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.     

mRNA expression of insulin receptor and leptin receptor in liver of nonalcoholic fatty liver disease from diabetic rats

AIM: To observe the pathologic changes of liver in diabetic rats and to investigate the role of mRNA expression of insulin receptor and leptin receptor in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). METHODS: Twenty male Sprague-Dawley rats were divided randomly into two groups: normal control group and diabetic group. After fed with high-fat diet for 4 weeks, diabetic rats were injected with streptozotocin at a dosage of 30 mg/kg intraperitoneally to induce NAFLD model of type 2 diabetes mellitus. Then the diabetic animals were fed with high-fat diet continuously for 12 weeks. At the end of the experiment, the rats were sacrificed, the concentrations of blood glucose, serum lipid, ALT and AST were measured biochemically. The levels of serum leptin and serum insulin were detected by enzyme-linked immunosorbent assay (ELISA) and radio immunoassay (RIA), respectively. The pathologic changes of liver were observed under light microscopy (LM) stained with HE, Sudan Ⅲ and Masson trichrome staining, respectively. The ultra-structural changes of liver were observed under transmission electron microscopy (TEM). Additionally, the mRNA expressions of PEPCK, G6Pase, insulin R and leptin R from rat livers were assayed by semi-quantitative RT-PCR. RESULTS: The levels of blood glucose, serum insulin, serum TG, ALT and AST increased significantly (P<0.01), serum TC elevated (P<0.05), and the levels of serum leptin decreased (P<0.01) in diabetic group compared to those in normal control group. Obvious liver fatty degeneration, piecemeal necrosis with accompanying inflammatory infiltration and fibrosis were found under LM. Hepatocytes pyknosis, lots of lipid deposits in cytoplasm of hepatocytes, proliferation of collagen in space of Disse were observed under TEM in diabetic group. The expression of insulin R and leptin R mRNA in liver from diabetic rats increased significantly (P<0.01) while the expression of PEPCK and G6Pase mRNA remained unchanged. CONCLUSION: Insulin resistance plays an important role in the pathogenesis of NAFLD. Low level of serum leptin, up-regulation of mRNA expression of insulin R and leptin R in liver caused by insulin resistance may be involved in this process.     

Effects of pyrrolidine dithiocarbamate on synthesis of hepatic glycogen in diabetic rats

AIM: To determine the effect of pyrrolidine dithiocarbamate on hepatic glycogen synthesis and its mechanism in diabetic rats. METHODS: Male Wistar rats were randomly divided into normal diet group and high-fat diet group. After 8 weeks of feeding, the rats in high-fat diet group were injected intraperitoneally with a single dose of streptozotocin (27 mg/kg) to induce type 2 diabetes. The diabetes rats were randomly divided into 3 groups: diabetes mellitus group (DM), PDTC-treated group (DM+PDTC) and insulin-treated group (DM+INS). The rats in PDTC-treated group were injected with PDTC (50 mg/kg) intraperitoneally daily. At the same time, the rats in normal diet group, DM group and insulin-treated group were injected with equivalent volume of saline in the same way. The rats in insulin-treated group were injected with insulin (1 U/kg) 1 h before killed. After the treatment was taken for 1 week, the levels of blood glucose were measured, then the animals in all groups were killed. The liver glycogen content was detected, and the levels of GSK-3β and Akt phosphorylation in the liver tissues were analyzed by Western blotting. RESULTS: The blood glucose level and liver glycogen content were significantly higher, and the levels of GSK-3β and Akt phosphorylation were lower in DM group than those in normal-diet group (P<0.01). Compared with DM group, the glycogen content, the phosphorylation of Akt and GSK-3β in the liver tissues in DM+PDTC group and DM+INS group increased significantly (P<0.01), and the blood glucose levels decreased (P<0.01). CONCLUSION: PDTC increases the synthesis of liver glycogen and decreases the level of blood glucose by regulating the activity of Akt and GSK-3β in the liver.     

Protective effect of curcumin on myocardium in diabetic rats

AIM: To study the effects of curcumin (Cur) on diabetic cardiomyopathy (DCM) in rats. METHODS: Male Wistar rats (n=75) were divided into control group and diabetes model group, in which the rats were fed with high-fat diet and then intraperitoneally injected with streptozotocin (STZ, 40 mg/kg). Fasting blood glucose was measured 72 h and 1 week after STZ injection. The diabetic rats were diagnosed when sustained fasting blood glucose levels ≥ 11.6 mmol/L. The diabetic rats were randomly divided into DCM group, DCM+Cur 100 mg/kg group and DCM+Cur 200 mg/kg group. After treatment for 16 weeks, glutathione peroxidase (GSH-Px) activity and malondialdehyde (MDA) level were measured, and the level of cardiac troponin I (cTnI) in the serum was determined by enzyme-linked immunosorbent assay. The protein expression of protein kinase C (PKC) was detected by Western blotting. RESULTS: Curcumin significantly decreased the blood glucose level, increased the body weight, inhibited MDA content and up-regulated the GSH-Px activity in the diabetic rats. Furthermore, curcumin treatment inhibited the diabetes-induced protein expression of PKC. CONCLUSION: Curcumin may have a protective effect on diabetic cardiomyopathy by attenuating oxidative stress.     

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.     

Grape seed proanthocyanidin regulates expression of GSTM through Nrf2 in renal tissues of STZ-induced diabetic rats

AIM: To investigate the potential mechanisms of renoprotective effect of grape seed proanthocyanidin (GSP) on diabetic nephropathy.METHODS: Male Wistar rats were injected with 1% streptozotocin (STZ) intravenously to induce diabetes mellitus (DM). The diabetic rats were randomly divided into 2 groups: diabetes group (DM group) and GSP treatment group (GSP group, GSP 250 mg·kg^-1·d^-1). The normal Wistar rats served as control (C group). Body weight (BW), systolic pressure, kidney weight/body weight (KW/BW), fasting plasma glucose (FPG), blood urea nitrogen (BUN), serum creatinine (SCr), glycosylated hemoglobin (HbA1c) and 24 h urine protein were determined 24 weeks after STZ intervention. The pathological changes of the renal tissues were observed. The protein levels of glutathione S-transferase mu (GSTM) and nuclear factor-erythroid 2-related factor 2 (Nrf2) in the renal tissues were determined by Western blotting and immunohistochemistry. RESULTS: Compared with C group, BW in diabetic rats decreased (P<0.01). The levels of systolic pressure, FPG, HbA1c, KW/BW, 24 h urine protein, BUN and SCr in DM group were higher than those in C group (P<0.01). After treated with GSP, the levels of systolic pressure, KW/BW, 24 h urine protein, BUN and SCr in DM rats were lower than those in DM rats without treatment (P<0.01 or P<0.05). The pathological changes were ameliorated in GSP group. The expression of GSTM and Nrf2 was up-regulated in the kidneys of diabetic rats and down-regulated to the normal levels after GSP treatment. CONCLUSION: The renoprotective effect of GSP is associated with the down-regulation of GSTM through modulating the expression of Nrf2.     

Effect of astragalus polysaccharin on expression of nephrin and podocin in podocytes of early diabetic nephropathy rats

AIM: To observe the effects of astragalus polysaccharin (APS) on the expression of nephrin and podocin in podocytes of diabetic nephropathy (DN) rats.METHODS: The rat model of diabetes was induced by intraperitoneal injection of streptozotocin (STZ).The diabetic rats were randomly divided into 2 groups by the treatment without or with APS: STZ group (n=8) and STZ+APS group (n=8).In addition, 8 non-treated rats served as control.All the rats were treated with APS or normal saline orally by gavage for 8 weeks.The concentration of blood glucose was monitored on week 2, 5 and 8 after treatment.Eight weeks later, the body weight and renal index were measured.Total urine protein in 24 h, blood urea nitrogen (BUN) and serum creatinine (SCr) were detected by biochemical methods.The pathological changes of the kidneys were also observed under light microscope.The protein levels of nephrin and podocin in the kidney tissues were also determined by Western blotting.RESULTS: After APS intervention, the levels of renal index, blood glucose concentration, 24-hour total urine protein, BUN and SCr were significantly lower and body weight was higher than those in STZ group (P<0.05).The renal pathological status in APS group was significantly improved and the expression levels of nephrin and podocin also markedly increased (P<0.05).CONCLUSION: APS might protect kidney against STZ-induced injury via increasing the expression of nephrin and podocin in podocytes.     

Effect of caveolin-1 expression on high-salt diet-induced endothelial dysfunction in type 1 diabetic rats

AIM: To investigate the underlying mechanisms responsible for endothelial dysfunction of type 1 diabetes mellitus (DM) rats fed with high-salt diet. METHODS: Type 1 DM was induced by intraperitoneal injection of streptozotocin (70 mg/kg). Normal and diabetic rats were fed high-salt food (HS, 8% NaCl) and standard food for 6 weeks, respectively. Isometric tension of the mesenteric arteries were measured. The expression of Akt, endothelial nitric oxide synthase (eNOS) and caveolin-1 (Cav-1) was examined by Western blot. RESULTS: The rats in DM+HS group exhibited more pronounced impairment of vasorelaxation to acetylcholine and insulin compared with either DM group or HS group (P<0.01). Akt and eNOS phosphorylation levels, and nitric oxide (NO) concentration in DM+HS group were significantly lower than those in DM group (P<0.01). The level of Cav-1 in DM+HS group was significantly higher than that in DM group and HS group. CONCLUSION: Impaired endothelial Akt activation, increased Cav-1 expression and resultant decreased eNOS activation contribute to aggravate high-salt diet-induced endothelial dysfunction and hypertension in DM rats.     

Changes of heart function and serum cardiac troponin I in early type 2 diabetic rats

AIM: To observe the changes of heart function and the expression of serum cardiac troponin I(cTnI) in early type 2 diabetic rats, and to explore the role of cTnI in the development of type 2 diabetes and early diabetic cardiomyopathy.METHODS: The type 2 diabetes rat model was established by an injection of streptozotocin after high fat diet(5 weeks). The rats were randomly divided into control group, model group of 2 weeks, and model group of 4 weeks. M-mode echocardiography was performed for echocardiographic measurements. Fasting blood glucose(FBG), total cholesterol(TC), triglyceride(TG), high density lipoprotein-cholesterol(HDL-C), low density lipoprotein- cholesterol(LDL-C), fasting insulin(FINS) and cTnI levels were tested. HE staining was used to observe the pathological changes of myocardial structures. The alteration of cTnI in myocardium was determined by Western blot.RESULTS: Compared with normal group, the levels of TC, TG and LDL-C in type 2 diabetic rats were significantly increased, HDL-C levels were significantly reduced. Cardiac histological analysis revealed that type 2 diabetes induced cardiomyocytes degeneration and necrosis. The expression of cTnI increased significantly in diabetic groups compared to control group, and that in model group of 4 weeks increased far more than that in model group of 2 weeks(P<0.05).CONCLUSION: The increased level of cTnI and the change of the heart function may be associated with the development diabetic cardiomyopathy. These changes are valuable for the early clinical diagnosis of myocardial injury in diabetic cardiomyopathy.     

Effects of curcumin analogue L6H4 on myocardial tissue of type 2 diabetic rats

AIM: To explore the effects of curcumin analogue L6H4 on the myocardial tissue of type 2 diabetic rats and its mechanism. METHODS: Male Sprague-Dawley rats were randomly divided into normal control (NC) group, high-fat (HF) group, high-fat treatment (FT) group, diabetes mellitus (DM) group and diabetes treatment (DT) group.The rats in the latter 4 groups were fed high-fat diet for 4 weeks, then the rats in DM groups and DT groups were intraperitoneally injected with streptozotocin (STZ) to induce type 2 diabetes, while the rats in FT group and DT group were given L6H4. The blood glucose and lipid levels were detected by biochemical method, and serum adiponectin (APN) levels were detected by ELISA. The serum insulin levels were measured by radioimmunoassay and homeostasis model assessment of insulin resistance (HOMA-IR) were calculated. The morphological changes of myocardium were observed by Masson staining and electron microscopy. The protein expression of adiponectin receptor 1 (AdipoR1) and transforming growth factor β1(TGF-β1) in myocardial tissue were determined by immunohistochemistry. The protein expression of adipoR1 was also detected by Western blot for verification. RESULTS: Compared with NC group, the blood glucose, lipids, insulin, HOMA-IR and TGF-β1 were increased in HF and DM group, but they were decreased after treated with L6H4. Compared with NC group, the concentration of serum APN were decreased and the expression of AdipoR1 in the myocardium were weakened in HF group and DM group, and they increased after treated with L6H4. The myocardial fibrosis was obvious in HF group and DM group, the mitochondria in cardiomyocytes expanded, and the cristae disordered, partial disappeared. These lesions were significantly reduced after L6H4 treatment. CONCLUSION: L6H4 exerts a protective effect on the heart in type 2 diabetic rats. The increased concentration of serum APN, the enhanced expression of AdipoR1, and the expression of TGF-β1 inhibited by APN may be involved in the mechanism of protection.     

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.     

Expression of cathepsin B and cystatin C and its potential role in diabetic rats

AIM: To observe the expressions of cathepsin B (CB) and cystatin C (CC) in different stage of diabetic rats and to investigates their potential roles.METHODS: Sixty rats were divided into diabetes mellitus group induced by intravenous injection of streptozotocin (55 mg/kg) and normal group injected with citrate buffer. Ten rats were sacrificed respectively at the end of fourth week, eighth week and sixteenth week in both groups. 24 h urine excretion was collected in rats before sacrifice. The blood and the kidney were also collected. The mRNA and protein expressions of CB and CC in kidney were detected by real time PCR and immunohistochemical staining, respectively.RESULTS: At the end of eighth week, the expression of Ccr, 24 h urinary protein excretion, CB, CC in diabetic rats increased significantly, compared to the results at the fourth week (P<0.01 or P<0.05). With the aggravation of diabetic nephropathy, the expressions of CC, colⅣ, FN and 24 h urinary protein excretion were up-regulated significantly (P<0.01 or P<0.05). The expression of CB in diabetic rats was up-regulated at eighth week significantly (P<0.01), whereas, at the end of sixteenth week it was down-regulated significantly (P<0.01). The 24 h urinary protein excretion, the expressions of colⅣ at protein and mRNA levels and FN were negatively correlated with CB (P<0.01).CONCLUSION: The unbalance of CB and CC exists in diabetic nephropathy renal tissue, which is likely to lead to the accumulation of extracellular matrix.     

Influence of Tangshenfang on diabetic liver injury and the expression of SIRT1 and PGC-1α in the liver tissue

AIM: To observe the effect of Tangshenfang (TS) on the liver protection and the levels of silent information regulator 1 (SIRT1) and peroxisom proliferator-activated receptor γ coactivator-1α (PGC-1α) in the liver tissue. METHODS: The rat model of diabetes mellitus (DM) was established by intravenous injection of streptozotocin (STZ;30 mg/kg) after having the high fat/high glucose diets for 1 month. The diabetic rats were randomly divided into DM group, DM with high-dose TS (TS^Hi) group, medium-dose TS (TS^Med) group and low-dose TS (TS^Low)group. The normal rats were served as control group. There were 8 rats in each group. After treatment with TS for 12 weeks, the serum biochemical indices including fasting blood glucose (FBG), triglyceride (TG), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were tested. Fasting insulin (FINS) was also detected by radioimmunoassay, and homeostatic model assessment for insulin resistance (HOMA-IR) was calculated. The serum levels of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) were measured by ELISA. The activity of SOD and content of MDA in the liver tissues were measured by the methods of hydroxylamine and thiobarbituric acid. The liver pathological changes were observed under light microscope with HE and Masson staining. The protein expression of SIRT1and PGC-1α in the liver tissues was determined by Western blot. RESULTS: In DM group, serum FBG, TG, ALT, AST, FINS, HOMA-IR, TNF-α and IL-1 were obviously increased compared with the control group (P<0.01). The fatty changes, local necrosis, inflammation and fibrosis in the liver tissues were observed. The content of MDA in liver increased, while the activity of SOD decreased markedly. The protein expression of SIRT1 and PGC-1α was decreased (P<0.05). In TS treatment groups, all these changes in DM rats were markedly reversed by TS, and the protein expression of SIRT1 and PGC-1α in the liver tissues was markedly increased. CONCLUSION: TS may protect the rats from diabetic liver injury by increasing the expression of SIRT1 and PGC-1α, and thereby improving insulin resistance and oxidative stress.     

Effects of extract of Ginkgo biloba on cognitive function and apoptosis of hippocampus neuronal cells in type 1 diabetic rats

AIM: To investigate the protective mechanism of extract of Ginkgo biloba (EGB) on apoptosis of hippocampus neuronal cells in type 1 diabetic encephalopathic rats. METHODS: Thirty-six male Sprague-Dauley rats were divided into 3 groups: control group, diabetic group and EGB-treated group. Streptozotocin was injected intraperitoneally to the animals in later two groups to induce diabetes. The rats in EGB-treated group were injected intraperitoneally with EGB, and the same volume of normal saline was injected to the rats in other groups. At the end of the 12th week, the spatial learning and memory abilities of rats in each group were examined by Morris water maze test. Blood glucose and serum insulin concentration were measured. The neuron densities in hippocampus were measured by Image-Pro Plus 6.0 software. The expressions of Bax, Bcl-2, caspase-3 were assayed by Western blotting and immunohistochemistry. RESULTS: Compared to control group, the level of blood glucose (P<0.01), the protein expression of Bax (P<0.01) and caspase-3 (P<0.01) in hippocampus neuronal cells, and the ratio of Bax/Bcl-2 (P<0.01) and the escape latency (P<0.01) in diabetic group, were significantly increased, while the serum insulin concentration (P<0.01), the neuronal density (P<0.05) in CA1,CA2 hippocampal regions and the platform searching score (P<0.01) were significantly deceased. After treated with EGB, the serum insulin concentration (P<0.05), the neuronal density (P<0.05) in CA1,CA2 hippocampal regions and the platform searching score (P<0.01) were significantly increased, while the level of blood glucose (P<0.01), the protein expression of Bax (P<0.05), caspase-3 (P<0.05) in hippocampus neuronal cells, the ratio of Bax/Bcl-2 (P<0.01) and the escape latency (P<0.05) were significantly deceased than those in diabetic group. The protein expression of Bcl-2 in hippocampus neuronal cells did not alter in any experimental rats. CONCLUSION: EGB improves the spatial learning and memory capacity in diabetic rats by decreasing the expression of Bax, Bax/Bcl-2 ratio and down-regulating caspase-3 to reduce neurocyte apoptosis and increase the neuron density in CA1, CA2 hippocampal regions, suggesting that effective regulation of neuron apoptosis associated genes may be one of the mechanisms for EGB to treat diabetic encephalopathy.     

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.     

Effects of extract of gingko biloba on expression of glucocorticoid receptor in hepatic tissues from type 2 diabetic rats

AIM: To study the effect and mechanism of extract of ginkgo biloba (EGB) on liver glucocorticoid receptor (GR) expression in type 2 diabetic rats. METHODS: Thirty male Sprague-Dawley rats were divided randomly into three groups: normal control group (n=10), type 2 diabetic group (n=10) and ginkgo biloba treated group (n=10). After fed with high-fat feeding for 4 weeks, the later two groups were injected with streptozotocin at a dose of 30 mg/kg intraperitoneally to induce type 2 diabetic rat model. The EGB treated group was gavaged with EGB at the dose of 50 mg·kg-1·d-1 for 12 weeks. At the end of experiment, the rats were sacrificed, the blood glucose, serum lipid and blood insulin were measured. The morphology of liver tissue was observed under light microscopy with HE staining. GR mRNA expression in liver was measured by RT-PCR. The level of GR protein expression in liver tissue was detected by immunohistochemistry. RESULTS: EGB reduced the levels of blood glucose, blood lipids, blood insulin in diabetic rats. EGB also relieved fatty degeneration and necrosis of the hepatic cells, ameliorated infiltration of inflammatory cells in the liver; and decreased GR expression at both mRNA and protein levels in diabetic liver. CONCLUSION: EGB may inhibit GR expression in liver of type 2 diabetic rats, which results in decreasing the level of blood glucose, blood lipid, blood insulin and relieving the liver damage in type diabetic rats.     

Intervention of gossypol and relationship between cognitive function and expressions of 11β-HSD1 and GR in brain of type 2 diabetic rats

AIM: To study the effect of gossypol on the cognitive function of type 2 diabetic rats, and to explore its mechanism. METHODS: Thirty male Sprague-Dawley rats were divided into three groups randomly: normal group, type 2 diabetic group and gossypol treated group. After fed with high-fat diet for 4 weeks, the later two groups were injected with streptozotocin intraperitoneally to establish type 2 diabetic rat model. The animals in gossypol treated group were given gossypol at dosage of 15 mg/kg once per day for 4 weeks by gavage. Since 5th week, the times of gavages were changed into once per week at the same dosage and lasted to 12th week. Learning and memory abilities of rats were assayed with Morris water maze test. The concentration of blood glucose was measured by biochemical method. The levels of serum corticosterone and insulin were detected by enzyme-linked immunosorbent assay and radioimmunoassay, respectively. The protein expressions of 11β-HSD1 and GR in cerebral cortex and hippocampus were determined by Western blotting. The morphological changes of cerebral cortex and hippocampus were observed under light microscope and transmission electronic microscope, respectively. RESULTS: Compared to normal group, the karyopyknosis, dilation of golgiosome and mitochondria swelling of neuron from cerebral cortex and hippocampus were prominent in diabetic group. The concentrations of blood glucose, serum corticosterone and insulin increased significantly (P<0.01). Protein expression of GR decreased (P<0.05), 11β-HSD1 protein tended to increase. Platform searching score was lower (P<0.01) and escape latency was longer (P<0.01) in diabetic group. After treated with gossypol, the concentrations of blood glucose, serum corticosterone and insulin declined (P<0.01). The protein expression of 11β-HSD1 was decreased (P<0.05) and GR was increased (P<0.05). Escape latency was shorter (P<0.01) and platform searching score was increased (P<0.01). CONCLUSION: Gossypol may improve the cognitive function of type 2 diabetic rats. Decreasing the level of 11β-HSD1 and increasing GR protein in the brain may be involved in the mechanism.