Does obesity differentially impact male and female responses to skeletal muscle vasodilation during exercise?

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BackgroundObesity increases risk of cardiovascular disease (CVD), and epidemiologic evidence suggests substantial sex differences in prevalence and burden of CVD. During dynamic exercise in healthy adults, we previously reported a more robust exercise vasodilator response in women compared to men. Therefore, we tested the hypothesis that obesity attenuates sex differences in exercise vasodilation. Obesity can reduce nitric oxide (NO) vascular signaling, thus we tested a second hypothesis that obese subjects exhibit lower NO‐mediated contribution to exercise vasodilation.Methods45 healthy lean young (18–40 year) adults (23 females; 22 males; BMI, 22 ± 2) and 26 obese young adults (16 females; 10 males; BMI, 37 ± 6) performed dynamic forearm exercise at 15% of maximal voluntary contraction for 10 minutes (20 contractions/min). Forearm vascular conductance (FVC) was calculated from forearm blood flow (FBF; Doppler ultrasound) and arterial pressure (brachial catheter), as FVC = FBF÷MAP. Lean forearm mass was determined (DEXA), and relative FVC (FVCrel; FBF • 100 mmHg−1 • 100 g−1 lean mass) was calculated. Baseline FVCrel was determined prior to exercise. Steady‐state exercise was reached within 2 minutes, and data were quantified from minute 4.5–5. Intra‐arterial infusion of L‐NMMA occurred from minutes 5–10 of exercise, and steady‐state data were quantified from minute 9.5–10. The change in FVCrel (ΔFVCrel) from baseline to steady‐state quantified the vasodilatory response to exercise, whereas the ΔFVCrel from steady‐state exercise to exercise+L‐NMMA quantified the contribution of NOS to exercise.ResultsResults are mean ± SD. Overall, women exhibited greater vasodilation (main effect for sex; ΔFVCrel, 18 ± 8 vs. 13 ± 6; p = 0.001). Furthermore, lean subjects exhibited greater vasodilation than obese subjects (main effect for group; ΔFVCrel, 17 ± 6 vs. 14 ± 9; p = 0.002). Contrary to the hypothesis, there was no sex‐by‐group interaction (p = 0.67). L‐NMMA infusion decreased steady‐state exercise FVCrel; but this response was not different by sex, obesity, or sex‐obesity interaction (p = 0.66).ConclusionsThese data indicate during dynamic exercise in young adults, exercise vasodilation: 1) is greater in females than males, 2) is reduced in obese compared to lean similarly between sexes, and 3) is mediated by a similar contribution of NO. Therefore, the differences observed in sex and group with steady‐state exercise are likely mediated by NO‐independent signaling.Support or Funding InformationHL105820, HL007936This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.