Measurement of serum paraoxonase-1 activity in the evaluation of liver function

Abstract

Paraoxonase-1 (PON1) is an esterase and lactonase synthesized by the liver and found in the circulation associated with high-density lipoproteins. The physiological function of PON1 seems to be to degrade specific oxidized cholesteryl esters and oxidized phospholipids in lipoproteins and cell membranes. PON1 is, therefore, an antioxidant enzyme. Alterations in circulating PON1 levels have been reported in a variety of diseases involving oxidative stress including chronic liver diseases. Measurement of serum PON1 activity has been proposed as a potential test for the evaluation of liver function. However, this measurement is still restricted to research and has not been extensively applied in routine clinical chemistry laboratories. The reason for this restriction is due to the problem that the substrate commonly used for PON1 measurement, paraoxon, is toxic and unstable. The recent development of new assays with non-toxic substrates makes this proposal closer to a practical development. The present editorial summarizes PON1 biochemistry and function, its involvement with chronic liver impairment, and some aspects related to the measurement of PON1 activity in circulation.

Investigation of the possible protective role of gallic acid on paraoxanase and arylesterase activities in livers of rats with acute alcohol intoxication

“…In chronic liver diseases, oxidative stress is one of the causes of the pathophysiological changes leading to liver cirrhosis and to hepatocellular carcinoma. Because PON 1 has a protective effect against oxidative stress, it is expected that there is a relationship between this enzyme and liver injury . In all the ethanol consumption groups of our study, paraoxonase levels were significantly decreased as compared with control group.…”

“…Because PON 1 has a protective effect against oxidative stress, it is expected that there is a relationship between this enzyme and liver injury. 16 In all the ethanol consumption groups of our study, paraoxonase levels were significantly decreased as compared with control group. Previous studies showed that heavy alcohol feeding in rats significantly reduces both serum and liver paraoxonase activities with a corresponding down-regulation of paraoxonase mRNA in the liver.…”

Serum paraoxonase-1 as biomarker for improved diagnosis of fatty liver in dairy cows

“…Secondly, the interpretation of the physiological significance of a measurement conducted with such an unnatural substrates is questionable. In addition, the enzyme’s activity on paraoxon is strongly influenced by the PON1 192 genetic polymorphism (which is not well studied in bovine) [24]. Recent significant advances in the search for reliable PON1 lactonase activity assays may facilitate the measurement in a routine clinical chemistry laboratory setting [25].…”

Hypercholesterolaemia, signs of islet microangiopathy and altered angiogenesis precede onset of type 2 diabetes in the Goto–Kakizaki (GK) rat

“…In addition, inhibition of liver PON-1 activity is an early biochemical change linked to increased lipid peroxidation and liver damage [34]. Notably, oxysterols increase total liver peroxides, IL-8 and CC-chemokine ligand-2 (CCL2) [35].…”