LDL is oxidized to oxidized LDL (OxLDL) that is rapidly taken up by macrophages leading to coronary artery disease (CAD). Paraoxonase (PON), a HDL-bound polymorphic enzyme, lowers OxLDL level and thus prevents CAD. The PI hypothesizes that light drinking (13-40 g/day) increases serum PON level and thereby lowers OxLDL by preventing its formation or by destroying it and thus has a cardioprotective effect, whereas heavy drinking (>80 g/day) has the opposite effects. The PI has the following new data to support his hypothesis: 1. Sewn PON activity is increased 3.95-fold (p<0.0O1) in light drinkers, but decreased by 45 percent (p<0.001) in heavy drinkers compared to nondrinkers. 2. HDL-PON inhibited LDL oxidation that is prevented by prior incubation of HDL with either anti-POP4 or EDTA. 3. HDL-PON also destroyed OxLDL and inhibited OxLDL uptake by macrophages. 4. Hepatic PON mRNA relative to GAPDH mRNA is increased by 59 percent (p < 0.001) in light alcohol-fed and decreased by 51 percent (p < 0.001) in heavy alcohol-fed rats compared to controls. Therefore, the PI proposes to delineate the action of alcohol in causing diametrically opposite effects on PON and OxLDL status. Studies in humans: The PI will determine serum PON activity and protein in light, heavy and non-drinker without liver disease before and after 4- & 8-week abstinence and correlate with plasma oxidized LDI status and incidence of CAD by qualified cardiologists. The PI will test serum samples from each study group for their ability to (i) inhibit LDL oxidation (ii) destroy OxLDL and (iii) prevent OxLDL uptake by macrophages. The PI will also genotype PON genes in the study groups to correlate their susceptibility to light and heavy alcohol drinking. Finally, the PI will test whether light or heavy drinking up-regulated or down-regulates PON3 allozyme. Studies in rats: Since PON is expressed only in the liver (except PON3), molecular regulation of POT by alcohol can only be studied in an animal system like rat under well-defined conditions, the PI will determine the effects of ethanol dosage and duration of exposure on hepatic PON concentration and its mRNA level b Western Blot and Northern Blot analyses, respectively. The PI will then determine whether ethanol regulates PCI mRNA at transcriptional or post-transcriptional level by Nuclear-run-on and mRNA stability assays. These investigations are likely to lead to new insights in our understanding of the cardioprotective effects of Ugh drinking and proatherogenic effects of heavy drinking both at clinical and at molecular levels.
| Lakshman, M Raj; Gottipati, Chandra S; Narasimhan, Shivani J et al. (2006) Inverse correlation of serum paraoxonase and homocysteine thiolactonase activities and antioxidant capacity of high-density lipoprotein with the severity of cardiovascular disease in persons with type 2 diabetes mellitus. Metabolism 55:1201-6 |
