Endothelial Dysfunction following Prolonged Sitting is Mediated by a Reduction in Shear Stress

Abstract

We and others recently reported that prolonged sitting impairs endothelial function in the leg vasculature; however, the mechanisms remain unknown. Herein, we tested the hypothesis that a sustained reduction in flow induced shear stress is the underlying mechanism by which sitting induces leg endothelial dysfunction. Specifically, we examined whether preventing the reduction in shear stress during sitting would abolish the detrimental effects of sitting on popliteal artery endothelial function. In 9 young healthy men, bilateral measurements of popliteal artery flow‐mediated dilation (FMD) were performed before and after a 3‐hour sitting period during which one foot was submerged in 42°C water (i.e. WETFOOT), while the contralateral leg remained dry and served as internal control (i.e., DRYFOOT). Local heating is an effective stimulus for dilating the skin circulation and increasing limb vascular conductance and thus, shear stress without producing systemic cardiovascular effects. During sitting, popliteal artery mean shear rate was significantly (P<0.05) reduced in the leg of the DRYFOOT (pre sit: 44.1±4.9s−1, post sit: 25.4±3.8s−1) and sustained in the leg of the WETFOOT (pre sit: 39.6±3.7s−1, post sit: 40.7±5.5s−1). Popliteal artery FMD was impaired after 3 hours of sitting in the leg of the DRYFOOT (pre sit: 5.9±0.9% vs. post sit: 2.9±1.0%) but not WETFOOT (pre sit: 7.3±1.7% vs. post sit: 10.6±2.0%). Collectively, these data demonstrate that preventing the reduction of flow induced shear stress during sitting with local heating abolishes the impairment in popliteal artery endothelial function. Thus, a reduction in shear stress mediates sitting‐induced leg endothelial dysfunction.Support or Funding InformationSupport: NIH K01 HL‐125503 and R21 DK‐105368 (JP)