Unlocking choline's potential in Alzheimer's disease: A narrative review exploring the neuroprotective and neurotrophic role of phosphatidylcholine and assessing its impact on memory and learning.

BACKGROUND AND AIMS

Growing evidence suggests nutritional intervention may influence the development and progression of Alzheimer's Disease (AD). Choline, an essential dietary nutrient plays a critical role in neurological development and brain function, however, its effects on AD in humans is unclear. The research aims to investigate mechanistic links between dietary choline intake and cognitive functioning, focusing on the role of phosphatidylcholine (PC) in neuroplasticity and its interaction with amyloid beta (Aβ) peptides in neuron membranes. Additionally, human evidence on the potential benefits of PC interventions on AD, cognition, and proposed mechanisms are evaluated.

METHODS

A reproducible systematic literature search was performed using a three-tranche strategy, consisting of a review, mechanism, and intervention search. Using PubMed as the main database, 1254 titles and abstracts were screened, 149 papers were read in full and 65 peer-reviewed papers were accepted, critically appraised, and analysed in a narrative review.

RESULTS

Predominantly preclinical evidence demonstrated that PC enhances neuroplasticity, a key biological substrate for cognition, by activating intracellular neuronal signalling pathways or through neuron membrane function. Molecular dynamic simulation methods provided a mechanistic understanding of the interconnection between neuronal PC content and the potential behaviour and trajectory of Aβ peptide aggregation. The results indicate that the neuronal membrane composition of PC is critical to inhibiting Aβ aggregation and neuronal damage, protecting the neuron from Aβ toxicity. This might provide a foundation for optimising cellular PC which may prove beneficial in the treatment or prevention of neurodegenerative disease. Altered PC metabolism in AD was evidenced in observational studies; however, whether this relationship represents a cause or consequence of AD remains to be determined. Human intervention studies did not produce conclusive evidence supporting its effectiveness in enhancing cognitive function. This lack of consistency primarily stems from methodological constraints within the conducted studies. Human observational research provided the most compelling evidence linking a higher dietary PC intake to a reduced risk of dementia and significant improvements in cognitive testing.

CONCLUSION

Despite the lack of randomised control trials (RCTs) assessing the efficacy of lecithin/PC to improve cognition in AD patients, there exists promising evidence supporting its neuroprotective and neurotrophic role. This review establishes an evidence-based framework through chains of mechanistic evidence, that may provide potential strategies for enhanced neuroprotection and reduced neurodegeneration caused by AD. Considering the escalating global burden of AD and the current shortcomings in effective treatments, this review together with the limitations and gaps identified in the existing research presents valuable insights that emphasise the urgency of more comprehensive research into the relationship between PC and AD.