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Updated: Jun 28, 2026
Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Published on: September 7, 2013
Evidence for the ectopic synthesis of melanin in human adipose tissue
Manpreet Randhawa1, Tom Huff, Julio C Valencia
1Molecular Biology and Microbiology Department and Center for the Study of Genomics in Liver Diseases, College of Science, George Mason University, Manassas, VA, USA.
Abstract:
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.
Insights
Human adipose tissue can produce melanin, a pigment typically found elsewhere. This study confirms functional melanin production in fat tissue, suggesting potential roles in inflammation and oxidative stress management.
Area of Science:
- Biochemistry
- Cell Biology
- Human Physiology
Background:
- Melanin is a pigment synthesized in specialized cells like melanocytes.
- Previous research indicated melanogenesis-related gene expression in human adipose tissue.
- The presence and function of melanin in adipose tissue remained largely uninvestigated.
Purpose of the Study:
- To confirm the expression of melanogenesis-related genes and proteins in human adipose tissue.
- To detect the presence of melanin within human adipose tissue.
- To investigate the functional activity of melanogenesis in adipose tissue and compare it with other tissues.
Main Methods:
- Real-time polymerase chain reaction (PCR) and immunohistochemical staining to detect mRNA and proteins.
- In situ hybridization to localize TYR mRNA in visceral adipocytes.
- Fontana-Masson staining and chemical analysis (melanin degradation, LC/UV/MS) to confirm melanin presence.
- L-[U-(14)C] tyrosine assay to measure melanogenic activity.
Main Results:
- Melanogenesis-related mRNAs and proteins were confirmed in human adipose tissue.
- Melanin was detected in human adipose tissue using multiple staining and chemical methods.
- Functional melanogenic activity was observed in adipose tissue extracts, with significant variability among individuals.
- TYR mRNA was localized within visceral adipocytes.
Conclusions:
- The melanin biosynthesis pathway is demonstrably functional in human adipose tissue.
- Ectopic melanin synthesis in adipose tissue, particularly in obesity, may have protective roles.
- Potential functions include anti-inflammatory effects and absorption of oxidative damage.
