Timosaponin B-II Ameliorates Palmitate-Induced Insulin Resistance and Inflammation via IRS-1/PI3K/Akt and IKK/NF-κB Pathways

2016 ◽  
Vol 44 (04) ◽  
pp. 755-769 ◽  
Author(s):  
Yong-Liang Yuan ◽  
Bao-Qin Lin ◽  
Chun-Feng Zhang ◽  
Ling-Ling Cui ◽  
Shi-Xia Ruan ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Hepg2 Cells ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Receptor Substrate 1 ◽  
Akt Activation ◽  
Related Proteins ◽  
Anemarrhena Asphodeloides

This study aimed to investigate the effect of timosaponin B-II (TB-II) on palmitate (PA)-induced insulin resistance and inflammation in HepG2 cells, and probe the potential mechanisms. TB-II, a main ingredient of the traditional Chinese medicine Anemarrhena asphodeloides Bunge, notably ameliorated PA-induced insulin resistance and inflammation, and significantly improved cell viability, decreased PA-induced production of tumor necrosis factor-[Formula: see text] (TNF-[Formula: see text]) and interleukin-6 (IL-6) levels. Further, TB-II treatment notably decreased malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels, and improved superoxide dismutase (SOD) and nitric oxide (NO). TB-II also reduced HepG2 cells apoptosis. Insulin receptor substrate-1 (IRS1)/phosphatidylinositol 3-kinase (PI3K)/Akt and inhibitor of nuclear factor [Formula: see text]-B kinase (IKK)/NF-[Formula: see text]B pathways-related proteins, and IKK[Formula: see text], p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, and Akt activation were determined by Western blot. Compared to model group, TB-II significantly downregulated the expression of p-NF-[Formula: see text]Bp65, p-IKK[Formula: see text], p-IRS-1, p-PI3K and p-Akt. TB-II is a promising potential agent for the management of palmitate-induced insulin resistance and inflammation, which might be via IR/IRS-1/PI3K/Akt and IKK/NF-[Formula: see text]B pathways.

scholarly journals Serine Phosphorylation Proximal to Its Phosphotyrosine Binding Domain Inhibits Insulin Receptor Substrate 1 Function and Promotes Insulin Resistance

2004 ◽  
Vol 24 (21) ◽  
pp. 9668-9681 ◽  
Author(s):  
Yan-Fang Liu ◽  
Avia Herschkovitz ◽  
Sigalit Boura-Halfon ◽  
Denise Ronen ◽  
Keren Paz ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Insulin Signaling ◽  
Insulin Treatment ◽  
Binding Domain ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Control Mechanisms ◽  
Insulin Receptor Substrate 1 ◽  
Phosphotyrosine Binding Domain

ABSTRACT Ser/Thr phosphorylation of insulin receptor substrate (IRS) proteins negatively modulates insulin signaling. Therefore, the identification of serine sites whose phosphorylation inhibit IRS protein functions is of physiological importance. Here we mutated seven Ser sites located proximal to the phosphotyrosine binding domain of insulin receptor substrate 1 (IRS-1) (S265, S302, S325, S336, S358, S407, and S408) into Ala. When overexpressed in rat hepatoma Fao or CHO cells, the mutated IRS-1 protein in which the seven Ser sites were mutated to Ala (IRS-17A), unlike wild-type IRS-1 (IRS-1WT), maintained its Tyr-phosphorylated active conformation after prolonged insulin treatment or when the cells were challenged with inducers of insulin resistance prior to acute insulin treatment. This was due to the ability of IRS-17A to remain complexed with the insulin receptor (IR), unlike IRS-1WT, which underwent Ser phosphorylation, resulting in its dissociation from IR. Studies of truncated forms of IRS-1 revealed that the region between amino acids 365 to 430 is a main insulin-stimulated Ser phosphorylation domain. Indeed, IRS-1 mutated only at S408, which undergoes phosphorylation in vivo, partially maintained the properties of IRS-17A and conferred protection against selected inducers of insulin resistance. These findings suggest that S408 and additional Ser sites among the seven mutated Ser sites are targets for IRS-1 kinases that play a key negative regulatory role in IRS-1 function and insulin action. These sites presumably serve as points of convergence, where physiological feedback control mechanisms, which are triggered by insulin-stimulated IRS kinases, overlap with IRS kinases triggered by inducers of insulin resistance to terminate insulin signaling.

scholarly journals Phosphatidylinositol 3′-kinase associates with an insulin receptor substrate-1 serine kinase distinct from its intrinsic serine kinase

1998 ◽  
Vol 335 (2) ◽  
pp. 397-404 ◽  
Author(s):  
Keith A. CENGEL ◽  
Rosanne E. KASON ◽  
Gregory G. FREUND
Keyword(s):  
Insulin Receptor ◽  
Immune Complexes ◽  
Kinase Activity ◽  
Sh2 Domain ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Serine Kinase ◽  
Insulin Receptor Substrate 1 ◽  
Pas Kinase

Serine phosphorylation of insulin receptor substrate-1 (IRS-1) has been proposed as a counter-regulatory mechanism in insulin and cytokine signalling. Here we report that IRS-1 is phosphorylated by a wortmannin insensitive phosphatidylinositol 3´-kinase (PI 3-kinase)-associated serine kinase (PAS kinase) distinct from PI 3-kinase serine kinase. We found that PI 3-kinase immune complexes contain 5-fold more wortmannin-insensitive serine kinase activity than SH2-containing protein tyrosine phosphatase-2 (SHP2) and IRS-1 immune complexes. Affinity chromatography of cell lysates with a glutathione S-transferase fusion protein for the p85 subunit of PI 3-kinase showed that PAS kinase associated with the p85 subunit of PI 3-kinase. This interaction required unoccupied SH2 domain(s) but did not require the PI 3-kinase p110 subunit binding domain. In terms of function, PAS kinase phosphorylated IRS-1 and, after insulin stimulation, PAS kinase phosphorylated IRS-1 in PI 3-kinase–IRS-1 complexes. Phosphopeptide mapping showed that insulin-dependent in vivo sites of IRS-1 serine phosphorylation were comparable to those of PAS kinase phosphorylated IRS-1. More importantly, PAS kinase-dependent phosphorylation of IRS-1 reduced by 4-fold the ability of IRS-1 to act as an insulin receptor substrate. Taken together, these findings indicate that: (a) PAS kinase is distinct from the intrinsic serine kinase activity of PI 3-kinase, (b) PAS kinase associates with the p85 subunit of PI 3-kinase through SH2 domain interactions, and (c) PAS kinase is an IRS-1 serine kinase that can reduce the ability of IRS-1 to serve as an insulin receptor substrate.

scholarly journals Serine Phosphorylation of Insulin Receptor Substrate-1: A Novel Target for the Reversal of Insulin Resistance

2001 ◽  
Vol 15 (11) ◽  
pp. 1864-1869 ◽  
Author(s):  
Gerasimos P. Sykiotis ◽  
Athanasios G. Papavassiliou
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Sedentary Lifestyle ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Selective Targeting ◽  
Individualized Approach ◽  
Serine Kinases ◽  
Novel Target

Abstract Insulin resistance, the failure to respond to normal circulating concentrations of insulin, is a common state associated with obesity, aging, and a sedentary lifestyle. Compelling evidence implicates TNFα as the cause and link between obesity and insulin resistance. Serine phosphorylation of insulin receptor substrate-1 seems prominent among the mechanisms of TNFα-induced insulin resistance. Recent advances indicate that serine kinases may phosphorylate and thus inhibit the tyrosine phosphorylation of insulin receptor substrate-1, revealing an integration point of TNFα and insulin signaling pathways. Selective targeting of the molecular scenery whereby this key phosphorylation occurs/operates represents a rich area for the development of rationally designed new antidiabetic drugs. In relation to efficacy and side effects, this prospect should permit a more precise and perhaps individualized approach to therapeutic intervention, allowing clinicians to focus the attack where the problem lies.

Palmitic Acid Regulates miRNA-3148 via Insulin Receptor Substrate-1 and is Involved in Insulin Resistance

2021 ◽  
Vol 11 (4) ◽  
pp. 767-771
Author(s):  
Xiaoxi Xiang ◽  
Changwei Zhang ◽  
Daying Long
Keyword(s):  
Insulin Resistance ◽  
Palmitic Acid ◽  
Insulin Receptor ◽  
Hepg2 Cells ◽  
Luciferase Reporter ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Over Expression ◽  
Reporter Assays ◽  
The Impact

Previous studies reported that saturated fatty acid palmitic acid (PA) is closely related to insulin resistance. miR-3148 regulates insulin receptor substrate-1 (IRS1) predicted by MiRDB analysis. However, whether PA regulates IRS1 via miR-3148 remains to be elucidated. Therefore, in this work, we assessed whether PA regulates miRNA-3148 via IRS1 in insulin resistance. We cultured HepG2 cells in vitro and classified them into control group (NC group), miR-3148 Mimics group, and miR-3148 Mimics+ pFBD-IRS1 group. We used qRT-PCR to detect miR-3148 and IRS1 mRNA; used Dual-Luciferase Reporter Assays to detect miR-3148 with 3′-UTR region of IRS1 mRNA; and utilized Western blot (WB) to detect IRS1, p-AKT, AKT and Tubulin. Our results showed that PA could increase miR-3148 and decrease IRS1 which is a target protein of miR-3148, as shown by Dual-Luciferase Reporter assays. miR-3148 significantly inhibited the impact of insulin on p-AKT level (P < 0.01) and over-expression of IRS1 by pFBD-IRS1 can partially alleviate the inhibitory effect of miR-3148 mimics on p-AKT. In HepG2 cells, PA regulates miR-3148. Via targeting IRS1 mRNA, miR-3148 impairs insulin signaling pathway, leading to insulin resistance. Over-expression of IRS1 by pFBD-IRS1 alleviates miR-3148-induced insulin resistance.

scholarly journals Insulin Resistance in Human Preeclamptic Placenta Is Mediated by Serine Phosphorylation of Insulin Receptor Substrate-1 and -2

2006 ◽  
Vol 91 (2) ◽  
pp. 709-717 ◽  
Author(s):  
Marco Scioscia ◽  
Khalid Gumaa ◽  
Sirilaksana Kunjara ◽  
Malcolm A. Paine ◽  
Luigi E. Selvaggi ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Insulin Signaling ◽  
Serine Phosphorylation ◽  
Regulatory Subunit ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Cross Sectional ◽  
Maternal Risk ◽  
Therapeutic Implications

Context: Preeclampsia is a severe complication of human pregnancy often associated with maternal risk factors. Insulin resistance represents a major risk for developing preeclampsia during pregnancy. Objective: A putative second messenger of insulin, inositol phosphoglycan P type (P-IPG), was previously shown to be highly increased during active preeclampsia. Its association with insulin resistance was investigated. Design and Setting: A cross-sectional study was carried out in a referral center. Patients: Nine preeclamptic (PE) and 18 healthy women were recruited and matched for maternal age, body mass index, parity, and ethnicity in a 1:2 ratio. Placental specimens were collected immediately after delivery. Intervention: Placental tissue was incubated with insulin and P-IPG production assessed. Insulin signaling proteins were subsequently studied by immunoblotting. Results: P-IPG extracted from human term placentas upon incubation with insulin was found to be far lower in those with preeclampsia than controls (P &lt; 0.001). Immunoblotting studies revealed serine phosphorylation of insulin receptor substrate-1 and -2 in PE placentas (P &lt; 0.001) with downstream impairment of insulin signaling. The activation of the p85 regulatory subunit of phosphatidylinositol 3- kinase was markedly decreased in PE samples (P &lt; 0.001). Conclusions: These findings highlight the importance of P-IPG in active preeclampsia and demonstrate a substantially different response to the insulin stimulus of human PE placentas. Acquired alterations in activation of proteins involved in insulin signaling may play a role in the complex pathogenesis of preeclampsia, probably as a consequence of the immunological dysfunction that occurs in this syndrome. These results seem to confirm an insulin-resistant state in PE placenta and shed a different light on its role in the pathogenesis of this disease with potential therapeutic implications.

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