1. WELCOME

2. Credit Seminar
on
SPEAKER
P.RAMESH
PH.D (ABC)

3. PPARs (peroxisome proliferator-activated receptors )
are nuclear receptors & function as “Transcription
factor”
Essential roles in regulation of cellular
differentiation, atherosclerosis & macrophage function
3 types have been identified: Alpha α, Gamma , and
Delta  (Beta β)
3
α (alpha) - expressed in

4. Cont…
β/δ (beta/delta) - expressed in many tissues but markedly
in brain, adipose tissue, and skin
γ (gamma) - although transcribed by the same gene, this
PPAR through alternative splicing is expressed in 3
isoforms:
γ1 - expressed in virtually all tissues
γ2 - expressed mainly in adipose tissue (30 A.As
longer)
4

5. PPAR is a ligand-activated transcriptional factor have a
dominant role in development of adipose cells
It is subfamily of structurally similar to nuclear receptor
PPAR functions as an obligate heterodimer with RXRs
High affinity binding to DNA by PPAR requires absolute
dimerization with RXR
(Tontonoz P, et al., 1994)
Domains of PPAR proteins present nearly all nuclear
hormone receptor
Retinoid X Receptor
5

6. Cont…
C
N
PPAR has two N-terminal variants formed by alternative
splicing
(Adams M, et al., 1997)
 PPAR 2 is expressed in more adipose selective manner
N-terminal region influences the response to ligand
6
binding of LBD by phosphorylation at ser112 al., 1996)
(Hu E, et

7. N
C
DNA-binding domain (DBD): Highly conserved domain
containing two zinc fingers which binds to specific
sequences of DNA called hormone response elements
(HRE)
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C-terminal region is responsible for dimerization with RXR
(Ren D, et al.,
& contains Transcriptional activation domain (AF2) 2002)

8. Cont…
C-terminal region also
form ligand binding
pocket, with many
hydrophobic residuces
occuring inside the pocket
Crystal structure of
PPAR LBD
8
(Gampe RT, et al., 2000)

9. Cont…
 PPAR activation induced by ligand dependent and
independent mechanisms
 Absence of ligand, corepressors bind to heterodimers &
recruit Histone deacetylases to repress transcription
 After ligand binding, increase PPAR affinity for number
of co-activators
 N-terminal regulatory domain: Contains the activation
function 1 (AF-1) whose action is independent of the
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presence of ligand
(Tontonoz P, et al., 1994)

10.  Co-activators: These are not themselves regulated at
expression level
CBP/p300
SRC family
TRAP220
PGC-1α
Co-repressors:
SMART
NCoR
RIP140
10

11. Cont…
Biological Ligands:
Polyunsaturated fatty acids
Prostanoids (15-deoxy-12,14 prostaglandin-J2)
Leukotriene LTB4
Oxidized fattyacids (9-HODE & 13-HODE)
Lysophosphatidic acid
Synthetic Ligands:
Thiazolidinedion (TZD) Anti-Diabetic Drug
Fibrates (Hyperlipidemia)
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(Debevec D, et al., 2007)

12. Adipocyte is central player in control of energy balance &
whole body lipid homeostasis
PPAR is dominant or “master” regulator of Adipogenesis
It induces differentiation of pre-adipocytes into
adipocytes & expressed in BAT and WAT
(Sears I, et al., 1996)
C/EBP-β/ bind to PPAR promoter & activates PPAR
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Upon ligand activation, PPAR induces many target genes
involved in Lipogenesis & Adipogenesis

13. KLF5
CHOP
KLF1
5
SREBP1
C
KLF2
C/EBP
PPAR
KROX20
C/EBP
C/EBP
C/EBP
GATA2
/3
Genes of
Adipocyte
differentiation
Anti-adipogenic factors
Activation
Inhibition
13
(Evan D, et al., 2006)

14. INSULIN
IGF-1
WNT10b
TGF
SHH
FGF
BMPs
SMO
PTC
Testosterone
IRS
-Catenin
AR
SMAD3
P
?
SMAD3
+
SHN2
SMAD1
P13K
AKT/PKB
C/EBP
CREB
FOXO1/A2
?
TCF/LEF
GATA2/3
?
PPAR
OTHERS
14
(Evan D, et al., 2006)

15. Anti-Diabetic drugs
Dietary fattyacids
PPAR
Intracellular fattyacids
Prostaglandins PGJ2
Ap2
CBP
RXR
SRC
LPL
CD36
p300
RNA pol-II
PEPCK
Aquaporin7
GLUT4
Perilipin
PGAR
GlyK
Fig: Role of PPAR pathway for Adipogenesis
15

16. 16

17. Triacylglycerols
(Chylomicrons)
Glucose
(Liver)
CD36
GLUT4
Liver
Fattyacids
Glucose
Glycerol-3-P
PEPCK
LPL
Aquaporin7
FattyacylcoA
Perilipin
Triacylglycerols
HSL
Glycerol
Adipocyte
Fattyacids
17

18. Triacylglycerols
(Chylomicrons)
Glucose
(Liver)
LPL
CD36
GLUT4
Liver
Fattyacids
Glucose
Glycerol-3-P
Aquaporin7
FattyacylcoA
PEPCK
Perilipin
Triacylglycerols
HSL
Glycerol
Adipocyte
Fattyacids
18

19. PPAR extensively studied in WAT differentiation & same
receptor is also important in BAT development & function
Thermogenic effect of PPAR in BAT is mediated by PGC1α, induced by cold exposure of animals
(Sears I, et al., 1996)
PGC-1α regulates activation of PPAR on thermogenesis
& fattyacid oxidation by interacting with PPAR/RXR
Stimulation of uncoupling protein (UCP-1), responsible
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for uncoupling β-oxidation
PPAR Coactivator-1

20. Cont…
Phosphorylated PGC-1α is recruited PPAR binding
site on UCP-1 promoter
PGC-1α is stabilized & activated by p38 MAP kinases
PGC-1α binds to PPAR by its LBD in a ligand
independent manner
LXXLL motif containing co-activator binds to PPAR
Insulin/akt pathway shutdown hepatic
gluconeogenesis, phosphorylation of PGC-1
(McInerney E, et al., 1998)
20

21. G
protein
ATP
cAMP
MAP
kinas
e
PGC1
P
PPAR
UCP-1
(Sears I, et al., 1996)

22. Cont…
22
Fig: Thermogenesis by UCP-1 in BAT

23. Insulin Resistance: is a condition in which body cells
become less sensitive to the glucose-lowering effects of
the hormone insulin
Type2 Diabetes mellitus: Pancreas secrete normal or
even greater than normal amount of insulin
Hallmark of type2 Diabetes is Insulin Resistance
In type2 Diabetes, plasma levels of FFAs & Glucose are
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increased

24. In T2DM inappropriate deposition of lipids in liver &
skeletal muscle
Thiazolidinedione (TZD), Rosiglitazone & Pioglitazone are
used for treatment of type2 Diabetes
(Haris P, et al., 1994)
Activation of PPAR target gene expression enhance to
store dietary fattyacids
Target genes contributing to this include
AP2, LPL, CD36, PEPCK & Aquaporin 7
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(Kishida K, et al., 2001)

25. Cont…
Adipose tissue is primary target for effects of TZD
It also promotes many signaling molecules called
Adipokines from adipocytes
Adiponectin
Resistin
TNFα
INFLAMMATORY
RESPONSE
MCP-1
IL-6, IL-1β
(Bouskila M, et al., 2005)
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26. Ligand activation (TZD) of
PPAR in adipocytes is
associated with decreased
production of TNFα, Resistin
& MCP-1
Increase of Adiponectin gene
Decreased Insulin Resistance
Suppression of Hepatic
glucose uptake & stimulates
muscle glucose uptake
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27. ADIPONECTINS:
 It is a protein hormone abundantly expressed in
adipocytes
 Adiponectin affects:
 Decreased gluconeogenesis
 Increased glucose uptake
 β-oxidation
 Triglyceride clearance
 Protection from endothelial dysfunction
 insulin sensitivity
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28. TNF-α:
Cont…
It is an inflammatory cytokine released in obese &
insulin resistance
Also propagates atherosclerotic lesion formation
It also promotes apoptosis in endothelial cells by
dephosphorylating protein kinase B or Akt &
contribute endothelial injury
28

29. Cont…
RESISTIN:
 It is recently discovered fat-specific hormone,
directly induces insulin resistance in muscle & liver
 Neutralization of resistin by specific antibodies
results in decreased blood glucose level
 It also express cell adhesion molecule (VCAM-1),
chemokine MCP-1(Atherosclerotic lesion formation)
with insulin resistance patients
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30. Insulin
Muscle
Liver
Adipocyte Hypertrophy
?
RESISTIN
Diet induced Obesity
Adipocyte
30
(Olavi U, et al., 2002)

31. Adipokines & Inflammation:
 Increased in adipose tissue (WAT) with obesity
during
inflammation (TNF-α, IL-6,IL-18, MIF, CRP &
PAI-1)
 Circulatory inflammatory markers are raised in
obese
 IL-6 released from adipose tissue stimulates hepatic
synthesis of CRP in obese
 Similary IL-18 is acivated by TNF-α
31
(Trayhurn P, et al., 2005)

32. Cont…
 Why Obese should be accompanied by
Inflammation???
 It is mainly due to HYPOXIA
 Adipose tissue (WAT) mass is very large in Obese &
Type-II diabetes are linked to inflammation
(Sears I, et al., 1996)
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33. TZD effects on Skeletal Muscle and Liver:
Skeletal Muscle is largest glucose utilizing organ, ability
of TZD is to improve whole body insulin resistance
PPARγ expression is very low in Skeletal muscle
compare to fat
Effect of PPARγ ligands on skeletal muscle for glucose
uptake are likely to be indirect
Direct of effect of PPARγ activation in muscle is still
33
unclear
(Castrillo A, et al., 2004)

34. Cont…
In liver also expression of PPARγ is very low, activation
of PPARγ signaling promotes lipid accumulation
(Hepatic Steatosis) in rodents
But does not appear in human hepatic steatosis
TZD is beneficial in treating nonalcoholic fatty liver
disease in humans
(Castrillo A, et al., 2004)
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35. PPARγ is induced differentiation of monocytes into
macrophages & highly expressed in Macrophages
It also differentiates of monocytes into dendritic cells
Oxidized ligands (9-HODE & 13-HODE) & lipoproteins
responsible for PPARγ signaling in myeloid cells
Upon ligand activation, it promotes expression of
genes CD36, LXR, Arg-1& IL-10
(Sears I, et al., 1996)
35

36. 36

37.  PPARγ is a lipid-activated member of the nuclear receptor
superfamily of transcription factors
 Biological receptor for the TZD class of antidiabetic drugs
 Master transcriptional regulator of adipocyte differentiation
& controls expression of a genes involved in lipid
metabolism
 PPARγ action in myeloid cells, such as macrophages and
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DCs, has been linked to the modulation of immune and

38. 38