Gene expression and immunohistochemistry in adipose tissue of HIV type 1-infected patients with nucleoside analogue reverse-transcriptase inhibitor-associated lipoatrophy

Genetic and cytometric analyses of subcutaneous adipose tissue in patients with hemophilia and HIV-associated lipodystrophy

Background

The authors recently performed plastic surgeries for a small number of patients with hemophilia, HIV infection, and morphologic evidence of lipodystrophy. Because the pathophysiological mechanism of HIV-associated lipodystrophy remains to be elucidated, we analyzed subcutaneous adipose tissues from the patients.

Methods

All six patients had previously been treated with older nucleoside analogue reverse-transcriptase inhibitors (NRTIs; stavudine, didanosine or zidovudine). Abdominal and inguinal subcutaneous fat samples were obtained from the HIV+ patients with hemophilia and HIV− healthy volunteers (n = 6 per group), and analyzed via DNA microarray, real-time PCR, flow cytometry and immunohistochemistry.

Results

The time from initial NRTI treatment to collecting samples were 21.7 years in average. Cytometric analysis revealed infiltration of inflammatory M1 macrophages into HIV-infected adipose tissue and depletion of adipose-derived stem cells, possibly due to exhaustion following sustained adipocyte death. Genetic analysis revealed that adipose tissue from HIV+ group had increased immune activation, mitochondrial toxicity, chronic inflammation, progressive fibrosis and adipocyte dysfunction (e.g. insulin resistance, inhibited adipocyte differentiation and accelerated apoptosis). Of note, both triglyceride synthesis and lipolysis were inhibited in adipose tissue from patients with HIV.

Conclusions

Our findings provide important insights into the pathogenesis of HIV-associated lipodystrophy, suggesting that fat redistribution may critically depend on adipocytes’ sensitivity to drug-induced mitochondrial toxicity, which may lead either to atrophy or metabolic complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12981-022-00432-9.

Associations between subcutaneous fat density and systemic inflammation differ by HIV serostatus and are independent of fat quantity

OBJECTIVES

Adipose tissue (AT) density measurement may provide information about AT quality among people living with HIV. We assessed AT density and evaluated relationships between AT density and immunometabolic biomarker concentrations in men with HIV.

DESIGN

Cross-sectional analysis of men enrolled in the Multicenter AIDS Cohort Study.

METHODS

Abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) density (Hounsfield units, HU; less negative = more dense) were quantified from computed tomography (CT) scans. Multivariate linear regression models described relationships between abdominal AT density and circulating biomarker concentrations.

RESULTS

HIV+ men had denser SAT (-95 vs -98 HU HIV-, P < 0.001), whereas VAT density was equivalent by HIV serostatus men (382 HIV-, 462 HIV+). Historical thymidine analog nucleoside reverse transcriptase inhibitor (tNRTI) use was associated with denser SAT but not VAT. In adjusted models, a 1 s.d. greater SAT or VAT density was associated with higher levels of adiponectin, leptin, HOMA-IR and triglyceride:HDL cholesterol ratio and lower hs-CRP concentrations in HIV- men. Conversely, in HIV+ men, each s.d. greater SAT density was not associated with metabolic parameter improvements and was significantly (P < 0.05) associated with higher systemic inflammation. Trends toward higher inflammatory biomarker concentrations per 1 s.d. greater VAT density were also observed among HIV+ men.

CONCLUSIONS

Among men living with HIV, greater SAT density was associated with greater systemic inflammation independent of SAT area. AT density measurement provides additional insight into AT density beyond measurement of AT quantity alone, and may have implications for metabolic disease risk.

Histological and Molecular Adipose Tissue Changes Are Related to Metabolic Syndrome Rather Than Lipodystrophy in Human Immunodeficiency Virus-Infected Patients: A Cross-Sectional Study

Background

In human immunodeficiency virus (HIV)-infected patients on combination antiretroviral therapy (cART), lipodystrophy shares many similarities with metabolic syndrome, but only metabolic syndrome has objective classification criteria. We examined adipose tissue changes related to lipodystrophy and metabolic syndrome to clarify whether it may be acceptable to focus diagnosis on metabolic syndrome rather than lipodystrophy.

Methods

This is a cross-sectional study of 60 HIV-infected men on cART and 15 healthy men. We evaluated lipodystrophy (clinical assessment) and metabolic syndrome (JIS-2009). We compared adipocyte size, leukocyte infiltration, and gene expression in abdominal subcutaneous adipose tissue biopsies of patients with and without lipodystrophy and with and without metabolic syndrome.

Results

Lipodystrophy was only associated with increased macrophage infiltration (P = .04) and adiponectin messenger ribonucleic acid ([mRNA] P = .008), whereas metabolic syndrome was associated with larger adipocytes (P < .0001), decreased expression of genes related to adipogenesis and adipocyte function (P values between <.0001 and .08), increased leptin mRNA (P = .04), and a trend towards increased expression of inflammatory genes (P values between .08 and .6).

Conclusions

Metabolic syndrome rather than lipodystrophy was associated with major unfavorable abdominal subcutaneous adipose tissue changes. In a clinical setting, it may be more relevant to focus on metabolic syndrome diagnosis in HIV-infected patients on cART with regards to adipose tissue dysfunction and risk of cardiometabolic complications.

HIV Persistence in Adipose Tissue Reservoirs

PURPOSE OF REVIEW

The purpose of this review is to examine the evidence describing adipose tissue as a reservoir for HIV-1 and how this often expansive anatomic compartment contributes to HIV persistence.

RECENT FINDINGS

Memory CD4 T cells and macrophages, the major host cells for HIV, accumulate in adipose tissue during HIV/SIV infection of humans and rhesus macaques. Whereas HIV and SIV proviral DNA is detectable in CD4 T cells of multiple fat depots in virtually all infected humans and monkeys examined, viral RNA is less frequently detected, and infected macrophages may be less prevalent in adipose tissue. However, based on viral outgrowth assays, adipose-resident CD4 T cells are latently infected with virus that is replication-competent and infectious. Additionally, adipocytes interact with CD4 T cells and macrophages to promote immune cell activation and inflammation which may be supportive for HIV persistence. Antiviral effector cells, such as CD8 T cells and NK/NKT cells, are abundant in adipose tissue during HIV/SIV infection and typically exceed CD4 T cells, whereas B cells are largely absent from adipose tissue of humans and monkeys. Additionally, CD8 T cells in adipose tissue of HIV patients are activated and have a late differentiated phenotype, with unique TCR clonotypes of less diversity relative to blood CD8 T cells. With respect to the distribution of antiretroviral drugs in adipose tissue, data is limited, but there may be class-specific penetration of fat depots. The trafficking of infected immune cells within adipose tissues is a common event during HIV/SIV infection of humans and monkeys, but the virus may be mostly transcriptionally dormant. Viral replication may occur less in adipose tissue compared to other major reservoirs, such as lymphoid tissue, but replication competence and infectiousness of adipose latent virus are comparable to other tissues. Due to the ubiquitous nature of adipose tissue, inflammatory interactions among adipocytes and CD4 T cells and macrophages, and selective distribution of antiretroviral drugs, the sequestration of infected immune cells within fat depots likely represents a major challenge for cure efforts.

Low expression of IL-18 and IL-18 receptor in human skeletal muscle is associated with systemic and intramuscular lipid metabolism-Role of HIV lipodystrophy

Introduction

Interleukin (IL)-18 is involved in regulation of lipid and glucose metabolism. Mice lacking whole-body IL-18 signalling are prone to develop weight gain and insulin resistance, a phenotype which is associated with impaired fat oxidation and ectopic skeletal muscle lipid deposition. IL-18 mRNA is expressed in human skeletal muscle but a role for IL-18 in muscle has not been identified. Patients with HIV-infection and lipodystrophy (LD) are characterized by lipid and glucose disturbances and increased levels of circulating IL-18. We hypothesized that skeletal muscle IL-18 and IL-18 receptor (R) expression would be altered in patients with HIV-lipodystrophy.

Design and methods

Twenty-three HIV-infected patients with LD and 15 age-matched healthy controls were included in a cross-sectional study. Biopsies from the vastus lateralis muscle were obtained and IL-18 and IL-18R mRNA expression were measured by real-time PCR and sphingolipids (ceramides, sphingosine, sphingosine-1-Phosphate, sphinganine) were measured by HPLC. Insulin resistance was assessed by HOMA and the insulin response during an OGTT.

Results

Patients with HIV-LD had a 60% and 54% lower level of muscular IL-18 and IL-18R mRNA expression, respectively, compared to age-matched healthy controls. Patients with HIV-LD had a trend towards increased levels of ceramide (18.3±4.7 versus 14.8±3.0,p = 0.06) and sphingosine (0.41±0.13 versus 0.32±0.07, and lower level of sphinganine (p = 0.06). Low levels of muscle IL-18 mRNA correlated to high levels of ceramides (r = -0.31, p = 0.038) and sphingosine-1P (r = -0.29, p = 0.046) in skeletal muscle, whereas such a correlation was not found in healthy controls. Low expression of IL-18 mRNA in skeletal muscle correlated to elevated concentration of circulating triglycerides (R_p = -0.73, p<0.0001). Neither muscle expression of IL-18 mRNA or ceramide correlated to parameters of insulin resistance.

Conclusion

IL-18 (mRNA) in skeletal muscle appears to be involved in the regulation of intramuscular lipid metabolism and hypertriglyceridemia.

High frequency of mitochondrial DNA mutations in HIV-infected treatment-experienced individuals

OBJECTIVES

We recently observed a decrease in deoxyribonucleotide (dNTP) pools in HIV-infected individuals on antiretroviral therapy (ART). Alterations in dNTPs result in mutations in mitochondrial DNA (mtDNA) in cell culture and animal models. Therefore, we investigated whether ART is associated with mitochondrial genome sequence variation in peripheral blood mononuclear cells (PBMCs) of HIV-infected treatment-experienced individuals.

METHODS

In this substudy of a case-control study, 71 participants were included: 22 'cases', who were HIV-infected treatment-experienced patients with mitochondrial toxicity, 25 HIV-infected treatment-experienced patients without mitochondrial toxicity, and 24 HIV-uninfected controls. Total DNA was extracted from PBMCs and purified polymerase chain reaction (PCR) products were subjected to third-generation sequencing using the PacBio Single Molecule Real-Time (SMRT) sequencing technology. The sequences were aligned against the revised Cambridge reference sequence for human mitochondrial DNA (NC_012920.1) for detection of variants.

RESULTS

We identified a total of 123 novel variants, 39 of them in the coding region. HIV-infected treatment-experienced patients with and without toxicity had significantly higher average numbers of mitochondrial variants per participant than HIV-uninfected controls. We observed a higher burden of mtDNA large-scale deletions in HIV-infected treatment-experienced patients with toxicity compared with HIV-uninfected controls (P = 0.02). The frequency of mtDNA molecules containing a common deletion (mt.δ4977) was higher in HIV-infected treatment-experienced patients with toxicity compared with HIV-uninfected controls (P = 0.06). There was no statistically significant difference in mtDNA variants between HIV-infected treatment-experienced patients with and without toxicity.

CONCLUSIONS

The frequency of mtDNA variants (mutations and large-scale deletions) was higher in HIV-infected treatment-experienced patients with or without ART-induced toxicity than in uninfected controls.

Analysis of Host Gene Expression Profile in HIV-1 and HIV-2 Infected T-Cells

HIV replication is closely regulated by a complex pathway of host factors, many of them being determinants of cell tropism and host susceptibility to HIV infection. These host factors are known to exert a positive or negative influence on the replication of the two major types of HIV, HIV-1 and HIV-2, thereby modulating virus infectivity, host response to infection and ultimately disease progression profiles characteristic of these two types. Understanding the differential regulation of host cellular factors in response to HIV-1 and HIV-2 infections will help us to understand the apparent differences in rates of disease progression and pathogenesis. This knowledge would aid in the discovery of new biomarkers that may serve as novel targets for therapy and diagnosis. The objective of this study was to determine the differential expression of host genes in response to HIV-1/HIV-2 infection. To achieve this, we analyzed the effects of HIV-1 (MN) and HIV-2 (ROD) infection on the expression of host factors in PBMC at the RNA level using the Agilent Whole Human Genome Oligo Microarray. Differentially expressed genes were identified and their biological functions determined. Host gene expression profiles were significantly changed. Gene expression profiling analysis identified a subset of differentially expressed genes in HIV-1 and HIV-2 infected cells. Genes involved in cellular metabolism, apoptosis, immune cell proliferation and activation, cytokines, chemokines, and transcription factors were differentially expressed in HIV-1 infected cells. Relatively few genes were differentially expressed in cells infected with HIV-2.

Improvement of lipoatrophy by switching from efavirenz to lopinavir/ritonavir

OBJECTIVE

To assess whether changes in antiretroviral drugs other than thymidine nucleoside reverse transcriptase inhibitors (NRTI) may have a body fat impact in HIV-infected patients with lipoatrophy.

METHODS

Ninety-six-week phase IV, open-label, multicentre, pilot randomized trial. HIV-infected patients with moderate/severe lipoatrophy at one or more body sites despite long-term thymidine NRTI-free therapy were randomized to continue their efavirenz (EFV)-based antiretroviral regimen or to switch from EFV to lopinavir/ritonavir (LPV/r). The primary endpoint was the absolute change in limb fat mass measured by dual X-ray absorptiometry from baseline to 96 weeks. Changes in other body fat measurements, subjective perception of lipoatrophy, subcutaneous fat gene expression and plasma lipids were also assessed.

RESULTS

Thirty-three patients (73% men, median age 52 years) were recruited. At 96 weeks, absolute limb fat mass increased in the LPV/r arm vs. the EFV arm (estimated difference +1082.1 g; 95% CI +63.7 to +2103.5; P = 0.04); this difference remained significant after adjustment by gender, age, fat mass, body mass index and CD4 cell count at baseline. Subjective lipoatrophy perception scores also improved in the LPV/r arm relative to the EFV arm. Adipogenesis, glucose and lipid metabolism, and mitochondrial gene expression increased in the LPV/r arm compared with the EFV arm at 96 weeks. HDL cholesterol decreased in the LPV/r arm relative to the EFV arm.

CONCLUSIONS

Switching from EFV to LPV/r in HIV-infected patients with lipoatrophy may offer further limb fat gain beyond thymidine NRTI discontinuation, although this strategy decreased plasma HDL cholesterol and caused changes in subcutaneous fat gene expression that may be associated with increased insulin resistance.

Differential subcutaneous adipose tissue gene expression patterns in a randomized clinical trial of efavirenz or lopinavir-ritonavir in antiretroviral-naive patients

Gene expression studies of subcutaneous adipose tissue may help to better understand the mechanisms behind body fat changes in HIV-infected patients who initiate antiretroviral therapy (ART). Here, we evaluated early changes in adipose tissue gene expression and their relationship to fat changes in ART-naive HIV-infected patients randomly assigned to initiate therapy with emtricitabine/tenofovir plus efavirenz (EFV) or ritonavir-boosted lopinavir (LPV/r). Patients had abdominal subcutaneous adipose tissue biopsies at baseline and week 16 and dual-energy-X-ray absorptiometry at baseline and weeks 16 and 48. mRNA changes of 11 genes involved in adipogenesis, lipid and glucose metabolism, mitochondrial energy, and inflammation were assessed through reverse transcription-quantitative PCR (RT-qPCR). Additionally, correlations between gene expression changes and fat changes were evaluated. Fat increased preferentially in the trunk with EFV and in the limbs with LPV/r (P < 0.05). After 16 weeks of exposure to the drug regimen, transcripts of CEBP/A, ADIPOQ, GLUT4, LPL, and COXIV were significantly down-regulated in the EFV arm compared to the LPV/r arm (P < 0.05). Significant correlations were observed between LPL expression change and trunk fat change at week 16 in both arms and between CEBP/A or COXIV change and trunk fat change at the same time point only in the EFV arm and not in the LPV/r arm. When combined with emtricitabine/tenofovir as standard backbone therapy, EFV and LPV/r induced differential early expression of genes involved in adipogenesis and energy metabolism. Moreover, these mRNA expression changes correlated with trunk fat change in the EFV arm. (This was a substudy of a randomized clinical trial [LIPOTAR study] registered at ClinicalTrials.gov under identifier NCT00759070.).

The development of simple anthropometric measures to diagnose antiretroviral therapy-associated lipodystrophy in resource limited settings

Background

Lipohypertrophy does not appear to be an adverse ART reaction while lipoatrophy is clearly associated with the use of stavudine (d4T) and zidovudine (AZT). In low and middle income countries d4T has only recently been phased out and AZT is still widely being used. Several case definitions have been developed to diagnose lipodystrophy, but none of them are generalizable to sub-Saharan Africa where black women have less visceral adipose tissue and more subcutaneous adipose tissue than white women. We aimed to develop a simple, objective measure to define lipoatrophy and lipohypertrophy by comparing patient report to anthropometric and dual-energy X-ray absorptiometry (DXA) -derived variables.

Methods

DXA and anthropometric measures were obtained in a cross sectional sample of black HIV-infected South African men (n = 116) and women (n = 434) on ART. Self-reported information on fat gain or fat loss was collected using a standard questionnaire. Receiver operating characteristic (ROC) curves were used to describe the performance of anthropometric and DXA-derived variables using patient reported lipoatrophy and lipohypertrophy as the reference standard.

Results

Lipoatrophy and lipohypertrophy were more common in women (25% and 33% respectively) than in men (10% and 13% respectively). There were insufficient numbers of men with DXA scans for meaningful analysis. The best predictors of lipoatrophy in women were the anthropometric variables tricep (AUC = 0.725) and thigh skinfold (AUC =0.720) thicknesses; and the DXA-derived variables percentage lower limb fat (AUC = 0.705) and percentage lower limb fat/height (AUC = 0.713). The best predictors of lipohypertrophy in women were the anthropometric variable waist/hip ratio (AUC = 0.645) and the DXA-derived variable percentage trunk fat/percentage limb fat (AUC = 0.647).

Conclusions

We were able to develop simple, anthropometric measures for defining lipoatrophy and lipohypertrophy, using a sample of black HIV-infected South African women with DXA scans. This is of particular relevance in resource limited settings, where health professionals need simple and inexpensive methods of diagnosing patients with lipoatrophy and lipohypertrophy.

An update on the pharmacological strategies in the treatment of HIV-1-associated adipose redistribution syndromes

INTRODUCTION

With the introduction of combination antiretroviral therapy (ART) for HIV infection in the mid-1990s, descriptions of morphological changes and metabolic disturbances in treated patients began to emerge. HIV-1/highly active ART-associated lipodystrophy syndrome (HALS) involves metabolic abnormalities and diverse forms of anomalous fat distribution. The current review focuses on the pathophysiological basis and the clinical evidence for the use of several medical strategies in the management of HALS.

AREAS COVERED

We have covered the most relevant studies related to the pharmacological strategies in the treatment of HALS, with attention to the current and novel antiretroviral agents.

EXPERT OPINION

The most commonly used strategies for HALS reversion have included modification of host-dependent factors, including those related to HIV-1 infection and those associated with ART. Preventive and medical strategies have been associated with moderate success. The only intervention that offers an immediate aesthetical improvement for patients with HALS so far has been plastic surgery.

The role of HIV and monocytes/macrophages in adipose tissue biology

OBJECTIVE

To assess the role of HIV and monocytes/macrophages in adipose tissue dysregulation.

METHODS

Cross-sectional study in 5 groups: HIV seronegative, HIV+ antiretroviral therapy (ART)-naive, HIV+ nonlipoatrophic on zidovudine- and/or stavudine-containing ART, HIV+ lipoatrophic on similar ART, and HIV+ on abacavir- or tenofovir-containing ART. HIV DNA in circulating monocyte subsets was quantitated by real-time polymerase chain reaction. Biopsied subcutaneous fat was examined for macrophage content by CD68 staining. Isolated adipocytes and macrophages were cultured and the supernatant assayed for secretory products by Luminex multiplex cytokine technology.

RESULTS

Sixty-nine subjects were enrolled. Lipoatrophic subjects had higher median HIV DNA levels (270.5 copies/10 cells) in circulating peripheral CD14CD16 co-expressing monocyte subsets compared with subjects who were ART-naive (25.0 copies), nonlipoatrophic (15.0 copies), or on abacavir/tenofovir (57.5 copies), P < 0.01. Group differences in adipocytes and adipose macrophage content were marginal. Although adipocyte secretory products were similar, HIV-infected subjects had higher adipose macrophage-derived interleukin (IL)-12p40, IL-6, IL-8, and monocyte inflammatory protein 1 alpha and lower eotaxin and interferon gamma levels than HIV seronegative subjects (P < 0.05). Within HIV-infected subjects, adipose macrophage secretory products were comparable between subjects naive with ART versus those on ART.

CONCLUSIONS

Circulating HIV-infected and proinflammatory CD14CD16 monocyte subsets contribute to the pathogenesis of HIV-associated lipoatrophy. Among HIV-infected individuals, macrophages, rather than adipocytes, are the primary source of low-grade inflammation in subcutaneous adipose tissue. HIV infection modifies these macrophages to a more proinflammatory phenotype, and these changes are not substantially mitigated by the use of ART.

Antiretroviral therapy-induced mitochondrial toxicity: potential mechanisms beyond polymerase-γ inhibition

We hypothesized that competition between nucleotide reverse-transcriptase inhibitor triphosphate and endogenous deoxyribonucleotide triphosphate (dNTP) may lead to depletion of dNTP pools and mitochondrial dysfunction independent of polymerase-γ (pol-γ) inhibition. We collected peripheral blood mononuclear cells from 75 adults (25 cases: HIV-infected patients with mitochondrial toxicity, 25 HIV-infected positive controls, and 25 HIV-negative controls). We observed statistically significant individual and group differences in ribonucleotide (RN) and deoxyribonucleotide (dRN) pools. The median values for the RN pools were 10,062 (interquartile range (IQR): 7,090-12,590), 4,360 (IQR: 3,058-6,838), and 2,968 (IQR: 2,538-4,436) pmol/10(6) cells for negative controls, positive controls, and cases, respectively. Cases had significantly higher absolute mitochondrial DNA copy number as compared with negative controls (P < 0.05). Moreover, cases had significantly higher expression levels of pol-γ, nucleotide transporters, cellular kinases, and adenosine triphosphate (ATP)-binding cassette (ABC) proteins as compared with controls. Antiretroviral therapy (ART) perturbs RN and dRN pools. Depletion of RN and dRN pools may be associated with ART-induced mitochondrial toxicity independent of pol-γ inhibition.

Differentially altered molecular signature of visceral adipose tissue in HIV-1-associated lipodystrophy

OBJECTIVE

Lipodystrophy in HIV-1-infected antiretroviral-treated patients is often associated with opposite alterations in adipose tissue depots as follows: lipoatrophy of subcutaneous adipose tissue (SAT) versus lipohypertrophy of visceral adipose tissue (VAT). We determined the specific molecular alterations in VAT relative to SAT in patients.

DESIGN

We analyzed the expression of marker genes of mitochondrial function, adipogenesis, and inflammation in a unique collection of 8 biopsies of omental VAT from HIV-1-infected antiretroviral-treated patients with lipodystrophy. For comparison, we analyzed SAT from 10 patients, and SAT and VAT from 10 noninfected individuals.

METHODS

Quantitative real-time polymerase chain reaction of mitochondrial DNA and gene transcripts; immunoblot and multiplex for quantification of specific proteins.

RESULTS

Similar mitochondrial DNA depletion and abnormal increases in mitochondrial protein levels were found in VAT and SAT from patients. Transcript levels of adipogenesis and metabolism marker genes were unaltered in VAT but were decreased in SAT. Tumor necrosis factor α and CD68 were similarly induced in both adipose depots from patients, but other markers of inflammation-related pathways showed distinct alterations as follows: interleukin 18 and interleukin 1 receptor antagonist were induced only in SAT, whereas interleukin 6, interleukin 8, and monocyte chemoattractant protein 1 expression was reduced in VAT but not in SAT.

CONCLUSIONS

Mitochondrial alterations are similar in VAT and SAT from patients, whereas adipogenic gene expression is decreased in SAT but unaltered in VAT, highlighting the relevance of adipogenic processes in the differential alterations of fat depots. Specific disturbances in inflammatory status in VAT relative to SAT are present. Milder induction of proinflammatory signaling in VAT could be involved in preventing fat wasting in this depot.

Exploring the pathophysiology behind the more common genetic and acquired lipodystrophies

Lipodystrophies are an immense group of genetic or acquired metabolic disorders that are characterized by varying degrees of body fat loss and in some instances localized accumulation of subcutaneous fat. Lipodystrophies are often tightly linked with profound metabolic complications; this strong bond emphasizes and reinforces the significance of adipose tissue as a dynamic endocrine organ. The extent of fat loss determines the severity of associated metabolic complications such as diabetes mellitus, hypertriglyceridemia and hepatic steatosis. The lipodystrophies can be divided into generalized, partial or local, depending on the degree and locality of the observable fat loss; moreover, the generalized and partial divisions can be partitioned further into inherited or acquired forms. The major genetic factors in the generalized forms of the lipodystrophies, particularly Congenital generalized lipodystrophy (CGL)-Berardinelli-Seip syndrome, are the AGPAT2, BSCL2, caveolin 1 (CAV1) and polymerase-I-and-transcriptrelease factor (PTRF) genes. In the acquired forms, genes such as LMNA, PPARG, CIDEC (cell-death-inducing DNA fragmentation factor a-like effector c) and PLIN1 are heavily involved in familial partial lipodystrophy (FPLD) type 2 (also known as the Dunnigan-Variety) and WRN along with RECQL5 in Werner Syndrome (WS). Autoimmune causes are particularly noted in acquired partial lipodystrophy (APL)-Barraquer-Simons syndrome and in AGL-Lawrence syndrome; panniculitis has been shown to have a substantial role in the former as well as in other forms of localized lipodystrophies. Patients with human immunodeficiency virus (HIV) exposed to protease inhibitors, nucleoside reverse transcriptase inhibitors (NRTIs) (for example, zidovudine and stavudine) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) (for example, efavirenz) while undergoing Highly Active Antiretroviral Therapy (HAART) have led to the current most-prevalent form of the lipodystrophies: lipodystrophy in HIV-infected patients (LD-HIV) and HAART-associated lipodystrophy syndrome (HALS).

HIV treatment and associated mitochondrial pathology: review of 25 years of in vitro, animal, and human studies

Antiretroviral therapy has dramatically reduced mortality in human immunodeficiency virus (HIV) infection. In 1988, the suggestion that the first antiretroviral drug, zidovudine, was the potential cause of muscle pathology in HIV-infected persons resulted in structural and biochemical patient studies demonstrating acquired mitochondrial dysfunction. Assessment of subsequent nucleoside analog reverse transcriptase inhibitor (NRTI) antiretroviral drugs has indicated that mitochondria are a common target of NRTI toxicity in multiple tissues, leading to a wide variety of pathology ranging from lipodystrophy to neuropathy. Overwhelmingly, these complications have emerged during post-licensing human studies. Subsequent animal and in vitro studies have then elucidated the potential pathological mechanisms, suggesting that NRTI-associated mitochondrial toxicity arises principally from inhibition of the sole mitochondrial DNA (mtDNA) polymerase gamma, leading to a reduction in mtDNA content (depletion). Millions of patients have been treated with mitochondrially toxic NRTIs and these drugs remain the backbone of antiretroviral rollout in much of sub-Saharan Africa. Here we describe the 25-year history of antiretroviral associated mitochondrial pathology and critically review the strength of evidence linking clinical, histopathological, and molecular data. We discuss recently described novel mechanisms of NRTI-associated mitochondrial damage and whether or not recently licensed NRTIs may be considered free from mitochondrial toxicity.

The immune cells in adipose tissue

Although the pathological role of the immune system in several metabolic disorders, including type 1 diabetes mellitus (T1DM) and Addison's disease, has long been recognized and studied, only in the last decade has it become apparent that the immune system plays a broad and more subtle role in local and systemic metabolism. It is now apparent that the immune system monitors and responds to specific metabolic cues in both pathologic and non-pathologic settings through a set of processes dubbed immunometabolism. Expansion of adipose tissue mass, activation of lipolysis, eating a high fat diet and even non-shivering thermogenesis all lead to the recruitment and activation of immune cells in key metabolic tissues. The responses are complex and not completely defined, and indeed, as is typical of rapidly evolving research areas, there are some conflicting reports, especially related to the metabolic consequences of manipulation of immune function. However, what is clear is the consensus that metabolic processes, especially obesity and obesity-related complications, activate both the innate and adaptive arms of the immune system. Canonical immune processes consist of discrete steps: surveillance, recognition, effector action and resolution. Over the last decade evidence for each part of the immune response has been found at the intersection of the immune system with metabolism. Although evidence for immune surveillance and modulation of metabolism has been found in the liver, muscle, hypothalamus and pancreas, immune cell function has been most intensively studied and best understood in adipose tissue where studies continue to provide insights into the intersection of the metabolic and immune systems. Here we review the modulation of immune cell populations in adipose tissue and discuss regulatory processes implicated in controlling the interface between metabolism and immunologic function.

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.

Polymorphisms in Fas gene is associated with HIV-related lipoatrophy in Thai patients

The present study aimed to evaluate the role of genetic polymorphisms in the emergence of lipoatrophy or lipodystrophy in HIV-infected patients with antiretroviral therapy (ART) in Thailand. Position 455 upstream of the Apolipoprotein C3 gene (ApoC3 T-455C, rs2854116), codon 64 of the Beta3 adrenergic receptor gene (ARβ3 Tcod64C, rs4994), and position 670 upstream of the Fas gene (Fas A-670G, rs1800682) were genotyped in 829 HIV-infected Thai patients who had started ART. Crude and adjusted incidence rate ratios (IRR) were calculated using Poisson regression. The serum levels of cholesterol, triglycerides, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were also analyzed. Multivariate analysis revealed an association between the Fas -670AA genotype, but not the ApoC3 -455 or ARβ3 cod64 genotypes, with the incidence of lipoatrophy after adjusting for gender and stavudine (d4T)-containing regimens (IRR=1.72, 95% CI=1.20-2.45, p=0.003). However, ApoC3 -455C homozygous patients showed elevated serum levels of triglycerides, while this genotype did not affect serum total cholesterol, HDL, or LDL levels in patients with lipoatrophy or lipodystrophy. In contrast, the ARβ3 cod64 genotype did not show any significant association with the serum levels of cholesterol, triglycerides, HDL, or LDL. In conclusion, Fas -670AA affected the incidence of lipoatrophy in HIV-1-infected Thai patients, while the ApoC3 -455C allele affected the serum levels of triglycerides. These results confirmed the role of genetics in the development of ART-related metabolic disorders.

Bitter melon seed oil-attenuated body fat accumulation in diet-induced obese mice is associated with cAMP-dependent protein kinase activation and cell death in white adipose tissue

The aim of this study was to investigate the antiadiposity effect of bitter melon seed oil (BMSO), which is rich in the cis-9, trans-11, trans-13 isomer of conjugated linolenic acid. In Expt. 1, C57BL/6J mice were fed a butter-based, high-fat diet [HB; 29% butter + 1% soybean oil (SBO)] for 10 wk to induce obesity. They then continued to receive that diet or were switched to an SBO-based, high-fat diet alone (HS; 30% SBO) or containing bitter melon seed oil (BMSO) (HBM; 15% SBO + 15% BMSO) for 5 wk. The body fat percentage was significantly lower in mice fed the HBM diet (21%), but not the HS diet, compared with mice fed the HB diet. In Expt. 2, mice were fed an SBO-based, high-fat diet containing 0 (HS), 5 (LBM), 10 (MBM), or 15% (HBM) BMSO for 10 wk. In the LBM, MBM, and HBM groups, the body fat percentage was significantly lower by 32, 35, and 65%, respectively, compared with the HS control. The reduction in the HBM group was significantly greater than that in the LBM or MBM group. BMSO administration increased phosphorylation of acetyl-CoA carboxylase, cAMP-activated protein kinase (PKA), and signal transducer and activator of transcription 3 in the white adipose tissue (WAT), suggesting that PKA and leptin signaling might be involved in the BMSO-mediated reduction in lipogenesis and increase in thermogenesis and lipolysis. However, compared with the HS control, the HBM group had a significantly higher TNFα concentration in the WAT accompanied by TUNEL-positive nuclei. We conclude that BMSO is effective in attenuating body fat accumulation through mechanisms associated with PKA activation and programmed cell death in the WAT, but safety concerns need to be carefully addressed.

HIV infection and antiretroviral therapy have divergent effects on mitochondria in adipose tissue

BACKGROUND

Although human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) affect mitochondrial DNA (mtDNA) content and function, comprehensive evaluations of their effects on mitochondria in muscle, adipose tissue, and blood cells are limited.

METHODS

Mitochondrial DNA quantification, mitochondrial genome sequencing, and gene expression analysis were performed on muscle, adipose tissue, and peripheral blood mononuclear cell (PBMC) samples from untreated HIV-positive patients, HIV-positive patients receiving nucleoside reverse transcriptase inhibitor (NRTI)-based ART, and HIV-negative controls.

RESULTS

The adipose tissue mtDNA/nuclear DNA (nDNA) ratio was increased in untreated HIV-infected patients (ratio, 353) and decreased in those receiving ART (ratio, 162) compared with controls (ratio, 255; P < .05 for both comparisons); the difference between the 2 HIV-infected groups was also significant (P = .002). In HIV-infected participants, mtDNA/nDNA in adipose tissue correlated with the level of activation (CD38+ /HLA-DR+) for CD4+ and CD8+ lymphocytes. No significant differences in mtDNA content were noted in muscle or PMBCs among groups. Exploratory DNA microarray analysis identified differential gene expression between patient groups, including a subset of adipose tissue genes.

CONCLUSIONS

HIV infection and ART have opposing effects on mtDNA content in adipose tissue; immune activation may mediate the effects of HIV, whereas NRTIs likely mediate the effects of ART.

Mitochondrial interference by anti-HIV drugs: mechanisms beyond Pol-γ inhibition

The combined pharmacological approach to the treatment of HIV infection, known as highly active antiretroviral therapy (HAART), has dramatically reduced AIDS-related morbidity and mortality. However, its use has been associated with serious adverse reactions, of which those resulting from mitochondrial dysfunction are particularly widespread. Nucleos(t)ide-reverse transcriptase inhibitors (NRTIs) have long been considered the main source of HAART-related mitochondrial toxicity due to their ability to inhibit Pol-γ, the DNA polymerase responsible for the synthesis of mitochondrial DNA. Nevertheless, accumulating evidence points to a more complex relationship between these organelles and NRTIs. Also, alternative pathways by which other groups of anti-HIV drugs (non-nucleoside reverse transcriptase inhibitors and protease inhibitors) interfere with mitochondria have been suggested, although their implications, both pharmacological and clinical, are open to debate. This review aims to provide a comprehensive overview of the mechanisms and factors which influence the mitochondrial involvement in the toxicity of all three major classes of anti-HIV drugs.

Proteomic profiling of adipose tissue from Zmpste24-/- mice, a model of lipodystrophy and premature aging, reveals major changes in mitochondrial function and vimentin processing

Lipodystrophy is a major disease involving severe alterations of adipose tissue distribution and metabolism. Mutations in genes encoding the nuclear envelope protein lamin A or its processing enzyme, the metalloproteinase Zmpste24, cause diverse human progeroid syndromes that are commonly characterized by a selective loss of adipose tissue. Similarly to humans, mice deficient in Zmpste24 accumulate prelamin A and display phenotypic features of accelerated aging, including lipodystrophy. Herein, we report the proteome and phosphoproteome of adipose tissue as well as serum metabolome in lipodystrophy by using Zmpste24(-/-) mice as experimental model. We show that Zmpste24 deficiency enhanced lipolysis, fatty acid biogenesis and β-oxidation as well as decreased fatty acid re-esterification, thus pointing to an increased partitioning of fatty acid toward β-oxidation and away from storage that likely underlies the observed size reduction of Zmpste24-null adipocytes. Besides the mitochondrial proteins related to lipid metabolism, other protein networks related to mitochondrial function, including those involved in tricarboxylic acid cycle and oxidative phosphorylation, were up-regulated in Zmpste24(-/-) mice. These results, together with the observation of an increased mitochondrial response to oxidative stress, support the relationship between defective prelamin A processing and mitochondrial dysfunction and highlight the relevance of oxidative damage in lipoatrophy and aging. We also show that absence of Zmpste24 profoundly alters the processing of the cytoskeletal protein vimentin and identify a novel protein dysregulated in lipodystrophy, High-Mobility Group Box-1 Protein. Finally, we found several lipid derivates with important roles in energy balance, such as Lysophosphatidylcholine or 2-arachidonoylglycerol, to be dysregulated in Zmpste24(-/-) serum. Together, our findings in Zmpste24(-/-) mice may be useful to unveil the mechanisms underlying adipose tissue dysfunction and its overall contribution to body homeostasis in progeria and other lipodystrophy syndromes as well as to develop novel strategies to prevent or ameliorate these diseases.

Comparison of dorsocervical with abdominal subcutaneous adipose tissue in patients with and without antiretroviral therapy-associated lipodystrophy

OBJECTIVE

Combination antiretroviral therapy (cART) is associated with lipodystrophy, i.e., loss of subcutaneous adipose tissue in the abdomen, limbs, and face and its accumulation intra-abdominally. No fat is lost dorsocervically and it can even accumulate in this region (buffalo hump). It is unknown how preserved dorsocervical fat differs from abdominal subcutaneous fat in HIV-1-infected cART-treated patients with (cART+LD+) and without (cART+LD-) lipodystrophy.

RESEARCH DESIGN AND METHODS

We used histology, microarray, PCR, and magnetic resonance imaging to compare dorsocervical and abdominal subcutaneous adipose tissue in cART+LD+ (n=21) and cART+LD- (n=11).

RESULTS

Albeit dorsocervical adipose tissue in cART+LD+ seems spared from lipoatrophy, its mitochondrial DNA (mtDNA; copies/cell) content was significantly lower (by 62%) than that of the corresponding tissue in cART+LD-. Expression of CD68 mRNA, a marker of macrophages, and numerous inflammatory genes in microarray were significantly lower in dorsocervical versus abdominal subcutaneous adipose tissue. Genes with the greatest difference in expression between the two depots were those involved in regulation of transcription and regionalization (homeobox genes), irrespective of lipodystrophy status. There was negligible mRNA expression of uncoupling protein 1, a gene characteristic of brown adipose tissue, in either depot.

CONCLUSIONS

Because mtDNA is depleted even in the nonatrophic dorsocervical adipose tissue, it is unlikely that the cause of lipoatrophy is loss of mtDNA. Dorsocervical adipose tissue is less inflamed than lipoatrophic adipose tissue. It does not resemble brown adipose tissue. The greatest difference in gene expression between dorsocervical and abdominal subcutaneous adipose tissue is in expression of homeobox genes.

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.

Disorders of fat partitioning in treated HIV-infection

HIV-associated lipodystrophy is clinically characterized by body fat changes including subcutaneous fat loss (lipoatrophy) with or without truncal fat accumulation (lipohypertrophy). Thymidine nucleoside reverse transcriptase inhibitors, stavudine and to a lesser extent zidovudine, are major contributors for lipoatrophy. Drug factors are not clear for lipohypertrophy. Restoration to health with effective viral suppression and weight gain may be factors playing significant roles in lipohypertrophy. Mitochondrial dysfunction and inflammation in subcutaneous adipose tissue are key factors in the pathogenesis of HIV-associated lipoatrophy. The pathogenesis of lipohypertrophy is less well understood. Switching from thymidine nucleoside reverse transcriptase inhibitors restores subcutaneous fat in patients with HIV-associated lipoatrophy, but improvement is slow and limited. Surgical filling cosmetically improves facial lipoatrophy. Exercise and diet may reduce increased visceral adipose tissue. Liposuction may be useful to remove superficial, localized fat accumuli.

Lipodystrophy: pathophysiology and advances in treatment

Lipodystrophy is a medical condition characterized by complete or partial loss of adipose tissue. Not infrequently, lipodystrophy occurs in combination with pathological accumulation of adipose tissue at distinct anatomical sites. Patients with lipodystrophy exhibit numerous metabolic complications, which indicate the importance of adipose tissue as an active endocrine organ. Not only the total amount but also the appropriate distribution of adipose tissue depots contribute to the metabolic state. Genetic and molecular research has improved our understanding of the mechanisms underlying lipodystrophy. Circulating levels of hormones secreted by the adipose tissue, such as leptin and adiponectin, are greatly reduced in distinct subpopulations of patients with lipodystrophy. This finding rationalizes the use of these adipokines or of agents that increase their circulating levels, such as peroxisome proliferator-activated receptor γ (PPARγ) agonists, for therapeutic purposes. Other novel therapeutic approaches, including the use of growth hormone and growth-hormone-releasing factors, are also being studied as potential additions to the therapeutic armamentarium. New insights gained from research and clinical trials could potentially revolutionize the management of this difficult-to-treat condition.

Apoptosis: a clinically useful measure of antiretroviral drug toxicity?

Antiretroviral therapy (ART) has improved life expectancy with HIV infection, but long-term toxicities associated with these medications are now a major global disease burden. There is a clear need to develop useful methods for monitoring patients on antiretroviral drugs for early signs of toxicity. Assays with predictive utility -- allowing therapy to be changed before serious end organ damage occurs -- would be ideal. Attempts to develop biochemical methods of monitoring ART toxicity have concentrated on the mitochondrial toxicity of nucleoside analogue reverse transcriptase inhibitors and have not generally lead to assays with widespread clinical applications. For example, plasma lactate and peripheral blood measurements of mitochondrial DNA associate with exposure to potentially toxic nucleoside analogue reverse transcriptase inhibitors but have not reliably predicted clinical toxicity. Better assays are needed, including markers of toxicity from additional drug classes. Apoptosis may be a potential marker of ART toxicity. Increased apoptosis has been demonstrated both in vitro and in vivo in association with various antiretroviral drug classes and a range of clinical toxicities. However, quantifying apoptosis on biopsy specimens of tissue (such as adipose tissue) is impractical for patient monitoring. Novel assays have been described that can quantify apoptosis using minute tissue samples and initial results from clinical samples suggest peripheral blood may have utility in predicting ART toxicities. The limitations and potential of such techniques for monitoring patients for drug side effects will be discussed.