Effects of Tai Chi exercise on homocysteine, limbic system, and attention control in cerebral small vessel disease

Background Elevated homocysteine (Hcy) is a risk factor for mild cognitive impairment in cerebral small vessel disease (CSVD-MCI), but the underlying neural pathways remain unelucidated. The limbic system is vulnerable to Hcy-related damage and plays a critical role in attention control; however, the Tai Chi-associated relationship in Hcy, limbic structures, and attention control has not been examined in CSVD-MCI. We therefore conducted cross-sectional and longitudinal analyses to (1) explore the relationship between Hcy, limbic system structural and functional properties, and attention control, and (2) test whether Tai Chi exercise improves attention control via limbic pathways. Methods Baseline (N = 58) and post Tai Chi exercise evaluations (N = 31) were conducted in patients with CSVD-MCI. We measured serum Hcy levels, regional structural properties and regional fractional amplitude of low-frequency fluctuations (fALFF), and attention control. Partial correlation and mediation analysis were conducted to examine relationships between Hcy levels, structural and functional properties in core limbic regions, and attention control at baseline in individuals with CSVD-MCI. Changes in the above variables and their relationship after Tai Chi exercise were examined using ANCOVA and partial correlation. Finally, we examined whether Tai Chi exercise moderated the relationship between changes in structural and functional properties in core limbic structures and attention control. Results At baseline, a relatively higher level of Hcy was indirectly associated with impaired attention control through reduced cortical thickness in the right parahippocampal gyrus. Tai Chi exercise improved attention control and significantly changed fALFF relative to the control group. Notably, Tai Chi-related functional changes in the bilateral caudate and right parahippocampal gyrus underlie attention control improvement. Conclusion This study reveals a potential vascular-neurobiological pathway centered in the limbic system involving cortical thinning and functional compensation, which could be modulated by Tai Chi exercise and the related attention control improvement in CSVD-MCI.