SERUM LIPIDS

SERUM LIPIDS

1. Triglycerides

   • 3 fatty acid esters with glycerol
   • Storage of fatty acids in adipose tissue

2. Cholesterol

   • Free
     • Slightly polar
   • Esterified
     • Non-polar
     • By the action of lecithin-cholesterol acyltransferase (LCAT)

3. Fatty acids

4. Absence of hydroxyl groups capable of interacting with water

   • Insoluble in water
   • Need special transport mechanisms in blood and extracellular fluids
     • LIPOPROTEINS
       • Water-soluble macromolecules
         • Metabolism
           • Exogenous pathway
             • Breakdown of dietary fats
               • Micelle formation
                 • Packed with apolipoproteins in enterocytes
                   • Chylomicron formation
                     • Transported by the lymphatic system to the left subclavian vein
                       • Maturation
                         • Obtaining of ApoC2
                           • Together with LPL mediates triglyceride lipolysis within the CM
                             • Breakdown in the liver
                         • Obtaining of ApoE
                           • Recognition of remnants in the hepatocyte for degradation
           • Endogenous pathway
             • VLDL
               • Synthesized in the liver
                 • Contains triglycerides, cholesterol phospholipids, vitamins and ApoB-100
                   • Obtains ApoC2 and ApoE
                     • LPL and ApoC2 initiate triglyceride lipolysis
                       • Conversion to IDL due to loss of ApoC2
                         • Conversion to LDL by degradation of triglyceride remnants
             • HDL
               • Synthesized in the liver
                 • Discoidal nascent shape
                 • Collect excess cholesterol in peripheral tissues
                   • Esterification of cholesterol by action of LCAT
                     • Ensures cholesterol stays within lipoprotein
                       • By action of CETP exchanges cholesterol for triglycerides with LDL
                     • Changed to spherical shape (HDL3)
                   • Leads it to the liver
         • Spheric structure
           • Non-polar center
             • Lipid content
           • Polar outer layer
             • Phospholipids
             • Free cholesterol
             • Apolipoproteins
               • ApoA
                 • HDL
               • ApoC
               • ApoE
               • ApoB-48
                 • Chylomicrons
               • ApoB-100
                 • VLDL
                 • LDL
         • Types
           • VLDL
             • Very Low Density Lipoproteins
               • Secreted by the liver
               • Transport triglycerides
           • LDL
             • Low Density Lipoproteins
               • Produced by the catabolism of VLDL
               • Transport cholesterol
                 • From the liver to peripheral tissues
           • HDL
             • Increased amount of apolipoproteins
             • High Density Lipoproteins
               • Secreted by liver and intestine
               • Transport cholesterol and phospholipids
                 • From peripheral tissues to to the liver
             • Prevents LDL oxidation
           • Chylomicrons (CM)
             • Big size
             • Transport triglycerides

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