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Human insulin release processes measured by intraportal sampling.
Niels Pørksen1, Thorbjørn Grøfte, Jacob Greisen
1Endocrinology and Metabolism M, Aarhus University Hospital, 8000 Aarhus C, Denmark. porksen@dadlnet.dk
American Journal of Physiology. Endocrinology and Metabolism
|February 8, 2002
Summary
Insulin is released in pulsatile bursts, not continuously. Portal vein sampling in humans reveals these bursts occur every 4.4 minutes, accounting for most insulin secretion and impacting insulin action.
Area of Science:
- Endocrinology
- Physiology
- Metabolic Research
Background:
- Insulin secretion occurs in pulsatile bursts superimposed on basal release.
- Previous estimates of pulsatile insulin secretion relied on peripheral vein sampling.
- Portal vein sampling offers improved sensitivity for analyzing insulin secretion patterns.
Purpose of the Study:
- To characterize the pulsatile insulin secretion mechanism in nondiabetic humans using portal vein sampling.
- To quantify the mass, frequency, amplitude, and contribution of pulsatile insulin secretion.
- To assess changes in insulin secretion patterns after a mixed meal.
Main Methods:
- Deconvolution analysis of portal vein insulin profiles in fasted, nondiabetic humans.
- Assessment of insulin secretion before and after a mixed meal.
- Spectral and autocorrelation analyses to confirm pulsatile frequency.
Main Results:
- Pulsatile insulin secretion in the portal vein occurs every 4.1 ± 0.2 minutes.
- Secretory bursts have amplitudes averaging 660% of basal release.
- These bursts account for 70 ± 4% of total insulin release.
- A mixed meal increased burst mass but not frequency or basal secretion.
Conclusions:
- Human portal vein insulin release is highly pulsatile with a mean periodicity of 4.4 ± 0.2 minutes.
- Pulsatile insulin secretion, with a high signal-to-noise ratio, dominates insulin release.
- Altered insulin release patterns may influence insulin action, highlighting the importance of pulsatile secretion.