Effect of Oral L-arginine 3.32 g a Day on Oxidative Stress Influencing Beta Cell Function and Insulin Resistance.

Inclusion Criteria: * consented male and female patients aged 20-70 years with Body Mass Index (BMI) \>25 kg/m2, * pre-diabetes (fasting glucose 100-125 mg/dL and HbA1c 5.7-6.5%) or metabolic syndrome, defined according to modified NCEP-ATP III criteria (Grundy SM et al., Circulation, 2005) as the presence of three or more of the following clinical features: blood glucose levels \>100 mg/dL, HDL-cholesterol \<40 mg/dL in males and \<50 mg/dL in females, triglycerides levels \>150 mg/dL, waist circumference \>102 cm in males and \>88 cm in females and hypertension, defined as repeated blood pressure measurements \>130/85 mmHg. Exclusion Criteria: * moderate to severe renal impairment (calculated creatinine clearance (CrCl) \<60 mL/min according to the Cockcroft-Gault formula); * hepatic dysfunction (ALT/AST \>3 x upper limit of normal and total bilirubin \>3 mg/dL); * hypoalbuminemia (serum albumin \<3 g/dL); * history of any past or current clinically significant cardiovascular diseases; * monogenic, secondary and pharmacological causes of diabetes and obesity; * any other clinical condition/disease that the Principal Investigator believes might confound study outcome; * patients on treatment with insulin or any anti-diabetic drugs or medications known to influence glucose tolerance will also be excluded; * pregnant or breast-feeding women.