How much fat loss is needed for lipoatrophy to become clinically evident?

Adipose Tissue Dysfunction and Energy Balance Paradigms in People Living With HIV

Over the past 4 decades, the clinical care of people living with HIV (PLWH) evolved from treatment of acute opportunistic infections to the management of chronic, noncommunicable comorbidities. Concurrently, our understanding of adipose tissue function matured to acknowledge its important endocrine contributions to energy balance. PLWH experience changes in the mass and composition of adipose tissue depots before and after initiating antiretroviral therapy, including regional loss (lipoatrophy), gain (lipohypertrophy), or mixed lipodystrophy. These conditions may coexist with generalized obesity in PLWH and reflect disturbances of energy balance regulation caused by HIV persistence and antiretroviral therapy drugs. Adipocyte hypertrophy characterizes visceral and subcutaneous adipose tissue depot expansion, as well as ectopic lipid deposition that occurs diffusely in the liver, skeletal muscle, and heart. PLWH with excess visceral adipose tissue exhibit adipokine dysregulation coupled with increased insulin resistance, heightening their risk for cardiovascular disease above that of the HIV-negative population. However, conventional therapies are ineffective for the management of cardiometabolic risk in this patient population. Although the knowledge of complex cardiometabolic comorbidities in PLWH continues to expand, significant knowledge gaps remain. Ongoing studies aimed at understanding interorgan communication and energy balance provide insights into metabolic observations in PLWH and reveal potential therapeutic targets. Our review focuses on current knowledge and recent advances in HIV-associated adipose tissue dysfunction, highlights emerging adipokine paradigms, and describes critical mechanistic and clinical insights.

HIV and antiretroviral therapy-related fat alterations

Early in the HIV epidemic, lipodystrophy, characterized by subcutaneous fat loss (lipoatrophy), with or without central fat accumulation (lipohypertrophy), was recognized as a frequent condition among people living with HIV (PLWH) receiving combination antiretroviral therapy. The subsequent identification of thymidine analogue nucleoside reverse transcriptase inhibitors as the cause of lipoatrophy led to the development of newer antiretroviral agents; however, studies have demonstrated continued abnormalities in fat and/or lipid storage in PLWH treated with newer drugs (including integrase inhibitor-based regimens), with fat gain due to restoration to health in antiretroviral therapy-naive PLWH, which is compounded by the rising rates of obesity. The mechanisms of fat alterations in PLWH are complex, multifactorial and not fully understood, although they are known to result in part from the direct effects of HIV proteins and antiretroviral agents on adipocyte health, genetic factors, increased microbial translocation, changes in the adaptive immune milieu after infection, increased tissue inflammation and accelerated fibrosis. Management includes classical lifestyle alterations with a role for pharmacological therapies and surgery in some patients. Continued fat alterations in PLWH will have an important effect on lifespan, healthspan and quality of life as patients age worldwide, highlighting the need to investigate the critical uncertainties regarding pathophysiology, risk factors and management.

Differential relationships of hepatic and epicardial fat to body composition in HIV

HIV-infected patients commonly experience changes in central and peripheral fat content as well as ectopic fat accumulation. However, whether hepatic and epicardial fat stores relate differentially to body composition or how these associations are modified by HIV status has not been well explored. A previously recruited sample of 124 HIV-infected patients and 58 healthy controls had undergone dual energy X-ray absorptiometry (DEXA) and computed tomography (CT) from which body composition measures, liver-spleen ratio, and epicardial fat volume were obtained. Unique to the HIV-infected group, there was a parabolic association between abdominal subcutaneous adipose tissue (SAT) area and liver-spleen ratio (P = 0.03, inflection point 324 cm²) such that hepatic fat content was greatest at the extremes of low and high SAT A quadratic model also closely described the relationship between mean leg fat and liver-spleen ratio among patients with HIV (P = 0.02, inflection point 4.7 kg), again suggesting greater liver fat content with both low and high leg fat. Notably, an analogous relationship of epicardial fat with SAT was not evident among HIV-infected individuals or healthy controls. In contrast, visceral adipose tissue (VAT) linearly related to both liver-spleen ratio in HIV and epicardial fat volume irrespective of HIV status in multivariable models. In conclusion, our analyses implicate both low and high SAT as risk factors for hepatic fat accumulation in HIV These findings add to growing evidence of SAT dysfunction in the setting of HIV infection, and highlight key physiologic differences between hepatic and epicardial fat depots.

Body Composition Changes After Initiation of Raltegravir or Protease Inhibitors: ACTG A5260s

BACKGROUND

Fat gain after antiretroviral therapy (ART) occurs, and its association with protease inhibitors (PIs) is unclear.

METHODS

Peripheral and central fat depots and lean mass were measured using standardized and centrally read abdominal CT scans and whole-body dual-energy absorptiometry scans over a 96-week period in human immunodeficiency virus (HIV)-infected treatment-naive participants. The patients were randomized to tenofovir-emtricitabine (TDF/FTC) plus atazanavir-ritonavir (ATV/r), darunavir-ritonavir (DRV/r), or raltegravir (RAL) in ACTG A5260s, a substudy of A5257. Within arm changes were assessed with signed-rank tests. The 96-week percentage changes in fat and lean mass in the 2 PI arms were not different, thus the PI arms were combined and compared to the RAL arm. Associations between baseline biomarkers and changes in body composition were assessed. All analyses used linear regression models.

RESULTS

328 patients were randomized (90% male, 44% white non-Hispanic). The median age was 36 years, HIV-1 RNA 4.6 log10 copies/mL, and CD4 349 cells/μL. Overall, at week 96, increases in limb fat (13.4%), subcutaneous (19.9%) and visceral abdominal fat (25.8%), trunk fat (18%), and lean mass (1.8%) were apparent (P < .001 for changes within each arm). Changes for all fat and lean outcomes were not different between the PI arms or between the RAL and the combined PI arms. Higher baseline HIV-1 RNA levels were associated with greater gains in peripheral and central fat.

CONCLUSIONS

In treatment-naive participants initiating ART with TDF/FTC, no differences in lean mass and regional fat were found with RAL when compared with ATV/r or DRV/r over 96 weeks.

CLINICAL TRIALS REGISTRATION

NCT00811954 and NCT00851799.

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.

Anthropometric differences between HIV-infected individuals prior to antiretroviral treatment and the general population from 1998-2007: the AIDS Clinical Trials Group Longitudinal Linked Randomized Trials (ALLRT) cohort and NHANES

OBJECTIVE

To assess differences in body circumferences and body mass index (BMI, kg/m(2)) between antiretroviral treatment (ART) naïve HIV-infected and HIV-uninfected persons.

METHODS

Waist, arm, and thigh circumferences and BMI were measured within the ALLRT and NHANES cohorts between 1998 and 2007. ALLRT is a prospective, longitudinal study of U.S. participants enrolled in randomized HIV treatment studies conducted by the AIDS Clinical Trials Group (ACTG). NHANES is a representative group of the US population. The cohorts were analyzed in two time periods, to account for trends towards increased adiposity. Anthropometrics were displayed in percentiles by age and sex. Multiple linear regression models examined differences between cohorts.

RESULTS

ALLRT had more males (82% versus 48%, p<0.0001), more black participants (32% versus 23%, p<0.0001), and less Hispanics (21% versus 30%, p<0.0001) than NHANES. Mean BMI was smaller in ALLRT males and females compared to NHANES by 1.6-2.4 kg/m(2) (p<0.0001). Mean waist and arm circumferences in both sexes and time periods were significantly smaller in ALLRT than in NHANES (p<0.0001). Mean thigh circumference in ALLRT was also smaller than NHANES among males (p<0.0001 in both time periods) and females (p = 0.01 in the early time period).

CONCLUSIONS

Differences in anthropometrics existed prior to ART initiation, in this large national cohort of HIV-infected individuals, compared to a representative HIV-uninfected cohort, indicating that HIV and its complications have important effects on body shape. Further longitudinal examination of anthropometrics in this HIV-infected cohort may provide additional insight into disease risk.

TRIAL REGISTRATION

NCT00001137 at www.clinicaltrials.gov.

Lipodystrophy in HIV patients: its challenges and management approaches

HIV-associated lipodystrophy is a term used to describe a constellation of body composition (lipoatrophy and lipohypertrophy) and metabolic (dyslipidemia and insulin resistance) alterations that accompany highly active antiretroviral therapy. These changes, which resemble metabolic syndrome, have been associated with a variety of adverse outcomes including accelerated cardiovascular disease. The body composition and metabolic changes appear to cluster in HIV infection, although they are distinct alterations and do not necessarily coexist. Epidemiological studies have demonstrated multiple pathogenic influences associated with host, disease, and treatment-related factors. The adverse treatment effects were more prominent in early regimens; continued drug development has led to the application of metabolically safer regimens with equal or greater potency than the regimens being replaced. Disease-related factors include HIV infection as well as inflammation, immune activation, and immune depletion. The body composition changes promote anxiety and depression in patients and may affect treatment adherence. Treatment of dyslipidemia and alterations in glucose metabolism is the same as in non-HIV-infected individuals. Lipoatrophy is managed by strategic choice of antivirals or by antiviral switching, and in some cases by plastic/reconstructive surgery. Lipohypertrophy has been managed mainly by lifestyle modification, ie, a hypocaloric diet and increased exercise. A growth hormone releasing factor, which reduces central fat, has recently become available for clinical use.

Peripheral and central fat changes in subjects randomized to abacavir-lamivudine or tenofovir-emtricitabine with atazanavir-ritonavir or efavirenz: ACTG Study A5224s

BACKGROUND

We compare the effect of 4 different antiretroviral regimens on limb and visceral fat.

METHODS

A5224s was a substudy of A5202, a trial of human immunodeficiency virus type 1 (HIV-1)-infected, treatment-naive subjects randomized to blinded abacavir-lamivudine (ABC-3TC) or tenofovir DF-emtricitabine (TDF-FTC) with open-label efavirenz (EFV) or atazanavir-ritonavir (ATV-r). The primary endpoint was the presence of lipoatrophy (≥ 10% loss of limb fat) at week 96 by intent-to-treat (ITT) analysis. Secondary endpoints included changes in limb and visceral fat. Statistical tests included linear regression, binomial, two-sample t test, and Fisher's exact test.

RESULTS

A5224s enrolled 269 subjects; 85% were male, and 47% were white non-Hispanic. The subjects had a median baseline HIV-1 RNA level of 4.6 log(10) copies/mL, a median age of 38 years, a median CD4+ cell count of 233 cells/μL, median limb fat of 7.4 kg, median visceral adipose tissue (VAT) of 84.1 cm(2), and VAT: total adipose tissue (TAT) ratio of 0.31. At week 96, estimated prevalence of lipoatrophy (upper 95% confidence interval [CI]) was 18% (25%) for ABC-3TC and 15% (22%) for TDF-FTC (P = .70); this was not significantly less than the hypothesized 15% for both (P ≥ .55 for both). The secondary as-treated (AT) analysis showed similar results. At week 96, the estimated mean percentage change from baseline in VAT was higher for the ATV-r group than for the EFV group (26.6% vs 12.4%; P = .090 in ITT analysis and 30.0% vs 14.5%; P = .10 in AT analysis); however, the percentage change in VAT:TAT was similar by ITT and AT analysis (P ≥ .60 for both). Results were similar for absolute changes in VAT and VAT:TAT.

CONCLUSIONS

ABC-3TC- and TDF-FTC-based regimens increased limb and visceral fat at week 96, with a similar prevalence of lipoatrophy. Compared to the EFV group, subjects assigned to ATV-r had a trend towards higher mean percentage increase in VAT.

CLINICAL TRIALS REGISTRATION

NCT00118898.

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.

From old to new nucleoside reverse transcriptase inhibitors: changes in body fat composition, metabolic parameters and mitochondrial toxicity after the switch from thymidine analogs to tenofovir or abacavir

INTRODUCTION

Thymidine analogs zidovudine (AZT) and stavudine (d4T) have been widely used because of their antiviral activity against HIV, but at the expense of high toxicity, mainly related to mitochondrial damage. Many studies have been performed replacing AZT or d4T with newer nucleoside analogs reverse transcriptase inhibitors (NRTIs) with less toxicity, such as tenofovir (TDF) or abacavir (ABC), maintaining virological efficacy.

AREAS COVERED

Relevant literature was identified using a PubMed search of articles published up to June 2010. Search terms included: 'thymidine analogs', 'stavudine', 'zidovudine', 'd4T', 'AZT', 'ZDV', 'treatment switch'. Original articles in which d4T or AZT had been replaced by TDF or ABC as switch strategies (with undetectable viral load) were reviewed where information about body fat distribution, mitochondrial functionality and/or plasma lipid parameters were available. Relevant references from these articles were also considered. Only studies performed in adult patients (18 years or older) are included. The readers will gain a better understanding of the toxicity caused by thymidine analogs, the treatment alternatives and the benefits observed after treatment switch to newer NRTIs.

EXPERT OPINION

Thymidine analogs AZT and d4T yield considerable toxicity and proactive switch to newer NRTIs such as TDF or ABC is necessary in order to avoid or partially reverse such side effects.

New and emerging agents in the management of lipodystrophy in HIV-infected patients

Lipodystrophy remains a major long-term complication in human immunodeficiency virus-infected patients under antiretroviral (ARV) therapy. Patients may present with lipoatrophy or lipohypertrophy or both. The choice of treatments to improve fat redistribution depends on the form of lipodystrophy and its duration. Measures known to improve lipoatrophy are switches in ARV therapy (stavudine or zidovudine to abacavir or tenofovir) and filling interventions. Pioglitazone may be added to these measures, although any benefits appear small. Uridine and leptin were found to be disappointing so far. Regarding lipohypertrophy, diet and exercise, recombinant human growth hormone, and metformin may reduce visceral fat, but may worsen subcutaneous lipoatrophy. Surgical therapy may be required. Attractive pharmacologic treatments include growth hormone-releasing factor and leptin. Adiponectin and adiponectin receptors are promising therapeutic targets to explore.

LIPODYSTROPHY SYNDROME IN HIV-INFECTED CHILDREN ON HAART

Lipodystrophy syndrome (LD) is common in HIV-infected children, particularly those taking didanosine, stavudine or zidovudine. Lipo-atrophy in particular causes major stigmatisation and interferes with adherence. In addition, LD may have significant long-term health consequences, particularly cardiovascular. Since the stigmatising fat distribution changes of LD are largely permanent, the focus of management remains on early detection and arresting progression. Practical guidelines for surveillance and avoidance of LD in routine clinical practice are presented. The diagnosis of LD is described and therapeutic options are reviewed. The most important therapeutic intervention is to switch the most likely offending antiretroviral to a non-LD-inducing agent as soon as LD is recognised. Typically, when lipoatrophy or lipohypertrophy is diagnosed the thymidine nucleoside reverse transcriptase inhibitor (NRTI) is switched to a non-thymidine agent such as abacavir (or tenofovir in adults). Where dyslipidaemia is predominant, a dietician review is helpful, and the clinician may consider switching to a protease inhibitor-sparing regimen or to atazanavir.

Subjective clinical lipoatrophy assessment correlates with DEXA-measured limb fat

OBJECTIVES

Although physician- and patient-rated diagnoses of lipoatrophy are currently used as a basis for inclusion into clinical trials, few studies have compared physician- or patient-rated lipoatrophy severity with objective measures. We aim to assess the validity of physician- and patient-rated diagnoses of lipoatrophy by evaluating the correlation between clinical assessments of lipoatrophy and objective fat indices.

METHODS

This cross-sectional study evaluated the association between clinical lipoatrophy scores and DEXA-measured limb fat (n = 154) and subcutaneous fat mitochondrial DNA (mtDNA) levels (n = 80) in HIV+ individuals.

RESULTS

There was a significant negative correlation between DEXA-measured limb fat and lipoatrophy scores generated by either the patients (r = -0.27, p = .008) or the physician (r = -0.48, p < .0001). Also, a significant positive correlation was found between the patient-generated lipoatrophy score and the physician score (r = 0.68, p < .0001). However, there was no correlation between fat mtDNA levels and DEXA-measured limb fat (r = -0.09, p = .42) or between physician- or patient-generated lipoatrophy scores (r = -0.09, p = .43, and r = 0.04, p = .71, respectively).

CONCLUSION

These results suggest that physician- and patient-rated lipoatrophy scores may be useful surrogates for more expensive measures of lipoatrophy, which could be reserved for research studies.

Approach to the human immunodeficiency virus-infected patient with lipodystrophy

Subcutaneous atrophy and central fat accumulation are common among HIV-infected patients receiving highly active antiretroviral therapy, and may be accompanied by dyslipidemia and insulin resistance. These fat changes, although commonly referred to together as lipodystrophy, are best considered as separate disorders, with distinct pathogeneses and treatment approaches. These morphological and metabolic abnormalities first appeared after introduction of protease inhibitors more than 10 yr ago, but research has demonstrated that their pathogenesis is multifactorial, with contributions from other antiretroviral medications, patient-related factors, and HIV itself. Switching to a less toxic highly active antiretroviral therapy regimen has shown partial effectiveness for the management of fat atrophy and lipid abnormalities. Lifestyle modification or surgical approaches are the treatment of choice for lipohypertrophy, although novel therapies targeting the GH axis show promise. HIV-related dyslipidemia may be difficult to treat, and can be complicated by drug-drug interactions between some lipid-lowering medications and antiretroviral medications. Treatment of diabetes in HIV-infected patients should generally follow established guidelines, but thiazolidinediones, rather than metformin, may be considered first-line treatment in a patient with lipoatrophy, given their potential to increase sc fat. The contribution of body fat changes and metabolic abnormalities to cardiovascular risk and the changing risk profiles of newer antiretroviral regimens are under intense investigation.