Diabetes Flashcards
Is insulin and anabolic or catabolic hormone? Describe what this means.
Anabolic This means it is an “add up” hormone - i.e. stimulates growth or development within a tissue
Which cells secrete insulin?
beta cells of Islet cells (islets of Langerhans) of the pancreas
What is the major action of insulin?
Insulin causes the up-regulation of GLUT-4 transport protein
Define: mitotic pathway
Mitotic pathways = encourage cell differentiation and growth. Insulin does this
At what stages of glycolysis does insulin work?
Reaction 1 (glucose –> glucose-6-phosphate)
Reaction 3 (fructose-6-phosphate –> fructose-1,6-bisphosphate)
Reaction 10 (phosphoinolpyruvate –> pyruvate)
What is the main function of insulin?
To drive glucose into cells and drives glycolysis
List the minor/alternative functions of insulin
- Inhibits nutrient breakdown (i.e. catabolism)
- Stimulates FA synthesis and esterification
- “store cupboard hormone” – storage of energy, repair and growth
Physiological effects of insulin - list the major stimulatory and inhibitory effects of the hormones
- Stimulatory*
- Glucose uptake into skeletal muscle and adipose tissue (GLUT-4 mediated)
- Amino acid uptake and protein synthesis (in muscle)
- Lipogenesis
- Glycogen synthesis
- Activity of Na/K ATPase pump
- NO synthesis & Renal Na reabsorption
- Inhibitory*
- Gluconeogenesis
- Proteolysis
- Lipolysis and ketogenesis
- Glycogenolysis
- Glucagon secretion
When are levels of insulin at their highest?
Post-prandially (i.e. after a meal)
Define hyperglycaemia
High blood glucose levels
- Normal ranges = 4-6 mmol/L during fasting*
- Diabetic ranges = >7 mmol/L during fasting *
What is a common cause of hyperglycaemia
Insulin deficiency (this is Type I diabetes)
List the osmotic symptoms of hyperglycaemia
- Polyuria – excessive urine
- Nocturia – urination at night
- Polydypsia – increased thirst
- Dehydration
- Pre-renal failure – acute kidney injury
How does the endothelium get damaged as a result of hyperglycaemia?
Oxidative stress occurs due to increases in glucose resulting in ROS.
ROS build up causes endothelial damage (most problematic in the glomerulus, eye and nerves)
How does hyperglycaemia affect ATP levels?
There is extracellular hyperglycaemia, but intracellular hypoglycaemia resulting in low ATP - consequence is that the cell must find alternative energy sources (eg: fats and ketones)
What are the consequences of mobilising fat stores and ketones?
- Mobilisation of adipose tissue to use fats (first triglycerides then free fatty acids)
- Eventually, amino acids will be used (substrate of gluconeogenesis – however, there is an insulin deficiency therefore it cannot be absorbed)
- Ketoacids are eventually used
- Utilised by CNS, synthesised in the liver (ketoacids –> actyl coA –> mitochondrial ATP)
- However in excess causes acidosis (specifically ketoacidosis) due to the production and build up of acetone and b-hydoxybutyrate
