Relation between insulin kinetics and insulin sensitivity in pregnancy

Abstract

Background: Different time-concentration profiles of plasma insulin following insulin modification of a frequently sampled intravenous glucose-tolerance-test (FSIVGTT) were observed in a study investigating maternal metabolism and fetal macrosomia. We aimed to investigate whether these differences were related to the volume of distribution of insulin, insulin clearance, or both. Design: Forty-four women were studied between 33 and 35 weeks' gestation using an insulin-modified FSIVGTT. Specific insulin was assayed with an enzyme-linked immunosorbent assay. Insulin sensitivity was calculated using the minimal model and the homeostasis model assessment (HOMA). The volume of distribution and clearance of insulin were calculated from measurements between 2 and 155 min after insulin modification using a one-compartment model. Results: In accordance with the method for deriving the volume of distribution, there was a significant negative correlation between the increment in insulin concentration and the volume of distribution (rho = -0.92, P < 0.0001). The insulin increment was also related negatively to the clearance of insulin (rho = -0.88, P < 0.0001). There was a significant correlation between the volume of distribution and both the insulin sensitivity index (rho = 0.56, P < 0.0001) and HOMA-%S (rho = 0.30, P = 0.048), and between the clearance of insulin and both the insulin sensitivity index (rho = 0.83, P < 0.0001)) and HOMA-%S (rho = 0.34, P = 0.025). Conclusion: The different time-concentration profiles of plasma insulin resulted from differences in the volume of distribution and clearance of insulin. There was a correlation between insulin kinetics and the insulin sensitivity index. Further research is required to investigate possible mechanisms by which insulin kinetics may be related to insulin sensitivity.