Pathology of Diabetes Mellitus Flashcards
What is the normal macroscopic structure of the pancreas?
Lobules of glandular tissue surrounded by fat
Insulin is secreted by what?
Beta cells (islet of langerhans)
Insulin is secreted into what?
Blood via capillaries
What is the function of Human Leukocyte Antigen?
Helps T-cells recognise self from non-self
What is insulitis?
Lymphocyte infiltration of islets (autoimmune mediated)
What is the result of insulitis?
Destruction of B cells
Reduced insulin
What is believed to be a cause of T1DM?
Environmental triggers: - Chemicals - Gut flora changed in infancy - Viral infection GENES
How are viruses suspected to cause T1DM?
Molecular mimicry
What is the cause of T2DM?
Reduced tissue sensitivity to insulin
Inability to secrete hight levels of insulin
What is T2DM?
A failure of the B-cells to meet an increased demand for insulin in the body
What is the environmental cause of T2DM?
Upper body fat mass
Increased intake of food
Lack of exercise
What is the effect of increased upper body fat mass? Why?
Increased free fatty acids in blood
Overweight adipocytes stressed to release FAs
Increased free fatty acids in blood leads to what?
Decreased insulin receptor sensitivity to insulin
How is the role of the pancreas changed in a patient with central adiposity?
More insulin is needed to move in the same amount of glucose
Decreased insulin receptor sensitivity to insulin causes what?
Decreased removal of glucose from the blood
So MORE insulin is secreted
What is peripheral insulin resistance?
Increased insulin needed to cope with decreased tissue sensitivity to insulin
No diabetes will occur in peripheral insulin resistance when?
When the individual can substantially increase insulin secretion
How is the amount of insulin secreted by the pancreas controlled?
GENES
Cant produce HIGH levels of insulin
Which genes are implicated for T2DM?
Genes for Beta cell high end insulin secretion
What factors do genes not appear to be for in T2DM?
Peripheral insulin resistance
Increased central adiposity
What is the ONLY genetic factor of T2DM?
Whether or not Beta cells can secrete insulin bigly
What is the annual mortality of T2DM?
5.4%
What is the LE of someone with T2DM?
Reduced by 5-10 years
What is the most common CoD in T2DM patients?
MI
Long term complications of T2DM are a result of what?
Prolonged poor glycaemic control
What is the main complication of T2DM?
Large vessel disease
Small vessel disease
What are the macrovascular complications of T2DM?
Acceleration of atherosclerosis
What are the increases in risk of CHD, MI and Stroke?
CHD - 2-20x
MI - 2-5x
Stroke 2-3x
What mechanisms are proposed for poor glycaemic control causing accelerated atherosclerosis in large vessels?
Glucose attaches to LDLs,
this stops LDLs binding to liver cell receptors
LDLs not removed by liver
–> Hyperlipidaemia
What mechanisms are proposed for poor glycaemic control causing accelerated atherosclerosis in small vessels?
DM causes molecules to flux into subendothelial space but not flux back out
Molecules trapped under endothelial cells
Thickening of the basal lamina
What is hyaline change?
Body-wide arteriolar disease causing ischaemia
What are the increased risks of amputation, end stage renal disease and blindness?
Amputation - 40x
ESRD - 25x
Blindness - 20x
What is a Kimmelstiel-Wilson lesion?
Nodule of connective tissue in the glomerulus caused by DM
How does glycosylation cause small vessel disease?
Non-enzymatic binding of glucoses to proteins which starts reversible and progresses
When does glycosylation cause irreversible damage in DM?
Covalent bonding of glucose to proteins
AGEs (advanced glycosylation end-product) formation
How is the activity of glycosylated collagen in arteriole walls changed in DM?
Glycosylated collagen binds to albumin causing albumin to accumulate in the subendothelial space of arterioles
Why do arteriolar basal lamina proteins become irremovable in DM?
GLYCOSYLATION proteins cross link to their neighbours
What is the net effect of glycosylation of proteins in the basal lamina of arterioles?
Small arteriolar disease
Accumulation of trapped plasma proteins
Accumulation of cross-linked basal lamina proteins
These persist in basal lamina even in normoglycaemia