Postprandial modulation of serum paraoxonase activity and concentration in diabetic and non-diabetic subjects

ObjectivesTo analyse the HDL associated anti-oxidant enzyme paraoxonase-1, during postprandial hyperlipaemia.Methods and resultsType 2 diabetic patients (n = 72), glucose intolerant patients (n = 10) and controls (n = 38) consumed a high fat:high carbohydrate meal. Blood samples were collected up to 4 h and analysed for lipids and paraoxonase-1. In vitro studies examined HDL function with respect to the enzyme. There were significant postprandial increases in serum triglycerides. Paraoxonase-1 activity decreased significantly throughout the postprandial phase. Concentrations of the enzyme initially decreased significantly, but returned to fasting concentrations at 4 h. Specific activities were significantly lower at 4 h, compared to fasting. The decrease in specific activity was linked to the dynamic phase of postprandial lipoprotein metabolism. Apo AI limited loss of paraoxonase-1. HDL isolated after being subjected to postprandial conditions in vitro had reduced capacity to associate with and stabilise PON1.ConclusionsPostprandial hyperlipaemia was associated with changes to serum paraoxonase-1, consistent with a reduced anti-oxidant potential of HDL. No differences were observed between diabetic and non-diabetic patients, suggesting that the effect was linked to postprandial hyperlipaemia. Modifications to paraoxonase-1 could contribute to increased risk of vascular disease associated with postprandial lipaemia, particularly in diabetic patients, who are already deficient in serum paraoxonase-1.