Diabetes Mellitus

Question 1

What is the composition of an islet cell?

Answer 1

Alpha cells-Glucagon
Beta cells- Insulin, C-peptide
Delta cells- Somatostatin
Gamma cells- Pancreatic polypeptide

Question 2

What is metabolism like in an untreated Type 1 DM patient?

Answer 2

Increased glucagon
Gluconeogenic
Breakdown of protein
Switch to fat oxidation
Increased ketone bodies
Ketoacidosis
Diabetic coma

Question 3

What are the secondary complications of diabetes?

Answer 3

Atherosclerosis (macrovasculature)
Nephropathy and retinopathy (microvasculature)
Nuropathy (NS)

Question 4

Which cells are effected in Type 1 DM and how?

Answer 4

Auto immune destruction of pancreatic beta cells

Question 5

What is used to model T1DM in rats?

Answer 5

Streptozotocin (STZ)

Question 6

How is vp1 possibly implicated in T1DM?

Answer 6

Over 60% T1DM cases had some vp1 positive islets
Expression of vp1 localises with insulin but not with glucagon
Suggestion of viral trigger

Question 7

How could viral infection trigger DM?

Answer 7

Cytolysis
Viral persistence causing prolonged localised inflammation
Damage to beta cells by the virus induced T cell activation (bystander activation)
Molecular mimicry

Question 8

Explain how immune cell infiltration has an effect on pathophysiology of DM

Answer 8

Infiltration of mononuclear immune cells (macs/APCs, T-lymphocytes)
Direct cell:cell killing (Fas/FasL, perforin/granzyme B)
Secretion of inflammatory mediators (cytokines, ROS)
Anti-islet autoantibodies

Question 9

Describe the role of inflammatory cytokines in pathophysiology of DM

Answer 9

Secreted by infiltrating immune cells
Bind to cell surface receptors on islet cells
multiple and diverse effects on cellular function
Act synergistically
Species difference in susceptibility

Question 10

What are the exogenous sources of reactive species?

Answer 10

Secretion from macrophages/APC

iNOS active duct cells

Question 11

What are the endogenous sources of reactive species?

Answer 11

Cytokine-induced iNOS expression

MnSOD

Question 12

What are the antioxidant defence mechanisms?

Answer 12

MnSOD
Catalase
Glutathione Peroxidase and reductase
Reduced expression in beta-cells

Question 13

What is the current approach to therapy for DM?

Answer 13

Currently, insulin replacement the only viable option

Question 14

How can insulin be delivered therapeutically?

Answer 14

Injection- slow/fast release, insulin pumps
Inhaled- exubera (discontinued)
Oral admin- ORMD-0801 (Phase 2 trials)
Liver-targeted- Thyroxyl insulin

Question 15

What are the problems associated with islet transplantation?

Answer 15

Number of donor pancreas'
Islet stress
re-vascularisation
Host rejection (alloimmune response)
Glucotoxicity
Recurrent autoimmunity
Islet yield
Blood-mediated inflammatory response

Question 16

Define Allotransplantation

Answer 16

Transplantation between individuals of the same species

Question 17

Define Autologous transplantation

Answer 17

Transplants between the same individual (self to self)

Question 18

Define Synergic transplants

Answer 18

Genetically identical transplants

Question 19

Define Xenotransplantation

Answer 19

Transplants between different species

Question 20

What is the current criteria for an islet transplant?

Answer 20

Severe/prolonged T1DM
Recurrent hypoglycaemia
Hypoglycaemia unawareness
Often remain on small dose of insulin
Immunological considerations
Require multiple donors and several transplants

Question 21

How is the issue of revascularisation tackled?

Answer 21

Growth factor supplementation, gene based approaches (over-expression of VEGF)

Question 22

How is the issue of inflammation tackled?

Answer 22

Drug targets
Gene based approaches: (Caspase-3 siRNA, iNOS shRNA, hIL-1RA expression, Over-express XIAP)
Encapsulation

Question 23

How is the issue of poor islet cell mass tackled?

Answer 23

Increased beta cell proliferation in transplanted tissue
Donor availability
Improved survival/retention of grafted tissues

Question 24

What are the sources for transplantation?

Answer 24

Cadaveric donors
Differentiation of non-beta cells
Mesenchymal stem cells
Embryonic stem cells
Induced pluripotent stem cells

Question 25

What is DIABECELL?

Answer 25

Porcine insulin-producing islets encapsulated in alginate

Question 26

What are the problem associated with DIABECELL?

Answer 26

Microencapsulated islets are irretrievable
Safety
Ethics

Question 27

What are the pros and cons of using the intra-hepatic via the portal vein as a islet transplant site?

Answer 27

Pros- high success rate, near optimal O2 tension, avoid systemic hyperinsulinaemia
Cons- Inflammatory response, immunosuppressant levels, difficult to biopsy, glucotoxicity

Question 28

What are the alternative sites for islet transplantation?

Answer 28

Kidney capsule
Anterior eye chamber
Subcutaneous
Intramuscular
Intrapancreatic

Question 29

What are the features of and instant blood-mediated inflammatory response (IBMIR)?

Answer 29

Non-specific innate response
Massive early cell loss
Expression of tissue factor and vascular injury during transplantation
Activation of coagulation system
Activation of complement

Question 30

What does IDN-6556 target?

Answer 30

The caspase cascade

Question 31

What are the effects of IDN-6556?

Answer 31

Improved glucose tolerance
Improved insulin content
Reduced apoptosis

Question 32

What are the types of encapsulation and some of their properties?

Answer 32

Macro-encapsulation
Micro-encapsulation in alginate- additional surface coat to modify properties, difficult to control the process and variable islet volume
Nano-encapsulation-conformational/surface coating
Immune evasion- cell surface coating

Question 33

What are the pitfalls of encapsulation?

Answer 33

Biocompatibility
Immune response
Hypoxia

Question 34

What gene based approaches can be used in islet transplantation?

Answer 34

Over-expressing a gene to promote engraftment
Over expressing genes to prevent cell loss
Expressing a construct to ‘silence’ expression of pro-apoptotic genes
Construction of Bipartite vectors