In an earlier report, we suggested that a polymorphism located in the 3′ untranslated region of the angiotensin II type 1 receptor gene (AT1R+1166 A/C) might interact with the angiotensin I converting enzyme (ACE) insertion/deletion (I/D) polymorphism to increase the risk of myocardial infarction. Since the AT1R+1166 A/C polymorphism does not appear to be functional, we postulated that it might be in linkage disequilibrium with an unidentified functional variant which would affect the regulation of the gene in response to angiotensin II. The present study was conducted to identify new polymorphisms of the AT1R gene that might be responsible for this interaction.
The first four exons, which are untranslated, and 2.2 kb in the 5′ flanking region of the AT1R gene were explored by polymerase chain reaction/single-strand conformation polymorphism. Seven polymorphisms were detected in the 5′ region at positions −1424, −810, −713, −521, −214, −213 and −153 upstream from the start of transcription. The genotypes of the −810, −713, −214, −213 and −153 polymorphisms were completely concordant. One substitution was detected at the 55th nucleotide of exon 4. These polymorphisms, together with the +1166 A/C polymorphism and a previously described T/C substitution at the 573th nucleotide of exon 5, were genotyped in the Etude Cas-Témoin de I'Infarctus du Myocarde (ECTIM) study, a multicentre study comparing 651 patients who had survived a myocardial infarction and 728 controls from Belfast (United Kingdom) and Lille, Strasbourg and Toulouse (France).
The newly identified polymorphisms were not in linkage disequilibrium with the +1166 A/C polymorphism and therefore could not explain the interaction observed with ACE I/D. None of the polymorphisms was associated with blood pressure levels in control subjects. In the four populations, the A allele of the −810 polymorphism was associated with a lower risk of myocardial infarction (population-adjusted odds ratio of 0.80, confidence interval 0.65–0.97, P < 0.05).
None of the newly identified polymorphisms could account for the previously described interaction between the AT1R+1166 A/C and the ACE I/D polymorphisms affecting the risk of myocardial infarction. However, the present study suggests that AT1R-810 T/A, or other polymorphisms which are in complete association with it, might be associated with the risk of myocardial infarction. Further studies are required to confirm this finding and to identify the functional variants.
1INSERM SC7, Paris, France
2INSERM U258, Paris, France
3MONICA Project of Strasbourg, France
4MONICA Project of Toulouse, France
5MONICA Project of Lille, France
6MONICA Project of Belfast, UK.
6Correspondence and requests for reprints to Laurence Tiret, INSERM U258, Hôpital Broussais, 96 rue Didot, F-75674 Paris, France. Tel: 33 1 43 95 95 63; fax: 33 1 45 43 42 69; e-mail: email@example.com
Sponsorship: Recruitment in the ECTIM Study was supported by grants from the Squibb Laboratory, the British Heart Foundation, INSERM and the Institut Pasteur-Lille.
Received 7 April 1998; Revised 15 June 1998 Accepted 16 June 1998