Radvanyi, ZsuzsaZsuzsaRadvanyiYoo, Eun JinEun JinYooKandasamy, PalanivelPalanivelKandasamySalas-Bastos, AdrianAdrianSalas-BastosMonnerat, SophieSophieMonneratRefardt, JulieJulieRefardtChrist-Crain, MirjamMirjamChrist-CrainHayashi, HimekaHimekaHayashiKondo, YasuhikoYasuhikoKondoJantsch, JonathanJonathanJantschRubio-Aliaga, IsabelIsabelRubio-AliagaSommer, LukasLukasSommerWagner, Carsten ACarsten AWagnerHediger, MatthiasMatthiasHediger0000-0003-1946-027XKwon, Hyug MooHyug MooKwonLoffing, JohannesJohannesLoffingPathare, GaneshGaneshPathare2024-10-252024-10-252024-01https://boris-portal.unibe.ch/handle/20.500.12422/171654The bone-derived hormone fibroblast growth factor-23 (FGF23) has recently received much attention due to its association with chronic kidney disease and cardiovascular disease progression. Extracellular sodium concentration ([Na+]) plays a significant role in bone metabolism. Hyponatremia (lower serum [Na+]) has recently been shown to be independently associated with FGF23 levels in patients with chronic systolic heart failure. However, nothing is known about the direct impact of [Na+] on FGF23 production. Here, we show that an elevated [Na+] (+20 mM) suppressed FGF23 formation, whereas low [Na+] (-20 mM) increased FGF23 synthesis in the osteoblast-like cell lines UMR-106 and MC3T3-E1. Similar bidirectional changes in FGF23 abundance were observed when osmolality was altered by mannitol but not by urea, suggesting a role of tonicity in FGF23 formation. Moreover, these changes in FGF23 were inversely proportional to the expression of NFAT5 (nuclear factor of activated T cells-5), a transcription factor responsible for tonicity-mediated cellular adaptations. Furthermore arginine vasopressin (AVP), which is often responsible for hyponatremia, did not affect FGF23 production. Next, we performed a comprehensive and unbiased RNA-seq analysis of UMR-106 cells exposed to low vs. high [Na+], which revealed several novel genes involved in cellular adaptation to altered tonicity. Additional analysis of cells with Crisp-Cas9 mediated NFAT5 deletion indicated that NFAT5 controls numerous genes associated with FGF23 synthesis, thereby confirming its role in [Na+]-mediated FGF23 regulation. In line with these in vitro observations, we found that hyponatremia patients have higher FGF23 levels. Our results suggest that [Na+] is a critical regulator of FGF23 synthesis.enFGF23 NFAT5 bone and kidney extracellular-sodium hyponatremia600 - Technology::610 - Medicine & healtharticle10.48350/1893023799280310.1016/j.jbc.2023.105480