Lecture 5 - cellular and molecular mechanisms of diabetes induced vascular complications

Question 1

What is atherosclerosis?

Answer 1

inflammatory and proliferation response to vessel wall injury

Question 2

what are the three layers of an artery

Answer 2

Tunica intima / media / adventia

Question 3

What is the progression of atherosclerosis

Answer 3

1. Fatty streak
2. Fibrous plaque
3. Advanced plaque
4. Complete occlusion thrombosis

Question 4

What are clinical manifestations of atherosclerosis?

Answer 4

Cardiac –> angina / MI
Cerebral –> stroke
Peripheral –> claudication /ischaemia / ulceration

Question 5

What are some cardiovascular risk factors?

Answer 5

Smoking / diabetes / diet / age / FH / sedentary lifestyle / alcohol / HTN / cholesterol / obesity

Question 6

What are risk factors for Type II diabetes ?

Answer 6

ethnicity / diet / genetics / obesity / sedentary lifestyle

Question 7

How do beta cells initially response to insulin resistance?

Answer 7

Elevate insulin levels by:
increased insulin production
increased beta cell mass

Question 8

What happens when beta cells are unable to compensate

Answer 8

T2DM

• decreased insulin secretion
• reduced beta cell mass
• decreased pro insulin biosynthesis

Question 9

What micro vascular complications of diabetes

Answer 9

nephropathy / neuropathy / retinopathy

Question 10

What are macro vascular complications of diabetes

Answer 10

CHD/ PVD/ stroke

Question 11

What is the role of the endothelial?

Answer 11

Anti-inflammatory 
Anti-hypertrophic
Anticoagulant / prothrombolytic 
endothelium dependent vasodilation
anti-thrombotic

Question 12

What is the role of NO in the endothelium?

Answer 12

• dilates blood vessel
• reduces platelet stickiness
• reduces monocyte stickiness –> plaque prevention
• reduces multiplication of smooth muscle cells in the arterial wall
• reduces release of radicals
• reduces oxidation of LDL

Question 13

What happens in endothelium signalling in a healthy state

Answer 13

PI3K pathway

• forms eNOS
• prostacyclin released
• NO released into smooth muscle cell

Question 14

What is endothelial dysfunction characterised by?

Answer 14

impaired relaxation
pro-thrombosis
pro-coagulation
pro-inflammation
insulin resistance

Question 15

What are the harmful substances that affect the endothelium

Answer 15

ROS/ ET/ AT-2 / EDCF

Question 16

What factors influence endothelial dysfunction in diabetes?

Answer 16

AGEs / lipids / glucose / cytokines / insulin / HTN / oxidative stress

Question 17

What increases the risk of vascular complications?

Answer 17

Hyperglycaemia

Question 18

How is blood glucose measured and what is the healthy range

Answer 18

HbA1c

4-6%

Question 19

What did the UKPDS:DCCT show about glycaemic control?

Answer 19

controls micro vascular complications but has no evidence of macrovascular benefit

Question 20

what did the ACCORD; ADVANCE; VADT clinical trial show about glycaemic control?

Answer 20

Intensive glycaemic treatment had little, if any additional benefit in patients with diabetes and established CAD.

Early glucose control seems to be important to reduce long-term complications.

Question 21

What is metabolic memory?

Answer 21

-sustained effects of prior glucose control
-Ongoing beneficial effects on diabetic complications
after a period of improved glycaemia followed by a
return to (often inferior) control

Question 22

What clinical trials have shown evidence for metabolic memory

Answer 22

UKPDS-legacy effect

DCCT-metabolic memory

Question 23

Describe models that have shown metabolic memory in cell culture models

Answer 23

Human SMC explant cultures

• fresh saphenous vein
• placed into explant culture
• Primary explants formed in 7-14days
• confluent SMC formed in 3-4 weeks
• Diabetic patients had dense / broad / disorganised SMC
• diabetic SMC was rhomboid shape rather than spindle

Question 24

What are the difference in the SMC f-actin cytoskeleton between diabetics and non-diabetics?

Answer 24

ND–> spindle formation + elongated f-actin

T2DM –> rhomboid morphology + fragmented f-actin

Question 25

What are other differences between ND SMC and T2DM SMC

Answer 25

• T2DM cells have a larger cell area

- T2DM cells have a poor replicating capacity

Question 26

Do T2DM SMC retain their abnormal structure?

Answer 26

Yes

Question 27

What is epigenetic change?

Answer 27

Change in phenotype but not a change in genotype?

Question 28

What are three factors involved in epigenetic expression?

Answer 28

Histone modification
DNA methylation
RNA

Question 29

What are miRNA

Answer 29

• short / single stranded non-coding RNAs
• regulate up to 50% of genes
• cell type/ tissue specific

Question 30

How do miRNA affect target gene expression?

Answer 30

mRNA degradation

translational repression

Question 31

What happens to miRNA in disease states?

+ potential use?

Answer 31

expression levels are modulated in a range of disease states

-targeted in new therapies

Question 32

Explain miRNA synthesis

Answer 32

-transcribed by RNA polymerase into primary miRNA
-converted by microprocessor complex to pre-miRNA
-exported into the cytoplasm by the RAN-GTP-dependent transporter Exportin-5
- Additional processing by the Dicer enzyme produces a miRNA/miRNA
-

Question 33

What occurs to miRNAs in T2DM patients?

Answer 33

specific miRNAs are elevated in SMC in T2DM patients

Question 34

Phenotype of SMC in T2DM patients

Answer 34

Rhomboid
Larger spread areas
Truncated, disrupted f-actin fibres
Impaired proliferation