Euglycemic Hyperinsulinemia Lowers Blood Pressure and Impedes Microvascular Perfusion More Effectively in Persons with Cardio-Metabolic Disease

In healthy humans, insulin at physiological concentrations exerts acute vasodilatory actions on both resistance and terminal arterioles, leading, respectively, to increased total blood flow and the microvascular network volume being perfused. The process of increasing capillary network volume is frequently referred to as “capillary recruitment”. Together these two vascular actions of insulin enhance the delivery of oxygen, nutrients, and insulin itself to tissues. Both processes are diminished by insulin resistance. Here we examined interactions between insulin’s acute (within 2 h) actions on blood pressure (both central and peripheral) and on capillary recruitment in healthy controls and in four distinct groups of people with heightened cardio-metabolic disease (CMD) risk: individuals with obesity, metabolic syndrome, and type 1 or type 2 diabetes. Insulin increased microvascular blood volume (MBV) more effectively in controls than in each of the four CMD risk groups (p < 0.001). Conversely, insulin lowered both central and peripheral systolic pressure (p < 0.05 or less) in each of the CMD risk groups but not in the controls. The insulin-induced blood pressure decrements were greater in the metabolic syndrome, type 2 diabetes, and obesity groups (p < 0.05 or less) than in the controls. The greater blood pressure declines likely reflect decreased sympathetic baroreceptor reflex tone. These effects on blood pressure combined with the diminished dilation of terminal arterioles due to microvascular insulin resistance in the CMD risk subjects led to decreased distal microvascular perfusion as evidenced by changes in MBV. These findings highlight the complex interplay between insulin’s actions on resistance and terminal arterioles in individuals with a high CMD risk, underscoring the importance of addressing microvascular dysfunction in these conditions.