Vitamin D Lowers Risk of Atherosclerosis in Diabetes Patients

Increased levels of vitamin D may help protect patients with type 2 diabetes from developing coronary vascular diseases such as atherosclerosis.

Vitamin D deficiency is associated with an increased risk of cardiovascular disease in patients with type 2 diabetes. To determine the mechanism that causes accelerated cardiovascular disease in these patients, investigators from Washington University School of Medicine (St. Louis, MO, USA) studied the effects of active vitamin D on macrophage cholesterol deposition. Macrophages can become engorged on cholesterol by engulfing oxidized forms of LDL (low-density lipoproteins). A large excess of cholesterol causes the macrophages to transform into foam cells, which are an integral feature of atherosclerotic plaques.

The investigators worked with cultures of macrophages obtained from five different population groups: obese, diabetic, hypertensive patients with vitamin D deficiency; obese, diabetic, hypertensive patients with normal vitamin D; obese, nondiabetic, hypertensive patients with vitamin D deficiency; nonobese, nondiabetic, nonhypertensive patients with vitamin D deficiency; and nonobese, nondiabetic, nonhypertensive patients with normal vitamin D. The cultures were grown with either vitamin D-deficient or vitamin D-enriched growth media that were supplemented with oxidized LDL.

Results published in the August 10, 2009, online edition of the journal Circulation revealed that vitamin D suppressed foam cell formation in the cultures from diabetic patients by reducing uptake of oxidized LDL cholesterol. Furthermore, deletion of the vitamin D receptor in macrophages from diabetic patients accelerated foam cell formation.

"Vitamin D inhibits the uptake of cholesterol by cells called macrophages,” explained senior author Dr. Carlos Bernal-Mizrachi, professor of endocrinology at Washington University School of Medicine. "When people are deficient in vitamin D, the macrophage cells eat more cholesterol, and they cannot get rid of it. The macrophages get clogged with cholesterol and become what scientists call foam cells, which are one of the earliest markers of atherosclerosis.”

The investigators believe that maintaining adequate vitamin D levels may slow or reverse the development of atherosclerosis in diabetic patients. "There is debate about whether any amount of sun exposure is safe, so oral vitamin D supplements may work best,” said Dr. Bernal-Mizrachi, "but perhaps if people were exposed to sunlight only for a few minutes at a time--that may be an option, too.”

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Washington University School of Medicine