Dietary Pattern, Gut Microbiota, and Alzheimer’s Disease

Abstract

Alzheimer's disease is the most common neurodegenerative disease. Until now, there has been no specific medicine that can cure Alzheimer's disease or effectively reverse the disease process. A good dietary pattern is an efficient way to prevent or delay the progression of the disease. Evidence suggests that diet may affect β-amyloid production and tau processing or may regulate inflammation, metabolism, and oxidative stress associated with Alzheimer's disease, which can be exerted by gut microbiota. The gut microbiota is a complex microbial community that affects not only various digestive diseases but also neurodegenerative diseases. Studies have shown that gut microbial metabolites, such as pro-inflammatory factors, short-chain fatty acids, and neurotransmitters, can affect the pathogenesis of Alzheimer's disease. Clinical studies suggested that the gut microbial composition of patients with Alzheimer's disease is different, in particular to lower abundances of Eubacterium rectale and Bacteroides fragilis, which have an antiinflammatory activity. The purpose of this review is to summarize the neuropathological pathogenesis of Alzheimer's disease, and the modulation of dietary patterns rather than single dietary components on Alzheimer's disease through the gut−brain axis was discussed.

Crosstalk between Gut and Brain in Alzheimer’s Disease: The Role of Gut Microbiota Modulation Strategies

“…Moreover, healthy dietary patterns can be beneficial for cognitive health and can show neuroprotective properties. The Mediterranean diet is deemed beneficial for AD patients as it is rich in many components such as legumes, fruits, vegetables, cereals, polyphenols, non-digestible carbohydrates, and unsaturated fatty acids [107]. Polyphenols (PPs) are naturally occurring bioactive compounds and the most abundant forms of antioxidants in the human diet [63].…”

“…Prebiotics promote the growth of beneficial bacteria (including lactobacillus and bifidobacteria), and improve dysbiosis and the associated inflammatory conditions that may ameliorate cognitive impairment [111]. Conversely, the Western diet, consisting of saturated and high trans-fat, high sugar with fewer vegetables and fruits is considered a nutrient-imbalanced diet pattern [107]. This diet may cause metabolic syndromes and diseases and can increase the chances of AD development.…”

Roles and Mechanisms of Gut Microbiota in Patients With Alzheimer’s Disease

“…Aβ aggregation and memory impairment, as well as astrocyte activation, with a significant reduction in the expression levels of brain-derived neurotrophic factor (BDNF), while enhancing the expression of brain parenchymal cell apoptosis markers such as cytochrome C, Bax, caspase-9, and caspase-3 (Song et al, 2013;Calabrese et al, 2014;Badshah et al, 2016). Some microbiota had an anti-inflammatory activity identified on the basis of human clinical data, including F. prausnitzii (Sokol et al, 2008;Wang et al, 2014), E. rectale, B. longum (NK46), and B. fragilis (Lee et al, 2019;Markowiak-Kopeć andŚliżewska, 2020;Sun et al, 2020d;Zhang M. et al, 2020). Lee et al found that B. longum (NK46) was orally administered to 5 × FAD mice and induced anti-inflammatory effects (decrease in LPS levels, NF-κB activation, and TNF-α expression), changes in the intestinal microbiota composition of the recipients (increase in Bacteroides abundance and reduction in abundance of Firmicutes and Proteobacteria phyla), and suppression of Aβ accumulation in the hippocampus (Lee et al, 2019).…”

“…Accumulation of Aβ fibrils is thought to be an initiating factor in AD and necessary for the formation of tau aggregates (Goedert, 2018). Normal tau is essential for neuron extension configuration, cell polarization, and axonal transport, while hyperphosphorylation of tau leads to instability of the cytoskeleton, collapse of microtubules, synaptic failure, impairment of communication, and neuronal death (Zhang M. et al, 2020). Recently, the link between Aβ and tau in AD has been clarified.…”

Microbiota modulation as preventative and therapeutic approach in Alzheimer’s disease

“…On the other hand, healthy dietary patterns show neuroprotective properties and can be beneficial to host cognitive health. On this regard, the Mediterranean diet is rich in many components considered helpful for AD subjects, among them vegetables, legumes, fruits, cereals and a high intake of unsaturated fatty acids and polyphenols [145]. In addition, oral bacteriotherapy has been recently identified as an accepted practice for the prevention and treatment of gastrointestinal infections [146] and inflammatory conditions [147,148].…”