title: Metabolomic linkage reveals functional interaction between glucose-dependent insulinotropic polypeptide and ghrelin in humans.
abstract: The gastric peptide ghrelin promotes energy storage, appetite, and food intake. Nutrient intake strongly suppresses circulating ghrelin via molecular mechanisms possibly involving insulin and gastrointestinal hormones. On the basis of the growing evidence that glucose-dependent insulinotropic polypeptide (GIP) is involved in the control of fuel metabolism, we hypothesized that GIP and/or insulin, directly or via changes in plasma metabolites, might affect circulating ghrelin. Fourteen obese subjects were infused with GIP (2.0 pmol·kg(-1)·min(-1)) or placebo in the fasting state during either euglycemic hyperinsulinemic (EC) or hyperglycemic hyperinsulinemic clamps (HC). Apart from analysis of plasma ghrelin and insulin levels, GC-TOF/MS analysis was applied to create a hormone-metabolite network for each experiment. The GIP and insulin effects on circulating ghrelin were analyzed within the framework of those networks. In the HC, ghrelin levels decreased in the absence (19.2% vs. baseline, P = 0.028) as well as in the presence of GIP (33.8%, P = 0.018). Ghrelin levels were significantly lower during HC with GIP than with placebo, despite insulin levels not differing significantly. In the GIP network combining data on GIP-infusion, EC+GIP and HC+GIP experiments, ghrelin was integrated into hormone-metabolite networks through a connection to a group of long-chain fatty acids. In contrast, ghrelin was excluded from the network of experiments without GIP. GIP decreased circulating ghrelin and might have affected the ghrelin system via modification of long-chain fatty acid pools. These observations were independent of insulin and offer potential mechanistic underpinnings for the involvement of GIP in systemic control of energy metabolism.
authors.affiliation: Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam, Germany. rudovich@dife.de
authors.forename: Natalia N
authors.initials: NN
authors.lastname: Rudovich
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Nikiforova
authors.forename: Baerbel
authors.initials: B
authors.lastname: Otto
authors.forename: Olga
authors.initials: O
authors.lastname: Pivovarova
authors.forename: Ozlem
authors.initials: O
authors.lastname: Gögebakan
authors.forename: Alexander
authors.initials: A
authors.lastname: Erban
authors.forename: Matthias
authors.initials: M
authors.lastname: Möhlig
authors.forename: Martin O
authors.initials: MO
authors.lastname: Weickert
authors.forename: Joachim
authors.initials: J
authors.lastname: Spranger
authors.forename: Matthias H
authors.initials: MH
authors.lastname: Tschöp
authors.forename: Lothar
authors.initials: L
authors.lastname: Willmitzer
authors.forename: Michael
authors.initials: M
authors.lastname: Nauck
authors.forename: Andreas F H
authors.initials: AF
authors.lastname: Pfeiffer
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism* / Q000494:pharmacology; D054439:Ghrelin / Q000097:blood*; D005934:Glucagon / Q000097:blood; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D055432:Metabolomics; D008875:Middle Aged; D050177:Overweight / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D054439:Ghrelin; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D005934:Glucagon