The Relationship Between Obesity And Puberty Onset In Females

Background and Aims:The prevalence of obesity has been increased from the last few decades,and it has become an increasing clinical and public health concern.Childhood obesity increases the risk for adult stage obesity and related metabolic complications.Puberty is an important event in the life of an individual in which sexual and somatic maturation is achieved.It was reported that obesity is positively associated with sexual maturation in both boys and girls in China.Overnutrition during early developmental stages permanently programs energy homeostasis that supports both metabolic complications and puberty onset.However,the effect of obesity on pubertal development is incompletely elucidated.The aim of this study is to investigate the relationship between obesity and puberty onset in females,and tries to explore the mechanism of this associationMethod:1.Participants were enrolled in the study from the Department of Endocrinology,Children’s Hospital of Zhejiang University School of Medicine.Sexual maturation was evaluated by physical assessment.Skeletal age was determined by a left-hand roentgenogram and assessed by a radiologist according to the technique of Gruelich and Pyle.Ovarian volume was estimated by trans-abdominal ultrasound.Basal estradiol,luteinizing hormone(LH)and follicle-stimulating hormone(FSH)were measured.CPP girls were diagnosed according to their clinical characters and the results of GnRH stimulation test.Total body fat mass and percent body fat(%BF)was assessed with DXA.2.Altogether 30 obese girls with or without precocious puberty,from 6 to 8 year old,were enrolled in the study from the same hospital.Blood samples of all the subjects were collected in the morning after an overnight fast.We used a unified and randomized program created by computer to select three girls from the obese and precocious puberty group and three girls from the control group.These six samples were used for proteomic analysis.iTRAQ was used to identify the proteins.Protein identification was performed using the MASCOT search engine(version 2.2.1;Matrix Science)and the Proteomics Tools(version 3.0.5;http://www.proteomics.ac.cn/).3.C57BL/6J mice were used in the current study.The pups were feeding on high fat diets after weaning.Body weight;body length and vaginal opening(VO)were checked.After these mice were deeply anesthetised with isoflurane,we got the blood and detected the serum sex hormone levels,S100A8/A9 and kisspeptin by ELISA kit.Mice were then perfused transcardially with 4%PFA in PBS.Brains were extracted and post-fixed in 4%PFA overnight and then moved to 30%sucrose in PBS.Until brains were saturated(36 h),coronal brain sections at 30 μm were cut using a freezing microtome.ELISA,Western-Blot,and confocal laser scanning microscopy were used to detective the GnRH,kiss,NKB,Dyn and S100A8/A9 expression in the hypothalamus.Results:1.Altogether,37 central precocious puberty(CPP)girls and 39 age-matched prepubertal girls(age,7 to 9 years)were enrolled in this study.The%BF of the CPP girls was significantly higher than control group(29.96±4.43 VS 27.49±3.56,p=0.009);while the BMI of the two groups was 16.61±1.62 and 15.38±1.42,respectively(p=0.001).ROC curve showed BMI,Est.VAT volume and%BF had higher sensitivity and specificity for the CPP diagnosis in Chinese girls.2.Altogether 42 differentially expressed proteins were obtained according to the iTRAQ,15 of which were up-regulated and 27 proteins were down-regulated.S100A8/A9 proteins in obese girls were obviously higher than those of the normal children;however these levels were significant decline after the puberty onset.3.Mice babies that were feeding HFD,have shown more weight gain(obesity)and early puberty(earlier vaginal opening)than control mice babies,the VO was 33 days and 37 days respectively with significant difference(t=-5.129,p=0.004).ELISA and WB showed S100A8/A9 expression was higher in obese female mice than control group,while S100A8/A9 was lower in obese with puberty subgroup than obese subgroup.Confocal laser scanning microscopy showed S100A8/A9 was located in the neuronal cells cytoplasm of the hypothalamus,and its expression was significantly increased in obese female mice,but decreased significantly after puberty onset.Conclusions:1.Higher BMI and%BF were found in CPP girls,and adiposity was positively associated with early pubertal onset in Chinese girls.DXA has been confirmed to be a reliable and accurate method for measuring fat mass in Chinese girls.BMI,Est.VAT volume and%BF had higher sensitivity and specificity for the CPP diagnosis.2.S100A8/A9 are two of the differences proteins between the obese girls with puberty onset and without puberty onset,and may be involved in the central regulation of the obese girls’ puberty onset.3.High-fat diet can lead to the early onset of puberty in female mice.S100A8/A9 may participate in the central control of the process.