INS and diabetes mellitus: It is important to underline that in the group of subjects that remained free of diabetes throughout the postintervention period, proinsulin/c-peptide ratio at the end of the 108 months of follow-up was 11.2 ± 13.8 and 47.3 ± 46.6 × 10−3 (p < 0.01) in l-arginine and in placebo groups, respectively, suggesting a very important protective effect of l-arginine on β-cell function.