WHOLE-BODY FAT OXIDATION IS RELATED TO IN-SITU ADIPOSE-TISSUE LIPOLYTIC RESPONSE TO ISOPROTERENOL IN MALES

A high 24-h respiratory quotient (RQ), i.e., low fat oxidation, predic ts weight gain. To determine whether impaired fat mobilization (lipoly sis) may contribute to weight gain, we studied the relation between li polytic response to nonselective p-adrenergic stimulation and RQ measu red in a respiratory chamber in 21 males (11 Caucasians, 10 Pima India ns; age 32 +/- 5 yr, weight 93 +/- 24 kg, body fat 30 +/- 8%; means +/ - SD) and 23 females (10 Caucasians, 13 Pima Indians; age 32 +/- 9 yr, weight 95 +/- 26 kg, body fat 44 +/- 8%). Lipolytic response was asse ssed as the relative increase in dialysate glycerol concentration (% a bove baseline) when isoproterenol (1 mu mol/l) was added to the perfus ate of a microdialysis probe inserted in the abdominal subcutaneous ad ipose tissue. In males, but not in females, basal RQ measured during s leep from 0500 to 0630 and adjusted for waist circumference was negati vely correlated to lipolytic response (r = -0.66, P = 0.001). The resu lts suggest that in males, impaired p-adrenergic-mediated lipolysis ma y contribute to low rates of fat oxidation, a condition known to predi spose to weight gain.