Metabolic And Endocrine Control During Special Circumstances

Question 1

Why is insulin considered an anabolic hormone ?

Answer 1

Because it promotes fuel storage for example conversion of glucose into glycogen.

Question 2

Why is glucagon , adrenaline , cortisol and thyroid hormone considered to be catabolic hormones ?

Answer 2

Because they promote the release from stores and utilisation

Question 3

What hormone is considered to be both anabolic and catabolic ?

Answer 3

Growth hormone - this is because they increase protein synthesis ( anabolic function) but also increase lipolysis and gluconeogenesis ( catabolic function )

Question 4

Outline the feeding cycle

Answer 4

1. Because of feeding there will be an increase in blood glucose levels. This will stimulate the release of insulin from the pancreas.
2. Insulin will increase glucose uptake and utilisation by muscle and adipose tissue via the GLUT4 channel.
3. Insulin ( anabolic hormone ) will also promote storage of glucose into glycogen in the liver and muscle.
4. Insulin will also promote lipogenesis and storage of fatty acids as TAG in adipose tissue.

Question 5

Outline the fasting cycle

Answer 5

1. Blood glucose levels will fall which would depress insulin secretion and instead stimulate glucagon release.
2. Glucagon will promote glycogenolysis in the liver.
3. Lipolysis in adipose tissue to provide fatty acids for use by other tissues.
4. Gluconeogenesis : to maintain supplies of glucose for the brain.

Question 6

What is the difference between fasting and starvation ?

Answer 6

Fasting - when we haven’t eaten in a while and out body can utilise other substitutes for glucose.

2. Starvation is where the body is absolutely deprived from all necessary energy substitutes.

Question 7

Outline the mechanism by which our body undergoes during starvation period.

Answer 7

1. Reduction of blood glucose will stimulate release of cortisol and glucagon.
2. This would stimulate gluconeogenesis , lipolysis and breakdown of proteins too.
3. Because of the reduction in insulin and anti-insulin effects of cortisol - most cells cannot actually utilise the glucose and fatty acids are used as substrates.
4. Liver begins to produce ketone bodies and brain utilises these
5. Once fat stores have depleted , must revert to the use of proteins as a source of energy.
6. Eventually death because of loss of muscle.

Question 8

During which period of pregnancy does the fetus usually grow the most ?

Answer 8

2/3 of the fetus grows over the last 1/3 of pregnancy.

Question 9

What are the two main phases of metabolic adaption during pregnancy ?

Answer 9

1. Anabolic phase ( prepatory phase to increase maternal nutrient stores ) - first half of pregnancy
2. Catabolic phase ( second half of pregnancy ) : maternal metabolism adapts to meet increasing demand by fetal-placenta, unit

Question 10

What occurs during the metabolic Anabolic phase during the first half of pregnancy?

Answer 10

1. Increase in maternal fat store
2. Small increase in level of insulin which allows adipose tissue to take up glucose more readily via GLUT4.
3. Nutrients are stored in order to meet future demands of rapid fetal growth in later gestation

Question 11

What occurs during the Catabolic phase of the second half of pregnancy?

Answer 11

• maternal metabolism adapts to meet the the increasing demands
  2. Decreased insulin sensitivity ( increased insulin resistance) - this reduces maternal utilisation of glucose by switching tissues to the use of fatty acids so glucose can be made to use for fetus.
  3. Delaying maternal deposits of nutrients after meals so nutrients can circulate in the blood for longer to allow them to be provided to fetus.
  4. Releasing fatty acids from stores built up during the first half of pregnancy so mother can utilise them instead of glucose , this is because glucose is the most important component to the fetus.

Question 12

Why during this second half pregnancy does the mother become a little resistant to insulin ?

Answer 12

• insulin levels continue to increase but the production of anti-insulin hormones by the fetal-placental unit increases at an even faster rate and the insulin:Anti-insulin ratio therefore falls.

An example of an anti-insulin hormone would be CRH.

Question 13

How does the fetus obtain nutrients from the mother ?

Answer 13

Through placental transfer via simple diffusion down a a concentration gradient. There is little active transport going on ( only for amino acids)

• glucose which is the most important fuel for the fetus os transferred into fetus via facilitated diffusion via GLUT1.

Question 14

What is the fetoplacental unit ?

Answer 14

The placenta , fetal adrenal glands and fetal liver constitute a new endocrine entity known as the fetoplacental unit.

This unit controls maternal metabolism to ensure its own survival.

Question 15

What is the main anti-insulin hormone secreted by the placenta ?

Answer 15

Corticotropin releasing hormonewhich increases CRH in maternal blood by 1000x. This results in more modest increase in ACTH and cortisol. This leads to transient hyperglycaemia after meals because of increased insulin resistance.

Hypoglycaemia can occur between meals because of constant withdrawal of glucose by fetus.

Question 16

Why is there an increased insulin secretion in pregnancy ?

Answer 16

1. Increase appetite in pregnancy means more glucose in ingested.
2. Oestrogens and progesterone increase sensitivity of maternal pancreatic beta cells to blood glucose by B cell hyperplasia and b cel hypertrophy.

Question 17

What is gestational diabetes ?

Answer 17

Disease in which pancreatic beta cells do not produce sufficient insulin to meet increased requirement in late pregnancy.

Question 18

What are the three causes of Gestational diabetes ?

Answer 18

1. Autoantibodies similar to those in type 1 diabetes detroy the beta cells.( less than 10%)
2. Genetic susceptibility( rare )
3. B cell dysfunction in setting of obesity and chronic insulin resistannce ( most common )

Question 19

What are the clinical implications of gestational diabetes ?

Answer 19

Increased incidence of miscarriage

Increased congenital malformation

Fetal macrosomia ( big body )

Shoulder dystocia

High BP and Protein in urine

Question 20

What are risk factors of gestational diabetes ?

Answer 20

Maternal age above 25

Body mass index above 25kg/M2

More common in Asian , Black , Hispanic ethnic groups

Family history of diabetes

Family history of macrosomia

Question 21

How to manage gestational diabetes ?

Answer 21

1) calorific reduction
2) insulin injection is persistent hyperglycaemia present
3) regular ultrasounds

Question 22

What are the benefits of exercise ?

Answer 22

Body composition changes ( decrease in adipose , increase in muscle )

2. Insulin sensitivity of tissues increases
3. Blood TAG decreases ( HDL INCREASES , LDL DEC)

4, blood pressure falls

5, feeling of wellbeing

Question 23

What. Is the cori cycle

Answer 23

The way lactate is recycled in the liver after anaerobic exercise.

It involves 2 lactate being converted into glucose in the liver , this glucose then goes to the muscles where it is again utilised for metabolism to produce 2 lactates again.

Question 24

Fatty acids usage as a fuel can be used in aerobic or anaerobic conditions or Both ?

Answer 24

ONLY aerobic conditions.

There is slow release from adipose tissue , limited carrying capacity of fatty acids in blood due to capacity limited by uptake across mitochondrial membrane.

Question 25

What are the three metabolic phases in a 1500m middle distance race ?

Answer 25

1. Initial phase : start uses creatine phosphate stores to produce ATP. And anaerobic glycogen metabolism.
2. Long middle phase : ATP is produced aerobically from muscle glycogen ( relies on adequate supply of o2)
3. Finishing sprint : again relies of anaerobic metabolism of g,ycigen and produced lactate.

Question 26

What occurs in terms of metabolism in marathon race ?

Answer 26

Low intensity , long duration race.

95% of the time it is aerobic
Use of muscle glycogen , liver glycogen and fatty acids.

Question 27

What occurs in terms of metabolism during a 100m , sprint ?

Answer 27

Short , high intensity exercise

Where you cannot deliver oxygen to muscles in time. Once high energy phosphate stores are used up you must create ATP anaerobically - this is inefficient and incomplete metabolism of glucose.

Produces lactate with subsequent build up of H+

Question 28

What are the changes. In hormones that occur during a course of running a marathon ?

Answer 28

1. Adrenaline secreted which stimulates glycogenolysis and lipolysis.
2. As a result of adrenaline secretion this inhibits insulin release.
3. Also Glucagon levels rise which stimulates glycogenolysis , gluconeogensis and lipolysis
4. Growth hormone rises rapidly which stimulates lipolysis and gluconeogenesis.
5. Cortisol rises slowly which stimulates lipolysis and gluconegensisi