SHMT2 and constipation disorder: Immunohistochemical and immunofluorescence analyses revealed elevated SHMT2 expression in brain and colon tissues in PD mouse models (p < 0.001), whereas in constipation models, SHMT2 was only elevated in the colon wall with no significant expression in the enteric nervous system.<h4>Conclusion</h4>Our findings offer new views on the molecular link between PD and constipation, suggesting SHMT2 as a possible biomarker and therapeutic target for PD symptoms.