title: Effects of prolonged hypoxia and bed rest on appetite and appetite-related hormones.
abstract: Environmental hypoxia and inactivity have both been shown to modulate appetite. To elucidate the independent and combined effects of hypoxia and bed rest-induced inactivity on appetite-related hormones and subjective appetite, eleven healthy, non-obese males underwent three experimental interventions in a cross-over and randomized fashion: 1) Hypoxic confinement combined with daily moderate-intensity exercise (HAMB, FiO2= 0.141 ± 0.004; PiO2= 90.0 ± 0.4 mmHg) 2) Bed rest in normoxia (NBR, FiO2= 0.209; PiO2= 133.1 ± 0.3 mmHg) and 3) Bed rest in hypoxia (HBR, FiO2= 0.141 ± 0.004; PiO2= 90.0 ± 0.4 mmHg). A mixed-meal tolerance test (MTT), followed by an ad libitum meal were performed before (Pre) and after 16-days (Post) of each intervention. Composite satiety scores (CSS) during the MTT were calculated from visual analogue scores, while fasting and postprandial concentrations of total ghrelin, peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and leptin were quantified from arterialized-venous samples. Postprandial CSS were significantly lower at Post compared to Pre in NBR only (P < 0.05) with no differences observed in ad libitum meal intakes. Postprandial concentrations and incremental area under the curve (AUC) for total ghrelin and PYY were unchanged following all interventions. Postprandial GLP-1 concentrations were only reduced at Post following HBR (P < 0.05) with resulting AUC changes being significantly lower compared to HAMB (P < 0.01). Fasting leptin was reduced following HAMB (P < 0.05) with no changes observed following NBR and HBR. These findings suggest that independently, 16-day of simulated altitude exposure (∼4000 m) and bed rest-induced inactivity do not significantly alter subjective appetite or ad libitum intakes. The measured appetite-related hormones following both HAMB and HBR point to a situation of hypoxia-induced appetite stimulation, although this did not reflect in higher ad libitum intakes.
  
  
  
  NCT02293772.
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia. Electronic address: tadej.debevec@ijs.si.
authors.forename: Tadej
authors.initials: T
authors.lastname: Debevec
authors.affiliation: MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham Medical School, School of Life Sciences, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Simpson
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Igor B
authors.initials: IB
authors.lastname: Mekjavic
authors.affiliation: Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Eiken
authors.affiliation: MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham Medical School, School of Life Sciences, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Macdonald
mesh_terms: D000328:Adult; D001066:Appetite; D001069:Appetite Regulation; D001510:Bed Rest; D018592:Cross-Over Studies; D004032:Diet; D015444:Exercise; D054439:Ghrelin / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000503:physiopathology; D020738:Leptin / Q000097:blood; D008297:Male; D019894:Peptide YY / Q000097:blood; D019518:Postprandial Period; D055815:Young Adult
chemical_list: D054439:Ghrelin; D020738:Leptin; D019894:Peptide YY; D052216:Glucagon-Like Peptide 1
keywords: Appetite regulation; Bed rest; High altitude anorexia; Hypoxemia; Inactivity