EFFECT OF LIPECTOMY ON GROWTH AND DEVELOPMENT OF HYPERINSULINEMIA ANDHYPERLIPIDEMIA IN THE ZUCKER RAT

The Zucker fat rat inherits obesity and hyperinsulinemia, exhibits ins ulin resistance, and is, therefore, a model of adult onset, or type II , diabetes. The purpose of this study was to determine if excision of fat depots from the infant Zucker (fa(+)/fa(+)) rat would affect growt h, fat cell number, hyperinsulinism, and hyperlipidemia. In the experi mental design, 10 percent of the total body weight (inguinal and inter scapular depots) was excised at 6 weeks of age from 18 fat and 18 lean (fa(+)/fa(-)) litter mates, with 18 fat and 18 lean rats serving as n onoperated controls. At intervals, serum glucose, insulin, cholesterol , and triglycerides were measured. Initially, the operated fat group w as significantly (p < 0.01) lighter than the nonoperated group. By 9 w eeks postoperatively, the operated fat rat group had regained weight a nd continued to grow at the same rate as the nonoperated fat rats beca use of intra-abdominal fat depots. Lipectomy had no effect on growth r ate of the lean rat group.;Although lipectomy caused no consistent cha nge in serum glucose or insulin levels, it caused a significant decrea se in lipid levels. For example, the operated fat rats had a reduction in cholesterol from 876 to 171 mg/dl by 15 weeks postoperatively, and serum cholesterol persisted at about 50 percent of the nonoperated gr oup throughout the rest of the study (38 weeks postoperatively). Even a greater reduction in triglyceride levels occurred, for example, from 7415 to 1082 mg/dl at 24 weeks postoperatively. Lipectomy did not cau se a change in lipid levels in the lean group. It is concluded that th e lipectomy in the Zucker fat group is an excellent model to evaluate the effects of changes in fat cell number on lipid metabolism.