Research shows vitamin D signaling is needed for normal muscle size and strength

Professor Jenny Gunton from the Westmead Institute for Medical Research. The Westmead Institute for Medical Research.

A recent study conducted at The Westmead Institute for Medical Research has shed light on the role of vitamin D in muscle cells. The study looked at the role of vitamin D in muscles in mice, and showed that vitamin D signaling (how cells communicate with one another) is needed for normal muscle size and strength.

Researchers found that mice missing the vitamin D receptor only in myocytes (muscle cells) had smaller muscles, and they were less strong. They also had significantly decreased running speed and didn’t run as far as mice with normal vitamin D action.

Lead researcher, Professor Jenny Gunton says, “For a long time, we have known that vitamin D deficiency is associated with muscle weakness and greater risk of falls and fractures. However, whether vitamin D played a direct role in muscle wasn’t known.

“We show that vitamin D receptor is present in low levels in normal muscle, and our study found that deleting muscle cell vitamin D receptors had important effects on muscle function.”

Professor Gunton says that, compared to a previous study she conducted that looked at mice missing vitamin D receptors across their whole body, this new study has highlighted some important differences.

“We found that mice missing muscle cell vitamin D receptors had normal body size but less muscle mass and more fat mass.

“In terms of choosing to run on a wheel in their cage, the mice had shorter running distance and slower speed. These might contribute to the lower muscle mass and increase in fat.

In terms of muscle strength, these mice also had a significantly decreased grip strength from a very early age.”

While more research is needed, Professor Gunton says that these results suggest that maintaining normal vitamin D signaling in muscle is important for preserving muscle bulk and function.

“These findings also have the potential to open up avenues to pursue new therapies that target muscle cell vitamin D receptors. These therapies could help to address or prevent age-related sarcopenia (degenerative loss of skeletal muscle mass) and other disorders related to muscle function.”

The research paper was published in the Journal of Cachexia, Sarcopenia and Muscle.

A case study in CMAJ highlights the dangers of taking too much vitamin D.

A 54-year-old man, after returning from a trip to Southeast Asia where he spent much of his holiday sunbathing, showed increased levels of creatinine, suggesting kidney damage or malfunction. After referral to a kidney specialist and further testing, it was discovered that he had been prescribed high doses of vitamin D by a naturopath, who recommended a dose of 8 drops every day. Over 2 ½ years, the patient, who did not have a history of bone loss or vitamin D deficiency, took 8-12 drops of vitamin D daily, totalling 8000-12 000 IU. As a result, he had very high levels of calcium in the blood, which left him with significant kidney damage.

“Although vitamin D toxicity is rare owing to a large therapeutic range, its widespread availability in various over-the-counter formulations may pose a substantial risk to uninformed patients,” writes Dr. Bourne Auguste, a Clinical Fellow in Home Dialysis at Toronto General Hospital and the University of Toronto.

The recommended daily allowance is 400-1000 IU, with 800-2000 IU recommended for adults at high-risk of osteoporosis and for older adults.

“Our experience informs us that patients and clinicians should be better informed about the risks regarding the unfettered use of vitamin D. Given new findings from the US Preventive Services Task Force, current Canadian guidelines regarding its use in low-risk individuals should be revisited,” the authors suggest.

“Use of vitamin D drops leading to kidney failure in a 54-year-old man” is published April 8, 2019.

 

 

Original here

“Vitamin D may help prevent rheumatoid arthritis, suggests study,” is the headline in The Guardian. This is in reference to a UK-based laboratory study looking into whether vitamin D could be used to suppress inflammation in individuals with rheumatoid arthritis.

Rheumatoid arthritis is an autoimmune disease, which means the immune system mistakenly attacks the body’s own cells. In rheumatoid arthritis, the immune system targets the cells that line the joints, causing them to become swollen (inflamed), stiff and painful.

Previous laboratory research has suggested that vitamin D has anti-inflammatory effects, so the current researchers wanted to see if it could help inflammatory conditions such as rheumatoid arthritis.

They analysed samples of joint fluid from people with rheumatoid arthritis and found that vitamin D did not have the expected anti-inflammatory effect that it usually does in healthy joint fluid. This was because it had a limited impact on the immune system cells, so making these immune system cells responsive to vitamin D could offer a new way to prevent flare-ups of the disease.

It could be that regularly taking a vitamin D supplement may prevent rheumatoid arthritis developing in the first place, but this is pure speculation at the moment.

For now, regardless of possible effects on inflammation, it’s recommended that all adults take a daily supplement containing 10mcg of vitamin D during the autumn and winter months. Continuing to take it during the spring and summer may have limited benefits but should be entirely safe.

Where did the story come from?

The study was carried out by a team of researchers from University College London and several institutions in Birmingham. It was funded by the European Union, National Institutes of Health, Arthritis Research UK and the Royal Society Wolfson Research Merit Award.

The study was published in the peer-reviewed Journal of Autoimmunity on an open-access basis, so it can be viewed online for free.

The Guardian’s coverage was generally balanced. However, its headline could be interpreted as referring to a much more advanced stage of research than actually was the case. The study didn’t look at the effects of giving vitamin D supplements to people with rheumatoid arthritis – it only looked at levels of vitamin D and inflammatory cells in samples in a laboratory setting.

What kind of research was this?

This was a laboratory study aiming to investigate whether vitamin D could suppress inflammation in individuals with rheumatoid arthritis and whether this effect, if confirmed, may have potential in the prevention or treatment of inflammatory disorders.

Previous laboratory research has suggested that vitamin D may be able to reduce the immune response when necessary. However, this has only involved tests on blood samples from healthy individuals. The researchers of this study wanted to look at the effects of vitamin D in individuals with inflammatory disease.

Laboratory studies are useful as early-stage research for getting an indication of biological processes and how things may work in the body. However, many more stages would be needed to better understand the role of vitamin D in rheumatoid arthritis before getting to the point of conducting a randomised controlled trial (RCT) to see whether taking vitamin D supplements would actually improve symptoms in individuals with the condition.

What did the research involve?

The researchers took samples of joint synovial fluid from 15 individuals with rheumatoid arthritis aged between 40 and 85. Synovial fluid acts much like biological engine oil by helping to keep the joints lubricated.

They analysed the samples for levels of specific white blood cells (T helper cells) and inflammatory proteins involved in the type of immune response associated with rheumatoid arthritis.

To compare responses with healthy tissue, the researchers also looked at anonymised blood samples from age- and gender-matched donors from the National Blood Service in Birmingham, UK.

The researchers cultured (grew in the lab) specific subtypes of T helper cells – Th1 and Th17 cells – known to have a role in inflammatory conditions such as rheumatoid arthritis. They then looked at the effect of vitamin D on these cells.

What were the basic results?

The researchers found that vitamin D was better able to suppress the production of inflammatory proteins by Th17 cells in the healthy blood samples than it was in the rheumatoid arthritis samples.

Vitamin D had no effect on Th1 immune cells in either of the samples.

Looking for a possible explanation, they found that vitamin D may have a reduced anti-inflammatory effect in people with rheumatoid arthritis because, in general, vitamin D had a limited effect on a type of T helper cell known as memory T cells. People with rheumatoid arthritis are thought to have higher-than-average levels of memory T cells in their synovial fluid.

How did the researchers interpret the results?

The researchers suggested: “Restoration of 1,25(OH)2D3 [the chemical formula for vitamin D] responses in memory T cells may provide a new strategy for treatment of inflammatory diseases such as rheumatoid arthritis.”

However, because vitamin D was found to have a limited effect on the T cells from the site of inflammation, they cautioned: “Vitamin D supplementation is unlikely to be successful as treatment for established active rheumatoid arthritis patients.”

Conclusion

Previous research has suggested that vitamin D has anti-inflammatory effects, so this laboratory study investigated whether vitamin D could be used to suppress inflammation in individuals with rheumatoid arthritis, to prevent flare-ups of symptoms.

However, it found that adding vitamin D to joint fluid samples from people with rheumatoid arthritis had limited success in suppressing the inflammatory response compared with the effect it has on blood from healthy donors. It seems that the memory T cells in the joint fluid samples taken from people with rheumatoid arthritis are not responsive.

If it were possible to make these cells respond to vitamin D, then this could be a new avenue for treatment. But if anything, it seems more likely that vitamin D may have potential as a way to prevent inflammatory conditions like rheumatoid arthritis from developing in the first place.

While this is an interesting possibility, this early-stage study only looked at a very small sample of people. Further laboratory studies would be needed to better understand the role of vitamin D in inflammatory conditions before research could move on to trial vitamin D supplements in the prevention or treatment of these conditions.

For the moment, we know that vitamin D is essential to keep bones, teeth and muscles healthy. It can be created by the body from direct sunlight and can also be found in a few food sources such as:

oily fish

red meat

liver

egg yolks

In the spring and summer months, most people should be able to get all the vitamin D they need from natural sunlight exposure, but taking a daily supplement of 10mcg of vitamin D is recommended during the autumn and winter months. However, there should be no risk to your health if you also choose to take a 10mcg supplement during spring and summer.

It’s advised that breastfed babies up to 1 year old should be given an 8.5 to 10mcg supplement, while children from 1 to 4 years old should be given a 10mcg supplement.