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Role Of Enzymes In Liver Disorders

Role Of Enzymes In Liver Disorders

Posted By HealthcareOnTime Team Posted on 2022-04-11

An enzyme is truly a catalyst speeding up every reaction with its magical touch. Our body relies entirely on enzymes for its chemical reactions. At times, these catalysts aid us by playing the role of an indicator. Thus, indicating the dysfunction of body's largest and most vital organ- Liver, makes it worth to redefine these enzymes as lifesaver. Detection of any change in liver enzyme levels is crucial in assessing the liver disorders. As liver performs numerous functions, no single test is sufficient to estimate its function; this account for several parameters to diagnose various liver disorders.

Role Of Enzymes In Liver Disorders

Liver-The Factory of Human Body
Liver has many functions in the body. This factory acts as a storage organ for the absorbed nutrients and detoxifies drugs and other chemicals. It breaks down the complex carbohydrates into its simplest form- glucose, as well as stores fat soluble vitamins. The majority of the serum proteins such as albumin, coagulation factors, plasma Carrier proteins, and lipoproteins are synthesized by the liver. Other functions that are carried out by this organ are, excretion of toxic ammonia and the synthesis of bile acid which functions as an emulsifier essential for absorption of fats and fat-soluble nutrients. Any change in liver functioning disrupts the array of activities performed by it.

Importance Of Enzyme Detection
laboratory tests for enzymes are fully automated and are commonly accepted as a part of routine annual checkup. Screening tests include measurement of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT). The challenges faced by the physicians are the patients having abnormal result on measurement of either serum aminotransferases or alkaline phosphatase that is otherwise asymptomatic.

In asymptomatic patients, persistent elevation of liver enzymes require further test to detect the cause of hepatobiliary (concerned with liver along with bile duct and gall bladder injury since the magnitude of enzyme does not always reflect severity of disease. Pattern of enzyme elevations are essential for proper evaluation of the condition. The pattern can either be Hepatic, wherein the elevation of enzymes results from liver tissue damage: or can be Cholestatic, where the bile flow is obstructed. Elevated levels of alanine aminotransferase and aspartate aminotransferase are observed in hepatic condition, while cholestatic includes elevation of alkaline phosphatase and gamma-glutamyl transferase levels.

Enzymes in Action
Alanine Aminotransferase (ALT)
Also known as serum glutamatic pyruvic transaminase (SGPT) ALT is an enzyme produced in different tissues but prominently in hepatocytes, and hence acts as specific marker of hepatocellular injury or damage. This enzyme reversibly catalyzes transamination of the alanine to pyruvate, an important intermediate in cellular energy production. Healthy individuals usually have low levels of ALT in the circulation as body uses it for breakdown of food into energy. Liver damage results in excessive release of ALT into blood, much before the onset of jaundice or any other symptom and thus enabling early detection Elevated ALT level are also associated with reduced insulin sensitivity, adiponectin and glucose tolerance as well as increased free fatty acids and triglycerides. ALT has a serum half-life of about 40 to 48 hours.

Normal range In females: 10-28 U/L; In males: 13-40 U/L
Aspartate Aminotransferase (AST)
Also known as serum glutamic oxaloacetic transaminase (SGOT), AST is an enzyme which carries out the reversible transfer of an alpha-amino group between aspartate and glutamate which is important in amino acid metabolism. It is produced in liver cells and also present in heart muscle, skeletal muscle, kidney tissues, etc. Elevation of AST levels in conjugation with ALT indicates hepatocellular injury. AST possesses serum half-life of about 16 to 18 hours.

Normal range In females: 0 - 31 U/L; In males: 0 - 37 U/L
Alkaline Phosphatase (ALP)
It is produced in the membrane of bile ducts lining and are also present in kidney, intestine, leukocytes, pancreas, bone, etc. This enzyme helps in transportation of lipid in the intestine and calcification of bone. It is present on the surface of bile duct epithelia, where it is required for fat digestion. Increase in the levels of ALP is found in condition like Cholestasis, that enhances the accumulation of bile salts and increases its release from the cell surface. Hence, ALP level rises late in bile duct obstruction slowly decreases on the resolution of the condition. Children and adolescents have high levels of ALP in blood due to the ongoing bone growth. Therefore, different normal reference value ranges of ALP test must be interpreted for children and adults.

Normal range In females: 42 - 98 U/L; In males, 53 - 128 U/L
Gamma-Glutamyl Transferase (GGT)
It is a microsomal enzyme found in several cells such as hepatocytes (liver cells), biliary epithelial cells, and other regions such as renal tubules, pancreas and intestine. This enzyme is involved in glutathione metabolism and carries out the transport of peptides into the cell across the cell membrane. Due to absence of GGT in bones, they do not play any major role in bones. Elevated levels of both GGT and ALP are observed in liver diseases. GGT is majorly associated with structural liver damage, hepatic microsomal enzyme induction.

Normal range In females: 0 - 38 U/L; In males, 0 - 55 U/L.
AST/ALT ratio
AST/ALT ratio provides more clinical utility than the assessment of elevated levels of AST & ALT individually. Different conditions can be differentiated on the basis of varying ratios.
1. Ratio helps to differentiate non-alcoholic steatohepatitis (NASH) from alcoholic liver
2. A ratio of less than 1: seen in acute viral Hepatitis and toxic hepatitis
3. A ratio greater than 1: indicates advanced liver fibrosis and chronic hepatitis C infection
4. Ratio greater than 2: is observed in alcoholic hepatitis
5. A mean ratio of 1.4: is found in patients with cirrhosis related to NASH
6. Above 4.5: is observed in Wilson's disease and similar such altered ratio is found even in Hyperthyroidism.

Liver Function Tests (LFT)
The backbone of liver diagnosis, it is the most commonly used non-invasive screening test for assessing liver disorders. There are lots of speculations surrounding the name of this test, it can rightly be called as 'liver injury tests'.

This test includes 3 main parameters
1. Proteins
Serum albumin is synthesized in the liver and its synthesis directly reflects the extent of functioning of liver cells. Hence, decrease in the level of albumin suggests liver damage. Except for the acute liver diseases, all other chronic diseases are indicated by decreased albumin level. In case of acute viral hepatitis, obstructive jaundice, and hepatotoxicity, the albumin levels are normal.

Globulin or gamma globulin proteins, in liver are produced by B lymphocytes of hepatocytes. Their levels elevate against the chronic liver diseases like chronic active hepatitis, and cirrhosis. Increased levels of IgG in autoimmune hepatitis, IgM in primary biliary cirrhosis and IgA is in alcoholic liver disease are observed.

Serum albumin/globulin ratio is also assessed to check the improper functioning of the liver.

Normal range Total protein: 5.7 - 8.2 g/dl, serum globulin: 2.5-3.4 g/dl, and serum albumin: 3.2-4.8 g/dl.

2. Bilirubin
It is the yellowish substance formed due to lysis of RBCS, which releases hemoglobin that further splits into heme and globin. This heme part is catabolized to produce bilirubin. Urine samples are mandatory for examining liver disorders, hemolytic anemia, and neonatal jaundice.

Unconjugated Bilirubin (Indirect): It is hydrophobic in nature and hence is bound to albumin for its transportation through blood to liver. Increased level is indicative of increased red cell destruction as in hemolytic anemia.

Normal range 0-0.90 mg/dl.

Conjugated Bilirubin (Direct): In the liver, unconjugated bilirubin gets attached with glucuronic acid and forms hydrophilic conjugated bilirubin, which is then excreted via bile into the small intestine. Elevated levels indicate decreased elimination of bilirubin from the liver cells and might be a result of viral hepatocellular disease, cholestatic injury, intrahepatic cholestasis, primary biliary cirrhosis, etc.

Normal range 0-0.30 mg/dl.

Total Bilirubin: It is the total count of both conjugated and unconjugated bilirubin. This blood tests determines elevated level of bilirubin substance that may indicate liver diseases.

Normal range 0.3 -1.20 mg/dl.

3. Enzymes
Elevated levels of the above mentioned enzymes ALT, AST, ALP, and GGT are assessed to detect liver damage or its dysfunction and disorders associated to liver.

Other Tests
1.5' Nucleotidase (5'NT) 5'NT is an intrinsic membrane transport protein generally disseminated throughout the body, hydrolyzing the 5'-nucleotides to their corresponding nucleosides. Despite its ubiquitous distribution, serum concentrations of 5'NT reflect hepatobiliary diseases especially, intrahepatic obstruction. The advantage of this test over ALP is that, the serum 5'NT activity is not elevated in any other cases such as, in infancy, childhood, pregnancy, or osteoblastic disorders.

2. Coagulation test
Abnormal or decreased clotting factor synthesis is associated with the impairment of hemostatic function linked to liver. To assess the liver impairment, clotting profile includes levels of prothrombin time (PT) and activated partial thromboplastin time (aPTT) which would be a predictive indicator of abnormal coagulation.

3. Lactate dehydrogenase (LDH)
LDH is an enzyme responsible for the production of energy in the cells as well as majorly found in heart, liver, kidney, lungs, and in blood cells in high amounts. It can be used as a general indicator of acute or chronic tissue damage. On damage to liver cells, LDH is released from cells into the blood circulation, and hence blood LDH levels are considered as an indicator of cell or tissue damage. LDH can also detected in tissue fluids such as cerebrospinal fluids, peritoneal fluid in the brain and lung injuries respectively.

Importance of Liver can be understood with the fact that, functional liver failure does not occur until much of the liver tissue has been damaged, but once it crosses this capacity the damage is irreparable. Hence, a preventive outlook is very crucial to maintain this super factory called liver stay healthy and monitor its proper functioning with timely screening.

Testing @ Thyrocare
Thyrocare offers Liver Function Tests Profile for the qualitative and quantitative analysis of serum proteins, bilirubin and enzymes indicative of liver functioning using advanced and sophisticated automated technology of Photometry at highly affordable rates.

The only organ with the blessing of regeneration, super power of detoxification & many more such astonishing functions, deserves utmost care... Love your liver!!


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