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IGF-I increases forearm blood flow without increasing forearm glucose uptake
M Pendergrass1, E Fazioni, D Collins
1Diabetes Division, Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78284, USA.
The American Journal of Physiology
|August 4, 1998
Summary
Increasing blood flow alone does not enhance muscle glucose uptake in healthy individuals. This suggests that improving glucose delivery requires both increased blood flow and the muscle's intrinsic ability to utilize glucose.
Area of Science:
- Endocrinology
- Metabolic Research
- Human Physiology
Background:
- Decreased insulin-mediated muscle glucose uptake is a hallmark of insulin resistance and type 2 diabetes.
- Impaired insulin-induced limb blood flow may reduce glucose delivery to muscles, contributing to insulin resistance.
Purpose of the Study:
- To investigate if increased forearm blood flow, induced by human insulin-like growth factor (IGF-I), can stimulate glucose uptake independently of enhancing intrinsic muscle glucose uptake capacity.
- To differentiate the effects of blood flow augmentation from direct stimulation of muscle glucose metabolism.
Main Methods:
- Intra-arterial infusion of human IGF-I at high (0.4 microg . kg-1 . min-1) and low (0.04 microg . kg-1 . min-1) doses in healthy controls.
- Forearm balance technique to measure forearm blood flow and arteriovenous glucose concentration difference.
- Calculation of forearm glucose uptake based on blood flow and glucose concentration gradients.
Main Results:
- High-dose IGF-I significantly increased forearm blood flow (approx. twofold) and forearm glucose uptake (P = 0.09).
- Low-dose IGF-I increased forearm blood flow (59%) but decreased the arteriovenous glucose difference, resulting in no significant change in glucose uptake.
- The increase in glucose uptake with high-dose IGF-I was not statistically significant, despite a marked increase in blood flow.
Conclusions:
- Augmenting forearm blood flow solely through IGF-I, without enhancing the muscle's intrinsic glucose extraction capability, does not significantly increase forearm muscle glucose uptake.
- These findings suggest that both adequate glucose delivery (blood flow) and intrinsic muscle metabolic capacity are crucial for insulin-mediated glucose uptake.