Microdialysis of glucose in subcutaneous adipose tissue up to 3 weeks in healthy volunteers

OBJECTIVE - To measure possible changes in dialysate glucose concentrations over time, to validate the diffusional model for glucose transport from tissue to the probe, and to evaluate the actual glucose concentration in adipose tissue. RESEARCH DESIGN AND METHODS - Glucose concentrations in the subcutaneous adipose tissue of five healthy subjects (age 25 +/- 2.7 years, BMI 23.2 +/- 2.3 kg/m(2) [mean +/- SD]) were measured by the microdialysis technique and compared with blood glucose. We applied microdialysis probes with hollow fibers of various membrane length (10-35 mm), used eight perfusion flow rates (0.5-20 mu l/min), and perfused four glucose solutions (0.0, 2.8, 8.3, 11.1 mmol/l). RESULTS - After implantation, a substantial decrease in glucose recovery to the lowest value of 26 +/- 10% of the final plateau value was noted during the first few hours (n = 4). Recovery increased and stabilized after 5-9 days at 84.0 +/- 7.4% of capillary blood glucose when a flow rate of 0.5 mu l/min was applied. According to the zero net-flux method, the glucose concentration in equilibrium, C-equi, with the surrounding tissue can be obtained. This concentration also decreases; however, 1 h after recovery, C-equi increases again over 1 or 2 days to a stable value that is not significantly different from the measured capillary blood glucose (P 0 mu l/min) is complicated for short-term clinical glucose measurements in adipose tissue. After stabilization, the mean equilibrium concentration of all subjects was equal to the mean capillary blood glucose concentration. Therefore, we conclude that capillary blood glucose concentration probably is the driving force for diffusion through the capillary wall into the probe and is not some interstitial concentration