title: Subject standardization, acclimatization, and sample processing affect gut hormone levels and appetite in humans.
abstract: OBJECTIVE
  Gut hormones represent attractive therapeutic targets for the treatment of obesity and type 2 diabetes. However, controversy surrounds the effects that adiposity, dietary manipulations, and bariatric surgery have on their circulating concentrations. We sought to determine whether these discrepancies are due to methodologic differences.
  
  
  METHODS
  Ten normal-weight males participated in a 4-way crossover study investigating whether fasting appetite scores, plasma acyl-ghrelin, active glucagon-like peptide-1 (GLP-1), and peptide YY3-36 (PYY3-36) levels are altered by study-induced stress, prior food consumption, and sample processing.
  
  
  RESULTS
  Study visit order affected anxiety, plasma cortisol, and temporal profiles of appetite and plasma PYY3-36, with increased anxiety and cortisol concentrations on the first study day. Plasma cortisol area under the curve (AUC) correlated positively with plasma PYY3-36 AUC. Despite a 14-hour fast, baseline hunger, PYY3-36 concentrations, temporal appetite profiles, PYY3-36 AUC, and active GLP-1 were affected by the previous evening's meal. Sample processing studies revealed that sample acidification and esterase inhibition are required when measuring acyl-ghrelin and dipeptidyl-peptidase IV inhibitor addition for active GLP-1. However, plasma PYY3-36 concentrations were unaffected by addition of dipeptidyl-peptidase IV.
  
  
  CONCLUSIONS
  Accurate assessment of appetite, feeding behavior, and gut hormone concentrations requires standardization of prior food consumption and subject acclimatization to the study protocol. Moreover, because of the labile nature of acyl-ghrelin and active GLP-1, specialized sample processing needs to be undertaken.
authors.affiliation: Centre for Diabetes and Endocrinology, Department of Medicine, University College London, Rayne Institute, London, United Kingdom.
authors.forename: Keval
authors.initials: K
authors.lastname: Chandarana
authors.forename: Megan E
authors.initials: ME
authors.lastname: Drew
authors.forename: Julian
authors.initials: J
authors.lastname: Emmanuel
authors.forename: Efthimia
authors.initials: E
authors.lastname: Karra
authors.forename: Cigdem
authors.initials: C
authors.lastname: Gelegen
authors.forename: Philip
authors.initials: P
authors.lastname: Chan
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Cron
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Batterham
mesh_terms: D000223:Adaptation, Psychological; D000328:Adult; D000704:Analysis of Variance; D001066:Appetite / Q000502:physiology*; D019540:Area Under Curve; D001835:Body Weight; D018592:Cross-Over Studies; D005247:Feeding Behavior; D005768:Gastrointestinal Hormones / Q000032:analysis / Q000378:metabolism; D054439:Ghrelin / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D006801:Humans; D006815:Hunger / Q000502:physiology*; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D019894:Peptide YY / Q000378:metabolism*; D011336:Probability; D012015:Reference Standards; D012016:Reference Values; D012307:Risk Factors; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013315:Stress, Psychological
chemical_list: D005768:Gastrointestinal Hormones; D054439:Ghrelin; D019894:Peptide YY; D052216:Glucagon-Like Peptide 1; D006854:Hydrocortisone