HDL-mediated endothelial NO bioavailability (29.5 ± 8.5 vs. 38.0 ± 8.9%; P < 0.001) and serum PON-1 activity [472 (213–799) vs. 671 (418–923) μmol p-nitrophenol/L/serum/min; P = 0.045] were reduced in adolescents with Type 1 diabetes compared with controls, whereas SO production (2.86 ± 3.59 vs. 1.91 ± 2.46 nmol O2−/250 000 cells; P = 0.140) was similar between the two groups (Table 1). Here, PON1 is linked to type 1 diabetes mellitus.