Total Bile Acids: The Value of Fifth Generation Tests
Total Bile Acids: The Value of Fifth Generation Tests
Bile acids are water-soluble, amphipathic end products of cholesterol metabolism and are involved in liver, biliary and intestinal diseases. They are formed in the liver and are absorbed in the small intestine before being excreted. The fundamental role of bile acids is to aid in the digestion and absorption of fats and fat-soluble vitamins in the small intestine.1
Intrahepatic Cholestasis of Pregnancy
Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder. It can be indicated by pruritus, jaundice, elevated total bile acids and/or serum transaminases and usually affects women during the second and third trimester of pregnancy.2,3
Intrahepatic Cholestasis of pregnancy or Obstetric Cholestasis is a condition that restricts the flow of bile through the gallbladder resulting in a build-up of bile acids in the liver.3 Due to the build-up, bile acids leak into the bloodstream where they are detected at concerning levels. It is an extremely serious complication of pregnancy that can lead to the increased risk of premature birth or even stillbirth, as such it is vital that women with the disease are monitored carefully.
In healthy pregnancies, there is very little increase in total bile acid levels although a slight increase is likely to be seen in the third trimester. Measurement of total bile acids in serum is thought to be the most suitable method of diagnosing and monitoring ICP.6
According to several reports total bile acid levels in ICP can reach as high as 100 times the upper limit of a normal pregnancy. It has been reported that a doubling in maternal serum bile acids, results in a 200% increased risk of stillbirth with total bile acids thought to trigger the onset of preterm labour. Additionally, bile acids can affect the foetal cardiovascular system as it has been found that there are often cardiac rhythm disturbances in the foetus due to the elevated bile acids in circulation.5
Although it is a rare condition, with only 0.3-0.5% of women likely to develop ICP, it can have extreme risks and so it is important to properly diagnose and monitor the condition.6 ICP increases the risk of meconium staining of the amniotic fluid and is reported to be a sign of foetal distress. This complication is found in 16-58% of all ICP cases, worryingly 100% of cases have resulted in foetal death. The frequency of this condition is found to be greater in pregnancies with higher levels of serum total bile acids.
Risk factors
There are several risk factors associated with ICP such as a family history of ICP, use of oral contraceptives, assisted reproduction techniques and multiple gestation. Genetic influence accounts for approximately 15% of ICP cases. Dietary selenium is a contributing environmental factor as serum selenium levels often decrease throughout pregnancy. Further to this, incidences of ICP rise in the winter months, most likely due to the fact selenium levels are naturally less during these months.7,8
Total Bile Acids
In addition to ICP, bile acid levels are also measured in the diagnosis of other liver disorders. The bile acids test in an extremely sensitive indicator of liver function, capable of detecting changes in hepatic function before clinical symptoms arise, thus providing valuable information that standard liver function tests cannot. As a result of its high sensitivity, bile acids can be used to assess liver function in transplant patients, allowing monitoring of the transplant success and of antirejection therapy. The bile acids test is most beneficial when used in conjunction with standard liver function tests such as ALT and AST which are markers of liver damage rather than liver function.
Measurement of Total Bile Acids
The enzyme cycling method, also known as the Fifth Generation Bile Acids test, is a method that allows for signal amplification through cycled regeneration reactions as can be seen in Figure 1. In the presence of Thio-NAD, the enzyme 3-α hydroxysteroid dehydrogenase (3-α HSD) converts bile acids to 3-keto steroids and Thio-NADH. The reaction is reversible and 3-α HSD can convert 3-keto steroids and Thio-NADH to bile acids and Thio-NAD. In the presence of excess NADH, the enzyme cycling occurs efficiently and the rate of formation of Thio-NADH is determined by measuring specific change of absorbance at 405 nm and is proportional to the amount of total bile acids in the sample. The analysing capability of the fifth generation total bile acids assay is far beyond the performance of conventional bile acid tests.10,11
Figure 1: The assay principle⁹
Inadequacies of Traditional Bile Acids Assays
Determining the cause and extent of liver damage is important in guiding treatment decisions and preventing disease progression. Standard liver function tests include; ALT, AST, ALP, GGT and Bilirubin. The measurement of TBA is most beneficial in conjunction with these standard liver tests and offers unrivalled sensitivity allowing identification of early stage liver dysfunction. There are several commercial methods available for the detection and measurement of TBA in serum. Traditional TBA tests based on the enzymatic method use nitrotetrazolium blue (NBT) to form a formazan dye. The reaction is measured at 546nm and the intensity of the colour is proportional to the concentration of bile acids.
Newer methods such as the enzyme cycling method or fifth generation methods offer many advantages including greater sensitivity, liquid reagents, small sample volumes and reduced instrument contamination from formazan dye. Additionally, the fifth generation assay does not suffer from interference from lipaemic or haemolytic samples. Both lipemia and haemolysis are common in new-borns and pregnant women, so this further supports that the fifth generation test is more sensitive for these sample types.12
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References
[1] The continuing importance of bile acids in liver and intestinal disease. A.f., Hofmann. 1999, Arch Intern Med, pp. 2647-2658.
[2] Diagnostic and Therapeutic Profiles of Serum Bile Acids in Women with Intrahepatic Cholestasis of Pregnancy – A Pseudo-Targeted Metabolomics Study. Cui, Yue. Xu, Biao. Zhang, Xiaoqing. He, Yifan. Shao, Yong. Ding, Min. s.l. : Clinica Chimica, 2018, Vol. 483.
[3] Randox Laboratories. Bile Acids Test for Obstetric Cholestasis – A serious complication of pregnancy. 2012.
[4] British Liver Trust (2019) Facts about Liver Disease, Available at: https://www.britishlivertrust.org.uk/about-us/media-centre/facts-about-liver-disease/ (Accessed: 18th June 2019).
[5] .Geenes, Victoria. Williamson, Catherine. 17, s.l. : World J Gastroenterol, 2009, Vol. 15.
[6] Howland, Genevieve. Cholestasis of Pregnancy: Why You Can’t Ditch the Itch. Mama Natural. [Online] December 22, 2018. [Cited: February 19, 2019.] https://www.mamanatural.com/cholestasis-of-pregnancy/.
[7] Bile Acid Levels and Risk of Adverse Perinatal Outcomes in Intrahepatic Cholestasis of Pregnancy: A Meta-Analysis. Cui, Donghua, et al.
[8] Intrahepatic Cholestasis of Pregnancy. Chivers, Sian. Williamson, Catherine. 7, 2018, Vol. 28.
[9] Masoud, N; Neill, S.H. Serum bile acids as a sensitive biological marker for evaluating hepatic effects of organic solvents. Available from URL: https://www.ncbi.nlm.nih.gov/pubmed/23885947 [Accessed 1 November 2018]
[10] Microassay of Serum Bile Acids by an Enzymatic Cycling Method. Komiyama, Y, et al. 10, s.l. : Chemical and Pharmaceutical Bulletin, 1982, Vol. 30.
[11] Evaluation of a Colorimetric Enzymatic Procedure for Determining the Total Bile Acids in the Blood. Agape, V, et al. 3, s.l. : Minerva Gastroenterologica e Dietologica, 1989, Vol. 35.
[12] Total Bile Acids Test & Clinical Diagnosis. Diazyme. 2019.
What you need to know this National Cholesterol Month
October 2018 marks National Cholesterol Month, an entire month devoted to raising funds for the charity HEART UK, and raising awareness of the dangers of high cholesterol.
But how much do we actually know about cholesterol? Do we even know what it is?
Many people are confused about how cholesterol differs from fat, which is understandable, given that cholesterol is found in foods that are sometimes high in fat.
But cholesterol is actually a type of lipid, as is fat. Like fat, cholesterol is essential for a range of bodily functions, but unlike fat, cholesterol can’t be exercised off, sweated out or burned for energy.
The body does require a small amount of blood cholesterol to build the structure of cell membranes, and make hormones like oestrogen, testosterone and adrenal hormones.
It also helps your metabolism work efficiently. For example, cholesterol is essential for your body to produce vitamin D and bile acids to help you digest your food. It is carried in the blood by proteins, with which it combines to make lipoproteins.
The 2 main types of lipoprotein are:
- High-density lipoprotein (HDL) which carries cholesterol away from the cells and back to the liver, where it’s either broken down or passed out of the body as a waste product. For this reason, HDL is referred to as “good cholesterol”, and higher levels are better.
- Low-density lipoprotein (LDL) which carries cholesterol to the cells that need it. If there’s too much cholesterol for the cells to use, it can build up in the artery walls. For this reason, LDL is known as “bad cholesterol.”
This cholesterol in the body comes from two main sources: the liver and diet. The liver, other organs and other cells in your body product about 75-80% of the cholesterol in the blood, while our diet contributes to about 20-25% of our cholesterol levels.
Foods high in saturated fat which can ultimately increase cholesterol levels include butter, hard margarines, fatty meat and meat products such as sausages, full fat chees, milk, cream and yoghurt.
Eating these foods in excess can therefore lead to a high level of cholesterol in the blood, called hyperlipidaemia.
High cholesterol itself doesn’t cause any symptoms, but it does increase your risk of serious health conditions including cardiovascular disease, heart attack and stroke because it builds up in the artery walls, restricting the blood flow to your heart, brain, and the rest of the body.
Given its vital role in the body, the serious conditions it can cause should it get too high, and the fact that if high, it does not produce any symptoms, it is extremely important to regularly monitor your cholesterol through blood testing.
Randox offers a range of cholesterol tests to ensure that individuals with high cholesterol get the earliest and most accurate diagnosis. In fact, Randox is responsible for more than 15% of all cholesterol tests carried out across the globe. Randox are tackling the need for better cholesterol testing with our wide range of niche and high-performance assays including sdLDL Cholesterol, Lipoprotein (a) and HDL3 Cholesterol.
For more information about National Cholesterol Month, or cholesterol testing at Randox, please contact the Randox PR team by emailing randoxpr@randox.com or phone 028 9442 2413
The Correlation Between Liver Cirrhosis and Lactic Acidosis
Lactic acid is an organic compound which produces the conjugate base lactate through a dissociation reaction. Due to it being a chiral compound, two optical isomers of lactate exist; D-Lactate and L-Lactate. The lactate dehydrogenase (LDH) enzyme can produce and metabolise both isomer forms to pyruvate, however due to the isomer-specific nature of LDH different forms of the enzyme are required. D-Lactate requires a D-LDH form whereas L-Lactate requires L-LDH. As a result of this requirement, combined with the fact that mammalian cells only contain L-LDH, the lactate produced in humans is almost exclusively L-Lactate.
One of the roles of L-Lactate is its involvement in the Cori Cycle, a metabolic pathway involved in the production of glucose. The cycle involves the rotatory transportation of lactate and glucose from the liver and the muscle. Lactate is produced in the muscle through glycolysis which is then transported to the liver through the blood stream. In the liver, the lactate is oxidised to pyruvate and then converted to glucose by gluconeogenesis, which is then transported back to the muscle for the process to start again. 1500 mmol of lactate is produced daily by the body and is cleared at a constant rate via the liver.
Problems can arise if the liver fails to regulate the lactate produced. Hyperlactamia is the name given to elevated levels of lactate in the body, as a result of the rate of production exceeding the rate of disposal. This is due to a lack of oxygen that reduces blood flow to the tissues. If levels continue to rise a patient is at risk of lactic acidosis.
The liver is an important tissue in the regulation of lactate, it is therefore no surprise that liver damage can prevent this process resulting in a further diagnosis of lactic acidosis. A healthy liver is a vital part of lactate regulation as it acts as the main consumer of lactate and contributes to 30-40% of lactate metabolism. Potential victims are patients who suffer with cirrhosis, a complication of liver disease, which is commonly caused by alcohol abuse and viral Hepatitis B and C.
Patients with liver cirrhosis have a higher risk of increased lactate levels. Increased levels of the lactate ions disturbs the acid-base equilibrium, causing a tilt towards lactic acidosis. The mortality rate of patients who develop lactic acidosis is high, prompt recognition and treatment of the underlying cause remain the only realistic hope for improving survival.
The Randox L-Lactate reagent allows for a prompt and accurate diagnosis of lactic acidosis.
Randox L-Lactate Reagent
The Randox L-Lactate key benefits include:
- Excellent working reagent stability of two weeks when stored at + 15 – +25°C
- Exceptional correlation of r = 0.99 when compared against other commercially available methods
- A wide measuring range of 0.100 – 19.7 mmol/l and so is capable of detecting abnormal levels in a sample
Other features:
- Colorimetric method
- Lyophilised reagents for enhanced stability
If you are a clinician or laboratory who are interested in running assays for Lactic Acidosis or Liver Disease, Randox offer a range of high-quality routine and niche assays including:L- Lactate, Ethanol, Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST) and Albumin which can be used to diagnose conditions commonly affecting the liver. These assays can be run on most automated biochemistry analysers.
Instrument Specific Applications (ISA’s) are available for a wide range of biochemistry analysers. Contact us to enquire about your specific analyser.
For more information, visit: https://www.randox.com/lactate/ or email: reagents@randox.com
Liver health: do you know your limits?
Are you taking part in Dry January? Giving up alcohol can do your insides a lot of good, and it’s great news for your liver in particular. It may be that after the festive period our liver needs a little bit of rest!
Did you know that alcohol consumption across the UK increases by a staggering 41 percent more than the annual monthly average in December? That’s more than anywhere else in the world.
The effects of alcohol on your health really depend on how much you drink and how often, but as the statistics show, more of us increase our uptake of alcohol over the festive period.
So how does this impact our body?
The results of over indulging vary from a hangover, a poor night’s sleep, to causing an irregular heartbeat, and in some cases, excessive alcohol intake can lead to liver damage. This can be a very serious condition, given the liver’s vital role in the body.
The liver plays a central role in all metabolic processes. In fat metabolism, it breaks down fats and produces energy. When we intake alcohol or drugs, the liver metabolizes the drug and detoxifies chemicals. And it also makes proteins important for blood clotting and other functions.
Following these processes, the liver also secretes bile that ends up back in the intestines and helps the digestion of fats and oils, otherwise known as lipids.
As Randox Health Expert Dr. Gary Smyth explains:
“The liver is one of the most complex organs in the body and also one of the most important. Although it is very resilient, each time it has to filter alcohol some of its cells die. The liver can develop new cells, but abuse over a prolonged period reduces its ability to regenerate, causing serious damage.”
It is not just heavy drinking over years that can cause liver disease – binge drinking is also a culprit and can lead to your liver becoming fatty and inflamed. The best advice is to drink in moderation. Simple tips like taking a glass of water in-between alcoholic drinks are key to staying hydrated.
Know your units;
- According to drinkaware.co.uk, unit guidelines are now the same for men and women.
- Both are advised not to regularly drink more than 14 units a week
- This equates to 6 pints of 4% beer / 6 glasses of 13% wine / 14 glasses (25ml) of 40% spirits
- But don’t save up your 14 units, it’s best to spread evenly across the week.
- If you want to cut down the amount you’re drinking, a good way is to have several drink-free days each week.
- If you’ve had a heavy drinking session, avoid alcohol for 48 hours.
What does one unit of alcohol look like?
One unit of alcohol is the amount of alcohol an average adult can process within one hour so that so that there’s no alcohol left in their bloodstream.
One unit of alcohol equates to:
- 218ml of standard 4.5% cider
- 76ml of standard 13% wine
- 25ml of standard 40% whiskey
- 250ml of standard 4% beer
- 250ml of a standard 4% alcopop
How many units are in my drink?
- Small glass white / rosé / red wine (125ml 12%) = 1.5 units
- Standard glass white / rosé / red wine (175 ml 12%) = 2.1 units
- Large glass white / red / rosé wine (250ml 12%) = 3 units
- Pint of lager / beer / cider (5.2%) = 3 units
- Bottle of lager / beer / cider (330ml 5%) = 1.7 units
- Single small shot of spirits (25ml 40%) = 1 unit*
*taken from NHS Live Well Guidelines
Having your liver health checked after Christmas is a great way of tracking any changes that you may need to make to your lifestyle, for better or for worse – essential for helping you prevent liver disease and allowing you to take early action if it is diagnosed.
At Randox we offer a comprehensive menu of liver function tests to determine the health of your liver. Provided by Randox to a wealth of hospitals, laboratories and research facilities across the globe, these tests are also directly available to you, the consumer, via our Randox Health clinics.
They include:
- Alanine Aminotransferase (ALT) – an enzyme mainly found in the liver. Liver injury or disease will release ALT into the bloodstream, thus elevating serum ALT levels. Moderately high or mildly elevated ALT levels can be associated with chronic liver disease, such as cirrhosis, which is scarring of the liver.
- Aspartate Aminotransferase (AST) – an enzyme found predominantly in the heart, liver and skeletal muscles. Cell injury or disease will release AST into the bloodstream, thus elevating blood AST levels. Increased AST levels may be associated with hepatitis (inflammation of the liver), cirrhosis (scarring of the liver), or drug-induced liver injury.
- Gamma-Glutamyltransferase (GGT) – an enzyme found mainly in the liver. Increased levels of GGT in the blood may indicate bile duct injury, hepatitis (inflammation of the liver), cirrhosis (scarring of the liver), liver necrosis (death of liver tissue), liver tumours or the use of drugs that are toxic to the liver. A high GGT level is frequently associated with increased alcohol consumption, as this liver enzyme is involved in the breakdown and removal of alcohol from the body.
- Glutamate Dehydrogenase (GLDH) – an enzyme located within the mitochondria (energy-producing machinery) of cells, particularly within liver tissue. Significant liver cell damage may cause release of GLDH into the bloodstream. Toxic liver damage, liver cell necrosis (cell death) or hypoxic liver disease (where liver cells are deprived of oxygen) may cause an increase in GLDH. Measurement of GLDH in combination with other liver markers may help distinguish between different causes of liver dysfunction.
- Bilirubin – a yellowish-brown pigment found in bile (a fluid produced in the liver that facilitates digestion in the intestine). Increased levels may be associated with liver or bile duct blockage (eg due to gallstones), hepatitis (inflammation of the liver), cirrhosis (scarring of the liver), trauma to the liver, a drug reaction, long-term alcohol abuse or rare inherited disorders (eg Dubin-Johnson syndrome which is characterised by mild jaundice).
- Albumin – produced by the liver, albumin is the most abundant protein in the blood. Albumin plays in important role in maintaining blood pressure and transporting a wide variety of small molecules, such as hormones, vitamins and drugs, throughout the body. Various conditions are associated with decreased albumin levels, including kidney and liver diseases.
- Copper – an essential mineral that plays a part in many enzyme systems within the body. Excess or deficiency of copper is very rare, however raised copper levels may be caused by chronic liver disease or acute hepatitis (inflammation of the liver).
And when used in conjunction with the wide variety of other tests available within the world’s most comprehensive and personalised health testing menu, you can obtain an understanding of your full body health like never before.
That’s why we don’t test in isolation, which can give a patchy representation of your health and can fail to pick up on related symptoms elsewhere in the body. We test up to 350 tests across 25 areas of your health – giving you the power to take your health into your own hands.
Contact the Randox Health team today to determine the health of your liver, and of your body.
Call 0800 2545 130 or click here.
