Samenvatting Learning goals case 8

Learning goals case 8
1. How is fat stored/released in/from the adipose tissue?
 Exogenous pathway
 Chylomicrons from the lymphatic system enter the circulation and immediately
receives APO Cll and apo E from HDL when it enters the blood.
 APO Cll makes the chylomicrons substrates for lipo protein lipase enzyme which
cleaves a TAG into fatty acids and glycerol. The muscle or adipose tissue is now
able to take up the free fatty acids.
 Chylomicrons remnants are going to the liver
 Apo E and ApoB48 on chylomicrons remnants are ligands for lipoprotein
receptors in the liver




Postprandial (after meal), lipogenesis in adipose tissue
 LPL is stimulated by insulin and breaks down triglycerides in the blood
 Free fatty acid is taken up in adipocyte through CD36 / FATP or FABPm
 In the adipocyte two thing can happen with the free fatty acids
 Oxidation fatty acids which is inhibited by insulin
 Storage in triglycerides in fat droplets
 Insulin also stimulates the translocation of GLUT4 into the membrane of the
adipocyte, therefore glucose can be absorbed
 Glucose can be converted into glycerol-3-phosphate which is used for the
triglycerides synthesis

, Fasting, lipolysis in adipocytes
 Is inhibited by insulin and stimulated by (nor)adrenalin and glucagon
 Catecholamine binds Gs protein coupled B-adrenergic receptor which activates cAMP
 Natriuretic peptides bind receptor, which activates eGMP
 cAMP and eGMP are activating PKA which stimulates lipolysis
 Insulin binds the insulin receptor and inhibits cAMP via a cascade, therefore it
inhibits lipolysis . Also lactate, some neuropeptides, catecholamines and other
metabolites can block this route when they bind to the Gi coupled receptor.
 Periplin A = protecting lipid droplet against lipolysis in the basal stae
 ABhD5 (CGI-58) = binds with periliplin 1 in the basal state when stimulated by PKA.




 Adipocyte triglyceride lipase (ATGL), hormone sensitive lipase (HSL) and MGL
detach one fatty acid after another
 ATGL lipase : hydrolyses TAG DAG + FFA
 HSL: hydrolyses DAG  MAG + FFA
 MGL: hydrolyses MAG  glycerol + FFA
 Fatty acids are transported in the blood by albumin to muscle
 Oxidation takes place in the mitochondria of two places;
 Muscles (90%)
 Adipose tissue (10%)




 Endogenous pathway
The liver is able to produce VLDL.