Abstract
Despite many clinical trials assessing the role of zinc in major depressive disorder (MDD), the conclusions still remain ambiguous. The aim of the present clinical study was to determine and comparison the zinc concentration in the blood of MDD patients (active stage or remission) and healthy volunteers (controls), as well as to discuss its potential clinical usefulness as a biomarker of the disease. In this study 69 patients with current depressive episode, 45 patients in remission and 50 controls were enrolled. The zinc concentration was measured by electrothermal atomic absorption spectrometry (ET AAS). The obtained results revealed, that the zinc concentration in depressed phase were statistically lower than in the healthy volunteers [0.89 vs. 1.06 mg/L, respectively], while the zinc level in patients achieve remission was not significantly different from the controls [1.07 vs. 1.06 mg/L, respectively]. Additionally, among the patients achieve remission a significant differences in zinc concentration between group with and without presence of drug-resistance in the previous episode of depression were observed. Also, patients in remission demonstrated correlation between zinc level and the average number of depressive episodes in the last year. Serum zinc concentration was not dependent on atypical features of depression, presence of psychotic symptoms or melancholic syndrome, age, age of onset or duration of disease, number of episodes in the life time, duration of the episode/remission and severity of depression measured by the Hamilton Rating Scale for Depression (HDRS), and the Montgomery-Asberg Depression Rating Scale (MADRS). Concluding, our findings confirm the correlation between zinc deficit present in the depressive episode, and are consistent with the majority of previous studies. These results may also indicate that serum zinc concentration might be considered as a potential biological marker of MDD.
Highlights
Zinc is a crucial element of living organisms, which is involved in many basic physiological processes
There is evidence that zinc deficiency leads to changes in the central nervous system (CNS) functioning, especially in the glutamatergic transmission in the limbic system and cerebral cortex, which playing an important role in the etiopathogenesis of depression [see (Mlyniec 2015) for review]
Serum zinc levels were measured by a electrothermal atomic absorption spectrometry (ET AAS) using a PerkinElmer spectrometer model 3110 (USA)
Summary
Zinc is a crucial element of living organisms, which is involved in many basic physiological processes (mainly as a cofactor of over 300 enzymes). Zinc ions can modulate a number of ligand- and voltage-gated ion channels, such as gamma-aminobutyric acid (GABAA) (Frederickson 1989; Marchetti 2014), N-methyl-Daspartate (NMDA) (Chen et al 1997; Szewczyk et al 2012), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate (KA) receptors, and may affect the serotonin receptors (Kalappa et al 2015; Veran et al 2012; Satała et al 2015) By influencing those receptors in the specific brain areas Zn2+ indirectly modulates synaptic plasticity, regulate neuronal signal transduction, and other processes, like memory and learning (Paoletti et al 2009; Yu et al 2013; Grabrucker 2014). Zinc affects emotional lability, psychomotor functions, attention (Szewczyk et al 2011; Swardfager et al 2013a), irritability (Russo 2011) and other emotional, executive and cognitive functions (Szewczyk et al 2011; Maes et al 1994, 1997; Swardfager et al 2013a; McLoughlin and Hodge 1990; Narang et al 1991; Salari et al 2015)
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