Transforming personalized nutrition practice

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.

Ontology-based decision support systems for diabetes nutrition therapy: A systematic literature review

Diabetes is a non-communicable disease that has reached epidemic proportions, affecting 537 million people globally. Artificial Intelligence can support patients or clinicians in diabetes nutrition therapy - the first medical therapy in most cases of Type 1 and Type 2 diabetes. In particular, ontology-based recommender and decision support systems can deliver a computable representation of experts' knowledge, thus delivering patient-tailored nutritional recommendations or supporting clinical personnel in identifying the most suitable diet. This work proposes a systematic literature review of the domain ontologies describing diabetes in such systems, identifying their underlying conceptualizations, the users targeted by the systems, the type(s) of diabetes tackled, and the nutritional recommendations provided. This review also delves into the structure of the domain ontologies, highlighting several aspects that may hinder (or foster) their adoption in recommender and decision support systems for diabetes nutrition therapy. The results of this review process allow to underline how recommendations are formulated and the role of clinical experts in developing domain ontologies, outlining the research trends characterizing this research area. The results also allow for identifying research directions that can foster a preeminent role for clinical experts and clinical guidelines in a cooperative effort to make ontologies more interoperable - thus enabling them to play a significant role in the decision-making processes about diabetes nutrition therapy.

Investigating the Role of 17β-Estradiol on the Serotonergic System, Targeting Soy Isoflavones as a Strategy to Reduce Menopausal Depression: A Mechanistic Review

Low serotonin is one factor implicated in the development of depression. 17β-estradiol (E2) has been shown to modulate gene expression regulating the neurotransmission of serotonin. Sex hormone levels fluctuate dramatically during the menopausal transition, coinciding with a 14-fold increased risk of depression. This review aimed to examine the effect of soy isoflavones to support decreased and variable E2 levels before and after menopause, linked to an investigation of the pathophysiological mechanisms underlying the protective influence of E2 on the serotonin pathway. The overall aim of this review is to assess the potential of soy isoflavones to reduce depression in middle-aged women. A systematic literature search was performed in three stages. 1,421 papers were screened for relevance to the research aims and objectives. 63 papers were selected based on pre-defined inclusion/exclusion criteria (13 reviews, 24 mechanistic and 26 intervention studies) and critically appraised. Available research supported the hypotheses that E2 increases serotonin synthesis and availability through stimulation of tryptophan hydroxylase-2 (TPH-2) and decreased degradation by monoamine oxidase-A (MAO-A). There was less scientific agreement on the effects of E2 on serotonin transporter (SERT) and serotonin receptors 1 A and 2 A. Studies varied widely on the effectiveness of soy isoflavones in reducing depressive symptoms in (peri)menopausal women. Animal and human studies acknowledge women's increased risk of depression linked to fluctuating E2 rather than absolute levels. However, mechanisms linking E2 variability with depression remain an underrepresented area of research. Study limitations and heterogeneity may contribute to varying results for soy isoflavones and some effects of E2 on the serotonin pathway.

Microbial Imbalance and Intestinal Permeability in the Pathogenesis of Rheumatoid Arthritis: A Mechanism Review with a Focus on Bacterial Translocation, Citrullination, and Probiotic Intervention

This review aims to investigate the role of intestinal permeability (IP) in rheumatoid arthritis (RA), following the hypotheses that leakage of intestinal microbes can influence increased citrullination of peptides leading to anti-citrullinated protein antibody (ACPA) production and inflammation in RA; and that leaked microbes can migrate to the peripheral joints, leading to immune responses and synovitis in peripheral joints. This review explored the evidence for the link between microbial dysbiosis and increased IP in the inflammatory state in RA, as well as the role of increased citrullination and bacterial translocation in the link between microbiota and immune responses in RA. Furthermore, this research aims to evaluate the potential effect of probiotics on RA symptoms and pathogenesis via proposed mechanisms, including the support of microbial balance and suppression of inflammatory factors in RA. A systematic literature search was conducted in three tranches (review, mechanism, intervention). 71 peer-reviewed papers met the inclusions criteria and are summarized in a narrative analysis. Primary studies were critically appraised, synthesized and their relevance to clinical practice evaluated. Evidence found in this mechanism review consistently supported intestinal dysbiosis and increased IP in arthritis. An altered intestinal microbiome was demonstrated in RA with specific microbes such as Collinsella and Eggerthella correlating with increased IP, mucosal inflammation, and immune responses. Hypercitrullination and ACPA production correlated with arthritic symptoms and intestinal microbes were shown to influence hypercitrullination. Some in vitro and animal studies demonstrated a link between leakage of microbes and bacterial translocation, but further research is needed to elucidate the link between IP and citrullination. Probiotic intervention studies evidenced reductions in inflammatory markers IL-6 and TNFα, associated with proliferation of synovial tissue and pain perception in RA joint inflammation. Despite some conflict in the literature, probiotics may present a promising nutritional intervention in the suppression of both, disease activity and inflammatory markers.Key teaching pointsThere is evidence for a dysbiotic profile of the RA gut with specific RA-associated microbes.Increased intestinal permeability and leakage of PAD enzyme facilitates citrullination of peptides.Hypercitrullination and ACPA production correlate to arthritic signs.Microbial leakage and translocation plays a role in the pathogenesis of RA.Probiotics (e.g. L. Casei 01) may reduce inflammation and ameliorate RA symptoms.

Review of Validated Methods to Evaluate Diet History in Diet Therapy and Counselling: An Overview and Analysis of Screeners Based on Food-Based Dietary Guidelines

Evidence-based dietetic practice calls for systematically developed assessment methods for nutritional assessment in dietetic counselling and therapy (DCT). Screeners can provide a quick and easy way to determine a client's diet quality and contribute to quality assurance in DCT. The aim of this systematic review was to give a comparative overview of screeners based on national food-based dietary guidelines (FBDGs) and to derive recommendations for developing an FBDG-based screener for DCT. The literature search in PubMed (MEDLINE), embase and Web of Science was conducted between May and July 2022, and updated in March 2023, in accordance with the consensus-based standards for the selection of health measurement instruments (COSMIN). The analysis focused on characteristics of screener design and measurement properties for screener testing. In total, 13 studies on 11 screeners based on FBDGs were included; 7 screeners were targeted to DCT. The content and scoring of screeners were based on the corresponding national FBDGs. The validity and/or reliability of screeners were investigated in 11 studies; responsiveness was not tested for any screener and practicality was considered in all studies. Based on the screeners reviewed, a systematic rationale to develop, enhance and test screeners based on national FBDGs was established.

Intermittent fasting and cognitive performance - Targeting BDNF as potential strategy to optimise brain health

Aging is the major risk factor for neurodegenerative diseases, accelerated by excessive calorie consumption and sedentary lifestyles. Bioenergetic challenges such as intermittent fasting (IF) have shown to promote lifespan and healthspan via an adaptive stress response. Activity-dependent brain-derived neurotrophic factor (BDNF) has emerged as key regulator of cognitive performance and brain health. This review aims to investigate the pathophysiological mechanisms linking IF and cognitive function with a focus on the role of BDNF, evaluating evidence from pre-clinical and human studies. A systematic literature search was performed. 82 peer-reviewed papers were accepted, critically appraised and summarised in a narrative analysis. Aging-related loss of BDNF has been associated with reduced synaptic plasticity, memory and learning as well as increased risk of cognitive impairment and Alzheimer's disease. IF was consistently reported to upregulate BDNF and improve cognitive performance in animal models. Further research is required to assess cognitive outcomes of IF in humans.

What is the promise of personalised nutrition?

Personalised nutrition (PN) is an emerging field that bears great promise. Several definitions of PN have been proposed and different modelling approaches have been used to claim PN effects. We tentatively propose to group these approaches into two categories, which we term outcome-based and population reference approaches, respectively. Understanding the fundamental differences between these two types of modelling approaches may allow a more realistic appreciation of what to expect from PN interventions presently and may be helpful for designing and planning future studies investigating PN interventions.

Link between microbiota and hypertension: Focus on LPS/TLR4 pathway in endothelial dysfunction and vascular inflammation, and therapeutic implication of probiotics

High blood pressure (BP) presents a significant public health challenge. Recent findings suggest that altered microbiota can exert a hypertensive effect on the host. One of the possible mechanisms involved is the chronic translocation of its components, mainly lipopolysaccharides (LPS) into systemic circulation leading to metabolic endotoxemia. In animal models, LPS has been commonly used to induce endothelial dysfunction and vascular inflammation. In human studies, plasma LPS concentration has been positively correlated with hypertension, however, the mechanistic link has not been fully elucidated. It is hypothesised here that the LPS-induced direct alterations to the vascular endothelium and resulting hypertension are possible targets for probiotic intervention. The methodology of this review involved a systematic search of the literature with critical appraisal of papers. Three tranches of search were performed: 1) existing review papers; 2) primary mechanistic animal, in vitro and human studies; and 3) primary intervention studies. A total of 70 peer-reviewed papers were included across the three tranches and critically appraised using SIGN50 for human studies and the ARRIVE guidelines for animal studies. The extracted information was coded into key themes and summarized in a narrative analysis. Results highlight the role of LPS in the activation of endothelial toll-like receptor 4 (TLR4) initiating a cascade of interrelated signalling pathways including: 1) Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase/ Reactive oxygen species (ROS)/ Endothelial nitric oxide synthase (eNOS) pathway leading to endothelial dysfunction; and 2) Mitogen-Activated Protein Kinase (MAPK) and Nuclear factor kappa B (NF-κB) pathways leading to vascular inflammation. Findings from animal intervention studies suggest an improvement in vasorelaxation, vascular inflammation and hypertension following probiotic supplementation, which was mediated by downregulation of LPS-induced pathways. Randomised controlled trials (RCTs) and systematic reviews provided some evidence for the anti-inflammatory effect of probiotics with statistically significant antihypertensive effect in clinical samples and may offer a viable intervention for the management of hypertension.

Genotype-guided dietary supplementation in precision nutrition

Achieving adequate micronutrient status, while avoiding deficiencies, represents a challenge for people globally. Consequently, many individuals resort to oral nutrient supplementation (ONS) in order to correct suboptimal dietary intakes. Advances in the fields of nutrigenetics and nutritional genomics have identified differences in response to micronutrient supplementation according to genetic makeup, adding dietary supplement use to the clinician's toolkit in the precision nutrition era. This review focuses on published evidence linking genetic variants to the responses associated with some of the most popular dietary supplements. With an increasing number of health professionals becoming involved in the prescription of ONS, identifying and matching individuals to the appropriate dietary supplement according to their genotype is important for achieving optimal health benefits and micronutrient equilibrium, while reducing the adverse events and financial costs often associated with excessive ONS.