Dietary tocotrienol and UVB-induced skin damage

Abstract

Among vitamin E forms, α-tocopherol appears predominantly in humans and animals, and tocotrienols very slightly. However, tocotrienols have been shown to have higher antioxidant, anticancer, and neuroprotective properties that different from α-tocopherol. We have observed that substantial amounts of tocotrienols are present in the skin of animals fed a diet containing a tocotrienol rich fraction together with α-tocopherol extracted from palm oil (T-mix), and that the addition of sesamin to T-mix produced much higher amounts of tocotrienols in the skin. We investigated whether dietary tocotrienols could protect the skin from damage induced by ultraviolet B (UVB) irradiation in hairless mice fed four diets: vitamin E-free, α-tocopherol alone, T-mix and T-mix with sesamin. We examined the protective effects of tocotrienol on intensity of sunburn in the short term exposure and tumor incidence in long term exposure to UVB. The strongest sunburn was observed in the VE-free group, and the next strongest in the α-tocopherol group. Weak sunburn was observed in the T-mix group and the weakest sunburn in the T-mix with sesamin group. Sesamin enhanced tocotrienol concentrations in the skin and improved the sunburn scores and incidence of tumors. These results suggest that dietary tocotrienols accumulate in the skin and protect the skin more strongly than α-tocopherol against damage induced by UVB. Miyazawa’s research group also evaluated the anti-inflammatory effect of γ-tocotrienol on UVB-induced inflammatory reaction extensively using immortalized human keratinocytes and HR-1 hairless mice. They showed that orally dosed γ-tocotrienol suppressed UVB-induced changes in skin thickness, Cyclooxygenase-2 protein expression, and hyperplas in hairless mice, while α-tocopherol did not. These results suggest oral tocotrienols have potential protective power against UVB-induced skin inflammation.