Effects of Fasting and Refeeding on the mRNA levels of Insulin-like Growth Factor-binding Proteins in Chick Liver and Brain

Abstract

The physiological functions of insulin-like growth factor-binding proteins (IGFBPs) in mammals have been evaluated in several studies. However, the physiological roles of IGFBPs in chickens have not yet been elucidated. In this study, we examined the effects of short-term (6 h) fasting and refeeding on the mRNA levels of IGFBPs in chick liver and brain. Eighteen 8-day-old chicks were weighed and allocated to three groups on the basis of body weight, and subjected to ad libitum feeding, 6 h of fasting, or 6 h of fasting followed by 6 h of refeeding. After the chicks were euthanized by decapitation, the liver and brain were excised, and the brain was dissected into six segments (telencephalon, optic lobes, cerebellum, rostral part of the brainstem, middle part of the brainstem, and caudal part of the brainstem). IGFBP mRNA levels were determined by qRT-PCR. Fasting significantly increased the mRNA levels of IGFBP-1 and -2 in the chick liver, and these changes were reversed by 6 h of refeeding. The mRNA levels of IGFBP-3 in the middle part of the brainstem and IGFBP-5 in the optic lobes were decreased by 6 h of fasting and were not reversed after 6 h of refeeding. These findings suggest that IGFBP-1 and -2 in the liver, IGFBP-3 in the middle part of the brainstem, and IGFBP-5 in the optic lobes may play physiological roles in response to short-term changes in the nutritional status of chicks.

Effects of Amino Acid Supplementation to a Low-Protein Diet on the Growth Performance and Protein Metabolism-related Factors in Broiler Chicks

“…Real-time PCR analysis was performed as previously described[ 31 , 32 , 33 ]. Total RNA was extracted from tissues using Sepazol-RNA I Super G (Nacalai Tesque, Inc., Kyoto, Japan).…”

“…mRNA levels were quantified for each primer using TB Green Premix Ex Taq II (Tli RNaseH Plus; Takara Bio Inc., Otsu, Japan) according to the supplier’s recommendations based on a relative standard curve using the Thermo Scientific Piko Real Real-Time PCR System (Thermo Fisher Scientific Oy, Vantaa, Finland). Primer sequences for IGF-1, IGF1R[ 31 ], IGFBP-1–3[ 32 ], atrogin-1, muscle RING-finger protein-1 (MuRF-1)[ 33 ], myoblast determination protein 1 (MyoD), myogenin (MyoG), and ribosomal protein S17 (RPS17)[ 34 ] may be found in previous studies. The following primer sequences were used for LC3B (NM_001031461) and glucocorticoid receptor (GCR, NM_001037826): LC3B sense, 5’-TCC GAG ATC AGC ATC CAA CT-3ʹ, LC3B antisense, 5’-CAC CAT GCT GTG TCC GTT C-3’; GCR sense, 5’-CAT GAA CCT CGA AGC TCG CAA G-3,’ and GCR antisense, 5’-ACC TCC AGC AGT GAC ACC AG-3’.…”

Central administration of insulin-like growth factor-2 suppresses food intake in chicks

“…Total RNA extraction and cDNA synthesis were performed as described previously [13]. Complementary DNA of IGFBPs were amplified using primers as described previously [14]. Complementary DNA of IGF-1 and IGF-1R were amplified using primers as described previously [12].…”