Abstract: Introduction: Impaired neovascularization of ischemic tissue is a hallmark of diabetic vasculopathy but thecauses leading to its pathogenesis are poorly understood. Thioredoxin interacting protein (TXNIP), an exquisitely glucose-sensitive gene that is overexpressed in diabetes, has been found to modulate vascular endothelial growth factor (VEGF). We hypothesized that hyperglycemia-induced dysregulation of TXNIP plays a causal role in the impaired angiogenesis of diabetes.
Objective: To investigate whether targeted silencing of TXNIP would rescue impaired angiogenesis in diabetes mellitus.
Methods: Endothelial cell (EC) migration, proliferation, tubulogenesis, VEGF production and sensitivity to VEGF action were assessed in a range of glucose conditions. TXNIP was modulated by siRNA-knockdown or by overexpression. Hindlimb ischemia was generated in streptozotocin-induced diabetic mice and siRNA delivered intramuscularly. Hindlimb perfusion, capillary density and VEGF levels were assessed.
Results: Increasing glucose concentrations (5-25 mmol/L) dose-dependently induced TXNIP, a finding associated with impairment of EC migration, proliferation, tubulogenesis, VEGF production and sensitivity to VEGF action. Overexpression of TXNIP in normoglycemia replicated all EC dysfunction seen in hyperglycemia. Notably, TXNIP silencing by siRNA rescued all hyperglycemia-induced EC dysfunction, restoring VEGF production and sensitivity to VEGF action to normoglycemic levels. Impaired angiogenesis in a diabetic hindlimb ischemia model was associated with TXNIP overexpression and reduced VEGF production. In vivo normalization of TXNIP expression by siRNA to non-diabetic levels rescued diabetes-related impairment of angiogenesis and functional recovery in the ischemic hindlimbs, with restoration of VEGF production.
Conclusions: TXNIP plays a causal role in the pathogenesis of hyperglycemia-induced impairment of EC function and angiogenesis. TXNIP inhibition can abrogate diabetes-related impairment in angiogenesis, with implications for the therapeutic modulation of diabetic vasculopathy.