Functional and Metabolic Imaging of the Cardiovascular System in Young Healthy South Asians and Caucasians Unveils Early Differences

South Asians, representing one-fifth of the world’s population, have a higher risk of developing cardiovascular disease (CVD) than Caucasians (1). Moreover, CVD is more aggressive in this population (1). Traditional risk factors per se do not explain these between-ethnic group differences (1,2). Insulin resistance (IR) and type 2 diabetes are also highly prevalent in South Asians (3). Because the mortality risk of CVD associated with type 2 diabetes is higher in South Asians than in Caucasians (2,4), the excess CVD risk in South Asians might be due to inherent ethnicity-associated structural cardiac features and/or a higher cardiac susceptibility to metabolic disorders. Because it is unknown whether differences already exist in cardiac dimensions and function at a young age between these ethnicities, we studied these features in young South Asians and Caucasians and subjected both groups to a short-term high-fat, highcaloric (HFHC) diet to study cardiac response to metabolic stress. Cardiac dimensions, cardiovascular function, and fat distribution were assessed with a 1.5-T magnetic resonance imaging/magnetic resonance spectroscopy scanner in young, healthy male South Asians and Caucasians (n 5 12 for each ethnicity; mean age 22.1 6 0.4 years; BMI 20.9 6 0.4 vs. 22.2 6 0.6 kg/m, respectively; P 5 0.11) before and after a 5-day HFHC diet (;3,775 kcal/day of which ;54% was fat). Subjects were recruited through advertisements in newspapers. A mixed-effects model was applied to assess mean differences before and after the intervention within and between groups and to determine differences indiet effect.Groups and intervention were modeled as fixed effects, and the subject-specific deviations from the group mean were modeled as random effects. Of note, the small sample size might limit generalizability of the findings. Fasting glucose and insulin levels were comparable at baseline but were significantly higher in South Asians after the HFHC diet. Oral glucose tolerance test data showed that South Asians had more IR at baseline. Furthermore, LDL