Medical Bulletin 04/December/2023

Here are the top medical news of the day:

Vitamin D supplements do not prevent bone fractures in children

A major clinical trial led by Queen Mary University of London and the Harvard T.H. Chan School of Public Health has found that vitamin D supplements do not increase bone strength or prevent bone fractures in children with vitamin D deficiency. The findings challenge widely held perceptions relating to the effects of vitamin D on bone health.

The potential for vitamin D supplements to improve bone strength has attracted growing interest in recent years, based on vitamin D’s role in promoting bone mineralisation. However, clinical trials designed to test whether vitamin D supplements can prevent bone fractures in children have not previously been conducted.

Working with partners in Mongolia, a setting with a particularly high fracture burden and where vitamin D deficiency is highly prevalent, researchers from Queen Mary and Harvard conducted a clinical trial to determine if vitamin D supplementation would decrease risk of bone fractures or increase bone strength in schoolchildren. The study, published today (1 December) in Lancet Diabetes & Endocrinology, is the largest randomised controlled trial of vitamin D supplementation ever conducted in children.

The trial findings are likely to prompt scientists, doctors and public health specialists to re-consider the effects of vitamin D supplements on bone health.

Dr Ganmaa Davaasambuu, said “The absence of any effect of sustained, generous vitamin D supplementation on fracture risk or bone strength in vitamin D deficient children is striking. In adults, vitamin D supplementation works best for fracture prevention when calcium is given at the same time – so the fact that we did not offer calcium alongside vitamin D to trial participants may explain the null findings from this study.”

Reference: Vitamin D supplements do not prevent bone fractures in children; The Lancet Diabetes & Endocrinology; DOI:10.1016/S2213-8587(23)00317-0

Research shows human behavior guided by fast changes in dopamine levels

What happens in the human brain when we learn from positive and negative experiences? To help answer that question and better understand decision-making and human behavior, scientists are studying dopamine.

Dopamine is a neurotransmitter produced in the brain that serves as a chemical messenger, facilitating communication between nerve cells in the brain and the body. It is involved in functions such as movement, cognition and learning. While dopamine is most known for its association with positive emotions, scientists are also exploring its role in negative experiences.

Now, a new study from researchers at Wake Forest University School of Medicine shows that dopamine release in the human brain plays a crucial role in encoding both reward and punishment prediction errors. This means that dopamine is involved in the process of learning from both positive and negative experiences, allowing the brain to adjust and adapt its behavior based on the outcomes of these experiences. The study was published today in Science Advances.

“Previously, research has shown that dopamine plays an important role in how animals learn from ‘rewarding’ (and possibly ‘punishing’) experiences. But, little work has been done to directly assess what dopamine does on fast timescales in the human brain,” said Kenneth T. Kishida, Ph.D., associate professor of physiology and pharmacology and neurosurgery at Wake Forest University School of Medicine. “This is the first study in humans to examine how dopamine encodes rewards and punishments and whether dopamine reflects an ‘optimal’ teaching signal that is used in today’s most advanced artificial intelligence research.”

Reference: Research shows human behavior guided by fast changes in dopamine levels; Science Advances; DOI: 10.1126/sciadv.adi4927

Can preeclampsia be prevented?

Preeclampsia is a mysterious condition that occurs in about one of 10 pregnancies without any early warning signs. After 20 weeks or more of normal blood pressure during the pregnancy, patients with preeclampsia will begin to experience elevated blood pressure and may also have increased levels of protein in their urine due to hypertension reducing the filtering power of the kidneys. Prolonged hypertension due to preeclampsia can lead to organ damage and life-threatening complications for mothers and fetuses.

There is no cure for the underlying causes of preeclampsia, so physicians focus on managing and monitoring patients’ blood pressure to allow for as close to a full-term gestation as possible. With severe disease, pre-term deliveries are necessary.

MCW scientists published results on a study of one of the emerging theories for what causes preeclampsia in Science Advances in December 2023. The experiments focus on a particular layer of cells of the placenta called the syncytiotrophoblast (STB), which is a key part of the barrier between the mother and developing fetus. This blockade helps keep a mother’s fully formed immune system from reacting to the fetus and potentially responding as if the fetus was a foreign threat such as a viral or bacterial invader.

The barrier also works in reverse to keep the fetus’s growing immune system from reacting to its mother’s cells and tissues. The study’s authors investigated the hypothesis that an abnormal amount of cellular and molecular stresses to the STB can damage the placenta and lead to preeclampsia.

“With our unique model, we can study the effects of contributing factors to preeclampsia throughout pregnancy,” Dr. Grobe says. “We can test specific signaling cascades in specific cells and tissues at specific times to observe their effects. We have only scratched the surface on what we can learn.”

Reference: Can preeclampsia be prevented?; Science Advances; DOI:10.1126/sciadv.adg8118