Aims/hypothesis In type 2 diabetes, in contrast to the welldocumented endothelial dysfunction, studies assessing vascular smooth muscle (VSM) function have yielded discrepant 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 microcirculation may be a distinctive feature in type 2 diabetes.

Therefore, in the upper as well as in the lower limb vasculature, repetitive exposure to increased shear stress over a long-term period results in improved FMD of large conduit arteries as well as greater vasodilatory capacity during isolated exercise in the predominantly trained muscles. Long-term training involving predominantly the lower limbs also results in enhanced vascular reactivity in upper limb conduit and resistance vessels.

This new, fully automatic, photoplethysmographic device yielded reliable TBP measurements and showed good agreement with the reference LD system over a wide range of values.

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