HRR: adipose tissue

Question 1

Describe the components of adipose tissue

Answer 1

A loose connective tissue consisting of adipocytes, resident M2 macrophages, vascular endothelial cells, T cells, and fibroblasts

Question 2

What are the two types of adipose tissue

Answer 2

White and brown

Question 3

What are the functions of white adipose tissue

Answer 3

To store energy and endocrine functioning

Question 4

What is the main function of brown adipose tissue

Answer 4

Generate body heat

Question 5

Which adipose tissue has more capillaries

Answer 5

Brown

Question 6

What is the structure of white adipose tissue

Answer 6

Unilocular with large lipid droplets (1 per cell)

Question 7

What is the structure of brown adipose tissue

Answer 7

Multilocular with many lipid droplets per cell

Question 8

Where is white adipose tissue found

Answer 8

As subcutaneous and visceral fat in the intra-abdominal cavities

Question 9

Where do we find brown adipose tissue

Answer 9

It is mostly found in infants, but in adults, it is cervical, supraclavicular, and paravertebral regions

Question 10

Describe hypertrophy of adipocytes

Answer 10

Increased size of tissue due to lipogenesis or excess TG accumulation

Question 11

Describe hyperplasia of adipocytes

Answer 11

Increase in the number of adipocytes due to adipogenesis via proliferation and differentiation

Question 12

What can happen as with adipocyte hyperplasia in obesity

Answer 12

The adipocytes may start to undergo necrosis due to a lack of blood supply

Question 13

What apolipoproteins do chylomicrons pick up in circulation

Answer 13

ApoCII and ApoE

Question 14

Describe how adipose tissue gains FA from chylomicrons

Answer 14

ApoCII on the chylomicron interacts with LPL from the adipose tissue. This causes the ApoCII to signal breakdown of the TGs within the chylomicron, forming glycerol and FA. The FA will enter adipose tissue, and the glycerol and chylomicron remnants return to the liver

Question 15

TG made in the liver is transported via…

Answer 15

VLDL

Question 16

How do we get the glycerol backbone needed to resynthesis TG in adipose tissue

Answer 16

Glucose! Glucose is converted to G3P, which converts to glycerol and combines with FAcoA to form TG

Question 17

What signals mobilization of stored TG

Answer 17

Glucagon and epinephrine

Question 18

What is the secondary messenger used by glucagon and epinephrine to release FA from adipocytes

Answer 18

cAMP/PKA

Question 19

What proteins in adipocytes are activated by PKA

Answer 19

Perilipin and hormone-sensitive lipase

Question 20

Describe how glucagon/epinephrine lead to FA entering the blood

Answer 20

They bind to a G2 receptors on the surface of the adipocyte, leading to cAMP release and PKA activation. PKA activates hormone sensitive lipase and perilipin, leading to TG stored in the lipid droplet to convert to FA and enter the cytosol of the adipocyte. The FA then transfers into the bloodstream and is carried by albumin until it reaches its next destination for use

Question 21

What are some consequences of elevated free fatty acids

Answer 21

1. Inhibited glycogen synthesis
2. Reduced insulin sensitivity
3. Increases glycogenolysis even though it may not be needed
4. May be involved in inflammatory processes that promote coronary artery disease
   All of these may be a future predictor of T2DM

Question 22

What can induce browning of white adipose tissue

Answer 22

A cold environment; it is an adaptive process

Question 23

What transcription factors are involved in beiging of white adipose tissue

Answer 23

PPARy, PRDM16, EBF2, PGC1-a

Question 24

What does UCP1 do

Answer 24

It uncouples the ETC from ATP synthase in brown adipocytes. It brings protons from the intermembrane space into the matrix, allowing the energy to be released as heat instead of using it to make ATP

Question 25

What does UCP1 do to O2 consumption and oxidation of NADH

Answer 25

Increases both

Question 26

How does adipose tissue serve as an endocrine function

Answer 26

Releases sex steroids, adipokines, and other hormones

Question 27

What is leptin

Answer 27

Secreted by adipocytes and mediates/controls appetite. It may also act as an inflammatory cytokine and may decrease insulin secretion

Question 28

What happens without leptin

Answer 28

We eat uncontrollably and gain weight

Question 29

Why does leptin therapy not aid in diet-induced obesity

Answer 29

A lot of times, those who are obese secrete higher levels of leptin. As such, they may develop leptin resistance causing the brain to not properly receive the satiety signal

Question 30

What is adiponectin

Answer 30

It plays a role in regulating blood glucose, lipid metabolism, and increases insulin sensitivity. It may decrease inflammation and apoptosis. This is kind of considered the good one.

Question 31

What kind of tissue is adiponectin highest in

Answer 31

Lean tissue (subq fat); decreases as adiposity increases

Question 32

Describe why we’d see TNF-a in adipose tissue

Answer 32

As adipocytes necrose, more M1 macrophages are recruited. These macrophages secrete high levels of TNF-a

Question 33

Describe IL-6 in adipose tissue

Answer 33

It is secreted by the tissue and stimulates lipolysis/VLDL secretion, decreases adiponectin, and attenuates insulin sensitivity in the liver

Question 34

What cytokine decreases adiponectin expression

Answer 34

IL-6

Question 35

What is resistin

Answer 35

It is secreted by M1 macrophages recruited to adipose tissue that promotes inflammation and enhances insulin resistance and oxidative stress by increasing NFkB transcription

Question 36

What is plasminogen activation inhibitor 1

Answer 36

It inhibits tissue plasminogen activator and urokinase, increasing clotting, atherosclerosis, insulin resistance. Increases risk of MI or stroke

Question 37

Compare pathological features of subq and visceral fat

Answer 37

Subq fat does not tend to undergo necrosis in the way visceral fat does. Meaning it has resident M2 macrophages that release anti-inflammatory molecules like adiponectin. Visceral fat is more likely to undergo necrosis, causing the recruitment of M1 macrophages that release inflammatory adipokines and reduce secretion of anti-inflammatory adipokines. This may lead to syndromes like T2DM, CVD, and other metabolic issues.

Question 38

What are the 3 mechanisms linking adiposity to insulin resistance

Answer 38

1. FFAs inhibit glucose uptake and glycogen synthesis 2. FFAs increase glycogenolysis 3. TNFa signaling inhibits IRS proteins downstream of the insulin receptor