Gabriel Cao

ACE Inhibition and AT1 Receptor Blockade Prevent Fatty Liver and Fibrosis in Obese Zucker Rats

Objective: Non‐alcoholic steatohepatitis (NASH), which is a common liver disease in industrialized countries, is associated with obesity, hypertension, and type‐2 diabetes (metabolic syndrome). Since angiotensin II (ANG II) has been suggested to play an important role in liver inflammation and fibrosis, the purpose of this study was to investigate whether therapy against renin‐angiotensin system (RAS) may provide some beneficial effect in liver of an animal model of metabolic syndrome.

Angiotensin-(1–7) reduces proteinuria and diminishes structural damage in renal tissue of stroke-prone spontaneously hypertensive rats

Angiotensin (ANG)-(1-7) constitutes an important functional end-product of the renin-angiotensin-aldosterone system that acts to balance the physiological actions of ANG II. In the kidney, ANG-(1-7) exerts beneficial effects by inhibiting growth-promoting pathways and reducing proteinuria. We examined whether a 2-wk treatment with a daily dose of ANG-(1-7) (0.6 mg·kg(-1)·day(-1)) exerts renoprotective effects in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP). Body weight, glycemia, triglyceridemia, cholesterolemia, as well as plasma levels of Na+ and K+ were determined both at the beginning and at the end of the treatment. Also, the weekly evolution of arterial blood pressure, proteinuria, and creatinine clearance was evaluated. Renal fibrosis was determined by Massons trichrome staining. Interleukin (IL)-6, tumor necrosis factor (TNF)-α, and nuclear factor-κB (NF-κB) levels were determined by immunohistochemistry and confirmed by Western blotting analysis. The levels of glomerular nephrin were assessed by immunofluorescence. Chronic administration of ANG-(1-7) normalized arterial pressure, reduced glycemia and triglyceridemia, improved proteinuria, and ameliorated structural alterations in the kidney of SHRSP as shown by a restoration of glomerular nephrin levels as detected by immunofluorescence. These results were accompanied with a decrease in both the immunostaining and abundance of IL-6, TNF-α, and NF-κB. In this context, the current study provides strong evidence for a protective role of ANG-(1-7) in the kidney.

Angiotensin-(1–7) attenuates diabetic nephropathy in Zucker diabetic fatty rats

Angiotensin (ANG)-(1-7) is known to attenuate diabetic nephropathy; however, its role in the modulation of renal inflammation and oxidative stress in type 2 diabetes is poorly understood. Thus in the present study we evaluated the renal effects of a chronic ANG-(1-7) treatment in Zucker diabetic fatty rats (ZDF), an animal model of type 2 diabetes and nephropathy. Sixteen-week-old male ZDF and their respective controls [lean Zucker rats (LZR)] were used for this study. The protocol involved three groups: 1) LZR + saline, 2) ZDF + saline, and 3) ZDF + ANG-(1-7). For 2 wk, animals were implanted with subcutaneous osmotic pumps that delivered either saline or ANG-(1-7) (100 ng·kg(-1)·min(-1)) (n = 4). Renal fibrosis and tissue parameters of oxidative stress were determined. Also, renal levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), ED-1, hypoxia-inducible factor-1α (HIF-1α), and neutrophil gelatinase-associated lipocalin (NGAL) were determined by immunohistochemistry and immunoblotting. ANG-(1-7) induced a reduction in triglyceridemia, proteinuria, and systolic blood pressure (SBP) together with a restoration of creatinine clearance in ZDF. Additionally, ANG-(1-7) reduced renal fibrosis, decreased thiobarbituric acid-reactive substances, and restored the activity of both renal superoxide dismutase and catalase in ZDF. This attenuation of renal oxidative stress proceeded with decreased renal immunostaining of IL-6, TNF-α, ED-1, HIF-1α, and NGAL to values similar to those displayed by LZR. Angiotensin-converting enzyme type 2 (ACE2) and ANG II levels remained unchanged after treatment with ANG-(1-7). Chronic ANG-(1-7) treatment exerts a renoprotective effect in ZDF associated with a reduction of SBP, oxidative stress, and inflammatory markers. Thus ANG-(1-7) emerges as a novel target for treatment of diabetic nephropathy.

Comparison of the renal, cardiovascular and hepatic toxicity data of original intravenous iron compounds

BACKGROUND Intravenous (i.v.) iron is essential for managing haemoglobin levels in haemodialysis patients. However, i.v. iron may cause variable degrees of toxicity. This is mainly related to the pharmacological characteristics of any given i.v. iron compound. METHODS This blinded study examines the effects of five i.v. iron preparations on haemodynamic and functional parameters. Sixty Sprague-Dawley rats (n = 10/group) received high or low molecular weight (HMW/LMW) iron dextran, ferric gluconate (FG), ferric carboxymaltose (FCM), iron sucrose (ISC) or isotonic saline solution (control). Five i.v. doses of iron (40 mg iron/kg) or saline were administered over 4 weeks. RESULTS Systolic blood pressure was significantly reduced in the LMW dextran group, whereas serum iron and percentage transferrin saturation were significantly elevated in all treatment groups. Creatinine clearance was reduced and urinary protein excretion increased in the FG group only (P < 0.01). Liver enzyme levels in the blood were increased (P < 0.01) in the FG and two dextran groups compared with the FCM and ISC groups. Analysis of liver, heart and kidney homogenates showed a significant increase in catalase and malondialdehyde levels in the FG group, and an increase in CuZn-superoxide dismutase and glutathione (GSH) peroxidase activity accompanied with a decrease in the reduced-to-oxidized GSH ratio in the FG and two dextran groups (P < 0.01). Tumour necrosis factor alpha and interleukin-6 levels were significantly elevated in liver, heart and kidney samples from the FG and two dextran groups but not the FCM, ISC or control groups. CONCLUSIONS These findings indicate that FG and HMW/LMW iron dextran have less favourable safety profiles than FCM and ISC in normal rats.

Antifibrotic effects of pioglitazone on the kidney in a rat model of type 2 diabetes mellitus.

BACKGROUND Recent evidence suggests that treatment of type 2 diabetes with thiazolidinediones [peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists], ameliorates glomerulosclerosis and tubulointerstitial fibrosis in the rat kidney. In the current work, we have investigated whether these drugs, and specifically pioglitazone (PGT), act by preventing fibrosis and kidney dysfunction mainly through antioxidant and anti-inflammatory effects, independently of glycaemic control. METHODS Male 2- to 3-month-old obese Zucker fa/fa (OZR) and ZDF fa/fa rats (ZDFR), and their control the lean Zucker rat (LZR), were used. Diabetic rats were given either a low dose (0.6 mg/kg/day) or a high dose (12 mg/ kg/day) of PGT in the chow for 2 or 4-5 months. Glycaemia, blood pressure, creatinine clearance and proteinuria were determined, and the underlying histopathology was defined with markers of fibrosis, glomerular damage, oxidative stress and inflammation by immunohistochemistry/ quantitative image analysis in tissue sections, and western blots and ad hoc assays in fresh tissue. RESULTS PGT at low doses given for 4-5 months considerably reduced blood pressure, proteinuria and creatinine clearance. This was associated with amelioration of renal tissue damage and fibrosis, evidenced by the glomerulosclerosis, tubulointerstitial fibrosis, tubular atrophy and podocyte injury indexes, and of oxidative stress and inflammation, as shown by the decrease in the respective markers, although glycaemia remained high and obesity was not affected. CONCLUSIONS These results indicate that low doses of PGT ameliorate renal fibrosis and preserve renal function in this animal model of metabolic syndrome, independently of glycaemic control or effects on body weight.

Comparison of Oxidative Stress and Inflammation Induced by Different Intravenous Iron Sucrose Similar Preparations in a Rat Model

Iron sucrose originator (ISORIG) has been used to treat iron deficiency and iron deficiency anemia for decades. Iron sucrose similars (ISSs) have recently entered the market. In this non-clinical study of non-anemic rats, five doses (40 mg iron/kg body weight) of six ISSs marketed in Asian countries, ISORIG or saline solution (control) were administered intravenously over four weeks to compare their toxicologic effects. Vasodilatory effects, impaired renal function and hepatic damage were only observed in the ISS groups. Significantly elevated serum iron and transferrin saturation levels were observed in the ISS groups suggesting a higher release of iron resulting in higher amounts of non-transferrin bound (free) iron compared to ISORIG. This might explain the elevated oxidative stress and increased levels of inflammatory markers and antioxidant enzymes in the liver, heart and kidneys of ISS-treated animals. Physico-chemical analyses showed that the molecular structure of most of the ISSs differed greatly from that of the ISORIG. These differences may be responsible for the organ damage and oxidative stress observed in the ISS groups. Significant differences were also found between different lots of a single ISS product. In contrast, polarographic analyses of three different ISORIG lots were identical, indicating that the molecular structure and thus the manufacturing process for ISORIG is highly consistent. Data from this study suggest that ISSs and ISORIG differ significantly. Therefore, before widespread use of these products it would be prudent to evaluate additional non-clinical and/or clinical data proving the safety, therapeutic equivalence and interchangeability of ISSs with ISORIG.

Differences between original intravenous iron sucrose and iron sucrose similar preparations.

Iron sucrose (Venofer; reference) has a good safety record and is prescribed in patients with anaemia and chronic kidney disease worldwide, but various iron sucrose similar (ISS) preparations are now utilized in clinical practice. This study evaluates possible differences between iron sucrose and ISS preparations on haemodynamic and oxidative stress markers in normal rats. 60 male and 60 female Sprague Dawley rats were divided into four groups and assigned to receive commercially available ISS test 1, ISS test 2, reference or isotonic saline solution (control). A single i.v. dose of iron (40 mg/kg) or saline (equivalent volume) was administered after 24 h and every 7 days for 4 weeks. Blood samples were collected for biological assessment of haemoglobin (Hb), serum iron and percentage transferrin saturation (TSAT), and urine samples were collected to investigate creatinine clearance and proteinuria. Animals were sacrificed after receiving an i.v. dose on days 1, 7 and 28, and kidney, liver, and heart homogenates were then collected to determine antioxidant enzyme levels. Tissues were processed using Prussian blue and immmunohistochemistry techniques to identify iron deposits, tissue ferritin and pro-inflammatory markers. Systolic blood pressure was significantly reduced in the ISS groups relative to the reference and control groups after 24 h and on days 7, 14 and 21 (p < 0.05). Creatinine clearance was reduced (p < 0.01) and proteinuria marked (p < 0.01) in the ISS groups at 24 h and on days 7 and 28 relative to the reference and control groups which did not differ throughout the study. Liver enzymes were also increased in the ISS groups at 24 h and on days 7 and 28. Both ISS test 1 and ISS test 2 groups presented a significant increase in catalase, thiobarbituric reactive species, Cu, Zn-superoxide dismutase (CuZnSOD) and glutathione peroxidase activity, and a decrease in glutathione levels (p < 0.01) in the liver, heart and kidney at 24 h and on day 7 relative to the reference and control groups. Serum iron and percentage TSAT were elevated in all groups (except control) (p < 0.01) but no differences in Hb concentration were observed between them. Finally, levels of the proinflammatory markers TNF-alpha and IL6 were significantly elevated in the ISS groups (liver, heart and kidney) compared with the reference and control groups on day 28 (p < 0.01). These findings suggest significant differences between the reference and ISS test 1/ISS test 2 regarding oxidative stress and the inflammatory responses of liver, heart and kidneys in normal rats. A possible explanation for these observations could be the stability of the iron complex.

Cardiovascular protective effects of nebivolol in Zucker diabetic fatty rats.

Background Although effective in reducing blood pressure, therapy with a first-generation β-blocker is currently controversial in metabolic syndrome due to its negative impact on carbohydrate and lipid metabolism. Objective and design We evaluated the effects of nebivolol, a third-generation highly selective β-blocker with additional vasodilating activity, versus the traditional β-blocker atenolol in controlling functional and morphological cardiovascular damage in a rat model of metabolic syndrome. Methods During 6 months, Zucker diabetic fatty (ZDF) rats and control lean Zucker rats (LZR) were studied. The experimental groups were: untreated ZDF, ZDF along with nebivolol, ZDF along with atenolol and LZR. Blood pressure, plasma insulin, triglycerides, cholesterol, glucose and platelet aggregation were evaluated. Malondialdehyde, reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio, CuZn superoxide dismutase, catalase and glutathione peroxidase were determined in heart homogenates and transforming growth factor β1 and plasminogen activator inhibitor-1 (PAI-1) expression, by immunohistochemistry (IHC). Vascular reactivity, vascular cell adhesion molecule-1, platelet endothelial cell adhesion molecule-1, PAI-1, enhanced nitric oxide synthase and collagen expression were evaluated in aorta. Results Nebivolol and atenolol presented a similar reduction in blood pressure. However, nebivolol showed a better lipid profile, preserved left ventricular function, a significant control in left ventricular geometry and moderated left ventricular hypertrophy versus atenolol. Significant reduction in platelet aggregation and a substantial endothelium-dependent and endothelium-independent relaxation in vessels were also shown in the nebivolol group versus atenolol group. Antioxidant defenses were preserved by nebivolol with a reduction in oxidative stress parameters. Vascular cell adhesion molecule-1, platelet endothelial cell adhesion molecule-1, PAI-1 and eNOS were favorably modulated with nebivolol in vessel wall. TGFβ1, PAI-1 and accumulation of collagen-III and collagen-I were also diminished in heart with nebivolol. Conclusion The present study provides substantial information supporting an actual protective role of nebivolol in comparison with atenolol in experimental metabolic syndrome.

Antifibrotic Effects of Pioglitazone at Low Doses on the Diabetic Rat Kidney Are Associated with the Improvement of Markers of Cell Turnover, Tubular and Endothelial Integrity, and Angiogenesis

Background/Aims: Pioglitazone and other thiazolidinediones are renoprotective in diabetic nephropathy at doses that normalize glycemia, presumably as a consequence of glycemic control. However, low doses of pioglitazone that did not normalize glycemia in rat models of type 2 diabetes prevented tubulointerstitial fibrosis and glomerulosclerosis through counteracting inflammation, oxidative stress, cell cycle arrest, and fibrosis. The current work tested whether this low-dose treatment also reduces other fibrosis and inflammation factors in the diabetic kidney and prevents tubular cell loss, endothelial damage, and abnormal angiogenesis. Methods: ZDF fa/fa rats (ZDF) were fed for 4 months chow with 0.001% pioglitazone, and the untreated ZDF and the non-diabetic lean Zucker rats (LZR) received regular chow. Proteinuria, creatinine clearance, blood pressure, and renal quantitative histopathology markers were determined. Results: Correction of renal function in ZDF by pioglitazone, occurring with a glycemia >250 mg/dl, was accompanied by normalization of the renal levels of connective tissue growth factor and fibronectin (fibrosis), TNF-α, interleukin-6 and MCP-1 (inflammation), megalin (tubular cells), the PCNA/caspase-3 ratio (positive cell turnover), VEGF (abnormal angiogenesis), and the ratio between eNOS and iNOS (endothelial dysfunction). Conclusion: This supports mechanisms for the renoprotective effects of pioglitazone in diabetes additional to glycemic control.

Assessment of the extent of oxidative stress induced by intravenous ferumoxytol, ferric carboxymaltose, iron sucrose and iron dextran in a nonclinical model.

Intravenous (i.v.) iron is associated with a risk of oxidative stress. The effects of ferumoxytol, a recently approved i.v. iron preparation, were compared with those of ferric carboxymaltose, low molecular weight iron dextran and iron sucrose in the liver, kidneys and heart of normal rats. In contrast to iron sucrose and ferric carboxymaltose, low molecular weight iron dextran and ferumoxytol caused renal and hepatic damage as demonstrated by proteinuria and increased liver enzyme levels. Higher levels of oxidative stress in these tissues were also indicated, by significantly higher levels of malondialdehyde, significantly increased antioxidant enzyme activities, and a significant reduction in the reduced to oxidized glutathione ratio. Inflammatory markers were also significantly higher with ferumoxytol and low molecular weight iron dextran rats than iron sucrose and ferric carboxymaltose. Polarographic analysis suggested that ferumoxytol contains a component with a more positive reduction potential, which may facilitate iron-catalyzed formation of reactive oxygen species and thus be responsible for the observed effects. Only low molecular weight iron dextran induced oxidative stress and inflammation in the heart.