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Objective To explore the effect of LYRM1 overexpression on production of reactive oxygen species (ROS) in skeletal muscle cells.Methods Rat myoblasts(L6) were transfected with either an empty vector or a LYRM1 expression vector.Cells were screened and the expression of LYRM1 protein in cells was identified.L6 cells were incubated in culture solution with H2-DCFDA after they were differentiated.Then fluorescence intensity of ROS in L6 was observed by fluorescence microscope,and the content of ROS was determined by flow cytometry.Results The relative fluorescence intensity of ROS in L6 overexpressing LYRM1 was 24.8933 ± 4.4574,while that in contrast cells was 13.1512 ± 0.7347,the difference between them was significant(t =24.12,P =0.00).Conclusions Overexpression LYRM1 can increase the production of ROS in skeletal muscle cells.LYRM1 overexpression may be influence the mitochondrial function and induce the mitochondrial damage of skeletal muscle cells.
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Objective To explore the role of free fatty acids(FFA) on expression of miR-335 in human matured adipocytes.Methods In order to induce differentiation,confluent human pre-adipocytes (day 0) were subsequently cultured in serum-free PAM containing 50 nmol/L insulin,100 nmol/L dexamethasone,0.5 mmol/L 3-isobutyl1-methylxanthine,and 100 μmol/L rosiglitazone.Then human matured adipocytes (day 16) were treated with 1 mmol/L FFA cocktail composed of lauric acid,myristic acid,linoleic acid,oleic acid,and arachidonic acids for 4,8 and 24 hours.Meanwhile,untreated cells were collected as control group.Total RNA from these adipocytes were extracted and the levels of miR-335 expression were evaluated by real-time PCR.Results The expression of miR-335 at 4,8 and 24 hours showed no statistical significance when compared to 0 hour in untreated matured adipocytes (all P ＞ 0.05).The relative expression of miR-335 after the intervention of FFA in human matured adipocytes were 9.03 ± 0.31,9.85 ±2.41 and 11.23 ± 0.62,respectively at 4,8 and 24 hours when used with snRU6 for normalization,and there was statistical signi-ficance compared with 0 hour in control group (all P ＜ 0.05).The levels of miR-335 were 4.73 ± 0.60,5.38 ± 1.25 and 4.57 ±0.52 at the same time point when used with miR-103 for normalization,and there was statistical significance compared with 0 hour in control group (all P ＜ 0.05).Conclusions FFA exert a positive effect on the miR-335 expression in human matured adipocytes,which provide the basis for the further study about the role of miR-335 in human adipocytes.
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Objective To observe the effect of uncoupler of mitochondrial oxidative phosphorylation——Cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) on mitochondrial function and insulin sensitivity in mature adipocytes.Me-thods 3T3-L1 pre-adipocytes were differentiated into mature adipocytes and then induced and maintained in medium that contained the chemical uncoupler 7.5 μmol/L FCCP.Glucose uptake was determined in the adipocytes by measu-ring 2-deoxy-D-[3H] glucose uptake.Western blot was used to detect the translocation of insulin-sensitive glucose transporter 4 (GLUT4) and measure the phosphorylation and total protein contents of insulin signaling proteins such as insulin receptor substrate(IRS)-1,Akt.The mitochondrial morphology was performed by transmission electron microscope.The mitochondrial DNA (mtDNA) copy number was evaluated by real time PCR.Luciferase-based luminescence assay was used to determine cellular ATP production.The mitochondrial membrane potential(△Ψm) and reactive oxygen species(ROS) were detected by flow cytometry.Results (1) Exposure of mature adipocytes to FCCP basal glucose uptake was similar to mature adipocytes without FCCP(t =-0.07,P ＞ 0.05) ; however,the insulin-stimulated glucose uptake was significantly decreased in FCCP group (t =5.87,P ＜ 0.01).(2)FCCP decreased insulin-stimulated GLUT4 translocation to the plasmalemma and inhibition of insulin-induced phosphorylation of IRS-1 and Akt in 3T3-L1 adipocytes.(3)The size of mitochondria in FCCP-treated adipocytes was smaller than that in 3T3-L1 adipocytes without FCCP,and the morphology was condensed and abnormal.(4) mtDNA copy number in FCCP-treated adipocytes was significantly lower than that in adipocytes without FCCP(t =-1.73,P ＜ 0.001).(5) Exposure of 3T3-L1 adipocytes to FCCP significantly decreased △Ψm (t =4.83,P ＜ 0.01) and total cellular ATP production compared with cells without FCCP (t =6.08,P ＜ 0.0001),as well as the increased intracellular ROS levels (t =-6.82,P ＜ 0.01).Conclusions FCCP may impair mitochondrial morphology and mitochondrion dysfunction,and inhibited the activation of insulin-induced phosphorylation of IRS-1 and Akt in 3T3-L1 adipocytes,which suggests that FCCP-induced insulin resistance may be correlated with the FCCP induced generation of ROS in 3T3-L1 adipocytes.
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<p><b>OBJECTIVE</b>Resistin was thought to link the obesity to type 2 diabetes. This study aimed to investigate the effect of resistin on insulinoma cell proliferation.</p><p><b>METHODS</b>pcDNA3.1-resistin was transfected into rat insulinoma cells RINm5F. Cell proliferation was assessed by the MTT assay. The resistin and SOCS3 mRNA levels were assessed by RT-PCR. The total Akt level and the phosphorylation status were assessed by Western blot.</p><p><b>RESULTS</b>The over-expressed resistin inhibited the RINm5F cell proliferation (p<0.05). SOCS-3 expression was up-regulated by resistin over-expression (3.2 folds over the control; p<0.05). Akt phosphorylation was down-regulated by resistin over-expression (0.6 fold over the control; p<0.05).</p><p><b>CONCLUSIONS</b>Resistin impairs the rat insulinoma cell RINm5F proliferation. This might be attributed to a down-regulation of Akt level caused by increased SOCS-3 expression.</p>
Subject(s)
Animals , Rats , Cell Line, Tumor , Cell Proliferation , Insulinoma , Pathology , Pancreatic Neoplasms , Pathology , Phosphorylation , Proto-Oncogene Proteins c-akt , Metabolism , Resistin , Genetics , Physiology , Suppressor of Cytokine Signaling 3 Protein , Suppressor of Cytokine Signaling Proteins , Genetics , TransfectionABSTRACT
<p><b>OBJECTIVE</b>Human STEAP4, a novel obesity-related gene, is associated with insulin sensitivity regulation in human adipocytes. This study aimed to explore the regulative role of TNFalpha on STEAP4 gene in matured human adipocytes.</p><p><b>METHODS</b>Human preadipocytes were cultured and differentiated into matured adipocytes in vitro. Fully differentiated adipocytes (Day 17) were treated with different concentrations of TNFalpha (0, 5, 10, 25 and 50 ng/mL) for 24 hrs. Total RNA and protein were extracted from the adipocytes. Levels of STEAP4 mRNA and protein expression were determined by real-time quantitative RT-PCR and Western blot respectively.</p><p><b>RESULTS</b>Different concentrations (5, 10, 25 and 50 ng/mL) of TNFalpha treatment for 24 hrs resulted in a significant increase in the STEAP4 mRNA expression of human matured adipocytes.The maximal effect was seen in the 50 ng/mL of TNFalpha treatment group. In parallel, STEAP4 protein synthesis in matured adipocytes increased in response to TNFalpha treatment of different concentrations (5, 10, 25 and 50 ng/mL) for 24 hrs. The maximal up-regulated effect was seen in the 25 ng/mL of TNFalpha treatment group.</p><p><b>CONCLUSIONS</b>TNFalpha can up-regulate STEAP4 mRNA expression in human matured adipocytes.</p>