What Are Bile Acids
In other areas of this website we discuss bile acid involvement in toxin removal. Here we exam what bile acids are, how they are made and some of their known functions.
How Bile Acids Are Formed
Bile acids are formed in the liver from cholesterol and represent the most abundant constituents in human bile. They are turned into bile salts by conjugating (combining) the bile acids most commonly with either the amino acid taurine or glycine (most commonly glycine). Conjugation makes them more water soluble and limits their passive reabsorption or precipitation as they pass down the bilary tree and into the intestines. They are released directly from the liver into the intestines during meals that contain fat, but are largely stored in the gall bladder and released into the intestines during a fatty meal to emusify fat and make it more absorbable by the body. (This is very similar to how we use soap to emulsify fat when washing dishes which helps us remove it from the dishes and wash it down the drain. ) It is the ability of the gall bladder to be able to concentrate and store the bile salts that allows the bile acids to be in high enough concentration to be able to thoroughly act on a fatty meal and allow absorption of the fats. This is why your gall bladder is important and should not be removed unless absolutely necessary as a last ditch effort. The bile salts are actively absorbed by the body through the intestines to be resused again. This release of bile from the liver and the circulation through the intestines to be picked back up, returned to the liver and reused again is called enterohepatic circulation.
Technically there are primary and secondary bile acids. Primary bile acids are created from cholesterol in the liver cells while secondary bile acids are thought to be created by gut bacteria by their deconjugating (unhooking) the bile salts from the glycine or taurine (or other amino acid) during normal enterohepatic circulation.
Dysregulation of bile acid can occur due to:
• issues with biosynthesis from cholesterol or due to inefective conjugation with amino acids
• issues with membrane transpot in the liver cell or the cells lining the illeum of the intestine
• issues with transport from the liver to the gall bladder or to the intestine
• issues with bacterial degradation in the intestine effecting enteroheptic cycling
Function of Bile Acids
• Elimination pathway of cholesterol
• When bile acids are high there is feedback to lower bile acid synthesis and when they are low, bile acid synthesis is increased. Since bile acids are made from cholesterol, when they are low, more cholesterol is made and when bile acids are high, less cholesterol is made.
- Make fats soluble and allow fat absorption including fat-soluble vitamins A,D,E and K.
- Bile acids stimulate bile flow and biliary phospholipid (protect bile duct from damage due to bile acids) secretion.
- Bile acids solubilize polyvalent metals such as iron and calcium in the duodenum to increase their absorption.
- Bile acids have antibacterial effects
- BIle acids stimulate mucin secretion.
- Bile acids stimulate colon motility
- Bile acids stimulate the release of motilin which coordinates the interdigestive migrating motility complex.
- Bile acids may inhibit bacterial adhesion to the gut wall and may bind enterotoxin in the intestine.
- Bile acids have a role as signaling molecules that govern glucose, fat and energy metabolism.
- Bile acids may be involved in removal of some toxins - see research below
If there are not enough bile acids, these functions can not take place properly. If there are too many bile acids they can become toxic to cells and cause diarrhea. This can occur inside the cell (where they are made) during cholestasis or outside the cell as takes place in the colon when there is bile malabsorption.
Things to support bile acids and bile flow and decrease cholestasis (reduced flow/blockage of bile)
Phosphatidylcholine makes up 90% of the total bile phospholipid content and inadequate intake of phosphatidylcholine or creation of phosphatidylcholine contributes to impaired biliary excretion of bile and toxins, and contributes to cholesterol crystallization and gallstone formation. Enhancing phosphatidylcholine or choline ingestion has been shown to increase phospholipids and prevent cholestasis and liver damage. Choline is used to make phosphatidylchoine and as an essential nutrient choline is necessary in the diet. However, it has been shown that most adults do not get the minimal daily intake necessary. Choline is found in liver, egg yolks, meat, fish, cruciferous or mustard family vegetables, peanuts and dairy products. Low choline is associated with fatty liver disease.
Bitter herbs have a stimulating effect on the digestive system and specifically stimulate bile flow. Any herb that tastes bitter will do this. Some well known bitter herbs are Gentian root, Dandelion root and leaf, Artichoke leaf and Milk thistle seed. All of these will stimulate bile secretion.
Bile acids are turned into bile salts by amino acid conjugation in the liver. Usually it is taurine or glycine that is added to the bile acid and glycine is used the most. This effects the properties of the bile acids keeping them from precipitating out making them more soluble at acidic levels found in the duodenum.
An oddity I have wondered about
Cholecystokinin is released when fat is ingested. It causes the increased production of bile and this stimulates the contraction of the gall bladder and release of bile into the duodenal part of the small intestine. Cholecystokinin can cause anxiety and panic attacks in people when it is in excess. Cholecystokinin is used in research to create anxiety to test anti-anxiety drugs. I have wondered if when the liver or gallbladder has functional or structural cholestasis if this causes increased cholecystokinin to be made and in turn induces anxiety. Although there are other reasons for anxiety in people with toxin issues, I have to wonder if this could be another reason.
Research On Bile Acids
Xenobiotic conjugation: a novel role for bile acids
Gary B. Quistad,Luana E. Staiger & David A. Schooley
Naturevolume 296, pages462–464 (1982) |
The conjugation of foreign compounds with hydrophilic natural products (for example, amino acids, glucuronic acid) represents an important biochemical mechanism of attenuating xenobiotic toxicity and of facilitating excretion of hydrophobic chemicals. Although several conjugation reactions are known is , bile acids have not been implicated previously in the conjugation of xenobiotics. The physiological importance of natural bile acids is based partly on their propensity to conjugate through their carboxyl groups with several amino acids (especially glycine and taurine), thereby creating effective emulsifying agents to aid the digestion of lipids. However, we now report that in several animal species, bile acids form metabolic conjugates through a hydroxyl group with an acidic metabolite of fluvalinate, a pyrethroid insecticide. Conjugates of this acidic metabolite with cholic, taurochenodeoxycholic and taurocholic acids are major secondary metabolites found in excreta of the cow, chicken and rat, respectively, and represent 5–12% of the faecal 14C-labelled residue.
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