The researchers, from Capital Medical University, had drawn a link between serum 25-hydroxyvitamin — or 25(OH)D — levels and the prevalence of PAD in type 2 diabetes patients, and attempted to elucidate the effects of vitamin D supplementation on PAD.
They recruited a total of 1,018 type 2 diabetes patients — whose mean age was between 58.59 and 69.93 years — for a cross-sectional study, measuring their serum 25(OH)D levels and PAD risk factors.
Subsequently, they reported that only 20.1% of the patients had a 25(OH)D level of at least 20ng/ml, and that the patients without PAD had significantlyhigher serum 25(OH)D levels (14.81ng/ml to 23.24ng/ml) than those with PAD (11.55ng/ml to 17.2ng/ml), whose overall prevalence among the current study’s population was 7.7%.
Among the patients with the highest serum 25(OH)D levels, the prevalence of PAD was 2.8%, while among those with the lowest serum 25(OH)D levels, the prevalence was 10.7%.
After adjusting for factors such as sex, age, BMI, smoking status, and season, the odds ratio of PAD in patients with a serum 25(OH)D level of between 10ng/ml and under 20ng/ml was 3.587.
Among those with a serum 25(OH)D level of below 10ng/ml, the odds ratio of PAD was 5.54.
These figures rose slightly when the influence of coronary heart disease, hypertension and cerebral infarction were taken into account.
However, they decreased after the duration of diabetes, glycated haemoglobin (HbA1c) and glomerular filtration rate were taken in into consideration
The researchers presented several possible mechanisms to explain the link between low serum vitamin D levels and the higher risk of PAD development.
They wrote: “In in vitro studies, vitamin D levels have shown an association between obesity, diabetes and dyslipidaemia, which are all significant risk factors for PAD.
“In the present study, even excluding the influence of PAD risk factors, the relationship between serum 25(OH)D levels and PAD was still present, which means maybe some other mechanisms are also involved.
“First,I in vivo studies, active vitamin D calcitriol inhibits endothelial cell activation and TNF-α adhesion molecule expression, which play a role in the various stages of atherosclerosis.
“Second, vitamin D can modulate and regulate the activity of inflammatory cytokines such as TNF-α and IL-10, thus influencing the atherosclerotic process.”
They added that vitamin D could raise platelet aggregation and thrombogenesis, and that low vitamin D levels could stimulate vascular hypertrophy and increase oxidative stress, resulting in the development of atherosclerosis.
Further intervention needed
The researchers said the study’s cross-sectional design could mean that some residual confounding factors may have remained, making it hard to draw a definitive conclusion on cause-effect relationships.
The study being conducted at a single hospital also meant the patients may not be representative of the actual demographic profile of Beijing.
At the same time, the study population was relatively small; a larger sample size may have offered clearer results.
The researchers also did not draw a distinction between symptomatic and non-symptomatic patients with PAD.
In conclusion, they wrote: “Reduced serum vitamin D levels increased the risk of PAD in type 2 diabetes patients. This association was still strong after adjustment for known PAD risk factors and related indications of diabetes.
“Considering PAD is a very common and severe complication of T2DM, randomised intervention clinical studies should be carried out to verify the effects of vitamin D supplementation on PAD.”
Source: BMC Cardiovascular Disorders
“Vitamin D deficiency is associated with risk of developing peripheral arterial disease in type 2 diabetic patients”
Authors: Jing Yuan, et al.