title: Evidence for acyl-ghrelin modulation of growth hormone release in the fed state.
abstract: 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.
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Ralf
authors.initials: R
authors.lastname: Nass
authors.forename: Leon S
authors.initials: LS
authors.lastname: Farhy
authors.forename: Jianhua
authors.initials: J
authors.lastname: Liu
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Prudom
authors.forename: Michael L
authors.initials: ML
authors.lastname: Johnson
authors.forename: Paula
authors.initials: P
authors.lastname: Veldhuis
authors.forename: Suzan S
authors.initials: SS
authors.lastname: Pezzoli
authors.forename: Mary Clancy
authors.initials: MC
authors.lastname: Oliveri
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gaylinn
authors.forename: H Mario
authors.initials: HM
authors.lastname: Geysen
authors.forename: Michael O
authors.initials: MO
authors.lastname: Thorner
mesh_terms: 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
chemical_list: D054439:Ghrelin; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone