M235T polymorphism of the angiotensinogen gene and hypertension in Chinese

OBJECTIVES: To compare the distributions of the genotypes and alleles of the M235T polymorphism of the angiotensinogen gene for hypertensive patients and normotensive controls. DESIGN: A study of association of genetic polymorphisms. SETTING: An outpatient clinic run by a university department handling referrals from primary care. PATIENTS: Two hundred and four subjects, 103 normal controls and 101 patients with newly diagnosed or documented hypertension. METHOD: Genomic DNA was extracted from peripheral blood leucocytes, amplified by polymerase chain reaction and digested with the restriction enzyme Tth 111 I. Methionine (M) and threonine (T) alleles were identified after electrophoresis. MAIN OUTCOME MEASURES: Prevalences of angiotensinogen genotypes and alleles for hypertensive patients and controls. Results: MM, TM and TT genotypes occurred in 3, 24 and 73% of controls and 1, 22 and 77% of hypertensive patients, respectively. The prevalences of the M and T alleles were 0.15 and 0.85 among controls and 0.12 and 0.88 among hypertensive patients. The prevalences of the angiotensinogen genotypes and alleles for controls and hypertensive patients did not differ significantly. CONCLUSIONS: Our findings differed from previous reports and suggested that this polymorphism is not associated with hypertension in this population.     

M235-->T polymorphism of the angiotensinogen gene predicts hypertension in the elderly

OBJECTIVE: To determine whether the M235-->T polymorphism (exon 2) of the angiotensinogen gene is associated with hypertension in elderly patients with isolated systolic hypertension [ISH: systolic blood pressure (SBP) > or = 160 mmHg, diastolic blood pressure (DBP) < 90 mmHg) or systolic-diastolic hypertension (SDH: DBP > or = 90 mmHg, SBP > or = 160 mmHg) compared with normotensive controls (SBP < 160 mmHg, DBP < 90 mmHg). DESIGN: A case-control study in 769 non-institutionalized, elderly (aged > or = 60 years; female:male ratio 0.85) residents of Dubbo, New South Wales. METHODS: Individuals were classified as having ISH (n = 171), having SDH (n = 218) and being normotensive controls (n = 366) with age and sex matching. MM, TT and MT genotypes were determined by a nested polymerase chain reaction strategy using DNA extracted from serum. The prediction of ISH or SDH by genotype or allele was examined in a multiple-logistic regression model that controlled for various confounders. RESULTS: SBP (mean +/- SD, mmHg)/DBP (mean +/- SD, mmHg) was 176 +/- 16/79 +/- 8 in the ISH group, 167 +/- 23/97 +/- 7 in the SDH group and 134 +/- 14/74 +/- 9 in the normotensive control group. The frequencies of M and T alleles in the normal population (0.69 and 0.31, respectively) were altered significantly in the ISH group (0.61 and 0.39, respectively; chi 2 = 6.0, P < 0.02) and the SDH group (0.62 and 0.38, respectively; chi 2 = 6.0, P < 0.02). The presence of the TT genotype predicted both ISH (odds ratio 1.9, 95% confidence interval 1.1-3.3) and SDH (1.7, 1.0-3.0) as did that of the T allele (ISH: 1.3, 1.0-1.7; SDH: 1.3, 1.0-1.7). CONCLUSIONS: The M235-->T polymorphism may be a marker for both forms of hypertension in the elderly. Whether the TT genotype represents a genetic risk factor for the development of hypertension in later life requires confirmation.     

Gender-specific association of M235T polymorphism in angiotensinogen gene and diabetic nephropathy in NIDDM

Cryoanalgesia versus sham treatment was applied to the ilioinguinal and iliohypogastric nerves after mesh repair of an inguinal hernia under local anesthesia in 48 male patients in a prospective, randomized, and observer- and patient-blinded trial. Pain was scored daily during rest, while coughing, and during mobilization to the sitting position for 1 wk and weekly for 8 wk on a four-point verbal rank scale. Use of supplementary analgesics and sensory disturbances were recorded. Assessments were made for allodynia, hyperalgesia, and mechanical pain detection thresholds 8 wk postoperatively. Cumulative pain scores for the first postoperative week were equal in the two groups, as was the use of analgesics. Eight weeks postoperatively, three cases of hyperalgesia to pinprick were detected in the cryoanalgesia group, and 10 patients in the cryoanalgesia group versus 5 in the sham-treatment group reported disturbed sensibility. We conclude that cryoanalgesia of the iliohypogastrical and ilioinguinal nerve does not decrease postherniorrhaphy pain. IMPLICATIONS: Does freezing of sensory nerves in the groin reduce pain after hernia repair? Extreme cold (-60 degrees C) was applied in a double-blind, randomized study. No difference in pain scores was found. Sensory disturbances were seen in treatment and control patients. Freezing cannot be recommended for pain relief after hernia repair.     

Angiotensinogen Met235-->Thr polymorphism in a London normotensive and hypertensive black and white population

We describe angiotensinogen gene (AGT) polymorphic frequencies in different ethnic groups in London, both normotensive and hypertensive. The methodology is a recently described direct PCR technique. Results show that there is a marked difference in T-235 frequency between ethnic groups. However, there was no apparent association of T-235 with hypertension.     

T235 variant of the angiotensinogen gene and blood pressure in the Chilean population

BACKGROUND: The angiotensinogen gene has recently been linked to essential hypertension. A variant within this gene, encoding threonine rather than methionine at amino acid position 235, was associated with essential hypertension. However, results of new studies have not confirmed this association, suggesting that ethnic differences may explain the different results. OBJECTIVE: To evaluate whether the T235 variant is associated with a higher incidence of essential hypertension among Hispanics (a group that has scarcely been evaluated) and to determine whether T235 is associated with variations in the plasma renin activity or the serum aldosterone level. PATIENTS AND METHOD: We studied 64 patients with essential hypertension and 62 normotensives, matched for age and sex. We obtained samples for determinations of plasma renin activity, serum aldosterone level and genome DNA from all subjects. The genomic DNA was amplified using the polymerase chain reaction technique and digested by the restriction enzyme streptococcus faecalis (Sfa NI) which cuts M235 only, not T235. RESULTS: The patients with essential hypertension had a higher prevalence of the risk variant T235 (alleles 77/128 = 60.2%) than did the normotensive controls (alleles 65/124 = 52.4%), but the difference was not statistically significant (chi2=1.53, P=0.22). The plasma renin activity levels in hypertensives were not statistically different for homozygous T235, heterozygous and homozygous M235 (1.0 +/- 0.96, 2.0 +/- 2.25 and 1.55 +/- 1.49 ng/ml per h, respectively, P=0.5 1). However, when we considered those hypertensives with low plasma renin activity levels (< 1 ng/ml per h), we found a high prevalence (72.7%) of subjects homozygous for the T235 variant. We found no association between the T235 variant and the serum aldosterone levels in hypertensive and normotensive subjects. CONCLUSIONS: We demonstrated that there is a high prevalence of T235 variant in our Hispanic population. The slight difference between prevalences of T235 variant among hypertensive and normotensive subjects that we found was not statistically significant and did not permit us to establish an association between T235 variant and essential hypertension. We believe that only studying a larger cohort of subjects could show whether there is a quantitative effect of the T allele on plasma renin activity levels.     

Association of angiotensinogen gene T235 variant with progression of immunoglobin A nephropathy in Caucasian patients

Genetic variability in the renin-angiotensin system may modify renal responses to injury and disease progression. We examined whether the M235T polymorphism of the angiotensinogen (AGT) gene, the insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene, and the A1166--> C polymorphism of the angiotensin II type 1 receptor gene may be associated with disease progression in 168 Caucasian patients with IgA nephropathy. All patients had serial measurements of their creatinine clearance, proteinuria, and blood pressure (mean+/-SD) with a follow-up of 6.1+/-4.7 yr. The genotype frequencies for each gene were consistent with Hardy-Weinberg equilibrium, and were similar to those of 100 Caucasian control subjects. We examined two primary outcomes: (a) the rate of deterioration of Ccr, and (b) the maximal level of proteinuria. We found that patients with the AGT MT (n = 79) and TT (n = 29) genotypes had a faster rate of deterioration of Ccr than those with the MM (n = 60) genotype (i.e., median values, -6.6 and -6.2 vs. -3. 0 ml/min/yr, respectively; P = 0.01 by Kruskal-Wallis test). Similarly, patients with AGT MT and TT genotypes had higher maximal values of proteinuria than those with the MM genotype (i.e., median values, 2.5 and 3.5 vs. 2.0 g/d, respectively; P < 0.02 by Kruskal-Wallis test). Neither the ACE insertion/deletion nor angiotensin II type I A1166--> C gene polymorphism was associated with disease progression or proteinuria in univariate analysis. Multivariant analysis, however, detected an interaction between the AGT and ACE gene polymorphisms with the presence of ACE/DD polymorphism adversely affecting disease progression only in patients with the AGT/MM genotype (P = 0.008). Neither of these gene polymorphisms was associated with systemic hypertension. Our results suggest that polymorphisms at the AGT and ACE gene loci are important markers for predicting progression to chronic renal failure in Caucasian patients with IgA nephropathy.     

Angiotensinogen polymorphism M235T, hypertension, and nephropathy in insulin-dependent diabetes

The allele 235T (a threonine in place of a methionine at position 235) of angiotensinogen has been found to be associated with a predisposition to essential hypertension. We investigated whether this allele also confers increased susceptibility to nephropathy in patients with insulin-dependent diabetes mellitus (IDDM). A group of 380 patients who had had IDDM for 15 to 20 years were genotyped at the angiotensinogen 235 locus. Included were 75 patients with normoalbuminuria (albumin excretion rate < 30 micrograms/min), two series of patients with microalbuminuria (n = 30 and n = 136), and two series with overt proteinuria (n = 41 and n = 98). Allele 235T frequency was higher among cases with microalbuminuria (0.41 in the two series combined) or overt proteinuria (0.40) than in the normoalbuminuria group (0.36). However, this difference was not statistically significant with this sample size (chi 2 = 1.2, P = NS with 2 df). Under a recessive model, allele 235T homozygotes had a 1.6-fold risk of developing nephropathy relative to carriers of other genotypes, but this value was not significantly different from 1(95% CI = 0.8 to 3.5). The strength of the association did not improve after stratification by degree of glycemic control. With respect to the hypertension in these IDDM patients, no association with allele 235T was found. Allele 235T frequencies in normotensive and hypertensive individuals were 0.363 and 0.353, respectively, among normoalbuminuric IDDM individuals (chi 2 = 0.01, P = NS) and 0.411 and 0.414 among microalbuminuric IDDM subjects (chi 2 = 0.0, P = NS). We conclude that the angiotensinogen polymorphism M235T might influence susceptibility to nephropathy in insulin-dependent diabetes, but its effect, if any, is rather small and independent of hypertension.     

The BDNF Val66Met polymorphism is associated with rumination in healthy adults.

This study examined associations between the tendency to ruminate and 2 polymorphisms: the Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene and 5-HTTLPR polymorphism in the serotonin transporter gene (SLC6A4). Participants were a homogeneous group of healthy, unmedicated, never depressed individuals with few current symptoms of depression (N = 71). Results indicated that met heterozygotes of the BDNF allele were significantly more likely to ruminate than individuals homozygous for the val BDNF allele. There was no association between rumination and the 5-HTTLPR polymorphism. Furthermore, the interaction between the 5-HTTLPR and BDNF polymorphisms did not predict rumination. Results suggest that variation in the BDNF gene may contribute to the tendency to ruminate. Because this association exists in healthy adults, it may represent a susceptibility factor for affective disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of N-glycosylation in human angiotensinogen

Human angiotensinogen, the specific substrate of renin, is a heterogeneous glycoprotein constitutively secreted by the liver. Different glycosylation levels may be responsible for its heterogeneity. It contains four putative asparagine-linked glycosylation sites (Asn-X-Ser/Thr). Systematic site-directed mutagenesis (Asn replaced with Gln) of these four sites was undertaken, and 11 (single, double, triple, and quadruple (N-4)) mutants were produced in COS-7 and/or CHO-K1 cells and characterized. All of the sites were N-glycosylated with preferential glycosylation of the Asn14 and the Asn271. The suppression of the Asn14 glycosylation site led to 5 times lower Km and a 10 times lower kcat. Angiotensinogen heterogeneity was much lower for the N-4 mutant protein, which produced a single form at 48 kDa. Pulse-chase experiments showed slight intracellular retention (15%) of the deglycosylated protein after 24 h. Interestingly, the N-4 mutant had a higher catalytic efficiency (kcat/Km = 5.0 versus 1.6 microM-1 . s-1) than the wild-type protein. The thermal stability of the N-4 protein was unaffected by deglycosylation, suggesting that it was correctly folded. This deglycosylated recombinant human angiotensinogen could be of value for x-ray crystallography studies.     

Diabetic nephropathy is associated with AGT polymorphism T235: results of a family-based study

Diabetic nephropathy is a serious and frequent complication of insulin-dependent diabetes mellitus (IDDM) that has a strong genetic component. Several case-control studies have reported conflicting results with regard to the role of angiotensinogen gene polymorphisms, specifically the M235T T allele, in the development of diabetic nephropathy. The primary limitation of the case-control approach is that bias may be introduced by unrecognized differences in the populations selected for cases and control subjects. In contrast, family-based approaches, such as the transmission/disequilibrium test, assess whether a particular variant, or allele, is transmitted preferentially from a parent having a single copy of that allele. Thus each family provides its own control, thereby eliminating spurious results caused by mismatched population samples. To take advantage of this study design for further investigation of M235T, we collected from the Joslin Diabetes Center in Boston 148 IDDM patients with diabetic nephropathy, 62 nephropathy-free patients with long-duration IDDM, and, very importantly, parents of all these individuals. We found that among males (but not females) the T allele of the M235T polymorphism was transmitted preferentially to those with nephropathy compared with IDDM patients without nephropathy (P=.05). Moreover, the T allele was transmitted preferentially to patients with the most severe manifestation of nephropathy, end-stage renal disease (P=.04). In conclusion, results obtained in our family-based study support a role of the angiotensinogen gene M235T polymorphism, and specifically the T allele, in the development of diabetic nephropathy in IDDM.     

Polymorphism in apolipoprotein(a) kringle IV 37(Met/Thr): frequency in a London population and its association with coronary artery disease

BACKGROUND: A raised concentration of lipoprotein(a) [Lp(a)] in human plasma has been considered as a risk factor for coronary artery disease (CAD). Apolipoprotein(a) and plasminogen genes are exceptionally similar to a variable number of plasminogen-like kringle IV repeats in the apo(a) gene. Polymorphisms have been previously identified in the apolipoprotein(a) kringle IV 37. HYPOTHESIS: In order to determine the frequency of the apolipoprotein(a) kringle IV 37 Met66-->Thr polymorphism in a London-based population and to assess the relationship of this polymorphism with CAD in Caucasian patients, we genotyped two groups of people of different ethnic origin (Caucasian and Afro-Caribbean) for the mutation using standard polymerase chain reaction (PCR) techniques. METHODS: The first group consisted of 182 unrelated Caucasian patients (107 men and 75 women, mean age 59.7 +/- 10.2 years) recruited at St. George's Hospital. They were defined as patients with 0, 1 or > or = 2 vessel disease patients depending on the degree of stenosis in none, one, or several major epicardial arteries. The second group comprised 64 unrelated patients of Afro-Caribbean origin attending a hypertension clinic at St. George's Hospital. RESULTS: It was shown that the prevalence of the Met66-->Thr mutation is markedly higher in Caucasians than in Afro-Caribbeans and that this mutation is not associated with either Lp(a) levels or severity of CAD.     

Tissue-specific regulation of angiotensinogen gene expression in spontaneously hypertensive rats

Angiotensinogen is expressed in many tissues besides the liver. Recent studies have suggested that abnormalities in the regulation of angiotensinogen gene expression may be involved in the development of hypertension. However, little information is available concerning the functional significance of tissue angiotensinogen. In this study, we measured plasma angiotensinogen concentration by radioimmunoassay and examined the expression of tissue angiotensinogen by Northern blot analysis in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Although plasma angiotensinogen concentration in SHR was comparable to that in WKY at 6 weeks of age, it was increased significantly at 14 weeks of age in SHR and became higher than that in WKY. The levels of hepatic angiotensinogen mRNA were similar in SHR and WKY, and the levels of aortic, adrenal, and renal angiotensinogen mRNAs were lower in SHR than in WKY at both 6 and 14 weeks of age. Brain angiotensinogen expression in SHR was higher than in WKY at 6 weeks of age and was comparable to that in WKY at 14 weeks of age. On the other hand, cardiac and fat angiotensinogen mRNA levels were significantly increased at 14 weeks of age in SHR. These results demonstrate that the expression of tissue angiotensinogen is regulated differently in SHR and WKY and indicate that the development of hypertension is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as cardiac and adipogenic angiotensinogen mRNA in SHR.     

Functional expression of the human angiotensinogen gene in transgenic mice

The renin-angiotensin system is a major determinant of arterial pressure and volume homeostasis in mammals through the actions of angiotensin II, the proteolytic digestion product of angiotensinogen. Molecular genetic studies in several human populations have revealed genetic linkage between the angiotensinogen gene and both hypertension and increased plasma angiotensinogen. Transgenic mice were generated with a human angiotensinogen genomic clone to develop an animal model to examine tissue- and cell-specific expression of the gene and to determine if overexpression of angiotensinogen results in hypertension. Human angiotensinogen mRNA was expressed in transgenic mouse liver, kidney, heart, adrenal gland, ovary, brain, and white and brown adipose tissue and, in kidney, was exclusively localized to epithelial cells of the proximal convoluted tubules. Plasma levels of human angiotensinogen were approximately 150-fold higher in transgenic mice than that found normally in human plasma. The blood pressure of mice bearing the human angiotensinogen gene was normal but infusion of a single bolus dose of purified human renin resulted in a transient increase in blood pressure of approximately 30 mm Hg within 2 min. These results suggest that abnormalities in the angiotensinogen gene resulting in increased circulating levels of angiotensinogen could potentially contribute in part to the pathogenesis of essential hypertension.     

Elevation of plasma angiotensinogen in rats with experimentally induced nephrosis

Oxidant injury contributes to myocardial stunning, and cardiac ischemic and reperfusion injury. Vitamin E is the major--and perhaps the only--lipid soluble, chain-breaking antioxidant in the heart. Vitamin E and its analogues potentially offer significant advantages for the prevention of ischemic and reperfusion injury. Recent investigations have suggested that modified vitamin E analogues may be more efficacious than vitamin E and may permit myocardial salvage from acute myocardial ischemic injury.     

关于膨胀机系统调试过程中的两个问题

叙述了膨胀机系统调试过程中，由于外部干扰因素的影响而产生的误动作。     

Comparative stability and clearance of [Met30]transthyretin and [Met119]transthyretin

[Met119]Transthyretin has been described as a non-amyloidogenic transthyretin variant. In Portugal, it has also been found in compound heterozygotic individual carriers of [Met30]transthyretin, the most prevalent variant associated with familial amyloidotic polyneuropathy. In these individuals, the evolution of the disease seems to be more benign than in typical [Met30]transthyretin carriers, suggesting a protective effect of [Met119]transthyretin on the pathogenic effects of [Met30]transthyretin. To study the mechanisms of this protective effect, we performed comparative in vivo clearance studies. Heterotetrameric [Met119]transthyretin showed a slower clearance, whereas homotetrameric [Met30]transthyretin presented a faster clearance. These data correlate with the relative TTR levels present in carriers of these mutations. Comparative analyses of the resistance to dissociation into monomers of serum transthyretin by 4M urea isoelectric focusing suggested a higher tetrameric stability of transthyretin in [Met119]transthyretin carriers, in contrast to a lower stability in [Met30]transthyretin carriers. The compound heterozygotes presented a pattern similar to the normal individuals. Our results suggest that the protective clinical effect of the Met119 mutation possibly involves the stabilisation of the tetrameric structure of transthyretin. Whether this behaviour correlates with the different metabolism found for the two variants is not known. The approaches reported here open some possibilities for the study and development of future therapeutic agents of familial amyloidotic polyneuropathy.     

Decreased fibronectin expression in Met/HGF-mediated tumorigenesis

The tyrosine kinase receptor Met and its ligand, hepatocyte growth factor (HGF)/scatter factor are involved in the etiology and progression of a number of human cancers. Coexpression of Met and HGF in mesenchymal cells increases the tumorigenic and metastatic potential of the cells. In the studies described here, we used differential display screening to identify changes in gene expression that are initiated by Met/HGF, and that may lead to these phenotypes. We learned that Met/HGF signaling resulted in greatly decreased fibronectin mRNA production in three different human and mouse tumor cell lines; these decreases in fibronectin mRNA were paralleled by decreases in fibronectin protein. We also found a progressive decrease in fibronectin in tumor explants and metastases derived from the Met/HGF transformed cells. The absence of fibronectin expression is a frequent cancer phenotype; our results indicate that decreases in fibronectin correlate with, but are not essential for, MetHGF/SF-mediated tumorigenesis.