3 - T1DM Flashcards
Define diabetes mellitus
Hypergycaemia
Caused by insufficient:
- Insulin secretion
- Insulin action
Associated with significant morbidity / mortality
In Caucasian Northern Europe, what is the most common aetiology of T1DM?
T-cell mediated autoimmune destruction of the Beta-cells within the pancreas.
How many people in the UK are diagnosed with DM?
4.7 million
How many are estimated to have DM by 2035?
> 5 million
How many people have been diagnosed with diabetes worldwide?
425 million
How much does diabetes cost the UK?
£10 billion
What % of this £10 billion is spent on preventable complications?
80%
What % of TOTAL NHS budget is spent on diabetes and complications?
10%
By 2035, what is the projected % spend of TOTAL NHS budget on diabetes and complications?
17%
What are the symptoms of diabetes?
Polyuria Polydipsia Unexplained weight loss Tiredness Blurred vision Diabetic ketoacidosis
How do you diagnose diabetes?
Either:
Fasting plasma glucose > 7.0 mmol/L
Random plasma glucose > 11.1 mmol/L
What is the gold standard for diabetes diagnosis?
Oral glucose tolerance test (OGTT) - 75g of glucose.
2h-post glucose-load plasma glucose > 11.1mmol/L
What test is required if patient is asymptomatic but blood glucose levels are suggestive of diabetes?
Repeat glucose measurement on a different day to confirm.
Why is misdiagnosing diabetes dangerous?
Affect life insurance
Ability to drive
Perform employment duties
Who is HbA1c not possible to use as a clinical diagnostic test?
Young people
T1DM
Pregnant
Haemoglobinopathies
What does HbA1c measure?
Measures glycated haemoglobin.
What are the 3 advantages of HbA1c?
1) No need to fast
2) Lower variability
3) More stable for transporting samples
What are the reference ranges for HbA1c?
<42mmol/L = normal
42-47 = pre-diabetes
> 47 = diabetes
What are the 2 features of a pancreatic beta cell?
Nucleus
Insulin secretory granules (fried eggs)
What are the 2 components of an insulin secretory granule?
Dense insulin core
Loose surrounding zone
In the production of insulin, what is the role of the ER?
ER produces a pro-hormone.
What is the role of the golgi apparatus in the production of insulin?
Cleaves the pro-hormone by pro-hormone-convertases
What pro-hormone convertases are present in the golgi apparatus?
PC2 and PC1/3
What are the two products of pro-hormone insulin cleavage?
1) Mature insulin
2) C-peptide
Which cells produce insulin?
Beta cells in the pancreatic islets of langerhans
Which cells produce glucagon?
Alpha cells
What are the 3 main targets of insulin / glucagon?
Muscle
Liver
Adipose tissue
What glucose transporter is responsible for bringing glucose into the beta cell?
GLUT1
Describe the process of insulin secretion.
Glucose transport into cell
Metabolism produces ATP
ATP-sensitive K+ channels close, resulting in depolarisation.
Voltage-gated calcium channels open, resulting in calcium influx.
Insulin secretory granules exocytosed
What is the incretin effect?
The markedly higher insulin response when glucose is ingested compared to when given through IV
Give 2 examples of an incretin?
GLP-1
GIP
What cells produce GLP-1?
Intestinal L-cells
What type of GPCR is GLP-1 receptor?
GalphaS
What pattern of insulin secretion occurs? What is it described as?
Biphasic
1st phase: Triggering stimulus releases granules already close to membrane of beta-cell immediately.
2nd phase: Expansion and replenishment of readily-releasable pool before second wave of insulin secretion.
What is PDX1?
What occurs in high glucose levels?
A transcription factor regulated by glucose
PDX1 activated to increase transcription of insulin gene.
What are the two pathways that are activated in response to insulin-receptor activation?
PI3K pathway
RAS/MAPK pathway
What subsequent processes is the PI3K pathway involved in?
Growth + differentiation
+ Metabolic actions
What subsequent processes is the RAS/MAPK pathway involved in?
Growth + differentiation
Survival + Gene expression
What are the 2 differences between T1A-DM and T1B-DM?
No autoimmune markers detectable in T1B-DM.
T1A = insulin deficiency T1B = Absolute deficiency
What 3 features are associated with T2DM?
Beta-cell failure / insulin resistance.
Later presentation
Associated with obesity
What is gestational diabetes mellitus?
Glucose intolerance / diabetes during pregnancy.
When does gestational diabetes mellitus usually occur?
During 2nd / 3rd trimester
Following parturition after gestational diabetes mellitus, what is the outcome in the context of the mother’s DM?
Can NOT have DM.
Will be at a higher risk of getting it.
What is maturity onset diabetes of the young? (MODY)
Monogenic cause of diabetes that occurs in young-adult life, as a result of a mutation in a gene responsible for pancreatic beta cell function, differentiation or proliferation.
Give 3 examples of genes that, if mutated, result in Maturity onset diabetes of the young (MODY)
Glucokinase
PDX1
HNF-1alpha
How is MODY diagnosed?
<25 years old
Familial inheritance
What % of DM patients have MODY?
1-2%
What is permanent neonatal DM ?(PNDM)
Monogenic cause of diabetes that occurs following birth.
What two important genes can cause permanent neonatal DM? What are they responsible in coding for?
KCNJ11 / ABCC8
The ATP-sensitive K+ ion channel
What is an emergency complication of T1DM?
DKA
What is the T2DM equivalent of DKA?
Hyperosmolar non-ketotic coma (HONK)
What are two important genes in the predisposition of T1DM?
HLA DR4
HLA DR3
What percentage of children with T1A-DM have either one of HLA-DR3/4?
90%
What is the original gene and its location in regard to HLA DR3/4?
HLA Class II
Chromosome 6
What does HLA stand for?
Human Leukocyte Associated
What are the 3 classes of HLA genes?
Class 1 = all nucleated cells (necessary for viral infection response)
Class 2 = APC cells
Class 3 = Complement
What factors can trigger T1DM?
Viruses Bacteria Gluten Toxins Cow's milk
What viruses can trigger T1DM?
Coxsackie B4 virus
Picornavirus
What is the usual natural history of the disease and its progression?
A progressive decline in insulin secretory capacity, as a result of continual auto-immune destruction of Beta-cells.
In the pathogenesis of T1DM, what is the honeymoon phase?
Occurs after first hyperglycaemia.
Pancreatic beta-cells and pancreatic stem cells regenerate themselves to increase beta-cell mass and normalise glucose level.
However, quickly gets overrun by autoimmune disease again.
What % of T1DM patients have the presence of autoantibodies circulating in their blood?
90%
What are autoantibodies a predictor of?
Risk of T1DM development.
Name the 4 auto-antibodies commonly found in
GAD65
Islet antigen-2
Insulin
Zinc transporter
What is Insulitis?
Invasion of pancreatic islets by lymphocytes (CD4+ / CD8+).
Characteristic of T1DM
How do you treat T1DM?
Insulin
How is insulin administration given to match normal physiology?
Basal dose
Short-acting insulin analogue following meal consumption.
Give 2 examples of long-acting insulin analogues
Glargine
Detemir
(1x daily)
Give 2 examples of short-acting insulin analogues
Lispro
Aspart
What are 4 other methods of treating T1DM?
Kidney / pancreas transplant
Insulin pumps (open / closed)
Islet transplant
Insulin inhalation
What is an issue with islet transplantation?
Requires 3 donors
Remission lasts 5 years before it occurs again.
What are the 4 future treatments for T1DM?
· Advanced closed-loop insulin pumps
· Cell-based therapies: islet transplantation (ongoing trials), stem cell therapies
· β-cell regenerative medicine
· Prevention / immune modulation
What is the bionic pancreas and how does it work?
Real time insulin / glucagon pump that alleviates the major clinical / personal issues that are bound to T1DM.
Blood glucose monitor and doses insulin / glucagon in relative amounts every 5 minutes.
Catheter requires changing weekly.
What is T1DM?
Absolute deficiency of insulin.
If diagnosis of T1DM occurs before 1 year of age, what two genetic conditions should be considered?
Maturity onset diabetes of the young
or other monogenic causes of diabetes, e.g. permanent neonatal diabetes mellitus
What is hypoglycaemia defined as in regards to blood glucose concentrations, in mmol/L?
<3.5mmol/L