Dietary macronutrients and feeding frequency affect fasting and postprandial concentrations of hormones involved in appetite regulation in adult dogs

Abstract

Identifying dietary effects on appetite-regulating hormones will enhance our understanding of appetite control. Before complex diets are tested, effects of specific macronutrients or feeding frequency should be identified. The objectives of this nutrition study were to identify differences in endocrine response with feeding frequency (Exp. 1) and after a single dose of a sole macronutrient (Exp. 2). A control diet supplying similar energy content from carbohydrate, protein, and fat was fed to maintain ideal BW. In Exp. 1, 8 healthy adult (1.9 ± 0.1 yr old) female hound cross dogs with an average BW of 22 kg (4.8 ± 0.8 BCS based on a 9-point scale) were randomly allotted to 1 of 2 treatments (fed once or twice daily) in a crossover design. After a 14-d adaptation period, a blood sample was taken (10 mL) before feeding, and samples were collected every 2 h postprandially for 24 h. In Exp. 2, dogs were randomly allotted to 1 of 4 treatments in a 4 × 4 Latin square design. After a 6-d adaptation period, the normal meal on d 7 was replaced with a bolus of maltodextrin (50 g in water; CARB), canned chicken (50 g; PROT), lard (25 g; fat), or water (200 mL). A blood sample (10 mL) was taken at 0, 30, 60, 90, 120, 150, 180, 240, 300, and 360 min postprandial. Total ghrelin, active glucagon-like peptide-1 (GLP-1), insulin, and glucose concentrations were measured. Data were analyzed to compare changes from baseline and area under the curve (AUC) among treatments. In Exp. 1, all hormones were quite variable throughout the day, with a few insulin and GLP-1 differences because of feeding frequency. In Exp. 2, CARB produced a marked peak in glucose and insulin concentrations compared with PROT, fat, or water, resulting in increased glucose (P < 0.001) and insulin (P = 0.07) incremental AUC values. On the other hand, the fat treatment led to increased GLP-1 concentrations over time. Ghrelin AUC was not different among treatments. The circulating hormone data were highly variable and indicate that diet plays a role in insulin and GLP-1 secretion, but more research is required to elucidate these effects.

Effects of dietary macronutrient composition and feeding frequency on fasting and postprandial hormone response in domestic cats

“…Similar to the previous studies in dogs ( 27 ) and cats ( 41 ) , we observed that the oral carbohydrate load elicited a rise in blood glucose and insulin and that their IAUC 0–6 h were higher than those when water, fat and protein were given. Due to these robust increases in postprandial glucose and insulin in the present study, significant ghrelin suppression after carbohydrate load was expected to be observed simultaneously.…”

“…The amount of each macronutrient dose fed to cats was based on the amount of energy provided by each macronutrient (about 335 kJ; 80 kcal) and how it compared with daily intake (approximately 25 % of daily ME). Based on a similar canine study performed in our laboratory ( 27 ) and other human studies ( 10 , 12 , 31 ) , a 6 h length of blood sampling was selected because the postprandial ghrelin response to diet was expected to return to baseline by then.…”

Effect of sterilization and of dietary fat and carbohydrate content on food intake, activity level, and blood satiety–related hormones in female dogs1

“…Carbohydrates are regarded most effective in suppressing ghrelin and in increasing insulin after a meal in humans, whereas fat is found to elicit a major increase of CCK and PYY (Karhunen et al, 2008). Available data in dogs is limited, with Greeley et al (1989) reporting a major increase of PYY after intraduodenal fat and Lubbs et al (2010) reporting a similar ghrelin response after oral loads of fat and carbohydrates, and a relationship between blood hormone variations and food intake is not consistently established (Bosch et al, 2009). On the other hand, there is evidence that estradiol attenuates the orexigenic effect of ghrelin (Clegg et al, 2007) and enhances the satiating potency of CCK (Butera et al, 1993) and PYY (Papadimitriou et al, 2007).…”

Circulating ghrelin and GLP-1 are not affected by habitual diet

“…One previous study among healthy men and women reported that GLP-1 increased dramatically after ingestion of fat alone, but the GLP-1 response was greatly reduced with the addition of carbohydrate [15]. Similarly, in a crossover study investigating different macronutrient preloads in dogs, dietary fat produced the greatest increase in circulating GLP-1 [16]. Our results suggest that while dietary lipid may increase GLP-1 concentrations on an acute basis, acclimation to a higher-fat diet over an 8-week period did not appear to affect GLP-1 response to a standard test meal.…”

“…Studies have demonstrated that GLP-1 acts at the brainstem and hypothalamus to decrease food intake and increase subjective satiety [13, 14]. Although little is known about the effects of specific macronutrients on GLP-1 secretion, limited data suggest that dietary fat may induce the greatest increase in acute GLP-1 secretion [15, 16]. Like ghrelin, longitudinal effects of chronic macronutrient intake on GLP-1 are unclear.…”