Effect of Vitamin E Isoforms on Bone Metabolism in C57BL/6 J Mice Fed a High Fat Diet

Abstract

Abstract Objectives The purpose of this study was to compare the effects of alpha tocopherol, gamma tocopherol, and the combination of alpha and gamma tocopherols on bone mineral density (BMD), bone mineral content (BMC), and bone metabolism in C57BL/6 J mice fed a high-fat diet. Methods A total of 75 male C57BL/6 mice were randomized to either a low fat diet (LFD) with 6% fat, a high fat diet (HFD) with 20% fat, HFD supplemented with alpha tocopherol (AT), gamma tocopherol (GT), or the combination of AT and GT. LFD and HFD were provided to corresponding groups of mice without vitamin E isoform supplements for 15 weeks to induce bone loss. At the end of the 15 weeks, AT, GT, and a combination of AT and GT were added to 3 of the HFD groups and fed for 10 weeks. LFD group and one of the HFD groups were continued on the same diet for another 10 weeks without additional supplements. All mice were euthanized at the end of the 25 weeks period. Left and right fibula bones were excised, cleaned, and scanned using the Lunar PIXImus dual-energy x-ray absorptiometry (DEXA) densitometer to assess BMD, BMC, lean tissue, and fat tissue content. Serum biomarkers of bone metabolism were evaluated post euthanization. Results HFD resulted in significantly lower fibular BMD and higher tibial bone fat content in comparison to LFD. Animals in the HFD supplemented with GT, but not AT, showed significantly reduced effect of HFD in lowering BMD. Additionally, in the group fed HFD supplemented with GT, a significantly higher concentration of alkaline phosphatase (ALP) and N-terminal propeptide of type I procollagen (PINP) were noted, compared to LFD. This may be indicative of increased bone formation resulting from GT incorporated into the HFD diet. Conclusions The findings of the study suggest that different isoforms of vitamin E affect bone density and bone metabolism differently. Within the different isoforms of vitamin E, gamma tocopherol may have protective effects in bone, especially in the situation of high fat diet induced bone loss. Further examination of the mechanistic action of vitamin E isoforms on skeletal health is warranted. Funding Sources Texas Woman's University.