Gliclazide improves anti-oxidant status and nitric oxide-mediated vasodilation in Type 2 diabetes

Current Position of Gliclazide and Sulfonylureas in the Contemporary Treatment Paradigm for Type 2 Diabetes: A Scoping Review

The increasing burden of type 2 diabetes (T2D), in relation to alarming rise in the prevalence; challenges in the diagnosis, prevention, and treatment; as well as the substantial impact of disease on longevity and quality of life, is a major concern in healthcare worldwide. Sulfonylureas (SUs) have been a cornerstone of T2D pharmacotherapy for over 60 years as oral antidiabetic drugs (OADs), while the newer generation SUs, such as gliclazide modified release (MR), are known to be associated with low risk of hypoglycemia in addition to the cardiovascular neutrality. This scoping review aimed to specifically address the current position of gliclazide MR among other SUs in the contemporary treatment paradigm for T2D and to provide a practical guidance document to assist clinicians in using gliclazide MR in real-life clinical practice. The main topics addressed in this paper include the role of early and sustained glycemic control and use of SUs in T2D management, the properties of gliclazide MR in relation to its effectiveness and safety, the use of gliclazide therapy in special populations, and the place of SUs as a class and gliclazide MR specifically in the current T2D treatment algorithm.

Hepatoprotective potential of alpha-lipoic acid against gliclazide-induced liver injury in high-glucose-exposed human liver cells and experimental type 2 diabetic rats

Growing clinical evidence shows that sulfonylurea therapy for patients with type 2 diabetic mellitus (T2DM) contributes to progressive worsening of their liver. The present study presents hepatotoxicity induced by gliclazide, a second-generation sulfonylurea, and alpha-lipoic acid (ALA) as a novel and promising drug for T2DM treatment. Normal human liver cells (HL-7702) were incubated with high-glucose DMEM in the presence or absence of gliclazide and ALA for 72 h, and cell viability and death were measured by flow cytometry. Next, Sprague-Dawley rats were subjected to 12 h of fasting, and fasting blood glucose was measured. The rats were randomized into four groups: HC (healthy control; n = 7), T2DM (diabetic rats without treatment; n = 9), GLC (diabetic rats with 15 mg/kg gliclazide treatment; n = 7) and GLC+ALA (diabetic rats with gliclazide and 60 mg/kg ALA treatment; n = 7). T2DM was induced by a bolus administration of 110 mg/kg nicotinamide and 55 mg/kg streptozotocin intraperitoneally. The experimental protocol lasted for 6 weeks after which the animals were sacrificed and pancreas, liver and blood samples were collected for biochemical, histological and molecular analyses. Compared to healthy control (HC) group, exposure of HL-7702 cells to high glucose induced significant cell death by 19 % (p < 0.001), which was exacerbated with gliclazide treatment by 29 % (p < 0.0001) but markedly reduced by 6 % to near HC value following ALA treatment. In vivo, GLC-treated rats had severe liver damage characterized by increased hepatocellular vacuolation, and significant expression of ED-1, iNOS and caspase-3 as well as markedly high levels of liver enzymes (aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase compared to T2DM rats. Interestingly, ALA administration prevented these pathological changes and protected the diabetic liver to levels comparable to HC rats. ALA showed hepatoprotective effect against gliclazide-induced hepatotoxicity by suppressing inflammation and apoptosis while activating antioxidant pathway in the diabetic liver. Abbreviations: ALA, Alpha-lipoic acid; ALT, Alanine aminotransferase; ALP, Alkaline phosphatase; AMPK, Adenosine monophosphate-activated protein kinase; AST, Aspartate aminotransferase; ATP, Adenosine triphosphate; DMEM, Dulbecco's Modified Eagle Medium; EDTA, ethylenediaminetetraacetic acid; FBG, Fasting blood glucose; FBS, Fetal bovine serum; GLC, Gliclazide; GLUT4, Glucose transporter type 4; GSH, Glutathione; H&E, Hematoxylin/Eosin; HbA1c, Glycosylated haemoglobin A1c; HC, Healthy control; HG, Hyperglycemic group; HOMA-β, Homeostasis model assessment of β-cell function; IL-1β, Interleukin-1β; IL-6, Interleukin-6; iNOS, Inducible nitric oxide synthase; KATP, ATP-dependent potassium channels; MDA, Malondialdehyde; MPTP, Mitochondrial permeability transition pore; NO, Nitric oxide; P/S, Penicillin/streptomycin; PAS, Periodic acid-Schiff; RIA, Radioimmunoassay; ROS, Reactive oxygen species; SOD, Superoxide dismutase; T2DM, Type 2 diabetes mellitus; TBARS, Thiobarbituric acid reactive substances; TNF-α, Tumor necrosis factor-alpha.

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

Sulfonylureas for Treatment of Periodontitis-Diabetes Comorbidity-Related Complications: Killing Two Birds With One Stone

Periodontitis is one of the most prevalent oral inflammatory diseases leading to teeth loss and oral health problems in adults. Periodontitis mainly affects periodontal tissue by affecting the host immune system and bone homeostasis. Moreover, periodontitis is associated with various systemic diseases. Diabetes is a metabolic disease with systemic effects. Both periodontitis and diabetes are common inflammatory diseases, and comorbidity of two diseases is linked to exacerbation of the pathophysiology of both diseases. Since bacterial dysbiosis is mainly responsible for periodontitis, antibiotics are widely used drugs to treat periodontitis in clinics. However, the outcomes of antibiotic treatments in periodontitis are not satisfactory. Therefore, the application of anti-inflammatory drugs in combination with antibiotics could be a treatment option for periodontitis-diabetes comorbidity. Anti-diabetic drugs usually have anti-inflammatory properties and have shown beneficial effects on periodontitis. Sulfonylureas, insulin secretagogues, are the earliest and most widely used oral hypoglycemic drugs used for type-2 diabetes. Studies have found that sulfonylurea drugs can play a certain role in the mitigation of periodontitis and inflammation. This article reviews the effects of sulfonylurea drugs on the mitigation of periodontitis-diabetes comorbidity-related inflammation, bone loss, and vascular growth as well as the involved molecular mechanisms. We discuss the possibility of a new application of sulfonylureas (old drug) to treat periodontitis-diabetes comorbidity.

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.

Combination of Captopril with Gliclazide Decreases Vascular and Renal Complications and Improves Glycemic Control in Rats with Streptozotocin- Induced Diabetes Mellitus

BACKGROUND

The common antihypertensive angiotensin-converting enzyme (ACE) inhibitor captopril was reported to possess anti-oxidant and anti-inflammatory effects in different experimental models. Diabetic vascular complications arise from increased vascular endothelial inflammation and oxidative stress as well as decreased nitric oxide bioavailability in the vessel walls due to poor glycemic control.

OBJECTIVE

This study aimed to evaluate the role of captopril and gliclazide in decreasing diabetes mellitus (DM) vascular complications caused by decreased cellular glucose uptake and impaired endothelial nitric oxide metabolism, as well as examine the effects of the combination on diabetic renal complication and plasma lipid profile.

METHODS

Adult male Wister rats received captopril (25 mg/kg/day) and/or gliclazide (10 mg/kg/- day) by oral gavage daily for one month after induction of DM using streptozotocin (50 mg/kg, i.p., once). Serum glucose and insulin levels, inflammatory mediators like TNF-α, oxidative stress biomarkers like glutathione and nitric oxide, and plasma lipid profile were measured. Besides, histopathological examination of the thoracic aorta and kidney tissues, Western blot assessed the expression of nitric oxide synthase (NOS) subtypes in the thoracic aorta.

RESULTS

Captopril significantly improved vascular architecture and oxidative stress and modulated nitric oxide synthesis via regulation of nitric oxide synthases, as well as decreased inflammation via down-regulating TNF-α, decreased systolic and diastolic blood pressure, and improved serum lipid profile in diabetic rats. Gliclazide increased serum insulin and decreased serum glucose, as well as its anti-oxidant and anti-inflammatory effects.

CONCLUSION

Captopril showed a promising protective effect against DM vascular complications, at least via nitric oxide modulating effect, anti-oxidant effect, and anti-inflammatory activity that appeared in biochemical and histopathological findings, lipid profile, renal function, and architecture improvements. Combining gliclazide with captopril gives an additive effect through enhanced glycemic control and increased anti-oxidant and anti-inflammatory properties above captopril alone.

Empagliflozin attenuates transient cerebral ischemia/reperfusion injury in hyperglycemic rats via repressing oxidative-inflammatory-apoptotic pathway

Hyperglycemia is one of the ischemic neuronal damage triggers that exacerbate the response to oxidative stress, inflammation, and apoptosis induced by cerebral ischemia/reperfusion (I/R) injury. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT 2) inhibitor, was shown to effectively reduce hyperglycemia and glucotoxicity besides improving glycemic control in diabetics. Therefore, the present study was conducted to investigate the neuroprotective effect of empagliflozin against cerebral I/R injury in hyperglycemic rats. Hyperglycemia was induced by streptozotocin (55 mg/kg), and transient cerebral I/R was induced by bilateral common carotid occlusion for 30 min followed by 24-h reperfusion. Either empagliflozin (10 mg/kg; i.p.) or gliclazide (2 mg/kg, p.o.) was administered at 1 and 24 h after reperfusion. Treatment with empagliflozin showed a significant amelioration of behavioral/neurological functions and histopathological changes observed in brain tissues of hyperglycemic rats subjected to cerebral I/R injury. Comparable to gliclazide, empagliflozin decreased cerebral infarct volume along with suppression of cerebral oxidative stress, inflammatory, and apoptotic markers in brain tissues of hyperglycemic I/R-injured rats. These findings suggested that empagliflozin can significantly alleviate neuronal damage resulting from global I/R injury induced in hyperglycemic rats. The proposed neuroprotective effect of empagliflozin may be attributed to its glycemic control effect and related antioxidant, anti-inflammatory, and antiapoptotic effects.

Gliclazide attenuates acetic acid-induced colitis via the modulation of PPARγ, NF-κB and MAPK signaling pathways

Ulcerative Colitis is a universal autoimmune disease with high incidence rates worldwide. It is characterized by the existence of many other concurrent immune-associated ailments, including diabetes. The used strategies for the management of this highly costing and complicated disease face great challenges. Therefore, the urge for new medication with fewer side effects and high efficacy is growing. The peroxisome proliferator-activated receptor-gamma (PPARγ) and nuclear factor Kappa-B (NF-κB) can be considered as crucial targets for the treatment of ulcerative colitis. Several studies reported the antioxidants, anti-inflammatory, and antiapoptotic actions of gliclazide and evaluated its cardioprotective and renoprotective effects. However, its impact on ulcerative colitis has never been investigated. This study delineated the effect of gliclazide administration on ulcerative colitis induced by acetic acid in rats and the underlying molecular mechanisms. Gliclazide (10 mg/kg; p.o) prominently decreased colon tissue injury as assessed by the histopathological analysis as well as myeloperoxidase, and intercellular adhesion molecule-1 levels. Gliclazide significantly alleviated the proinflammatory mediator, IL-6, promoted the anti-inflammatory cytokine, IL-10 and, withheld oxidative stress in the injured colon tissues. The protective effect of gliclazide was mediated through the upregulation of PPARγ and downregulation of NF-κB expression. The diminution of ulcerative colitis was also accompanied by an inhibition of the elevated activity and expression of mitogen-activated protein kinases and caspase-3 as assessed by Western blot and immunohistochemistry, respectively. Our findings spotlight, for the first time, the potential of the antidiabetic agent, gliclazide, to attenuate the experimentally induced ulcerative colitis. Therefore, gliclazide might be a propitious agent for the management of ulcerative colitis in diabetic patients.

Association of Glycemic Indices (Hyperglycemia, Glucose Variability, and Hypoglycemia) with Oxidative Stress and Diabetic Complications

Oxidative stress (OS) is defined as a disturbance in the prooxidant-antioxidant balance of the cell, in favor of the former, which results in the antioxidant capacity of the cell to be overpowered. Excess reactive oxygen species (ROS) production is very harmful to cell constituents, especially proteins, lipids, and DNA, thus causing damage to the cell. Oxidative stress has been associated with a variety of pathologic conditions, including diabetes mellitus (DM), cancer, atherosclerosis, neurodegenerative diseases, rheumatoid arthritis, ischemia/reperfusion injury, obstructive sleep apnea, and accelerated aging. Regarding DM specifically, previous experimental and clinical studies have pointed to the fact that oxidative stress probably plays a major role in the pathogenesis and development of diabetic complications. It is postulated that hyperglycemia induces free radicals and impairs endogenous antioxidant defense systems through several different mechanisms. In particular, hyperglycemia promotes the creation of advanced glycation end-products (AGEs), the activation of protein kinase C (PKC), and the hyperactivity of hexosamine and sorbitol pathways, leading to the development of insulin resistance, impaired insulin secretion, and endothelial dysfunction, by inducing excessive ROS production and OS. Furthermore, glucose variability has been associated with OS as well, and recent evidence suggests that also hypoglycemia may be playing an important role in favoring diabetic vascular complications through OS, inflammation, prothrombotic events, and endothelial dysfunction. The association of these diabetic parameters (i.e., hyperglycemia, glucose variability, and hypoglycemia) with oxidative stress will be reviewed here.

SERS-based vibration model and trace detection of drug molecules: Theoretical and experimental aspects

Prescription drug abuse can lead to serious medical negligence, so there is an urgent need to address its screening problem. Gliclazide is widely used as an antihypertensive drug for lowering blood sugar, but its excessive intake can cause serious harm to human body. Here we take gliclazide as an example to provide a method to realize the screening of drug abuse. Flower-like silver nanoparticles were prepared as surface enhanced Raman scattering (SERS) substrate, which can quantitatively and accurately detect the concentration of gliclazide. To understanding the enhanced activity of flower-like silver substrates, the Finite-Difference Time-Domain (FDTD) simulation model was established, and the simulation results showed that flower-like silver had high SERS substrate activity as well as enhanced hot spots at the rough particle surface and the adjacent particles. The experimental results indicated that the flower-shaped silver had an excellent Raman enhancement effect using R6G as detection molecules. When the gliclazide solutions with different concentration gradients were tested, the molecular vibrational modes were also obtained using Gaussian calculations. The rapid and accurate detection of gliclazide concentration was processed by Principal Component Analysis, which were consistent with the experiment, suggesting the importance of the combination of experiment and calculation. Finally, SERS substrate test was performed on the daily medication gliclazide tablets (II), which proved that the flower-like silver still has great Raman enhancement effect on the detection of actual samples.

Antioxidant properties of drugs used in Type 2 diabetes management: could they contribute to, confound or conceal effects of antioxidant therapy?

OBJECTIVES

This is a narrative review, investigating the antioxidant properties of drugs used in the management of diabetes, and discusses whether these antioxidant effects contribute to, confound, or conceal the effects of antioxidant therapy.

METHODS

A systematic search for articles reporting trials, or observational studies on the antioxidant effect of drugs used in the treatment of diabetes in humans or animals was performed using Web of Science, PubMed, and Ovid. Data were extracted, including data on a number of subjects, type of treatment (and duration) received, and primary and secondary outcomes. The primary outcomes were reporting on changes in biomarkers of antioxidants concentrations and secondary outcomes were reporting on changes in biomarkers of oxidative stress.

RESULTS

Diabetes Mellitus is a disease characterized by increased oxidative stress. It is often accompanied by a spectrum of other metabolic disturbances, including elevated plasma lipids, elevated uric acid, hypertension, endothelial dysfunction, and central obesity. This review shows evidence that some of the drugs in diabetes management have both in vivo and in vitro antioxidant properties through mechanisms such as scavenging free radicals and upregulating antioxidant gene expression.

CONCLUSION

Pharmaceutical agents used in the treatment of type 2 diabetes has been shown to exert an antioxidant effect..

Population pharmacokinetics of gliclazide in normal and diabetic rabbits

Gliclazide is a second-generation sulphonylurea drug widely used in the treatment of type 2 diabetes. However, there is no single report to describe the population pharmacokinetics of gliclazide in animal models. This study was aimed to evaluate the population pharmacokinetics (PK) of gliclazide in normal and alloxan-induced diabetic rabbits using nonlinear mixed effects modeling. A total of 90 New Zealand white rabbits were administered with three doses (4.13, 8.27 and 16.53 mg/kg b.wt) of gliclazide by an oral route. Blood samples were collected up to 24 hr and the gliclazide concentrations in rabbit were determined using the HPLC method. The non-compartmental and classical compartmental PK analyses were performed using Phoenix WinNonlin. Population PK analysis of gliclazide was performed using nonlinear mixed-effects model software NONMEM and Phoenix NLME considering the weight, age, sex, health and dose as covariates. The final population values for clearance (CL), volume of distribution (V) and the absorption rate constant (k_a ) were 5270 ml/hr, 55700 ml and 0.708 hr^-1 , respectively. The inter-individual variability in gliclazide CL, V and k_a was 16.3%, 14.9% and 26.5%, respectively. There was no significant difference between NONMEM and Phoenix NLME pharmacokinetic results. The visual predictive check and bootstrap analysis confirmed the predictive ability, model stability and precision of the parameter estimates from this model. This population PK model demonstrated that gliclazide pharmacokinetics is best described by one-compartment model with first-order absorption in rabbits. Body weight is a covariate that significantly influences gliclazide kinetic disposition in rabbits.

The place of gliclazide MR in the evolving type 2 diabetes landscape: A comparison with other sulfonylureas and newer oral antihyperglycemic agents

The sulfonylureas are effective oral glucose-lowering agents with a long history of clinical use. While all have the same general mechanism of action, their pharmacokinetic properties are influenced by factors such as dosage, rate of absorption, duration of action, route of elimination, tissue specificity, and binding affinity for pancreatic β-cell receptor. The result is a class of agents with similar HbA1c-lowering efficacy, but well-documented differences in terms of effects on hypoglycemia, and cardiovascular and renal safety. This review examines the differences between currently available sulfonylureas with a focus on how gliclazide modified release (MR) differs from other members of this class and from newer oral antihyperglycemic agents in the form of dipeptidyl peptidase-4 (DPP4) and sodium- glucose cotransporter 2 (SGLT2) inhibitors. The first part focuses on major outcome trials that have been conducted with the sulfonylureas and new oral agents. Consideration is then given to factors important for day-to-day prescribing including efficacy and durability, weight changes, hypoglycemia, renal effects and cost. Based on current evidence, third-generation sulfonylureas such as gliclazide MR possess many of the properties desired of a type 2 diabetes drug including high glucose-lowering efficacy, once-daily oral administration, few side effects other than mild hypoglycemia, and cardiovascular safety.

Influence of aprepitant on the pharmacodynamics and pharmacokinetics of gliclazide in rats and rabbits

Background

Concomitant drug administration is a general phenomenon in patients with chronic diseases such as diabetes mellitus. Among the currently available oral antidiabetic drugs, gliclazide is a commonly prescribed drug considering its multiple benefits in diabetic patients. Aprepitant is a commonly prescribed antiemetic drug which is mainly metabolized by CYP3A4, reported to have modest inductive and inhibitory effects on CYP2C9 and CYP3A4, respectively. Since gliclazide is metabolized by CYP2C9 (major) and CYP3A4 (minor), it is very difficult to predict the influence of aprepitant and its metabolic interaction with gliclazide. Considering the complexity associated with the combination of aprepitant and gliclazide, this study was designed to evaluate the influence of aprepitant on the pharmacodynamics (PD) and pharmacokinetics (PK) of gliclazide in animal models.

Methods

The PD interaction studies were conducted in both rodent (normal and alloxan-induced diabetic rats) and non-rodent (rabbits) animal models (n = 6) while the PK interaction study was conducted in normal rabbits (n = 6). An extrapolated human therapeutic oral dose of gliclazide, aprepitant and their combination were administered to rats and rabbits with 7 days washout between each treatment. For the multiple-dose interaction study, the same groups were administered with an interacting drug (aprepitant) for 7 days and then the combination of aprepitant and gliclazide on the 8th day. From the collected animal blood samples, blood glucose (by Glucose-Oxidase/Peroxidase method), insulin (by ELISA method) and gliclazide concentration levels (by HPLC method) were determined. Non-compartmental PK analysis was conducted by Phoenix WinNonlin software to determine the PK parameters of gliclazide. Statistical analysis was performed by student’s paired t-test.

Results

The pharmacodynamic activity (blood glucose reduction and insulin levels) of gliclazide was significantly (p < 0.05) influenced by aprepitant in normal and diabetic condition without any convulsions in animals. There was a significant (p < 0.05) increase in concentration levels and Area Under the Curve of gliclazide while significant (p < 0.05) decrease in clearance levels of gliclazide in rabbits. The PK interaction with gliclazide is relatively more with the multiple dose treatment of aprepitant over single dose treatment.

Conclusion

In combination, aprepitant significantly influenced the pharmacodynamic activity of gliclazide in animal models. Considering this, care should be taken when this combination is prescribed for the clinical benefit in diabetic patients.

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.

Review: Insulin secretion: function and therapy of pancreatic beta-cells in diabetes

nsulin is secreted from the beta-cells of the pancreatic islets in response to an elevation of blood glucose concentration. This review describes a current view of the metabolic control of insulin secretion and the molecular mechanisms involved, including the role played by the beta-cell to ensure correct release of insulin as a result of electrical signals. It then considers what goes wrong in type 2 diabetes, a disease resulting from insufficient insulin secretion. It focuses on the influence of genetics exploring the theory of a genetic predisposition to type 2 diabetes, as well as the roles played by age and obesity. Finally, the mode of action of the hypoglycaemic sulphonylureas is discussed and the potential implications for the beta-cell associated with a sulphonylurea-based therapy.

Altered activities of kininase II, an angiotensin converting enzyme, prekallikrein, and nitric oxide in Kuwaiti patients with type 2 diabetes

The current investigation was conducted to examine kininase II or angiotensin converting enzyme (ACE), plasma prekallikrein (PK), and nitric oxide (NO) concentrations in healthy Kuwaiti subjects and newly diagnosed Kuwaiti type 2 diabetic patients before and after treatment for 6 weeks with metformin hydrochloride 500 mg twice daily after meal. With the consent of volunteers, blood and urine samples were collected after an overnight fasting. Samples were collected from the diabetic patients before and after treatment for 6 weeks. Enzyme linked immunosorbent assay (ELISA) was carried out on the aliquoted samples to measure the concentration of kininase II. NO was detected via colorimetry. Plasma Kininase II or ACE levels were significantly ( P <0.01) increased by 18% in untreated diabetics when compared with healthy volunteers. However, after treatment there was a significant decrease of 20% in their ACE levels. Plasma prekallikrein levels were raised significantly ( P <0.01) by 28% in diabetic patients in contrast with the control subjects and the levels were significantly reduced ( P <0.0001) by 44% after treatment with metformin hydrochloride. NO levels were found to be significantly decreased in plasma by 56% and in urine by 62% in untreated diabetic patients as compared with the healthy subjects. However, when the treated diabetic patients were compared with untreated diabetics, there was an increase of 50% in plasma and 37% in urine samples. The high levels of kininase II, prekallikrein, and reduced NO may be partly responsible for the induction of renal, cardiac, and hypertensive complications associated with type 2 diabetes. Reduced NO level is an indication of endothelial dysfunction resulting in increased blood pressure. Oral anti-diabetic treatment is associated with protective effects through the reduction of kininase II (ACE), prekallikrein, and elevation of NO levels.

Postprandial Dysmetabolism and Oxidative Stress in Type 2 Diabetes: Pathogenetic Mechanisms and Therapeutic Strategies

Postprandial dysmetabolism in type 2 diabetes (T2D) is known to impact the progression and evolution of this complex disease process. However, the underlying pathogenetic mechanisms still require full elucidation to provide guidance for disease prevention and treatment. This review focuses on the marked redox changes and inflammatory stimuli provoked by the spike in blood glucose and lipids in T2D individuals after meals. All the causes of exacerbated postprandial oxidative stress in T2D were analyzed, also considering the consequence of enhanced inflammation on vascular damage. Based on this in-depth analysis, current strategies of prevention and pharmacologic management of T2D were critically reexamined with particular emphasis on their potential redox-related rationale.

Effects of sulfonylureas on tumor growth: a review of the literature

Type 2 diabetes mellitus patients are at higher cancer risk, probably because of hyperinsulinemia and insulin growth factor 1 pathway activation. The effects of antidiabetic drugs on cancer risk have been described and discussed in several studies suggesting opposite effects of the biguanide metformin and sulfonylureas on cancer incidence and mortality. The anticancer mechanisms of metformin have been clarified, and some clinical studies, particularly in breast cancer patients, have been published or are currently ongoing; however, data about the effects of sulfonylureas on cancer growth are less consistent. The aims of this work are to review preclinical evidence of second-generation sulfonylureas effects on tumor growth, to clarify the potential mechanisms of action, and to identify possible metabolic targets for patient selection. Most evidence is on the adenosine triphosphate-sensitive potassium channels inhibitor glibenclamide, which interacts with reactive oxygen species production thus inducing cancer cell death. Among diarylsulfonylureas, next-generation DW2282 derivatives are particularly promising because of the proapoptotic activity in multidrug-resistant cells.

Deoxycholic Acid as a Modifier of the Permeation of Gliclazide through the Blood Brain Barrier of a Rat

Major problem for diabetic patients represents damage of blood vessels and the oxidative stress of the brain cells due to increased concentration of free radicals and poor nutrition of brain cells. Gliclazide has antioxidative properties and poor blood brain barrier (BBB) penetration. Bile acids are known for their hypoglycemic effect and as promoters of drug penetration across biological membranes. Accordingly, the aim of this study is to investigate whether the bile acid (deoxycholic acid) can change the permeation of gliclazide, through the blood brain barrier of a rat model type-1 diabetes. Twenty-four male Wistar rats were randomly allocated to four groups, of which, two were given alloxan intraperitoneally (100 mg/kg) to induce diabetes. One diabetic group and one healthy group were given a bolus gliclazide intra-arterially (20 mg/kg), while the other two groups apart from gliclazide got deoxycholic acid (4 mg/kg) subcutaneously. Blood samples were collected 30, 60, 150, and 240 seconds after dose, brain tissues were immediately excised and blood glucose and gliclazide concentrations were measured. Penetration of gliclazide in groups without deoxycholic acid pretreatment was increased in diabetic animals compared to healthy animals. Also in both, the healthy and diabetic animals, deoxycholic acid increased the permeation of gliclazide through that in BBB.

Honey--a novel antidiabetic agent

Diabetes mellitus remains a burden worldwide in spite of the availability of numerous antidiabetic drugs. Honey is a natural substance produced by bees from nectar. Several evidence-based health benefits have been ascribed to honey in the recent years. In this review article, we highlight findings which demonstrate the beneficial or potential effects of honey in the gastrointestinal tract (GIT), on the gut microbiota, in the liver, in the pancreas and how these effects could improve glycemic control and metabolic derangements. In healthy subjects or patients with impaired glucose tolerance or diabetes mellitus, various studies revealed that honey reduced blood glucose or was more tolerable than most common sugars or sweeteners. Pre-clinical studies provided more convincing evidence in support of honey as a potential antidiabetic agent than clinical studies did. The not-too-impressive clinical data could mainly be attributed to poor study designs or due to the fact that the clinical studies were preliminary. Based on the key constituents of honey, the possible mechanisms of action of antidiabetic effect of honey are proposed. The paper also highlights the potential impacts and future perspectives on the use of honey as an antidiabetic agent. It makes recommendations for further clinical studies on the potential antidiabetic effect of honey. This review provides insight on the potential use of honey, especially as a complementary agent, in the management of diabetes mellitus. Hence, it is very important to have well-designed, randomized controlled clinical trials that investigate the reproducibility (or otherwise) of these experimental data in diabetic human subjects.

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.

Gliclazide may have an antiapoptotic effect related to its antioxidant properties in human normal and cancer cells

Experimental and clinical studies suggest that gliclazide may protect pancreatic β-cells from apoptosis induced by an oxidative stress. However, the precise mechanism(s) of this action are not fully understood and requires further clarification. Therefore, using human normal and cancer cells we examined whether the anti-apoptotic effects of this sulfonylurea is due to its free radical scavenger properties. Hydrogen peroxide (H₂O₂) as a model trigger of oxidative stress was used to induce cell death. Our experiments were performed on human normal cell line (human umbilical vein endothelial cell line, HUVEC-c) and human cancer cell lines (human mammary gland cell line, Hs578T; human pancreatic duct epithelioid carcinoma cell line, PANC-1). To assess the effect of gliclazide the cells were pre-treated with the drug. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay was employed to measure the impact of gliclazide on cell viability. Generation of reactive oxygen species, mitochondrial membrane potential (∆Ψ_m), and intracellular Ca²⁺ concentration [Ca²⁺] were monitored. Furthermore, the morphological changes associated with apoptosis were determined using double staining with Hoechst 33258-propidium iodide (PI). Gliclazide protects the tested cells from H₂O₂-induced cell death most likely throughout the inhibition of ROS production. Moreover, the drug restored loss of ΔΨ_m and diminished intracellular [Ca²⁺] evoked by H₂O₂. Double staining with Hoechst 33258-PI revealed that pre-treatment with gliclazide diminished the number of apoptotic cells. Our findings indicate that gliclazide may protect both normal and cancer human cells against apoptosis induced by H₂O₂. It appears that the anti-apoptotic effect of the drug is most likely associated with reduction of oxidative stress.

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.

Microvascular reactivity in type 1 diabetics

OBJECTIVE

To evaluate whether differences are present in microvascular response to the schemia induced by dynamic videocapillaroscopy (VCD), through analysis of the measured capillar transverse segment area (CTSA) in patients with type 1 diabetes mellitus (T1DM).

METHODS

The vascular reactivity of the CTSA was studied by VCD, using a reactive hyperemia test in 61 volunteers, being 31 healthy controls without diabetes family history (Group 1) and 30 patients with T1DM without complications (Group 2). The images were captured every two seconds, during reperfusion after one minute induced ischaemia, and they were analyzed by the program Studio Version 8 and Motic Image Plus. The pre-ischemia capillary transverse segment (basal area, BA), the maximum strain post-ischemia (maximum area, MA), and time to achieve it (MAt) were measured during reperfusion, and the increased area percentage (Ap) was estimated.

RESULTS

The mean differences between groups were evaluated by the t-test. The median comparisons between the groups were studied by the Mann-Whitney test. There was no difference in BA between the groups. The Ap was significantly lower among the diabetic patients, and there was a significant increase in the Mat among the patients of Group 2 when compared to Group 1.

CONCLUSIONS

These data suggest that type 1 diabetes provokes earlier endothelial dysfunction, before the onset of clinically detectable degenerative complications. The outcomes from these alterations need further studies.

Cellular glucose transport and glucotransporter 4 expression as a therapeutic target: clinical and experimental studies

INTRODUCTION

The normalization of cellular glucose assimilation is the basic aim of metabolic therapy in type 2 diabetes mellitus (T2DM). It requires parallel changes in the process of cellular glucose transport (CGT). Therefore the level of CGT could be regarded as a therapeutic target for oral hypoglycemic drugs in T2DM. To explore this hypothesis, CGT levels before and after sulfonylurea therapy were investigated. Peripheral blood lymphocytes were used as a cell model for testing CGT.

MATERIALS AND METHODS

CGT was assessed by experimental in vitro tests allowing timed comparative observation of the transport process during the incubation of lymphocytes with 2-[(3)H(G)] glucose under basal conditions and after the addition of sulfonylurea or sulfonylurea plus insulin. The incubation tests were performed at baseline in 28 persons with newly diagnosed, therapy-naive T2DM and in 20 control subjects. In the diabetic patients the tests for CGT were repeated after 3 months of sulfonylurea therapy. The level of glucotransporter 4 (GLUT4) expression was also assessed by flow cytometry before and after the therapy.

RESULTS

Before treatment, CGT was significantly lower in the subjects with T2DM. The cells responded to the addition of sulfonylurea by a moderate increase in CGT. This response was augmented by the addition of insulin to sulfonylurea in the culture medium.

CONCLUSIONS

The three-month therapy with sulfonylurea resulted in a significant increase in CGT in all types of culture tests. This sulfonylurea-related improvement in CGT was associated with a near normalization of GLUT4 expression in the cells.

High glucose-induced oxidative stress alters estrogen effects on ERalpha and ERbeta in human endothelial cells: reversal by AMPK activator

Estrogen appears to protect against cardiovascular disease in pre-menopausal women. However, these protective effects are absent in women with diabetes. The hyperglycemia and consequent oxidative stress observed in diabetes cause endothelial dysfunction, but specific effects on endothelial estrogen responses are not known. In this study, we hypothesized that high glucose conditions would alter the regulation of the estrogen receptors (ERs), ERalpha and ERbeta, in endothelial cells, possibly through increased oxidative stress. The role of the AMPK activator AICAR was examined on modulating the effects of high glucose. Cultured human endothelial cells were exposed to physiologically relevant doses of 17-beta-estradiol (E2) for 24h in presence of normal (5.5mM) and high (30.5mM) levels of glucose. Protein levels of estrogen receptors, ERalpha and ERbeta, were measured through western blotting. Oxidative stress was measured by the dihydroethidium (DHE) assay for superoxide. Under normal glucose, E2 increased the levels of ERalpha relative ERbeta; however, high glucose reversed the estrogen effects on endothelial ER expression. AMPK activation restored the physiological estrogen responses, likely through amelioration of oxidative stress. Control of oxidative stress by AMPK activation or anti-oxidants could restore normal estrogen responses even in presence of hyperglycemia.

Influence of non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine) on the pharmacodynamic activity of gliclazide in animal models

BACKGROUND

Type 2 diabetes may occur as a result of HIV infection and/or its treatment. Gliclazide is a widely used drug for the treatment of type 2 diabetes. Efavirenz and nevirapine are widely used non-nucleoside reverse transcriptase inhibitors for the treatment of HIV infection. The role of Efavirenz and nevirapine on the pharmacodynamic activity of gliclazide is not currently known. The objective of this study was to examine the effect of oral administration of efavirenz and nevirapine on blood glucose and investigate their effect on the activity of gliclazide in rats (normal and diabetic) and rabbits to evaluate the safety and effectiveness of the combination.

METHODS

Studies in normal and alloxan induced diabetic rats were conducted with oral doses of 2 mg/kg bd. wt. of gliclazide, 54 mg/kg bd. wt. of efavirenz or 18 mg/kg bd. wt. of nevirapine and their combination with adequate washout periods in between treatments. Studies in normal rabbits were conducted with 5.6 mg/1.5 kg bd. wt. of gliclazide, 42 mg/1.5 kg bd. wt. of efavirenz or 14 mg/1.5 kg bd. wt. of nevirapine and their combination given orally. Blood samples were collected at regular time intervals in rats from retro orbital puncture and by marginal ear vein puncture in rabbits. All the blood samples were analysed for blood glucose by GOD/POD method.

RESULTS

Efavirenz and nevirapine alone have no significant effect on the blood glucose level in rats and rabbits. Gliclazide produced hypoglycaemic/antidiabetic activity in normal and diabetic rats with peak activity at 2 h and 8 h and hypoglycaemic activity in normal rabbits at 3 h. In combination, efavirenz reduced the effect of gliclazide in rats and rabbits, and the reduction was more significant with the single dose administration of efavirenz than multiple dose administration. In combination, nevirapine has no effect on the activity of gliclazide in rats and rabbits.

CONCLUSION

Thus, it can be concluded that the combination of efavirenz and gliclazide may need dose adjustment and care should be taken when the combination is prescribed for their clinical benefit in diabetic patients. The combination of nevirapine and gliclazide was safe. However, further studies are warranted.

Suppression of KATP channel activity protects murine pancreatic beta cells against oxidative stress

The enhanced oxidative stress associated with type 2 diabetes mellitus contributes to disease pathogenesis. We previously identified plasma membrane-associated ATP-sensitive K+ (KATP) channels of pancreatic beta cells as targets for oxidants. Here, we examined the effects of genetic and pharmacologic ablation of KATP channels on loss of mouse beta cell function and viability following oxidative stress. Using mice lacking the sulfonylurea receptor type 1 (Sur1) subunit of KATP channels, we found that, compared with insulin secretion by WT islets, insulin secretion by Sur1-/- islets was less susceptible to oxidative stress induced by the oxidant H2O2. This was likely, at least in part, a result of the reduced ability of H2O2 to hyperpolarize plasma membrane potential and reduce cytosolic free Ca2+ concentration ([Ca2+]c) in the Sur1-/- beta cells. Remarkably, Sur1-/- beta cells were less prone to apoptosis induced by H2O2 or an NO donor than WT beta cells, despite an enhanced basal rate of apoptosis. This protective effect was attributed to upregulation of the antioxidant enzymes SOD, glutathione peroxidase, and catalase. Upregulation of antioxidant enzymes and reduced sensitivity of Sur1-/- cells to H2O2-induced apoptosis were mimicked by treatment with the sulfonylureas tolbutamide and gliclazide. Enzyme upregulation and protection against oxidant-induced apoptosis were abrogated by agents lowering [Ca2+]c. Sur1-/- mice were less susceptible than WT mice to streptozotocin-induced beta cell destruction and subsequent hyperglycemia and death, which suggests that loss of KATP channel activity may protect against streptozotocin-induced diabetes in vivo.

Intensive blood glucose control and vascular outcomes in patients with type 2 diabetes

BACKGROUND

In patients with type 2 diabetes, the effects of intensive glucose control on vascular outcomes remain uncertain.

METHODS

We randomly assigned 11,140 patients with type 2 diabetes to undergo either standard glucose control or intensive glucose control, defined as the use of gliclazide (modified release) plus other drugs as required to achieve a glycated hemoglobin value of 6.5% or less. Primary end points were composites of major macrovascular events (death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke) and major microvascular events (new or worsening nephropathy or retinopathy), assessed both jointly and separately.

RESULTS

After a median of 5 years of follow-up, the mean glycated hemoglobin level was lower in the intensive-control group (6.5%) than in the standard-control group (7.3%). Intensive control reduced the incidence of combined major macrovascular and microvascular events (18.1%, vs. 20.0% with standard control; hazard ratio, 0.90; 95% confidence interval [CI], 0.82 to 0.98; P=0.01), as well as that of major microvascular events (9.4% vs. 10.9%; hazard ratio, 0.86; 95% CI, 0.77 to 0.97; P=0.01), primarily because of a reduction in the incidence of nephropathy (4.1% vs. 5.2%; hazard ratio, 0.79; 95% CI, 0.66 to 0.93; P=0.006), with no significant effect on retinopathy (P=0.50). There were no significant effects of the type of glucose control on major macrovascular events (hazard ratio with intensive control, 0.94; 95% CI, 0.84 to 1.06; P=0.32), death from cardiovascular causes (hazard ratio with intensive control, 0.88; 95% CI, 0.74 to 1.04; P=0.12), or death from any cause (hazard ratio with intensive control, 0.93; 95% CI, 0.83 to 1.06; P=0.28). Severe hypoglycemia, although uncommon, was more common in the intensive-control group (2.7%, vs. 1.5% in the standard-control group; hazard ratio, 1.86; 95% CI, 1.42 to 2.40; P<0.001).

CONCLUSIONS

A strategy of intensive glucose control, involving gliclazide (modified release) and other drugs as required, that lowered the glycated hemoglobin value to 6.5% yielded a 10% relative reduction in the combined outcome of major macrovascular and microvascular events, primarily as a consequence of a 21% relative reduction in nephropathy. (ClinicalTrials.gov number, NCT00145925.)

Evaluation of gliclazide ability to attenuate the hyperglycaemic 'memory' induced by high glucose in isolated human endothelial cells

BACKGROUND

Patients with long-term exposure to high levels of hyperglycaemia remain more susceptible to diabetes-related complications, even with subsequent lower levels of hyperglycaemia. We sought to confirm the hypothesis that exposure to continuous increased glucose results in a memory of cellular stress in isolated endothelial cells, even when switched back to normal glucose, and to investigate the ability of gliclazide to attenuate this phenomenon.

METHODS

Human umbilical vein endothelial cells were incubated for 21 days in normal glucose (5 mmol/L), high glucose (30 mmol/L), or high glucose for 14 days followed by normal glucose for 7 days (memory condition). The effects of gliclazide (10 micromol/L) and glibenclamide (1 micromol/L) were evaluated in the memory condition and added to the culture media early (first 14 days), late (last 7 days), or throughout the study. Oxidative stress and cell apoptosis parameters were investigated.

RESULTS

Continuous high glucose increased reactive oxygen species, 8-OHdG, nitrotyrosine, caspase-3, and reduced Bcl-2 expression. These deleterious effects were also observed in the memory condition. Gliclazide applied early or throughout the study improved all parameters. In contrast, glibenclamide showed no relevant effect on study parameters.

CONCLUSIONS

Our results suggest that gliclazide prevents endothelial cell apoptosis by reducing oxidative stress. The results appear to confirm the hypothesis that exposure of cells to continuous increased glucose results in a hyperglycaemic cellular memory that remains, even when cells are switched back to normal glucose. Gliclazide attenuated this cellular memory, decreasing oxidative stress and protecting vascular endothelial cells from apoptosis.

Aerobic exercise training improves the role of high-density lipoprotein antioxidant and reduces plasma lipid peroxidation in type 2 diabetes mellitus

In this study, we analyzed the effect of aerobic exercise training (AET) and of a single bout of exercise on plasma oxidative stress and on antioxidant defenses in type 2 diabetes mellitus (DM) and in healthy control subjects (C). DM and C did not differ regarding triglycerides, high-density lipoprotein cholesterol (HDL-c), insulin, and HOMA index at baseline and after AET. To measure the lag time for low-density lipoprotein (LDL) oxidation (LAG) and the maximal rate of conjugated diene formation (MCD), participants' plasma HDL(2) and HDL(3) were incubated with LDL from pooled healthy donors' plasma. In the presence of HDL(3), both LAG and MCD were similar in C and DM, but only in DM did AET improve LAG and reduce MCD. In the presence of HDL(2), the lower baseline LAG in DM equaled C after AET. MCD was unchanged in DM after AET, but was lower than C only after AET. Furthermore, after AET plasma thiobarbituric acid-reactive substances were reduced only in DM subjects. Despite not modifying the total plasma antioxidant status and serum paraoxonase-1 activity in both groups, AET lowered the plasma lipid peroxides, corrected the HDL(2), and improved the HDL(3) antioxidant efficiency in DM independent of the changes in blood glucose, insulin, and plasma HDL concentration and composition.

A BRIEF COMMUNICATION

Gliclazide, a sulfonylurea widely used for treatment of diabetes mellitus, is known to scavenge reactive oxygen species. To clarify whether its antioxidative ability interferes with the glycation processes, we incubated bovine serum albumin (BSA) with 1 M glucose or 1 m M methylglyoxal, in the presence or absence of gliclazide, and observed the formation of advanced glycation end products (AGEs). AGE production was assessed by AGE-specific fluorescence, an enzyme-linked immunosorbent assay (ELISA), and Western blotting. The fluorescence at excitation/emission wavelengths of 320/383 nm and 335/385 nm was definitely increased by incubating BSA with 1 M glucose or 1 m M methylglyoxal, and 1 m M gliclazide significantly blunted the fluorescent augmentation, in both wavelengths, in a dose-dependent fashion. Gliclazide almost equaled to aminoguanidine, a putative antiglycation agent, in the inhibitory effect on the glucose-induced fluorescence, while the methylglyoxal-derived fluorescent formation was less suppressed by gliclazide than by aminoguanidine. The AGE concentrations determined by ELISA showed similar results. Incubation of BSA with 1 M glucose or 1 m M methylglyoxal yielded an apparent increase in carboxymethyllysine or argpyrimidine. Both AGEs were significantly lowered by 1 m M gliclazide and a reduction of glucose-derived carboxymethyllysine was comparable to that caused by aminoguanidine. The results of Western blotting supported the findings in ELISA. To our knowledge, the present study provides the first evidence of the antiglycation effect of gliclazide on in vitro AGE formation from glucose and methylglyoxal.

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.

Gliclazide protects human islet beta-cells from apoptosis induced by intermittent high glucose

BACKGROUND

Decreased beta-cell mass, mainly due to apoptosis, is crucial for the development and progression of type 2 diabetes. Chronic exposure to high glucose levels is a probable underlying mechanism, whereas the role of oral anti-diabetic agents (sulphonylureas in particular) is still unsettled.

METHODS

To directly investigate more on such issues, we prepared isolated human islets, which were then cultured for 5 days in continuous normal glucose concentration (NG, 5.5 mmol/L) or normal and high (HG, 16.7 mmol/L) glucose levels (alternating every 24 h), with or without the addition of therapeutical concentration (10 micromol L) of gliclazide or glibenclamide.

RESULTS

Intermittent high glucose caused a significant decrease of glucose-stimulated insulin secretion, which was not further affected by either sulphonylurea. Apoptosis, as assessed by electron microscopy, was also significantly increased by alternating high glucose exposure, which was accompanied by altered mitochondria morphology and density volume, and increased concentrations of nitrotyrosine, a marker of oxidative stress. Gliclazide, but not glibenclamide, was able to significantly reduce high glucose induced apoptosis, mitochondrial alterations, and nitrotyrosine concentration increase.

CONCLUSION

Therefore, gliclazide protected human beta-cells from apoptosis induced by intermittent high glucose, and this effect was likely to be due, at least in part, to the anti-oxidant properties of the molecule.

Effect of gliclazide modified release on adiponectin, interleukin-6, and tumor necrosis factor-alpha plasma levels in individuals with type 2 diabetes mellitus

OBJECTIVE

The aim of the study was to evaluate the effect of gliclazide modified release (MR) treatment on adiponectin, interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) plasma concentrations in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

24 randomly selected type 2 diabetic patients, aged 61.2 +/- 15.4 years, with poorly controlled glucose level (mean glycated hemoglobin [HbA1c] 7.6 +/- 1.1%) despite treatment with diet and/or oral hypoglycemic agents, were included in the study. All of the patients, after a 2-week run-in period, were given gliclazide MR for 12 weeks. At baseline, and after gliclazide MR treatment, HbA(1c) and plasma concentrations of IL-6, TNF-alpha, and adiponectin were measured.

RESULTS

Gliclazide MR treatment produced significant reductions in fasting plasma glucose (from 7.6 +/- 1.4 to 6.6 +/- 1.2 mmol/L, p < 0.01), HbA(1c) (from 7.6 +/- 1.1 to 6.9 +/- 0.8%, p < 0.01), and plasma IL-6 concentrations (from 2.5 +/- 1.8 to 1.8 +/- 1.2 pg/mL, p < 0.05). A significant increase in plasma adiponectin level was noted (from 6.4 +/- 3.3 to 7.6 +/- 4.4 mug/mL, p < 0.05). Plasma TNF-alpha concentrations and homeostasis model assessment of insulin resistance (HOMA-IR) decreased after treatment, but these changes did not reach statistical significance.

CONCLUSIONS

Gliclazide MR improves glycemic control and, in addition, has a positive influence on the plasma level of some inflammatory markers and adiponectin. Increased plasma adiponectin and decreased plasma IL-6, and TNF-alpha levels may explain, at least in part, the anti-atherogenic action of this drug reported elsewhere.

Should diabetic patients be asked to test their blood glucose 90 to 120 minutes after the beginning of their meals?

There are three distinct objectives in reducing the post-prandial blood glucose peaks: 1st to reduce the risk of foetal macrosomia in pregnancy, 2nd to reduce cardiovascular morbi-mortality, 3rd to lower the HbA1c. With 6-7 glycaemic controls per day and fractionning their meals, motivated women with gestational diabetes reach this goal. But there is no data today directly proving that post-prandial glycaemia is specifically related to the development of micro and macrovascular complications. So to reduce the cardiovascular risk, there are more arguments in favour of lowering HbA1c or prescribing statins than in prescribing a hypoglycaemic drug acting selectively on post-prandial glycaemia. Lastly, to reduce HbA1c near to the goal of 7%, the most important is to reduce the preprandial glycaemia below 1.20 g/l. The patients must be required to monitor their post-prandial glycaemia 2 hours after the beginning of the meal only when the aim is to lower the HbA1c below 7% or 6.5%, for example during pregnancy, or in case of discrepancy between glycaemia at 8 a.m. and 7 p.m. (below 1.20 g/)l and HbA1c (above 7%). In other cases, in type 2 diabetes, two glycaemias per day, fasting and vesperal, seems sufficient.

Gliclazide treatment lowers serum ICAM-1 levels in poorly controlled type 2 diabetic patients

OBJECTIVE

To investigate the potential effect of gliclazide on serum ICAM-1 (intercellular adhesion molecule-1) and VCAM-1 (vascular cell adhesion molecule-1) levels in poorly controlled type 2 diabetic patients.

PATIENTS AND METHODS

The study included 104 patients, randomly divided into two groups. Group A comprised 53 patients (26 men) treated with gliclazide with a mean age of 67.5+/-9.9 years, a mean diabetes duration of 13.4+/-5.4 years and a mean HbA1c of 8.6+/-1.1%. Group B comprised 51 patients (25 men) treated with glibenclamide with a mean age of 66.4+/-10.9 years, a mean diabetes duration of 13.2+/-6.1 years and a mean HbA1c of 8.4+/-1.3%. A third group of 30 healthy controls (15 men) with a mean age of 63.3+/-10.4 years was also included. Serum levels of ICAM-1 and VCAM-1 were measured at the beginning of the study and after six months of treatment.

RESULTS

Pretreatment serum ICAM-1 and VCAM-1 levels did not differ between groups A and B, while they were significantly higher (P=0.0001) than in healthy controls. No significant difference in HbA1c, body mass index, blood pressure control and lipid profile between the two groups was observed after the sixth month of treatment. In group A, serum ICAM-1 levels after six months of treatment were significantly reduced from 623.12+/-61.17 ng/ml to 370.14+/-49.92 ng/ml (P=0,01), while no reduction was found in VCAM-1 levels. In group B, no reduction was found in serum ICAM-1 and VCAM-1 levels after the end of the study.

CONCLUSIONS

Our results suggest that gliclazide treatment reduces serum ICAM-1 levels in poorly controlled type 2 diabetic patients. This reduction is independent of the hypoglycaemic action of gliclazide.

Lymphocyte ecto-5'-nucleotidase in obese type 2 diabetic patients treated with gliclazide

OBJECTIVE

Lymphocyte 5'-nucleotidase is sensitive to superoxide anion, and is an indicator of oxidative stress in humans. The aim of this study was to assess the effect of the sulfonylurea drugs gliclazide and glibenclamide on lymphocyte ecto-5'-nucleotidase of type 2 diabetic patients.

METHODS

Thirty obese type 2 diabetic patients were treated for three months after randomisation either with gliclazide or glibenclamide. Basic laboratory parameters (glycaemia, fructosamine, C-peptide), plasma malondialdehyde levels (MDA) as well as lymphocyte 5'-nucleotidase activity were determined, for all patients and 16 healthy controls, before and after the treatment.

RESULTS

5'-nucleotidase activity in diabetic patients before treatment with gliclazide was 1.61 +/- 0.16 nmol/min/10(6) lymphocytes, and was significantly (P < 0.01) increased compared with the level in healthy controls. After three months of gliclazide treatment, ecto-5'-nucleotidase activity fell significantly by 47.39% and 36% in unstimulated Con A- and PMA-stimulated lymphocytes, respectively. Glibenclamide treatment had no effect on ecto-5'-nucleo-tidase of type 2 diabetic patients. Glycoregulation was improved, as plasma fructosamine decreased from 53.4 to 42.1 and from 50.5 to 43.4 U/g proteins after gliclazide and glibenclamide treatment, respectively. Plasma MDA levels markedly decreased after gliclazide but not glibenclamide treatment.

CONCLUSION

These results show that gliclazide treatment inhibits the activity of lymphocyte ecto-5'-nucleotidase and presumably de-creases the concentration of adenosine at the cell surface. A decrease in 5'-nucleotidase activity and attenuation of adenosine production may be a factor in the protection of tissue injury in type 2 diabetic patients.

Gliclazide inhibits differentiation-associated biologic events in human monocyte-derived macrophages

We investigated the in vitro effect of gliclazide on human monocyte-derived macrophage scavenger receptor expression and activity, foam cell formation, and lipopolysaccharide-induced cytokine production. Differentiation of human monocytes into macrophages in the presence of gliclazide (1-10 microg/mL) decreased CD36 expression by 20% to 50%, with maximal effect occurring at 2.5 microg/mL (P<.05). This effect was mimicked by vitamin E (50 micromol/L) and N-acetyl-L-cysteine (10 mmol/L). Incubation of the cells with gliclazide and N-acetyl-L-cysteine also reduced CD36 activity by 30% (P<.02). Despite these effects, neither gliclazide nor vitamin E did affect foam cell formation. In contrast, gliclazide significantly reduced lipopolysaccharide-stimulated macrophage tumor necrosis factor alpha and interleukin 6 secretion (P<.05). Overall, these data indicate that gliclazide, at concentrations in the therapeutic range, may regulate some key biologic events associated with the process of monocyte differentiation into macrophages.

Influence of nicorandil on the pharmacodynamics and pharmacokinetics of gliclazide in rats and rabbits

Chronic diabetes precipitates ischaemic heart disease (IHD) and many other disorders. IHD inturn is shown in the form of angina initially. According to EUROPA study, the incidence of angina is high in type II diabetics. Gliclazide, a second generation sulphonylurea derivative is widely used in the treatment of type-II diabetes and is known to release insulin by K(+) channel inhibition. Nicorandil, a newer antianginal drug widely used now a days acts by opening potassium channels in the cardiac muscle cell and also by releasing nitric oxide. However its action on pancreatic cell K(+) channel is not known. Since there is possibility for drug interaction leading to decreased activity of gliclazide the present study was conducted to evaluate the effect of the combination. Studies in normal and alloxan induced diabetic rats were conducted with oral doses of 2 mg/kg bd. wt. of gliclazide, 1.8 mg/kg bd. wt. of nicorandil and their combination with adequate washout periods in between treatments. Studies in normal rabbits were conducted with 5.6 mg/1.5 kg bd. wt. of gliclazide, 1.4 mg/1.5 kg bd. wt. of nicorandil and their combination given orally. Blood samples were collected in rats from retro orbital puncture at 0, 1, 2, 3, 4, 6, 8, 10 and 12 h and by marginal ear vein puncture in rabbits at 0, 1, 2, 3, 4, 6, 8, 12, 16, 20 and 24 h. All the blood samples were analysed for glucose by GOD/POD method. The blood samples of rabbits were analysed by HPLC for gliclazide. Gliclazide produced hypoglycaemic/antidiabetic activity in normal and diabetic rats with peak activity at 1 h and 8 h and hypoglycaemic activity in normal rabbits at 3 h, while nicorandil alone produced significant hyperglycaemia at 4 h and reduced the effect of gliclazide with no significant change in pharmacokinetics when administered in combination. The interaction observed appears to be pharmacodynamic at the receptor level as expected.

Effects of gliclazide beyond metabolic control

Evidence implicates hyperglycemia-derived oxygen free radicals as mediators of diabetic complications. Recent studies demonstrate that hyperglycemia-induced overproduction of superoxide seems the first and key event in the activation of all pathways involved in the pathogenesis of diabetic complications. Superoxide overproduction is accompanied by increased nitric oxide generation and, consequently, formation of the strong oxidant peroxynitrite, and by poly(adenosine diphosphate ribose) polymerase activation, which in turn further activates the pathways involved in the pathogenesis of diabetic complications. This process results in acute endothelial dysfunction and activation of inflammation in diabetic blood vessels that, convincingly, contribute to the development of diabetic complications. Gliclazide is an oral hypoglycemic agent that belongs to the class of sulfonylureas: basic and clinical evidences suggest that gliclazide works as an antioxidative drug, independently from its ability to reduce hyperglycemia. The availability of a compound that simultaneously decreases hyperglycemia, restoring insulin secretion, and inhibits oxidative stress produced by high glucose seems to be an interesting therapeutic prospect for the prevention of vascular complications of diabetes.

Effect of vitamin E and C supplementation combined with oral antidiabetic therapy on the endothelial dysfunction in the neonatally streptozotocin injected diabetic rat

BACKGROUND

This study investigates the contribution of vitamin supplementation to the efficacy of oral antidiabetic therapy on the reversal of endothelial dysfunction in a model of type-2 diabetes in rat.

METHODS

Diabetes was induced by streptozotocin injection to neonatal rats which were breastfed for 4 weeks, then fed 6 weeks with normal food or food supplemented with 2% vitamin E and 4% vitamin C. Some diabetic rats were treated with gliclazide for 6 weeks. Endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside (SNP) were recorded in thoracic aortic rings. Plasma insulin, HbA(1c) and antioxidant vitamins (A, C and E); plasma and aortic malondialdehyde (MDA) levels were determined.

RESULTS

Induction of diabetes resulted in decreased body weight and increased blood glucose, plasma insulin and HbA(1c) levels compared to controls. Acetylcholine relaxation was impaired in diabetic aorta, while SNP relaxation remained unchanged. Aortic MDA level was significantly higher, while plasma vitamin levels were lower in diabetic rats. Diminished acetylcholine response, enhanced aortic MDA level and decreased plasma vitamin levels were all restored after gliclazide and/or vitamin therapy. However, vitamin supplementation in control rats significantly impaired acetylcholine relaxations and increased aortic MDA levels.

CONCLUSIONS

Apparently, a selective endothelial dysfunction accompanies the imbalance in oxidant/antioxidant status in the type-2 diabetes model of rat and gliclazide and/or vitamin supplementation improves the impairment in diabetic vasculature. However, vitamin supplementation triggers oxidative stress in normal aortic tissue, thereby, leads to endothelial dysfunction; indicating that nutritional extra-supplementation of antioxidant vitamins isn't advisable for normal subjects, although it's beneficial in disease status.

Comparison of the antioxidant and vascular effects of gliclazide and glibenclamide in Type 2 diabetic patients: a randomized crossover study

The aim of the present study is to compare the short-term effects of gliclazide and glibenclamide on the oxidative state and vascular endothelium function of Type 2 diabetic patients in an observer-blinded, randomized crossover study. Thirteen Type 2 diabetic patients were enrolled: one group of seven patients took daily 160 mg of gliclazide for the first 4 weeks and then daily 5 mg of glibenclamide for the next 4 weeks; another group of six patients took daily 5 mg of glibenclamide for the first 4 weeks and 160 mg of gliclazide for the next 4 weeks. Forearm blood flow (FBF) measurement for endothelial function and biochemical analyses were conducted before and after each crossover treatment. Four weeks of treatment with either sulfonylurea showed the similar antihyperglycemic effects and enhancement of the peak FBF and total reactive hyperemic flow (flow debt repayment: FDR) during reactive hyperemia. Treatment with gliclazide resulted in the significant reduction to about 60% of baseline in urinary 8-iso-prostaglandin F2alpha (8iPGF2alpha) excretion while no such change was detected in the glibenclamide period. The increases in peak FBF and FDR were in parallel with its anti-hyperglycemic effect, but not with antioxidant state. Results suggest that gliclazide and glibenclamide can protect vascular endothelium from hyperglycemia-induced injury in Type 2 diabetic patients.

Effect of AT1 receptor blockade on hepatic redox status in SHR: possible relevance for endothelial function?

The study investigated whether the amelioration of endothelial dysfunction by candesartan (2 mg.kg-1.day-1; 10 wk) in spontaneously hypertensive rats (SHR) was associated with modification of hepatic redox system. Systolic arterial pressure (SAP) was higher (P < 0.05) in SHR than in Wistar-Kyoto rats (WKY) and was reduced (P < 0.05) by candesartan in both strains. Acetylcholine (ACh) relaxations were smaller (P < 0.05) and contractions induced by ACh + NG-nitro-l-arginine methyl ester (l-NAME) were greater (P < 0.05) in SHR than in WKY. Treatment with candesartan enhanced (P < 0.05) ACh relaxations in SHR and reduced (P < 0.05) ACh + l-NAME contractions in both strains. Expression of aortic endothelial nitric oxide synthase (eNOS) mRNA was similar in WKY and SHR, and candesartan increased (P < 0.05) it in both strains. Aortic mRNA expression of the subunit p22phox of NAD(P)H oxidase was higher (P < 0.05) in SHR than in WKY. Treatment with candesartan reduced (P < 0.05) p22phox expression only in SHR. Malonyl dialdehyde (MDA) levels were higher (P < 0.05), and the ratio reduced/oxidized glutathione (GSH/GSSG) as well as glutathione peroxidase activity (GPx) were lower (P < 0.05) in liver homogenates from SHR than from WKY. Candesartan reduced (P < 0.05) MDA and increased (P < 0.05) GSH/GSSG ratio without affecting GPx. Vessel, lumen, and media areas were bigger (P < 0.05) in SHR than in WKY. Candesartan treatment reduced (P < 0.05) media area in SHR without affecting vessel or lumen area. The results suggest that hypertension is not only associated with elevation of vascular superoxide anions but with alterations of the hepatic redox system, where ANG II is clearly involved. The results further support the key role of ANG II via AT1 receptors for the functional and structural vascular alterations produced by hypertension.