Abstract
Objective:
Persons living with HIV (PLWH) well-treated on antiretroviral therapies remain at risk for ensuing arterial disease. We investigated the relationship between adipose depots and biomarkers of arterial injury and inflammation to gain insight into the link between body composition and CVD risk.
Designs/Methods:
155 HIV-infected and 70 non-HIV-infected individuals were well-phenotyped for body composition. Adipose depots were assessed via single-slice abdominal CT. Circulating markers of arterial disease and generalized inflammation [lipoprotein-associated phospholipase A2 (LpPLA2), oxidized LDL (oxLDL), high sensitivity cardiac troponin T (hs-cTnT), high sensitivity C reactive protein (hsCRP)] were evaluated.
Results:
Despite similar BMI and visceral adipose tissue (VAT), HIV-infected individuals had significantly lower subcutaneous adipose tissue (SAT, 199[126,288] vs. 239[148,358]cm2, P=.04) compared to non-HIV-infected individuals. Among HIV-infected individuals, reduced SAT inversely correlated with LpPLA2 (ρ=−0.19, P=.02) and hs-cTnT (ρ=−0.24, P=.004), whereas increased VAT significantly and positively related to LpPLA2 (ρ=0.25, P=.003), oxLDL (ρ=0.28, P=.0005), hs-cTnT (ρ=0.28, P=.0007), and hsCRP (ρ=0.32, P=<.0001). Similar analyses among the non-HIV-infected individuals revealed significant relationships between SAT and LpPLA2 (ρ=−0.24, P=.05), as well as VAT and LpPLA2 (ρ=0.37, P=.002), oxLDL (ρ=0.24, P=.05), and hsCRP (ρ=0.29, P=.02). In modeling performed among the HIV group, simultaneously controlling for VAT, SAT, age, and relevant HIV-related parameters, reduced SAT was an independent predictor of LpPLA2 (P=.04) and hs-cTnT (P=.005) and increased VAT was an independent predictor of LpPLA2 (P=.001), oxLDL (P=.02), hs-cTnT (P=.04), and hsCRP (P=.04)
Conclusion:
Fat redistribution phenotypes, characterized by SAT loss and/or VAT accumulation, may be linked to arterial injury and inflammation in HIV.
Keywords: HIV, subcutaneous adipose tissue, visceral adipose tissue, arterial inflammation, LpPLA2, hs-cTnT, oxLDL
Introduction
Persons living with HIV (PLWH) well-treated on antiretroviral therapies (ART) remain at increased risk for arterial disease, including atherosclerotic plaque formation[1–4], as compared to persons living without HIV (PLWOH). Inflammation plays an integral role in the underlying pathogenesis for atherosclerotic disease, as circulating monocytes adhere to the vascular endothelium and differentiate into macrophages within the intima. LDL particles are engulfed by these macrophages potentiating the formation of lipid-laden foam cells, which are the nidus of atheroma progression. Even in the setting of good virologic control and contemporary ART use, PLWH demonstrate chronic immune activation and systemic inflammation[2, 5, 6], which has critical implications for cardiovascular risk[7].
Circulating markers of inflammation have been identified to be useful in risk stratification of cardiovascular disease (CVD) and arterial disease. Lipoprotein-associated phospholipase A2 (LpPLA2) may be a useful marker of arterial inflammation as it is recognized to be released from rupture-prone arterial plaque[8–10]. LpPLA2 functions to oxidize phospholipids found on LDL particles within the arterial intima. Oxidation of LDL more readily occurs in a pro-inflammatory milieu and is an important mechanism of plaque formation. Subclinical arterial plaque deposition may have further consequences, inciting myocardial injury, which can be assessed by high sensitivity cardiac troponin T (hs-cTnT). Indices of arterial inflammation and subclinical atherosclerosis are increased in HIV[8, 11], and the systemic mechanisms which may contribute to increased CVD risk in this population remain unclear.
Among PLWH, adipose dysfunction remains prevalent, whether related to antiretroviral therapies or the virus itself [12] or the aging process. In this regard, unfavorable changes in fat redistribution, including visceral adipose tissue (VAT) accumulation and subcutaneous adipose tissue (SAT) loss, demonstrated among PLWH have been linked to adipose dysfunction and may contribute to a highly inflamed phenotype with broader immunomodulatory effects. In the context of fat redistribution and adipose dysfunction, localized inflammation within the adipose depot could potentially contribute to systemic inflammation through paracrine activity. In the current study, we investigated for the first time the relationship between body composition, specifically related to the visceral and subcutaneous depots, and specific biomarkers of arterial injury and inflammation to gain insight into the potential link between adiposity and CVD risk in HIV. We hypothesized that markers of arterial disease and generalized inflammation would be increased in relation to VAT accumulation and SAT loss, a metabolic phenotype and pattern of fat redistribution associated with pronounced inflammation in the HIV population.
Methods
Study Participants
155 HIV-infected and 70 non-HIV-infected individuals were previously recruited between 2006–2011. HIV-infected individuals were recruited from HIV medical clinics and community health centers and through newspaper advertisements in the Boston area. Non-HIV-infected individuals were similarly recruited from the identical communities using the same advertisements. Individuals were included in the HIV group if there was a known history of HIV for >5 years. No changes to ART regimens were allowed within the past 3 months. Data on ART use was collected by self-report. Aside from HIV serostatus and ART use, inclusion and exclusion criteria were similar for both groups. Individuals were between 18–60 years of age with a body mass index (BMI) between 20–35 kg/m2 and had no known cardiac disease. Active use of anti-inflammatory medications was not permitted. Individuals were excluded for any acute infectious illness. All participants provided informed consent to participate. This study was approved by the institutional review board of Massachusetts General Hospital. Data relevant to coronary artery disease have been previously reported in this cohort [1, 2, 11, 13], whereas data on body composition and arterial injury and inflammation are the focus of the current study.
Evaluation of Body Composition
The waist to hip ratio was assessed by dividing the iliac waist circumference by the circumference at the broadest part of the hip. To assess abdominal VAT and SAT area, a cross-sectional computed tomography (CT) scan at the level of the L4 pedicle was performed. Scan parameters for each image were standardized (144 table height, 80 kV, 70 mA, 2 seconds, 10mm slice thickness, 48cm FOV). Fat attenuation coefficients were set at −50 to −250 HU. Following image acquisition, an offline analysis of tracings was performed utilizing commercial software (Vitrak, Merge e/Film) to quantitate abdominal VAT and SAT area.
Circulating Markers of Arterial Disease and Generalized Inflammation
During the study, samples were collected and stored frozen at −80oC. Markers were assessed after the completion of the study. LpPLA2 was measured using activity assay reagents (Diadexus, South San Francisco, CA) on a Vista Dimension 1500 system (Siemens Healthcare Diagnostics, Glasgow, DE). LpPLA2 assay specifics include a measurement range 10 nmol/min/mL to 400 nmol/min/mL and inter-assay coefficients of variation (CVs) 1.7% to 3.2% at values between 97 nmol/min/mL and 304 nmol/min/mL. Hs-cTnT was evaluated via the Cobas e601 instrument system (Roche Diagnostics, Indianapolis, IN). Hs-cTnT assay specifics include a measurement range 3.0 ng/L to 10,000 ng/L and inter-assay CVs 3.6% to 2.3% at values between 28 ng/L and 4962 ng/L. For values below the limit of detection for the hs-cTnT assay, imputed values just below the limit of detection were used for purposes of data analysis (i.e. hs-cTnT 2.99 ng/L). Oxidized LDL (oxLDL) was measured by ELISA as per manufacturer instructions (Mercodia, Uppsala, Sweden). Assay specifics for oxLDL include a measurement range of 8 to 150 U/L and inter-assay CVs ranged from 8.3% to 7.4% at values between 8.5 U/L and 32 U/L. High sensitivity C-reactive protein (hsCRP) was assessed using ELISA (LabCorp).
HIV-specific Parameters
HIV viral load was determined by ultrasensitive RT PCR (Roche COBAS Amplicor) (lower limit of detection, 50 copies/mL). For values below the limit of detection, imputed values just below the limit of detection were used for purposes of data analysis (i.e. viral load 49 copies/mL). CD4 and CD8 T cell counts were assessed by flow cytometry.
Statistical Analysis
Normality of distribution was assessed using the Shapiro-Wilks test. Data are presented as mean ± standard deviation if normally distributed or median [IQR] if not normally distributed. Categorical variables are reported as proportions. Between group comparisons (HIV vs. non-HIV) were made using the Student’s t-test for normally distributed variables or Wilcoxon Rank Sums test for non-normally distributed variables. Spearman’s correlation coefficient was used to perform linear regression to relate body composition to markers of arterial injury and inflammation by HIV status. Multivariate regression was performed among the HIV group to assess independent effects of HIV-related parameters and adipose depots on markers of arterial injury and inflammation. VAT and SAT were chosen as independent variables of body composition for the model given the significance of these measures in the univariate modeling and to address the aim of this investigation to assess the contribution of specific adipose depots. Given the importance of viral effects and the aging process to adipose dysregulation and redistribution as well as chronic inflammation and vascular disease, HIV-related variables, including duration of HIV, duration of ART use, CD4+ nadir count, viral load and age, were entered into the model to determine the whether the adipose depots were independently linked to markers of arterial injury and inflammation. In order to perform an ROC analysis, we transformed dependent variables (markers of arterial injury and inflammation) into dichotomous variables using accepted cutoffs or the median value when clinical cutoffs were not available: LpPLA2>200.0 nmol/min/mL (high risk), oxLDL> 43.9 (median value), hs-cTnT>3.00 ng/L (limit of detection), hsCRP>3.0 mg/L (high risk). Statistical significance was defined as P<0.05. All analyses were performed using SAS JMP (version 12.0).
Results
Demographics and Clinical Characteristics
HIV-infected and non-HIV-infected individuals were of similar age (47±7 vs. 46±7 years), race (53 vs. 51% Caucasian) and sex (61 vs. 59% male), respectively (all P>.05). The HIV group demonstrated a history of infection for 14±6 years, a duration of ART use for 8±5 years and good immunological parameters with CD4+ count 552±290 cells/μL and log10 viral load 1.82±0.49 copies/mL. (Table 1) A modest percentage of HIV-infected individuals self-reported prior use of zidovudine (47.7%) or stavudine (22.6%), and current use of zidovudine (10.3%) or stavudine (1.9%) was reported by even fewer.
Table 1.
Baseline Demographic and Clinical Characteristics
| HIV-Infected Individuals (n=155) |
Non-HIV-Infected Individuals (n=70) |
P Value | |
|---|---|---|---|
| Demographics | |||
| Age (years) | 47±7 | 46±7 | 0.17 |
| Race (%) | 0.38 | ||
| Caucasian | 53 | 51 | |
| African American | 40 | 37 | |
| Male Sex (%) | 61 | 59 | 0.70 |
| Current Tobacco use (%) | 44 | 40 | 0.56 |
| Current Diabetes (%) | 10 | 7 | 0.43 |
| Current Statin Use (%) | 14 | 4 | 0.03 |
| HIV Parameters | |||
| CD4+ T cell count (cells/μL) | 552±290 | N/A | -- |
| CD4+ T cell nadir (cells/(μL) | 193±164 | N/A | -- |
| CD8+ T cell count (cells/(μL) | 912±486 | N/A | -- |
| Log HIV RNA Viral Load (copies/mL) | 1.82±0.49 | N/A | -- |
| Undetectable HIV Viral Load (%) | 86% | N/A | -- |
| Duration HIV (years) | 14±6 | N/A | -- |
| Duration ART use (years) | 8±5 | N/A | -- |
| Current PI use (%) | 55 | N/A | -- |
| Current NRTI use (%) | 95 | N/A | -- |
| Current NNRTI use (%) | 37 | N/A | -- |
| History of HCV infection (%)* | 27 | 9 | 0.0008 |
| Body Composition and Metabolic Parameters | |||
| BMI(kg/m2) | 27±5 | 27±5 | 0.31 |
| Waist to Hip Ratio | 0.94±0.07 | 0.92±0.07 | 0.19 |
| SAT (cm2) | 199 [126,288] | 239 [148,358] | 0.04 |
| VAT (cm2) | 109 [61,210] | 103 [54,174] | 0.35 |
| VAT to SAT Ratio | 0.54 [0.30,1.13] | 0.42 [0.23, 0.79] | 0.03 |
| Triglycerides (mg/dL) | 97[77,172] | 84[62,121] | 0.001 |
| HDL (mg/dL) | 50[41,62] | 49[42,64] | 0.81 |
| LDL (mg/dL) | 98[78,124] | 105[89,127] | 0.25 |
| ALT (U/dl) | 35±28 | 25±17 | 0.0006 |
| AST (U/dL) | 39±30 | 28±16 | 0.001 |
| Markers of Arterial Injury and Inflammation | |||
| LpPLA2 Activity (nmol/min/mL) | 184.3[152.6,229.7] | 173.0[146.7,216.6] | 0.12 |
| Oxidized LDL (U/L) | 43.9[33.4,53.5] | 44.4[35.8,56.4] | 0.48 |
| hs-cTnT (ng/L) | 3.09[2.99,6.44] | 2.99[2.99,3.99] | 0.03 |
| hsCRP (mg/L) | 1.4[0.5,3.9] | 1.3[0.5,3.5] | 0.67 |
Data reported as mean ± standard deviation, percentage, or median [interquartile range].
History of HCV infection based on self-report
Abbreviations: N/A, not applicable; ART, antiretroviral therapy; PI, protease inhibitor; NRTI, nucleoside/nucleotide reverse transcriptase inhibitors; NNRTI, non-nucleoside reverse transcriptase inhibitors; HCV, hepatitis C virus; BMI, body mass index; VAT, visceral adipose tissue; SAT, subcutaneous adipose tissue; HDL, high-density lipoprotein; LDL, low-density lipoprotein; ALT, alanine aminotransferase; AST, aspartate aminotransferase; LpPLA2, lipoprotein-associated phospholipase A2; hs-cTnT, high sensitivity cardiac troponin T; hsCRP, high-sensitivity C-reactive protein
Assessment of Body Composition and Metabolic Parameters
Despite similar BMI (27±5 vs. 27±5 kg/m2, P=.31), waist to hip ratio (0.94±0.07 vs. 0.92±0.07, P=.19) and VAT (109[61,210] vs. 103[54,174]cm2, P=.35), HIV-infected individuals had significantly lower SAT (199[126,288] vs. 239[148,358]cm2, P=.04) compared to non-HIV-infected individuals. In addition, the VAT to SAT ratio (0.54[0.30,1.13] vs. 0.42[0.23,0.79]cm2, P=.03) was significantly increased in the HIV vs. non-HIV group. Metabolic parameters including triglycerides (97[77,172] vs. 84[62,121] mg/dL, P=.001), ALT (35±28 vs. 25±17 U/dL, P=.0006) and AST (39±30 vs. 28±16 U/dL, P=.001) were significantly higher among HIV vs. non-HIV-infected individuals. (Table 1)
Markers of Arterial Disease and Generalized Inflammation
Hs-cTnT (3.09[2.99,6.44] vs. 2.99[2.99,3.00]ng/L, P=.03) was significantly greater among HIV-infected vs. non-HIV-infected individuals. Detectable hs-cTnT values were obtained in 50% of HIV-infected individuals compared to 41% of non-HIV-infected individuals. Other markers LpPLA2 (184.2[152.6,229.7] vs. 173.0[146.7,216.6] nmol/min/mL, P=.12), oxLDL (43.9[33.4,53.5] vs. 44.4[35.8,56.4] U/L, P=.48), and hsCRP (1.4[0.5,3.9] vs. 1.3[0.5,3.5]cm2, P=.67) were similar between the HIV and non-HIV groups as previously reported[11]. (Table 1)
Relationship of Adipose Depots and Markers of Arterial Disease and Generalized Inflammation among HIV-infected and non-HIV-infected individuals
Among HIV-infected individuals, reduced SAT inversely correlated with LpPLA2 (ρ=−0.19, P=.02) and hs-cTnT (ρ=−0.24, P=.004). Increased VAT significantly and positively related to LpPLA2 (ρ=0.25, P=.003), oxLDL (ρ=0.28, P=.0005), hs-cTnT (ρ=0.28, P=.0007), and hsCRP (ρ=0.32, P=<.0001). (Table 2) Additionally, LpPLA2 (ρ=0.38, P=<.0001) and hs-cTnT (ρ=0.40, P=<.0001) demonstrated a significant correlation with the VAT to SAT ratio, while oxLDL (ρ=0.16, P=.06) and hsCRP (ρ=0.16, P=0.06) tended to be correlated with the VAT to SAT ratio among the HIV group. (Table 2)
Table 2.
Correlations of Body Composition with Markers of Arterial Injury and Inflammation
| LpPLA2 Activity (nmol/min/mL) |
Oxidized LDL (U/L) |
Hs-cTnT (ng/L) |
hsCRP (mg/L) |
|||||
|---|---|---|---|---|---|---|---|---|
| ρ | P Value | ρ | P Value | ρ | P Value | ρ | P Value | |
| HIV-Infected Individuals (n=155) | ||||||||
| BMI (kg/m2) | −0.05 | 0.50 | 0.22 | 0.007 | −0.02 | 0.83 | 0.36 | <0.0001 |
| Waist to Hip Ratio | 0.16 | 0.06 | 0.21 | 0.02 | 0.24 | 0.007 | 0.28 | 0.002 |
| SAT (cm2) | −0.19 | 0.02 | 0.12 | 0.16 | −0.24 | 0.004 | 0.17 | 0.04 |
| VAT (cm2) | 0.25 | 0.003 | 0.28 | 0.0005 | 0.28 | 0.0007 | 0.32 | <0.0001 |
| VAT to SAT Ratio | 0.38 | <0.0001 | 0.16 | 0.06 | 0.40 | <0.0001 | 0.16 | 0.06 |
| Non-HIV-Infected Individuals (n=70) | ||||||||
| BMI (kg/m2) | 0.03 | 0.84 | 0.05 | 0.71 | 0.04 | 0.73 | 0.18 | 0.14 |
| Waist to Hip Ratio | 0.32 | 0.01 | 0.31 | 0.01 | 0.18 | 0.17 | 0.24 | 0.06 |
| SAT (cm2) | −0.24 | 0.05 | −0.07 | 0.58 | −0.19 | 0.12 | 0.15 | 0.24 |
| VAT (cm2) | 0.37 | 0.002 | 0.24 | 0.05 | 0.10 | 0.42 | 0.29 | 0.02 |
| VAT to SAT Ratio | 0.49 | <0.0001 | 0.19 | 0.12 | 0.30 | 0.01 | 0.20 | 0.11 |
Relationships were assessed by Spearman’s Correlation Coefficient.
Abbreviations: LpPLA2, lipoprotein-associated phospholipase A2; LDL, low density lipoprotein; hs-cTnT, high sensitivity cardiac troponin T; hsCRP, high-sensitivity C-reactive protein; BMI, body mass index; SAT, subcutaneous adipose tissue; VAT, visceral adipose tissue
Similar analyses among non-HIV-infected individuals revealed significant relationships between SAT and LpPLA2 (ρ=−0.24, P=.05), as well as VAT and LpPLA2 (ρ=0.37, P=.002), oxLDL (ρ=0.24, P=.05), and hsCRP (ρ=0.29, P=.02). The VAT to SAT ratio was positively correlated to LpPLA2 (ρ=0.49, P=<.0001) and hs-cTnT (ρ=0.30, P=.01) in the non-HIV group. (Table 2)
Multivariate Regression Modeling Among HIV-infected individuals to Assess Effects of HIV- and Adipose-Related Indices on Markers of Arterial Disease and Generalized Inflammation
In separate models controlling for SAT, VAT, age, duration of HIV infection, duration of ART use, nadir CD4+ count, and viral load among the HIV group, reduced SAT was independently associated with LpPLA2 (β estimate −0.0896, P=.04) and hs-cTnT (β estimate −0.0195, P=.005) and increased VAT was independently associated with LpPLA2 (β estimate 0.2194, P=.001), oxLDL (β estimate 0.0478, P=.02), hs-cTnT (β estimate 0.0212, P=.04), and hsCRP (β estimate 0.0103, P=.04). (Table 3) We determined the AUC for these models after applying an ROC analysis: LpPLA2 (AUC=0.78, P=.007), oxLDL (AUC=0.76, P=.01), hs-cTnT (AUC=0.78, P=.004), hsCRP (AUC=0.78, P=.03).
Table 3.
Model to Assess Determinants of Markers of Arterial Injury and Inflammation among HIV-infected Individuals
| LpPLA2 Activity (nmol/min/mL) |
Oxidized LDL (U/L) |
Hs-cTnT (ng/L) |
hsCRP (mg/L) |
|||||
|---|---|---|---|---|---|---|---|---|
| β Estimate | P Value | β Estimate | P Value | β Estimate | P Value | β Estimate | P Value | |
| (R2=0.20; P=0.02) | (R2=0.20; P=0.02) | (R2=0.20; P=0.02) | (R2=0.20; P=0.02) | |||||
| SAT (cm2) | −0.0896 | 0.04 | 0.0192 | 0.13 | −0.0195 | 0.005 | 0.0041 | 0.20 |
| VAT (cm2) | 0.2194 | 0.001 | 0.0478 | 0.02 | 0.0212 | 0.04 | 0.0103 | 0.04 |
| Duration of HIV (years) | −0.0842 | 0.94 | 0.0905 | 0.78 | 0.3214 | 0.07 | −0.2068 | 0.01 |
| Duration of ART use (years) | 1.8323 | 0.18 | 0.5445 | 0.17 | −0.1945 | 0.36 | 0.1373 | 0.17 |
| CD4+ nadir count (cells/μL) | −0.0168 | 0.62 | −0.0023 | 0.82 | −0.0060 | 0.27 | −0.0027 | 0.29 |
| Log10 HIV viral load (copies/mL) | −13.8512 | 0.41 | −3.5921 | 0.46 | 4.9540 | 0.06 | 2.0334 | 0.10 |
| Age (years) | −0.5370 | 0.55 | −0.0267 | 0.92 | −0.0488 | 0.73 | 0.0958 | 0.15 |
R2 represents the coefficient of determination and the proportion of variance explained by the model. P value represents significance by the whole model ANOVA test.
Abbreviations: LpPLA2, lipoprotein-associated phospholipase A2; LDL, low density lipoprotein; hs-cTnT, high sensitivity cardiac troponin T; hsCRP, high-sensitivity C-reactive protein; SAT, subcutaneous adipose tissue; VAT, visceral adipose tissue
Discussion
We demonstrate that specific measures of fat redistribution relate to markers of arterial disease among HIV-infected individuals well-phenotyped for body composition changes. These are the first data among PLWH to relate markers of arterial disease, LpPLA2, oxLDL, and hs-cTnT, to the visceral and subcutaneous depots. Specifically, increased VAT and decreased SAT each had distinct associations to these markers in the HIV population, and the regional pattern of fat redistribution may be more critical to ensuing inflammation [14]. Assessment of visceral and subcutaneous distributions, among PLWH, could potentially help discern those who may be greater risk for inflammatory-mediated CVD.
PLWH may be predisposed to atrophy of the subcutaneous depot in the setting of toxic ART side effects or direct viral actions on the adipocytes. Shifts in macrophage populations at the tissue level in the context of adipose redistribution, for example in HIV-associated lipoatrophy, may contribute to inflammation in the subcutaneous depot [15]. In support of this hypothesis, prior findings have demonstrated tissue-specific inflammation, and loss of peripheral subcutaneous fat in association with in situ inflammation utilizing FDG-PET imaging techniques to assess metabolic activity in the fat [16]. Data in the current study now show that reduced SAT may also be related to arterial disease and generalized inflammation, as evidenced by significant inverse relationships to LpPLA2, hs-cTnT, and hsCRP, among HIV-infected individuals.
Several more recent studies demonstrate increases in VAT regardless of specific class when initiating contemporary ART [17, 18], and SAT loss may have less clinical relevance with use of contemporary regimens. In the current study, approximately 1/3 of HIV-infected individuals were exposed to prior use of a thymidine analogue. Visceral adiposity is related to increased overall CVD mortality [19], and emerging literature demonstrates that VAT-derived exosomes may promote proatherogenic effects via macrophage foam cell regulation in animal models of obesity [20]. A plausible mechanism for the increased risk of arterial disease in HIV may similarly link the increased pro-inflammatory milieu in expanded VAT to systemic effects on the vasculature.
LpPLA2 is increased in generalized obesity [21], and human adipocytes have been reported to be a source of LpPLA2 [22]. Moreover, application of a LpPLA2 inhibitor also reduced oxLDL production from human adipocytes [22]. Excess VAT has been correlated with oxLDL among PLWOH [23]. In contrast, few data are available on these markers of arterial disease in relation to body composition among PLWH. Circulating oxLDL has been shown to be increased among those PLWH demonstrating a lipodystrophy phenotype [24], but not related to specific depots as shown by our data in the current study. The relationship of LpPLA2 and hs-cTnT to the visceral and subcutaneous depots has not previously been explored in HIV. Few studies have demonstrated a link between troponin and general body composition (i.e BMI) among the non-HIV population [25].
Hs-cTnT is a marker of myocardial injury that occurs as a result of ischemia, which could be precipitated by atherosclerotic plaque, but is not specific to this and could be increased in other CVD states, including reduced coronary flow reserve and heart failure [26–28]. Fat redistribution could be indicative that other ectopic fat depots, such as epicardial, pericardial, or perivascular fat, are present in measurable amounts. In this way, reduced SAT and/or excess VAT could be an overall indicator of fat redistribution, and dysfunctional adipose depots closer in proximity to the vasculature and/or myocardium may actually drive increased CVD risk, including both arterial disease, myocardial fibrosis, and diastolic dysfunction, the prevalence of which is increased in HIV[2, 29].
In the general population without known CVD risk, VAT has been linked to increased arterial inflammation using imaging techniques such as 18FDG-PET/CT [30], a good surrogate for the in vivo measurement of macrophage activity in the arterial wall which correlates well with circulating inflammatory biomarkers [31]. Prior studies among PLWH have demonstrated that excess VAT and/or reduced SAT relate to indices of CVD, including carotid artery stiffness and presence of coronary plaque among single sex cohorts [32, 33]. We now extend this work to show the relative importance of the VAT and VAT/SAT ratio in the HIV population, without known CVD, to broad indices of systemic and arterial injury and inflammation.
In multivariate modeling, we demonstrate that adipose depots may contribute to an inflamed phenotype independent of HIV-related parameters, including duration of HIV infection, duration of ART use, nadir CD4 count and viral load. This is an important observation in the context of a well-treated HIV population, and highlights fat redistribution as a potential mechanism for ensuing inflammation despite adequate immunological control. There is emerging evidence to suggest that fat depots serve as a viral reservoirs [34, 35]. Localized inflammation within the fat depot originating from pathologic macrophage infiltration may contribute systemically to inflammatory-mediated metabolic complications. Further studies linking in situ depot-specific tissue inflammation, macrophage infiltration, and arterial inflammation will be important to perform.
There are limitations to the current study. The study was cross-sectional in nature, so we cannot fully assess the causality of the relationship between body composition and arterial inflammation. Moreover, we used markers of arterial injury and inflammation as a proxy for CVD. Nonetheless, in a well-phenotyped group with significant changes in fat redistribution, we demonstrate consistent links between body composition and arterial injury and inflammation. Based on these initial findings, it would be important to assess for changes in fat redistribution longitudinally and determine whether unfavorable changes in the VAT and SAT developing over time contribute to arterial injury and inflammation.
These data are representative of a cohort of long-term survivors who are heavily treatment experienced and may not reflect contemporary populations of persons living with HIV and the new ART regimens. In addition, specific ART, such as thymidine analogues, may have larger contributions to fat dysfunction and redistribution that could not be individually assessed in the current study. Moreover, with the growing epidemic of obesity in HIV, combined accumulation of VAT and SAT may be another phenotype on the spectrum of body composition changes which requires further evaluation as a contributor to systemic inflammation and CVD.
In the context of SAT loss and/or VAT accumulation among HIV-infected individuals, dysfunctional and inflamed adipose tissue, may be linked to arterial disease. Circulating biomarkers of arterial injury and inflammation may be useful to identify those with evidence of fat redistribution who may be at risk for CVD. Strategies to restore normal adipose biology and reduce adipose dysfunction may have therapeutic benefit to dampen arterial injury and inflammation in the HIV population among whom traditional risk factor modification does not completely mitigate CVD risk.
Acknowledgments
The investigators would like to thank the nursing staff on the MGH TCRC as well as the volunteers who participated in this study.
Funding: This work was supported by Bristol Myers Squibb, Inc; K23 HL092792 to JL; K23 HL136262 to SS; M01 RR01066, UL1 RR025758 and UL1 TR001102, Harvard Clinical and Translational Science Center, from the National Center for Research Resources; and P30 DK040561 from the Nutrition Obesity Research Center at Harvard. Funding sources had no role in the design of the study, data analysis or the writing of the manuscript.
Footnotes
Clinical Trial Registration: NCT00455793
Declaration of Interest: SS, KVF, MT, RC, PM have nothing to declare. MVZ participated in a Scientific Advisory Board meeting for Roche Diagnostics and received research funding from Gilead Sciences; CD received research funding from Roche Diagnostics, served as a consultant for Abbott Diagnostics, FujiRebio, Metanomics, Ortho Diagnostics and Siemens Healthcare, and received honorarium from Medscape and royalties from UpToDate; SEL is a non-paid Board member of the community non-profit organization Healing Our Community Collaborative and received one-time compensation for CME educational offerings sponsored by the Association of Nursing in AIDS Care and New England AIDS Education and Training Center; JL participated in a Scientific Advisory Board meeting for Gilead Sciences and served as a consultant for Viiv Healthcare; SKG has received research funding from Gilead Sciences, KOWA, and Theratechnologies, and served as a consultant for Navidea Inc. and Theratechnologies--all declarations of interest of co-authors are unrelated to this manuscript.
References
- 1.Lo J, Abbara S, Shturman L, Soni A, Wei J, Rocha-Filho JA, et al. Increased prevalence of subclinical coronary atherosclerosis detected by coronary computed tomography angiography in HIV-infected men. AIDS 2010,24:243–253. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Fitch KV, Srinivasa S, Abbara S, Burdo TH, Williams KC, Eneh P, et al. Noncalcified coronary atherosclerotic plaque and immune activation in HIV-infected women. J Infect Dis 2013,208:1737–1746. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Subramanian S, Tawakol A, Burdo TH, Abbara S, Wei J, Vijayakumar J, et al. Arterial inflammation in patients with HIV. JAMA 2012,308:379–386. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Zanni MV, Toribio M, Robbins GK, Burdo TH, Lu MT, Ishai AE, et al. Effects of Antiretroviral Therapy on Immune Function and Arterial Inflammation in Treatment-Naive Patients With Human Immunodeficiency Virus Infection. JAMA Cardiol 2016,1:474–480. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.de Armas LR, Pallikkuth S, George V, Rinaldi S, Pahwa R, Arheart KL, et al. Reevaluation of immune activation in the era of cART and an aging HIV-infected population. JCI Insight 2017,2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Hileman CO, Funderburg NT. Inflammation, Immune Activation, and Antiretroviral Therapy in HIV. Curr HIV/AIDS Rep 2017,14:93–100. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Boccara F Cardiovascular complications and atherosclerotic manifestations in the HIV-infected population: type, incidence and associated risk factors. AIDS 2008,22 Suppl 3:S19–26. [DOI] [PubMed] [Google Scholar]
- 8.Mangili A, Ahmad R, Wolfert RL, Kuvin J, Polak JF, Karas RH, et al. Lipoprotein-associated phospholipase A2, a novel cardiovascular inflammatory marker, in HIV-infected patients. Clin Infect Dis 2014,58:893–900. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Lavi S, McConnell JP, Rihal CS, Prasad A, Mathew V, Lerman LO, et al. Local production of lipoprotein-associated phospholipase A2 and lysophosphatidylcholine in the coronary circulation: association with early coronary atherosclerosis and endothelial dysfunction in humans. Circulation 2007,115:2715–2721. [DOI] [PubMed] [Google Scholar]
- 10.Kolodgie FD, Burke AP, Skorija KS, Ladich E, Kutys R, Makuria AT, et al. Lipoprotein-associated phospholipase A2 protein expression in the natural progression of human coronary atherosclerosis. Arterioscler Thromb Vasc Biol 2006,26:2523–2529. [DOI] [PubMed] [Google Scholar]
- 11.Fitch KV, DeFilippi C, Christenson R, Srinivasa S, Lee H, Lo J, et al. Subclinical myocyte injury, fibrosis and strain in relationship to coronary plaque in asymptomatic HIV-infected individuals. AIDS 2016,30:2205–2214. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Caron-Debarle M, Lagathu C, Boccara F, Vigouroux C, Capeau J. HIV-associated lipodystrophy: from fat injury to premature aging. Trends Mol Med 2010,16:218–229. [DOI] [PubMed] [Google Scholar]
- 13.Burdo TH, Lo J, Abbara S, Wei J, DeLelys ME, Preffer F, et al. Soluble CD163, a novel marker of activated macrophages, is elevated and associated with noncalcified coronary plaque in HIV-infected patients. J Infect Dis 2011,204:1227–1236. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Pou KM, Massaro JM, Hoffmann U, Vasan RS, Maurovich-Horvat P, Larson MG, et al. Visceral and subcutaneous adipose tissue volumes are cross-sectionally related to markers of inflammation and oxidative stress: the Framingham Heart Study. Circulation 2007,116:1234–1241. [DOI] [PubMed] [Google Scholar]
- 15.Shikuma CM, Gangcuangco LM, Killebrew DA, Libutti DE, Chow DC, Nakamoto BK, et al. The role of HIV and monocytes/macrophages in adipose tissue biology. J Acquir Immune Defic Syndr 2014,65:151–159. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Torriani M, Zanni MV, Fitch K, Stavrou E, Bredella MA, Lim R, et al. Increased FDG uptake in association with reduced extremity fat in HIV patients. Antivir Ther 2013,18:243–248. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.McComsey GA, Moser C, Currier J, Ribaudo HJ, Paczuski P, Dube MP, et al. Body Composition Changes After Initiation of Raltegravir or Protease Inhibitors: ACTG A5260s. Clin Infect Dis 2016,62:853–862. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.McComsey GA, Kitch D, Sax PE, Tebas P, Tierney C, Jahed NC, et al. Peripheral and central fat changes in subjects randomized to abacavir-lamivudine or tenofovir-emtricitabine with atazanavir-ritonavir or efavirenz: ACTG Study A5224s. Clin Infect Dis 2011,53:185–196. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Britton KA, Massaro JM, Murabito JM, Kreger BE, Hoffmann U, Fox CS. Body fat distribution, incident cardiovascular disease, cancer, and all-cause mortality. J Am Coll Cardiol 2013,62:921–925. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Xie Z, Wang X, Liu X, Du H, Sun C, Shao X, et al. Adipose-Derived Exosomes Exert Proatherogenic Effects by Regulating Macrophage Foam Cell Formation and Polarization. J Am Heart Assoc 2018,7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.da Silva IT, Timm Ade S, Damasceno NR. Influence of obesity and cardiometabolic makers on lipoprotein-associated phospholipase A2 (Lp-PLA2) activity in adolescents: the healthy young cross-sectional study. Lipids Health Dis 2013,12:19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Jackisch L, Kumsaiyai W, Moore JD, Al-Daghri N, Kyrou I, Barber TM, et al. Differential expression of Lp-PLA2 in obesity and type 2 diabetes and the influence of lipids. Diabetologia 2018,61:1155–1166. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Paradis ME, Hogue MO, Mauger JF, Couillard C, Couture P, Bergeron N, et al. Visceral adipose tissue accumulation, secretory phospholipase A2-IIA and atherogenecity of LDL. Int J Obes (Lond) 2006,30:1615–1622. [DOI] [PubMed] [Google Scholar]
- 24.Duong M, Petit JM, Martha B, Galland F, Piroth L, Walldner A, et al. Concentration of circulating oxidized LDL in HIV-infected patients treated with antiretroviral agents: relation to HIV-related lipodystrophy. HIV Clin Trials 2006,7:41–47. [DOI] [PubMed] [Google Scholar]
- 25.Ndumele CE, Coresh J, Lazo M, Hoogeveen RC, Blumenthal RS, Folsom AR, et al. Obesity, subclinical myocardial injury, and incident heart failure. JACC Heart Fail 2014,2:600–607. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Omland T, de Lemos JA, Sabatine MS, Christophi CA, Rice MM, Jablonski KA, et al. A sensitive cardiac troponin T assay in stable coronary artery disease. N Engl J Med 2009,361:2538–2547. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Beatty AL, Ku IA, Christenson RH, DeFilippi CR, Schiller NB, Whooley MA. High-sensitivity cardiac troponin T levels and secondary events in outpatients with coronary heart disease from the Heart and Soul Study. JAMA Intern Med 2013,173:763–769. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Taqueti VR, Everett BM, Murthy VL, Gaber M, Foster CR, Hainer J, et al. Interaction of impaired coronary flow reserve and cardiomyocyte injury on adverse cardiovascular outcomes in patients without overt coronary artery disease. Circulation 2015,131:528–535. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Holloway CJ, Ntusi N, Suttie J, Mahmod M, Wainwright E, Clutton G, et al. Comprehensive cardiac magnetic resonance imaging and spectroscopy reveal a high burden of myocardial disease in HIV patients. Circulation 2013,128:814–822. [DOI] [PubMed] [Google Scholar]
- 30.Figueroa AL, Takx RA, MacNabb MH, Abdelbaky A, Lavender ZR, Kaplan RS, et al. Relationship Between Measures of Adiposity, Arterial Inflammation, and Subsequent Cardiovascular Events. Circ Cardiovasc Imaging 2016,9:e004043. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Tawakol A, Migrino RQ, Bashian GG, Bedri S, Vermylen D, Cury RC, et al. In vivo 18F-fluorodeoxyglucose positron emission tomography imaging provides a noninvasive measure of carotid plaque inflammation in patients. J Am Coll Cardiol 2006,48:1818–1824. [DOI] [PubMed] [Google Scholar]
- 32.Palella FJ Jr., McKibben R, Post WS, Li X, Budoff M, Kingsley L, et al. Anatomic Fat Depots and Coronary Plaque Among Human Immunodeficiency Virus-Infected and Uninfected Men in the Multicenter AIDS Cohort Study. Open Forum Infect Dis 2016,3:ofw098. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Glesby MJ, Hanna DB, Hoover DR, Shi Q, Yin MT, Kaplan R, et al. Abdominal Fat Depots and Subclinical Carotid Artery Atherosclerosis in Women With and Without HIV Infection. J Acquir Immune Defic Syndr 2018,77:308–316. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Damouche A, Lazure T, Avettand-Fenoel V, Huot N, Dejucq-Rainsford N, Satie AP, et al. Adipose Tissue Is a Neglected Viral Reservoir and an Inflammatory Site during Chronic HIV and SIV Infection. PLoS Pathog 2015,11:e1005153. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Couturier J, Suliburk JW, Brown JM, Luke DJ, Agarwal N, Yu X, et al. Human adipose tissue as a reservoir for memory CD4+ T cells and HIV. AIDS 2015,29:667–674. [DOI] [PMC free article] [PubMed] [Google Scholar]