AJP - Regulatory, Integrative and Comparative Physiology, Vol 272, Issue 3 962-R968, Copyright © 1997 by American Physiological Society
Low-frequency ultradian insulin rhythms are coupled to cardiovascular, autonomic, and neuroendocrine rhythms
D. S. Shannahoff-Khalsa, B. Kennedy, F. E. Yates and M. G. Ziegler
Institute for Nonlinear Science, University of California, San Diego, La Jolla 92093-0402, USA.
Plasma insulin levels were assayed to compare with earlier reported rhythms
of the cardiovascular, autonomic, and neuroendocrine systems in 10 resting
normal adults over 5-6 h. Our earlier report included time-series analysis
for impedance cardiography measures of stroke volume, heart rate, cardiac
output, thoracic fluid index, ejection velocity index, and ventricular
ejection time; automated cuff measures of systolic, diastolic, and mean
arterial pressures; the nasal cycle as a marker of lateralized autonomic
tone; and indwelling venous catheters for sampling blood every 7.5 min to
assay for adrenocorticotropic hormone, luteinizing hormone, epinephrine,
and norepinephrine. Insulin was later assayed from the same plasma samples.
Time-series analysis using the fast orthogonal search method of Korenberg
detected insulin periodicities at ranges of 220-340, 115-145, 70-100, and
40-65, with significance across subjects at ranges of 115-145, 70-100, and
40-65 min. Significant periods for the other parameters were reported
earlier at 220-340, 170-215, 115-145, 70-100, and 40-65 min, with periods
at 115-145, 70-100, and 40-65 min dominating across parameters. These
results suggest that insulin secretion has a common pacemaker (the
hypothalamus) or a mutually entrained pacemaker with the autonomic,
cardiovascular, and neuroendocrine systems.
