Biochemical Consequences Of Protein And Energy Imbalances Flashcards
What are the three key foodstuffs that omnivores from the gut?
Glucose
Amino acids
Long chain fatty acids
What happens to most glucose once it is absorbed in omnivores?
80% taken is taken up into muscle cells and stored as glycogen
20% goes to liver - glycogen
How is glucose taken up into muscle cells?
Insulin dependent system of uptake
GLUT4 transporters on membrane
Insulin released when glucose is high therefore GLUT4 allows glucose into muscle cells when glucose is high
How is glucose taken into liver cells?
GLUT2 transporter
Has a very high Km therefore only works at very high concentrations of glucose.
Where are GLUT-2 transporters found?
Hepatocytes
B cells in pancreas
What happens to glucose which is not converted into glycogen?
Respiration
What happens when there is excess Acetyl CoA ?
Converted into long-chain fatty acids through fatty acid synthesis
Stored in adipocytes
How does insulin exert its effect?
Brings about a signalling cascade leading to the DEPHOSPHORYLATION of a series of regulatory enzymes.
How does glucagon exert its effect?
Leads to the phosphorylation of the same enzymes as insulation - like an off switch.
Other than glycogen, how can glucose be stored?
Go to adipocytes and is made into glycerol
How can fatty acids be sourced?
Excess Acetyl CoA
Absorbed from gut as chylomicrons - enter tissues where a lipase extracts the fats.
What happens to fatty acids once they enter adipocytes?
Fats are esterified with glycerol to make triglycerides for storage
What happens if there are high levels of fatty acids?
Converted into Acetyl CoA and enter the CAC
How can amino acids be utilised?
Versatile metabolic substrates
When you delaminates them you can use them for lots of different purposes including converting them into PYRUVATE, ACETYL COA, and OAA
Other than for metabolism, how can amino acids be utilised?
Put into muscle protein.
Can also be taken and used as a metabolic intermediate when low glucose.
How do the main nutrients absorbed by omnivores and carnivores differ?
The main nutrient absorbed by carnivores is AMINO ACIDS
What are the two types of amino acid?
Glucogenic
Can be converted to pyruvate or oxaloacetate
Ketogenic
Can be converted to Acetyl CoA
(NB SOME CAN DO BOTH)
How does glucagon exert its effect?
Low blood sugar
Release of glucagon from alpha cells
Binds to receptor on responsive tissue
- Adenyly cyclise - cAMP- PKA activated - phosphorylation of regulatory enzymes
What are the key energy sources for fasting omnivores?
How are they sourced?
How do they provide an energy source?
Fatty acids
Triglycerides in adipocytes broken down to long chain fatty acids
Fatty acids converted to Acetyl CoA
What is another name for long chain fatty acids?
NEFAs
How are NEFAs useful in blood work?
Good indicator of how much fat is being mobilised
Most fat after a MEAL is carried in the blood as chylomicrons or phospholipid particles whereas mobilised fats are carried as NEFAs
How can glycerol be used?
Can be used as a gluconeogenic substrate in the liver.
What issues need to be resolved when using amino acids as a metabolic intermediate?
How can this be resolved?
Need to be deaminated
Produces ammonia
Enters the urea cycle and gets turned into urea
How does starvation affect the blood work of omnivores?
Increases fat mobilisation
Blood levels of NEFAs UP
Where do most NEFAs go when they are created?
What effect can this have?
LIVER
Accumulation of FAs in the liver leads to HEPATIC LIPIDOSIS / fatty liver
How can you get hepatic lipidosis?
Increased fat mobilisation
Increased fat ingestion (more common in humans)
How does hepatic lipidosis effect the liver?
Impedes flow of blood through sinusoids
Lipid droplets fill cells and marginalise cytosol Therefore reduced intracellular processes
How can increased Acetyl CoA (from increased NEFA production) affect the body?
What conditions are associated with this process.
Turns on KETOGENESIS and the formation of ketone bodies
Can lead to (diabetic) ketoacidosis, bovine ketosis and twin lamb disease (pregnancy toxaemia
How can you test for ketone bodies?
Urine
What would you expect to see from a cow with ketosis?
Slow,
Depressed
Head pressing
When are ketone bodies particularly physiologically necessary?
Can be converted back into Acetyl co a at target tissue
In BRAIN, can’t use LCFAs as they travel bound to albumin - cant cross BBB
Ketone bodies are short chain FAs and are water soluble - CAN cross BBB as they don’t require carrier molecules
Why does Acetyl CoA accumulate?
Fat mobilisation
Intermediates taken out of the CAC and converted to glucose therefore less Acetyl CoA used in CAC
What VFAs are produced by rumen bacteria?
Acetate
Proprionate
Butyrate
How are the different VFAs used ?
Acetate and Butyrate can be converted into Acetyl CoA or enter the CAC
- Acetyl CoA can be converted into LCFAs which can be used by other tissues or stored in adipocytes as triglycerides
Proprionate can be converted into OAA then converted into glucose via gluconeogenesis
What is the major source of blood glucose in ruminants?
PROPRIONATE
(-> OOA —> Glucose)
Transported from the liver to the blood
What is the normal blood glucose of ruminants?
Approximately half the blood glucose of omnivores
2.5 mmol (vs 4.5 mmol)
What condition results from high ketone bodies and hypoglycaemia?
What changes would be seen in the blood?
Slow cow syndrome
Low glucose
High ketone bodies and NEFAs
What might cause a cow to become hypoglycaemic?
High production
Twin pregnancies
What is primary ketosis?
Not taking in enough energy
Negative energy balance
MANY in herd would be affected
What is secondary ketosis?
Stop taking in food secondary to something else - symptom of another disease
NOT THE ONLY THING THAT IS WRONG
One cow usually affected
What conditions can result in secondary ketosis?
Laminitis
LDA/RDA
Metritis (retaining foetal membranes)
Mastitis
(Especially around parturition)
How are amino acids used in ruminants?
Gluconeogenesis - important for preventing ketosis
Microbes can make amino acids out of urea
What are the sources of amino acids in ruminants?
MICROBIAL PROTEIN (therefore need to make sure microbes are proliferating
Can be supplemented by feeding HEAT TREATED SOY BEAN
How is heat treated soy bean a useful element of feed?
Not metabolised by microbes therefore goes straight into small intestine where it can be broken down to AMINO ACIDS
(Most amino acids which aren’t protected will be metabolised by the microbes)
