Thigh Fat and Muscle each Contribute to Excess Cardiometabolic Risk in South Asians, Independent of Visceral Adipose Tissue

Objective: To compare fat distribution and associations between fat depots and cardiometabolic traits in South Asians and Europeans. Methods: Five hundred and fourteen South Asians and 669 Europeans, aged 56-86. Questionnaires, record review, blood testing, and coronary artery calcification scores provided diabetes and clinical plus subclinical coronary heart disease (CHD) diagnoses. Abdominal visceral (VAT) and subcutaneous adipose tissue, thigh subcutaneous adipose tissue (TSAT), intermuscular and intramuscular thigh fat and thigh muscle were measured by CT. Results: Accounting for body size, South Asians had greater VAT and TSAT than Europeans, but less thigh muscle. Associations between depots and disease were stronger in South Asians than Europeans. In multivariable analyses in South Asians, VAT was positively associated with diabetes and CHD, while TSAT and thigh muscle were protective for diabetes, and thigh muscle for CHD. Differences in VAT and thigh muscle only partially explained the excess diabetes and CHD in South Asians versus Europeans. Insulin resistance did not account for the effects of TSAT or thigh muscle. Conclusions: Greater VAT and TSAT and lesser thigh muscle in South Asians contributed to ethnic differences in cardiometabolic disease. Effects of TSAT and thigh muscle were independent of insulin resistance.