APPP 23, 26, and 27: Liver Lipoproteins Flashcards
What is coronary heart disease (CHD)?
occlusion of blood flow through some part of the coronary arteries
What is ischemia?
lack of oxygen (blood flow)
What is myocardial infarct?
dead heart muscle caused by lack of blood flow
What are the coronary arteries (left and right branches)?
supply blood to the heart muscle itself
What happens if the diameter of the lumen of the coronary arteries is reduced by more than 50%
ischemia will develop, and the patient will develop tightness or pain the chest
- note that pain does not always accompany myocardial ischemia (silent ischemia)
What are important risk factors for coronary heart disease?
lipid abnormalities
- elevations in low density lipoprotein (LDL) cholesterol
- elevated triglycerides
- low high density lipoprotein (HDL) cholesterol
What are lipid abnormalities also associated with?
increased risk of cerebrovascular and peripheral vascular disease
What is severe hypertriglyceridaemia also associated with?
risk of pancreatitis (inflammation of the pancreas)
What does CHD present as? (4)
- angina – chest pain that usually comes on during exertion
- myocardial infarction (MI) – heart attack
- chronic heart failure
- sudden death
What is atherosclerosis?
process of accumulation of lipid leading to thickening of arterial blood vessels
- progressive disease beginning with the development of fatty streaks and potentially leading to complicated atherosclerotic plaques that can rupture, set up thrombosis, and occlude the lumen
- predominantly a disease of arteries (both large and medium-sized) that occurs in areas of high sheer stress – high pressure, high speed blood going by
What is an important risk factor for atherosclerosis?
hyperlipidemia
- good association between serum cholesterol and CHD mortality rate
- note: this is only ONE of many factors
How does low-density cholesterol (LDL) and high-density cholesterol (HDL) affect atherogenesis?
- LDL: correlates
- HDL: protective
What are the major fixed risk factors for CHD?
- age – older
- gender – male
- family history – genetic defects that influence one’s ability to process lipids in its various forms
Why is CHD present more in males?
estrogen is protective because it has multiple beneficial effects on lipids (increases cholesterol removal by the liver) and vascular tone in addition to its antioxidant properties
- females catch up after menopause
What are the acquired (modifiable) risk factors for CHD? (5)
- hyperlipidemia – especially high cholesterol as shown by high LDL
- hypertension – accelerates development of atheroma and is more important than cholesterol after age 45, produces increased shear stress on vessel endothelium)
- diabetes – affects vascular endothelium and lipids
- obesity
- smoking – endothelial damage
- physical inactivity
- low HDL
- elevated TG
Are risk factors for CHD synergistic or additive?
synergistic
- 50% of atherosclerosis cannot be explained by standard risk factors (smoking, diet, lifestyle, and high cholesterol)
- large number of people who develop CHD have the same basic cholesterol numbers as those who do not
What are the functions of cholesterol? (3)
- critical component of cell membranes
- precursor of aldosterone (important in regulation of blood pressure)
- precursor of estrogens and androgens, testosterone
Where does the cholesterol we need come from?
- 75% produced within our bodies, mainly from the liver
- 25% from food
What is HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase?
key enzyme in the hepatic synthesis (major source of cholesterol) of cholesterol
What do hepatic LDL receptors do?
facilitate the clearance and uptake of plasma LDL cholesterol
- chief factor controlling plasma LDL levels
What happens when adequate cholesterol becomes available by receptor-mediated uptake?
rate of synthesis of LDL receptors is reduced and the critical enzyme (HMG CoA reductase) involved in cholesterol synthesis is inhibited
What are bile acids?
the main metabolites of cholesterol that are synthesized exclusively in the liver
Where is cholesterol and bile acids secreted?
secreted into the bile, and therefore into the intestine
How much cholesterol and bile are reabsorbed?
- 50% of cholesterol
- 97% of bile acids
- returned to liver in portal circulation
What are the 3 main factors that may induce a high plasma cholesterol concentration?
- diet rich in cholesterol, or excessive carbohydrates which may be converted to cholesterol
- physical inactivity or sedentary lifetyle
- genetic factors – ie. defect of LDL receptor
What are lipoproteins?
soluble complex macromolecules that carry lipids (cholesterol, triglycerides) that are not soluble in blood between gut, liver, and tissues
What are the 5 major types of lipoproteins?
- chylomicrons
- very low density lipoproteins (VLDL)
- intermediate-density lipoproteins (IDL)
- low-density lipoproteins (LDL)
- high-density lipoproteins (HDL)
What are chylomicrons?
carry exogenous dietary cholesterol and triglyceride (compound made of three fatty acids on glycerol backbone – makes up 80-90% of the lipoprotein) packaged in the intestine