Diabetes

Question 1

describe the normal metabolism of glucose

Answer 1

eat –> glucose in blood causes beta cells in islets of langerham of pancreas to release insulin –> insulin moves to liver, muscles + adipose tissues –> binds to insulin receptor –> allows glucose uptake by cell –> stored as energy

Question 2

what is the main complication of T1D?

Answer 2

beta cells are damaged –> no insulin released –> impaired glucose uptake –> high glucose in blood + urine (body think it hasnt been fed/ starving itself –> increased ratio of glucagon:insulin –> increase catabolism of glycogen (glycogenolysis), fat + protein –> increase fatty acid synthesis = ketone bodies synthesis –> decrease blood pH+ dehydration

if not treated with exogenous insulin = can cause unconsciousness

Question 3

describe the pathogenesis of T1D (immune cells)

Answer 3

1) APC (B cells, macrophages, DC) recognise beta cells as foreign, phagocytose + present antigen fragments on MHC 2 –> present to autoreactive CD4 T cells (that have escapes neg selection)
2) CD8 T cells recognise MHC 1 presenting immunogenic self antigens –> kill beta cells
3) innate + adaptive (B + T ) cells will release proinflammatory cytokines & ROS –> exacebate beta cell destruction
4) activated B cells produce autoantibodies = measured as biomarkers for diagnosing T1D

Question 4

classifcaition of diabetes?

Answer 4

1) T1D (insulin dependant, juvenile diabetes)
- autoimmunty destruciton of insulin-producing beta cells
- 5-10%

2) T2D (insulin independant)
- insulin resistance + insulin deficiency

3) other types
- genetic defects affecting beta cell function + insulin action
- 1-2% cases

4) gestational diabetes
- insulin resistnace / decrease insulin synthesis during pregnancy
- 3-5% all pregnancies

Question 5

T1D diagnostic criteria

Answer 5

1) fasting plasma glucose level > 7 mmol per L (126mg/dL)
2) random venous plasma glucose level of >11.1 mmol / L (200mg/dL) in patient with classic hyperglycaemic symptoms
3) plasma glucose levels >11.1mmol/L (200mg/dL) measured after glucose load (1.75g/kg)

4) glycated Hb HbAc1 > 6.5%
- when glucose levels high = glucose attaches to Hb on rbc = becomes glycated hb = reflects avg BG over lifespan of rbc containing it

5) autoantibodies- B AND T cells produce antibodies that react to self beta cell antigens
- escaped neg selection due to:
1. suboptimal presentation of beta cell antigen on MHC 2 of APC to TCR in thymus (weak interaction of beta cell antigen to MHC 2) = escape neg selection

2. decreased thymic INS experssion = (1) reduce neg selection of autoreactive T cells
   (2) limit thymic development of beta cell specific T reg cell (FOXp3+ )
3. mutation in PTPN33 gene = increase phosphatatse activity to TCR signalling pathway =
   (1) limit T cell gene exp
   (2) limit prod of inflammatory cytokines
   ==> reduce neg selection (dont know which T cell is auto-reactive)

Question 6

what are the enviornemntal factors causing T1D?

Answer 6

1) infection / microbes/ gut microbiome
- Hygiene hypothesis: early child exposure to infection/microbes can increase tolerance to self antigens

2) virus infection: certain antigens can trigger local inflamation + attract other reactive lymphocytes

3) sunlight + vit D
- increase T1D in cananda + scandanavian due to lack of sunlight

4) diet:
- accelerator hypothesisis: modern diet of high sugar can put stress on beta cells

Question 7

what is the current treatment for T1D?

Answer 7

EXOGENOUS INSULIN

1) multiple BGL measurements (>4x)
2) daily multiple-dose insulin injections to mimic pscyhologic insulin release ( ~ 4 injections per day)
3) detecting hypoglycaemia events (sudden decrease in BGL)

Question 8

what is metabolic complication of T1D?

Answer 8

1) ketoacidosis
2) hyperglycaemia (no insulin)
3) hypoglycamia (side effect of blood sugar lowering medications)

lack of insulin release causes high glucose concentration in blood + urine –> increases glucagon: insulin ratio –> increase catabolsim of glycogen (glycogenolysis), fat, protein –> adipose tissue releases fatty acids (lipolysis) –> liver converts fatty acids into KETONE BODIES (beta oxidation) –> ketone bodies undergo beta oxidation = low pH

1) acidosis
2) acetone fruity breath

2) HYPOGLYCAEMIA:

1. decreased bgl due to suboptimal insulin treatment
2. if not treated can lead to loss of consciousness+ seizure (occures 1-4x per 50 patient years)
3. treatment= quick sugar source
4. if recurrent hypoglycameia=. results in hypoglycaemia unawareness (dont seek sugar source)
5. assocaited w 4-10% T1D related deaths

Question 9

describe hypoglycaemia in T1D

Answer 9

1) side effect of suboptimal insulin treatment = decreased blood glucose levels
2) treatment= sugar source
3) causes loss of consciousness / seizure (happens 1-4 times ervery 50 patient years)
4) ongoing hypoglaemica events can cause unawanreness (dont seek sugar source)
5) associated 4-10% with T1D related deaths

Question 10

what are the microvascular complications of T1D?

Answer 10

HYPERGLYCAEMIA IS PRIMARY RISK FACTOR

• intensive management of BGL: can have slower progression + reduced chance of microvascular complications
• if BGL not properly managed = glucose attaches to pbody proteins, results in:
  1) retinopathy
  2) diabetic nephropathy
  3) nerve: decreased sensation in toes + fingers
  4) affects autonomic nervous system = poor blood supply

1) retinopathy
- new blood vessels form at back of the eye & burst causing vitreous hemorrhage (blood leaks around viterous humour of eye)
- >80% T1D develop retinopathy
- can lead to blindness if not proper manged

2) diabetic nephropathy
- caused by increased albumin excretion in urine
- high glucose in blood due to no insulin production = glucose sticks to Hb protein on rbc = kidney tries extra hard to eliminate glucose through urine = but since glomerulus only filters small particles , glucose binded to Hb can damage glomerula = decrease glomerular filtration rate
- may need kidney tarnsplant

LONG TERM COMPLICATIONS
3) nerve damage:
decreased sensation in fingers + toes = glove and stocking symptoms

4) autonomic nervous system issues:
- hypoglycaemia unawarness
- excessive sweating
- postural hypotension ( Low BP when stand up)
- POOR BLOOD SUPPLY

nerve damage + poor blood supply = can cause ULCERS = AMPUTATIONS

Question 11

describe diabetic retinopathy

Answer 11

• intensive management of BGl can slow progression + reduce incidence of microvascular complications of T1D
• new blood vessels form at back of eye –> can burst and lead to virteous haemorrhage (blood leaks into vitreous humour of eye)
• if not treated can lead to blindness
• more than 80% T1D patients develop it

Question 12

what are the long term complicartions of T1D?

Answer 12

1) nerve damage = decreased sensation in fingers and toes = glove and stocking symptoms

2) autonomic nervous system
- hypoglycaemia unawareness
- excsssiev sweating
- postural hypotension
- poor blood supply

nerve damage + poor blood supply = cause ULCERS = require AMPUTATION

3) macrovascular complicatison
- coronary heart disease
- cerebrovascular disease
- peripheral artery disease

Question 13

what macrovascular diseases can T1D incrase the risk of ?

Answer 13

1) coronary heart disease
2) cerebrovascular disease
3) peripheral artery disease

Question 14

acinus vs islets of langerhans

Answer 14

acinus= exocrine function = secretes products into a duct that opens into epithelium

part 1: acinar cells
- stored in ZYMOGEN GRANULES (protect pancreatic cells from destruction)

1) amylase = breaks down carb
2) lipase = breaks down lipids
3) trypsinogen = breaks down proteins

• stimulated by Ach + CCK
  (acetylcholine + Cholecystokinin)

part 2: ductal cells

• produce aq solution containing bicarbonate = helps neutralise acidic stomach
• stimulated by secretion, Ach, CCK

islets of langerhans = endocrine function = secretes hormones into blood directly

1) beta cells = insulin
2) alpha cells = glucagon
3) delta cells = somatostatin
4) gamma cells (F or PP cells) = pancreatic polypeptide
5) epsilon cells= grehlin

Question 15

whats the role of pancreas

Answer 15

releases hormones/ enzymes to digest macronutrients + maintain energy / metbaolism homeostasis

Question 16

what abnormalities occur to pancreas + islets in T1D?

Answer 16

Endocrine compartment:

• varibale distribution of immune infiltrating cells
• beta cell depletion + decreased insulin expression

exocrine compartment:

• loss of pancreatic volume
• exocrine gland atrophy

non endocrine islet cells
- possible changes in islet vasculature & Extracelllular strucutre, still under investigation

Question 17

what happens when there is stress/ infection ?

Or

how does polyuria, dehydrateion & polydipsisa occur?

Answer 17

stress/infection –> releases epinephrine –> stimualtes glucagon release = increases glucagon: isnulin ration –> causes liver to produce glucose (gluconeogenesis )–> increase BGL = kidney tries to remove increased blood glucose along with water + solute (osmotic diuresis)
–> results in polyuria, dehydration + poly

Question 18

what are the stimulators and inhibitors of glucagon + insulin release

Answer 18

insulin stimulated by:

• ^ BGL
• ^ GLP-1, GIP
• ^ fatty acid + amino acid in blood

inhibited by:

• noradrenaline (stress, want ^ glucose in blood)
• somatostatin (tries to delay nutrient absorption in GI tract)

glucagon stimualted by:

• Adrenaline (stress)
• CCK (favours digestion)

glucagon inhibited by:

• insulin (to keep both levels within a range)
• somatostatin

Question 19

describe the insulin synthesis + secretion pathway

Answer 19

insulin synthesis:
INS transcribed on chr 11 –> signal peptide cleaves off –> A+B peptide join by disulphide bonds –> forms insulin + C peptide

when eat - glucose enters blood - glucose binds to beta cells of islets of langerhans of pancreas - moves through GLUT 1/2/3 transporters –> Glucokinase convert glucsoe –> glucose6phosphate –> change in ATP:ADP ratio inactivate ATP sensitivei K channels –> membrane depolarisation –> activates & open voltage gated Ca channels –> Ca move out, casuses insulin exocytosis

Question 20

what is the importance of C peptide

Answer 20

used in research studies to determine beta cell function

C peptide is the 3rd peptide made after INS gene (chr 11) is transcribed–> A+B peptides are joined by disulphide bonds + C peptide
less C peptide = less insulin

1) determine those at risk of developing T1D
2) determine residual beta cell mass & fucntion in long standing T1D patients
3) determine beta cell funciton in those whove gotten pancraes/islet transplant

Question 21

how is glucagon syntehsised

Answer 21

encoded by GCG gene on chr 2
stored in alpha cells –> stimulation by Adrenaline + CCK –> cause glucagon release

pre/pro-glucagon –> pro glucagon –> glucagon

Question 22

what does CCK stimualte?

Answer 22

CCK stimualtes :

1) acinus cells (ACh + CCK)
- release digestive enzymes into ducts open into epithelium
- amylase = digest carb
- lipase = digest lipids
- trypsinogen = digest proteins

2) ductal cells (Ach + CCK + secretin)
- release aq soltuion of bicarbonate to neutralise stomach acid
- stimualted by ACh + CCK + Secretin

3) stimualtes glucagon release

Question 23

how to measure glucose?

Answer 23

monitor blood glucose levels at least 4 times a day

1) take finger blood prick
glucose oxidase will convert glucose –> gluconolactone
O2 –> H2O2 = will be detected

2) electrodes are used
- electrical current = proportional to conc of blood glucose
- more current = more BGL

if BGL are:

• above 7.8mmol/L = hyperglycemia
• betwen 3.3-7.8 mmol/L = normal range
• below 3.3mmol/L = hypoglycemia

Question 24

how to measure insulin + C peptide?

Answer 24

measuring insulin:

1) to detect insulomas (insulin secreting tumours)
2) of limited use to diabetes (patients can undergo honey moon period where they are experience diabetes, but have residual insulin left )

measuring C-peptide (precursor of insulin + main target for T cells)
- present in peripheral blood of T1D onset

1) determine indivduals suceptibe to t1d
2) determine beta cell mass & function in long standing T1D patients
3) determien beta cell mass and funciton in pancreas/islet tnrasplants

Question 25

how does diabetic ketoacidosis occur? or explain glucagon:insulin ratio cause & effect

Answer 25

ketoacidosis lack of insulin --> unable to cause glucose uptake in liver, adipose, muscle cells --> unable to generate energy = body thinks its starving itself --> Adenaline (stress) + CCK stimulates glucagon release--> increases glucagon : insulin ratio --> adipose tissue releases free fatty acids (lipolysis) --> liver converts into ketone bodies (beta oxidation) , results in: 1) decreased PkA = decrease pH = ketoacidosis 2) acetone (fruity breath) stress: epinephrine released --> stimulates glucagon secretion: increases glucagon:insulin ratio --> contributes to increased ketone bodies glucagon increases gluconeogenesis + glycogenolysis --> increase BGL = high glucose in blood = body would want to increase excretion via kidneys = weakens glomerulus & decreases GFR= increase glucose secretion with water + solutes (osmotic diuresis ) --> POLYURIA, DEHYDRATION, POLYDIPSIA

Question 26

describe difference between type 1 & type 2 diabetes

Answer 26

1) t1d = hyperglycemia results from reduced/ no beta cell mass 2) t2d = hyperglycemia results from: - down regulation of insulin receptors on liver, adipose, muscle cells - insulin resistance - beta cells try to overcompensate by producing more insulin since it thinks the insulin is not working = weakens beta cells --> causes beta cell dysfunction = leads to hyperglycemia 3) insulin exogenous treatment = t1d + t2d (late stages of disease) 4) t2d = preventable by lifestyle modification

Question 27

what genes confer the highest risk to t1d? describe these genes

Answer 27

HLA genes confer highest risk - HLA genes = group of genes on chr 6, divided into 3 classes 3 genes on CLass 2 of HLA gene are invovled in susceptibily risk to T1D: 1) DQ2 > 3.6 2) DQ8 > 11.4 3) DQ2; DQ8 => 16.6 gives highest risk of T1D (highest odds ratio)

Question 28

what are the funcitons of HLA molecules?

Answer 28

1) shape the T cell repertoire during T cell development : - determine which thymocyte is deleted + positively selected for 2) present antigens on MHC class 2- present & activate CD4 T cells in the periphery

Question 29

what are the hypothesis of why there is no central tolerance/ negative selection established in T cells?

Answer 29

1) high risk alleles of HLA genotype: can increase presentation of pro-insulin/ c-peptide to immune cells 2) Central tolernace / negative selection = process in T cell maturation in THYMUS - eliminates T cells that bind and react to self antigens presented on MHC class 2 (HLA 2) - usually those T cells that self-react in thymus are elimiated to estbalihs central tolerance but. .. in T1D: particular HLA molecules (Dq2/dq8) dont present beta cell antigens EFFCIENTLY in the thymus 1) beta cells antigens have weak interactions with HLA 2 molecule of APC = suboptimal presentation to TCR = there is no way to see which T cell will react to self = no way to eliminate those self-reactive ones 2) those TCels will escape thymus --> move into pancreas + draining lymph nodes = where there are hgih conc of beta cell antigens presented on MHC2 of APC = TCell recongises them as foreign & attacks = causes beta cell destruction 3) makes memory T cells specific to targeting beta cell antigens dysregulation of negative selection = generates a peripheral pool of anti-self T cells = increases avidity + affinity + likely to have a pathogenic effect

Question 30

what are the NON HLA genes involved in genetic susceptibility to T1D?

Answer 30

- non-HLA genes confer smaller risk of T1D than HLA genes | - many non-HLA genes assocaited w immune function

Question 31

how does T cell escape negative selection?

Answer 31

HLA + NON -HLA genes: 1) HLA genes (SQ2/8): - serotype odds ratio can change susceptibility of developing T1D 1. high risk allele of HLA genotype: can incrase presentation of PRO-INSULIN/C-PEPTIDE to immune cells - hypothesis: 1. weak interaction bw beta cell antigen + HLA/MHC molecule on APC --> supotimal expression of beta cell antigens to TCR in THYMUS --> TCR are not exposed enoguh to beta cell antigens--> not able to determine which TCells are self-resctive= cant escape negative selection 2) escape thymus --> pancreas /draining lymph nodes = where large amount of beta cell antigens are = TCells will recongise + destruct beta cell antigens 3) produce memory T cells specific to beta cell antigens (although presence of this does not correlate with T1D- can be seen in normal ppl too) 2) NON HLA GENES: > INS > PTPN22 INS: - VNTR= upstream of INS exons = has 3 classes: class 1: predisposing allele (responsible for decreased INS expression) class 3: protective alleles (increased INS expression) - increase INS expression = decreased T1D risk (class 3) - decrease INS expression = increased T1D risk: (class 1) 1. reduce neg selection = allows insulin specific single positive thymocytes survive 2. limit thymic development of beta cell specific T regulatory expression (FOXP33+ CD4 t cells) PTPN22: phosphotase activity - normal: when TCR binds antigen presented on MHC moelcules = signal transduciton pathway = activate TF = increase T cell gene exprression - C -T mutation of PTPN22 gene = increases phosphatase activity of PTPN22 = phosphorylates Lck + ZAP70 = 1) limit TCR signalling = reduce T cell gene expression

Question 32

what are the biomarkets that distinguish T1D from T2D?

Answer 32

1) IAA ( insulin auto-antibodies )= first detected 2) GADA + IAA = most frequent in children 3) high affinity IAA + GADA = reflects progression to multiple islet autoantibodies + diabetes 4) other autoantibodies (IA-2, ZnT8) = typically appear later, indicate further progression of disease

Question 33

what 4 self antigens do pancreatic beta cells produce

Answer 33

1) insulin = prod by beta cells 2) GAD65 (glutamic acid decarboxylase) = not exclusive to pancreatic beta cells 3) IA-2 (tyrosine phosphatase like islet antigen 2) (356-760).= not exclusive to pnacreatic bet cells 4) ZNT8, zinc transporter huge role in insulin secretion + storage = highly expressed in endocrine pancreas + extra-pancreatic sites, NOT in exocrine pancreas

Question 34

what evidence supports the fact that islet autoantibodies DOES NOT mean one has T1D?

Answer 34

1) islet autoantibodies does not have cytotoxic effect on islets in vitro (mix them tog, islets still continue to make insulin normally) 2) maternal transfer of autoatnibodies into fetus= does not increase child getting T1D 3) person with X linked gammaglobuliaemia (someone who doesnt make antibodies) can still get T1D

Question 35

how are beta cell specific T cell PHENOTYPES different in healthy vs T1D ppl?

Answer 35

beta cell specific T cells in peripheral blood are RARE in T1D patients + can sometimes be found in healthy ppl. ==> DIFFERNECE IN PHENOTYPES of beta cell specific T cells bw health + T1D ppl: healthy ppl beta cell specific T cells are: 1) naive phenotype (not activaited) 2) regulatory responses (IL-10 supressimmun response) T1D patient: 1) memory + effector phenotype (already activated) 2) produce inflammatory cytokines (PTPN22 mutation) (IFN-g) ==> causes ongoing beta cell destruction

Question 36

what is the pathologic hallmark of t1D? + DESCRIBE INSULITIS

Answer 36

INSULITIS- where immune cells infiltrate the islets = causes beta cell loss (little insulins staining)

Question 37

DESCRIBE INSULITIS

Answer 37

insulis is pathologic hallmark of T1D: occurs when immune cells infiltrate the pancreatic islets & cause beta destruction & decrease insulin characteristics in pancreatic tissues: 1) increased beta cell destruction 2) decrease insulin staining 3) increased glucagon 4) infiltration is NOT homogenous (diff parts of islet are infiltrated at diff rates + diff amounts) - only 10-30% of ilsets are dmaaged at any 1 time - small amount of islets damaged for T1D to occur 5) insulitis is lobular (some parts are more infiltrated than others) - in insulin positive cells = insulitis can be PERI-insulitis (periphery islets) or INTRA-insulitis (within islets parenchyma) 6) there are pseudoatrophic islets with NO beta cells, but still have ALPHA + DELTA - cells present: - CD4 = produce inflammatory cytokines = exacebate beta cell destruction - CD8 = recognise beta cell antigen on MHC 1= directly kill - APC: dendritic + macrophages

Question 38

what genetic factors give people high risk for T1D?

Answer 38

1) HLA serotype: DQ2;DQ9 2) INS genes: patients homozygous for VNTR class 1 (predisposing allele) - reduce neg selecrition of insulin specific single positive thymocytes - limit thymic development of beta cell specific regulatory T cells (Foxp3+ cd4+ t cells)

Question 39

WHAT IS SPECIAL ABOUT PRO-INSULIN

Answer 39

- main target for T cells

Question 40

patients with long standing T1D have:

Answer 40

1) beta cell specific CD8 T cells detected in T1D patients - found MHC tetramers to present peptides from diff beta cell antigens: GAD65, IA-2, IGRP, IAAP 2) even up to 8 yearts after clinical diagnosis: some still showed CD8 T cell autoreactivities against islet autoantigens - HLA class 1 tetramer w insulin derived peptide (proinsulin/c-peptide) - HLA classs 1 tetramer w IGRP derived peptide 3) newly diagnosed T1D patients: - had low-grade enteroVIRAL infection in islets - viral infection + innate immune activation = 1. overexpression IFN stimualted genes 2. ^ production of IFNa in pancreas 4) hyper-expression of HLA class 1 + 2 moleculees in islets

Question 41

what does upregulation of HLA class 1 mean?

Answer 41

increase HLA class 1 expression + presentation of beta cell autoantigens beta cells antigens present on HLA class 1 of beta cell surface TCR recognises & binds to HLA class 1 on beta cell surface CD8 T cells secrete PERFORIN granzyme = punch holes into beta cell membrane = induce apoptosis + cause Ca influx

Question 42

what are the hypothesis of why there is no central tolerance/ negative selection established in T cells?

Answer 42

1) high risk alleles of HLA genotype: can increase presentation of pro-insulin/ c-peptide to immune cells 2) Central tolernace / negative selection = process in T cell maturation in THYMUS - eliminates T cells that bind and react to self antigens presented on MHC class 2 (HLA 2) - usually those T cells that self-react in thymus are elimiated to estbalihs central tolerance but. .. in T1D: particular HLA molecules (Dq2/dq8) dont present beta cell antigens EFFCIENTLY in the thymus 1) beta cells antigens have weak interactions with HLA 2 molecule of APC = suboptimal presentation to TCR = there is no way to see which T cell will react to self = no way to eliminate those self-reactive ones 2) those TCels will escape thymus --> move into pancreas + draining lymph nodes = where there are hgih conc of beta cell antigens presented on MHC2 of APC = TCell recongises them as foreign & attacks = causes beta cell destruction 3) makes memory T cells specific to targeting beta cell antigens dysregulation of negative selection = generates a peripheral pool of anti-self T cells = increases avidity + affinity + likely to have a pathogenic effect

Question 43

what are the NON HLA genes involved in genetic susceptibility to T1D?

Answer 43

- non-HLA genes confer smaller risk of T1D than HLA genes | - many non-HLA genes assocaited w immune function

Question 44

how does T cell escape negative selection?

Answer 44

HLA + NON -HLA genes: 1) HLA genes (SQ2/8): - serotype odds ratio can change susceptibility of developing T1D 1. high risk allele of HLA genotype: can incrase presentation of PRO-INSULIN/C-PEPTIDE to immune cells - hypothesis: 1. weak interaction bw beta cell antigen + HLA/MHC molecule on APC --> supotimal expression of beta cell antigens to TCR in THYMUS --> TCR are not exposed enoguh to beta cell antigens--> not able to determine which TCells are self-resctive= cant escape negative selection 2) escape thymus --> pancreas /draining lymph nodes = where large amount of beta cell antigens are = TCells will recongise + destruct beta cell antigens 3) produce memory T cells specific to beta cell antigens (although presence of this does not correlate with T1D- can be seen in normal ppl too) 2) NON HLA GENES: > INS > PTPN22 INS: - VNTR= upstream of INS exons = has 3 classes: class 1: predisposing allele (responsible for decreased INS expression) class 3: protective alleles (increased INS expression) - increase INS expression = decreased T1D risk (class 3) - decrease INS expression = increased T1D risk: (class 1) 1. reduce neg selection = allows insulin specific single positive thymocytes survive 2. limit thymic development of beta cell specific T regulatory expression (FOXP33+ CD4 t cells) PTPN22: phosphotase activity - normal: when TCR binds antigen presented on MHC moelcules = signal transduciton pathway = activate TF = increase T cell gene exprression - C -T mutation of PTPN22 gene = increases phosphatase activity of PTPN22 = phosphorylates Lck + ZAP70 = 1) limit TCR signalling = reduce T cell gene expression

Question 45

what are the biomarkets that distinguish T1D from T2D?

Answer 45

1) IAA ( insulin auto-antibodies )= first detected 2) GADA + IAA = most frequent in children 3) high affinity IAA + GADA = reflects progression to multiple islet autoantibodies + diabetes 4) other autoantibodies (IA-2, ZnT8) = typically appear later, indicate further progression of disease

Question 46

what 4 self antigens do pancreatic beta cells produce

Answer 46

1) insulin = prod by beta cells 2) GAD65 (glutamic acid decarboxylase) = not exclusive to pancreatic beta cells 3) IA-2 (tyrosine phosphatase like islet antigen 2) (356-760).= not exclusive to pnacreatic bet cells 4) ZNT8, zinc transporter huge role in insulin secretion + storage = highly expressed in endocrine pancreas + extra-pancreatic sites, NOT in exocrine pancreas

Question 47

what evidence supports the fact that islet autoantibodies DOES NOT mean one has T1D?

Answer 47

1) islet autoantibodies does not have cytotoxic effect on islets in vitro (mix them tog, islets still continue to make insulin normally) 2) maternal transfer of autoatnibodies into fetus= does not increase child getting T1D 3) person with X linked gammaglobuliaemia (someone who doesnt make antibodies) can still get T1D

Question 48

how are beta cell specific T cell PHENOTYPES different in healthy vs T1D ppl?

Answer 48

beta cell specific T cells in peripheral blood are RARE in T1D patients + can sometimes be found in healthy ppl. ==> DIFFERNECE IN PHENOTYPES of beta cell specific T cells bw health + T1D ppl: healthy ppl beta cell specific T cells are: 1) naive phenotype (not activaited) 2) regulatory responses (IL-10 supressimmun response) T1D patient: 1) memory + effector phenotype (already activated) 2) produce inflammatory cytokines (PTPN22 mutation) (IFN-g) ==> causes ongoing beta cell destruction

Question 49

what is the pathologic hallmark of t1D? + DESCRIBE INSULITIS

Answer 49

INSULITIS- where immune cells infiltrate the islets = causes beta cell loss (little insulins staining)

Question 50

DESCRIBE INSULITIS

Answer 50

insulis is pathologic hallmark of T1D: occurs when immune cells infiltrate the pancreatic islets & cause beta destruction & decrease insulin characteristics in pancreatic tissues: 1) increased beta cell destruction 2) decrease insulin staining 3) increased glucagon 4) infiltration is NOT homogenous (diff parts of islet are infiltrated at diff rates + diff amounts) - only 10-30% of ilsets are dmaaged at any 1 time - small amount of islets damaged for T1D to occur 5) insulitis is lobular (some parts are more infiltrated than others) - in insulin positive cells = insulitis can be PERI-insulitis (periphery islets) or INTRA-insulitis (within islets parenchyma) 6) there are pseudoatrophic islets with NO beta cells, but still have ALPHA + DELTA - cells present: - CD4 = produce inflammatory cytokines = exacebate beta cell destruction - CD8 = recognise beta cell antigen on MHC 1= directly kill - APC: dendritic + macrophages

Question 51

how have other potnetial biomarkers been observed ?

Answer 51

1. transcript analysis of whole blood samples/ peripheral blood mononuclear cells 2. responses in standardised reporter cell lines exposed to serum 3. metabolomic analysis of serum 4. most direct = observe presence of T cells specific to autoantigens in Beta cells

Question 52

WHAT IS SPECIAL ABOUT PRO-INSULIN

Answer 52

- main target for T cells

Question 53

patients with long standing T1D have:

Answer 53

1) beta cell specific CD8 T cells detected in T1D patients - found MHC tetramers to present peptides from diff beta cell antigens: GAD65, IA-2, IGRP, IAAP 2) even up to 8 yearts after clinical diagnosis: some still showed CD8 T cell autoreactivities against islet autoantigens - HLA class 1 tetramer w insulin derived peptide (proinsulin/c-peptide) - HLA classs 1 tetramer w IGRP derived peptide 3) newly diagnosed T1D patients: - had low-grade enteroVIRAL infection in islets - viral infection + innate immune activation = 1. overexpression IFN stimualted genes 2. ^ production of IFNa in pancreas 4) hyper-expression of HLA class 1 + 2 moleculees in islets

Question 54

what does upregulation of HLA class 1 mean?

Answer 54

increase HLA class 1 expression + presentation of beta cell autoantigens beta cells antigens present on HLA class 1 of beta cell surface TCR recognises & binds to HLA class 1 on beta cell surface CD8 T cells secrete PERFORIN granzyme = punch holes into beta cell membrane = induce apoptosis + cause Ca influx

Question 55

how do CD8 T cells target beta cells

Answer 55

CD8 T cells recognise beta cell antigen presented on MHC1 of beta cell surface --> bind = intracellular signalling = secrete perforins = lyse holes in membrane of b-cell membrane -->contain serine proteases that signal apoptosis --> release cytokines + beta cell epitopes: epitope spreading = more antibodies to be made against INS, GAD65, IA-2, ZnT8, Pro-insulin, IGRP, IAAP, ChG) = progressive insulin loss

Question 56

what are the risk factors for people developing T1D depending on: - First degreee relative (FDR) - HLA risk allele

Answer 56

low risk = no FDR + no HLA risks alleles intermediate risk = no or 1 affected FDR + HLA risk alllele high risk = 1 or multiple affected FDR + HLA risk alelele very high risk = multiple affected FDR or identical twins affected + HLA risk allele

Question 57

compare the odds ratio of HLA vs NON-HLA genes

Answer 57

odds ratio of NON-HLA genes is SMALLER that HLA genes - INS + PTPN22 = highest odds ratio amongst NON-hla genes

Question 58

what is the relationship between no. of islet autoantibodies and risk of T1D?

Answer 58

as you increase the no. of islet antibodies produced (from CD4 T cells signalling to B cells to make antibodies) = you increase the probability of developing diabetes

Question 59

what are the risk categories of developing T1D

Answer 59

low risk: - single islet autoantibody (low affinity) - older age - non susceptible HLA alleles intermediate risk - single islet autoantibody (high affinity) - proinsulin reactive IAA, middle/C terminal reactive GAD65 - young age - HLA DR3/4 high risk: - 2 or 3 islet Abs (IA2A, Ant8A) - young age - low first phase insulin (HLA risk genotype) very high risk: - 4 islet ab - ab to IA2b epitopes - higher titre - multiple IgG subclasses responses - young age @ initiation - impaired glucose tolerance (HLA risk genotype)

Question 60

why do we need more biomarkers for disease risks?

Answer 60

because we want to be able to identify people at risk of developing T1D, before stage 1 - having presence of single autoantibody is NOT enough to predict who has T1D (<30% of ppl w signle autoantibody progresses to clinical disease stage) - identify other biomarkers that will increase accuracy of predicitng who will develop T1D

Question 61

how have other potnetial biomarkers been observed ?

Answer 61

1. transcript analysis of whole blood samples/ peripheral blood mononuclear cells 2. responses in standardised reporter cell lines exposed to serum 3. metabolomic analysis of serum 4. most direct = observe presence of T cells specific to autoantigens in Beta cells

Question 62

how do we predict the development of T1D

Answer 62

1. genetic markers - family history - HLA DR-DQ genotype 2. T1D relevant immune markers - autoantibodies against insulin, GAD65, IA-2, ZnT8 3. immune markers associated with disease progression - antibody affinity + epitopes - IVGTT = tests insulin secrtion + specifity after intravenous glucose infusion - OGTT = tests fasting plasma gluc levels, HbA1C, T cell immunity markers = test bodys ability to handle glucose 4. disease development - for indivduals with OR wihtout family history of T1D, if they have multiple islet antibodies - they are defs gona get T1D

Question 63

what does it mean to say CLINICAL course of T1D is Heterogenous

Answer 63

- in ppl who have multiple islet cell autoantibodies + LOW first phase insulin response= each person has DIFF RATE + DEGREE of beta cell destruction = different amount of residual beta cell mass + function

Question 64

what are the 3 main types of clinical presentations (acute, sub-acute, asymptomatic)

Answer 64

acute: | 1)