Adipose Tissue

Question 1

What tissue gives structure to adipose tissue?

Answer 1

Reticular tissue

High density of reticular fibers (type 3 collagen)

Question 2

Adipose tissue characteristics

Answer 2

Highly vascularized

Found: subcutaneous areas, body cavities, surrounding organs and tissues (nerves, vessels)

Question 3

Adipose tissue fxn

Answer 3

reservoir for lipid storage:
Structural components for cells (lipids)
Energy sources for cells (fatty acids)
Provides lipid molecules for steroid hormone production

Temperature insulation (due to poor thermal conduction of adipose tissue
Protection of underlying structures

Question 4

Unilocular Fat

Answer 4

Yellow Fat-most common type
Single lipid droplet fills the majority of cellular cytoplasm
–nucleus and cytoplasm are “squeezed” into the periphery of adipocytes

Question 5

Multiocular Fat

Answer 5

“brown fat”-limited amount in adults
infants and animals that hibernate

lipids of brown fat are broken down for production of heat–controlled by sympathetic nervous system

Question 6

Brown Fat cytoplasm: multiocular

Answer 6

numerous lipid droplets
many mitochondria
central nucleus

Question 7

Heat production of multiocular fat

Answer 7

catabolism of fatty acids from lipid droplets is uncoupled from ATP synthesis

Question 8

Thermogenin

Answer 8

• Transmembrane protein of mitochondria
• Allows shunting of energy away from ATP production and into heat production
• All energy for metabolism of fatty acids from multilocular adipose tissue is given off as heat

Question 9

Lipid Transport

Answer 9

Lipids need special systems to be transported within the water-based blood and tissue fluid- transported attached to proteins

This configuration allows them to be “soluble” in the plasma and allows cells to control entry and exit of lipid molecules

Major lipoprotein groups (modes of lipid transport)
VLDL, LDL, HDL, IDL and chylomicrons

Question 10

Chylomicron

Answer 10

Small particles formed in the intestine: transported in plasma (to liver, fat cells)

Chylomicrons are triglycerides packaged with:
Cholesterol, phospholipids, and proteins

Question 11

Lipid storage

Answer 11

Most stored fatty acids have their origin in dietary fats
During digestion, triglycerides are split into monoglycerides and fatty acids in the GI tract for transport to adipocytes-(Transported in the blood as chylomicrons)

Question 12

Adipocytes also receive lipids from:

Answer 12

Triglycerides synthesized in the liver and transported in the form of VLDL

Conversion of glucose to fatty acids and glycerol; these are then formed into triglycerides for storage

Question 13

Triglycerides are transported in the blood as?

Answer 13

Chylomicrons & VLDL

FFA bound to proteins

Question 14

Lipoprotein lipase

Answer 14

Enzyme within endothelial cells of capillaries

Breaks down lipoproteins and releases:
FFA (free fatty acids)
Glycerol

Question 15

Excess glucose is also processed by?

Answer 15

Adipocytes
Insulin stimulates the uptake of glucose

Insulin stimulates adipocyte synthesis of FFAs from glucose
Then stored within the lipid droplet of adipocyte

Question 16

Lipid storage IN the adipocyte:

Answer 16

FFAs diffuse from the capillary into the adipocyte
Once inside the adipocyte, FFAs are repackaged with glycerol to re-form triglycerides

Triglycerides are stored in droplet(s) within the cytoplasm of the adipocyte

Question 17

Release of lipids from adipocytes

Lipids are mobilized from adipocytes in response to:

Answer 17

Hormonal stimuli that promote triglyceride release
Growth hormone (GH)
Thyroid hormone (T3/T4)
Glucocorticoids (cortisol)

Neurogenic stimuli
Norepinephrine (NE) from sympathetic nerve endings stimulates triglyceride release

Question 18

Liberation of triglycerides from adipocytes into the blood is driven by:

Answer 18

hormones and the sympathetic nervous system

serves to increase lipids/FFAs for cell energy

Question 19

Hormone sensitive lipase (HSL)

Answer 19

Becomes active when triglyceride release from adipocytes is stimulated

HSL hydrolyzes triglycerides into FFAs and glycerol

FFAs and glycerol diffuse into capillaries for distribution
FFAs are bound to albumin for transport in the blood

Question 20

What hormones activate HSL?

Answer 20

Thyroid Hormone
Growth Hormone
Epinephrine/Norepinephrine – sympathetic system
Cortisol

Question 21

Are lipids mobilized uniformly?

Answer 21

Fats in subcutaneous, mesenteric, and retroperitoneal areas are mobilized first

Adipose tissue in hands, feet, and retro-orbital fat pads resist long periods of starvation

Question 22

Leptin

Answer 22

Protein produced by adipocytes

Regulates metabolism, energy intake and production

Question 23

Leptin acts mainly in the hypothalamus to?

Answer 23

Decrease food intake (decreases hunger)

Increase energy utilization (liberate FFAs)

General regulation of the amount of adipose tissue in the body

Question 24

Types of Obesity

Answer 24

Exogenous - caloric intake > caloric expenditure

Endogenous - metabolic cause - < 1% of all cases

Question 25

Most at risk for obesity

Answer 25

minorities
low income
low education

Question 26

Consequences of obesity

Answer 26

Hypertension
Coronary artery disease
Dyslipidemia
Stroke – cerebrovascular accident (CVA)
Type II diabetes
Gall bladder disease
Osteoarthritis (OA)
Sleep apnea
Cancer

Question 27

Normal body fat content

Answer 27

Males = 11-15%
Females = 21-28%

Question 28

Chronic Activity and Lipid Mobilization

Answer 28

Increased sensitivity of adipocytes to norepinephrine and epinephrine
Allows for greater, more efficient mobilization of fats when stimulated by sympathetic nervous system

Question 29

Increased use of lipids by chronically trained muscle

Answer 29

Increase capillary/muscle fiber ratio
Increase # of mitochondria
Increase in oxidative enzymes which allow for increased aerobic capacity