Biochemical functions of the hepatocyte and liver, possibilities of biochemical diagnosis of damage hepatocyte and liver function.

Introduction

The liver is a vital organ involved in numerous metabolic, synthetic, detoxifying, and storage functions. Hepatocytes, the primary functional cells of the liver, perform these tasks and play a central role in maintaining homeostasis. Biochemical assessment of liver function is essential in diagnosing hepatic injury, disease progression, and treatment response.

Main Biochemical Functions of the Hepatocyte

1. Carbohydrate Metabolism

- Glycogenesis and glycogenolysis

- Gluconeogenesis

- Regulation of blood glucose levels

coagulation cascade

2. Lipid Metabolism

- Fatty acid oxidation and synthesis

- Triglyceride and lipoprotein synthesis (e.g., VLDL)

- Cholesterol synthesis and bile acid formation

3. Protein Metabolism

- Synthesis of plasma proteins: albumin, clotting factors (II, VII, IX, X)

- Urea cycle: detoxification of ammonia

- Amino acid interconversion and transamination

4. Detoxification and Biotransformation

- Phase I (oxidation, reduction, hydrolysis) via cytochrome P450 enzymes

- Phase II (conjugation: glucuronidation, sulfation, acetylation)

- Breakdown and removal of hormones, drugs, toxins

5. Storage and Immune Function

- Stores glycogen, vitamins (A, D, B12), iron (ferritin), and copper

- Kupffer cells contribute to innate immunity by removing pathogens and debris from the blood

Biochemical Diagnosis of Liver Function and Damage

**Liver Enzymes (Markers of Hepatocellular Injury):**

- Alanine aminotransferase (ALT): specific to hepatocytes

- Aspartate aminotransferase (AST): also found in heart and muscle

- Elevated ALT/AST indicates hepatocellular damage

**Cholestasis Markers:**

- Alkaline phosphatase (ALP)

- Gamma-glutamyltransferase (GGT)

- Bilirubin (direct and indirect)

**Synthetic Function Tests:**

- Serum albumin: low levels suggest chronic liver disease

- Prothrombin time (PT): prolonged in impaired clotting factor synthesis

**Others:**

- Ammonia: elevated in liver failure

- Alpha-fetoprotein (AFP): tumor marker for hepatocellular carcinoma

Conclusion

The liver is central to numerous metabolic and regulatory processes. Hepatocyte dysfunction affects carbohydrate, lipid, protein, and detoxification pathways. Biochemical tests are indispensable tools for diagnosing liver damage, monitoring disease progression, and guiding therapy.

References

1. Guyton and Hall Textbook of Medical Physiology, 14th Edition

2. Lehninger Principles of Biochemistry, 7th Edition

3. Lippincott Illustrated Reviews: Biochemistry, 7th Edition