Serum ethylamine levels as an indicator of l-theanine consumption and the risk of type 2 diabetes in a general Japanese population: The hisayama study

Toshiharu Ninomiya, Noriyuki Kanzaki, Yoichiro Hirakawa, Masahito Yoshinari, Mayu Higashioka, Takanori Honda, Mao Shibata, Satoko Sakata, Daigo Yoshida, Takanori Teramoto, Susumu Takemoto, Shozo Nishimoto, Jun Hata, Takanari Kitazono

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Abstract

OBJECTIVE This study investigated the association between serum ethylamine levels as an indicator of L-theanine consumption and the development of type 2 diabetes in a Japanese community. RESEARCH DESIGN AND METHODS A total of 2,253 community-dwelling Japanese individuals aged 40-79 years without diabetes were monitored for 7 years. Serum ethylamine levels were divided into quartiles: ≤0.86, 0.87-2.10, 2.11-5.28, and ≥5.29 ng/mL. Kinetic analysis of serum ethylamine concentrations was performed after ingestion of L-theanine-rich green tea products containing 8 mg of L-theanine by 12 healthy volunteers. RESULTS During follow-up, 282 subjects developed type 2 diabetes. The age- and sexadjusted cumulative incidence of type 2 diabetes decreased significantly with elevating levels of serum ethylamine (P for trend = 0.04). This association remained unchanged after adjusting for potential confounding factors. The multivariableadjusted hazard ratio (HR) for type 2 diabetes was significantly lower in the fourth quartile of serum ethylamine than in the first quartile (HR 0.69, 95% CI 0.49-0.98). This trend of decrease in diabetic risk across serum ethylamine levels was more prominent in middle-aged subjects and in subjects with prediabetes, obesity, or insulin resistance. Kinetic analysis estimated that the minimum concentration at the steady state was >5.90 ng/mL in the case of twice-daily ingestion with an interval of 12 h. CONCLUSIONS Higher serum ethylamine was significantly associated with lower risk of the development of type 2 diabetes in a general Japanese population. The measurement of serum ethylamine concentration would be a useful biomarker for the objective estimation of L-theanine consumption.

Original languageEnglish
Pages (from-to)1234-1240
Number of pages7
JournalDiabetes care
Volume42
Issue number7
DOIs
Publication statusPublished - 2019

All Science Journal Classification (ASJC) codes

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Advanced and Specialised Nursing

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