Reduced insulin sensitivity in young, normoglycaemic subjects alters microvascular tissue oxygenation during postocclusive reactive hyperaemia

Abstract

New Findings What is the central question of the study?Are measures of reduced insulin sensitivity in young, normoglycaemic subjects correlated with near‐infrared spectroscopy‐derived microvascular responsiveness [tissue oxygen saturation reperfusion rate (STO2 upslope)] during postocclusive reactive hyperaemia? What is the main finding and its importance?A sevenfold range of hepatic insulin sensitivity is significantly correlated (r = 0.44, P = 0.02) with STO2 upslope after transient tissue ischaemia. Near‐infrared spectroscopy may be an important tool for determining altered microvascular function before onset of hyperglycaemia. Identification of pre‐type 2 diabetes much earlier than with the present clinical criteria is important for pre‐emptive measures against microvascular deterioration. Abstract Near‐infrared spectroscopy (NIRS) measurement of postocclusive reactive hyperaemia (PORH) tissue oxygen saturation reperfusion rate [STO2 upslope (as a percentage per minute)] has recently been correlated with the percentage of flow‐mediated dilatation (%FMD). Cardiovascular disease is associated with impairments in %FMD. Reduced insulin sensitivity may negatively affect the vascular system for many years before prediabetes/type 2 diabetes states. The aim of this study was to determine whether static and dynamic STO2 parameters during PORH are correlated with reduced insulin sensitivity in young, normoglycaemic subjects. Glucose and insulin were measured during an oral glucose tolerance test in 18‐ to 26‐year‐old, healthy subjects (11 men and 11 women), and STO2 was measured during PORH of antebrachial muscle. Hepatic (ISIHOMA) and whole‐body (ISICOMP) insulin sensitivities were calculated. The STO2 upslope was negatively correlated with minimal STO2 (r = −0.5, P = 0.01). The change of STO2 from minimum to baseline (ΔSTO2) was significantly negatively correlated with fasting insulin (r = −0.5, P = 0.01) and a positively correlated with ISIHOMA (r = 0.65, P = 0.001). The minimum STO2 was significantly negatively correlated with ISIHOMA, and STO2 upslope was significantly positively correlated with ISIHOMA (r = 0.44, P = 0.02). The minimum STO2 (a measure of O2 extraction while the cuff was inflated), ΔSTO2 (a measure of the amount of reperfusion) and STO2 upslope (a measure of responsiveness of the microcirculation to ischaemia) were all positively correlated with ISIHOMA, one of the longest‐used measures of insulin sensitivity. The NIRS‐derived STO2 might be a useful tool for assessing how levels of reduced insulin sensitivity in young, normoglycaemic adults affect the microvasculature.

Suitability of the muscle O2 resaturation parameters most used for assessing reactive hyperemia: a near-infrared spectroscopy study

“…Muscle O 2 resaturation rate parameters (StO 2slope _ 10s , StO 2slope _ 30s , and StO 2slope _ until_base ) are largely adopted to assess reactive hyperemia in hypertensive individuals, 4 gestational diabetic women, 14 and older adults at risk for CVD disease, 7 , 10 , 17 among other clinical groups. 13 , 18 Our findings demonstrated that only StO 2slope _ 10s was significantly slower in older adults with CVD risk factors compared to healthy older adults and to healthy young individuals, suggesting that StO 2slope_10s may be a more sensitive NIRS parameter for assessing reactive hyperemia. The StO 2slope _ 10s has typically been adopted to assess O 2 resaturation rate, since previous studies have reported that this parameter is correlated with reactive hyperemia measured in the brachial artery 20 and with FMD response.…”

“… 8 - 10 The sudden increase in the StO 2 signal during reperfusion enables various StO 2 parameters to be calculated, which, in general, are interpreted as measures of microvascular function. 3 The majority of StO 2 parameters adopted in previous studies include reperfusion rate (i.e., upslope of the StO 2 signal during the initial 10 s and 30 s, and until the StO 2 signal reaches baseline values), 11 - 13 magnitude of reperfusion (i.e., total area under the curve [AUC] of StO 2 and the difference between the lowest and highest StO 2 value), 4 , 13 - 17 and others (e.g., time to StO 2 baseline, time to StO 2 maximum, and AUC above the baseline). 13 , 15 , 18 , 19 …”

Putting the muscle back in microcirculation: From firefighters to near‐infrared spectroscopy

“…Building on this observation, using the same NIRS‐based reactive hyperaemia approach described above, Townsend, Deysher, Wu, and Barstow (2019) showed that although tissue reperfusion after arterial cuff occlusion was positively related to whole‐body insulin sensitivity (a precursor of cardiovascular disease), it was also negatively correlated with absolute tissue desaturation, and that the skeletal muscle metabolic rate (i.e. the change in tissue saturation throughout the cuff occlusion period) was positively related to whole‐body insulin sensitivity.…”

Mild obesity does not affect the forearm muscle microvascular responses to hyperglycemia

“…In order to simultaneously assess these responses, we combined NIRS-derived assessments of forearm muscle function and brachial artery FMD tests performed in obese and lean participants before and subsequent to an oral glucose tolerance test. [17][18][19][20][21] 2 | ME THODS…”

“…Thus, this study aimed to evaluate whether mild obesity‐specific differences in forearm microvascular and brachial artery adjustments occurred in response to a load in glucose. In order to simultaneously assess these responses, we combined NIRS–derived assessments of forearm muscle function and brachial artery FMD tests performed in obese and lean participants before and subsequent to an oral glucose tolerance test 17–21 …”