1
|
Li J, Huang G. Insulin receptor alternative splicing in breast and prostate cancer. Cancer Cell Int 2024; 24:62. [PMID: 38331804 PMCID: PMC10851471 DOI: 10.1186/s12935-024-03252-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 02/01/2024] [Indexed: 02/10/2024] Open
Abstract
Cancer etiology represents an intricate, multifactorial orchestration where metabolically associated insulin-like growth factors (IGFs) and insulin foster cellular proliferation and growth throughout tumorigenesis. The insulin receptor (IR) exhibits two splice variants arising from alternative mRNA processing, namely IR-A, and IR-B, with remarkable distribution and biological effects disparities. This insightful review elucidates the structural intricacies, widespread distribution, and functional significance of IR-A and IR-B. Additionally, it explores the regulatory mechanisms governing alternative splicing processes, intricate signal transduction pathways, and the intricate association linking IR-A and IR-B splicing variants to breast and prostate cancer tumorigenesis. Breast cancer and prostate cancer are the most common malignant tumors with the highest incidence rates among women and men, respectively. These findings provide a promising theoretical framework for advancing preventive strategies, diagnostic modalities, and therapeutic interventions targeting breast and prostate cancer.
Collapse
Affiliation(s)
- Jinyu Li
- Department of Medical Oncology, The Second Hospital of Dalian Medical University, No. 467 Zhongshan Road, Shahekou District, Dalian, 116023, Liaoning, China
| | - Gena Huang
- Department of Medical Oncology, The Second Hospital of Dalian Medical University, No. 467 Zhongshan Road, Shahekou District, Dalian, 116023, Liaoning, China.
| |
Collapse
|
2
|
Mirzadeh Z, Faber CL, Schwartz MW. Central Nervous System Control of Glucose Homeostasis: A Therapeutic Target for Type 2 Diabetes? Annu Rev Pharmacol Toxicol 2022; 62:55-84. [PMID: 34990204 PMCID: PMC8900291 DOI: 10.1146/annurev-pharmtox-052220-010446] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Historically, pancreatic islet beta cells have been viewed as principal regulators of glycemia, with type 2 diabetes (T2D) resulting when insulin secretion fails to compensate for peripheral tissue insulin resistance. However, glycemia is also regulated by insulin-independent mechanisms that are dysregulated in T2D. Based on evidence supporting its role both in adaptive coupling of insulin secretion to changes in insulin sensitivity and in the regulation of insulin-independent glucose disposal, the central nervous system (CNS) has emerged as a fundamental player in glucose homeostasis. Here, we review and expand upon an integrative model wherein the CNS, together with the islet, establishes and maintains the defended level of glycemia. We discuss the implications of this model for understanding both normal glucose homeostasis and T2D pathogenesis and highlight centrally targeted therapeutic approaches with the potential to restore normoglycemia to patients with T2D.
Collapse
Affiliation(s)
- Zaman Mirzadeh
- Ivy Brain Tumor Center, Department of Neurosurgery, Barrow Neurological Institute, Phoenix, Arizona 85013, USA;
| | - Chelsea L Faber
- Ivy Brain Tumor Center, Department of Neurosurgery, Barrow Neurological Institute, Phoenix, Arizona 85013, USA;
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, Seattle, Washington 98109, USA;
| | - Michael W Schwartz
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, Seattle, Washington 98109, USA;
| |
Collapse
|
3
|
Cen HH, Hussein B, Botezelli JD, Wang S, Zhang JA, Noursadeghi N, Jessen N, Rodrigues B, Timmons JA, Johnson JD. Human and mouse muscle transcriptomic analyses identify insulin receptor mRNA downregulation in hyperinsulinemia-associated insulin resistance. FASEB J 2022; 36:e22088. [PMID: 34921686 PMCID: PMC9255858 DOI: 10.1096/fj.202100497rr] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 11/18/2021] [Accepted: 11/23/2021] [Indexed: 01/03/2023]
Abstract
Hyperinsulinemia is commonly viewed as a compensatory response to insulin resistance, yet studies have demonstrated that chronically elevated insulin may also drive insulin resistance. The molecular mechanisms underpinning this potentially cyclic process remain poorly defined, especially on a transcriptome-wide level. Transcriptomic meta-analysis in >450 human samples demonstrated that fasting insulin reliably and negatively correlated with INSR mRNA in skeletal muscle. To establish causality and study the direct effects of prolonged exposure to excess insulin in muscle cells, we incubated C2C12 myotubes with elevated insulin for 16 h, followed by 6 h of serum starvation, and established that acute AKT and ERK signaling were attenuated in this model of in vitro hyperinsulinemia. Global RNA-sequencing of cells both before and after nutrient withdrawal highlighted genes in the insulin receptor (INSR) signaling, FOXO signaling, and glucose metabolism pathways indicative of 'hyperinsulinemia' and 'starvation' programs. Consistently, we observed that hyperinsulinemia led to a substantial reduction in Insr gene expression, and subsequently a reduced surface INSR and total INSR protein, both in vitro and in vivo. Bioinformatic modeling combined with RNAi identified SIN3A as a negative regulator of Insr mRNA (and JUND, MAX, and MXI as positive regulators of Irs2 mRNA). Together, our analysis identifies mechanisms which may explain the cyclic processes underlying hyperinsulinemia-induced insulin resistance in muscle, a process directly relevant to the etiology and disease progression of type 2 diabetes.
Collapse
Affiliation(s)
- Haoning Howard Cen
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Bahira Hussein
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - José Diego Botezelli
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Su Wang
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jiashuo Aaron Zhang
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nilou Noursadeghi
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Niels Jessen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark
| | - Brian Rodrigues
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - James A Timmons
- Augur Precision Medicine LTD, Stirling University Innovation Park, Stirling, Scotland.,William Harvey Research Institute, Queen Mary University of London, London, UK
| | - James D Johnson
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
4
|
Choubey A, Girdhar K, Kar AK, Kushwaha S, Yadav MK, Ghosh D, Mondal P. Low-dose naltrexone rescues inflammation and insulin resistance associated with hyperinsulinemia. J Biol Chem 2020; 295:16359-16369. [PMID: 32943552 DOI: 10.1074/jbc.ra120.013484] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 09/14/2020] [Indexed: 11/06/2022] Open
Abstract
The incidence of diabetes, obesity, and metabolic diseases has reached an epidemic status worldwide. Insulin resistance is a common link in the development of these conditions, and hyperinsulinemia is a central hallmark of peripheral insulin resistance. However, how hyperinsulinemia leads to systemic insulin resistance is less clear. We now provide evidence that hyperinsulinemia promotes the release of soluble pro-inflammatory mediators from macrophages that lead to systemic insulin resistance. Our observations suggest that hyperinsulinemia induces sirtuin1 (SIRT1) repression and stimulates NF-κB p65 nuclear translocation and transactivation of NF-κB to promote the extracellular release of pro-inflammatory mediators. We further showed that low-dose naltrexone (LDN) abrogates hyperinsulinemia-mediated SIRT1 repression and prevents NF-κB p65 nuclear translocation. This, in turn, attenuates the hyperinsulinemia-induced release of pro-inflammatory cytokines and reinstates insulin sensitivity both in in vitro and in vivo diet-induced hyperinsulinemic mouse model. Notably, our data indicate that Sirt1 knockdown or inhibition blunts the anti-inflammatory properties of LDN in vitro Using numerous complementary in silico and in vitro experimental approaches, we demonstrated that LDN can bind to SIRT1 and increase its deacetylase activity. Together, these data support a critical role of SIRT1 in inflammation and insulin resistance in hyperinsulinemia. LDN improves hyperinsulinemia-induced insulin resistance by reorienting macrophages toward anti-inflammation. Thus, LDN treatment may provide a novel therapeutic approach against hyperinsulinemia-associated insulin resistance.
Collapse
Affiliation(s)
- Abhinav Choubey
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, India; BioX Centre, Indian Institute of Technology Mandi, Mandi, India
| | - Khyati Girdhar
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, India; BioX Centre, Indian Institute of Technology Mandi, Mandi, India
| | - Aditya K Kar
- CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow, Uttar Pradesh, India
| | - Shaivya Kushwaha
- CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow, Uttar Pradesh, India
| | - Manoj Kumar Yadav
- Department of Bioinformatics, SRM University, Delhi-NCR, Sonipat, Haryana, India
| | - Debabrata Ghosh
- CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow, Uttar Pradesh, India
| | - Prosenjit Mondal
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, India; BioX Centre, Indian Institute of Technology Mandi, Mandi, India.
| |
Collapse
|
5
|
Biswas B, Dey G, Dogra S, Mukhopadhyay A, Chowdhury SR, Mondal P, Ghosh S. Molecular Scale Optimum Hydrophobicity To Establish an Enhanced Probe-Protein Interaction: Near-Infrared Imaging of Albumin Biosynthesis Modulation. ACS APPLIED BIO MATERIALS 2019; 2:3372-3379. [PMID: 35030779 DOI: 10.1021/acsabm.9b00362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Albumin is the most abundant serum protein and shows variation in its synthesis rate in different physiological and pathophysiological conditions. Thus, there might be an association expected between serum albumin concentration and body health. A library of NIR probes engineered with the optimum hydrophobicity has been developed and characterized using spectroscopy techniques and was employed to understand the variation of hepatic albumin synthesis rates on physiological and pathophysiological states. Given the importance of hydrophobicity in rendering an effective interaction of small molecules with biomolecules, strategic structure interaction relationship studies led us toward the development of a potent emissive molecular probe through chemical library development. By exploration of these newly developed molecular probes, our study elegantly showed how a pathophysiological condition like the hyperinsulinemic state significantly downregulates albumin biosynthesis in HepG2 cells using fluorescence microscopy as a tool. An excellent correlation between the albumin transcript level and fluorescence intensity inside the cells has been observed. The key role of hydrophobicity resulting in an effective interaction of the probes with albumin, thus leading to strong optical signals, has been experimentally demonstrated in this report. Also, a siRNA interference technique has been utilized to establish the excellent selectivity of the developed probes with excitation as well as emission in the NIR region. We therefore have established through our experimental findings that suitable cell permeable emissive molecular markers with a high degree of albumin specificity can be used as a good optical tool for studying the effect of hyperinsulinemia on albumin biosynthesis modulation.
Collapse
Affiliation(s)
- Bidisha Biswas
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Gourab Dey
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Surbhi Dogra
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Antara Mukhopadhyay
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Shubhajit Roy Chowdhury
- School of Computing and Electrical Engineering, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Prosenjit Mondal
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| | - Subrata Ghosh
- School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175001, India
| |
Collapse
|
6
|
Tricò D, Natali A, Arslanian S, Mari A, Ferrannini E. Identification, pathophysiology, and clinical implications of primary insulin hypersecretion in nondiabetic adults and adolescents. JCI Insight 2018; 3:124912. [PMID: 30568042 DOI: 10.1172/jci.insight.124912] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 11/06/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Excessive insulin secretion may lead to glucose dysregulation. Our aim was to identify primary (independent of insulin resistance) insulin hypersecretion in subjects with normal glucose tolerance and its role in the progression of dysglycemia. METHODS In 1,168 adults, insulin secretion rate (ISR) and β cell function were estimated by C-peptide modeling during an oral glucose tolerance test (OGTT) and an i.v. glucose tolerance test. Whole-body insulin sensitivity was measured by a hyperinsulinemic-euglycemic clamp. After regressing ISR on insulin sensitivity, subjects in the upper tertile of the distribution of residuals were defined as primary hypersecretors. This approach was applied to a biethnic cohort of 182 obese adolescents, who received an OGTT, a hyperglycemic, and a euglycemic clamp. RESULTS Adult hypersecretors showed older age, more familial diabetes, sedentary lifestyle, increased fat mass, and worse lipid profile compared with the rest of the cohort, despite virtually identical BMI and insulin sensitivity. Insulin secretion was increased by 53% due to enhanced (+23%) β cell glucose sensitivity. Despite the resulting hyperinsulinemia, glucose tolerance was worse in hypersecretors among both adults and adolescents, coupled with higher indices of liver insulin resistance and increased availability of gluconeogenic substrates. At the 3-year follow-up, adult hypersecretors had increased incidence of impaired glucose tolerance/type 2 diabetes. CONCLUSION Primary insulin hypersecretion, independent of insulin resistance, is associated with a worse clinical and metabolic phenotype in adults and adolescents and predicts deterioration of glucose control over time. FUNDING The relationship between insulin sensitivity and cardiovascular disease (RISC) Study was partly supported by EU grant QLG1-CT-2001-01252.
Collapse
Affiliation(s)
- Domenico Tricò
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.,Institute of Life Sciences, Sant'Anna School of Advanced Studies, Pisa, Italy
| | - Andrea Natali
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Silva Arslanian
- Center for Pediatric Research in Obesity and Metabolism, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Division of Pediatric Endocrinology, Diabetes and Metabolism, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Andrea Mari
- Institute of Neuroscience, National Research Council, Padua, Italy
| | - Ele Ferrannini
- Institute of Clinical Physiology, National Research Council, Pisa, Italy
| |
Collapse
|
7
|
Alternative mRNA Splicing in the Pathogenesis of Obesity. Int J Mol Sci 2018; 19:ijms19020632. [PMID: 29473878 PMCID: PMC5855854 DOI: 10.3390/ijms19020632] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 02/21/2018] [Accepted: 02/21/2018] [Indexed: 12/22/2022] Open
Abstract
Alternative mRNA splicing is an important mechanism in expansion of proteome diversity by production of multiple protein isoforms. However, emerging evidence indicates that only a limited number of annotated protein isoforms by alternative splicing are detected, and the coding sequence of alternative splice variants usually is only slightly different from that of the canonical sequence. Nevertheless, mis-splicing is associated with a large array of human diseases. Previous reviews mainly focused on hereditary and somatic mutations in cis-acting RNA sequence elements and trans-acting splicing factors. The importance of environmental perturbations contributed to mis-splicing is not assessed. As significant changes in exon skipping and splicing factors expression levels are observed with diet-induced obesity, this review focuses on several well-known alternatively spliced metabolic factors and discusses recent advances in the regulation of the expressions of splice variants under the pathophysiological conditions of obesity. The potential of targeting the alternative mRNA mis-splicing for obesity-associated diseases therapies will also be discussed.
Collapse
|
8
|
Furnica RM, Istasse L, Maiter D. A severe but reversible reduction in insulin sensitivity is observed in patients with insulinoma. ANNALES D'ENDOCRINOLOGIE 2017; 79:30-36. [PMID: 29241949 DOI: 10.1016/j.ando.2017.08.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/24/2017] [Accepted: 08/24/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Hypoglycemic manifestations are highly variable in patients with an insulinoma and largely independent of tumour size and severity of insulin hypersecretion. OBJECTIVES We investigated the clinical, biological and tumoral characteristics of insulinomas in a large monocentric series of patients and we evaluated their insulin sensitivity before and after successful pancreatic surgery. PATIENTS AND METHODS This was a retrospective analysis of 40 patients treated for an insulinoma between 1982 and 2012 in our academic hospital. Insulin sensitivity and beta cell function were evaluated by a HOMA test outside hypoglycaemic episodes in a large subset of these patients. RESULTS The mean age at onset of symptoms was 48.8±20.1 years and the mean age at diagnosis was 50.7±19.9 years. Neuroglycopenic symptoms were observed in 90% of patients. The most effective preoperative imaging technique to localize the tumour was endoscopic ultrasound. Insulin sensitivity was greatly reduced in patients with insulinoma (38.9%±22.3%), while beta cells function was increased (359.0±171.5%), but to a variable extent (range: 110.6-678.6%). After complete resection of the tumour and remission of hypoglycemic episodes, insulin sensitivity increased in all evaluated subjects (72.8±36.7%) and normalized in the majority. CONCLUSION Although neuroglycopenic symptoms are present in most patients, diagnosis of insulinoma is often delayed. Endoscopic ultrasound remains the most sensitive preoperative technique to localize the tumour. We also show that in response to chronic hyperinsulinemia, patients with insulinoma develop protective mechanisms responsible for a marked insulin resistance, which is reversible after complete resection of the tumour.
Collapse
Affiliation(s)
- Raluca Maria Furnica
- Department of Endocrinology, Université catholique de Louvain, Cliniques Universitaires Saint-Luc, avenue Hippocrate 10, 1200 Brussels, Belgium.
| | - Laure Istasse
- Department of Endocrinology, Université catholique de Louvain, Cliniques Universitaires Saint-Luc, avenue Hippocrate 10, 1200 Brussels, Belgium
| | - Dominique Maiter
- Department of Endocrinology, Université catholique de Louvain, Cliniques Universitaires Saint-Luc, avenue Hippocrate 10, 1200 Brussels, Belgium
| |
Collapse
|
9
|
Lay AC, Hurcombe JA, Betin VMS, Barrington F, Rollason R, Ni L, Gillam L, Pearson GME, Østergaard MV, Hamidi H, Lennon R, Welsh GI, Coward RJM. Prolonged exposure of mouse and human podocytes to insulin induces insulin resistance through lysosomal and proteasomal degradation of the insulin receptor. Diabetologia 2017; 60:2299-2311. [PMID: 28852804 PMCID: PMC6448913 DOI: 10.1007/s00125-017-4394-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/28/2017] [Indexed: 12/12/2022]
Abstract
AIMS/HYPOTHESIS Podocytes are insulin-responsive cells of the glomerular filtration barrier and are key in preventing albuminuria, a hallmark feature of diabetic nephropathy. While there is evidence that a loss of insulin signalling to podocytes is detrimental, the molecular mechanisms underpinning the development of podocyte insulin resistance in diabetes remain unclear. Thus, we aimed to further investigate podocyte insulin responses early in the context of diabetic nephropathy. METHODS Conditionally immortalised human and mouse podocyte cell lines and glomeruli isolated from db/db DBA/2J mice were studied. Podocyte insulin responses were investigated with western blotting, cellular glucose uptake assays and automated fluorescent imaging of the actin cytoskeleton. Quantitative (q)RT-PCR was employed to investigate changes in mRNA. Human cell lines stably overproducing the insulin receptor (IR) and nephrin were also generated, using lentiviral constructs. RESULTS Podocytes exposed to a diabetic environment (high glucose, high insulin and the proinflammatory cytokines TNF-α and IL-6) become insulin resistant with respect to glucose uptake and activation of phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signalling. These podocytes lose expression of the IR as a direct consequence of prolonged exposure to high insulin concentrations, which causes an increase in IR protein degradation via a proteasome-dependent and bafilomycin-sensitive pathway. Reintroducing the IR into insulin-resistant human podocytes rescues upstream phosphorylation events, but not glucose uptake. Stable expression of nephrin is also required for the insulin-stimulated glucose uptake response in podocytes and for efficient insulin-stimulated remodelling of the actin cytoskeleton. CONCLUSIONS/INTERPRETATION Together, these results suggest that IR degradation, caused by high levels of insulin, drives early podocyte insulin resistance, and that both the IR and nephrin are required for full insulin sensitivity of this cell. This could be highly relevant for the development of nephropathy in individuals with type 2 diabetes, who are commonly hyperinsulinaemic in the early phases of their disease.
Collapse
Affiliation(s)
- Abigail C Lay
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Jenny A Hurcombe
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Virginie M S Betin
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Fern Barrington
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Ruth Rollason
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Lan Ni
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Lawrence Gillam
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Grace M E Pearson
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Mette V Østergaard
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
- Global Research, Novo Nordisk A/S, Måløv, Denmark
| | - Hellyeh Hamidi
- Wellcome Trust Centre for Cell-Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biology, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Rachel Lennon
- Wellcome Trust Centre for Cell-Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biology, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Gavin I Welsh
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK
| | - Richard J M Coward
- Bristol Renal, Bristol Medical School, University of Bristol, Whitson Street, Bristol, BS1 3NY, UK.
| |
Collapse
|
10
|
Hamza SM, Sung MM, Gao F, Soltys CLM, Smith NP, MacDonald PE, Light PE, Dyck JRB. Chronic insulin infusion induces reversible glucose intolerance in lean rats yet ameliorates glucose intolerance in obese rats. Biochim Biophys Acta Gen Subj 2016; 1861:313-322. [PMID: 27871838 DOI: 10.1016/j.bbagen.2016.11.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/10/2016] [Accepted: 11/17/2016] [Indexed: 01/19/2023]
Abstract
BACKGROUND Although insulin resistance (IR) is a key factor in the pathogenesis of type 2 diabetes (T2D), the precise role of insulin in the development of IR remains unclear. Therefore, we investigated whether chronic basal insulin infusion is causative in the development of glucose intolerance. METHODS Normoglycemic lean rats surgically instrumented with i.v. catheters were infused with insulin (3mU/kg/min) or physiological saline for 6weeks. At infusion-end, plasma insulin levels along with glucose tolerance were assessed. RESULTS Six weeks of insulin infusion induced glucose intolerance and impaired insulin response in healthy rats. Interestingly, the effects of chronic insulin infusion were completely normalized following 24h withdrawal of exogenous insulin and plasma insulin response to glucose challenge was enhanced, suggesting improved insulin secretory capacity. As a result of this finding, we assessed whether the effects of insulin therapy followed by a washout could ameliorate established glucose intolerance in obese rats. Obese rats were similarly instrumented and infused with insulin or physiological saline for 7days followed by 24h washout. Seven day-insulin therapy in obese rats significantly improved glucose tolerance, which was attributed to improved insulin secretory capacity and improved insulin signaling in liver and skeletal muscle. CONCLUSION Moderate infusion of insulin alone is sufficient to cause glucose intolerance and impair endogenous insulin secretory capacity, whereas short-term, intensive insulin therapy followed by insulin removal effectively improves glucose tolerance, insulin response and peripheral insulin sensitivity in obese rats. GENERAL SIGNIFICANCE New insight into the link between insulin and glucose intolerance may optimize T2D management.
Collapse
Affiliation(s)
- Shereen M Hamza
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, AB, Canada
| | - Miranda M Sung
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, AB, Canada
| | - Fei Gao
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, AB, Canada
| | - Carrie-Lynn M Soltys
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, AB, Canada
| | - Nancy P Smith
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Peter E Light
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Jason R B Dyck
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, AB, Canada; Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada.
| |
Collapse
|
11
|
Amin MM, Asaad GF, Abdel Salam RM, El-Abhar HS, Arbid MS. Novel CoQ10 antidiabetic mechanisms underlie its positive effect: modulation of insulin and adiponectine receptors, Tyrosine kinase, PI3K, glucose transporters, sRAGE and visfatin in insulin resistant/diabetic rats. PLoS One 2014; 9:e89169. [PMID: 24586567 PMCID: PMC3930675 DOI: 10.1371/journal.pone.0089169] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 01/16/2014] [Indexed: 11/19/2022] Open
Abstract
As a nutritional supplement, coenzyme Q10 (CoQ10) was tested previously in several models of diabetes and/or insulin resistance (IR); however, its exact mechanisms have not been profoundly explicated. Hence, the objective of this work is to verify some of the possible mechanisms that underlie its therapeutic efficacy. Moreover, the study aimed to assess the potential modulatory effect of CoQ10 on the antidiabetic action of glimebiride. An insulin resistance/type 2 diabetic model was adopted, in which rats were fed high fat/high fructose diet (HFFD) for 6 weeks followed by a single sub-diabetogenic dose of streptozotocin (35 mg/kg, i.p.). At the end of the 7th week animals were treated with CoQ10 (20 mg/kg, p.o) and/or glimebiride (0.5 mg/kg, p.o) for 2 weeks. CoQ10 alone opposed the HFFD effect and increased the hepatic/muscular content/activity of tyrosine kinase (TK), phosphatidylinositol kinase (PI3K), and adiponectin receptors. Conversely, it decreased the content/activity of insulin receptor isoforms, myeloperoxidase and glucose transporters (GLUT4; 2). Besides, it lowered significantly the serum levels of glucose, insulin, fructosamine and HOMA index, improved the serum lipid panel and elevated the levels of glutathione, sRAGE and adiponectin. On the other hand, CoQ10 lowered the serum levels of malondialdehyde, visfatin, ALT and AST. Surprisingly, CoQ10 effect surpassed that of glimepiride in almost all the assessed parameters, except for glucose, fructosamine, TK, PI3K, and GLUT4. Combining CoQ10 with glimepiride enhanced the effect of the latter on the aforementioned parameters. Conclusion: These results provided a new insight into the possible mechanisms by which CoQ10 improves insulin sensitivity and adjusts type 2 diabetic disorder. These mechanisms involve modulation of insulin and adiponectin receptors, as well as TK, PI3K, glucose transporters, besides improving lipid profile, redox system, sRAGE, and adipocytokines. The study also points to the potential positive effect of CoQ10 as an adds- on to conventional antidiabetic therapies.
Collapse
MESH Headings
- Animals
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/enzymology
- Diabetes Mellitus, Experimental/metabolism
- Drug Interactions
- Glucose Transport Proteins, Facilitative/metabolism
- Hypoglycemic Agents/pharmacology
- Hypoglycemic Agents/therapeutic use
- Insulin Resistance
- Liver/drug effects
- Liver/metabolism
- Male
- Membrane Proteins/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Nicotinamide Phosphoribosyltransferase/metabolism
- Peroxidase/metabolism
- Phosphatidylinositol 3-Kinases/metabolism
- Protein-Tyrosine Kinases/metabolism
- Rats
- Receptor for Advanced Glycation End Products
- Receptor, Insulin/metabolism
- Receptors, Adiponectin/metabolism
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/metabolism
- Transferases/metabolism
- Ubiquinone/analogs & derivatives
- Ubiquinone/pharmacology
- Ubiquinone/therapeutic use
Collapse
Affiliation(s)
- Mohamed M. Amin
- Department of Pharmacology, Medical Division, National Research Center, Cairo, Egypt
| | - Gihan F. Asaad
- Department of Pharmacology, Medical Division, National Research Center, Cairo, Egypt
| | - Rania M. Abdel Salam
- Department of Pharmacology & Toxicology, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Hanan S. El-Abhar
- Department of Pharmacology & Toxicology, Faculty of Pharmacy, Cairo University, Cairo, Egypt
- * E-mail:
| | - Mahmoud S. Arbid
- Department of Pharmacology, Medical Division, National Research Center, Cairo, Egypt
| |
Collapse
|
12
|
Wang T, Ning G, Bloomgarden Z. Diabetes and cancer relationships. J Diabetes 2013; 5:378-90. [PMID: 23574745 DOI: 10.1111/1753-0407.12057] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 03/10/2013] [Accepted: 03/24/2013] [Indexed: 12/29/2022] Open
Abstract
Diabetes and cancer are both heterogeneous and multifactorial diseases with tremendous impact on health worldwide. Epidemiologic evidence suggests that certain malignancies may be associated with diabetes, as well as with diabetes risk factors and, perhaps, with certain diabetes treatments. Numerous biological mechanisms could account for these relationships. Insulin-like growth factor (IGF)-1, IGF-2, IGF-1 receptors, insulin, and the insulin receptor play roles in the development and progression of cancers. Although evidence from randomized controlled trials does not support or refute associations of diabetes and its treatments with either increased or reduced risk of cancer incidence or prognosis, consideration of malignancy incidence rates and the magnitude of the trials that would be required to address these issues explains why such studies may not be readily undertaken.
Collapse
Affiliation(s)
- Tiange Wang
- Key Laboratory for Endocrine and Metabolic Diseases of Ministry of Health, Shanghai, China; Shanghai Clinical Center for Endocrine and Metabolic Diseases, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; E-Institute of Shanghai Universities, Shanghai, China
| | | | | |
Collapse
|
13
|
Bonaventura MM, Rodriguez D, Ferreira ML, Crivello M, Repetto EM, Bettler B, Libertun C, Lux-Lantos VA. Sex differences in insulin resistance in GABAB1 knockout mice. Life Sci 2013; 92:175-82. [PMID: 23178152 DOI: 10.1016/j.lfs.2012.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 10/16/2012] [Accepted: 11/07/2012] [Indexed: 11/17/2022]
Abstract
AIMS We have previously demonstrated that the absence of functional GABA B receptors (GABABRs) disturbs glucose homeostasis in GABAB1KO mice. The aim of this work was to extend our studies of these alterations in GABAB1KO mice and investigate the sexual differences therein. MAIN METHODS Male and female, GABAB1KO and WT mice were used. Glucose and insulin tolerance tests (GTT and ITT), and insulin and glucagon secretion tests (IST and GST) were performed. Blood glucose, serum insulin and hyperglycemic hormones were determined, and HOMA-IR calculated. Skeletal muscle insulin receptor β subunit (IRβ), insulin receptor substrates 1/2 (IRS1, IRS2) and hexokinase-II levels were determined by Western blot. Skeletal muscle insulin sensitivity was assessed by in vivo insulin-induced Akt phosphorylation (Western blot). Food intake and hypothalamic NPY mRNA expression (by qPCR) were also evaluated. KEY FINDINGS Fasted insulin and HOMA-IR were augmented in GABAB1KO males, with no alterations in females. Areas under the curve (AUC) for GTT and ITT were increased in GABAB1KO mice of both genders, indicating compromised insulin sensitivity. No genotype differences were observed in IST, GST or in IRβ, IRS1, IRS2 and hexokinase-II expression. Akt activation was severely impaired in GABAB1KO males while no alterations were observed in females. GABAB1KO mice showed increased food intake and NPY expression. SIGNIFICANCE Glucose metabolism and energy balance disruptions were more pronounced in GABAB1KO males, which develop peripheral insulin resistance probably due to augmented insulin secretion. Metabolic alterations in females were milder and possibly due to previously described reproductive disorders, such as persistent estrus.
Collapse
Affiliation(s)
- M M Bonaventura
- Instituto de Biología y Medicina Experimental-CONICET, Buenos Aires, Argentina
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Topiramate-induced modulation of hepatic molecular mechanisms: an aspect for its anti-insulin resistant effect. PLoS One 2012; 7:e37757. [PMID: 22649556 PMCID: PMC3359316 DOI: 10.1371/journal.pone.0037757] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 04/27/2012] [Indexed: 02/06/2023] Open
Abstract
Topiramate is an antiepileptic drug known to ameliorate insulin resistance besides reducing body weight. Albeit liver plays a fundamental role in regulation of overall insulin resistance, yet the effect of topiramate on this organ is controversial and is not fully investigated. The current work aimed to study the potential hepatic molecular mechanistic cassette of the anti-insulin resistance effect of topiramate. To this end, male Wistar rats were fed high fat/high fructose diet (HFFD) for 10 weeks to induce obese, insulin resistant, hyperglycemic animals, but with no overt diabetes. Two HFFD-groups received oral topiramate, 40 or 100 mg/kg, for two weeks. Topiramate, on the hepatic molecular level, has opposed the high fat/high fructose diet effect, where it significantly increased adiponectin receptors, GLUT2, and tyrosine kinase activity, while decreased insulin receptor isoforms. Besides, it improved the altered glucose homeostasis and lipid profile, lowered the ALT level, caused subtle, yet significant decrease in TNF-α, and boosted adiponectin in a dose dependent manner. Moreover, topiramate decreased liver weight/, visceral fat weight/, and epididymal fat weight/body weight ratios. The study proved that insulin-resistance has an effect on hepatic molecular level and that the topiramate-mediated insulin sensitivity is ensued partly by modulation of hepatic insulin receptor isoforms, activation of tyrosine kinase, induction of GLUT2 and elevation of adiponectin receptors, as well as their ligand, adiponectin, besides its known improving effect on glucose tolerance and lipid homeostasis.
Collapse
|
15
|
Belfiore A, Frasca F, Pandini G, Sciacca L, Vigneri R. Insulin receptor isoforms and insulin receptor/insulin-like growth factor receptor hybrids in physiology and disease. Endocr Rev 2009; 30:586-623. [PMID: 19752219 DOI: 10.1210/er.2008-0047] [Citation(s) in RCA: 719] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In mammals, the insulin receptor (IR) gene has acquired an additional exon, exon 11. This exon may be skipped in a developmental and tissue-specific manner. The IR, therefore, occurs in two isoforms (exon 11 minus IR-A and exon 11 plus IR-B). The most relevant functional difference between these two isoforms is the high affinity of IR-A for IGF-II. IR-A is predominantly expressed during prenatal life. It enhances the effects of IGF-II during embryogenesis and fetal development. It is also significantly expressed in adult tissues, especially in the brain. Conversely, IR-B is predominantly expressed in adult, well-differentiated tissues, including the liver, where it enhances the metabolic effects of insulin. Dysregulation of IR splicing in insulin target tissues may occur in patients with insulin resistance; however, its role in type 2 diabetes is unclear. IR-A is often aberrantly expressed in cancer cells, thus increasing their responsiveness to IGF-II and to insulin and explaining the cancer-promoting effect of hyperinsulinemia observed in obese and type 2 diabetic patients. Aberrant IR-A expression may favor cancer resistance to both conventional and targeted therapies by a variety of mechanisms. Finally, IR isoforms form heterodimers, IR-A/IR-B, and hybrid IR/IGF-IR receptors (HR-A and HR-B). The functional characteristics of such hybrid receptors and their role in physiology, in diabetes, and in malignant cells are not yet fully understood. These receptors seem to enhance cell responsiveness to IGFs.
Collapse
Affiliation(s)
- Antonino Belfiore
- Endocrinology, Department of Clinical and Experimental Medicine, University of Catania, Ospedale Garibaldi-Nesima, 95122 Catania, Italy.
| | | | | | | | | |
Collapse
|
16
|
Cox ME, Gleave ME, Zakikhani M, Bell RH, Piura E, Vickers E, Cunningham M, Larsson O, Fazli L, Pollak M. Insulin receptor expression by human prostate cancers. Prostate 2009; 69:33-40. [PMID: 18785179 DOI: 10.1002/pros.20852] [Citation(s) in RCA: 158] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Although recent laboratory and population studies suggest that prostate cancer may be responsive to insulin, there is a gap in knowledge concerning the expression of insulin receptors on benign or malignant prostate tissue. METHODS We immunostained 644 cores on tissue microarrays prepared from 29 prostate tissue samples without malignancies, 78 Gleason grade 3 cancers, 21 Gleason grade 4 cancers and 33 Gleason grade 5 cancers with antibodies against the insulin-like growth factor I receptor and the insulin receptor. RESULTS We observed immunoreactivity with both antibodies, which implies the presence of hybrid receptors as well as IGF-I receptors and insulin receptors. Insulin receptor staining intensity was significantly (P < 0.001) higher on malignant than benign prostate epithelial cells. Analysis of information from public gene expression databases confirmed that co-expression of insulin receptor mRNA and IGF-I receptor mRNA is common in prostate cancer specimens. RT-PCR methods provided evidence for the presence of mRNA for both IR-A and IR-B insulin receptor isoforms. CONCLUSION These observations document the presence of insulin receptors on primary human prostate cancers. The findings are relevant not only to ongoing clinical trials of drug candidates that target IGF-I and/or insulin receptors, but also to the hypothesis that obesity-associated hyperinsulinemia mediates the adverse effect of obesity on prostate cancer prognosis.
Collapse
Affiliation(s)
- Michael E Cox
- The Prostate Center at Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Insulin resistance and amyloidogenesis as common molecular foundation for type 2 diabetes and Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2008; 1792:482-96. [PMID: 19026743 DOI: 10.1016/j.bbadis.2008.10.014] [Citation(s) in RCA: 240] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2008] [Revised: 10/18/2008] [Accepted: 10/21/2008] [Indexed: 12/22/2022]
Abstract
Characterized as a peripheral metabolic disorder and a degenerative disease of the central nervous system respectively, it is now widely recognized that type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share several common abnormalities including impaired glucose metabolism, increased oxidative stress, insulin resistance and amyloidogenesis. Several recent studies suggest that this is not an epiphenomenon, but rather these two diseases disrupt common molecular pathways and each disease compounds the progression of the other. For instance, in AD the accumulation of the amyloid-beta peptide (Abeta), which characterizes the disease and is thought to participate in the neurodegenerative process, may also induce neuronal insulin resistance. Conversely, disrupting normal glucose metabolism in transgenic animal models of AD that over-express the human amyloid precursor protein (hAPP) promotes amyloid-peptide aggregation and accelerates the disease progression. Studying these processes at a cellular level suggests that insulin resistance and Abeta aggregation may not only be the consequence of excitotoxicity, aberrant Ca(2+) signals, and proinflammatory cytokines such as TNF-alpha, but may also promote these pathological effectors. At the molecular level, insulin resistance and Abeta disrupt common signal transduction cascades including the insulin receptor family/PI3 kinase/Akt/GSK3 pathway. Thus both disease processes contribute to overlapping pathology, thereby compounding disease symptoms and progression.
Collapse
|
18
|
Piao W, Wang Y, Adachi Y, Yamamoto H, Li R, Imsumran A, Li H, Maehata T, Ii M, Arimura Y, Lee CT, Shinomura Y, Carbone DP, Imai K. Insulin-like growth factor-I receptor blockade by a specific tyrosine kinase inhibitor for human gastrointestinal carcinomas. Mol Cancer Ther 2008; 7:1483-93. [PMID: 18566219 DOI: 10.1158/1535-7163.mct-07-2395] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and proliferation of gastrointestinal (GI) cancers. In this study, we sought to evaluate the effect of a new tyrosine kinase inhibitor of IGF-IR, NVP-AEW541, on the signal transduction and the progression of GI carcinomas. We assessed the effect of NVP-AEW541 on signal transduction, proliferation, survival, and migration in four GI cancer cells: colorectal adenocarcinoma HT29, pancreatic adenocarcinoma BxPC3, esophageal squamous cell carcinoma TE1, and hepatoma PLC/PRF/5. The effects of NVP-AEW541 alone and with chemotherapy were studied in vitro and in nude mouse xenografts. We also analyzed the effects of NVP-AEW541 on insulin signals and hybrid receptor formation between IGF-IR and insulin receptor. NVP-AEW541 blocked autophosphorylation of IGF-IR and both Akt and extracellular signal-regulated kinase activation by IGF but not by insulin. NVP-AEW541 suppressed proliferation and tumorigenicity in vitro in a dose-dependent manner in all cell lines. The drug inhibited tumor as a single agent and, when combined with stressors, up-regulated apoptosis in a dose-dependent fashion and inhibited mobility. NVP-AEW541 augmented the effects of chemotherapy on in vitro growth and induction of apoptosis. Moreover, the combination of NVP-AEW541 and chemotherapy was highly effective against tumors in mice. This compound did not influence hybrid receptor formation. Thus, NVP-AEW541 may have significant therapeutic utility in human GI carcinomas both alone and in combination with chemotherapy.
Collapse
Affiliation(s)
- Wenhua Piao
- First Department of Internal Medicine, Sapporo Medical University, Chuo-ku, Sapporo 060-8543, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Frasca F, Pandini G, Sciacca L, Pezzino V, Squatrito S, Belfiore A, Vigneri R. The role of insulin receptors and IGF-I receptors in cancer and other diseases. Arch Physiol Biochem 2008; 114:23-37. [PMID: 18465356 DOI: 10.1080/13813450801969715] [Citation(s) in RCA: 274] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
There is evidence, both in vitro and in vivo, that receptor tyrosine kinases play a key role in the formation and progression of human cancer. In particular, the insulin-like growth factor receptor (IGF-IR), a tyrosine kinase receptor for IGF-I and IGF-II, has been well documented in cell culture, animal studies, and humans to play a role in malignant transformation, progression, protection from apoptosis, and metastasis. In addition, the hormone insulin (which is very closely related to the IGFs) and its tyrosine kinase receptor (the IR, which is very closely related to the IGR-IR) have been documented both in vitro and in vivo to play a key role in cancer biology. Indeed, several epidemiological studies have shown that insulin resistance status, characterized by hyperinsulinaemia, is associated with an increased risk for a number of malignancies, including carcinomas of the breast, prostate, colon and kidney. Recent data have elucidated some molecular mechanisms by which IR is involved in cancer. IR is over-expressed in several human malignancies. Interestingly, one of the two IR isoform (IR-A) is especially over-expressed in cancer. IR-A is the IR foetal isoform and has the peculiar characteristic to bind not only insulin but also IGF-II. In addition, the IR contributes to formation of hybrid receptors with the IGF-IR (HR). By binding to hybrid receptors, insulin may stimulate specific IGF-IR signalling pathways. Over-expression of IR-A is, therefore, a major mechanism of IGF system over-activation in cancer. In this respect, IR-A isoform and hybrid receptors should be regarded as potential molecular targets, in addition to IGF-IR, for novel anti-cancer therapy. These findings may have important implications for both the prevention and treatment of common human malignancies. They underline the concept that hyperinsulinaemia, associated with insulin resistance and obesity, should be treated by changes in life style and/or pharmacological approaches to avoid an increased risk for cancer. Moreover, native insulin and insulin analogue administration should be carefully evaluated in terms of the possible increase in cancer risk.
Collapse
Affiliation(s)
- Francesco Frasca
- Department of Internal Medicine, Endocrinology Unit, University of Catania, Via Palermo 636, Catania, Italy.
| | | | | | | | | | | | | |
Collapse
|
20
|
Shanik MH, Xu Y, Skrha J, Dankner R, Zick Y, Roth J. Insulin resistance and hyperinsulinemia: is hyperinsulinemia the cart or the horse? Diabetes Care 2008; 31 Suppl 2:S262-8. [PMID: 18227495 DOI: 10.2337/dc08-s264] [Citation(s) in RCA: 518] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Insulin resistance, recently recognized as a strong predictor of disease in adults, has become the leading element of the metabolic syndrome and renewed as a focus of research. The condition exists when insulin levels are higher than expected relative to the level of glucose. Thus, insulin resistance is by definition tethered to hyperinsulinemia. The rising prevalence of medical conditions where insulin resistance is common has energized research into the causes. Many causes and consequences have been identified, but the direct contributions of insulin itself in causing or sustaining insulin resistance have received little sustained attention. We examine situations where insulin itself appears to be a proximate and important quantitative contributor to insulin resistance. 1) Mice transfected with extra copies of the insulin gene produce basal and stimulated insulin levels that are two to four times elevated. The mice are of normal weight but show insulin resistance, hyperglycemia, and hypertriglyceridemia. 2) Somogyi described patients with unusually high doses of insulin and hyperglycemia. Episodes of hypoglycemia with release of glucose-raising hormones, postulated as the culprits in early studies, have largely been excluded by studies including continuous glucose monitoring. 3) Rats and humans treated with escalating doses of insulin show both hyperinsulinemia and insulin resistance. 4) The pulsatile administration of insulin (rather than continuous) results in reduced requirements for insulin. 5) Many patients with insulinoma who have elevated basal levels of insulin have reduced (but not absent) responsiveness to administered insulin. In summary, hyperinsulinemia is often both a result and a driver of insulin resistance.
Collapse
Affiliation(s)
- Michael H Shanik
- Division of Endocrinology, North Shore-Long Island Jewish Health System, Lake Success, New York, USA
| | | | | | | | | | | |
Collapse
|
21
|
Bonaventura MM, Catalano PN, Chamson-Reig A, Arany E, Hill D, Bettler B, Saravia F, Libertun C, Lux-Lantos VA. GABAB receptors and glucose homeostasis: evaluation in GABAB receptor knockout mice. Am J Physiol Endocrinol Metab 2008; 294:E157-67. [PMID: 17971510 DOI: 10.1152/ajpendo.00615.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GABA has been proposed to inhibit insulin secretion through GABAB receptors (GABABRs) in pancreatic beta-cells. We investigated whether GABABRs participated in the regulation of glucose homeostasis in vivo. The animals used in this study were adult male and female BALB/C mice, mice deficient in the GABAB1 subunit of the GABABR (GABAB(-/-)), and wild types (WT). Blood glucose was measured under fasting/fed conditions and in glucose tolerance tests (GTTs) with a Lifescan Glucose meter, and serum insulin was measured by ELISA. Pancreatic insulin content and islet insulin were released by RIA. Western blots for the GABAB1 subunit in islet membranes and immunohistochemistry for insulin and GABAB1 were performed in both genotypes. BALB/C mice preinjected with Baclofen (GABABR agonist, 7.5 mg/kg ip) presented impaired GTTs and decreased insulin secretion compared with saline-preinjected controls. GABAB(-/-) mice showed fasting and fed glucose levels similar to WT. GABAB(-/-) mice showed improved GTTs at moderate glucose overloads (2 g/kg). Baclofen pretreatment did not modify GTTs in GABAB(-/-) mice, whereas it impaired normal glycemia reinstatement in WT. Baclofen inhibited glucose-stimulated insulin secretion in WT isolated islets but was without effect in GABAB(-/-) islets. In GABAB(-/-) males, pancreatic insulin content was increased, basal and glucose-stimulated insulin secretion were augmented, and impaired insulin tolerance test and increased homeostatic model assessment of insulin resistance index were determined. Immunohistochemistry for insulin demonstrated an increase of very large islets in GABAB(-/-) males. Results demonstrate that GABABRs are involved in the regulation of glucose homeostasis in vivo and that the constitutive absence of GABABRs induces alterations in pancreatic histology, physiology, and insulin resistance.
Collapse
Affiliation(s)
- M M Bonaventura
- Instituto de Biología y Medicina Experimental-Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Pandini G, Frasca F, Mineo R, Sciacca L, Vigneri R, Belfiore A. Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved. J Biol Chem 2002; 277:39684-95. [PMID: 12138094 DOI: 10.1074/jbc.m202766200] [Citation(s) in RCA: 343] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The insulin receptor (IR) and the insulin-like growth factor I receptor (IGF-IR) have a highly homologous structure, but different biological effects. Insulin and IGF-I half-receptors can heterodimerize, leading to the formation of insulin/IGF-I hybrid receptors (Hybrid-Rs) that bind IGF-I with high affinity. As the IR exists in two isoforms (IR-A and IR-B), we evaluated whether the assembly of the IGF-IR with either IR-A or IR-B moieties may differently affect Hybrid-R signaling and biological role. Three different models were studied: (a) 3T3-like mouse fibroblasts with a disrupted IGF-IR gene (R(-) cells) cotransfected with the human IGF-IR and with either the IR-A or IR-B cDNA; (b) a panel of human cell lines variably expressing the two IR isoforms; and (c) HepG2 human hepatoblastoma cells predominantly expressing either IR-A or IR-B, depending on their differentiation state. We found that Hybrid-Rs containing IR-A (Hybrid-Rs(A)) bound to and were activated by IGF-I, IGF-II, and insulin. By binding to Hybrid-Rs(A), insulin activated the IGF-I half-receptor beta-subunit and the IGF-IR-specific substrate CrkII. In contrast, Hybrid-Rs(B) bound to and were activated with high affinity by IGF-I, with low affinity by IGF-II, and insignificantly by insulin. As a consequence, cell proliferation and migration in response to both insulin and IGFs were more effectively stimulated in Hybrid-R(A)-containing cells than in Hybrid-R(B)-containing cells. The relative abundance of IR isoforms therefore affects IGF system activation through Hybrid-Rs, with important consequences for tissue-specific responses to both insulin and IGFs.
Collapse
Affiliation(s)
- Giuseppe Pandini
- Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, University of Catania, Ospedale Garibaldi, 95123 Catania, Italy
| | | | | | | | | | | |
Collapse
|
23
|
Sesti G, Federici M, Lauro D, Sbraccia P, Lauro R. Molecular mechanism of insulin resistance in type 2 diabetes mellitus: role of the insulin receptor variant forms. Diabetes Metab Res Rev 2001; 17:363-73. [PMID: 11747141 DOI: 10.1002/dmrr.225] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Type 2 diabetes is a heterogeneous and polygenic disorder resulting from interaction of genetic factors with environmental influences. Numerous candidate genes for insulin signaling proteins have been screened, but no single major susceptibility gene for type 2 diabetes has been identified. Due to its pivotal role in insulin action, the insulin receptor was considered a plausible candidate gene. The insulin receptor exists in two isoforms differing by the absence (Ex11(-)) or presence (Ex11(+)) of a 12 amino acid sequence in the COOH-terminus of the alpha-subunit, as a consequence of alternative splicing of exon 11. The Ex11(-) binds insulin with two-fold higher affinity than the Ex11(+). This difference is paralleled by a decreased sensitivity for metabolic actions of insulin. Some, but not all, studies have reported that expression of the low-affinity Ex11(+) is increased in target tissues from type 2 diabetic patients, thus suggesting that alterations in abundance of the two isoforms might contribute to insulin resistance. Insulin and type 1 IGF receptors have been shown to form hybrid receptors in tissues co-expressing both molecules. Hybrid receptors bind IGF-I, but not insulin, with high affinity, and behave as IGF-I holoreceptors, rather than insulin receptors, in terms of receptor autophosphorylation, and hormone internalization. It has been shown that the abundance of hybrid receptors is increased in skeletal muscle and adipose tissue from type 2 diabetic patients, and is negatively correlated with in vivo insulin sensitivity. Mutations in the insulin receptor gene have been identified in studies which examined an appropriately sized population of patients with type 2 diabetes. The prevalence of mutations in the insulin receptor gene ranged from 0.4%-7.8%. This review will focus on the structural and functional heterogeneity of the insulin receptor, and will discuss the pathogenetic role of insulin receptor variant forms and polymorphisms in the development of the common form of type 2 diabetes.
Collapse
Affiliation(s)
- G Sesti
- University of Catanzaro-Magna, Graecia, Italy.
| | | | | | | | | |
Collapse
|
24
|
Sugimoto K, Murakawa Y, Zhang W, Xu G, Sima AA. Insulin receptor in rat peripheral nerve: its localization and alternatively spliced isoforms. Diabetes Metab Res Rev 2000; 16:354-63. [PMID: 11025559 DOI: 10.1002/1520-7560(200009/10)16:5<354::aid-dmrr149>3.0.co;2-h] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Diabetic neuropathy accompanies both Type 1 and Type 2 diabetes, although it shows in both humans and animal models distinct differences between the two types of diabetes. Progressive paranodal degenerations occurring in Type 1, but not in Type 2, diabetes is believed to account for the more severe functional deficits in Type 1 diabetic rats. This suggests that factors other than hyperglycemia, such as insulin deficiency, may play a pathogenetic role. In this study, we investigated the immunolocalization of the insulin receptor (IR) and the expression of its two alternatively spliced isoforms in adult rat peripheral nerve. METHODS Adult male Wistar rats 6-8 months of age were examined. Both light and ultrastructural immunohistochemistry was employed for localization of IR. The antibody was a mouse monoclonal antibody raised against the beta-subunit of human IR. Reverse transcription polymerase chain reaction (RT-PCR) was used to identify the two IR isoforms in peripheral nerve and seven other organs. Localization of the mRNA message was assessed by in situ hybridization. RESULTS IR was localized to paranodal terminal Schwann cell loops and microvilli and to the paranodal axolemma. Furthermore, IR immunoreactivity was also present in Schmidt-Lantermann incisures. Endoneurial vessels showed IR localization on plasma membranes and in endocytotic vesicles of endothelial cells and pericytes. A high intensity of immunostained IR was found in close proximity to interendothelial tight junctions. Peripheral nerve showed, like the brain, predominantly the high affinity IR lacking exon 11. The mRNA message was localized to Schwann cells, endothelial cells and pericytes. CONCLUSION Peripheral nerve expresses predominantly the high affinity IR, which is localized to strategic structures associated with the blood-nerve barrier and the paranodal ion-channel barrier.
Collapse
Affiliation(s)
- K Sugimoto
- Department of Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | | | | | | | | |
Collapse
|
25
|
Abstract
Type 2 diabetes is a polygenic and heterogeneous disease resulting from interaction of genetic factors with environmental influences. Numerous candidate genes have been investigated, but no single major susceptibility gene for Type 2 diabetes has been identified. The insulin receptor was considered a plausible candidate gene. The insulin receptor exists in two isoforms differing by the absence (Ex11-) or presence (Ex11+) of 12 amino acids in the C-terminus of the alpha-subunit due to alternative splicing of exon 11.Ex11- binds insulin with two-fold higher affinity than Ex11+. This difference is paralleled by a decreased sensitivity for metabolic actions of insulin. Some, but not all, studies have reported that expression of the low-affinity Exll+ is increased in Type 2 diabetes, suggesting that alterations in abundance of the two isoforms mnight contribute to insulin resistance. Insulin and Type 1 insulin-like growth factor (IGF) receptors have been shown to form hybrid receptors in tissues co-expressing both molecules. Hybrid receptors bind IGF-I, but not insulin, with high affinity, and behave as IGF-I receptors rather than insulin receptors in terms of receptor autophosphorylation and hormone internalisation. It has been shown that the abundance of hybrid receptors is increased in skeletal muscle and fat from Type 2 diabetic patients, and is negatively correlated with in vivo insulin sensitivity. Mutations in the insulin receptor gene were identified in studies which examined an appropriately sized population of Type 2 diabetic patients. The prevalence of mutations in the insulin receptor gene ranged from 0.4 to 7.8%.
Collapse
Affiliation(s)
- G Sesti
- Department of Internal Medicine, University of Rome, Tor Vergata, Italy.
| |
Collapse
|
26
|
Frittitta L, Sbraccia P, Costanzo BV, Tassi V, D'Adamo M, Spampinato D, Ercolino T, Purrello F, Tamburrano G, Vigneri R, Trischitta V. High insulin levels do not influence PC-1 gene expression and protein content in human muscle tissue and hepatoma cells. Diabetes Metab Res Rev 2000; 16:26-32. [PMID: 10707036 DOI: 10.1002/(sici)1520-7560(200001/02)16:1<26::aid-dmrr78>3.0.co;2-n] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND To verify whether insulin levels influence PC-1 tissue content, we studied PC-1 gene expression and protein content in skeletal muscle of patients with insulinoma, a model of primary hyperinsulinemia. Data were compared with those obtained in matched insulin sensitive or resistant healthy subjects. In addition, the effect of high insulin concentration on PC-1 protein content was studied in HepG2 cells. METHODS The following measurements were performed: insulin sensitivity by euglycemic clamp; PC-1 protein content and insulin receptor autophosphorylation by specific ELISAs; PC-1 gene expression by competitive polymerase chain reaction (PCR); phosphatidyl-inositol-3 kinase by immunoprecipitation and thin layer chromatography; glycogen synthesis by (14)C-glucose incorporation. RESULTS Muscle PC-1 content was similar in the insulinoma patients and in insulin sensitive controls but higher (p<0.01) in insulin resistant controls (21.9+/-4.6 ng/mg protein, 23.8+/-3.9, 48.0+/-8.7, respectively). PC-1 protein content was inversely correlated with insulin sensitivity (r=-0.5, p<0.015) but with neither plasma insulin nor glucose levels. PC-1 protein content was correlated with PC-1 gene expression (r=0.53, p<0.05, n=14). Exposure to high insulin (100 nmol/l for 16 h) caused a significant (p<0.05-0.01) impairment of insulin receptor autophosphorylation, phosphatidyl-inositol-3 kinase activity and glycogen synthesis, but not of PC-1 protein content (114+/-3 vs 102+/-14 ng/mg protein) in HepG2 cells. CONCLUSION These findings suggest that chronic high insulin levels do not influence PC-1 expression.
Collapse
Affiliation(s)
- L Frittitta
- Institute of Internal Medicine, Endocrine and Metabolic Diseases, University of Catania, Garibaldi Hospital, Catania, Italy.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Frasca F, Pandini G, Scalia P, Sciacca L, Mineo R, Costantino A, Goldfine ID, Belfiore A, Vigneri R. Insulin receptor isoform A, a newly recognized, high-affinity insulin-like growth factor II receptor in fetal and cancer cells. Mol Cell Biol 1999; 19:3278-88. [PMID: 10207053 PMCID: PMC84122 DOI: 10.1128/mcb.19.5.3278] [Citation(s) in RCA: 650] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Insulin-like growth factor II (IGF-II) is a peptide growth factor that is homologous to both insulin-like growth factor I (IGF-I) and insulin and plays an important role in embryonic development and carcinogenesis. IGF-II is believed to mediate its cellular signaling via the transmembrane tyrosine kinase type 1 insulin-like growth factor receptor (IGF-I-R), which is also the receptor for IGF-I. Earlier studies with both cultured cells and transgenic mice, however, have suggested that in the embryo the insulin receptor (IR) may also be a receptor for IGF-II. In most cells and tissues, IR binds IGF-II with relatively low affinity. The IR is expressed in two isoforms (IR-A and IR-B) differing by 12 amino acids due to the alternative splicing of exon 11. In the present study we found that IR-A but not IR-B bound IGF-II with an affinity close to that of insulin. Moreover, IGF-II bound to IR-A with an affinity equal to that of IGF-II binding to the IGF-I-R. Activation of IR-A by insulin led primarily to metabolic effects, whereas activation of IR-A by IGF-II led primarily to mitogenic effects. These differences in the biological effects of IR-A when activated by either IGF-II or insulin were associated with differential recruitment and activation of intracellular substrates. IR-A was preferentially expressed in fetal cells such as fetal fibroblasts, muscle, liver and kidney and had a relatively increased proportion of isoform A. IR-A expression was also increased in several tumors including those of the breast and colon. These data indicate, therefore, that there are two receptors for IGF-II, both IGF-I-R and IR-A. Further, they suggest that interaction of IGF-II with IR-A may play a role both in fetal growth and cancer biology.
Collapse
Affiliation(s)
- F Frasca
- Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, University of Catania, Ospedale Garibaldi, 95123 Catania, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Lou Y, Zee RY, Li M, Morris BJ. Insulin receptor exon 11+/- isoform mRNA in spontaneously hypertensive and adrenocorticotropin-hypertensive rats. J Hypertens 1998; 16:1009-14. [PMID: 9794742 DOI: 10.1097/00004872-199816070-00015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To test the hypothesis that insulin resistance of the spontaneously hypertensive rat (SHR) and adrenocorticotropin-hypertensive rat is related to a difference in the proportion of the functionally different, alternatively spliced exon 11 isoforms of the insulin receptor. DESIGN We determined the proportions of mRNA for the exon 11+ and exon 11- isoforms in various tissues of SHR and Wistar-Kyoto rats aged 3, 6, 9 and 12 weeks, which span the pre-hypertensive phase through to established hypertension, as well as in Sprague-Dawley rats with adrenocorticotropin-induced hypertension and Sprague-Dawley controls. METHODS Detection of mRNA involved a reverse-transcriptase polymerase chain reaction technique specific for each isoform and quantification was by slot and dot blot hybridization. RESULTS Mean proportions of exon 11+ mRNA in SHR, Wistar-Kyoto rats, adrenocorticotropin-hypertensive rats and Sprague-Dawley control rats at each age were 95% for liver, 82% for adipose tissue, 77% for kidney, 66% for adrenal, 53% for heart, 26% for cerebral cortex, 23% for hypothalamus, and 3% for skeletal muscle. There was also no difference in concentration of total insulin receptor mRNA. CONCLUSIONS The absence of any difference in proportions of insulin receptor mRNA isoforms argues against the hypothesis that an alteration of differential splicing plays a role in the models of hypertension studied.
Collapse
Affiliation(s)
- Y Lou
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, New South Wales, Australia
| | | | | | | |
Collapse
|
29
|
Sbraccia P, Giaccari A, D'Adamo M, Caiola S, Morviducci L, Zorretta D, Maroccia E, Buongiorno A, Tamburrano G. Expression of the two insulin receptor isoforms is not altered in the skeletal muscle and liver of diabetic rats. Metabolism 1998; 47:129-32. [PMID: 9472957 DOI: 10.1016/s0026-0495(98)90207-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Alternative splicing of the 36-base pair exon 11 of the human insulin receptor (IR) gene and of the corresponding domain of the rat IR gene results in the synthesis of two IR isoforms with distinct functional characteristics. Altered expression of these IR isoforms has been previously demonstrated in the skeletal muscle of patients with non-insulin-dependent diabetes mellitus (NIDDM); however, this observation was not confirmed by other studies and is still a matter of debate. To assess whether the reported altered isoform expression is due to the secondary metabolic derangement of diabetes, we examined alternative splicing of IR mRNAs (IR36+ and IR36-, corresponding to human Ex11+ and Ex11-) in the skeletal muscle and liver of 6-hour fasting 90% pancreatectomized insulin-resistant diabetic and control Sprague-Dawley rats, using the reverse transcriptase-polymerase chain reaction (PCR) technique. Both diabetic and control rats showed the same pattern of IR mRNA expression: the liver exclusively expressed IR36+ mRNA, whereas only IR36- mRNA was detected in muscle. In conclusion, diabetes mellitus per se does not alter the expression of IR isoforms in the liver and skeletal muscle, and therefore, at least in this animal model of NIDDM, impaired insulin action develops independently from a relative increase in IR36+ mRNA expression in skeletal muscle.
Collapse
Affiliation(s)
- P Sbraccia
- Division of Endocrinology I, Università La Sapienza, Rome, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Wiersma MM, Auboeuf D, Nieuwenhuizen-Bakker IM, Radder JK, Riou JP, Vidal H. Insulin receptor mRNA splicing and altered metabolic control in aged and mildly insulin-deficient rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:E607-15. [PMID: 9142881 DOI: 10.1152/ajpendo.1997.272.4.e607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Using reverse transcription-competitive polymerase chain reaction, we measured the abundance of the mRNAs encoding the two spliced isoforms of insulin receptor in aged and mildly insulin-deficient rats. Twelve-month-old rats were characterized by peripheral insulin resistance and decreased glucose tolerance. Mild insulin deficiency, obtained by neonatal streptozotocin treatment, was associated with glucose intolerance due to reduced glucose-stimulated insulin response. Both models were associated with a decrease in the relative abundance of the mRNA with exon 11 in liver, heart, adipose tissue, and tibialis muscle, whereas a slight increase was seen in the extensor digitorum longus and no change in the soleus muscle. In the three muscles, the expression of the form without exon 11 largely predominated (>90%). In heart and adipose tissue, the two isoforms were expressed at a similar level in control rats. In both tissues, the form without exon 11 increased in streptozotocin-treated rats, whereas the absolute level of the form with exon 11 decreased in old rats. Although a decreased level of the variant with exon 11 correlated with insulin resistance of whole body glucose uptake, our results indicated that changes in the expression of the insulin receptor variants were secondary events and thus not the cause of the insulin resistance in old and mildly insulin-deficient rats.
Collapse
Affiliation(s)
- M M Wiersma
- Department of Endocrinology and Metabolic Diseases, University Hospital Leiden, The Netherlands
| | | | | | | | | | | |
Collapse
|
31
|
Larsson H, Ahrén B. Failure to adequately adapt reduced insulin sensitivity with increased insulin secretion in women with impaired glucose tolerance. Diabetologia 1996; 39:1099-107. [PMID: 8877295 DOI: 10.1007/bf00400660] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To study the islet adaptation to reduced insulin sensitivity in normal and glucose intolerant post-menopausal women, we performed a euglycaemic, hyperinsulinaemic clamp in 108 randomly selected women, aged 58-59 years. Of the 20 women with the lowest insulin sensitivity, 11 had impaired glucose tolerance (IGT) whereas 9 had normal glucose tolerance (NGT). These women together with 15 women with medium insulin sensitivity and 16 women with high insulin sensitivity and NGT were further examined with arginine stimulation at three glucose levels (fasting, 14 and > 25 mmol/l). In NGT, the acute insulin response (AIR) to 5 g i.v. arginine at all three glucose levels and the slopeAIR, i.e. the glucose potentiation of insulin secretion, were markedly increased in the women with the lowest insulin sensitivity and NGT compared to those with medium or high insulin sensitivity. In contrast, in low insulin sensitivity, AIR was significantly lower in IGT than in NGT (at glucose 14 mmol/l p = 0.015, and at > 25 mmol/l p = 0.048). The potentiation of AIR induced by low insulin sensitivity in women with NGT was reduced by 74% (AIR at 14 mmol/l glucose) and 57% (AIR at > 25 mmol/l glucose), respectively, in women with IGT. Also the slopeAIR was lower in IGT than in NGT (p = 0.025); the increase in slope AIR due to low insulin sensitivity was abolished in IGT. In contrast, glucagon secretion was not different between women with IGT as opposed to NGT. We conclude that as long as there is an adequate beta-cell adaptation to low insulin sensitivity with increased insulin secretory capacity and glucose potentiation of insulin secretion, NGT persists.
Collapse
Affiliation(s)
- H Larsson
- Department of Medicine, Lund University, Malmö, Sweden
| | | |
Collapse
|