P175 AN ACUTE BOUT OF PROLONGED SITTING IMPAIRS ENDOTHELIAL FUNCTION AND INCREASES PLASMA CONCENTRATIONS OF ENDOTHELIN-1 IN OVERWEIGHT/OBESE ADULTS: IMPLICATIONS FOR GLUCOSE AND INSULIN METABOLISM

Abstract

Background: Compared to regular active breaks, prolonged uninterrupted sitting amplifies postprandial glucose and insulin in overweight/obese adults with and without type 2 diabetes; and impairs lower limb endothelial function (a predictor of cardiovascular disease) in healthy adults. However, the effects of prolonged sitting on endothelial function in those at heightened risk of cardiometabolic disease have not been investigated. Methods: Overweight/obese (BMI > 25kg/m2) adults (35–75y) completed two laboratory-based conditions in a random order: (i) 5h prolonged uninterrupted sitting (SIT); and (ii) 5h sitting interrupted with 3min of light-intensity simple resistance activities every 30min (SRA). Femoral artery endothelial function (flow mediated dilation; FMD) and shear rate was assessed at baseline, 1, 2 and 5h. Hourly plasma was collected for glucose, insulin and endothelin-1 measurement. Muscle sympathetic nervous activity (MSNA) was measured at 5h. 2Preliminary results: In the current sample (n = 7), SIT impaired FMD (−2.6±0.9%; p < 0.05) and shear rate iAUC (−39±14%; p < 0.05), compared to SRA. There was an increase in glucose (40±28%; p = 0.18) and insulin (46±25%; p = 0.16) iAUC, and mean endothelin-1 plasma concentration (0.28±0.09 pg/ml; p < 0.05) in SIT, compared to SRA. MSNA (n = 4) was reduced in SIT, compared to SRA (−4±1 bursts/min; p < 0.05). Testing and analysis (n = 20 participants) is expected to be complete by August, 2017. Conclusions: These findings are consistent with a potential mechanistic link between sitting- induced endothelial dysfunction, vasoconstriction and insulin resistance, via reduced delivery of glucose and insulin to nutritive vascular beds in muscle. Endothelial dysfunction associated with prolonged sitting may be related to reduced shear rate, and impaired MSNA.