A study published in the Journal of Biological Chemistry shows that low vitamin D levels may increase the risk for heart disease in diabetics. In earlier research, researchers found that vitamin D appears to play a key role in heart disease. This new study takes that research a step further, suggesting that when vitamin D levels are low, a particular class of white blood cells is more likely to adhere to cells in the walls of blood vessels.
Vitamin D conspires 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 this study, the researchers examined 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.
“We took everything into account,” said author Amy Riek, Washington University in St. Louis. “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.”
The researchers are unsure 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.