Preventable factors in childhood that lead to insulin resistance, diabetes mellitus and the metabolic syndrome: the EarlyBird diabetes study 1

Contrasting impact of androgens on male and female adiposity, fat distribution and insulin resistance in childhood and adolescence (EarlyBird 75)

OBJECTIVES

To investigate associations between androgens (testosterone, dehydroepiandrosterone sulphate [DHEAS] and androstenedione), adiposity, fat distribution and insulin resistance (IR) during childhood and adolescence.

METHODS

Three hundred and seven children (170 [55.4%] boys; 137 [44.6%] girls) recruited at age 5 and studied annually until age 16: androgens (liquid chromatography tandem-mass spectrometry), anthropometry, body composition (dual-energy x-ray absorptiometry) and IR (homeostasis model assessment).

RESULTS

Early adiposity was associated with earlier detection of androstenedione in both sexes, and DHEAS in boys. At puberty, higher androgen levels were associated with favourable metabolic changes in boys, but adverse metabolic effects in girls. In boys, higher free testosterone (FT) was associated with lower body fat and android/gynoid fat ratio (AGR) (both P < .001), but in girls higher total testosterone was associated with higher AGR. In girls only, higher androstenedione (P = .02) and FT (P = .01) was associated with higher IR during puberty.

CONCLUSIONS

In pre-pubertal children, adiposity is associated with higher secretion of androgen precursors. After pubertal onset, higher testosterone is associated with lower adiposity and AGR in boys, but higher AGR and IR in girls. Therefore, androgens have modest sex-specific associations with children's total body fat, fat distribution and IR.

Contributions of Fat and Carbohydrate Metabolism to Glucose Homeostasis in Childhood Change With Age and Puberty: A 12-Years Cohort Study (EARLYBIRD 77)

Puberty-a period when susceptibility to the onset of Type 2 diabetes (T2D) increases-is marked with profound physiological and metabolic changes. In the EarlyBird cohort, children who developed impaired fasting glycemia in adolescence already exhibited higher fasting blood glucose at 5 years of age, independent of their body mass index (BMI), suggesting that pubertal factors may modify existing predisposition. Understanding how the physiological changes during childhood influence glucose homeostasis and how the central energy metabolism may help deciphering the mechanisms that underlie the risk of developing T2D in children and adults. We investigated these associations by analyzing glycemic variations with molecular markers of central energy metabolism, substrate oxidation status and pubertal stages in the EarlyBird cohort. The EarlyBird study is a non-interventional, prospective cohort study, that recruited 307 healthy UK children at age 5, and followed them annually throughout childhood for 12 years. Longitudinal data on blood biochemistry, respiratory exchange ratio, and anthropometry, available from 150 children were integrated with fasting glycemia. The gradual rise in blood glucose during childhood associates with age-dependent changes in molecular processes and substrate oxidation status, namely (i) greater pre-pubertal fat utilization, ketogenesis, and fatty acid oxidation, and (ii) greater pubertal carbohydrate oxidation and glycolytic metabolism (Cori and Cahill Cycles) associated with different amino acid exchanges between muscle and other tissues (proline, glutamine, alanine). Since children's metabolic and nutritional requirements evolve during childhood, this study has potential clinical implications for the development of nutritional strategies for disease prevention in children.

Genetic Susceptibility Determines β-Cell Function and Fasting Glycemia Trajectories Throughout Childhood: A 12-Year Cohort Study (EarlyBird 76)

OBJECTIVE

Previous studies suggested that childhood prediabetes may develop prior to obesity and be associated with relative insulin deficiency. We proposed that the insulin-deficient phenotype is genetically determined and tested this hypothesis by longitudinal modeling of insulin and glucose traits with diabetes risk genotypes in the EarlyBird cohort.

RESEARCH DESIGN AND METHODS

EarlyBird is a nonintervention prospective cohort study that recruited 307 healthy U.K. children at 5 years of age and followed them throughout childhood. We genotyped 121 single nucleotide polymorphisms (SNPs) previously associated with diabetes risk, identified in the adult population. Association of SNPs with fasting insulin and glucose and HOMA indices of insulin resistance and β-cell function, available from 5 to 16 years of age, were tested. Association analysis with hormones was performed on selected SNPs.

RESULTS

Several candidate loci influenced the course of glycemic and insulin traits, including rs780094 (GCKR), rs4457053 (ZBED3), rs11257655 (CDC123), rs12779790 (CDC123 and CAMK1D), rs1111875 (HHEX), rs7178572 (HMG20A), rs9787485 (NRG3), and rs1535500 (KCNK16). Some of these SNPs interacted with age, the growth hormone-IGF-1 axis, and adrenal and sex steroid activity.

CONCLUSIONS

The findings that genetic markers influence both elevated and average courses of glycemic traits and β-cell function in children during puberty independently of BMI are a significant step toward early identification of children at risk for diabetes. These findings build on our previous observations that pancreatic β-cell defects predate insulin resistance in the onset of prediabetes. Understanding the mechanisms of interactions among genetic factors, puberty, and weight gain would allow the development of new and earlier disease-management strategies in children.

Insulin Resistance during normal child growth and development is associated with a distinct blood metabolic phenotype (Earlybird 72)

BACKGROUND

While insulin resistance (IR) is associated with specific metabolite signatures in adults, there have been few truly longitudinal studies in healthy children, either to confirm which abnormalities are present, or to determine whether they precede or result from IR. Therefore, we investigated the association of serum metabolites with IR in childhood in the Earlybird cohort.

METHODS

The Earlybird cohort is a well-characterized cohort of healthy children with annual measurements from age 5 to 16 years. For the first time, longitudinal association analyses between individual serum metabolites and homeostatic model assessment (HOMA) of insulin resistance (HOMA-IR) have been performed taking into account the effects of age, growth, puberty, adiposity, and physical activity.

RESULTS

IR was higher in girls than in boys and was associated with increasing body mass index (BMI). In longitudinal analysis IR was associated with reduced concentrations of branched-chain amino acids (BCAA), 2-ketobutyrate, citrate and 3-hydroxybutyrate, and higher concentrations of lactate and alanine. These findings demonstrate the widespread biochemical consequences of IR for intermediary metabolism, ketogenesis, and pyruvate oxidation during normal child growth and development.

CONCLUSIONS

Longitudinal analysis can differentiate metabolite signatures that precede or follow the development of greater levels of IR. In healthy normal weight children, higher levels of IR are associated with reduced levels of BCAA, ketogenesis, and fuel oxidation. In contrast, elevated lactate concentrations preceded the rise in IR. These changes reveal the metabolite signature of insulin action during normal growth, and they contrast with previous findings in obese children and adults that represent the consequences of IR and obesity.

Insulin resistance is higher in prepubertal girls but switches to become higher in boys at age 16: A Cohort Study (EarlyBird 57)

BACKGROUND

The risk of type 2 diabetes is increasing in teenage girls, and is associated with their greater insulin resistance (IR).

HYPOTHESIS

We hypothesized that the adverse metabolic profile of girls (compared with boys) would persist from childhood through adolescence.

PATIENTS AND METHODS

Community-based longitudinal cohort of 292 children (147 boys) studied annually from 9 to 16 years.

MEASURES

IR (homeostasis-model-assessment-2), high-density lipoprotein-cholesterol (HDL-C), triglycerides, % body-fat (dual-energy x-ray absorptiometry), pubertal stage (age at peak height velocity), physical activity (accelerometry). Multi-level modelling established the age-related trends in IR and lipids and the influence of covariates.

RESULTS

Each year from 9 to 15 years, girls had 21% to 63% higher IR than boys (girls mean IR 0.73-1.33, boys 0.51-0.89, P < .005). At 16 years the gender difference was not significant (girls IR 0.60, boys 0.56, P = .45). Girls had lower HDL-C from 9 to 12 years, higher triglycerides from 9 to 14 years, greater adiposity throughout, and earlier puberty, but boys were more active than girls (all P < .05). After adjustment for %-fat, puberty and activity, the gender difference in IR between girls and boys aged 9 to 15 years became non-significant (IR girls 0.66-1.01, boys 0.65-1.04, P > .07). However, after adjustment at 16 years, girls' IR was 25% lower than boys' (girls 0.44, boys 0.63, P = .001), and they had 22% higher HDL-C (P < .001) and 20% lower triglycerides (P = .003).

CONCLUSIONS

The higher IR of prepubertal and early pubertal girls diminishes during late puberty, and boys begin to exhibit greater metabolic risk. Despite being leaner and more active, boys at 16 years have higher IR than girls, suggesting future higher risk for diabetes, thus we reject our hypothesis.

Consensus Clustering of temporal profiles for the identification of metabolic markers of pre-diabetes in childhood (EarlyBird 73)

In longitudinal clinical studies, methodologies available for the analysis of multivariate data with multivariate methods are relatively limited. Here, we present Consensus Clustering (CClust) a new computational method based on clustering of time profiles and posterior identification of correlation between clusters and predictors. Subjects are first clustered in groups according to a response variable temporal profile, using a robust consensus-based strategy. To discover which of the remaining variables are associated with the resulting groups, a non-parametric hypothesis test is performed between groups at every time point, and then the results are aggregated according to the Fisher method. Our approach is tested through its application to the EarlyBird cohort database, which contains temporal variations of clinical, metabolic, and anthropometric profiles in a population of 150 children followed-up annually from age 5 to age 16. Our results show that our consensus-based method is able to overcome the problem of the approach-dependent results produced by current clustering algorithms, producing groups defined according to Insulin Resistance (IR) and biological age (Tanner Score). Moreover, it provides meaningful biological results confirmed by hypothesis testing with most of the main clinical variables. These results position CClust as a valid alternative for the analysis of multivariate longitudinal data.

Generational change in fasting glucose and insulin among children at ages 5-16y: Modelled on the EarlyBird study (2015) and UK growth standards (1990) (EarlyBird 69)

AIM

Pre-diabetes is a state of beta-cell stress caused by excess demand for insulin. Body mass is an important determinant of insulin demand, and BMI has risen substantially over recent time. We sought to model changes in the parameters of glucose control against rising BMI over the past 25years.

METHODS

Using random coefficient mixed models, we established the correlations between HbA1C, fasting glucose, fasting insulin, HOMA2-IR and BMI in contemporary (2015) children (N=307) at ages 5-16y from the EarlyBird study, and modelled their corresponding values 25years ago according to the distribution of BMI in the UK Growth Standards (1990).

RESULTS

There was little change in HbA1C or fasting glucose over the 25y period at any age or in either gender. On the other hand, the estimates for fasting insulin and HOMA2-IR were substantially higher in both genders in 2015 compared with 1990.

CONCLUSION

Insofar as it is determined by body mass, there has been a substantial rise in beta cell demand among children over the past 25years. The change could be detected by fasting insulin and HOMA2-IR, but not by fasting glucose or HbA1C.

Exploring the Adolescent Fall in Physical Activity: A 10-yr Cohort Study (EarlyBird 41)

INTRODUCTION

Contemporary adolescents are deemed inactive, especially girls, but whether for biological reasons associated with their maturation, changes in their behavior or because of environmental constraints, is uncertain. We examined the trends in physical activity (PA) in relation to both biological and environmental factors in an attempt to establish what drives activity patterns from childhood through adolescence.

METHODS

Physical activity (7-d Actigraph accelerometry) was measured annually from 5 to 15 yr in a single cohort of some 300 UK children. Total PA (TPA; in-school and out-of-school separately and combined as whole day) and intensity-specific PA (sedentary, light, and moderate-and-vigorous [MVPA]) were analyzed. Biological age (years before/after measured peak height velocity) and pubertal stage (self-reported pubic hair development-Tanner staging) were also measured as was socioeconomic status (postcode-derived index of multiple deprivation [IMD]).

RESULTS

Total PA was stable from 5 to 8 yr (trend P = 0.10) but fell progressively from 9 to 15 yr (by approximately 30% in girls and approximately 20% in boys, both P < 0.001; sex interaction, P < 0.01). Half of this fall was attributable to light intensity PA and only a quarter to MVPA. The decline in PA was related similarly to chronological and biological age, whereas pubertal stage explained the more rapid PA decline in girls (puberty-adjusted sex interaction, P = 0.51). Total PA fell to the same extent for in-school and out-of-school settings (both P < 0.001), and for lower and higher IMD areas (both P < 0.001). Total PA tracked moderately to strongly from childhood into adolescence (r = 0.58; P < 0.001).

CONCLUSIONS

The adolescent decline in PA is consistent across different environmental settings, attributable to falls in light-intensity/habitual activity and influenced by puberty, suggesting that the inactivity of adolescence may, in part, be under biological control.

Anti-Müllerian hormone in children: a ten-year prospective longitudinal study (EarlyBird 39)

BACKGROUND

Anti-Müllerian hormone (AMH) is produced by Sertoli cells of the testes and granulosa cells of the ovary. There are limited prospective longitudinal data assessing AMH concentrations throughout childhood in both sexes.

OBJECTIVE

This study aimed to examine AMH throughout childhood with particular reference to the relationship of AMH to pubertal development in both sexes.

DESIGN

This is a prospective longitudinal non-intervention cohort study with annual sampling for participants aged 5-14 years.

SETTING

Community cohort study.

PARTICIPANTS

A total of 307 healthy children (170 boys) recruited at 5 years from randomly selected schools in Plymouth, UK, participated in this study. Data sets are complete in 76% of the children at 14 years of age.

MAIN OUTCOME MEASURE(S)

Annual measures of serum AMH, follicle stimulating hormone (FSH) and luteinising hormone (LH), Tanner stage (TS).

RESULTS

Boys: AMH was stable from 5 to 7 years, increased slightly from 8 to 10 years, then declined at TS2. This decline was preceded by rising FSH and the appearance of LH. AMH correlated inversely with gonadotrophic hormones during puberty. Girls: AMH increased slightly between 6 and 10 years, peaking during the final prepubertal year before returning to near baseline levels at TS3. Inverse correlations between AMH and FSH were apparent during the prepubertal years.

CONCLUSIONS

Our longitudinal data clarified the development of individual AMH levels over a 10-year period. We described modest late prepubertal peaks in both boys and girls, and confirmed the pubertal decline in boys. The inverse association of AMH with gonadotrophins in young females supports its role as a marker of ovarian function, while the precise role for AMH in relation to testicular function in young males remains unclear.

Awareness of body weight by mothers and their children: repeated measures in a single cohort (EarlyBird 64)

BACKGROUND

Mothers often do not realize when their child is overweight. We aimed to compare mothers' perceptions of children's weight before and during puberty, and to explore factors at 7 years predicting recognition of overweight at 16 years.

METHODS

Mothers of 237 children (136 boys) from the EarlyBird study estimated their own weight category and that of their child aged 7 years and 16 years. The children estimated their own weight category at 16 years. Annual measures: body mass index standard deviation score (BMIsds), per cent fat, physical activity. Pubertal development assessed by age at peak height velocity (APHV). MATERNAL MEASURES: BMI, education, socio-economic status.

RESULTS

At 7 years 21% of girls and 16% of boys were overweight or obese, rising to 27% and 22% respectively at 16 years. The accuracy of the mother's perception of her child's weight category improved from 44% at 7 years to 74% at 16 years, but they were less able to judge overweight in sons than daughters. The mothers' level of concern about overweight was greater for girls than boys, and increased for girls (52% mothers of overweight/obese girls were worried at 7 years, 62% at 16 years), but remained static in the boys (42% vs. 39%). Over 80% of the youngsters realized when they were overweight, but 25% normal-weight girls also classed themselves as overweight. Only BMI predicted a mother's ability to correctly perceive her child's weight. Neither her awareness, nor concern, about the child's weight at 7 years had any impact on the trajectory of the child's BMI from 7 years to 16 years.

CONCLUSIONS

Parents are central to any successful weight reduction programme in their children, but will not engage while they remain ignorant of the problem. Crucially, any concern mothers may have about their child's excess weight at 7 years appears to have no impact on subsequent weight change.

Childhood obesity: evidence for distinct early and late environmental determinants a 12-year longitudinal cohort study (EarlyBird 62)

BACKGROUND/OBJECTIVE

The prevalence of childhood obesity continues to rise in most countries, but the exposures responsible remain unclear. The shape of the body mass index (BMI) distribution curve defines how a population responds, and can be described by its three parameters-skew (L), median (M) and variance (S). We used LMS analysis to explore differences in the BMI trajectories of contemporary UK children with those of 25 years ago, and to draw inferences on the exposures responsible.

SUBJECTS/METHODS

We applied Cole's LMS method to compare the BMI trajectories of 307 UK children (EarlyBird cohort) measured annually from 5-16 years (2000-2012) with those of the BMI data set used to construct the UK 1990 growth centiles, and used group-based trajectory modelling (GBTM) to establish whether categorical trajectories emerged.

RESULTS

Gender-specific birth weights were normally distributed and similar between both data sets. The skew and variance established by 5 years in the 1990 children remained stable during the remainder of their childhood, but the pattern was different for children 25 years on. The skew at 5 years among the EarlyBird children was greatly exaggerated, and involved selectively the offspring of obese parents, but returned to 1990 levels by puberty. As the skew diminished, so the variance in BMI rose sharply. The median BMI of the EarlyBird children differed little from that of 1990 before puberty, but diverged from it as the variance rose. GBTM uncovered four groups with distinct trajectories, which were related to parental obesity.

CONCLUSIONS

There appear to be two distinct environmental interactions with body mass among contemporary children, the one operating selectively according to parental BMI during early childhood, the second more generally in puberty.

Mood and its association with metabolic health in adolescents: a longitudinal study, EarlyBird 65

BACKGROUND

Mood comprises two main traits - positive and negative affect, both associated with depression and anxiety. Studies in children have linked depression with obesity, but the association with metabolic health is unclear.

OBJECTIVE

To explore the relationship between mood and metabolic health in adolescents.

METHODS

We studied 208 healthy children (115 boys) enrolled in the longitudinal EarlyBird Diabetes Study, and reviewed at 7 and 16 yr. Participants completed the Positive Affect and Negative Affect Schedule - Child Form (PANAS-C) at 16yr to assess positive and negative affect, together representing mood. Measures at 7 and 16 yr: body mass index (BMI), fat (%; dual energy X-ray absorptiometry), physical activity (accelerometer), metabolic risk z-score comprising homeostasis model assessment-insulin resistance (HOMA-IR), triglycerides, total cholesterol/high density lipoprotein (HDL) ratio and blood pressure. Pubertal development was determined by age at peak height velocity.

RESULTS

Positive affect was higher in boys than girls, (50 vs. 46, p = 0.001), negative affect higher in girls than boys (26 vs. 22, p < 0.001). Those with lower mood were fatter (r = -0.24, p < 0.001), had higher HOMA-IR (r = -0.12, p = 0.05), higher cholesterol:HDL ratio (r = -0.14, p = 0.02), were less active (r = 0.20, p = 0.003) and had earlier pubertal development (r = 0.19, p = 0.004). Inverse associations between mood and metabolic risk z-score and change in metabolic risk z-score 7-16yr (β = -0.26, p = 0.006, and -0.40, p = 0.004, respectively) were independent of adiposity, physical activity and puberty and sex.

CONCLUSIONS

Low mood in healthy children is associated with poorer metabolic health independently of adiposity. These findings may have implications for the physical and mental health of contemporary youngsters, given their increasing obesity and cardiometabolic risk.

Adiposity, chronic inflammation, and the prepubertal decline of sex hormone binding globulin in children: evidence for associations with the timing of puberty (Earlybird 58)

BACKGROUND

The regulation and role of SHBG in children are poorly defined. Here we investigated whether adiposity-related mechanisms regulate SHBG and whether SHBG levels are associated with the age of puberty.

METHODS

Longitudinal modelling of annual physiological and endocrine measurements from age 5 to 15 years in a cohort of 347 Plymouth schoolchildren.

RESULTS

SHBG levels were highest at age 5 years and then declined. Mean (SE) SHBG levels were higher in boys than girls at age 5 years [mean (SE) difference 7.68 (3.80) nmol/L; P = .045] but lower in boys by age 15 years [difference 12.19 (3.4) nmol/L; P < .001]. SHBG correlated inversely with adiposity [body mass index SD score (BMI SDS)], insulin, IGF-I, C-reactive protein (CRP), and leptin and positively with adiponectin but not with dehydroepiandrosterone sulphate, androstenedione, or T. In linear mixed models, five adiposity-related covariates (insulin, leptin, adiponectin, IGF-I, and CRP) all exerted significant main effects on SHBG (boys P = .04 to < .001; girls P = .007 to < .001). However, the further addition of BMI SDS rendered the effects of leptin, insulin, and adiponectin nonsignificant, whereas CRP and IGF-I remained significant. In separate models, the individual effects on SHBG of insulin, leptin, IGF-I, and adiponectin, but not CRP, were displaced by BMI SDS. Finally, in linear regression, BMI SDS little affected R(2) resulting from the five adiposity-related signals. Girls with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, tended to have earlier LH secretion, and earlier age at peak height velocity and menarche. In contrast, boys with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, but there were no relationships between SHBG and earlier onset of LH secretion or age at peak height velocity.

CONCLUSIONS

Adiposity-related endocrine mechanisms and chronic inflammation were associated with the prepubertal decline of SHBG, and lower SHBG levels anticipated earlier puberty. These findings may be relevant to the occurrence of earlier puberty in recent decades.

A biological, latent variable model of health (EarlyBird 68)

OBJECTIVE

To determine whether factor analysis of a set of health-related biomarkers provides evidence of an underlying common dimension of variation, and to explore the relationship between this dimension of variation with positive and negative affect.

METHOD

Twelve health-related metabolic, immune and body-composition biomarkers at ages 5, 7, 9, 11, 14 and 16years were obtained from the EarlyBird longitudinal cohort of 347 children and supplemented by positive affect (PA) and negative affect (NA) measured at age 16years.

RESULTS

At each age, principal factor analysis revealed that nine of the 12 biomarkers consistently loaded on the first extracted factor, accounting for 25% of the variance at age 5, and 37-44% of the variance at 7-16years. High loading biomarkers included physical indicators of adiposity, insulin resistance, C-reactive protein, triglycerides, and cholesterol. Factor scores at different ages correlated between .48 and .85. Correlations between the first factor scores and mood measured at age 16 were r=-.17 (p=.02) for PA and r=.13 (p=.07) for NA.

CONCLUSIONS

There is a latent variable, h, that accounts for about a third of the variance of a set of health related physical and biochemical biomarkers. h is comparatively stable during childhood and is a weak predictor of mood. These data provide a rationale for aggregating biomarkers in psychoneuroimmunological research. The concept of h provides a possible biological rationale for the role of common factors in disease onset and progression, mental illness, and functional disorders.

PGC1α promoter methylation in blood at 5-7 years predicts adiposity from 9 to 14 years (EarlyBird 50)

The early environment, acting via epigenetic processes, is associated with differential risk of cardiometabolic disease (CMD), which can be predicted by epigenetic marks in proxy tissues. However, such measurements at time points disparate from the health outcome or the environmental exposure may be confounded by intervening stochastic and environmental variation. To address this, we analyzed DNA methylation in the peroxisome proliferator-activated receptor γ coactivator 1α promoter in blood from 40 children (20 boys) collected annually between 5 and 14 years of age by pyrosequencing. Body composition was measured annually by dual X-ray absorptiometry, physical activity by accelerometry, and pubertal timing by age at peak high velocity. The effect of methylation on transcription factor binding was investigated by electrophoretic mobility shift assays. Seven cytosine guanine dinucleotide (CpG) loci were identified that showed no significant temporal change or association with leukocyte populations. Modeling using generalized estimating equations showed that methylation of four loci predicted adiposity up to 14 years independent of sex, age, pubertal timing, and activity. Methylation of one predictive locus modified binding of the proadipogenic pre-B-cell leukemia homeobox-1/homeobox 9 complex. These findings suggest that temporally stable CpG loci measured in childhood may have utility in predicting CMD risk.

Metabolic risk in contemporary children is unrelated to socio-economic status: longitudinal study of a UK urban population (EarlyBird 42)

Lifestyle interventions to improve health in young children tend to target areas of relative deprivation, but the evidence for so doing is largely historical. Accordingly, we have re-examined the link between deprivation, obesity and metabolic risk in contemporary UK children. Using a postcode-based index of multiple deprivation (IMD), we assessed 269 children from the community-based EarlyBird Study, attending 53 schools representing a wide socio-economic range. Annual measures of fatness from 5 to 8 yr included body mass index (BMI), waist circumference (WC), and sum of five skinfolds (SSF). A metabolic risk score, based on blood pressure, lipids and insulin resistance, was derived from annual fasting blood samples. There were no significant associations between deprivation and any measure of adiposity in girls (all p > 0.37). In boys, there was a weak but consistently inverse relationship between deprivation and WC (r = -0.19, p = 0.03) and BMI (r = -0.14, p = 0.09) at 8 yr. Changes in adiposity over 3 yr were unrelated to deprivation in boys. In girls there was a slight but significant increase in SSF only (1 mm/yr per 20 IMD units, p = 0.001). Importantly, in both genders, metabolic risk score was unrelated to deprivation throughout (r values -0.05 to -0.13, all p > 0.12), as was change in metabolic risk (all p > 0.30). Our data do not support the assumption that obesity, metabolic disturbance and thus risk of type 2 diabetes are more prevalent among poorer children. In today's increasingly obesogenic environment, youngsters from all backgrounds appear to be vulnerable, with population-wide implications for public health spending, and the prevention of diabetes in contemporary youth.

Divergence between HbA1c and fasting glucose through childhood: implications for diagnosis of impaired fasting glucose (Early Bird 52)

OBJECTIVE

An HbA1c threshold of ≥ 6.5% has recently been adopted for the diagnosis of diabetes in adults, and of ≥ 5.7% to identify adults at risk. Little,however, is known of HbA1c's behaviour or diagnostic value in youth. Our aim was to describe the course of HbA1c during childhood, and its association with fasting glucose.

RESEARCH DESIGN AND METHODS

HbA1c and glucose were measured every year in a cohort of 326 healthy children (162 boys) from 5 to 15 years. Mixed effects modelling was used to establish the determinants of HbA1c and its development over time. ROC analysis was used to determine the diagnostic value of HbA1c in the 55 individuals who showed impaired fasting glucose(IFG – glucose ≥ 5.6 mmol/L).

RESULTS

Glucose rose progressively from 4.3 mmol/L at 5 years to 5.1 mmol/Lat 15 years, and although there were positive associations between HbA1c and glucose, from 10 to 13 years, HbA1c fell while glucose continued to rise. IFG developed in 55 children, but HbA1c exceeded 5.7% in only 16 of them. The maximum area under the ROC curve was 0.71 at the age of 14 (p<0.001), and the sensitivity and specificity were optimal at 50 and 80% respectively,corresponding to HbA1c of 5.4%.

CONCLUSIONS

Although HbA1c retains a positive association with glucose throughout childhood, it is weak, and their trends diverge from 10 years,suggesting that factors other than glycaemia systematically influence the variance of HbA1c in youth. These findings therefore limit the interpretation of HbA1c for the diagnosis of IFG during childhood.

Body fat in children does not adversely influence bone development: a 7-year longitudinal study (EarlyBird 18)

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Both negative and positive associations have been reported between body fat and bone density. Extra mechanical loading from excess fat may lead to greater bone mass. Excess ectopic fat may lead to bone demineralisation through inflammatory pathways.

WHAT THIS STUDY ADDS

Longitudinally collected data from narrow-angle beam densitometry gives a novel insight into bone growth through adolescence. There is no evidence of a deleterious effect of body fat on children's growing bones after adjustment for height and age. Body fat, mediated by puberty, is associated with larger bones in boys and bones that are both denser and larger in girls.

OBJECTIVE

Bone growth is an important determinant of peak bone mass and fracture risk, but there is limited data on the impact of fat-on-bone development at a time when childhood obesity is reaching epidemic proportions. Accordingly, we explored the effect of body fat (BF) on bone growth over time in the context of age, pubertal tempo and gender.

METHOD

A cohort of 307 children was measured biannually from 9-16 years for height and weight, and every 12 months for percent BF, bone area (BA), bone mineral content and areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry. Pubertal tempo was determined quantitatively by age at peak height velocity.

RESULTS

Percent BF increased and then fell in the boys, but increased throughout in the girls. aBMD and BA increased in both genders (P < 0.001). Greater BF was associated with higher aBMD and BA in girls (P < 0.001), but only BA in boys (P < 0.001). The extra aBMD associated with increased BF was greater in older girls. The rise in aBMD and BA was associated with earlier puberty in both genders (P < 0.001). The impact of BF on aBMD was greater in later puberty in girls (0.0025 g cm(-2) per 10% BF at 10 years versus 0.016 g cm(-2) per 10% BF at 14 years, P < 0.001).

CONCLUSION

Greater BF is associated with larger bones, but also denser bones in girls. The effects of fat and puberty are complex and gender specific, but BF of contemporary UK children does not appear to be deleterious to bone quality.

Evidence of early beta-cell deficiency among children who show impaired fasting glucose: 10-yr cohort study (EarlyBird 56)

OBJECTIVE

Impaired fasting glucose (IFG) is a predictor of future diabetes and is increasingly common in children, but the extent to which it results from excess insulin demand or failure of supply is unclear. Our aim was to compare the behaviour of insulin sensitivity and beta-cell function in children who developed IFG with those whose glucose levels remained within the normal range.

METHODS

We examined trends in fasting glucose, insulin sensitivity (HOMA-S) and beta-cell function (HOMA-B) in 327 healthy children annually from 5 to 15 yr, and the parents at baseline.

RESULTS

Fifty-five children showed IFG, mostly after age 11 yr. Fasting glucose rose progressively and was higher throughout in those who developed IFG compared with those who did not (p < 0.001). Beta-cell function was lower from the age of 5 yr in those who developed IFG (p = 0.006), but there was no difference in BMI (p = 0.71). A difference in insulin sensitivity was revealed on adjustment for covariates (p = 0.03). Glucose was higher (p < 0.001), beta-cell function lower (p = 0.01), and insulin sensitivity the same (p = 0.86) in the mothers of children who showed IFG, compared with those who did not.

CONCLUSIONS

IFG is common in contemporary children, and appears to be related to a defect in beta-cell function already present at 5 yr. Similar findings in the mothers of IFG children suggest that the beta-cell defect may be transmissible.

Differences in body composition and metabolic status between white U.K. and Asian Indian children (EarlyBird 24 and the Pune Maternal Nutrition Study)

BACKGROUND/AIMS

The concept of the 'thin-fat' Indian baby is well established, but there is little comparative data in older children, and none that examines the metabolic correlates. Accordingly, we investigated the impact of body composition on the metabolic profiles of Asian Indian and white U.K. children.

METHODS

Body mass index (BMI), waist circumference, sum of four skin-folds, % body fat (by dual-energy X-ray absorptiometry), glucose, insulin, insulin resistance (Homeostasis Model Assessment), trigylcerides, cholesterol [total, low-density lipoprotein, high-density lipoprotein {HDL}, total/HDL ratio] and blood pressure (systolic, diastolic and mean arterial) were measured in 262 white Caucasian children from Plymouth, U.K. (aged 6.9 ± 0.2 years, 57% male), and 626 Indian children from rural villages around Pune, India (aged 6.2 ± 0.1 years, 53% male).

RESULTS

Indian children had a significantly lower BMI (boys: -2.1 kg m(-2) , girls: -3.2 kg m(-2) , both P < 0.001), waist circumference (P < 0.001) and skin-fold thickness (P < 0.001) than white U.K. children, yet their % body fat was higher (boys +4.5%, P < 0.001, girls: +0.5%, P = 0.61). Independently of the differences in age and % body fat, the Indian children had higher fasting glucose (boys +0.52 mmol L(-1) , girls +0.39 mmol L(-1) , both P < 0.001), higher insulin (boys +1.69, girls +1.87 mU L(-1) , both P < 0.01) and were more insulin resistant (boys +0.25, girls +0.28 HOMA-IR units, both P < 0.001).

CONCLUSIONS

The 'thin-fat' phenotype observed in Indian babies is also apparent in pre-pubertal Indian children who have greater adiposity than white U.K. children despite significantly lower BMIs. Indian children are more insulin resistant than white U.K. children, even after adjustment for adiposity.

The convergence of type 1 and type 2 diabetes in childhood: the accelerator hypothesis

It seems likely that type 1 and type 2 diabetes lie at different points of the same spectrum, separated by the misunderstanding that one belongs to childhood and the other to adulthood. The spectrum is that of tempo--the rate at which beta cell function is lost over time. A combination of beta cell up-regulation (insulin demand, largely determined by obesity) and the genetically-determined immune response to it ('autoimmunity') determines tempo, ranging from slow to fast with every variant in between. There is good evidence that people who go on to develop type 1 (fast) diabetes are, like those who develop type 2 (slow diabetes), insulin resistant, and overwhelming evidence that body mass plays a key role. The prevention of type 1 diabetes may lie in weight restriction from an early age.

The contribution of parental BMI to the metabolic health of their offspring: a longitudinal cohort study (EarlyBird 55)

OBJECTIVE

The objective of this study was to establish the extent to which parental factors influence the metabolic health of their offspring.

DESIGN

The study was designed as a prospective longitudinal cohort study

SUBJECTS

The study's subjects were 226 healthy trios from a 1995 to 1996 birth cohort randomly recruited in the city of Plymouth, UK MEASUREMENTS: Body mass index (BMI) and metabolic z-score (derived from natural log HOMA-IR, triglycerides, total/high-density lipoprotein cholesterol ratio), measured at nine annual time points, from 5 to 13 years.

RESULTS

As expected, the metabolic z score was closely related to BMI in both genders and at all ages (r = 0.40-0.57, P < 0.001). Accordingly, there were large and significant differences in the metabolic z-score between children categorized as normal weight or overweight/obese. At 13 years, for example, the metabolic z score of the overweight/obese girls was 14-fold greater than that of the normal-weight girls (P < 0.001). However, parental BMI and metabolic status had little effect on these differences. Indeed, mixed effects modelling showed that, as the child's BMI increased, so the influence of parental factors became less relevant. Time-lag analyses confirmed that weight gain preceded metabolic disturbances in the children.

CONCLUSION

The impact of obesity on the metabolic health of contemporary children is a function of their own weight gain, rather than that of their parents, and is therefore potentially preventable.

Age before stage: insulin resistance rises before the onset of puberty: a 9-year longitudinal study (EarlyBird 26)

OBJECTIVE

Insulin resistance (IR) is associated with diabetes. IR is higher during puberty in both sexes, with some studies showing the increase to be independent of changes in adiposity. Few longitudinal studies have reported on children, and it remains unclear when the rise in IR that is often attributed to puberty really begins. We sought to establish from longitudinal data its relationship to pubertal onset, and interactions with age, sex, adiposity, and IGF-1.

RESEARCH DESIGN AND METHODS

The EarlyBird Diabetes study is a longitudinal prospective cohort study of healthy children aged 5-14 years. Homeostasis model assessment (HOMA-IR), skinfolds (SSF), adiposity (percent fat, measured by dual-energy X-ray absorptiometry), serum leptin, and IGF-1 were measured annually in 235 children (134 boys). Pubertal onset was adduced from Tanner stage (TS) and from the age at which luteinizing hormone (LH) first became serially detectable (≥0.2 international units/L).

RESULTS

IR rose progressively from age 7 years, 3-4 years before TS2 was reached or LH became detectable. Rising adiposity and IGF-1 together explained 34% of the variance in IR in boys and 35% in girls (both P < 0.001) over the 3 years preceding pubertal onset. The contribution of IGF-1 to IR was greater in boys, despite their comparatively lower IGF-1 levels.

CONCLUSIONS

IR starts to rise in mid-childhood, some years before puberty. Its emergence relates more to the age of the child than to pubertal onset. More than 60% of the variation in IR prior to puberty was unexplained. The demography of childhood diabetes is changing, and prepubertal IR may be important.

Direction of causality between body fat and insulin resistance in children--a longitudinal study (EarlyBird 51)

OBJECTIVE

To investigate the direction of causality in the association between adiposity and insulin resistance in children.

METHODS

Body composition by DEXA, and insulin resistance by HOMA-2 IR were measured annually in 238 children aged from 7-13 years. Longitudinal modelling was used to establish whether baseline and/or trends in adiposity were associated with change in IR or whether, conversely, baseline and/or trends in IR were associated with change in adiposity.

RESULTS

Baseline adiposity was associated with change in IR in the short-term (p < 0.001) but less so in the long-term (p < 0.09) in both genders. Baseline IR was not associated with short-term change in adiposity in either gender (p > 0.42). In the long-term, baseline IR appeared to be positively associated with change in adiposity in boys (p = 0.02) but inversely associated with change in adiposity (the higher the baseline IR, the lower the gain in %fat) in girls (p < 0.001).

CONCLUSIONS

The dominant direction of causality appears to be from adiposity to insulin resistance. In boys, adiposity appears to be both a cause and an effect of IR in the long term. In girls, however, higher insulin resistance appeared to limit further gain in body fat in the long term, an observation consistent with insulin desensitization as an adaptive response to weight gain.

The relationship of height and body fat to gender-assortative weight gain in children. A longitudinal cohort study (EarlyBird 44)

OBJECTIVE

Height, body fat and body mass index (BMI) are correlated in children, so we hypothesized that the gender-assortative associations in BMI recently reported in contemporary children might extend to their height and body fat.

DESIGN

Prospective longitudinal cohort study.

SUBJECTS

A total of 226 healthy trios (mother, father and child) from a 1995?1996 birth cohort randomly recruited in the city of Plymouth, UK.

MEASUREMENTS

Height, weight, and BMI (kg/m(2)) were measured in each of the parents and, in addition, sum of five skin-folds (SF) in their children at 5, 6, 7 and 8 y.

RESULTS

BMI and SF were strongly height-dependent in the children by 8 y (r = 0.41-0.56). SF was gender-assortative insofar as the mean SF was significantly greater in the daughters (but not the sons) of obese mothers (obese vs. normal weight: +2.5 cm p < 0.001) and in the sons (but not the daughters) of obese fathers (obese vs. normal: +1.3 cm p < 0.001). As expected, offspring height correlated with that of their parents, but overweight/obese children were systematically taller than normal weight children (boys: +1.02 SDS, girls: +1.14 SDS, p < 0.01), and this difference was independent of parental height or BMI.

CONCLUSIONS

Height is transmitted by both parents, and the body fat of overweight/obese children largely by the same-sex parent, but the extra height associated with more fat in the child is unrelated to the height or weight of either parent. The secular trend in height among contemporary children may simply reflect their rising body fat. Excess fat is unhealthy, so the trend in height may not be healthy either.

Consistency of children's dietary choices: annual repeat measures from 5 to 13 years (EarlyBird 49)

The objective of the present study was to explore the consistency of dietary choices made by children as they grow up. The dietary habits of 342 healthy children were reported annually from 5 to 13 years on a forty-five-item FFQ and analysed by factor analysis. The same two principal dietary patterns – ‘Healthy’ and ‘Unhealthy’ – emerged each year, and their consistency was assessed using Tucker's congruence coefficient (φ). Individual dietary z-scores for both of these patterns were then calculated every year for each child, and their consistency was measured by Pearson's correlation coefficient (r). Linear mixed-effects modelling was used to investigate individual trends and to quantify reliability of the individual dietary z-scores. Dietary patterns were moderately consistent and systematic over time (0·65 ≤ φHealthy ≤ 0·76; 0·62 ≤ φUnhealthy ≤ 0·78). Individual choices were also consistent year-on-year (0·64 ≤ rHealthy ≤ 0·71; 0·57 ≤ rUnhealthy ≤ 0·68). Reliability rose from 70 % with a single measure to over 90 % with four consecutive measures. The quality of diet diminished over time in 29 % of the children and improved in only 14 %. Dietary habits appear to be set early and seldom improve spontaneously.

Changes in resting energy expenditure and their relationship to insulin resistance and weight gain: a longitudinal study in pre-pubertal children (EarlyBird 17)

BACKGROUND & AIMS

In adults, adjustments in resting energy expenditure (REE) are used to defend energy balance against disturbance caused by over-and under-nutrition, and may be linked to changes in insulin resistance and leptin. Little is known of these associations in children. Our aim was to test the hypothesis that long-term weight gain in children is met with adaptive changes in resting energy expenditure, mediated by insulin resistance and/or leptin.

METHODS

REE by indirect calorimetry, anthropometry, body composition by DEXA, insulin resistance (HOMA-IR) and serum leptin were measured annually in 232 children from the age of 7-10 y.

RESULTS

REE rose from 7 to 10 y, and the rise exceeded that predicted by the concurrent rise in fat and fat-free mass by 184 kcal/day in the boys and by 160 kcal/day in the girls. However, there were no significant relationships in either gender between this 'excess' rise in REE and change in body composition (r < or = 0.08, p > or = 0.42). The rise in both boys and girls was associated with, but not explained by, a rise in insulin resistance (p < or = 0.002). There was no association with serum leptin (p > or = 0.32).

CONCLUSIONS

The data do not support the hypothesis of adaptive changes in REE in pre-pubertal children, and insulin resistance explains very little of the pre-pubertal rise in REE. The rise in REE beyond that explained by changes in body composition may reflect an increase in energy requirements prior to puberty.

Gender differences in the relationship between heart rate control and adiposity in young children: a cross-sectional study (EarlyBird 33)

BACKGROUND

The role of the autonomic nervous system in the complex link between insulin resistance and cardiovascular risk remains unclear. Increased sympathetic nervous system activity has been implicated in the pathophysiology of insulin resistance but is confounded by a number of factors.

METHODS

We have therefore examined the relationship among cardiac autonomic control, insulin resistance, habitual physical activity, resting energy expenditure (REE), and anthropometric variables in a subset (107 boys, 101 girls, age 9 +/- 0.25 yr) of the EarlyBird cohort. Cardiac autonomic activity was assessed using time domain and power spectral density analysis methods of heart rate variability. Insulin resistance was measured using homeostasis model assessment of insulin resistance (HOMA2-IR).

RESULTS

Girls, in comparison to boys, showed significantly higher resting heart rate and lower systolic blood pressure (BP); were more insulin resistant; undertook less physical activity, and had lower fat-free mass and REE. Increasing fasting insulin and increasing insulin resistance were associated with increasing BP.

CONCLUSION

The data suggest early gender differences in predictors of cardiac autonomic control. Pubertal staging was not undertaken in this study, and we plan to evaluate this in future studies to further clarify these associations.

Objectively measured physical activity and its association with adiponectin and other novel metabolic markers: a longitudinal study in children (EarlyBird 38)

OBJECTIVE

Recent evidence suggests that, in children, traditional markers of metabolic disturbance are related only weakly to physical activity. We therefore sought to establish the corresponding relationships with newer metabolic markers.

RESEARCH DESIGN AND METHODS

This was a nonintervention longitudinal study of 213 healthy children recruited from 54 schools in Plymouth, U.K. MTI accelerometers were used to make objective 7-day recordings of physical activity at ages 5 +/- 0.3 (mean +/- SD), 6, 7, and 8 years. Overall physical activity was taken as the average of the four annual time points. The metabolic markers at 8 years were adiponectin, leptin, high-sensitivity C-reactive protein (hsCRP), and insulin resistance (homeostasis model assessment). Potential confounders included percent body fat measured by dual-energy X-ray absorptiometry and diet measured by food frequency questionnaire.

RESULTS

Whereas physical activity did not correlate with insulin resistance (r = -0.01), leptin (r = +0.04), or hsCRP (r = +0.01) independently of percent body fat, it did correlate with adiponectin, but inversely (r = -0.18, P = 0.02). This unexpected inverse relationship was strongest among the less active children (physical activity < median: r = -0.30, P = 0.01) but negligible in the more active children (physical activity > median: r = +0.04, P = 0.76). Adiponectin was significantly higher (0.52 SD, P < 0.01) in the least active tertile compared with the other two tertiles. Insulin resistance, however, did not differ across the physical activity tertiles (P = 0.62).

CONCLUSIONS

Adiponectin levels in children are highest among those who are least active, but their insulin resistance is no different. Adiponectin has a known insulin-sensitizing effect, and our findings are consistent with a selective effect at low levels of physical activity.

Contribution of early weight gain to childhood overweight and metabolic health: a longitudinal study (EarlyBird 36)

BACKGROUND

Early weight gain (0-5 years) is thought to be an important contributor to childhood obesity and consequently metabolic risk. There is a scarcity of longitudinal studies in contemporary children reporting the impact of early weight gain on metabolic health.

OBJECTIVE

We aimed to assess the impact of early weight gain on metabolic health at 9 years of age.

METHOD

Two hundred thirty-three children (134 boys, 99 girls) with a gestational age of >37 weeks were assessed at birth, 5 years of age, and 9 years of age. Measures included weight SD scores at each time point and excess weight gained (Delta weight SD score) between them. The outcome measure included composite metabolic score (sum of internally derived z scores of insulin resistance, mean blood pressure, triglyceride level, and total cholesterol/high-density lipoprotein cholesterol ratio).

RESULTS

Weight SD score increased by 0.29 SD score in girls and 0.26 SD score in boys from 0 to 5 years of age and by 0.03 SD score in girls and 0.11 SD score in boys from 5 to 9 years of age. Weight SD score correlated poorly to moderately before 5 years of age but strongly after 5 years of age. Birth weight SD score predicted (girls/boys) 2.4%/0% of the variability in composite metabolic score at 9 years of age. Adding Delta weight SD score (0-5 years old) contributed (girls/boys) 11.2%/7.0% to the score, and adding Delta weight SD score (5-9 years old) additionally contributed (girls/boys) 26.4%/16.5%. Importantly, once weight SD score at 9 years of age was known, predictive strength was changed little by adding Delta weight SD score.

CONCLUSIONS

Most excess weight before puberty is gained before 5 years of age. Weight at 5 years of age bears little relation to birth weight but closely predicts weight at 9 years of age. Single measures of current weight are predictive of metabolic health, whereas weight gain within a specific period adds little. A single measure of weight at 5 years of age provides a pointer to future health for the individual. If metabolic status at 9 years of age means future risk, diabetes/cardiovascular prevention strategies might better focus on preschool-aged children, because the die seems to be largely cast by 5 years of age, and a healthy weight early in childhood may be maintained at least into puberty.

Cytokines and beta-cell biology: from concept to clinical translation

The tale of cytokines and the beta-cell is a long story, starting with in vitro discovery in 1984, evolving via descriptive and phenomenological studies to detailed mapping of the signalling pathways, gene- and protein expression patterns, molecular and biochemical effector mechanisms to in vivo studies in spontaneously diabetic and transgenic animal models. Only very recently have steps been taken to translate the accumulating compelling preclinical data into clinical trials. The aim of this chapter is to present an overview of early and recent key observations from our own groups as well as other laboratories that serve to illuminate the road from concept to clinical translation.

Size at birth, obesity and blood pressure at age five

BACKGROUND

The fetal origins hypothesis indicates that morphometric evidence of fetal nutritional deprivation is predictive of excessive weight gain/obesity, insulin resistance, and cardiovascular disease after birth. However, it is unclear whether these effects are present in offspring with "normal" birth weights in contemporary Western society, whether they are population specific, and how early in life they appear. This study was designed to examine these questions in a select populace of morphometrically diverse offspring to test the null hypothesis that morphometric evidence of nutritional restriction in utero has no effect on the presence of either obesity or increased blood pressure at ages 5 and 6.

METHODS

We present a prospective study of 101 offspring born of well-nourished, middle and upper socioeconomic-class women who participated in studies of diet and exercise during pregnancy. At birth and age 5 to 6 the offspring underwent morphometric evaluation with the additional measurement of blood pressure at age 5 to 6.

RESULTS

There were no significant negative correlations between neonatal morphometrics and either blood pressure or obesity at age 5 to 6. There were, however, direct positive correlations between birth weight and both weight and BMI at age 5 to 6 (p < 0.0001).

CONCLUSIONS

In this specific populace, morphometrics at age 5 to 6 correlated with size at birth. However, there was no relationship between mophometric evidence of in utero nutritional deprivation at birth and either blood pressure or obesity at age 5 to 6.

Validation of foot-to-foot bioelectrical impedance analysis with dual-energy X-ray absorptiometry in the assessment of body composition in young children: the EarlyBird cohort

Foot-to-foot bioelectrical impedance analysis (BIA) is simple and non-invasive, making it particularly suitable for use in children. There is insufficient evidence of the validity of foot-to-foot BIA compared with dual-energy X-ray absorptiometry (DEXA) as the criterion method in healthy young children. Our objective was to assess the validity of foot-to-foot BIA against DEXA in a large cohort of healthy young children. Body composition was measured by foot-to-foot BIA and DEXA in 203 children (mean age 8·9 (sd0·3) years). Bland–Altman and simple linear regression analyses were used to determine agreement between methods. BIA overestimated fat-free mass by a mean of 2·4 % in boys and 5·7 % in girls, while fat mass was underestimated by 6·5 % in boys and 10·3 % in girls. The percentage fat recorded by BIA was, accordingly, also lower than by DEXA (boys 4·8 %; girls 12·8 %). In boys, however, there were correlations between the size of the difference between methods and the size of the measure under consideration such that in smaller boys fat-free mass was underestimated (r − 0·57;P < 0·001) while fat mass and percentage fat were overestimated (r0·74 for fat mass;r0·69 for percentage fat; bothP < 0·001) with the reverse in bigger boys. Mean differences between techniques were greater in the girls than in the boys but in boys only, the direction of the differences was dependent upon the size of the child. Therefore, BIA may be useful for large-scale studies but is not interchangeable with DEXA and should be interpreted with caution in individuals.

The gender insulin hypothesis: why girls are born lighter than boys, and the implications for insulin resistance

Girls are born lighter than boys. The consistency of this observation across different populations is striking, suggesting that it may have fundamental significance for those conditions linked with lower birth weight, such as diabetes. Previous hypotheses relating low birth weight to subsequent diabetes have addressed differences in insulin resistance within the sexes, not between them. Here, we propose that gender-specific genes affecting insulin sensitivity are responsible for the gender difference in birth weight--the genetically more insulin resistant female fetus is less responsive to the trophic effects of insulin and is therefore smaller. These genes also render female subjects more susceptible to diabetes, explaining why reports of type 2 diabetes (T2D) in younger populations show a female preponderance. Consistent with our proposal, concentrations of insulin and/or its propeptides are higher at birth in female populations and they are intrinsically more insulin resistant throughout life, with attendant impact on their metabolism, and the regressions describing the relationship between insulin resistance and adiposity in female and male subjects have similar gradients, but different constants. These gender-specific genes have a demonstrable impact on fetal growth and insulin resistance. Diabetes and cardiovascular disease are thought to be driven by insulin resistance, and the observations reported here may help to focus the search for genes that control it.

Little evidence for early programming of weight and insulin resistance for contemporary children: EarlyBird Diabetes Study report 19

OBJECTIVE

The aim of this study was to evaluate whether adaptive responses made to the uterine or very early infant environment are affecting the current metabolic health of young children in the United Kingdom.

METHODS

Participants were 300 healthy children and their parents from the EarlyBird Diabetes Study cohort. Children were recruited from randomly selected schools at 5 years of age. Retrospective measures were maternal prepregnancy weight (n = 230), maternal fasting glucose levels at 28 weeks of pregnancy (n = 27), birth weight, and infant weight at ages 3 and 6 weeks. Prospective measures were insulin resistance, height, weight, and percentage of body fat (sum of 5 skinfold measurements) at ages 5, 6, 7, and 8 years.

RESULTS

Maternal third-trimester fasting glucose levels were associated positively with birth weight but were not associated with either weight or insulin resistance for the same children at 8 years. Birth weight was unrelated to insulin resistance at 8 years. There were no relationships between weight change in the first weeks of life and weight, percentage of fat, or insulin resistance at 8 years. Longer breastfeeding correlated inversely, although weakly, with percentage of body fat for boys only. Current weight was correlated with insulin resistance at 8 years.

CONCLUSIONS

For these contemporary children, neither the gestational environment nor early postnatal growth predicted insulin resistance, which was best predicted by current weight. There was no evidence that predictive adaptive responses made by the fetus or infant affected the child's weight or insulin resistance later in childhood.

Variation in physical activity lies with the child, not his environment: evidence for an ‘activitystat’ in young children (EarlyBird 16)

OBJECTIVE

There is currently wide interest in the physical activity of children, but little understanding of its control. Here, we use accelerometers to test the hypothesis that habitual activity in young children is centrally, rather than environmentally, regulated. By central regulation we mean a classic biological feedback loop, with a set-point individual to the child, which controls his/her activity independently of external factors.

DESIGN

Non-intervention, observational and population-based, set in the home and at school.

RESULTS

Girls were systematically less active than boys, and both weekday/weekend day and year-on-year activities were correlated (r=0.43-0.56). A fivefold variation in timetabled PE explained less than 1% of the total variation in physical activity. The activity cost of transport to school was only 2% of total activity, but over 90% of it was recovered elsewhere in the day. The weekly activity recorded by children in Plymouth was the same (to within <0.3%) as that recorded independently in Glasgow, 800 km away. Total daily activity was unrelated to time reportedly spent watching TV.

INTERPRETATION

The correlations within groups and the similarities between them suggest that physical activity in children is under central biological regulation. There are implications both for public health planners and for the potentially novel signalling pathways involved.

The great weight gain experiment, accelerators, and their implications for autoantibodies in diabetes

Perspective on the paper by Reinehr et al (see page 473)

IOTF thresholds for overweight and obesity and their relation to metabolic risk in children (EarlyBird 20)

The International Obesity TaskForce has published paediatric cutoffs from the age of 2 years for overweight and obesity, based on adult thresholds. We question their rationale. The adult cutoffs were based on known health risk; the children's were not. Data from the EarlyBird Study show that BMI category for overweight and obesity in young children are poor markers of insulin resistance and, by implication, of metabolic risk and diabetes. Moreover, BMI is known to track poorly from early childhood to adulthood. We know even less about the tracking of insulin resistance and other indices of metabolic risk from the earliest years. Until we understand more about which children acquire such risk factors, any such thresholds for overweight and obesity should be used with caution in the very young, as they may unnecessarily stigmatise the heavier child.

Metabolic risk in early childhood: the EarlyBird Study

OBJECTIVE

For a decade or more, poor nutrition during gestation, expressed as low weight at birth, was held to be the factor responsible for insulin resistance later in life. Birth weights, however, are rising and insulin-resistant states, such as diabetes, faster still. Alternative explanations are needed for insulin resistance in contemporary society. This review cites data from the EarlyBird study on the relationships of insulin resistance and metabolic disturbance in early childhood.

DESIGN

EarlyBird is a nonintervention prospective cohort study that asks the question 'Which children develop insulin resistance, and why?' It is unique in taking serial blood samples from a young age with which to monitor the behaviour of insulin resistance and its metabolic correlates, and in its comprehensive assessment of factors known or thought to influence insulin resistance

SUBJECTS

In all, 307 randomly selected healthy school children at school entry (mean age 4.9 y) and at 12 and 24 months later.

MEASUREMENTS

In the children: Birth weight and, at each time point height, weight, body mass index (BMI, kg/m(2)), skinfolds at five sites, circumferences, resting energy expenditure, physical activity, body composition, heart rate variability, diet, HOMA-IR and HOMA-ISC, blood pressure, full blood count, haemoglobin and haematocrit, HbA1C, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, uric acid, IGF-1, gonadotrophins and SHBG. In their parents: At baseline height, weight, BMI, waist circumference, HOMA-IR and HOMA-ISC, full blood count, haematocrit, HbA1C, total cholesterol, HDL cholesterol, calculated LDL cholesterol, triglycerides, uric acid, gonadotrophins and SHBG.

RESULTS

Four observations are reported here: (1) There are clear correlations in contemporary children between insulin resistance and weight at 5 y, but none with birth weight. (2) Females throughout life are intrinsically more insulin resistant than males. (3) The substantial variation of physical activity among young children is attributable to the child, and not to his environment. (4) There is dissociation in young children between fatness and insulin resistance.

CONCLUSION

There is much yet to be learned about the development of obesity and insulin resistance in children. The notions of overnutrition and underactivity alone are too simplistic.

Genetic regulation of birth weight and fasting glucose by a common polymorphism in the islet cell promoter of the glucokinase gene

Rare mutations in the glucokinase (GCK) gene cause fasting hyperglycemia and considerably influence birth weight when present in a mother or her offspring. The role of common variation of GCK is uncertain. A polymorphism at position -30 of the GCK beta-cell-specific promoter, present in 30% of the population, has been variably associated with type 2 diabetes and diabetes-related quantitative traits. Using 1,763 U.K. Caucasian normoglycemic adult subjects, we demonstrated that the A allele at GCK(-30) is associated with a 0.06-mmol/l increase in fasting plasma glucose (FPG) (P = 0.003). The A allele was also associated with an increase in FPG in 755 women who were 28 weeks pregnant (0.075 mmol/l, P = 0.003). We then went on to analyze the effect of GCK(-30) on birth weight using 2,689 mother/child pairs. The presence of the A allele in the mother was associated with a 64-g (25-102 g) increase in offspring birth weight (P = 0.001). We did not detect a fetal genotype effect. The increase in offspring birth weight in the 30% of mothers carrying an A allele at GCK(-30) is likely to reflect an elevated FPG during pregnancy. This study establishes that common genetic variation, in addition to rare mutations and environmental factors, can affect both FPG and birth weight.

The impact of pregnancy weight and glucose on the metabolic health of mother and child in the south west of the UK

OBJECTIVE

to explore relationships between maternal pre-pregnancy weight, third trimester glucose, baby birth weight, weight and metabolic health of the mother and child 5 years after birth.

DESIGN

an observational study set within a non-intervention, longitudinal cohort study looking at insulin resistance in children.

SETTING

a teaching hospital in the south west of the United Kingdom.

PARTICIPANTS

300 mothers and their five-year-old children from randomly selected Plymouth schools, stratified according to socioeconomic status.

MEASUREMENTS

were obtained from obstetric records maternal pre-pregnant weight, random and fasting third trimester blood glucose, baby birth weight. Five years later the following measurements were made of the mother and child: height, weight, glucose and insulin resistance.

FINDINGS

five years after the pregnancy, 33% of the mothers were overweight, with an additional 19% obese. In the children 13% of boys were overweight (4% obese), and in the girls, 26% were overweight (5% obese). In the five-year-old children, weight (r=0.28, p<0.001) but not birth weight (r=0.03, p=0.573), correlated with insulin resistance. Maternal pre-pregnant weight was related to both random and fasting third trimester glucose, and to insulin resistance 5 years later. Third trimester fasting glucose, even within a normal range, was a better predictor than random glucose of the baby's birth weight (r=0.39, p=0.044) and the mother's future insulin resistance (r=0.67, p<0.001). No maternal measures predicted insulin resistance in the child at 5 years.

CONCLUSIONS

maternal weight had an important influence on the gestational environment, and predicted insulin resistance 5 years later. Fasting glucose, even within the reference range, was a better predictor than random glucose of the baby's birth weight and the mother's future insulin resistance.

IMPLICATIONS FOR PRACTICE

these concern the importance of pre-conception weight management, and support replacement of routine random glucose sampling during the third trimester with an earlier, fasting measurement.