Time-dependent modulation of rat serum paraoxonase 1 activity by fasting

Functionally defective high-density lipoprotein and paraoxonase: a couple for endothelial dysfunction in atherosclerosis

The endothelium is the primary target for biochemical or mechanical injuries caused by the putative risk factors of atherosclerosis. Endothelial dysfunction represents the ultimate link between atherosclerotic risk factors that promote atherosclerosis. HDL-C is thought to exert at least some parts of its antiatherogenic facilities via stimulating endothelial NO production, nearby inhibiting oxidative stress and inflammation. HDL-C is capable of opposing LDL's inductive effects and avoiding the ox-LDL's inhibition of eNOS. Paraoxonase 1 (PON1) is an HDL-associated enzyme esterase which appears to contribute to the antioxidant and antiatherosclerotic capabilities of HDL-C. "Healthy HDL," namely the particle that contains the active Paraoxonase 1, has the power to suppress the formation of oxidized lipids. "Dysfunctional HDL," on the contrary, has reduced Paraoxonase 1 enzyme activity and not only fails in its mission but also potentially leads to greater formation of oxidized lipids/lipoproteins to cause endothelial dysfunction. The association of HDL-C PON1 and endothelial dysfunction depends largely on the molecules with exact damaging effect on NO synthase coupling. Loss of nitric oxide bioavailability has a pivotal role in endothelial dysfunction preceding the appearance of atherosclerosis. Analyses of HDL-C and Paraoxonase1 would be more important in the diagnosis and treatment of atherosclerosis in the very near future.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Fasting status and thermally oxidized sunflower oil ingestion affect the intestinal antioxidant enzyme activity and gene expression of male Wistar rats

The effect of thermally oxidized sunflower oil ingestion on antioxidant levels, enzyme activities and expressions in the small intestine of fed and fasted rats was studied. For three consecutive days, 12 male Wistar rats received 0.5 g of unused sunflower oil/100 g of body weight (controls, C) while another 12 were given 0.5 g of thermally oxidized sunflower oil/100 g of body weight (test group, T). On the night of day 3, 6 rats from each group were fasted (FC and FT, respectively) while the other 6 animals from each group were given free access to food (NFC and NFT, respectively). On day 4, FC and NFC rats received 1 g of unused oil/100 g of body weight, while FT and NFT rats were given 1 g of altered oil/100 g of body weight. Small intestines were extracted after 4 h exposure to the oils. Fasting and oil alteration significantly interacted modifying total, Se-GPx (both, P < 0.001) and non-Se-GPx (P < 0.05) activity, and GPx and Cu,Zn-SOD expressions (both P < 0.001). FT rats showed a significant increase in TBARS (P < 0.05) and catalase activity (P < 0.001) and a decrease in SOD, Se- and non-Se-dependent GPx activities (at least, P < 0.05) with respect to FC and NFT animals. SOD and GPx expressions decreased (p<0.001) but that of TNFalpha increased significantly (P < 0.001) in FT rats with respect to FC and NFT animals. Lengthy fasting and consumption of food containing oxidized fat should both be avoided to prevent intestinal oxidative stress.

Gender related differences in paraoxonase 1 response to high-fat diet-induced oxidative stress

OBJECTIVE

To evaluate the influence of the pro-oxidant and proinflammatory state related to dietary obesity on serum paraoxonase 1 (PON1) activity in male and female rats.

METHODS AND PROCEDURES

Adult Wistar rats of both genders were fed on a high-fat diet to induce weight gain or standard diet for 14 weeks. Body weight was assessed weekly and food intake fortnightly throughout the dietary treatment. Biometrical parameters and serum lipid profile, glucose, insulin, and adipokine levels were measured. To assess the effect of dietary obesity on oxidative stress, levels of liver and serum thiobarbituric acid reactive substances, liver protein carbonyl groups, liver antioxidant enzymes activities, and serum PON1 activities were measured.

RESULTS

High-fat diet feeding induced a significant body weight gain in both male and female rats, as well as a reduction of liver antioxidant protection. High-fat diet increased serum lipid peroxides in male rats and reduced serum PON1 activities and serum apolipoprotein A-I (apoA-I) levels in females, although did not alter serum PON1 or apolipoprotein J (apoJ) levels.

DISCUSSION

Our results reveal a gender dimorphism in the high-fat diet-induced reduction of serum PON1 activity, which is likely to be related to the greater obese and proinflammatory state achieved in female rats. We suggest that the enhanced oxidative stress caused by dietary increased body weight, on leading to high-density lipoprotein (HDL), apoA-I or PON1 oxidation could entail the destabilization of the PON1 association to HDL or a direct inactivation of PON1 enzymatic activity, thus accounting for the decreased serum PON1 activities observed in female rats.