Prospective study on the association between serum amino acid profiles and depressive symptoms among the Japanese working population.

Objective: Accumulating evidence suggests that amino acids, particularly tryptophan and glutamate, play an important role in the pathology of depression, but prospective epidemiologic data on this issue is scarce. We examined the association between circulating amino acids and the risk of depressive symptoms in a Japanese working population.
Methods: Participants were 841 workers who were free from depressive symptoms and provided blood at baseline and completed 3-yr follow-up survey. 30 varieties of amino acid concentrations in serum were measured using liquid chromatography/mass spectrometry. Depressive symptoms were defined using the Center for Epidemiologic Studies Depression Scale. Logistic regression was used to calculate the odds ratios of depressive symptoms according to serum amino acids with adjustment for lifestyle factors.
Results: A total of 151 (18.0%) workers were newly identified as having depressive symptoms at the follow-up. Baseline tryptophan and glutamate concentrations in serum were not appreciably associated with the risk of depressive symptoms. Risk of depressive symptoms tended to increase with increasing arginine concentrations; the multivariable-adjusted odds ratio for the highest versus lowest tertile of serum arginine was 1.65 (95% confidence interval: 0.96-2.83; P for trend = 0.07). No clear association was found for other amino acids.
Conclusions: Results of the present study do not support a significant role of circulating amino acids in the development of depressive symptoms among Japanese.
Competing Interests: T.K. and M.E. are health professionals at the Furukawa Electric Corporation. Author I. Kabe is a health professional at the Kubota Corporation. All authors declare no conflict of interest, patents, products in development or marketed products etc. This does not alter the authors’ adherence to PLOS ONE policies on sharing data and materials.