Correlation Between Menopausal Age And Epigenetics

Part I Repetitive element DNA methylation associated with menopausal ageObjective: To investigate associations between age of menopause and the DNA methylation levels of two repetitive elements,Alu and LINE-1.Methods: We performed plasma DNA extraction on 161 subjects and serum cell-free DNA extraction on 120 subjects.We grouped women by menopausal age as follows: ≤ 48 years(earlier menopause),≥ 52 years(later menopause),and 48-52 years(control).Methylation of Alu and LINE-1 was measured by Methy Light PCR.Results: The results showed that DNA methylation of both Alu and LINE-1 was inversely correlated with menopausal age in the plasma DNA cohort(r = 0.079,P < 0.001 for Alu;r = 0.045,P = 0.007 for LINE-1)as well as in the serum DNA cohort(r = 0.087,P = 0.001 for Alu;r = 0.041,P = 0.026 for LINE-1).Alu methylation in both the plasma and serum DNA cohorts and LINE-1 methylation in the plasma cohort were remarkably higher in the earlier menopause group than in the later menopause and control groups(P < 0.01 and P < 0.05,respectively).In the serum DNA cohort,LINE-1 methylation in the later menopause group was significantly lower than that in the earlier menopause group and control group(P < 0.05).Conclusion: Methylation levels of Alu and LINE-1 were significantly associated with menopausal age.Women with earlier menopause showed hypermethylation in both repetitive elements,while women with later menopause showed hypomethylation.These findings suggest that altered DNA methylation in leukocytes and serum cell-free DNA may represent a biomarker of menopausal age.Part II Correlation between SCD1 methylation and menopausal ageObjective: To investigate associations between age of menopause and the DNA methylation levels of SCD1.Methods: We performed subcutaneous adipose tissue DNA extraction on 85 subjects.We grouped women by menopausal age as follows: ≤ 48 years(earlier menopause),≥ 52 years(later menopause),and 48-52 years(control).Methylation of SCD1 was measured by Methy Light PCR.Results: The results showed that DNA methylation of SCD1 was inversely correlated with menopausal age(r = 0.370,P < 0.001).SCD1 methylation was remarkably higher in the earlier menopause group than in the later menopause and control groups(P < 0.001,respectively).And in the later menopause group,SCD1 methylation was significantly lower than that in control group(P = 0.027).Conclusion: Methylation levels of SCD1 were significantly associated with menopausal age.Women with earlier menopause showed hypermethylation,while women with later menopause showed hypomethylation.These findings suggest that altered DNA methylation in subcutaneous adipose tissue DNA may represent a biomarker of menopausal age.Part III Effects of estrogen replacement therapy on the expression of SCD1 and DNMTs in ovariectomized ratsObjective: To explore the changes of SCD1 and DNMTs m RNA levels after ovariectomy and estrogen replacement therapy.Methods: We established a rat model of menopause(OVE group)and estrogen replacement therapy(OVE+E2 group),and sham operation as control group.ELISA kit was used to detect the levels of estradiol(E2)and follicle stimulating hormone(FSH).The expression levels of SCD1,DNMT1,DNMT3 A and DNMT3 B m RNA were determined by real-time fluorescent quantitative PCR.Results: The weight gain of OVE group was significantly higher than that of OVE+E2 group and control group(P < 0.001),and the weight of OVE+E2 group was also higher than that of control group(P < 0.001).The serum level of FSH in OVE group was significantly higher than that of OVE+E2 group and control group(P < 0.001),and serum E2 level in OVE group was significantly lower than that of OVE+E2 group and control group(P < 0.001).However,there was no significant difference in serum FSH and E2 levels between OVE+E2 group and control group(P > 0.05).Compared with control group,the m RNA levels of SCD1 and DNMT1 in OVE group significantly increased,while that of DNMT3 A and DNMT3 B decreased(all P < 0.01).However,the m RNA levels of SCD1 significantly decreased(P < 0.001)and that of DNMT1(P = 0.024),DNMT3A(P < 0.001),DNMT3B(P < 0.001)increased in OVE+E2 group compared with control group.There was significant differences between OVE+E2 group and OVE group(all P < 0.01).Conclusion: From the changes of m RNA levels,we infer that DNMT3 A and DNMT3 B may be involved in the methylation of SCD1.Considering the effect of estrogen replacement therapy,we believe that estrogen involved in the epigenetic processes of lipid metabolism,and SCD1 gene may be one of the important factors.