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      Spironolactone Protects against Diabetic Cardiomyopathy in Streptozotocin-Induced Diabetic Rats

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          Abstract

          Spironolactone (SPR) has been shown to protect diabetic cardiomyopathy (DCM), but the specific mechanisms are not fully understood. Here, we determined the cardioprotective role of SPR in diabetic mice and further explored the potential mechanisms in both in vivo and in vitro models. Streptozotocin- (STZ-) induced diabetic rats were used as the in vivo model. After the onset of diabetes, rats were treated with either SPR (STZ + SPR) or saline (STZ + NS) for 12 weeks; nondiabetic rats were used as controls (NDCs). In vitro, H9C2 cells were exposed to aldosterone, with or without SPR. Cardiac structure was investigated with transmission electron microscopy and pathological examination; immunohistochemistry was performed to detect nitrotyrosine, collagen-1, TGF- β1, TNF- α, and F4/80 expression; and gene expression of markers for oxidative stress, inflammation, fibrosis, and energy metabolism was detected. Our results suggested that SPR attenuated mitochondrial morphological abnormalities and sarcoplasmic reticulum enlargement in diabetic rats. Compared to the STZ + NS group, cardiac oxidative stress, fibrosis, inflammation, and mitochondrial dysfunction were improved by SPR treatment. Our study showed that SPR had cardioprotective effects in diabetic rats by ameliorating mitochondrial dysfunction and reducing fibrosis, oxidative stress, and inflammation. This study, for the first time, indicates that SPR might be a potential treatment for DCM.

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          RAGE-induced cytosolic ROS promote mitochondrial superoxide generation in diabetes.

          Damaged mitochondria generate an excess of superoxide, which may mediate tissue injury in diabetes. We hypothesized that in diabetic nephropathy, advanced glycation end-products (AGEs) lead to increases in cytosolic reactive oxygen species (ROS), which facilitate the production of mitochondrial superoxide. In normoglycemic conditions, exposure of primary renal cells to AGEs, transient overexpression of the receptor for AGEs (RAGE) with an adenoviral vector, and infusion of AGEs to healthy rodents each induced renal cytosolic oxidative stress, which led to mitochondrial permeability transition and deficiency of mitochondrial complex I. Because of a lack of glucose-derived NADH, which is the substrate for complex I, these changes did not lead to excess production of mitochondrial superoxide; however, when we performed these experiments in hyperglycemic conditions in vitro or in diabetic rats, we observed significant generation of mitochondrial superoxide at the level of complex I, fueled by a sustained supply of NADH. Pharmacologic inhibition of AGE-RAGE-induced mitochondrial permeability transition in vitro abrogated production of mitochondrial superoxide; we observed a similar effect in vivo after inhibiting cytosolic ROS production with apocynin or lowering AGEs with alagebrium. Furthermore, RAGE deficiency prevented diabetes-induced increases in renal mitochondrial superoxide and renal cortical apoptosis in mice. Taken together, these studies suggest that AGE-RAGE-induced cytosolic ROS production facilitates mitochondrial superoxide production in hyperglycemic environments, providing further evidence of a role for the advanced glycation pathway in the development and progression of diabetic nephropathy.
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            Reduced mitochondrial oxidative capacity and increased mitochondrial uncoupling impair myocardial energetics in obesity.

            Obesity is a risk factor for cardiovascular disease and is strongly associated with insulin resistance and type 2 diabetes. Recent studies in obese humans and animals demonstrated increased myocardial oxygen consumption (MVO2) and reduced cardiac efficiency (CE); however, the underlying mechanisms remain unclear. The present study was performed to determine whether mitochondrial dysfunction and uncoupling are responsible for reduced cardiac performance and efficiency in ob/ob mice. Cardiac function, MVO2, mitochondrial respiration, and ATP synthesis were measured in 9-week-old ob/ob and control mouse hearts. Contractile function and MVO2 in glucose-perfused ob/ob hearts were similar to controls under basal conditions but were reduced under high workload. Perfusion of ob/ob hearts with glucose and palmitate increased MVO2 and reduced CE by 23% under basal conditions, and CE remained impaired at high workload. In glucose-perfused ob/ob hearts, mitochondrial state 3 respirations were reduced but ATP/O ratios were unchanged. In contrast, state 3 respiration rates were similar in ob/ob and control mitochondria from hearts perfused with palmitate and glucose, but ATP synthesis rates and ATP/O ratios were significantly reduced in ob/ob, which suggests increased mitochondrial uncoupling. Pyruvate dehydrogenase activity and protein levels of complexes I, III, and V were reduced in obese mice. These data indicate that reduced mitochondrial oxidative capacity may contribute to cardiac dysfunction in ob/ob mice. Moreover, fatty acid but not glucose-induced mitochondrial uncoupling reduces CE in obese mice by limiting ATP production and increasing MVO2.
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              The role of oxidative stress and antioxidants in diabetic complications.

              Diabetes is considered to be one of the most common chronic diseases worldwide. There is a growing scientific and public interest in connecting oxidative stress with a variety of pathological conditions including diabetes mellitus (DM) as well as other human diseases. Previous experimental and clinical studies report that oxidative stress plays a major role in the pathogenesis and development of complications of both types of DM. However, the exact mechanism by which oxidative stress could contribute to and accelerate the development of complications in diabetic mellitus is only partly known and remains to be clarified. On the one hand, hyperglycemia induces free radicals; on the other hand, it impairs the endogenous antioxidant defense system in patients with diabetes. Endogenous antioxidant defense mechanisms include both enzymatic and non-enzymatic pathways. Their functions in human cells are to counterbalance toxic reactive oxygen species (ROS). Common antioxidants include the vitamins A, C, and E, glutathione (GSH), and the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GRx). This review describes the importance of endogenous antioxidant defense systems, their relationship to several pathophysiological processes and their possible therapeutic implications in vivo.
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                Author and article information

                Contributors
                Journal
                J Diabetes Res
                J Diabetes Res
                JDR
                Journal of Diabetes Research
                Hindawi
                2314-6745
                2314-6753
                2018
                14 October 2018
                : 2018
                : 9232065
                Affiliations
                1Division of Endocrinology and Metabolism, Huashan Hospital, Fudan University, 12 Wulumuqi Road, Shanghai 200040, China
                2Institute of Endocrinology and Diabetology, Fudan University, 12 Wulumuqi Road, Shanghai 200040, China
                3Department of Endocrinology, The Second People's Hospital, 4 Duchun Road, Wuhu, Anhui 241001, China
                4Department of Endocrinology, The Second Affiliated Hospital, Soochow University, 1055 Sanxiang Rd, Suzhou, Jiangsu 215000, China
                5Department of Cardiology, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai 200032, China
                Author notes

                Academic Editor: Ilaria Campesi

                Author information
                http://orcid.org/0000-0002-8941-8061
                http://orcid.org/0000-0002-1828-8765
                http://orcid.org/0000-0002-4286-8380
                http://orcid.org/0000-0001-5366-1353
                Article
                10.1155/2018/9232065
                6204188
                30406151
                6f427ccd-05eb-4261-b01f-326493b77eda
                Copyright © 2018 Wenjuan Liu et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 16 March 2018
                : 16 July 2018
                : 2 August 2018
                Funding
                Funded by: National Natural Science Foundation of China
                Award ID: 81370938
                Funded by: Foundation of Shanghai Municipal Commission of Health and Family Planning
                Award ID: XYQ2011002
                Award ID: XYQ2013120
                Funded by: Shanghai Research Project
                Award ID: 17441903100
                Categories
                Research Article

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