A descriptive analysis on hypertension in adult twins in China / 中华流行病学杂志

Objective: To describe the distribution characteristics of hypertension among adult twins in the Chinese National Twin Registry (CNTR) and to provide clues for exploring the role of genetic and environmental factors on hypertension. Methods: A total of 69 220 (34 610 pairs) of twins aged 18 and above with hypertension information were selected from CNTR registered from 2010 to 2018. Random effect models were used to describe the population and regional distribution of hypertension in twins. To estimate the heritability, the concordance rates of hypertension were calculated and compared between monozygotic twins (MZ) and dizygotic twins (DZ). Results: The age of all participants was (34.1±12.4) years. The overall self-reported prevalence of hypertension was 3.8%(2 610/69 220). Twin pairs who were older, living in urban areas, married, overweight or obese, current smokers or ex-smokers, and current drinkers or abstainers had a higher self-reported prevalence of hypertension (P<0.05). Analysis within the same-sex twin pairs found that the concordance rate of hypertension was 43.2% in MZ and 27.0% in DZ, and the difference was statistically significant (P<0.001). The heritability of hypertension was 22.1% (95%CI: 16.3%- 28.0%). Stratified by gender, age, and region, the concordance rate of hypertension in MZ was still higher than that in DZ. The heritability of hypertension was higher in female participants. Conclusions: There were differences in the distribution of hypertension among twins with different demographic and regional characteristics. It is indicated that genetic factors play a crucial role in hypertension in different genders, ages, and regions, while the magnitude of genetic effects may vary.

Genetic and Environmental Effects on the Abdominal Aortic Diameter Development / Efeitos Genéticos e Ambientais no Desenvolvimento do Diâmetro da Aorta Abdominal

Abstract Background: Configuration of the abdominal aorta is related to healthy aging and a variety of disorders. Objectives: We aimed to assess heritable and environmental effects on the abdominal aortic diameter. Methods: 114 adult (69 monozygotic, 45 same-sex dizygotic) twin pairs (mean age 43.6 ± 16.3 years) underwent abdominal ultrasound with Esaote MyLab 70X ultrasound machine to visualize the abdominal aorta below the level of the origin of the renal arteries and 1-3 cm above the bifurcation. Results: Age- and sex-adjusted heritability of the abdominal aortic diameter below the level of the origin of the renal arteries was 40% [95% confidence interval (CI), 14 to 67%] and 55% above the aortic bifurcation (95% CI, 45 to 70%). None of the aortic diameters showed common environmental effects, but unshared environmental effects were responsible for 60% and 45% of the traits, respectively. Conclusions: Our analysis documents the moderate heritability and its segment-specific difference of the abdominal aortic diameter. The moderate part of variance was explained by unshared environmental components, emphasizing the importance of lifestyle factors in primary prevention. Further studies in this field may guide future gene-mapping efforts and investigate specific lifestyle factors to prevent abdominal aortic dilatation and its complications.

Resumo Fundamento: A configuração da aorta abdominal relaciona-se com o envelhecimento saudável e uma série de distúrbios. Objetivos: Avaliar efeitos herdáveis e ambientais no diâmetro da aorta abdominal. Métodos: 114 pares de gêmeos adultos (69 monozigóticos e 45 dizigóticos do mesmo sexo), com idade média de 43,6 ± 16,3 anos, foram submetidos a ultrassonografia abdominal com o aparelho Esaote MyLab 70X para visualização da aorta abdominal abaixo da origem das artérias renais e 1-3 cm acima da bifurcação aórtica. Resultados: A herdabilidade ajustada para idade e sexo do diâmetro da aorta abdominal abaixo da origem das artérias renais foi 40% [intervalo de confiança (IC) 95%, 14 – 67%] e acima da bifurcação, 55% (IC 95%, 45 – 70%). Nenhum dos diâmetros aórticos apresentou efeitos ambientais comuns, mas os efeitos ambientais não compartilhados foram responsáveis por 60% e 45% dos traços, respectivamente. Conclusões: Nossa análise mostrou herdabilidade moderada e diferença do diâmetro da aorta abdominal com especificidade de segmento. A parte moderada da variância foi explicada pelo componente ambiental não compartilhado, enfatizando a importância do estilo de vida na prevenção primária. Estudos adicionais nesse campo poderão guiar futuros esforços de mapeamento genético e investigar fatores específicos de estilo de vida para prevenir dilatação da aorta abdominal e suas complicações.

Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study

Objectives Decreased thyroid volume has been related to increased prevalence of thyroid cancer. Subjects and methods One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63). Results Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%). Conclusions Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.

Glaucoma crónico de ángulo estrecho en gemelas dicigóticas / Chronic narrow-angle glaucoma found in dizygotic twins

Caso clínico: se informa el caso de una pareja de gemelas dicigóticas con diagnóstico de glaucoma crónico de ángulo estrecho en 2004, cuyol padre murió ciego; una hija de una de ellas fue diagnosticada posteriormente como afectada de glaucoma crónico de ángulo abierto. Se determinó la cigosidad de las gemelas mediante protocolo establecido al respecto. En los 4 ojos de las pacientes se determinaron presiones intraoculares por aplanación en cifras que fluctuaban entre 26-32 mmHg, cámaras anteriores y ángulos camerulares estrechos, perimetrías computarizadas tubulares en 3 ojos respetando los 5° centrales y en otro tubular que respetaba los 10° centrales con atrofias ópticas en evolución en los 4 ojos. Se efectuó trabeculectomía bilateral en ambas pacientes y se mantuvo el control de su enfermedad glaucomatosa. Conclusiones: se plantea la necesidad de la búsqueda de otros afectados en un núcleo familiar donde se diagnostiquen pacientes con glaucoma crónico de ángulo estrecho

Clinical case: here is the case of a dizygotic twin pair diagnosed with chronic narrow-angle glaucoma in 2994. Their father had died blind and a daughter of one of them was later diagnosed as a chronic open-angle glaucoma patient. A specific protocol allowed determining the zygocity of the twins. The intraocular pressures in the four eyes of the patients were measured with applanation tonometry and ranged 26-32 mmHg, narrow anterior chambers and camerular angles, computerized tubular perimetries in three eyes around central 5° and another tubular perimetry of central 10°, with developing atrophies in the four eyes. Both patients underwent bilateral trabeculectomy and the control over their glaucoma disease was kept. Conclusions: It is necessary to look for other people affected in a family setting where there exists diagnosis of chronic narrow-angle glaucoma

Genetic and environmental determinants of menstrual characteristics.

Background: The impact of women's menstrual cycle on her quality of life, health, work, and community is substantial. Menstrual disturbance is linked with general ill conditions such as migraine, asthma, and endocrinopathies. The clinical significance of medical interventions to prevent these conditions becomes clear if the role of genetic or environment is clarified. Aims: To identify the genetic and environmental contribution on menstrual characteristics. Setting and Design: This was a cross-sectional study in 2 Asian countries. Materials and Methods: 2 cohorts of monozygotic and dizygotic twins born between (1945-1988, n = 122) and (1951-1993, n = 71) were taken. A standard questionnaire was designed inclusive of socio- demographic characteristics of subjects as well as menstrual history (duration, interval, amount, irregularity). Subjects were interviewed by phone. Statistical Analysis: Quantitative variables were analyzed using Falconars' formula as well as maximum likelihood analysis. Structural modeling was then applied to twin correlations to provide estimates of the relative genetic and/or environmental factors contribution in determining the measured trait. Results: Menstrual characteristics were found to be under environmental influence where the best fitting model for menstrual interval and duration was common environment. CDF plotting confirmed the results for both variables. Proband-wise concordance analysis for amount of menstruation, amenorrhea, and irregular menstruation revealed no genetic influence. The best fitting model for menstrual irregularity was CE (C73%, E27%). The same model was defined for amenorrhea (C48%, E52%). Conclusions: Environmental factors are most likely responsible to determine the menstrual flow, its integrity, and regularity. These factors need to be studied further.

Blood Chimerism in a Dizygotic Dichorionic Pregnancy / 대한진단검사의학회지

Blood chimerism in twins is known to occur through the transfer of hematopoietic stem cells between the fetuses via a common placenta. We present a case of blood chimerism in a dizygotic dichorionic twin pregnancy. The female twin was delivered at 34 weeks of gestation, and the male twin was stillborn. Pathologic examination confirmed dichorionic diamniotic placentas. The karyotype of the female child was obtained using peripheral blood sample, and it revealed a mixture of 46,XX and 46,XY cells (chi 46,XY[13]/46,XX[7]). FISH analysis performed on the buccal cells by using CEP X/Y probe (Abbott Molecular Inc., USA) revealed 100% XX signals (nuc ish Xcen(DXZ1x2)[500]). Gross examination of the external genitalia and abdominal ultrasonography revealed no definitive abnormal findings in relation to sex differentiation. When XX/XY chimerism is present in blood lymphocytes, careful examination of external genitalia and reproductive organs and further studies are required to detect chimerism in non-hematopoetic tissues. This is a rare case of blood chimerism in dichorionic placentas, in contrast to those in monochorionic placentas.

Diabetes melito do tipo 1A na primeira infância de gêmeos dizigóticos: associação entre fatores genéticos e ambientais / Early infancy onset of type 1A diabetes mellitus in dizygotic twins: association with genetic and environmental factors

O Diabetes Mellitus tipo 1A diagnosticado antes do 1° ano de vida é uma condição rara, podendo haver uma associação entre fatores genéticos e ambientais (infecção) que explique tal precocidade. Foi descrita a presença do genoma do Citomegalovírus (CMV) nos linfócitos, em cerca de 15 por cento de novos casos de DM1. Relatamos os casos de desenvolvimento do diabetes em gêmeos dizigóticos do sexo masculino, nos primeiros 9 meses de idade com identidade nos alelos HLA (DR3/DR4) e história de infecção pelo CMV em ambos, comprovada por IgG+ e PCR urinária. Apenas o 2° gemelar apresentava o anticorpo anti-GAD positivo (9,6 UI/mL). Apesar de tratar-se de gêmeos dizigóticos, cuja taxa de concordância para diabetes, na literatura, é de 3,8 por cento, assumem risco equivalente a monozigóticos (de 40 por cento) por apresentarem HLA de alto risco para o diabetes. Acreditamos que tanto a concordância temporal como o início precoce do diabetes são decorrentes da associação entre infecção por CMV e forte suscetibilidade genética.

The onset of type 1A diabetes before the first year of age is a rare condition and is probably due to an interaction between genetic and environmental factors (infection), which, together, may explain such an early event. Studies say that about 15 percent of newly diagnosed type 1 diabetic patients had human Cytomegalovirus (CMV) specific viral genome in their lymphocytes. We report two cases of dizygotic twins with type 1 diabetes onset in their first 9 months of age, with genetic homogeneity (for HLA DR3/DR4 alleles), a history of CMV infection (positive IgG and urinary PCR) and positive antibody anti-GAD (9.6 UI/ml), present only in the second twin. Although they were dizygotic twins, which concordance rate is 3.8 percent, they assume the equivalent risk as monozygotic (40 percent) as they have similar high risk genotype (HLA) for type 1 diabetes. We believe that both time concordance and also the early onset of diabetes are due to an association between infection and the high genetic liability.

Genetic and Environmental Influences on Birthweight in a Sample of Korean Twins

This study is the first report of genetic and environmental influences on birthweight using Korean twins. The sample consisted of 255 monozygotic (MZ) and 178 dizygotic (DZ) twin pairs drawn from the Seoul Twin Family Study. Intraclass twin correlations were computed for the twins' birthweights obtained from parents (typically mothers) of the twins. To estimate genetic and shared and nonshared environmental influences on birthweight, standard univariate model-fitting analyses were performed using a software, Mx. For each gender, MZ twin correlations were higher than DZ twin correlations, suggesting existence of genetic influences on birthweight; however, DZ twin correlations were higher than half the MZ twin correlations, indicating that shared environmental factors are also important. For each zygosity, twin correlations were not significantly different between males and females, implicating that genes and environments that cause individual differences in birthweight may not vary between males and females. Model-fitting analyses based on the data pooled across gender yielded estimates of 17% for genetic, 60% for shared environmental, and 23% for nonshared environmental influences on birthweight.

Crescimento fetal / Fetal growth

No presente texto os autores revisam os fatores que determinam e influenciam o crescimento fetal, assim como os métodos para sua avaliação, sem, no entanto pretender esgotar o assunto

Genética dos transtornos afetivos / Genetic of affective disorders

Os autores revisam neste artigo o conjunto de evidências genético-epidemiológicas que indicam a presença de fatores genéticos na vulnerabilidade para os transtornos afetivos. Apresentam também os dados obtidos até o momento, através de estratégias de genética molecular na busca de genes de susceptibilidade para o transtorno afetivo bipolar e para a depressão.

Análise da morfologia oclusal dos primeiros molares permanentes em gêmeos / Analysis occlusal morphology of first molars in twins

Os dentes podem ser utilizados como amostras para o estudo da natureza e do momento da ocorrência dos distúrbios que acontecem no início da vida até após a adolescência. O arranjo bilateral dos dentes possibilitam comparaçöes do tamanho e da morfologia, nos lados direito e esquerdo, promovendo interessantes questöes sobre simetria e assimetria morfológica. A análise da morfologia oclusal dos primeiros molares permanentes, considerando a concordância assimétrica, em uma amostra de 36 pares de gêmeos monozigóticos e dizigóticos, mostrou resultados de concordância de 83 por cento a 92 por cento, principalmente em gêmeos monozogóticos

Aspectos genéticos da esclerose múltipla: I. Estudos em gêmeos / Genetic aspects in multiple sclerosis: I. Twin studies

Foi feita análise crítica dos estudos em gêmeos realizados na esclerose múltipla (EM). A taxa de concordância em gêmeos monozigóticos é significativamente maior do que em gêmeos dizigóticos. A média da herdabilidade da EM foi estimada em aproximadamente 28 por cento; porém ainda nao foram identificados os genes que constituem fator de risco para o desenvolvimento da EM. A EM pode ser considerada uma doença poligênica desencadeada por fatores ambientais em indivíduo geneticamente suscetível.

Estudio genético en gemelos / Genetic study in twins

Durante el período junio 1987 a enero 1988 se estudiaron, en forma consecutiva 35 pares de gemelos nacidos en dos maternidades de hospitales del área Norte de Santiago, con el propósito de buscar evidencia de factores genéticos que eventualmente influyen en las posibilidades de gemelaridad, comparando las frecuencias génicas de diversos grupos sanguíneos entre gemelos monozigóticos, mellizos dizigóticos y controles de una misma área geográfica. Dieciséis de ellos fueron considerados monozigóticos (MZ) después del estudio de cinco sistemas de grupos sanguíneos (ABO, Rh, (C,D,E,c, e), MNSs, Kidd, Duffy), aplicando el método de Smith y Penrose. La edad materna fue más alta en los mellizos dizigóticos (DZ), que en los monozigóticos (promedio = 30,1 años vs. 26,8 años, respectivamente). La historia familiar de gemelaridad fue positiva en 73%de MZ y 82%de DZ. Los sistemas Duffy y Kidd no estaban en equilibrio de Hardy-Weinberg, debido a déficit de heterozigotos para dichos caracteres entre los MZ y también los DZ. Se encontraron significativamente aumentados los haplotipos MS y Ms en ambos grupos de mellizos con respecto a una población general de la misma área geográfica. Estos resultados sugieren la presencia de un determinante genético que favorece la producción de gemelaridad de DZ como también de MZ. Se requeriría un mayor número de casos para probar esta hipótesis