Protective effect of pyrrolidine dithiocarbamate on cardiac muscles in diabetic rats

AIM: To investigate the effect of pyrrolidine dithiocarbamate (PDTC) on reducing blood glucose level and its protective effect on cardiac muscles in diabetic rats.METHODS: Thirty-seven male Wistar rats were randomly divided into normal control (NC) group and the high-fat diet (HFD) group. After 8 weeks of feeding, the rats in high-fat diet group were given a single dose of streptozotocin (STZ, 27 mg/kg) by intraperitoneal injection to induce type 2 diabetes. The diabetic rats were randomly divided into diabetes mellitus (DM) group and PDTC treatment(PDTC) group. The rats in PDTC group were intraperitoneally injected with PDTC (50 mg/kg) once daily. The rats in NC group and DM group were injected with equivalent volume of saline in the same way. After 1-week treatment, the level of blood glucose was measured, and all animals were killed. The concentration of malondialdehyde (MDA) and the activity of superoxide dismutases (SOD) and glutathione peroxidase (GSH-Px) were determined using commercial kits. The ultrastructural changes of the cardiac tissues were observed under transmission electron microscope. The expression of inducible nitric oxide synthase(iNOS) and content of nitrotyrosine was examined by the method of immunohistochemistry.RESULTS: The levels of blood glucose and MDA were significantly higher, while the activity of SOD and GSH-Px was lower in DM group than those in NC group (P<0.01). Treatment with PDTC markedly decreased the blood glucose and MDA content, and increased the activity of SOD and GSH-Px. Severe degeneration, necrosis, mitochondrial damage and inflammatory cell infiltration were found in the cardiac tissues in DM group. Treatment with PDTC markedly attenuated mitochondrial damage. The expression of iNOS and content of nitrotyrosine in cardiac tissues were significantly higher in DM group than those in NC group, and those were reduced after administration of PDTC.CONCLUSION: High glucose induces oxidative stress, increases the expression of iNOS and content of nitrotyrosine, and impairs the structure and function of myocardium. PDTC reduces blood glucose level, decreases the expression of iNOS and content of nitrotyrosine, and delays or attenuates the development of diabetic cardiomyopathy in diabetic rats.     

Effect of endoplasmic reticulum stress protein BiP on type 2 diabetic neuropathic pain in rats treated with curcumin

AIM: To investigate the effects of immunoglobulin heavy chain-binding protein (BiP),an endoplasmic reticulum stress protein, on mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), spinal dorsal horn and dorsal root ganglion (DRG) in type Ⅱ diabetic neuropathic pain rats treated with curcumin. METHODS: The rats were fed with a high-fat and high-fructose diet for 8 weeks to induce insulin resistance, and then were intraperitoneally injected with streptozotocin (STZ, 35 mg/kg). Eighty-one rats were selected into experimental design as their blood glucose ≥ 16.7 mmol/L 3 d after STZ injection and their MWT and TWL were decreased to 85% of the baseline values 14 d after STZ injection. The rats were divided into 3 groups (n=27 each): DNP group: type 2 diabetic neuropathic pain; DCur group: type 2 diabetic neuropathic pain and intraperitonal injection of curcumin at a dose of 100 mg·kg^-1·d^-1; DSC group: type 2 diabetic neuropathic pain and intraperitonal injection of corn oil at a dose of 4 mL/kg. Another 27 normal SD male rats fed with normal forage were adopted as control group (C group). MWT and TWL were measured at the time points of 3 d, 7 d and 14 d after curcumin injection. The lumbar segment 4~6 of the spinal cord and the corresponding DRG were removed at the same time. The expression of BiP was determined by immunohistochemical staining and Western blotting. RESULTS: Compared with C group, the rats in DNP group developed hyperglycemia and a decrease in MWT and TWL, as well as an increase in the activity of BiP in spinal dorsal horn and DRG (P<0.05). Compared with DNP group, the rats in DCur group at the time point of 7 d significantly attenuated mechanical allodynia and thermal hyperalgesia, and these effects were correlated with the inhibition of BiP hyper-activation at the time point of 14 d after treatment with curcumin (P<0.05). No significant difference of MWT, TWL and the expression of BiP between DNP group and SC group was observed. CONCLUSION: BiP participates in the pathogenesis of type Ⅱ diabetic neuropathic pain. Curcumin attenuates the MWT and TWL in type 2 diabetic neuropathic pain rats. The mechanism may be involved in the inhibition of BiP expression by curcumin.     

Study on the role of oxidative stress in the kidneys of diabetic rats

AIM: To investigate the changes of oxidative stress in the kidneys and their roles in nephropathy in diabetic rats. METHODS: Diabetic rats were induced by streptozotocin (STZ). 36 rats were divided into three groups randomly: (1) NC group, normal control rats; (2) DM group, diabetic rats received protamine zinc insulin (PZI) 2U-4U/2 d; (3) DT group, diabetic rats received PZI 9-12 U/kg body weigh/day. 12 weeks later, rats were killed, blood glucose, blood cholesterol, serum creatinine, blood urea nitrogen, HbA1c, urinary creatinine, and urinary protein for 24 h were measured. The activities of antioxidant enzymes in renal cortex, including total superoxide dismutase (TSOD), Cu-Zn superoxide dismutase (Cu-Zn SOD), Mn superoxide dismutase (Mn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and maleic dialdehyde (MDA) were measured by chromatometry. RT-PCR was performed to detect the expression of different antioxidant enzymes mRNA. RESULTS: For all the targets we measured, there was no significant difference between NC and DT groups. Compared with the other two groups, the levels of blood glucose, cholesterol, trigalloyl glycerol, HbA1c in DM group increased significantly. The activities of TSOD, Cu-Zn SOD and CAT decreased significantly. The activity of GSH-Px increased significantly. There was no significant difference among the activities of Mn SOD in all three groups. The level of MDA in DM group was much higher than that in NC or DT group. The relative expression levels of GSH-Px and Cu-Zn SOD mRNA in DM group were higher than those in other two groups, while the relative expression level of CAT decreased. Mn SOD mRNA was expressed without significant difference in all groups. Compared with NC or DT group, urinary protein in DM group increased significantly, while creatinine clearance rate decreased. CONCLUSIONS: Hyperglycemia affected the expression of antioxidant enzymes. Oxidative stress was caused by hyperglycemia in diabetic rats and may be an important factor in the etiology of diabetic nephropathy.     

Effect of erlotinib on renal injury in rats with STZ-induced diabetic nephropathy

AIM: To investigate the effect of epidermal growth factor receptor (EGFR) inhibitor erlotinib on kidney injury in diabetic nephropathy (DN) rat and the underlying mechanism. METHODS: The rat model of DN was induced by intraperitoneal injection of streptozotocin (STZ) at dose of 55 mg/kg. One week after STZ injection, the rats with blood glucose level exceeding 16.7 mmol/L were identified as diabetic. Diabetic rats were randomly divided into 2 groups:STZ group and STZ+erlotinib group. In addition, the normal rats were used as control group. The rats in STZ+erlotinib group were treated with erlotinib at 100 mg·kg^-1·d^-1 for 4 weeks(5th~8th week). The fasting blood glucose (FBG), serum creatinine (SCr) and 24 h urine protein were measured. The pathological changes of the kidney were observed by HE staining and Masson staining. The protein levels of EGFR, p-EGFR, transforming growth factor β1 (TGFβ1), Smad2/3, p-Smad2/3, collagen Ⅳ (ColⅣ) and fibronectin in the kidney tissues were determined by Western blot. The reactive oxygen species (ROS) level and malondialdehyde (MDA) content in the renal tissues were futher analyzed. RESULTS: Compared with control group, the levels of FBG, 24 h urine protein and Scr were significantly increased in STZ group (P<0.01). Compared with STZ group, the levels of FBG, 24 h urine protein and SCr in STZ+erlotinib group were markedly decreased (P<0.05). In additon, the glomerular structure was restored to normal, the proliferative degree of mesangial cells markedly attenuated, and the epithelial cells were in alignment in STZ+erlotinib group. Moreover, erlotinib significantly inhibited the protein levels of p-EGFR, TGFβ1, p-Smad2/3, ColⅣ and fibronectin in the kidney tissues of STZ rats. In addition, erlotinib also significantly inhibited the levels of ROS and MDA in the kidney tissues of STZ rats. CONCLUSION: Erlotinib ameliorates STZ-induced diabetic nephropathy possibly through inhibiting the activation of EGFR/TGFβ1-Smad2/3 signaling pathway in association with suppression of fibrosis and oxidative stress.     

Effect of curcumin on p-ERK1/2-AP-1 cascade and diabetic neuropathic pain in rats

AIM: To evaluate the role of p-ERK1/2-AP-1 cascade in the process of curcumin against diabetic neuropathic pain (DNP) in rats.METHODS: Ninety-six male Sprague-Dawley rats were randomly divided into 4 groups (n=24): normal control group, DNP group, DNP with solvent group and DNP with curcumin (100 mg/kg) group. The rat model of diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 75 mg/kg). Mechanical allodynia and thermal hyperalgesia were tested by mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) 2 weeks after induction,respectively. The diabetic rats were treated with curcumin (100 mg·kg^-1·d^-1, ip) for 2 weeks. The conditions of hyperalgesia and allodynia were determined 2 d before STZ injection, 14 d after STZ injection, and 3 d, 7 d, 14 d after administered with curcumin. The change of p-ERK1/2 was measured by the methods of Western blotting and immunohistochemistry. The expression of AP-1 in spinal cord dorsal horn and dorsal root ganglion (DRG) was detected by electromobility shift assay (EMSA).RESULTS: Compared with normal control group, the rats in DNP group developed hyperglycemia and a decrease in MWT and TWL associated with an increase in the activity of p-ERK1/2 and AP-1 in dorsal horn and DRG(P<0.05). Compared with DNP group, 7-day treatment with curcumin significantly attenuated mechanical allodynia and thermal hyperalgesia, and these effects were correlated with inhibiting the hyper-activation of p-ERK1/2 and AP-1 14 days after treatment with curcumin (P<0.05).CONCLUSION: Curcumin has beneficial effects on hyperalgesia in STZ-induced peripheral neuropathic pain. Activation of p-ERK1/2 and AP-1 may be the key mechanism of DNP in spinal cord and DRG.     

Protective effects of luteolin on STZ-induced diabetic kidneys

AIM: To explore the protective effects of luteolin on the diabetic kidneys. METHODS: Male Sprague-Dawley rats were randomly divided into 5 groups: normal control group, diabetic model group and the groups of diabetic rats treated with luteolin at a low dose, a middle dose and a high dose. The diabetic model was induced by a single intraperitoneal injection of streptozotocin (STZ,65 mg/kg). Blood glucose, urine protein, the activity of superoxide dismutase and catalase in serum and kidney, and the content of malonaldehyde(MDA) in kidney were analyzed by biochemical methods. Western blotting was used to detect the protein expression of transforming growth factor-β₁(TGF-β₁) and plasminogen activator inhibitor-1(PAI-1) in the renal cortex. The morphological changes of the renal tissues were observed under microscope. RESULTS: Compared with diabetic model group, luteolin significantly reduced the level of blood glucose (P<0.01), the content of urine protein (P<0.01) and MDA (P<0.01) in the kidneys, and increased the activity of superoxide dismutase and catalase (P<0.01) in serum and kidneys in the diabetic rats. The protein levels of TGF-β₁ and PAI-1 in the renal cortex were dramatically decreased as the rats were treated with luteolin. CONCLUSION: Luteolin may exert an important protective effect on diabetic kidneys by relieving oxidative stress and inhibiting the protein expression of TGF-β₁ and PAI-1 in the renal tissues of STZ-induced diabetic rats.     

Effect of insulin combined with selenium on myocardial remodeling in diabetic rats

AIM: To investigate the effects of insulin combined with selenium on myocardial remodeling in streptozotocin (STZ)-induced diabetic rats.METHODS: The animal model of diabetic cardiomyopathy was induced by intraperitoneal injection of STZ (50 mg/kg) in rats. The level of blood glucose was estimated using One Touch SureStep blood glucose meter. Hemoglobin A1c level was detected by microcolumn assay. Triglyceride and total cholesterol were measured by enzymatic method. Collagen content in the myocardium was determined by Mallory staining. The expression of tumor necrosis factor α (TNF-α) in the serum and myocardium was observed by the methods of ELISA and immunohistochemistry, respectively.RESULTS: Compared with control group, the animals in model group showed metabolic disorders of glucose and lipid, and the cardiac function declined significantly (P<0.01).The myocardial cells showed disorder of distribution, filament breakage and collagen hyperplasia,and serum and myocardial TNF-α levels were significantly elevated.Insulin in combination with selenium significantly decreased the levels of blood glucose and lipid, and markedly inhibited the expression of TNF-α in the serum and myocardium than those in the rats administered with insulin alone (P<0.01).CONCLUSION: Combination of insulin and selenium significantly improves the structure and function of the heart by down-regulation of TNF-α.     

Curcumin inhibits lipid peroxidation and the expression of TGF-β1 and PDGF in the liver of rats with hepatic fibrosis

AIM: To investigate changes of the level of reactive oxygen species (ROS),malondialdehyde (MDA),transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor (PDGF) expression in a rat hepatic fibrosis model and the effect of curcumin ,and discuss the mechanism of the prophylactic effect of curcumin on hepa tic fibrosis.METHODS: Rat models of hepatic fibrosis were established by intraperitoneally injection of carbon tetrachloride.Curcumin of 20 mg,10 mg,5mg per 100 gram weight of rat was given to these rats respectively at the same time.Normal,fibrosis model and positive groups were made as controls.After eight weeks,all rats were executed and the blood and liver were kept.Serum level of ROS was tested by chromatometry.Content of MDA in liver homogenate was tested by thiobarbituric acid (TBA) method.Expressions of TGF-β1 and PDGF in liver were detected by immunohistochemical method. RESULTS: Serum level of ROS in fibrotic group increased significantly compared with that of normal group,and which was depressed obviously in curcumin groups(P＜0.05).Content of MDA in liver of curcumin group reduced significantly compared with that of fibrotic group (P＜0.01).Expressions of TGF-β1 and PDGF in fibrotic group increased significantly compared with those of normal group,which were depressed obviously in curcumin groups (P＜0.01).CONCLUSION: Curcumin could inhibit expression of TGF-β1,PDGF and lipid peroxidation in liver.These may be mechanisms of curcumin preventing hepatic fibrosis.     

Alleviation of aortic vascular dysfunction in STZ/HFD-induced type 2 diabetic rats by nFGF1

AIM: To investigate the protective effect of non-mitogenic fibroblast growth factor 1 (nFGF1) on the aortic vascular function in streptozotocin (STZ)/high-fat diet (HFD)-induced type 2 diabetic rats and its underlying mechanisms. METHODS: Five-week-old male SD rats (n=30) were randomly divided into 3 groups (n=10 in each group), including normal control group, type 2 diabetic group and nFGF1 treatment group (type 2 diabetic rats were intraperitoneally injected with 0.5 mg/kg nFGF1 every other day for 4 weeks). After the rats were sacrificed, blood glucose, cholesterol and triglyceride levels, aorta diastolic function and superoxide dismutase (SOD) level in the aorta of each group were measured. Besides, the protein levels of cyclooxygenase-2 (COX-2), phosphorylated extracellular signal-regulated kinase (p-ERK) and endothelial nitric oxide synthase (eNOS) in the aorta were determined by Western blot. RESULTS: nFGF1 markedly lowered blood glucose, cholesterol and triglyceride levels, enhanced aorta SOD activity and upregulated protein level of eNOS in the type 2 diabetic rats. Furthermore, the increased protein levels of COX-2 and p-ERK in the type 2 diabetic rats were largely abrogated by nFGF1. CONCLUSION: nFGF1 effectively attenuates aortic vascular dysfunction in the type 2 diabetic rats, which may be associated with decreasing blood glucose, cholesterol and triglyceride levels, reducing inflammation and oxidative stress response, and activating eNOS signaling pathway.     

Regulatory effect of miR-146 on diabetic cardiomyopathy

AIM: To investigate the role of microRNA-146 (miR-146) in the pathogenesis of diabetic cardiomyopathy (DCM), and to observe the expression levels of miR-146 and its downstream target genes. METHODS: Male C57BL/6 mice (n=60) were randomly divided into experimental group (DCM, n=30) and control group (control, n=30). The mice in DCM group were intraperitoneally injected with low dose (50 mg/kg) of streptozo-tocin (STZ) to induce diabetic myocardial model, and the mice in control group were given intraperitoneal injection of citrate buffer. At the end of 12 weeks, the hearts were removed, HE and Masson staining were performed to observe the cardiac pathological changes. RT-qPCR were used to detect the expression of miR-146 a and miR-146b and the the mRNA expression of related downstream genes interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6). Western blot was used to determined the protein levels of IRAK1 and TRAF6. RESULTS: At the end of 12 weeks, HE staining showed the hypertrophy and structural disorder of the myocardial cells in DCM group. Masson staining showed that the collagen fibers of myocardium were increased in DCM group; RT-qPCR showed that the levels of miR-146a and miR-146b in DCM group were significantly decreased compared with control group (P<0.01). The mRNA levels of IRAK1 was increased (P<0.01), and the mRNA levels of TRAF6 was declined (P<0.01). Western blot showed that compared with control group, the protein expression of IRAK1 was increased in DCM group, and the protein expression of TRAF6 was decreased with statistically significant.CONCLUSION: miR-146 may involve in the occurrence and development of diabetic cardiomyopathy by regulating inflammatory reactions and targeting IRAK1.     

Effect of JNK/MCP-1 signaling pathway on anti-diabetic neuropathic pain by curcumin in type 2 diabetic rats

AIM:To investigate the effect of JNK/MCP-1 signaling pathway on anti-diabetic neuropathic pain by curcumin in type 2 diabetic rats. METHODS:The male Sprague-Dawley rats were induced as the model of the type 2 diabetic neuropathic pain rats, they were randomly divided into 6 groups (n=27): type 2 diabetic neuropathic pain (DNP) group, type 2 diabetic neuropathic pain and intraperitoneal injection of curcumin (Cur) group, type 2 diabetic neuropathic pain and solvent control (DSC) group, type 2 diabetic neuropathic pain and JNK inhibitor (DJ) group, type 2 diabetic neuropathic pain and JNK inhibitor solvent control (DJS) group, type 2 diabetic neuropathic pain and monocyte chemoattractant protein 1 (MCP-1) agonist (DM) group. Another 27 normal SD rats were selected as control group. Mechanical withdrawal threshod and thermal withdrawal latency were measured at 3rd d, 7th d and 14th d after dosing, then the lumbar segment 4~6 of the spinal cord and L4~6 DRG were removed at the same time. ELISA was used to measure MCP-1 level. The expression of p-JNK was determined by Western blotting. RESULTS:Compared with DNP group, p-JNK was significantly decreased at 7th d and 14th d in Cur group, DJ group and DM group after treatment (P<0.05). Compared with C group, the MCP-1 was significantly declined in other 6 group after streptozotocin injection (P<0.05). Compared with DNP group, MCP-1 were significantly increased at 7th d and 14th d in Cur group and DJ group after treatment (P<0.05), and that in DM group was greatly decreased (P<0.05). CONCLUSION: The expression of p-JNK and MCP-1 was increased in DNP rats with spinal cord and dorsal root ganglion. The mechanism of curcumin reducing the neuropathic pain in type 2 diabetic rats might be through regulating the JNK/MCP-1 pathway.     

Oxidative stress and P53 involve in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells

AIM: To explore the mechanism of fluctuant high blood glucose-induced apoptosis of renal tubular epithelial cells. METHODS: Cultured human renal tubular epithelial cells (HK-2) were treated with stable high glucose or fluctuant high glucose. Antioxidant and specific inhibitor of P53 were applied for identifying the role of oxidative stress and P53 in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells. Additionally, SD rats were randomly divided into normal control group (A), stable high blood glucose group (B) and fluctuant high blood glucose group (C). Diabetic rats were induced by intraperitoneal injection of streptozocin(STZ,65 mg/kg), and the fluctuant high blood glucose animal model was induced by intraperitoneal injection of ordinary insulin and glucose at different time points every day. The activity of superoxide dismutase (SOD) and the content of malonaldehyde (MDA) were detected by the method of colorimetry. The protein expression of NADPH oxidase 4(Nox4) and P53 were examined by immunohistochemistry and Western blotting. Apoptosis was assessed by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). RESULTS: The cultured HK-2 cells treated with fluctuant high glucose had significantly higher apoptotic rate and expression level of P53 protein than those in the cells treated with stable high glucose. Compared with the culture solution of the cels treated with stable high glucose, the SOD activity was decreased and the concentration of MDA was increased in the culture solution of the cells treated with fluctuant high glucose. The antioxidant and specific inhibitor of P53 significantly inhibited the p-P53 expression and decreased the apoptotic rate. After 12 experimental weeks, the cell apoptotic index and protein expression of Nox4 and p-P53 in the kidney tubular epithelial cells isolated from the diabetic rats were significantly increased in C group as compared with B group. CONCLUSION: Oxidative stress and P53 are involved in fluctuant high glucose-induced apoptosis of renal tubular epithelial cells.     

Quercetin inhibits inflammasome activation in diabetic rats and attenuates myocardial injury

AIM:To observed the effect of quercetin on NLRP3 inflammasome activation in the rats with diabetic cardiomyopathy (DCM) and its protective effect on the myocardium. METHODS:Male SD rats (n=40) were randomly divided into normal control group (n=10) and model group (n=30). The rats in model group were intraperitoneally injected with streptozotocin at 60 mg/kg to establish the model of diabetes mellitus (DM). Blood glucose was measured weekly. After 4 weeks, the rats with random blood glucose ≥ 16.6 mmol/L were selected as DM animals. The rats with DM were randomly divided into 3 groups:DM group, DM+vehicle group and DM+quercetin group. The rats in DM+quercetin group were intragastric infusion with quercetin at 100 mg/kg per day. The cardiac function was measured at the end of the 16th week. The methods of Masson staining and HE staining were used to observe the morphological changes of the myocardial tissues. Western blot, ELISA and immunohistochemistry were used to observe the changes of NLRP3, ASC, caspase-1, interleukin (IL)-1β and IL-18. TUNEL staining was used to observe myocardial apoptosis. RESULTS:Quercetin significantly inhibited the activation of NLRP3 inflammasome in the myocardium of the DM rats (P<0.05). The levels of IL-1β and IL-18 in DM+quercetin group were significantly decreased, quercetin reduced cardiac tissue apoptosis, and the cardiac function in DM+quercetin group was significantly improved (P<0.05) compared with DM group and DM+vehicle grpup. CONCLUSION:Quercetin significantly inhibits the activation of NLRP3 inflammasome, and reduces the levels of inflammation and myocardial apoptosis, thus protecting the heart function of DCM rats.     

Protective effects of riboflavin on diabetic nephropathy in STZ-induced diabetic rats

AIM: To explore the protective effects of riboflavin on the kidney in streptozotocin (STZ)-induced diabetic rats. METHODS: Male Sprague-Dawley rats were randomly divided into 3 groups: normal control group, diabetic model group and riboflavin-treated group. Diabetes was induced by a single injection of STZ (dissolved in 0.01 mol/L citrate buffer, pH 4.5, 65 mg/kg, ip) in rats. The biochemical methods were used to measure the contents of urine protein and malondialdehyde in the kidney, and the activities of superoxide dismutase (SOD) and catalase (CAT) in serum and renal tissues. Furthermore, the protein expression of TGF-β1 and plasminogen activator inhibitor-1(PAI-1) in renal cortex was detected by Western blotting. The morphological changes of renal tissue were observed under microscope.RESULTS: Compared to the diabetic model group, riboflavin significantly increased the activities of SOD and CAT (P<0.01) in the serum and renal tissues, and decreased the contents of urine protein and MDA (P<0.01) in the renal tissues in riboflavin-treated group. The levels of TGF-β1 and PAI-1 in the renal cortex were dramatically decreased in the treated diabetic rats compared to the diabetic model rats (P<0.01).CONCLUSION: Riboflavin inhibits the protein expression of TGF-β1 and PAI-1 in renal tissue of STZ-induced diabetic rats. Riboflavin may alleviate the pathologic changes and play an important protective role in diabetic kidneys.     

Effects of resveratrol on cardiac dysfunction and ASMase-ceramide pathway in type 2 diabetic rats

AIM:To investigate the effects of resveratrol (RSV) on cardiac dysfunction and acid sphingomyelinase (ASMase)-ceramide pathway in diabetic rats. METHODS:Type 2 diabetes mellitus (T2DM) model was established by a high-fat diet combined with STZ intraperitoneac injection (30 mg/kg). SD rats (n=20) were randomly divided into control group, T2DM group; T2DM+RSV group (diabetic rats were given resveratrol at 100 mg·kg·d^-1 by intragastric administration for the treatment) and RSV group (some of control rats were selected to give the same dose of RSV for drug control group). The M-mode Doppler ultrasonography was performed to observe the changes of cardiac function and structure in the rats. The levels of serum glucose, lipid and superoxide dismutase (SOD) activity, malondialdehyde (MDA) content in heart tissues were measured. Oil red O staining and Sirius red staining were performed to observe lipid accumulation and cardiac fibrosis in heart tissues. The cardiac ceramide concentration in diabetic rats was analyzed by high-performance liquid chromatography. The protein expression of ASMase and peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α) in the hearts was determined by Western blot. RESULTS:Compared with the control group, the levels of fasting blood glucose, total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) were significantly elevated in T2DM group. The values of ±dp/dt_max, fractional shortening and ejection fraction were declined, and the left ventricle internal dimension at end-systole (LVIDs) and left ventricle internal at end-diastole (LVIDd) were increased. Furthermore, increased MDA content and more lipid accumulation were also observed in diabetic hearts, while the SOD activity, ATP content and PGC-1α expression were reduced in diabetic hearts. However, all these parameters were reversed by addition of RSV, concomitant with decreased ASMase expression and ceramide content. CONCLUSION:RSV dramatically alleviates diabetes-induced cardiac dysfunction and cardiac fibrosis, which may attribute to inhibition of ASMase-ceramide activation.     

Protective effect of DIZE on heart function of rats with diabetic cardiomyopathy

AIM: To observed the protective effect of diminazene aceturate (DIZE), an angiotensin-converting enzyme 2 (ACE2) activator, on rats with diabetic cardiomyopathy (DCM). METHODS: Male Wistar rats (n=30) were randomly divided into normal control group, DCM group and DIZE treatment group (DIZE group). The rats in DCM group and DIZE group were intraperitoneally injected with streptozotocin (65 mg/kg) to establish diabetic model. After 12 weeks, the diabetic rats were infused with DIZE at 15 mg·kg^-1·d^-1 or the same volume of saline for 4 weeks using osmotic minipump. The cardiac function was measured at the end of the 16th week. The methods of Mason staining and HE staining were used to observe the morphological changes of the myocardial tissue. Western blot, ELISA and immunohistochemistry were used to observe the changes of ACE2, angiotensin (Ang)Ⅱ, Ang-(1-7), interleukin (IL)-1, IL-6 and connective tissue growth factor (CTGF). RESULTS: DIZE significantly improved the expression of ACE2 in diabetic rats (P<0.05). Compared with DCM group, the levels of IL-1 and IL-6 in DIZE group were significantly decreased, and the cardiac function in DIZE group was significantly improved (P<0.05). CONCLUSION: ACE2 endogenous agonist DIZE significantly increases the ACE2 level and reduces the level of inflammation, thus protecting the heart function of DCM rats.     

Piperlongumine protects mice against diabetic cardiomyopathy by alleviating inflammation

AIM:To investigate the effect of piperlongumine (PL) on myocardial injury and fibrosis in diabe-tic cardiomyopathy (DCM) models. METHODS:To imitate cardiomyocytes in a high glucose environment, H9C2 cells were stimulated by high glucose (33 mmol/L), and then the cells were divided into control group, high glucose group, low dose (2.5 μmol/L) of PL group and high dose (5 μmol/L) of PL group. The mRNA levels of inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and the protein levels of pro-fibrotic markers including transforming growth factor-β (TGF-β) and collagen IV were determined. C57BL/6 mice were randomly divided into control group, type 1 diabetes mellitus group, low dose (2.5 mg/kg) of PL group and high dose (5 mg/kg) of PL group. The mice were intraperitoneally injected with streptozotocin at dose of 50 mg/kg for 5 consecutive days. The fasting glucose le-vels higher than or equal to 12 mmol/L meant the establishment of type 1 diabetes mellitus. The treatment with PL was initiated. The fasting blood glucose was detected every 2 weeks. After echocardiography at the 13th week, the mice were killed after anesthesia at the 13th weekend. The blood was collected to measure the serum levels of creatine kinase isoenzyme MB (CK-MB) and lactate dehydrogenase (LDH). The heart tissues were prepared with formaldehyde for 24 h, and was embedded in paraffin for pathological sectioning. HE staining and Sirius red staining were conducted. The morphological changes were observed under microscope. RESULTS:In the H9C2 cell model induced by high glucose, the mRNA expression levels of TNF-α and IL-6, as well as the protein expression levels of TGF-β and collagen IV were significantly higher than those in control group. The above indexes were decreased after PL treatment (P<0.05). PL alleviated the disorder of basic structure, and cardiac fibrosis in the DCM mice. After the administration of PL, the serum levels of CK-MB and LDH were decreased significantly (P<0.05). CONCLUSION:PL is a potential cardioprotective agent in treatment of DCM as it can inhibit inflammation and mitigate the diabetic myocardial injury.     

Hypolipemic and hypoglycemic effects of total triterpenoids from Psidium guajava leaves on type 2 diabetic rats

AIM: To investigate the effects of total triterpenoids from Psidium guajava leaves (TTPGL) on blood glucose and lipids in type 2 diabetic rats. METHODS: The diabetic rats were induced by intraperitoneal injection of streptozotocin at dose of 35 mg/kg and feeding with high-fat diet. The animals were divided into 5 groups: diabetic model control group (model), TTPGL treatment groups (with the doses of 60, 120 and 240 mg/kg, respectively) and rosiglitazone treatment group (3 mg/kg). Another 12 normal SD rats were used as the normal controls. The rats received daily treatment for 6 weeks, and then the levels of fasting blood glucose (FBG), fasting insulin (FINS), triglyceride (TG), total cholesterol (TCH), free fatty acid (FFA), glycosylated hemoglobin (GHb) and glycosylated serum proteins (GSP) were measured. The protein expression of peroxisome proliferator-activated receptor γ (PPARγ) in adipose tissues was detected by Western blotting. RESULTS: Compared with normal control group, the levels of FBG, GHb and blood lipids were increased in type 2 diabetic rats. The FINS, insulin sensitivity index, and the protein expression of PPARγ in adipose tissues were decreased. Compared with model group, the levels of FBG and GSP were decreased,and the FINS, insulin sensitivity index, and the protein expression of PPARγ in adipose tissues significantly increased in TTPGL treatment groups (with the doses of 120 and 240 mg/kg). The levels of serum TG,TCH and FFA were significantly lower in TTPGL treatment groups (P<0.01 or P<0.05) as compared with the model controls. CONCLUSION: TTPGL decreases the levels of blood glucose and lipids in diabetic rats. TTPGL also increases serum insulin level and improves insulin sensitivity. The action mechanism of TTPGL may be related to the increase in the protein expression of PPARγ.     

Oxidative stress-activated JNK-MAPK signaling pathway is involved in fluctuant high glucose-induced injury of hepatocytes

AIM: To explore the mechanisms of fluctuant high blood glucose-induced apoptosis of hepatocytes. METHODS: SD rats were randomly divided into normal control group (N), stable high blood glucose group (S), fluctuant high blood glucose group (F) and insulin group (I). Diabetic rats were induced by intraperitoneal injection of streptozotocin (65 mg/kg), and the fluctuant high blood glucose animal model was induced by intraperitoneal injection of ordinary insulin and glucose at different time points every day. The blood glucose fluctuation patterns of the animals in F group within 12 weeks were similar every day and no significant difference of the HbA1c concentration was observed compared with S group, indicating that the fluctuant hyperglycemia was successfully established in F group. The activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the content of malondialdehyde (MDA) and nitric oxide (NO) in the homogenate of the liver tissues were detected by colorimetry. The mRNA and protein levels of JNK, p-JNK, Bax and Bcl-2 were examined by RT-PCR and Western blot. RESULTS: After 12 weeks, the increases in the intakes of food and water, the urine output, and the abnormal liver function were observed in S group, I group and F group. Compared with N group, the MDA level was increased, the content of NO and the activity of SOD and GSH-Px were decreased, and up-regulation of JNK mRNA and p-JNK and Bax proteins, and down-regulation of Bcl-2 were also found in S group, I group and F group. The above effects were more obviously showed in F group. CONCLUSION: Oxidative stress activates JNK-MAPK signaling pathway, which is involved in fluctuant high glucose-induced apoptosis of hepatocytes.