Effects of fasting on endothelial function in type 2 diabetes mellitus patients: cohort study

Background The aim of this study was to investigate the effect of Ramadan fasting (RF) on markers of endothelial function and metabolic parameters in patients with type 2 diabetes mellitus (T2DM) and healthy controls. Methods This cohort study involved 305 subjects: 167 T2DM and 138 healthy volunteers subjects. The following parameters were evaluated: body mass index (BMI), diet inflammatory index (DII), serum glucose and lipid profile and high-sensitivity C-reactive protein (hs-CRP) during three separate visits, before Ramadan (baseline), the last week of Ramadan, and during the last week of the month following Ramadan. In each visit, reactive hyperaemia index (RHI) in all participants was assessed. In diabetic patients, serum homocyteine (Hcys) was mesured at baseline and during RF. The primary endpoint was change in RHI, a validated and non-invasive measure of endothelial function. The secondary end point was change in clinical, metabolic parameters, and Hcys. Analyses used non-parametric tests and multivariable regression with multiple imputation. Results RF significantly decreased RHI [−0.2 UI (95% CI −0.3 to −0.09); p < 0.001] and increased serum homocysteine [1.2 µmol/L (95% CI 0.7–1.8); p < 0.001] in T2DM compared to baseline levels.RF did not significantly change RHI in healthy volunteers. A significant increase in blood glucose ( p < 0.001) and LDL cholesterol ( p = 0.003) was observed during Ramadan compared to baseline, whereas HDL cholesterol, DII, and BMI decreased. Among healthy volunteers, similar changes in metabolic parameters were observed, with hs-CRP increasing during Ramadan compared to baseline ( p = 0.01). Conclusion RF seems to be associated with unfavorable effects on endothelial function in diabetic patients but not in healthy subjects. RHI testing could help identifying diabetic patients who should not observe RF or should be closely monitored during fasting.