In situ hybridization of a human TYR RNA probe on sections of visceral adipose tissues from morbidly obese and non-obese subjects demonstrated cytoplasmic and membrane-associated

staining pattern (20x magnification).

A and B. T7 (cTYR) probe, morbidly obese subject. C. T7 (cTYR) probe, lean subject.

D. SP6 (control) probe, visceral adipose tissue from a morbidly obese subject.

A. B.

D.C.

E. F.

H.G.

Figure 6. Immunohistochemical staining

of visceral adipose tissue with

TYR, TYRP1 and TYRP2 Ab

A, C, E, G: morbidly obese subject.

B, D, F, H: non-obese subject.

A and B: Tyrosinase;

C and D: Tyrosinase-related protein Tyrp2 (dopachrome tautomerase);

E and F: Tyrosinase-related

protein Tyrp1;

G and H: Negative control (secondary antibodies) and

DAPI.

Relative abundance of MC1R, TYR, TYRP1 and TYRP2 transcripts in adipose samples from obese and lean subjects

Results of the L-[U-14C] tyrosine assay that measures the total outputs of melanogenic pathway

in tissue extracts.

Most important questions:

A.

Whymelanin is present in adipose?

What regulates its biosynthesis?

Melanocyte-stimulating hormone (α-MSH)

• Stimulates the production and release of melanin by melanocytes in skin and hair.

• Anorexigenic peptide (suppresses appetitis, decrease body weight and food intake)

• α-MSH signaling interplays with sensitivity to insulin

DIFFERENTIATING ADIPOCYTES ARE RESPONSIVE to α-MSH

2 hours 6 hours

24 hours0 hours 2 hours 6 hours 24 hours0 hours

α-MSH in human subjects:

α-MSH correlates closely with fat mass (P < 0.001), percentage body fat (P < 0.001) and leptin (P < 0.05).

Hoggard N. et al., Clin Endocrinol (Oxf). 2004 Jul;61(1):31-9.

Plasma α-MSH, pmol/l

Plasma AGRP, pg/ml

Lean Humans (N=11)

15.8 +/- 1.2 5.8 +/- 1.0

Obese humans (N=18)

49.4 +/- 2.4 10.1 +/- 0.9

Significant? P < 0.001 P < 0.001

This is an indication of central α-MSH resistance in human

obesity

So,

obese adipocytes are exposed to

increased amount of

α-MSH

α-MSH α-MSH α-MSHα-MSH

α-MSH

α-MSHα-MSH

α-MSHα-MSH

α-MSHα-MSH

TYR, DCT, TYRP1

Is it good for adipocyte to produce melanin?

1) Melanin is a strong anti-inflammatory agent (when injected in mice) – suppesses ILs and TNF-α production

2) Melanin prevents oxidative damage inside the cells, serving as the molecular dump for free radicals

3) Obese adipocytes are under heavy oxidative stress (beta-oxidation produces tons of radicals)

Hypothesis: • It is beneficial for obese adipocytes

to produce melanin, as it prevents cell death under oxidative duress.

• Side effects:

- Suppression of the production of inflammatory substances by adipose

- Suppression of systemic inflammation of obesity- Suppression of IR- Supression of secondary complications of

obesity (metabolic syndrome, NAFLD, CVD)

Collateral hypothesis:

Melanin biosynthesis system is extremely polymorphic in humans;

Variation in melanogenesis in adipose may reflect

variation of predisposition

to the development of secondary disorders

in obese persons.

Therapeutic idea• Let’s stimulate melanogenesis in adipose

to prevent NAFLD and CVD in obesity and

metabolic syndrome;

Two synthetic analogs of α-MSH, based upon a cyclical peptide called Melanotan II are being developed for human use,

one by an Australian company, the other by Palatin Thechnologies (NJ)

Bremelanotide (formerly PT-141); is tested for therapeutic tanning and sexual dysfunction

May be the war against obesity is futile. It goes for so long already, without much success.

Stimulation of melanin biosynthesis in obese individuals may turn off proinflammatory function of adipose, Decrease morbidity in obese individuals,Cut economic losses in society Remove some stigma from obesity

Acknowledgement:

METABOLIC SYNDROME RELATED STUDIES:

GMU Team:Mohammed Jarrar (PhD Student) – now PhD

Manpreet Randhawa (PhD Student) – now PhD

Tom Huff (melanin specs)

Dr. Vikas Chandhoke

(who initiated GMU-INOVA collaboration)

METABOLIC SYNDROME RELATED STUDIES:

INOVA Team:Dr. Zobair Younossi (Clinical Team leader)

Maria Stepanova - statistician

A Team of Surgeons and Hepatologists who provided

well characterized samples for the study

Immunostainings of the adipose tissue for melanin studies were performed in the lab of

Prof. Vincent Hearing (NIH, NCI)Study of the melanin in the adipose was supported by Jeffress Foundation