Parathyroid hormone contributes to regulating milk calcium content and modulates neonatal bone formation cooperatively with calcium

To determine whether PTH and calcium (Ca) interact in neonatal bone formation, female lactating mice either heterozygous (PTH(+/-)) or homozygous (PTH(-/-)) for targeted deletion of the pth gene were fed either a normal (1% Ca, 0.6% phosphate) or high-Ca diet (2% Ca and 0.4% phosphate). Dietary effects on milk Ca content and Ca-regulating hormones were determined in dams, and the effects of milk content were assessed on bone turnover in 3-wk-old pups. On the normal diet, milk Ca and 1,25-dihydroxyvitamin D(3) levels were lower, but milk PTH-related protein levels were higher in the PTH(-/-) dams compared with the PTH(+/-) dams. On the high-Ca diet, milk Ca levels were higher, but milk 1,25-dihydroxyvitamin D(3) and PTH-related protein levels were lower in both PTH(+/-) and PTH(-/-) dams. In pups fed by PTH(-/-) dams compared with pups fed by PTH(+/-) dams on normal diets, bone mineral density, trabecular bone volume relative to tissue volume, and the number of osteoblasts were reduced in both PTH(+/-) (32.5 +/- 1.2 vs. 39.6 +/- 1.5 mg/cm(2), P < 0.05; 23.3 +/- 1.6 vs. 29.2 +/- 2.8%, P < 0.01; and 94.2 +/- 8.2 vs. 123.5 +/- 3.5/mm(2), P < 0.01, respectively) and PTH(-/-) (20.4 +/- 0.9 vs. 27.0 +/- 1.2 mg/mm(2), P < 0.05; 16.8 +/- 1.9 vs. 19.3 +/- 2.1%, P < 0.05; and 48.6 +/- 7.9 vs. 90.5 +/- 8.6/mm(2), P < 0.01, respectively) pups but were lower in the PTH(-/-) pups compared with the PTH(+/-) pups. In contrast, in pups fed by either PTH(+/-) or PTH(-/-) dams on the high-Ca diet, bone mineral density, bone volume/tissue volume, and osteoblast numbers were significantly higher, in both PTH(+/-) (50.5 +/- 1.7 vs. 58.7 +/- 2.0 mg/mm(2), P < 0.05; 37.9 +/- 5.2 vs. 46.1 +/- 5.1, P < 0.05; and 120.5 +/- 9.2 vs. 159.3 +/- 14.7/mm(2), P < 0.01, respectively) and PTH(-/-) (33.0 +/- 1.2 vs. 47.5 +/- 2.2 mg/mm(2), P < 0.001; 23.8 +/- 3.1 vs. 35.9 +/- 2.0, P < 0.05; and 78.7 +/- 10.1 vs. 99.8 +/- 13.6/mm(2), P < 0.05, respectively), and were highest in the PTH(+/-) pups fed by the PTH(+/-) dams on the high-Ca diet. These results indicate that PTH can modulate Ca content of milk, and that PTH and Ca can each exert cooperative roles on osteoblastic bone formation in the neonate.

Genetic influences on growth and body composition in mice: multilocus interactions

BACKGROUND

The genetic architecture of body weight and body composition is complex because these traits are normally influenced by multiple genes and their interactions, even after controlling for the environment. Bayesian methodology provides an efficient way of estimating these interactions.

SUBJECTS AND MEASUREMENTS

We used Bayesian model selection techniques to simultaneously estimate the main effects, epistasis and gene-sex interactions on age-related body weight (at 3, 6 and 10 weeks, denoted as WT3wk, WT6wk and WT10wk) and body composition (organ weights and fat-related traits) in an F(2) sample obtained from a cross between high-growth (M16i) mice and low-growth (L6) mice.

RESULTS

We observed epistatic and main-effect quantitative trait loci (QTL) that controlled both body weight and body composition. Epistatic effects were generally more significant for WT6wk than WT10wk. Chromosomes 5 and 13 interacted strongly to control body weight at 3 weeks. A pleiotropic QTL on chromosome 2 was associated with body weight and some body composition phenotypes. Testis weight was regulated by a QTL on chromosome 13 with a significantly large main effect (2log(e)BF approximately 15).

CONCLUSION

By analyzing epistatic interactions, we detected QTL not found in a previous analysis of this mouse population. Hence, the detection of gene-gene interactions may provide new information about the genetic architecture of complex obesity-related traits and may lead to the detection of additional obesity genes.

Children developing type 1 diabetes before 6 years of age have increased linear growth independent of HLA genotypes

AIMS/HYPOTHESIS

High birthweight and increased childhood growth are risk factors for type 1 diabetes. Relative birthweight is associated with HLA genotypes that confer a high risk of diabetes. Our aims were to test whether young children prior to clinical onset of type 1 diabetes have increased: (1) birthweight or birth length standard deviation scores (SDS); (2) height development SDS; or (3) BMI SDS during first 18 months of life and whether these parameters are related to HLA genotypes or mid-parental height (MPH).

METHODS

Birthweight, birth length, weight and height were obtained from 58 type 1 diabetes children and 155 controls matched for HLA or not in the Diabetes Prediction in Skåne study.

RESULTS

Birth length SDS corrected for MPH was increased in children developing diabetes compared with all (p < 0.048) and with non-HLA- (p < 0.050) but not with HLA-matched controls. Children developing diabetes had increased height gain at 0 to 18 months of age (p < 0.005). Diabetic children were significantly taller from 6 to 18 months of age when correcting for MPH compared with non-HLA-matched as well as HLA-matched controls, but BMI was not increased.

CONCLUSIONS/INTERPRETATION

Birth length SDS was associated with diabetes risk HLA. When corrected for MPH, children developing diabetes were taller at birth than non-HLA- but not taller than HLA-matched controls. Diabetic children had increased MPH-corrected height up to 18 months of age compared with both HLA- and non-HLA-matched controls. High-risk HLA affects prenatal growth, but other factors may explain the increased postnatal linear growth in children developing diabetes.

Association analysis of the IGF1 gene with childhood growth, IGF-1 concentrations and type 1 diabetes

AIMS/HYPOTHESIS

Insulin-like growth factor-1 is a major childhood growth factor and promotes pancreatic islet cell survival and growth in vitro. We hypothesised that genetic variation in IGF1 might be associated with childhood growth, glucose metabolism and type 1 diabetes risk. We therefore examined the association between common genetic variation in IGF1 and predisposition to type 1 diabetes, childhood growth and metabolism.

MATERIALS AND METHODS

Variants in IGF1 were identified by direct resequencing of the exons, exon-intron boundaries and 5' and 3' regions in 32 unrelated type 1 diabetes patients. A tagging subset of these variants was genotyped in a collection of type 1 diabetes families (3,121 parent-child trios). We also genotyped a previously reported CA repeat in the region 5' to IGF1. A subset of seven tag single nucleotide polymorphism (SNPs) that captured variants with minor allele frequency (MAF) > or =0.05 was genotyped in 902 children from the Avon Longitudinal Study of Parents And Children with data on growth, IGF-1 concentrations, insulin secretion and insulin action.

RESULTS

Resequencing detected 27 SNPs in IGF1, of which 11 had a MAF > 0.05 and were novel. Variants with MAF > or = 0.10 were captured by a set of four tag-SNPs. These SNPs showed no association with type 1 diabetes. In children, global variation in IGF1 was weakly associated with IGF-1 concentrations, but not with other phenotypes. The CA repeat in the region 5' to IGF1 showed no association with any phenotype.

CONCLUSIONS/INTERPRETATION

Common genetic variation in IGF1 alters IGF-1 concentrations but is not associated with growth, glucose metabolism or type 1 diabetes.

Abnormal sex chromosome constitution and longitudinal growth: serum levels of insulin-like growth factor (IGF)-I, IGF binding protein-3, luteinizing hormone, and testosterone in 109 males with 47,XXY, 47,XYY, or sex-determining region of the Y chromosome (SRY)-positive 46,XX karyotypes

CONTEXT

Growth is a highly complex process regulated by the interaction between sex steroids and the GH IGF-axis. However, other factors such as sex chromosome-related genes play independent roles.

AIM

The aim of the study was to evaluate the role of abnormal chromosome constitution for longitudinal growth in relation to reproductive hormones, IGF-I, and IGF binding protein (IGFBP)-3.

SETTING

The study was conducted at an outpatient clinic, Copenhagen University Hospital.

PARTICIPANTS

Participants included 86 47,XXY males, 14 46,XX-males, and nine 47,XYY.

MAIN OUTCOME MEASURES

Standing and sitting height, serum levels of reproductive hormones, IGF-I, and IGFBP-3 were measured.

RESULTS

In boys with 47,XXY and 47,XYY karyotypes, growth was accelerated already in childhood, compared with healthy boys. 46,XX-males were significantly shorter than healthy boys but matched the stature of healthy girls. In 47,XXY sitting height to height ratios were lower than expected, whereas body proportions in 46,XX-males and 47,XYY were normal. In all subjects serum levels of IGF-I and IGFBP-3 were within normal limits. The boys with 46,XX and 47,XXY karyotypes presented with low normal testosterone and elevated LH levels after puberty, whereas the sex hormone secretion of the 47,XYY boys remained normal.

CONCLUSION

We found accelerated growth in early childhood in boys with 47,XXY and 47,XYY karyotypes, whereas 46,XX-males were shorter than controls. These abnormal growth patterns were not reflected in circulating levels of IGF-I and IGFBP-3. The boys with 46,XX and 47,XXY karyotypes developed hypogonadism in puberty, but androgen secretion in 47,XYY boys remained normal. The abnormal stature of these patients may be a result of abnormal gene expression due to the underlying chromosome aberration resulting in excessive expression of growth-related genes.

The role of genes in growth and later health

Genetic factors are of importance for the development of the metabolic syndrome and type 2 diabetes, but despite extensive research the identification of the underlying genes has not been fruitful. This report focuses on the interactions between intrauterine growth and genes in relation to adult health outcomes based upon findings from the Helsinki Birth Cohort Study. Candidate genes for type 2 diabetes and the metabolic syndrome have been focused upon and we report on interactions between polymorphisms of the peroxisome proliferator-activated receptor (PPAR)gamma-2, plasma cell glycoprotein (PC-1) and the glucocorticoid receptor (GR) genes and - prenatal growth in relation to adult health outcomes. In elderly individuals the effects of the Pro12Pro/Pro12Ala polymorphisms of the PPARgamma-2 gene depend on their body size at birth. Individuals, who had a small body size at birth and were carriers of the Ala allele, seem to be protected against insulin resistance and type 2 diabetes in later life. Similar gene environment interactions will be described in relation to the PC-1 and the GR genes. We propose that these findings reflect gene-early environment interactions and can be attributed to the phenomenon of developmental plasticity.

Growth pattern and risk of schizophrenia

BACKGROUND

Foetal nutrition and growth seem to affect the risk of developing schizophrenia. Exposure to famine during foetal development and low birthweight increase the risk. However, few studies have investigated the association between schizophrenia and adult height and weight or patterns of growth.

METHOD

The study population consisted of two subpopulations: families with at least one member with schizophrenia, and families of offspring of mothers with psychotic disorder, and controls. Using a seven-parameter model of height growth curves, we compared the parameters of persons who later developed schizophrenia and their unaffected siblings from the same families. We also studied how growth curve parameters differed in children with genetic risk for schizophrenia and controls, and whether weight, height and body mass index (BMI) at different ages predicted later development of schizophrenia.

RESULTS

The predicted growth curves based on a parametric model were nearly identical for persons with schizophrenia and their unaffected siblings. Adult height of daughters of mothers with psychoses was borderline significantly (p=0.0536) lower compared to controls, while no difference was detected among sons (p=0.3283).

CONCLUSIONS

No association between growth characteristics and schizophrenia in families with at least one member with schizophrenia was found. Family-related factors should be taken into account as possible confounders in future studies on growth and schizophrenia.

In silico exploration of the effects of host genotype and nutrition on the genetic parameters of lambs challenged with gastrointestinal parasites

An in silico mathematical model was used to explore the effect of, and the interaction between, (i) nutrition, (ii) genotype for growth and (iii) genotype for resistance, on the estimates of genetic parameters for resistance and performance in a population of lambs trickle-challenged daily with 3,000 L3s of Teladorsagia circumcincta. A previously published model for nematode infections in sheep was developed to include heritable variation in sheep growth traits, as well as in immunologically controlled traits such as establishment of incoming larvae, mortality of the adult worms and fecundity of the adult female worms. The simulated population comprised 10,000 lambs, these being the offspring of 250 sires mated to 5,000 dams. The model assumed the lambs to be parasitologically naïve at weaning (2 months of age), at which point the trickle challenge commenced and the model was updated daily until slaughter (at 6 months of age). Dietary treatments included a good and a poor quality feed, offered ad libitum. Two genotypes for growth were assumed: (i) fast and (ii) slow growing. Three genotypes for resistance were used: (i) benchmark, (ii) susceptible and (iii) resistant, differing in their ability to cope with nematode infections. Genetic parameters for output traits, including growth rate, food intake, worm burden and faecal egg count were estimated using a linear mixed model, fitting sire as a random effect to capture genetic effects. Heritabilities and correlations were found to change over time. In general, the heritabilities of immunity traits increased over time, whereas genetic correlations between production and immunity traits became weaker. Diet had a significant effect on the means and the estimated correlations of output traits, while genotypes for growth and resistance had smaller effects. These results suggest that discrepancies between published genetic parameters for nematode resistance may be a function of environmental factors rather than differences in host genotype.

The 23K variant of the R23K polymorphism in the glucocorticoid receptor gene protects against postnatal growth failure and insulin resistance after preterm birth

CONTEXT

Preterm birth is associated with postnatal growth failure, abdominal fat accumulation, insulin resistance, and hypertension, resembling increased glucocorticoid bioactivity.

OBJECTIVE

We tested the effects of the R23K and N363S polymorphisms in the glucocorticoid receptor gene, associated with decreased and increased sensitivity to cortisol, respectively, on linear growth and the adult metabolic profile in a cohort (n = 249) of men and women born less than 32 gestational weeks and followed up prospectively from birth until 19 yr of age.

DESIGN AND PARTICIPANTS

This was a birth cohort study that included 249 19-yr-old survivors born at a gestational age less than 32 wk from the Dutch Project on Preterm and Small-for-Gestational-Age Infants cohort.

SETTING

This project was a nationwide multicenter follow-up study.

MAIN OUTCOME MEASURES

Linear growth and adult body composition, fasting cortisol, glucose, insulin, and cholesterol concentrations, and blood pressure were measured.

RESULTS

The 23K variant (n = 24) was associated with lower fasting insulin levels [mean difference after log transformation: -0.09 (95% confidence interval -0.16, -0.01) mU/liter] and a lower homeostatic model assessment for insulin resistance index [mean difference after log transformation: -0.09 (95% confidence interval -0.16, -0.01)] as well as with a taller stature departing from the age of 1 yr onward. 23K carriers showed complete catch-up growth between the ages of 3 months and 1 yr, and attained height was similar to the population reference mean, whereas stature in noncarriers was on average 0.5 sd below this mean. In contrast, the N363S polymorphism was not associated with any of the outcomes.

CONCLUSIONS

Carriers of the 23K variant are, at least in part, protected against postnatal growth failure and insulin resistance after preterm birth.

Effects of quantitative trait loci on chromosomes 1, 2, 4, and 7 on growth, carcass, and meat quality traits in backcross Meishan x Large White pigs

The aim of this work was to estimate whether genetic dissection of QTL on chromosomes 1, 2, 4, and 7, detected in an F2 Meishan x Large White population, can be achieved with a recombinant back-cross progeny test approach. For this purpose, a first generation of backcross (BC1) was produced by using frozen semen of F1 Large White x Meishan boars with Large White females. Four BC1 boars were selected because of their heterozygosity for at least 1 of the 4 regions. The BC1 boars were crossed with Large White sows, and the resulting BC2 offspring were measured for several growth and body composition traits. Contrary to the F2 animals, BC2 animals were also measured for meat quality traits in adductor, gluteus superficialis (GS), longissimus dorsi, and biceps femoris (BF) muscles. Each BC1 boar was tested for a total of 39 traits and for the 4 regions with statistical interval mapping analyses. The QTL effects obtained in BC1 families showed some differences compared with those described in F1 families. However, we confirmed QTL effects for growth in the SW1301-SW2512 markers interval on chromosome 1 and also for body composition in the SW1828-SW2512 markers interval on chromosome 1, in the SW2443-SWR783 markers interval on chromosome 2, and in the SW1369-SW632 markers interval on chromosome 7. In addition, we detected new QTL for growth traits on chromosome 2 and for meat quality traits on chromosomes 1 and 2. Growth of animals from weaning to the end of the test was influenced by the IGF2 gene region on chromosome 2. Concerning meat quality, ultimate pH of adductor, longissimus dorsi, and BF were affected by the interval delimited by UMNP3000 and SW2512 markers on chromosome 1, and a* of GS, L* of BF, and water-holding capacity of GS were affected by QTL located between marker loci SW2443 and SWR783 on chromosome 2. Recombinant progeny testing appeared to be a suitable strategy for the genetic dissection of the QTL investigated.

Prevalence, segregation, and phenotype of the mitochondrial DNA 3243A>G mutation in children

OBJECTIVE

We studied the prevalence, segregation, and phenotype of the mitochondrial DNA 3243A>G mutation in children in a defined population in Northern Ostrobothnia, Finland.

METHODS

Children with diagnoses commonly associated with mitochondrial diseases were ascertained. Blood DNA from 522 selected children was analyzed for 3243A>G. Children with the mutation were clinically examined. Information on health history before the age of 18 years was collected from previously identified adult patients with 3243A>G. Mutation segregation analysis in buccal epithelial cells was performed in mothers with 3243A>G and their children whose samples were analyzed anonymously.

RESULTS

Eighteen children were found to harbor 3243A>G in a population of 97,609. A minimum estimate for the prevalence of 3243A>G was 18.4 in 100,000 (95% confidence interval, 10.9-29.1/100,000). Information on health in childhood was obtained from 37 adult patients with 3243A>G. The first clinical manifestations appearing in childhood were sensorineural hearing impairment, short stature or delayed maturation, migraine, learning difficulties, and exercise intolerance. Mutation analysis from 13 mothers with 3243A>G and their 41 children gave a segregation rate of 0.80. The mothers with heteroplasmy greater than 50% tended to have offspring with lower or equal heteroplasmy, whereas the opposite was true for mothers with heteroplasmy less than or equal to 50% (p = 0.0016).

INTERPRETATION

The prevalence of 3243A>G is relatively high in the pediatric population, but the morbidity in children is relatively low. The random genetic drift model may be inappropriate for the transmission of the 3243A>G mutation.

Phenotypic effects of null and haploinsufficiency of acid-labile subunit in a family with two novel IGFALS gene mutations

CONTEXT

IGF-I deficiency may result from impairment of GH secretion or action, or from defects in IGF-I synthesis, transport, or action. Complete deficiency of the acid-labile subunit (ALS), previously described in two male patients, the only known inherited alteration in IGF-I transport, is characterized by severe circulating IGF-I and IGF binding protein (IGFBP)-3 deficiency with only mild growth retardation.

OBJECTIVE

Our objective was to study the characterization, at biochemical and molecular levels, of the cause for severe circulating IGF-I and IGFBP-3 deficiency in a male patient with mild growth retardation.

PATIENTS

We report an adolescent male with delayed growth and pubertal development (Tanner stage I, -2.00 sd score for height at the age of 15.3 yr), profound circulating IGF-I and IGFBP-3 deficiency, and poor response to GH treatment.

RESULTS

The index case, as well as one of his brothers, and his sister were found to be compound heterozygotes for two novel IGFALS gene mutations: C540R, a missense point mutation; and S195_197Rdup, a 9-bp duplication. The parents and youngest brother were found to be carriers for one of these two mutations. The three affected siblings had marked reduction of IGF-I and IGFBP-3 levels, undetectable serum levels of ALS, inability to form ternary complexes, and moderate insulin resistance. All of them attained a normal near-adult height (between -1.0 and -0.5 sd score), which was nonetheless lower than that of their heterozygous brother. The IGF system was only modestly affected in the heterozygous carriers.

CONCLUSIONS

This study confirms the critical role of ALS in forming ternary complexes and the maintenance of normal levels of IGF-I and IGFBP-3. Insulin resistance, pubertal delay in male patients, and poor GH responsiveness seem to be frequent findings in ALS deficiency. However, haploinsufficiency of the IGFALS gene has no discernible clinical effects with only modest impact on the IGF system.

Growth parameters in maternal uniparental disomy 7 and 14

INTRODUCTION

Growth retardation has been reported in most cases of maternal uniparental disomy (UPD) 7 and 14, but has never been evaluated in a systematic approach. In this study, an analysis is presented of the auxological data from the literature at birth and on the occasion of the last evaluation of 34 cases with maternal UPD 7 (21 heterodisomy, 13 isodisomy) and 29 cases with maternal UPD 14 (22 heterodisomy, 7 isodisomy). For maternal UPD 7, statistical analysis revealed that length and weight at birth as well as on the occasion of the last evaluation were strongly below average (-2.94 SD and -2.62 SD, and -3.39 SD and -3.11 SD, respectively), whereas at both evaluations occipitofrontal head circumference (OFC) was only slightly below the average (-1.00 SD and -0.85 SD). For maternal UPD 14 at birth, growth retardation is rather concordant for length, weight, and OFC (-2.78 SD, -2.84 SD, and -1.69 SD). Later in life body mass index (BMI) is above average (1.06 SD) and continuously increasing before and after puberty (-0.58 SD and 2.07 SD).

CONCLUSION

Growth retardation and relative macrocephaly are of prenatal onset and still present in adults with maternal UPD 7. For patients with maternal UPD 14, growth curves for height, BMI and OFC differ strongly. Genomic imprinting might be a major causative factor, but it seems to function differently for maternal UPD 7 and maternal UPD 14.

Polymorphisms in the bovine leptin promoter associated with serum leptin concentration, growth, feed intake, feeding behavior, and measures of carcass merit

Leptin is the hormone product of the obese gene synthesized and secreted predominantly by white adipocytes. It functions as a lipostatic signal regulating BW, food intake, energy expenditure, reproduction, and certain immune system functions. Although previous studies have identified polymorphisms in the coding regions of the leptin gene in cattle that show considerable associations with feed intake, milk quality and quantity, and carcass fatness, no such associations have been reported for the leptin promoter. The current study reports associations between SNP in the 5' untranslated promoter region of the bovine leptin gene with serum leptin concentration, growth, BW, feed intake, feeding behavior, and carcass merit in hybrid cattle (n = 150). The study showed that animals with the TT genotype of a less frequent cytosine/thymine (C/ T) substitution (UASMS2; frequency of thymine allele equals 0.21) detected at position 528 in the bovine leptin promoter (GenBank Accession No. AB070368) show 48 and 39% increases in serum leptin concentration (P < 0.001), 39 and 31% increases in backfat thickness (P < 0.001), and 13 and 9% increase in marbling score (P = 0.01), compared with CC or CT genotypes, respectively. Animals with the TT genotype also show significantly higher feed intake (P < 0.001), growth rate, metabolic BW (P < 0.05), and live weight at slaughter (P < 0.10). Animals with the GG genotype of a more frequent cytosine/guanine (C/G) substitution (UASMS3; frequency of G allele equals 0.59) at position 1759 in the bovine leptin promoter (GenBank Accession No. AB070368) also show higher feed intake (P = 0.001), growth rate (P < 0.10), and BW (P < 0.01). The thymine allele of UASMS2 and the guanine allele of UASMS3 were separately associated with higher feeding duration (P < 0.05). The two SNP show significant linkage disequilibrium and could also be relevant in predicting other characteristics, such as milk yield and quality in cattle. These results, however, represent the initial associations of the polymorphisms with these traits, and further efforts are required to validate these findings in other populations.

Growth outcomes for Australian Aboriginal children aged 11 years who were born with intrauterine growth retardation at term gestation

Long-term poor growth outcomes are well documented for intrauterine growth-retarded babies (IUGR) in developed populations but there is a paucity of IUGR studies from disadvantaged populations where the greatest burden of IUGR occurs. Using a Northern Territory, Aboriginal cohort recruited at birth and followed up at a mean age of 11.4 years, comparisons of body size were made between children born at term who had been IUGR (n = 121) and those non-IUGR (n = 341), and between those IUGR babies who had an appropriate ponderal index at birth (n = 72) and those with a low ponderal index (n = 49). Compared with non-IUGR children, at follow-up the IUGR children were almost 2 cm shorter (P = 0.10), 4 kg lighter (P < 0.01) and their head circumferences were almost a 1 cm smaller (P < 0.01). For the 121 term IUGR children, there were no significant differences in growth outcomes according to ponderal index measures at birth. These findings from an Australian Aboriginal sample are consistent with other comparisons of IUGR and non-IUGR children in developed populations and suggest there may be no additional effects of IUGR on growth in childhood for disadvantaged populations similar to the Aboriginal population in the Northern Territory.

Dissection of a genetically complex cluster of growth and obesity QTLs on mouse chromosome 2 using subcongenic intercrosses

In a previous study we characterized the B6.CAST-(D2Mit329-D2Mit457)N(6) (B62D) congenic strain, which possesses CAST/EiJ (CAST) chromosome 2 donor alleles from 74 to 180 Mbp on a C57BL6/J (B6) background. This strain exhibited significant decreases in body weight and adiposity attributable to the weight gain 2 (Wg2) quantitative trait locus (QTL). To refine the location of Wg2, we used a two-stage genetic dissection strategy consisting of a B62D x B6 backcross, which mapped Wg2 to the proximal portion of the B62D donor region, followed by the development of seven overlapping subcongenic F(2) intercrosses targeting the Wg2 genomic interval. Surprisingly, five of the seven intercrosses displayed significant differences, dependent on genotype, in body weight and/or fat pad mass. These effects were the result of at least four independent QTLs that were named Wg2a, b, c, and d. In contrast to the lean and low body weight phenotype of the B62D parental strain, mice homozygous for CAST congenic alleles (cast/cast) at Wg2a were significantly heavier at 6 and 9 weeks of age, while cast/cast mice at Wg2c had higher levels of total fat. Consistent with the prior observed effects of Wg2, cast/cast mice at Wg2b displayed significant decreases in 6- and 9-week body weight as well as a decrease in total fat pad mass. All of the QTLs had additive effects on body composition except Wg2d, which displayed underdominance for total fat mass. Significant differences in weight and adiposity were also observed in genetically identical b6/b6 homozygous mice across the panel of subcongenics, suggesting either maternal or paternal contributions to body composition. These data represent a significant advancement toward the identification of mouse chromosome 2 growth and obesity quantitative trait genes.

Neutral sphingomyelinase (SMPD3) deficiency causes a novel form of chondrodysplasia and dwarfism that is rescued by Col2A1-driven smpd3 transgene expression

Neutral sphingomyelinase SMPD3 (nSMase2), a sphingomyelin phosphodiesterase, resides in the Golgi apparatus and is ubiquitously expressed. Gene ablation of smpd3 causes a generalized prolongation of the cell cycle that leads to late embryonic and juvenile hypoplasia because of the SMPD3 deficiency in hypothalamic neurosecretory neurons. We show here that this novel form of combined pituitary hormone deficiency is characterized by the perturbation of the hypothalamus-pituitary growth axis, associated with retarded chondrocyte development and enchondral ossification in the epiphyseal growth plate. To study the contribution by combined pituitary hormone deficiency and by the local SMPD3 deficiency in the epiphyseal growth plate to the skeletal phenotype, we introduced the full-length smpd3 cDNA transgene under the control of the chondrocyte-specific promoter Col2a1. A complete rescue of the smpd3(-/-) mouse from severe short-limbed skeletal dysplasia was achieved. The smpd3(-/-) mouse shares its dwarf and chondrodysplasia phenotype with the most common form of human achondrodysplasia, linked to the fibroblast-growth-factor receptor 3 locus, not linked to deficits in the hypothalamic-pituitary epiphyseal growth plate axis. The rescue of smpd3 in vivo has implications for future research into dwarfism and, particularly, growth and development of the skeletal system and for current screening and future treatment of combined dwarfism and chondrodysplasia.

Heritability variations of morphometric traits in West Bengal (India) children aged 4-19 years: a mixed-longitudinal growth study

BACKGROUND

Longitudinal and semi-longitudinal growth studies on siblings reflecting heritability changes during growth are very scarce. Moreover, studies of variables other than height, weight and BMI are virtually non-existent.

AIM

The study compared changes in the heritability of six body lengths, four body breadths, and three indices between ages 4 and 19 years on the basis of a mixed-longitudinal sample of siblings, and examined whether heritability estimates change during the growth period. The data consisted of 238 brothers and 214 sisters from 134 middle-class nuclear families living in Kolkata (India). The analysis of sibling correlation was performed by maximum likelihood. The age-related patterns of heritabilities of the various traits were described by a cubic spline.

RESULTS

The heritability was very high and significant in most traits, and at all considered ages. Mean heritability in the 10 morphometric traits was 69.3%, which was higher than the heritability values for the three indices.

CONCLUSIONS

These results confirmed the existence of age-related trends in heritability of the considered morphometric traits. The sharp decline of the heritabilities at adolescence in most of the morphometric traits, and the acromio-iliac index in particular, may be due to the large inter-individual variation in the age at which the adolescent growth spurt is reached in both sexes.

Detailed analysis of variation at and around mitochondrial position 16189 in a large Finnish cohort reveals no significant associations with early growth or metabolic phenotypes at age 31 years

CONTEXT

Mitochondrial dysfunction is increasingly implicated in pathogenesis of adult metabolic disease. Rare mitochondrial (mt) DNA mutations impair glucose homeostasis, but the contribution of common variants is unclear. In small studies, variation within the OriB origin of replication (at mt16189 in particular) has been associated with both early growth and adult metabolic phenotypes and may contribute to life-course relationships between the two.

OBJECTIVE

The aim was to study a large well-characterized cohort to determine whether previously reported small-scale associations between OriB sequence variation and early growth and adult metabolic phenotypes are robust.

DESIGN/SETTING/PARTICIPANTS

This was a genetic association study of 5470 individuals from the population-based Northern Finland Birth Cohort of 1966, followed prospectively from pregnancy to age 31 yr.

MAIN OUTCOME MEASURES

We measured indices of early growth (including birth weight, placental weight, and ponderal index) and adult metabolic homeostasis (including body mass index, fasting glucose and insulin, indices of insulin action and secretion) and their relationship to variation in the OriB region.

RESULTS

Previously reported associations could not be confirmed. There were no significant (P < 0.01, uncorrected) associations between OriB sequence variation and measures of early growth including birth weight (P = 0.52, comparing individuals with mt16189T to those with a homopolymeric C-tract) and placental weight (P = 0.49). There were no significant associations with adult metabolic phenotypes including fasting glucose (P = 0.07), fasting insulin (P = 0.42), and homeostatic model assessment-derived measures of insulin sensitivity or secretion (P = 0.45 and P = 0.56, respectively).

CONCLUSION

Despite substantial power to detect previously reported effects, mtDNA variations around OriB are not major contributors to variation in early growth and metabolic phenotypes during early adulthood.

Unique mechanisms of growth regulation and tumor suppression upon Apc inactivation in the pancreas

beta-catenin signaling is heavily involved in organogenesis. Here, we investigated how pancreas differentiation, growth and homeostasis are affected following inactivation of an endogenous inhibitor of beta-catenin, adenomatous polyposis coli (Apc). In adult mice, Apc-deficient pancreata were enlarged, solely as a result of hyperplasia of acinar cells, which accumulated beta-catenin, with the sparing of islets. Expression of a target of beta-catenin, the proto-oncogene c-myc (Myc), was increased in acinar cells lacking Apc, suggesting that c-myc expression is essential for hyperplasia. In support of this hypothesis, we found that conditional inactivation of c-myc in pancreata lacking Apc completely reversed the acinar hyperplasia. Apc loss in organs such as the liver, colon and kidney, as well as experimental misexpression of c-myc in pancreatic acinar cells, led to tumor formation with high penetrance. Surprisingly, pancreas tumors failed to develop following conditional pancreas Apc inactivation. In Apc-deficient acini of aged mice, our studies revealed a cessation of their exaggerated proliferation and a reduced expression of c-myc, in spite of the persistent accumulation of beta-catenin. In conclusion, our work shows that beta-catenin modulation of c-myc is an essential regulator of acinar growth control, and unveils an unprecedented example of Apc requirement in the pancreas that is both temporally restricted and cell-specific. This provides new insights into the mechanisms of tumor pathogenesis and tumor suppression in the pancreas.

A growth QTL (Pbwg1) region of mouse chromosome 2 contains closely linked loci affecting growth and body composition

Previous QTL studies have identified 24 QTLs for body weight and growth from 3 to 10 weeks after birth in an intersubspecific backcross mouse population between C57BL/6J and wild Mus musculus castaneus that has 60% of the body size of C57BL/6J. The castaneus allele at the most potent QTL (Pbwg1) on proximal chromosome 2 retards growth. In this study we have developed a congenic strain with a 44.1-Mb interval containing the castaneus allele at Pbwg1 by recurrent backcrossing to C57BL/6J. The congenic mouse developed was characterized by significantly higher body weight gain between 1 and 3 weeks of age and lower weight of white fat pads at 10 weeks of age than C57BL/6J. However, no clear difference in body weight at 1-10 weeks of age was observed between congenic and C57BL/6J strains. QTL analysis with 269 F(2) mice between the two strains did not identify any QTLs for body weight at 1, 3, 6, and 10 weeks of age, but it discovered eight closely linked QTLs affecting body weight gain from 1 to 3 weeks of age, lean body weight, weight of white fat pads, and body length within the Pbwg1 region. The castaneus alleles at all fat pad QTLs reduced the phenotypes, whereas at the remaining growth and body composition QTLs, they increased the trait values. These results illustrate that Pbwg1, which initially appeared to be a single locus, was resolved into several loci with opposite effects on the composition traits of overall body weight. This gives a reason for the loss of the Pbwg1 effect found in the original backcross population.

Global growth deficiencies in mice lacking the ribosomal protein HIP/RPL29

Because of their deleterious effects on developing organisms, ribosomal protein (RP) mutations have been poorly described in mammals, and only a few heterozygous mutations have been shown to be viable. This observation is believed to be due to the fact that each RP is an essential component in the assembly of a functional stable ribosome. Here, we created gene targeted mutant mice lacking HIP/RPL29, an RP associated with translationally active ribosomes in eukaryotes. In contrast to other RP mutants, HIP/RPL29 null mice are viable but are up to 50% smaller than their control littermates at weaning age. In null embryos, delayed global growth is first observed around mid-gestation, and postnatal lethality due to low birth weight results in distortion of the Mendelian ratio. Prenatal growth defects are not fully compensated for during adulthood, and null animals display proportionately smaller organs and stature, and reach sexual maturity considerably later when compared with their control siblings. Additionally, HIP/RPL29 null embryonic fibroblasts have decreased rates of proliferation and protein synthesis and exhibit reduced steady state levels of core RPs. Altogether, our findings provide conclusive genetic evidence that HIP/RPL29 functions as an important regulator of global growth by modulating the rate of protein synthesis.

Postnatal body growth is dependent on the transcription factors signal transducers and activators of transcription 5a/b in muscle: a role for autocrine/paracrine insulin-like growth factor I

The transcription factors signal transducers and activators of transcription (STAT)5a and STAT5b (STAT5) are essential mediators of many actions of GH, including transcription of the IGF-I gene. Here, we present evidence that skeletal muscle STAT5 is important for postnatal growth and suggest that this is conveyed by the production of localized IGF-I. To investigate the role of STAT5 signaling in skeletal muscle, mice with a skeletal-muscle-specific deletion of the Stat5a and Stat5b genes (Stat5MKO mice) were used. IGF-I mRNA levels were reduced by 60% in muscle tissue of these mice. Despite only a 15% decrease in circulating IGF-I, 8-wk-old male Stat5MKO mice displayed approximately 20% reduction in body weight that was accounted for by a reduction in lean mass. The skeletons of Stat5MKO mice were found to be smaller than controls, indicating the growth defect was not restricted to skeletal muscle. These results demonstrate an as yet unreported critical role for STAT5 in skeletal muscle for local IGF-I production and postnatal growth and suggest the skeletal muscle as a major site of GH action.

Variation analysis of beta3-adrenergic receptor and melanocortin-4 receptor genes in childhood obesity

BACKGROUND

Decreased energy expenditure and increased food intake are principal causes for obesity. In the present study, genotypes of beta(3)-adrenergic receptor (beta(3)AR) and of melanocortin-4 receptor (MC4R), both of which are believed to have a close link to the cause of obesity, were analyzed and compared with phenotypes of childhood obesity.

METHODS

Thirty-five obese children with moderate to severe obesity were enrolled. Direct sequencing of the MC4R coding region and pinpoint-polymerase chain reaction were used to detect genomic variation in the beta(3)AR gene using peripheral blood-derived DNA.

RESULTS

Allele frequency of Trp64Arg variation in the beta(3)AR gene in the obese subjects was 0.16, which is comparable with that in the healthy general population in eastern Asia. Comparison of phenotypical characteristics did not show a significant difference between Trp/Trp and Trp/Arg subjects. It was notable that body height SD was significantly higher in the Trp/Trp than the Trp/Arg subjects (0.93 +/- 1.0 SD vs 0.07 +/- 1.3 SD, P= 0.03). Annual weight gains were far beyond a hypothetical fat gain in an Arg64 heterozygote with decreased energy consumption, suggesting increased food intake in childhood obesity. There was, however, no variation in the MC4R gene despite thorough sequencing of the entire coding region.

CONCLUSIONS

The Trp64Arg variation in the beta(3)AR gene has no relationship to the degree or the incidence of childhood obesity. The majority of childhood obesity can be characterized as tall stature, more rapid weight gain than that expected by decreased energy expenditure. Further investigation is necessary in regard to the increased food intake as a major cause of childhood obesity.