Evidence for acyl-ghrelin modulation of growth hormone release in the fed state.
BACKGROUND
The timing and frequency of GH secretory episodes is regulated by GHRH and somatostatin. This study provides evidence for amplification of these GH pulses by endogenous acyl-ghrelin.


METHODS
Blood was sampled every 10 min for 26.5 h during a fed admission with standardized meals and also during the final 24 h of a 61.5-h fast. GH secretion profiles were derived from deconvolution of 10-min sampling data, and full-length acyl-ghrelin levels were measured using a newly developed two-site sandwich assay.


METHODS
The study was conducted at a university hospital general clinical research center.


METHODS
Participants included eight men with mean (+/- sd) age 24.5 +/- 3.7 yr (body mass index 24 +/- 2.1 kg/m(2)).


RESULTS
Correlations were computed between amplitudes of individual GH secretory events and the average acyl-ghrelin concentration in the 60-min interval preceding each GH burst. In the fed state, the peak correlations were positive for all subjects and significantly higher than in the fasting state when acyl-ghrelin levels declined [mean (+/- sem): 0.7 (0.04) vs. 0.29 (0.08), P = 0.017]. In addition, long-term fasting was associated with an increase in the GH secretory pulse mass and amplitude but not frequency [fed vs. fasting pulse mass: 0.22 (0.05) vs. 0.44 (0.06) microg/liter, P = 0.002; amplitude: 5.2 (1.3) vs. 11.8 (1.9) microg/liter/min, P = 0.034; pulses per 24 h: 19.4 (0.5) vs. 22.0 (1.4), P = 0.1].


CONCLUSIONS
Our data support the hypothesis that under normal conditions in subjects given regular meals endogenous acyl-ghrelin acts to increase the amplitude of GH pulses.
Nass
Ralf
R
Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
Farhy
Leon S
LS
Liu
Jianhua
J
Prudom
Catherine E
CE
Johnson
Michael L
ML
Veldhuis
Paula
P
Pezzoli
Suzan S
SS
Oliveri
Mary Clancy
MC
Gaylinn
Bruce D
BD
Geysen
H Mario
HM
Thorner
Michael O
MO
D000215:Acylation; D000293:Adolescent; D000328:Adult; D005215:Fasting / Q000097:blood; D054439:Ghrelin / Q000502:physiology*; D013007:Growth Hormone-Releasing Hormone / Q000502:physiology; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D008297:Male
D054439:Ghrelin; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone