INS and diabetes mellitus: In addition, our finding that Lp(a) is associated with eNOS-derived arterial O2.− production in nondiabetic, but not in patients with diabetes is indicative of the potential involvement of local vascular insulin signaling in this process, as insulin resistant patients with low plasma Lp(a) levels are likely to demonstrate increased arterial O2.− production through additional, Lp(a)-independent, mechanisms.