Angiotensin-Converting Enzyme Gene

Tiirk Kardiyol Dem

Arş

2002: 30: 743-748

Angiotensin-Converting Enzyme Gene

Polymorphism in Turkish Hypertensive Patients and its Association with Left Ventricular

Hypertrophy

Hakan TEZCAN, Serhan TUGLULAR*, Candan ÇİFTÇİOGLU*, Ali Serdar FAK, Turgay IŞ BİR**, Çetin ÖZEN ER*, Emel AKOGLU*, AhmetOKTAY

Department of Cardiology, Department of f111ernal Medicine, Division of Nephrology*, Marmara University School of Medicine, and Department of Moleclllar Medicine, lnstitllte of Experimenta/ Medical Researclı**, Istanbul University, Istanbul. T11rkey

TÜRK HİPERTANSİP HASTALARDA

ANJİYO TENSİN-KONVERTİNG ENZİM GEN POLİMORFİZMİ VE SOL VENT RİKÜL HİPERTROFİSİ İLİŞKİSİ

ÖZE T

Anjiyotensin-konverting en:im (AKE) gen polimorfizmi ile sol

ventrikiillıipertrofisi

(SVH) arasmdaki ilişki farklı po- plllasyonlarda

çalışılmış

ve

çelişkili

son11çlar alınmıştır.

Bu

çalı

şmaillll amacı esansiyel lıipertansiyonu olan Tiirk hastalarda AKE genotipi ve all el dağılı mım araşiirmak ve b11111111 sol ventrikül hiper/ rojisiyle ilişkisini ortaya koy- mak/Ir.

Çalışmaya benzer yaş ve cinsiyelle 1 li lıipertansif hasta ve 75 sa,~lıklı kontrol a/mmıştır. Sol ventrikiil kiitle indek- si (SVKI) heriki gmpta da iki boyllllll ekokardiyografiyle

hesaplandı. AKE geninin 16. inrron11ndaki insersi- yon(l)ldelesyon (D) polinıoıfizmini

araştırmak

üzere poli- meraz zincir reaksiyonu k11llam/dı.

DD, ID ve ll geııotipi dağ

ı/mu

hastalar (%42, %49 ve

%9) ve ko ntrol gm b u (%35, %53 ve %12) a rasmda farklı bul11nmadı. Her iki gruptaki aile/ dağılımı da farklı buluıı­

madı; has/Cl ve kontrol gmplan için, D alleli o/o66'ya karşı

62 , 1 alleli o/o34'e karş

ı

%38 olarak

saptandı.

Hipertansij gmpta SVH

sıklığı

%35 idi. AKE genalip

dağılımı

(DD, ID, ll) sol

ventrikiillıipertrofisi

olan (%41, %57, %2) ve olma)• an lıastalarda (%42, %45, o/ol 3)

farklı bulunmadı.

SVKI heriiç

genotipt

efaklı saptanmadt, ortalama değerler

DD için 113±37 gfnı

2;

ID için 11 0±36 glrrP; ve ll için 96 ±1 i gfm2 (p=0.5) idi.

Son11ç olarak esansiyel hipertansiyonu olan Tiirk hasta- larda AKE geni /ID polinıoıfizminin genatipik dağılımı ve al/el

sıklığı sağlıklı

kontrollere göre farkit bulunmadı. Ay- nca AKE geni polimoıfiznıinin sol ventrikiil hipertro/isi ve sol ventrikiil kiitlesi ile anlam lt bir ilişkisi o/madığt or- taya kondu. Tiirk Kardiyol Dem Arş 2002; 30: 743-748 Anahtar kelime/er: ACE gen po/imorfizmi, lı

ipertansiyon

,

sol

velllrikiillıipertrofisi

Rcceived date: I I June 2002, accepted date: 5 November 2002 Corresponding address: Dr. Hakan Tezcan, Address P.K. 40, Aci- badem 8 I 020 Istanbul - Turkey

Left ventricular hype rtrophy (LVH) is an indepen- dent ris k factor for cardiovascular morbidi ty and mortality (I-4). 'rhe path ogenetic background leading to L VH is m ultifacto ria l and both hemodynamic (i ncreased perip hera l vascular resistance, volume oveload ) and no nhemodynamic facto rs (age, sex,obesity, gene tics) seem to be involved in i ts de- velopm ent. The fact that many subjects with LVH are actually normotensive individuals further empha- s izes the possible role of nonhemodynam ic factors in its pa thogenesis (4). The evidence that left ventricu- lar mass is a famil ial trait f urther s upports the gene- tic theory in etiology (5,6).

Renin ang ia tensin system (RAS) is also implicated in the develop ment of L VH. Ang iatensin II (AII) fa- c il itates LV H throug h enhancement of prote in synthes is in cardi ac and vascu lar smooth muscle cells (7-9) . There is increased expressian of Ali in the hypertroph ied ven tricle s uggesting its intracardiac formation, independent of circulating RAS (10) . The role of RAS is additionally s upported by experimen- tal and elinical stud ies which have shown that angio- tensin converting enzyme inhibitors (ACEI) can pre- vent or lead to the regression of hypertensive L VH

(I 1,12).

The human ACE gene is located on chromosome I 7 at position 23 (17q23). A deletion polynıorphism of a 2 87-base pair fragment of intron 16 of the ACE gene was detected (13,14), resulting in a lle le D if de- Jetion is present and in allele I (insertion) if absent and the three resulring genotypes are: D D, ID, II.

Homozygous presence o f the deletion polymorphism

(DD) was s hown to be associated with higher plas-

ı urK ^1\aruıyvı

v ern

11rş ~vv~; :ıv: I&.~J·!&.~o

cally result in increased All formation in cardiac and vascular tissues. Furthermore, the presence of allele D has been associated with target organ damage inc- luding hypertensive retinopathy, microalbuminuria and LVH in some studies (17, 18). The ACE gene

polyınorphism has therefore been investigated for its possible association with essenti al hype rtension or ische mic heart disease and the findings seem to vary betwee n populations of different genetic and envi- ronmental backgrounds (19-2 1).

These intriguing findings !ed to the speculation that the DD genotype may be the genetic factor involved in the development of L VH in essential hypertension through its influence on the local formation of All within the cardiac tissue.

A number of studies addressi ng this issue in diffe- rent populations had conflicting results (17,18,22-25).

The aim of the present study was to determine the a iletic frequency and the genotype distribution for ACE gene polymorphism in Turkish patients with essential hypertension and to correlate the genetic find ings w ith the presence of L VH.

MATERIAL AND METHODS Subjects

In 1998-1999, 1 l7 patients (85 fe male, 32 male) with es-

senıial

hypertension olderthan 18 years were randomly se- lected in the

outpaıient

clinic of internal medicine to parti- cipate in this study, which was a part of a larger elin ical trial. All subjects were white adults of caucasion Turkish desce nt Causes of secondary hypertension were excluded in all patients. Subjects with coronary artery di sease, con- ges tive heart failure, any form of cardiomyopathy, valvu- lar heart disease, arrhythmias and diabetes were excluded.

Essential hypertension was defined according to the Sixth Report of the Joint National Committee, as

sysıolic

blood pressure (SBP) of 140-170 mmHg a nd/or diastolic blood press u re (DBP) of 90- 109 mmHg on at least three different occas ions with absence of evidence for secondary hyper- tension. Seventy five normotensive (BP< I30/85 mmHg) individuals with sim ilar age and gender comprised the co ntr o l g roup. N one of the patients were on drug treatment at the time of the study. They had never been treated for hypertension or had been off therapy at least 4 weeks be- fore the study. Informed consent was taken from all sub- jects and the stud y was approved by the local ethics com- mittee.

Echocardiographic Methods

Both the study and the control groups underwent 20- and M-mode echocardiographic evaluation for LV mass index (LV Ml) calculations. ATL UM9 (Bothel, Ca., USA) devi-

744

ce was used in all echocardiographic studies. Echocardiog- raphic examination was undertaken at rest with subjects in supine left lateral position using standard parasternal and apical views. M-mode measurements were obtained accor- ding to the recommendations of American Society of Ec- hocardiograp hy (26). Echocardiographic examination and mass calculatio ns were performed by the same cardiolo- gist. The intraobserver variability for echocardiographic measurements and calculations was below 5%. Left ventri- cular mass (L VM) was derived using the formula deseri- bed by Devereux et aJ.<27l. Left

venıricular

mass was cor-

recıed

for body surface area (L VMI) and expressed in units of gramsimeter squared (gfm2). Left ventricular hyp ertrophy w as defin ed as L VMI

~

134 g/rrll in males

and~

110 g!m2 in females

(28>.

Determination of ACE Genotypes:

Genomic DNA was extracted from peripheral mononucle- ar cells with sodium dodecyl sulfate lysis, ammonium ace-

ıate

extraction, and ethanol precipitation (29l. A polymerase chain reaction (PCR) was used for

amplifıcation

and accu- rate genotyping of the ACE gene as previously defined

(30.31)_

Statistical Analysis

All data are expressed as mean ± SD. Chi - square was used to comp are the allele and genotype frequencies bet- ween patients with essential

hype~tension

versus controls and between patients with versus without L VH. Analysis of variance (ANOV A) was performed to test the in fluence of ACE genoty pes on left ventricular mass. A p value of less than 0.05 was assumed to indi cate statistical signifi- cance.

RESULTS

Characteristics of the study population are summari- zed in Table

ı.

The patients and th e control group did not di ffer significantly with regard to age and gender. Mean SBP and DBP in hypertensive group were significantly higher than the control group (p<0.05). The echocardiographic evaluation of the study population revcal ed the presence of L V H in 35% of the patients white there were no cases of L VH in the control group.

The a lle le frequencies and di stribution of ACE ge- notypes in patients with hypertension compared to controls are given in Table 2. The respective frequ- encies of DD, ID and II genotypes were 42%, 49%

and 9% in the hypertensive group versus 35%, 53%

and 12% in the control group. The overall frequenc i- es of D and I alleles were 67% and 33% versus 62%

and 38% in hyperte nsive and control groups respec-

tively. Th ere was no significant differe nce in e ither

allele or genotype distribution between Turkish pati-

H. Tezcan et al.: Angiotensin-Converting Enzyme Gene

Polymorplıisnı

in Turkish

Hyperıensive

Patients and its Association with LVH

Table ı. Characteristics of the stud y population Patients Controls

Number

ı ı7

75

Maıe

1 Female* 32/85 24/51

Age (years)*

50±ıo

48±9

SBP (mmHg)

ı51±21 ııo±ı2

DBP (mmHg)

97±ı4

75±5

Duration of HT (years)

7.5±ı

-

LVH 42 (35%) -

Data presen/ed are

nıean

value± SD, SBP=systolic blood pres-

sııre,

DBP=diastolic blood pressure, HT=

lıypertension,

LVH=

/efi

ventricularlıypertroplıy.

* p>0.05 for patie/1/s vs. comrol s.

ents with essential hyperte ns ion and healthy local control s.

Although baseline characteristics (duration of hyper- tens ion, stage of hypertension, number of drugs u sed) of patients w ith or without L VH were similar (Table 3), no s ignificant difference was found for the presence or absence of L VH in patients w ith essenti- al hypertens ion accordi ng to their ACE genotypes or a lleles as summarized in Tab le 4. The L VMI va! us were 113 ± 37 glm 2 in DD, 1 lO± 36glm2 in ID and 96±1 1 glm2 in II genotypes (Table 5). Although the LVMI value is lower in II genotype, the correlation of genotype data w ith L VMI also proved statistically non-significant (p>0.05, by ANOV A).

DISCUSSION

Left ventricular mass is a complex phenotype that is influenced by interact ing genetic and environmental factors. The RAS has been postulated to be involved in the pathogenesis of LVH. A number of experi- mental and elinical observations showed an a ssocia-

tion between the ACE gene polyınorphis m and LV mass. Individuals with DD genotype were s hown to have hig her plas ma ACE levels ( ı 5,ı 6) and activated RAS may exert trophic influe nces on cardiomyocy- tes (7,8). There is little information regarding the expression levels of ACE in cardiac and vascular tis- sues in the carriers of different ACE polymorphisın

genotypes. Higher in-situ A II formation ınay also fac ilitate cellular hypertrophy and extracell ular mat- rix formation (22).

Data from various populations on the re lationship between ACE gene phenotype and LVH are contro- versial. D allele of ACE gene was found to be an in- dependent risk factor for target organ damage in es- sential hypertension. In 106 caucasian Europeans with essential hypertension Pontremoli et al. s howed that DD and ID genotypes were significa ntly associ- ated with the presence of retinopathy, microalbumi- nuria and L VH (ı 7). In 140 untreated southern Ital ian patients Perticone et a l. demonstrated that L VMI was significantly enhanced in patients with the DO genotype (25) . In a J apanese study the genotype of the ACE gene was found to be a s ignificant predictor of left ventricular hypertrophy (22). However on a large group of subjec ts from the Framinghaın Heart Study, no role of the ACE gene influencing Ieft ventricular mass was shown (2,4). Similarl~ Kupari et al. failed to show a major influence of ACE gene va- riation on LV mass and function (23). Both studies were done in samples of the general population and included smail percentages of s ubjects with hyper- tension. Findings of another population-based study from Germany conducted by Schunkert et al.(ı 8)

s uggest that L VH is partially deterınin ed by genetic d isposition and DO genotype is a potential genetic marker for L VH in only ıniddle-aged men.

In our study the ACE genotype and alle lic distributi- on was found to be similar in Turkish patients with

Table 2 . Genotypic and allelic distribution of ACE gene in h ypertensive patients and controls

Groups Genotypes* Alleles*

DD ID ll D

ı

n(%) n(%) n(%) n(%) n(%)

Patients n=

ı ı

7 48(42) 58(49) 11 (9)

ı54(66)

80(34)

Controls n=75 26(35) 40(53)

9(ı2)

92(62) 58(38)

Türk Kardiyol Dem

Arş

2002; 30: 743-748

Table 3. C haracteristics of patients w ith and without L VH

Patients with LVH

Patieııts

w ithout L V H p value

n=41 11=76

Duration of HT (years) 6.5±7 9.5±8 0.06

Stage of HT* (n/%) 0. 1 9**

Stage

ı

1 5 (%37) 36 (%47)

Stage 2 1 4 (%34) 31 (%41)

Stage 3 12 (%29) 9 (%12)

Number of drugs u sed 0. 08**

o 4 (%LO) 14(%18)

ı

28 (%68) 50 (%66)

2 7 (%17) 12 (%16)

3 2 (%5) -

Data presented are mean value± SD, HT=

lıypertension,

LVH= /eft veliiricu/ar

lıypertroplıy.*

Stage of

lıypertension

is

detemıined

accor- ding to

Sixtlı

Report of

tlıe

Joint National Commitlee (JNC VI). **p>0.05 by

clıi-square.

Table 4. Genotypic and a llelic distribution of ACE gene in hypertensive patients with and without LVH

Groups

Genoıypes*

Alleles*

DD ID ll D I

n(%) n(%) n(%) n(%) n(%)

LVH n=41 16(41 ) 24(57) 1(2) 56(68) 26(32)

No LVH n=76 32(42) 34(45) 1 0(13) 98(64) 54(36)

* p>0.05 by

c/ı

i square,Jor parielli s

witlı

LVH vs no LVH, LVH= lefr vemricular

lıypertroplıy

essential hypertension and normotensive healthy controls. The lack of association between 1/D poly- morphism of the ACE gene and the presence of es- sential hypertension in our study is in accordance with two other studies performed in the same popu- lation. Topaloğlu et al.(32) studied the same issue in Turkish pediatric patients with essential hyperte nsi- on. They made genetic analysis in both children and their parents and found no sign ificant difference bet- ween e ither hypertensive and normotensive chi ldren or between their parents. Araz M et al. also found no

Table 5. LVMI valuesfor the three ACE genotypes

Genotypes LVMI

(g/ın²)*

DD 113 ± 37

ID 110 ± 36

ll 96 ± ll

Data presented are mean value ± SD ,

LVMI = left vemricular mass index,* p>0.05 by ANOVA

746

correlation between gene polyınorphism and the de- velopment of hypertens ion in Turkis h type 2 diabetic patients (33).

The seco nd major finding of our s tudy was that th e distribution for ACE genotypes and alleles were si- milar in hypertensive patients with and without L VH. The difference in L VMI values among the carriers of the three genotypes was also stati stically non-significant.

Although our study has a relatively smail sample si- ze and may not be representative of the genetat po- pulation, the findings are consistent with the results of the well-conducted large scale study based on the s ubjects from the Framingham Heart Study. Other studies supporting the presence of an association can be criticized for smail sample size, selection bias and suboptima l characterization of phenotypes.

Conflicting results may a lso be explained by nonuni-

form genetic background of different study populati-

H. Tezcan et al.: Angiotensin-Converting Enzyme Gene

Polymorplıism

in Turkish Hypertensive Patients and its Association

witlı

LVI-I

ons. Besides, in some of the studies the confounding effect of antihyperte nsive treatment should also be taken into consideration.

In conclusion, our data suggests the absence of an associatio n between the I/D polymorphism of the ACE gene and essential hyperte nsion. The genotypic va riation showed no influence on left ventricular mass . We believe that current evidence fails to sup- port the role of the ACE gene polymorphism as a de- terminant a nd marker of left ventricul ar hypertrophy.

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