BCH Hormone Regulation of Fats

Question 1

What are fats?

Answer 1

Fatty acid esterified with glycerol to form triacylglycerol (TAG)

Question 2

Describe fats

Answer 2

Fats are simple lipids, organic compounds poorly soluble in water but soluble in organic solvents. Fats form the bulk of adipose tissues (adipocytes) free fatty acid and TAG contribute significantly to the energy requirements in the body
Fat molecules are a large store of energy and an average 70 KG man has 15 KG of fat in the body and….135,000 kcal of energy by far the largest of energy in the body

Question 3

Transport of TAG

Answer 3

TAG in the food are transported from the intestine as chylomicrons into the liver for storage.
The three fatty acids are transported to various tissues re-esterified and stored as tag in tissues such as adipose muscle

Question 4

Fat metabolism organs and function

Answer 4

Liver
Adipose tissue
muscle
brain

These tissues Contain different sets of enzymes for:
storage
Use
And generation of fuel

These tissues do not work in isolation but their activities are so integrated in a network that one tissue may provide the substitute for another, or process compounds produced by another organ

Question 5

Communication among tissues is controlled by

Answer 5

the availability of substrates
hormones
and the nervous system

Question 10

Starvation or fasting

Answer 10

Starvations fosters thoughts if miss you the second after the absorptive period

Question 11

What is the absorptive period

Answer 11

The. 2 to 4 hours after the ingestion of a normal meal

Question 12

What occurs during fasting

Answer 12

In the absence of food the plasma level of glucose, amino acids and TAG fall causing a decrease of ins/gly ratio as occurs in the fed state.

The decrease in insulin/glycogen ratio and the decrease in availability of circulating substrates with degradation of glycogen, TAG and protein makes the fasting/starvation period a catabolic one

This sets in motion an exchange of substrates among the body tissues where the fuels are principally utilized mainly liver, muscle adipose tissue and the brain

Question 13

Describe the exchange of substrates during fasting

Answer 13

This exchange divided by two priorities

1. They need to sustain adequate blood levels of glucose for the use of the brain erythrocytes and other glucose requiring tissues
2. The need to mobilize FFA from adipose tissue and the synthesis of ketones from the liver for the use by all other tissues for energy requirement

Question 14

Discuss the fat reserve of a 70 KG man

Answer 14

An average 70 KG man normally has a reserve of 15 KG fat six KG protein and 0.2 KG carbohydrate (as glycogen) these are equivalent to 135,000 kcal, 24,000 kcal and 800kcal of energy respectively

The fat stores alone are enough to meet energy needs for about three months.

Question 15

Why is Protein is normally not an energy source

Answer 15

Protein is normally not an energy source as it has other important functions in the body such as the structural components of the body, enzymes etc

Therefore only about 1/3 of the body protein to be utilized for energy beyond which vital organs are fatally impaired

Question 16

Fat stores alone are enough to meet energy needs for how long?

Answer 16

About three months

Question 17

The regulation of intermediary metabolism in the fasting state like in the fed state is controlled by four mechanisms

Answer 17

1. Availability of substrates
2. allosteric regulation of enzymes (activating or inhibitory)
3. Covalent modification of enzymes
4. Induction expression of enzyme synthesis

Question 18

Are substrates available by the diet in the fasting state? Explain why?

Answer 18

In the fasting state, substrates are not available by the diet but from catabolism of stores and or tissue eg. glucose is from glycogen, FFA and glycerol from the TAG in adipose tissue, amino acid from proteolysin
Also in the fasting state most of the enzymes regulated by covalent modification are phosphorylated and inactive

Question 19

What happens to the liver tissue During Fasting?

Answer 19

1. Increase in glycogen degradation: Hepatic glycogen are virtually consumed in under 24 hours of fasting/starvation
2. The obligatory glucose requirements of the brain, RBCs and other organs are met by gluconeogenesis. Gluconeogenesis plays an important role in maintaining blood glucose during both overnight and prolonged fasting. The liver first uses glycogen degradation and then gluconeogenesis to maintain optimal glucose levels for energy metabolism.
   Glucose formed during gluconeogenesis is derived from glucogenic amino acids, lactate from the muscle and glycerol from the adipose tissue.
   In the first week of fasting 150 g of protein is utilized for gluconeogenesis

Increase in glucagon in plasma result in an increase includes glucogenolysis and an increase in gluconeogenesis

3. Increase in FFA oxidation provides an ADP and ATP for gluconeogenesis
4. Increase in the synthesis of ketone bodies for use by peripheral tissues and brain thus reducing the need for gluconeogenesis from amino acids thus preserving protein

Question 20

What happens to the skeletal muscle During Fasting?

Answer 20

Resting muscle uses FFA as a fuel, in contrast exercising muscle uses glucose from glycogen stores.
As the glycogen reserves are depleted by starvation and exercise, FFA from TAG become the energy source.

There is a decrease in glucose uptake because of decreased insulin.
Initially, the muscles uses fatty acids from adipose tissue and ketones as fuel, later ketones are spared and fatty acids are oxidized (used) exclusively.

This causes an increase in Ketone in blood for the use of the brain.

Thus as Ketone is increasing in blood, for brain use, the muscle is the decreasingly utilizing the compounds.

During the first few days there is a rapid breakdown of muscle protein providing amino acid for gluconeogenesis in the liver.

After several weeks, the rate of muscle proteoglycan declines paralleling a decline in the need for glucose used by the brain which has now begun using ketone bodies

Question 21

What happens to the brain During Fasting?

Answer 21

Initially uses glucose
In prolonged fasting (2-3 weeks) glucose is spared and ketones become the fuel used by the brain thus sparing proteolysin and muscle wasting

Question 22

What happens to the kidney during Fasting?

Answer 22

Kidney plays a role in prolonged starvation
50% of Gluconeogenesis occurs in the kidney in late fasting.
The kidney also provides compensation for the acidosis that accompanies the increased production of Ketone bodies in the blood.

The nitrogen byproduct of the enzymatic process in the kidney, picks hydrogen ions from Ketone body dissociation and is excreted in the urine as urea decreasing the acid load of the body

Question 23

What is BMI

Answer 23

Is also known as Quetelet index it takes into account the body frame and composition of the individual.
Method developed by a Belgium polymath Adolphe between 1830 and 1850

Question 24

What happens to the adipose tissue During Fasting?

Answer 24

Because of low plasma insulin glucose transport into adipose tissue is low resulting in low fatty acid and low TAG synthesis

Fasting/starvation enhances the release of catecholamines in the sympathetic nerve endings in adipose tissue.

These hormones and glucagon are activators of hormone-substitute lipase that causes degradation of stored TAG

Free fatty acid thus released or transported to various tissues and a used as fuels because lipoprotein lipase activity is also low in fasting, circulating tag of lipoproteins is not available to adipose tissue.