Purpose: Metformin is the first-line antidiabetic drug and shown to reduce cardiovascular risk independent from its glucose lowering action. Particularly in poorly controlled diabetes, tissue factor (TF) is expressed in the vasculature and accounts for thromboembolic complications. Here, we aimed to assess the effect of metformin on TF activity and markers of vascular inflammation in poorly controlled type 2 diabetes.
Methods: In a cohort of patients with uncontrolled type 2 diabetes (glycosylated hemoglobin 8.39 ± 0.24%, 68.1 ± 2.6 mmol/mol, n = 46) of whom half of the individuals were treated with metformin and the other half did not receive metformin as part of an anti-diabetic combination therapy, we assessed TF activity and markers of vascular inflammation. In vitro, human monocytic cells (THP-1) were exposed to metformin and TF expression measured in the presence and absence of the AMP-activated protein kinase (AMPK) activator 5-aminoimidazole-4-carboxamide riboside (AICAR) or the AMPK inhibitor compound C.
Results: In the patients, metformin treatment was associated with lower levels of TF protein (241.5 ± 19 vs. 315.4 ± 25 pg/mL, p = 0.03) and reduced TF activity (408.9 ± 49 vs. 643.8 ± 47 U/mL, p = 0.001) compared with controls. Moreover, the patients on metformin showed lower levels of vascular cell adhesion molecule (VCAM)1 (26.6 ± 1.4 vs. 35.03 ± 3.1 ng/mL, p = 0.014) and higher expression of miR-126-3p/U6sno (11.39 ± 2.8 vs. 4.26 ± 0.9, p = 0.006), a known post-transcriptional down regulator of TF and VCAM1. In vitro, metformin dose-dependently reduced lipopolysaccharide (LPS)-induced TF expression in THP-1 cells. The AMPK activator AICAR alone lowered TF expression in THP-1, while the AMPK inhibitor compound C abrogated the metformin-dependent reduction in TF expression.
Conclusions: Our data are the first to report that metformin is associated with reduced plasma TF procoagulant activity possibly explaining-at least in part-the vasculoprotective properties of metformin.
Keywords: Metformin; cardiovascular disease; coagulation; diabetes mellitus; microRNA; thrombosis; tissue factor; vascular complications; vascular inflammation.