前脂肪细胞因子-1在脂肪细胞分化中作用的研究进展

近年发现,脂肪组织是一个重要的内分泌器官。前脂肪细胞因子-1(Pref-1)由前脂肪细胞合成并分泌,可抑制脂肪的生成。并可能通过胰岛素／胰岛素受体底物／Ras／丝裂原活化蛋白激酶／ Pref-1和Notch／HES-1／Pref-1通路,调节下游有关糖脂代谢基因的表达。大的可溶性Pref-1片段能以内分泌的方式抑制体内脂肪细胞的分化。以上研究为肥胖症的发生、发展及治疗提供了新的认识。     

Role of PARL-PINK1-Parkin pathway in adipocyte differentiation

ObjectiveAdipogenesis determines the number of adipocytes which is increased when individuals become obese. Mitochondria undergo remarkable morphological and functional changes during adipogenesis. PTEN-induced kinase 1 (PINK1) is pivotal to maintain mitochondrial homeostasis in neural cells. The present study aimed at investigating effects of PINK1 on adipogenesis and energy metabolism.MethodsExpression of presenilin associated rhomboid-like protein (PARL), PINK1 and Parkin, as well as the interaction among these proteins was temporally examined during adipogenesis. In addition, the alterations of mitochondrial mass and the energy metabolism were also analyzed.ResultsAdipogenic process can be dissected into 3 stages according to the participation of PARL-PINK1-Parkin system. (1) When pre-adipocytes are switched to differentiation, f-PINK1 is subjected to PARL cleavage to generate s-PINK1 at the early stage of differentiation (0–4 day). Mitochondrial mass is increased for generating ambient energy to meet the demands for cellular remodeling. (2) At the second stage (5–6 day), s-PINK1 persistently accumulates in mitochondria and translocates into cytoplasm to mediate Parkin degradation. Mitochondria are fragmented to reduce their mass. (3) At the late stage (7–8 day), only residual autophagy activity is remained when excess mitochondria have been eliminated. This mitochondria clearance maintains energy consumption of mature adipocytes at the minimal levels for storing energy. PARL silencing aborts adipogenesis by inhibiting PPARγ expression and the finely-orchestrated events.ConclusionsOur findings reveal the sequential adipogenic events directed by PARL-PINK1-Parkin system, add more evidence supporting the convergence of pathogenesis leading to neurodegenerative and metabolic diseases, and provide substantial information for developing novel therapeutic strategies by manipulating adipogenesis.     

Klotho protein promotes adipocyte differentiation

Mice with homozygous disruption of the klotho exhibit multiple age-related disorders and have barely detectable amounts of white adipose tissue. Although klotho expression in cultured adipocytes has been reported, little is known about its function in adipocytes. In the present study, we investigated the role of klotho on adipocyte differentiation. Adipocyte differentiation was induced by incubation of confluent 3T3-L1 cells with insulin, dexamethasone, and 1-methyl-3-isobutyl-xanthin. Klotho-siRNA and expression vector were produced for klotho suppression and overexpression, respectively. Klotho protein was purified for determination of the hormonal effect of klotho. Klotho mRNA and protein expression increased up to the 3rd d of differentiation. A peroxisome proliferator-activated receptor-gamma agonist increased klotho expression during the early period of adipocyte differentiation. The mRNA expression of adipocyte differentiation markers, such as CCAAT/enhancer-binding protein (C/EBP)alpha, C/EBPbeta, C/EBPdelta, peroxisome proliferator-activated receptor-gamma, and fatty acid binding protein 4, was decreased by klotho suppression, and increased 1.9- to 3.8-fold by klotho overexpression. The results of Oil Red O staining also suggested that klotho overexpression promoted adipocyte differentiation. Klotho protein stimulation resulted in a 2.4- to 4.6-fold increase in mRNA expression of differentiation markers compared with control, and the time course depended on adipocyte induction status. Western blot analysis showed that protein levels of C/EBPalpha and C/EBPdelta were increased by Klotho protein stimulation. These results suggest that klotho works as a hormonal factor to promote adipocyte differentiation in the early days, during the period of transient proliferation in the differentiation process, and that klotho may play an essential role in adipocyte differentiation.     

脂肪细胞分化的调控通路研究

脂肪细胞分化是一个由多个转录因子共同调控的复杂过程.这些转录因子包括CCAAT增强子结合蛋白(C/EBP)、过氧化物酶体增殖物活化受体(PPAR)家族、Wnt通路、固醇调节元件结合蛋白(SREBP)等.因此,揭示脂肪细胞分化的细胞和分子机制,将为治疗肥胖和代谢综合征提供重要的理论基础.现综述脂肪细胞分化及参与其调控的各...     

Effects of phosphatidylethanol on mouse adipocyte differentiation and expression of stearoyl-CoA desaturase 1

BACKGROUND: Phosphatidylethanol (PEth) is an aberrant phospholipid formed in vivo only in the presence of ethanol. In circulation PEth is associated with lipoproteins and is transferred from one lipoprotein to another. Lipoprotein-associated PEth affects endothelial and smooth muscle cells of blood vessels, but its effects on other cell types have not been explored. Adipocytes have a central role in metabolic syndrome and obesity. In this study we tested whether lipoprotein-associated PEth affects stearoyl-CoA desaturase 1 (SCD1) which plays a major role in lipid-mediated signaling in the differentiation of adipocytes. METHODS: Mouse 3T3-L1 preadipocytes were differentiated to adipocytes in the presence of high-density lipoproteins (HDL) isolated from the plasma of healthy volunteers or PEth-containing HDL modified in vitro. After incubation, fat accumulation, SCD1 mRNA expression, SCD1 protein content, and fatty acid composition of adipocytes were determined. RESULTS: Phosphatidylethanol-containing HDL particles inhibited adipocyte differentiation and decreased the 18:1/18:0 ratio of cellular fatty acids by 28% compared with native HDL particles. Moreover, PEth-containing HDL reduced the SCD1 protein content by 39%. CONCLUSIONS: Lipoprotein-associated PEth may mediate the effects of ethanol on SCD1 and differentiation of preadipocytes to adipocytes.     

Endothelin-1 suppression of rat adipocyte precursor cell differentiation in serum-free culture.

The effect of endothelin-1 (ET-1) on differentiation of rat adipocyte precursor cells in serum-free culture and of the adipogenic fibroblast cell line TA1 was studied. ET-1 inhibited differentiation of rat adipocyte precursor cells into adipocytes in a dose-dependent fashion, while the peptide exerted no effect on TA1 cells. Rat adipose precursor cells possessed a single class of high affinity ET-1 receptor with a Kd of 0.71 nM and a binding capacity of 47,000 sites/cell. Affinity cross-linking of [125I]ET-1 showed two bands with molecular masses of 86 and 50 kilodaltons in rat adipose precursor cells and a single broad band with a molecular mass of 55-60 kilodaltons in TA1 cells. Pertussis toxin and the protein kinase-C inhibitors, H-7 and staurosporine, all of which enhanced adipocyte differentiation of rat adipose precursor cells, partially reversed ET-1 inhibition. These results showed the divergent effect of ET-1 on adipocyte conversion and indicated the possible involvement of a pertussis toxin-sensitive pathway and protein kinase-C at least in part in the inhibitory action of ET-1 on adipocyte differentiation.     

Antiplatelet agent cilostazol potentiates adipocyte differentiation of 3T3-L1 cells

Cilostazol is an antiplatelet drug, which has beneficial effects in treatment of intermittent claudication and decreases serum triacyiglycerol level in these patients. In this study, we examined adipogenic potency of cilostazol using 3T3-L1 preadipocyte cell line because cilostazol is one of the tissue specific phosphodiesterase (PDE) inhibitors. Addition of cilostazol into the differentiation medium including insulin and dexamethasone, induced the adipocyte differentiation without isobutyl methylxanthine (IBMX). Compared with the cells incubated with vehicle, the cells treated with cilostazol contain much more lipid droplets in the cells 6 days after induction of differentiation. Adipocyte specific gene like stearoyl-CoA desaturase was strongly induced after addition of cilostazol. C/EBPbeta, which is induced by IBMX was also induced by cilostazol. These findings suggest a possibility that adipogenic effect of cilostazol is one of the mechanisms, by which this agent decreases blood triacylglycerol level in the intermittent claudication patients.     

人参皂甙Rb1促进3T3-L1脂肪细胞分化并抑制脂解

目的 观察人参皂甙Rb1（Rb1）对3T3-L1脂肪细胞分化和脂肪分解的作用，并探讨人参抗糖尿病的作用机制。方法 在3T3-L1脂肪细胞诱导分化过程中，分别加入不同浓度的Rb1作用6d，各组脂肪细胞分别进行油红O染色，甘油三酯（TG）含量、^3H-葡萄糖转运率检测，并用实时定量PCR和免疫印迹对脂肪细胞PPARγ2、CCAAT增强子结合蛋白（C／EBPα）、脂肪酸结合蛋白（ap2）和葡萄糖转运体（Glut）1、Glut4的mRNA和蛋白水平进行测定；运用表面等离子体共振技术（SPR）测定Rb1与PPARγ结合亲和力；在分化成熟的脂肪细胞加入Rb1孵育后，测定释放到上清液的甘油含量。结果Rb1能促进3T3-L1脂肪细胞的分化程度，并呈剂量依赖关系，10μmol／L浓度使细胞内TG含量增加约56％，同时PPARγ2和C／EBPα的mRNA和蛋白水平均显著升高，其下游基因ap2的mRNA水平也明显增加。分化过程中加入Rb1的脂肪细胞基础和胰岛素介导的葡萄糖转运率增加。Glut4的mRNA和蛋白水平均上升，而Glut1则未见显著变化；SPR检测结果显示Rb1具有PPARγ结合活性，提示Rb1是PPARγ的配体；在诱导分化成熟的脂肪细胞中，Rb1抑制基础脂肪分解，10μmol／L浓度使上清甘油含量下降约50％，但对异丙肾上腺素介导的脂解没有影响。结论 Rb1作为PPARγ的配体，通过上调PPARγ2,2C／EBPα的表达促进脂肪细胞的脂肪形成；增加基础和胰岛素刺激的葡萄糖利用；同时抑制基础脂解。以上结果表明人参和人参皂甙抗糖尿病的作用可能与促进脂肪细胞分化，增加胰岛素敏感性和抑制基础脂解有关。     

Serotonin as an inhibitor of gastrin

A dose of exogenous serotonin (0.1 mg/kg/min) previously described to cause maximal acid inhibition, was infused into six chronically awake dogs and significantly inhibited acid output. Integrated basal gastrin output was inhibited from a mean of 232.6 pg-min/ml to 31.6 pg-min/ml (p < 0.05) by serotonin infusion. Antral explantation significantly increased gastrin levels from a mean control level of 163 +/- 71.1 pg/ml to a mean of 991.0 +/- 663.4 pg/ml (p < 0.05). These elevated gastrin levels were then not significantly inhibited by serotonin. The effect of serotonin on gastrin output has not previously been documented. Whereas acid inhibition was uniformly achieved, serotonin inhibited basal gastrin output (integrated gastrin output) but not a stimulated level of gastrin output. Serotonin may be an important 'enterogastrone', and its release may play a role both in acid inhibition and in preventing ulcer disease.     

Early expression of p107 is associated with 3T3-L1 adipocyte differentiation

In response to hormonal stimulation quiescent 3T3-L1 preadipocyte cells reenter the cell cycle and undergo a mitotic expansion phase prior to terminal differentiation. The cell cycle regulatory proteins p130 and p107 undergo dramatic changes in protein levels within 24 h of differentiation. The role of these proteins in regulating adipocyte mitotic clonal expansion and/or differentiation are unclear. It has recently been demonstrated that adipocyte proliferation can be uncoupled from adipocyte differentiation through the use of the pharmacological MEK inhibitor PD98059 or the tyrosine phosphatase inhibitor, sodium vanadate. We examined the expression of p130 and p107 in stimulated 3T3-L1 cells in the presence of either PD98059, U0126 or sodium vanadate. While inhibition of MEK blocked proliferation, the cells underwent differentiation normally. In contrast, vanadate blocked differentiation without affecting proliferation. Inhibition of MEK did not affect the increase in p107 expression in stimulated cells indicating that induction of p107 is independent of MAP kinase signaling. Vanadate treatment caused a significant delay in p107 expression in the first 24 h following stimulation. Under these conditions, p130 expression was relatively unchanged. Our results indicate that a rapid increase in p107 expression correlates with a commitment to undergo adipocyte differentiation. The data further suggest that the rapid induction of p107 is not required for cellular proliferation during the mitotic clonal expansion phase. Taken together, these findings provide correlative data that implicate p107 in the terminal differentiation, but not proliferation, of quiescent preadipocytes following hormonal stimulation.