PPARs signaling pathway is involved in diabetic hepatopathy in mice

AIM: To investigate the role of peroxisome proliferator-activated receptors (PPARs)-inflammation signaling pathways in diabetic hepatopathy. METHODS: Diabetic mouse model was established by feeding the mice with a high-energy diet for 4 weeks combined with intraperitoneal injection of streptozotocin (STZ; 40 mg·kg^-1·d^-1 for 5 d). The hepatopathy model was confirmed by histopathological observation and the indexes of liver function, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), after another 4 weeks. Moreover, fasting blood glucose (FBG), and serum levels of total cholesterol (TC), triglyceride (TG) and insulin were measured, and the HOMA insulin resistance index (HOMA-IR) was calculated. The mRNA and protein expression levels of PPARs and inflammation-related factors were measured by qPCR and Western blot, respectively. RESULTS: After treatment with STZ for 7 d, the FBG of mice exceeded 11.1 mmol/L, suggesting that the diabetic model was established. After 4 weeks, the structural deformation of the hepatocytes (including hepatocytes containing abundant fat vacuoles, and inflammatory cell infiltration), and the increases in the serum levels of insulin, HOMA-IR, TC, TG, ALT, AST and ALP were observed (P<0.01), indicating the occurrence and progression of hepatopathy in diabetic mice. Meanwhile, compared with the control group, the mRNA and protein expression of PPARα, PPARβ and PPARγ decreased, but the expression of nuclear factor-κB (NF-κB), cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) significantly increased in the diabetic hepatopathy mice (P<0.01). CONCLUSION: Down-regulation of PPARα, PPARβ and PPARγ and activation of NF-κB-COX-2/iNOS signaling pathways may be involved in the diabetic hepatopathy in mice induced by long-term high-energy diet feeding combined with intraperitoneal injection of STZ.     

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 EGCG on GLUT2/G6PD/GS expression and blood glucose level in type 2 diabetic rats

AIM To investigate whether epigallocatechin gallate （EGCG） improves blood glucose in type 2 diabetic rats through glucose transporter 2 （GLUT2）-glucose-6-phosphate dehydrogenase （G6PD）-glycogen synthase （GS） pathway. METHODS Type 2 diabetes mellitus （T2DM） model was established in male Sprague-Dawley （SD） rats by feeding with high-fat diet and injection of streptozotocin （STZ）. The rats were divided into 5 groups （n=10）： control （Con） group, T2DM model （M） group, metformin （Met; 200 mg/kg, ig） group, T2DM+low-dose （50 mg/kg, ig） EGCG （EL） group, and T2DM+high-dose （100 mg/kg, ig） EGCG （EH） group. Diabetic rats were given drugs for 8 weeks. After 8 weeks of administration, the rats were killed, and the blood and liver tissues were collected. The levels of fasting blood glucose （FBG）, fasting serum insulin （FINS） and serum glycosylated hemoglobin were measured by biochemical tests. Liver glycogen were test by periodic acid-Schiff （PAS） staining. The mRNA expression of G6PD in the liver was detected by real-time PCR. The protein levels of GS and GLUT2 were determined by Western blot and immunohistochemistry. RESULTS T2DM rat model was established successfully. Compared with Con group, the levels of FBG, FINS and serum glycosylated hemoglobin in M group were increased significantly （P<0.05）, while the insulin sensitivity index （ISI）, the liver glycogen, the G6PD mRNA expression, and the protein levels of GS and GLUT2 were decreased significantly （P<0.05）. Compared with M group, the levels of FBG and serum glycosylated hemoglobin in Met group and EH group were decreased significantly （P<0.05）, while the ISI, the liver glycogen, the G6PD mRNA expression, and the protein levels of GS and GLUT2 were increased significantly （P<0.05）. CONCLUSION EGCG reduces the blood glucose level in T2DM rats, which may be related to the regulation of GLUT2-G6PD-GS signaling pathway.     

Administration of magnolol postpones development of hypertension in juvenile spontaneous hypertensive rats

AIM:To investigate the effects of magnolol (MAG) on blood pressure and aortic vasodilatation to insulin in juvenile spontaneous hypertensive rats (SHR). METHODS:Four-week-old male SHR and age-matched normotensive Wistar-Kyoto (WKY) control rats were used. SHR and WKY rats were randomized into 2 groups and treated daily by gavage with vehicle (distilled water) or MAG (100 mg·kg-1·d-1). After 3 weeks of treatment, blood pressure, aortic vasorelaxation, fasting glucose and plasma insulin levels, the expressions of PPARγ and TRB3, and insulin-stimulated Akt/endothelial nitric oxide synthase (eNOS) activation were measured. In vitro, human umbilical vein endothelial cells (HUVECs) were cultured in the medium containing glucose (25 mmol/L) and palmitate (500 μmol/L). RESULTS:Treatment of young SHR with MAG for 3 weeks decreased blood pressure, improved insulin-induced aortic vasodilation, and Akt and eNOS activation , increased PPARγ expression and decreased TRB3 expression. In cultured HUVECs, MAG incubation increased PPARγ exprssion, decreased TRB3 expression, and elevated insulin-induced phosphorylated Akt and eNOS levels and NO production, which were reversed by PPARγ antagonist. CONCLUSION: Treatment of young SHR with MAG at the prehypertensive stage decreases blood pressure via improving vascular insulin resistance that is at least partly attributable to up-regulation of PPARγ, down-regulation of TRB3 and consequently activation of Akt and eNOS in blood vessel .     

Role of Wnt pathway in Aβ deposition in hippocampus of insulin resistant rats before and after treated with rosiglitazone

AIM: To investigate the relationship between classical Wnt pathway with β-amyloid peptide(Aβ) deposition in hippocampus of insulin resistance(IR) rat model and to observe the above-mentioned proteins and the correlation with peroxisome proliferator-activated receptor γ(PPARγ) by treating the IR rats with rosiglitazone.METHODS: The rat models of IR and TZD were made. The plasma insulin and the plasma glucose levels were tested by RIA and glucose-oxidase methods, respectively. The indexes of insulin resistance were calculated by HOMA-IR. The proteins of Aβ, Wnt3a, β-catenin and PPARγ were analyzed by Western blotting.RESULTS: The plasma insulin in IR group was significantly higher than that in control group. Insulin resistance, which was calculated by HOMA-IR, was significantly higher in IR group than that in control group. The levels of Aβ and β-catenin in IR group were higher than those in control group, while the levels of Wnt3a and PPARγ were decreased. After treatment with rosiglitazone, Aβ was reduced but Wnt3a, β-catenin and PPARγ were increased.CONCLUSION: In hippocampus of IR rats, Aβ is deposited and the levels of Wnt3a and Wnt are reduced. Rosiglitazone, as a PPARγ agonist, can upregulate the activity of Wnt pathway and reduce Aβ deposition in rat hippocampus.     

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.     

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.     

Oxymatrine ameliorates high fat-induced insulin resistance in ApoE-/- mice

ATM: To investigate the effect of oxymatrine (OXY) on high fat-induced insulin resistance in mice, and to investigate the mechanism. METHODS: ApoE^-/-mice with high-fat diet for 16 weeks were divided into insulin resistance group, and OXY groups at concentrations of 25, 50 and 100 mg/kg. C57BL/6J mice served as normal control group. The mice in OXY groups were gavaged with OXY for 8 weeks. Glucose tolerance test in the mice was performed. Fasting blood glucose (FBG), total cholesterol (TC), triglyceride (TG), fatty acid (FFA) and fasting insulin (FINS) in the plasma were measured. The mRNA expression of insulin receptor (INSR), insulin receptor substrate-2 (IRS-2), glucose transporter 2 (GLUT2) in the liver tissues was examined by RT-qPCR. The protein levels of GLUT2, INSR, IRS-2, p-INSR, p-IRS-2, PI3K, p-PI3K, serine/threonine protein kinase (AKT) and p-AKT were examined by Western blot.RESULTS: OXY reduced the levels of FBG, TC, TG, FFA and FINS, and attenuated insulin resistance. Compared with insulin resistance group, the mRNA expression of INSR, IRS-2 and GLUT2 significantly increased in OXY groups (P<0.05). The protein levels of p-INSR/INSR, p-IRS-2/IRS-2, p-PI3K/PI3K, p-AKT/AKT and GLUT2 also increased in OXY groups (P<0.05).CONCLUSION: OXY ameliorates high fat-induced insulin resistance in mice via PI3K/AKT pathway.     

Protective effect of adiponectin on glucose and lipid metabolism by suppressing MHCⅡ expression

AIM: To investigate whether the protective effect of adiponectin on glucose and lipid metabolism is achieved through down-regulating major histocompatibility complex class Ⅱ (MHCⅡ) in the adipose tissue. METHODS: Adiponectin knockout (KO) mice and C57BL/6(WT) mice were fed with high-fat diet and standard diet for 24 weeks, respectively. The body weight, fasting blood glucose (FBG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), hepatic histology, and class Ⅱ trans-activator (CⅡTA), histocompatibility 2 class Ⅱ antigen E beta (H2-Eb1) and cluster of differentiation 74(CD74) mRNA and MHC Ⅱ protein levels in adipose tissue were measured at sacrifice. siRNA targeting MHC Ⅱ and overexpression vector was used in 3T3-L1 cells to explore the effect of adiponectin on the protein level of MHCⅡ. RESULTS: The levels of body weight, FBG, FINS, HOMA-IR, TC, TG, LDL-C, hepatic steatosis, CⅡTA, H2-Eb1 and CD74 mRNA expression, and MHCⅡ protein expression in the KO mice were higher than those in the WT mice that fed with high-fat diet or standard diet. In 3T3-L1 cells, inhibition of adiponectin reversed MHC Ⅱ protein level induced by specific siRNA. The expression of MHC Ⅱ in adipocytes decreased after adiponectin was overexpressed. CONCLUSION: Adiponectin improves glucose and lipid metabolism through suppressing the expression of MHCⅡ in the adipose tissue.     

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.     

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.     

Somatostatin expression in rat islet of steroid diabetes mellitus

AIM: To investigate the effects of dexamethasone(DEX) on the pancreatic endocrine function when steroid diabetes mellitus(SDM) occurred. METHODS: 140 rats were randomly assigned to 4 groups according to the clinic doses of DEX administration, Radioimmunoassay and in situ hybridization were applied to evaluate islet hormone changes in pancreas and blood.RESULTS: Changes in fasting blood glucose(FBG) 、fasting serum insulin(FINS) caused by DEX were dose and time-dependent. Changes in somatostatin(SS)mRNA and protein in islet as well as FINS occurred earlier than that of FBG. CONCLUSION: The super-physiological DEX influenced the expression SS and insulin secretion in islet, which may play an important role in SDM.     

Effects of liraglutide on adiponectin and insulin resistance in rats with non-alcoholic fatty liver disease

AIM：To investigate the effects of glucagon-like peptide 1 analog, liraglutide, on adiponectin and insulin resistance in the rats with diet-induced non-alcoholic fatty liver disease (NAFLD). METHODS：Male rats were randomly divided into 3 groups:normal diet (ND) group (n=10), high-fat diet (HFD) group (n=10), and HFD with intraperitoneal injection of liraglutide group (n=10, first 12 weeks with HFD, later 4 weeks with liraglutide). All treatments continued for 16 weeks, and then the rats were killed ethically and the blood samples and liver tissues were collected. The levels of alanine aminotransferase (ALT), fasting blood glucose (FBG), total cholesterol (TC) and triglyceride (TG) were detected by a biochemical automatic analyzer. The levels of free fatty acids (FFAs), fasting insulin (FINS) and adiponectin were measured by RIA and ELISA. RESULTS：Compared with HFD group, the body weight, liver index, homeostasis assessment-insulin resistance (HOMA-IR), the serum levels of TG, TC, ALT and FBG, and the liver levels of TG, TC and FFAs in the rats in liraglutide group were apparently lower, the degree of hepatic steatosis and inflammatory activity significantly decreased (P<0.05), and the level of adiponectin in the serum and liver homogenate increased ob-viously (P<0.05). The level of adiponectin in the liver homogenate was negatively correlated with the levels of FFAs in the liver homogenate. CONCLUSION:Liraglutide is beneficial for NAFLD rats to improve insulin resistance and reduce hepatic steatosis by increasing the level of adiponectin in the serum and liver tissues.     

Effect of peroxisome proliferator-activated receptor γ agonist rosiglitazone on intestinal injury in rats undergoing orthotopic autologous liver transplantation by inhibiting inflammatory response

AIM: To investigate the effect of rosiglitazone, a peroxisome proliferators-activated receptor γ(PPARγ) agonist, on the expression of PPARγ, the activation of NF-κB and intestine injury in the rats undergoing orthotopic autologous liver transplantation(OALT).METHODS: Sprague-Dawley male rats were randomly divided into 4 groups:control group, sham group, OALT group and rosiglitazone(0.3 mg/kg, iv) pretreatment(ROS+OALT) group. The OALT model was established, and the intestinal tissues were collected 8 h after the liver reperfusion. The intestinal tissue sections were stained to visualize the damage. The expression of PPARγ and NF-κB in the tissues, the concentrations of diamine oxidase(DAO) and fatty acid-binding protein 2(FABP2) in the serum and the concentration of TNF-α and IL-6 in the tissues were measured.RESULTS: Compared with sham group, the intestinal mucosa of the rats showed obvious pathological injury after liver reperfusion in OALT group and ROS group, the Chiu,s scores of intestinal mucosa was significantly higher, and the serum concentrations of DAO and FABP2 increased(P<0.05). After rosiglitazone pretreatment, the injury of intestinal mucosa of the rats was alleviated, the Chiu,s scores was lower and the serum concentrations of DAO and FABP2 decreased(P<0.05), the PPARγ expression was obviously up-regulated in the intestinal tissues, the nuclear translocation of NF-κB was reduced and the concentrations of IL-6 and TNF-α were decreased.CONCLUSION: During perioperative period of OALT in rats, the inflammatory responses are obvious. Furthermore, obvious intestinal injury occurs. PPARγ agonist rosiglitazone obviously up-regulates PPARγ expression and inhibits the inflammation in the intestines, thus protecting against intestinal injury in rats undergoing OALT.     

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.     

Activation of PPARs is involved in effect of bezafibrate on diabetic hepatopathy in mice

AIM: To investigate the effects of bezafibrate (BEZ) on diabetic hepatopathy in mice. METHODS: Diabetic hepatopathy model was established by a long-high-energy diet combined with streptozotocin (40 mg·kg^-1·d^-1× 5 d, ip), and then bezafibrate (75 mg·kg^-1·d^-1, ig) was supplemented for 4 weeks. Fasting blood glucose (FBG) was detected every week. The structure of liver was observed by HE staining, and the liver function was measured by observing the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Total cholesterol (TC), triglyceride (TG), insulin and HbA1c were determined by commercial kits, and then HOMA insulin resistance index (HOMA-IR) was calculated. The expression of peroxisome proliferator-activated receports (PPARs) at mRNA and protein levels was determined by RT-qPCR and Western blot, respectively. RESULTS: After 7 days of treatment with streptozotocin, the FBG level of the mice exceeded 11.1 mmol/L. At the end of the experiment, the structural deformation of the hepatocytes (containing abundant fat vacuoles, infiltrated by inflammatory cells, etc.) was observed, with the increases in insulin, HbA1c, HOMA-IR, TC, TG, ALT and AST in diabetic mice (P<0.01). Meanwhile, the expression of PPARα, PPARβ and PPARγ at mRNA and protein levels was decreased (P<0.01). Bezafibrate treatment markedly attenuated the structural and functional damages of the liver in the diabetic mice (P<0.01), and reduced the levels of FBG, insulin, HbA1c, HOMA-IR, TC and TG (P<0.05). Bezafibrate also up-regulated the expression of PPARα, PPARβ and PPARγ (P<0.01). CONCLUSION: Bezafibrate attenuates hepatic injury in diabetic mice via the activation of PPARs-related signaling pathway.     

Effect of hydrogen sulfide on myocardial fibrosis and PPARγ and NF-κB expression in rat model of diabetes

AIM: To explore the effects of hydrogen sulfide (H₂S) on the myocardial fibrosis in a rat model of diabetes and its mechanism.METHODS: Single intraperitoneal injection of streptozotocin (STZ) was utilized to establish a rat model of diabetes. Sodium hydrosulfide was used as an exogenous donor of hydrogen sulfide. Male SD rats were randomly divided into control group, STZ group, STZ+H₂S group and H₂S group. Eight weeks later, HE and VG staining methods were used to observe the collagen distribution and collagen volume fraction was measured by image analysis. The expression levels of type I collagen, PPARγ and NF-κB in the cardiac tissues were determined by Western blotting.RESULTS: Compared with control group, collagen distribution and the expression levels of type I collagen and NF-κB in the cardiac tissues were markedly increased (P<0.05), while PPARγ was significantly decreased in STZ group (P<0.05), but these indexes were reversed significantly in STZ+H₂S group (P<0.05). The expression levels of type I collagen, PPARγ and NF-κB had no significant difference between H₂S group and control group.CONCLUSION: Hydrogen sulfide attenuates cardiac fibrosis in diabetic rats, and its mechanism may be related to PPARγ-NF-κB signaling pathway.     

Effects of intranasal Escherichia coli on glucolipid metabolism in high-fat diet-induced obese mice

AIM: To study whether the pulmonary infection of Escherichia coli (E. coli) interferes the glucolipid metabolism in high-fat diet-induced obese mice. METHODS: High-fat diet-induced obese mice (n=48) and normal chow-fed control mice (n=48) were intranasally infused with 40 μL fluid containing 4×10⁹ CFUs E. coli. The serum, periepididymal adipose tissue and liver were obtained at 0 d, 1 d, 2 d, 3 d and 4 d after infection. The body mass, periepididymal adipose tissue and liver were weighed, and the levels of fasting blood glucose (FBG), fasting blood insulin (FINS), free fatty acid (FFA) and very-low-density lipoprotein (VLDL) were measured by ELISA. The serum total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), and hepatic TG contents were detected, and the hepatic steatosis was observed under microscope with oil red O staining. RESULTS: Compared with day 0, the body mass, fat mass and fat index were decreased significantly from day 1 to day 4 after infection (P<0.05). The levels of FBG, FINS and HOMA-IR were apparently raised from day 2 to day 4 after infection (P<0.05). The contents of serum FFA, TG and VLDL were increased markedly from day 1 to day 4 after infection (P<0.05). However, the concentrations of serum TC, LDL-C and HDL-C were decreased obviously from day 1 to day 3 (P<0.05). The liver mass, liver index and TG content were significantly increased from day 1 to day 4 (P<0.05). Consistently, the lipid droplet accumulation in the liver cells was increased obviously at day 2 and day 4 after infection. Compared with control group, except the levels of serum TC, LDL-C and HDL-C in obese group substantially decreased, the other indexes were increased by different degrees during the whole experiment period (P<0.05). CONCLUSION: Pulmonary infection of Escherichia coli exacerbates the disorder of glucose and lipid metabolism in high-fat diet-induced obese mice, which contributes the development of insulin resistance and hepatic steatosis.     

Effects of piceatannol on rat kidney with diabetic nephropathy in early stage

AIM: To observe the effect of piceatannol on the kidney of diabetic nephropathy rats in early stage, and to explore the possible mechanisms.METHODS: The rats were randomly divided into 5 groups:control group, model group, low dose of piceatannol treatment group, medium dose of piceatannol treatment group and high dose of piceatannol treatment group. The rat model of diabetic nephropathy was induced accordingly, and the rats received 20 mg/kg, 40 mg/kg or 60 mg/kg of piceatannol by gavage once a day for 4 weeks. Blood glucose was detected by glucometer. The urea nitrogen and creatinine levels in the serum were measured by urease-glutamate dehydrogenase enzymatic and inosine acid oxidase methods, respectively, and 24 h urinary microalbumin was analyzed by immune transmission turbidimetry test. Moreover, the pathological changes of the kidney tissues were observed under microscope with HE staining. The protein expression of TGF-β1 and Smad 7 and the phosphorylation levels of Smad2 and Smad3 were determined by Western blot. RESULTS: Compared with model group, piceatannol treatment significantly decreased the levels of blood glucose, blood urea nitrogen and urinary microalbumin, but had no effects on serum creatinine. Furthermore, HE staining showed that the increased mesangial cells, matrix hyperplasia and degenerated epithelial cells in model group were markedly inhibited after piceatannol treatment. Additionally, piceatannol treatment also reduced the protein expression of TGF-β1 and Smad 7, and the phosphorylation levels of Smad2 and Smad3. CONCLUSION: Piceatannol attenuates pathological progression in the kidney of diabetic nephropathy rats in early stage, which may be through inhibiting TGF-β/Smad signaling pathway.