Modulation of Gut Microbiota Through Dietary Intervention in Neuroinflammation and Alzheimer's and Parkinson's Diseases.

PURPOSE OF REVIEW: The gut microbiota plays a crucial role in the pathogenesis of neuroinflammation and Alzheimer's and Parkinson's diseases. One of the main modulators of the gut microbiota is the diet, which directly influences host homeostasis and biological processes. Some dietary patterns can affect neurodegenerative diseases' progression through gut microbiota composition, gut permeability, and the synthesis and secretion of microbial-derived neurotrophic factors and neurotransmitters. This comprehensive review critically assesses existing studies investigating the impact of dietary interventions on the modulation of the microbiota in relation to neurodegenerative diseases and neuroinflammation. RECENT FINDINGS: There are limited studies on the effects of specific diets, such as the ketogenic diet, Mediterranean diet, vegetarian diet, and Western diet, on the progression of neuroinflammation and Alzheimer's and Parkinson's diseases through the gut-brain axis. The ketogenic diet displays promising potential in ameliorating the clinical trajectory of mild cognitive impairment and Alzheimer's disease. However, conflicting outcomes were observed among various studies, highlighting the need to consider diverse types of ketogenic diets and their respective effects on clinical outcomes and gut microbiota composition. Vegetarian and Mediterranean diets, known for their anti-inflammatory properties, can be effective against Parkinson's disease, which is related to inflammation in the gut environment. On the other hand, the westernization of dietary patterns was associated with reduced gut microbial diversity and metabolites, which ultimately contributed to the development of neuroinflammation and cognitive impairment. Various studies examining the impact of dietary interventions on the gut-brain axis with regard to neuroinflammation and Alzheimer's and Parkinson's diseases are thoroughly reviewed in this article. A strong mechanistic explanation is required to fully understand the complex interactions between various dietary patterns, gut microbiota, and microbial metabolites and the effects these interactions have on cognitive function and the progression of these diseases.

TSPO deficiency accelerates amyloid pathology and neuroinflammation by impairing microglial phagocytosis.

Increasing evidence has placed inflammation and immune dysfunction at the center of the pathogenesis of Alzheimer's disease (AD). The mitochondrial protein translocator protein (18 kDa) (TSPO) is highly upregulated in microglia and astrocytes in response to inflammatory stimulation. However, the biological action of TSPO in the pathogenesis of AD has not been determined to date. In this study, we showed that TSPO expression was upregulated in brain tissues from AD patients and AD model mice. APP/PS1 mice lacking TSPO generated significantly higher levels of Aß1-40 and Aß1-42 peptides and more Aß plaques, as well as enhanced microglial activation, in the brain. TSPO-deficient microglia cultured in vitro showed a significant decrease in the ability to phagocytose Aß peptides or latex beads and generated more proinflammatory cytokines (TNF-α and IL-1ß) in response to Aß peptides. Our findings suggest that TSPO has protective functions against neuroinflammation and Aß pathogenesis in AD. TSPO may be a potential drug target for the development of drugs that have therapeutic or preventive effects in neuroinflammatory diseases.

Dietary EPA-Enriched Phospholipids Alleviate Chronic Stress and LPS-Induced Depression- and Anxiety-Like Behavior by Regulating Immunity and Neuroinflammation.

SCOPE: A growing number of studies have reported the effects of eicosapentaenoic acid (EPA) and terrestrial phospholipids on ameliorating mood disorders. Marine-derived EPA-enriched phospholipids (EPA-PL) exhibit the structural characteristics of EPA and phospholipids. However, the effect of dietary EPA-PL, and the differences between amphiphilic EPA-PL and lyophobic EPA on mood disorders had not been studied. METHODS AND RESULTS: A comparative investigation to determine the effects of dietary EPA-enriched ethyl ester (EPA-EE) and EPA-PL on improving depression- and anxiety-like behavior in a mouse model is performed, induced by 4 week chronic unpredictable mild stress (CUMS) coupled with lipopolysaccharide (LPS) challenge. It is found that dietary 4 week 0.6% (w/w) EPA-PL rescued depression- and anxiety-like behavior to a greater extent than did EPA-EE. Moreover, dietary EPA-PL significantly reduced the immobility time by 56.6%, close to the normal level, in forced swimming test, which revealed a reversal of depression-like behavior. Further studies revealed that dietary EPA-PL regulated immunity, monoamine systems, and the hypothalamic-pituitary-adrenal (HPA) axis by multi-target interactions, including inhibition of neuroinflammation and apoptosis. CONCLUSION: EPA-PL exerted superior effects to EPA-EE in alleviating depression- and anxiety-like behavior. The data suggest potential novel candidate or targeted dietary patterns to prevent and treat mood disorder.

Emerging role of gut microbiota in modulation of neuroinflammation and neurodegeneration with emphasis on Alzheimer's disease.

Alzheimer's disease (AD) is a complex multifactorial disease involving chronic neuroinflammation and neurodegeneration. It has been recently recognized that gut microbiota interacts with the brain, and it is termed as microbiota-gut-brain axis. Modulation of this axis has been recently reported to affect the pathogenesis of neurodegenerative diseases, such as AD. Gut microbiota has a pivotal role in regulating multiple neuro-chemical pathways through the highly interconnected gut-brain axis. Recent emerging evidences have highlighted that the intestinal microflora takes part in bidirectional communication between the gut and the brain. Due to this, the researchers have suggested that human gut microflora may even act as the "second brain" and may be responsible for neurodegenerative disorders like Alzheimer's disease. Dysbiosis of gut microbiota can induce increased intestinal permeability and systemic inflammation. This may lead to the development of AD pathologies and cognitive impairment via the neural, immune, endocrine, and metabolic pathways. Thus, the modulation of gut microbiota through personalized diet, oral bacteriotherapy may lead to alteration of gut microbiota their products including amyloid protein. It has been demonstrated that modulation of the gut microbiota induces beneficial effects on neuronal pathways consequently leading to delay the progression of Alzheimer's disease. Thus, this approach may provide a novel therapeutic option for treatment of AD.

The effects of modified anti-inflammatory diet on fatigue, quality of life, and inflammatory biomarkers in relapsing-remitting multiple sclerosis patients: a randomized clinical trial.

BACKGROUND: The role of dietary interventions in improving the symptoms of Multiple Sclerosis (MS) has always been considered, but few studies have been conducted in this area. This study aimed to investigate the effects of modified anti-inflammatory diet on fatigue, quality of life, and inflammatory markers among patients with Relapsing-Remitting Multiple Sclerosis (RRMS). METHODS: This randomized clinical trial was conducted on 100 patients with RRMS. The patients were randomly divided into the diet group (anti-inflammatory diet) or the control group (healthy diet recommendations) for 12 weeks. Fatigue and quality of life were assessed by Modified Fatigue Impact Scale (MFIS) and Multiple Sclerosis Quality of Life (MSQoL-54), respectively. Anthropometric measures and inflammatory biomarkers, including Interleukin 17 (IL-17), Interleukin 4 (IL-4), and high sensitivity C-Reactive Protein (hs-CRP), were assessed at baseline and end of the study. RESULTS: The results showed a significant improvement in MFIS as well as in physical and mental components of MSQoL-54 (p = 0.001, p = 0.015, and p = 0.003, respectively) in the diet group compared to the control group. The results also showed a significant increase in IL-4 level (p = 0.022). However, no significant changes were detected in IL-17 and hs-CRP levels (p = 0.091, 0.418, respectively). CONCLUSION: Modified anti-inflammatory diet could improve fatigue and quality of life and increase IL-4 level.

Nutritional Supplementation Reduces Lesion Size and Neuroinflammation in a Sex-Dependent Manner in a Mouse Model of Perinatal Hypoxic-Ischemic Brain Injury.

Perinatal hypoxia-ischemia (HI) is a major cause of neonatal brain injury, leading to long-term neurological impairments. Medical nutrition can be rapidly implemented in the clinic, making it a viable intervention to improve neurodevelopment after injury. The omega-3 (n-3) fatty acids docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3), uridine monophosphate (UMP) and choline have previously been shown in rodents to synergistically enhance brain phospholipids, synaptic components and cognitive performance. The objective of this study was to test the efficacy of an experimental diet containing DHA, EPA, UMP, choline, iodide, zinc, and vitamin B12 in a mouse model of perinatal HI. Male and female C57Bl/6 mice received the experimental diet or an isocaloric control diet from birth. Hypoxic ischemic encephalopathy was induced on postnatal day 9 by ligation of the right common carotid artery and systemic hypoxia. To assess the effects of the experimental diet on long-term motor and cognitive outcome, mice were subjected to a behavioral test battery. Lesion size, neuroinflammation, brain fatty acids and phospholipids were analyzed at 15 weeks after HI. The experimental diet reduced lesion size and neuroinflammation specifically in males. In both sexes, brain n-3 fatty acids were increased after receiving the experimental diet. The experimental diet also improved novel object recognition, but no significant effects on motor performance were observed. Current data indicates that early life nutritional supplementation with a combination of DHA, EPA, UMP, choline, iodide, zinc, and vitamin B12 may provide neuroprotection after perinatal HI.