CT Fat Density Accurately Reflects Histologic Fat Quality in Adults With HIV On and Off Antiretroviral Therapy

Adolescent and young adult Hodgkin lymphoma patients at risk for subcutaneous fat gain during early cancer treatment: a brief report

Computed tomography scans were assessed for subcutaneous fat area and density at thoracic vertebra 4 in 65 adolescent and young adult (AYA) patients with Hodgkin lymphoma. Subcutaneous fat was quantified over 3 timepoints; (1) baseline, (2) end of initial anthracycline treatment (EOT) and (3) 1 year. Fat area increased at EOT (62.3 ± 5.4 cm/m2 vs 53.5 ± 5.0 cm/m2, p < 0.01) and 1 year (65.8 ± 5.6 cm/m2 vs 53.5 ± 5.0 cm/m2, p < 0.01) compared to baseline. Fat density significantly decreased at EOT (-91.2 ± 1.4 HU vs -86.5 ± 1.4 HU, p < 0.01) and at 1 year (-90.3 ± 1.6 HU vs -86.5 ± 1.4 HU, p = 0.01) compared to baseline. Female, radiation receiving, and anthracycline dosage >250mg/m2subgroups experienced significant fat gain (p < 0.05 for all). Female AYA Hodgkin lymphoma patients receiving radiation, and/or high-dose anthracyclines may be at higher risk of subcutaneous fat gain during therapy.

Epicardial fat density, coronary artery disease and inflammation in people living with HIV

Studies have shown an increased risk of coronary artery disease (CAD) in the human immunodeficiency virus (HIV) population. Epicardial fat (EF) quality may be linked to this increased risk. In our study, we evaluated the associations between EF density, a qualitative characteristic of fat, and inflammatory markers, cardiovascular risk factors, HIV-related parameters, and CAD. Our study was cross-sectional, nested in the Canadian HIV and Aging Cohort Study, a large prospective cohort that includes participants living with HIV (PLHIV) and healthy controls. Participants underwent cardiac computed tomography angiography to measure volume and density of EF, coronary artery calcium score, coronary plaque, and low attenuation plaque volume. Association between EF density, cardiovascular risk factors, HIV parameters, and CAD were evaluated using adjusted regression analysis. A total of 177 PLHIV and 83 healthy controls were included in this study. EF density was similar between the two groups (-77.4 ± 5.6 HU for PLHIV and -77.0 ± 5.6 HU for uninfected controls, P = .162). Multivariable models showed positive association between EF density and coronary calcium score (odds ratio, 1.07, P = .023). Among the soluble biomarkers measured in our study, adjusted analyses showed that IL2Rα, tumor necrosis factor alpha and luteizing hormone were significantly associated with EF density. Our study showed that an increase in EF density was associated with a higher coronary calcium score and with inflammatory markers in a population that includes PLHIV.

Role of epicardial adipose tissue in human atrial fibrillation

A recent meta-analysis among which four reports were conducted in Japan demonstrated that epicardial adipose tissue (EAT) is closely associated with an increased risk of atrial fibrillation (AF) recurrence after catheter ablation. We previously investigated the role of EAT in AF in humans. Left atrial (LA) appendage samples were obtained from AF patients during cardiovascular surgery. Histologically, the severity of fibrotic EAT remodeling was associated with LA myocardial fibrosis. Total collagen in the LA myocardium (i.e., LA myocardial fibrosis) was positively correlated with proinflammatory and profibrotic cytokines/chemokines, including interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α, in EAT. Human peri-LA EAT and abdominal subcutaneous adipose tissue (SAT) were obtained by autopsy. EAT- or SAT-derived conditioned medium was applied to the rat LA epicardial surface using an organo-culture system. EAT-conditioned medium induced atrial fibrosis in organo-cultured rat atrium. The profibrotic effect of EAT was greater than that of SAT. The fibrotic area of the organo-cultured rat atrium treated with EAT from patients with AF was greater than in patients without AF. Treatment with human recombinant angiopoietin-like protein 2 (Angptl2) induced fibrosis in organo-cultured rat atrium, which was suppressed by concomitant treatment with anti-Angptl2 antibody. Finally, we attempted to detect fibrotic EAT remodeling on computed tomography (CT) images, which demonstrated that the percent change in EAT fat attenuation was positively correlated with EAT fibrosis. Based on these findings, we conclude that the percent change in EAT fat attenuation determined using CT non-invasively detects EAT remodeling.

Ectopic Fat and Cardiac Health in People with HIV: Serious as a Heart Attack

PURPOSE OF REVIEW

This study aims to summarize knowledge of alterations in adipose tissue distribution among people with HIV (PWH), with a focus on the cardiac depot and how this relates to the known higher risk of cardiovascular disease in this unique population.

RECENT FINDINGS

Similar to the general population, cardiac fat depots mirror visceral adipose tissue in PWH. However, altered fat distribution, altered fat quality, and higher prevalence of enlarged epicardial adipose tissue depots are associated with increased coronary artery disease among PWH. Adipose tissue disturbances present in PWH ultimately contribute to increased risk of cardiovascular disease beyond traditional risk factors. Future research should aim to understand how regulating adipose tissue quantity and quality can modify cardiovascular risk.

Relationship of Subcutaneous Adipose Tissue Inflammation-Related Gene Expression With Ectopic Lipid Deposition in Persons With HIV

OBJECTIVE

Fat redistribution from subcutaneous adipose tissue (SAT) to the abdominal viscera, pericardium, liver, and skeletal muscle contributes to the rising burden of cardiometabolic disease among persons with HIV (PWH). Previous studies found SAT inflammation in PWH impairs lipid storage and persists despite plasma viral suppression on antiretroviral therapy (ART). In this study, we identified SAT immune-related genes associated with ectopic fat deposition in PWH on long-term ART.

DESIGN AND METHODS

A total of 92 PWH with well-controlled viremia underwent computed tomography imaging and abdominal SAT biopsy for gene expression analysis. SAT gene expression was measured using a NanoString panel of 255 immune-related genes. Associations between gene expression and computed tomography measurements of the volume and attenuation (radiodensity) of metabolically relevant ectopic fat depots were assessed using multivariable linear regression and network analysis.

RESULTS

Greater SAT volume was associated with higher visceral and pericardial adipose tissue volume, but lower skeletal muscle attenuation. Lower SAT attenuation, a measure of lipid content, was associated with lower visceral adipose tissue attenuation. Hierarchical clustering identified a subset of macrophage-related genes in SAT, including CCL2, CCL22, CCL13, CCR1, CD86, CD163, IL-6, IL-10, MRC1, and TREM2, which were associated with an increased lipid deposition in multiple ectopic depots.

CONCLUSION

Altered expression of macrophage-related genes in SAT is associated with differences in ectopic fat depot morphometrics among PWH on long-term ART, including in the pericardial and visceral compartments. These findings provide basis for future studies to assess host, virus, and treatment factors shaping the SAT immune environment and its effects on morphometric changes and metabolic comorbidities in PWH.

Visceral adipose tissue quality was associated with nonalcoholic fatty liver disease, independent of its quantity

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is a serious liver disease. Recent studies have shown that both visceral adipose tissue (VAT) quantity and density (as an indirect measure of quality) are associated with metabolic profiles. Therefore, we investigated the association between VAT quantity and quality, and the prevalence and incidence of NAFLD.

METHODS AND RESULTS

In this cross-sectional, retrospective cohort study, the prevalence and incidence of NAFLD were analyzed in 627 and 360 middle-aged subjects, respectively. VAT was evaluated using an unenhanced computed tomography scan, while NAFLD was evaluated using ultrasonography. The VAT area was normalized to the square value of the subjects' height in meters, the visceral fat area (VFA) index. The VAT density was described as the visceral fat density (VFD). The VFA index and VFD had an interaction effect on the prevalence of NAFLD (P = 0.0059). The VFA index (adjusted odds ratio [OR], 1.04; 95% confidence interval [CI], 1.01-1.07; P = 0.0145, per 1.0 cm²/m²) and the VFD (OR, 0.90; 95% CI, 0.84-0.96; P = 0.0026, per 1.0 Hounsfield unit [HU]) were independently associated with the prevalence of NAFLD. In our cohort, 36 subjects developed NAFLD. The VFD (adjusted hazards ratio [HR], 0.84; 95% CI, 0.77-0.91; P < 0.0001, per 1.0 HU) was independently associated with the incidence of NAFLD, whereas the VFA index was not.

CONCLUSION

Both the VFA index and VFD were independently associated with NAFLD prevalence. The VFD might be more related to the incidence of NAFLD than the VFA index.

Detection of fibrotic remodeling of epicardial adipose tissue in patients with atrial fibrillation: Imaging approach based on histological observation

Background

Fibrotic remodeling of epicardial adipose tissue (EAT) is crucial for proinflammatory atrial myocardial fibrosis, which leads to atrial fibrillation (AF).

Objectives

We tested the hypothesis that the ratio of central to marginal adipocyte diameter in EAT represents its fibrotic remodeling. Based on a similar concept, we also tested whether the percent (%) change in EAT fat attenuation determined using computed tomographic (CT) images can detect this remodeling.

Methods

Left atrial appendages were obtained from 76 consecutive AF patients during cardiovascular surgery. EAT in the central area (central EAT: C-EAT) and that adjacent to the atrial myocardium (Marginal EAT: M-EAT) were evaluated histologically. CT images for all of the 76 patients were also analyzed.

Results

The adipocyte diameter was smaller, fibrotic remodeling of EAT (EAT fibrosis) was more severe, and infiltration of macrophages and myofibroblasts was more extensive in M-EAT than in C-EAT. EAT fibrosis was positively correlated with adipocyte diameter in C-EAT and negatively correlated in M-EAT, resulting in a positive correlation between EAT fibrosis and the ratio of central to marginal adipocyte diameter (C/M diameter ratio; r = 0.73, P < .01). The C/M diameter ratio was greater in patients with persistent AF than in those with paroxysmal AF. CT images demonstrated that the %change in EAT fat attenuation was positively correlated with EAT fibrosis.

Conclusion

Our results suggest that the central-to-marginal adipocyte diameter ratio is tightly associated with fibrotic remodeling of EAT. In addition, the %change in EAT fat attenuation determined using CT imaging can detect remodeling noninvasively.

Tesamorelin improves fat quality independent of changes in fat quantity

OBJECTIVES

Fat quality and quantity may affect health similarly or differently. Fat quality can be assessed by measuring fat density on CT scan (greater density = smaller, higher quality adipocytes). We assessed the effects of tesamorelin, a growth hormone-releasing hormone analogue that reduces visceral fat (VAT) quantity in some people living with HIV (PWH), on fat density.

DESIGN

Participants from two completed, placebo-controlled, randomized trials of tesamorelin for central adiposity treatment in PWH were included if they had either a clinical response to tesamorelin (VAT decrease ≥8%, ≈70% of participants) or were placebo-treated.

METHODS

CT VAT and subcutaneous fat (SAT) density (Hounsfield Units, HU) were measured by a central blinded reader.

RESULTS

Participants (193 responders, 148 placebo) were 87% male and 83% white. Baseline characteristics were similar across arms, including VAT (-91 HU both arms, P = 0.80) and SAT density (-94 HU tesamorelin, -95 HU placebo, P = 0.29). Over 26 weeks, mean (SD) VAT and SAT density increased in tesamorelin-treated participants only [VAT: +6.2 (8.7) HU tesamorelin, +0.3 (4.2) HU placebo, P < 0.0001; SAT: +4.0 (8.7) HU tesamorelin, +0.3 (4.8) HU placebo, P < 0.0001]. The tesamorelin effects persisted after controlling for baseline VAT or SAT HU and area, and VAT [+2.3 HU, 95% confidence interval (4.5-7.3), P = 0.001) or SAT (+3.5 HU, 95% confidence interval (2.3-4.7), P < 0.001] area change.

CONCLUSION

In PWH with central adiposity who experienced VAT quantity reductions on tesamorelin, VAT and SAT density increased independent of changes in fat quantity, suggesting that tesamorelin also improves VAT and SAT quality in this group.

Hepatic Steatosis and Ectopic Fat Are Associated With Differences in Subcutaneous Adipose Tissue Gene Expression in People With HIV

Persons with human immunodeficiency virus (PWH) have subcutaneous adipose tissue (SAT) dysfunction related to antiretroviral therapy and direct viral effects, which may contribute to a higher risk of nonalcoholic fatty liver disease compared with human immunodeficiency virus-negative individuals. We assessed relationships between SAT expression of major adipocyte regulatory and lipid storage genes with hepatic and other ectopic lipid deposits in PWH. We enrolled 97 PWH on long-term antiretroviral therapy with suppressed plasma viremia and performed computed tomography measurements of liver attenuation, a measure of hepatic steatosis, skeletal muscle (SM) attenuation, and the volume of abdominal subcutaneous, visceral, and pericardial adipose tissue. Whole SAT gene expression was measured using the Nanostring platform, and relationships with computed tomography imaging and fasting lipids were assessed using multivariable linear regression and network mapping. The cohort had a mean age of 47 years, body mass index of 33.4 kg/m2, and CD4 count of 492 cells/mm3. Lower liver attenuation, a marker of greater steatosis, was associated with differences in SAT gene expression, including lower lipoprotein lipase and acyl-CoA dehydrogenase, and higher phospholipid transfer protein. Lower liver attenuation clustered with lower visceral adipose tissue (VAT) attenuation and greater VAT volume, pericardial fat volume and triglycerides, but no relationship was observed between liver attenuation and SAT volume, SM attenuation, or low-density lipoprotein. Conclusion: Liver attenuation was associated with altered SAT expression of genes regulating lipid metabolism and storage, suggesting that SAT dysfunction may contribute to nonalcoholic fatty liver disease in PWH. SAT gene-expression relationships were similar for VAT volume and attenuation, but not SM, indicating that ectopic lipid deposition may involve multiple pathways.

Antiretroviral Therapy Initiation Is Associated With Decreased Visceral and Subcutaneous Adipose Tissue Density in People Living With Human Immunodeficiency Virus

BACKGROUND

Adipose tissue (AT) alterations are common in people living with human immunodeficiency virus (PLWH). Decreases in AT density suggest disrupted adipocyte function/hypertrophy. We assessed changes in AT density after antiretroviral therapy (ART) initiation and associations with immunometabolic parameters.

METHODS

In a prospective randomized clinical trial of ART initiation, L4-L5 abdominal CT scans measured subcutaneous AT (SAT) and visceral AT (VAT) area and density in treatment-naive PLWH randomized to tenofovir-emtricitabine plus ritonavir-boosted atazanavir, ritonavir-boosted darunavir, or raltegravir. Linear regression models compared week 0 and week 96 levels, and 96-week changes, in SAT and VAT density (in Hounsfield units [HU]). Spearman correlations assessed relationships between AT density and immunometabolic parameters.

RESULTS

Of the 228 participants, 89% were male and 44% were white non-Hispanic. Median age was 36 years, baseline HIV-1 RNA was 4.6 log10 copies/mL, and CD4+ T-cell count was 344 cells/μL. Over 96 weeks, SAT and VAT HU decreased significantly in all arms. Less dense week 96 SAT and VAT density correlated with higher high-density lipoprotein (HDL) cholesterol and adiponectin (r = 0.19-0.30) levels and lower interleukin 6, non-HDL cholesterol, triglyceride, leptin, and homeostatic model assessment of insulin resistance (r = -0.23 to -0.68) levels at week 96 after adjusting for baseline CD4+ T-cell count, HIV-1 RNA, and baseline AT area.

CONCLUSIONS

Following virologic suppression, lower SAT and VAT density was associated with greater plasma measures of systemic inflammation, lipid disturbances, and insulin resistance independent of AT area, suggesting that changes in AT density with ART may lead to adverse health outcomes independent of AT quantity.

CLINICAL TRIALS REGISTRATION

NCT00851799.

Obesity and Weight Gain in Persons with HIV

PURPOSE OF REVIEW

The proportion of overweight and obese persons with HIV (PWH) has increased since the introduction of antiretroviral therapy (ART). We aim to summarize recent literature on risks of weight gain, discuss adipose tissue changes in HIV and obesity, and synthesize current understanding of how excess adiposity and HIV contribute to metabolic complications.

RECENT FINDINGS

Recent studies have implicated contemporary ART regimens, including use of integrase strand transfer inhibitors and tenofovir alafenamide, as a contributor to weight gain, though the mechanisms are unclear. Metabolic dysregulation is linked to ectopic fat and alterations in adipose immune cell populations that accompany HIV and obesity. These factors contribute to an increasing burden of metabolic diseases in the aging HIV population. Obesity compounds an increasing burden of metabolic disease among PWH, and understanding the role of fat partitioning and HIV- and ART-related adipose tissue dysfunction may guide prevention and treatment strategies.

Sex Differences in the Association of Fat and Inflammation Among People with Treated HIV Infection

INTRODUCTION

Ectopic fat deposition may contribute to chronic inflammation in people with HIV (PWH). To provide information for future mechanistic studies of metabolic risk in this population, we sought to determine which fat measures relate more strongly to inflammation and whether the fat-inflammation relationship is modified by sex or HIV status.

METHODS

We conducted a cross-sectional study of 105 PWH and 20 age- and sex-matched HIV-negative controls. Interleukin-6 (IL-6) and high-sensitivity C reactive protein (hs-CRP) levels were measured from plasma. Pericardial fat (PCF) and thoracic periaortic adipose tissue (TAT) volumes and peri-right coronary artery (RCA), left atrium (LA) roof, and liver densities were measured from cardiac CT scans. Unadjusted and multivariate adjusted linear regression models were used to determine the relationship between ectopic fat measures and inflammation biomarkers.

RESULTS

Forty participants had BMI < 25, 33 had BMI 25 to 30, and 52 had BMI > 30. Systolic blood pressure and insulin resistance increased with BMI. Participants with higher BMI had a higher CD4+ count. In models adjusted for demographics, HIV status, and metabolic risk factors, BMI was positively associated with IL-6 and hs-CRP. Ectopic PCF and TAT volumes were positively associated with IL-6 and hs-CRP; however, these relationships were somewhat attenuated in adjusted models. LA roof (but not peri-RCA) fat radiodensity was inversely associated with hs-CRP in fully adjusted models, and the association with IL-6 was borderline statistically signifi-cant (P = 0.054). IL-6 was more strongly associated with BMI and LA roof density in women than in men (P for interaction = 0.05).

CONCLUSIONS

Among PWH receiving antiretroviral therapy, higher BMI and excessive ectopic fat burden were associated with circulating markers of systemic inflammation. Because these measures appear to be more strongly related to inflammation among women than men, future clinical studies of metabolic risk and inflammation among PWH should include sex-stratified analyses.