Acute effects of acylated ghrelin on salbutamol-induced metabolic actions in humans

The aim of this study is to describe a potential modulatory effect of acute acylated ghrelin (AG) administration on the glucose, insulin, and free fatty acids (FFA) responses to salbutamol (SALBU). Six healthy young male volunteers underwent the following four testing sessions in random order at least 7 days apart: (a) acute AG administration (1.0 μg/kg i.v. as bolus at 0′); (b) SALBU infusion (0.06 μg/kg/min i.v. from −15′ to +45′); (c) SALBU infusion + AG; and (d) isotonic saline infusion. Blood samples for glucose, insulin, and FFA levels were collected every 15 min. As expected, with respect to saline, SALBU infusion induced a remarkable increase in glucose (10.8 ± 5.6 mmol/l × min; P < 0.05), insulin (2436.8 ± 556.9 pmol/l × min; P < 0.05), and FFA (18.9 ± 4.5 mmol/l × min; P < 0.01) levels. A significant increase in glucose (7.4 ± 3.9 mmol/l × min; P < 0.05) and FFA levels (10.0 ± 2.8 mmol/l × min; P < 0.01) without significant variations in insulin levels were recorded after AG administration. Interestingly, the hyperglycemic effect of AG appeared to be significantly potentiated during SALBU infusion (26.7 ± 4.8 mmol/l × min; P < 0.05). On the other hand, the stimulatory effect of SALBU on insulin and FFA was not significantly modified by AG administration. The results of this study show that acute AG administration has a synergic effect with β₂-adrenergic receptor activation by SALBU on blood glucose increase, suggesting that their pharmacological hyperglycemic action takes place via different mechanisms. On the other hand, AG has a negligible influence on the other pharmacological metabolic effects of SALBU infusion.