Association between vitamin D levels and insulin resistance in patients with type 2 diabetes mellitus

Abstract

Background: Insulin resistance (IR) is a major contributor to type 2 diabetes mellitus (T2DM) and is associated with various metabolic disorders. Vitamin D deficiency (VDD) has been linked to an increased risk of T2DM, but the relationship between vitamin D status and IR in T2DM patients remains unclear. This study explores this association in a male population with T2DM in Baghdad, Iraq.Methods: A case-control study was conducted on 190 male participants: 40 healthy controls and 150 patients categorized into different groups; 40 diabetic patients, 55 with coronary artery disease (CAD) and T2DM (CAD+DM), and 55 with only CAD. Physicians diagnosed them, and they were evaluated by physical and full medical history. All the sample set parameters were measured in the fasting state for each group. The biochemical tests included body mass index (BMI), vitamin D levels, insulin levels, fasting tests glucose (FBG), and HbA1c were measured. Insulin resistance was calculated using the HOMA-IR model.Results: Vitamin D levels were significantly lower in all diabetic groups (DM, CAD+DM) compared to the control group (p<0.001). All diabetic patients had insulin resistance. BMI was significantly higher in the CAD and CAD+DM groups compared to controls (p<0.00001, p<0.004). FBG, HbA1c, insulin levels, and HOMA-IR were all significantly higher in diabetic patients compared to controls (p<0.001 for all). Furthermore, increased HbA1c, fasting insulin, and homeostatic model assessment for insulin resistance (HOMA-IR) were associated with CAD progression in T2DM patients (p < 0.001).Conclusion: This study suggests that vitamin D deficiency may contribute to insulin resistance in male T2DM patients in Baghdad, Iraq. Maintaining optimal vitamin D levels may be beneficial in diabetes management in this population. Incorporating vitamin D screening into routine check-ups for T2DM patients could aid in early detection and prevention of insulin resistance-associated complications.Keywords: Diabetes mellitus; Insulin resistance; Vitamin D; Coronary artery disease