This document discusses adipokines, hormones secreted by adipose tissue. It focuses on leptin, adiponectin, resistin, and other adipokines. Leptin regulates appetite and metabolism. Its levels correlate with fat mass. Adiponectin reduces inflammation and insulin resistance. Resistin causes insulin resistance. The document examines the functions of these adipokines in processes like fertility, pregnancy, puberty, angiogenesis, and atherosclerosis. It provides details on receptors, mechanisms of action, and the roles of adipokines in conditions such as obesity and insulin resistance.

1. PRESENTOR : Dr. KAPIL
MODERATOR: Dr. BD BANERJEE

2. DEFINITION
 Adipose tissue is now recognized as an endocrine
organ capable of secreting a variety of biologically
active components which are called adipokines.
 Adipokines affect appetite and satiety, glucose and
lipid metabolism, blood pressure regulation,
inflammation and immune functions.

3. ADIPOKINES
 Leptin
 Adiponectin
 Resistin
 Adipsin
 Apelin
 Visfatin
 Vaspin
 Omentin
 Lipocalin-2

4. LEPTIN
 Leptin is a 16 kDa non glycosylated peptide
hormone encoded by the gene obese(ob)
 Circulating leptin levels are directly correlated
with adipose tissue mass
 Leptin is secreted in a pulsatile fashion and
has significant diurnal variation with higher
levels in the evening and early morning hours.

5. FUNCTIONS
 The primary actions originally described for leptin are
mediated via binding to Ob-R in the brain, resulting in
suppression of appeite and increased energy
expenditure.
 Appetite suppression is mediated via binding of leptin
to its full length receptor (Ob-Rb)in the hypothalamic
satiety centres, with stumulation of
anorexigenic/catabolic neurons and suppression of
orexigenic/anabolic neurons

6. LEPTIN RECEPTOR

7. LEPTIN-MECHANISM OF ACTION

8. OTHER PERIPHERAL FUNCTIONS:
 LEPTIN AND HAEMATOPIESIS
 Ob-R is expressed in haemopoietic cells and leptin is
linked to proliferation and differentiation of
haemopoietic precursors.
 High concentration of human leptin promote platelet
aggregation

9. LEPTIN-ANGIOGENESIS
 Leptin receptors are expressed in human vasculature
 Stimulates endothelial cell growth and angiogenesis
 So topical application of leptin also induces dose
dependent acceleration in wound repair

10. LEPTIN AND REPRODUCTION:
 Expression of Ob-R has also been demonstrated in
human granulosa cells
 Significant increase in circulating leptin levels cause
ovarian hyper stimulation suggesting that leptin plays
a role in follicular growth and maturation

11. PLACENTAL LEPTIN
 Placental leptin is likely to affect maternal, placental
and fetal function through both autocrine and
paracrine mechanisms.
 Placental leptin has physiological affects on the
placenta including angiogenesis, growth and
immunomodulation

12. LEPTIN IN FERTILITY
 Studies have shown that leptin treated females had
significantly elevated serum levels of LH, increased
ovarian and uterian weight
 And leptin treated males had significantly elevated
serum levels of FSH, increased testicular and seminal
vesicle weights, greater seminal vesicle epithelial width
and elevated sperm counts.

13. LEPTIN IN PREGNANCY
 Serum leptin is particularly elevated during second
and third trimesters.
 Uterine contractions are inhibited by leptin
 Leptin plays a role in hyperemesis gravidarum

14. LEPTIN IN PUBERTY
 Leptin may act on hypothalamic cells to stimulate
release of LHRH, thereby triggering gonadotropin
release.
 The subsequent release of follicle stimulating
hormone and LH stimulates gonadal steroid secretion,
leading to development of the reproductive tract and
induction of puberty.

15. LEPTIN AND INSULIN
 Hyperinsulinemia is associated with increased plasma
leptin concentration.
 Insulin appears to act directly at the level of adipocyte
by increasing leptin secretion and gene expression

16. ROLE OF LEPTIN IN OSTEOARTHRITIS

17. ADIPONECTIN
 Adiponectin appears to be a second well known
adipocytokine released by fat cells.
 Adiponectin (also known as 30-kDa adipocyte
complement-related protein; Acrp30) is a 247 amino-
acid protein monomer which forms trimers which
further polymerize into larger polymeric complexes
varying in size between 180kDa (hexameres; LMW) or
400-600kDa (16-meres; HMW) .

19. DIFFERENT MOLECULAR FORMS

20. ADIPONECTIN RECEPTORS

21. FUNCTIONS:
 Enhancement of insulin sensitivity
 Anti-inflammatory properties
 Inhibition of the development of atherosclerosis

22. MOLECULAR MECHANISM

23. INSULIN SENSITIZING ACTION

25. ADIPONECTIN IN ATHEROSLEROSIS

26. RESISTIN:
• Resistin is a dimeric protein containing 108 amino acids
that received its name from its apparent induction of
insulin resistance in mice.
• It belongs to the found in inflammatory zones
(FIZZ) family (also known as RELMs, resistin-like
molecules).
Resistin (FIZZ3) has been found in
adipocytes, macrophages, and other cell types.

27. FUNCTIONS:
 Induces severe hepatic insulin resistance
 Resistin has been reported to inhibit dopamine and
nor adrenaline release in the hypothalamus

28. ADEPSIN:
 Also called human complement factor D
(enzyme in the alternative pathway of complement
activation)
 Functions:
 Stimulates triglyceride storage,
 enhances fatty acid reesterification and inhibits
lipolysis

29. APELIN
 A bioactive peptide, secreted mainly from adipocytes
and stromal vascular cells
 Functions:
 Inhibits glucose induced insulin secretion;
 inducing NO production and inhibiting angiotensin II
cellular signaling.

30. VISFATIN
 An insulin mimetic adipokine recently discovered and
released prevalently by visceral WAT
 Visfatin is also identical to pre-B-cell colony
enhancing factor
 Under endotoxin stimulation it is also produced by
neutrophils
 FUNCTIONS: Hypoglycemic effect by stimulating
glucose uptake, promotes insulin sensitivity;also
induces chemotaxis.

31. VASPIN
 visceral adipose tissue-derived serine protease
inhibitor
 Serine protease inhibitor
FUNCTIONS:
 Improves insulin sensitivity.
 suppresses the production of resistin, leptin and TNF-
α

32. OMENTIN
 A secretory protein ,recently identified a new
adipokine.
FUNCTIONS:
 Enhances insulin stimulated glucose transport in
subcutaneous as well as omental adipocytes.

33. LIPOCALIN-2
 It is also known as neutrophil gelatinase associated
lipocalin
 It is a 25kDa secretory glycoprotein, originally identified
in mouse kidney cells and human neutrophil granules.
FUNCTIONS:
 seems to have dual effects on inflammation, pro & anti-
inflammatory effects.
 So increased levels of LCN2 in obesity and IR may
constitute a protective mechanism against inflammation.

34. Thank you