Switching on and Maintaining a Fuel Supply

Question 1

How much glucose does a foetus near term use?
→ How does it cross the placenta?

What occurs with any excess glucose?

What is the dominant hormone in the foetus?
→ What does it do?

How does breast milk eventually meet the baby’s energy needs?

Answer 1

• 5g Glucose/kg/day
  → Facilitated diffusion
• Converted into Fat stores in 3rd Trimester by anabolic hormones, like Insulin
• INSULIN
  → ↑Glucose uptake, Glycogenesis, Lipogenesis
• 1. Little milk is produced at first
     
     2. Newborn meets energy demands (5g Glucose/kg/day) by using its fat stores
     3. Milk is later available as high-fat food; contains Lipase to help breakdown fat

Question 2

ENERGY STORES IN NEWBORN:
How does a newborn’s metabolic state adapt?

What occurs to the actions of Insulin after birth? What does this lead to?

What happens with Glucagon levels at birth? Why does this happen?
→ What is this called?
→ What does this do?

Answer 2

• Goes from a foetal, anabolic state → neonatal, catabolic state
• Anabolic actions of Insulin opposed by Catabolic hormones - Glucagon, Adrenaline, Cortisol, GH
  o This leads to the release of glucose from stores and breakdown of fats for energy
• Huge RISE - Due to rapid fall in blood Glucose after cutting umbilical cord
  → POST-NATAL FAST
  → Activates Gluconeogenesis and Glycogenolysis, Lipolysis, and Ketogenesis

Question 3

DISORDERS OF METABOLISM:
What’s it like in a Preterm baby?

What’s it like in an IUGR baby?

What’s it like in a baby of a Diabetic mother? What does this lead to?
→ What else causes Congenital Hyperinsulinaemia? What are the signs seen here?

What can cause Counterregulatory (Catabolic) Hormone Deficiency?

Answer 3

• • High demands with little nutrient stores
  • Underdeveloped metabolism
  • Poor fat absorption
• High demands with little nutrient stores in Liver, Muscle, Fat
• • High maternal glucose = High foetal glucose
  • Foetal and Neonatal Hyperinsulinaemia leads to excessive Anabolism (storage) = Macrosomia and Hypoglycaemia
  → Beckwith-Wiedemann Syndrome - Macroglossia, Macrosomia, Midline abdo. wall defects, Ear creases, Hypoglycaemia
• • HPA-axis Insufficiency - e.g. due to Septo-optic Dysplasia
  • Waterhouse-Friederichsen Syndrome - Adrenal Haemorrhage → Adrenal Dysfunction secondary to Hypoxia/Sepsis

Question 4

INBORN ERRORS OF METABOLISM:
What is Type 1 Glycogen Storage Disease? What does this lead to?

What is Galactosaemia? What does this lead to?

What is MCAD (Medium Chain Acyl-CoA Dehydrogenase) Deficiency?

Answer 4

• Deficiency in G-6-Pase - Hypoglycaemia and Lactic Acidosis due to Anaerobic metabolism, Hepatomegaly when older
• Deficiency in Gal-1-Pase = ↓Conversion of Galactose to Glucose, so Gal-1-P levels become Toxic = Hypoglycaemia, Jaundice, Poor feeding/Vomiting, Cataracts, Brain damage, Sepsis
• Unable to use fatty acids for Gluconeogenesis = Hypoglycaemia