1
|
Krycer JR, Quek LE, Francis D, Zadoorian A, Weiss FC, Cooke KC, Nelson ME, Diaz-Vegas A, Humphrey SJ, Scalzo R, Hirayama A, Ikeda S, Shoji F, Suzuki K, Huynh K, Giles C, Varney B, Nagarajan SR, Hoy AJ, Soga T, Meikle PJ, Cooney GJ, Fazakerley DJ, James DE. Insulin signaling requires glucose to promote lipid anabolism in adipocytes. J Biol Chem 2020; 295:13250-13266. [PMID: 32723868 DOI: 10.1074/jbc.ra120.014907] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/14/2020] [Indexed: 12/12/2022] Open
Abstract
Adipose tissue is essential for metabolic homeostasis, balancing lipid storage and mobilization based on nutritional status. This is coordinated by insulin, which triggers kinase signaling cascades to modulate numerous metabolic proteins, leading to increased glucose uptake and anabolic processes like lipogenesis. Given recent evidence that glucose is dispensable for adipocyte respiration, we sought to test whether glucose is necessary for insulin-stimulated anabolism. Examining lipogenesis in cultured adipocytes, glucose was essential for insulin to stimulate the synthesis of fatty acids and glyceride-glycerol. Importantly, glucose was dispensable for lipogenesis in the absence of insulin, suggesting that distinct carbon sources are used with or without insulin. Metabolic tracing studies revealed that glucose was required for insulin to stimulate pathways providing carbon substrate, NADPH, and glycerol 3-phosphate for lipid synthesis and storage. Glucose also displaced leucine as a lipogenic substrate and was necessary to suppress fatty acid oxidation. Together, glucose provided substrates and metabolic control for insulin to promote lipogenesis in adipocytes. This contrasted with the suppression of lipolysis by insulin signaling, which occurred independently of glucose. Given previous observations that signal transduction acts primarily before glucose uptake in adipocytes, these data are consistent with a model whereby insulin initially utilizes protein phosphorylation to stimulate lipid anabolism, which is sustained by subsequent glucose metabolism. Consequently, lipid abundance was sensitive to glucose availability, both during adipogenesis and in Drosophila flies in vivo Together, these data highlight the importance of glucose metabolism to support insulin action, providing a complementary regulatory mechanism to signal transduction to stimulate adipose anabolism.
Collapse
Affiliation(s)
- James R Krycer
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Lake-Ee Quek
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; School of Mathematics and Statistics, University of Sydney, Sydney, New South Wales, Australia
| | - Deanne Francis
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Armella Zadoorian
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Fiona C Weiss
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Kristen C Cooke
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Marin E Nelson
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Alexis Diaz-Vegas
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Sean J Humphrey
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Richard Scalzo
- Faculty of Engineering and Information Technologies, University of Sydney, Sydney, New South Wales, Australia
| | - Akiyoshi Hirayama
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan; AMED-CREST, Japan Agency for Medical Research and Development (AMED), Otemachi, Chiyoda-Ku, Tokyo, Japan
| | - Satsuki Ikeda
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Futaba Shoji
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Kumi Suzuki
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Kevin Huynh
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Corey Giles
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Bianca Varney
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Shilpa R Nagarajan
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Andrew J Hoy
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Tomoyoshi Soga
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan; AMED-CREST, Japan Agency for Medical Research and Development (AMED), Otemachi, Chiyoda-Ku, Tokyo, Japan
| | - Peter J Meikle
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Gregory J Cooney
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Daniel J Fazakerley
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - David E James
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
| |
Collapse
|
2
|
Tanataweethum N, Zhong F, Trang A, Lee C, Cohen RN, Bhushan A. Towards an Insulin Resistant Adipose Model on a Chip. Cell Mol Bioeng 2020; 14:89-99. [PMID: 33643468 DOI: 10.1007/s12195-020-00636-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 07/07/2020] [Indexed: 12/25/2022] Open
Abstract
Introduction Adipose tissue and adipocytes are primary regulators of insulin sensitivity and energy homeostasis. Defects in insulin sensitivity of the adipocytes predispose the body to insulin resistance (IR) that could lead to diabetes. However, the mechanisms mediating adipocyte IR remain elusive, which emphasizes the need to develop experimental models that can validate the insulin signaling pathways and discover new mechanisms in the search for novel therapeutics. Currently in vitro adipose organ-chip devices show superior cell function over conventional cell culture. However, none of these models represent disease states. Only when these in vitro models can represent both healthy and disease states, they can be useful for developing therapeutics. Here, we establish an organ-on-chip model of insulin-resistant adipocytes, as well as characterization in terms of insulin signaling pathway and lipid metabolism. Methods We differentiated, maintained, and induced insulin resistance into primary adipocytes in a microfluidic organ-on-chip. We then characterized IR by looking at the insulin signaling pathway and lipid metabolism, and validated by studying a diabetic drug, rosiglitazone. Results We confirmed the presence of insulin resistance through reduction of Akt phosphorylation, Glut4 expression, Glut4 translocation and glucose uptake. We also confirmed defects of disrupted insulin signaling through reduction of lipid accumulation from fatty acid uptake and elevation of glycerol secretion. Testing with rosiglitazone showed a significant improvement in insulin sensitivity and fatty acid metabolism as suggested by previous reports. Conclusions The adipose-chip exhibited key characteristics of IR and can serve as model to study diabetes and facilitate discovery of novel therapeutics.
Collapse
Affiliation(s)
- Nida Tanataweethum
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616 USA
| | - Franklin Zhong
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616 USA
| | - Allyson Trang
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616 USA
| | - Chaeeun Lee
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616 USA
| | - Ronald N Cohen
- Section of Endocrinology, Department of Medicine, The University of Chicago, Chicago, IL 60637 USA
| | - Abhinav Bhushan
- Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL 60616 USA
| |
Collapse
|
3
|
Kearney AL, Cooke KC, Norris DM, Zadoorian A, Krycer JR, Fazakerley DJ, Burchfield JG, James DE. Serine 474 phosphorylation is essential for maximal Akt2 kinase activity in adipocytes. J Biol Chem 2019; 294:16729-16739. [PMID: 31548312 DOI: 10.1074/jbc.ra119.010036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 09/15/2019] [Indexed: 01/06/2023] Open
Abstract
The Ser/Thr protein kinase Akt regulates essential biological processes such as cell survival, growth, and metabolism. Upon growth factor stimulation, Akt is phosphorylated at Ser474; however, how this phosphorylation contributes to Akt activation remains controversial. Previous studies, which induced loss of Ser474 phosphorylation by ablating its upstream kinase mTORC2, have implicated Ser474 phosphorylation as a driver of Akt substrate specificity. Here we directly studied the role of Akt2 Ser474 phosphorylation in 3T3-L1 adipocytes by preventing Ser474 phosphorylation without perturbing mTORC2 activity. This was achieved by utilizing a chemical genetics approach, where ectopically expressed S474A Akt2 was engineered with a W80A mutation to confer resistance to the Akt inhibitor MK2206, and thus allow its activation independent of endogenous Akt. We found that insulin-stimulated phosphorylation of four bona fide Akt substrates (TSC2, PRAS40, FOXO1/3a, and AS160) was reduced by ∼50% in the absence of Ser474 phosphorylation. Accordingly, insulin-stimulated mTORC1 activation, protein synthesis, FOXO nuclear exclusion, GLUT4 translocation, and glucose uptake were attenuated upon loss of Ser474 phosphorylation. We propose a model where Ser474 phosphorylation is required for maximal Akt2 kinase activity in adipocytes.
Collapse
Affiliation(s)
- Alison L Kearney
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kristen C Cooke
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Dougall M Norris
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Armella Zadoorian
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - James R Krycer
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Daniel J Fazakerley
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - James G Burchfield
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia .,Sydney Medical School, University of Sydney, Sydney, New South Wales 2006, Australia
| |
Collapse
|
4
|
Krycer JR, Yugi K, Hirayama A, Fazakerley DJ, Quek LE, Scalzo R, Ohno S, Hodson MP, Ikeda S, Shoji F, Suzuki K, Domanova W, Parker BL, Nelson ME, Humphrey SJ, Turner N, Hoehn KL, Cooney GJ, Soga T, Kuroda S, James DE. Dynamic Metabolomics Reveals that Insulin Primes the Adipocyte for Glucose Metabolism. Cell Rep 2018; 21:3536-3547. [PMID: 29262332 DOI: 10.1016/j.celrep.2017.11.085] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/06/2017] [Accepted: 11/22/2017] [Indexed: 01/13/2023] Open
Abstract
Insulin triggers an extensive signaling cascade to coordinate adipocyte glucose metabolism. It is considered that the major role of insulin is to provide anabolic substrates by activating GLUT4-dependent glucose uptake. However, insulin stimulates phosphorylation of many metabolic proteins. To examine the implications of this on glucose metabolism, we performed dynamic tracer metabolomics in cultured adipocytes treated with insulin. Temporal analysis of metabolite concentrations and tracer labeling revealed rapid and distinct changes in glucose metabolism, favoring specific glycolytic branch points and pyruvate anaplerosis. Integrating dynamic metabolomics and phosphoproteomics data revealed that insulin-dependent phosphorylation of anabolic enzymes occurred prior to substrate accumulation. Indeed, glycogen synthesis was activated independently of glucose supply. We refer to this phenomenon as metabolic priming, whereby insulin signaling creates a demand-driven system to "pull" glucose into specific anabolic pathways. This complements the supply-driven regulation of anabolism by substrate accumulation and highlights an additional role for insulin action in adipocyte glucose metabolism.
Collapse
Affiliation(s)
- James R Krycer
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia
| | - Katsuyuki Yugi
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan; YCI Laboratory for Trans-Omics, Young Chief Investigator Program, RIKEN Center for Integrative Medical Sciences, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; PRESTO, Japan Science and Technology Agency, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan
| | - Akiyoshi Hirayama
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan; AMED-CREST, AMED, 1-7-1 Otemachi, Chiyoda-Ku, Tokyo 100-0004, Japan
| | - Daniel J Fazakerley
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia
| | - Lake-Ee Quek
- Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia; School of Mathematics and Statistics, The University of Sydney, Sydney NSW 2006, Australia
| | - Richard Scalzo
- Centre for Translational Data Science, University of Sydney, Sydney, NSW 2006, Australia
| | - Satoshi Ohno
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Mark P Hodson
- Metabolomics Australia Queensland Node, Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, QLD 4072, Australia; School of Pharmacy, Faculty of Health and Behavioural Sciences, University of Queensland, Brisbane, QLD 4072, Australia; Metabolomics Research Laboratory, Victor Chang Innovation Centre, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia
| | - Satsuki Ikeda
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan
| | - Futaba Shoji
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan
| | - Kumi Suzuki
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan
| | - Westa Domanova
- Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia; School of Physics, University of Sydney, Sydney, NSW 2006, Australia
| | - Benjamin L Parker
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia
| | - Marin E Nelson
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia
| | - Sean J Humphrey
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia
| | - Nigel Turner
- School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Kyle L Hoehn
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Gregory J Cooney
- Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia
| | - Tomoyoshi Soga
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan; AMED-CREST, AMED, 1-7-1 Otemachi, Chiyoda-Ku, Tokyo 100-0004, Japan
| | - Shinya Kuroda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan; CREST, Japan Science and Technology Agency, Bunkyo-ku, Tokyo 113-0033, Japan.
| | - David E James
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia.
| |
Collapse
|
5
|
Tan SX, Fisher-Wellman KH, Fazakerley DJ, Ng Y, Pant H, Li J, Meoli CC, Coster ACF, Stöckli J, James DE. Selective insulin resistance in adipocytes. J Biol Chem 2015; 290:11337-48. [PMID: 25720492 DOI: 10.1074/jbc.m114.623686] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Indexed: 12/14/2022] Open
Abstract
Aside from glucose metabolism, insulin regulates a variety of pathways in peripheral tissues. Under insulin-resistant conditions, it is well known that insulin-stimulated glucose uptake is impaired, and many studies attribute this to a defect in Akt signaling. Here we make use of several insulin resistance models, including insulin-resistant 3T3-L1 adipocytes and fat explants prepared from high fat-fed C57BL/6J and ob/ob mice, to comprehensively distinguish defective from unaffected aspects of insulin signaling and its downstream consequences in adipocytes. Defective regulation of glucose uptake was observed in all models of insulin resistance, whereas other major actions of insulin such as protein synthesis and anti-lipolysis were normal. This defect corresponded to a reduction in the maximum response to insulin. The pattern of change observed for phosphorylation in the Akt pathway was inconsistent with a simple defect at the level of Akt. The only Akt substrate that showed consistently reduced phosphorylation was the RabGAP AS160 that regulates GLUT4 translocation. We conclude that insulin resistance in adipose tissue is highly selective for glucose metabolism and likely involves a defect in one of the components regulating GLUT4 translocation to the cell surface in response to insulin.
Collapse
Affiliation(s)
- Shi-Xiong Tan
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia
| | - Kelsey H Fisher-Wellman
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia
| | | | - Yvonne Ng
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia
| | - Himani Pant
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia
| | - Jia Li
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia
| | - Christopher C Meoli
- From the Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales 2010, Australia, the Charles Perkins Centre, School of Molecular Biosciences and
| | - Adelle C F Coster
- the School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | | | - David E James
- the Charles Perkins Centre, School of Molecular Biosciences and the School of Medicine, University of Sydney, New South Wales 2006, Australia, and
| |
Collapse
|
6
|
Abstract
A greater understanding of the factors causing the enhanced release of leptin by adipocytes in obesity is needed. Experiments were designed to determine the effects of actinomycin D on leptin release by isolated rat adipocytes during primary culture for 24 hr. In adipocytes from fed hypothyroid rats, the initial rate of leptin release over the first 6 hr was not maintained over the next 18 hr. The decline in leptin release by adipocytes in primary culture between 6 and 24 hr was reduced markedly by either dexamethasone or actinomycin D. Both actinomycin D and dexamethasone also reduced the loss of leptin mRNA seen over the 24-hr incubation. Maximal effects on leptin release and leptin mRNA accumulation required only 0.1 microM of actinomycin D, a concentration that had no significant effect on the 18S RNA content of adipocytes at the end of a 24-hr incubation. In contrast to the reduced loss of leptin mRNA seen at 24 hr, the loss of glyceraldehyde-3-phosphate dehydrogenase messenger ribonucleic acid (GAPDH mRNA) was enhanced in the presence of 0.1 microM of actinomycin D. The effects of dexamethasone could be differentiated from those of actinomycin D by the finding that cycloheximide blocked the reduced loss of leptin mRNA due to dexamethasone while having no effect on that due to actinomycin D. These results point to a unique regulation of leptin release and leptin mRNA levels by actinomycin D.
Collapse
Affiliation(s)
- J N Fain
- Department of Biochemistry, College of Medicine, University of Tennessee at Memphis, 38163, USA.
| | | |
Collapse
|
7
|
Holloszy JO, Hansen PA. Regulation of glucose transport into skeletal muscle. Rev Physiol Biochem Pharmacol 1996; 128:99-193. [PMID: 8791721 DOI: 10.1007/3-540-61343-9_8] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- J O Holloszy
- Washington University School of Medicine, Department of Internal Medicine, St. Louis, MO 63110, USA
| | | |
Collapse
|
8
|
Jochen AL, Hays J, Mick G. Inhibitory effects of cerulenin on protein palmitoylation and insulin internalization in rat adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1259:65-72. [PMID: 7492617 DOI: 10.1016/0005-2760(95)00147-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Protein acylation by long-chain fatty acids has been suggested as a necessary step in membrane trafficking. Because several insulin effects are dependent upon membrane trafficking, the cellular effects of the protein acylation inhibitor cerulenin were examined. Cerulenin blocked palmitoylation of selected rat adipocyte proteins including CD36, the dominant marker for palmitoylation in adipocytes. To measure cerulenin's effects on insulin internalization, rat adipocytes were incubated with 125I-insulin at 37 degrees C in the presence or absence of cerulenin. Surface-bound and intracellular insulin were discriminated by the sensitivity of the former to rapid dissociation by a pH 3 buffer at 4 degrees C. Insulin internalization was inhibited 85% by 0.3 mM cerulenin. Inhibition required preincubation with the agent, was irreversible, was not dependent upon protein synthesis, and was not the result of ATP depletion. Cerulenin was also found to inhibit insulin-stimulated glucose uptake and acetyl-CoA carboxylase activity. Cerulenin had no effect on basal glucose uptake and utilization or on the uptake and retention of fatty acids. In summary, protein acylation may be an important step in insulin-regulated cellular functions dependent upon membrane trafficking, such as insulin internalization.
Collapse
Affiliation(s)
- A L Jochen
- Department of Medicine, Zablocki Veterans Administration Medical Center, Medical College of Wisconsin, Milwaukee 53226, USA
| | | | | |
Collapse
|
9
|
Almås B, Pryme IF, Vedeler A, Hesketh JE. Insulin: signal transmission and short-term effects on the cytoskeleton and protein synthesis. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1992; 24:183-91. [PMID: 1733785 DOI: 10.1016/0020-711x(92)90246-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- B Almås
- Department of Biochemistry, University of Bergen, Norway
| | | | | | | |
Collapse
|
10
|
Stevenson RW, McPherson RK, Genereux PE, Danbury BH, Kreutter DK. Antidiabetic agent englitazone enhances insulin action in nondiabetic rats without producing hypoglycemia. Metabolism 1991; 40:1268-74. [PMID: 1961119 DOI: 10.1016/0026-0495(91)90027-t] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The new antihyperglycemic agent englitazone (CP-68,722) was examined in nondiabetic rats. Administration of englitazone at 50 mg/kg/d for 8 days did not produce overt hypoglycemia but it lowered basal plasma insulin by 59% and 41% in rats fed ad libitum and fasted overnight on the last day, respectively. Drug treatment also lowered (P less than .05) plasma nonesterified fatty acids (1.09 +/- 0.05 to 0.36 +/- 0.05 mmol/L) and cholesterol (2.41 +/- 0.08 to 2.06 +/- 0.07 mmol/L) in fasted rats, and glycerol (0.25 +/- 0.02 to 0.14 +/- 0.02 mmol/L) in fed rats but had no effect on 3-hydroxybutyrate or lactate levels despite the hypoinsulinemia. Disposition of an oral glucose load (1 g/kg) in drug-treated fed rats was identical to that in control rats despite a 40% reduction in the area under the plasma insulin curve. Insulin-stimulated 2-deoxy-D-3H-glucose uptake was significantly (P less than .05) enhanced in adipocytes prepared from both fasted and fed drug-treated rats (0.56 +/- 0.07 to 0.84 +/- 0.03 and 0.79 +/- 0.02 to 1.00 +/- 0.02 nmol/5 min, respectively, at insulin concentration of 2,500 microU/mL). There was also a significant increase in the basal rate of 2-deoxyglucose uptake (0.07 +/- 0.01 to 0.24 +/- 0.07 nmol/5 min) in adipocytes from fasted rats only. Insulin-stimulated lipogenesis from 3H-2-glucose was enhanced in adipocytes from drug-treated fed rats (7.72 +/- 0.09 to 10.19 +/- 0.10 nmol glucose/45 min at insulin concentration of 2,500 microU/mL) but no effect was observed in adipocytes from fasted rats (2.57 +/- 0.30 to 2.33 +/- 0.16 nmol glucose/45 min).(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- R W Stevenson
- Department of Metabolic Diseases, Pfizer Inc, Groton, CT 06340
| | | | | | | | | |
Collapse
|
11
|
Coordinated regulation of glutamine:fructose-6-phosphate amidotransferase activity by insulin, glucose, and glutamine. Role of hexosamine biosynthesis in enzyme regulation. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99202-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
|
12
|
Epand RM, Stafford AR, Debanne MT. Action of insulin in rat adipocytes and membrane properties. Biochemistry 1991; 30:2092-8. [PMID: 1998671 DOI: 10.1021/bi00222a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Several small peptides inhibit insulin-promoted glucose uptake in rat adipocytes. At 10 microM peptide concentration, the extent of their inhibition of the insulin effect is related to the ability of these peptides to raise the bilayer- to hexagonal-phase transition temperature in model membranes. Hexane and DL-threo-dihydrosphingosine lower this phase transition temperature in model membranes, and they promote glucose uptake in adipocytes. There is thus an empirical relationship between the action of membrane additives on glucose uptake in adipocytes and their effect on the hexagonal-phase-forming tendency in model membranes. The most potent of the bilayer-stabilizing peptides tested in this work is carbobenzoxy-D-Phe-L-Phe-Gly. This peptide also inhibits insulin-stimulated protein synthesis in adipocytes. In contrast, DL-threo-dihydrosphingosine stimulates protein synthesis. The uptake of [125I]iodoinsulin by adipocytes is inhibited by carbobenzoxy-D-Phe-L-Phe-Gly. The mechanism of action of the bilayer-stabilizing peptides includes inhibition of insulin-dependent protein phosphorylation in adipocytes. The peptides are not specific inhibitors of a single function but are suggested to cause their effects by altering the physical properties of the membrane in a nonspecific manner. These results demonstrate that insulin-dependent functions of rat adipocytes can be modified by membrane additives in a manner predictable from the properties of these additives in model membranes.
Collapse
Affiliation(s)
- R M Epand
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada
| | | | | |
Collapse
|
13
|
Gulve EA, Cartee GD, Zierath JR, Corpus VM, Holloszy JO. Reversal of enhanced muscle glucose transport after exercise: roles of insulin and glucose. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:E685-91. [PMID: 2240207 DOI: 10.1152/ajpendo.1990.259.5.e685] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Exercise stimulates insulin-independent glucose transport in skeletal muscle and also increases the sensitivity of the glucose transport process in muscle to insulin. A previous study [D. A. Young, H. Wallberg-Henriksson, M. D. Sleeper, and J. O. Holloszy. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E331-E335, 1987] showed that the exercise-induced increase in glucose transport activity disappears rapidly when rat epitrochlearis muscles are incubated for 3 h in vitro in the absence of insulin and that 7.5 microU/ml insulin in the incubation medium apparently slowed the loss of enhanced sugar transport. We examined whether addition of insulin several hours after exercise increases glucose transport to the same extent as continuous insulin exposure. Addition of 7.5 microU/ml insulin 2.5 h after exercise (when glucose transport has returned to basal levels) increased sugar transport to the same level as that which resulted from continuous insulin exposure. This finding provides evidence for an increase in insulin sensitivity rather than a slowing of reversal of the exercise-induced increase in insulin-independent glucose transport activity. Glucose transport was enhanced only at submaximal, not at maximal, insulin concentrations. Exposure to a high concentration of glucose and a low insulin concentration reduced the exercise-induced increase in insulin-sensitive glucose transport. Incubation with a high concentration of 2-deoxy-D-glucose (2-DG) did not alter the increase in insulin sensitivity, even though a large amount of 2-DG entered the muscle and was phosphorylated.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- E A Gulve
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | | | | | | | | |
Collapse
|
14
|
Traxinger R, Marshall S. Glucose regulation of insulin receptor affinity in primary cultured adipocytes. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)30597-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
15
|
Wertheimer E, Sasson S, Cerasi E. Regulation of hexose transport in L8 myocytes by glucose: possible sites of interaction. J Cell Physiol 1990; 143:330-6. [PMID: 2332455 DOI: 10.1002/jcp.1041430217] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Previous work demonstrated that glucose controls its own transport rate in rat skeletal muscle: exposure to high glucose levels down-regulates muscle hexose transport, while glucose withdrawal results in elevated transport rates (J. Biol. Chem. 261:16827-16833, 1986). The present study investigates the mechanism of this autoregulatory system. Preincubation of L8 myocytes at 16 mM glucose reduced subsequent 2-deoxy-D-glucose (dGlc) uptake by 40% within 3 h. Cycloheximide (1 microM) mimicked the action of glucose; the effects of glucose and cycloheximide were not additive. At 50 microM, cycloheximide prevented the modulations of glucose transport induced by exposure of muscle cells to high or low glucose concentrations. Inhibition of glycosylation with tunicamycin A1 reduced the basal dGlc uptake, but did not prevent its up-regulation following glucose withdrawal. Inhibition of RNA synthesis by actinomycin D prevented the down-regulatory effect of glucose. These results indicate that continuous protein synthesis and protein glycosylation are required for the maintenance of the steady-state dGlc uptake. We suggest that glucose exerts its autoregulatory effect on hexose transport by modifying the incorporation of active glucose transporters into the plasma membrane rather than changing their rate of degradation. It is hypothesized that this effect is mediated by a non-glycosylated protein involved in the translocation or activation of glucose transporters.
Collapse
Affiliation(s)
- E Wertheimer
- Department of Endocrinology and Metabolism, Hebrew University Hadassah Medical Center, Jerusalem, Israel
| | | | | |
Collapse
|
16
|
Traxinger RR, Marshall S. Role of Amino Acids in Modulating Glucose-Induced Desensitization of the Glucose Transport System. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)30022-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
17
|
Pettengell K, Frost SC. Effect of phenylarsine oxide on protein synthesis in 3T3-L1 adipocytes. Biochem Biophys Res Commun 1989; 161:633-9. [PMID: 2735914 DOI: 10.1016/0006-291x(89)92646-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In this report, we show that insulin stimulated the incorporation of tracer [3H]leucine into protein of 3T3-L1 adipocytes within 2 min of insulin addition. The concentration of insulin required to elicit 50% activation was 4nM. Phenylarsine oxide, an inhibitor of insulin-stimulated glucose transport, blocked not only insulin-stimulated protein synthesis but constitutive protein synthesis as well (Ki, 3 microM). Importantly, protein synthesis was not required for insulin-activated glucose transport since cycloheximide added either before or after insulin had no effect on the stimulated rates of glucose transport.
Collapse
Affiliation(s)
- K Pettengell
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610
| | | |
Collapse
|
18
|
|