Table 2.

Fold-changes in intestinal hormones after 2-h dark-phase feeding compared to the preprandial light phase

	Treatmenta
Hormoneb	Standard Diet/Standard Diet	Standard Diet/high-Protein Diet	Western-Type Diet/Standard Diet	Western-Type Diet/High-Protein Diet
Amylin	2.2 ± 0.5	3.0 ± 0.4	3.8 ± 0.8	2.0 ± 0.5#
GIP	3.7 ± 0.6	4.6 ± 0.5	13.1 ± 1.3*+	16.3 ± 1.0*+#
Insulin	1.1 ± 0.2	3.0 ± 0.8*	2.4 ± 0.4*	2.1 ± 0.2*
Leptin	0.6 ± 0.2	0.5 ± 0.1	0.5 ± 0.2	0.5 ± 0.1
PP	1.0 ± 0.1	1.2 ± 0.3	2.1 ± 0.6	2.3 ± 0.4*+
Peptide YY	1.1 ± 0.2	4.0 ± 0.7#	1.2 ± 0.5	2.2 ± 0.3*+

^aAfter development of diet-induced obesity on a Western-type diet or feeding of a standard diet, rats were fed a standard or high-protein diet for 32 days, resulting in four experimental groups: standard diet/standard diet, standard diet/high-protein diet, Western-type diet/standard diet, and Western-type diet/high-protein diet. The four groups fed ad libitum with standard or high-protein diet, respectively, were euthanized by decapitation to obtain trunk blood between 3 and 4 p.m. during the light phase (n = 5/group). Afterward, in the remaining rats, food was removed for 2 h. At the beginning of the dark phase at 6 p.m., preweighed rat chow (standard or high-protein diet, respectively) was provided, and rats were left undisturbed for 2 h. After this period, food intake was assessed and rats (n = 5/group) were euthanized to obtain trunk blood, and plasma levels of hormones were assessed.

^bData are fold changes of plasma levels from light to the dark phase and expressed as means ± SE. Significant differences are indicated for the change in plasma levels from light to dark phase. GIP, gastric inhibitory polypeptide; PP, pancreatic polypeptide.

^*P < 0.05 vs. standard diet/standard diet;

⁺P < 0.05 vs. standard diet/high-protein diet; and

^#P < 0.05 vs. Western-type diet/standard diet.