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Objective To investigate the effects of bone morphogenetic protein-7 ( BMP7 ) on insulin signaling transduction in C2C12 myotubes and HepG2 hepatocytes, and the underlying mechanisms were studied preliminarily.Methods The C2C12 myotubes and HepG2 cells were treated with BMP7 at different concentrations.The insulin signal transduction was analyzed by Western blot.Meanwhile, total RNA was extracted and quantitative PCR was employed for detecting the effects of BMP7 on gene expressions of effectors involved in insulin signal pathway.Furthermore, JNK signal pathway was also measured.Results The protein levels of p-IR, p-Akt and p-GSK3β, as well as glucose uptake, were significantly stimulated by insulin in the C2C12 myotubes and HepG2 cells.However, these stimulations induced by insulin were largely attenuated by BMP7.The mRNA levels of Akt1, Igf1r, Insr, and Irs1 were not altered by the treatment of BMP7.The JNK signal pathway was activated by a 5-min exposure of BMP7 in the HepG2 cells, and this activation was gradually reduced along with the treating time.Conclusion BMP7 attenuates the insulin signal transduction in the HepG2 cells and C2C12 myotubes, and this attenuation effect may be through JNK activation.
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Objective To study the mechanism of insulin resistance in the cholesterol gallstone formation from insulin signal transduction pathway so as to reveal the possible mechanism and the effective role of Albiflorin Granule on preventing the cholesterol gallstones. Methods Serum triglycerides (TG), free fatty acid (FFA), and total cholesterol (TC) from different groups were measured and liver cells InsR, PKB, IKK-β protein expression levels were detected by western blotting. Results Albiflorin significantly decreased the cholesterol gallstone formation rate, increased glucose infusion rate in gallstone guinea pigs and improved insulin resistance. Compared with the normal group, insulin receptor and PKB protein expression in GS group were significantly reduced. IKK-β protein in the GS group increased significantly and Albiflorin could reduce IKK-β protein expression in guinea pig liver cells. Conclusions The model of insulin resistance in cholesterol gallstone guinea pig was successfully established, which plays an important role in the cholesterol gallstone formation. All aspects of insulin signaling pathway are involved in gallstone formation. Albiflorin can regulate various aspects of insulin signal transduction pathway to prevent the formation of gallbladder.
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OBJECTIVE@#To study the mechanism of insulin resistance in the cholesterol gallstone formation from insulin signal transduction pathway so as to reveal the possible mechanism and the effective role of Albiflorin Granule on preventing the cholesterol gallstones.@*METHODS@#Serum triglycerides (TG), free fatty acid (FFA), and total cholesterol (TC) from different groups were measured and liver cells InsR, PKB, IKK-β protein expression levels were detected by western blotting.@*RESULTS@#Albiflorin significantly decreased the cholesterol gallstone formation rate, increased glucose infusion rate in gallstone guinea pigs and improved insulin resistance. Compared with the normal group, insulin receptor and PKB protein expression in GS group were significantly reduced. IKK-β protein in the GS group increased significantly and Albiflorin could reduce IKK-β protein expression in guinea pig liver cells.@*CONCLUSIONS@#The model of insulin resistance in cholesterol gallstone guinea pig was successfully established, which plays an important role in the cholesterol gallstone formation. All aspects of insulin signaling pathway are involved in gallstone formation. Albiflorin can regulate various aspects of insulin signal transduction pathway to prevent the formation of gallbladder.
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AIM@#To investigate the molecular signaling mechanism by which the plant-derived, pentacyclic triterpene maslinic acid (MA) exerts anti-diabetic effects.@*METHOD@#HepG2 cells were stimulated with various concentrations of MA. The effects of MA on glycogen phosphorylase a (GPa) activity and the cellular glycogen content were measured. Western blot analyses were performed with anti-insulin receptor β (IRβ), protein kinase B (also known as Akt), and glycogen synthase kinase-3β (GSK3β) antibodies. Activation status of the insulin pathway was investigated using phospho-IRβ, as well as phospho-Akt, and phospho-GSK3β antibodies. The specific PI3-kinase inhibitor wortmannin was added to the cells to analyze the Akt expression. Enzyme-linked immunosorbent assay (ELISA) was used to measure the effect of MA on IRβ auto-phosphorylation. Furthermore, the effect of MA on glycogen metabolism was investigated in C57BL/6J mice fed with a high-fat diet (HFD).@*RESULTS@#The results showed that MA exerts anti-diabetic effects by increasing glycogen content and inhibiting glycogen phosphorylase activity in HepG2 cells. Furthermore, MA was shown to induce the phosphorylation level of IRβ-subunit, Akt, and GSK3β. The MA-induced activation of Akt appeared to be specific, since it could be blocked by wortmannin. Finally, MA treatment of mice fed with a high-fat diet reduced the model-associated adiposity and insulin resistance, and increased the accumulated hepatic glycogen content.@*CONCLUSION@#The results suggested that maslinic acid modulates glycogen metabolism by enhancing the insulin signaling pathway and inhibiting glycogen phosphorylase.
Subject(s)
Animals , Humans , Male , Mice , Diabetes Mellitus , Drug Therapy , Genetics , Metabolism , Drugs, Chinese Herbal , Enzyme Inhibitors , Glycogen , Metabolism , Glycogen Phosphorylase , Genetics , Metabolism , Hep G2 Cells , Insulin , Metabolism , Mice, Inbred C57BL , Signal Transduction , TriterpenesABSTRACT
PURPOSE: Alzheimer's disease (AD) results in memory impairment and neuronal cell death in the brain. Previous studies demonstrated that intracerebroventricular administration of streptozotocin (STZ) induces pathological and behavioral alterations similar to those observed in AD. Agmatine (Agm) has been shown to exert neuroprotective effects in central nervous system disorders. In this study, we investigated whether Agm treatment could attenuate apoptosis and improve cognitive decline in a STZ-induced Alzheimer rat model. MATERIALS AND METHODS: We studied the effect of Agm on AD pathology using a STZ-induced Alzheimer rat model. For each experiment, rats were given anesthesia (chloral hydrate 300 mg/kg, ip), followed by a single injection of STZ (1.5 mg/kg) bilaterally into each lateral ventricle (5 microL/ventricle). Rats were injected with Agm (100 mg/kg) daily up to two weeks from the surgery day. RESULTS: Agm suppressed the accumulation of amyloid beta and enhanced insulin signal transduction in STZ-induced Alzheimer rats [experimetal control (EC) group]. Upon evaluation of cognitive function by Morris water maze testing, significant improvement of learning and memory dysfunction in the STZ-Agm group was observed compared with the EC group. Western blot results revealed significant attenuation of the protein expressions of cleaved caspase-3 and Bax, as well as increases in the protein expressions of Bcl2, PI3K, Nrf2, and gamma-glutamyl cysteine synthetase, in the STZ-Agm group. CONCLUSION: Our results showed that Agm is involved in the activation of antioxidant signaling pathways and activation of insulin signal transduction. Accordingly, Agm may be a promising therapeutic agent for improving cognitive decline and attenuating apoptosis in AD.
Subject(s)
Animals , Male , Rats , Agmatine/therapeutic use , Alzheimer Disease/chemically induced , Cognition Disorders/chemically induced , Disease Models, Animal , Streptozocin/toxicityABSTRACT
Insulin resistance model of 3T3-L1 adipocytes were prepared with plamotic acid.Adipocytes with generated insulin resistance were cultured with different concentrations of globular domain of adiponectin(gAd:250,500,1 000 ng/ml).The cell culture medium glucose content was detected with the glucose oxidase method,the mRNA expressions of insulin receptor substrate-1 (IRS-1),phosphatidylinositol-3 kinase(PI3K),and protein kinase B(PKB) were detected with real-time quantitative PCR method.The phosphorylation of IRS-1 was detected by Western blot.Compared with the control group,the experimental group showed significantly increased glucose consumption (P ＜ 0.01),and with the increasing gAd concentration,glucose consumption was gradually increasing.IRS-1 phosphorylation was increased gradually with the increasing concentration of gAd.These results suggest that gAd can promote glucose uptake by 3T3-L1 adipocyte model with generated insulin resistance.This may be correlated with promoting insulin signal transduction and improving insulin resistance in adipocytes.
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Objective To explore the effects of electroacupuncture on the expression of glucose transporter 4 (GLUT4) and protein kinase Bβ (Akt2) in the skeletal muscles of insulin-resistant (IR) rats. Methods Twentyfour male Wistar rats were randomly divided into a normal control group, a model group and an electroacupuncture (EA) group. The rats of the model group and the EA group were fed with high fat diets to establish a model of insulin resistance. The rats in the EA group were then treated with electroacupuncture for 2 weeks, while those in the model group were not. Blood samples were collected to evaluate fasting insulin (FINS) and fasting blood glucose (FBG) to calculate the insulin sensitivity index (ISI). GLUT4 and Akt2 mRNA in the skeletal muscles were determined with reverse transcription-polymerase chain reactions (RT-PCRs) after 2 weeks of EA treatment. Results Compared with the control group, the FINS in the model group increased significantly, and ISI decreased significantly. Compared with the model group, the FINS in the EA group decreased significantly and ISI increased significantly. The expression of GLUT4 and Akt2 mRNA in the model group was significantly lower than in the control group or the EA group. Conclusion Electroacupuncture might improve the condition of IR rats, probably by enhancing the transposition of GLUT4 in the phosphatidylinositol 3-kinase/protein kinase signaling pathway.
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BACKGROUND: The glucose uptake rate is the limiting step in glucose utilization and storage. The failure of insulin to stimulate glucose uptake in muscle appears to be a primary defect of insulin resistance. This study was undertaken to examine the effect of physiological hyperinsulinemia on the phosphorylation of the insulin receptor (IR-beta), insulin receptor substrate (IRS), Akt kinase and GSK-3 in isolated skeletal muscle, in people with type 2 diabetes (n=9) and control subjects (n=11). METHODS: 75g OGTT and euglycemic hyperinsulinemic clamp test were done. And vastus lateralis muscle was obtained before and 30 min into the euglycemic clamp. Western blots were performed for tyrosine phosphorylation of insulin receptor substrate (IRS) and phosphorylation of the insulin receptor(IR-beta), Akt and GSK-3. RESULT: There were no statistical differences in the mean age, BMI and body fat between the control subjects and diabetic patients. The fasting blood sugar and HbA1c in controls and diabetic patients were 98.+/-1.3 and 208.1+/-16.5 ng/dl, and 5.4+/-0.5 and 9.2+/-0.6%, and 1.4+/-0.2 in the control subjects, and 72.2+/-52.3% (p<0.01) and 10.2+/-6.3 (p<0.01) in the diabetic patients, respectively. The insulin resistance from the euglycemic hyperinsulinemic clamp tests were 8.2+/-0.6 mg/kg/min and 3.7+/-1.1 ng/kg/min in the control subjects and in the diabetic patients, respectively (p<0.01). Compared with the normal controls, insulin-stimulated IR phosphorylation was no different to that in the diabetic patients. However, insulin-stimulated IRS phosphorylation, insulin-stimulated Akt phosphorylation and insulin-stimulated GSK-3 phosphorylation were reduced in the diabetic patients compared with the normal controls by 24, 43 and 25%, respectively (p<0.05). CONCLUSION: In korean type 2 diabetic patients, the insulin resistance may be due to the impairment of the upstream insulin signal molecular network. Further studies will focus on determining whether these signaling defects are the cause of the development of insulin resistance, or secondary to the altered metabolic state, associated with type 2 diabetes mellitus