The antioxidant effect of angiotensin II receptor blocker, losartan, in streptozotocin-induced diabetic rats

Is losartan a promising agent for the treatment of type 1 diabetes-induced testicular germ cell apoptosis in rats?

BACKGROUND

Diabetes mellitus (DM) is common metabolic disease that poses a major risk to public health and fertility. Previous studies indicate that DM may cause male infertility by triggering oxidative stress and germ cell apoptosis in the testis. Due to the undesirable effects of known antidiabetic drugs, scientists have begun to investigate the use of alternative drugs to control infertility complications observed in men. In this context, present study aimed to investigate the possible antiapoptotic effect of losartan against DM-induced testicular germ cell apoptosis.

METHODS AND RESULTS

Expreimental DM model was induced by intraperitoneal injection of streptozocin (STZ, 55 mg/kg) to 28 rats, which were then randomly assigned to 4 groups; 1 mL saline solution was given to DM + saline group by oral gavage, 5 mg/kg/day oral losartan was given to DM + low-dose losartan, 20 mg/kg/day oral losartan was given to DM + mid-dose losartan and, 80 mg/kg/day oral losartan was given to DM + high-dose losartan group for 4 weeks. Bax, Bcl-2 and cleaved-Caspase 3 immunoexpression, terminal-deoxynucleotidyl transferase dutp nick end labeling (TUNEL), Annexin-V and Real Time PCR analyses performed to evaluate antiapoptotic effects of losartan on diabetic rats' testis. In addition, biochemical analyzes carried out to evaluate change in oxidative stress.

CONCLUSION

The results showed that losartan may have dose-related antiapoptotic effects on rats' testis via decreasing oxidative stress.

Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes

The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.

Immune Checkpoint-Bioengineered Beta Cell Vaccine Reverses Early-Onset Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease that results from autoreactive T cells destroying insulin-producing pancreatic beta (β) cells. The development of T1DM is associated with the deficiency of co-inhibitory immune checkpoint ligands (e.g., PD-L1, CD86, and Gal-9) in β cells. Here, a new translational approach based on metabolic glycoengineering and bioorthogonal click chemistry, which bioengineers β cells with co-inhibitory immune checkpoint molecules that induce antigen-specific immunotolerance and reverse early-onset hyperglycemia is reported. To achieve this goal, a subcutaneous injectable acellular pancreatic extracellular matrix platform for localizing the bioengineered β cells while creating a pancreas-like immunogenic microenvironment, in which the autoreactive T cells can interface with the β cells, is devised.

Protective Role of Angiotensin II Type 1 Receptor Blocker on Short Time Effect of Oleic Acid Induced Lung and Kidney Injury

Backgrounds:

Acute respiratory distress syndrome (ARDS) causes high mortality rate in clinic, and the pathogenesis of this syndrome may interact with renin angiotensin system (RAS) components. The main objective of this study was to determine the protective role of AT1R antagonist (losartan) on oleic acid (OA) induced ARDS and kidney injury.

Methods:

The animal model of ARDS was performed by intravenous administration of 250 μl/kg oleic acid (OA). Male and female rats were subjected to received intravenously vehicle (saline, groups 1 and 4), OA (groups 2 and 5), or losartan (10 mg/kg) plus OA (groups 3 and 6), and six hour later, the measurements were performed.

Results:

Co-treatment of OA and losartan increased the serum levels of blood urea nitrogen significantly (P < 0.05) and creatinine insignificantly in both gender. However, the OA induced kidney damage was decreased by losartan significantly in male (P < 0.05) and insignificantly in female rats. In addition, co-treatment of OA and losartan decreased lung water content significantly in male rats (P < 0.05). Based on tissue staining, no significant difference in lung tissue damages were observed between the groups, however some exudate were observed in lung male rats treated with OA alone which were abolished by losartan.

Conclusions:

Losartan may protect the kidney and lung against OA induced tissue injury in male rats. This protective action is not certain in female rats.

Mid-dose losartan mitigates diabetes-induced hepatic damage by regulating iNOS, eNOS, VEGF, and NF-κB expressions

Background/aim

Losartan, an antihypertensive drug, is highly preferred in patients with diabetes mellitus (DM) and hypertension because of its retarding effect on diabetic nephropathy. In this study, we investigated the potential therapeutic effect of different doses of losartan on hepatic damage in a streptozotocin (STZ, 50 mg/kg)-induced DM model in rats.

Materials and methods

In this study, five different groups were formed: control, DM, low-dose losartan (5 mg/kg), mid-dose losartan (20 mg/kg), and high-dose losartan (80 mg/kg). Liver tissues of experimental groups were evaluated immunohistochemically for TUNEL, iNOS, eNOS, VEGF, and NF-κB pathways. In addition to immunohistochemical analysis, analyses of SOD and MDA, which are oxidative stress markers, were also performed and the results were evaluated together.

Results

When biochemical and immunohistochemical findings were evaluated together, it was found that the results obtained from the mid-dose losartan group were closer to those of the control than the other groups.

Conclusion

This study indicated that mid-dose losartan administration may have a therapeutic effect by inhibiting apoptosis and regulating iNOS, eNOS, VEGF, and NF-κB protein expressions in DM-induced hepatic damage.

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Validation of 111In-Exendin SPECT for the Determination of the β-Cell Mass in BioBreeding Diabetes-Prone Rats

The changes in β-cell mass (BCM) during the development and progression of diabetes could potentially be measured by radionuclide imaging using radiolabeled exendin. In this study, we investigated the potential of ¹¹¹In-diethylenetriaminepentaacetic acid-exendin-3 (¹¹¹In-exendin) in a rat model that closely mimics the development of type 1 diabetes (T1D) in humans: BioBreeding diabetes-prone (BBDP) rats. BBDP rats of 4-18 weeks of age were injected intravenously with ¹¹¹In-exendin, and single-photon emission computed tomography (SPECT) images were acquired. The accumulation of the radiotracer was measured as well as the BCM and grade of insulitis by histology. ¹¹¹In-exendin accumulated specifically in the islets, resulting in a linear correlation with the BCM (%) (Pearson r = 0.89, P < 0.0001, and r = 0.64 for SPECT). Insulitis did not have an influence on this correlation. These results indicate that ¹¹¹In-exendin is a promising tracer to determine the BCM during the development of T1D, irrespective of the degree of insulitis.

Paquinimod prevents development of diabetes in the non-obese diabetic (NOD) mouse

Quinoline-3-carboxamides (Q compounds) are immunomodulatory compounds that have shown efficacy both in autoimmune disease and cancer. We have in here investigated the impact of one such compound, paquinimod, on the development of diabetes in the NOD mouse model for type I diabetes (T1D). In cohorts of NOD mice treated with paquinimod between weeks 10 to 20 of age and followed up until 40 weeks of age, we observed dose-dependent reduction in incidence of disease as well as delayed onset of disease. Further, in contrast to untreated controls, the majority of NOD mice treated from 15 weeks of age did not develop diabetes at 30 weeks of age. Importantly, these mice displayed significantly less insulitis, which correlated with selectively reduced number of splenic macrophages and splenic Ly6Chi inflammatory monocytes at end point as compared to untreated controls. Collectively, these results demonstrate that paquinimod treatment can significantly inhibit progression of insulitis to T1D in the NOD mouse. We propose that the effect of paquinimod on disease progression may be related to the reduced number of these myeloid cell populations. Our finding also indicates that this compound could be a candidate for clinical development towards diabetes therapy in humans.

The Protective Effect of L-arginine in Cisplatin-induced Nephrotoxicity in Streptozotocin-induced Diabetic Rats

Background:

Cisplatin (CP) is accompanied with a nephrotoxicity. L-arginine (LA) plays an important role in the regulation of renal function. The present study was designed to investigate the protective role of LA supplementation in CP-induced nephrotoxicity in a diabetic rat's model.

Materials and Methods:

Sixteen adult female and male Wistar rats were used and they received a single dose of streptozotocin (STZ) (60 mg/kg i.p.). Diabetic female and male rats were arranged as groups 1–5 and groups 6–10, respectively. Groups 1 and 6 (LA groups) received LA alone. Groups 2 and 7 (CP groups) received CP alone. Groups 3 and 8 (CP + LA [PT] groups) received LA as prophylaxis and then treated with LA and CP. Groups 4 and 9 (CP + LA [T] groups) were treated with LA and CP simultaneously. Groups 5 and 10 (CP + LA [P] groups) received LA as prophylaxis and then treated with CP.

Results:

The serum creatinine (Cr) level of males in Groups 8 and 9 was significantly increased when compared with LA and CP (P < 0.05), whereas no differences were observed in Cr level in female groups. Blood urea nitrogen/Cr ratio and kidney weight were reduced in all CP-receiving male rats. Such observation was not seen in female rats. Different results related to weight loss were obtained between male and female animals. The kidney tissue damage score in CP + LA (PT) male group was significantly greater than CP group (P < 0.05).

Conclusion:

Our findings indicate that administration of LA in female and male rats has no protective effect on the severity of nephrotoxicity induced by CP in diabetic rats.

Antioxidant and antiapoptotic effects of sea cucumber and valsartan against doxorubicin-induced cardiotoxicity in rats: The role of low dose gamma irradiation

Doxorubicin (DOX) is a highly effective antineoplastic drug; however, the clinical use of DOX is limited by its dose dependent cardiotoxicity. This study was conducted to evaluate the cardioprotective effect of sea cucumber and valsartan against DOX-induced cardiotoxicity in rats. Also, the role of exposure to low dose γ radiation (LDR) on each of them was investigated, since LDR could suppress various reactive oxygen species-related diseases. Rats received DOX (2.5mg/kg, ip) in six equal injections over a period of 2weeks, sea cucumber (14.4mg/kg, p.o) and valsartan (30mg/kg, p.o) for 8 successive weeks. Exposure to LDR (0.5Gy) was performed one day prior to DOX. Results revealed that DOX administration elevated serum levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK-MB) and troponin-I as well as increased cardiac lipid peroxide content and myeloperoxidase (MPO) activity. Additionally, it increased cardiac expressions of iNOS and caspase-3, accompanied by reduction in cardiac total protein and glutathione (GSH) contents. Treatment with sea cucumber or valsartan improved the cardiotoxicity of DOX. Their adjuvant therapy with LDR offers an additional benefit to the cardioprotection of the therapeutic drugs. These results confirmed by histopathological examination. In conclusion, sea cucumber and valsartan alone or combined with LDR attenuated DOX-induced cardiotoxicity via their antioxidant and anti-apoptotic activities and thus might be useful in the treatment of human patients under doxorubicin chemotherapy.

Protective effect of telmisartan treatment against arsenic-induced testicular toxicity in rats

Oxidative/nitrosative stress, inflammation, and apoptosis play a crucial role in the pathogenesis of arsenic-induced testicular injury. Telmisartan, the angiotensin II-receptor antagonist, possesses antioxidant and anti-inflammatory activities. The protective effect of telmisartan against arsenic-induced testicular damage was investigated in rats. Testicular damage was induced by sodium arsenite (10 mg kg-1/day, p.o., for 2 consecutive days). Telmisartan (10 mg kg-1/day, i.p.) was given for 3 consecutive days, starting 1 day before sodium arsenite administration. Telmisartan significantly attenuated the arsenic-induced decrease in the levels of serum testosterone and testicular reduced glutathione, and significantly decreased the elevation of the levels of testicular malondialdehyde, nitric oxide, and arsenic levels, as well as myeloperoxidase activity resulting from sodium arsenite administration. Histopathological and immunohistochemical examination revealed that telmisartan markedly attenuated testicular tissue changes, and decreased the arsenic-induced expression of vascular endothelial growth factor, inducible nitric oxide synthase, tumor necrosis factor-α, cyclooxygenase-2, nuclear factor-κB, and caspase-3. Telmisartan, via its antioxidant and/or anti-inflammatory effects, may represent a potential candidate to protect against the deleterious effects of arsenic on testicular tissue.

The effect of angiotensin-converting enzyme inhibition on inflammatory and angiogenic factors in hypercholesterolemia

BACKGROUND

Renin-angiotensin system (RAS) can be activated during hyperlipidemia. Angiotensin II increases the migration of monocytes, cytokine levels, and gene expressions of VEGF and VCAM-1. With this in mind, the present work attempted to investigate the effect of angiotensin-converting enzyme (ACE) inhibition on VEGF, VCAM-1, and nitric oxide (NO) serum levels in hypercholesterolemic rats.

METHODS

Forty male Wistar rats were divided into 4 groups including normal diet+saline injection (control), hypercholesterol diet+saline injection, normal diet+captopril injection, and hypercholesterol diet+captopril injection. Before and after the beginning of the diet and after the treatment, the serum levels of cholesterol, triglycerides, LDL, HDL, and NO were measured. Finally, gene expressions of VCAM-1 and VEGF in the vascular cells from aorta were determined.

RESULTS

Hypercholesterolemic diet increased the serum levels of cholesterol, LDL (p<0.001), triglycerides (p<0.01) and decreased HDL (p<0.001). Captopril caused a reduction in the serum levels of cholesterol, LDL (p<0.001), and triglycerides (p<0.05) as well as an increase in HDL levels (p<0.01). Although the serum levels of NO decreased after hypercholesterolemic diet (p<0.001), no significant change was observed after the treatment. Increased gene expressions of VEGF (p<0.05) and VCAM-1 (p<0.01) in hypercholesterolemia were regressed in captopril treated rats (p<0.01 and p<0.05, respectively).

CONCLUSION

Captopril, an ACE inhibitor, improves hyperlipidemia and prevents from overexpression of genes for VEGF and VCAM-1, that are implicated in the inflammation and angiogenesis.

Tetramethylpyrazine Protects against Hydrogen Peroxide-Provoked Endothelial Dysfunction in Isolated Rat Aortic Rings: Implications for Antioxidant Therapy of Vascular Diseases

Background and Objectives. Oxidative stress can initiate endothelial dysfunction and atherosclerosis. This study evaluated whether tetramethylpyrazine (TMP), the predominant active ingredient in Rhizoma Ligustici Wallichii (chuanxiong), prevents endothelial dysfunction in a rat model of oxidative stress. Methods. Isolated rat aortic rings were pretreated with various drugs before the induction of endothelial dysfunction by hydrogen peroxide (H₂O₂). Changes in isometric tension were then measured in acetylcholine- (ACh-) relaxed rings. Endothelial nitric oxide synthase (eNOS) expression was evaluated in the rings by Western blotting, and superoxide anion (O₂^∙−) content was assessed in primary rat aortic endothelial cells by dihydroethidium- (DHE-) mediated fluorescence microscopy. Results. ACh-induced endothelium-dependent relaxation (EDR) was disrupted by H₂O₂ in endothelium-intact aortic rings. H₂O₂-impaired relaxation was ameliorated by acute pretreatment with low concentrations of TMP, as well as by pretreatment with catalase and the NADPH oxidase inhibitors, apocynin and diphenyleneiodonium (DPI). TMP, apocynin, and DPI also reduced O₂^∙− accumulation in endothelial cells,but TMP failed to alter eNOS expression in aortic rings incubated with H₂O₂. Conclusions. TMP safeguards against oxidative stress-induced endothelial dysfunction, suggesting that the agent might find therapeutic utility in the management of vascular diseases. However, TMP's role in inhibiting NADPH oxidase and its vascular-protective mechanism of action requires further investigation.

Protective effect of magnesium on renal function in STZ-induced diabetic rats

Background

Diabetic nephropathy is a serious complication of T1D (type one diabetes mellitus). Persistent hyperglycemia and subsequent hypomagnesemia is believed to develop kidney damage by activation of oxidative stress. We conducted this study to investigate the renoprotective effect of magnesium sulfate (MgSO₄) on renal histopathology and oxidative stress in diabetic rats.

Methods

The study included 70 male rats. The animals were divided into seven groups: control (CRL), control receiving MgSO₄ (CRL + Mg1 & CRL + Mg8), diabetic (DM1 & DM8) and diabetic receiving MgSO₄ (DM + Mg1 & DM + Mg8). Rats were given 20 mg/kg (i.p) Streptozocin (STZ) for 5 consecutive days in (MLD) multiple low doses to induce T1D. At day 10 treatment groups were received MgSO₄ (10 g/l) in drinking water, for 1 or 8 weeks. The blood glucose, BUN and creatinine levels were measured. Renal tissue levels of malondialdehyde (MDA) were measured by thiobarbituric acid (TBA) method to evaluate the oxidative stress. Renal histopathology was done using H & E staining method.

Results

Treatment with MgSO₄ significantly decreased the blood glucose in DM + Mg1 and DM + Mg8 groups as compared with DM1 and DM8. Magnesium treatment also decreased serum BUN and tissue level of MDA significantly in both short and long term treatment. The body weight loss and kidney weight to body weight ratio was improved by MgSO₄. Histological results showed there were no differences between DM and DM + Mg groups.

Conclusion

Our findings showed that diabetic nephropathy is associated with high blood glucose level and oxidative stress (significant increase in MDA level). The renal dysfunction and oxidative stress can be improved by magnesium sulfate administration. It is suggested that protection against development of diabetic nephropathy by MgSO₄ treatment involves changes in the blood glucose and oxidative stress.

The diabetic vasculature: physiological mechanisms of dysfunction and influence of aerobic exercise training in animal models

Diabetes mellitus (DM) is associated with a number of complications of which chronic vascular complications are undoubtedly the most complex and significant consequence. With a significant impact on health care, 50-80% of people with diabetes die of cardiovascular disease (including coronary artery disease, stroke, peripheral vascular disease and other vascular disease), making it the major cause of morbidity and mortality in diabetic patients. A healthy lifestyle is essential in the management of DM, especially the inclusion of aerobic exercise, which has been shown effective in reducing the deleterious effects in vasculature. Interest in exercise studies has increased significantly with promising results that demonstrate a future for investigation. Considering the importance of this emerging field, the aim of this mini-review is to summarize and integrate animal studies investigating physiological mechanisms of vascular dysfunction and remodeling in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) and how these are influenced by chronic aerobic exercise training.

The effects of unripe grape extract on systemic blood pressure, nitric oxide production, and response to angiotensin II administration

Background:

Hypertension is the most common disease in the world. In Iranian folk medicine, unripe grape juice has been used as antihypertention remedy, but no data is documented for this popular belief. This study was designed to determine the effect of unripe grape extract (UGE) on blood pressure and the response to angiotensin II in rat.

Materials and Methods:

Unripe grape was collected, air dried, and extracted and concentrated. Four groups of Wistar rats received single doses of 125, 250, and 500 mg/kg of UGE or saline, respectively. The direct blood pressure and the serum nitrite level were measured one hour post UGE administration. The animals also were subjected to the infusion of various angiotensin II concentrations (100, 300, and 1000 μg/kg/min), and blood pressure was determined.

Results:

Mean arterial, systolic, and diastolic pressures (MAP, SP, and DP) in all UGE treated groups were less than the control group, but only at the dose of 125 mg/kg (Group 1) they were significantly different (P < 0.05). The level of nitrite in groups 1-3 were significantly greater than the control group (P < 0.05). No significant differences were detected for the MAP, SP, and DP to different concentrations of angiotensin II among these groups.

Conclusion:

UGE potentially attenuate MAP, SP, and DP via vasodilatation induced by nitric oxide production.

Elevated circulating alpha-klotho by angiotensin II receptor blocker losartan is associated with reduction of albuminuria in type 2 diabetic patients

INTRODUCTION

The aging-suppression gene α-klotho is potentially reno-protective. Animal studies suggest that angiotensin II may be a negative regulator of α-klotho expression. Therefore, we hypothesize that renin-angiotensin system antagonism may increase α-klotho secretion in type 2 diabetes (T2DM).

SUBJECTS AND METHODS

In this post-hoc analysis of a randomized crossover study, 33 T2DM subjects with albuminuria received either 50 mg of losartan or 20 mg of quinapril (both 50% maximal dose) daily for 4 weeks with 4-week wash-out period in between.

RESULTS

Our data showed that losartan, but not quinapril, significantly increased circulating α-klotho level by an average of 23% (from 542 pg/ml to 668 pg/ml, p=0.001). Linear regression revealed that, besides different mode of treatment, increment in plasma α-klotho was associated with decrement in urine albumin/creatinine ratio (β=-0.263, p=0.029).

CONCLUSIONS

The angiotensin receptor blocker losartan increases circulating α-klotho in T2DM with albuminuria. The clinical significance of this rise in α-klotho associated with losartan intervention deserves further investigation.

Interaction between advanced glycation end products formation and vascular responses in femoral and coronary arteries from exercised diabetic rats

Background

The majority of studies have investigated the effect of exercise training (TR) on vascular responses in diabetic animals (DB), but none evaluated nitric oxide (NO) and advanced glycation end products (AGEs) formation associated with oxidant and antioxidant activities in femoral and coronary arteries from trained diabetic rats. Our hypothesis was that 8-week TR would alter AGEs levels in type 1 diabetic rats ameliorating vascular responsiveness.

Methodology/Principal Findings

Male Wistar rats were divided into control sedentary (C/SD), sedentary diabetic (SD/DB), and trained diabetic (TR/DB). DB was induced by streptozotocin (i.p.: 60 mg/kg). TR was performed for 60 min per day, 5 days/week, during 8 weeks. Concentration-response curves to acetylcholine (ACh), sodium nitroprusside (SNP), phenylephrine (PHE) and tromboxane analog (U46619) were obtained. The protein expressions of eNOS, receptor for AGEs (RAGE), Cu/Zn-SOD and Mn-SOD were analyzed. Tissues NO production and reactive oxygen species (ROS) generation were evaluated. Plasma nitrate/nitrite (NO_x⁻), superoxide dismutase (SOD), catalase (CAT), thiobarbituric acid reactive substances (TBARS) and N^ε-(carboxymethyl) lysine (CML, AGE biomarker). A rightward shift in the concentration-response curves to ACh was observed in femoral and coronary arteries from SD/DB that was accompanied by an increase in TBARS and CML levels. Decreased in the eNOS expression, tissues NO production and NO_x⁻ levels were associated with increased ROS generation. A positive interaction between the beneficial effect of TR on the relaxing responses to ACh and the reduction in TBARS and CML levels were observed without changing in antioxidant activities. The eNOS protein expression, tissues NO production and ROS generation were fully re-established in TR/DB, but plasma NO_x⁻ levels were partially restored.

Conclusion

Shear stress induced by TR fully restores the eNOS/NO pathway in both preparations from non-treated diabetic rats, however, a massive production of AGEs still affecting relaxing responses possibly involving other endothelium-dependent vasodilator agents, mainly in coronary artery.

Hesperidin prevents retinal and plasma abnormalities in streptozotocin-induced diabetic rats

Diabetic retinopathy is a complex disease that potentially involves increased production of advanced glycosylation end products (AGEs) and elevated aldose reductase (AR) activity, which are related with oxidative stress and inflammation. The aim of this study was to investigate the effects of hesperidin on retinal and plasma abnormalities in streptozotocin-induced diabetic rats. Hesperidin (100, 200 mg/kg daily) was given to diabetic rats for 12 weeks. The blood-retina breakdown (BRB) was determined after 2 weeks of treatment followed by the measurement of related physiological parameters with ELISA kits and immunohistochemistry staining at the end of the study. Elevated AR activity and blood glucose, increased retinal levels of vascular endothelial growth factor (VEGF), ICAM-1, TNF-&#945;, IL-1&#946; and AGEs as well as reduced retina thickness were observed in diabetic rats. Hesperidin treatment signi&#64257;cantly suppressed BRB breakdown and increased retina thickness, reduced blood glucose, AR activity and retinal TNF-&#945;, ICAM-1, VEGF, IL-1&#946; and AGEs levels. Furthermore, treatment with hesperidin signi&#64257;cantly reduced plasma malondialdehyde (MDA) levels and increased SOD activity in diabetic rats. These data demonstrated that hesperidin attenuates retina and plasma abnormalities via anti-angiogenic, anti-inflammatory and antioxidative effects, as well as the inhibitory effect on polyol pathway and AGEs accumulation.

Combined treatment with a dipeptidyl peptidase-IV inhibitor (sitagliptin) and an angiotensin II type 1 receptor blocker (losartan) promotes islet regeneration via enhanced differentiation of pancreatic progenitor cells

AIM

The existence of pancreatic progenitor cells (PPCs) with differentiation capacity in the adult pancreas has rendered that promotion of islet regeneration is feasible. The dipeptidyl peptidase-IV inhibitor sitagliptin and the angiotensin II type 1 receptor (AT(1) receptor) blocker losartan have a common target action in the pancreata. Thus, we evaluated the synergistic/additive effects of these two drugs on the differentiation of islet progenitors.

METHODS

The acute and chronic effects of sitagliptin and losartan, individually or in combination, on islet regeneration in vivo were investigated by using a streptozotocin-induced type 1 diabetes mouse model. Their effects were also examined on an in vitro PPCs model derived from human foetal pancreas.

RESULTS

A chronic combination treatment enhanced glucose tolerance in diabetic mice associated with an increased ratio of β cells to islet; an acute combination treatment resulted in a marked increase in the production of neurogenin 3 (NGN3(+)) cells in proximity to CK7(+) ductal cell and an increased presence of insulin(+) /CK7(+) cells. The in vitro study revealed that a combination treatment significantly enhanced mRNA expression of NGN3, NKX6.1 and PDX-1 during PPCs differentiation into human islet-like cell clusters (ICCs). Despite no apparent changes in insulin release, the combined treatment resulted in increasing production of peroxisome proliferator-activated receptor γ (PPARγ) during PPC differentiation.

CONCLUSIONS

These data indicate that combined sitagliptin-losartan treatment can improve islet function by promoting the differentiation of PPCs into ICCs, perhaps via a mechanism involving PPARγ production, and could thereby, contribute to islet regeneration.

Pre-treatment with curcumin enhances plasma concentrations of losartan and its metabolite EXP3174 in rats

The study was carried out in the Wistar rats to investigate the effect of curcumin pre-treatment on the pharmacokinetics of the hypertension-treating drug losartan and its metabolite EXP3174 following single oral administration. In the treatment group, rats were gavaged with losartan 10 mg/kg after repeat oral doses of curcumin (100 mg/kg, for 7 d), while rats in the control group were administrated only with the same dose losartan. The results showed that curcumin significantly increased the plasma concentrations of losartan and its metabolite EXP3174. The present study implicated the existence of herb-drug interaction between curcumin and losartan, and further evaluation of the possible interaction during curcumin administration needs to be considered.

Chronic activation of endogenous angiotensin-converting enzyme 2 protects diabetic rats from cardiovascular autonomic dysfunction

In this study, we evaluated whether the activation of endogenous angiotensin-converting enzyme 2 (ACE2) would improve the cardiovascular autonomic dysfunction of diabetic rats. Ten days after induction of type 1 diabetes (streptozotocin, 50 mg kg(-1) i.v.), the rats were treated orally with 1-[(2-dimethylamino)ethylamino]-4-(hydroxymethyl)-7-[(4-methylphenyl) sulfonyl oxy]-9H-xanthene-9-one (XNT), a newly discovered ACE2 activator (1 mg kg(-1) day(-1)), or saline (equivalent volume) for 30 days. Autonomic cardiovascular parameters were evaluated in conscious animals, and an isolated heart preparation was used to analyse cardiac function. Diabetes induced a significant decrease in the baroreflex bradycardia sensitivity, as well as in the chemoreflex chronotropic response and parasympathetic tone. The XNT treatment improved these parameters by ≈ 76% [0.82 ± 0.09 versus 1.44 ± 0.17 Ratio between changes in pulse interval and changes in mean arterial pressure (ΔPI/ΔmmHg)], ∼85% (-57 ± 9 versus -105 ± 10 beats min(-1)) and ≈ 205% (22 ± 2 versus 66 ± 12 beats min(-1)), respectively. Also, XNT administration enhanced the bradycardia induced by the chemoreflex activation by v 74% in non-diabetic animals (-98 ± 16 versus -170 ± 9 Δbeats min(-1)). No significant changes were observed in the mean arterial pressure, baroreflex tachycardia sensitivity, chemoreflex pressor response and sympathetic tone among any of the groups. Furthermore, chronic XNT treatment ameliorated the cardiac function of diabetic animals. However, the coronary vasoconstriction observed in diabetic rats was unchanged by ACE2 activation. These findings indicate that XNT protects against the autonomic and cardiac dysfunction induced by diabetes. Thus, our results provide evidence for the viability and effectiveness of oral administration of an ACE2 activator for the treatment of the cardiovascular autonomic dysfunction caused by diabetes.

A risk-analysis approach to the evaluation of analytical quality

BACKGROUND

Setting specifications for analytical quality is always difficult. The risk-management approach might be a way to do so. In this approach, the definition of the required analytical quality is based on the evaluation of patient risk. Risk derives from the probability of error and from the damage that such an error might cause.

METHODS

Eight Italian laboratories took part in this experiment. Measurements of glucose and total calcium were taken as examples. Analytical quality was evaluated using a specific ring trial with a frozen serum pool and by means of internal quality-control data. The total allowable error was defined according to biological variation specifications. The probability of error was extracted from the imprecision and comparative bias data of each laboratory. The damage caused by a wrong result was evaluated using the absolute probability judgment approach.

RESULTS

According to the iso-risk plots (standardized hyperboles on a graph where the x-axis represents damage and the y-axis represents probability) for glucose, all the laboratories were working with an analytical quality that guaranteed low risk for patients. On the contrary, for total calcium none of the laboratories exhibited sufficient quality to guarantee low risk for patients, the presence of bias being the most relevant problem.

CONCLUSIONS

The results seem to demonstrate the applicability of the risk approach to the analytical phase, indicating a new possible way to define analytical quality targets.

ACE2-angiotensin-(1-7)-Mas axis and oxidative stress in cardiovascular disease

The renin-angiotensin-aldosterone system (RAAS) is a pivotal regulator of physiological homeostasis and diseases of the cardiovascular system. Recently, new factors have been discovered, such as angiotensin-converting enzyme 2 (ACE2), angiotensin-(1-7) and Mas. This newly defined ACE2-angiotensin-(1-7)-Mas axis was shown to have a critical role in the vasculature and in the heart, exerting mainly protective effects. One important mechanism of the classic and the new RAAS regulate vascular function is through the regulation of redox signaling. Angiotensin II is a classic prooxidant peptide that increases superoxide production through the activation of NAD(P)H oxidases. This review summarizes the current knowledge about the ACE2-angiotensin-(1-7)-Mas axis and redox signaling in the context of cardiovascular regulation and disease. By interacting with its receptor Mas, angiotensin-(1-7) induces the release of nitric oxide from endothelial cells and thereby counteracts the effects of angiotensin II. ACE2 converts angiotensin II to angiotensin-(1-7) and, thus, is a pivotal regulator of the local effects of the RAAS on the vessel wall. Taken together, the ACE2-angiotensin-(1-7)-Mas axis emerges as a novel therapeutic target in the context of cardiovascular and metabolic diseases.