According to the researchers, blood vessels are not as likely to clog in diabetics who have sufficient levels of vitamin D. However, in those with low levels, immune cells trap cholesterol in the blood vessels close to the heart, resulting in blockage.
A study published in 2011 said that vitamin D can improve cholesterol levels and heart disease biomarkers in diabetics.
Carlos Bernal-Mizrachi, MD, lead investigator of the trial, said:
"About 26 million Americans now have type 2 diabetes. 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."
During prior research, Bernal-Mizrachi, who is an assistant professor of medicine and of cell biology and physiology, and his team discovered that vitamin D seems to play an important part in heart disease. The recent trial goes one step further, stating that when levels are low, a certain kind of white blood cell is more likely to stick to cells in the blood vessel walls.
Vitamin D works together with microphages (a type of immune cell) to clear arteries or block them. These immune cells are born as white blood cells called monocytes, which move and spread through the blood. However, when monocytes meet inflammation they turn into macrophages, which do not move around.
During the recent trial, the experts examined 43 type 2 diabetics' vitamin D levels, and the vitamin D levels of 25 non-diabetics of the same sex, body type, and age.
The researchers discovered that in diabetics who had insufficient vitamin D levels, or less than 30 nanograms per milliliter of blood, the macrophages were more apt to stick to the blood vessel walls, which can lead to cholesterol buildup in the cells. In time, this will result in hardening of the arteries and obstructed movement of blood.
"We took everything into account. We 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," said Amy E. Riek, MD, a teacher in medicine.
The authors said that it is uncertain whether giving vitamin D to diabetics can alter their chances of getting clogged arteries, a condition called atherosclerosis. Currently, the experts are giving vitamin D to mice to determine whether it can stop monocytes from clinging to blood vessel walls close to the heart, and they are carrying out two studies on human patients.
One of the studies involves the researchers giving diabetics with hypertension vitamin D to find out whether their blood pressure is lowered by the treatment. For the other study, the experts are giving African Americans with type 2 diabetes vitamin D, in addition to their normal every day drugs, in order to determine if the supplements can delay or reverse the development of heart disease.
In the near future, the experts hope to reveal the effects of vitamin D on risk factors linked to cardiovascular disease.
"In the future, we hope to generate medications, potentially even vitamin D itself, that help prevent the deposit of cholesterol in the blood vessels. Previous studies have linked vitamin D deficiency in these patients to increases in cardiovascular disease and in mortality. Other work has suggested that vitamin D may improve insulin release from the pancreas and insulin sensitivity. Our ultimate goal is to intervene in people with diabetes and to see whether vitamin D might decrease inflammation, reduce blood pressure and lessen the likelihood that they will develop atherosclerosis or other vascular complications."
Written by Christine Kearney