Diabetics with low vitamin D levels are more likely to develop clogged arteries compared to diabetics with adequate vitamin D levels, according to a new study published in the Journal of Biological Chemistry. The findings suggest in patients with insufficient vitamin D, immune cells bind to blood vessels near the heart, then trap cholesterol to block those blood vessels.
“About 26 million Americans now have type 2 diabetes," said principal investigator Carlos Bernal-Mizrachi, MD, an assistant professor of medicine and of cell biology and physiology at Washington University School of Medicine. “And as obesity rates rise, we expect even more people will develop diabetes. Those patients are more likely to experience heart problems due to an increase in vascular inflammation, so we have been investigating why this occurs."
In earlier research, the researchers found vitamin D appears to play a key role in heart disease. This new study takes their work a step further, suggesting that when vitamin D levels are low, a particular class of white blood cell is more likely to adhere to cells in the walls of blood vessels. Vitamin D works with immune cells called macrophages either to keep arteries clear or to clog them. The macrophages begin their existence as white blood cells called monocytes that circulate in the bloodstream. But when monocytes encounter inflammation, they are transformed into macrophages, which no longer circulate.
In the new study, researchers looked at vitamin D levels in 43 people with type 2 diabetes and in 25 others who were similar in age, sex and body weight but didn’t have diabetes. They found that in diabetes patients with low vitamin D—less than 30 nanograms per milliliter of blood—the macrophage cells were more likely to adhere to the walls of blood vessels, which triggers cells to get loaded with cholesterol, eventually causing the vessels to stiffen and block blood flow. The researchers looked at blood pressure, cholesterol, diabetes control, body weight and race, but only vitamin D levels correlated to whether these cells stuck to the blood vessel wall.
The researchers said what’s not yet clear is whether giving vitamin D to people with diabetes will reverse their risk of developing clogged arteries, a condition called atherosclerosis. They now are treating mice with vitamin D to see whether it can prevent monocytes from adhering to the walls of blood vessels near the heart, and they also are conducting two clinical trials in patients.
In one of those studies, the researchers are giving vitamin D to people with diabetes and hypertension to see whether the treatment may lower blood pressure. In the second study, blacks with type 2 diabetes are getting vitamin D along with their other daily medications, and the research team is evaluating whether vitamin D supplements can slow or reverse the progression of heart disease.
