PON1 and breast cancer: Leptin, which is secreted at elevated levels due to adipocyte dysfunction, leads to a decrease in high-density lipoprotein (HDL) and triglyceride levels, which in turn reduces the fractions of HDL, thus leading to the underexpression of PON1.136 A genetic alteration in the genes involved in oxidative stress pathways can increase the risk of breast cancer due to the role that oxidative stress plays in the development of breast cancer.