Vitamin D levels and microvascular complications in type 2 diabetes

Abstract

Background:Vitamin D has important actions on glucose metabolism. These include improved insulin exocytosis, direct stimulation of insulin receptor, improved uptake of glucose by peripheral tissues, improving insulin resistance. It has got various pleiotropic effects like suppression of cell mediated immunity, regulation of cell proliferation, stimulation of neurotropic factors such as nerve growth factor, Glial cell line-derived neurotrophic factor, neurotropin, suppression of RAAS, reduction of albuminuria, immunomodulatory effects, and anti-inflammatory effects. Thus, vitamin D is implicated in many ways in the pathogenesis of retinopathy, neuropathy and nephropathy.Objectives:To study the correlation of vitamin D levels with microvascular complications in type 2 diabetes.Materials and Methods:Cross-sectional case-control study of 18 patients (18-70 years), who met the American Diabetes Association 2011 criteria for type 2 diabetes, was conducted. Age and sex matched healthy controls were taken. Subjects were evaluated for the presence of microvascular complications by clinical evaluation, urine examination, fundus examination, nerve conduction studies, and various biochemical tests. 25-OH cholecalciferol levels were done for each. Cut off level for vitamin D deficiency was 20 ng/ml.Results:Mean vitamin D was lower in type 2 diabetics than healthy subjects (19.046 vs. 27.186 ng/ml). Prevalence of vitamin D deficiency and insufficiency was found to significantly higher in diabetics when compared to healthy subjects (P = 0.0001). Vitamin D deficiency was found to be significantly associated with neuropathy (χ2 = 5.39, df = 1, P = 0.020), retinopathy, (χ2 = 6.6, df = 1, P = 0.010) and nephropathy (χ2 = 10. 52, df = 1, P = 0.001). Lower levels of vitamin D were found to be associated with increasing prevalence of combinations of microvascular complications namely neuropathy with retinopathy (P = 0.036), neuropathy with nephropathy (P = 0.029), retinopathy with nephropathy (P = 0.022) and neuropathy with retinopathy with nephropathy (P = 0.0001).

The effects of calcitriol on albuminuria in patients with type 2 diabetes mellitus

“…Our results regarding 25-(OH)D was significantly correlated with albuminuria in Chinese type 2 diabetic patients are consistent with several clinical studies that have reported that low 25-(OH)D levels were associated with an increased risk of albuminuria in diabetic and non-diabetic patients [18][19][20]. Direct cellular effects of vitamin D deficiency, including podocyte loss and increasing glomerulosclerosis, may be contributing to the increasing risk of albuminuria [10].…”

Lack of Definite Association of Vitamin D Deficiency with Diabetic Neuropathy. Investigation in Greek and in Bangladeshi Patients

“…Vitamin D has been shown to have a neuroprotective effect (15) and to be implicated in the pathogenesis of diabetes mellitus (13,16) and a low level of vitamin D in patients with DN may simply indicate its insufficiency in patients with diabetes.…”

Adequate vitamin D status is associated with the reduced odds of prevalent diabetic retinopathy in African Americans and Caucasians

“…A number of studies have compared 25(OH)D concentrations between groups of individuals with and without diabetic retinopathy in case–control designs [3, 11, 13, 17, 22] with a protective association of 25(OH)D on prevalent retinopathy found in three studies [3, 11, 13]. The majority of other studies consist of cross-sectional designs recruiting participants from clinical settings [5, 6, 9, 10, 12, 14, 15, 19, 21, 23] with half of these studies supporting a protective association of vitamin D with retinopathy [5, 6, 9, 10, 12].…”