The Effects Of Dietary-induced Obesity On The Development Of Testis And Its Mechanism In Pubertal Rats

Background:Alimentary obesity (or Simple obesity) is an over hyperplasia disease,which was correlatedwith life style, have character of over nutrition, hypo motility and behavior disorder with adiposetissue all over the body. It isn't pathology obesity which originated from some heritage disease ormetabolism disease.With development of living standard, taking too much fat has made theadolescent obesity popular all over the world, moreove, people become paid much attention tothis nutrition disease. Both in developed country and developing county, the disease is tendencyto arise, especially in the cities' boys. The prevalence rates of obesity in both adults and childrenin the world have significantly increased over the past decade and continue to increase.Obesity isassociated with complications such as dyslipidemia, hypertension, and insulin resistance and isan important risk factor for cardiovascular disease (CVD) and type 2 diabetes.Obesity inchildhood is a major risk factor for adult obesity. Adult obesity is a strong predict factor forsenectitude death. Teenagers are the most important stages development of testis.There wasshown some changes of reproduction endocrine and gonads develop dysfunction in theadolescent obesity, thereby, it influenced the genesis of germ. Provided that we deal with itirrationality, there will cause to infertility.Nowadays, Many researches care for the physiology andpathology changes in female obesity, however, the study of the changes of male obesity were rare,especially the adolescent male.The relationship between the changes of testis reproductionendocrine and leptin is less in the world. Thus, we have selected the establishment ofdiet-induced obesity model in pubertal male rats with high fat diet. We try to demonstrate the effects of dietary-induced obesity on the development of testis and its mechanism in pubertalrats,further understanding the mechanism of obesity and the express of Ob-R in thetestis. Moreover, the research can give us some advices to recognize the harmful of alimentaryobesity, we can be provided some theories with take measure to manage the adipositas in clinical,like some scientific, reasonable and effective therapies.Objective:(1)To study the effects of dietary-induced obesity on the development process of testes inpubertal male rats which were feeded with high fat diet, and investigate the changes ofspermatogenic cells cycle in testes with obesity. To illuminate the influence of puberty male ratswith obesity to the testicle spermatogenic cell function in the earlier period.(2)To understand the expression of androgen receptor and insulin growth factor-â… receptor inthe testis, and examine the content of serum leptin, observe the expression of leptin receptor inthe spermatogenic cells. Try to explore the nosogenesis of adolescent obesity and the reason oftesticular dysgenesis.Materials and methods:21-day-old male SD rats (body weight are from 40 to 60g) were randomly divided into thecontrol group (n=32) with common diet and the experimental group (n=48) with high fat diet.The diets were supplied for three times one day, and has no addition after complete eating, Therats were housed in a standard animal facility under controlled temperature (18～25℃) andphotoperiod (12h light: 12h dark), with free access to water. The experiment was done afterfeeding weeks 3,4,5 and 6 respectively.Then the body weight, Lee's index, body length, the fatof epididymis, testis weight and epididymis weight were measured. The concentration oftriglyceride and total cholesterol was detected by automatic biochemistry analyzer. Themorphological characteristics of seminiferous tubule was analyzed by histochemical method, thedistribution and expression of androgen receptor, insulin growth factor-I receptor and leptinreceptor of spermatogenic cells by immunohistochemistry. The contents of serum testosteroneand estradiol were detected by Chemiluminescentimmunoassay (CLIA) method. To investigatethe changes of spermatogenic cells cycle in testes of puberty male rats with obesity by flowcytometry method. The content of leptin in serum was examined by ELISA.Results: 1. The establishment of diet-induced obesity model: Compared with those in the control group,body weight in the high fat diet feeding group increased obviously (P＜0.01). The body weight inexperimental group was higher 23 % than that in control group at six weeks old. With thedevelopment of obesity, body weight of obese rats was over 26.6ï¼…more than that of the normal ratsin the end of experiments.. In the whole rats of experiment, there are 2 obese rats in the controlgroup, and 29 obese rats in the high fat diet feeding group(x²=20.908, P＜0.001). The high fat dietdid induce obesity in puberal rats. the proportion of the diet-induced obesity rat was 64.4ï¼…. Therewere remarkably increased the levels of plasma TG. in the end of experiment, there are obviouslydifferences between two group. TG were decrease with the development of rat. after feeding fourweeks, The content of TC in the experimental group were increased (P＜0.05). After five and sixweeks, there are obviously differences between two groups (P＜0.01).2. With the development of rats, the levels of testosterone are increased in every week betweentwo groups. however, there are decreased obviously in every week in the experimental group. Theconcentrations of estradiol were still lower at six, seven, eight weeks old. However, it wasdramatically increased in the experimental group at nine weeks old, and there are significantdifferences between the two groups (P＜0.01).3. In the control group, rats'seminiferous tubule developed well, spermatogenic cell hasarranged compact, frame distinct, the proliferation of spermatogenous cells which paste toendepidermis basal membrane were good, there are include spermatogenous cell, primaryspermatocyte and spermoblast of every developmental stage cells in the tubule. In the end ofexperiment, the tubule was developing full maturity. The tubule wall was thinningz, cells arranged indisorder and displacement which away from the basement membrane of seminiferous tubules afterfour weeks, the sperm was decreased in the eight weeks years old. in the end, the arrangement ofspermatogenic epithelium cells were not in order, spermatogenic cellular layers were reduced and thenumber of mature sperm decreased obviously.4. Changes of spermatogenic cells cycle: Compared with the control group, cell percentageof G₀/G₁ phase spermatogenic cells obviously increased at there week (P＜0.05). with thedevelopment of obesity, The percentage of S phase spermatogenic cells significant declined(P＜0.01), while the percentage of G₂/M phase spermatogenic cells were higher than the normalcontrol group (P＜0.05). The changes of the proportion of testes cells population revealed that: In obesity, spermatogenous cells converted to primary spermatocytes were increased, howerer, theprimary spermatocytes were transformed disorder, and then the numer of spermatoblasts andsperms were reduced.5. Androgen receptor and Insulin growth factor-I receptor expression and distribution:Androgen receptor: The specific AR immunostaining was observed in Leydig cells,peritubular myoid cells, Sertoli cells,smooth muscle cells and endotheliocytes of bloodvessels,but no in spermatogenic cells.AR content in testis was highest on feeding three weeks,and lowest on nine years old in the control group. Compared with control group, there was nosignificant difference in the obesity rats of the six years old of AR content. AR concentrationswere gradually to weaken expressed significantly during development from feeding fourweeks. Meanwhile, we can see there were significantly differences in the obese rats' leydig cellsfrom feeding three weeks (P＜0.01).Insulin growth factor-â… receptor: IGF-1R content in testis was lowest on feeding threeweeks, and highest on nine years old in the control group. Compared with control group, therewas significant difference in the obesity rats in the six years old of IGF-1R content(P＜0.05). Then, IGF-IR concentrations were gradually to more weaken expressed duringdevelopment from feeding four weeks (P＜0.01). but no significant difference after feeding fiveweeks, seminiferous epithelium has already developed maturely in the end of the experiment,The sperm was decreased, IGF-IR expressed mainly in spermatogenous cells, there wereremarkably differences between two groups (P＜0.01).6. The content of leptin and Ob-R expression and distribution: The levels of leptin in thediet-induced obesity group was gradually increased, and there are significant differences betweenthe two groups after feeding 4 weeks (P＜0.01). It was demonstrated that leptin levels are noinversely correlated with testosterone. The content of Ob-R increased in the control group.However, the expression of Ob-R was gradually decreased of obesity rats. There weresignificantly differences than that of control group in every from feeding three weeks. Moreover,the expression rates of Ob-R in spermatogenic cells were also differences(P＜0.01). the result wasto confirm that there was present leptin resistance phenomenon in the alimentary obesity rats.Conclusions: 1. Alimentary obesity in puberal can lead to the microstructure of testis and the secretion ofgonadal hormone disorder.2. The changes of the proportion of testes cells population revealed that: in obesity,spermatogenous cells converted to primary spermatocytes were increased, howerer, the primaryspermatocytes were transformed disorder, and then the numer of spermatoblasts and sperms werereduced.3. It was demonstrated that the effects of obesity on the development of testis are correlated withthe degression of plasma testosterone, the weaken expression of AR, the reduction expression of ob-Rand the weaken expression of IGF-IR...