Diabetes Flashcards
(31 cards)
What is type 1 diabetes mellitus?
Type 1 diabetes mellitus
Insulin-dependent diabetes (IDDM)
- Patients who lack insulin. Treatment – insulin injections
- Mainly young (Juvenile onset)
What are the symptoms of type 1 diabetes?
•Classic symptoms- Thirst, Tiredness, Weight loss
Polyuria (containing glucose + ketone bodies)
Ketoacidosis
Hyperglycaemic coma
What causes type 1 diabetes?
- Results from autoimmune destruction of the β-cells of the islets of Langerhans. Sometimes follows viral infection such as mumps, rubella, or measles.
- As there is no feedback inhibition by insulin on α-cells, glucagon levels remain high, therefore also a disease of glucagon excess
What are the metabolic consequences of diabetes?
- Blood insulin levels low despite high blood glucose, whereas glucagon levels are raised
- Insulin:glucagon ratio cannot increase even when dietary glucose enters from the gut. Metabolism stuck in the starved phase
- Low insulin:glucagon ratio leads to induction of catabolic enzymes and repression of anabolic enzymes
What is the type 1 diabetic state in the liver?
- Despite high blood glucose, liver remains gluconeogenic because of high glucagon. Lactate and amino acids such as alanine from protein breakdown are main substrates for glucose production hence muscle wasting.
- Glycogen synthesis and glycolysis also inhibited; therefore liver cannot adequately buffer blood glucose.
- Fatty acids from lipolysis enter liver and provide energy to support gluconeogenesis while excess fatty acids are converted to TAGs and VLDL.
- Excess acetyl CoA from fatty acid oxidation converted to ketone bodies and if not used sufficiently rapidly can lead to ketoacidosis due to accumulation of ketone bodies and H+ ions in the blood.
What is the effect of type 1 diabetes on ketone bodies?
Occurs normally under all conditions but increases dramatically during starvation
Prolonged low insulin:glucagon ratio result in:
- increased mobilisation of fatty acids from adipose tissue
- increased amounts of the enzymes required to synthesize and utilize ketone bodies
Why does increased lipid mobilization stimulate ketone body formation?
- In the liver, the increased demand for gluconeogenesis results in depletion of oxaloacetate
- This decreases the capacity of the TCA cycle which increases the levels of acetyl-CoA present
- Acetyl-CoA is the substrate for production of ketone bodies
How do ketone bodies form?
What is the type 1 diabetic state in muscle?
- Relatively little glucose entry into muscle and peripheral tissues because of insulin lack. This contributes to hyperglycaemia
- Fatty acid and ketone body oxidation used as the major source of fuel
- Proteolysis occurs to provide carbon skeletons for gluconeogenesis leading to muscle wasting
What is the type 1 diabetic state in adipose tissue?
- Despite the high glucose concentrations in the plasma, uptake of glucose is diminished by loss of insulin
- Low insulin:glucagon ratio enhances lipolysis leading to continuous breakdown of triacylglycerol and release of fatty acids and glycerol into the blood stream to support energy production in peripheral tissues and gluconeogenesis in the liver
What is the type 1 diabetic state in plasma and urine?
- Constant production of excess glucose while utilising less leads to hyperglycaemia
- Glucose concentration exceeds renal threshold and is excreted in the urine (glycosuria) with loss of water and development of thirst
- Fatty acid synthesis greatly diminished in the diabetic state; VLDL secreted by the liver and chylomicrons entering from the gut cannot be metabolised properly as expression of lipoprotein lipase is regulated by insulin. Results in hypertriglyceridaemia and hyperchylomicronaemia and susceptibility to cardiovascular events.
What are the short-term Possible life-threatening consequences of diabetes?
•Hyperglycaemia and ketoacidosis
Characteristic of type 1 diabetes
•Hyperosmolar hyperglycaemic state (Non-ketotic hyperosmolar coma)
Characteristic of type 2 diabetes
What are the long-term Possible consequences of diabetes?
- Predisposition to CV disease and organ damage
- Retinopathy – cataracts, glaucoma and blindness
- Nephropathy
- Neuropathy
Why is Glucose toxic in excess?
High concentration of glucose results in:
- generation of ROS
- osmotic damage to cells
- glycosylation leading to alterations in protein function
- formation of advanced glycation end products (AGE) which increase ROS and inflammatory proteins
What are the 2 major tests for diagnosing diabetes?
Fasting blood glucose levels (WHO criteria)
After an overnight fast a blood glucose value of 126mg/dl (7.0mM) and above on at least two occasions indicates diabetes (normal range are between 70-110 mg/dl, i.e. less than 6.1mM)
Glucose tolerance test (WHO criteria)
Performed in morning after an overnight fast. Fasting blood sample is removed and subject drinks ‘glucola‘ drink containing 75g of glucose. Blood glucose is then sampled at 20 min, 1 hr and 2 hr.
What test result indicates diabetes?
Diabetic: glucose remains >11.1 mM at 2 hr
What is HbA1c?
HbA1c – glycated haemoglobin
Lifespan of RBCs is 8-12 weeks, so HbA1c measurements can be used to reflect average blood glucose levels over that duration, providing a useful longer-term gauge of blood glucose control.
What is the HbA1c target for diabetics?
How is type 1 diabetes treated?
Aim – mimic normal daily insulin secretion. Endogenous insulin secretion normally peaks within one hour after a meal with insulin secretion and plasma glucose levels returning to basal levels within two hours of the end of the meal-induced hyperglycaemia.
Complete the table with types of insulin used to treat type 1 diabetes
What is type 2 diabetes?
Type 2 diabetes mellitus (Non-Insulin-dependent diabetes mellitus (NIDDM)
Disease where there is not enough insulin to keep the blood glucose normal
It is a combination of:
- Impaired insulin secretion
- Increased peripheral insulin resistance
- Increased hepatic glucose output
What are the causes of type 2 diabetes?
Failure of the body to respond properly to insulin:
- Insensitivity of target cells to insulin (defects in receptors and cell signalling)
- Impaired insulin secretion (amyloid deposits reducing β-cell mass)
Linked to obesity
What are the mechanisms of insulin resistance?
Can be caused by a number of possible defects
- Mutations in insulin receptor gene (very rare)
- Most important are defects in insulin signalling pathway
Peripheral insulin resistance is induced by…
- presence of excess fatty acids - inhibit peripheral glucose disposal and enhance hepatic glucose output
- dysregulated adipokines from adipose tissue
- also induced by defects in cellular translocation of Glut-4 (and glucose uptake). This has been observed in adipocytes (but not skeletal muscle) in both obesity and diabetes.
