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.     

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.     

Analgesic effect of angiotensin angiotensin Ⅱ type 2 receptor antagonist EMA401 on neuropathic pain in rats and its mechanism

AIM: To explore whether angiotensin Ⅱ type 2 receptor antagonist EMA401 decreases neuropathic pain and the expression of growth-associated protein-43 (GAP-43), protein kinase C (PKC) and calmodulin (CaM) in dorsal root ganglia (DRG) during chronic constriction injury (CCI) in rats. METHODS: SD rats were used to establish CCI model and randomly divided into 4 groups. The rats in model group were given equal volume of normal saline by intragastric administration. The rats in low dose (LD) group were given 5 mg/kg EMA401 by intragastric administration. The rats in middle dose (MD) group were given 10 mg/kg EMA401 by intragastric administration. The rats high dose (HD) group were given 20 mg/kg EMA401 by intragastric administration. The rats in sham operation group received equal volume of normal saline by intragastric administration. Thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were measured before operation and 7 d, 14 d and 28 d after CCI. After behavioral test, DRG of lumbar spinal was obtained from each group, and was used to determine Ca²⁺ concentration by o-cresolphthalein complexone microplating method, and the expression of GAP-43, PKC and CaM at mRNA and protein levels by Western blotting and RT-PCR. RESULTS: Compared with model group, EMA401 significantly increased the TWL and MWT (P<0.05). Meanwhile, EMA401 significantly reduced Ca²⁺ concentration and the expression of GAP-43, PKC and CaM at mRNA and protein levels in the DRG (P<0.05). CONCLUSION: EMA401 may attenuate neuropathic pain of CCI by inhibiting Ca²⁺ concentration and the expression of GAP-43, PKC and CaM.     

Role of NF-κB in diabetic neuropathy

AIM:To investigate the role of NF-κB in diabetic neuropathy. METHODS:The diabetic rats were induced by intraperitoneal injection of streptozocin (STZ). The pain behavior test was used to detect the mechanical and thermal withdraw threshold of the rats’ bilateral hind paws. The protein levels of p-NF-κB and t-NF-κB in the rats’ L4 and L5 dorsal root ganglions (DRG) were determined by Western blotting. The expression of Nav1.7 in DRG of diabetic neuropathy rats with or without NF-κB inhibitor PDTC was detected by the method of immunohistochemistry. RESULTS:The mechanical and thermal withdraw threshold of bilateral hind paws in the diabetic rats was decreased from 4 weeks to 12 weeks after injection of STZ. The protein levels of p-NF-κB in L4 and L5 DRG were significantly increased in the rats with diabetic neuropathy. Intrathecal administration of NF-κB inhibitor PDTC attenuated the increase in p-NF-κB and Nav1.7 in L4 and L5 DRG. Pain behaviors were also alleviated by PDTC. CONCLUSION: The increase in p-NF-κB is closely rela-ted to the generation of diabetic neuropathy. Inhibition of NF-κB blocks pain behaviors and the over-expression of Nav1.7 in DRG.     

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.     

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.     

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.     

Alteration of leukocyte iNOS-mRNA expression in rat with diabetic mellitus induced by streptozocin

AIM: To clarify the relationship between expression of leukocyte iNOS-mRNA and pancreatic islet function in the diabetic rats induced by streptozocin (STZ). METHODS: Wistar rats were randomly divided into the control group (n=10) and the diabetic group (n=15). Expression of iNOS-mRNA in the peripheral blood leukocyte, liver and lung were detected with in situ hybridization and the blood sugar and insulin were also measured. RESULTS: It showed that the blood glucose content increased from (8.95±1.80) to (22.84±4.90) mmol·L^-1, however, the plasma insulin content decreased from (81.76±2.12) to (58.92±18.20) mU·L^-1 at the third day after the β cell was disfunctioned by STZ injection. No expression of leukocyte iNOS-mRNA in normal rat was detected. The percent rate of positive cells were significantly increased in the rats with diabetes. CONCLUSION: The expression of leukocyte iNOS-mRNA is positively related to the damage of β cells caused by STZ.     

Effects of icariin on expression of transforming growth factor β1 and type Ⅳ collagen in diabetic rat testis

AIM: To determine the beneficial effects of icariin on streptozotocin (STZ)-induced diabetic testopathy in rats. METHODS: The diabetic animal model was induced in male Sprague-Dawley rats by an injection of streptozotocin (40 mg/kg, iv). The rats were randomly divided into 3 groups: control group, model group and icariin (80 mg/kg, ig) group. Twelve weeks after injected with streptozotocin, all rats were anaesthetized and killed to remove the testes from scrotum. Serum concentrations of glucose and testosterone, and the levels of succinate dehydrogenase (SDH), acid phosphatase (ACP), γ-glutamyl transpeptidase (γ-GT) and lactate dehydrogenase (LDH) in testes were measured. The morphology of the testicular tissues was observed under light microscope. Immunohistochemistry was employed to determine the protein levels of TGF-β₁ and type Ⅳ collagen. RESULTS: Compared with control group, the content of serum glucose increased while the serum level of testosterone and the activitiy of SDH, ACP, γ-GT and LDH in testis decreased in model group (P<0.01). The histopathological examination showed that the diameters of seminiferous tubules and various grades of spermatocytes in the testis were markedly decreased. Compared with control group, the expression of TGF-β₁ and collagen Ⅳ was significantly increased in model group. These alterations were significantly attenuated in icariin group (P<0.01). CONCLUSION: Icariin evidently relieves testicular damage in rats with diabetic testopathy by improving the secretion of testosterone and reducing the expression of TGF-β₁ and collagen Ⅳ at protein level.     

Effects of mibefradil administered intrathecally on the expression of nNOS in spinal cord of the rats following chronic compression of dorsal root ganglion

AIM: To investigate the effect of mibefradil administered intrathecally on the pain threshold and the expression of neuron nitric oxide synthase (nNOS) in the spinal cord of the rats following chronic compression of dorsal root ganglion. METHODS: The chronic compression of dorsal root ganglion (CCD) model was adopted. Three different doses of mibefradil, a T-type calcium channel blocker, were administered singly intrathecally to the rats after CCD 5 days. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were determined with von Frey hair and thermal radiation apparatus before mibefradil administered and after mibefradil administered 30 min, 60 min, 120 min, 240 min, and 480 min. Changes of nNOS expression in neurons of the spinal dorsal horn were detected by immunohistochemistry method, and the number of the nNOS positive neurons was counted under microscope. RESULTS: MWT and TWL declined significantly from the first day to the 21st day after CCD. Mibefradil administered intrathecally attenuated significantly both mechanical and thermal hyperagesia of the rats, and markedly inhibited the increase in the nNOS expression. CONCLUSION: These data show that T type calcium channel plays a key role in the CCD-induced mechanical and thermal hyperalgesia and possibly involves in the nNOS expression in the spinal.     

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.     

Renal protective effect of spirinolactone and cilazapril on diabetic rats

AIM: To assess the renal protective effect of the combination use of spirinolactone and cilazapril on streptozotocin(STZ)-induced diabetic rats with single nephrectomy. METHODS: Diabetic nephropathies were induced by intraperitoneal injection of STZ in the rats with single nephrectomy. The rats were randomly divided into 5 groups: normal control; diabetes; diabetes treated with spirinolactone; diabetes treated with cilazapril; diabetic rats treated with spirinolactone and cilazapril. The expression of NF-κB and PAI-1 in the glomeruli was detected by immunohistochemical staining. RT-PCR was performed to evaluate the mRNA expression of AT-1R. RESULTS: Increased 24 h urinary protein, decreased Ccr and the pathological injury of the renal tissues were improved by the treatment with either spirinolactone or cilazapril alone and further ameliorated by using the combination of the two drugs. The activity of NF-κB and PAI-1 was higher in the renal tissues of diabetic rats than that in control group, and further attenuated by the combination therapy in both cases (P<0.05). The over-expression of AT-1R mRNA observed in the diabetic rats was attenuated by treating with spirinolactone or cilazapril and further reduced by the combination use of the two drugs (P<0.05).CONCLUSION: The combination use of spirinolactone and cilazapril confers superiority over monotherapy on the effect of renal protection. The mechanism may be partly correlated with synergistic suppression of the increasing activity of NF-κB and PAI-1 as well as the over-expression of AT-1R mRNA in renal tissues.     

Expression of TGF-β1 and Smad2/3 in kidney of STZ-induced diabetic nephropathy rats

AIM: To study the role of TGF-β/Smad pathway in the development of renal fibrosis in diabetic nephropathy.METHODS: Rats were induced to diabetic nephropathy by using tail intravenous injection of STZ.The expression of TGF-β₁, Smad2/3 protein and mRNA in kidney were examined at 2, 4, 8 and 16 weeks after STZ induction.CTGF, collagen-Ⅲ, PAI-1 mRNA expression in kidney at 16 weeks of STZ-induced diabetic nephropathy and normal rats were studied by RT-PCR.RESULTS: Weak TGF-β₁, Smad2/3 protein were detected in normal renal tissues while strong TGF-β₁, Smad2/3 staining were observed in renal tissues of diabetic nephropathy (0.057±0.030/0.223±0.040;0.017±0.010/0.153±0.010, respectively, P<0.05).The TGF-β₁, Smad2/3 protein expression were constantly high with the development of diabetic nephropathy and fibrosis (0.153±0.010, 0.122±0.050, 0.141±0.070 and 0.216±0.030 for 2, 4, 8 and 16 weeks, respectively).The TGF-β₁, Smad2 mRNA expression also increased with the development of diabetic nephropathy (2.86, 3.25 fold compared to control, respectively).The expression of TGF-β₁, Smad2, CTGF, collagen-Ⅲ and PAI-1 mRNA were significantly higher in kidney of 16 week diabetic nephropathy rats than that in normal ones (3.92, 2.95, 1.57, 1.95 and 1.97 folds compare to control, respectively, P<0.05).CONCLUSION: The results indicate that TGF-β₁/ Smad2 pathway activity might play an important role in pathophysiological process of diabetic nephropathy.It may be involved in diabetic renal fibrosis through up-regulation of CTGF and PAI-1 to promote extracellular matrix deposition.     

Influence of Xiaoke keli Ji on glycemia and serum lipoprotein levels in diabetic nephropathy rats

AIM:To observe the changes of glycemia and serum cholesterol and triglyceride in diabetic nephropathy rats and therapeutic effects of Xiaoke Keli Ji.METHODS:3/4 nephrectomy was adopted firstly, three weeks later streptozotocin(STZ) was administered intraperitoneally to establish diabetic nephropathy model in rats. Animals were divided into four groups:model group, Xiaoke Keli Ji treatment group, positive control group and sham group. Changes of serum sugar and serum creatinine, cholesterol and triglyceride were examined at 1, 2, 3, 4, 5 weeks after STZ injection. Renal tissue samples were adopted at 6th week and studied by light microscopy.RESULTS:Model group demonstrated different degree of glomerular sclerosis. Lesions in treatment group were alleviated. Serum creatinine, serum sugar and serum cholesterol were higher at 1, 2, 3, 4, 5 weeks after STZ injection in model group than that of the sham group (P＜0. 05), serum triglyceride was higher at 1, 2, 3, 5 weeks after STZ injection in model group than that of the sham group(P＜0. 05). Xiaoke Keli Ji reduced those changes. Serum sugar was in positive correlation with serum lipoprotein.CONCLUSION:Diabetic nephropathy model was duplicated successfully. High serum sugar may lead to high serum lipoprotein, Xiaoke Keli Ji may treat diabetic nephropathy by reducing serum sugar and serum cholesterol and triglyceride.     

Effects of diabetes on the development of heart failure in streptozotocin-induced diabetic rat model with acute myocardial infarction

AIM: To evaluate the time course and effect of diabetes on the development of heart failure (HF) in poorly controlled streptozotocin (STZ) -induced diabetic rat model for 70 d with acute myocardial infarction (AMI) in vivo. METHODS: All SD rats were randomized into four groups. Diabetes were induced by a single intraperitoneal injection of STZ (65 mg/kg), and 70 d later after the induction, AMI models were made with the ligation of left anterior descending coronary artery. The time course of diabetic effects on the development of heart failure in rats before and after AMI was observed. The survival rate of the rats and ultrastructure change of myocardium, the hemodynamics, the extent of the myocardial fibrosis, and the cardiac hypertrophy were also determined. RESULTS: After the ligation of left anterior descending coronary artery, the diabetic rats showed worse LV function and accelerated left ventricular (LV) remodeling compared with the non-diabetic ones. Myocardial fibrosis in both diabetic and non-diabetic rats subjected to AMI was similar in the early phase, while it was quite different after 1 month. CONCLUSION: Heart failure progression is accelerated in diabetic rat with AMI.     

Role of MCU in bupivacaine-induced spinal cord neurotoxic injury in diabetic rats

AIM: To investigate the role of mitochondrial calcium uniporter (MCU) in bupivacaine (B)-induced spinal cord injury in diabetic (D) rats.METHODS: Healthy male Sprague-Dawley rats, weighing 180~220 g, were divided into normal rats and diabetic rats. After intraperitoneal injection of streptozotocin for building diabetic rat mo-del, 48 male rats were randomly divided into 6 groups with 8 rats in each group as following:control (C) group (normal rats by intrathecal injection of normal saline), D group (diabetic rats by intrathecal injection of normal saline), C+B group (normal rats by intrathecal injection of bupivacaine), D+B group (diabetic rats by intrathecal injection of bupivacaine), D+R₁+B group (diabetic rats by intrathecal injection of 10 μmol/L Ru360 and bupivacaine) and D+R₂+B group (diabetic rats by intrathecal injection of 50 μmol/L Ru360 and bupivacaine). The changes of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured before modeling, after modeling, and 12 h, 24 h and 48 h after intrathecal injection. Lumbar enlargement was removed from spinal cord after rats were killed. MCU expression was tested by RT-qPCR and Western bolt. The levels of malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were determined by ELISA. Spinal neuronal apoptosis was measured using TUNEL assay.RESULTS: Compared with D group, the expression of MCU, the values of PWMT and PWTL, the levels of MDA and 8-OHdG, and the apoptotic rate of spinal cord neurons were significantly increased in D+B group (P<0.05). Compared with D+B group, the expression of MCU, the values of PWMT and PWTL, the levels of MDA and 8-OHdG, and the apoptotic rate of spinal cord neurons were significantly decreased in D+R₂+B group (P<0.05).CONCLUSION: Bupivacaine enhances oxidative stress and aggravates spinal cord injury via up-regulating MCU activity in diabetic rats.     

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.     

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.     

Renoprotective effect of L-carnitine on streptozotocin-induced diabetic nephropathy in rats

AIM: To investigate whether L-carnitine (LC) treatment confers renoprotection in a rat model of streptozotocin (STZ)-induced diabetic nephropathy (DN). METHODS: Diabetic animal model was established by intraperitoneal injection of STZ (65 mg/kg) in Sprague-Dawley rats. Diabetic rats were treated with LC (50 mg·kg^-1·d^-1 or 200 mg·kg^-1·d^-1 intravenously) daily for 12 weeks. The effects of LC on STZ-induced DN were evaluated by assessing renal function, urinary protein excretion, histopathological changes, macrophage infiltration, the expression of proinflammatory and prosclerotic cytokines, and the expression of nuclear factor-κB (NF-κB) and apoptosis-related gene. RESULTS: LC administration significantly decreased glomerulosclerosis, preserved the number of podocytes, and reduced macrophage infiltration. These changes were accompanied by improvements in urinary protein excretion and renal dysfunction. LC treatment suppressed the expression of proinflammatory and prosclerotic cytokines, and these changes were paralleled by significant attenuation of NF-κB and apoptosis-related gene expression. CONCLUSION: LC has a renoprotective effect against STZ-induced DN in rats.