AUTHOR=Lee Jin San , Soh Yunsoo , Kim Hyug-Gi , Lee Kyung Mi , Kwon Young Nam , Yoon Sung Sang , Park Key-Chung , Rhee Hak Young 

TITLE=Interactive Effects of Apolipoprotein E ε4 and Triiodothyronine on Memory Performance in Patients With Subjective Cognitive Decline

JOURNAL=Frontiers in Medicine

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2020.00298

DOI=10.3389/fmed.2020.00298

ISSN=2296-858X

ABSTRACT=<p><bold>Background:</bold> The aim of the present study was to investigate the associations between thyroid hormones, cognitive performance, and apolipoprotein E (<italic>APOE</italic>) genotype in euthyroid patients with subjective cognitive decline (SCD).</p><p><bold>Methods:</bold> We recruited 197 euthyroid patients that fulfilled the criteria for SCD. All participants were classified into <italic>APOE</italic> ε4 carriers and non-carriers based on the presence of the <italic>APOE</italic> ε4 allele. Patients with SCD who had the <italic>APOE</italic> ε2/ε4 genotype were excluded from the study. We then performed correlation and regression analyses to evaluate the associations between cognitive performance and thyroid hormones in <italic>APOE</italic> ε4 carriers and non-carriers.</p><p><bold>Results:</bold> We found no significant differences in cognitive function between <italic>APOE</italic> ε4 carriers and non-carriers. However, higher levels of triiodothyronine (T3) were associated with better verbal memory performance (immediate and delayed recall tasks) in <italic>APOE</italic> ε4 carriers, whereas a negative association was found in <italic>APOE</italic> ε4 non-carriers. Furthermore, there was a significant interactive effect of <italic>APOE</italic> ε4 status and T3 levels on verbal memory performance (immediate and delayed recall tasks).</p><p><bold>Conclusions:</bold> These findings suggest that in patients with SCD, T3 might have a protective effect on memory in those who are <italic>APOE</italic> ε4 carriers. The differential susceptibility hypothesis would thus support a gene-by-hormone crossover interaction between <italic>APOE</italic> ε4 allele and T3 in this study. Early identification and intervention of high-risk individuals for cognitive decline is important to establish new strategies for preventing dementia.</p>