title: Dietary Caprylic Acid (C8:0) Does Not Increase Plasma Acylated Ghrelin but Decreases Plasma Unacylated Ghrelin in the Rat.
abstract: Focusing on the caprylic acid (C8:0), this study aimed at investigating the discrepancy between the formerly described beneficial effects of dietary medium chain fatty acids on body weight loss and the C8:0 newly reported effect on food intake via ghrelin octanoylation. During 6 weeks, Sprague-Dawley male rats were fed with three dietary C8:0 levels (0, 8 and 21% of fatty acids) in three experimental conditions (moderate fat, caloric restriction and high fat). A specific dose-response enrichment of the stomach tissue C8:0 was observed as a function of dietary C8:0, supporting the hypothesis of an early preduodenal hydrolysis of medium chain triglycerides and a direct absorption at the gastric level. However, the octanoylated ghrelin concentration in the plasma was unchanged in spite of the increased C8:0 availability. A reproducible decrease in the plasma concentration of unacylated ghrelin was observed, which was consistent with a decrease in the stomach preproghrelin mRNA and stomach ghrelin expression. The concomitant decrease of the plasma unacylated ghrelin and the stability of its acylated form resulted in a significant increase in the acylated/total ghrelin ratio which had no effect on body weight gain or total dietary consumption. This enhanced ratio measured in rats consuming C8:0 was however suspected to increase (i) growth hormone (GH) secretion as an increase in the GH-dependent mRNA expression of the insulin like growth Factor 1 (IGF-1) was measured (ii) adipocyte diameters in subcutaneous adipose tissue without an increase in the fat pad mass. Altogether, these results show that daily feeding with diets containing C8:0 increased the C8:0 level in the stomach more than all the other tissues, affecting the acylated/total ghrelin plasma ratio by decreasing the concentration of circulating unacylated ghrelin. However, these modifications were not associated with increased body weight or food consumption.
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Lemarié
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Erwan
authors.initials: E
authors.lastname: Beauchamp
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Dayot
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Duby
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Legrand
authors.affiliation: Laboratory of Biochemistry and Human Nutrition, Agrocampus Ouest-INRA (USC 1378), Rennes, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Rioux
mesh_terms: D000107:Acetylation; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D002210:Caprylates / Q000008:administration & dosage / Q000494:pharmacology*; D019587:Dietary Supplements; D054439:Ghrelin / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002210:Caprylates; D054439:Ghrelin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; C031492:octanoic acid