Endothelial nitric oxide synthase genotype and haplotype are not associated with diabetic retinopathy in diabetes type 2 patients

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been associated with the development of diabetic retinopathy (DR) in patients with type 1 diabetes mellitus (T1DM), but not with T2DM. However, no previous study has analyzed combinations of genetic markers (haplotypes), which can be more informative. We studied three eNOS genetic polymorphisms: a single nucleotide polymorphism in the promoter region (T(-786)C), in exon 7 (Glu298Asp), and a variable number of tandem repeats in intron 4 (b/a) in 103 healthy controls, and in 170 patients with T2DM (without DR, N=114; with DR, N=56). We also examined the association of eNOS gene haplotypes with T2DM and with DR. No differences were found in the frequencies of genotypes and alleles of the three polymorphisms among the three groups of subjects. However, the "C-Glu-b" haplotype was more common in healthy controls (24%) than in T2DM patients (7%) (P=0.0001). Finally, no significant difference in the distribution of eNOS haplotypes frequencies was found when T2DM patients with or without DR were compared (P=0.7372). These findings suggest no association between DR and individual eNOS haplotypes in T2DM patients. The "C-Glu-b" haplotype, however, may have a protective effect against T2DM. Further studies should be conducted to address the molecular basis for such an effect.     

Modulation of nitric oxide formation by endothelial nitric oxide synthase gene haplotypes

Nitric oxide (NO) is a major regulator of the cardiovascular system. However, the effects of endothelial nitric oxide synthase (eNOS) gene polymorphisms or haplotypes on the circulating concentrations of nitrite (a sensitive marker of NO formation) and cGMP are unknown. Here we examined the effects of eNOS polymorphisms in the promoter region (T-786C), in exon 7 (Glu298Asp), and in intron 4 (4b/4a) and eNOS haplotypes on the plasma levels of nitrite and cGMP. We hypothesized that eNOS haplotypes could have a major impact on NO formation. We genotyped 142 healthy subjects by PCR-RFLP. To assess NO formation, the plasma concentrations of nitrite and cGMP were determined using an ozone-based chemiluminescence assay and an enzyme immunoassay. Haplotypes were inferred using the PHASE 2.1 program. No significant differences were found in age, body mass index, systolic and diastolic arterial blood pressure, heart rate, total cholesterol, triglycerides, cGMP, or nitrite among the genotype groups for the three polymorphisms studied here (all p>0.05). Interestingly, the C-4b-Glu haplotype was associated with lower plasma nitrite concentrations than those found in the other haplotype groups (p<0.05), but not with different cGMP levels (p>0.05). These findings suggest that eNOS gene variants combined within a specific haplotype modulate NO formation, although individual eNOS polymorphisms probably do not have major effects.     

内皮型一氧化氮合酶基因多态性与高血压合并脑 梗塞的关系

目的:探讨内皮型一氧化氮合酶(eNOS)基因894G/T多态性与原发性高血压(EH)合并脑梗塞(CI)的关系。方法:应用聚合酶链反应限制性片段长度多态性方法检测湖北地区汉族74例健康者(NT组)、103例原发性高血压无合并症者(EH组)及70例原发性高血压合并脑梗塞者(EH-CI组)的eNOS基因型;生化技术测定其血脂、一氧化氮代谢物(NOM)水平。结果:EH组及EH-CI组患者的T等位基因频率分别为0.224和0.321,均显著高于NT组(P<0.05);且两者之间的T等位基因频率差异显著性(P<0.05);EH-CI组中,GT+TT基因型者的舒张压显著高于GG基因型者(P<0.05),而NOM显著低于GG基因型者。结论:eNOS基因894位G/T多态性可能与汉族高血压病患者伴脑梗塞有关,该位点多态性可能使T等位基因携带者NOM减少,进而参与EH-CI发病。     

A preliminary study on T-786C endothelial nitric oxide synthase gene and renal hemodynamic and blood pressure responses to dietary sodium

The purpose of the present study was to examine the role of the T-786C endothelial nitric oxide synthase (eNOS) gene polymorphism on changes in renal hemodynamics and blood pressure due to Na(+) loading. Twenty-eight older (63+/-1 years), moderately obese (39+/-2 % fat) hypertensives had their glomerular filtration rate (GFR), renal plasma flow (RPF), blood pressure (BP) and plasma nitric oxide (NO(x)) levels determined after eight days of low (20 mEq) and high (200 mEq) Na(+) diets. The two Na(+) diets were separated by a 1-week washout period. Subjects were genotyped for the eNOS-786 site and were grouped on whether they were homozygous or heterozygous for the C allele (TC+CC, n=13) or only homozygous for the T allele (TT, n=15). The TC+CC genotype group had a significantly greater increase in diastolic (P=0.021) and mean arterial (P=0.018) BP and a significant decline in both RPF (P=0.007) and GFR (P=0.029) compared to the TT genotype group with Na(+) loading. Furthermore, Na(+) loading resulted in a significant (P=0.036) increase in plasma NO(x) in the TT, but not in the TC+CC genotype group as well as a trend (P=0.051) for an increase in urine NO(x) in TC+CC, but not in the TT genotype group. The increase in BP during Na(+) loading in older hypertensives was associated with the eNOS genotype and may be related to changes in renal hemodynamics due to changes in NO metabolism.     

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 ≤ 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.     

Hyperglycaemia Enhances Nitric Oxide Production in Diabetes: A Study from South Indian Patients

Background

We have previously reported that increased glucose levels were associated with higher serum nitric oxide (NO) levels in fructose-fed insulin resistant rats. However, the relationship between hyperglycemia and serum NO level was not clear. Therefore, the present study was designed to find the association between hyperglycemia and serum NO levels in Type 2 diabetic (T2DM) patients and T2DM with cardiovascular complication.

Methods

Endothelial cells (HUVEC) were treated with of D-glucose (10-100mM), and NO levels and NOS gene expression was measured. Hyperglycaemia was induced in Sprague-Dawley rats, and serum NO levels were measured after 8 weeks. For clinical evaluation, five groups of patients were recruited: Control (CT, n=48), Type 2 diabetes (T2DM, n=26), T2DM with hypertension (DMHT, n=46), Coronary artery diseases (CAD, n=29) and T2DM with coronary artery diseases (DMCD, n=38). NO (nitrite + nitrate) levels were measured from human serum.

Results

We found a significant (p<0.05) and dose-dependent increase in NO levels in HUVEC cells after 4 hours of high glucose exposure. eNOS and iNOS gene expression was increased in HUVEC cells after different concentrations and time periods of glucose treatment. We also observed significant (149.1±25μM, p<0.01) increase in serum NO levels in hyperglycaemic rats compared to control (76.6±13.2μM). Serum NO level was significantly higher in T2DM (111.8 μM (81.7-122.4), p<0.001) and DMCD patients ((129.4 μM (121.2-143.5), p <0.001) but not in CAD patients (76.4 μM (70.5-87)), as compared to control (68.2 μM (56.4-82.3)). We found significantly lower NO levels (83.5 μM (60.5-122.9)) in subjects suffering from diabetes since more than 5 years, compared to subjects (115.3 μM (75.2-127.1), p<0.001) with less than 5 years.

Conclusion

In conclusion, high NO levels were observed in South Indian diabetic patients. Higher glucose levels in serum might be responsible for activation of endothelial cells to enhance NO levels.     

Relationship of eNOS gene variants to diseases that have in common an endothelial cell dysfunction

The endothelial cell (EC) dysfunction is a common characteristic of various pathologies that include atherosclerosis, hypertension, and Fabry's disease. Aware of the role of eNO and ACE in EC dysfunction, we questioned whether polymorphism of eNOS and/or ACE gene may be a common denominator in these pathologies. Patients with CHD (108), HT (109), Fabry's disease (37) and healthy subjects (control, 141) were genotyped for the eNOSG894T by RFLP-PCR technique and for eNOS4b/a, and ACEI/D polymorphisms by PCR amplification. The results of these studies were statistically evaluated. Compared to controls, the frequency of the eNOSG894T (T allele) was higher in CHD (P=0.03) and Fabry (P=0.01), while the eNOS4b/a (a allele) in CHD (P=0.01) and HT patients (P=0.01). The proportion of the ACEI/D was similar in all subjects. In CHD patients at "low risk" of atherogenic factors, the frequency of the T and a alleles of eNOS gene was high (P=0.03 and 0.02, respectively). Carriers of the T allele of eNOSG894T were over-represented (P=0.04) in Fabry subgroup with renal failure. Compared to women, the eNOS894T alleles were more frequent (P=0.03) in men with CHD and HT, whereas ACE I/D in men (P=0.03) with HT. These findings suggest: (i) the frequency of eNOSG894T and/or eNOS4b/a is significantly associated with coronary dysfunction; (ii) eNOS4b/a confers a relatively high risk of hypertension in subjects with atherogenic risk factors; (iii) the frequency of eNOSG894T is high in Fabry hemizygotes with renal complications. Therefore, eNOS gene polymorphism represent a frequent risk factor for vascular abnormalities in CHD, HT and Fabry's disease, afflictions which have in common, the endothelial dysfunction.     

eNOS genotype-dependent correlation between whole blood lead and plasma nitric oxide products concentrations.

Experimental data indicate that lead exposure decreases nitric oxide (NO) availability. However, no previous study has examined whether lead exposure affects plasma nitrite/nitrate (NO(x)) concentrations in humans. In addition, the T(-786)C polymorphism affects endothelial NO synthase (eNOS) expression and endogenous NO release. Here, we investigated whether there is an association between the circulating concentrations of NO(x) and the concentrations of lead in whole blood (B-Pb) and in plasma (P-Pb) from lead-exposed subjects. In addition, we also evaluated whether eNOS genotype for the T(-786)C polymorphism affects NO(x) concentrations in lead-exposed subjects. We studied 104 subjects exposed to lead who were non-smokers, 18-60 years of age, and not alcohol consumers. Genomic DNA was isolated from blood samples and genotypes for the T(-786)C polymorphism were determined by PCR and restriction fragment length digestion. Circulating NO(x) was determined by chemiluminescence. B-Pb and P-Pb were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. No significant correlations were found between NO(x) and B-Pb and P-Pb measured in the 104 subjects (all P > 0.05). However, while no significant correlation was found in subjects with TT genotype, a negative correlation was found between plasma NO(x) and B-Pb (r = 0.230, P = 0.048) and P-Pb (r = 0.194, P = 0.110) in subjects from TC + CC genotypes group. Our study shows a negative correlation between plasma NO(x) concentrations and B-Pb in carriers of the "C" allele, thus suggesting a possible mechanism possibly involved in lead exposure-induced increase in the susceptibility to cardiovascular diseases.     

Endothelial nitric oxide synthase gene polymorphisms and cardiovascular damage in hypertensive subjects: an Italian case-control study

Background

Nitric oxide (NO) synthesized by endothelial nitric oxide synthase (eNOS) plays an important role in regulation of endothelial function and in the control of blood pressure. However, the results from some studies on the association between three clinically relevant eNOS gene polymorphisms (G894T, T786C and intron 4b/a) and essential hypertension are unclear. We designed a case-control study to evaluate the influence of eNOS polymorphisms on target organ damage in 127 hypertensives and 67 normotensives. Clinical evaluation, biochemical parameters, Urinary Albumin Excretion (UAE) and echocardiogram were performed to characterize target organ damage. eNOS polymorphism were recognized by PCR method.

Results

The distribution of eNOS genotypes was similar in hypertensives and normotensives but 4aa was present in the 2.5% of hypertensives and completely absent in normotensives. Subjects with 4bb, G894T, and T786C genotypes showed an increased prevalence of target organ damage. Moreover prevalence of G894T and introne 4 variants was significantly higher in hypertensives than in normotensives both with cardiovascular damage. Logistic regression analysis didn't show any association between eNOS polymorphisms, Body Mass Index (BMI), hypertension, gender and cardiovascular damage. Only the age (OR 1.11; IC 95% 1.06–1.18) was predictive of cardiovascular damage in our population.

Conclusion

Our results seem to indicate a lack of association with eNOS variants and cardiovascular damage onset.     

Maturation enhances fluid shear-induced activation of eNOS in perfused ovine carotid arteries

The present study tests the hypothesis that age-dependent increases in endothelial vasodilator capacity are due to maturational increases in endothelial nitric oxide (NO) synthesis and release. Intact 4-cm carotid artery segments taken from term fetal lambs and nonpregnant adult sheep were perfused by using a closed system that enabled independent control of flow and inflow pressure and facilitated complete recovery of all NO released. Fluid shear stress induced a graded release of NO (in nmol NO x min x cm(-2) of luminal surface area) that was significantly greater in adult (890 +/- 140) than in fetal (300 +/- 40) carotid arteries at corresponding values of shear stress (5.9 +/- 0.3 dyn/cm2) but was independent of inflow pressure in both age groups. These age-related differences in NO release were not attributable to corresponding differences in endothelial NO synthase (eNOS) abundance, as eNOS protein levels (in ng of eNOS/cm2 of luminal surface area) were similar in adult (14 +/- 2) and fetal (12 +/- 1) arteries. Adult (80 +/- 15) and fetal (89 +/- 32) levels of eNOS mRNA (in 10(6) copies/cm2 of luminal surface area) were also similar. However, when NO release was normalized relative to the associated mass of eNOS protein to estimate eNOS-specific activity in situ, this value (in nmol NO x microg of eNOS(-1) x min(-1)) was significantly greater in adult (177 +/- 44) than in fetal (97 +/- 36) arteries when the endothelium was maximally activated by A-23187. Similarly, the slope of the relation between fluid shear stress and estimated eNOS-specific activity (in nmol NO x microg of eNOS(-1) x min(-1) per dyn/cm2) was also significantly greater in adult (6.8 +/- 0.1) than in fetal (2.9 +/- 0.1) arteries, which suggests that eNOS may be more sensitive to or more efficiently coupled to activating stimuli in adult compared with fetal arteries. We conclude that maturational increases in endothelial vasodilator capacity are attributable to age-dependent increases in NO release secondary to elevated eNOS-specific activity and involve more efficient coupling between endothelial activation and enhancement of eNOS activity in adult compared with fetal arteries.     

Gene polymorphisms in patients with type 2 diabetes and diabetic nephropathy

A considerable variability in the incidence and prevalence of diabetic nephropathy (DN) coheres with an important contribution of multigenetic predisposition in the development of DN. Some genes, which probably participate in the pathogenesis of diabetic nephropathy, also play a role in the regulation of blood pressure, familial hyperlipidemia, familial hypertension and other diseases of the cardiovascular system. We have examined the association of diabetic nephropathy, nephropathy of non-diabetic origin, hypertension and of type 2 diabetes itself with several genetic polymorphisms (the insertion/deletion polymorphism in the gene for angiotensin-converting enzyme, the G/T polymorphism in the glucose transporter 1 gene, the G/T (894) polymorphism and the T/C (−786) polymorphism in the eNOS gene in three groups of patients with diabetes mellitus: 1) patients without diabetic nephropathy (DM); 2) patients with DN; 3) patients with nephropathy of non-diabetic origin (NDRD). Angiotensin-converting enzyme is an important factor in a development of arterial hypertension, but in our groups of Central European diabetic patients the I/D polymorphism was not associated with diabetic nephropathy. Furthermore, we have confirmed that the T/C (T786C) polymorphism in the eNOS gene is associated with metabolic syndrome including type 2 diabetes.     

Association of eNOS gene polymorphisms with essential hypertension in the Han population in southwestern China

Endothelial nitric oxide synthase (eNOS) plays an important role in maintaining blood pressure homeostasis and vascular integrity. Polymorphisms in the eNOS gene have been found to be associated with hypertension in different human populations, including Northern and Southern Chinese Han populations. To examine the relationship of three eNOS gene polymorphisms, T-786C (rs2070744), G894T (rs1799983), and G10T (rs7830), with hypertension in the Han population in southwestern China, we carried out a study of the genotypes of three SNPs in 510 hypertensive and 510 normotensive subjects from the Yunnan Province by using PCR-RFLP and sequencing. Our SNP analyses showed that the distribution of the T-786C polymorphism did not differ between patients and controls, and that G894T and G10T are significantly associated with hypertension in females, adjusted for covariates. Compared with the other haplotypes, haplotype H1 (TGG), carrying protective 10G and 894G alleles, significantly decreased the risk of increased essential hypertension in females, with an odds ratio of 0.68 (P = 10(-5)). These results suggest that the eNOS polymorphism is one of the factors contributing to the predisposition for essential hypertension in the Han population in southwestern China.     

Anatomy of a founder effect: myotonic dystrophy in Northeastern Quebec

Founder effects are largely responsible for changes in frequency profiles of genetic variants in local populations or isolates. They are often recognized by elevated incidence of certain hereditary disorders as observed in regions of Charlevoix and Saguenay-Lac-Saint-Jean (SLSJ) in Northeastern Quebec. Dominantly transmitted myotonic dystrophy (DM1) is highly prevalent in SLSJ where its carrier rate reaches 1/550, compared with 1/5,000 to 1/50,000 elsewhere. To shed light on the origin of DM1 in this region, we have screened 50 nuclear DM1 families from SLSJ and studied the genetic variation in a 2.05 Mb (2.9 cM) segment spanning the site of the expansion mutation. The markers analyzed included 22 biallelic SNPs and two microsatellites. Among 50 independent DM1 chromosomes, we distinguished ten DM1-associated haplotypes and grouped them into three haplotype families, A, B and C, based on the relevant extent of allele sharing between them. To test whether the data were consistent with a single entry of the mutation into SLSJ, we evaluated the age of the founder effect from the proportion of recombinant haplotypes. Taking the prevalent haplotype A1_21 (58%) as ancestral to all the disease-associated haplotypes in this study, the estimated age of the founder effect was 19 generations, long predating the colonization of Nouvelle-France. In contrast, considering A1_21 as ancestral to the haplotype family A only, yielded the estimated founder age of nine generations, consistent with the settlement of Charlevoix at the turn of 17th century and subsequent colonization of SLSJ. We conclude that it was the carrier of haplotype A (present day carrier rate of 1/730) that was a driver of the founder effect, while minor haplotypes B and C, with corresponding carrier rates of 1/3,000 and 1/10,000, respectively, contribute DM1 to the incidence level known in other populations. Other studies confirm that this might be a general scenario in which a major driver mutation/haplotype issued from a founder effect is found accompanied by distinct minor mutations/haplotypes occurring at background population frequencies.Electronic Supplementary Material Supplementary material is available for this article at     

Insulin resistance,intramyocellular lipid content,and plasma adiponectin in patients with type 1 diabetes

Insulin resistance is a key pathogenic factor of type 2 diabetes (T2DM); in contrast, in type 1 diabetes (T1DM) it is considered a secondary alteration. Increased intramyocellular lipid (IMCL) content accumulation and reduced plasma adiponectin were suggested to be pathogenic events of insulin resistance in T2DM. This study was designed to assess whether IMCL content and plasma adiponectin were also associated with the severity of insulin resistance in T1DM. We studied 18 patients with T1DM, 7 older and overweight/obese patients with T2DM, and 15 nondiabetic, insulin-resistant offspring of T2DM parents (OFF) and 15 healthy individuals (NOR) as appropriate control groups matched for anthropometric features with T1DM patients by means of the euglycemic hyperinsulinemic clamp combined with the infusion of [6,6-2H2]glucose and 1H magnetic resonance spectroscopy of the calf muscles. T1DM and T2DM patients showed reduced insulin-stimulated glucose metabolic clearance rate (MCR: 5.1 +/- 0.6 and 3.2 +/- 0.8 ml x kg(-1) min(-1)) similar to OFF (5.3 +/- 0.4 ml x kg(-1) x min(-1)) compared with NOR (8.5 +/- 0.5 ml x kg(-1) min(-1), P < 0.001). Soleus IMCL content was increased in T1DM (112 +/- 15 AU), T2DM (108 +/- 10 AU) and OFF (82 +/- 13 AU) compared with NOR (52 +/- 7 AU, P < 0.05) and the result was inversely proportional to the MCR (R2 = 0.27, P < 0.001); an association between IMCL content and Hb A1c was found only in T1DM (R2 = 0.57, P < 0.001). Fasting plasma adiponectin was reduced in T2DM (7 +/- 1 microg/ml, P = 0.01) and OFF (11 +/- 1 microg/ml, P = 0.03) but not in T1DM (25 +/- 6 microg/ml), whose plasma level was increased with respect to both OFF (P = 0.03) and NOR (16 +/- 2 microg/ml, P = 0.05). In conclusion, in T1DM, T2DM, and OFF, IMCL content was associated with insulin resistance, demonstrating that IMCL accretion is a marker of insulin resistance common to both primary genetically determined and secondary metabolic (chronic hyperglycemia) alterations. The increased adiponectin levels in insulin-resistant patients with T1DM, in contrast to the reduced levels found in patients with T2DM and in OFF, demonstrated that the relationship of adiponectin to insulin resistance in humans is still unclear.     

Contribution of nitric oxide to cutaneous microvascular dilation in individuals with type 2 diabetes mellitus

Microvascular pathophysiology associated with type 2 diabetes mellitus (T2DM) contributes to several aspects of the morbidity associated with the disease. We quantified the contribution of nitric oxide (NO) to the cutaneous vasodilator response to nonpainful local warming in subjects with T2DM (average duration of diabetes mellitus 7 +/- 1 yr) and in age-matched control subjects. We measured skin blood flow in conjunction with intradermal microdialysis of N(G)-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or vehicle during 35 min of local warming to 42 degrees C. Microdialysis of sodium nitroprusside (SNP) was used for assessment of maximum cutaneous vascular conductance (CVC). Resting CVC was higher in T2DM subjects at vehicle sites (T2DM: 19 +/- 2 vs. control: 11 +/- 3%maxCVC; P < 0.05); this difference was abolished by l-NAME (T2DM: 10 +/- 1 vs. control: 8 +/- 1%maxCVC; P > 0.05). The relative contribution of NO to the vasodilator response to local warming was not different between groups (T2DM: 46 +/- 4 vs. control: 44 +/- 6%maxCVC; P > 0.05). However, absolute CVC during local warming was approximately 25% lower in T2DM subjects (T2DM: 1.79 +/- 0.15 AU/mmHg; controls: 2.42 +/- 0.20 AU/mmHg; P < 0.01), and absolute CVC during SNP was approximately 20% lower (T2DM: 1.91 +/- 0.12 vs. control: 2.38 +/- 0.13 AU/mmHg; P < 0.01). We conclude that the relative contribution of NO to vasodilation during local warming is similar between subjects with T2DM and control subjects, although T2DM was associated with a lower absolute maximum vasodilation.     

Mice with targeted deletion of eNOS develop hyperdynamic circulation associated with portal hypertension

Systemic vasodilation is the initiating event of the hyperdynamic circulatory state, being most likely triggered by increased levels of vasodilators, primarily nitric oxide (NO). Endothelial NO synthase (eNOS) is responsible for this event. We tested the hypothesis that gene deletion of eNOS and inducible NOS (iNOS) may inhibit the development of the hyperdynamic circulatory state in portal hypertensive animals. To test this hypothesis, we used mice lacking eNOS (eNOS-/-) or eNOS/iNOS (eNOS/iNOS-/-) genes. A partial portal vein ligation (PVL) was used to induce portal hypertension. Sham-operated animals were used as a control. Hemodynamic characteristics were tested 2 wk after surgery. As opposed to our hypothesis, PVL also caused significant reduction in peripheral resistance in eNOS-/- compared with sham animals (0.33 +/- 0.02 vs. 0.41 +/- 0.03 mmHg. min x kg body wt x ml(-1); P = 0.04) and in eNOS/iNOS-/- animals with PVL compared with that of the sham-operated group (0.44 +/- 0.02 vs. 0.54 +/- 0.04; P = 0.03). This demonstrates that, despite gene deletion of eNOS, the knockout mice developed hyperdynamic circulation. Compensatory vasodilator molecule(s) are upregulated in place of NO in the systemic and splanchnic circulation in portal hypertensive animals.     

Endothelial dysfunction and arterial pressure regulation during early diabetes in mice: roles for nitric oxide and endothelium-derived hyperpolarizing factor

We determined whether nitric oxide (NO) counters the development of hypertension at the onset of diabetes in mice, whether this is dependent on endothelial NO synthase (eNOS), and whether non-NO endothelium-dependent vasodilator mechanisms are altered in diabetes in mice. Male mice were instrumented for chronic measurement of mean arterial pressure (MAP). In wild-type mice, MAP was greater after 5 wk of N(omega)-nitro-L-arginine methyl ester (L-NAME; 100 mg x kg(-1) x day(-1) in drinking water; 97 +/- 3 mmHg) than after vehicle treatment (88 +/- 3 mmHg). MAP was also elevated in eNOS null mice (113 +/- 4 mmHg). Seven days after streptozotocin treatment (200 mg/kg iv) MAP was further increased in L-NAME-treated mice (108 +/- 5 mmHg) but not in vehicle-treated mice (88 +/- 3 mmHg) nor eNOS null mice (104 +/- 3 mmHg). In wild-type mice, maximal vasorelaxation of mesenteric arteries to acetylcholine was not altered by chronic L-NAME or induction of diabetes but was reduced by 42 +/- 6% in L-NAME-treated diabetic mice. Furthermore, the relative roles of NO and endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced vasorelaxation were altered; the EDHF component was enhanced by L-NAME and blunted by diabetes. These data suggest that NO protects against the development of hypertension during early-stage diabetes in mice, even in the absence of eNOS. Furthermore, in mesenteric arteries, diabetes is associated with reduced EDHF function, with an apparent compensatory increase in NO function. Thus, prior inhibition of NOS results in endothelial dysfunction in early diabetes, since the diabetes-induced reduction in EDHF function cannot be compensated by increases in NO production.     

SUMO4基因多态性与2型糖尿病的关系

为了探讨北京汉族人群小泛素样修饰蛋白4(Small ubiquitin-like modifier 4, SUMO4)基因多态性与2型糖尿病(Type 2 diabetes mellitus, T2DM)的关系, 文章采用病例对照设计, 选取404例T2DM患者(T2DM组)以及年龄、性别匹配的500例健康对照者(Control组)作为研究对象, 应用聚合酶链反应-高分辨熔解曲线(PCR-HRM)技术结合测序验证法, 检测SUMO4基因3个单核苷酸多态性位点(rs237025、rs237024及rs600739)的基因型与等位基因分布情况, 比较T2DM组糖化血红蛋白(Hemoglobin A_1c, HbA_1c)在各基因型间的分布, 并进行单倍型分析。结果显示：①rs237025的G等位基因在T2DM组出现的频率更高(0.334 vs. 0.282, P =0.017); GA基因型携带者患T2DM的风险是AA基因型携带者的1.563倍(P=0.001; OR, 1.563; 95% CI, 1.189-2.053); 在显性模型(GG+GA vs. AA)分析中, G等位基因携带者(GG+GA)患T2DM的风险是AA基因型携带者的1.525倍(P =0.002; OR, 1.525; 95% CI, 1.169-1.989)。而rs237024和rs600739多态性未发现与T2DM的易感性相关(P >0.05)。②在T2DM组, rs237025的G等位基因携带者、rs237024的TT基因型携带者及rs600739的GG基因携带者具有较高的HbA_1c水平, 但各基因型携带者之间HbA_1c水平并无统计学差异(P >0.05)。③单倍型AAC、AGC及GGT与T2DM的易感性正相关(OR>1); 而单倍型AAT、GAC与T2DM的易感性负相关(OR<1)。据此得出结论：rs237025多态性与北京汉族人群T2DM的易感性相关, rs237024和rs600739多态性可能与T2DM的易感性不相关。     

SUMO4基因多态性与2型糖尿病的关系

为了探讨北京汉族人群小泛素样修饰蛋白4(Small ubiquitin-like modifier 4,SUMO4)基因多态性与2型糖尿病(Type 2 diabetes mellitus,T2DM)的关系,文章采用病例对照设计,选取404例T2DM患者(T2DM组)以及年龄、性别匹配的500例健康对照者(Control组)作为研究对象,应用聚合酶链反应-高分辨熔解曲线(PCR-HRM)技术结合测序验证法,检测SUMO4基因3个单核苷酸多态性位点(rs237025、rs237024及rs600739)的基因型与等位基因分布情况,比较T2DM组糖化血红蛋白(Hemoglobin A1c,HbA1c)在各基因型间的分布,并进行单倍型分析。结果显示:①rs237025的G等位基因在T2DM组出现的频率更高(0.334 vs.0.282,P=0.017);GA基因型携带者患T2DM的风险是AA基因型携带者的1.563倍(P=0.001;OR,1.563;95%CI,1.189-2.053);在显性模型(GG+GA vs.AA)分析中,G等位基因携带者(GG+GA)患T2DM的风险是AA基因型携带者的1.525倍(P=0.002;OR,1.525;95%CI,1.169-1.989)。而rs237024和rs600739多态性未发现与T2DM的易感性相关(P>0.05)。②在T2DM组,rs237025的G等位基因携带者、rs237024的TT基因型携带者及rs600739的GG基因携带者具有较高的HbA1c水平,但各基因型携带者之间HbA1c水平并无统计学差异(P>0.05)。③单倍型AAC、AGC及GGT与T2DM的易感性正相关(OR>1);而单倍型AAT、GAC与T2DM的易感性负相关(OR<1)。据此得出结论:rs237025多态性与北京汉族人群T2DM的易感性相关,rs237024和rs600739多态性可能与T2DM的易感性不相关。     

GTP Cyclohydrolase I Gene Polymorphisms Are Associated with Endothelial Dysfunction and Oxidative Stress in Patients with Type 2 Diabetes Mellitus

Background

The genetic background of atherosclerosis in type 2 diabetes mellitus (T2DM) is complex and poorly understood. Studying genetic components of intermediate phenotypes, such as endothelial dysfunction and oxidative stress, may aid in identifying novel genetic components for atherosclerosis in diabetic patients.

Methods

Five polymorphisms forming two haplotype blocks within the GTP cyclohydrolase 1 gene, encoding a rate limiting enzyme in tetrahydrobiopterin synthesis, were studied in the context of flow and nitroglycerin mediated dilation (FMD and NMD), intima-media thickness (IMT), and plasma concentrations of von Willebrand factor (vWF) and malondialdehyde (MDA).

Results

Rs841 was associated with FMD (p = 0.01), while polymorphisms Rs10483639, Rs841, Rs3783641 (which form a single haplotype) were associated with both MDA (p = 0.012, p = 0.0015 and p = 0.003, respectively) and vWF concentrations (p = 0.016, p = 0.03 and p = 0.045, respectively). In addition, polymorphism Rs8007267 was also associated with MDA (p = 0.006). Haplotype analysis confirmed the association of both haplotypes with studied variables.

Conclusions

Genetic variation of the GCH1 gene is associated with endothelial dysfunction and oxidative stress in T2DM patients.