The Effects of Diet and Ultra Violet B Exposure on Vitamin D Levels and Muscle Performance In Mice (Mus musculus)

• Main Author: Tsao, Natalie
• Other Authors: Syme, Douglas A., Barclay, Robert M. R., Burton, Jodie M.
• Format: Master Thesis
• Language: English
• Published: Science 2019
• Subjects: Mice; Vitamin D; Muscle Performance; Fast-twitch Muscles; Slow-twitch Muscles; Ultraviolet B; Education > Health; Animal Pathology; Food Science and Technology; Animal Physiology; Physiology; Veterinary Science; Zoology; Arctic
• Online Access: http://hdl.handle.net/1880/111017; https://doi.org/10.11575/PRISM/37082

Vitamin D is a steroid that promotes healthy bone structure and muscle function. It is obtained from the diet and synthesized in the skin during UV-B exposure from sunlight. In muscle, it influences calcium transport and promotes growth, with varied responses depending on muscle type. I hypothesized that reduced vitamin D in the diet and removal of UVB light, as occurs during hibernation or the Polar winter, will impact circulating levels of vitamin D to the extent that muscle contractile performance is altered. I also hypothesize that fast-twitch muscles will show greater responses of muscle contractile capabilities to treatments compared to slow-twitch muscles. Mice were used as a model, and fed diets with normal or low vitamin D, and exposed to normal or no UV-B doses for 3 months. Neither fast nor slow muscle types showed significant differences between treatment groups in force, power, force-velocity measures, or rates of fatigue. Serum vitamin D levels, measured at the midpoint and endpoint of the treatment, varied substantially among individuals, but not, on average, among treatment groups, indicating mechanisms of compensatory homeostasis in the face of reduced vitamin D supply. These results suggest that intermittent interruptions in dietary vitamin D or light exposure in mammals, such as those that hibernate or live above the Arctic Circle, do not impair muscle contractile function.