Introduction of hyperglycemia and dyslipidemia in the pathogenesis of diabetic vascular complications

Anti-Inflammatory Effects of SGLT2 Inhibitors: Focus on Macrophages

A growing body of evidence indicates that nonglycemic effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors play an important role in the protective effects of these drugs in diabetes, chronic kidney disease, and heart failure. In recent years, the anti-inflammatory potential of SGLT2 inhibitors has been actively studied. This review summarizes results of clinical and experimental studies on the anti-inflammatory activity of SGLT2 inhibitors, with a special focus on their effects on macrophages, key drivers of metabolic inflammation. In patients with type 2 diabetes, therapy with SGLT2 inhibitors reduces levels of inflammatory mediators. In diabetic and non-diabetic animal models, SGLT2 inhibitors control low-grade inflammation by suppressing inflammatory activation of tissue macrophages, recruitment of monocytes from the bloodstream, and macrophage polarization towards the M1 phenotype. The molecular mechanisms of the effects of SGLT2 inhibitors on macrophages include an attenuation of inflammasome activity and inhibition of the TLR4/NF-κB pathway, as well as modulation of other signaling pathways (AMPK, PI3K/Akt, ERK 1/2-MAPK, and JAKs/STAT). The review discusses the state-of-the-art concepts and prospects of further investigations that are needed to obtain a deeper insight into the mechanisms underlying the effects of SGLT2 inhibitors on the molecular, cellular, and physiological levels.

Diabetes and the associated complications: The role of antioxidants in diabetes therapy and care

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by high blood sugar levels (hyperglycemia). Poorly managed diabetes can lead to complications affecting multiple organ systems. Antioxidants play a crucial role in reducing oxidative stress caused by reactive oxygen species (ROS), primarily triggered by uncontrolled high blood sugar levels in diabetes. Antioxidants like vitamin C, E, selenium, and alpha-lipoic acid, when used as supplements, have shown promise in reducing oxidative stress markers and improving antioxidant status in laboratory and animal studies and diabetic patients. Antioxidant supplementation may help reduce the risk of diabetic complications such as neuropathy, nephropathy, retinopathy, and cardiovascular disease. Additionally, antioxidants also have anti-inflammatory properties, which could be beneficial in reducing inflammation associated with diabetes. Antioxidant supplementation has been shown to enhance endothelial function, insulin sensitivity, and glucose metabolism, thereby aiding in glycemic control and overall diabetic management. Combining antioxidants with certain medications may have therapeutic benefits, such as effectively neutralizing free radicals and enhancing the regulation of antioxidant defense systems. This review presents an update on diabetes, the sources of free radical generation, the body's natural defense mechanisms, the clinical evidence regarding using antioxidants in managing diabetic complications, and the potential new therapeutic approaches. Overall, antioxidant supplementation may offer some benefits in managing diabetic complications. However, further studies are needed to understand the mechanisms of action, determine the optimal supplementation, explore potential interactions with other medications, and conduct long-term studies to establish the possible use of antioxidants for optimal benefits in diabetes care.

Spilanthes filicaulis (Schumach. & Thonn.) C. D Adam leaf extract prevents assault of streptozotocin on liver cells via inhibition of oxidative stress and activation of the NrF2/Keap1, PPARγ, and PTP1B signaling pathways

BACKGROUND

Spilanthes filicaulis (Schumach. & Thonn.) C. D Adam is a shrubby plant of the Asteraceae family that has medicinal benefits for the pharmaceutical and cosmetic industries.

PURPOSE

The purpose of this study was to assess the effectiveness of Spilanthes filicaulis leaf extract in a streptozotocin (STZ)-induced rat model and the associated signaling pathways.

METHODS

A sample of 25 male Wistar rats was randomly assigned to groups I, II, III, IV, and V. Each group included five animals, i.e., control rats, diabetic control rats, diabetic rats treated with metformin, and diabetic rats treated with 150 mg/kg/bw and 300 mg/kg/bw of the methanolic extract of S. filicaulis leaves (MESFL). Treatment was administered for 15 successive days via oral gavage. After 15 days, the rats were evaluated for fasting blood glucose (FBG), glycated hemoglobin (HbA1c), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), reduced glutathione (GSH), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (MDA), hexokinase, and glucose-6-phosphatase activities. Gene expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor gamma (PPAR-γ), kelch-like ECH-associated protein 1 (Keap1), protein tyrosine phosphatase 1B (PTP1B) and the antiapoptotic protein caspase-3 were examined.

RESULTS

MESFL was administered to diabetic rats, and changes in body weight, fasting blood glucose (FBG) and HbA1c were restored. Furthermore, in diabetic rats, S. filicaulis significantly reduced the levels of triglycerides (TGs), total cholesterol (TC), low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) and significantly increased HDL. S. filicaulis improved ALT, AST, and ALP enzyme activity in diabetic rats. MDA levels decreased considerably with increasing activity of antioxidant enzymes, such as GST, SOD, CAT and GSH, in diabetic liver rats treated with S. filicaulis. Diabetic rats treated with MESFL and metformin exhibited upregulated mRNA expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor gamma (PPAR-γ). Kelch-like ECH-associated protein 1 (Keap1) and protein tyrosine phosphatase 1B (PTP1B) mRNA expression in the liver was downregulated in diabetic rats treated with MESFL and metformin. In addition, MESFL downregulated the mRNA expression of caspase-3 in diabetic rats.

CONCLUSION

It can be concluded from the data presented in this study that MESFL exerts a protective effect on diabetic rats due to its antidiabetic, antioxidant, antihyperlipidemic and antiapoptotic effects and may be considered a treatment for T2DM.

Oleic Acid and Succinic Acid: A Potent Nutritional Supplement in Improving Hepatic Glycaemic Control in Type 2 Diabetic Sprague-Dawley Rats

Nutritional supplements are gaining traction for their effects in mitigating the impacts of various health conditions. In particular, many supplements are being proposed to reduce the impacts of type 2 diabetes (T2D), a metabolic condition that has reached global epidemic proportions. Recently, a supplement of oleic acid (OA) and succinic acid (SA; 1 : 1, w/w) was reported to improve glycaemic control in type 2 diabetic (T2D) Sprague-Dawley (S-D) rats through ameliorating insulin release and sensitivity. Here, we investigate the effects of the supplement (OA and SA) on hepatic and pancreatic function in T2D S-D rats. Eighteen (18) S-D rats were rendered diabetic and were divided into three equal groups: diabetic control, diabetic treatment, and diabetic glibenclamide. Another 12 S-D rats were obtained and served as the normal groups. The animals were treated daily with the vehicle, OA and SA (800 mg/kg body weight (bw); 1 : 1), or glibenclamide (10 mg/kg bw) which served as the positive control. The findings indicated that treatment with the supplement resulted in a 35.69 ± 4.22% reduction (p=0.006) in blood glucose levels (BGL). Analysis of hepatic enzymes depicted that the nutritional supplement reduced the activity of the gluconeogenesis enzyme, glucose-6-phosphatase (G6P) while improved the activity of catabolic enzymes such as glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK). Furthermore, the supplement attenuated oxidative stress through restoration of catalase (CAT) and superoxide dismutase (SOD), while reducing malondialdehyde (MDA) levels. Finally, the supplement showed no liver or kidney toxicity and improved the size and number of pancreatic islets of Langerhans, indicating its potential application in treating T2D. The study highlighted that a supplement of the two organic acids may be beneficial in reducing the rate of pathogenesis of type 2 diabetes. Therefore, it may offer therapeutic value as a dietary or nutritional supplement in the approach against diabetes and its complications.

Assessment of the antidiabetic potential of extract and novel phytoniosomes formulation of Tradescantia pallida leaves in the alloxan-induced diabetic mouse model

Diabetes inflicts health and economic burdens on communities and the present antidiabetic therapies have several drawbacks. Tradescantia pallida leaves have been used as a food colorant and food preservative; however, to our knowledge antidiabetic potential of the leaves of T. pallida has not been explored yet. The current study aimed to investigate the antidiabetic potential of T. pallida leaves extract and its comparison with the novel nisosome formulation of the extract. The leaves extract and phytoniosomes of T. pallida in doses of 15, 25 and 50 mg/kg were used to assess the oral glucose loaded, and alloxan-induced diabetic mice models. The biological parameters evaluated were; change in body weight, blood biochemistry, relative organ to body weight ratio and histopathology of the liver, pancreas and kidney. Results revealed that the extract 50 mg/kg and phytoniosomes 25 and 50 mg/kg remarkably reduced the blood glucose level in all hyperglycemic mice by possibly inhibiting α-amylase and α-glucosidase production. Body weight and blood biochemical parameters were considerably improved in phytoniosomes 50 mg/kg treated group. The relative body weight was similar to those of healthy mice in extract 50 mg/kg, phytoniosomes 25 mg/kg, and phytoniosomes 50 mg/kg treated groups. Histopathology showed the regeneration of cells in the CHN50 treated group. Hyphenated chromatographic analysis revealed potent metabolites, which confirmed the antidiabetic potential of the extract by inhibiting α-amylase and α-glucosidase using in silico analysis. The present data suggested that phytoniosomes have shown better antidiabetic potential than crude extract of these leaves.

Disturbed Lipid Metabolism in Diabetic Patients with Manifest Coronary Artery Disease Is Associated with Enhanced Inflammation

Background: Diabetic vasculopathy plays an important role in the pathophysiology of coronary artery disease (CAD) with oxidative stress as a strong mediator. This study aims to elucidate the underlying pathomechanisms of diabetic cardiac vasculopathy leading to coronary disease with an emphasis on the role of oxidative stress. Therefore, novel insights into antioxidant pathways might contribute to new strategies in the treatment and prevention of diabetic CAD. Methods: In 20 patients with insulin-dependent or non-insulin dependent diabetes mellitus (IDDM/NIDDM) and 39 non-diabetic (CTR) patients, myocardial markers of oxidative stress, vasoactive proteins, endothelial nitric oxide synthase (eNOS), activated phosphorylated eNOS (p-eNOS), and antioxidant enzymes, e.g., tetrahydrobiopterin generating dihydrofolate reductase (DHFR), heme oxygenase (HO-1), as well as serum markers of inflammation, e.g., E-selectin, interleukin-6 (IL-6), and lipid metabolism, e.g., high- and low-density lipoptrotein (HDL- and LDL-cholesterol) were determined in specimens of right atrial tissue and in blood samples from type 2 diabetic and non-diabetic patients undergoing coronary artery bypass graft (CABG) surgery. Results: IDDM/NIDDM increased markers of inflammation (e.g., E-selectin, p = 0.005 and IL-6, p = 0.051), decreased the phosphorylated myocardial p-eNOS (p = 0.032), upregulated the myocardial stress response protein HO-1 (p = 0.018), and enhanced the serum LDL-/HDL-cholesterol ratio (p = 0.019). However, the oxidative stress markers in the myocardium and the expression of vasoactive proteins (eNOS, DHFR) showed only marginal adverse changes in patients with IDDM/NIDDM. Conclusion: Dyslipidemia and myocardial inflammation seem to be the major determinants of diabetic CAD complications. Dysregulation in pro-oxidative enzymes might be attributable to the severity of CAD and oxidative stress levels in all included patients undergoing CABG.

Maackiain Protects the Kidneys of Type 2 Diabetic Rats via Modulating the Nrf2/HO-1 and TLR4/NF-κB/Caspase-3 Pathways

BACKGROUND

Type 2 diabetes (T2D) is aglobal health burden that accounts for about 90% of all cases of diabetes. Injury to the kidneys is aserious complication of type 2 diabetes. Maackiain, apterocarpan extracted from roots of Sophora flavescens, has been traditionally used for various disease conditions. However, nothing is known about its possible potential effect on HFD/STZ-T2D-induced nephrotoxicity.

METHODS

In this study, T2D rat model is created by high-fat diet (HFD) for 2 weeks with injection of asingle dose of streptozotocin (35mg/kg body weight). T2D rats were orally administered with maackiain (10 and 20mg/kg body weight) for 7 weeks.

RESULTS

Maackiain suppressed T2D-induced alterations in metabolic parameters, lipid profile and kidney functionality markers. By administering 10 and 20mg/kg maackiain to T2D rats, it was able to reduce lipid peroxidation while improving antioxidant levels (SOD, CAT, and GSH). Furthermore, the present study demonstrated the molecular mechanisms through which maackiain attenuated T2D-induced oxidative stress (mRNA: Nrf2, Nqo-1, Ho-1, Gclc and Gpx-1; protein: NRF2, NQO-1, HO-1 and NOX-4), inflammation (mRNA: Tlr, Myd88, IκBα, Mcp-1, Tgf-β, col4, Icam1, Vcam1 and E-selectin; Protein: TLR4, MYD88, NF-κB, IκBα, MCP-1; levels: TNF-α and MCP-1) and apoptosis (mRNA: Bcl-2, Bax, Bad, Apaf-1, Caspase-9 and Caspase-3; protein: Bcl-2, Bax, Caspase-3 and Caspase-9) mediated renal injury. Additionally, significant improvement in kidney architecture was observed after treatment of diabetic rats with 10 or 20mg/kg maackiain.

CONCLUSION

Maackiain protects the kidney by decreasing oxidative stress, inflammation, and apoptosis to preserve normal renal function in type 2 diabetes.

Diabetes Mellitus and Its Metabolic Complications: The Role of Adipose Tissues

Many approaches have been used in the effective management of type 2 diabetes mellitus. A recent paradigm shift has focused on the role of adipose tissues in the development and treatment of the disease. Brown adipose tissues (BAT) and white adipose tissues (WAT) are the two main types of adipose tissues with beige subsets more recently identified. They play key roles in communication and insulin sensitivity. However, WAT has been shown to contribute significantly to endocrine function. WAT produces hormones and cytokines, collectively called adipocytokines, such as leptin and adiponectin. These adipocytokines have been proven to vary in conditions, such as metabolic dysfunction, type 2 diabetes, or inflammation. The regulation of fat storage, energy metabolism, satiety, and insulin release are all features of adipose tissues. As such, they are indicators that may provide insights on the development of metabolic dysfunction or type 2 diabetes and can be considered routes for therapeutic considerations. The essential roles of adipocytokines vis-a-vis satiety, appetite, regulation of fat storage and energy, glucose tolerance, and insulin release, solidifies adipose tissue role in the development and pathogenesis of diabetes mellitus and the complications associated with the disease.

Proteomic analysis of oxidative stress response in human umbilical vein endothelial cells (HUVECs): role of heme oxygenase 1 (HMOX1) in hypoxanthine-induced oxidative stress in HUVECs

Background

Erectile dysfunction (ED) is a well-known complication of diabetes, affecting up to 75% of diabetic men. Although the etiology of diabetic ED is multifactorial, endothelial dysfunction is considered to be a pillar of its pathophysiology. Endothelial dysfunction is caused by the harmful effects of high glucose levels and increased oxidative stress on the endothelial cells that comprise the vascular endothelium. The aim of this study was to identify the proteomic changes caused by high glucose-induced oxidative stress and explore the role of heme oxygenase 1 (HMOX1) in it.

Methods

The cellular proteomic response to hypoxanthine-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) was analyzed by isobaric tags for relative and absolute quantitation (iTRAQ) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Differentially expressed proteins (DEPs) were analyzed through Network and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Further validation assays was performed to validate the role of HMOX1.

Results

The results showed that 66 and 76 DEPs were markedly upregulated and downregulated, respectively, for HUVECs oxidative stress. Among these proteins, we verified eight dysregulated genes by quantitative reverse transcription PCR, including nucleolin (NCL), X-ray repair cross-complementing protein 6 (XRCC6), ubiquinol-cytochrome C reductase binding protein (UQCRB), non-POU domain containing octamer binding (NONO), heme oxygenase 1 (HMOX1), nucleobindin 1 (NUCB1), DEK, and chromatin target of prmt1 (CHTOP). Further, using overexpression and genetic knockdown approaches, we found that HMOX1 was critical for the oxidative stress response in HUVECs.

Conclusions

We found that HMOX1 was closely related to the oxidative stress response induced by hypoxanthine. To the best of our knowledge, this study is the first overview of the responses of HUVECs to oxidative stress. The findings will contribute to analyses of the detailed molecular mechanisms involved in the pathogenesis of endothelial dysfunction and related molecular mechanisms in ED patients.

The effect of dried Ziziphus vulgaris on glycemic control, lipid profile, Apo-proteins and hs-CRP in patients with type 2 diabetes mellitus: A randomized controlled clinical trial

We aimed to evaluate the effect of dried Ziziphus vulgaris [Z. vulgaris] consumption on liver enzymes, blood pressure, inflammatory status, glycemic control, and lipid concentrations in type 2 diabetes patients. Seventy-six diabetic participants (aged 20-65 years) randomly assigned to intervention (n = 38) and placebo (n = 38) groups. The intervention group received 30 g/day dried Z. vulgaris for 12 weeks. At the end of the study, there was a significant reduction in the percentage change of weight, body mass index [BMI], insulin, homeostasis model assessment-insulin resistance [HOMA-IR], Apoprotein B100 [ApoB100], and high-sensitive c-reactive protein [hs-CRP] in the intervention group compared to the controls. Also, increased values of quantitative insulin check index [QUICKI] and Apoprotein A-I [ApoA-I] in Z. vulgaris group compared to the controls were observed. In conclusion, consumption of dried Z. vulgaris fruit could have beneficial effects on improving the glycemic control and reducing the cardiovascular risk factors in the diabetic patients. PRACTICAL APPLICATIONS: In the present study we found that consumption of 30 g/day dried Z. vulgaris fruit in patients with type 2 diabetes for 12 weeks has beneficial anti-inflammatory, anti-hyperglycemic, and anti-hyperlipidemic effects on type 2 diabetes mellitus [T2DM] patients compared to the control group. Thus, it seems reasonable to design a large-scale clinical trial to determine the potential adverse effects of higher doses of this fruit and identify the therapeutic doses for the complementary treatment in T2DM medication. The medication with this popular fruit as an ingredient could be easily accepted by diabetic patients and may reduce the dependency and dosage of some of the routine diabetes medications which often have some adverse side effects.

Antidiabetic, Antihyperlipidemic, Antioxidant, Anti-inflammatory Activities of Ethanolic Seed Extract of Annona reticulata L. in Streptozotocin Induced Diabetic Rats

Annona reticulata L. (Bullock's heart) is a pantropic tree commonly known as custard apple, which is used therapeutically for a variety of maladies. The present research was carried out to evaluate the possible protective effects of Annona reticulata L. (A. reticulata) ethanolic seed extract on an experimentally induced type 2 diabetes rat model. Male Albino Wistar rats were randomly divided into five groups with six animals in each group viz., control rats in group I, diabetic rats in group II, diabetic rats with 50 and 100 mg/kg/bw of ethanolic seed extract of A. reticulata in groups III and IV, respectively, and diabetic rats with metformin in group V. Treatment was given for 42 consecutive days through oral route by oro-gastric gavage. Administration of A. reticulata seed extract to diabetes rats significantly restored the alterations in the levels of body weight, food and water intake, fasting blood glucose (FBG), insulin levels, insulin sensitivity, HbA1c, HOMA-IR, islet area and insulin positive cells. Furthermore, A. reticulata significantly decreased the levels of triglycerides, cholesterol, LDL, and significantly increased the HDL in diabetic rats. A. reticulata effectively ameliorated the enzymatic (ALT, AST, ALP, GGT) and modification of histopathological changes in diabetic rats. The serum levels of the BUN, creatinine levels, uric acid, urine volume, and urinary protein were significantly declined with a significant elevation in CCr in diabetic rats treated with A. reticulata. MDA and NO levels were significantly reduced with an enhancement in SOD, CAT, and GPx antioxidant enzyme activities in the kidney, liver, and pancreas of diabetic rats treated with A. reticulata. Diabetic rats treated with A. reticulata have shown up-regulation in mRNA expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H:quinone oxidoreductase 1 (NQO1), Heme oxygenase-1 (HO-1) and protein expression level of Nrf2 with diminution in Keap1 mRNA expression level in pancreas, kidney, and liver. From the outcome of the current results, it can be inferred that seed extract of A. reticulata exhibits a protective effect in diabetic rats through its anti-diabetic, anti-hyperlipidemic, antioxidant and anti-inflammatory effects and could be considered as a promising treatment therapy in the treatment of diabetes mellitus.

Phytochemical analysis and antidiabetic potential of Elaeagnus umbellata (Thunb.) in streptozotocin-induced diabetic rats: pharmacological and computational approach

Background

The fruit of Elaeagnus umbellata has high medicinal values and is an excellent source of phytochemicals. This study was aimed to evaluate the antioxidant, enzyme inhibitory and antidiabetic potential of Elaeagnus umbellata.

Methods

The antioxidant potential of the crude extract and subfractions of E. umbellata fruit were determined using DPPH (2, 20-diphenyl-1-picrylhydrazyl) and ABTS (2, 2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid) assays. The enzyme inhibitory potentials of extracts against α-amylase and α-glucosidase enzymes were also determined. The in vivo anti-hyperglycemic effects of the extract in STZ-induced type 2 diabetes were determined using Sprague Dawley adult rats. HPLC system (Agilent 1260) was used for the identification of bioactive compounds present in extracts. Molecular docking was used to identify and compare the interaction between the compounds (active constituents) and standard inhibitor acarbose with the α-amylase and α-glucosidase active sites.

Results

The chloroform, ethyl acetate, and butanol fractions showed significant antioxidant potential with IC₅₀ values of 40, 45 and 60 μg/mL against DPPH and 57, 70 and 120 μg/mL against ABTS free radicals respectively. The chloroform and ethyl acetate were highly active against α-amylase and α-glucosidase (IC₅₀ values 58 and 200 μg/ml against α-amylase 60 and 140 μg/ml against α-glucosidase. The crude extract, chloroform, and ethyl acetate fractions were more potent in controlling the hyperglycemia in STZ-induced type 2 diabetes in rats and considerable reduction of glucose level was observed compared to the non-treated group. Furthermore, the extracts were also found useful in controlling the secondary complications associated with type 2 diabetes mellitus which was evident from the observed substantial reduction in the blood level of serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase, alkaline phosphatase, total cholesterol, low-density lipoproteins, and triglycerides. The molecular docking approach indicated the favorable inhibitory interaction between the docked compounds and the active sites of the α-amylase and α-glucosidase. All docked compounds occupied the same binding site as occupied by acarbose.

Conclusion

It was concluded that E. umbellata can be used in the treatment of type 2 diabetes and oxidative stress. The extracts were also found to be effective in relieving the secondary complications associated with type 2 diabetes.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2381-8) contains supplementary material, which is available to authorized users.

Metabolic switching in the hypoglycemic and antitumor effects of metformin on high glucose induced HepG2 cells

Metformin, a widely prescribed drug for the management of type 2 diabetes mellitus, has potential anticancer effect. Diabetes patients regularly taking metformin have been reported with decreased cancer risk and improved cancer prognosis in recent years. A cell model of high glucose induced HepG2 cells was conducted to mimic insulin resistance, and a ¹H NMR-based metabolomics approach in conjunction with molecular biology was performed to investigate the metabolic changes of high glucose induced HepG2 cells in response to different doses of metformin treatment and to study the differences and links between hypoglycemic and antitumor effects of metformin. Metformin with hypoglycemic effect rectified glucose metabolic imbalance and regulated oxidative stress, energy and amino acid metabolism. Metformin inhibited tumor cell proliferation and induced apoptosis through activation of AMPK/mTOR pathway and further influencing energy metabolism, phospholipid metabolism and glucose catabolism. The integrated metabolomics approach showed its potential in clarifying the different action on metformin treatment and understanding the pleiotropic effect of metformin.

Antihyperlipidemic and antiapoptotic potential of zingerone on alcohol induced hepatotoxicity in experimental rats

The ultimate aim of this present study was to investigate the antihyperlipidemic and antiapoptotic potential of zingerone (ZO) on alcohol induced hepatotoxicity in experimental rats. Male albino wistar rats were divided in four groups. Groups 1 and 2 rats received isocaloric glucose and dimethyl sulphoxide (2% DMSO), liver toxicity was induced in groups 3 and 4 by supplementing 30% ethanol post orally for 60 days. In addition to, groups 2 and 4 received zingerone (20 mg/kg body weight in 2% DMSO) daily during the final 30 days of the experimental period. Ethanol alone administered rats showed increased levels/activities of plasma total cholesterol (TC), triglycerides (TG), free fatty acids (FFA), phospholipids (PL), low density lipoproteins (LDL), very low density lipoproteins (VLDL), tissue TC, TG, FFA, PL, HMG-CoA reductase, phase I xenobiotic enzymes, collagen and fat accumulation, DNA damage and increased Bax, caspase-3 and caspase-9 expressions and decrease in the levels/activities of plasma high density lipoproteins (HDL), lipoprotein lipase (LPL), lecithin cholesterol acyl transferase (LCAT), phase II xenobiotic enzymes and a decreased Bcl-2 expression. Zingerone supplementation was able to counter and reverse the ethanol induced changes in all the above parameters in experimental rats. Together results portray zingerone exhibits antihyperlipidemic and antiapoptotic potential on alcohol induced hepatotoxicity.

Antidiabetic effects of Mangifera indica Kernel Flour-supplemented diet in streptozotocin-induced type 2 diabetes in rats

Our previous report showed that Mangifera indica kernel flour (MIKF) is a rich source of pharmacologically important flavonoids and phenolic acids; and that its methanolic extract inhibits some key enzymes linked to the pathology and complications of type 2 diabetes (T2D) in vitro. Hence, this study evaluated the antidiabetic effects of 10% and 20% MIKF-supplemented diets in T2D in rats. T2D was induced in rats using a high-fat diet (HFD), low-dose streptozotocin (HFD/STZ) model, by feeding the rats with HFD for 2 weeks followed by single dose administration of STZ (40 mg/kg body weight, intraperitoneally). The diabetic rats were later fed the MIKF-supplemented diets, or administered with metformin (25 mg/kg b.w.) for 21 days; the control rats were fed basal diet during this period. Intake of the MIKF-supplemented diets resulted in significant (P < 0.05) improvement in the fasting blood glucose, hepatic glycogen, glycosylated hemoglobin, lipid profile, plasma electrolytes, hepatic and pancreatic malonaldehyde, and the liver function markers of the diabetic rats, compared with the diabetic control rats. The ameliorative effect of 20% MIKF-supplemented was comparable (P > 0.05) with that of metformin administration in the diabetic rats. It is concluded that M. indica kernel flour has antidiabetic effects in T2D rats, and could therefore be a promising nutraceutical therapy for the management of T2D and its associated complications.

Weeds as Alternative Useful Medicinal Source: Mimosa pudica Linn. on Diabetes Mellitus and its Complications

Diabetes mellitus is one of the major reasons for mortality worldwide and numerous scientific studies are going on to find plausible solutions to overcome and manage diabetes and its related infirmities. Traditional medicines use medicinal plants as anti-diabetic agents and despite being a disturbing weed to farming landMimosa pudicaLinn. has a high traditional usage for various purposes including anti-diabetic complications. The objective of this article is to accumulate and organise literatures based on traditional claims and correlate those with current findings on the use ofM. pudicain the management of diabetes mellitus.M. pudicais a creeping perennial shrub which is a common weed widely distributed in Southeast Asia specially in India, Bangladesh, Malaysia, China, Philippine etc. This plant has various species of whichM. pudicais a well recognised plant of medicinal origin which has been traditionally used as folk medicine in India, Bangladesh and Philippine, Chinese, herbal and siddha medicines. It has wound healing, anti-diabetic, anti-diarrhoeal, antimicrobial, anti-cancer, anti-infections, anti-worm, anti-proliferative, anti-snake venom, anti-depressant and anxiolytic etc. activities. The objective of this article is to provide up-to-date information on the traditional and scientific studies based on this plant on the frontier of diabetes mellitus. The methodology followed was to methodically collect, organise and chart the recent advances in the use ofM. pudicain diabetes and its related complications like vascular complications, diabetic wound, hyperlipidemia etc. Various scientific studies and traditional literatures clearly support the use ofM. pudicaas an anti-diabetic agent among other uses. So far, the anti-diabetic compounds have not been isolated from this plant and this can be a good scientific study for the future anti-diabetic implications.

Symplocos cochinchinensis attenuates streptozotocin-diabetes induced pathophysiological alterations of liver, kidney, pancreas and eye lens in rats

The beneficial effects of hydroethanol extract of Symplocos cochinchinensis (SCE) has been explored against hyperglycemia associated secondary complications in streptozotocin induced diabetic rat model. The experimental groups consist of normal control (NC), diabetic control (DC), DC + metformin 100 mg kg(-1) bwd, DC + SCE 250 and DC + SCE 500. SCEs and metformin were administered daily for 21 days and sacrificed on day 22. Oral glucose tolerance test, plasma insulin, % HbA1c, urea, creatinine, aspartate aminotransferase, alanine aminotransferase, albumin, total protein etc. were analysed. Aldose reductase (AR) activity in the eye lens was also checked. On day 21, DC rats showed significantly abnormal glucose response, HOMA-IR, % HbA1c, decreased activity of antioxidant enzymes and GSH, elevated AR activity, hepatic and renal oxidative stress markers like malondialdehyde, protein carbonyls compared to NC. DC rats also exhibited increased level of plasma urea and creatinine. Treatment with SCE protected from the deleterious alterations of biochemical parameters in a dose dependent manner including histopathological alterations in pancreas. SCE 500 exhibited 46.28% of glucose lowering effect and decreased HOMA-IR (2.47), % HbA1c (6.61), lens AR activity (15.99%), and hepatic, renal oxidative stress and function markers compared to DC group. Considerable amount of liver and muscle glycogen was replenished by SCE treatment in diabetic animals. Although metformin showed better effect, the activity of SCE was very much comparable with this drug.

High glucose induces human endothelial dysfunction through an Axl-dependent mechanism

BACKGROUND

The receptor tyrosine kinase Axl and its ligand growth arrest-specific protein 6 (Gas6) are involved in the diabetic vascular disease. The aim of this study was to explore the role of Gas6/Axl system in high glucose (HG)-induced endothelial dysfunction.

METHODS

We investigated the effect of various glucose concentrations on Axl signaling in human microvascular endothelial cells (HMEC-1 s).

RESULTS

Human plasma Gas6 value inversely correlated with glucose status, endothelial markers. HG decreased Gas6/Axl expression and increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression in HMEC-1 s. HG significantly decreased HMEC-1 s cell viability and tube formation and promoted monocyte-EC adhesion. Down-regulation of Akt phosphorylation was found in HG culture. Axl transfection significantly reversed HG-induced Akt phosphorylation, VCAM-1 expression and endothelial dysfunction. We also found additive changes in Axl-shRNA-infected HMEC-1 cells in HG culture. Furthermore, Axl overexpression in HMEC-1 s significantly reversed HG-induced vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) expression. In addition, significantly lower Axl and VEGFR2 expression in arteries were found in diabetic patients as compared with non-diabetic patients.

CONCLUSIONS

This study demonstrates that HG can alter Gas6/Axl signaling and may through Akt and VEGF/VEGFR2 downstream molecules and suggests that Gas6/Axl may involve in HG-induced EC dysfunction.

Green Tea Attenuates Oxidative Stress and Downregulates the Expression of Angiotensin II AT(1) Receptor in Renal and Hepatic Tissues of Streptozotocin-Induced Diabetic Rats

This study investigates the potential of green tea to modulate oxidative stress and angiotensin II AT₁ receptor expression in renal and hepatic tissues of diabetic rats. Three groups of rats were studied after 8 weeks following diabetes induction: normal, streptozotocin-induced diabetic (diabetic control), and green-tea-treated diabetic rats. Total antioxidant, catalase, and malondialdehyde levels were assayed by standard procedures. Levels of AT₁ receptor labeling, in renal and hepatic tissues of the three rat groups, were immunohistochemically investigated using an anti-AT₁ receptor antibody. Levels of total antioxidant and catalase were significantly reduced, whereas malondialdehyde levels and AT₁ receptor labeling were significantly increased in renal and hepatic tissues of diabetic control rats compared to normal rats. Compared to diabetic control rats, total antioxidant and catalase levels were significantly increased, whereas malondialdehyde levels and AT₁ receptor labeling in the green-tea-treated diabetic group were significantly reduced throughout hepatic lobules and renal cortical and medullary vascular and tubular segments to levels comparable to those observed in normal rats. The capacity of green tea to modulate diabetes-induced oxidative stress and AT₁ receptor upregulation may be beneficial in opposing the deleterious effects of excessive angiotensin II signaling, manifested by progressive renal and hepatic tissue damage.

Effects of salvianolic scid A on plantar microcirculation and peripheral nerve function in diabetic rats

Salvianolic acid A (SalA) is the main efficacious, water-soluble constituent of Salvia miltiorrhiza Bunge. This study evaluated the effects of SalA on plantar microcirculation and peripheral nerve dysfunction in streptozotocin (STZ )-induced type 2 diabetic rats. The rats were given a high-fat and high-sucrose diet for a month followed by intraperitoneal injection of STZ (30 mg/kg). Oral administration of SalA (1 and 3mg/kg, respectively) was performed daily for 10 weeks after modeling. Diabetic rats were given a high-fat diet, while age-matched healthy rats were given a standard chow. Plantar microcirculation was measured by Laser Doppler flowmetry, and peripheral nerve function was measured with regard to pain withdrawal latency and motor nerve conduction velocity. The results show that the plantar blood perfusion and vasodilation reactivities decreased significantly, and latency of pain withdrawal and motor nerve conduction velocity rose in diabetic rats compared with the normal control group. SalA increased peripheral blood perfusion and vascular activities; improved peripheral nerve function; and decreased AGEs levels, vascular eNOS expression, and blood glucose, lipid, vWF and malondialdehyde levels in diabetic rats. The beneficial effects of SalA on plantar microcirculation and peripheral nerve function in diabetic rats might be attributed to improvements in lipid and glucose metabolism in diabetic rats, the inhibition of AGEs formation and the development of oxidative stress-related nervous and vascular damage. Based on these findings, we proposed that therapeutic use of SalA to prevent the development of diabetic foot problems.

Endothelial inflammation induced by excess glucose is associated with cytosolic glucose 6-phosphate but not increased mitochondrial respiration

AIMS/HYPOTHESIS

Exposure of endothelial cells to high glucose levels suppresses responses to insulin, including induction of endothelial nitric oxide synthase activity, through pro-inflammatory signalling via the inhibitor of nuclear factor kappaB (IkappaB)alpha-nuclear factor kappaB (NF-kappaB) pathway. In the current study, we aimed to identify metabolic responses to glucose excess that mediate endothelial cell inflammation and insulin resistance. Since endothelial cells decrease their oxygen consumption rate (OCR) in response to glucose, we hypothesised that increased mitochondrial function would not mediate these cells' response to excess substrate.

METHODS

The effects of glycolytic and mitochondrial fuels on metabolic intermediates and end-products of glycolytic and oxidative metabolism, including glucose 6-phosphate (G6P), lactate, CO(2), NAD(P)H and OCR, were measured in cultured human microvascular endothelial cells and correlated with IkappaBalpha phosphorylation.

RESULTS

In response to increases in glucose concentration from low to physiological levels (0-5 mmol/l), production of G6P, lactate, NAD(P)H and CO(2) each increased as expected, while OCR was sharply reduced. IkappaBalpha activation was detected at glucose concentrations >5 mmol/l, which was associated with parallel increases of G6P levels, whereas downstream metabolic pathways were insensitive to excess substrate.

CONCLUSIONS/INTERPRETATION

Phosphorylation of IkappaBalpha by excess glucose correlates with increased levels of the glycolytic intermediate G6P, but not with lactate generation or OCR, which are inhibited well below saturation levels at physiological glucose concentrations. These findings suggest that oxidative stress due to increased mitochondrial respiration is unlikely to mediate endothelial inflammation induced by excess glucose and suggests instead the involvement of G6P accumulation in the adverse effects of hyperglycaemia on endothelial cells.

Biological mechanisms of stroke prevention by physical activity in type 2 diabetes

The principal modifiable risk factors for stroke are hypertension, diabetes mellitus, hypercholesterolaemia, hyperhomocysteinaemia, smoking and limited physical activity. However, it is not clear whether physical inactivity is a risk factor per se, or because it predisposes to pathological conditions that are risk factors for stroke. The limited availability of effective therapeutic approaches for stroke emphasizes the crucial role of prevention of risk factors. The global burden associated with type 2 diabetes is large and continues to grow. Convincing epidemiologic data support the role of physical activity in preventing type 2 diabetes. The increasing evidence of physical activity in preventing diabetic complications, including stroke, has generated interest in the molecular basis underlying these beneficial effects. The aim of the present review is to discuss the biological mechanisms underlying the effect of physical activity in preventing stroke in type 2 diabetes.

Structure-based design of robust glucose biosensors using a Thermotoga maritima periplasmic glucose-binding protein

We report the design and engineering of a robust, reagentless fluorescent glucose biosensor based on the periplasmic glucose-binding protein obtained from Thermotoga maritima (tmGBP). The gene for this protein was cloned from genomic DNA and overexpressed in Escherichia coli, the identity of its cognate sugar was confirmed, ligand binding was studied, and the structure of its glucose complex was solved to 1.7 Angstrom resolution by X-ray crystallography. TmGBP is specific for glucose and exhibits high thermostability (midpoint of thermal denaturation is 119 +/- 1 degrees C and 144 +/- 2 degrees C in the absence and presence of 1 mM glucose, respectively). A series of fluorescent conjugates was constructed by coupling single, environmentally sensitive fluorophores to unique cysteines introduced by site-specific mutagenesis at positions predicted to be responsive to ligand-induced conformational changes based on the structure. These conjugates were screened to identify engineered tmGBPs that function as reagentless fluorescent glucose biosensors. The Y13C*Cy5 conjugate is bright, gives a large response to glucose over concentration ranges appropriate for in vivo monitoring of blood glucose levels (1-30 mM), and can be immobilized in an orientation-specific manner in microtiter plates to give a reversible response to glucose. The immobilized protein retains its response after long-term storage at room temperature.

Ketone bodies alter dinitrophenol-induced glucose uptake through AMPK inhibition and oxidative stress generation in adult cardiomyocytes

In aerobic conditions, the heart preferentially oxidizes fatty acids. However, during metabolic stress, glucose becomes the major energy source, and enhanced glucose uptake has a protective effect on heart function and cardiomyocyte survival. Thus abnormal regulation of glucose uptake may contribute to the development of cardiac disease in diabetics. Ketone bodies are often elevated in poorly controlled diabetics and are associated with increased cellular oxidative stress. Thus we sought to determine the effect of the ketone body beta-hydroxybutyrate (OHB) on cardiac glucose uptake during metabolic stress. We used 2,4-dinitrophenol (DNP), an uncoupler of the mitochondrial oxidative chain, to mimic hypoxia in cardiomyocytes. Our data demonstrated that chronic exposure to OHB provoked a concentration-dependent decrease of DNP action, resulting in 56% inhibition of DNP-mediated glucose uptake at 5 mM OHB. This was paralleled by a diminution of DNP-mediated AMP-activated protein kinase (AMPK) and p38 MAPK phosphorylation. Chronic exposure to OHB also increased reactive oxygen species (ROS) production by 1.9-fold compared with control cells. To further understand the role of ROS in OHB action, cardiomyocytes were incubated with H(2)O(2). Our results demonstrated that this treatment diminished DNP-induced glucose uptake without altering activation of the AMPK/p38 MAPK signaling pathway. Incubation with the antioxidant N-acetylcysteine partially restored DNP-mediated glucose but not AMPK/p38 MAPK activation. In conclusion, these results suggest that ketone bodies, through inhibition of the AMPK/p38 MAPK signaling pathway and ROS overproduction, regulate DNP action and thus cardiac glucose uptake. Altered glucose uptake in hyperketonemic states during metabolic stress may contribute to diabetic cardiomyopathy.

Formation of methionine sulfoxide during glycoxidation and lipoxidation of ribonuclease A

Chemical modification of proteins by reactive oxygen species affects protein structure, function and turnover during aging and chronic disease. Some of this damage is direct, for example by oxidation of amino acids in protein by peroxide or other reactive oxygen species, but autoxidation of ambient carbohydrates and lipids amplifies both the oxidative and chemical damage to protein and leads to formation of advanced glycoxidation and lipoxidation end-products (AGE/ALEs). In previous work, we have observed the oxidation of methionine during glycoxidation and lipoxidation reactions, and in the present work we set out to determine if methionine sulfoxide (MetSO) in protein was a more sensitive indicator of glycoxidative and lipoxidative damage than AGE/ALEs. We also investigated the sites of methionine oxidation in a model protein, ribonuclease A (RNase), in order to determine whether analysis of the site specificity of methionine oxidation in proteins could be used to indicate the source of the oxidative damage, i.e. carbohydrate or lipid. We describe here the development of an LC/MS/MS for quantification of methionine oxidation at specific sites in RNase during glycoxidation or lipoxidation by glucose or arachidonate, respectively. Glycoxidized and lipoxidized RNase were analyzed by tryptic digestion, followed by reversed phase HPLC and mass spectrometric analysis to quantify methionine and methionine sulfoxide containing peptides. We observed that: (1) compared to AGE/ALEs, methionine sulfoxide was a more sensitive biomarker of glycoxidative or lipoxidative damage to proteins; (2) regardless of oxidizable substrate, the relative rate of oxidation of methionine residues in RNase was Met29>Met30>Met13, with Met79 being resistant to oxidation; and (3) arachidonate produced a significantly greater yield of MetSO, compared to glucose. The methods developed here should be useful for assessing a protein's overall exposure to oxidative stress from a variety of sources in vivo.