Beta-adrenergic Stimulation and Blockade of the Release of Gastric Inhibitory Polypeptide and Insulin in Man

The effect of beta-adrenergic receptor stimulation with isoproterenol and blockade with propranolol on the release of gastric inhibitory polypeptide (GIP) and insulin was investigated in seven healthy volunteers. In the control experiment, the concentration of GIP in plasma increased from 30.1 (18.9-58.8) to 77.2 (44.2-121) pM after 30 g oral glucose. The concentration of insulin in serum increased from 7 (4-12) to 34 (13-76) mU/l. During infusion with isoproterenol, plasma GIP increased from 29.9 (25.7-39.1) to 47.1 (37.2-83.8) pM and insulin from 9 (5-15) to 37 (16-72) mU/l before oral glucose. After oral glucose, further increases of GIP to 111 (68.8-171) pM and of insulin to 103 (33-131) mU/l were observed. When propranolol was given in addition during this beta-receptor stimulation, plasma GIP after glucose increased to 82.2 (49.7-145) pM and serum insulin to 61 (9-133) mU/l. An isoproterenol-induced increase in the concentration of GIP and insulin was thus counteracted by propranolol. This strongly indicates that not only the insulin release but also the entero-insular axis as a total is influenced by beta-adrenergic mechanisms.