Figure 5

Figure 5

VD₃ promotes the synthesis and processing of GLP-1 in the gut under short-term fasting conditions. (A–D) Zebrafish were fed with or without VD₃ for a month and fasted for 24 h. The gene expression of gip, gipr, pyya, pyyb, sglt (A) and gcga, gcgb, pcsk1, pcsk2 (B) in the gut was analyzed (n = 4/group). GLP-1 levels in the serum (C) and the intestine (D) were measured (n = 3 replicates, 4~5 fish/replicate). (E–H) WT and cyp2r1^−/− zebrafish at 3 mpf fasted for 24 h. The gene expression of gip, gipr, pyya, pyyb, sglt (E), and gcga, gcgb, pcsk1, pcsk2 (F) in the intestine was analyzed (n = 5/genotype). GLP-1 levels in the serum (G) (n = 4 replicates, 3 fish/replicate) and the intestine (H) (n = 3/ genotype) were measured. * p < 0.05, ** p < 0.01, ns: no statistical significance.