The influence of prolonged sitting with brief hourly stair climbing on postprandial circulating microvesicles

Sedentary behaviour is a major risk factor for chronic diseases of the cardiovascular system, including impairments in vascular function. Physical inactivity such as prolonged sitting alters concentrations of circulating microvesicles. Vascular function is partially regulated by microvesicles (MVs), as the molecules they transport facilitate cell-to-cell communication leading to structural and functional changes of blood vessels and their component cells. Along with inactivity impairments, high carbohydrate diet transiently impedes postprandial vascular function. However, regular and acute aerobic exercise counteracts this dysfunction. Further, interrupting prolonged sitting with short bouts of exercise improves cardiorespiratory fitness and postprandial markers of cardiometabolic health, particularly in overweight individuals. The purpose of this study was to examine the influence of hourly stair snack interruptions to prolonged sitting and high or low carbohydrate diets on postprandial circulating MVs in two populations. Individuals of healthy weight (n = 11; males) and elevated waist circumference (n = 3/5; males/females) completed three experimental trials in a randomized crossover design: i) sedentary with low carbohydrate meals, ii) sedentary with high carbohydrate meals, and iii) hourly stair snacks (ascending 55 steps in 15-30s) with high carbohydrate meals. MVs of leukocyte, granulocyte, platelet, activated-, and apoptotic-endothelial cell derivations were quantified using a Cytoflex flow cytometer. Linear mixed model analysis demonstrated that neither diet (high or low carbohydrate) nor incorporation of hourly stair snacks altered concentrations of postprandial circulating MVs from pre-prandial baseline state throughout a five-hour bout of sitting. An absence of influence was observed in both healthy weight individuals and those with elevated waist circumference. Minor differences were observed in select MV populations with diet or condition; however, the transient changes are likely not physiologically significant given the natural variability of MV populations in circulation. This result is consistent with the limited volume and intensity of the stair snack intervention and complexity of factors influencing MV release that extend beyond the scope of the study. The results of this study suggest that an acute bout of prolonged sitting does not alter concentrations of circulating MVs and this influence is not changed by carbohydrate consumption. These findings are an important step in beginning to understand how sedentary behaviour alters vascular function and for establishing practical and accessible exercise interventions.