Abstract
BackgroundThe alterations of biological markers are thought to be effective tools to understand the pathophysiology and management of major depressive disorder (MDD). A lot of researches has implied many markers for depression, but any of them fully discovered the association between the markers and depression. The present study investigated the serum levels of amino acids and non-enzymatic antioxidants in major depression, and also explained their association with depression.MethodsThis study examined 247 MDD patients and 248 healthy controls (HCs) matched by age and sex. The Hamilton Depression Rating Scale (Ham-D) was used to all the participants to measure the severity of depression. Quantification of serum amino acids, vitamin A and E were carried out using the HPLC system whereas vitamin C levels were measured by UV-spectrophotometer. All the statistical analysis was performed by SPSS statistical software (version 23.0). The independent sample t-test, the Mann-Whitney U test, and the Fisher’s exact test were applied to detect the group differences where a Bonferroni correction applied to the p value.ResultsIt was observed that serum levels of four amino acids (methionine, phenylalanine, tryptophan, and tyrosine) along with three non-enzymatic antioxidants (vitamin A, E, and C) were significantly dropped in MDD patients compared to HCs (Cohen’s d (d): − 0.45, − 0.50, − 0.68, − 0.21, − 0.27, − 0.65, and − 0.24, respectively). Furthermore, Ham-D scores of cases were negatively correlated with serum levels of methionine (r = − 0.155, p = 0.015) and tyrosine (r = − 0.172, p = 0.007).ConclusionThe present study suggests that lowered serum methionine, phenylalanine, tryptophan, tyrosine, and non-enzymatic antioxidants are associated with depression. The reduction of these parameters in MDD patients may be the consequence, and not the cause, of major depression.
Highlights
The alterations of biological markers are thought to be effective tools to understand the pathophysiology and management of major depressive disorder (MDD)
Among all analyzed amino acids, serum levels of methionine, phenylalanine, tryptophan, and tyrosine were found notably declined in MDD patients as compared with healthy controls (HCs) (p < 0.05) with Cohen’s d effect size differences of − 0.45, − 0.50, − 0.68, and − 0.21, respectively (Table 2)
Our study found that serum concentrations of vitamin A, E and C were significantly lower in MDD patients in comparison to HCs (p < 0.05) with Cohen’s d effect size differences of − 0.27, − 0.65, and − 0.24, respectively (Table 3)
Summary
The alterations of biological markers are thought to be effective tools to understand the pathophysiology and management of major depressive disorder (MDD). In Bangladesh, WHO reported 4.1% of the adult population has depression [2] Several factors, such as genetics, alterations in brain structure and function, changes in biological markers, and nutritional status contribute to the development of MDD or increase the risk of developing the disorder [3,4,5,6]. It is well known that the neurotransmitters serotonin and norepinephrine are intimately related to depression The precursors of these neurotransmitters are the amino acids tryptophan and tyrosine, respectively and depleted levels of these amino acids are observed in MDD patients [11]. Methionine helps the body to produce S-adenosyl-l-methionine (SAMe) which is found to be lower in depressed patients according to two studies while another study suggests that the depletion was not so significant [15,16,17]
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