Current Developments in Nutrition (Jul 2024)

Effects of d-alanine Intake on Amino Acid Metabolism and Kidney Function in Healthy Adults: A Multicenter, Randomized Pilot Study

  • Megumi Oshima,
  • Tadashi Toyama,
  • Tatsuhiko Toyama,
  • Yusuke Nakade,
  • Toshiaki Tokumaru,
  • Keisuke Sako,
  • Sho Kajikawa,
  • Daiki Hayashi,
  • Hajime Sanada,
  • Takahiro Yuasa,
  • Akihiko Koshino,
  • Keisuke Horikoshi,
  • Taichiro Minami,
  • Shunsuke Tsuge,
  • Akira Tamai,
  • Shiori Nakagawa,
  • Ryo Nishioka,
  • Takeshi Zoshima,
  • Kiyoaki Ito,
  • Shinji Kitajima,
  • Ichiro Mizushima,
  • Akinori Hara,
  • Norihiko Sakai,
  • Miho Shimizu,
  • Masashi Mita,
  • Yasunori Iwata,
  • Takashi Wada

Journal volume & issue
Vol. 8, no. 7
p. 103787

Abstract

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Background: d-alanine administration prevented kidney damage in a murine acute kidney injury model. Further data are needed on the influence of d-alanine on kidney function in humans. Objective: This study investigated the effects of d-alanine intake on amino acid metabolism and kidney function in healthy volunteers. Methods: This multicenter pilot study randomly assigned individuals from the general Japanese population to receive 3 g or 6 g of d-alanine intake per day for 7 d in a 1:1 ratio. The primary endpoint was the mean change in plasma and urine d-alanine levels from baseline to 7 d after intake. The secondary endpoints were mean changes in kidney function and other clinical factors. Safety was assessed by evaluating adverse events and clinical parameters. Results: We randomly assigned 24 participants to the 3-g (n = 12) and 6-g d-alanine (n = 12) groups. The mean baseline estimated glomerular filtration rate (eGFR) was 73 mL/min/1.73 m2. The mean plasma d-alanine concentration increased from baseline by 77.5 ± 34.3 and 192.1 ± 80.9 nmol/mL in the 3-g and 6-g d-alanine groups (both p < 0.0001), respectively, in a dose-dependent manner (between-group difference: 114.6 nmol/mL; 95% CI: 62.1–167.2; P = 0.0002). A similar increase was observed for the urine d-alanine to creatinine ratio. The mean eGFR was elevated by 5.7 ± 8.8 mL/min/1.73 m2 in the 6-g d-alanine group (P = 0.045) but did not significantly change in the 3-g d-alanine group. Nonserious adverse events were reported in 11 participants. Conclusions: d-alanine intake increased plasma and urine d-alanine levels and was well tolerated in participants with normal kidney function. These results will be useful in future trials investigating the effects of d-alanine intake on kidney disease progression in patients with chronic kidney disease.This trial was registered at the UMIN Clinical Trials Registry as UMIN000051466.

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