Role of leptin during childhood growth and development

Adiponectin blood levels and autism spectrum disorders: a systematic review

OBJECTIVE

To review the relationship between adiponectin levels and autism spectrum disorders (ASDs) in children.

BACKGROUND

ASDs are associated with pervasive social interaction and communication abnormalities. Researchers have studied various pathophysiological mechanisms underlying ASDs to identify predictors for an early diagnosis to optimize treatment outcomes. Immune dysfunction, perhaps mediated by a decrease in anti-inflammatory adipokine, adiponectin, along with changes in other adipokines, may play a central role in increasing the risk for ASDs. However, other factors, such as low maternal vitamin D levels, atherosclerosis, diabetes, obesity, cardio-metabolic diseases, preterm delivery, and oxytocin gene polymorphism may also contribute to increased risk for ASDs.

METHODS

Searches on the database; PubMed, Google Scholar, and Cochrane using keywords; adiponectin, adipokines, ASD, autism, autistic disorder, included English-language studies published till September 2022. Data were extracted on mean differences between adiponectin levels in children with and without ASDs.

RESULTS

The search yielded six studies providing data on adiponectin levels in young patients with ASDs. As can be seen from Table 1, four of the six studies were positive for an inverse correlation between ASD and adiponectin levels. In addition, two of the four positive and one negative studies found low adiponectin levels associated with and the severity of autistic symptoms. However, results from one reviewed study were insignificant.

CONCLUSION

Most studies reviewed yielded lower adiponectin levels in children with ASDs as well as the severity of autistic symptoms.

Identification and Optimization of Contributing Factors for Precocious Puberty by Machine/Deep Learning Methods in Chinese Girls

BACKGROUND AND OBJECTIVES

As the worldwide secular trends are toward earlier puberty, identification of contributing factors for precocious puberty is critical. We aimed to identify and optimize contributing factors responsible for onset of precocious puberty via machine learning/deep learning algorithms in girls.

METHODS

A cross-sectional study was performed among girls aged 6-16 years from 26 schools in Beijing based on a cluster sampling method. Information was gleaned online via questionnaires. Machine/deep learning algorithms were performed using Python language (v3.7.6) on PyCharm platform.

RESULTS

Of 11308 students enrolled, there are 5527 girls, and 408 of them had experienced precocious puberty. Training 13 machine learning algorithms revealed that gradient boosting machine (GBM) performed best in predicting precocious puberty. By comparison, six top factors including maternal age at menarche, paternal body mass index (BMI), waist-to-height ratio, maternal BMI, screen time, and physical activity were sufficient in prediction performance, with accuracy of 0.9530, precision of 0.9818, and area under the receiver operating characteristic curve (AUROC) of 0.7861. The performance of the top six factors was further validated by deep learning sequential model, with accuracy reaching 92.9%.

CONCLUSIONS

We identified six important factors from both parents and girls that can help predict the onset of precocious puberty among Chinese girls.

Leptin in sperm analysis can be a new indicator

Purpose Radiotherapy, chemotherapy, various tumors and invasive surgery can result in ejaculatory dysfunction and testicular insufficiency. Sperm cryopreservation is the only method which can provide a baby for couples. Cryopreservation freezes tissues and cells, allowing them to be stored for future use by stopping all biological activities. Cryopreservation can cause some harmful changes in the structure and function of the sperm. Leptin molecule plays many roles in most biological processes including the satiety and cell renewal, proliferation, angiogenesis, modulation of energy expenditure and regulation of the neuroendocrine system. Leptin was also reported to be associated with spermatogenesis in several studies. Methods This study aims to use leptin molecule as a parameter for sperm motility and DNA fragmentation before and after the cryopreservation. In this study, semen samples were taken from 30 normospermic male volunteers. Each semen sample was examined for the same parameters before and after the cryopreservation. Samples were analyzed before and after cryopreservation in terms of sperm motility by morphological sperm analysis with spermac stain dye, DNA fragmentation by TUNEL assay, ultrastructural analysis with transmission electron microscopy (TEM), seminal leptin levels by ELISA method and reactive oxygen species (ROS) levels by colorimetric method. Results Decreased sperm motility, distribution of sperm morphology and increased DNA fragmentation were determined after cryopreservation. Similarly, seminal ROS and leptin levels were also increased significantly. There was a negative correlation between seminal leptin and sperm motility. Additionally, there was a positive correlation between seminal leptin and DNA fragmentation. Conclusion According to these results, leptin molecule can be used as a marker for sperm motility and DNA fragmentation before and after cryopreservation. We think that the results of this study can contribute to further studies in the clinical aspect.

Visceral fat thickness and its associations with pubertal and metabolic parameters among girls with precocious puberty

PURPOSE

This study aimed to investigate associations of central obesity with sexual maturation and metabolic parameters in Korean girls with precocious puberty.

METHODS

This retrospective study evaluated data from 72 girls under 8 years of age with a chief complaint of early breast development. The patients were categorized as central precocious puberty (CPP) subjects or non-CPP subjects based on their gonadotropin-releasing hormone stimulation test results. Visceral fat thickness (VFT) was measured using ultrasonography and defined as the distance from the linea alba to the aorta. Patient anthropometric, metabolic, and hormonal parameters were also evaluated.

RESULTS

Increased VFT was correlated with an earlier onset of thelarche among all study subjects (r=-0.307, P=0.034). Overweight CPP subjects showed higher insulin resistance than normal weight CPP subjects. Insulin resistance was not significantly different between overweight and normal weight non-CPP subjects. VFT was not significantly different between CPP and non-CPP subjects (2.22±0.79 cm vs. 2.74±1.47 cm, P=0.169). However, overweight and obese CPP subjects (body mass index percentile>85%) had lower VFT than non-CPP obese subjects.

CONCLUSION

Central obesity, defined using ultrasonography-measured VFT, might be associated with early pubertal development in Korean girls. However, VFT was not higher in CPP than non-CPP patients and was not significantly correlated with insulin resistance. Further longitudinal studies with a larger cohort are needed.

Investigating the relationship between precocious puberty and obesity: a cross-sectional study in Shanghai, China

OBJECTIVES

Obesity is reported to be closely relevant to early sexual development but the relationship between sexual precocity and obesity or central obesity is still inconsistent, especially in boys. We aimed to investigate the relationship between precocious puberty and obesity as well as central obesity.

DESIGN

A large population-based cross-sectional study using multistage, stratified cluster random sampling.

SETTING

Data from the Shanghai Children's Health, Education and Lifestyle Evaluation (SCHEDULE) study in June 2014.

PARTICIPANTS

17 620 Chinese children aged 6-12 years.

PRIMARY AND SECONDARY OUTCOME MEASURES

Obesity was defined by WHO Child Growth Standards. Central obesity was defined by sex-specific waist-to-height ratio (WHtR) cut-offs (WHtR ≥0.48 for boys, WHtR ≥0.46 for girls). Precocious puberty was identified by Tanner stage of breast, pubic hair and testicle development. A χ² test was performed to compare rates. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the association between precocious puberty and general obesity and central obesity. Probit analysis was used for estimating the median age at entry into Tanner stage 2 or greater for breast, pubic hair and testicle development. Linear regression was utilised to compare the effects of WHtR and body mass index (BMI) on sex development indicators.

RESULTS

25.98% and 38.58% of boys with precocious puberty were respectively accompanied by obesity (OR=2.15, 95% CI=1.31 to 3.50) or central obesity (OR=2.10, 95% CI=1.46 to 3.03); meanwhile, 13.86% and 29.42% of girls with precocious puberty were respectively accompanied by obesity (OR=9.00, 95% CI=5.60 to 14.46) or central obesity (OR=5.40, 95% CI=4.10 to 7.12). The median ages of breast, pubic hair and testicle development decreased with BMI increase and median ages of thelarche and testicular development rather than pubarche were earlier in children with central obesity.

CONCLUSIONS

Earlier pubertal development was positively associated with obesity and central obesity in Chinese children.

Low serum adiponectin levels in children and adolescents with diabetic retinopathy

OBJECTIVE

The aim of this study was to elucidate the role of adiponectin, leptin, TNF-α and IL-6 on the early detection of the microvascular complications of type I diabetes.

MATERIALS AND METHODS

A total of 88 children were included in the study. There were 60 type I diabetic patients and 28 healthy control children.

RESULTS

The gender, age, weight, height, BMI and puberty status characteristics were similar in the patient and control groups (p>0.05). The serum leptin, TNF-α and IL-6 levels were similar between the patient and control groups (p>0.05) and the only difference was in the serum adiponectin level which was higher in the patient group (p:0.042). We also found no association between the adiponectin, leptin, TNF-α and IL-6 levels and diabetes duration (p>0.05). Leptin was high in the pubertal period (p:0.016), while adiponectin TNF-α and IL-6 levels were similar in the prepubertal and pubertal periods (p>0.05). The serum leptin level was high in microalbuminuria patients (p<0.041). The serum adiponectin, TNF-α, and IL-6 levels were not different in patients with and without microalbuminuria (p>0.05). The serum adiponectin level was lower in diabetic retinopathy patients (p:0.003), while the serum leptin level was higher (p:0.003). The TNF-α and IL-6 levels were similar in patients with and without retinopathy (p>0.05).

CONCLUSION

We found increased serum adinopectin levels in children and adolescents with type I diabetes mellitus and low levels in diabetic retinopathy patients. Patients with low serum adiponectin levels and high leptin levels should be more closely monitored for chronic complication development and better metabolic control should be aimed for.

The Hypothalamic-Pituitary-Adrenal Axis in the Neuroendocrine Regulation of Food Intake and Obesity: The Role of Corticotropin Releasing Hormone

The aim of this paper is to review the present knowledge on the role of the hypothalamic-pituitary-adrenal axis in the control of food intake and the pathogenesis of obesity and to discuss, on the basis of available literature, the interactions between other neurosystems and this hormonal axis. Food intake is influenced by a system of physiologic signals and behavioral controls consisting of positive and negative sensory feedback mechanisms. It is regulated by a complex neuroendocrine system consisting of peripheral signals (cortisol, leptin) in constant interplay with central neurosystems such as the cocaine-amfetamine-regulated transcript system. In these neurosystems, corticotropin-releasing hormone, pro-opiomelanocortin, melanin-concentrating hormone and neuropeptide Y are actively involved. The corticotropin-releasing hormone system is widely distributed throughout the brain, but it is particularly abundant in the medial parvocellular division of the paraventricular nucleus. Within the brain corticotropin-releasing hormone with its two receptor types, its binding protein and its closely related peptide urocortin forms a network of neuronal pathways capable of interacting with other circuitries controlling food intake and sympathetically-mediated thermogenesis. A defect in the synthesis and release of corticotropin-releasing hormone has been implicated in the development of obesity in laboratory animals. This condition is alleviated by exogenous corticotropin-releasing hormone treatment. The relationship between the neuropeptide Y system and the hypothalamic-pituitary-adrenal axis is complex and seems to include positive feedback between neuropeptide Y and corticosteroids and negative feedback between corticotropin-releasing hormone and neuropeptide Y. Leptin is involved in the regulation of energy balance by interacting with the hypothalamic-pituitary-adrenal axis. In the past, we have shown by cross-correlation analysis, that under physiological conditions cortisol and plasma leptin levels are related to each other in a time-related negative and positive fashion over 24h.

Puberty in girls of the 21st century

Several studies have noted contemporary girls are undergoing pubertal maturation at younger ages. During this same time period many Western nations have experienced an obesity epidemic, prompting investigators and public health officials to consider the association of these 2 events, and if other exposures might impact this relationship. There are several potential mechanisms that could impact the relationship of pubertal timing in girls with greater body mass, including direct effects of obesity on pubertal timing as well underlying exposures that impact body mass as well as timing of pubertal maturation. These underlying conditions include chemical compounds that could impact synthesis or action of sex hormones, called endocrine disrupting chemicals (EDs). We examine the decline in the age of breast development and potential genetic and environmental influences, the obesity epidemic in the US and other nations, and potential mechanisms to explain the relationship between greater body mass index with earlier puberty in girls.

Variations of plasma leptin and adiponectin levels in autistic patients

Autism is a neurodevelopmental disorder with pathogenesis not completely understood. Although a genetic origin has been recognized, it has been hypothesized a role for environmental factors, immune dysfunctions, and alterations of neurotransmitter systems. In young autistic patients we investigated plasma leptin and adiponectin levels over a year period. Thirty-five patients, mean age at the basal time 14.1+/-5.4 years, were enrolled. Controls were 35 healthy subjects, sex and age matched. Blood samples were withdrawn in the morning at the baseline and 1 year after. In patients leptin concentrations significantly increased, while adiponectin did not significantly change. Leptin values in patients were significantly higher than those found in controls at each time; adiponectin values did not differ at each time between patients and controls. Since patients were not obese, we could hypothesize that leptin might participate to clinical manifestations other than weight balance. The role of adiponectin in autism is still debatable.

Risperidone associated weight, leptin, and anthropometric changes in children and adolescents with psychotic disorders in early treatment

OBJECTIVE

To document prospective weight and anthropometric changes in children and adolescents during the first 12 weeks of treatment with risperidone and evaluate metabolic outcomes including plasma leptin levels.

METHOD

Eight patients with psychotic disorders (ages 11-17) who had started risperidone (mean: 1.80 mg/day; sd = 1.04) in the prior 4 weeks participated in this observational study. Fasting morning blood samples were obtained at baseline and week 8 to assess glucose, leptin, cortisol, insulin, and triglycerides. Measures of body mass index (BMI), weight, waist and hip circumference, blood pressure, and heart rate were obtained weekly.

RESULTS

Participants increased in mean weight (4.16 kg; sd = 4.36; p = 0.03) and BMI (1.47 kg/m(2); sd = 1.53; p = 0.03) with five out of eight gaining at least 7% of baseline body weight. They had a 4.03 cm (sd = 3.82; p = 0.02) increase in waist circumference and a 5.17 cm (sd = 3.68; p = 0.01) increase in hip circumference. Leptin trended higher, but did not reach statistical significance. There were no significant changes in glucose, insulin, cortisol, blood pressure, or heart rate.

CONCLUSION

Subjects experienced significant increases in weight, BMI, hip and waist circumference during the first 3 months of treatment. Better powered research with more advanced anthropometric assessment is warranted to further elucidate mechanisms of antipsychotic associated weight gain in youth.

Adolescent obesity and puberty: the "perfect storm"

Obesity is the most serious long-term health risk currently facing America's adolescents. Weight gain during adolescence carries a higher risk for adult obesity and the metabolic syndrome. This review highlights early adolescence as a particularly high-risk time for weight gain due to the synergy of naturally occurring metabolic changes along with increasing behavioral risk factors. One of the first potential health effects of abnormal weight gain during this period is earlier puberty, usually manifested as thelarche. The obesity epidemic is clearly implicated in the national trend toward earlier thelarche, although the data are not as strong in relation to menarche. Leptin activation of the hypothalamic-pituitary axis, combined with insulin resistance, and increased adiposity may result in the higher estrogen levels that are linked to breast development. Young adolescents also experience a sharp decline in their level of physical activity, worsening nutritional habits, and other important psychosocial and developmental risk factors that may contribute to obesity and estrogen-dependent disease in later life, including polycystic ovary syndrome and breast cancer. Unfortunately, the very psychosocial factors that contribute to abnormal weight gain during early adolescence make prevention and treatment in this population particularly challenging. Therefore, intervening prior to pubertal onset becomes even more important given the risk factors present once puberty begins.

Msx2 exerts bone anabolism via canonical Wnt signaling

Msx2 is a homeodomain transcription factor first identified in craniofacial bone and human femoral osteoblasts. We hypothesized that Msx2 might activate skeletal Wnt signaling. Therefore, we analyzed the effects of CMV-Msx2 transgene (Msx2Tg) expression on skeletal physiology and composition. Skeletal Msx2 expression was increased 2-3-fold by Msx2Tg, with expanded protein accumulation in marrow, secondary ossification centers, and periosteum. Microcomputed tomography established increased bone volume in Msx2Tg mice, with increased numbers of plate-like trabeculae. Histomorphometry revealed increased bone formation in Msx2Tg mice versus non-Tg siblings, arising from increased osteoblast numbers. While decreasing adipogenesis, Msx2Tg increased osteogenic differentiation via mechanisms inhibited by Dkk1, an antagonist of Wnt receptors LRP5 and LRP6. Bone from Msx2Tg mice elaborated higher levels of Wnt7 canonical agonists, with diminished Dkk1, changes that augment canonical signaling. Analysis of non-Tg and Msx2Tg siblings possessing the TOPGAL reporter confirmed this; Msx2Tg up-regulated skeletal beta-galactosidase expression (p </= 0.01), along with Wnt7a and Wnt7b, and reduced circulating Dkk1. To better understand molecular mechanisms, we studied C3H10T1/2 osteoprogenitor cells. As in bone, Msx2 increased Wnt7 genes and down-regulated Dkk1, while inducing the osteoblast gene alkaline phosphatase. Msx2-directed RNA interference increased Dkk1 expression and promoter activity, while reducing Wnt7a, Wnt7b, and alkaline phosphatase. Moreover, Msx2 inhibited Dkk1 promoter activity and reduced RNA polymerase association with Dkk1 chromatin. RNA interference-mediated knockdown of Wnt7a, Wnt7b, and LRP6 significantly reduced Msx2-induced alkaline phosphatase. Msx2 exerts bone anabolism in part by reducing Dkk1 expression and enhancing Wnt signaling, thus promoting osteogenic differentiation of skeletal progenitors.

[Hormonal axes in obesity: cause or effect?]

Several endocrine changes have been described in the obesity state. The corticotropic axis is hyperresponsive and there is enhancement of hormonal clearance, but cortisol levels are within the normal range. It is important to characterize a pseudo-Cushing in obesity. Leptin seems to be a permissive hormone for the beginning of puberty. In adults, gonadotropines are normal, and hyperandrogenism and hyperestrogenism are found. In women, insulin resistance has a central role in polycystic ovarian syndrome (POS), which is associated to ovarian hyperandrogenemia. In obese subjects, growth hormone (GH) is generally low and IGF1 is normal. Thyroid function is commonly normal in obese subjects.

Metabolic syndrome in youths

The metabolic syndrome (MetS), characterized by a clustering of cardiovascular disease and type 2 diabetes (T2DM) risk factors, has become prevalent in children and adolescents in recent years. However, the reported prevalence data on the MetS in youths has varied markedly, in large part, because of the disagreement among the variously proposed definitions of the MetS. Obesity is defined by using body mass index, waist circumference, or percent overweight, pointing to the need for standardized use of anthropometric variables to define obesity with a well-defined reference year for each ethnic population. In addition, slightly different cutoff values are used for triglycerides, high-density lipoprotein cholesterol, blood pressure, and fasting plasma glucose. Therefore, International Diabetes Federation recently proposed unified, easy-to-use criteria for diagnosing the MetS in youths. To provide insight into the mechanisms underlying the MetS in youths, the degree of insulin sensitivity/resistance and its correlation with the serum lipid and blood pressure levels have been evaluated. In addition, the serum levels of adipocytokines, such as adiponectin, leptin, tumor necrosis factor-alpha, resistin, interleukin-6, plasminogen activator inhibitor-1, and their correlation with childhood obesity have been extensively investigated. Recommendations for future research include exploring ways to assess visceral adiposity, to identify better biochemical markers for prediction of T2DM and disease progression, and to effectively intervene to prevent the MetS in youths.

Effects of diacylglycerol oil on adiposity in obese children: initial communication

Several studies have shown that diacylglycerol (DAG) oil may suppress accumulation of body fat in adults compared to triacylglycerol (TAG) oil. In this study, we investigated the effect of DAG oil as part of dietetic therapy in obese children. The participants were 11 male and female obese children who were under treatment at the outpatient clinic (four boys, seven girls, age: 7-17 years old). Daily-use cooking oil was changed to DAG oil, and the effects on abdominal fat areas, adipocytokines, and serum lipids were investigated. The total and subcutaneous fat areas significantly decreased in the 5th month after ingestion of DAG oil. Leptin was significantly lower than the initial level after ingestion of DAG oil. The ingestion of DAG oil decreased both the abdominal fat area and leptin in obese children, suggesting that DAG oil prevents obesity in children as well as in adults.

Reliability of bioimpedance analysis compared with other adiposity measurements in children: The FLVS II Study

OBJECTIVE

To evaluate the reproducibility of the measurement of% body fat by bipedal biometrical impedance analysis (BIA) compared with anthropometric measurements of adiposity in children and the correlations between these methods in children and adults.

METHODS

A cross-sectional study in a total of 1080 adults and children enrolled in 1999 in the Fleurbaix-Laventie Ville Santé II (FLVS II) population-based study in northern France. The reproducibility of anthropometrical and BIA methods was determined by a nested analysis of variance of repeated measurements by 2 investigators and a bipedal BIA device (Tanita TBF 310) in 64 pupils of two 5th grade classes. The correlation of BIA and anthropometric adiposity measurements with the unknown relative fat mass or volume of the body estimated by a latent adiposity variable (LAV) was established by the triads' method in 1080 subjects of the FLVS II cohort.

RESULTS

The reproducibility was similar for the sum of skinfolds, waist circumference and BIA% fat measurements (intraclass correlation coefficients: 0.979-0.992). Correlation coefficient between BIA body fat% and the LAV was higher than 0.86 in all sex and Tanner stage related groups, and similar in children and adults, except in pubertal boys (0.76).

CONCLUSION

With a high level of reproducibility, foot-to-foot BIA analysis provides a valuable measurement of total% fat for epidemiologic studies in children. However further studies are needed before extrapolating these results to overweight children.

Leptin levels in rat offspring are modified by the ratio of linoleic to alpha-linolenic acid in the maternal diet

The supply of polyunsaturated fatty acids (PUFA) is important for optimal fetal and postnatal development. We have previously shown that leptin levels in suckling rats are reduced by maternal PUFA deficiency. In the present study, we evaluated the effect of maternal dietary intake of (n-3) and (n-6) PUFA on the leptin content in rat milk and serum leptin levels in suckling pups. For the last 10 days of gestation and throughout lactation, the rats were fed an isocaloric diet containing 7% linseed oil (n-3 diet), sunflower oil (n-6 diet), or soybean oil (n-6/n-3 diet). Body weight, body length, inguinal fat pad weight, and adipocyte size of the pups receiving the n-3 diet were significantly lower during the whole suckling period compared with n-6/n-3 fed pups. Body and fat pad weights of the n-6 fed pups were in between the other two groups at week one, but not different from the n-6/n-3 group at week 3. Feeding dams the n-3 diet resulted in decreased serum leptin levels in the suckling pups compared with pups in the n-6/n-3 group. The mean serum leptin levels of the n-6 pups were between the other two groups but not different from either group. There were no differences in the milk leptin content between the groups. These results show that the balance between the n-6 and n-3 PUFA in the maternal diet rather than amount of n-6 or n-3 PUFA per se could be important for adipose tissue growth and for maintaining adequate serum leptin levels in the offspring.

Incomplete modified fast in obese early pubertal girls leads to an increase in 24-hour growth hormone concentration and a lessening of the circadian pattern in leptin

We studied nutrition and GH in eight obese girls, aged 6-11 yr. Blood was sampled every 15 min for 24 h. A 48-h diet providing 25% of assumed caloric needs was imposed, with repeat sampling during the last 24 h. Six nonfasting lean girls were also studied, and their mean GH was 3 times that of the obese girls in the fed state (P = 0.024). Dieting increased mean GH by 60% (P = 0.0028). There was no difference in pulse number for either group, but total secretion for lean girls was 3.9 times greater than that in obese girls during the fed state. With dieting, obese girls increased their total GH secretion by 60% (P = 0.010), but maintained lower total secretion, approximately 40% that of lean girls (P = 0.014). Mean leptin in obese girls in the fed state was 6.2 times greater than mean leptin in lean girls (P = 0.0001), with higher concentrations at night (P < 0.05) and lowering of total mean leptin while dieting. We conclude that in early pubertal obese girls, short-term caloric restriction partially reverses the low GH state that is characteristic of obesity. The change is concomitant with a decrease in leptin and a lessening of circadian differences.

Developmental regulation of leptin gene expression in rat brain and pituitary

We have previously reported the expression of leptin mRNA and protein in adult rat brain and pituitary gland. We report here the presence of leptin and leptin receptor mRNA in neonatal female rat brain and pituitary using RT-PCR as well as leptin and leptin receptor immunoreactivity in neonatal rat brain. In addition, we describe age-related changes in leptin mRNA expression in female rat brain and pituitary from postnatal day 2 to 28, evaluated using semi-quantitative RT-PCR analysis. Age-related differences in leptin (ob) mRNA levels were tissue-dependent. The most striking developmental changes were noted in the pituitary and cerebral cortex. In the pituitary, ob mRNA levels were maximal during postnatal days 7-14 and fell sharply by postnatal day 22. In cortex, ob mRNA levels were low in neonatal pups (day 2-7) but increased significantly between postnatal days 14 and 28. Leptin mRNA was detectable at postnatal day 2 in hypothalamus and subcutaneous fat. No significant differences in the level of expression were observed between postnatal day 2 and 28. Serum leptin levels were highest at day 7-14 and decreased significantly by day 21-28, coincident with the fall in pituitary leptin expression. The high levels of leptin expression in the neonatal pituitary suggest that this gland may contribute to the circulating leptin levels during early postnatal development, when adipose deposits are minimal. These data indicate that regulation of leptin gene expression in the postnatal period is tissue-dependent, a finding, which suggests that local leptin expression may have important functional significance in the development of the brain-pituitary system.

Influence of leptin on changes in body fat during growth in African American and white children

OBJECTIVE

The aim of this study was to determine whether initial levels or temporal changes in fasting leptin were associated with longitudinal changes in body-fat mass in children.

RESEARCH METHODS AND PROCEDURES

The study group consisted of 85 children (42 white and 43 African American) with a mean initial age of 8.1 +/- 0.1 years. The children had between three and six annual visits for repeated measurements of body composition by DXA and fasting leptin level. Fat mass and fasting leptin level were not normally distributed and were log-transformed. Data were analyzed using SAS Proc mixed growth models, with log fat as the dependent variable.

RESULTS

Initial leptin level was a significant predictor of the change in fat mass over time (p < 0.0001), with high initial leptin levels resulting in increased fat gain, independent of initial fat levels. This relationship remained significant when the data were analyzed separately by race (whites, p < 0.0001; African Americans, p = 0.008). The relationship between the initial level of leptin and the change in fat mass was not modified by race, sex, or Tanner Stage. The rate of change in leptin during the study was significantly related to the rate of change in fat mass in African Americans (p = 0.008) but not in whites (p = 0.490).

DISCUSSION

In conclusion, high fasting leptin level at the start of the study was significantly associated with increasing fat mass in this cohort, indicating that the children may be developing resistance to the effects of leptin.

Consequences of sport training during puberty

Growth at puberty depends on one's genetic potential, nutritional status and a series of hormones. Energy expenditure may modify the effects of these three factors on the linear growth rate and the relative proportions of fat-free and fat mass. Participation in sports where weight control is not required does not seem to affect pubertal timing or alter linear growth rate. The growth and maturation of athletes in weight control sports have the additional burden of energy output greater than intake; however, in only a minority the energy deficit is great enough to slow growth and maturation. Studies focusing on male wrestlers and female gymnasts are reviewed. In the wrestlers the hormonal picture is consistent with mild-to-moderate GH resistance and perhaps mild maturational delay, especially in the lower weight classes. The deficits in lean body mass and fat mass "catch-up" quickly following the end of training and competitive season. The situation with the gymnasts is somewhat different, the goal being to develop muscular strength within a shorter and lighter physique. Marked under-nutrition can keep these adolescents pre-pubertal for many years of training and competition. Whether subsequent growth is disproportionate or not remains indeterminate, but the marked delay in the onset of estrogen action can permanently cause the skeleton to be under-mineralized. In conclusion, most athletes continue to track along the centiles of their genetic potential. To define the mechanisms of growth and maturational delay one must longitudinally study children in weight-control sports.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.