REGULATION OF LIPOLYSIS HG THE SYMPATHETIC NERVOUS-SYSTEM - A MICRODIALYSIS STUDY IN NORMAL AND SPINAL CORD-INJURED SUBJECTS

To evaluate the regulation of lipolysis by the sympathetic nervous sys tem, eight spinal cord-injured (SCI) subjects with a lesion above T5 r esulting in a decentralization of the lower-body sympathetic nervous s ystem and adrenal medulla (age, 36 +/- 2 years; weight, 82 +/- 5 kg; b ody fat mass, 26.8 +/- 3.0 kg; all mean +/- SE) and nine control subje cts (age, 33 +/- 2; weight, 80 +/- 3; NS; body fat mass, 16.1 +/- 1.5 kg; P < .01) were investigated after fasting overnight. Each subject w as studied with subcutaneous microdialysis and Xe-133-clearance adipos e tissue blood flow (ATBF) in the umbilical and clavicular regions dur ing postabsorptive rest and after sympathoexcitatory stimulation by me ans of mental stress and isometric handgrip exercise. SCI subjects had an increased body fat mass, hyperinsulinemia, and an elevated lipolyt ic rate at rest compared with control subjects. ATBF and lipolysis wer e activated to a normal extent following mental stress and isometric h andgrip exercise in the umbilical region in control subjects. ATBF was increased in tissue above but not below the lesion level in SCI subje cts following mental stress, Glycerol release was not different betwee n groups in either tissue region despite significantly lower noradrena line and adrenaline levels in SCI subjects, This finding argues agains t a significant adrenergic control of the lipolytic rate at rest, Furt hermore, the small differences in stimulated glycerol release between groups, as well as the increased plasma glycerol levels in SCI subject s, cast doubt on the view that interruption of adrenergic activity bel ow the lesion is the sole mechanism underlying the increased body fat mass in SCI subjects. Copyright (C) 1997 by W.B. Saunders Company.