(endo) microvascular and macrovascular complications of diabetes mellitus Flashcards
define microvascular (complications of diabetes)
long-term complications that affect small blood vessels
e.g. neuropathy, nephropathy, retinopathy
define macrovascular (complications of diabetes)
long-term complications that affect large blood vessels
e.g. cerebrovascular disease, ischaemic heart disease, peripheral vascular disease
what increases the risk of developing microvascular complications of diabetes?
1) extent of hyperglycaemia i.e. HbA1c levels
2) rising systolic BP and risk of MI
what are the target HbA1c levels to reduce the risk of microvascular complications?
53 mmol/mol
how do increasing HbA1c levels affect microvascular complications of diabetes?
= increase risk of microvascular complication in the following order
1) retinopathy
2) nephropathy
3) neuropathy
4) microalbuminuria
prevention of microvascular complications in diabetes requires reduction in which two parameters mainly?
1) HbA1c
2) blood pressure
besides HbA1c and BP, which factors increase the risk of developing microvascular complications?
1) (longer) duration of diabetes
2) smoking
3) genetic factors
4) hyperlipidaemia
5) hyperglycaemic memory
explain the link between duration of diabetes and risk of developing microvascular complications
the longer a patient has had diabetes + associated hyperglycaemia, the more likely they are to develop microvascular complications
explain the link between hyperlipidaemia and risk of developing microvascular complications
the greater the levels of hyperlipidaemia, the greater the risk of developing microvascular complications of diabetes
explain the link between smoking and risk of developing microvascular complications
smoking causes endothelial dysfunction
= increased risk of microvascular complications
explain the link between genetic factors and risk of developing microvascular complications
some individuals may be genetically prone to developing microvascular complications despite having reasonable glycaemic control
what is hyperglycaemic memory?
the idea that individuals with a period of past poor glycaemic control may have caused irreversible damage in such a way that increases the risk of complications
(despite the chance that the patients may NOW have good glycaemic control)
explain the link between hyperglycaemic memory and risk of developing microvascular complications
inadequate glucose control in the past can result in a higher risk of complications, even if HbA1c is improved now
how does hyperglycaemic memory come about?
periods of hyperglycaemia (poorly controlled)
= can cause epigenetic modifications
= increase the risk of complications
(does not matter if HbA1c is improved/better controlled now)
briefly explain the mechanism of damage in terms of microvascular complications
hyperglycaemia + hyperlipidaemia
= oxidative stress
= increased formation of mitochondrial superoxide free radicals in the endothelium
= activation of inflammatory signalling cascade
= inflammation + endothelial damage
= leaky capillaries, ischaemia (+ retinopathy, nephropathy, neuropathy)
why are the effects of persistent hyperglycaemia long-lasting?
poorly-controlled persistent hyperglycaemia causes long-lasting epigenetic modifications
= persistent expression of pro-inflammatory genes
= even if HbA1c is better controlled now, there is always an increased risk of complications
what is diabetic retinopathy?
a microvascular complication of diabetes that causes damage to the vessels supplying the retina
what is diabetic retinopathy the main cause of?
- visual loss in people w diabetes
- blindness in people of working age
why is annual retinal screening essential in people with diabetes?
patients are usually asymptomatic in the early stages of diabetic retinopathy
= SO, screening is essential to identify + treat it early while treatment is still possible and before visual loss/blindness
what are the possible stages of diabetic retinopathy?
- background retinopathy
- pre-proliferative retinopathy
- proliferative retinopathy
- maculopathy
what are the characteristic features of background retinopathy?
- hard exudates (cheese colour, as a result of lipid leakage)
- microaneurysms
- blot haemorrhages
why do hard exudates form in background retinopathy?
inflammation of the vessels supplying the retina
= leads to leaky capillaries
= lipid leakage
what are the characteristic features of pre-proliferative retinopathy?
- soft exudates (i.e. cotton wool spots)
= form due to retinal ischaemia
what occurs in pre-proliferative retinopathy that leads to the formation of soft exudates?
retinal ischaemia
due to endothelial dysfunction as a result of inflammation of the retinal capillaries