DIABETES MELLITUS Flashcards
Where is insulin secreted from?
The beta cells of the islets of langerhans in the pancreas
What is secreted from the delta cells of the islets of Langerhans in the pancreas?
Somatostatin
What is secreted from the alpha cells of the islets of Langerhans in the pancreas?
Glucagon
What is secreted from the F cells of the islets of Langerhans?
Pancreatic polypeptide
In those patient’s receiving insulin treatment, what marker can be used to assess beta-cell activity?
C-peptide
What stimulates increased secretion of insulin?
Glucose diffusing into the cell causing a rise in intracellular ATP
What are the effects of insulin?
Increased uptake of metabolites (including glucose)
Conversion of metabolites to stored from (eg. glycogenesis)
Decreased breakdown of stored metabolites
Recruitment of glucose channels to the cell membranes
Use of glucose for energy over other metabolites
What is the half life of insulin?
5 minutes
What is the half life of proinsulin?
20 minutes
Where is insulin broken down?
Mainly kidney and liver
What are the effects of glucagon?
Inhibition of glucose and amino acid uptake
Breakdown of stored metabolites into useable metabolites
Use of fatty acids for energy over other metabolites
Promotes hepatic output of ketone bodies
What is the definition of hyperglycaemia?
Fasting concentration of more than 7.8 mmol/L
What is the definition of hypoglycaemia?
Blood glucose concentration of less than 2.5 mmol/L
What are the main types of primary diabetes mellitus?
Type 1 Type 2 MODY Pregnancy related diabetes Latent autoimmune diabetes of adults (LADA)
What is the cause of type 1 diabetes?
Autoimmune destruction of beta-islets of Langerhans resulting in an insulin deficiency.
What are the endocrine causes of secondary diabetes?
Cushing's syndrome Thyrotoxicosis Phaeochromocytoma Acromegaly Glucagonoma
What are the hepatic and pancreatic causes of secondary diabetes?
Cirrhosis of liver Chronic pancreatitis Pancreatectomy Haemochromatosis in the pancreas Pancreatic carcinoma Cystic fibrosis affecting pancreas
What drugs can induce diabetes?
Thiazide diuretics Corticosteroids Beta blockers Statins Anti-psychotics such as clozapine Immunosuppressants - ciclosporin
What are the genetic syndromes associated with secondary diabetes mellitus?
Friedreich’s ataxia
Dystrophia myotonica
How do type 1 diabetic patients often present?
Ketoacidotic crisis
What are the features of ketoacidosis?
Polyuria - bedwetting Excessive thirst Lethargy Anorexia Hyperventilation Ketotic breath Dehydration Vomiting Abdominal pain Coma
Is glycosuria diagnostic of diabetes?
No. About 1% of the population has renal glycosuria, an inherited autosomal trait associated with a low renal threshold for glucose.
What is the mechanism for ketoacidosis?
Body is unable to use the glucose in the blood due to lack of insulin. Fatty acids are released from adipose tissue which are converted to ketone bodies. Ketone bodies are acidic.
What infections are people with diabetes particularly prone to?
Fungal infection (pruritis vulvae and balanitis) Bacterial infections (staphylococcal skin infections)
What is impaired glucose tolerance?
A state of glucose tolerance between normal and diabetic states. Occurs in both obese and non-obese.
Are patients with a type 1 diabetic parent more likely to develop diabetes if it is their father or mother who is the diabetic?
Father
At what age is the peak incidence of disease for type 1 diabetes?
Two peaks. One in pre-school and one in teenagers.
Normally before 15 years old
What are the environmental factors thought to predispose someone to type 1 diabetes?
Hygiene Parasites Coexisting infections - TB or malaria Enteroviruses Bacteria Early exposure to cow's milk Certain toxins.
Do the autoantibodies cause type 1 diabetes?
No. They are thought to be just a marker of disease and may be used to predict onset of disease.
What is latent autoimmune diabetes of adults (LADA)?
An autoimmune form of diabetes which is often misdiagnosed as type II diabetes due to the late onset of the disease.
What are the risk factors associated with developing type 2 diabetes?
Genetic markers Female gender Increasing age Diet - Westernisation of diet Sedentary lifestyle Obesity Stress Low weight at birth and at 12 months
What is the mechanism of disease in type 2 diabetes?
Resistance to the normal actions of insulin by cell membrane receptors
What is the association between polycystic ovary syndrome and type 2 diabetes?
PCOS leads to insulin resistance. As a consequence, the patient develops hyperinsulinaemia which may stimulate androgen production by acting as a gonadotrophin.
What are the criteria for testing someone who is asymptomatic but over the age of 45 for prediabetes?
Any of the following: First degree relative with diabetes Overweight or obese Previous gestational diabetes Polycystic ovary syndrome Essential hypertension Hypertriglyceridaemia Low HDL cholesterol High-risk ethnic group Premature cardiovascular disease Therapy with corticosteroids, thiazides or beta-blockers Primary hyperuricaemia or gout Cushing's syndrome Acromegaly Turner's syndrome Down syndrome
How long after the development of symptoms of type 1 diabetes are the autoantibodies detectable?
Before symptoms. Months to years before symptoms.
What are the autoantibody markers associated with type 1 diabetes?
Islet cell antibodies (ICA)
Insulin autoantibodies (IAA)
Glutamate decarboxylase (GAD)
Insulinoma-related antigen 2 (1A-2)
Which is associated with a higher risk of developing type 2 diabetes? Impaired fasting glucose or impaired glucose tolerance.
Impaired glucose tolerance
What is the form of management of impaired glucose tolerance to prevent it progressing to type 2 diabetes?
Lifestyle changes
What is the single most common cause of limb amputations?
Diabetes mellitus
What is the single most common cause of blindness in middle aged adults in developed countries?
Diabetes mellitus
What is the single most common cause of renal failure in middle aged adults in the developed world?
Diabetes mellitus
What are the main groups of complications of diabetes mellitus?
Macrovascular disease Microvascular disease Hyperglycaemia and DKA Increased susceptibility to infection Pregnancy related complications Psychosocial complications
What are the main macrovascular complications of diabetes mellitus?
Stroke
Cardiovascular disease
Renovascular disease
Peripheral vascular disease
What are the three main sites affected by diabetic microvascular disease?
Retina (retinopathy) Renal glomerulus (nephropathy) Nerve sheaths (neuropathy)
Within how many years of diagnosis do diabetic patients tend to develop macrovascular complications?
10-20 years
What is the hallmark indicator of nephropathy?
Proteinuria
What are the molecular consequences of hyperglycaemia?
Development of advanced glycation end products (AGEs)
Increased production of reactive oxygen species
Activation of NFκB (an intracellular transcription factor that mediate proinflammatory responses)
Sorbitol accumulation
Activation of protein kinase Cβ
What is the normal range for percentage of haemoglobin that is glycated (HbA1c)?
4-5.9% (20-41 mmol/mol)
How long does HbA1c reflect?
Roughly 2-3 months (half life of a red blood cell)
What is the HbA1c used for?
To measure average diabetes control over a 2-3 month period.
In a diabetic patient with a haemoglobinopathy or who is pregnant, what measurement can be used instead of HbA1c?
Glycated plasma proteins (fructosamine) levels
Glycated albumin levels