L29 Flashcards
what do BMI measurements mean
underweight < 18.5
normal = 18.5 - 24.9
overweight = 25-29.9
obese > 30
stage 1 obesity = 30-34.9
stage 2 obesity = 35 - 39.9
extremely obese > 40
what is the % of BMI range in NZ
1% underweight
33% normal weight
35% overweight
31% obese
therefore 2 in 3 adults in NZ are overweight (66%)
what is waist circumference a measure of
adiposity
what do you need to have to be diagnosed with metabolic syndrome
you need to have 3 or more of the following
elevated. ….
- adiposity
- blood pressure
- blood glucose
- triglycerides
- decrease in HDL
what are the risk factors for extrinsic changes in the heat
volume expansion leading to increased CO and hypertension
increases cardiovascular tone from decreased NO
increased triglycerides and FFA (hypoadiponectinemia)
what are the risk factors risk factors
the main ones are altered substrate metabolism
- increased FA oxidation
- decreased glucose utilisation
- reduced cardiac efficiency
lipotoxicity and altered Ca dynamics in cardiomyocytes
what are the mechanisms contributing to cardiac dysfunction in obesity
- Hemodynamic load (volume expansion)
- Heart fat - conduction system
- Adipocytes - Adipokines - myocardial fibrosis
- Microangiopathy (micro = disease of the small vessels) - endothelial dysfunction
hemodynamic load and size relationship
Someone that is taller and bigger would have a larger heart which is the same for someone with obesity
why does an increase in body mass cause a increase in blood flow
because there is more tissue to be perfused
per 100g of excess body fat, how much does blood flow increase
2–3 mL/min/100 g
theefore 100 kg of excess body fat requires an extra 3 L/min blood flow
describe the CO for someone weighing 70kg, 120kg and 170 kg
Subject of 70 kg 6.0 L/min CO
Subject of 120 kg 7.5 L/min CO
Subject of 170 kg 9.0 L/min CO
what happens to hemodynamic load in obesity
Increased mass result in increase in preload (more filling)
Cardiac output increased (HR and SV increased)
TPR will decrease! (sole effect of volume increase, more tissue to perfuse)
therefore in obesity you have a High output - low resistance state - more body mass
in obesity you have a High output - low resistance state
why does having more body mass cause this to happen
People that are obese also have more sympathetic input to the hear to get it to beat more (because you need more perfusion)
what kind of cardiac remodeling happens with obesity
dilated cardiomyopathy, heart failure
caused by volume overload (eccentric remoderling)
describe how remodelling in the heart happens with obesity
you start out with volume overload causing the left side to become bigger (eccentric remodeling)
as the body mass increases it has consequences on many body systems. one of the things it causes is hypertension
hypertension causes pressure overload concentric remoderling of the heat
remoderling of the heart in obesity can be broken don into 2 processes
what are these
Primary
Volume overload
- LA and LV eccentric hypertrophy
Secondary
- Pressure overload
- LV concentric hypertrophy
what is important to note from cardiac remodelling in obesity
obesity is just volume overload ( primary)
it is the hypertension (that is caused by being obese) that causes pressure overload (secondary)
when does pressure overload happen with obesity
Mild obese with severe systemic hypertension
when does volume overload happen with obesity
Morbidly obese with mild systemic hypertension
describe fat in a healthy heart compared to an obese heart
In a healthy heart there is a little bit of fat on the outside. It is good that this is there as the heart prefers FFA for energy and it is there as a store for when you need it
In the obese situation the epicardial fat becomes thicker and starts to get into the myocardium
what is the difference between epicardial fat and pericardial fat
epicardial fat is good and pericardial is bad
epicardial is part of the heart and it the FFA storage
pericardial is in the pericardial sac (in between the layers) and epicardial
what happens when you get a severe amount of epicardial fat
deposition (thick layer of fat on the outside of the heart)
and infiltration (when fat enters the myocardium)
what does excess hart fat (deposition and infiltration) cause
- Mechanical impairment
- Thermoregulation (higher body core temperature)
- Cardiac conduction
- Endocrine effects (adipokines, cytokines)
what is heart fats effect on the conduction system
LV and RV hypertrophy
eccentric and concentric remodeling
Fatty infiltration in conduction system
Prolongation of QT interval (Fat insulates for temp and for electricity therefore the conduction system is slowed down. To effect conduction it depends where the fat infiltrates the heart)
Adipokines, cytokines release
the above can cause Sleep apnea - cardiac arrhythmias - sudden death
what is a fat cell made up of and what do they secrete
A fat cell is nothing more than a nucleus and lipid droplets for energy stores
The lipid droplet secrets factors called adipokines
what are some examples of adipokines
Leptin, Non-Esterified Fatty Acids (NEFA), TNF-α, IL-6, C-reactive protein, angiotensinogen, adiponectin, reactive oxygen species (ROS)
how does increased adipose tissue cause inflammation
Normally this release is not a lot and it is in balance with what is needed
When you increase your weight them more fat is being stored and the adipocytes will hypertrophy and become bigger. This causes them to secrete more
As they keep increasing then they will attract macrophages as they are no longer seen as a good thing therefore they causes an inflammatory response
other than a inflammatory response what else does an increase in insulin resistance cause
Insulin resistance/ Hyperinsulinemia
what is Hyperinsulinemia
Insulin resistance
how do adipokines cause fibrosis
With hypertension you get in increase in ECM structure causing an increase in fibrosis
Adipokines has effects on most cells including cardiomyocytes and fibroblasts therefore as a response to these adipokines you get cardiac remodeling of the ECM (outside of the myocardium) which causes collagen synthesis, changes in isoform and changes in cross linking which leads to fibrosis which leads to heart failure
what happens when you get adipocytes in the vasculature
When the animal is obese there is a clear difference
There is more fat cells which causes structural changes in the vasculature
the vesicle become not well arranged and they have different sizes at different parts of the vessel
fa the soround blood vessels is called…..
perivascular fat
in obesity what causes perivascular fat to become bigger
the more FFA they are exposed to the bigger they get
how does perivascular fat effect the blood vessels
He adipokines will effect the smooth muscle cells and the vasculature of the vessels
The effects of the adipose tissue is usually greater in the smaller vessels compared to in hypertension where it is usually greater in the larger vessels
why is this
adipose changes the balance between vasoconstriction (endothelin 1) and vasodilation (NO)
what is Microangiopathy
disease of the small vessels
what can Microangiopathy (disease of the small vessels) cause
- Retinopathy
- Nephropathy
- Neuropathy
what is the overall effect of obesity on cardiovascular pathophysiology
More fat = hypertrophy of adipocytes = more adipokines released which disrupts the balance which is bad
