The effect of telmisartan on myocardial remodeling and expression of PPARγ in myocardial tissue in high-fat fed OLETF rats / 天津医药

Objective To investigate the effect of telmisartan on the expression of peroxisome proliferator activated receptor gamma(PPARγ)and its regulation in myocardial remodeling in spontaneously type 2 diabetic male Otsuka Long-Evans Tokushima Fatty(OLETF)rats fed with high-fat diet.Methods Twenty-eight four-week-old male OLETF rats were fed with high-fat diet. From 22-week of age, the pre-diabetic OLETF rats were randomly assigned to three groups:telmisartan-treated group[O-T group,5 mg/(kg·d),n=10],pioglitazone-treated group[O-P group,10 mg/(kg·d),n=8]and untreated group ( O-C group, equal volume of normal saline, n=10), continuously administration for 22-week. Twelve sex and age matched Long-Evans Tokushima Otsuka(LETO)rats were used as control(LETO group).At 22 and 48-week of age, the glucose tolerance of the rats was assessed by the oral glucose tolerance test(OGTT).At 48 weeks of age,five rats were randomly selected from each group,and clamp experiments were carried out.The glucose infusion rate from 60 min to 120 min(GIR60-120)was measured.All rats were sacrificed and the myocardial tissues were dissected.The ratio of heart weight to body weight(HW/BW)was calculated.Blood samples were collected,and serum PPARγ,tumor necrosis factor-alpha(TNF-α),interleukin-6(IL-6)and adiponectin were measured using ELISA and radioimmunoassay.The mRNA expressions of IL-6,PPARγ1 and PPARγ2 were measured by real-time PCR.The protein expression levels of PPARγ,adiponectin,IL-6 and NF-κB were determined by Western blot assay.The myocardial pathological changes were observed under light microscope (HE staining, Masson staining and PAS staining), and ultrastructural changes were observed under transmission electron microscope.Results At 22-week of age,neither type 2 diabetes mellitus(T2DM)nor IGT were found in three groups.At 48-week of age,T2DM was found in seven rats of O-C group,and IGT was found in two rats.T2DM was found in one rat of O-C group,and IGT was found in three rats.Neither T2DM nor IGT was found in the other two groups.GIR60-120and HW/BW were all significantly lower in the O-P group and O-T group than those of the O-C group at 48-week of age (P<0.05). Systolic blood pressure(SBP)and diastolic blood pressure(DBP)were significantly lower in O-T group than those in other three groups(P<0.05).Compared with the O-C group,the serum levels of PPARγ and adiponectin were significantly up-regulated,whereas the serum levels of IL-6 and TNF-α were down-regulated by telmisartan administration in O-T group (P<0.05).There were no significant differences in the above indexes between O-P and O-T groups.The results of real-time PCR and Westen blot assay showed that the mRNA expression of PPARγ1 was increased,and IL-6 expression decreased in O-T group compared with those of O-C group. The protein expressions of PPARγ and adiponectin were increased, and protein expressions of NF-κB and IL-6 were significantly decreased in O-P group and O-T group compared with those of O-C group(P<0.05).In the O-C group,the arrangernent of myocardial cells was irregular,myocardial fibers were swollen,a large amount of fibrotic tissue in the myocardial interstitium, and glycogen accumulation under light and electron microscope. Besides, myofibril breakage and perinuclear space expansion, myocardial mitochondria were apparently damaged or even dissolved. Compared with the O-C group, myocardial fibers arranged neatly, no obvious glycogen deposition and the ultrastructural changes of myocardium were obviously reduced in O-T group and O-P group. Conclusion Telmisartan can increase the expression level of PPARγ in the serum and myocardial tissue, reduce myocardial fibrosis and alleviate cardiac remodeling in the high-fat-diet OLETF rats.

Beneficial Effects of Aerobic Exercise Training Combined with Rosiglitazone on Glucose Metabolism in Otsuka Long Evans Tokushima Fatty Rats

BACKGROUND: Regular aerobic exercise is essential for the prevention and management of type 2 diabetes mellitus and may be particularly beneficial for those treated with thiazolidinediones, since it may prevent associated weight gain. This study aimed to evaluate the effect of combined exercise and rosiglitazone treatment on body composition and glucose metabolism in obese diabetes-prone animals. METHODS: We analyzed metabolic parameters, body composition, and islet profiles in Otsuka Long Evans Tokushima Fatty rats after 28 weeks of aerobic exercise, rosiglitazone treatment, and combined exercise and rosiglitazone treatment. RESULTS: Combined exercise with rosiglitazone showed significantly less increase in weight and epididymal fat compared to rosiglitazone treatment. Aerobic exercise alone and combined rosiglitazone and exercise treatment led to similar retention of lean body mass. All experimental groups showed a decrease in fasting glucose. However, the combined exercise and rosiglitazone therapy group showed prominent improvement in glucose tolerance compared to the other groups. Rescue of islet destruction was observed in all experimental groups, but was most prominent in the combined therapy group. CONCLUSION: Regular aerobic exercise combined with rosiglitazone treatment can compensate for the adverse effect of rosiglitazone treatment and has benefit for islet preservation.

Femoral bone structure in Otsuka Long-Evans Tokushima Fatty rats

OBJECTIVES: Type 2 diabetes mellitus (T2DM) increases fracture risk despite normal to high levels of bone mineral density. Bone quality is known to affect bone fragility in T2DM. The aim of this study was to clarify the trabecular bone microstructure and cortical bone geometry of the femur in T2DM model rats. METHODS: Five-week-old Otsuka Long-Evans Tokushima Fatty (OLETF; n = 5) and Long-Evans Tokushima Otsuka (LETO; n = 5) rats were used. At the age of 18 months, femurs were scanned with micro-computed tomography, and trabecular bone microstructure and cortical bone geometry were analyzed. RESULTS: Trabecular bone microstructure and cortical bone geometry deteriorated in the femur in OLETF rats. Compared with in LETO rats, in OLETF rats, bone volume fraction, trabecular number and connectivity density decreased, and trabecular space significantly increased. Moreover, in OLETF rats, cortical bone volume and section area decreased, and medullary volume significantly increased. CONCLUSIONS: Long-term T2DM leaded to deterioration in trabecular and cortical bone structure. Therefore, OLETF rats may serve as a useful animal model for investigating the relationship between T2DM and bone quality.

Chronic Alcohol Consumption Results in Greater Damage to the Pancreas Than to the Liver in the Rats

Alcohol consumption increases the risk of type 2 diabetes. However, its effects on prediabetes or early diabetes have not been studied. We investigated endoplasmic reticulum (ER) stress in the pancreas and liver resulting from chronic alcohol consumption in the prediabetes and early stages of diabetes. We separated Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type-2 diabetic animal model, into two groups based on diabetic stage: prediabetes and early diabetes were defined as occurrence between the ages of 11 to 16 weeks and 17 to 22 weeks, respectively. The experimental group received an ethanol-containing liquid diet for 6 weeks. An intraperitoneal glucose tolerance test was conducted after 16 and 22 weeks for the prediabetic and early diabetes groups, respectively. There were no significant differences in body weight between the control and ethanol groups. Fasting and 120-min glucose levels were lower and higher, respectively, in the ethanol group than in the control group. In prediabetes rats, alcohol induced significant expression of ER stress markers in the pancreas; however, alcohol did not affect the liver. In early diabetes rats, alcohol significantly increased most ER stress-marker levels in both the pancreas and liver. These results indicate that chronic alcohol consumption increased the risk of diabetes in prediabetic and early diabetic OLETF rats; the pancreas was more susceptible to damage than was the liver in the early diabetic stages, and the adaptive and proapoptotic pathway of ER stress may play key roles in the development and progression of diabetes affected by chronic alcohol ingestion.

Effect of Pioglitazone on Interleukin-18 and Toll-Like Receptor 4 Expression in OLETF Rats with Insulin Resistance / 天津医药

Objective To investigate change of TLR4 in OLETF (Otsuka Long-Evans Tokushima fatty) rats with in-sulin resistance (IR), and to study the effect of pioglitazone (PIO) on the expression of TLR4, and to explore the possible mechanisms of the PIO reducing the risk of cardiovascular diseases. Methods Twenty four OLETF rats were fed with high-fat diet for 20 weeks to establish the IR model then they were randomly assigned into two groups:the model group (group M), in which the rats were fed with high-fat diet;the PIO group (group P), in which the rats were fed with PIO in addition to high-fat diet . Control group include 12 OLETF rats fed with normal diet (group NC). After 20 weeks of drug intervention, plasma levels of FINS (Fasting INSulin), FBG (Fasting Blood Glucose), blood lipid, IL-18 and TLR4 were assessed in every group. Results Comparing with group NC, FBG, Blood lipid, IL-18 and TLR4 were significantly increased in group M(P＜0.05 or P＜0.01), comparing with group M, FBG, Blood lipid were improved in group P, and serum IL-18, TLR4 were signifi-cantly lower in the group P than that in group M(P＜0.05 or P＜0.01). Conclusion TLR4 may be involved in IR by pro-moting inflammatory response, and PIO can significantly improve IR and inflammatory, and reduce the risk of cardiovascular diseases by inhibiting the expression of TLR4.

Anti-diabetic effects of benfotiamine on an animal model of type 2 diabetes mellitus / 대한수의학회지

Although benfotiamine has various beneficial anti-diabetic effects, the detailed mechanisms underlying the impact of this compound on the insulin signaling pathway are still unclear. In the present study, we evaluated the effects of benfotiamine on the hepatic insulin signaling pathway in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which are a type 2 diabetes mellitus model. OLETF rats treated with benfotiamine showed decreased body weight gain and reduced adipose tissue weight. In addition, blood glucose levels were lower in OLETF rats treated with benfotiamine. Following treatment with benfotiamine, the levels of Akt phosphorylation (S473/T308) in the OLETF groups increased significantly compared to the OLETF control group so that they were almost identical to the levels observed in the control group. Moreover, benfotiamine restored the phosphorylation levels of both glycogen synthase kinase (GSK)-3alpha/beta (S21, S9) and glycogen synthase (GS; S641) in OLETF rats to nearly the same levels observed in the control group. Overall, these results suggest that benfotiamine can potentially attenuate type 2 diabetes mellitus in OLETF rats by restoring insulin sensitivity through upregulation of Akt phosphorylation and activation of two downstream signaling molecules, GSK-3alpha/beta and GS, thereby reducing blood glucose levels through glycogen synthesis.

Microarray Analysis for Genes Associated with Angiogenesis in Diabetic OLETF Keratocytes

The purpose of this study was to identify the differences in angiogenesis gene expression between normal and diabetic keratocytes stimulated with interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha). Primarily cultured normal and diabetic keratocytes were treated with 20 ng/mL of IL-1a and TNF-alpha for 6 hr. cDNA was hybridized to an oligonucleotide microarray. Microarray analysis was used to identify differentially expressed genes that were further evaluated by real-time polymerase chain reaction (RT-PCR). Diabetes keratocytes overexpressed vital components of angiogenesis including Agtr1, and under-expressed components related to the blood vessel maturation, including Dcn. Cytokine-treated diabetic keratocytes differentially expressed components of angiogenesis. OLETF keratocytes after treatment with IL-1alpha and TNF-alpha showed the newly expressed 15 and 14 genes, respectively. Newly and commonly under-expressed five genes followed by treatment with both IL-1alpha and TNF-alpha were also evident. RT-PCR showed results similar to the microarray results. Agtr1 and Itga1 showed an increased expression in diabetic keratocytes compared with normal corneal keratocytes, especially after TNF-alpha treatment. Il6 appeared strong expression after interleukin-1alpha treatment, but showed down expression after TNF-alpha treatment. Further studies to analyze and confirm the significance of the identified angiogenetic genes of diabetes are needed.

Effect of liraglutide on serum AGEs and inflammatory factors in IGT-OLETF rats / 解放军医学杂志

Objectiven To investigate the effect of liraglutide on serum advanced glycosylated end products (AGEs), inflammatory factors and glycometabolism in OLETF rats with impaired glucose tolerance (IGT). Methods Thirty-two 12-weekold OLETF rats were randomly assigned into 4 groups (8 each) and received intraperitoneal injection of saline (OLETF-saline group) or liraglutide 50, 100 or 200μg/kg twice a day for 12 weeks (liraglutide intervention groups). Eight LETO rats served as the normal control group and received saline injection. Twelve weeks after the treatment, all the rats were examined for fasting and 2h postprandial plasma glucose after Oral Glucose Tolerance Test (OGTT), and serum AGEs and inflammatory factors were determined by enzyme linked immunosorbent assay (ELISA). Results Before liraglutide intervention, the levels of fasting plasma glucose (FPG), plasma glucose 2 hours after OGTT (2hPG), and fasting plasma insulin (FPI) were significantly higher in IGT-OLETF rats than in LETO rats. While 12 weeks after liraglutide intervention, the levels of FPG, 2hPG, FPI, AGEs and the inflammatory factors TNF-α, Hs-CRP and IL-6 declined obviously in IGT-OLETF rats compared with that in OLETF-saline rats (P<0.05). When the liraglutide intervention ended, 87.5% of the rats in OLETF-saline group developed diabetes, but no sign of diabetes was found in the rats of liraglutide intervention groups. Conclusion Liraglutide may effectively improve IGT and insulin-resistance, decrease the AGEs and inflammatory factors by inhibiting nonenzymatic glucosylation and inflammation to delay or prevent the development of diabetes in IGT-OLETF rats.

COMP-Angiopoietin-1 Promotes Cavernous Angiogenesis in a Type 2 Diabetic Rat Model

Cartilage oligomeric matrix protein-angiopoietin-1 (COMP-Ang1) is an angiogenic factor for vascular angiogenesis. The aim was to investigate the effect of an intracavernosal injection of COMP-Ang1 on cavernosal angiogenesis in a diabetic rat model. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats made up the experimental group (1 yr old) and Long-Evans Tokushima Otsuka (LETO) rats made up the control group. The experimental group was divided into vehicle only, 10 microg COMP-Ang1, and 20 microg COMP-Ang1. COMP-Ang1 was injected into the corpus cavernosum of the penis. After 4 weeks, the penile tissues of the rats were obtained for immunohistochemistry and Western blot analysis. The immunoreactivity of PECAM-1 and VEGF was increased in the COMP-Ang1 group compared with the vehicle only group. Moreover, the expression of PECAM-1 and VEGF was notably augmented in the 20 microg Comp Ang-1 group. In the immunoblotting study, the expression of PECAM-1 and VEGF protein was significantly less in the OLEFT rats than in the control LETO rats. However, this expression was restored to control level after intracavernosal injection of COMP-Ang1. These results show that an intracavernosal injection of COMP-Ang1 enhances cavernous angiogenesis by structurally reinforcing the cavernosal endothelium.

Reduction of Food Intake by Fenofibrate is Associated with Cholecystokinin Release in Long-Evans Tokushima Rats

Fenofibrate is a selective peroxisome proliferator-activated receptor alpha (PPARalpha) activator and is prescribed to treat hyperlipidemia. The mechanism through which PPARalpha agonists reduce food intake, body weight, and adiposity remains unclear. One explanation for the reduction of food intake is that fenofibrate promotes fatty acid oxidation and increases the production of ketone bodies upon a standard experimental dose of the drug (100~300 mg/kg/day). We observed that low-dose treatment of fenofibrate (30 mg/kg/day), which does not cause significant changes in ketone body synthesis, reduced food intake in Long-Evans Tokushima (LETO) rats. LETO rats are the physiologically normal controls for Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which are obese and cholecystokinin (CCK)-A receptor deficient. We hypothesized that the reduced food intake by fenofibrate-treated LETO rats may be associated with CCK production. To investigate the anorexic effects of fenofibrate in vivo and to determine whether CCK production may be involved, we examined the amount of food intake and CCK production. Fenofibrate-treated OLETF rats did not significantly change their food intake while LETO rats decreased their food intake. Treatment of fenofibrate increased CCK synthesis in the duodenal epithelial cells of both LETO and OLETF rats. The absence of a change in the food intake of OLETF rats, despite the increase in CCK production, may be explained by the absence of CCK-A receptors. Contrary to the OLETF rats, LETO rats, which have normal CCK receptors, presented a decrease in food intake and an increase in CCK production. These results suggest that reduced food intake by fenofibrate treatment may be associated with CCK production.

The Effect of Platelet-rich Plasma on Wounds of OLETF Rats Using Expression of Matrix Metalloproteinase-2 and -9 mRNA

BACKGROUND: Complicated diabetic patients show impaired, delayed wound healing caused by multiple factors. A study on wound healing showed that platelet-rich plasma (PRP) was effective in normal tissue regeneration. Nonetheless, there is no evidence that when plateletrich plasma is applied to diabetic wounds, it normalizes the diabetic wound healing process. In this study, we have analyzed matrix metalloproteinase (MMP)-2, MMP-9 expression to investigate the effect of PRP on diabetic wounds. METHODS: Twenty-four-week-old male Otsuka Long-Evans Tokushima Fatty rats were provided by the Tokushima Research Institute. At 50 weeks, wounds were arranged in two sites on the lateral paraspinal areas. Each wound was treated with PRP gel and physiologic saline gauze. To determine the expression of MMP-2, MMP-9, which was chosen as a marker of wound healing, reverse transcription polymerase chain reaction (RT-PCR) was performed and local distribution and expression of MMP-2, MMP-9 was also observed throughout the immunohistochemical staining. RESULTS: RT-PCR and the immunohistochemical study showed that the levels of MMP-2, MMP-9 mRNA expression in PRP applied tissues were higher than MMP-2, MMP-9 mRNA expression in saline-applied tissues. MMP-9 mRNA expression in wounds of diabetic rats decreased after healing began to occur. But no statistical differences were detected on the basis of body weight or fasting blood glucose levels. CONCLUSIONS: This study could indicate the extracellular matrix-regulating effect observed with PRP. Our results of the acceleration of wound healing events by PRP under hyperglycemic conditions might be a useful clue for future clinical treatment for diabetic wounds.

Differential Expression of Metabolism-related Genes in Liver of Diabetic Obese Rats

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of spontaneous type 2 diabetes (T2D), develops hyperglycemic obesity with hyperinsulinemia and insulin resistance after the age of 25 weeks, similar to patients with noninsulin-dependent diabetes mellitus (DM). In the present study, we determined whether there are differences in the pattern of gene expression related to glucose and lipid metabolism between OLETF rats and their control counterparts, Long-Evans Tokushima (LETO) rats. The experiment was done using 35-week-old OLETF and LETO rats. At week 35 male OLETF rats showed overt T2D and increases in blood glucose, plasma insulin, plasma triglycerides (TG) and plasma total cholesterol (TC). Livers of diabetic OLETF and LETO rats also showed differences in expression of mRNA for glucose and lipid metabolism related genes. Among glucose metabolism related genes, GAPDH mRNA was significantly higher and FBPase and G6Pase mRNA were significantly lower in OLETF rats. For lipid metabolism related genes, HMGCR, SCD1 and HL mRNA were substantially higher in OLETF rats. These results indicate that gluconeogenesis in OLETF rats is lower and glycolysis is higher, which means that glucose metabolism might be compensated for by a lowering of the blood glucose level. However, lipid synthesis is increased in OLETF rats so diabetes may be aggravated. These differences between OLETF and LETO rats suggest mechanisms that could be targeted during the development of therapeutic agents for diabetes.

Effect of 17-beta Estradiol on Adipocyte Lipin-1 Expression in OLETF Rat

BACKGROUND: 17 beta-estradiol is known to play an important role in glucose homeostasis. Lipin-1 is a nuclear protein that is essential in adipocyte differentiation and it is considered to play a role in ectopic fat deposition and the redistribution of fat. The aim of this study was to evaluate the effect of 17 beta-estradiol on the lipin-1 expression in the adipocytes of OLETF rats, which is an animal model of diabetes. METHODS: The OLETF rats were divided into 3 groups, 1) the sham-operation group (SHAM) 2) the castrated group (CAST) and 2) the castrated and estradiol treatment group (EST), and all the rats were at 6 weeks of age. LETO rats were used as a control group (LETO). 0.1 mg of estradiol valerate was injected subcutaneously every 4 weeks in the rats of the EST group. The visceral and subcutaneous tissues were isolated to evaluate the lipin-1 protein expression. The lipin-1 expression was measured in human visceral and subcutaneous preadipocytes. RESULTS: Less body weight gain was observed in the EST group compared with that of the SHAM group. In addition, improvement in the glucose tolerance was observed in the EST group. The lipin-1 expression in visceral fat was decreased in the SHAM and CAST groups, but it was but recovered in the EST group. The lipin-1 expression in the subcutaneous fat was decreased in the SHAM, CAST, and EST groups. CONCLUSION: Long term estradiol treatment in OLETF rats reduces the body weight gain and improves the glucose tolerance. Estradiol enhances the lipin-1 protein expression in the visceral adipocytes, but not in the subcutaneous adipocytes.

Effects of Rosiglitazone on Inflammation in Otsuka Long-Evans Tokushima Fatty Rats / 당뇨병

BACKGROUND: Inflammation plays a role in the response to metabolic stress in type 2 diabetes. However, the effects of rosiglitazone on inflammation of skeletal muscle have not been fully examined in type 2 diabetes. METHODS: We investigated the effects of the insulin-sensitizing anti-diabetic agent, rosiglitazone, on the progression of skeletal muscle inflammation in Otsuka Long-Evans Tokushima Fatty (OLETF) type 2 diabetic rats. We examined the expression of serologic markers (serum glucose, insulin and free fatty acid) and inflammatory cytokines (tumor-necrosis factor-alpha, interleukin [IL]-1beta and IL-6) in OLETF rats from early to advanced diabetic stage (from 28 to 40 weeks of age). RESULTS: Serum glucose and insulin concentrations were significantly decreased in rosiglitazone-treated OLETF rats compared to untreated OLETF rats. Rosiglitazone treatment significantly decreased the concentrations of serum inflammatory cytokines from 28 to 40 weeks of age. The mRNA expression of various cytokines in skeletal muscle was reduced in rosiglitazone-treated OLETF rats compared with untreated OLETF rats. Furthermore, rosiglitazone treatment resulted in the downregulation of ERK1/2 phosphorylation and NF-kappaB expression in the skeletal muscle of OLETF rats. CONCLUSION: These results suggest that rosiglitazone may improve insulin sensitivity with its anti-inflammatory effects on skeletal muscle.

Ultrastructural Investigation of the Retinal Changes in Diabetic Rat (OLETF)

PURPOSE: To compare retinal ultra-structures of diabetic rats (OLETF, Otsuka Long-Evans Tokushima Fatty) with those of agematched non-diabetic rats (LETO, Long-Evans Tokushima Otsuka) using transmission electron micrography (TEM). METHODS: The body weights and blood sugar levels of the OLETF rats and LETO rats (n=5) were measured at 10 and 50 weeks of age. Using a TEM, we compared the ultra-structural changes between the retinas of the 50-week-old OLETF and LETO rats. We analyzed the sizes of the pericytes and the thicknesses of the retinal capillary basement membranes between the two groups. Comparisons were made using a Scion Image(R). RESULTS: The mean body weight and blood sugar levels of the 50-week-old OLETF rats were significantly higher than those of the LETO rats (p(R)0.05). The thicknesses of the retinal capillary basement membranes in the outer plexiform layer and the size of pericytes were significantly increased in the OLETF rats at 50 weeks of age (p<0.05). The number of nuclei in the inner nuclear layer and the outer nuclear layer (photoreceptor cell nuclei) significantly decreased (p<0.05). However, the height of the RPE cells and basal in-foldings showed no significant differences between the OLETF and LETO rats. CONCLUSIONS: The retinal changes in the OLETF rats were observed relatively early at 50 weeks of age. These changes are similar to those seen in human diabetic retinopathy. Change in the capillaries is one feature of early retinal change. OLETF rats may be a useful animal model in NIDDM to examine diabetic retinal changes.

mRNA expressions of chemerin and its receptor 1 in adipose tissue of OLETF rats / 中华内分泌代谢杂志

The mRNA expressions of chemerin and its receptor CMKLR1 in adipose tissue of OLETF rats and LETO rats were detected by real-time PCR. The results showed that the two genes mRNA expressions in subcutaneous and visceral adipose tissue in OLETF group were significantly higher than those in LETO group (P< 0.05 or P<0.01) and expressions of them in visceral adipose tissue were higher than those in subcutaneous adipose tissue(P<0. 05 or P<0. 01), suggesting that chemerin and CMKLR1 may be involved in the pathogenesis of obesity, insulin resistance, and type 2 diabetes mellitus.

Metformin down-regulates the expression of regulators of G protein signaling in OLETF rats / 中国糖尿病杂志

Objective To investigate the expression of regulators of G protein signaling(RGS), including RGS2, RGS3 and RGS4 in OLETF rats, as well as the effects of metformin on these expressions. Methods LETO rats were used as control group. Eight-week-old male OLETF rats were assigned to two guoups randomly:model and trial(metfomin dose during 8~(th) to 22~(nd) weeks:300mg kg~(-1)·d~(-1);during 23rd to 28th weeks:400 mg·kg~(-1) ·d~(-1))groups. Expressions of RGS mRNA in aorta and heart werequantified by real-time PCR. Results RGS2, RGS3 and RGS4 mRNA of the thoracic aorta and left ventricle were significantly higher in model group than in control group (P<0.01). Compared with model group, metformin significantly reduced their mRNA in trial group (P<0.01). Conclusions Upregulation of RGS2, RGS3 and RGS4 mRNA expression in the thoracic aorta and left ventricle of OLETF rats is in correlation with cardiovascular lesions; while downregulation of their expression is in correlation with the action of metformin.

Overexpression of AMPKalpha1 Ameliorates Fatty Liver in Hyperlipidemic Diabetic Rats

5'-AMP-activated protein kinase (AMPK) is a heterotrimeric complex consisting of a catalytic (alpha) and two regulatory (beta and gamma) subunits. Two isoforms are known for catalytic subunit (alpha1, alpha2) and are encoded by different genes. To assess the metabolic effects of AMPKalpha1, we examined the effects of overexpression of adenoviral-mediated AMPKalpha1 in hyperlipidemic type 2 diabetic rats. The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an established animal model of type 2 diabetes that exhibits chronic and slowly progressive hyperglycemia and hyperlipidemia. Thirty five-week-old overt type 2 diabetic rats (n=10) were administered intravenously with Ad.AMPKalpha1. AMPK activity was measured by phosphorylation of acetyl CoA carboxlyase (ACC). To investigate the changes of gene expression related glucose and lipid metabolism, quantitative real-time PCR was performed with liver tissues. Overexpression of AMPKalpha1 showed that blood glucose concentration was decreased but that glucose tolerance was not completely recovered on 7th day after treatment. Plasma triglyceride concentration was decreased slightly, and hepatic triglyceride content was markedly reduced by decreasing expression of hepatic lipogenic genes. Overexpression of AMPKalpha1 markedly improved hepatic steatosis and it may have effective role for improving hepatic lipid metabolism in hyperlipidemic state.

Protective Effects of Lithospermic Acid B on Diabetic Nephropathy in OLETF Rats Comparing with Amlodipine and Losartan / 당뇨병

BACKGROUND: Lithospermic acid B (LAB), an active component isolated from Salvia miltiorrhizae, has been reported to have renoprotective effects in type 1 and type 2 diabetic animal models. We examined the effects of LAB on the prevention of diabetic nephropathy compared with amlodipine, a calcium channel blocker, and losartan, an angiotensin receptor blocker, in Otsuka Long-Evans-Tokushima Fatty (OLETF) rats, an animal model of type 2 diabetes. METHODS: LAB (20 mg/kg), amlodipine (10 mg/kg), or losartan (10 mg/kg) was given orally once daily to 10-week-old male OLETF rats for 28 weeks. RESULTS: None of LAB, losartan, and amlodipine exhibited effects on blood glucose levels. Treatment with amlodipine or losartan resulted in similar reductions in blood pressure; however, LAB was less effective in lowering blood pressure. Albuminuria was markedly suppressed by losartan and LAB, but not by amlodipine. LAB treatment decreased levels of renal lipid peroxidation, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta1 (TGF-beta1). CONCLUSION: These results suggest that LAB has beneficial effects on the diabetic nephropathy in OLETF rats by decreasing oxidative stress and inflammation as potent as losartan.

Altered Renal Sodium Transporter Expression in an Animal Model of Type 2 Diabetes Mellitus

Hemodynamic factors play an important role in the development and/or progression of diabetic nephropathy. We hypothesized that renal sodium transporter dysregulation might contribute to the hemodynamic alterations in diabetic nephropathy. Otsuka Long Evans Tokushima Fatty (OLETF) rats were used as an animal model for type 2 diabetes. Long Evans Tokushima (LETO) rats were used as controls. Renal sodium transporter regulation was investigated by semiquantitative immunoblotting and immunohistochemistry of the kidneys of 40-week-old animals. The mean serum glucose level in OLETF rats was increased to 235+/-25 mg/dL at 25 weeks, and the hyperglycemia continued up to the end of 40 weeks. Urine protein/ creatinine ratios were 10 times higher in OLETF rats than in LETO rats. At 40th week, the abundance of the epithelial sodium channel (ENaC) beta-subunit was increased in OLETF rats, but the abundance of the ENaC gamma-subunit was decreased. No significant differences were observed in the ENaC alpha-subunit or other major sodium transporters. Immunohistochemistry for the ENaC beta-subunit showed increased immunoreactivity in OLETF rats, whereas the ENaC gamma-subunit showed reduced immunoreactivity in these rats. In OLETF rats, ENaC beta-subunit upregulation and ENaC gamma-subunit downregulation after the development of diabetic nephropathy may reflect an abnormal sodium balance.