The digestive system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Bile salts are produced by the liver from cholesterol and stored in the gallbladder. They are released into the duodenum in response to food intake. Their main action is to emulsify dietary fats so they may easily cross the brush border of the intestine. Conditions such as liver disease or obstruction of the bile ducts can affect the production and release of bile salts, respectively. The resulting malabsorption of fats can lead to steatorrhea. Because the absorption of fat-soluble vitamins such as A, D, K, and E may also be affected; patients may also suffer from the effects of deficiency of one or more of these vitamins. Lack of vitamin A has been associated with the development of night blindness. Because vitamin D is involved in the absorption of calcium from the gut, deficiency of this vitamin can lead to bone demineralization. Vitamin K is important for the synthesis of clotting factors by the liver and deficiency of this vitamin impair clotting function.
Functions of the Liver
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The liver produces about 1 L of bile per day, and this passes into the gall bladder where it is concentrated to about one-fifth of its volume. Bile consists of electrolytes, protein, bilirubin, bile salts and lipids. Bile acids (cholic acid and chenodeoxycholic acid) are produced in the liver from cholesterol. In the gut, bacterial action on cholic and chenodeoxycholic acids produces secondary bile acids such as deoxycholic acid and lithocholic acid. The bile acids conjugate with glycine or taurine to form bile salts (Figure 37.5). Bile salts are more water soluble and less lipid soluble, which limits the passive absorption in the small intestine so that the bile salts remain within the gut. The main function of bile salts is the emulsification of dietary fat, which is essential for fat absorption. In addition, bile salts are also important for the absorption of fat-soluble vitamins, especially vitamins A, D, E and K. At the terminal ileum, bile salts are reabsorbed by the apical sodium-dependent bile transporter. The reabsorbed bile salts are carried to the liver in the portal circulation, mostly bound to plasma proteins. The recirculation of bile salts is referred to as enterohepatic circulation.
Liver physiology
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
The liver produces about 1 L of bile per day, and this passes into the gall bladder where it is concentrated to about one-fifth of its volume. Bile consists of electrolytes, protein, bilirubin, bile salts and lipids. Bile acids (cholic acid and chenodeoxycholic acid) are produced in the liver from cholesterol. In the gut, bacterial action on cholic and chenodeoxycholic acids produces secondary bile acids such as deoxycholic acid and lithocholic acid. The bile acids conjugate with glycine or taurine to form bile salts (Figure 6.5). Bile salts are more water soluble and less lipid soluble, which limits the passive absorption in the small intestine so that the bile salts remain within the gut. The main function of bile salts is the emulsification of dietary fat, which is essential for fat absorption. In addition, bile salts are also important for the absorption of fat-soluble vitamins, especially vitamins A, D, E and K. At the terminal ileum, bile salts are reabsorbed by the apical sodium-dependent bile transporter. The reabsorbed bile salts are carried to the liver in the portal circulation, mostly bound to plasma proteins. The recirculation of bile salts is referred to as enterohepatic circulation.
Virulence gene repression promotes Listeria monocytogenes systemic infection
Published in Gut Microbes, 2020
Rita Pombinho, Ana Vieira, Ana Camejo, Cristel Archambaud, Pascale Cossart, Sandra Sousa, Didier Cabanes
Bile salts are amphipathic molecules synthesized from cholesterol in the liver and secreted into the small intestine from the gall bladder.5 They are major bile components able to degrade lipid-containing membranes and represent a key challenge to bacterial survival in the gastrointestinal tract.6 Bacterial tolerance to bile salts is closely related to the activity of bile salt hydrolases (BSH) that catalyze the hydrolysis of glycodeoxycholate- (GDCA) and taurodeoxycholate- (TDCA) conjugated bile salts, thereby impairing bile toxicity toward bacteria. BSH is required for Lm resistance to bile and virulence.7 Deconjugation of bile acids by BSH induces the release of free cholic acids (CA), that are exported by Lm through the MdrT efflux pump. mdrT is controlled by BrtA, a bile sensor which loses the ability to repress mdrT in the presence of CA.8
The characterisation, pharmacokinetic and tissue distribution studies of TPGS modified myricetrin mixed micelles in rats
Published in Journal of Microencapsulation, 2019
Chunmei Wei, Qilong Wang, Wen Weng, Qiuyu Wei, Yujiao Xie, Michael Adu-Frimpong, Elmurat Toreniyazov, Hao Ji, Ximing Xu, Jiangnan Yu
Based on the status of myricetrin as generally recognised safe (GRAS) compound as indicated by the US Flavour and Extract Manufacturer Association (FEMA) and other regulatory bodies, we tested the myricetrin-loaded formulations in experimental animals (Maronpot et al.2015). Besides, bile salts are produced via the metabolism of cholesterol in the liver and stored in the gallbladder secreted by the liver, which can form stable mixed micelles with phospholipids, glycerol and fatty acids (Dong et al.2013). Phospholipids, as an important component of cell membranes, can maintain membrane fluidity (Kumar et al.2016). Vitamin E TPGS is a water-soluble derivative of natural vitamin E synthesised by esterification of D-α-tocopheryl acid succinate with polyethylene glycol 1000 (Jin et al.2013), which represent a well-known class of biocompatible and non-cytotoxic biomolecules (Song et al.2016). Polyvinylpyrrolidone (PVP) is a kind of water-soluble non-ionic polymer, which has a long history in the pharmaceutical field as a drug delivery system for insoluble drugs (Zhu et al.2010). The plasma concentration-time distribution curves of the free myricetrin, MLM and MLTM were depicted in Figure 5, while the various pharmacokinetics parameters determined in this report are depicted in Table 3.
Bile salt metabolism is not the only factor contributing to Clostridioides (Clostridium) difficile disease severity in the murine model of disease
Published in Gut Microbes, 2020
Caitlin A. Jukes, Umer Zeeshan Ijaz, Anthony Buckley, Janice Spencer, June Irvine, Denise Candlish, Jia V. Li, Julian R. Marchesi, Gillian Douce
In the context of C. difficile germination, one role performed by bacterial members of the gut microbiome is to modify bile acids (BAs). Primary bile salts produced in the liver are released in the small bowel and assist in the uptake of lipids and lipid-soluble vitamins from the diet. The breakdown of BAs is complex and involves several enzymes16 expressed by gut bacteria, the two most important in the context of C. difficile, being bile salt hydrolases (BSH) and the 7α-dehydroxylation (7αDH) enzymes.17,18 Modification is relevant as primary bile acid (pBA) taurocholic acid (TCA) induce spore germination whereas modified secondary bile acid (sBA), deoxycholic acid (DCA), are poor germinates and inhibit vegetative cell outgrowth.19–21 BSH are expressed by several members of the microbiota and are important for the removal of the amino acid sidechains, which allow other enzymes including the 7α-dehydroxylases to function (Supplementary Figure 1). This secondary process is more specialized and restricted to a few species including Clostridium scindens, Clostridium hylemonae, Clostridium sordellii, Clostridium hiranonis and various unclassified Eubacteria.22,23
Related Knowledge Centers
- Acid
- Cholic Acid
- Glycine
- Steroid
- Taurine
- Liver
- Bile
- Large Intestine
- Taurocholic Acid
- Glycocholic Acid