Diabetes Mellitus Flashcards
What is the main hormone in the fasting state?
Glucagon
What releases glucagon
Alpha cells (islet of langerhan of endocrine pancreas
What is the hepatic action of glucagon
Increase hepatic glucose output by increasing
Gluconeogensis
Glycogenolysis
What effect does glucagon have on peripheral tissue
Decreases glucose uptake
Stimulates the release of gluconeogenic precursors (glycerol/ AA)
What are gluconeogenic precursors and how are they formed
Glycerol and AA
through lipolysis and muscle glycogenolysis
Give examples of counter-regulatory hormones of insulin
Glucagon, adrenaline, cortisol, GH
What releases insulin?
Beta cells (islet of langerhan- endocrine pancreas)
What effect does insulin have on glucagon?
Inhibitory paracrine effect
Summarise how glucose causes insulin to be secreted by B cells (normal action)
- Glucose enters B cell through GLUT2 glucose transporter
- Glucose is metabolised by glucokinase
- This causes K+ channels to close -> cell depolarisation
- Causes Ca2+ channels open -> Ca2+ influx
- Causes insulin secretory granules to release insulin out of cell
Summarise how insulin acts on fat and muscle cells (normal mechanism action)
- Insulin binds to insulin sensitive receptors
- Causes signalling cascade
- Causes mobilization of intracellular GLUT4 vesicles to CSM
- Integration of vesicles to CSM
- This allows entry of glucose into cell
What are the normal actions of insulin?
Liver: decr hepatic glucose output-> suppresses gluconeogenesis and glycogenolysis
Increases glucose uptake in insulin sensitive tissue
Suppresses lipolysis and breakdown of muscle
What occurs when fasting - energy source for different tissues?
- Glucose is from liver (hepatic gluconeogenesis and glycogenolysis)
- Glucose is supplied to insulin independent tissue (brain and rbc)
- Low insulin level and high glucagon levels
- Lipolysis (12hrs<)
- Muscle use FFA for fuel
What process does insulin inhibit?
Lipolysis
What is the distribution to ingested glucose
40% liver
60% peripheries (mostly muscle)
Define T2DM
Chronic hyperglycaemia due to insulin resistance and disorder of carb metabolism
Describe the epidemiology for T2DM
- South Asians, Africans, Caribbean
- 40 yrs<
- Men
What are the risk factors for T2DM?
- Lifestyle (obese, sedentary, high alcohol intake, poor diet)
- Ethnicity
- Sex
- Hypertension
- Hypercholesterolaemia
- Increasing age
- Large waist size
- Family history - much stronger than t1dm
Describe the clincal presentation for T2DM
Symptoms:
- Polydipsia, polyuria, glucouria, blurred vision, unintentional weight loss,
- fatigue, central obestity, recurrent infections, genital thrush
- may be asymptomatic
Signs:
- Acanthosis nigricans (skin condition causing dark pigmentation of skin folds eg neck) - severe insulin resistance
What are the 4 main investigations and results for T2DM
- HbA1c >48mmol/L (6.5%)
- Fasting plasma glucose >7.0mmol/L with symptoms
- Random plasma glucose >11.1mmol/L with symptoms
- OGTT
fasting >7mmol/L
2hr >11.1mmol/L
What are the causes for T2DM
- genes and environement
- pregnancy (gestational diabetes)
- medication (thiazides, steroids)
- other endocrine diseases (hyperthyroidism, cushings, acromegaly)
What is the first line treatment for T2DM
Diet and exercise changes to target weight loss and reduce carb intake
Describe the pathophysiology of T2DM
- Periperhal insulin resistance = decr. glucose uptake
insulin can bind but malfunction in insulin intracellular pathway activation
so decr. in GLUT4 expression so decr. in glucose uptake - Decr. in insulin secretion due to B cell destruction (glucotoxicity) b amyloid deposits in pancreas
- Hepatic insulin resistance = excessive glucose production
- This causes hyperglycaemia
- Causing glycosuria
What is the first oral mono-therapy used for T2DM?
Metformin (biguanide)
What is the action of metformin?
Increases insulin sensitivity inskeletal muscle
Helps with weight loss
Reduces hepatic gluconeogeneis
What 3 factors define diabetic ketoacidosis?
Hyperglycaemia (plasma glucose >11mmol/L)
Raised plasma ketones (plasma ketone >3mmol/L)
Acidosis (Blood pH <7.3, bicarb <15mmol/L)
What is diabetic ketoacidosis?
Uncontrolled catabolism with associated insulin deficiency
What are the clinical features of DKA?
Vomiting
Abdo pain
Dehydration
Polydipsia and polyuria
Fruity breath
Hyperventilation- deep breathing (kussmaul HV)
Coma
Tachy/ hypotension
Low BP
What is the management for DKA?
- IV: fluid replacement
- IV insulin
- Electrolytes (K+)
What are the complications of DKA
Cerebral oedema
aspiration pneumonia
Hypokalaemia/magneasemia/phosphateaemia
Thromboembolism
Death
What are the tests and results for DKA?
Urine stick: glycosuria, ketonuria
Blood test:
Raised urea, creatinine (bc pre-renal failure)
Bicarb (<15mmol/L)
Hyperglycaemia (plasma glucose >48mmol/L)
Blood ketone (>3)
Blood pH <7.3
Raised K+ on presentation
What can trigger ketoacidosis?
Infection
Surgery
Error in insulin treatment
Undiagnosed diabetes
Does DKA often occur in T2DM?
Rare due to low insulin production/ not complete resistance which inhibits lipolysis
May occur in very late stages w absolute insulin def.
More common in T1DM