Paraoxonase 1 (PON1) is an arylesterase associated with serum high density lipoprotein particles. Its name is derived from hydrolyzing one of several organophosphate compounds, namely paraoxon. Recent studies have shown that PON1 plays a protective role in diseases associated with oxidative stress such as atherosclerosis and diabetes mellitus. Studies have demonstrated reduction-oxidative state changes involving PON1 in humans and laboratory animal models. Although there is less information about the role of this enzyme in veterinary medicine, new data suggest that PON1 might be a new oxidative stress marker in animal patients, similarly to humans.

The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no effect on photosynthetic CO2 assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions. In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity is needed for synthesis of carbon skeletons required as the acceptors for NH4+ assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and accumulation of Glu.

We investigated the measurement of paraoxonase 1 (PON1), as a potential marker of redox state changes in dairy cows, its involvement in lipid metabolism and compared it with superoxide dismutase (SOD) activity changes. We also evaluated lipid metabolism parameters associated with dairy production. PON1 paraoxonase and arylesterase acitvities, SOD activity, beta-hydroxybutyrate (BHB), uric acid (UA), high density lipoprotein (HDL), low density lipoprotein (LDL), cholesterol and triglyceride concentrations were measured in Holstein-Friesian, Polish Red and Norwegian breeds serum in two production cycles. Our data showed a significant postpartum depletion in PON1 activity and lipoprotein and lipid products concentrations, with elevated BHB values. However, there were no significant changes in SOD activity and uric acid concentrations in Holstein-Friesian and Polish Red breeds after calving. At lactation peak there was a significant SOD activity decrease correlated with standardized PON1 activity depletion in all examined breeds. The results suggest that PON1 might be a better parameter for minimal redox state changes in serum, shortly after labour in the examined breeds.

The objective of this study was to investigate paraoxonase-1 (PON-1) activity in different lactation stages. The study was conducted on Holstein -Friesian dairy cows in 2nd and 3rd lactation. A significant decrease in paraoxonase activity was found in the postpartum period and during peak of lactation. Serum triglyceride and cholesterol concentration were also markedly reduced during postpartum period. The concentrations of uric acid in serum was 23% higher during lactation peak in comparison with dry and postpartum period. The results indicate that lower serum paraoxonase activity and higher concentration of uric acid are associated with oxidative character of transition period and lipid functional antioxidative protection during intensive milk production.

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