The effects of localized heating on insulin‐stimulated leg blood flow

Abstract

Vasodilator actions of insulin contribute to glucose disposal in skeletal muscle. Previous studies have shown that increased physical activity, or even a single bout of leg exercise, improves insulin‐stimulated leg blood flow; however, the mechanisms by which exercise mediates this apparent improvement in vascular insulin sensitivity remain largely unknown. Herein we tested the hypothesis that increased limb blood flow‐induced shear stress primes the vasculature to become more insulin‐sensitive. Eleven young healthy subjects (eight men, three women) underwent one‐hour of single‐leg heating (limb immersion in a 40–42°C water bath) to increase blood flow, while the contralateral leg remained outside of the water bath serving as a non‐heated internal control. The heating was followed by a 60‐minute cooldown. Thereafter, bilateral measures of popliteal artery blood flow (via Doppler ultrasound) were performed at baseline and at 45 and 60 minutes during systemic infusion of insulin to mimic postprandial levels. Dextrose was co‐infused at varying rates to maintain euglycemia. As expected, 60 minutes of leg heating increased popliteal artery blood flow by ~3‐fold, relative to the non‐heated control leg. Leg blood flow returned to basal levels following cooldown. Consistent with the hypothesis, popliteal artery blood flow was significantly elevated after 45 minutes, but not 60 minutes, of insulin infusion in the previously heated leg; whereas no significant changes were noted in the control leg throughout. These preliminary results indicate that one‐hour of single‐leg heating improves insulin‐stimulated popliteal artery blood flow, supporting the notion that increased blood flow‐induced shear stress sensitizes the vasculature to the actions of insulin. Additional experiments are underway to confirm these findings.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.