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.

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.

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.

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.

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.

Chlamydia Pneumoniae Infection Initiates the Development of Atherosclerosis in OLETF and LETO Rats: The Role of Platelet-derived Growth Factor-B

BACKGROUND AND OBJECTIVES: Chlamydia pneumoniae (CP) has been linked with atherosclerosis. While several studies have shown that CP contributes to the acceleration of atherosclerotic lesions, any studies on the initiation of atherosclerosis are sparse. The present study investigated whether CP infection could initiate atherosclerotic lesions in rats that are known to be resistant to atherosclerosis; further, we investigated if these lesions do form, then how does the CP participate in this and develop of atherosclerosis in these rats. MATERIALS AND METHODS: Thirty 11-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats, thirty type 2 diabetic rats and thirty age-matched Long-Evans Tokushima Fatty (LETO) rats that were maintained on a high-cholesterol diet were either mock-inoculated or inoculated intranasally 3 times at 11, 13 and 15 weeks of age. The serum levels of the lipid profiles, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1) and C-reactive protein (CRP) were measured by performing ELISA at 24 weeks and 40 weeks of age. The atherosclerotic lesion areas were analyzed, and immunohistochemical staining using chlamydia genus-specific monoclonal antibody and PDGF-B was performed in the ascending aorta at 40 weeks of age. RESULTS: Immunohistochemical staining with using specific monoclonal antibody demonstrated CP infection in the vessel walls. The serum PAI-1 level of the OLETF rats was higher than that of the LETO rats (p<0.05) regardless of the state of the CP infection, but there were no differences in the serum MCP-1 and CRP levels between the OLETF rats and the LETO rats. While no atherosclerotic lesion was observed in the mock-infected LETO rats, early-to-advanced atherosclerotic lesions were found in the other rat groups. CP-infected OLETF rats showed more advanced atherosclerotic lesions and greater mean lesion areas than the other rat groups (LT-N, 0 mm2; LETO-CP, 3.29+/-1.23 mm2; OT-N, 4.91+/-2.11 mm2; OT-CP, 9.20+/-4.62 mm2)(p<0.05). The characteristics of the atherosclerotic lesions in the rats were intimal thickening that was mainly composed of smooth muscle cells. The atherosclerotic lesion area positively correlated with the presence and the extent of PDGF-B staining in the aortic wall (p<0.01). CONCLUSION: Chronic infection of CP in the vessel walls initiated the development of atherosclerosis in the LETO rats and it accelerated the atherosclerosis in the OLETF rats. CP-induced smooth muscle proliferation and the resultant intimal thickening may be mediated by PDGF-B in these atherosclerotic lesions.

Effects of GLP-1 treatment on protection of B cells in Otsuka Long-Evans Tokushima fatty rats / 北京大学学报(医学版)

Objective: To investigate the effect of GLP1 on the blood glucose in type 2 diabetic rats,and its protective effects on the islet B cells.Methods: Thirty rats were divided into three groups: spontaneous type 2 diabetes animal model OLETF rats,GLP-1 [from the twelfth week 56 ?g/(kg?d),sc] therapy group and LETO rats as control.In the 14th and 20th weeks,standard OGTT including fast and 2 h-plasma glucose were measured respectively.In the 14th weeks,3 rats from each group were killed randomly,and the rest of the rats were killed until the 20th week.Immunostaining with the marker of PCNA,TUNEL,and insulin assessed metabolic changes in the islet. Ultrastructure of the B cell was observed with the electronic microscope.Results: In the 14th and 20th week,AUC for insulin were higher in treated animals(10.86?1.56 vs.9.07?1.28,P

Insulin and Glucagon Secretions, and Morphological Change of Pancreatic Islets in OLETF Rats, a Model of Type 2 Diabetes Mellitus

This study was performed to observe the changes of glucose-related hormones and the morphological change including ultrastructure of the pancreatic islets in the male Otsuka Long-Evans Tokushima Fatty rat. Area under the curve (AUC) of glucose at the 30th (709 +/- 73 mg.h/dL) and at the 40th week (746 +/- 87 mg.h/ dL) of age were significantly higher than that at the 10th week (360 +/- 25 mg.h/ dL). AUC of insulin of the 10th week was 2.4 +/- 0.9 ng.h/mL, increased gradually to 10.8 +/- 8.3 ng.h/mL at the 30th week, and decreased to 1.8 +/- 1.2 ng.h/mL at the 40th week. The size of islet was increased at 20th week of age and the distribution of peripheral alpha cells and central beta cells at the 10th and 20th weeks was changed to a mixed pattern at the 40th week. On electron microscopic examination, beta cells at the 20th week showed many immature secretory granules, increased mitochondria, and hypertrophied Golgi complex and endoplasmic reticulum. At the 40th week, beta cell contained scanty intracellular organelles and secretory granules and apoptosis of acinar cell was observed. In conclusion, as diabetes progressed, increased secretion of insulin was accompanied by increases in size of islets and number of beta-cells in male OLETF rats showing obese type 2 diabetes. However, these compensatory changes could not overcome the requirement of insulin according to the continuous hyperglycemia after development of diabetes.

Angiotensin-Converting Enzyme Inhibitor Ramipril Improves Coronary Microvascular Remodeling in Type II Diabetic Rats

BACKGROUND AND OBJECTIVES: Coronary microvascular remodeling is one of the complications associated with diabetic cardiovascular disease. We investigated the effect of long-term treatment with ramipril, an angiotensin converting enzyme inhibitor, on coronary microvascular remodeling on a type II diabetic model, the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. MATERIALS AND METHODS: Twenty OLETF diabetic, and twenty LETO non-diabetic rats at twenty-four weeks old, were randomized into 4 equal groups for treatment with either an aqueous solution of ramipril (5 mg/kg, n=10 for two groups) or saline (n=10 for two groups) for 24 weeks on a daily basis. The blood glucose levels, body weights and blood pressures of the rats were checked on a regular basis. Masson's trichrome and picrosirius red stains were used for the morphometric analysis of the thickening of the coronary arterial wall and the degree of perivascular fibrosis. The myocardial collagen content was determined by measuring the levels of myocardial hydroxyproline. RESULTS: Marked thickening of the coronary microvascular wall and prominent perivascular fibrosis were detected in the hearts of OLETF rats to a greater extent than in the LETO rats (p<0.01). Ramipril significantly prevented coronary microvascular remodeling in OLETF rats (p<0.01), but there was no significant difference in the collagen content/dry heart weight ratio between the groups. CONCLUSION: Long-term treatment with ramipril has an antifibrotic effect, and improves the coronary microvascular remodeling in diabetic OLETF rats.

Effect of diet with various fatty acid composition on insulin resistance in male OLETF rats / 中华内分泌代谢杂志

The effect of diet with various fatty acid composition on insulin resistance in male OLETF ratswas observed. The results showed that it was beneficial to insulin sensitivity in rats fed with ? 3 polyunsaturated fatty acid rich food.