title: The effect of fasting and refeeding on mRNA expression of PepT1 and gastrointestinal hormones regulating digestion and food intake in zebrafish (Danio rerio).
abstract: In vertebrates, a significant part of ingested protein is absorbed as di- and tripeptides through a brush border membrane proton/oligopeptide transporter protein called PepT1. The aim of the present study was to determine the effect of short-term food deprivation and refeeding in adult zebrafish (Danio rerio) on gastrointestinal mRNA expression of PepT1 as well as on the satiety hormones cholecystokinin (CCK), gastrin-releasing peptide (GRP) and ghrelin (GHR) in order to elucidate a potential mechanism driving compensatory growth. Sixty adult zebrafish were stocked in a 40-L aquarium and fed daily a commercial flake diet to satiation for 10 days where the digestive tracts (DT) of sampled fish (n = 5) were dissected out. Samplings were repeated following 1, 2 and 5 days of food deprivation and after 1, 2 and 5 days of refeeding. The RNA was extracted from all sampled DTs and analyzed by quantitative real-time PCR for the mRNA expression of PepT1, rRNA 18S, CCK, GRP and GHR. PepT1 mRNA expression increased with successive refeedings reaching a level approximately 8 times higher than pre-fast levels. CCK, GRP and GHR mRNA levels also decreased during fasting, but increased only to pre-fasting levels with refeeding. Overall, the results suggest that PepT1 may be a contributing mechanism to compensatory growth that could influence CCK secretion and GRP and GHR activity.
authors.affiliation: Israel Oceanographic and Limnological Research, The National Center for Mariculture, P.O.B. 1212, 88112, Eilat, Israel. Koven@ocean.org.il.
authors.forename: William
authors.initials: W
authors.lastname: Koven
authors.affiliation: Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Patricia
authors.initials: P
authors.lastname: Schulte
mesh_terms: D000818:Animals; D002766:Cholecystokinin / Q000235:genetics / Q000378:metabolism; D004063:Digestion / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D019886:Gastrin-Releasing Peptide / Q000235:genetics / Q000378:metabolism; D054439:Ghrelin / Q000235:genetics / Q000378:metabolism; D000074011:Peptide Transporter 1; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins
chemical_list: D054439:Ghrelin; D000074011:Peptide Transporter 1; D012333:RNA, Messenger; D027981:Symporters; D029961:Zebrafish Proteins; C000613207:slc15a1b protein, zebrafish; D019886:Gastrin-Releasing Peptide; D002766:Cholecystokinin