The agerelated changes of dietary phosphate responsiveness in plasma 1,25dihydroxyvitamin D levels and renal Cyp27b1 and Cyp24a1 gene expression is associated with renal αKlotho gene expression in mice

Abstract

In this study, we investigated the relationship between agerelated changes in renal αKlotho gene expression, vitamin D metabolism and the responsiveness of dietary phosphate in 1, 2 and 13 monthold mice fed a high phosphate (phosphate 1.2%) diet or low phosphate (phosphate 0.02%) diet for 5 days. We found that 1,25dihydroxyvitamin D levels in plasma were significantly lower in the high phosphate group than the low phosphate group for 1 and 2 monthold mice, but not 13 monthold mice. In addition, in the high phosphate group plasma 1,25dihydroxyvitamin D levels were decreased in 2 monthold mice relative to 1 monthold mice, but 13 monthold mice had higher levels than 2 monthold mice. In fact, plasma 1,25dihydroxyvitamin D levels showed a significant correlation with vitamin D metabolism gene Cyp27b1 and Cyp24a1 mRNA expression in the high phosphate group. Interestingly, renal αKlotho mRNA and protein levels were significant change with age. Furthermore, αKlotho mRNA expression showed a significant negative correlation with plasma 1,25dihydroxyvitamin D levels in the high phosphate group. Our results suggest that agerelated alterations in renal αKlotho expression could affect the responsiveness of dietary phosphate to vitamin D metabolism.