LIPOLYTIC EFFECT OF IN-VIVO LEPTIN ADMINISTRATION ON ADIPOCYTES OF LEAN AND OB OB MICE, BUT NOT DB/DB MICE/

The present study has examined the effect of a single in vivo intraper itoneal injection of the adipocyte-derived hormone, leptin, on the in vitro lipolysis of fat cells of different types of mice. Administratio n of 1 and 10 mg leptin per kg body weight to ob/ob mice significantly increased (P < 0.0001) the basal lipolytic activity compared to ob/ob mice receiving vehicle solution (phosphate-buffered saline, PBS), The highest leptin dose tested (10 mg/kg body weight) produced a threefol d increase in basal lipolysis, In lean mice administration of 10 mg le ptin per kilogram of body weight produced an increase in basal lipolys is of 52.7% (P < 0.01), However, in db/db mice none of the three lepti n doses injected had a significant effect on the lipolytic activity of adipocytes relative to basal lipolysis observed in db/db mice injecte d with PBS only. These data provide evidence for a lipolytic effect of leptin on white adipose tissue, which operates independently from cha nges in food intake, body weight, and the size of the fat stores. (C) 1998 Academic Press.