Estrogen inhibits renal Na-Pi Co-transporters and improves klotho deficiency-induced acute heart failure

Abstract

Objective and hypothesis: Klotho is an aging-suppressor gene. Mutation of Klotho gene causes hyperphosphatemia and acute heart failure. However, the relationship of hyperphosphatemia and acute heart failure is unclear. We hypothesize that hyperphosphatemia mediates Klotho deficiency-induced acute heart failure and further that therapeutic reduction of hyperphosphatemia prevents acute heart failure in Klotho mutant (KL(-/-)) mice.

Methods and results: A significant elevation of serum phosphorus levels and a large reduction of heart function were found in KL(-/-) mice by six weeks of age. Normalization of serum phosphorus levels by low phosphate diet (LPD) rescued Klotho deficiency-induced heart failure and extended lifespan in male mice. Klotho deficiency impaired cardiac mitochondrial respiratory enzyme function and increased superoxide production, oxidative stress, and cardiac cell apoptosis in male KL(-/-) mice which can be eliminated by LPD. LPD, however, did not rescue hyperphosphatemia or heart failure in female KL(-/-) mice. LPD did not affect estrogen depletion in female KL(-/-) mice. Normalization of serum estrogen levels by treatment with 17β-estradiol prevented hyperphosphatemia and heart failure in female KL(-/-) mice. Mechanistically, treatment with 17β-estradiol rescued hyperphosphatemia via inhibiting renal Na-Pi co-transporter expression. Normalization of serum phosphorus levels by treatment with 17β-estradiol also abolished cardiac mitochondrial respiratory enzyme dysfunction, ROS overproduction, oxidative stress and cardiac cell apoptosis in female KL(-/-) mice.

Conclusion: Klotho deficiency causes acute heart failure via hyperphosphatemia in male mice which can be prevented by LPD. 17β-estradiol prevents Klotho deficiency-induced hyperphosphatemia and heart failure by eliminating upregulation of renal Na-Pi co-transporter expression in female mice.

Keywords: Apoptosis; Estrogen; Hyperphosphatemia; Na-pi co-transporter; Oxidative stress; heart failure.