红景天苷通过激活3T3-L1前脂肪细胞Nrf2/HO-1信号通路及下调脂肪生成转录因子表达来抑制脂肪生成

目的:研究红景天苷对3T3-L1前脂肪细胞增殖分化及Nrf2/HO-1信号通路和脂肪生成转录因子的影响。方法:按文献介绍的方法诱导3T3-L1前脂肪细胞分化,然后分别用红景天苷(50和100μM)、吡格列酮(100μM)及红景天苷(100μM)与HO-1抑制剂ZnPP(3μM)共同处理3T3-L1细胞7天,分别于2、5、7天后进行胞内脂质含量测定,7天后进行胞内TG含量检测,实时定量PCR检测细胞中PPARγ、C/EBPα、SREBP-1c、aP2、adiponectin mRNA表达, Western blot检测胞浆和胞核中Nrf2及细胞中HO-1蛋白表达。结果:红景天苷(50和100μM)可显著抑制胞内脂质的积聚和TG生成,降低脂肪生成相关转录因子PPARγ、C/EBPα、SREBP-1c、aP2、adiponectin mRNA表达,抑制Nrf2核易位,上调HO-1蛋白表达,且量效关系明显;当与ZnPP联用后,上述作用被明显削弱。结论:红景天苷对3T3-L1前脂肪细胞分化和脂肪生成具有显著的抑制作用,其作用机制可能与其激活Nrf2/HO-1信号通路及抑制PPARγ、C/EBPα、SREBP-1c、aP2、adiponectin等脂肪生成转录因子的表达有关。

油菜种子发育早期的油体发生与调控

以甘蓝型油菜( Brassica napus L.)品种‘Westar’和‘Topas’为材料,通过超微结构观察和荧光定量PCR技术对油菜胚胎发育早期油体的发生、油体蛋白及脂肪酸合成转录因子基因的表达情况进行分析。结果显示:油体出现在油菜胚胎发育早期,在授粉9 ~ 11 d后(球形胚时期)的胚体和胚柄中均存在直径小于0. 5 μm的油体;荧光定量实验结果表明,除 BnCLO3 的表达量在整个胚胎发育阶段无明显变化外,其他油体蛋白基因 Oleosins 、 Steroleosins 和 BnCLO1 的表达量在心形胚时期就明显增多并持续增长;脂肪酸合成转录因子 BnLEC1 、 BnL1L 、 BnWRI1 和 BnFUS3 在胚胎发育阶段,基因表达规律均呈先上升再下降的趋势,但达到最高值的时间存在差异,其中 BnLEC1 最早, BnL1L 其次, BnWRI1 和 BnFUS3 较晚。研究结果表明甘蓝型油菜在球形胚时期出现油体,其结构蛋白和转录调控因子基因的表达自心形胚开始明显增多。

C/EBPα regulates SIRT1 expression during adipogenesis

SIRT1 plays an important role in adipogenesis, but how SIRT1 is regulated in adipogenesis is largely unknown. In this study, we show that both SIRT1 protein and mRNA levels were increased along with CCAAT/enhancer-binding protein a （C/EBPa） during adipocyte differentiation. C/EBPa, but not C/EBPap30, activated SIRT1 promoter in both HeLa cells and 3T3-L1 preadipocytes. Furthermore, C/EBPa upregulated SIRT1 mRNA and protein levels in HeLa cells and increased SIRT1 expression in a p53-independent manner in Soas2 cells. In preadipocytes, ectopic expression of C/EBPa upregulated SIRT1 protein level and knockdown of C/EBPa led to the decrease of SIRTI pro- tein level. Moreover, by promoter deletion analysis, gel shift assay and chromatin immunoprecipitation, we found that C/EBPa bound to the SIRT1 promoter at a consensus C/EBPα binding site. These data demonstrate that C/ EBPα regulates SIRT1 expression during adipogenesis by directly binding to the SIRT1 promoter.

硒元素对非酒精性单纯性脂肪肝大鼠PPARα、C/EBPα、SREBP-1c及SREBP-2的影响

目的探讨硒元素对高脂饮食诱导的单纯性脂肪肝模型大鼠的保护作用及作用机制。方法 SPF级SD大鼠40只,完全随机分为正常对照组(NC)、模型对照组(HF)、硒元素低剂量(L-Se,0. 5mg/kg)组、硒元素高剂量(H-Se,1. 0 mg/kg)组,各组大鼠体重差异无统计学意义(P> 0. 05),观察硒元素对体重、血清TC、TG、HDL-C、LDL-C、ALT、AST含量,肝中TC、TG含量及蛋白脂肪酶(LPL)和肝脂酶(HL)活性的影响。HE和油红O染色观察肝脏组织病理的变化。RT-PCR测定各组大鼠PPARα、C/EBPα、SREBP-1c及SREBP-2 m RNA的表达情况。结果应用硒元素(0. 5～1. 0 mg/kg)干预后,大鼠血清TC、LDL-C、ALT、AST及肝指数水平明显降低,肝总脂酶活性明显升高,RT-PCR结果显示,硒元素各剂量组能显著下调肝脏SREBP-1c及C/EBPαm RNA的表达,上调PPARαm RNA的表达(均P <0. 05),但SREBP-2 m RNA表达比较差异无统计学意义。同时可明显减轻大鼠肝肿大,改善肝细胞的脂肪变性,抑制附睾脂肪组织增大。结论硒元素可通过纠正血脂紊乱,改善肝功能和肝细胞脂肪变性防治单纯性脂肪肝,其作用机制可能与上调PPARα、下调C/EBPα、SREBP-1c m RNA表达,提高肝总脂酶活性,进而增加TG分解,降低TG合成有关。

Adipose-derived stem cells transfected with pEGFP-OSX enhance bone formation during distraction osteogenesis

This study was designed to investigate the effects of local delivery of adipose-derived stem cells （ADSCs） transfected with transcription factor osterix （OSX） on bone formation during distraction osteogenesis. New Zealand white rabbits （n=54） were randomly divided into three groups （18 rabbits per group）. A directed cloning technique was used for the construction of recombinant plasmid pEGFP-OSX, where EGFP is the enhanced green fluorescence protein. After osteodistraction of the dght mandible of all experimental rabbits, rabbits in group A were treated with ADSCs transfected with pEGFP-OSX, group B with ADSCs transfected with pEGFP-N1, and group C with physiological saline. Radiographic and histological examinations were processed after half of the animals within each group were humanely killed by injection of sodium pentothal at Week 2 or 6 after surgery. The distraction bone density was measured as its projectional bone mineral density （BMD）. Three parameters were measured, namely, the thickness of new trabeculae （TNT）, and the volumes of the newly generated cortical bone （NBV1） and the cancellous bone （NBV2） of the distracted regions. Good bone generation in the distraction areas was found in group A, which had the highest BMD, TNT, and NBV in the distraction zones among the groups. There was no significant difference in bone generation in the distraction areas between groups B and C. The results indicate that the transplantation of ADSCs transfected with pEGFP-OSX can effectively promote bone generation during distraction in vivo.

CKIP-1 suppresses the adipogenesis of mesenchymal stem cells by enhancing HDACl-associated repression of C/EBPα

Mesenchymal stem cells （MSCs） are considered as the developmental origin of multiple Uneage cells including osteocytes, adipocytes, and muscle cells. Previous studies demonstrated that the PH domain.containing protein CKIP-1 plays an important role in the devel- opment of osteobiasts and cardiomyocytes. However, whether CKIP-1 is involved in the generation of adipocytes as weU as the MSC differentiation remains unknown. Here we show that CKIP-1 is a novel regulator of MSCs differentiating into adipocytes. MSCs derived from CKIP-l-deficient mice display enhanced adipogenesis upon induction. Further analysis showed that CKIP-1 interacts with the histone deacetylase HDAC1 in the nucleus and inhibits the transcription of CCAAT/enhancer-binding protein α （C/EBPcx）, which is a crucial adipogenic transcription factor. Ectopic expression of CKI P-1 in a MSC-Uke cell line C3H/10T1/2 reduced the gener- ation of adipocytes due to suppression of adipogenic factors, including C/EBPα. Moreover, CKI P-l-deficient mice showed an increase in body weight and white adipose tissue gains when fed on a high-fat diet. Collectively, these results suggest that CKIP-1 is a novel inhibitor of MSC-originated adipogenesis by enhancing HDACl-associated repression of C/EBPα.

Activating transcription factor 5 regulates lipid metabolism in adipocytes

Activating transcription factor 5(ATF5) is a member of the activating transcription factor/cA MP response element binding protein(ATF/CREB) family, and is highly expressed in liver and adipose tissue. Previous reports have shown that ATF5 promoted 3T3-L1 preadipocytes differentiation. In this study, we found that ATF5 was highly expressed in mature adipocytes, suggesting a potential role of ATF5 in mature adipocytes, which has not been reported previously. To understand the function of ATF5 in mature adipocytes, we knocked down the expression of ATF5 in 3T3-L1 mature adipocytes and observed decreased lipid droplets. Consistent with the in vitro experiment, the knockdown of ATF5 in white adipose tissue led to less adipose tissue and smaller adipocytes size. Further research revealed that the inhibition of ATF5 diminished the adipocytes size via the inhibition of fatty acid synthetase, stearyl coenzyme A desaturation enzyme 1, and the induction of carnitine palmitoyl transferase 1, one key enzyme of lipid metabolism. In addition, ATF5 knockdown in inguinal white adipose tissue improved whole body insulin sensitivity.Our work provides a new understanding of ATF5 function in mature adipocytes and a potential therapeutic target of diabetes.