Influence of Prior Walking on Postprandial Metabolism and Endothelial Function.

Overview

The present study will investigate the effect of prior walking on postprandial metabolism and endothelial function in healthy South Asian and White European women. Participants will complete two, 2-day trials in a random, crossover design separated by at least 3 weeks to control for the menstrual cycle phase. On day 1, participants will either rest or complete a 60 minute walk at 60% maximal oxygen uptake. On day 2, participants will arrive at 08:00 having fasted overnight and a baseline venous blood sample and endothelial function measurement will be taken. Participants will consume a high-fat breakfast and lunch and 12 subsequent venous blood samples will be taken throughout the day at standardised intervals to measure a variety of coronary heart disease risk markers. A second endothelial function measurement will be completed 2 hours after the breakfast. Blood pressure will be measured every hour. It is expected that the South Asian participants will have impaired metabolism and endothelial function compared to their European counterparts but the bout of exercise performed on day 1 will mitigate these responses.

South Asian individuals have a higher-than-average risk of coronary heart disease. The reasons for this are unclear, but physical inactivity and/or poor responsiveness to exercise may play a role. Previous research from our laboratory has shown that coronary heart disease risk markers in the postprandial period are elevated in South Asian men, but acute exercise was equally, if not more, effective for reducing these risk markers in South Asian than White European men. However, the effect of acute exercise on coronary heart disease risk markers has not been examined in South Asian women. Therefore, the purpose of the present study is to compare the effect of acute exercise on endothelial function and coronary heart disease risk markers in women of South Asian versus White European descent. On visit 1, participants will attend the laboratory to undergo preliminary assessments and to be familiarised with the laboratory environment and study procedures. Specifically, health status, habitual physical activity, dietary habits and anthropometric data (height, weight, waist and hip circumference, body fat) will be collected. Two preliminary exercise tests will be performed as follows: 1) submaximal-incremental treadmill walking test and 2) incremental treadmill running test to exhaustion to measure maximal oxygen uptake. On visit 2, participants will undergo a magnetic resonance imaging (MRI) scan to quantify regional body composition comprising abdominal subcutaneous adipose tissue, visceral adipose tissue, liver fat percentage, thigh intramuscular adipose tissue and thigh muscle volume. On visits 3-6 participants will complete two, 2-day trials in a random, crossover design seperated by at least 3 weeks to control for the menstrual cycle phase. On day 1 of both trials, participants will arrive fasted at 08:00 and a baseline blood sample, blood pressure and endothelial function measurement will be taken. Participants will consume a standardised high fat breakfast at 09:00 and lunch at 13:00. At 15:30 the participants will walk for 60 minutes at 60% maximal oxygen uptake and complete a second endothelial function measurement at 16:45. Participants will leave the laboratory with a standardised evening meal to consume before 22:00. The control trial will be the same, except no exercise will be performed. On day 2, participants will arrive at 08:00 having fasted overnight for 10h (except plain water). A cannula will be inserted into the antecubital vein for collection of venous blood samples. Blood pressure will be measured at 08:00 (0h) and again at hourly intervals throughout the day. Endothelial function will measured at 08:15 (0.25h) and again at 3h. At 0h, a fasting blood sample will be collected. Subsequent venous blood samples will be collected at 1.5, 1.75, 2, 3, 4, 5, 5.5, 5.75, 6, 7, 8 and 9h. Participants will consume a standardised high fat breakfast at 1h and a standardised high fat lunch at 5h. The meals consist of 57% fat, 32% carbohydrate and 11% protein. The meals provide 14.3 kcal per kg of body mass. Participants will rest in the laboratory throughout day 2 of both the exercise and control trials.