Brandon S Klinedinst1,2, Nathan F Meier3, Brittany Larsen2,4, Yueying Wang5, Shan Yu5, Jonathan P Mochel4, Scott Le1, Tovah Wolf6, Amy Pollpeter7, Colleen Pappas1, Qian Wang1, Karin Allenspach8, Li Wang5, Daniel Russell9, David A Bennett10, Auriel A Willette1,2,7,11. 1. Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa, USA. 2. Neuroscience Program, Iowa State University, Ames, Iowa, USA. 3. Department of Kinesiology, Concordia University, Irvine, California, USA. 4. Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA. 5. Department of Statistics, Iowa State University, Ames, Iowa, USA. 6. Department of Nutrition and Dietetics, Western Carolina University, Cullowhee, North Carolina, USA. 7. Bioinformatics and Computational Biology Program, Iowa State University, Ames, Iowa, USA. 8. Department of Veterinary Clinical Sciences, Iowa State University, Ames, Iowa, USA. 9. Department of Human Development and Family Studies, Iowa State University, Ames, Iowa, USA. 10. Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, Illinois, USA. 11. Department of Neurology, University of Iowa, Iowa City, Iowa, USA.
Abstract
OBJECTIVE: The high prevalence of vitamin D deficiency and obesity drives the need for successful strategies that elevate vitamin D levels, prevent adipogenesis, and stimulate lipolysis. This study provides a theoretical model to evaluate how physical activity (PA) and sunlight exposure influence serum vitamin D levels and regional adiposity. This study hypothesized a posteriori that sunlight is associated with undifferentiated visceral adiposity by increasing the ratio of brown to white adipose tissue. METHODS: Using 10-year longitudinal data, accelerometry, a sun-exposure questionnaire, and regional adiposity quantified by dual-energy x-ray absorptiometry imaging, a structural-equation mediation model of growth curves was constructed with a data-driven methodology. RESULTS: Sunlight and PA conjointly increased serum vitamin D. Changes in vitamin D levels partially mediated how sunlight and PA impacted adiposity in visceral and subcutaneous regions within a subjective PA model. In an objective PA model, vitamin D was a mediator for subcutaneous regions only. Interestingly, sunlight was associated with less adiposity in subcutaneous regions but greater adiposity in visceral regions. CONCLUSIONS: Sunlight and PA may increase vitamin D levels. For the first time, this study characterizes a positive association between sunlight and visceral adiposity. Further investigation and experimentation are necessary to clarify the physiological role of sunlight exposure on adipose tissue.
OBJECTIVE: The high prevalence of vitamin Ddeficiency and obesity drives the need for successful strategies that elevate vitamin D levels, prevent adipogenesis, and stimulate lipolysis. This study provides a theoretical model to evaluate how physical activity (PA) and sunlight exposure influence serum vitamin D levels and regional adiposity. This study hypothesized a posteriori that sunlight is associated with undifferentiated visceral adiposity by increasing the ratio of brown to white adipose tissue. METHODS: Using 10-year longitudinal data, accelerometry, a sun-exposure questionnaire, and regional adiposity quantified by dual-energy x-ray absorptiometry imaging, a structural-equation mediation model of growth curves was constructed with a data-driven methodology. RESULTS: Sunlight and PA conjointly increased serum vitamin D. Changes in vitamin D levels partially mediated how sunlight and PA impacted adiposity in visceral and subcutaneous regions within a subjective PA model. In an objective PA model, vitamin D was a mediator for subcutaneous regions only. Interestingly, sunlight was associated with less adiposity in subcutaneous regions but greater adiposity in visceral regions. CONCLUSIONS: Sunlight and PA may increase vitamin D levels. For the first time, this study characterizes a positive association between sunlight and visceral adiposity. Further investigation and experimentation are necessary to clarify the physiological role of sunlight exposure on adipose tissue.
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