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Introduction: Enterohepatic circulation (EHC) of conjugated bile acids is an important physiological process crucial for bile acids to function as detergents and signal carriers. Perturbation of the EHC by disease or drugs may lead to serious and life-threatening liver and gastrointestinal disorders. In this proof-of-concept study in pigs, we investigate the potential of N-(4-[ 18 F]fluorobenzyl)cholylglycine ([ 18 F]FBCGly) as tracer for quantitative positron emission tomography (PET) of the EHC of conjugated bile acids., Methods: The biodistribution of [ 18 F]FBCGly was investigated by PET/CT in domestic pigs following intravenous and intraileal administration of the tracer. Hepatic kinetics were estimated from PET and blood data using a 2-tissue compartmental model and dual-input of [ 18 F]FBCGly. The ileal uptake of [ 18 F]FBCGly was investigated with co-injection of nifedipine and endogenous cholyltaurine. Dosimetry was estimated from the PET data using the Olinda 2.0 software. Blood, bile and urine samples were analyzed for possible fluorine-18 labelled metabolites of [ 18 F]FBCGly., Results: [ 18 F]FBCGly was rapidly taken up by the liver and excreted into bile, and underwent EHC without being metabolized. Both nifedipine and endogenous cholyltaurine inhibited the ileal uptake of [ 18 F]FBCGly. The flow-dependent hepatic uptake clearance was estimated to median 1.2 mL blood/min/mL liver tissue. The mean residence time of [ 18 F]FBCGly in hepatocytes was 4.0 ± 1.1 min. Critical organs for [ 18 F]FBCGly were the gallbladder wall (0.94 mGy/MBq) and the small intestine (0.50 mGy/MBq). The effective dose for [ 18 F]FBCGly was 36 μSv/MBq., Conclusion: We have shown that [ 18 F]FBCGly undergoes EHC in pigs without being metabolized and that its ileal uptake is inhibited by nifedipine and endogenous bile acids. Combined with our previous findings in rats, we believe that [ 18 F]FBCGly has potential as PET tracer for assessment of EHC of conjugated bile acids under physiological conditions as well as conditions with perturbed hepatic and ileal bile acid transport., Competing Interests: Conflicts of interest The authors declare that they have no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Type 2 Diabetes (T2D) is expected to be the seventh most significant cause of death worldwide by 2030. Although research into its mechanism has received the attention it deserves, our understanding of T2D is still limited. This case-control study employs untargeted metabolomics to explore novel T2D plasma biomarkers in the Emirati population. Ninety-two UAE nationals were included in the cohort, with fifty T2D and forty-two non-T2D profiles. Participants were then stratified into three groups based on metabolic profiles, clinically verified diabetic status, and current HbA1c values: namely controlled diabetics, uncontrolled diabetics and prediabetics, and non-diabetics. The study identified fifteen significant differentially abundant metabolites between the uncontrolled diabetics group and the prediabetics or controlled diabetics group. Interestingly, some metabolites essential for the corticosteroid and thyroid signaling pathways were found to be significantly elevated in poorly controlled T2D, including cortisol, glycocholic acid, bile acids, thyroxine, and the tryptophan metabolite, 5-hydroxyindoleacetic acid. These findings align with those from prior western cohorts and suggest an intriguing linkage between T2D glycemic control and thyroid and adrenal signaling that may provide new diagnostic and prognostic indicators. RESEARCH SIGNIFICANCE: This study investigates the underlooked metabolomic role and correlation with T2D in the UAE population. The report indicates fifteen significant differentially abundant metabolites between on diabetics, uncontrolled diabetics and or controlled diabetics or prediabetics. This panel of metabolites such as thyroxine and corticosteroids should be considered further as potential diagnostic or prognostic biomarkers for T2D in the region., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to declare., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Introduction: The aim of this study was to evaluate porcine palatal mucosa dissolution by sodium hypochlorite (NaOCl) with or without an auxiliary dissolving agent containing glycocholic acid and a mixture of surfactants (Keratobacter [KB]; Saint Joseph DID, Valencia, Spain)., Methods: One hundred forty samples were obtained from porcine palatal mucosa and weighed using a high-precision balance. The samples were randomly divided into 4 experimental groups (n = 35) based on the test solution used: distilled water (the negative control), CanalPro NaOCl 6% (Coltene Whaledent, Altstätten, Switzerland), KB, and a 9:1 vol/vol mixture of NaOCl with KB (NaOCl + KB). After 5, 10, 15, and 20 minutes of immersion in the solutions at 27°C ± 1°C, the samples were weighted by a blinded assessor. The intergroup weight at the different time points was statistically analyzed using the analysis of variance test with the Bonferroni posttest., Results: All test groups presented with tissue dissolution although complete dissolution did not occur in any sample. The largest percent in weight reduction occurred between time points (t) = 0 minutes and t = 5 minutes for the NaOCl + KB group (22.5%) followed by KB (18.5%) for the same time period. NaOCl presented with similar tissue dissolution activity during the different time points, ranging from 7.8% (t = 10 minutes-t = 15 minutes) to 6.8% (t = 15 minutes-t = 20 minutes). Significant weight differences were found among the different experimental groups after 5, 10, and 15 minutes of incubation, with the only exception being KB versus NaOCl + KB. No significant differences were found when comparing the test groups at t = 20 minutes., Conclusions: The addition of KB to NaOCl increased porcine palatal mucosa dissolution in vitro., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

A rapid, accurate and sensitive stable isotope dilution ultra performance liquidchromatography electrospray ionization tandem mass spectrometry (ID-UPLC-ESI-MS/MS) method for the determination of glycocholic acid (GCA) in human serum was developed and validated. Serum samples were spiked with D 5 -glycocholic acid and then pretreated with protein precipitation. The analysis was performed on a Waters BEH C18 column (100 mm×2.1mm, 1.7μm), followed by ESI-MS/MS detection in negative ion mode under multiple reaction monitoring mode. The calibration curves covered a concentration range from 0.2 to 400ng/mL. The limit of detection and limit of quantification was 0.01ng/mL and 0.05ng/mL, respectively. The method showed satisfactory precision on intra-day (2.3-6.1%) and inter-day (2.4-4.6%) analyses and achieved good recovery at three spiked levels (103.7-114.3%). Moreover, this established method was successfully applied for quantification of GCA in serum samples from healthy volunteers, patients with hepatocellular carcinoma (HCC) and patients with other cancers. We demonstrated that the level of GCA in patients with HCC was significantly higher not only than that in healthy controls, but also than that in patients with other cancer, whereas no significant difference of GCA level was observed between healthy control group and other cancers group., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Bile salts play crucial roles in allowing the gastrointestinal system to digest, transport and metabolize nutrients. They function as nutrient signaling hormones by activating specific nuclear receptors (FXR, PXR, Vitamin D) and G-protein coupled receptors [TGR5, sphingosine-1 phosphate receptor 2 (S1PR2), muscarinic receptors]. Bile acids and insulin appear to collaborate in regulating the metabolism of nutrients in the liver. They both activate the AKT and ERK1/2 signaling pathways. Bile acid induction of the FXR-α target gene, small heterodimer partner (SHP), is highly dependent on the activation PKCζ, a branch of the insulin signaling pathway. SHP is an important regulator of glucose and lipid metabolism in the liver. One might hypothesize that chronic low grade inflammation which is associated with insulin resistance, may inhibit bile acid signaling and disrupt lipid metabolism. The disruption of these signaling pathways may increase the risk of fatty liver and non-alcoholic fatty liver disease (NAFLD). Finally, conjugated bile acids appear to promote cholangiocarcinoma growth via the activation of S1PR2., (Copyright © 2014. Published by Elsevier Inc.)

This study has been aimed at improving some steps in the gas-liquid chromatographic determination of sulfated bile acids. The best conditions for the enzymatic hydrolysis with cholylglycine hydrolase of sulfolithocholylglycine and sulfolithocholyltaurine are described. Recoveries of more than 85% were obtained after prolonging the incubation to 12 h. A single-step procedure for solvolysis and methylation of bile acids was achieved by using, as a water scavenger, 2,2-dimethoxypropane added directly to the hydrolysis mixture. This procedure avoided the difficulty of the extraction of sulfated bile acids from aqueous solutions.

The adsorption of bile salts to fiber has been measured using fiber prepared from different varieties of carrot at different developmental ages. We investigated the carrot varieties Altrinchan and Chantenay and used the bile salts deoxycholate and glycocholate. The method used to measure adsorption distinguished between true adsorption and apparent adsorption due to bile salts trapped within the interstices of the fiber matrix. Adsorption ability was influenced by the developmental age of the carrot but not by variety. Adsorption ability was at a maximum when the carrot fresh weight was at a maximum. The adsorption ability measured was true adsorption and was not dependent on the water holding capacity of the fiber. Deoxycholate was better adsorbed than glycocholate and the results suggest that the developmental age of a fiber source could be important when formulating diets designed to influence bile salt metabolism.

The binding of conjugated bile salts to pancreatic colipase and lipase has been studied by equilibrium dialysis and gel filtration. The results indicate that at physiological ionic strength and pH, conjugated bile salts bind as micelles to colipase: 12-15 moles/mole of colipase for the dihydroxy conjugates and 2-4 for the trihydroxy conjugates. No binding of bile salt takes place from monomeric solutions. Under the same experimental conditions, only 1-2 moles of conjugated dihydroxy bile salts bind to pancreatic lipase.

Breath-hydrogen production after oral glucose administration was examined in patients suspected of having small-intestinal colonisation and compared with the 14C-glycine-cholate breath test (14C-G.C.) and with bacteriological examination of the small intestine. Of 17 patients, 12 had bacteriological evidence of small-intestinal colonisation. Each breath test showed 8 of the 12 patients to be colonised, but only 5 patients gave positive results with both tests. Nevertheless, using both tests only 1 patients out of 12 with small-intestinal colonisation would have been missed. There were no false-positive results in the 5 bacteriologically normal patients when the breath-hydrogen test was used. It is concluded that simultaneous use of these two relatively simple breath tests may improve the indirect diagnosis of small-intestinal colonisation.

Dietary vegetable fibers have physico-chemical properties which may influence their role in nutrition. A method is described which measures bile acid adsorption to fibers of differing water holding capacity. Such absorption studies are complicated by the water held in the fiber matrix which includes bile acid in solution. The entrapped solution gives some apparent adsorption but this can be removed by washing the fibers with water. This method differentiates between strong adsorption and reversible adsorption. This enables dietary vegetable fibers to be classified according to their bile acid absorption capacity which may be useful in selecting fibers for clinical trials.

Studies were made of a) the relationship of bile acid structure and analytical recoveries (measured by 3-hydroxysteroid oxidoreductase) following vigorous alkaline hydrolysis of bile acid conjugates and b) the relationship of structure and hydrolysis time of taurine- and glycine bile acid conjugates in a reaction catalyzed by glycocholic acid hydrolase. Alkaline hydrolysis resulted in good recoveries of hydroxy and 7 and 12- oxo-bile acids but poor recoveries of 3-oxo-bile acids. Borohydride reduction of the 3-oxo-acids prevented these losses. Complete enzymatic hydrolysis of glycine conjugated bile acids was about five times more rapid than that of taurine conjugates. Hydrolysis of conjugates containing oxo groups was slow. Borohydride reduction of oxo-acids corrected this and did not inhibit enzymatic hydrolysis. It was concluded that both vigorous alkaline and enzymatic hydrolysis are satisfactory in bile acid assays if borohydride reduction is instituted before the hydrolytic step. However, due to the presence of possible enzyme inhibitors and solubility difficulties, strong alkaline hydrolysis is preferable to enzymatic hydrolysis in fecal bile acid determinations at this time.

The binding in vitro of the sodium salts of cholic acid, chenodeoxycholic acid, deoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, taurodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, and glycodeoxycholic acid by alfalfa, bran, cellulose, lignin, and cholestyramine was measured. Cholestyramine bound an average of 81.3% of all the bile acids and salts tested whereas cellulose bound only negligible amounts (1.4%). Of the other substances tested, lignin bound 29.2%, alfalfa, 15.9% and bran, 9.0%. No distinct pattern of binding was discerned. It is therefore apparent that the validity of statements concerning the effect of fiber on bile salf metabolism rests upon the specificity of the composition of the fiber involved and the bile acids or salts tested.

The pattern of association of the trihydroxy bile salts in aqueous electrolyte solutions was investigated utilizing the light-scattering technique. The turbidity of the bile salts sodium cholate, sodium taurocholate, and sodium glycocholate was determined over the concentration range of 0-25 mg/ml at 25 degrees. For sodium cholate, the concentration of the supporting electrolyte was varied from 0.15 to 0.5 M. For all bile salts in 0.15 M electrolyte, the turbidity was determined in sodium fluoride, sodium chloride, sodium bromide, and sodium iodide. Comparison of the light-scattering data with amonomer-micellar model showed that qualitative agreement was obtained; however, quantitative agreement could not be achieved. Further examination of the data showed that the light-scattering results were in good agreement with a model that includes dimers, trimers, and a higher aggregate containing approximately eight monomeric units.

Investigations into the choice of immunogen, ligand, antiserum and assay conditions for the radioimmunoassay of conjugated cholic acid have been performed with a view to producing optimal assay conditions. Cholic acid-BSA was found to be the best immunogen to produce antibodies to conjugated cholic acid and the response was of an IgG type. Incorporating a spacer (hexanoic acid) between hapten and carrier protein resulted in a decrease in antiserum titre. Optimal conditions for the assay were found using [125I]histamine-glycocholic acid as ligand with a dilution of antiserum to produce 60% binding of ligand and a pH of 7.4. Using these assay conditions no serum effects were found; extraction of serum prior to assay was therefore unnecessary. The assay was sensitive enough to detect post-prandial increased in serum bile acid concentrations following a liquid test meal; no increase was observed throughout the same time period in a fasting control.

A longitudinal study in 60 women was undertaken to observe the changes, if any, in serum bile acids after taking oral combination pills containing either 50 or 30 microgram of ethinyl estradiol. The women were followed up to 12 months. Serum bile acids (cholyglycine conjugates) were estimated by radioimmunoassay. The combination contraceptives had no appreciable effect on serum bile acids.

The effect of cholesterol on the fluidity of the phospholipid matrix in mixed micelles derived from bile salts and lecithin has been determined by the paramagnetic probe technique. It was found that correlation times for the cholestane spin label were discontinuous functions of cholesterol content and that these discontinuities correlate with the equilibrium solubility limit for cholesterol in this quaternary system. The origin of these discontinuities is attributed to the existence of another aggregate in addition to the discshaped mixed micelle in lipid solutions supersaturated with cholesterol.

Bile salt hydrolase (cholylglycine hydrolase, EC 3.5.1.24) has been purified to homogeneity (792-fold) from Clostridium perfringens using high performance DEAE-chromatography. The purified enzyme showed a single detectable protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a relative molecular weight ca. 56,000. The intact enzyme had a relative molecular weight (Mr) of ca. 250,000 as determined by nondenaturing PAGE. The NH2-terminal sequence of bile salt hydrolase was determined to be Met-(Ser/Cys)-Arg-Thr-Lys-Leu-Val-Ileu-Thr-Ileu-Gly-Ala-Ser. The purified enzyme was active towards both glycine and taurine conjugates of cholate. The apparent Km and Vmax of the enzyme for glycocholate was estimated to be 0.5 mM and 107 nmol/min.mg protein, respectively. The pH optimum was in the range of 5.8 to 6.4. The enzyme was inhibited 85%, 81%, and 83% by 2 mM iodoacetate, p-chloromercuribenzoate, and phenylmethanesulfonylfluoride, respectively. Rabbit polyclonal antibody was prepared and used to demonstrate a single form of the enzyme in crude cell extracts.