Enpp1 is an anti-aging factor that regulates Klotho under phosphate overload conditions

Control of phosphate metabolism is crucial to regulate aging in mammals. Klotho is a well-known anti-aging factor that regulates phosphate metabolism: mice mutant or deficient in Klotho exhibit phenotypes resembling human aging. Here we show that ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1) is required for Klotho expression under phosphate overload conditions. Loss-of-function Enpp1 ttw/ttw mice under phosphate overload conditions exhibited phenotypes resembling human aging and Klotho mutants, such as short life span, arteriosclerosis and osteoporosis, with elevated serum 1,25(OH)2D3 levels. Enpp1ttw/ttw mice also exhibited significantly reduced renal Klotho expression under phosphate overload conditions, and aging phenotypes in these mice were rescued by Klotho overexpression, a low vitamin D diet or vitamin D receptor knockout. These findings indicate that Enpp1 plays a crucial role in regulating aging via Klotho expression under phosphate overload conditions

Selective Estrogen Receptor Modulators Suppress Hif1α Protein Accumulation in Mouse Osteoclasts.

Anti-bone resorptive drugs such as bisphosphonates, the anti-RANKL antibody (denosumab), or selective estrogen receptor modulators (SERMs) have been developed to treat osteoporosis. Mechanisms underlying activity of bisphosphonates or denosumab in this context are understood, while it is less clear how SERMs like tamoxifen, raloxifene, or bazedoxifene inhibit bone resorption. Recently, accumulation of hypoxia inducible factor 1 alpha (Hif1α) in osteoclasts was shown to be suppressed by estrogen in normal cells. In addition, osteoclast activation and decreased bone mass seen in estrogen-deficient conditions was found to require Hif1α. Here, we used western blot analysis of cultured osteoclast precursor cells to show that tamoxifen, raloxifene, or bazedoxifene all suppress Hif1α protein accumulation. The effects of each SERM on osteoclast differentiation differed in vitro. Our results suggest that interventions such as the SERMs evaluated here could be useful to inhibit Hif1α and osteoclast activity under estrogen-deficient conditions

SERM effects on osteoclastogenesis vary in estrogen-free culture conditions.

<p>Osteoclast progenitors from wild-type mice were cultured with tamoxifen (TAM, 1μM) (<b>A</b>), raloxifene (RAL, 1μM) (<b>B</b>) or bazedoxifene (BZA, 1μM) (<b>C</b>) in the presence or absence of M-CSF 50ng/ml (M) and RANKL 25ng/ml (R) in phenol red-free medium. <i>Cathepsin K</i>, <i>NFATc1</i> and <i>DC-STAMP</i> expression as analyzed by realtime PCR. Data represent mean <i>Cathepsin K</i>, <i>NFATc1 or DC-STAMP</i> expression relative to <i>β-actin</i> ± SD (<i>n</i> = 3). *<i>P</i><0.05; **<i>P</i><0.01; ***<i>P</i><0.001; NS, not significant (unpaired two-tailed Student’s <i>t</i>-test). Representative data of at least three independent experiments are shown.</p

Hif1α protein accumulation is suppressed by SERMs.

<p>Western blot analysis of Raw264.7 cells cultured in hypoxic conditions with or without tamoxifen (TAM, 0.5μM, 0.25μM) (A), raloxifene (RAL, 1μM) (B), or bazedoxifene (BZA, 1μM) (C) or estradiol (E2, 1μM). Vinculin expression serves as an internal control. In all panels, –(minus) symbols in the hypoxia row indicate normoxic conditions. Representative data of at least three independent experiments are shown.</p