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Gamwell JM, Paphiti K, Hodson L, Karpe F, Pinnick KE, Todorčević M. An optimised protocol for the investigation of insulin signalling in a human cell culture model of adipogenesis. Adipocyte 2023; 12:2179339. [PMID: 36763512 PMCID: PMC9980465 DOI: 10.1080/21623945.2023.2179339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 02/07/2023] [Indexed: 02/11/2023] Open
Abstract
While there is no standardized protocol for the differentiation of human adipocytes in culture, common themes exist in the use of supra-physiological glucose and hormone concentrations, and an absence of exogenous fatty acids. These factors can have detrimental effects on some aspects of adipogenesis and adipocyte function. Here, we present methods for modifying the adipogenic differentiation protocol to overcome impaired glucose uptake and insulin signalling in human adipose-derived stem cell lines derived from the stromal vascular fraction of abdominal and gluteal subcutaneous adipose tissue. By reducing the length of exposure to adipogenic hormones, in combination with a physiological glucose concentration (5 mM), and the provision of exogenous fatty acids (reflecting typical dietary fatty acids), we were able to restore early insulin signalling events and glucose uptake, which were impaired by extended use of hormones and a high glucose concentration, respectively. Furthermore, the addition of exogenous fatty acids greatly increased the storage of triglycerides and removed the artificial demand to synthesize all fatty acids by de novo lipogenesis. Thus, modifying the adipogenic cocktail can enhance functional aspects of human adipocytes in vitro and is an important variable to consider prior to in vitro investigations into adipocyte biology.
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Affiliation(s)
- Jonathan M. Gamwell
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
| | - Keanu Paphiti
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
| | - Leanne Hodson
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
- NIHR Oxford Biomedical Research Centre, OUH Foundation Trust, Oxford, UK
| | - Fredrik Karpe
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
- NIHR Oxford Biomedical Research Centre, OUH Foundation Trust, Oxford, UK
| | - Katherine E. Pinnick
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
| | - Marijana Todorčević
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Headington, UK
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The aetiology and molecular landscape of insulin resistance. Nat Rev Mol Cell Biol 2021; 22:751-771. [PMID: 34285405 DOI: 10.1038/s41580-021-00390-6] [Citation(s) in RCA: 211] [Impact Index Per Article: 70.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2021] [Indexed: 02/07/2023]
Abstract
Insulin resistance, defined as a defect in insulin-mediated control of glucose metabolism in tissues - prominently in muscle, fat and liver - is one of the earliest manifestations of a constellation of human diseases that includes type 2 diabetes and cardiovascular disease. These diseases are typically associated with intertwined metabolic abnormalities, including obesity, hyperinsulinaemia, hyperglycaemia and hyperlipidaemia. Insulin resistance is caused by a combination of genetic and environmental factors. Recent genetic and biochemical studies suggest a key role for adipose tissue in the development of insulin resistance, potentially by releasing lipids and other circulating factors that promote insulin resistance in other organs. These extracellular factors perturb the intracellular concentration of a range of intermediates, including ceramide and other lipids, leading to defects in responsiveness of cells to insulin. Such intermediates may cause insulin resistance by inhibiting one or more of the proximal components in the signalling cascade downstream of insulin (insulin receptor, insulin receptor substrate (IRS) proteins or AKT). However, there is now evidence to support the view that insulin resistance is a heterogeneous disorder that may variably arise in a range of metabolic tissues and that the mechanism for this effect likely involves a unified insulin resistance pathway that affects a distal step in the insulin action pathway that is more closely linked to the terminal biological response. Identifying these targets is of major importance, as it will reveal potential new targets for treatments of diseases associated with insulin resistance.
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Jang JH, Park JE, Han JS. Scopoletin increases glucose uptake through activation of PI3K and AMPK signaling pathway and improves insulin sensitivity in 3T3-L1 cells. Nutr Res 2019; 74:52-61. [PMID: 31945607 DOI: 10.1016/j.nutres.2019.12.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 12/01/2019] [Accepted: 12/04/2019] [Indexed: 12/16/2022]
Abstract
Coumarins have been shown to reduce blood glucose levels and improve insulin sensitivity in other studies. The purpose of this study was to investigate the effects of scopoletin, which is a type of coumarin family, on glucose uptake in 3T3-L1 cells to test the hypothesis that scopoletin exerts an antidiabetic function on adipocytes. Scopoletin significantly increased glucose uptake, which was associated with increased expression of the plasma membrane glucose transporter type 4 (PM-GLUT4) in 3T3-L1 adipocytes. This increase in PM-GLUT4 expression was promoted by phosphorylation of protein kinase B, activation of phosphatidylinositol-3-kinase (PI3K), and enhanced intracellular glucose uptake. Scopoletin also promoted phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and enhanced PM-GLUT4 expression. Scopoletin-induced glucose uptake in 3T3-L1 adipocytes was inhibited by treatment with the PI3K inhibitor wortmannin and the AMPK inhibitor compound C. These results suggest that scopoletin has an antidiabetic effect by stimulating GLUT4 translocation to the PM through activation of the PI3K and AMPK pathways in 3T3-L1 adipocytes, thereby upregulating glucose uptake.
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Affiliation(s)
- June Hyuk Jang
- Department of Food Science and Nutrition, Pusan National University, Busan 46241, Republic of Korea; Department of Food Science and Nutrition and Kimchi Research Institute, Pusan National University, Busan 46241, Republic of Korea
| | - Jae Eun Park
- Department of Food Science and Nutrition, Pusan National University, Busan 46241, Republic of Korea; Department of Food Science and Nutrition and Kimchi Research Institute, Pusan National University, Busan 46241, Republic of Korea
| | - Ji Sook Han
- Department of Food Science and Nutrition, Pusan National University, Busan 46241, Republic of Korea; Department of Food Science and Nutrition and Kimchi Research Institute, Pusan National University, Busan 46241, Republic of Korea.
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Kua KL, Hu S, Wang C, Yao J, Dang D, Sawatzke AB, Segar JL, Wang K, Norris AW. Fetal hyperglycemia acutely induces persistent insulin resistance in skeletal muscle. J Endocrinol 2019; 242:M1-M15. [PMID: 30444716 PMCID: PMC6494731 DOI: 10.1530/joe-18-0455] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 11/14/2018] [Indexed: 12/13/2022]
Abstract
Offspring exposed in utero to maternal diabetes exhibit long-lasting insulin resistance, though the initiating mechanisms have received minimal experimental attention. Herein, we show that rat fetuses develop insulin resistance after only 2-day continuous exposure to isolated hyperglycemia starting on gestational day 18. Hyperglycemia-induced reductions in insulin-induced AKT phosphorylation localized primarily to fetal skeletal muscle. The skeletal muscle of hyperglycemia-exposed fetuses also exhibited impaired in vivo glucose uptake. To address longer term impacts of this short hyperglycemic exposure, neonates were cross-fostered and examined at 21 days postnatal age. Offspring formerly exposed to 2 days late gestation hyperglycemia exhibited mild glucose intolerance with insulin signaling defects localized only to skeletal muscle. Fetal hyperglycemic exposure has downstream consequences which include hyperinsulinemia and relative uteroplacental insufficiency. To determine whether these accounted for induction of insulin resistance, we examined fetuses exposed to late gestational isolated hyperinsulinemia or uterine artery ligation. Importantly, 2 days of fetal hyperinsulinemia did not impair insulin signaling in murine fetal tissues and 21-day-old offspring exposed to fetal hyperinsulinemia had normal glucose tolerance. Similarly, fetal exposure to 2-day uteroplacental insufficiency did not perturb insulin-stimulated AKT phosphorylation in fetal rats. We conclude that fetal exposure to hyperglycemia acutely produces insulin resistance. As hyperinsulinemia and placental insufficiency have no such impact, this occurs likely via direct tissue effects of hyperglycemia. Furthermore, these findings show that skeletal muscle is uniquely susceptible to immediate and persistent insulin resistance induced by hyperglycemia.
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Affiliation(s)
- Kok Lim Kua
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Shanming Hu
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Chunlin Wang
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Jianrong Yao
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Diana Dang
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Alex B. Sawatzke
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Jeffrey L. Segar
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Kai Wang
- Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, Iowa, United States
| | - Andrew W. Norris
- Stead Family Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
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Galangin and Pinocembrin from Propolis Ameliorate Insulin Resistance in HepG2 Cells via Regulating Akt/mTOR Signaling. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 2018:7971842. [PMID: 30420897 PMCID: PMC6215570 DOI: 10.1155/2018/7971842] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/16/2018] [Indexed: 01/19/2023]
Abstract
Insulin resistance has a critical role in type 2 diabetes. The aim of this study was to investigate the effect of pinobanksin, galangin, chrysin, and pinocembrin from propolis on insulin resistance. Our study shows that galangin and pinocembrin can ameliorate insulin resistance; on the contrary, pinobanksin and chrysin are ineffective. Galangin and pinocembrin treatments substantially increase glucose consumption and glycogen content by enhancing the activities of hexokinase and pyruvate kinase. Galangin treatment with 80 μM increased hexokinase and pyruvate kinase activities by 21.94% and 29.12%, respectively. Moreover, we hypothesize that galangin and pinocembrin may have a synergistic effect on the improvement of insulin resistance via Akt/mTOR signaling pathway, through distinctly upregulating the phosphorylation of IR, Akt, and GSK3β and remarkably downregulating the phosphorylation of IRS. Most notably, this is the first study to our knowledge to investigate pinocembrin about the alleviation of insulin resistance. Our results provide compelling evidence for the depth development of propolis products to ameliorate insulin resistance.
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Naufahu J, Elliott B, Markiv A, Dunning-Foreman P, McGrady M, Howard D, Watt P, Mackenzie RWA. High-Intensity Exercise Decreases IP6K1 Muscle Content and Improves Insulin Sensitivity (SI2*) in Glucose-Intolerant Individuals. J Clin Endocrinol Metab 2018; 103:1479-1490. [PMID: 29300979 DOI: 10.1210/jc.2017-02019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 12/20/2017] [Indexed: 12/13/2022]
Abstract
CONTEXT Insulin resistance (IR) in skeletal muscle contributes to whole body hyperglycemia and the secondary complications associated with type 2 diabetes. Inositol hexakisphosphate kinase-1 (IP6K1) may inhibit insulin-stimulated glucose transport in this tissue type. OBJECTIVE Muscle and plasma IP6K1 were correlated with two-compartment models of glucose control in insulin-resistant hyperinsulinemic individuals. Muscle IP6K1 was also compared after two different exercise trials. DESIGN Nine prediabetic [hemoglobin A1c; 6.1% (0.2%)] patients were recruited to take part in a resting control, a continuous exercise (90% of lactate threshold), and a high-intensity exercise trial (6 30-second sprints). Muscle biopsies were drawn before and after each 60-minute trial. A labeled ([6,62H2]glucose) intravenous glucose tolerance test was performed immediately after the second muscle sample. RESULTS Fasting muscle IP6K1 content did not correlate with insulin sensitivity (SI2*) (P = 0.961). High-intensity exercise reduced IP6K1 muscle protein and messenger RNA expression (P = 0.001). There was no effect on protein IP6K1 content after continuous exercise. Akt308 phosphorylation of was significantly greater after high-intensity exercise. Intermittent exercise reduced hepatic glucose production after the same trial. The same intervention also increased SI2*, and this effect was significantly greater compared with the effect of continuous exercise improvements. Our in vitro experiment demonstrated that the chemical inhibition of IP6K1 increased insulin signaling in C2C12 myotubes. CONCLUSIONS The in vivo and in vitro approaches used in the current study suggest that a decrease in muscle IP6K1 may be linked to whole body increases in SI2*. In addition, high-intensity exercise reduces hepatic glucose production in insulin-resistant individuals.
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Affiliation(s)
- Jane Naufahu
- Faculty of Science and Technology, Department of Life Sciences, University of Westminster, London, United Kingdom
| | - Bradley Elliott
- Faculty of Science and Technology, Department of Life Sciences, University of Westminster, London, United Kingdom
| | - Anatoliy Markiv
- Biosciences Education, King's College London, London, United Kingdom
| | - Petra Dunning-Foreman
- Faculty of Science and Technology, Department of Life Sciences, University of Westminster, London, United Kingdom
| | - Maggie McGrady
- Faculty of Science and Technology, Department of Life Sciences, University of Westminster, London, United Kingdom
| | - David Howard
- Department of Oncology, Charing Cross Hospital, Imperial NHS Trust Hospitals, London, United Kingdom
| | - Peter Watt
- Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Eastbourne, United Kingdom
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Ariga M, Yoneyama Y, Fukushima T, Ishiuchi Y, Ishii T, Sato H, Hakuno F, Nedachi T, Takahashi SI. Glucose deprivation attenuates sortilin levels in skeletal muscle cells. Endocr J 2017; 64:255-268. [PMID: 27980238 DOI: 10.1507/endocrj.ej16-0319] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
In skeletal muscle, sortilin plays a predominant role in the sorting of glucose transporter 4 (Glut4), thereby controlling glucose uptake. Moreover, our previous study suggested that the sortilin expression levels are also implicated in myogenesis. Despite the importance of sortilin in skeletal muscle, however, the regulation of sortilin expression has not been completely understood. In the present study, we analyzed if the sortilin expression is regulated by glucose in C2C12 myocytes and rat skeletal muscles in vivo. Sortilin protein expression was elevated upon C2C12 cell differentiation and was further enhanced in the presence of a high concentration of glucose. The gene expression and protein degradation of sortilin were not affected by glucose. On the other hand, rapamycin partially reduced sortilin induction by a high concentration of glucose, which suggested that sortilin translation could be regulated by glucose, at least in part. We also examined if the sortilin regulation by glucose was also observed in skeletal muscles that were obtained from fed or fasted rats. Sortilin expression in both gastrocnemius and extensor digitorum longus (EDL) muscle was significantly decreased by 17-18h of starvation. On the other hand, pathological levels of high blood glucose did not alter the sortilin expression in rat skeletal muscle. Overall, the present study suggests that sortilin protein levels are reduced under hypoglycemic conditions by post-transcriptional control in skeletal muscles.
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MESH Headings
- Adaptor Proteins, Vesicular Transport/agonists
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/metabolism
- Animals
- Blood Glucose/analysis
- Cell Differentiation
- Cell Line
- Diabetes Mellitus, Experimental/blood
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Down-Regulation/drug effects
- Fasting/metabolism
- Food Deprivation
- Glucose/metabolism
- Hindlimb
- Male
- Mechanistic Target of Rapamycin Complex 1
- Multiprotein Complexes/antagonists & inhibitors
- Multiprotein Complexes/metabolism
- Muscle Cells/cytology
- Muscle Cells/drug effects
- Muscle Cells/metabolism
- Muscle Cells/pathology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Protein Kinase Inhibitors/pharmacology
- RNA, Messenger/metabolism
- Rats, Wistar
- Sirolimus/pharmacology
- TOR Serine-Threonine Kinases/antagonists & inhibitors
- TOR Serine-Threonine Kinases/metabolism
- Up-Regulation/drug effects
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Affiliation(s)
- Miyako Ariga
- Department of Animal Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
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Jiménez-Osorio AS, Monroy A, Alavez S. Curcumin and insulin resistance-Molecular targets and clinical evidences. Biofactors 2016; 42:561-580. [PMID: 27325504 DOI: 10.1002/biof.1302] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/29/2016] [Accepted: 05/03/2016] [Indexed: 12/20/2022]
Abstract
Curcumin ((1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), the main component of the Indian spice turmeric, has been used in traditional medicine to improve diabetes and its comorbidities. Since the last two decades, scientific research has shown that in addition to its antioxidant properties, curcumin could also work as protein homeostasis regulator and it is able to modulate other intracellular pathways. Curcumin supplementation has been proposed to improve insulin resistance (IR) through the activation of the insulin receptor and its downstream pathways in several experimental models, pointing out that its clinical use may be a good and innocuous strategy to improve IR-related diseases. IR is associated with many diseases and syndromes like carbohydrate intolerance, diabetes, metabolic syndrome, and cardiovascular disease. Therefore, it is imperative to identify safe therapeutic interventions aimed to reduce side effects that could lead the patient to leave the treatment. To date, many clinical trials have been carried out using turmeric and curcumin to improve metabolic syndrome, carbohydrate intolerance, diabetes, and obesity in individuals with IR. Results so far are inconclusive because dose, time of treatment, and type of curcumin can change the study outcome significantly. However, there is some clinical evidence suggesting a beneficial effect of curcumin on IR. In this review, we discuss the factors that could influence curcumin effects in clinical trials aimed to improve IR and related diseases, and the conclusions that can be drawn from results obtained so far. © 2016 BioFactors, 42(6):561-580, 2016.
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Affiliation(s)
| | - Adriana Monroy
- Oncología y Dirección de Investigación, Hospital General de México "Dr. Eduardo Liceaga,", México D.F, México
| | - Silvestre Alavez
- Departamento de Ciencias de la Salud, Universidad Autónoma Metropolitana, Unidad Lerma, Estado de México, México
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Acupuncture Alters Expression of Insulin Signaling Related Molecules and Improves Insulin Resistance in OLETF Rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 2016:9651592. [PMID: 27738449 PMCID: PMC5055976 DOI: 10.1155/2016/9651592] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/27/2016] [Indexed: 11/17/2022]
Abstract
To determine effect of acupuncture on insulin resistance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats and to evaluate expression of insulin signaling components. Rats were divided into three groups: Sprague-Dawley (SD) rats, OLETF rats, and acupuncture+OLETF rats. Acupuncture was subcutaneously applied to Neiguan (PC6), Zusanli (ST36), and Sanyinjiao (SP6); in contrast, acupuncture to Shenshu (BL23) was administered perpendicularly. For Neiguan (PC6) and Zusanli (ST36), needles were connected to an electroacupuncture (EA) apparatus. Fasting blood glucose (FPG) was measured by glucose oxidase method. Plasma fasting insulin (FINS) and serum C peptide (C-P) were determined by ELISA. Protein and mRNA expressions of insulin signaling molecules were determined by Western blot and real-time RT-PCR, respectively. OLETF rats exhibit increased levels of FPG, FINS, C-P, and homeostasis model assessment-estimated insulin resistance (HOMA-IR), which were effectively decreased by acupuncture treatment. mRNA expressions of several insulin signaling related molecules IRS1, IRS2, Akt2, aPKCζ, and GLUT4 were decreased in OLETF rats compared to SD controls. Expression of these molecules was restored back to normal levels upon acupuncture administration. PI3K-p85α was increased in OLETF rats; this increase was also reversed by acupuncture treatment. Acupuncture improves insulin resistance in OLETF rats, possibly via regulating expression of key insulin signaling related molecules.
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Fang BJ, Shen JY, Zhang H, Zhou S, Lyu CZ, Xie YQ. Albiflorin Granule significantly decreased the cholesterol gallstone formation by the regulation of insulin transduction signal. ASIAN PAC J TROP MED 2016; 9:877-881. [PMID: 27633302 DOI: 10.1016/j.apjtm.2016.07.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 06/16/2016] [Accepted: 07/01/2016] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE To study the mechanism of insulin resistance in the cholesterol gallstone formation from insulin signal transduction pathway so as to reveal the possible mechanism and the effective role of Albiflorin Granule on preventing the cholesterol gallstones. METHODS Serum triglycerides (TG), free fatty acid (FFA), and total cholesterol (TC) from different groups were measured and liver cells InsR, PKB, IKK-β protein expression levels were detected by western blotting. RESULTS Albiflorin significantly decreased the cholesterol gallstone formation rate, increased glucose infusion rate in gallstone guinea pigs and improved insulin resistance. Compared with the normal group, insulin receptor and PKB protein expression in GS group were significantly reduced. IKK-β protein in the GS group increased significantly and Albiflorin could reduce IKK-β protein expression in guinea pig liver cells. CONCLUSIONS The model of insulin resistance in cholesterol gallstone guinea pig was successfully established, which plays an important role in the cholesterol gallstone formation. All aspects of insulin signaling pathway are involved in gallstone formation. Albiflorin can regulate various aspects of insulin signal transduction pathway to prevent the formation of gallbladder.
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Affiliation(s)
- Bang-Jiang Fang
- Emergency Department, Long Hua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China
| | - Jun-Yi Shen
- Emergency Department, Long Hua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China
| | - Hua Zhang
- Traumatology Department, Affiliated Hospital of Hainan Medical University, Haikou 571199, Hainan, China
| | - Shuang Zhou
- Changhai Hospital of Traditional Chinese Medicine, Second Military University, Shanghai 200433, China.
| | - Chuan-Zhu Lyu
- Traumatology Department, Affiliated Hospital of Hainan Medical University, Haikou 571199, Hainan, China
| | - Yi-Qiang Xie
- College of Traditional Chinese Medicine, Hainan Medical University, Haikou 571199, Hainan, China
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Ramachandran V, Saravanan R. Glucose uptake through translocation and activation of GLUT4 in PI3K/Akt signaling pathway by asiatic acid in diabetic rats. Hum Exp Toxicol 2015; 34:884-93. [DOI: 10.1177/0960327114561663] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this study, we examined the in vivo effect and the mechanism of asiatic acid (AA) on glucose uptake in an insulin target skeletal muscle. Diabetic rats showed significantly increased levels of plasma glucose, thiobarbituric acid reactive substances, and lipid hydroperoxides, decreased levels of insulin and antioxidants, and impairment in insulin-signaling proteins such as insulin receptor (IR), insulin receptor substrate (IRS)-1/2, phosphoinositide 3-kinase (PI3K), Akt, and glucose transporter 4 (GLUT4) proteins. Oral treatment with AA (20 mg/kg body weight) showed near-normalized levels of plasma glucose, lipid peroxidation products, and antioxidants and improved insulin, IR, IRS-1/2, PI3K, Akt, and GLUT4 proteins. These findings suggest that AA improves glucose response by increasing GLUT4 in skeletal muscle through Akt and antioxidant defense in plasma and it also improves glucose homeostasis.
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Affiliation(s)
- V Ramachandran
- Faculty of Science, Department of Biochemistry and Biotechnology, Annamalai University, Annamalainagar, Tamil Nadu, India
| | - R Saravanan
- Faculty of Science, Department of Biochemistry and Biotechnology, Annamalai University, Annamalainagar, Tamil Nadu, India
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12
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Fortes MAS, Pinheiro CHJ, Guimarães-Ferreira L, Vitzel KF, Vasconcelos DAA, Curi R. Overload-induced skeletal muscle hypertrophy is not impaired in STZ-diabetic rats. Physiol Rep 2015. [PMID: 26197932 PMCID: PMC4552534 DOI: 10.14814/phy2.12457] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The aim of this study was to evaluate the effect of overload-induced hypertrophy on extensor digitorum longus (EDL) and soleus muscles of streptozotocin-induced diabetic rats. The overload-induced hypertrophy and absolute tetanic and twitch forces increases in EDL and soleus muscles were not different between diabetic and control rats. Phospho-Akt and rpS6 contents were increased in EDL muscle after 7 days of overload and returned to the pre-overload values after 30 days. In the soleus muscle, the contents of total and phospho-Akt and total rpS6 were increased in both groups after 7 days. The contents of total Akt in controls and total rpS6 and phospho-Akt in the diabetic rats remained increased after 30 days. mRNA expression after 7 days of overload in the EDL muscle of control and diabetic animals showed an increase in MGF and follistatin and a decrease in myostatin and Axin2. The expression of FAK was increased and of MuRF-1 and atrogin-1 decreased only in the control group, whereas Ankrd2 expression was enhanced only in diabetic rats. In the soleus muscle caused similar changes in both groups: increase in FAK and MGF and decrease in Wnt7a, MuRF-1, atrogin-1, and myostatin. Differences between groups were observed only in the increased expression of follistatin in diabetic animals and decreased Ankrd2 expression in the control group. So, insulin deficiency does not impair the overload-induced hypertrophic response in soleus and EDL muscles. However, different mechanisms seem to be involved in the comparable hypertrophic responses of skeletal muscle in control and diabetic animals.
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Affiliation(s)
- Marco Aurélio S Fortes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Carlos Hermano J Pinheiro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Lucas Guimarães-Ferreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil Exercise Metabolism Research Group, Center of Physical Education and Sports, Federal University of Espírito Santo, Vitória, Brazil
| | - Kaio F Vitzel
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Diogo A A Vasconcelos
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Rui Curi
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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13
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Glimepiride promotes osteogenic differentiation in rat osteoblasts via the PI3K/Akt/eNOS pathway in a high glucose microenvironment. PLoS One 2014; 9:e112243. [PMID: 25391146 PMCID: PMC4229122 DOI: 10.1371/journal.pone.0112243] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 10/14/2014] [Indexed: 12/21/2022] Open
Abstract
Our previous studies demonstrated that glimepiride enhanced the proliferation and differentiation of osteoblasts and led to activation of the PI3K/Akt pathway. Recent genetic evidence shows that endothelial nitric oxide synthase (eNOS) plays an important role in bone homeostasis. In this study, we further elucidated the roles of eNOS, PI3K and Akt in bone formation by osteoblasts induced by glimepiride in a high glucose microenvironment. We demonstrated that high glucose (16.5 mM) inhibits the osteogenic differentiation potential and proliferation of rat osteoblasts. Glimepiride activated eNOS expression in rat osteoblasts cultured with two different concentrations of glucose. High glucose-induced osteogenic differentiation was significantly enhanced by glimepiride. Down-regulation of PI3K P85 levels by treatment with LY294002 (a PI3K inhibitor) led to suppression of P-eNOS and P-AKT expression levels, which in turn resulted in inhibition of RUNX2, OCN and ALP mRNA expression in osteoblasts induced by glimepiride at both glucose concentrations. ALP activity was partially inhibited by 10 µM LY294002. Taken together, our results demonstrate that glimepiride-induced osteogenic differentiation of osteoblasts occurs via eNOS activation and is dependent on the PI3K/Akt signaling pathway in a high glucose microenvironment.
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Krause MP, Riddell MC, Hawke TJ. Effects of type 1 diabetes mellitus on skeletal muscle: clinical observations and physiological mechanisms. Pediatr Diabetes 2011; 12:345-64. [PMID: 20860561 DOI: 10.1111/j.1399-5448.2010.00699.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Matthew P Krause
- Dept of Pathology & Molecular Medicine, McMaster University, 1200 Main St., W. Hamilton, ON, Canada L8N 3Z5
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Ma P, Xiong W, Liu H, Ma J, Gu B, Wu X. Extrapancreatic roles of glimepiride on osteoblasts from rat manibular bone in vitro: Regulation of cytodifferentiation through PI3-kinases/Akt signalling pathway. Arch Oral Biol 2011; 56:307-16. [DOI: 10.1016/j.archoralbio.2010.10.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 09/27/2010] [Accepted: 10/07/2010] [Indexed: 10/18/2022]
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Ohta Y, Kinugawa S, Matsushima S, Ono T, Sobirin MA, Inoue N, Yokota T, Hirabayashi K, Tsutsui H. Oxidative stress impairs insulin signal in skeletal muscle and causes insulin resistance in postinfarct heart failure. Am J Physiol Heart Circ Physiol 2011; 300:H1637-44. [PMID: 21335475 DOI: 10.1152/ajpheart.01185.2009] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin resistance has been shown to occur as a consequence of heart failure. However, its exact mechanisms in this setting remain unknown. We have previously reported that oxidative stress is enhanced in the skeletal muscle from mice with heart failure after myocardial infarction (MI) (30). This study is aimed to investigate whether insulin resistance in postinfarct heart failure is due to the impairment of insulin signaling in the skeletal muscle caused by oxidative stress. Mice were divided into four groups: sham operated (sham); sham treated with apocynin, an inhibitor of NAD(P)H oxidase activation (10 mmol/l in drinking water); MI; and MI treated with apocynin. After 4 wk, intraperitoneal insulin tolerance tests were performed, and skeletal muscle samples were obtained for insulin signaling measurements. MI mice showed left ventricular dilation and dysfunction by echocardiography and increased left ventricular end-diastolic pressure and lung weight. The decrease in glucose level after insulin load significantly attenuated in MI compared with sham. Insulin-stimulated serine phosphorylation of Akt and glucose transporter-4 translocation were decreased in MI mice by 61 and 23%, respectively. Apocynin ameliorated the increase in oxidative stress and NAD(P)H oxidase activities measured by the lucigenin assay in the skeletal muscle after MI. It also improved insulin resistance and inhibited the decrease of Akt phosphorylation and glucose transporter-4 translocation. Insulin resistance was induced by the direct impairment of insulin signaling in the skeletal muscle from postinfarct heart failure, which was associated with the enhanced oxidative stress via NAD(P)H oxidase.
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Affiliation(s)
- Yukihiro Ohta
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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Solinas G, Karin M. JNK1 and IKKbeta: molecular links between obesity and metabolic dysfunction. FASEB J 2010; 24:2596-611. [PMID: 20371626 DOI: 10.1096/fj.09-151340] [Citation(s) in RCA: 240] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Inflammation is thought to underlie the pathogenesis of many chronic diseases. It is now established that obesity results in a state of chronic low-grade inflammation thought to contribute to several metabolic disorders, including insulin resistance and pancreatic islet dysfunction. The protein kinases JNK1 and IKKbeta have been found to serve as critical molecular links between obesity, metabolic inflammation, and disorders of glucose homeostasis. The precise mechanisms of these linkages are still being investigated. However, as we discuss here, JNK1 and IKKbeta are activated by almost all forms of metabolic stress that have been implicated in insulin resistance or islet dysfunction. Furthermore, both JNK1 and IKKbeta are critically involved in the promotion of diet-induced obesity, metabolic inflammation, insulin resistance, and beta-cell dysfunction. Understanding the molecular mechanisms by which JNK1 and IKKbeta mediate obesity-induced metabolic stress is likely to be of importance for the development of new treatments for a variety of obesity-associated diseases.
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Affiliation(s)
- Giovanni Solinas
- Laboratory of Metabolic Stress Biology, Department of Medicine, Physiology, University of Fribourg, Chemin du Musée 5, CH-1700 Fribourg, Switzerland.
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Liu M, Wu K, Mao X, Wu Y, Ouyang J. Astragalus polysaccharide improves insulin sensitivity in KKAy mice: regulation of PKB/GLUT4 signaling in skeletal muscle. JOURNAL OF ETHNOPHARMACOLOGY 2010; 127:32-7. [PMID: 19800959 DOI: 10.1016/j.jep.2009.09.055] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2009] [Revised: 09/23/2009] [Accepted: 09/24/2009] [Indexed: 05/05/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Astragalus polysaccharide (APS) is an important bioactive component of Astragalus membranaceus Bunge (Leguminosae) that has been used in traditional Chinese medicine for treating diabetes. AIM OF THE STUDY To study the mechanisms by which APS ameliorates diabetes, we examined whether treatment with APS improves insulin sensitivity in insulin-resistant mice and whether this is associated with an improvement of dysregulated protein kinase B and glucose transporter 4 expressions in skeletal muscle. METHODS APS (700 mg kg(-1)day(-1)) or vehicle was administered to 12-week-old diabetic KKAy and nondiabetic C57BL/6J mice for 8 weeks. Changes in body weight, blood glucose level, insulin resistance index, and oral glucose tolerance were routinely evaluated. The expressions of protein kinase B and glucose transporter 4 in skeletal muscle tissues were determined with Western blot. RESULTS KKAy mice developed persistent hyperglycemia, impaired glucose tolerance and insulin resistance. Insulin-stimulated protein kinase B phosphorylation and glucose transporter 4 translocation were significantly decreased in KKAy compared to age-matched C57BL/6J mice. APS treatment ameliorated hyperglycemia and insulin resistance. Although the content of protein kinase B and glucose transporter 4 in KKAy skeletal muscle were not affected by APS, insulin-induced protein kinase B Ser-473 phosphorylation and glucose transporter 4 translocation in skeletal muscle were partially restored by APS treatment. In contrast, APS did not have any effect on C57BL/6J mice. CONCLUSIONS These results indicate that APS can regulate part of the insulin signaling in insulin-resistant skeletal muscle, and that APS could be a potential insulin sensitizer for the treatment of type 2 diabetes.
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Affiliation(s)
- Min Liu
- Department of Pathophysiology, Medical College of Wuhan University, Hubei Provincial Key Laboratory of Allergy and Immune-Related Diseases, Wuhan 430071, China
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Zhang JF, Yang JPO, Wang GH, Xia Z, Duan SZ, Wu Y. Role of PKCzeta translocation in the development of type 2 diabetes in rats following continuous glucose infusion. Diabetes Metab Res Rev 2010; 26:59-70. [PMID: 20013954 DOI: 10.1002/dmrr.1056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
AIM We investigated the molecular mechanisms of hyperglycaemia-induced insulin resistance and type 2 diabetes in rats receiving a continuous glucose infusion (GI). METHODS Female Wistar rats were infused with either 2.8 mol/L glucose or saline (2 mL/h) for durations varying from 0 to 15 days. Blood samples were analysed daily to determine glucose and insulin dynamics. Subsets of animals were sacrificed and soleus muscles were extracted for determination of protein expression, subcellular location, and activities of insulin-signalling proteins. RESULTS Rats accommodated this systemic glucose oversupply and developed insulin resistance on day 5 (normoglycaemia/hyperinsulinaemia) and type 2 diabetes on day 15 (hyperglycaemia/normoinsulinaemia). The effect of GI on protein kinase Czeta (PKCzeta) activity was independent of changes in phosphatidylinositol 3-kinase activity, and occurred in parallel with an increase in PDK1 activity. Activated PKCzeta was mainly located in the cytosol after 5 days of GI that was coincident with the translocation of GLUT4 to the plasma membrane, and normoglycaemia. After 15 days of GI, PKCzeta translocated from the cytosol to the plasma membrane with a concomitant decrease in PDK1 activity. This caused an increase in the association between PKCzeta and PKB and a decrease in PDK1-PKB reactions at the plasma membrane, leading to reduced PKB activity. The activity of PKCzeta per se was also compromised. The PKCzeta and PKB activity reduction and the blunted insulin-stimulated GLUT4 translocation eventually led to hyperglycaemia and diabetes. CONCLUSION Translocation of PKCzeta may play a central role in the development of type 2 diabetes.
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Affiliation(s)
- Jing-fang Zhang
- Department of Pathophysiology, Medical College, Wuhan University, Wuhan, Hubei, China
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Aging-associated dysfunction of Akt/protein kinase B: S-nitrosylation and acetaminophen intervention. PLoS One 2009; 4:e6430. [PMID: 19641606 PMCID: PMC2712760 DOI: 10.1371/journal.pone.0006430] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 07/01/2009] [Indexed: 11/22/2022] Open
Abstract
Background Aged skeletal muscle is characterized by an increased incidence of metabolic and functional disorders, which if allowed to proceed unchecked can lead to increased morbidity and mortality. The mechanism(s) underlying the development of these disorders in aging skeletal muscle are not well understood. Protein kinase B (Akt/PKB) is an important regulator of cellular metabolism and survival, but it is unclear if aged muscle exhibits alterations in Akt function. Here we report a novel dysfunction of Akt in aging muscle, which may relate to S-nitrosylation and can be prevented by acetaminophen intervention. Principal Findings Compared to 6- and 27-month rats, the phosphorylation of Akt (Ser473 and Thr308) was higher in soleus muscles of very aged rats (33-months). Paradoxically, these increases in Akt phosphorylation were associated with diminished mammalian target of rapamycin (mTOR) phosphorylation, along with decreased levels of insulin receptor beta (IR-β), phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and phosphorylation of phosphoinositide-dependent kinase-1 (PDK1) (Ser241). In vitro Akt kinase measurements and ex vivo muscle incubation experiments demonstrated age-related impairments of Akt kinase activity, which were associated with increases in Akt S-nitrosylation and inducible nitric oxide synthase (iNOS). Impairments in Akt function occurred parallel to increases in myocyte apoptosis and decreases in myocyte size and the expression of myosin and actin. These age-related disorders were attenuated by treating aged (27-month) animals with acetaminophen (30 mg/kg body weight/day) for 6-months. Conclusions These data demonstrate that Akt dysfunction and increased S-nitrosylation of Akt may contribute to age-associated disorders in skeletal muscle and that acetaminophen may be efficacious for the treatment of age-related muscle dysfunction.
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Shi Z, Liu J, Guo Q, Ma X, Shen L, Xu S, Gao H, Yuan X, Zhang J. Association of TRB3 gene Q84R polymorphism with type 2 diabetes mellitus in Chinese population. Endocrine 2009; 35:414-9. [PMID: 19291425 DOI: 10.1007/s12020-009-9162-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 01/13/2009] [Accepted: 02/23/2009] [Indexed: 10/21/2022]
Abstract
BACKGROUND TRB3, a human homolog of Drosophila Tribbles, has been shown as a critical negative regulator of Akt (also known as protein kinase B), which is a key component in insulin signaling. In addition, TRB3 is another PPAR-target gene and functions as an important link between glucose and lipid metabolism. The Q84R polymorphic variant of TRB3 has been linked to insulin resistance and related clinical outcomes. However, it is unclear whether this polymorphism is associated with type 2 diabetes mellitus (T2DM) in the Chinese population. METHODS In this study, we genotyped Q84R polymorphism in 177 patients with T2DM and 245 control subjects in Chinese population by using the polymerase chain reaction/ligase detection reaction (PCR/LDR) assay. RESULTS No significant difference in the Q84R genotype frequency was observed between T2DM patients and controls (P = 0.642). In T2DM group, the Q84R variant in cases was associated with higher FINS, higher HOMA-IR, and lower LnISI (P = 0.003, 0.001, and 0.001, respectively). However, the changes in HOMA-IR and LnISI were not significant in controls (the P value is 0.098 and 0.203, respectively). In addition, FINS levels were also significantly increased from Q84Q to R84 in controls (P = 0.036). CONCLUSION Our data indicate that the TRB3 Q84R polymorphism is not associated with T2DM in Chinese population. However, the Q84R variant is associated with insulin resistance among T2DM patients in Chinese population.
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Affiliation(s)
- Zhiyong Shi
- Lanzhou University, Lanzhou City 730000, Gansu Province, People's Republic of China
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Katta A, Karkala SK, Wu M, Meduru S, Desai DH, Rice KM, Blough ER. Lean and obese Zucker rats exhibit different patterns of p70s6 kinase regulation in the tibialis anterior muscle in response to high-force muscle contraction. Muscle Nerve 2009; 39:503-11. [PMID: 19296503 DOI: 10.1002/mus.21255] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Increased phosphorylation of the 70-kDa ribosomal S6 kinase (p70S6k) signaling is strongly correlated with the degree of muscle adaptation following exercise. Herein we compare the phosphorylation of p70S6k, Akt, and mammalian target of rapamycin (mTOR) in the tibialis anterior (TA) muscles of lean and obese Zucker rats following a bout of eccentric exercise. Exercise increased p70S6k (Thr389) phosphorylation immediately after (33.3+/-7.2%) and during [1 h (24.0+/-14.9%) and 3 h (24.6+/-11.3%)] recovery in the lean TA and at 3 h (33.5+/-8.0%) in the obese TA Zucker rats. mTOR (Ser2448) phosphorylation was elevated in the lean TA immediately after exercise (96.5+/-40.3%) but remained unaltered in the obese TA. Exercise increased Akt (Thr308) and Akt (Ser473) phosphorylation in the lean but not the obese TA. These results suggest that insulin resistance is associated with alterations in the ability of muscle to activate p70S6k signaling following an acute bout of exercise.
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Affiliation(s)
- Anjaiah Katta
- Department of Pharmacology, Physiology, and Toxicology, Marshall University, Joan C. Edwards School of Medicine, Huntington, West Virginia, USA
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Sugimoto K, Rashid IB, Shoji M, Suda T, Yasujima M. Early changes in insulin receptor signaling and pain sensation in streptozotocin-induced diabetic neuropathy in rats. THE JOURNAL OF PAIN 2007; 9:237-45. [PMID: 18331706 DOI: 10.1016/j.jpain.2007.10.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
Abstract
UNLABELLED The objective of the present study was to evaluate the time course of changes in peripheral nerve insulin receptor (IR) signaling and compare observed findings with behavioral responses to noxious mechanical and thermal stimuli in streptozotocin (STZ)-diabetic rats over 12 weeks of diabetes. Diabetic rats developed mechanical hyperalgesia, as indicated by decreased paw withdrawal thresholds to mechanical stimuli that were detectable after 2 weeks of diabetes; they also developed thermal hypoalgesia, as indicated by increased tail flick latencies to thermal stimuli that were detectable at 1 week of diabetes. Western blot analysis revealed decreased phosphorylated: total IR protein ratio that was detectable as early as 2 weeks of diabetes, whereas phosphorylated:total Akt protein ratio was decreased at 2 weeks and increased at 12 weeks of diabetes with unchanged PI-3K protein levels. To our knowledge, the present study is the first to demonstrate that impaired peripheral nerve IR signaling, as indicated by decreased phosphorylated:total IR protein ratio, coincides with early mechanical hyperalgesia and thermal hypoalgesia in STZ-diabetic rats. This finding may improve understanding of how altered pain sensation develops rapidly in this model. PERSPECTIVE This study examined peripheral nerve IR signaling during the early course of altered nociception in STZ-diabetic rats. In diabetic rats, impaired peripheral nerve IR signaling is observed shortly after STZ injection, as is altered nociception. This finding suggests a possible role of impaired IR signaling in diabetic sensory neuropathy.
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Affiliation(s)
- Kazuhiro Sugimoto
- Department of Laboratory Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
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Lee YJ, Lee YJ, Han HJ. Regulatory mechanisms of Na(+)/glucose cotransporters in renal proximal tubule cells. Kidney Int 2007:S27-35. [PMID: 17653207 DOI: 10.1038/sj.ki.5002383] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glucose is a key fuel and an important metabolic substrate in mammals. Renal proximal tubular cells (PTCs) not only reabsorb filtered glucose but are also believed to play a role in the glucotoxicity associated with renal pathogenesis, such as in diabetes. The proximal tubule environment is where 90% of the filtered glucose is reabsorbed by the low-affinity/high-capacity Na(+)/glucose cotransporter 2 (SGLT2) and facilitated diffusion glucose transporter 2 (GLUT2). Both active and facilitative glucose transporters have distinct distribution profiles along the proximal tubule related to their particular kinetic characteristics. A number of mechanisms contribute to the changes in the cellular functions, which occur in response to exposure to various endogenous factors. Hyperglycemia was reported to regulate the renal SGLT activities through the reactive oxygen species-nuclear factor-kappaB pathways, which suggests that the transcellular glucose uptake within the PTCs contribute to the development of diabetic-like nephropathy. Angiotensin II (ANG II) plays an important role in its development through epidermal growth factor receptor (EGFR) transactivation. Therefore, a combination of high glucose, ANG II, and EGF are involved in diabetic-like nephropathy by regulating the SGLT activity. In addition, endogenously enhanced SGLTs have a cytoprotective function. The renal proximal tubules play a major role in regulating the plasma glucose levels, and there is increasing interest in the renal glucose transporters on account of their potential implications in the treatment of various conditions including diabetes mellitus.
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Affiliation(s)
- Y J Lee
- Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
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Umpierrez GE, Smiley D, Gosmanov A, Thomason D. Ketosis-prone type 2 diabetes: effect of hyperglycemia on beta-cell function and skeletal muscle insulin signaling. Endocr Pract 2007; 13:283-90. [PMID: 17599861 DOI: 10.4158/ep.13.3.283] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To determine the underlying mechanism for the severe and transient beta-cell dysfunction and impaired insulin action in obese African American patients with ketosis-prone diabetes. METHODS The effect of sustained hyperglycemia (glucotoxicity) and increased free fatty acids (lipotoxicity) on beta-cell function was assessed by changes in insulin secretion during a 20-hour glucose (200 mg/m2 per minute) and a 48-hour Intralipid (40 mL/h) infusion, respectively. Insulin-activated signaling pathways and pattern of Akt-1 and Akt-2 expression and insulin-stimulated phosphorylation were analyzed in skeletal muscle biopsy specimens. Studies were performed in an obese African American woman within 48 hours after resolution of diabetic ketoacidosis and 1 week after discontinuation of insulin treatment. RESULTS Dextrose infusion rapidly increased C-peptide levels from a baseline of 3.2 ng/mL to a mean of 7.1 +/- 0.5 ng/mL during the first 8 hours of infusion; thereafter, C-peptide levels progressively declined. Lipid infusion was not associated with any deleterious effect on insulin and C-peptide secretion. Initial in vitro stimulation of muscle tissue with insulin resulted in a substantial and selectively decreased Akt-2 expression and insulin-stimulated phosphorylation on the serine residue. Improved metabolic control resulted in 70% greater Akt expression at near-normoglycemic remission in comparison with the period of hyperglycemia. CONCLUSION Hyperglycemia, but not increased free fatty acid levels, led to progressive beta-cell dysfunction and impaired insulin secretion. Hyperglycemia was also associated with diminished skeletal muscle Akt expression and phosphorylation in an African American woman with ketosis-prone diabetes, and this defect improved notably with aggressive insulin therapy. These results indicate the importance of glucose toxicity in the pathogenesis of ketosis-prone diabetes in obese African American patients.
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Leclercq IA, Da Silva Morais A, Schroyen B, Van Hul N, Geerts A. Insulin resistance in hepatocytes and sinusoidal liver cells: mechanisms and consequences. J Hepatol 2007; 47:142-56. [PMID: 17512085 DOI: 10.1016/j.jhep.2007.04.002] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hepatic insulin resistance is an important underlying cause of the metabolic syndrome that manifests itself in diseases such as diabetes type II, atherosclerosis or non-alcoholic fatty liver disease (NAFLD). In this paper, we summarize comprehensively the current state of knowledge pertaining to the molecular mechanisms that lead to insulin resistance in hepatocytes and sinusoidal liver cells. In hepatocytes, the insulin resistant state is brought about by at least one, but more likely by a combination, of the following pathological alterations: hyperglycaemia and hyperinsulinaemia, formation of advanced glycation end-products, increased free fatty acids and their metabolites, oxidative stress and altered profiles of adipocytokines. Insulin resistance in hepatocytes distorts directly glucose metabolism, especially the control over glucose output into the circulation and interferes with cell survival and proliferation, while hepatic fatty acid synthesis remains stimulated by compensatory hyperinsulinaemia, resulting in steatosis. Very few studies have addressed insulin resistance in sinusoidal liver cells. These cells are not simply bystanders and passive witnesses of the changes affecting the hepatocytes. They are target cells that will respond to the pathological alterations occurring in the insulin resistant state. They are also effector cells that may exacerbate insulin resistance in hepatocytes by increasing oxidative stress and by secreting cytokines such as TNF and IL-6. Moreover, activation of sinusoidal endothelial cells, Kupffer cells and stellate cells will lead to chemo-attraction of inflammatory cells. Finally, activation of stellate cells will set in motion a fibrogenic response that paves the way to cirrhosis.
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Affiliation(s)
- Isabelle A Leclercq
- Laboratory of Gastroenterology, Faculty of Medicine, Université catholique de Louvain, GAEN 53/79, Avenue Mounier, 53, B-1200 Brussels, Belgium.
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Renström F, Burén J, Svensson M, Eriksson JW. Insulin resistance induced by high glucose and high insulin precedes insulin receptor substrate 1 protein depletion in human adipocytes. Metabolism 2007; 56:190-8. [PMID: 17224332 DOI: 10.1016/j.metabol.2006.09.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Accepted: 09/08/2006] [Indexed: 11/25/2022]
Abstract
The aim of this study was to investigate whether high glucose and/or high insulin produces cellular insulin resistance in human adipocytes and, if so, to evaluate the time course and content of key proteins in the insulin signaling pathway. Subcutaneous fat biopsies were taken from 27 nondiabetic subjects. Insulin action in vitro was studied by measurement of glucose uptake after incubation at a physiologic glucose level (6 mmol/L) for 24 hours or with the last 2, 6, or 24 hours at a high glucose level (20 mmol/L) with or without high insulin (10(4)microU/mL). High glucose alone for 24 hours produced a small but significant impairment (by approximately 20%, P < .05) of insulin's effect to stimulate glucose transport, whereas nonstimulated glucose uptake was left intact. In contrast, the combination of high glucose and high insulin for 6 hours or more reduced basal glucose uptake by approximately 40% (P < .05). In addition, insulin-stimulated glucose uptake capacity was reduced by approximately 40% already after 2 hours (P < .05) and reached a maximal decline (by approximately 50%, P < .05) after a 6-hour culture in high glucose and high insulin. Treatment with high glucose and high insulin in combination for at least 6 hours reduced cellular insulin receptor substrate (IRS)-1, but not IRS-2, protein content by approximately 45% or more (P < .05). Moreover, after 24 hours, the ability of insulin to activate protein kinase B (ie, the phosphorylated protein kinase B [pPKB]-protein kinase B ratio) was decreased by approximately 50% (P < .05). No significant effects were seen on insulin signaling proteins or glucose transporter 4 after a long-term high-glucose culture. Culture with high insulin alone (and low glucose, 6 mmol/L) decreased basal and insulin-stimulated glucose uptake in conformity with the high-glucose/high-insulin setting. However, IRS-1 protein content remained unchanged. We conclude that, in adipocytes from healthy humans, high insulin alone for 2 hours or more decrease glucose uptake capacity. Likewise, high glucose and high insulin in combination for 2 hours or more decrease glucose uptake to the same extent as when cells were cultured with high insulin alone but, in addition, with a diminishment in IRS-1 protein lagging behind. Thus, IRS-1 depletion appears to be a secondary phenomenon in this model of insulin resistance. High glucose alone induces only a minor insulin resistance in human fat cells.
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Affiliation(s)
- Frida Renström
- Department of Public Health and Clinical Medicine, Medicine, Umeå University Hospital, S-901 85 Umeå, Sweden
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Ordóñez P, Moreno M, Alonso A, Fernández R, Díaz F, González C. Insulin sensitivity in streptozotocin-induced diabetic rats treated with different doses of 17beta-oestradiol or progesterone. Exp Physiol 2006; 92:241-9. [PMID: 17068109 DOI: 10.1113/expphysiol.2006.035006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It has been reported that in streptozotocin (STZ)-induced diabetes, hyperglycaemia leads to progressive insulin resistance of the peripheral tissues. In this study, we tried to elucidate the effects of hyperglycaemia on insulin sensitivity and insulin signalling in ovariectomized (STZ)-induced diabetic rats. In addition, we attempted to demonstrate the role of 17beta-oestradiol and progesterone on insulin sensitivity, focusing on their effects on key proteins of skeletal muscle, insulin receptor (IR) and glucose transporter-4 (Glut-4). Our results show that hyperglycaemia could modulate insulin signalling, at the IR and Glut-4 level, in different ways depending on exposure time. 17beta-Oestradiol and progesterone have different effects on insulin signalling. 17beta-Oestradiol treatment improves insulin sensitivity, but its action is dependent on the exposure time and its plasma level. During the early period of treatment (days 6-11), this hormone counteracts the effects of hyperglycaemia downstream of the IR, whereas during the later period of treatment (days 11-16), it may counteract the effects of hyperglycaemia by modulating IR relative tyrosine phosphorylation. By contrast, progesterone only improves insulin sensitivity during the early period of treatment (days 6-11), and this effect is not associated with changes in IR and Glut-4 content. Both hormones have a protective role in skeletal muscle against the effects of glucose toxicity, but their effects begin at different stages of treatment. These new findings improve our understanding of insulin resistance in type 1 diabetes mellitus and of the risk/benefit ratio when 17beta-oestradiol and progesterone are used in oral contraceptives or hormone replacement therapy taken by menopausal women with controlled type 1 diabetes mellitus.
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Affiliation(s)
- Patricia Ordóñez
- Department of Functional Biology, Physiology Area, University of Oviedo, C/ Julián Clavería s/n 3306, Oviedo, Spain
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Nedachi T, Kanzaki M. Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes. Am J Physiol Endocrinol Metab 2006; 291:E817-28. [PMID: 16735448 DOI: 10.1152/ajpendo.00194.2006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
It is well established that insulin stimulation of glucose uptake in skeletal muscle cells is mediated through translocation of GLUT4 from intracellular storage sites to the cell surface. However, the established skeletal muscle cell lines, with the exception of L6 myocytes, reportedly show minimal insulin-dependent glucose uptake and GLUT4 translocation. Using C(2)C(12) myocytes expressing exofacial-Myc-GLUT4-enhanced cyan fluorescent protein, we herein show that differentiated C(2)C(12) myotubes are equipped with basic GLUT4 translocation machinery that can be activated by insulin stimulation ( approximately 3-fold increase as assessed by anti-Myc antibody uptake and immunostaining assay). However, this insulin stimulation of GLUT4 translocation was difficult to demonstrate with a conventional 2-deoxyglucose uptake assay because of markedly elevated basal glucose uptake via other glucose transporter(s). Intriguingly, the basal glucose transport activity in C(2)C(12) myotubes appeared to be acutely suppressed within 5 min by preincubation with a pathophysiologically high level of extracellular glucose (25 mM). In contrast, this activity was augmented by acute glucose deprivation via an unidentified mechanism that is independent of GLUT4 translocation but is dependent on phosphatidylinositol 3-kinase activity. Taken together, these findings indicate that regulation of the facilitative glucose transport system in differentiated C(2)C(12) myotubes can be achieved through surprisingly acute glucose-dependent modulation of the activity of glucose transporter(s), which apparently contributes to obscuring the insulin augmentation of glucose uptake elicited by GLUT4 translocation. We herein also describe several methods of monitoring insulin-dependent glucose uptake in C(2)C(12) myotubes and propose this cell line to be a useful model for analyzing GLUT4 translocation in skeletal muscle.
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Affiliation(s)
- Taku Nedachi
- TUBERO/Tohoku University Biomedical Engineering Research Organization, Tohoku University 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
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Oak SA, Tran C, Pan G, Thamotharan M, Devaskar SU. Perturbed skeletal muscle insulin signaling in the adult female intrauterine growth-restricted rat. Am J Physiol Endocrinol Metab 2006; 290:E1321-30. [PMID: 16449300 DOI: 10.1152/ajpendo.00437.2005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the molecular mechanism(s) linking fetal adaptations in intrauterine growth restriction (IUGR) to adult maladaptations of type 2 diabetes mellitus, we investigated the effect of prenatal seminutrient restriction, modified by early postnatal ad libitum access to nutrients (CM/SP) or seminutrient restriction (SM/SP), vs. early postnatal seminutrient restriction alone (SM/CP) or control nutrition (CM/CP) on the skeletal muscle postreceptor insulin-signaling pathway in the adult offspring. The altered in utero hormonal/metabolic milieu was associated with no change in basal total IRS-1, p85, and p110beta subunits of PI 3-kinase, PKCtheta, and PKCzeta concentrations but an increase in basal IRS-2 (P < 0.05) only in the CM/SP group and an increase in basal phospho (p)-PDK-1 (P < 0.05), p-Akt (P < 0.05), and p-PKCzeta (P < 0.05) concentrations in the CM/SP and SM/SP groups. Insulin-stimulated increases in p-PDK-1 (P < 0.05) and p-Akt (P < 0.0007), with no increase in p-PKCzeta, were seen in both CM/SP and SM/SP groups. SHP2 (P < 0.03) and PTP1B (P < 0.03) increased only in SM/SP with no change in PTEN in CM/SP and SM/SP groups. Aberrations in kinase and phosphatase moieties in the adult IUGR offspring were initiated in utero but further sculpted by the early postnatal nutritional state. Although the CM/SP group demonstrated enhanced kinase activation, the SM/SP group revealed an added increase in phosphatase concentrations with the net result of heightened basal insulin sensitivity in both groups. The inability to further respond to exogenous insulin was due to the key molecular distal roadblock consisting of resistance to phosphorylate and activate PKCzeta necessary for GLUT4 translocation. This protective adaptation may become maladaptive and serve as a forerunner for gestational and type 2 diabetes mellitus.
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Affiliation(s)
- Shilpa A Oak
- Division of Neonatology and Developmental Biology, David Geffen School at Medicine at University of California at Los Angeles, CA 90095-1752, USA
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Anitha M, Gondha C, Sutliff R, Parsadanian A, Mwangi S, Sitaraman SV, Srinivasan S. GDNF rescues hyperglycemia-induced diabetic enteric neuropathy through activation of the PI3K/Akt pathway. J Clin Invest 2006; 116:344-56. [PMID: 16453021 PMCID: PMC1359053 DOI: 10.1172/jci26295] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Accepted: 11/22/2005] [Indexed: 12/15/2022] Open
Abstract
Diabetes can result in loss of enteric neurons and subsequent gastrointestinal complications. The mechanism of enteric neuronal loss in diabetes is not known. We examined the effects of hyperglycemia on enteric neuronal survival and the effects of glial cell line-derived neurotrophic factor (GDNF) on modulating this survival. Exposure of primary enteric neurons to 20 mM glucose (hyperglycemia) for 24 hours resulted in a significant increase in apoptosis compared with 5 mM glucose (normoglycemia). Exposure to 20 mM glucose resulted in decreased Akt phosphorylation and enhanced nuclear translocation of forkhead box O3a (FOXO3a). Treatment of enteric neurons with GDNF ameliorated these changes. In streptozotocin-induced diabetic mice, there was evidence of myenteric neuronal apoptosis and reduced Akt phosphorylation. Diabetic mice had loss of NADPH diaphorase-stained myenteric neurons, delayed gastric emptying, and increased intestinal transit time. The pathophysiological effects of hyperglycemia (apoptosis, reduced Akt phosphorylation, loss of inhibitory neurons, motility changes) were reversed in diabetic glial fibrillary acidic protein-GDNF (GFAP-GDNF) Tg mice. In conclusion, we demonstrate that hyperglycemia induces neuronal loss through a reduction in Akt-mediated survival signaling and that these effects are reversed by GDNF. GDNF may be a potential therapeutic target for the gastrointestinal motility disorders related to diabetes.
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Affiliation(s)
- Mallappa Anitha
- Division of Digestive Diseases, Emory University, Atlanta, Georgia 30307, USA
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Bertacca A, Ciccarone A, Cecchetti P, Vianello B, Laurenza I, Maffei M, Chiellini C, Del Prato S, Benzi L. Continually high insulin levels impair Akt phosphorylation and glucose transport in human myoblasts. Metabolism 2005; 54:1687-93. [PMID: 16311104 DOI: 10.1016/j.metabol.2005.06.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Accepted: 06/06/2005] [Indexed: 11/16/2022]
Abstract
Chronic hyperinsulinemia is both a marker and a cause for insulin resistance. This study analyzes the effect of long-term exposure to high insulin levels on the insulin-signaling pathway and glucose transport in cultured human myoblasts. Human myoblasts were grown in the presence of low (107 pmol/L, SkMC-L) or high (1430 pmol/L, SkMC-H) insulin concentrations for 3 weeks. Glucose transport, insulin receptor (IR), and IR substrate 1 (IRS1) phosphorylation, phosphatidylinositol 3'-kinase (PI3K) activity, as well as Akt-Ser473 phosphorylation have been investigated at the end of the incubation period and after a further short-term insulin stimulation. At the end of the incubation period, IR, IRS1, p85/PI3K, Akt, and GLUT4 protein expression levels were similar in both culture conditions. Basal glucose transport was similar in SkMC-L and SkMC-H, but after short-term insulin stimulation significantly increased (P < .01) only in SkMC-L. IR binding was down-regulated in SkMC-H (P < .01), but IR and IRS1 tyrosine phosphorylation and PI3K activity were significantly higher (P < .01) in SkMC-H than SkMC-L. Despite increased PI3K activation, Akt-Ser473 phosphorylation was similar in SkMC-L and SkMC-H. After a short-term insulin stimulation (10 nmol/L insulin for 10 minutes), IR and IRS1 tyrosine phosphorylation, PI3K activation, and Akt-Ser473 phosphorylation significantly increased (P < .01 and P < .05 for Akt) in SkMC-L but not in SkMC-H. Serine phosphorylation of IRS1 was similar in SkMC-L and SkMC-H. Moreover, in the SkMC-H, insulin stimulation was associated with the inhibition of IRS1 tyrosine dephosphorylation (P < .05). In summary, continuous exposure of cultured myoblasts to high insulin levels induces a persistent up-regulation of IR, IRS1, and PI3K activity associated with the demodulation of insulin signaling. Moreover, the impairment of the insulin-signaling steps between PI3K and Akt is concomitant with the desensitization of glucose transport. These alterations may contribute to the derangement insulin-signaling pathway states of hyperinsulinemia such as obesity and type 2 diabetes.
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Affiliation(s)
- Anna Bertacca
- Section of Diabetes, Department of Endocrinology and Metabolism, School of Medicine, Ospedale Cisanello, University of Pisa, 56124 Pisa, Italy
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Ruzzin J, Jensen J. Contraction activates glucose uptake and glycogen synthase normally in muscles from dexamethasone-treated rats. Am J Physiol Endocrinol Metab 2005; 289:E241-50. [PMID: 15741240 DOI: 10.1152/ajpendo.00587.2004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucocorticoids cause insulin resistance in skeletal muscle. The aims of the present study were to investigate the effects of contraction on glucose uptake, insulin signaling, and regulation of glycogen synthesis in skeletal muscles from rats treated with the glucocorticoid analog dexamethasone (1 mg x kg(-1) x day(-1) ip for 12 days). Insulin resistance in dexamethasone-treated rats was confirmed by reduced insulin-stimulated glucose uptake (approximately 35%), glycogen synthesis (approximately 70%), glycogen synthase activation (approximately 80%), and PKB Ser(473) phosphorylation (approximately 40%). Chronic dexamethasone treatment did not impair glucose uptake during contraction in soleus or epitrochlearis muscles. In epitrochlearis (but not in soleus), the presence of insulin during contraction enhanced glucose uptake to similar levels in control and dexamethasone-treated rats. Contraction also increased glycogen synthase fractional activity and dephosphorylated glycogen synthase at Ser(645), Ser(649), Ser(653), and Ser(657) normally in muscles from dexamethasone-treated rats. After contraction, insulin-stimulated glycogen synthesis was completely restored in epitrochlearis and improved in soleus from dexamethasone-treated rats. Contraction did not increase insulin-stimulated PKB Ser(473) or glycogen synthase kinase-3 (GSK-3) phosphorylation. Instead, contraction increased GSK-3beta Ser(9) phosphorylation in epitrochlearis (but not in soleus) in muscles from control and dexamethasone-treated rats. In conclusion, contraction stimulates glucose uptake normally in dexamethasone-induced insulin resistant muscles. After contraction, insulin's ability to stimulate glycogen synthesis was completely restored in epitrochlearis and improved in soleus from dexamethasone-treated rats.
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Affiliation(s)
- Jérôme Ruzzin
- Dept. of Physiology, National Institute of Occupational Health, PO Box 8149 Dep., N-0033, Oslo, Norway
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Aas V, Rokling-Andersen M, Wensaas AJ, Thoresen GH, Kase ET, Rustan AC. Lipid metabolism in human skeletal muscle cells: effects of palmitate and chronic hyperglycaemia. ACTA ACUST UNITED AC 2005; 183:31-41. [PMID: 15654918 DOI: 10.1111/j.1365-201x.2004.01381.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This review focuses on the effect of exogenous factors known to be of importance for the development of insulin resistance in differentiated human myotubes. Recent data from our laboratory on the effects of fatty acid pre-treatment and chronic glucose oversupply on fatty acid and glucose metabolism, without and with acute insulin are presented, and discussed in the context of other recent publications in the field. Pre-treatment of myotubes with palmitate, chronic hyperglycaemia, and acute high concentrations of insulin changed fatty acid metabolism in favour of accumulation of intracellular lipids. Acute insulin exposure increased (14)C-oleate uptake and levels of free fatty acids (FFA) and triacylglycerol (TAG). Palmitate pre-treatment further increased oleate uptake, both under basal conditions and in the presence of insulin, with a marked increase in the phospholipid (PL) fraction, with a concomitant reduction in oleate oxidation. Chronic hyperglycaemia also promoted increased lipogenesis and elevated levels of cellular lipids. Changes in fatty acid metabolism in human muscle, in particular fatty acid oxidation, are probably crucial for the molecular mechanism behind skeletal muscle insulin resistance and impaired glucose metabolism. Differentiated human skeletal muscle cells may be an ideal system to further explore the mechanisms regulating lipid metabolism.
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Affiliation(s)
- V Aas
- Department of Pharmacology, School of Pharmacy, University of Oslo, N-0316 Oslo, Norway
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Bernard JR, Crain AM, Rivas DA, Herr HJ, Reeder DW, Yaspelkis BB. Chronic aerobic exercise enhances components of the classical and novel insulin signalling cascades in Sprague-Dawley rat skeletal muscle. ACTA ACUST UNITED AC 2005; 183:357-66. [PMID: 15799772 DOI: 10.1111/j.1365-201x.2005.01408.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
AIM The aim of this study was to provide a more extensive evaluation of the effects of chronic aerobic exercise on various components of the insulin signalling cascade in normal rodent skeletal muscle because of the limited body of literature that exists in this area of investigation. METHODS Male Sprague-Dawley rats were assigned to either control (n = 7) or chronic aerobic exercise (n = 7) groups. Aerobic exercise animals were run 3 day week(1) for 45 min on a motor-driven treadmill (32 m min(1), 15% grade) for a 12 week period. Following the training period, all animals were subjected to hind limb perfusion in the presence of 500 microU mL(1) insulin to determine what effect chronic aerobic training had on various components of the insulin signalling cascade, c-Cbl protein concentration and c-Cbl phosphorylation. RESULTS Twelve weeks of aerobic training did not alter skeletal muscle Akt 1/2 protein concentration, Akt Ser 473 phosphorylation, Akt Thr 308 phosphorylation, Akt 1 activity, aPKC-zeta protein concentration, aPKC-lambda protein concentration or c-Cbl protein concentration. In contrast, chronic aerobic exercise increased insulin-stimulated phosphatidylinositol 3-kinase, Akt 2 kinase and aPKC-zeta/lambda kinase activities, as well as c-Cbl tyrosine phosphorylation, in a fibre type specific response to aerobic training. In addition, chronic aerobic exercise enhanced insulin-stimulated plasma membrane glucose transporter 4 (GLUT4) protein concentration. CONCLUSION Collectively, these findings suggest that chronic aerobic exercise enhances components of both the classical and novel insulin signalling cascades in normal rodent skeletal muscle, which may contribute to an increased insulin-stimulated plasma membrane GLUT4 protein concentration.
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Affiliation(s)
- J R Bernard
- Exercise Biochemistry Laboratory, Department of Kinesiology, College of Health and Human Development, California State University Northridge, 91330-8287, USA
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Aas V, Kase ET, Solberg R, Jensen J, Rustan AC. Chronic hyperglycaemia promotes lipogenesis and triacylglycerol accumulation in human skeletal muscle cells. Diabetologia 2004; 47:1452-61. [PMID: 15309295 DOI: 10.1007/s00125-004-1465-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 04/19/2004] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS The present study was conducted to evaluate the effect of hyperglycaemia in itself on glucose and lipid metabolism in human skeletal muscle cells. METHODS Satellite cells were isolated from biopsy samples from the vastus lateralis muscle and differentiated into multinucleated myotubes in cultures. Metabolism studies were performed using isotopes ([3H]deoxyglucose, [14C]glucose, [14C]oleic acid and [14C]palmitic acid), and mRNA and protein levels were analysed by real-time RT-PCR and western blotting respectively. RESULTS Exposure of myotubes to 20 mmol/l glucose for 4 days reduced insulin-stimulated glucose uptake and glycogen synthesis to 57+/-5% (p<0.0001) and 56+/-5% (p<0.0001) of normoglycaemic (5.5 mmol/l glucose) controls respectively. Basal glucose uptake and glycogen synthesis were both reduced, whereas glucose oxidation was unaltered. Total cell content of glycogen and expression of GLUT1 and GLUT4 mRNA were not affected. There was a significant increase in the incorporation of glucose into cellular NEFA (88+/-17% increase, p=0.006), triacylglycerol (44+/-21% increase, p=0.04) and cholesterol ester (89+/-36% increase, p=0.02) in hyperglycaemic myotubes compared with controls. Diacylglycerol tended to be increased though not significantly, and phospholipid formation were unchanged. Relative to controls, total cell content of triacylglycerol was increased by 25+/-7% (p=0.02) and acyl-CoA:1,2-diacylglycerol acyltransferase 1 activity was increased by 34+/-4% (p=0.004), whereas acyl-CoA:1,2-diacylglycerol acyltransferase 1 mRNA expression was unchanged. Total cellular uptake of palmitic acid was reduced by 18+/-3% (p=0.006) in hyperglycaemic cells compared with controls, while uptake of oleic acid was unchanged. Oxidation of palmitic acid or oleic acid was not affected by hyperglycaemia. CONCLUSIONS/INTERPRETATION Chronic hyperglycaemia increased triacylglycerol accumulation and the incorporation of carbohydrate into triacylglycerol (i.e. de novo lipogenesis) concomitantly with a reduced insulin-stimulated glucose uptake and glycogen synthesis. Enhanced acyl-CoA:1,2-diacylglycerol acyltransferase 1 activity supported the increased triacylglycerol synthesis during hyperglycaemia.
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Affiliation(s)
- V Aas
- Department of Pharmacology, School of Pharmacy, University of Oslo, Oslo, Norway.
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Gosmanov AR, Umpierrez GE, Karabell AH, Cuervo R, Thomason DB. Impaired expression and insulin-stimulated phosphorylation of Akt-2 in muscle of obese patients with atypical diabetes. Am J Physiol Endocrinol Metab 2004; 287:E8-E15. [PMID: 15010337 DOI: 10.1152/ajpendo.00485.2003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although a pharmacological dose of insulin produces a dramatic increase in phosphorylation and activity of Akt isoforms 1 and 2 in mammalian skeletal muscle, few studies have examined the effect of physiological concentrations of insulin on the phosphorylation of Akt-1 and -2 in normal and diabetic tissue. This study examined the patterns of insulin-stimulated Akt isoform phosphorylation and protein expression in muscle biopsies obtained from obese patients with atypical diabetes immediately after a hyperglycemic crisis and again after near-normoglycemic remission. In obese patients with new-onset diabetes mellitus presenting with hyperglycemic crisis (plasma glucose 30.5 +/- 4.8 mM), in vitro stimulation of vastus lateralis muscle biopsies with 100 microU/ml (0.6 nM) insulin increased insulin receptor phosphorylation threefold and Akt-1 phosphorylation on Ser(473) twofold, whereas Akt-2 phosphorylation was not stimulated. After 10-wk intensive insulin therapy that led to near-normoglycemic remission and discontinuation of insulin therapy, both Akt-2 expression and insulin-stimulated Akt-2 Ser(474) phosphorylation doubled. Hyperglycemic crisis did not affect insulin-stimulated threonine phosphorylation of either Akt-1 or Akt-2. The decreased Akt-2 expression at presentation was accompanied by reduced GLUT4 protein expression and increased expression of enzymes counterregulatory to insulin action. Thus a physiological concentration of insulin stimulated Akt-1 and Akt-2 phosphorylation in human skeletal muscle in the absence of hyperglycemia, but Akt-2 expression and stimulation appeared to be impaired in muscle of obese patients with atypical diabetes presenting with severe hyperglycemia.
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Affiliation(s)
- Aidar R Gosmanov
- Dept. of Physiology, College of Medicine, Univ. of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA
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38
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Abstract
Insulin is a key hormone regulating the control of metabolism and the maintenance of normoglycaemia and normolipidaemia. Insulin acts by binding to its cell surface receptor, thus activating the receptor's intrinsic tyrosine kinase activity, resulting in receptor autophosphorylation and phosphorylation of several substrates. Tyrosine phosphorylated residues on the receptor itself and on subsequently bound receptor substrates provide docking sites for downstream signalling molecules, including adapters, protein serine/threonine kinases, phosphoinositide kinases and exchange factors. Collectively, those molecules orchestrate the numerous insulin-mediated physiological responses. A clear picture is emerging of the way in which insulin elicits several intracellular signalling pathways to mediate its physiologic functions. A further challenge, being pursued by several laboratories, is to understand the molecular mechanisms that underlie insulin action at the peripheral level, deregulation of which ultimately leads to hyperglycaemia and Type 2 diabetes. We review how circulating factors such as insulin itself, TNF-alpha, interleukins, fatty acids and glycation products influence insulin action through insulin signalling molecules themselves or through other pathways ultimately impinging on the insulin-signalling pathway. Understanding how the mechanism by which molecular insulin action is modulated by these factors will potentially provide new targets for pharmacological agents, to enable the control of altered glucose and lipid metabolism and diabetes.
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Affiliation(s)
- L Pirola
- INSERM Unit 145, Faculty of Medicine, Nice, France
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Krisan AD, Collins DE, Crain AM, Kwong CC, Singh MK, Bernard JR, Yaspelkis BB. Resistance training enhances components of the insulin signaling cascade in normal and high-fat-fed rodent skeletal muscle. J Appl Physiol (1985) 2004; 96:1691-700. [PMID: 14707149 DOI: 10.1152/japplphysiol.01054.2003] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our laboratory recently reported that chronic resistance training (RT) improved insulin-stimulated glucose transport in normal rodent skeletal muscle, owing, in part, to increased GLUT-4 protein concentration (Yaspelkis BB III, Singh MK, Trevino B, Krisan AD, and Collins DE. Acta Physiol Scand 175: 315-323, 2002). However, it remained to be determined whether these improvements resulted from alterations in the insulin signaling cascade as well. In addition, the possibility existed that RT might improve skeletal muscle insulin resistance. Thirty-two male Sprague-Dawley rats were assigned to four groups: control diet (Con)-sedentary (Sed); Con-RT; high-fat diet (HF)-Sed; and HF-RT. Animals consumed their respective diets for 9 wk; then RT animals performed 12 wk of training (3 sets, 10 repetitions at 75% one-repetition maximum, 3x/wk). Animals remained on their dietary treatments over the 12-wk period. After the training period, animals were subjected to hindlimb perfusions. Insulin-stimulated insulin receptor substrate-1-associated phosphatidylinositol-3 kinase activity was enhanced in the red gastrocnemius and quadriceps of Con-RT and HF-RT animals. Atypical PKC-zeta/lambda and Akt activities were reduced in HF-Sed and normalized in HF-RT animals. Resistance training increased GLUT-4 protein concentration in red gastrocnemius and quadriceps of Con-RT and HF-RT animals. No differences were observed in total protein concentrations of insulin receptor substrate-1, Akt, atypical PKC-zeta/lambda, or phosphorylation of Akt. Collectively, these findings suggest that resistance training increases insulin-stimulated carbohydrate metabolism in normal skeletal muscle and reverses high-fat diet-induced skeletal muscle insulin resistance by altering components of both the insulin signaling cascade and glucose transporter effector system.
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Affiliation(s)
- Adam D Krisan
- Exercise Biochemistry Laboratory, Department of Kinesiology, College of Health and Human Development, California State University Northridge, Northridge, CA 91330-8287, USA
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Lajoie C, Calderone A, Trudeau F, Lavoie N, Massicotte G, Gagnon S, Béliveau L. Exercise training attenuated the PKB and GSK-3 dephosphorylation in the myocardium of ZDF rats. J Appl Physiol (1985) 2003; 96:1606-12. [PMID: 14698990 DOI: 10.1152/japplphysiol.00853.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cardiac dysfunction is a severe secondary effect of Type 2 diabetes. Recruitment of the protein kinase B/glycogen synthase kinase-3 pathway represents an integral event in glucose homeostasis, albeit its regulation in the diabetic heart remains undefined. Thus the following study tested the hypothesis that the regulation of protein kinase B/glycogen synthase kinase-3 was altered in the myocardium of the Zucker diabetic fatty rat. Second, exercise has been shown to improve glucose homeostasis, and, in this regard, the effect of swimming training on the regulation of protein kinase B/glycogen synthase kinase-3 in the diabetic rat heart was examined. In the sedentary Zucker diabetic fatty rats, glucose levels were elevated, and cardiac glycogen content increased, compared with wild type. A 13-wk swimming regimen significantly reduced plasma glucose levels and cardiac glycogen content and partially normalized protein kinase B-serine473, protein kinase B-threonine308, and glycogen synthase kinase-3alpha phosphorylation in Zucker diabetic fatty rats. In conclusion, hyperglycemia and increased cardiac glycogen content in the Zucker diabetic fatty rats were associated with dysregulation of protein kinase B/glycogen synthase kinase-3 phosphorylation. These anomalies in the Zucker diabetic fatty rat were partially normalized with swimming. These data support the premise that exercise training may protect the heart against the deleterious consequences of diabetes.
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Affiliation(s)
- Claude Lajoie
- Department of Kinesiology, University of Montreal, Montreal, Québec H3C 3J7, Canada
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Steiler TL, Galuska D, Leng Y, Chibalin AV, Gilbert M, Zierath JR. Effect of hyperglycemia on signal transduction in skeletal muscle from diabetic Goto-Kakizaki rats. Endocrinology 2003; 144:5259-67. [PMID: 12960081 DOI: 10.1210/en.2003-0447] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We determined basal and insulin-stimulated responses on signaling intermediates in soleus skeletal muscle from male Wistar and diabetic Goto-Kakizaki (GK) rats. Rats were infused with glucose (5 or 20 mm) for 3 h, followed by a continuous infusion of saline or insulin (3 U/kg.h) for 20 min. Under euglycemic and hyperglycemic conditions, basal and insulin-stimulated action on phosphatidylinositol (PI) 3-kinase, protein kinase B/Akt, and ERK were reduced in GK rats, whereas insulin-stimulated protein kinase C (PKC)zeta activity was not altered. Interestingly, basal PKCzeta activity was increased under hyperglycemic conditions in GK and Wistar rats. This finding of increased PKCzeta activity was confirmed in vitro in isolated soleus muscle exposed to high extracellular glucose, and occurred concomitant with an increase in PI-dependent kinase 1 (PDK-1) activity. The glucose effects were not specific to PKCzeta, because an increase in phosphorylation of PKCalpha/beta and PKCdelta, but not PKCtheta, in isolated soleus muscle exposed to 25 mm glucose was observed. In conclusion, insulin signaling defects in diabetic GK rats are not corrected by an acute normalization of glycemia. Interestingly, acute hyperglycemia leads to a parallel increase in PDK-1, PKCalpha/beta, PKCdelta, and PKCzeta phosphorylation/activity via a PI 3-kinase-protein kinase B/Akt-independent mechanism. The long-term consequence of elevated PDK-1 and PKC phosphorylation/activity should be considered in the context of diabetes mellitus, as hyperglycemia is a clinical feature of this disease.
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Affiliation(s)
- Tatiana L Steiler
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
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Heled Y, Shapiro Y, Shani Y, Moran DS, Langzam L, Braiman L, Sampson SR, Meyerovitch J. Physical exercise enhances protein kinase C delta activity and insulin receptor tyrosine phosphorylation in diabetes-prone psammomys obesus. Metabolism 2003; 52:1028-33. [PMID: 12898468 DOI: 10.1016/s0026-0495(03)00154-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We recently reported that physical exercise prevents the progression of type 2 diabetes mellitus in Psammomys obesus, an animal model of nutritionally induced type 2 diabetes mellitus. In the present study we characterized the effect of physical exercise on protein kinase C delta (PKC delta) activity, as a mediator of the insulin-signaling cascade in vivo. Three groups of Psammomys obesus were exposed to a 4-week protocol: high-energy diet (HE/C), high-energy diet and exercise (HE/EX), or low-energy diet (LE/C). None of the animals in the HE/EX group became diabetic, whereas all the animals in the HE/C group became diabetic. After overnight fast, intraperitoneal (IP) insulin (1U) caused a greater reduction in blood glucose levels in the HE/EX and LE/C groups compared to the HE/C group. Tyrosine phosphorylation of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and phosphatidylinositol 3 kinase (PI3 kinase) was significantly higher in the HE/EX and LE/C groups compared with the HE/C group. Finally, IR-associated PKC delta was higher in the HE/EX and LE/C groups compared to the HE/C group. Coprecipitation of PKC delta with IR was higher in the HE/EX and LE/C groups compared to the HE/C group. Thus, we suggest that 4 weeks of physical exercise results in improved insulin-signaling response in Psammomys obesus accompanied by a direct connection between PKC delta and IR. We conclude that this mechanism may be involved in the preventive effect of exercise on type 2 diabetes mellitus in Psammomys obesus.
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Affiliation(s)
- Yuval Heled
- Heller Institute of Medical Research and the Pediatric Division, Sheva Medical Center, Tel Aviv, Israel
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43
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Kanoh Y, Sajan MP, Bandyopadhyay G, Miura A, Standaert ML, Farese RV. Defective activation of atypical protein kinase C zeta and lambda by insulin and phosphatidylinositol-3,4,5-(PO4)(3) in skeletal muscle of rats following high-fat feeding and streptozotocin-induced diabetes. Endocrinology 2003; 144:947-54. [PMID: 12586772 DOI: 10.1210/en.2002-221017] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
UNLABELLED Insulin-stimulated glucose transport in skeletal muscle is thought to be effected at least partly through atypical protein kinase C isoforms (aPKCs) operating downstream of phosphatidylinositol (PI) 3-kinase and 3-phosphoinositide-dependent protein kinase-1 (PDK-1). However, relatively little is known about the activation of aPKCs in physiological conditions or insulin-resistant states. Presently, we studied aPKC activation in vastus lateralis muscles of normal chow-fed and high-fat-fed rats and after streptozotocin (STZ)-induced diabetes. In normal chow-fed rats, dose-dependent increases in aPKC activity approached maximal levels after 15-30 min of stimulation by relatively high and lower, presumably more physiological, insulin concentrations, achieved by im insulin or ip glucose administration. Insulin-induced activation of aPKCs was impaired in both high-fat-fed and STZ-diabetic rats, but, surprisingly, IRS-1-dependent and IRS-2-dependent PI 3-kinase activation was not appreciably compromised. Most interestingly, direct in vitro activation of aPKCs by PI-3,4,5-(PO(4))(3), the lipid product of PI 3-kinase, was impaired in both high-fat-fed and STZ-diabetic rats. Defects in activation of aPKCs by insulin and PI-3,4,5-(PO(4))(3) could not be explained by diminished PDK-1-dependent phosphorylation of threonine-410 in the PKC-zeta activation loop, as this phosphorylation was increased even in the absence of insulin treatment in high-fat-fed rats. CONCLUSIONS 1) muscle aPKCs are activated at relatively low, presumably physiological, as well as higher supraphysiological, insulin concentrations; 2) aPKC activation is defective in muscles of high-fat-fed and STZ-diabetic rats; and 3) defective aPKC activation in these states is at least partly due to impaired responsiveness to PI-3,4,5-(PO(4))(3), apparently at activation steps distal to PDK-1-dependent loop phosphorylation.
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Affiliation(s)
- Yoshinori Kanoh
- Research Service, James A. Haley Veterans Administration Medical Center and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612, USA
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Gosmanov AR, Schneider EG, Thomason DB. NKCC activity restores muscle water during hyperosmotic challenge independent of insulin, ERK, and p38 MAPK. Am J Physiol Regul Integr Comp Physiol 2003; 284:R655-65. [PMID: 12433675 DOI: 10.1152/ajpregu.00576.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In isosmotic conditions, insulin stimulation of PI 3-K/Akt and p38 MAPK pathways in skeletal muscle inhibits Na(+)-K(+)-2Cl(-) cotransporter (NKCC) activity induced by the ERK1,2 MAPK pathway. Whether these signaling cascades contribute to NKCC regulation during osmotic challenge is unknown. Increasing osmolarity by 20 mosM with either glucose or mannitol induced NKCC-mediated (86)Rb uptake and water transport into rat soleus and plantaris skeletal muscle in vitro. This NKCC activity restored intracellular water. In contrast to mannitol, hyperosmolar glucose increased ERK1,2 and p38 MAPK phosphorylation. Glucose, but not mannitol, impaired insulin-stimulated phosphorylation of Akt and p38 MAPK in the plantaris and soleus muscles, respectively. Hyperosmolarity-induced NKCC activation was insensitive to insulin action and pharmacological inhibition of ERK1,2 and p38 MAPK pathways. Paradoxically, cAMP-producing agents, which stimulate NKCC activity in isosmotic conditions, suppressed hyperosmolar glucose- and mannitol-induced NKCC activity and prevented restoration of muscle cell volume in hyperosmotic media. These results indicate that NKCC activity helps restore muscle cell volume during hyperglycemia. Moreover, hyperosmolarity activates NKCC regulatory pathways that are insensitive to insulin inhibition.
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Affiliation(s)
- Aidar R Gosmanov
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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45
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Cai F, Helke CJ. Abnormal PI3 kinase/Akt signal pathway in vagal afferent neurons and vagus nerve of streptozotocin-diabetic rats. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 110:234-44. [PMID: 12591159 DOI: 10.1016/s0169-328x(02)00652-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The PI3 (phosphatidylinositol-3) kinase/Akt (protein kinase B) signal pathway is involved in the molecular signaling that regulates retrograde axonal transport of neurotrophins in the nervous system. Previous work showed that a reduced retrograde axonal transport of endogenous nerve growth factor (NGF) and neurotrophin-3 (NT-3) in the vagus nerve of diabetic rats occurred in the presence of normal production of neurotrophins and neurotrophin receptors. To assess the potential involvement of an impaired PI3 kinase/Akt signal pathway in the diabetes-induced reduction in retrograde axonal transport of neurotrophins in the vagus nerve, we characterized diabetes-induced changes in the PI3 kinase/Akt signal pathway in the vagus nerve and vagal afferent neurons. Control and streptozotocin (STZ)-induced diabetic rats with a duration of 16 weeks, kinase assays, Western blotting, and immunocytochemistry were used to show that diabetes resulted in alterations in activity and protein expression of the PI3 kinase/Akt signal pathway in the vagus nerve and vagal afferent neurons. Diabetes caused a significant decrease in enzymatic activity of PI3 kinase and Akt (52 and 36% of control, respectively) in the vagus nerve. The reduced enzymatic activity was not associated with decreased protein expression of the p85 subunit of PI3 kinase, Akt and phosphorylation of Akt (ser473). In contrast, there was a significant increase in the phosphorylation of p70s6 kinase (thr421/ser424) along with a normal protein expression of p70s6 kinase in the vagus nerve of diabetic rats. However, diabetes induced an overall decrease in immunoreactivity of the p85 subunit of PI3 kinase, phospho-Akt (ser473) and phospho-p70s6/p85s6 kinase (thr421/ser424) in vagal afferent neurons. Thus, impaired PI3 kinase/Akt signal pathway may partly account for the reduced retrograde axonal transport of neurotrophins in the vagus nerve of STZ-induced diabetic rats.
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Affiliation(s)
- Fang Cai
- Department of Pharmacology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
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46
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Orzechowski A. Justification for antioxidant preconditioning (or how to protect insulin-mediated actions under oxidative stress). J Biosci 2003; 28:39-49. [PMID: 12682423 DOI: 10.1007/bf02970130] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Insulin resistance is characterized by impaired glucose utilization in the peripheral tissues, accelerated muscle protein degradation, impaired antioxidant defences and extensive cell death. Apparently, both insulin and IGF-1 at physiological concentrations support cell survival by phosphatidylinositol 3 kinase-dependent and independent mechanisms. Postprandial hyperglycemia and hyperinsulinemia are found in insulin resistance, which accompanies the so-called noninsulin dependent diabetes mellitus (diabetes type 2). Evidence also indicates that increased susceptibility of muscle cells and cardiomycoytes to oxidative stress is among the harmful complications of insulin resistance and diabetes. Limited knowledge showing benefits of preconditioning with anti- oxidants (vitamin C, E, a-lipoic acid, N-acetylcysteine) in order to protect insulin action under oxidative stress prompted the author to discuss the theoretical background to this approach. It should be stressed that antioxidant preconditioning is relevant to prevention of both diabetes- and insulin resistance-associated side-effects such as low viability and cell deletion. Furthermore, antioxidant conditioning promises to provide higher efficacy for clinical applications in myoblast transfer therapy and cardiomyoplasty.
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Affiliation(s)
- A Orzechowski
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw Agricultural University, 02-787 Warsaw, Nowoursynowska 159, Poland.
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Tremblay F, Lavigne C, Jacques H, Marette A. Dietary cod protein restores insulin-induced activation of phosphatidylinositol 3-kinase/Akt and GLUT4 translocation to the T-tubules in skeletal muscle of high-fat-fed obese rats. Diabetes 2003; 52:29-37. [PMID: 12502490 DOI: 10.2337/diabetes.52.1.29] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Diet-induced obesity is known to cause peripheral insulin resistance in rodents. We have recently found that feeding cod protein to high-fat-fed rats prevents the development of insulin resistance in skeletal muscle. In the present study, we have further explored the cellular mechanisms behind this beneficial effect of cod protein on skeletal muscle insulin sensitivity. Rats were fed a standard chow diet or a high-fat diet in which the protein source was either casein, soy, or cod proteins for 4 weeks. Whole-body and muscle glucose disposal were reduced by approximately 50% in rats fed high-fat diets with casein or soy proteins, but these impairments were not observed in animals fed cod protein. Insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrate (IRS) proteins were similar in muscle of chow- and high-fat-fed rats regardless of the dietary protein source. However, IRS-1-associated phosphatidylinositol (PI) 3-kinase activity was severely impaired (-60%) in muscle of high-fat-fed rats consuming casein or soy protein. In marked contrast, feeding rats with cod protein completely prevented the deleterious effect of fat feeding on insulin-stimulated PI 3-kinase activity. The activation of the downstream kinase Akt/PKB by insulin, assessed by in vitro kinase assay and phosphorylation of GSK-3beta, were also impaired in muscle of high-fat-fed rats consuming casein or soy protein, but these defects were also fully prevented by dietary cod protein. However, no effect of cod protein was observed on atypical protein kinase C activity. Normalization of PI 3-kinase/Akt activation by insulin in rats fed high-fat diets with cod protein was associated with improved translocation of GLUT4 to the T-tubules but not to the plasma membrane. Taken together, these results show that dietary cod protein is a natural insulin-sensitizing agent that appears to prevent obesity-linked muscle insulin resistance by normalizing insulin activation of the PI 3-kinase/Akt pathway and by selectively improving GLUT4 translocation to the T-tubules.
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Affiliation(s)
- Frédéric Tremblay
- Department of Anatomy and Physiology, Laval University Hospital Research Center, Ste-Foy, Québec, Canada
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48
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Gum RJ, Gaede LL, Koterski SL, Heindel M, Clampit JE, Zinker BA, Trevillyan JM, Ulrich RG, Jirousek MR, Rondinone CM. Reduction of protein tyrosine phosphatase 1B increases insulin-dependent signaling in ob/ob mice. Diabetes 2003; 52:21-8. [PMID: 12502489 DOI: 10.2337/diabetes.52.1.21] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin receptor (IR) signal transduction and a drug target for treatment of type 2 diabetes. Using PTP1B antisense oligonucleotides (ASOs), effects of decreased PTP1B levels on insulin signaling in diabetic ob/ob mice were examined. Insulin stimulation, prior to sacrifice, resulted in no significant activation of insulin signaling pathways in livers from ob/ob mice. However, in PTP1B ASO-treated mice, in which PTP1B protein was decreased by 60% in liver, similar stimulation with insulin resulted in increased tyrosine phosphorylation of the IR and IR substrate (IRS)-1 and -2 by threefold, fourfold, and threefold, respectively. IRS-2-associated phosphatidylinositol 3-kinase activity was also increased threefold. Protein kinase B (PKB) serine phosphorylation was increased sevenfold in liver of PTP1B ASO-treated mice upon insulin stimulation, while phosphorylation of PKB substrates, glycogen synthase kinase (GSK)-3alpha and -3beta, was increased more than twofold. Peripheral insulin signaling was increased by PTP1B ASO, as evidenced by increased phosphorylation of PKB in muscle of insulin-stimulated PTP1B ASO-treated animals despite the lack of measurable effects on muscle PTP1B protein. These results indicate that reduction of PTP1B is sufficient to increase insulin-dependent metabolic signaling and improve insulin sensitivity in a diabetic animal model.
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Affiliation(s)
- Rebecca J Gum
- Metabolic Disease Research, Abbott Laboratories, Abbott Park, Illinois 60064, USA.
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Meyer MM, Levin K, Grimmsmann T, Perwitz N, Eirich A, Beck-Nielsen H, Klein HH. Troglitazone treatment increases protein kinase B phosphorylation in skeletal muscle of normoglycemic subjects at risk for the development of type 2 diabetes. Diabetes 2002; 51:2691-7. [PMID: 12196460 DOI: 10.2337/diabetes.51.9.2691] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We investigated whether the effect of troglitazone on glucose disposal is associated with altered insulin signaling. Nondiabetic first-degree relatives of type 2 diabetic patients (age 30 +/- 2 years, BMI 30 +/- 1 kg/m(2); n = 20) were randomized in a double-blind manner to 3 months of troglitazone (200 mg/day) or placebo treatment. Before and after treatment, 3-h euglycemic-hyperinsulinemic glucose clamps (40 mU. m(-2). min(-1)) were performed, and muscle biopsies were obtained immediately before and after the clamps. In the biopsies, insulin receptor kinase (IRK) activity, insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI3K) activity, Ser(473) and Thr(308) phosphorylation of protein kinase B (PKB), and protein expression of IRS-1, IRS-2, phosphoinositol-dependent kinase-1 (PDK-1), PKB, and GLUT-4 were determined. After troglitazone treatment, insulin-stimulated glucose disposal was increased compared with pretreatment and placebo (279 +/- 37 vs. 211 +/- 26 and 200 +/- 25 mg. m(-2). min(-1); both P < 0.05). IRK and PI3K activities were not altered by troglitazone, but PKB Ser(473) phosphorylation was enhanced compared with pretreatment and placebo at the clamp insulin level (138 +/- 36 vs. 77 +/- 16 and 55 +/- 13 internal standard units; both P < 0.05) and with pretreatment at the basal level (31 +/- 9 vs. 14 +/- 4 internal standard units; P < 0.05). PKB Thr(308) phosphorylation also tended to be higher, but this was not statistically significant. Troglitazone did not alter insulin receptor number or IRS-1, IRS-2, PKB, PDK-1, or GLUT-4 protein expression. We conclude that increased PKB phosphorylation may contribute to the insulin-sensitizing effects of thiazolidinediones in human skeletal muscle.
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Affiliation(s)
- Marco M Meyer
- Medizinische Klinik 1, Medizinische Universität zu Lübeck, Lübeck, Germany
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50
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Anthony JC, Reiter AK, Anthony TG, Crozier SJ, Lang CH, MacLean DA, Kimball SR, Jefferson LS. Orally administered leucine enhances protein synthesis in skeletal muscle of diabetic rats in the absence of increases in 4E-BP1 or S6K1 phosphorylation. Diabetes 2002; 51:928-36. [PMID: 11916909 DOI: 10.2337/diabetes.51.4.928] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In this study, food-deprived (18 h) control rats and rats with alloxan-induced diabetes were orally administered saline or the amino acid leucine to assess whether it regulates protein synthesis independently of a change in serum insulin concentrations. Immediately after leucine administration, diabetic rats were infused with insulin (0.0, 4.0, or 20 pmol small middle dot min(-1) small middle dot kg(-1)) for 1 h to examine the role of the hormone in the protein synthetic response to leucine. In control rats, leucine stimulated protein synthesis by 58% and increased phosphorylation of the translational repressor, eukaryotic initiation factor (eIF) 4E-binding protein (BP)-1, 4E-BP1, fivefold. Consequently, association of the mRNA cap-binding protein eukaryotic initiation factor (eIF)4E with 4E-BP1 was reduced to 50% of control values, and eIF4G*eIF4E complex assembly was increased 80%. Furthermore, leucine increased the phosphorylation of the 70-kDa ribosomal protein S6 (rp S6) and the ribosomal protein S6 kinase (S6K1). Diabetes attenuated protein synthesis compared with control rats. Nonetheless, in diabetic rats, leucine increased protein synthesis by 53% without concomitant changes in the phosphorylation of 4E-BP1 or S6K1. Skeletal muscle protein synthesis was stimulated in diabetic rats infused with insulin, but rates of synthesis remained less than values in nondiabetic controls that were administered leucine. Phosphorylation of 4E-BP1 and S6K1 was increased in diabetic rats infused with insulin in a dose-dependent manner, and the response was enhanced by leucine. The results suggest that leucine enhances protein synthesis in skeletal muscle through both insulin-dependent and -independent mechanisms. The insulin-dependent mechanism is associated with increased phosphorylation of 4E-BP1 and S6K1. In contrast, the insulin-independent effect on protein synthesis is mediated by an unknown mechanism.
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Affiliation(s)
- Joshua C Anthony
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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