The Role of Zinc Intake in Serotonin and Cortisol Level in Patient with Depression

Background: Low zinc levels affect the relationship between the glutamatergic and serotonergic systems in major depressive disorders that cause stress and inflammation. Decreased zinc in the hippocampus can activate the HPA axis associated with increased in cortisol. Several studies documented the relationship between zinc and clinical depression. However, further research including biological measurements is needed to support these studies. Objective: To analyze the correlation between zinc intake with serotonin and cortisol serum in patients with depression Methods: This was an observational study with a cross sectional design. Subjects were patients with depression who admitted to Dr. Kariadi Hospital, Tugurejo Hospital, Diponegoro National Hospital and Permata Medika Hospital. The level of depression was determined using Beck Depression Inventory-II (BDI-II). The food frequency questionnaire (FFQ) was used to assess daily zinc intake. The levels of serum serotonin and cortisol were measured using the ELISA technique. Results: Of the 53 subjects, there was a significant correlation between zinc intake with serotonin serum level (p=0.038); however, there was no significant correlation between zinc intake with cortisol serum level (p=0.845). Conclusion: High zinc intake is correlated with serotonin level in patient with depression


INTRODUCTION
Depression is a mental disorder associated with decreased productivity, poor psychosocial outcomes and decreased quality of life and wellbeing.According to the World Health Organization (WHO), the total number of people living with depression in the world is about 350 million.Nearly half of these people live in South-East Asia and Western Pacific. 1 In Indonesia, with a variety of biological, psychological and social factors with diversity in the population, the total estimated number of cases of mental disorders increase.This may result burden and decrease in human productivity.Data of Basic Health Research of Ministry of Health of the Republic of Indonesia in 2018 showed the prevalence of depression among the population of aged 15 years and above was about 14 million people or 6.1%, with a prevalence of 4.7% in Central Java. 2 Although there are many effective treatments for depression, pharmacotherapy is usually costly and has potential side effects and psychotherapy requires time and commitment.Take the widely promoted monoaminergic antidepressant, for example, more than 30% of the patients did not respond to this treatment. 3herefore, there is a need to investigate alternative treatment or prevention strategies.
Recent research has focused on the role of micronutrient in various mental health disorders including depression. 4,5Zinc is one of micronutrients essential for optimal function of the human body, especially the brain and neural structures, where it is found at the highest concentration in the hippocampus and amygdala regions of the brain. 6he essential trace ion zinc participates in numerous biological processes.Zinc regulates intracellular signal transduction and contributes to efficient synaptic transmission in the central nervous system. 7Zinc deficiency is a recognized global public health concern in developing countries and is also becoming a prevalent concern in the aging population of developed countries. 8inc deficiency is also associated with neuropsychiatric manifestation, including cognitive and behavioral changes and depression. 9A case-control study showed that serum zinc levels in patients with depression were significantly lower than in normal controls. 10urthermore, a meta-analysis study concluded that zinc supplementation may improve depression in individuals treated with antidepressant. 11he interaction of zinc and the serotonergic receptor 5-hydroxytryptamine 1A (5-HT1A) in a mouse test with reduced antidepressant administration showed that zinc modulates serotonergic receptors that can improve depression. 12Serotonin is involved in various central nervous system functions to regulate pain, sleep, blood pressure, mood, and behaviour.The role of serotonergic transmission in depression is well known so that it is one of the mechanisms of action in anti-depressant drugs.Effect on serotonergic receptors is one of the explanations of the antidepressant-like properties of zinc, which are observed in both preclinical and clinical studies.Satała et al. extensively explored the pharmacological profile of zinc at the 5-HT1A receptors using the agonist of 5-HT1A, [3H]-8-OH-DPAT. 13The interaction of zinc with glutamate and the specific Nmethyl-D-aspartate (NMDA) receptor is another mechanism in reducing symptoms of depression. 14Low zinc levels disrupt the relationship between the glutamatergic and serotonergic systems in major depressive disorders causing stress and inflammation. 15ome studies showed that increased glucocorticoids in stress and inflammation in the dysregulation of the Hypothalamic Pituitary Adrenal (HPA) axis produce symptoms of depression.Decreased zinc level in the hippocampus activates the HPA axis associated with increased cortisol. 16The role of dietary zinc intake in serotonin and cortisol levels has never been reported in depression patients.This study aimed to analyze the correlation between zinc intake with serotonin and cortisol serum in patient with depression.

Study Design and Participants
This was an observational study with cross-sectional design.Subjects participated in this study were patients with diagnosis of depression under treatment based on the medical records who admitted to Psychiatry Clinic at Dr. Kariadi Hospital, Tugurejo Hospital, Diponegoro National Hospital, and Permata Medika Hospital between January -December 2019 with age ranged from 18 to 60 years old.Beck Depression Inventory -II (BDI-II) was administered by authors who were psychiatrist to determine level of depression.Subjects signed a consent form that approved by our institutional review board No. 126/EC/KEPK-FK-UNDIP/VI/2020.

Measurements
Subjects filled the demographic questionnaires including sex, occupation, marital status, education, income, and history of psychosocial stressors.Subjects underwent a full medical evaluation, which were medical history, physical and psychiatric examination.Subjects who had diabetes mellitus, cardiovascular disease, renal disease, gastrointestinal disease, malignancy, smoking, pregnancy and breastfeeding were excluded.Body weight and height were measured to calculate the body mass index (BMI).
Zinc intake was calculated from a dietary intakes assessment using food frequency questionnaires (FFQ). 17FQ was administered by trained physician and data conversion was carried by nutritionist.Zinc daily intake of each participant was obtained from the conversion of FFQ in gram.Zinc daily intake level was categorized as insufficient when the zinc intake was below 77% of daily requirement and normal when the zinc intake was above or the same as daily requirement. 18,19erum were obtained from peripheral blood vein at 8.00 -9.30 am for each subject.The Sandwich ELISA method using Serotonin high sensitive ELISA kit, IBL International GMBH (Hamburg, Germany) and Microplate Reader Biorad 680 were applied to measure the serotonin level.Architect Cortisol Reagen (Illinois, USA), and Architect i2000SR were used to measure the serum cortisol level.Normal serum serotonin levels ranged from 101-283 ng/ml and normal serum cortisol level ranged from 10-20 g/dL. 20Table 2 summarizes the correlation between zinc intake and serum serotonin and cortisol levels.It showed a significant positive correlation between zinc intake and serum serotonin level (p=0.038)but not with serum cortisol level (p=0.0845).
Table 3 shows the result of the bivariate analysis between demographic variables i.e., occupation, marital status, education, monthly income, length of antidepressant therapy, stressor, nutritional status, sex, age and BDI-II and serum serotonin and cortisol levels.From this analysis, we found a significant negative correlation between BMI and serum serotonin levels in the subjects.(p=0.039) with a weak level of coefficient correlation (r=-0.284).The higher the BMI, the lower the serum serotonin levels.There was a significant negative correlation between the length of therapy and serum cortisol levels of subjects (p=0.042) and there was a significant negative correlation between gender and serum cortisol levels (p=0.001).

DISCUSSION
This study showed a significant correlation between zinc intake and serum serotonin levels in patients with depression.A publication demonstrates differences in serum concentrations in patient with depression. 10In the etiology of depression there is a monoamine hypothesis which states that depression is associated with a decrease in the amount or function of serotonin in cortex and limbic system.In this study the measured zinc intake was obtained from interview using food frequency questionnaire similar to a study conducted by Li et al which assessed total zinc level using a 24-h recall survey. 21Serotonin levels play a role in the mechanism of action of antidepressants.The relationship between zinc intake and depression can be explained by various mechanisms.Zinc homeostasis in the brain is regulated by the food intake containing zinc.Zinc has a synergistic * Significant (p < 0,05); a Spearman's correlation b Pearson correlation effect like SSRIs that can regulate 5-HT1A receptors that can inhibit agonist and antagonist binding at synapses.Zinc can also affect serotonin neurotransmission, NMDAR activation and BDNF activity involved in depression. 22In addition, zinc also has antiinflammatory and antioxidant properties that contribute to depression. 23inc plays a significant role with respect to the stress response.Proper maintenance of zinc status can help stabilize serum cortisol levels over time and zinc intake has been shown to temporarily inhibit cortisol secretions. 16However, prolonged stress will deplete zinc concentrations in the blood.Zinc deficiency has been demonstrated to increase plasma cortisol and proinflammatory cytokine of interleukin-6 (IL-6), IL-1 and nitric oxide levels.The mechanism of food consumption-induced cortisol stimulation is not known, it may be due to stimulation of pituitary ACTH secretion by amino acid products or protein digestion, release of gut messengers that secondarily release ACTH or release locally generated ACTH from the intestine.The results also indicated that there was no significant correlation between zinc intake and serum cortisol levels in patients with depression.This may be because cortisol is a biological marker of stress in general and not a specific marker for depression. 24We found that almost all subjects had normal serum cortisol levels which was possible because the subjects were already on antidepressant treatment and were not currently exposed to stressful stimuli.Across multiple mental healthrelated measures, a polymorphism (5-HTTLPR) within the serotonin transporter gene promoter has been associated with differential psychological sensitivity to stressful experience.The short/short genotype of the 5-HTTLPR is associated with greater cortisol reactivity to social threat.When short/short individuals experience stressful life events, they might be at greater risk for the adverse psychological and physical health consequences associated with heightened cortisol exposure. 25lthough acute or chronic stress can be measured in physiological parameters such as heart rate, blood pressure, and various metabolic hormones, it is difficult to understand whether changes in levels of circulating stress mediators such as cortisol can reflect acute, chronic or diurnal stress. 24,26In the analysis of confounding variables on serotonin levels, it was found that serum serotonin levels were correlated by body mass index.Abnormal BMI is also related to the availability of serotonin transporters that disrupted in individual with obesity.This is consistent with a study assessed the correlation between plasma tryptophan levels and BMI with symptoms of depression. 27Another study demonstrated that BMI and body fat mass were associated decreased serotonin production in children and adolescents with severe obesity.A chronic lowgrade inflammatory state is a trait in obesity and assumed to be one of the underlying pathomechanism.This mechanism increase tryptophan catabolism via the kynurenine pathway regulated by nutritional and inflammatory signals and linked to decrease in serotonin production. 28,291][32] Animal and human studies also suggested that female sex hormone influence the HPA axis and corticoid receptors in the hypothalamus and amygdala. 33,34Decreased serotonin levels is one of the pathophysiology mechanism of depression. 35The limitation of our study was the subjects were patients with depression under treatment, however we analyzed the correlation between length of therapy with serotonin and cortisol level.We found that there was no significant correlation between length of therapy with serotonin but there was a significant correlation between length of therapy with cortisol level.Serum cortisol levels were influenced by the length of therapy.This can be because the use of long-term antidepressants can affect the HPA axis through changes in glucocorticoid and mineralocorticoid receptors so that serum cortisol levels will decrease.Changes in these receptors affect the effectiveness of therapy.Long term use of antidepressants for both SSRI and non-SSRI can reduce the intensity of HPA axis activity that eventually reduces serum cortisol levels. 36

CONCLUSION
From the study, we conclude that there was a significant correlation between zinc intake and serum serotonin levels, thus the higher the zinc intake the higher the serum serotonin levels.There was no significant correlation between zinc intake and serum cortisol levels.In addition, BMI has a significant correlation with serotonin levels.The length of antidepressant therapy and gender significantly correlated with serum cortisol levels.Further research is needed to assess other risk factors affecting serum serotonin and cortisol levels.

Table 1
Demographic Characteristics of Subjects

Table 2 .
Correlation between zinc intake and serum serotonin level The correlation between zinc intake and serotonin and cortisol levels was analyzed.Pearson test was done to analyze the role of age in serotonin and cortisol level and the Spearman correlation test to analyze the role of, length of therapy, stressor, nutritional status, sex, and BDI-II score in serum serotonin and cortisol level.The p value is considered significant if p<0.05.

Table 3 .
Correlation between demographic variables and serum serotonin and cortisol levels