Kerstin Borgmann, Annette Raabe, Sebastian Reuther, Silke Szymczak, Thorsten Schlomm, Hendrik Isbarn, Maria Gomolka, Andreas Busjahn, Michael Bonin, Andreas Ziegler, Ekkehard Dikomey

Radiotherapy and Oncology 96 (2010) 19-24

Purpose: Comparing the chromosomal radiosensitivity of prostate cancer patients with that of healthy donors.
Materials and methods: The study was performed on 81 prostate cancer patients characterised by a clinical stage of predominantly pT2c or pT3a and a median age of 67 years. As healthy donors 60 male monozygotic twin pairs were recruited with a median age of 28 years. Chromosomal radiosensitivity was measured using both G0- and G2-assay.
Results: No difference between healthy donors and prostate cancer patients was detected concerning G0- radiosensitivity, since medians were similar (Hodges-Lehmann estimate: -0.05, 95% CI: -0.18 to -0.08, p = 0.4167). However, a pronounced difference was determined for G2-radiosensitivity with prostate cancer patients showing a significantly higher sensitivity compared to healthy donors (Hodges-Lehmann estimate: -0.41, 95% CI: -0.53 to -0.30, p = 1.75-9). Using the 90% quantile of G2-radiosensitivity in healthy donors as a threshold for discrimination the fraction of prostate cancer patients with elevated radiosensitivity increased to 49%.
Conclusion: G2-, but not G0-radiosensitivity is a promising marker for predisposition of prostate cancer.

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Busjahn CA, Schulz-Menger J, Abdel-Aty H, Rudolph A, Jordan J, Luft FC, Busjahn A

Eur Heart J. 2009 Apr 30. [Epub ahead of print]

Aims Earlier studies in monozygotic (MZ) and dizygotic (DZ) twins showed genetic variance on echocardiographically determined heart size. However, cardiovascular magnetic resonance (CMR) is more precise and reproducible. We performed a twin study relying on CMR, focusing on left ventricular (LV) mass and papillary muscle, since there are no genetic reports on this structure. Methods and results We measured left heart dimensions of 25 healthy twin pairs with a 1.5T MR scanner, analysed with the mass(c), Medis Software. We performed heritability analysis and tests for genetic influences shared between cardiac structures. We found that CMR-based heritability estimates (h(2) = 84%) substantially exceeded estimates based on echocardiography. We also found significant genetic influence on papillary muscle mass (h(2) = 82%). Bivariate analysis of papillary and LV muscle mass revealed significant genetic influences shared by both phenotypes (genetic correlation 0.59) and suggested an additional genetic component specific to papillary muscle. We observed correlations between body mass index, surface area, and systolic blood pressure with cardiac dimensions, even in this small study. Environmental influences were relevant as well, indicating reciprocal influences on papillary vs. LV muscle mass. Conclusion Cardiovascular magnetic resonance, even with few subjects, allows a genetic assessment of cardiac structures that cannot be attained with echocardiography. Hitherto fore unappreciated relationships can be uncovered by this method.

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Tania Perrinjaquet-Moccetti, Andreas Busjahn, Caesar Schmidlin, Annette Schmidt, Barbara Bradl, Cem Aydogan

Phytotherapy Research Volume 22 Issue 9, Pages 1239 - 1242

Hypertension is a harmful disease factor that develops unnoticed over time. The treatment of hypertension is aimed at an early diagnosis followed by adequate lifestyle changes rather than pharmacological treatment. The olive leaf extract EFLA943, having antihypertensive actions in rats, was tested as a food supplement in an open study including 40 borderline hypertensive monozygotic twins. Twins of each pair were assigned to different groups receiving 500 or 1000 mg/day EFLA943 for 8 weeks, or advice on a favourable lifestyle. Body weight, heart rate, blood pressure, glucose and lipids were measured fortnightly. Blood pressure changed significantly within pairs, depending on the dose, with mean systolic differences of 6 mmHg (500 mg vs control) and 13 mmHg (1000 vs 500 mg), and diastolic differences of 5 mmHg. After 8 weeks, mean blood pressure remained unchanged from baseline in controls (systolic/diastolic: 133 5/77 6 vs 135 11/80 7 mmHg) and the low-dose group (136 7/77 7 vs 133 10/76 7), but had significantly decreased for the high dose group (137 10/80 10 vs 126 9/76 6). Cholesterol levels decreased for all treatments with significant dose-dependent within-pair differences for LDL-cholesterol. None of the other parameters showed significant changes or consistent trends. Concluding, the study confirmed the antihypertensive and cholesterol-lowering action of EFLA943 in humans.

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Borgmann K, Haeberle D, Doerk T, Busjahn A, Stephan G, Dikomey E.

Radiother Oncol. 2007 May;83(2):196-202.

BACKGROUND AND PURPOSE: The radiosensitivity of human lymphocytes measured using a G0- or G2-assay has been linked with an individual's risk of developing normal tissue complications following radiotherapy. This study was performed to increase basic knowledge of the genetics of the human radiation response, and chromosomal aberration induction in particular.
MATERIALS AND METHODS: The study was carried out with blood samples taken from 15 monozygotic twin pairs. G0-assay was performed for cells irradiated with 6 Gy counting only deletions and G2-assay for cells irradiated with 0.5 Gy scoring only chromatid breaks.
RESULTS: The mean number of deletions measured at 6 Gy for all 30 samples using the G0-assay amounted to 2.96+/-0.37 (means+/-SD), which corresponds to a coefficient of variation (CV) of 13%. There is a highly significant intra-pair correlation for this number among twins (r(2)=0.911) demonstrating that this parameter is mostly determined by genetic factors. According to the mean number of deletions, a theoretical classification based on the definition <=MV-SD as resistant, MV+/-SD as normal and >=MV+SD as sensitive was made, identifying two pairs as sensitive or resistant, respectively, while nine were normal and two pairs are intermediate. For chromatid breaks measured at 0.5 Gy with the G2-assay the mean number was 1.35+/-0.42 (means+/-SD) corresponding to a CV of 31%. There was again a strong intra-pair correlation among twins with r(2)=0.837 showing that this sensitivity is also determined mostly by genetic factors. There was, however, no inter-assay correlation between the G0- and G2-sensitivity (r(2)=0.006) demonstrating that these two sensitivities depend on different genetic factors.
CONCLUSION: The chromosomal radiosensitivity of lymphocytes as defined by G0- or G2-assay is largely determined by different genetic factors, which may allow the use of genetic profiling as an indicator of the respective individual radiosensitivity.

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Busjahn A.

Twin Res Hum Genet. 2006 Dec;9(6):778-82.

no abstract available

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Knoblauch H, Busjahn A, Wegener B.

Arch Sex Behav (2007) 36:135137

no abstract available

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Firouzi M, Kok B, Spiering W, Busjahn A, Bezzina CR, Ruijter JM, Koeleman BP, Schipper M, Groenewegen WA, Jongsma HJ, de Leeuw PW

J Hypertens. 2006 Feb;24(2):325-30.

OBJECTIVE: Gap junctions, formed by connexins (Cx), are important in the regulation of vascular tone. Previously, we reported two closely linked polymorphisms (-44G --> A and +71A --> G) within regulatory regions of the gene for Cx40, a major connexin in the vascular wall and the kidney. In the present study, we examined the hypothesis that these polymorphic variants are associated with hypertension and that they interact with blood pressure in healthy individuals.
METHODS: Cx40 genotypes were determined in 191 subjects with essential hypertension, 198 normotensive individuals, and a healthy control population (178 twin pairs, 108 monozygotic, 70 dizygotic).
RESULTS: We found a significant contribution of the minor Cx40 allele or genotype (-44AA/+71GG) to the risk of hypertension in men (P = 0.013 or P = 0.035; odds ratio, 1.87 or 2.10, respectively), but not in women. Moreover, in the healthy control population a significant effect of Cx40 genotype and sex on systolic blood pressure was found (P < 0.05 and P < 0.0001, respectively). Women carrying the minor Cx40 genotype had significantly higher systolic blood pressure compared with non-carriers (P < 0.05). In men, systolic blood pressure in carriers of the minor Cx40 genotype was not significantly different from the other two genotypes, possibly because of the small number of men in this group. However, men carrying the -44GA/+71AG genotype had higher standing systolic blood pressure compared with the more common Cx40 genotype (-44GG; P = 0.033).
CONCLUSION: These findings suggest that the Cx40 polymorphisms may form a genetic susceptibility factor for essential hypertension in men.

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Jordan J, Brabant G, Brinsuk M, Tank J, Horn R, Luft FC, Busjahn A

Am J Physiol Regul Integr Comp Physiol. 2005 May;288(5):R1411-6

Free and receptor-bound leptin may be regulated by different mechanisms. Genes that influence the concentration of these fractions may have an important functional bearing. We determined circulating leptin receptor concentrations, bound as well as free leptin concentrations, and body composition in 24 monozygotic (MZ) and in 22 dizygotic (DZ) twin pairs. Bound leptin and leptin receptor concentrations were inversely correlated with body fat content. Free leptin concentrations were directly correlated with body fat content. The correlations in age- and sex-adjusted free leptin, bound leptin, and leptin receptor concentrations were higher between MZ twins than between DZ twins. Adjusted heritability (h2) estimates were 0.28 for free leptin, 0.73 for bound leptin, and 0.55 for leptin receptor. The genetic correlation with body fat was -0.58 for the leptin receptor, -0.20 for bound leptin, and 0.93 for free leptin. Our data are consistent with a strong genetic influence on leptin receptor and bound leptin and a weaker genetic influence on free leptin concentrations. The same genes that lower bound leptin and leptin receptor concentrations may increase fat mass or vice versa.

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Aydin A, Bahring S, Dahm S, Guenther UP, Uhlmann R, Busjahn A, Luft FC.

J Mol Med. 2005 Feb;83(2):159-65

We screened a white population for single nucleotide polymorphisms (SNPs) in five long QT syndrome genes, namely, KCNQ1 (LQT1), HERG (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6). We found 35 SNPs, 10 of which have not been previously described. Ten SNPs were in KCNE1, six in HERG, eight in KCNQ1, four in KCNE2, and seven in SCN5A. Four SNPs were associated with QTc interval in our 141 subjects, one in KCNE1, one in KCNE2, and two in SCN5A. Two of these SNPs have not been described. We conclude that these five long QT syndrome genes contain common variants, some of which are associated with QTc interval in normal persons. We suggest that analysis of these SNPs in a much larger cohort would enable establishment of common haplotypes that are associated with QTc. These haplotypes could facilitate prediction of arrhythmia risk in the general population.

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Busjahn A, Seebohm G, Maier G, Toliat MR, Nurnberg P, Aydin A, Luft FC, Lang F.

Cell Physiol Biochem. 2004;14(3):135-42.

The serum and glucocorticoid inducible kinase (SGK1) is well known to up-regulate the renal epithelial Na(+) channel ENaC. Excessive SGK1 activity would be expected to cause renal Na(+) retention and blood pressure increase. Certain polymorphisms of the SGK1 gene (E8CC/CT;I6CC) are indeed associated with moderately enhanced blood pressure. We have recently disclosed another function of SGK1, i.e. the stimulation of the slowly activating K(+) channel KCNE1/KCNQ1. Among the functions of this channel is the repolarisation of cardiac myocytes. Accordingly, defective KCNE1 and/or KCNQ1 lead to long QT syndrome, a disorder causing fainting and sudden cardiac death. In the present study we demonstrate that coexpression of SGK1 in Xenopus oocytes increases KCNQ1/KCNE1 induced current without significantly altering voltage dependence, activation and deactivation kinetics. To test for the relevance of SGK1 in human cardiac repolarization, we analysed the ECG of monozygotic (MZ) (126 pairs) and dizygotic (DZ) (70 pairs) twin subjects and parents of DZ twins. The E8CC/CT;I6CC polymorphism was indeed significantly (p<0.025) associated with shortened age and gender corrected QT interval. No significant differences were observed in any other ECG parameter, including heart rate, P, PQ and QRS. We conclude that the regulation of KCNE1/KCNQ1 by SGK1 is similarly relevant for the repolarization of cardiac myocytes as for regulation of renal ENaC activity and blood pressure control.

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Marina Brinsuk, Jens Tank, Friedrich C. Luft, Andreas Busjahn, Jens Jordan

Arterioscler Thromb Vasc Biol. 2004;24:207-211

OBJECTIVE: Venous function contributes to the pathogenesis of thrombophlebitis, venous thrombosis, and possibly to arterial hypertension. Venous disease is presumably heritable; however, the genetic variance of venous function is unknown.
METHODS AND RESULTS: We determined the heritability of venous function in 46 twin pairs (24 monozygotic, age 35+/-11 years, 14 men, 34 women; 22 dizygotic, age 30+/-8 years, 19 men, 25 women). After a resting phase in the supine position, we determined venous function in both legs by impedance plethysmography. Venous capacity was determined by a standardized protocol. In addition, we obtained venous pressure volume curves by slowly deflating a thigh cuff from 60 to 0 mm Hg. Venous compliance was determined as the steepest part of the venous pressure volume curve. Heritability was estimated using a path modeling approach. Unadjusted heritability was 0.6 (P<0.05) for venous capacity and 0.9 (P<0.05) for venous compliance. The heritability estimate for venous capacity decreased to 0.3 after adjustment for age, body mass index, and body fat. The heritability estimate for venous compliance remained essentially unchanged after adjustment for sex and age.
CONCLUSIONS: We conclude that venous function is strongly influenced by genetic factors. The genes involved may influence venous disease states.

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Dieter M, Palmada M, Rajamanickam J, Aydin A, Busjahn A, Boehmer C, Luft FC, Lang F

Obes Res. 2004 May;12(5):862-70

OBJECTIVE: Serum- and glucocorticoid-inducible kinase 1 (SGK1) inhibits the ubiquitin ligase neuronal cell expressed developmentally downregulated 4-2 (Nedd4-2), which retards the retrieval of the epithelial Na+ channel ENaC. Accordingly, SGK1 enhances ENaC abundance in the cell membrane. The significance of this effect is shown by an association of an E8CC/CT;I6CC polymorphism in the SGK1 gene with increased blood pressure. However, strong expression of SGK1 in enterocytes not expressing ENaC points to further functions of SGK1. This study was performed to test for regulation of Na+-coupled glucose transporter 1 (SGLT1) by Nedd4-2, SGK1, and/or the related kinases SGK3 and PKB. Additional studies searched for an association of the SGK1 gene with BMI. RESEARCH METHODS AND PROCEDURES: mRNA encoding SGLT1, wild-type Nedd4-2, inactive (C938S)Nedd4-2, wild type SGK1, constitutively active (S422D)SGK1 or inactive (K127N)SGK1, wild-type SGK3, and constitutively active (T308DS473D)PKB or inactive (T308AS473A)PKB were injected into Xenopus oocytes, and glucose transport was quantified from glucose-induced current (I(glc)). BMI was determined in individuals with or without the E8CC/CT;I6CC polymorphism. RESULTS: I(glc) was significantly decreased by coexpression of Nedd4-2 but not of (C938S)Nedd4-2. Coexpression of SGK1, (S422D)SGK1, SGK3, or (T308DS473D)PKB, but not of (K127N)SGK1 or (T308AS473A)PKB, enhanced I(glc) and reversed the effect of Nedd4-2. SGK1 and SGK3 phosphorylated Nedd4-2. Deletion of the SGK/PKB phosphorylation sites in Nedd4-2 blunted the kinase effects. BMI was significantly (p < 0.008) greater in individuals with the E8CC/CT;I6CC polymorphism than in individuals without. DISCUSSION: Overactivity of SGK1 may lead not only to excessive ENaC activity and hypertension but also to enhanced SGLT1 activity and obesity.

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Bezzina CR, Verkerk AO, Busjahn A, Jeron A, Erdmann J, Koopmann TT, Bhuiyan ZA, Wilders R, Mannens MM, Tan HL, Luft FC, Schunkert H, Wilde AA.

Cardiovasc Res. 2003 Jul 1;59(1):27-36.

OBJECTIVE: Genetic variants of cardiac ion channels may influence cardiac repolarization. Thereby such variants may modulate the penetrance of primary electrical disorders, contribute to differences in susceptibility to drug-induced QT-prolongation between individuals, or contribute to rhythm disturbances in the context of structural heart disease. Since the current encoded by KCNH2 (HERG; I(Kr)) is a primary determinant of repolarization, we conducted association studies between the respective alleles of the common amino acid-changing polymorphism at codon 897 (2690A>C; K897T) within HERG and rate-corrected QT interval (QTc).
METHODS AND RESULTS: Association analysis in Caucasian subjects (n=1030) revealed a significant association of this polymorphism with QTc (P=0.0025) with CC homozygotes having a significantly shorter QTc (388.5+/-2.9 ms) compared to AA homozygotes (398.5+/-0.9) and heterozygotes (AC, 397.2+/-1.2). The latter two genotypes were associated with comparable mean QTc's, suggesting that the 2690C-allele is recessive. After stratification by sex, the polymorphism was more predictive of QTc in females (P=0.0021), a finding that was replicated in a second population sample (n=352) from the same ethnic background (P=0.044). To assess whether this polymorphism could represent a 'functional' polymorphism, we compared the biophysical properties of K897- and T897-HERG channels by whole-cell voltage clamp. Compared to the K897 channel, the T897 channel displayed a shift of -7 mV in voltage dependence of activation and increased rates of current activation and deactivation.
CONCLUSION: As confirmed in modeling studies, these changes are expected to shorten action potential duration by an increase in I(Kr). This recapitulates the shorter QTc in females homozygous for the 2690C-allele.

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Busjahn A, Luft FC

Cell Physiol Biochem 2003;13(1):51-8

no abstract available

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Schreiber A, Busjahn A, Luft FC, Kettritz R.

J Am Soc Nephrol 2003 Jan;14(1):68-75

Isolated human neutrophils exhibit a bimodal membrane proteinase 3 (PR3) expression. PR3 is the main target antigen in Wegener granulomatosis (WG). Cells with low expression can be easily distinguished from cell subsets with high expression. In a recent study, a large neutrophil subset expressing membrane PR3 (mPR3(+)) was a risk factor for systemic ANCA-associated vasculitis. PR3 membrane expression patterns are quite stable in a given individual, raising the possibility of genetic variance. The aims of this study were: (1) to investigate the association of mPR3 expression and the risk of WG in an independent German cohort; (2) to test the hypothesis that mPR3 expression on neutrophils is genetically influenced; and (3) to investigate whether or not mPR3 expression is a function of intracellular PR3 content. mPR3 expression was assessed by FACS analysis in isolated human neutrophils. Neutrophil mPR3 expression was studied in 35 patients with WG, 15 patients with other inflammatory diseases, 125 healthy volunteers, and 27 (15 monozygotic and 12 dizygotic) pairs of twins. The intracellular PR3 content was assessed by intracellular flow cytometry and by Western blotting after separating mPR3 low and high expressing cells by FACSort. FACS analysis in a subset of 16 healthy subjects showed a highly conserved PR3 phenotype in two independent investigations >12 mo apart (r = 0.937). Patients with WG demonstrated a significantly higher percentage of mPR3(+) neutrophils than healthy controls and patients with other inflammatory diseases. The mPR3(+) percentage was highly correlated in MZ twins (r = 0.99) compared with DZ twins (r = 0.06). The intracellular PR3 content was not different in persons with low or high mPR3 expression, nor was the PR3 content different in cells with low or high mPR3 expression within a given individual. These data indicate that WG patients have a higher percentage of mPR3-expressing neutrophils. Furthermore, mPR3 expression is influenced by genetic variance. Finally, mPR3 expression is independent of intracellular PR3 content.

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Dorret Boomsma, Andreas Busjahn and Leena Peltonen

Nature Reviews Genetics 2002;3:872-882

Twin studies have been a valuable source of information about the genetic basis of complex traits. To maximize the potential of twin studies, large, worldwide registers of data on twins and their relatives have been established. Here, we provide an overview of the current resources for twin research. These can be used to obtain insights into the genetic epidemiology of complex traits and diseases, to study the interaction of genotype with sex, age and lifestyle factors, and to study the causes of co-morbidity between traits and diseases. Because of their design, these registers offer unique opportunities for selected sampling for quantitative trait loci linkage and association studies.

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Busjahn A, Freier K, Faulhaber HD, Li GH, Rosenthal M, Jordan J et al.

Biol.Psychol. 2002;61:97-107

We tested the hypothesis that the beta-2 adrenergic receptor (beta-2 AR) gene locus, with known effects on blood pressure regulation, is also involved in psychological coping styles. 166 pairs of monozygotic (MZ) and dizygotic (DZ) twins and DZ twin parents were investigated. We found common genetic variance for the coping factor Emotional Coping and blood pressure. Using three microsatellites we found linkage between the beta-2 AR gene locus and the coping factor Active Coping. Using allele-specific PCR of all the single nucleotide polymorphisms (SNPs) in the gene causing amino acid substitutions we identified associations between the +491 G/A SNP and various coping factors. We conclude that the beta-2 AR gene is relevant to coping. These preliminary findings suggest a molecular genetic underpinning of the relationship between psychological and physiological phenotypes important to cardiovascular risk.

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Busjahn,A.; Aydin,A.; Uhlmann,R.; Krasko,C.; Bahring,S.; Szelestei,T.; Feng,Y.; Dahm,S.; Sharma,A.M.; Luft,F.C.; Lang,F.

Hypertension 2002;40:256-60.

The serum- and glucose-regulated kinase (SGK1) gene has recently been identified as an important aldosterone-induced protein kinase that mediates trafficking of the renal epithelial Na(+) channel (ENaC) to the cell membrane. Thus, SGK1 is an appealing candidate for blood pressure regulation and possibly essential hypertension. To test this hypothesis, we recruited monozygotic (126 pairs) and dizygotic (70 pairs) normotensive twin subjects and parents of dizygotic twins. Blood pressure was measured in a controlled fashion: recumbent, sitting, and upright. We documented genetic variance on blood pressure in all positions. We then relied on microsatellite markers at the SGK1 gene locus (D6S472, D6S1038, and D6S270) and 2 single nucleotide polymorphisms within the SGK1 gene. We found significant linkage of the SGK1 gene locus to diastolic blood pressure (P<0.0002) and suggestive evidence for linkage for systolic blood pressure (P<0.04), documenting the locus as a quantitative trait locus for blood pressure. We next performed association, using all dizygotic twins and a monozygotic member from each pair. We found significant associations between both single nucleotide polymorphism variants and blood pressure, as well as a significant interaction between the single nucleotide polymorphisms enhancing the effect. This combined effect of the polymorphisms was confirmed in an independent sample of 260 young normotensive men. We conclude that the SGK1 gene is relevant to blood pressure regulation and probably to hypertension in man.

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Gollasch,M.; Tank,J.; Luft,F.C.; Jordan,J.; Maass,P.; Krasko,C.; Sharma,A.M.; Busjahn,A.; Bahring,S.

Journal of Hypertension 2002;20:927-33.

Background The baroreflex, which is important for the minute-to-minute regulation of blood pressure and heart rate, is influenced by genetic variance. Ion channels are important to baroreflex afferent and efferent function. Mice missing the beta1 subunit of the Ca2+-sensitive potassium channel (BK) are hypertensive and have a reset baroreflex. We tested the hypothesis that variants in the gene (KCNMB1) coding for the BK beta1 subunit are associated with baroreflex function.
Methods We studied six sing le-nucleotide polymorphisms (SNPs) in KCNMB1.
Results Four SNPs in intron 3, exon 4a, exon 4b and exon 4c gave significant results. For instance, exon 4b SNP AA individuals had higher heart rate variability, compared to CA, or CC persons, in particular in the high-frequency range. The low-frequency range showed no association. Consistent with the heart rate variability data, homozygous AA persons had greater baroreflex slopes than CA or CC persons, also in the high-frequency range. These associations could not be shown in the low-frequency range for heart rate variability and baroreflex slopes.
Conclusions These data support the notion that variants in channel genes may be responsible for the great range in heart rate variability and baroreflex function observed in humans. Such variation may also play a role in the development of hypertension.

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Guo-Hua Li; Faulhaber H-D.; Rosenthal, M.; Schuster, H.; Jordan, J.; Timmermann B.; Hoehe M.R.; Luft F.C.; Busjahn, A.

Psychophysiology, 2001; 38 485-489

We tested the hypothesis that blood pressure (BP) responses to physical and mental stress are associated with polyphormisms in the beta-2 adrenergic receptor (AR) gene. We studied normotensive, young, monozygotic (MZ) and dizygotic (DZ) twins. The subjects underwent automated BP measurements at the brachial and digital arteries and were subjected to mental arithmetic and cold pressor stress. We used allele-specific PCR to genotype four single nucleotide polymorphisms in the beta-2 AR gene. The most functionallly relevant polymorphism in the beta-2 AR gene, Arg 16/Gly, was associated with systolic and diastolic BP under resting conditions, during mental arithmetic, and during the cold pressor test, as well as with the increase in diastolic BP during both forms of stress. These findings support a role for the beta-2 AR gene in BP regulation. They also indicate that the beta-2 AR gene influences the level of not only resting but also stress-related BP.

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Tank, J.; Jordan, J.; Diedrich, A.; Stoffels, M.; Franke, G.; Faulhaber, H. D.; Luft, F. C.; Busjahn, A.

Hypertension. 2001; 37 (3):907-910

Blood pressure and heart rate are strongly influenced by genetic factors; however, despite the pivotal role of genetics in short-term cardiovascular regulation, little is known about the genetic contribution to baroreflex function. We assessed genetic influence on baroreflex sensitivity (BRS) in 149 twin pairs (88 monozygotic of age 33+/-13 years and BMI 23+/-4 kg/m(2) and 61 dizygotic of age 33+/-11 years and BMI 24+/-4 kg/m(2)). ECG and finger arterial blood pressures were measured continuously under resting conditions. BRS values were calculated by use of cross-spectral analysis (baroreflex slope calculated as mean value of transfer function between systolic blood pressure and the R-R interval in the low-frequency band [BRSLF] and baroreflex slope calculated as the mean value of transfer function between systolic blood pressure and R-R interval in the respiratory frequency band [BRSHF]) and the sequence technique (BRS+, BRS-). Heritability (h(2)) was estimated with a path-modeling approach. BRS values did not differ significantly between groups (monozygotic, BRSLF, 17+/-13; BRSHF, 21+/-18; BRS+, 19+/-16; and BRS-, 21+/-15, and dizygotic, BRSLF, 16+/-9; BRSHF, 20+/-14; BRS+, 18+/-10; and BRS-, 20+/-11 ms/mm Hg), and were significantly correlated (P:<0.001). When variances and covariances for monozygotic and dizygotic twins were compared, significant correlations were found for BRS in monozygotic (range, r=0.38 to 0.48) but not in dizygotic twin pairs (r=-0.03 to 0.09). Thus, BRS is heritable; the variability can be explained by genetic influences (P:<0.01; h(2) range, 0.36 to 0.44). The genetic influence on BRS remained strong after correction for BMI and blood pressure. Therefore, BRS is strongly genetically determined, probably by different genes than are resting blood pressure and BMI.

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Busjahn A, Knoblauch H, Faulhaber HD, Aydin A, Uhlmann R, Tuomilehto J, Kaprio J, Jedrusik P, Januszewicz A, Strelau J, Schuster H, Luft FC, Muller-Myhsok B

Nat Genet 2000 Dec;26(4):398-399

no abstract available

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Busjahn A, Li GH, Faulhaber HD, Rosenthal M, Becker A, Jeschke E, Schuster H, Timmermann B, Hoehe MR, Luft FC

Hypertension 2000 Feb;35(2):555-60

Genetic variability, which influences cardiovascular phenotypes in normal persons, is likely to be relevant to cardiovascular disease. We studied normal monozygotic and dizygotic twins and found strong genetic influences on blood pressure and heart size. We then relied on the dizygotic twins and their parents to apply molecular genetic techniques. We performed a linkage analysis with markers close to the beta-2 adrenergic receptor (AR) gene locus in the dizygotic twins and their parents and found strong evidence for linkage to the quantitative traits of blood pressure and heart size. We then used allele-specific polymerase chain reaction to genotype the subjects further. We performed an association analysis and found that 4 functionally relevant polymorphisms in the beta-2 AR gene, namely Arg16/Gly, Gln27/Glu, Thr164/Ile, and a variant in the promoter region (-47C/T), were variably associated with blood pressure and heart size differences but were in linkage dysequilibrium with each other. A subsequent conditional analysis suggested that the Arg16/Gly polymorphism exerted the predominant effect. These findings underscore the importance of the beta-2 AR gene to blood pressure regulation, heart size, and probably to the development of hypertension. We suggest that a combined linkage and association approach will elucidate the genetic variability influencing blood pressure and other cardiovascular phenotypes.

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Knoblauch H, Muller-Myhsok B, Busjahn A,Ben Avi L, Bahring S, Baron H, Heath SC, Uhlmann R, Faulhaber HD, Shpitzen S, Aydin A, Reshef A, Rosenthal M, Eliav O, Muhl A, Lowe A, Schurr D, Harats D, Jeschke E, Friedlander Y, Schuster H, Luft FC, Leitersdorf E

Am J Hum Genet 2000 Jan;66(1):157-66

A cholesterol-lowering gene has been postulated from familial hypercholesterolemia (FH) families having heterozygous persons with normal LDL levels and homozygous individuals with LDL levels similar to those in persons with heterozygous FH. We studied such a family with FH that also had members without FH and with lower-than-normal LDL levels. We performed linkage analyses and identified a locus at 13q, defined by markers D13S156 and D13S158. FASTLINK and GENEHUNTER yielded LOD scores >5 and >4, respectively, whereas an affected-sib-pair analysis gave a peak multipoint LOD score of 4.8, corresponding to a P value of 1.26x10-6. A multipoint quantitative-trait-locus (QTL) linkage analysis with maximum-likelihood binomial QTL verified this locus as a QTL for LDL levels. To test the relevance of this QTL in an independent normal population, we studied MZ and DZ twin subjects. An MZ-DZ comparison confirmed genetic variance with regard to lipid concentrations. We then performed an identity-by-descent linkage analysis on the DZ twins, with markers at the 13q locus. We found strong evidence for linkage at this locus with LDL (P<.0002), HDL (P<.004), total cholesterol (P<.0002), and body-mass index (P<.0001). These data provide support for the existence of a new gene influencing lipid concentrations in humans.

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Busjahn-A; Knoblauch-H; Faulhaber-HD; Boeckel-T; Rosenthal-M; Uhlmann-R; Hoehe-M; Schuster-H; Luft-FC

CIRCULATION-. JUN 22 1999; 99 (24) : 3161-3164

Background: The rate-corrected QT interval (QTc) is heritable, and the discovery of quantitative trait loci that influence the QTc would be an important step in identifying the genes responsible for life-threatening arrhythmias in the general population. We studied 66 pairs of unselected normal dizygotic (DZ) twin subjects and their parents in a sib-pair analysis. We tested for linkage of gene loci harboring genes known to cause the long-QT syndrome (LQT) to the quantitative trait QTc.Methods and Results-We found genetic variance on QRS duration, QRS axis, T-wave axis, and QTc. Women had a longer QTc than men. Microsatellite markers were tested in the vicinity of the gene loci for the 5 known LQT genes. We found significant linkage of QTc with the loci for LQT1 on chromosome 11 and LQT4 on chromosome 4 but not to LQT2, LQT3, or LQT5, We also found linkage of the QRS axis with LQT2 and LQT3.Conclusions-We suggest that these quantitative trait loci may represent the presence of variations in LQT genes that could be important to the risk for rhythm disturbances in the general population.

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Busjahn A,Aydin A, von Treuenfels N, Faulhaber H-D, Gohlke H-R, Knoblauch H, Schuster H, and Luft FC

J. Hypertens. 1999; 10: 1437-1441

Background a-adducin is a cytoskeletal protein involved with sodium-pump activity in the renal tubule. The a-adducin gene locus has been linked to hypertension and a polymorphism identified which is associated with hypertension; however, the role of the a-adducin gene locus in normal blood pressure regulation is not defined. We performed a combined linkage and association study in normotensive MZ and DZ twins and their parents to address this issue.
Methods We studied 126 MZ and 70 DZ twin pairs and parents of DZ twins. Blood pressure and cold-pressor blood pressure values were obtained. Cardiac dimensions were measured echocardiographically. Three microsatellites adjacent to the a-adducin gene were studied as well as the 460 Trp mutation in the a-adducin gene. Results We obtained strong evidence for linkage (p<0.001) between the a-adducin gene locus and systolic blood pressure. However, we were not able to associate the 460 Trp mutation with higher blood pressures, cold-pressor responses, or cardiac dimensions.
Conclusions The a-adducin gene locus is relevant to blood pressure regulation in normal subjects. Failure to find association between higher blood pressures and the 460 Trp mutation suggests that this mutation may become important only when hypertension is triggered, or that other variations in a-adducin are present which have not yet been discovered.

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Knoblauch-H; Busjahn-A; Muller-Myhsok-B; Faulhaber-HD; Schuster-H; Uhlmann-R; Luft-FC

Arterioscler Thromb Vasc Biol 1999 Dec;19(12):2940-4

The peroxisome proliferator-activated receptor gamma (PPARgamma) gene has been implicated in morbid obesity and is important to lipid and carbohydrate metabolism. However, the relevance of gene variations in healthy nonobese subjects has not been defined. We recruited monozygotic and dizygotic healthy nonobese twin subjects to test the hypothesis that the PPARgamma gene is important to body mass index and lipid concentrations in healthy nonobese subjects. Both linkage and association strategies were used in the same dizygotic twins. The PPARgamma gene locus was linked (P<0.01) to high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and body mass index as quantitative traits. A biallelic variant in the PPARgamma gene was associated with high-density lipoprotein cholesterol and body mass index (P<0.05). We also looked for linkage between the same variables and the retinoic X receptor gene locus. This locus was linked to total and low-density lipoprotein cholesterol as well as triglycerides. We conclude that the PPARgamma gene is highly relevant to lipid metabolism and body mass index, not only in the morbidly obese but also in healthy nonobese subjects. The same appears to be true for its binding partner. Sequencing these genes in twins would serve to identify gene variations contributing to body mass index and lipid concentrations in healthy nonobese subjects.

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Nagy-Z; Busjahn-A; Bahring-S; Faulhaber-HD; Gohlke-HR; Knoblauch-H; Rosenthal-M; Mller-Myhsok-B; Schuster-K; Luft-FC

JOURNAL-OF-THE-AMERICAN-SOCIETY-OF-NEPHROLOGY. AUG 1999; 10 (8) : 1709-1716

Blood pressure (BP) is heritable and finding quantitative trait loci that influence BP is an important step in identifying genes responsible for BP regulation. Sixty-six pairs of dizygotic (DZ) twin subjects and their parents were used in a sib-pair analysis to look for linkage of selected candidate genes to the quantitative trait BP. Microsatellite markers were tested in the vicinity of the gene loci for insulin-like growth factor-1 (IGF-1), Liddle syndrome, autosomal-dominant hypertension with brachydactyly, angiotensinogen, angiotensin II type I receptor, angiotensin-converting enzyme, renin, and lipoprotein lipase. BP was measured in a standardized manner. Heart size was determined echocardiographically. Significant linkage was found at the IGF-1, Liddle syndrome, and AT(1) receptor gene for systolic BP. Linkage for diastolic BP was found at the autosomal-dominant hypertension with brachydactyly locus. Both systolic and diastolic BP were linked to the renin gene locus. The linkage was most consistent for the IGF-1 gene locus and systolic Bg. Linkage was also found between the IGF-1 gene locus and posterior cardiac wall thickness, septal thickness, and left ventricular mass index. It is suggested that these quantitative trait loci may be important for the subsequent detection of allelic variants for elevated BP. Furthermore, these results linking the IGF-1 gene locus to both BP and cardiac dimensions underscore the importance of the IGF-1 gene as a candidate gene for cardiovascular disease.

Busjahn-A; Faulhaber-HD; Freier-K; Luft-FC

PSYCHOSOMATIC-MEDICINE. JUL-AUG 1999; 61 (4) : 469-475

Objective: Coping styles are generally considered to be environmentally driven, primarily by family influences. However, because personality traits are commonly influenced by genetic effects, we hypothesized that heredity is also important for coping. Methods: We tested this hypothesis by assessing 19 coping styles, as well as four secondary coping factors, by questionnaire in 212 pairs of monozygotic and dizygotic twins. We then examined heredity by structural equation modeling. Results: All coping styles showed evidence of genetic influences. The coping styles shared one common genetic factor. In addition, each coping style was also influenced by other separate genetic factors. Shared environment had no significant influence on coping styles. Three of 19 more specific coping styles showed shared environmental effects as well as genetic influences, 14 were solely under genetic influences, and two showed only shared environment effects. Conclusions: We suggest that hereditary effects on certain coping style preferences cannot be explained solely by genetic influences on major personality traits and temperament. An analysis of the relationships between coping and personality in twin subjects may elucidate the distinction between genetic and environmental effects.

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Busjahn-A; Voss-A; Knoblauch-H; Knoblauch-M; Jeschke-E; Wessel-N; Bohlender-J; McCarron-J; Faulhaber-HD; Schuster-H; Dietz-R; Luft-FC

Am-J-Cardiol. 1998 Mar 15; 81(6): 755-60

Decreased heart rate variability (HRV) is associated with congestive heart failure, post-myocardial infarction, ventricular arrhythmias, sudden cardiac death, and advancing age. A deletion/insertion polymorphism in the angiotensin-converting enzyme (ACE) gene and a substitution (M235T) in the angiotensinogen gene have been associated with risk for heart disease. The aim of this study was to determine the heritability of HRV and related parameters in monozygotic and dizygotic twins and to assess the influence of ACE and angiotensinogen polymorphisms. We studied 95 MZ pairs and 46 DZ pairs. We measured HRV and related parameters, ACE and angiotensinogen levels, plasma norepinephrine, ACE, and angiotensinogen genotypes. We found that HRV and related parameters were significantly influenced by genetic variability, although nonshared genetic effects were also important. Angiotensinogen and plasma norepinephrine were generally correlated with decreased HRV, whereas ACE was correlated with perturbances of normal rhythmic HRV. Nevertheless, the DD ACE genotype was associated with increased HRV (p <0.05), whereas angiotensinogen polymorphisms had no effect. We conclude that HRV and related parameters are in part heritable. Interestingly, the DD ACE genotype is associated with increased HRV.

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BECKER-A; BUSJAHN-A; FAULHABER-HD; BHRING-S; ROBERTSON-J; SCHUSTER-H; LUFT-FC

J Reprod Med-. 1997; 42:

Objective: Twin zygosity determination can be performed with anthropologic, serologic and genetic markers; however, these methods are more than occasionally inefficient, often expensive and sometimes inaccurate. We used microsatellites as DNA markers and developed a largly automated, rapid and efficient method of determining zygosity.
Study design: We used five highly polymorphic tandem repeat loci, coamplified by polymerase chain reaction (PCR) using fluorescence-labeled primers. Thirty-six samples were simultaniously analyzed by electrophoresis and laser detection. The PCR products were sized by automated fragment analysis.
Results: We typed 132 pairs of monozygotic (MZ) and dizygotic (DZ) twins. With five markers, the probability that any twin pair was MZ if all markers were concordant was 99%.
Conclusion: This method is a rapid and reliable approach to zygosity detection.

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Knoblauch H, Busjahn A, Mnter S, Faulhaber H-D, Schuster H, Luft FC.

Arterioscler Thromb Vasc Biol 1997; 17:2054-2060 .

We studied 100 healthy monozygotic and 72 dizygotic twin pairs (mean age, 34 +/- 14 years) to test for genetic influences on blood lipids and to examine relevant gene loci. Total cholesterol (TC), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), and triglyceride (TG) levels were determined after a 12-hour fast. Zygosity was determined with the use of microsatellite markers. Heritability estimates were conducted by using the lisrel 8 program; a sib-pair analysis was conducted by using the sibpal program. Linear regression analyses were carried out between identical-by-descent status and squared within-pair differences of TC, LDL-C, HDL-C, and TG values. Heritability estimates of the lipid serum concentrations ranged from .58 to .66. A significant linkage relationship was found for HDL-C (P = .008) and TGs (P = .05) with D8S261 on chromosome 8p. However, no linkage was found between any of the lipid variables and the lipoprotein lipase gene locus (LPL GZ14/15 and D8S282). Because D8S261 is located approximately halfway between the LPL and macrophage scavenger receptor genes, we examined the nearby markers D8S549 and D8S1731. Linkage was found for HDL-C and D8S549 (P = .001) and for HDL-C and D8S1731 (P = .04). On the other hand, we found no linkage between the LDL receptor gene locus and LDL-C serum concentrations nor between the LPL gene locus and the various other lipid fractions. Our data suggest a significant influence of the macrophage scavenger receptor gene locus on HDL-C and weak influence on TG levels. We suggest that inherited variability in the macrophage scavenger receptor gene has an influence on serum lipid concentrations.

BUSJAHN-A; KNOBLAUCH-H; KNOBLAUCH-M; BOHLENDER-J; MENZ-M; FAULHABER-HD; BECKER-A; SCHUSTER-H; LUFT-FC;

HYPERTENSION-. JAN 1997; 29 (1) Part 2 : 165-170.

We tested the hypotheses that angiotensin converting enzyme insertion/deletion (I/D) and angiotensinogen 235 methionine/threonine (M/T) substitution gene polymorphisms influence angiotensin converting enzyme and angiotensinogen serum concentrations and cardiac dimensions in 91 monozygotic and 41 dizygotic twin pairs. Cardiac dimensions were determined echocardiographically. Angiotensin converting enzyme levels were 24 +/ 11, 43 +/ 18, and 58 +/ 24 U/L for the II, ID, and DD genotypes, respectively (P < .01). Posterior wall thickness was 8.1 +/ 1.3, 8.6 +/ 1.7, and 8.9 +/ 1.9 mm for these genotypes (P < .05). Angiotensin converting enzyme levels were correlated with posterior wall thickness (r = .15, P < .05). The intrapair differences in angiotensin converting enzyme levels for monozygotic, concordant dizygotic, and discordant dizygotic twins were 1.36 +/ 1.6, 1.86 +/ 1.6, and 17.25 +/ 4.3 U/L, respectively. The angiotensinogen M/T genotypes exerted no influence on cardiac dimensions or on angiotensinogen concentrations. The additive genetic effect on angiotensin converting enzyme levels (0.49), on posterior wall thickness (0.26), and on septum thickness (0.37) was significant (P < .01), although shared and nonshared environmental effects were also identified. Our data confirm the impressive effect that the angiotensin converting enzyme D allele exerts on angiotensin converting enzyme plasma levels. Furthermore, our data also suggest that the angiotensin converting enzyme gene locus is primarily responsible for angiotensin converting enzyme plasma levels. Our twin study also indicates that the angiotensin converting enzyme gene locus is genetically linked to posterior wall thickness. The correlation between angiotensin converting enzyme levels and posterior wall thickness suggests that this effect is exerted by angiotensin converting enzyme. We were unable to demonstrate genetic linkage between the angiotensinogen gene locus and cardiac dimensions in this study.

BUSJAHN-A; FAULHABER-HD; VIKEN-RJ; ROSE-RJ; LUFT-FC

JOURNAL-OF-HYPERTENSION. OCT 1996; 14 (10) : 1195-1199.

Objectives To determine the genetic and environmental contributions to resting blood pressure, the level of blood pressure during the cold pressor test and the increase in blood pressure with the cold pressor test in an adult cohort of normotensive twins. Design and methods Ninety one monozygotic and 41 dizygotic normal twin pairs were recruited by advertisement. The mean age was 34 +/- 14 years (mean +/- SD), Systolic blood pressure (SEP), diastolic blood pressure (DBP) and heart rate were measured continuously at the finger (using a Finapres device) and verified at the upper arm oscillometrically (using a Dinamap device) every minute. The cold pressor test was conducted by immersing the nondominant hand into cold (< 4 degrees C) water for 2 min, Statistical analysis was performed by using the SPSS program; parameters of the quantitative genetic models were estimated by path analysis techniques using the LISREL 8 program.
Results Heritability estimates of additive genetic effects were statistically significant for SBP and DBP but not for heart rate during rest and during the cold pressor test. Furthermore, the path analysis indicated shared as well as specific genetic components both for the blood pressure level at rest and for that during the cold pressor test, However, the genetic influences on the blood pressure level at rest and on the increase in blood pressure during the cold pressor test (the blood pressure level during the cold pressor test minus that during rest) were entirely independent of one another.
Conclusions A significant genetic covariation exists for SEP and DBP during rest and during the cold pressor test, as well as a significant genetic variation that is specific to the cold pressor stress condition, These findings suggest that different genes or sets of genes contribute to blood pressure regulation during rest and to blood pressure reactivity to cold pressor stress.