Lactate Metabolism of Adipose Tissue Investigation of Physiological and Pathophysiological Conditions in Man

The technique of open flow microperfusion was redesigned and evaluated in order to investigate influences like hyperinsulinemia or exercise on lactate metabolism of subcutaneous adipose tissue. Open flow microperfusion is based on a double lumen catheter which is inserted into the tissue region of interest and is perfused by an isotonic fluid. In the present thesis it was clearly demonstrated that, using the technique of open flow microperfusion, the interstitial compartment of subcutaneous adipose tissue is investigated. During basal and hyperinsulinemic euglycemic clamp conditions, the subcutaneous adipose lactate concentration was significantly higher when compared with the arterialized plasma lactate concentration. It was demonstrated that insulin stimulates the lactate production of subcutaneous adipose tissue but no significant correlation was found between increasing plasma insulin and subcutaneous lactate concentrations during hyperglycemic clamp conditions. The subcutaneous adipose lactate concentration, when measured during cycle ergometer exercise, showed a delayed and lower peak than the capillary blood lactate concentration and therefore, did not show a relation to the capillary blood lactate concentration being strong enough to serve as an alternative to blood sampling.