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Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome.

ABSTRACT: INTRODUCTION:Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are produced in the liver and are further metabolized by gut bacteria. They have major regulatory and signaling functions and seem dysregulated in Alzheimer's disease (AD). METHODS:Serum levels of 15 primary and secondary BAs and their conjugated forms were measured in 1464 subjects including 370 cognitively normal older adults, 284 with early mild cognitive impairment, 505 with late mild cognitive impairment, and 305 AD cases enrolled in the AD Neuroimaging Initiative. We assessed associations of BA profiles including selected ratios with diagnosis, cognition, and AD-related genetic variants, adjusting for confounders and multiple testing. RESULTS:In AD compared to cognitively normal older adults, we observed significantly lower serum concentrations of a primary BA (cholic acid [CA]) and increased levels of the bacterially produced, secondary BA, deoxycholic acid, and its glycine and taurine conjugated forms. An increased ratio of deoxycholic acid:CA, which reflects 7?-dehydroxylation of CA by gut bacteria, strongly associated with cognitive decline, a finding replicated in serum and brain samples in the Rush Religious Orders and Memory and Aging Project. Several genetic variants in immune response-related genes implicated in AD showed associations with BA profiles. DISCUSSION:We report for the first time an association between altered BA profile, genetic variants implicated in AD, and cognitive changes in disease using a large multicenter study. These findings warrant further investigation of gut dysbiosis and possible role of gut-liver-brain axis in the pathogenesis of AD.

SUBMITTER: MahmoudianDehkordi S

PROVIDER: S-EPMC6487485 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome.

MahmoudianDehkordi Siamak S Arnold Matthias M Nho Kwangsik K Ahmad Shahzad S Jia Wei W Xie Guoxiang G Louie Gregory G Kueider-Paisley Alexandra A Moseley M Arthur MA Thompson J Will JW St John Williams Lisa L Tenenbaum Jessica D JD Blach Colette C Baillie Rebecca R Han Xianlin X Bhattacharyya Sudeepa S Toledo Jon B JB Schafferer Simon S Klein Sebastian S Koal Therese T Risacher Shannon L SL Kling Mitchel Allan MA Motsinger-Reif Alison A Rotroff Daniel M DM Jack John J Hankemeier Thomas T Bennett David A DA De Jager Philip L PL Trojanowski John Q JQ Shaw Leslie M LM Weiner Michael W MW Doraiswamy P Murali PM van Duijn Cornelia M CM Saykin Andrew J AJ Kastenmüller Gabi G Kaddurah-Daouk Rima R

Alzheimer's & dementia : the journal of the Alzheimer's Association 20181015 1

<h4>Introduction</h4>Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are produced in the liver and are further metabolized by gut bacteria. They have major regulatory and signaling functions and seem dysregulated in Alzheimer's disease (AD).<h4>Methods</h4>Serum levels of 15 primary and secondary BAs and their conjugat ...[more]

PMID: 30337151

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Project description:BackgroundCancer cachexia is a multifactorial metabolic syndrome in which bile acid (BA) metabolism might be involved. The aim of the present study was to clarify the contribution of liver and gut microbiota to BA metabolism disturbance in cancer cachexia and to check the possibility of targeting BA metabolism using agents such as tauroursodeoxycholic acid (TUDCA) for cancer cachexia therapy.MethodsThe BA profiles in liver, intestine, and serum of mice with cancer cachexia induced by inoculation of colon C26 tumour cells were analysed using metabolomics methods and compared with that of control mice. Proteomic analysis of liver protein expression profile and 16S rRNA gene sequencing analysis of gut microbiota composition in cancer cachexia mice were conducted. Expression levels of genes related to farnesoid X receptor (FXR) signalling pathway in the intestine and liver tissues were analysed using RT-PCR analysis. The BA profiles in serum of clinical colon cancer patients with or without cachexia were also analysed and compared with that of healthy volunteers. The effects of TUDCA in treating cancer cachexia mice were observed.ResultsIn the liver of cancer cachexia mice, expression of BA synthesis enzymes was inhibited while the amount of total BAs increased (P < 0.05). The ratios of conjugated BAs/un-conjugated BAs significantly increased in cancer cachexia mice liver (P < 0.01). Gut microbiota dysbiosis such as decrease in Lachnospiraceae and increase in Enterobacteriaceae was observed in the intestine of cancer cachexia mice, and microbial metabolism of BAs was reduced. Increase in expression of FGF15 in intestine (P < 0.01) suggested the activation of FXR signalling pathway which might contribute to the regulation of BA synthesis enzymes, transporters, and metabolic enzymes. Increase in the BA conjugation was observed in the serum of cancer cachexia mice. Results of clinical patients showed changes in BA metabolism, especially the increase in BA conjugation, and also suggested compensatory mechanism in BA metabolism regulation. Oral administration of 50 mg/kg TUDCA could significantly ameliorate the decrease in body weight (P < 0.001), muscle loss (P < 0.001), and atrophy of heart and liver (P < 0.05) in cancer cachexia mice without influence on tumour growth.ConclusionsBile acid metabolism dysregulation such as decrease in BA synthesis, increase in BA conjugation, and decrease in BA microbial metabolism was involved in development of cancer cachexia in mice. Targeting BA metabolism using agents such as TUDCA might be helpful for cancer cachexia therapy.

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Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome.

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Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome.

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