Biology of Obesity: Adipose Tissue Function

Question 1

What determines the number of fat cells & their distribution

Answer 1

Genetics

Question 2

When does they number of fat cells stay set?

Answer 2

In adulthood.
Can increase in number, but once developed stay forever.

Question 3

Can you reduce they number of fat cells in your body?

Answer 3

No, you can shrink the cells but not decrease the number of them.

Question 4

define cellulite

Answer 4

Fat deposited beneath the skin
Due to genetic deposition

Question 5

functions of adipose tissue (7)

Answer 5

1. cell membrane (structure/flexibility)
2. energy production/energy reserve
3. lipoproteins (transport & deliver)
4. organ protection
5. thermal regulation
6. carrier for vitamins (ADEK)
7. nerve insulation

Question 6

where is fat stored

Answer 6

adipocytes, released when needed

Question 7

how is fat stored inside of adipose

Answer 7

Triglyceride/triacylglycerol

Question 8

What happens when energy is low

Answer 8

• insulin drops, epinephrine rises
  -epiniphrine binds to the adipocyte and causes lipolysis
  -increase in energy demand, the fatty acids and glycerol can leave the adipocyte and enter the blood
  -uptake and oxidation in tissues (sk. muscle tissue) generate energy to meet increased demand

Question 9

What happens after eating

Answer 9

-insulin keeps the fatty acids inside the adipocyte
-if eating frequently, and consume foods higher in carbohydrate then insulin levels stay high

Question 10

what are the 2 types of adipose tissue

Answer 10

1. white adipose tissue (WAT)-energy storing
2. brown adipose tissue (BAT)- energy burning

Question 11

amount and distribution of adipose tissue depends on what (3)

Answer 11

age, species, biological sex

Question 12

characteristics and function of brown adipose tissue (3)

Answer 12

-many mitchocondrial (produce heat thermogenisis)
-more blood vessels (give colour)
-more metabolically active (relative to white)

Question 13

who tends to have BAT opposed to WAT

Answer 13

infants, slender and younger women.
Lower amount in people with increased BMI & increased BF%

Question 14

characteristics & function of WAT (4)

Answer 14

-actually yellow
-primary site for energy storage and release of hormones that modulate metabolism and insulin resistance
-provides cushioning & insulation
-subcutaneous and viscreal

Question 15

characteristics & function of subcutaneous adipose tissue (SCAT) 4

Answer 15

-located just under the skin throughout the body
-represent the majority of our total body fat mass
-main source of energy
-general indication od substrate availibility for physical work. When depot becomes full fat must be stored eslewhere

Question 16

characteristics & function of viscreal adipose tissue (VAT) 4

Answer 16

-located in and around viscreal organs
-stored fat as a result of SCAT depots being full
-genetics play a role in fat distribution patterns
-fat in this area is pro inflammatory

Question 17

how does adipose tissue regulate metabolism

Answer 17

secretes hormones that are signals percieved by the brain as important indicators of energy stores (impacts appetite, food intake, nutrient absorption & energy expenditure)

Question 18

what is caloric intake controlled by

Answer 18

appetite (hypothalamus)

Question 19

what is calorie use controlled by

Answer 19

metabolic rate (thyroid hormones/ physical activity levels)

Question 20

where are calories stored

Answer 20

adipose tissue

Question 21

what is the role of the hypothalamus

Answer 21

directs bodily functions; the brains control centre for energy balance

Question 22

define hedonic & homeostatic hunger

Answer 22

homeostatic- physical ques of hunger
hedonic- hunger from external ques (social/emotional/environmental/situational)

Question 23

define appetite, satiety & satiation

Answer 23

appetite- desire for particualr food
satiety- feeling of being full after eating
satiation- feeling satisfied after eating

Question 24

what happens during homeostatic regulation

Answer 24

-hypothalamus recieves signals from periphery
-input from GI, brain & adipokines
-output via motor neurons to GI, etc.
-this stimulates/inhibits hormone release from various areas of the body

Question 25

hormones that stimulate feeding

Answer 25

-Ghrelin- released mainly from stomach. peaks before a meal. Stimulates appetite and eating -Glucagon- Released from pancreas when blood glucose falls, indirectly activates feeding (glucagon increases, insulisn decreases and vice versa)

Question 26

what 2 effects happen during short term regulation of food intake

Answer 26

1. GI filling inhibits feeding -distended stomach, stimulates stretch receptors, vagus nerve send inhibitory signals to hypothalamus to suppress feeding centres= reduced appetite 2. Food in mouth signals oral receptors, signals to hypothalamus= reduced appetite (less intense & shorter than GI filling)

Question 27

what hormones suppress appetite (3). Where to they secrete from and what macronutrient stimulates their release?

Answer 27

1. Cholecystokinin(CCK): released from duodenum in response to fats & proteins. Cause hypothalamus to reduce appetite. 2. Glucagon like peptide 1 (GLP-1): Released from lower small bowel in response to carbohydrates. Stimulates insulin release. Lowers glucagon. 3. Insulin: Released from pancreas when blood glucose rises.

Question 28

what regulates long term regulation of food intake (2)

Answer 28

1. Nutrients- more glucose, AA, fatty acids available= decreased appetite 2. temperature regulation- cold= increased feeding, mediated by metabolic rate

Question 29

feedback signals of long term (intermediate) regulation of food intake

Answer 29

- decreased blood glucose=increased appetite -increased blood letoacids, signals hypothalamus satiety centre increases feeling of fullness -adipose secretes hormones= more leptin released from adipose tisse to blood -leptin binds to receptors in hypothalamus to suppress appetite and food intake and decrease insulin release from pancreas

Question 30

What is leptin & its function

Answer 30

-hormone released from adipocytes -regulates processes relevant to energy homeostasis (food intake, energy expenditure, activity, reproductive functions) -role in defending against excessive body fat. -extreme obesity happens when they fail to excrete leptin/don't express the leptin receptor

Question 31

what does leptin do in short term and long term body weight regulation? (starvation & increased energy)

Answer 31

starvation: loss of body fat, adipose is critically low, decrease in leptin results in increase of food intake and decrease in EE/cessation of reproductive function & somatic growth to conserve energy consumption: increased energy consumption and accumulation of body fat stores, leptin increases with subsequent decrease in food and increase in sympathetic NS, tone & EE

Question 32

Role of leptin in body weight regulation

Answer 32

tells the brain how much fuel in reserve -as BMI/body weight drops so does leptin

Question 33

what happens with leptin deficency

Answer 33

Mice & Humans- hyperphagia (abnormally excessive eating- very rare in humans), obesity, impaired thermogenisis, hyperinsulinemia, hyperlipidemia. Humans also have high plasma leptin (mice do not)

Question 34

How can leptin be high in cases of obesity? (3)

Answer 34

-leptin resistence caused by hyperleptinemia -possible that food intake is altering ability of the leptin to impact energy regulation -possibly that leptin was designed primarily to detect periods of energy depletion (negative energy balance) rather than the other extreme.

Question 35

"can we shed weight or shed fat?" Talk about: liposuction, ozempic (GLP-1 agonist), lifestyle change.

Answer 35

1. liposuction- Few metabolic health gains, could help to now improve on lifestyle change. Liposuction takes away the subcutaneous fat, not viscreal fat (will make no change metaboliczally) 2. GLP-1 agonist- will also cause muscle loss, other medication side effects to deal with, cost 3. Lifestyle change- shrinks existing fat cells.

Question 36

can we shrink existing fat cells?

Answer 36

Yes, it is difficult because it is easy to add more to the fat cell to allow it to grow than it is to decrease the amount of fat in the cell.

Question 37

what are 2 parts to Deposition of fat & what drives the deposition process

Answer 37

1. De Novo Lipogenesis- making of new fat cell. Occurs in adipose tissue and liver 2. Re-Esterification- storing fat that is already made Insulin drives the process (inhibits lipolysis)

Question 38

What are some ways to break chronically high levels of insulin (6)

Answer 38

1. reduce amount of carbohydrates 2. fasting/time restricted feeding 3. fixing high cortisol levels 4. improving sleep 5. exercising 6. all of the above