Hepatic insulin extraction and insulin clearance in patients with essential hypertension

To understand the mechanism of hyperinsulinemia in patients with high blood pressure, we studied 20 untreated essential hypertensives and 20 age, sex and body mass index-matched normotensive control subjects. C-peptide concentrations and C-peptide to insulin molar ratio in response to a 75 g oral glucose challenge were used to evaluate the beta cells function and for calculation of hepatic extraction of insulin. Modified insulin suppression test was employed to compared the insulin-stimulated glucose uptake and insulin clearance rate between two groups. Patients with hypertension had significantly higher plasma glucose, insulin and C-peptide responses as compared to normal subjects (P < 0.05, p < 0.01, and P < 0.03, respectively). Mean steady state plasma glucose (SSPG) concentrations were also higher in hypertensive group than normotensive group (11.5 +/- 1.4 vs 6.7 +/- 0.9 mmol/L, p < 0.01) despite that mean steady state plasma insulin (SSPI) values were relatively similar, indicating the presence of insulin resistance. Hepatic insulin extraction was found to be elevated in patients with high blood pressure when compared to normal subjects (82 +/- 3 vs 72 +/- 2%, p < 0.05). However, there were no difference in insulin clearance rate between two groups (592 +/- 38 vs 559 +/- 40 mL/m2/min, p = NS). In conclusion, hyperinsulinemia in patients with hypertension result from hypersecretion of beta cells and increased hepatic extraction of insulin. No difference was found in insulin clearance rate between hypertensive and normotensive subjects.