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Results for “INSULIN”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Fumosorinone, a novel PTP1B inhibitor, activates insulin signaling in insulin-resistance HepG2 cells and shows anti-diabetic effect in diabetic KKAy mice

Insulin resistance is a characteristic feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of the insulin signaling pathways, and its increased activity and expression are implicated in the pathogenesis of insulin resistance. Therefore, the inhibition of PTP1B is anticipated to become a potential therapeutic strategy to treat T2DM. Fumosorinone (FU), a new natural product isolated from insect fungi Isaria fumosorosea, was found to inhibit PTP1B activity in our previous study. Herein, the effects of FU on insulin resistance and mechanism in vitro and in vivo were investigated. FU increased the insulin-provoked glucose uptake in insulin-resistant HepG2 cells, and also reduced blood glucose and lipid levels of type 2 diabetic KKAy mice. FU decreased the expression of PTP1B both in insulin-resistant HepG2 cells and in liver tissues of diabetic KKAy mice. Furthermore, FU increased the phosphorylation of IRβ, IRS-2, Akt, GSK3β and Erk1/2 in insulin-resistant HepG2 cells, as well as the phosphorylation of IRβ, IRS-2, Akt in liver tissues of diabetic KKAy mice. These results showed that FU increased glucose uptake and improved insulin resistance by down-regulating the expression of PTP1B and activating the insulin signaling pathway, suggesting that it may possess antidiabetic properties. - Highlights: • Fumosorinone is a new PTP1B inhibitor isolated from insect pathogenic fungi. • Fumosorinone attenuated the insulin resistance both in vitro and in vivo. • Fumosorinone decreased the expression of PTP1B both in vitro and in vivo. • Fumosorinone activated the insulin signaling pathway both in vitro and in vivo.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Dual Exosite-binding Inhibitors of Insulin-degrading Enzyme Challenge Its Role as the Primary Mediator of Insulin Clearance in Vivo

Insulin-degrading enzyme (IDE, insulysin) is the best characterized catabolic enzyme implicated in proteolysis of insulin. Recently, a peptide inhibitor of IDE has been shown to affect levels of insulin, amylin, and glucagon in vivo. However, IDE –/– mice display variable phenotypes relating to fasting plasma insulin levels, glucose tolerance, and insulin sensitivity depending on the cohort and age of animals. As such, here, we interrogated the importance of IDE-mediated catabolism on insulin clearance in vivo. Using a structure-based design, we linked two newly identified ligands binding at unique IDE exosites together to construct a potent series of novel inhibitors. These compounds do not interact with the catalytic zinc of the protease. Because one of these inhibitors (NTE-1) was determined to have pharmacokinetic properties sufficient to sustain plasma levels >50 times its IDE IC 50 value, studies in rodents were conducted. In oral glucose tolerance tests with diet-induced obese mice, NTE-1 treatment improved the glucose excursion. Yet in insulin tolerance tests and euglycemic clamp experiments, NTE-1 did not enhance insulin action or increase plasma insulin levels. Importantly, IDE inhibition with NTE-1 did result in elevated plasma amylin levels, suggesting the in vivo role of IDE action on amylin may be more significant than an effect on insulin. Furthermore, using the inhibitors described in this report, we demonstrate that in HEK cells IDE has little impact on insulin clearance. In total, evidence from our studies supports a minimal role for IDE in insulin metabolism in vivo and suggests IDE may be more important in helping regulate amylin clearance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Saturated fatty acids-induced miR-424–5p aggravates insulin resistance via targeting insulin receptor in hepatocytes

Highlights: • miR-424–5p expression is upregulated by SFA or HFD-induced obesity in hepatocytes. • Mechanistically, miR-424–5p targets 3′UTR of INSR directly, thereby downregulating INSR at the post-transcriptional step. • The ectopic expression of miR-424–5p impairs insulin signaling and insulin-induced glycogen synthesis in hepatocytes. • This study highlights the potential role of miR-424–5p in the insulin signaling pathway through the repression of INSR. The excessive intake of saturated fatty acids (SFA) causes obesity and liver steatosis, which are major risk factors for insulin resistance and type 2 diabetes. Although the expression of certain microRNAs (miRNAs) targeting the insulin signaling molecules are regulated aberrantly in SFA-induced obesity, their implications on hepatic insulin resistance are largely unknown. This study examined the associations of miR-424–5p, which is induced by SFA, with the development of insulin resistance. SFA palmitate (PA)-treated HepG2 cells and high fat diet (HFD)-induced obese mouse livers showed an impairment of insulin signaling due to a significant decrease in INSR and IRS-1 expression. Based on expression profiling and qRT-PCR analysis, miR-424–5p, which presumably targets the 3′UTR of INSR, was upregulated in both PA-treated HepG2 cells and the liver of HFD-fed mice. miR-424–5p was found to target the 3′UTR of INSR directly and downregulated INSR expression at the post-transcriptional step. Furthermore, the overexpression of miR-424–5p suppressed INSR expression significantly, leading to impaired insulin signaling and glycogen synthesis in hepatocytes. A novel mechanism for how SFA-induced miR-424–5p impairs insulin signaling through the targeting of INSR is reported. In addition, the crucial role and underlying mechanism of miR-424–5p in the obesity-induced hepatic insulin resistance is explained.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocation of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

MicroRNA-99a inhibits insulin-induced proliferation, migration, dedifferentiation, and rapamycin resistance of vascular smooth muscle cells by inhibiting insulin-like growth factor-1 receptor and mammalian target of rapamycin

Patients with type 2 diabetes mellitus (T2DM) are characterized by insulin resistance and are subsequently at high risk for atherosclerosis. Hyperinsulinemia has been associated with proliferation, migration, and dedifferentiation of vascular smooth muscle cells (VSMCs) during the pathogenesis of atherosclerosis. Moreover, insulin-like growth factor-1 receptor (IGF-1R) and mammalian target of rapamycin (mTOR) have been demonstrated to be the underlying signaling pathways. Recently, microRNA-99a (miR-99a) has been suggested to regulate the phenotypic changes of VSMCs in cancer cells. However, whether it is involved in insulin-induced changes of VSCMs has not been determined. In this study, we found that insulin induced proliferation, migration, and dedifferentiation of mouse VSMCs in a dose-dependent manner. Furthermore, the stimulating effects of high-dose insulin on proliferation, migration, and dedifferentiation of mouse VSMCs were found to be associated with the attenuation of the inhibitory effects of miR-99a on IGF-1R and mTOR signaling activities. Finally, we found that the inducing effect of high-dose insulin on proliferation, migration, and dedifferentiation of VSMCs was partially inhibited by an active mimic of miR-99a. Taken together, these results suggest that miR-99a plays a key regulatory role in the pathogenesis of insulin-induced proliferation, migration, and phenotype conversion of VSMCs at least partly via inhibition of IGF-1R and mTOR signaling. Our results provide evidence that miR-99a may be a novel target for the treatment of hyperinsulinemia-induced atherosclerosis. - Highlights: • Suggesting a new mechanism of insulin-triggered VSMC functions. • Providing a new therapeutic strategies that target atherosclerosis in T2DM patients. • Providing a new strategies that target in-stent restenosis in T2DM patients.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Oleanolic acid supplement attenuates liquid fructose-induced adipose tissue insulin resistance through the insulin receptor substrate-1/phosphatidylinositol 3-kinase/Akt signaling pathway in rats

Oleanolic acid, a triterpenoid contained in more than 1620 plants including various fruits and foodstuffs, has numerous metabolic effects, such as hepatoprotection. However, its underlying mechanisms remain poorly understood. Adipose tissue insulin resistance (Adipo-IR) may contribute to the development and progress of metabolic abnormalities through release of excessive free fatty acids from adipose tissue. This study investigated the effect of oleanolic acid on Adipo-IR. The results showed that supplement with oleanolic acid (25 mg/kg, once daily, by oral gavage) over 10 weeks attenuated liquid fructose-induced increase in plasma insulin concentration and the homeostasis model assessment of insulin resistance (HOMA-IR) index in rats. Simultaneously, oleanolic acid reversed the increase in the Adipo-IR index and plasma non-esterified fatty acid concentrations during the oral glucose tolerance test assessment. In white adipose tissue, oleanolic acid enhanced mRNA expression of the genes encoding insulin receptor, insulin receptor substrate (IRS)-1 and phosphatidylinositol 3-kinase. At the protein level, oleanolic acid upregulated total IRS-1 expression, suppressed the increased phosphorylated IRS-1 at serine-307, and restored the increased phosphorylated IRS-1 to total IRS-1 ratio. In contrast, phosphorylated Akt to total Akt ratio was increased. Furthermore, oleanolic acid reversed fructose-induced decrease in phosphorylated-Akt/Akt protein to plasma insulin concentration ratio. However, oleanolic acid did not affect IRS-2 mRNA expression. Therefore, these results suggest that oleanolic acid supplement ameliorates fructose-induced Adipo-IR in rats via the IRS-1/phosphatidylinositol 3-kinase/Akt pathway. Our findings may provide new insights into the mechanisms of metabolic actions of oleanolic acid. - Highlights: • Adipose insulin resistance (Adipo-IR) contributes to metabolic abnormalities. • We investigated the effect of oleanolic acid (OA) on adipo-IR in fructose-fed rats. • OA attenuated fructose-induced increase in Adipo-IR index and NEFA concentrations. • OA modulated adipose IRS-1/phosphatidylinositol 3-kinase/Akt signaling. • OA ameliorates Adipo-IR via the IRS-1/PI3K/Akt signaling pathway in rats.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Transcriptome and secretome profiling of sensory neurons reveals sex differences in pathways relevant to insulin sensing and insulin secretion

Sensory neurons in the dorsal root ganglia (DRG) convey somatosensory and metabolic cues to the central nervous system and release substances from stimulated terminal endings in peripheral organs. Sex-biased variations driven by the sex chromosome complement (XX and XY) have been implicated in the sensory–islet crosstalk. However, the molecular underpinnings of these male–female differences are not known. Here, we aim to characterize the molecular repertoire and the secretome profile of the lower thoracic spinal sensory neurons and to identify molecules with sex-biased insulin sensing- and/or insulin secretion-modulating activity that are encoded independently of circulating gonadal sex hormones. We used transcriptomics and proteomics to uncover differentially expressed genes and secreted molecules in lower thoracic T5-12 DRG sensory neurons derived from sexually immature 3-week-old male and female C57BL/6J mice. Comparative transcriptome and proteome analyses revealed differential gene expression and protein secretion in DRG neurons in males and females. Furthermore, the transcriptome analysis identified, among others, higher insulin signaling/sensing capabilities in female DRG neurons; secretome screening uncovered several sex-specific candidate molecules with potential regulatory functions in pancreatic β cells. Together, these data suggest a putative role of sensory interoception of insulin in the DRG–islet crosstalk with implications in sensory feedback loops in the regulation of β-cell activity in a sex-biased manner. Finally, we provide a valuable resource of molecular and secretory targets that can be leveraged for understanding insulin interoception and insulin secretion and inform the development of novel studies/approaches to fathom the role of the sensory–islet axis in the regulation of energy balance in males and females.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Scope and Limitations of Fmoc Chemistry SPPS-Based Approaches to the Total Synthesis of Insulin Lispro via Ester Insulin

We have systematically explored three approaches based on 9-fluorenylmethoxycarbonyl (Fmoc) chemistry solid phase peptide synthesis (SPPS) for the total chemical synthesis of the key depsipeptide intermediate for the efficient total chemical synthesis of insulin. The approaches used were: stepwise Fmoc chemistry SPPS; the “hybrid method”, in which maximally protected peptide segments made by Fmoc chemistry SPPS are condensed in solution; and, native chemical ligation using peptide-thioester segments generated by Fmoc chemistry SPPS. A key building block in all three approaches was a Glu[O-β-(Thr)] ester-linked dipeptide equipped with a set of orthogonal protecting groups compatible with Fmoc chemistry SPPS. We report the most effective method for the preparation of the 51 residue ester-linked polypeptide chain of ester insulin was the use of unprotected peptide-thioester segments, prepared from peptide-hydrazides synthesized by Fmoc chemistry SPPS, and condensed by native chemical ligation. High-resolution X-ray crystallography confirmed the disulfide pairings and three-dimensional structure of synthetic insulin lispro prepared from ester insulin lispro by this route. Further optimization of these pilot studies could yield an efficient total chemical synthesis of insulin lispro (Humalog) based on peptide synthesis by Fmoc chemistry SPPS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Reduced peripheral activity leading to hepato‐preferential action of basal insulin peglispro compared with insulin glargine in patients with type 1 diabetes

Aims Basal insulin peglispro ( BIL ), a novel PEGylated basal insulin with a large hydrodynamic size, has a delayed absorption and reduced clearance that prolongs the duration of action. The current study compared the effects of BIL and insulin glargine ( GL ) on endogenous glucose production ( EGP ), glucose disposal rate ( GDR ) and lipolysis in patients with type 1 diabetes. Materials and Methods This was a randomized, open‐label, four‐period, crossover study. Patients received intravenous infusions of BIL and GL , each at two dose levels selected for partial and maximal suppression of EGP , during an 8 to 10 h euglycemic clamp procedure with d ‐[3‐ 3 H] glucose. Results Following correction for equivalent human insulin concentrations ( EHIC ), low‐dose GL infusion resulted in similar EGP at the end of the clamp compared to low‐dose BIL infusion ( GL / BIL ratio of 1.03) but a higher GDR ( GL / BIL ratio of 2.42), indicating similar hepatic activity but attenuated peripheral activity of BIL . Consistent with this, the EHIC ‐corrected GDR / EGP at the end of the clamp was 1.72‐fold greater for GL than BIL following low‐dose administration. At the lower dose of BIL and GL (concentrations in the therapeutic range), BIL produced less suppression of lipolysis compared with GL as indicated by free fatty acid and glycerol levels at the end of the clamp. Conclusions Compared with GL , BIL restored the hepato‐peripheral insulin action gradient seen in normal physiology via its peripherally restricted action on target tissues related to carbohydrate and lipid metabolism.

Mudaliar, S.↗
DOE OSTI2018

Ensemble cryoEM elucidates the mechanism of insulin capture and degradation by human insulin degrading enzyme

Insulin degrading enzyme (IDE) plays key roles in degrading peptides vital in type two diabetes, Alzheimer's, inflammation, and other human diseases. However, the process through which IDE recognizes peptides that tend to form amyloid fibrils remained unsolved. We used cryoEM to understand both the apo- and insulin-bound dimeric IDE states, revealing that IDE displays a large opening between the homologous ~55 kDa N- and C-terminal halves to allow selective substrate capture based on size and charge complementarity. We also used cryoEM, X-ray crystallography, SAXS, and HDX-MS to elucidate the molecular basis of how amyloidogenic peptides stabilize the disordered IDE catalytic cleft, thereby inducing selective degradation by substrate-assisted catalysis. Furthermore, our insulin-bound IDE structures explain how IDE processively degrades insulin by stochastically cutting either chain without breaking disulfide bonds. Together, our studies provide a mechanism for how IDE selectively degrades amyloidogenic peptides and offers structural insights for developing IDE-based therapies.

Zhang, Zhening↗
DOE OSTI2018

FoxO1 inhibition promotes differentiation of human embryonic stem cells into insulin producing cells

Highlights: • The level of p-FoxO1 protein increases during differentiation of hESCs into IPCs. • FoxO1 knockdown promotes IPC differentiation of hESCs. • FoxO1 overexpression inhibits IPC differentiation of hESCs. • Inhibition of FoxO1 by AS promotes the differentiation of hESCs into IPCs. • AS may promote IPC maturation via modulating subcellular location of FoxO1 and Pdx1. Insulin-producing cells (IPCs) derived from human embryonic stem cells (hESCs) hold great potential for cell transplantation therapy in diabetes. Tremendous progress has been made in inducing differentiation of hESCs into IPCs in vitro, of which definitive endoderm (DE) protocol mimicking foetal pancreatic development has been widely used. However, immaturity of the obtained IPCs limits their further applications in treating diabetes. Forkhead box O1 (FoxO1) is involved in the differentiation and functional maintenance of murine pancreatic β cells, but its role in human β cell differentiation is under elucidation. Here, we showed that although FoxO1 expression level remained consistent, cytoplasmic phosphorylated FoxO1 protein level increased during IPC differentiation of hESCs induced by DE protocol. Lentiviral silencing of FoxO1 in pancreatic progenitors upregulated the levels of pancreatic islet differentiation-related genes and improved glucose-stimulated insulin secretion response in their progeny IPCs, whereas overexpression of FoxO1 showed the opposite effects. Notably, treatment with the FoxO1 inhibitor AS1842856 displayed similar effects with FoxO1 knockdown in pancreatic progenitors. These effects were closely associated with the mutually exclusive nucleocytoplasmic shuttling of FoxO1 and Pdx1 in the AS1842856-treated pancreatic progenitors. Our data demonstrated a promising effect of FoxO1 inhibition by the small molecule on gene expression profile during the differentiation, and in turn, on determining IPC maturation via modulating subcellular location of FoxO1 and Pdx1. Therefore, we identify a novel role of FoxO1 inhibition in promoting IPC differentiation of hESCs, which may provide clues for induction of mature β cells from hESCs and clinical applications in regenerative medicine.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Endothelin-1 exacerbates development of hypertension and atherosclerosis in modest insulin resistant syndrome

Endothelin-1 (ET-1) is known as potent vasoconstrictor, by virtue of its mitogenic effects, and may deteriorate the process of hypertension and atherosclerosis by aggravating hyperplasia and migration in VSMCs. Our previous study demonstrated that insulin infusion caused sequential induction of hyperinsulinemia, hyperendothelinemia, insulin resistance, and then hypertension in rats. However, the underlying mechanism of ET-1 interfere insulin signaling in VSMCs remains unclear. To characterize insulin signaling during modest insulin resistant syndrome, we established and monitored rats by feeding high fructose-diet (HFD) until high blood pressure and modest insulin resistance occurred. To explore the role of ET-1/ET{sub A}R during insulin resistance, ET{sub A}R expression, ET-1 binding, and insulin signaling were investigated in the HFD-fed rats and cultured A-10 VSMCs. Results showed that high blood pressure, tunica medial wall thickening, plasma ET-1 and insulin, and accompanied with modest insulin resistance without overweight and hyperglycemia occurred in early-stage HFD-fed rats. In the endothelium-denuded aorta from HFD-fed rats, ET{sub A}R expression, but not ET{sub B}R, and ET-1 binding in aorta were increased. Moreover, decreasing of insulin-induced Akt phosphorylation and increasing of insulin-induced ERK phosphorylation were observed in aorta during modest insulin resistance. Interestingly, in ET-1 pretreated VSMCs, the increment of insulin-induced Akt phosphorylation was decreased whereas the increment of insulin-induced ERK phosphorylation was increased. In addition, insulin potentiated ET-1-induced VSMCs migration and proliferation due to increasing ET-1 binding. ETAR antagonist reversed effects of ET-1 on insulin-induced signaling and VSMCs migration and proliferation. In summary, modest insulin resistance syndrome accompanied with hyperinsulinemia leading to the potentiation on ET-1-induced actions in aortic VSMCs. ET-1 via ET{sub A}R pathway suppressed insulin-induced AKT activation, whereas remained insulin-induced ERK activation. ET-1 and insulin synergistically potentiated migration and proliferation mainly through ET{sub A}R/ERK dependent pathway, which is dominant in VSMCs during modest insulin resistance syndrome. Therefore, ET-1 and ET{sub A}R are potential targets responsible for the observed synergism effect in the hypertensive atherosclerotic process through enhancement of ET-1 binding, ET-1 binding, ET{sub A}R expression, and ET-1-induced mitogenic actions in aortic VSMCs. - Highlights: • ET-1/ET{sub A}R signaling and insulin-induced pERK were high in modest insulin resistance. • ET-1 via ET{sub A}R suppressed insulin-induced pAKT but remained intact pERK in VSMCs. • Insulin potentiated ET-1-induced VSMC mitogenic action was ET{sub A}R/ERK dependent.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Leptin-induced basal Akt phosphorylation and its implication in exercise-mediated improvement of insulin sensitivity

Highlights: • Acute exercise stimulates leptin release while chronic exercise decreased basal serum leptin. • Leptin increased basal levels of insulin signaling and glucose uptake. • Leptin decreased insulin-stimulated insulin signaling and glucose uptake. • Blocking JAK2 signaling decreased leptin-stimulated insulin signaling. • Blocking JAK2 signaling restored leptin-attenuated insulin sensitivity. Physical exercise is an efficient therapeutical tool in the management of insulin resistance (IR) and related metabolic diseases. Leptin, the well-known obesity hormone and the absence of which leads to IR, showed controversial effects on IR as research continues. Thus, in this study, a detailed investigation of the effect of leptin on exercise-mediated improvement of insulin sensitivity and its underlying mechanism was carried out. Using a rat model of chronic or acute swimming exercise training, we found that serum leptin increased 1 h after either acute exercise or the last session of chronic exercise, when impaired insulin action was observed in previous reports. However, chronic exercise reducd basal serum leptin levels and promoted insulin sensitivity compared with sedentary controls or rats subjected to one bout of aerobic exercise. Our animal results indicated the potential linkage between leptin and insulin sensitivity, which is further investigated in the skeletal muscle L6 cells. Leptin treatment in L6 cells promoted the basal levels of insulin signaling as well as glucose uptake, while blocking JAK2 signaling with either pharmacological intervention (JAK2 inhibitor AG490) or genetic manipulation (siRNA knockdown) decreased the basal levels of insulin signaling. Furthermore, leptin treatment inhibited insulin-stimulated insulin signaling and glucose uptake, while blocking JAK2 signaling restored leptin-attenuated insulin sensitivity. Taken together, our results demonstrated that reduced serum leptin, at least in part, contributes to exercise-mediated improvement of insulin sensitivity, indicating JAK2 as a potent therapeutical target of insulin resistance.

60 APPLIED LIFE SCIENCES↗