Sex differences in resting energy expenditure and their relation to insulin resistance in children (EarlyBird 13)

The role of oestrogen in determining sexual dimorphism in energy balance

Energy balance is determined by caloric intake and the rate at which energy is expended, with the latter comprising resting energy expenditure, physical activity and adaptive thermogenesis. The regulation of both energy intake and expenditure exhibits clear sexual dimorphism, with young women being relatively protected against weight gain and the development of cardiometabolic diseases. Preclinical studies have indicated that females are more sensitive to the satiety effects of leptin and insulin compared to males. Furthermore, females have greater thermogenic activity than males, whereas resting energy expenditure is generally higher in males than females. In addition to this, in post-menopausal women, the decline in sex steroid concentration, particularly in oestrogen, is associated with a shift in the distribution of adipose tissue and overall increased propensity to gain weight. Oestrogens are known to regulate energy balance and weight homeostasis via effects on both food intake and energy expenditure. Indeed, 17β-oestradiol treatment increases melanocortin signalling in the hypothalamus to cause satiety. Furthermore, oestrogenic action at the ventromedial hypothalamus has been linked with increased energy expenditure in female mice. We propose that oestrogen action on energy balance is multi-faceted and is fundamental to determining sexual dimorphism in weight control. Furthermore, evidence suggests that the decline in oestrogen levels leads to increased risk of weight gain and development of cardiometabolic disease in women across the menopausal transition.

Association between pubertal development stages and body adiposity in children and adolescents

Background

The study aimed to analyze the association between pubertal development stages and adiposity in children and adolescents.

Methods

Cross-sectional study conducted in 2007 in Florianópolis, Brazil, with 2339 schoolchildren 32 aged 8 to 14 years old (1107 males). The outcome (adiposity) was evaluated using Z score and 33 percentilee values > = 85 of four skinfolds (triceps, subscapular, suprailiac and calf) and waist 34 circumference. Total body adiposity (Z score of the sum of skinfolds), central adiposity (Z score 35 of waist circumference) and peripheral adiposity (Z scores of triceps and calf skinfolds) were 36 estimated. Pubertal development stages was self-assessed according to Tanner stages of development. Thirty-seven Children and adolescents were classified according to tertiles of age for each pubertal development stages 38 stage - early, normal and late. Statistical analysis was performed using univariate and 39 multivariate Poisson regression models.

Results

Children and adolescent from both sexes with early pubertal development stages presented higher prevalence of central adiposity (waist circumference), with adjusted prevalence ratio (CI 95%) of 2.21 (1.12; 4.35) for males and 2.18 (1.04; 4.57) for females (reference group: normal pubertal development stages). Among females, there was a reduction in the prevalence of excess adiposity with decreased occurrence of early pubertal development stages. There was a strong relationship between adiposity and pubertal development stages.

Conclusions

Excess adiposity was higher in both sexes for those with early pubertal development stages.

Effect of Serum Leptin on Weight Gain Induced by Olanzapine in Female Patients with Schizophrenia

BACKGROUND

Olanzapine (OLZ) treatment is associated with a high risk of weight gain, and may cause abnormalities in glycolipid metabolism. Therefore, the underlying mechanism of OLZ-related weight gain is needed to clarify but not yet been adequately determined. In recent years, adipocytokines such as leptin, adiponectin, and tumor necrosis factor (TNF)-α, which play important roles in energy homeostasis, have been suggested as biomarkers of weight gain. Here, we determined if baseline plasma concentrations of leptin, adiponectin, and TNF-α predict weight gain following OLZ treatment.

METHODS

We recruited 31 schizophrenia outpatients (12 men and 19 women, 28.8 ± 10.2 years old) that were unmedicated or on another antipsychotic monotherapy medication. Baseline body mass index (BMI) and plasma levels of leptin, adiponectin, and TNF-α were obtained. All patients started or were switched to OLZ monotherapy for a maximum of 1 year. BMI was also obtained at the endpoint.

RESULTS

Mean BMI change following OLZ treatment was 2.1 ± 2.7 kg/m2. BMI change from baseline to endpoint negatively-correlated with baseline leptin levels in female patients (r = -0.514, P = 0.024), but not male patients. Baseline adiponectin or TNF-α levels were not correlated with BMI change.

CONCLUSION

Baseline plasma leptin can have an effect on subsequent weight gain following OLZ treatment in female patients with schizophrenia.

Prevalence and trends in obesity among China's children and adolescents, 1985-2010

Objectives

We examined the prevalence of and trends in obesity among children and adolescents in China (1985–2010).

Methods

We used data from the 1985, 1991, 1995, 2000, 2005, and 2010 Chinese National Surveys on Students’ Constitution and Health (CNSSCH). The CNSSCH is a national survey of physical fitness and health status in Chinese students that uses multistage stratified sampling of 31 provinces and municipalities. A subject was considered obese or overweight if weight-for-height exceeded the 20% or 10% of standard weight-for-height. The standard weight-for-height was the 80th percentile for sex- and age-specific growth charts.

Results

The age-adjusted prevalence of obesity and of overweight and obesity combined was 8.1% (95% CI, 8.0–8.3%) and 19.2% (95% CI, 19.1–19.4%) among children and adolescents 7–18 years in age. Obesity was more likely to be present among children or adolescents who were male (RR, 1.93; 95% CI, 1.90–1.97), urban (RR, 1.99; 95% CI, 1.95–2.02), or 10–12 years (RR, 1.43; 95% CI, 1.40–1.46). Trend analyses of the 25-year period revealed a significant increasing trend in males (RR, 1.59; 95% CI, 1.58–1.60) and in females (RR, 1.49; 95% CI, 1.48–1.50). The rate of increase in obese or overweight prevalence was highest in boys from rural areas (9% annual increase).

Conclusions

During 1985–2010, there was a significant and continuous increase in the prevalence of obesity in children and adolescents. Obesity is epidemic in China, but may be reduced with evidence-based interventions (e.g., school intervention programs).

Neural growth hormone implicated in body weight sex differences

As for many human diseases, the incidence of obesity and its associated health risks are sexually dimorphic: worldwide the rate of obesity is higher in women. Sex differences in metabolism, appetite, body composition, and fat deposition are contributing biological factors. Gonadal hormones regulate the development of many sexually dimorphic traits in humans and animals, and, in addition, studies in mice indicate a role for direct genetic effects of sex chromosome dosage on body weight, deposition of fat, and circadian timing of feeding behavior. Specifically, mice of either sex with 2 X chromosomes, typical of normal females, have heavier body weights, gain more weight, and eat more food during the light portion of the day than mice of either sex with a single X chromosome. Here we test the effects of X chromosome dosage on body weight and report that gonadal females with 2 X chromosomes express higher levels of GH gene (Gh) mRNA in the preoptic area (POA) of the hypothalamus than females with 1 X chromosome and males. Furthermore, Gh expression in the POA of the hypothalamus of mice with 2 X chromosomes correlated with body weight; GH is known to have orexigenic properties. Acute infusion of GH into the POA increased immediate food intake in normal (XY) males. We propose that X inactivation-escaping genes modulate Gh expression and food intake, and this is part of the mechanism by which individuals with 2 X chromosomes are heavier than individuals with a single X chromosome.

Secular trends of obesity prevalence in urban Chinese children from 1985 to 2010: gender disparity

Based on the data from six Chinese National Surveys on Students Constitution and Health (CNSSCH) from 1985 to 2010, we explored the secular trend in the prevalence of obesity in urban Chinese children over a period of 25 years. The aim of this study was to examine the gender disparities in the prevalence of childhood obesity over time. The standardized prevalence of obesity in Chinese children increased rapidly during the past 25 years from 0.2% in 1985 to 8.1% in 2010. The increasing trend was significant in all age subgroups (p<0.01). Although the prevalence of obesity continuously increased in both boys and girls, the changing pace in boys was faster than that in girls. Age-specific prevalence odds ratios (PORs) of boys versus girls for obesity increased over time during the 25 year period. The prevalence of obesity in boys was significantly higher than in girls in all age-specific subgroups from 1991 and after. The gradually expanding gender disparity suggests the prevalence of obesity in boys contribute to a large and growing proportion of obese children. Therefore, it is critical for developing and implementing gender-specific preventive guidelines and public health policies in China.

Sex differences in regional body fat distribution from pre- to postpuberty

Few large studies have evaluated the emergence of sexual dimorphism in fat distribution with appropriate adjustment for total body composition. The objective of this study was to determine the timing and magnitude of sex differences in regional adiposity from early childhood to young adulthood. Regional fat distribution was measured using dual-energy X-ray absorptiometry (trunk and extremity fat using automatic default regions and waist and hip fat using manual analysis) in 1,009 predominantly white participants aged 5-29 years. Subjects were divided into pre (Tanner stage 1), early (Tanner stages 2-3), late (Tanner stages 4-5), and post (males > or =20 years and females > or =18 years) pubertal groups. Sexual dimorphism in trunk fat (adjusted for extremity fat) was not apparent until late puberty, when females exhibited 17% less (P < 0.001) trunk fat than males. By contrast, sex differences in waist fat (adjusted for hip fat) were apparent at each stage of puberty, the effect being magnified with age, with prepubertal girls having 5% less (P = 0.027) and adult women having 48% less (P < 0.0001) waist fat than males. Girls had considerably more peripheral fat whether measured as extremity or hip fat at each stage. Sex differences in regional adiposity were significantly greater in young adults than in late adolescence. Exclusion of overweight participants did not materially affect the estimates. Sexual dimorphism in fat patterning is apparent even prepubertally with girls having less waist and more hip fat than boys. The magnitude of the sex difference is amplified with maturation, and particularly from late puberty to early adulthood.

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.

Sex differences in obesity and the regulation of energy homeostasis

Obesity prevalence is generally higher in women than in men, and there is also a sex difference in body fat distribution. Sex differences in obesity can be explained in part by the influence of gonadal steroids on body composition and appetite; however, behavioural, socio-cultural and chromosomal factors may also play a role. This review, which evolved from the 2008 Stock Conference on sex differences in obesity, summarizes current research and recommendations related to hormonal and neuroendocrine influences on energy balance and fat distribution. A number of important gaps in the research are identified, including a need for more studies on chromosomal sex effects on energy balance, the role of socio-cultural (i.e. gender) factors in obesity and the potential deleterious effects of high-fat diets during pregnancy on the foetus. Furthermore, there is a paucity of clinical trials examining sex-specific approaches and outcomes of obesity treatment (lifestyle-based or pharmacological), and research is urgently needed to determine whether current weight loss programmes, largely developed and tested on women, are appropriate for men. Last, it is important that both animal and clinical research on obesity be designed and analysed in such a way that data can be separately examined in both men and women.

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.