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Ngakou Mukam J, Mvongo C, Nkoubat S, Fankem GO, Mfopa A, Noubissi PA, Fokam Tagne MA, Kamgang R, Essame Oyono JL. Early-induced diabetic obese rat MACAPOS 2. BMC Endocr Disord 2023; 23:64. [PMID: 36935499 PMCID: PMC10026472 DOI: 10.1186/s12902-022-01252-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 12/15/2022] [Indexed: 03/21/2023] Open
Abstract
BACKGROUND Diabetes mellitus is a metabolic disease characterized by an abnormally high blood glucose level. Glucose intolerance and insulin resistance are two characteristics that promote the onset and development of type 2 diabetes. The aim of this study was to create a diabetic rat model from obese rat MACAPOS 2. METHODS A group of rats was subjected to a high-fat diet (HFD) compared to a control group (NC) which received a normal diet. After 16 weeks of HFD, Lee index was calculated, obese rats were subjected to an oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). One group of HFD rats (HFDZ) received streptozotocin 22.5 mg/kg (iv). One week later, weight gain, water and food intakes, urine volume and fasting blood glucose levels were evaluated. Animals were also subjected to glucose tolerance and insulin tolerance tests. RESULTS After 16 weeks of HFD, rats became obese, glucose intolerant and resistant to insulin. The body weight of rats was significantly high (+ 26.23%) compared to normal rats, glycemia remained significantly high (+ 45.46%, P < 0.01) two hours after administration of glucose in high-fat diet rats, water intake and urine volume were comparable to those of NC. In HFD, the streptozotocin injected after one week (HFDZ), amplified glucose intolerance. During ITT, glycemia remained significantly (P < 0.01) high from 15 min; and did not vary during the 60 min of ITT. The fasting glycemia one week after streptozotocin injection was significantly high (288 mg/dL) compared to HFD (114 mg/dL), associated whit a significant (P < 0.01) increase in water intake and 24 h urine volume. CONCLUSION These results showed that MACAPOS 2 associated with a low dose of streptozotocin (22.5 mg/dL) early leads to the diabetes in obese albinos Wistar rats and could be a real model to study the type 2 diabetes mellitus.
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Affiliation(s)
- Joseph Ngakou Mukam
- Animal Physiology Laboratory, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon
| | - Clémence Mvongo
- Department of Life Sciences, High Teacher Training College of Bertoua, University of Bertoua, Bertoua, Cameroon
| | - Sandrine Nkoubat
- Animal Physiology Laboratory, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon
| | - Gaëtan Olivier Fankem
- Animal Physiology Laboratory, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon
| | - Adamou Mfopa
- Laboratory of Human Metabolism and non-Communicable Diseases, Institute of Medical Research and Medicinal Plants Studies (IMPM), Yaoundé, Cameroon
| | - Paul Aimé Noubissi
- Department of Animal Biology and Conservation, Faculty of Science, University of Buea, Buea, Cameroon
| | | | - René Kamgang
- Animal Physiology Laboratory, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon
- Laboratory of Human Metabolism and non-Communicable Diseases, Institute of Medical Research and Medicinal Plants Studies (IMPM), Yaoundé, Cameroon
| | - Jean-Louis Essame Oyono
- Laboratory of Human Metabolism and non-Communicable Diseases, Institute of Medical Research and Medicinal Plants Studies (IMPM), Yaoundé, Cameroon
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Manio MCC, Matsumura S, Masuda D, Inoue K. CD36 is essential for endurance improvement, changes in whole-body metabolism, and efficient PPAR-related transcriptional responses in the muscle with exercise training. Physiol Rep 2018; 5:e13282. [PMID: 28526781 PMCID: PMC5449563 DOI: 10.14814/phy2.13282] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 04/18/2017] [Indexed: 11/24/2022] Open
Abstract
Although circulating fatty acids are utilized as energy substrates, they also function as ligands to the peroxisome‐proliferator activated receptors (PPARs), a family of fatty acid sensing transcription factors. Exercise training leads to various adaptations in the muscle such as elevation of glycogen content, mitochondrial number as well as upregulation of fatty acid uptake and utilization through downstream transcriptional adaptations. In line with this, CD36 has been shown to be critical in controlling fatty acid uptake and consequently, fatty acid oxidation. We show that exercise training could not ameliorate impaired endurance performance in CD36 KO mice despite intact adaptations in muscle glycogen storage and mitochondrial function. Changes in whole‐body metabolism at rest and during exercise were also suppressed in these animals. Furthermore, there was inefficient upregulation of PPAR and PPAR‐related exercise‐responsive genes with chronic training in CD36 KO mice despite normal upregulation of Pgc1a and mitochondrial genes. Our findings supplement previous observations and emphasize the importance of CD36 in endurance performance, energy production and efficient downstream transcriptional regulation by PPARs.
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Affiliation(s)
- Mark Christian C Manio
- Laboratory of Nutrition Chemistry, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Shigenobu Matsumura
- Laboratory of Nutrition Chemistry, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Daisaku Masuda
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kazuo Inoue
- Laboratory of Nutrition Chemistry, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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3
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Evaluation of treadmill exercise effect on muscular lipid profiles of diabetic fatty rats by nanoflow liquid chromatography-tandem mass spectrometry. Sci Rep 2016; 6:29617. [PMID: 27388225 PMCID: PMC4937420 DOI: 10.1038/srep29617] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 06/22/2016] [Indexed: 01/01/2023] Open
Abstract
We compare comprehensive quantitative profiling of lipids at the molecular level from skeletal muscle tissues (gastrocnemius and soleus) of Zucker diabetic fatty rats and Zucker lean control rats during treadmill exercise by nanoflow liquid chromatography-tandem mass spectrometry. Because type II diabetes is caused by decreased insulin sensitivity due to excess lipids accumulated in skeletal muscle tissue, lipidomic analysis of muscle tissues under treadmill exercise can help unveil the mechanism of lipid-associated insulin resistance. In total, 314 lipid species, including phospholipids, sphingolipids, ceramides, diacylglycerols (DAGs), and triacylglycerols (TAGs), were analyzed to examine diabetes-related lipid species and responses to treadmill exercise. Most lysophospholipid levels increased with diabetes. While DAG levels (10 from the gastrocnemius and 13 from the soleus) were >3-fold higher in diabetic rats, levels of most of these decreased after exercise in soleus but not in gastrocnemius. Levels of 5 highly abundant TAGs (52:1 and 54:3 in the gastrocnemius and 48:2, 50:2, and 52:4 in the soleus) displaying 2-fold increases in diabetic rats decreased after exercise in the soleus but not in the gastrocnemius in most cases. Thus, aerobic exercise has a stronger influence on lipid levels in the soleus than in the gastrocnemius in type 2 diabetic rats.
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Pedersen DJ, Diakanastasis B, Stöckli J, Schmitz-Peiffer C. Protein kinase Cε modulates insulin receptor localization and trafficking in mouse embryonic fibroblasts. PLoS One 2013; 8:e58046. [PMID: 23469261 PMCID: PMC3585804 DOI: 10.1371/journal.pone.0058046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/30/2013] [Indexed: 12/03/2022] Open
Abstract
We have previously shown that deletion of protein kinase C epsilon (PKCε) in mice results in protection against glucose intolerance caused by a high fat diet. This was in part due to reduced insulin uptake by hepatocytes and insulin clearance, which enhanced insulin availability. Here we employed mouse embryonic fibroblasts (MEFs) derived from wildtype (WT) and PKCε-deficient (PKCε−/−) mice to examine this mechanistically. PKCε−/− MEFs exhibited reduced insulin uptake which was associated with decreased insulin receptor phosphorylation, while downstream signalling through IRS-1 and Akt was unaffected. Cellular fractionation demonstrated that PKCε deletion changed the localization of the insulin receptor, a greater proportion of which co-fractionated with flotillin-1, a marker of membrane microdomains. Insulin stimulation resulted in redistribution of the receptor in WT cells, while this was markedly reduced in PKCε−/− cells. These alterations in insulin receptor trafficking were associated with reduced expression of CEACAM1, a receptor substrate previously shown to modulate insulin clearance. Virally-mediated reconstitution of PKCε in MEFs increased CEACAM1 expression and partly restored the sensitivity of the receptor to insulin-stimulated redistribution. These data indicate that PKCε can affect insulin uptake in MEFs through promotion of receptor-mediated endocytosis, and that this may be mediated by regulation of CEACAM1 expression.
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Affiliation(s)
- David J. Pedersen
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Barbara Diakanastasis
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Jacqueline Stöckli
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
- * E-mail:
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Chellan N, Muller CJF, de Beer D, Joubert E, Page BJ, Louw J. An in vitro assessment of the effect of Athrixia phylicoides DC. aqueous extract on glucose metabolism. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2012; 19:730-736. [PMID: 22516895 DOI: 10.1016/j.phymed.2012.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 02/15/2012] [Accepted: 03/09/2012] [Indexed: 05/31/2023]
Abstract
Athrixia phylicoides DC. is an aromatic shrub indigenous to the eastern parts of Southern Africa. Indigenous communities brew "bush tea" from dried twigs and leaves of A. phylicoides, which is consumed as a beverage and used for its medicinal properties. Plant polyphenols have been shown to be beneficial to Type 2 diabetes mellitus (T2D) and obesity. Aqueous extracts of the plant have been shown to be rich in polyphenols, in particular phenolic acids, which may enhance glucose uptake and metabolism. The aim of this study was to determine the phenolic composition of a hot water A. phylicoides extract and assess its in vitro effect on cellular glucose utilisation. The most abundant phenolic compounds in the extract were 6-hydroxyluteolin-7-O-glucoside, chlorogenic acid, protocatechuic acid, a di-caffeoylquinic acid and a methoxy-flavonol derivative. The extract increased glucose uptake in C2C12, Chang and 3T3-L1 cells, respectively. Intracellular glucose was utilised by both oxidation (C2C12 myocytes and Chang cells; p < 0.01 and p < 0.05, respectively) and by increased glycogen storage (Chang cells; p < 0.05). No cytotoxicity was observed in Chang cells at the concentrations tested. The effects of the extract were not dose-dependent. A. phylicoides aqueous extract stimulated in vitro glucose uptake and metabolism, suggesting that consumption of this phenolic-rich extract could potentially ameliorate metabolic disorders related to obesity and T2D.
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Affiliation(s)
- N Chellan
- Diabetes Discovery Platform, Medical Research Council, PO Box 19070, Tygerberg 7505, South Africa.
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Iyoda T, Zhang F, Sun L, Hao F, Schmitz-Peiffer C, Xu X, Cui MZ. Lysophosphatidic acid induces early growth response-1 (Egr-1) protein expression via protein kinase Cδ-regulated extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) activation in vascular smooth muscle cells. J Biol Chem 2012; 287:22635-42. [PMID: 22577133 DOI: 10.1074/jbc.m111.335695] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Lysophosphatidic acid (LPA) modulates vascular cell function in vitro and in vivo via regulating the expression of specific genes. Previously, we reported that a transcriptional mechanism controls LPA-induced expression of Egr-1 in vascular smooth muscle cells. Egr-1 is a master transcription factor mediating the expression of various genes that have been implied to modulate a broad spectrum of vascular pathologies. In this study, we determined the essential intracellular signaling pathway leading to LPA-induced Egr-1 expression. Our data demonstrate that activation of ERK1/2 and JNK, but not p38 MAPK, is required for LPA-induced Egr-1 expression in smooth muscle cells. We provide the first evidence that MEK-mediated JNK activation leads to LPA-induced gene expression. JNK2 is required for Egr-1 induction. Examining the upstream kinases that mediate ERK and JNK activation, leading to Egr-1 expression, we found that LPA-induced activation of MAPKs and expression of Egr-1 are dependent on PKC activation. We observed that LPA rapidly activates PKCδ and PKCθ. Overexpression of dominant-negative PKCδ, but not dominant-negative PKCθ, diminished activation of ERK and JNK and blocked LPA-induced expression of Egr-1 mRNA and protein. We also evaluated LPA receptor involvement. Our data reveal an intracellular regulatory mechanism: LPA induction of Egr-1 expression is via LPA cognate receptor (LPA receptor 1)-dependent and PKCδ-mediated ERK and JNK activation. This study provides the first evidence that PKCδ mediates ERK and JNK activation in the LPA signaling pathway and that this pathway is required for LPA-induced gene regulation as evidenced by Egr-1 expression.
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Affiliation(s)
- Takuya Iyoda
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Tennessee 37996, USA
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Schmitz-Peiffer C, Biden TJ. Protein kinase C function in muscle, liver, and beta-cells and its therapeutic implications for type 2 diabetes. Diabetes 2008; 57:1774-83. [PMID: 18586909 PMCID: PMC2453608 DOI: 10.2337/db07-1769] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 04/15/2008] [Indexed: 01/27/2023]
Affiliation(s)
| | - Trevor J. Biden
- From the Garvan Institute of Medical Research, Darlinghurst, Australia
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8
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Cazzolli R, Mitchell TW, Burchfield JG, Pedersen DJ, Turner N, Biden TJ, Schmitz-Peiffer C. Dilinoleoyl-phosphatidic acid mediates reduced IRS-1 tyrosine phosphorylation in rat skeletal muscle cells and mouse muscle. Diabetologia 2007; 50:1732-42. [PMID: 17593346 DOI: 10.1007/s00125-007-0709-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2007] [Accepted: 04/20/2007] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS Insulin resistance in skeletal muscle is strongly associated with lipid oversupply, but the intracellular metabolites and underlying mechanisms are unclear. We therefore sought to identify the lipid intermediates through which the common unsaturated fatty acid linoleate causes defects in IRS-1 signalling in L6 myotubes and mouse skeletal muscle. MATERIALS AND METHODS Cells were pre-treated with 1 mmol/l linoleate for 24 h. Subsequent insulin-stimulated IRS-1 tyrosine phosphorylation and its association with the p85 subunit of phosphatidylinositol 3-kinase were determined by immunoblotting. Intracellular lipid species and protein kinase C activation were modulated by overexpression of diacylglycerol kinase epsilon, which preferentially converts unsaturated diacylglycerol into phosphatidic acid, or by inhibition of lysophosphatidic acid acyl transferase with lisofylline, which reduces phosphatidic acid synthesis. Phosphatidic acid species in linoleate-treated cells or muscle from insulin-resistant mice fed a safflower oil-based high-fat diet that was rich in linoleate were analysed by mass spectrometry. RESULTS Linoleate pretreatment reduced IRS-1 tyrosine phosphorylation and p85 association. Overexpression of diacylglycerol kinase epsilon reversed the activation of protein kinase C isoforms by linoleate, but paradoxically further diminished IRS-1 tyrosine phosphorylation. Conversely, lisofylline treatment restored IRS-1 phosphorylation. Mass spectrometry indicated that the dilinoleoyl-phosphatidic acid content increased from undetectable levels to almost 20% of total phosphatidic acid in L6 cells and to 8% of total in the muscle of mice fed a high-fat diet. Micelles containing dilinoleoyl-phosphatidic acid specifically inhibited IRS-1 tyrosine phosphorylation and glycogen synthesis in L6 cells. CONCLUSIONS/INTERPRETATION These data indicate that linoleate-derived phosphatidic acid is a novel lipid species that contributes independently of protein kinase C to IRS-1 signalling defects in muscle cells in response to lipid oversupply.
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Affiliation(s)
- R Cazzolli
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia
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Specific protein kinase C isoforms as transducers and modulators of insulin signaling. Mol Genet Metab 2006; 89:32-47. [PMID: 16798038 DOI: 10.1016/j.ymgme.2006.04.017] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2006] [Revised: 04/23/2006] [Accepted: 04/23/2006] [Indexed: 12/14/2022]
Abstract
Recent studies implicate specific PKC isoforms in the insulin-signaling cascade. Insulin activates PKCs alpha, betaII, delta and zeta in several cell types. In addition, as will be documented in this review, certain members of the PKC family may also be activated and act upstream of PI3 and MAP kinases. Each of these isoforms has been shown one way or another either to mimic or to modify insulin-stimulated effects in one or all of the insulin-responsive tissues. Moreover, each of the isoforms has been shown to be activated by insulin stimulation or conditions important for effective insulin stimulation. Studies attempting to demonstrate a definitive role for any of the isoforms have been performed on different cells, ranging from appropriate model systems for skeletal muscle, liver and fat, such as primary cultures, and cell lines and even in vivo studies, including transgenic mice with selective deletion of specific PKC isoforms. In addition, studies have been done on certain expression systems such as CHO or HEK293 cells, which are far removed from the tissues themselves and serve mainly as vessels for potential protein-protein interactions. Thus, a clear picture for many of the isoforms remains elusive in spite of over two decades of intensive research. The recent intrusion of transgenic and precise molecular biology technologies into the research armamentarium has opened a wide range of additional possibilities for direct involvement of individual isoforms in the insulin signaling cascade. As we hope to discuss within the context of this review, whereas many of the long sought-after answers to specific questions are not yet clear, major advances have been made in our understanding of precise roles for individual PKC isoforms in mediation of insulin effects. In this review, in which we shall focus our attention on isoforms in the conventional and novel categories, a clear case will be made to show that these isoforms are not only expressed but are importantly involved in regulation of insulin metabolic effects.
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Taneja N, Coy PE, Lee I, Bryson JM, Robey RB. Proinflammatory interleukin-1 cytokines increase mesangial cell hexokinase activity and hexokinase II isoform abundance. Am J Physiol Cell Physiol 2004; 287:C548-57. [PMID: 15070811 DOI: 10.1152/ajpcell.00126.2003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mesangial cell hexokinase (HK) activity is increased by a diverse array of factors that share both an association with pathological conditions and a common requirement for classic MAPK pathway activation. To better understand the relationship between glucose (Glc) metabolism and injury and to indirectly test the hypothesis that these changes constitute a general adaptive response to insult, we have sought to identify and characterize injury-associated factors that couple to mesangial cell HK regulation. Proinflammatory interleukin-1 (IL-1) cytokines activate the MAPK pathway and have known salutary effects in this cell type. We therefore examined their ability to influence mesangial cell HK activity, Glc utilization, MAPK pathway activation, and individual HK isoform abundance. IL-1β increased HK activity in both a time- and concentration-dependent manner: activity increased maximally by ∼50% between 12 and 24 h with an apparent EC50of 3 pM. IL-1α mimicked, but did not augment, the effects of IL-1β. Specific IL-1 receptor antagonism and selective MAPK/ERK kinase or upstream Ras inhibition prevented these increases, whereas PKC inhibition did not. Changes in HK activity were associated with both increased Glc metabolism and selective increases in HKII isoform abundance. We conclude that IL-1 cytokines can regulate cellular Glc phosphorylating capacity via an IL-1 receptor-, Ras-, and classic MAPK pathway-mediated increase in HKII abundance. These findings suggest a novel, previously undescribed mechanism whereby metabolism may be coupled to inflammation and injury.
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Affiliation(s)
- Navin Taneja
- Dept. of Medicine, Section of Nephrology, University of Illinois at Chicago College of Medicine, 820 South Wood Street, Rm. 418W CSN (M/C 793), Chicago, IL 60612-7315, USA
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11
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Doi M, Yamaoka I, Fukunaga T, Nakayama M. Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes. Biochem Biophys Res Commun 2004; 312:1111-7. [PMID: 14651987 DOI: 10.1016/j.bbrc.2003.11.039] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To examine which branched-chain amino acids affect the plasma glucose levels, we investigated the effects of leucine, isoleucine, and valine (0.3 g/kg body weight p.o.) in normal rats using the oral glucose tolerance test (OGTT, 2 g/kg). A single oral administration of isoleucine significantly reduced plasma glucose levels 30 and 60 min after the glucose bolus, whereas administration of leucine and valine did not produce a significant decrease. Oral administration of valine significantly enhanced the plasma glucose level at 30 min after the glucose administration and leucine had a similar effect at 120 min. At each measurement timepoint, the insulin levels of the treated groups were lower than that of the control group. We then investigated the effects of leucine, isoleucine or valine at the same concentration (1 mM) on glucose metabolism in C(2)C(12) myotubes in the absence of insulin. Glucose consumption was elevated by 16.8% in the presence of 1 mM isoleucine compared with the control. Conversely, 1 mM leucine or valine caused no significant changes in glucose consumption in the C(2)C(12) myotubes. The 2-deoxyglucose uptake of C(2)C(12) myotubes significantly increased upon exposure to 1-10 mM isoleucine and 5-10 mM leucine. However, isoleucine caused no significant difference in glycogen synthesis in C(2)C(12) myotubes, although leucine and valine caused a significant increase in intracellular glycogen compared with the control. The isoleucine effect on glucose uptake was mediated by phosphatidylinositol 3-kinase (PI3K), but was independent of mammalian target of rapamycin (mTOR). These results suggest that isoleucine stimulates the insulin-independent glucose uptake in skeletal muscle cells, which may contribute to the plasma glucose-lowering effect of isoleucine in normal rats.
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Affiliation(s)
- Masako Doi
- Division of Pharmacology, Drug Safety and Metabolism, Otsuka Pharmaceutical Factory, Inc. Muya-cho, 772-8601, Naruto, Tokushima, Japan.
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Al-Khalili L, Cartee GD, Krook A. RNA interference-mediated reduction in GLUT1 inhibits serum-induced glucose transport in primary human skeletal muscle cells. Biochem Biophys Res Commun 2003; 307:127-32. [PMID: 12849991 DOI: 10.1016/s0006-291x(03)01124-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Using RNA interference (RNAi), we specifically down-regulate protein expression in differentiated human skeletal myotube cultures. Serum stimulation of myotubes increases glucose uptake. Using a sensitive photolabeling technique, we demonstrate that this increase in glucose uptake is accompanied by increased cell-surface content of glucose transporter (GLUT) 1. Using RNAi, we specifically reduce GLUT1 mRNA and protein expression, leading to inhibition of serum-mediated increase in glucose transport. Thus, we demonstrate the utility of RNAi in a primary human differentiated cell system, and apply this methodology to demonstrate that serum-mediated increase in glucose transport in human skeletal muscle cells is dependent on GLUT1.
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Affiliation(s)
- Lubna Al-Khalili
- Department of Surgical Science, Karolinska Institute, S-171 77, Stockholm, Sweden
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13
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Wang L, Rolfe M, Proud CG. Ca(2+)-independent protein kinase C activity is required for alpha1-adrenergic-receptor-mediated regulation of ribosomal protein S6 kinases in adult cardiomyocytes. Biochem J 2003; 373:603-11. [PMID: 12720544 PMCID: PMC1223514 DOI: 10.1042/bj20030454] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2003] [Revised: 04/29/2003] [Accepted: 04/30/2003] [Indexed: 02/04/2023]
Abstract
The alpha(1)-adrenergic agonist, phenylephrine (PE), exerts hypertrophic effects in the myocardium and activates protein synthesis. Both Ca(2+)-dependent protein kinase C (PKC, PKCalpha) and Ca(2+)-independent PKC isoforms (PKCdelta and epsilon ) are detectably expressed in adult rat cardiomyocytes. Stimulation of the alpha(1)-adrenergic receptor by PE results in activation of Ca(2+)-independent PKCs, as demonstrated by translocation of the delta and epsilon isoenzymes from cytosol to membrane fractions. PE also induces activation of p70 ribosomal protein S6 kinases (S6K1 and 2) in adult cardiomyocytes. We have studied the role of Ca(2+)-independent PKCs in the regulation of S6K activity by PE. Activation of S6K1/2 by PE was blocked by the broad-spectrum PKC inhibitor bisindolylmaleimide (BIM) I, whereas Gö6976, a compound that only inhibits Ca(2+)-dependent PKCs, did not inhibit S6K activation. Rottlerin, which selectively inhibits PKCdelta, also prevented PE-induced S6K activation. The isoform-specific PKC inhibitors had similar effects on the phosphorylation of eukaryotic initiation factor 4E (eIF4E)-binding protein 1, a translation repressor that, like the S6Ks, lies downstream of the mammalian target of rapamycin (mTOR). Infection of cells with adenoviruses encoding dominant-negative PKCdelta or epsilon inhibited the activation of extracellular-signal-regulated kinase (ERK) by PE, and also inhibited the activation and/or phosphorylation of S6Ks 1 and 2. The PE-induced activation of protein synthesis was abolished by BIM I and markedly attenuated by rottlerin. Our data thus suggest that Ca(2+)-independent PKC isoforms play an important role in coupling the alpha(1)-adrenergic receptor to mTOR signalling and protein synthesis in adult cardiomyocytes.
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Affiliation(s)
- Lijun Wang
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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14
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Serra C, Federici M, Buongiorno A, Senni MI, Morelli S, Segratella E, Pascuccio M, Tiveron C, Mattei E, Tatangelo L, Lauro R, Molinaro M, Giaccari A, Bouché M. Transgenic mice with dominant negative PKC-theta in skeletal muscle: a new model of insulin resistance and obesity. J Cell Physiol 2003; 196:89-97. [PMID: 12767044 DOI: 10.1002/jcp.10278] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Protein kinase C theta (PKC-theta) is the PKC isoform predominantly expressed in skeletal muscle, and it is supposed to mediate many signals necessary for muscle histogenesis and homeostasis, such as TGFbeta, nerve-dependent signals and insulin. To study the role of PKC-theta in these mechanisms we generated transgenic mice expressing a "kinase dead" mutant form of PKC-theta (PKC-thetaK/R), working as "dominant negative," specifically in skeletal muscle. These mice are viable and fertile, however, by the 6-7 months of age, they gain weight, mainly due to visceral fat deposition. Before the onset of obesity (4 months of age), they already show increased fasting and fed insulin levels and reduced insulin-sensitivity, as measured by ipITT, but normal glucose tolerance, as measured by ipGTT. After the 6-7 months of age, transgenic mice develop hyperinsulinemia in the fasting and fed state. The ipGTT revealed in the transgenic mice both hyperglycemia and hyperinsulinemia. At the molecular level, impaired activation of the IR/IRS/PI3K pathway and a significant decrease both in the levels and in insulin-stimulated activation of the serine/threonine kinase Akt were observed. Taken together these data demonstrate that over-expression of dominant negative PKC-theta in skeletal muscle causes obesity associated to insulin resistance, as demonstrated by defective receptor and post-receptorial activation of signaling cascade.
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Affiliation(s)
- C Serra
- Department of Histology and Medical Embryology, University of Rome La Sapienza, Rome, Italy
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