Adipose Tissue Function: Endocrine Nature & its role in Pathology of Obesity

Question 1

why is adipose tissue said to define obesity (2)

Answer 1

1. 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.
2. Not all fat is the same (viscreal vs subcutaneous

Question 2

How can 2 people have the same BMI but have different metabolic profiles?

Answer 2

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)

Question 3

what are adipokines

Answer 3

-proteins produced by fat cells/adipocytes that play a role in energy/metabolic status in the body (obesity, inflammation ect…)

Question 4

adipokine functions (4)

Answer 4

1. control appetite, fat storage & metabolism
2. regulate BP
3. modulate inflammation & immune response
4. influence mood, cognition & stress response

Question 5

name the 6 types of adipokines

Answer 5

1. Resistin
2. Leptin
3. Adiponectin
4. TNF-alpha
5. IL-6 (interleukin 6)
6. PAI-1 (plasminogen activator inhibitor-1)

Question 6

define cytokine

Answer 6

a broad category of molecules or proteins that carry a messege.
-released by the lymphocytes & macrophages

Question 7

how does adipokines help our understanding of the link between obesity and other pathologies?

Answer 7

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.

Question 8

role of leptin in obesity

Answer 8

-prevent lipotoxicity (lipid accumulation) in the peripheral tissues (pancreas, heart, liver…)
-exerts many metabolic and endocrine influences
-helps control appetite regulation and energy homeostasis

Question 9

role of adiponectin

Answer 9

-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

Question 10

why is dysfunctional adipose tissue not good?

Answer 10

-inhibits release of adiponectin
-decreased insulin sensitivity
-pro atherosclerosis & inflammatory

Question 11

role of resistin

Answer 11

• produced and released from adipose to serve endocrine functions (insulin resistence)
  -affects energy balance and metabolism

Question 12

role of PAI-1

Answer 12

-precursor of plasmin (plasmin breaks apart fibrin/blood clots)
-vascular homeostasis

Question 13

why is increased PAI-1 a problem?

Answer 13

less likely to break down blood clots (peripheral atherosclerosis), can lead to thrombosis

Question 14

why is a chronic positive energy balance bad?

Answer 14

this means you take in more energy (eating) than you exert out (exercising)
-leads to expansion of adipose via hypertrophy & hyperplasia of adipose cells

Question 15

where does fat go when there is an overflow of fat

Answer 15

-overflows into other tissues
-fat cells undergo mechanical stress & the inflammatory system kicks in

Question 16

define ectopic fat

Answer 16

fat in an area where fat is not designed to be stored.
-could be around organs

Question 17

how does adipose tissue define obesity (1)

Answer 17

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

Question 18

describe the lipid overflow hypothesis

Answer 18

1. increase in energy intake, decrease in energy expenditure
2. buffering of excess energy in healthy adipose tissue
3. exhaustion of buffering capacity of adipose tissue
4. lipid overflow into liver, muscle or epicardium, resulting in metabolic abnormalities

Question 19

Why is ectopic fat accumulation a health hazard? (3)

Answer 19

1. disruption of metabolic homeostasis (liver, muscle, pancreas)
2. adverse effects on myocardial function
3. Lipotoxicity at organ level (tissue damage & activates several inflammatory pathways including cell death & several types of cancer).

Question 20

what adipokine is responsible for metabolic consequences of obesity?

Answer 20

cytokines released from the inflammatory environment

Question 21

Adipose and inflammatory Process

Answer 21

1. Immune system responds to distressed adipocytes & pro inflammatory markers rise (TNF-alpha, IL-6 & C-reactive protein)
2. Excess adipose tissue causes abnormal cytokine production, increased CRP & activates pro inflammatory pathways
3. Chronic low grade inflammation (insulin resistence=T2D, endothelial dysfuntion=CVD, dyslipidema=CVD, hypertension vascular inflammation=CVD).

Question 22

Adipocytes synthesize & secrete which hormones (6)

Answer 22

1. cytokines (TNF-1/IL-6)
2. growth factors
3. other immune system proteins
4. PAI-1 (vascular homeostasis)
5. angiotensinogen (regulates BP)
6. adiponectin (regulates glucose homeostasis)