Dietary interventions and cognition of Alzheimer's disease patients: a systematic review of randomized controlled trial

Causal associations of antioxidants with Alzheimer's disease and cognitive function: a Mendelian randomisation study

BACKGROUND

Circulating antioxidants are associated with a lower risk of Alzheimer's disease (AD) in observational studies, suggesting potential target areas for intervention. However, whether the associations are causal remains unclear. Here, we studied the causality between antioxidants and AD or cognitive function using two-sample Mendelian randomisation (MR).

METHODS

Single nucleotide polymorphisms strongly (p<5×10-8) associated with antioxidants (vitamin A, vitamin C, zinc, selenium, β-carotene and urate) and outcomes (AD, cognitive performance and reaction time) were obtained from the largest and most recent genome-wide association studies (GWAS). MR inverse variance weighting (IVW) and MR pleiotropy residual sum and outlier test (MR-PRESSO) were used for data analysis.

RESULTS

Higher genetically determined selenium level was associated with 5% higher risk of AD (OR 1.047, 95% CI 1.005 to 1.091, p=0.028) using IVW. Higher genetically determined urate level was associated with worse cognitive performance (β=-0.026, 95% CI -0.044 to -0.008, p=0.005) using MR-PRESSO. No association between the other antioxidants and AD, cognitive performance and reaction time was found. Similar results were found in the sensitivity analyses.

CONCLUSION

Our results suggest that lifelong exposure to higher selenium may be associated with a higher risk of AD, and higher urate levels could be associated with worse cognitive performance. Further analyses using larger GWAS of antioxidants are warranted to confirm these observations. Our results suggest that caution is needed in the interpretation of traditional observational evidence on the neuroprotective effects of antioxidants.

ESPEN guideline on nutrition and hydration in dementia - Update 2024

BACKGROUND & AIMS

Dementia is accompanied by a variety of changes that result in an increased risk of malnutrition and low-intake dehydration. This guideline update aims to give evidence-based recommendations for nutritional care of persons with dementia in order to prevent and treat these syndromes.

METHODS

The previous guideline version was reviewed and expanded in accordance with the standard operating procedure for ESPEN guidelines. Based on a systematic search in three databases, strength of evidence of appropriate literature was graded by use of the SIGN system. The original recommendations were reviewed and reformulated, and new recommendations were added, which all then underwent a consensus process.

RESULTS

40 recommendations for nutritional care of older persons with dementia were developed and agreed, seven at institutional level and 33 at individual level. As a prerequisite for good nutritional care, organizations caring for persons with dementia are recommended to employ sufficient qualified staff and offer attractive food and drinks with choice in a functional and appealing environment. Nutritional care should be based on a written care concept with standardized operating procedures. At the individual level, routine screening for malnutrition and dehydration, nutritional assessment and close monitoring are unquestionable. Oral nutrition may be supported by eliminating potential causes of malnutrition and dehydration, and adequate social and nursing support (including assistance, utensils, training and oral care). Oral nutritional supplements are recommended to improve nutritional status but not to correct cognitive impairment or prevent cognitive decline. Routine use of dementia-specific ONS, ketogenic diet, omega-3 fatty acid supplementation and appetite stimulating agents is not recommended. Enteral and parenteral nutrition and hydration are temporary options in patients with mild or moderate dementia, but not in severe dementia or in the terminal phase of life. In all stages of the disease, supporting food and drink intake and maintaining or improving nutrition and hydration status requires an individualized, comprehensive approach. Due to a lack of appropriate studies, most recommendations are good practice points.

CONCLUSION

Nutritional care should be an integral part of dementia management. Numerous interventions are available that should be implemented in daily practice. Future high-quality studies are needed to clarify the evidence.

Large Neutral Amino Acids Moderate the Effects of Metabolic Syndrome on Cognitive Performance in Middle-Aged Adults

INTRODUCTION

Two large neutral amino acids (LNAA), tryptophan and tyrosine, are precursors to cerebral neurotransmitters and are involved in cognitive function. Higher levels of LNAA in young adults are associated with improved cognition, although these associations appear to reverse over time. Given that exposure to metabolic syndrome (MetS) may induce premature cognitive aging, the current project aims to fill the gap in the literature by examining the effect of LNAA on cognitive performance in midlife adults with metabolic risks.

METHODS

Eighty-eight adults, ages 40-61 years, participated in this cross-sectional study. LNAA metabolites were quantified, MetS components were measured using high-performance liquid chromatography, and MetS components were assessed in the laboratory. Composite verbal memory and executive functioning scores were computed using principal component analysis. We used linear regression models to test the interaction between LNAA and MetS while covarying for sex, age, and education.

RESULTS

The kynurenine/tryptophan ratio moderated the relation between MetS and verbal memory, even after adjusting for relevant covariates. Tyrosine metabolites were not significant moderators of the association between MetS and executive functioning.

CONCLUSION

Our findings suggest that the detected weaker memory performance in adults with a high number of MetS components may be related to relative tryptophan depletion and possible decreases in serotonin production. Further investigation is warranted to examine the potential role of LNAA in associations between cognitive performance and metabolic risks over time.

Mapping new pharmacological interventions for cognitive function in Alzheimer's disease: a systematic review of randomized clinical trials

Background and Objective: Alzheimer's disease (AD) is a progressive neurodegenerative disorder, that is, characterized by cognitive decline. To date, there are no effective treatments for AD. Therefore, the objective of this study was to map new perspectives on the effects of pharmacological treatment on cognitive function and the overall psychological state in patients with AD. Methods: Two independent researchers searched for randomized clinical trials (RCTs) exploring new pharmacological approaches related to cognition in Alzheimer's disease in adults from 2018 to 2023 in PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 17 RCTs were included in this review. Results: The results show that in recent years, new drugs have been tested in patients with Alzheimer's disease, including masitinib, methylphenidate, levetiracetam, Jiannao Yizhi, and Huannao Yicong formulas. Most studies have been conducted in populations with mild to moderate Alzheimer's disease. Conclusion: Although some of the drugs found suggested improvement in cognitive function, the scarcity of available studies highlights the need for further research in this area. Systematic review registration: [www.crd.york.ac.uk/prospero], identifier [CRD42023409986].

Effect of nutrition in Alzheimer's disease: A systematic review

Background and objective

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by declining cognitive ability. Currently, there are no effective treatments for this condition. However, certain measures, such as nutritional interventions, can slow disease progression. Therefore, the objective of this systematic review was to identify and map the updates of the last 5 years regarding the nutritional status and nutritional interventions associated with AD patients.

Study design

A systematic review.

Methods

A search was conducted for randomized clinical trials, systematic reviews, and meta-analyses investigating the association between nutritional interventions and AD published between 2018 and 2022 in the PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 38 studies were identified, of which 17 were randomized clinical trials, and 21 were systematic reviews and/or meta-analyses.

Results

The results show that the western diet pattern is a risk factor for developing AD. In contrast, the Mediterranean diet, ketogenic diet, and supplementation with omega-3 fatty acids and probiotics are protective factors. This effect is significant only in cases of mild-to-moderate AD.

Conclusion

Certain nutritional interventions may slow the progression of AD and improve cognitive function and quality of life. Further research is required to draw more definitive conclusions.

Insights into the Pathophysiology of Alzheimer's Disease and Potential Therapeutic Targets: A Current Perspective

The aging population increases steadily because of a healthy lifestyle and medical advancements in healthcare. However, Alzheimer's disease (AD) is becoming more common and problematic among older adults. AD-related cases show an increasing trend annually, and the younger age population may also be at risk of developing this disorder. AD constitutes a primary form of dementia, an irreversible and progressive brain disorder that steadily damages cognitive functions and the ability to perform daily tasks. Later in life, AD leads to death as a result of the degeneration of specific brain areas. Currently, the cause of AD is poorly understood, and there is no safe and effective therapeutic agent to cure or slow down its progression. The condition is entirely preventable, and no study has yet demonstrated encouraging findings in terms of treatment. Identifying this disease's pathophysiology can help researchers develop safe and efficient therapeutic strategies to treat this ailment. This review outlines and discusses the pathophysiology that resulted in the development of AD including amyloid-β plaques, tau neurofibrillary tangles, neuroinflammation, oxidative stress, cholinergic dysfunction, glutamate excitotoxicity, and changes in neurotrophins level may sound better based on the literature search from Scopus, PubMed, ScienceDirect, and Google Scholar. Potential therapeutic strategies are discussed to provide more insights into AD mechanisms by developing some possible pharmacological agents for its treatment.

Treatment of dementia: recommendations of the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology

ABSTRACT There is currently no cure for neurodegenerative or vascular dementias, but some pharmacological and non-pharmacological interventions may contribute to alleviate symptoms, slow disease progression and improve quality of life. Current treatment approaches are based on etiology, symptom profile and stage of dementia. This manuscript presents recommendations on pharmacological and non-pharmacological treatments of dementia due to Alzheimer’s disease, vascular cognitive impairment, frontotemporal dementia, Parkinson’s disease dementia, and dementia with Lewy bodies.

Tratamento da demência: recomendações do Departamento Científico de Neurologia Cognitiva e do Envelhecimento da Academia Brasileira de Neurologia

RESUMO Atualmente não há tratamento curativo para as demências neurodegenerativas ou para a demência vascular, mas algumas intervenções farmacológicas e não farmacológicas podem contribuir para aliviar os sintomas, retardar a progressão da doença e melhorar a qualidade de vida. As abordagens terapêuticas atuais são baseadas na etiologia, no perfil dos sintomas e no estágio da demência. Neste artigo apresentamos recomendações sobre os tratamentos farmacológicos e não farmacológicos da demência devida à doença de Alzheimer, comprometimento cognitivo vascular, demência frontotemporal, demência da doença de Parkinson e demência com corpos de Lewy.

The Potential Role of Gut Microbiota in Alzheimer’s Disease: from Diagnosis to Treatment

Gut microbiota is emerging as a key regulator of many disease conditions and its dysregulation is implicated in the pathogenesis of several gastrointestinal and extraintestinal disorders. More recently, gut microbiome alterations have been linked to neurodegeneration through the increasingly defined gut microbiota brain axis, opening the possibility for new microbiota-based therapeutic options. Although several studies have been conducted to unravel the possible relationship between Alzheimer’s Disease (AD) pathogenesis and progression, the diagnostic and therapeutic potential of approaches aiming at restoring gut microbiota eubiosis remain to be fully addressed. In this narrative review, we briefly summarize the role of gut microbiota homeostasis in brain health and disease, and we present evidence for its dysregulation in AD patients. Based on these observations, we then discuss how dysbiosis might be exploited as a new diagnostic tool in early and advanced disease stages, and we examine the potential of prebiotics, probiotics, fecal microbiota transplantation, and diets as complementary therapeutic interventions on disease pathogenesis and progression, thus offering new insights into the diagnosis and treatment of this devastating and progressive disease.

Epigenetic regulation in Alzheimer's disease: is it a potential therapeutic target?

Introduction: Alzheimer's disease (AD) is the most common neurodegenerative disorder and the primary form of dementia in the elderly. Changes in DNA methylation and post-translational modifications of histone tails are increasingly observed in AD tissues, and likely contribute to disease onset and progression. The reversibility of these epigenetic marks offers the potential for therapeutic interventions.Areas covered: After a concise and updated overview of DNA methylation and post-translational modifications of histone tails in AD tissues, this review provides an overview of the animal and cell culture studies investigating the potential of targeting these modifications to attenuate AD-like features. PubMed was searched for relevant literature between 2003 and 2021.Expert opinion: Methyl donor compounds and drugs acting on histone tail modifications attenuated the AD-like features and improved cognition in several transgenic AD mice; however, there are concerns about safety and tolerability for long-term treatment in humans. The challenges will be to take advantage of recent epigenome-wide investigations to identify the principal targets for future interventions, and to design novel, selective and safer agents. Natural compounds exerting epigenetic properties could represent a promising opportunity to delay disease onset in middle-aged individuals at increased AD risk.

In Pursuit of Healthy Aging: Effects of Nutrition on Brain Function

Consuming a balanced, nutritious diet is important for maintaining health, especially as individuals age. Several studies suggest that consuming a diet rich in antioxidants and anti-inflammatory components such as those found in fruits, nuts, vegetables, and fish may reduce age-related cognitive decline and the risk of developing various neurodegenerative diseases. Numerous studies have been published over the last decade focusing on nutrition and how this impacts health. The main objective of the current article is to review the data linking the role of diet and nutrition with aging and age-related cognitive decline. Specifically, we discuss the roles of micronutrients and macronutrients and provide an overview of how the gut microbiota-gut-brain axis and nutrition impact brain function in general and cognitive processes in particular during aging. We propose that dietary interventions designed to optimize the levels of macro and micronutrients and maximize the functioning of the microbiota-gut-brain axis can be of therapeutic value for improving cognitive functioning, particularly during aging.

Importance of EPA and DHA Blood Levels in Brain Structure and Function

Brain structure and function depend on a constant and sufficient supply with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by blood. Blood levels of EPA and DHA reflect dietary intake and other variables and are preferably assessed as percentage in erythrocytes with a well-documented and standardized analytical method (HS-Omega-3 Index^®). Every human being has an Omega-3 Index between 2 and 20%, with an optimum of 8–11%. Compared to an optimal Omega-3 Index, a lower Omega-3 Index was associated with increased risk for total mortality and ischemic stroke, reduced brain volume, impaired cognition, accelerated progression to dementia, psychiatric diseases, compromises of complex brain functions, and other brain issues in epidemiologic studies. Most intervention trials, and their meta-analyses considered EPA and DHA as drugs with good bioavailability, a design tending to produce meaningful results in populations characterized by low baseline blood levels (e.g., in major depression), but otherwise responsible for many neutral results and substantial confusion. When trial results were evaluated using blood levels of EPA and DHA measured, effects were larger than comparing EPA and DHA to placebo groups, and paralleled epidemiologic findings. This indicates future trial design, and suggests a targeted use EPA and DHA, based on the Omega-3 Index.

The Immunopathogenesis of Alzheimer's Disease Is Related to the Composition of Gut Microbiota

The microbiota-gut-brain axis plays an important role in the development of neurodegenerative diseases. Commensal and pathogenic enteric bacteria can influence brain and immune system function by the production of lipopolysaccharides and amyloid. Dysbiosis of the intestinal microbiome induces local and consecutively systemic immune-mediated inflammation. Proinflammatory cytokines then trigger neuroinflammation and finally neurodegeneration. Immune-mediated oxidative stress can lead to a deficiency of vitamins and essential micronutrients. Furthermore, the wrong composition of gut microbiota might impair the intake and metabolization of nutrients. In patients with Alzheimer's disease (AD) significant alterations of the gut microbiota have been demonstrated. Standard Western diet, infections, decreased physical activity and chronic stress impact the composition and diversity of gut microbiota. A higher abundancy of "pro-inflammatory" gut microbiota goes along with enhanced systemic inflammation and neuroinflammatory processes. Thus, AD beginning in the gut is closely related to the imbalance of gut microbiota. Modulation of gut microbiota by Mediterranean diet, probiotics and curcumin can slow down cognitive decline and alter the gut microbiome significantly. A multi-domain intervention approach addressing underlying causes of AD (inflammation, infections, metabolic alterations like insulin resistance and nutrient deficiency, stress) appears very promising to reduce or even reverse cognitive decline by exerting positive effects on the gut microbiota.

Can We Treat Neuroinflammation in Alzheimer's Disease?

Alzheimer's disease (AD), considered the most common type of dementia, is characterized by a progressive loss of memory, visuospatial, language and complex cognitive abilities. In addition, patients often show comorbid depression and aggressiveness. Aging is the major factor contributing to AD; however, the initial cause that triggers the disease is yet unknown. Scientific evidence demonstrates that AD, especially the late onset of AD, is not the result of a single event, but rather it appears because of a combination of risk elements with the lack of protective ones. A major risk factor underlying the disease is neuroinflammation, which can be activated by different situations, including chronic pathogenic infections, prolonged stress and metabolic syndrome. Consequently, many therapeutic strategies against AD have been designed to reduce neuro-inflammation, with very promising results improving cognitive function in preclinical models of the disease. The literature is massive; thus, in this review we will revise the translational evidence of these early strategies focusing in anti-diabetic and anti-inflammatory molecules and discuss their therapeutic application in humans. Furthermore, we review the preclinical and clinical data of nutraceutical application against AD symptoms. Finally, we introduce new players underlying neuroinflammation in AD: the activity of the endocannabinoid system and the intestinal microbiota as neuroprotectors. This review highlights the importance of a broad multimodal approach to treat successfully the neuroinflammation underlying AD.

Vitamins in Alzheimer's Disease-Review of the Latest Reports

Alzheimer's disease (AD) is the most common form of dementia, and the aging of the population means that the number of cases is successively increasing. The cause of the disease has not been established, but it is suggested that many factors affect it, including nutritional aspects. As part of the work, the PubMed database has been searched, beginning from 2005, for terms related to key nutritional aspects. A diet rich in antioxidant vitamins can improve the cognitive functions of patients. Thanks to an adequate intake of B vitamins, homocysteine levels are reduced, which indirectly protects against the development of the disease. A properly balanced diet, as well as the use of appropriate supplementation, can contribute to improving the clinical condition of patients with AD.