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

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.

The induction of a nucleoplasmic reticulum by prelamin A accumulation requires CTP:phosphocholine cytidylyltransferase-α

Farnesylated prelamin A accumulates when the final endoproteolytic maturation of the protein fails to occur and causes a dysmorphic nuclear phenotype; however, the morphology and mechanisms of biogenesis of these changes remain unclear. We show here that acute prelamin A accumulation after reduction in the activity of the ZMPSTE24 endoprotease by short interfering RNA knockdown, results in the generation of a complex nucleoplasmic reticulum that depends for its formation on the enzyme CTP:phosphocholine-cytidylyltransferase-α (CCT-α, also known as choline-phosphate cytidylyltransferase A). This structure can form during interphase, confirming that it is independent of mitosis and therefore not a consequence of disordered nuclear envelope assembly. Serial-section dual-axis electron tomography reveals that these invaginations can take two forms: one in which the inner nuclear membrane infolds alone with an inter membrane space interior, and the other in which an invagination of both nuclear membranes occurs, enclosing a cytoplasmic core. Both types of invagination can co-exist in one nucleus and both are frequently studded with nuclear pore complexes (NPC), which reduces NPC abundance on the nuclear surface.

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

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

HIV and HAART-Associated Dyslipidemia

Effective highly active antiretroviral therapy (HAART) for human immunodeficiency virus-1 (HIV) infection has led to marked improvement in life-expectancy for those infected with HIV. Despite reductions in the incidence of AIDS with effective treatment, patients continue to experience considerable morbidity and mortality from non-AIDS illness such as premature cardiovascular disease, liver failure and renal failure. These morbidities, particularly premature cardiovascular disease, are thought to be related to a combination of the effects of an ageing HIV-infected population coupled with long-term effects of HIV infection and antiretroviral therapy (ART). One of the principle drivers behind the well documented increase in the risk of cardiovascular disease in HIV-infected patients is dyslipidemia.

This review will focus on the clinical presentation of HIV and ART-associated dyslipidemia, what is known of its patho-physiology, including associations with use of specific antiretroviral medications, and suggest screening and management strategies.

Balancing mitochondrial redox signaling: a key point in metabolic regulation

Mitochondrial reactive oxygen species (mROS) have emerged as signaling molecules in physiology primarily as a result of studies of uncoupling mechanisms in mitochondrial respiration. The discovery that this mechanism negatively regulates mROS generation in many cell types has drawn the attention of the scientific community to the pathological consequences of excess mROS production. From reports of the energetic fluxes in cells grown under normal conditions, the hypothesis that mROS are an integrated physiological signal of the metabolic status of the cell has emerged. Here, we consider recent studies that support this point of view in two key nutrient sensors of the body, beta cells and the hypothalamus, which are the main coordinators of endocrine and nervous controls of energy metabolism and adipose tissue, which is of paramount importance in controlling body weight and, therefore, the development of obesity and type 2 diabetes. In this context, finely balanced mROS production may be at the core of proper metabolic maintenance, and unbalanced mROS production, which is largely documented, might be an important trigger of metabolic disorders.

HIV protease inhibitors inhibit FACE1/ZMPSTE24: a mechanism for acquired lipodystrophy in patients on highly active antiretroviral therapy?

HIV-PIs (HIV protease inhibitors) have proved to be of great benefit for the millions of people suffering from AIDS. However, one of the side effects of this component of combined highly active antiretroviral therapy is lipodystrophy, which affects a large number of the patients taking this class of drug. It has been shown that many of these protease inhibitors inhibit the ZMPSTE24 enzyme responsible for removing the farnesylated tail of prelamin A, which is a nuclear lamina component that has been implicated in some of the nuclear laminopathies. Build up of this protein somehow leads to acquired lipodystrophy, possibly through its interaction with a transcription factor called SREBP-1 (sterol-regulatory-element-binding protein-1). The downstream effect of this is altered fatty acid metabolism and sterol synthesis, which may cause lipodystrophy in patients. The build-up of this protein also appears to have morphological consequences on the nucleus and we reveal, by dual-axis electron tomography, a complex nucleoplasmic reticulum that forms after HIV-PI treatment as a result of acute farnesylated prelamin A accumulation. A greater understanding of the molecular mechanisms leading to lipodystrophy will hopefully facilitate the design of improved HIV-PIs that do not cause this debilitating side effect.

Xenobiotic-metabolizing cytochromes p450 in human white adipose tissue: expression and induction

Lipophilic pollutants can accumulate in human white adipose tissue (WAT), and the consequences of this accumulation are still poorly understood. Cytochromes P450 (P450s) have recently been found in rat WAT and shown to be inducible through mechanisms similar to those in the liver. The aim of our study was to describe the cytochrome P450 pattern and their induction mechanisms in human WAT. Explants of subcutaneous and visceral WAT and primary culture of subcutaneous adipocytes were used as WAT models, and liver biopsies and primary culture of hepatocytes were used as liver models to characterize P450 expression in both tissues. The WAT and liver models were then treated with typical P450 inducers (rifampicin, phenobarbital, and 2,3,7,8-tetrachlorodibenzo-p-dioxin) and lipophilic pollutants (lindane, prochloraz, and chlorpyrifos), and the effects on P450 expression were studied. P450 expression was considerably lower in WAT than in the liver, except for CYP1B1 and CYP2U1, which were the most highly expressed adipose P450s in all individuals. 2,3,7,8-Tetrachlorodibenzo-p-dioxin and prochloraz induced CYP1A1 and CYP1B1 expression in both tissues. The aryl hydrocarbon receptor was also present in WAT. In contrast, neither phenobarbital nor rifampicin treatment induced CYP2 or CYP3 mRNA in WAT, and constitutive androstane receptor and pregnane X receptor were almost undetectable. These results suggest that the mechanisms by which P450s of family 1 are regulated in the liver are also functional in human WAT, but those regulating CYP2 and CYP3 expression are not.

Impact of stimulatory pathways on adipogenesis and HIV-therapy associated lipoatrophy

OBJECTIVE

Current understanding of adipogenesis derives mainly from studies with in vitro cell culture systems with divergent experimental requirements. We aimed to investigate the discrepancy between the anti-adipogenic effects of the HIV protease-inhibitor indinavir (IDV) in vitro and the lack of evidence that IDV inhibits adipogenesis in humans.

DESIGN AND METHODS

We studied cell viability and adipogenesis in murine 3T3-F442A, 3T3-L1 and primary human subcutaneous preadipocytes (phsPA). Differentiation was studied after activation of the established four signalling pathways in different combinations. We analyzed CCAAT/enhancer-binding protein (C/EBP) alpha and peroxisome proliferator-activated receptor (PPAR) gamma expression and triacylglyceride accumulation. Cells were exposed to IDV at concentrations around therapeutic C(max) levels and higher (10 muM and 20 muM) for up to 30 days.

RESULTS

Under insulin and fetal calf serum (FCS) input, IDV inhibited 3T3-F442A differentiation, an effect that was partially rescued by the addition of 3-isobutyl-1-methylxanthine (IBMX) stimulation. Combined stimulation with FCS, insulin, dexamethasone (DEX) and IBMX led to normal 3T3-L1 differentiation even in the presence of IDV. However, omission of IBMX rendered this cell line sensitive to IDV's anti-adipogenic effects. Differentiation of phsPA requiring complete adipogenic stimulation was not affected by IDV presence.

CONCLUSIONS

Our data suggest that the potency of IDV to impair differentiation under partial stimulation disappears when all of the differentiation pathways are activated. Such compensatory mechanisms might be responsible for the inability of the drug to affect adipogenesis in vivo.

Mitochondrial DNA depletion and respiratory chain activity in primary human subcutaneous adipocytes treated with nucleoside analogue reverse transcriptase inhibitors

Mitochondrial dysfunction as a consequence of mitochondrial DNA (mtDNA) depletion due to therapy with nucleoside analogue reverse transcriptase inhibitors (NRTI) has been proposed as a pathogenic mechanism leading to lipoatrophy in HIV-infected patients. The aim of our study was to investigate the impact of NRTI treatment on mtDNA abundance and the activities of respiratory chain complexes in primary human subcutaneous preadipocytes (phsPA). We studied adipocyte phenotypes, viability, and differentiation (CCAAT/enhancer-binding protein alpha [C/EBPalpha] and peroxisome proliferator-activated receptor gamma [PPARgamma] expression) and adiponectin production, mtDNA content, mitochondrial membrane potential, mitochondrial mass, and respiratory chain enzyme and citrate synthase activities in both proliferating and differentiating phsPA. Cells were exposed to zidovudine (6 microM), stavudine (d4T; 3 microM), and zalcitabine (ddC; 0.1 microM) for 8 weeks. NRTI-induced mtDNA depletion occurred in proliferating and differentiating phsPA after exposure to therapeutic drug concentrations of d4T and ddC. At these concentrations, ddC and d4T led to an almost 50% decrease in the number of mtDNA copies per cell without major impact on adipocyte differentiation. Despite mtDNA depletion by NRTI, the activities of the respiratory chain complexes, the mitochondrial membrane potential, and the mitochondrial mass were found to be unaffected. Severe NRTI-mediated mtDNA depletion in phsPA is not inevitably associated with impaired respiratory chain activity or altered mitochondrial membrane potential.

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.