Higher levels of sedentary behaviour (sitting during waking hours) are associated with chronic low-grade inflammation; and, elevated risk of cardiovascular disease (CVD), diabetes, and all-cause mortality. Compared to regular active breaks from sitting, prolonged uninterrupted sitting acutely (over 1 day) amplifies postprandial glucose and insulin responses, alters the postprandial plasma lipidome, and impairs lower limb endothelial function (a predictor of CVD). We aimed to investigate the effects of an acute bout of prolonged sitting on vascular inflammatory mechanisms.
In an on-going trial, 20 overweight/obese (BMI >25 kg/m2) adults (35-75 years) will complete two laboratory-based experimental conditions in a random order: (i) 5 h prolonged uninterrupted sitting (SIT); and (ii) 5 h sitting interrupted with 3min of light-intensity simple resistance activities every 30min (SRA). Plasma will be collected at baseline, 1, 2 and 5 h for analysis of soluble intracellular (I)CAM-1 and vascular (V)CAM-1 levels. Baseline and 5-h plasma samples will also be collected for ex vivo analysis of vascular inflammatory mechanisms. Cultured primary human coronary artery endothelial cells will be incubated in diluted plasma, and stimulated with TNFα (0.1 ng/ml), cell surface ICAM-1 and VCAM-1 expression will be determined by flow cytometry.
Preliminary results from 7 participants are presented here. Completion of participant testing (n=20) and data analysis is anticipated by August, 2017. Plasma levels of circulating sVCAM-1 tended to be higher in SIT, compared to SRA, at 2h (696 ± 84 vs. 607 ± 43 ng/ml; p=0.14) and 5 h (670 ± 83 vs. 598 ± 35 ng/ml; p=0.28), respectively. No differences were observed for sICAM-1 levels.
An increase in plasma sVCAM-1 levels with prolonged sitting may have implications for leukocyte adhesion and atherogenesis. This study will further investigate the ability of plasma to inhibit inflammation-induced coronary artery endothelial cell CAM expression ex vivo.