::  A N C H A   L A B  ::

Human adipocytes are capable of melanin biosynthesis, which is elevated in obesity

Manpreet Randhawa, Tom Huff, Julio Valencia, Zobair Younossi, Vikas Chandhoke, Vincent J. Hearing, Ancha Baranova

This is a collaborative project between:

Molecular and Microbiology Department, College of Science,George Mason University, Fairfax, VA

Translational Reseach Institute, Inova Hospital, VA

Pigment Cell Division, NCI, NIH

This study was published in: FASEB J. 2009 Mar;23(3):835-43.

Melanin is a common pigment in animals. In humans, melanin is produced in melanocytes, in retinal pigment epithelium (RPE) cells, in the inner ear, and in the central nervous system. Previously, we noted that human adipose tissue expresses several melanogenesis-related genes. In the current study, we confirmed the expression of melanogenesis-related mRNAs and proteins in human adipose tissue using real-time polymerase chain reaction and immunohistochemical staining. TYR mRNA signals were also detected by in situ hybridization in visceral adipocytes. The presence of melanin in human adipose tissue was revealed both by Fontana-Masson staining and by permanganate degradation of melanin coupled with liquid chromatography/ultraviolet/mass spectrometry determination of the pyrrole-2,3,5-tricarboxylic acid (PTCA) derivative of melanin. We also compared melanogenic activities in adipose tissues and in other human tissues using the L-[U-(14)C] tyrosine assay. A marked heterogeneity in the melanogenic activities of individual adipose tissue extracts was noted. We hypothesize that the ectopic synthesis of melanin in obese adipose may serve as a compensatory mechanism that uses its anti-inflammatory and its oxidative damage-absorbing properties. In conclusion, our study demonstrates for the first time that the melanin biosynthesis pathway is functional in adipose tissue.


This research has been supported by a grant from the Thomas F. Jeffress and Kate Miller Jeffress Memorial Trust and by the Intramural Research Program of the National Cancer Institute at NIH . A.B. and M.R. are grateful to Shobha M. Gowder for initial technical assistance with the project and F. Otaizo for the help with the first round of RT-PCR experiments.

The study is currently being extended in order to check whether induction of the melanigenesis in the adipose could be used as therapeutical intervention in obese and overweight individulas aimed at the prevention of co-morbidities.

Press-releases associated with this publication can be downloaded from here:

FASEB Journal press release:

GMU press-release:

This paper has been also reviewed by Prof. Shosuke Ito in the Commentary: Melanin seem to be everywhere in the body, but for what? published in Pigment Cell Melanoma Res. 2009 Feb;22(1):12-3.

Some figures:

Figure 1 and Figure 2.

Figure 3.

Figure 1. Fontana-Masson stain of human adipose tissue demonstrates melanin pigment (black staining) mainly in the periphery of the adipocytes.
A and B. Multiple conglomerates of melanin granules are present at the periphery of the adipocytes in adipose tissue from morbidly obese subjects (20x magnification).
C and D. Melanin granules are scarce in the adipocytes of adipose tissue from non-obese subjects (20x magnification).
E. No melanin granules were observed in the microvessels located in the adipose tissue (20x magnification).
D. Melanin staining in skin tissue used as a positive control (10x magnification).

Figure 2. Immunohistochemical staining of visceral adipose tissue sections from morbidly obese and from non-obese subjects for human TYR, TYRP1 and TYRP2 proteins (20x magnification). Red: TYR, TYRP1 or TYRP2 staining. Blue: DAPI (nuclei).
A, C, E, G: Visceral adipose tissue from a morbidly obese subject.
B, D, F, H: Visceral adipose tissue from a 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.

Figure 3. The presence of melanin in extracts of adipose tissue as revealed by LC-UV-MS.
A. Homogenized samples of adipose tissue separated into three phases: supernatant (fat), aqueous and sediment. Cell debris sediments from adipose tissue samples from morbidly obese subjects contain visible amounts of black pigment. a and b: adipose sediments of non-obese subjects; c and d: adipose sediments from obese subjects.
B: The CAD of the PTCA precursor ion at mass-to-charge ratio (m/z) 198 produces abundant product ions at m/z 154 and 110 peaks.
C. LC-MS Multi-ion SIM chromatogram of PTCA peak at a retention time of 6 min.
D. Negative ESI mass spectra of PTCA peak at 6 min. E. HPLC – UV/VIS Chromatograms at 270 nm.