Associations between birth size and later height from infancy through adulthood: An individual based pooled analysis of 28 twin cohorts participating in the CODATwins project

BACKGROUND

There is evidence that birth size is positively associated with height in later life, but it remains unclear whether this is explained by genetic factors or the intrauterine environment.

AIM

To analyze the associations of birth weight, length and ponderal index with height from infancy through adulthood within mono- and dizygotic twin pairs, which provides insights into the role of genetic and environmental individual-specific factors.

METHODS

This study is based on the data from 28 twin cohorts in 17 countries. The pooled data included 41,852 complete twin pairs (55% monozygotic and 45% same-sex dizygotic) with information on birth weight and a total of 112,409 paired height measurements at ages ranging from 1 to 69 years. Birth length was available for 19,881 complete twin pairs, with a total of 72,692 paired height measurements. The association between birth size and later height was analyzed at both the individual and within-pair level by linear regression analyses.

RESULTS

Within twin pairs, regression coefficients showed that a 1-kg increase in birth weight and a 1-cm increase in birth length were associated with 1.14-4.25 cm and 0.18-0.90 cm taller height, respectively. The magnitude of the associations was generally greater within dizygotic than within monozygotic twin pairs, and this difference between zygosities was more pronounced for birth length.

CONCLUSION

Both genetic and individual-specific environmental factors play a role in the association between birth size and later height from infancy to adulthood, with a larger role for genetics in the association with birth length than with birth weight.

Heritability of arterial stiffness and carotid intima-media thickness: an Italian twin study

BACKGROUND AND AIMS

Carotid intima-media thickness (IMT) and arterial stiffness parameters, including aortic augmentation index (AIx) and pulse wave velocity (PWV), are independent predictors of stroke and cardiovascular disease. Genetic effects on these traits were never explored in a Mediterranean country. The present study aims to quantify the contribution of genes, environment and age to carotid IMT and aortic Aix and PWV.

METHODS AND RESULTS

The twin design was used. A total of 348 adult twins from the Italian Twin Register underwent measurements of carotid IMT and aortic PWV and AIx in three university hospitals located in Rome, Padua and Perugia. Carotid IMT was measured by B-mode ultrasound, aortic PWV and AIx by Arteriograph. Genetic modelling was performed to decompose total variance of traits into genetic, shared and unshared environmental and age components. For each phenotype, the best-fitting model included additive genetic, unshared environmental and age effects. For IMT, heritability was 0.32 (95% confidence interval (CI): 0.25-0.38), unshared environmental component was 0.25 (0.18-0.32) and age contribution was 0.44 (0.39-0.49). For AIx and PWV, heritabilities were 0.42 (0.29-0.55) and 0.49 (0.35-0.62), unshared environmental components were 0.31 (0.22-0.44) and 0.37 (0.26-0.51) and age contributions were 0.27 (0.16-0.39) and 0.14 (0.06-0.24), respectively.

CONCLUSION

This study shows substantial genetic and unshared environmental influences on carotid intima-media thickness and arterial stiffness and confirms the relevant role of age in the aetiology of these traits. Further support is provided for prevention and health promotion strategies based on modifiable factors.

Minimal incidence of neonatal/infancy onset diabetes in Italy is 1:90,000 live births

Until early 2000, permanent and transient neonatal diabetes mellitus (NDM), defined as diabetes with onset within 6 weeks from birth that requires insulin therapy for at least 2 weeks, were considered exceedingly rare conditions, with a global incidence of 1:500,000-1:400,000 live births. The new definition of NDM recently adopted, that includes patients with diabetes onset within 6 months of age, has prompted studies that have set the incidence of the permanent form alone between 1:210,000 and 1:260,000 live births. Aim of the present work was to ascertain the incidence of NDM (i.e. permanent + transient form) in Italy for years 2005-2010. Patients referred to the Italian reference laboratory for NDM between years 2005 and 2010 and screened for mutations in common NDM genes (KCNJ11, ABCC8, and INS) and for uniparental isodisomy of chromosome 6 (UDP6) were reviewed. A questionnaire aimed at identifying NDM cases investigated in other laboratories was sent to 54 Italian reference centers for pediatric diabetes. Twenty-seven patients with NDM born between 2005 and 2010 were referred to the reference laboratory. In this group, a mutation of either KCNJ11, ABCC8 or INS was found in 18 patients, and a case with UDP6 was identified. Questionnaires revealed 4 additional cases with transient neonatal diabetes due to UDP6. Incidence of NDM was calculated at 1:90,000 (CI: 1:63,000-1:132,000) live births. Thus, with the definition currently in use, about 6 new cases with NDM are expected to be born in Italy each year.

Permanent diabetes during the first year of life: multiple gene screening in 54 patients

AIMS/HYPOTHESIS

The aim of this study was to investigate the genetic aetiology of permanent diabetes mellitus with onset in the first 12 months of age.

METHODS

We studied 46 probands with permanent, insulin-requiring diabetes with onset within the first 6 months of life (permanent neonatal diabetes mellitus [PNDM]/monogenic diabetes of infancy [MDI]) (group 1) and eight participants with diabetes diagnosed between 7 and 12 months of age (group 2). KCNJ11, INS and ABCC8 genes were sequentially sequenced in all patients. For those who were negative in the initial screening, we examined ERN1, CHGA, CHGB and NKX6-1 genes and, in selected probands, CACNA1C, GCK, FOXP3, NEUROG3 and CDK4. The incidence rate for PNDM/MDI was calculated using a database of Italian patients collected from 1995 to 2009.

RESULTS

In group 1 we found mutations in KCNJ11, INS and ABCC8 genes in 23 (50%), 9 (19.5%) and 4 (8.6%) patients respectively, and a single homozygous mutation in GCK (2.1%). In group 2, we identified one incidence of a KCNJ11 mutation. No genetic defects were detected in other loci. The incidence rate of PNDM/MDI in Italy is estimated to be 1:210,287.

CONCLUSIONS/INTERPRETATION

Genetic mutations were identified in ~75% of non-consanguineous probands with PNDM/MDI, using sequential screening of KCNJ11, INS and ABCC8 genes in infants diagnosed within the first 6 months of age. This percentage decreased to 12% in those with diabetes diagnosed between 7 and 12 months. Patients belonging to the latter group may either carry mutations in genes different from those commonly found in PNDM/MDI or have developed an early-onset form of autoimmune diabetes.

Serum elements and oxidative status in clinically isolated syndromes: imbalance and predictivity

BACKGROUND

Metals are suspected of being involved in the pathogenesis of various neurologic diseases. We previously found a complex imbalance in serum chemical elements and oxidative status in patients with clinically definite multiple sclerosis (CDMS).

OBJECTIVE

To understand whether this imbalance affects people with clinically isolated syndrome (CIS) and, if so, whether it predicts conversion to CDMS.

METHODS

We studied 22 chemical elements and the oxidative status in 49 patients with CIS, 49 patients with CDMS, and 49 healthy donors (HD). Univariate and multivariate approaches were used to identify profiles for each group. A logistic regression analysis was used to identify the predictive potential of baseline data (elements, oxidative status, and MRI findings) for conversion to CDMS over 36 months.

RESULTS

Several elements and oxidative status values differed significantly among the 3 groups. Discriminant analysis revealed a major contribution of Ca, Fe, Sn, Zn, serum antioxidant capacity, and serum oxidative status, which resulted in distinct profiles (the prediction of group membership was 96% [cross-validated 92%] for HD, 92% [cross-validated 92%] for CDMS, and 90% [cross-validated 86%] for CIS). A weighted combination of element concentrations and oxidative status values, adjusting for all other predictors, would predict a reduction in the risk of conversion to CDMS within 3 years (odds ratio 0.37; 95% confidence interval 0.18-0.76; p = 0.007), thereby proving more effective than MRI at baseline.

CONCLUSIONS

The peculiar imbalance in serum elements and oxidative status that characterizes patients with CIS and may predict conversion to CDMS warrants studies on larger sample sizes.

Teratogenic effects of antiepileptic drugs: use of an International Database on Malformations and Drug Exposure (MADRE)

PURPOSE

The study goal was to assess teratogenic effects of antiepileptic drugs (AEDs) through the use of a surveillance system (MADRE) of infants with malformations.

METHODS

Information on all malformed infants (1990-1996) with maternal first-trimester drug exposure was collected by the International Clearinghouse for Birth Defects and Monitoring Systems (ICBDMS). Cases were defined as infants presenting with a specific malformation, and controls were defined as infants presenting with any other birth defect. Exposure was defined by the use of AEDs during the first trimester of pregnancy. The association of AEDs with malformations was then estimated by calculating the odds ratios with 95% confidence intervals and testing their homogeneity among registries.

RESULTS

Among 8005 cases of malformations, 299 infants were exposed in utero to AEDs. Of those exposed to monotherapy, 65 were exposed to phenobarbital, 10 to methylphenobarbital, 80 to valproic acid, 46 to carbamazepine, 24 to phenytoin, and 16 to other AEDs. Associations were found for spina bifida with valproic acid. Infants exposed to phenobarbital and to methylphenobarbital showed an increased risk of oral clefts. Cardiac malformations were found to be associated with phenobarbital, methylphenobarbital, valproic acid, and carbamazepine. Hypospadias was associated with valproic acid. Porencephaly and other specified anomalies of brain, anomalies of face, coarctation of aorta, and limb reduction defects were found to be associated with valproic acid.

CONCLUSIONS

Using the MADRE system, we confirmed known teratogenic effects of AEDs. We also found increased risks for malformations that had never been reported associated with AEDs or for which the association was suggested by case reports.

Regional differences in known risk factors and the higher incidence of breast cancer in San Francisco

BACKGROUND

The age-adjusted incidence of breast cancer in the San Francisco Bay Area has consistently been higher than that in other regions of the United States. The distribution of established risk factors for breast cancer (i.e., parity, age at first full-term pregnancy, breast-feeding, age at menarche, and age at menopause) and probable risk factors (e.g., alcohol consumption) also differs across geographic regions.

PURPOSE

A study was planned to explore the extent to which differences in the regional distribution of established and probable risk factors could explain the increased incidence of breast cancer in the San Francisco Bay Area.

METHODS

Age-adjusted breast cancer incidence rates for January 1978 through December 1982 were obtained for the San Francisco Bay Area and other regions from the Surveillance, Epidemiology, and End Results (SEER) Program. Risk factor data from January 1980 through December 1982 were computed from the Cancer and Steroid Hormone Study, a population-based, case-control study of women 22-55 years of age who resided in eight SEER regions. Two different statistical methods were used to compute the relative risk (RR) of breast cancer associated with residence in the San Francisco Bay Area versus other regions, after adjusting for regional differences in known risk factors.

RESULTS

Substantial differences in the distribution of breast cancer risk factors were found between the San Francisco Bay Area and other regions. Nearly all of these differences would be expected to lead to an elevated incidence of breast cancer in the San Francisco Bay Area. With the use of incidence rates adjusted only for age, the RR for San Francisco Bay Area residence from January 1978 through December 1982 compared with residence in seven other SEER areas was 1.14 for white women and 1.10 for black women. Depending on the statistical method used, the RR was reduced to approximately 0.96-0.99 for white women and 0.75-0.83 for black women, after further adjusting for established and probable risk factors (parity, age at first full-term pregnancy, breast-feeding, age at menarche, age at menopause, and alcohol consumption). Without adjustment for alcohol consumption, the corresponding results were 0.97-1.02 for white women and 0.77-0.88 for black women.

CONCLUSIONS

Among both white women and black women, the elevated breast cancer incidence rate in the San Francisco Bay Area can be completely accounted for by regional differences in known risk factors.