Varghese RT, et al. – In this study, analysts tried to compare the performance of population–based kinetics to directly measured C–peptide kinetics when used to calculate β–cell responsivity indices. The outcomes demonstrate the use of population–based measures of C–peptide kinetics to estimate β–cell function during oral glucose tolerance test (OGTT).

Methods

• Analysts applied somatostatin to inhibit endogenous insulin secretion in 56 nondiabetic subjects.
• Subsequently, they administered a C–peptide bolus and applied the changing concentrations to calculate individual kinetic parameters of C–peptide clearance.
• Furthermore, they were studied on 2 occasions in random order applying an oral glucose tolerance test (OGTT).
• On one occasion, free fatty acid (FFA) elevation to cause insulin resistance, was achieved by infusion of intralipid+heparin.
• They further calculated disposition Index (DI) by the oral minimal model using either population–based or individual C–peptide kinetics.

Results

• As per the results, marked differences were observed in the exchange parameters (k12 and k21) of the model describing C–peptide kinetics, but smaller differences in the fractional clearance, i.e. the irreversible loss from the accessible compartment (k01), obtained from population–based estimates compared to experimental measurement.
• The evidence showed that DI estimated using individual kinetics correlated well with those estimated using population–based kinetics since it is predominantly influenced by k01.