Association of serum paraoxonase activity with lipid profile, APO-A and APO-B in subjects with different levels of HDL

Importance of Polymorphisms in the Gene of Paraoxonase-1 (SNP rs662) and Apolipoprotein A-I (SNP rs670 and rs5069) in Non-Smoking and Smoking Healthy Subjects and Patients with Acute Pancreatitis

Oxidative stress has been implicated in the initiation of acute pancreatitis (AP). HDL is considered to be a preventing factor against cell membrane oxidation, thanks to the presence on its surface of apolipoprotein A-I (apoA-I) and paraoxonase-1 (PON1), which activity can be modified by genetic and environmental factors. The impact of SNP rs662 in the PON1 gene and SNP rs670 and rs5069 in the APOAI gene on PON1 activities and its concentration in the population of AP patients and healthy volunteers was investigated. In the group of patients with AP, a decreased HDL concentration and PON1 activities were observed. A decrease in the aryloesterase and lactonase activities of PON1 in AP patients with the TT genotype for SNP rs662 (especially in smokers) was found. In the group of patients with the AA genotype (rs670), the highest concentrations of HDL and apoA-I were observed, which were gradually decreasing in the course of AP. Changes in the concentration of apoA-I were associated with the changes in the concentration and activities of PON1 in the AP patients with the AA genotype for SNP rs670. A decreasing apoA-I concentration contributing to lowering PON1 concentration and its activities during the hospitalization of AP patients with the CC genotype for SNP rs5069 were shown. Therefore, more susceptibility of persons with the CC genotype for SNP rs5069 to pro/antioxidative imbalance was shown. In this process, an important role was played by the HDL level and its interaction with PON1 and apoA-I.

In vivo/in silico insight into the effect of titanium dioxide nanoparticle on serum paraoxonase 1 activity in rat

Serum paraoxonase1 (PON1) has special function in human body organism including the antioxidant and anti-atherogenic properties. In the present study, the effect of TiO₂ nanoparticles on the activity and structure of the PON1 has been evaluated through in vivo and in silico methods. After treatments of the rats with different doses of TiO₂ NPs, blood samples were collected and serum PON1 activity was measured by phenylacetate and paraoxon as substrate. In addition, the effects of TiO₂ NP on enzyme structure were analyzed through Molecular dynamic (MD) simulation via Gromacs software package to obtain RMSD, RMSF, Rg, SASA, and secondary structures values. A significant reduction (p < 0.05) in arylesterase & paraoxonase activities of serum PON1 were monitored in Spectrometric assays when rats were treated with 150 and 200 mg/kg doses of TiO₂ NPs. RMSD, RG, RMSF, and SASA values in the presence of TiO₂ have been increased while RMSF values of the L1 and L2 loops (gate of the catalytic site) have been reduced. Moreover, Hydrogen bonds and secondary structure values of the enzyme decreased in the presence of TiO₂ NP. All of these MD simulation results could indicate the instability of the PON1 structure bounded to TiO₂ NP. TiO₂ NP could cause a disturbance in the enzyme structure and function of PON1 based on the results. PON1 prevents oxidation of LDL and can delay atherosclerosis progression while in the presence of TiO₂ NP these protective effects could be endangered.Communicated by Ramaswamy H. Sarma.

Pollutants and nutrition: Are methylmercury effects on blood pressure and lipoprotein profile comparable to high-fat diet in mice?

Human exposure to methylmercury (MeHg) due to contaminated fish intake as part of a high-fat (HFD), high-carbohydrate diets is a reality today for many populations. HFD is associated with hypertension and hyperlipidemia, primary cardiovascular disease (CVD) risk factors. Some studies suggest that MeHg induces those risk factors. We evaluated the effect of MeHg exposure in mice fed with HFD or control diet for eight weeks. In the last experimental 15 days, the half group received a MeHg solution (20 mg/L) replacing water. Blood pressure (BP), heart rate, lipoprotein concentrations, and paraoxonase activity were evaluated. Liver cholesterol, triacylglycerol, and IBA-1+ cells, as well as transcriptional levels of genes related to lipid metabolism and inflammatory response, were also assessed. HFD and both MeHg groups presented increased BP and total cholesterol (TC). In the liver, HFD but not MeHg was related to an increase in TC. Also, MeHg intoxication reduced paraoxonase activity regardless of diet. MeHg intoxication and HFD increased steatosis and the number of IBA-1+ cells and modified some gene transcripts associated with lipid metabolism. In conclusion, we demonstrated that MeHg effects on CVD risk factors resemble those caused by HFD.

Prolonged bedrest reduces plasma high-density lipoprotein levels linked to markedly suppressed cholesterol efflux capacity

Recent observations strongly connect high-density lipoproteins (HDL) function and levels with coronary heart disease outcomes and risk for infections and sepsis. To date, our knowledge of factors determining this connection is still very limited. The immobility associated with prolonged bedrest is detrimental to health, affecting several systems, including the cardiovascular, pulmonary, gastrointestinal, musculoskeletal and urinary. Effects of prolonged bedrest on the composition and functional properties of HDL remain elusive. We evaluated metrics of HDL composition and function in healthy male volunteers participating in a randomized, crossover head-down bedrest study. We observed that HDL cholesterol efflux capacity was profoundly decreased during bedrest, mediated by a bedrest associated reduction in plasma levels of HDL-cholesterol and major apolipoproteins (apo) apoA-I and apoA-II. Paraoxonase activity, plasma anti-oxidative capacity and the activities of lecithin-cholesterol acyltransferase and cholesteryl ester transfer protein were not affected. No change was observed in the content of HDL-associated serum amyloid A, a sensitive marker of inflammation. Resistive vibration exercise countermeasure during bedrest did not correct impaired cholesterol efflux capacity and only tended to increase arylesterase activity of HDL-associated paraoxonase. In conclusion, prolonged bedrest reduces plasma HDL levels linked to markedly suppressed HDL cholesterol efflux capacity. Resistive vibration exercise during bedrest did not correct HDL levels and impaired cholesterol efflux capacity.