Time-Frequency Analysis of Cardiovascular and Cardiorespiratory Interactions During Orthostatic Stress by Extended Partial Directed Coherence

In this study, the linear method of extended partial directed coherence (ePDC) was applied to establish the temporal dynamic behavior of cardiovascular and cardiorespiratory interactions during orthostatic stress at a 70° head-up tilt (HUT) test on young age-matched healthy subjects and patients with orthostatic intolerance (OI), both male and female. Twenty 5-min windows were used to analyze the minute-wise progression of interactions from 5 min in a supine position (baseline, BL) until 18 min of the orthostatic phase (OP) without including pre-syncopal phases. Gender differences in controls were present in cardiorespiratory interactions during OP without compromised autonomic regulation. However in patients, analysis by ePDC revealed considerable dynamic alterations within cardiovascular and cardiorespiratory interactions over the temporal course during the HUT test. Considering the young female patients with OI, the information flow from heart rate to systolic blood pressure (mechanical modulation) was already increased before the tilt-up, the information flow from systolic blood pressure to heart rate (neural baroreflex) increased during OP, while the information flow from respiration to heart rate (respiratory sinus arrhythmia) decreased during the complete HUT test. Findings revealed impaired cardiovascular interactions in patients with orthostatic intolerance and confirmed the usefulness of ePDC for causality analysis.

Study of impaired cardiovascular and respiratory coupling during orthostatic stress based on joint symbolic dynamics

The present study investigates the instantaneous coupling among the cardiac, vascular, and respiratory systems, using the heart rate, respiration, and systolic and diastolic blood pressure variability in 12 healthy and 16 vasovagal syncope female subjects during a head-up tilt (HUT) testing protocol at 70° This study contributes to the coupling analysis by using a nonlinear joint symbolic dynamics (JSD) in a high-temporal resolution scheme, based on 5 min segments of the time series that are shifted every minute. For each segment, a bivariate JSD matrix was constructed to obtain global and local coupling indices in accordance to Shannon's entropy and the probability of occurrence of various bivariate words, respectively. The novel approach revealed important findings in the coupling dynamics of the systems, thus allowing the detection of group differences during the early orthostatic phase, and during the HUT test, before the occurrence of any pre-syncopal symptoms. In patients, the global indices indicated a significant decrease of cardiovascular coupling, starting at 10 min after the tilt-up, manifested by reduced baroreflex sensitivity and cardiorespiratory coupling that was initiated 8 min after the onset of the orthostatic phase (OP). A decreased autonomic control on cardiovascular-respiratory couplings was further evidenced by increased alterations of the JSD indices during the OP compared to the supine position in patients compared to controls. Furthermore, findings based on local indices demonstrated that female patients showed reductions and disengagements in cardiovascular (p < 0.001) and cardiorespiratory (p < 0.01) couplings, as early as the first 5 min and during the complete OP.

Dynamics of the cardiovascular autonomic regulation during orthostatic challenge is more relaxed in women

Linear dynamic analysis of cardiovascular and respiratory time series was performed in healthy subjects with respect to gender by shifted short-term segments throughout a head-up tilt (HUT) test. Beat-to-beat intervals (BBI), systolic (SYS) and diastolic (DIA) blood pressure and respiratory interval (RESP) time series were acquired in 14 men and 15 women. In time domain (TD), the descending slope of the auto-correlation function (ACF) (BBI_a31cor) was more pronounced in women than in men (p<0.05) during the HUT test and considerably steeper (p<0.01) at the end of orthostatic phase (OP). The index SYS_meanNN was slightly but significantly lower (p<0.05) in women during the complete test, while higher respiratory frequency and variability (RESP_sdNN) were found in women (p<0.05), during 10–20 min after tilt-up. In frequency domain (FD), during baseline (BL), BBI-normalized low frequency (BBI_LFN) and BBI_LF/HF were slightly but significantly lower (p<0.05), while normalized high frequency (BBI_HFN) was significantly higher in women. These differences were highly significant from the first 5 min after tilt-up (p<0.01) and highly significant (p<0.001) during 10–14 min of OP. Findings revealed that men showed instantaneously a pronounced and sustained increase in sympathetic activity to compensate orthostatism. In women, sympathetic activity was just increased slightly with delayed onset without considerably affecting sympatho-vagal balance.

Orthostatic stress causes immediately increased blood pressure variability in women with vasovagal syncope

The cardiovascular and respiratory autonomic nervous regulation has been studied mainly by hemodynamic responses during different physical stressors. In this study, dynamics of autonomic response to an orthostatic challenge was investigated by hemodynamic variables and by diverse linear and nonlinear indices calculated from time series of beat-to-beat intervals (BBI), respiratory cycle duration (RESP), systolic (SYS) and diastolic (DIA) blood pressure. This study included 16 young female patients (SYN) with vasovagal syncope and 12 age-matched female controls (CON). The subjects were enrolled in a head-up tilt (HUT) test, breathing normally, including 5min of baseline (BL, supine position) and 18min of 70° orthostatic phase (OP). To increase the time resolution of the analysis the time series were segmented in five-minute overlapping windows with a shift of 1min. Hemodynamic parameters did not show any statistical differences between SYN and CON. Time domain linear analysis revealed increased respiratory frequency and increased blood pressure variability (BPV) in patients during OP meaning increased sympathetic activity and vagal withdrawal. Frequency domain analysis confirmed a predominance of sympathetic tone by steadily increased values of low over high frequency power in BBI and of low frequency power in SYS and DIA in patients during OP. The nonlinear analysis by symbolic dynamics seemed to be highly suitable for differentiation of SYN and CON in the early beginning of OP, i.e., 5min after tilt-up. In particular the index SYS_plvar3 showed less patterns of low variability in patients reflecting a steadily increase in both BPV and sympathetic activity. The proposed dynamical analysis could lead to a better understanding of the temporal underlying mechanisms in healthy subjects and patients under orthostatic stress.

Men and women should be separately investigated in studies of orthostatic challenge due to different gender-related dynamics of autonomic response

In studies of autonomic regulation during orthostatic challenges only a few nonlinear methods have been considered without investigating the effect of gender in young controls. Especially, the temporal development of the autonomic regulation has not yet been explicitly analyzed using short-term segments in supine position, transition and orthostatic phase (OP). In this study, nonlinear analysis of cardiovascular and respiratory time series was performed to investigate how nonlinear indices are dynamically changing with respect to gender during orthostatic challenges. The analysis was carried out using shifted short-term segments throughout a head-up tilt test in 24 healthy subjects, 12 men (26  ±  4 years) and 12 age-matched women (26  ±  5 years), at supine position and during OP at 70°. The nonlinear methods demonstrated statistical differences in the autonomic regulation between males and females. Orthostatic stress caused significantly decreased heart rate variability due to increased sympathetic activity mainly in men, already at the beginning and during the complete OP, revealed by (a) increased occurrence of specific word types with constant fluctuations as pW111 from symbolic dynamics, (b) augmented fractal correlation properties by the short-term index alpha1 from detrended fluctuation analysis, (c) increased slope indices (21ati and 31ati) from auto-transinformation and (d) augmented time irreversibility indices demonstrating more temporal asymmetries and nonlinear dynamics in men than in women. After tilt-up, both men and women increased their sympathetic activity but in a different way. Time-dependent gender differences during orthostatic challenge were shown directly between men and women or indirectly comparing baseline and different temporal stages of OP. The proposed dynamical study of autonomic regulation has the advantage of screening the fluctuations of the sympathetic and vagal activities that can be quantified by the temporal behavior of nonlinear indices. The findings in this paper strongly suggest the need for gender separation in studies of the dynamics of autonomic regulation during orthostatic challenge.

Gender differences in cardiovascular and cardiorespiratory coupling in healthy subjects during head-up tilt test by Joint Symbolic Dynamics

Gender related-differences in the autonomic regulation of the cardiovascular and cardiorespiratory systems have been studied mainly by hemodynamic responses during different physical stressors. In this study, the influence of gender on the autonomic response to an orthostatic challenge was investigated by obtaining the cardiovascular and cardiorespiratory coupling using the nonlinear technique known as joint symbolic dynamics (JSD) representation. This study includes 24 healthy young subjects. Males (N=12) and age-matched females (N=12) were enrolled in a head-up tilt (HUT) test, breathing normally, including 5 minutes of supine position (baseline) and 25-40 minutes of 70° orthostatic phase. The cardiovascular and cardiorespiratory couplings were obtained at baseline, early and middle orthostatic phases. Although in baseline there were some gender differences, parameters from JSD showed highly significant (p=0.0004) differences in specific cardiovascular coupling patterns in the early tilt phase. Furthermore, JSD analysis revealed that in males, due to increased sympathetic activity, exist a lower degree of cardiovascular coupling accompanied with an increased occurrence of tachycardic patterns. On the other hand, the cardiorespiratory coupling revealed only very few slightly significant differences in all three phases.

[Genetic study of the vasovagal syncope associated to the Arg389Gly polymorphism of the beta1 adrenergic receptor]

The purpose of this study was to evaluate the correlation between the vasovagal syncope (VVS) and the beta1 adrenergic receptor polymorphism at the 389 position. Seventy individuals with VVS were selected. DNA was extracted from peripheral blood by salting out and subjected to the amplification-restriction test. Genotype identification was made by polyacrylamide gel electrophoresis. A higher frequency in genotype and allele frequencies were found in individuals with positive tilted table test respect individuals with negative test, as well as a marked preference of the GlyGly phenotype in women. Genotype Arg389Gly was the most frequent between individuals with positive response in passive phase with respect to those in the induced phase. When the genotype was analyzed based on the hemodynamic response (VASIS) a gradient is observed in the frequency of Arg389Gly with the highest major frequency in the cardio-inhibitory response followed by the mixed response, and finally the vasodepressor response. These results suggest that the SVV has a genetic component associated with the Arg389Gly polymorphism of the adrenergic receptor. The Gly allele has a high risk association and it is maintained in the population through heterozygosis.

The Arg389Gly beta1-adrenergic receptor gene polymorphism and susceptibility to faint during head-up tilt test

AIMS

To investigate the association of the Gly389 allele with positive head-up tilt test (HUT) in a Mexican Mestizo population.

METHODS AND RESULTS

HUT results were compared between carriers (one or two copies of the Gly389 allele) and non-carriers (Arg389Arg genotype) of the Gly389 allele of the beta(1)AR gene in 50 patients with unexplained syncope. Thirty-three patients (66%) had a positive HUT. Patients with a positive HUT had a higher Gly389 allele frequency compared with those with a negative test (30.3 vs. 3%; OR 13; pC = 0.012). Moreover, when comparing positive HUT in passive drug-free phase, positive HUT in pharmacological (nitrate) phase, and negative (both phases), a decreasing gradient in the frequencies of the Gly389 allele was found among the three groups: 45.4, 22.7, and 3%, respectively.

CONCLUSION

An association of positive tilt table testing to a single nucleotide polymorphism with a Gly to Arg switch at position 389 of the beta(1)AR was found. This polymorphism may contribute to susceptibility to faint during orthostatic challenge.

[KCNQ 1 (KvLQT1) missense mutation causing congenital long QT syndrome (Jervell-Lange-Nielsen) in a Mexican family]

BACKGROUND

Long QT syndromes (LQTS) are inherited cardiac disorders caused by mutations in the genes that encode sodium or potassium transmembrane ion channel proteins. More than 200 mutations, in at least six genes, have been found in these patients. The Jervell and Lange-Nielsen (JLN) syndrome is the recessive form of the disease and is associated with deafness. Few families with JLN syndrome and genetic studies are reported in the literature.

METHODS

The KCNQ1 (KvLQT1) gene in a Mexican family with Jervell-Lange-Nielsen long QT syndrome was analyzed using an automated sequence method.

RESULTS

A missense mutation was found in the three affected individuals. This mutation is associated with complete loss of channel function. Correlation with the phenotype showed a prolonged QTc interval and deafness in the two siblings homozygous to the mutation. The mother, who was heterozygous for the mutation, also had prolonged QTc interval without deafness. The father and younger brother had normal QTc intervals. The mutation was not found in 50 healthy controls studied.

CONCLUSIONS

We describe for the first time a mutation in the KCNQ1 gene in a Mexican family with JLN long QT syndrome. This mutation produces an amino acid change (Gly-Arg) at protein level at the 168 residue. This mutation has been previously reported in Caucasian families with LQTS.

HLA genes in Mexican Teeneks: HLA genetic relationship with other worldwide populations

The HLA allele frequency distribution of the Mexican Teenek Indians has been studied and compared with those of other First American Natives and worldwide populations (a total of 15694 chromosomes from 73 different populations were analyzed). This study corroborate the restricted HLA polymorphism in the Amerindian populations and demonstrate how the Amerindians show a relatively homogeneity as opposed to other First Native American groups. Finally, the present data support previous ones that state the lack of complete correlation between language and genetics in micro-environmental studies; Teenek Mayan language does not correspond with a close Mayan (Guatemala) relatedness.

Tumor necrosis factor-alpha -308 promoter polymorphism contributes independently to HLA alleles in the severity of rheumatoid arthritis in Mexicans

The aim of this study was to determine the frequency and potential relevance of the promoter polymorphisms of the tumor necrosis factor-alpha (TNF-alpha) in the severity of rheumatoid arthritis (RA) in Mexicans. HLA-DR and polymorphisms at positions -238 and -308 of TNF-alpha gene were determined in 137 Mexican RA patients (44 with severe and 93 with non-severe RA) as well as in 169 healthy controls (99 were typed for HLA-DR). We observed an increased frequency of HLA-DR4 in severe RA compared to healthy controls (pC=0.02, OR=2.33). TNF polymorphism analysis showed a significant increased frequency of TNF -238 GG genotype in the whole group of RA patients when compared to healthy controls (pC=0.007, OR=4.71). When the analyses were carried out separately in severe and non-severe RA patients, the increased frequency of -238 GG genotype only was observed in patients with non-severe forms of the disease. Analysis of -308 polymorphism showed increased frequency of -308 T2 (A) allele in severe RA when compared to non-severe disease (pC=0.011, OR=3.29) and to healthy controls (pC=0.002, OR=3.97). The data demonstrate that -308 T2 (A) allele is associated with susceptibility to develop severe RA in Mexicans. This association could be independent from HLA-DR alleles and might be used as a prognostic marker for severe RA.

Matrix gamma-carboxyglutamic acid protein (MGP) G-7A and T-138C gene polymorphisms in Indian (Mayo and Teenek) and Mestizo populations from Mexico

Matrix gamma-carboxyglutamic acid protein (MGP) genotypes (G-7A and T-138C) were determined in 266 individuals from three Mexican populations. Mexicans showed increased frequencies of the G-7A G allele and the G7-A GG genotype compared to Europeans. For the T-138C genotype, we found differences among the Mexicans. This study could help to define the significance of MGP polymorphisms as genetic markers in Amerindian populations.

Tumor necrosis factor-alpha promoter polymorphism in Mexican patients with Chagas’ disease

The aim of this study was to investigate whether the promoter's polymorphisms at the TNF alpha (TNF-alpha) gene were associated with the genetic susceptibility to Chagas' disease. We analyzed the TNF-alpha (positions -308, and -238) polymorphisms in a sample of 54 serologically positive chagasic individuals and in 169 healthy controls. The patients were divided according to clinical characteristics as asymptomatics (n = 27), and chronic chagasic cardiopathy (CCC) patients (n = 27). The whole group of patients showed increased frequencies of -308 T2 (A) allele when compared to healthy controls (pC = 0.008, OR = 3.03). When the analysis was carried out separately in asymptomatic and CCC patients, increased frequencies of T2 (A) allele and T1T2 (AG) genotype in the group of patients with CCC were found when compared to asymptomatic individuals (pC = 0.0002 and pC = 0.003, respectively) and healthy controls (pC = 4 x 10(-7), OR = 7.02, and pC = 0.0006, OR = 5.29, respectively). The present study demonstrates that Chagas' disease is associated with TNF-alpha polymorphisms in the Mexican population. The TNF-308 T2 allele could be directly involved in the genetic susceptibility to the chronic phase of the disease.

Association study of LMP gene polymorphisms in Mexican patients with spondyloarthritis

To evaluate the role of LMP (low molecular weight protein) genes as susceptibility markers for spondyloarthritis (SpA), LMP gene polymorphisms were analyzed in 223 Mexican patients with SpA (81 undifferentiated SpA [U-SpA], 117 with ankylosing spondylitis [AS], 25 with reactive arthritis) and in 139 ethnically matched healthy individuals. LMP genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism. The LMP2 and LMP7 allele frequencies were similar in patients and healthy controls. Genotype analysis revealed an increased frequency of LMP2 R/R genotype in the whole group of SpA (pC = 0.003, OR = 2.06, 95%CI = 1.3-3.25) and in the clinical subgroups of AS (pC = 0.039, OR = 1.88, 95%CI = 1.1-3.22) and U-SpA (pC = 0.003, OR = 2.56, 95%CI = 1.37-4.8) compared with healthy controls. Analysis in the LMP7 did not reveal significant differences in patients and healthy controls. The HLA-B27-negative AS subgroup also showed an increased frequency of LMP2 R/R genotype (pC = 0.027, OR = 4.81, 95%CI = 1.21-22.13). The LMP2-R/R AS patients were younger than LMP2-H/R and H/H patients at onset of the disease (16.0 +/- 6.8 years for R/R, 22.0 +/- 11.2 years for H/R and 28.6 +/- 10.9 years for H/H) (p < 0.05). The data suggest that, besides HLA-B27, LMP2 genotypes are also involved in the genetic susceptibility to develop AS in Mexicans. Furthermore, the age at onset of this disease might also be influenced by genotypes of this gene.

Comparative study of the residues 63 and 67 on the HLA-B molecule in patients with Takayasu's Arteritis

Takayasu's Arteritis (TA) has been associated with the Major Histocompatibility Complex (MHC) genes; nevertheless, results in several populations have been heterogeneous. Studies both in Mexican and Asian populations suggest that residues at positions 63 (glutamic acid) and 67 (serine) of the HLA-B molecule could be the genetic markers for TA. In the present work, we analyzed the sequence of HLA-B alleles in 26 TA patients and 62 healthy controls. HLA-B subtyping analysis showed that all B52 alleles were B*5201, whereas only one HLA-B39 allele was B*3902. Sequencing of HLA-B alleles showed that 19 out of 26 patients studied (73.0%) presented at least an allele with glutamic acid at position 63 and serine at position 67. This condition was observed in only 21.0% of the healthy controls (pC = 0.00001, OR = 10.23). Out of the seven remaining patients, one presented glutamic acid at position 63 and four showed serine at position 67. Two patients (2/26 = 7.7%) and 24 healthy controls (24/62 = 38.7%) did not show similarity at the mentioned positions (pC = 0.016, OR = 0.13). These data corroborate the participation of positions 63 and 67 in the genetic susceptibility to TA and explain the high heterogeneity of alleles associated with the disease in several populations.

Cytochrome P4501A1 polymorphisms in the Amerindian and Mestizo populations of Mexico

Several polymorphisms in the CYP1A1 locus have been identified and their genotypes appear to exhibit population frequencies that depend on ethnicity. We studied two CYP1A1 polymorphic sites (position 4889 and 6235) in a group of 212 unrelated healthy individuals belonging to three different Mexican populations (106 Mexican Mestizos, 52 Teenek and 54 Mayos). Comparison among Mexican populations showed increased frequency of the *Ile allele (A on position 4889) in Mexican Mestizos when compared to Amerindians (p < 0.05). The analysis of position 6235 showed increased frequencies of *m2 (C in this position) allele in Teenek when compared to Mestizos and Mayos (p < 0.05) and of *m2/*m2 genotype when compared to Mestizos (p < 0.05). Amerindian populations (from Mexico and South America) presented the lowest frequencies of *Ile (position 4889) and *m1 (position 6235) alleles, however these frequencies vary according to the ethnic group studied. Mexican Amerindian groups together with other South Amerindian populations showed the highest frequencies for *Val at position 4889 and the *m2 allele at position 6235. The present study corroborates the high frequencies of*Val and *m2 alleles in the Amerindian populations and detects some differences between Mexican populations that correlate with linguistic differences. Our data could be helpful in understanding the distribution of these polymorphisms and in clarifying their roles as genetic and evolution markers in Amerindian populations.

Angiotensin-converting enzyme gene (ACE) insertion/deletion polymorphism in Mexican populations

The angiotensin-converting enzyme gene (ACE) insertion/deletion polymorphism was determined in 211 Mexican healthy individuals belonging to different Mexican ethnic groups (98 Mestizos, 64 Teenek, and 49 Nahuas). ACE polymorphism differed among Mexicans with a high frequency of the D allele and the D/D genotype in Mexican Mestizos. The D/D genotype was absent in Teenek and present in only one Nahua individual (2.0%). When comparisons were made, we observed that Caucasian, African, and Asian populations presented the highest frequencies of the D allele, whereas Amerindian (Teenek and Pima) and Australian Aboriginals showed the highest frequencies of the I allele. The distribution of I/D genotype was heterogeneous in all populations: Australian Aboriginals presented the lowest frequency (4.9%), whereas Nahuas presented the highest (73.4%). The present study shows the frequencies of a polymorphism not analyzed previously in Mexican populations and establishes that this polymorphism distinguishes the Amerindian populations of other groups. On the other hand, since ACE alleles have been associated with genetic susceptibility to developing cardiovascular diseases and hypertension, knowledge of the distribution of these alleles could help to define the true significance of ACE polymorphism as a genetic susceptibility marker in the Amerindian populations.

HLA-DRB1 alleles encoding the “shared epitope” are associated with susceptibility to developing rheumatoid arthritis whereas HLA-DRB1 alleles encoding an aspartic acid at position 70 of the β-chain are protective in Mexican mestizos

The risk to develop rheumatoid arthritis (RA) has been associated with the presence of HLA-DRB1 alleles encoding the "shared epitope" (SE). Additionally, HLA-DRB1 alleles encoding an aspartic acid at position 70 (D70+ ) have been associated with protection against the development of RA. In this study we tested the association between either SE or D70+ and rheumatoid arthritis in Mexican Mestizos. We included 84 unrelated Mexican Mestizos patients with RA and 99 unrelated healthy controls. The HLA-typing was performed by PCR-SSO and PCR-SSP. We used the chi-squared test to detect differences in proportions of individuals carrying at least one SE or D70+ between patients and controls. We found that the proportion of individuals carrying at least one HLA-DRB1 allele encoding the SE was significantly increased in RA cases as compared to controls (p(c) = 0.0004, OR = 4.1, 95% CI = 2.2-7.7). The most frequently occurring allele was HLA-DRB1*0404 (0.161 vs 0.045). Moreover, we observed a significantly increased proportion of HLA-DRB1 SE+ cases with RF titers above the median (p = 0.005). Conversely, the proportion of individuals carrying at least one HLA-DRB1 allele encoding the D70+ was significantly decreased (p(c) = 0.004, OR = 0.4, 95% CI 0.2-0.7) among RA patients compared with controls. In conclusion, the SE is associated with RA in Mexican Mestizos as well as with the highest titers of RF.

MHC class II alleles in Mexican patients with rheumatic heart disease

BACKGROUND

Rheumatic heart disease (RHD) is an autoimmune sequel of group A streptococcal infection that has been associated with the presence of some major histocompatibility complex (MHC) genes. Thus, the aim of the present study was to investigate the role of class II alleles in the genetic susceptibility to RHD in Mexican patients and establish the relationship of these alleles with the pattern of valve damage.

METHODS

HLA-DR, -DQA1 and -DQB1 allele frequencies were determined by PCR-SSO reverse dot blot and PCR-SSP in 98 Mexican Mestizo patients with RHD and 99 healthy controls. Patients were divided into mitral valve damage (n=46), multivalvular lesion (n=49) and aortic damage (n=3).

RESULTS

RHD patients presented an HLA-DR16 increased frequency (pC=0.009, OR=3.9) and a decreased HLA-DR11 frequency (pC=0.018) when compared to healthy controls. HLA-DR16 subtyping showed that DRB1*1602 was the DR16 allele increased in patients (pC=0.007, OR=5.3). Haplotype analysis showed increased frequency of DR16-DQA1*0501-DQB1*0301 in RHD patients when compared to healthy controls (pC=0.011). HLA-DR16 frequency remained significantly increased on patients with multivalvular lesion (pC=0.004, OR=4.8).

CONCLUSIONS

Our data suggest an important participation of Amerindian autochthonous HLA-DR16 (DRB1*1602) allele and DR16-DQA1*0501-DQB1*0301 haplotype as markers for RHD genetic susceptibility in the Mexican Mestizo population. HLA-DR16 allele could also play an important role in determining the pattern of valve damage on these patients.

Tumor necrosis factor-alpha promoter polymorphisms in Mexican patients with rheumatic heart disease

The major histocompatibility genes (MHC) have been associated with the genetic susceptibility to rheumatic heart disease (RHD). Results have been inconsistent and new genes located on the MHC region such as tumor necrosis factor (TNF-alpha) need to be analyzed. TNF-alpha polymorphisms (positions -238 and -308) were determined in 87 RHD Mexican Mestizo patients and 101 healthy controls. Patients were classified into mitral valve damage (MVD) and multivalvular lesion (MVL) categories. TNF-238 G allele and GG genotype were increased in patients when compared to healthy controls (pC=0.001, OR=14.1 and pC=0.003, OR=14.1, respectively). Also, decreased frequencies of TNF-238 A allele (pC=0.001) and AG genotype (pC=0.003) were found. TNF-308 polymorphism analysis showed increased frequencies of T2 (A) allele (pC<10(-3), OR=10.8) and T1T2 (AG) genotype (pC<10(-3), OR=9.85) and decreased frequencies of T1 (G) allele and T1T1 (GG) genotype (pC<10(-3)). When comparing valvular damage to healthy controls, patients with MVD showed increased frequencies of -238 GG (pC=0.03, OR=ND), -308 T1T2 (AG) (pC<10(-3), OR=14) and -308 T2 (A) (pC<10(-3), OR=11.7). Also, this group showed decreased frequencies of T1 (G) allele and T1T1 (GG) genotype (pC<10(-3)). Patients with MVL presented increased frequency of -308 T2 (A) allele (pC=0.0003, OR=8.65) and decreased frequencies of -308 T1 (G) allele and -308 T1T1 (GG) genotype (pC=0.0003 and pC=0.006, respectively). Distribution of -238 and -308 polymorphisms were similar between MVD and MVL. The data demonstrate that RHD is associated with TNF-alpha polymorphisms in the Mexican population; however, these polymorphisms do not have relation with the valve damage.

Distribution of HLA-B alleles in Mexican Amerindian populations

In the present study we analyzed by PCR-SSO technique the HLA-B gene frequencies in 281 healthy individuals from four Mexican Amerindian populations (66 Mayos, 90 Mazatecans, 72 Nahuas and 53 Teenek). The most frequent alleles in all studied populations were HLA-B35, HLA-B39, and HLA-B40; however, some differences were observed between populations. The HLA-B35 allele was the most frequent in three of the four populations studied (Mayos, Nahuas and Teenek), whereas in Mazatecans the most frequent allele was HLA-B39. HLA-B40 presented frequencies higher than 10% in all groups. On the other hand, only Mayos presented an HLA-B51 gene frequency higher than 10%. When comparisons were made, important differences between groups were observed. The Teenek group presented an increased frequency of HLA-B35 when compared to Mazatecans and the HLA-B52 allele was increased in Nahuas and Teenek when compared to Mayos. An increased frequency of HLA-B39 was observed in Mazatecans when compared to Nahuas, Mayos and Teenek. Also, an increased frequency of HLA-B51 was observed in Mayos when compared to Mazatecans and Nahuas. These data corroborate the restricted polymorphism of HLA-B alleles and the high frequency of HLA-B35, HLA-B39 and HLA-B40 alleles in autochthonous American populations. In spite of the restriction in this polymorphism, differences in frequencies of HLA-B alleles could be helpful in distinguishing each of these populations.

HLA-DR antigen frequencies in Mexican patients with dengue virus infection: HLA-DR4 as a possible genetic resistance factor for dengue hemorrhagic fever

The human leukocyte antigen DRB1 locus (HLA-DRB1) was typed in genomic DNA extracted from whole blood samples of 34 Mexican dengue hemorrhagic fever (DHF) patients and 47 dengue fever (DF) patients, by polymerase chain reaction-sequence-specific oligonucleotide reverse dot blot. HLA-DRB1*04 was negatively associated with risk of DHF (OR 0.31, 95% CI 0.11-0.85). HLA-DR4 homozygous individuals were 11.6 times less likely to develop DHF in comparison to DR4 negative persons (OR 0.08, 95% CI 0.01-0.75). After adjusting for gender and infection type by logistic regression, DR4 positive individuals were 3.6 times less likely to develop DHF than DR4 negative persons (OR 0.28, 95% CI 0.12-0.66). A secondary dengue virus infection was also positively linked with DHF risk (OR 2.89, 95% CI 0.92-9.07). This data suggests that genes of the major histocompatibility complex play a major role in the susceptibility and/or resistance to develop DHF. In Mexicans, HLA-DR4 may be a genetic factor that is protective against DHF. Because HLA-DR4 has been positively selected in Latin American populations, these results may apply also to other similar ethnic groups, particularly those with high percentages of admixture with indigenous Amerindian genes.

Effect of HLA-B and HLA-DR genes on susceptibility to and severity of spondyloarthropathies in Mexican patients

OBJECTIVE

To investigate the role of HLA-B and HLA-DR genes as contributors to genetic susceptibility and clinical expression of the spondyloarthropathies (SpA) in the Mexican population.

METHODS

The study included 172 patients with SpA (undifferentiated SpA 83, ankylosing spondylitis (AS) 64, and reactive arthritis 25) and 99 healthy controls. The HLA-B and HLA-DR alleles were detected by the polymerase chain reaction with sequence-specific primers technique. Patient assessment included demographic data, diagnostic categories, and disease patterns. Statistical methods included the Mantel-Haenzel chi(2) test, Fisher's exact test, and Woolf method for odds ratio (OR). Differences of continuous variables between HLA allele groups were calculated by Student's t test.

RESULTS

Increased frequencies of HLA-B27 (pCh10(-3), OR=28.7), HLA-DR1 (pC=0.045, OR=2.77), and HLA-B15 (p=0.034, pC=NS, OR=2.04) alleles in the whole group were found. HLA-B27 strength of association (OR) was 41.4 in AS; 20.9 in undifferentiated SpA; 27.2 in reactive arthritis. HLA-DR1 and HLA-B15 were increased in undifferentiated SpA (pC=0.045, OR=2.98 and p=0.004, pC=NS, OR=2.75). By analysing 58 HLA-B27 negative patients it was found that HLA-B15 and HLA-DR1 associations with SpA were independent of HLA-B27; increased frequencies of HLA-B15 were found in the whole SpA group and in patients with undifferentiated SpA (pC=0.03, OR=3.09 and pCh0.01, OR=3.77) and of HLA-DR1 in the latter (p=0.04, pC=NS, OR=3.15). HLA-B27 positive patients were younger than HLA-B27 negative patients at onset (p=0.03), but HLA-DR1 positive patients were older than HLA-DR1 negative patients (p=0.03). Bath indices for disease activity and functioning were higher in HLA-B27 positive patients (p=0.006 and p=0.004 v HLA-B27 negative patients). In contrast, neither HLA-DR1 nor HLA-B15 influenced these indices.

CONCLUSION

Apart from HLA-B27, there is a significant association of HLA-DR1 and HLA-B15 with SpA in Mexicans which is independent of B27. HLA-B27 is associated with younger age at onset and increased disease severity and HLA-DR1 with older age at onset. The strength of HLA-B15, HLA-B27, and HLA-DR1 associations varied in different forms of SpA.

[Alleles of the major histocompatibility system associated with susceptibility to the development of Takayasu's arteritis]

OBJECTIVE

Since 1972, the relationship between HLA alleles and the susceptibility for Takayasu arteritis (TA) has been studied on different populations. Hence the results up to date are heterogeneous, the objective of the present review is to analyze the relationship between the presence of HLA alleles and the susceptibility for the development of TA considering the ethnic origin of the studied populations.

MATERIAL AND METHODS

We carried out a bibliographic review from clinical articles of case and controls studies on different populations on which the relationship between HLA alleles and the susceptibility for TA was studied, published since 1972 until February 2000.

RESULTS

We reviewed articles of studies on Asian, Arab, North-American and Mexican Mestizo populations. On Asian populations TA was associated with HLA-A31, -B52, -B39, -B5 and -DR2, on Arabs with HLA-A2, -A9, -B35 and -DR7, on North-Americans with HLA-DR4 and on Mexican Mestizo with HLA-B5, -B52 and -DR6. On the other hand, recent reports establish that several HLA-B alleles (HLA-B52 and HLA-B39) associated with the disease share some residues important on the antigen presentation.

CONCLUSIONS

Hence the heterogeneity of the results obtained up to date, it stands out the increase on HLA-B52 and HLA-DR4 reported on ethnically different populations. More recent data point the possible participation of an epitope located on the peptide-binding site of the HLA-B molecule (positions 63 and 67) that seems to be shared by several alleles associated with the disease. These residues might be participating on the presentation of an unknown antigen that would unchain the disease on the genetically susceptible individuals group.

Heat shock protein 70 gene polymorphisms in Mexican patients with spondyloarthropathies

OBJECTIVE

To investigate the role of HSP70 genes as contributors to genetic susceptibility of the spondyloarthropathies (SpA) in the Mexican population.

METHODS

The study included 150 patients with SpA (undifferentiated spondyloarthropathy (uSpA) 68, ankylosing spondylitis (AS) 60, and reactive arthritis 22) and 158 healthy controls. HSP70-1, HSP70-2 and HSP70-hom genotypes were analysed by the polymerase chain reaction-restriction fragment length polymorphism technique. Statistical methods included the Mantel-Haenzel, chi(2), Fisher's exact test, and Woolf's method for odds ratio (OR).

RESULTS

HSP70-2 B/B genotype frequency was increased in the whole group of patients with SpA (pC<0.05, OR=4.3), as well as in the different clinical subgroups (pC<0.05, OR=4.2 for AS; pC<0.05, OR=4.4 for uSpA; and pC<0.05, OR=4.1 for ReA). This frequency remained significantly increased when the patients with B27 negative SpA were analysed. On the other hand, HSP70-hom locus analysis showed significantly increased frequency of A allele in the whole group of SpA (pC<0.05, OR=3.4), as well as in the groups with AS (pC<0.05, OR=5.6) and with uSpA (pC<0.05, OR=3.1), when compared with healthy controls. In this case, also, the genotype A/A was increased in the whole group of SpA (pC<0.05, OR=4.5), as well as in patients with AS (pC<0.05, OR=6.4) and with uSpA (pC<0.05, OR=3.7). When the patients with B27 negative SpA were analysed the frequencies of HSP70-hom A allele and A/A genotype remained significantly increased in the whole group of SpA (pC<0.05, OR=3.2 for the A allele and pC<0.05, OR=4.2 for the A/A genotype) and in the uSpA subgroup (pC<0.05, OR=3.8 for the A allele and pC<0.05, OR=4.3 for the A/A genotype).

CONCLUSION

In addition to the association of SpA with HLA-B27, there is a significant association of HSP70-2 and HSP70-hom alleles with SpA in Mexicans. This association seems to be independent of the susceptibility conferred by HLA-B27 in the group of patients with uSpA.

Influence of the apolipoprotein E polymorphism on plasma lipoproteins in a Mexican population

The influence of apolipoprotein E (APOE) genotypes on plasma lipid levels was determined in 278 Mexican individuals. The most frequent genotype was E3/3 (80.5%) followed by E3/4 (12.5%), E2/3 (5.0%), E2/4 (1.4%), and E4/4 (0.3%). Our data are similar to those previously described for Mexican-American and American Indian populations, which show the highest frequency worldwide of the APOE*3 and the E3/3 genotype. Compared to female carriers of the E3/3 genotype, women with the E3/4 genotype presented increased low-density lipoprotein cholesterol (117 +/- 28.0 mg/dL vs. 134.0 +/- 31.7 mg/dL, p < 0.05), and total cholesterol (179.4 +/- 33.4 mg/dL vs. 197.5 +/- 35.4 mg/dL, p < 0.01). Also, we detected increased high-density lipoprotein concentrations in women with the E2/3 genotype (53.7 +/- 19.5 mg/dL) when compared to women with the E3/3 genotype (45.2 +/- 12.0 mg/dL) (p < 0.032). Our data suggest that genetic variation at the APOE locus in the Mexican population is a genetic factor that influences plasma lipid levels. This effect was observed only in the female population. Additional studies attempting to correlate APOE polymorphism with plasma lipid profile in a large number of individuals would be helpful in establishing the true significance of this polymorphism in the Mexican population.

Tumor necrosis factor-alpha promoter polymorphisms in Mexican patients with systemic lupus erythematosus (SLE)

The major histocompatibility (MHC) genes including TNF-alpha, HSP70 and HLA genes have been associated with systemic lupus erythematosus (SLE) in several populations. In this study we analyze the polymorphism of TNF-alpha promoter in 51 Mexican Mestizo SLE patients and 55 ethnically-matched healthy controls by polymerase chain reaction methods. No statistically significant differences were observed in the TNF -308 allele and genotype distribution between patients and healthy controls. However, we found a significant increase in the TNF G/A -238 genotype and in the TNFA -238 allele frequencies in the SLE group when compared with healthy controls (Pc = 0.03, OR = 4.77 and Pc = 0.02, OR = 3.62, respectively). DRB1 analysis showed a similar distribution in patients and controls. Linkage disequilibrium was observed for five haplotypes: DRB1*1401-TNFA-238 (D = 0.84; D' = 1.0; P = 0.015); DRB1*0301-TNFA-238 (D = 1.38; D' = 0.41; P = 0.042); DRB1*1106-TNF2-308 (D = 0.9; D' = 1.0; P = 0.0006); DRB1*1104-TNF2-308 (D = 0.83; D' = 0.45; P = 0.02) and DRB1*1406-TNF2-308 (D = 0.83; D' = 0.45; P = 0.02). Our data suggest that the association between the TNF-alpha -238 polymorphism and SLE could play a major role in disease susceptibility.

Immunogenetics and clinical aspects of Takayasu's arteritis patients in a Mexican Mestizo population

OBJECTIVE

The aim of the present work was to study the association between HLA alleles and Takayasu's arteritis in Mexican Mestizo patients.

METHODS

The study included 26 Mexican Mestizo patients with Takayasu's arteritis and 99 healthy unrelated individuals. HLA-A, -B and -DR alleles were determined by polymerase chain reaction PCR-SSP RESULTS: Increased gene frequencies were demonstrated for HLA-B15(p=0.009,pC=0.020,OR=3.24,EF=11.9%) and HLA-B52 (p=0.008, pC=0.027, OR=5.16, EF=7.7%), and a decreased frequency for the HLA-A24 allele in patients compared to normal controls (p=0.035, pC=NS, PF=11.1%). When HLA typing was correlated to clinicalfeatures in 24 cases, wefound an increasedfrequencies of HLA-DR14 in patients with systemic arterial hypertension (p=0.005, pC=0.004, OR=24.6, EF=38.3%) and HLA-A2 on patients with pulmonary involvement (p=0.034, pC=0.036, OR=3.67, EF=40.4%) when compared to patients without these clinical manifestations.

CONCLUSION

These data confirm HLA-B52 as a relevant susceptibility allele for Takayasu's arteritis and suggest that HLA-B15 could be important as a marker of the disease in Mexican patients. Other class I and/or class II alleles could also be relevant as markers for the clinical features present in these patients.

Polymorphism and distribution of HLA-DR2 alleles in Mexican populations

DRB1*15/16 nucleotide polymorphism was analyzed in 68 DR2 positive individuals (18 Mexican Mestizos, 30 Mazatecans and 20 Nahuas), carrying a total of 75 DR2 haplotypes. HLA-DR2 was one of the most frequent specificities detected in Mazatecans and Nahuas with gene frequency (gf) of 0.232 and 0.141, respectively. In these populations DRB1*16 was the most frequent DR2 split (gf = 0.183 in Mazatecans and gf = 0.135 in Nahuas), whereas in Mexican Mestizos the most frequent was DRB1*15 (gf = 0.065). Four DRB1-DQB1 combinations in Mexican Mestizos, two in Mazatecans and one in Nahuas were in linkage disequilibrium. In spite of the restricted polymorphism, there were differences on DRB1*15/16 alleles found in Mexicans. DRB1*1501 a Caucasian allele was predominant in Mexican Mestizos, whereas DRB1*1602 an Amerindian allele was characteristic on Indian populations. An important difference was detected among the Amerindian populations studied since DRB1*1502 was only present in Mazatecans. This data corroborates the restricted polymorphism of DRB1*15/16 and the high frequency of DRB1*16 subtype in autochthonous American populations and suggest that the differences in gene frequencies of DRB1*15/16 alleles could be helpful in distinguishing each of these population.

HLA genes in Mexican Mazatecans, the peopling of the Americas and the uniqueness of Amerindians

The HLA allele frequency distribution of the Mexican Mazatecan Indians (Olmec culture) has been studied and compared with those of other First American Natives and worldwide populations (a total of 12,100 chromosomes; 6,050 individuals from 59 different populations). The main conclusions are: 1) An indirect evidence of Olmec and Mayan relatedness is suggested, further supporting the notion that Olmecs may have been the precursors of Mayans; 2) Language and genetics do not completely correlate in microenvironmental studies; and 3) Peopling of the Americas was probably more complex than postulated by Greenberg and others (three peopling waves). Significant genetic input from outside is not noticed in Meso and South American Amerindians according to the phylogenetic analyses; while all world populations (including Africans, Europeans, Asians, Australians, Polynesians, North American Na-Dene Indians and Eskimos) are genetically related. Meso and South American Amerindians tend to remain isolated in the Neighbor-Joining, correspondence and plane genetic distance analyses.

DNA sequencing of HLA-B alleles in Mexican patients with Takayasu arteritis

Takayasu arteritis (TA) is characterized by a 'pulseless' condition and occurs frequently in young females from Asian and South American countries. It has been associated with Mayor Histocompatibility Complex (MHC) genes in different populations. Recent data indicate direct participation of HLA-B alleles in the susceptibility to the disease. This fact was explored in an associative study with TA to establish if some region in the exon 2, intron 2 or in the exon 3 of HLA-B alleles is common in the alleles associated with TA and at the same time to know if a specific sequence or an epitope, more than an allele, would be responsible for the susceptibility to this vasculitis. We studied HLA-B alleles of 12 Mexican patients with TA using PCR-SSP and sequencing. The analysis by PCR-SSP in 12 patients showed that five of them showed the B*15 allele, three the B*40 allele and two the B*39 allele, the remaining two presented the B*44 allele. Sequence analysis enabled us to define that the B*39 subtypes are B*3908; B*15 subtypes are B*1510, B*1515, B*1522 and B*1531; and the B*40 subtypes are B*4005 and B*4008. An individual with B*51 (B*5107) and another with B*52 (B*5201) alleles were also identified. The sequences of the intron 2 seem be heterogeneous. Analysis at the 63 and 67 positions of HLA-B alleles showed that 9 of them have similarity in some of these positions with the residues detected in the B*5201 and B*3902 alleles associated with TA in Asian populations. The results indicate that there is heterogeneity in the alleles associated with TA in Mexicans but, in spite of that heterogeneity, the alleles associates can be separated into three groups: B*39, B*15 and B*40, whose subtypes are rare and apparently of recent generation in Mexico, probably by recombination events at intron 2 level. The sequences analysis also shows that most of the alleles detected in the Mexican patients share two epitopes described in the susceptibility alleles in Asian populations, suggesting that these epitopes could be responsible for the susceptibility to develop the disease in spite of the allele in which are found.

Lack of association between the polymorphism at the heat-shock protein (HSP70-2) gene and systemic lupus erythematosus (SLE) in the Mexican mestizo population

Major histocompatibility complex (MHC) alleles have been recognized as genetic factors for developing systemic lupus erythematosus (SLE). In the present study we analyzed whether a heat-shock protein gene (HSP70-2) is involved in determining susceptibility to develop SLE in a Mexican Mestizo population. A HSP70-2 Pst I polymorphism was detected by a restriction fragment length polymorphism analysis of polymerase chain reaction (PCR-RFLP) in 107 SLE patients and 158 healthy controls. No statistically significant differences were observed in the HSP70-2 allele distribution between patients and healthy controls. HLA-DR analysis showed an increased frequency of HLA-DR3 allele in the patients group (P < 0.05, OR = 2.26, EF = 6.0%). On the other hand, when we analyzed HSP70-2 polymorphism in relation to HLA-DR3 allele, we could only detect an increased frequency of AB genotype in the DR3 negative patients (pC < 0.05, RR = 2.6, EF = 11.3%). Linkage disequilibrium was observed for three haplotypes: HLA-DR3-HSP70-2A (D = 0.03, D' = 0.67, P < 0.01); HLA-DR1-HSP70-2A (D = 0.03, D' = 0.86, P < 0.01) and HLA-DR8-HSP70-2B (D = 0.02, D' = 0.46, P = 0.02). Our data indicate that HSP70-2 gene polymorphism as opposed to the other ethnic groups does not appear to be relevant in SLE susceptibility in Mexican patients and that the distribution of the different alleles depend on the frequency of HLA alleles associated with them.

HLA-DR4 allele frequencies on Indian and Mestizo population from Mexico

Using PCR-SSOP and sequencing, we examined DRB1*04 nucleotide polymorphism in 137 DR4-positive Mexican healthy individuals (46 Mexican Mestizos, 64 Mazatecans, and 27 Nahuas), carrying a total of 147 DR4 haplotypes. Eleven different DRB1*04 alleles were detected in Mexican Mestizo population, whereas, in the two Indian groups a restricted polymorphism was observed (5 variants in Mazatecans and 4 in Nahuas). DRB1*0407 was the most frequent allele (gf = 0.106 in Mexican Mestizos, gf = 0.281 in Mazatecans, and gf = 0.189 in Nahuas). In spite of the restriction in polymorphism, there were differences on DRB1*04 alleles found in Mexicans mainly between Mazatecan and Nahua populations. DRB1*0403 was characteristic allele in Nahua ethnic group, whereas, 0404 and 0411 were predominant alleles in Mazatecans. This data corroborates the restricted polymorphism of DRB1*04 alleles in American populations. In spite of the restriction in this polymorphism, differences in frequencies of DRB1*04 alleles could help distinguish each population.

Heat-shock protein (HSP70-2) allelic frequencies in three distinct Mexican populations

The major histocompatibility complex (MHC) genes are highly polymorphic and therefore have been useful in population genetics and disease association studies. We analyzed restriction fragment length polymorphism of HSP70-2 alleles in healthy unrelated Mestizo, Mazatecan and Nahua populations. Both Indian groups, Mazatecans and Nahuas, were in Hardy-Weinberg equilibrium, while Mestizos were in disequilibrium (chi 2 = 0.399; P < 0.05). The Mazatecan Indians presented a high frequency of BB homozygosity (17.35%) compared to Mestizos (5%) (P = 0.01). Mexican ethnic groups present differences in distribution of BB genotype. The low frequency of BB genotype in Mestizos may be the result of a negative selection process.

HLA-DRB and HLA-DQB loci in the genetic susceptibility to develop glaucoma in Mexicans

PURPOSE

Glaucoma is a clinically heterogeneous disease with a pathophysiology that may include genetic susceptibility, possibly associated with an immunologic disorder. The aim of this study was to determine whether the DNA polymorphisms located in the HLA-DRB1 and HLA-DQB1 genes show a specific association pattern in Mexican mestizo patients with primary open-angle glaucoma.

METHODS

This was a cross-sectional, case-control, multicenter study. We analyzed the HLA-DRB1 and DQB1 loci of 81 Mexican mestizo nonrelated patients with primary open-angle glaucoma and 98 healthy ethnic matched control subjects. Patients were diagnosed clinically and by visual fields examination. HLA typing was performed by PCR-SSO reverse dot blot.

RESULTS

We documented increased frequencies of HLA-DRB1*0301, DRB1*1101, DRB1*0701, DRB1*1402, DQB1*0302, and DQB1*0301; however, none of them were significantly different from normal control subjects. Haplotype analysis showed that the HLA-DRB1*0407-DQB1*0302 haplotype is significantly increased in patients compared with control subjects (P = .0001).

CONCLUSIONS

The haplotype HLA-DRB1*0407-DQB1*0302 is common among Mexican mestizo (haplotype frequency = 0.102), and it was increased in our patients (haplotype frequency = 0.259, P = .0001). This may reflect an independent association of this haplotype with the disease as the result of linkage disequilibrium or the influence of a neighboring gene. The pathophysiology of this illness is uncertain, and further studies are needed regarding the genetic susceptibility to develop primary open-angle glaucoma.