SOMATOSTATIN ENHANCES INSULIN-STIMULATED GLUCOSE-UPTAKE IN THE PERFUSED HUMAN FOREARM

Somatostatin is widely used in experimental metabolic studies to contr ol hormone actions. It has also been suggested that, in addition to it s well known suppressive effects, somatostatin per se may increase ins ulin sensitivity. In order to examine this suggestion, we gave six hea lthy male volunteers (age 33 +/- 1 yr, mean +/- SEM; body mass index, 24.1 +/- 0.6 kg/m(2)) either a local intraarterial (brachial artery) o r a systemic venous infusion of 25 mu g/h somatostatin twice. The stud y consisted of a 1-h basal period and a 2-h systemic hyperinsulinemic (0.4 mU/ kg . min) euglycemie clamp. Compared with the systemic contro l infusion, local forearm perfusion with somatostatin caused a 55% inc rease in insulin-stimulated forearm glucose uptake (0.74 +/- 0.18 vs. 0.47 +/- 0.19 mmol/L, P < 0.05). Intraarterial somatostatin perfusion did not alter basal forearm glucose uptake (0.14 +/- 0.07 us. 0.17 +/- 0.12 mmol/L), the amount of glucose administered during the clamp (M- value, 3.2 +/- 0.5 vs. 3.0 +/- 0.6 mg/kg . min), or the levels of insu lin, C-peptide, glucagon, or GH. Intermediary metabolite exchange acro ss the forearm, total forearm blood flow, and oxygen saturations also remained stable. Glucose concentrations were slightly higher (0.06 +/- 0.01 mmol/L) in arterial than in arterialized blood, whereas lactate concentrations were comparatively decreased (108 +/- 51 mu mol/L) in a rterial blood. Our data suggest that somatostatin increases insulin-st imulated muscle utilization of glucose through local mechanisms. Altho ugh the nature of this increase remains to be established, it should b e taken into consideration in metabolic studies using somatostatin.