Obesity, hyperinsulinemia, and portal blood flow. A theoretic study of the effects of increased portal blood flow upon fasting peripheral insulin concentrations.

A mathematical model of steady state insulin metabolism was developed to predict the effects of blood flow changes upon fasting arterial insulin concentration. In addition to blood flows to major organs and tissues, the model includes representations for insulin feedback regulation of hepatic insulin clearance and pancreatic insulin secretion. Within the range of insulin sensitivities assumed for hepatic and pancreatic feedback regulation and the range of initial insulin secretion rates employed, the model predicts that the fasting arterial insulin concentration rises by up to 20 muU. per milliliter as portal blood flow increases. The necessary elevations in portal blood flow lie well inside the range of increased total hepatic blood flow observed in obese subjects. The results of this study suggest that a significant portion of the elevation in fasting insulin concentrations seen in obesity may be the result of increased portal blood flow and that other clinical observations and metabolic changes that accompany obesity may also be related to altered portal flow.