Degree of adiposity and dietary macronutrient composition affect incretin hormone secretion in humans and mice, but little is known about their effect in cats. In this study, 7 overweight cats were fed a maintenance diet (MD) for at least 2 wk followed by a reduced calorie diet (RCD), which was lower in fat and higher in carbohydrates and fiber. Cats were fed ad libitum initially, and then, food was restricted to achieve 1%-2% loss of body weight weekly (11 wk). When lean, cats were fed MD for 2 wk. A standardized meal test (SMT) using a third diet was performed after at least 7 d on each diet, before and after weight loss (four SMT's total). Glucose, insulin, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic peptide (GIP) concentrations were measured immediately before and over 6 h after feeding the SMT. Area under the curve (AUC) was compared for GLP-1, GIP, and insulin concentrations using 2-way analysis of variance. Leaner cats had increased GIPAUC compared to obese cats (P = 0.025). There was a trend toward increased GIPAUC on RCD compared to the MD (P = 0.085). There was a moderate negative correlation between body fat percentage and GLP-1AUC (r = -0.45; P = 0.05). There was no effect of diet on GLP-1AUC. In conclusion, degree of adiposity and dietary macronutrient content could be important in determining GIP responses not only acutely but also on a long-term basis. Further investigation of GIP responses in cats should take both diet and degree of adiposity into account.
Keywords: Diabetes; GIP; GLP-1; Incretin; K cells; L cells.
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