Insulin at physiological concentrations increases microvascular perfusion in human myocardium

Area of Science:

• Cardiovascular Physiology
• Endocrinology
• Metabolic Studies

Background:

• Vascular endothelium plays a key role in regulating blood flow and nutrient delivery.
• Insulin and feeding are known to increase microvascular perfusion in skeletal muscle and cardiac regions.
• The effect of physiological insulin concentrations on human myocardial microcirculation requires further investigation.

Purpose of the Study:

• To determine if insulin, at concentrations relevant to normal physiology, enhances microvascular perfusion in the human myocardium.
• To investigate the specific parameters of microvascular function affected by insulin in the heart.

Main Methods:

• Utilized myocardial contrast echocardiography (MCE) and insulin-clamp techniques in 13 healthy young adults.
• Measured cardiac microvascular blood volume (MBV), microvascular flow velocity (MFV), and microvascular blood flow (MBF) at baseline and during insulin infusion.
• Assessed brachial artery parameters to evaluate systemic vascular responses.

Main Results:

• Insulin infusion significantly increased myocardial MBV by 23% at 60 minutes and 41% at 120 minutes (P < 0.01 and P = 0.001, respectively).
• Insulin-mediated myocardial MBF increased significantly, driven by the rise in MBV, while MFV remained unchanged.
• Brachial artery diameter, flow velocity, and total blood flow also increased significantly with insulin infusion.

Conclusions:

• Insulin, at physiologically relevant concentrations, increases microvascular perfusion in human heart muscle by augmenting cardiac MBV.
• This insulin-mediated effect on cardiac microcirculation is observed in healthy, insulin-sensitive individuals.
• The findings suggest a significant role for insulin in regulating myocardial oxygen and substrate delivery.