Hypobaric hypoxia modulated structural characteristics of circulating cell-free DNA in high-altitude pulmonary edema

The utility of cell-free (cf) DNA has extended as a surrogate or clinical biomarker for various diseases. However, a more profound and expanded understanding of the diverse cfDNA population and its correlation with physiological phenotypes and environmental factors is imperative for using its full potential. The high-altitude (HA; altitude > 2,500 m above sea level) environment characterized by hypobaric hypoxia offers an observational case-control design to study the differential cfDNA profile in patients with high-altitude pulmonary edema (HAPE) (number of subjects, n = 112) and healthy HA sojourners (n = 111). The present study investigated cfDNA characteristics such as concentration, fragment length size, degree of integrity, and subfractions reflecting mitochondrial-cfDNA copies in the two groups. The total cfDNA level was significantly higher in patients with HAPE, and the level increased with increasing HAPE severity (P = 0.0036). A lower degree of cfDNA integrity of 0.346 in patients with HAPE (P = 0.001) indicated the prevalence of shorter cfDNA fragments in circulation in patients compared with the healthy HA sojourners. A significant correlation of cfDNA characteristics with the peripheral oxygen saturation levels in the patient group demonstrated the translational relevance of cfDNA molecules. The correlation was further supported by multivariate logistic regression and receiver operating characteristic curve. To our knowledge, our study is the first to highlight the association of higher cfDNA concentration, a lower degree of cfDNA integrity, and increased mitochondrial-derived cfDNA population with HAPE disease severity. Further deep profiling of cfDNA fragments, which preserves cell-type specific genetic and epigenetic features, can provide dynamic physiological responses to hypoxia.NEW & NOTEWORTHY This study observed altered cell-free (cf) DNA fragment patterns in patients with high-altitude pulmonary edema and the significant correlation of these patterns with peripheral oxygen saturation levels. This suggests deep profiling of cfDNA fragments in the future may identify genetic and epigenetic mechanisms underlying physiological and pathophysiological responses to hypoxia.

Differential methylation in EGLN1 associates with blood oxygen saturation and plasma protein levels in high-altitude pulmonary edema

BACKGROUND

High-altitude (HA, 2500 m) hypoxic exposure evokes a multitude of physiological processes. The hypoxia-sensing genes though influence transcriptional output in disease susceptibility; the exact regulatory mechanisms remain undetermined in high-altitude pulmonary edema (HAPE). Here, we investigated the differential DNA methylation distribution in the two genes encoding the oxygen-sensing HIF-prolyl hydroxylases, prolyl hydroxylase domain protein 2 (PHD2) and factor inhibiting HIF-1α and the consequent contributions to the HAPE pathophysiology.

METHODS

Deep sequencing of the sodium bisulfite converted DNA segments of the two genes, Egl nine homolog 1 (EGLN1) and Hypoxia Inducible Factor 1 Subunit Alpha Inhibitor (HIF1AN), was conducted to analyze the differential methylation distribution in three study groups, namely HAPE-patients (HAPE-p), HAPE-free sojourners (HAPE-f) and healthy HA natives (HLs). HAPE-p and HAPE-f were permanent residents of low altitude (< 200 m) of North India who traveled to Leh (3500 m), India, and were recruited through Sonam Norboo Memorial (SNM) hospital, Leh. HLs were permanent residents of altitudes at and above 3500 m. In addition to the high resolution, bisulfite converted DNA sequencing, gene expression of EGLN1 and HIF1AN and their plasma protein levels were estimated.

RESULTS

A significantly lower methylation distribution of CpG sites was observed in EGLN1 and higher in HIF1AN (P < 0.01) in HAPE-p compared to the two control groups, HAPE-f and HLs. Of note, differential methylation distribution of a few CpG sites, 231,556,748, 231,556,804, 231,556,881, 231,557,317 and 231,557,329, in EGLN1 were significantly associated with the risk of HAPE (OR = 4.79-10.29; P = 0.048-004). Overall, the methylation percentage in EGLN1 correlated with upregulated plasma PHD2 levels (R = - 0.36, P = 0.002) and decreased peripheral blood oxygen saturation (SpO₂) levels (R = 0.34, P = 0.004). We also identified a few regulatory SNPs in the DNA methylation region of EGLN1 covering chr1:231,556,683-231,558,443 suggestive of the functional role of differential methylation distribution of these CpG sites in the regulation of the genes and consequently in the HIF-1α signaling.

CONCLUSIONS

Significantly lower methylation distribution in EGLN1 and the consequent physiological influences annotated its functional epigenetic relevance in the HAPE pathophysiology.

The deleterious impact of a non-synonymous SNP on protein structure and function is apparent in hypertension

Essential hypertension (EH) is a significant health issue around the globe. The indifferent therapy regimen suggests varied physiological functions due to the lifestyle and genetic presentations of an individual. The endothelial nitric oxide synthase (NOS3) gene is a crucial vascular system marker in EH that contributes significantly to the phenotype. Hence, the present study aimed to employ the candidate gene approach and investigate the association between NOS3 single nucleotide polymorphism (SNP) E298D (G894T/rs1799983) by applying several in silico tools and validation through human samples screening. We corroborated computational findings through a case-control study comprising 294 controls and 299 patients; the 894T allele emerged significantly as the risk allele (odds ratio=2.07; P=6.38E-05). The in silico analyses highlighted the significance of E298D on the native structure and function of NOS3. The dynamics simulation study revealed that the variant type 298D caused structural destabilization of the protein to alter its function. Plasma nitrite levels were reduced in patients (P=0.0002), and the same correlated with the 894T allele. Furthermore, correlations were apparent between clinical, genotype, and routine biochemical parameters. To conclude, the study demonstrated a perceptible association between the SNP E298D and NOS3 protein structure stability that appears to have a bearing on the enzyme's function with a deleterious role in EH.

Susceptibility of CTLA-4 -1661A/G polymorphism towards severity of rheumatic heart disease

AIM

Genetic contribution in acute rheumatic fever (ARF)/rheumatic heart disease (RHD) has been suggested but not according to severity of the valve involvement. This study attempts to identify the relevance of CTLA-4 polymorphism with severity of the disease.

METHODS

In a case-control design, 291 healthy controls and 83 patients were genotyped for association between RHD and single-nucleotide polymorphisms -1661A/G of CTLA-4.

RESULTS

Segregation of patients on the basis of severity i.e., MVL (Mitral Valve Lesion) and CVL (Combined Valve Lesion) revealed that the frequency of CTLA-4 -1661G allele depleted as the disease progressed to CVL (p < 0.05). Patients in the age group of 31-45 years were significantly more susceptible (p < 0.046). Whereas, female patients were more susceptible than the male patients.

CONCLUSION

Our study suggests the risk associated with decreased frequency of CTLA-4 -1661G allele in the CVL group and in females.

High-altitude pulmonary edema is aggravated by risk-loci and associated transcription factors in HIF-prolyl hydroxylases

High-altitude (HA, > 2500 meters) hypoxic exposure evokes several physiological processes that may be abetted by differential genetic distribution in sojourners, who are susceptible to various HA disorders, such as high-altitude pulmonary edema (HAPE). The genetic variants in hypoxia-sensing genes influence the transcriptional output, however the functional role has not been investigated in HAPE. This study explored the two hypoxia-sensing genes, prolyl hydroxylase domain protein 2 (EGLN1) and factor inhibiting HIF-1α (HIF1AN) in HA adaptation and maladaptation in three well-characterized groups: highland natives, HAPE-free controls and HAPE-patients. The two genes were sequenced and subsequently validated through genotyping of significant SNPs, haplotyping and MDR. Three EGLN1 SNPs rs1538664, rs479200 and rs480902 and their haplotypes emerged significant in HAPE. Blood gene expression and protein levels also differed significantly (P < 0.05) and correlated with clinical parameters and respective alleles. The RegulomeDB annotation exercises of the loci corroborated regulatory role. Allele-specific differential expression was evidenced by luciferase assay followed by electrophoretic mobility shift assay, LC-MS/MS and supershift assays, which confirmed allele-specific transcription factor (TF) binding of FUS RNA binding protein (FUS) with rs1538664A, Rho GDP dissociation inhibitor 1 (RhoGDH1) with rs479200T and Hypoxia up-regulated protein 1 (HYOU1) with rs480902C. Docking simulation studies were in sync for the DNA-TF structural variations. There was strong networking among the TFs that revealed physiological consequences through relevant pathways. The two hydroxylases appear crucial in the regulation of hypoxia-inducible responses.

In silico designing, in vitro and in vivo evaluation of potential PPAR-γ agonists derived from aryl propionic acid scaffold

Attributed to several side effects, especially on hepatic tissues and body weight, there is always an urge of innovation and upgrading in already existing medication being used in maintaining diabetic condition. Therefore, in the present work, forty-eight molecules derived from arylpropionic acid scaffold were synthesized and their evaluation against diabetes was carried out. The synthesis of these molecules attributed to excellent dock score displayed by all the structures performed against PPAR-γ receptor site. Subsequently, all the derivatives were primarily deduced for their antidiabetic potential by OGTT. The compounds that showed significant antidiabetic activity in OGT Test and also exhibited high dock scores were assessed further by in vitro PPAR transactivation assay to assure analogy between in vivo and in vitro studies. The antidiabetic activity of these active compounds was then evaluated on STZ induced diabetic model in vivo. The most active compounds were scrutinized for its effect on PPAR-γ gene expression and hepatotoxic effect. Finally, it was recapitulated that these derivatives can provide a new prospect towards the development of antidiabetic agents with fewer side effects.

Vascular homeostasis at high-altitude: role of genetic variants and transcription factors

High-altitude pulmonary edema occurs most frequently in non-acclimatized low landers on exposure to altitude ≥2500 m. High-altitude pulmonary edema is a complex condition that involves perturbation of signaling pathways in vasoconstrictors, vasodilators, anti-diuretics, and vascular growth factors. Genetic variations are instrumental in regulating these pathways and evidence is accumulating for a role of epigenetic modification in hypoxic responses. This review focuses on the crosstalk between high-altitude pulmonary edema-associated genetic variants and transcription factors, comparing high-altitude adapted and high-altitude pulmonary edema-afflicted subjects. This approach might ultimately yield biomarker information both to understand and to design therapies for high-altitude adaptation.

Susceptibility to high-altitude pulmonary edema is associated with circulating miRNA levels under hypobaric hypoxia conditions

Hypobaric hypoxia poses stress to sojourners traveling to high-altitude. A cascade of physiological changes occurs to cope with or adapt to hypobaric hypoxia. However, an insufficient physiological response to the hypoxic condition resulting from imbalanced vascular homeostasis pathways results in high-altitude pulmonary edema (HAPE). The present study aims to identify the implication of miRNAs associating with HAPE and adaptation. We analyzed the expression of 1,113 miRNAs in HAPE-patients (HAPE-p), HAPE-free controls (HAPE-f), and highland natives (HLs). Based on miRNA profiling and in silico analyses, miR-124-3p emerged relevantly. We observed a significant overexpression of miR-124-3p in HAPE-p. In silico analyses revealed a direct interaction of miR-124-3p with vascular homeostasis and hypoxia-associated genes NOS3 (endothelial nitric oxide synthase), Apelin, and ETS1 (V-Ets avian erythroblastosis virus E2 oncogene homolog 1). Moreover, the transcript and biolevel expression of these genes were significantly decreased in HAPE-p when compared with HAPE-f or HLs. Our in vitro analysis in human umbilical vein endothelial cells demonstrated a significant knockdown of these genes both at transcript and protein levels following miR-124-3p overexpression. Conclusively, our results showed that miR-124-3p might play a plausible role in HAPE pathophysiology by inhibiting the expression of NOS3, Apelin, and ETS1.

Structural and functional alterations of nitric oxide synthase 3 due to missense variants associate with high-altitude pulmonary edema through dynamic study

The human endothelial nitric oxide synthase (NOS3) is 28 Kbp at 7q36.1 and encodes protein comprising of 1280 amino acids. Being a major source of nitric oxide, the enzyme is crucial to the vascular homeostasis and thereby to be an important pharmaceutical target. We hence have been investigating this molecule in a high-altitude disorder namely, high-altitude pulmonary edema (HAPE). We performed a genome-wide association study (GWAS) in a case-control design of sojourners that included healthy controls and HAPE patients (n = 200) each. Four NOS3 missense SNPs i.e. rs1799983 (E298D), rs3918232 (V827M), rs3918201 (R885M) and rs3918234 (Q982L), were associated significantly with HAPE (P-value < 0.05). Furthermore, extensive in silico analyses were performed to predict the detrimental effect of the four variant types and their three most relevant co-factors namely, heme, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) that are accountable for amendment of protein stability leading to structural de-construction. Subsequently, we validated the findings in a larger sample size of the two study groups. HAPE patients had a higher frequency of the four variants and significantly decreased levels of circulating nitric oxide (NO) (P-value < 0.001). The in silico and human subjects findings complement each other. This study explored the impact of HAPE-associated NOS3 variants with its protein structure stability and holds promise to be current and future drug targets.Communicated by Ramaswamy H. Sarma.

Salt-sensitive phenotypes: A community-based exploratory study from northeastern India

Background

Salt sensitivity is known to increase the risk of cardiovascular diseases in both normotensive and hypertensive subjects. The population in the northeastern region of India consumes excess dietary salt but their saltsensitive phenotype is not known.

Methods

We did a community-based exploratory study using volunteers in the northeastern region of India to determine salt-sensitive (SS) and salt-resistant (SR) phenotypes. A total of 374 (206 normotensive and 168 hypertensive) subjects who gave informed consent were stabilized for salt with 7 days of a low-salt (2.9 g/day) diet followed by 7 days of a high-salt (15.2 g/day) diet. SS was defined as an increase of mean arterial blood pressure ≥9 mmHg after a high-salt diet.

Results

We noted an increase in systolic blood pressure of 9.3 mmHg in normotensive subjects and 10.7 mmHg in hypertensive subjects, with a modest effect on diastolic blood pressure (6.9 mmHg in normotensive and 8.2 mmHg in hypertensive subjects) after a high-salt diet. Salt-sensitive phenotype was present in 40.8% of normotensive and 47.6% of hypertensive subjects. Resistance to introduction of high salt was observed in 43.7% of normotensive and 33.9% of hypertensive subjects. Consumption of extra salt (adjusted OR 1.99, 95% CI 1.25-3.18) was independently associated with salt sensitivity.

Conclusion

Salt sensitivity was found in a large proportion of normotensive and hypertensive subjects. Restriction of salt intake could be an effective intervention to control hypertension among salt-sensitive subjects.

Elevated blood plasma levels of epinephrine, norepinephrine, tyrosine hydroxylase, TGFβ1, and TNFα associated with high-altitude pulmonary edema in an Indian population

Biomarkers are essential to unravel the locked pathophysiology of any disease. This study investigated the role of biomarkers and their interactions with each other and with the clinical parameters to study the physiology of high-altitude pulmonary edema (HAPE) in HAPE-patients (HAPE-p) against adapted highlanders (HLs) and healthy sojourners, HAPE-controls (HAPE-c). For this, seven circulatory biomarkers, namely, epinephrine, norepinephrine, tyrosine hydroxylase, transforming growth factor beta 1, tumor necrosis factor alpha (TNFα), platelet-derived growth factor beta beta, and C-reactive protein (CRP), were measured in blood plasma of the three study groups. All the subjects were recruited at ~3,500 m, and clinical features such as arterial oxygen saturation (SaO₂), body mass index, and mean arterial pressure were measured. Increased levels of epinephrine, norepinephrine, tyrosine hydroxylase, transforming growth factor-beta 1, and TNFα were observed in HAPE-p against the healthy groups, HAPE-c, and HLs (P<0.0001). CRP levels were decreased in HAPE-p against HAPE-c and HLs (P<0.0001). There was no significant difference or very marginal difference in the levels of these biomarkers in HAPE-c and HLs (P>0.01). Correlation analysis revealed a negative correlation between epinephrine and norepinephrine (P=4.6E−06) in HAPE-p and positive correlation in HAPE-c (P=0.004) and HLs (P=9.78E−07). A positive correlation was observed between TNFα and CRP (P=0.004) in HAPE-p and a negative correlation in HAPE-c (P=4.6E−06). SaO₂ correlated negatively with platelet-derived growth factor beta beta (HAPE-p; P=0.05), norepinephrine (P=0.01), and TNFα (P=0.005) and positively with CRP (HAPE-c; P=0.02) and norepinephrine (HLs; P=0.04). Body mass index correlated negatively with epinephrine (HAPE-p; P=0.001) and positively with norepinephrine and tyrosine hydroxylase in HAPE-c (P<0.05). Mean arterial pressure correlated positively with TNFα in HAPE-p and norepinephrine in HLs (P<0.05). Receiver operating characteristic curve analysis yielded a positive predictive value for these biomarkers with HAPE (area under the curve >0.70, P<0.05). The results clearly suggest that increased plasma levels of these circulatory biomarkers associated with HAPE.

Impact of interactions between risk alleles on clinical endpoints in hypertension

OBJECTIVE

Impairment of the renin-angiotensinogen-aldosterone system (RAAS), one of the characteristics of essential hypertension (EH), imbalances vascular homeostasis. Despite inconsistent reports on individual single nucleotide polymorphisms (SNPs) as a major predictor of EH, interactions among RAAS genetic variants are rarely investigated.

METHODS

Using SNP markers, we studied potential interactions between angiotensin 1 converting enzyme (ACE), angiotensinogen (AGT), angiotensin II-type 1 receptor (AGTR1), and α adducin (ADD1) variants and their correlation with clinical endpoints in 545 individuals with hypertension and 400 age- and ethnicity-matched unrelated controls. Generalised multifactor dimensionality reduction (GMDR) analysis identified the models for genotype interaction.

RESULTS

Although the results on single genes were significant, gene-gene interactions were more reliable and promising as markers in predisposing hypertension. The best models to represent association of multi-locus interactions with augmented hypertension susceptibility were: (a) within gene 4-locus model comprised of AGT SNPs -217G/A, -20A/C, -6G/A and 235M/T (p=0.022, OR 6.1); and (b) between genes 5-locus model comprised of AGT -217G/A, -20A/C, -6G/A, 235M/T and ACE I/D (p=0.05, OR 4.6). Stratification of 4- and 5-locus GMDR models on the basis of risk alleles from ≤1 to ≥7 increased the ORs from 2.8 to 36.1 and from 0.9 to 16.1, respectively. Moreover, compared to ≤1 risk alleles the ≥7 interacting risk alleles in both 4- and 5-locus models showed an increment of 14.2% and 11.1% in systolic blood pressure, 7.7% and 1.1% in diastolic blood pressure, and 10.5% and 5.1% in mean arterial pressure, respectively, in patients.

CONCLUSIONS

Interactions among the genetic loci of RAAS components may be used as a predictor for susceptibility to hypertension.

Polymorphisms and haplotype of ROCK2 associate with high altitude essential hypertension in native high altitude Ladakhi Indian population: a preliminary study

BACKGROUND AND OBJECTIVES

High-altitude essential hypertension (HAEH) is a disease occurring in permanent residents of high-altitude regions. The disease is characterized with SBP ≥140 mmHg and DBP ≥90 mmHg. HAEH is known to run in families, i.e. the disease has genetic component. Rho-associated coiled-coil containing protein kinase 2 (ROCK2) is a stress-activated serine-threonine kinase known to disturb vascular-homeostasis leading to an increase in systemic vascular resistance, hallmark of HAEH. ROCK2 is implicated in sea-level essential hypertension but its role in HAEH is yet to be elucidated.

METHODS

The present study deals with genotyping 13 polymorphisms of ROCK2 gene in demographicaly matched human cases (n = 65) and controls (n = 38) by Sequenom MS (TOF)-based MassARRAY platform using iPLEX Gold technology.

RESULTS

A significant association was observed for GG genotype (SNP, rs978906), AA genotype (SNP, rs6753921), GG genotype (SNP, rs10495582) and AA genotype (SNP, rs2230774) with HAEH (p < 0.05). The 4 SNPs were tagged to each other and formed a 35 kb LD block (r(2 )> 0.90). Haplotype AGCC, composed of wild-type alleles of the SNPs was over represented in controls. In contrast, haplotype GAGA, composed of variant-alleles was observed to be in higher proportion in cases. Moreover, SBP levels (mmHg) were higher in cases with risk genotype against the ones having protective genotype (p = 0.05). Bioinformatic analysis revealed binding of a critical transcription factor, SRF to variant-allele G of SNP rs10495582. SRF has been reported in previous studies to promote ROCK2 transcriptional expression.

INTERPRETATION AND CONCLUSIONS

The data clearly suggests association of ROCK2 polymorphisms and haplotypes with HAEH.

Phenotype, Body Composition, and Prediction Equations (Indian Fatty Liver Index) for Non-Alcoholic Fatty Liver Disease in Non-Diabetic Asian Indians: A Case-Control Study

OBJECTIVE

In this study, we have attempted comparison of detailed body composition phenotype of Asian Indians with non-alcoholic fatty liver disease (NAFLD) vs. those without, in a case controlled manner. We also aim to analyse prediction equations for NAFLD for non-diabetic Asian Indians, and compare performance of these with published prediction equations researched from other populations.

METHODS

In this case-control study, 162 cases and 173 age-and sex-matched controls were recruited. Clinical, anthropometric, metabolic, and body composition profiles, and liver ultrasound were done. Fasting insulin levels, value of homeostasis model assessment of insulin resistance (HOMA-IR), and serum high sensitive C-reactive protein (hs-CRP) levels were evaluated. Multivariate logistic and linear regression analyses were used to arrive at prediction equations for fatty liver [Indian fatty liver index (IFLI)].

RESULTS

As compared to those without fatty liver, those with fatty liver exhibited the following; Excess dorsocervical fat ('Buffalo hump'), skin tags, xanthelasma, 'double chin', arcus; excess total, abdominal and subcutaneous adiposity, and high blood pressure, blood glucose, measures of insulin resistance (fasting insulin and HOMA-IR values), lipids and hs-CRP levels. Two prediction equations were developed; Clinical [Indian Fatty Liver Index-Clinical; IFLI-C]: 1(double chin) +15.5 (systolic blood pressure) +13.8 (buffalo hump); and IFLI-Clinical and Biochemical (CB): serum triglycerides+12 (insulin)+1(systolic blood pressure) +18 (buffalo hump). On ROC Curve analysis, IFLI performed better than all published prediction equations, except one.

CONCLUSION

Non-diabetic Asian Indians with NAFLD researched by us were overweight/obese, had excess abdominal and subcutaneous fat, multiple other phenotypic markers, had higher insulin resistance, glycemia, dyslipidemia and subclinical inflammation than those without. Prediction score developed by us for NAFLD; IFLI-C and IFLI-CB, should be useful for clinicians and researchers.

ROCK2 and MYLK variants under hypobaric hypoxic environment of high altitude associate with high altitude pulmonary edema and adaptation

Objective

To date, a major class of kinases, serine–threonine kinase, has been scantly investigated in stress-induced rare, fatal (if not treated early), and morbid disorder, high altitude pulmonary edema (HAPE). This study examined three major serine–threonine kinases, ROCK2, MYLK, and JNK1, along with six other genes, tyrosine hydroxylase, G-protein subunits GNA11 and GNB3, and alpha1 adrenergic receptor isoforms 1A, 1B, and 1D as candidate gene markers of HAPE and adaptation.

Methods

For this, 57 variants across these nine genes were genotyped in HAPE patients (n=225), HAPE controls (n=210), and highlanders (n=259) by Sequenom MS (TOF)-based MassARRAY® platform using iPLEX™ Gold technology. In addition, to study the gene expression, quantitative real-time polymerase chain reaction was performed in human peripheral blood mononuclear cells of the three study groups.

Results

A significant association was observed for C allele (ROCK2 single-nucleotide polymorphism, rs10929728) with HAPE (P=0.03) and C, T, and A alleles (MYLK single-nucleotide polymorphisms, rs11717814, rs40305, and rs820336) with both HAPE and adaptation (P=0.001, P=0.006, and P=0.02, respectively). ROCK2 88 kb GGGTTGGT haplotype was associated with lower risk of HAPE (P=0.0009). MYLK 7 kb haplotype CTA, composed of variant alleles, was associated with higher risk of HAPE (P=0.0006) and lower association with adaptation (P=1E–06), whereas haplotype GCG, composed of wild-type alleles, was associated with lower risk of HAPE (P=0.001) and higher association with adaptation (P=1E–06). Haplotype–haplotype and gene–gene interactions demonstrated a correlation in working of ROCK2 and MYLK.

Conclusion

The data suggest the association of ROCK2 with HAPE and MYLK with HAPE and adaptation in Indian population. The outcome has provided new insights into the physiology of HAPE and adaptation.

Lungs at high-altitude: genomic insights into hypoxic responses

Hypobaric hypoxia at high altitude (HA) results in reduced blood arterial oxygen saturation, perfusion of organs with hypoxemic blood, and direct hypoxia of lung tissues. The pulmonary complications in the cells of the pulmonary arterioles due to hypobaric hypoxia are the basis of the pathophysiological mechanisms of high-altitude pulmonary edema (HAPE). Some populations that have dwelled at HA for thousands of years have evolutionarily adapted to this environmental stress; unadapted populations may react with excessive physiological responses that impair health. Individual variations in response to hypoxia and the mechanisms of HA adaptation provide insight into physiological responses. Adaptive and maladaptive responses include alterations in pathways such as oxygen sensing, hypoxia signaling, K+- and Ca2+-gated channels, redox balance, and the renin-angiotensin-aldosterone system. Physiological imbalances are linked with genetic susceptibilities, and nonhomeostatic responses in gene regulation that occur by small RNAs, histone modification, and DNA methylation predispose susceptible humans to these HA illnesses. Elucidation of the interaction of these factors will lead to a more comprehensive understanding of HA adaptations and maladaptations and will lead to new therapeutics for HA disorders related to hypoxic lungs.

Interactions between the genes of vasodilatation pathways influence blood pressure and nitric oxide level in hypertension

BACKGROUND

This study investigates the contribution of genetic interactions between the β-2 adrenergic receptor (ADRB2) and nitric oxide synthase (NOS3) genes to the complex etiology of hypertension.

METHODS

Using single nucleotide polymorphism (SNP) markers, we studied potential interactions between ADRB2 and NOS3 variants and their correlation with clinical, biochemical, and expression levels in 546 individuals with hypertension and 884 age-, sex-, and ethnicity-matched unrelated control subjects. Generalized multifactor dimensionality reduction (GMDR) analysis identified the models for genotype interaction.

RESULTS

The best models to represent association of genotypes with augmented hypertension susceptibility were the 4- and 5-locus interacting GMDR models of ADRB2 and NOS3 compared with within-gene 6-locus ADRB2 and 2-locus NOS3 (odds ratio (OR) = 4.8, P = 0.04; OR = 5.6, P = 0.02, respectively). Stratification of 4- and 5-locus GMDR models on the basis of risk alleles (in increasing order) increased the ORs from 1.26 to 14.17 and from 0.81 to 14.18, respectively, and correlated linearly with increased systolic blood pressure, diastolic blood pressure, and mean arterial pressure and decreased nitric oxide level (P ≤ 0.0004). We performed various analyses, such as single-locus, genetic interactions, sliding-window, and comparative analysis. Each analysis consistently revealed the 46A allele of ADRB2 46G/A SNP and 4a allele of NOS3 4b/4a SNP to be associated with risk of hypertension. These risk-conferring markers were associated with decreased ADRB2 and NOS3 expression and decreased nitric oxide level in the patients (P ≤ 0.04).

CONCLUSIONS

Evidence of interaction between the genetic loci of ADRB2 and NOS3 points to varied clinical, biochemical, and expression levels and a role in hypertension susceptibility.

MicroRNAs: An Apparent Switch for High-Altitude Pulmonary Edema

BACKGROUND

High-altitude (HA) attracts people for its beauty and adventure. Interestingly, however, it affects the normal physiology and health due to the hypobaric hypoxic environment. Normal individuals acclimatize efficiently, but susceptible individuals encounter HA related disorders. Among these disorders, high-altitude pulmonary edema (HAPE) results into casualties. During acclimatization, body makes sequential changes in the expression of genes to counterbalance the hypobaric hypoxia induced stress. In this context, gene regulatory elements, such as transcription factors, DNA methylation and microRNAs (miRNAs) become relevant. This review, however, will primarily focus on miRNAs because of its decisive role in maintaining physiological homeostasis, both under normoxic and hypoxic conditions.

METHODS

Availing the literature, an in-silico study was performed to explore the anticipated role of miRNAs in HAPE pathophysiology.

RESULTS

We observed robust target based networking among the miRNAs. miR-16, 20b, 22, 206 and 17/92 were reported to have decreased expression in response to hypoxia and inhibit ion channels and increase pulmonary arterial pressure leading to vascular dysfunction and loss of cellular integrity. Whereas, miR-23b, 26a and 155 inhibit TGF signaling and contribute to increased pulmonary pressure, while miR-210 inhibits mitochondrial function. Incidentally, these physiological func- tions associate with HAPE, favoring possible role of miRNAs.

CONCLUSION

It is concluded that the expression of individual/groups of miRNAs may change differentially under hypobaric hypoxia to modulate human physiology; however, this needs to be validated for HAPE pathophysiology.

Independent associations of low 25 hydroxy vitamin D and high parathyroid hormonal levels with nonalcoholic fatty liver disease in Asian Indians residing in north India

OBJECTIVE

We analysed the associations of 25 hydroxy vitamin D [25(OH) D] and parathyroid hormone (PTH) levels with clinical, anthropometric, biochemical and body composition parameters in Asian Indians with nonalcoholic fatty liver disease (NAFLD).

METHODS

In this case-control study, 162 cases and 173 age and sex matched controls were recruited. Clinical, anthropometric, biochemical parameters and liver ultrasound were done. Percentage body fat (%BF), lean body mass and bone mineral density (BMD) were assessed by dual energy X-ray absorptiometry (DXA). Fasting insulin levels, value of homeostasis model assessment of insulin resistance (HOMA-IR), serum 25(OH) D, calcium and PTH levels were measured.

RESULTS

Subjects with NAFLD had lower serum 25(OH) D (19.4 ± 8.5 vs. 27.8 ± 9.4 ng/ml, p = 0.0001) and higher serum PTH (54.9 ± 19.5 vs.41.5 ± 18.3 pg/ml, p = 0.0001) levels as compared to controls. We observed significantly high values of systolic blood pressure (p = 0.002), waist circumference (p = 0.05), serum triglycerides (p = 0.002), total cholesterol (p = 0.002), alanine transaminase (p = 0.05), fasting insulin (p = 0.02) and HOMA-IR (p = 0.03) in the lowest 25(OH) D quartile. Multivariable-logistic regression showed that low serum 25(OH) D [OR (95%CI): 4.46 (2.58-7.72), p = 0.0001] and high PTH [OR (95%CI): 2.21 (1.50-3.30), p = 0.0001] level were independently associated with NAFLD.

CONCLUSION

Low serum 25(OH) D and high PTH levels were independently associated with the presence of NAFLD in Asian Indians residing in north India.

Genetic variation in the patatin-like phospholipase domain-containing protein-3 (PNPLA-3) gene in Asian Indians with nonalcoholic fatty liver disease

BACKGROUND

The association of the rs738409 polymorphism of patatin-like phospholipase-3 (PNPLA3) with nonalcoholic fatty liver disease (NAFLD) has been suggested in other populations, but not in Asian Indians. We investigated the association of the rs738409 polymorphism of PNPLA3 with clinical, anthropometric, and biochemical profiles in Asian Indians with NAFLD.

METHODS

In this case-control study, 162 cases and 173 controls were recruited. Abdominal ultrasound, clinical, anthropometry, and biochemical profiles were determined. Fasting insulin levels and values for homeostasis model assessment of insulin resistance (HOMA-IR) were determined. Polymerase chain reaction and restriction fragment length polymorphism of the PNPLA3 gene were performed. The associations of this polymorphism with clinical, anthropometric, and biochemical profiles were investigated.

RESULTS

A higher frequency of C/G and G/G genotypes of the rs738409 polymorphism was obtained in cases as compared to controls (P=0.04), and as a consequence the frequency of the minor allele G was significantly higher in cases (P=0.003). In this study, the G allele was associated with significantly higher fasting insulin (P=0.002), HOMA-IR (P=0.05), alanine transaminase (P=0.003), and aspartate transaminase (P=0.04) values only in cases, but not in the controls. The values of serum triglycerides and total cholesterol were slightly higher in cases with G/C+G/G genotypes but statistically not significant (P>0.05). Using a multivariate logistic regression model after adjusting for age, sex, body mass index, and fasting insulin, subjects with the G/G genotype showed higher risk of NAFLD [odds ratio (OR), 1.98, 95% confidence interval (CI) 1.43-2.73, P=0.04). The relationships of the rs738409 polymorphism with the metabolic parameters were not significant after adjustment for multiple comparisons.

CONCLUSION

Asian Indians in north India carrying the allele rs738490 of PNPLA3 is predispose to develop NAFLD.

Interactions between the FTO and GNB3 genes contribute to varied clinical phenotypes in hypertension

BACKGROUND

The genes FTO and GNB3 are implicated in essential hypertension but their interaction remains to be explored. This study investigates the role of interaction between the two genes in the pathophysiology of essential hypertension.

METHODS/PRINCIPAL FINDINGS

In a case-control study comprising 750 controls and 550 patients, interaction between the polymorphisms of FTO and GNB3 was examined using multifactor dimensionality reduction (MDR). The influence of interaction on clinical phenotypes like systolic and diastolic blood pressure, mean arterial pressure and body mass index was also investigated. The 3-locus MDR model comprising FTO rs8050136C/A and GNB3 rs1129649T/C and rs5443C/T emerged as the best disease conferring model. Moreover, the interacted-genotypes having either 1, 2, 3, 4 or 5 risk alleles correlated with linearly increasing odds ratios of 1.91 (P = 0.027); 3.93 (P = 2.08E-06); 4.51 (P = 7.63E-07); 7.44 (P = 3.66E-08) and 11.57 (P = 1.18E-05), respectively, when compared with interacted-genotypes devoid of risk alleles. Furthermore, interactions among haplotypes of FTO (H1-9) and GNB3 (Ha-d) differed by >1.5-fold for protective-haplotypes, CTGGC+TC [H2+Ha] and CTGAC+TC [H4+Ha] (OR = 0.39, P = 0.003; OR = 0.22, P = 6.86E-05, respectively) and risk-haplotypes, AAAGC+CT [H3+Hc] and AAAGC+TT [H3+Hd] (OR = 2.91, P = 9.98E-06; OR = 2.50, P = 0.004, respectively) compared to individual haplotypes. Moreover, the effectiveness of gene-gene interaction was further corroborated with a 1.29-, 1.25- and 1.38-fold higher SBP, MAP and BMI, respectively, in patients having risk interacted-haplotype H3+Hc and 2.48-fold higher SBP having risk interacted-haplotype H3+Hd compared to individual haplotypes.

CONCLUSION

Interactions between genetic variants of FTO and GNB3 influence clinical parameters to augment hypertension.

Association of peroxisome proliferator activated receptor-γ gene with non-alcoholic fatty liver disease in Asian Indians residing in north India

BACKGROUND

Genetics of non-alcoholic fatty liver (NAFLD) in Asian Indians has been inadequately studied. We investigated the association of polymorphisms C161T and Pro12Ala of peroxisome proliferator-activated receptor gamma (PPARγ) with clinical and biochemical parameters in Asian Indians with NAFLD.

METHODS

In this case-control study, 162 NAFLD cases and 173 controls were recruited. Abdominal ultrasound, clinical and biochemical profiles, fasting insulin levels and value of homeostasis model assessment of insulin resistance were determined. Polymerase chain reaction-restriction fragment length polymorphisms of two polymorphisms were performed. The association of these polymorphisms with clinical and biochemical parameters was analysed.

RESULTS

Higher frequency of Ala and T alleles of PPARγ was obtained in cases. Ala/Ala genotype of PPARγ (Pro12Ala) was associated with significantly higher serum triglycerides (TG), alkaline phosphatase (ALK) and waist-hip ratio in cases as compared to controls. In C161T polymorphism, TT genotype was significantly increased TG (p=0.04), total cholesterol (p=0.01), ALK (p=0.04) and gamma-glutamyl transpeptidase (p=0.007) in cases. The linkage disequilibrium for these two single-nucleotide polymorphisms of PPARγ was differed in cases (D1=0.1; p=0.006) and controls (D1=0.07; p=0.1). Using a multivariate analysis after adjusting for age, sex and body mass index, the presence of NAFLD was linked to these two polymorphisms (odds ratio 1.64 (95% CI: 1.09-2.45, p=0.05)].

CONCLUSION

Asian Indians in north India carrying the alleles Ala and T of PPARγ (Pro12Ala and C161T) polymorphisms are predisposed to develop NAFLD.

Association of the Myostatin gene with obesity, abdominal obesity and low lean body mass and in non-diabetic Asian Indians in north India

BACKGROUND

To determine the association of the A55T and K153R polymorphisms of the Myostatin gene with obesity, abdominal obesity and lean body mass (LBM) in Asian Indians in north India.

MATERIALS AND METHODS

A total of 335 subjects (238 men and 97 women) were assessed for anthropometry, % body fat (BF), LBM and biochemical parameters. Associations of Myostatin gene polymorphisms were evaluated with anthropometric, body composition and biochemical parameters. In A55T polymorphism, BMI (p=0.04), suprailiac skinfold (p=0.05), total skinfold (p=0.008), %BF (p=0.002) and total fat mass (p=0.003) were highest and % LBM (p=0.03) and total LBM (Kg) were lowest (p=0.04) in subjects with Thr/Thr genotype as compared to other genotypes. Association analysis of K153R polymorphism showed that subjects with R/R genotype had significantly higher BMI (p=0.05), waist circumference (p=0.04), %BF (p=0.04) and total fat mass (p=0.03), and lower %LBM (p=0.02) and total LBM [(Kg), (p=0.04)] as compared to other genotypes. Using a multivariate logistic regression model after adjusting for age and sex, subjects with Thr/Thr genotype of A55T showed high risk for high %BF (OR, 3.92, 95% Cl: 2.61-12.41), truncal subcutaneous adiposity (OR, 2.9, 95% Cl: 1.57-6.60)] and low LBM (OR, 0.64, 95% CI: 0.33-0.89) whereas R/R genotype of K153R showed high risk of obesity (BMI; OR, 3.2, 95% CI: 1.2-12.9; %BF, OR, 3.6, 95% CI: 1.04-12.4), abdominal obesity (OR, 2.12, 95% CI: 2.71-14.23) and low LBM (OR, 0.61, 95% CI: 0.29-0.79).

CONCLUSIONS/SIGNIFICANCE

We report that variants of Myostatin gene predispose to obesity, abdominal obesity and low lean body mass in Asian Indians in north India.

SREBP-2 1784 G/C genotype is associated with non-alcoholic fatty liver disease in north Indians

BACKGROUND

Genetics of non-alcoholic fatty liver (NAFLD) in Asian Indians has been inadequately investigated. This study aims to determine the association of the 1784G>C polymorphism in the SREBP-2 gene with NAFLD in Asian Indians in north India.

METHODS

In this study, (n=335); 162 obese with NAFLD, 91 obese without NAFLD and 82 non-obese without NAFLD subjects were recruited. Abdominal ultrasound, clinical profile, anthropometry, metabolic profile, serum levels of alanine aminotransferase, aspartate aminotransferase, fasting insulin and high sensitivity C-reactive protein (hs-CRP) were analysed. Polymerase chain reaction and restriction fragment length polymorphism were used to identify individual genotypes, and the association of this polymorphism with clinical and biochemical parameters was assessed.

RESULTS

The observed frequency of G allele was 0.73 and C allele was 0.27. Frequency of C/C genotype was higher in NAFLD as compared to obese and non-obese subjects (p=0.003). In NAFLD subjects 57.4% were G/G homozygous, 31.5% G/C heterozygous and 11.1% were C/C homozygous. The SREBP-2 genotype frequencies deviated from the Hardy Weinberg Equilibrium (X² = 6.39, p = 0.0114). Mean values of TG (p = 0.002), TC (p =0.002), ALT (p =0.04) and AST (p =0.03) levels were significantly higher in NAFLD subjects with G/C genotype as compared to G/G genotypes in obese and non-obese groups. Fasting insulin (p =0.03), HOMA (p =0.009) and hs-CRP levels were significantly higher in NAFLD subjects with G/C genotype as compared to obese and non obese subjects with G/G genotypes.

CONCLUSION

In this study, conducted for the first time in Asian Indians, SREBP-2 1784 G>C genotype was associated with NAFLD.

The epistasis between vascular homeostasis genes is apparent in essential hypertension

OBJECTIVE

The epistasis influence of vascular homeostasis genes is vital to multigenetic diseases. This study was designed to perceive the possible role of epistasis in the etiology of essential hypertension.

METHODS

We investigated seven polymorphisms of ACE, CYP11B2 and NOS3 epistatically, and SBP, DBP, MAP, ACE activity, plasma aldosterone concentration (PAC) and NOx level in 860 age- and ethnicity-matched unrelated north-Indian subjects.

RESULTS

The hypertension risk in individuals with interacted-genotypes (IwIw+IwIc)+(4aa), (IcIc)+(4bb+4ba) and IcIc+4aa of the CYP11B2 and NOS3 was significantly higher with odds ratio 5.5 (95% CI=2.9-10.6, P<0.0001), 2.4 (95% CI=1.4-4.1, P<0.0008) and 7.5 (95% CI=1.6-34.8, P=0.010), respectively. The odds ratio for hypertension with interacted-haplotypes (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) of CYP11B2 and NOS3 was 5.3 (95% CI=2.0-14.2, P=0.005) and 3.9 (95% CI=1.4-10.4, P=0.04), respectively; whereas for the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G), the odds ratio was 0.7 (95% CI=0.5-0.9, P=0.03). While the interacted-genotypes, IcIc+4aa correlated with higher SBP and MAP (P=0.006; P=0.04), the interacted-haplotypes, (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) correlated with higher MAP and lower NOx level (P=0.02 and P=0.03, respectively), and the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G) correlated with lower PAC and MAP (P=0.024 and P=0.018, respectively).

CONCLUSIONS

The epistasis between CYP11B2 and NOS3 and its correlation with varied clinical and biochemical parameters signify its possible contribution in the complex etiology of hypertension.

High-altitude disorders: pulmonary hypertension: pulmonary vascular disease: the global perspective

Globally, it is estimated that > 140 million people live at a high altitude (HA), defined as > 2,500 m (8,200 ft), and that countless others sojourn to the mountains for work, travel, and sport. The distribution of exposure to HA is worldwide, including 35 million in the Andes and > 80 million in Asia, including China and central Asia. HA stress primarily is due to the hypoxia of low atmospheric pressure, but dry air, intense solar radiation, extreme cold, and exercise contribute to acute and chronic disorders. The acute disorders are acute mountain sickness (also known as soroche), HA cerebral edema, and HA pulmonary edema (HAPE). Of these, HAPE is highly correlated with acute pulmonary hypertension. The first chronic syndrome described in HA dwellers in Peru was chronic mountain sickness (Monge disease), which has a large component of relative hypoventilation and secondary erythrocytosis. The prevalence of chronic mountain sickness in HA dwellers ranges from 1.2% in native Tibetans to 5.6% in Chinese Han; 6% to 8% in male residents of La Paz, Bolivia; and 15.6% in the Andes. Subacute mountain sickness is an exaggerated pulmonary hypertensive response to HA hypoxia occurring over months, most often in infants and very young children. Chronic pulmonary hypertension with heart failure but without hypoventilation is seen in Asia. Not only does HA pulmonary hypertension exact health consequences for the millions affected, but also the mechanisms of disease relate to pulmonary hypertension associated with multiple other disorders. Genetic understanding of these disorders is in its infancy.

Effect of chronic intra-peritoneally administered chimeric peptide of met-enkephalin and FMRFa-[D-Ala2]YFa-on antinociception and opioid receptor regulation

The physiological role of NPFF/FMRFa family of peptides is complex and exact mechanism of action of these peptides is not yet completely understood. In same line of scrutiny, previously we reported an enzymatically stable chimeric analog of YGGFMKKKFMRFamide (YFa) i.e., [D-Ala(2)]YAGFMKKKFMRFamide ([D-Ala(2)]YFa) which have a role in antinociception and modulatory effect on opioid analgesia. In continuation, presently we investigated using tail-flick test whether [D-Ala(2)]YFa on systemic administration induced any antinociception in rats and if so then which specific opioid receptor(s) mu, delta or kappa mediated it. Further, the antinociceptive effect of [D-Ala(2)]YFa on 6 days chronic intra-peritoneal (i.p.) treatment in rats was examined and finally, effect of this chronic treatment on the differential expression of opioid receptors was assessed. [D-Ala(2)]YFa on i.p. administration induced dose dependent antinociception which was mainly mediated by delta (DOR) and partially by mu (MOR) and kappa (KOR) opioid receptors. Moreover, its antinociceptive effect remained comparable throughout the chronic treatment even during insufficient availability of DOR1. Importantly, during this treatment the mRNA expression of all three opioid receptors (MOR1, KOR1 and DOR1) was increased as assessed by real-time RTPCR though subsequent western blot analysis revealed a selective increase in the protein level of DOR1, only. Thus, pharmacological behavior of [d-Ala(2)]YFa suggests that competency of an opioid agonist to bind with multiple opioid receptors may enhance its potency to induce tolerance free analgesia.

CYP11B2 gene haplotypes independently and in concurrence with aldosterone and aldosterone to renin ratio increase the risk of hypertension

OBJECTIVES

Aldosterone synthase produces aldosterone, which regulates electrolytes and thereby blood pressure. Polymorphisms in aldosterone-synthase gene (CYP11B2) may associate with heterogeneous aldosterone production and hypertension. Hence, we investigated -344T/C, Iw/Ic polymorphisms of CYP11B2, plasma renin activity (PRA) and aldosterone concentration (PAC).

DESIGN AND METHODS

Consecutive ethnically-matched 450 hypertensive patients and 360 controls were screened by PCR-RFLP for genotypes and haplotypes; PRA and PAC were measured.

RESULTS

The Iw/Ic polymorphism distribution differed significantly between the two groups (LRT chi(2)=15.8, df=2, P=0.000). The mutant allele-Ic and genotype-Ic/Ic were overrepresented in patients (35% versus 27% and 13% versus 7%). Overrepresentation of T-Ic haplotype in patients was identified as risk haplotype (P=0.000). Patients had significantly higher PAC and aldosterone-to-renin ratio (ARR; P=0.000), which was Ic-allele dependent.

CONCLUSIONS

The haplotype T-Ic associated with hypertension susceptibility. Correlation between Ic-allele and raised ARR likely serve in hypertension management.

Effect of chronic intra-peritoneally administered chimeric peptide of met-enkephalin and FMRFa-[D-Ala2]YFa-on antinociception and opioid receptor regulation

The physiological role of NPFF/FMRFa family of peptides is complex and exact mechanism of action of these peptides is not yet completely understood. In same line of scrutiny, previously we reported an enzymatically stable chimeric analog of YGGFMKKKFMRFamide (YFa) i.e., [D-Ala(2)]YAGFMKKKFMRFamide ([D-Ala(2)]YFa) which have a role in antinociception and modulatory effect on opioid analgesia. In continuation, presently we investigated using tail-flick test whether [D-Ala(2)]YFa on systemic administration induced any antinociception in rats and if so then which specific opioid receptor(s) mu, delta or kappa mediated it. Further, the antinociceptive effect of [D-Ala(2)]YFa on 6 days chronic intra-peritoneal (i.p.) treatment in rats was examined and finally, effect of this chronic treatment on the differential expression of opioid receptors was assessed. [D-Ala(2)]YFa on i.p. administration induced dose dependent antinociception which was mainly mediated by delta (DOR) and partially by mu (MOR) and kappa (KOR) opioid receptors. Moreover, its antinociceptive effect remained comparable throughout the chronic treatment even during insufficient availability of DOR1. Importantly, during this treatment the mRNA expression of all three opioid receptors (MOR1, KOR1 and DOR1) was increased as assessed by real-time RTPCR though subsequent western blot analysis revealed a selective increase in the protein level of DOR1, only. Thus, pharmacological behavior of [d-Ala(2)]YFa suggests that competency of an opioid agonist to bind with multiple opioid receptors may enhance its potency to induce tolerance free analgesia.

Effect of chronic intra-peritoneally administered chimeric peptide of met-enkephalin and FMRFa-[D-Ala2]YFa-on antinociception and opioid receptor regulation

The physiological role of NPFF/FMRFa family of peptides is complex and exact mechanism of action of these peptides is not yet completely understood. In same line of scrutiny, previously we reported an enzymatically stable chimeric analog of YGGFMKKKFMRFamide (YFa) i.e., [D-Ala(2)]YAGFMKKKFMRFamide ([D-Ala(2)]YFa) which have a role in antinociception and modulatory effect on opioid analgesia. In continuation, presently we investigated using tail-flick test whether [D-Ala(2)]YFa on systemic administration induced any antinociception in rats and if so then which specific opioid receptor(s) mu, delta or kappa mediated it. Further, the antinociceptive effect of [D-Ala(2)]YFa on 6 days chronic intra-peritoneal (i.p.) treatment in rats was examined and finally, effect of this chronic treatment on the differential expression of opioid receptors was assessed. [D-Ala(2)]YFa on i.p. administration induced dose dependent antinociception which was mainly mediated by delta (DOR) and partially by mu (MOR) and kappa (KOR) opioid receptors. Moreover, its antinociceptive effect remained comparable throughout the chronic treatment even during insufficient availability of DOR1. Importantly, during this treatment the mRNA expression of all three opioid receptors (MOR1, KOR1 and DOR1) was increased as assessed by real-time RTPCR though subsequent western blot analysis revealed a selective increase in the protein level of DOR1, only. Thus, pharmacological behavior of [d-Ala(2)]YFa suggests that competency of an opioid agonist to bind with multiple opioid receptors may enhance its potency to induce tolerance free analgesia.

Multi-locus interactions of vascular homeostasis genes in essential hypertension: a gender-based study

BACKGROUND

Studies on genes of endothelial and vascular homeostasis are inadequate in females.

METHODS

We investigated the role of 7 variants of ACE, AGT and NOS3 and their correlation with NO(x) levels and ACE activity in hypertension susceptibility in 910 case-controls of both genders.

RESULTS

Prevalence of alleles D of ACE I/D; -6A of AGT -6G/A; -786C, 894T and 4a of NOS3 -786T/C, 894G/T and 4b/4a polymorphisms was observed in patients (P< or =0.05). The 3 genotypes-combinations containing 6+5 wild-type alleles of AGT and NOS3 were significantly less prevalent in patients (P< or =0.0003). The haplotypes 235T/174T/-6A of AGT (P=4E-3) and -786T/894G/4a and -786C/894G/4a of NOS3 (P=2E-3, P=0.011, respectively) were significantly more prevalent in patients. The AGT and NOS3 findings were similar in males. Genotypes-combinations with 6+5 wild-type alleles of AGT correlated with higher NO(x) levels (P=0.03). The NOS3 genotypes-combinations having 6 and 6+5 wild-type alleles correlated with decreased ACE activity (P=0.025, P=0.0015, respectively) and increased NO(x) levels (P=0.001, P=0.0001, respectively) in patients. In gene-gene interactions, ACE D allele associated with < or =4 wild-type alleles containing genotypes-combinations of AGT and NOS3 in patients (P< or =0.04).

CONCLUSION

Within gene and between genes interactions of variants influence ACE activity and NO(x) levels and associate with EH.

COX2 and p53 risk-alleles coexist in COPD

BACKGROUND

Cigarette smoke stimulates airway epithelial cells to release pro-inflammatory cytokines which influence various inflammation-related genes, including COX2, whereas p53 expression is known to alter in such a condition. Since both the genes share several common physiological functions including inflammation and oxidative stress, we investigated within gene and gene-gene interactions towards susceptibility to the disease.

METHOD

In a prospective gene-association study we conducted PCR-RFLP for genotyping the COX2 -765G/C and 8473T/C and p53 72Pro/Arg polymorphisms in 229 COPD patients and 147 healthy controls.

RESULTS

The -765GC+CC genotypes of COX2 and Pro/Pro+Pro/Arg genotypes of p53 were prevalent in patients with significant odds ratio, 2.05 and 2.30, respectively (p=0.001; p=0.009, respectively), as a consequence, the -765C and 72Pro alleles were prevalent (p<or=0.001). Individually, the 8473T/C polymorphism did not associate with the disease (p=NS), however, it did in the haplotype -765C:8473C, which was significantly higher in patients (p<0.0001). Based on its prevalence, the three alleles were identified as risk-alleles in patients. The combinations of the genotypes containing 3, 4 and 5 risk alleles of the 3 polymorphisms were significantly over-represented in patients, whereas, the genotypes combinations containing 0, 1 and 2 risk alleles were significantly higher in controls (p=0.0004). The pairwise gene-gene interactions validated prevalence of risk-alleles associated pairing of genotypes such as the Pro/Pro+ Pro/Arg with -765GC+-765CC in patients (p=0.01).

CONCLUSION

The prevalence of COX2 and p53 risk-alleles contributes towards susceptibility to the disease.

YFa, a chimeric opioid peptide, induces kappa-specific antinociception with no tolerance development during 6 days of chronic treatment

Our previous study showed that YGGFMKKKFMRFamide (YFa), a chimeric peptide of Met-enkephalin, and Phe-Met-Arg-Phe-NH2 induced naloxone-reversible antinociception and attenuated the development of tolerance to morphine analgesia. In continuation, the present study investigated which specific opioid receptors-mu, delta or kappa-mediate the observed YFa antinociception pharmacologically using specific antagonists and whether chronic administration of YFa at 26.01 micromol/kg per day induces tolerance and its effect on the expression of mu and kappa opioid receptors from day 4 to day 6, with endomorphine-1 (EM-1) and saline taken as positive and negative controls, respectively. Quantitative differential expression analysis was carried out by real-time reverse-transcriptase polymerase chain reaction, and the corresponding changes in protein levels were assessed by Western blot. A pharmacological investigation revealed that nor-binaltorphimine, a specific kappa opioid receptor-1 (KOR1) antagonist, completely antagonized the antinociception induced by 39.01 micromol/kg of YFa. Importantly, its chronic intraperitoneal administration did not result in significant tolerance over 6 days, whereas EM-1 induced significant tolerance after day 4. Differential expression analysis revealed that EM-1 caused up-regulation of mu opioid receptor-1 on day 4, followed by down-regulation on later days. Interestingly, YFa treatment caused a decrease on day 4, followed by an increase in the expression of KOR1 from day 5 onward. In conclusion, YFa induces kappa-specific antinociception, with no development of tolerance during 6 days of chronic treatment, which further articulates new directions for improved designing of peptide-based analgesics that may be devoid of adverse effects like tolerance.

YFa, a chimeric opioid peptide, induces kappa-specific antinociception with no tolerance development during 6 days of chronic treatment

Our previous study showed that YGGFMKKKFMRFamide (YFa), a chimeric peptide of Met-enkephalin, and Phe-Met-Arg-Phe-NH2 induced naloxone-reversible antinociception and attenuated the development of tolerance to morphine analgesia. In continuation, the present study investigated which specific opioid receptors-mu, delta or kappa-mediate the observed YFa antinociception pharmacologically using specific antagonists and whether chronic administration of YFa at 26.01 micromol/kg per day induces tolerance and its effect on the expression of mu and kappa opioid receptors from day 4 to day 6, with endomorphine-1 (EM-1) and saline taken as positive and negative controls, respectively. Quantitative differential expression analysis was carried out by real-time reverse-transcriptase polymerase chain reaction, and the corresponding changes in protein levels were assessed by Western blot. A pharmacological investigation revealed that nor-binaltorphimine, a specific kappa opioid receptor-1 (KOR1) antagonist, completely antagonized the antinociception induced by 39.01 micromol/kg of YFa. Importantly, its chronic intraperitoneal administration did not result in significant tolerance over 6 days, whereas EM-1 induced significant tolerance after day 4. Differential expression analysis revealed that EM-1 caused up-regulation of mu opioid receptor-1 on day 4, followed by down-regulation on later days. Interestingly, YFa treatment caused a decrease on day 4, followed by an increase in the expression of KOR1 from day 5 onward. In conclusion, YFa induces kappa-specific antinociception, with no development of tolerance during 6 days of chronic treatment, which further articulates new directions for improved designing of peptide-based analgesics that may be devoid of adverse effects like tolerance.

Endothelial nitric oxide synthase gene haplotypes and circulating nitric oxide levels significantly associate with risk of essential hypertension

Nitric oxide (NO), a potent vasodilator, plays a pivotal role in blood pressure regulation. Endothelial NO synthase gene (NOS3) polymorphisms influence NO levels. Here, we investigated the role of the -922A/G, -786T/C, 4b/4a, and 894G/T polymorphisms of the NOS3 and NO(x) levels in 800 consecutive unrelated subjects comprising 455 patients of essential hypertension and 345 controls. The polymorphisms were investigated independently and as haplotypes. Plasma NO(x) levels (nitrate and nitrite) were estimated by the Griess method. Genotype frequencies for the -786T/C, 4b/4a, and 894G/T polymorphisms differed significantly (P<0.001) between patients and controls and were associated with an increased risk of hypertension (OR=2.0, OR=3.8, OR=1.6, respectively). The 4-locus haplotypes ATaG (H1), ATaT (H2), and GCaG (H3) were significantly associated with essential hypertension and served as susceptible haplotypes (P<or=0.0001). On the other hand, haplotypes ATbG (H4) and GTbG (H5) were negatively associated with hypertension and served as protective haplotypes (P<0.0001). NO(x) levels were significantly lower in patients than controls (P<0.0001). The individual polymorphisms showed marginal association with NO(x) level; however, the susceptible haplotype H2 associated significantly with lower NO(x) levels in patients (P<0.001) and conversely the haplotype H4 with higher NO(x) levels in controls (P<0.001). In conclusion, the 4b/4a and likely -786T/C polymorphisms were identified as the determinants modifying the risk of hypertension. This study identifies the NOS3 variants and haplotypes as genetic risk factors and as useful markers of increased susceptibility to the risk of essential hypertension.

YFa, a chimeric opioid peptide, induces kappa-specific antinociception with no tolerance development during 6 days of chronic treatment

Our previous study showed that YGGFMKKKFMRFamide (YFa), a chimeric peptide of Met-enkephalin, and Phe-Met-Arg-Phe-NH2 induced naloxone-reversible antinociception and attenuated the development of tolerance to morphine analgesia. In continuation, the present study investigated which specific opioid receptors-mu, delta or kappa-mediate the observed YFa antinociception pharmacologically using specific antagonists and whether chronic administration of YFa at 26.01 micromol/kg per day induces tolerance and its effect on the expression of mu and kappa opioid receptors from day 4 to day 6, with endomorphine-1 (EM-1) and saline taken as positive and negative controls, respectively. Quantitative differential expression analysis was carried out by real-time reverse-transcriptase polymerase chain reaction, and the corresponding changes in protein levels were assessed by Western blot. A pharmacological investigation revealed that nor-binaltorphimine, a specific kappa opioid receptor-1 (KOR1) antagonist, completely antagonized the antinociception induced by 39.01 micromol/kg of YFa. Importantly, its chronic intraperitoneal administration did not result in significant tolerance over 6 days, whereas EM-1 induced significant tolerance after day 4. Differential expression analysis revealed that EM-1 caused up-regulation of mu opioid receptor-1 on day 4, followed by down-regulation on later days. Interestingly, YFa treatment caused a decrease on day 4, followed by an increase in the expression of KOR1 from day 5 onward. In conclusion, YFa induces kappa-specific antinociception, with no development of tolerance during 6 days of chronic treatment, which further articulates new directions for improved designing of peptide-based analgesics that may be devoid of adverse effects like tolerance.

The genetic aspects of pre-eclampsia: achievements and limitations

Pre-eclampsia, a life-threatening disease during pregnancy, is a leading cause of global maternal mortality. Although there is substantial evidence of a genetic background, the complexity of the processes involved and nature of the maternal-fetal phenomenon do not make the search for the causative genes easy. Recent retrospective studies on the subject suggest the heritable allelic variations, particularly the utero-placental renin-angiotensin system with defective placental vascular development, could become the cornerstone for the genetics of pre-eclampsia and hence might well be associated with such defective development. Moreover, the role of immune mechanisms (immune maladaptation) deserves not to be ignored. Large-scale studies entailing genomewide scanning, sib-pair linkage analysis, and family-based association studies with appropriate power to detect genes with a lower relative risk are necessary to understand the puzzle of the disease. Moreover, recently, the importance of epigenetic features and the effect of imprinted genes related to trophoblast growth as well as fetal development on hypertension in pregnancy have been highlighted. All these possibilities are intuitively attractive and are supported by some circumstantial evidence. Although the consistent tenor of a series of papers instill some confidence, we need meticulously designed larger-scale investigations including large numbers of affected women and their babies to provide the analytic stringency essential to study the polygenic multifactorial basis of pre-eclampsia.

Endothelial nitric oxide synthase gene variants contribute to oxidative stress in COPD

Nitric oxide (NO) plays critical role in endothelial dysfunction and oxidative stress in COPD, pointing to the significance of endothelial nitric oxide synthase gene (eNOS) variants. We investigated the association of -786T/C, -922A/G, 4B/4A, and 894G/T polymorphisms of eNOS with the disease and its impact on nitrite and malonaldehyde levels in 190 COPD patients and 134 healthy controls, all smokers. The -786C, -922G and 4A alleles were significantly over-represented in patients (p=0.02, p=0.02, and p=0.03, respectively). The haplotypes, -786C:4A, 4A:894G, -786C:894G, and -786C:4A:894G were significantly over-represented in patients (p<0.0001, p =0.02, p=0.02, and p <0.0001, respectively), whereas, haplotypes, -786T:4B, 4B:894G, -786T:894G, and -786T:4B:894G were significantly under-represented in the patients (p<0.0001). The patients had significantly increased levels of nitrite (p=0.003) and malonaldehyde (p<0.0001). Combination of genotypes containing -786C and 4A alleles were greater in patients (p 0.05), and these combinations associated with decreased FEV1 value and nitrite level (p=0.03 and p=0.04, respectively) and with increased malonaldehyde levels (p=0.02). The eNOS -786C, -922G, and 4A alleles, these alleles associated haplotypes and genotype combinations were over-represented in patients. The variants and their combinations of four polymorphisms of eNOS contribute to disturbed pulmonary function and oxidative stress in COPD.

Expression and functional activity of pro-oxidants and antioxidants in murine heart exposed to acute hypobaric hypoxia

Under hypobaric hypoxia, antioxidant defenses of the heart are stressed by the enhanced production of ROS. Mammalian heart acclimatizes to hypoxia through altered gene expression, which we studied in murine heart exposed to 10h of acute hypobaric hypoxia (AHH), equivalent to 15000ft, using cDNA arrays. Functional classification of genes with a > or =2-fold change revealed a number of pro-oxidants like Cyba, Xdh, Txnip, Ppp1r15b and antioxidants like Cat, Gpx1, Mt1, Mgst1. Interestingly, the protein level of Cyba, a subunit of NADPH oxidase, was markedly decreased in AHH exposed heart, suggesting the involvement of some stress response pathways. The AHH exposure also caused a significant reduction (50%) in the level of GSH (P<0.05). The present study provides a retrospective insight on the cellular antioxidant defense mechanisms under AHH.

Association of CYP2E1 and NAT2 gene polymorphisms with chronic obstructive pulmonary disease

BACKGROUND

Detoxification genes are potential candidates in the susceptibility of patients with chronic obstructive pulmonary disease. Polymorphisms in these genes alter the metabolism of xenobiotics such as present in cigarette smoke.

METHODS

We conducted a case-control study to investigate total 9 polymorphisms of CYP2E1, CYP2D6 and NAT2 genes by PCR-RFLP.

RESULTS

The -1053C/T and -1293G/C promoter polymorphisms of CYP2E1 were found to be in complete linkage disequilibrium (LD) (D'=1.00, r(2)=1.0, p<0.0001), whereas -1293G/C and 7632T/A polymorphisms of the same gene were also in significant LD (D'=0.5183, r(2)=1.0, p=0.01) in patients. The patients over-represented the -1293GC+CC genotypes of -1293G/C polymorphism of CYP2E1 (p=0.03) and NAT2*4/7, NAT2()5/6, NAT2*5/7, NAT2*6/6 and NAT2*6/7 genotypes of NAT2 (p=0.01, p=0.039, p=0.01, p=0.032, p=0.006, respectively), resulting in to higher frequency of -1293C (OR=7.02, 95% CI=1.63-30.15, p=0.002), NAT2*6 (OR=1.90, 95% CI=1.27-2.83, p=0.001) and NAT2*7 (OR=2.91, 95% CI=1.65-5.12, p=0.0001) alleles. The 7632T/A and 9893C/G polymorphisms of CYP2E1 and 1934G/A polymorphism of CYP2D6 did not associate with the disease (p>0.05). The haplotypes -1293G:9893C and -1293G:7632T:9893C were under-represented (p<0.001), whereas haplotypes -1293C:7632T, -1293C:9893C, -1293C:9893G and -1293C:7632T:9893C of the 4 CYP2E1 polymorphisms were over-represented in patients (p<0.05).

CONCLUSION

The CYP2E1 and NAT2 variants associated with COPD.

T lymphocyte subset profile and serum alpha-1-antitrypsin in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder characterized by the presence of non-fully reversible airflow limitation. The study was undertaken to investigate the involvement of alpha-1-antitrypsin (alpha(1)AT) and T lymphocyte subsets in the pathogenesis of COPD. Blood samples of 50 subjects, including 25 healthy volunteers and 25 patients with COPD, were analysed. Serum trypsin inhibitory capacity (STIC) was determined by enzymatic assay. CD4(+) and CD8(+) T lymphocytes were enumerated in heparinized blood using a fluorescence activated cell sorter counter. The STIC in COPD patients was found to be decreased significantly than in controls (P < 0.01). In COPD patients with lower expression levels of alpha(1)AT, a highly significant decrease in the number of CD4(+) T lymphocytes (P < 0.0009) and CD4/CD8 ratio was observed compared with control subjects (P < 0.008). The mean +/- standard error of CD8(+) lymphocytes was found to be little different (only marginally decreased) in COPD patients compared to healthy controls; however, an alteration in the individual count of CD8(+) lymphocytes cells was observed in COPD patients. Using linear regression analysis, a negative correlation was observed between STIC and CD4(+) lymphocytes and CD8(+) lymphocytes (r = -0.40, P < 0.04; r = -0.42, P < 0.03, respectively) in COPD patients. An alteration in alpha(1)AT and T lymphocyte subsets in COPD patients suggested that interplay of these factors may be responsible for the progression of COPD.

Correlation of oxidative status with BMI and lung function in COPD

OBJECTIVES

The imbalance in oxidative status together with nutrition depletion and low body weight play a vital role in the pathogenesis and severity of chronic obstructive pulmonary disease (COPD). The study was undertaken to ascertain if a relationship existed between oxidative status and BMI in COPD. In addition, association of oxidative status and BMI with lung function of the disease was also examined.

MATERIALS AND METHODS

In 202 COPD patients and 136 healthy controls plasma lipid peroxidation (LPO), reduced glutathione (GSH), glutathione peroxidase (GPx), catalase (CAT) activities, BMI and FEV(1)% predicted were looked for interactions.

RESULTS

The patients had increased LPO (p=0.006) and decreased antioxidants (GSH, p=0.005; GPx, p=0.035 and CAT, p=0.008, respectively). Of note are the correlations of oxidative stress markers with BMI and FEV(1)% predicted in the patients. LPO inversely and GSH, GPx, and CAT positively correlated with both BMI (p=0.007, p<0.001, p=0.045 and p=0.009, respectively), and FEV(1)% of predicted (LPO, p=0.001; GSH, p<0.001; GPx, p=0.043 and CAT, p<0.001) in the patients. Further, a positive correlation existed between BMI and FEV(1)% predicted (p=0.016) in COPD.

CONCLUSION

The intimate relationship of oxidative status with BMI and lung function, and the direct correlation between BMI and FEV(1) may potentiate severity of the disease.

Genetic polymorphisms of GSTP1 and mEPHX correlate with oxidative stress markers and lung function in COPD

The genetic susceptibility to COPD might depend on variations in detoxification enzymes that activate and detoxify cigarette smoke products, which otherwise generate oxidative stress causing pathogenesis. In a case-control study of 202 COPD patients and 136 normals, we examined the association of polymorphisms I105V, A114V of GSTP1 and Y113H, H139R of mEPHX individually or in combination with disease and their contribution to oxidative stress markers such as MDA, GSH, GPx and airflow obstruction. Patients were over-represented by the alleles 105V, 114V of GSTP1 and 113H, 139H of mEPHX (chi(2)=10.63, p=0.001, chi(2)=13.92, p<0.001, chi(2)=13.02, p<0.001 and chi(2)=4.48, p=0.034, respectively) and the haplotypes of same alleles i.e. 105V-114V and 113H-139H (chi(2)=14.58, p<0.001 and chi(2)=23.14, p<0.001). Moreover, there was marked over-representation of combination of genotypes, I105I+A114A of GSTP1 (53% vs. 36%) in controls; whereas, the combinations with 105V/114V alleles (64% vs. 47%) of GSTP1 (OR=1.99; 95% CI=1.28-3.09; p=0.002) and the homozygotes H113H+H139H (27% vs.10%) of mEPHX (OR=3.26; 95% CI=1.73-6.15; p=0.0001) in patients. Patients had significantly elevated MDA level (p<0.001) and decreased GSH level (p<0.001) and GPx activity (p=0.035), respectively. Of note, the genotypes, I105V/V105V, A114V/V114V of GSTP1 and Y113H/H113H of mEPHX associated with increased MDA level (p=0.04, p=0.03 and p=0.003), decreased GSH level (p=0.019, p=0.007 and p=0.0006) and lower FEV1 (p=0.23, p=0.037 and p=0.029), respectively, in patients; so was the correlation of these biomarkers and lung function with the combinations of the genotypes. In conclusion, 105V/114V alleles of GSTP1 and 113H/139H alleles of mEPHX and the combination of genotypes with same alleles associated with imbalanced oxidative stress and lung function in patients, signifying the importance in the disease.

Transcriptional downregulation of sterol metabolism genes in murine liver exposed to acute hypobaric hypoxia

Ascent to high-altitude results in decreased inspired partial pressure of oxygen because of a decrease in barometric pressure. Altitude acclimatization requires physiological and metabolic changes to improve tolerance to altitude hypoxia. Cellular response to hypoxia results into changes in the profile of gene expression and the present study explored the same in murine model. Liver being the largest metabolic organ, the molecular details of acute hypobaric hypoxia (AHH) induced transcriptional changes in the tissue were investigated. Swiss albino mice were exposed to hypobaric hypoxia ( approximately 426mmHg) in a decompression chamber and cDNA microarray was used to study the transcriptional profile in liver. Notably, by the tenth hour several of the genes involved in sterol metabolism such as SREBF1, INSIG1, HMGCS1, FDFT1, SQLE, and HSD3B4 were downregulated more than 2-fold suggesting that AHH suppresses sterol biosynthesis in the liver. Real-time PCR helped validate the downregulation of SREBF1, HMGCS1, FDFT1, and HSD3B4 genes. However, no significant change was observed in the serum cholesterol levels throughout the AHH exposure. The findings are indicative of transcriptional downregulation of SREBP target genes as a part of acclimatization response to hypoxia. The study highlights the significance of SREBP in the regulation of sterol metabolism under the acute hypoxic response.

Heterozygotes of NOS3 Polymorphisms Contribute to Reduced Nitrogen Oxides in High-Altitude Pulmonary Edema

STUDY OBJECTIVES

High-altitude pulmonary edema (HAPE), which develops on exertion under hypoxic conditions, aggravates due to endothelial dysfunction. Repeat events of the disorder suggests of genetic susceptibility. Endothelial nitric oxide synthase gene (NOS3), a regulator of vasodilation, has emerged as a strong candidate marker. In the present study, we investigated G894T, 27-base-pair 4b/4a (variable number of tandem repeat), -922A/G, and -786T/C polymorphisms of NOS3, individually or in combination, for an association with HAPE.

DESIGN

A cross-sectional case control study.

SETTINGS

Blood samples of HAPE-resistant lowlanders (HAPE-r) were obtained at sea level, and blood samples of patients with HAPE (HAPE-p) were obtained at Sonam Norboo Memorial Hospital, Leh, at 3,500 m.

PARTICIPANTS

The study groups consisted of 60 HAPE-r inducted two to three times to altitudes > 3,600 m; and 72 HAPE-p, who had HAPE on their first visit to high altitude.

RESULTS

Nitrogen oxides (NOx) at 77.9 +/- 28.6 micromol/L were significantly elevated in HAPE-r as compared to 42.39 +/- 12.93 micromol/L in HAPE-p (p < 0.0001). Genotype distribution of G894T and 4b/4a polymorphisms was significantly different in the two groups (p = 0.001 and 0.009, respectively). Haplotype analysis revealed -922A/G and -786T/C polymorphisms in complete linkage disequilibrium. The wild-type haplotypes G-b (G894T, 4b/4a), G-A (G894T, -922A/G), and G-b-A (G894T, 4b/4a, -922A/G) were significantly overrepresented in HAPE-r (p < 0.0001, p = 0.03, and p = 0.02, respectively). The heterozygote genotype combination GTba as compared to wild-type combination GGbb was significantly higher in HAPE-p (chi2 = 18.62, p = 0.00009; odds ratio, 7.20; 95% confidence interval, 2.82 to 18.38). The combination of four heterozygotes GTbaAGTC was overrepresented in HAPE-p (p = 0.04), whereas the wild-type genotype combination GGbbAATT was overrepresented in HAPE-r (p = 0.002). Furthermore, the GGbb combination correlated with significantly elevated NOx as compared to remaining combinations as a whole in both HAPE-r and HAPE-p (p = 0.01 and 0.004, respectively).

CONCLUSIONS

Reduced NOx and combination of heterozygotes associate with the susceptibility to HAPE. The study impels another step toward application of NOx as a diagnostic marker for HAPE. The NOS3 GTba and GTbaAGTC genotype combinations may find application as genetic markers for predicting the risk for HAPE.