Dislipidemias Flashcards
What is the changes in CVD prevalence in Canada in the last decade?
- 40% ↓ in mortality from CVD due to
- Improvements in control of CVD risk factors and medical management of patients with CVD, less invasive surgeries
- New clinical data available → may enhance prevention and management of CVD
- Despite these improvements, CVD remains a major societal burden - still very prevalent, but the mortality has decreased
Role of the Cardiovascular System
– Regulates blood flow to tissues
- Delivers oxygenated blood and nutrients
- Retrieves waste products
– Thermoregulation
– Hormone transport
– Maintenance of fluid volume
– Regulation of pH
– Gas exchange
Major Forms of Cardiovascular Disease
- Hypertension
- Atherosclerosis
- Coronary heart disease (CHD)- also know as cardiac disease-> affects artery of the heart
- Peripheral vascular disease
– Cerebrovascular disease (stroke)
– Deep vein thrombosis- mainly in the lower part of the leg
• Congestive heart failure- can lead to cardiac cachexia
Atherosclerosis definition
What does it result it?
Thickening of the blood vessel walls caused by presence of atherosclerotic plaque – Results in restriction of blood flow
What are the conditions associated with Atherosclerosis
- Myocardial infarction (MI)- clot in the artery, or just restricted artery
- Cerebrovascular accident (CVA; stroke)
- Peripheral vascular disease (PVD)
- Coronary heart disease (CHD)
- Congestive heart failure (CHF) when severe CHD or MI occurs
Atherosclerosis – Pathophysiology
- Complex and incompletely understood process
- Involves endothelial cells, smooth muscle cells, platelets, and leukocytes
- Begins as a response to endothelial lining injury that results in an inflammatory process
- Results in restriction of arterial blood flow
When do the symptoms of Atherosclerosis develop?
Asymptomatic until it progresses to ischemic heart disease
What are the steps of Formation of the atherosclerotic plaque
increase in LDL to HLD ratio-> increased risk of atherosclerosis LDL particles bind to LDL receptors in the epithelial cells
Superoxide anion will act upon trapped LDL monocytes contact with arterial wall and monocyte enters the sub-endothelial space
‘Monocytes differentiate into macrophages and take up oxidized LDL-> intracellular accumulation of cholesterol and foam cell formation
Macrophages activate T cell which produce inflammatory chemicals-> increased inflammatory responses
Cytokines are also being released-> more inflammation
Growth factors attract smooth muscle cells
Smooth muscles cells migrate to the sub-endothelial cells and differentiate
Free cholesterol is released into entima
Cytokines stimulate smooth muscle cell proliferation and collagen is made-> fibrous gap
Smooth muscle cells can accumulate lipids and can turn int smooth muscle derived foam cells -> plaque blood vessels grow into the plaque
Calcium salts are attracted to the plaque, leading to calcification and hardening of the plaque
This plaque cna then rapture and release it’s contents-> can lead to thrombosis
Potential primary causes of atherogenesis
- High blood pressure
- Chemicals from tobacco
- Oxidized LDL
- Glycated proteins-
!!chronic!! hyperglycaemia such as in Diabetes e.g. glycated Hb; these glyctaed proteins induce stress on arterial walls
- Decreased nitric oxide (NO)- NO is produced within our cells and has vasodilation effect less No-> smaller arterial radius
- Angiotensin II- causes vasoconstriction all these factors can lead to Damage to the endothelial wall
What is a biochemical biomarker of atherosclerosis? What are the levels?
CRP is a biomarker fo atherosclerosis; people with CVD have slightly elevated values of CRP (low grade inflammation): below 10, more than 3-> different from acute inflammation
Atherosclerosis – Risk Factors
A lot overlap with HTN •
Risk factors have an additive effect
- Family history - Especially a first-degree relative — a parent, sibling or child — who experienced a heart attack or stroke or developed peripheral artery disease at a relatively young age
- Age and sex – More prevalent over the age of 65 and in men - estrogen is protective against atherosclerosis - post-meonpausal women show increase in CVD occurence
- Obesity – Positively associated with dyslipidemia, hypertension, physical inactivity, and diabetes
- Hypertension – May initiate an atherosclerotic lesion – Can also cause plaque to rupture
- Physical inactivity (can be reversed)
- Diabetes mellitus
- Impaired fasting glucose/metabolic syndrome (aka pre-diabetes)
- Cigarette smoke
- Obstructive sleep apnea as there’s a lack of oxygen being delivered to cells and cause endothelial damage
What is the age/sex demographic that experiences hihger risk of CVD?
More prevalent over the age of 65 and in men
What is obesity associated with such that there’s increased risk of atherosclerosss?
Positively associated with dyslipidemia, hypertension, physical inactivity, and diabetes
How is atheroscleorsis connected with hypertension?
Hypertension may initiate an atherosclerotic lesion
– Can also cause plaque to rupture
how is Obstructive sleep apnea connected to atherosclerosis?
less oxygen in developed to cells-> can result in cell damage
Major risk factors for atherosclerosis- organized by non-reversible/reversible characteristic
WHat are the cut-offs for low HDL-C levels?
Can they be reversed?
<1.0 mmol/L men
<1.3 mmol/L women
Can be reversed
Where can chylomcirons be formed and what do they contain?
Can be formed by the intestinal cells only
Carriers of ingested fat
What are chylomicrons made of?
Chylomicrons: the core is mostly TG, some CE and non-esterified cholesterol on the surface of the chylomicron
Surface of all lipoproteins is made of _-
Surface of all lipoproteins is made of phospholipids
Where are chylomicrons released into?
lymph, not blood!!
What is the role of LPL and where is it found?
on the lining of our vessels we have LPL-> will hydrolyze TG into FA and glycerol to be taken up by the cells (mainly taken up by adipose cells)
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Whtat happens to the chylomicron as it circualtes around the body?
It’s TGs content gradually gets depleted by LPL-> > chylomicron remnant will have less TG in proportion to more of cholesterol esters
What is the activator LPL?
ApoC-II
What will occur to the chylomicron remnant in the end? WHat is the next step?
will be taken up by the liver and degraded
TGS from the diet and endogenous sources will be repackaged into VLDL
What are the sources of TGs in VLDL
both exogenous and endogenous
Chylomicron vs VLDL
Chylomicrons and VLDL particles each contain surface apolipoprotein-B (apoB). Chylomicrons are assembled primarily in the intestine and contain a smaller version, apoB-48, whereas VLDL particles contain the larger apoB-100 surface protein and are primarily assembled in the liver.
Chylomicrons only have exogneous fats; VLDL as both enogenous and exogenous
What happens to VLDL as it circulates
VLDL will circulate into tissues, will exchange with HDL (cholesterol from HDL, TGs to HDL)
LPL will be activated by ApoC-II on the VLDL-> hydrolysis of TGs occurs-> FA are taken up by tissues
VLDL remnant will be created -> less TGs, more CE (similar to chylomicrons)
VLLD receptors found in the liver and other tissues (e.g. endothelium) will recognize this VLDL remnant, and will take it up
What are the 2 fates of VLDL?
- Most of circulating VLDL will be picked up by the receptors through the recognition of ApoE
- The rest will be recognized by hepatic lipase found in the liver-> will continue to degrade TGs in the core of VLDL remnant-> LDL will be created (has mostly cholesterol esters, vert little TGs)
__ is responsible for the inverse transport of cholesterol - from tissue to liver
HDL is responsible for the inverse transport of cholesterol - from tissue to liver
maturation of HDL:
When they are secreted, they are secreted as nascent HLD- not a globular particle yet-> have an empty core- phospholipid layer wiith ApoA-I and ApoE attached to it
as it circulates-> will accumulate cholesterol in the core
Cholesterol will Be esterified in CE by LCAT-> will become a globular HDL2 particle
WHat is CETP and it’s function?
CETP (cholesterol ester transfer) step
Cholesterol-ester transfer protein - will transfer CE from HDL to VLDL; TGs from VLDL to HDL
LPL results in chylomicron remnants
__ results in chylomicron remnants
Overview of Endogenous and Exogenous Cholesterol Transport
LDL can be picked up by __
LDL can be picked up by both liver and extra-hepatic tissues
Characteristics of chylomicrons
Lipid type + apo proteins
- More TG in the core,
- B-48, E, A-I, A-IV, C-II, C-III
Characteristics of VLDL
Lipid type + apo proteins
- B-100, E, C
- More TG
Characteristics of LDL
Lipid type + apo proteins
- Mostly CE
- B-100
Characteristics of HDL
Lipid type + apo proteins
- mostly PL, CE
- A-I, A-II, C, E
Cut-offs for normal total cholesterol levels
< 5.2 mmol/L
Cut-offs for normal HDL-C levels
The higher the better (has protective properties)
1-1.5 mmol/l
>1.0 men
>1.3 women- women tend to have higher levels of HDL->thus higher recommendations
Cut-offs for normal LDL-C levels
<2.6 mmol/L
Cut-offs for normal TG levels
<1.7 mmol/L
Which components are measured in Plasma Lipoprotein levels lab tests
these 4 are obtained in routine measurements for lipid profiles
Total cholesterol
LDL
HDL
TG
Apoproteins: Functions
Synthesis/secretion of specific lipoproteins
Stabilize surface coat of lipoproteins
Activate enzymes (e.g. apo C-II activates LPL)
Interact with cell surface receptors (B-100 and LDL receptors)
What is the primary determinant of metabolci fate of lipoproteisn
apoproteins
What are the aporproteins serve as markers/diagnostics of?
- Reflect changes in lipoprotein composition
- Indicative of # of lipoproteins in plasma (concentration)
- Apoprotein levels maybe better predictors of heart disease than lipid levels and may correlate with the severity of the disease
- Aid in diagnostic of lipoprotein disorders and risk for developing CHD or CVD
which market is now being used to measure lipid profile?
ApoB
Relative frequency of genotypes of Apo-E
ApoE has different has 3 allleles
ApoE 2 is the least common, ApoE 3 is the most common
What is the influence of Apo E-2/E-2 on VLDL?
Apo E-2/E-2 does not bind to LDL receptorsà↑ VLDL remnants
marker of increased risk of displipidemia as ApoE-II cannot bind to LDL receptor-> VLDL that has ApoE-II will remain in the circulation-> resultign in high levels of VLDL in the circulation
ApoE-4 is associated with an increased risk of_
ApoE-4 is associated with an increased risk of Alzheimer
What are the 2 categories of Dyslipidemia Classification?
primary and secondary
Primary vs secondary dislipidemia causes
Primary: single or poly-genetic abnormalities affecting lipoprotein function resulting in hyperlipidemia or hypolipidemia
Secondary: environmental causes +/- predisposition
Primary vs secondary dislipidemia- which is more common?
secondary
Primary vs secondary dislipidemia- when do they occur?
primary -> happens early in life (due to genetic bases)
secondary -> happens later in life
What is diagnosis of primary dyslipidemia based on?
• History (age at onset, family members,…)
- Physical signs (e.g. xanthomas- happen mostly at joints and elbows )
- Lab analysis: lipid profile, apoproteins, LPL activity
- Appearance of serum
- Genetic sequencing for rare cases
Synonym for pirmary Dyslipidemias
Familial
Name hypolipoproteinemias
– Abetalipoproteinemia
– Familial hypobetalipoproteinemia
– Familial alpha-lipoprotein deficiency (Tangier disease)
Describe Abetalipoproteinemia
- Defect in apoprotein B synthesis-> no ApoB is made
- No chylo, VLDL, LDL formed and TGs accumulate in liver and intestine
Describe Familial hypobetalipoproteinemia
some ApoB is made, but lower than needed-> Lower LDL levels
• LDL concentration is 10-50% of normal but chylomicron formation occurs
Describe Familial alpha-lipoprotein deficiency (Tangier disease)
- Virtual absence of HDL (Apo-AI), CE accumulate in tissues
- Chylo, VLDL, LDL are all normal
- Moderate hyperTG
Are Hyperlipoproteinemias or Hyporlipoproteinemias more common
Hyperlipoproteinemias
I-
- Name
- CVD risk-
- Main lipoprotein affected
- Serum lipids-
- Main symptoms-
- Specific marker-
- Hyperchylomicronemia
- CVD risk- 0
- Main lipoprotein affected- Chylomicrons (↑ chylo fasting)
- Serum lipids- ↑↑ TG (>11 mM vs the norm of ,1.7mmol/L), ↓HDL-C
- Main symptoms- early, skin xanthomas, pancreatitis, lipemia retinalis, hepatosplenomegaly
- Specific marker- absence or deficiency of LPL or apo C-II
IIa –name
- CVD risk-
- Main lipoprotein affected-
- Serum lipids-
- Main symptoms-
- Specific marker-
- Hypercholesterolemia
- CVD risk- +
- Main lipoprotein affected- ↑LDL-C TG: N or H
- Serum lipids- high LDL
- Main symptoms- vascular diseases xanthelasma (eye)
- Specific marker- Mutation of LDL receptor or polygenic
IIb –name
- CVD risk-
- Main lipoprotein affected-
- Serum lipids-
- Main symptoms-
- Specific marker-
- Combined hyperlipoproteinemia
- CVD risk- +++
- Main lipoprotein affected- ↑LDL and VLDL ↑apo-B
- Serum lipids- ↑Chol (8-15 mM) and ↑TG (2-11 mM); ↓HDL-C
- Main symptoms- Variable, vascular diseases
- Specific marker- Mutation of LDL receptor or apo B
III –name
- CVD risk-
- Main lipoprotein affected-
- Serum lipids-
- Main symptoms-
- Specific marker-
- Dysbetalipoproteinemia
- CVD risk- +++
- Main lipoprotein affected- ↑ b-VLDL; ↑LDL and VLDL
- Serum lipids- ↑Chol (by a lot) and ↑TG (significant increase); ↓HDL-C
- Main symptoms- Tuberoeruptive and palmar xanthomas
- Specific marker- Apo E2/E2
IV –name
- CVD risk-
- Main lipoprotein affected-
- Serum lipids-
- Main symptoms-
- Specific marker-
- Hypertriglyceridemia
- CVD risk- +
- Main lipoprotein affected- High VLDL
- Serum lipids- ↑TG (4.5-11 mM) ↓HDL-C
- Main symptoms- Similar to I; Exacerbated by alcool and diabetes
- Specific marker-
V-name
CVD risk-
Main lipoprotein affected-
Serum lipids-
Main symptoms-
Specific marker-
- mixed hyperlipidemia
- CVD risk- n/a
- Main lipoprotein affected- high VLDL and chylomicrons
- Serum lipids- ↑↑TG (very hihg); ↓HDL-C
- Main symptoms- Similar to I; Exacerbated by alcool and diabetes
- Specific marker-serum aspect: chylo band over VLDL
Serum patterns of hyperlipoproteinemia
I- Hyperchylomicronemia (lot’s of chylomicrons)-> band of TGs, milky appearance
IIA high LDL, less TGs- normal looking serum
IIB- TGs accumulation from high VLDL-> pale colour
III- Beta VLDL accumulation causes white band due to TGs; also a paler color
IV- mixed typed, high VLDL -> white
V- white-> mixture of VLDL and chylomicron
Secondary dyslipidemia may exacerbate __
• May exacerbate primary dyslipidemia
Effects on Tot-Chol, LDL-C, HDL-C, TG
of a diet high in CH
Increased Tot-Chol,
Increased LDL-C,
Same HDL-C
Effects on Tot-Chol, LDL-C, HDL-C, TG
of a diet high in saturated fat
Inceased Tot-Chol,
Icnreased LDL-C,
Increased HDL-C- that’s why saturated fats are actually not that critically bad
TG-> same
Effects on Tot-Chol, LDL-C, HDL-C, TG
of a diet high in trans fat
Increased Tot-Chol,
Increased LDL-C,
Decreased HDL-C
TG-> same
Effects on Tot-Chol, LDL-C, HDL-C, TG
of a diet high in sugars
Same total CH and LDL-C
Decreased HDL-C
Inceased TG
Effects of alcohol, smoking and lack of physical activity n lipid profiles
Alcohol increases HDL-C and TG
Smoking- increases or doesn’t affect Tot CH and LDL-C, but decreases HDL-C
Physical inactivity decreases HDL-C and increased TG
Effects of diabetes, hypothyrodism, renal failure, obesity, choleastasis, cirrhosis, myelomas, cushings sndrome on lipid profiles
- increase total Chol is increased by diseases , but have varied effects of HLD and LDL
- All diseases increase Total CH, but have different impacts on HDL and LDL
- mostly increase TG
- mostly decrease HDL
- Cushing’s, hypothyroidism and diabetes increase LDL-C, which is the most atherogenic-> will increase the risk of CVD
Effects of
thiazide diuretics, beta-blockers, corticosteroids, estrogens, progesterone, benzodiazepine, retinoic acid, antiretroviral drugs on lipid profiles
Most of the drugs, apart form progesterone increase TG
Thiazide diuretics elevate all the markers, but maybe HDL-C ( can either elevate or leave unchanged)
Retinoic acid increase all the markers, but HDL-C (it decreases HDL-C)
Corticosteroids elevate all the markers
Estrogens increase HDL-C and TG and lower the others
Why is there an increased substrate flux to the liver in both postprandial and postabsortive states in obesity
Postprandial:
- Due to excess calories (lipids and carbohydrates)
- Most commonly there’s an increased substrate flux to liver observed in obese individuals as people with excess weight tend to eat more, especially CHO and fat
Postabsorptive
- Due to high adipose tissue and hormone-sensitive lipase (HSL) activity (because of insulin resistance) resulting in increased FFA flux to liver (situation of insulin resistance is commonly seen in obesity)
Affect of alcohol on TG is nthe circulation
when ethanol is present-> excess alcohol-> blockage of oxidation of Acyl-Coa-> promotion of conversion of Acyl-CoA into TGs-> increases TGs in circulation due to alcohol presence
What are the 3 intake factors that need to be regualted in individuals with dislipidemia
diet high in sugar, fat and alcohol contributes to TGs elevation in circulation
to manage lipid levels-> manage these factors
What hapens when there’s excess fatty acid and CHO intake and how can it lead to Hypertriglyceridemia of Obesity
having excess fatty acid and CHO coming to the liver-> will lead to excess LDL production
this results in more lipolysis by LPL and uptake of TGs into tissues and their storage->
increase in fat and body weight
if increased lipolysis levels by the liver equal to increased level of fat production, LDL levels can still be normal
thus not all obese people will have elevated LDL levels (this is still however accompanied by higher fat stores)
Hypercholesterolemia of Obesity:
- The increase in overproduciton is higher than the chnages in lipolysis (absence of lypolitic effect)
this can be due to e.g. problems with LPL-> no lipolytic effect on VLDL and TGs-> accumulation of LDL and TGs in the circulation
2.
Hypercholesterolemia of Obesity
starts with excess total calories (either from fat or sugar)-> overproduction of VLDL
increase in lipolysis, creating VLDL remnant and being converted into LDL
the problem is at the uptake of LDL particles due to reduced activity of LDL receptors-> LDL accumulation
there are many reasons for them to be effected: e.g. diet high in saturated fat and CH
results in VLDL particle accumulation in the circulation -> Higher LDL-C
Possible mechanisms for HDL-cholesterol lowering in obesity
this has to do with higher production of VLDL-TG and increased transfer of CH form HDL to VLDL; and increase TG transport from VLDL to HDL
This results in a decrease in HDL-C
this will result in an increased catabolism of HDL by excess adipose tissue and increased uptake by the liver-> decreased HDL levels
Both the severity (high BMI) and distribution (abdominal) obesity are associated with low __
Both the severity (high BMI) and distribution (abdominal) obesity are associated with low HDL-C
The connection of BMI and HDL-C/LDL connection
– Inverse linear relationship between BMI and HDL
– Stronger association of BMI with HDL than LDL
Abdominal fat/totoal fat and HLD connection
– Stronger association with HDL than total body fat
– Stronger association in men and post-menopausal women: as accumulation of visceral fat is mostly seen in men and PM women
• e.g. 5 times more likely to have low HDL with high visceral fat
Possible mechanisms of reduced HDL-C in obesity
– Association with hyperTG:
More VLDL-> more transfer of CE from HDL; TG from VLDL ->
HDL will become richer in TGs than CE-> this will trigger hepatic lipase (which usually recognizes VLDL)-> will recognize TG-rich HDL and hydrolyse those TG-> this will stimulate HDL particle uptake by the liver-> decreased HDL levels
But not the only mechanism, also:
– ↑ uptake of HDL2 by adipocytes
– ↑ clearance of apolipoprotein A-1-> HDL catabolism
Who to screen?