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Abstract: TH-PO538

Dietary Protein and Branched Chain Amino Acids Protect the Kidney from Phosphate Burden

Session Information

Category: Bone and Mineral Metabolism

  • 401 Bone and Mineral Metabolism: Basic

Authors

  • Shimada, Karin, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Matsui, Isao, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Matsumoto, Ayumi, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Hashimoto, Nobuhiro, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Yasuda, Seiichi, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Kajimoto, Sachio, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Doi, Yohei, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Yamaguchi, Satoshi, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Kubota, Keiichi, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Oka, Tatsufumi, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Sakaguchi, Yusuke, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Inoue, Kazunori, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Hamano, Takayuki, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
  • Isaka, Yoshitaka, Osaka University Graduate School of Medicine, Suita, Osaka-Fu, Japan
Background

Phosphate homeostasis is critically important for the maintenance of health. High phosphate intake has been reported to be harmful for the kidney. Although levels of dietary phosphate intake closely correlate with dietary protein intake, effects of dietary protein on phosphate toxicity remain uncertain.

Methods

Phosphate-induced chronic kidney disease (CKD) model were prepared by feeding a diet containing 2% phosphate to male Wistar rats for 6 weeks. Rats were randomly divided into 3 groups based on concomitant feeding of 12.5%, 25%, or 37.5% casein. Similar models were prepared by feeding ovalbumin instead of casein. We also analyzed effects of dietary branched chain amino acids (BCAA) on phosphate-induced kidney injury.

Results

Dietary casein suppressed serum levels of creatinine and phosphate, but elevated serum urea nitrogen, in a dose dependent manner. Dietary casein did not affect levels of food intake nor fecal phosphate. Although dietary casein elevated urinary protein in normal Wistar rats without phosphate burden, dietary casein did not increase urinary protein in phosphate-fed CKD rats. Both real time PCR and histological analyses revealed that dietary casein protected the kidney from phosphate-induced toxicity. Dietary casein maintained the mitochondrial integrity in tubular cells, and thereby suppressed oxidative stress. Ovalbumin showed even better renoprotective effects with unchanged serum urea nitrogen and suppressed urinary protein. To investigate underlying mechanisms of renoprotection by dietary proteins, we measured plasma amino acid levels and found that both dietary casein and ovalbumin elevated plasma valine, leucine, and isoleucine. Dietary supplementation of BCAA abrogated the toxic effects of phosphate to the kidney in a manner similar to that observed in ovalbumin-fed rats. Although dietary casein and ovalbumin increased water intake and urinary volume, BCAA affected neither of them.

Conclusion

Dietary protein protects the kidney from phosphate burden. BCAA supplementation may be even better way to suppress phosphate toxicity to the kidney.

Funding

  • Private Foundation Support