FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W1988049600> ?p ?o ?g. }

• W1988049600 endingPage "589" @default.
• W1988049600 startingPage "579" @default.
• W1988049600 abstract "Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone that has an antioxidative protective effect on various tissues. Here, we determined whether GLP-1 has a role in the pathogenesis of diabetic nephropathy using nephropathy-resistant C57BL/6-Akita and nephropathy-prone KK/Ta-Akita mice. By in situ hybridization, we found the GLP-1 receptor (GLP-1R) expressed in glomerular capillary and vascular walls, but not in tubuli, in the mouse kidney. Next, we generated C57BL/6-Akita Glp1r knockout mice. These mice exhibited higher urinary albumin levels and more advanced mesangial expansion than wild-type C57BL/6-Akita mice, despite comparable levels of hyperglycemia. Increased glomerular superoxide, upregulated renal NAD(P)H oxidase, and reduced renal cAMP and protein kinase A (PKA) activity were noted in the Glp1r knockout C57BL/6-Akita mice. Treatment with the GLP-1R agonist liraglutide suppressed the progression of nephropathy in KK/Ta-Akita mice, as demonstrated by reduced albuminuria and mesangial expansion, decreased levels of glomerular superoxide and renal NAD(P)H oxidase, and elevated renal cAMP and PKA activity. These effects were abolished by an adenylate cyclase inhibitor SQ22536 and a selective PKA inhibitor H-89. Thus, GLP-1 has a crucial role in protection against increased renal oxidative stress under chronic hyperglycemia, by inhibition of NAD(P)H oxidase, a major source of superoxide, and by cAMP-PKA pathway activation. Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone that has an antioxidative protective effect on various tissues. Here, we determined whether GLP-1 has a role in the pathogenesis of diabetic nephropathy using nephropathy-resistant C57BL/6-Akita and nephropathy-prone KK/Ta-Akita mice. By in situ hybridization, we found the GLP-1 receptor (GLP-1R) expressed in glomerular capillary and vascular walls, but not in tubuli, in the mouse kidney. Next, we generated C57BL/6-Akita Glp1r knockout mice. These mice exhibited higher urinary albumin levels and more advanced mesangial expansion than wild-type C57BL/6-Akita mice, despite comparable levels of hyperglycemia. Increased glomerular superoxide, upregulated renal NAD(P)H oxidase, and reduced renal cAMP and protein kinase A (PKA) activity were noted in the Glp1r knockout C57BL/6-Akita mice. Treatment with the GLP-1R agonist liraglutide suppressed the progression of nephropathy in KK/Ta-Akita mice, as demonstrated by reduced albuminuria and mesangial expansion, decreased levels of glomerular superoxide and renal NAD(P)H oxidase, and elevated renal cAMP and PKA activity. These effects were abolished by an adenylate cyclase inhibitor SQ22536 and a selective PKA inhibitor H-89. Thus, GLP-1 has a crucial role in protection against increased renal oxidative stress under chronic hyperglycemia, by inhibition of NAD(P)H oxidase, a major source of superoxide, and by cAMP-PKA pathway activation. Diabetic nephropathy (DN) is a serious complication of diabetes and the leading cause of end-stage renal disease in developed countries. Recent evidence indicates that oxidative stress has a central role in the development and progression of DN.1.Brownlee M. The pathobiology of diabetic complications: a unifying mechanism.Diabetes. 2005; 54: 1615-1625Crossref PubMed Scopus (3984) Google Scholar, 2.Forbes J.M. Coughlan M.T. Cooper M.E. Oxidative stress as a major culprit in kidney disease in diabetes.Diabetes. 2008; 57: 1446-1454Crossref PubMed Scopus (936) Google Scholar The increase in systemic oxidative stress becomes prominent from the incipient stage of DN.3.Fujita H. Sakamoto T. Komatsu K. et al.Reduction of circulating superoxide dismutase activity in type 2 diabetic patients with microalbuminuria and its modulation by telmisartan therapy.Hypertens Res. 2011; 34: 1302-1308Crossref PubMed Scopus (26) Google Scholar In the kidney, reactive oxygen species (ROS) including superoxide anion (O2•−) are excessively produced by chronic hyperglycemia, leading to increased levels of renal oxidative stress. NAD(P)H oxidase is the most important source of superoxide anion,4.Guzik T.J. Mussa S. Gastaldi D. et al.Mechanisms of increased vascular superoxide production in human diabetes mellitus: role of NAD(P)H oxidase and endothelial nitric oxide synthase.Circulation. 2002; 105: 1656-1662Crossref PubMed Scopus (890) Google Scholar, 5.Satoh M. Fujimoto S. Haruna Y. et al.NAD(P)H oxidase and uncoupled nitric oxide synthase are major sources of glomerular superoxide in rats with experimental diabetic nephropathy.Am J Physiol Renal Physiol. 2005; 288: F1144-F1152Crossref PubMed Scopus (302) Google Scholar, 6.Soccio M. Toniato E. Evangelista V. et al.Oxidative stress and cardiovascular risk: the role of vascular NAD(P)H oxidase and its genetic variants.Eur J Clin Invest. 2005; 35: 305-314Crossref PubMed Scopus (74) Google Scholar, 7.Wardle E.N. Cellular oxidative processes in relation to renal disease.Am J Nephrol. 2005; 25: 13-22Crossref PubMed Scopus (38) Google Scholar and this enzyme is shown to be upregulated in the diabetic kidney.5.Satoh M. Fujimoto S. Haruna Y. et al.NAD(P)H oxidase and uncoupled nitric oxide synthase are major sources of glomerular superoxide in rats with experimental diabetic nephropathy.Am J Physiol Renal Physiol. 2005; 288: F1144-F1152Crossref PubMed Scopus (302) Google Scholar,8.Fujita H. Fujishima H. Morii T. et al.Modulation of renal superoxide dismutase by telmisartan therapy in C57BL/6-Ins2(Akita) diabetic mice.Hypertens Res. 2012; 35: 213-220Crossref PubMed Scopus (39) Google Scholar, 9.Gorin Y. Block K. Hernandez J. et al.Nox4 NAD(P)H oxidase mediates hypertrophy and fibronectin expression in the diabetic kidney.J Biol Chem. 2005; 280: 39616-39626Crossref PubMed Scopus (445) Google Scholar, 10.Kitada M. Koya D. Sugimoto T. et al.Translocation of glomerular p47phox and p67phox by protein kinase C-beta activation is required for oxidative stress in diabetic nephropathy.Diabetes. 2003; 52: 2603-2614Crossref PubMed Scopus (193) Google Scholar A recent in vitro study using human HEK293 cells demonstrated that NAD(P)H oxidase NOX1-dependent ROS production is reduced by the elevation of cAMP and subsequent activation of protein kinase A (PKA).11.Kim J.S. Diebold B.A. Babior B.M. et al.Regulation of Nox1 activity via protein kinase A-mediated phosphorylation of NoxA1 and 14-3-3 binding.J Biol Chem. 2007; 282: 34787-34800Crossref PubMed Scopus (79) Google Scholar Furthermore, treatment with cAMP-elevating agents such as isoproterenol and forskolin normalized the levels of NAD(P)H oxidase activity and superoxide in aortic vascular smooth muscle cells of spontaneously hypertensive rats.12.Saha S. Li Y. Anand-Srivastava M.B. Reduced levels of cyclic AMP contribute to the enhanced oxidative stress in vascular smooth muscle cells from spontaneously hypertensive rats.Can J Physiol Pharmacol. 2008; 86: 190-198Crossref PubMed Scopus (33) Google Scholar Thus, the cAMP-PKA pathway appears to work as an important inhibitory factor for NAD(P)H oxidase–dependent production of ROS or superoxide. Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone that stimulates insulin secretion from pancreatic β-cells in a glucose-dependent manner.13.Baggio L.L. Drucker D.J. Biology of incretins: GLP-1 and GIP.Gastroenterology. 2007; 132: 2131-2157Abstract Full Text Full Text PDF PubMed Scopus (2616) Google Scholar Activation of the GLP-1 receptor (GLP-1R) stimulates adenylate cyclase and enhances the production of cAMP, the primary effector of GLP-1-induced insulin secretion.13.Baggio L.L. Drucker D.J. Biology of incretins: GLP-1 and GIP.Gastroenterology. 2007; 132: 2131-2157Abstract Full Text Full Text PDF PubMed Scopus (2616) Google Scholar, 14.Holz G.G. Epac: a new cAMP-binding protein in support of glucagon-like peptide-1 receptor-mediated signal transduction in the pancreatic beta-cell.Diabetes. 2004; 53: 5-13Crossref PubMed Scopus (294) Google Scholar Furthermore, increased levels of cAMP activate PKA or cAMP-regulated guanine nucleotide exchange factor II (Epac2), and contribute to mediating various physiological actions including insulin secretion.14.Holz G.G. Epac: a new cAMP-binding protein in support of glucagon-like peptide-1 receptor-mediated signal transduction in the pancreatic beta-cell.Diabetes. 2004; 53: 5-13Crossref PubMed Scopus (294) Google Scholar, 15.Leech C.A. Chepurny O.G. Holz G.G. Epac2-dependent rap1 activation and the control of islet insulin secretion by glucagon-like peptide-1.Vitam Horm. 2010; 84: 279-302Crossref PubMed Scopus (54) Google Scholar The GLP-1R is expressed in pancreatic β-cells and in multiple extrapancreatic tissues including the gut, brain, heart, lung, and kidney.16.Hirata K. Kume S. Araki S. et al.Exendin-4 has an anti-hypertensive effect in salt-sensitive mice model.Biochem Biophys Res Commun. 2009; 380: 44-49Crossref PubMed Scopus (133) Google Scholar, 17.Bullock B.P. Heller R.S. Habener J.F. Tissue distribution of messenger ribonucleic acid encoding the rat glucagon-like peptide-1 receptor.Endocrinology. 1996; 137: 2968-2978Crossref PubMed Scopus (417) Google Scholar Given the evidence indicating that cAMP and PKA pathways link to antioxidative effects, it is likely that GLP-1 protects various tissues from oxidative injury. However, the roles of GLP-1 in the kidney and DN have not been fully elucidated. First, the precise localization of GLP-1R in the kidney remains unclear. Second, it is unknown whether gain or loss of GLP-1R signaling modulates renal function and the progression of renal injury under conditions of chronic hyperglycemia. In the present study, we investigated the role of endogenous GLP-1R signaling in DN. First, we examined the localization of GLP-1R in the mouse kidney by in situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Next, we studied two Ins2 Akita diabetic mouse models showing different susceptibility to the development and progression of DN, DN-resistant C57BL/6-Ins2 Akita (C57BL/6-Akita), and DN-prone KK/Ta-Ins2 Akita (KK/Ta-Akita).18.Fujita H. Fujishima H. Chida S. et al.Reduction of renal superoxide dismutase in progressive diabetic nephropathy.J Am Soc Nephrol. 2009; 20: 1303-1313Crossref PubMed Scopus (141) Google Scholar, 19.Fujita H. Fujishima H. Takahashi K. et al.SOD1, but not SOD3, deficiency accelerates diabetic renal injury in C57BL/6-Ins2(Akita) diabetic mice.Metabolism. 2012; 61: 1714-1724Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar We examined the renal phenotypes of C57BL/6-Akita mice with GLP-1R deficiency, and in complementary experiments, we tested whether a GLP-1R agonist, liraglutide, ameliorates nephropathic changes in KK/Ta-Akita mice that develop progressive DN.18.Fujita H. Fujishima H. Chida S. et al.Reduction of renal superoxide dismutase in progressive diabetic nephropathy.J Am Soc Nephrol. 2009; 20: 1303-1313Crossref PubMed Scopus (141) Google Scholar As recent studies have highlighted the lack of sensitivity and specificity of multiple GLP-1R antisera,20.Panjwani N. Mulvihill E.E. Longuet C. et al.GLP-1 receptor activation indirectly reduces hepatic lipid accumulation but does not attenuate development of atherosclerosis in diabetic male ApoE(−/−) mice.Endocrinology. 2013; 154: 127-139Crossref PubMed Scopus (251) Google Scholar, 21.Pyke C. Knudsen L.B. The glucagon-like peptide-1 receptor—or not?.Endocrinology. 2013; 154: 4-8Crossref PubMed Scopus (126) Google Scholar we used in situ hybridization analysis to assess Glp1r expression in kidneys of 8-week-old male C57BL/6-wild-type (C57BL/6-WT) mice. As shown in Figure 1, Glp1r mRNA transcripts were localized along glomerular capillary walls and throughout vascular walls, but not in tubules and collecting ducts, in the kidney. In particular, the in situ hybridization analysis revealed that the Glp1r is predominantly expressed in renal blood vessels. To further verify these findings, we examined Glp1r mRNA expression in isolated enriched preparations of glomeruli, tubuli, and renal arteries. Consistent with the results of in situ hybridization analysis, Glp1r mRNA transcripts were detected in RNA from glomeruli and to a greater extent in renal arteries, but not in tubuli (Figure 1e and f). We next confirmed the lack of Glp1r expression in newly generated lines of Akita mice lacking the Glp1r. Figure 2a shows the data of RT-PCR analysis in 30-week-old GLP-1R-deficient C57BL/6 strain mice (Glp1r−/−) and GLP-1R-present littermates (Glp1r+/+). A complete absence of renal glomerular Glp1r mRNA was confirmed in Glp1r−/− mice. The levels of glomerular Glp1r mRNA transcripts were similar between nondiabetic C57BL/6-WT and diabetic C57BL/6-Akita mice. As shown in Figure 2b, GLP-1R deficiency did not affect islet topography and the number of insulin+ cells in the C57BL/6-Akita mice. Table 1 shows biochemical and physiological parameters at 30 weeks of age in the WT and Akita Glp1r−/− and Glp1r+/+ mice. GLP-1R deficiency did not affect plasma levels of active GLP-1, glucose, and insulin. Furthermore, there were no significant differences in body weight, systolic blood pressure, blood urea nitrogen, and plasma lipids between Glp1r+/+ and Glp1r−/− C57BL/6-Akita mice. Interestingly, Glp1r−/− C57BL/6-Akita mice exhibited significantly higher levels of urinary albumin, glomerular filtration rate (GFR), and kidney weight relative to Glp1r+/+ C57BL/6-Akita mice. The mild changes in the renal phenotype of Glp1r−/− C57BL/6-Akita mice were detected by 15 weeks of age (data not shown), and these mice developed overt renal diabetic changes by 30 weeks of age. In contrast, we did not observe similar changes in renal parameters in Glp1r+/+ C57BL/6-WT mice.Table 1Biochemical and physiological parameters in 30-week-old male miceC57BL/6-WTC57BL/6-AkitaGlp1r+/+Glp1r−/−Glp1r+/+Glp1r−/−n510510BW (g)30.2±0.628.5±0.523.4±0.4*P<0.00122.0±0.7*P<0.001SBP (mmHg)99±199±1116±4†P<0.01115±3†P<0.01BG (mg/dl)153±5156±5500±38*P<0.001506±21*P<0.001Plasma insulin (ng/ml)0.63±0.050.54±0.110.09±0.02*P<0.0010.06±0.02*P<0.001Plasma active GLP-1 (pg/ml)11.7±2.011.2±2.912.1±2.99.3±2.6BUN (mg/dl)20.9±1.120.9±1.234.2±1.8*P<0.00136.7±1.6*P<0.001Cre (mg/dl)0.74±0.020.70±0.020.84±0.070.83±0.04TC (mg/dl)78.2±5.075.4±2.484.0±4.486.2±4.6TG (mg/dl)123±5109±9121±7113±13ACR (μg/mg creatinine)9.7±1.310.1±0.950.0±3.5‡P<0.05 vs. Glp1r+/+ C57BL/6-WT86.2±15.6*P<0.001, §P<0.05GFR (μl/min/g BW)10.0±0.510.2±0.516.9±0.8*P<0.00120.1±0.5*P<0.001, ¶P<0.01 vs. Glp1r+/+ C57BL/6-Akita.LKW/BW (g/kg)5.2±0.16.5±0.39.3±0.4*P<0.00112.9±0.6*P<0.001, ¶P<0.01 vs. Glp1r+/+ C57BL/6-Akita.Abbreviations: ACR, urinary albumin-to-creatinine ratio; BG, blood glucose; BUN, blood urea nitrogen; BW, body weight; Cre, plasma creatinine; GFR, glomerular filtration rate; GLP-1, glucagon-like peptide-1; LKW, left kidney weight; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride; WT, wild type.Values are means±s.e.m.* P<0.001† P<0.01‡ P<0.05 vs. Glp1r+/+ C57BL/6-WT§ P<0.05¶ P<0.01 vs. Glp1r+/+ C57BL/6-Akita. Open table in a new tab Abbreviations: ACR, urinary albumin-to-creatinine ratio; BG, blood glucose; BUN, blood urea nitrogen; BW, body weight; Cre, plasma creatinine; GFR, glomerular filtration rate; GLP-1, glucagon-like peptide-1; LKW, left kidney weight; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride; WT, wild type. Values are means±s.e.m. Figure 3 shows glomerular histopathology at 30 weeks of age in Glp1r+/+ versus Glp1r−/− C57BL/6-WT and C57BL/6-Akita mice. Interestingly, periodic acid–Schiff (PAS) staining examination revealed increased mesangial expansion in Glp1r−/− C57BL/6-Akita mice as compared with Glp1r+/+ C57BL/6-Akita mice. Nondiabetic C57BL/6-WT mice displayed normal glomerular histology. Obvious tubulointerstitial injury was not observed in any groups (data not shown). Fibronectin (FN) is an extracellular matrix component and is present along glomerular basement membranes. An increase in FN deposition is observed during glomerular injury,22.Van Vliet A. Baelde H.J. Vleming L.J. et al.Distribution of fibronectin isoforms in human renal disease.J Pathol. 2001; 193: 256-262Crossref PubMed Scopus (56) Google Scholar and hence FN is used as a marker of diabetic glomerular injury. Compared with Glp1r+/+ C57BL/6-Akita mice, Glp1r−/− C57BL/6-Akita mice displayed significantly increased FN accumulation in glomerular capillary walls (Figure 3a and c). WT1 staining analysis revealed a significant reduction of podocyte number in Glp1r−/− C57BL/6-Akita mice relative to Glp1r+/+ C57BL/6-Akita mice (Figure 3a and d). Furthermore, through electron microscopic analysis, we observed irregular thickening of the glomerular basement membrane (GBM) in Glp1r−/− C57BL/6-Akita mice (Figure 3a). Morphometric analysis revealed a significant increase in GBM thickness in Glp1r-−/− C57BL/6-Akita mice (Figure 3e). Figure 4 shows renal cAMP and PKA activity levels at 30 weeks of age in Glp1r+/+ versus Glp1r−/− C57BL/6-WT and C57BL/6-Akita mice. Renal levels of both cAMP and PKA activity were markedly reduced in Glp1r−/− C57BL/6-WT and Glp1r−/− C57BL/6-Akita mice. In contrast, levels of renal cAMP and PKA activity were similar in Glp1r+/+ mice. These findings indicate that renal cAMP and PKA activity are regulated by the presence or absence of the Glp1r, independent of levels of glycemia in mice. The degree of renal oxidative stress was assessed using dihydroethidium (DHE) histochemistry and thiobarbituric acid–reactive substance (TBARS) assay at 30 weeks of age in Glp1r+/+ versus Glp1r−/− C57BL/6-WT and C57BL/6-Akita mice. As shown in Figure 5a and b, the glomeruli in C57BL/6-Akita diabetic mouse groups showed intense DHE fluorescence, indicating increased glomerular superoxide production. Notably, glomerular DHE fluorescence was stronger in kidneys from Glp1r−/− C57BL/6-Akita mice. Renal levels of TBARS, a sensitive marker of oxidative stress, were elevated in C57BL/6-Akita diabetic mouse groups (Figure 5e) and significantly greater in Glp1r−/− C57BL/6-Akita mice, suggesting that GLP-1R deficiency contributes to increasing renal oxidative stress in the setting of diabetes (Figure 5e). Recent experimental studies have reported that NAD(P)H oxidase NOX4 component is a major source of renal superoxide in the diabetic state,9.Gorin Y. Block K. Hernandez J. et al.Nox4 NAD(P)H oxidase mediates hypertrophy and fibronectin expression in the diabetic kidney.J Biol Chem. 2005; 280: 39616-39626Crossref PubMed Scopus (445) Google Scholar and that chronic hyperglycemia enhances renal activity of NAD(P)H oxidase.10.Kitada M. Koya D. Sugimoto T. et al.Translocation of glomerular p47phox and p67phox by protein kinase C-beta activation is required for oxidative stress in diabetic nephropathy.Diabetes. 2003; 52: 2603-2614Crossref PubMed Scopus (193) Google Scholar, 23.Thallas-Bonke V. Thorpe S.R. Coughlan M.T. et al.Inhibition of NADPH oxidase prevents advanced glycation end product-mediated damage in diabetic nephropathy through a protein kinase C-alpha-dependent pathway.Diabetes. 2008; 57: 460-469Crossref PubMed Scopus (283) Google Scholar Consistent with these findings, we observed that glomerular NOX4 expression and renal NAD(P)H oxidase activity were increased in C57BL/6-Akita diabetic mice relative to nondiabetic mice (Figure 5a, c and f). Reduction of glomerular NO accelerates the progression of albuminuria and mesangial expansion in diabetic mice.24.Zhao H.J. Wang S. Cheng H. et al.Endothelial nitric oxide synthase deficiency produces accelerated nephropathy in diabetic mice.J Am Soc Nephrol. 2006; 17: 2664-2669Crossref PubMed Scopus (288) Google Scholar, 25.Kanetsuna Y. Takahashi K. Nagata M. et al.Deficiency of endothelial nitric-oxide synthase confers susceptibility to diabetic nephropathy in nephropathy-resistant inbred mice.Am J Pathol. 2007; 170: 1473-1484Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar, 26.Wang C.H. Li F. Hiller S. et al.A modest decrease in endothelial NOS in mice comparable to that associated with human NOS3 variants exacerbates diabetic nephropathy.Proc Natl Acad Sci USA. 2011; 108: 2070-2075Crossref PubMed Scopus (49) Google Scholar Therefore, we examined glomerular NO levels by evaluation of the fluorescent intensity of the diaminofluorescein-2 diacetate reaction. As shown in Figure 5a and d, C57BL/6-Akita diabetic mice showed decreased glomerular NO levels. Semiquantitative analysis of glomerular NO fluorescence intensity revealed significantly lower glomerular NO levels in diabetic Glp1r−/− C57BL/6-Akita mice (Figure 5d). In contrast, there was no significant difference in glomerular NO levels between the two C57BL/6-WT nondiabetic mouse groups (Figure 5a and d). Thrombospondin-1 (TSP-1) is a homeotrimetric glycoprotein identified as an endogenous activator of transforming growth factor-β1 (TGF-β1).27.Daniel C. Schaub K. Amann K. et al.Thrombospondin-1 is an endogenous activator of TGF-beta in experimental diabetic nephropathy in vivo.Diabetes. 2007; 56: 2982-2989Crossref PubMed Scopus (91) Google Scholar TGF-β1 and connective tissue growth factor (CTGF) are well-known fibrogenic cytokines implicated in the development of renal hypertrophy and mesangial expansion in diabetic nephropathy.28.Reeves W.B. Andreoli T.E. Transforming growth factor beta contributes to progressive diabetic nephropathy.Proc Natl Acad Sci USA. 2000; 97: 7667-7669Crossref PubMed Scopus (204) Google Scholar, 29.Elmarakby A.A. Sullivan J.C. Relationship between oxidative stress and inflammatory cytokines in diabetic nephropathy.Cardiovasc Ther. 2010; 30: 49-59Crossref PubMed Scopus (449) Google Scholar Hence, we examined renal glomerular expression of TSP-1, TGF-β1, and CTGF in 30-week-old mice. Strikingly, Glp1r−/− C57BL/6-Akita mice exhibited increased TSP-1 expression in glomerular capillary walls (Figure 6a and b) and significantly higher glomerular mRNA levels of TGF-β1 and CTGF (Figure 6c and d). In contrast, these glomerular changes were not observed in nondiabetic Glp1r+/+ C57BL/6-WT mice that displayed normal glomerular histology. We next assessed whether the activation of GLP-1R using the GLP-1R agonist liraglutide suppresses the progression of renal injury in KK/Ta-Akita mice, a mouse model of progressive DN.18.Fujita H. Fujishima H. Chida S. et al.Reduction of renal superoxide dismutase in progressive diabetic nephropathy.J Am Soc Nephrol. 2009; 20: 1303-1313Crossref PubMed Scopus (141) Google Scholar Mice were treated with liraglutide alone or in combination with an adenylate cyclase inhibitor SQ22536 or a selective PKA inhibitor H-89. Table 2 shows physiological and biochemical data after a 4-week treatment period in 8-week-old KK/Ta-Akita mice. Although all groups of mice were similar with respect to body weight, systolic blood pressure, blood glucose, plasma insulin, blood urea nitrogen, plasma creatinine, and serum lipids, mice treated with liraglutide alone exhibited lower levels of urinary albumin-to-creatinine ratio, GFR, and kidney weight. These results suggest that liraglutide attenuates the development of diabetic renal changes such as overt albuminuria, glomerular hyperfiltration, and renal hypertrophy without affecting the severity of diabetes and diabetes-related factors. Furthermore, SQ22536 and H-89 abolished the renal protective effects of liraglutide.Table 2Physiological and biochemical parameters after a 4-week treatment with liraglutide either alone or in combination with SQ22536 or H-89 in male KK/Ta-Akita miceParameterVehicleLiraglutide+SQ22536Liraglutide+H-89Liraglutide alonen6666BW (g)21.5±1.422.0±0.522.6±0.420.1±0.7SBP (mmHg)116±3112±7114±4115±6BG (mg/dl)504±41481±31507±39492±22Plasma insulin (ng/ml)0.06±0.040.08±0.020.07±0.020.06±0.05BUN (mg/dl)38.0±1.440.3±2.640.0±2.632.2±1.5Cre (mg/dl)0.94±0.080.94±0.080.95±0.070.73±0.04TC (mg/dl)136±14128±10122±8135±4TG (mg/dl)229±21238±20272±30268±20ACR (μg/mg creatinine)603±56618±100760±84201±26*P<0.01GFR (μl/min/g BW)16.4±0.8NDND10.8±1.1*P<0.01LKW/BW (g/kg)14.9±1.512.3±0.512.1±0.310.6±0.5†P<0.05 vs. vehicle.Abbreviations: ACR, urinary albumin-to-creatinine ratio; BG, blood glucose; BUN, blood urea nitrogen; BW, body weight; Cre, plasma creatinine; GFR, glomerular filtration rate; LKW, left kidney weight; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride.Values are means ±s.e.m.* P<0.01† P<0.05 vs. vehicle. Open table in a new tab Abbreviations: ACR, urinary albumin-to-creatinine ratio; BG, blood glucose; BUN, blood urea nitrogen; BW, body weight; Cre, plasma creatinine; GFR, glomerular filtration rate; LKW, left kidney weight; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride. Values are means ±s.e.m. We next examined changes in renal histopathology, oxidative stress, NO, cAMP, and PKA activity after a 4-week treatment with liraglutide, with or without SQ22536 or H-89, in 8-week-old KK/Ta-Akita mice. As shown in Figure 7a (PAS staining) and 7b, moderate mesangial expansion was observed in vehicle-treated KK/Ta-Akita mice; however, mesangial expansion was reduced by liraglutide administration. FN accumulation in glomerular capillary walls was significantly diminished in the KK/Ta-Akita mice treated with liraglutide alone (Figure 7a and c). Furthermore, the KK/Ta-Akita mice treated with liraglutide alone exhibited higher podocyte number (Figure 7a and d) and lower GBM thickness (Figure 7a and e) than vehicle-treated KK/Ta-Akita mice. Notably, the amelioration of glomerular histopathological damage by liraglutide was eliminated in KK/Ta-Akita mice treated with liraglutide in combination with either SQ22536 or H-89. Figure 8 shows renal cAMP and PKA activity levels in 8-week-old KK/Ta-Akita mice. KK/Ta-Akita mice treated with liraglutide alone for 4 weeks displayed higher renal levels of cAMP and PKA activity than vehicle-treated KK/Ta-Akita mice. In contrast, renal cAMP did not increase after treatment with SQ22536, and was only modestly increased in mice treated with H-89, whereas PKA activity levels were not increased in kidneys of KK/Ta-Akita mice treated with liraglutide in combination with SQ22536 or H-89. Figure 9 shows the degree of renal oxidative stress and glomerular NO levels in 8-week-old KK/Ta-Akita mice. The treatment with liraglutide alone for 4 weeks significantly reduced glomerular levels of superoxide and NOX4 expression and increased glomerular NO levels in KK/Ta-Akita mice (Figure 9a–d). Furthermore, we observed significant reduction of renal TBARS and NAD(P)H oxidase activity levels in the KK/Ta-Akita mice treated with liraglutide alone as compared with vehicle-treated KK/Ta-Akita mice (Figure 9e and f). In contrast, the renoprotective effects of liraglutide were abolished by coadministration of either SQ22536 or H-89. The present study, using in situ hybridization and RT-PCR analyses, demonstrates that Glp1r mRNA transcripts are localized in glomerular capillary walls and throughout vascular walls, but not in tubules and collecting ducts, in the mouse kidney. More recently, Panjwani et al.20.Panjwani N. Mulvihill E.E. Longuet C. et al.GLP-1 receptor activation indirectly reduces hepatic lipid accumulation but does not attenuate development of atherosclerosis in diabetic male ApoE(−/−) mice.Endocrinology. 2013; 154: 127-139Crossref PubMed Scopus (251) Google Scholar have demonstrated that commercially available widely used GLP-1R antisera are neither sensitive nor specific, and detect comparable immunoreactive bands in tissue extracts of both Glp1r+/+ and Glp1r−/− mice.20.Panjwani N. Mulvihill E.E. Longuet C. et al.GLP-1 receptor activation indirectly reduces hepatic lipid accumulation but does not attenuate development of atherosclerosis in diabetic male ApoE(−/−) mice.Endocrinology. 2013; 154: 127-139Crossref PubMed Scopus (251) Google Scholar Similar concerns surrounding the use of commercially available GLP-1R antisera have been raised by other groups.21.Pyke C. Knudsen L.B. The glucagon-like peptide-1 receptor—or not?.Endocrinology. 2013; 154: 4-8Crossref PubMed Scopus (126) Google Scholar Hence, to avoid the pitfalls inherent in using antisera with suboptimal sensitivity and specificity, we used in situ hybridization and RT-PCR analysis to assess the expression and localization of Glp1r expression within the kidney. To explore whether the presence or absence of GLP-1R signaling has a crucial role in the development and progression of DN, we disrupted the Glp1r gene in the DN-resistant mouse model C57BL/6-Akita and investigated its renal phenotype. The C57BL/6-Akita mice exhibit less oxidative and diabetic renal damage despite having relatively high renal activity of NAD(P)H oxidase, a major source of superoxide, because superoxide dismutase antioxidant defense system works well in their kidneys.18.Fujita H. Fujishima H. Chida S. et al.Reduction of renal superoxide dismutase in progressive diabetic nephropathy.J Am Soc Nephrol. 2009; 20: 1303-1313Crossref PubMed Scopus (141) Google Scholar Interestingly, the present data indicate that loss of the GLP-1R induces the upregulation of glomerular NOX4 expression and further elevation of renal NAD(P)H oxidase activity, resulting in elevation of glomerular superoxide and renal oxidative stress levels in the C57BL/6-Akita mice. These renal alterations secondary to GLP-1R deficiency contribute to the development of overt DN in the DN-resistant C57BL/6-Akita mice, as evidenced by pronounced mesangial expansion, podocyte reduction, and GBM thickening. Therefore, it is conceivable that loss of GLP-1 action resulting from GLP-1R deficiency directly reduces the renal antioxidant defense capacity against increased oxidative stress under hyperglycemic conditions. Furthermore, consistent with the lack of a significant" @default.
• W1988049600 created "2016-06-24" @default.
• W1988049600 creator A5009374010 @default.
• W1988049600 creator A5016507641 @default.
• W1988049600 creator A5016608041 @default.
• W1988049600 creator A5044415438 @default.
• W1988049600 creator A5044499778 @default.
• W1988049600 creator A5047099462 @default.
• W1988049600 creator A5052412166 @default.
• W1988049600 creator A5055016294 @default.
• W1988049600 creator A5057472647 @default.
• W1988049600 creator A5075630675 @default.
• W1988049600 creator A5075793122 @default.
• W1988049600 creator A5086504375 @default.
• W1988049600 date "2014-03-01" @default.
• W1988049600 modified "2023-10-10" @default.
• W1988049600 title "The protective roles of GLP-1R signaling in diabetic nephropathy: possible mechanism and therapeutic potential" @default.
• W1988049600 cites W1573925283 @default.
• W1988049600 cites W1954980722 @default.
• W1988049600 cites W1977179808 @default.
• W1988049600 cites W1981905227 @default.
• W1988049600 cites W1982575337 @default.
• W1988049600 cites W1983883248 @default.
• W1988049600 cites W1992116679 @default.
• W1988049600 cites W1994831991 @default.
• W1988049600 cites W1998141110 @default.
• W1988049600 cites W2006128241 @default.
• W1988049600 cites W2011601530 @default.
• W1988049600 cites W2012258975 @default.
• W1988049600 cites W2016388970 @default.
• W1988049600 cites W2018509996 @default.
• W1988049600 cites W2034383851 @default.
• W1988049600 cites W2035040393 @default.
• W1988049600 cites W2040772170 @default.
• W1988049600 cites W2050866589 @default.
• W1988049600 cites W2066254515 @default.
• W1988049600 cites W2070786318 @default.
• W1988049600 cites W2083990676 @default.
• W1988049600 cites W2084948079 @default.
• W1988049600 cites W2087202910 @default.
• W1988049600 cites W2090360729 @default.
• W1988049600 cites W2096275714 @default.
• W1988049600 cites W2102115518 @default.
• W1988049600 cites W2104529598 @default.
• W1988049600 cites W2113839433 @default.
• W1988049600 cites W2114218148 @default.
• W1988049600 cites W2115724806 @default.
• W1988049600 cites W2116831537 @default.
• W1988049600 cites W2125075201 @default.
• W1988049600 cites W2127883421 @default.
• W1988049600 cites W2129347273 @default.
• W1988049600 cites W2134975242 @default.
• W1988049600 cites W2139947959 @default.
• W1988049600 cites W2142503533 @default.
• W1988049600 cites W2142693924 @default.
• W1988049600 cites W2145360453 @default.
• W1988049600 cites W2145824107 @default.
• W1988049600 cites W2146190354 @default.
• W1988049600 cites W2146242381 @default.
• W1988049600 cites W2146538047 @default.
• W1988049600 cites W2155210704 @default.
• W1988049600 cites W2159691173 @default.
• W1988049600 cites W2171779326 @default.
• W1988049600 cites W2173192280 @default.
• W1988049600 cites W2471605942 @default.
• W1988049600 cites W4211246765 @default.
• W1988049600 cites W840007291 @default.
• W1988049600 doi "https://doi.org/10.1038/ki.2013.427" @default.
• W1988049600 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/24152968" @default.
• W1988049600 hasPublicationYear "2014" @default.
• W1988049600 type Work @default.
• W1988049600 sameAs 1988049600 @default.
• W1988049600 citedByCount "224" @default.
• W1988049600 countsByYear W19880496002014 @default.
• W1988049600 countsByYear W19880496002015 @default.
• W1988049600 countsByYear W19880496002016 @default.
• W1988049600 countsByYear W19880496002017 @default.
• W1988049600 countsByYear W19880496002018 @default.
• W1988049600 countsByYear W19880496002019 @default.
• W1988049600 countsByYear W19880496002020 @default.
• W1988049600 countsByYear W19880496002021 @default.
• W1988049600 countsByYear W19880496002022 @default.
• W1988049600 countsByYear W19880496002023 @default.
• W1988049600 crossrefType "journal-article" @default.
• W1988049600 hasAuthorship W1988049600A5009374010 @default.
• W1988049600 hasAuthorship W1988049600A5016507641 @default.
• W1988049600 hasAuthorship W1988049600A5016608041 @default.
• W1988049600 hasAuthorship W1988049600A5044415438 @default.
• W1988049600 hasAuthorship W1988049600A5044499778 @default.
• W1988049600 hasAuthorship W1988049600A5047099462 @default.
• W1988049600 hasAuthorship W1988049600A5052412166 @default.
• W1988049600 hasAuthorship W1988049600A5055016294 @default.
• W1988049600 hasAuthorship W1988049600A5057472647 @default.
• W1988049600 hasAuthorship W1988049600A5075630675 @default.
• W1988049600 hasAuthorship W1988049600A5075793122 @default.
• W1988049600 hasAuthorship W1988049600A5086504375 @default.
• W1988049600 hasBestOaLocation W19880496001 @default.
• W1988049600 hasConcept C111472728 @default.

• next