver insulin signaling. We therefore suggest that the metabolic effects mediated by loss of IL-18 signaling are only present in a female sex hormone free environment.

Naringin prevents HIV-1 protease inhibitors-induced metabolic complications in vivo

Background

Insulin resistance, glucose intolerance and overt diabetes are known metabolic complications associated with chronic use of HIV-Protease Inhibitors. Naringin is a grapefruit-derived flavonoid with anti-diabetic, anti-dyslipidemia, anti-inflammatory and anti-oxidant activities.

Objectives

The study investigated the protective effects of naringin on glucose intolerance and impaired insulin secretion and signaling in vivo.

Methods

Male Wistar rats were divided into six groups (n = 6) and were daily orally treated with distilled water {3.0 ml/kg body weight (BW)}, atazanavir (133 mg/kg BW), saquinavir (333 mg/kg BW) with or without naringin (50 mg/kg BW), respectively for 56 days. Body weights and water consumption were recorded daily. Glucose tolerance tests were carried out on day 55 of the treatment and thereafter, the rats were sacrificed by halothane overdose.

Results

Atazanavir (ATV)- or saquinavir (SQV)-treated rats exhibited significant weight loss, polydipsia, elevated Fasting blood glucose (FBG), reduced Fasting Plasma Insulin (FPI) and expression of phosphorylated, Insulin Receptor Substrate-1 (IRS-1) and Akt proteins, hepatic and pancreatic glucokinase levels, and also increasing pancreatic caspase-3 and -9 as well as UCP2 protein expressions compared to controls, respectively. These effects were completely reversed by naringin treatment.

Conclusion

Naringin prevents PI-induced glucose intolerance and impairment of insulin signaling and as nutritional supplement it could therefore alleviate metabolic complications associated with antiretroviral therapy.

Role of Gag mutations in PI resistance in the Swiss HIV cohort study: bystanders or contributors?

Background

HIV Gag mutations have been reported to confer PI drug resistance. However, clinical implications are still controversial and most current genotyping algorithms consider solely the protease gene for assessing PI resistance.

Objectives

Our goal was to describe for HIV infections in Switzerland the potential role of the C-terminus of Gag (NC-p6) in PI resistance. We aimed to characterize resistance-relevant mutational patterns in Gag and protease and their possible interactions.

Methods

Resistance information on plasma samples from 2004-12 was collected for patients treated by two diagnostic centres of the Swiss HIV Cohort Study. Sequence information on protease and the C-terminal Gag region was paired with the corresponding patient treatment history. The prevalence of Gag and protease mutations was analysed for PI treatment-experienced patients versus PI treatment-naive patients. In addition, we modelled multiple paths of an assumed ordered accumulation of genetic changes using random tree mixture models.

Results

More than half of all PI treatment-experienced patients in our sample set carried HIV variants with at least one of the known Gag mutations, and 17.9% (66/369) carried at least one Gag mutation for which a phenotypic proof of PI resistance by in vitro mutagenesis has been reported. We were able to identify several novel Gag mutations that are associated with PI exposure and therapy failure.

Conclusions

Our analysis confirmed the association of Gag mutations, well known and new, with PI exposure. This could have clinical implications, since the level of potential PI drug resistance might be underestimated.

Adipose Tissue in HIV Infection

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

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.

Improved adipose tissue function with initiation of protease inhibitor-only ART

OBJECTIVES

Use of ART containing HIV PIs has previously been associated with toxicity in subcutaneous adipose tissue (SAT), potentially contributing to the development of lipodystrophy and insulin resistance. However, the effect of PIs on SAT function in ART-naive patients independent of other ART classes is unknown. This study aimed to elucidate the effect of initiating PI-only ART on SAT function in ART-naive subjects.

METHODS

In the HIVNAT-019 study, 48 HIV-infected, ART-naive Thai adults commencing PI-only ART comprising lopinavir/ritonavir/saquinavir for 24 weeks underwent assessments of fasting metabolic parameters and body composition. In a molecular substudy, 20 subjects underwent SAT biopsies at weeks 0, 2 and 24 for transcriptional, protein, mitochondrial DNA (mtDNA) and histological analyses. ClinicalTrials.gov registration number: NCT00400738.

RESULTS

Over 24 weeks, limb fat increased (+416.4 g, P = 0.023), coinciding with larger adipocytes as indicated by decreased adipocyte density in biopsies (-32.3 cells/mm2, P = 0.047) and increased mRNA expression of adipogenesis regulator PPARG at week 2 (+58.1%, P = 0.003). Increases in mtDNA over 24 weeks (+600 copies/cell, P = 0.041), decreased NRF1 mRNA expression at week 2 (-33.7%, P < 0.001) and increased COX2/COX4 protein ratio at week 24 (+288%, P = 0.038) indicated improved mitochondrial function. Despite decreased AKT2 mRNA at week 2 (-28.6%, P = 0.002) and increased PTPN1 mRNA at week 24 (+50.3%, P = 0.016) suggesting insulin resistance, clinical insulin sensitivity [by homeostasis model assessment (HOMA-IR)] was unchanged.

CONCLUSIONS

Initiation of PI-only ART showed little evidence of SAT toxicity, the changes observed being consistent with a return to health rather than contributing to lipodystrophy.

[Wasting syndrome in HIV-infected patients]

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

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

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

IL-4 and IL-6 levels and adipose tissue distribution in HIV-1 patients under antiretroviral therapy

PURPOSE

Combined antiretroviral therapy (cART) for the treatment of HIV-1 infection has been associated with complications, including lipodystrophy. Several interleukins have been implicated in the pathology and physiology of lipodystrophy. The present study aimed to compare the levels of IL-4 and IL-6 in HIV-1 patients under cART with and without, clinically and fat mass ratio defined, lipodystrophy and in four different groups of fat distribution: (1) no lipodystrophy; (2) isolated central fat accumulation; (3) isolated lipoatrophy and (4) mixed forms of lipodystrophy.

METHODS

In the present cross-sectional study we evaluated IL-4 and IL-6 levels, insulin resistance and insulin sensitivity indexes in 86 HIV-infected adults under cART.

RESULTS

No significant differences in IL-4 and IL-6 levels between the four groups of body composition were observed. Patients with HOMA-IR >4 presented higher levels of IL-6 and lower levels of IL-4, although without statistical significance. No correlation between IL-6, or IL-4, HOMA-IR and quantitative body fat mass distribution was found.

CONCLUSION

Although there was a tendency for patients with isolated lipoatrophy and isolated fat accumulation to present higher IL-6 levels, these differences were not statistically significant. No differences were found relating IL-4 levels.

Predictors of Ectopic Fat in Humans

In the last decade there has been increasing focus on body fat distribution, rather than on the degree of obesity. More recently, great interest has also been dedicated to ectopic fat deposition in overnourished individuals that reflects a failure of the system of intracellular lipid homeostasis, which, in normal conditions, prevents lipotoxicity in the organs, by confining lipid overload to cells specifically designed to store large quantities of surplus calories, the white adipocytes. Consequently, excess body weight leads to fat infiltration of multiple organs including liver, pancreas, skeletal muscle, and heart thus forming "ectopic fat". Although overfeeding is considered the main predictor of ectopic fat deposition, other factors may be also involved. The purpose of this review is to evaluate the current available data on the predictors of ectopic fat deposition in humans.

In vitro and in vivo effects of IGF-I on adiposity in HIV-associated metabolic disease: a pilot study

BACKGROUND AND AIMS

We tested the effects of recombinant insulin-like growth factor-I (IGF-I) in an adipocyte model of HIV lipodystrophy and in an open label study on body composition and metabolism in patients with HIV lipodystrophy.

METHODS

The effects of IGF-I on ritonavir-induced adipocyte cell death were studied in vitro. We assessed lipid accumulation, IGF signaling, apoptosis, and gene expression. We conducted a 24-week open label trial of recombinant IGF-I in ten adults with HIV associated lipoatrophy. Laboratory assessments included glucose, insulin, lipids, and IGF-I. At weeks 0 and 24, body composition studies were performed including skinfold measurement, dual-energy x-ray absorptiometry, and computed tomography of the abdomen and thigh.

RESULTS

In vitro, ritonavir increased delipidation and apoptosis of adipocytes, whereas co-treatment with IGF-I attenuated the effect. In the clinical study, subcutaneous adipose tissue did not increase in patients after treatment with IGF-I; however, there was a decrease in the proportion of abdominal fat (39.8 ± 7% vs. 34.6 ± 7%, p = 0.007). IGF-I levels increased with treatment (143 ± 28 μg/L at week 0 vs. 453 ± 212 μg/L at week 24, p = 0.002), whereas IGFBP-3 levels declined (3.554 ± 1.146 mg/L vs. 3.235 ± 1.151 mg/L, p = 0.02). Insulin at week 12 decreased significantly (90.1 ± 39.8 pmol/L vs. 33.2 ± 19.6 pmol/L, p = 0.002). There was a nonsignificant decrease in visceral adipose tissue (155.2 ± 68 cm² at week 0 vs. 140.6 ± 70 cm² at week 24, p = 0.08).

CONCLUSIONS

Use of recombinant IGF-I may lower fasting insulin and abdominal fat in patients with lipoatrophy associated with HIV infection. Further evaluation of this agent for treatment of HIV-associated lipodystrophy may be warranted.

Nutrition and the HIV-associated lipodystrophy syndrome

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

Benefits of leptin therapy in HIV patients

Leptin therapy in human recombinant form has recently been used in HIV-associated lipodystrophy syndrome on experimental basis in some small short-term clinical trials. It has shown its beneficial effects only in hypoleptinemic HIV-infected patients by causing definite improvement in their insulin sensitivity, glucose tolerance, lipid status, and truncal obesity. Leptin prevents lipotoxicity and activates insulin signaling pathways through several postulated mechanisms. Central leptin insufficiency with peripheral hyperleptinemia has come out to be a significant contributor to the development of obesity and metabolic syndrome. In this article, we will review the basis of leptin therapy in HIV patients, with its promises. However, further larger clinical trials are needed to prove its long-term efficacy in the control of metabolic complications related to HIV therapy.

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.

Associations between HIV and human pathways revealed by protein-protein interactions and correlated gene expression profiles

Background

AIDS is one of the most devastating diseases in human history. Decades of studies have revealed host factors required for HIV infection, indicating that HIV exploits host processes for its own purposes. HIV infection leads to AIDS as well as various comorbidities. The associations between HIV and human pathways and diseases may reveal non-obvious relationships between HIV and non-HIV-defining diseases.

Principal Findings

Human biological pathways were evaluated and statistically compared against the presence of HIV host factor related genes. All of the obtained scores comparing HIV targeted genes and biological pathways were ranked. Different rank results based on overlapping genes, recovered virus-host interactions, co-expressed genes, and common interactions in human protein-protein interaction networks were obtained. Correlations between rankings suggested that these measures yielded diverse rankings. Rank combination of these ranks led to a final ranking of HIV-associated pathways, which revealed that HIV is associated with immune cell-related pathways and several cancer-related pathways. The proposed method is also applicable to the evaluation of associations between other pathogens and human pathways and diseases.

Conclusions

Our results suggest that HIV infection shares common molecular mechanisms with certain signaling pathways and cancers. Interference in apoptosis pathways and the long-term suppression of immune system functions by HIV infection might contribute to tumorigenesis. Relationships between HIV infection and human pathways of disease may aid in the identification of common drug targets for viral infections and other diseases.

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

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

Adipose tissue biology and HIV-infection

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

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.

Pathogenesis and treatment of HIV lipohypertrophy

PURPOSE OF REVIEW

This review addresses our current understanding of the pathogenesis of HIV-associated lipohypertrophy and describes an evidence-based approach to treatment.

RECENT FINDINGS

Although the pathogenesis of HIV-associated lipohypertrophy remains elusive, recent clinical and laboratory investigations in fatty acid metabolism and growth hormone dynamics have furthered our understanding of the condition. These findings have also paved the way for new therapeutic interventions, of which tesamorelin, an analog of growth hormone-releasing hormone (GHRH), has gained recognition as a promising treatment strategy against visceral fat accumulation. Recent randomized placebo-controlled trials of tesamorelin demonstrated significant reductions in visceral adipose tissue, improvement in lipid parameters, and minimal adverse effects on glucose tolerance. Optimal therapeutic dosing and treatment duration, though, are not yet known. Whether treatment with GHRH-analogs will translate into improved long-term metabolic and cardiovascular outcomes also remains to be seen.

SUMMARY

Although the pathogenesis of HIV lipohypertrophy remains unclear, several theories and observations have led to the development of treatment strategies to counter fat accumulation and its accompanying metabolic complications. Based on clinical trials, analogs of the growth hormone (GH)/GHRH axis appear to be most effective in reducing visceral adipose tissue.

Species-specific strategies underlying conserved functions of metabolic transcription factors

The winged helix protein FOXA2 and the nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) are highly conserved, regionally expressed transcription factors (TFs) that regulate networks of genes controlling complex metabolic functions. Cistrome analysis for Foxa2 in mouse liver and PPARγ in mouse adipocytes has previously produced consensus-binding sites that are nearly identical to those used by the corresponding TFs in human cells. We report here that, despite the conservation of the canonical binding motif, the great majority of binding regions for FOXA2 in human liver and for PPARγ in human adipocytes are not in the orthologous locations corresponding to the mouse genome, and vice versa. Of note, TF binding can be absent in one species despite sequence conservation, including motifs that do support binding in the other species, demonstrating a major limitation of in silico binding site prediction. Whereas only approximately 10% of binding sites are conserved, gene-centric analysis reveals that about 50% of genes with nearby TF occupancy are shared across species for both hepatic FOXA2 and adipocyte PPARγ. Remarkably, for both TFs, many of the shared genes function in tissue-specific metabolic pathways, whereas species-unique genes fail to show enrichment for these pathways. Nonetheless, the species-unique genes, like the shared genes, showed the expected transcriptional regulation by the TFs in loss-of-function experiments. Thus, species-specific strategies underlie the biological functions of metabolic TFs that are highly conserved across mammalian species. Analysis of factor binding in multiple species may be necessary to distinguish apparent species-unique noise and reveal functionally relevant information.

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

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

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

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

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.

HIV-protease inhibitors suppress skeletal muscle fatty acid oxidation by reducing CD36 and CPT1 fatty acid transporters

Infection with human immunodeficiency virus (HIV) and treatment with HIV-protease inhibitor (PI)-based highly active antiretroviral therapies (HAART) is associated with dysregulated fatty acid and lipid metabolism. Enhanced lipolysis, increased circulating fatty acid levels, and hepatic and intramuscular lipid accumulation appear to contribute to insulin resistance in HIV-infected people treated with PI-based HAART. However, it is unclear whether currently prescribed HIV-PIs directly alter skeletal muscle fatty acid transport, oxidation, and storage. We find that ritonavir (r, 5micromol/l) plus 20micromol/l of atazanavir (ATV), lopinavir (LPV), or darunavir (DRV) reduce palmitate oxidation(16-21%) in differentiated C2C12 myotubes. Palmitate oxidation was increased following exposure to high fatty acid media but this effect was blunted when myotubes were pre-exposed to the HIV-PIs. However, LPV/r and DRV/r, but not ATV/r suppressed palmitate uptake into myotubes. We found no effect of the HIV-PIs on FATP1, FATP4, or FABPpm but both CD36/FAT and carnitine palmitoyltransferase 1 (CPT1) were reduced by all three regimens though ATV/r caused only a small decrease in CPT1, relative to LPV/r or DRV/r. In contrast, sterol regulatory element binding protein-1 was increased by all 3 HIV-PIs. These findings suggest that HIV-PIs suppress fatty acid oxidation in murine skeletal muscle cells and that this may be related to decreases in cytosolic- and mitochondrial-associated fatty acid transporters. HIV-PIs may also directly impair fatty acid handling and partitioning in skeletal muscle, and this may contribute to the cluster of metabolic complications that occur in people living with HIV.

Adipocyte extracellular matrix composition, dynamics and role in obesity

The central role of the adipose tissue in lipid metabolism places specific demands on the cell structure of adipocytes. The protein composition and dynamics of the extracellular matrix (ECM) is of crucial importance for the functioning of those cells. Adipogenesis is a bi-phasic process in which the ECM develops from a fibrillar to a laminar structure as cells move from the commitment phase to the growth phase characterized by storage of vast amounts of triglycerides. Mature adipocytes appear to spend a lot of energy on the maintenance of the ECM. ECM remodeling is mediated by a balanced complement of constructive and destructive enzymes together with their enhancers and inhibitors. ECM remodeling is an energy costing process regulated by insulin, by the energy metabolism, and by mechanical forces. In the obese, overgrowth of adipocytes may lead to instability of the ECM, possibly mediated by hypoxia.

Endoplasmic reticulum stress-induced apoptosis in the development of diabetes: is there a role for adipose tissue and liver?

Diabetes mellitus (DM) is a multifactorial chronic metabolic disease characterized by hyperglycaemia. Several different mechanisms have been implicated in the development of the disease, including endoplasmic reticulum (ER) stress. ER stress is increasingly acknowledged as an important mechanism in the development of DM, not only for β-cell loss but also for insulin resistance. Accumulating evidence suggests that ER stress-induced apoptosis may be an important mode of β-cell loss and therefore important in the development of diabetes. Recent data also suggest a role of ER stress-induced apoptosis in liver and adipose tissue in relation to diabetes, but more extensive studies on human adipocyte and hepatocyte (patho)physiology and ER stress are needed to identify the exact interactions between environmental signals, ER stress and apoptosis in these organs.

HIV protease inhibitors and insulin resistance: lessons from in-vitro, rodent and healthy human volunteer models

PURPOSE OF REVIEW

Although the use of HIV protease inhibitors is linked to the development of insulin resistance and other metabolic changes that greatly increase the risk for cardiovascular disease, the molecular mechanisms responsible remain incompletely understood. This review summarizes recent advances that have been made in understanding the relative contributions of individual protease inhibitors to both acute and chronic insulin resistance together with newly identified cellular mediators.

RECENT FINDINGS

Individual protease inhibitors, alone and in combination, have differing propensities to induce insulin resistance, reflecting relative differences in both affinities for identified molecular targets and pharmacokinetic profiles. Several of the most recent protease inhibitors approved for clinical use or in development appear to be less likely to induce insulin resistance. In addition to direct effects on glucose transporter-4 activity, induction of oxidative stress, proteosome inhibition, alteration of adipokine levels, and changes in suppressors of cytokine signaling-1 have been implicated.

SUMMARY

A better understanding of the propensity of individual HIV protease inhibitors to produce insulin resistance will allow the tailoring of individual treatment plans based upon overall risk for diabetes. The elucidation of the molecular mechanisms for alterations in glucose homeostasis will facilitate the development of newer generations of HIV protease inhibitors that maintain their clinical efficacy without contributing to the development of diabetes mellitus and other proatherogenic effects.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Serum retinol-binding protein 4 correlates with obesity, insulin resistance, and dyslipidemia in HIV-infected subjects receiving highly active antiretroviral therapy

Highly active antiretroviral therapy (HAART) contributes to the development of metabolic complications including dyslipidemia, insulin resistance (IR), and lipodystrophy (LD). Recent studies reported that retinol-binding protein 4 (RBP4) is associated with IR, dyslipidemia, and obesity in non-HIV-infected populations. The aim of this study was to evaluate the associations between RBP4 and LD or metabolic abnormalities in HIV-infected subjects receiving HAART. We performed a cross-sectional study with 113 HIV-infected subjects receiving HAART for more than 6 months. Body composition and abdominal fat were measured by bioelectrical impedance analysis and ultrasonography, and fasting serum RBP4 was measured by enzyme-linked immunosorbent assay. Retinol-binding protein 4 levels in subjects with LD were similar to those without LD (P = .839). Retinol-binding protein 4 had significantly positive correlations with waist circumference (r = 0.298, P = .002), waist-to-hip ratio (r = 0.336, P = .001), body mass index (r = 0.310, P = .002), total body fat mass (r = 0.323, P = .001), total cholesterol (r = 0.188, P = .048), log (triglyceride) (r = 0.269, P = .004), and log (homeostasis model assessment of IR) (r = 0.207, P = .036), and negative correlations with quantitative insulin sensitivity check index (r = -0.209, P = .034) after adjustment for age and sex. In stepwise multivariate linear regression analysis, waist-to-hip ratio was the most significant independent predictor of increased RBP4 (standardized beta = .351, P = .001). These results suggest that serum RBP4 is associated with obesity, IR, and dyslipidemia in HIV-infected subjects receiving HAART.

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.

Protease inhibitors used in the treatment of HIV+ induce beta-cell apoptosis via the mitochondrial pathway and compromise insulin secretion

Inclusion of HIV protease inhibitors (PIs) in the treatment of people living with HIV+ has markedly decreased mortality but also increased the incidence of metabolic abnormalities, causes of which are not well understood. Here, we report that insulinopenia is exacerbated when Zucker fa/fa rats are exposed to a PI for 7 wk, suggesting that chronic PI exposure adversely affects pancreatic islet beta-cell function. In support of this possibility, we find increased apoptosis, as reflected by TUNEL fluorescence analyses, and reduced insulin-secretory capacity in insulinoma cells and human pancreatic islet cells after in vitro exposures (48-96 h) to clinically relevant PIs (ritonavir, lopinavir, atazanavir, or tipranavir). Furthermore, pancreatic islets isolated from rats administered an HIV-PI for 3 wk exhibit greater cell death than islets isolated from vehicle-administered rats. The higher incidence of HIV-PI-induced cell death was associated with cleavage and, hence, activation of caspase-3 and poly(ADP)-ribose polymerase but not with activation of phospho-pancreatic endoplasmic reticulum (ER) kinase or induction of ER stress apoptotic factor C/EBP homologous protein. Exposure to the HIV-PIs, however, led to activation of mitochondria-associated caspase-9, caused a loss in mitochondrial membrane potential, and promoted the release of cytochrome c, suggesting that HIV-PIs currently in clinically use can induce beta-cell apoptosis by activating the mitochondrial apoptotic pathway. These findings therefore highlight the importance of considering beta-cell viability and function when assessing loss of glycemic control and the course of development of diabetes in HIV+ subjects receiving a protease inhibitor.

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.

Effects of boosted tipranavir and lopinavir on body composition, insulin sensitivity and adipocytokines in antiretroviral-naive adults

OBJECTIVES

Thymidine-based nucleoside analogue reverse transcriptase inhibitors and some protease inhibitors of HIV are associated with lipoatrophy, relative central fat accumulation and insulin resistance. The latter associations have not been well evaluated prospectively in adults commencing antiretroviral therapy. We studied the effects of protease inhibitor-based antiretroviral regimens on body composition, insulin sensitivity and adipocytokine levels.

DESIGN

48-week substudy of a randomized, open-label, three-arm trial.

SETTING

Hospital and community HIV clinics.

PARTICIPANTS

140 HIV-infected adults naive to antiretroviral therapy.

INTERVENTION

Tipranavir/ritonavir [500/200 mg twice a day (TPV/r200)] or [500/100 mg twice a day (TPV/r100)] or lopinavir/ritonavir [400/100 mg twice a day (LPV/r)], each with tenofovir + lamivudine.

MAIN OUTCOME MEASURES

Body composition [dual-energy x-ray absorptiometry for limb fat; L4, abdominal computed tomography for visceral adipose tissue (VAT)]; and fasting metabolic parameters. The primary analysis was change in limb fat mass in each TPV/r group vs. LPV/r.

RESULTS

Limb fat increased in all three groups: LPV/r (1.17 kg) versus TPV/r200 (0.83 kg; P = 0.16) and TPV/r100 (0.41 kg; P = 0.07). VAT decreased in all groups: LPV/r (-3 cm) vs. TPV/r200 (-9 cm; P = 0.04) and TPV/r100 (-6 cm; P = 0.40). No significant change in insulin sensitivity was observed, including by oral glucose tolerance testing. The increase in leptin levels was significantly correlated with the increase in limb fat mass (r = 0.67; P < 0.0001). Despite increased limb fat, adiponectin levels increased, but significantly more with TPV/r200 (+6010 ng/ml; P < 0.0001) or TPV/r100 (+4497 ng/ml; P = 0.002) when compared with LPV/r (+1360 ng/ml).

CONCLUSION

Unlike many other antiretroviral regimens, TPV/r or LPV/r with tenofovir-lamivudine increased subcutaneous fat without evidence for increasing visceral fat or insulin resistance over 48 weeks.

Effects of ritonavir on adipocyte gene expression: evidence for a stress-related response

To understand the molecular mechanisms underlying the development of dyslipidemia and lipodystrophy that occurs after administration of aspartic acid protease inhibitors, we examined transcriptional profiles using cDNA microarrays in 3T3-L1 adipocytes exposed to 10 micromol/l ritonavir for 2-21 days. The expression levels of approximately 12,000 transcripts were assessed using the MgU74Av2 mouse microarray chip. Ritonavir altered gene expression of inflammatory cytokines, stress response genes localized to endoplasmic reticulum, oxidative stress genes, apoptosis-related genes, and expression of genes involved in cell adhesion and extracellular matrix remodeling. Microarray analysis also identified a novel gene downregulated by ritonavir, Cidea, whose expression levels may affect free-fatty acid metabolism. These changes suggest a unique, stress-related pattern in adipocytes induced by chronic exposure to the protease inhibitor, ritonavir.

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

BACKGROUND

Treatment of HIV with some protease inhibitors has been associated with dyslipidemia, insulin resistance and fat redistribution. It has been hypothesized that some protease inhibitors may alter the differentiation of subcutaneous and visceral adipocytes in a disparate manner. The aim of this study was to investigate whether isolated human preadipocytes display regio-specific sensitivity to the effects of ritonavir and atazanavir by examining differentiation, as well as adipokine secretion, following a 10-day drug exposure.

METHODS

Paired subcutaneous and omental human preadipocytes (n = 8) were induced to differentiate for 6 days, before being exposed to atazanavir or ritonavir (1-10 micromol/l) for 10 days. Lipid metabolism was assessed by Oil Red O staining and glycerol 3-phosphate dehydrogenase enzyme activity, whereas leptin and adiponectin secretion were assessed by enzyme-linked immunosorbent assay.

RESULTS

There was no difference in differentiation between subcutaneous and omental adipocytes. Repeated exposure to ritonavir, but not to atazanavir, led to significant reductions in adipocyte differentiation. There were no differences in adiponectin secretion for any of the atazanavir treatments in both subcutaneous and omental adipocytes, whereas significant reductions were evident at 10 mumol/l for ritonavir exposed subcutaneous adipocytes. In contrast, both atazanavir and ritonavir were associated with altered leptin secretion.

CONCLUSIONS

Ritonavir, but not atazanavir exposure, can inhibit differentiation of subcutaneous and omental adipocytes to a similar extent. Regio-specific differences, however, were apparent for adiponectin and leptin secretion. The role of region-specific alterations in adipokine secretion and apoptosis in the pathogenesis of HIV-lipodystrophy requires further attention.

HIV-associated lipodystrophy: a review of underlying mechanisms and therapeutic options

Lipodystrophy (LD) is a common adverse effect of HIV treatment with highly active antiretroviral therapy, which comprises morphological and metabolic changes. The underlying mechanisms for LD are thought to be due to mitochondrial toxicity and insulin resistance, which results from derangements in levels of adipose tissue-derived proteins (adipocytokines) that are actively involved in energy homeostasis. Several management strategies for combating this syndrome are available, but they all have limitations. They include: switching from thymidine analogues to tenofovir or abacavir in lipoatrophy, or switching from protease inhibitors associated with hyperlipidaemia to a protease-sparing option; injection into the face with either biodegradable fillers such as poly-L-lactic acid and hyaluronic acid (a temporary measure requiring re-treatment) or permanent fillers such as bio-alcamid (with the risk of foreign body reaction or granuloma formation); and structured treatment interruption with the risk of loss of virological control and disease progression. There is therefore a need to explore alternative therapeutic options. Some new approaches including adipocytokines, uridine supplementation, glitazones, growth hormone (or growth hormone-releasing hormone analogues), metformin and statins (used alone or in combination) merit further investigation.