Differential expression of glucose metabolism-related genes and AMP-activated protein kinases in crop tissue of male and female pigeons (Columba livia domestica) during the incubation and chick-rearing periods.

The objective of this study was to explore the carbohydrate contents of crop milk, insulin and glucose concentrations in serum and the expression patterns of AMP-activated protein kinases (AMPKs) and genes related to glucose metabolism in pigeon crops during the breeding period. Crop milk was collected from squabs of rearing Day 1 (R1) to R6. Contents of total sugar and reducing sugar increased to the maximum levels at R6 (p < 0.05). Forty-two pairs of adult pigeons were allotted to seven groups by different breeding stages, and their crops and serum were sampled. No significant differences were found in either insulin or glucose levels in serum. The glucose transporter 2 gene level was the greatest at R15 in females, whereas it was at R7 in males. However, sodium-dependent glucose transporters 1 expression in both sexes decreased from incubation Day 17 (I17) to R7. In females, glucokinase expression peaked at R1, and at R1 and R7 in males. Pyruvate kinase mRNA levels peaked at R7 in females and at R15 males. The mRNA abundance of fructose-1,6-bisphosphatase 1 in both sexes and glucose-6-phosphatase in females decreased after I10. While phosphoenolpyruvate carboxykinase 1 expression decreased after I17 (p < 0.05). Protein levels of AMPKα in crops were minimized at R1 (p < 0.05). In females, expression of AMPKα1 and AMPKα2 was inhibited at I17 and R1 (p < 0.05). In males, AMPKα1 expression was decreased at R7 (p < 0.05) and AMPKα2 was reduced at I10 and R1. pAMPK expression was the lowest at I17 in females, and it was at R7 and R25 in males. Conclusively, glycolysis in pigeon crops was enhanced during chick-rearing, while gluconeogenesis was significantly inhibited. The stability of the insulin level suggests that it was probably not involved in the regulation of glucose metabolism in crop tissues.

MicroRNA-126 expression is decreased in cultured primary chicken hepatocytes and targets the sprouty-related EVH1 domain containing 1 mRNA.

The microRNA-126 (miR-126) is a miRNA expressed in highly vascularized tissues, and it is believed to play a role in angiogenesis by repressing sprouty-related EVH1 domain containing 1 (Spred1). In the current study, we determined the expression pattern of chicken miR-126 (gga-miR-126) and predicted and validated its target genes. The quantitative reverse-transcription (qRT) PCR analysis showed that miR-126 was expressed in various chicken tissues with the highest level in lung. In liver, the expression level of miR-126 increased from 0 to 7 wk of age. The expression of miR-126 in primary chicken hepatocytes decreased with culturing. A miR-126 binding site was predicted in the 3' UTR (untranslated region) of chicken Spred1. Dual-luciferase reporter assays indicated that miR-126 could bind to the predicted site to repress the expression of Spred1. These data validate Spred1 as a target gene of chicken miR-126. These results will help further understand the function and regulation of miR-126 and Spred1 in chickens.

[Identification and genetic analysis of SNPs in duck adiponectin gene].

Single nucleotide polymorphisms (SNPs) within the duck adiponectin gene were detected by single strand conformation polymorphism (SSCP) using 5 pairs of primers to amplify an area spanning the open reading frame. Eight duck breeds, including Kunshan Sheldrake, Cherry Valley Meat duck, Gaoyou duck, Shanma duck, Jinding duck, Longbai duck, Jingjiang Sheldrake and White feather Muscovy duck, were used. Seven nucleotide variations were found, of which G430A, A457G, and T523C resulted in amino acid changes of A144T, I153V, and Y175H, respectively. The remaining 4 SNPs were C507T, T540C, C576T and C597T. Eight genotypes (AA, AB, AC, BB, BC, CC, DD, and DE) were detected in the 8 breeds. Chi(2) analysis showed that the distribution of the eight genotypes was very different among the different breeds (P < 0.01). Ex-cept for the Jingding duck, all breeds were in accordance with the Hardy-Weinberg equilibrium. Genetic analysis indicated that homozygosity was highest in the Jinding duck, lowest in the Gaoyou duck and similar in other breeds. Polymorphism information content (PIC) was low in the Jinding, high in the Gaoyou and intermediate in other breeds. These results showed that the adiponectin gene had a high level of polymorphism in different duck breeds, and could be used as a candidate gene to analyze the correlation between its polymorphism and fat traits in duck.