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Zhao W, Lu J, Zhang L, Lu W, Zhu W, Bao Y, Zhou J. Relationship between time in range and corneal nerve fiber loss in asymptomatic patients with type 2 diabetes. Chin Med J (Engl) 2022; 135:1978-1985. [PMID: 36070458 PMCID: PMC9746728 DOI: 10.1097/cm9.0000000000002140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Corneal confocal microscopy (CCM) is a noninvasive technique to detect early nerve damage of diabetic sensorimotor polyneuropathy (DSPN). Time in range (TIR) is an emerging metric of glycemic control which was reported to be associated with diabetic complications. We sought to explore the relationship between TIR and corneal nerve parameters in asymptomatic patients with type 2 diabetes (T2DM). METHODS In this cross-sectional study, 206 asymptomatic inpatients with T2DM were recruited. After 7 days of continuous glucose monitoring, the TIR was calculated as the percentage of time in the glucose range of 3.9 to 10.0 mmol/L. CCM was performed to determine corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length (CNFL). Abnormal CNFL was defined as ≤15.30 mm/mm 2 . RESULTS Abnormal CNFL was found in 30.6% (63/206) of asymptomatic subjects. Linear regression analyses revealed that TIR was positively correlated with CCM parameters both in the crude and adjusted models (all P < 0.05). Each 10% increase in TIR was associated with a 28.2% (95% CI: 0.595-0.866, P = 0.001) decreased risk of abnormal CNFL after adjusting for covariates. With the increase of TIR quartiles, corneal nerve fiber parameters increased significantly (all P for trend <0.01). The receiver operating characteristic curve indicated that the optimal cutoff point of TIR was 77.5% for predicting abnormal CNFL in asymptomatic patients. CONCLUSIONS There is a significant independent correlation between TIR and corneal nerve fiber loss in asymptomatic T2DM patients. TIR may be a useful surrogate marker for early diagnosis of DSPN.
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Affiliation(s)
- Weijing Zhao
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
| | - Jingyi Lu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
- Shanghai Clinical Center for Metabolic Diseases, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Diabetes Institute, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China
| | - Lei Zhang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
| | - Wei Lu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
| | - Wei Zhu
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
| | - Yuqian Bao
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
| | - Jian Zhou
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital; Shanghai Clinical Center for Diabetes; Shanghai Key Clinical Center for Metabolic Disease; Shanghai Diabetes Institute; Shanghai Key Laboratory of Diabetes Mellitus, Shanghai 200233, China
- Department of Endocrinology and Metabolism, Jinshan Branch of Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 201500, China
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Tang Z, Chen S, Ni Y, Zhao R, Zhu X, Yang X, Zhang X. Role of Na +, K +-ATPase ion pump in osteoinduction. Acta Biomater 2021; 129:293-308. [PMID: 34087440 DOI: 10.1016/j.actbio.2021.05.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 12/14/2022]
Abstract
Porous biphasic calcium phosphate bioceramic (BCP) possesses osteoinductivity to induce the osteoblastic commitment of mesenchymal stem cells (MSCs) and ectopic bone formation. However, the underlying mechanism remains enigmatic. We performed a gene array analysis of MSCs cocultured with BCP to screen for candidate osteoinductive modulators. Na+, K+-ATPase (NKA), an ion transporter, therefore was identified as a crucial ion transporter in regulating the osteogenesis of the cells. NKA activator, a polyclonal antibody, enriched the cytomembrane abundance of NKA and lead to an enhanced osteogenic effect of BCP. As indicated in gene array analysis and suggested by co-immunoprecipitation assay, protein phosphatase 2A (PP2A) was elevated by BCP to dephosphorylate NKA and prevent its endocytosis. The inhibition of NKA by ouabain resulted in an adverse effect on osteoinductivity of BCP. We further altered NKA activity in mice implanted with BCP and found that the intensity and incidence of osteoinduction was increased by the NKA activator. We went one step further by investigating the potential of targeting NKA in osteoporotic bone regeneration. Activating NKA upregulated osteogenic gene expression and calcium deposition ability of osteoporotic osteoblasts. Furthermore, activation of NKA in mice ameliorated estrogen-deficiency induced bone loss, in terms of increased bone mass and improved bending strength. With this osteoinductive bioceramic derived ion transporter target, we demonstrate that the activation of NKA has significant potential to revolutionize the regeneration of bone. STATEMENT OF SIGNIFICANCE: In this study, we identified an important role of Na+, K+-ATPase (NKA) have played in osteoinductivity of biphasic calcium phosphate bioceramic (BCP). Furthermore, we demonstrated the therapeutic potential of targeting NKA in osteoporotic bone regeneration. Numerous gene and protein targets to treat osteoporosis were discovered every year, mainly obtained by genomic and proteomic screenings of a large population. In contrast, our study identified an unrevealed bone regenerating target from the upregulated genes induced by an osteoinductive biomaterial. The approach was cost-saving since it did not require a large sample pool. Furthermore, the target derived from this approach was proven to be anabolic. Identification of an anabolic agent holds significant value since most of the current anti-osteoporotic therapies are antiresorptive.
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Osborn JW, Tyshynsky R, Vulchanova L. Function of Renal Nerves in Kidney Physiology and Pathophysiology. Annu Rev Physiol 2021; 83:429-450. [PMID: 33566672 DOI: 10.1146/annurev-physiol-031620-091656] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Renal sympathetic (efferent) nerves play an important role in the regulation of renal function, including glomerular filtration, sodium reabsorption, and renin release. The kidney is also innervated by sensory (afferent) nerves that relay information to the brain to modulate sympathetic outflow. Hypertension and other cardiometabolic diseases are linked to overactivity of renal sympathetic and sensory nerves, but our mechanistic understanding of these relationships is limited. Clinical trials of catheter-based renal nerve ablation to treat hypertension have yielded promising results. Therefore, a greater understanding of how renal nerves control the kidney under physiological and pathophysiological conditions is needed. In this review, we provide an overview of the current knowledge of the anatomy of efferent and afferent renal nerves and their functions in normal and pathophysiological conditions. We also suggest further avenues of research for development of novel therapies targeting the renal nerves.
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Affiliation(s)
- John W Osborn
- Department of Surgery, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA;
| | - Roman Tyshynsky
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Lucy Vulchanova
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA
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4
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Biological Activity of c-Peptide in Microvascular Complications of Type 1 Diabetes-Time for Translational Studies or Back to the Basics? Int J Mol Sci 2020; 21:ijms21249723. [PMID: 33419247 PMCID: PMC7766542 DOI: 10.3390/ijms21249723] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 12/15/2022] Open
Abstract
People with type 1 diabetes have an increased risk of developing microvascular complications, which have a negative impact on the quality of life and reduce life expectancy. Numerous studies in animals with experimental diabetes show that c-peptide supplementation exerts beneficial effects on diabetes-induced damage in peripheral nerves and kidneys. There is substantial evidence that c-peptide counteracts the detrimental changes caused by hyperglycemia at the cellular level, such as decreased activation of endothelial nitric oxide synthase and sodium potassium ATPase, and increase in formation of pro-inflammatory molecules mediated by nuclear factor kappa-light-chain-enhancer of activated B cells: cytokines, chemokines, cell adhesion molecules, vascular endothelial growth factor, and transforming growth factor beta. However, despite positive results from cell and animal studies, no successful c-peptide replacement therapies have been developed so far. Therefore, it is important to improve our understanding of the impact of c-peptide on the pathophysiology of microvascular complications to develop novel c-peptide-based treatments. This article aims to review current knowledge on the impact of c-peptide on diabetic neuro- and nephropathy and to evaluate its potential therapeutic role.
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5
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Biological activity versus physiological function of proinsulin C-peptide. Cell Mol Life Sci 2020; 78:1131-1138. [PMID: 32959070 PMCID: PMC7897624 DOI: 10.1007/s00018-020-03636-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 08/07/2020] [Accepted: 09/03/2020] [Indexed: 11/06/2022]
Abstract
Proinsulin C-peptide (C-peptide) has drawn much research attention. Even if the peptide has turned out not to be important in the treatment of diabetes, every phase of C-peptide research has changed our view on insulin and peptide hormone biology. The first phase revealed that peptide hormones can be subject to processing, and that their pro-forms may involve regulatory stages. The second phase revealed the possibility that one prohormone could harbor more than one activity, and that the additional activities should be taken into account in the development of hormone-based therapies. In the third phase, a combined view of the evolutionary patterns in hormone biology allowed an assessment of C-peptide´s role in physiology, and of how biological activities and physiological functions are shaped by evolutionary processes. In addition to this distinction, C-peptide research has produced further advances. For example, C-peptide fragments are successfully administered in immunotherapy of type I diabetes, and plasma C-peptide levels remain a standard for measurement of beta cell activity in patients. Even if the concept of C-peptide as a hormone is presently not supported, some of its bioactivities continue to influence our understanding of evolutionary changes of also other peptides.
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6
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Is GPR146 really the receptor for proinsulin C-peptide? Bioorg Med Chem Lett 2020; 30:127208. [DOI: 10.1016/j.bmcl.2020.127208] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 04/16/2020] [Accepted: 04/18/2020] [Indexed: 01/01/2023]
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7
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Poteryaeva ON, Usynin IF. [Molecular mechanisms of action and physiological effects of the proinsulin C-peptide (a systematic review)]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2020; 66:196-207. [PMID: 32588825 DOI: 10.18097/pbmc20206603196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The C-peptide is a fragment of proinsulin, the cleavage of which forms active insulin. In recent years, new information has appeared on the physiological effects of the C-peptide, indicating its positive effect on many organs and tissues, including the kidneys, nervous system, heart, vascular endothelium and blood microcirculation. Studies on experimental models of diabetes mellitus in animals, as well as clinical trials in patients with diabetes, have shown that the C-peptide has an important regulatory effect on the early stages of functional and structural disorders caused by this disease. The C-peptide exhibits its effects through binding to a specific receptor on the cell membrane and activation of downstream signaling pathways. Intracellular signaling involves G-proteins and Ca2+-dependent pathways, resulting in activation and increased expression of endothelial nitric oxide synthase, Na+/K+-ATPase and important transcription factors involved in apoptosis, anti-inflammatory and other intracellular defense mechanisms. This review gives an idea of the C-peptide as a bioactive endogenous peptide that has its own biological activity and therapeutic potential.
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Affiliation(s)
- O N Poteryaeva
- Institute of Biochemistry, Federal Research Center of Fundamental and Translation Medicine, Novosibirsk, Russia
| | - I F Usynin
- Institute of Biochemistry, Federal Research Center of Fundamental and Translation Medicine, Novosibirsk, Russia
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8
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Hellström W, Hansen-Pupp I, Hellgren G, Engström E, Stigson L, Sävman K, Ley D, Löfqvist C. C-peptide suppression during insulin infusion in the extremely preterm infant is associated with insulin sensitivity. J Clin Endocrinol Metab 2019; 104:3902-3910. [PMID: 31058966 DOI: 10.1210/jc.2018-02681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 04/30/2019] [Indexed: 11/19/2022]
Abstract
CONTEXT Little is known about the individual response of glucose-regulating factors to administration of exogenous insulin infusion in extremely preterm infants. OBJECTIVE To evaluate longitudinal serum concentrations of insulin, C-peptide, and plasma glucose levels in a high frequency sampling regimen in extremely preterm infants treated with insulin due to hyperglycemia. DESIGN Prospective longitudinal cohort study. SETTING Two university hospitals in Sweden between December 2015 and September 2016. PATIENTS AND INTERVENTION Serum samples were obtained from nine extremely preterm infants, gestational age between 22(+3) and 26(+5) weeks(+days), with hyperglycemia (plasma-glucose >10 mmol/L) at the start of insulin infusion, at 12, 24, and every 24 hours thereafter during ongoing infusion, and 12, 24, and 72 hours after the end of insulin infusion. MAIN OUTCOME MEASURES Longitudinal serum concentrations of insulin and C-peptide and plasma glucose levels. RESULTS During insulin infusion, the serum C-peptide concentrations decreased compared to at start of infusion (p = 0.036), and then increased after ending the infusion. Individual insulin sensitivity based on the non-fasting plasma glucose/insulin ratio at the start of insulin infusion correlated with the initial decrease in serum ΔC-peptide[After 12h] (p = 0.007) and the degree of lasting decrease in serum ΔC-peptide[After end of infusion] (p = 0.015). CONCLUSION Exogenous insulin infusion suppressed the C-peptide concentration to individually different degrees. In addition, the effect of insulin infusion on β-cells may be linked to individual insulin sensitivity, where a low insulin sensitivity resulted in a more pronounced decrease in C-peptide during insulin infusion.
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Affiliation(s)
- William Hellström
- Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ingrid Hansen-Pupp
- Department of Pediatrics, Institute of Clinical Sciences Lund, Lund University and Skane University Hospital, Lund, Sweden
| | - Gunnel Hellgren
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Section for Ophthalmology, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Eva Engström
- Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lennart Stigson
- Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Karin Sävman
- Department of Pediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - David Ley
- Department of Pediatrics, Institute of Clinical Sciences Lund, Lund University and Skane University Hospital, Lund, Sweden
| | - Chatarina Löfqvist
- Section for Ophthalmology, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Institute of Health and Care Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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9
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Martin JH, Aitken RJ, Bromfield EG, Cafe SL, Sutherland JM, Frost ER, Nixon B, Lord T. Investigation into the presence and functional significance of proinsulin C-peptide in the female germline†. Biol Reprod 2019; 100:1275-1289. [PMID: 30715203 DOI: 10.1093/biolre/ioz008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 12/10/2018] [Accepted: 01/28/2019] [Indexed: 08/02/2024] Open
Abstract
Diabetes is associated with poor oocyte quality and the dysregulation of ovarian function and is thus a leading contributor to the increasing prevalence of female reproductive pathologies. Accordingly, it is well-established that insulin fulfills a key role in the regulation of several facets of female reproduction. What remains less certain is whether proinsulin C-peptide, which has recently been implicated in cellular signaling cascades, holds a functional role in the female germline. In the present study, we examined the expression of insulin, C-peptide, and its purported receptor; GPR146, within the mouse ovary and oocyte. Our data establish the presence of abundant C-peptide within follicular fluid and raise the prospect that this bioactive peptide is internalized by oocytes in a G-protein coupled receptor-dependent manner. Further, our data reveal that internalized C-peptide undergoes pronounced subcellular relocalization from the ooplasm to the pronuclei postfertilization. The application of immunoprecipitation analysis and mass spectrometry identified breast cancer type 2 susceptibility protein (BRCA2), the meiotic resumption/DNA repair protein, as a primary binding partner for C-peptide within the oocyte. Collectively, these findings establish a novel accumulation profile for C-peptide in the female germline and provide the first evidence for an interaction between C-peptide and BRCA2. This interaction is particularly intriguing when considering the propensity for oocytes from diabetic women to experience aberrant meiotic resumption and perturbation of traditional DNA repair processes. This therefore provides a clear imperative for further investigation of the implications of dysregulated C-peptide production in these individuals.
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Affiliation(s)
- Jacinta H Martin
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - R John Aitken
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Elizabeth G Bromfield
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Shenae L Cafe
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Jessie M Sutherland
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Emily R Frost
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Brett Nixon
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
| | - Tessa Lord
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, The Hunter Medical Research Institute, New Lambton Heights and the University of Newcastle, Callaghan, Newcastle, Australia
- School of Molecular Biosciences, Centre for Reproductive Biology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
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10
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Abstract
Kidney disease is a serious development in diabetes mellitus and poses an increasing clinical problem. Despite increasing incidence and prevalence of diabetic kidney disease, there have been no new therapies for this condition in the last 20 years. Mounting evidence supports a biological role for C-peptide, and findings from multiple studies now suggest that C-peptide may beneficially affect the disturbed metabolic and pathophysiological pathways leading to the development of diabetic nephropathy. Studies of C-peptide in animal models and in humans with type 1 diabetes all suggest a renoprotective effect for this peptide. In diabetic rodents, C-peptide reduces glomerular hyperfiltration and albuminuria. Cohort studies of diabetic patients with combined islet and kidney transplants suggest that maintained C-peptide secretion is protective of renal graft function. Further, in short-term studies of patients with type 1 diabetes, administration of C-peptide is also associated with a lowered hyperfiltration rate and reduced microalbuminuria. Thus, the available information suggests that type 1 diabetes should be regarded as a dual hormone deficiency disease and that clinical trials of C-peptide in diabetic nephropathy are both justified and urgently required.
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Affiliation(s)
- N J Brunskill
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
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11
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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12
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Wahren J, Larsson C. C-peptide: new findings and therapeutic possibilities. Diabetes Res Clin Pract 2015; 107:309-19. [PMID: 25648391 DOI: 10.1016/j.diabres.2015.01.016] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 01/15/2015] [Indexed: 12/18/2022]
Abstract
Much new information on C-peptide physiology has appeared during the past 20 years. It has been shown that C-peptide binds specifically to cell membranes, elicits intracellular signaling via G-protein and Ca2+ -dependent pathways, resulting in activation and increased expression of endothelial nitric oxide synthase, Na+, K+ -ATPase and several transcription factors of importance for anti-inflammatory, anti-oxidant and cell protective mechanisms. Studies in animal models of diabetes and early clinical trials in patients with type 1 diabetes demonstrate that C-peptide in replacement doses elicits beneficial effects on early stages of diabetes-induced functional and structural abnormalities of the peripheral nerves, the kidneys and the retina. Much remains to be learned about C-peptide's mechanism of action and long-term clinical trials in type 1 diabetes subjects will be required to determine C-peptide's clinical utility. Nevertheless, even a cautious evaluation of the available evidence presents the picture of a bioactive endogenous peptide with therapeutic potential.
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Affiliation(s)
- John Wahren
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Cebix AB, Stockholm, Sweden.
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13
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Landreh M, Jörnvall H. C-peptide evolution: generation from few structural restrictions of bioactivities not necessarily functional. FEBS Lett 2015; 589:415-8. [PMID: 25595456 DOI: 10.1016/j.febslet.2015.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 12/30/2014] [Accepted: 01/07/2015] [Indexed: 11/28/2022]
Abstract
The proinsulin C-peptide has molecular, cellular and organismal activities but lacks disease-associated mutations or short-term loss-of-function effects. This dilemma between activity and function may be explained from its evolutionary setting with insulin as an ancestral partner. The charge, approximate length and flexibility of C-peptide are all that is required for the insulin interactions, while remaining aspects are free to evolve, where new bioactivities can emerge. They can initially be transient, weak, and non-functional, but may gradually be consolidated. In this manner, C-peptide may have acquired multiple bioactivities, explaining why some yet have limited functions but could represent early-stage hormonal-like activities.
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Affiliation(s)
- Michael Landreh
- Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Hans Jörnvall
- Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, SE-171 77 Stockholm, Sweden.
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14
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Kubota M, Sato Y, Khookhor O, Ekberg K, Chibalin AV, Wahren J. Enhanced insulin action following subcutaneous co-administration of insulin and C-peptide in rats. Diabetes Metab Res Rev 2014; 30:124-31. [PMID: 24027001 DOI: 10.1002/dmrr.2471] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/12/2013] [Accepted: 09/07/2013] [Indexed: 12/27/2022]
Abstract
BACKGROUND This study was undertaken to examine if C-peptide (C) may interact with hexameric insulin and facilitate its disaggregation into the physiologically active monomeric form. METHODS Regular insulin (I) or an insulin analogue (IA) were injected s.c. in rats together with C or its C-terminal pentapeptide (PP). I or IA and C or PP were administered either as a physical mixture or into two separate s.c. depots. Whole body glucose utilization was evaluated using the euglycemic clamp technique. Phosphorylation of Akt/PKB and GSK in liver and skeletal muscles and ⁸⁶Rb⁺ uptake by L6 cells were measured. RESULTS S.c. injection of a mixture of I and C or I and PP resulted in a 30-55% greater (P < 0.01-0.001) and 15-27% (P < 0.05-0.001) longer stimulation of whole body glucose utilization than after separate injections. Insulin-stimulated phosphorylation of Akt/PKB in liver increased 35% more after injection of I and C in mixture compared with after separate injections. Phosphorylation of GSK3 was augmented by 50% (P < 0.05) following the injection of I and C in mixture compared with separate injections. Stimulation of myotubes with premixed I and C (1 nM) elicited 20% additional increase in ouabain-sensitive ⁸⁶Rb⁺ uptake (P < 0.05) in comparison with the effect when I and C were added separately. CONCLUSIONS Subcutaneous co-administration of insulin and C results in augmented insulin bioactivity at the level of tissue glucose uptake, intracellular signalling, and enzyme activation. These effects may be attributed to augmented C mediated disaggregation of hexameric insulin into its physiologically active monomeric form.
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MESH Headings
- Animals
- C-Peptide/administration & dosage
- C-Peptide/chemistry
- C-Peptide/genetics
- C-Peptide/pharmacology
- Cell Line
- Drug Combinations
- Drug Implants
- Drug Therapy, Combination
- Enzyme Activation/drug effects
- Glycogen Synthase Kinase 3/chemistry
- Glycogen Synthase Kinase 3/metabolism
- Humans
- Hypoglycemic Agents/administration & dosage
- Hypoglycemic Agents/chemistry
- Hypoglycemic Agents/pharmacology
- Insulin Lispro/administration & dosage
- Insulin Lispro/genetics
- Insulin Lispro/pharmacology
- Insulin, Regular, Human/administration & dosage
- Insulin, Regular, Human/genetics
- Insulin, Regular, Human/pharmacology
- Liver/drug effects
- Liver/enzymology
- Liver/metabolism
- Male
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/metabolism
- Oligopeptides/administration & dosage
- Oligopeptides/chemistry
- Oligopeptides/genetics
- Oligopeptides/pharmacology
- Peptide Fragments/administration & dosage
- Peptide Fragments/chemistry
- Peptide Fragments/genetics
- Peptide Fragments/pharmacology
- Phosphorylation/drug effects
- Protein Processing, Post-Translational/drug effects
- Proto-Oncogene Proteins c-akt/agonists
- Proto-Oncogene Proteins c-akt/metabolism
- Random Allocation
- Rats
- Rats, Wistar
- Recombinant Proteins/administration & dosage
- Recombinant Proteins/chemistry
- Recombinant Proteins/pharmacology
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Affiliation(s)
- M Kubota
- Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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15
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pH-Dependent Interaction between C-Peptide and Phospholipid Bicelles. JOURNAL OF BIOPHYSICS 2012; 2012:185907. [PMID: 22848213 PMCID: PMC3405660 DOI: 10.1155/2012/185907] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 05/22/2012] [Indexed: 12/20/2022]
Abstract
C-peptide is the connecting peptide between the A and B chains of insulin in proinsulin. In this paper, we investigate the interaction between C-peptide and phospholipid bicelles, by circular dichroism and nuclear magnetic resonance spectroscopy, and in particular the pH dependence of this interaction. The results demonstrate that C-peptide is largely unstructured independent of pH, but that a weak structural induction towards a short stretch of β-sheet is induced at low pH, corresponding to the isoelectric point of the peptide. Furthermore, it is demonstrated that C-peptide associates with neutral phospholipid bicelles as well as acidic phospholipid bicelles at this low pH. C-peptide does not undergo a large structural rearrangement as a consequence of lipid interaction, which indicates that the folding and binding are uncoupled. In vivo, local variations in environment, including pH, may cause C-peptide to associate with lipids, which may affect the aggregation state of the peptide.
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16
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Galuska D, Pirkmajer S, Barrès R, Ekberg K, Wahren J, Chibalin AV. C-peptide increases Na,K-ATPase expression via PKC- and MAP kinase-dependent activation of transcription factor ZEB in human renal tubular cells. PLoS One 2011; 6:e28294. [PMID: 22162761 PMCID: PMC3230608 DOI: 10.1371/journal.pone.0028294] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 11/04/2011] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Replacement of proinsulin C-peptide in type 1 diabetes ameliorates nerve and kidney dysfunction, conditions which are associated with a decrease in Na,K-ATPase activity. We determined the molecular mechanism by which long term exposure to C-peptide stimulates Na,K-ATPase expression and activity in primary human renal tubular cells (HRTC) in control and hyperglycemic conditions. METHODOLOGY/PRINCIPAL FINDINGS HRTC were cultured from the outer cortex obtained from patients undergoing elective nephrectomy. Ouabain-sensitive rubidium ((86)Rb(+)) uptake and Na,K-ATPase activity were determined. Abundance of Na,K-ATPase was determined by Western blotting in intact cells or isolated basolateral membranes (BLM). DNA binding activity was determined by electrical mobility shift assay (EMSA). Culturing of HRTCs for 5 days with 1 nM, but not 10 nM of human C-peptide leads to increase in Na,K-ATPase α(1)-subunit protein expression, accompanied with increase in (86)Rb(+) uptake, both in normal- and hyperglycemic conditions. Na,K-ATPase α(1)-subunit expression and Na,K-ATPase activity were reduced in BLM isolated from cells cultured in presence of high glucose. Exposure to1 nM, but not 10 nM of C-peptide increased PKCε phosphorylation as well as phosphorylation and abundance of nuclear ERK1/2 regardless of glucose concentration. Exposure to 1 nM of C-peptide increased DNA binding activity of transcription factor ZEB (AREB6), concomitant with Na,K-ATPase α(1)-subunit mRNA expression. Effects of 1 nM C-peptide on Na,K-ATPase α(1)-subunit expression and/or ZEB DNA binding activity in HRTC were abolished by incubation with PKC or MEK1/2 inhibitors and ZEB siRNA silencing. CONCLUSIONS/SIGNIFICANCE Despite activation of ERK1/2 and PKC by hyperglycemia, a distinct pool of PKCs and ERK1/2 is involved in regulation of Na,K-ATPase expression and activity by C-peptide. Most likely C-peptide stimulates sodium pump expression via activation of ZEB, a transcription factor that has not been previously implicated in C-peptide-mediated signaling. Importantly, only physiological concentrations of C-peptide elicit this effect.
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Affiliation(s)
- Dana Galuska
- Section of Integrative Physiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Sergej Pirkmajer
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Romain Barrès
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Karin Ekberg
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - John Wahren
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Alexander V. Chibalin
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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17
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Nordquist L, Palm F, Andresen BT. Renal and vascular benefits of C-peptide: Molecular mechanisms of C-peptide action. Biologics 2011; 2:441-52. [PMID: 19707375 PMCID: PMC2721399 DOI: 10.2147/btt.s3221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
C-peptide has long been thought to be an inert byproduct of insulin production, but it has become apparent, and accepted, that C-peptide has important biological properties. C-peptide displays beneficial effects in many tissues affected by diabetic complications, such as increased peripheral blood flow and protection from renal damage. However, the mechanisms mediating these effects remain unclear. C-peptide interacts with cellular membranes at unidentified sites distinctive of the insulin family of receptors, and signals to multiple targets known to play a role in diabetes and diabetic complications, such as Na+/K+-ATPase and NOS. In general, the physiological and molecular effects of C-peptide resemble insulin, but C-peptide also possesses traits separate from those of insulin. These basic studies have been confirmed in human studies, suggesting that C-peptide may lend itself to clinical applications. However, the molecular and physiological properties of C-peptide are not completely elucidated, and large clinical studies have not begun. In order to further these goals, we critically summarize the current state of knowledge regarding C-peptide’s renal and vascular effects and the molecular signaling of C-peptide.
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Affiliation(s)
- Lina Nordquist
- Department of Medical Cell Biology, Division of Integrative Physiology, Uppsala University, Uppsala, Sweden
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18
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Affiliation(s)
- Patrizia Luppi
- Division of Immunogenetics, Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, Rangos Research Center, 530 45th Street, Pittsburgh, PA 15201, USA
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19
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Lee SK, Lee JO, Kim JH, Jung JH, You GY, Park SH, Kim HS. C-peptide stimulates nitrites generation via the calcium-JAK2/STAT1 pathway in murine macrophage Raw264.7 cells. Life Sci 2010; 86:863-8. [PMID: 20388518 DOI: 10.1016/j.lfs.2010.03.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Revised: 03/19/2010] [Accepted: 03/22/2010] [Indexed: 01/25/2023]
Abstract
AIMS C-peptide is a product of pro-insulin cleavage. Numerous studies have demonstrated that C-peptide, although not influencing blood glucose control, may play a role in preventing and potentially reversing some of the chronic complications of type 1 diabetes. The aim of this paper was to present a novel function of C-peptide, focusing on its role in nitric oxide (NO) generation. MAIN METHODS Murine macrophage Raw264.7 cells and primary peritoneal macrophages were incubated under control conditions, or with C-peptide. Expression level of iNOS and phosphorylation status of JAK2/STAT1 were analyzed by Western blot. Fluorometric NO assay kit was used to assess the concentration of nitrite in culture medium. Intracellular calcium concentration was measured with calcium indicator dyes, such as Fura-2 and Fluo-3 AM. KEY FINDINGS C-peptide increased the level of nitrites in murine macrophage Raw264.7 cells. The nitrites production induced by lipopolysaccharide (LPS) was further enhanced by co-treatment of C-peptide. This up-regulation of nitrites generation also correlated with the induction of inducible nitric oxide synthase (iNOS), a prominent marker of macrophage activation. In addition, C-peptide increased the intracellular concentration of calcium levels. Moreover, C-peptide-induced nitrites generation and increase in calcium was observed in freshly isolated primary peritoneal macrophages. In addition, C-peptide specifically affected the Janus activated kinase (JAK)/signal transducer and activated transcription (STAT) pathway. Finally, C-peptide-mediated nitrites generation and JAK2/STAT1 phosphorylation were not detected in the presence of the intracellular calcium chelator, BAPTA-AM. SIGNIFICANCE These results suggest that C-peptide may elicit immune modulatory function via modulation of the calcium/JAK-STAT pathway.
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Affiliation(s)
- Soo Kyung Lee
- Department of Anatomy, Korea University College of Medicine, Seoul 136-701, Republic of Korea
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20
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Nordquist L, Shimada K, Ishii T, Furuya DT, Kamikawa A, Kimura K. Proinsulin C-peptide prevents type-1 diabetes-induced decrease of renal Na+-K+-ATPase alpha1-subunit in rats. Diabetes Metab Res Rev 2010; 26:193-9. [PMID: 20225182 DOI: 10.1002/dmrr.1071] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AIMS/HYPOTHESIS C-peptide reduces renal damage in diabetic patients and experimental animal models. In vitro studies suggest that the renal effects of C-peptide may, in part, be explained by stimulation of Na(+)/K(+)-ATPase activity. However, the responses of Na(+)/K(+)-ATPase expression in the kidney of diabetic animals to C-peptide administration remain unclear. The aim of this study was to clarify the responses. METHODS Type 1 diabetic rats were produced by injecting streptozotocin (STZ), and some of the rats were treated with either C-peptide or insulin by the aid of an osmotic pump for 1 week. The mRNA expression and immunohistochemical localization of Na(+)/K(+)-ATPase alpha1-, alpha2- and beta3-subunits were investigated in the kidney of these rats. RESULTS Na(+)/K(+)-ATPase alpha1-subunit was abundantly expressed in the medullary collecting ducts of control animals, but the expression was markedly decreased in the diabetic state with concomitant decrease in its mRNA expression. Similar decreases were observed in the insulin-treated diabetic rats, whereas in the C-peptide-treated diabetic rats, there was no reduction in the alpha1-expression. The beta3-subunit was expressed in podocytes and parietal cells in the glomeruli, vascular endothelial cells, and cortical collecting ducts, but lesser signals were observed in the proximal and distal tubules. However, the beta3-subunit did not appear to be affected by the diabetic state. CONCLUSIONS Diabetes selectively reduced Na(+)/K(+)-ATPase alpha1-subunit expression and abundance. Chronic administration of C-peptide prevented this decrease. This implies a role for C-peptide in the long-term regulation of Na(+)/K(+)-ATPase function.
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Affiliation(s)
- Lina Nordquist
- Laboratory of Biochemistry, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
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21
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Suhail M. Na, K-ATPase: Ubiquitous Multifunctional Transmembrane Protein and its Relevance to Various Pathophysiological Conditions. J Clin Med Res 2010; 2:1-17. [PMID: 22457695 PMCID: PMC3299169 DOI: 10.4021/jocmr2010.02.263w] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/05/2010] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED The Na(+), K(+)-ATPase (NKA) is an ubiquitous enzyme consisting of α, β and γ subunits, and is responsible for the creation and maintenance of the Na(+) and K(+) gradients across the cell membrane by transporting 3 Na(+) out and 2 K(+) into the cell. Sodium pump regulation is tissue as well as isoform specific. Intracellular messengers differentially regulate the activity of the individual NKA isozymes. Regulation of specific NKA isozymes gives cells the ability to precisely coordinate NKA activity to their physiological requirements. It is the only known receptor for the cardiac glycosides used to treat congestive heart failure and cardiac arrhythmias. Endogenous ligands structurally similar to cardiac glycosides may act as natural regulators of the sodium pump in heart and other tissues. Identification of naturally occurring regulators of NKA could initiate the discovery of new hormone-like control systems involved in the etiology of selected disease processes, hence the importance of understanding the relation of the sodium pump and its ligands to disease. Diabetes has a marked effect on the metabolism of a variety of tissues and because the NKA is critical for the membrane potential and many transports, a change in its activity in diabetes would have profound consequence in these tissues. NKA is also involved in hypertension, salt balance, cardiovascular and renal disorders, sperm capacitation, cell volume regulation, apoptosis, rheumatoid arthritis, sepsis, neurological disorders, lung edema clearance and preeclampsia. NKA activity and expression in the collecting duct of kidney are modulated physiologically by hormones like aldosterone, vasopressin, and insulin. NKA enzyme activity and subunit levels are reduced in carcinoma, NKA-β levels were highly reduced in an invasive form of human renal clear cell carcinoma, androgen-dependent prostate cancer, in early stages of urothelial cancer, as well as in poorly differentiated, highly motile carcinoma cell lines obtained from various tissues suggesting a functional link between reduced NKA-β expression and cancer progression. It could be a target for the development of anticancer drugs as it serves as a signal transducer, it is a player in cell adhesion and its aberrant expression and activity are implicated in the development and progression of different cancers. KEYWORDS Na(+), K(+)-ATPase (NKA); Cardiotonic steroids (CTS); Diabetes; Hypertension; Cardiovascular and renal disorders; Signal transducer; Anticancer drugs.
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Affiliation(s)
- Mohd Suhail
- Department of Biochemistry, University of Allahabad, Allahabad-211002, India
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22
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Lindahl E, Nyman U, Zaman F, Palmberg C, Cascante A, Shafqat J, Takigawa M, Sävendahl L, Jörnvall H, Joseph B. Proinsulin C-peptide regulates ribosomal RNA expression. J Biol Chem 2009; 285:3462-9. [PMID: 19917601 DOI: 10.1074/jbc.m109.053587] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Proinsulin C-peptide is internalized into cells, but a function of its intracellular localization has not been established. We now demonstrate that, upon cellular entry, C-peptide is localized to the nucleoli, where it promotes transcription of genes encoding for ribosomal RNA. We find that C-peptide binds to histones and enhances acetylation of lysine residue 16 of histone H4 at the promoter region of genes for ribosomal RNA. In agreement with synchrony of ribosomal RNA synthesis and cell proliferation, we show that C-peptide stimulates proliferation in chondrocytes and HEK-293 cells. This regulation of ribosomal RNA provides a mechanism by which C-peptide can exert transcriptional effects and implies that the peptide has growth factor activity.
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Affiliation(s)
- Emma Lindahl
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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23
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Oran PE, Jarvis JW, Borges CR, Nelson RW. C-peptide microheterogeneity in type 2 diabetes populations. Proteomics Clin Appl 2009; 4:106-11. [PMID: 21137020 DOI: 10.1002/prca.200800249] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 08/11/2009] [Accepted: 09/24/2009] [Indexed: 12/31/2022]
Abstract
PURPOSE The purpose of this study was to investigate naturally occurring C-peptide microheterogeneity in healthy and type 2 diabetes (T2D) populations. EXPERIMENTAL DESIGN MS immunoassays capable of simultaneously detecting intact C-peptide and variant forms were applied to plasma samples from 48 healthy individuals and 48 individuals diagnosed with T2D. RESULTS Common throughout the entire sample set were three previously unreported variations of C-peptide. The relative contribution of one variant, subsequently identified as C-peptide (3-31), was found to be more abundant in the T2D population as compared to the healthy population. Dipeptidyl peptidase IV is suspected to be responsible for this particular cleavage product, which is consistent with the pathophysiology of T2D. CONCLUSIONS AND CLINICAL RELEVANCE C-peptide does not exist in the human body as a single molecular species. It is qualitatively more heterogeneous than previously thought. These results lay a foundation for future studies devoted to a comprehensive understanding of C-peptide and its variants in healthy and diabetic populations.
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Affiliation(s)
- Paul E Oran
- The Biodesign Institute at Arizona State University, Tempe, 85287, USA
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24
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Abstract
Although long believed to be inert, C-peptide has now been shown to have definite biological effects both in vitro and in vivo in diabetic animals and in patients with type 1 diabetes. These effects point to a protective action of C-peptide against the development of diabetic microvascular complications. Underpinning these observations is undisputed evidence of C-peptide binding to a variety of cell types at physiologically relevant concentrations, and the downstream stimulation of multiple cell signaling pathways and gene transcription via the activation of numerous transcription factors. These pathways affect such fundamental cellular processes as re-absorptive and/or secretory phenotype, migration, growth, and survival. Whilst the receptor remains to be identified, experimental data points strongly to the existence of a specific G-protein-coupled receptor for C-peptide. Of the cell types studied so far, kidney tubular cells express the highest number of C-peptide binding sites. Accordingly, C-peptide exerts major effects on the function of these cells, and in the context of diabetic nephropathy appears to antagonise the pathophysiological effects of major disease mediators such as TGFbeta1 and TNFalpha. Therefore, based on its cellular activity profile C-peptide appears well positioned for development as a therapeutic tool to treat microvascular complications in type 1 diabetes.
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Affiliation(s)
- Claire E Hills
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
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25
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Abstract
Proinsulin C-peptide has been found to exert beneficial effects in many tissues affected by diabetic microvascular complications, including the kidneys. Glomerular hyperfiltration and microalbuminuria are early markers of diabetic nephropathy. C-peptide at physiological concentrations effectively reduces diabetes-induced glomerular hyperfiltration via constriction of the afferent arteriole, dilation of the efferent arteriole, and inhibition of tubular reabsorption in experimental models of type 1 diabetes. The glomerular hypertrophy and mesangial matrix expansion seen in early diabetes can be reduced or prevented by C-peptide administration, possibly via interference with TGF-beta1 and TNFalpha signaling. Several of C-peptide's reno-protective effects have been confirmed in human studies; reduced glomerular hyperfiltration and diminished urinary albumin excretion have been documented in type 1 diabetes patients receiving replacement doses of C-peptide for periods of up to 3 months. In this review, we critically summarize the current state of knowledge regarding C-peptide's renal effects, and discuss possible mechanisms of its beneficial effects in diabetic nephropathy.
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Affiliation(s)
- Lina Nordquist
- Department of Medical Cell Biology, Division of Integrative Physiology, Uppsala University, 75123 Uppsala, Sweden
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26
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Kamiya H, Zhang W, Sima AAF. The beneficial effects of C-Peptide on diabetic polyneuropathy. Rev Diabet Stud 2009; 6:187-202. [PMID: 20039008 DOI: 10.1900/rds.2009.6.187] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Diabetic polyneuropathy (DPN) is a common complication in diabetes. At present, there is no adequate treatment, and DPN is often debilitating for patients. It is a heterogeneous disorder and differs in type 1 and type 2 diabetes. An important underlying factor in type 1 DPN is insulin deficiency. Proinsulin C-peptide is a critical element in the cascade of events. In this review, we describe the physiological role of C-peptide and how it provides an insulin-like signaling function. Such effects translate into beneficial outcomes in early metabolic perturbations of neural Na+/K+-ATPase and nitric oxide (NO) with subsequent preventive effects on early nerve dysfunction. Further corrective consequences resulting from this signaling cascade have beneficial effects on gene regulation of early gene responses, neurotrophic factors, their receptors, and the insulin receptor itself. This may lead to preventive and corrective results to nerve fiber degeneration and loss, as well as, promotion of nerve fiber regeneration with respect to sensory somatic fibers and small nociceptive nerve fibers. A characteristic abnormality of type 1 DPN is nodal and paranodal degeneration with severe consequences for myelinated fiber function. This review deals in detail with the underlying insulin-deficiency-related molecular changes and their correction by C-peptide. Based on these observations, it is evident that continuous maintenance of insulin-like actions by C-peptide is needed in peripheral nerve to minimize the sequences of metabolic and molecular abnormalities, thereby ameliorating neuropathic complications. There is now ample evidence demonstrating that C-peptide replacement in type 1 diabetes promotes insulin action and signaling activities in a more enhanced, prolonged, and continuous fashion than does insulin alone. It is therefore necessary to replace C-peptide to physiological levels in diabetic patients. This will have substantial beneficial effects on type 1 DPN.
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Affiliation(s)
- Hideki Kamiya
- Department of Pathology, Wayne State University, Detroit, MI, USA
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27
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Abstract
OBJECTIVES This is a review of emerging interventions from the recent preclinical and clinical literature that demonstrate the potential for effectiveness in the therapy of diabetic neuropathy (DN). DN is the most common complication of diabetes mellitus and up to 50% of patients with type 1 and type 2 forms have some or other form of neuropathy. The pathology of DN is characterized by progressive nerve fibre loss that gives rise to positive and negative clinical signs and symptoms such as pain, paraesthesiae and loss of sensation. KEY FINDINGS There are very few drugs available to directly treat DN. Those that are clinically indicated provide symptomatic relief but do not repair or reverse underlying nerve damage. However, some agents are in clinical development that may support adult neurons and direct reparative processes after injury stages. Several disease modifying drugs such as aldose reductase inhibitors and protein kinase C inhibitors are in phase III development. Agents on the horizon include neurotrophic factors, growth factors, gene therapy, immunotherapy, poly(ADP-ribose) polymerase inhibitors and non-immunosuppressive immunophilin ligands. SUMMARY Progress has been made toward understanding the biochemical mechanisms leading to diabetic neuropathy, and as a result, new treatment modalities are being explored. The pathogenesis, types and approaches for treating DN together with the newer therapeutic interventions on the horizon are discussed.
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Affiliation(s)
- Danish Mahmood
- Department of Pharmacology, Hamdard University, Hamdard Nagar, New Delhi 110062, India
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28
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Nordquist L, Brown R, Fasching A, Persson P, Palm F. Proinsulin C-peptide reduces diabetes-induced glomerular hyperfiltration via efferent arteriole dilation and inhibition of tubular sodium reabsorption. Am J Physiol Renal Physiol 2009; 297:F1265-72. [PMID: 19741019 DOI: 10.1152/ajprenal.00228.2009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
C-peptide reduces diabetes-induced glomerular hyperfiltration in diabetic patients and experimental animal models. However, the mechanisms mediating the beneficial effect of C-peptide remain unclear. We investigated whether altered renal afferent-efferent arteriole tonus or alterations in tubular Na+ transport (T(Na)) in response to C-peptide administration mediate the reduction of diabetes-induced glomerular hyperfiltration. Glomerular filtration rate, filtration fraction, total and cortical renal blood flow, total kidney O2 consumption (QO2), T(Na), fractional Na+ and Li+ excretions, and tubular free-flow and stop-flow pressures were measured in anesthetized adult male normoglycemic and streptozotocin-diabetic Sprague-Dawley rats. The specific effect of C-peptide on transport-dependent QO2 was investigated in vitro in freshly isolated proximal tubular cells. C-peptide reduced glomerular filtration rate (-24%), stop-flow pressure (-8%), and filtration fraction (-17%) exclusively in diabetic rats without altering renal blood flow. Diabetic rats had higher baseline T(Na) (+40%), which was reduced by C-peptide. Similarly, C-peptide increased fractional Na+ (+80%) and Li+ (+47%) excretions only in the diabetic rats. None of these parameters was affected by vehicle treatments in either group. Baseline QO2 was 37% higher in proximal tubular cells from diabetic rats than controls and was normalized by C-peptide. C-peptide had no effect on ouabain-pretreated diabetic cells from diabetic rats. C-peptide reduced diabetes-induced hyperfiltration via a net dilation of the efferent arteriole and inhibition of tubular Na+ reabsorption, both potent regulators of the glomerular net filtration pressure. These findings provide new mechanistic insight into the beneficial effects of C-peptide on diabetic kidney function.
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Affiliation(s)
- Lina Nordquist
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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29
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Abstract
In recent years, accumulating evidence indicates a biological function for proinsulin C-peptide. These results challenge the traditional view that C-peptide is essentially inert and only useful as a surrogate marker of insulin release. Accordingly, it is now clear that C-peptide binds with high affinity to cell membranes, probably to a pertussis-toxin-sensitive G-protein-coupled receptor. Subsequently, multiple signalling pathways are potently and dose-dependently activated in multiple cell types by C-peptide with the resulting activation of gene transcription and altered cell phenotype. In diabetic animals and Type 1 diabetic patients, short-term studies indicate that C-peptide also enhances glucose disposal and metabolic control. Furthermore, results derived from animal models and clinical studies in Type 1 diabetic patients suggest a salutary effect of C-peptide in the prevention and amelioration of diabetic nephropathy and neuropathy. Therefore a picture of Type 1 diabetes as a dual-hormone-deficiency disease is developing, suggesting that the replacement of C-peptide alongside insulin should be considered in its management.
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30
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Role of C-Peptide in the regulation of microvascular blood flow. EXPERIMENTAL DIABETES RESEARCH 2008; 2008:176245. [PMID: 18670621 PMCID: PMC2491698 DOI: 10.1155/2008/176245] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Accepted: 06/23/2008] [Indexed: 02/06/2023]
Abstract
During the recent years, the role of C-peptide, released from the pancreatic beta cell, in regulating microvascular blood flow, has received increasing attention. In type 1 diabetic patients, intravenous application of C-peptide in physiological concentrations was shown to increase microvascular blood flow, and to improve microvascular endothelial function and the endothelial release of NO. C-peptide was shown to impact microvascular blood flow by several interactive pathways, like stimulating Na+K+ATPase or the endothelial release of NO. There is increasing evidence, that in patients with declining beta cell function, the lack of C-peptide secretion might play a putative role in the development of microvascular blood flow abnormalities, which go beyond the effects of declining insulin secretion or increased blood glucose levels.
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31
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Mavrakanas T, Bastide D. [C-peptide: a by-product of insulin biosynthesis or an active peptide hormone?]. Presse Med 2008; 38:68-72. [PMID: 18951760 DOI: 10.1016/j.lpm.2008.07.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Revised: 05/27/2008] [Accepted: 07/02/2008] [Indexed: 10/21/2022] Open
Affiliation(s)
- Thomas Mavrakanas
- Laboratoire de pharmacologie A, Faculté de médecine, Université Aristote de Thessalonique, 54248 Thessalonique, Grèce.
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32
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Morla L, Crambert G, Mordasini D, Favre G, Doucet A, Imbert-Teboul M. Proteinase-activated receptor 2 stimulates Na,K-ATPase and sodium reabsorption in native kidney epithelium. J Biol Chem 2008; 283:28020-8. [PMID: 18678869 DOI: 10.1074/jbc.m804399200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Proteinase-activated receptors 2 (PAR2) are expressed in kidney, but their function is mostly unknown. Since PAR2 control ion transport in several epithelia, we searched for an effect on sodium transport in the cortical thick ascending limb of Henle's loop, a nephron segment that avidly reabsorbs NaCl, and for its signaling. Activation of PAR2, by either trypsin or a specific agonist peptide, increased the maximal activity of Na,K-ATPase, its apparent affinity for sodium, the sodium permeability of the paracellular pathway, and the lumen-positive transepithelial voltage, featuring increased NaCl reabsorption. PAR2 activation induced calcium signaling and phosphorylation of ERK1,2. PAR2-induced stimulation of Na,K-ATPase Vmax was fully prevented by inhibition of phospholipase C, of changes in intracellular concentration of calcium, of classical protein kinases C, and of ERK1,2 phosphorylation. PAR2-induced increase in paracellular sodium permeability was mediated by the same signaling cascade. In contrast, increase in the apparent affinity of Na,K-ATPase for sodium, although dependent on phospholipase C, was independent of calcium signaling, was insensitive to inhibitors of classical protein kinases C and of ERK1,2 phosphorylation, but was fully prevented by the nonspecific protein kinase inhibitor staurosporine, as was the increase in transepithelial voltage. In conclusion, PAR2 increases sodium reabsorption in rat thick ascending limb of Henle's loop along both the transcellular and the paracellular pathway. PAR2 effects are mediated in part by a phospholipase C/protein kinase C/ERK1,2 cascade, which increases Na,K-ATPase maximal activity and the paracellular sodium permeability, and by a different phospholipase C-dependent, staurosporine-sensitive cascade that controls the sodium affinity of Na,K-ATPase.
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Affiliation(s)
- Luciana Morla
- Université Pierre et Marie Curie, Univ Paris 06, UMR 7134, 75005 Paris
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C-Peptide effects on renal physiology and diabetes. EXPERIMENTAL DIABETES RESEARCH 2008; 2008:281536. [PMID: 18509500 PMCID: PMC2396455 DOI: 10.1155/2008/281536] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 04/10/2008] [Indexed: 02/07/2023]
Abstract
The C-peptide of proinsulin is important for the biosynthesis of insulin and has for a long time been considered to be biologically inert. Animal studies have shown that some of the renal effects of the C-peptide may in part be explained by its ability to stimulate the Na,K-ATPase activity. Precisely, the C-peptide reduces diabetes-induced glomerular hyperfiltration both in animals and humans, therefore, resulting in regression of fibrosis. The tubular function is also concerned as diabetic animals supplemented with C-peptide exhibit better renal function resulting in reduced urinary sodium waste and protein excretion together with the reduction of the diabetes-induced glomerular hyperfiltration. The tubular effectors of C-peptide were considered to be tubule transporters, but recent studies have shown that biochemical pathways involving cellular kinases and inflammatory pathways may also be important. The matter theory concerning the C-peptide effects is a metabolic one involving the effects of the C-peptide on lipidic metabolic status.This review concentrates on the most convincing data which indicate that the C-peptide is a biologically active hormone for renal physiology.
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C-peptide and its C-terminal fragments improve erythrocyte deformability in type 1 diabetes patients. EXPERIMENTAL DIABETES RESEARCH 2008; 2008:730594. [PMID: 18483566 PMCID: PMC2375968 DOI: 10.1155/2008/730594] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 02/27/2008] [Indexed: 12/13/2022]
Abstract
Aims/hypothesis. Data now indicate that proinsulin C-peptide exerts important physiological effects and shows the characteristics of an endogenous peptide hormone. This study aimed to investigate the influence of C-peptide and fragments thereof on erythrocyte deformability and to elucidate the relevant signal transduction pathway.
Methods. Blood samples from 23 patients with type 1 diabetes and 15 matched healthy controls were incubated with 6.6 nM of either human C-peptide, C-terminal hexapeptide, C-terminal pentapeptide, a middle fragment comprising residues 11–19 of C-peptide, or randomly scrambled C-peptide. Furthermore, red blood cells from 7 patients were incubated with C-peptide, penta- and hexapeptides with/without addition of ouabain, EDTA, or pertussis toxin. Erythrocyte deformability was measured using a laser diffractoscope in the shear stress range 0.3–60 Pa. Results. Erythrocyte deformability was impaired by 18–25% in type 1 diabetic patients compared to matched controls in the physiological shear stress range 0.6–12 Pa (P < .01–.001). C-peptide, penta- and hexapeptide all significantly improved the impaired erythrocyte deformability of type 1 diabetic patients, while the middle fragment and scrambled C-peptide had no detectable effect. Treatment of erythrocytes with ouabain or EDTA completely abolished the C-peptide, penta- and hexapeptide effects. Pertussis toxin in itself significantly increased erythrocyte deformability. Conclusion/interpretation. C-peptide and its C-terminal fragments are equally effective in improving erythrocyte deformability in type 1 diabetes. The C-terminal residues of C-peptide are causally involved in this effect. The signal transduction pathway is Ca2+-dependent and involves activation of red blood cell Na+, K+-ATPase.
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Intracellular signalling by C-peptide. EXPERIMENTAL DIABETES RESEARCH 2008; 2008:635158. [PMID: 18382618 PMCID: PMC2276616 DOI: 10.1155/2008/635158] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 02/06/2008] [Indexed: 12/11/2022]
Abstract
C-peptide, a cleavage product of the proinsulin molecule, has long been regarded as biologically inert, serving merely as a surrogate marker for insulin release. Recent findings demonstrate both a physiological and protective role of C-peptide when administered to individuals with type I diabetes. Data indicate that C-peptide appears to bind in nanomolar concentrations to a cell surface receptor which is most likely to be G-protein coupled. Binding of C-peptide initiates multiple cellular effects, evoking a rise in intracellular calcium, increased PI-3-kinase activity, stimulation of the Na(+)/K(+) ATPase, increased eNOS transcription, and activation of the MAPK signalling pathway. These cell signalling effects have been studied in multiple cell types from multiple tissues. Overall these observations raise the possibility that C-peptide may serve as a potential therapeutic agent for the treatment or prevention of long-term complications associated with diabetes.
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Michell A, Debnam E, Unwin R. Regulation of Renal Function by the Gastrointestinal Tract: Potential Role of Gut-Derived Peptides and Hormones. Annu Rev Physiol 2008; 70:379-403. [DOI: 10.1146/annurev.physiol.69.040705.141330] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- A.R. Michell
- Department of Biochemical Pharmacology, William Harvey Research Institute, St. Bartholomew's Hospital Medical School, London EC1M 6BQ, United Kingdom;
| | - E.S. Debnam
- Department of Physiology, Royal Free and University College Medical School, London NW3 2PF, United Kingdom;
| | - R.J. Unwin
- Department of Physiology, Royal Free and University College Medical School, London NW3 2PF, United Kingdom;
- Centre for Nephrology, Royal Free and University College Medical School, London NW3 2PF, United Kingdom;
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Marx N. C-peptide as a Mediator of Lesion Development in Early Diabetes—A Novel Hypothesis. Trends Cardiovasc Med 2008; 18:67-71. [DOI: 10.1016/j.tcm.2007.12.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 12/13/2007] [Accepted: 12/17/2007] [Indexed: 11/26/2022]
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Sima AAF, Zhang W, Li ZG, Kamiya H. The effects of C-peptide on type 1 diabetic polyneuropathies and encephalopathy in the BB/Wor-rat. EXPERIMENTAL DIABETES RESEARCH 2008; 2008:230458. [PMID: 18437223 PMCID: PMC2323445 DOI: 10.1155/2008/230458] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Accepted: 01/07/2008] [Indexed: 12/29/2022]
Abstract
Diabetic polyneuropathy (DPN) occurs more frequently in type 1 diabetes resulting in a more severe DPN. The differences in DPN between the two types of diabetes are due to differences in the availability of insulin and C-peptide. Insulin and C-peptide provide gene regulatory effects on neurotrophic factors with effects on axonal cytoskeletal proteins and nerve fiber integrity. A significant abnormality in type 1 DPN is nodal degeneration. In the type 1 BB/Wor-rat, C-peptide replacement corrects metabolic abnormalities ameliorating the acute nerve conduction defect. It corrects abnormalities of neurotrophic factors and the expression of neuroskeletal proteins with improvements of axonal size and function. C-peptide corrects the expression of nodal adhesive molecules with prevention and repair of the functionally significant nodal degeneration. Cognitive dysfunction is a recognized complication of type 1 diabetes, and is associated with impaired neurotrophic support and apoptotic neuronal loss. C-peptide prevents hippocampal apoptosis and cognitive deficits. It is therefore clear that substitution of C-peptide in type 1 diabetes has a multitude of effects on DPN and cognitive dysfunction. Here the effects of C-peptide replenishment will be extensively described as they pertain to DPN and diabetic encephalopathy, underpinning its beneficial effects on neurological complications in type 1 diabetes.
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Affiliation(s)
- Anders A F Sima
- Department of Pathology, Wayne State University, Detroit, MI 48201, USA.
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Nordquist L, Lai EY, Sjöquist M, Patzak A, Persson AEG. Proinsulin C-peptide constricts glomerular afferent arterioles in diabetic mice. A potential renoprotective mechanism. Am J Physiol Regul Integr Comp Physiol 2007; 294:R836-41. [PMID: 18077505 DOI: 10.1152/ajpregu.00811.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
OBJECTIVE an increased glomerular filtration rate (GFR) has been postulated as a potential mechanism involved in the progression of diabetic nephropathy. Studies suggest that C-peptide exerts a renoprotective effect on diabetes. The peptide decreases hyperfiltration in patients with type 1 diabetes, as well as in diabetic animal models. In this study, we investigated whether C-peptide causes a change in arteriolar diameter. RESEARCH DESIGN AND METHODS C57-Bl mice were made diabetic by means of a single intravenous injection of alloxan 2 wk prior to the experiment. Age-matched normoglycemic mice served as controls. Afferent arterioles, intact with the glomeruli, were dissected and microperfused. The effect of luminal application of C-peptide, compared with scrambled C-peptide or vehicle, was investigated. The effect of the Rho-kinase inhibitor Y-27632 was also investigated. RESULTS C-peptide constricted afferent arterioles in diabetic mice by -27% compared with the control value. Normoglycemic arterioles administered C-peptide displayed a delayed and minute response (-4%). Scrambled C-peptide or vehicle administration, whether administered to hyperglycemic or normoglycemic mice, did not induce any effect. Addition of Y-27632 abolished the effect of C-peptide. CONCLUSION C-peptide induces constriction of afferent arterioles in diabetic mice. This can reduce enhanced GFR and may be one of the mechanisms in the renoprotective action of C-peptide in diabetes.
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Affiliation(s)
- Lina Nordquist
- Department of Medical Cell Biology, Division of Physiology, University of Uppsala, Uppsala, Sweden
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40
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Regulation of the Na,K-ATPase: Special implications for cardiovascular complications of metabolic syndrome. PATHOPHYSIOLOGY 2007; 14:153-8. [DOI: 10.1016/j.pathophys.2007.09.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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41
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Araya KA, David Pessoa Mahana C, González LG. Role of cannabinoid CB1 receptors and Gi/o protein activation in the modulation of synaptosomal Na+,K+-ATPase activity by WIN55,212-2 and delta(9)-THC. Eur J Pharmacol 2007; 572:32-9. [PMID: 17644088 DOI: 10.1016/j.ejphar.2007.06.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 05/29/2007] [Accepted: 06/07/2007] [Indexed: 11/21/2022]
Abstract
In the present study, we evaluated the effects of the synthetic cannabinoid receptor agonist (R)-(+)-[2,3-Dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN55,212-2) and the active component of Cannabis delta-9-tetrahydrocannabinol (triangle up(9)-THC) on Na(+),K(+)-ATPase activity in synaptosomal mice brain preparation. Additionally, the potential exogenous cannabinoids and endogenous opioid peptides interaction as well as the role of G(i/o) proteins in mediating Na(+),K(+)-ATPase activation were also explored. The ouabain-sensitive Na(+),K(+)-ATPase activity was measured in whole-brain pure intact synaptosomes (obtained by Percoll gradient method) of female CF-1 mice and was calculated as the difference between the total and the ouabain (1 mM)-insensitive Na(+),K(+)-ATPase activities. Incubation in vitro of the synaptosomes with WIN55,212-2 (0.1 pM-10 microM) or triangle up(9)-THC (0.1 pM-0.1 microM), in a concentration-dependent manner, stimulated ouabain-sensitive Na(+),K(+)-ATPase activity. WIN55,212-2 was less potent but more efficacious than triangle up(9)-THC. N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM-251) (10 nM), a CB(1) cannabinoid receptor selective antagonist, had not effect per se but antagonized the enhancement of Na(+),K(+)-ATPase activity induced by both, WIN55,212-2 and triangle up(9)-THC. AM-251 produced a significant reduction in the E(max) of cannabinoid-induced increase in Na(+),K(+)-ATPase activity, but did not significantly modify their EC(50). On the other hand, co-incubation with naloxone (1 microM), an opioid receptor antagonist, did not significantly modify the effect of WIN55,212-2 and completely failed to modify the effect of triangle up(9)-THC on synaptosomal Na(+),K(+)-ATPase. Finally, pre-incubation with 0.5 microg of pertussis toxin (G(i/o) protein blocker) completely abolished the enhancement of ouabain-sensitive Na(+),K(+)-ATPase activity induced by WIN55,212-2. A lower dose, 0.25 microg, decreased the E(max) of WIN55,212-2 by 70% but did not significantly affect its EC(50). These results suggest that WIN55212-2 and triangle up(9)-THC indirectly enhance Na(+),K(+)-ATPase activity in the brain by activating cannabinoid CB(1) receptors in a naloxone-insensitive manner. In addition, the effect of WIN55,212-2 on neuronal Na(+),K(+)-ATPase is apparently due to activation of G(i/o) proteins.
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Affiliation(s)
- Katherine A Araya
- Department of Pharmacy (Division of Molecular Pharmacology), Faculty of Chemistry, Pontificia Universidad Católica de Chile, Casilla 306, Santiago, 6094411, Chile
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Bugliani M, Torri S, Lupi R, Del Guerra S, Grupillo M, Del Chiaro M, Mosca F, Boggi U, Del Prato S, Marchetti P. Effects of C-peptide on isolated human pancreatic islet cells. Diabetes Metab Res Rev 2007; 23:215-9. [PMID: 16874846 DOI: 10.1002/dmrr.674] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Recent data have demonstrated that pro-insulin-derived C-peptide can affect the function of several different cell types. We hypothesized that C-peptide might have an influence on the function and survival of isolated human islets. METHODS Islets were prepared by combining enzymatic digestion and density gradient centrifugation, and the effects of human C-peptide were evaluated acutely and after 24-h incubation. Insulin secretion, apoptosis, quantitative RT-PCR and western-blotting experiments were then performed. RESULTS Glucose-stimulated insulin secretion was not affected by C-peptide and, accordingly, mRNA expression of glucose transporter 2 and glucokinase did not differ between islets pre-cultured or not with the hormone. However, apoptosis was significantly lower in islets exposed to C-peptide than in control islets. This was accompanied by a significant increase of mRNA and protein expression of Bcl2, an anti-apoptotic molecule, with no change in the expression of Bax, a pro-apoptotic molecule. CONCLUSION These results show that in human islets pro-insulin C-peptide has no direct effects on insulin secretion, but it decreases islet cell apoptosis. A direct role of C-peptide on beta-cell mass regulation is therefore suggested.
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Affiliation(s)
- Marco Bugliani
- Department of Endocrinology and Metabolism - Metabolic Unit, University of Pisa, Pisa, Italy
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Zhang W, Kamiya H, Ekberg K, Wahren J, Sima AAF. C-peptide improves neuropathy in type 1 diabetic BB/Wor-rats. Diabetes Metab Res Rev 2007; 23:63-70. [PMID: 16845685 DOI: 10.1002/dmrr.672] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND The spontaneously diabetic BB/Wor-rat is a close model of human type 1 diabetes and develops diabetic polyneuropathy (DPN) similar to that seen in type 1 patients. Here we examine the therapeutic effects of C-peptide, delivered as continuous infusion or once daily subcutaneous injections on established DPN. METHODS Diabetic rats were treated from four to seven months duration of diabetes with full continuous replacement dose of rat C-peptide via (a) osmopumps (OS), (b) full replacement dose (HSC) or (c) one-third of full replacement dose (LSC) by once daily injections. RESULTS Diabetic rats treated with OS showed improvements in motor nerve conduction velocity (p < 0.001), sural nerve myelinated fibre number (p < 0.005), size (p < 0.05), axonal area (p < 0.001), regeneration (p < 0.001) and overall neuropathy score (p < 0.001). The progressive decline in sensory nerve conduction velocity was fully prevented. The frequencies of Wallerian degeneration were decreased (p < 0.005). HSC-treated rats showed prevention of further progression of DPN (p < 0.001), whereas LSC-treated rats showed a milder progression of DPN (p < 0.001) compared to untreated rats as assessed by neuropathy score. CONCLUSION We conclude that (1) C-peptide is effective in the treatment of established DPN, (2) its effect is dose-dependent and (3) replacement by continuous infusion is the most effective administration of C-peptide.
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Affiliation(s)
- Weixian Zhang
- Department of Pathology, Wayne State University, School of Medicine, Detroit, MI 48201, USA
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Kamiya H, Zhang W, Ekberg K, Wahren J, Sima AAF. C-Peptide reverses nociceptive neuropathy in type 1 diabetes. Diabetes 2006; 55:3581-7. [PMID: 17130507 DOI: 10.2337/db06-0396] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We examined the therapeutic effects of C-peptide on established nociceptive neuropathy in type 1 diabetic BB/Wor rats. Nociceptive nerve function, unmyelinated sural nerve fiber and dorsal root ganglion (DRG) cell morphometry, nociceptive peptide content, and the expression of neurotrophic factors and their receptors were investigated. C-peptide was administered either as a continuous subcutaneous replacement dose via osmopumps or a replacement dose given once daily by subcutaneous injection. Diabetic rats were treated from 4 to 7 months of diabetes and were compared with control and untreated diabetic rats of 4- and 7-month duration. Osmopump delivery but not subcutaneous injection improved hyperalgesia and restored the diabetes-induced reduction of unmyelinated fiber number (P < 0.01) and mean axonal size (P < 0.05) in the sural nerve. High-affinity nerve growth factor (NGF) receptor (NGFR-TrkA) expression in DRGs was significantly reduced at 4 months (P < 0.01). Insulin receptor and IGF-I receptor (IGF-IR) expressions in DRGs and NGF content in sciatic nerve were significantly decreased in 7-month diabetic rats (P < 0.01, 0.05, and 0.005, respectively). Osmopump delivery prevented the decline of NGFR-TrkA, insulin receptor (P < 0.05), and IGF-IR (P < 0.005) expressions in DRGs and improved NGF content (P < 0.05) in sciatic nerve. However, subcutaneous injection had only marginal effects on morphometric and molecular changes in diabetic rats. We conclude that C-peptide exerts beneficial therapeutic effects on diabetic nociceptive neuropathy and that optimal effects require maintenance of physiological C-peptide concentrations for a major proportion of the day.
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Affiliation(s)
- Hideki Kamiya
- Department of Pathology, Scott Hall 9275, 540 E. Canfield Ave., Detroit, MI 48201, USA
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Walcher D, Babiak C, Poletek P, Rosenkranz S, Bach H, Betz S, Durst R, Grüb M, Hombach V, Strong J, Marx N. C-Peptide Induces Vascular Smooth Muscle Cell Proliferation. Circ Res 2006; 99:1181-7. [PMID: 17068290 DOI: 10.1161/01.res.0000251231.16993.88] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Increased levels of C-peptide, a cleavage product of proinsulin, circulate in patients with insulin resistance and early type 2 diabetes mellitus. Recent data suggest a potential causal role of C-peptide in atherogenesis by promoting monocyte and T-lymphocyte recruitment into the vessel wall. The present study examined the effect of C-peptide on vascular smooth muscle cells (VSMCs) proliferation and evaluated intracellular signaling pathways involved. In early arteriosclerotic lesions of diabetic subjects, C-peptide colocalized with VSMCs in the media. In vitro, stimulation of human or rat VSMCs with C-peptide induced cell proliferation in a concentration-dependent manner with a maximal 2.6±0.8-fold induction at 10 nmol/L human C-peptide (
P
<0.05 compared with unstimulated cells; n=9) and a 1.8±0.2-fold induction at 0.5 nmol/L rat C-peptide (
P
<0.05 compared with unstimulated cells; n=7), respectively, as shown by [H3]-thymidin incorporation. The proliferative effect of C-peptide on VSMCs was inhibited by Src short interference RNA transfection, PP2, an inhibitor of Src-kinase, LY294002, an inhibitor of PI-3 kinase, and the ERK1/2 inhibitor PD98059. Moreover, C-peptide induced phosphorylation of Src, as well as activation of PI-3 kinase and ERK1/2, suggesting that these signaling molecules are involved in C-peptide–induced VSMC proliferation. Finally, C-peptide induced cyclin D1 expression as well as phosphorylation of Rb in VSMCs. Our results demonstrate that C-peptide induces VSMC proliferation through activation of Src- and PI-3 kinase as well as ERK1/2. These data suggest a novel mechanism how C-peptide may contribute to plaque development and restenosis formation in patients with insulin resistance and early type 2 diabetes mellitus.
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MESH Headings
- Animals
- Arteriosclerosis/metabolism
- Arteriosclerosis/pathology
- C-Peptide/pharmacology
- Cell Proliferation/drug effects
- Cells, Cultured
- Cyclin D1/metabolism
- Diabetic Angiopathies/metabolism
- Diabetic Angiopathies/pathology
- Enzyme Activation/drug effects
- Humans
- Intracellular Membranes/metabolism
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3/metabolism
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/pathology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphorylation/drug effects
- Phosphotransferases/metabolism
- Proto-Oncogene Proteins c-akt/metabolism
- Rats
- Retinoblastoma Protein/metabolism
- Signal Transduction
- src-Family Kinases/metabolism
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Affiliation(s)
- Daniel Walcher
- Department of Internal Medicine II, Cardiology, University of Ulm, Germany
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Rebsomen L, Pitel S, Boubred F, Buffat C, Feuerstein JM, Raccah D, Vague P, Tsimaratos M. C-peptide replacement improves weight gain and renal function in diabetic rats. DIABETES & METABOLISM 2006; 32:223-8. [PMID: 16799398 DOI: 10.1016/s1262-3636(07)70272-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
AIM Recent experimental and clinical data suggest that C-peptide replacement during type 1 diabetes exerts beneficial effects on diabetic nephropathy. The aim of this study was to determine if physiological C-peptide administration in replacement dose during 28 days had beneficial effects on metabolic status and renal functions in type-1 diabetic rats. METHODS Four groups of rats were investigated: a non diabetic group treated with buffer (C group, n=6), three streptozotocin diabetic-induced groups treated with either buffer (D group, n=6), insulin (D-I group, n=6) or rat homologous C-peptide (D-C group, n=6). Weight gain was measured every week. All animals were housed in metabolic cages on day 28 for assessment of metabolic data. Blood and urine samples were collected to allow measurement of plasmatic osmolality, C-peptide concentration, sodium, and glucose losses and proteinuria. Glomerular filtration rate (GFR) was determined by creatinine clearance. RESULTS All streptozotocin-treated animals were diabetic. Glycaemic control (mg/dl), was markedly improved in D-I (133+/-65) when compared with either D (547+/-49, P<0.05) or D-C (520+/-48, P<0.05) groups. Conversely, weight gain during the study, was improved in D-I and D-C as compared with D animals (135+/-13 and 41+/-18 vs 18+/-21 respectively), despite different glycaemic control. Diabetes-induced glomerular hyperfiltration (ml/min/kg), urinary protein leakage (g/kg/day), and Na urinary losses (mmol/100 g/day) respectively, were significantly (P<0.05) reduced in D-C (3.95+/-0.6; 0.08+/-0.06; 1.5+/-0.9) in comparison with D (4.95+/-0.8; 0.18+/-0.16; 3.7+/-2.1) and D-I (5+/-0.9; 0.19+/-0.11; 2.7+/-0.8) animals. Plasmatic osmolality was significantly increased in D group whereas there were no differences between C group and D-C group. Food and water intakes, urinary volume as well as urinary glucose losses were not significantly different between D-C and D groups. CONCLUSIONS C-peptide administration in replacement dose to streptozotocin diabetic rats induces weight gain regardless hyperglycaemia or glycosuria. Diabetic animals supplemented with C-peptide exhibit better renal function resulting in reduced urinary sodium waste and protein excretion together with reduction of the diabetes-induced glomerular hyperfiltration.
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Affiliation(s)
- L Rebsomen
- UPRES EA 21-93, Laboratoire de diabétologie, Faculté de Médecine de Marseille, Université de la Méditerranée, 13385 Marseille Cedex 05
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Huang YB, Li J, Gao X, Sun JR, Lu Y, Feng T, Fei J, Cui DF, Xia QC, Ren J, Zhang YS. Human proinsulin C-peptide from a precursor overexpressed in Pichia pastoris. Acta Biochim Biophys Sin (Shanghai) 2006; 38:586-92. [PMID: 16894482 DOI: 10.1111/j.1745-7270.2006.00200.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
In this article we report the production of human proinsulin C-peptide with 31 amino acid residues from a precursor overexpressed in Pichia pastoris. A C-peptide precursor expression plasmid containing nine C-peptide genes in tandem was constructed and used to transform P. pastoris. Transformants with a high copy number of the C-peptide precursor gene integrated into the chromosome of P. pastoris were selected. In high-density fermentation in a 300 liter fermentor using a simple culture medium composed mainly of salt and methanol, the C-peptide precursor was overexpressed to a level of 2.28 g per liter. A simple procedure was established to purify the expression product from the culture medium. The purified C-peptide precursor was converted into C-peptide by trypsin and carboxypeptidase B joint digestion. The yield of C-peptide with a purity of 96% was 730 mg per liter of culture. The purified C-peptide was characterized by mass spectrometry, N- and C-terminal amino acid sequencing, and sodium dodecylsulfate-polyacrylamide gel electrophoresis.
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Affiliation(s)
- Yang-Bin Huang
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Joshua IG, Zhang Q, Falcone JC, Bratcher AP, Rodriguez WE, Tyagi SC. Mechanisms of endothelial dysfunction with development of type 1 diabetes mellitus: role of insulin and C-peptide. J Cell Biochem 2006; 96:1149-56. [PMID: 16187296 DOI: 10.1002/jcb.20620] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Complications associated with insulin-dependent diabetes mellitus (type-1diabetes) primarily represent vascular dysfunction that has its origin in the endothelium. While many of the vascular changes are more accountable in the late stages of type-1diabetes, changes that occur in the early or initial functional stages of this disease may precipitate these later complications. The early stages of type-1diabetes are characterized by a diminished production of both insulin and C-peptide with a significant hyperglycemia. During the last decade numerous speculations and theories have been developed to try to explain the mechanisms responsible for the selective changes in vascular reactivity and/or tone and the vascular permeability changes that characterize the development of type-1diabetes. Much of this research has suggested that hyperglycemia and/or the lack of insulin may mediate the observed functional changes in both endothelial cells and vascular smooth muscle. Recent studies suggest several possible mechanisms that might be involved in the observed decreases in vascular nitric oxide (NO) availability with the development of type-1 diabetes. In addition more recent studies have indicated a direct role for both endogenous insulin and C-peptide in the amelioration of the observed endothelial dysfunction. These results suggest a synergistic action between insulin and C-peptide that facilitates increase NO availability and may suggest new clinical treatment modalities for type-1 diabetes mellitus.
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Affiliation(s)
- Irving G Joshua
- Department of Physiology and Biophysics, School of Medicine, University of Louisville, Louisville, Kentucky 40292, USA.
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49
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Maezawa Y, Yokote K, Sonezaki K, Fujimoto M, Kobayashi K, Kawamura H, Tokuyama T, Takemoto M, Ueda S, Kuwaki T, Mori S, Wahren J, Saito Y. Influence of C-peptide on early glomerular changes in diabetic mice. Diabetes Metab Res Rev 2006; 22:313-22. [PMID: 16389646 DOI: 10.1002/dmrr.612] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND C-peptide has been shown to ameliorate diabetes-induced functional and structural renal changes in animal models as well as in patients with type 1 diabetes. This study aims to examine the molecular effects of C-peptide on early glomerular changes in a mouse model of type 1 diabetes. METHODS Fourteen days after induction of diabetes by streptozotocin (STZ), the animals received rat C-peptide for either 24 h or 7 days. Urinary albumin excretion was measured by ELISA. Glomerular mRNA expression of the transforming growth factor (TGF)-beta(1) and type IV collagen was quantified by real-time PCR. The effect of C-peptide on type IV collagen gene expression in cultured murine podocytes was also examined. RESULTS C-peptide decreased urinary albumin excretion from 0.29 to 0.18 microg/min (-40.7%, P < 0.01). The transcript level of (alpha3)IV collagen in glomeruli was up-regulated 2.2-fold in diabetic mice and was inhibited by 45-70% (P < 0.05) upon C-peptide treatment. C-peptide suppressed glomerular expression of TGF-beta(1) by 36.6% after 7 days (P < 0.05) but not 24 h after injection. In vitro studies using cultured podocytes revealed that C-peptide dose-dependently inhibited TGF-beta-induced up-regulation of type IV collagen. Moreover, both pertussis toxin (PTX) and a specific inhibitor for extracellular signal-regulated kinase (ERK) pathway reversed the inhibitory effect of C-peptide on TGF-beta. Finally, C-peptide was shown to up-regulate the activity of ERK in podocytes. CONCLUSIONS These findings indicate that C-peptide suppresses specific aspects of early glomerular changes in a mouse model of diabetes and that the effect is at least in part mediated via interaction with the TGF-beta signal in glomerular podocytes.
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Affiliation(s)
- Yoshiro Maezawa
- Department of Clinical Cell Biology and Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chiba 260-8670, Japan
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50
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Lindenblatt N, Braun B, Menger MD, Klar E, Vollmar B. C-peptide exerts antithrombotic effects that are repressed by insulin in normal and diabetic mice. Diabetologia 2006; 49:792-800. [PMID: 16496122 DOI: 10.1007/s00125-006-0152-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2005] [Accepted: 11/24/2005] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS Diabetic macro- and microangiopathy are associated with a high risk of vascular complications. The diabetic patient exhibits a pathological coagulation state, with an increased synthesis of coagulation factors and plasminogen activator inhibitor 1 (PAI-1) as well as an enhanced aggregation of platelets. Previous studies have shown that C-peptide can reduce leucocyte-endothelial cell interaction and improve microvascular blood flow in patients with type 1 diabetes. In the present study, we examined in vivo whether C-peptide is able to reduce platelet activation and through that microvascular thrombus formation. MATERIALS AND METHODS In the microvessels of cremaster muscle preparations taken from normal and diabetic mice, ferric chloride-induced thrombus formation was analysed using intravital fluorescence microscopy. RESULTS I.V. administration of C-peptide in high dose (70 nmol/kg), but not in low dose (7 nmol/kg), caused a significant delay in arteriolar and venular thrombus growth in normal and diabetic mice. This effect was repressed by cremaster muscle superfusion with insulin (100 microU/ml) in diabetic animals, but particularly in normal animals. In parallel, immunohistochemistry demonstrated a higher number of PAI-1-expressing vessels in cremaster muscle tissue from control animals and from animals treated with C-peptide and insulin compared with tissue from animals with C-peptide treatment application alone. CONCLUSIONS/INTERPRETATION We conclude that C-peptide possesses antithrombotic actions in vivo. A causal role of PAI-1 in this scenario needs to be further addressed. However, the reversal of C-peptide action by insulin may invalidate the use of this peptide as a treatment option to improve rheology and microcirculation in diabetic patients.
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Affiliation(s)
- N Lindenblatt
- Department of Experimental Surgery, University of Rostock, Schillingallee 70, 18055, Rostock, Germany
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