Reduced Insulin Sensitivity in Young, Normoglycemic Subjects, Alters Tissue Oxygenation During Post Occlusive Reactive Hyperemia

Abstract

INTRODUCTION: Near-infrared spectroscopy (NIRS) measures of the tissue oxygen saturation ([StO2]) reperfusion rate during post occlusive reactive hyperemia (PORH) has recently been correlated with flow mediated dilation (%FMD) of the popliteal artery (McLay et.al. 2016). Cardiovascular disease is associated with impairments in %FMD. Reduced insulin sensitivity may negatively affect the vascular system for many years prior to a pre-diabetic/diabetic diagnosis. PURPOSE: To determine if static and dynamic, [StO2] parameters during PORH are correlated with metabolic markers in healthy, young, normoglycemic subjects. METHODS: Glucose (G) and insulin (I), both in fasting (F) conditions and during an oral glucose tolerance test (OGTT), were measured in twenty-three, young (18-26y), healthy subjects (12M/11F). Each subject underwent upper limb, PORH with oxy- ([O2Hb]) and deoxy- [hemoglobin + myoglobin], ([HHb]) measured in the skeletal muscle of the antebrachium by NIRS. [StO2] was calculated [O2Hb]/ Total hemoglobin ([O2Hb] + [HHb]) at rest, during the cuff, and during PORH. Parameters describing the amplitude and time course of the response were measured. Hepatic insulin sensitivity (ISIHOMA), whole body insulin sensitivity (Matsuda Index), area under the curve for I and GLU, FI and FG and 2-HR GLU were measured. RESULTS: FI (range 2.43 - 12.51 μIU/ml) was significantly negatively correlated (r=0.43, P=0.02) with the amount of change of [StO2] during reperfusion (Δ [StO2]) (range 13.94 - 38.66%) and significantly positively correlated (r=0.52, P=0.005) with the minimum [StO2], a measure of extraction, during the cuff (Min [StO2]) (range 35.97 - 61.87%). ISIHOMA (range 0.37-2.07) was significantly positively correlated (r=0.57, P=0.002) with Δ [StO2] and significantly negatively correlated (r=0.56, P=0.006) with Min [StO2]. There was no significant correlation between any metabolic parameter and [StO2] upslope (initial slope of [StO2] following cuff release). CONCLUSIONS: Δ [StO2], a measure of the amount of reperfusion, and Min [StO2], a measure of extraction during the cuff, were correlated with FI and ISIHOMA, two of the longest used markers of metabolic function. NIRS-derived [StO2] may be a useful tool for assessing levels of reduced insulin sensitivity in normoglycemic, young adults.