Positive correlation of paraoxonase 1 (PON1) activity with serum insulin level and HOMA-IR in dementia. A possible advantageous role of PON1 in dementia development.

Paraoxonase 1 (PON1) activity and metabolic syndrome traits were evaluated in 169 demented patients (81 recognized as AD, 32 as VaD, 56 as MD) and in 64 control individuals. Paraoxonase activity was determined spectrophotometrically using phenyloacetate as substrate. Metabolic syndrome was recognized according to AHA/NHLBI criteria. In the whole group with dementia significant positive correlation between PON1 activity/HDL cholesterol ratio (i.e. HDL corrected PON1 activity) and insulin level as well as HOMA IR index, was observed. The multivariate analysis showed that the PON1/HDL-C ratio was also significantly positively associated with the presence of metabolic syndrome (with insulin resistance as a major underlying trait) both in dementia and in control group. High insulin level and HOMA-IR are considered to be the traits of insulin resistance. It has however to be taken into account that they both could also depend on insulin production and release which, as was recently stated in cell experiments, are enhanced by PON1. The observed positive correlation suggests an advantageous role of the enzyme in metabolic syndrome influence on dementia development.