Increased serum miR-7 is a promising biomarker for type 2 diabetes mellitus and its microvascular complications.

Aims: To investigate the alteration pattern and physiologic state of islet-specific miR-7 in the serum of patients with type 2 diabetes mellitus (T2DM) and T2DM-associated microvascular complications (T2DMC) and to evaluate its clinical significance.

Methods: The levels of serum miR-7 were firstly examined and compared in 76 T2DM patients, 76 T2DMC patients and 74 age-gender matched controls using RT-qPCR. Subsequently, the physiologic state of serum miR-7 was characterized by determining its concentrations in isolated exosomes and corresponding exosome-free samples from the same three cohorts' samples. Moreover, statistical analyzes were performed to evaluate the associations of serum miR-7 with T2DM and T2DMC.

Results: Serum miR-7 was significantly elevated in the T2DM patients [(401.0±34.37) fmol/L, P<0.001] and in the T2DMC patients [(501.4±81.69) fmol/L, P<0.001] when compared with the controls [(175.7±16.59) fmol/L]. Circulating miR-7 was mainly existed as exosome-free form rather than in membrane-bound exosomes. The concentrations of exosome-free miR-7 were markedly higher in the T2DM group [(107.2±9.63) fmol/L, P<0.001] and in the T2DMC group [(122.1±10.80) fmol/L, P<0.001] compared to the control group [(54.18±2.37) fmol/L]. Logistic regression and ROC curve analyses revealed the serum miR-7 was significantly associated with T2DM and microvascular complications (P<0.05).

Conclusion: Increased serum miR-7 might have the potential as a promising marker for T2DM and its microvascular complications.