miR-410-3P inhibits adipocyte differentiation by targeting IRS-1 in cancer-associated cachexia patients.

BACKGROUNDS: Cancer-associated cachexia (CAC) is a metabolic syndrome characterized by progressive depletion of adipose and muscle tissue that cannot be corrected by conventional nutritional therapy. Adipose tissue, an important form of energy storage, exhibits marked loss in the early stages of CAC, which affects quality of life and efficacy of chemotherapy. MicroRNAs (miRNAs) are a class of noncoding RNAs that widely exist in all kinds of eukaryotic cells and play regulatory roles in various biological processes. However, the role of miRNAs in adipose metabolism in CAC has rarely been reported. This study attempted to identify important miRNAs in adipose metabolism in CAC and explore their mechanism to identify a new predictive marker or therapeutic target for CAC-related adipose tissue loss (CAL). METHODS: In this study, miRNA sequencing was firstly used to identify differentially expressed miRNAs related to CAL and the reliability of the conclusions was verified in large population samples. Furthermore, functional experiments were performed by up and down regulating miR-410-3p in adipocytes. The binding of miR-410-3p to Insulin Receptor Substrate 1 (IRS-1) was verified by Luciferase reporter assay and functional experiments of IRS-1 were performed in adipocytes. Finally, the expression of miR-410-3p in serum exosomes was detected. RESULTS: miR-410-3p was selected as differentially expressed miRNA through screening and validation. Adipogenesis was suppressed in miR-410-3p upregulation experiment and increased in downregulation experiment. Luciferase reporter assay showed that miR-410-3p binds to 3' non-coding region of IRS-1 and represses its expression and ultimately inhibits adipogenesis. miR-410-3p was highly expressed in serum exosomes of CAC patients, which was consistent with results in adipose tissue. CONCLUSIONS: The expression of miR-410-3p was higher in subcutaneous adipose tissues and serum exosomes of CAC patients, which significantly inhibits adipogenesis and lipid accumulation. The study shows that miR-410-3p could downregulate IRS-1 and downstream adipose differentiation factors including C/EBP-a and PPAR-γ by targeting 3' noncoding region.

SOX21-AS1 modulates neuronal injury of MMP+-treated SH-SY5Y cells via targeting miR-7-5p and inhibiting IRS2.

Parkinson's disease (PD), caused by the decreased number of dopaminergic neurons in the substantia nigra, is identified as the second most familiar age-dependent neurodegenerative disease to the public. Long non-coding RNAs (lncRNAs) have been reported to participate in the development of PD. In our research, the expression of lncRNA SRY-box transcription factor 21 antisense divergent transcript 1 (SOX21-AS1) was up-regulated in 1-methyl-4-phenylpyridinium (MMP+)-treated SH-SY5Y cells. In addition, SOX21-AS1 depletion weakened the cell injury induced by MMP+. Moreover, SOX21-AS1 knockdown decreased Reactive Oxygen Species (ROS) generation and levels of TNF-α, IL-1ß and IL-6, but increased SOD activity. However, SOX21-AS1 up-regulation led to opposite results. Further, SOX21-AS1 could bind with miR-7-5p, whose overexpression relieved MMP+-induced cell injury. Additionally, insulin receptor substrate 2 (IRS2) served as the target gene of miR-7-5p, and its expression was positively modulated by SOX21-AS1. Similarly, IRS2 knockdown also had alleviative effects on cell injury stimulated by MMP+ treatment. In sum up, our study demonstrated a new regulatory network consisted of SOX21-AS1, miR-7-5p and IRS2 in SH-SY5Y cells, supplying with a better comprehension about the pathogenic mechanism of PD.

MicroRNA-203a regulates pancreatic ß cell proliferation and apoptosis by targeting IRS2.

The main pathogenesis of type 1 diabetes mellitus (T1DM) is autoimmune-mediated apoptosis of pancreatic islet ß cells. We sought to characterize the function of microRNA-203a (miR-203a) on pancreatic islet ß cell proliferation and apoptosis. In situ hybridization was used to detect the expression of miR-203a in islet ß cells in normal and hyperglycaemic non-obese diabetic (NOD) mice. Cell proliferation was measured by cell counting kit eight and cell apoptosis was detected using flow cytometry. Insulin receptor substrate 2 (IRS2/Irs2) was determined to be a direct target of miR-203a by Luciferase reporter assay. We detected the effects of miR-203a overexpression or inhibition on proliferation and apoptosis of IRS2-overexpressing or IRS2-knockdown MIN6 cells respectively, and preliminarily explored the downstream targets of the IRS2 pathway. NOD mice model was used to detect miR-203a inhibitor treatment for diabetes. Our experiment showed miR-203a was upregulated in pancreatic ß cells of hyperglycaemic NOD mice. Elevated miR-203a expression inhibited the proliferation and promoted the apoptosis of MIN6 cells. IRS2/Irs2 is a novel target gene directly regulated by miR-203a and miR-203a overexpression downregulated the expression of IRS2. Irs2 silencing reduced cell proliferation and increased apoptosis. Irs2 overexpression could abolish the pro-apoptotic and anti-proliferative effects of miR-203a on MIN6 cells. Hyperglycemia in newly hyperglycemic NOD mice was under control after treatment with miR-203a inhibitor. Our study suggests that miR-203a regulates pancreatic ß cell proliferation and apoptosis by targeting IRS2, treatment with miR-203a inhibitors and IRS2 might provide a new therapeutic strategy for T1DM.

RETRACTED: Long noncoding RNA LBX2-AS1 drives the progression of hepatocellular carcinoma by sponging microRNA-384 and thereby positively regulating IRS1 expression.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors. The authors reported that the in vivo study was performed without the approval from an ethics committee. This is despite previously reporting that the in vivo experiments involved animals were approved by the Animal Care and Use Ethics Committee at their hospital. All authors have agreed to retract the article and apologise to the readership of the journal for any inconvenience caused. Further concern was raised about several figures of the article": "A pair of flow-cytometry plots share most of their points in common, and appear to have been derived from the same data set." The Editors of Pathology Research and Practice consider these concerns as well justified.

MiRNA-200a-3p suppresses the proliferation, migration and invasion of non-small cell lung cancer through targeting IRS2.

OBJECTIVE: To uncover the biological role of microRNA-200a-3p (miRNA-200a-3p) in the progression of non-small cell lung cancer (NSCLC) and the underlying mechanism. PATIENTS AND METHODS: The expression levels of miRNA-200a-3p and IRS2 in NSCLC tissues and cell lines were examined through quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between the miRNA-200a-3p level and pathological characteristics of NSCLC patients was analyzed. The prognostic value of miRNA-200a-3p in NSCLC was assessed through the Kaplan-Meier method. The potential interaction between miRNA-200a-3p and IRS2 was explored through Dual-Luciferase Reporter Gene Assay and Spearman correlation test. The regulatory effects of miRNA-200a-3p/IRS2 on the proliferative, migratory, and invasive abilities of NSCLC were evaluated by Cell Counting Kit-8 (CCK-8) and the transwell assay. The protein levels of the epithelial-mesenchymal transition (EMT)-related genes in NSCLC cells influenced by miRNA-200a-3p were detected by Western blot. RESULTS: MiRNA-200a-3p was downregulated in NSCLC tissues and cell lines. The expression level of miRNA-200a-3p was related to tumor size, TNM staging, and lymphatic metastasis of NSCLC. The low level of miRNA-200a-3p predicted worse prognosis in NSCLC patients. The overexpression of miRNA-200a-3p inhibited A549 cells from proliferating, migrating, and invading. The protein levels of E-cadherin were upregulated, while N-cadherin and Vimentin were downregulated in A549 cells overexpressing miRNA-200a-3p. The Dual-Luciferase Reporter Gene Assay verified the binding between miRNA-200a-3p and IRS2. The level of IRS2 was negatively regulated by miRNA-200a-3p. Moreover, the overexpression of IRS2 could reverse the regulatory role of miRNA-200a-3p in the cellular behaviors of A549 cells. CONCLUSIONS: MiRNA-200a-3p suppresses the proliferative, migratory, and invasive abilities of NSCLC by targeting IRS2, thus alleviating the progression of NSCLC.

MiRNA-7b-5p attenuates the progression of osteoporosis by inhibiting adipose differentiation of hMSCs via regulating IRS2.

OBJECTIVE: To elucidate whether microRNA-7b-5p (miRNA-7b-5p) could inhibit adipose differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) through regulating IRS2, thereby alleviating the progression of osteoporosis. MATERIALS AND METHODS: Expression levels of miRNA-7b-5p and IRS2 in hMSCs at different stages of adipogenic differentiation and osteogenic differentiation were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) and Western blot. After transfection of miRNA-7b-5p mimic or pcDNA-IRS2 in hMSCs, lipid droplet formation in cells was observed by oil red O staining. Expressions of C/EBPα and PPARγ were detected by qRT-PCR and Western blot. The potential target gene of miRNA-7b-5p was predicted by bioinformatics and verified by dual-luciferase reporter gene assay. Finally, expressions of IRS2 in hMSCs transfected with miRNA-7b-5p-NC, miRNA-7b-5p mimic or co-transfected with miRNA-7b-5p mimic and pcDNA-IRS2 were examined. RESULTS: Expressions of miRNA-7b-5p and IRS2 gradually decreased with the prolongation of adipogenic differentiation, but increased during osteogenic differentiation of hMSCs. Transfection of miRNA-7b-5p mimic reduced oil red O staining after adipogenic differentiation and downregulated mRNA and protein levels of C/EBPα and PPARγ. Transfection of pcDNA-IRS2 increased oil red O staining after osteogenic differentiation and upregulated mRNA and protein levels of C/EBPα and PPARγ. Dual-luciferase reporter gene results showed that miRNA-7b-5p could bind to IRS2. Overexpression of IRS2 reversed the downregulated mRNA and protein levels of adipogenic-related genes C/EBPα and PPARγ due to the overexpression of miRNA-7b-5p. CONCLUSIONS: MiRNA-7b-5p inhibits the adipogenic differentiation of hMSCs through IRS2, thus alleviating the development of osteoporosis.

Centella asiatica (L.) extract attenuates inflammation and improve insulin sensitivity in a coculture of lipopolysaccharide (LPS)-induced 3T3-L1 adipocytes and RAW 264.7 macrophages.

Insulin resistance in obese condition is related to chronic low-grade inflammation which leads to insulin signaling impairment. Centella asiatica (L.) is an herb that exhibits anti-inflammatory and blood sugar-lowering activity (hypoglycemia). The study aims to investigate the molecular mechanism of C. asiatica extract in insulin sensitivity improvement in a coculture of lipopolysaccharide (LPS)-induced 3T3-L1 adipocytes and RAW 264.7 macrophages. A coculture of 3T3-L1 adipocytes and RAW 264.7 macrophages were incubated with LPS to induce insulin resistance in the adipocytes. An extract of C. asiatica was added to coculture cells and after 24 hours, insulin sensitivity and inflammatory response were determined, including glucose consumption, glucose transporter-4 (GLUT-4), insulin receptor substrate-1 (IRS-1), and interleukin-6 (IL-6) mRNA expression. C. asiatica extract at a concentration of 500 µg/mL increased glucose consumption and induced GLUT-4 and IRS-1 mRNA expression significantly in a coculture of LPS-induced 3T3-L1 adipocytes and RAW 264.7 macrophages. The pro-inflammatory cytokines IL-6 mRNA expression was decreased in the coculture cells after treatment with C. asiatica extract at a concentration of 500 µg/mL. This result indicates that C. asiatica has an effect to stimulate glucose consumption in the coculture cells that might be mediated via GLUT-4/IRS-1 pathway as a result of IL-6 inhibition. These findings suggest that the C. asiatica extract inhibits inflammation and improves insulin sensitivity in a coculture of LPS-induced 3T3-L1 adipocytes and RAW 264.7 macrophages.

Insulin Receptor Substrate-1 (IRS-1) and IRS-2 expression levels are associated with prognosis in non-small cell lung cancer (NSCLC).

The insulin-like growth factor-1 (IGF-1) signaling pathway has been implicated in non-small cell lung cancer (NSCLC) outcomes and resistance to targeted therapies. However, little is known regarding the molecular mechanisms by which this pathway contributes to the biology of NSCLC. The insulin receptor substrate (IRS) proteins are cytoplasmic adaptor proteins that signal downstream of the IGF-1R and determine the functional outcomes of this signaling pathway. In this study, we assessed the expression patterns of IRS-1 and IRS-2 in NSCLC to identify associations between IRS-1 and IRS-2 expression levels and survival outcomes in the two major histological subtypes of NSCLC, adenocarcinoma (ADC) and squamous cell carcinoma (SCC). High IRS-2 expression was significantly associated with decreased overall survival in adenocarcinoma (ADC) patients, whereas low IRS-1 cytoplasmic expression showed a trend toward association with decreased overall survival in squamous cell carcinoma (SCC) patients. Tumors with low IRS-1 and high IRS-2 expression were found to be associated with poor outcomes in ADC and SCC, indicating a potential role for IRS-2 in the aggressive behavior of NSCLC. Our results suggest distinct contributions of IRS-1 and IRS-2 to the biology of ADC and SCC that impact disease progression.

The Mechanism of Phillyrin from the Leaves of Forsythia suspensa for Improving Insulin Resistance.

Three lignans, phillyrin, forsythia ester A, and rosin-ß-D-furan glucose, were isolated from Forsythia suspensa which is a famous Traditional Chinese Medicine used for clearing heat and detoxifying, reducing swelling and dispersing knot, and dispersing wind heat. In this study, the effects of phillyrin, forsythia ester A, and rosin-ß-D-furan glucose on insulin resistance of 3T3-L1 adipocytes were investigated by the method of glucose oxidase-peroxidase (GOD-POD) and the mechanism was assayed by the method of western blot. The results indicated that phillyrin, forsythia ester A, and rosin-ß-D-furan glucose could improve the glucose uptake in 3T3-L1 adipocytes under insulin resistance (IR). Among them, phillyrin showed significant activity in increasing glucose consumption at the concentrations of 100 µM and 200 µM (P < 0.001). The mechanism of improving insulin resistance may be that phillyrin could raise the protein phosphorylation of IRS-1 and Akt and the expression levels of GLUT4 protein.

Diabetic Hemodialysis: Vitamin D Supplementation and its Related Signaling Pathways Involved in Insulin and Lipid Metabolism.

BACKGROUND: This study was conducted to determine the effects of vitamin D supplementation on some of the gene expressions related to insulin and lipid metabolism in diabetic hemodialysis (HD) patients. METHODS: A double-blind, randomized, placebo-controlled clinical trial was carried out in 55 patients with diabetic HD. The current project used two groups in which each subject received vitamin D supplements (50,000 IU, n=28) or placebo (50,000 IU, n=27) every 2 weeks for 12 weeks. Gene expression analyses (RT-PCR) were included to obtain the rate of gene expression of the related insulin and lipid metabolism genes in peripheral blood mononuclear cells (PBMCs) of patients with diabetic HD. RESULTS: Our data revealed that consumption of vitamin D supplementation enables to overexpress the peroxisome proliferation-activated receptor gamma (PPAR-γ) (P=0.001), AKT (P=0.04), PI3K (P=0.02), insulin receptor substrate-1 (IRS1) (P0.008) and glucose transporter type 4 (GLUT-4) (P=0.01) and downregulate the expression of protein kinase C (PKC) (P=0.001) in patients with diabetic HD than control group following the 12-week intervention. In addition, vitamin D supplementation downregulated low-density lipoprotein receptor (LDLR) (P=0.03) expression in the subjects with diabetic HD than the control group. Vitamin D supplementation did not show any effects on the expression of pyruvate dehydrogenase kinase 1 (PDK1) (P=0.37), IRS2 (P=0.90) and lipoprotein (a) [Lp(a)] (P=0.05). CONCLUSION: Our findings confirmed that diabetic HD subjects who received the vitamin D supplementation (for 12 weeks), showed a significant overexpression in the PPAR-γ, AKT, PI3K, IRS1 and GLUT4 genes, and also showed a significant downregulation in the PKC and LDLR genes. Moreover, no effects on PDK1, IRS2 and Lp(a) expression were observed.

The Diurnal Rhythm of Insulin Receptor Substrate-1 (IRS-1) and Kir4.1 in Diabetes: Implications for a Clock Gene Bmal1.

Purpose: Diabetes leads to the downregulation of the retinal Kir4.1 channels and Müller cell dysfunction. The insulin receptor substrate-1 (IRS-1) is a critical regulator of insulin signaling in Müller cells. Circadian rhythms play an integral role in normal physiology; however, diabetes leads to a circadian dysrhythmia. We hypothesize that diabetes will result in a circadian dysrhythmia of IRS-1 and Kir4.1 and disturbed clock gene function will have a critical role in regulating Kir4.1 channels. Methods: We assessed a diurnal rhythm of retinal IRS-1 and Kir4.1 in db/db mice. The Kir4.1 function was evaluated using a whole-cell recording of Müller cells. The rat Müller cells (rMC-1) were used to undertake in vitro studies using a siRNA. Results: The IRS-1 exhibited a diurnal rhythm in control mice; however, with diabetes, this natural rhythm was lost. The Kir4.1 levels peaked and troughed at times similar to the IRS-1 rhythm. The IRS-1 silencing in the rMC-1 led to a decrease in Kir4.1 and BMAL1. The insulin treatment of retinal explants upregulated Kir4.1 possibly via upregulation of BMAL1 and phosphorylation of IRS-1 and Akt-1. Conclusions: Our studies highlight that IRS-1, by regulating BMAL1, is an important regulator of Kir4.1 in Müller cells and the dysfunctional signaling mediated by IRS-1 may be detrimental to Kir4.1.

Commutative regulation between endothelial NO synthase and insulin receptor substrate 2 by microRNAs.

Endothelial NO synthase (eNOS) expression is regulated by a number of transcriptional and post-transcriptional mechanisms, but the effects of competing endogenous RNAs (ceRNAs) on eNOS mRNA and the underlying mechanisms are still unknown. Our bioinformatic analysis revealed three highly expressed eNOS-targeting miRNAs (miR-15b, miR-16, and miR-30b) in human endothelial cells (ECs). Among the 1103 mRNA targets of these three miRNAs, 15 mRNAs share a common disease association with eNOS. Gene expression and correlation analysis in patients with cardiovascular diseases identified insulin receptor substrate 2 (IRS2) as the most correlated eNOS-ceRNA. The expression levels of eNOS and IRS2 were coincidentally increased by application of laminar shear but reduced with eNOS or IRS2 siRNA transfection in human ECs, which was impeded by Dicer siRNA treatment. Moreover, luciferase reporter assay showed that these three miRNAs directly target the 3'UTR of eNOS and IRS2. Overexpression of these three miRNAs decreased, whereas inhibition of them increased, both mRNA and protein levels of eNOS and IRS2. Functionally, silencing eNOS suppressed the Akt signal pathway, while IRS2 knockdown reduced NO production in ECs. Thus, we identified eNOS and IRS2 as ceRNAs and revealed a novel mechanism explaining the coincidence of metabolic and cardiovascular diseases.

Morin Exerts Anti-Diabetic Effects in Human HepG2 Cells Via Down-Regulation of miR-29a.

Diabetes mellitus is a complex metabolic disease around the world that is characterized by hyperglycemia resulting from impaired insulin secretion, insulin action, or both. MicroRNA-29a is an important regulator of insulin signaling and gluconeogenesis pathways through IRS2, PI3K and PEPCK expressions which up regulates in Diabetes. Morin is a substantial bioflavonoid which has insulin mimetic effect, and interacting with nucleic acids and proteins. In this study HepG2 cells, were exposed to high glucose to induce diabetic condition. We have determined whether high glucose stimulation might promotes miR-29a expression level in HepG2 cells and subsequently evaluated the Morin treatment effects on this state. In HepG2 cells, high glucose increases miR-29a expression level and decreases its target genes, IRS2 and PI3K expression, and increases associated downstream gene in gluconeogenic pathway, PEPCK. Morin treatment down regulates miR-29a expression level and improves insulin signaling and glucose metabolism. To confirm the inhibitory effects of Morin on miR-29a, we have transfected cells with mimic and inhibitor-miR-29a. This study for the first time identifies that Morin improves diabetic condition through down regulation of the miR-29a level, and suggest that this new inhibitor of miR-29a may be a useful biomedicine to treat diabetes.

Expressions of IGF-1, ERK, GLUT4, IRS-1 in metabolic syndrome complicated with colorectal cancer and their associations with the clinical characteristics of CRC.

BACKGROUND: Epidemiological data have revealed that colorectal cancer (CRC) risk is increased in patients with Metabolic syndrome. OBJECTIVE: To explore the expressions of IGF-1, ERK, GLUT4, IRS-1 in MS patients with CRC and their associations with the clinical characteristics of CRC. METHODS: We investigated the expressions of IGF-1, ERK, GLUT4 and IRS-1 in greater omental adipose tissues of 168 MS patients with/without CRC, 85 CRC patients without MS and 98 healthy controls by RT-PCR, and analyzed the relationships between their expressions and clinical characteristics of CRC. RESULTS: The expression levels of IGF-1 and ERK in MS patients with/without CRC were higher while the expression levels of GLUT4 were lower compared with CRC patients without MS and healthy controls (P< 0.01). The expression levels of IGF-1 and ERK in MS patients with CRC were higher while expression levels of GLUT4 were lower compared to MS patients without CRC (P< 0.01). Expression levels of ERK, IGF-1, GLUT4 were associated with clinical characteristics of CRC, including tumor size, distant metastasis and advanced stages (III/IV) (P< 0.05). CONCLUSIONS: Expressions of IGF-1, ERK and GLUT4 in greater omental adipose tissues might be useful biomarkers and predictive targets in the diagnosis of CRC.

Downregulation of miR-493 promoted melanoma proliferation by suppressing IRS4 expression.

Accumulating evidence indicated that aberrantly expressed microRNAs play critical roles in the initiation and progression of human cancers. However, the underlying functions of miR-493 in human melanoma remains unknown. Here, our study found that miR-493 expression was downregulated in human melanoma tissues and cells. Overexpression of miR-493 suppressed cell proliferation and cell cycle in human melanoma cell line A375. IRS4 was defined as a target for downregulation by miR-493 and was confirmed by luciferase assay. We also found that knockdown of IRS4 counteracted the proliferation promotion by miR-493 inhibitor. In summary, these results demonstrated that miR-493 acts as a tumor suppressor and inhibits cell proliferation and cell cycle in human melanoma by directly targeting IRS4.

Insulin resistance and exendin-4 treatment for multiple system atrophy.

See Stayte and Vissel (doi:10.1093/awx064) for a scientific commentary on this article. Multiple system atrophy is a fatal sporadic adult-onset neurodegenerative disorder with no symptomatic or disease-modifying treatment available. The cytopathological hallmark of multiple system atrophy is the accumulation of α-synuclein aggregates in oligodendrocytes, forming glial cytoplasmic inclusions. Impaired insulin/insulin-like growth factor-1 signalling (IGF-1) and insulin resistance (i.e. decreased insulin/IGF-1) have been reported in other neurodegenerative disorders such as Alzheimer's disease. Increasing evidence also suggests impaired insulin/IGF-1 signalling in multiple system atrophy, as corroborated by increased insulin and IGF-1 plasma concentrations in multiple system atrophy patients and reduced IGF-1 brain levels in a transgenic mouse model of multiple system atrophy. We here tested the hypothesis that multiple system atrophy is associated with brain insulin resistance and showed increased expression of the key downstream messenger insulin receptor substrate-1 phosphorylated at serine residue 312 in neurons and oligodendrocytes in the putamen of patients with multiple system atrophy. Furthermore, the expression of insulin receptor substrate 1 (IRS-1) phosphorylated at serine residue 312 was more apparent in inclusion bearing oligodendrocytes in the putamen. By contrast, it was not different between both groups in the temporal cortex, a less vulnerable structure compared to the putamen. These findings suggest that insulin resistance may occur in multiple system atrophy in regions where the neurodegenerative process is most severe and point to a possible relation between α-synuclein aggregates and insulin resistance. We also observed insulin resistance in the striatum of transgenic multiple system atrophy mice and further demonstrate that the glucagon-like peptide-1 analogue exendin-4, a well-tolerated and Federal Drug Agency-approved antidiabetic drug, has positive effects on insulin resistance and monomeric α-synuclein load in the striatum, as well as survival of nigral dopamine neurons. Additionally, plasma levels of exosomal neural-derived IRS-1 phosphorylated at serine residue 307 (corresponding to serine residue 312 in humans) negatively correlated with survival of nigral dopamine neurons in multiple system atrophy mice treated with exendin-4. This finding suggests the potential for developing this peripheral biomarker candidate as an objective outcome measure of target engagement for clinical trials with glucagon-like peptide-1 analogues in multiple system atrophy. In conclusion, our observation of brain insulin resistance in multiple system atrophy patients and transgenic mice together with the beneficial effects of the glucagon-like peptide-1 agonist exendin-4 in transgenic mice paves the way for translating this innovative treatment into a clinical trial.

Induction of miR-96 by Dietary Saturated Fatty Acids Exacerbates Hepatic Insulin Resistance through the Suppression of INSR and IRS-1.

Obesity is defined as the excessive accumulation of body fat that ultimately leads to chronic metabolic diseases. Diets rich in saturated fatty acids (SFA) exacerbate obesity and hepatic steatosis, which increase the risk of hepatic insulin resistance and type 2 diabetes (T2DM). Although microRNAs (miRNAs) play an important role in a range of biological processes, the implications of SFA-induced miRNAs in metabolic dysregulation, particularly in the pathogenesis of hepatic insulin resistance, are not well understood. This study investigated the implications of miR-96, which is induced strongly by SFA, in the development of hepatic insulin resistance. The liver of HFD mice and the palmitate-treated hepatocytes exhibited an impairment of insulin signaling due to the significant decrease in INSR and IRS-1 expression. According to expression profiling and qRT-PCR analysis of the miRNAs, the expression level of miR-96 was higher in hepatocytes treated with palmitate. Moreover, miR-96 was also upregulated in the liver of HFD mice. Interestingly, miR-96 targeted the 3'UTRs of INSR and IRS-1 directly, and repressed the expression of INSR and IRS-1 at the post-transcriptional level. Accordingly, the overexpression of miR-96 was found to cause a significant decrease in INSR and IRS-1 expression, thereby leading to an impairment of insulin signaling and glycogen synthesis in hepatocytes. These results reveal a novel mechanism whereby miR-96 promotes the pathogenesis of hepatic insulin resistance resulted from SFA or obesity.

Effect of Three Statins on Glucose Uptake of Cardiomyocytes and its Mechanism.

BACKGROUND The aim of this study was to investigate the effects of different statins on glucose uptake and to confirm its mechanism in primary cultured rat cardiomyocytes after administration of atorvastatin, pravastatin, and rosuvastatin. MATERIAL AND METHODS Primary cultured rat cardiomyocytes were randomly assigned to 5 groups: normal control group (OB), insulin group (S1), statin 1-µM (S2), 5-µM (S3), and 10-µM (S4) groups for 3 different statins. The 2-[3H]-DG uptake of each group was determined and the mRNA and protein expression levels of glucose transporter type 4 (GLUT4), insulin receptor substrate (IRs), and RhoA were assessed. RESULTS After treatment with different concentrations of statins and insulin, the 2-[3H]-DG uptake showed a significant negative correlation with the concentration of atorvastatin (P<0.05), and no significant correlation with pravastatin and rosuvastatin. The mRNA and protein expression levels of GLUT4 and IRs-1 in primary cultured cardiomyocytes were both significantly reduced by atorvastatin treatment (P<0.05). Pravastatin and rosuvastatin showed no significant effects on GLUT4 and IRs-1 expression. The mRNA and protein expression levels of RhoA both showed no significant difference when treated with the 3 statins. CONCLUSIONS These results confirm that atorvastatin can inhibit insulin-induced glucose uptake in primary cultured rat cardiomyocytes by regulating the PI3K/Akt insulin signal transduction pathway.

[EFFECT OF SHORT-TERM DRY IMMERSION ON PROTEOLYTIC SIGNALING IN HUMAN SOLEUS MUSCLE].

The signaling processes initiating proteolytic events in m. soleus of humans during short-term exposure in the non-weight bearing conditions were analyzed. Dry immersion (DI) was used to induce weight deprivation over 3 days. Western blotting was used to define the IRS-1 content, total and phosphorylated neuronal NO-synthase (nNOS), AMP-activated protein kinase (AMPK) that control the anabolic and catabolic pathways, and concentrations of cytoskeletal protein desmin and Ca²âº-activated protease calpin. Already on day-3 of DI calpain-dependent proteolysis manifests itself by reductions in both the total content and level of nNOS phosphorilation. Moreover, AMPK phosphorilation was decreased drastically.

Insulin Receptor Substrate Adaptor Proteins Mediate Prognostic Gene Expression Profiles in Breast Cancer.

Therapies targeting the type I insulin-like growth factor receptor (IGF-1R) have not been developed with predictive biomarkers to identify tumors with receptor activation. We have previously shown that the insulin receptor substrate (IRS) adaptor proteins are necessary for linking IGF1R to downstream signaling pathways and the malignant phenotype in breast cancer cells. The purpose of this study was to identify gene expression profiles downstream of IGF1R and its two adaptor proteins. IRS-null breast cancer cells (T47D-YA) were engineered to express IRS-1 or IRS-2 alone and their ability to mediate IGF ligand-induced proliferation, motility, and gene expression determined. Global gene expression signatures reflecting IRS adaptor specific and primary vs. secondary ligand response were derived (Early IRS-1, Late IRS-1, Early IRS-2 and Late IRS-2) and functional pathway analysis examined. IRS isoforms mediated distinct gene expression profiles, functional pathways, and breast cancer subtype association. For example, IRS-1/2-induced TGFb2 expression and blockade of TGFb2 abrogated IGF-induced cell migration. In addition, the prognostic value of IRS proteins was significant in the luminal B breast tumor subtype. Univariate and multivariate analyses confirmed that IRS adaptor signatures correlated with poor outcome as measured by recurrence-free and overall survival. Thus, IRS adaptor protein expression is required for IGF ligand responses in breast cancer cells. IRS-specific gene signatures represent accurate surrogates of IGF activity and could predict response to anti-IGF therapy in breast cancer.