SYNERGISTIC EFFECTS OF FEEDING AND DEXAMETHASONE ON SERUM LEPTIN LEVELS

The objectives of this study were to determine the time course of the stimulatory effect of dexamethasone on serum leptin and whether it dep ends on food intake. Dexamethasone (4mg) was administered I.V. over 1 minute to healthy human volunteers (n=8) under fasting and feeding con ditions (2000 kcal given at three meals over 7 hours). At 10 hours, se rum leptin levels were increased only in the fed subjects (delta lepti n 10.6+/-1.6 vs -2.4+/-1.9 ng/ml, p=0.01, n=8). To assess the interact ive effect of food and dexamethasone on serum leptin, a subgroup (n=4) was studied under 4 conditions: 1) dexamethasone/fast; 2) dexamethaso ne/food; 3) saline/fast; 4) saline/food. Serum leptin declined from ba seline under the fasting conditions, with or without dexamethasone. Fe eding prevented the drop in serum leptin. in the dexamethasone/ food c ondition, leptin levels rose from baseline after 7 hours and doubled a fter 10 hours (p<0.05). The rise in serum leptin was significantly gre ater in the food/dexamethasone condition compared to all other conditi ons (p<0.05). In summary, dexamethasone has no independent effect on s erum leptin in the absence of food intake. Rather, dexamethasone appea rs to potentiate the food-induced increase in serum leptin. This syner gism may be mediated by insulin and/or other factors associated with f ood ingestion.