Changes in circulating leptin, leptin receptor, and gonadal hormones from infancy until advanced age in humans

Sexual dimorphism of leptin and adiposity in children between 0 and 10 years: a systematic review and meta-analysis

Background

Differences in adolescents and adults by sex in blood levels of leptin and adiposity have been described; however, it is not yet clear if these differences arise from the prepubertal stage in subjects with a normal-weight. Therefore, we examine whether there are differences by sex in levels of blood leptin and adiposity in children with a normal-weight between 0 and 10 years old.

Methods

Search strategy: eligible studies were obtained from three electronic databases (Ovid, Embase and LILACS) and contact with experts. Selection criteria: healthy children up to 10 years of age with normal-weight according to age.

Data collection and analyses: data were extracted by four independent reviewers using a predesigned data collection form. For the analysis, we stratified according to age groups (newborns, 0.25–0.5 years, 3–5.9 years, 6–7.9 years, 8–10 years). The statistical analysis was performed in the R program.

Results

Of the initially identified 13,712 records, 21 were selected in the systematic review and meta-analysis. The sex was associated with the overall effect on blood leptin (pooled MD = 1.72 ng/mL, 95% CI: 1.25–2.19) and body fat percentage (pooled MD = 3.43%, 95% CI: 2.53–4.33), being both higher in girls. This finding was consistent in the majority of age groups.

Conclusion

The results of our meta-analyses support the sexual dimorphism in circulating blood leptin and body fat percentage between girls and boys with normal-weight from prepuberty.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-022-00454-y.

Differences by sex in blood leptin and body fat percentage in children are present before 10 years old

Girls have higher circulating leptin and body fat percentage than boys

The sex differences in blood leptin and adiposity in children increase progressively with the age

The effect of acute step-aerobic exercise on adiponectin and leptin levels in premenopausal women

BACKGROUND

It is well known that the prevalence of obesity, cardiovascular disease and metabolic syndrome is increasing during the transition to menopausal stages. The aim of this study was to investigate the effects of acute step-aerobic exercise on levels of leptin and adiponectin, which are adipose tissue-derived adipocytokines, associated with obesity, hypertension and other diseases in sedentary premenopausal women.

METHODS

Twenty-four sedentary premenopausal volunteer women between the ages of 40-45 (premenopause group) and 24 healthy adults between the ages of 21-39 (control group) were enrolled in this study. Moderate intensity step-aerobic exercise (50-60% of HR<inf>max</inf>) was applied for 60 min to the premenopausal subjects. Venous blood samples were obtained before and after the exercise. Adiponectin and leptin levels were determined using the ELISA method.

RESULTS

No statistically significant difference was found in terms of BMI values, and leptin levels between the premenopause and control group, while differences of adiponectin were statistically significant. Plasma leptin levels of the premenopausal women decreased whereas adiponectin levels increased meaningfully after the acute aerobic exercise (P<0.05). When the premenopausal women were grouped according to BMI, there were no significant differences between BMI≤30 and >30 groups in terms of leptin and adiponectin levels measured before and after exercise.

CONCLUSIONS

Our results may suggest that acute step aerobic exercise in premenopausal women alters leptin and adiponectin levels in favor of the organism. However, further studies are needed.

Temporal Leptin to Determine Cardiovascular and Metabolic Fate throughout the Life

Leptin links peripheral adiposity and the central nervous system (CNS) to regulate cardiometabolic physiology. Within the CNS, leptin receptor-expressing cells are a counterpart to circulating leptin, and leptin receptor-mediated neural networks modulate the output of neuroendocrine and sympathetic nervous activity to balance cardiometabolic homeostasis. Therefore, disrupted CNS leptin signaling is directly implicated in the development of metabolic diseases, such as hypertension, obesity, and type 2 diabetes. Independently, maternal leptin also plays a central role in the development and growth of the infant during gestation. Accumulating evidence points to the dynamic maternal leptin environment as a predictor of cardiometabolic fate in their offspring as it is directly associated with infant metabolic parameters at birth. In postnatal life, the degree of serum leptin is representative of the level of body adiposity/weight, a driving factor for cardiometabolic alterations, and therefore, the levels of blood leptin through the CNS mechanism, in a large part, are a strong determinant for future cardiometabolic fate. The current review focuses on highlighting and discussing recent updates for temporal dissection of leptin-associated programing of future cardiometabolic fate throughout the entire life.

Androgens During Infancy, Childhood, and Adolescence: Physiology and Use in Clinical Practice

We provide an in-depth review of the role of androgens in male maturation and development, from the fetal stage through adolescence into emerging adulthood, and discuss the treatment of disorders of androgen production throughout these time periods. Testosterone, the primary androgen produced by males, has both anabolic and androgenic effects. Androgen exposure induces virilization and anabolic body composition changes during fetal development, influences growth and virilization during infancy, and stimulates development of secondary sexual characteristics, growth acceleration, bone mass accrual, and alterations of body composition during puberty. Disorders of androgen production may be subdivided into hypo- or hypergonadotropic hypogonadism. Hypogonadotropic hypogonadism may be either congenital or acquired (resulting from cranial radiation, trauma, or less common causes). Hypergonadotropic hypogonadism occurs in males with Klinefelter syndrome and may occur in response to pelvic radiation, certain chemotherapeutic agents, and less common causes. These disorders all require testosterone replacement therapy during pubertal maturation and many require lifelong replacement. Androgen (or gonadotropin) therapy is clearly beneficial in those with persistent hypogonadism and self-limited delayed puberty and is now widely used in transgender male adolescents. With more widespread use and newer formulations approved for adults, data from long-term randomized placebo-controlled trials are needed to enable pediatricians to identify the optimal age of initiation, route of administration, and dosing frequency to address the unique needs of their patients.

Lean body mass accretion is elevated in response to dietary vitamin D: A dose-response study in female weanling rats

Vitamin D status positively relates to lean body mass in infants. This study tested the effect of vitamin D on body composition and growth-related hormones. It was hypothesized that low vitamin D status programs for higher fat mass accretion. Female weanling Sprague-Dawley rats (4 weeks; n = 6/diet) were randomized to AIN-93G diets with modified vitamin D contents for 8 weeks: group 1 (1 IU vitamin D₃/g diet), group 2 (2 IU vitamin D₃/g diet), and group 3 (4 IU vitamin D₃/g diet). At week 0, 4, and 8 of study, measurements included: serum 25(OH)D₃, IGF-1, IGFBP3, leptin, and whole body composition assessed with DXA. Differences among groups were tested using mixed model ANOVA with Tukey's post hoc t-tests. No differences were observed in baseline body composition and biomarkers, nor did body weight and food intake differ over the study. At week 8, serum 25(OH)D₃ in group 3 was higher (P < .0001) compared to groups 1 and 2. At 8 weeks, lean mass (P < .05) and lean mass accretion (P < .05) were significantly higher in groups 2 and 3 compared to group 1. Serum IGF-1 concentration declined over time (P < .001) with smaller declines at week 8 in group 3 (P < .05). Serum IGFBP3 concentration was lower at week 4 in group 2 compared to groups 1 and 3. Serum leptin concentration and fat mass were not affected by diet. These results suggested that the achievement of higher vitamin D status may support a lean body phenotype without altering weight gain.

Changes in the Responsiveness of the Hypothalamic-Pituitary-Gonadal Axis to Kisspeptin-10 Administration during Pubertal Transition in Boys

In human, no studies are available regarding changes in kisspeptin1 receptor (KISS1R) sensitivity during pubertal transition. In this study, healthy boys were classified into 5 Tanner stages of puberty (n = 5/stage). Human kisspeptin-10 was administered to boys at each Tanner stage and to adult men (n = 5) as an IV bolus for comparison. Serial blood samples were collected for 30 min pre- and 120 min post-kisspeptin injection periods at 30 min interval for measuring plasma LH and testosterone levels. There was insignificant effect of kisspeptin on LH and testosterone levels in boys of Tanner stages I-III. At Tanner stage IV, the effect of kisspeptin on plasma LH was insignificant. However, a paired t-test on a log-transformed data showed a significant (P < 0.05) increase in mean peak post-kisspeptin testosterone level. In Tanner stage V, a significant (P < 0.05) increase was observed in mean post-kisspeptin peak LH level as compared to the mean basal LH value. Post-kisspeptin plasma testosterone levels were also significantly (P < 0.05) increased as compared to the pre-kisspeptin level in Tanner stage V. Our data suggest that sensitivity of KISS1R on GnRH neurons with reference to LH stimulation in boys develops during the later part of puberty reaching to adult level at Tanner stage V. This trial is registered with WHO International Clinical Trial Registration ID NCT03286517.

Loss of PI3K p110α in the Adipose Tissue Results in Infertility and Delayed Puberty Onset in Male Mice

Deletion of PI3K catalytic subunit p110α in adipose tissue (aP2-Cre/p110α^flx/flx, α−/− hereafter) results in increased adiposity, glucose intolerance, and liver steatosis. Because this endocrine organ releases hormones like leptin, which are important in reproductive physiology, we investigated the reproductive phenotype of α−/− males. Compared to controls, α−/− males displayed delayed onset of puberty accompanied by a reduction in plasma LH levels and testicular weight. At postnatal day 30, α−/− mice exhibited normal body weight but elevated fasted plasma leptin levels. Testicular leptin gene expression was increased, whereas expression of the cholesterol transporter StAR and of P450 cholesterol side chain cleavage enzyme was decreased. Adult α−/− males were infertile and exhibited hyperandrogenemia with normal basal LH, FSH, and estradiol levels. However, neither sperm counts nor sperm motility was different between genotypes. The mRNA levels of leptin and of 17-beta-dehydrogenase 3, and enzyme important for testosterone production, were significantly higher in the testis of adult α−/− males. The mRNA levels of ERα, an important regulator of intratesticular steroidogenesis, were lower in the testis of adult and peripubertal α−/− males. We propose that chronic hyperleptinemia contributes to the negative impact that disrupting PI3K signaling in adipocytes has on puberty onset, steroidogenesis, and fertility in males.

Evaluation of Serum Leptin Levels and Growth in Patients with β-Thalassaemia Major

Background. Iron deposition in the body can damage the endocrine glands of patients with β-thalassaemia major (β-TM). Leptin plays a key role in the regulation of appetite, body fat mass, and endocrine function. Objectives. This study aimed to evaluate the relationship between serum leptin and growth and pubertal development in patients with β-TM, as well as whether serum leptin can predict growth retardation and delayed puberty in these patients. Methods. Fifty β-TM patients (aged 8–20 years) and 75 age-matched healthy controls were recruited. Anthropometric data and sexual maturity ratings were assessed. Serum leptin was measured by ELISA. Results. Serum leptin levels were significantly lower in patients with β-TM than in healthy individuals (P < 0.001). Leptin levels were also significantly reduced in female patients with short stature (P < 0.002) and in patients who displayed delayed puberty (P = 0.032) compared to those with normal stature who had reached puberty. The sensitivity of leptin for predicting short stature and delayed puberty among patients was 84.6% and 92.3%, respectively. Conclusion. Low serum leptin is sensitive to predict short stature and significant in β-TM females only. This link could thus be used as a guide for further therapeutic or hormonal modulation.

Endocrine disorders in adolescent and young female athletes: impact on growth, menstrual cycles, and bone mass acquisition

CONTEXT

Puberty is a crucial period of dramatic hormonal changes, accelerated growth, attainment of reproductive capacity, and acquisition of peak bone mass. Participation in recreational physical activity is widely acknowledged to provide significant health benefits in this period. Conversely, intense training imposes several constraints, such as training stress and maintenance of very low body fat to maximize performance. Adolescent female athletes are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function. The "adaptive" changes in the hypothalamic-pituitary-gonadal, -adrenal, and somatotropic axes and the secretory role of the adipose tissue are reviewed, as are their effects on growth, menstrual cycles, and bone mass acquisition.

DESIGN

A systematic search on Medline between 1990 and 2013 was conducted using the following terms: "intense training," "physical activity," or "exercise" combined with "hormone," "endocrine," and "girls," "women," or "elite female athletes." All articles reporting on the endocrine changes related to intense training and their potential implications for growth, menstrual cycles, and bone mass acquisition were considered.

RESULTS AND CONCLUSION

Young female athletes present a high prevalence of menstrual disorders, including delayed menarche, oligomenorrhea, and amenorrhea, characterized by a high degree of variability according to the type of sport. Exercise-related reproductive dysfunction may have consequences for growth velocity and peak bone mass acquisition. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine system may orient research to develop innovative strategies (ie, based on nutritional or pharmacological approaches and individualized modalities of training and competition) to improve the medical care of these adolescents and protect their reproductive function.

Nutrition and pubertal development

Nutrition is one of the most important factors affecting pubertal development. Puberty entails a progressive nonlinear process starting from prepubescent to full sexual maturity through the interaction and cooperation of biological, physical, and psychological changes. Consuming an adequate and balanced healthy diet during all phases of growth (infancy, childhood and puberty) appears necessary both for proper growth and normal pubertal development. Girls begin puberty at an earlier age compared to past decades. Excessive eating of many processed, high-fat foods, may be the cause of this phenomenon. Overweight or obese children are more likely to enter puberty early. Some evidence suggests that obesity can accelerate the onset of puberty in girls and may delay the onset of puberty in boys. Moreover, the progression of puberty is affected by nutrition. On the other hand, puberty triggers a growth spurt, which increases nutritional needs including macro and micronutrients. Increased caloric, protein, iron, calcium, zinc and folate needs have to be provided during this critical period of rapid growth. Severe primary or secondary malnutrition also can delay the onset and progression of puberty. The higher incidence of anorexia nervosa and bulimia in adolescents imposes a nutritional risk on pubertal development. Moreover, many environmental endocrine disruptors (EDs) have been identified that can significantly impair the normal course of puberty. This mini-review sums up some important findings in this important complex that link nutrition and pubertal development.

Soluble mediators regulating immunity in early life

Soluble factors in blood plasma have a substantial impact on both the innate and adaptive immune responses. The complement system, antibodies, and anti-microbial proteins and peptides can directly interact with potential pathogens, protecting against systemic infection. Levels of these innate effector proteins are generally lower in neonatal circulation at term delivery than in adults, and lower still at preterm delivery. The extracellular environment also has a critical influence on immune cell maturation, activation, and effector functions, and many of the factors in plasma, including hormones, vitamins, and purines, have been shown to influence these processes for leukocytes of both the innate and adaptive immune systems. The ontogeny of plasma factors can be viewed in the context of a lower effectiveness of immune responses to infection and immunization in early life, which may be influenced by the striking neonatal deficiency of complement system proteins or enhanced neonatal production of the anti-inflammatory cytokine IL-10, among other ontogenic differences. Accordingly, we survey here a number of soluble mediators in plasma for which age-dependent differences in abundance may influence the ontogeny of immune function, particularly direct innate interaction and skewing of adaptive lymphocyte activity in response to infectious microorganisms and adjuvanted vaccines.

Assessing neonatal heat balance and physiological strain in newborn infants nursed under radiant warmers in intensive care with fentanyl sedation

PURPOSE

To assess heat balance status of newborn infants nursed under radiant warmers (RWs) during intensive care.

METHODS

Heat balance, thermal status and primary indicators of physiological strain were concurrently measured in 14 newborns nursed under RWs for 105 min. Metabolic heat production (M), evaporative heat loss (E), convective (C) and conductive heat flow (K), rectal temperature (T re) and mean skin temperatures (T sk) were measured continuously. The rate of radiant heat required for heat balance (R req) and the rate of radiant heat provided (R prov) were derived. The rate of body heat storage (S) was calculated using a two-compartment model of 'core' (T re) and 'shell' (T sk) temperatures.

RESULTS

Mean M, E, C and K were 10.5 ± 2.7 W, 5.8 ± 1.1 W, 6.2 ± 0.8 W and 0.1 ± 0.1 W, respectively. Mean R prov (1.7 ± 2.6 W) and R req (1.7 ± 2.7 W) were similar (p > 0.05). However, while the resultant mean change in body heat content after 105 min was negligible (-0.1 ± 3.7 kJ), acute time-dependent changes in S were evidenced by a mean positive heat storage component of +6.4 ± 2.6 kJ and a mean negative heat storage component of -6.5 ± 3.7 kJ. Accordingly, large fluctuations in both T re and T sk occurred that were actively induced by changes in RW output. Nonetheless, no active physiological responses (heart rate, breathing frequency and mean arterial pressure) to these bouts of heating and cooling were observed.

CONCLUSIONS

RWs maintain net heat balance over a prolonged period, but actively induce acute bouts of heat imbalance that cause rapid changes in T re and T sk. Transient bouts of heat storage do not exacerbate physiological strain, but could in the longer term.

Increased leptin/adiponectin ratio and free leptin index are markers of insulin resistance in obese girls during pubertal development

BACKGROUND

Modifications in body fat in obese patients during puberty determine changes in adipokines that affect insulin sensitivity.

AIMS

We hypothesized that the leptin/adiponectin (L/A) ratio and free leptin index (FLI) are good markers of insulin resistance (IR) and total body fat (TBF) during pubertal development.

METHODS

A prospective study of 32 obese girls (OG) and age-matched control girls (CG) was performed. OG were divided into those that maintained a weight loss (WL) of >1 SD of initial body mass index (BMI) (WL group, n = 25) and those without WL (NWL group, n = 7). Oral glucose tolerance tests (OGTT) were performed to evaluate IR. Correlations of adipokines, L/A, and FLI with BMI, waist circumference, percentage of TBF (%TBF) and IR were performed over pubertal development.

RESULTS

The L/A ratio and FLI were increased in OG at baseline. Both indexes decreased in the WL group as puberty progressed, with no change in CG or NWL. In the WL group, a correlation between L/A and FLI with OGTT and %TBF, and L/A and homeostasis model assessment (HOMA) was found throughout the study.

CONCLUSION

The L/A ratio and FLI are good markers to follow changes in IR and %TBF after WL during puberty. Insulin more accurately reflects the changes in IR than HOMA.

Are volumetric bone mineral density and bone micro-architecture associated with leptin and soluble leptin receptor levels in adolescent idiopathic scoliosis?--A case-control study

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is associated with low bone mineral density (BMD). The underlying etiology and how it may relate to the development of osteopenia remains unknown. Leptin has been postulated as one of the etiologic factors of AIS because of its profound effects on bone metabolism and pubertal growth. Its modulator, soluble leptin receptor (sOB-R), may affect leptin bioavailability and signaling. This study aimed to investigate whether serum leptin and sOB-R levels may be associated with bone quality, and whether these relationships may differ between young adolescent girls with and without AIS.

METHODS

This was a case-control study involving 94 newly diagnosed AIS girls (Cobb angle 12-48°) aged 12 to 14 years old and 87 age and gender-matched normal controls. Subjects with BMI>23.0 Kg/m(2) were excluded. Anthropometric measurements including body weight, height, arm span and sitting height were taken. Serum total leptin and sOB-R were assayed with ELISA. Non-dominant distal radius was scanned with High Resolution pQCT for assessing bone quality in terms of bone morphometry, volumetric BMD (vBMD) and trabecular bone micro-architecture.

RESULTS

Compared with normal controls, AIS girls had numerically higher sOB-R (p = 0.006), lower average vBMD (p = 0.048), lower cortical vBMD (p = 0.029), higher cortical bone perimeter (p = 0.014) and higher trabecular area (p = 0.027), but none remained statistically significant after the Hochberg-Benjamini procedure. Correlation analysis on serum leptin level indicated that distinctive correlations with trabecular bone parameters occurred only in AIS.

CONCLUSION

This study showed that bone quality in AIS girls was deranged as compared with controls. In addition, the distinct differences in correlation pattern between leptin and trabecular bone parameters indicated possible abnormalities in bone metabolism and dysfunction of the leptin signaling pathway in AIS.

Serum levels of leptin receptor in patients with systemic sclerosis

Microvascular damage is one of the primary pathologic components of systemic sclerosis (SSc). Serological abnormalities of angiogenic and angiostatic factors in SSc have previously been described. Like these factors, the plasma levels of leptin were significantly elevated in patients with SSc in comparison to normal controls. However, leptin receptor has not been examined in patients with SSc. The current study used sandwich ELISA to evaluate the serum levels of leptin receptor in patients with SSc. Serum samples were obtained from 36 patients with SSc. Samples were also obtained from 12 healthy control subjects and 10 patients with scleroderma spectrum disorder (SSD) who did not fulfill the criteria for SSc but who had the potential to develop SSc. Mean serum leptin receptor levels were significantly higher in patients with SSD than in patients with SSc (255.7 ng/mL vs. 184.6 ng/mL, p < 0.05 according to a Mann-Whitney test). There were no statistically significant differences between healthy control subjects and patients with SSc. Clinical parameters were evaluated, and the frequency of esophageal reflux was significantly lower in patients with elevated serum leptin receptor levels than in those with reduced levels (6.3% vs. 35.3%, p < 0.05). In summary, these results suggest that the serum levels of leptin receptor are a clinically useful marker of SSD, and measurement of serum leptin receptor over time in patients with SSD may lead to early detection of SSc.

Endothelial dysfunction, inflammation, and oxidative stress in obese children and adolescents: markers and effect of lifestyle intervention

With an increasing prevalence, pediatric obesity is often a prelude to adulthood obesity, and represents a major public health issue. Comorbidities are very common and severe in obese adults, justifying the search for earlier markers or risk factors for cardiovascular diseases in obese children. Endothelial dysfunction has been found to be present in the early stages of atherosclerosis, and can be non-invasively assessed with widely accepted and well-standardized techniques at the macrocirculation level. Endothelial dysfunction at the microcirculation level is less documented in obese children. Obesity in children has been repeatedly and independently correlated to endothelial dysfunction, inflammation and oxidative stress markers, although the relationship between these factors remains to be investigated. However, this would not only allow substantial improvements in risk stratification, but also provide essential data regarding the evolution of endothelial dysfunction in childhood obesity, especially during puberty when pro-inflammatory and pro-oxidative changes, with relative insulin resistance, occur. Therapeutic strategies such as lifestyle interventions in early childhood obesity appear all the more necessary, optimally including both exercise and diet because of their known effects on inflammatory and oxidative stress markers, potentially reversing endothelial dysfunction.

Genetic and environmental contributions to weight, height, and BMI from birth to 19 years of age: an international study of over 12,000 twin pairs

OBJECTIVE

To examine the genetic and environmental influences on variances in weight, height, and BMI, from birth through 19 years of age, in boys and girls from three continents.

DESIGN AND SETTINGS

Cross-sectional twin study. Data obtained from a total of 23 twin birth-cohorts from four countries: Canada, Sweden, Denmark, and Australia. Participants were Monozygotic (MZ) and dizygotic (DZ) (same- and opposite-sex) twin pairs with data available for both height and weight at a given age, from birth through 19 years of age. Approximately 24,036 children were included in the analyses.

RESULTS

Heritability for body weight, height, and BMI was low at birth (between 6.4 and 8.7% for boys, and between 4.8 and 7.9% for girls) but increased over time, accounting for close to half or more of the variance in body weight and BMI after 5 months of age in both sexes. Common environmental influences on all body measures were high at birth (between 74.1-85.9% in all measures for boys, and between 74.2 and 87.3% in all measures for girls) and markedly reduced over time. For body height, the effect of the common environment remained significant for a longer period during early childhood (up through 12 years of age). Sex-limitation of genetic and shared environmental effects was observed.

CONCLUSION

Genetics appear to play an increasingly important role in explaining the variation in weight, height, and BMI from early childhood to late adolescence, particularly in boys. Common environmental factors exert their strongest and most independent influence specifically in pre-adolescent years and more significantly in girls. These findings emphasize the need to target family and social environmental interventions in early childhood years, especially for females. As gene-environment correlation and interaction is likely, it is also necessary to identify the genetic variants that may predispose individuals to obesity.

Bone mass acquisition in female rhythmic gymnasts during puberty: no direct role for leptin

OBJECTIVES

Although hypoleptinaemia has been reported in female peripubertal athletes, data are lacking on leptin and bone mass variations in puberty and the effects of leptin on bone mineralization during this period. This study therefore investigated the variations in leptin level and bone mineral density (BMD) in young elite female rhythmic gymnasts (FRG) according to pubertal stage. The effects of leptin, IGF-1 and sex hormones on bone mineral acquisition were also evaluated.

PATIENTS AND MEASUREMENTS

Plasma leptin levels were analysed in 43 elite FRG (mean age: 13.3 +/- 1.8 years range: 10.6-17.2, body mass index: 17.52 +/- 1.85 kg/m(2), training status: 17.9-23.8 h/week) according to their pubertal stage (Tanner I, n = 7; II, n = 10; III, n = 9; IV, n = 8; V, n = 9). IGF-1, IGFBP-3 and sex hormones were also evaluated. BMD was measured by dual-energy X-ray absorptiometry at various bone sites.

RESULTS

Plasma leptin increased throughout pubertal growth and the values measured in Tanner stages IV-V were significantly higher than in stages I-II. Gains in BMD were measured throughout puberty at all bone sites, particularly between Tanner stages II and IV. In simple correlation analysis, BMD at all bone sites was positively correlated with plasma leptin, age, bone age, BMI, oestrogen, testosterone, IGF-1 and IGFBP-3. However, multivariate analysis using a linear regression model by block (including bone age, anthropometric data and biological parameters) was then performed to determine the factors independently associated with each BMD site, and only bone age, fat-free soft tissue and BMI remained independent predictors.

CONCLUSION

In FRG characterized by high training volume and low fat mass, plasma leptin levels increased throughout puberty and were partially related to body composition changes. Despite the simultaneous increases in plasma leptin and BMD during pubertal growth, it was not possible to differentiate the leptin impact on bone independently from anthropometric parameters.

Leptin receptor (LEPR) SNP polymorphisms in HELLP syndrome patients determined by quantitative real-time PCR and melting curve analysis

Background

Several studies have shown overexpression of leptin in microarray experiments in pre-eclampsia (PE) and in hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome. We decided to study four leptin receptor (LEPR) SNP polymorphisms in HELLP syndrome patients by using quantitative real-time PCR and melting curve analysis.

Methods

DNA was isolated from blood samples from 83 normotensive pregnant women and 75 HELLP syndrome patients. Four SNPs, LEPR c.326A>G (K109), LEPR c.668A>G (Q223R), LEPR c.1968G>C (K656N) and LEPR c.3024A>G (S1008) were determined by quantitative real-time PCR and melting curve analysis. Investigators were blinded to clinical outcomes.

Results

LEPR c.326A>G, LEPR c.668A>G, LEPR c.1968G>C and LEPR c.3024A>G allele, genotype and haplotype polymorphisms were not different in HELLP syndrome patients and normotensive healthy pregnants. There were strong linkage disequilibrium (LD) between loci c.326A>G and c.6687A>G (D' = 0.974), and c.668A>G and c.1968G>C (D' = 0.934), and c.326A>G and c.1968G>C (D' = 0.885), and c.1968G>C and c.3024A>G (D' = 1.0). However, linkages of c.3024A>G with c.668A>G (D' = 0.111) and c.326A>G (D' = 0.398) were weak. The Hardy-Weinberg equilibrium was observed for all polymorphisms. However the LEPR c.326A>G AG genotype was twice more frequent and the (AG AG GG AG) haplotype was three times more frequent in HELLP syndrome patients. The introduced quantitative real-time PCR combined with melting curve analysis is a fast and reliable method for the determination of LEPR SNPs.

Conclusion

Although certain LEPR haplotypes are more frequent in HELLP syndrome, we conclude that there is no compelling evidence that the four studied LEPR SNP polymorphisms associated with the development of HELLP syndrome.

Gender in childhood obesity: family environment, hormones, and genes

BACKGROUND

The prevalence of obesity among children in the United States represents a pool of latent morbidity. Though the prevalence of obesity has increased in both boys and girls, the causes and consequences differ between the sexes. Thus, interventions proposed to treat and prevent childhood obesity will need to account for these differences.

OBJECTIVE

This review examines gender differences in the presentation of obesity in children and describes environmental, hormonal, and genetic factors that contribute to observed gender differences.

METHODS

A search of peer-reviewed, published literature was performed with PubMed for articles published from January 1974 through October 2008. Search terms used were obesity, sex, gender, hormones, family environment, body composition, adiposity, and genes. Studies of children aged 0 to 18 years were included, and only articles published in English were reviewed for consideration. Articles that illustrated gender differences in either the presentation or underlying mechanisms of obesity in children were reviewed for content, and their bibliographies were used to identify other relevant literature.

RESULTS

Gender differences in childhood obesity have been understudied partially because of how we define the categories of overweight and obesity. Close examination of studies revealed that gender differences were common, both before and during puberty. Boys and girls differ in body composition, patterns of weight gain, hormone biology, and the susceptibility to certain social, ethnic, genetic, and environmental factors.

CONCLUSION

Our understanding of how gender differences in pediatric populations relate to the pathogenesis of obesity and the subsequent development of associated comorbid states is critical to developing and implementing both therapeutic and preventive interventions.

The relationship between leptin, gonadotropic hormones, and body composition during puberty in a Dutch children cohort

OBJECTIVE

To investigate the relationship between leptin concentrations, gonadotropic hormone concentrations, and body composition during puberty in a Dutch children cohort.

DESIGN

In a cohort of 98 children, we determined anthropometric measurements, body composition, and concentrations of leptin, FSH, and LH.

RESULTS

Sex differences were observed from Tanner stage 1 onwards in weight, body fat percentage, and leptin/fat mass ratio. In boys and girls, the relationship between leptin concentrations and FM was weaker at Tanner stage 2 (R(2)=0.33 and R(2)=0.39; P<0.001), 3 (R(2)=0.27 and R(2)=0.36; P<0.002), and 4 (R(2)=0.21 and R(2)=0.28; P<0.03) than at Tanner stage 1 (R(2)=0.51 and R(2)=0.67; P<0.001) and 5 (R(2)=0.46 and R(2)=0.78; P<0.01). In girls, a peak in leptin concentrations (8.5+/-6.0 ng/ml) preceded a peak in LH and FSH concentrations (15.1+/-3.5 and 5.0+/-4.5 IU/l). A lead/lag relationship was observed of leptin at Tanner stage 1 to LH and FSH at Tanner stage 2 (R(2)=0.12, P<0.05 and R(2)=0.18, P<0.05). In boys, there was no peak in leptin, LH, and FSH; additionally, leptin at Tanner stage 3 was related FSH at Tanner stage 4 (R(2)=0.17, P<0.04).

CONCLUSION

In boys and girls during puberty, factors independent of fat mass become (transiently) more important in the regulation of plasma leptin concentrations. Moreover, in girls, leptin is suggested to act as a permissive factor for the onset of puberty, while, in boys, leptin has a different timing and possibly different function.

The effect of puberty on insulin resistance in obese children

OBJECTIVE

Insulin resistance (IR) increases during puberty in normal children. IR is the first adverse metabolic event of obesity, and the marker of the metabolic syndrome. We aimed to study the effect of puberty on IR in obese and normal-weight children.

DESIGN

Cross-sectional evaluation of fasting glucose, insulin concentrations, and homeostasis model assessment of IR (HOMA-IR) in obese and control children throughout puberty.

PATIENTS AND METHODS

We recruited 424 obese children (207 pre-pubertal and 217 pubertal divided in Tanner stages 2-3, 4, and 5) and estimated IR using the HOMA-IR index. Data were compared to those obtained in 123 healthy normal-weight children (40 pre-pubertal and 83 pubertal divided in Tanner stages 2-3, 4, and 5).

RESULTS

In the obese children mean HOMA-IR increased progressively across Tanner stages, and was significantly higher in all groups (pre-pubertal and Tanner stages 2-3, 4, and 5) of obese than in control children. HOMA-IR was significantly correlated with BMI.

CONCLUSIONS

HOMA-IR in obese children increases at puberty more than in normal-weight children and does not return to pre-pubertal values at the end of puberty.

Effects of weight loss after bariatric surgery for morbid obesity on vascular endothelial growth factor-A, adipocytokines, and insulin

BACKGROUND

Adipocytes regulate blood vessel formation, and in turn endothelial cells promote preadipocyte differentiation through the expression of proangiogenic factors, such as vascular endothelial growth factor (VEGF)-A. Some adipocytokines and hormones also have an effect on vascular development.

OBJECTIVES

Our objectives were to analyze the relationship between weight and circulating VEGF-A in morbidly obese subjects before and after bariatric surgery, and investigate the relationship between circulating VEGF-A and certain adipocytokines and hormones regulating adipocytes.

METHODS

A total of 45 morbidly obese women and nine lean females were included in the study. Patients underwent bariatric surgery: vertical banded gastroplasty (n=17), gastric bypass (n=17), and biliopancreatic diversion (n=11). Serum samples for VEGF-A, adiponectin, leptin, ghrelin, and insulin were obtained preoperatively and 9-12 months after surgery.

RESULTS

Obese patients showed significantly higher VEGF-A levels than controls (306.3+/-170.3 vs. 187.6+/-91.9 pg/ml; P=0.04), decreasing to 246.1+/-160.4 after surgery (P<0.001), with no differences among surgical procedures. In controls there was an inverse correlation between VEGF-A and ghrelin (r=-0.85; P<.01), but not in obese patients. Leptin and insulin concentrations were increased in obese patients, with a significant decrease shown after weight loss with surgery. Conversely, adiponectin concentrations were lower in obese patients, with a significant increase shown after weight loss with surgery. Ghrelin was higher in controls than obese patients, decreasing after gastric bypass and biliopancreatic diversion, but not after vertical banded gastroplasty.

CONCLUSION

Serum VEGF-A levels are significantly higher in obese patients than in lean controls, decreasing after weight loss with bariatric surgery, behaving similarly to other hormones related to adipose mass like leptin and insulin.

[Leptin: aspects on energetic balance, physical exercise and athletic amenorhea]

The aim of this manuscript was to review the knowledge about leptin, detailing its relationship with energetic intake and physical activity. Leptin is an adipocyte hormone, recognized mainly for its putative role in control of energy expenditure, food intake, body weight and reproductive function. Leptin has still important peripheral actions, including its role on the ovarian tissue. The intracellular signaling mechanisms are recognized in hypothalamus, but in peripheral tissue are not fully understood. The exercise, when practiced by women, if not appropriately planned according to food intake, can modify the leptin release. When energy imbalances induced by exercise and/or deficient food ingestion occurs, low leptin levels are observed, leading to a reduction in GnRH (gonadotropin-release hormone), in LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in pituitary, and consequently a minor release of ovarian estrogens. This process is named hypothalamic amenorrhea, and has repercussions in the woman's health. In this perspective, it is important to emphasize the need to evaluate the energy expenditure from exercise and to formulate adequate alimentary plans to these individuals.

Leptin-adiposity relationship changes, plus behavioral and parental factors, are involved in the development of body weight in a Dutch children cohort

BACKGROUND

The development of body weight is determined by different factors, namely genetic, behavioral, parental and physiological.

OBJECTIVE

To investigate whether genetic, behavioral, parental and physiological factors are involved and the extent of involvement in the development of body weight at ages 12 and 13 y in a Dutch children cohort.

METHODS

In a Dutch cohort of 94 children at ages 12 and 13 y, we determined anthropometric measurements, body composition, leptin concentrations, TFEQ scores, physical activity, as well as 3 polymorphisms, and in the parents we determined anthropometric measurements and TFEQ scores.

RESULTS

11% of the children in the cohort were classified as overweight. The genotype frequency distributions of the PPARy2, GRL and CNTF genes at ages 12 and 13 y were not significantly different for the overweight children compared to the lean children. Overweight children showed higher dietary restraint and disinhibition scores. Overweight children's parents had a higher BMI, dietary restraint and disinhibition scores, compared to lean children's parents. A peak in leptin concentrations between 7 and 13 y was shown at 12 y. In lean boys, the decrease in leptin concentrations between 12 and 13 y was related to an increase in fat free mass. At the age of 12 y predominantly the physiological factors were predictors for body weight, and at the age of 13 y both the physiological and behavioral factors were predictors for body weight.

CONCLUSION

We conclude from this longitudinal study, that leptin appeared to play an important role in the development of body weight during puberty, in addition to behavioral and parental factors.

Nutrition, inflammation, and leptin levels in aging and frailty

OBJECTIVES

To examine nutritional indices and levels of leptin and inflammatory markers across age and frailty.

DESIGN

Observational study.

SETTING

Continuing care wards and a day hospital in Cardiff, South Wales, United Kingdom.

PARTICIPANTS

Thirty dependent patients (mean age 84.9) needing continuing inpatient care, 40 patients with falls attending a day hospital (mean age 84.2), 40 independent controls (mean age 82.7), and 30 young controls (mean age 23.3).

MEASUREMENTS

Functional status, including the five frailty indicators proposed by Fried et al., anthropometry, and serum markers of nutrition and inflammation.

RESULTS

The continuing care patients were frail, all having three to five frailty indicators. Day hospital patients were of intermediate frailty (mean Fried score 2.97), and the independent group was fittest (0.83). Body mass index, triceps skinfold thickness (TSF), and mid-arm muscle area were lowest in continuing care patients. With increasing patient frailty, albumin levels fell significantly (P<.005) and C-reactive protein (CRP) levels increased significantly (P<.005). Continuing care patients had significantly lower leptin levels (P<.005) and significantly higher interleukin (IL)-6 levels (P<.005). There was a significant correlation between log transformed leptin and TSF for each patient group.

CONCLUSION

The frailest older people displayed features of cachexia. Their leptin levels were appropriately low given their low body fat, and IL-6 and CRP levels were high. The mechanism of their cachexia may therefore be similar to that proposed in heart failure and cancer: disturbed hypothalamic feedback of leptin or effects of proinflammatory cytokines.

Oscillations in total body fat content through life: an evolutionary perspective

Adipose tissue is considered an efficient system in which to store energy. Throughout life, the total amount of body fat exhibits some oscillations. Typically, there are three specific periods in which there are notable increases in fat mass, specifically early in life, during pregnancy and lactation, and with ageing. The existence of the first two peaks in fat mass has been interpreted, from an evolutionary point of view, as a beneficial manoeuvre to protect against the scarcity of energy to the offspring of the species. Nevertheless, the role of increasing body fat with ageing is more dubious. However, recent evidence suggests that the gain in adiposity in senescence may also be interpreted in the same evolutionary context. The aim of this review is to focus on the age-related changes in fat depots. In addition, an evolutionary explanation to the observed changes has been emphasized.

Childhood obesity and its relation to serum adiponectin and leptin: a report from a population-based study

This study examined the relationships between serum adiponectin (AD) and leptin (LP) levels, and obesity using a population-based cohort consisted of 315 (9-10 year olds: G1) and 308 (12-13 year olds: G2) school children. Serum AD, LP and other markers were compared according to the presence of obesity. The prevalence rates of obesity were 14.9% in G1 and 9.4% in G2. The medians of serum AD (microg/dl: non-obese/obese) were statistically lower in obese children (9.6/8.3 in G1, p<0.05; 8.9/6.6 in G2, p<0.05), and the medians of serum LP (ng/dl) were statistically higher in obese children (3.7/12.5 in G1, p<0.05; 2.9/8.4 in G2, p<0.05). The serum LP levels were significantly positively correlated with percent overweight (POW) irrespective of age and sex, and the serum AD levels were significantly negatively correlated with POW except for boys in G1. Multivariate regression analyses revealed that LP, LDL-cholesterol and gender in G1, and LP, AD, blood pressure and gender in G2 were significantly correlated with POW. A large-scale, population-based study revealed that AD was lower and LP higher in obese children, and that the obese status in G2 was related to a worse metabolic profile than the case in G1.

Regulation of circulating leptin and its soluble receptor during pubertal development in the male rhesus monkey (Macaca mulatta)

In humans, circulating leptin levels are low in early childhood and rise until puberty, whereas the reverse occurs for the soluble leptin receptor (sOB-R). In women, leptin remains high and sOB-R remains low, but in men leptin declines after adolescence and sOB-R increases. These observations suggest that leptin may regulate the production of sOB-R, and that the increased testosterone in adolescent boys may be responsible for the gender differences in leptin and sOB-R. To test this hypothesis, leptin was administered continuously to agonadal juvenile male monkeys for 16 days. No change in sOB-R was observed. Intact juvenile male monkeys were given pulsatile doses of gonadotropins for a period of 7 weeks to induce precocious puberty and assess the effect on plasma testosterone, leptin, and sOB-R. By 4 weeks testosterone had reached adult levels. No changes were observed in leptin, but by week 4, sOB-R was higher than pretreatment values and remained higher at week 7. These data suggest that leptin may not play a significant role in regulating the production of sOB-R and that gender differences in sOB-R in humans may be driven by the increased production of testosterone at puberty in males.

Leptin and the regulation of the hypothalamic-pituitary-adrenal axis

Leptin, the product of the obesity gene (ob) predominantly secreted from adipocytes, plays a major role in the negative control of feeding and acts via a specific receptor (Ob-R), six isoforms of which are known at present. Evidence has been accumulated that leptin, like other peptides involved in the central regulation of food intake, controls the function of the hypothalamic-pituitary-adrenal (HPA) axis, acting on both its central and peripheral branches. Leptin, along with Ob-R, is expressed in the hypothalamus and pituitary gland, where it modulates corticotropin-releasing hormone and ACTH secretion, probably acting in an autocrine-paracrine manner. Only Ob-R is expressed in the adrenal gland, thereby making it likely that leptin affects it by acting as a circulating hormone. Although in vitro and in vivo findings could suggest a glucocorticoid secretagogue action in the rat, the bulk of evidence indicates that leptin inhibits steroid-hormone secretion from the adrenal cortex. In keeping with this, leptin was found to dampen the HPA axis response to many kinds of stress. In contrast, leptin enhances catecolamine release from the adrenal medulla. This observation suggests that leptin activates the sympathoadrenal axis and does not appear to agree with its above-mentioned antistress action. Leptin and/or Ob-R are also expressed in pituitary and adrenal tumors, but little is known about the role of this cytokine in the pathophysiology.

p.Q223R leptin receptor polymorphism associated with obesity in Brazilian multiethnic subjects

Several genes play a major role in obese phenotypes, and studies suggest that genetic variations among individuals, as well as their lifestyles, may bring about different body compositions. Among these genes, LEP, which codifies leptin, and the LEPR gene encoding its receptor were extensively studied for variants that could explain the obese phenotype. The LEPR p.Q223R gene polymorphism was analyzed in a sample of obese and nonobese individuals from Brazil to evaluate the role of this polymorphism in the obese phenotype in the population. Two hundred obese patients (60 males, 140 females, body mass index (BMI) >30 kg/m2) were screened, together with 150 lean or normal healthy individuals (63 males, 87 females, BMI <24 kg/m2). Genomic DNA was extracted and amplified by polymerase chain reaction (PCR). PCR products were digested with the restriction of endonuclease MspI, and separated by electrophoresis through an 8% polyacrilamide gel stained with silver nitrate. There was a significant difference in LEPR p.Q223R polymorphism frequency when comparing obese and lean subjects, with an odds ratio of 1.92 and a 95% confidence interval of 1.15-3.22 (P = 0.013). There is a strong association of the LEPR p.Q223R gene polymorphism with obesity in Brazil.

Normative data for adiponectin, resistin, interleukin 6, and leptin/receptor ratio in a healthy Spanish pediatric population: relationship with sex steroids

OBJECTIVES

To investigate the circulating levels of adiponectin, resistin, interleukin 6 (IL-6), and leptin/receptor ratio in healthy Spanish children throughout the different stages of pubertal development. To analyze the relationship between adipokines and sex steroid level changes during puberty.

STUDY DESIGN

Serum adiponectin, resistin, IL-6 levels, and leptin/receptor ratio were studied in 160 healthy Spanish children grouped according to their pubertal stage (Tanner I, 23 girls and 22 boys; Tanner II, 19 girls and 16 boys; Tanners III and IV, 21 girls and 20 boys; and Tanner V, 20 girls and 19 boys). In addition, circulating levels of sex hormone-binding globulin (SHBG) were determined in every subject, and testosterone and estradiol levels in boys and girls respectively.

RESULTS

Adiponectin levels decreased in boys from mid puberty (P < 0.05) to become significantly lower than in girls (P < 0.001), whereas IL-6 decreased in both sexes (P < 0.05). Resistin levels and leptin/receptor ratio showed no differences between sexes or according to pubertal stage, except in adult females, who had the highest levels of both parameters (P < 0.001). Serum IL-6 levels correlated significantly (P < 0.05) with testosterone and estradiol levels (r=-0.37 and -0.42 respectively), whereas estradiol, but not testosterone, correlated with leptin/receptor ratio (r=0.59; P < 0.001). Furthermore, a positive relationship was found between SHBG and adiponectin and IL-6 (P < 0.001 and P < 0.05 respectively). In addition, a direct correlation between leptin/receptor and body mass index was found in both sexes (P < 0.001).

CONCLUSION

Variations in adipokine profiles throughout pubertal development appear to be related with progression of gonadal function.

Diencephalic syndrome due to hypothalamic tumor: a model of the relationship between weight and puberty onset

CONTEXT

Changes in body weight, statural growth rate, and puberty may be the presenting symptoms of hypothalamic-pituitary tumors.

OBJECTIVE

The objective of the study was to assess the relationship between the tumor and its treatment and the weight, growth rate, and onset of puberty, using the diencephalic syndrome of emaciation as model.

PATIENTS

Eleven patients seen before 1 yr of age, except one aged 9 yr, for diencephalic syndrome of emaciation due to hypothalamic pilocytic astrocytoma, were treated by surgical resection (n = 9), cranial irradiation (n = 7), and/or chemotherapy (n = 10).

RESULTS

At diagnosis, growth rate was normal, despite the emaciation, and there was no hypothalamic-pituitary deficiency, except in the oldest patient. After tumor treatment, all had GH and thyroid-stimulating hormone deficiencies, but only three, who underwent major surgical resection, also had ACTH deficiency and diabetes insipidus. Eight became obese, and all but the oldest had transient precocious puberty. Plasma leptin concentrations were very low at diagnosis, increased after tumor treatment, and decreased transiently in one boy when the testosterone increased. The plasma soluble leptin receptor concentrations changed in the opposite direction, leading to an increase in the free leptin index, including in the three patients whose tumor was reduced without surgery. The body mass index was correlated positively with plasma leptin (rho = 0.73, P = 0.0004) and free leptin index (rho = 0.63, P < 0.004) and negatively with ghrelin (rho = -0.49, P < 0.03) concentrations.

CONCLUSIONS

The obesity that occurs after treatment of hypothalamic tumors is not due to dysregulation of leptin secretion because it and plasma soluble leptin receptor remain regulated by factors like testosterone. This study also shows the influence of weight, possibly via leptin secretion, on the transient hypothalamic-pituitary-gonadal activation that occurs during the first year of life.

Gap analysis of pediatric reference intervals for risk biomarkers of cardiovascular disease and the metabolic syndrome

The childhood obesity epidemic has begun to compromise the health of the pediatric population by promoting premature development of atherosclerosis and the metabolic syndrome (MS), both of which significantly increase the risk of cardiovascular disease (CVD) early in life. As a result, recently, there has been increased recognition of the need to assess and closely monitor children and adolescents for risk factors of CVD and components of the MS. Serum/Plasma biomarkers including total cholesterol, triglycerides, HDL-C, LDL-C, insulin and C-peptide have been used for this purpose for many years. Recently, emerging biomarkers such as apolipoprotein AI, apolipoprotein B, leptin, adiponectin, free fatty acids, and ghrelin have been proposed as tools that provide valuable complementary information to that obtained from traditional biomarkers, if not more powerful predictions of risk. In order for biomarkers to be clinically useful in accurately diagnosing and treating disorders, age-specific reference intervals that account for differences in gender, pubertal stage, and ethnic origin are a necessity. Unfortunately, to date, many critical gaps exist in the reference interval database of most of the biomarkers that have been identified. This review contains a comprehensive gap analysis of the reference intervals for emerging and traditional risk biomarkers of CVD and the MS and discusses the clinical significance and analytical considerations of each biomarker.

Orexigenic Effects of a Growth Hormone Secretagogue and Nitric Oxide in Aged Rats and Dogs: Correlation With the Hypothalamic Expression of Some Neuropeptidergic/Receptorial Effectors Mediating Food Intake

Hypothalamic neurochemical alterations in mammals underlie disturbances of food intake. There is scarce information on these topics in elderly persons; therefore, the aims of the present study were: (i) to evaluate the orexigenic effects of a growth hormone secretagogue, administered to young and old rats and dogs, alone or in combination with molsidomine, a donor of nitric oxide and (ii) to evaluate by reverse transcription-polymerase chain reaction in the whole hypothalamus of young and old rats messenger RNA levels of a wide number of anabolic and catabolic peptides, receptors, and enzymes involved in the control of feeding behavior, relating the detected titers, whenever possible, to the feeding responses to growth hormone secretagogue. In all, the results obtained strengthen the proposition that, in the hypothalamus of old rats, anti-anorexigenic compensatory mechanisms are operative, aimed at maintaining a "normal" feeding pattern. Thus, the occurrence of a primary, age-related alteration in the feeding mechanisms is unlikely.

Circulating soluble leptin receptor, leptin, and insulin resistance before and after weight loss in obese children

OBJECTIVE

To study the relationships between leptin, soluble leptin receptor (sOB-R), and insulin resistance in obese children before and after weight reduction.

METHODS

We determined fasting serum leptin, sOB-R, and insulin resistance index (Homeostasis model assessment (HOMA)) in 36 obese children at baseline and 1 y later and compared them to 72 lean children matched for age, gender, and pubertal stage. The changes of leptin (Deltaleptin) and sOB-R (DeltasOB-R) over the 1 y period were correlated to the changes of HOMA (DeltaHOMA), the changes of weight status, and the changes of percentage body fat (Delta%BF) based on skinfold measurements. Multiple linear regression analyses were conducted for the dependent variables Deltaleptin and DeltasOB-R, including DeltaBMI and DeltaHOMA as independent variables adjusted for age, gender, and pubertal stage. Changes of leptin and sOB-R levels were analyzed in 11 obese children after they had lost weight substantially (decrease SDS-BMI>0.5) and compared to 11 obese children without substantial weight loss matched for age, gender, and pubertal stage.

RESULTS

Obese children showed significantly (P<0.001) higher leptin and lower sOB-R levels. Deltaleptin correlated significantly to DeltaSDS-BMI (r=0.28, P<0.05), Delta%BF (r=0.44, P<0.05), and DeltaHOMA (r=0.42, P<0.01), while DeltasOB-R correlated significantly to DeltaSDS-BMI (r=-0.42, P<0.01) and Delta%BF (r=-0.47, P<0.01), but not to DeltaHOMA. In contrast to DeltasOB-R, Deltaleptin correlated significantly to DeltaHOMA (P=0.02) in multiple linear regression analysis. Substantial weight loss led to a significant increase in sOB-R (P=0.02) and to a decrease in HOMA (P=0.02). In children without substantial weight loss, there were no changes in sOB-R, while HOMA (P=0.04) and leptin (P=0.02) increased significantly.

CONCLUSIONS

The decrease of sOB-R and the increase of leptin levels in obese children normalized after weight loss. Therefore, these changes are consequences rather than the cause of overweight. In contrast to sOB-R, leptin levels are associated with insulin resistance.

ObRa and ObRe are differentially expressed in adipose tissue in aged food-restricted rats: effects on circulating soluble leptin receptor levels

In rodents, soluble leptin receptor (SLR) may be generated by alternative splicing of ObR mRNA and/or as a cleavage product of ObR membrane-anchored receptors. In this study, we investigated the contribution of both processes on the generation of SLR in 3-, 8-, and 24-month-old Wistar rats fed ad libitum (AL) or under food restriction (FR). To this end, we determined serum SLR levels and analyzed ObRa and ObRe mRNA expression under these physiological conditions. Additionally, we studied the cellular distribution of ObRa and the generation of SLR by N-ethyl-maleimide-induced shedding from ObRa membrane receptors in isolated adipocytes. Serum SLR levels were significantly increased in 8- and 24-month-old rats under FR, whereas similar amounts were found in rats of different ages fed AL. ObRa and ObRe mRNA expression in epididymal adipose tissue increased with aging. In contrast, after FR, ObRe mRNA expression decreased, whereas ObRa mRNA expression further increased compared with 8- and 24-month-old rats fed AL. Additionally, FR promoted a change in the distribution of ObRa between internal and plasma membranes in isolated adipocytes, increasing its presence at the cell surface. Finally, the generation of SLR by N-ethyl-maleimide-induced shedding from ObRa was also increased under FR. These data suggest that shedding of ObRa membrane-anchored receptors, rather than ObRe expression, might preferentially contribute to the generation of the increased levels of SLR in serum under conditions of FR.

Relationship between serum concentrations of leptin, soluble leptin receptor, testosterone and IGF-I, and growth during the first year of postnatal life in the male rhesus monkey, Macaca mulatta

OBJECTIVES

Subnormal leptin levels in low birth weight infants may allow for catch-up growth during infancy. Scant data are available that relate growth with circulating leptin during normal infancy in primates. The current study objective was to examine the association between serum leptin, its soluble receptor (sOB-R), testosterone and IGF-I concentrations, and body weight during infancy in male rhesus monkeys.

DESIGN

Hormone levels were assessed longitudinally in animals (n = 7) from birth until 1 year of age.

RESULTS

Body weight increased during the first 6 months of life and was strongly correlated with rising IGF-I levels and, as IGF-I plateaued and then declined during the second half of the year, body weight gain decelerated. In contrast, leptin levels declined gradually with age during the first year of life in conjunction with increasing body weight. There was no association between body weight gain and serum leptin levels or between serum testosterone and leptin values. Since sOB-R levels also declined with leptin values, it does not appear that levels of bioavailable leptin changed during infancy.

CONCLUSIONS

The data do not support the contention that leptin regulates growth during infancy, but the close association between IGF-I levels and body weight suggested that this hormone may regulate growth in infant male monkeys. The failure to observe an association between serum testosterone and leptin concentrations suggested that leptin is not involved in the activation of the hypothalamic-pituitary -testicular axis during this developmental period.

Pubertal neuromaturation, stress sensitivity, and psychopathology

Normal adolescent development is often accompanied by transient emotional and behavioral problems. For most individuals with postpubertal-onset adjustment problems, there is a resolution by early adulthood and relative stability through the adult life span. But for a minority, adjustment problems escalate during adolescence and portend the development of serious mental illness in adulthood. In this article, we explore adolescent behavioral changes and neurodevelopmental processes that might contribute to stress sensitivity and vulnerability for the emergence of the mental disorders. Of particular interest is the role that hormonal changes might play in the expression of genetic vulnerabilities for psychopathology. Drawing on recent findings from clinical research and behavioral neuroscience, we describe the ways in which postpubertal hormones might alter brain function and, thereby, behavior. It is concluded that there are both activational and organization effects of hormones on the adolescent brain, and these contribute to developmental discontinuities in behavioral adjustment. Implications for adult psychopathology and preventive intervention are discussed.

Aging and pathogenesis of erectile dysfunction

The prevalence and the severity of erectile dysfunction (ED) increase with advancing age; different pathogenetic factors could contribute to age-related ED. We studied organic, relational and intrapsychic components of ED as a function of patients' age in a consecutive series of 977 patients with ED, using the specifically designed structured interview SIEDY. A complete physical examination and a series of biochemical, hormonal, psychometric and penile vascular tests were also performed. Relational factors seems to be more relevant in patients aged over 60 y, while intrapsychic disturbances play a major role in younger subjects. Organic factors are the most important determinant of ED in all age groups, but their contribution is more important in older patients. In fact, basal and dynamic peak cavernosal velocity at Doppler ultrasound penile examination was reduced in older patients. Among hormonal factors, the body mass index-dependent reduction of testosterone in older patients does not seem to play a crucial role in the pathogenesis of ED. No significant correlation was observed between testosterone level and the severity of ED, although patients reporting hypoactive sexual desire showed significantly lower testosterone levels when compared with the rest of the sample. A better understanding of the relative contribution of age-related pathogenetic factors of ED could be of help in the design of appropriate therapeutic approaches.

Racial difference in circulating sex hormone-binding globulin levels in prepubertal boys

Racial differences in disease risk (eg, osteoporosis, metabolic cardiovascular syndrome, and prostate cancer) may arise partly on a hormonal basis. While reports of racial differences in gonadal steroid hormone levels in middle-aged men have produced conflicting results, there is evidence that high sex hormone-binding globulin (SHBG) and estradiol levels are more common among young adult African American men than white men. To determine whether this difference relates to pituitary-testicular functioning or to other factors, we conducted a cross-sectional study of 47 healthy prepubertal African American and white boys aged 5 to 9 years at the time of their annual school physical examination. Height, weight, blood pressure, waist and hip circumference, and Tanner staging were determined, and a fasting blood sample was obtained. The African Americans studied were slightly older than the whites (mean +/- SD, 82.4 +/- 15.0 vs 70.5 +/- 10.3 months, P = .003). African Americans were also slightly taller and heavier and had a lower waist-to-hip ratio, but these differences could be explained by the difference in age. Mean SHBG levels were 25% higher (P = .15) in African Americans than in whites (197 +/- 104 vs 157 +/- 79 nmol/L), and when adjusted for age, values were 46 nmol/L higher among African Americans. The fifth quintile for SHBG (values > 245 nmol/L) included 1 (4.2%) of 24 whites and 8 (35%) of 23 African Americans studied (P = .003). There was no significant correlation between age, body mass index, waist circumference, or fasting insulin and SHBG. Total testosterone, the free androgen index, and dehydroepiandrosterone increased with age in both groups, but after adjusting for age, no racial differences were found. Estradiol, estrone, and inhibin B levels, as well as systolic and diastolic blood pressures, were also comparable in both groups. We conclude that high levels of SHBG are more common among African American than in white boys and hypothesize that this difference and its effect on the ratio between bound and free steroid hormones may contribute to racial differences in disease risk in adult men.

Serum leptin levels in Ache Amerindian females with normal adiposity are not significantly different from American anorexia nervosa patients

Serum leptin, a polypeptide hormone secreted primarily by adipocytes, is a reflection of somatic fat availability in humans and other vertebrates. Among Ache Amerindians, leptin levels are very low in contrast to other populations, despite comparable adiposity with individuals exhibiting much higher leptin levels. In order to gain a greater understanding of these differences, leptin levels were compared between Ache Amerindian females (n = 12, mean age = 32.2 +/- 14.0 SD), American females diagnosed with anorexia nervosa (n = 22, mean age = 23.0 +/- 4.0), and non-anorectic American controls (n = 23, mean age = 23.0 +/- 4.0). Ache leptin (5.6 +/- 3.2 ng/ml) was not significantly different from anorectic patients (5.6 +/- 3.7 ng/ml; P > 0.98) despite greater adiposity (Ache 33.3% +/- 4.4% vs. anorectic 7.0% +/- 2.0%; P < 0.0001). Ache adiposity was also higher than American controls (leptin 19.1 +/- 8.1 ng/ml; fat 28% +/- 5.0%; P < 0.004) underscoring the uniqueness of Ache leptin profiles. This suggests a greater range of population variation in leptin physiology than previously suspected and intimates the potential role of chronic environmental conditions.

Endocrinology of anorexia of ageing

Appetite and food intake decrease with normal ageing, predisposing to the development of under-nutrition. Under-nutrition is common in older people and has been implicated in the development and progression of chronic diseases commonly affecting the elderly, as well as in increasing mortality. An understanding of the factors that contribute to the physiological and pathological declines in food intake in older people is likely to aid in the development of effective forms of prevention and treatment. Ageing affects many of the endocrine factors involved in the control of appetite and feeding but few studies have been performed in humans to clarify these changes. Possible hormonal causes of the anorexia of ageing include increased activity of cholecystokinin, leptin and various cytokines and reduced activity of ghrelin and testosterone.