[Diabetes mellitus, oxidative stress and advanced glycation endproducts]

Inflammation level in type 2 diabetes is associated with dietary advanced glycation end products, Mediterranean diet adherence and oxidative balance score: A pathway analysis

AIMS

The aim of this study was to evaluate the effects of dietary advanced glycation end products (dAGE) intake, Mediterranean diet adherence screener (MEDAS), and oxidative balance score (OBS) on inflammation among individuals with type 2 diabetes.

METHODS

The study was conducted with 96 adults (aged between 32 and 64 years) with type 2 diabetes. The average daily dAGE intakes, energy and macronutrient intakes of the participants were taken with the three-day food consumption recording method. OBS and MEDAS score was used. At the same time, routine blood lipids, HbA1c, fasting blood glucose and inflammation marker C-reactive protein (CRP) were measured.

RESULTS

Dietary AGE intake was associated with fasting blood glucose, HbA1c, CRP and blood pressures (p < 0.01). The relationship between OBS and dAGE intake was significant (β = -0.36; 95 % Cl = -0.500, -0.220; p < 0.001). MEDAS has a negative and statistically significant effect on dAGE intake (β = -0.56; 95 % Cl = -0.696, -0.444; p < 0.001). There was a significant and positive effect of dAGE on CRP when other variables (MEDAS, OBS) affecting dAGE were also included in the analysis (β = 0.79; 95 % CI = 0.664, 0.917; p < 0.001).

CONCLUSIONS

Our findings may have important implications for explaining the development of inflammation in type 2 diabetes patients with high dAGE intake.

Influence of Diabetes-Induced Glycation and Oxidative Stress on the Human Rotator Cuff

Most shoulder rotator cuff tears (RCTs) are caused by non-traumatic age-related rotator cuff degeneration, of which hyperglycemia is a risk factor due to its glycation reaction and oxidative stress. We aimed to identify the influence of diabetes-induced glycation and oxidative stress in patients with non-traumatic shoulder RCTs. Twenty patients, aged over 50 years, with non-traumatic shoulder RCTs participated in this study. Patients with a history of diabetes mellitus or preoperative HbA1c ≥ 6.5% were assigned to the diabetic group (n = 10), and the rest to the non-diabetic group (n = 10). Cell proliferation; expression of genes related to oxidative stress, glycation reaction, inflammation, and collagen; intracellular reactive oxygen species (ROS) levels; and apoptosis rates were analyzed. The diabetic group had significantly lower cell proliferation than the non-diabetic group. In the diabetic group, the mRNA expression levels of NOX1, NOX4, IL6, RAGE, type III collagen, MMP2, TIMP1, and TIMP2 were significantly higher; type I collagen expression was significantly lower; and the rate of ROS-positive cells and apoptotic cells, as well as the expression of advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE), was significantly higher. In conclusion, hyperglycemia caused by diabetes mellitus increased AGE and RAGE expression, and led to increased NOX expression, ROS production, and apoptosis in the human rotator cuff. This provides scope to find a preventive treatment for non-traumatic RCTs by inhibiting glycation and oxidative stress.

A Clinical Score to Predict "Corrected Thrombolysis in Myocardial Infarction Frame Count" in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Corrected thrombolysis in myocardial infarction frame count (cTFC) is an objective, simple, and reproducible method to assess coronary blood flow which is a surrogate for cardiovascular outcomes. It is important to learn which factors are associated with cTFC. The goal of this study was to determine predictive models for epicardial blood flow assessed by cTFC and develop a diagnostic predictive model that indicates the individualized assessment of epicardial blood flow prior to primary percutaneous coronary intervention. This is a retrospective study including 3205 patients with ST-segment elevation myocardial infarction who underwent pPCI. The primary outcome was cTFC. Multivariable linear regression analysis was performed. Subsequently, a nomogram was developed to predict cTFC according to the candidate predictors. Median age was 58; the number of male patients was 2381 (74.3%). Median value of cTFC was 22 and interquartile range (IQR): 16.5-28.0). Age, diabetes mellitus (DM), total ischemic time, systolic blood pressure (SBP), heart rate (HR), and history of statin use remained in both full and reduced models. Our model may potentially allow clinicians to identify patients at high risk for impaired epicardial perfusion.

CGMS and Glycemic Variability, Relevance in Clinical Research to Evaluate Interventions in T2D, a Literature Review

Glycemic variability (GV) appears today as an integral component of glucose homeostasis for the management of type 2 diabetes (T2D). This review aims at investigating the use and relevance of GV parameters in interventional and observational studies for glucose control management in T2D. It will first focus on the relationships between GV parameters measured by continuous glucose monitoring system (CGMS) and glycemic control and T2D-associated complications markers. The second part will be dedicated to the analysis of GV parameters from CGMS as outcomes in interventional studies (pharmacological, nutritional, physical activity) aimed at improving glycemic control in patients with T2D. From 243 articles first identified, 63 articles were included (27 for the first part and 38 for the second part). For both analyses, the majority of the identified studies were pharmacological. Lifestyle studies (including nutritional and physical activity-based studies, N-AP) were poorly represented. Concerning the relationships of GV parameters with those for glycemic control and T2D related-complications, the standard deviation (SD), the coefficient of variation (CV), the mean blood glucose (MBG), and the mean amplitude of the glycemic excursions (MAGEs) were the most studied, showing strong relationships, in particular with HbA1c. Regarding the use and relevance of GV as an outcome in interventional studies, in pharmacological ones, SD, MAGE, MBG, and time in range (TIR) were the GV parameters used as main criteria in most studies, showing significant improvement after intervention, in parallel or not with glycemic control parameters' (HbA1c, FBG, and PPBG) improvement. In N-AP studies, the same results were observed for SD, MAGE, and TIR. Despite the small number of N-AP studies addressing both GV and glycemic control parameters compared to pharmacological ones, N-AP studies have shown promising results on GV parameters and would require more in-depth work. Evaluating CGMS-GV parameters as outcomes in interventional studies may provide a more integrative dimension of glucose control than the standard postprandial follow-up. GV appears to be a key component of T2D dysglycemia, and some parameters such as MAGE, SD, or TIR could be used routinely in addition to classical markers of glycemic control such as HbA1c, fasting, or postprandial glycemia.

Nephroprotective effect of Artemisia herba alba aqueous extract in alloxan-induced diabetic rats

BACKGROUND AND AIM

In the present study, we investigate the phytochemical composition and the nephroprotective effects as well as the antioxidant properties of Artemisia herba alba aqueous extract in alloxan-induced experimental diabetes in rats.

EXPERIMENTAL PROCEDURE

Wistar rats were divided into four groups of seven rats each: Group I: Normal control (NC) received saline solution at 9‰ given by intraperitoneal way; Group II: Diabetic control (DC) received alloxan (150 mg/kg b.w) intraperitoneally; Group III: Normal control (NC + AHA) received saline solution at 9‰ and treated orally by AHA aqueous extract (400 mg/kg/b.w); Group IV: Diabetic control (DC + AHA) received alloxan solution (150 mg/kg b.w) intraperitoneally and treated by aqueous extract of AHA (400 mg/kg/b.w/day) orally after one week of alloxan administration. After 30 days, blood and tissue samples were collected for biochemical and histopathological analysis, respectively. Glomerular damage markers, including creatinine, serum urea, urine creatinine and urine urea levels were estimated. Creatinine clearance was also assessed. Oxidative stress parameters were assessed in the kidney homogenate.

RESULTS AND CONCLUSION

Alloxan-exposure resulted in significant increase in blood glucose and serum level of glomerular damage markers. The antioxidant enzyme activities were significantly downregulated associated with an increase in malondialdehyde (MDA) level over the baseline values. Artemisia herba alba aqueous extract supplementation significantly improved the studied parameters. In concluding, the results obtained suggests that Artemisia herbs-alba aqueous extract supplementation reduces alloxan-induced free radical generation, potentiates the antioxidant defense system and alleviates renal sensitivity to oxidative stress.

Mitigating effects of antioxidant properties of Artemisia herba alba aqueous extract on hyperlipidemia and oxidative damage in alloxan-induced diabetic rats

Chronic hyperglycemia and excess reactive oxygen species overproduced in diabetes were associated with oxidative stress, led to continuous injury and functions damage to different organs: eyes, kidneys, neural and cardiovascular system. The present study was undertaken to evaluate the protective effect of Artemisia herba alba (AHA) leaf powder against alloxane-induced oxidative damage in diabetic rats. Rats were randomly divided into four groups: Group I controls received saline solution 9%; Group II was treated with 150 mg alloxane/(kg body weight) administered by intraperitoneal. Rats of Group III have received saline solution and treated with 400 mg AHA/(kg body weight). Animals of Group IV were treated with alloxane and AHA. Alloxane exposure led to increased blood glucose, total cholesterol, triglycerides, malondialdehyde, and a decrease in the antioxidants enzymes activities (catalase, glutathione peroxidase and glutathione-S-transferase). Administration of AHA aqueous extract ameliorated these parameters. These results demonstrate that AHA ameliorates hyperglycemia, hyperlipidemia and oxidative damage in alloxan-induced diabetes in rats.

Monitoring the antioxidant activities by extracting the polyphenolic contents of algae collected from the Bosphorus

The identification and quantification of ascorbic acid, phenolic acids and flavonoids were carried out simultaneously with a rapid method of reverse-phase high-performance liquid chromatography (RP-HPLC). Total flavonoid contents were being determined by UV-Vis spectrophotometry, and total phenolic contents were determined by UV-Vis spectrophotometry using the Folin-Ciocalteu Reagent (FCR) method. In all of the individual contents and total phenolic content analysis, the best results were obtained with the methanol-water solvent system. The methanol-hexane solvent system was selected as the best for the extraction of total flavonoid contents. The reason for this difference is the flavonoids in the analyzed samples which were the lipophilic character. Examining the algae species, the highest contents were achieved from Ulva lactuca and Ceramium rubrum species. Depending on industrial activity and the population density, regional characteristics have been shown to be effective in the changes of these contents which show antioxidant properties.

Impact of ultrasound and conventional extraction techniques on bioactive compounds and biological activities of blue butterfly pea flower (Clitoria ternatea L.)

The present study was conducted to evaluate the influence of ultrasound on bioactive compounds and biological activities of blue butterfly pea flower (Clitoria ternatea L.). For this purpose, optimized conditions (temperature 50 °C, time 150 min, solid to liquid ratio 1 g:15 ml, 70% amplitude and 240 W, 20 kHz frequency, 3 s on and 3 s off) of ultrasound (US) and conventional extraction (AGE: Agitation, water bath for 150 min, 50 °C at 150 rmp) were used. The results showed significant (p < 0.05) effect of US and AGE on total phenolics (TPCs), flavonoids (TFCs) and antioxidant activities (DPPH, ABTS, FRAP, reducing activity, Cu²⁺ and H₂O₂) of butterfly pea flower extract (BPFE). The results showed an increased trend in yield, TPCs, TFCs and antioxidant activities of US treated BPFE with comparison to AGE. However, insignificant (p > 0.05) effect of US and AGE over TFlaCs and PACs were observed. Moreover, the results of Fourier-transform infrared spectroscopy (FTIR) showed little changes in spectrum and US does not affect the functional group of bioactive compounds structure. Additionally, extracts (500-2000 µg/ml) protect pBR322 plasmid DNA damage induced by (1 mM H₂O₂ and 1 mM FeSO₄), plasma oxidation (induced by 250 µM CuCl₂) and inhibit erythrocyte hemolysis (induced by 200 mM AAPH, 34.6 to 66.73%). Sonication can be applied successfully for the extraction of bioactive compounds from plant materials with high biological activities.

Glycation Damage: A Possible Hub for Major Pathophysiological Disorders and Aging

Glycation is both a physiological and pathological process which mainly affects proteins, nucleic acids and lipids. Exogenous and endogenous glycation produces deleterious reactions that take place principally in the extracellular matrix environment or within the cell cytosol and organelles. Advanced glycation end product (AGE) formation begins by the non-enzymatic glycation of free amino groups by sugars and aldehydes which leads to a succession of rearrangements of intermediate compounds and ultimately to irreversibly bound products known as AGEs. Epigenetic factors, oxidative stress, UV and nutrition are important causes of the accumulation of chemically and structurally different AGEs with various biological reactivities. Cross-linked proteins, deriving from the glycation process, present both an altered structure and function. Nucleotides and lipids are particularly vulnerable targets which can in turn favor DNA mutation or a decrease in cell membrane integrity and associated biological pathways respectively. In mitochondria, the consequences of glycation can alter bioenergy production. Under physiological conditions, anti-glycation defenses are sufficient, with proteasomes preventing accumulation of glycated proteins, while lipid turnover clears glycated products and nucleotide excision repair removes glycated nucleotides. If this does not occur, glycation damage accumulates, and pathologies may develop. Glycation-induced biological products are known to be mainly associated with aging, neurodegenerative disorders, diabetes and its complications, atherosclerosis, renal failure, immunological changes, retinopathy, skin photoaging, osteoporosis, and progression of some tumors.

Clinical variables and ethnicity may influenced by polymorphism of CAT -262C/T and MnSOD 47C/T antioxidant enzymes in Algerian type1 diabetes without complications

The latest studies in Algeria show that the frequency of type 1 diabetes (T1D) without complications is lower than that with complications and represents a significant burden in terms of cost and treatment. For this reason, we are interested in uncomplicated type1 diabetes and risk factors that are related to polymorphisms of antioxidant enzymes in order to prevent its complications. A total of 260 blood samples of young Algerian adults were examined. The genotypic analysis of Catalase gene (CAT -262C/T, rs1001179) and the superoxide dismutase gene (MnSOD 47C/T, rs4880) was performed by real-time PCR using TaqMan technology. The genotypic distribution of the CAT -262C/T promoter gene's polymorphism showed a significant difference between control and T1D patients for the CC genotype (p = 0.009; OR = 0.30) and for the T allele (p = 0.002; OR = 2.82). In addition, the genotypic distribution of the MnSOD 47C/T gene showed an association with T1D for the CT genotype (p = 0.040; OR = 2.37). Our results revealed that polymorphisms of CAT and MnSOD may be associated with physiopathology causing the onset of T1D. Our data, suggest that the genotypic frequencies of these SNPs appear to be influenced by clinical variables and by the Arab-Berber ethnic origin of the Algerian population.

Feruloylated oligosaccharides from maize bran alleviate the symptoms of diabetes in streptozotocin-induced type 2 diabetic rats

This study investigated the therapeutic effect of feruloylated oligosaccharides (FOs) extracted from maize bran on type 2 diabetic rats and its potential mechanism. Streptozotocin (STZ) induced type 2 diabetic male rats were orally administered with different levels of FOs for 8 weeks, and ferulic acid (FA) treatment was conducted as the positive control. Among all the treatments, the oral administration of 600 mg per kg bw per d FOs showed the best therapeutic effects on the diabetic rats by significantly lowering the levels of fasting plasma glucose (FPG), fasting insulin, TG, LDL-c, aspartate transaminase, creatine kinase and lactate dehydrogenase in plasma, while increasing the level of plasma HDL-c. In addition, the intake of FOs at 600 mg per kg bw per d exhibited the best antioxidant effects in the plasma, liver, kidney and heart of the diabetic rats, and the highest inhibitory effects on the formation of AGEs and CML in the organs, which might explain the alleviating effects of FOs on abdominal aorta injury observed in the current study. FOs presented better regulation effects on FPG, plasma lipid and the protection of abdominal aorta than FA under the same administered dosage. Based on these outcomes, FOs from maize bran could be beneficial for prevention or early treatment of diabetes mellitus.

Protective effect of rosmarinic acid and carnosic acid against streptozotocin-induced oxidation, glycation, inflammation and microbiota imbalance in diabetic rats

This study evaluated the protective effects of two rosemary components, rosmarinic acid (RA) and carnosic acid (CA), against hypoglycemia, hyperlipidemia, oxidative stress and an imbalanced gut microbiota architecture in diabetic rats. Treatment with RA and CA (30 mg kg-1) decreased the levels of fasting plasma glucose (23.7%, 15.6%), total cholesterol (30.4%, 14.1%) and triglyceride (65.7%, 47.8%) at 15 weeks. RA and CA also exhibited an anti-oxidative and anti-glycative effect by lowering the formation of malondialdehyde and advanced glycation end products. In addition, they showed protective effects against tissue damage and inflammation in the abdominal aorta, based on microscopic observations and the analysis of protein expression. Finally, the prebiotic effects of RA and CA on gut microbiota were demonstrated by increasing the population of diabetes-resistant bacteria and decreasing the amounts of diabetes-sensitive bacteria. Overall, RA showed a stronger protective effect than CA in mitigating diabetic symptoms in rats.

In Vivo Subacute Toxicity and Antidiabetic Effect of Aqueous Extract of Nigella sativa

Context. Nigella sativa seeds are usually used as traditional medicine for a wide range of therapeutic purposes. Objective. To investigate the subacute toxicity of NS aqueous extract and select its lowest dose to study its antidiabetic effect. Methods. 5 AqE.NS doses (2, 6.4, 21, 33, and 60 g/Kg) were daily administered to mice by gavage. Biochemical parameters measurements and histological study of the liver and the kidney were performed after 6 weeks of supplementation. Thereafter, and after inducing diabetes by alloxan, rats were treated by 2 g/Kg of AqE.NS during 8 weeks. Metabolic parameters were measured on sera. A horizontal electrophoresis of plasmatic lipoprotein was conducted. Glycogen, total lipids, and triglycerides were measured in the liver. TBARS were evaluated on adipose tissue, liver, and pancreas. Results. AqE.NS showed no variation in urea and albumin at the 5 doses, but hepatotoxicity from 21 g/Kg was confirmed by histopathological observations of the liver. In diabetic rats, AqE.NS significantly decreased glycemia, TG, T-cholesterol, LDL-c, and TBARS and showed a restored insulinemia and a significant increase in HDL-c. Results on the liver indicated a decrease in lipids and a possible glycogenogenesis. Conclusion. AqE.NS showed its safety at low doses and its evident antihyperglycemic, antihyperlipidemic, and antioxidant effect.

Scoparone attenuates high glucose-induced extracellular matrix accumulation in rat mesangial cells

Scoparone, a major constituent of Artemisia capillaries, has a variety of biological properties including anticoagulant, hepatoprotective, anti-tumor, anti-fibrosis, anti-inflammatory, antioxidant, and antidiabetic activities. However, the renoprotective effect of scoparone under diabetic conditions remains elusive. Thus, the present study was undertaken to examine the role of scoparone in high glucose-induced mesangial cell proliferation and extracellular matrix (ECM) accumulation and elucidate the possible mechanism of action of scoparone. Our results demonstrated that treatment with scoparone significantly inhibited the proliferation of mesangial cells under high glucose conditions. In addition, scoparone reversed high glucose-induced fibronectin and collagen IV expression in mesangial cells, as well as suppressed reactive oxygen species production and NOX2/4 expression in high glucose-exposed mesangial cells. Mechanistic studies revealed that scoparone prevented the activation of ERK1/2 signaling pathway in high glucose-exposed mesangial cells, and an ERK inhibitor (U0126) protected mesangial cells treated with high glucose. Taken together, these results demonstrated that scoparone protects mesangial cells against high glucose damage in part through the inactivation of ERK signaling pathway. These findings suggest that scoparone may represent a potential drug for the treatment of diabetic nephropathy.

Mangiferin attenuates diabetic nephropathy by inhibiting oxidative stress mediated signaling cascade, TNFα related and mitochondrial dependent apoptotic pathways in streptozotocin-induced diabetic rats

Oxidative stress plays a crucial role in the progression of diabetic nephropathy in hyperglycemic conditions. It has already been reported that mangiferin, a natural C-glucosyl xanthone and polyhydroxy polyphenol compound protects kidneys from diabetic nephropathy. However, little is known about the mechanism of its beneficial action in this pathophysiology. The present study, therefore, examines the detailed mechanism of the beneficial action of mangiferin on STZ-induced diabetic nephropathy in Wister rats as the working model. A significant increase in plasma glucose level, kidney to body weight ratio, glomerular hypertrophy and hydropic changes as well as enhanced nephrotoxicity related markers (BUN, plasma creatinine, uric acid and urinary albumin) were observed in the experimental animals. Furthermore, increased oxidative stress related parameters, increased ROS production and decreased the intracellular antioxidant defenses were detected in the kidney. Studies on the oxidative stress mediated signaling cascades in diabetic nephropathy demonstrated that PKC isoforms (PKCα, PKCβ and PKCε), MAPKs (p38, JNK and ERK1/2), transcription factor (NF-κB) and TGF-β1 pathways were involved in this pathophysiology. Besides, TNFα was released in this hyperglycemic condition, which in turn activated caspase 8, cleaved Bid to tBid and finally the mitochorndia-dependent apoptotic pathway. In addition, oxidative stress also disturbed the proapoptotic-antiapoptotic (Bax and Bcl-2) balance and activated mitochorndia-dependent apoptosis via caspase 9, caspase 3 and PARP cleavage. Mangiferin treatment, post to hyperglycemia, successfully inhibited all of these changes and protected the cells from apoptotic death.

Effect of Sophora subprosrate polysaccharide on oxidative stress induced by PCV2 infection in RAW264.7 cells

In this study, an oxidative stress model was first developed in a mouse macrophage cell line (RAW264.7 cells) by infecting the cells with porcine circovirus type 2 (PCV2). The regulatory effect of Sophora subprosrate polysaccharide (SSP) on PCV2-induced oxidative stress was investigated. The results showed that after infection with PCV2, reactive oxygen species (ROS) and nitric oxide (NO) production, myeloperoxidase (MPO) activity, and inducible nitric oxide synthase (iNOS) expression were significantly increased. Meanwhile, the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) and hydroxyl radical prevention capacity were greatly reduced. These data indicate successful creation of an oxidative stress model in RAW264.7 cells. A dramatic decrease in cell viability was observed in the cells exposed to oxidative stress compared to the control. When the cells were treated with SSP in concentrations of 100, 200 or 400 μg/mL post PCV2 infection, an increase in the GSH/GSSG ratio and hydroxyl radical prevention capacity was observed. We also observed decreased ROS and NO production, MPO activity, and iNOS expression in the infected cells. Our results demonstrated that PCV2 infection was able to induce oxidative stress in RAW264.7 cells and that SSP could reduce the negative effects resulting from the PCV2 infection.

Modulating efficacy of Rebaudioside A, a diterpenoid on antioxidant and circulatory lipids in experimental diabetic rats

The present study was to evaluate the protective effects of Rebaudioside A (Reb A) on antioxidant status and lipid profile in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in Wistar rats by a single intraperitoneal administration of STZ (40mg/kg b.w). Diabetic rats showed significantly increased levels of plasma glucose, thiobarbituric acid reactive substances, hydroperoxides and decreased levels of insulin. The activity of enzymatic antioxidants (superoxide dismutase, catalase and glutathione peroxidase) and the levels of non enzymatic antioxidants (vitamin C, vitamin E and reduced glutathione) were decreased in diabetic rats. The levels of total cholesterol (TC), triglycerides (TGs), free fatty acids (FFAs), phospholipids (PLs), low density lipoproteins (LDL-cholesterol) and very low-density lipoproteins (VLDL-cholesterol) in the plasma significantly increased, while plasma high-density lipoproteins (HDL-cholesterol) were significantly decreased in diabetic rats. Oral administration of Reb A (200mg/kg b.w) brought back plasma glucose, insulin, lipid peroxidation products, enzymatic, non-enzymatic antioxidants and lipid profile levels to near normal. The results of the present investigation suggests that Reb A, a natural sweetener exhibits antilipid peroxidative, antihyperlipidemic and antioxidant properties.

The association effect of insulin and clonazepam on oxidative stress in liver of an experimental animal model of diabetes and depression

CONTEXT

It is known that oxidative stress occurs in peripheral blood in an experimental animal model of diabetes and depression, and acute treatment with insulin and clonazepam (CNZ) has a protective effect on oxidative stress in this model.

OBJECTIVE

This study evaluated the effect of insulin plus CNZ on oxidative stress parameters in the liver of diabetic male rats induced with streptozotocin (STZ) and subjected to forced swimming test (FST).

MATERIALS AND METHODS

Diabetes was induced by a single intraperitoneal (i.p.) dose of STZ 60 mg/kg in male Wistar rats. Insulin (4 IU/kg) plus CNZ acute i.p. treatment (0.25 mg/kg) was administered 24, 5 and 1 h before the FST. Nondiabetic control rats received i.p. injections of saline (1 mL/kg). Protein oxidative damage was evaluated by carbonyl formation and the antioxidant redox parameters were analyzed by the measurements of enzymatic activities of the superoxide dismutase (SOD), catalase and glyoxalase I (GLO). Glycemia levels also were determined.

RESULTS

Our present study has shown an increase in carbonyl content from diabetic rats subjected to FST (2.04 ± 0.55), while the activity of catalase (51.83 ± 19.02) and SOD (2.30 ± 1.23) were significantly decreased in liver from these animals, which were reverted by the treatment. Also, the activity of GLO (0.15 ± 0.02) in the liver of the animals was decreased.

DISCUSSION AND CONCLUSION

Our findings showed that insulin plus CNZ acute treatment ameliorate the antioxidant redox parameters and protect against protein oxidative damage in the liver of diabetic rats subjected to FST.

Relationship between histochemical, structural characteristics and oxidative stability of rhea limb muscles

Histochemical and structural characteristics were investigated in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) limb muscles of Rhea americana. The average myofibre area cross-section was greater in GN than IF muscle (p<0.001), whereas the fibre density per section was higher in IF than GN muscle. The only type of myofibre found in both the rhea limb muscles analysed in this study was fast-twitch oxidative-glycolytic fibres (FOG). Immunolabelling analysis and ultrastructural observation of myofibres confirmed the contractile and metabolic characteristics of rhea myofibres, revealing the absolute fast isoform of myosin heavy chain and the abundance of glycogen and mitochondria inside the cells, mainly in IF muscle. These findings converged with previous results on the biochemical and physicochemical characteristics of rhea meat to provide further evidence that myofibre composition substantially influences the oxidative reactions of the muscle and therefore the meat quality, but more in-depth examination is needed to establish the links between myofibre characteristics, myofibre glycogen concentration and meat stability during storage.

Transcriptomic analysis in diabetic nephropathy of streptozotocin-induced diabetic rats

Diabetic nephropathy (DN) is a major complication of diabetes and is caused by an imbalance in the expression of certain genes that activate or inhibit vital cellular functions of kidney. Despite several recent advances, the pathogenesis of DN remains far from clear, suggesting the need to carry out studies identifying molecular aspects, such as gene expression, that could play a key role in the development of DN. There are several techniques to analyze transcriptome in living organisms. In this study, the suppression subtractive hybridization (SSH) method was used to generate up- and down-regulated subtracted cDNA libraries in the kidney of streptozotocin (STZ)-induced diabetic rats. Northern-blot analysis was used to confirm differential expression ratios from the obtained SSH clones to identify genes related to DN. 400 unique SSH clones were randomly chosen from the two subtraction libraries (200 of each) and verified as differentially expressed. According to blast screening and functional annotation, 20.2% and 20.9% of genes were related to metabolism proteins, 9% and 3.6% to transporters and channels, 16% and 6.3% to transcription factors, 19% and 17.2% to hypothetical proteins, and finally 24.1 and 17.2% to unknown genes, from the down- and up-regulated libraries, respectively. The down- and up-regulated cDNA libraries differentially expressed in the kidney of STZ diabetic rats have been successfully constructed and some identified genes could be highly important in DN.

Protective Effect of Proanthocyanidin against Diabetic Oxidative Stress

We investigated the antidiabetic potential of proanthocyanidin and its oligomeric form in STZ-induced diabetic model rats and db/db type 2 diabetic mice. Proanthocyanidin ameliorated the diabetic condition by significant decreases of serum glucose, glycosylated protein, and serum urea nitrogen as well as decreases of urinary protein and renal-AGE in STZ-induced diabetic rats and decrease of serum glucose as well as significant decrease of glycosylated protein in db/db type 2 diabetic mice. The suppression of ROS generation and elevation of the GSH/GSSG ratio were also observed in the groups administered proanthocyanidin. Moreover, proanthocyanidin, especially its oligomeric form, affected the inflammatory process with the regulation of related protein expression, iNOS, COX-2 and upstream regulators, NF-κB, and the IκB-α. In addition, it had a marked effect on hyperlipidemia through lowering significant levels of triglycerides, total cholesterol, and NEFA. Moreover, expressions in the liver of SREBP-1 and SREBP-2 were downregulated by the administration of proanthocyanidins. The protective effect against hyperglycemia and hyperlipidemia in type 1 and 2 diabetic models was significantly strong in the groups administered the oligomeric rather than polymeric form. This suggests that oligomers act as a regulator in inflammatory reactions caused by oxidative stress in diabetes.

Mechanisms responsible for the vascular effect of aqueous Trigonella foenum-graecum leaf extract in diabetic rats

BACKGROUND AND OBJECTIVE

Since a beneficial vascular effect of aqueous leaf extract of Trigonella foenum-graecum (TFG) has previously been reported, this study was conducted to evaluate the underlying mechanisms, including the role of nitric oxide (NO) and cyclooxygenase pathways, in diabetic rats.

MATERIALS AND METHODS

Male Wistar rats were divided into control, extract-treated control, diabetic, and extract-treated diabetic groups. Diabetes was induced by a single i.p. injection of streptozotocin (STZ; 60 mg/kg). Treatment groups received TFG extract (200 mg/kg; ip.) every other day for 1 month. Contractile reactivity of the thoracic aorta to KCl and noradrenaline (NA) and relaxation response to acetylcholine (ACh) were determined. For determination of the participation of NO and prostaglandins in the relaxation response to ACh, aortic rings were incubated for 30 min before the experiment with N-nitro-l-arginine methyl ester (L-NAME) and/or indomethacin (INDO).

RESULTS

The diabetic state significantly increased the maximum contractile response to KCl and NA (P < 0.01-0.005) and reduced the maximum relaxation due to ACh (P < 0.01) as compared to controls and treatment with TFG extract in the diabetic group significantly improved these changes relative to the untreated diabetic group (P < 0.05). With L-NAME pretreatment, no significant difference between diabetic and extract-treated diabetic groups was found out. On the other hand, there was a significant difference between these two groups following INDO pretreatment (P < 0.05).

CONCLUSION

Intraperitoneal administration of aqueous leaf extract of TFG for one month could improve some functional indices of the vascular system in the diabetic state and endothelium-derived prostaglandins are essential in this respect.

Protein and lipid oxidative damage in streptozotocin-induced diabetic rats submitted to forced swimming test: the insulin and clonazepam effect

Diabetes may modify central nervous system functions and is associated with moderate cognitive deficits and changes in the brain, a condition that may be referred to as diabetic encephalopathy. The prevalence of depression in diabetic patients is higher than in the general population, and clonazepam is being used to treat this complication. Oxidative stress may play a role in the development of diabetes complications. We investigated oxidative stress parameters in streptozotocin-induced diabetic rats submitted to forced swimming test (STZ) and evaluated the effect of insulin (STZ-INS) and/or clonazepam (STZ-CNZ and STZ-INS-CNZ) acute treatment on these animal model. Oxidative damage to proteins measured as carbonyl content in plasma was significantly increased in STZ group compared to STZ treated groups. Malondialdehyde plasma levels were significantly reduced in STZ-INS and STZ-INS-CNZ groups when compared to STZ rats, being significantly reduced in STZ-INS-CNZ than STZ-INS rats. The activities of the antioxidant enzymes catalase, superoxide dismutase and glutathione peroxidase showed no significant differences among all groups of animals. These findings showed that protein and lipid damage occurs in this diabetes/depression animal model and that the associated treatment of insulin and clonazepam is capable to protect against oxidative damage in this experimental model.

The Association between Serum GGT Concentration and Diabetic Peripheral Polyneuropathy in Type 2 Diabetic Patients

BACKGROUND

Diabetic peripheral polyneuropathy (DPP) is one of the common complications of diabetes mellitus (DM) and can lead to foot ulcers or amputation. The pathophysiology of DPP includes several factors such as metabolic, vascular, autoimmune, oxidative stress and neurohormonal growth-factor deficiency and recent studies have suggested the use of serum gamma-glutamyl transferase (GGT) as an early marker of oxidative stress. Therefore, we investigated whether serum GGT may be useful in predicting DPP.

METHODS

We assessed 90 patients with type 2 DM who were evaluated for the presence of DPP using clnical neurologic examinations including nerve conduction velocity studies. We evaluated the association between serum GGT and the presence of DPP.

RESULTS

The prevalence of DPP was 40% (36 cases) according to clinical neurological examinations. The serum GGT concentration was significantly elevated in type 2 diabetic patients with DPP compared to patients without DPP (P < 0.01). There were other factors significantly associated with DPP including smoking (P = 0.019), retinopathy (P = 0.014), blood pressure (P < 0.05), aspartate aminotransferase (P = 0.022), C-reactive protein (P = 0.036) and urine microalbumin/creatinine ratio (P = 0.004). Serum GGT was independently related with DPP according to multiple logistic analysis (P < 0.01).

CONCLUSION

This study shows that increased levels of serum GGT may have important clinical implications in the presence of DPP in patients with type 2 diabetes.

Glycation and lipid peroxidation in children and adolescents with type 1 diabetes mellitus with and without diabetic complications

Glycation and oxidative stress lead to formation of compounds that have several biological effects and contribute to the development of the complications of diabetes mellitus. All steps of glycoxidation generate oxygen free radicals, some of them in common with lipid peroxidation pathways. Some oxidation or lipid peroxidation products may bind to proteins and amplify glycoxidation-generated lesions. The aim of this study was to measure glycation and lipid peroxidation parameters and examine the relationship between them in patients with type 1 diabetes mellitus (DM1) with (+DC) and without (-DC) diabetic complications. Fifty patients with DM1 aged from 7-19 years and with duration of DM1 (DD) at least 5 years were included. Twenty-four patients were -DC and 26 were +DC. Twelve healthy children formed a control group. There were significantly higher values of fructosamine (FAM), HbA(1c), serum advanced glycation endproducts (s-AGEs) and lipid peroxides (LPO) in the +DC group compared with -DC, and significantly higher values of HbA(1c), FAM and LPO in both diabetic groups than in controls. The s-AGEs level in the -DC group was similar to that in controls. In the total diabetic group, regardless of DC, there was a significant negative correlation between LPO and HDL-C (r = -0.379; p <0.05), and a positive correlation between LPO and triacylglycerol (TAG) (r = 0.852; p <<0.05), FAM (r = 0.414; p <0.05) and s-AGEs (r = 0.454; p <0.05). In the +DC group LPO correlated negatively with HDL-C (r = -0.392, p <0.05) and positively with TAG (r = 0.848; p <<0.05), FAM (r = 0.457; p = 0.02), and s-AGEs (r = 0.516, p = 0.02), whereas in the -DC group LPO correlated only with HDL-C (r = -0.441; p = 0.03) and TAG (r = 0.769; p <<0.05). We demonstrated a linkage between enhanced formation of AGEs and lipid peroxidation products and the presence of diabetic complications. Thus, the overproduction of glycation and lipid peroxidation products may take part in DC development as early as in childhood and adolescence.

Hyperglycemia-induced alterations in synaptosomal membrane fluidity and activity of membrane bound enzymes: beneficial effect of N-acetylcysteine supplementation

Diabetic encephalopathy is characterized by impaired cognitive functions that appear to underlie neuronal damage triggered by glucose driven oxidative stress. Hyperglycemia-induced oxidative stress in diabetic brain may initiate structural and functional changes in synaptosomal membranes. The objective of the present study was to examine the neuroprotective role of N-acetylcysteine (NAC) in hyperglycemia-induced alterations in lipid composition and activity of membrane bound enzymes (Na(+),K(+)-ATPase and Ca(2+)-ATPase) in the rodent model of type 1 diabetes. Male Wistar rats weighing between 180 and 200 g were rendered diabetic by a single injection of streptozotocin (50 mg/kg body weight, i.p.). The diabetic animals were administered NAC (1.4-1.5 g/kg body weight) for eight weeks and lipid composition along with membrane fluidity were determined. A significant increase in lipid peroxidation was observed in cerebral cortex of diabetic rats. NAC administration on the other hand lowered the hyperglycemia-induced lipid peroxidation to near control levels. The increased lipid peroxidation following chronic hyperglycemia was accompanied by a significant increase in the total lipids which can be attributed to increase in the levels of cholesterol, triglycerides and glycolipids. On the contrary phospholipid and ganglioside levels were decreased. Hyperglycemia-induced increase in cholesterol to phospholipid ratio reflected decrease in membrane fluidity. Fluorescence polarization (p) with DPH also confirmed decrease in synaptosomal membrane fluidity that influenced the activity of membrane bound enzymes. An inverse correlation was found between fluorescence polarization with the activities of Na(+),K(+)-ATPase (r(2)=0.416, P<0.05) and Ca(2+) ATPase (r(2)=0.604, P<0.05). NAC was found to significantly improve lipid composition, restore membrane fluidity and activity of membrane bound enzymes. Our results clearly suggest perturbations in lipid composition and membrane fluidity as a major factor in the development of diabetic encephalopathy. Furthermore, NAC administration ameliorated the effect of hyperglycemia on oxidative stress and alterations in lipid composition thereby restoring membrane fluidity and activity of membrane bound enzymes.

Decreased in vivo oxidative stress and decreased platelet activation following metformin treatment in newly diagnosed type 2 diabetic subjects

BACKGROUND

In type 2 diabetes, metformin reduces cardiovascular risk beyond the effect of glycaemic control. Since oxidative stress and the consequent enhanced platelet activation contribute to accelerated atherosclerosis in diabetes, we hypothesized that metformin could reduce oxidative stress in this condition.

METHODS

We randomized 26 newly diagnosed type 2 diabetic subjects to assume either metformin (M, n = 13) or gliclazide (G, n = 13) for 12 weeks. Drugs were titrated as needed to achieve good glycaemic control. Before and after treatment, we determined blood glucose, insulin, HbA(1c), vitamin A and E levels and 8-iso-PGF(2alpha) and 11-dehydro-thromboxane B(2) urinary excretion, an in vivo oxidative stress and a thromboxane-dependent platelet activation marker, respectively.

RESULTS

Notwithstanding a comparable improvement in metabolic control, 8-iso-PGF(2alpha) (M from 708 +/- 32 to 589 +/- 45 pg/mg cr, p < 0.001; G from 646 +/- 80 to 665 +/- 79, pg/mg cr, p = ns) and 11-dehydro-thromboxane B(2) (M from 2190 +/- 196 to 1753 +/- 150 pg/mg cr, p < 0.05; G from 2048 +/- 202 to 1923 +/- 223, pg/mg cr, p = ns) urinary excretion decreased after metformin but not after gliclazide treatment. After metformin, vitamin A and E levels significantly increased while they remained unchanged after gliclazide.

CONCLUSIONS

These data suggest that metformin could improve oxidative stress, preserve antioxidant function and restrain platelet activation in type 2 diabetes.

Ameliorative effects of proanthocyanidin on oxidative stress and inflammation in streptozotocin-induced diabetic rats

Recent evidence strongly suggests that oxidative stress due to redox imbalance is causally associated with inflammatory processes and various diseases including diabetes. We examined the effects of proanthocyanidin from persimmon peel, using both oligomers and polymers, against oxidative stress with elucidation of the underlying mechanisms in streptozotocin-induced diabetic rats. The elevation of lipid peroxidation in the kidney and serum under the diabetic condition was decreased by the administration of proanthocyanidin. The suppression of reactive oxygen species generation and elevation of the reduced glutathione/oxidized glutathione ratio were observed in the groups administered proanthocyanidin. These results support the protective role of proanthocyanidin from oxidative stress induced by diabetes. Moreover, proanthocyanidin, especially its oligomeric form, affected the inflammatory process with regulation of related protein expression, inducible nitric oxide synthase, cyclooxygenase-2, and upstream regulators, nuclear factor kappaB, and inhibitor-binding protein kappaB-alpha. Proanthocyanidin ameliorated the diabetic condition by decreases of serum glucose, glycosylated protein, serum urea nitrogen, urinary protein, and renal advanced glycation endproducts. In particular, oligomeric proanthocyanidin exerted a stronger protective activity than the polymeric form. This suggests that the polymerization of proanthocyanidin has an effect on its protective effect against diabetes. The present study supports the beneficial effect of proanthocyanidin against diabetes and oxidative stress-related inflammatory processes.

[Conclusions, future prospects and recommendations]

Understanding the notion of oxidative stress implies a good knowledge of the reactivity of the different reactive oxygen species (ROS). Cell damage can be induced by an overproduction of these species and/or by a deficiency in the protective antioxidant systems. Nevertheless, ROS do not display only deleterious effects and play key-roles in cell signalisation and regulation of the expression of redox sensitive genes. Besides ROS, reactive nitrogen species (RNS) with nitric oxide (*NO) as leader element, are widely involved in biology and lead to the term "nitrosative stress" that particularly describes the damage induced by peroxynitrite, a species formed by reaction between superoxide anion and degrees NO. Nutritional strategies have been based on antioxidant-rich diets, or on supplementation with antioxidants; they could constitute adjunct therapies of interest. Given all these data, radical biochemistry must be considered as a specific discipline.

[New aspects of diabetes]

Type II diabetes is a serious, insidious disease which is growing at an impressive rate, with 200 million diabetics worldwide and as many who ignore their state. Having been seriously studied over more than a century and a half, an enormous quantity of knowledge regarding this disease has been accumulated. The research we are conducting has allowed us to identify the most important actors responsible for diabetes. These are glucose which leads to glyoxal and to methylglyoxal which in turn reacts with innumerable targets in the organism (including insulin) unless prevented from doing so by detoxifying mechanisms (e.g., glyoxalases). The role of microorganisms in the occurrence and development of diabetes has also to be seriously examined.