Molecular methods for the study of the genetic determinants of nephropathy in type 1 (insulin-dependent) diabetes

Recently, evidence has accumulated that genetic factors may contribute to the development of diabetic nephropathy in patients with type 1 (insulin-dependent) diabetes mellitus. To identify variation at a gene locus, newly developed methods are introduced which employ denaturing gradient gel electrophoresis (DGGE) to study sequence differences in polymerase chain reaction (PCR)-amplified DNA fragments as well as in genomic DNA. These techniques are illustrated with studies of the angiotensinogen gene and the insulin receptor gene. In preliminary data from a comparison between individuals with and without diabetic nephropathy, we found no DNA sequence difference in the part of the angiotensinogen gene coding for angiotensin I. We did find, however, different distributions of a DNA polymorphism detected with the probe corresponding to exons 7 and 8 of the insulin receptor gene inRsaI DGGE blots in a comparison of patients with slow and fast progressing nephropathy. The interpretation of this finding and the need for further studies are discussed. In conclusion, the advent of methods of molecular genetics makes possible studies on genetic determinants of diabetic nephropathy. However, more clinical and epidemiological data are needed to find out how many genes are involved and how they interact with exposure to diabetes. Foremost, DNA from families with two or more siblings with diabetic nephropathy must be collected so that genetic studies will be possible.     

中国苗族人群血管紧张素原和血管紧张素转化酶基因多态性与冠心病的关系

目的 研究血管紧张素原(ACT)基因M235T分子变异和血管紧张素转化酶(ACE)基因I/D多态性与冠状动脉粥样硬化的关系.方法 采用聚合酶链反应一限制性片段长度多态性(PCR-RFLP)技术检测冠心病(CHD)组151例和正常对照组127例AGT基因多态性,采用聚合酶链反应技术检测CHD组151例和正常对照组127例ACE基因I/D多态性.结果 CHD组AGT-TT基因型频率为76.26%,显著高于对照组44.10%(P<0.01).ACE-DD基因型频率为35.10%,显著高于对照组14.96%(P<0.01).结论 在中国苗族人群中,AGT基因TT基因型和AGE基因DD基因型是CHD发病既相互独立又具有协同作用的危险因子.     

血管紧张素原基因启动子区A-20C和A-6G单核苷酸多态性与原发性高血压的相关性研究

目的 探讨血管紧张素原(AGT)基因启动子区A-20C和A-6G单核苷酸多态性与原发性高血压病(EH)之间的关系.方法 应用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)对200例汉族高血压患者和192例汉族正常血压者的AGT基因-20A/C和-6A/G多态性进行检测,测定空腹血糖、三酰甘油(TG)、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)及高密度脂蛋白胆固醇(HDL-C)等生物化学指标,分析各基因型和等位基因频率与原发性高血压的关系.结果 -20A/C各基因型及等位基因频率在高血压组及对照组间差别无统计学意义(χ2=2.226,P =0.136;χ2=1.78,P =0.182);-6A/G各基因型及等位基因频率在高血压组及对照组间差别亦无统计学意义(χ2=0.012,P =0.911;χ2=0.052,P =0.82).结论 AGT基因-20A/C和-6A/G多态性与原发性高血压发病无关.     

Comparison of the impact of vaginal and oral administration of combined hormonal contraceptives on hepatic proteins sensitive to estrogen

OBJECTIVE: We evaluated the effects of a new combined hormonal contraceptive vaginal ring (CVR) delivering the nonandrogenic progestin Nestorone (NES) and ethinyl estradiol (EE) on several key estrogen-sensitive hepatic proteins that may be markers for the risk of arterial or venous disease events and on blood pressure (BP). Because the pharmacologic androgenicity of the progestin in these formulations influences the hepatic impact of EE, we selected an oral contraceptive (OC) delivering the androgenic progestin levonorgestrel (LNG) and EE as the comparator. We also investigated the effect of delivery route, which is known to modify the hepatic effects of estradiol, but has not been widely studied with EE. STUDY METHODS: Women, aged 18-34 years, with no contraindications to the use of combined OCs, were randomized to three cycles of treatment with a CVR delivering NES/EE (150/15 microg/day) or a combined OC providing LNG and EE (150/30 microg per tablet). Each cycle consisted of 21 days of active treatment, followed by 7 days without treatment. During the last weeks of the pretreatment and third treatment cycles, blood samples were obtained for determinations of plasma concentrations of angiotensinogen, an estrogen-sensitive hepatic protein, and serum concentrations of sex hormone-binding globulin (SHBG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and estrogen- and androgen-sensitive proteins. BP was also measured. RESULTS: Of 47 women randomized, 45 completed the study (CVR: 23; OC: 22). Within-group comparisons over time by repeated-measure analysis of variance demonstrated statistically significant changes over time with both treatments for all hepatic proteins (p < .02) but not for TC. The within-group effects, presented as relative percent difference [95% confidence interval (CI)], were greatest for angiotensinogen [CVR: 227% (195-262%); OC: 251.3% (218-288%)] and SHBG [CVR: 306% (237-389%); OC: 55% (30-86)]. Both treatments were associated with small changes in systolic BP and diastolic BP (DBP), but only the within-group change in DBP for the OC group was statistically significant (p = .04). Between-treatment comparisons of third treatment cycle mean values were performed by analysis of covariance (baseline values as covariate). No statistically significant between-treatment differences were found for angiotensinogen, sensitive only to estrogen, or BP. Statistically significant treatment differences were found for all estrogen- and androgen-sensitive proteins (p < or = .002) but not for TC. When presented as relative percent difference between the effects of treatment (CVR-OC/OC; 95% CI of percent difference), the difference was largest for SHBG (159% [117-210%]); smaller relative percent differences were found for HDL-C [31.9% (18.5-46.8%)], LDL-C [23.6% (33.4% to -2.4%)] and TG [39.0% (14.0-69.4%)], but not TC. CONCLUSION: Vaginal delivery of a combined hormonal contraceptive did not reduce the EE-associated changes in estrogen-sensitive hepatic proteins observed after use of a combined OC. Significant treatment differences between the NES/EE CVR and the LNG/EE OC were found for SHBG, HDL-C, LDL-C, and TG, proteins sensitive to androgen as well as estrogen. No treatment difference was observed for angiotensinogen, which is sensitive only to estrogen. The observed treatment differences were therefore most likely due to the difference in androgenicity between NES and LNG.     

Angiotensin-converting enzyme and angiotensinogen gene polymorphism in hypertrophic cardiomyopathy

To examine the contribution of the renin-angiotensin system to hypertrophic cardiomyopathy (HCM), the authors studied 96 patients with HCM (mean age 50 years, 55% male), 105 of their unaffected siblings and offspring, and 160 healthy subjects without known hypertension and left ventricular hypertrophy who were frequency matched by age and sex. Patients were divided into familial or sporadic HCM (FHCM or SHCM) groups with or without affected family members. The T allele frequency was higher in the SHCM group than in unaffected siblings and offspring (88% versus 78%, χ²=4.6, P<0.05). The M allele frequency was higher in unaffected siblings and offspring than in patients with SHCM (23% versus 12%, χ²=4.6, P<0.05). The T allele frequency among unaffected siblings and offspring was similar to that observed in healthy subjects (78% versus 78%). The molecular variant of angiotensinogen T235 seems to be a predisposing factor for cardiac hypertrophy in HCM and carries an approximately twofold increased risk. The authors also determined angiotensin-converting enzyme gene insertion/deletion polymorphism. The D allele frequency was higher in SHCM than in FHCM. The findings suggest that HCM, especially in solitary cases, is partially determined by genetic disposition. These results also suggest that angiotensin-converting enzyme and angiotensinogen gene polymorphism are genetic contributing factors associated with cardiac hypertrophy in HCM.     

Biochemistry and Regulation of Angiotensinogen

Angiotensin II and angiotensin III, the active peptides of the renin-angiotensin system, are produced by a cascade of enzymatic reactions, whose initial step is the reaction between renin and its substrate, angiotensinogen. In plasma, the concentration of angiotensinogen is a limiting factor : the Km of the enzymatic reaction is between 1 and 2 wμ depending on the species. It is therefore of interest to measure its level in plasma and tissues and to examine the main factors which may influence its synthesis and release. The complete purification of angiotensinogen has made possible the preparation of specific antibodies which cross-react with both angiotensinogen and its residue, des-angio I-angiotensinogen, and are currently used in radioimmunoassays and immunohistochemical studies.

A small amount of angiotensinogen is stored in hepatic cells, where it can be detected by immunofluorescence and measured by radioimmunoassay. It is also present in proximal tubular cells of the kidney, probably reabsorbed from glomerular filtrate, but it is absent from juxtaglomerular cells. Several hormones are able to increase liver synthesis of angiotensinogen and its release. Thyroxine, angiotensin II, dexamethasone, ethinyl-estradiol and binephrectomy increase both synthesis and release. Adrenalectomy and converting-enzyme inhibition are accompanied by an increased peripheral consumption of plasma angiotensinogen, and by accumulation of des-angio I-angiotensinogen whose metabolism and role are unknown.

The major role of angiotensinogen in renal hemodynamics is demonstrated by its effects on the isolated perfused kidney, an experimental observation which parallels the clinical observation of women on estroprogestative therapy, whose renal blood flow is     

血管紧张素原基因M235T变异与血栓的相关性研究

本文采用ＰＣＲ，酶切方法，对８５例正常人与６７例血栓中患者的ＡＧＴ变异进行了研究，结果发现；ＡＧＴ分子变异Ｍ２３５Ｔ与血栓明显相关（Ｘ＾２＝７．９１，Ｐ〈０．０１）。     

Angiotensinogen gene expression in extrahepatic rat tissues: Application of a solution hybridization assay

Summary Angiotensin II has numerous biological effects in a hitherto unsuspected variety of tissues. The generation of angiotensin in tissue requires the local presence of its high molecular weight precursor angiotensinogen and is best tested by investigating angiotensinogen gene expression. A quantitative solution hybridization assay for rapid and sensitive measurement of angiotensinogen mRNA was therefore established to study the extrahepatic expression of the angiotensinogen gene. We used a 714 bases BamHI angiotensinogen cDNA fragment cloned into vector pSPT18 and developed a sensitive and rapid assay with a detection limit of 0.5 pg RNA. Quantification of angiotensinogen mRNA from male Sprague-Dawley rats resulted in the following tissue levels (n = 10 for all tissues, except pituitary where n = 5), was expressed as fg mRNA per jig total RNA, in descending order: liver (9950), hypothalamus (6050), midbrain (4450), brainstem (3950), total brain (2325), aorta (625), kidney (338), adrenal gland (170), and heart atrium (140). The high sensitivity of the assay in addition also allowed for the first time measurement of angiotensinogen mRNA in the low gene expression tissues pituitary (70), heart ventricle (30), and testis (30). This assay will allow detailed studies on the regulation of tissue angiotensinogen and the pathophysiological role of the tissue renin angiotensin systems. Send offprint requests to: D. Ganten at the above address     

慢性肾脏病患者尿血管紧张素原与肾脏肾素血管紧张素系统活性的相关性

目的 探讨慢性肾脏病（CKD）患者尿血管紧张素原（AGT）与肾损伤指标及肾脏局部肾素血管紧张素系统（RAS）活性的关系。 方法 用放射免疫法和酶联免疫吸附法（ELISA）测定血、尿RAS组分的浓度,并用免疫组织化学方法评价肾内肾素、AGT、血管紧张素Ⅱ（Ang Ⅱ）和血管紧张素Ⅱ受体的表达。分析129例CKD患者尿AGT与临床指标的相关性以及73例行肾组织活检的CKD患者尿AGT与肾脏局部RAS组分表达的相关性。 结果 129例CKD患者尿AGT （159.08±125.18）μg/g Cr,Scr（113.20±105.05） μmol/L,估算肾小球滤过率(eGFR)（58.52±27.15） ml·min-1·(1.73 m2)-1,尿蛋白量（2.03±2.65） g/24 h,尿AngⅡ（164.71±139.25） ng/g Cr,尿Ⅳ型胶原（447.60±800.66）μg/g Cr,尿钠（162.17±81.61） mmol/24 h。 经Pearson单因素相关分析,尿AGT与eGFR （r = -0.55,P < 0.01）、尿钠 （r = -0.20, P < 0.05）呈负相关;与Scr（r = 0.51,P < 0.01）、24 h尿蛋白量（r = 0.30,P < 0.01）、尿Ang Ⅱ（r = 0.20, P < 0.05）及尿Ⅳ型胶原（r = 0.47,P < 0.01）呈正相关。多元回归分析发现尿AGT与eGFR呈负相关（P < 0.01）,与Scr（P < 0.01）、24 h尿蛋白量（P < 0.05）、尿AngⅡ（P < 0.05）、尿Ⅳ型胶原（P < 0.01）呈正相关。73例CKD患者肾活检组织中,尿AGT与肾脏AGT（r = 0.45,P < 0.01）、AngⅡ（r = 0.52,P < 0.01）和AngⅡ 1型受体（r = 0.28,P < 0.05）免疫组化阳性面积呈正相关。 结论 尿AGT可能是反映CKD肾脏损伤尤其是慢性损伤程度的指标,可作为肾脏局部AngⅡ活性的无创评价指标。     

Obesity-related genes variability in Czech patients with sporadic colorectal cancer: preliminary results

Background  Genetic variability in obesity-related genes and the resulting phenotypes are being recognized as major risk factors for colorectal cancer and/or severity of the disease. Materials and methods  A total of 102 patients (aged 68 ± 10.2 years, 79 men and 23 women) and 101 age-matched (68.1 ± 5.4 years old) individuals without colorectal cancer, 59 men and 42 women, were recruited. All the individuals were genotyped for the following subset of polymorphisms in obesity-related genes: angiotensinogen gene (M235T and -6A/G), in IL-6 gene (-174 G/C and -596 A/G), in leptin gene (-2548 A/G), and polymorphism Gln223Arg within the leptin receptor (LEPR) gene. Results  A significant increase in frequency of double heterozygote genotype (MTAG) of both angiotensinogen polymorphisms in males with colorectal cancer was observed when compared to control men [odds ratio (OR) = 3.77, P _corr = 0.001]. A marginally significant difference in genotype distribution of -174 G/C IL-6 polymorphism between the patients in stage I–II compared to patients in III–IV was found (P _g = 0.05, P _a = 0.173). The GG genotype of -174 G/C IL-6 polymorphism in the patients in stage III–IV carries an increased risk compared to those in stage I–II (OR = 2.83, P _corr = 0.06). Similarly, a difference in genotype distribution of Gln223Arg in LEPR gene between the patients staged I–II compared to III–IV was observed (P _g = 0.05). The AA genotype was shown to be risky for the patients staged III–IV (OR = 3.35, P _corr = 0.06). Conclusions  The investigated single nucleotide polymorphisms within the genes encoding for obesity-related genes were observed to be associated both with clinical manifestation of colorectal cancer and with severity of the disease. Thus, we suggest that defined genetic variability in the genes might become DNA markers for colorectal cancer in the future.