General MEH Flashcards
(34 cards)
Where in the pancreas and in what cells are insulin and glucagon produced?
Islets of Langerhans
Alpha cells - glucagon
Beta cells - insulin
How many polypeptides is insulin and how many disulphide bonds are there?
2 polypeptide chains
3 disulphide bonds
What is the name of the protein that is cleaved from the middle of the insulin polypeptide to create 2 chains? What is its clinical significance?
C-peptide
C-peptide is released into the blood in equimolar amounts with mature insulin, so measurement of C-peptide is a good indication of endogenous insulin synthesis in the body.
What amino acids do disulphide bonds form between?
Form between 2 thiol groups of cysteine residues.
Which receptors does insulin bind to?
Tyrosine-kinase receptors
Which receptors does glucagon bind to?
GPCRs (Gs)
How is insulin stored in Beta cells in the pancreas?
Stored as crystalline zinc-insulin complex
What are the 3 main tissues in the body that insulin acts on?
Liver, skeletal muscle and adipose tissue (as well as being required for normal growth and development of most tissues).
Out of insulin and glucagon, which is anabolic and which is catabolic?
Insulin - anabolic
Glucagon - catabolic
What is diabetic ketoacidosis?
Lack of insulin body increases lipolysis, and fatty acids are converted to ketone bodies in a process called beta oxidation. The ketone bodies create a metabolic acidosis in the body (bicarbonate system tries to buffer this but eventually can’t) - creates life-threatening condition.
What is the triad of symptoms of diabetes? What causes each symptom?
Polyuria - excess glucose in kidney, not all of it can be reabsorbed, increases water loss.
Polydipsia - excess thirst due to water loss.
Weight loss - loss of insulin leads to unopposed glucagon and catabolic effects in the body.
Name some symptoms of diabetic ketoacidosis.
Vomiting Nausea Abdominal pain Hyperventilation (to try to compensate for metabolic acidosis) Dehydration
What are the glucose concentrations that would indicate a diagnosis of diabetes?
Venous plasma glucose concentration > 11.1mmol/L
Fasting plasma glucose concentration > 7mmol/L
Plasma glucose concentration > 11.1mmol/L 2 hours after 75g anhydrous glucose in an oral glucose tolerance test.
What does the drug metformin do?
Reduces gluconeogenesis.
What do sulphonylureas do?
Increase insulin release from remaining beta cells, and reduce insulin resistance.
What are the macroscopic consequences of diabetes/persistent hyperglycaemia?
Increased risk of stroke
Increased risk of MI
Poor blood supply to peripheries (especially feet)
What are the microvascular complications of diabetes/persistent hyperglycaemia?
Diabetic retinopathy
Diabetic nephropathy
Diabetic neuropathy
Diabetic feet
What causes the microvascular complications of diabetes?
In tissues such as retina, kidneys and peripheral nerves, glucose enters the cell based on [glucose] outside the cell (not insulin), therefore hyperglycaemia leads to increased glucose in the cell, which can damage the cell.
What enzyme metabolises glucose?
Aldose reductase
What is HbA1c? What is its clinical significance?
Glycated haemoglobin - produced when glucose in the blood reacts with Hb. The percentage of haemoglobin that is glycated is a good indicator of how effective blood glucose control has been.
What is sorbitol?
Produced in the breakdown of glucose by aldose reductase (NADPH is used, meaning less protection against oxidative damage).
What is Metabolic Syndrome?
A group of symptoms including insulin resistance, dyslipidaemia, glucose intolerance and hypertension associated with central adiposity.
What are the 3 layers of the adrenal cortex and what does each layer produce?
Zona Glomerulosa (outermost) - mineralocorticoids e.g. Aldosterone
Zona Fasiculata - glucorticoids e.g. Cortisol
Zona Reticularis - androgens and some glucocorticoids
What is produced in the medulla of the adrenal glands?
Adrenaline
Noradrenaline
