GIP-induced vasodilation in human adipose tissue involves capillary recruitment

Area of Science:

• Metabolism
• Physiology
• Endocrinology

Background:

• Glucose-dependent insulinotropic polypeptide (GIP) and hyperinsulinemia are known to increase blood flow and triglyceride clearance in subcutaneous abdominal adipose tissue.
• The precise mechanism by which this increase occurs, specifically whether it involves capillary recruitment, has not been fully elucidated.

Purpose of the Study:

• To investigate whether the increase in adipose tissue blood flow (ATBF) induced by GIP in combination with hyperinsulinemia involves capillary recruitment in lean healthy humans.

Main Methods:

• Eight lean healthy volunteers underwent a hyperglycemic-hyperinsulinemic clamp to simulate postprandial glucose and insulin levels.
• Subcutaneous abdominal adipose tissue blood flow (ATBF) was measured using the 133Xenon clearance technique.
• Microvascular blood volume in adipose tissue was assessed using contrast-enhanced ultrasound imaging during GIP or saline infusion.

Main Results:

• During saline infusion and clamp, ATBF and microvascular blood volume remained unchanged.
• GIP infusion combined with the clamp resulted in a fourfold increase in ATBF (from 2.7 to 11.4 mL/min/100 g).
• Contrast-enhanced ultrasound showed a significant increase in microvascular blood volume following GIP infusion, indicating capillary recruitment.

Conclusions:

• The observed increase in ATBF during GIP infusion in lean subjects is mediated by capillary recruitment.
• This capillary recruitment likely enhances the interaction between circulating lipoproteins and lipoprotein lipase.
• The findings suggest a mechanism promoting increased lipid uptake by adipose tissue.