Vitamin D Deficiency Linked to Impaired Mitochondrial Function in Skeletal Muscle

Vitamin D deficiency may impair muscle function through a reduction in energy production in the muscles, according to a new study published in the Journal of Endocrinology. Impaired muscular mitochondrial function was found in vitamin D deficient mice, which could suggest preventing vitamin D deficiency in older adults could help maintain better muscle strength and function, according to the study authors; however, further research is required to confirm this effect in humans.

Multiple studies have linked low vitamin D levels to poor muscle strength, particularly in the elderly, according to the researchers. Mitochondria, specialized cell organelles, convert nutrients into energy to meet the demands of the body, including skeletal muscle.

Previous studies have indicated impaired muscle strength in people with vitamin D deficiency may be linked to impaired muscle mitochondrial function. However, determining the role of vitamin D in muscle performance of older people is difficult because they may suffer from a number of pre-existing health conditions that can also affect their vitamin D status.

The researchers in this study used a mouse model to determine the effects of diet-induced vitamin D deficiency on skeletal muscle mitochondrial function. Mice were either fed a diet with normal quantities of vitamin D, or with no vitamin D to induce deficiency, for a period of 3 months. Typical vitamin D levels in humans range between 40 and 50 nmol.L-1, and a diagnosis of acute vitamin D deficiency is given when levels drop below 12 nmol.L-1.

On average, the mice in this study had vitamin D levels of 30 nmol.L1, with diet-induced vitamin D deficiency leading to levels of 3 nmol.L-1, which, while more extreme than typically observed in humans, is still within the clinically-recognized range. Tissue and blood samples were collected monthly to quantify vitamin D and calcium concentrations and to assess markers of muscle mitochondrial function and number.

After 3 months of diet-induced vitamin D deficiency, skeletal muscle mitochondrial function was found to be impaired by up to 37%, which was not due to a reduced number of mitochondria or a reduction in muscle mass, according to the researchers. The findings suggest vitamin D deficiency could impair mitochondrial function and reduce the amount of energy produced in the muscles, leading to poor muscle function, according to the study authors. Further research investigating the direct effect of vitamin D deficiency on muscle function and strength will be required to confirm this finding, they added.

“Our results show there is a clear link between vitamin D deficiency and oxidative capacity in skeletal muscle,” said Andrew Philp, PhD, BSc, in a press release. “They suggest that vitamin D deficiency decreases mitochondrial function, as opposed to reducing the number of mitochondria in skeletal muscle. We are particularly interested to examine whether this reduction in mitochondrial function may be a cause of age-related loss in skeletal muscle mass and function.”

Although the study indicates vitamin D deficiency has influence over mitochondrial function in skeletal muscle, the research team was unable to determine precisely how this process occurred. Philp and his team plan to conduct future research aiming to establish how vitamin D deficiency alters mitochondrial control and function in skeletal muscle.

REFERENCE

Vitamin D deficiency may impair muscle function [news release]. EurekAlert; April 16, 2021. Accessed April 16, 2021. https://www.eurekalert.org/pub_releases/2021-04/sfe-vdd041221.php