Högskolan i Skövde

Exercise is known to affect body composition and overall health. However, the effects of physical activity on vitamin D mobilization and molecular mechanisms, such as receptor-level expression changes, remain unclear in healthy individuals. Vitamin D plays a crucial role in maintaining skeletal integrity, supporting immune function and contributing to muscle performance. Therefore, understanding how exercise affects vitamin D mobilization may have important health implications. Additionally, the short-term impact of exercise on liver and kidney function has not yet been fully explored. This study aimed to investigate the effects of a four-week high-intensity exercise intervention on four healthy individuals. Measurements pre- and post-intervention included body composition, circulating vitamin D levels, liver enzymes, kidney markers, and gene expression analysis of VDR and PDIA3 using SYBR green qPCR. Although no statistically significant changes were observed, trends showed a slight increase in vitamin D levels, a minor decrease in fat percentage, and a slight increase in muscle mass. Liver enzymes increased slightly except for gamma GT, which decreased, suggesting minor improvements in liver function. Few changes were found in potassium and eGFR (Cystatin), which suggested improved kidney function. VDR and PDIA3 showed a trend towards downregulation. In conclusion, a four-week exercise intervention may not be sufficient for eliciting major physiological or molecular responses in vitamin D metabolism. Future studies involving longer exercise interventions are essential to further evaluate the role of exercise in regulating the examined physiological markers and gene expression patterns.

Popular scientific summary

Regular exercise is known to have many positive effects on the body, such as better muscle strength, heart health and helping with weight management. It may also help release vitamin D stored in body fat, which can potentially increase its circulating levels in the blood. Vitamin D is important for bone health, immune function and muscle performance. So, understanding how exercise affects its levels could have important health benefits. However, it is still unclear how short-term exercise affects blood markers such as vitamin D levels and liver and kidney function, especially in healthy individuals. The aim of this research was to study the effects that a four-week high-intensity exercise intervention would have on vitamin D levels in the bloodstream and body composition, including fat percentage and muscle mass, and liver, and kidney biomarkers. As the vitamin D receptor (VDR) and protein disulfide isomerase A3 (PDIA3) are genes related to vitamin D, they were also studied.

Four healthy females participated in this study, completing a structured exercise program where they reached their maximum heart rate at least once during each exercise session. To investigate the changes that would potentially occur, measurements were taken before and after the intervention, including blood samples, body composition assessments and gene expression analysis.

After four-weeks, a slight increase in vitamin D was observed, although not enough to be considered statistically significant. Participants also showed a small reduction in body fat and a minor increase in muscle mass, which are early indications of improved body composition. Blood biomarkers suggested normal physiological responses to exercise: a slight increase in potassium levels (likely due to increased muscle activity), a slight reduction in kidney filtration rate (which may reflect improved kidney function) and changes in liver enzymes consistent with recent physical activity. One of the enzymes (gamma GT) decreased after the intervention which can mean a possible improvement in liver function. The gene expression results for VDR and PDIA3 were shown to be decreased.

Overall, this study shows that even a relatively short period of exercise can start to produce effects on the body in the form of e.g., reduced fat percentage and increased vitamin D levels in the blood. However, studies with more participants and longer exercise durations are needed to further investigate whether these changes are reliable. These findings are relevant to society since they can introduce exercise as a non-pharmacological way to improve vitamin D levels, organ health and promote a healthy lifestyle.