Introduction: Type 2 diabetes is associated with vascular dysfunction, elevated blood pressure, and alterations in factors influencing cardiovascular health. Reduced nitric oxide and Klotho levels may contribute to the exacerbation of endothelial dysfunction and an increased risk of cardiovascular complications. Evidence regarding the effects of high-intensity interval training (HIIT) and vitamin D supplementation on serum soluble Klotho and nitric oxide metabolites in type 2 diabetes is limited, and the combined effects of these two interventions in women with type 2 diabetes have been less investigated. The present study aimed to examine the effects of 12 weeks of HIIT and vitamin D supplementation on serum soluble Klotho, nitric oxide metabolites, and blood pressure in women aged 35–50 years with type 2 diabetes.
Methods: This randomized controlled trial was conducted using a pretest–posttest design with a control group. Forty women with type 2 diabetes, aged 35–50 years, were purposively selected and randomly allocated to four equal groups: HIIT, HIIT plus vitamin D, vitamin D, and control. The exercise groups performed a 12-week HIIT protocol, three sessions per week, consisting of running at 75–90% of heart rate reserve and low-intensity active recovery at 40–50% of heart rate reserve. The supplementation groups received 50,000 IU of vitamin D once weekly. The study variables were measured 48 hours before and after the intervention. Data were analyzed using two-way repeated-measures analysis of variance followed by Bonferroni post hoc tests at a significance level of p < 0.05.
Results: After 12 weeks of intervention, serum soluble Klotho and nitric oxide metabolites increased significantly in the HIIT plus vitamin D group compared with the HIIT, vitamin D, and control groups (p < 0.001). The time × exercise × vitamin D supplementation interaction was significant for both serum soluble Klotho and nitric oxide metabolites (p < 0.001), with greater changes observed in the HIIT plus vitamin D group compared with the other groups. However, none of the main or interaction effects for systolic or diastolic blood pressure were statistically significant (p > 0.05).
Conclusion: Twelve weeks of HIIT combined with vitamin D supplementation may increase serum soluble Klotho and nitric oxide metabolites in women aged 35–50 years with type 2 diabetes. Targeted HIIT combined with correction of vitamin D deficiency may be considered as a non-pharmacological approach for improving factors related to vascular function in patients with type 2 diabetes.
Keywords: High-intensity interval training; vitamin D supplementation; Klotho; nitric oxide metabolites; type 2 diabetes