Antioxidant protection provided by different doses of alpha-tocopherol was compared by determining nitric oxide synthase (NOS) activity in blood vessels of spontaneously hypertensive rats (SHR) treated with alpha-tocopherol. SHR were divided into four groups namely hypertensive control (C), treatment with 17 mg of alpha-tocopherol/kg diet (alpha1), 34 mg of alpha-tocopherol/kg diet (alpha2), and 170 mg of alpha-tocopherol/kg diet (alpha3). Wister Kyoto (WKY) rats were used as normal control (N). Blood pressure were recorded from the tail by physiography every other night for the duration of the study period of 3 months. At the end of the trial, animals were sacrificed. The NOS activity in blood vessels was measured by [3H]arginine radioactive assay and the nitrite concentration in plasma by spectrophotometry at wavelength 554 nm using Greiss reagent. Analysis of data was done using Student's t test and Pearson's correlation. The computer program Statistica was used for all analysis. Results of our study showed that for all the three alpha-tocopherol-treated groups, blood pressure was significantly (P < .001) reduced compared to the hypertensive control and maximum reduction of blood pressure was shown by the dosage of 34 mg of alpha-tocopherol/kg diet (C: 209.56 +/- 8.47 mm Hg; alpha2: 128.83 +/- 17.13 mm Hg). Also, NOS activity in blood vessels of SHR was significantly lower than WKY rats (N: 1.54 +/- 0.26 pmol/mg protein, C: 0.87 +/- 0.23 pmol/mg protein; P < .001). Although alpha-tocopherol in doses of alpha1, alpha2, and alpha3 increased the NOS activity in blood vessels, after treatment only that of alpha2 showed a statistical significance (P < .01). Plasma nitrite concentration was significantly reduced in SHR compared to normal WKY rats (N: 54.62 +/- 2.96 mol/mL, C: 26.24 +/- 2.14 mol/mL; P < .001) and accordingly all three groups showed significant improvement in their respective nitrite level (P < .001). For all groups, NOS activity and nitrite level showed negative correlation with blood pressure. It was significant for NOS activity in hypertensive control (r = -0.735, P = .038), alpha1 (r = -0.833, P = .001), and alpha2 (r = -0.899, P = .000) groups. For plasma nitrite, significant correlation was observed only in group alpha1 (r = -0.673, P = .016) and alpha2 (r = -0.643, P = .024). Only the alpha2 group showed significant positive correlation (r = 0.777, P = .003) between NOS activity and nitrite level. In conclusion it was found that compared to WKY rats, SHR have lower NOS activity in blood vessels, which upon treatment with antioxidant alpha-tocopherol increased the NOS activity and concomitantly reduced the blood pressure. There was correlation of lipid peroxide in blood vessels with NOS and nitric oxide, which implies that free radicals may be involved in the pathogenesis of hypertension.
Essential hypertension is a major public health concern worldwide where its prevalence accounts for various cerebrovascular diseases. A common molecular variant of angiotensinogen (AGT), the precursor of potent vasoactive hormone angiotensin II, has been incriminated as a marker for genetic predisposition to essential hypertension in some ethnics. This case-control study was designed not only to determine the association of the AGT M235T gene variants with essential hypertension, but also its relationship to Plasma Renin Activity (PRA) in subjects attending the Health Clinic, Kuala Lumpur, Malaysia.
Angiotensin II type 1 receptor (AGT1R) gene 1166A > C polymorphism has been shown to be associated with essential hypertension and aortic stiffness as measured by carotid femoral pulse wave velocity (PWV). This study was carried out to investigate the association of the 1166A > C polymorphism with blood pressure (BP) and PWV among Malay hypertensive and normotensive subjects. Two hundred and one hypertensive subjects without evidence of cardiovascular (CV) complications and 201 age- and sex-matched normotensive subjects were studied in a cross-sectional design. Blood pressures (BP) and PWV were measured, and 1166A > C genotype was determined by polymerase chain reaction followed by restriction enzyme digestion. The 1166C allele frequency was 7.96% and 7.73% among Malay hypertensive and normotensive subjects, respectively. There was no association of the 1166A > C polymorphism with BP in the hypertensive, normotensive or overall Malay populations. PWV was significantly higher among 1166C allele carriers as compared to non-carriers (10.52 +/- 1.82 vs. 10.15 +/- 1.80, p = 0.040) in the overall population, but not in the hypertensive and normotensive populations separately. In conclusion, the frequency of 1166C polymorphism is similar among Malay hypertensive and normotensive subjects. This polymorphism has no association with BP but may have an influence on PWV in Malays, which needs further investigation.
BACKGROUND: Data comparing the effect of losartan and perindopril on aortic stiffness among hypertensive subjects without A(1166)C polymorphism was not available.
METHODS: The short-term and long-term effects of losartan (50 mg) and perindopril (4 mg) on aortic stiffness measured as carotid femoral pulse wave velocity (PWV) were compared in 39 middle-aged Malay subjects with mild-to-moderate hypertension in a 4-month, double-blind, randomized, controlled, parallel-design study.
RESULTS: Four-month treatment with both drugs showed a significant reduction in blood pressure (BP) (P < .005) and PWV (P < .05) as compared to the baseline. On the other hand 1-month treatment showed a significant reduction in BP only in perindopril group (P < .05) but not in the losartan group. There was no significant reduction in pulse pressure and PWV after 1 month treatment by both drugs. No significant difference was seen in reduction in BP after 1 month and 4 months treatment between the two drugs. Similarly no significant difference was seen in reduction in PWV between the two drugs after 1 month (P = .613) and 4 months (P = .521) of treatment. Reduction in PWV by losartan (r = 0.470) and perindopril (r = 0.457) correlated significantly only with reduction in DBP (P < .05) and remained significant even after controlling for reduction in DBP (P < .05). Reduction in PWV by both losartan and perindopril was independent of reduction in BP by these drugs.
CONCLUSIONS: These results showed that long-term treatment with losartan shows similar pressure independent reduction in PWV as perindopril among Malay hypertensive subjects with a homogenous "AA" genotype for angiotensin II type 1 receptor and may serve as a suitable alternative to perindopril.
BACKGROUND: Knowledge of candidate gene polymorphisms in a population is useful for a variety of gene-disease association studies, particularly for some complex traits. A single nucleotide variant of the angiotensinogene gene (AGT M235T) and endothelial nitric oxide synthase gene (eNOS G894T) have been associated with hypertension.
METHOD: A cross-sectional study consisting of 200 hypertensives and 198 age- and sex-matched controls was conducted. Subjects involved in this study were pure Malay for 3 generations. The AGT M235T and eNOS G894T polymorphisms were determined by PCR-RFLP method.
RESULTS: The distribution of M235T genotype in the population was 3.5% for MM, 30.4% for MT and 66.1% for TT. No significant difference was observed in genotype (chi(2)=1.30, p=0.52) and allele (chi(2)=0.87, p=0.35) frequencies among the 2 study group. In contrast, the distribution of genotypes for G894T was 74.1% for GG, 24.6% for GT and 1.3% for TT, respectively. Similarly, no significant difference was observed in genotype (chi(2)=0.94, p=0.33) and allele (chi(2)=0.60, p=0.44) frequencies between both study groups.
CONCLUSION: The AGT M235T and eNOS G894T polymorphisms are unlikely to play an important role in the pathogenesis of hypertension in Malays.
Study site: Outpatient clinic, Hospital Universiti Sains Malaysia (HUSM); government clinics, Kelantan, Malaysia.
Normotensive subjects with family history of hypertension (FHT) have been reported to have increased left ventricular mass index and reduced ventricular compliance. Of interest is whether blood pressure variability (BPV), which has been associated with target organ damage, is then part of this complex inherited syndrome? The objectives of this study are to determine whether there are any significant differences in BPV, arterial compliance and humoral factors in subjects with FHT as compared to controls. Thirty-five subjects with self reported FHT and 35 matched controls underwent 24 hour BP monitoring (BR-102, Schiller Inc. Germany). Arterial compliance was measured using systolic pulse wave tonometry (HDI/Pulsewave Cardiovascular Profiling Instrument, Hypertension Diagnostic Inc. USA). None of the subjects were hypertensive or diabetic. Out of these numbers, 25 subjects with FHT and 26 controls had measurements of plasma catecholamines, plasma renin and serum aldosterone. Catecholamines were assayed with high performance liquid chromatography, while both renin and aldosterone measurements were by radioimmunoassay. Subjects with FHT have higher night time BPV. There was no significant difference in arterial compliances between both groups. There were increased level of norepinephrine (NE) in subjects with FHT but epinephrine (E), renin and aldosterone levels were similar in both groups. There were no correlations between NE and BPV but E was negatively associated with daytime and mean arterial systolic BPV. In conclusion subjects with FHT demonstrated a higher night time BPV and NE level as compared to controls.
The deletion (D) allele of the angiotensin-converting enzyme (ACE) gene has been studied in various populations in relation to hypertension (HTN) and type 2 diabetes mellitus (T2DM) with contradictory results. This study sought to determine the association of insertion (I)/D polymorphism of the ACE gene in hypertensive and T2DM subjects in a Malaysian population.
An insertion/deletion (I/D) polymorphism of Alpha2B-Adrenoceptor (ADRA2B) gene located on chromosome 2 has been studied extensively in related to cardiovascular diseases. The main aim of the present study was to examine the potential association of D allele frequency of I/D polymorphism of ADRA2B gene in Malaysian essential hypertensive subjects with or without type 2 diabetes mellitus (T2DM). This study includes 70 hypertensive subjects without T2DM, 65 hypertensive subjects with T2DM and 75 healthy volunteers as control subjects. Genotyping of I/D polymorphism was performed by conventional PCR method. There was significant difference found in age, body mass index, systolic/diastolic blood pressure and high density lipoprotein cholesterol level between the case and control subjects. DD genotypic frequency of I/D polymorphism was significantly higher in hypertensive subjects (42.84% vs. 29.33%; P-=0.029) and in hypertensive with T2DM subjects (46.15% vs. 29.33%; P=0.046) than control group. D allele frequency was higher in hypertensive group (67.41%) than control subjects (52.67%). However, no significant difference was found between the three genotypes of I/D polymorphism of ADRA2B gene and the clinical characteristics of the subjects. The result obtained in this study show D allele of ADRA2B gene was associated with essential hypertension with or without T2DM in Malaysian subjects.
The renin-angiotensin aldosterone system (RAAS) plays an important role in regulating the blood pressure and the genetic polymorphisms of RAAS genes has been extensively studied in relation to the cardiovascular diseases in various populations with conflicting results. The aim of this study was to determine the association of five genetic polymorphisms (A6G and A20C of angiotensinogen (AGT), MboI of renin, Gly460Trp of aldosterone synthase and Lys173Arg of adducin) of RAAS genes in Malaysian essential hypertensive and type 2 diabetic subjects.
CYP2C8 is involved in the cytochrome P450 (CYP) epoxygenase pathway. Arachidonic acid metabolites such as epoxyeicosatrienenoic acids and hydroxyeicosatetrenoic acids, produced may have a role in hypertension. We aimed to develop a medium through-put method for screening samples of known and new mutations of CYP2C8 using denaturing high performance liquid chromatography (DHPLC).
Polymorphisms within the beta2-adrenergic receptor (ADRB2) gene have been repeatedly linked to hypertension. Among the ADRB2 polymorphisms detected, Arg16Gly and Gln27Glu codons are considered the two most important variations. The amino acid substitution at these codons may lead to abnormal regulation of ADRB2 activity. The aim of the present study was to assess the association between ADRB2 polymorphisms and hypertension. This case-control study consisted of 100 unrelated subjects (50 hypertensive and 50 matched normal controls). Arg16Gly and the Gln27Glu polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism assay. There were no significant evidence of association in allelic and genotypes distribution of Arg16Gly and Glu27Gln with blood pressure and hypertension. These findings suggest that the variation within codon 16 and 27 of ADRB2 gene were unlikely to confer genetic susceptibility for hypertension in our population samples.
OBJECTIVES: In this cross-sectional study we compared the central aortic systolic pressure (CASP), peripheral brachial systolic pressure (PSP), peripheral brachial diastolic pressure (PDP) and augmentation index (AIx) between normotensive offspring of nonhypertensive parents (ONT) and normotensive offspring with at least one hypertensive parent (OHT).
METHODOLOGY: A total of 100 healthy ONT (mean age 20.95 ± 2.06) and 100 healthy OHT (mean age 20.89 ± 2.12) individuals were recruited. Parental history of hypertension was determined by detailed history taking. CASP, PSP, PDP and AIx were measured using the BPro device. All blood pressure (BP) measurements were calibrated using oscillometric BP readings.
RESULTS: The OHT group had higher PSP (117.57 ± 10.06 versus 114.52 ± 8.94, P < 0.05), PDP (72.39 ± 7.28 versus 70.39 ± 6.50, P < 0.05) and CASP (103.72 ± 8.95 versus 101.37 ± 7.74, P < 0.05) compared to the ONT group. There was no significant difference in AIx in the ONT group (57.97 ± 11.02 versus 58.08 ± 12.16, P = 0.95) in comparison to the OHT group. However, following adjustments for certain cardiovascular risk factors, only PSP (117.33 versus 114.76, P < 0.05) remained significantly higher in the OHT group compared to the ONT group. Analysis of adjusted data within sex showed that CASP was higher in the female OHT group compared to the female ONT group, whereas PDP were higher in the male OHT group compared to the male ONT group.
CONCLUSION: Alterations in PSP, PDP and CASP are already present in early life in normotensive offspring of hypertensive parents, with possible differences in mechanism between different sexes.
Study site: Clinical Research Laboratory in Cyberjaya University College of Medical Sciences, Selangor, Malaysia
The sympathetic nervous system plays a major role in blood pressure regulation. Beta 2 (β2) adrenoceptor gene polymorphisms have been associated with hypertension in different populations with conflicting results. We examined the association of three common polymorphisms, Arg16Gly, Gln27Glu, and Thr164Ile, of the β2 adrenoceptor gene in Malaysian hypertensive subjects. A total of 160 hypertensive and control subjects were recruited. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and anthropometric measurements were obtained from each subject. Biochemical analyses of lipid profiles were conducted with an autoanalyzer. DNA samples were extracted from blood and buccal cells. Genotyping was accomplished with polymerase chain reaction-restriction fragment length polymorphism. SBP, DBP, body mass index, and biochemical factors all differed significantly between case and control subjects (P < 0.05). The genotype frequencies of Arg16Arg, Arg16Gly, and Gly16Gly were 22.5, 70, and 7.5% among cases and 33.1, 63.1, and 3.8% among controls, respectively. The genotype frequencies of Gln27Gln, Gln27Glu, and Glu27Glu among cases were 41.1, 50, and 1.9% compared to 77.5, 20.6, and 1.9% among controls, respectively. In this study, the Gln27Glu polymorphism was significantly associated with Malaysian hypertensive subjects (P < 0.05). Therefore, the Gln27Glu polymorphism of the β2 adrenoceptor could be a risk factor associated with hypertension among Malaysians.
Irregular atrial pressure, defective folate and cholesterol metabolism contribute to the pathogenesis of hypertension. However, little is known about the combined roles of the methylenetetrahydrofolate reductase (MTHFR), apolipoprotein-E (ApoE) and angiotensin-converting enzyme (ACE) genes, which are involved in metabolism and homeostasis. The objective of this study is to investigate the association of the MTHFR 677 C>T and 1298A>C, ACE insertion-deletion (I/D) and ApoE genetic polymorphisms with hypertension and to further explore the epistasis interactions that are involved in these mechanisms. A total of 594 subjects, including 348 normotensive and 246 hypertensive ischemic stroke subjects were recruited. The MTHFR 677 C>T and 1298A>C, ACE I/D and ApoEpolymorphisms were genotyped and the epistasis interaction were analyzed. The MTHFR 677 C>T and ApoE polymorphisms demonstrated significant associations with susceptibility to hypertension in multiple logistic regression models, multifactor dimensionality reduction and a classification and regression tree. In addition, the logistic regression model demonstrated that significant interactions between the ApoE E3E3, E2E4, E2E2 and MTHFR 677 C>T polymorphisms existed. In conclusion, the results of this epistasis study indicated significant association between the ApoE and MTHFR polymorphisms and hypertension.
Several studies show that the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with hypertension in various populations. The present study sought to determine the association of the I/D gene polymorphism among Malay male essential hypertensive subjects in response to ACE inhibitors (enalapril and lisinopril).
This study aims to investigate the effects of tumor necrosis factor alpha (TNF-α) G308A gene polymorphism on essential hypertension (EHT) with or without type 2 diabetes mellitus (T2DM). The project was conducted on buccal epithelial and blood cells for case and control patients, respectively. Epithelial cells were obtained from the inner part of the cheeks. Techniques including DNA extraction, polymerase chain reaction (PCR), and restriction fragment length polymorphism (RFLP) were utilized to assess biomarkers of DNA damage. Our results demonstrated significant differences between wild and mutated genotypes among EHT patients without T2DM. We also found a significant association between wild and mutated allele frequencies in EHT patients (P < 0.05). Clinical characteristics between the groups (EHT with or without T2DM and controls) showed statistically significant association (P < 0.05). Overall, we show that G308A polymorphism of the TNF-αgene may be a significant genetic risk factor for EHT without T2DM patients in Malaysia.
Hypertension and atherosclerosis are among the most common causes of mortality in both developed and developing countries. Experimental animal models of hypertension and atherosclerosis have become a valuable tool for providing information on etiology, pathophysiology, and complications of the disease and on the efficacy and mechanism of action of various drugs and compounds used in treatment. An animal model has been developed to study hypertension and atherosclerosis for several reasons. Compared to human models, an animal model is easily manageable, as compounding effects of dietary and environmental factors can be controlled. Blood vessels and cardiac tissue samples can be taken for detailed experimental and biomolecular examination. Choice of animal model is often determined by the research aim, as well as financial and technical factors. A thorough understanding of the animal models used and complete analysis must be validated so that the data can be extrapolated to humans. In conclusion, animal models for hypertension and atherosclerosis are invaluable in improving our understanding of cardiovascular disease and developing new pharmacological therapies.
The aim of this study was to determine whether C34T, a common polymorphism of the adenosine monophosphate deaminase 1 gene (AMPD1), is associated with essential hypertension (EH). We hypothesize that C34T is associated with the development of EH. A case-control design was used for this study. The DNA was extracted using a commercial kit from the whole blood of 200 patients with hypertension and 200 subjects without hypertension from selected Malaysian ethnicities (Malays, Chinese, and Indians). Polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) and agarose gel electrophoresis were used for genotyping. The C34T gene polymorphism of AMPD1 was significantly associated with EH in the Malaysian subjects (P < 0.0001). The genotype frequencies of CC, CT, and TT were 6%, 79%, and 15%, respectively, among hypertensive subjects, while no TT genotypes were observed in the normotensive subjects. Further, the frequency of hypertension was higher among T allele carriers than C carriers (OD = 9.94; 95%CI = 6.851-14.434). There were significant differences in the systolic blood pressure, diastolic blood pressure, and pulse pressure (P ˂ 0.05) between the normotensive and hypertensive Malaysian subjects; we believe those difference were caused by the C34T polymorphism. For the first time in Malaysia, the current study provides evidence that a common polymorphism of the AMPD1 gene (C34T) is strongly associated with EH.
Adiponectin exerts vasodilatory effects. Irbesartan, an angiotensin receptor blocker, possesses partial peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist activity and increases circulating adiponectin. This study explored the effect of irbesartan alone and in combination with adiponectin on blood pressure, renal hemodynamic excretory function, and vasoactive responses to angiotensin II and adrenergic agonists in spontaneously hypertensive rat (SHR). Irbesartan was given orally (30 mg/kg/day) for 28 days and adiponectin intraperitoneally (2.5 μg/kg/day) for last 7 days. Groups of SHR received either irbesartan or adiponectin or in combination. A group of Wistar Kyoto rats (WKY) served as controls. Metabolic data and plasma samples were taken on days 0, 21, and 28. In acute studies, the renal vasoconstrictor actions of angiotensin II (ANGII), noradrenaline (NA), phenylephrine (PE), and methoxamine (ME) were determined. SHR control rats had a higher mean blood pressure than the WKY (132 ± 7 vs. 98 ± 2 mmHg), lower plasma and urinary adiponectin, creatinine clearance, urine flow rate and sodium excretion, and oxidative stress markers compared to WKY (all P