Vascular smooth muscle function in type 2 diabetes mellitus: a systematic review and meta-analysis
Résumé
Aims/hypothesis In type 2 diabetes, in contrast to the well-documented endothelial dysfunction, studies assessing vas-cular smooth muscle (VSM) function have yielded discrep-ant results over the last two decades. We therefore sought to determine whether or not VSM function is impaired in individuals with type 2 diabetes. Methods We conducted a systematic search of MEDLINE, Cochrane, Scopus and Web of Science databases, from their respective inceptions until December 2012, for articles evaluating VSM function in individuals with type 2 diabetes. A meta-analysis was performed to compare the standardised mean difference (SMD) in VSM function between individuals with type 2 diabetes and age-matched controls. Subgroup analyses and meta-regression were used to identify sources of heterogeneity. Results Twenty-seven articles (1,042 individuals with type 2 diabetes and 601 control subjects) were included in this analysis. VSM function was significantly impaired in diabetic compared with control subjects (SMD −0.68, 95% CI −0.84, −0.52; p<0.001). Although moderate heterogeneity among studies was found (I 2 =52%), no significant publication bias was detected. Subgroup analyses showed a further decline in VSM function assessed in the microcirculation compared with the macrocirculation of individuals with type 2 diabetes (p=0.009). In meta-regression, VSM function in the microcirculation was inversely associated with BMI and triacylglycerols and was positively associated with HDL-cholesterol. Conclusions/interpretation In addition to the endothelium, the VSM is a source of vascular dysfunction in type 2 diabetes. An exacerbation of VSM function in the microcir-culation may be a distinctive feature in type 2 diabetes. Abbreviations DBP Diastolic blood pressure HOMA-IR HOMA of insulin resistance NMD Nitrate-mediated dilation of brachial artery SAQOR Systematic appraisal of quality for observational research SBP Systolic blood pressure SMD Standardised mean difference VSM Vascular smooth muscle