Concordance of in vivo microdialysis and in vitro techniques in the studies of adipose tissue metabolism

BACKGROUND: Adipose tissue metabolism can be investigated directly in vivo by microdialysis and indirectly in vitro using isolated adipocytes. The in vitro studies are relatively easy to make and they give information about s pecific tissue metabolism. The in vivo studies, on the other hand, are supp osed to give relevant data about tissue physiology interacting with other m etabolic systems at the body level. OBJECTIVE: To investigate the concordance between the results on responsive ness to stimulation of lipolysis from in vivo microdialysis and in vitro is olated adipocytes, SUBJECTS: Altogether 22 massively obese otherwise health y subjects (seven men and 15 women, age 41 (26-55) y, BMI 51.5 (37.5-73.9) kg/m(2), mean (range)) going through the gastric banding operation particip ated in the study. METHODS: The microdialysis study was done after an overnight fast at rest. Lipolysis was stimulated with isoprenaline that was perfused into the subcu taneous abdominal adipose tissue. Local blood flow was estimated by ethanol dilution method. Adipose tissue biopsy for the in vitro study was taken fr om subcutaneous abdominal region during the operation. Lipolysis in freshly isolated adipocytes was stimulated with different concentrations of adrena line or isoprenaline. RESULTS: Significant positive correlations were observed between the values of relative stimulation of lipolysis in isolated adipocytes and in the mic rodialysis study. These correlations improved after correcting for cell siz e or fat mass. CONCLUSION: The microdialysis study in vivo and lipolysis assay with isolat ed adipocytes in vitro provide concordant and complementary information of adipose tissue metabolism in the same individual.