Polymorphisms at newly identified lipid-associated loci are associated with blood lipids and cardiovascular disease in an Asian Malay population

Abstract

We conducted a cross-sectional study of Malay participants aged 40–80 years (n = 2,932) to examine the associations between polymorphisms at newly identified, lipid-associated loci with blood lipid levels and prevalent cardiovascular disease (CVD) in a Malay population in Asia. A polymorphism adjacent to the TRIB1 locus (rs17321515) was associated with elevated total cholesterol and LDL-cholesterol (LDL-C) after adjustment for age and sex (both P values <0.007) and with increased risk of coronary heart disease and CVD [odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.03–1.46; and OR 1.2, 95% CI 1.02–1.42, respectively] under an additive model of inheritance. In addition, using recessive models of inheritance, polymorphisms on chromosome 19 adjacent to the CILP2 and PBX4 loci (rs16996148) and on chromosome 1 at the GALNT2 locus (rs4846914) were associated with elevated HDL-C (P = 0.005) and lower LDL-C (P = 0.048), respectively. Although novel, the former is consistent with the association between this polymorphism and lower blood triglycerides observed in the initial studies conducted in populations of European ancestry. Neither showed statistically significant association with CVD. These observations should form the basis of further investigation to identify the causative polymorphisms at this locus, and also to understand the mechanistic roles that this protein may play in lipoprotein metabolism in Asians and other populations. We conducted a cross-sectional study of Malay participants aged 40–80 years (n = 2,932) to examine the associations between polymorphisms at newly identified, lipid-associated loci with blood lipid levels and prevalent cardiovascular disease (CVD) in a Malay population in Asia. A polymorphism adjacent to the TRIB1 locus (rs17321515) was associated with elevated total cholesterol and LDL-cholesterol (LDL-C) after adjustment for age and sex (both P values <0.007) and with increased risk of coronary heart disease and CVD [odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.03–1.46; and OR 1.2, 95% CI 1.02–1.42, respectively] under an additive model of inheritance. In addition, using recessive models of inheritance, polymorphisms on chromosome 19 adjacent to the CILP2 and PBX4 loci (rs16996148) and on chromosome 1 at the GALNT2 locus (rs4846914) were associated with elevated HDL-C (P = 0.005) and lower LDL-C (P = 0.048), respectively. Although novel, the former is consistent with the association between this polymorphism and lower blood triglycerides observed in the initial studies conducted in populations of European ancestry. Neither showed statistically significant association with CVD. These observations should form the basis of further investigation to identify the causative polymorphisms at this locus, and also to understand the mechanistic roles that this protein may play in lipoprotein metabolism in Asians and other populations. Blood lipids are key modifiable risk factors for coronary heart disease (CHD) and other cardiovascular diseases (CVDs) (1Brown B.G. Stukovsky K.H. Zhao X.Q. Simultaneous low-density lipoprotein-C lowering and high-density lipoprotein-C elevation for optimum cardiovascular disease prevention with various drug classes, and their combinations: a meta-analysis of 23 randomized lipid trials.Curr. Opin. Lipidol. 2006; 17: 631-636Crossref PubMed Scopus (141) Google Scholar). They show significant heritability (2Heller D.A. de Faire U. Pedersen N.L. Dahlen G. McClearn G.E. Genetic and environmental influences on serum lipid levels in twins.N. Engl. J. Med. 1993; 328: 1150-1156Crossref PubMed Scopus (398) Google Scholar). Recently, through genome-wide association studies, we and others have identified single-nucleotide polymorphisms (SNPs) at six novel loci associated with blood lipid concentrations (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google Scholar, 4Kooner J.S. Chambers J.C. Aguilar-Salinas C.A. Hinds D.A. Hyde C.L. Warnes G.R. Gomez Perez F.J. Frazer K.A. Elliott P. Scott J. et al.Genome-wide scan identifies variation in MLXIPL associated with plasma triglycerides.Nat. Genet. 2008; 40: 149-151Crossref PubMed Scopus (267) Google Scholar, 5Sandhu M.S. Waterworth D.M. Debenham S.L. Wheeler E. Papadakis K. Zhao J.H. Song K. Yuan X. Johnson T. Ashford S. et al.LDL-cholesterol concentrations: a genome-wide association study.Lancet. 2008; 371: 483-491Abstract Full Text Full Text PDF PubMed Scopus (284) Google Scholar–6Willer C.J. Sanna S. Jackson A.U. Scuteri A. Bonnycastle L.L. Clarke R. Heath S.C. Timpson N.J. Najjar S.S. Stringham H.M. et al.Newly identified loci that influence lipid concentrations and risk of coronary artery disease.Nat. Genet. 2008; 40: 161-169Crossref PubMed Scopus (1330) Google Scholar) and CHD (6Willer C.J. Sanna S. Jackson A.U. Scuteri A. Bonnycastle L.L. Clarke R. Heath S.C. Timpson N.J. Najjar S.S. Stringham H.M. et al.Newly identified loci that influence lipid concentrations and risk of coronary artery disease.Nat. Genet. 2008; 40: 161-169Crossref PubMed Scopus (1330) Google Scholar). These observations were made primarily in individuals of European ancestry. Our initial study did include a multiethnic population derived from the 1998 National Health Survey in Singapore (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google Scholar). This was a randomly selected sample of the population in Singapore. The study population comprised primarily Chinese. Despite oversampling of the minority ethnic groups in Singapore (Malays and Asian Indians), the numbers of these ethnic groups were small (781 Malays and 587 Asian Indians). More importantly, no data on the presence of CVD were available in that population that would allow us to assess the association between the presence of these polymorphisms and the risk of CVD. The importance of studying these other ethnic groups becomes apparent when we examine the epidemiology of CVDs in the world today (7Yusuf S. Reddy S. Ounpuu S. Anand S. Global burden of cardiovascular diseases: part I: general considerations, the epidemiologic transition, risk factors, and impact of urbanization.Circulation. 2001; 104: 2746-2753Crossref PubMed Scopus (2111) Google Scholar). Socioeconomic development, accompanied by rapid urbanization, has resulted in an epidemiologic transition in the burden of diseases from those associated with infection and malnutrition to those associated with noncommunicable chronic diseases. CVDs, ischemic heart disease in particular, represent some of the major causes of morbidity and mortality in developed countries today. In developing countries, this transition is still in progress, and many populations in Asia can be expected to experience a doubling of the burden of CVD over the next several decades. As a consequence, there has been emerging interest in the risk factors driving this increase and in potential preventive measures that can be taken in these countries. Most studies in this region have focused on Japanese, Chinese, and South Asians (8Yusuf S. Reddy S. Ounpuu S. Anand S. Global burden of cardiovascular diseases: Part II: variations in cardiovascular disease by specific ethnic groups and geographic regions and prevention strategies.Circulation. 2001; 104: 2855-2864Crossref PubMed Scopus (932) Google Scholar). Asia also comprises a large number of islands that have been jointly referred to as “other Asian islands.” The populations of these islands are ethnically distinct from those of China, Japan, and South Asia and can be expected to experience a greater increase in the burden of CVD than either India or China. Malays and other related ethnic groups represent 300–400 million persons inhabiting these other Asian islands. This ethnic group represents a large understudied population in relation to CVD. Differences in genetic architecture between these and other ethnic groups could mean that the genetic variants identified that show associations with blood lipids and CVD in populations of European ancestry may have different effects in Malays compared with populations of Chinese or European ancestry. Furthermore, exposure to different lifestyles and environments in these populations resident in Asia may further modify the effect of genetic variation on blood lipids and CVD risk. To fill this knowledge gap, we examined a large cross-sectional population of Malays that was recruited independently from the population included in our original study. We assessed the association between polymorphisms at these novel loci and 1) blood lipid levels and 2) prevalent CHD and CVD. The Singapore Malay Eye Study is a population-based, cross-sectional epidemiological study of 3,280 adults residing in Singapore, aged 40 to 79 years. All participants were of Malay ethnicity. Although no data are available from participants from this particular study, recent genome-wide studies carried out in Chinese, Malays, and Asian Indians in Singapore suggest that all three ethnic groups are genetically homogeneous and distinct from each other, as well as from HapMap populations of European (Utah residents with Northern and Western European ancestry from the Centre Etude Polymorphism Humain collection) and West African (Yoruba in Ibadan, Nigeria) ancestry (unpublished data available to editors and reviewers on request). The study was approved by the Singapore Eye Research Institute Institutional Review Board. Informed consent was obtained from all participants. Details of the study design, sampling plan, and methodology have been reported elsewhere (9Foong A.W. Saw S.M. Loo J.L. Shen S. Loon S.C. Rosman M. Aung T. Tan D.T. Tai E.S. Wong T.Y. Rationale and methodology for a population-based study of eye diseases in Malay people: The Singapore Malay eye study (SiMES).Ophthalmic Epidemiol. 2007; 14: 25-35Crossref PubMed Scopus (377) Google Scholar, 10Shankar A. Leng C. Chia K.S. Koh D. Tai E.S. Saw S.M. Lim S.C. Wong T.Y. Association between body mass index and chronic kidney disease in men and women: population-based study of Malay adults in Singapore.Nephrol. Dial. Transplant. 2007; 23: 1910-1918Crossref PubMed Scopus (84) Google Scholar–11Su D.H. Wong T.Y. Wong W.L. Saw S.M. Tan D.T. Shen S.Y. Loon S.C. Foster P.J. Aung T. Diabetes, hyperglycemia, and central corneal thickness: the Singapore Malay Eye Study.Ophthalmology. 2007; 115: 964-968Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar). Essentially, in April 2004, the Ministry of Home Affairs in Singapore provided an initial computer-generated list of 16,069 Malay names, derived from a simple random sampling of all Malay adults aged 40–79 years residing in 15 residential districts in the southwestern part of Singapore. The residential districts selected for this study were classified according to postal sectors and were chosen because according to the 2000 Singapore Census (12Leow Singapore Census of of Scholar, Singapore Census of and of the residents were a of the Singapore population in of age and we that our from this study population are to the Malay population in Singapore. this list of 16,069 names, we derived a sampling of using an random sampling from each from age 40 years and the 15 residential individuals were to be to A was or from the residential there in the was or was the 3,280 participants part in the study. the to and were the 3,280 consent for participants for genetic A total of participants were with for all were in this These are in Although the study was primarily to assess the and risk factors for eye disease in Malays, of the of the study was to examine the association between and CVD. The levels of CVD risk factors as well as the presence of CVD were as part of the a was as at were classified those did or did was 1) than 2) or or A of or or of was CHD included either or and CVD included CHD or was with according to the All a of the six polymorphisms identified in our genome-wide association study (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google Scholar) were in this study A polymorphism was included in this when was identified as a lipid-associated locus, showed an association with was in this study. cholesterol, LDL-cholesterol and were from using in the LDL-C and HDL-C were using was using on a an by the National with to the and was the reported a of or the random plasma was was using using the of in Study A.S. T. D. A to from serum a new of in Study Med. PubMed Scopus Google Scholar). were carried out using for between the were assessed by in participants with for all polymorphisms (n = by sex showed associations in the for and men and were in were for age and adjustment for body mass and were carried The associations with prevalent CHD or CVD were assessed using for age and In with for associations from the National Research Institute group on in Association T. M. E. G. G. D. et 2007; PubMed Scopus Google was obtained using the genetic model in the initial study (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google was an additive using a general and recessive models were carried P values were derived from ratio on models with or genetic with blood lipid concentrations were assessed after individuals (n = a of the of the study the a of a of a of and a of individuals reported than of these with CVD were than those They were also to be to be to have and to have lower with CVD were also to and lower total cholesterol and LDL-C than those of study CVD (n = CVD (n = mass index cholesterol than heart disease of cardiovascular are mean or for is the mean in a new cardiovascular are mean or for is the mean the polymorphisms with their in the Malay polymorphism showed significant from and was included in The for the other were We compared the lipid levels and the of in those with data those with significant were between those included in this and those in and from for examined (n = single-nucleotide in a new single-nucleotide the associations between the polymorphisms and plasma lipids as well as CHD and CVD. an additive model of inheritance, of the polymorphisms (rs17321515) showed a statistically significant association with total cholesterol and LDL-C The polymorphism also showed a significant association with the presence of These associations statistically significant after adjustment for body mass and the presence of for of and also did the associations observed of association between and CHD was carried out after prevalent from the The ratio (OR) was increased from confidence interval (95% CI) P = to (95% CI P = of at newly identified lipid-associated loci with lipid levels and risk of heart and to the at each with 1 the major and the for each as in and to the at each with 1 the major and the for each as in and to the at each with 1 the major and the for each as in for age and for body mass and cholesterol (n = a of (n = were from these mean (n = a of (n = were from these mean (n = a of (n = were from these heart disease (95% (n = 2,932) disease (95% (n = 2,932) 95% 95% confidence P and to the at each with 1 the major and the for each as in for age and for body mass and a of (n = were from these in a new 95% 95% confidence P We also carried out under and recessive models of In these adjacent to the showed a association with HDL-C under an additive model (P = showed a statistically significant association with HDL-C under a recessive model (P = no association with In addition, on chromosome 1 adjacent to the locus for GALNT2 also showed a association with LDL-C (P = 0.048), with CHD or CVD. We in a Malay population in Singapore, for out of six loci identified through genome-wide association studies of blood lipid In our original study, the polymorphism adjacent to was associated with variation in and in individuals of European in In the study, with a sample of Malays, the A was associated with increased levels of total cholesterol and LDL-C in those of European The effect for in LDL-C was to and in the as that observed in populations of European ancestry. The presence of the polymorphism was also associated with an increased risk for prevalent CHD and CVD. In the association between the polymorphism and CHD was large for each of the A the effect on total cholesterol and LDL-C and This is consistent with the large effect of at the locus on CHD risk a effect on blood In the study by et J.C. E. variations in and coronary heart Med. 2006; PubMed Scopus Google a 1 lower LDL-C associated with variants was associated with an in the risk of CHD in a lower LDL-C was associated with a in the risk of CHD in This is to exposure to in the presence of the genetic M.S. J.L. 2006; PubMed Scopus Google Scholar). this polymorphism may have a effect on the risk of CVD. TRIB1 of a of that as in A. E. novel of 2006; PubMed Scopus Google Scholar) that is to and the A. K. Heath E. E. and of 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). The study also reported that in TRIB1 was elevated in when compared with that this protein may have a in the of CVD. In our original a polymorphism on chromosome in an region between CILP2 and PBX4 (rs16996148) was identified in association with lower also showed an association with lower (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google Scholar). In the study, the association with LDL-C was in the and of the as that observed in populations of European did we did a statistically significant association of the with HDL-C under a recessive model of inheritance. This represents a novel Although we did examine the association with in the study, the elevated HDL-C is consistent with the study, the between and HDL-C and the lower levels of triglycerides associated with the in the original study (3Kathiresan S. Melander O. Guiducci C. Surti A. Burtt N.P. Rieder M.J. Cooper G.M. Roos C. Voight B.F. Havulinna A.S. et al.Six new loci associated with blood low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides in humans.Nat. Genet. 2008; 40: 189-197Crossref PubMed Scopus (1142) Google Scholar). in the and in data under a general effects model were the effect on also to be The roles that CILP2 or PBX4 play in lipoprotein metabolism are at this should be that in the study by et (6Willer C.J. Sanna S. Jackson A.U. Scuteri A. Bonnycastle L.L. Clarke R. Heath S.C. Timpson N.J. Najjar S.S. Stringham H.M. et al.Newly identified loci that influence lipid concentrations and risk of coronary artery disease.Nat. Genet. 2008; 40: 161-169Crossref PubMed Scopus (1330) Google the association between polymorphisms in this region with was observed over a region of and a in the Although the on this to the and of U. K. a 2001; PubMed Scopus Google a of the suggest that is in Furthermore, have been to influence through that include the of T. with the by of 2001; Full Text Full Text PDF PubMed Google Scholar, M. T. and of Full Text Full Text PDF PubMed Scopus Google a potential in cholesterol polymorphism on chromosome 1 adjacent to the GALNT2 locus showed a association with LDL-C under a recessive model of inheritance. This association was observed in either of the original studies these novel The did show association with in this to those observed in individuals of European ancestry. for this of These have been to be Differences in between these and the variants in Malays compared with individuals of European ancestry at these loci could in in our study the sampling in the study was to that for the Asian population in our study, the participants in this study were than those in our study related to the association between variants and have the importance of that may in J. C. R. et the of genetic can be J. Genet. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). We also the that random sampling variation or the that the original may have been to in genome-wide association could have resulted in in the The to study a large sample of Malays, an ethnic group that represents a large of individuals at risk of developing CVD in the is of the of our study. We the to association with CVD for the for we were to the association between this polymorphism and has been observed in a population in the (6Willer C.J. Sanna S. Jackson A.U. Scuteri A. Bonnycastle L.L. Clarke R. Heath S.C. Timpson N.J. Najjar S.S. Stringham H.M. et al.Newly identified loci that influence lipid concentrations and risk of coronary artery disease.Nat. Genet. 2008; 40: 161-169Crossref PubMed Scopus (1330) Google Scholar). to the of could have to of the We that of CVD would have between the small effect on blood and would have to our the and we that this would have the of our is the that our study participants were examined in the was a of the study because of that us from all participants in the the of in this study is on a plasma may this were carried out for as a this did the associations the basis of these we that was a in the associations blood lipids were also in the We that this a impact on the in this The lipid by the is serum C.A. D.M. The effect of on the of low-density and high-density lipoprotein J. Med. Full Text PDF PubMed Scopus Google and this is the we did blood in this study. to the other lipid HDL-C a small in the and C.A. D.M. The effect of on the of low-density and high-density lipoprotein J. Med. Full Text PDF PubMed Scopus Google Scholar, Blood cholesterol influence of on cholesterol and Med. PubMed Scopus Google Scholar). In addition, we a LDL-C of the LDL-C using the to related to variation of blood in relation to the in the participants were Although LDL-C using a some between the and the are S. D. R. E. low-density lipoprotein for cholesterol in 2007; PubMed Scopus Google Scholar, R. M. J. The between and lipid in with or with A Full Text PDF PubMed Scopus Google and of a low-density lipoprotein cholesterol in and J. Full Text Full Text PDF PubMed Scopus Google Scholar). we assessed the association between LDL-C and the genetic variants on a to specific to we that our in the are to in the we that related to the of blood lipids in the may the of the association us to the effect of these polymorphisms of This could have to the to some of the other associations observed in populations of European ancestry. to the cross-sectional of the study, we were to the that the association between and was by effects on blood lipid and of participants with CHD or CVD a of we that the lipid levels in the were to be a of for the and that to for lipid levels would the This is in the lower levels of total cholesterol and LDL-C in those with CVD compared with those CVD. In addition, we the that the observed association between and is to a related to the presence of this To of these would data from a study in lipid levels were to the of studies would represent an next in the investigation of the association related to these In we have associations between total cholesterol and LDL-C and a polymorphism adjacent to the TRIB1 locus in a Malay The polymorphism is also associated with CHD and CVD. In addition, we also observed an association between a polymorphism on chromosome 19 adjacent to the CILP2 and PBX4 and elevated novel, is consistent with the association between this polymorphism and lower blood triglycerides observed in the initial studies conducted in populations of European ancestry. this was observed under a recessive model of inheritance, a different model from that in the initial studies through the association between this polymorphism and lipid was This in other a polymorphism at the GALNT2 locus on chromosome 1 showed a association with lower LDL-C under a recessive model of inheritance, an association that was observed in the initial These observations should form a basis for further investigation to identify the causative polymorphisms at this locus and to understand the mechanistic roles that this protein may play in lipoprotein metabolism in Asians and other populations. with