Impaired paraoxonase-1 status in obese children. Relationships with insulin resistance and metabolic syndrome

•This is a case-control study in obese and lean children and adolescents.•We measured serum PON1 activity concentration and metabolic variables.•Obese children had lower PON1 activities than lean children.•PON1 was associated with the BMI, % fat and metabolic syndrome.•There were no differences in PON1 genotype between obese and lean children.

ObjectivesTo investigate the relationships between serum paraoxonase-1 (PON1), insulin resistance, and metabolic syndrome (MetS) in childhood obesity.Design and methodsWe studied 110 obese children and 36 non-obese children with a similar gender and age distribution. We measured serum PON1 activity against 5-thiobutyl butyrolactone (TBBLase) and against paraoxon (paraoxonase). PON1 concentration was measured separately as were the levels of several standard metabolic variables. The homeostasis model assessment (HOMA) index was calculated as an estimate of insulin resistance.ResultsTBBLase was significantly decreased in obese children (P = 0.008), while paraoxonase activity and PON1 concentrations showed non-significant trends towards decrease and increase, respectively (P = 0.054 and P = 0.060). TBBLase and paraoxonase specific activities were significantly decreased (P = 0.004 and P = 0.018, respectively). TBBLase specific activity was inversely associated with BMI, percentage body fat, insulin, HOMA, triglycerides, and C-reactive protein, and directly associated with HDL-cholesterol. Paraoxonase specific activity showed similar associations with BMI, percentage fat, HDL-cholesterol, and C-reactive protein. Obese children with MetS had lower TBBLase activities than obese children without MetS (P = 0.018). Linear regression analyses showed that TBBLase was independently associated with HDL-cholesterol, BMI, percentage body fat and PON155 polymorphism, but paraoxonase activity was associated only with PON1192 polymorphism.ConclusionsOur results suggest that PON1 may play a role in the onset and development of metabolic alterations in childhood obesity leading to diabetes and cardiovascular disease later in life. However, being derived from statistical association study, this finding cannot be seen as showing cause–effect.