diabetes pathophysiology Flashcards
2 glands of the pancreas
digestive
endocrine
digestive function of the pancreas
exocrine tissue
secretes alkaline pancreatic juice into duodenum through the pancreatic duct to help digestion
Do islets have ducts/how do they secrete?
no ducts
secrete directly into bloodstream
cells of islets
alpha
beta
delta
F cells
What do F cells secrete?
pancreatic polypeptides
structure of islet cells
core - insulin producing beta cells
mantle - A, D, F cells
What do alpha cells secrete and what happens?
glucagon
raises blood glucose
What do beta cells secrete and what happens?
insulin
lowers blood glucose
What do delta cells produce and what happens?
gastrin and somatostatin
somatostatin inhibits secretion of glucagon and insulin
cause of T1DM
insulin deficiency
What is T2DM?
inadequate response to insulin
adult onset
manifestation of diabetes
hyperglycemia (high blood glucose levels)
How many chains long is insulin?
2
A and B chain
What is insulin’s pro hormone called?
pro insulin
What connects the A and B chain of insulin?
disulfide bridges and a C peptide (connecting)
How does the GLUT-4 transporter work?
- insulin binds to the cell membrane
- intracellular signal is sent
- GLUT-4 transporter inserted into the cell membrane from its inactive state
- transport of glucose across the membrane
How is glucose transported across the cell membrane?
using carriers called glucose transporters
Where are GLUT-4 transporters?
skeletal muscle
adipose tissue
What is GLUT-4 transporter dependent on?
insulin
When is GLUT-4 transporter active and inactive?
inactive inside the cell membrane
active when insulin causes it to move from its inactive site to the membrane
Where are GLUT-2 transporters?
beta cells
liver cells
When are GLUT-2 transporters used?
when glucose levels are high
has a low affinity for glucose
Where are GLUT-1 transporters?
in all tissues
important for the nervous system
Do GLUT-1 transporters require the action of insulin?
no
Which GLUT transporter needs insulin to become activated?
GLUT-4
2 types of T1DM?
type 1A - autoimmune T-cell mediated
type 1B - idiopathic
What causes gestational diabetes?
excess hormone production during pregnancy causes insulin resistance
risks of gestational diabetes
macrosomia microsomia neonatal hypoglycemia polycythemia electrolyte disorders respiratory distress syndrome
beta cell destruction in T1 vs T2
T1 yes
T2 no
islet antibodies in T1 vs T2
T1 yes
T2 no
genetic link in T1 vs T2
T1 strong
T2 very strong
age of onset of T1 vs T2
T1 < 30
T2 >40
onset of symptoms in T1 vs T2
T1 fast onset
T2 slower onset
management of T1 vs T2
T1 insulin administered
T2 diet control and oral hypoglycaemic agents
body weight in T1 vs T2
T1 low or normal
T2 obese
extreme hyperglycaemia in T1 vs T2
T1 causes diabetic ketoacidosis
T2 causes hyperosmolar non-ketotic hyperglycaemia
What causes T1DM?
severe lack of insulin caused by autoimmune mediated destruction of islet beta cells
mechanism of beta cell destruction
T cells damage beta cells
- T helpers activate macrophages
- cytotoxic T cells directly kill beta cells
cytokines (macrophages and cytotoxic Ts) damage beta cells
autoantibodies against beta cells and insulin found in 70-80% of patients
difference between type 1A and B
1A
- immunologically mediated beta cell destruction
- environmental agent that excites an immune response
1B
- no autoimmunity present for beta cell destruction
- African/Asian descent
- strongly inherited
causes of T2DM
metabolic syndrome:
- triglycerides
- HDL
- hypertension
- systemic inflammation
- macrovascular disease
- obesity
- insulin resistance
- impaired suppression of glucose by the liver
diagnosis (3 polys)
polyuria (excess urination)
polydipsia (thirst)
polyphagia (hunger)
3 diabetic emergencies
- hypoglycaemia
- diabetic ketoacidosis
- hyperosmolar non-ketotic hyperglycaemia
What is hypoglycaemia?
glucose levels < 3.5 mm/l or 63 mg/dl
causes of hypoglycaemia
- missed/delayed/inadequate meal
- increased dose of insulin
- increase exercise
- increased alcohol consumption
- liver disease
- blood lowering drugs with oral agents
treatment of hypoglycaemia
10-20g carbohydrate meal
repeat after 10-20 mins if glucose <60 mg/dl or symptomatic
foods with 15g carbs
- half cup of orange/grapefruit/apple juice or soda
- 1 cup fat free milk
- 1/3 cup grape/cranberry juice
- 1tbsp sugar
- 5/6 pieces lifesavers
- 3/4 glucose tabs
hypoglycaemia if unable to swallow
- IV glucose (30-50ml dextrose 20-50%)
- children IV dextrose 0.2 mg/kg
- viscous glucose gel to mouth or jam/honey
3 signs of diabetic ketoacidosis
- hyperglycaemia
- hyperketoanaemia
- metabolic acidosis
treatment for diabetic ketoacidosis
- fluid replacement - 0.9% NaCl
- infusion of insulin
- potassium (not in 1st hr unless <3 mmol/l)
- treatment of any associated infection
What causes hyperosmolar non-ketotic hyperglycaemia?
osmotic diuresis
symptoms of osmotic diuresis
dehydration
increased blood viscosity
can lead to thromboembolism
differences between DKA and HNKH
DKA has more insulin deficiency
HNKH has higher glucose levels and more fluid deficiency
What is HNKH characterised by?
lack of ketosis
pro-inflammatory mediators promote insulin resistance
symptoms of HNKH
confusion to coma
sometimes seizures
bloods for HNKH
K and Na normal
creatinine high
treatment for HNKH
- fluid replacement - NaCl 0.9% or 0.45%, K if needed
- insulin - not aggressive (fluid replacement lowers glucose)
- treatment for thromboembolism
What age group does HNKH occur in?
middle aged or elderly people
synergistic factors for HNKH
- insulin deficiency
- increased levels of counter-regulatory or stress hormones
- increased gluconeogenesis and glyconeolysis
- inadequate use of glucose by peripheral tissue
What causes insulin resistance in HNKH?
- proinfmalatory mediators like TNF-alpha, IL-6, IL-1
- they release counter regulatory hormones
- cause insulin resistance and hyperglycaemia
What can insulin levels do and not do in HNKH?
insulin levels are sufficient to prevent excessive lipolysis but not to use glucose properly
diagnosis for HNKH? (7)
- non-ketotic hyperglyaemia
- mild acidosis without ketone production
- slight confusion to coma
- sometimes seizures
- plasma Na and K normal
- creatinine high
- fluid deficit is 10L (can lead to circulatory collapse)
How does fluid replacement help in HNKH?
stabilises BP
improves circulation and urine output
other diabetic complications
- impaired vision/retinopathy/cataract/glaucoma
- nephropathy: renal failure
- sensory loss, motor weakness
- postural hypotension
- GIT problems
- foot disease
- MI/ischaemia
- TIA/stroke
- dental
- increased infection risk
diabetes drug treatment (basic 3 steps)
- monotherapy: single non-insulin blood glucose lowering therapy
- dual therapy: 2 therapies (non-insulin)
- triple therapy: 3 non insulin OR any treatment combination containing insulin
T2DM - when is metformin given?
HbA1c rises to 48 mmol/mol
on lifestyle interventions
When to add on treatment to metformin?
HbA1c rises to 58 mmol/mol
When is triple therapy considered?
HbA1c rises to 58 mmol/mol
HbA1c aim for dual therapy?
53 mmol/mol
HbA1c aim for triple therapy?
53 mmol/mol
What is added in dual therapy? (metformin)
either:
- sulfonylurea
- pioglitazone
- DPP4 inhibitor
- SGLT-2 inhibitor
first line therapy if metformin is c/i or not tolerated
DPP-4i
pioglitazone
sulfonylurea