Switching on and maintaining a fuel supply Flashcards
How does the foetus get nutrition?
- through the placenta
- glucose and amino acids= facilitated diffusion according to the diffusion gradient
What is the metabolism like in the womb?
- anabolic
Which week is the rate of building up the body the highest?
- 20 weeks of gestation
When the foetus is near term, how much glucose does it use per day?
- 5g of glucose/kg/day
In the foetus, what is the dominant hormone?
- insulin
- insulin works as GH in the foetus (not to maintain blood sugar levels)
- helps build body through anabolic processes
What are the main actions of insulin?
- glucose uptake into body tissues e.g. muscles, fat, liver
- decrease lipolysis (fat breakdown)
- decrease amino acid release from muscles
- decreases gluconeogenesis in the liver
- decreases ketogenesis in the liver
After birth what does the metabolism need to be switched to?
- from anabolism to catabolism
- bc outside the nutrient supply isnt continuous
What does outside feeding depend on?
- nutrient supply depends on feeding period and fasting periods in between
- when fasting, catabolism is important
What happens to feeding in the first 24 hours of it coming out?
- very little milk is available
- so baby gets low nutrition supply
What is colustrum?
- first milk produced by the mammary glands
What does the baby eat in the first day?
- average colustrum intake = 7mls per feed in the first 24 hours
- if baby has 6-8 feeds= about 30mls/kilo/day of milk intake in the firstday
- this is too less than the 60mls/kilo/day routinely prescribed to newborn babies
How much food is prescribed to newborn babies in a day?
60mls/kilo/day routinely prescribed to newborn babies
What stores are there at birth by weight?
- 1% glycogen
- 16% fat
What happens to glucose levels as the baby is born?
- as baby is born, sharp drop in plasma glucose levels
- even if baby is not fed, glucose levels come up to normal in plasma
- this is bc of hormones like glucagon which surge in the plasma
- glucagon activates gluconeogenesis (production of glucose from stores) and opposes insulin actions
What happens if glucose levels reach 2mg/dl?
- in adults, person would be weak
- babies are fine bc they can cope with hypoglycaemia
- newborn baby has very low cerebral metabolic rate (as the baby develops, this metabolic rate increases)
- so glucose demand is less
What are postnatal fasts?
- breaks the baby has between feeds
What happens in postnatal fasts?
- baby needs to utilise glucose from stores
What is gluconeogenesis?
- process which provides glucose from body stores
- e.g.g from AA, glycogen, fats through lactate, pyruvate, alanine and glycerol
What is ketogenesis?
- ketone bodies produced from fats
- newborn babies use ketone bodies (primary energy source= fuel for brain)
How is ketone used in adults?
- primary energy sources for brain= GLUCOSE
= use KETONES when starving
What does the enzyme glucose 6 phosphatase do?
glucose 6 phosphate to glucose
What does the enzymes fructose 1, 6 bisphosphatase do?
fructose 1, 6 diphosphate to fructose 6 phosphate
What is the structure of fats?
- have 3 carbon backbone (triglyceride backbone)
- also have fatty acid tails
How does the fatty acid tail determine the type of fat?
- if fatty acid unsaturated= has double bond in it= has kink in tail= so fat doesnt pack very well= tends to be liquid e.g. olive oil
- if fat is saturated= single bond= no kink in tail= fat can pack well= will be solid
How is fat oxidised?
- remove glycerol group from fats
- remove C 2 at a time
- carbons bound to coenzyme A
- form acetyl CoA
PROCESS CALLED B OXIDATION - acetyl groups used to form ketone bodies e.g. acetone and B hydroxybutyrate= USED FOR CEREBRAL FUEL
- acetyl groups enter Kreb’s cycle- energy source or converted to pyruvate and goes through gluconeogenesis
What is the difference with how much 1g of fat gives and how much 1g of glucose gives?
- 1g of fat gives 9-10Kcals of energy
- 1g of glucose gives 4Kcals of energy
What is breast milk made of?
- 50% fat and 40% carbohydrate
How is the milk broken down?
- lactose is broken down into glucose
- fat is broken down by lipase which is in breast milk
What happens in the fed state of the baby?
- baby just eaten
- full of glucose
- glucose needs to be stored
- glycogen in muscles, amino acids for proteins, fat etc.
What happens in a fasting state of the baby?
- after feeding and absorbing finished
- blood glucose goes down
- insulin is stopped
- cortisol and glucagon rise
- they mobilize the stores
FATS broken to FREE FATTY ACIDS= go to liver= converted to ketones or glucose
MUSCLES yield AMINO ACIDS and LACTATE= go to liver= convert to glucose
What are diseases relating to metabolism in a baby?
- glucose demand > supply
- hyperinsulinism
- glucagon, adrenaline, cortisol failure
- enzyme deficiencies in pathways
At how many weeks does the foetus grow the quickest?
20 weeks so the demand for glucose is the highest
What happens if a baby is born preterm at 24 weeks?
- baby growing very quickly= has high metabolic demands
- metabolism completely set on anabolic
- takes while for baby to switch to catabolic
- the stores the baby has have low nutrients and poor fat absorption
How much fat does a baby absorb?
babies only absorb about 70% of the fat they intake, and the smaller the baby is the lesser the fat is absorbed
How do you feed a preterm baby?
- start with small amounts of breast milk
- gradually increase
- by 7-10 days of life= will be on full feed (breast milk)
- also give IV glucose, amino acids and fats
What happens if a full term baby is skinny?
- means they havent grown as must as they should in utero
- they have small nutrient stores
- so gluconeogenic pathway is immature
How are skinny babies managed?
- support by breast feeding
- keep an eye on them (so they dont develop hypoglycaemia)
- if hypoglycaemic, give IV glucose
Why is a baby of a diabetic mother fat?
- mother diabetic
- high maternal glucose
- facilitated diffusion in placenta
- foetus has high glucoe
- foetus has high insulin= works as GH (lays stores down)
- so baby overgrowth= FAT BABY
What happens to the baby of a diabetic mother?
- hepatomegaly (enlarged liver)
- lots of subcutaneous fat stores
- look disproportionate and bigger than normal (macrosomia)
When the baby of a diabetic mother is born, what does it have?
- higher than normal insulin levels
- lead to hypoglycaemia
- reduced ketogenesis = DANGEROUS
What are causes of hyperinsulinaemia?
- Beckwith Wiedemann
- Islet cell dysregulation
What is Beckwith Wiedemann?
- macroglossia= large tongue
- macosomia= larger than normal
- midline abdominal defects (exomphalos, umbilical hernia, diastasis recti)
- ear creases/ear pits
- hypoglyacemic
What happens in Islet cell dysregulation?
- hyperactive islet cells (which produce insulin)
- blood sugar is hard to control in these babies
- MIGHT NEED TO DO pancreatectomy to control blood glucose= remove pancreas to get control of blood glucose
What is CAH?
- 21 hydroxylase deficiency
- enzyme in the steroid hormone synthesis pathway
- usually converts steroids to cortisol and aldosterone
- bc of deficiency in the enzyme= too much testosterone and there is virilization of the female
- cortisol deficiency- HYPOGLYCAEMIA
- aldosterone deficiency- salt wasting crisis-hyponatrimeia
- baby is boy from outside but has no testes
What is Waterhouse-friderichsen?
- severe adrenal haemorrhage with adrenal gland dysfunction secondary to sepsis or hypoxia
What are inborn errors of metabolism?
- Glycogen storage disease type I
- Galactosaemia
What happens in glycogen storage disease type 1?
- deficiency of the rate limiting enzyme glucose 6 phosphatase
- converts glucose 6 phosphate to glucose
- replenishes the blood with glucose (need for brain)
- patient has hypoglycaemia and lactic acidosis
- older child= hepatomegaly= bc of excess glycogen stores
- managed by giving corn starch feeds- slowly release glucose
What is galactosemia?
- lactose is broken down to galactose and glucose in the body
- galactose is then broken down to glucose by galactose 1 phosphate uridyl transferease (Gal-1-put) which is missing in galactosaemia
- leads to toxic levels of galactose 1 phosphate
- patient will present with
−hypoglycemia
−jaundice and liver disease
−poor feeding and vomiting
−cataracts and brain damage
−e coli sepsis
