Lecture 24

Question 1

What are the different forms of diabetes?

Answer 1

Diabetes Insipidus
Diabetes Mellitus (insulin dependent, insulin independent)
Gestational Diabetes
Bronze Diabetes

Question 2

What are the symptoms which are common to all types of diabetes?

Answer 2

Excessive thirst, production of large volumes of urine, associated with blurred vision and may cause extreme fatigue

Question 3

What is polydipsia?

Answer 3

Excessive thirst

Question 4

What is polyuria?

Answer 4

Production of large volumes of urine

Question 5

What is bronze diabetes?

Answer 5

A secondary event from the hereditary haemochromatosis disease where there is iron accumulation in the liver and pancreas damaging these tissues and causing pigmented skin and glucose intolerance

Question 6

What is diabetes insipidus?

Answer 6

Rare condition caused by a deficiency of ADH, resulting in an inability to concentrate urine causing chronic water diuresis

Question 7

What treatments exist for diabetes insipidus?

Answer 7

Administration of the deficient ADH

Question 8

Where does the disease of diabetes insipidus occur?

Answer 8

Posterior pituitary due to either trauma or brain tumors causing compression of adjacent pituitary gland, mutations in the vasopressin-neurophin II gene, mutations in vasopressin receptor or transporter protein genes in kidney

Question 9

What characterizes Diabetes Mellitus?

Answer 9

Fluctuations in blood glucose caused by a lack of insulin production or effect, resulting in hyperglycaemia

Question 10

What is hyperglycaemia?

Answer 10

High blood glucose levels
>7.8 mmol/L fasting
>11mmol/L 2h postprandial
(normal is 2mmol/L)

Question 11

What is the effect of the hyperglycaemia seen in diabetes mellitus?

Answer 11

hyperosmosis is caused by the high sugar concentration, this causes dehydration of body tissues which drives plydipsia, consequently there is an increase in plasma volume which is compensated fro by the kidney via polyuria

Question 12

How does diabetes mellitus cause blurred vision?

Answer 12

The fluctuating blood glucose levels result in osmotic pressure variations altering the curvature of the lens

Question 13

What are the different types of diabetes?

Answer 13

type I Insulin dependant (insufficent insulin levels)

type II insulin independant (insuffiecent insulin production and action)

Question 14

How does the pancreas usually act to control blood glucose levels?

Answer 14

Pancreas will detect high insulin levels and secrete insulin (produced by the beta cells in the islets of langerhans of the pancreas) causing glucose storage as glycogen in the liver
As glucose is used up in the periphery, the pancreas senses this and releases glucagon to induce glucose release

Question 15

What are the epidemiological factors of type I diabetes mellitus and what is treatment for this condition?

Answer 15

Treatment is insulin replacement
Patients with this condition typically have a low life expectancy as complications such as heart disease and kidney damage are common
Has an onset of >20 years
combination of environmental and inherited factors
Has a slow progressive onset and will only appear clinically after 80% of Beta cells are lost

Question 16

What is the environmental factor that may play a role in type I diabetes mellitus?

Answer 16

Viral infection of the beta cells may lead to expression of an abnormal MHC II, or a foreign protein such as one found in milk (speculated) is similar to a component of found on normal Beta cells
Both of these environmental factors will induce and autoimmune response against the Beta cells leading to their destruction

Question 17

What occurs to beta cells in type II diabetes mellitus?

Answer 17

Due to constantly high levels of glucose in the diet the beta cells must hypersecrete insulin ending in a failure of the beta cells to cope causing a loss of the insulin synthesizing abilities of the cells

Question 18

What occurs to peripheral cells in type I Idiabetes mellitus?

Answer 18

They become resistant to the effects of insulin due to a down regulation of the insulin receptor, this decreases intracellular signalling and therefore results in lower activity of the GLUT transporter and a reduction of the glucose uptake by the cell

Question 19

What factors play a role in the onset of type II diabetes mellitus?

Answer 19

Lifestyle factors such as high sugar consumption, obesity and a lack of exercise
Genetic factors also play a role with a 60% concordance rate between twins suggesting a larger genetic factor than type I diabtete mellitus

Question 20

How can diet and exercise changes help to prevent type II diabetes mellitus?

Answer 20

This reduces the level of glucose in the blood (which is the factor which causes damage)
It also creates an increased demand for glucose by the cell preventing the down regulation of the insulin receptor
Hypoglycaemic drugs are used to increase insulin production from Beta cells

Question 21

What is gestational diabetes?

Answer 21

Hyperglycaemia caused during pregnancy which stops after birth, this may be caused by resistin production by the placenta

Question 22

What are the pathological effects of hyperglycemia?

Answer 22

Glycosylation and glycation of proteins impairing their function leading to structural changes in connective tissue and damage to nerves and blood vessels
Aldose reductase in induced by high glucose levels metabolising glucose to sorbitol which induces cell swelling as it poisons the Na+/K+ Pump
Activation of protein kinase C altering contractility of vasculature changing permeability causing neuropathy, vascular complications and nephropathy

Question 23

What are the chronic complications of hyperglycemia seen in diabetes mellitus?

Answer 23

Cardiovascular problems such as stroke, coronary heart disease and peripheral vascular disease due to large blood vessel damage
Damage to small blood vessels causing retinopathy and nephropathy
Damage to nerves
Increased susceptibility to fungal and bacterial infections
Diabetic foot and ulcers due to neuropathy and peripehral vascular disease
Increased risk of cataracts

Question 24

What induces the cardiovascular complications seen in D.Mellitus?

Answer 24

Early and accelerated atherosclerosis
Myocardial infarction is a common cause of death
20-40% of diabetics develop renal failure due to increased glomerular pressure causing protein deposition causing glomerulosclerosis
Also prone to kidney infection

Question 25

What causes diabetic foot?

Answer 25

Degeneration of neurons and lack of insulating myelin caused by sorbitol damage and depletion of myoinositol causing a reduction in neurotransmitter production can result in a loss of sensation to the foot this results in the patient being unable to feel the typically painful formation of ulcers on the lower limb

Question 26

What causes the ocular complications of d.mellitus?

Answer 26

Atherosclerosis of blood vessels in the eye, causing ischemia, followed by the generation of new blood vessels can cause scars to form blurring vision
Cataracts is also more common due to sorbitol damaging the crystalline lens
This typically occurs 10 years after the onset of diabetes