A stimulating effect of glucose on somatostatin release is impaired in noninsulin-dependent diabetes mellitus.

The effect of oral glucose (1 g/kg BW) on levels of immunoreactive somatostatin (SLI) in peripheral venous plasma was investigated in young and older nondiabetic subjects (mean ages, 25.8 and 56.7 yr, respectively) as well as in subjects with decreased iv glucose tolerance (K value less than 1.0) and in diet-treated diabetic patients with fasting hyperglycemia (blood glucose, greater than 7.0 mmol/liter). SLI was assayed after extraction of plasma on silica glass beads. In control experiments (glucose omitted), SLI levels tended to decline. Ingestion of glucose was followed by a moderate (52% or less) increase in SLI levels in subjects with normal or decreased iv glucose tolerance. The stimulating effect was sustained for 90 or 120 min after glucose ingestion and the increase in plasma SLI was significant (P less than 0.05-0.02) whether in relation to prestimulatory values or control experiments. In contrast, in overtly diabetic patients, glucose ingestion was not followed by increased SLI levels. It is concluded that oral glucose stimulates SLI secretion in individuals of different ages and with varying degrees of glucose tolerance, but the response is impaired in type 2 diabetic patients with fasting hyperglycemia.