2. Introduction
Classes of lipids
Cholesterol
Triglycerides
Phospholipids
Plasma cholesterol and TG :Clinically important risk factors for
atherosclerosis.
LIPOPROTIEN
Poorly water soluble
Absorbed from GIT
Consist of hydrophobic core and less hydrophobic surface coat
TYPES :
Chylomicrons
VLDL
LDL
HDL
3. Transport and storage of lipids
1. Exogenous (dietary ) lipid pathway
2. Endogenous pathway
3. Reverse cholesterol transport
4. Exogenous lipid pathway
Small intestine
Blood circulation
Fatty acids
Dietary lipids
Chylomicrons
Energy
production
Stored as TG
5. Endogenous pathway
Fasting : liver is the source of plasma lipids
TGs and Cholesterol ester : synthesised by liver and secreted as VLDL
VLDL > hydrolysis by LPL > fatty acids to tissues + IDL
IDL converted to LDL by hepatic lipase
LDL : atherogenic lipo protein
Regulation of plasma LDL concentration: Receptor mediated endocytosis in
cells or liver
Supply of cholesterol through this pathway downregulates further expression
of LDL receptor gene > Decreases synthesis and activity of HMG CoA reductase
This negative feedback loop along with modulation of cholesterol
esterification controls the intracellular free cholesterol level.
6. Reverse cholesterol transport
Process in which cholesterol is removed from the peripheral tissues and
returned to liver.
HDL are the main lipoprotein along with lipid poor Apo A1 are involved in this
process.
HDL produced in liver and catabolized in intestine
HDL able to accept more free cholesterol from atherogenic lipoproteins and
peripheral tissues to the liver
A circulating enzyme called LCAT (lecithin cholesterol acyltransferase)
esterifies these HDL.
7. Dyslipidemia
Dyslipidemia refers to levels that are either higher or lower.than the normal range of blood
fats.Among these hyperlipidemia is most commonest cause.
Characterised by an abnormalities in the lipid profile,consisting of a variety
of disorders with raised total cholesterol, LDL or TG or conversely ,lower
levels of HDL
8. Classification and causes
Primary hyperlipidemia : Genetic disorder of lipid metabolism
,characterised by genetic mutation which causes impaired clearance of LDL
from the circulation due to absence of LDL receptors.
Eg : familial hypercholesterolemia.
Secondary hyperlipidemia : hyperlipidemia secondary to a disease /
disorder other than genetic defect.
9.
10. Dyslipidemia symptoms
Dyslipidemia doesn't have symptoms at all, but it can cause othersymptomatic
vascular disease, like coronary artery disease.
Eyelid xanthelasmas, tendinous xanthomas at the elbow, kneetendons and
Achilles and arcus cornea are caused by high levels ofLDL.
Acute pancreatitis is caused by high levels of TGs.Patients that have familial
hypercholesterolemia in homozygous formcan have the above findings with
planar xanthomas.
Patients that have elevation of TGs in severe condition can expect having
eruptivexanthomas over their elbow, back, trunks, knees, buttocks, feet and
hands.
Those with rare dysbetalipoproteinemia can expect having palmar xanthomas
and tuberous xanthomas.
Retinal arteries and veins can have a creamy white appearance dueto the
severe hypertriglyceridemia. You can also have a milkyappearance in your
blood plasma when you have high lipid levels.You can expect symptoms like
paresthesias, confusion and dypsnea.
