Effect and mechanism of Vaspin on insulin resistance of 3T3-L1 adipocytes induced by palmitic acid / 中华临床营养杂志

Objective To investigate the effects of vaspin on insulin resistants of 3T3-L1 adipocyte through the insulin receptor substrates (IRS) /phosphatidylinositol 3-kinase (PI3K) /protein kinase B (Akt) /glucose transporter (Glut) signaling pathway.Methods 3T3-L1 cells cultured by palmitic acid (PA) were used to establish insulin resistance models,which were divided into PA group,PA + 100 ng/ml vaspin group,PA+200 ng/ml vaspin group,PA+400 ng/ml vaspin group and PA+400 ng/ml vaspin+wortmannin (PI3K inhibitor) group.Glucose uptake and consumption were assessed by 2-deoxy H3-D-glucose incorporation and glucose oxidase-peroxidase respectively.IRS/PI3K/Akt/Glut signaling pathway was evaluated using reverse transcription polymerase chain reaction and Western blot analysis.Results Compared with PA group,glucose uptake and consumption increased gradually with the increasing of vaspin concentration in other groups (P ＜ 0.05).mRNA levels of IRS-1,Akt and Glut 4 increased gradually as vaspin concentration increasing (P＜0.05),and the ratios of p-IRS-1 to IRS-1,p-Akt to Akt and Glut 4 protein level also showed the same trends (P＜0.05).However,glucose uptake and consumption in PA+400 ng/ml vaspin+wortmannin group were less than that of PA +400 ng/ml vaspin group (P＜0.05).PA+400 ng/ml vaspin+wortmannin group showed lower mRNA and protein phosphorylation levels of IRS-1,Akt and Glut 4 (P＜0.05),and that the ratios of p-IRS-1 to IRS-1,p-Akt to Akt and Glut 4 protein levels decreased (P＜0.05).Conclusions Vaspin can improve the insulin sensitivity of 3T3-L1 adipocyte by activating IRS/PI3K/Akt/Glut signaling pathway.

Effect of flavonoids from Abelmoschus manihot on proliferation, differentiation of 3T3-L1 preadipocyte and insulin resistance / 中国中药杂志

Abelmoschus manihot was rich in flavonoids, which has been reported the activity on protecting angiocarpy and improving renal function. This study aimed to explore the action mechanism of five flavonoids from A. manihot on how to ameliorating insulin resistance through the regulation of the glucose and expression of PPARγ, C/EBPα, SREBP-1, resistin, visfatin, adiponectin in 3T3-L1 adipocytes. After the 3T3-L1 preadipocytes were differentiated into mature adipocytes, insulin resistance model was built. Insulin resistance adipocytes were treated with 5, 100 μmol•L⁻¹ quercetin, isoquercitrin, hyperoside, quercitrin-3'-O-glucoside, gossypetin-8-O-β-glucoside. The glucose was indirectly determined by BCA kit. The mRNA expression levels of PPARγ, C/EBPα, SREBP-1, resistin, visfatin, adiponectin were detected by real-time quantitative PCR. Results showed that five flavonoids at 5 μmol•L⁻¹ could accelerate preadipocytes proliferation and inhibit that at 100 μmol•L⁻¹ Compared with the normal group, glucose uptake reduced significantly in model group (P<0.01). With the treatment of five flavonoids at 100 μmol•L⁻¹, glucose consumption increased significantly (P<0.01). The high expression of PPARγ, C/EBPα, adiponectin expression was significantly increased (P<0.01), and low expression of SREBP-1, resistin, visfatin after respective administration with five flavonoids at 100 μmol•L-1 promoted adipocyte differentiation. This study showed that, HY, JY, QT, QG, GG can control preadipocytes proliferation, promote adipocyte differentiation and regulate the expression of relative factors with lipid metabolism, such as PPARγ, C/EBPα, SREBP-1, adiponectin, resistin, visfatin, increasing glucose utilization and improving insulin resistance in 3T3-L1 adipocyte.

Bioconversion of Citrus unshiu peel extracts with cytolase suppresses adipogenic activity in 3T3-L1 cells

BACKGROUND/OBJECTIVES: Citrus flavonoids have a variety of physiological properties such as anti-oxidant, anti-inflammation, anti-cancer, and anti-obesity. We investigated whether bioconversion of Citrus unshiu with cytolase (CU-C) ameliorates the anti-adipogenic effects by modulation of adipocyte differentiation and lipid metabolism in 3T3-L1 cells. MATERIALS/METHODS: Glycoside forms of Citrus unshiu (CU) were converted into aglycoside forms with cytolase treatment. Cell viability of CU and CU-C was measured at various concentrations in 3T3L-1 cells. The anti-adipogenic and lipolytic effects were examined using Oil red O staining and free glycerol assay, respectively. We performed real time-polymerase chain reaction and western immunoblotting assay to detect mRNA and protein expression of adipogenic transcription factors, respectively. RESULTS: Treatment with cytolase decreased flavanone rutinoside forms (narirutin and hesperidin) and instead, increased flavanone aglycoside forms (naringenin and hesperetin). During adipocyte differentiation, 3T3-L1 cells were treated with CU or CU-C at a dose of 0.5 mg/ml. Adipocyte differentiation was inhibited in CU-C group, but not in CU group. CU-C markedly suppressed the insulin-induced protein expression of CCAAT/enhancer-binding protein alpha (C/EBPalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma) as well as the mRNA levels of CEBPalpha, PPARgamma, and sterol regulatory element binding protein 1c (SREBP1c). Both CU and CU-C groups significantly increased the adipolytic activity with the higher release of free glycerol than those of control group in differentiated 3T3-L1 adipocytes. CU-C is particularly superior in suppression of adipogenesis, whereas CU-C has similar effect to CU on stimulation of lipolysis. CONCLUSIONS: These results suggest that bioconversion of Citrus unshiu peel extracts with cytolase enhances aglycoside flavonoids and improves the anti-adipogenic metabolism via both inhibition of key adipogenic transcription factors and induction of adipolytic activity.

Anti-Obesity Effects on Unripe Rubus coreanus Miquel Extract in High Fat Diet-Induced Obese Mice.

Aims: The objective of the present study was to evaluate the anti-obesity effects of unripe Rubus coreanus Miquel (uRC) in 3T3-L1 adipocytes and body weight, epididymal fat and perirenal fat weight, and lipid profiles in diet-induced obese (DIO) C57BL/6 mice. Methodology: The lipid accumulation in 3T3-L1 adipocytes was carried out Oil Red O staining. And uRC (50 and 100 mg/kg/day) were orally administered for 90 days from the day of feeding with high fat diet (HFD). The serum total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL)-cholesterol and low density lipoprotein(LDL)-cholesterol and glucose levels were measured using Alere cholesterol LDXⓇ system. And the serum glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen(BUN) and creatinine levels were measured using the respective kits. Results: Our results indicated that treatment with uRC dose-dependently inhibited lipid accumulation in 3T3-L1 adipocytes. Moreover, after oral administration for 12 weeks, uRC (50 and 100mg/kg/day) extract produced a significant decrease in the serum total cholesterol (TC), lowdensity lipoprotein (LDL) cholesterol, glucose and glutamic-oxaloacetic transaminase (GOT) levels of HFD-induced obese mice. Similarly, uRC extract elevated serum high density lipoprotein (HDL) cholesterol. These results suggest that uRC extract may be a useful resource for the management of obesity. Conclusion: These results suggest that uRC extract may be a useful resource for the management of obesity.

Blood glucose lowering effect of ophiopogonis tuber extract and mechanism of anti-insulin-resistance / 解放军医学杂志

Objective To study the hypoglycemic effect and insulin sensitization mechanism of ophiopogonis tuber extracts on the 3T3-L1-induced adipocytes, and also in rats with reproduction of type 2 diabetes mellitus (T2DM). Methods 3T3-L1 cells were induced and differentiated into adipocytes. After the intervention with ophiopogonpolysaccharide (OPSR) and ophiopogonin (OPG), glucose consuming rate was detected for screening the extracts which may have effective hypoglycemic effects. The insulin resistance (IR) adipocyte model was established by dexamethasone induction, and then it was treated with OPSR. The protein expression levels of leptin, adiponectin and resistin were detected by Western blotting. The T2DM rat model was reproduced and then treated with OPSR for 4 weeks. Body weight (BW), triglyeride (TG), fasting blood glucose (FBG) and fasting insulin (FINs) of the rats were measured respectively. Results OPSR in dosage of 0.5-50mg/L promoted glucose consumption of adipocytes in a dose-dependent manner, the glucose consumption ratios were 32.27%, 75.14% and 90.47% respectively. OPG of 50mg/L showed very weak activity with glucose consumption ratio of only 8.49%. OPSR could significantly promote the protein expression of leptin and adiponectin, and showed an inhibitory effect on the protein expression of resistin (P<0.05). After treatment with OPSR for 4 weeks, the BW of rats increased obviously, while TG, FBG and HOMA-IR decreased significantly (P<0.05 or P<0.01). Conclusions OPSR may promote glucose transport and utilization of adipocytes, decrease the level of FBG and TG, and improve the condition of IR in T2DM rats. The mechanism of blood glucose lowering effect may be attributed to secretion of adipokines, such as leptin, adiponectin and resistin by IR adipocytes.

Effect of Tumor Necrosis Factor-α on Resistin Expression in 3T3-L1 Adipocytes and Its Mechanism / 华中科技大学学报（医学）（英德文版）

In order to investigate the effect of tumor necrosis factor-α (TNFα) on resistin expression in 3T3-L1 adipocytes, and further explore its mechanisms, the differentiated 3T3-L1 adipocytes were incubated with 0, 1, 10, 100 ng/mL TNFα respectively for 24 h, and then the expression of resistin was determined. The differentiated 3T3-L1 adipocytes were incubated with 100 ng/mL TNFα for 3, 6, 24 h respectively, and then the expression of resistin mRNA was analyzed.3T3-L1 adipocytes were induced to differentiate into mature adipocytes. The cells were randomly divided into 4 groups for culture. In the control group, no drugs were added. Cells of TNFα group were treated with 100 ng/mL TNFα. In Ro-31-8220 group, 5μmol/L protein kinase C inhibitor Ro-31-8220 was added. With TNFα+Ro-31-8220 group, 100 ng/mL TNFα were added 1 h after the addition of 5 μmol/L Ro-31-8220. All adipocytes were cultured for 24 h. Reverse transcriptionpolymerase chain reaction (RT-PCR) and Western blotting were employed to detect the expression of resistin gene. Our results showed that resistin protein and mRNA in 3T3-L1 adipocytes were inhibited by TNFα at different concentrations (P＜0.01), and the inhibitory effect increased with the concentration (P＜0.01). At the same concentrations, the inhibitory effect increased with time (P ＜0.01). Ro-31-8220 could inhibit its expression and the inhibitive effect remained unchanged with addition of TNFα(P＞0.05). It was concluded that TNFα could inhibit the expression of resistin in 3T3-L1 adipocytes. The mechanism may be that the expression of resistin is partly controlled by protein kinase C signal conduction pathway.

TNF-? impairs glucose uptake and IRS-1 associated signaling pathway by stimulated insulin in 3T3-L1 adipocytes / 中国免疫学杂志

Objective:To investigate glucose uptake and IRS-1-associated signaling pathway by stimulated insulin under TNF-? treatment.Methods:3T3-L1 adipocytes were treated with TNF-? within 6 hours and 24 hours respectively. 2-deoxy ~3H glucose was used to measure glucose uptake and western blot was used to measure IRS-1, PKB protein, tyrosine and serine307 phosphorylation on IRS-1, and PKB phosphorylation.Results:On basal status, glucose uptake of 3T3-L1 cells and phospho-tyrosine of IRS-1, PKB phosphorylation, and serine307 phosphorylation on IRS-1 were all low. Insulin stimulation induced glucose uptake and IRS-1 tyrosine phosphorylation, serine307 phosphorylation, PKB phosphorylation rapidly. TNF-? inhibited insulin-induced glucose uptake, tyrosine phosphorylation of IRS-1 and PKB phosphorylation. Rapamycin reversed the effects of TNF-?. Treated with TNF-? within 6 hours increased serine307 phosphorylation but had no effect on IRS-1 protein level. TNF-?-induced serine307 phosphorylation of IRS-1 was not affected by rapamycin. IRS-1 level was decreased under 24 hours TNF-? treatment and rapamycin can reverse the effect.Conclusion:TNF-? induced insulin resistance in 3T3-L1 adipocytes mightbe related to impaired IRS-1 tyrosine phosphorylation, rapamycin could reverse the effects of TNF-?. Treated with TNF-? within 6 hours stimulate phosphrylation of serine307 of IRS-1 and 24 hours treatment decreased IRS-1 protein level. Rapamycin antagonist TNF-?-induced loses of IRS-1.