EVIDENCE FOR A ROLE OF INSULIN IN THE REGULATION OF ABDOMINAL ADIPOSE-TISSUE LIPOPROTEIN-LIPASE RESPONSE TO EXERCISE TRAINING IN OBESE WOMEN

Abdominal and femoral adipose tissue lipoprotein lipase (AT-LPL) activities were measured in ten obese pre-menopausal women (mean age 35 +/- 5 years) who took part in a six month endurance exercise training programme. The programme involved four to five 90 min training sessions per week at about 50 to 55% of maximal endurance power (VO2max). Before training, the ratio of insulin to glucose area measured during an oral glucose tolerance test (OGTT) was significantly correlated with fat mass (r = 0.72, P < 0.05) as well as with abdominal AT-LPL activity (r = 0.69, P < 0.05). The training programme induced a significant increase in VO2max (P < 0.05) whereas no significant change in the mean body composition was observed. Abdominal as well as femoral AT-LPL activities were significantly reduced after the exercise training programme (P < 0.05) whereas plasma post-heparin (PH) LPL activity was significantly increased by training (P < 0.05). No significant association was observed between changes in VO2max and in body composition parameters and changes in abdominal or femoral AT-LPL activities. However, changes in insulin sensitivity, as estimated by changes in the insulin area/glucose area ratio were positively correlated with changes in abdominal AT-LPL activity expressed on a per cell (r = 0.72, P < 0.05) or per surface area (r = 0.81. P < 0.01) basis. These results suggest that the reduction in AT-LPL activity in both fat depots following endurance training in obese women can occur despite the lack of significant decrease in body weight and average fat cell size. These results also suggest that the improvement in insulin sensitivity is an important correlate of the reduction of abdominal AT-LPL activity following endurance exercise training in obese women. Finally, this study provides further evidence for an important role of insulin in the regulation of abdominal AT-LPL activity in obese women.