Abstract
ObjectiveAccumulating 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.MethodsParticipants 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.ResultsA 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.ConclusionsResults of the present study do not support a significant role of circulating amino acids in the development of depressive symptoms among Japanese.
Highlights
Depression is a common mental health issue, which reduces productivity at work, lowers the quality of life, as well as increases mortality [1]
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
Summary
Depression is a common mental health issue, which reduces productivity at work, lowers the quality of life, as well as increases mortality [1]. Changes in the serotonergic [3, 4], dopaminergic [5], noradrenergic [3, 4], and glutamatergic [6, 7] systems are suggested to be involved in depression. A shortage or impaired processing of these amino acids may result in decreased levels of mood-regulating neurotransmitters, which are thought to be involved in depression [8]. When present in excess, excitatory amino acids such as of glutamate are known to act as potent neuronal excitotoxins, triggering neurotoxicity in pathology of depression [6], and increased concentrations of excitatory amino acids may occur in the brain as a result of peripheral alteration of the availability or metabolism of these amino acids [9]
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