Vitamin D Supplementation Reduces Both Oxidative DNA Damage and Insulin Resistance in the Elderly with Metabolic Disorders

Abstract

Background: Research evidence indicates that vitamin D deficiency is involved in the pathogenesis of insulin resistance (IR) and associated metabolic disorders including hyperglycemia and dyslipidemia. It also suggested that vitamin D deficiency is associated with elevated levels of oxidative stress and its complications. Therefore, the aim of our study was to determine the effect of vitamin D supplementation on DNA damage and metabolic parameters in vitamin D deficient individuals aged >45 with metabolic disorders. Material and Methods: Of 98 initially screened participants, 92 subjects deficient in vitamin D were included in the study. They were randomly assigned to the following group: with vitamin D supplementation (intervention group, n = 48) and without supplementation (comparative group, n = 44). The patients from both groups were divided into two subgroups according to the presence or absence of type 2 diabetes (T2DM). The intervention group was treated with 2000 International Unit (IU) cholecalciferol/day between October and March for three months. At baseline and after three-month supplementation vitamin D concentration (25-OH)D3 and endogenous and oxidative DNA damage were determined. In addition, fast plasma glucose (FPG), fasting insulin, HbA1c and lipid fraction (total cholesterol (TC), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), triglyceride (TG)), as well as anthropometric measurements (weight, height) were gathered. The following IR-related parameters were calculated Homeostatic Model Assesment – Insulin Resistance (HOMA-IR) and TG/HDL ratio. Results: Three-month vitamin D supplementation increased the mean vitamin D concentration to generally accepted physiological level independently of T2DM presence. Importantly, vitamin D exposure decreased the level of oxidative DNA damage in lymphocytes of patients of intervention group. Among studied metabolic parameters, vitamin D markedly increased HDL level, decreased HOMA-IR, TG/HDL ratio. Furthermore, we found that HbA1c percentage diminished about 0.5% in T2DM patients supplemented with vitamin D. Conclusion: The current study demonstrated that daily 2000I U intake of vitamin D for three months decreased the level of oxidative DNA damage, a marker of oxidative stress, independently on T2DM presence. Furthermore, vitamin D reduced metabolic parameters connected with IR and improved glucose and lipid metabolism. Therefore, our results support the assertion that vitamin D, by reducing oxidative stress and improving of metabolic profile, may decrease IR and related diseases.

Dietary Intake of Vitamin D from Dairy Products Reduces the Risk of Osteoporosis

“…Vitamin D status is related to bone mineral density (BMD) not only in vitamin D deficient consumers, but also in vitamin D insufficient subjects [27]. A clinical trial on vitamin D status and BMD in 7441 postmenopausal women with osteoporosis showed a significant positive correlation between serum 25(OH)D and BMD in the trochanteric area of the hip with a threshold below 50 nmol/L [38].…”

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

“…We have shown that three-month supplementation with vitamin D of the elderly with metabolic disorders markedly elevates HDL level, reduces HOMA-IR, and TG/HDL ratio. Moreover, we observed that HbA1c percentage decreased about 0.5% in T2DM patients after vitamin D supplementation [ 5 ]. In turn, Upreti et al have revealed that six-month supplementation with vitamin D of T2DM patients leads to distinct reduction of HbA1c [ 6 ].…”

“…It should be underlined that adipose tissue secretes numerous adipocytokines involved in inflammation, a typical feature of insulin resistance, obesity, and T2DM [ 11 ]. Numerous studies have revealed that vitamin D reduces the extent of inflammation and chronic hyperglycemia-generated oxidative stress [ 5 , 15 ]. Appealingly, vitamin D was demonstrated to modulate hepatic lipid and glucose metabolism [ 16 ].…”

Clinical Significance of Analysis of Vitamin D Status in Various Diseases

“…High insulin levels may cause obesity, hypertension, low HDL cholesterol, high triglycerides, and diabetes [63]. It is interesting that vitamin D deficiency in the body contributes to the deepening of insulin resistance, resulting in metabolic disorders (hyperglycemia, dyslipidemia) [64].…”