Contribution of organ blood flow, intrinsic tissue clearance and glycaemia to the regulation of glucose use in obese and type 2 diabetic rats: A PET study

Background and aimsChronic hyperglycaemia aggravates obesity and diabetes mellitus. The use of glucose by body organs depends on several factors. We sought to investigate the role of blood flow, intrinsic tissue glucose clearance and blood glucose levels in regulating tissue glucose uptake under fasting conditions (FCs) and in response to acute hyperglycaemia (AH) in obese and type 2 diabetic rats.Methods and resultsThirty-six Zucker rats were studied by positron emission tomography to quantify perfusion and glucose uptake during FC and after AH in the liver, myocardium, skeletal muscle and subcutaneous adipose tissue. Progressively higher glucose uptake rates were observed from lean to obese (p < 0.05) and to diabetic rats (p < 0.05) in all tissues during both FC and AH. In FC, they were increased of 7–18 times in obese rats and 11–30 times in diabetic rats versus controls. Tissue glucose uptake was increased by over 10-fold during AH in controls; this response was severely blunted in diseased groups. AH tended to stimulate organ perfusion in control rats. Tissue glucose uptake was a function of intrinsic clearance and glycaemia (mass action) in healthy animals, but the latter component was lost in diseased animals. Differences in perfusion did not account for those in glucose uptake.ConclusionsEach organ participates actively in the regulation of its glucose uptake, which is dependent on intrinsic tissue substrate extraction and extrinsic blood glucose delivery, but not on perfusion, and it is potently stimulated by AH. Obese and diabetic rats had an elevated organ glucose uptake but a blunted response to acute glucose intake.