Effect of gastric inhibitory polypeptide on bovine fat metabolism.
Gastric inhibitory polypeptide (GIP), a hormone secreted by the gastrointestinal tract in response to nutrient absorption, exerts anabolic effects on adipose tissue in some species. Cattle fed on grass silage diets tend to deposit more fat than animals fed on dried forages. We investigated the effect of diet on blood GIP concentrations in cattle. Plasma concentrations tended to be higher in cattle fed grass silage alone or supplemented with fishmeal (0.61 ng/ml) compared with animals fed dried grass/barley (0.43 ng/ml, P > 0.1) and were inversely correlated with plasma insulin concentrations (r = -0.727, P < 0.01). The effects of increasing concentrations (0, 0.1, 1.0, 10.0 nM) of GIP and glucagon-like peptide-1 (GLP-1) on basal and insulin-stimulated lipogenesis in bovine adipose tissue in vitro were investigated after 4 and 24 h of incubation. No conclusive effects were obtained with either peptide. Subsequently, the effect of exogenous administration of GIP (10 or 50 ng/kg liveweight per min) on whole-body fat metabolism was investigated in two steers in vivo. Plasma concentration and flux rate of palmitate was increased by GIP only at the higher infusion level suggesting lipolysis and possibly fatty acid re-esterification was stimulated at high concentration. We conclude that although gut peptides may regulate nutrient utilisation, it is unlikely that they play a major role in promoting fat accretion in cattle. However, the small number of animals used in these studies indicates the need for caution and further studies are warranted.
Dawson
J M
JM
Division of Nutritional Biochemistry, School of Biological Sciences, University of Nottingham, Loughborough, Leics, UK. janet.dawson@nottingham.ac.uk
Greathead
H M
HM
Sessions
V A
VA
Tye
F M
FM
Buttery
P J
PJ
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004032:Diet; D004435:Eating; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005749:Gastric Inhibitory Polypeptide / Q000097:blood / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D050356:Lipid Metabolism; D008055:Lipids / Q000096:biosynthesis; D008066:Lipolysis; D019308:Palmitic Acid / Q000097:blood; D010446:Peptide Fragments / Q000494:pharmacology; D010945:Plants, Edible; D011498:Protein Precursors / Q000494:pharmacology; D014508:Urea / Q000097:blood
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008055:Lipids; D010446:Peptide Fragments; D011498:Protein Precursors; D019308:Palmitic Acid; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D014508:Urea; D005934:Glucagon