Epigenetic Loci of Blood Pressure.

HomeCirculation: Genomic and Precision MedicineVol. 12, No. 1Epigenetic Loci of Blood Pressure Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessReview ArticlePDF/EPUBEpigenetic Loci of Blood PressureUnderlying Hemodynamics in Adolescents and Adults Catriona Syme, PhD, Jean Shin, PhD, Louis Richer, PhD, Daniel Gaudet, MD, PhD, Myriam Fornage, PhD, Tomas Paus, MD, PhD and Zdenka Pausova, MD Catriona SymeCatriona Syme The Hospital for Sick Children (C.S., J.S., Z.P.) Departments of Physiology and Nutritional Sciences (C.S., J.S., Z.P.) *Drs Syme and Shin are joint first authors Search for more papers by this author , Jean ShinJean Shin The Hospital for Sick Children (C.S., J.S., Z.P.) Departments of Physiology and Nutritional Sciences (C.S., J.S., Z.P.) *Drs Syme and Shin are joint first authors Search for more papers by this author , Louis RicherLouis Richer Department of Health Sciences, Université du Québec à Chicoutimi, Canada (L.R.). Search for more papers by this author , Daniel GaudetDaniel Gaudet Community Genomic Centre, Université de Montréal, Chicoutimi, Canada (D.G.) Search for more papers by this author , Myriam FornageMyriam Fornage University of Texas Health Science Center at Houston (M.F.). Search for more papers by this author , Tomas PausTomas Paus Departments of Psychology and Psychiatry, University of Toronto, Canada (T.P.). Bloorview Research Institute, Toronto, Canada (T.P.). Search for more papers by this author and Zdenka PausovaZdenka Pausova Zdenka Pausova, MD, The Hospital For Sick Children Departments of Physiology and Nutritional Sciences, University of Toronto, Peter Gilgan Centre for Research and Learning, 686 Bay St, 10–9705, Toronto, ON M5G 0A4, Canada. Email E-mail Address: [email protected] The Hospital for Sick Children (C.S., J.S., Z.P.) Departments of Physiology and Nutritional Sciences (C.S., J.S., Z.P.) Search for more papers by this author Originally published15 Jan 2019https://doi.org/10.1161/CIRCGEN.118.002341Circulation: Genomic and Precision Medicine. 2019;12:e002341High blood pressure (BP) is the strongest modifiable risk factor of cardiovascular disease worldwide. BP increases because of an increase in ≥1 of 3 hemodynamic factors: stroke volume (SV), total peripheral resistance (TPR), and heart rate. Hemodynamics changes during life: during adolescence, for example, growing body mass—and an elongating arterial path and larger vessels—leads to decreased heart rate and TPR and increased SV to sustain tissue perfusion.1,2Epigenetic studies of DNA methylation (DNAm) can reveal novel mechanistic pathways of complex traits, such as BP.3 DNAm, most commonly the addition of a methyl group to cytosines in CpG dinucleotides (CpGs), modulates gene expression through local and chromatin-organization effects.4 Variations in DNAm are determined genetically but may also arise cotranscriptionally in genes (and their regulatory elements) responding to external and internal environments.4,5Recently, a meta-EWAS (meta-epigenome wide association study) of BP performed in ≈17 000 adults identified 13 differentially methylated CpGs.3 Here, we examined these CpGs for associations with BP and underlying hemodynamics in 135 adolescents (12–19 years, 50% female) and 110 middle-aged adults (38–62 years, 58% females) from the Saguenay Youth Study.6 Systolic BP, diastolic BP, SV, TPR, and heart rate were assessed beat-by-beat with a Finometer during a 52-min protocol mimicking daily-life activities, including changes in posture and mental stress (Figure). DNAm was assessed in genomic DNA extracted from peripheral blood cells using the Infinium HumanMethylation450K BeadChip. Phenotyping preceded epityping by 1 month in adolescents and followed epityping by 3 years in adults. Adolescents and adults were epityped in different batches.Download figureDownload PowerPointFigure. Associations of the studied CpG dinucleotides (CpGs) with blood pressure (BP) and BP hemodynamics in adolescents and adults. A, A recent meta-EWAS3 (meta-epigenome wide association study) identified 13 CpGs associated with BP. Here, we estimated associations of DNA methylation (DNAm) with systolic BP (SBP) or diastolic BP (DBP) in a pooled sample of adolescents and adults (N=245) to derive comparable estimates of association at these same 13 CpGs, using the model: . DNAm was adjusted for technical batch effects and blood-cell proportions, and BP was averaged across the 52-min cardiovascular protocol. Y axes indicate the magnitude of association given by the change in DNAm for 1 mm Hg increase in BP. Turquoise lines show magnitude of associations reported in Richard et al.3 Pooled data included families; thus, we used a hierarchical bootstrap approach for CIs of the estimates (Shin et al.10). In addition, we took into account correlation structure within an individual’s measurements by drawing each bootstrap sample based on the participant’s identifier so that all or none of the participant’s data appear in each bootstrap sample. The 95% CI were constructed based on the 2.5th and 97.5th percentiles of the distribution with 5000 replicates. Estimates and CIs are shown for this basic model [1], and after excluding individuals taking antihypertensive medication (0 adolescents and 9 adults), and adjusting for current smoking (yes/no) or for body weight. Analyzing statistical significance required a change to the model to leverage our repeated measures of BP (BPRM). Thus, we tested the associations of BPRM with DNAm (adjusted as above and additionally transformed with a rank-based inverse-normal transformation [INT]) using a linear mixed-effects model with a nested random effect (participant ID within family ID) to incorporate family relatedness and repeated measurements and the autoregressive order 1 covariance structure: . Closed rectangles: P<0.05; red stars: P<0.05/26 (Bonferroni-corrected significance for 13 CpGs×2 BP variables). B, 1-min means of SBP, DBP, stroke volume (SV), total peripheral resistance (TPR), and heart rate (HR) across the 52-min protocol that included changes in posture (10-min each supine and standing, then sitting for duration) and mental stress (2-min math test preceded by 40-s explanation) in adolescents (n=135) and adults (n=110). C, For each of the 3 Bonferroni-significant CpGs from (A), left: estimates of DNAm associations with mean hemodynamic variables using [1] in the pooled sample, adolescents only, and adults only (turquoise lines show magnitude of associations reported [in adults] in Richard et al.3); right: estimates for associations of SBP, DBP, SV, TPR, and HR at each min of protocol (Ytime) with DNAm in adolescents and adults, separately, by fitting (at each time point): Correlations of repeated measures of hemodynamics for each individual were considered using the bootstrap approach described above (95% CIs [shaded bands]). Additionally, we performed likelihood tests, using mixed-effects models [2] including interaction terms. Three-way interactions (DNAm×age×age group) were not significant. Two-way interactions (DNAm×age) testing DNAm-BP associations by age were: cg06690548 (P=0.07) and cg14476101 (P=0.12). ID indicates identifier.In the pooled sample (adolescents and adults together), all of the 13 meta-EWAS identified CpGs3 showed the same direction effect, 9 were associated with BP at nominal significance, and 3 of these 9 remained significant after Bonferroni correction (Figure). These were (1) cg14476101 in PHGDH on chromosome 1 (P=1.6×10-3), (2) cg06690548 in SLC7A11 on chromosome 4 (P=1.3×10-3), and (3) cg18120259 on chromosome 6 in a gene dessert (P=1.4×10-4). Effect sizes were ≈3-fold greater than those reported in the meta-EWAS3 (Figure).Next, we examined whether the 3 CpGs associated with BP are also associated with BP-determining hemodynamic factors. We performed these analyses separately in adolescents and adults because BP hemodynamics vary between the 2 age categories (Figure). Two of these 3 CpGs showed marked age-category and BP hemodynamics specificities:The CpG cg14476101 in PHGDH was associated with BP in adolescents (P=9.9×10-4), but not adults (Figure). The effect size in adults was similar to that reported in the meta-EWAS3 but was not significant because of the substantially smaller sample size (110 versus ≈17 000 adults). The magnitude of the association in adolescents was 5.6-fold greater than that in the meta-EWAS.3 The association was negative and accompanied by a negative association with SV (P=1.4×10-3; Figure). These associations were attenuated when additionally adjusted for body weight (Figure), suggesting they may be related to body-tissue growth during adolescence (typically accompanied by BP elevation because of enhanced preload and related SV augmentation1,2). PHGDH encodes the rate-limiting enzyme of serine synthesis, essential for biomacromolecule synthesis and tissue growth, and its deletion in mice reduces body growth.7 Here, higher SV and BP were associated with lower DNAm at this CpG, which was previously associated with higher expression of PHGDH.5 As such, this CpG in PHGDH (a growth-related molecule) may identify a pathway induced as part of the vascular adaptation to body-tissue growth during adolescence. Body-tissue growth is of a greater extent in adolescence (muscle, bone, and adipose tissues) than adulthood (mostly only adipose tissue), which may explain why the associations with SV and BP are of a greater magnitude in adolescents than adults. Consistently, in the present study, the CpG near PHGDH was additionally associated with body weight and body mass index, and these associations were also of a greater magnitude in adolescents (−0.0016 [0.0003], P=6.1×10-7 and −0.0044 [0.0009], P=1.0×10-6, respectively) than adults (−0.0003 [0.0004], P=0.36 and −0.009 [0.001], P=0.37, respectively). Though, the magnitude in adults was similar to that reported previously8 but it was not significant due to our smaller sample size.The CpG cg06690548 in SLC7A11 was associated with BP in adults (P=1.5×10-3), but not in adolescents (Figure). The association in adults was 4.7-fold greater than that in the meta-EWAS. It was negative and accompanied by a negative association with TPR (P=0.04; Figure). Both associations remained similar when excluding participants on BP-lowering medication or additionally adjusting for smoking or body weight (Figure). SLC7A11 enhances antioxidant defense, protecting against endothelial dysfunction and vascular inflammation that increase vascular tone and stiffness and thus TPR and BP.9 Antioxidant defense depends principally on glutathione. SLC7A11 encodes the cystine/glutamate transporter, which is involved in the synthesis of glutathione.9 Here, higher TPR and BP were associated with lower DNAm at this CpG, which was previously associated with higher expression of SLC7A11.3. As such, this CpG in SLC7A11 (a protective antioxidant molecule) may identify a pathway induced as part of the vascular adaptation to oxidative stress that increases with age. Future experimental research is required to confirm this possibility.Both above-discussed CpGs are located within regulatory regions of their respective genes, which contain binding sites of multiple transcription factors. As binding of these factors (and related transcription of DNA to RNA) modulates DNAm in-around their bindings sites,4 BP-associated DNAm decreases may be induced cotranscriptionally. As such, some differentially methylated CpGs in relation to cardiovascular traits may be downstream and not causal.3Our study is small and thus underpowered for smaller effects. This limitation is, however, partially counteracted by high fidelity phenotyping (standardized hour-long protocol performed in all in morning). We examined SV with a noninvasive Finometer because invasive methods are unsuitable for population-based studies. DNAm was studied in peripheral blood cells and, as such, lacks other tissue specificity. Additional potential limitations are time lag and batch effects with regards to the adolescent and adult samples (as described above). Furthermore, the differences in the associations between adolescents and adults have not been replicated and require further study. Finally, cross-sectional studies cannot support conclusions on causality or definite mechanisms.The present study supports the existence of novel age-specific BP-regulatory pathways that may be involved in vascular adaptation to body growth during development and oxidative stress during aging.AcknowledgmentsWe thank the following individuals for their contributions in data acquisition and management in the SYS (Saguenay Youth Study): Manon Bernard (database architect, The Hospital for Sick Children), Hélène Simard and her team of research assistants (Cégep de Jonquière), and Jacynthe Tremblay and her team of research nurses (Chicoutimi Hospital). We thank all participants who took part in the SYS.Sources of FundingThe SYS (Saguenay Youth Study) has been funded by the Canadian Institutes of Health Research (Drs Paus and Pausova), Heart and Stroke Foundation of Canada (Dr Pausova), and the Canadian Foundation for Innovation (Dr Pausova). Dr Syme is funded by the SickKids Research Institute.DisclosuresNone.Footnotes*Drs Syme and Shin are joint first authorshttps://www.ahajournals.org/journal/circgenZdenka Pausova, MD, The Hospital For Sick Children Departments of Physiology and Nutritional Sciences, University of Toronto, Peter Gilgan Centre for Research and Learning, 686 Bay St, 10–9705, Toronto, ON M5G 0A4, Canada. Email zdenka.[email protected]caReferences1. Smulyan H, et al. Influence of body height on pulsatile arterial hemodynamic data.J Am Coll Cardiol. 1998; 31:1103–1109.CrossrefMedlineGoogle Scholar2. de Simone G, et al. Stroke volume and cardiac output in normotensive children and adults. Assessment of relations with body size and impact of overweight.Circulation. 1997; 95:1837–1843.LinkGoogle Scholar3. Richard MA, et al; DNA methylation analysis identifies loci for blood pressure regulation.Am J Hum Genet. 2017; 101:888–902. doi: 10.1016/j.ajhg.2017.09.028CrossrefMedlineGoogle Scholar4. Schübeler D. 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Cysteine, glutathione, and thiol redox balance in astrocytes.Antioxidants (Basel). 2017; 6:E62. doi: 10.3390/antiox6030062CrossrefMedlineGoogle Scholar10. Shin Jet al. Confidence intervals for candidate gene effects and environmental factors in population-based association studies of families.Ann. Hum. Genet. 2007; 71:421–432. doi:10.1111/j.1469-1809.2007.00350.xCrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited By Dos Santos Oliveira N, Serpeloni F and Gonçalves de Assis S (2021) The interplay between DNA methylation and cardiac autonomic system functioning: a systematic review, International Journal of Environmental Health Research, 10.1080/09603123.2021.2000590, 33:1, (54-70), Online publication date: 2-Jan-2023. January 2019Vol 12, Issue 1 Advertisement Article InformationMetrics © 2019 American Heart Association, Inc.https://doi.org/10.1161/CIRCGEN.118.002341PMID: 30645168 Manuscript receivedApril 25, 2018Manuscript acceptedDecember 17, 2018Originally publishedJanuary 15, 2019 Keywordshemodynamicsepigeneticsadolescentblood pressureheart rateadultPDF download Advertisement SubjectsEpigeneticsHigh Blood Pressure