The antidiabetic effects of cysteinyl metformin, a newly synthesized agent, in alloxan- and streptozocin-induced diabetic rats

The antioxidant, antidiabetic, and antihyperlipidemic effects of the polyphenolic extract from Salvia blancoana subsp. mesatlantica on induced diabetes in rats

Currently, several studies have demonstrated the benefits of medicinal plants in managing type 2 diabetes. In this work, we evaluated the beneficial effects of the polyphenolic extract (PESB) from Salvia blancoana subsp. mesatlantica in the management of hypercaloric-feeding and small-dose alloxan-brought type 2 diabetes in rats. We analyzed the chemical constituents of the extract, including flavones and flavonols content, to understand its biological action. The antioxidant activities were evaluated by total antioxidant action, scavenging effect of the free radical DPPH, and reducing power. The obtained results showed that the value of TFC was estimated at 31.90 ± 0.34 mgEQ/g in the PESB extract. The total antioxidant capacity was estimated at 593.51 ± 4.09 mg (EAA)/g, the value of DPPH IC50 was 7.3 ± 0.00 μg/mL, and the value of EC50 of reducing power was estimated at 6.43 ± 0.01 μg/mL. In total, 14 phenolic compounds were identified and the naringin was the most dominant (63.19%) while the vanillin was the less recorded (0.10%). Serum glucose decreased significantly (p < 0.05) in rats given PESB (100 mg/kg) after four weeks. Glibenclamide (GLB) and PESB reduced HbA1c and increased plasma insulin in diabetic rats, restoring HOMA-β and HOMA-IR levels to near-normal. Additionally, diabetic rats treated with GLB or PESB showed statistically equivalent results to those of non-diabetic rats regarding hepatic enzymes, renal and lipid markers, as well as cardiovascular indices. The weight loss was significantly lower in diabetic rats receiving a dose of PESB (100 mg/kg), and GLB compared to corresponding untreated diabetic rats (p < 0.01). PESB and GLB showed a prominent protective function in the pancreas, liver, and kidney tissues. This investigation demonstrates the capacity of extracts from leaves of S. blancoana subsp. mesatlantica to manage diabetes mellitus due to their richness in a wide range of bioactive compounds. Therefore, more investigations are required to estimate the safety of the plant use.

Artemisia herba-alba aqueous extract improves insulin sensitivity and hepatic steatosis in rodent model of fructose-induced metabolic syndrome

CONTEXT

Fructose consumption is associated with the development of obesity and metabolic syndrome (MetS) in human and animal models.

OBJECTIVE

This study investigates the ability of an aqueous extract of Artemisia herba-alba Asso (AH) to ameliorate fructose-induced MetS in Male Wistar rats.

METHODS

AH extract at doses of 100, 200 and 400 mg/kg b.w./day was administered for six weeks to MetS animals.

RESULTS

Liquid fructose (10% w/v) intake did not vary total animal body weight, whereas, it produced moderate hyperglycemia associated with metabolic and histological alterations. Treating MetS rats with AH extract improved insulin sensitivity, alleviated atherogenic dyslipidaemia and decreased lipid deposition in their hepatic tissues. Additionally, AH extract was found to raise GSH level and antioxidant enzymes (GPx, GST and CAT) activities in rat livers homogenates.

CONCLUSION

The results here reported demonstrated, for the first time, that A. herba-alba have therapeutic proprieties against fructose-induced MetS in rodent model.

Molecular docking analysis and anti-hyperglycaemic activity of Synacinn™ in streptozotocin-induced rats

Synacinn™ is a standardized polyherbal supplement formulated from Cinnamomum zeylanicum Blume, Curcuma zanthorrhiza Roxb., Syzygium polyanthum (Wight) Walp., Orthosiphon stamineus Benth. and Andrographis paniculata (Burm.f.) Nees. It is designed for the synergistic treatment of diabetes mellitus and its complications. Although the beneficial effects are yet to be verified scientifically, it is traditionally used to improve general health in patients with diabetes. This study aimed to evaluate the anti-hyperglycemic effects of Synacinn™ in a streptozotocin-induced type 1 diabetes rat model. Initially, Synacinn™ was used for in vivo acute oral toxicity tests and 14 day repeated dose toxicity tests to determine the toxicity levels. An efficacy study of Synacinn™ was carried out via the oral administration of 10, 50, 100, 250, and 250 (b.i.d.) mg kg⁻¹ doses to streptozotocin-induced diabetic rats. After 28 days, blood serum was collected to measure the fasting blood glucose, triglyceride, cholesterol, alanine aminotransferase, alkaline phosphatase, creatinine, and uric acid levels. The liver, kidney, and pancreas structures were histopathologically analyzed. In silico binding interaction studies of five phytochemicals in Synacinn™ identified via HPLC with glucokinase were performed using molecular docking analysis. The results showed that although no mortality was observed during the acute oral toxicity tests, notable damage to the liver and kidney occurred during the 14 day repeated dose testing at Synacinn™ levels of 600 mg kg⁻¹ and 2000 mg kg⁻¹. Treatment with 250 mg kg⁻¹ (b.i.d.) Synacinn™ of the streptozotocin-induced type 1 diabetic rats significantly (p < 0.05) improved the fasting blood glucose (59%), triglyceride (58%), cholesterol (47%), alanine aminotransferase (60%), alkaline phosphatase (90%), and creatinine (32%) levels. Synacinn™ also improved the relative weights of liver (35%), kidney (36%), and pancreatic (36%) tissue. Histological analysis showed improvements in the conditions of the central vein of the liver, the kidney Bowman's capsule and glomerulus, and the pancreatic islets of Langerhans. HPLC analysis of a standardized extract identified five active phytochemicals: andrographolide (17.36 mg g⁻¹), gallic acid (11.5 mg g⁻¹), curcumin (2.75 mg g⁻¹), catechin (3.9 mg g⁻¹), and rosmarinic acid (5.54 mg g⁻¹). Molecular docking studies with glucokinase showed that andrographolide yields the highest binding energy (−12.1 kcal mol⁻¹), followed by catechin (−10.2 kcal mol⁻¹), rosmarinic acid (−8.6 kcal mol⁻¹), curcumin (−7.8 kcal mol⁻¹), and gallic acid (−5.6 kcal mol⁻¹). These current findings suggest that Synacinn™ at a dose of 250 mg kg⁻¹ was non-toxic to rats. A twice-daily 250 mg kg⁻¹ dose of Synacinn™ is an effective anti-hyperglycemic agent, lowering blood glucose, triglyceride, and cholesterol levels, and assisting the recovery of organ impairment caused by streptozotocin in type 1 diabetic rats.

Synacinn™, a standardized polyherbal supplement, was shown to improve hyperglycemic conditions and related complications in STZ-induced rats.

Neurobehavioral, apoptotic, and DNA damaging effects of sub-chronic profenofos exposure on the brain tissue of Cyprinus carpio L.: Antagonistic role of Geranium essential oil

Currently, the contamination of water with different insecticides like profenofos (PFF) is a critical concern in the aquatic ecosystem. There are limited studies available on the negative impacts of PFF on common carp fish (Cyprinus carpio L.). Therefore, the existing study was designed to investigate the effect of PFF exposure (1/10 of the 96 h-LC50) on the neurobehavior, growth performance, chemical composition, oxidative status, DNA damage, apoptotic status and histological indices of the brain and gill tissues. In addition, this study seeks to detect the ability of geranium essential oil (GEO) dietary supplementation to mitigate the negative impacts of PFF. Accordingly, a total of 120 healthy fish were divided into four groups: the control group, fed on basal diet only; the other groups were fed on a basal diet supplemented with 400 mg kg^-1 GEO, basal diet and PFF in water (PFF group), and supplemented diet with GEO and PFF in water (GEO + PFF), respectively, for 60 days. The results showed that PFF significantly reduced fish growth performance, crude protein, and lipid contents. It caused several behavioral alterations including spiral movement, decreased activeness, and changes in feeding behavior. Moreover, PFF increased the DNA tail length, tail moment, and the level of 8-hydroxy-2'-deoxyguanosine. Histologically, PFF induced a wide array of circulatory, inflammatory, regressive and progressive alterations in the brain and gill tissues. PFF significantly downregulated Bcl-2 and upregulated caspase-3 immuno-expression in both organs. Further, it considerably depleted the antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. The GEO supplementation did not reach the respective control values but markedly improved most of the behavioral, physical, biochemical, oxidative, apoptotic, and inflammatory markers, altered by PFF exposure. It also protected the gill and brain tissues from the branchial and encephalopathic effects of PFF. These findings suggest that GEO dietary supplements could be advantageous for mitigating PFF negative impacts and presenting a promising feed additive for common carp in aquaculture.

Metformin Ameliorates Oxidative Stress Induced by Diabetes Mellitus and Hepatocellular Carcinoma in Rats

Background

Several studies have found an association between Diabetes mellitus (DM) and an increased risk for hepatocellular carcinoma (HCC). Evidence suggests that Metformin (Met) may have a therapeutic and protective effect against both DM and HCC. Therefore, the aim of this study was to evaluate the antioxidant effect of Met against DM and HCC-induced oxidative stress in rat model.

Methods

Forty-two male albino rats were randomly divided into six groups. Group 1 (Gp1) was the control group, Gp2 received an intraperitoneal (i.p.) injection with streptozotocin (STZ), Gp3 was injected i.p. with diethyl nitrosamine (DEN), Gp4 received an oral administration of Met, Gp5 and Gp6 received the same injections as Gp2 and Gp3, respectively, then received an additional injection of Met. Oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and malondialdehyde (MDA), were examined. Furthermore, biochemical parameters including liver function tests were assessed. Histopathological and immunohistochemical alterations of the liver were also examined.

Results

Our results demonstrate that Gp2 and Gp3 had significant signs of liver dysfunction and had elevated levels of MDA and reduced levels of SOD, CAT, and GSH. Additionally, Gp2 and Gp3 showed significant alterations in the liver architecture shown by high PCNA and caspase-3 expression. In the Gp5 and Gp6, treatment with Met showed an improvement in liver function, oxidative stress biomarkers, and reduced histopathological changes in hepatocytes.

Conclusion

This study offers insight into the potential for Metformin as a novel therapeutic against the oxidative stress induced by DM or HCC.

Metformin as a protective agent against natural or chemical toxicities: a comprehensive review on drug repositioning

BACKGROUND

Metformin is the first prescribed drug for hyperglycemia in type 2 diabetes mellitus. Mainly by activating AMPK pathway, this drug exerts various functions that among them protective effects are of the interest.

PURPOSE

Herein, we aimed to gather data about the protective impacts of metformin against various natural or chemical toxicities.

RESULTS

An extensive search among PubMed, Scopus, and Google Scholar was conducted by keywords related to protection, toxicity, natural and chemical toxins and, metformin. Our literature review showed metformin alongside its anti-hyperglycemic effect has a wide range of anti-toxic effects against anti-tumour and routine drugs, natural and chemical toxins, herbicides and, heavy metals.

CONCLUSION

It is evident that metformin is a potent drug against the toxicity of a broad spectrum of natural, chemical toxic agents which is proved by a vast number of studies. Metformin mainly through AMPK axis can protect different organs against toxicities. Moreover, metformin preserves DNA integrity and can be an option for adjuvant therapy to ameliorate side effect of other therapeutics.

Hyperglycemia (high-glucose) decreases L-cysteine and glutathione levels in cultured monocytes and blood of Zucker diabetic rats

L-Cysteine (LC) is an essential precursor of GSH biosynthesis. GSH is a major physiological antioxidant, and its depletion increases oxidative stress. Diabetes is associated with lower blood levels of LC and GSH. The mechanisms leading to a decrease in LC in diabetes are not entirely known. This study reports a significant decrease in LC in human monocytes exposed to high glucose (HG) concentrations as well as in the blood of type 2 diabetic rats. Thus, a significant decrease in the level of LC in response to exposure to HG supports the assertion that uncontrolled hyperglycemia contributes to a reduction of blood levels of LC and GSH seen in diabetic patients. Increased requirement of LC to replace GSH needed to scavenge excess ROS generated by hyperglycemia can result in lower levels of LC and GSH. Animal and human studies report that LC supplementation improves GSH biosynthesis and is beneficial in lowering oxidative stress and insulin resistance. This suggests that hyperglycemia has a direct role in the impairment of LC and GSH homeostasis in diabetes.

Narrative review of the effects of antidiabetic drugs on albuminuria

Diabetes mellitus is the most prevalent metabolic disorder worldwide. Glycemic control is the main focus of antidiabetic therapy. However, there are data suggesting that some antidiabetic drugs may have intrinsic beneficial renal effects and protect against the development and progression of albuminuria, thus minimizing the risk of diabetic nephropathy. These pharmacological agents can suppress upstream molecular pathways involved in the pathophysiology of diabetes-induced renal dysfunction such as oxidative stress, inflammatory responses, and apoptosis. In this narrative review, the pathophysiology of albuminuria in patients with diabetic nephropathy is discussed. Furthermore, the renoprotective effects of antidiabetic drugs, focusing on albuminuria, are reviewed.

Antidiabetic and antihyperlipidemic potential of ethanol extract of Salacia lehmbachii stem bark in alloxan-induced diabetic rats

Background Salacial lehmbachii stem bark is used traditionally for the treatment of diabetes mellitus and its associated complications. Treatment of diabetes is necessary to reduce these complications. Methods In this study, the antidiabetic and antihyperlipidemic potential of S. lehmbachii ethanol stem bark extract was evaluated in alloxan-induced diabetic rats at a dose of 100 mg/kg, 200 mg/kg, and 400 mg/kg p.o. daily for 21 days. Blood glucose levels, serum total cholesterol (TC), triglycerides (TG), high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL) were assessed in the animals. Results Treatment of alloxan-induced diabetic rats with S. lehmbachii stem bark extract showed significant (p<0.01) reduction in blood glucose levels when compared with diabetic control. The elevated levels of serum cholesterol, triglycerides, LDL, and VLDL were significantly (p<0.01) reduced by S. lehmbachii stem bark extract, while the level of HDL significantly (p<0.01) increased. Conclusions The results obtained suggest that S. lehmbachii stem bark extract has the potential to treat diabetes condition and hyperlipidemic disorders.

Investigation of the Role of a Supplementation with Taurine on the Effects of Hypoglycemic-Hypotensive Therapy Against Diabetes-Induced Nephrotoxicity in Rats

This study has examined the role of supplementing a treatment of diabetic rats with captopril (CAP), metformin (MET) or CAP-MET with the antioxidant amino acid taurine (TAU) on biochemical indices of diabetes-induced metabolic changes, oxidative stress and nephropathy. To this end, groups of 6 male Sprague-Dawley rats (250-375 g) were made diabetic with a single, 60 mg/kg, intraperitoneal dose of streptozotocin (STZ) in 10 mM citrate buffer pH 4.5 and, after 14 days, treated daily for up to 42 days with either a single oral dose of CAP (0.15 mM/kg), MET (2.4 mM/kg) or TAU (2.4 mM/kg), or with a binary or tertiary combination of these agents. Rats receiving only 10 mM citrate buffer pH 4.5 or only STZ served as negative and positive controls, respectively. All rats were sacrificed by decapitation on day 57 and their blood and kidneys collected. In addition, a 24 h urine sample was collected starting on day 56. Compared to normal rats, untreated diabetic ones exhibited frank hyperglycemia (+313%), hypoinsulinemia (-76%) and elevation of the glycated hemoglobin value (HbA1c, +207%). Also they showed increased plasma levels of Na+ (+35%), K+ (+56%), creatinine (+232%), urea nitrogen (+158%), total protein (-53%) and transforming growth factor-β1 (TGF-β1, 12.4-fold) values. These changes were accompanied by increases in the renal levels of malondialdehyde (MDA, +42%), by decreases in the renal glutathione redox state (-71%), and activities of catalase (-70%), glutathione peroxidase (-71%) and superoxide dismutase (-85%), and by moderate decreases of the urine Na+ (-33%) and K+ (-39%) values. Following monotherapy, MET generally showed a greater attenuating effect than CAP or TAU on the changes in circulating glucose, insulin and HbA1c levels, urine total protein, and renal SOD activity; and CAP appeared more potent than TAU and MET, in that order, in antagonizing the changes in plasma creatinine and urea nitrogen levels. On the other hand, TAU generally provided a greater protection against changes in glutathione redox state and in CAT and GPx activities, with other actions falling in potency between those of CAP and MET. Adding TAU to a treatment with CAP, but not to one with MET, led to an increase in protective action relative to a treatment with drug alone. On the other hand, the actions of CAP-MET, which were about equipotent with those of MET, became enhanced in the presence of TAU, particularly against the changes of the glutathione redox state and activities of antioxidant enzymes. In short, the present results suggest that the addition of TAU to a treatment of diabetes with CAP or CAP-MET, and sometimes to one with MET, will lead to a gain in protective potency against changes in indices of glucose metabolism and of renal functional impairment and oxidative stress.

Hydroxyapatite calvaria graft repair in experimental diabetes mellitus in rats

Among the systemic conditions that impact negatively on the planning and execution of surgical procedures, diabetes mellitus (DM) is the primary clinical condition responsible for complications. This study investigated bone formation in critical defects surgically filled with hydroxyapatite (HA) in diabetic rats. A descriptive, randomized sample and blinded analysis were conducted to test bone regeneration in critical bone defects surgically performed in rat calvaria. Twenty adult male Wistar rats were randomly divided into two groups: control, normoglycemic animals (CG); and test, streptozotocin-induced hyperglycemic animals (TG). A circular bone defect was filled with HA and maintained subperiosteally. The clinical parameters evaluated were body weight, water and food intake, fasting blood glucose, and bone alkaline phosphatase. Bone-grafted area samples were submitted for histomorphometric and stereological analysis. The TG showed a significantly higher rate of new bone formation compared with the CG, sacrificed 15 days after surgery (p < 0.0001). However, at the end of the study, there was no significant difference in the amount of bone formed between groups (p = 0.077). In parallel, with the increase in osteoblastic activity observed in the TG by the measurement of systemic bone alkaline phosphatase (p = 0.016), the analysis of polarized microscopy and stereology demonstrated a lower level collagen maturation and mineralization in the TG. Quantitatively, the TG showed significantly better results for bone gain in the first 15 days. Qualitative assessments, however, showed fewer collagen fibers and bone maturation in the TG compared with the CG both at 15 and 45 days. Therefore, the postoperative evaluation of bone grafts with HA in hyperglycemic situations should consider the systemic and local effects of this condition on the quality of bone repair, rather than identifying the filling or stability of the grafted area after the process. We conclude that clinically detectable bone repair in diabetic animal models submitted to hydroxyapatite grafts may be satisfactory in the early stages. However, hyperglycemia compromises the quality of the newly formed bone and the collagen cross-linking involved in this process.

Curcumin alleviates liver oxidative stress in type 1 diabetic rats

The aim of the present study was to determine the effects of curcumin on antioxidants using a rat model of type 1 diabetes. Seven-week-old male Sprague-Dawley rats were injected with Streptozotocin (STZ) intraperitoneally to induce this model, and then treated with 1.0% curcumin (weight ratio) mixed in their diet for 21 days. The present study included three groups: Control group (NC), diabetic rat model group (DC) and a curcumin treated group (Diab-Cur). The results demonstrated that curcumin treatment markedly decreased the blood glucose levels, plasma malondialdehyde concentration and plasma activity of glutathione peroxidase (GSH-Px) and catalase (CAT); however, it increased the plasma superoxide dismutase (SOD) and insulin levels. Curcumin treatment increased the expression of the CAT, GSH-Px, HO-1 and norvegicus NAD(P)H quinone dehydrogenase 1, and decreased the SOD1 expression, which, led to a diminished oxidative stress status. In addition, curcumin treatment significantly increased the protein expression of Keap1 in the Diab-Cur group when compared with the DC group, decreased cytosolic concentrations of Nrf2 while increasing nuclear accumulation of Nrf2. The results provide evidence that oxidative stress in the STZ-induced diabetic rat model may be attenuated by curcumin via the activation of the Keap1-Nrf2-ARE signaling pathway, as evidenced by a decrease in the blood glucose concentration and an increase in the transcription of several antioxidant genes.

Evaluating Pharmacological Effects of Two Major Components of Shuangdan Oral Liquid: Role of Danshensu and Paeonol in Diabetic Nephropathy Rat

Shuangdan oral liquid (SDO) containing radix Salviae miltiorrhizae (Chinese name Danshen) and cortex moutan (Chinese name Mudanpi) is a traditional Chinese medicine using for treating vascular diseases. Danshensu (DSS) is a main effective monomer composition derived from radix Salviae miltiorrhizae and paeonol (Pae) from cortex moutan. Although the two herbs are widely used in traditional Chinese medicine, the pharmacological functions of their active compositions were not reported. Therefore, the research of DSS and Pae in mechanisms and pharmacodynamics interaction can provide scientific evidence to support clinical application. The diabetic nephropathy (DN) rats which were induced by streptozotocin (STZ) were treated with SDO, DSS, Pae, and DSS+Pae for eight weeks. The positive effects on DN animal models were investigated by detection of physiological and biochemical indexes and oxidative stress markers, within five treatments: SDO, DSS, Pae, DSS+Pae and insulin group. Compared with the model group, the DSS+Pae group improved the renal function, blood lipid metabolism and blood viscosity, increased the vitality of T-SOD or T-AOC and decreased the level of MDA or NO after the treatment. The study was successfully showed that the DSS+Pae group could delay the process of DN, especially in the renal injury part of histopathology changes. Our results suggest that the co-administration of DSS and Pae significantly may play a protective role in DN rats through decreasing the oxidative stress and improving the blood lipid metabolism mechanisms.

L-Cysteine supplementation increases adiponectin synthesis and secretion, and GLUT4 and glucose utilization by upregulating disulfide bond A-like protein expression mediated by MCP-1 inhibition in 3T3-L1 adipocytes exposed to high glucose

Adiponectin is an anti-diabetic and anti-atherogenic adipokine; its plasma levels are decreased in obesity, insulin resistance, and type 2 diabetes. An adiponectin-interacting protein named disulfide bond A-like protein (DsbA-L) plays an important role in the assembly of adiponectin. This study examined the hypothesis that L-cysteine (LC) regulates glucose homeostasis through the DsbA-L upregulation and synthesis and secretion of adiponectin in diabetes. 3T3L1 adipocytes were treated with LC (250 and 500 µM, 2 h) and high glucose (HG, 25 mM, 20 h). Results showed that LC supplementation significantly (p < 0.05) upregulated the DsbA-L, adiponectin, and GLUT-4 protein expression and glucose utilization in HG-treated adipocytes. LC supplementation significantly (p < 0.05) promoted the secretion of total and HMW adiponectin secretion in HG-treated adipocytes. In addition, LC significantly (p < 0.05) decreased ROS production and MCP-1 secretion in HG-treated cells. We further investigated whether MCP-1 has any role of LC on DsbA-L expression and adiponectin levels in 3T3-L1 cells. Treatment with LC prevented the decrease in DsbA-L, adiponectin, and GLUT-4 expression in 3T3L1 adipocyte cells exposed to MCP-1. Thus, this study demonstrates that DsbA-L and adiponectin upregulation mediates the beneficial effects of LC on glucose utilization by inhibiting MCP-1 secretion in adipocytes and provides a novel mechanism by which LC supplementation can improve insulin sensitivity in diabetes.

Changes in protein and gene expression of angiotensin II receptors (AT1 and AT2) in aorta of diabetic and hypertensive rats

Diabetes and hypertension have been associated with cardiovascular diseases and stroke. Some reports have related the coexistence of hypertension and diabetes with increase in the risk of developing vascular complications. Recently some studies have shown results suggesting that in the early stages of diabetes and hypertension exist a reduced functional response to vasopressor agents like angiotensin II (Ang II), which plays an important role in blood pressure regulation mechanism through the activation of its AT1 and AT2 receptors. For that reason, the aim of this work was to study the gene and protein expression of AT1 and AT2 receptors in aorta of diabetic SHR and WKY rats. Diabetes was induced by the administration of streptozotocin (60 mg/kg i.p.). After 4 weeks of the onset of diabetes, the protein expression was obtained by western blot and the mRNA expression by RT-PCR. Our results showed that the hypertensive rats have a higher mRNA and protein expression of AT1 receptors than normotensive rats while the AT2 expression remained unchanged. On the other hand, the combination of diabetes and hypertension increased the mRNA and protein expression of AT1 and AT2 receptors significantly. In conclusion, our results suggest that diabetes with hypertension modifies the mRNA and protein expression of AT1 and AT2 receptors. However, the overexpression of AT2 could be associated with the reduction in the response to Ang II in the early stage of diabetes.

Rehmannia glutinosa (Gaertn.) DC. polysaccharide ameliorates hyperglycemia, hyperlipemia and vascular inflammation in streptozotocin-induced diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Rehmannia glutinosa (Gaertn.) DC. (RG) has been widely used as traditional Chinese herbal medicine for treatment of diabetes and its complications. The polysaccharide fraction of RG has been proposed to possess hypoglycemic effect by intraperitoneal administration, however, the mechanisms responsible for the hypoglycemic effect of RG polysaccharide (RGP) remain poorly understood. Here we studied the anti-hyperglycemic and anti-hyperlipidemic effect of oral administration of a purified RGP and its underlying mechanisms in streptozotocin (STZ)-induced diabetic mice.

MATERIALS AND METHODS

The preliminary structure of RGP was determined by GC and FT-IR. Mice were injected with STZ to induce type 1 diabetes. RGP at doses of 20, 40 and 80 mg/kg/day was orally administered to mice for 4 weeks, and metformin was used as positive control. After 4 weeks, the blood biochemical parameters, the pancreatic insulin contents, in vitro insulin secretion, the hepatic glycogen contents and mRNA expression of phosphoenolpyruvate carboxyl kinase (PEPCK) were assayed.

RESULTS

RGP was composed of rhamnose, arabinose, mannose, glucose and galactose in the molar ratio of 1.00:1.26:0.73:16.45:30.40 with the average molecular weight of 63.5 kDa. RGP administration significantly decreased the blood levels of glucose, total cholesterol, triglycerides, low density lipoprotein-cholesterol, and increased the blood levels of high density lipoprotein-cholesterol and insulin in diabetic mice, concurrent with increases in body weights and pancreatic insulin contents. The in vitro study revealed that RGP significantly enhanced both basal and glucose-stimulated insulin secretions, as well as islet insulin contents in the pancreatic islets of diabetic mice. Moreover, RGP reversed the increased mRNA expression of PEPCK and the reduced glycogen contents in the liver of diabetic mice. Furthermore, RGP exhibited potent anti-inflammatory and anti-oxidative activities, as evidenced by the decreased blood levels of TNF-α, IL-6, monocyte chemoattractant protein-1, MDA, and also the elevated blood levels of SOD and GPx activities in diabetic mice.

CONCLUSIONS

Taken together, RGP can effectively ameliorate hyperglycemia, hyperlipemia, vascular inflammation and oxidative stress in STZ-induced diabetic mice, and thus may be a potential therapeutic option for type 1 diabetes.

Vitamin D and L-cysteine levels correlate positively with GSH and negatively with insulin resistance levels in the blood of type 2 diabetic patients

Background/Objectives:

Vitamin D, L-cysteine (LC) and glutathione (GSH) levels are lower in the blood of diabetic patients. This study examined the hypothesis that the levels of vitamin D and LC correlate with those of GSH in the blood of type 2 diabetic patients (T2D), and that vitamin D and LC upregulate glutamate–cysteine ligase (GCLC), which catalyzes GSH biosynthesis, in cultured monocytes.

Subjects/Methods:

Fasting blood was obtained after written informed consent from T2D (n=79) and healthy controls (n=22). U937 monocytes were pretreated with 1,25 (OH)₂ vitamin D (0–25 nM) or LC (0–500 μM) for 24 h and then exposed to control or high glucose (25 mM) for 4 h.

Results:

Plasma levels of vitamin D, LC, GSH and GCLC protein were significantly lower in T2D versus those in age-matched healthy controls. Multiple linear regression analyses and adjustment for body weight showed a significant positive correlation between plasma levels of vitamin D (r=0.26, P=0.05) and LC (r=0.81, P=0.001) and that of GSH, and between LC and vitamin D (r=0.27, P=0.045) levels. Plasma levels of GSH (r=−0.34, P=0.01) and LC (r=−0.33, r=0.01) showed a negative correlation with triglyceride levels. Vitamin D correlated inversely with HbA_1C (−0.30, P=0.01) and homeostatic model assessment insulin resistance (r=−0.31, P=0.03), which showed a significant positive correlation with triglycerides (r=0.44, P=0.001) in T2D. Cell culture studies demonstrate that supplementation with vitamin D and LC significantly increased GCLC expression and GSH formation in control and high-glucose-treated monocytes.

Conclusions:

This study suggests a positive relationship between the concentrations of the micronutrients vitamin D and LC and that of GSH. Some of the beneficial effects of vitamin D and LC supplementation may be mediated by an increase in the levels of GSH and a decrease in triglyceride levels in T2D patients.

Antidiabetic and antihyperlipidemic effects of an ethanolic extract of the whole plant of Tridax procumbens (Linn.) in streptozotocin-induced diabetic rats

Objective:

To study the antidiabetic and antihyperlipidemic effects of an ethanolic extract of the whole plant of Tridax procumbens (Asteraceae) in streptozotocin-induced diabetic rats.

Materials and Methods:

The whole plant of T. procumbens was collected in different regions of Madurai districts, Tamil Nadu. The air dried whole plant of T. procumbens was extracted with ethanol (95%) in a Soxhlet apparatus for 72 h. Diabetes was induced in male Wistar rats by streptozotocin (50 mg/jk, i.p.) and nicotinamide (120 mg/kg, i.p) injection. The dry mass of the extract was used for preliminary phytochemical and pharmacological analysis. Diabetic rats were treated with glibenclamide (0.25 mg/kg, p.o.) or T. procumbens extract (250 and 500 mg/k, p.o.) for 21 consecutive days. The blood samples were collected at regular intervals to access hypoglycemic effect of an ethanolic extract of the whole plant of T. procumbens. At the end of the experiment, serum lipid profile and liver enzymes levels were analyzed for all the experimental animals and compared with diabetic control.

Results:

The preliminary phytochemical analysis of an ethanolic extract of the whole plant of T. procumbens indicated the presence of alkaloids, tannins, flavonoids, saponins, and phenolic compounds. The ethanolic extract of the whole plant of T. procumbens at 250 and 500 mg/kg has significant antidiabetic and antihyperlipidemic activities. The diabetic control animals exhibited a significant decrease in body weight compared with control animals. T. procumbens inhibited streptozotocin-induced weight loss and significantly alter the lipid levels.

Conclusion:

The ethanolic extract of the whole plant of T. procumbens showed significant antidiabetic and antihyperlipidemic activities against streptozotocin-induced diabetes in rats.

The role of antioxidants and other agents in alleviating hyperglycemia mediated oxidative stress and injury in liver

Several antioxidants and agents having similar antioxidant effects are known to exert beneficial effects in ameliorating the injurious effects of hyperglycemia on liver in different diabetic in vitro and in vivo models. The review deals with some of the agents which have been shown to exert protective effects on liver against hyperglycemic insult and the various mechanisms involved. The different classes of agents which protect the diabetic liver or decrease the severity of hyperglycemia mediated injury include flavonoids, catechins, and other polyphenolic compounds, curcumin and its derivatives, certain vitamins, hormones and drugs, trace elements, prototypical antioxidants and amino acids. Some of the pronounced changes mediated by the antioxidants in liver exposed to hyperglycemia include decreased oxidative stress, and alterations in carbohydrate and lipid metabolism. Other mechanisms through which the agents ameliorate hyperglycemia mediated liver injury include decrease in oxidative DNA and protein damage, restoration of mitochondrial structural and functional integrity, decrease in inflammation and improved insulin signaling. Thus, antioxidants may prove to be an important mode of defense in maintaining normal hepatic functions in diabetes.

Antidiabetic, antihyperlipidemic and antioxidant activities of a novel proteoglycan from ganoderma lucidum fruiting bodies on db/db mice and the possible mechanism

Previously, we screened a proteoglycan for anti-hyperglycemic, named FYGL, from Ganoderma Lucidum. For further research of the antidiabetic mechanisms of FYGL in vivo, the glucose homeostasis, activities of insulin-sensitive enzymes, glucose transporter expression and pancreatic function were analyzed using db/db mice as diabetic models in the present work. FYGL not only lead to a reduction in glycated hemoglobin level, but also an increase in insulin and C-peptide level, whereas a decrease in glucagons level and showed a potential for the remediation of pancreatic islets. FYGL also increased the glucokinase activities, and simultaneously lowered the phosphoenol pyruvate carboxykinase activities, accompanied by a reduction in the expression of hepatic glucose transporter protein 2, while the expression of adipose and skeletal glucose transporter protein 4 was increased. Moreover, the antioxidant enzyme activities were also increased by FYGL treatment. Thus, FYGL was an effective antidiabetic agent by enhancing insulin secretion and decreasing hepatic glucose output along with increase of adipose and skeletal muscle glucose disposal in the late stage of diabetes. Furthermore, FYGL is beneficial against oxidative stress, thereby being helpful in preventing the diabetic complications.

Antioxidant potential of zinc-flavonol complex studied in streptozotocin-diabetic rats

BACKGROUND

Diabetic oxidative stress coexists with a reduction in the antioxidant status, which can further increase the deleterious effects of free radicals. Zinc is an essential trace element with significant antidiabetic activity. However, the acceptance of zinc compounds as promising therapeutic antidiabetic agents has been slowed due to concerns regarding chronic toxicity. Recently, we have designed, synthesized and characterized a novel zinc-flavonol complex and evaluated its antidiabetic efficacy in streptozotocin (STZ)-diabetic rats. The aim of the present study was to evaluate the role of the zinc-flavonol complex in the antioxidant status of diabetic rats.

METHODS

Diabetes was induced in rats by i.p. injection of STZ. Diabetic rats were then treated with the zinc-flavonol complex (5 mg/kg, p.o.) for 30 days. The extent of oxidative stress was assessed by determining lipid peroxide levels, pancreatic tissue antioxidant enzyme activities and plasma concentrations of non-enzymatic antioxidants. In addition, nuclear levels of nuclear factor (NF)-κB p65, pancreatic nitric oxide (NO), and plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were determined. Pancreatic tissues were examined histologically.

RESULTS

Oral treatment with the zinc-flavonol complex significantly improved antioxidant levels and alleviated levels of oxidative stress markers. Furthermore, significant increases were seen in NF-κB p65, NO, TNF-α, IL-1β and IL-6 levels. Histological observations revealed that the zinc-flavonol complex effectively protects pancreatic β-cells against oxidative damage.

CONCLUSION

  The results of the present study indicate that the zinc-flavonol complex has an antioxidative and anti-inflammatory role in the diabetic milieu.

The role of apurinic/apyrimidinic endonuclease on the progression of streptozotocin-induced diabetic nephropathy in rats

Apurinic/apyrimidinic endonuclease (APE) acts as a regulator of p53 or vice versa in the cellular response to oxidative stress. Since oxidative stress-induced apoptosis is suggested in the pathophysiology of diabetic nephropathy, we proposed that APE may have a feasible role in the progression of diabetic complications. We investigated the interrelationship between APE and p53 in streptozotocin-induced diabetic rat kidneys. Variable parameters on kidneys were checked 12 weeks after streptozotocin administration with or without chitosan oligosaccharide (COS) treatment. Streptozotocin administration caused changes as seen in early diabetic nephropathy with increased kidney size, increased p53, decreased APE, and increased cleaved caspase-3. COS was not suspected as being detrimental to renal measurements, and caused the augmentation of APE after streptozotocin administration. The augmented APE, in association with increased p53, suppressed cleaved caspase-3. 8-OHdG was mainly immunolocalized in the distal tubules, but also in the proximal tubules after streptozotocin administration without COS treatment, while APE was observed in proximal tubules in all groups. These results suggested that p53-dependent apoptosis resulting in suppressed APE might be an underlying mechanism of streptozotocin-induced nephropathy.

Hesperidin and naringin attenuate hyperglycemia-mediated oxidative stress and proinflammatory cytokine production in high fat fed/streptozotocin-induced type 2 diabetic rats

Abnormal regulation of glucose and impaired carbohydrate utilization that result from a defective or deficient insulin are the key pathogenic events in type 2 diabetes mellitus (T2DM). The present study was hypothesized to investigate the beneficial effects of hesperidin and naringin on hyperglycemia-induced oxidative damage in HFD/STZ-induced diabetic rats. Diabetes was induced by feeding rats with an HFD for 2 weeks followed by an intraperitoneal injection of STZ (35 mg/kg body weight). An oral dose of 50mg/kg hesperidin or naringin was daily given for 4 weeks after diabetes induction. At the end of the experimental period, blood was obtained from jugular vein and livers were rapidly excised and homogenized for biochemical assays. In the diabetic control group, levels of glucose, glycosylated hemoglobin (HbA1c%), MDA, NO, TNF-α and IL-6 were significantly increased, while serum insulin, GSH, vitamin C, and vitamin E levels were decreased. Both hesperidin and naringin administration significantly reversed these alterations. Moreover, supplementation with either compound significantly ameliorated serum and liver MDA, NO and glutathione, and liver antioxidant enzymes. Although detailed studies are required for the evaluation of the exact mechanism of the ameliorative effects of hesperidin and naringin against diabetic complications, these preliminary experimental findings demonstrate that both hesperidin and naringin exhibit antidiabetic effects in a rat model of T2DM by potentiating the antioxidant defense system and suppressing proinflammatory cytokine production.

Assessment of antidiabetogenic potential of fermented soybean extracts in streptozotocin-induced diabetic rat

Most of the available drugs for the treatment of diabetes mellitus (DM) produce detrimental side effects, which has prompted an ongoing search for plant with the antidiabetic potential. The present study investigated the effect of soybean extracts fermented with Bacillus subtilis MORI, fermented soybean extracts (BTD-1) was investigated in streptozotocin (STZ)-induced diabetic rats. The possible effects of BTD-1 against hyperglycemia and free radical-mediated oxidative stress was investigated by assaying the plasma glucose level and the activity of enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). A significant increase in the levels of both plasma glucose and reactive oxygen species (ROS) was observed in the diabetic rats when compared to normal control group. After administration of BTD-1 (500 and 1000 mg/kg/day), the elevated plasma glucose level was significantly reduced while the plasma insulin level and the activities of SOD, GSH-Px, CAT and MDA were significantly increased. The results suggest that administration of BTD-1 can inhibit hyperglycemia and free radical-mediated oxidative stress. The administration of BTD-1 also inhibited the contractile response by norepinephrine (10(-10)-10(-5) M) in the presence of endothelium, and caused significant relaxation by carbachol (10(-8)-10(-5) M) in rat aorta. These findings indicate that BTD-1 improves vascular functions on STZ-induced diabetic rats. Therefore, subchronic administration of BTD-1 could prevent the functional changes in vascular reactivity in STZ-induced diabetic rats. The collective findings support that administration of BTD-1 may prevent some diabetes-related changes in vascular reactivity directly and/or indirectly due to its hypoglycaemic effect and inhibition of production of ROS.

Renal podocyte injury in a rat model of type 2 diabetes is prevented by metformin

Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Metformin, an oral hypoglycemic drug, possesses antioxidant effects. The aim of this paper is to investigate the protective effects of metformin on the injury of renal podocytes in spontaneously diabetic Torii (SDT) rats, a new model for nonobese type 2 diabetes. Metformin (350 mg/kg/day) was given to SDT rats for 17 weeks. Blood glucose, glycated haemoglobin (HbA1c), and albuminuria were examined. Kidney histopathology, renal 8-hydroxydeoxyguanosine (8-OHdG) levels and apoptosis were examined. In 43-week-old SDT rats, severe hyperglycemia was developed, and albuminuria was markedly increased. Diabetes induced significant alterations in renal glomerular structure. In addition, urinary and renal 8-OHdG levels were highly increased, and podocyte loss was shown through application of the TUNEL and synaptopodin staining. However, treatment of SDT rats with metformin restored all these renal changes. Our data suggested that diabetes-induced podocyte loss in diabetic nephropathy could be suppressed by the antidiabetes drug, metformin, through the repression of oxidative injury.

L-cysteine supplementation as an adjuvant therapy for type-2 diabetes

Diabetes remains a major public health issue. According to the American Diabetes Association, 23.5 million, or 10.7% of people in the USA aged 20 years and older, have diabetes. Type-2 diabetes is treated both by controlling the diet and with oral hypoglycemic drugs. However, for many patients, achieving a tight control of glucose is difficult with current regimens. This chapter discusses a relatively low-cost dietary supplement that could be used as an adjuvant therapy for type-2 diabetes. A review of the literature indicates that cysteine-rich whey protein improves glucose metabolism in diabetic animals and type-2 diabetic patients. Similarly, in animal studies, improvement in glucose metabolism is observed after supplementation with L-cysteine, or molecules containing a cysteine moiety. This chapter discusses the biochemical mechanisms by which L-cysteine can upregulate the insulin-dependent signaling cascades of glucose metabolism. Further studies are needed to examine whether clinical interventions using L-cysteine as an adjuvant therapy indeed help to control glycemia and vascular inflammation in the diabetic patient population.

Hypoglycemic and antioxidant effects of leaf essential oil of Pelargonium graveolens L'Hér. in alloxan induced diabetic rats

Background

Rose-scented geranium (Pelargonium graveolens L’Hér.), which is used in traditional Tunisian folk medicine for the treatment of hyperglycaemia, is widely known as one of the medicinal herbs with the highest antioxidant activity. The present paper is conducted to test the hypoglycemic and antioxidative activities of the leaf essential oil of P. graveolens.

Methods

The essential oil P. graveolens was administered daily and orally to the rats at two doses of 75 mg/kg and 150 mg/kg body weight (b.w.) for 30 days. The chemical composition of P. graveolens essential oil, body weight, serum glucose, hepatic glycogen, thiobarbituric acid-reactive substances (TBARS), the components of hepatic, and renal and serum antioxidant systems were evaluated. The hypoglycemic effect of rose-scented geranium was compared to that of the known anti-diabetic drug glibenclamide (600 μg/kg b.w.).

Results

After the administration of two doses of essential oil of Pelargonium graveolens L’Hér. together with glibenclamide which is known by its antidiabetic activities and used as reference (600 μg/kg b.w.), for four weeks, the serum glucose significantly decreased and antioxidant perturbations were restored. The hypoglycemic effect of P. graveolens at the dose of 150 mg/kg b.w. was significantly (p< 0.05) more effective than that of glibenclamide. It is through the histological findings in hepatic and renal tissues of diabetic rats that these beneficial effects of geranium oils were confirmed.

Conclusions

It suggests that administration of essential oil of P. graveolens may be helpful in the prevention of diabetic complications associated with oxidative stress. Our results, therefore, suggest that the rose-scented geranium could be used as a safe alternative antihyperglycemic drug for diabetic patients.

β-Casomorphin-7 cause decreasing in oxidative stress and inhibiting NF-κB-iNOS-NO signal pathway in pancreas of diabetes rats

β-Casomorphin-7 (β-CM-7) is a milk biological active peptide. The present study is aimed to investigate the protective effects of β-CM-7, against oxidative stress in pancreas of streptozotocin-induced diabetic rats by assaying malondialdehyde (MDA), nitric oxide (NO) level, the activity of enzymatic antioxidants such as superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px), and NF-κB, inducible nitric oxide synthase (iNOS) gene expression. A significant increase in the level of oxidative stress was observed in pancreas of the diabetic rats when compared to control rats. After 15 d oral administration of β-CM-7 (7.5 × 10(-8) mol/d), the pancreas MDA level was markedly reduced. Oral administration of β-CM-7 to diabetic rats showed an obviously increase in the activity of catalase in pancreas, oral administration of β-CM-7 to the diabetic group of rats also showed a reduction of NF-κB and iNOS gene expression in pancreas. The elevated pancreas NO level was markedly reduced by the oral administration of β-CM-7. Thus, the results of the present study suggest that β-CM-7 may cause protective effects such as pronounced decreasing in oxidative stress and inhibiting NF-κB-iNOS-NO signal pathway in pancreas of diabetes rats.

Antihyperglycemic and antioxidant effects of a flavanone, naringenin, in streptozotocin-nicotinamide-induced experimental diabetic rats

In the present study, the putative antihyperglycemic and antioxidant effects of a flavanone, naringenin, were evaluated in comparison with those of glyclazide, a standard drug for therapy of diabetes mellitus. Diabetes was induced experimentally in 12-h-fasted rats by intraperitoneal injections of first streptozotocin (50 mg/kg b.w.) and then of nicotinamide (110 mg/kg b.w.) after a 15-min interval. Untreated diabetic rats revealed the following in comparison with normal rats: significantly higher mean levels of blood glucose and glycosylated hemoglobin, significantly lower mean levels of serum insulin, significantly lower mean activities of pancreatic antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase), significantly lower mean levels of plasma non-enzymatic antioxidants (reduced glutathione, vitamin C , vitamin E), significantly elevated mean levels of pancreatic malondialdehyde (MDA) and significantly elevated mean activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Following oral administration of naringenin (50 mg/kg b.w./day) to diabetic rats for 21 days, the following observations were made in comparison with untreated diabetic rats: significantly lower mean levels of fasting blood glucose and glycosylated hemoglobin, significantly elevated serum insulin levels, significantly higher mean activities of pancreatic enzymatic antioxidants, significantly higher mean levels of plasma non-enzymatic antioxidants, lower mean pancreatic tissue levels of MDA and lower mean activities of ALT, AST, ALP and LDH in serum. The values obtained in the naringenin-treated animals approximated those observed in glyclazide-treated animals. Histopathological studies appeared to suggest a protective effect of naringenin on the pancreatic tissue in diabetic rats. These results suggest that naringenin exhibits antihyperglycemic and antioxidant effects in experimental diabetic rats.

Metformin attenuates streptozotocin-induced diabetic nephropathy in rats through modulation of oxidative stress genes expression

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion and/or action. One of the most important complications of this metabolic disease is diabetic nephropathy. Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Recent studies have established that metformin, an oral hypoglycemic drug, possesses antioxidant effects. However, whether metformin can protect against diabetic nephropathy has not been reported before. The overall objectives of the present study are to elucidate the potential nephroprotective effect of metformin in a rat diabetic nephropathy model and explore the exact underlying mechanism(s) involved. The effect of metformin on the biochemical changes associated with hyperglycemia induced by streptozotocin was investigated in rat kidney tissues. In addition, energy nucleotides (AMP and ATP), and Acetyl-CoA in the kidney homogenates and mitochondria, and the mRNA expression of oxidative stress and pro-inflammatory mediators were assessed. Our results showed that treatment of normoglycemic rats with metformin caused significant increase in ATP, Acetyl-CoA, and CoA-SH contents in kidney homogenates and mitochondria along with profound decrease in AMP level. On the other hand, treatment of diabetic nephropathy rats with metformin normalized all biochemical changes and the energy status in kidney tissues. At the transcriptional levels, metformin treatment caused significant restoration in diabetic nephropathy-induced oxidative stress mRNA levels, particularly GSTα, NQO1, and CAT genes, whereas inhibited TNF-α and IL-6 pro-inflammatory genes. Our data lend further credence for the contribution of metformin in the nephroprotective effect in addition to its well known hypoglycemic action.

Glibenclamide or metformin combined with honey improves glycemic control in streptozotocin-induced diabetic rats

Diabetes mellitus is associated with deterioration of glycemic control and progressive metabolic derangements. This study investigated the effect of honey as an adjunct to glibenclamide or metformin on glycemic control in streptozotocin-induced diabetic rats. Diabetes was induced in rats by streptozotocin. The diabetic rats were randomized into six groups and administered distilled water, honey, glibenclamide, glibenclamide and honey, metformin or metformin and honey. The animals were treated orally once daily for four weeks. The diabetic control rats showed hypoinsulinemia (0.27 ± 0.01 ng/ml), hyperglycemia (22.4 ± 1.0 mmol/L) and increased fructosamine (360.0 ± 15.6 µmol/L). Honey significantly increased insulin (0.41 ± 0.06 ng/ml), decreased hyperglycemia (12.3 ± 3.1 mmol/L) and fructosamine (304.5 ± 10.1 µmol/L). Although glibenclamide or metformin alone significantly (p < 0.05) reduced hyperglycemia, glibenclamide or metformin combined with honey produced significantly much lower blood glucose (8.8 ± 2.9 or 9.9 ± 3.3 mmol/L, respectively) compared to glibenclamide or metformin alone (13.9 ± 3.4 or 13.2 ± 2.9 mmol/L, respectively). Similarly, glibenclamide or metformin combined with honey produced significantly (p < 0.05) lower fructosamine levels (301.3 ± 19.5 or 285.8 ± 22.6 µmol/L, respectively) whereas glibenclamide or metformin alone did not decrease fructosamine (330.0 ± 29.9 or 314.6 ± 17.9 µmol/L, respectively). Besides, these drugs or their combination with honey increased insulin levels. Glibenclamide or metformin combined with honey also significantly reduced the elevated levels of creatinine, bilirubin, triglycerides, and VLDL cholesterol. These results indicate that combination of glibenclamide or metformin with honey improves glycemic control, and provides additional metabolic benefits, not achieved with either glibenclamide or metformin alone.

Chromium dinicocysteinate supplementation can lower blood glucose, CRP, MCP-1, ICAM-1, creatinine, apparently mediated by elevated blood vitamin C and adiponectin and inhibition of NFkappaB, Akt, and Glut-2 in livers of zucker diabetic fatty rats

Chromium and cysteine supplementation can improve glucose metabolism in animal studies. This study examined the hypothesis that a cysteinate complex of chromium is significantly beneficial than either of them in lowering blood glucose and vascular inflammation markers in Zucker diabetic fatty (ZDF) rats. Starting at the age of 6 wk, ZDF rats were supplemented orally (daily gavages for 8 more weeks) with saline-placebo (D) or chromium (400 microg Cr/Kg body weight) as chromium dinicocysteinate (CDNC), chromium dinicotinate (CDN) or chromium picolinate (CP) or equimolar L-cysteine (LC, img/Kg body weight), and fed Purina 5008 diet for 8 wk. ZDF rats of 6 wk age before any supplementations and onset of diabetes were considered as baseline. D rats showed elevated levels of fasting blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and oxidative stress (lipid peroxidation) and lower adiponectin and vitamin C, when compared with baseline rats. In comparison to D group, CDNC group had significantly lower blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and lipid peroxidation and increased vitamin C and adiponectin levels. CDN, CP or LC showed significantly less or no effect on these biomarkers. Only CDNC lowered blood creatinine levels in comparison to D. While CDN and CP had no effect, activation of NFkappaB, Akt and glucose transporter-2 levels were decreased, insulin receptor substrate 1 (IRS-1) activation increased in livers of CDNC-rats. CDNC effect on glycemia, NFkappaB, Akt and IRS-1 in liver was significantly greater compared with LC. Blood chromium levels did not differ between Cr-groups. Exogenous vitamin C supplementation significantly inhibited MCP-1 secretion in U937 monocytes cultured in high-glucose-medium. CDNC is a potent hypoglycemic compound with anti-inflammatory activity apparently mediated by elevated blood vitamin C and adiponectin and inhibition of NFkappaB, Akt, and Glut-2 and increased IRS-1 activation in livers of type 2 diabetic rats.

Comparison of antioxidant effects of honey, glibenclamide, metformin, and their combinations in the kidneys of streptozotocin-induced diabetic rats

Hyperglycemia-induced increase in oxidative stress is implicated in diabetic complications. This study investigated the effect of metformin and/or glibenclamide in combination with honey on antioxidant enzymes and oxidative stress markers in the kidneys of streptozotocin (60 mg/kg; intraperitoneal)-induced diabetic rats. Diabetic rats were randomized into eight groups of five to seven rats and received distilled water (0.5 mL); honey (1.0 g/kg); metformin (100 mg/kg); metformin (100 mg/kg) and honey (1.0 g/kg); glibenclamide (0.6 mg/kg); glibenclamide (0.6 mg/kg) and honey (1.0 g/kg); metformin (100 mg/kg) and glibenclamide (0.6 mg/kg); or metformin (100 mg/kg), glibenclamide (0.6 mg/kg) and honey (1.0 g/kg) orally once daily for four weeks. Malondialdehyde (MDA) levels, glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly elevated while catalase (CAT) activity, total antioxidant status (TAS), reduced glutathione (GSH), and GSH:oxidized glutathione (GSSG) ratio was significantly reduced in the diabetic kidneys. CAT, glutathione reductase (GR), TAS, and GSH remained significantly reduced in the diabetic rats treated with metformin and/or glibenclamide. In contrast, metformin or glibenclamide combined with honey significantly increased CAT, GR, TAS, and GSH. These results suggest that combination of honey with metformin or glibenclamide might offer additional antioxidant effect to these drugs. This might reduce oxidative stress-mediated damage in diabetic kidneys.

Protective effect of beta-casomorphin-7 on type 1 diabetes rats induced with streptozotocin

The present study was aimed to investigate the possible effects of beta-casomorphin-7, against hyperglycemia and free radical-mediated oxidative stress in streptozotocin-induced diabetic rats by assaying the blood glucose level and the activity of plasma enzymatic antioxidants, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px). A significant increase in the levels of both blood glucose and oxidative stress with a predominant decrease in antioxidant status was observed in the diabetic rats when compared to control rats. After 15 days oral administration of beta-casomorphin-7 (7.5 x 10(-8) mol/day), the elevated blood glucose level was reduced. Oral administration of beta-CM-7 to diabetic rats showed an increase in the level of plasma insulin, the elevated plasma glucagon level was markedly reduced by the oral administration of beta-CM-7. Oral administration of beta-CM-7 to the diabetic group of rats also showed a significant elevation in the activity of SOD and catalase. Thus, the results of the present study suggest that beta-casomorphin-7 can protect rats from hyperglycemia and free radical-mediated oxidative stress in diabetic rats.

Resveratrol attenuates hyperglycemia-mediated oxidative stress, proinflammatory cytokines and protects hepatocytes ultrastructure in streptozotocin-nicotinamide-induced experimental diabetic rats

The present study was hypothesized to investigate the hepatoprotective nature of resveratrol in averting hyperglycemia-mediated oxidative stress by measuring extent of oxidant stress and levels of proinflammatory cytokines and antioxidant competence in the hepatic tissues of streptozotocin-nicotinamide-induced diabetic rats. After the experimental period of 30 days, the pathophysiological markers such as serum bilirubin and hepatic aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were studied in addition to hepatic TNF-alpha, IL-1 beta, IL-6, NF-kappaB p65 and nitric oxide (NO) levels in control and experimental groups of rats. The levels of vitamin C, vitamin E and reduced glutathione (GSH) and activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR) were determined in the liver tissues. Extent of oxidative stress was also assessed by hepatic lipid peroxides, hydroperoxides and protein carbonyls. A portion of liver was processed for histological and ultrastructural studies. Oral administration of resveratrol (5mg/kg b.w.) to diabetic rats showed a significant decline in hepatic proinflammatory cytokines and notable attenuation in hepatic lipid peroxides, hydroperoxides and protein carbonyls. The diminished activities of hepatic enzymic antioxidants as well as the decreased levels of hepatic non-enzymic antioxidants of diabetic rats were reverted to near normalcy by resveratrol administration. Moreover, the histological and ultrastructural observations evidenced that resveratrol effectively rescues the hepatocytes from hyperglycemia-mediated oxidative damage without affecting its cellular function and structural integrity. The findings of the present investigation demonstrated the hepatocyte protective nature of resveratrol by attenuating markers of hyperglycemia-mediated oxidative stress and antioxidant competence in hepatic tissues of diabetic rats.

Hypoglycemic and antioxidant effects of phenolic extracts and purified hydroxytyrosol from olive mill waste in vitro and in rats

This study aimed to evaluate the effect of phenolic extract and purified hydroxytyrosol (HT) from olive mill waste (OMW) on oxidative stress and hyperglycemia in alloxan-induced diabetic rats. The OMW biophenols were extracted using ethyl acetate. The obtained extract was fractionated by solid phase extraction (SPE) experimentation to generate two fractions: (F1) and (F2). HPLC-UV and HPLC-MS analysis showed that (F1) was made of known OMW monomeric phenolics mainly hydroxytyrosol (HT) while (F2) contained oligomeric and polymeric phenols such as verbascosid and ligstrosid. (HT) was purified from (F1) using silica gel-column chromatography and silica gel-TLC techniques. In incubated pancreas, supplementation of OMW fractions enhanced insulin secretion. The administration of OMW extract fractions (F1) and (F2) as well as purified (HT) in diabetic rats caused a decrease in glucose level in plasma and an increase in renal superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activities in liver and kidney. Furthermore, a protective action against hepatic and renal toxicity in diabetic rats was clearly observed. Furthermore, a significant decrease in hepatic and renal indices toxicity was observed, i.e. alkalines phosphatases (ALP), aspartate and lactate transaminases (AST and ALT) activities and the thiobarbituric acid-reactive substances (TBARs), total and direct bilirubin, creatinine and urea levels. In addition, (F1), (F2) and especially (HT) decreased triglycerides (TG), total-cholesterol (T-Ch) and higher HDL-cholesterol (HDL-Ch) in serum. These beneficial effects of OMW biophenols were confirmed by histological findings in hepatic, renal and pancreatic tissues of diabetic rats. This study demonstrates for the first time that OMW polyphenols and especially (HT) are efficient in inhibiting hyperglycemia and oxidative stress induced by diabetes and suggests that administration of HT may be helpful in the prevention of diabetic complications associated with oxidative stress.