A Novel LC-MS/MS Analysis of Vitamin D Metabolites in Mice Serum and Hair: Impact of Diet and Light Exposure

Muhammad K Hakeem Asma Al-Menhali Sampath K Elangovan ILTAF SHAH ^*

• United Arab Emirates University, Al-Ain, United Arab Emirates

Numerous physiological systems, such as the functioning of the immune system, bone health, and the regulation of expression of genes, depend critically on vitamin D. The objective of this study was to develop and validate an LC-MS/MS method to examine the effects of light exposure and dietary vitamin D consumption on the levels of vitamin D and its metabolites in a mouse model when they are exposed to same growth conditions throughout the year. Considering the significance of vitamin D for health, it is critical to understand how it is metabolized and the factors that affect its levels. We examined serum and hair samples from mice under various experimental conditions for vitamin D and its metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A vitamin D-deficient diet, a vitamin D-standard diet, and changes in ambient light exposure from complete darkness to a regular cycle of light and dark were among these conditions. Mice fed a standard vitamin D diet and exposed to a regular light-dark cycle exhibited significantly higher levels of 25OHD3 in both serum and hair, indicating the synergistic effect of dietary vitamin D intake and light exposure. Mice fed a standard vitamin D diet but kept in continuous darkness showed moderately elevated 25OHD3 levels, demonstrating the efficacy of dietary vitamin D in maintaining adequate levels despite the absence of light. Conversely, mice fed a vitamin D-deficient diet and housed in darkness displayed 25OHD3 levels below the limit of quantification, highlighting the combined detrimental effects of dietary deficiency and lack of light exposure. This study provides valuable insights into the complex interplay between dietary vitamin D intake, light exposure, and the regulation of vitamin D metabolism in mice. Moreover, our results underscore the potential implications for human health, suggesting the importance of adequate vitamin D intake and sunlight exposure in maintaining optimal vitamin D levels. Further research in this area has the potential to unveil additional factors influencing vitamin D metabolism, offering valuable insights into strategies for optimizing vitamin D levels in both animal models and human subjects.