Gender Differences And Mechanisms In H.pylori-induced Atherosclerosis

BackgroundThe role of Helicobacter pylori（H.pylori）infection in atherosclerosis is inconsistent and sometimes controversial.Substantial sex differences exist in cardiovascular diseases（CVDs）including atherosclerosis.Reactive oxygen species（ROS）and endothelial dysfunction play critical roles in atherosclerosis.The present study was to test the hypothesis that H.pylori infection was associated with carotid atherosclerosis,and promotes atherosclerosis development selectively in male mice through ROS-induced endothelial dysfunction.Gut microorganisms significantly contribute to atherosclerosis development and related CVDs.Helicobacter pylori（H.pylori）is a gram-negative bacterium that colonizes gastric epithelium in a significant portion of the global population.Population studies have indicated that H.pylori infection is independently associated with the development of atherosclerosis.A meta-analysis with 19,691 study subjects showed that H.pylori infection increased the risk of adverse cardiovascular events by51%,mostly due to myocardial infarction and cerebrovascular disease.A recent study with 208,196 patients revealed a significant decrease in composite endpoints for CAD and death for younger patients（<65 years old）with early H.pylori eradication therapy,but not for older patients（≥65 years old）or control subjects.However,the association of H.pylori infection and carotid atherosclerosis in Chinese patients has not been defined in an adequate sample size and how H.pylori infection could lead to atherosclerosis only in younger males remains unknown.Superoxide dismutases（SODs）,glutathione peroxidase（Gpx）,and catalase are important antioxidant enzymes that could decrease ROS production and prevent oxidative stress-induced cell damage.A recent study indicated that H.pylori infection could lead to inflammation and increased systemic ROS production in the vascular wall.However,differences between males and females and potential mechanism（s）remains unknown.The present study was therefore designed to test the hypotheses that H.pylori infection induces endothelial dysfunction and atherosclerosis selectively in male but not in female mice through increased ROS production via decreased expression of antioxidant enzymes.The objectives were:1)to determine if there were significant sex differences in endothelial dysfunction and atherosclerosis with H pylori infection;2)to define the role of ROS in sex differences in endothelial dysfunction with H.pylori infection;and 3)to determine the role of antioxidant enzymes in H pylori infection-induced ROS production and atherosclerosis in male mice.ObjectivesThe present study aimed to determine if H.pylori infection was associated with carotid atherosclerosis,and to test the hypothesis that H.pylori infection promotes atherosclerosis development selectively in male through ROS-induced endothelial dysfunction.MethodsTo determine if H.pylori infection was associated with carotid atherosclerosis,17,613 males and females with both carotid ultrasonic examination and 13C-urea breath test for H.pylori infection were screened from a major Chinese university hospital from March 2012-March 2017for the study.Baseline demographics,cardiac risk factors,and laboratory studies were obtained.After exclusion for pre-specified conditions,12,836individuals were included in the analysis,including 8,157 men（63.5%）and4,679 women（36.5%）.Analysis was also made from 5-years follow-up data for 1,216 subjects（869 males and 347 females）with and without H.pylori infection for development and progression of carotid atherosclerosis.To test the hypothesis that H.pylori infection promotes atherosclerosis development selectively in male through ROS-induced endothelial dysfunction.Age-matched male and female C57BL/6 mice and LDLR^-/-mice were infected with Cag A⁺H.pylori.ROS production,endothelial function and atherosclerosis were measured in Cag A⁺H.pylori and PBS infected mice.Protein expression of GPx,catalase,SOD-1 was evaluated using Western blot analysis.TG⁺/LDLR^-/-mice were generated to determine if overexpression of SOD1 and GPx could prevent H.pylori infection-induced ROS production and atherosclerosis.Results1.After adjusting for age,sex,body mass index,lipid profile,hypertension,renal function,diabetes mellitus,and smoking,H.pylori infection was found as an independent risk factor for carotid atherosclerosis in males under 50 years old,but not in older males or females（odds ratio 1.229,95%CI 1.054-1.434,p=0.009）.Follow-up data analysis showed that the incidence of carotid atherosclerosis from no atherosclerosis to detectable lesions was significantly higher in young males with persistent H.pylori infection than those without H.pylori infection（p=0.028）after 3 years.2.H.pylori infection attenuated acetylcholine（ACh）-induced endothelium-dependent aortic relaxation,and enhanced early atherosclerosis formation in male but not in female mice,associated with increased ROS formation compared with controls.Antioxidant enzymes SOD1 and GPx significant decreased in H.pylori-infected male but not female C57BL/6 mice,compared with controls.N-acetylcysteine treatment effectively prevented H.pylori infection-induced ROS production,and preserved ACh-induced aortic relaxation in male C57BL/6 mice.Concomitant overexpression of SOD1,SOD3 and GPx effectively attenuated excessive aortic ROS formation and atherosclerosis in male LDLR^-/-mice with H.pylori infection on a high fat diet.ConclusionThese data suggested that:1.H.pylori infection might be an important risk factor for carotid atherosclerosis in young Chinese males under 50;2.H.pylori infection selectively impairs endothelial function and promotes atherosclerosis through ROS production in male mice due to decreased expression of SOD1 and GPx.