1. Diabetes Mellitus

2. Diabetes Mellitus DM is a state of hyperglycaemia
Fasting plasma glucose:
Normal < 6 mmol/L
Impaired = mmol/L
DM  ≥ mmol/L
Random plasma glucose (or 2hr oGTT)
DM >/= 11.1 mmol/L

3. Type 1 Type 2 A state of insulin resistance
Autoimmune or viral destruction of pancreatic β cells
Inability to produce insulin
Young onset (< 40 years)
Managed with insulin injections
Type 2
A state of insulin resistance
Typically, onset after 40 years
Associated with the metabolic syndrome
Managed with lifestyle / medical / insulin treatment

4. Insulin A peptide hormone secreted by the pancreatic β-cells
Anabolic hormone:
The ONLY hormone able to lower blood glucose

5. The Metabolic Effects of Insulin
LIVER
↑ glycogen synthesis
↓ glycogenolysis
↓ gluconeogenesis
SKELETAL MUSCLE
↑ glucose uptake
↓ protein breakdown
↑ protein synthesis
ADIPOSE
↓ lipolysis
↑ triglyceride synthesis

6. How does it elicit these effects?
By binding to the tetrameric Insulin Receptor Tyrosine Kinase (RTK)
Insulin receptor is expressed on every cell in the body
BUT 40 receptors per RBC
And 1000s on hepatocytes, skeletal muscle cells and adipocytes...the principal insulin responsive tissues

7. METABOLIC PATHWAY (PI3-KINASE)
MITOGENIC PATHWAY (MAP-KINASE)
Cell growth
Differentiation
Survival

8. Insulin signalling pathway
Insulin binds to the α-subunit of the Insulin RTK
Eliciting tyrosine phosphorylation of the Insulin RTK β-subunits
The Insulin RTK is associated with intracellular docking proteins, the prototype of which is Insulin Receptor Substrate-1 (IRS-1)

9. IRS-1 possesses multiple tyrosine residues which are phosphorylated upon insulin binding to the Insulin-RTK
Due to the MULTIPLE tyrosine residues on IRS-1 the insulin signal is AMPLIFIED.
The phosphorylated tyrosines on IRS-1 interact with intracellular signal molecules possessing an Src-homology-2 domain....

10. One of which is p85, the regulatory subunit of PI3-kinase
PI3-Kinase also possesses a catalytic domain (p110) which phosphorylates the 3’ position of phosphatidylinositides to produce phosphatidylinositol-3-phosphates, most notably PIP-3
PIP-3 regulates downstream signalling molecules e.g.:
PDK-1 (phosphoinositide dependent kinase-1)
The atypical PKCs

11. The serine/threonine protein kinase B (Akt) lies downstream of, and is activated by, PDK-1 but may also be activated by PIP-3.
Akt is a KEY protein kinase of the insulin signalling cascade and promotes

12. Akt promotes:
GLUT-4 translocation to the plasma membrane for skeletal muscle and adipose tissue glucose uptake.
The ACTIVATION of:
glycogen synthase storage of glucose as glycogen
Fatty acid synthase storage of glucose as TAG
Acetyl coA carboxylase...storage of glucose as TAG
mTOR increased protein synthesis

13. Akt promotes: The INHIBITION OF
Hormone sensitive lipase reduced lipolysis
Regulates the transcription of specific metabolic enzymes in the hepatocyte to reduce glycogenolysis and gluconeogenesis

14. Diabetes Mellitus
Is a state of insulin resistance leading to hyperglycaemia
Insulin resistance is induced by
FAT
(an expansion of adipose tissue mass)

15. What does it do? White adipose tissue ENDOCRINE ORGAN
Triglyceride store
ENDOCRINE ORGAN

16. Adipose..an endocrine organ
White AT secretes bioactive proteins termed adipokines e.g.:
Leptin
Adiponectin
Resistin
Retinol binding protein-4 (RBP-4)
Monocyte chemoattractant protein-1 (MCP-1)

17. Adipokines
Adipokines control WHOLE BODY metabolism communicating the nutrient status of the body with the principal tissues of metabolism
Adipokines can be classified as insulin-sensitising or insulin-resistance inducing as determined by their peripheral effects
Insulin-sensitising: Adiponectin
Insulin-resistance inducing: Resistin, RBP-1, MCP-1

18. If there is an expansion of adipose tissue mass (as is the case in obesity)...........
Metabolic stress is imparted to the adipocyte leading to......
Aberrant adipokine secretion:
there is increased secretion of insulin- resistance conferring adipokines
reduced adiponectin secretion.....
Pro-inflammatory macrophages of the M1 phenotype are recruited from the blood to the adipose tissue and secrete MORE insulin-resistance inducing cytokines e.g. TNF-α and IL-6
HOW?
PERIPHERAL INSULIN RESISTANCE

19. TNF-α and IL-6 activate inhibitory serine kinases
e.g. C-JNK
Phosphorylation of serine residues on IRS-1 in the liver and AT
Attenuated insulin signal transduction

20. TNF-α also...
Suppresses the catabolic
AMP-Kinase pathway
in the peripheral tissues
↓Fatty acid oxidation
↑Build-up of toxic lipid metabolites e.g. DAG
INSULIN RESISTANCE

21. The Metabolic Effects of Insulin
Insulin resistance...
SKELETAL MUSCLE
↓ glucose uptake
LIVER
↓inhibition of gluconeogenesis and glycogenolysis
↑glucose output
ADIPOSE:
↑lipolysis
The Metabolic Effects of Insulin
LIVER
↑ glycogen synthesis
↓ glycogenolysis
↓ gluconeogenesis
SKELETAL MUSCLE
↑ glucose uptake
↓ protein breakdown
↑ protein synthesis
ADIPOSE
↓ lipolysis
↑ triglyceride synthesis

22. Insulin resistance A state of hyperglycaemia and hyperlipidaemia
Glucolipotoxicity
State of insulin resistance further confounded

23. Treatment of T2DM Diet and exercise
Sulphonylureas or Metformin depending on renal function and obesity
SUs....weight gain
Metformin...should not be used in renal impairment
Glitazones
Hyperglycaemia
Diet and Excersise
No control after 3 months
Normal renal function
Impaired renal function
Metformin
Sulphonylurea
Poor control?
2 of: metformin, SU or glitazone

24. MOA of Sulphonylureas
Inhibit the ATP-sensitive K+ channel in the β-cell
Membrane depolarisation
Influx of calcium
↑Intra-cellular Ca2+
Insulin release

25. MOA Metformin A biguanide MOA: Activates hepatic AMP-Kinase
AMP-Kinase is a sensor of intracellular energy status
AMP-Kinase is activated by low intracellular ATP
And works to increase intracellular ATP by promoting catabolic processes e.g. fatty acid oxidation
And inhibits ATP consuming processes

26. Metormin By its action on AMP-Kinase Metformin PROMOTES: And INHIBITS:
Muscle glucose transport
Fatty acid oxidation
And INHIBITS:
Hepatic glucose production
VLDL synthesis
↓ plasma glucose & TAG ↓glucolipotox
↑ insulin sensitivity

27. PPAR Ligands
PPARs: member of the steroid hormone family of ligand activated transcription factors
Nuclear receptor
Isoforms α and γ control the expression of specific genes involved in metabolism
This is exploited by pharmacological ligands
PPAR-α ligands: FIBRATES
PPAR-γ ligands: GLITAZONES

28. MOA of PPAR ligands
Structure of the nuclear receptor:
The PPAR is present in a heterodimeric complex with a RXR
RXR heterodimer is constitutively bound to the promoter regions of target genes
In the absence of a ligand, the AF2 domain conformation promotes interaction of the RXR-PPAR complex with a corepressor complex
Corepressor blocks access of transcription machinery to the promoter
There is no transcription of target genes (x)
NH2
AF1
DNA
LIGAND
AF2
COOH
Ligand binding domain
Activation function 1
DNA binding domain
Activation function 2
The PPAR receptor in the absence of a ligand:
PPAR
PPAR
Ligand binding domains

29. MOA of PPAR ligands
Ligand e.g. FIBRATE/GLITAZONE diffuses across the nuclear membrane
Binds to PPAR ligand binding domain
Conformational change in AF2 domain
Co-activator binding
5. Co-activator recruits transcription machinery 6. Target gene transcription

30. PPAR-α ligands DRUG: Fibrates e.g. fenofibrates
SITE OF ACTION: Hepatocyte
EFFECT: Improve lipid profiles
(↓VLDL & ↑HDL)
FOR: Treatment of hypercholesterolaemia
HOW?.....

31. N.B. in a state of insulin resistance there is ↑lipolysis and therefore ↑FFA flux to the liver3
1. PPAR-α activation:
↑expression of Acetyl coA synthase
ACS
FFA
FACoA 2
2. There is also ↑expression of CPT (carnitine palmitoyltransferases). CPT 1&2 transfer FACoA from the cytosol to the mitochondrial matrix for β-oxidation 1
3. There is also ↓ expression of FA synthase (FAS) in the cytosol:
There is reduced production of TAG
And therefore reduced output of VLDL (60% TAG)
FAS x
Acetyl CoA
TAG
VLDL
4. PPAR-α activation also stimulates the production of apolipoproteins A-I and A-II, 2 major HDL lipoproteins
Overall effect of PPAR-α activation: the alleviation of dyslipidaemia

32. PPAR- γ Ligands DRUG: Glitazones e.g. pioglitazone, rosiglitazone
SITE OF ACTION: Adipose tissue
EFFECT: Improve tissue insulin sensitivity and therefore normalise blood glucose profiles
FOR: Treatment of T2DM
HOW?.....

33. 3. ↓obesity induced inflammation
Activation of PPAR- γ
↑ lipogenesis
Due to increased transcription of Lipoprotein lipase, Fatty acid transport proteins, Acetyl CoA synthase genes
↓ lipolysis
3. ↓obesity induced inflammation
PPAR- γ regulates the transcription of adipokines and cytokines e.g. TNF-α
4. Also has anti-atherogenic properties

34. Activation of PPAR- γ contd.:
1+2+3 = ↓ lipotoxicity & ↓ inflammation = ↑ insulin sensitivity ↑ glucose disposal & control of hyperglycaemia
SIDE EFFECT: WEIGHT GAIN!!!!

35. Dual PPAR-α and -γ ligands
Many diabetic patients also exhibit dyslipidaemia
Why not treat them with combined PPAR-α and –γ ligands, “glitazars”?

36. Glitazars
Looked good in animal studies but have been withdrawn due to safety concerns
E.g. ragaglitazar was developed in c.2004 but induced anemia and urothelial (bladder) cancer
E.g. rosiglitazone is no longer prescribed in Europe. Despite reducing HbA1c by 15-20%, CV risk increases by 2.1x
The best way to treat diabetes mellitus: diet and excersise

37. Outline the biochemistry of diabetes mellitus and its treatment
Define diabetes mellitus
The physiological role of insulin
The induction of insulin resistance
Management:
Diet and excersise
Metformin/SUs
PPARs: MOA, PPAR-α and PPAR- γ and glitazars