Gamma-tocotrienol is required for normal vitamin D metabolism in female rats

Objective: To study the effects of vitamin E deficiency and supplementation of vitamin D and bone metabolism in female Sprague-Dawley rats.
Materials and Methods: Rats weighing between 200 and 250 g were divided into six groups, that is, rats fed on (a) normal rat chow diet (RC), (b) vitamin E-deficient diet (VED) (c) VED diet supplemented with 60 mg/kg α-tocopherol acetate (ATF), (d) VED diet supplemented with 60 mg/kg γ-tocotrienol (GTT), (e) VED diet supplemented with 60 mg/kg Tocomin ® (TOC) and (f) baseline control group which was killed without treatment (BC). Treatment was given for 2 months. Serum 1,25-dihydroxyvitamin D₃, serum total calcium, urine calcium, left femur, and fourth lumbar vertebra calcium content and left femur length were measured.
Results: In the VED and ATF groups, activation of vitamin D to 1,25-dihydroxyvitamin D3 was inhibited and calcium reabsorption in the kidneys were increased. Both the effects seen in ATF and GTT groups were observed in the TOC group. The GTT group was protected from the effects of the vitamin E-deficient diet. Calcium content of the fourth lumbar vertebra was also decreased by vitamin E- deficiency, which was not reversed by vitamin E supplementation.
Conclusion: γ-tocotrienol and not α-tocopherol protects vitamin D metabolism and calcium homeostasis from the effects of vitamin E-deficiency.