Week 1 - Diabetes

Define diabetes

Endocrine system disorder characterised by hyperglycaemia due to abnormal secretion or function of insulin

Explain the normal pathway when blood sugar increases

1. High blood sugar levels after eating

2. This stimulates beta cells of Islets of Langherhan within the pancreas to secrete insulin into the bloodstream

3. Insulin binds to receptors on liver and muscle cells, stimulating the uptake of glucose which is stored as glycogen

4. Blood sugar decreases to homeostasis

Explain the normal pathway when blood sugar decreases

1. Low blood sugar levels after fasting

2. This stimulates the alpha cells of the Islets of Langherhan within the pancreas to secrete glucagon into the bloodstream

3. Glucagon binds to receptors on liver and muscle cells, stimulating glycogen breakdown to release glucose into the bloodstream

4. Blood sugar increases to homeostasis

State blood sugar levels at homeostasis

90mg/100ml

Briefly differentiate between Type 1 & Type 2 Diabetes

• Type 1 - autoimmune disease that damages beta cells and therefore can no longer produce insulin, causing abrupt symptoms

• Type 2 - chronic hyperglycaemia reduces the body’s sensitivity and responsiveness to insulin, causing progressive symptoms

State alternative names for Type 1 & Type 2 Diabetes

• Type 1 - insulin-dependent

• Type 2 - insulin-independent

State and briefly explain other types of diabetes

• Gestational Diabetes - from pregnancy

• Diabetes Insipidus - hormonal issue causing dilute urine

Explain the pathophysiology of Type 1 Diabetes

• The body’s immune system mistakenly attacks and destroys beta cells of the pancreas, therefore can no longer produce inuslin

• Caused by:

  • Genetics causes immune system to stimulate cytotoxic T lymphocytes, destroying own cells

  • Environmental factors such as a viruses either infecting beta cells or having similar structure to beta cells, causing the immune system to attack them.

Explain the treatment of Type 1 Diabetes

Endogenous insulin injections for life

Explain the pathophysiology of Type 2 Diabetes

• Chronic hyperglycaemia from poor diet, physical inactivity or obesity causes the pancreas to work harder and produce more insulin

• Hyperinsulinaemia causes inuslin resistance in which liver/body cells fail to respond to insulin and receptors die off

• Eventually B cells fail and insulin production is decreased further contributing to the diabetes

State what occurs to insulin in Type 2 Diabetes

Hyperinsulinaemia - high levels of insulin in the bloodstream

Explain the treatment options for Type 2 diabetes

• Lifestyle changes such as diet changes, physical activity and weight loss

• Diabetes medications such as Metformin

• Endogenous insulin injections

Explain the 3 overall functions of insulin

• Regulates carbohydrate metabolism

• Regulates lipid metabolism

• Regulates protein metabolism

State the 5 ways that insulin regulates carbohydrate metabolism

• Increases glucose uptake into the liver and muscle cells

• Increases glycogenesis

• Increases glycolysis

• Decreases glycogenolysis

• Decreases gluconeogenesis

Explain glycogenesis

Glucose conversion to glycogen for storage in liver and muscle cells

Explain glycolysis

Breakdown of glucose via first step of cellular respiration for production of ATP to meet energy requirements at the time. Once energy requirements are met, excess glycerol and fatty acids form triglycerides and are stored in adipose tissue.

Explain glycogenolysis

Glycogen breakdown into glucose to be released into the bloodstream

Explain gluconeogenesis

Glucose production from non-carbohydrate sources such as amino acids, glycerol, etc.

State the 2 ways that insulin regulate lipid metabolism

• Increases lipogenesis

• Decreases lipolysis

Explain lipolysis

Breakdown of fat into glycerol and fatty acids for energy

State the 3 ways insulin regulates protein metabolism

• Increases protein synthesis

• Increases amino acid uptake into cells

• Decreases protein catabolism

Explain why polyuria is a symptom of diabetes mellitus

Hyperglycaemia causes glucose to surpass the normal threshold excreted in the kidneys. Glucose is an osmotic diuretic in which there is increased water excreted into urine causing frequent urination.

Explain why polydipsia is a symptom of diabetes mellitus

Hyperglycaemia causes water to be drawn out of cells into the blood via osmotic forces. This causes intracellular dehydration, stimulating thirst. Polyuria further contributes.

Explain why polyphagia and weight loss are symptom of diabetes mellitus

Insulin resistance/lack of insulin results in glucose failure to be taken up by liver and body cells. This causes breakdown of carbs, proteins and fats within cells in order to meet energy requirements, causing weight loss and increased hunger.

Explain why recurrent infections are a symptom of diabetes mellitus

Hyperglycaemia impairs immune function and provides energy for growth of microorganisms, causing frequent infections.

Explain why sore healing sores are a symptom of diabetes mellitus

Hyperglycaemia damages blood vessels decreasing blood flow to peripheries. Additionally decreased immune function also impairs healing.

Explain why blurry vision is a symptom of diabetes mellitus

Hyperglycaemia causes glucose to be absorbed by fluid in the lens. Glucose is broken down into sorbital which draws water into the lens by osmosis, causing swelling and changes in shape causing blurring vision during periods of hyperglycaemia.

Additionally, chronic hyperglycaemia damages blood vessels in the retina that affecting vision.

Explain a non-ketotic hyperosmolar coma

An acute life-threatening complication of diabetes in which there is severe hyperglycaemia and severe cellular dehydration without the presence of ketones that causes confusion, sensory loss, slurred speech, seizures and even death.

Explain ketoacidosis

An acute complication of diabetes in which body cells have no glucose/energy, causing lipolysis and ketogenesis forming ketones. Excess ketones can result in acidosis and fruity-smelling breath.

Explain hypoglycaemia

An acute complication of diabetes, typically for Type 1 diabetics in which their dose of endogenous insulin is too high due to imbalances in food and activity levels. This activates the sympathetic NS and causes cold and clammy skin, dizziness, fatigue, confusion, increased heart rate, etc.

Explain diabetic retinopathy

A chronic complication of diabetes in which hyperglycaemia damages endothelium of blood vessels in the retina, leading to swelling and haemorrhage that impairs vision.

Explain cerebrovascular/heart/peripheral artery diseases

Chronic complications of diabetes in which hyperglycaemia damages endothelium of blood vessels, causing inflammation, atherosclerosis and subsequent, stroke, MI and reduced blood supply to tissues and organs causing gangrenous necrosis.

Explain diabetic neuropathy

A chronic complication of diabetes in which hyperglycaemia damages nerves due to capillary damage that reduces blood supply to nerves as well as interfering with chemical balance within neurons, causing numbness and tingling.

Explain diabetic nephropathy

A chronic complication of diabetes in which hyperglycaemia damages glomeruli of the kidneys, leading to renal failure.

Explain diabetic pneumopathy

A chronic complication of diabetes in which hyperglycaemia damages pulmonary capillaries, nerves and elastic tissue in the lungs, stiffening tissue and causing pulmonary fibrosis as well as impairing gas exchange.

State which cells of the body are insulin-dependent

Cells in:

• Capillaries

• Retina

• Kidneys

• Nerves

Explain the importance of this

These cells take up glucose in the absence of insulin, therefore in hyperglycaemia, the increase in glucose uptake into the cells makes them susceptible to damage.