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Centenarians have a decreased susceptibility to ageing-associated illnesses, chronic inflammation and infectious diseases.sup.1-3. Here we show that centenarians have a distinct gut microbiome that is enriched in microorganisms that are capable of generating unique secondary bile acids, including various isoforms of lithocholic acid (LCA): iso-, 3-oxo-, allo-, 3-oxoallo- and isoallolithocholic acid. Among these bile acids, the biosynthetic pathway for isoalloLCA had not been described previously. By screening 68 bacterial isolates from the faecal microbiota of a centenarian, we identified Odoribacteraceae strains as effective producers of isoalloLCA both in vitro and in vivo. Furthermore, we found that the enzymes 5[alpha]-reductase (5AR) and 3[beta]-hydroxysteroid dehydrogenase (3[beta]-HSDH) were responsible for the production of isoalloLCA. IsoalloLCA exerted potent antimicrobial effects against Gram-positive (but not Gram-negative) multidrug-resistant pathogens, including Clostridioides difficile and Enterococcus faecium. These findings suggest that the metabolism of specific bile acids may be involved in reducing the risk of infection with pathobionts, thereby potentially contributing to the maintenance of intestinal homeostasis. The microbiota of centenarians (aged 100 years and older) comprise gut microorganisms that are capable of generating unique secondary bile acids, including isoallolithocholic acid, a bile acid with potent antimicrobial effects against Gram-positive--but not Gram-negative--multidrug-resistant pathogens., Author(s): Yuko Sato [sup.1] [sup.2] [sup.3] , Koji Atarashi [sup.1] [sup.2] [sup.3] , Damian R. Plichta [sup.4] , Yasumichi Arai [sup.5] , Satoshi Sasajima [sup.1] [sup.3] , Sean M. Kearney [...]

BACKGROUND. Mirabegron is a [beta]3-adrenergic receptor ([beta]3-AR) agonist approved only for the treatment of overactive bladder. Encouraging preclinical results suggest that [beta]3-AR agonists could also improve obesity-related metabolic disease by increasing brown adipose tissue (BAT) thermogenesis, white adipose tissue (WAT) lipolysis, and insulin sensitivity. METHODS. We treated 14 healthy women of diverse ethnicities (27.5 [+ or -] 1.1 years of age, BMI of 25.4 [+ or -] 1.2 kg/[m.sup.2]) with 100 mg mirabegron (Myrbetriq extended-release tablet, Astellas Pharma) for 4 weeks in an open-label study. The primary endpoint was the change in BAT metabolic activity as measured by [[sup.18]F]-2-fluoro -D-2-deoxy-D-glucose ([sup.18]F-FDG) PET/CT. Secondary endpoints included resting energy expenditure (REE), plasma metabolites, and glucose and insulin metabolism as assessed by a frequently sampled intravenous glucose tolerance test. RESULTS. Chronic mirabegron therapy increased BAT metabolic activity. Whole-body REE was higher, without changes in body weight or composition. Additionally, there were elevations in plasma levels of the beneficial lipoprotein biomarkers HDL and ApoA1, as well as total bile acids. Adiponectin, a WAT-derived hormone that has antidiabetic and antiinflammatory capabilities, increased with acute treatment and was 35% higher upon completion of the study. Finally, an intravenous glucose tolerance test revealed higher insulin sensitivity, glucose effectiveness, and insulin secretion. CONCLUSION. These findings indicate that human BAT metabolic activity can be increased after chronic pharmacological stimulation with mirabegron and support the investigation of [beta]3-AR agonists as a treatment for metabolic disease. TRIAL REGISTRATION. Clinicaltrials.gov NCT03049462. FUNDING. This work was supported by grants from the Intramural Research Program of the NIDDK, NIH (DK075112, DK075116, DK071013, and DK071014)., Introduction The rising rates of obesity are a global health epidemic. In the US alone, by 2030 it is predicted that 86% of adults will be overweight or obese (1). [...]

The gastrointestinal tracts of mammals are colonized by hundreds of microbial species that contribute to health, including colonization resistance against intestinal pathogens (1). Many antibiotics destroy intestinal microbial communities and increase susceptibility to intestinal pathogens (2). Among these, Clostridium difficile, a major cause of antibiotic-induced diarrhoea, greatly increases morbidity and mortality in hospitalized patients (3). Which intestinal bacteria provide resistance to C. difficile infection and their invivo inhibitory mechanisms remain unclear. Here we correlate loss of specific bacterial taxa with development of infection, by treating mice with different antibiotics that result in distinct microbiota changes and lead to varied susceptibility to C. difficile. Mathematical modelling augmented by analyses of the microbiota of hospitalized patients identifies resistance-associated bacteria common to mice and humans. Using these platforms, we determine that Clostridium scin dens abile acid 7α-dehydroxylating intestinal bacterium, is associated with resistance to C. difficile infection and, upon administration, enhances resistance to infection in a secondary bile acid dependent fashion. Using a workflow involving mouse models, clinical studies, metagenomic analyses, and mathematical modelling, we identify a probiotic candidate that corrects a clinically relevant microbiome deficiency. These findings have implications for the rational design of targeted antimicrobials as well as microbiome-based diagnostics and therapeutics for individuals at risk of C. difficile infection., Infection with C. difficile is a growing public health threat (3). Susceptibility to infection is associated with antibiotic use (3), and faecal microbiota transplant, which restores microbiota complexity, can resolve [...]

Most Gram-positive bacteria inhabiting the gastrointestinal tract are capable of hydrolysing bile salts. Bile salt hydrolysis is thought to play an important role in various biological processes in the host. Therefore, correct annotation of bacterial bile salt hydrolases (Bsh) in public databases (EC 3.5.1.24) is of importance, especially for lactobacilli, which are considered to play a major role in bile salt hydrolysis in vivo. In the present study, all enzymes listed in public databases that belong to the Bsh family and the closely related penicillin V acylase (Pva; EC 3.5.1.11) family were compared with the sequences annotated as Bsh in Lactobacillus plantarum WCFS1, as an example. In Gram-positive bacteria, a clear distinction was made between the two families using sequence alignment, phylogenetic clustering, and protein homology modelling. Biochemical and structural data on experimentally verified Bsh and Pva enzymes were used for validation of function prediction. Hidden Markov models were constructed from the sequence alignments to enable a more accurate prediction of Bsh-encoding genes, and their distinction from those encoding members of the Pva family. Many Pva-related sequences appeared to be annotated incorrectly as Bsh in public databases. This refinement in the annotation of Bsh family members influences the prediction of the function of bsh-like genes in species of the genus Lactobacillus, and it is discussed in detail.

Bile acids are surface-active steroid compounds with toxic effects for bacteria. Recently, the isolation and characterization of a bacterium, Pseudomonas sp. strain Chol1, growing with bile acids as the carbon and energy source was reported. In this study, initial reactions of the aerobic degradation pathway for the bile acid cholate were investigated on the biochemical and genetic level in strain Chol1. These reactions comprised A-ring oxidation, activation with coenzyme A (CoA), and [beta]-oxidation of the acyl side chain with the [C.sub.19]-steroid dihydroxyandrostadienedione as the end product. A-ring oxidizing enzyme activities leading to [[DELTA].sub.1,4]-3-ketocholyl-CoA were detected in cell extracts and confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Cholate activation with CoA was demonstrated in cell extracts and confirmed with a chemically synthesized standard by LC-MS/MS. A transposon mutant with a block in oxidation of the acyl side chain accumulated a steroid compound in culture supernatants which was identified as 7[alpha],12[alpha]-dihydroxy-3-oxopregna-l,4-diene-20- carboxylate (DHOPDC) by nuclear magnetic resonance spectroscopy. The interrupted gene was identified as encoding a putative acyl-CoA-dehydrogenase (ACAD). DHOPDC activation with CoA in cell extracts of strain Choll was detected by LC-MS/MS. The growth defect of the transposon mutant could be complemented by the wild-type ACAD gene located on the plasmid pBBR1MCS-5. Based on these results, the initiating reactions of the cholate degradation pathway leading from cholate to dihydroxyandrostadienedione could be reconstructed. In addition, the first bacterial gene encoding an enzyme for a specific reaction step in side chain degradation of steroid compounds was identified, and it showed a high degree of similarity to genes in other steroid-degrading bacteria.

Primary bile acids are synthesized from cholesterol in the liver and thereafter are secreted into the bile and small intestine. Gut flora modify primary bile acids to produce secondary bile acids leading to a chemically diverse bile acid pool that is circulated between the small intestine and liver. A majority of primary and secondary bile acids in higher vertebrates have a 3[alpha]-hydroxyl group. Here, we characterize a line of knockout mice that cannot epimerize the 3[beta]-hydroxyl group of cholesterol and as a consequence synthesize a bile acid pool in which 3[beta]-hydroxylated bile acids predominate. This alteration causes death in 90% of newborn mice and decreases the absorption of dietary cholesterol in surviving adults. Negative feedback regulation of bile acid synthesis mediated by the farnesold X receptor (FXR) is disrupted in the mutant mice. We conclude that the correct stereochemistry of a single hydroxyl group at carbon 3 in bile acids is required to maintain their physiologic and regulatory functions in mammals. cholesterol turnover | lipid metabolism | liver disease | mouse model | nuclear receptor

Research has been conducted on substrate specificities between Escherichia coli AcrB and AcrD. The functional chimeras of these proteins demonstrate that large periplasmis loops of these proteins are responsible for drug specificity.

Sham-operated and cecectomized rats were fed for 21 d a cholesterol-free purified diet containing (200 g/kg) either normal cornstarch (CS) or high amylose cornstarch (HACS). In both types of rats, those fed the HACS diet had a significantly lower plasma total cholesterol concentration and a significantly larger intestinal bile acid pool than those fed the CS diet. In cecectomized rats, those fed the HACS diet had significantly lower plasma HDL and LDL cholesterol concentrations, a significantly greater fecal bile acid excretion and a significantly lower hepatic 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase mRNA concentration than those fed the CS diet. The plasma triglyceride concentration and LDL-receptor mRNA concentration were not affected by the diet or cecectomy. In sham-operated rats, the propionate concentration in the cecal contents was significantly greater in those fed the HACS diet than in those fed the CS diet. Compared with sham-operated rats, cecectomized rats had significantly enhanced cholesterol 7[alpha]-hydroxylase activity. In intact rats, biliary bile acid flux into the small intestine was significantly greater in those fed the HACS diet than in those fed the CS diet. Thus, the hypocholesterolemic effect of HACS appears to be mediated by accelerated fecal excretion of bile acids and increases in the intestinal pool and biliary flux of bile acids, and not by cecal fermentation products. KEY WORDS: * high amylose cornstarch * cecectomy * plasma cholesterol * rats

Research has been conducted on the substituted cinnamic acids. The asymmetric epoxidation of these acids which has been obtained in the presence of keto bile acid derivatives as optically active carbonyl inducers has been investigated and is described.

Huntington's disease (HD) is an untreatable neurological disorder caused by selective and progressive degeneration of the caudate nucleus and putamen of the basal ganglia. Although the etiology of HD pathology is not fully understood, the observed loss of neuronal cells is thought to occur primarily through apoptosis. Furthermore, there is evidence in HD that cell death is mediated through mitochondrial pathways, and mitochondrial deficits are commonly associated with HD. We have previously reported that treatment with tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, prevented neuropathology and associated behavioral deficits in the 3-nitropropionic acid rat model of HD. We therefore examined whether TUDCA would also be neuroprotective in a genetic mouse model of HD. Our results showed that systemically administered TUDCA led to a significant reduction in striatal neuropathology of the R6/2 transgenic HD mouse. Specifically, R6/2 mice began receiving TUDCA at 6 weeks of age and exhibited reduced striatal atrophy, decreased striatal apoptosis, as well as fewer and smaller size ubiquitinated neuronal intranuclear huntingtin inclusions. Moreover, locomotor and sensorimotor deficits were significantly improved in the TUDCA-treated mice. In conclusion, TUDCA is a nontoxic, endogenously produced hydrophilic bile acid that is neuroprotective in a transgenic mouse model of HD and, therefore, may provide a novel and effective treatment in patients with HD.

Most Gram-positive bacteria are susceptible to the bactericidal action of fatty acids and bile acids. Because dietary calcium phosphate (CaP[sub.i]) lowers the intestinal concentration of these antimicrobial agents, high CaP[sub.i] intake may enhance intestinal colonization of Gram-positive pathogens and the subsequent pathogenesis. In this study, we tested this hypothesis in a rat model using Listeria monocytogenes. Rats were fed diets containing low (20 [micro]mol/g diet) or high (160 [micro]mol/g diet) amounts of CaP[sub.i]. Dietary fat was provided as corn oil or milk fat. Rats were orally inoculated with L. monocytogenes. When rats consumed diets containing corn oil, high CaP[sub.i] intake indeed stimulated colonization of L. monocytogenes and increased L. monocytogenes translocation and diarrhea. In addition, supplemental CaP[sub.i] enhanced ex vivo growth of L. monocytogenes in fecal extracts of rats fed corn oil diets, suggesting that high CaP[sub.i] intake decreased a luminal inhibitory factor. The concentrations of bile salts and fatty acids, which were highly listericidal in vitro, were indeed considerably decreased in fecal water of rats in the high calcium corn oil group. Surprisingly, dietary CaP[sub.i] did not affect colonization and translocation of L. monocytogenes in rats fed the milk fat diet, nor did CaP[sub.i] enhance ex vivo growth in fecal extracts. This absence of Listeria stimulation was associated with a lack of effect of dietary CaP[sub.i] on fecal soluble fatty acids. In addition, residual soluble bile salts were higher in rats fed the high CaP[sub.i] milk fat diet compared with the high CaP[sub.i] corn oil diet. These results suggest that the stimulating effect of CaP[sub.i] on L. monocytogenes infection depends on the type of dietary fat consumed. Key Words: * calcium * dietary fat * fatty acids * bile acids * infection * rats

Research has been conducted on the bile acids. The use of these acids as the building block for the dendritic unit construction has been explored and the results indicate that these molecules have globular shapes with the nanometric dimensions.

Research demonstrates that intestinal Lactobacillus accumulates bile acids as shown by the accumulation of cholic acid. Data indicate that the acid uptake is mediated by the transmembrane proton gradient.

Recently published work that establishes a specific role for the nuclear receptor FXR in cholesterol catabolism pathways and in repression of the CYP7A1 gene and regulation by nuclear receptors, is discussed in this review article. The rate-limiting step of the neutral bile biosynthesis pathway is catalyzed by the cytochrome P450 cholesterol 7alpha-hydroxylase or CYP7A1. Lipid homeostasis in vertebrates, that is, the acquisition, synthesis and metabolism of cholesterol, is important. As mediators of organ physiology, nuclear hormone receptors, and other proteins are thought to play a vital role in the processes by controlling the transcription of genes encoding the transporters, the apoplipoproteins, as well as catabolic and synthetic enzymes. Implications for future drug development in treatment of hypercholesterolemia and cholestasis are important.

The authors dicuss the role of the nuclear bile acid receptor FXR/BAR as an intracellular bile acide sensor in lipid and bile accid homeostasis.

Research describes a mathematical model incorporating parameters of cell adsorption that influence the survival of bifidobacteria after exposure to gastic and intestinal fluids. Data show that cell death rate in the beads decreases in relation to alginate concentration and the bead size.

This study was designed to investigate the effects of pectin on cholesterol and bile acid metabolism and to elucidate the mechanisms involved in its hypolipidemic effect in rats. The key regulatory enzymes in cholesterol and bile acid metabolism, 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and cholesterol 7[Alpha]-hydroxylase, were determined. Circulating, hepatic, and biliary lipid concentrations and fecal bile acid excretion were also measured. Male Wistar rats were fed a fiber-free or a pectin-supplemented (7 g/100 g) diet for 4 wk. Bile flow and the biliary secretion of both bile acids and cholesterol were not significantly different than controls in pectin-fed rats. The addition of pectin to the diet resulted in lower serum and liver cholesterol concentrations (-27 and -17%, respectively). Fecal bile acid excretion (+168%) and the hepatic activity of cholesterol 7[Alpha]-hydroxylase (+70%) were significantly higher in pectin-fed animals. HMG-CoA reductase activity was also significantly greater (+11%) in the presence of dietary pectin. Results of our study indicate that pectin, by enhancing fecal bile acid excretion, may cause increased hepatic synthesis of bile acids and liver depletion of cholesterol in rats, which results in a higher rate of cholesterol synthesis and reduced serum cholesterol concentrations. INDEXING KEY WORDS: cholesterol; bile acids; fiber; pectin; rats

Sources of dietary fiber known to alter cholesterol metabolism and/or bile acid pool size were fed to rats, and activity of the rate-limiting step in bile acid synthesis, cholesterol 7[Alpha]-hydroxylase, was measured. In the first experiment, semipurified diets containing 5% cellulose, psyllium hydrocolloid, pectin or oat bran as dietary fiber sources or 2% cholestyramine were fed to groups of 10 male Wistar rats for 4 wk. In the second experiment, groups of six rats were fed diets containing 5% cellulose, rice bran, oat bran or psyllium with and without 0.25% cholesterol. In the first experiment, the activity of cholesterol 7[Alpha]-hydroxylase (pmol [centered dot] [min.sup.-1] [centered dot] mg [protein.sup.-1] was highest in the cholestyramine-treated group (95.6 [+ or -] 3.6), followed by groups fed psyllium (35.5 [+ or -] 3.5) or pectin (36.0 [+ or -] 4.5), which exhibited more than twice the enzyme activity of groups fed cellulose (16.9 [+ or -] 1.9) or oat bran (12.3 [+ or -] 2.0). In the second experiment, feeding cholesterol resulted in significantly higher enzyme activity when cellulose (65%), oat bran (118%) and rice bran (60%) were fed, but no difference in activity was observed when cholesterol was added to the psyllium-containing diet. Higher activity of cholesterol 7[Alpha]-hydroxylase when pectin or psyllium rather than cellulose was fed may explain the almost twofold higher bile acid pool sizes previously reported in response to feeding either of these fibers. These data support the hypothesis that the hypocholesterolemic effect of soluble fibers is modulated through increased synthesis and therefore pool size of bile acids. INDEXING KEY WORDS: cholesterol-7[alpha]-hydroxylase; rats; dietary fiber; cholesterol

The purification of the cholate-inducible NADH-dependent flavin oxidoreductase from Eubacterium sp. strain VPI 12708, and the cloning, sequencing and characterization of its associated gene (baiH) were reported. The baiH gene was located on a previously described cholate-inducible operon. It was homologous to that of NADH oxidase from Thermoanaerobium brockii, trimethylamine dehydrogenase from methylotrophic bacterium W3A1 and Old Yellow Enzyme from Saccharomyces carlsbergensis. Potential ligands for an iron-sulfur cluster, a putative dinucleotide-binding domain and two other well-conserved domains of unknown function were found.

Bile acids promote synthesis and secretion of thermostable direct hemolysin (TDH) in Vibrio parahaemolyticus. TDH secretion in V. parahaemolyticus, cultured in the presence of bile components taurocholic acid (TC) and glycocholic acid (GC), increases significantly. TDH in the lysates of cells grown in the presence of TC and GC is also significantly higher than the control, indicating that the bile acids enhance the synthesis of TDH within the bacterial cells. Thus, conjugated bile acids play a significant role in the pathogenicity of V. parahaemolyticus in the human intestine.

Research has been conducted on nuclear bile acid receptor. The authors have tested the hypotheses that this receptor is important for the gene encoding cholesterol 7(alpha)-hydroxylase which is the first step in the bile acid biosynthesis, and they report the results.

Glucomannan, a viscous polysaccharide, and chitosan, a derivative of chitin, have both been demonstrated to lower cholesterol in animals. However, the mechanism of cholesterol lowering has not been established for either material. This study was conducted to determine the effect of glucomannan (G), chitosan (CH), or an equal mixture of the two (G + CH) on cholesterol absorption and fat and bile acid excretion. Rats were fed a modified AIN-93G diet for 18 d containing 0.125 g/100 g cholesterol and initially 10 g/100 g of the test materials or cellulose (C) as the control. However, the concentration of test materials and cellulose was reduced to 7.5 g/100 g after 1 wk due to lower weight gain compared with controls. Total liver cholesterol was significantly reduced in G, CH and G + CH groups compared with the C group. The intestinal contents supernatant viscosity of the C and the CH groups was negligible, whereas both G and G + CH produced high viscosities. Cholesterol absorption, measured by the fecal isotope ratio method, was significantly reduced from 37.5% in the C group to 20.2% in G, 18.2% in G + CH and 9.4% in CH. Daily fecal fat excretion did not differ between the C and G groups, but was significantly greater in G + CH and CH compared with the C and G groups. Daily fecal bile acid excretion was significantly greater in the CH and G + CH groups compared with the C and G groups. These results suggest that G lowered liver cholesterol by a viscosity-mediated interference of cholesterol absorption. In contrast, CH appears to lower cholesterol through a different mechanism. J. Nutr. 130: 2753-2759, 2000. KEY WORDS: * glucomannan * chitosan * cholesterol * bile acids * fecal fat * rats

Bile acids regulate the transcription of genes that control cholesterol homeostasis through molecular mechanisms that are poorly understood. Physiological concentrations of free and conjugated chenodeoxycholic acid, lithocholic acid, and deoxycholic acid activated the farnesoid X receptor (FXR; NR1H4), an orphan nuclear receptor. As ligands, these bile acids and their conjugates modulated interaction of FXR with a peptide derived from steroid receptor coactivator 1. These results provide evidence for a nuclear bile acid signaling pathway that may regulate cholesterol homeostasis., Cholesterol homeostasis is achieved through the coordinate regulation of dietary cholesterol uptake, endogenous biosynthesis, and the disposal of cholesterol in the form of bile acids. Bile acids are not simply [...]

Bile acids are essential for the solubilization and transport of dietary lipids and are the major products of cholesterol catabolism. Results presented here show that bile acids are physiological ligands for the farnesoid X receptor (FXR), an orphan nuclear receptor. When bound to bile acids, FXR repressed transcription of the gene encoding cholesterol 7 [Alpha]-hydroxylase, which is the rate-limiting enzyme in bite acid synthesis, and activated the gene encoding intestinal bile acid-binding protein, which is a candidate bile acid transporter. These results demonstrate a mechanism by which bile acids transcriptionally regulate their biosynthesis and enterohepatic transport., The enzymatic conversion of cholesterol to bile acids is regulated through feed-forward activation by oxysterols and feedback repression by bile acids (1, 2). Because the feed-forward pathway is mediated by [...]