Polymorphisms in the type I deiodinase gene and frontal function in recurrent depressive disorder

Area of Science:

• Neuroscience
• Genetics
• Psychiatry

Background:

• Depression is often linked to impaired cognitive functions, such as memory and executive functions.
• Thyroid hormones (TH), particularly triiodothyronine (T3), influence cognitive processes and their regulation involves deiodinase type 1 (D1).
• Genetic variations in the DIO1 gene, which codes for D1, may affect TH levels and consequently cognitive functioning.

Purpose of the Study:

• To examine the association between two specific DIO1 gene polymorphisms (DIO1a-C/T and DIO1b-A/G) and cognitive functions in patients with recurrent depressive disorder (rDD).
• To specifically assess the impact on frontal functions, including working memory, executive functions, and verbal fluency.

Main Methods:

• Genotyping of DIO1 gene variants (DIO1a-C/T and DIO1b-A/G) in 128 rDD patients using polymerase chain reaction (PCR).
• Cognitive function assessment through standardized tests: Trail Making Test, Stroop Test, and Verbal Fluency Test (VFT).

Main Results:

• No significant overall association was found between the studied DIO1 polymorphisms and cognitive functioning in patients with rDD.
• A significant relationship was observed between the CT and TT genotypes of the DIO1a variant and verbal fluency.
• No significant differences in genotype distribution were noted concerning demographic or medical variables.

Conclusions:

• The investigated DIO1 gene polymorphisms do not appear to be significant risk or protective factors for cognitive impairment in depressive patients.
• Functional variants within the DIO1 gene, impacting T3 levels, do not seem to be directly associated with cognitive functions in this cohort.
• Given the DIO1 gene's role in depression, further research with larger sample sizes is recommended to explore potential associations more thoroughly.