Adipose tissue as an endocrine organ: Adipose tissue has been recognized as the quantitatively most important energy store of the human body for many years, in addition to its functions as mechanical and thermal insulator. During the last 10 years, adipose tissue has come into focus as an endocrine organ important for development of many diseases related to obesity including insulin resistance, type 2 diabetes, dyslipidemia, hypertension and cardiovascular disease. Adipose tissue secretes a variety of bioactive peptides that play important roles in insulin action, energy homeostasis, inflammation, and cell growth. These secretory proteins from the adipose organ are named adipokines and have many physiological effects on different organs including the brain, bone, reproductive organs, liver, skeletal muscles, immune cells and blood vessels. Adipokines may locally regulate fat mass by modulating adipocyte size/number or angiogenesis and inversely increased fat mass leads to dysregulation of adipocyte functions.

1. Isfahan University of Medical Science, School of Pharmacy
Department of Clinical Biochemistry
June 25, 2012 1 Total slides : 51

2. Adipokines
The link between obesity and its complications
Supervised by:
Dr. Mohsen Ani
Presented by:
A.N. Emami Razavi

3. O u t lin e s
 A d ip o s e t is s u e
 O b e s it y & r e la t e d c o m p lic a t io n s
 A d ip o c y t e s a s a n e n d o c r in e c e lls
 A d ip o k in e s
June 25, 2012 3 Total slides : 51

4. Adipose tissue
An overview

5. Adipose tissue
 Adipose tissue or fat is loose connective tissue
composed of adipocytes. Its main role is to store
energy in the form of fat, although it also cushions
and insulates the body.

6. Two types of adipose tissue exist: white adipose tissue (WAT)
and brown adipose tissue (BAT).
WAT
Characteristics of brown and white adipocytes
Multilocular adipocyte
Brown adipocyte Lipid storage and mobilization (++)
Mitochondria (+++)
Fatty acid oxidation (+++)
Respiratory chain (+++)
UCP1 (+++)
PGC-1α (+++)
White adipocyte
BAT
Unilocular adipocyte ( 200µm)
Lipid storage and mobilization (+++)
Mitochondria (+)
Fatty acid oxidation (+)
Respiratory chain (+)
UCP1 (0)
PGC-1α (+)
For letter symbols, see slide 36

7. Anatomical features
 In humans, adipose tissue is located beneath the skin (subcutaneous fat),
and is also found around internal organs (visceral fat). Adipose tissue is
found in specific locations which are referred to as 'adipose depots.'

8. Fat cells
 Adipose cells store
majority of the body’s fat,
vary in size and number
 Increase in body fatness is
due to:
 Fat cell hypertrophy
 Fat cell hyperplasia
June 25, 2012 8 Total slides : 51

9. Fat Cell Development
During growth, When energy intake After fat cells have enlarged and With fat loss, the size of the
fat cells increase exceeds expenditure, energy intake continues to exceed fat cells shrinks, but not the
in number. fat cells increase in size. expenditure, fat cells increase in number.
number again.

10. Fat cell number
 Fat cell develop:
 Last trimester of pregnancy
 First year of life
 During adolescent
 Average non-obese person: 25-30 bill.
 Moderately obese: 60-100 bill.
 Massively obese: 300 bill.+
 Number of fat cells appears to be biggest factor in
determining risk for obesity.
June 25, 2012 10 Total slides : 51

11. Adipose tissue as an endocrine organ
 Adipose tissue has been recognized as the quantitatively most important
energy store of the human body for many years, in addition to its functions
as mechanical and thermal insulator. During the last 10 years, adipose
tissue has come into focus as an endocrine organ important for
development of many diseases related to obesity including insulin
resistance, type 2 diabetes, dyslipidemia, hypertension and cardiovascular
disease. Adipose tissue secretes a variety of bioactive peptides that play
important roles in insulin action, energy homeostasis, inflammation, and
cell growth. These secretory proteins from the adipose organ are named
adipokines and have many physiological effects on different organs
including the brain, bone, reproductive organs, liver, skeletal muscles,
immune cells and blood vessels. Adipokines may locally regulate fat mass
by modulating adipocyte size/number or angiogenesis and inversely
increased fat mass leads to dysregulation of adipocyte functions.
June 25, 2012 11 Total slides : 51

12. The Fat Cell Is a Veritable Endocrine Factory
Cytokines
Proteins of the
Proteins involved in
alternative
glucose homeostasis
complement system
Fa t c e l l
Proteins for
Proteins involved in
regulation of blood
homeostasis
pressure
Proteins involved in Acute phase and
lipid metabolism stress response
proteins
Fat cells are continually absorbing or releasing substances in response to the body’s energy needs

13. Adipokines from adipose tissue
Cytokines
TNF-α Leptin
IL-1β IL-10
IL-6 IL-8

14. Adipokines from adipose tissue
Proteins involved in glucose
homeostasis
Adiponectin Resistine

15. Adipokines from adipose tissue
Proteins of the alternative
complement system
Acylation
Adipsin stimulating
protein

16. Adipokines from adipose tissue
Proteins involved in
homeostasis
Plasminogen
activator Tissue factor
inhibitor-1
(PAI-1)

17. Adipokines from adipose tissue
Proteins for regulation of
blood pressure
Angiotensinogen

18. Adipokines from adipose tissue
Proteins involved in lipid
metabolism
Retinol binding Cholesterol ester
protein transfer protein
(RBP) (CETP)

19. Adipokines from adipose tissue
Acute phase and stress
response proteins
Haptoglobin Metallothionein

20. Cellular origin of the peptides secreted
by human adipose tissue
Adipocytes  Adipokines Stromavascular fraction cells
 cytokines & chemiokines
Monocyte chemoattractant protein 1 (MCP1)
Leptin
Macrophage inflammatory protein (MIP)
Adiponectin
Tumor necrosis α (TNFα)
Serum amyloids
Interleukins 1β, 6, 8, 10, ….
Retinol binding protein 4 (RBP4)
Chemiokines
Apelin
Resistin
FIAF/PGAR
Apelin
…

22. Obesity
 Obesity results from an
imbalance between lipogenesis
(fat synthesis) and lipolysis (fat
destruction ). Lipogenesis which
occurs in liver and adipose tissue
involves fatty acid synthesis
followed by triglyceride
synthesis.
 Differentiation of the pre-
adipocytes to mature fat cells is
referred to as adipogenesis and
should not be confused with
lipogenesis.
June 25, 2012 22 Total slides : 51

23. June 25, 2012 23 Total slides : 51

24. Musculoskeletal Cardiovascular
Problems Problems
Gastrointestinal Complications Respiratory
and Liver Problems Problems
of
obesity
Diabetes Mellitus
Cancer

25. Cardiovascular Problems
 Obesity is a significant risk factor for predicting
cardiovascular disease
 Risks
 ↑ Low-density lipoproteins (LDLs)
 ↑ Triglycerides
 ↓ High-density lipoproteins (HDLs)
 Hypertension
 ↑ Circulating blood volume
 Abnormal vasoconstriction
 ↓ Vascular relaxation
 ↑ Cardiac output
June 25, 2012 25 Total slides : 51

26. Respiratory Problems
 Severe obesity may be associated with
 Sleep apnea
 Obesity hypoventilation syndrome
 ↓ Chest wall compliance
 ↑ Work of breathing
 ↓ Total lung capacity and functional residual capacity
June 25, 2012 26 Total slides : 51

27. Diabetes Mellitus
 Hyperinsulinemia
 Insulin resistance
 Type 2 diabetes
 80% of patients with type 2 diabetes are obese
 Weight loss and exercise improve glucose control
June 25, 2012 27 Total slides : 51

28. Musculoskeletal Problems
 Osteoarthritis
 Trauma to weight-bearing joints
 Hyperuricemia
 Gout
June 25, 2012 28 Total slides : 51

29. Gastrointestinal and Liver Problems
 Gastroesophageal reflux disease (GERD)
 Gallstones
 Nonalcoholic steatohepatitis (NASH)
 Can eventually lead to cirrhosis
 Weight loss can improve NASH
June 25, 2012 29 Total slides : 51

30. Cancer
 Obesity is one of the most important known
preventable causes of cancer
 Women
 Breast, endometrial, ovarian, cervical
 Possibly from ↑ estrogen postmenopause
 Men
 Prostate
 Both genders: Colon
June 25, 2012 30 Total slides : 51

31. History of adipose derived hormones
 Communication between adipose and other tissues has been
hypothesized since at least the 1940s to be bidirectional.
 However, the importance of adipose tissue as an endocrine
organ was only fully appreciated in 1994 with the discovery of
Leptin, the protein product of the Ob gene.

32. leptin
 Leptin is a 16 kDa polypeptide
product of the obese (ob) gene.
 Leptin, expressed and secreted
primarily by adipocytes, acts via a
family of receptor (ob-R) isoforms
to mediate an ever growing wide
range of physiological effects.
 These receptors have divergent
signaling capabilities, regulating
pathways which include
JAK/STATs and MAP kinases.

33. Leptin expression
 Leptin expression is influenced by energy stores in
fat.
 Leptin levels increase within hours after a meal in
rodents and after several days of overfeeding in
humans.
 Insulin stimulates leptin expression and secretion in
primary adipocytes.
 Other factors, such as dexamethasone, thyrotrophin
(TSH) , TNF-α and IL-6 also regulate leptin release.

34.  Leptin concentrations in the blood are in the range of
several ng/ml, both as an active free form and as an inactive
bound form which occurs by its association with plasma
proteins and the leptin receptor isoform.
 Leptin receptors (OB-R) are expressed in variety of
tissues, which suggested that it has a wide range of actions.
However, leptin receptor mutations cause early onset obesity
in rodents. This is consistent with measurements of high leptin
concentration and low leptin receptor expression in most
diabetic patients.

35. Signalling Pathway of Leptin Action
 Leptin binding to the leptin receptor leads to the formation of
a Ob-R/JAK2 (Janusactivated kinase) complex that triggers
phosphorylation. JAK2 phosphorylation leads to activation of
the PI3K and MAPK pathways that regulate apoptosis, energy
homeostasis and gene transcription. Leptin signaling occurs
mainly through signal transducers and activators of
transcription (STAT3). Phosphorylation of STAT3 triggers
dimerization and translocation to the nucleus which leads to
activation of gene transcription. The targets include: genes of
suppressors of the cytokine signaling family (SOCS3).
Therefore, leptin regulates various signaling pathways and
impacts gene transcription.

37. Physiological effects of Leptin
 Regulation of food intake ,energy expenditure and
body weight .
 Thermo genesis .
 Reproductive function .
 Suppressed bone formation .
 Directly act on the cells of liver and muscles .
 Related to inflammatory response .
 Contribute to early hematopoiesis.

38. Role of leptin in regulation of food intake and
body weight
 Decrease hunger and food consumption - inhibition of
neuropeptide Y synthesis .
 Food intake linked to its ability to regulate the neuroendocrine
system .

39. Neuropeptide Y
 36 a.a residue produce in the arcuate nucleus of the
hypothalamus . Rich in tyrosine residues .
 Appetite stimulating hypothalamic peptide

40. Neuropeptide Y
 Found in many organ, high level of NPY are found in
brainstem and hypothalamus .
 Stimulates leptin production in adipose tissue by increasing
food intake and insulin secretion.
 Action through the parasympathetic nervous system.

41. Leptin and food intake

42. Mice with and without Leptin
Without leptin, this mouse With leptin treatment, this mouse
weighs almost three times as lost a significant amount of weight,
much as a normal mouse. but still weighs almost one and a
half times as much as a normal
mouse.

44. Role of leptin in thermogenesis

45. Role of leptin in lipid metabolism
 Leptin activated lipid oxidation, at least partially by
inducing the expression of enzymes involved in lipid
metabolism.
 Activate 5 –AMP-activated protein kinase (AMPK)
 Inhibits acetyl coenzyme-A carboxylase (ACC)
 Increase insulin sensitivity
 Inhibits intracellular lipid concentration
 Leptin also stimulated apoptosis of adipocytes
through activation of caspase-8.

46. Leptin resistance
 The ability of leptin to decrease body fat content
suggests leptin is an anti-obesity hormone.
 However, high leptin levels have been found in obese
and diabetic mice and humans, which is defined as
“leptin resistence”. Sometimes it is combined with
low-level expression of leptin receptors. Another
mechanisms are:
 Mutation of the gene for leptin receptors in the brain
 Post receptor abnormalities in leptin signal transduction
 Impaired leptin transport across blood- brain barrier

47. Leptin, obesity and diabetes
 Disruption of leptin action is thought to play a role in
development of diabetes. This hypothesis is supported by data
showing that mutations of the ob gene cause early onset
obesity and type II diabetes in mice and humans.
 A frameshift/premature stop mutation, c.398delG (Delta133G
mutation) caused a congenital leptin deficiency and led to
severe early-onset obesity.
 A homozygous frameshift mutation (delta133) in the human
leptin (ob) gene was associated with undetectable serum leptin
and extreme obesity.

48. Leptin effects on immune system
 Leptin stimulates the proliferation of stem cells and regulates
hematopoiesis.
 It participates in innate immunity by promoting the maturation
and survival of dendritic cells (DC) and stimulates
macrophage proliferation, phagocytosis, and production of
proinflammatory cytokines.
 Leptin plays a direct role in adaptive immunity by regulating
the expression of Ob-R on both T and B cells and promoted
the suvival of T and B cells by suppressing Fas-mediated
apoptosis.
 Leptin increase the production of IL-2 and IFN-γ by T
lymphocytes.

49. Adiponectin
 A protein is also called ADIPOQ, gelatine-binding 28,
Acrp30, discovered in 1995.
 A peptide hormone made by adipocytes in response to high fat
reserves:
 Increases FA uptake by myocytes and the rate of FA oxidation.
 Slows FA synthesis in the liver.
 Slows gluconeogenesis in the liver.
 Acts through AMP-dependent protein kinase (AMPK).
 Humans who are obese or who suffer from Type II
diabetes show reduced levels of adiponectin.
 Drugs (thiazolidinediones) used to treat Type
II diabetes elevate expression of adiponectin.

50. Plasma concentration
 Adiponectin is abundant in human plasma, with concentrations
ranging from 5 to 30mg/ml, thus accounting for approximately
0.01% of total plasma protein
 This concentration is three orders of magnitude higher than
concentrations of most other hormones

51. Adiponectin and Fat Mass
 There seems to be a clear relationship between adiponectin
and fat mass in humans.
 However, in contrast to leptin, adiponectin levels are
significantly reduced among obese subjects in comparison
with lean control subjects.
 Arita et al showed that mean plasma adiponectin levels were
3.7 mg/ml in a group of obese patients, whereas in non-obese
subjects these values reached a mean of 8.9 mg/ml
 In a recent longitudinal study, plasma adiponectin
concentrations decreased with increasing adiposity in a group
of children evaluated at 5 and 10 years of age

52. Adiponectin and Fat Mass
 Adiponectin is the only adipose-specific protein known to date
that is negatively regulated in obesity
 In a group of normal weight and obese women plasma
adiponectin was negatively correlated not only with body mass
index and body fat mass, but also with serum leptin
concentration, fasting insulin and calculated insulin resistance
 Another study, performed in 967 Japanese subjects with
normal weight, has shown that plasma adiponectin is
negatively correlated with body mass index, systolic and
diastolic blood pressure, fasting plasma glucose, insulin,
insulin resistance, total and LDL-cholesterol, TG and uric
acid, and positively correlated with HDL-cholesterol

53. Adiponectin and DM, CAD
 Like plasma leptin levels, adiponectin concentrations seem to
be gender-dependent, being higher among women than men
 plasma adiponectin levels are reduced not only among obese
patients but also among patients with some of the disease
states frequently associated with obesity, such as type 2 DM
and CAD
 Multivariate analysis demonstrated that hypoadiponectinemia
was more intensively related to the degree of insulin resistance
and hyperinsulinemia than to the degree of adiposity or
glucose intolerance

54. Adiponectin and DM, CAD
 first degree relatives of type 2 diabetic patients have reduced
adiponectin mRNA expression in adipose tissue compared with
controls, although they have normal levels of circulating adiponectin
 Recent genome-wide scans have mapped a diabetes susceptibility
locus to chromosome 3q27, where the adiponectin gene (apM1) is
located
 Evidence of an association between type 2 diabetes and single
nucleotide polymorphisms at positions 45 and 276, and in the
proximal promoter and exon 3 of the adiponectin gene has been
reported
 Some missense mutations in the globular domain have been also
associated with low adiponectin levels and type 2 diabetes

55. Adiponectin and Serum lipid concentrations
 In a large number of non-diabetic women with dyslipidemia,
Matsubara et al. have shown that plasma adiponectin is
negatively correlated with serum triglyceride, atherogenic
index, apo B or apo E, and positively correlated with serum
HDL-cholesterol or apo A-I levels.
 These data suggest that low adiponectin concentrations are
associated with some of the well-known risk factors for
atherosclerosis, such as low HDL-cholesterol levels or
hypertriglyceridemia.
 A relationship between hypoadiponectinemia and the
metabolic syndrome seems likely

56. Adiponectin and Body Weight loss
 Recent evidence also suggests that weight loss induces an increase in
adiponectin levels in obesity.
 In a group of 22 obese patients, who were treated by gastric partition
surgery, a 46% increase in mean plasma adiponectin level was
accompanied by a 21% reduction in mean body mass index
 Changes in plasma adiponectin were related to changes in body mass
index, waist and hip circumferences, and steady-state plasma glucose
levels
 These data suggest the existence of a negative feedback mechanism
between adipose mass and the production of adiponectin in humans

57. Adiponectin and TZD
 Thiazolidinedione treatment enhances endogenous adiponectin
production
 In a group of mildly overweight subjects with glucose
intolerance the administration of troglitazone for 12 weeks
significantly increased the plasma adiponectin concentration in
a dose-dependent way
 In a recent randomized double-blind placebo controlled trial
performed in 64 type 2 diabetic patients, rosiglitazone therapy
for 6 months was accompanied by a more than 2-fold increase
in plasma adiponectin levels

58. Adiponectin and TZD
 Similar results have been reported with pioglitazone
 Furthermore, circulating adiponectin levels were found to be
suppressed 5-fold in patients with severe insulin resistance in
association with dominant-negative PPAR-g mutations
 thus suggesting that adiponectin may be a biomarker of in vivo
PPAR-g activation

59. Adiponectin and CRF, Type 1 DM, Anorexia
Norvosa
 In a study, performed in 227 hemodialysis patients, plasma
adiponectin levels were 2.5 times higher among dialysis
patients than among healthy subjects, and they were higher
among women than among men
 Plasma adiponectin concentrations have been found to be
significantly elevated in a group of 46 type 1 diabetic patients
in relation to healthy controls
 Insulin replacement therapy did not affect adiponectin levels
in a subgroup of seven patients.
 A preliminary report also showed that adiponectin levels were
moderately elevated in 26 female patients with anorexia
nervosa

60. Control of the
synthesis of Adiponectin
 The only hormone implicated in the regulation of adiponectin
expression has been insulin
 TNF-a is one of the candidate molecules responsible for
causing insulin resistance
 The expression and secretion of adiponectin from adipocytes
are significantly reduced by TNF-a
 Therefore, increased TNF-a might be partially responsible for
the decreased adiponectin production in obesity
 adiponectin itself may increase insulin sensitivity through an
inhibition of both the production and action of TNF-a
 It has also been hypothesized that adiponectin and TNF-a may
antagonize each other or perform opposite functions locally in
adipose tissue or in the arterial wall

61. Adiponectin as a Biomarker of the Metabolic
syndrome
 The metabolic syndrome:
 common basis for the development of atherogenic
cardiovascular diseases.
 Decreased plasma concentrations of adiponectin:
 plays a significant role in the development of the MS.
 the plasma concentration of adiponectin was
significantly correlated with each component of the
metabolic syndrome.

62. Definition of the Metabolic Syndrome
 The presence of at least 3 of the following abnormalities;
2. Abdominal obesity: WC>=85cm in men or >=90cm in women
3. Hypertriglyceridemia: a serum triglyceride
concentration>=150mg/dl
4. Low HDL cholesterolemia: a serum HDL cholesterol
concentration<40mg/dl
5. Hypertension: SBP>=130mmHg, DBP>=85mmHg and/or
having received antihypertensive medication
6. High fasting glucose: serum glucose concentration>=110
mg/dl

63. Potential therapeutic applications
 Evidence reported so far suggests that adiponectin possesses
antihyperglycemic, anti-atherogenic and anti-inflammatory
properties.
 Increased serum adiponectin levels are associated with
increased insulin sensitivity and glucose tolerance
 adiponectin – or drugs that stimulate adiponectin secretion or
action –might play a role in the therapeutic armamentarium
against disease states associated with insulin resistance,
mainly type 2 diabetes mellitus and obesity
 Low levels of adiponectin have also been implicated in the
severe insulin resistance that accompanies lipoatrophy
 Therapy with adiponectin may also play a role in reversing
insulin resistance in lipodystrophic disorders.

64. Potential therapeutic applications
 The anti-inflammatory effects of adiponectin indicate that it is
an interesting protective factor for atherosclerosis
development, especially in those clinical situations associated
with low plasma levels of adiponectin.
 It is conceivable that the use of recombinant adiponectin may
become beneficial in the prevention of cardiovascular disease
in selected patients.
 The recent finding that adiponectin deficiency aggravates
neointimal thickening, and that supplementation with
adiponectin attenuates neointimal thickening in mechanically
injured arteries, suggests that increasing plasma adiponectin
might be useful in preventing vascular restenosis after vascular
intervention

65. Adiponectin - structure

66. Adiponectin action : activation AMPK

68. Molecular Mechanisms of Adiponectin Action
Kadowaki et al. Endocrine Reviews 26 (3): 439 - 451, 2005

69. Adiponectin R1 and R2 are Expressed in Heart,
Liver, Kidney, Skeletal Muscle and Other Tissues
 Brain
 Heart
 Kidney
 Liver
 Lung
 Skeletal Muscle
 Spleen
 Testis
Yamauchi T., et al Nature 423, 762-769

70. Resistin
 Resistin has been named for the fact that it conveys the
resistance to insulin
 Resistin is a cysteine-rich protein secreted by adipose tissue of
mice and rats. In other mammals, at least primates, pigs and
dogs, resistin is secreted by immune and epithelial cells.

71. Resistin
 Resistin is a 114 amino-acid peptide present in humans most
likely in the form of a few splice variants. Monomeric
peptides may create oligomeric structures
 It is secreted as a disulfide-linked homodimer via disulfide
bonds at cysteine residue (Cys26)

72. Resistin and obesity
 Circulating resistin levels are increased in mouse models of
obesity and in obese humans and are decreased by the anti-
diabetic drug rosiglitazone, and increased in diet-induced and
genetic forms of obesity
 Administration of anti-resistin antibody has been shown to
improve blood sugar and insulin action in mice with diet-
induced obesity.
 Similarly resistin has been implicated in the pathogenesis of
diabetic complication and diabetes.
 Moreover, treatment of normal mice with recombinant resistin
impairs glucose tolerance and insulin action. Insulin-
stimulated glucose uptake by adipocytes is enhanced by
neutralization of resistin and is reduced by resistin treatment.

73. Resistin and inflammation
 Resistin mRNA has been found in human PBMC and was increased by
pre-treatment with certain cytokines such as IL-6 and TNF-alpha, IL-1,
IL-12 or lipopolysacharride. Interestingly resistin itself leads to increased
release of numerous pro-inflammatory cytokines TNF-alpha and IL-12,
from macrophages and monocytes.
 Resistin induce the nuclear translocation of NF-kappaB transcription
factor and resistin pro-inflammatory effects are reduced in the conditions
of NF-kappaB inhibition. Thus pro-inflammatory actions of resistin are
related to the activation of NFkappaB pathway, which makes resistin’s
actions on the immune system in a direct opposition to adiponectin’s.
 Finally an important effect of resistin on inflammation is related to it’s
ability to induce vascular adhesion molecule expression, thus increasing
leukocyte infiltration to tissues, including fat.

74. Glitozones and resistin
 Rosiglitazone and other glitazones lower glucose and
lipid levels in patients with type 2 diabetes by
activating the nuclear receptor peroxisome
proliferator- activated receptor g (PPARg)1.
 Rosiglitazone treatment was shown to reduce resistin
expression in 3T3-L1 adipocytes in vitro and in the
white adipose tissue (WAT) of mice fed a high fat
diet. These data raised the interesting possibility that
decreases in resistin levels might be integral to the
antidiabetic actions of PPARg agonists.

75. Visfatin
 Visfatin is the most recently identified adipocytokine
(known previously as pre-B cell colony enhancing
factor; PBEF) which appears to be preferentially
produced by visceral adipose tissue, and has insulin-
mimetic actions.
 Visfatin expression is increased in animal models of
obesity and its plasma concentrations are increased in
humans with abdominal obesity or type 2 diabetes
mellitus.

76.  Visfatin binds to the insulin
receptor at a site distinct from
insulin and exerts
hypoglycemic effect by
reducing glucose release from
hepatocytes and stimulating
glucose utilization in
peripheral tissues. The latter
property could make this
molecule very useful in the
potential treatment of
diabetes. Interestingly, known
as PBEF, visfatin was also
identified in inflammatory
cells and it’s levels were
increased in various
inflammatory conditions

81. Angiotensinogen
 Angiotensinogen, a precursor to the major proatherogenic
vasoconstrictor angiotensin II (AT-II), is expressed and
produced in adipocytes. AT-II directly stimulates ICAM-1,
VCAM-1, MCP-1 and M-CSF expression in vascular cells by
activating NF-κΒ-regulated genes. AT-II also promotes the
formation of free oxygen radicals from NO, thereby
decreasing the availability of NO and incurring damage to the
vascular tissue. Augmented angiotensinogen production by
adipose tissue in obesity has been linked to angiogenesis and
the development of hypertension, both of which are known to
be associated with endothelial dysfunction.

83. Obesity and inflammation
Obesity has been suggested to be an inflammatory
disease, or at least a disease with an inflammatory
component to it. Pro-inflammatory molecules as
CRP, IL-6, TNF-alpha,
Nutrition. 2001 Nov-Dec;17(11-12):953-66;
Intercellular adhesion molecule-1 (ICAM-1), and
vascular adhesion molecule-1 (VCAM-1)
Circulation. 2002 Feb 19;105(7):804-9 have been
shown to be high in overweight or obese subjects.

84. TNFα
 TNF-α is now recognized as a multi-functional
regulatory cytokine, involved in inflammation,
apoptosis, cell survival, cytotoxicity, and insulin
resistance.
 TNF-α is a 26-kDa plasma membrane-bound protein
that is cleaved into a 17-kDa biologically active
protein.
 There are two receptors for TNF-α, type I and type II
that regulate different functions.

85. TNFα and obesity
 Both mRNA and TNFα protein were elevated in the
adipose tissue of obese animals and humans.
 Adipose tissue also expressed both types of TNFα
receptors.
 Long term exposure of cultured cells or animals to
TNFα induced insulin resistance, characterized by
hyperinsulinemia and an increased prevalence of
obesity, hypertension, dyslipidemia and type 2
diabetes

86. TNFα and insulin resistance
 Several hypotheses have been proposed to explain how TNFα induces
insulin resistance in adipocytes.
 For example, TNFα inhibited insulin-stimulated IRS-1 phosphorylation.
Thus, it might inhibit PI3K and inhibit a pathway that regulates glucose
uptake.
 In addition, TNFα up regulates transcription of many preadipocyte genes
and proinflammatory cytokines, such as IL-6 and MCP-1. These proteins
were elevated in the plasma or adipose tissue of diabetic patients.
 TNFα also inhibited adiponectin expression, which may impaire insulin
action.
 Furthermore, TNFα directly stimulated lipolysis, which caused in
increased plasma free fatty acids. This also caused hepatic insulin
resistance by inhibiting insulin suppression of glycogenolysis.

87. TNFα and inflammation
 TNFα, an inflammatory cytokine released in greater quantities
by obese humans and patients with insulin resistance, not only
initiates but also propagates atherosclerotic lesion formation.
TNFα activates the transcription factor nuclear factor-κΒ
(NFκΒ), which accelerates experimental atherogenesis, in part
by inducing the expression of VCAM-1, ICAM-1, MCP-1 and
E-selectin in aortic endothelial and vascular smooth muscle
cells. TNFα reduces NO bioavailability in endothelial cells
and impairs endothelium-dependent vasodilatation, promoting
endothelial dysfunction. TNFα may also promote apoptosis in
endothelial cells by dephosphorylating protein kinase B, or
Akt, and thereby, contribute to endothelial injury, an effect
counteracted by insulin.

88. file:///H:/files/seminar obesity/obesity sites/TNF-alpha_files/tnfpathway.gif

89. IL-6
 IL-6 is another cytokine that has long been
recognized for its effects on the immune system
 It is associated with obesity and insulin resistance,
too
 Like TNF-o
plasma IL-6 Adipocytes secretes 2 to 3 times more
IL-6 than stromovascular cells

90. IL-6, obesity and inflammation
 The in vivo release of IL-6 from fat contributes more than one
third of the basal circulating IL-6 and explains the positive
correlation between serum levels of IL-6 and obesity.
 signals are passed either through (JAK-STAT) or (ERK-
MAPK) pathways or both.
 IL-6 induces fever and the acute phase response, which is
defined as the complex series of inflammatory reactions
initiated in response to infection, physical trauma, or
malignancy.
 Therefore, enlarged adipose tissue has the potential to
exacerate both responses.

91. IL-6 and insulin resistance
 IL-6 induces SOCS3 transcription and inhibits JAK/STAT
activation, which caused inhibition of insulin receptor (IR)
phosphorylation and insulin receptor substrate (IRS)
phosphorylation . Thus, increased glyconeogenesis and
decreased gluconeogenesis decrease glycogen storage, a
consequence of insulin resistance.
 IL-6 suppresses insulin-induced lipogenesis and reduces
expression of GLUT4 via repressed PKB/ERK pathway.
 Furthermore, IL-6 decreased adiponectin gene expression and
secretion in a dose- and time-dependent manner in 3T3L1
adipocytes. All of these changes contribute to a glucose
intolerant state.

92. JAK-STAT signaling pathway
 The JAK-STAT signaling pathway takes part in the
regulation of cellular responses to cytokines and
growth factors. Employing Janus kinases (JAKs) and
Signal Transducers and Activators of Transcription (STATs),
the pathway transduces the signal carried by these
extracellular polypeptides to the cell nucleus, where activated
STAT proteins modify gene expression. Although STATs
were originally discovered as targets of Janus kinases, it has
now become apparent that certain stimuli can activate them
independently of JAKs. The pathway plays a central role in
principal cell fate decisions, regulating the processes of
cell proliferation, differentiation and apoptosis. It is
particularly important in hematopoiesis - production of
blood cells.

93. Mechanism

94. Suppressor of cytokine signaling 3

95. CRP
 cAMP Receptor Protein (CRP) is a dimer of two
identical subunits each of which is 209 amino acids in
length.

96. CRP
 Circulating plasma CRP levels are elevated in obese subjects
and the levels are also directly correlated with the amount of
body fat,
 Elevated plasma levels of C-reactive protein (CRP) have
become one of the strongest independent predictors of CHD
 CRP induces the expression of VCAM-1, ICAM-1, selectins,
and MCP- 1 in cultured endothelial cells via increased
secretion of ET-1, a potent endogenous vasoconstrictor, and
IL-6
 CRP downregulates eNOS mRNA and protein expression. The
diminished NO activity may in turn inhibit angiogenesis, an
important compensatory response in chronic ischemia

97. CRP
 Furthermore, in vascular smooth muscle cells, CRP
upregulates angiotensin type 1 receptor (AT1-R) mRNA and
protein levels and increased AT1-R expression on the cell
surface.
 AT1-R is a key atherosclerotic switch that facilitates
angiotensin-II induced reactive oxygen species production,
vascular smooth muscle cell migration and proliferation, and
vascular remodeling.
 The effect of CRP on endothelial dysfunction is potentiated by
hyperglycemia and these effects are attenuated by
rosiglitazone, an insulin sensitizing thiazolidinedione anti-
diabetic drug.

98. CRP
 CRP may also play a coordinating role by amplifying
the proinflammatory activity of other adipokines. For
example, it increases the expression and activity of
PAI-1 in endothelial cells
 Plasminogen activator inhibitor-1 (PAI-1) suppresses
fibrinolysis by inhibiting plasminogen activation, and
is an active contributor to atherogenesis by promoting
thrombus formation. Plasma PAI-1 levels are
positively correlated with cardiovascular risk and
mortality, and recently, the development of diabetes

99. Elevated CRP Levels in Obesity:
NHANES 1988-1994
Percent with CRP > 0.22 mg/dL
25
20
15
10
5
0
Normal Overweight Obese
Visser M et al. JAMA 1999;282:2131-2135.

100. Inflammation of coronary artery
 Inflammation in a coronary artery produces a cascade of events that can
prove fatal. Pretreatment with the antithrombotic agent clopidogrel prior to
angioplasty and stenting reduced rates of myocardial infarction and death
in patients with the highest levels of C-reactive protein, a marker of
inflammation.

101. Serum Amyloid A
 Serum amyloid A (SAA) proteins are a family of apolipoproteins found
predominantly associated with high-density lipoprotein (HDL) in plasma,
with different isoforms being unequally expressed constitutively and in
response to inflammatory stimuli.
 Serum amyloid A (SAA) is an acute phase reactant like CRP, which has
been associated with systemic inflammation, linked to atherosclerosis and
used as a predictor for coronary artery disease and cardiovascular outcome.
 SAA levels correlate significantly with insulin resistance and obesity in
type 2 DM patients. Adipose tissue has been shown to express SAA at low
levels under normal conditions but expression in adipose tissue is
dramatically upregulated in the diabetic state.
 The increase in acute phase reactant proteins may affect lipid metabolism
and thus contribute to the dyslipidemia associated with diabetes. Serum
amyloid A displaces apolipoprotein A1 from HDL cholesterol, increasing
HDL binding to macrophages, and thus, decreasing cardioprotective HDL
cholesterol.

102. Enzymatic and protein changes within high-density
lipoprotein (HDL) during an acute phase reaction
Copyright ©2005 American College of Cardiology Foundation. Restrictions may apply.

103. Cardiovascular Metabolic Syndrome
(Syndrome X)
Low grade inflammation Prothrombotic state
Hyperglycaemia CVD
Dyslipidemia Hypertension
Genetics+
Lifestyle

104. Obesity
I.c. TG accumulation
Free radical production
β cell damage
Insulin deficiency

107. Role of obesity in insulin resistance
↑ Caloric
intake ↑ Free
Oxidative
Visceral Sedentary
fatty acids
stress Insulin
Obesity lifestyle ↑ Glucose resistance
Inflammation
Genetic ↑ Lipids
factors
Adapted from Wellen KE, Hotamisligil GS. J Clin Invest. 2005;115:1111-9.

108. Fat Cell Products and Hypertension
 Visceral l Portal
 Hepatic
 Plasma
Insulin
Fat Stores FFA
Clearance
Insulin
Vascular  Renal Na+
Constriction Reabsorption
Angiotensinogen Angiotensin II
Angiotensin I
Hypertension
Bray GA. Contemp Diagn Obes. 1998.

109. Clinical manifestations of insulin resistance
Type 2 diabetes and
glycemic disorders
Atherosclerosis
Dyslipidemia
Insulin
resistance – Low HDL
– Small, dense LDL
Visceral Glucotoxicity – Hypertriglyceridemia
Obesity Lipotoxicity Hypertension
↓ Adiponectin Endothelial dysfunction/
inflammation (hsCRP)
Impaired thrombolysis
↑ PAI-1
Courtesy of Selwyn AP, Weissman PN.

110. Hypertension
 Hyperinsulinemia can enhance renal sodium reabsorption
and vascular reactivity
 Angiotensinogen from fat cells can increase angiotensin II
and thus blood pressure
 Both systolic and diastolic blood pressure increase with
increasing body mass index

111. Metabolic Syndrome, Insulin Resistance, and
Atherosclerosis
Hyperinsulinemia/hyperproinsulinemia
Insulin resistance
Glucose Increased Decreased Increased BP
intolerance triglycerides HDL cholesterol Endothelial dysfunction
Increased
Small, dense PAI-1
LDL
Atherosclerotic
cardiovascular
disease
MacFarlane S et al. J Clin Endocrinol Metab. 2001;86:713-718.

112. Effects of Thiazolidinediones Mediated
via Adipose Tissue
Thiazolidinediones Adipose tissue
PPARγ
Decreased FFA and TNFα release
Decreased tissue triglycerides
Increased adiponectin
Muscle Liver β-cell Vascular
Increased Decreased Increased Increased
glucose glucose insulin endothelial
utilization output secretion function
Adapted from Goldstein BJ. Am J Cardiol. Suppl 2002.

113. FFA and Adipokines in
Endothelial Dysfunction
Increased visceral fat
Thiazolidinediones
Increased lipolysis
Increased TNFα Decreased adiponectin
Increased FFA levels
- -
-
Insulin NO production
Shear stress Endothelium Vascular dilation
Adapted from Steinberg H et al. Diabetes. 2000;49:1231.

114. Medical Complications of Obesity
Pulmonary disease Idiopathic intracranial
abnormal function hypertension
obstructive sleep apnea Stroke
hypoventilation syndrome
Cataracts
Nonalcoholic fatty liver Coronary heart disease
disease
Diabetes
steatosis
steatohepatitis Dyslipidemia
cirrhosis Hypertension
Gall bladder disease Severe pancreatitis
Gynecologic abnormalities Cancer
abnormal menses breast, uterus, cervix
infertility colon, esophagus, pancreas
polycystic ovarian syndrome kidney, prostate
Osteoarthritis
Phlebitis
Skin venous stasis
Gout

115. Potential therapeutic strategies associated with
Nicotinic
acid fatty acid metabolism
HM74a
Inducers Ligands
A
C
Gi
PGC1α
Nuclear
Inhibitors cAMP receptors
PKA
Fat Lipid
mass? utilization
ATGL HSL
Lipolysis A combination of PGC-1α inducers and nuclear receptor
Antilipolysis as a strategy to combat the ligands may constitute a strategy to combat obesity
metabolic syndrome
Trends Endocrinol Metab 2006 ;17 :314-320. Trends Endocrinol Metab 2003;14 :439-441.

116. adipokines and cardiovascular disease
Both abdominal (visceral) fat and insulin resistance may contribute to cardiovascular
disease in obesity.

117. Summary of “adipocyte-vascular axis” and role of major adipocyte - derived factors
(leptin resistin and ghrelin) in in the regulation of vascular and immune functions.
Detailed description is provided in individual sections in the text of the paper.

118. PPAR signaling pathway

119. Proposed mechanisms for obesity-related
hypertension

120. ROLE OF ADIPONECTIN IN THE REGULATION OF CARBOHYDRATE
AND LIPID METABOLISM

125. The potential effects of adiponectin (and
resistin) on adaptive immunity
Tilg and Moschen Nature Reviews Immunology 6, 772–783 (October 2006) | doi:10.1038/nri1937

126. The Role of Adipocytokines in Adipocyte-
Related Pathological Processes

127. Effects of obesity on growth-factor
production

128. Effects of obesity on hormone production

129. Obesity, hormones and endometrial cancer

139. Molecular links between Obesity and
Atheroslcerosis
 Among the adipokines, CRP and IL-6 are the two most strongly associated
with increased cardiovascular disease risk and the prediction of future
cardiovascular disease or type 2 diabetes. The wide-ranging direct effects
of CRP on endothelial and smooth muscle cells argue favorably for CRP as
a key cellular mediator linking obesity, the metabolic syndrome of insulin
resistance and type 2 diabetes, to increased atherogenesis. Emerging data
suggest the beneficial effects of TZDs, and possibly statins and ACEIs,
may in part be mediated via the reduction of the levels and the direct
effects of the adipokines on atherogenesis. Further investigations into the
molecular links between obesity and atherosclerosis will unravel
innovative therapeutic strategies to improve cardiovascular health in
people affected by obesity linked insulin resistance, the metabolic
syndrome and type 2 diabetes.

140. Anti- and proinflammatory adipokines

141. Effects of the metabolic syndrome of insulin resistance on
endothelial dysfunction

142. Adipokines serve as the cellular mediators of the metabolic
syndrome and endothelial dysfunction.

144. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
Adiponectin ↓ ICAM-1, VCAM-1, E-Selectin Plasma levels inversely correlated
with obesity and insulin resistance
↓NFκB
↑ insulin sensitivity
↓transformation of macrophages to
foam cells ↓ TNF-induced changes in
adhesion molecule expression
↓ VSMC proliferation and
migration

145. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
Angiotensinogen ↓ NO availability ↑ development of hypertension
↑ NFκB
↑ ICAM-1, V-CAM-, MCP-1 and
M-CSF
↓ angiogenesis

146. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
CRP ↓ NO by destabilizing eNOS mRNA ↑ PAI-1 expression and activity
and ↓ protein expression in endothelial cells
↑ ET-1 and IL-6 release
↑ VCAM-1, ICAM-1, selectins and CRP levels correlate with the
MCP-1 in EC metabolic syndrome and predicts
↑ LDL uptake in EC future CHD
↓ angiogenesis
↑ apoptosis in EC predicts development of diabetes
↑ ROS
↑ SMC proliferation and migration Hyperglycemia potentiates
and restenosis 73 proatherogenic action of CRP
↑ AT1-R on VSMC 11

147. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
IL-6 ↑ ICAM-1, E-Selectin, VCAM-1, ↑ preadipocyte differentiation
MCP-1
↓insulin receptor signal
↑ SMC proliferation and migration transduction
↑ systemic insulin resistance
↑ hepatic CRP production

148. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
Leptin ↑ NO by increasing eNOS ↑ glucose transport
production
↑ ET-1 Reverses insulin resistance in
↑ proliferation and migration of EC lipodystrophy
and VSMC
↑ ROS accumulation and oxidative ↑ sympathetic tone
stress
↑ VSMC apoptosis ↑ blood pressure
↑ angiogenesis
↑ release of monocyte colony-
stimulating factor
↑ cholesterol accumulation under
hyperglycemia

149. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
PAI-1 ↑ thrombus formation PAI-1 expression stimulated by
TNF-α, ang II, FFAs
↑ restenosis

150. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
Resistin ↑ ET-1 release ↑ insulin resistance in muscle and
liver
↑ expression of adhesion molecules
and chemokines ↓ glucose uptake and insulin
action
↓ TRAF-3
TZD downregulates resistin
expression

151. Effects of Adipokines on Vascular Homeostasis and the
Metabolic Syndrome of Insulin Resistance
Adipokines Vascular action Insulin action and resistance
TNF-α NO bioavailability ↓ adipose cell differentiation
↓ insulin signal transduction
↓ vasodilatation ↑ systemic insulin resistance
↑ lipolysis
↑ NFκB via ROS ↑ FFAs
↑ VCAM-1, ICAM-1, E-selectin and
MCP-1 in EC and VSMC
↑ apoptosis in EC

152. Peroxisomes proliferator activated receptors
(PPAR)

PPARs were originally cloned as nuclear receptors that mediate the
effects of synthetic compounds called peroxisome proliferators on gene
transcription. Three PPAR isotypes have been described: α, β, and γ.
Binding of the ligands to these receptors results in activation of target
gene transcription. Endocr Rev. 1999 Oct;20(5):649-88. The target
genes of PPARs are involved in lipid transport and metabolism,
including trans-membrane fatty acid uptake , fatty acid binding in
cells, fatty acid oxidation in microsomes peroxisomes and
mitochondria, as well as lipoprotein synthesis and transport. PUFA
binds to all three receptors, while long chain unsaturated fatty acids
(linoleic acid), branched chain fatty acids, Leukotriene B4 and
eicosanoids bind mainly to PPAR α. Prostaglandin J2 and
Prostaglandin 15-deoxy-D are the endogenous ligands for PPAR-γ.

153. PPAR isotypes
 PPAR-α is predominantly expressed in brown adipose
tissue and liver as well as kidney heart and skeletal muscle.
 PPAR β has greatest expression in gut, kidney and heart.
PPAR-β is linked to colon cancer . PPAR-β regulates the
expression of acyl-CoA synthetase2 in the brain, thus
playing a role in basic lipid metabolism.
 PPAR γ is mainly expressed in adipose tissue, and at
lower levels in the colon, and immune system. No
significant expression of PPAR-γ has been demonstrated
in the skeletal muscle the main site of glucose disposal.

157. STAT
 The Signal Transducers and Activator of Transcription
(STAT, also, called signal transduction and transcription)
proteins regulate many aspects of cell growth, survival and
differentiation. The transcription factors of this family are
activated by the Janus Kinase JAK and dysregulation of this
pathway is frequently observed in primary tumors and leads to
increased angiogenesis, enhanced survival of tumors and
immunosuppression. Knockout studies have provided
evidence that STAT proteins are involved in the development
and function of the immune system and play a role in
maintaining immune tolerance and tumor surveillance.

158. Janus kinase
 Janus kinase (JAK, or "Just another kinase") is a family of
intracellular non-receptor tyrosine kinases that transduce
cytokine-mediated signals via the JAK-STAT pathway. They
were initially named "just another kinase" 1 & 2 (since they
were just two of a large number of discoveries in a PCR-based
screen of kinases[1]), but were ultimately published as "Janus
kinase". The name is taken from the two-faced Roman god of
doorways, Janus, because the JAKs possess two near-identical
phosphate-transferring domains. One domain exhibits the
kinase activity while the other negatively regulates the kinase
activity of the first.

159. Tank you

160. Any
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