Switching On and Maintaining Fuel Supply

Question 1

Does foetal size change according to dietary intake of their mother?

Answer 1

No it is preserved relative to intake

If the mother does not eat enough, then it is the mother that loses weight not the baby

Reduction in fetal size can occur if the minimum number of calories are not taken in

Question 2

How many grams of glucose does a foetus use per day?

Answer 2

5g/ kg/ day

Glucose and Amino acids move across the placenta by facilitated diffusion

Question 3

Which hormone is the most dominant in the third trimester of the foetus?

Answer 3

Insulin

Due to hyperplasia of Beta cells of pancreas

Insulin levels rise for foetus to lay down fat stores

Question 4

When is fat laid down during the pregnancy?

Answer 4

3rd trimester, important in first few days postnatally

Question 5

Which hormone is dominant in the post-natal metabolic adaptation state (fasting state)?

Answer 5

Counter regulatory hormones

Glucagon

Cortisol

Question 6

How does insulin act in the adult body?

Answer 6

Controls blood glucose levels

Question 7

How does insulin act in the foetus?

Answer 7

Anabolic hormone
Removes glucose from circulation and stores it in tissues:

• Increases glucose uptake into muscle, fat + liver
• Decreases lipolysis
• Decreases amino acid release from muscle
• Decreases gluconeogenesis in liver
• Decreases Ketogenesis in liver

Question 8

What does the baby rely on once it is born?

Answer 8

Breast Milk

Only a small amount is available initially

Question 9

What is colostrum?

Answer 9

First milk that isn’t enough to meet baby’s energy requirements

Baby uses energy stores

The milk becomes more nutritious and fatty later on

Question 10

Difference between pre-term and term babies?

Answer 10

Term babies have fat stores which they rely on initially

Question 11

What is the energy requirement of a new born baby?

Answer 11

4-6g glucose/kg/day

Question 12

What changes from fetal anabolic metabolic state to neonatal state?

Answer 12

Catabolic enzyme systems (not needed in utero) must be switched on in order for baby to reply on body stores between feeds

Question 13

Which organ has the uses the highest amount of energy at rest?

Answer 13

The brain

Question 14

How does the brain manage its high demand of energy?

Answer 14

Cerebral Metabolic Rate (CMR) is relatively low at birth

It increases as the brain develops

Question 15

When does catecholamine surge occur?

Answer 15

At birth. Surge in adrenergic hormones which causes more glucagon to be secreted. Cutting the cord causes fall in gluclose and glucagon opposes it to activate gluconeogenesis and glycogenolysis

Question 16

How are stores converted to fuels?

Answer 16

in womb, build up stores. After birth, catabolic processes increase availibility of substance by switched on catabolic hormones

Question 17

Which hormones oppose anabolic actions of insulin promoting energy release after birth?

Answer 17

glucagon
adrenaline
coristol
growth hormone

Question 18

when are the catabolic hormones switched on?

Answer 18

during labour and delivery. Surge in adrenaline switches on counter-regulatory catabolism and glucagon increases to switch off actions of insulin

Question 19

What determines whether a baby is chubby or skinny?

Answer 19

Missed trimester = no fat being laid down

Term infant = fat laid down in final semester to get through metabolic changes

Baby is usually 16% fat

Question 20

Why doesn’t the foetus need to convert stores to fuel?

Answer 20

Receives energy from placenta

Substrate is built up anabolically and stored in foetus under insulin

Question 21

How does the baby get its energy once its born?

Answer 21

Switching on catabolic hormones (counter-regulatory)

Done in the foetus during labour and delivery

Question 22

What processes occur during a postnatal fast?

Answer 22

Gluconeogenesis = making glucose from non carbohydrate sources (muscle + fat) e.g. lactate, pyruvate, alanine and glycerol

Ketogenesis = production of ketones from the breakdown of fat (normal metabolism esp in the brain)

Question 23

What is an indication of insipient starvation?

Answer 23

Adult ketogensis

Question 24

What is gluconeogenesis?

Answer 24

Glucose –> 2x Pyurvate
Anarobic
Pyruvate goes into krebs cylce
glycolysis in reverse is gluconeogenesis

Question 25

What is the rate limiting enzymes in gluconeogenesis?

Answer 25

G6Pase
(Glucose-6 phosphatase)

F1,6Biphosphosphatase
(F16BPase)

Question 26

What are the structures of fats?

Answer 26

Glycerol backbone
Fatty acids chains – unsaturated or saturated
Ester bonds between the two

Question 27

What happens when we breakdown fats and how are ketone bodies formed?

Answer 27

Remove the glycerol

Get rid of terminal two carbon group sequentially from fatty acid chains = Beta oxidation (mitochondria of hepatocytes)

Carbon group gets bound to coenzyme A forming acetyl CoA

Acetyl CoA enters TCA cycle and is further metabolised

In liver acetyl CoA is converted into ketone bodies which are then released into the circulation