Twin study of genetic and environmental effects on lipid levels

A study of 106 pairs of monozygotic (MZ) and 94 pairs of dizygotic (DZ) twins tested the hypothesis that part of the previously described genetic influence on blood lipid levels can be ascribed to closer similarities among MZ than among DZ twin pairs in environmental factors that affect lipid levels. Participants were adult twin volunteers (age 17-66; 64 male and 136 female pairs) who were selected from the NH & MRC Twin Registry or were respondents to advertisements. They completed a 4-day weighed food diary from which mean nutrient intake was derived. Information on lifestyle and demographic variables was obtained by questionnaire and a nonfasting blood sample was taken for measures of total, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol and the HDL2 and HDL3 subfractions. Height and weight were measured, and body mass index (BMI) was calculated (kg/m2). Estimates of the heritability of sex-adjusted lipid levels were 0.72 for total cholesterol, 0.79 for HDL cholesterol, 0.69 for HDL2, 0.20 for HDL3, 1.06 for LDL cholesterol, and 0.44 for sex-adjusted BMI. In all cases except for HDL3, genetic variance was statistically significant. After adjusting for the effects of environmental variables in three different ways, the estimates of heritability were somewhat lower for total cholesterol, HDL2, and BMI, and those for HDL cholesterol (borderline) and LDL cholesterol (definitely) remained statistically significant but were decreased. A genetic influence on HDL3 was not found. Adjusted heritability estimates obtained from one method of analysis were 0.35 for total cholesterol, 0.49 for HDL, 0.04 for HDL2, -0.34 for HDL3, 0.66 for LDL, and 0.32 for BMI. These results suggest that the assumptions made in the classical twin study approach are not appropriate when examining genetic effects on lipid levels or BMI, or indeed on any biological variable that may be affected by environmental factors that tend to be more similar in MZ twins than in DZ twins. In these circumstances, more complex models may be needed to differentiate between genetic and environmental influences.     

青岛市成人双生子血脂相关指标的遗传度研究

目的了解成人双生子血清总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、甘油三酯(TG)的水平及其遗传度。方法选择青岛市双生子库中316对18到60岁的健康成人双生子,用自动生化分析仪检测其空腹血清TC、HDL-C、LDL-C、TG的浓度。鉴定卵性后,用Mx软件拟合遗传模型,调整性别、年龄后,计算血脂相关指标的遗传度。结果双生子空腹血清TC、HDL-C、LDL-C、TG水平的均值分别为(4.52±1.08)、(1.46±0.39)、(2.58±0.79)、(1.11±0.77)mmol/L。Mx软件拟合结构方程模型结果显示,TC、HDL-C和LDL-C三项指标的最适模型为AE模型,其遗传度依次为53%、62%和57%。TG的最适模型为CE模型,遗传度为0。结论遗传因素和环境因素对TC、HDL-C和LDL-C的浓度都有重要影响,而TG主要受到环境因素的影响。     

血压的遗传度分析

目的利用双生子资料探讨不同年龄组血压的遗传度的大小。方法在1999年大面积的横断面调查中,收集8岁及以上的双胞胎1101对,主要来自安庆的四县一郊,经统一调查表收集双生子的人口学及各种环境因素和职业暴露情况,用水银柱式血压计测量血压。结果对血压值经典的Holziger方法进行血压的遗传度分析,按年龄分层后儿童青少年血压的遗传度较低,总体研究对象的SBP的遗传度为0.278,DBP的遗传度为0.368.异卵双生子的对内差大于同卵双生子,差别达到显着性水平,且随着年龄的增加,差值增加。结论遗传因素是影响血压的重要因素。     

Heritability of blood pressure in 7- to 12-year-old Chinese twins, with special reference to body size effects

Systolic and diastolic blood pressures and body-size indices such as body height, body weight, sitting height, chest circumference, skinfold thickness, and body mass index (BMI) were assessed in 110 pairs of like-sex Chinese twins (75 monozygotic and 35 dizygotic) aged 7-12 years. Significant correlations of blood pressure with body-size indices were found. Prior to adjusting for body-size effects, three twin methods yielded low heritability estimates for both systolic (0.32-0.41) and diastolic (0.32-0.51) pressures. Adjusting systolic pressure for body height and BMI via multiple regression nearly halved heritability estimates, but adjusting diastolic pressure for body height and skinfold thickness only changed the estimates slightly.     

3~7岁儿童气质遗传度双生子测评分析

目的 利用双生子人群估计3~7岁儿童气质的遗传度。方法 采用随机抽样法,通过Carey儿童气质问卷对131对3~7岁双生子气质进行测评。对测评结果进行结构方程模型拟合,估算各气质维度的遗传度。结果 3~7岁儿童气质类型的遗传度为45.96%;特殊环境因素对气质维度的影响（方差为4%~36%）具有普遍性,除趋避性、坚持性和男童活动水平外,其他气质维度均存在共同环境效应（方差为13%~65%）,年龄效应方差（0%~8%）则不明显;校正年龄后,活动水平、节律性、趋避性、适应性、反应强度、情绪本质、坚持性、注意分散度及反应强度的遗传度分别为：男童35.83%、46.55%、82.67%、64.91%、45.09%、44.00%、83.95%、64.93%、40.88%;女童81.14%、21.66%、82.67%、80.39%、67.28%、44.00%、83.96%、64.93%、40.88%。结论 3~7岁儿童气质受遗传与环境因素的共同影响,男女节律性、情绪本质、反应阈、男童活动水平与反应强度可能更多受环境因素的影响。     

3～6岁双生子体型遗传分析

目的分析3～6岁幼儿体型各因子的遗传度,探讨遗传与环境因素对其体型发育的影响。方法采用Heath-Carter体型法对72对3～6岁同性别双生子[同卵双生子(MZ)42对,异卵双生子(DZ)30对]的体型进行分析,用Holzinger公式估算体型各因子遗传度。结果二维空间的体型离散距离(SDD)和三维空间体型位置距离(SAD)显示,MZ的体型较DZ更为接近;体型各因子对间方差在2类双生子间均无明显差异,中因子和外因子的对内方差DZ均明显大于MZ、组内相关系数MZ均明显大于DZ;内、中、外3个因子的遗传度分别为0.38、0.67、0.73。结论遗传与环境因素对3～6岁幼儿体型发育均有一定影响,内因子主要受环境影响,中、外因子受遗传因素影响较大。     

青岛市成人双生子吸烟饮酒遗传度分析

目的分析遗传因素对双生子吸烟、饮酒的影响。方法以青岛地区自愿参加本研究的年龄≥24周岁的双生子为对象，在卵型鉴定的基础上。采用Holzinger方法分析其吸烟、饮酒的遗传度。结果估计吸烟的遗传度为（66．5±5．53）％，重度吸烟的遗传度为（43．0±5．75）％。男性同卵双生子在吸烟行为上Kappa一致性检验K=0．453，P〈0．001。异卵双生于K=0．307，P=0．005；饮酒的遗传度为（60．8±7．79）％，大量饮酒的遗传度为（22．2±9．80）％。男性同卵双生于在饮酒行为上Kappa一致性检验K=0．518。P〈0．001，异卵双生子K=0．160，P=0．224。结论吸烟、饮酒受遗传因素影响较大；重度吸烟、大量饮酒受遗传因素影响较小。男性同卵双生子在吸烟、饮酒行为上呈现中度一致性．男性异卵双生子、女性双生子一致性差异无统计学意义。     

Distribution and Determinants of Plasma Homocysteine Levels in Rural Chinese Twins across the Lifespan

Plasma homocysteine (Hcy) is a modifiable, independent risk factor for cardiovascular disease (CVD) and is affected by both environmental and genetic factors. This study aimed to describe the gender- and age-specific distribution of Hcy concentration for 1117 subjects aged 10–66 years, a subset of a community-based rural Chinese twin cohort. In addition, we examined environmental and genetic contributions to variances in Hcy concentration by gender and age groups. We found that the distribution pattern for Hcy varied by both age and gender. Males had higher Hcy than females across all ages. Elevated Hcy was found in 43% of male adults and 13% of female adults. Moreover, nearly one fifth of children had elevated Hcy. Genetic factors could explain 52%, 36% and 69% of the variation in Hcy concentration among children, male adults and female adults, respectively. The MTHFR C677T variant was significantly associated with Hcy concentrations. Smokers with the TT genotype had the highest Hcy levels. Overall, our results indicate that elevated Hcy is prevalent in the children and adults in this rural Chinese population. The early identification of elevated Hcy will offer a window of opportunity for the primary prevention of CVD and metabolic syndrome.     

童年中期双生子下肢长相关指标的遗传学分析

目的分析遗传与环境因素对童年中期双生子儿童下肢长相关指标的影响,并分析其中年龄和性别的作用。方法对呼和浩特市和包头市5~8岁171对双生子儿童下肢长相关指标进行测量,使用Mx软件拟合最佳模型,计算校正年龄前后各指标遗传与环境方差组分。结果各指标最佳拟合模型均为ACES,校正年龄后遗传度分别为:身高:男43%,女60%);坐高:男62%,女62%;下肢长:男50%,女62%;下肢长指数:男18%,女36%。身高、下肢长和下肢长指数的遗传度存在一定性别差异。结论童年中期下肢长相关指标发育受环境因素的影响较大,应通过加强营养与锻炼及控制相关疾病等改善下肢长度发育,促使儿童生长发育潜力得到更好的发挥。     

不同发育期双生子皮褶厚度及体成分分析

目的 分析遗传与环境因素不同发育期双生子皮褶厚度及体成分的作用特点。方法 测量376对6～18岁同性别双生子(同卵245对,异卵131对)肱三头肌、肩胛下皮褶厚度,用长岭和Brozek公式估算体成分;用Mx软件拟合最佳模型,计算各指标遗传与环境方差组分,分析年龄、性别和不同发育期的作用。结果 全部双生子分性别校正年龄后,各指标遗传度在0.59～0.87之间;不同发育期各指标遗传度存在差异,肱三头肌皮褶、肩胛下皮褶、2处皮褶厚度之和、体脂百分比的遗传度男生在青春期前期最低,分别为0.55,0.62,0.53,0.51,女生在青春期晚期最低,分别为0.53,0.43,0.24,0.40;男、女瘦体重遗传度随青春期发育进程呈增加趋势。结论 遗传因素对儿童青少年皮褶厚度和体成分起主要作用,但年龄、性别和不同发育阶段对其也有一定影响。     

青岛市成人双生子体型指征的遗传度研究

目的探讨遗传因素对体质指数(BMI)和腰臀围比值(WHR)等体型指征的影响程度。方法青岛地区自愿参加本研究的496对24周岁及以上的双生子。在卵型鉴定的基础上。应用Mx软件构建结构方程模型分析遗传度。结果估计体质指数的遗传度为76％，男、女性分别为33％，74％；腰臀围比值的遗传度为62％，男、女性分别为0．12％，74％。结论在体型指征的相关指标中，BMI和WHR均受遗传因素影响较大。其中，女性的BMI和WHR受遗传因素的影响可能大于环境因素；男性体质指数受环境因素影响大于遗传因素，腰臀围比值则可能不受遗传因素影响。     

Do genetic factors contribute to the association between birth weight and blood pressure?

OBJECTIVES: To evaluate whether genetic factors contribute to the association between low birth weight and increased blood pressure among adolescents. DESIGN: Historical cohort study of twin pairs. It was evaluated whether (1) a negative association between birth weight and systolic blood pressure was found in the overall twin sample and (2) whether the intrapair difference in birth weight correlated with the intrapair difference in systolic blood pressure-thereby controlling for the effect of genetic factors (all in monozygotic and on average half in dizygotic pairs). SETTING: The Minnesota Twin Family Study. PARTICIPANTS: 1311 pairs of adolescent twins. MAIN RESULTS: A negative association between birth weight and systolic blood pressure was retrieved in the overall sample. The regression coefficient after controlling for current weight was -1.88 mm Hg/kg (SE 0.61), which corresponds to results from previous studies of singleton adolescents. The regression coefficient fell to -0.64 mm Hg/kg (SE 0.86) when the intrapair analyses were used. The largest reduction was observed among monozygotic twins: from -2.44 mm Hg/kg (SE 0.75) in the overall monozygotic twin sample to -1.06 mm Hg/kg (SE 1.14) in the analyses of the within monozygotic pair differences. CONCLUSION: The association between low birth weight and increased blood pressure later in life is well established. "The fetal programming hypothesis" suggests that the association is caused by intrauterine malnutrition while a new hypothesis "the fetal insulin hypothesis" proposes that genetically determined insulin resistance also contributes significantly to the association. A recent twin study of middle aged twins showed no evidence for an influence of genetic factors while this larger study provides support for the fetal insulin hypothesis: the association between birth weight and blood pressure attenuated among adolescents when genetic factors were controlled. Together this suggests an important contribution of genetic factors to the association between fetal growth and systolic blood pressure in adolescence.     

食品级藏灵菇培养液对高脂血症患者血脂血压的影响

目的观察食品级藏灵菇培养液对高脂血症患者血脂、血压的调节效果.方法选择高脂血症患者90例,随机分为对照组、牛奶组和试验组,每组30例,试验组每日睡前摄入藏灵菇培养液4 ml/kg体重,牛奶组喝等剂量牛奶,连续服用20天;对照组除不饮用藏灵菇培养液和牛奶外其他试验条件与试验组和牛奶组保持一致.3组试验前后分别测定血脂(总胆固醇、甘油三酯、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇)、血压.结果服用藏灵菇培养液的高脂血症患者试验前后血清总胆固醇的降低幅度大于牛奶组和对照组(P＜0.05),牛奶组与对照组之间差异无显著性(P＞0.05).甘油三酯、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇及血压试验前后的改变3组间差异均无显著性(P＞0.05).结论服用藏灵菇培养液对高脂血症患者血脂中的胆固醇有一定的降低作用.     

A genetic and environmental analysis of a twin family study of alcohol use,anxiety, and depression

Alcohol consumption, anxiety, and depression were measured by questionnaire in 572 twin families ascertained from the Institute of Psychiatry (London) normal twin register, each family consisting of an adult twin pair, their parents, and siblings-a total of 1,742 individuals. A multivariate normal model for pedigree analysis was applied to each variable, with power transformations fitted to maximise the fit with distributional assumptions. The effect of shared twin environment was estimated by considering the measured cohabitation history of twin pairs. For log-transformed alcohol consumption, amongst current drinkers this effect was the same for MZ and DZ pairs but depended on the cohabitation status of pairs. For both anxiety and depression the effect was clearly not the same for MZ and DZ pairs. Therefore the basic assumption of the classical twin method appears to be invalid for all three traits. Estimates of heritability derived from these analyses were compared with those obtained (1) by applying the classical twin method to twin data only, and (2) by a pedigree analysis ignoring the effect of shared twin environment. For all variables there were considerable differences between estimates based on the three models. This study illustrates that data from twins and their relatives which includes information on cohabitation history might distinguish shared genes and shared environment as causes of familial aggregation. In these behavioral traits the effect of shared twin environment may depend on zygosity and play a major role in explaining familial aggregation in twin family data.     

双胞胎居民不同时段的血压趋势和遗传度分析

目的：通过双胞胎资料研究人群不同时段血压的波动趋势和遗传度。方法：采用统一的调查表收集双生子的人口学及各种环境因素和职业暴露情况,用水银柱式血压计测量4个不同时段的血压。结果：对血压值经经典的Holziger方法进行血压的遗传度分析,不同时优的血压的遗传度是有差别的。收缩压在中乖遗传度为最高（0．97）,舒张压下乖为最高（0．76）,不同性别的收缩压随时间的回归分析显示相同的波动趋势,即早晨最低,上午升高,下午升高到最高点,晚上下降。但舒张压是早晨较低,中午最低,下午最高,晚上下降,且不同性别也表现出相同的变动趋势。结论：不同时段的血压的遗传度是不同的。