Effects of a High-Fat or High-Sucrose Diet on Ultraviolet B Irradiation-Induced Carcinogenesis and Tumor Growth in Melanin-Possessing Hairless Mice

ABSTRACT

We herein compared the effects of the chronic feeding of high-fat (HF), high-sucrose (HS), and low-fat/low-sucrose (control) diets on carcinogenesis following chronic ultraviolet B (UVB) irradiation in hairless mice. UVB irradiation-induced carcinogenesis was more prominent in HF diet-fed group than in control diet- and HS diet-fed groups. The HS diet group, as well as the HF diet one, showed tumor development and growth, increased skin matrix metalloproteinase (MMP) and blood plasminogen activator inhibitor-1 (PAI-1) levels, and decreased blood leptin and adiponectin levels after long-term UVB irradiation. These changes were smaller in the HS diet group than in the HF diet group. In addition, no difference was noted in the above changes between the control and HS diet groups. The increase induced in adipose tissue weight by the HF diet was markedly reduced by UVB irradiation. This result suggests that the abundant availability of lipids in hypertrophic adipose tissue may be related to tumor incidence and growth through increases in blood PAI-1 and skin MMP-9 expression levels and decreases in blood adiponectin levels by UVB irradiation. In conclusion, HF diet-induced hypertrophic adipose tissue is an important cancer risk factor that promotes UV irradiation-induced carcinogenesis and tumor growth.

Acknowledgments

Animal experiments were performed according to the Ethical Guidelines of the Animal Experimentation, Ehime University and Japanese Pharmacological Society, and Guide for the Care and Use of Laboratory Animals by the National Institutes of Health. Animal experiments were approved by the Ethics Committee on Animal Experimentation, Ehime University (approval number: YA-8-1).

M. Sumiyoshi designed the experiment, performed all experimental analyses, and wrote the manuscript. Y. Kimura designed and conducted all the experimental work, wrote the manuscript, and discussed it with all the authors. All authors read and approved the final manuscript.

This manuscript is dedicated to Dr. M Sumiyoshi, aged 42 years, who passed away on December 11, 2014. I wish to express my posthumous gratitude to Dr. M. Sumiyoshi for her great commitment to carrying out the tests, the discussion of the results, and the writing of the text, and to the overall process of preparing this study.

Conflict of interest

The authors report no conflicts of interest in this work.

Funding

This work was supported by a Grant-in-Aid for Young Scientists (B) (Nos. 22790619; A representative: M. Sumiyoshi) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. There were no sources of funding.