Effect of Fasting on the Spexin System in Broiler Chickens.

Spexin (SPX) is a highly conservative peptide hormone containing 14 amino acids and was discovered in 2007 by bioinformatics methods. However, nothing is yet known about its role in the metabolism of birds, including broilers. The aim of this study was to investigate the effect of short-term fasting (2, 4, and 8 h) on the concentration of SPX in blood serum and the expression levels of the genes encoding this peptide (SPX1) and its receptors, GALR2 and GALR3, in the tissues involved in carbohydrate and lipid metabolism (muscles, adipose tissue, and liver). We also analyzed the mRNA expression of these genes in various chicken tissues. Moreover, we studied the correlation between the serum level of SPX and other metabolic parameters (insulin, glucagon, glucose, triglycerides, and cholesterol). Using RT-qPCR, we found that SPX1, GALR2, and GALR3 are expressed in all investigated tissues in broiler chicken. Moreover, using a commercially available radio-immunoassay, we noted an increase of the SPX level in blood serum after 4 and 8 h of fasting compared to nonfasted animals (p < 0.05). This increase was positively correlated with glucagon concentration (r = 0.341; p < 0.05) and negatively with glucose concentration (r = -0.484; p < 0.01). Additionally, we discovered that in the short term, food deprivation leads to the expression regulation of SPX1, GALR2, and GLAR3 in tissues associated with metabolism of carbohydrates and lipids. The obtained results indicate that SPX is involved in the regulation of metabolism in broiler chickens.