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Objective:To observe the effect of rhGLP-1 (7-36) on Akt/GSK3 signaling pathway in hepatocytes.Methods:Human HL7702 cell line was cultured to the logarithmic growth stage and divided into experimental group and blank control group. The cultures were incubated with 100nM medium containing rhglp-1 (7-36) and without rhglp-1 (7-36) for 90min. The levels of Akt, Glycogen synthase Kinase 3 (GSK3) and Glycogen synthase (GS) in the two groups were detected by Western Blot.Results:Compared with blank control group, the protein expression of p-Akt (Thr308) in experimental group (1.81±0.28) was significantly increased ( P=0.01), but the protein expression of Akt and p-Akt (Ser473) was not significantly changed. The protein expression levels of p-GSK3α (Ser21) (1.27±0.09) and p-GSK3β (Ser9) (1.24±0.09) in the experimental group were significantly increased ( P=0.003, 0.002), while the protein expression levels of GSK3α and GSK3β were not significantly changed. The protein expression level of p-GS (Ser641) (0.70±0.16) was decreased in the experimental group ( P=0.03), but the protein expression level of GS did not change significantly. Conclusion:Glp-1 can inhibit GSK3/GS signaling pathway, activate GS activity and promote glycogen synthesis.
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OBJECTIVES@#Insulin signaling pathway plays an important role in metabolic associated fatty liver disease (MAFLD), however, the association between polymorphisms of genes related to insulin signaling pathway and MAFLD remains unclear. This study aims to investigate the association between insulin signaling pathway-related gene polymorphisms and gene-gene interactions with MAFLD susceptibility in obese children so as to provide scientific basis for further study of genetic mechanism.@*METHODS@#A total of 502 obese children with MAFLD who admitted to Hunan Provincial Children's Hospital from September 2019 to October 2021, were recruited as a case group, and 421 obese children with non-MAFLD admitted during the same period were recruited as a control group. Socio-demographic information, preterm birth history, eating habits, and exercise status of the subjects were collected by inquiry survey, and anthropometric information was collected by physical measurement. At the same time, 2 mL of venous blood was collected to extract DNA, and the polymorphism of insulin signaling pathway-related genes (5 representative candidate genes, 12 variants) was detected. Multivariate Logistic regression analysis was used to investigate the association between insulin signaling pathway-related gene polymorphisms and MAFLD in obese children.@*RESULTS@#After adjusting for confounder factors, INS rs3842748 was significantly associated with the risk of MAFLD in obese children in allele, heterozygous, and dominant models [OR and 95% CI 1.749 (1.053 to 2.905), 1.909 (1.115 to 3.267), 1.862 (1.098 to 3.157), all P<0.05]; INS rs3842752 was significantly associated with the risk of MAFLD in obese children in heterozygous and dominant models [OR and 95% CI 1.736 (1.028 to 2.932), 1.700 (1.015 to 2.846), all P<0.05]. NR1H3 rs3758674 was significantly correlated with the risk of MAFLD in obese children in allele model [OR and 95% CI 0.716 (0.514 to 0.997), P<0.05]. SREBP-1c rs2297508 was significantly associated with the risk of MAFLD in obese children in allele and dominant models [OR and 95% CI 0.772 (0.602 to 0.991) and 0.743 (0.557 to 0.991), all P<0.05]. SREBP-1c rs8066560 was significantly associated with the risk of MAFLD in obese children in allele, heterozygous, and dominant models [OR and 95% CI 0.759 (0.589 to 0.980), 0.733 (0.541 to 0.992), 0.727 (0.543 to 0.974), all P<0.05]. NR1H3 rs3758674 mutant C and SREBP-1c rs2297508 mutant G had interaction in the development of MAFLD in obese children [OR and 95% CI 0.407 (0.173 to 0.954), P<0.05].@*CONCLUSIONS@#The INS, NR1H3, and SREBP-1c gene polymorphisms in the insulin signaling pathway are associated with the susceptibility of MAFLD in obese children, but the functions and mechanisms of these genes need to be further studied.
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Child , Infant, Newborn , Humans , Female , Pediatric Obesity/genetics , Sterol Regulatory Element Binding Protein 1 , Premature Birth , Non-alcoholic Fatty Liver Disease , Signal Transduction/genetics , InsulinsABSTRACT
Gut microbial metabolite trimethylamine-N-oxide (TMAO) is associated with type 2 diabetes (T2DM). Decreased insulin sensitivity is a significant etiological factor of T2DM. Adipocytes, myocytes, and hepatocytes are the three major target cells for insulin. This study aims to investigate the effects and mechanisms of TMAO on the insulin sensitivity of these target cells. Research results indicate that in different ages of db/db diabetic mice, plasma TMAO levels were increased. TMAO significantly inhibits the insulin signaling pathways in these three major insulin target cells, reduces glucose uptake in 3T3-L1 adipocytes and L6 myocytes and downregulates genes related to gluconeogenesis in primary mouse hepatocytes. Furthermore, in mice with normal insulin sensitivity, elevating plasma TMAO levels to those seen in db/db mice using a minipump results in impaired glucose tolerance and hyperinsulinemia. All animal experiments were carried out with approval of the Experimental Animal Welfare Ethics Committee of the Institute of Materia Medica (Chinese Academy of Medical Sciences and Peking Union Medical College). Mechanistic studies suggest that TMAO exposure increases the levels of endoplasmic reticulum stress-related proteins in these three major insulin target cells. In summary, TMAO directly attenuates insulin sensitivity in insulin target cells, and its mechanism of action may involve enhancing endoplasmic reticulum stress.
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To investigate the effects and mechanism of the combination of Morus alba L. (Sangzhi) alkaloids(SZ-A) and metformin (Met) on glucose metabolism in type 2 diabetic mice, KKAy mice were divided into four groups according to the glucose and lipid indexes: control group (control), Morus alba L. (Sangzhi) alkaloids group (SZ-A, 100 mg·kg-1), metformin group (Met, 100 mg·kg-1) and combined administration group (combination, Comb, 100 mg·kg-1 SZ-A + 100 mg·kg-1 Met). All groups were administered by gavage once daily for 7 weeks accompanied with monitoring food intake, water intake, body weight as well as glycemia. Additionally, oral glucose tolerance test (OGTT), insulin tolerance test (ITT) and oral sodium pyruvate tolerance test (OPTT) were performed at week 2, week 5, week 6, respectively. The experiments were approved by the Institutional Animal Care and Use Committee of the Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College (00004332). We determined the weight and lipid content of liver, and then performed the histopathological analysis after sacrificed. Furthermore, Western blot assay was used to detect the protein levels of key molecules of PI3K/PDK1/Akt/GLUT signaling pathway in liver, muscle and adipose tissue. Compared to the SZ-A or Met monotherapy group, SZ-A + Met significantly improved the glucose metabolism disorder, which was showed in reduced food intake, water intake, the level of fasting blood glucose, postprandial blood glucose and glycosylated hemoglobin A1c (HbA1c) of KKAy mice, as well as improved glucose tolerance, enhanced insulin sensitivity and inhibited gluconeogenesis. In addition, SZ-A + Met obviously up-regulated the protein expression levels in PI3K/PDK1/Akt/GLUT signaling pathway in liver, muscle and adipose tissue of KKAy mice. Moreover, the liver lipid accumulation and blood aminotransferase level of KKAy mice in the combined administration group were significantly reduced. Therefore, we concluded that the combination of SZ-A and Met improved glucose metabolism and inhibited the occurrence and development of T2DM via promoting glucose uptake and utilization, suggesting that the combination of SZ-A and Met is a more useful treatment for T2DM.
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This study explored the in vivo effects and mechanisms of the modern classical prescription Supplemented Gegen Qinlian Decoction Formula(SGDF) against diabetic kidney disease(DKD). Sixty rats were randomly divided into the normal group, model group, SGDF group, and rosiglitazone(ROS) group. The modified DKD rat model was established by employing the following three methods: exposure to high-fat diet, unilateral nephrectomy, and intraperitoneal injection of streptozotocin(STZ). After modeling, rats in the four groups were treated with double distilled water, SGDF suspension, and ROS suspension, respectively, by gavage every day. At the end of the 6 th week of drug administration, all the rats were sacrificed for collecting urine, blood, and kidney tissue, followed by the examination of rat general conditions, urine and blood biochemical indicators, glomerulosclerosis-related indicators, podocyte pyroptosis markers, insulin resistance(IR)-related indicators, and key molecules in the insulin receptor substrate(IRS) 1/phosphatidylinositol-3-kinase(PI3 K)/serine threonine kinase(Akt) signaling pathway. The results showed that SGDF and ROS improved the general conditions, some renal function indicators and glomerulosclerosis of DKD model rats without affecting the blood glucose(BG). Besides, they ameliorated the expression characteristics and levels of podocyte pyroptosis markers, alleviated IR, and up-regulated the protein expression levels of the key molecules in IRS1/PI3 K/Akt pathway to varying degrees. In conclusion, similar to ROS, SGDF relieves DKD by targeting multiple targets in vivo. Specifically, it exerts the therapeutic effects by alleviating podocyte pyroptosis and IR. This study has preliminarily provided the pharmacological evidence for the research and development of new drugs for the treatment of DKD based on SGDF.
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Animals , Rats , Diabetes Mellitus , Diabetic Nephropathies/drug therapy , Drugs, Chinese Herbal , Insulin Resistance , Podocytes , PyroptosisABSTRACT
Insulin resistance refers to the impaired ability of insulin to regulate glucose metabolism in peripheral organs, which is considered to be the etiology of type 2 diabetes. This study aims to explore the mechanism of improving insulin resistance by compatibility of Salviae Miltiorrhizae Radix et Rhizoma and Carthami Flos (DH). Insulin resistance was conducted on C56BL/6J mice by treatment of high fat diet. The energy intake and body weight, plasma levels of triglycerides, total cholesterol, insulin and glucose, oral glucose tolerance test (OGTT) and insulin tolerance test (ITT), as well as gene transcription and protein expression levels of insulin signaling pathway in liver, heart, kidney, and skeletal muscle of insulin resistance mice were evaluated. Animal experiments and welfare were performed in compliance with the guidelines of Animal Ethics Committee of Nanjing University of Chinese Medicine. The results showed that DH treatment significantly alleviated the excessive food intake and weight gain, and significantly decreased the levels of plasma triglycerides and total cholesterol, and constantly mitigated the hyperinsulinemia in insulin resistance mice. The results of OGTT and ITT suggested that DH treatment dramatically improved the response of insulin resistance mice to insulin stimulated glucose metabolism. Furthermore, the imbalance of metabolic arm and mitogenic arm of insulin signaling pathway in insulin resistance mice was normalized after DH treatment. DH treatment regulated insulin signaling pathway and improved the ability of glucose metabolism of insulin resistance mice.
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@#Non-coding RNA (ncRNA) is a type of RNA that has no or limited protein-coding ability. It mainly includes microRNA (miRNA), long non-coding RNA (lncRNA), circular RNA (circRNA), transfer RNA (tRNA), PIWI-interacting RNA (piRNA), and small nucleolar RNA (snoRNA).At present, research has found that ncRNA plays a central role in regulating the function of pancreatic β cells, and that defects of insulin signaling is an important cause of diabetes.This article reviews the relationship between ncRNA and insulin signaling pathway in recent years, and discusses the possibility of ncRNA as a potential therapeutic target and clinical diagnostic marker for diabetes, hoping to provide some reference for the treatment and diagnosis of diabetes.
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Disulfide-bond A oxidoreductase-like protein (DsbA-L) is a molecular chaperone involved in the multimerization of adiponectin. Recent studies have found that DsbA-L is related to metabolic diseases including gestational diabetes mellitus (GDM), and can be regulated by peroxisome proliferator-activated receptor γ (PPARγ) agonists; the specific mechanism, however, is uncertain. Furthermore, the relationship between DsbA-L and the novel adipokine chemerin is also unclear. This article aims to investigate the role of DsbA-L in the improvement of insulin resistance by PPARγ agonists in trophoblast cells cultured by the high-glucose simulation of GDM placenta. Immunohistochemistry and western blot were used to detect differences between GDM patients and normal pregnant women in DsbA-L expression in the adipose tissue. The western blot technique was performed to verify the relationship between PPARγ agonists and DsbA-L, and to explore changes in key molecules of the insulin signaling pathway, as well as the effect of chemerin on DsbA-L. Results showed that DsbA-L was significantly downregulated in the adipose tissue of GDM patients. Both PPARγ agonists and chemerin could upregulate the level of DsbA-L. Silencing DsbA-L affected the function of rosiglitazone to promote the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)/AKT pathway. Therefore, it is plausible to speculate that DsbA-L is essential in the environment of PPARγ agonists for raising insulin sensitivity. Overall, we further clarified the mechanism by which PPARγ agonists improve insulin resistance.
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Objective: To investigate the effect of urolithin A (UA) on liver insulin signaling pathway in type 2 diabetes model mice and its relationship with autophagy. Methods: C57BL/6 mice were randomly divided into four groups according to body weight, namely control group, model group, UA (50 mg/kg) group, UA (50 mg/kg) combined with chloroquine (50 mg/kg) group. After 6 weeks of high-fat diet, a type 2 diabetes model was established by ip streptozotocin (STZ). The mice in each group were ig administrated for 7 weeks, and their body weight, water intake, blood lipids, fasting blood glucose (FBG), and fasting insulin (FINS) levels were measured; HE staining was used to observe pathological changes in mouse liver tissue; Western blotting was used to detect mouse phosphorylated protein kinase B (p-Akt), glucose transporter 2 (Glut2), phosphorylated glycogen synthase kinase-3β(p-GSK3β) and autophagy-related protein microtubule-related protein 1 light chain 3 II/I (LC3II/I) and selective autophagy linker protein (p62) expression levels. Results: Compared with the model group, UA significantly improved liver tissue steatosis and edema in diabetic model mice, significantly reduced plasma triacylglycerol, free fatty acids, low-density lipoprotein-cholesterol, FBG, FINS levels, and increased high-density lipoprotein-cholesterol level (P < 0.01); UA significantly reduced HOMA-IR and increased ISI (P < 0.01), up-regulated the protein expression of p-Akt, Glut2, p-GSK3β, and LC3II/I in liver tissues, and inhibited the expression of p62 protein (P < 0.01). Combined with chloroquine, FBG, FINS, and HOMA-IR in mice were increased, and ISI was decreased (P < 0.05); Liver tissue edema and steatosis were significantly aggravated; The expression levels of p-Akt, Glut2, LC3II/I protein in liver tissue were decreased, and p62 protein expression levels were increased (P < 0.05), indicating that the autophagy inhibitor chloroquine significantly weakened the effect of UA. Conclusion: UA may improve liver insulin resistance in diabetic mice by activating liver autophagy.
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Objective::To observe the effect of Erchentang, Chaihu Shugansan, Erchentang+ Chaihu Shugansan and metformin on insulin receptor substrate-1(IRS-1)and insulin receptor substrate-2(IRS-2)mRNA and protein expression in liver tissues of model rats with polycystic ovary syndrome(PCOS), and to explore the biological mechanism of relieving depression and resolving phlegm to improve insulin resistance of polycystic ovary syndrome. Method::A model of polycystic ovary syndrome was replicated in rats by subcutaneous injection of dehydroepiandrosterone(DHEA) under the neck and back.The control group was the normal group, The model rats were divided into model group, Erchentang group(9.135 g·kg-1), Chaihu Shugansan group(6.615 g·kg-1), Erchentang+ Chaihu Shugansan group (Hefang group, 9.135 g·kg-1+ 6.615 g·kg-1), and metformin group(0.158 mg·kg-1). The corresponding drugs were given by intragastric administration once a day for 4 weeks. The ovarian and liver tissues of rats were isolated, and serum testosterone(T)and estradiol(E2)hormone levels in each group were detected by enzyme-linked immunosorbent assay(ELISA), the histopathological changes of ovary in each group were detected by hematoxylin-eosin (HE) staining, IRS-1 and IRS-2 mRNA and protein expression levels in rat liver tissues were detected by quantitative real-time fluorescence PCR(Real-time PCR)and Western blot. Result::Compared with normal group, the serum T and E2 level of model group were significantly decreased (P<0.01), the histology of ovary showed a large number of saccate dilated follicles, thin granular cell layer and rare corpus luteum, IRS-1, IRS-2 mRNA and protein levels in liver tissues decreased significantly (P<0.01). Compared with model group, the serum T and E2 level of each group significantly decreased (P<0.01), histopathology of ovarian tissue showed that the number of saccular dilated follicles decreased, and the granulosa cell layer thickened, showing follicles of all levels, IRS-1, IRS-2 mRNA and protein expression were significantly increased in Erchentang group(P<0.05, P<0.01), IRS-1 mRNA and protein expression were significantly increased in Chaihu Shugansan group(P<0.01), IRS-2 mRNA and protein expression were on the rise, IRS-1 mRNA and protein expression and IRS-2 mRNA expression were significantly increased in the Hefang group (P<0.05), while IRS-2 mRNA was on the rise, IRS-1 protein and IRS-2 mRNA and protein expression were significantly increased in metformin group (P<0.01), while IRS-1 mRNA showed an upward trend. Conclusion::Erchentang improved the insulin resistance of PCOS model rats more significantly than Chaihu Shugansan, and its mechanism may be related to IRS-1, IRS-2 mRNA and protein expression levels of key signaling molecules regulating insulin signal transduction pathway.
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Disulfide-bond A oxidoreductase-like protein (DsbA-L) is a molecular chaperone involved in the multimerization of adiponectin. Recent studies have found that DsbA-L is related to metabolic diseases including gestational diabetes mellitus (GDM), and can be regulated by peroxisome proliferator-activated receptor γ (PPARγ) agonists; the specific mechanism, however, is uncertain. Furthermore, the relationship between DsbA-L and the novel adipokine chemerin is also unclear. This article aims to investigate the role of DsbA-L in the improvement of insulin resistance by PPARγ agonists in trophoblast cells cultured by the high-glucose simulation of GDM placenta. Immunohistochemistry and western blot were used to detect differences between GDM patients and normal pregnant women in DsbA-L expression in the adipose tissue. The western blot technique was performed to verify the relationship between PPARγ agonists and DsbA-L, and to explore changes in key molecules of the insulin signaling pathway, as well as the effect of chemerin on DsbA-L. Results showed that DsbA-L was significantly downregulated in the adipose tissue of GDM patients. Both PPARγ agonists and chemerin could upregulate the level of DsbA-L. Silencing DsbA-L affected the function of rosiglitazone to promote the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)/AKT pathway. Therefore, it is plausible to speculate that DsbA-L is essential in the environment of PPARγ agonists for raising insulin sensitivity. Overall, we further clarified the mechanism by which PPARγ agonists improve insulin resistance.
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Objective: To observe effect of Mori Folium-containing serum on glucose consumption and cell activity of fat cell line 3T3-L1 insulin resistance (IR) model, in order to screen out the optimal concentration of drug-containing serum, detect effect of Mori Folium on the content of inflammatory factors, and explore the possible mechanism. Method: 3T3-L1 preadipocytes in logarithmic growth phase were selected, and induced with 10 mg·L-1 insulin (Ins), 0.25 mmol·L-1 dexamethasone (DEX) and 0.5 mmol·L-1 3-isobutyl-methylxanthine(IBMX) for 48 h and then with 10 mg·L-1 Ins for 48 h. After the cells were differentiated into mature adipocytes, they were induced with 1 μmol·L-1 DEX for 96 h to establish IR model. Glucose content in the supernatant of cells was detected by glucose oxidase after serum containing Mori Folium cultured for 12,24,36, 72 h. Methyl-thiazdyl-tetrazolium(MTT) was used to detect the effect of serum containing Mori Folium on IR cells activity. The content of tumor necrosis factor-α(TNF-α) was determined by enzyme-linked immunosorbent assay (ELISA). Meanwhile, the effects of inflammatory factors on the expressions of insulin signaling pathway proteins insulin receptor (InsR), insulin receptor substrate (IRS), p-IRS1 and glucose transporter 4 (GLUT4) were determined by Western blot. Result: Serum containing Mori Folium could significantly increase the glucose consumption rate and cell activity of IR cells (Pα (PPPConclusion: Mori Folium can significantly improve IR status of 3T3-L1 cells, and its mechanism may be related to inhibiting TNF-α and promoting the expressions of insulin signaling pathway proteins.
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Objective Recent studies have shown that rhein could improve glucose metabolism,while the specific mechanism is not yet clear，the aim of this study is to explore the effects of rhein on the insulin signaling pathway in C2C12 cells.Methods To measure the optimum substrate and optimum enzyme concentrations of rhein and the protein tyrosine phosphatase-1B(PTP1B)and calculate the half maximal inhibitory concentration of rhein on PTP1B(IC50). Differentiated and maturated C2C12 myotubes were divided into two groups, the rhein group and the control group. The rhein groups were treated with different rhein concentrations(0.1,1, 10,100 μmol/L) , the positive control group was given 10 nmol/L insulin stimulation for 0.5 hours and the blank control group was treated with equal volume solvent. Related proteins in the insulin signaling pathway were detected by Western blotting and PTP-1B activity was measured by immunoprecipitation.Results The IC50 of rhein to PTP1B was 80.5 μmol/L,and when C2C12 myotubes were treated with 100 μmol/L rhein, the activity of PTP1B decreased significantly. Compared with the blank control group, the rhein groups' phosphorylation levels in insulin receptor and insulin receptor substrates were enhanced and the levels of GLUT4 were obviously improved in C2C12 cells. Moreover, the protein levels of insulin receptor and insulin receptor substrates were not affected significantly.Conclusion Rhein could reduce the activity of PTP1B and enhance insulin signaling transduction. Therefore，we speculated that the enhancement of insulin signaling may be related to the decrease of PTP1B activity in skeletal muscle cells.
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It is well established that cardiovascular diseases are the leading causes of diabetes-related death. Endothelial dysfunction is widely accepted as the initial and critical factor contributing to diabetic vascular diseases. Insulin resistance may result in vascular endothelial dysfunction, which in turn aggravates diabetic vascular diseases. Via PI3K/Akt signaling pathway, insulin inhibits the function of FoxOs, which, endothelial FoxO1 especially, exerts an important role in atherosclerosis and angiogenesis. In this regard, Wang et al. characterized 10 FoxO1 target genes regulated by insulin in endothelial cells, among which, CITED2, a transcriptional coregulator, was selected to extensively investigate its role and the underlying mechanism of insulin-regulated angiogenesis. CITED2 was significantly increased in vascular endothelial cells in diet-induced mice, ob/ob mice, as well as obese type 2 diabetic patients, all of those models or subjects are accompanied by insulin resistance. In endothelial cells, insulin significantly down-regulated CITED2 expression through insulin receptor-PI3K-Akt-FoxO1 pathway. Inhibition of CITED2 resulted in significant increases in proliferation and tube formation of endothelial cells. Overexpression of CITED2, however, repressed the transactivation of HIF. The study on the mouse model with hind limb ischemia showed that endothelial CITED2 deficiency gave rise to significant increases of expression of endothelin-1, a well-known HIF target gene, induced by ischemia or hypoxia, suggesting that CITED2 inhibited endothelial angiogenesis via suppressing HIF transactivation. In summary, insulin resistance accompanying obesity and type 2 diabetes leads to enhanced CITED2 expression, consequently impairing HIF signaling and proangiogenic capacity in endothelial cells. Inhibition of CITED2 will be a promising novel way to deal with ischemic cardiovascular diseases in diabetic patients.
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Insulin resistance (IR) is a complex metabolic disorder related to several diseases including type 2 diabetes (T2DM), hypertension and dyslipidemia. These diseases are all independent risk factors for cardiovascular disease. Lipid metabolism disorder has toxic effects on cells and may cause or aggravate IR in performance of elevated plasma levels of triglyceride (TG) and free fatty acids (FFA), the last one is an independent risk factor for IR. It has been clear that FFA may induce IR by endoplasmic reticulum (ER) stress, oxidative stress, apoptosis and inflammation, although the specific mechanisms remained unknown. The present paper summarizes the related molecules involved in the pathogenic process of IR and its mechanism, might provide a theoretical basis for the molecular mechanism of IR caused by FFA, and therapeutic reference for clinical treatment of IR and prevention of T2DM.
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Adipose tissue hypoxia has been recognized as the initiation of insulin resistance syndromes. The aim of the present study was to investigate the effects of mangiferin on the insulin signaling pathway and explore whether mangiferin could ameliorate insulin resistance caused by hypoxia in adipose tissue. Differentiated 3T3-L1 adipocytes were incubated under normal and hypoxic conditions, respectively. Protein expressions were analyzed by Western blotting. Inflammatory cytokines and HIF-1-dependent genes were tested by ELISA and q-PCR, respectively. The glucose uptake was detected by fluorescence microscopy. HIF-1α was abundantly expressed during 8 h of hypoxic incubation. Inflammatory reaction was activated by up-regulated NF-κB phosphorylation and released cytokines like IL-6 and TNF-α. Glucose uptake was inhibited and insulin signaling pathway was damaged as well. Mangiferin substantially inhibited the expression of HIF-1α. Lactate acid and lipolysis, products released by glycometabolism and lipolysis, were also inhibited. The expression of inflammatory cytokines was significantly reduced and the damaged insulin signaling pathway was restored to proper functional level. The glucose uptake of hypoxic adipocytes was promoted and the dysfunction of adipocytes was relieved. These results showed that mangiferin could not only improve the damaged insulin signaling pathway in hypoxic adipocytes, but also ameliorate inflammatory reaction and insulin resistance caused by hypoxia.
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Animals , Humans , Mice , 3T3-L1 Cells , Adipocytes , Allergy and Immunology , Adipokines , Genetics , Allergy and Immunology , Cell Hypoxia , Glucose , Metabolism , Hypoxia-Inducible Factor 1, alpha Subunit , Genetics , Allergy and Immunology , Insulin , Metabolism , Insulin Resistance , NF-kappa B , Genetics , Allergy and Immunology , Oxygen , Metabolism , Tumor Necrosis Factor-alpha , Genetics , Allergy and Immunology , Xanthones , PharmacologyABSTRACT
Objective To explore the protective effects of dipeptidyl peptidase-4 inhibitor (DPP-4I) on AD-like neurodegenerative changes and its mechanism. Methods The human neuroblastoma cell line SH-SY5Y on the logarithmic phase was divided into six groups:control group (CON group, treated with PBS contained 1‰DMSO for 12 h), wortmannin intervention group (W group, treated with 0.03 μmol/L wortmannin for 12 h), DPP-4I intervention group (DPP-4I group, treated with 10μmol/L DPP-4I for 12 h), both DPP-4I and wortmannin intervention group (DPP-4I+W group, pre-treated with 10 μmol/L DPP-4I for 2 h, then 0.03 μmol/L wortmannin for 12 h), DPP-4I, wortmannin and Ex9-39 intervention group (DPP-4I+W+Ex9-39 group, pre-treated with 10μmol/L Ex9-39 for 2 h, then 10μmol/L DPP-4I for 2 h followed by 0.03μmol/L wortmannin for 12 h), and Ex9-39 intervention group (Ex9-39 group, treated with 10μmol/L Ex9-39 for 12 h). MTT assay was used to detect the cell vitality. Western blot assay was used to detect the level of total tau protein (tau-5) and phosphorylated tau at different sites (pSpS199/202, pT231 and pS396), the level of phosphorylated neurofilaments (NF-H, NF-M) and phosphorylation of critical enzyme in PI3K/Akt/GSK-3β signaling pathway. Results (1) The cell vitality decreased, the levels of pSpS199/202, pT231, pS396 and NF-H/M increased significantly in W group than those in CON group. However, comparing with CON group, the above mentioned parameters reversed in DPP-4I group. Comparing with W group, the cell vitality increased and phosphorylated levels of above mentioned indices were decreased in DPP-4I+W group. (2) The cell vitality showed a decline trend while the levels of phosphorylation tau at three different sites and NF-H/M were higher in Ex9-39 group than those in CON group. Comparing with DPP-4I+W group, the results of the phosphorylated levels showed the same changes in DPP-4I+W+Ex9-39 group. (3) Comparing with CON group, the expression levels of phosphorylated PI3K, Akt and GSK3β increased significantly in DPP-4I group, while those decreased in W group. Additionally, the expression levels of phosphorylated PI3K, Akt and GSK3β were significantly increased in DPP-4I+W group than those in W group. Conclusion DPP-4I can enhance the level of GLP-1 and activate PI3K/Akt/GSK-3βinsulin signaling pathway to improve the hyperphosphorylated tau and NFs induced by wortmannin, and to protect AD-like neurodegeneration.
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Objective To investigate the effects of JNK inhibition on insulin signaling pathway. Methods HepG2 cells were treated with different kinds of JNK inhibitors for 12 h, and then the cells were treated with 10 nmol/L insulin for 5 min to stimulate insulin signaling pathway. Mitogen-activated protein kinases ( MAPK ) and insulin signaling pathways were analyzed by Western blot using the total cell lysates. Results JNK activity was significantly inhibited by JNK inhibitor JNKi-Ⅷand results showed that JNKi-Ⅷtreatment could reduce insulin signaling pathway in a dose-dependent manner. Furthermore, other JNK inhibitors including JNKi-Ⅴ, JNKi-Ⅲ, and SP600125 blocked JNK activity in HepG2 cells. Similar to JNKi-Ⅷ, these JNK inhibitors also impaired insulin signaling transduction in a dose-dependent manner. Conclusion In HepG2 hepatocytes, JNK activity inhibition blocks insulin signaling transduction.
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Aim To investigate the effects of starfish saponins(Sfs) on insulin signaling pathway in orotic acid-induced NAFLD rats.Methods 1% orotic acid was used to establish NAFLD model in male Wistar rats for six weeks.The NAFLD rats were randomly divided into two groups(eight rats in each group) and then fed with the corresponding diets: Model group(1% orotic acid)and Sfs group(1% orotic acid containing 0.04% starfish saponins).After starfish saponins feeding for 8 weeks, hepatic lipids content, liver function indices and relevant protein expression in muscle insulin signaling pathway were measured.Results Compared with model group, starfish saponins reduced hepatic lipids content and improved liver functions.In addition, it effectively ameliorated insulin resistance by improving insulin signaling pathway and improved glucose uptake in muscle.Conclusion The amelioration effect of starfish saponins on impaired insulin signaling pathway in muscle is observed in orotic acid-induced NAFLD rats.
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Objective To investigate the expression of microRNA (miRNA) in placenta tissue, explore the function of miRNA in pathogenesis of gestational diabetes mellitus (GDM). Methods Placenta tissue from pregnant women with GDM and normal controls were selected from January 2013 to January 2014. Expression of miRNAs were detected by sequencing technique and quantity real time PCR(qRT-PCR). Target genes of miRNA were analyzed by KEGG. Results 52 insulin signaling pathway related miRNAs including 47 up-regulated and 5 down-regulated were differentially expressed in GDM compared with normal control. Expression of placental hsa-miR-548am-5p and hsa-miR-95-5p were significantly increased , but hsa-miR-1246 was significantly lower (P <0.05) in GDM group than normal control; all the results were consistent with sequencing results. Key points of insulin signaling pathway could regulate expression of targets such as PI3K. Conclusion miRNA expression in GDM placenta was abnormal.A variety of exp ressions of miRNAs were involved in the pathogenesis of GDM by regulating insulin signaling pathway.