Double the Cardiovascular Risk for Diabetics with Low Levels of Vitamin D

Researchers at the Washington University in St. Louis School of Medicine have identified why diabetics with low levels of vitamin D are at almost twice the risk for cardiovascular disease.

According to principal investigator Carlos Bernal-Mizrachi, MD, a Washington University endocrinologist at Barnes-Jewish Hospital and Assistant Professor of Medicine and Cell Biology and Physiology, and his team of researchers, vitamin D inhibits the uptake of cholesterol by macrophages. A lack of vitamin D allows more cholesterol to be ingested by the macrophages, of which they are then unable to get rid themselves. The excess cholesterol leads to the formation of foam cells, which are, according to the researchers, “one of the earliest markers of atherosclerosis.” The researchers also believe that, in diabetics with low levels of vitamin D, the macrophages with excess amounts of cholesterol can stiffen vessels and block blood flow.

For the study, Bernal-Mizrachi and his team examined macrophages taken from patients with and without diabetes and with and without vitamin D deficiency. The cells were then exposed to cholesterol and high and low levels of vitamin D. When macrophages from diabetic patients were exposed to low levels of vitamin D in the culture dishes, those cells were “much more likely to become foam cells,” according to the researchers.

However, the team believes the problem is easy to fix. In environments with high levels of vitamin D, macrophages do not take in as much cholesterol and do not become foam cells. Bernal-Mizrachi said he believes that it may be simple to slow or reverse the development of atherosclerosis in diabetic patients, by bringing their vitamin D back up to an “adequate” level.

"There is debate about whether any amount of sun exposure is safe, so oral vitamin D supplements may work best," said Bernal-Mizrachi, "but perhaps if people were exposed to sunlight only for a few minutes at a time, that may be an option, too."

Study findings were published in Circulation.