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Abstract
Carbohydrate, lipid, and protein metabolism are largely controlled by the interplay of various hormones, which includes those secreted by the pancreatic islets of Langerhans. While typically representing only 1% to 2% of the total pancreatic mass, the islets have a remarkable ability to adapt to disparate situations demanding a change in hormone release, such as peripheral insulin resistance. There are many different routes to the onset of insulin resistance, including obesity, lipodystrophy, glucocorticoid excess, and the chronic usage of atypical antipsychotic drugs. All of these situations are coupled to an increase in pancreatic islet size, often with a corresponding increase in insulin production. These adaptive responses within the islets are ultimately intended to maintain glycemic control and to promote macronutrient homeostasis during times of stress. Herein, we review the consequences of specific metabolic trauma that lead to insulin resistance and the corresponding adaptive alterations within the pancreatic islets.
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Affiliation(s)
- Susan J. Burke
- Laboratory of Islet Biology and Inflammation, Pennington Biomedical Research Center, Baton Rouge, LA 70808
| | - Michael D. Karlstad
- Department of Surgery, Graduate School of Medicine, University of Tennessee Health Science Center, Knoxville, TN 37920
| | - J. Jason Collier
- Laboratory of Islet Biology and Inflammation, Pennington Biomedical Research Center, Baton Rouge, LA 70808
- Department of Surgery, Graduate School of Medicine, University of Tennessee Health Science Center, Knoxville, TN 37920
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Zhang BQ, Wang G, Zhang JP, Hu JY, Xiao R, Lei ZY, Ruan J, Dang YM, Zhang DX, Bian XW, Huang YS. Protective effects of enalapril, an angiotensin-converting enzyme inhibitor, on multiple organ damage following scald injury in rats. Biotechnol Appl Biochem 2013; 59:307-13. [PMID: 23586864 DOI: 10.1002/bab.1027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 06/14/2012] [Indexed: 01/11/2023]
Abstract
The aim of this study is to investigate the effects of enalapril, an angiotensin-converting enzyme inhibitor, on multiple organ damage after scald injury. Healthy adult rats (half male and half female; 8-12 weeks old) were randomly assigned to the following treatments: sham operation, scald injury, and intraperitoneal enalapril (1, 2, and 4 mg/kg body weight) treatment after scalding. At 1, 12, and 24 H postscald, left ventricular and aortic hemodynamics were measured using a multichannel physiological recorder. Functional and pathological changes of the heart, liver, and kidney were examined by biochemical and histological methods. Compared with sham controls, untreated scalded animals showed decreased hemodynamic parameters and increased myocardial angiotensin II, serum creatine kinase heart isoenzyme, and serum cardiac troponin I and histopathological inflammation in the myocardium 12 H postscald. These hemodynamic, functional, and pathological changes were attenuated by 1 mg/kg enalapril. Enalapril reversed scald-induced elevations in aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and blood creatinine 12 H postscald, and ameliorated focal necrosis in the liver and erythrocyte cast formation in renal tubules. However, higher doses of enalapril yielded less or no improvement in organ dysfunction. Enalapril at 1 mg/kg attenuates scald-induced multiple organ damage in rats.
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Affiliation(s)
- Bing-Qian Zhang
- Institute of Burn Research of PLA, National Key Laboratory of Trauma, Burn and Combined Injury, Third Military Medical University, Chongqing, People's Republic of China
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Zhang Z, Liu C, Gan Z, Wang X, Yi Q, Liu Y, Wang Y, Lu B, Du H, Shao J, Wang J. Improved Glucose-Stimulated Insulin Secretion by Selective Intraislet Inhibition of Angiotensin II Type 1 Receptor Expression in Isolated Islets of db/db Mice. Int J Endocrinol 2013; 2013:319586. [PMID: 24371439 PMCID: PMC3859026 DOI: 10.1155/2013/319586] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 10/13/2013] [Accepted: 10/31/2013] [Indexed: 12/20/2022] Open
Abstract
Recent evidence supported the presence of a local renin-angiotensin system (RAS) in the pancreas, which is implicated in many physiological and pathophysiological processes. We utilized small interfering RNA (siRNA) to investigate the effects of angiotensin II type 1 receptor (AT1R) knockdown on glucose-stimulated insulin secretion (GSIS) in isolated islets of db/db mice and to explore the potential mechanisms involved. We found that Ad-siAT1R treatment resulted in a significant decrease both in AT1R mRNA level and in AT1R protein expression level. With downexpression of AT1R, notable increased insulin secretion and decreased glucagon secretion levels were found by perifusion. Simultaneously, significant increased protein levels of IRS-1 (by 85%), IRS-2 (by 95%), PI3K(85) (by 112.5%), and p-Akt2 (by 164%) were found by western blot. And upregulation of both GLUT-2 (by 190%) and GCK (by 121%) was achieved after AT1R inhibition by Ad-siAT1R. Intraislet AT1R expression level is a crucial physiological regulator of insulin sensitivity of β cell itself and thus affects glucose-induced insulin and glucagon release. Therefore, the characteristics of AT1R inhibitors could make it a potential novel therapeutics for prevention and treatment of type 2 diabetes.
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Affiliation(s)
- Zhen Zhang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Chunyan Liu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Zhenhua Gan
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Xinyi Wang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Qiuyan Yi
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Yanqing Liu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Yingzhijie Wang
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Bin Lu
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Hong Du
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
| | - Jiaqing Shao
- Department of Endocrinology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
- *Jiaqing Shao: and
| | - Jun Wang
- Department of Cardiology, Jinling Hospital, Southern Medical University, 305 Zhongshan East Road, Nanjing, Jiangsu Province 210002, China
- *Jun Wang:
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Burks TN, Andres-Mateos E, Marx R, Mejias R, Van Erp C, Simmers JL, Walston JD, Ward CW, Cohn RD. Losartan restores skeletal muscle remodeling and protects against disuse atrophy in sarcopenia. Sci Transl Med 2011; 3:82ra37. [PMID: 21562229 DOI: 10.1126/scitranslmed.3002227] [Citation(s) in RCA: 179] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Sarcopenia, a critical loss of muscle mass and function because of the physiological process of aging, contributes to disability and mortality in older adults. It increases the incidence of pathologic fractures, causing prolonged periods of hospitalization and rehabilitation. The molecular mechanisms underlying sarcopenia are poorly understood, but recent evidence suggests that increased transforming growth factor-β (TGF-β) signaling contributes to impaired satellite cell function and muscle repair in aged skeletal muscle. We therefore evaluated whether antagonism of TGF-β signaling via losartan, an angiotensin II receptor antagonist commonly used to treat high blood pressure, had a beneficial impact on the muscle remodeling process of sarcopenic mice. We demonstrated that mice treated with losartan developed significantly less fibrosis and exhibited improved in vivo muscle function after cardiotoxin-induced injury. We found that losartan not only blunted the canonical TGF-β signaling cascade but also modulated the noncanonical TGF-β mitogen-activated protein kinase pathway. We next assessed whether losartan was able to combat disuse atrophy in aged mice that were subjected to hindlimb immobilization. We showed that immobilized mice treated with losartan were protected against loss of muscle mass. Unexpectedly, this protective mechanism was not mediated by TGF-β signaling but was due to an increased activation of the insulin-like growth factor 1 (IGF-1)/Akt/mammalian target of rapamycin (mTOR) pathway. Thus, blockade of the AT1 (angiotensin II type I) receptor improved muscle remodeling and protected against disuse atrophy by differentially regulating the TGF-β and IGF-1/Akt/mTOR signaling cascades, two pathways critical for skeletal muscle homeostasis. Thus, losartan, a Food and Drug Administration-approved drug, may prove to have clinical benefits to combat injury-related muscle remodeling and provide protection against disuse atrophy in humans with sarcopenia.
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Affiliation(s)
- Tyesha N Burks
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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