Material metabolism in the liver
- 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