Different oral and gut microbial profiles in those with Alzheimer's disease consuming anti-inflammatory diets

Abstract

The number of people living with Alzheimer's disease (AD) is increasing alongside with aging of the population. Systemic chronic inflammation and microbial imbalance may play an important role in the pathogenesis of AD. Inflammatory diets regulate both the host microbiomes and inflammatory status. This study aimed to explore the impact of inflammatory diets on oral-gut microbes in patients with AD and the relationship between microbes and markers of systemic inflammation. The dietary inflammatory properties and the oral and gut microorganisms were analyzed using the dietary inflammatory index (DII) and 16S RNA in 60 patients with AD. The α-diversity was not related to the DII (p > 0.05), whereas the β-diversity was different in the oral microbiomes (R2 = 0.061, p = 0.013). In the most anti-inflammatory diet group, Prevotella and Olsenella were more abundant in oral microbiomes and Alistipes, Ruminococcus, Odoribacter, and unclassified Firmicutes were in the gut microbiomes (p < 0.05). Specific oral and gut genera were associated with interleukin-6 (IL)-6, complement 3 (C3), high-sensitivity C-reactive protein (hs-CRP), IL-1β, IL-4, IL-10, IL-12, and tumor necrosis factor-α (TNF-α) (p < 0.05). In conclusion, anti-inflammatory diets seem to be associated with increased abundance of beneficial microbes, and specific oral and gut microbial composition was associated with inflammatory markers.

Oral Microbiome Stamp in Alzheimer’s Disease

“…Relative abundance analysis revealed the downward trends in phyla Proteobacteria , Actinobacteria , and Bacteroidota in the AD group. At the same time, Firmicutes was significantly more abundant in AD patients, which aligns with the results of Chen et al [ 41 , 42 ]. The results on the lower abundance of s_Haemophilus_parainfluenzae , s_Prevotella_melaninogenica , s_Prevotella_histicola , and s__Actinomyces_oris in AD patients are partly consistent with Liu et al data [ 12 ].…”

The role of microbiome-host interactions in the development of Alzheimer´s disease

“…There are several studies investigating a possible connection between the oral microbiome community structure and AD. Through a MEDLINE search (search terms: 'oral microbiota', 'oral microbiome' and 'alzheimer', 'dementia', 'cognitive', 'cognition'), we identified 13 studies investigating the connections between AD and the oral microbiome (Cockburn et al, 2012;Bathini et al, 2020;Holmer et al, 2021;Wu et al, 2021;Yang et al, 2021;Chen et al, 2022a;Chen et al, 2022b;Chen et al, 2022c;Cirstea et al, 2022;Fu et al, 2022;Taati Moghadam et al, 2022;Tadjoedin et al, 2022). For Chen et al 2022a andCirstea et al, 2022, full-text manuscripts could not be obtained.…”

“…Five studies (Cockburn et al, 2012;Bathini et al, 2020;Holmer et al, 2021;Yang et al, 2021;Chen et al, 2022c) additionally included a third group of MCI patients, or people with subjective cognitive decline, or further differentiated into mild and moderate AD (Chen et al, 2022c). Chen et al (b) had no healthy control group, but divided their AD patients into three groups regarding the patients' nutritional habits (Chen et al, 2022b), based on the so-called 'dietary inflammatory index' (DII) (Phillips et al, 2019). One study employed a longitudinal design without a control group, but with a comparison of the oral microbiota before and after a 24-week oral health intervention (Chen et al, 2022a).…”

“…One study employed a longitudinal design without a control group, but with a comparison of the oral microbiota before and after a 24-week oral health intervention (Chen et al, 2022a). Therefore, the studies of Chen et al, 2022a;Chen et al, 2022b) are excluded from the discussion regarding possible differences between patients and healthy controls. Nevertheless, they should be mentioned in the broader context of the oral microbiome in AD.…”

Association of composite dietary antioxidant index with depression and all-cause mortality in middle-aged and elderly population

“…The flexible vegetarian diet that emphasizes increased vegetable consumption and reduced meat intake, is very effective in weight loss 13 . Anti-inflammatory diets focusing on fish, fruits, and vegetables have also been demonstrated a suppressive effect on the risk of Alzheimer's disease, Parkinson's disease, atherosclerosis, heart disease, and muscle wasting 14 – 17 . Furthermore, a meta-analysis showed that the addition of the antioxidant vitamin E to the treatment of depression and anxiety might be beneficial 18 .…”