Tesis doctoral de Fernando Martínez García
Background microalbuminuria has become a marker of risk not only for renal, but also for cardiovascular disease in diabetes, hypertension (htn) and in the general population. Moreover, changes in microalbuminuria over time seem to have prognostic implications. Factors related to the development of microalbuminuria have been extensively analyzed in cross-sectional and follow-up studies over the last several years. Although blood pressure levels, hyperglucemia, hyperinsulinemia and insulin resistance are probably the main factors which lead to its development, epidemiological and animal studies support a role for genetic factors. There are several strategies to investigate the genetics of complex diseases. Between them the genome wide scan association analysis has been successfully used in complex diseases such as coronary heart disease or type 1 and type 2 diabetes. Therefore the objective of the present work it is to unravel the genetic factors contributing to renal damage in essential hypertension. objectives the aim of the study was to identify a significantly different genotype, allele or haplotype frequencies between hypertensives with or without persistent microalbuminuria by means of a dense panel of snps all across the genome and possible quantitative trait loci for uae. We also searched for candidate genes for albuminuria and microalbuminuria in htn within the associated chromosomal regions and assembled our results with those previously published in the literature to construct a snp panel for assessment of the risk to develop an increment in urinary albumin excretion. materials and methods the study design was a case-control study. Both cases and controls were selected from one prospective cohort aiming to identify the clinical factors associated with microalbuminuria. All the patients were less than 50 years, hypertensive grade i and naí¯ve regarding to the treatment at the time of the recruitment. Cases were those who developed microalbuminuria (uae¿ 30 mg/day) during the follow up and controls were those who remained with an uae less than 30 mg/day. Uae was assessed in 24 hour urinary and in two or three samples if there were discrepancies with the measurement or if the urine was not collected properly. Blood of cases and controls was extracted with to perform the genotyping. We genotyped more than 250000 snps all across the genome with the nsp array of the affymetrix gene-chip human mapping 500k according to the manufacturer instructions. Brlmm algorithm was used to infer the genotypes from the row data. Low quality samples (call rate < 90%), those samples with very high ibs and those which did not cluster as the rest in the multidimensional scaling plot for the ibs pairwise distances were not included in the analysis. Only snps in hwe, with a call rate >90% and with maf¿0.1 were included. Those snps with significant differences between batches of cases or batches of controls or with different missing rated were also filtered. The genomic control inflation factor and the q-q plot for the observed and expected p-values were used to evaluate the quality of the analysis. Bonferroni p-value was used to consider a result as statistically significant. we used the spss v.15.0 to perform the general statistics and plink v1.06 to perform the genetic association analysis. results the final sample size comprised of 201 controls and 102 cases. Among the cases, 86 (84.3%) had an uae between 30-299 mg/day and 16 patients (15.7%) had uae values equal or higher than 300 mg/day. As expected the cases were older than the controls and also had greater values of 24 hour bp, bmi, and fasting glucose. Interestingly there were no differences regarding to the office bp levels. The gfr estimated by mdrd was significantly lower in cases than in controls but not the cc estimated by cockcroft-gault formula. Regarding lipids, the ldl was significantly lower in cases than in controls due to the major percentage of individuals under statins treatment. Also the number of lowering blood pressure drugs was significantly higher in cases than it was in controls as well as the percentage of individuals with metabolic syndrome according to the atpiii criteria. a few polymorphisms and haplotypes have resulted in an association with the presence of an increment in uae expressed as a qualitative or as a quantitative trait in our cohort of young hypertensive patients. the significantly associated loci were 8p22 for uae as a qualitative trait and 8q12.1, 2p11.2, 9p22.2 and 18q23 for the quantitative trait. Some possible candidate genes within the significantly associated chromosome regions are: msr1 for the qualitative trait and impad1, reep1, bnc2, and cndp1 for the quantitative trait. there was another group of snps which did not reach the statistical significance but they seemed to stand out from the rest of snps. These suggestive associations were found in the following loci: 10q11.21, 12q24.23, 2q32.2, 11p12, 16q23.1, 8p21.2, 5q23.2, 7p14.1, 8p11.21, 2p16.1 and 7p14.2 for the qualitative trait and 3q27.1, 12p13.2, 4q13.1, 10p11.22, 15q26.2, 4q28.3, 16q21, 4q32.1 and 16p13.2 for the quantitative trait. Some possible candidate genes within the regions with suggestive association are: cxcl12, adam7, adamdc1, adam28, pebp1, elmo, elmo3 for the qualitative trait and mcf2l2, lox1, epha5, cdh11, nrp1, mctp2, pcdh10 and pcdh18 for the quantitative trait. conclusions gwas strategy has enabled the identification of some genomic areas which can lead to an increase in uae in hypertensive patients. We were able to replicate some of the previously described areas or genes associated with renal damage using the same or different strategies (linkage studies or candidate gene study). The possible candidate genes identified in our study are mainly involved in lipid metabolism, inflammation or intracellular signalling which are known mechanisms than can lead to microalbuminuria in htn. Further replication and functional studies are needed to assess the possible role of these regions and candidate genes in the development of microalbuminuria in essential hypertension.
Datos académicos de la tesis doctoral «Elucidating the genetic susceptibility of hypertension associated microalbuminuria: genome wide scan«
- Título de la tesis: Elucidating the genetic susceptibility of hypertension associated microalbuminuria: genome wide scan
- Autor: Fernando Martínez García
- Universidad: Universitat de valéncia (estudi general)
- Fecha de lectura de la tesis: 23/03/2010
Dirección y tribunal
- Director de la tesis
- Felipe Javier Chaves Martínez
- Tribunal
- Presidente del tribunal: rafael Carmena rodriguez
- José Luis Rodicio diaz (vocal)
- roland Schmieder (vocal)
- Juan Carlos Martín escudero (vocal)
