Lecture 7: Glucose Control + Diabetes Flashcards
What are the 2 types of metabolic states?
- Absorptive state
2. Postabsorptive state
What is the absorptive state?
- After a meal: absorbing nutrients from diet and storing it in the body
What is the reabsorptive state?
- Between meal: stored energy is metabolised for use
Why is glucose control important?
The brain can only get ATP from glucose, therefore must be maintained
Where is glucose stored and what is it stored as?
Stored in liver & skeletal muscle as glycogen
What is glycogenesis? What is its consequence?
Production of glycogen from glucose - decreases blood glucose
What is glycogenolysis? What is its consequence?
Break down of glycogen to release glucose - increases blood glucose
What is glyconeogenesis? What is its consequence?
Production of glucose from amino acids - increases blood glucose
Pancreas function
Produces hormones to control blood glucose (insulin & glucagon)
What type of cell is insulin?
beta
What type of cell is glucagon?
alpha
What does insulin favour?
GLUCOSE UPTAKE AND STORAGE
Can glucose diffuse across the cell membrane?
NO
How is glucose transported?
By a carrier
What facilitates glucose transport?
INSULIN
Does insulin stimulate glycogenesis?
YES
Does insulin stimulate glycogenolysis?
NO
Does insulin stimulate gluconeogenesis?
NO
How goes insulin - glucose uptake work?
- You eat something and insulin is released
- Insulin binds to the insulin receptors on the membrane
- This signals the release of GLUT4 from secretory vesicles inside the cell
- GLUT4 is embedded in the membrane so glucose can be transported into the cell
What cells do not require insulin for uptake?
Neurons, RBCs, blood vessels, kidneys, the lens of the eye
Are insulin-dependent or independent cells most affected in diabetes?
INSULIN-INDEPENDENT
What does glucagon favour?
Release of glucose into the blood
What does glucagon stimulate?
Glycogenolysis & Gluconeogenesis
What does glucagon inhibit?
Glycogenesis
What happens when blood glucose increases?
LOOK AT DIAGRAM
How does glucose homeostasis work?
LOOK AT DIAGRAM
What is the pathophysiology of type 1 diabetes?
- Autoimmune destruction of beta cells: inability to produce insulin
What is the pathophysiology of type 2 diabetes?
- Insulin resistance: insulin is produced BUT insulin receptors are unresponsive or insufficient in number, and the body compensates by increasing insulin production
- Decreased production of insulin: beta cells become fatigued, causing hyperglycemia
- Inappropriate glucose production: liver releases glucose when not needed (which increases BG)
Type 1 vs type 2 diabetes: level of insulin secretion
1: none or almost none
2. may be normal or exceed normal
Type 1 vs type 2 diabetes: typical age of onset
- childhood
2. adulthood
Type 1 vs type 2 diabetes: percentage of diabetics
- 10-20%
2. 80-90%
Type 1 vs type 2 diabetes: basic defect
- destruction of beta cells (therefore insulin not produced)
- reduced sensitivity of insulin’s target cells
Type 1 vs type 2 diabetes: treatment
- insulin injections; dietary management; exercise
2. dietary control & weight reduction; exercise; oral hypoglycemic drugs
Methods for diagnosing diabetes
- Fasting plasma glucose
- Random plasma glucose
- Two-hour oral glucose tolerance test
What happens in an oral glucose tolerance test?
- Patients consume 150g of carbohydrates/day for 3 days prior
- Fast overnight
- Measure fasting plasma glucose
- Ingest 75g glucose drink
- Measure plasma glucose after 2 hours
Normal glucose tolerance: fasting plasma glucose
<6.1
Normal glucose tolerance: 2-hour OGTT plasma glucose
<7.8
Impaired fasting glucose: fasting plasma glucose
6.1-6.9
Impaired fasting glucose: 2-hour OGTT plasma glucose
<7.8
Impaired glucose tolerance: 2-hour OGTT plasma glucose
7.8-11
Diabetes: fasting plasma glucose
> 7
Diabetes: 2-hour OGTT plasma glucose
> 11.1
Acute consequences of diabetes
- Glucose in urine
- Excessive urination
- Excessive thirst
- Excessive hunger
- Weight loss
- Fatigue
What does hyperglycemia do to blood vessels?
Causes endothelial cells of BV take in glucose and form glycoproteins
- these damage the basement membrane, leading to microvascular and macrovascular disease
What is microvascular disease (retinopathy)?
- retinal capillaries become leaky and develop microaneurysms
- microaneurysms can haemorrhage causing bleeding in retina
- lack of oxygen to retina is compensated by growth of new blood vessels that are weak and prone to damamge
What does microvasular disease (retinopathy) cause?
Blurred vision or blindness
What is microvascular disease (nephropathy)?
- Small blood vessels that supply the kidneys become leaky
What is macrovascular disease?
- Coronary artery disease
- Stroke
- Peripheral vascular disease (reduction of blood flow to extremities)
What is sensory neuropathy?
Loss of sensation, abnormal pain or painful sensations in hands and feet
What is autonomic neuropathy?
Faecal incontenence, urine retention, erectile disfunction
What causes neuropathy?
- Neurons are insulin-independent and can take up lots of glucose during hyperglycemia
- Glucose is converted inside the neuron which as an osmotic effect (cell swelling and death)
- Blood supply to nerves is impaired (lack of oxygen and nutrients)
What are the 5 reasons for increased infections?
- Senses: numbness - decreased warning signs of damage
- Hypoxia: lack of oxygen - increased infection susceptibility
- Pathogens: like high glucose
- Blood supply: decreased blood supply - decreased supply of white blood cells
- WBCs: impaired function in diabetics
What is diabetic foot?
- Peripheral vascular disease –> poor blood flow –> slow wound healing
- Sensory neuropathy (inability to detect pain)
- Susceptibility to infection
- Amputation
