The association between near-infrared spectroscopy assessment of microvascular reactivity and flow-mediated dilation is disrupted in individuals at high risk for cardiovascular disease.

OBJECTIVE: This study aimed to evaluate the correlation between the NIRS-derived reperfusion slope and %FMD in the arm of healthy and at high risk for CVD individuals. METHODS: Twelve healthy (24 ± 4 years) and twelve at high risk for cardiovascular disease (65 ± 11 years) individuals participated in the study. The individuals were submitted to a conduit artery FMD followed by a NIRS-VOT microvascular function test in the arm. Microvascular responsiveness was calculated as the forearm reperfusion slope, and macrovascular function was assessed as the percent of change in FMD (%FMD) of the brachial artery. RESULTS: There was a significant correlation between reperfusion slope and %FMD (R = 0.61, P < 0.05) in the healthy group; however, no significant correlation between FMD and reperfusion slope (R = -0.21, P > 0.05) was found in individuals at high risk for CVD. CONCLUSION: The correlation between NIRS-derived reperfusion slope and %FMD was disrupted in the arm of individuals at high risk for cardiovascular disease compared to healthy individuals. The findings of the present study reinforce the importance of examining vascular function at microvasculature and conduit artery level, especially in populations with risk factors for CVD.

Noninvasive and in vivo assessment of upper and lower limb skeletal muscle oxidative metabolism activity and microvascular responses to glucose ingestion in humans.

This study investigated changes in muscle oxidative metabolism and microvascular responsiveness induced by glucose ingestion in the upper and lower limbs using near-infrared spectroscopy (NIRS). Fourteen individuals (aged 27 ± 1.4 years) underwent 5 vascular occlusion tests (VOT) (pre-intervention (Pre), 30 min, 60 min, 90 min, and 120 min after glucose challenge). NIRS-derived oxygen saturation (StO2) was measured on the forearm and leg muscle at each VOT. Muscle oxidative metabolism was determined by the StO2 downslope during cuff inflation (deoxygenation slope); microvascular responsiveness was estimated by the StO2 upslope (reperfusion slope) following cuff deflation. There was a significant increase in arm (p < 0.05; 1-ß = 0.860) and leg (p < 0.05; 1-ß = 1.000) oxidative metabolism activity as represented by the faster deoxygenation slope at 60, 90, and 120 min (0.08 ± 0.03, 0.08 ± 0.03, 0.08 ± 0.02%·s-1, respectively) (leg) and at 90 min (0.16 ± 0.08%·s-1) (arm) observed after glucose ingestion when compared with their respective Pre values (leg = 0.06 ± 0.02; arm = 0.11 ± 0.04%·s-1). There was a significant increase in arm (p < 0.05; 1-ß = 0.880) and leg (p < 0.05; 1-ß = 0.983) reperfusion slope at 60 min (arm = 3.63 ± 2.1%·s-1; leg = 1.56 ± 0.6%·s-1), 90 min (arm = 3.91 ± 2.1%·s-1; leg = 1.60 ± 0.6%·s-1), and 120 min (arm = 3.91 ± 1.6%·s-1; leg = 1.54 ± 0.6%·s-1) when compared with their Pre values (arm = 2.79 ± 1.7%·s-1; leg = 1.26 ± 0.5%·s-1). Our findings showed that NIRS-VOT technique is capable of detecting postprandial changes in muscle oxidative metabolism activity and microvascular reactivity in the upper and lower limb. Novelty NIRS-VOT is a promising noninvasive clinical approach that may help in the early, limb-specific detection of impairments in glucose oxidation and microvascular function.

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 ±â€¯1.3) and 17 obese individuals (BMI = 33.9 ±â€¯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 StO2) and the area under the curve (StO2AUC) of oxygen saturation (StO2) signal during reperfusion. The difference between the minimal and the maximal value of StO2 was calculated as the Amplitude of the StO2 response. The Slope 2 StO2 of the obese individuals was smaller (0.68 ±â€¯0.07%·s-1) than the Slope 2 StO2 of the lean individuals (1.08 ±â€¯0.13%·s-1;P < 0.05). The StO2AUC of the obese was smaller (978 ±â€¯169%·s-1) than the StO2AUC of the lean individuals (1708 ±â€¯168%·s-1; P < 0.001). The amplitude of StO2 was smaller in obese individuals than the lean ones (30.4 ±â€¯2.9 vs 21.6 ±â€¯1.3 StO2 (%), respectively; P < 0.05). There was a significant correlation between Slope 2 StO2 and StO2AUC 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.