Age-related changes of vitamin E: α-tocopherol levels in plasma and various tissues of mice and hepatic α-tocopherol transfer protein

Purpose Despite numerous studies on the RRR-and all-rac-alpha-tocopherol isoform of vitamin E (VE) during aging, this relationship has not been examined in specific tissues. Since a-tocopherol is the most abundant of VE's eight isoforms, and VE is an important antioxidant that impacts the aging process, we analyzed alpha-tocopherol levels in plasma and tissues of mice at progressive ages. Moreover, we examined protein and mRNA expression levels of hepatic alpha-tocopherol transfer protein (alpha-TTP), which specifically binds alpha-tocopherol, during aging. Methods The alpha-tocopherol levels in plasma, liver, cerebrum, hippocampus, cerebellum, heart, kidney, epididymal adipose tissue, testis, pancreas, soleus muscle, plantaris muscle, and duodenum from male C57BL/6NCr mice at 3, 6, 12, 18, and 24 months of age were determined by HPLC and fluorescence detection. Also, hepatic alpha-TTP protein and mRNA expression levels were analyzed by Western blot and qPCR, respectively. Results Tissue-specific, age-related changes of a-tocopherol levels normalized by tissue weight were observed in the liver, cerebrum, hippocampus, cerebellum, heart, kidney, and epididymal adipose tissue. Specifically, alpha-tocopherol levels in epididymal adipose tissue increased greatly as mice aged from 6 to 24 months. Although hepatic alpha-TTP protein levels also showed age-related changes, alpha-TTP mRNA expression levels measured after overnight fasting were not altered. Conclusions In this study, we determined that alpha-tocopherol levels and hepatic alpha-TTP protein levels of mice undergo significant tissue-specific, age-related changes. This is the first report to investigate VE in terms of the alpha-tocopherol levels in plasma and various tissues of mice and hepatic alpha-TTP protein levels during aging.