Effects of dietary myo-inositol supplementation on the expression of fibroblast growth factor 23 (FGF23) and αKlotho in two commercial laying hen strains.

Phosphate homeostasis is controlled by fibroblast growth factor 23 (FGF23) produced by bone cells in mammals and primarily acting in the kidney. For its phosphaturic effect and for suppression of production of active vitamin D, it requires αKlotho as a co-receptor. FGF23 and αKlotho have emerged as disease biomarkers. Relatively little is known about their significance in laying hens that are in particular need of balanced mineral homeostasis for eggshell formation. Dietary myo-inositol (MI) and phosphate metabolism are interdependent, and this study aimed to explore FGF23 and αKlotho expression in two commercial hen strains fed different amounts of MI. Forty Lohmann Brown Classic (LB) and Lohmann LSL-Classic (LSL) 26-week-old hens received standard diets with 0, 1, 2, or 3 g supplemental MI per kg feed for four weeks, and gene expression of FGF23 and αKlotho was measured by quantitative real-time PCR in different organs. Statistical analysis was performed with the MIXED procedure, and correlation analysis with markers of phosphate homeostasis and hepatic inflammation applying Pearson's correlation coefficient or Spearman's Rho. Three g supplemental MI per kg feed resulted in lower hepatic FGF23 expression only in LB hens. Regardless of MI supplementation, tibial FGF23 expression tended to be lower in LSL than LB hens. Moreover, supplemental MI did not significantly impact αKlotho expression, but hepatic αKlotho expression was higher in LSL than LB hens without MI supplementation and tibial and renal αKlotho expression was significantly higher in LB than in LSL hens, regardless of dietary MI. To summarize, MI supplements at 3 g/kg reduced hepatic FGF23 expression in LB, but not in LSL hens at the peak of egg-laying. Further studies might be needed to elucidate the effect before sexual maturity.