The Regulation Of BPa On11β-HSD1in Children Adipose Tissue And Adipocytes And Its Mechanism

The incidence of obesity has risen dramatically over the last decade, which maybe due to the drimetical changes of life styles. Bisphenol A (BPA) is anenvironmental endocrine disruptor produced worldwide. This compound is abuilding block of polycarbonate plastics often used for baby bottles, toys, food andbeverage containers and other plastics. Thus, children are more susceptible to thisenvironmental pollutant. A study from the National Center for Health Statistics ofthe Centers for Disease Control and Prevention reported that BPA was detected in92.6%of the persons urine samples, moreover, the geometric mean concentrationsof BPA in children was higher than that in adults. It was reported that prenatalexposure to BPA could increase the body weight of offsprings, increase the size ofadipocytes, and increase lipid accumulation. Therefore, BPA was considered as animportant environmental adipogenesis factor.It was already known that glucocorticoids (GC) play an important role in theregulation of adipocytes differentiation, lipid accumulation and metabolism. The GCenzyme11β-hydroxysteroid dehydrogenase type1(11β-HSD1) converts inactiveGC to active corticosterone or cortisol, which amplifies local GC action. Theoverexpression of11β-HSD1in adipose tissue is associated with central obesity andinsulin-resistance. Many obesity-related factors, such as steroids, adipocytokine,inflammatory cytokines, and high fat diet could promote lipid accumulation byincreasing11β-HSD1expression. On the other hand, by using specific11β-HSD1inhibitor, GC level in adipose tissue was decreased, and obesity and insulin-resistance were ameliorated. So,11β-HSD1regulation plays a key role in thedevelopment of obesity and insulin-resistance.So far, the mechanisms of BPA involved in obesity are still unclear. It washypothesised that BPA increased lipid accumulation by upregulating11β-HSD1, if itdid, what was the concentration range, and how did it act? We explore the molecularmechanism of BPA action on children adipose tissue and human adipocytes, whichwould provide evidence for warning of hazards of daily life exposure of BPA onhuman health, as well as development of relevant preventive measures.Objective:1. To observe the effect of BPA on11β-HSD1expression and enzumeactivity on children abdomen omentum (OM) adipose tissue and human adipocytes.2. Explore the mechanism involved in low concentration of BPA regulating11β-HSD1expression and adipocyte differentiation and lipid accumulation.Methods:1. Effect of BPA on11β-HSD1expression and enzyme activity in childrenadipose tissue: Fat biopsies were obtained from children (boys:3.2-9.8years, BMISDS:-0.80~0.91, n=7; girls: age3.0-13.2years, BMI SDS:-0.86~1.02, n=10)undergoing abdominal surgery. Pieces of adipose tissue were incubated with BPA(10nM,1μM,80μM) for24hours. Real-time PCR method was used for detection ofthe peroxisome proliferator activated receptor-γ (PPAR-γ) and lipoprotein lipase(LPL) mRNA expression level, radioimmunoassay was used for detection of adiposetissue11β-HSD1enzyme activity.2. The mechanism of BPA regulating11β-HSD1:3-isobutyl-1-methyxanthine (MIX), dexamethasone, insulin and rosiglitazone weretaken together to induce the differentiation after human preadipocytes wereconfluenced. At proliferation stage, preadipocytes were treated with BPA (10nM,1μM,80μM) for24hours; and at differentiation stage, the cells were treated withBPA from day4to the end of differenation day18. And on day6, the cells weretreated with BPA (10nM) and specific11β-HSD1inhibitor carbenoxolone (CBX) alone or in combination to day18, after which adipocytes were harvested. Atproliferation stage, preadipocytes were treated with BPA (10nM) and glucocorticoidreceptor antagonist mifepristone (Mifepristone, RU486) alone or combined for24hours, dexamethasone was included as a positive control, and then cells wereharvested. Oil red O staining was used for observing the morphology of adipocytes.Real-time PCR method was used for detection of the mRNA expression levels.Results:1. BPA at10nM,1μM,80μM, significantly increased children adiposetissue11β-HSD1mRNA expression (P<0.05), only10nM and80μM increasd11β-HSD1activity in children adipose tissue. PPAR-γ and LPL mRNA expressionwere all significantly raised at these concentrations (P<0.05).2. At terminaldifferentiation stage, Oil red O staining showed that the lipid droplets wereapproximately45%in the untreated cultures, and67%,49%and89%with BPA at10nM,1μM and80μM, respectively. BPA at10nM and80μM but not at1μMcould significantly increase adipocytes11β-HSD1, PPAR-γ, and LPL mRNAexpression (P<0.05).3. CBX inhibited the effect of BPA increasing11β-HSD1,PPAR-γ, and LPL on adipocytes (P<0.05). RU486blocked the effects of BPA on theincreasing11β-HSD1on preadipocytes (P<0.05).Conclusion:1. BPA at low concentration could increase11β-HSD1mRNAexpression and activity in children adipose tissue, which amplifies local GC action,promotes adipocytes differentiation and lipid accumulation. GR was an importantpathway involved in this regulation.