Centenarians, or individuals who have lived more than a century, represent the ultimate model of successful longevity associated with decreased susceptibility to ageing-associated illness and chronic inflammation [1][2][3] . The gut microbiota is considered to be a critical determinant of human health and longevity [4][5][6][7][8] . Here we show that centenarians (average 107 yo) have a distinct gut microbiome enriched in microbes capable of generating unique secondary bile acids, including iso-, 3-oxo-, and isoallo-lithocholic acid (LCA), as compared to elderly (85-89 yo) and young (21-55 yo) controls. Among these bile acids, the biosynthetic pathway for isoalloLCA had not been described previously. By screening 68 bacterial isolates from a centenarian's faecal microbiota, we identified Parabacteroides merdae and Odoribacteraceae strains as effective producers of isoalloLCA. Furthermore, we generated and tested mutant strains of P. merdae to show that the enzymes 5a-reductase (5AR) and 3bhydroxysteroid dehydrogenase (3bHSDH) were responsible for isoalloLCA production. This secondary bile acid derivative exerted the most potent antimicrobial effects among the tested bile acid compounds against gram-positive (but not gram-negative) multidrug-resistant pathogens, including Clostridioides difficile and vancomycin-resistant Enterococcus faecium.These findings suggest that specific bile acid metabolism may be involved in reducing the risk of pathobiont infection, thereby potentially contributing to longevity. MainThe microbiome has long been recognized as a key player in determining the health status of ageing individuals through its role in controlling digestive functions, bone density, neuronal activity, immunity, and resistance to pathogen infection [9][10][11][12][13] . Microbial consortia in elderly individuals often show increased interindividual variability and reduced diversity, and are thus being linked to immunosenescence, chronic systemic inflammation, and frailty 6,14 . An integrated understanding of the dynamic balance and functions of microbial members with respect to ageing is essential for establishing a strategy toward rational manipulation of the microbiota for restoring and/or maintaining tissue homeostasis and overall health.Centenarians (aged 100 years and older) are known to be less susceptible to age-related diseases including hypertension, diabetes, obesity, and cancer 3,15 . Moreover, centenarians have likely survived periods of hunger and several bouts with infectious diseases such as influenza, tuberculosis, shigellosis, and salmonellosis 16 . It has been postulated that there are centenarian-specific members of the gut microbiota which, rather than representing a mere consequence of ageing, might actively contribute to maintaining homeostasis, resilience, and healthful ageing [4][5][6]8 . In this study, we aimed

Gaskins (2020) The 'invivo lifestyle' of bile acid 7αdehydroxylating bacteria: comparative genomics, metatranscriptomic, and bile acid metabolomics analysis of a defined microbial community in gnotobiotic mice,

We have developed a simple and accurate HPLC method for measurement of fecal bile acids using phenacyl derivatives of unconjugated bile acids, and applied it to the measurement of fecal bile acids in cirrhotic patients. The HPLC method has the following steps: 1 ) lyophilization of the stool sample; 2 ) reconstitution in buffer and enzymatic deconjugation using cholylglycine hydrolase/sulfatase; 3 ) incubation with 0.1 N NaOH in 50% isopropanol at 60°C to hydrolyze esterifi ed bile acids; 4 ) extraction of bile acids from particulate material using 0.1 N NaOH; 5 ) isolation of deconjugated bile acids by solid phase extraction; 6 ) formation of phenacyl esters by derivatization using phenacyl bromide; and 7 ) HPLC separation measuring eluted peaks at 254 nm.

Unusual bile acids, such as unsaturated ketonic and 7beta-hydroxylated bile acids, have been detected in urine early in life. To elucidate the normal profiles of usual and unusual urinary bile acids in the neonatal and pediatric periods, we measured the concentrations of 28 kinds in urine from normal newborns, infants, and children by gas chromatography-mass spectrometry. The mean total bile acid/Cr ratio in 7-d-old infants was significantly higher than in subjects of other age groups (birth, 2-4 mo, 5-7 mo, 11-12 mo, 2-3 y, 9-14 y, and adult) (p < 0.05). Relatively large amounts of unusual bile acids were detected during infancy, especially during the period up to 1 mo of age. At that time, 1beta,3alpha,7alpha,12alpha-tetrahydroxy-5bet a-cholan-24-oic, 7alpha, 12alpha-dihydroxy-3-oxo-5beta-chol-1-en-24-oic, and 7alpha,12alpha-dihydroxy-3-oxo-4-cholen-24-oic acids were predominant among the unusual urinary bile acids present. Moreover, the levels of 3alpha,7beta,12alpha-trihydroxy-5beta-cholan+ ++-24-oic acid increased significantly after 2-4 mo of age. These results indicate that bile acid synthesis and metabolism in the liver of developing infants are significantly different from that occurring in the liver of adults. Significant amounts of urinary isomerized 7beta-hydroxylated bile acids were detected after late infancy, probably because of changes in the intestinal bacterial flora response to a change in nutrition. We describe, for the first time, evidence of the epimerization of the 7alpha-hydroxyl group of cholic acid, which may be unique to human development.

The scope of an enantioselective cyclopentannelation reaction that makes use of allenyl ether-derived nucleophiles has been probed. The enantioselectivity is induced by a traceless chiral auxiliary that is easily derived from camphor. It has been shown that for gamma-substituted allene ethers that are axially chiral, very high enantiomeric excesses of cyclopentenone products are observed in the matched cases. Two fundamentally different mechanisms are observed, one for the cyclizations of allenyl ketones (see eq 7), the other for the cyclizations of allenyl alcohols (see eq 11). The methodology is versatile, efficient, and well-suited for applications in synthesis.