Abstract
Background: Schizophrenia is associated with a deficiency of dietary antioxidants like vitamin B6, B9, and B12 resulting in defective methylation leading to hyperhomocysteinemia. Hyperhomocysteinemia causes mitochondrial DNA damage, oxidative stress, vascular damage, and lipid peroxidation. Oxidative stress and increase in reactive oxygen species result in 8-oxodG production which induces apoptosis of both astrocytes and thyrocytes thus predisposing them to thyroid dysfunction and neurodegeneration. Furthermore, the presence of excessive free radicals increases thyroid thermogenesis causing hyperthyroidism or its excess may cause hypothyroidism by inhibiting iodide uptake. In the present study, we evaluated the various biomarkers associated with thyroid dysfunction in schizophrenics. Materials and Methods: 288 patients suffering from schizophrenia and 100 control subjects were screened for liver function tests (LFTs) such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total bilirubin (TB). Also, the stress markers, namely malondialdehyde (MDA), homocysteine, cysteine, methionine, the thyroid profile including triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), thyroxine peroxide antibody (TPO-Ab); TSH receptor-Ab (TSHr-Ab), dietary antioxidants, lipids, cytokines, aminoacids and hormones, vitamins and trace elements, and other biochemical parameters. Results: The LFTs showed elevated levels of ALT (45.57 ± 4.87 Vs. 26.41 ± 3.76 U/L), AST (40.55 ± 1.34 Vs. 21.92 ± 3.65 U/L), ALP (121.54 ± 4.87 Vs. 83.76 ± 5.87 U/L), and total bilirubin (2.63 ± 0.987 Vs. 1.10 ± 0.056 mg/dl), in schizophrenics than controls. Increased levels of MDA (3.71 ± 0.967 Vs. 1.68 ± 0.099) and homocysteine (17.56 ± 2.612 Vs. 6.96 ± 1.987 μmol/L were observed in schizophrenics compared to the controls, indicating increased stress. Levels of cysteine and methionine were decreased in schizophrenics than the controls (1.08 ± 0.089 Vs. 4.87 ± .924 μmol/L and 17.87 ± 1.23 Vs. 99.20 ± 5.36 μmol/L). The levels of TPO-Ab (IU/ml), Tg-Ab (pmol/L), and TSHr-Ab (IU/L) were observed to be higher in the patients’ group as compared to control subjects (9.84 ± 2.56 Vs. 5.81 ± 1.98, 55.50 ± 2.98 Vs. 32.95 ± 2.87 and 2.95 ± 0.0045 Vs. 1.44 ± 0.0023 respectively). Levels of Vitamin B6, B9, and B12 were also significantly decreased in the patients compared to the healthy controls. Conclusion: The schizophrenics, demonstrated altered liver function, increased stress markers, and decreased dietary antioxidants. Reduced primary and secondary antioxidant levels, may result in hyperhomocysteinemia and cause further DNA and mitochondrial damage. Therefore, homocysteine and/or prolactin levels may serve as candidate prognostic markers for schizophrenia. Also, both neurological symptoms and the susceptibility to thyroid disorders may be prevented in the initial stages of this debilitating disorder by appropriate dietary supplementation of antioxidants which can rectify a reduction in primary and secondary antioxidants, and disturbed prolactin-serotonin-dopamine interactions in schizophrenics.
Highlights
Schizophrenia is a neuropsychiatric disorder manifested by disruptive thinking, quantifiable language disturbances, perception, and self-sense (Barnham et al, 2004; Ciobica et al, 2011)
The present study showed that in schizophrenics susceptible to thyroid disorders, deficiency in vitamins B6, B9, and B12 mediates hyperhomocysteinemia resulting in the reduction of antioxidative enzymes leading to oxidative injury
The levels of glutamate and cysteine were lower in schizophrenics, mediating oxidative insult while the decline in arginine levels result in decreased Nitric Oxide (NO) levels leading to schizophrenic symptoms
Summary
Schizophrenia is a neuropsychiatric disorder manifested by disruptive thinking, quantifiable language disturbances, perception, and self-sense (Barnham et al, 2004; Ciobica et al, 2011). Schizophrenia accounts for 1.1% of adults with nearly 21 million individuals being affected in the United States alone (Santos et al, 2012). It is among the seven most disabling diseases in patients between 20–45 years of age being more common than cardiovascular diseases, HIV, and diabetes. We evaluated the various biomarkers associated with thyroid dysfunction in schizophrenics
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