Chiranthodendron pentadactylon Larreat (Sterculiaceae), a Potential Nephroprotector against Oxidative Damage Provoked by STZ-Induced Hyperglycemia in Rats

BACKGROUND

Chiranthodendron pentadactylon, known in Mexico as the "tree of the little hands", flower's infusion is used to treat kidney failure associated with diseases such as diabetes. The aim of this work is to evaluate the antioxidant effect of the methanolic extract of its flowers on oxidative damage in kidneys caused by streptozotocin in rats.

METHODS

The extract phytochemical profile was performed with HPLC. Antioxidant potential in vitro was determined with DPPH and total phenolic tests; antioxidant evaluation in vivo was performed in diabetic rats administered daily via the intragastric route (100 and 200 mg/kg) for 6 weeks; serum glucose/creatinine, food/water consumption, and urinary volume were measured. Relative weight, protein/DNA ratios and oxidative stress were measured in renal tissue.

RESULTS

The extract showed 20.53% of total phenolic content and IC50 of 18.05 µg/mL in DPPH, and this was associated with ferulic acid, phloretin and α-amyrin. Both doses showed a moderate decrease in the protein/DNA ratio in renal tissue, and the same behavior was observed for total urinary protein loss and serum creatinine, while the best antioxidant effect was exerted by a lower dose, which increased catalase activity and decreased lipid peroxidation in the kidneys.

CONCLUSIONS

Results demonstrated that C. pentadactylon methanolic flower's extract improves renal function through antioxidant mechanisms during experimental diabetes.

Protective effect of the tunneling nanotube-TNFAIP2/M-sec system on podocyte autophagy in diabetic nephropathy

Podocyte injury leading to albuminuria is a characteristic feature of diabetic nephropathy (DN). Hyperglycemia and advanced glycation end products (AGEs) are major determinants of DN. However, the underlying mechanisms of podocyte injury remain poorly understood. The cytosolic protein TNFAIP2/M-Sec is required for tunneling nanotubes (TNTs) formation, which are membrane channels that transiently connect cells, allowing organelle transfer. Podocytes express TNFAIP2 and form TNTs, but the potential relevance of the TNFAIP2-TNT system in DN is unknown. We studied TNFAIP2 expression in both human and experimental DN and the renal effect of tnfaip2 deletion in streptozotocin-induced DN. Moreover, we explored the role of the TNFAIP2-TNT system in podocytes exposed to diabetes-related insults. TNFAIP2 was overexpressed by podocytes in both human and experimental DN and exposre of podocytes to high glucose and AGEs induced the TNFAIP2-TNT system. In diabetic mice, tnfaip2 deletion exacerbated albuminuria, renal function loss, podocyte injury, and mesangial expansion. Moreover, blockade of the autophagic flux due to lysosomal dysfunction was observed in diabetes-injured podocytes both in vitro and in vivo and exacerbated by tnfaip2 deletion. TNTs allowed autophagosome and lysosome exchange between podocytes, thereby ameliorating AGE-induced lysosomal dysfunction and apoptosis. This protective effect was abolished by tnfaip2 deletion, TNT inhibition, and donor cell lysosome damage. By contrast, Tnfaip2 overexpression enhanced TNT-mediated transfer and prevented AGE-induced autophagy and lysosome dysfunction and apoptosis. In conclusion, TNFAIP2 plays an important protective role in podocytes in the context of DN by allowing TNT-mediated autophagosome and lysosome exchange and may represent a novel druggable target.Abbreviations: AGEs: advanced glycation end products; AKT1: AKT serine/threonine kinase 1; AO: acridine orange; ALs: autolysosomes; APs: autophagosomes; BM: bone marrow; BSA: bovine serum albumin; CTSD: cathepsin D; DIC: differential interference contrast; DN: diabetic nephropathy; FSGS: focal segmental glomerulosclerosis; HG: high glucose; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; LMP: lysosomal membrane permeabilization; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PI3K: phosphoinositide 3-kinase; STZ: streptozotocin; TNF: tumor necrosis factor; TNFAIP2: tumor necrosis factor, alpha-induced protein 2; TNTs: tunneling nanotubes; WT: wild type.

Multimodal Comparison of Diabetic Neuropathy in Aged Streptozotocin-Treated Sprague-Dawley and Zucker Diabetic Fatty Rats

The development and progression of diabetic polyneuropathy (DPN) are due to multiple mechanisms. The creation of reliable animal models of DPN has been challenging and this issue has not yet been solved. However, despite some recognized differences from humans, most of the current knowledge on the pathogenesis of DPN relies on results achieved using rodent animal models. The simplest experimental DPN model reproduces type 1 diabetes, induced by massive chemical destruction of pancreatic beta cells with streptozotocin (STZ). Spontaneous/transgenic models of diabetes are less frequently used, mostly because they are less predictable in clinical course, more expensive, and require a variable time to achieve homogeneous metabolic conditions. Among them, Zucker diabetic fatty (ZDF) rats represent a typical type 2 diabetes model. Both STZ-induced and ZDF rats have been extensively used, but only very few studies have compared the long-term similarities and differences existing between these two models. Moreover, inconsistencies have been reported regarding several aspects of short-term in vivo studies using these models. In this study, we compared the long-term course of DPN in STZ-treated Sprague-Dawley and ZDF rats with a multimodal set of readout measures.

The Effect of Two Different Doses of Astaxanthin on Alveolar Bone Loss in an Experimental Model of Periodontitis in Diabetic Rats

This study evaluated the effects of astaxanthin (ASX) on alveolar bone loss, receptor activator of nuclear factor-κB ligand (RANKL), and osteoprotegerin (OPG) activity in ligature-induced periodontitis in diabetic rats. Diabetes mellitus (DM) was induced with 50 mg/kg intraperitoneal streptozotocin in 40 male Wistar rats. The Wistar rats were divided into six experimental groups: non-ligated (NL; n = 6); ligature only (L; n = 6); DM only (D; n = 6); DM + ligature (DP; n = 6); DM + ligature + 1 mg/kg/day ASX (ASX 1 group; n = 8); and DM + ligature + astaxanthin 5 mg/kg/day ASX (ASX 5 group; n = 8). Silk ligatures were placed along the gingival margin of the left mandibular first molar tooth. The study duration was 11 days, after which the animals were euthanised. Changes in alveolar bone levels were clinically measured, and RANKL and OPG activities were immunohistochemically examined. Alveolar bone loss was the most significant in the DP group (p < 0.05). Decreased alveolar bone loss was observed in the ASX 5 group (p < 0.05). Although RANKL activity was highest in the DP group, it was observed at lower levels in the groups to which ASX was administered. OPG activity did not differ between groups (p > 0.05). The results of this study suggested that 1 and 5 mg/kg ASX administration reduced RANKL activity and alveolar bone loss in rats with experimentally induced periodontitis.

Antidiabetic efficacy of a honey-royal jelly mixture: Biochemical study in rats

OBJECTIVES

The current tools for the management of diabetes mellitus (DM) do not prevent its development or complications, so investigations into promising new treatments, for example, honey-royal jelly (H-RJ) mixtures, are needed. This study was conducted to evaluate the effect of royal jelly on DM by measuring the biochemical parameters (fasting blood glucose and glycated hemoglobin [HbA1c]) accompanying streptozotocin (i.p. 75 mg/kg once)-induced type 1 DM (T1DM) in rats. Other objectives were to evaluate the effects of H-RJ on lipid parameters.

METHODS

Ten healthy control male Sprague-Dawley rats (120-150 g) were compared to untreated T1DM (n = 10), metformin-treated T1DM (n = 10), and H-RJ-treated T1DM rats (n = 10) on plasma and whole-blood glycemic control indices (fasting blood glucose, HbA1c %, insulin, and insulin resistance) and plasma lipid profile (triglycerides [TGs] and total, low-density lipoprotein -, high-density lipoprotein -, and very low-density lipoprotein [VLDL]-cholesterol). Diabetes was induced by a single intraperitoneal injection of streptozotocin (SZT) at 75 mg/kg body weight (BW). The T1DM-H-RJ rat group received daily RJ (100 mg/kg BW). Parametric data are presented as mean ± SD and were analyzed for comparison using one-way ANOVA in SPSS software.

RESULTS

H-RJ normalized glycemic control indices, but its effect on lipid parameters was variable. H-RJ and metformin had comparable effects. The H-RJ treatment caused a significant reduction in plasma VLDL-C content in comparison to the control treatment and metformin. The limitation of this study is that it was restricted to T1DM and did not involve type 2 DM. In addition, the study was limited to male Sprague-Dawley rats, with no females.

CONCLUSION

The H-RJ mixture is a promising antidiabetic alternative medicine. It effectively reduces VLDL-C and TG in diabetic rats.

Systemic AAV10.COMP-Ang1 rescues renal glomeruli and pancreatic islets in type 2 diabetic mice

INTRODUCTION

Diabetic hyperglycemia causes progressive and generalized damage to the microvasculature. In renal glomeruli, this results in the loss of podocytes with consequent loss of constitutive angiopoietin-1 (Ang1) signaling, which is required for stability of the glomerular endothelium. Repeated tail vein injection of adenovirus expressing COMP-Ang1 (a stable bioengineered form of Ang1) was previously reported to improve diabetic glomerular damage despite the liver and lungs being primary targets of adenoviral infection. We thus hypothesized that localizing delivery of sustained COMP-Ang1 to the kidney could increase its therapeutic efficacy and safety for the treatment of diabetes.

RESEARCH DESIGN AND METHODS

Using AAVrh10 adeno-associated viral capsid with enhanced kidney tropism, we treated 10-week-old uninephrectomized db/db mice (a model of type 2 diabetes) with a single dose of AAVrh10.COMP-Ang1 delivered via the intracarotid artery, compared with untreated diabetic db/db control and non-diabetic db/m mice.

RESULTS

Surprisingly, both glomerular and pancreatic capillaries expressed COMP-Ang1, compensating for diabetes-induced loss of tissue Ang1. Importantly, treatment with AAVrh10.COMP-Ang1 yielded a significant reduction of glycemia (blood glucose, 241±193 mg/dL vs 576±31 mg/dL; glycosylated hemoglobin, 7.2±1.5% vs 11.3±1.3%) and slowed the progression of albuminuria and glomerulosclerosis in db/db mice by 70% and 61%, respectively, compared with untreated diabetic db/db mice. Furthermore, COMP-Ang1 ameliorated diabetes-induced increases of NF-kBp65, nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase-2 (Nox2), p47phox and productions of myeloperoxidase, the inflammatory markers in both renal and pancreatic tissues, and improved beta-cell density in pancreatic islets.

CONCLUSIONS

These results highlight the potential of localized Ang1 therapy for treatment of diabetic visceropathies and provide a mechanistic explanation for reported improvements in glucose control via Ang1/Tie2 signaling in the pancreas.

SGLT2 inhibition to address the unmet needs in diabetic nephropathy

Current treatment of diabetic nephropathy is effective; however, substantial gaps in care still remain and new therapies are urgently needed to reduce the global burden of the complication. Desirable properties of an "ideal" new drug should include primary prevention of microalbuminuria, additive/synergistic anti-proteinuric effect in combination therapy with renin angiotensin system blockers, reduction of chronic kidney disease progression to lower the risk of end-stage renal disease, and cardiovascular protection. Growing evidence suggests that sodium-glucose cotransporter 2 inhibitors (SGLT2i) may fulfil many of these criteria and represent novel tools to cover the unmet needs in diabetic nephropathy care. However, the underlying mechanisms of SGLT2i renal benefits are still poorly understood and promising results from cardiovascular outcome trials with SGLT2i need confirmation in dedicated renal outcome trials.

New Insights into the Mechanisms of Action of Topical Administration of GLP-1 in an Experimental Model of Diabetic Retinopathy

The main goals of this work were to assess whether the topical administration of glucagon-like peptide-1 (GLP-1) could revert the impairment of the neurovascular unit induced by long-term diabetes (24 weeks) in diabetic mice and to look into the underlying mechanisms. For that reason, db/db mice were treated with eye drops of GLP-1 or vehicle for 3 weeks. Moreover, db/+ mice were used as control. Studies performed in vivo included electroretinogramand the assessment of vascular leakage by using Evans Blue. NF-κB, GFAP and Ki67 proteins were analyzed by immunofluorescence (IF). Additionally, caspase 9, AMPK, IKBα, NF-κB, AKT, GSK3, β-catenin, Bcl-xl, and VEGF were analyzed by WB. Finally, VEGF, IL-1β, IL-6, TNF-α, IL-18, and NLRP3 were studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. We found that topical administration of GLP-1 reverted reactive gliosis and albumin extravasation, and protected against apoptosis and retinal dysfunction. Regarding the involved mechanisms, GLP-1 exerted an anti-inflammatory action by decreasing NF-κB, inflammosome, and pro-inflammatory factors. In addition, it also decreased VEGF expression. Furthermore, GLP-1 promoted cell survival by increasing the anti-apoptotic protein Bcl-xl and the signaling pathway Akt/GSK3b/β-catenin. Finally, Ki67 results revealed that GLP-1 treatment could induce neurogenesis. In conclusion, the topical administration of GLP-1 reverts the impairment of the neurovascular unit by modulating essential pathways involved in the development of diabetic retinopathy (DR). These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of GLP-1 in early stages of DR.

Anti-inflammatory and insulin secretory activity in experimental type-2 diabetic rats treated orally with magnesium

Background

Diabetes mellitus causes low-grade chronic inflammation which leads to the development of long-term complications. Oral magnesium (Mg) intake amongst other effects was reported to reduce the levels of inflammatory markers. This study investigated the anti-inflammatory and insulin secretory activities in experimental type-2 diabetic rats (n=32) orally treated with Mg.

Methods

Experimental type-2 diabetic rats were induced with high fat diet and alloxan (50 mg/kg, single i.p.) for over 10 weeks prior to the experimental procedures. Male Wistar rats were divided into 4 equal groups: control, untreated experimental diabetics, and experimental diabetics treated orally with either metformin (Met) (250 mg/kg), or Mg (250 mg/kg), respectively, for 14 days. The blood glucose (BG) levels were monitored before experimental induction of diabetes and thereafter on days 1, 7, 10, and 14, respectively. Serum insulin, C-reactive protein (CRP), interleukin-6 (IL-6), and lipid profile were assessed using laboratory kits while pancreatic beta cell function (BCF) and insulin resistance were estimated using homeostasis model assessment equations.

Results

Significant increase in the BG level was observed in all experimental diabetic groups on day 1 compared to controls. On day 14, BG, BCF, triglyceride, cholesterol, and low-density lipoprotein levels were increased while the high-density lipoprotein level was reduced in untreated diabetics compared to other groups. Insulin and insulin resistance were increased in all groups compared to control. Serum insulin and IL-6 were reduced while CRP was elevated in diabetic treated groups (Met and Mg) compared to untreated diabetics.

Conclusions

This study shows a hypoglycemic, lipid regulatory, insulin stimulatory, and anti-inflammatory effect of oral Mg treatment in experimental type-2 diabetic rats.

Effects of DAPAgliflozin on CARDiac substrate uptake, myocardial efficiency, and myocardial contractile work in type 2 diabetes patients-a description of the DAPACARD study

BACKGROUND

Diabetes increases the risk for cardiovascular (CV) events. It has recently been shown that the use of sodium-glucose cotransporter 2 (SGLT2) inhibitors leads to a reduction in CV outcomes in patients with type 2 diabetes mellitus (T2DM), including mortality and heart failure hospitalization. The exact mechanisms of how SGLT2 inhibitors lead to this CV risk reduction remain incompletely understood. The study of DAPAgliflozin on CARDiac substrate uptake, myocardial efficiency and myocardial contractile work in type 2 diabetes patients (DAPACARD) (NCT03387683) explores the possible effects of dapagliflozin, an SGLT2 inhibitor, on cardiac work, metabolism, and biomarker levels.

METHODS

DAPACARD is an international, randomized, double-blind trial that aims to examine the effects of dapagliflozin versus matching placebo in 52 patients with T2DM that are on stable metformin therapy prior to and during the 6 weeks of treatment. The primary efficacy endpoint is change in global longitudinal strain of the left ventricle (GLSLV) measured with magnetic resonance imaging (MRI) between baseline (pre-treatment) and end of study (on-treatment). The secondary endpoint is the corresponding change in myocardial efficiency measured as external left ventricular work divided by total left ventricular work, which is estimated using [11C]-acetate clearance using positron emission tomography (PET).

CONCLUSION

The DAPACARD study is an extensive investigation of cardiac function and metabolism, by advanced imaging with PET and MRI, as well as biomarkers, performed in order to further explore how the SGLT2 inhibitor dapagliflozin could influence cardiovascular outcomes in patients with T2DM.

Methylene blue alleviates endothelial dysfunction and reduces oxidative stress in aortas from diabetic rats

Endothelial dysfunction and the related increase in reactive oxygen species (ROS) production are important events in the pathophysiology of diabetes mellitus (DM). Methylene blue (MB) has been systematically investigated for its protective effects against refractory hypotension and mitochondrial dysfunction. We have previously demonstrated that MB improved mitochondrial respiration and partially decreased oxidative stress in diabetic rat hearts. The present study was aimed to investigate whether MB modulates vascular function and ROS production in thoracic aortic rings isolated from rats with streptozotocin-induced DM (after 4 weeks of hyperglycemia). The effects of MB (0.1 μM, 30 min ex vivo incubation) on vascular reactivity in organ chamber (phenylephrine-induced contraction, acetylcholine-induced relaxation) and H₂O₂ production (assessed by ferrous iron xylenol orange oxidation assay) were investigated in vascular preparations with intact endothelium and after denudation. DM elicited a significant alteration of vascular function: increased contractility to phenylephrine, attenuation of acetylcholine-dependent relaxation, and augmented H₂O₂ generation. Ex vivo incubation with MB partially reversed all these changes (by approximately 70%) in vascular segments with intact endothelial layer (but not in denuded vessels). In conclusion, MB might be useful in alleviating endothelial dysfunction and mitigating endothelial oxidative stress, observations that clearly require further investigation in the setting of cardiometabolic disease.

Effects of CO2 water-bath treatment on blood flow and angiogenesis in ischemic hind limb of diabetic rat

The effects of CO₂ water-bath therapy on the hind limb of diabetic animals with or without peripheral ischemia were examined. Diabetes was induced in rats by administering streptozotocin (65 mg·kg^-1), and the animals were then divided into 3 groups. After 4 weeks, peripheral ischemia was induced by ligation of the femoral artery for 2 weeks in 2 groups (diabetic ischemic) of diabetic rats, whereas the femoral artery was not occluded in the third group (diabetic). All these animals were subjected to water-bath therapy (with or without CO₂ mixing; 20 min·day^-1 for 5 days·week^-1) for a period of 4 weeks. Both peak and mean flows, unlike minimal flow, in diabetic ischemic limbs were increased about a twofold by CO₂ water-bath treatment. Morphological examination of hind limb tissue sections revealed about a twofold increase in the small artery count in diabetic ischemic animals upon CO₂ water-bath treatment. These results indicate that CO₂ water-bath therapy augments the blood flow and development of angiogenesis in the skeletal muscle of diabetic ischemic animals and thus may be of some benefit for the treatment of peripheral arterial disease in diabetes.

Mild diabetes: long-term effects on gastric motility evaluated in rats

Moderate hyperglycaemic levels seem to be related to abnormal gastric motility in diabetes mellitus. However, experimental models designed to evaluate the relationship between motility and diabetes over time are not yet well established. Our objective was to investigate the long-term effects of mild diabetes on gastric motility in rats. Newborn male rats received streptozotocin (mild diabetes groups - MD) or vehicle (control groups - C), and both groups were evaluated after 3 (C3 and MD3) and 6 months (C6 and MD6) postinduction. Mild diabetic animals (MD3 and MD6) showed moderately elevated blood glucose and decreased insulin levels compared with control (C3 and C6). Insulin secretion was enhanced in MD6 compared with MD3, most likely due to partial β-cell regeneration indicated by HOMA-β. In HOMA-IR, it was noticed that MD6 animals had impaired insulin response compared with MD3. Gastric emptying was faster, amplitude of contraction was stronger in MD6 compared with MD3, and in both groups, the differences were significant when compared with control animals. A significant abnormal rhythmic index was calculated for the mild diabetic groups, despite unchanged mean frequency of contraction. In conclusion, despite increased insulin levels over time, constant levels of moderate hyperglycaemia are also related to abnormal gastric motility and impairment of gastric function.

Effect of apelin-13 on erythrocyte deformability during ischaemia-reperfusion injury of heart in diabetic rats

OBJECTIVES

Erythrocyte deformability and plasma viscosity are of crucial importance for the perfusion of tissues and organs. The aim of this study was to evaluate the effect of apelin-13 on erythrocyte deformability during IR heart injury in diabetic rats.

METHODS

Eighteen Wistar Albino rats were included in the study after streptozotocin (55 mg/kg) treatment for four weeks of observation for diabetes existence. The animals were randomly assigned to one of five experimental groups. In the Group C, DC (sham-control group) and DCA (sham-control group-apelin-13), the coronary artery was not occluded or re-perfused. In the Group DIR, a branch of the left coronary artery was occluded for 30 minutes followed by 90 minutes of re-perfusion to produce IR. In the Group DIRA, a branch of the left coronary artery was occluded for 30 minutes followed by 90 minutes of re-perfusion to produce IR, and apelin-13 was administrated via 10 µg.kg-1 IP route 30 minutes before ligating the left coronary artery.Deformability measurements were performed in erythrocyte suspensions containing Htc 5% in a PBS buffer.

RESULTS

The deformability index was significantly increased in diabetic rats; however, it was similar in Group DC, DCA and DIRA. It was significantly increased in the Group DIR when compared to the Group C, DIRA, DCA and DC. The relative resistance was increased in IR models.

CONCLUSION

Erythrocyte deformability was decreased in rats having diabetes and IR injury. This injury might lead to further problems in microcirculation. It was shown that apeline-13 may be useful in enhancing the adverse effects of this type of injury (Fig. 1, Ref. 35).

The Effect of Thymoquinone on Nuclear Factor Kappa B Levels and Oxidative DNA Damage on Experimental Diabetic Rats

Background:

Thymoquinone (TQ), the basic bioactive phytochemical constituent of seed oil of Nigella sativa, is one of these herbal drugs known for antidiabetic effects. This study was carried out to assess the effects of the possible role of TQ on nuclear factor kappa B (NF-κB) and oxidative DNA damage levels in experimental diabetic rats.

Materials and Methods:

Twenty-eight male Wistar Albino rats (200–250 g) were used as experimental subjects. The rats were divided into four groups, including the control, control supplemented with TQ (CT), diabetic (D), and diabetic supplemented with TQ (DT), each containing seven rats. The D and the DT groups were treated with 45 mg/kg streptozotocin (STZ) (intraperitoneal). TQ was administered 30 mg/kg/day for 21 days by oral gavage in the DT and the T groups.

Results:

It was determined that glucose, glycosylated hemoglobin (HbA1c) levels and alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transpeptidase activities were decreased significantly and approached the control group in the DT group after TQ supplement (P < 0.05). Urea levels were the lowest in CT (P < 0.05). Oxidative DNA damage (8 hydroxy-2-deoxyguanosine) was increased in both of the diabetic groups (D and DT). The NF-κB levels were the highest in Group D (P < 0.05).

Conclusion:

It was observed that increased glucose and HbA1c levels and the indicators of liver and kidney damages were decreased significantly after TQ supplementation. Oxidative DNA damage and NF-κB levels were increased in the diabetic group, and TQ administration caused a statistically insignificant reduction.

SUMMARY

In this study, the effects of thymoquinone (TQ), the basic bioactive phytochemical constituent of seed oil of Nigella sativa, on nuclear factor kappa B (NF-κB), oxidative DNA damage levels, and, some biochemical parameters was invesigated. It was observed that some biochemical parameters (glucose, glycosylated hemoglobin (HbA1c), ALT, AST, GGT) were close to the control group after TQ treatment in diabetic group. Oxidative DNA damage (8 hydroxy 2 deoxyguanosine) and NF-κB were highest levels and TQ implementation caused statistically insignificant decrease, in the diabetic group.

Abbreviations used: 8-OHdG: 8 hydroxi-2-deoxiguanosin; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; GGT: Gamma-glutamyl transpeptidase; HbA1c: Glycosylated hemoglobin; NF-κB: Nuclear factor kappa protein; STZ: Streptozotocin; TQ: Thymoquinone.

Changes on the Pancreas in Experimental Diabetes and the Effect of Lycopene on These Changes: Pdx-1, Ngn-3, and Nestin Expressions

The aim of the present study was to investigate changes occurring in the number of beta cells, as well as the expressions of Ngn-3, nestin and Pdx-1 of pancreatic progenitor cells in the pancreas of experimentally-induced adult diabetic rats and to determine the effect of orally-administered lycopene on these changes. Following the administration of 50 mg/kg streptozotocin to rats, four groups of animals were established: control + corn oil, control + lycopene, diabetic + corn oil and diabetic + lycopene. The animals in the control + lycopene and diabetic + lycopene groups received 4 mg/kg lycopene for a period of four weeks. The expressions of insulin, Ngn-3, nestin, and Pdx-1 were determined through immunohistochemistry in sections taken from pancreas tissue samples at the end of the experiment. The number of insulin-positive cells was found to be significantly low in the diabetic groups compared to the control groups. In addition, the presence of Ngn-3 and nestin-positive cells within the exocrine pancreas surrounding the islands was noted in the diabetic groups. Lycopene, in general did not have any effect in any of the parameters analyzed in the present study. It is suggested that these cells would function as stem cells to replace the lost beta-cell population. It is also suggested that it is possible to demonstrate the antioxidant effects of lycopene in the pancreas of diabetic rats by increasing the dose and duration of lycopene administration. Anat Rec, 300:2200-2207, 2017. © 2017 Wiley Periodicals, Inc.

Changes in the Pancreas in Experimental Diabetes and the Effect of Lycopene on These Changes: Proliferating, Apoptotic, and Estrogen Receptor α Positive Cells

This study aimed to investigate the changes occurring in estrogen receptor (ER) α-positive cells, proliferating cells, apoptotic cells and malondialdehyde (MDA) expression in the pancreas of experimentally induced adult diabetic rats and to determine the effect of orally administered lycopene on these changes. Experimental diabetes was induced using a single dose of 50 mg/kg streptozotocin (STZ). Following the administration of STZ, four groups of animals were established: Control + corn oil, control + lycopene, diabetic + corn oil and diabetic + lycopene. The expressions of ER α, Ki-67, and MDA were determined through immunohistochemistry in sections taken from pancreas tissue samples at the end of the experiment. Apoptotic cells were determined through the TUNEL method. In the diabetic groups, the densities of ER α expression in islets and ER α-positive cells in exocrine parts increased. Whereas the number of proliferating Ki-67 positive cells was higher in the diabetic groups, no significant difference was observed in terms of apoptotic cell number between the control and diabetic groups. Lycopene in general did not have any effect on any of the parameters analyzed in the study. The presence of ER α-positive cells around the islets was demonstrated for the first time in diabetic groups. Based on these observations, demonstrating the antioxidant effects of lycopene in the pancreas of diabetic rats may be possible by increasing the dose and/or the duration of lycopene. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:2000-2007, 2017. © 2017 Wiley Periodicals, Inc.

Glucagon secretion from pancreatic α-cells

Type 2 diabetes involves a ménage à trois of impaired glucose regulation of pancreatic hormone release: in addition to impaired glucose-induced insulin secretion, the release of the hyperglycaemic hormone glucagon becomes dysregulated; these last-mentioned defects exacerbate the metabolic consequences of hypoinsulinaemia and are compounded further by hypersecretion of somatostatin (which inhibits both insulin and glucagon secretion). Glucagon secretion has been proposed to be regulated by either intrinsic or paracrine mechanisms, but their relative significance and the conditions under which they operate are debated. Importantly, the paracrine and intrinsic modes of regulation are not mutually exclusive; they could operate in parallel to control glucagon secretion. Here we have applied mathematical modelling of α-cell electrical activity as a novel means of dissecting the processes that underlie metabolic regulation of glucagon secretion. Our analyses indicate that basal hypersecretion of somatostatin and/or increased activity of somatostatin receptors may explain the loss of adequate counter-regulation under hypoglycaemic conditions, as well as the physiologically inappropriate stimulation of glucagon secretion during hyperglycaemia seen in diabetic patients. We therefore advocate studying the interaction of the paracrine and intrinsic mechanisms; unifying these processes may give a more complete picture of the regulation of glucagon secretion from α-cells than studying the individual parts.

Key pathways in renal disease progression of experimental diabetes

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes mellitus and the leading cause of end-stage kidney disease. Both diabetes and chronic kidney disease are risk factors for cardiovascular disease, and diabetic patients with renal involvement are three times more likely to eventually die of cardiovascular disease than diabetic patients without signs of renal failure. In type 2 diabetes, microalbuminuria is a marker of renal dysfunction and a crucial predictor of cardiovascular disease. Inhibitors of angiotensin II synthesis/activity, while preventing micro- or macroalbuminuria, also reduced cardiovascular events in diabetic patients. However, the effectiveness of renin angiotensin system blocking agents depends on the time when treatment is started, and imperfect renoprotection may occur if therapy begins at an advanced disease phase. This raises the need to identify novel multidrug approaches that simultaneously inhibit additional pathways other than angiotensin II for those diabetic patients who remain at high risk of both poor renal and cardiovascular outcomes. Studies in animal models of diabetes have contributed to defining relevant cellular mechanisms underlying the pathogenesis of DN that could represent possible targets for therapies. The pathogenesis of DN is multifactorial, involving a complex series of molecular processes. In this review, we report evidence obtained in experimental models of DN on some specific processes and pathways implicated in DN that may be crucial for managing this disease.

Mapping time-course mitochondrial adaptations in the kidney in experimental diabetes. Clin Sci (Lond). 2016;130:711-720. [PMID: 26831938 DOI: 10.1042/cs20150838]

Oxidative phosphorylation (OXPHOS) drives ATP production by mitochondria, which are dynamic organelles, constantly fusing and dividing to maintain kidney homoeostasis. In diabetic kidney disease (DKD), mitochondria appear dysfunctional, but the temporal development of diabetes-induced adaptations in mitochondrial structure and bioenergetics have not been previously documented. In the present study, we map the changes in mitochondrial dynamics and function in rat kidney mitochondria at 4, 8, 16 and 32 weeks of diabetes. Our data reveal that changes in mitochondrial bioenergetics and dynamics precede the development of albuminuria and renal histological changes. Specifically, in early diabetes (4 weeks), a decrease in ATP content and mitochondrial fragmentation within proximal tubule epithelial cells (PTECs) of diabetic kidneys were clearly apparent, but no changes in urinary albumin excretion or glomerular morphology were evident at this time. By 8 weeks of diabetes, there was increased capacity for mitochondrial permeability transition (mPT) by pore opening, which persisted over time and correlated with mitochondrial hydrogen peroxide (H2O2) generation and glomerular damage. Late in diabetes, by week 16, tubular damage was evident with increased urinary kidney injury molecule-1 (KIM-1) excretion, where an increase in the Complex I-linked oxygen consumption rate (OCR), in the context of a decrease in kidney ATP, indicated mitochondrial uncoupling. Taken together, these data show that changes in mitochondrial bioenergetics and dynamics may precede the development of the renal lesion in diabetes, and this supports the hypothesis that mitochondrial dysfunction is a primary cause of DKD.

Changes in glucose transporter expression and nitric oxide production are associated with liver injury in diabetes

In diabetes mellitus (DM), both hyperglycaemia and hyperlipidaemia can initiate accumulation of fat in the liver, which might be further mediated by inducible nitric oxide synthase. We have studied changes in GLUT1, nitric oxide (NO(·)) concentration and liver damage in two rat DM models. STZ model was induced by strepozotocin 50 mg/kg. HS model was induced by high-fat diet and 30 mg/kg streptozotocin. GLUT1 expression was studied by means of real-time RT-PCR and immunohistochemistry. Production of NO(·) was monitored by means of erythrocyte sedimentation rate spectroscopy of Fe-DETC-NO complex. Liver damage was assessed using histological activity index (HAI). NO(·) concentration was increased in the liver of STZ rats, but it did not change in HS rats (control 36.8 ± 10.3; STZ 142.1 ± 31.1; HS 35.4 ± 9.8 ng/g). Liver HAI was higher in STZ group, 8.6 ± 0.17 versus HS 4.7 ± 0.31, p < 0.05. GLUT1 protein expression was elevated only in STZ group, 16 ± 3 cells/mm(2) versus Control 5 ± 2 cells/mm(2), p = 0.007. Hyperglycaemia sooner causes severe liver damage in rat models of DM, compared with hyperlipidaemia, and is associated with increased NO(·) production. GLUT1 transporter expression might be involved in toxic effects of glucose in the liver. We have obtained novel data about association of GLUT1 expression and NO(·) metabolism in the pathogenesis of liver injury in DM. Increased GLUT1 expression was observed together with overproduction of NO(·) and pronounced liver injury in severely hyperglycaemic rats. On the contrary, moderately hyperglycaemic hyperlipidaemic rats developed only moderate liver steatosis and no increase in GLUT1 and NO(·). GLUT1 overexpression might be implicated in the toxic effects of glucose in the liver. Glycotoxicity is associated with oxidative stress and NO(·) hyperproduction. GLUT1 and NO(·) metabolism might become novel therapeutic targets in liver steatosis.

Dolichos biflorus Linn. ameliorates diabetic complications in streptozotocin induced diabetic rats

Background:

Horsegram (Dolichos biflorus Linn.) is a known antilithiatic, hypolipedemic and has free radical scavenging activity and increased production of reactive oxygen species play a role in pathophysiological mechanisms that trigger diabetic complications.

Aim:

To see the effect of daily oral feeding of D.biflorous on nephropathy and retinopathy in streptozotocin (STZ) induced-diabetic rats.

Materials and Methods:

A total of 24 healthy rats were randomly grouped into controls, diabetic and diabetic on Dolichos. Diabetes was induced by a single dose of STZ (55 mg/kg) and animals were given prepared food and water ad libitum. Dolichos was orally given at 300 mg/kg/day to rats in diabetic on Dolichos group for next 30 days. Fasting blood glucose levels was monitored at beginning and at the end of the experiment while assessment of serum creatinine levels and histopathological study of kidney and retina was carried only at the end of the experiment. Statistical differences between groups were analyzed using analysis of variance followed by, Bonferroni test as posthoc test.

Results:

Results indicated improvement in serum creatinine levels and reduced glomerular sclerosing and Bowman's space with interstitial alterations and significantly reduced renal hypertrophy in diabetic rat son Dolichos diabetic rats (P < 0.001). Retinal layers showed inconsistent improvement in the width of the neuronal layers and decreased vacuolization of plexiform layers and retinal vessel density.

Conclusion:

D. biflorus at doses of 300 mg/kg/day for 30 days resulted in gradual but significant decreased diabetic nephropathy.

Effect of experimental diabetes and insulin replacement on intestinal metabolism and excretion of 4-nitrophenol in rats

Luminal appearance of 4-nitrophenol (PNP) metabolites (4-nitrophenol-β-glucuronide (PNP-G) and 4-nitrophenol-sulfate (PNP-S)) and activity of the related metabolic enzymes have been investigated in control and experimental diabetic rats. Experimental diabetes was induced by administration of streptozotocin (65 mg/kg i.v.). PNP (500 μmol/L) was luminally perfused in the small intestine and the metabolites were determined in the perfusion solution. Effect of insulin replacement was also investigated in the diabetic rats. It was found that experimental diabetes increased the luminal appearance of PNP-G, which could be completely compensated by rapid-acting insulin administration (1 U/kg i.v.). Activities of the enzymes involved in PNP-G production (UDP-glucuronyltransferase and β-glucuronidase) were also elevated; however, these changes were only partially compensated by insulin. Luminal appearance of PNP-S was not significantly changed by administration of streptozotocin and insulin. Activities of the enzymes of PNP-S production (sulfotransferases and arylsulfatases) did not change in the diabetic rats. The results indicate that experimental diabetes can provoke changes in intestinal drug metabolism. It increased intestinal glucuronidation of PNP but did not influence sulfate conjugation. No direct correlation was found between the changes of metabolic enzyme activities and the luminal appearance of the metabolites.

Morphological restructuring of myocardium during the early phase of experimental diabetes mellitus

The purpose of this study was to determine the specific features of the morphological restructuring of the myocardium in the early stage of experimental diabetes mellitus (DM). Experimental type 1 DM rat model was developed by intraperitoneal injection of alloxan solution at a dose of 30 mg per 100 g body mass. After 1 month, 3 mL of blood was drawn by heart puncture and the plasma separated by centrifugation for biochemical analysis. Plasma glucose, insulin, and glycosylated haemoglobin in whole blood were determined. Light microscopy and morphometric studies were conducted of histological slices of the hearts of experimental animals. The investigation of heart morphology showed a statistically significant alteration in chamber wall thickness in the right auricle in rats with alloxan-induced DM. A change in cardiomyocyte diameter in myocardium slices was observed in all chambers of DM rats except for the left ventricle. Average cardiomyocyte diameter in rats with experimental DM increased by 26.6% and 15.5% in the right auricle and right ventricle, respectively, while average cardiomyocyte diameter in the left auricle decreased by 20.8%. Histological investigation of the heart following alloxan injection demonstrated, under the epicardium, distended vessels of the venous collecting microcirculatory system. Aggregation and agglutination of red blood cells and endothelial cell destruction were found in some vessels. In the early stage of DM development, structural alterations in the microcirculatory channels and myocardiocytes can be observed in the heart. These structural alterations were most evident in the right chambers of the heart.

Histological investigation of the impact of streptozotocin-induced experimental diabetes on the healthy gingivae of rats

This study was aimed at the histological investigation of the impact of experimental diabetes on the healthy gingiva of rats. Thirty male Wistar rats were used in this study. The animals were randomly divided into two groups (n = 15) prior to the experiment. Group 1 experimental diabetes was created by streptozotocin injection in 15 rats. Group 2 comprised the control group (15 rats). On the 7th, 14th and 21st days after the induction of diabetes by streptozotocin, five animals from each group were euthanized by cardiac puncture. The gingiva of the maxillary left first molar tooth of the sacrificed animals was extracted for histological examination. Histological examination demonstrated that, when compared to the control group, the diabetes group displayed marked hyperkeratosis and parakeratosis of the gingival epithelium on day 21 post-induction. Furthermore, the diabetes group presented with an increased number of inflammatory cells and vasodilatation of the capillaries, in comparison to the controls. The overall evaluation of the findings obtained in this study suggested that diabetes alone could cause changes in the periodontium and affect periodontal health.

Comparison of the effect of intravitreal bevacizumab and intravitreal fasudil on retinal VEGF, TNFα, and caspase 3 levels in an experimental diabetes model

AIM

To evaluate the influence of an intravitreal injection of bevacizumab and fasudil on the retinal vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNFα), and caspase 3 levels in a diabetic rabbit model.

METHODS

The study included 6 healthy rabbits (Group 1), 6 rabbits with experimentally induced diabetes mellitus (DM) (Group 2), 7 rabbits with experimentally induced DM to which intravitreal bevacizumab was administered (Group 3), and 7 rabbits with experimentally induced DM to which intravitreal fasudil was administered (Group 4). An intravitreal injection of 1.25mg/50µL bevacizumab in the right eye of rabbits in Group 3 and an intravitreal injection of 0.0064mg/50µL fasudil in the right eye of rabbits in Group 4 were administered on day 21 after the induction of DM. The studied eyes of the rabbits were enucleated three days after the intravitreal injection. The TNFα, VEGF, and caspase 3 levels were determined using the ELISA method.

RESULTS

There was a statistically significant difference in the VEGF and caspase 3 levels between groups (P=0.005 and P =0.013, respectively), but the TNFα level did not differ significantly between groups (P=0.792). It was found that VEGF levels were significantly lower in Group 1 and Group 3 than in Group 2 using the Mann-Whitney U test with the Bonferroni correction (P=0.004 for both comparison). There was no statistically significant difference between other groups with regard to VEGF levels (the P value ranged between 0.015 and 0.886). Although the P values of the caspase 3 levels were 0.015 for Group 1 and Group 4, 0.038 for Group 2 and Group 3, and 0.018 for Group 3 and Group 4, these P values remained above the threshold P value of 0.0083, which was the statistically significant level for post hoc tests.

CONCLUSION

An intravitreal injection of bevacizumab decreased both the VEGF level, which plays a role in angiogenesis, and the caspase 3 level, which plays a role in apoptosis. Although not as effective as bevacizumab, fasudil had a beneficial effect on the VEGF levels but significantly increased the caspase 3 levels.

Diabetes-induced changes in the 5-hydroxytryptamine inhibitory receptors involved in the pressor effect elicited by sympathetic stimulation in the pithed rat

1. We investigated the effect of alloxan-induced diabetes on the inhibitory mechanisms of 5-hydroxytryptamine (5-HT) in the pressor responses induced by stimulation of sympathetic vasopressor outflow in pithed rats, and analysed the type and/or subtype of 5-HT receptors involved. 2. Diabetes was induced in male Wistar rats by a single s.c. injection of alloxan, then 4 weeks later, they were anaesthetized, pretreated with atropine and pithed. Electrical stimulation of the sympathetic outflow from the spinal cord (0.1, 0.5, 1 and 5 Hz) resulted in frequency-dependent increases in blood pressure. 3. Intravenous infusions of 5-HT (1-80 microg kg(-1) min(-1)) reduced the pressor effects obtained by electrical stimulation. The 5-HT(1) receptor agonist 5-carboxamidotryptamine, 5-CT (5 microg kg(-1) min(-1)), caused an inhibition of the pressor response, whereas the selective 5-HT(2) receptor agonist, alpha-methyl-5-HT (5 microg kg(-1) min(-1)) and the selective 5-HT(3) receptor agonist, 1-phenylbiguanide (40 microg kg(-1) min(-1)), did not modify the sympathetic pressor responses. 5-HT had no effect on exogenous noradrenaline (NA)-induced pressor responses. 4. The inhibition of electrically induced pressor responses by 5-HT (10 microg kg(-1) min(-1)) was unable to be elicited after i.v. treatment with methiothepin (100 microg kg(-1)) because of the marked inhibition produced by methiothepin alone. The 5-HT-induced inhibition was blocked after i.v. administration of WAY-100,635 (100 microg kg(-1)) and not affected by ritanserin (1 mg kg(-1)), MDL 72222 (2 mg kg(-1)). 5. The selective 5-HT(1A) receptor agonist, 8-hydroxydipropylaminotretalin hydrobromide (8-OH-DPAT) (5-20 microg kg(-1) min(-1)) but neither the rodent 5-HT(1B) receptor agonist, CGS-12066B (5 microg kg(-1) min(-1)), nor the selective nonrodent 5-HT(1B) and 5-HT(1D) receptor agonist, L-694,247 (5 and 40 microg kg(-1) min(-1)), inhibited the electrically induced pressor response. The selective 5-HT(1A) receptor antagonist, WAY-100,635 (100 microg kg(-1)), blocked the inhibition induced by 8-OH-DPAT (10 microg kg(-1) min(-1)). 8-OH-DPAT had no effect on exogenous NA-induced pressor responses. 6. Experimental diabetes produces changes in the inhibitory effect induced by 5-HT on electrically induced sympathetic pressor responses, such that the inhibitory action induced by 5-HT in diabetic pithed rats is mediated by prejunctional 5-HT(1A) receptors.

Insulin and insulin receptors in rodent brain

While insulin effects on the central nervous system (CNS) mediated through hypoglycaemia are well known, direct insulin effects on the CNS remain controversial. Recently, we found insulin receptors in all areas of the rat brain, with highest concentrations in the olfactory bulb, cerebral cortex and hypothalamus; all areas involved in feeding. Insulin receptors in brain were, by multiple criteria, similar to insulin receptors on classical target tissues for insulin, such as liver and fat. Insulin itself has been identified in the rat brain at concentrations on average ten times higher than in plasma. Highest concentrations were found in the olfactory bulb and hypothalamus. Brain insulin was indistinguishable from purified insulin by its behaviour in the radioimmunoassay, radioreceptor assay, bioassay and gel chromatography. In two experimental models representing extremes of plasma insulin concentrations (obese hyperinsulinaemic mice and diabetic insulinopenic rats) there were no significant changes in the concentration of insulin receptors in brain while liver receptors were modified in the expected way. This may reflect the protective influence of the blood-brain barrier or some special quality of brain insulin receptors. Insulin concentrations in brain were also unchanged in both models, which is probably indicative of the local synthesis of insulin. The role of insulin in the CNS is unknown. Besides well known metabolic actions of insulin, new roles can be postulated such as neurotransmission, neuromodulation and paracrine signalling.