Hyperaldosteronism in Klotho-deficient mice

Fischer SS, Kempe DS, Leibrock CB, Rexhepaj R, Siraskar B, Boini KM, Ackermann TF, Foller M, Hocher B, Rosenblatt KP, Kuro-o M, Lang F. Hyperaldosteronism in Klotho-deficient mice. Am J Physiol Renal Physiol 299: F1171-F1177, 2010. First published August 18, 2010; doi:10.1152/ajprenal.00233.2010.-Klotho is a membrane protein participating in the inhibitory effect of FGF23 on the formation of 1,25-dihydroxyvitamin-D-3 [1,25(OH)(2)D-3]. It participates in the regulation of renal tubular phosphate reabsorption and stimulates renal tubular Ca2+ reabsorption. Klotho hypomorphic mice (klotho(hm)) suffer from severe growth deficit, rapid aging, and early death, events largely reversed by a vitamin D-deficient diet. The present study explored the role of Klotho deficiency in mineral and electrolyte metabolism. To this end, klothohm mice and wild-type mice (klotho(+/+)) were subjected to a normal (D+) or vitamin D-deficient (D-) diet or to a vitamin D-deficient diet for 4 wk and then to a normal diet (D-/+). At the age of 8 wk, body weight was significantly lower in klotho(hm)D(+) mice than in klotho(+/+)D(+) mice, klotho(hm)D(-) mice, and klotho(hm)D(-/+) mice. Plasma concentrations of 1,25(OH)(2)D-3, adrenocorticotropic hormone (ACTH), antidiuretic hormone (ADH), and aldosterone were significantly higher in klotho(hm)D(+) mice than in klotho(+/+)D(+) mice. Plasma volume was significantly smaller in klotho(hm)D(-/+) mice, and plasma urea, Ca2+, phosphate and Na+, but not K+ concentrations were significantly higher in klotho(hm)D(+) mice than in klotho(+/+)D(+) mice. The differences were partially abrogated by a vitamin D-deficient diet. Moreover, the hyperaldosteronism was partially reversed by Ca2+-deficient diet. Ussing chamber experiments revealed a marked increase in amiloride-sensitive current across the colonic epithelium, pointing to enhanced epithelial sodium channel (ENaC) activity. A salt-deficient diet tended to decrease and a salt-rich diet significantly increased the life span of klotho(hm)D(+) mice. In conclusion, the present observation disclose that the excessive formation of 1,25(OH)(2)D-3 in Klotho-deficient mice results in extracellular volume depletion, which significantly contributes to the shortening of life span.