Genetic polymorphisms in the Renin-Angiotensin system in high-altitude and low-altitude Native American populations

Genome-Wide DNA Methylation Changes Associated With High-Altitude Acclimatization During an Everest Base Camp Trek

The individual physiological response to high-altitude hypoxia involves both genetic and non-genetic factors, including epigenetic modifications. Epigenetic changes in hypoxia factor pathway (HIF) genes are associated with high-altitude acclimatization. However, genome-wide epigenetic changes that are associated with short-term hypoxia exposure remain largely unknown. We collected a series of DNA samples from 15 participants of European ancestry trekking to Everest Base Camp to identify DNA methylation changes associated with incremental altitude ascent. We determined genome-wide DNA methylation levels using the Illumina MethylationEPIC chip comparing two altitudes: baseline 1,400 m (day 0) and elevation 4,240 m (day 7). The results of our epigenome-wide association study revealed 2,873 significant differentially methylated positions (DMPs) and 361 significant differentially methylated regions (DMRs), including significant positions and regions in hypoxia inducible factor (HIF) and the renin–angiotensin system (RAS) pathways. Our pathway enrichment analysis identified 95 significant pathways including regulation of glycolytic process (GO:0006110), regulation of hematopoietic stem cell differentiation (GO:1902036), and regulation of angiogenesis (GO:0045765). Lastly, we identified an association between the ACE gene insertion/deletion (I/D) polymorphism and oxygen saturation, as well as average ACE methylation. These findings shed light on the genes and pathways experiencing the most epigenetic change associated with short-term exposure to hypoxia.

Geographical ancestry affects normal hemoglobin values in high-altitude residents

Increasing the hemoglobin (Hb) concentration is a major mechanism adjusting arterial oxygen content to decreased oxygen partial pressure of inspired air at high altitude. Approximately 5% of the world's population living at altitudes higher than 1,500 m shows this adaptive mechanism. Notably, there is a wide variation in the extent of increase in Hb concentration among different populations. This short review summarizes available information on Hb concentrations of high-altitude residents living at comparable altitudes (3,500-4,500 m) in different regions of the world. An increased Hb concentration is found in all high-altitude populations. The highest mean Hb concentration was found in adult male Andean residents and in Han Chinese living at high altitude, whereas it was lowest in Ethiopians, Tibetans, and Sherpas. A lower plasma volume in Andean high-altitude natives may offer a partial explanation. Indeed, male Andean high-altitude natives have a lower plasma volume than Tibetans and Ethiopians. Moreover, Hb values were lower in adult, nonpregnant females than in males; differences between populations of different ancestry were less pronounced. Various genetic polymorphisms were detected in high-altitude residents thought to favor life in a hypoxic environment, some of which correlate with the relatively low Hb concentration in the Tibetans and Ethiopians, whereas differences in angiotensin-converting enzyme allele distribution may be related to elevated Hb in the Andeans. Taken together, these results indicate different sensitivity of oxygen dependent control of erythropoiesis or plasma volume among populations of different geographical ancestry, offering explanations for differences in the Hb concentration at high altitude.

Comparative transcriptomic and proteomic analyses provide insights into functional genes for hypoxic adaptation in embryos of Tibetan chickens

The Tibetan chicken is a unique breed that has adapted to the high-altitude hypoxic conditions of the Tibetan plateau. A number of positively selected genes have been reported in these chickens; however, the mechanisms of gene expression for hypoxia adaptation are not fully understood. In the present study, eggs from Tibetan and Chahua chickens were incubated under hypoxic and normoxic conditions, and vascularization in the chorioallantoic membrane (CAM) of embryos was observed. We found that the vessel density index in the CAM of Tibetan chickens was lower than in Chahua chickens under hypoxia conditions. Transcriptomic and proteomic analyses of CAM tissues were performed in Tibetan and Chahua chicken embryos under hypoxic incubation using RNA-Seq and iTRAQ. We obtained 160 differentially expressed genes and 387 differentially expressed proteins that were mainly enriched in angiogenesis, vasculature development, blood vessel morphogenesis, blood circulation, renin-angiotensin system, and HIF-1 and VEGF signaling pathways. Twenty-six genes involved in angiogenesis and blood circulation, two genes involved in ion transport, and six genes that regulated energy metabolism were identified as candidate functional genes in regulating hypoxic adaptation of chicken embryos. This research provided insights into the molecular mechanism of hypoxia adaptation in Tibetan chickens.

Geographic distribution of the 3435C>T polymorphism of the MDR1 gene in Peruvian populations

Background The MDR1 gene presents several genetic polymorphisms with pharmacological implications. Therefore, the aim of the present study is to establish the genotype and allele frequencies of 3435C>T polymorphism of MDR1 gene into Peruvian populations (Coastal, Andean and Amazonian ecoregions), even considering the altitude (lowland <2500 m and highland >2500 m). Methods The polymorphism was analyzed by TaqMan genotyping assays in a group of 181 healthy unrelated Peruvian individuals. The comparison of genotype and allele frequencies of 3435C>T polymorphism was made with the Pearson test (X2), and, to calculate the genotype distributions, the Hardy-Weinberg equilibrium (HWE) was used. Results In all populations evaluated in this study, the genotype frequency distributions met HWE assumptions. The comparison between genotype and allele frequencies showed significant differences (p < 0.05), when the Andean, Coastal and Amazonian populations were compared. Also, significant differences (p < 0.05) were obtained when these populations were compared considering their altitudes. Likewise, in comparison with countries like USA, Finland, Nigeria and Kenya, the results showed significant differences (p < 0.05). Conclusions This investigation allowed us to establish the genotype and allele frequencies of 3435C>T polymorphism in different Peruvian populations, considering the geographic localization and even the altitude.

Human Genetic Adaptation to High Altitudes: Current Status and Future Prospects

The question of whether human populations have adapted genetically to high altitude has been of interest since studies began there in the early 1900s. Initially there was debate as to whether genetic adaptation to high altitude has taken place based, in part, on disciplinary orientation and the sources of evidence being considered. Studies centered on short-term responses, termed acclimatization, and the developmental changes occurring across lifetimes. A paradigm shift occurred with the advent of single nucleotide polymorphism (SNP) technologies and statistical methods for detecting evidence of natural selection, resulting in an exponential rise in the number of publications reporting genetic adaptation. Reviewed here are the various kinds of evidence by which adaptation to high altitude has been assessed and which have led to widespread acceptance of the idea that genetic adaptation to high altitude has occurred. While methodological and other challenges remain for determining the specific gene or genes involved and the physiological mechanisms by which they are exerting their effects, considerable progress has been realized as shown by recent studies in Tibetans, Andeans and Ethiopians. Further advances are anticipated with the advent of new statistical methods, whole-genome sequencing and other molecular techniques for finer-scale genetic mapping, and greater intradisciplinary and interdisciplinary collaboration to identify the functional consequences of the genes or gene regions implicated and the time scales involved.

Frequency of Alu insertions within the ACE and PR loci in Northwestern Mexicans

OBJECTIVE

Presently, non-LTR retrotransposons are the most active mobile elements in the human genome. Among these, Alu elements are highly represented in the modern population. Worldwide, distribution of Alu polymorphisms (insertion/deletion; I/D) shows variability between different populations. Two Alu insertion loci, ACE and PR, are significant biomarkers that have served in several genotype-phenotype association studies. In Mexico, studies concerning the frequency of these biomarkers have been conducted mainly in subpopulations from central and southern regions. Here, we screened a population sample of the northwestern region to gain further knowledge regarding the prevalence of Alu polymorphisms within ACE and PR loci.

RESULTS

For ACE locus, the observed genotype frequencies were 26.5, 51.0 and 22.5% for II, ID, and DD, respectively; and allelic frequencies for I and D were 52 and 48%. Whereas respective genotype frequencies for PR locus were 2.7, 26.5 and 70.8%, and the corresponding allele frequencies were 16 and 84%. Furthermore, the insertion frequency within ACE locus was similar between central, western and northwestern subpopulations, and rather higher in southeastern subpopulation (p < 0.05). Although the occurrence of Alu polymorphisms within PR locus has not been widely examined, the insertion frequency was higher in northwestern subpopulation, as compared with western and southeastern subpopulations (p < 0.05). Based on the frequency of Alu insertions found in ACE and PR loci, subpopulations from the northwestern, western and central regions share a common genetic origin, but apparently not with the subpopulation from the southeastern region, in accordance with the notion that assumes the existence of a broad genomic diversity in the Mexican population. In addition, the high prevalence of Alu insertions reveals their potential application as biomarkers with prognostic value for the associated diseases; e.g., as part of the standard protocols for clinical diagnosis.

Genetic determination of the vascular reactions in humans in response to the diving reflex

The purpose of this study was to investigate the genetic mechanisms of the defense vascular reactions in response to the diving reflex in humans with polymorphisms in the genes ADBR2, ACE, AGTR1, BDKRB2, and REN We hypothesized that protective vascular reactions, in response to the diving reflex, are genetically determined and are distinguished in humans with gene polymorphisms of the renin-angiotensin and kinin-bradykinin system. A total of 80 subjects (19 ± 1.4 yr) participated in the study. The intensity of the vascular response was estimated using photoplethysmogram. The I/D polymorphism (rs4340) of ACE was analyzed by PCR. REN (G/A, rs2368564), AGTR1 (A/C, rs5186), BDKRB2 (T/C, rs1799722), and ADBR2 (A/G, rs1042713) polymorphisms were examined using the two-step multiplex PCR followed by carrying allele hybridization on the biochip. Subjects with the BDKRB2 (C/C), ACE (D/D), and ADBR2 (G/G, G/A) genotypes exhibited the strongest peripheral vasoconstriction in response to diving. In subjects with a combination of the BDKRB2 (C/C) plus ACE (D/D) genotypes, we observed the lowest pulse wave amplitude and pulse transit time values and the highest arterial blood pressure during face immersion compared with the heterozygous individuals, suggesting that these subjects are more susceptible to diving hypoxia. This study observed that humans with gene polymorphisms of the renin-angiotensin and kinin-bradykinin systems demonstrate various expressions of protective vascular reactions in response to the diving reflex. The obtained results might be used in estimation of resistance to hypoxia of any origin in human beings or in a medical practice.NEW & NOTEWORTHY Our study demonstrates that the vascular reactions in response to the diving reflex are genetically determined and depend on gene polymorphisms of the kinin-bradykinin and the renin-angiotensin systems.

Association of the polymorphism 12109g>A from the REN gene as a risk factor for preterm birth

INTRODUCTION

Preterm birth is the most important cause of neonatal mortality and morbidity. It is a multifactorial disease with different etiologies, including genetic factors. Genetic variability is represented by single nucleotide polymorphisms (SNPs) in genes of proteins involved in the contractile activity. We determine the association between SNP 12109G> A in REN associated with preterm birth and premature rupture of membrane.

MATERIALS AND METHODS

A study of cases ( N=112, 22-36 weeks of gestation; mean: 31, 95% confidence interval 30.7-32.2) and controls ( N=66; 38-40 weeks of gestation from the last menstrual period; mean: 39.8, 95% confidence interval 38.9-39.4) was performed. Genomic DNA was isolated in all patients from peripheral blood. The SNP 12109G> A ( Mbo I) in REN was typified by PCR-restriction fragment length polymorphism.

RESULTS

A significant difference in the case group for the SNP 12109G>A was observed. The A allele was increased in women with preterm birth (81% cases vs. 15% control, p<0.0000004). There was also a significant difference between genotypes, mainly an excess of G/A heterozygotes in women with preterm birth (60% cases vs. 23% controls). The phenotype 12109G> A has odds ratio 6.62 (95% confidence interval 3.14-14.15), which means a high risk of preterm birth/premature rupture of membrane in presence of allele A, both in homozygotes and in heterozygotes.

CONCLUSION

Allelic frequency of A of SNP 12109G>A was higher in women with preterm birth than in women with normal vaginal delivery and could be considered a risk factor.

Genetic polymorphisms of the renin-angiotensin system in preterm delivery and premature rupture of membranes

Introduction. Premature rupture of membranes (PRM) is a late pregnancy complication commonly associated with preterm delivery (PD).Although several markers related to the renin-angiotensin system (RAS) have been evaluated in certain pregnancy complications, only the angiotensin-converting enzyme (ACE) I/D variant has been studied in PD-PRM.The aim of this survey was to investigate the association of the polymorphisms (angiotensin II type 1 [AT1] receptor T174M and M235T, renin G2805A,ACE I/D and AT1-receptor A1166C) of the genes of RAS in women with PD-PRM.

Design. Deoxyribonucleic acid samples from 89 Mexican Mestizo women with PD and PRM and 224—288 controls were studied. Polymorphisms were analysed by polymerase chain reaction-sequence specific primer assays. restricted fragment length polymorphism or sequence specific prim assays.

Results. For all loci , genotype distribution was in agreement with Hardy—Weinberg expectations in the control group. Significant intergroup difference (case vs. control) was seen for angiotensinogen (AGT) M235T polymorphism, with an increased allele M235 in affected cases (50% vs. 40% in controls).Analysis of two- locus haplotype agrees with an independent segregation of physically unlinked genes. Haplotype AGT 174T-235M was also increased (50 % vs. 40% in controls).

Conclusions. Physically unlinked genes involved in RAS segregate independently. The AGT 174—235 region is associated with PD-PRM in this population.

The association of angiotensin-converting enzyme gene insertion/deletion polymorphisms with adaptation to high altitude: A meta-analysis

Background:

Fluid retention is linked to the physiology and pathophysiology of humans at high altitude (HA). The angiotensin-converting enzyme (ACE) gene plays a role in the regulation of plasma volume and vascular tone.

Materials and methods:

In this meta-analysis, eligible studies published before 1 September 2015 that focused on the association between the ACE insertion/deletion (I/D) polymorphism and HA adaption were identified by searching the PubMed, Web of Science, Embase and Medline online databases. We used a fixed-effects model and assessed the study qualities multiple times.

Results:

The seven selected studies included a total of 582 HA-native individuals and 497 low-altitude controls, and these subjects were analyzed for the ACE I/D gene polymorphism. A significant association was found between the ACE DD genotype and HA maladaptation. The results for genotype DD versus ID + II were as follows: Odds ratio (OR) = 0.46; 95% CI 0.31–0.70; p = 0.0002. The results for genotype ID versus DD were as follows: OR = 1.97; 95% CI 1.27–3.06; p = 0.002.

Conclusions:

Our findings suggested that the DD genotype of ACE is a risk factor for HA maladaptation and that the presence of fewer ACE DD allele carriers in a population indicates a greater ability of that population to adapt to HA.

HIF2A Variants Were Associated with Different Levels of High-Altitude Hypoxia among Native Tibetans

Hypoxia inducible factors, including HIF1A and HIF2A, play central roles in response to high-altitude hypoxia and genetic variants of HIF1A or HIF2A were associated with high-altitude sickness or adaptation. However, it remains to determine whether they are associated with tolerance to different levels of high-altitude selection pressure among native Tibetans. We recruited 189 Tibetan subjects living at 2,700 meters (Low level of high altitude, LHA), 197 at 3,200 meters (Middle level of high altitude of high altitude, MHA), 249 at 3,700 meters (High level of high altitude, HHA) and 269 at 4,700 meters (Very high level of high altitude, VHA) and performed association analysis of twelve tSNPs (tagging SNPs) in HIF1A and HIF2A with high-altitude. We found (1) a increasing trend of HIF2A rs5621780-C(18.4%, 15.9%, 32.8% and 31.1%, respectively, in LHA, MHA, HHA and VHA)(P = 3.56E-9); (2) increasing trends of HIF2A rs6756667-A(68.7%, 73.4%, 79.9% and 89.6%), rs7589621- G(74.6%, 77.9%, 83.7%, and 92.1%) and rs1868092-A(64.1%, 67.3%, 75.1% and 84.4%) (P = 3.56E-9, 4.68E-16, 1.17E-13 and 7.09E-14, respectively); (3) a increasing trend of haplotype AG (68.7%, 73.1%, 79.9% and 89.6%) (P = 2.22E-7) which was constructed by rs6756667 and rs7589621; (4) a strong linear correlation between major alleles of rs6756667-A (R2 = 0.997, P = 0.002), rs7589621-G (R2 = 0.994, P = 0.003), rs1868092-A (R2 = 0.985, P = 0.008) and altitude by linear correlation test. The associations between HIF2A variants and different level of high altitude support that extremely high-altitude hypoxia challenge imposes selective effects on HIF2A variants among native Tibetans.

Association between genetic polymorphisms of ACE & eNOS and diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, with multiple genetic and environmental factors involving in its etiology. ACE and eNOS gene were considered to have important roles in the development and progression of DN. In this study, a case-control study was carried out to investigate the effects of 7 SNPs in ACE gene and 2 SNPs in eNOS gene in the development of DN in Northern China.7 SNPs including A240T, A2350G, A5466C, A2215G, T3892C, C1237T and C3409T of ACE gene and 2 SNPs (G894T and T786C) of eNOS gene were genotyped by polymerase chain reaction restriction fragment length polymorphism method. 431 type 2 diabetic patients with nephropathy (cases) were compared to 420 type 2 diabetic patients without nephropathy (controls) in the study. Data were analyzed by SPSS 17.0 and HaploView software. The frequency distribution of A2350G, 4 haplotyps in ACE gene and G894T in eNOS gene were demonstrated to be different between case and control groups significantly. Whereas other SNPs and haplotypes had no differences in two cohorts. The results revealed that variations of ACE and eNOS gene had association with DN, which indicated ACE and eNOS gene may play an important role in pathogenesis of DN in Northern Chinese Han population.

Characterization of the relationship between APOBEC3B deletion and ACE Alu insertion

The insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE), commonly associated with many diseases, is believed to have affected human adaptation to environmental changes during the out-of-Africa expansion. APOBEC3B (A3B), a member of the cytidine deaminase family APOBEC3s, also exhibits a variable gene insertion/deletion polymorphism across world populations. Using data available from published reports, we examined the global geographic distribution of ACE and A3B genotypes. In tracking the modern human dispersal routes of these two genes, we found that the variation trends of the two I/D polymorphisms were directly correlated. We observed that the frequencies of ACE insertion and A3B deletion rose in parallel along the expansion route. To investigate the presence of a correlation between the two polymorphisms and the effect of their interaction on human health, we analyzed 1199 unrelated Chinese adults to determine their genotypes and other important clinical characteristics. We discovered a significant difference between the ACE genotype/allele distribution in the A3B DD and A3B II/ID groups (P = 0.045 and 0.015, respectively), indicating that the ACE Alu I allele frequency in the former group was higher than in the latter group. No specific clinical phenotype could be associated with the interaction between the ACE and A3B I/D polymorphisms. A3B has been identified as a powerful inhibitor of Alu retrotransposition, and primate A3 genes have undergone strong positive selection (and expansion) for restricting the mobility of endogenous retrotransposons during evolution. Based on these findings, we suggest that the ACE Alu insertion was enabled (facilitated) by the A3B deletion and that functional loss of A3B provided an opportunity for enhanced human adaptability and survival in response to the environmental and climate challenges arising during the migration from Africa.

Association of polymorphisms in angiotensin and aldosterone synthase genes of the renin–angiotensin–aldosterone system with high-altitude pulmonary edema

Studies on different populations have suggested variability in individual susceptibility to altitude sickness depending on genetic makeup. The renin–angiotensin–aldosterone system (RAAS) pathway plays a key role in regulation of vascular tone and circulatory homeostasis. The present study was undertaken to investigate the possible association of the RAAS in the development of high-altitude pulmonary edema (HAPE) in lowlanders exposed to high altitude. Three categories of subjects were selected: individuals who developed HAPE on acute induction to high altitude ( HAPE); individuals tolerant to high-altitude exposure who showed no symptoms of HAPE (resistant controls; rCON); and natives of high altitude ( HAN). Genetic variants in the genes of the RAAS such as renin ( REN), angiotensin ( AGT), angiotensin-converting enzyme ( ACE), aldosterone synthase ( CYP11B2) and angiotensin II receptor type 1 ( AGTR1) have been investigated. The T174M polymorphism in AGT showed a significant difference in HAPE and HAN and also HAN and controls. Also, genotyping in the CYP11B2 T-344C promoter region resulted in a significant difference between HAPE and HAN both at genotypic and allelic levels. The genotypic difference was statistically insignificant for the AGTR1 A1166C 3’ UTR. The present investigation demonstrates a possible association between the polymorphisms existing in the RAAS pathway T174M and CYP11B2 C-344T and sensitivity of an individual to develop HAPE. The results also indicate the existence of ethnic variation between the HAN and the other two groups comprising lowlanders.

No association between ACE gene variation and endurance athlete status in Ethiopians

PURPOSE

The most widely studied candidate gene for endurance performance is the angiotensin-converting enzyme (ACE) gene. The best endurance runners in the world hail from Kenya and Ethiopia, so the lack of association between the ACE gene and elite endurance athlete status we previously reported in Kenyans requires replication in Ethiopians.

METHODS

DNA was extracted from buccal swabs collected from subjects filling four groups: elite endurance runners from the Ethiopian national athletics team specializing in 5 km to marathon distances (n = 76), controls demographically matched to the elite endurance athletes (n = 410), controls representing the general Ethiopian population (n = 317), and sprint and power event athletes from the Ethiopian national athletics team (n = 38). ACE I/D and A22982G (rs4363) genotype frequencies were determined for each of these groups, and differences between groups were assessed using χ(2) tests.

RESULTS

There were no significant deviations from Hardy-Weinberg equilibrium in endurance athletes or either control group. Endurance athletes did not differ significantly in ACE I/D genotype frequency when compared with the endurance athlete-matched control group (P = 0.16), general controls (P = 0.076), or sprint and power athletes (P = 0.39) (endurance athletes: 15.8% II, endurance athlete-matched controls: 8.8% II, general controls: 7.6% II, sprint and power athletes: 10.5% II). Similarly, no significant differences were found in ACE A22982G genotype between groups (endurance athletes: 13.2% AA, endurance athlete-matched controls: 12.2% AA, general controls: 12.0% AA, sprint and power athletes: 13.2%; endurance athletes vs endurance athlete-matched controls: P = 0.97, endurance athletes vs general controls: P = 0.95, endurance athletes vs sprint and power athletes: P = 0.52).

CONCLUSIONS

As previously shown in elite Kenyan athletes, ACE I/D and A22982G polymorphisms are not associated with elite endurance athlete status in Ethiopians.

Maternal/newborn genotype contribution of the renin–angiotensin system (Met235Thr, Thr174Met, I/D-ACE, A2350G-ACE, A1166C-AT2R1, C3123A- AT2R2, 83A/G-REN) to the risk of pre-eclampsia: a Romanian study

Introduction: We evaluated the association of the mutated genotypes Met235Thr-AGT, Thr174Met-AGT, I/D-ACE, A2350G-ACE, A1166C-AT2R1, C3123A-AT2R2, 83A/G-REN with the risk and outcome of pre-eclampsia; we also investigated whether genes in newborns increase maternal risk of pre-eclampsia.

Materials and methods: Thirty-six pairs of pre-eclamptic women and their newborns were genotyped, along with 71 pairs of controls (mothers/newborns) using PCR-RFLP analysis.

Results: The Thr235/Thr235 (OR 3.44, p = 0.01), DD (OR 2.66, p = 0.039), CC1166 (OR 5.56, p = 0.04), AA3123 (OR 3.77, p = 0.03) and GG83 (OR 8.32, p = 0.006) genotypes are significantly associated with pre-eclampsia. Women with pre-eclampsia positive for Met235Thr (34.64 ± 3.92 weeks vs. 38 ± 2 weeks), Thr174Met (32.58 ± 3.92 weeks vs. 36.38 ± 3.25 weeks), I/D (34.47 ± 3.67 weeks vs. 38.33 ± 3.5 weeks) delivered at a significant lower gestational age compared with pre-eclamptic women with a normal genotype. Newborns from women with pre-eclampsia positive for Thr174Met (2190 ± 820.21 g vs. 2702.08 ± 967.23 g), I/D (2399.33 ± 938.38 g vs. 3191.66 ± 684.40 g) had a significant lower birth weight compared with newborns from women with normal pregnancies. When both the mother and the newborn were positive for Met235Thr, I/D, A2350G, A1166C or 83A/G polymorphisms, the risk for pre-eclampsia was significantly increased at 6.67 ( p < 0.01), 5 ( p < 0.01), 3.33 ( p = 0.006), 2.72 ( p = 0.04) and 7.8 ( p < 0.01), respectively.

Conclusions: The results of our study confirm that, in pre-eclampsia, both maternal and newborn genetic variations implicated in blood pressure regulation are important.

Donor and recipient ACE I/D genotype are associated with loss of renal function in children following renal transplantation

Genetic polymorphisms of the RAS correlate with allograft function. We therefore analyzed common RAS polymorphisms in kidney donors and in children following RTx to determine the relationship between genotype and decline in GFR, blood pressure, and LVM. A total of 107 children who underwent RTx were included: 70 male, 37 female, mean age 8.8±4.9 yr, mean follow up 5.4 yr. The following RAS polymorphisms were studied in all 107 recipients, 48 donors, and 120 healthy controls: Renin (Renin Mbol 18G/A), ACE I/D; angiotensinogen (AGT M235T), and angiotensin II receptor type-1 (AT1R A1166C). Only patients homozygous for the ACE D allele had a significantly steeper decline in GFR compared with homozygous carriers of the ACE I allele (slope DD: -4.3±0.8 vs. II: -1.3±1.1 mL/min/1.73 m2 per yr; p=0.035). In four cases, a DD recipient received a kidney from a DD donor, and these patients showed a more pronounced decline in GFR (-5.2±0.5 mL/min/1.73 m2 per yr; p=0.002). MABP was not different before vs. after RTx and was independent of ACE I/D genotype. LVMI increased significantly in the majority of patients (36.6±13.9 g/m2.7 six months before RTx vs. 46.4±15.3 g/m2.7 12 months after RTx, p=0.015). However, this difference disappeared after stratification by ACE I/D genotype. The ACE DD genotype is a potential marker for identifying patients at high risk of poor allograft outcome.

Renin gene haplotype diversity and linkage disequilibrium in two Mexican and one German population samples

INTRODUCTION

Renin is the main rate-limiting enzyme in the renin-angiotensin-aldosterone system. Its gene, REN, is a candidate crucial factor in essential hypertension and cardiovascular disease. The aim of this study was to evaluate allele and haplotype distributions of REN polymorphisms, and to estimate normalised linkage disequilibrium (D') in Mexican and German populations.

MATERIALS AND METHODS

Four groups were studied for the REN single nucleotide polymorphisms (SNPs) 1205C>T, 1303G>A, and 10607G>A, in population samples of Mexican Mestizo (n = 86), Mexican Huichol (n = 49), German (n = 39), and individuals with hypertension diagnosis (n = 66). Polymorphisms were detected by PCR-RFLP. Genotype, allele and haplotype frequencies were estimated.

RESULTS

SNP 1205C>T and 10607G>A allele and genotype distribution showed inter-group differences. The 1205T and 10607A allele showed a significance difference in hypertensive population. Haplotype analysis also showed some inter-group differences, especially in 1205C-1303G-10607G, 1205C-1303G-10607A and 1205T-1303G-10607G haplotypes. The segregation analysis disclosed complete linkage disequilibrium between 1205 and 1303 loci.

CONCLUSION

These results provide an example of genetic diversity in related populations and illustrate the convenience of increasing the number of loci in associative studies between diseases and candidate genes.

Renin angiotensin system polymorphisms in patients with metabolic syndrome (MetS)

BACKGROUND

The genes associated with hypertension could be genetic risk factors for metabolic syndrome (MetS).

AIM

To determine the frequency of M235T and T174M-AGT, I/D-ACE and A1166C-AGTR1 in hypertensive patients with MetS and to evaluate the relationship between these polymorphisms and central obesity and dyslipidemia, respectively.

MATERIALS AND METHODS

We performed AGT, AGTR1 and ACE genotyping in 56 hypertensive women (24 with MetS) and 71 normotensive women using PCR-RFLP methods and PCR, respectively.

RESULTS

Hypertensive patients carrying the mutated TT235, MM174 and DD genotypes had an 1.53 (p=0.56), 1.78 (p=0.52) and 1.28 (p=0.78)-fold increased risk to develop MetS. Hypertensive carriers of both mutated TT235 and MM174 or TT235 and D/D or TT235 and CC+AC genotypes had an 8.15 (p=0.04), 4.83 (p=0.04) and 10.53 (p=0.05)-fold increased risk to develop MetS. Hypertensive patients with MetS and TT, D/D or CC genotypes had higher body mass index compared to hypertensive patients without MetS (p</=0.05 for all the genotypes). Hypertensive patients with MetS and TT235, MM174, D/D or CC1166 genotypes had higher triglyceride levels, lower HDL-cholesterol levels and higher waist circumference compared to hypertensive patients without MetS (p</=0.05, except for the association between CC1166 and HDL-cholesterol level).

CONCLUSIONS

The effect of the T174M, I/D and A1166C polymorphisms on MetS may depend on the M235T polymorphism. Among hypertensive subjects with MetS, the presence of TT235, MM174, DD and CC1166 genotypes could be a risk factor for central obesity and dyslipidemia.

Identifying positive selection candidate loci for high-altitude adaptation in Andean populations

High-altitude environments (>2,500 m) provide scientists with a natural laboratory to study the physiological and genetic effects of low ambient oxygen tension on human populations. One approach to understanding how life at high altitude has affected human metabolism is to survey genome-wide datasets for signatures of natural selection. In this work, we report on a study to identify selection-nominated candidate genes involved in adaptation to hypoxia in one highland group, Andeans from the South American Altiplano. We analysed dense microarray genotype data using four test statistics that detect departures from neutrality. Using a candidate gene, single nucleotide polymorphism-based approach, we identified genes exhibiting preliminary evidence of recent genetic adaptation in this population. These included genes that are part of the hypoxia-inducible transcription factor ( HIF ) pathway, a biochemical pathway involved in oxygen homeostasis, as well as three other genomic regions previously not known to be associated with high-altitude phenotypes. In addition to identifying selection-nominated candidate genes, we also tested whether the HIF pathway shows evidence of natural selection. Our results indicate that the genes of this biochemical pathway as a group show no evidence of having evolved in response to hypoxia in Andeans. Results from particular HIF -targeted genes, however, suggest that genes in this pathway could play a role in Andean adaptation to high altitude, even if the pathway as a whole does not show higher relative rates of evolution. These data suggest a genetic role in high-altitude adaptation and provide a basis for genotype/phenotype association studies that are necessary to confirm the role of putative natural selection candidate genes and gene regions in adaptation to altitude.

Lower mortality from coronary heart disease and stroke at higher altitudes in Switzerland

BACKGROUND

Studies assessing the effect of altitude on cardiovascular disease have provided conflicting results. Most studies were limited because of the heterogeneity of the population, their ecological design, or both. In addition, effects of place of birth were rarely considered. Here, we examine mortality from coronary heart disease and stroke in relation to the altitude of the place of residence in 1990 and at birth.

METHODS AND RESULTS

Mortality data from 1990 to 2000, sociodemographic information, and places of birth and residence in 1990 (men and women between 40 and 84 years of age living at altitudes of 259 to 1960 m) were obtained from the Swiss National Cohort, a longitudinal, census-based record linkage study. The 1.64 million German Swiss residents born in Switzerland provided 14.5 million person-years. Relative risks were calculated with multivariable Poisson regression. Mortality from coronary heart disease (-22% per 1000 m) and stroke (-12% per 1000 m) significantly decreased with increasing altitude. Being born at altitudes higher or lower than the place of residence was associated with lower or higher risk.

CONCLUSIONS

The protective effect of living at higher altitude on coronary heart disease and stroke mortality was consistent and became stronger after adjustment for potential confounders. Being born at high altitude had an additional and independent beneficial effect on coronary heart disease mortality. The effect is unlikely to be due to classic cardiovascular disease risk factors and rather could be explained by factors related to climate.

DD genotype of angiotensin-converting enzyme in type 2 diabetes mellitus with renal disease in Mexican Mestizos

AIM

The DD genotype of angiotensin-converting enzyme (ACE) has been suggested as a major contributor of diabetic nephropathy in several populations. The purpose of the present study was to determine whether micro/macroalbuminuria is associated with ACE insertion/deletion (I/D) polymorphism in Mexican Mestizos with type 2 diabetes mellitus.

METHODS

A total of 435 patients with type 2 diabetes mellitus, of whom 233 had albuminuria, were characterized for the ACE I/D polymorphism by the polymerase chain reaction method.

RESULTS

Clinical and biochemical characteristics and frequencies according to DD, ID and II genotypes in patients with and without albuminuria showed no significant differences. However, only females with micro/macroalbuminuria showed higher frequency of a DD genotype than those without albuminuria (27.9%, 21.2% and 10.5%, respectively; P <or= 0.044). In addition, female patients with macroalbuminuria without dialysis showed no significant differences with patients undergoing dialysis.

CONCLUSION

The ACE DD genotype is a risk factor for the development of renal disease in Mexican Mestizo females with type 2 diabetes, indicating a possible DD genotype-associated sex effect in renal disease.

Keeping pace with ACE: are ACE inhibitors and angiotensin II type 1 receptor antagonists potential doping agents?

In the decade since the angiotensin-converting enzyme (ACE) gene was first proposed to be a 'human gene for physical performance', there have been numerous studies examining the effects of ACE genotype on physical performance phenotypes such as aerobic capacity, muscle function, trainability, and athletic status. While the results are variable and sometimes inconsistent, and corroborating phenotypic data limited, carriers of the ACE 'insertion' allele (the presence of an alu repeat element in intron 16 of the gene) have been reported to have higher maximum oxygen uptake (VO2max), greater response to training, and increased muscle efficiency when compared with individuals carrying the 'deletion' allele (absence of the alu repeat). Furthermore, the insertion allele has been reported to be over-represented in elite athletes from a variety of populations representing a number of endurance sports. The mechanism by which the ACE insertion genotype could potentiate physical performance is unknown. The presence of the ACE insertion allele has been associated with lower ACE activity (ACEplasma) in number of studies, suggesting that individuals with an innate tendency to have lower ACE levels respond better to training and are at an advantage in endurance sporting events. This could be due to lower levels of angiotensin II (the vasoconstrictor converted to active form by ACE), higher levels of bradykinin (a vasodilator degraded by ACE) or some combination of the two phenotypes. Observations that individuals carrying the ACE insertion allele (and presumably lower ACEplasma) have an enhanced response to training or are over-represented amongst elite athletes raises the intriguing question: would individuals with artificially lowered ACEplasma have similar training or performance potential? As there are a number of drugs (i.e. ACE inhibitors and angiotensin II type 1 receptor antagonists [angiotensin receptor blockers--ARBs]) that have the ability to either reduce ACEplasma activity or block the action of angiotensin II, the question is relevant to the study of ergogenic agents and to the efforts to rid sports of 'doping'. This article discusses the possibility that ACE inhibitors and ARBs, by virtue of their effects on ACE or angiotensin II function, respectively, have performance-enhancing capabilities; it also reviews the data on the effects of these medications on VO2max, muscle composition and endurance capacity in patient and non-patient populations. We conclude that, while the direct evidence supporting the hypothesis that ACE-related medications are potential doping agents is not compelling, there are insufficient data on young, athletic populations to exclude the possibility, and there is ample, albeit indirect, support from genetic studies to suggest that they should be. Unfortunately, given the history of drug experimentation in athletes and the rapid appropriation of therapeutic agents into the doping arsenal, this indirect evidence, coupled with the availability of ACE-inhibiting and ACE-receptor blocking medications may be sufficiently tempting to unscrupulous competitors looking for a shortcut to the finish line.

Adaptation to high altitude in Sherpas: association with the insertion/deletion polymorphism in the Angiotensin-converting enzyme gene

OBJECTIVE

Sherpas are well-known for their physical strength at high altitudes. They adapt to high altitude so well that little acute or chronic mountain sickness has been documented in them. The possible genetic basis for this adaptation is, however, unclear. The objective of this study was to elucidate the genetic background underlying this characteristic among Sherpas with respect to the angiotension-converting enzyme (ACE) gene.

METHODS

We enrolled 105 Sherpa volunteers in Namche Bazaar (3440 meters) and 111 non-Sherpa Nepalese volunteers in Kathmandu Valley (1330 meters) in Nepal. Information about high-altitude exposure and physiological phenotypes was obtained via fieldwork investigation. The genotype of the insertion/deletion (I/D) polymorphism in the ACE gene was identified by polymerase chain reaction. Serum ACE activity was also measured.

RESULTS

The distribution of the I dominant genotype (II & ID) and the I allelic frequency were significantly more prevalent in Sherpas (II & ID: 94.3%, I allele: 73.3%) than in non-Sherpas (II & ID: 85.6%, P = .035; I allele: 64.0%, P = .036). Moreover, despite residing at high altitude, the circulating ACE levels of Sherpas were statistically similar to those of non-Sherpas at low altitudes (Sherpas: 14.5 +/- 0.4 IU/L/37 degrees C; non-Sherpas: 14.7 +/- 0.4 IU/L/37 degrees C; P = .755).

CONCLUSIONS

These findings suggest that the overrepresented I allele of the ACE gene in Sherpas might be one of the fundamental genetic factors responsible for maintaining physiological low-altitude ACE activity at high altitude, which may have an advantageous physiological role in adapting to a high-altitude environment.

Detecting natural selection in high-altitude human populations

High-altitude natives have distinctive biological characteristics that appear to offset the stress of hypoxia. Evolutionary theory reasons that they reflect genetic adaptations resulting from natural selection on traits with heritable variation. Furthermore, high-altitude natives of the Andean and Tibetan Plateaus differ from one another, perhaps resulting from different evolutionary histories. Three approaches have developed a case for the possibility of population genetic differences: comparing means of classical physiological traits measured in samples of natives and migrants between altitudes, estimating genetic variance using statistical genetics techniques, and comparing features of species with different evolutionary histories. Tibetans have an inferred autosomal dominant major gene for high oxygen saturation that is associated with higher offspring survival, a strong indicator of ongoing natural selection. New approaches use candidate gene and genomic analyses. Conclusive evidence about population genetic differences and associations with phenotypes remains to be discovered.

Evidence for a genetic basis for altitude-related illness

Altitude-related illnesses are a family of interrelated pulmonary, cerebral, hematological, and cardiovascular medical conditions associated with the diminished oxygen availability at moderate to high altitudes. The acute forms of these debilitating and potentially fatal conditions, which include acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE), often develop in incompletely acclimatized lowlanders shortly after ascent, whereas, the chronic conditions, such as chronic mountain sickness (CMS) and high altitude pulmonary hypertension (HAPH), usually afflict native or long-term highlanders and may reflect a loss of adaptation. Anecdotal reports of particularly susceptible people or families are frequently cited as evidence that certain individuals have an innate susceptibility (or resistance) to developing these conditions and, in recent decades, there have been a number of studies designed to characterize the physiology of individuals predisposed to these conditions, as well as to identify the specific genetic variants that contribute to this predisposition. This paper reviews the epidemiological evidence for a genetic component to the various forms of altitude-related illness, such as innate susceptibility, familial clustering, and patterns of population susceptibility, as well as the molecular evidence for specific genetic risk factors. While the evidence supports some role for genetic background in the etiology of altitude-related illness, limitations in individual studies and a general lack of corroborating research limit the conclusions that can be drawn about the extent of this contribution and the specific genes or pathways involved. The paper closes with suggestions for future work that could support and expand on previous studies, as well as provide new insights.

No Association Between Variants in the ACE and Angiotensin II Receptor 1 Genes and Acute Mountain Sickness in Nepalese Pilgrims to the Janai Purnima Festival at 4380 m

Koehle, Michael S., Pei Wang, Jordan A. Guenette, and Jim L. Rupert. No association between variants in the ACE and angiotensin II receptor 1 genes and acute mountain sickness in Nepalese pilgrims to the Janai Purnima Festival at 4380 m. High Alt. Med. Biol. 7:281-289, 2006.--Acute mountain sickness (AMS) causes significant morbidity among visitors to altitude. The primary contributors to developing AMS are altitude and rate of ascent; however, the substantial variation in susceptibility between individuals has led a number of investigators to propose that there may be genetic predilection to the disease. The ACE I/D polymorphism has been shown to predict performance among elite mountaineers. This study compares genotype and allele frequencies at the ACE I/D locus, two other loci in the ACE gene, and one locus in the angiotensin-2 receptor gene between individuals who did, or did not, express signs of AMS while attending a high altitude religious festival in Nepal (4380 m). Subjects (80 males, 23 females) were recruited and genotyped. All subjects were Nepalese. Forty-four of the subjects had been diagnosed with AMS by physicians at a high altitude health camp; the rest were free from altitude illness. All subjects were genotyped at polymorphic loci in the genes encoding angiotensin converting enzyme (ACE) and angiotensin II receptor type 1 gene (AGTR1). The polymorphisms examined were two single nucleotide polymorphisms (SNPs) in ACE (ACE(A-240T), dbSNP rs4291; and ACE(A2350G), dbSNP rs4343), the intronic Alu insertion in ACE (ACE I/D), and the SNP ATR(A1166C), (dbSNP rs17231380) in AGTR1d. All polymorphisms in ACE were found to be in linkage disequilibrium. No significant associations were found between AMS incidence and any of the alleles, suggesting that variants at these loci do not contribute to susceptibility to AMS in this population.

Interaction between GNB3 C825T and ACE I/D polymorphisms in essential hypertension in Koreans

Essential hypertension (EH) is considered a typical polygenic disease, so the evaluation of gene-gene interactions rather than the determination of single gene effects is crucial to understanding any genetic influences. The G-protein beta3-subunit (GNB3) 825T allele, associated with enhanced G-protein signalling, is a strong candidate for interactions with polymorphisms, such as insertion/deletion (I/D) polymorphism of angiotensin I-converting enzyme (ACE) gene. We investigated whether there is an association between GNB3 C825T and ACE I/D polymorphisms for the development of EH. We carried out a case-control study of 688 hypertensive and 924 normotensive subjects recruited from South Korea. The GNB3 C825T and ACE I/D genotypes were determined by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism methods, respectively. The distributions of alleles and genotypes for the GNB3 C825T and ACE I/D polymorphisms were not found to be significantly associated with hypertensive status in either males or females. Logistic regression analysis indicated that the GNB3 825T allele carriers were positively associated with EH in males (odds ratio (OR) for TT/CT, 1.459; 95% confidence interval (CI), 1.048-2.033, P=0.0255). In analysis of gene-gene interaction, we found that there was a significant interaction between the GNB3 825T and ACE D alleles (P<0.05). OR for EH was significantly higher in 825T allele carriers with ACE D allele (OR, 1.490; 95% CI, 1.117-1.987, P=0.0067). A significant interaction between the GNB3 825T and the ACE D alleles may contribute to the predisposing effect for the development of EH in Koreans.

Association between a functional polymorphism in the renin-angiotensin system and completed suicide

Suicide has been suggested to involve disturbances in the stress response system and to be related to genetics. The renin-angiotensin system (RAS) has been shown to affect the stress response, and several functional polymorphisms in RAS-related genes have been predicted to alter protein function. We hypothesized that the dysregulation of RAS was involved in suicide, and examined the association between completed suicides and four functional polymorphisms of RAS-related genes: the angiotensinogen M235T, angiotensin-converting enzyme (ACE) insertion(I)/deletion(D), angiotensin type-1 receptor A1166C, and G-protein-beta3 C825T gene polymorphisms. The I allele of the ACE I/D polymorphism was found to be more frequent in completed suicides than in controls (P = 0.014). The I allele was also found to be more frequent in male completed suicides (P = 0.022) than in male controls, while this was not the case in females. These results suggest that the alteration of RAS function caused by the genetic polymorphism is involved in the susceptibility to suicide in males.

Epidemiology, Risk Factors, and Genetics of High-Altitude–Related Pulmonary Disease

High-altitude-related pulmonary disease is a spectrum of acute and chronic illnesses with a well-described epidemiology. The risk for these illnesses is related to well-known environmental risk factors and lesser-known but important genetic factors. Prevention of acute high-altitude illness is possible in most visitors from lower elevations. Chronic high-altitude illnesses have an important worldwide impact.

Racial and Ethnic Differences in Microalbuminuria Prevalence in a Diabetes Population: The Pathways Study

The objective of this study was to determine whether racial or ethnic differences in prevalence of diabetic microalbuminuria were observed in a large primary care population in which comparable access to health care exists. A cross-sectional analysis of survey and automated laboratory data 2969 primary care diabetic patients of a large regional health maintenance organization was conducted. Study data were analyzed for racial/ethnic differences in microalbuminuria (30 to 300 mg albumin/g creatinine) and macroalbuminuria (>300 mg albumin/g creatinine) prevalence among diabetes registry-identified patients who completed a survey that assessed demographics, diabetes care, and depression. Computerized pharmacy, hospital, and laboratory data were linked to survey data for analysis. Racial/ethnic differences in the odds of microalbuminuria and macroalbuminuria were assessed by unconditional logistic regression, stratified by the presence of hypertension. Among those tested, the unadjusted prevalence of micro- or macroalbuminuria was 30.9%, which was similar among the various racial/ethnic groups. Among those without hypertension, microalbuminuria was twofold greater (odds ratio [OR] 2.01; 95% confidence interval [CI] 1.14 to 3.53) and macroalbuminuria was threefold greater (OR 3.17; 95% CI 1.09 to 9.26) for Asians as compared with whites. Among those with hypertension, adjusted odds of microalbuminuria were greater for Hispanics (OR 3.82; 95% CI 1.16 to 12.57) than whites, whereas adjusted odds of macroalbuminuria were threefold greater for blacks (OR 3.32; 95% CI 1.26 to 8.76) than for whites. For most racial/ethnic minorities, hypertriglyceridemia was significantly associated with greater odds of micro- and macroalbuminuria. Among a large primary care population, racial/ethnic differences exist in the adjusted prevalence of microalbuminuria and macroalbuminuria depending on hypertension status. In this setting, racial/ethnic differences in early diabetic nephropathy were observed despite comparable access to diabetes care.