Near-infrared spectroscopy assessment of microvasculature detects difference in lower limb vascular responsiveness in obese compared to lean individuals

Background: Microvascular dysfunction is an early complication in obesity-related cardiovascular disease (CVD) that can lead to changes in hemodynamic function and endothelial cell expression throughout the vasculature that is vessel specific. This study aimed to evaluate whether the near-infrared spectroscopy (NIRS) combined with a vascular occlusion (VOT) assessment was capable of detecting differences in vascular responsiveness within the microvasculature of the lower limb between lean and obese individuals. Methods and results: Twenty lean (BMI = 21.6 +/- 1.3) and 17 obese individuals (BMI = 33.9 +/- 1.1) participated in the study. Individuals underwent a VOT (5 min of baseline, 5 min of occlusion, and 8 min following cuff release) and vascular responsiveness was evaluated by the Slope 2 (Slope 2 StO(2)) and the area under the curve (StO2(Auc)) of oxygen saturation (StO(2)) signal during reperfusion. The difference between the minimal and the maximal value of StO(2) was calculated as the Amplitude of the StO(2) response. The Slope 2 StO(2) of the obese individuals was smaller (0.68 +/- 0.07%s(-1)) than the Slope 2 StO(2) of the lean individuals (1.08 +/- 0.13%-s -1 ;P < 0.05). The StO(2) Auc of the obese was smaller (978 +/- 169%s(-1)) than the StO2(Auc) of the lean individuals (1708 +/- 168%s(-1); P < 0.001). The amplitude of StO(2) was smaller in obese individuals than the lean ones (30.4 +/- 2.9 vs 21.6 +/- 1.3 StO(2) (%), respectively; P < 0.05). There was a significant correlation between Slope 2 StO(2) and StO2(Auc) for lean individuals (r = 0.745; P < 0.001). Conclusion: This study demonstrated differences in vascular responses within the microvasculature of the lower limb between lean and obese individuals.