Plasma free fatty acids metabolic profile with LC-MS and appetite-related hormones in South Asian and white European men in relation to adiposity, physical activity and cardiorespiratory fitness: a cross sectional study

South Asians have a greater cardiovascular disease (CVD) and type 2 diabetes (T2D) risk than white Europeans, but the mechanisms are poorly understood. This study examined ethnic differences in free fatty acids (FFAs) metabolic profile (assessed using liquid chromatography-mass spectrometry), appetite-related hormones and traditional CVD and T2D risk markers in blood samples collected from 16 South Asian and 16 white European men and explored associations with body composition, objectively-measured physical activity and cardiorespiratory fitness. South Asians exhibited higher concentrations of five FFAs (laurate, myristate, palmitate, linolenic, linoleate; P≤0.040), lower acylated ghrelin (ES=1.00, P=0.008) and higher leptin (ES=1.11, P=0.004) than white Europeans; total peptide YY was similar between groups (P=0.381). South Asians exhibited elevated fasting insulin, C-reactive protein, interleukin-6, triacylglycerol and ratio of total cholesterol to high density lipoprotein cholesterol (HDL-C) and lower fasting HDL-C (all ES≥0.74, P≤0.053). Controlling for body fat percentage (assessed using air displacement plethysmography) attenuated these differences. Despite similar habitual moderate-to-vigorous physical activity (ES=0.18, P=0.675), V̇ O2max was lower in South Asians (ES=1.36, P=0.001). Circulating FFAs in South Asians were positively correlated with body fat percentage (r2=0.92), body mass (r2 =0.86) and AUC glucose (r2=0.89) whereas in white Europeans FFAs were negatively correlated with total step counts (r2 =0.96). In conclusion, South Asians exhibited a different FFA profile, lower ghrelin, higher leptin, impaired CVD and T2D risk markers and lower cardiorespiratory fitness than white Europeans