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Feng Liu,
Tao Yang,
Bin Wang,
Min Zhang, Nan Gu,
Jie Qiu,
Hong-qi Fan,
Chun-mei Zhang,
Li Fei,
Xiao-qing Pan,
Mei Guo,
Rong-hua Chen,
Xi-rong Guo
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ABSTRACT: The aim of the present study was to observe the effects of resistin on insulin sensitivity and glucose output in rat-derived hepatocytes.
The rat hepatoma cell line H4IIE was cultured and stimulated with resistin; supernant glucose and glycogen content were detected. The insulin receptor substrate (IRS)-1 and IRS-2, protein kinase B/Akt, glycogen synthase kinase-3beta(GSK-3 beta), the suppressor of cytokine signaling 3 (SOCS-3) protein content, as well as the phosphorylation status were assessed by Western blotting. Specific antisense oligodeoxynucleotides directed against SOCS-3 were used to knockdown SOCS-3.
Resistin induced insulin resistance, but did not affect glucose output in rat hepatoma cell line H4IIE. Resistin attenuated multiple effects of insulin, including insulin-stimulated glycogen synthesis and phosphorylation of IRS, protein kinase B/Akt, as well as GSK-3beta. Resistin treatment markedly induced the gene and protein expression of SOCS-3, a known inhibitor of insulin signaling. Furthermore, a specific antisense oligodeoxynucleotide directed against SOCS-3 treatment prevented resistin from antagonizing insulin action.
The major function of resistin on liver is to induce insulin resistance. SOCS-3 induction may contribute to the resistin-mediated inhibition of insulin signaling in H4IIE hepatocytes.
Acta Pharmacologica Sinica 02/2008; 29(1):98-104. · 1.95 Impact Factor
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Feng Liu,
Hong-Qi Fan,
Jie Qiu,
Bin Wang,
Min Zhang, Nan Gu,
Chun-Mei Zhang,
Li Fei,
Xiao-Qing Pan,
Mei Guo,
Rong-Hua Chen,
Xi-Rong Guo
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ABSTRACT: To confirm whether insulin regulates resistin expression and secretion during differentiation of 3T3-L1 preadipocytes and the relationship of resistin with insulin resistance both in vivo and in vitro.
Supernatant resistin was measured during differentiation of 3T3-L1 preadipocytes. L6 rat myoblasts and hepatoma cell line H4IIE were used to confirm the cellular function of resistin. Diet-induced obese rats were used as an insulin resistance model to study the relationship of resistin with insulin resistance.
Resistin expression and secretion were enhanced during differentiation 3T3-L1 preadipocytes. This cellular differentiation stimulated resistin expression and secretion, but was suppressed by insulin. Resistin also induced insulin resistance in H4IIE hepatocytes and L6 myoblasts. In diet-induced obese rats, serum resistin levels were negatively correlated with insulin sensitivity, but not with serum insulin.
Insulin can inhibit resistin expression and secretion in vitro, but insulin is not a major regulator of resistin in vivo. Fat tissue mass affects insulin sensitivity by altering the expression and secretion of resistin.
World Journal of Gastroenterology 02/2008; 14(1):95-100. · 2.47 Impact Factor
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ABSTRACT: To investigate the effect of resistin overexpression on 3T3-L1 adipocyte lipid and glucose metabolism.
Expression vector for rat resistin gene was constructed and transfected into 3T3-L1 adipocytes. Cell differentiation and lipid accumulation was determined by Oil Red O staining. Differentiation marker genes (pref-1, C/EBPalpha, FAS) and glucose transporter 4 (GLUT4) gene mRNA expressions were evaluated by reverse transcription-PCR (RT-PCR). Triglyceride (TG) and free fatty acids (FFAs) in adipocytes were measured by colorimetric kit.
(1) In resistin-overexpressed adipocytes, the lipid droplets presented at the second day which was earlier than the control cells. (2) The expression of C/EBPalpha and FAS genes in resistin-overexpressed adipocytes were up-regulated and the pref-1 was down-regulated compared with that of the control cells. (3) In resistin-overexpressed adipocytes, cellular TG and FFAs levels were significantly increased (P<0.05). (4) There was no difference in the expression of GLUT4 gene between 3T3-L1 adipocytes and resistin-overexpressed adipocytes (P> 0.05).
Overexpression of resistin can affect 3T3-L1 adipocyte lipid metabolism and thereby result in obesity and insulin resistance, but have no effect on GLUT4 gene expression.
Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 06/2007; 24(3):251-5.
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ABSTRACT: To assess the effects and mechanisms of the action of resistin on basal and insulin-stimulated glucose uptake in rat skeletal muscle cells.
Rat myoblasts (L6) were cultured and differentiated into myotubes followed by stimulation with single commercial resistin (130 ng/mL, 0-24 h) or cultured supernatant from 293-T cells transfected with resistin-expressing vectors (130 ng/mL, 0-24 h). Liquid scintillation counting was used to quantitate [3H] 2-deoxyglucose uptake. The translocation of insulin-sensitive glucose transporters GLUT4 and GLUT1, synaptosomal-associated protein 23 (SNAP23) and GLUT protein content, as well as the tyrosine phosphorylation status and protein content of insulin receptor substrate (IRS)-1, were assessed by Western blotting.
Treatment of L6 myotubes with single resistin or cultured supernatant containing recombinant resistin reduced basal and insulin-stimulated 2-deoxyglucose uptake and impaired insulin-stimulated GLUT4 translocation. While SNAP23 protein content was decreased, no effects were noted in GLUT4 or GLUT1 protein content. Resistin also diminished insulin-stimulated IRS-1 tyrosine phosphorylation levels without affecting its protein content. The effects of recombinant resistin from 293-T cells transfected with resistin-expressing vectors were greater than that of single resistin treatment.
Resistin regulated IRS-1 function and decreased GLUT4 translocation and glucose uptake in response to insulin. The downregulated expression of SNAP23 may have been partly attributed to the decrease of glucose uptake by resistin treatment. These observations highlight the potential role of resistin in the pathophysiology of type 2 diabetes related to obesity.
Acta Pharmacologica Sinica 04/2007; 28(3):410-6. · 1.95 Impact Factor
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ABSTRACT: To investigate the direct effects of resistin and resistin-binding peptide (RBP) on lipid metabolism and endocrine function in adipose tissue.
Rat white adipose tissue was cultured in vitro and incubated for 24 h with 30 ng/mL recombinant rat resistin protein (rResistin) or combined with RBP of varying concentrations(1x10(-12) mol/L, 1x10(-10) mol/L, 1x10(-8) mol/L). Free fatty acids (FFA) released into medium was measured by a colorimetric kit. The levels of protein secretion and mRNA expression of TNF-alpha and adiponectin were detected by ELISA kit and RT-PCR respectively.
The levels of FFA released into medium were significantly increased after 24 h of exposure to rResistin, but significantly decreased after RBP was applied, although there was no difference between the 3 concentrations. The protein level and gene expression of TNF-alpha in adipose tissue were significantly increased after 24 h of exposure to rResistin, but only obviously decreased after incubated with 1x10(-8) mol/L RBP. The levels of protein secretion and mRNA expression of adiponectin in adipose tissue were significantly decreased after 24 h of exposure to rResistin, but increased after incubated with RBP with the higher concentrations.
RBP can effectively antagonize the role of resistin on the lipid metabolism and endocrine function of adipose tissue.
Acta Pharmacologica Sinica 03/2007; 28(2):221-6. · 1.95 Impact Factor
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ABSTRACT: Aim: To investigate the direct effects of resistin and resistin-binding peptide (RBP) on lipid metabolism and endocrine function in adipose tissue. Methods: Rat white adipose tissue was cultured in vitro and incubated for 24 h with 30 ng/mL recombinant rat resistin protein (rResistin) or combined with RBP of varying concentrations(1×10-12mol/L, 1×10-10mol/L, 1×10-8mol/L). Free fatty acids (FFA) released into medium was measured by a colorimetric kit. The levels of protein secretion and mRNA expression of TNF- and adiponectin were detected by ELISA kit and RT-PCR respectively. Results: The levels of FFA released into medium were significantly increased after 24 h of exposure to rResistin, but significantly decreased after RBP was applied, although there was no difference between the 3 concentrations. The protein level and gene expression of TNF- in adipose tissue were significantly increased after 24 h of exposure to rResistin, but only obviously decreased after incubated with 1×10-8mol/L RBP. The levels of protein secretion and mRNA expression of adiponectin in adipose tissue were significantly decreased after 24 h of exposure to rResistin, but increased after incubated with RBP with the higher concentrations. Conclusion: RBP can effectively antagonize the role of resistin on the lipid metabolism and endocrine function of adipose tissue.
Acta Pharmacologica Sinica 02/2007; 28(2):221 - 226. · 1.95 Impact Factor
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ABSTRACT: Objective
To investigate the effect of the calcium channel blocker verapamil on adipocyte differentiation and its mechanism of action.Methods
Preadipocytes from 3T3-L1 strain mouse embryos were cultured and differentiated into matured adipocytes in vitro. Verapamil was added to the culture medium in the concentration of 30 μmol/L on Day 0. Cell differentiation was determined by Oil Red O staining and marker gene mRNA expression was evaluated and compared by RT-PCR. The fluo-3/AM probe and laser scanning confocal microscopy were used to measure intracellular calcium concentrations.Results The differentiation rate of 3T3-L1 preadipocytes exposed to verapamil was lower than that of untreated cells. Verapamil promoted the retention of pref-1 gene expression. Lipoprotein lipase expression in the verapamil group was significantly lower than that in the control group on Day 4, Day 6 and Day 8 (P < 0.05) and resistin expression was significantly lower than that in the control group on Day 6, Day 8 and Day 10 (P < 0.05). Fatty acid synthase expression in the verapamil group was significantly lower than that in the control group from Day 2 (P < 0.05). Intracellular concentrations of calcium [Ca2+]i in the verapamil group were significantly decreased compared with those in the control group on Day 2, Day 4 and Day 6 (P < 0.05), while there was no obvious difference between the two groups on Day 0 (P > 0.05).Conclusion
In 3T3-L1 preadipocytes verapamil significantly reduced adipocyte differentiation, down-regulated the mRNA expression of three marker genes for adipocytes differentiation, and prolonged the mRNA expression of an inhibitor of differentiation. The inhibitory effect of verapamil on differentiation may involve its role as a blocker of calcium influx in adipocytes.
Journal of Nanjing Medical University 23(6):403-409.
