Radical scavenging effect of gliclazide in diabetic rats fed with a high cholesterol diet

Use of Ferulic Acid in the Management of Diabetes Mellitus and Its Complications

Diabetes mellitus, a metabolic disease mainly characterized by hyperglycemia, is becoming a serious social health problem worldwide with growing prevalence. Many natural compounds have been found to be effective in the prevention and treatment of diabetes, with negligible toxic effects. Ferulic acid (FA), a phenolic compound commonly found in medicinal herbs and the daily diet, was proved to have several pharmacological effects such as antihyperglycemic, antihyperlipidemic and antioxidant actions, which are beneficial to the management of diabetes and its complications. Data from PubMed, EM-BASE, Web of Science and CNKI were searched with the keywords ferulic acid and diabetes mellitus. Finally, 28 articles were identified after literature screening, and the research progress of FA for the management of DM and its complications was summarized in the review, in order to provide references for further research and medical applications of FA.

Activation of renal CSE/H2S pathway by alpha-lipoic acid protects against histological and functional changes in the diabetic kidney

INTRODUCTION

We previously reported that alpha-lipoic acid (ALA) supplementation protects against progression of diabetic kidney disease (DKD). In this study, we aim to investigate whether the mechanism of renal protection by ALA involves renal cystathionine γ-lyase/hydrogen sulfide (CSE/H₂S) system in type 2 diabetes mellitus (T2DM).

METHODS

Thirty-seven male Sprague-Dawley rats underwent 12 h of overnight fasting. To induce T2DM, 30 of these rats received intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). T2DM rats then received either oral administration of ALA (60 mg/kg/day) or intraperitoneal administration of 40 mg/kg/day DL-propargylglycine (PAG, a CSE inhibitor) or both for 6 weeks after which rats were sacrificed and samples collected for analysis. Untreated diabetic and non-diabetic rats served as diabetic and healthy controls respectively.

RESULTS

T2DM was characterized by reduced pancreatic β-cell function and hyperglycemia. Histologically, untreated diabetic rats showed significantly damaged pancreatic islets, glomerular and tubular injury, with elevated levels of renal function markers compared to healthy control rats (p < 0.001). These pathological changes worsened significantly following PAG administration (p < 0.05). While some renal protection was observed in ALA+PAG rats, ALA administration in untreated diabetic rats provided superior protection comparable to healthy control rats, with improved antioxidant status, lipid profile and reduced inflammation. Mechanistically, ALA significantly activated renal CSE/H₂S system in diabetic rats, which was markedly suppressed in PAG-treated rats (p < 0.001).

CONCLUSION

Our data suggest that ALA protects against DKD development and progression by activating renal CSE/H₂S pathway. Hence, CSE/H₂S pathway may represent a therapeutic target in the treatment or prevention of DKD in diabetic patients.

Supplementation of conventional anti-diabetic therapy with alpha-lipoic acid prevents early development and progression of diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Current pharmacological interventions only retard DN progression. Alpha-lipoic acid (ALA) is a potent antioxidant with beneficial effect in other diabetic complications. This study investigates whether ALA supplementation prevents early development and progression of DN.

METHOD

Fifty-eight male Sprague-Dawley rats were randomly assigned to healthy control and diabetic groups and subjected to overnight fasting. Type 2 diabetes mellitus (T2DM) was induced in diabetic group by intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). On day 3 after T2DM induction, diabetic rats received oral daily administration of ALA (60 mg/kg), gliclazide (15 mg/kg), ramipril (10 mg/kg) or drug combinations for 6 weeks. Untreated diabetic rats served as diabetic control. Blood, kidneys and pancreas were harvested for biochemical and histological analyses.

RESULT

Induction of T2DM resulted in hypoinsulinemia, hyperglycemia and renal pathology. ALA supplementation maintained β-cell function, normoinsulinemia and normoglycemia in diabetic rats, and prevented renal pathology (PAS, KIM-1, plasma creatinine, total protein, blood urea nitrogen, uric acid and urine albumin/creatinine ratio) and triglycerides level compared to diabetic control (p < 0.001). Additionally, ALA supplementation significantly prevented elevated serum and tissue malondialdehyde, collagen deposition, α-SMA expression, apoptosis and serum IL-1β and IL-6 levels while it markedly increased renal glutathione content and plasma HDL-C compared to diabetic control group (p < 0.001).

CONCLUSION

ALA supplementation prevents early development and progression of DN by exerting anti-hyperglycemic, antioxidant, anti-inflammatory, anti-fibrotic and anti-apoptotic effects. Our findings provide additional option for clinical treatment of DN in T2DM patients.

Combination Therapy of Alpha-Lipoic Acid, Gliclazide and Ramipril Protects Against Development of Diabetic Cardiomyopathy via Inhibition of TGF-β/Smad Pathway

Background: Diabetic cardiomyopathy (DCM) is a major long-term complication of diabetes mellitus, accounting for over 20% of annual mortality rate of diabetic patients globally. Although several existing anti-diabetic drugs have improved glycemic status in diabetic patients, prevalence of DCM is still high. This study investigates cardiac effect of alpha-lipoic acid (ALA) supplementation of anti-diabetic therapy in experimental DCM. Methods: Following 12 h of overnight fasting, 44 male Sprague Dawley rats were randomly assigned to two groups of healthy control (n = 7) and diabetic (n = 37) groups, and fasting blood glucose was measured. Type 2 diabetes mellitus (T2DM) was induced in diabetic group by intraperitoneal (i.p.) administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). After confirmation of T2DM on day 3, diabetic rats received monotherapies with ALA (60 mg/kg; n = 7), gliclazide (15 mg/kg; n = 7), ramipril (10 mg/kg; n = 7) or combination of the three drugs (n = 7) for 6 weeks while untreated diabetic rats received distilled water and were used as diabetic control (n = 9). Rats were then sacrificed, and blood, pancreas and heart tissues were harvested for analyses using standard methods. Results: T2DM induction caused pancreatic islet destruction, hyperglycemia, weight loss, high relative heart weight, and development of DCM, which was characterized by myocardial degeneration and vacuolation, cardiac fibrosis, elevated cardiac damage markers (plasma and cardiac creatine kinase-myocardial band, brain natriuretic peptide and cardiac troponin I). Triple combination therapy of ALA, gliclazide and ramipril preserved islet structure, maintained body weight and blood glucose level, and prevented DCM development compared to diabetic control (p < 0.001). In addition, the combination therapy markedly reduced plasma levels of inflammatory markers (IL-1β, IL-6 and TNF-α), plasma and cardiac tissue malondialdehyde, triglycerides and total cholesterol while significantly increasing cardiac glutathione and superoxide dismutase activity and high-density lipoprotein-cholesterol compared to diabetic control (p < 0.001). Mechanistically, induction of T2DM upregulated cardiac expression of TGF-β1, phosphorylated Smad2 and Smad3 proteins, which were downregulated following triple combination therapy (p < 0.001). Conclusion: Triple combination therapy of ALA, gliclazide and ramipril prevented DCM development by inhibiting TGF-β1/Smad pathway. Our findings can be extrapolated to the human heart, which would provide effective additional pharmacological therapy against DCM in T2DM patients.

A potential role of calpains in sulfonylureas (SUs) -mediated death of human pancreatic cancer cells (1.2B4)

Sulfonylureas (SUs) are suggested to accelerate the pancreatic β-cells mass loss via apoptosis. However, little is known whether calpains mediate this process. The aim of the present study is to evaluate the involvement of calpains in SUs-induced death of human pancreatic cancer (PC) cell line 1.2B4. The cells were exposed to: glibenclamide, glimepiride and gliclazide for 72 h. The expression analysis of caspase-3 (CASP-3), TP53, calpain 1 (CAPN-1), calpain 2 (CAPN-2) and calpain 10 (CAPN-10) was detected using RT-PCR method. Intracellular Ca²⁺ concentrations, CASP-3 activity and total calpain activity were also evaluated. Our results have shown that glibenclamide and glimepiride decrease 1.2B4 cells viability with accompanied increase in intracellular Ca²⁺ concentration and increased expression of apoptosis-related CASP-3 and TP53. Gliclazide did not affect 1.2B4 cell viability and Ca²⁺ concentration, however, it downregulated CASP-3 and upregulated TP53. Interestingly, 50 μM glimepiride increased expression of CAPN-1, CAPN-2 and CAPN-10 whereas 50 μM glibenclamide solely upregulated CAPN-2 expression. We have shown that 10 μM and 50 μM glibenclamide and glimepiride increased the activity of CASP-3, but decreased total calpain activity. Our results suggest that calpains may be involved in glibenclamide- and glimepiride-induced death of PC cells. However, further investigation is required to confirm the engagement of calpains in SUs-mediated death of PC cells, especially studies on protein level of particular isoforms of calpains should be conducted.

Geraniol ameliorates diabetic nephropathy via interference with miRNA-21/PTEN/Akt/mTORC1 pathway in rats

Deregulated activity of protein kinase B/mammalian target of rapamycin complex-1 (Akt/mTORC1) incites crucial pathological characteristics of diabetic nephropathy. The acyclic monoterpene geraniol has been recently reported to possess antidiabetic effects; however, its potential renoprotective effect in diabetes has not yet been elucidated. This study aimed to assess the possible modulatory effect of geraniol on the Akt/mTORC1 pathway in diabetes-induced nephropathy in rats compared to the standard antidiabetic drug gliclazide. Geraniol and gliclazide was administered daily to diabetic rats for 6 weeks starting on the 3rd-day post diabetes induction by streptozotocin (STZ). Geraniol amended the deteriorated renal function (serum creatinine; blood urea nitrogen). It exerted a remarkable antihyperglycemic effect that is comparable to that of gliclazide and suppressed the fibrotic marker, transforming growth factor-β. Geraniol restored redox balance and inhibited lipid peroxidation by reducing nicotine amide adenine dinucleotide phosphate oxidase and enhancing the antioxidant enzyme, superoxide dismutase. These beneficial effects were associated with a robust downregulation of miRNA-21 and consequently, reversion of tumor suppressor protein phosphatase and tension homolog (PTEN)/Akt/mTORC1 cue and its downstream proteins required for mesangial cell proliferation and matrix protein synthesis. The current study indicates that geraniol interfered with miRNA-21/ PTEN/AKT/mTORC1 pathway signaling that contributes largely to the progression of mesangial expansion and extracellular matrix deposition in diabetic nephropathy.

Gliclazide attenuates cisplatin-induced nephrotoxicity through inhibiting NF-κB and caspase-3 activity

Cisplatin (CP), as a chemotherapeutic drug, causes nephrotoxicity that has limited the clinical utility of CP. Gliclazide (GLZ), as an antihyperglycemic drug, at low dose has antioxidant property. In this study, we aimed to investigate the protective effect of GLZ against CP-induced acute renal injury. Sixty-four BALB/c mice were randomly divided into eight groups. The groups were included as control, GLZ (5, 10, and 25 mg/kg), CP, and GLZ (5, 10, and 25 mg/kg) + CP. Renal function markers (serum creatinine and blood urea nitrogen), oxidative stress markers (malondialdehyde and glutathione), apoptotic marker (caspase-3), and NF-κB were histopathologically evaluated. The results of our study showed that increased urea and creatinine were evidence of CP-induced nephrotoxicity. Histopathological examination revealed tubular epithelial and Bowman degeneration, edema, and cytoplasmic vacuolation in renal tissue structure. Administration of GLZ reduced oxidative stress, caspase-3, and NF-κB activity, and improved kidney function markers in CP-treated mice compared with CP alone group. Also, we observed that the histological tissue structure of the kidney was maintained. GLZ at dose of 25 mg/kg had higher protective effect as compared with other doses. Overall, our study suggests that GLZ with antioxidant, antiapoptotic, and anti-inflammatory properties may be a promising new therapeutic agent to prevent CP-induced nephrotoxicity.

Manganese Superoxide Dismutase Dysfunction and the Pathogenesis of Kidney Disease

The mitochondria are a major source of reactive oxygen species (ROS). Superoxide anion (O₂^•–) is produced by the process of oxidative phosphorylation associated with glucose, amino acid, and fatty acid metabolism, resulting in the production of adenosine triphosphate (ATP) in the mitochondria. Excess production of reactive oxidants in the mitochondria, including O₂^•–, and its by-product, peroxynitrite (ONOO^–), which is generated by a reaction between O₂^•– with nitric oxide (NO^•), alters cellular function via oxidative modification of proteins, lipids, and nucleic acids. Mitochondria maintain an antioxidant enzyme system that eliminates excess ROS; manganese superoxide dismutase (Mn-SOD) is one of the major components of this system, as it catalyzes the first step involved in scavenging ROS. Reduced expression and/or the activity of Mn-SOD results in diminished mitochondrial antioxidant capacity; this can impair the overall health of the cell by altering mitochondrial function and may lead to the development and progression of kidney disease. Targeted therapeutic agents may protect mitochondrial proteins, including Mn-SOD against oxidative stress-induced dysfunction, and this may consequently lead to the protection of renal function. Here, we describe the biological function and regulation of Mn-SOD and review the significance of mitochondrial oxidative stress concerning the pathogenesis of kidney diseases, including chronic kidney disease (CKD) and acute kidney injury (AKI), with a focus on Mn-SOD dysfunction.

Pathogenic Pathways and Therapeutic Approaches Targeting Inflammation in Diabetic Nephropathy

Diabetic nephropathy (DN) is associated with an increased morbidity and mortality, resulting in elevated cost for public health systems. DN is the main cause of chronic kidney disease (CKD) and its incidence increases the number of patients that develop the end-stage renal disease (ESRD). There are growing epidemiological and preclinical evidence about the close relationship between inflammatory response and the occurrence and progression of DN. Several anti-inflammatory strategies targeting specific inflammatory mediators (cell adhesion molecules, chemokines and cytokines) and intracellular signaling pathways have shown beneficial effects in experimental models of DN, decreasing proteinuria and renal lesions. A number of inflammatory molecules have been shown useful to identify diabetic patients at high risk of developing renal complications. In this review, we focus on the key role of inflammation in the genesis and progression of DN, with a special interest in effector molecules and activated intracellular pathways leading to renal damage, as well as a comprehensive update of new therapeutic strategies targeting inflammation to prevent and/or retard renal injury.

miRNA‑mRNA regulatory network analysis of mesenchymal stem cell treatment in cisplatin‑induced acute kidney injury identifies roles for miR‑210/Serpine1 and miR‑378/Fos in regulating inflammation

The present study aimed to identify microRNAs (miRNAs) that may be crucial for the mechanism of mesenchymal stem cell (MSC) treatment in cisplatin-induced acute kidney injury (AKI) and to investigate other potential drugs that may have a similar function. Transcriptomics (GSE85957) and miRNA expression (GSE66761) datasets were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) were identified using the linear models for microarray data method and mRNA targets of DEMs were predicted using the miRWalk2.0 database. The crucial DEGs were screened by constructing a protein-protein interaction (PPI) network and module analysis. Functions of target genes were analyzed using the database for annotation, visualization and integrated discovery. Small molecule drugs were predicted using the connectivity map database. As a result, 5 DEMs were identified to be shared and oppositely expressed in comparisons between AKI model and control groups, and between MSC treatment and AKI model groups. The 103 DEGs were overlapped with the target genes of 5 common DEMs, and the resulting list was used for constructing the miRNA-mRNA regulatory network, including rno-miR-210/Serpine1 and rno-miR-378/Fos. Serpine1 (degree=17) and Fos (degree=42) were predicted to be hub genes according to the topological characteristic of degree in the PPI network. Function analysis indicated Serpine1 and Fos may be inflammation-related. Furthermore, gliclazide was suggested to be a potential drug for the treatment of AKI because the enrichment score was the closest to −1 (−0.9). In conclusion, it can be speculated that gliclazide may have a similar mechanism to MSC as a potential therapeutic agent for cisplatin-induced AKI, by regulating miR-210/Serpine1 and miR-378-/Fos-mediated inflammation and cell apoptosis.

Hypoglycaemic effects of glimepiride in sulfonylurea receptor 1 deficient rat

BACKGROUND AND PURPOSE

Sulfonylureas (SUs) have been suggested to have an insulin-independent blood glucose-decreasing activity due to an extrapancreatic effect. However, a lack of adequate in vivo evidence makes this statement controversial. Here, we aimed to evaluate whether glimepiride has extrapancreatic blood glucose-lowering activity in vivo.

EXPERIMENTAL APPROACH

Sulfonylurea receptor 1 deficient (SUR1^-/- ) rats were created by means of transcription activator-like effector nucleases (TALEN)-mediated gene targeting technology. Type 2 diabetic models were established by feeding a high-fat diet and administering a low-dose of streptozotocin. These rats were then randomly divided into four groups: glimepiride, gliclazide, metformin and saline. All rats were treated for 2 weeks.

KEY RESULTS

Glimepiride decreased blood glucose levels and increased insulin sensitivity without elevating insulin levels. Gliclazide showed similar effects as glimepiride. Both agents were weaker than metformin. Further mechanistic investigations revealed that glimepiride increased hepatic glycogen synthesis and decreased gluconeogenesis, which were accompanied by the activation of Akt in the liver. Moreover, glimepiride increased both total and membrane glucose transporter 4 (GLUT4) levels in muscle and fat, which might be attributed to insulin receptor-independent IRS1/Akt activation.

CONCLUSION AND IMPLICATIONS

Glimepiride possesses an extrapancreatic blood glucose-lowering effect in vivo, which might be attributed to its direct effect on insulin-sensitive tissues. Therefore, the combination of glimepiride with multiple insulin injections should not be excluded per se.

Involvement of glucose-regulated protein 78 and spliced X-box binding protein 1 in the protective effect of gliclazide in diabetic nephropathy

AIMS

To testing whether endoplasmic reticulum (ER) stress contributes to the development of diabetic nephropathy. Investigated the effect of gliclazide, an oral antihyperglycemic agent, in a rat model of diabetic nephropathy and the underlying mechanism related to the ER stress response.

METHODS

Sixty SD rats were divided into six groups. Diabetic nephropathy was induced in 30 rats with a streptozotocin (STZ) injection and high fat diet, which were then treated with saline, gliclazide or 4-PBA. 20 rats were treated with Tunicamycin (TM) one-time intraperitoneal injection, following treated with saline or gliclazide. Blood glucose, kidney index and function were evaluated. Light and transmission electron microscopy (TEM) were used to observe kidney histological changes. Quantitative real-time PCR and western blot were performed to access the mRNA and protein levels of glucose-regulated protein 78 (GRP78) and spliced X-box binding protein 1 (sXBP1) in glomeruli.

RESULT

STZ-induced diabetic rats evidenced nephropathy by higher serum creatinine (sCr), blood urea nitrogen (BUN), microalbuminuria (MAU), and kidney index. Histological examination and TEM assay showed abnormal renal structures including thick glomerular basement membrane and mesangial cell expansion. The same changes were found in TM-treated rats. Gliclazide-treated had similar kidney index, but lower glucose levels, sCr, BUN, and MAU, compared with both saline and 4-PBA-treated diabetic rats or saline-treated TM rats. Synchronize with significantly lower Grp78 and sXbp1 mRNA and protein levels.

CONCLUSION

Diabetes-induced nephropathy is associated with ER stress. Gliclazide treatment lessens diabetic nephropathy, probably partially by suppressing the GRP78- and sXBP1-mediated ER response.

Sulfonylureas at the Glomerular Battlefield

The kidney is important in the context of diabetes not only because it is involved in normal glucose homeostasis, but also because it is one of the most important end organs to be involved in diabetes complications. Glomeruli are the meeting point of both microvascular, or renal; and macrovascular, or cardiovascular, health in diabetes. Sulfonylureas are effective glucose-lowering drugs. While a sulfonylurea-based glucose-lowering strategy is nephro-safe and nephro-protective, this aspect of sulfonylurea pharmaco-biology has not been highlighted earlier. In this editorial, we discuss current preclinical and clinical trial evidence regarding the performance of modern sulfonylureas at the glomerular battlefield.

Targeting inflammation in diabetic nephropathy: a tale of hope

INTRODUCTION

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Beyond the new anti-diabetic drugs that possess markedly cardiovascular and renal protective effects, no novel direct therapies for DN have become available on the market in the last twenty years. Recently well-designed clinical trials for the treatment of DN, with attractive pathogenetic rationale, e.g. bardoxolone and atrasentan, were canceled or stopped because of safety concerns or lack of reaching the end points, respectively.

AREAS COVERED

In this review, we focus on the involvement of inflammation in the pathogenesis of DN. We update information from recent experimental and clinical studies that reported beneficial effects of several agents targeting chemokines, cytokines, transcription factors and kinases as well as several compounds with anti-inflammatory properties on DN.

EXPERT OPINION

Inflammation plays a key role in the DN progression. Preclinical studies have identified several anti-inflammatory molecules that effective decrease albuminuria and/or proteinuria. However, limited clinical trials in humans have been performed to confirm these results. Inhibitors of CCL2/CCR2, IL-1β and JAK/STAT pathways, and Nrf2 inducers are promising therapeutic options to improve the renal outcome of patients with DN, but appropriate clinical trials are necessary.

Potential Applications of Gliclazide in Treating Type 1 Diabetes Mellitus: Formulation with Bile Acids and Probiotics

A major advancement in therapy of type 1 diabetes mellitus (T1DM) is the discovery of new treatment which avoids and even replaces the absolute requirement for injected insulin. The need for multiple drug therapy of comorbidities associated with T1DM increases demand for developing novel therapeutic alternatives with new mechanisms of actions. Compared to other sulphonylurea drugs used in the treatment of type 2 diabetes mellitus, gliclazide exhibits a pleiotropic action outside pancreatic β cells, the so-called extrapancreatic effects, such as antiinflammatory and cellular protective effects, which might be beneficial in the treatment of T1DM. Results from in vivo experiments confirmed the positive effects of gliclazide in T1DM that are even more pronounced when combined with other hypoglycaemic agents such as probiotics and bile acids. Even though the exact mechanism of interaction at the molecular level is still unknown, there is a clear synergistic effect between gliclazide, bile acids and probiotics illustrated by the reduction of blood glucose levels and improvement of diabetic complications. Therefore, the manipulation of bile acid pool and intestinal microbiota composition in combination with old drug gliclazide could be a novel therapeutic approach for patients with T1DM.

Endoglin Mediates Vascular Endothelial Growth Factor-A-Induced Endothelial Cell Activation by Regulating Akt Signaling

In diabetic nephropathy, differential expression of growth factors leads to vascular changes, including endothelial cell activation, monocyte infiltration, and inflammation. Endoglin plays an important role in endothelial function and is also associated with inflammation. In the kidney, vascular endoglin expression is increased in animal models of renal injury, where it contributes to disease severity, possibly by promoting endothelial cell activation and inflammation. Herein, we investigated whether endoglin expression is associated with diabetic nephropathy. In addition, we examined whether reducing endothelial endoglin expression in vitro affects endothelial cell activation and monocyte adhesion and, if so, which intracellular pathways are involved. Finally, we analyzed whether glomerular endoglin expression is correlated with endothelial cell activation in patients with diabetic nephropathy. Endoglin levels were significantly increased in mice with type 1 diabetes compared with control mice. Reducing endoglin expression in cultured endothelial cells significantly impaired the vascular endothelial growth factor-A-induced up-regulation of activation markers and monocyte adhesion. This was mediated by increased phosphorylation of Akt, thereby inhibiting activating transcription factor 2 phosphorylation, which regulates vascular cell adhesion molecule-1 (VCAM1) gene transcription in these cells. Last, endoglin colocalized with VCAM-1 in the glomeruli of diabetic patients, glomerular VCAM-1 expression was significantly increased in these patients, and this increase in VCAM-1 expression was correlated with increased glomerular endoglin expression. Thus, targeting endoglin function may have therapeutic value in patients at risk for diabetic nephropathy.

Different sulfonylureas induce the apoptosis of proximal tubular epithelial cell differently via closing KATP channel

BACKGROUND

Sulfonylureas (SUs) are widely prescribed for the treatment of type 2 diabetes (T2DM). Sulfonylurea receptors (SURs) are their main functional receptors. These receptors are also found in kidney, especially the tubular cells. However, the effects of SUs on renal proximal tubular epithelial cells (PTECs) were unclear.

METHODS

Three commonly used SUs were included in this study to investigate if different SUs have different effects on the apoptosis of PTECs. HK-2 cells were exposed to SUs for 24 h prior to exposure to 30 mM glucose, the apoptosis rate was evaluated by Annexin/PI flow cytometry. Bcl-2, Bax and the ratio of LC3II to LC3I were also studied by western blot in vitro. Diazoxide was used to evaluate the role of KATP channel in SUs-induced apoptosis of PTECs. A Student's t-test was used to assess significance for data within two groups.

RESULTS

Treatment with glibenclamide aggravated the apoptosis of HK-2 cells in high-glucose, as indicated by a significant decrease in the expression of Bcl-2 and increase in Bax. Additionally, the decreased LC3II/LC3I reflects that the autophagy was inhibited by glibenclamide. Similar but less pronounced change was found in glimepiride group, however, nearly opposite effects were found in gliclazide group. Further, the effects of glibenclamide on apoptosis promotion and the decreased LC3II/LC3I were ameliorated obviously by treatment with 100uM diazoxide. The potential protection effect of gliclazide was also inhibited after opening the KATP channel.

CONCLUSION

Our results suggest that, the effects of glibenclamide and glimepiride on PTECs apoptosis, especially the former, were achieved in part by closing the KATP channel. In contrast to glibenclamide and glimepiride, therapeutic concentrations of gliclazide showed an inhibitory effect on apoptosis of PTECs, which may have a benefit in the preservation of functional PTECs mass.

Gliclazide

Gliclazide is a second-generation oral hypoglycemic drug used for the treatment of noninsulin-dependent diabetes mellitus. It belongs to the sulfonylurea class that stimulates insulin secretion from pancreatic β-cells by inhibiting ATP-dependent potassium channels. Gliclazide also possesses unique antioxidant properties and other beneficial hemobiological effects. This profile represents a comprehensive description of the physical properties, chemical synthesis, spectroscopic characterization (FTIR, ¹H NMR, ¹³C NMR, UV, and single-crystal X-ray), methods of analysis, pharmacological actions, and pharmacokinetic and pharmacodynamic properties of the title drug.

New molecular insights in diabetic nephropathy

Diabetes mellitus represents one of the major causes of functional kidney impairment. The review highlights the most significant steps made over the last decades in understanding the molecular basis of diabetic nephropathy (DN), which may provide reliable biomarkers for early diagnosis and prognosis, along with new molecular targets for personalized medicine. There is an increased interest in developing new therapeutic strategies to slow DN progression for improving patients' quality of life and reducing all-cause morbidity and disease-associated mortality. It is highly important to have a science-based medical attitude when facing diabetic patients with associated comorbidities and risk of rapid evolution toward end-stage renal disease. The data discussed herein were mainly from MEDLINE and PubMed articles published in English from 1990 to 2015 and from up-to-date. The search term was "diabetic nephropathy and oxidative stress".

Comparing kidney outcomes in type 2 diabetes treated with different sulphonylureas in real-life clinical practice

AIM

Although several sulphonylureas are widely used in type 2 diabetes (T2D), their differential impacts on long-term major kidney outcomes remain unclear. This study aimed to investigate the effects of the two most commonly prescribed sulphonylureas, glimepiride and gliclazide, on kidney outcomes in patients with T2D.

METHODS

A total of 4486 patients treated with either glimepiride or gliclazide for more than 2 years were followed for up to 5.5 years (median: 4.7 years). A propensity score based on baseline characteristics was used to match 1427 patients treated with glimepiride with 1427 gliclazide-treated patients; incidences of end-stage renal disease (ESRD) and sustained doubling of creatinine to>132.6 μmol/L (1.5mg/dL) were also compared.

RESULTS

In the matched cohort with 12,122 person-years of follow-up, there was no significant difference between groups in risk of ESRD [hazard ratio (HR): 0.57, 95% confidence interval (CI): 0.29-1.12] or doubling of creatinine (HR: 0.74, 95% CI: 0.44-1.26), although there was a trend towards higher risks in the glimepiride group. Subgroup analyses showed that, compared with glimepiride, gliclazide was associated with a lower risk of doubling of creatinine in patients with preserved renal function (glomerular filtration rate ≥ 60 mL/min/1.73 m(2), HR: 0.21, 95% CI: 0.04-0.99) and good glycaemic control (HbA1c < 7%, HR: 0.35, 95% CI: 0.14-0.86), and in older subjects (≥ 62 years, HR: 0.52, 95% CI: 0.27-0.99).

CONCLUSION

In a real-life setting, there was no significant difference in clinical outcomes of kidney disease for patients treated with glimepiride vs gliclazide. However, gliclazide appeared to protect against renal complication progression in certain populations.

In vivo and in vitro attenuation of naloxone-precipitated experimental opioid withdrawal syndrome by insulin and selective KATP channel modulator

RATIONALE

Opiate exposure for longer duration develops state of dependence in humans and animals, which is revealed by signs and symptoms of withdrawal precipitated by opioid receptor antagonists. The sudden withdrawal of opioids produces a withdrawal syndrome in opioid-dependent subjects. Insulin and ATP-sensitive potassium (KATP) channel-mediated glucose homeostasis have been shown to modulate morphine withdrawal.

OBJECTIVE

Present study has been structured to investigate the role of insulin and pharmacological modulator of KATP channel (gliclazide) in experimental morphine withdrawal syndrome, both invivo and invitro.

METHODS

In this study, naloxone-precipitated morphine withdrawal syndrome in mice (invivo) as well as in rat ileum (invitro) were utilized to assess opioid withdrawal phenomenon. Morphine withdrawal syndromes like jumping and rearing frequency, forepaw licking, circling, fore paw tremor, wet dog shake, sneezing, overall morphine withdrawal severity (OMWS), serum glucose, brain malondialdehyde (MDA), glutathione (GSH), nitrite/nitrate, and calcium (Ca(+2)) were assessed.

RESULTS

Naloxone has significantly increased morphine withdrawal syndrome, both invivo and invitro. Insulin and gliclazide have significantly attenuated, naloxone induced behavioral changes like jumping and rearing frequency, forepaw licking, wet dog shake, sneezing, straightening, circling, OMWS, and various biochemical impairments such as serum glucose, brain MDA, GSH, nitrite/nitrate, and Ca(+2) in morphine-dependent animals (invivo). In vitro, insulin and gliclazide have significantly reduced naloxone-induced contraction in morphine-withdrawn rat ileum preparation.

CONCLUSIONS

Insulin and gliclazide (KATP channel blocker) have attenuated naloxone-precipitated morphine withdrawal syndrome, both invivo and invitro. Thus, insulin and KATP channel modulation may provide new avenues for research in morphine withdrawal.

Network analysis identifies SOD2 mRNA as a potential biomarker for Parkinson's disease

Increasing evidence indicates that Parkinson's disease (PD) and type 2 diabetes (T2DM) share dysregulated molecular networks. We identified 84 genes shared between PD and T2DM from curated disease-gene databases. Nitric oxide biosynthesis, lipid and carbohydrate metabolism, insulin secretion and inflammation were identified as common dysregulated pathways. A network prioritization approach was implemented to rank genes according to their distance to seed genes and their involvement in common biological pathways. Quantitative polymerase chain reaction assays revealed that a highly ranked gene, superoxide dismutase 2 (SOD2), is upregulated in PD patients compared to healthy controls in 192 whole blood samples from two independent clinical trials, the Harvard Biomarker Study (HBS) and the Diagnostic and Prognostic Biomarkers in Parkinson's disease (PROBE). The results from this study reinforce the idea that shared molecular networks between PD and T2DM provides an additional source of biologically meaningful biomarkers. Evaluation of this biomarker in de novo PD patients and in a larger prospective longitudinal study is warranted.

Liver X receptors preserve renal glomerular integrity under normoglycaemia and in diabetes in mice

AIMS/HYPOTHESIS

Liver X receptors (LXRs) α and β are nuclear hormone receptors that are widely expressed in the kidney. They promote cholesterol efflux from cells and inhibit inflammatory responses by regulating gene transcription. Here, we hypothesised (1) that LXR deficiency would promote renal decline in a mouse model of diabetes by accelerating intraglomerular cholesterol accumulation and, conversely, (2) that LXR agonism would attenuate renal decline in diabetes.

METHODS

Diabetes was induced with streptozotocin (STZ) and maintained for 14 weeks in Lxrα/β (+/+) (Lxrα, also known as Nr1h3; Lxrβ, also known as Nr1h2) and Lxrα/β (-/-) mice. In addition, STZ-injected DBA/2J mice were treated with vehicle or the LXR agonist N,N-dimethyl-hydroxycholenamide (DMHCA) (80 mg/kg daily) for 10 weeks. To determine the role of cholesterol in diabetic nephropathy (DN), mice were placed on a Western diet after hyperglycaemia developed.

RESULTS

Even in the absence of diabetes, Lxrα/β (-/-) mice exhibited a tenfold increase in the albumin:creatinine ratio and a 40-fold increase in glomerular lipid accumulation compared with Lxrα/β (+/+) mice. When challenged with diabetes, Lxrα/β (-/-) mice showed accelerated mesangial matrix expansion and glomerular lipid accumulation, with upregulation of inflammatory and oxidative stress markers. In the DN-sensitive STZ DBA/2J mouse model, DMHCA treatment significantly decreased albumin and nephrin excretion (by 50% each), glomerular lipids and plasma triacylglycerol (by 70%) and cholesterol (by 48%); it also decreased kidney inflammatory and oxidative stress markers compared with vehicle-treated mice.

CONCLUSIONS/INTERPRETATION

These data support the idea that LXR plays an important role in the normal and diabetic kidney, while showing that LXR, through its inhibitory effect on inflammation and cholesterol accumulation in glomeruli, could also be a novel therapeutic target for DN.

The role of adrenomedullin in the renal NADPH oxidase and (pro)renin in diabetic mice

Adrenomedullin has an antioxidative action and protects organs in various diseases. To clarify the role of adrenomedullin in diabetic nephropathy, we investigated the NADPH oxidase expression, renin-secreting granular cell (GC) hyperplasia, and glomerular matrix expansion in the streptozotocin (STZ)-induced diabetic adrenomedullin gene knockout (AMKO) mice compared with the STZ-diabetic wild mice at 10 weeks. The NADPH oxidase p47phox expression and lipid peroxidation products were enhanced in the glomeruli of the diabetic mice compared with that observed in the controls in both wild and AMKO mice. These changes were more obvious in the AMKO mice than in the wild mice. Glomerular mesangial matrix expansion was more severe in the diabetic AMKO mice than in the diabetic wild mice and exhibited a positive correlation with the degree of lipid peroxidation products in the glomeruli. Proteinuria was significantly higher in the diabetic AMKO mice than in the diabetic wild mice. The GC hyperplasia score and the renal prorenin expression were significantly increased in the diabetic AMKO mice than in the diabetic wild mice, and a positive correlation was observed with the NADPH oxidase expression in the macula densa. The endogenous adrenomedullin gene exhibits an antioxidant action via the inhibition of NADPH oxidase probably by suppressing the local renin-angiotensin system.

Protective effects of beta glucan and gliclazide on brain tissue and sciatic nerve of diabetic rats induced by streptozosin

There have not been yet enough studies about effects of beta glucan and gliclazide on oxidative stress created by streptozotocin in the brain and sciatic nerve of diabetic rats. The aim of this paper was to investigate the antioxidant effects of gliclazide and beta glucan on oxidative stress and lipid peroxidation created by streptozotosin in brain and sciatic nerve. Total of 42 rats were divided into 6 groups including control, diabetic untreated (DM) (only STZ, diabetic), STZ (DM) + beta glucan, STZ (DM) + gliclazide, only beta glucan treated (no diabetic), and only gliclazide treated (no diabetic). The brain and sciatic nerve tissue samples were analyzed for malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and paraoxonase (PON-1) levels. We found a significant increase in MDA, TOS, and OSI along with a reduction in TAS level, catalase, and PON-1 activities in brain and sciatic nerve of streptozotocin-induced diabetic rats. Also, this study shows that in terms of these parameters both gliclazide and beta glucan have a neuroprotective effect on the brain and sciatic nerve of the streptozotocin-induced diabetic rat. Our conclusion was that gliclazide and beta glucan have antioxidant effects on the brain and sciatic nerve of the streptozotocin-induced diabetic rat.

Treating diabetes today with gliclazide MR: a matter of numbers

Type 2 diabetes mellitus (T2DM) is a progressive disease characterized by worsening hyperglycaemia. Lowering haemoglobin A1c to below or around 7% has been shown to reduce microvascular and neuropathic complications of diabetes. The ongoing uncertainty regarding whether intensive glycaemic control can reduce the increased risk of cardiovascular disease (CVD) in people with T2DM stirred the launch of the recent long-term megatrials. These trials compared the effects of intensive vs. standard control on vascular complications in relatively high CV risk participants with T2DM. While in Veterans Affairs Diabetes Trial, and Action to Control Cardiovascular Risk in Diabetes, the effect of glucose optimization resulted either in no protection or in an excessive CVD death, the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation trial showed that intensive glycaemic control reduced the risk of combined major macrovascular and microvascular events. In this trial, the glucose control strategy was based on gliclazide MR at randomization in all patients and then further sequential addition of other glucose-lowering drugs. Several studies showed that gliclazide has antioxidant properties, reduces markers of endothelial inflammation, and prevents glucose-induced apoptosis of endothelial cells. These positive antioxidant effects are not confined to the vascular wall but they are effective also in the β cells. These properties are important because (i) in patients with atherosclerotic process, microvascular abnormalities may hasten disease progression and (ii) slowing the microvascular complications may have a potentially remarkable effect on the natural history of macrovascular disease.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Effects of gliclazide on endothelial function in patients with newly diagnosed type 2 diabetes

Endothelial dysfunction is thought to be a critical event in the pathogenesis of vasculopathy in type 2 diabetes and oxidant stress is a major etiological factor. Gliclazide, a second generation sulfonylurea, contains an azabicyclo-octyl ring, which has been described to have antioxidant properties. However, the effect of gliclazide on endothelial function is unknown. Therefore, in this study, we examined the effect of gliclazide on endothelial function in patients with newly diagnosed type 2 diabetes (diabetic group; n=33). A control group of non-diabetic subjects was also enrolled (n=25). All of the diabetic patients were treated with gliclazide for 12 weeks. Endothelial function was evaluated by flow-mediated vasodilation (FMD) before and after treatment. We also determined the number of circulating endothelial progenitor cells (EPCs), which were defined by CD45(low)/CD34(+)/VEGFR2(+) and quantified by flow cytometry, because these cells may offer a new biomarker for circulatory diseases. Oxidative stress was evaluated in terms of the serum levels of malondialdehyde, superoxide dismutase and nitric oxide. FMD, circulating EPC count and superoxide dismutase activity were significantly lower in the diabetic group than in the control group at baseline (P<0.05), and improved significantly following gliclazide treatment (P<0.05). Malondialdehyde and nitric oxide levels were higher in the diabetic group than in the control group at baseline (P<0.05), and decreased following gliclazide treatment. These results suggest that gliclazide could improve endothelial function in diabetes, which may be related to its antioxidant properties.

Resveratrol protects diabetic kidney by attenuating hyperglycemia-mediated oxidative stress and renal inflammatory cytokines via Nrf2-Keap1 signaling

Hyperglycemia-mediated oxidative stress plays a crucial role in the progression of diabetic nephropathy. Hence, the present study was hypothesized to explore the renoprotective nature of resveratrol by assessing markers of oxidative stress, proinflammatory cytokines and antioxidant competence in streptozotocin-nicotinamide-induced diabetic rats. Oral administration of resveratrol to diabetic rats showed a significant normalization on the levels of creatinine clearance, plasma adiponectin, C-peptide and renal superoxide anion, hydroxyl radical, nitric oxide, TNF-α, IL-1β, IL-6 and NF-κB p65 subunit and activities of renal aspartate transaminase, alanine transaminase and alkaline phosphatase in comparison with diabetic rats. The altered activities of renal aldose reductase, sorbitol dehydrogenase and glyoxalase-I and elevated level of serum advanced glycation end products in diabetic rats were also reverted back to near normalcy. Further, resveratrol treatment revealed a significant improvement in superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase activities and vitamins C and E, and reduced glutathione levels, with a significant decline in lipid peroxides, hydroperoxides and protein carbonyls levels in diabetic kidneys. Similarly, mRNA and protein analyses substantiated that resveratrol treatment notably normalizes the renal expression of Nrf2/Keap1and its downstream regulatory proteins in the diabetic group of rats. Histological and ultrastructural observations also evidenced that resveratrol effectively protects the kidneys from hyperglycemia-mediated oxidative damage. These findings demonstrated the renoprotective nature of resveratrol by attenuating markers of oxidative stress in renal tissues of diabetic rats.

Ameliorative effects of glycyrrhizin on streptozotocin-induced diabetes in rats

Objectives

Glycyrrhizin is the main water-soluble constituent of the root of liquorice (Glycyrrhiza glabra). The study investigates the effect of glycyrrhizin on streptozotocin (STZ)-induced diabetic changes and associated oxidative stress, including haemoglobin-induced free iron-mediated oxidative reactions.

Methods

Male Wistar rats were grouped as normal control, STZ-induced diabetic control, normal treated with glycyrrhizin, diabetic treated with glycyrrhizin and diabetic treated with a standard anti-hyperglycaemic drug, glibenclamide. Different parameters were studied in blood and tissue samples of the rats.

Key findings

Glycyrrhizin treatment improved significantly the diabetogenic effects of STZ, namely enhanced blood glucose level, glucose intolerant behaviour, decreased serum insulin level including pancreatic islet cell numbers, increased glycohaemoglobin level and enhanced levels of cholesterol and triglyceride. The treatment significantly reduced diabetes-induced abnormalities of pancreas and kidney tissues. Oxidative stress parameters, namely, serum superoxide dismutase, catalase, malondialdehyde and fructosamine in diabetic rats were reverted to respective normal values after glycyrrhizin administration. Free iron in haemoglobin, iron-mediated free radical reactions and carbonyl formation in haemoglobin were pronounced in diabetes, and were counteracted by glycyrrhizin. Effects of glycyrrhizin and glibenclamide treatments appeared comparable.

Conclusion

Glycyrrhizin is quite effective against hyperglycaemia, hyperlipidaemia and associated oxidative stress, and may be a potential therapeutic agent for diabetes treatment.

Relationship between oxidative stress and inflammatory cytokines in diabetic nephropathy

The prevalence of diabetes has dramatically increased worldwide due to the vast increase in the obesity rate. Diabetic nephropathy is one of the major complications of type 1 and type 2 diabetes and it is currently the leading cause of end-stage renal disease. Hyperglycemia is the driving force for the development of diabetic nephropathy. It is well known that hyperglycemia increases the production of free radicals resulting in oxidative stress. While increases in oxidative stress have been shown to contribute to the development and progression of diabetic nephropathy, the mechanisms by which this occurs are still being investigated. Historically, diabetes was not thought to be an immune disease; however, there is increasing evidence supporting a role for inflammation in type 1 and type 2 diabetes. Inflammatory cells, cytokines, and profibrotic growth factors including transforming growth factor-β (TGF-β), monocyte chemoattractant protein-1 (MCP-1), connective tissue growth factor (CTGF), tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-18 (IL-18), and cell adhesion molecules (CAMs) have all been implicated in the pathogenesis of diabetic nephropathy via increased vascular inflammation and fibrosis. The stimulus for the increase in inflammation in diabetes is still under investigation; however, reactive oxygen species are a primary candidate. Thus, targeting oxidative stress-inflammatory cytokine signaling could improve therapeutic options for diabetic nephropathy. The current review will focus on understanding the relationship between oxidative stress and inflammatory cytokines in diabetic nephropathy to help elucidate the question of which comes first in the progression of diabetic nephropathy, oxidative stress, or inflammation.

Gliclazide Attenuates the Intracellular Ca2+Changes InducedIn Vitroby Ischemia in the Retinal Slices of Rats with Streptozotocin-Induced Diabetes

PURPOSE

To investigate the dynamics of the intracellular Ca2+ concentration ([Ca2+]i) during retinal ischemia in rats with streptozotocin (STZ)-induced diabetes and the effect of gliclazide, a sulfonylurea with a potent free-radical scavenging activity on ischemia-induced [Ca2+]i dynamics.

METHODS

Rats with STZ (65 mg/kg) induced diabetes were divided into three groups: the untreated diabetic group, the gliclazide-treated group, and the glibenclamide-treated group. An ischemic condition was imposed in vitro on the retinal slices by perfusion with an oxygen/glucose deprived solution. The [Ca2+]i was measured in individual layers of the rat retinal slices loaded with the Ca2+ indicator fluo-3.

RESULTS

As compared to that in the normal rat retina, both the amplitude and the kinetics of the [Ca2+]i increase were suppressed in the intermediate layers of the retinal slices from the diabetic rats under the ischemic condition. These changes were attenuated by the administration of gliclazide but not by that of glibenclamide.

CONCLUSIONS

Hyperglycemia influences ischemia-induced [Ca2+]i dynamics predominantly in the intermediate layers of the retina, and gliclazide, as compared to glibenclamide without a free radical scavenging activity, potently attenuates the ischemia-induced changes in the calcium dynamics.

Expression of NG,NG-dimethylarginine dimethylaminohydrolase and protein arginine N-methyltransferase isoforms in diabetic rat kidney: effects of angiotensin II receptor blockers

OBJECTIVE

The nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine (ADMA) is generated by protein arginine N-methyltransferase (PRMT)-1 and is metabolized by N(G),N(G)-dimethylarginine dimethylaminohydrolase (DDAH). We tested the hypothesis that increased serum ADMA (S(ADMA)) in the streptozotocin (STZ)-induced diabetic rat model of diabetes is mediated by an angiotensin receptor blocker-sensitive change in DDAH or PRMT expression.

RESEARCH DESIGN AND METHODS

Data were compared from four groups of rats: sham-injected controls, untreated STZ-induced diabetic rats at 4 weeks, STZ-induced diabetic rats administered the angiotensin II (Ang II) receptor blocker telmisartan for 2 weeks, and control rats administered telmisartan for 2 weeks.

RESULTS

Immunostaining and Western blotting of microdissected nephron segments localized DDAH I in the proximal tubules and DDAH II in the glomeruli, afferent arterioles, macula densa, and distal nephron. Renal Ang II and S(ADMA) increased with diabetes but were normalized by 2 weeks of telmisartan. DDAH I expression was decreased in diabetic kidneys, while DDAH II expression was increased. These changes were reversed by telmisartan, which also reduced expression of PRMT-1 and -5. Telmisartan increased expressions of DDAH I but decreased DDAH II in Ang II-stimulated kidney slices ex vivo.

CONCLUSIONS

Renal Ang II and S(ADMA) are increased in insulinopenic diabetes. They are normalized by an Ang II receptor blocker, which increases the renal expression of DDAH I, decreases PRMT-1, and increases renal NO metabolites.

Ferulic acid prevents pathological and functional abnormalities of the kidney in Otsuka Long-Evans Tokushima Fatty diabetic rats

We investigated the preventive effects of ferulic acid (FA) and alpha-tocopherol (AT) on the progression of diabetic nephropathy. Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats were used as type 2 diabetes and non-diabetes models, respectively. Two-thirds of the OLETF rats were fed 0.2% FA-containing or 0.5% AT-containing chow. Diabetic nephropathy was assessed based on urinary protein excretion and pathological changes which were scored based on the percentages of extracellular matrix area in the glomerular area. Furthermore, renal messenger RNA (mRNA) expression of intercellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2) and transforming growth factor-beta1 (TGF-beta1) was quantified by real-time polymerase chain reaction. After 12 weeks of FA- or AT-supplementation, urinary protein in untreated-OLETF group was significantly higher than that in LETO group, thus FA-supplementation significantly decreased urinary protein excretion. Pathological scores in FA-supplemented group were significantly lower than those in untreated OLETF group. Supplementation with either FA or AT significantly prevented the elevation of TGF-beta1 mRNA expression caused by diabetes. Treatment with neither FA nor AT had a significant effect on COX-2 or ICAM-1 mRNA expressions. We have demonstrated the preventative effects of FA on diabetic nephropathy via suppression of TGF-beta1 upregulation, furthermore FA may be more potent than AT.

Suppressing renal NADPH oxidase to treat diabetic nephropathy

Renal nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase is an important source of oxidative stress and its expression is enhanced in the glomerulus and distal tubules of diabetic nephropathy. High glucose-induced protein kinase C signalling or renal angiotensin II signalling increases the membrane translocation of cytosolic component p47phox. NADPH oxidase-derived reactive oxygen species (ROS) in the podocytes damage the glomerular basement membrane and the slit diaphragm causing proteinuria, and mesangial and glomerular endothelial NADPH oxidase increase TGF-beta and cause collagen and fibronectin accumulation. Tubular NADPH oxidase stimulated by angiotensin II or aldosterone contributes to sodium retention and to tubulointerstitial damage. Thus, inhibition of the renal renin-angiotensin II-aldosterone system with angiotensin-converting enzyme inhibitor, angiotensin II type 1 receptor blocker or selective aldosterone inhibitor indirectly suppresses NADPH oxidase reducing renal ROS, proteinuria and glomerulosclerosis. Statins are also effective in blocking the membrane translocation of Rac, especially in diabetes with hypercholesterolemia where ROS is produced by the intrinsic NADPH oxidase and by the activated macrophages. A medical herb, picrorhiza, inhibits the membrane translocation of p47phox, is a specific inhibitor of NADPH oxidase and, more so than superoxide dismutase mimetics, may be a promising strategy for the treatment of diabetic nephropathy.

Comparisons between the beneficial effects of different sulphonylurea treatments on ischemia-induced retinal neovascularization

The aim of this study was to assess the potential beneficial effects of gliclazide and other sulphonylureas on ischemia-induced retinal neovascularization. To produce an animal model of oxygen-induced ischemic retinopathy, 7-day-old (P7) mice were exposed to a 75% oxygen environment for 5 days. On their return to ambient air at P12, these mice were then treated with gliclazide, glibenclamide, glimepiride, or N-acetylcysteine. Gliclazide, but not glibenclamide or glimepiride, markedly suppresses retinal neovascularization. N-Acetylcysteine, however, only moderately suppresses retinal neovascularization. The number of neovascular nuclei in the retinal cross sections decreased by 29% in the gliclazide-treated mice (P<0.05 vs control). The induction of VEGF mRNA expression at P13 is significantly suppressed in the gliclazide group, relative to the control group (-44%, P<0.05). The VEGF protein expression levels at P15 were also suppressed in the gliclazide group (-43%, P<0.01). The 8-isoprostane production levels at P15 were suppressed in both the gliclazide group (-20%, P<0.05) and the N-acetylcysteine-treated group (-31%, P<0.01). Gliclazide inhibits ischemia-induced retinal neovascularization, and this is likely to be mediated in part through the downregulation of VEGF and the suppression of oxidative stress.

Double-Edged Action of SOD Mimetic in Diabetic Nephropathy

Oxidative stress plays an important role in the pathogenesis of diabetic complications, and we investigated the effect of superoxide dismutase (SOD) mimetic, tempol, in diabetic nephropathy. Streptozotocin-induced diabetic rats were treated with tempol from 2 weeks until 8 weeks. The expression of NADPH oxidase, catalase, and myeloperoxidase (MPO), superoxide dismutase activity, and production of peroxide and hypochlorite were evaluated. Tempol treatment prevented the increase in NADPH oxidase and peroxide production in the glomeruli of diabetic rat. Catalase was decreased without change in SOD activity, and MPO was enhanced in the kidney of diabetic rats. Tempol treatment stimulated SOD activity and increased the conversion of superoxide to hydrogen peroxide, and hydrogen peroxide on its hand was converted to hypochlorite by the increased MPO. The reduction of peroxide by tempol was followed by the decrease in TGF-beta and mesangial matrix expansion. However, tempol did not reduce hypochlorite or urinary protein excretion. In conclusion, tempol inhibited glomerular matrix expansion via suppression of peroxide production and TGF-beta, but it failed to reduce proteinuria, probably due to the increased hypochlorite production in diabetic nephropathy.

Activation of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase by advanced glycation end products links oxidative stress to altered retinal vascular endothelial growth factor expression

Increasing evidence indicates that advanced glycation end products (AGEs) promote retinal alterations through oxidative stress. However, the pathways involved in AGE-induced generation of reactive oxygen species (ROS) in retinal cells are poorly defined. In the present study, we investigated the role of nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) oxidase in AGE-induced ROS intracellular generation and vascular endothelial growth factor (VEGF) expression in bovine retinal endothelial cells (BRECs). Incubation of BRECs with 100 microg/mL AGEs increased ROS generation and VEGF expression in these cells. Treatment of the cells with the NADPH oxidase inhibitors, apocynin and diphenylene iodonium, inhibited these effects. In retinal endothelial cells exposed to AGEs, translocation of protein kinase C (PKC)-beta2 and p47phox was observed. Inhibition of PKC by treatment of the cells with calphostin C, GF10923X, and LY379196 totally suppressed AGE-mediated p47phox translocation and ROS generation. Incubation of BRECs with gliclazide inhibited AGE-induced PKC-beta2 and p47phox translocation and totally abrogated AGE-mediated ROS generation and VEGF expression. Overall, these results demonstrate that AGEs induce intracellular ROS generation and VEGF expression in retinal endothelial cells through a PKC-dependent activation of NADPH oxidase. Inhibition of retinal NADPH oxidase expression and ROS generated by this system provides a new potential mechanism by which gliclazide may affect retinal VEGF expression and exert a beneficial effect on diabetic retinopathy.

Association of gliclazide and left ventricular mass in type 2 diabetic patients

Diabetes is a state of increased oxidant stress and there is evidence that oxidation may play a role in the genesis of higher left ventricular mass. Gliclazide has been shown to possess free radical scavenging properties. We assessed whether gliclazide may have a beneficial effect on left ventricular mass via reducing 8-iso-prostaglandin F(2alpha) concentrations, a reliable marker of oxidant injury. A total of 41 patients were randomized into two groups. All patients had been taking glibenclamide for more than 3 months before being randomized to switch either an equipotent dose of gliclazide (n=21) or to continue on glibenclamide (n=20). Baseline characteristics were similar in both groups. At 6 months, gliclazide-treated patients showed a significant regression in left ventricular mass index compared with the glibenclamide-treated group (-16% versus 3%, P=0.003). Gliclazide patients had significantly lower plasma 8-iso-prostaglandin F(2alpha) compared with baseline (299+/-101 pg/ml versus 400+/-112 pg/ml, P=0.001) and the glibenclamide-treated patients (299+/-101 pg/ml versus 388+/-114 pg/ml, P=0.01) after 6-month therapy. The magnitude of left ventricular mass index regression correlated univariately with the magnitude of inhibition of 8-iso-prostaglandin F(2alpha) formation (r=0.74, P<0.0001). Multivariate analysis revealed that regression of left ventricular mass index significantly correlated with the changes of 8-iso-prostaglandin F(2alpha) (P<0.0001, adjusted R(2)=0.55). Our findings demonstrated for the first time that in addition to its primary hypoglycemia, gliclazide may have an additional effect on reducing left ventricular mass, possibly through attenuation of free radical formation.

Glibenclamide prevents increased extracellular matrix formation induced by high glucose concentration in mesangial cells

Other than stimulation of cell contractility, little is known about the potential metabolic effects induced by sulfonylureas, independently of insulin action. Previous studies from our laboratory demonstrated complete abrogation of glomerulosclerosis in an experimental model of type 1 diabetes chronically (9 mo) treated with low-dose sulfonylureas (Biederman JI, Vera E, Pankhaniya R, Hassett C, Giannico G, Yee J, Cortes P. Kidney Int 67: 554-565, 2005). Therefore, the effects of glibenclamide (Glib) on net collagen I, collagen IV, and fibronectin medium net secretion and cell layer collagen I deposition were investigated in mesangial cells continuously exposed to 25 mM glucose for 8 wk and treated with predetermined increasing concentrations of Glib for the same period. Clinically relevant concentrations (0.01 microM) of Glib fully suppressed the high glucose-enhanced accumulation of collagen I, collagen IV, and fibronectin in the medium and inhibited collagen I deposition in the cell layer. These effects occurred while transforming growth factor (TGF)-beta1 medium concentration remained elevated and glucose uptake was increased to levels above those in 25 mM glucose-incubated cultures. The decreased collagen I accumulation occurred simultaneously with enhanced collagen I mRNA expression in concert with marked suppression of plasminogen inhibitor type-1 (PAI-1) mRNA and protein expression. This strongly suggests an accelerated matrix turnover favoring breakdown. Glib-induced effects demonstrated a biphasic pattern, being absent or reversed in cells treated with higher Glib concentrations (0.1 or 1 microM). Therefore, chronic Glib treatment at low concentrations markedly diminishes the high glucose-induced enhanced accumulation of extracellular matrix components by suppression of steady-state PAI-1 transcriptional activity. These results and those previously reported in vivo suggest that long-term Glib treatment may prevent glomerulosclerosis in insulin-deficient diabetes.

Chronic inhibition of nitric oxide production aggravates diabetic nephropathy in Otsuka Long-Evans Tokushima Fatty rats

BACKGROUND

Nitric oxide (NO) is known to play a role in diabetic nephropathy, but the molecular basis for this effect remains unclear.

METHOD

Otsuka Long-Evans Tokushima Fatty spontaneous diabetic rat models were used along with Long-Evans Tokushima Otuska rat models as age-matched controls. Either L-arginine (a NO precursor) or L-NAME (a nitric oxide synthase inhibitor) was administered from the age of 22 weeks. Clinical parameters and serum and urinary NO2+NO3 levels were measured, in addition to renal histological findings and ED-1-positive cell counts in glomeruli.

RESULTS

There were no significant differences in creatinine clearance between any of the groups at any point. The levels of urinary NO2+NO3 in the diabetic group were significantly lower than those in the control groups after 40 weeks; that in the L-NAME diabetic group was significantly lower than in the other diabetic groups at 52 weeks. Compared with the other diabetic groups, the L-NAME diabetic group had significantly higher urinary protein excretion levels, histological scores, and numbers of ED-1-positive cells in glomeruli. Diabetic rats administered L-arginine excreted more urinary protein than the diabetic controls.

CONCLUSION

Diabetic nephropathy was exacerbated drastically by a nitric oxide synthase inhibitor and mildly by a NO precursor. These data suggested that NO may modify type 2 diabetic nephropathy in Otuska Long-Evans Tokushima Fatty rats through factors other than hemodynamics.

Role of macula densa neuronal nitric oxide synthase in renal diseases

Macula densa cells have an important role in the regulation of glomerular blood flow and glomerular filtration by its regulation of afferent arteriolar vascular tone. Nitric oxide derived from neuronal nitric oxide synthase (nNOS) in macula densa can dilate afferent arterioles. Macula densa nNOS is important for renin secretion, and its expression is regulated by dietary salt, renal angiotensin II, intracellular pH, and other factors. In salt-sensitive hypertension, nNOS is suppressed, whereas in SHR or in the early phase of diabetes, nNOS is increased in macula densa along with NADPH oxidase, which limits NO bioavailability. Renal damage induced by hypertension, diabetes, and hyperlipidemia could be prevented by enhancement of nNOS in macula densa with ACEI, dipyridamole, alpha(1)-receptor blocker, a low-salt diet, or sodium bicarbonate. Sodium bicarbonate is a safe and clinically available enhancer of nNOS in macula densa that increases glomerular blood flow and prevents the reduction of GFR in radiocontrast nephropathy and chronic renal failure. In conclusion, the enhancement of nNOS in the macula densa can be a promising strategy to prevent reduction of renal function.

Leukocyte recruitment and vascular injury in diabetic nephropathy

Different types of activated leukocytes play a crucial role in the pathogenesis of most kidney diseases from acute to chronic stages; however, diabetic nephropathy was not considered an inflammatory disease in the past. This view is changing now because there is a growing body of evidence implicating inflammatory cells at every stage of diabetic nephropathy. Renal tissue macrophages, T cells, and neutrophils produce various reactive oxygen species, proinflammatory cytokines, metalloproteinases, and growth factors, which modulate the local response and increase inflammation within the diabetic kidney. Although the precise mechanisms that direct leukocyte homing into renal tissues are not fully identified, it has been reported that intercellular adhesion molecule-1 and the chemokines CCL2 and CX3CL1 probably are involved in leukocyte migration in diabetic nephropathy. This review focuses on the molecular mechanisms of leukocyte recruitment into the diabetic kidney and the involvement of immigrated immune cells in the damage to renal tissues.

Intercellular adhesion molecule-1 deficiency is protective against nephropathy in type 2 diabetic db/db mice

Diabetic nephropathy is a leading cause of end-stage renal failure and is a growing concern given the increasing incidence of type 2 diabetes. Diabetic nephropathy is associated with progressive kidney macrophage accumulation and experimental studies suggest that intercellular adhesion molecule (ICAM)-1 facilitates kidney macrophage recruitment during type 1 diabetes. To ascertain the importance of ICAM-1 in promoting type 2 diabetic nephropathy, the development of renal injury in ICAM-1 intact and deficient db/db mice with equivalent hyperglycemia and obesity between ages 2 and 8 mo was examined and compared with results with normal db/+ mice. Increases in albuminuria (11-fold), glomerular leukocytes (10-fold), and interstitial leukocytes (three-fold) consisting of predominantly CD68+ macrophages were identified at 8 mo in diabetic db/db mice compared with nondiabetic db/+ mice. In comparison to db/db mice, ICAM-1-deficient db/db mice had marked reductions in albuminuria at 6 mo (77% downward arrow) and 8 mo (85% downward arrow). There was also a significant decrease in glomerular (63% downward arrow) and interstitial (83% downward arrow) leukocytes in ICAM-1-deficient db/db mice, which were associated with reduced glomerular hypertrophy and hypercellularity and tubular damage. The development of renal fibrosis (expression of TGF-beta1, collagen IV, and interstitial alpha-smooth muscle actin) was also strikingly attenuated in the ICAM-1-deficient db/db mice. Additional in vitro studies showed that macrophage activation by high glucose or advanced glycation end products could promote ICAM-1 expression on tubular cells and macrophage production of active TGF-beta1. Thus, ICAM-1 appears to be a critical promoter of nephropathy in mouse type 2 diabetes by facilitating kidney macrophage recruitment.