The effect of prior walking on coronary heart disease risk markers in South Asian and European men.

Purpose: Heart disease risk is elevated in South Asians possibly due to impaired postprandial metabolism. Running has been shown to induce greater reductions in postprandial lipaemia in South Asian than European men but the effect of walking in South Asians is unknown. Methods: Fifteen South Asian and 14 White European men aged 19-30 years completed two, 2-d trials in a randomised crossover design. On day 1, participants rested (control) or walked for 60 min at approximately 50% maximum oxygen uptake (exercise). On day 2, participants rested and consumed two high fat meals over a 9h period during which 14 venous blood samples were collected. Results: South Asians exhibited higher postprandial triacylglycerol (geometric mean (95% confidence interval) 2.29(1.82 to 2.89) vs. 1.54(1.21 to 1.96) mmol·L-1·hr-1), glucose (5.49(5.21 to 5.79) vs. 5.05(4.78 to 5.33) mmol·L-1·hr-1), insulin (32.9(25.7 to 42.1) vs. 18.3(14.2 to 23.7) µU·mL-1·hr-1) and interleukin-6 (2.44(1.61 to 3.67) vs. 1.04(0.68 to 1.59) pg·mL-1·hr-1) than Europeans (all ES ≥ 0.72, P≤0.03). Between-group differences in triacylglycerol, glucose and insulin were not significant after controlling for age and percentage body fat. Walking reduced postprandial triacylglycerol (1.79(1.52 to 2.12) vs. 1.97(1.67 to 2.33) mmol·L-1·hr-1) and insulin (21.0(17.0 to 26.0) vs. 28.7(23.2 to 35.4) µU·mL-1·hr-1) (all ES ≥ 0.23. P≤0.01), but group differences were not significant. Conclusions: Healthy South Asians exhibited impaired postprandial metabolism compared with White Europeans, but these differences were diminished after controlling for potential confounders. The small-moderate reduction in postprandial triacylglycerol and insulin after brisk walking was not different between the ethnicities

CIRCULATING IRISIN LEVELS IN RESPONSE TO ACUTE AND CHRONIC EXERCISE IN OBESE ADULTS

Nathan C. Winn, Ying Liu, Timothy D. Heden, Lauryn M. Nyhoff, Leryn J. Boyle, and Jill A. Kanaley FACSM University of Missouri, Columbia, MO Irisin is a recently discovered myokine that has been proposed to be secreted into circulation by skeletal muscle in response to exercise. In rodents, irisin activates thermogenic programs in white adipose tissue and improves glucose homeostasis. It is unknown how acute and chronic aerobic exercise alters circulating levels of irisin in obese humans. PURPOSE: We sought to determine whether circulating irisin is exercise-responsive in obese humans. METHODS: A) Eleven obese females (37.3 + 2.1 kg/m2) completed, in random order, a single bout of continuous moderate exercise (CME; 55 min, 55% VO2peak) and high-intensity interval exercise (HIIE; 4 x 4 min intervals at 85%VO2peak separated by 4 x 3 min active recovery periods at 50% VO2peak) at least 7 days apart. Plasma irisin concentrations were measured at 3 time intervals (rest t=0 min, during exercise t=30 min, and post-exercise t=100 min). B) Pre- and post- exercise training irisin concentrations were measured in 13 and 6 obese adults (34.6 + 3.02 kg/m2 and 34.55 + 3.03kg/m2) completing 15 d and 12 wk of aerobic exercise training. RESULTS: Body weight and resting blood chemistry did not differ between CME and HIIE training days (p \u3e0 .05). A two-way repeated measures ANOVA did not reveal a significant interaction or main effect of exercise intensity (p \u3e 0.05) on circulating irisin levels. Irisin concentrations were not different across time within CME (t= 0, 30, 100 min; 2.14 + 0.08, 2.02 + 0.19, 2.21 + 0.13 μg/ml, p \u3e0.05) or HIIE (t= 0, 30, 100 min; 2.04 + 0.16, 2.21 + 0.11, 2.08 + 0.14 μg/ml, p \u3e0.05), respectively. Chronic exercise training had no effect on plasma irisin (p \u3e 0.05). In addition, no significant associations were made between plasma irisin and metabolic parameters. CONCLUSION: To our knowledge these are the first data that have directly measured plasma irisin during and after acute exercise of differing intensities in obese humans. Our novel findings suggest that circulating irisin is not responsive to acute or chronic aerobic exercise in obese adults. Future studies are needed to elucidate the mechanisms underlying the physiological effects of irisin levels in human