Adipose Tissue Function: Endocrine Nature & its role in Pathology of Obesity Flashcards
why is adipose tissue said to define obesity (2)
- Heterogeneity- the diversity of people and their genetics
-obesity has many faces and can cause different co-morbidities in people.
-Even though 2 people may have the same BMI, some may come with pathological consequences, others may not. - Not all fat is the same (viscreal vs subcutaneous
How can 2 people have the same BMI but have different metabolic profiles?
the type of fat they store. One could have more subcutaneous fat (less health risk) and the other could be storing more viscreal fat (comes with more health risks)
what are adipokines
-proteins produced by fat cells/adipocytes that play a role in energy/metabolic status in the body (obesity, inflammation ect…)
adipokine functions (4)
- control appetite, fat storage & metabolism
- regulate BP
- modulate inflammation & immune response
- influence mood, cognition & stress response
name the 6 types of adipokines
- Resistin
- Leptin
- Adiponectin
- TNF-alpha
- IL-6 (interleukin 6)
- PAI-1 (plasminogen activator inhibitor-1)
define cytokine
a broad category of molecules or proteins that carry a messege.
-released by the lymphocytes & macrophages
how does adipokines help our understanding of the link between obesity and other pathologies?
as obese state level increases so does leptin, resistin, TNF-alpha, IL-6 & PAI-1 and the lean state levels decrease.
As adiponectin decreases in obese state, the lean state increases.
role of leptin in obesity (3)
-prevent lipotoxicity (lipid accumulation) in the peripheral tissues (pancreas, heart, liver…)
-exerts many metabolic and endocrine influences
-helps control appetite regulation and energy homeostasis
role of adiponectin (6)
-has effects on systemic inflammation, vascular function, cell growth, regulates glucose and fatty acid breakdown
-regulates sensitivity to insulin. (lower weight= more adiponectin, higher weight (dysfunctional adipose tissue)=less adiponectin)
-gluscose homeostasis
why is dysfunctional adipose tissue not good? (3)
-inhibits release of adiponectin
-decreased insulin sensitivity
-pro atherosclerosis & inflammatory
role of resistin
- produced and released from adipose to serve endocrine functions (insulin resistence)
-affects energy balance and metabolism
role of PAI-1
-precursor of plasmin (plasmin breaks apart fibrin/blood clots)
-vascular homeostasis
why is increased PAI-1 a problem?
less likely to break down blood clots (peripheral atherosclerosis), can lead to thrombosis
why is a chronic positive energy balance bad?
this means you take in more energy (eating) than you exert out (exercising)
-leads to expansion of adipose via hypertrophy & hyperplasia of adipose cells
where does fat go when there is an overflow of fat
-overflows into other tissues
-fat cells undergo mechanical stress & the inflammatory system kicks in
define ectopic fat
fat in an area where fat is not designed to be stored.
-could be around organs
how does adipose tissue define obesity (1)
- excess abdominal fat may be an indication of the inability of subcutaneous adipose to act as an ‘energy sink’ result in excess energy stores to accumulate in undesirable locations
describe the lipid overflow hypothesis (4)
- increase in energy intake, decrease in energy expenditure
- buffering of excess energy in healthy adipose tissue
- exhaustion of buffering capacity of adipose tissue
- lipid overflow into liver, muscle or epicardium, resulting in metabolic abnormalities
Why is ectopic fat accumulation a health hazard? (3)
- disruption of metabolic homeostasis (liver, muscle, pancreas)
- adverse effects on myocardial function
- Lipotoxicity at organ level (tissue damage & activates several inflammatory pathways including cell death & several types of cancer).
what adipokine is responsible for metabolic consequences of obesity?
cytokines released from the inflammatory environment
Adipose and inflammatory Process
- Immune system responds to distressed adipocytes & pro inflammatory markers rise (TNF-alpha, IL-6 & C-reactive protein)
- Excess adipose tissue causes abnormal cytokine production, increased CRP & activates pro inflammatory pathways
- Chronic low grade inflammation (insulin resistence=T2D, endothelial dysfuntion=CVD, dyslipidema=CVD, hypertension vascular inflammation=CVD).
Adipocytes synthesize & secrete which hormones (6)
- cytokines (TNF-1/IL-6)
- growth factors
- other immune system proteins
- PAI-1 (vascular homeostasis)
- angiotensinogen (regulates BP)
- adiponectin (regulates glucose homeostasis)
