Abnormalities in the relationship of paraoxonase 1 with HDL and apolipoprotein A1 and their possible connection to HDL dysfunctionality in type 2 diabetes

Lipid parameters, lipid risk indexes and lipid-related oxidative stress markers (paraoxonase 1 [PON1] and lipid peroxides [LPO]) reflect the actual status of lipid metabolism in type 2 diabetes (T2DM). We hypothesized that relationships of high-density lipoprotein cholesterol (HDL-c) with PON1 and apolipoprotein A1 (ApoA1) and/or PON1 with ApoA1 under conditions of hyperglycaemia and oxidative stress might reveal HDL functionality. We investigated relationships between PON1, LPO, and lipid risk markers in T2DM subjects and compared them with those in healthy subjects.A total of 107 Caucasian subjects, 67 T2DM outpatients (mean age 52.2 ± 6.9 years) and 40 healthy subjects (mean age 48.1 ± 7.5 years) were included in the study. Serum levels of total cholesterol (CHOL-T), HDL-c, low-density lipoprotein cholesterol (LDL-c), triglycerides (TG), apolipoprotein B (ApoB), ApoA1, LPO, and PON1 activity were measured. Non-HDL-c, ApoB/ApoA1 and non-HDL/HDL (lipid risk indexes) were calculated.Higher levels of TG, LPO (P 0.0001), nonHDL/HDL and ApoB/ApoA1 (P 0.001, 0.05, respectively), and lower levels of HDL-c, ApoA1, and PON1 (P 0.0001) were observed in T2DM subjects than in controls. There is a lack of relationship among PON1, HDL-c, and ApoA1 in T2DM patients. PON1 activity positively correlated with these parameters (P 0.0001) in controls. Strong correlations between non-HDL-c and ApoB (r = 0.956 vs. 0.756; P 0.0001), LPO and TG (r = 0.831 vs. 0.739; P 0.0001) were recorded in both study groups (P 0.0001).Impaired anti-oxidant and anti-atherogenic HDL properties associated with weakened PON1 function and lipid peroxidation may contribute to the development of atherosclerosis-related diseases in T2DM.