Lipolysis, Fatty Acid Oxidation, Ketone bodies

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In what physiological condition (fed or fasted) and in what tissues does lipolysis occur?

Occurs in the fasted state in the adipose tissue

Does (aerobic) exercise stimulate lipolysis?

Yes it does

What hormones play a role in this process?

...

Does a low carb diet induce lipolysis?

Yes because when there isn't a lot of glucose around the body needs to break down TAGs to be used for energy

What enzyme is the key enzyme for lipolysis or hydrolysis of TAG?

Hormone sensitive lipase

How is lipolysis regulated by hormones (insulin, glucagons and catecholomine)?

A decrease in insulin will cause HSL-deP to be inactive.
An increase in glucagon and catecholamines will cause HSL-P to be activated
Together this causes an increase in TAGs being broken down to 3FFA + glycerol which will be converted to FFA

What is the difference between HSL and LPL? (HSL)

HSL hyrodlyzes fatty acids at the sn1 and sn3 position; catalyzes the release of the second fatty acid from DAG and release 1 FA forming MAG: key enzyme for breaking down TAGs into FA and glycerol needs to be phosphorylated. THis occurs in the adipose tissue when hormones epinephrine and glucagon are high

What is the difference between HSL and LPL? (LPL)

Synthesized and secreted into the circulation by adipose tissue and muscle; catalyzes the hydrolysis of TAGs to FFA and glycerol
Located in the luminal face of the endothelial cells of capillaries. Translocates to the surface of lipid droplets upon hormonal stimulation
Activated when in the fasted state and control uptake of FA; Fed state increased in adipose tissue; fasted state: increased in muscle

In what physiological conditions (fed or fasted state) and in what tissues does fatty acid oxidation increase?

In the fasting state in the muscle and liver

Where does fatty acid oxidation occur in the cell?

Mitochondria

What is the relationship between fatty acid oxidation and plasma FFA?

As plasma levels of FFA increase, FA oxidation increases; plasma level of FFA are high in starvation and low in postprandial (fasting state)

How is fatty acyl CoA transported into the mitochondria?

...

Which enzymes are involved in the process?

...

How does malonyl CoA regulate CPT1?

Increased malonyl-CoA levels during fed inhibits CPT1 (acetyl-CoA from glycolysis from high carb diet)
If CTP1 activity is decreased, decrease in fatty acyl molecules going to mitochondria. Then decreased malonyl CoA levels during fasted stated stimulates CPT1 activity

What is the end product of fatty acid oxidation?

Acyl-CoA 2C shorter than starting molecule

Are odd chain fatty acids glucogenic?

Yes because odd chain fatty acids are oxidized and produce acetyl CoA molecules and addition 3 C molecules - precursor for gluconeogenesis

In what physiological conditions (fed or fasted state) and in what tissues does ketone body synthesis occur?

Fasted state in the mitochondria of the liver

Ketones are produced from what metabolic substrate?

Acetyl-CoA

How was this substrate produced?

In the well fed state acetyl CoA is produced during beta oxidation
In the fasted state fatty acid mobilization increases and the liver converts acetyl CoA to ketone bodies

What is the principal driver of ketone body synthesis?

Increased free fatty acids during prolonged starvation

Can the liver utilize ketone bodies? Why or why not?

The liver cannot because it doesn't have succinyl CoA transferase however the liver produces ketone bodies

What are ketone bodies?

Water soluble metabolites of fatty acids that are readily transported to other organs for oxidation of CO2 and H2O

What is the major lipid component of chyomicrons?

Largest lipoprotein
Highest % weight triacylglycerols

What is the major lipid component of VLDL?

2nd highest TAG % weight

What is the major lipid component of LDL?

Highest in cholesteryl esters

What is the major lipid component of HDL?

Highest in density due to high protein/lipid ratio

Where are chylomicrons synthesized?

SI

What is the function of chylomicrons?

...

What is the function of VLDL

...

What is the main function of HDL or HDL cycle?

...

What can increase the free cholesterol pool in the cell?

...

What is the role of adipose tissue LPL in lipoprotein metabolism?

...

What happens to plasma TG levels if LPL activity is decreased?

...

What are the 4 major groups of lipoproteins?

Chylomicrons
VLDL
LDL
HDL

Which apoproteins are associated with chylomicrons?

Apo B48
Apo C2 & 3
Apo E

Which apoproteins are associated with VLDL?

Apo B100
Apo C2 & 3
Apo E

Which apoproteins are associated with LDL?

Apo B100

Which apoproteins are associated with HDL?

Apo A1 & 2

Which lipoprotein is most abundant in plasma?

LDL and HDL

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