title: Magnesium deficiency increases serum fibroblast growth factor-23 levels in rats.
abstract: A magnesium (Mg)-deficient diet results in decreased serum phosphorus (P) levels and increased urinary P excretion; however, the mechanisms responsible for these effects are unclear. Fibroblast growth factor-23 (FGF-23) is a potent regulator of P homeostasis. To determine the mechanisms responsible for the change in serum levels and urinary excretion of P with Mg deficiency, the present study examined the effects of Mg deficiency on serum FGF-23 levels. Male rats were randomized by weight into two groups and fed a control diet (Mg concentration: 0.05%) or a Mg-deficient diet (Mg concentration: Mg-free) for 21 days. Serum P levels in rats fed the Mg-deficient diet were significantly lower than in rats fed the control diet. Furthermore, urinary P excretion was significantly higher in rats fed the Mg-deficient diet compared to rats fed the control diet. Conversely, the tubular reabsorption rate of P was significantly lower in rats fed the Mg-deficient diet than in the controls. Serum FGF-23 levels in rats fed the Mg-deficient diet were significantly higher than those in animals fed the control diet. The results from the present study indicate that 1) Mg deficiency increases serum FGF-23 levels; and 2) Mg deficiency causes increased urinary P excretion via inhibition of renal P reabsorption, resulting in a lowering of serum P levels. Moreover, we suggest that the high serum FGF-23 levels induced by Mg deficiency contribute to the decrease in renal P reabsorption.
authors.affiliation: Department of Nutrition, Junior College of Tokyo University of Agriculture, Tokyo 156-8502, Japan. matsu@nodai.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsuzaki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kajita
authors.forename: Misao
authors.initials: M
authors.lastname: Miwa
mesh_terms: D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000097:blood / Q000652:urine; D002762:Cholecalciferol / Q000097:blood; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D007684:Kidney Tubules / Q000378:metabolism; D008274:Magnesium / Q000097:blood / Q000652:urine; D008275:Magnesium Deficiency / Q000097:blood*; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000097:blood / Q000652:urine; D051381:Rats; D017208:Rats, Wistar
chemical_list: D010281:Parathyroid Hormone; D002762:Cholecalciferol; D010758:Phosphorus; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D008274:Magnesium; D002118:Calcium
keywords: fibroblast growth factor-23; magnesium deficiency; rats; serum phosphorus; urinary phosphorus