Oscillations in Insulin Secretion During Constant Glucose Infusion in Normal Man: Relationship to Changes in Plasma Glucose*
- 1 August 1988
- journal article
- research article
- Published by The Endocrine Society in Journal of Clinical Endocrinology & Metabolism
- Vol. 67 (2), 307-314
- https://doi.org/10.1210/jcem-67-2-307
Abstract
Peripheral plasma or serum concentrations of glucose, insulin, C-peptide, glucagon, and cortisol and insulin secretory rates (ISR) were determined at 15-min intervals in eight normal subjects during a constant iv infusion of 4.5 mg glucose/kg .cntdot. min for a 24-h period. During each sampling interval, the secretory rate of insulin was calculated by deconvolution of the peripheral plasma C-peptide concentration using C-peptide kinetic parameters derived after bolus injections of C-peptide in individual subjects. Periodogram analysis of the individual glucose curves demonstrated a circadian rhythm in all subjects, with a major nocturnal acrophase occurring at an average clock time of 0228 h (range, 0045-0350 h). In five of the eight subjects, a minor acrophase occurred at an average time of 1774 h (range, 1530-2045 h). This diurnal variation in plasma glucose levels was not paralleled by a similar pattern in insulin secretion. Although glucose was infused at a constant rate, significant pulses were found in glucose, insulin, and C-peptide levels and ISR; the pulse durations of these parameters were 182 .+-. 30 (.+-.SE), 89 .+-. 5, 100 .+-. 8, and 85 .+-. 5 min, respectively, and their periodicities were 208 .+-. 33, 106 .+-. 7, 114 .+-. 10, and 106 .+-. 7 min. The durations and frequencies for pulses of insulin, C-peptide, and ISR were not significantly different, whereas glucose pulses had a longer duration and were less frequent (P < 0.05, by analysis of variance). On the average, 54 .+-. 9% of the C-peptide pulses and 47 .+-. 8% of the ISR pulses were concomitant with a pulse in glucose levels. Moreover, approximately half of the C-peptide and ISR pulses that were not concomitant with a glucose pulse occurred in synchrony with a shoulder on the up-stroke or down-stroke of glucose pulses. Analysis of glucagon and cortisol profiles revealed no significant associations with the insulin and glucose oscillations. In conclusion, during a constant glucose infusion in normal subjects, regular oscillations of insulin secretion occur at 80- to 120-min intervals. Their tight coupling with glucose oscillations and the lack of association with fluctuations of glucagon and cortisol suggest that these oscillations represent a dynamic property of the insulin-glucose feedback loop.This publication has 19 references indexed in Scilit:
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