Regulation of Non‐esterified Fatty Acid and Glycerol Concentration by Insulin in Normal Individuals and Patients with Type 2 Diabetes

Plasma glycerol and non‐esterified fatty acid (NEFA) concentrations were determined in the basal state and in response to physiological hyperinsulinaemia in 30 non‐obese individuals, 15 with Type 2 diabetes and 15 with normal glucose tolerance. Patients with Type 2 diabetes had higher basal concentrations of both glycerol (81 ± 7 (± SE) vs 61 ± 7 μmol l−1, p<0.05) and NEFA (842 ± 40 vs 630 ± 46 μmol l−1, p<0.002). Plasma NEFA and glycerol concentrations fell in both groups when steady‐state plasma insulin concentrations were raised to approximately 450 pmol l−1 by an infusion of exogenous insulin, but plasma concentrations of glycerol (28 ± 3 vs 13 ± 3 μmol l−1, p<0.002) and NEFA (186 ± 15 vs 109 ± 14 μmol l−1, p<0.001) were still higher in patients with Type 2 diabetes. Percentage decrease in glycerol from basal levels in response to insulin was significantly less in patients with Type 2 diabetes than in control subjects (64 ± 3 vs 80 ± 3 %, p<0.005); percentage decrease in plasma NEFA concentration was similar in the two groups (78 ± 3 vs 80 ± 4 %). These results suggest that both plasma glycerol and NEFA concentrations are higher than normal in patients with Type 2 diabetes when measured at the same insulin concentration, both under basal conditions and in response to physiological hyperinsulinaemia. However, in patients with Type 2 diabetes the percentage decrease in plasma glycerol concentration was significantly less than the percentage decrease in NEFA concentration (64 ± 3 vs 78 ± 3 %, p<0.001).