Prehepatic insulin production in man: kinetic analysis using peripheral connecting peptide behavior

Area of Science:

• Endocrinology
• Metabolic Research
• Physiology

Background:

• Accurate measurement of insulin production is crucial for understanding glucose homeostasis.
• Previous methods for assessing insulin secretion had limitations in dynamic conditions.

Purpose of the Study:

• To quantitatively evaluate prehepatic insulin production in humans.
• To analyze insulin secretion dynamics under various physiological conditions (fasting, glucose stimulation).

Main Methods:

• Kinetic analysis of plasma C-peptide levels using a two-compartment model.
• Computer-assisted analysis (least squares spline fitting) of C-peptide data.
• Studies conducted during insulin secretion suppression and stimulation.

Main Results:

• Basal prehepatic insulin production was measured at 15-4 mU/70 kg/min.
• Insulin production significantly decreased during fasting and exogenous insulin administration.
• Oral glucose tolerance tests and IV glucose injections demonstrated marked, rapid increases in insulin production.

Conclusions:

• C-peptide kinetic analysis provides a reliable method for quantifying human prehepatic insulin production.
• Insulin secretion is highly dynamic and responsive to glucose availability.
• Calculated portal vein insulin levels were significantly higher than peripheral levels.