Arginase inhibition improves endothelial function in patients with type 2 diabetes mellitus despite intensive glucose-lowering therapy.

BACKGROUND: Arginase is implicated in the pathogenesis behind endothelial dysfunction in type 2 diabetes mellitus (T2DM) by its inhibition of nitric oxide formation. Strict glycaemic control is not sufficient to improve endothelial function or cardiovascular outcomes in patients with T2DM, thus other treatment strategies are needed. We hypothesized that arginase inhibition improves endothelial function beyond glucose-lowering therapy following glucose optimization in patients with poorly controlled T2DM. METHODS AND RESULTS: Endothelial function was evaluated in 16 patients with poorly controlled T2DM (visit 1) and 16 age-matched controls using venous occlusion plethysmography. T2DM patients were re-evaluated (visit 2) after intensive glucose-lowering regimen. Endothelium-dependent (EDV) and -independent (EIDV) vasodilatations were evaluated before and after 120 min intra-arterial infusion of the arginase inhibitor N(ω)-hydroxy-nor-L-arginine (nor-NOHA). HbA1c was reduced from 87 ± 17 (visit 1) to 65 ± 11 mmol mol-1 (visit 2, P < 0.001). Basal EDV, but not EIDV, was significantly lower in patients with T2DM than in healthy subjects (P < 0.05). EDV and EIDV were unaffected by glucose-lowering regimen in patients with T2DM. Arginase inhibition enhanced EDV in T2DM patients both at visit 1 and visit 2 (P < 0.01). There was no difference in improvement in EDV between the two occasions. EIDV was unaltered by nor-NOHA in T2DM at visit 1, but was slightly improved at visit 2. CONCLUSIONS: Arginase inhibition improves endothelial function in patients with poorly controlled T2DM, which is maintained following glucose optimization. Thus, arginase inhibition is a promising therapeutic target beyond glucose lowering for improving endothelial function in T2DM patients.

Arginase inhibition improves endothelial function in patients with familial hypercholesterolaemia irrespective of their cholesterol levels.

BACKGROUND: Elevated LDL cholesterol is an important risk factor for atherosclerosis. Endothelial dysfunction, an early event in the development of atherosclerosis, is characterized by a reduction in nitric oxide (NO) bioavailability. Arginase has emerged as a key regulator of endothelial function through competition with NO synthase for the common substrate l-arginine. Arginase in endothelial cells is activated by oxidized LDL. The study aim was to investigate the importance of arginase for endothelial dysfunction in patients with familial hypercholesterolaemia (FH). METHODS AND RESULTS: Endothelial function was evaluated in 12 patients with heterozygous FH and 12 age-matched healthy normocholesterolaemic subjects using forearm venous occlusion plethysmography. The evaluations in FH patients occurred when they were on lipid-lowering therapy and 4 weeks after withdrawal of treatment. Endothelium-dependent vasodilatation (EDV) was assessed by intrabrachial artery infusion of serotonin, and endothelium-independent dilatation was assessed by infusion of nitroprusside before and after 120 min administration of the arginase inhibitor N (ω) -hydroxy-nor-l-arginine (nor-NOHA; 0.1 mg min(-1)). In FH patients LDL cholesterol increased from 4.3 ± 0.9 mmol L(-1) at baseline to 7.6 ± 1.9 mmol L(-1) at follow-up (P < 0.001). Arginase inhibition enhanced EDV in FH patients by a similar degree independent of lipid-lowering therapy. The improvement in EDV by arginase inhibition was significantly greater in FH patients than in the control group. CONCLUSION: Arginase inhibition results in greater improvement in endothelial function in patients with FH compared to healthy controls irrespective of their cholesterol levels. Arginase may be a promising therapeutic target for improving endothelial function in patients with hypercholesterolaemia.