EFFECTS OF LOW-DOSE L-ARGININE ON INSULIN-MEDIATED VASODILATATION ANDINSULIN SENSITIVITY

The present study was carried out to evaluate the effect of a low-dose intravenous supplementation of L-arginine on insulin-mediated vasodil atation and insulin sensitivity. The study was performed in healthy su bjects (n = 7) and patients with obesity (n = 9) and non-insulin-depen dent diabetes mellitus (NIDDM) (n = 9). Insulin-mediated vasodilatatio n was measured by venous occlusion plethysmography during the insulin suppression test, evaluating insulin sensitivity. Experiments were per formed twice in each subject in the presence or absence of a concomita nt infusion of L-arginine (0.52 mg kg(-1) min(-1). L-Arginine restored the impaired insulin-mediated vasodilatation observed in obesity (22. 4 +/- 4.1%, P<0.01 vs. without L-arginine) and NIDDM (20.3 + 3.2%, P<0 .01 vs. without L-arginine). In healthy subjects, no effect on insulin mediated-vasodilatation was observed (24.8 +/- 3.1% vs. 21.4 + 3.1%). Insulin sensitivity was improved significantly (P<0.001) in all three groups by infusion of L-arginine. No effect of L-arginine was observe d on insulin, insulin-like growth factor I(IGF-I), free fatty acids (F FAs) or C-peptide levels during the insulin suppression test. Our data indicate that defective insulin-mediated vasodilatation in obesity an d NIDDM can be normalized by intravenous L-arginine. Furthermore, L-ar ginine improves insulin sensitivity in obese patients and NIDDM patien ts as well as in healthy subjects, indicating a possible mechanism tha t is different from the restoration of insulin-mediated vasodilatation .