The role of liver in material metabolism

Material metabolism in the liver

liver metabolism
  • carbohydrate metabolism
  • lipid metabolism
  • protein metabolism
  • vitamin metabolism
  • hormone metabolism 

Carbohydrate metabolism

Functions

Maintaining the constancy of the concentration of sugar in blood; supplying energy to peripheral tissues, especially to brain and erythrocytes.

Main pathways for carbohydrate metabolism

  • gluconeogenesis
  • glycogenesis and glycogenolysis
  • glycolysis 

Carbohydrate metabolism in varied nutrient conditions in liver

    --  glycogenesis↑
          --  excess carbohydrate is converted to fatty acids and exported in VLDL form
  • postabsorptive state：
     --  glycogenolysis↑→release glucose to replenish blood sugar
  • starvation state：
     --  gluconeogenesis
     --  lipid mobilization↑→acetone body↑→saving glucose

Lipid metabolism


Functions: 

Play important role in digestion, absorption, synthesis, catabolism and transportation of lipids.  

 Main pathways lipid metabolism

  • oxidation of fatty acids
  • synthesis of fatty acids and esterification
  • formation of ketone bodies
  • synthesis of lipoproteins and apolipoproteins (VLDL、HDL、apoC II)
  • degradation of lipoproteins

Role of liver in varied processes of lipid metabolism

  • digestion and absorption：
    --  biliation.  Bile acid is essential for lipid digestion and  absorption
     --  liver dysfunction→fatty diarrhea
  • synthesis：
     --  fatty acid, triacylglycerol, ketone body, cholesterol, phospholipid
     --  liver dysfunction→fatty liver, Ch/ChE↑
  • catabolism：
     --  β-oxidation of fatty acids, degradation and excretion of cholesterol, degradation of LDL
  • tranportation：
     --  synthesis and secretion of VLDL, HDL, apoC II, and LCAT

Protein metabolism


Functions: synthesis (γglobulin is excepted), secretion and elimination (albumin is excepted) of plasma proteins.

Liver dysfunction:

  • albumin↓→edema, A/G↓
  • plasma thromboplastin component ↓ →disturbance of blood coagulation
  • blood ammonia↑
  • amine↑→hepatic encephalopathy 

Vitamin metabolism

Functions

  • absorption of fat-soluble vitamins
  • storage of vitamins (VA, VK,VE,VB12)
  • transportation of vitamins synthesis of retinol-binding protein and VitD-binding protein
  • transformation of vitamins
  • β-carotene→VitA Vit D3 → 25-(OH)-Vit D3 water-soluble vitamins →cofactors

Liver dysfunction

  • biliary obstruction→VitK↓→hemorrhagic tendency
  • hepatic rickets

Hormone metabolism

Functions: inactivation of hormones
Manner: biotransformation

Liver dysfunction:

  • Spider angioma of skin
  • liver pulms
  • cutaneous pigmentation
  • hypoglycemia


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