A phenomenological model of plasma FFA, glucose, and insulin concentrations during rest and exercise

A phenomenological mathematical model for predicting FFA-glucose-insulin dynamics during rest and exercise was developed. The dynamical effects of insulin on glucose and FFA were divided into three parts: (i) insulin-mediated glucose uptake by tissues, (ii) insulin-mediated suppression of endogenous glucose production, and (iii) anti-lipolytic effects of insulin. Labeled and unlabeled intravenous glucose tolerance test data were used to estimate the parameters of the glucose model, which facilitated separation of insulin action on glucose utilization and production. The model successfully captured the FFA-glucose interactions at the systemic level. The model also successfully predicted mild-to-moderate exercise effects on FFA, glucose, and insulin dynamics. Model predictions of FFA, glucose and insulin profiles were validated with existing literature data. This composite model provides a new test platform for the development of closed-loop glucose control algorithms.