In this research, the participants went out in the sun without sunscreen or protective clothing for half an hour after several months of not being in the sun. They were divided into two groups according to the degree of sun damage. We analyzed the relationship between the subcutaneous fat volume and the degree of sun damage, and the result showed that participant who has more subcutaneous fat volume would be less likely to get a sunburn.
For former studies, they explored the possibility of getting sun damage with race, gender, income, sexual orientation, marital status, general health and family cancer history, and found that those who got more frequent sun damage were likely to be younger, non-hispanic white, not married, in excellent or very good health, annual household income higher than $75,000 and no previous history of cancer[9,10,11]. Some studies found that people with dark skin is less likely to have sun damage[12], because black skin is rich in the corresponding melanin barrier[13,14]. Another study investigated the relationship among the body mass index, the height and the risk of cutaneous melanoma, found no evidence of association between genetically predicted BMI and melanoma, and observed a positive association with genetically-predicted height[15]. The cutaneous melanoma is the product of long-term sunlight stimulation[16,17], but our study researched the results of short-term sunlight exposure. Through controlled trials, another study found that mice on a high-fat diet group were found to show resistance to radiation skin damage. Besides, with mature adipocytes isolated from dermal and subcutaneous adipose tissue were co-cultured with human keratinocytes and cutaneous fibroblasts, Researchers found that Mature fat cells promote their migration and repair.[18] And in our study, we controlled variables like race, gender, age, income, marital state, etc, excluded the factors of using sunscreen or protective clothing, explored the relationship between the subcutaneous fat volume and whether they had a sun damage, and found a negative relationship.
Adipose tissue is a very sophisticated organ regulating both energy storage and metabolic management of our body, as well as the main branches of immune system. The adipose tissue is linked with our brain and regulates other organ systems. Adipose tissue secrets active substance regulates turnover, regeneration homeostasis of epidermis, dermis and cutaneous appendages[19]. Sunburn is an acute inflammatory response[20,21]. Adiponectin belongs to one of the endocrine factors secreted by adipose tissue and is a classic anti-inflammatory factor that reduces the inflammatory response of various cell types by AdipoR1 and R2[22,23]. Mature fat cells promote the migration of cutaneous keratinocytes and fibroblasts, palmitic acid, the most abundant fatty acid, contributes to the migration of skin fibroblasts[18]. Human mesenchymal stem cells have been described for the cure of limited local injuries and seem to improve angiogenesis and the reconstitution of dermal architecture[24,25]. Vascular transports the nutrients required for epidermis, dermal repair (Fig. 3).
Furthermore, fatty acid binding protein 4 can penetrate into skin cells to promote DNA repair of irradiated damaged skin fibroblasts[18]. Sunburn is the reddening of the skin that occurs after having been overexposed to the Sun radiation or other types of ultraviolet light, because melanin is not able to protect the skin when there is a high degree of exposure to the Sun (or a source of ultraviolet light)[26]. And it was searched that different types of skin are differently sensitive to UVR-induced immunosuppression[27], so gene may have an impact on the degree of sun damage. Our data shows that people have less subcutaneous fat are likely to have more serious sunburn. Former studies established a strong correlation between single-nucleotide polymorphisms of the FTO gene and human obesity[28–31]. Methylation at the 6 position of adenosine (m6 A) in RNA is rapidly and transiently induced at DNA damage sites in response to ultraviolet irradiation, which occurs on numerous poly(A) + transcripts and is regulated by the methyltransferase METTL3 (methyltransferase-like 3) and the demethylase FTO (fat mass and obesity-associated protein)[32]. Therefore, FTO may relate to skin reaction to sun exposure.
Some studies have demonstrated that subcutaneous adipose tissue is very sensitive to irradiation and ultraviolet light in daylight can have an effect on subcutaneous adipose tissue, causing subcutaneous fat to decrease[33,34]. Subcutaneous adipose tissue may transfer to some extent the thermal and radiation effects of sunlight on the epidermis and dermis layers.
This article will make people more vigilant about surgical behaviors such as liposuction and have a deeper understanding of the importance of subcutaneous fat. In future studies, the role of subcutaneous adipose tissue in the protection of the dermis, epidermal layer and in sun protection can be explored in depth.