1793-P: C-Peptide Kinetics: The Van Cauter Population Model May Not Be Applicable to Post–Gastric Bypass Adults with Postprandial Hyperinsulinemic Hypoglycemia

Insulin secretion is key to understand postprandial hyperinsulinemic hypoglycemia (PHH), an increasingly recognized and potentially debilitating complication of gastric bypass (GB) surgery. To assess it noninvasively, the Oral C-peptide Minimal Model (OCMM) can be used. This requires to know C-peptide (CP) metabolic clearance rate (MCR) usually fixed to the values predicted by the Van Cauter (VC) population model, but this has never been assessed in PHH individuals. Here, the aim is to fill this gap. Two groups of post-GB adults with PHH underwent either a 75g oral glucose (11F/5M; age=43±8 y; BMI=28.2±7.1kg/m2) or a 60g mixed-meal (9F/3M; age=44±10y; BMI=27.4±3.9kg/m2) tolerance test with sampling for plasma glucose and CP over 3.5 and 3h, respectively. The OCMM was used to describe CP concentration with CP kinetics fixed to VC or estimated based on data (DB). Model performance was assessed by its ability to predict CP data. In both groups, the VC approach underestimated CP-peak and overestimated CP-tail, while the DB one well predicted CP data in all subjects (Figure 1A). As a consequence, MCR resulted significantly higher with DB than VC approach (Figure 1B). The present findings question the validity of the VC population model to predict CP kinetics in PHH patients and call for CP bolus experiments to develop a reliable kinetic model in this population.