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.

Keywords: broiler chicken; fasting; spexin.

Figure 1

mRNA expression of SPX1 (A), GALR2 (B), and GALR3 (C) genes in various chicken tissues. Comparison of SPX amino acid sequences in chickens, humans, mice, and rats (D). Results (graph: A–C) are shown as the means ± SEMfor each value (n = 6). The dots and symbols represent the individual values obtained.

Figure 2

Serum SPX concentration changes during short-term fasting. Results are shown as the means ± SEM for each value (n = 8). The dots represent the individual values obtained. Statistically significant changes are marked as asterisk symbol * p < 0.05 compared to time 0.

Figure 3

Correlations between circulating SPX concentration and insulin (A), glucagon (B), glucose (C), triglycerides (D), and NEFA (E) in nonfasted and 2, 4, and 8 h fasted chickens. The values for r and p are indicated in each graph. Solid and dashed lines show the mean and 95% confidence intervals, respectively, following linear-regression analysis; the symbols show the r-Pearson, p-values, and regression formulas. The r-Pearson reflects the correlation, and the p-value indicates the significance of the correlation.

Figure 4

SPX1, GALR2, and GALR3 mRNA changes in liver (A–C), fat tissue (D–F), and muscle (G–I) in response to short-term food deprivation. Results are shown as the means ± SEM for each value (n = 6). The dots represent the individual values obtained. Statistically significant changes are marked as asterisk symbol * p < 0.05 and ** p < 0.01 compared to time 0.