The vicious circle between homocysteine, methyl group-donating vitamins and chronic levodopa intake in Parkinson's disease

Parkinson's disease and vitamins: a focus on vitamin B12

Parkinson's disease (PD) has been linked to a vast array of vitamins among which vitamin B12 (Vit B12) is the most relevant and often investigated specially in the context of intrajejunal levodopa infusion therapy. Vit B12 deficiency, itself, has been reported to cause acute parkinsonism. Nevertheless, concrete mechanisms through which B12 deficiency interacts with PD in terms of pathophysiology, clinical manifestation and progression remains unclear. Recent studies have suggested that Vit B12 deficiency along with the induced hyperhomocysteinemia are correlated with specific PD phenotypes characterized with early postural instability and falls and more rapid motor progression, cognitive impairment, visual hallucinations and autonomic dysfunction. Specific clinical features such as polyneuropathy have also been linked to Vit B12 deficiency specifically in context of intrajejunal levodopa therapy. In this review, we explore the link between Vit B12 and PD in terms of physiopathology regarding dysfunctional neural pathways, neuropathological processes as well as reviewing the major clinical traits of Vit B12 deficiency in PD and Levodopa-mediated neuropathy. Finally, we provide an overview of the therapeutic effect of Vit B12 supplementation in PD and posit a practical guideline for Vit B12 testing and supplementation.

Decreased hepatic enzymes reflect the decreased vitamin B6 levels in Parkinson's disease patients

The study aims to investigate the vitamin B6 levels in Parkinson's disease (PD) patients and their association with liver enzymes and evaluate how much dysregulation is associated with levodopa dose. Furthermore, to evaluate the effect of Opicapone, a catechol-o-methyl-transferase inhibitor, on vitamin B6 levels by monitoring the AST and ALT levels in patients treated with Levodopa-Carbidopa Intestinal Gel Infusion (LCIG). For these aims, serum vitamin B6 levels were measured (PD, n = 72 and controls, n = 31). The vitamin B6 level was compared with the total levodopa dose, clinical parameters, and blood homocysteine, albumin, and hemoglobin levels in PD patients. Correlations between vitamin B6 levels and AST and ALT levels, as well as the ratio ALT/AST, were analyzed. Changes in the AST and ALT levels and ALT/AST were analyzed in the patients treated with LCIG before and after the therapy (n = 24) and in the patients treated with LCIG + Opicapone before and after Opicapone treatment (n = 12). We found vitamin B6 levels were significantly lower in PD patients. Total levodopa dose and albumin levels were independently associated with vitamin B6 levels. Decreased vitamin B6 levels appeared as lower AST and ALT levels and ALT/AS. Treatment with LCIG decreased the AST and ALT levels and ALT/AST. Adjunctive therapy with Opicapone to LCIG ameliorated the decreased ALT and ALT/AST. We conclude that the ALT and ALT/AST can be useful parameters for monitoring vitamin B6 levels and Opicapone can ameliorate the dysregulated vitamin B6 in PD patients.