Insulin stimulated glucose disposal in peripheral tissues studied with microdialysis and stable isotope tracers

Background & aims: Methods to study glucose kinetics in vivo in specific tissues or tissue beds in humans are often not feasible due to invasiveness or costs of equipment needed. Here we investigate whether the loss (fractional extraction) of 2H7-glucose infused via a microdialysis catheter can be used to study glucose disposal in skeletal muscle and subcutaneous adipose tissue. Methods and results: A perfusion period of 2 h was needed to ensure an isotopic steady state in the microdialysis catheters in skeletal muscle and adipose tissue. In six healthy volunteers the fractional extraction increased during a hyperinsulinemic euglycemic clamp in both skeletal muscle and adipose tissue. Following 48 h of starvation in the same subjects, insulin was not able to increase the fractional extraction of 2H7-glucose from the microdialysis in comparison with a baseline measurement. Conclusions: In response to insulin infusion, the fractional extraction of 2H7-glucose from a microdialysis catheter increases in skeletal muscle and subcutaneous adipose tissue and this increase is blunted during insulin resistance induced by starvation. These results validate that the fractional extraction of a glucose tracers infused via microdialysis can be used as an index of glucose disposal in peripheral tissues or tissue beds.