Effect of Fasting on the Spexin System in Broiler Chickens

Abstract

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.

Spexin Promotes the Proliferation and Differentiation of C2C12 Cells In Vitro—The Effect of Exercise on SPX and SPX Receptor Expression in Skeletal Muscle In Vivo

“…During the differentiation process we showed that the expression of GalR2 decreased while the expression of GalR3 increased. Many earlier studies have confirmed that SPX is widely expressed in many tissues of mammals, birds and other groups of animals [ 2 , 3 , 25 , 26 ], which indirectly suggests that SPX could play a role in the regulation of the metabolism of different tissues. Studies on the expression of GalR2 and GalR3 receptors in muscle tissue as well as in C2C12 cells have been more limited; however, both mRNA and protein studies indicate that both galanin receptor isoforms are expressed in muscle tissue.…”

The Role of Peptide Hormones Discovered in the 21st Century in the Regulation of Adipose Tissue Functions

“…This same effect was noted in serum in rats [ 166 ]. Our research performed in broiler chickens also proved that SPX expression is regulated by fasting time in fat tissue, the liver, and muscle, which also indicates that the SPX system could be a potent regulator of carbohydrate and lipid metabolism in birds [ 153 ].…”

“…Despite the fact that the research on this peptide is relatively recent, the knowledge about it has systematically increased. Research conducted on many different groups of animals showed a wide expression of this peptide in many different tissues, including fat tissue/adipocytes [ 152 , 153 , 154 , 155 , 156 , 157 , 158 ]. The first study that connected SPX with fat tissue metabolism were experiments performed by Walewski et al in 2014.…”

Impact of spexin on metabolic diseases and inflammation: An updated minireview

“…25 In chicken broilers, serum SPX began to increase after 2 h fasting and a statistically significant increase was observed after 4 and 8 h. 26 Moreover, after fasting, SPX transcripts were increased in the liver and decreased in adipose tissue and muscle, which are important tissues in the coordination of energy homeostasis. 26…”

“…It was also demonstrated that short-term food deprivation (7 days) increased SPX mRNA levels in the hypothalamus, and this returned to baseline levels after refeeding. 25 In chicken broilers, serum SPX began to increase after 2 h fasting and a statistically significant increase was observed after 4 and 8 h. 26 Moreover, after fasting, SPX transcripts were increased in the liver and decreased in adipose tissue and muscle, which are important tissues in the coordination of energy homeostasis. 26 Overall, SPX seems to be an orexigenic factor under negative energy balance.…”