Less favorable body composition and adipokines in South Asians compared with other US ethnic groups: results from the MASALA and MESA studies

Abstract

Background: Small studies have shown that South Asians (SAs) have more total body, subcutaneous, visceral and hepatic fat and abnormal adipokine levels compared with Whites. However, comprehensive studies of body composition and adipokines in SAs compared with other ethnic groups are lacking.

Methods: Using harmonized data, we performed a cross-sectional analysis of two community-based cohorts: Mediators of Atherosclerosis of South Asians Living in America (MASALA, n=906) and Multi-Ethnic Study of Atherosclerosis (MESA which included 2622 Whites, 803 Chinese Americans, 1893 African Americans and 1496 Latinos). General linear models were developed to assess the ethnic differences in ectopic fat (visceral, intermuscular and pericardial fat; and hepatic attenuation), lean muscle mass and adipokines (adiponectin and resistin). Models were adjusted for age, sex, site, alcohol use, smoking, exercise, education, household income and body mass index. Ectopic fat models were additionally adjusted for hypertension, diabetes, high-density lipoprotein and triglycerides. Adipokine models were adjusted for subcutaneous, visceral, intermuscular and pericardial fat; and hepatic attenuation.

Results: Compared with all ethnic groups in MESA (Whites, Chinese Americans, African Americans and Latinos), SAs had greater intermuscular fat (pairwise comparisons with each MESA group, P<0.01), lower hepatic attenuation (P<0.001) and less lean mass (P<0.001). SAs had greater visceral fat compared with Chinese Americans, African Americans and Latinos (P<0.05) and greater pericardial fat compared with African Americans (P<0.001). SAs had lower adiponectin levels compared with other ethnic groups (P<0.01; except Chinese Americans) and higher resistin levels than all groups (P<0.001), even after adjusting for differences in body composition.

Conclusion: There are significant ethnic differences in ectopic fat, lean mass and adipokines. A less favorable body composition and adipokine profile in SAs may partially explain the increased predisposition to cardiometabolic disease. The mechanisms that underlie these differences warrant further investigation.

Figure 1. (A-F): Fully-Adjusted Body Composition Measures Across Ethnic Groups

Body composition was compared across ethnic groups in a multivariate model. Covariates included: age, sex, study site, alcohol use, smoking history, socioeconomic status, exercise and BMI. For abdominal and ectopic fat measures, additional covariates included: diabetes, hypertension, HDL, and triglycerides. Data represent mean and 95% confidence interval. (A – Subcutaneous fat area, B – Visceral fat area, C – Total intermuscular fat area, D – Pericardial fat volume, E – Hepatic attenuation, F – Total lean muscle mass area.) For pericardial fat and hepatic attenuation analyses, N for MESA ethnic groups are as follows: White – 2622, Chinese American – 803, African American – 1893, and Latino – 1496. For subcutaneous fat area, visceral fat area, total intermuscular fat area, and total lean muscle mass area analyses, N for MESA ethnic groups are as follows: Whites – 785, Chinese Americans – 251, African Americans – 407, and Latino – 501. *p < 0.001: Results of pairwise comparisons of body composition between South Asians and each of the other race / ethnic groups. **p < 0.05: Results of pairwise comparisons of body composition between South Asians and each of the other race / ethnic groups. ^#p < 0.01: Results of pairwise comparisons of body composition between South Asians and each of the other race / ethnic groups. Abbreviations: BMI – body mass index, HDL – high-density lipoprotein, HU – Hounsfield units.

Figure 2. Fully-Adjusted Adipokine Levels Across Ethnic Groups

Left: Adiponectin (ng/mL) Right: Resistin (ng/mL) Adipokine levels were compared across ethnic groups in a multivariate model. Covariates included: age, sex, study site, alcohol use, smoking history, socioeconomic status, exercise, BMI, subcutaneous fat area, visceral fat area, total intermuscular fat area, pericardial fat volume and hepatic attenuation. Data represent mean and 95% confidence interval. For these analyses, N for MESA ethnic groups are as follows: Whites – 785, Chinese Americans – 251, African Americans – 407, and Latino – 501. *p < 0.001: Results of pairwise comparisons of adipokine levels (adiponectin and resistin) between South Asians and each of the other race / ethnic groups. ^#p < 0.01: Results of pairwise comparisons of body composition between South Asians and each of the other race / ethnic groups.