👤 Ahmed Mijiyawa

Dietary bile acids (BAs) have been shown to affect food intake in chicks; however, the underlying central mechanisms remain unclear. This study investigated the effects of taurochenodeoxycholic acid (TCDCA), sodium taurocholate (STC), chenodeoxycholic acid (CDCA), taurocholic acid (TCA), hyodeoxycholic acid (HDCA), allocholic acid (ACA), and a mixed BA (MBA; 4.6% hyodicolate, 72.6% hyodeoxycholate, and 18.3% chenodeoxycholate) on feed intake and hypothalamic mRNA expression of appetite-related neuropeptides in chicks. To determine the effects, intracerebroventricular (ICV) injections of three doses (0.25, 0.5, and 1 μg) of each BA were administered to 5-day-old layer-type chicks, and feed intake was recorded at 30, 60, and 120 minutes post-injection. Quantitative PCR was used to determine the hypothalamic mRNA expression of neuropeptide Y (NPY) and its receptors, agouti-related peptide (AgRP), pro-opiomelanocortin (POMC), and melanocortin receptors. Results showed that feed intake decreased after ICV administration of CDCA, CA, HDCA, MBA, and STC, whereas ACA and TCDCA increased intake (P < 0.05). TCDCA upregulated NPY5R, while CDCA downregulated NPY4R (P < 0.05). STC and CA increased POMC and MC4R expression and reduced AgRP (P < 0.05), whereas HDCA decreased AgRP (P < 0.05). ACA reduced MC4R expression, and MBA downregulated both NPY4R and NPY5R (P < 0.05). The result suggests that both orexigenic and anorexigenic neuropeptide genes are involved in the effects of BAs. The effect of BAs acts in a dose-dependent manner in the hypothalamus to influence feed intake. Show less

Amino acids in the brain modulate eating behavior and energy balance. The aim of the present study was to investigate the effects of DL-methionine (DL-Met), l-lysine monohydrochloride (L-Lys-HCl), and taurine (Tau) on feed intake and the mRNA expression levels of appetite-related hypothalamic neuropeptides in chicks. DL-Met, l-Lys-HCl, or Tau was intracerebroventricularly (ICV) administered to 5-day-old layer-type chicks, and the feed intake was recorded until 1 h post-injection. Quantitative PCR was performed to determine the hypothalamic mRNA expression levels of neuropeptide Y (NPY) and its receptors, agouti-related protein (AgRP), pro-opiomelanocortin (POMC), cocaine- and amphetamine-regulated transcript (CART), and melanocortin receptors. Our results indicated that injection time and treatment have a significant effect on food intake. Food intake decreased significantly at 30 and 60 min after ICV administration of DL-Met (1.678 μmol), l-Lys-HCl (6.856 μmol), and Tau (5.006 μmol) compared to the control group (P > 0.05). On the contrary, a high dose of each amino acid did not alter feed intake (P > 0.05). The result showed that ICV injection of DL-Met (1.678 μmol) significantly decreased the mRNA expressions of NPY,NPY4R, and NPY6R (P < 0.05), but had no significant effect on the mRNA expressions of NPY1R, NPY5R, and AgRP in the hypothalamus (P > 0.05). Similarly, ICV injection of l-Lys-HCl (6.856 μmol) and Tau (5.006 μmol) significantly decreased mRNA levels of NPY, NPY4R, and NPY6R (P < 0.05), without affecting the mRNA expressions of NPY1R, NPY5R, and AgRP (P > 0.05). DL-Met had no effect on anorexigenic gene expression (P > 0.05). l-Lys-HCl upregulated MC1R (P < 0.05), and Tau upregulated POMC and MC3R (P < 0.05), and both had no influence on CART, MC4R, or MC5R (P > 0.05). The result suggests that both orexigenic and anorexigenic neuropeptide genes are involved in the effects of DL-Met, l-Lys-HCl, and Tau. The effect of DL-Met, l-Lys-HCl, and Tau acts in a dose-dependent manner in the hypothalamus to influence feed intake. Show less