Prevention of diabetic nephropathy in rats through enhanced renal antioxidative capacity by inhibition of the proteasome

AimsOxidative stress may play an important role in the pathogenesis of diabetic nephropathy (DN). Recent studies have shown that the ubiquitin–proteasome pathway (UPP) and oxidative stress have interaction. We aimed to investigate whether inhibiting the proteasome has a preventive effect on DN through suppression of renal oxidative stress.Main methodsMale Sprague–Dawley rats were randomly divided into three groups: a normal control (NC) group, a streptozotocin-induced DN model group, and a DN plus MG132 (10 μg/kg) treatment group.Key findingsIncreased 24-h urinary protein excretion rate (UPER) and renal pathological changes were all improved after MG132 administration. Furthermore, enhanced renal 26S proteasome activity and concentration in DN rats were effectively reduced after MG132 administration. Increased p47phox and nitrotyrosine (NT) expressions in kidneys of DN rats were decreased after MG132 treatment. Renal mRNA and protein expressions of NF-E2 related factor 2 (Nrf2) were up-regulated by MG132 in comparison to DN alone. Decreased renal mRNA expression of superoxide dismutase 1 (SOD1), catalase (CAT) and glutathione peroxidase (GPx) in DN rats was heightened after MG132 intervention. Depressed activities of renal SOD, CAT and GPx in DN rats were also improved by MG132 treatment. Increased renal nuclear factor κB (NF-κB) activity was inhibited after MG132 administration in DN rats at the end of 12 weeks.SignificanceOur present data suggest that inhibition of the proteasome by low-dose MG132 has a preventive effect on DN development and progression in rats through the up-regulation of antioxidant genes.     

Attenuation of plasma dyslipidemia and oxidative damage by dietary caloric restriction in streptozotocin-induced diabetic rats

Oxidative stress has been proposed as the pathogenic mechanism linking insulin resistance with endothelial dysfunction during diabetes. The present study investigated the attenuation of plasma dyslipidemia and oxidative damage by caloric restriction in experimental diabetes. Forty male Wistar rats were divided into ad libitum and calorie-restricted groups. The calorie-restricted group was subjected to 30% caloric restriction for 63 days before induction of diabetes to 50% of both groups. Caloric restriction significantly (p<0.01) reduced the body weights, reactive oxygen species (ROS), catalase, total cholesterol levels and non-significantly reduced SOD activities in non-diabetic and diabetic rats. Caloric restriction was also found to improve blood glucose levels, glycated hemoglobin, malondialdehyde, triglyceride, oxidized glutathione and reduced glutathione levels and significantly (p<0.05) increased GPx and GR activities in the experimental animals. The non-diabetic rats fed ad libitum had the most significant increases in body weight which could be due to dyslipidemia. These results indicate that dietary caloric restriction attenuates the oxidative damage and dyslipidemia exacerbated during diabetes as evidenced by the significant reduction in their body weights, ROS, total cholesterol levels and the increases in GPx activity and redox status.     

Protective Role of PGC-1α in Diabetic Nephropathy Is Associated with the Inhibition of ROS through Mitochondrial Dynamic Remodeling

The overproduction of mitochondrial reactive oxygen species (ROS) plays a key role in the pathogenesis of diabetic nephropathy (DN). However, the underlying molecular mechanism remains unclear. Our aim was to investigate the role of PGC-1α in the pathogenesis of DN. Rat glomerular mesangial cells (RMCs) were incubated in normal or high glucose medium with or without the PGC-1α-overexpressing plasmid (pcDNA3-PGC-1α) for 48 h. In the diabetic rats, decreased PGC-1α expression was associated with increased mitochondrial ROS generation in the renal cortex, increased proteinuria, glomerular hypertrophy, and higher glomerular 8-OHdG (a biomarker for oxidative stress). In vitro, hyperglycemia induced the downregulation of PGC-1α, which led to increased DRP1 expression, increased mitochondrial fragmentation and damaged network structure. This was associated with an increase in ROS generation and mesangial cell hypertrophy. These pathological changes were reversed in vitro by the transfection of pcDNA3-PGC-1α. These data suggest that PGC-1α may protect DN via the inhibition of DRP1-mediated mitochondrial dynamic remodeling and ROS production. These findings may assist the development of novel therapeutic strategies for patients with DN.     

Antioxidant enzymes gene expression and antihypertensive effects of seaweeds Ulva linza and Lessonia trabeculata in rats fed a high-fat and high-sucrose diet

The objective of this work was to evaluate the antihypertensive and antioxidant effect of seaweeds (Ulva linza and Lessonia trabeculata) in rats which were fed a hypercaloric diet. Seaweed at 400 mg kg^?1 of body weight was administered for 8 weeks to Wistar rats that were fed with a standard diet or a hypercaloric diet. Intra-abdominal fat, insulin resistance, and lipid profile of the rats were determined. Liver was isolated to determine antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)] activity and gene expression. The administration of seaweed to the rats reduced the levels of intra-abdominal fat, arterial blood pressure, insulin resistance, and cholesterol and triglyceride serum levels. U. linza reduced the GPx activity in control animals but increased it in animals with MS, which could be reduced by using L. trabeculata. Both seaweeds diminished the SOD and GPx expression and increased CAT in control group. Both seaweeds reduced the CAT expression in animals with metabolic syndrome. Combined effects of the different compounds found in the seaweeds explain the regulating effect over different antioxidant enzymes and metabolic pathways that protect the animals fed a hypercaloric diet against the development of hypertension, hyperglycemia, and obesity.     

Effective Delivery of Endogenous Antioxidants Ameliorates Diabetic Nephropathy

Background

Diabetic nephropathy (DN) is thought to be partially due to the injury of renal cells and the renal micro-environment by free radicals. Free radial scavenging agents that inhibit free radical damage may well prevent the development of underlying conditions such as mesangial expansion (by inhibiting extracellular matrix expression) in these patients.

Methods

Using techniques for intra-cellular delivery of peptides, we made metallothionein (MT) and superoxide dismutase (SOD), potent endogenous antioxidants, readily transducible into cell membrane and tested their protective effect against the development of DN in OLETF rats. Herein, we study antioxidant peptides for their ability to prevent oxidative damage to primary rat mesangial cells (MCs), which are important constituents of renal glomeruli.

Results

Intraperitoneal administration of these antioxidants resulted in delivery to the kidney and decreased ROS and the expression of downstream signals in renal cells and postponed the usual progression to DN. In in vitro experiments, MT and SOD were efficiently transferred to MCs, and the increased removal of ROS by MT and SOD was proportional to the degree of scavenging enzymes delivered. MT and SOD decreased three major oxidative injuries (hyperglycemia, AGE and ROS exposure) and also injuries directly mediated by angiotensin II in MCs while changing downstream signal transduction.

Conclusions

The protective effects of MT and SOD for the progression of DN in experimental animals may be associated with the scavenging of ROS by MT and SOD and correlated changes in signal transduction downstream. Concomitant administration of these antioxidant peptides may prove to be a new approach for the prevention and therapy of DN.     

Comparison of the renal effects of bisphenol A in mice with and without experimental diabetes. Role of sexual dimorphism

Bisphenol-A (BPA), a chemical -xenoestrogen- used in the production of the plastic lining of food and beverage containers, is present in the urine of almost the entire population. Recent studies have shown that BPA exposure is associated with podocytopathy, increased urinary albumin excretion (UAE), and hypertension. Since these changes are characteristic of early diabetic nephropathy (DN), we explored the renal effects of BPA and diabetes including the potential role of sexual dimorphism. Male and female mice were included in the following animals' groups: control mice (C), mice treated with 21.2 mg/kg of BPA in the drinking water (BPA), diabetic mice induced by streptozotocin (D), and D mice treated with BPA (D + BPA). Male mice form the D + BPA group died by the tenth week of the study due probably to hydro-electrolytic disturbances.Although BPA treated mice did not show an increase in serum creatinine, as observed in D and D + BPA groups, they displayed similar alteration to those of the D group, including increased in kidney damage biomarkers NGAL and KIM-1, UAE, hypertension, podocytopenia, apoptosis, collapsed glomeruli, as well as TGF-β, CHOP and PCNA upregulation. UAE, collapsed glomeruli, PCNA staining, TGF-β, NGAL and animal survival, significantly impaired in D + BPA animals. Moreover, UAE, collapsed glomeruli and animal survival also displayed a sexual dimorphism pattern.In conclusion, oral administration of BPA is capable of promoting in the kidney alterations that resemble early DN. Further translational studies are needed to clarify the potential role of BPA in renal diseases, particularly in diabetic patients.     

Thyroid hormone-induced haemoglobin changes and antioxidant enzymes response in erythrocytes

Thyroid hormones modulate haemoglobin and reactive oxygen species (ROS) production, leading to antioxidant changes. This study evaluated the antioxidant response to ROS in erythrocytes in hypothyroid and hyperthyroid rats. Wistar rats were divided into four groups: control; hyperthyroid (T4-12 mg 1(-1) in drinking water); sham operated (simulation of thyroidectomy); and hypothyroid (thyroidectomized). Four weeks after, blood was collected and haemoglobin and T(4) levels, lipid peroxidation (LPO), protein oxidation, superoxide dismutase (SOD), catalase (CAT) , glutathione S-transferase (GST) and glutathione peroxidase (GPx) activities, and total radical antioxidant potential (TRAP) were measured. SOD, CAT and GST immunocontent was evaluated. Haemoglobin levels were increased in hyperthyroid erythrocytes. LPO and carbonyls were augmented (65% and 55%, respectively) in hyperthyroid and reduced (31% and 56%, respectively) in hypothyroid group. SOD and CAT activities have not changed, as well as CAT immunocontent. TRAP was diminished in both hyperthyroid and hypothyroid groups (36% and 37%, respectively). GST activity and immunocontent, as well as GPx activity, were increased in hyper and hypothyroid rats. The data suggest that thyroid hormone changes determine ROS concentration changes and decrease of some antioxidant defences that would lead to a compensatory answer of the GST and GPx enzymes, which could be consider as credible biomarkers.     

Role of 12-lipoxygenase in decreasing P-cadherin and increasing angiotensin II type 1 receptor expression according to glomerular size in type 2 diabetic rats

12-lipoxygenase (12-LO) was implicated in the development of diabetic nephropathy (DN), in which the proteinuria was thought to be associated with a decreased expression of glomerular P-cadherin. Therefore, we investigated the role of 12-LO in the glomerular P-cadherin expression in type 2 diabetic rats according to the glomerular sizes. Rats fed with high-fat diet for 6 wk were treated with low-dose streptozotocin. Once diabetes onset, diabetic rats were treated with 12-LO inhibitor cinnamyl-3,4-dihydroxy-cyanocinnamate (CDC) for 8 wk. Then glomeruli were isolated from diabetic and control rats with a sieving method. RT-PCR, Western blotting, and immunofluorescent staining were used for mRNA and protein expressions of P-cadherin and angiotensin II (Ang II) type 1 receptor (AT1). We found that CDC did not affect the glucose levels but completely attenuated diabetic increases in glomerular volume and proteinuria. Diabetes significantly decreased the P-cadherin mRNA and protein expressions and increased the AT1 mRNA and protein expressions in the glomeruli. These changes were significantly prevented by CDC and recaptured by direct infusion of 12-LO product [12(S)-HETE] to normal rats for 7 days. The decreased P-cadherin expression was similar between large and small glomeruli, but the increased AT1 expression was significantly higher in the large than in the small glomeruli from diabetic and 12(S)-HETE-treated rats. Direct infusion of normal rats with Ang II for 14 days also significantly decreased the glomerular P-cadherin expression. These results suggest that diabetic proteinuria is mediated by the activation of 12-LO pathway that is partially attributed to the decreased glomerular P-cadherin expression.     

Lidocaine affects the redox environment and the antioxidant enzymatic system causing oxidative stress in the hippocampus and amygdala of adult rats

AIMS: Our objective was to investigate if oxidative stress is involved in the neural damage caused by lidocaine. MAIN METHODS: Male Wistar rats were used. The control group received 0.9% saline ip and the treated group received a single 60 mg/kg lidocaine dose ip. On days 1, 2, 5, and 10 after dosing, ten rats were sacrificed and their brains were quickly removed. The amygdala and hippocampus were dissected. Five samples were used to determine lipid peroxidation, reactive oxygen species (ROS), reduced glutathione (GSH), and oxidized glutathione (GSSG). Another five were used to measure antioxidant activities of glutathione peroxidase (GPX), catalase, Cu-Zn SOD (superoxide dismutase), Mn SOD, and total SOD. KEY FINDINGS: Ten days after injection of lidocaine, lipid peroxidation increases in the hippocampus because the ROS are enhanced from day 5, whereas in the amygdala lipid peroxidation and the ROS were enhanced only on the first day postinjection. Lidocaine causes an increased concentration of GSH and GSSG in the hippocampus from the first day. In the amygdala the GSH and GSSG content were increased at day 10. In the hippocampus the catalase activity was enhanced, whereas the total SOD and Cu-Zn SOD activities were decreased. In the amygdala the lidocaine enhances the activities of catalase and GPX, but no SOD isoenzymes were modified. SIGNIFICANCE: In this research we demonstrated that lidocaine affects the redox environment and promotes increases of the oxidative markers both in the hippocampus and amygdala but in a different pattern.     

Testicular oxidative damage and role of combined antioxidant supplementation in experimental diabetic rats

The present study was designated to assess oxidative damage and its effect on germ cell apoptosis in testes of streptozotocin (STZ)-induced diabetic rats. The role of antioxidant supplementation with a mixture of vitamins E and C and alpha lipoic acid for protection against such damage was also evaluated. Forty-five adult male rats were randomly divided into three groups: group I, control, non-diabetic rats; group II, STZ-induced, untreated diabetic rats; group III, STZ-induced diabetic rats supplemented with a mixture of vitamins E and C and alpha lipoic acid. Glycated hemoglobin (HbA_1C), glucose, and insulin levels were estimated in blood samples. Malondialdehyde (MDA), the activities of the enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and caspase-3 in addition to testosterone (T) level were all determined in testicular tissues. Histopathological studies using H&E stain, as well as, immunohistochemical detection of apoptosis using (TUNEL) method were also performed. Blood glucose and HbA_1c were significantly increased while insulin was significantly decreased in STZ-induced diabetic rats as compared with controls. In rat testicular tissues, MDA, and caspase-3 activity were significantly elevated while SOD and GPx enzymatic activities as well as T level were significantly decreased in diabetic rats as compared with control group. Antioxidant supplementation to diabetic rats restored the testicular enzymatic activities of SOD and GPx to almost control levels, in addition, MDA and caspase-3 activity decrease while T increase significantly as compared with untreated diabetic group. Prominent reduction of germ cell apoptosis was found in diabetic rats supplemented with antioxidants. An important role of testicular oxidative damage and germ cell apoptosis in diabetes-induced infertility could be suggested, treatment with antioxidants has a protective effect by restoring SOD and GPx antioxidant enzymatic activity.     

Evaluation of metalloprotease inhibitors on hypertension and diabetic nephropathy

This study examined the effects of two new selective metalloprotease (MMP) inhibitors, XL081 and XL784, on the development of renal injury in rat models of hypertension, Dahl salt-sensitive (Dahl S) and type 2 diabetic nephropathy (T2DN). Protein excretion rose from 20 to 120 mg/day in Dahl S rats fed a high-salt diet (8.0% NaCl) for 4 wk to induce hypertension. Chronic treatment with XL081 markedly reduced proteinuria and glomerulosclerosis, but it also attenuated the development of hypertension. To determine whether an MMP inhibitor could oppose the progression of renal damage in the absence of changes in blood pressure, Dahl S rats were fed a high-salt diet (4.0% NaCl) for 5 wks to induce renal injury and then were treated with the more potent and bioavailable MMP inhibitor XL784 either given alone or in combination with lisinopril and losartan. Treatment with XL784 or the ANG II blockers reduced proteinuria and glomerulosclerosis by ~30% and had no effect on blood pressure. Proteinuria fell from 150 to 30 mg/day in the rats receiving both XL784 and the ANG II blockers, and the degree of renal injury fell to levels seen in normotensive Dahl S rats maintained from birth on a low-salt diet. In other studies, albumin excretion rose from 125 to >200 mg/day over a 4-mo period in 12-mo-old uninephrectomized T2DN rats. In contrast, albumin excretion fell by >50% in T2DN rats treated with XL784, lisinopril, or combined therapy. XL784 reduced the degree of glomerulosclerosis in the T2DN rats to a greater extent than lisinopril, and combined therapy was more effective than either drug alone. These results indicate that chronic administration of a selective MMP inhibitor delays the progression, and may even reverse hypertension and diabetic nephropathy.     

Resveratrol ameliorates early diabetic nephropathy associated with suppression of augmented TGF-β/smad and ERK1/2 signaling in streptozotocin-induced diabetic rats

Diabetic nephropathy (DN) is the major cause of end-stage renal disease. The early changes in DN are characterized by an increased in kidney size, glomerular volume, and kidney function, followed by the accumulation of glomerular extracellular matrix, increased urinary albumin excretion (UAE), glomerular sclerosis, and tubular fibrosis. Resveratrol (RSV) has been shown to ameliorate hyperglycemia and hyperlipidemia in streptozotocin-induced diabetic rats. In the present study, we examined the beneficial effects of RSV on DN and explored the possible mechanism of RSV action.Male Sprague–Dawley rats were injected with streptozotocin at 65 mg/kg body weight. The induction of diabetes mellitus (DM) was confirmed by a fasting plasma glucose level ≥300 mg/dL and symptoms of polyphagia and polydipsia. The DM rats were treated with or without RSV at 0.75 mg/kg body weight 3 times a day for 8 weeks. Animals were sacrificed and kidney histology was examined by microscopy. Urinary albumin excretion, glomerular hypertrophy and expressions of fibronectin, collagen IV, and TGF-β in the glomeruli were alleviated in RSV-treated DM rats, but not in untreated DM rats. In addition, RSV treatment reduced the thickness of the glomerular basement membrane (GBM) to the original thickness and increased nephrin expressions to normal levels in DM rats. Moreover, RSV inhibited phosphorylation of smad2, smad3 and ERK1/2 in diabetic rat kidneys. This is the first report showing that RSV alleviates early glomerulosclerosis in DN through TGF-β/smad and ERK1/2 inhibition. In addition, podocyte injuries of diabetic kidneys are lessened by RSV.     

Aortic-banding induces myocardial oxidative stress and changes in concentration and activity of antioxidants in male Wistar rats

Myocardial activity and gene expression of antioxidant defenses and oxidative damage were examined in an experimental model of pressure overload hypertrophy. Male Wistar rats were divided into abdominal aortic-banded or sham-operated groups. After 30 days, arterial pressure and heart rate were measured. Heart, lung, and liver were extracted and weighted to evaluate cardiac hypertrophy and pulmonary and hepatic congestion. Heart homogenates were prepared to quantify lipid peroxidation (LPO); the activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR); and Cu-Zn SOD and GST concentrations. Total glutathione (GSH) myocardial content was also measured. Arterial pressure (142 +/- 17 mmHg) and cardiac hypertrophy index (3.4 +/- 0.45 mg/g) were significantly increased (by 38% and 22%, respectively, p<0.0001) in the aortic-banded group. LPO was enhanced by 55% in the aortic-banded group (11891 +/- 766 cps/mg protein, p<0.001) compared with that in the controls. SOD activity and concentration were higher (40% and 38%, 15.15 +/- 1.03 U/mg protein, 49.187 pixels, respectively, p<0.05) in the aortic-banded group than in the controls. Aortic-banding induced a decrease by 28% in GST (48 +/- 10 pmol/min/mg protein, p<0.005), by 36% in GPx (38.2 +/- 9.5 nmol/min/mg protein, p<0.005), by 31% in GR activities (1.55 +/- 0.23 nmol/mg protein, p<0.0005), and by 43% in GSH content (0.13 +/- 0.02 nmol/mg protein, p<0.005). In conclusion, in this model it was observed that myocardial oxidative stress induces alterations in antioxidant enzyme activities and protein expression. The follow up of these parameters could afford an early therapeutical window to avoid heart failure progression.     

Effect of an inhibitor of nitric oxide production on Cu−Zn/SOD and its cofactors in diabetic rats

The aim of this study was to investigate the effect of an inhibitor of nitric oxide production, N(omega)-nitro-L-arginine methyl esther (L-NAME) on Cu-Zn/SOD (superoxide dismutase) enzyme activity and copper and zinc concentrations in diabetes-induced rats. The control group consisted of 12 male albino Sprague-Dawley rats, 10-12 wk of age and weighing 300 g. Twenty-six albino Sprague-Dawley rats, 10-12 wk of age and weighing 315 g, constituted the experimental group. The experimental group was divided into two groups. The first group (n=12) constituted streptozotocininduced (55 mg/kg, intraperitoneally) diabetic rats and the second group (n=14) was administered L-NAME (1 mg/kg/d) after streptozotocin induction. For determination of Cu-Zn/SOD activity, spectrophotometry was used. Zinc and copper concentrations were determined by atomic absorption spectrophotometry. Results showed that Cu-Zn/SOD activity was increased significantly in both experimental groups compared to controls, and the increase in the second group was higher than in the first group (p<0.01, p<0.01, p<0.05). Plazma zinc concentration was increased in the second group when compared with controls (p<0.05). Plasma copper was decreased significantly in the second group compared to controls and the first group (p<0.001, p<0.001). Red cell copper concentration was decreased significantly in the first group compared to controls (p<0.05). This study showed that L-NAME administration has ensured an additive effect on the antioxidant defense system, which was proved by the increase in Cu-Zn/SOD activity. This increase might have a protective effect against tissue damage in the acute period, with corresponding changes in zinc and copper concentrations.     

Is there a link between salt-intake and atrial natriuretic peptide system during hypertension induced by nitric oxide blockade?

Long-term nitric oxide (NO) blockade is known to induce a severe and progressive hypertension. The influence of the salt-intake on atrial natriuretic peptide (ANP) system in this hypertension model is unknown. The aim of this study was to evaluate ANP plasma levels, content and mRNA in atria of male Wistar rats chronically treated with oral Nomega-nitro-L-arginine methyl ester (L-NAME) after 4 weeks of high-salt diet. The high-salt diet induced an increase (P < 0.05) in ANP plasma levels in normotensive rats and no significant changes in hypertensive animals. We observed a significant increase in the ANP content in the left and right atria of hypertensive rats (P < 0.001) when compared to normotensive ones. However, no significant changes were observed during high-salt diet in normotensive and hypertensive animals. Northern blot analysis revealed that ANP gene expression is higher in the right and left atria of hypertensive rats when compared to normotensive rats. However, we found no significant changes in ANP mRNA of rats treated with high-salt diet in normotensive and hypertensive rats when compared to low-salt diet. The present observations indicate no interaction between salt-intake and activation of the ANP system during chronic nitric oxide synthase (NOS) inhibition.     

Renoprotective effects of berberine and its possible molecular mechanisms in combination of high-fat diet and low-dose streptozotocin-induced diabetic rats

Berberine (BBR), an effective compound of Chinese traditional herbal medicine, has preventive effects on diabetes and its complications. In this study, we investigated the therapeutic effects and underlying molecular mechanisms of BBR in rats with high-fat diet and streptozotocin (STZ)-induced diabetic nephropathy model. BBR (50, 100, 200 mg/kg/d) were orally administered to male Sprague–Dawley rats after STZ injection and conducted for 8 weeks. Renal damage was evaluated by kidney weight to body weight ratio (KW/BW), urine microalbumin (UMAlb), urine protein for 24 h (UP24 h), urine creatinine (UCr), and histological examination. Type IV collagen and transforming growth factor-beta1 (TGF-β₁) were detected by immunohistochemistry and ultrastructure of glomeruli was observed. Fasting blood glucose (FBG),serum creatinine (SCr), blood urea nitrogen (BUN), total cholesterol (TC), triglyceride (TG), high-density lipoprotein-cholesterol (HDL-c), low-density lipoprotein-cholesterol (LDL-c) in serum and G protein-coupled receptor kinases (GRKs), cAMP in kidney were measured. Remarkable renal damage, hyperglycemia and hyperlipidemia were observed in DN rats. BBR could restore renal functional parameters, suppress alterations in histological and ultrastructural changes in the kidney tissues, improve glucose and lipid metabolism disorders, and increase cAMP levels compared with those of DN model group. Furthermore, BBR down-regulated total protein expression of GRK2, GRK3 and up-regulated expression of GRK6 of renal cortex in DN rats, but had a slight effects on GRK4 and GRK5. These studies demonstrate, for the first time, that BBR exerts renoprotection in high-fat diet and STZ-induced DN rats by modulating the proteins expression of GRKs in G protein- AC-cAMP signaling pathway.     

Berberine regulates the expression of E-prostanoid receptors in diabetic rats with nephropathy

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in diabetic patients. Effective therapies to prevent the development of this disease and to improve advanced kidney injury are required. Berberine (BBR) has preventive effects on diabetes and its complications. This study is to investigate the effects of BBR on the expression of E-prostanoid receptors (EPs) in rats with high-fat diet and streptozotocin (STZ)-induced DN and underlying molecular mechanisms of BBR on DN rats. DN model was induced in male Sprague–Dawley rats with high-fat diet and low dose of STZ injection. BBR (50, 100, 200 mg/kg/d) were orally administered to rats after STZ injection and conducted for 8 weeks. The levels of interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂) in renal cortex were measured by enzyme-linked immunosorbent assay. Expression of EPs receptors (EP1–EP4) were determined by western blotting. Remarkable renal damage, hyperglycemia and hyperlipidemia were observed in DN rats. BBR could restore renal functional parameters, suppress alterations in histological and ultrastructural changes in the kidney tissues, improve glucose and lipid metabolism disorders, and increase cAMP levels compared with those of DN model group (Wang et al. in Mol Biol Rep 40:2405–2418, 2013). The level of IL-6 and PGE₂ were significantly increased in DN model group compared with normal group, BBR could apparently reduced the level of IL-6 and PGE₂. Furthermore, the expression of EP1 and EP3 were both increased and EP4 was lessened in the DN model group compared with normal group, BBR could down-regulate total protein expression of EP1 and EP3 of renal cortex in DN rats and up-regulate the expression of EP4, and there is no significant difference on the expression of EP2 among all groups. These studies demonstrate, for the first time, that BBR exerts renoprotection in high-fat diet and STZ-induced DN rats by modulating the proteins expression of EPs in EP–G protein–cAMP signaling pathway.     

Antioxidant efficacy of black pepper (Piper nigrum L.) and piperine in rats with high fat diet induced oxidative stress

The present study was aimed to explore the effect of black pepper (Piper nigrum L.) on tissue lipid peroxidation, enzymic and non-enzymic antioxidants in rats fed a high-fat diet. Thirty male Wistar rats (95-115 g) were divided into 5 groups. They were fed standard pellet diet, high-fat diet (20% coconut oil, 2% cholesterol and 0.125% bile salts), high-fat diet plus black pepper (0.25 g or 0.5 g/kg body weight), high-fat diet plus piperine (0.02 g/kg body weight) for a period of 10 weeks. Significantly elevated levels of thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and significantly lowered activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and reduced glutathione (GSH) in the liver, heart, kidney, intestine and aorta were observed in rats fed the high fat diet as compared to the control rats. Simultaneous supplementation with black pepper or piperine lowered TBARS and CD levels and maintained SOD, CAT, GPx, GST, and GSH levels to near those of control rats. The data indicate that supplementation with black pepper or the active principle of black pepper, piperine, can reduce high-fat diet induced oxidative stress to the cells.     

Changes in oxidative balance in rat pericytes exposed to diabetic conditions

Recent data indicate that the oxidative stress plays an important role in the pathogenesis of diabetes and its complications such as retinopathy, nephropathy and accelerated atherosclerosis. In diabetic retinopathy, it was demonstrated a selective loss of pericytes accompanied by capillary basement membrane thickening, increased permeability and neovascularization. This study was designed to investigate the role of diabetic conditions such as high glucose, AGE-Lysine, and angiotensin II in the modulation of antioxidant enzymes activities, glutathione level and reactive oxygen species (ROS) production in pericytes. The activity of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and total glutathione (GSH) was measured spectrophotometrically. The production of ROS was detected by spectrofluorimetry and fluorescence microscopy after loading the cells with 2'-7' dichlorofluoresceine diacetate; as positive control H2O2 was used. Intracellular calcium was determined using Fura 2 AM assay. The results showed that the cells cultured in high glucose alone, do not exhibit major changes in the antioxidant enzyme activities. The presence of AGE-Lys or Ang II induced the increase of SOD activity. Their combination decreased significantly GPx activity and GSH level. A three times increase in ROS production and a significant impairment of intracellular calcium homeostasis was detected in cells cultured in the presence of the three pro-diabetic agents used. In conclusion, our data indicate that diabetic conditions induce in pericytes: (i) an increase of ROS and SOD activity, (ii) a decrease in GPx activity and GSH level, (iii) a major perturbation of the intracellular calcium homeostasis. The data may explain the structural and functional abnormalities of pericytes characteristic for diabetic retinopathy.