Medical Bulletin 15/January/2024

Here are the top medical news of the day:

Researchers uncover blood flow regulation of brain pericyte development

In a study published online in Cell Reports, DU Jiulin’s group at the Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology of the Chinese Academy of Sciences, and the collaborators, created a zebrafish model for in vivo labeling of brain pericytes and systematically explored the developmental dynamics of brain pericytes during the early embryonic stage. The researchers revealed the promoting effect of blood flow on the proliferation of pericytes after ingress into the brain and showed that this process relies on the activation of the mechanosensitive ion channel Piezo1 in vascular endothelial cells (ECs) and its downstream Notch signaling.

Brain function relies on a complex and effective vascular network that provides necessary nutrients and removes waste products. To maintain the homeostasis of neural tissues and normal neural activity, the brain vasculature forms the blood–brain barrier (BBB) during development, strictly controlling substance exchange between blood and brain parenchyma. Abnormalities in the BBB are closely associated with various brain diseases, such as Alzheimer’s disease.

Pericytes, as mural cells tightly attached to the outer side of EC tubes in capillaries, play a crucial role in maintaining the integrity of the BBB. Therefore, understanding the development of brain pericytes is essential for studying the formation and maintenance of the BBB. Previous research had indicated that blood flow, the most important functional behavior of blood vessels, participates in regulating the development of brain ECs. However, whether blood flow affects the growth of brain pericytes remained an unexplored question.

Reference: Researchers uncover blood flow regulation of brain pericyte development; Cell Reports DOI:10.1016/j.celrep.2023.113652

Preeclampsia and preterm birth risk may be reduced by calcium dose lower than current WHO standard

According to two trials of 11,000 pregnant women in India and in Tanzania, low-dose calcium supplementation (500 milligrams per day) appears as effective at reducing the risk of preeclampsia and preterm birth as high-dose calcium supplementation (1,500 milligrams per day). The study was published in The New England Journal of Medicine.

The World Health Organization currently recommends high-dose calcium supplementation—equivalent to three calcium pills a day—for pregnant women in contexts with low-calcium diets, predominantly low- and middle-income countries. Lowering the pill burden to one 500mg calcium pill per day would reduce adherence barriers for women and reduce costs for governments and health programs without sacrificing health benefits.

While calcium supplementation is a known intervention to help prevent preeclampsia and preterm birth—it is estimated to halve a pregnant woman’s risk of developing preeclampsia and reduce an infant’s risk of being born preterm by 25%—the study is the first to evaluate the efficacy of a low-dose regimen versus a high-dose regimen. The findings provide an opportunity to revise the WHO’s current recommendation that women with low-calcium diets—most women who live in low- and middle-income countries—receive high-dose calcium supplementation throughout pregnancy.

The study found that low-dose calcium supplementation was as effective as high-dose calcium supplementation in preventing the risk of preeclampsia. In the India trial, the incidence of preeclampsia was 3.0% among women taking 500mg of calcium per day and 3.6% among women taking 1,500mg of calcium per day. In the Tanzania trial, the incidence of preeclampsia was 3.0% and 2.7%, respectively.

“Overall, our findings show that a single pill per day can be as effective as three,” said joint first author Christopher Sudfeld, associate professor of global health and nutrition. “With a reduced pill burden for women and lower costs for governments and programs that buy calcium pills, calcium supplementation should be considered widely implementable in the places it’s needed most—and should start saving thousands of maternal and newborn lives.”

Reference: Preeclampsia and preterm birth risk may be reduced by calcium dose lower than current WHO standard; New England Journal of Medicine; DOI: 10.1056/NEJMoa2307212

Black people face strokes at higher rates, younger ages than white people

Black people consistently had a higher rate of stroke than white people over a recent 22-year period, according to a study published in the January 10, 2024, online issue of Neurology, the medical journal of the American Academy of Neurology. The study also found that the average age of Black people experiencing stroke was nearly 10 years younger than that of white people, another inequity that grew over time.

“We found that the rate of stroke is decreasing over time in both Black and white people—a very encouraging trend for U.S. prevention efforts,” said study author Tracy E. Madsen, MD, PhD, of Brown University in Providence, Rhode Island. “But there was an inequity from the beginning of the study, with the rate of stroke always being higher for Black people than their white counterparts. The disparity did not decrease in 22 years, especially among younger and middle-aged adults.”

Researchers evaluated stroke trends over time using data from hospitals in southern Ohio and northern Kentucky from 1993 to 2015. Stroke cases were recorded across a full year every five years—about 1,950 cases per year for a total of 9,728. Using U.S. Census data, they were able to calculate stroke incidence rates per 100,000 people.

The overall rate of stroke decreased from 230 cases per 100,000 people in 1993 to 188 cases per 100,000 people in 2015. For Black people, the rates went from 349 to 311 and for white people they declined from 215 to 170.

The rate of stroke among Black people continued to be 50 to 80% higher than the rate among white people across the 22 years, even after adjusting for age and sex—a disparity that was particularly stark in younger and middle-aged Black adults. The disparity shrank in older age groups, a difference the researchers say may be due to different survival rates in Black and white people.

While the rate of stroke was decreasing, the study found that strokes were occurring at younger ages over time, and this change was larger in Black people, exacerbating an existing disparity. Strokes struck Black people at an average age of 66 at the beginning of the study and at age 62 by the end of the study. For white people, the average age was 72 at the beginning of the study and 71 two decades later.

“These disparities present a major ongoing public health concern,” Madsen said. “More work is clearly needed to address systemic and policy problems, as well as factors at the provider and patient levels. These findings are a clear, urgent call for concrete efforts to build more equitable means of stroke prevention and care.”

Reference: Black people face strokes at higher rates, younger ages than white people, AMERICAN ACADEMY OF NEUROLOGY; Neurology