LRRK2 and Cognitive impairment: If we take up the point of view that high serum tHcy level and low serum VitB12 and folate levels were associated with progression of motor or cognitive impairment, what could be the basic underlying mechanism?—Schaffner et al. (35) uncovered that 5'-deoxyadenosylcobalamin (AdoCbl), the physiological form of VitB12, modulated PD leucine-rich repeat kinase-2 (LRRK2) kinase activity through allosteric regulation.