PON1 and diabetes mellitus: Reductions in PON1 activity and protein levels in diabetes have been attributed to different mechanisms: (a) reductions in apolipoproteins in HDL may affect the separation of PON1 from HDL and its subsequent instability, (b) the increase in oxidized lipids caused by oxidative stress may contribute to the inactivation of PON1 [246], (c) increased triglycerides in HDL may affect PON1 activity and (d) increases in blood glucose may reduce PON1 activity through protein glycation, including PON1 [248,249].