Essential Roles Of11β-HSD1in Regulating Brown Adipocyte Function

Brown adipose tissue (BAT) increases energy expenditure and is an attractivetherapeutic target for obesity.11β-hydroxysteroid dehydrogenase type1(11β-HSD1),an amplifier of local glucocorticoid activity, has been shown to modulate whiteadipose tissue (WAT) metabolism and function. In the present study, we investigatedthe roles of11β-HSD1in regulating BAT function.We observed a significant increase in the expression of BAT-specific genes,including UCP1, Cidea, Cox7a1and Cox8b, in BVT.2733(a selective inhibitor of11β-HSD1)-treated and11β-HSD1knockdown brown adipocyte. In contrast, aremarkable decrease in BAT-specific gene expression was detected in brownadipocytes when11β-HSD1was over-expressed, which was normalized by byBVT.2733treatment. Consistent with the in vitro results, expression of a range ofgenes related to brow fat function in high fat diet (HFD) fed mice treated withBVT.2733.Our results indicate that11β-HSD1acts as a vital regulator that controls theexpression of genes related to brown fat function and as such may become a potentialtarget in preventing obesity.Our research was divided into three parts.Part I: Essential Roles of glucocorticoid in regulating brown fat functionPart II: Essential Roles of11β-HSD1in regulating primary brown adipocytefunctionPart III:11β-HSD1inhibitor promotes brown fat function and protects againstdiet-induced obesity in diet-induced obese mice Part I: Essential Roles of glucocorticoid in regulatingbrown fat functionObjective. It is well known that glucocorticoid plays a pivotal role inmodulating white adipose tissue(WAT) metabolism and function. However, theeffects of glucocorticoid on brown adipose tissue (BAT) thermogenesis is still unclear.Most in vitro studies reported that glucocorticoids could decrease UCP1geneexpression in brown fat cells, which was further confirmed by various in vivo studies.In contrast, in some animal models of foetus and newborn, UCP1content in BAT ismuch higher in glucocorticoid-treated groups compared with controls. Therefore,the effects of glucocorticoid on BAT are still controversial. The aim of the presentstudy was to investigate glucocorticoid regulation of UCP gene expression in thedexamethasone treated mice.Methods. C57BL/6J mice were administrated with dexamethasone (dex) orvehicle (con). We examined the effects of on the functional genes and UCP1inbrown adipose tissue obtained from dexamethasone treated mice. In vitro, UCP geneexpression was investigated in glucocorticoid, including active(dexamethasone) andinactive glucocorticoid(cortisone), treated primary brown adipocyte cells.Results. We found that dexamethasone treated brown fat cells exhibitedsignificantly larger lipid droplets than control cells as evident in inverted microscopy.We also observed a significant decrease in brown fat functional genes expression,including UCP1, Cidea, Cox7a1and Cox8b in dexamethasone treated mice. In vitro,we also found that of UCP1gene expression was significantly decreased in eitherdexamethasone or cortisone treated cells, indicating that11β-HSD1, an activator ofglucocorticoid synthesis, may serve as a genuine regulator of BAT function.Conclusions. These results suggest that glucocorticoids could decrease UCP1gene expression in brown fat cells. And since11β-HSD1functions as an activator ofglucocorticoid synthesis, it is indicated that modulating11β-HSD1expression and/oractivity could impact BAT function. Part II: Essential Roles of11β-HSD1in regulatingprimary brown adipocyte functionObjective. As an amplifier of local glucocorticoid activity,11β-hydroxysteroiddehydrogenase type1(11β-HSD1) plays a pivotal role in modulating WATmetabolism and function. However, until now the role of11β-HSD1in BAT stillremains unclear. Our results in part I suggestted that glucocorticoids could decreaseUCP1gene expression in brown fat cells. And since11β-HSD1functions as anactivator of glucocorticoid synthesis, it is indicated that modulating11β-HSD1expression and/or activity could impact BAT function.In the present study, weinvestigated the essential roles of11β-HSD1in brown adipocyte metabolism andfunction.Methods. To exam the role of11β-HSD1in BAT, primary adipocyte cellstreated with BVT.2733, an11β-HSD1selective inhibitor, and stable11β-HSD1knockdown or overexpression cell lines were generated using lentiviral-mediatedexpression of shRNA specific for11β-HSD1. We examined the effects of11β-HSD1on the mRNA expression of functional genes, fatty beta-oxidation-relatedgenes and lipid droplet proteins in brown adipose cells.Results. We observed a significant increase in brown fat functional genesexpression, including UCP1, Cidea, Cox7a1and Cox8b, in BVT.2733-treated and11β-HSD1knockdown brown adipocyte. In contrast, a remarkable decrease inbrown fat functional genes expression was detected in11β-HSD1overexpressionbrown adipocytes, and the expression could be recovered dramatically withBVT.2733treatment. Furthermore, we also observed that the size of lipid droplets inmature brown adipocyte was significantly decreased in BVT.2733-treated and11β-HSD1knockdown cells. And consistent with reduced lipid droplet size, therewas a significant increase in the expression levels of genes involved in fatty acidβ-oxidation, including CPT1, LCAD, PPARα, and UCP3. In addition, levels ofperilipin, adipophilin and TIP47were all increased in brown adipocyte in the absenceof11β-HSD1, while the expression of FSP27, a protein that promotes energy storage, was significantly decreased.Conclusions. Our results indicate that11β-HSD1acts as a vital regulator thatcontrols the expression of genes related to brown fat function. And the results alsoshowed that inhibition of11β-HSD1in brown adipocyte induced a smaller lipiddroplet size with corresponding changes in genes that contribute to ipid dropletformation. Pa·rt III:11β-HSD1inhibitor promotes brown fat functionand protects against diet-induced obesity in diet-inducedobese miceObjective. Recently, brown adipose tissue (BAT) has been demonstrated toincrease energy expenditure, indicating BAT could be an attractive therapeutic targetfor inducing weight loss. Our results in part II indicated that loss of11β-HSD1inbrown adipocyte resulted in an increase of the expression of brown fat functionalgenes and fatty acid beta-oxidation related genes.11β-HSD1shall become a vitalregulator in brown fat function, and even become a notable target for obesity. Thepurpose of the present study is to examine the effect of BVT.2733, a selective11β-HSD1inhibitor, on brown adipocyte metabolism and function in high fat diet(HFD) induced obese mice.Methods. High fat diet treated C57BL/6J mice were administrated withBVT.2733or vehicle (HFD). We examined the effects of11β-HSD1on the mRNAexpression of functional genes, fatty beta-oxidation-related genes and lipid dropletproteins in brown adipose tissue obtained from BVT.2733or HFD mice.Results. Consistent with the in vitro results, we also demonstrated thatBVT.2733induced the brown fat functional genes expression in HFD mice. Inaddition, BVT.2733also decreased body weight gain and improved glucose tolerancein HFD mice.Conclusions. our data presented here point to a critical role for11β-HSD1inregulating brown fat function, which may represent a promising therapeutic target forthe treatment of obesity and metabolic syndrome.