Formation of delta 22-bile acids in rats is not gender specific and occurs in the peroxisome

Supplementation of Bile Acids and Lipase in Broiler Diets for Better Nutrient Utilization and Performance: Potential Effects and Future Implications – A Review

Bile acids are used for better emulsification, digestion and absorption of dietary fat in chicken, especially in early life. Similarly, exogenous lipases have also been used for the improvement of physiological limitation of the chicken digestive system. Owing to potential of both bile acids and lipases, their use has been increased in recent years, for better emulsification of dietary fat and improvement of growth performance in broilers. In the past, pancreatic lipases were used for supplementation, but recently, microbial lipase is getting attention in poultry industry as a hydrolysis catalyst. Bile acids strengthen the defence mechanism of body against bacterial endotoxins and also play a key role in lipid regulation and sugar metabolism as signaling molecules. It has been demonstrated that bile acids and lipases may improve feed efficiency by enhancing digestive enzyme activity and ultimately leading to better fat digestion and absorption. Wide supplemental range of bile acids (0.004% to 0.25%) and lipases (0.01% to 0.1%) has been used in broiler diets for improvement of fat digestibility and their performance. Combinations of different bile acids have shown more potential to improve feed efficiency (by 7.14%) even at low (0.008%) levels as compared to any individual bile acid. Lipases at a lower level of 0.03% have exhibited more promising potential to improve fat digestibility and feed efficiency. However, contradicting results have been published in literature, which needs further investigations to elucidate various nutritional aspects of bile acids and lipase supplementation in broiler diet. This review focuses on providing insight on the mechanism of action and potential application of bile acids and lipases in broiler diets. Moreover, future implications of these additives in poultry nutrition for enhancing nutrient utilization and absorption are also discussed.

Key discoveries in bile acid chemistry and biology and their clinical applications: history of the last eight decades

During the last 80 years there have been extraordinary advances in our knowledge of the chemistry and biology of bile acids. We present here a brief history of the major achievements as we perceive them. Bernal, a physicist, determined the X-ray structure of cholesterol crystals, and his data together with the vast chemical studies of Wieland and Windaus enabled the correct structure of the steroid nucleus to be deduced. Today, C24 and C27 bile acids together with C27 bile alcohols constitute most of the bile acid "family". Patterns of bile acid hydroxylation and conjugation are summarized. Bile acid measurement encompasses the techniques of GC, HPLC, and MS, as well as enzymatic, bioluminescent, and competitive binding methods. The enterohepatic circulation of bile acids results from vectorial transport of bile acids by the ileal enterocyte and hepatocyte; the key transporters have been cloned. Bile acids are amphipathic, self-associate in solution, and form mixed micelles with polar lipids, phosphatidylcholine in bile, and fatty acids in intestinal content during triglyceride digestion. The rise and decline of dissolution of cholesterol gallstones by the ingestion of 3,7-dihydroxy bile acids is chronicled. Scientists from throughout the world have contributed to these achievements.

A description of large-scale metabolomics studies: increasing value by combining metabolomics with genome-wide SNP genotyping and transcriptional profiling

The metabolome, defined as the reflection of metabolic dynamics derived from parameters measured primarily in easily accessible body fluids such as serum, plasma, and urine, can be considered as the omics data pool that is closest to the phenotype because it integrates genetic influences as well as nongenetic factors. Metabolic traits can be related to genetic polymorphisms in genome-wide association studies, enabling the identification of underlying genetic factors, as well as to specific phenotypes, resulting in the identification of metabolome signatures primarily caused by nongenetic factors. Similarly, correlation of metabolome data with transcriptional or/and proteome profiles of blood cells also produces valuable data, by revealing associations between metabolic changes and mRNA and protein levels. In the last years, the progress in correlating genetic variation and metabolome profiles was most impressive. This review will therefore try to summarize the most important of these studies and give an outlook on future developments.

Discovery of sexual dimorphisms in metabolic and genetic biomarkers

Metabolomic profiling and the integration of whole-genome genetic association data has proven to be a powerful tool to comprehensively explore gene regulatory networks and to investigate the effects of genetic variation at the molecular level. Serum metabolite concentrations allow a direct readout of biological processes, and association of specific metabolomic signatures with complex diseases such as Alzheimer's disease and cardiovascular and metabolic disorders has been shown. There are well-known correlations between sex and the incidence, prevalence, age of onset, symptoms, and severity of a disease, as well as the reaction to drugs. However, most of the studies published so far did not consider the role of sexual dimorphism and did not analyse their data stratified by gender. This study investigated sex-specific differences of serum metabolite concentrations and their underlying genetic determination. For discovery and replication we used more than 3,300 independent individuals from KORA F3 and F4 with metabolite measurements of 131 metabolites, including amino acids, phosphatidylcholines, sphingomyelins, acylcarnitines, and C6-sugars. A linear regression approach revealed significant concentration differences between males and females for 102 out of 131 metabolites (p-values<3.8×10(-4); Bonferroni-corrected threshold). Sex-specific genome-wide association studies (GWAS) showed genome-wide significant differences in beta-estimates for SNPs in the CPS1 locus (carbamoyl-phosphate synthase 1, significance level: p<3.8×10(-10); Bonferroni-corrected threshold) for glycine. We showed that the metabolite profiles of males and females are significantly different and, furthermore, that specific genetic variants in metabolism-related genes depict sexual dimorphism. Our study provides new important insights into sex-specific differences of cell regulatory processes and underscores that studies should consider sex-specific effects in design and interpretation.

Bile salts of vertebrates: structural variation and possible evolutionary significance

Biliary bile salt composition of 677 vertebrate species (103 fish, 130 reptiles, 271 birds, 173 mammals) was determined. Bile salts were of three types: C(27) bile alcohols, C(27) bile acids, or C(24) bile acids, with default hydroxylation at C-3 and C-7. C(27) bile alcohols dominated in early evolving fish and amphibians; C(27) bile acids, in reptiles and early evolving birds. C(24) bile acids were present in all vertebrate classes, often with C(27) alcohols or with C(27) acids, indicating two evolutionary pathways from C(27) bile alcohols to C(24) bile acids: a) a 'direct' pathway and b) an 'indirect' pathway with C(27) bile acids as intermediates. Hydroxylation at C-12 occurred in all orders and at C-16 in snakes and birds. Minor hydroxylation sites were C-1, C-2, C-5, C-6, and C-15. Side chain hydroxylation in C(27) bile salts occurred at C-22, C-24, C-25, and C-26, and in C(24) bile acids, at C-23 (snakes, birds, and pinnipeds). Unexpected was the presence of C(27) bile alcohols in four early evolving mammals. Bile salt composition showed significant variation between orders but not between families, genera, or species. Bile salt composition is a biochemical trait providing clues to evolutionary relationships, complementing anatomical and genetic analyses.

Conjugation with taurine prevents side-chain desaturation of ursodeoxycholic and beta-muricholic acids in bile fistula rats

The metabolism of intravenously infused bile salts, tauroursodeoxycholate, tauro-beta-muricholate and their corresponding unconjugated forms in the liver was investigated in bile salt-depleted bile fistula rats. The biliary bile salt composition was determined by gas chromatography-mass spectrometry using chemical positive ionization and electron-impact methods. For an infusion rate of 2 micromol/min/kg, all bile salts were efficiently secreted in bile, inducing similar choleresis. Only tauroconjugated bile salts were recovered; no glucuronide or glyco derivatives were detected. The infusion of free ursodeoxycholate led to the appearance of a metabolite identified as a Delta22 derivative (12%). A similar biotransformation rate (11%) was observed following free beta-muricholate infusion. In contrast, no metabolite was observed after infusion of the tauroconjugated form of ursodeoxycholate and beta-muricholate. The unsaturation process probably depends on the availability of the carboxyl group for the starting step of the beta-oxidation mechanism. In conclusion, the current in vivo study demonstrates a hepatic origin for Delta22 bile salts. It also shows that free bile salts were sensitive to Delta22 formation while conjugation with taurine totally prevented the side-chain oxidation of the two 7beta-hydroxylated bile salts.

Chemical synthesis of (22E)-3 alpha,6 beta,7 beta-trihydroxy-5 beta-chol-22-en-24-oic acid and its taurine and glycine conjugates: a major bile acid in the rat

A method for the synthesis of Delta(22)-beta-muricholic acid (Delta(22)-beta-MCA), (22E)-3 alpha,6 beta,7 beta-trihydroxy-5 beta-chol-22-en-24-oic acid, and its taurine and glycine conjugates (Delta(22)-beta-muricholyltaurine and Delta(22)-beta-muricholylglycine) is described. The key intermediate, 3 alpha,6 beta,7 beta-triformyloxy-23,24-dinor-5 beta-cholan-22-al, was prepared from beta-muricholic acid (beta-MCA) via the 24-nor-22-ene and 24-nor-22,23-diol derivatives. Wittig reaction of the aldehyde with (carbomethoxymethylene) triphenylphosphorane and subsequent hydrolysis gave (unconjugated) Delta(22)-beta-MCA. Condensation reaction of the unconjugated acid with taurine or glycine methyl ester using diethylphosphorocyanide yielded the naturally occurring taurine or glycine conjugate (N-acylamidate) of Delta(22)-beta-MCA. These synthetic reference compounds are now available for investigation of the metabolism of beta-MCA by bacterial and hepatic enzymes in the rat and should also be useful as substrates for reductive deuteration or tritiation to give the 22,23-(2)H or (3)H-beta-MCA.

Catabolites of cholesterol synthesis pathways and forskolin as activators of the farnesoid X-activated nuclear receptor

The nuclear receptors are a family of transcriptional mediators that, upon activation, bind DNA and regulate gene transcription. Among these receptors, the farnesoid X-activated receptor (FXR) has recently been identified as one activated by bile acids and farnesol. To investigate the potential of other sterols to activate FXR, as well as to examine relevant relationships among identified activators of FXR, the current study used a mammalian cell transcription assay to quantify and compare activation potential. In addition to the classical bile acids deoxycholate (DCA) and chenodeoxycholate (CDCA), FXR was shown to be transcriptionally active in the presence of the androgen catabolites 5alpha-androstan-3alpha-ol-17-one (androsterone) and 5beta-androstan-3alpha-ol-17-one (etiocholanolone), as well as the sterol bronchodilatory drug forskolin. Conversely, cholesterol and several other key precursors to the androgens and bile acids were either not active or only slightly active. Furthermore, it was observed that the bile acid ursodeoxycholate (UDCA) could inhibit DCA and CDCA activation of FXR in a manner parallel to its ability to antagonize DCA and CDCA induction of apoptosis. By far, the most efficacious activator of FXR was forskolin. Interestingly, although it is classically viewed as an initiator of the adenylate cyclase/protein kinase A (PKA) pathway, PKA inhibition did not inhibit forskolin's activation of FXR nor was cyclic AMP (cAMP) able to stimulate FXR-mediated transcription. These data would suggest that forskolin acts as a ligand for FXR rather than as a secondary activator of FXR and could have important implications with respect to its potential toxicity and pharmacological use.

Differences in the metabolism and disposition of ursodeoxycholic acid and of its taurine-conjugated species in patients with primary biliary cirrhosis

The clinical effectiveness of ursodeoxycholate in the treatment of liver disease may be limited by its poor absorption and extensive biotransformation. Because in vitro and in vivo studies suggest that the more hydrophilic bile acid tauroursodeoxycholate has greater beneficial effects than ursodeoxycholate, we have compared for the first time the absorption, metabolism, and clinical responses to these bile acids in patients with primary biliary cirrhosis (PBC). Twelve female patients with PBC were sequentially administered tauroursodeoxycholate and ursodeoxycholate (750 mg/d for 2 months) in a randomized, cross-over study. Bile acids were measured in serum, duodenal bile, urine, and feces by gas chromatography-mass spectrometry (GC-MS). Biliary ursodeoxycholate enrichment was higher during tauroursodeoxycholate administration (32.6% vs. 29.2% during ursodeoxycholate; P <.05). Lithocholic acid concentration was consistently higher in all biological fluids during ursodeoxycholate administration. Fecal bile acid excretion was the major route of elimination of both bile acids; ursodeoxycholate accounted for 8% and 23% of the total fecal bile acids during tauroursodeoxycholate and ursodeoxycholate administration, respectively (P <.05). Tauroursodeoxycholate was better absorbed than ursodeoxycholate, and, although it was partially deconjugated and reconjugated with glycine, it underwent reduced biotransformation to more hydrophobic metabolites. This comparative study suggests that tauroursodeoxycholate has significant advantages over ursodeoxycholate that may be of benefit for long-term therapy in PBC.

Metabolic fate and hepatocyte toxicity of reverse amide analogs of conjugated ursodeoxycholate in the rat

Reverse amide analogs of conjugated bile acids were tested for their effects on the viability of cultured primary rat hepatocytes, for their transport and metabolism in the intact rat, and for their susceptibility to hydrolysis by intestinal bacteria. Succinylnorursodeoxycholanylamide (SNUDCN) and its parent C23 amine showed the same general lack of toxicity toward hepatocytes as the normal conjugates of ursodeoxycholic acid, at concentrations up to 500 microM. The 3alpha,7alpha,12alpha-trihydroxy analog and its parent amine were more toxic than the corresponding dihydroxy compounds, although their effects were similar to those observed for the normal conjugates of cholic acid. Following intraduodenal infusion, greater than 80% of administered SNUDCN appeared in the bile of bile fistula rats. Analysis of bile fractions indicated the presence of SNUDCN (81.5 mol% of original amount) and two metabolites, the taurine conjugate of SNUDCN (9.4 mol%) and SNUDCN containing an additional hydroxy group (9.1 mol%). Although SNUDCN underwent an efficient first pass enterohepatic circulation, it displayed a shorter biological half life than taurocholate (T1/2: 8.9 h vs 39.6 h, respectively). The reverse amide analogs were not hydrolyzed by any of a variety of intestinal bacteria known to hydrolyze normal conjugated bile acids. Despite the shorter half-life, the reverse amide analogs may be of potential use in the targeting of therapeutic bile acids to the colon.