The Role And Related Mechanism Of Androgen In Left Ventricular Hypertrophy In Postmenopausal Hypertension Via MTOR/ P70S6K1/4EBP1 Pathway

Background: Left ventricular hypertrophy(LVH)is one of the major hypertension-mediated organ damage(HMOD)in hypertensive patients.Gender affects the formation and development of LVH.The incidence of LVH in postmenopausal women is much higher than that of premenopausal women and men in the same age group.The prevalence of hypertension and HMOD in postmenopausal women increase significantly,which is believed to be related to the change in the sex hormone axis in women after menopause.Direct and indirect clinical evidence suggests that androgen plays a key role in the risk of cardiovascular disease in both men and women.However,most current studies have focused on the relationship between serum total testosterone and blood pressure regulation in male patients.Studies on the role of bioavailable testosterone(Bio T)in postmenopausal hypertensive women with LVH have rarely been reported.Objective: The present study was designed to master the endogenous androgen levels in postmenopausal hypertensive women.On the other hand,we can provide a new predictor and theoretical basis for the prevention and treatment of HMOD in postmenopausal hypertension patients by exploring the correlation between androgen and LVH in postmenopausal hypertensive women.Methods: This study was designed as a cross-sectional study.A total of 609 postmenopausal women admitted to lanzhou University Second Hospital from December 2018 to December 2020 were included in this study,including 231 healthy postmenopausal women and 378 hypertensive postmenopausal women.According to the left ventricular mass index(LVMI)value assessed by echocardiography,postmenopausal hypertensive patients were divided into LVH group(LVMI>95 g/m2)and non-LVH group(LVMI?95 g/m2).Through 1:1 propensity score matching to balance the intergroup covariates of age and body mass index,160 healthy postmenopausal women and 320 postmenopausal hypertensive women(160 in the LVH group and 160 in the non-LVH group)were included in this study for final analysis.The general information(age,education level),lifestyle(smoking and drinking),family history of hypertension and the use of antihypertensive drugs were collected through questionnaires.Physical examination included measurement of height,weight and waist circumference.Total triglyceride,total cholesterol(TC),low density lipoprotein cholesterol,serum creatinine and blood urea nitrogen were measured by automatic clinical analyzer.The electrochemiluminescence analysis system was used to detect steroid sex hormones.Mammalian target of rapamycin(m TOR),p70 ribosome S6 protein kinase(p70S6K),sex hormone binding globulin(SHBG)and androgen receptor were detected by enzyme-linked immunosorbent assay.The portable cuff type ambulatory blood pressure automatic recording system(MOBIL,Mobil-O-Graph NG)was used to measure and record the 24 h BP.After correcting for confounding factors by various models,multivariable logistic regression was used to evaluate the influencing factors of LVH in postmenopausal women with hypertension.Multivariable linear regression assessed the association between LVMI and FAI and SHBG in postmenopausal hypertensive patients.In addition,possible associations between LVH and free androgen index(FAI)and SHBG in postmenopausal hypertensive women with controlled and uncontrolled blood pressure were also assessed by subgroup analysis.Data were analyzed using R and SPSS25.0 statistical software.Results: This set of data found: The rates of antihypertensive drugs(?-blockers,calcium channel antagonists,and diuretics)were significantly different among the three groups of postmenopausal women(P<0.05);The utilization rate of angiotensin-converting enzyme inhibitors and angiotensin receptor blocker of antihypertensive drugs in non-LVH group was significantly higher than that in LVH group(ACEI 24% vs 13%,ARB 53% vs 38%,P<0.05);Compared with the non-LVH group,the LVH group had a larger proportion of family history of hypertension(36%vs 22%,P<0.05).The levels of TT,free testosterone,Bio T,FAI,TC and m TOR in postmenopausal women were statistically different among the three groups(P<0.05);The levels of free testosterone,Bio T,FAI,TC,m TOR and p70S6 K in LVH group were higher than those in non-LVH group(P<0.05);The level of SHBG in LVH group was lower than that in non-LVH group(P<0.05);No statistical differences in prolactin,follicle stimulating hormone,luteinizing hormone,estradiol and progesterone levels were observed among the three groups(P>0.05).The diastolic interventricular septal thickness,diastolic left ventricular posterior wall thickness and relative ventricular wall thickness in LVH group were higher than those in non-LVH group(P<0.05);The 24 hour mean systolic blood pressure(SBP),24 hour mean diastolic blood pressure(DBP),24 hour SBP load and 24 hour DBP load in LVH group were higher than those in non-LVH group(P<0.05);Compared with the LVH group,the spoon-type blood pressure of the non-LVH group accounted for a higher proportion,while the anti-spoon-type blood pressure accounted for a lower proportion in the non-LVH group(P<0.05);The arteriosclerosis index in LVH group was significantly higher than that in non-LVH group(P<0.05).After correcting for confounding factors by various models,the influence of related serological indicators on LVH in 320 postmenopausal women with hypertension was further investigated.FAI and SHBG were found to be the influencing factors of LVH in postmenopausal women with hypertension.Patients with elevated SHBG were 5% less likely to develop LVH than those without elevated SHBG(OR: 0.950,95% CI 0.922-1.578).Postmenopausal hypertensive patients with elevated FAI were 16% more likely to have LVH than those without elevated FAI(OR:1.608,95% CI 0.807-3.202)To further explore the correlation between LVMI and FAI and SHBG in postmenopausal hypertensive patients,it was found that LVMI increased by61.82g/m2 for every 1 unit increase in FAI.In addition,SHBG decreased by 1 nmol/l,and LVMI increased by 0.177g/m2 after adjusting for confounding factors(family history of hypertension,antihypertensive drug use(ACEI and ARB),TC,24-hour mean systolic/diastolic blood pressure,24-hour systolic/diastolic load,and 24-hour systolic/diastolic variability).A subgroup analysis of 320 postmenopausal women with hypertension yielded the following results:(1)patients in the controlled BP group had a lower risk of LVH for every additional unit of SHBG compared with the uncontrolled BP group(OR0.987 vs 0.844);(2)The risk of LVH for each additional unit of FAI in the uncontrolled BP group was higher than that in the controlled BP group(OR 4.054 vs3.913).Conclusion: FAI and SHBG are one of the influencing factors of LVH in postmenopausal hypertensive women.The risk of LVH in postmenopausal hypertensive women is increased with increased FAI levels and decreased with decreased SHBG levels.Early detection of FAI and SHBG levels has certain clinical significance in evaluating the incidence of LVH postmenopausal women with hypertension.Background: Left ventricular hypertrophy(LVH)is one of the most important manifestations of hypertension-mediated target organ damage.The prevalence of hypertension and LVH in postmenopausal women was significantly higher than that in men of the same age.The occurrence of LVH in postmenopausal hypertension patients is closely associated with the changes of sex hormone axis in postmenopausal women.However,a number of clinical studies have confirmed that it is not enough to explain the occurrence of postmenopausal hypertension and heart damage from a single estrogen reduction.The previous clinical and experimental results of our team have confirmed that testosterone levels in postmenopausal women or aged female spontaneously hypertensive rats(SHR)are increased,and testosterone plays a potential role in postmenopausal hypertension and target organ damage.Signaling transduction of the mammalian rapamycin receptor(m TOR)pathway is one of the important regulators of normal cardiac growth and pathological hypertrophy,and thus has the potential as a drug therapeutic target.Therefore,we hypothesize that the m TOR signaling pathway is involved in LVH in ovariectomized(OVX)SHR,and further demonstrate that rapamycin blocks the m TOR pathway to delay cardiomyocyte hypertrophy on the basis of antihypertensive therapy.Objective: This study was designed to explore the role of testosterone in SHR cardiac hypertrophy after OVX and demonstrate that the mechanism may be related to activation of the m TOR pathway.This study also explored whether the m TOR inhibitor rapamycin can delay the development of SHR cardiac hypertrophy after ovariectomy,thus confirming its further therapeutic effect on this type of hypertensive cardiac hypertrophy on the basis of antihypertensive therapy.Methods: This study was performed using in vivo experiments.We designed two phased experimental studies.The experimental contents were as follows:experiment 1: female Wistar-Kyoto(WKY)rats were used as control group,and female SHR(200±12g)were randomly divided into 4 groups with 10 rats in each group:(1)WKY group;(2)sham-operated group;(3)OVX group;(4)OVX+estrogen group;(5)OVX+ estrogen + testosterone group(estrogen: 9.6 mg/kg/day,ig;testosterone:2.85 mg/kg/weekly,im).experiment 2: according to the experimental model of group 5(OVX+ E + T)in the first stage experiment,the model was made again and randomly divided into five groups for three weeks of intervention according to previous studies and pre-experimental results: 1)low-dose group(chlorthalidone8mg/kg/day,ig + rapamycin 0.8mg/kg/day,ip);(2)medium-dose group(chlorthalidone 8mg/kg/day,ig + rapamycin 1.5mg/kg/day,ip);(3)high-dose group(chlorthalidone 8mg/kg/day,ig + rapamycin 2mg/kg/day,ip);(4)chlorthalidone group(8mg/kg/day,ig);(5)vehicle group(2mg/kg/day,ip).Successful molded rats were selected based on serial vaginal smear results after ovariectomy.The rat tail artery pressure was measured at the same time every week.Cardiac structure and function were evaluated by echocardiography after drug intervention.Serum estrogen and testosterone levels were determined by enzyme-linked immunosorbent assay.Cross-section area and diameter of left ventricular cardiomyocytes were determined by wheat germ agglutinin(WGA)staining.The m RNA content of m TORC1,p70 ribosomal S6 kinase(p70S6K1),4E binding protein 1(4EBP1),atrial natriuretic peptide(ANP),?-myosin heavy chain(?-MHC),matrix metalloproteinase9(MMP-9)and tissue inhibitor of metalloproteinase1(TIMP-1)were measured by real-time quantitative PCR(RT-q PCR).Protein content of the m TORC1,p70S6k1,4EBP1 and eukaryotic translation initiation factor 4E(e IF4E)was assessed by western blot(WB).The statistical analysis was performed using SPSS22.0 statistical software.Results: Testosterone induced the development of LVH in OVX female SHR:the serum testosterone level,heart weight index and heart weight/tibial length ratio in OVX+ estrogen + testosterone group were higher than those in WKY,sham,OVX and OVX+ estrogen groups(P<0.05).There were no differences in BP levels between rats prior to drug intervention(P>0.05).Systolic and diastolic blood pressure levels were both higher in the OVX+ estrogen + testosterone group than in the OVX+ estrogen group at the end of day 30(P<0.05).The levels of diastolic interventricular septal thickness(IVS),left ventricular posterior wall thickness(LVPWT)and left ventricular mass(LVM)in the testosterone intervention group were higher than those in the other four groups(P<0.05).WGA staining test results showed that the cross-sectional area and diameter of cardiomyocytes increased significantly in OVX+ estrogen +testosterone group(P<0.05).The results of WB found that OVX increased the expression levels of m TOR,4EBP1 and eukaryotic translation initiation factor 4E(e IF4E)proteins compared with Sham group,and further increased under the intervention of testosterone(P<0.05).The RT-q PCR results showed that estrogen alone can reduce the m RNA expression of ANP and ?-MHC in OVX SHR myocardial tissue(P<0.05).Compared with the other four groups,the m RNA expression levels of ANP,?-MHC and MMP-9 in myocardial tissue of the OVX+ estrogen+ testosterone group increased(P<0.05),and the expression level of TIMP-1 decreased(P<0.05).On the basis of antihypertensive therapy,the m TORC1 inhibitor rapamycin further delayed testosterone-induced OVX female SHR LVH: heart weight index,and heart weight/tibial length ratio in the high-dose group were lower than those in the low-dose and medium-dose groups(P<0.05).Systolic blood pressure levels were lower in the high-dose group than in the low-dose and medium-dose groups at day 14 and day 21,respectively(P<0.05).The diastolic IVS,LVPWT and LVM in the high-dose group were lower than those in the low-dose and medium-dose groups(P<0.05).There was a difference in LVM between the low-dose group and the medium-dose group(P<0.05).WGA staining results showed that the cross-sectional area and diameter of cardiomyocytes in the high-dose group were lower than those of the other four groups(P<0.05).The expression levels of m TOR,p70S6K1,4EBP1 and e IF4 E protein in the myocardial tissue of the high-dose group were lower than those of the low-dose group and the middle-dose group(P<0.05).The expression levels of m TOR,p70S6K1,4EBP1 and e IF4 E protein in the medium-dose group were reduced compared with the low-dose group(P<0.05).RT-q PCR results showed that the m RNA expression levels of m TOR,p70S6K1,4EBP1,e IF4 E and MMP-9 were lower in the high-dose group(P<0.05),the m RNA expression of TIMP-9 increased(P<0.05).Conclusion: The regulation of m TOR/p70S6K1/4EBP1 signaling pathway may be one of the important mechanisms for the occurrence of myocardial hypertrophy in testosterone induced OVX SHR.Rapamycin specifically identifies and blocks testosterone induced OVX SHR myocardial hypertrophy through m TOR signaling pathway.Therefore,on the basis of antihypertensive therapy,m TOR inhibitors may provide a new therapeutic candidate for delaying myocardial remodeling and cardiac insufficiency in postmenopausal hypertensive women.Hypertension is one of the major risk factor for all-cause morbidity and mortality worldwide and is associated with an increased risk of cardiovascular disease.Hypertension affects over 1.2 billion individuals worldwide and has become the most critical and expensive public health problem.There were gender differences in the prevalence of hypertension in different age groups.The prevalence of hypertension in women is lower than in men until the age of 50,while the prevalence of hypertension in women begins to rise after menopause and gradually exceeds that of men after 70 years of age.The reason for the above phenomenon is related to the disorder of sex hormone levels after menopause.Estrogens are hormones steroids that play a key role in the pathophysiological regulation of target organs through binding to their receptors.The decrease in estrogen levels after menopause may lead to an increased prevalence of hypertension.In addition to estrogen,androgens are currently considered to play a key role in the risk of cardiovascular disease in women and men.The effect of androgens as dominant hormones in men has been fully established.However,the role of androgens and their receptors in hypertension in women remains controversial.Based on the above analysis,this article summarizes the relationship between androgens and their receptors and hypertension in the female population.