LABORATORY DIAGNOSIS IN LIVER DISEASESProf. Dr. Arzu SEVEN

The metabolic pathways of glycolysis,the Krebs cycle,amino acid synthesis and degradation and the process of oxidative phosphorylation are all carried out in hepatocytes,which are well endowed with mitochondria.

The liver contains an extensive reticuloendothelial system for the synthesis of blood cells.

PROTEİN SYNTHESİS İN LİVER Albumin Transthyretin(prealbumin) Igs Ceruloplasmin α1-antitrypsin Haptoglobulin β2-microglobulin Transferrin α-fetoprotein Some coagulation factors

Albumin is the major protein product of the liver.

İt has a long biological half-life in plasma (about 20 days ) Hypoalbuminemia is a feature of advanced

chronic liver disease.

METABOLİC LİVER DİSEASES Clinical conditions associated with

abnormal concentrations of liver_produced proteins in plasma :

1. Genetic deficiency of α1-antitripsin presents in infancy as liver disease or in adulthood as lung disease

Hepatic α1-antitrypsin belongs to the serpins, one of the family of serine protease inhibitors

2. Genetic deficiency of ceruloplasmin leads to Wilson’s disease, a condition associated with liver and CNS damage.

Ceruloplasmin is the major cupper containing protein of liver and plasma functions as a ferrooxidase

hepatic manifestations are fulminant hepatitis + chronic hepatitis + cirrhosis

Neuropsychiatric changes include behavioral changes + psychosis + extrapyramidal/pyramidal signs

Cupper accumulates in liver, brain,cornea, kidney and joints

Corneal rings(Kayser_Fleischer) Hemolysis + proximal renal tubular

dysfunction + osteopenia + osteoarthropathy

Lab: Serum ceruloplasmin Urinary Cu>100 μg/d Hepatic Cu>250 μg/d AST>ALT Untreated Wilson’s disease is fatal

Treatment: Chelation therapy with D-penicillamine(1-

2g/d)

3. Liver cancer is associated with particularly high plasma α-fetoprotein (AFP) concentrations.

AFP and albumin have sequence homology in the fetus, AFP appears to serve physiologic

functions similiar to albumin in adult By the end of first year of life, AFP in plasma

is replaced by albumin

4. Hemochromatosis Hereditary hemochromatosis (HHC) is an

autosomal recessive disorder of iron retention that damages liver, pancreas , heart joints, gonads and skin

Lethargy + hepatomegaly + skin pigmentation(grayish color) + sometimes DM

Diagnosis by analysis of serum iron, ferritin and transferrin saturation

DRUG METABOLİSM

Most drugs are metabolized by the liver. Low substrate specificity of some hepatic

enzymes produces a wide-ranging capability for drug metabolism

Hepatic metabolism usually increases the hydrophilicity of drugs and therefore their ability to be excreted.

Metabolites produced are less pharmacologically active than the substrate drug.

However some inactive prodrugs are converted to their active forms as a result of liver processing

Metabolism proceeds in 2 phases: Phase I-addition of the polar group: The polarity of the drug is increased by

oxidation or hydroxylation catalyzed by cytocrome P-450 oxidases

Phase II-conjugation Cytoplasmic enzymes conjugate the

functional groups introduced in the first phase by glucuronidation/sulfation/ acetylation /methylation

Cytocrome P-450 enzymes : Heme containing proteins Colocalize with NADPH:cyt P 450 reductase

Present in endoplasmic reticulum In liver and in the epithelium of endoplasmic

reticulum There are 12 cyt P450 gene families CYP1, CYP2 and CYP3 are responsible for

most of phase I drug metabolism Induction and inhibition of cyt P-450 enzymes

is the mechanism of drug interactions.

Cytocrome P-450 gene polymorphisms determine response to many drugs

ALCOHOLIC LIVER DISEASE Excess intake of ethyl alcohol remains the

most common cause of liver disease in the western world.

Alcohol leads to alcoholic hepatitis, steatosis due to fat deposition/fibrosis(cirrhosis) liver failure

Alcohol acetaldehyde acetate A B A:alcohol dehydrogenase(NAD⁺) B:aldehyde dehydrogenase(NAD⁺)

Ethanol oxidation as a result of increased NADH/NAD⁺ alters the redox potential of hepatocyte

This inhibits oxidation of lactate to pyruvate (a step that requires NAD⁺ as a cofactor)

lactic acidosis + risk for hypoglycemia

NADH/NAD⁺ inhibition of β-oxidation + TG synthesis

Hepatic steatosis secreted into plasma as VLDL

Ethanol consumption affects the ubiqutin system of protein degradation, proteosome activity is decreased

hepatocyte signalling system is deregulated

apoptosis (feature of alcoholic liver disease)

Liver function tests: Bilirubin Aminotransferases (AST and ALT ) Alkaline phosphatase (ALP ) Gamma- glutamyl transpeptidase ( γ GT ) Plasma proteins Prothrombin time

AST-ALT Sensitive,albeit non-specific index of Acute damage to hepatocytes irrespective of

aetiology Hepatitis,toxic injury,drug overdose

ALP İntra-or extrahepatic cholestasis Tumours Cirrhosis Liver is not the sole source of ALP activity Substantial amounts ara present in

bone,small intestine,placenta and kidney.

In normal blood,ALP activity is derived mainly from bone and liver,with small amounts from intestine.

Placental ALP appears in maternal blood in the third trimester of pregnancy.

The liver and bone isoenzymes can be separated by electrophoresis.

Elevated γ GT suggests that the liver is

the source of increased ALP.

γ GT

Microsomal enzyme,widely distributed in tissues including liver and renal tubules

A very sensitive index of liver pathology İncreases in cholastasis

Alcohol and pheytoin induce enzyme activity. Prothrombin time (PT )

A measure of the activities of certain coagulation factors,made by the liver

A very short half-life İncreased PT may be the earliest indicator of

reduced hepatic synthesis.

Acute liver disease

Acute liver damage occurs for one of the three reasons:

Poisoning İnfection İnadequate perfusion

Chronic liver disease

Three forms of chronic liver damage are: Alcoholic fatty liver Chronic active hepatitis Primary biliary cirrhosis

Cirrhosis is the terminal stage of chronic liver damage and only occasionally follows an acute course.

The most common causes of cirrhosis are

Chronic excess alcohol ingestion Viral hepatitis Autoimmune diseases