Differential responses of the incretin hormones GIP and GLP-1 to increasing doses of dietary carbohydrate but not dietary protein in lean rats.
Previous studies have shown that oral ingestion of nutrients stimulates secretion of the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1); however, it is unclear whether there is a dose-dependent response between the amount of nutrient ingested and the secretion of the hormones in vivo. Using our lymph fistula rat model, we previously demonstrated that both GIP and GLP-1 responded dose dependently to increasing amounts of infused dietary lipid and that the GLP-1-secreting cells were more sensitive to changes in intestinal lipid content. In the present study, we investigated the dose-dependent relationships between incretin secretion and the two remaining macronutrients, carbohydrate and protein. To accomplish this objective, the major mesenteric lymphatic duct of male Sprague-Dawley rats was cannulated. Each animal received a single bolus (3 ml) of saline, dextrin, whey protein, or casein hydrolysate (0.275, 0.55, 1.1, 2.2, 4.4 kcal) via a surgically inserted duodenal or ileal feeding tube. Lymph was continuously collected for 3 h and analyzed for GIP and GLP-1 content. Both GIP and GLP-1 outputs responded dose dependently to increasing amounts of dietary carbohydrate but not protein. Additionally, we found that the GIP-secreting cells were more sensitive than the GLP-1-secreting cells to changes in intestinal carbohydrate content.
Yoder
Stephanie M
SM
Department of Pathology, Univ. of Cincinnati, OH, USA. yodersy@mail.uc.edu
Yang
Qing
Q
Kindel
Tammy L
TL
Tso
Patrick
P
D000818:Animals; D002364:Caseins / Q000008:administration & dosage; D003912:Dextrins / Q000008:administration & dosage; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004750:Enteral Nutrition / Q000295:instrumentation; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D054795:Incretins / Q000378:metabolism*; D008196:Lymph / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008297:Male; D008643:Mesentery; D008894:Milk Proteins / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D013851:Thinness; D000067816:Whey Proteins
D002364:Caseins; D003912:Dextrins; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D054795:Incretins; D008894:Milk Proteins; D000067816:Whey Proteins; D005749:Gastric Inhibitory Polypeptide; C475729:casein hydrolysate; D052216:Glucagon-Like Peptide 1