Biochemical Consequences of Protein and Energy Imbalances Flashcards
What are the 3 major constituents absorbed from the gastrointestinal tract in an omnivore?
Glucose
Long chain fatty acids
Amino acids
Which hormone drives storage of products absorbed from the gastrointestinal tract?
Insulin
Outline storage of glucose in an omnivore
80% stored as muscle glycogen
20% stored as liver glycogen
Excess glucose converted to pyruvate then long chain fatty acids
Give 2 parts of the body that are obligate users of glucose
Brain
Red blood cells
Outline the process by which red blood cells get energy…
Glycolysis
Obligate anaerobic metabolism
How are triglycerides made?
From glycerol and fatty acids
Where are triglycerides made?
Adipocytes
How are long chain fatty acids utilised as an energy source?
Beta-oxidisation
When might long chain fatty acids be used as an energy source?
When glucose is being conserved
How are amino acids stored?
Muscle protein
Builds up muscle mass
Source of energy
Outline metabolism of excess amino acids…
2 pathways - most can go either way but some are 1 or the other
Glucogenic to pyruvate
Ketogenic to acetyl co-enzyme A
Outline how a carnivore’s metabolism differs from that of an omnivore…
Major foodstuff is protein
Metabolism dependent on amino acids
Increased liver metabolism
Glucose made via gluconeogenesis
Outline how glucagon effects the switch to fasting metabolism…
Binds to cell surface receptors
Activates G-protein coupled receptor
Activates cAMP which activates protein kinase A
Protein kinase A phosphorylates metabolic hormones to regulate them
What molecule is activated by insulin?
Phosphastase
Which hormone initiates the fasting metabolism?
Glucagon
In omnivores, why does glycogenolysis occur in fasting?
To boost blood glucose
Where does glycogenolysis occur?
The liver
In omnivores, what is the classical fasting response to spare glucose?
Activation of hormone sensitive lipase
Breakdown of triglycerides
Release of long chain fatty acids into the blood
Tissue with oxygen beta-oxidise long chain fatty acids and use the citric acid cycle for non-toxic energy
What is the byproduct of breakdown of triglycerides, and how is it used in omnivores?
Glycerol - goes through gluconeogenesis to boost blood sugar
Outline how muscle storage of amino acids can be used for energy
Muscle protein broken down to release amino acids into amino acid pool
Amino acids undergo gluconeogenesis in liver
When is muscle storage of amino acids used as an energy source?
Extended fast (last resort as needed for other functions)
For how long a fast will omnivore body stores of glycogen last?
~1 day
For how long a fast will omnivore body stores of triglyceride last?
Variable - weeks to months
Give an example of a condition inducing perceived starvation
Diabetes (lack of insulin causes effective excess of glucagon)
Outline the effect of starvation on triglyceride stores
Breakdown into long chain fatty acids is upregulated, increasing their concentration in the blood
Give the risk associated with beta-oxidation of long chain fatty acids in the liver
Ketosis
Outline how ketosis occurs
- Beta-oxidisation of long chain fatty acids leads to accumulation of acetyl co-enzyme A
- Acetyl co-enzyme A use is decreased due to:
+ High cell energy charge (no need for citric acid cycle - turned off allosterically by cell ATP)
+ Depletion of citric acid cycle intermediates (used to make glucose) - Build-up of acetyl co-enzyme A by default makes ketone bodies
Name the ketone bodies…
Acetoacetate
3-hydroxybutyrate
Acetone
How is 3-hydroxybutyrate used within the body?
- Oxidised for energy
- Broken down into 2 acetyl co-enzyme As
- Acetyl co-enzyme A used in other tissues for citruc acid cycle
- Important in brain (short chain fatty acids are water soluble and can cross BBB - conserves glucose)
Why are ketone bodies useful?
Oxidised in tissues for energy
Describe ketoacidosis…
pH falls due to acidic effect of ketone bodies
Give 2 examples of conditions in which ketoacidosis may occur…
- Type 1 diabetes
- Production diseases
Twin lamb disease
Bovine ketosis
What is the major product absorbed from the ruminant gastrointestinal tract?
Volatile fatty acids (from rumen fermentation)
Name the volatile fatty acids
Acetate (2 carbons)
Proprionate (3 carbons)
Butyrate (4 carbons)
What is butyrate?
Volatile fatty acid
4 carbon short chain fatty acid
Ketone body
Which volatile fatty acids are converted to acetyl co-enzyme A in ruminant metabolism?
Acetate (2 carbons)
Butyrate (4 carbons)
How are acetate and butyrate used for energy in ruminant metabolism?
Converted to acetyl co-enzyme A
Used in citric acid cycle
What is done with excess short chain fatty acids in ruminant metabolism?
Conversion to long chain fatty acids
Used in tissue or stored
What is the major energy storage product in ruminants?
Triglycerides
Describe the liver glycogen levels in a ruminant
Low
Describe ruminant blood sugar
Low (about half the level of dogs’)
How do ruminants make glucose?
From proprionate (gluconeogenesis)
How is most ruminant glucose used?
Put into blood for essential function
Outline prevention of ketoacidosis in high-producing animals
Increase concentrates in diet
What is the major form of protein fed to ruminants?
Heat-treated soybean
What is the purpose of heat-treating soybeans in ruminant diets?
Harder for rumen microflora to ferment into volatile fatty acids
Protein digested in abomasum and absorbed in small intestine as gluconeogenic substrates
Describe the difference between ketoacidosis and rumen acidosis…
Ketoacidosis is a fall in the blood pH
Rumen acidosis is a fall in the pH of the rumen contents
Why does rumen acidosis occur?
Changing diet too quickly leads to lactic acidosis in the rumen
What are the outcomes of ketoacidosis?
Decreased milk production
Hepatic lipidosis
What is the effect of increasing concentrates in the diet of a ruminant?
More proprionate absorbed (undergoes gluconeogenesis)
When is hepatic lipidosis seen in the ruminant?
Ketoacidosis
Starvation
Obesity
