Mass spectrometric determination of IgG subclass-specific glycosylation profiles in siblings discordant for myositis syndromes.

Many autoimmune conditions are believed to result from chronic inflammation as a consequence of the interaction of genetic and environmental factors in susceptible individuals. One common feature in some autoimmune diseases is the decrease in terminal galactosylation of the constant region N-glycan of the total plasma immunoglobulin. To determine whether a similar pattern is characteristic for the autoimmune disorder myositis, we analyzed the antibody subclass specific glycosylation in patients with myositis, their asymptomatic siblings, and healthy unrelated age- and sex-matched controls. The antibody subclass specific glycosylation was determined from the LC-MS analyses of the IgG glycopeptides generated by trypsin digestion of the antibody heavy chain. The glycosylation profiles of the IgG subclasses were determined relative to the total abundance of all glycoforms. We found elevated amounts of glycoforms lacking terminal galactose in myositis patients. Pairwise statistical analyses reveals that galactosylation is statistically different between the myositis patients and control groups. Furthermore, the trend analysis for glycosylation indicates a pattern of decreasing galactosylation in the order controls ≥ siblings ≥ myositis patients, suggesting the existence of a genetic, immune-related predisposition in the group of asymptomatic siblings that can be detected before the onset of clinical symptoms at the level of plasma proteins.

Oxidative stress in twin neonates is influenced by birth weight and weight discordance.

OBJECTIVES: To evaluate the extent of oxidative stress in neonates born from multiple gestation pregnancies who are at high risk of prematurity and growth abnormalities. DESIGN AND METHODS: Blood samples were collected from umbilical cord of 72 twins, born at gestational age of 28-38 weeks, and 20 consecutive control singletons. Oxidative stress parameters (15-F(2t)-isoprostane, a marker of lipid peroxidation, and total antioxidant capacity, tAOC), were measured in cord plasma. RESULTS: Levels of 15-F(2t)-isoprostane showed a moderate negative correlation with birth weight and were higher in small co-twins of discordant pairs; tAOC was positively correlated with birth weight but no significant difference was found between co-twins. CONCLUSIONS: Oxidative stress levels in twins are mainly influenced by birth weight and weight discordance. We suggest that evaluation of cord blood 15-F(2t)-isoprostane might be of clinical value as maker of pre- and perinatal distress in twinning.

An observational study of early neonatal biochemical parameters in twins.

Early neonatal biochemical values are generally considered to reflect maternal values. However, studies have been inconclusive due to the statistical methods used. We hypothesized that there would not be important differences in plasma biochemistry between newborn twins, suggesting a common mechanism of control, and that differences between unrelated infant pairs would be greater. All twins over a 5-year period who had plasma biochemistry measured within 6 hours of birth were identified retrospectively. An unrelated control infant was matched to one of each twin pair. The 95% limits of agreement for plasma urea, creatinine, and sodium were calculated for twin pairs and unrelated matched infant pairs. Fifty-three twin pairs were studied. For urea, creatinine, and sodium, 95% of differences between twins were less than or equal to 1.5 mmol/L (8.9 mg/dL), 9.2 µmol/L (0.1 mg/dL), and 5.1 mmol/L (11.7 mg/dL), respectively. In unrelated infant pairs, the corresponding values were 4.0 mmol/L (24.3 mg/dL), 33.9 µmol/L (0.4 mg/dL), and 8.2 mmol/L (18.9 mg/dL). Differences between unrelated infant pairs were significantly wider than differences between twins ( p < 0.001). This study has demonstrated a close and significant agreement in urea, sodium, and creatinine when measured soon after birth in twin pairs compared with unrelated infants, implying a common mechanism of control.

Heritabilities of Alcohol Use Disorders Identification Test (AUDIT) scores and alcohol biomarkers in Koreans: the KoGES (Korean Genome Epi Study) and Healthy Twin Study.

BACKGROUND: Both the Alcohol Use Disorders Identification Test (AUDIT) and alcohol biomarkers are used to screen for alcohol problems. The purpose of this study was to examine the genetic and environmental contributions to the AUDIT score and alcohol biomarkers in Koreans. METHODS: The study included 1678 current alcohol drinkers: 818 Korean twins and 860 their families. The Korean version of AUDIT and alcohol biomarkers, i.e., gamma glutamyltransferase (GGT), alanine aminotransferase (ALT), mean corpuscular volume (MCV), and triglycerides (TG), were studied. The analyses were conducted using variance components method to estimate heritability and common environmental effects, and bivariate analyses for genetic and environmental correlations between the AUDIT score and the biomarkers after adjustment for age, gender, interaction of age and gender, smoking status, the amount of consumed alcohol, body mass index, and education. RESULTS: Heritabilities for the AUDIT score were 0.35 and 0.40-0.71 for biomarkers (P<0.001). The risk of alcohol problems using AUDIT score was positively associated with the levels of biomarkers (GGT, MCV, and TG) in men, while the relationship was significant only for MCV in women. Genetic or environmental correlations between the AUDIT score and some of the biomarkers (GGT and MCV) were significant in men, but not significant in women. CONCLUSIONS: We found a significant genetic contribution to the AUDIT score and the alcohol biomarkers. As there were significant genetic and environmental relationships between the AUDIT score and the alcohol biomarkers in men, future studies are warranted to identify common genes and environmental effects affecting the relationships.

Ghrelin levels in cord blood from concordant and discordant twin pairs: association with birth weight and postnatal catch-up growth.

OBJECTIVE: To determine whether cord blood ghrelin levels in discordant and concordant twins predict postnatal catch-up growth. METHODS: After obtaining parental consent, cord blood samples were collected at delivery for total ghrelin analysis. Infant weight, length and head circumference were obtained at birth, 2, 4, and 6 months of age. Data points post-discharge were obtained from the pediatrician's office or via parent contact. Pearson correlation evaluated the relationship between cord blood ghrelin levels and postnatal catch-up growth. RESULTS: There was a statistically significant correlation between cord blood ghrelin levels and birth weight among concordant twins, but not among the discordant twins. Cord blood ghrelin levels did not predict postnatal growth at 6 months of age overall, but did so in the subset of monochorionic, discordant pairs. CONCLUSION: Cord blood ghrelin levels did not correlate overall with birth size or postnatal catch-up growth in concordant and discordant twin pairs, but did so in selected subsets. Further studies are needed.

First trimester maternal serum ADAM12s levels in twin pregnancies.

BACKGROUND: A disintegrin and metalloprotease 12s (ADAM12s) is a potential first trimester serum marker for fetal trisomy and adverse pregnancy outcome in singletons. In this study, ADAM12s levels in first trimester serum of uncomplicated and complicated twins were evaluated. METHODS: ADAM12s was studied in maternal serum of 215 twin pregnancies, collected between 2004 and 2008. ADAM12s was measured 'blind to outcome' using AutoDelfia (PerkinElmer, Turku, Finland). As a reference, data from 2423 singletons were used. RESULTS: The median ADAM12s level was increased in euploid twins [1.61 multiples of the median (MoM); n = 209] compared with singletons. The median ADAM12s MoM was significantly lower in monochorionic (1.36 MoM; n = 41) compared with dichorionic twins (1.67 MoM; n = 168) (Mann-Whitney U test, p = 0.005). Trisomy 21 was identified in two pregnancies. Median ADAM12s MoM in twins complicated by hypertensive disorders (1.77 MoM, n = 35) or small for gestational age fetus (1.54 MoM; n = 24) was not significantly different from uncomplicated twins (1.64 MoM; n = 134). CONCLUSION: Median ADAM12s MoM in euploid twins was increased compared with singletons. Monochorionic had significantly lower median ADAM12s MoM than dichorionic twins. Median ADAM12s MoMs were not significantly different in twins complicated by hypertensive disorders or small for gestational age fetus compared with uncomplicated twins.

Genetic effects on toxic and essential elements in humans: arsenic, cadmium, copper, lead, mercury, selenium, and zinc in erythrocytes.

BACKGROUND AND OBJECTIVES: An excess of toxic trace elements or a deficiency of essential ones has been implicated in many common diseases or public health problems, but little is known about causes of variation between people living within similar environments. We estimated effects of personal and socioeconomic characteristics on concentrations of arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), selenium (Se), and zinc (Zn) in erythrocytes and tested for genetic effects using data from twin pairs. METHODS: We used blood samples from 2,926 adult twins living in Australia (1,925 women and 1,001 men; 30-92 years of age) and determined element concentrations in erythrocytes by inductively coupled plasma-mass spectrometry. We assessed associations between element concentrations and personal and socioeconomic characteristics, as well as the sources of genetic and environmental variation and covariation in element concentrations. We evaluated the chromosomal locations of genes affecting these characteristics by linkage analysis in 501 dizygotic twin pairs. RESULTS: Concentrations of Cu, Se, and Zn, and of As and Hg showed substantial correlations, concentrations of As and Hg due mainly to common genetic effects. Genetic linkage analysis showed significant linkage for Pb [chromosome 3, near SLC4A7 (solute carrier family 4, sodium bicarbonate cotransporter, member 7)] and suggestive linkage for Cd (chromosomes 2, 18, 20, and X), Hg (chromosome 5), Se (chromosomes 4 and 8), and Zn {chromosome 2, near SLC11A1 [solute carrier family 11 (proton-coupled divalent metal ion transporters)]}. CONCLUSIONS: Although environmental exposure is a precondition for accumulation of toxic elements, individual characteristics and genetic factors are also important. Identification of the contributory genetic polymorphisms will improve our understanding of trace and toxic element uptake and distribution mechanisms.

Heritability and environmental factors affecting vitamin D status in rural Chinese adolescent twins.

CONTEXT: Factors associated with the high prevalence of vitamin D deficiency in China are not well described, especially among Chinese adolescents. OBJECTIVES: The aim of the study was to examine important environmental or sociodemographic factors influencing 25-hydroxyvitamin D [25(OH)D] levels and estimate its heritability. DESIGN: A sample of 226 male and female adolescent twins aged 13-20 yr from a large prospective twin cohort of rural Chinese children and adolescents that has been followed for 6 yr were evaluated. MAIN OUTCOME MEASURE(S): Blood level of 25(OH)D was measured using tandem mass spectrometry methodology. RESULTS: The overall mean (SD) 25(OH)D level was 18.0 (9.4) ng/ml, with wide variation by gender and season. In males (47.4% of subjects), the mean (SD) 25(OH)D level was 12.1 (4.2) ng/ml in non-summer and 27.4 (8.8) ng/ml in summer; in females, it was 10.1 (4.1) ng/ml in non-summer and 19.5 (6.3) ng/ml in summer. A multivariate model that included gender, age, season, physical activity, and student status demonstrated that male gender, summer season, and high physical activity significantly increased 25(OH)D levels. Summer season and male gender also significantly decreased the risk of being in the lowest 25(OH)D tertile. Overall, 68.9% of the variability in 25(OH)D level was attributable to additive genetic influence. Stratification by gender found that in males, 85.9% of the variability in 25(OH)D level was attributable to such influence, but in females, it was only 17%. CONCLUSION: In this sample of rural Chinese adolescents, 25(OH)D level was influenced by gender, season, and physical activity level. There was a strong genetic influence on 25(OH)D level in males only.

The effect of genetic variation in the type 1 deiodinase gene on the interindividual variation in serum thyroid hormone levels: an investigation in healthy Danish twins.

INTRODUCTION: Genetic factors have a considerable influence on serum thyroid hormone levels. The C785T and A1814G polymorphisms, located in the 3' untranslated region of the type 1 deiodinase (D1) gene have been associated with serum FT4 and rT3 levels. OBJECTIVE: In healthy Danish twins, we examined the association of these polymorphisms with serum thyroid hormone levels and determined the proportion of genetic influence explained by these variants. We analysed the underlying functional mechanism by performing mRNA stability measurements and analysed the effect of these variants on D1 activity. METHODS: Serum thyroid measurements and genotypes of the D1-C785T and D1-A1814G polymorphisms were determined in 1192 twins. Structural equation modelling was used to determine heritability estimates. Functional analyses were carried out in D1-transfected JEG3 cells. RESULTS: Carriers of the D1-785T allele had 3.8% higher FT4 and 14.3% higher rT3 levels, resulting in a lower T3/T4 and T3/rT3 ratio and a higher rT3/T4 ratio. This polymorphism explained 0.87% and 1.79%, respectively, of the variation in serum FT4 and rT3. The D1-A1814G polymorphism was not associated with serum thyroid hormone levels. No differences in D1 mRNA decay rate or D1 activity were observed between wild-type D1 and the two variants. CONCLUSION: The D1-C785T polymorphism is consistently and significantly associated with serum thyroid hormone levels. However, the proportion of genetic influence explained by this particular polymorphism is small. No effect of the polymorphism on D1 mRNA decay rate or D1 activity was observed. The underlying functional mechanism needs to be elucidated.

CD36 gene promoter polymorphisms are associated with low density lipoprotein-cholesterol in normal twins and after a low-calorie diet in obese subjects.

Common polymorphisms of the CD36 fatty acid transporter gene have been associated with lipid metabolism and cardiovascular disease. Association of a CD36 promoter single nucleotide polymorphism genotype with anthropometry and serum lipids was investigated in normal subjects, and in obese subjects during an 8-week low calorie diet and 6-month weight-maintenance period. 2728 normal female Twins UK subjects (mean body mass index 24.8 +/- 4.4 kg/m2; age 47.3 +/- 12.5 y) and 183 obese male and female Spanish subjects (mean body mass index 30.6 +/- 3.0 kg/m2; age 35.0 +/- 5.0 y) were genotyped for the CD36-22674 T/C (rs2151916) promoter single nucleotide polymorphism. In the Twins UK full cohort, the C-allele was associated with lower low density lipoprotein-cholesterol (p = .02, N = 2396). No associations were found in the obese Spanish subjects at baseline, but 6 months after the end of the low-calorie diet, the C-allele was associated with lower total- (p = .03) and low density lipoprotein-cholesterol (p = .01) and higher high density lipoprotein-cholesterol (p = .01). Intake of saturated fatty acids was lower in carriers of the C-allele at baseline, but not significantly so (p = .11). However, 6 months after the end of the low-calorie diet, elements of the lipid profile were correlated with saturated fatty acid intake: total cholesterol r = .21, p = .060; low density lipoprotein-cholesterol: r = .25, p = .043; high density lipoprotein-cholesterol: r = -.26, p = .007. CD36 promoter SNP allele -22674C is therefore associated with lower serum low-density lipoprotein-cholesterol in normal female twins and with improved lipid profile during weight loss and maintenance in obese subjects.

Second-trimester maternal serum free-beta-human chorionic gonadotropin and alpha-fetoprotein levels in normal twin and singleton pregnancies: a report of local Chinese population.

OBJECTIVES: The study evaluated the differences between Chinese normal twin and singleton pregnancies in the levels of maternal serum free-beta-human chorionic gonadotropin (free beta-hCG) and alpha-fetoprotein (AFP) used in second-trimester Down syndrome (DS) screening. METHODS: The concentrations of maternal serum markers of 456 twin pregnancies and 12 067 singleton controls in gestational 15 to 20 weeks were measured by time-resolved fluoroimmunoassay, and the levels of markers were compared between the twins and singletons. RESULTS: Significant differences were found between the levels of free beta-hCG in twins and twice of those in singletons in 16, 17 and 19 gestational weeks (p < 0.05 for all); while considering AFP, significant differences were found in 16 and 19 gestational weeks (p < 0.05 for both). No correlations were found in twins between the levels of markers and maternal weights in most gestational weeks (Free beta-hCG: p > 0.05 for 15 to 18 and 20 gestational weeks; AFP: p > 0.05 for 16 to 20 gestational weeks). CONCLUSIONS: The Chinese gestational age-specific levels of maternal serum markers in normal twins are not twice as those in singletons. The current weight-correction model for DS screening may be not feasible for twins.

Cerebral white matter in early puberty is associated with luteinizing hormone concentrations.

Puberty is a period in which cerebral white matter grows considerably, whereas gray matter decreases. The first endocrinological marker of puberty in both boys and girls is an increased secretion of luteinizing hormone (LH). Here we investigated the phenotypic association between LH, global and focal gray and white matter in 104 healthy nine-year-old monozygotic and dizygotic twins. Volumetric MRI and voxel-based morphometry were applied to measure global gray and white matter and to estimate relative concentrations of regional cerebral gray and white matter, respectively. A possible common genetic origin of this association (genetic correlation) was examined. Results showed that higher LH levels are associated with a larger global white matter proportion and with higher regional white matter density. Areas of increased white matter density included the cingulum, middle temporal gyrus and splenium of the corpus callosum. No association between LH and global gray matter proportion or regional gray matter density was found. Our data indicate that a common genetic factor underlies the association between LH level and regional white matter density. We suggest that the increase of white matter growth during puberty reported earlier might be directly or indirectly mediated by LH production. In addition, genes involved in LH production may be promising candidate genes in neuropsychiatric illnesses with an onset in early adolescence.

Maternal circulating endothelial progenitor cells in normal singleton and twin pregnancy.

OBJECTIVE: The objective of the study was to determine the levels of circulating endothelial progenitor cells (EPCs), which are peripheral blood mononuclear cells (PBMNCs) that contribute to vascular repair in normal pregnancy. STUDY DESIGN: The concentration of EPCs in maternal blood was measured in healthy nonpregnant women (group A, n = 8), normal singleton pregnancies (group B, n = 24), and normal twin pregnancies (group C, n = 21). RESULTS: In group A, the mean (SD) level of EPCs was 77.0% (8.6%) adherent PBMNCs. In group B, the mean level was lower than in group A and decreased with gestation from 61.3% (14.9%) in the first trimester to 56.0% (16.2%) in the second trimester and 52.0% (8.7%) in the third trimester (P = .001). Similarly, the level of EPCs in group C was lower than in group A and decreased with gestation from 64.6% (9.6%) in the first trimester to 65.2% (12.7%) in the second trimester and 56.4% (12.6%) in the third trimester (P = .002). CONCLUSION: Normal pregnancy is associated with a decrease in maternal circulating levels of EPCs.

[Study on the activity of serum bone alkaline phosphatase and its relations to the heritability among pre-puberty twins].

OBJECTIVE: To evaluate calcium deficiency and demand in pre-puberty twins and to analyze the heritability of serum bone alkaline phosphatase (BALP). METHODS: A total of 73 pairs of twins aged 9-16 years were examined by BALP test. Microsatellite polymorphism was used to diagnose the zygosity of twins, while both intraclass correlation coefficient method and Christian formula were performed to investigate heritability of serum BALP. RESULTS: The results of zygosity diagnosis displayed that 34 pairs of twins were monozygotic (MZ) twins and 39 pairs were dizygotic (DZ) twins. 97.9% of the subjects appeared unusual in the activity of BALP, with activity of BALP > 250 U/L in 43.1% of subjects and 200-250 U/L in 54.8% of the subjects. The intake of calcium was unsatisfied in 48.4% of the boys and 39.0% in girls. Less than 10.0% of the subjects were satisfied with the intake of calcium in each age group while over 45.0% of the subjects in 10-13 age group were deficient in calcium. Differences between the means of BALP in different sex groups (t = 1.633, P = 0.105) and different age groups (F = 0.323, P = 0.924) were not statistically significant. Heritability analysis displayed that intra-class variation, inter-class variation, intra-class correlation coefficient were 191.54, 1462.22, 0.77 in MZ twins, and those were 491.03, 1475.57, 0.50 in DZ twins respectively with the heritability of BALP activity as 0.54. CONCLUSION: Calcium deficiency is commonplace in pre-puberty twins. Our data showed that the BALP activity was influenced both by genetic (54%) and environmental (46%) factors.

[Analysis on the association between two polymorphism haplotypes of lipoprotein lipase gene and serum lipids in twins of China].

OBJECTIVE: To investigate the association between haplotypes of S447X and Hind III polymorphisms of lipoprotein lipase (LPL) gene and serum lipids in a population-based twin cohort study in China. METHODS: Twin subjects were collected based on the twin registry system of China. All twins were investigated by a standard questionnaire and physical examinations. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to detect the genotypes of S447X and Hind III polymorphisms. Linkage disequilibrium test and haplotypes were estimated between two polymorphisms. RESULTS: Nine hundred and eighty-seven pairs of twins were eligible for analysis. The two polymorphisms of LPL gene were significantly linkage disequilibrium. In female twins, the H- allele of Hind III polymorphism was significantly related to lower levels of triglycerides(TG) and lower risk of high TG dislipidemia, but those associations disappeared after adjusting the polymorphism of S447X. The H- X haplotype of those two polymorphisms was significantly related to lower TG and TG/HDL (decreasing 12.9% and 14.9% respectively), as well as significantly to lower risk of high TG dislipidemia (OR = 0.40). CONCLUSION: The haplotypes of S447X and Hind III polymorphisms were significantly related to the favorable effect of lipids,but this effect was mostly determined by the polymorphism of S447X, while the effect of Hind III polymorphism was indirectly influenced by the linkage disequilibrium with S447X polymorphism.

Heritability of longitudinal measures of body mass index and lipid and lipoprotein levels in aging twins.

Body-mass index (BMI), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels are known to be highly heritable. We evaluated the genetic and environmental relationships of these measures over time in an analysis of twin pairs. Monozygotic (235 pairs) and dizygotic (260 pairs) male twins were participants in the National Heart Lung and Blood Institute Veteran Twin Study, and were followed with three clinical exams from mean age 48 years to mean age 63 years. Structural equation modeling (SEM) with adjustment for APOE genotype (a significant contributor to TC and LDL-C) was used to assess longitudinal patterns of heritability. Results indicated a contribution of genetic factors to BMI, TC, LDL-C, HLD-C, and TG. Modest increases over time were observed in the heritability of BMI (from 0.48 to 0.61), TC (from 0.46 to 0.57), LDL-C (from 0.49 to 0.64), and HDL-C (from 0.50 to 0.62), but this trend was not present for TG. There was a corresponding decrease in shared environmental influences over time for these traits, although shared environment was a significant contributor only for HDL-C. Moreover, we observed that genetic influences for all measures were significantly correlated over time, and we found no evidence of age-specific genetic effects. In summary, longitudinal analyses of twin data indicate that genetic factors do not account for a significant proportion of the variation in age-related changes of BMI or lipid and lipoprotein levels.

Evidence of genetic effects on blood lead concentration.

BACKGROUND: Lead is an environmental pollutant that causes acute and chronic toxicity. Surveys have related mean blood lead concentrations to exogenous sources, including industrial activity, use of lead-based paints, or traffic density. However, there has been little investigation of individual differences in lead absorption, distribution, or toxicity, or of genetic causes of such variation. OBJECTIVES: We assessed the genetic contribution to variation in blood lead concentration in adults and conducted a preliminary search for genes producing such variation. METHODS: Erythrocyte lead concentration was measured by inductively coupled plasma mass spectrometry in venous blood samples from 2,926 Australian adult male and female twins. Mean lead concentrations were compared by place of residence, social class and education, and by the subjects' age, sex, alcohol intake, smoking habits, iron status, and HFE genotype. RESULTS: After adjustment for these covariates, there was strong evidence of genetic effects but not for shared environmental effects persisting into adult life. Linkage analysis showed suggestive evidence (logarithm of odds = 2.63, genome-wide p = 0.170) for a quantitative trait locus affecting blood lead values on chromosome 3 with the linkage peak close to SLC4A7, a gene whose product affects lead transport. CONCLUSIONS: We conclude that genetic variation plays a significant role in determining lead absorption, lead distribution within the body, or both.

A longitudinal genetic study of plasma lipids in adolescent twins.

Plasma lipids such as high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol and triglyceride levels contribute to variation in the risk of cardiovascular disease. The early stages of atherosclerosis in childhood have also been associated with changes in triglycerides, LDL and HDL. Heritability estimates for lipids and lipoproteins for adolescents are in the range .71 to .82, but little is known about changes of genetic and environmental influences over time in adolescence. We have investigated the contribution of genetic and environmental influences to variation in lipids in adolescent twins and their nontwin siblings using longitudinal twin and family data. Plasma HDL and LDL cholesterol, total cholesterol and triglycerides data from 965 twin pairs at 12, 14 and 16 years of age and their siblings have been analyzed. Longitudinal genetic models that included effects of age, sex and their interaction were fitted to assess whether the same or different genes influence each trait at different ages. Results suggested that more than one genetic factor influences HDL, LDL, total cholesterol and triglycerides over time at ages 12, 14 and 16 years. There was no evidence of shared environmental effects except for HDL and little evidence of long-term nonshared environmental effects was found. Our study suggested that there are developmental changes in the genes affecting plasma lipid concentrations across adolescence.

[Change of dehydroepiandrosterone in serum of 6 - 18 year-old twin girls in Qingdao City].

OBJECTIVE: To explore the change of serum dehydroepiandrosterone (DHEAS) concentrations throughout the puberty of girls and estimate the effects of genetic and environmental factors on serum DHEAS. METHODS: The study population consists of 360 girls aged 6 to 18 years:132 pairs monozygotic twins and 48 pairs dizygotic twins, who were all from Qingdao city, Shan-dong province. Anthropometric measurement and pubertal development stage were determined by Tanner standard, fasting serum DHEAS contents were assayed by RIA. RESULTS: Serum DHEAS concentrations increased from Tanner I to IV and decreased later, heritability of pubertal girl's serum DHEAS was 0.65. The heritability of 3 different pubertal stages (pre-thelarche, post-thelarche and pre-menarche, and post-menarche) were 0.92, 0.73 and 0.67 respectively. CONCLUSION: Serum DHEAS concentrations of pubertal girls could be mainly influenced by the genetic factors, especially in the period of adrenarche. Therefore, genetic influence might be important in adrenarche-related metabolic disorders.