Hypertrophy In Diabetic Rats Research Articles

24-OR: Augmented Heparanase Secretion in Diabetes Regulates Development of Cardiac Hypertrophy

HSPG consist of a core protein to which several linear heparan sulphate (HS) side chains are linked. Heparanase (Hpa) is exceptional in its ability to degrade HS. This property is used to regulate cardiac metabolism by releasing LPL, for its onward movement to the vascular lumen to hydrolyze lipoprotein-TG for FA provision to the heart. We hypothesized that another function of Hpa is its ability to promote cardiac hypertrophy. Hearts from mice with global overexpression of Hpa appeared larger, had higher heart weight/tibia length ratios, and exhibited posterior wall thickening. This evidence of cardiac hypertrophy was not reflected in alterations in cardiac function; ejection fraction, fractional shortening, and stroke volume were largely unaffected. This suggested a physiological rather than pathological hypertrophy, and is linked to a role for Hpa in regulation of arterial structure and mechanics. Hearts from animals with cardiac-specific overexpression of VEGFB also released greater amounts of Hpa, and this coincided with a hypertrophic phenotype. Heart function in these VEGFB-Tg rats remained similar to wild-type, and was likely a consequence of the expanded coronary vasculature and metabolic reprogramming that favoured glucose utilization. Rats made diabetic with STZ did not show any changes in cardiac Hpa gene or protein expression. Nevertheless, immediately after retrograde perfusion, the diabetic hearts released significantly greater amounts of Hpa with evidence of relative cardiac hypertrophy. This cardiac hypertrophy in diabetic rats was pathological with ventricular wall thinning and reduced cardiac function. Our data imply that Hpa can stimulate cardiac hypertrophy that remains physiological when there is associated development of coronary vasculature with metabolic flexibility. With diabetes and the occurrence of microangiopathy along with metabolic inflexibility, hypertrophy progresses towards being pathological, leading to heart failure. Disclosure C.Lee: None. R.Shang: None. B.Hussein: None. B.Rodrigues: None. Funding Canadian Institutes of Health Research (PJT178134); Heart and Stroke Foundation of Canada (G190026493)

Cardiovascular Property of Resistance Training With an Emphasis on PI3K/AKT1 Genes Expression in Type 2 Diabetic Rats

Background: The potential role of exercise in physiological cardiac hypertrophy is rooted in both hormonal and genetic components. Objectives: The aim of this study was to determine the impact of resistance exercise on the expression of PI3K and AKT1 in cardiac tissue of type 2 diabetes (T2D) rats and their physiological cardiac hypertrophy. Methods: First, 21 male Wistar rats (220±20 g) were obese with 6-week high-fat diet (HFD) and were randomly assigned into non-diabetes, control T2D, and exercise diabetes groups. After inducing obesity, T2D was induced by intraperitoneal injection of streptozotocin (25 mg/kg) for diabetes groups. Rats in the exercise group completed a 6-week resistance exercise program, 5 sessions per week. PI3K/AKT1 expression and the weight ratio of left ventricular to heart, heart to body, and left ventricular to body were compared by analysis of variance (ANOVA) between groups. Results: In response to the induction of diabetes, the expression of PI3K/AKT1 in heart tissue decreased significantly compared to that of non-diabetic rats (P=0.001 and P=0.001, respectively). Further, resistance training led to a significant increase in PI3K expression (P=0.028) and AKT1 (P=0.032) and the weight ratio of left ventricular to heart (P=0.001), heart to the body (P=0.001), and left ventricular to the body (P=0.001) compared to control diabetic rats. Conclusion: Resistance training is associated with physiological cardiac hypertrophy in diabetic rats, and this improvement may be attributed to the PI3K/AKT1 signaling pathway.

Fucoxanthin regulates Nrf2/Keap1 signaling to alleviate myocardial hypertrophy in diabetic rats

To investigate the protective effect of fucoxanthin (FX) against diabetic cardiomyopathy and explore the underlying mechanism. Rat models of diabetes mellitus (DM) induced by intraperitoneal injection of streptozotocin (60 mg/kg) were randomized into DM model group, fucoxanthin treatment (DM+FX) group and metformin treatment (DM+ Met) group, and normal rats with normal feeding served as the control group. In the two treatment groups, fucoxanthin and metformin were administered after modeling by gavage at the daily dose of 200 mg/kg and 230 mg/kg, respectively for 12 weeks, and the rats in the DM model group were given saline only. HE staining was used to examine the area of cardiac myocyte hypertrophy in each group. The expression levels of fibrotic proteins TGF-β1 and FN proteins in rat hearts were detected with Western blotting. In the cell experiment, the effect of 1 μmol/L FX on H9C2 cell hypertrophy induced by exposure to high glucose (HG, 45 mmol/L) was evaluated using FITC-labeled phalloidin. The mRNA expression levels of the hypertrophic factors ANP, BNP and β-MHC in H9C2 cells were detected using qRT-PCR. The protein expressions of Nrf2, Keap1, HO-1 and SOD1 proteins in rat heart tissues and H9C2 cells were determined using Western blotting. The DCFH-DA probe was used to detect the intracellular production of reactive oxygen species (ROS). In the diabetic rats, fucoxanthin treatment obviously alleviated cardiomyocyte hypertrophy and myocardial fibrosis, increased the protein expressions of Nrf2 and HO-1, and decreased the protein expressions of Keap1 in the heart tissue (P < 0.05). In H9C2 cells with HG exposure, fucoxanthin significantly inhibited the enlargement of cell surface area, lowered the mRNA expression levels of ANP, BNP and β-MHC (P < 0.05), promoted Nrf2 translocation from the cytoplasm to the nucleus, and up-regulated the protein expressions its downstream targets SOD1 and HO-1 (P < 0.05) to enhance cellular antioxidant capacity and reduce intracellular ROS production. Fucoxanthin possesses strong inhibitory activities against diabetic cardiomyocyte hypertrophy and myocardial fibrosis and is capable of up-regulating Nrf2 signaling to promote the expression of its downstream antioxidant proteins SOD1 and HO-1 to reduce the level of ROS.

Diabetic cardiomyopathy was attenuated by cinnamon treatment through the inhibition of fibro-inflammatory response and ventricular hypertrophy in diabetic rats.

Diabetic cardiomyopathy (DCM) is a chronic complication of diabetes that emphasizes the urgency of developing new drug therapies. With an illustrious history in traditional medicine to improve diabetes, cinnamon has been shown to possess blood lipids lowering effects and antioxidative and anti-inflammatory properties. However, the extent to which it protects the diabetic heart has yet to be determined. Forty-eight rats were administered in the study and grouped as: control; diabetic; diabetic rats given 100, 200, or 400 mg/kg cinnamon extract, metformin (300 mg/kg), valsartan (30 mg/kg), or met/val (combination of both drugs), via gavage for six weeks. Fasting blood sugar (FBS) and markers of cardiac injury including creatine kinase-muscle/brain (CK-MB), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) were evaluated in blood samples. Malondialdehyde (MDA) levels, the total contents of thiol, superoxide dismutase (SOD), and catalase (CAT) activities were measured. Histopathology study and gene expression measurement of angiotensin II type 1 receptor (AT1), atrial natriuretic peptide (ANP), beta-myosin heavy chain (β-MHC), and brain natriuretic peptide (BNP) were done on cardiac tissue. FBS and cardiac enzyme indicators were reduced in all treated groups. A reduction in MDA level and enhancement in thiol content alongside with increase of SOD and CAT activities were observed in extract groups. The decrease of inflammation and fibrosis was obvious in treated groups, notably in the high-dose extract group. Furthermore, all treated diabetic groups showed a lowering trend in AT1, ANP, β-MHC, and BNP gene expression. Cinnamon extract, in addition to its hypoglycemic and antioxidant properties, can prevent diabetic heart damage by alleviating cardiac inflammation and fibrosis. PRACTICAL APPLICATIONS: This study found that cinnamon extract might protect diabetic heart damage by reducing inflammation and fibrosis in cardiac tissue, in addition to lowering blood glucose levels and increasing antioxidant activity. Our data imply that including cinnamon in diabetic participants' diets may help to reduce risk factors of cardiovascular diseases.

The effect of aerobic exercise along with resveratrol supplementation on myocardial AMPK and MAFbx gene expression of diabetic rats

Background and Aim: Diabetes is a metabolic disease that is associated with heart injury. It has been shown that exercise training and resveratrol can improve the cardiac structure and function of diabetic subjects. The aim of the present study was to examine the effect of aerobic training along with resveratrol on gene expression of AMPK and MAFbx on myocardial AMPK and MAFbx gene expression of diabetic rats. Materials and Methods: In this experimental study, 40 males Wistar rats were randomly were divided into 5 groups: control (CN), diabetes (DM), diabetes-Resveratrol (RDM), diabetes-aerobic exercise (TDM), diabetes-aerobic exercise-Resveratrol (RTDM).Training groups have performed a running program on the treadmill for 8 weeks. Resveratrol (20 mg/kg) was injected subcutaneously 8 weeks for RDM and TRDM groups. 48 hours after the last training session, rats were anesthetized. Changes in the expression of AMPK and MAFbx myocardial genes were quantified using real-time PCR methods. Results: The results of the present study showed a reduction in AMPK expression (P &lt; 0.001) and an increase in MAFbx (P &lt; 0.001) in cardiomyocytes in DM groups compared to CN group. AMPK expression was significantly increased in TRDM group compared to DM (p=0.009), RDM (p=0.011) and TDM (p=0.043) groups. MAFbx expression of cardiomyocytes in RDM (p=0.012), TDM (p&lt;0.001) and TRDM (p&lt;0.001) groups had significantly reduction compared to DM group. Also, MAFbx expression was significantly reduction in TRDM groups compared to RDM (p=0.041) groups. Conclusion: Long-term aerobic exercise, with and without resveratrol consumption it may cause to reduce the genomic indicators of atrophy and increase myocardial hypertrophy in diabetic rats. Key Words: AMPK; Diabetic Rats; Exercise; MAFbx; Resveratrol

The effect of aerobic exercise along with resveratrol supplementation on AMPK and MAFbx gene expression of myocardial diabetic rats

Background and Aim: Diabetes is a metabolic disease that is associated with heart injury. It has been shown that exercise training and resveratrol can improve the cardiac structure and function of diabetic subjects. The aim of the present study was to examine the effect of aerobic training along with resveratrol on gene expression of AMPK and MAFbx on cardiac tissue of diabetic experimental model. Materials and Methods: In this experimental study, 40 males Wistar rats were randomly were divided into 5 groups: control (CN), diabetes (DM), diabetes-Resveratrol (RDM), diabetes-aerobic exercise (TDM), diabetes-aerobic exercise-Resveratrol (RTDM).Training groups have performed a running program on the treadmill for 8 weeks. Resveratrol (20 mg/kg) was injected subcutaneously 8 weeks for RDM and TRDM groups. 48 hours after the last training session, rats were anesthetized. Changes in the expression of AMPK and MAFbx myocardial genes were quantified using real-time PCR methods. Results: The results of the present study showed a reduction in AMPK expression (P &lt; 0.001) and an increase in MAFbx (P &lt; 0.001) in cardiomyocytes in DM groups compared to CN group. AMPK expression was significantly increased in TRDM group compared to DM (p=0.009), RDM (p=0.011) and TDM (p=0.043) groups. MAFbx expression of cardiomyocytes in RDM (p=0.012), TDM (p&lt;0.001) and TRDM (p&lt;0.001) groups had significantly reduction compared to DM group. Also, MAFbx expression was significantly reduction in TRDM groups compared to RDM (p=0.041) groups. Conclusion: Long-term aerobic exercise, with and without resveratrol consumption it may cause to reduce the genomic indicators of atrophy and increase myocardial hypertrophy in diabetic rats. Key Words: AMPK; Diabetic Rats; Exercise; MAFbx; Resveratrol

Role of autophagy in Parkin over-expression-induced reduction of cardiac hypertrophy in diabetic rats

Objective To evaluate the role of autophagy in Parkin over-expression-induced reduction of cardiac hypertrophy in diabetic rats. Methods Thirty-two healthy SPF male Sprague-Dawley rats, aged 2 months, weighing 200-230 g, were divided into 4 groups (n=8 each) using a random number table method: non-diabetes mellitus (DM) group (group Non-DM), DM group, DM plus AAV9-CMV-Parkin group (group DM+ P) and DM puls AAV9-CMV-Parkin puls autophagy inhibitor 3-methyladenine (3-MA) group (group DM+ P+ MA). DM was induced by intraperitoneal streptozotocin (STZ) 60 mg/kg and confirmed by blood glucose level >16.7 mmol/L, and Parkin overexpression was achieved with adeno-associated virus serotype 9 as a vector.AAV9-CMV-Parkin 1×1012 mg/kg was injected into the tail vein at 3 weeks after STZ injection in group DM+ P.In group DM+ P+ MA, AAV9-CMV-Parkin 1×1012 mg/kg was injected into the tail vein at 3 weeks after STZ injection, and 3 weeks later 3-MA 15 mg/kg was injected into the tail vein, once a week for 6 weeks in total.Cardiac diastolic and systolic function was detected using B-mode ultrasonography.Cardiomyocytes were obtained for microscopic examination of the cross-sectional area (with a light microscope) and for determination of the expression of microtubule-associated protein 1 light chain 3, P62 and Parkin. Results Compared with group Non-DM, the cross-sectional area of cardiomyocytes was significantly increased, and the diastolic and systolic function was decreased in DM group (P<0.05). Compared with group DM, the cross-sectional area of cardiomyocytes was significantly decreased, the diastolic and systolic function was improved, the expression of microtubule-associated protein 1 light chain 3 and Parkin in myocardial tissues was up-regulated, and the expression of P62 was down-regulated in group DM+ P (P<0.05). Compared with group MD+ P, the cross-sectional area of cardiomyocytes was significantly increased, the diastolic and systolic function was decreased, the expression of microtubule-associated protein 1 light chain 3 was down-regulated, and the expression of P62 was up-regulated in group DM+ P+ MA(P<0.05) Conclusion Autophagy is involved in Parkin over-expression-induced reduction of cardiac hypertrophy in diabetic rats. Key words: Autophagy; Ubiquitin-protein ligases; Diabetes mellitus; Cardiomegaly

Deep ocean minerals inhibit IL-6 and IGFIIR hypertrophic signaling pathways to attenuate diabetes-induced hypertrophy in rat hearts.

We previously reported that deep sea water (DSW) prolongs the life span of streptozotocin (STZ)-induced diabetic rats by the compensatory augmentation of the insulin like growth factor (IGF)-I survival signaling and inhibition of apoptosis. Here, we investigated the effects of DSW on cardiac hypertrophy in diabetic rats. Cardiac hypertrophy was induced in rats by using STZ (65 mg/kg) administered via IP injection. DSW was prepared by mixing DSW mineral extracts and desalinated water. Different dosages of DSW-1X (equivalent to 37 mg Mg2+·kg-1·day-1), 2X (equivalent to 74 mg Mg2+·kg-1·day-1) and 3X (equivalent to 111 mg Mg2+·kg-1·day-1) were administered to the rats through gavage for 4 wk. Cardiac hypertrophy was evaluated by the heart weight-to-body weight ratio and the cardiac tissue cross-sectional area after hematoxylin and eosin staining. The protein levels of the cardiac hypertrophy signaling molecules were determined by Western blot. Our results showed that the suppressive effects of the DSW treatment on STZ-induced cardiac hypertrophy were comparable to those of MgSO4 administration and that the hypertrophic marker brain natriuretic peptide (BNP) was decreased by DSW. In addition, DSW attenuated both the eccentric hypertrophy signaling pathway, IL-6-MEK-STAT3, and the concentric signaling pathway, IGF-II-PKCα-CaMKII, in DM rat hearts. The cardiac hypertrophy-associated activation of extracellular signal-regulated kinase (ERK) and the upregulation of the transcription factor GATA binding protein 4 (GATA4) were also negated by treatment with DSW. The results from this study suggest that DSW could be a potential therapeutic agent for the prevention and treatment of diabetic cardiac hypertrophy.NEW & NOTEWORTHY Deep sea water, containing high levels of minerals, improve cardiac hypertrophy in diabetic rats through attenuating the eccentric signaling pathway, IL-6-MEK5-STAT3, and concentric signaling pathway, IGF2-PKCα-CaMKII. The results from this study suggest that deep sea water could be a potential therapeutic agent for the prevention and treatment of diabetic cardiac hypertrophy.

Simvastatin Improves Cardiac Hypertrophy in Diabetic Rats by Attenuation of Oxidative Stress and Inflammation Induced by Calpain-1-Mediated Activation of Nuclear Factor-κB (NF-κB).

BackgroundSimvastatin, an HMG-CoA reductase inhibitor, has been reported to exert multiple protective effects on the cardiovascular system. However, the molecular mechanism remains to be examined. The present study was designed to study the effects of simvastatin on cardiac hypertrophy in diabetic rats and to explore its potential mechanism.Material/MethodsSprague-Dawley rats were assigned into a control (Con) group, a streptozotocin (STZ) group, and a STZ+simvastatin (STZ+SIM) group. The level of reactive oxygen species (ROS) was measured by using dihydroethidium (DHE) staining. The protein expressions of p65, IκBα, vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), calpain-1, and endothelial nitric oxide synthase (eNOS) were examined by Western blot analysis. qPCR was used to detect the levels of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP).ResultsSimvastatin improved the cardiac hypertrophy of diabetic rats, as demonstrated by decreases in the ratios of left ventricular weight/body weight (LVW/BW) and heart weight/body weight (HW/BW) and by the downregulation of mRNA expression of BNP and ANP in the heart tissue. Simvastatin decreased the protein expressions of VCAM-1, ICAM-1, IL-6, and TNF-α, increased eNOS protein expression, and limited an increase in ROS levels in the heart tissue. Simvastatin increased IκBα protein expression in cytoplasm and inhibited the translocation of p65, the subunit of nuclear factor-κB (NF-κB) to the nucleus from the cytoplasm of the heart tissue. Furthermore, simvastatin attenuated the activity of calpain and calpain-1 protein expression in heart tissue.ConclusionsSimvastatin attenuates cardiac hypertrophy in diabetic rats, which might be due to the attenuation of oxidative stress and inflammation induced by calpain-1-mediated activation of NF-κB.

Abstract 57: Impaired Aldehyde Dehydrogenase 2 Activity Contributes To Inhibition Of Mitochondrial Respiration In Hyperglycemic Rats

Aldehyde dehydrogenase (ALDH) 2 is a mitochondrial isozyme of the heart involved in the metabolism of toxic aldehydes produced from oxidative stress. A decrease in ALDH2 levels and activity was reported in the hearts of experimental hyperglycemia along with an increase in 4-hydroxy-2-nonenal (4HNE). 4HNE is produced in the mitochondria upon lipid peroxidation and known to form adduct with mitochondrial proteins. We hypothesize that reduced ALDH2 activity impairs mitochondrial respiration due to 4HNE adducts formation, ultimately resulting in cardiac damage in hyperglycemia. A single dose (65 mg/kg; i.p.) of streptozotocin in rats resulted in hyperglycemia with a blood glucose level of 443 ± 9 mg/dl versus 121 ± 7 mg/dl in control animals, p&lt;0.0001. N=7-11 in both groups. After 6 months of hyperglycemia, heart function was recorded and the rats were sacrificed. Increases in cardiomyocyte cross sectional area (446 ± 32 μm 2 Vs 221 ± 10 μm 2 ; p&lt;0.0001) indicated cardiac hypertrophy in diabetic rats. Both diastolic and systolic dysfunctions were recorded with diabetic rats compared to controls. For instance, % fractional shortening was lower in diabetic group versus control; (p&lt;0.0001). Most importantly, myocardial ALDH2 activity and levels were reduced and immunostaining for 4HNE protein adducts was increased in diabetic hearts compared to controls. The mitochondrial oxygen consumption rate (OCR), an index of mitochondrial respiration, was decreased in mitochondria isolated from diabetic hearts compared to controls (p&lt;0.0001). To check the direct effect of 4HNE and ALDH2 inhibition, we treated H9C2 cardiomyocytes with 4HNE and disufiram, an ALDH inhibitor, respectively, which reduced mitochondrial respiration (p&lt;0.0001) and cell viability (p&lt;0.0001) along with reduced ALDH2 activity and increased 4HNE adducts formation. We conclude that chronic hyperglycemia-induced 4HNE accumulation due to low ALDH2 activity in the heart leads to defective mitochondrial respiration and cardiac damage and dysfunction.

Fufang Xue Shuan Tong capsules inhibit renal oxidative stress markers and indices of nephropathy in diabetic rats.

Fufang Xue Shuan Tong (FXST) capsules, a traditional Chinese medicine, have been used to treat diabetic nephropathy for many years. FXST has been shown to attenuate elevated levels of oxidative stress in the retina of diabetic rats. However, whether FXST protects kidneys through the same mechanism(s) remains unclear. In this study, diabetes was induced in rats by administration of a high-fat diet and low-dose streptozotocin. Rats were administered low (450 mg/kg/day), middle (900 mg/kg/day) or high (1800 mg/kg/day) doses of FXST orally for 3 months. Another group was administered 50 mg/kg/day orally for the same period. The results indicated that all doses of FXST reduced urinary protein excretion and creatinine clearance and ameliorated the diabetic nephropathy-related mesangial matrix expansion. However, only middle and high doses of FXST prevented glomerular hypertrophy in diabetic rats, and the high dose showed the greatest inhibitory effect with regard to mesangial matrix expansion. Furthermore, superoxide dismutase activities were significantly elevated, whereas malondialdehyde levels were significantly reduced in the renal cortex following FXST treatment. The kidney-protective role of FXST is not inferior to that of captopril, one of the most commonly used drugs for the treatment of diabetic nephropathy. In conclusion, FXST retards the progression of diabetic nephropathy, while high-dose FXST shows the most prominent effect in counteracting the pathological changes of diabetic nephropathy. The renoprotective action of FXST is induced by the reduction of oxidative stress in diabetic nephropathy.

Effects of Hyperbaric Oxygen on Metabolic Capacity of the Skeletal Muscle in Type 2 Diabetic Rats with Obesity

We investigated whether hyperbaric oxygen enhances the oxidative metabolic capacity of the skeletal muscle and attenuates adipocyte hypertrophy in type 2 diabetic rats with obesity. Five-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats were used as diabetic animals and nondiabetic controls, respectively, and assigned to control and hyperbaric oxygen groups. Animals in the hyperbaric oxygen group were exposed to an atmospheric pressure of 1.25 with an oxygen concentration of 36% for 3 h daily. The glucose level at 27 weeks of age was significantly higher in OLETF rats than in LETO rats, but the elevation was inhibited in OLETF rats exposed to hyperbaric oxygen. The slow-to-fast fiber transition in the skeletal muscle was observed in OLETF rats, but the shift was inhibited in OLETF rats exposed to hyperbaric oxygen. Additionally, the oxidative enzyme activity of muscle fibers was increased by hyperbaric oxygen. The adipocyte size was larger in OLETF rats than in LETO rats, but hypertrophied adipocytes were not observed in OLETF rats exposed to hyperbaric oxygen. Hyperbaric oxygen enhances glucose and lipid metabolism in the skeletal muscle, indicating that hyperbaric oxygen can prevent elevation of glucose and adipocyte hypertrophy in diabetic rats with obesity.

Effect of telmisartan on the expression of cardiac adiponectin and its receptor 1 in type 2 diabetic rats

This study investigated the effect of telmisartan on the expression of cardiac adiponectin and its receptor 1 in type 2 diabetic rats. Thirty-six male Wistar rats were randomly divided into control (C, n = 10) and diabetic (n = 26) groups. Type 2 diabetes was induced by high-fat and high-sugar diet and intraperitoneal injection of a low dose of streptozotocin (STZ). After induction of diabetes, diabetic rats were again randomly divided into diabetic (D, n = 10) and diabetic treated (DT, n = 10) groups. Telmisartan (5 mg/kg/day) was administrated to diabetic treated rats by gavage for 12 weeks. Twelve weeks later, the heart function was investigated. Plasma and myocardial adiponectin levels were detected by enzyme-linked immunosorbent assay (ELISA). The cardiac mRNA expression of adiponectin receptor 1 (adipiR1) was assayed by reverse transcript-polymerase chain reaction (RT-PCR). The cardiac protein expression of adipiR1, AMP-activated protein kinase (AMPK)-α, phospho-AMPK-α (Thr172) and glucose transporter 4(GLUT4) was determined by Western blotting. The ratio of heart weight to body weight was significantly increased in diabetic rats compared with control. The decreased levels of plasma and myocardial adiponectin and the decreased protein and mRNA expression of myocardial adipoR1 led to the decreased myocardial phosphorylation of AMPK-α (Thr172) and the decreased protein expression of myocardial GLUT4 in diabetic rats. Consequently, the heart function was decreased in diabetic rats. Telmisartan treatment significantly attenuated the increased ratio of heart weight to body weight in diabetic rats. The levels of plasma and myocardial adiponectin and the expression of myocardial adipoR1 in diabetic rats were upregulated by telmisartan. Subsequently, the levels of myocardial phospho-AMPK-α (Thr172) and the expression of myocardial GLUT4 in diabetic rats were increased by telmisartan. Consequently, the heart function was improved in diabetic rats treated with telmisartan. These results suggest that the levels of myocardial adiponectin and its receptor 1 are decreased in type 2 diabetic rats. Telmisartan treatment up-regulates the levels of myocardial adiponectin and its receptor 1, resulting in the increase in myocardial phospho-AMPK-α (Thr172) and GLUT4 expression, which may contribute to the improvement of heart function and the decrease in cardiac hypertrophy in diabetic rats.

Breviscapine ameliorates hypertrophy of cardiomyocytes induced by high glucose in diabetic rats via the PKC signaling pathway

To investigate the influence of breviscapine on high glucose-induced hypertrophy of cardiomyocytes and the relevant mechanism in vitro and in vivo. Cultured neonatal cardiomyocytes were divided into i) control; ii) high glucose concentrations; iii) high glucose+PKC inhibitor Ro-31-8220; iv) high glucose+breviscapine; or v) high glucose+NF-kappaB inhibitor BAY11-7082. Cellular contraction frequency and volumes were measured; the expression of protein kinase C (PKC), NF-kappaB, TNF-alpha, and c-fos were assessed by Western blot or reverse transcription-polymerase chain reaction (RT-PCR). Diabetic rats were induced by a single intraperitoneal injection of streptozotocin, and randomly divided into i) control rats; ii) diabetic rats; or iii) diabetic rats administered with breviscapine (10 or 25 mg x kg(-1) x d(-1)). After treatment with breviscapine for six weeks, the echocardiographic parameters were measured. All rats were then sacrificed and heart tissue was obtained for microscopy. The expression patterns of PKC, NF-kappaB, TNF-alpha, and c-fos were measured by Western blot or RT-PCR. Cardiomyocytes cultured in a high concentration of glucose showed an increased pulsatile frequency and cellular volume, as well as a higher expression of PKC, NF-kappaB, TNF-alpha, and c-fos compared with the control group. Breviscapine could partly prevent these changes. Diabetic rats showed relative cardiac hypertrophy and a higher expression of PKC, NF-kappaB, TNF-alpha, and c-fos; treatment with breviscapine could ameliorate these changes in diabetic cardiomyopathy. Breviscapine prevented cardiac hypertrophy in diabetic rats by inhibiting the expression of PKC, which may have a protective effect in the pathogenesis of diabetic cardiomyopathy via the PKC/NF-kappaB/c-fos signal transduction pathway.

Tranilast Inhibits Glucose-induced Insulin Secretion from Pancreatic β-Cells

Tranilast, N-(3,4-demethoxycinnamoyl)-anthranilic acid, is an anti-allergic agent identified as an inhibitor of mast cell degranulation. Recently, tranilast was shown to decrease albuminuria in a rat model of diabetic nephropathy and to ameliorate vascular hypertrophy in diabetic rats, suggesting that it may be clinically useful in the treatment of diabetic complications. However, the effects of tranilast on glucose tolerance have not been elucidated. Thus, the aim of this study is to investigate the effect of tranilast on insulin secretion in pancreatic beta-cells. Treatment with tranilast significantly suppressed insulin secretion in INS-1E cells and rat islets induced by 16.7 mmol/l glucose. Furthermore, tranilast inhibited tolbutamide-induced insulin secretion. Treatment with tranilast increased (86)Rb (+) efflux from COS-1 cells in which pancreatic beta-cell-type ATP-sensitive K (+) (K (ATP)) channels were reconstructed and suppressed the cytosolic ATP/ADP ratio in INS-1E cells. Interestingly, treatment with tranilast enhanced glucose uptake in INS-1E cells. In the present study, we demonstrated that tranilast inhibited glucose- and tolbutamide-induced insulin secretion through the activation of K (ATP) channels in pancreatic beta-cells.

Phlorizin Prevents Glomerular Hyperfiltration but not Hypertrophy in Diabetic Rats

The relationships of renal and glomerular hypertrophies to development of hyperfiltration and proteinuria early in streptozotocin-induced diabetes were explored. Control, diabetic, phlorizin-treated controls, and diabetic male Fischer rats were used. Phlorizin (an Na+-glucose cotransport inhibitor) was given at a dose sufficient to normalize blood glucose. Inulin clearance (Cinulin) and protein excretion rate (PER) were measured. For morphometry, kidney sections were stained with periodic acid Schiff. At one week, diabetes PER increased 2.8-folds (P < .001), Cinulin increased 80% (P < .01). Kidney wet and dry weights increased 10%–12% (P < .05), and glomerular tuft area increased 9.3% (P < .001). Phlorizin prevented proteinuria, hyperfiltration, and kidney hypertrophy, but not glomerular hypertrophy. Thus, hyperfiltration, proteinuria, and whole kidney hypertrophy were related to hyperglycemia but not to glomerular growth. Diabetic glomerular hypertrophy constitutes an early event in the progression of glomerular pathology which occurs in the absence of mesangial expansion and persists even after changes in protein excretion and GFR are reversed through glycemic control.

Therapeutic Potential of Angiostatin in Diabetic Nephropathy

Angiostatin is a proteolytic fragment of plasminogen and a potent angiogenic inhibitor. Previous studies have shown that angiostatin inhibits retinal neovascularization and reduces retinal vascular permeability in diabetic retinopathy. Here, it is reported for the first time that angiostatin is also implicated in diabetic nephropathy (DN). Angiostatin levels are dramatically decreased in the kidney of streptozotocin-induced diabetic rats. Consistently, diabetic kidneys also showed decreased expression and proteolytic activities of matrix metalloproteinase-2, an enzyme that releases angiostatin from plasminogen. Adenovirus-mediated delivery of angiostatin significantly alleviated albuminuria and attenuated the glomerular hypertrophy in diabetic rats. Moreover, angiostatin treatment downregulated the expression of vascular endothelial growth factor and TGF-beta1, two major pathogenic factors of DN, in diabetic kidneys. In cultured human mesangial cells, angiostatin blocked the overexpression of vascular endothelial growth factor and TGF-beta1 that were induced by high glucose while increasing the levels of pigment epithelium-derived factor, an endogenous inhibitor of DN. Moreover, angiostatin effectively inhibited the high-glucose-and TGF-beta1-induced overproduction of proinflammatory factors and extracellular matrix proteins via blockade of the Smad signaling pathway. These findings suggest that the decrease of angiostatin levels in diabetic kidney may contribute to the pathologic changes such as inflammation and fibrosis in DN. Therefore, angiostatin has therapeutic potential in DN as a result of its anti-inflammatory and antifibrosis activities.

Pentoxifylline Ameliorates Renal Tumor Necrosis Factor Expression, Sodium Retention, and Renal Hypertrophy in Diabetic Rats

Background/Aim: Diabetic nephropathy contributes substantially to cardiovascular morbidity and mortality associated with diabetes. Urinary tumor necrosis factor (TNF) excretion is increased during diabetes and serves as an important mediator of pathological changes during the initial stages of diabetic nephropathy, including sodium retention and renal hypertrophy. We tested the hypothesis that pentoxifylline (PTF), an agent that inhibits TNF synthesis, could prevent sodium retention and renal hypertrophy during diabetes. Methods: Proximal and distal tubule TNF expression, urinary TNF excretion, sodium retention, and renal hypertrophy were examined in control, diabetic, and PTF-treated diabetic rats. Results: TNF mRNA and protein levels were increased in proximal tubule cells isolated from diabetic rats compared to control rats. In contrast, TNF expression in distal tubule cells was not increased during diabetes. PTF prevented the increase in TNF mRNA and protein in proximal tubule cells during diabetes and reduced urinary TNF excretion. PTF therapy decreased whole animal sodium retention by enhancing urinary sodium excretion in diabetic rats. In addition, PTF reduced renal hypertrophy in diabetic rats. Conclusions: The proximal tubule is an important site of TNF production during diabetes and PTF is an effective therapy for preventing the pathological changes accompanying early diabetic nephropathy.

Calcineurin is activated in diabetes and is required for glomerular hypertrophy and ECM accumulation.

Diabetic nephropathy is characterized by the rapid onset of hypertrophy and ECM expansion. Previously, we showed that calcineurin phosphatase is required for hypertrophy and ECM synthesis in cultured mesangial cells. Therefore, we examined the effect of calcineurin inhibition on renal hypertrophy and ECM accumulation in streptozotocin-induced diabetic rats. After 2 wk of diabetes, calcineurin protein was increased in whole cortex and glomeruli in conjunction with increased phosphatase activity. Daily administration of cyclosporin A blocked accumulation of both calcineurin protein and calcineurin activity. Also associated with calcineurin upregulation was nuclear localization of the calcineurin substrate NFATc1. Inhibition of calcineurin reduced whole kidney hypertrophy and abolished glomerular hypertrophy in diabetic rats. Furthermore, calcineurin inhibition substantially reduced ECM accumulation in diabetic glomeruli but not in cortical tissue, suggesting a differential effect of calcineurin inhibition in glomerular vs. extraglomerular tissue. Corresponding increases in fibronectin mRNA and transforming growth factor-beta mRNA were observed in tubulointerstitium but not in glomeruli. In summary, calcineurin plays an important role in glomerular hypertrophy and ECM accumulation in diabetic nephropathy.

Antibodies against vascular endothelial growth factor improve early renal dysfunction in experimental diabetes.

Vascular endothelial growth factor (VEGF) is a cytokine that potently stimulates angiogenesis, microvascular hyperpermeability, and endothelium-dependent vasodilation, effects that are largely mediated by endothelial nitric oxide synthase (eNOS). The expression of VEGF is pronounced in glomerular visceral epithelial cells, but its function in renal physiology and pathophysiology is unknown. VEGF expression is upregulated by high ambient glucose concentrations in several cell types in vitro and in glomeruli of diabetic rats. To assess the role of VEGF in the pathophysiology of early renal dysfunction in diabetes, monoclonal anti-VEGF antibodies (Ab) were administered to control and streptozotocin-induced diabetic rats for 6 wk after induction of diabetes. Based on in vitro binding studies, an adequate serum VEGF inhibitory activity was achieved during the entire course of anti-VEGF Ab administration. Anti-VEGF Ab treatment but not administration of isotype-matched control Ab decreased hyperfiltration, albuminuria, and glomerular hypertrophy in diabetic rats. VEGF blockade also prevented the upregulation of eNOS expression in glomerular capillary endothelial cells of diabetic rats. Antagonism of VEGF had no effect on GFR and glomerular volume in control rats. These results identify VEGF as a pathogenetic link between hyperglycemia and early renal dysfunction in diabetes. Targeting VEGF may prove useful as a therapeutic strategy for the treatment of early diabetic nephropathy.