Acute cardiac overload does not induce cardiac or skeletal expression of fibroblast growth factor 23 in rats

Elevated fibroblast growth factor 23 (FGF23) is associated with cardiovascular events, particularly heart failure. Although FGF23 has been reported to induce cardiac hypertrophy, recent studies demonstrated that cardiac hypertrophy and myocardial infarction induce FGF23 production by cardiomyocytes. We aimed to explore whether acute cardiac overload increases cardiac and skeletal FGF23 expression and circulating FGF23 levels. METHODS: We administered 30 μL/g bodyweight of isotonic saline intraperitoneally in rats to induce acute cardiac overload. We measured serum FGF23 levels and other parameters of mineral metabolism at 2, 6, and 24 h after saline or sham injection. We also analyzed gene expression in the heart, calvarium, femur, and kidney at 2 and 24 h after injection. RESULTS: Acute saline injection induced cardiac overload as evidenced by a significant upregulation of brain natriuretic peptide along with a trend towards increased expression of atrial natriuretic peptide and mild hyponatremia. However, there were no changes in serum FGF23 levels or FGF23 expression in the heart, calvarium, or femur. CONCLUSIONS: Acute cardiac overload by saline injection in rats did neither induce FGF23 expression in the heart or bone nor did it increase serum FGF23 levels. These findings suggest that more severe or long-term cardiac damage is required for induction of FGF23 expression.