Leucine and isoleucine were shown to stimulate insulin-independent glucose uptake in skeletal muscle cells in vitro. In this study, we examined the effects of leucine and isoleucine on blood glucose in food-deprived rats and on glucose metabolism in skeletal muscle in vivo. Furthermore, we investigated the possible involvement of the energy sensor, 5'-AMP-activated protein kinase (AMPK), in the modulation of glucose uptake in skeletal muscle, which is independent of insulin, and also in leucine- or isoleucine-stimulated glucose uptake. Oral administration of isoleucine, but not leucine, significantly decreased the plasma glucose concentration. An i.v. bolus of 2-[1,2-3H]-deoxyglucose (2-[3H]DG) was administered to calculate glucose uptake. Glucose uptake in the skeletal muscle did not differ after leucine administration, but glucose uptake in the muscles of rats administered isoleucine was 73% greater than in controls, suggesting that isoleucine increases skeletal muscle glucose uptake in vivo. On the contrary, in the skeletal muscles, administration of leucine but not isoleucine significantly increased [U-14C]-glucose incorporation into glycogen compared with controls. AMPK alpha1 activity in skeletal muscle was not affected by leucine or isoleucine administration. However, isoleucine, but not leucine, significantly decreased AMPK alpha2 activity. The decrease in AMPK alpha2 activity was thought to be due to decreases in AMP content and the AMP:ATP ratio, which were related to the isoleucine administration. This is the first report of isoleucine stimulating glucose uptake in rat skeletal muscle in vivo, and these results indicate that there might be a relation between the reduction in blood glucose and the increase in skeletal muscle glucose uptake that occur with isoleucine administration in rats. The alterations in glucose metabolism caused by isoleucine may result in an improvement of the availability of ATP in the absence of increases in AMP-activated protein kinase activity in skeletal muscle.
Hypoglycemic effect of isoleucine involves increased muscle glucose uptake and whole body glucose oxidation and decreased hepatic gluconeogenesis. Am J Physiol Endocrinol Metab 292: E1683-E1693, 2007. First published February 13, 2007; doi:10.1152/ajpendo.00609.2006.-Isoleucine, a branched chain amino acid, plays an important role in the improvement of glucose metabolism as evidenced by the increase of insulin-independent glucose uptake in vitro. This study evaluated the effect of isoleucine on glucose uptake and oxidation in fasted rats and on gluconeogenesis in vivo and in vitro. Oral administration of isoleucine decreased the plasma glucose level by 20% and significantly increased muscle glucose uptake by 71% without significant elevation of the plasma insulin level compared with controls at 60 min after administration. Furthermore, expiratory excretion of 14 CO2 from [U-14 C]glucose in isoleucine-administered rats was increased by 19% compared with controls. Meanwhile, isoleucine decreased AMP levels in the liver but did not affect hepatic glycogen synthesis. Under insulin-free conditions, isoleucine significantly inhibited glucose production when alanine was used as a glucogenic substrate in isolated hepatocytes. This inhibition by isoleucine was also associated with a decline in mRNA levels for phosphoenolpyruvate carboxykinase and glucose-6-phosphatase (G6Pase) and a decreased activity of G6Pase in isolated hepatocytes. These findings suggest that a reduction of gluconeogenesis in liver, along with an increase of glucose uptake in the muscle, is also involved in the hypoglycemic effect of isoleucine. In conclusion, isoleucine administration stimulates both glucose uptake in the muscle and whole body glucose oxidation, in addition to depressing gluconeogenesis in the liver, thereby leading to the hypoglycemic effect in rats.insulin; amino acid; leucine; hepatocyte; glucose production PREVIOUS STUDIES HAVE SHOWN that amino acids decrease insulinstimulated glucose uptake and glucose utilization (7,11,33,34). As an alternative to glucose oxidation, amino acids, including the glucogenic amino acids (alanine, valine, or glutamine), may serve as fuel, and therefore, amino acids are considered to be able to increase glucose production and blood glucose levels. Also, amino acids (especially leucine) stimulate protein synthesis via the mammalian target of rapamycin (mTOR) (1, 37), whereas amino acids can also induce degradation of the insulin receptor substrate-1 (IRS-1) by stimulating mTOR and S6 kinase-1 (S6K1), leading to desensitization of insulin signaling (20,30,34). In addition, leucine reduces the duration of insulin-induced IRS-1-associated phosphatidylinositol 3-kinase (PI3 kinase) in skeletal muscle (3). Given these results, it is to be expected that amino acids will decrease glucose oxidation and cause an amino acidinduced insulin resistance.However, it has been reported that amino acid infusion causes a decrease in blood glucose levels and increases glucose oxidation in humans (31, 32), although there ...
Introduction: The BET bromodomain proteins, including BRD2, BRD3, and BRD4, have emerged as major epigenetic regulators of proliferation and differentiation and also have been associated with predisposition to dyslipidemia or improper regulation of adipogenesis, elevated inflammatory profile, and increased susceptibility to autoimmune disease. OTX015, a novel thienotriazolodiazepine compound, was identified in a cell-based screen for inhibitors of cell adhesion. Subsequently, it was evaluated for inhibition of the binding between acetylated histone and BRD2, BRD3, and BRD4 and antiproliferative effects in both in vitro and in vivo tumor models. Material and Methods: To assess binding of OTX015 to BRD2, BRD3, and BRD4, BRD-expressing CHO cell lysate (from CHO cells transfected with expression plasmids for Flag-tagged BRD2, BRD3, or BRD4 or vector alone), europium-conjugated anti-Flag antibody, XL-665-conjugated streptavidin, and biotinylated OTX015 were incubated at room temperature for 0.2 to 2h. Fluorescence was measured by TR-FRET using an EnVision 2103 Multilabel Reader and EC50 for binding was calculated by nonlinear regression using PRISM version 5.02. Using a similar system, the effect of OTX015 on binding of BRD2, BRD3, and BRD4 to acetylated histone H4 (AcH4) was evaluated by incubating biotin-conjugated -AcH4, BRD-expressing CHO cell lysate, europium-conjugated anti-Flag antibody, and XL-665-conjugated streptavidin. Fluorescence was measured by TR-FRET using an EnVision 2103 Multilabel Reader and percent binding was calculated by defining the value of the sample without biotin conjugate dAcH4 as 0% and the sample without OTX015 as 100%. The IC50 value was calculated by nonlinear regression using PRISM version 5.02. Effects of OTX015 on cancer cell proliferation were evaluated by incubating human tumor cells for 72 h with increasing concentrations of OTX015 and assessing proliferation using a tetrazolium salt (WST-8)-based colorimetric assay. To assess antiproliferative effects in vivo, BLAB/c-nu/nu mice bearing established Ty82 BRD-NUT midline carcinoma xenografts were given OTX015 (0, 10, 30 or 100 mg/kg qd or 10 mg/kg bid) by oral gavage over 14 days. Animals were sacrificed on day 15 and tumors were extracted and weighed. Results: OTX015 was a potent inhibitor of BRD2, BRD3, and BRD4, with EC50 values from 10 to 19 nM. Binding of OTX015 to BRD2, BRD3, and BRD4 was inhibited by addition of OTX015 in a concentration-dependent manner, suggesting competitive inhibition. OTX015 inhibited the binding of BRD2, BRD3, and BRD4 to AcH4, with IC50 values from 92 to 112 nM. OTX015 inhibited the growth of a variety of human cancer cell lines; for most hematologic malignancies tested, GI50 values ranged from 60 to 200 nM. Oral administration of OTX015 significantly inhibited the growth of Ty82 BRD-NUT midline carcinoma tumors in nude mice, showing 79% TGI at 100 mg/kg qd and 61% TGI at 10 mg/kg bid. Conclusions: OTX015 is a potent inhibitor of BRD2, BRD3, and BRD4 and inhibits the binding of BRD2, BRD3, and BRD4 to AcH4. OTX015 showed significant anti-tumor activity both in vitro and in vivo tumor models. These findings encouraged the clinical development of OTX015, which is currently in Phase 1 studies in patients with advanced hematologic malignancies (ClinicalTrials.gov Identifier NCT01713582). Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C244. Citation Format: J. Kay Noel, Kazunori Iwata, Shinsuke Ooike, Kunio Sugahara, Hideo Nakamura, Masanori Daibata. Development of the BET bromodomain inhibitor OTX015. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C244.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.