Hyperglycemia triggers RyR2-dependent alterations of mitochondrial calcium homeostasis in response to cardiac ischemia-reperfusion: Key role of DRP1 activation

Hyperglycemia increases the heart sensitivity to ischemia-reperfusion (IR), but the underlying cellular mechanisms remain unclear. Mitochondrial dynamics (the processes that govern mitochondrial morphology and their interactions with other organelles, such as the reticulum), has emerged as a key factor in the heart vulnerability to IR. However, it is unknown whether mitochondrial dynamics contributes to hyperglycemia deleterious effect during IR. We hypothesized that (i) the higher heart vulnerability to IR in hyperglycemic conditions could be explained by hyperglycemia effect on the complex interplay between mitochondrial dynamics, Ca2+ homeostasis, and reactive oxygen species (ROS) production; and (ii) the activation of DRP1, a key regulator of mitochondrial dynamics, could play a central role. Using transmission electron microscopy and proteomic analysis, we showed that the interactions between sarcoplasmic reticulum and mitochondria and mitochondrial fission were increased during IR in isolated rat hearts perfused with a hyperglycemic buffer compared with hearts perfused with a normoglycemic buffer. In isolated mitochondria and cardiomyocytes, hyperglycemia increased mitochondrial ROS production and Ca2+ uptake. This was associated with higher RyR2 instability. These results could contribute to explain the early mPTP activation in mitochondria from isolated hearts perfused with a hyperglycemic buffer and in hearts from streptozotocin-treated rats (to increase the blood glucose). DRP1 inhibition by Mdivi-1 during the hyperglycemic phase and before IR induction, normalized Ca2+ homeostasis, ROS production, mPTP activation, and reduced the heart sensitivity to IR in streptozotocin-treated rats. In conclusion, hyperglycemia-dependent DRP1 activation results in higher reticulum-mitochondria calcium exchange that contribute to the higher heart vulnerability to IR.

Analysis of immunohistomorphological changes in the colonic mucosa in a high-saturated fat and high-cholesterol fed streptozotocin/nicotinamide diabetic rat model

The mucosal surface of gastrointestinal tract is lined with epithelial cells that establish an effective barrier between the lumen and internal environment through intercellular junctions, preventing the passage of potentially harmful substances. The "intestinal barrier function" consist of a defensive system that prevent the passage of antigens, toxins, and microbial products, while maintains the correct development of the epithelial barrier, the immune system and the acquisition of tolerance toward dietary antigens and intestinal microbiota. Intestinal morphology changes subsequent to nutritional variations, stress, aging or diseases, which can also affect the composition of the microbiota, altering the homeostasis of the intestine. A growing body of evidence suggests that alterations in intestinal barrier function favor the development of exaggerated immune responses, leading to metabolic endotoxemia, which seems to be the origin of many chronic metabolic diseases such as type 2 diabetes mellitus (T2DM). Although the mechanisms are still unknown, the interaction between dietary patterns, gut microbiota, intestinal mucosa, and metabolic inflammation seems to be a key factor for the development of T2DM, among other diseases. This chapter details the different techniques that allow evaluating the morphological and molecular alterations that lead of the intestinal barrier dysfunction in a T2DM experimental model. To induce both diabetic metabolic disturbances and gut barrier disruption, Wistar rats were fed a high-saturated fat and high-cholesterol diet and received a single dose of streptozotocin/nicotinamide. This animal model may contribute to clarify the understanding of the role of intestinal barrier dysfunction on the late-stage T2DM etiology.

Empagliflozin attenuates liver fibrosis in high-fat diet/streptozotocin-induced mice by modulating gut microbiota

The effects of SGLT2 inhibitors on hepatic fibrosis in diabetes remain unclear. This study aimed to investigate the effects of empagliflozin on liver fibrosis in high-fat diet/streptozotocin-induced mice and the correlation with gut microbiota. After the application of empagliflozin for 6 weeks, we performed oral glucose tolerance and intraperitoneal insulin tolerance tests to assess glucose tolerance and insulin resistance, and stained liver sections to evaluate histochemical and hepatic pathological markers of liver fibrosis. Moreover, 16S rRNA amplicon sequencing was performed on stool samples to explore changes in the composition of intestinal bacteria. We finally analysed the correlation between gut microbiome and liver fibrosis scores or indicators of glucose metabolism. The results showed that empagliflozin intervention improved glucose metabolism and liver function with reduced liver fibrosis, which might be related to changes in intestinal microbiota. In addition, the abundance of intestinal probiotic Lactobacillus increased, while Ruminococcus and Adlercreutzia decreased after empagliflozin treatment, and correlation analysis showed that the changes in microbiota were positively correlated with liver fibrosis and glucose metabolism. Overall, considering the contribution of the gut microbiota in metabolism, empagliflozin might have improved the beneficial balance of intestinal bacteria composition. The present study provides evidence and indicates the involvement of the gut-liver axis by SGLT2 inhibitors in T2DM with liver fibrosis.

Bavachin ameliorates neuroinflammation and depressive-like behaviors in streptozotocin-induced diabetic mice through the inhibition of PKCδ

Depression and diabetes are closely linked; however, the pathogenesis of depression associated with diabetes is unclear, and there are no clinically effective antidepressant drugs for diabetic patients with depression. Bavachin is an important active ingredient in Fructus Psoraleae. In this study, we evaluated the anti-neuroinflammatory and antidepressant effects associated with diabetes and the molecular mechanisms of bavachin in a streptozotocin-induced diabetes mouse model. We found that bavachin clearly decreased streptozotocin (STZ)-induced depressive-like behaviors in mice. It was further found that bavachin significantly inhibited microglia activation and the phosphorylation level of PKCδ and inhibited the activation of the NF-κB pathway in vivo and in vitro. Knockdown of PKCδ with siRNA-PKCδ partially reversed the inhibitory effect of bavachin on the NF-κB pathway and the level of pro-inflammatory factors. We further found that PKCδ directly bound to bavachin based on molecular docking and pull-down assays. We also found that bavachin improved neuroinflammation-induced neuronal survival and functional impairment and that this effect may be related to activation of the ERK and Akt pathways mediated by the BDNF pathway. Taken together, these data suggested that bavachin, by targeting inhibition PKCδ to inhibit the NF-κB pathway, further reduced the inflammatory response and oxidative stress and subsequently improved diabetic neuronal survival and function and finally ameliorated diabetes-induced depressive-like behaviors in mice. For the first time, we found that bavachin is a potential agent for the treatment of diabetes-associated neuroinflammation and depression and that PKCδ is a potential target for the treatment of diabetes-associated neuroinflammation, including depression.

USP28 Serves as a Key Suppressor of Mitochondrial Morphofunctional Defects and Cardiac Dysfunction in the Diabetic Heart

BACKGROUND

The majority of people with diabetes are susceptible to cardiac dysfunction and heart failure, and conventional drug therapy cannot correct diabetic cardiomyopathy progression. Herein, we assessed the potential role and therapeutic value of USP28 (ubiquitin-specific protease 28) on the metabolic vulnerability of diabetic cardiomyopathy.

METHODS

The type 2 diabetes mouse model was established using db/db leptin receptor-deficient mice and high-fat diet/streptozotocin-induced mice. Cardiac-specific knockout of USP28 in the db/db background mice was generated by crossbreeding db/m and Myh6-Cre+/USP28fl/fl mice. Recombinant adeno-associated virus serotype 9 carrying USP28 under cardiac troponin T promoter was injected into db/db mice. High glucose plus palmitic acid-incubated neonatal rat ventricular myocytes and human induced pluripotent stem cell-derived cardiomyocytes were used to imitate diabetic cardiomyopathy in vitro. The molecular mechanism was explored through RNA sequencing, immunoprecipitation and mass spectrometry analysis, protein pull-down, chromatin immunoprecipitation sequencing, and chromatin immunoprecipitation assay.

RESULTS

Microarray profiling of the UPS (ubiquitin-proteasome system) on the basis of db/db mouse hearts and diabetic patients' hearts demonstrated that the diabetic ventricle presented a significant reduction in USP28 expression. Diabetic Myh6-Cre+/USP28fl/fl mice exhibited more severe progressive cardiac dysfunction, lipid accumulation, and mitochondrial disarrangement, compared with their controls. On the other hand, USP28 overexpression improved systolic and diastolic dysfunction and ameliorated cardiac hypertrophy and fibrosis in the diabetic heart. Adeno-associated virus serotype 9-USP28 diabetic mice also exhibited less lipid storage, reduced reactive oxygen species formation, and mitochondrial impairment in heart tissues than adeno-associated virus serotype 9-null diabetic mice. As a result, USP28 overexpression attenuated cardiac remodeling and dysfunction, lipid accumulation, and mitochondrial impairment in high-fat diet/streptozotocin-induced type 2 diabetes mice. These results were also confirmed in neonatal rat ventricular myocytes and human induced pluripotent stem cell-derived cardiomyocytes. RNA sequencing, immunoprecipitation and mass spectrometry analysis, chromatin immunoprecipitation assays, chromatin immunoprecipitation sequencing, and protein pull-down assay mechanistically revealed that USP28 directly interacted with PPARα (peroxisome proliferator-activated receptor α), deubiquitinating and stabilizing PPARα (Lys152) to promote Mfn2 (mitofusin 2) transcription, thereby impeding mitochondrial morphofunctional defects. However, such cardioprotective benefits of USP28 were largely abrogated in db/db mice with PPARα deletion and conditional loss-of-function of Mfn2.

CONCLUSIONS

Our findings provide a USP28-modulated mitochondria homeostasis mechanism that involves the PPARα-Mfn2 axis in diabetic hearts, suggesting that USP28 activation or adeno-associated virus therapy targeting USP28 represents a potential therapeutic strategy for diabetic cardiomyopathy.

Structural changes in testes of Streptozotocin induced diabetic rats and possible protective effect of royal jelly: light and electron microscopic study

Diabetes mellitus (DM) is one of the most common metabolic diseases causing damage in many organs in the body including the testes. Royal Jelly (RJ) is one of the honey bee products that has antioxidant, anti-inflammatory and antidiabetic properties. This study was performed to evaluate the changes in the microscopic structure of the testes in Streptozotocin (STZ)-induced diabetic rats, and the possible protective role of RJ. 60 adult male albino rats were divided into three groups. Group I Control group, Group II STZ group, and Group III STZ+RJ group. Group II received a single dose of STZ (50 mg/kg) by intraperitoneal injection. Group III received a single dose of STZ as in the second group then received RJ orally by intragastric tube in dose of (100 mg/kg/day) for 4 weeks after confirmation of diabetes. Light and electron microscopic studies were performed. Group II revealed marked structural changes affecting seminiferous tubules with sever reduction in germinal epithelium and loss of mature spermatozoa in their lumina. The interstitial tissue revealed degenerated Leydig cells and congested blood vessels. Mallory trichrome stained section of group II revealed marked increase in the amount of collagen fibers. Group III revealed highly preserved testicular architecture almost near to that appeared in the control group except few tubules that were damaged. In conclusion, RJ protected the testicular structure from the damaging effect of diabetic oxidative stress through its antioxidant effect thus preserving male fertility.

Tangshen formula improves diabetic nephropathy in STZ-induced diabetes rats fed with hyper-methionine by regulating the methylation status of kidney

BACKGROUND

The objective of this study was to examine and analyze differential methylation profiles in order to investigate the influence of hyper-methioninemia (HM) on the development of diabetic nephropathy (DN). Male Wistar rats, aged eight weeks and weighing 250-300 g, were randomly assigned into four groups: a control group (Healthy, n = 8), streptozocin-induced rats (STZ group, n = 8), HM + STZ group (n = 8), and the Tangshen Formula (TSF) treatment group (TSF group, n = 8). Blood glucose levels and other metabolic indicators were monitored before treatment and at four-week intervals until 12 weeks. Total DNA was extracted from the aforementioned groups, and DNA methylation landscapes were analyzed via reduced representative bisulfite sequencing.

RESULTS

Both the STZ group and HM + STZ group exhibited increased blood glucose levels and urinary albumin/creatinine ratios in comparison with the control group. Notably, the HM + STZ group exhibited a markedly elevated urinary albumin/creatinine ratio (411.90 ± 88.86 mg/g) compared to the STZ group (238.41 ± 62.52 mg/g). TSF-treated rats demonstrated substantial reductions in both blood glucose levels and urinary albumin/creatinine ratios in comparison with the HM + STZ group. In-depth analysis of DNA methylation profiles revealed 797 genes with potential therapeutic effects related to TSF, among which approximately 2.3% had been previously reported as homologous genes.

CONCLUSION

While HM exacerbates DN through altered methylation patterns at specific CpG sites, TSF holds promise as a viable treatment for DN by restoring abnormal methylation levels. The identification of specific genes provides valuable insights into the underlying mechanisms of DN pathogenesis and offers potential therapeutic targets for further investigation.

Ginger Supplementation Attenuated Mitochondrial Fusion and Improved Skeletal Muscle Size in Type 2 Diabetic Rats

BACKGROUND/AIM

Oxidative stress, regulated by SOD2 and mitochondrial dynamics, contributes to muscle atrophy in diabetes. Ginger root extract (GRE) reduces oxidative stress. However, its effect on oxidative stress, mitochondrial dynamics, and muscle atrophy is not known in the diabetic muscle. This study examined the effect of GRE on intramuscular oxidative stress, mitochondrial dynamics, and muscle size in diabetic rats.

MATERIALS AND METHODS

Twenty-six male Sprague-Dawley rats were randomly divided into control diet (CON; n=10), high-fat diet with one dose of 35 mg/kg streptozotocin (HFD; n=9), and high-fat diet with one dose of 35 mg/kg streptozotocin and 0.75% w/w GRE (GRE; n=7) fed for seven weeks. Subsequently, the muscle was analyzed for cross-sectional area (CSA), H2O2 concentration, and DRP-1, MFN2, Parkin, PINK1, SOD2 mRNA. Additionally, the protein levels of SOD2, DRP-1, DRP-1ser616, LC3AB, MFN2, OPA1, Parkin, and PINK1 were analyzed. CSA, H2O2 concentration, and gene and protein expression levels were analyzed using a one-way ANOVA. Correlations among intramuscular H2O2, CSA, and SOD2 protein were assessed using Pearson's bivariate correlation test.

RESULTS

In the soleus, the GRE group had a greater CSA and lower intramuscular H2O2 concentration compared to the HFD group. Compared to the HFD group, the GRE group had higher SOD2 and DRP-1 mRNA levels and lower MFN2 and total OPA1 protein levels. H2O2 concentration was negatively correlated with CSA and positively correlated with SOD2.

CONCLUSION

GRE attenuated intramuscular H2O2, mitochondrial fusion, and muscle size loss. These findings suggest that GRE supplementation in diabetic rats reduces oxidative stress, which may contribute to muscle size preservation.

Ocular surface changes in mice with streptozotocin-induced diabetes and diabetic polyneuropathy

PURPOSE

Diabetes mellitus (DM) is a leading risk factor for corneal neuropathy and dry eye disease (DED). Another common consequence of DM is diabetic peripheral polyneuropathy (DPN). Both complications affect around 50 % of the DM patients but the relationship between DM, DED and DPN remains unclear.

METHODS

In this study, we examined mice with early onset of DM and PN after streptozotocin (STZ)-induced diabetes (DPN). We compared the early morphological changes of the sciatic nerve, dorsal root and trigeminal ganglia with the changes in the ocular surface, including tear proteomic and we also investigated respective changes in the gene expressions and morphological alterations in the eye tissues involved in tear production.

RESULTS

The lacrimal gland, conjunctival goblet cells and cornea showed morphological changes along with alterations in tear proteins without any obvious signs of ocular surface inflammation. The gene expression for respectively altered tear proteins i.e., of Clusterin in cornea, Car6, Adh3a1, and Eef1a1 in eyelids, and Pigr in the lacrimal gland also showed significant changes compared to control mice. In the trigeminal ganglia like in the dorsal root ganglia neuronal cells showed swollen mitochondria and, in the latter, there was a significant increase of NADPH oxidases and MMP9 suggestive of oxidative and neuronal stress. In the dorsal root ganglia and the sciatic nerve, there was an upregulation of a number of pro-inflammatory cytokines and pain-mediating chemokines.

CONCLUSION

The early ocular changes in DM Mice only affect the lacrimal gland. Which, is reflected in the tear film composition of DPN mice. Due to the high protein concentration in tear fluid in humans, proteomic analysis in addition to noninvasive investigation of goblet cells and cornea can serve as a tools for the early diagnosis of DPN, DED in clinical practice. Early treatment could delay or even prevent the ocular complications of DM such as DED and PN.

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker on oxidative stress and metabolism of elements in kidney of STZ-induced diabetic rats

In diabetes, increased oxidative stress and impaired trace element metabolism play an important role in the pathogenesis of diabetic nephropathy. The objective of this research was to examine the outcomes of blocking the renin-angiotensin system, using either the angiotensin-converting enzyme inhibitor (ACEI), perindopril, or the angiotensin II type 1 (AT1) receptor blocker, irbesartan, on oxidative stress and trace element levels such as Zn, Mg, Cu, and Fe in the kidneys of diabetic rats that had been induced with streptozotocin. Thirty-two Wistar albino male rats were equally divided into four groups. The first group was used as a control. The second group of rats developed diabetes after receiving a single intraperitoneal dose of STZ. The third and fourth groups of rats had STZ-induced diabetes and received daily dosages of irbesartan (15 mg/kg b.w/day) and perindopril (6 mg/kg b.w/day) treatment, respectively. Biochemical analysis of the kidneys showed a distinct increase in oxidative stress, indicated by heightened levels of malondialdehyde (MDA) and decreased superoxide dismutase (SOD) activities, as well as reduced glutathione (GSH) levels in the kidneys of diabetic rats. In the kidneys of diabetic rats, the mean levels of Fe and Cu were found to be significantly higher than those of the control group. Additionally, the mean levels of Zn and Mg were significantly lower in the diabetic rats compared to the control rats. Both perindopril and irbesartan decreased significantly MDA content and increased SOD activities and GSH levels in the kidneys of rats with diabetes. The Zn and Mg concentrations in the kidneys of diabetic rats treated with perindopril and irbesartan were markedly higher than in untreated STZ-diabetic rats, while the Cu and Fe concentrations were significantly lower. The urinary excretion of rats treated with perindopril and irbesartan showed a pronounced increase in Cu levels, along with a significant reduction in Zn and Mg levels. Although diabetic rats demonstrated degenerative morphological alterations in their kidneys, both therapies also improved diabetes-induced histopathological modifications in the kidneys. Finally, the present results suggest that manipulating the levels of Zn, Mg, Cu, and Fe - either through ACE inhibition or by blocking AT1 receptors - could be advantageous in reducing lipid peroxidation and increasing antioxidant concentration in the kidneys of diabetic rats.

The effect of hyperglycemia on the activation of peritoneal macrophages of albino rats

Hyperglycemia is one of the main damaging factors of diabetes mellitus (DM). The severity of this disease is most clearly manifested under conditions of the inflammatory process. In this work, we have studied the activation features of rat peritoneal macrophages (MPs) under conditions of high glucose concentration in vitro. Comparison of the independent and combined effects of streptozotocin-induced DM and hyperglycemia on proliferation and accumulation of nitrites in the MPs culture medium revealed similarity of their effects. Elevated glucose levels and, to a lesser extent, DM decreased basal proliferation and NO production by MPs in vitro. The use of the protein kinase C (PKC) activator, phorbol ester (PMA), abolished the proinflammatory effect of thrombin on PMs. This suggests the involvement of PKC in the effects of the protease. At the same time, the effect of thrombin on the level of nitrites in the culture medium demonstrates a pronounced dose-dependence, which was not recognized during evaluation of proliferation. Proinflammatory activation of MPs is potentiated by hyperglycemia, one of the main pathological factors of diabetes. Despite the fact that high concentrations of glucose have a significant effect on proliferation and NO production, no statistically significant differences were found between the responses of MPs obtained from healthy animals and from animals with streptozotocin-induced DM. This ratio was observed for all parameters studied in the work, during analysis of cell proliferation and measurement of nitrites in the culture medium. Thus, the results obtained indicate the leading role of elevated glucose levels in the regulation of MPs activation, which is comparable to the effect of DM and even "masks" it.

Morphological and molecular changes in the Harderian gland of streptozotocin-induced diabetic rats

Using a rat model of type 1 diabetes (T1D) obtained by treatment with streptozotocin, an antibiotic that destroys pancreatic β-cells, we evaluated the influence of subsequent hyperglycemia on the morphology and physiology of the Harderian gland (HG). HG is located in the medial corner of the orbit of many terrestrial vertebrates and, in rodents, is characterized by the presence of porphyrins, which being involved in the phototransduction, through photo-oxidation, produce reactive oxygen species activating the autophagy pathway. The study focused on the expression of some morphological markers involved in cell junction formation (occludin, connexin-43, and α-tubulin) and mast cell number (MCN), as well as autophagic and apoptotic pathways. The expression of enzymes involved in steroidogenesis [steroidogenic acute regulatory protein (StAR), and 3β-hydroxysteroid dehydrogenase (3β-HSD)] and the level of lipid peroxidation by thiobarbituric acid reactive species assay were also evaluated. The results strongly indicate, for the first time, that T1D has a negative impact on the pathophysiology of rat HG, as evidenced by increased oxidative stress, morphological and biochemical alterations, hyperproduction and secretion of porphyrins, increased MCN, reduced protein levels of StAR and 3β-HSD, and, finally, induced autophagy and apoptosis. All the combined data support the use of the rat HG as a suitable experimental model to elucidate the molecular damage/survival pathways elicited by stress conditions.

Knockout of Matrix Metalloproteinase 2 Opposes Hypertension- and Diabetes-induced Nephropathy

ABSTRACT

The progression of chronic kidney disease results from the accumulation of extracellular matrix leading to end-stage renal disease. We previously demonstrated that a broad-spectrum matrix metalloproteinase (MMP) inhibitor reduced renal injury in rat models of hypertension and diabetes. However, the isoforms and mechanisms involved are unclear. This study examined the role of MMP2 during the development of proteinuria and renal injury after induction of hypertension or diabetes in Dahl salt-sensitive (SS) and MMP2 knockout (KO) rats. Mean arterial pressure rose from 115 ± 2 to 145 ± 2 mm Hg and 116 ± 1 to 152 ± 3 mm Hg in MMP2 KO and SS rats fed a high-salt (8% NaCl) diet for 3 weeks. The degree of proteinuria, glomerular injury, renal fibrosis, and podocyte loss was lower in MMP2 KO rats than in SS rats. Blood glucose and HbA1c levels, and mean arterial pressure rose to the same extent in streptozotocin-treated SS and MMP2 KO rats. However, the degree of proteinuria, glomerulosclerosis, renal fibrosis, renal hypertrophy, glomerular permeability to albumin, and the renal expression of MMP2 and TGFβ1 were significantly reduced in MMP2 KO rats. Glomerular filtration rate fell by 33% after 12 weeks of diabetes in streptozotocin-treated SS rats compared with time-control rats, but glomerular filtration rate only fell by 12% in MMP2 KO rats. These results indicate that activation of MMP2 plays an essential role in the pathogenesis of hypertensive and diabetic nephropathy and suggests that an MMP2 inhibitor might slow the progression of chronic kidney disease.

Laboratory and clinical findings in mouse models of diabetic nephropathy induced with streptozotocin

BACKGROUND

Diabetic nephropathy (DN) represents a microvascular complication of diabetes mellitus (DM). Despite the increasing incidence and prevalence of DN, conservative therapy only reduces risk factors and hemodialysis. This research aimed at finding DN animal model that can be tried to be given an alternative treatment. DN was assessed by evaluating body weight, blood glucose, proteinuria, and kidney histopathology.

METHODS

Wistar novergicus male rats were induced with 75 mg of streptozotocin per kg BW to obtain a diabetic nephropathy model. The 18 rats were divided into 2 groups consisting of 9 rats in the negative group (G0) and 9 rats in the positive group (G1). Indicators of body weight, blood glucose levels, urine protein and kidney histopathology determine the incidents of DN animal models.

RESULT

Rats induced using 75 mg of streptozotocin per kg body weight (BW) indicated weight loss, increased blood glucose, urine protein levels and histopathological features of DN.

CONCLUSION

Seventy-five mg of streptozotocin per kg BW can induce a diabetic nephropathy animal model in Wistar norvegicus rats.

Neuroprotective Effects of Probiotic Lactobacillus reuteri GMNL-263 in the Hippocampus of Streptozotocin-Induced Diabetic Rats

Diabetes-related brain complications have been reported in clinical patients and experimental models. The objective of the present study was to investigate the neuroprotective mechanisms of Lactobacillus reuteri GMNL-263 in streptozotocin (STZ)-induced diabetic rats. In this study, three different groups, namely control group, STZ-induced (55 mg/kg streptozotocin intraperitoneally) diabetic rats (DM), and DM rats treated with Lactobacillus reuteri GMNL-263 (1 × 109 CFU/rat/day), were utilized to study the protective effect of GMNL-263 in the hippocampus of STZ-induced diabetic rats. The results demonstrated that GMNL-263 attenuated diabetes-induced hippocampal damage by enhancing the cell survival pathways and repressing both inflammatory and apoptotic pathways. Histopathological analysis revealed that GMNL-263 prevented structural changes in the hippocampus in the DM group and decreased the level of inflammation and apoptosis in the hippocampus of DM rats. The IGF1R cell survival signaling pathway also improved after GMNL-263 treatment. These results indicate that probiotic GMNL-263 exerts beneficial effects in the brain of diabetic rats and has potential ability for clinical application.

Ulinastatin ameliorated streptozotocin-induced diabetic nephropathy: Potential effects via modulating the components of gut-kidney axis and restoring mitochondrial homeostasis

Growing evidence supports the role of the gut-kidney axis and persistent mitochondrial dysfunction in the pathogenesis of diabetic nephropathy (DN). Ulinastatin (UTI) has a potent anti-inflammatory effect, protecting the kidney and the gut barrier in sepsis, but its effect on DN has yet to be investigated. This study aimed to assess the potential mitigating effect of UTI on DN and investigate the possible involvement of gut-kidney axis and mitochondrial homeostasis in this effect. Forty male Wistar rats were divided equally into four groups: normal; UTI-treated control; untreated DN; and UTI-treated DN. At the end of the experiment, UTI ameliorated DN by modulating the gut-kidney axis as it improved serum and urinary creatinine, urine volume, creatinine clearance, blood urea nitrogen, urinary albumin, intestinal morphology including villus height, crypt depth, and number of goblet cells, with upregulating the expression of intestinal tight-junction protein claudin-1, and counteracting kidney changes as indicated by significantly decreasing glomerular tuft area and periglomerular and peritubular collagen deposition. In addition, it significantly reduced intestinal and renal nuclear factor kappa B (NF-κB), serum Complement 5a (C5a), renal monocyte chemoattractant protein-1 (MCP-1), renal intercellular adhesion molecule 1 (ICAM1), and renal signal transducer and activator of transcription 3 (STAT3), mitochondrial dynamin related protein 1 (Drp1), mitochondrial fission 1 protein (FIS1), mitochondrial reactive oxygen species (ROS), renal hydrogen peroxide (H2O2), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. Furthermore, it significantly increased serum short chain fatty acids (SCFAs), and mitochondrial ATP levels and mitochondrial transmembrane potential. Moreover, there were significant correlations between measured markers of gut components of the gut-kidney axis and renal function tests in UTI-treated DN group. In conclusion, UTI has a promising therapeutic effect on DN by modulating the gut-kidney axis and improving renal mitochondrial dynamics and redox equilibrium.

Dose-dependent progression of multiple low-dose streptozotocin-induced diabetes in mice

This study investigated the effects of different multiple low doses of streptozotocin (STZ), namely 35 and 55 mg/kg, on the onset and progression of diabetes in mice. Both doses are commonly used in research, and although both induced a loss of beta cell mass, they had distinct effects on whole glucose tolerance, beta cell function, and gene transcription. Mice treated with 55 mg/kg became rapidly glucose intolerant, whereas those treated with 35 mg/kg had a slower onset and remained glucose tolerant for up to a week before becoming equally glucose intolerant as the 55 mg/kg group. Beta cell mass loss was similar between the two groups, but the 35 mg/kg-treated mice had improved glucose-stimulated insulin secretion in gold-standard hyperglycemic clamp studies. Transcriptomic analysis revealed that the 55 mg/kg dose caused disruptions in nearly five times as many genes as the 35 mg/kg dose in isolated pancreatic islets. Pathways that were downregulated in both doses were more downregulated in the 55 mg/kg-treated mice, whereas pathways that were upregulated in both doses were more upregulated in the 35 mg/kg-treated mice. Moreover, we observed a differential downregulation in the 55 mg/kg-treated islets of beta cell characteristic pathways, such as exocytosis or hormone secretion. On the other hand, apoptosis was differentially upregulated in 35 mg/kg-treated islets, suggesting different transcriptional mechanisms in the onset of STZ-induced damage in the islets. This study demonstrates that the two STZ doses induce distinctly mechanistic progressions for the loss of functional beta cell mass.

Regulation of uterus and placenta remodeling under high estradiol levels in gestational diabetes mellitus models†

The present study aimed to investigate the regulation of placentas and uterus remodeling and involvement of estradiol in gestational diabetes mellitus. To achieve this, we established in vitro and in vivo models for gestational diabetes mellitus placentas by culturing human placental choriocarcinoma cells (BeWo) under hyperglycemic concentration and treating pregnant rats with streptozotocin. We evaluated the expression of angiogenesis-related proteins. The expression of the anti-angiogenic factor, excess placental soluble fms-like tyrosine kinase 1 was increased in our in vitro gestational diabetes mellitus model compared with the control. Moreover, the expressions of placental soluble fms-like tyrosine kinase 1 and the von Willebrand factor were also significantly elevated in the placenta of streptozotocin-treated rats. These data indicate the disruption of angiogenesis in the gestational diabetes mellitus placentas. The expression levels of connexin 43, a component of the gap junction and collagen type I alpha 2 chain, a component of the extracellular matrix, were decreased in the gestational diabetes mellitus uterus. These results suggest that uterus decidualization and placental angiogenesis are inhibited in gestational diabetes mellitus rats. Our results also showed upregulation of the expression of genes regulating estradiol synthesis as well as estrogen receptors in vivo models. Accordingly, the concentration of estradiol measured in the culture medium under hyperglycemic conditions, as well as in the serum and placenta of the streptozotocin-treated rats, was significantly elevated compared with the control groups. These results suggest that the dysregulated remodeling of the placenta and uterus may result in the elevation of estradiol and its signaling pathway in the gestational diabetes mellitus animal model to maintain pregnancy.

CXCL5 suppression recovers neovascularization and accelerates wound healing in diabetes mellitus

BACKGROUND

Higher chemokine C-X-C motif ligand 5 (CXCL5) level was observed in type 2 diabetes mellitus (DM) patients; however, its role in diabetic vasculopathy was not clarified. This study aimed to explore the impacts and mechanistic insights of CXCL5 in neovasculogenesis and wound healing in DM.

METHODS

Endothelial progenitor cells (EPCs) and human aortic endothelial cells (HAECs) were used in vitro. Streptozotocin-induced diabetic mice and Leprdb/JNarl mice were used as type 1 and type 2 DM models. Moreover, CXCL5 knockout mice were used to generate diabetic mice. Hindlimb ischemia surgery, aortic ring assays, matrigel plug assay, and wound healing assay were conducted.

RESULTS

CXCL5 concentrations were increased in plasma and EPCs culture medium from type 2 DM patients. CXCL5 neutralizing antibody upregulated vascular endothelial growth factor (VEGF)/stromal cell-derived factor-1 (SDF-1) and promoted cell function in EPCs from type 2 DM patients and high glucose-treated EPCs from non-DM subjects as well as HAECs. CXCL5 directly up-regulated interleukin (IL)-1β/IL-6/tumor necrosis factor-α and down-regulated VEGF/SDF-1 via ERK/p65 activation through chemokine C-X-C motif receptor 2 (CXCR2). CXCL5 neutralizing antibody recovered the blood flow after hindlimb ischemia, increased circulating EPC number, and enhanced VEGF and SDF-1 expression in ischemic muscle. CXCL5 suppression promoted neovascularization and wound healing in different diabetic animal models. The above observation could also be seen in streptozotocin-induced CXCL5 knockout diabetic mice.

CONCLUSIONS

CXCL5 suppression could improve neovascularization and wound healing through CXCR2 in DM. CXCL5 may be regarded as a potential therapeutic target for vascular complications of DM.

Kir4.1 deletion prevents salt-sensitive hypertension in early streptozotocin-induced diabetic mice via Na + -Cl - cotransporter in the distal convoluted tubule

OBJECTIVES

Functional impairment of renal sodium handling and blood pressure (BP) homeostasis is an early characteristic manifestation of type 1 diabetes. However, the underlying mechanisms remain unclear.

METHODS

Metabolic cages, radio-telemetry, immunoblotting, and electrophysiology were utilized to examine effects of high salt (8% NaCl, HS) intake on Na + /K + balance, BP, Na + -Cl - cotransporter (NCC) function, and basolateral K + channel activity in the distal convoluted tubule (DCT) under diabetic conditions.

RESULTS

Improper Na + balance, hypernatremia, and a mild but significant increase in BP were found in streptozotocin (STZ)-induced diabetic mice in response to HS intake for 7 days. Compared to the vehicle, STZ mice showed increased Kir4.1 expression and activity in the DCT, a more negative membrane potential, higher NCC abundance, and enhanced hydrochlorothiazide-induced natriuretic effect. However, HS had no significant effect on basolateral Kir4.1 expression/activity and DCT membrane potential, or NCC activity under diabetic conditions, despite a downregulation in phosphorylated NCC abundance. In contrast, HS significantly downregulated the expression of Na + -H + exchanger 3 (NHE3) and cleaved epithelial sodium channel-γ in STZ mice, despite an increase in NHE3 abundance after STZ treatment. Kir4.1 deletion largely abolished STZ-induced upregulation of NCC expression and prevented BP elevation during HS intake. Interestingly, HS causes severe hypokalemia in STZ-treated kidney-specific Kir4.1 knockout (Ks-Kir4.1 KO) mice and lead to death within a few days, which could be attributed to a higher circulating aldosterone level.

CONCLUSIONS

We concluded that Kir4.1 is required for upregulating NCC activity and may be essential for developing salt-sensitive hypertension in early STZ-induced diabetes.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

Effect of intrathecal NIS-lncRNA antisense oligonucleotides on neuropathic pain caused by nerve trauma, chemotherapy, or diabetes mellitus

BACKGROUND

Blocking increased expression of nerve injury-specific long non-coding RNA (NIS-lncRNA) in injured dorsal root ganglia (DRG) through DRG microinjection of NIS-lncRNA small hairpin interfering RNA or generation of NIS-lncRNA knockdown mice mitigates neuropathic pain. However, these strategies are impractical in the clinic. This study employed a Food and Drug Administration (FDA)-approved antisense oligonucleotides strategy to examine the effect of NIS-lncRNA ASOs on neuropathic pain.

METHODS

Effects of intrathecal injection of NIS-lncRNA antisense oligonucleotides on day 7 or 14 after chronic constriction injury (CCI) of the sciatic nerve, fourth lumbar (L4) spinal nerve ligation, or intraperitoneal injection of paclitaxel or streptozotocin on the expression of DRG NIS-lncRNA and C-C chemokine ligand 2 (CCL2, an NIS-lncRNA downstream target) and nociceptive hypersensitivity were examined. We also assessed whether NIS-lncRNA antisense oligonucleotides produced cellular toxicity.

RESULTS

Intrathecal NIS-lncRNA antisense oligonucleotides attenuated CCI-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and ongoing nociceptive responses, without changing basal or acute nociceptive responses and locomotor function. Intrathecal NIS-lncRNA antisense oligonucleotides also blocked CCI-induced increases in NIS-lncRNA and CCL2 in the ipsilateral L3 and L4 DRG and hyperactivities of neurones and astrocytes in the ipsilateral L3 and L4 spinal cord dorsal horn. Similar results were found in antisense oligonucleotides-treated mice after spinal nerve ligation or intraperitoneal injection of paclitaxel or streptozotocin. Normal morphologic structure and no cell loss were observed in the DRG and spinal cord of antisense oligonucleotides-treated mice.

CONCLUSION

These findings further validate the role of NIS-lncRNA in trauma-, chemotherapy-, or diabetes-induced neuropathic pain and demonstrate potential clinical application of NIS-lncRNA antisense oligonucleotides for neuropathic pain management.

Polyethylene glycol capped gold nanoparticles ameliorate renal ischemia-reperfusion injury in diabetic mice through AMPK-Nrf2 signaling pathway

The aim of this study is to investigate the protective effect of polyethylene glycol capped gold nanoparticles (PEG-AuNPs) on renal ischemia-reperfusion injury (I/R)-induced acute kidney injury (AKI) in diabetic mice via the activation of adenosine 5' monophosphate-activated protein kinase-nuclear factor erythroid-2-related factor-2 (AMPK-Nrf2) pathway. Diabetes was induced in male mice (12/group) by streptozotocin (50 mg/kg) for 5 consecutive days. After 4 weeks, the mice have intravenously received doses of PEG-AuNPs (40, 150, and 400 µg/kg body weight) for 3 consecutive days, and then animals were subjected to 30 min ischemia and 48 h reperfusion. Following the treatment with three different doses of PEG-AuNPs, the levels of blood urea nitrogen (BUN) and creatinine were reduced. Obvious reduction in renal tubular atrophy, glomerular damage, mitochondrial damage, and necrotic area were ultra-structurally detected, and renal interstitial inflammation and apoptosis were diminished. Moreover, PEG-AuNPs increased the recovering of damaged renal cells, suppressed significantly levels of malondialdehyde (MDA), downregulated significantly the level of inflammatory cytokines (TNF-α and IL-1β), and upregulated the AMPK-Nrf2 pathway. PEG-AuNPs exhibited a promising alternative therapeutic target for diabetic renal I/R-induced AKI through upregulation of AMPK/PI3K/AKT path which additionally stimulated Nrf2-regulated antioxidant enzymes in a dose-dependent manner.

Recurrent hypoglycemia increases hepatic gluconeogenesis without affecting glycogen metabolism or systemic lipolysis in rat

INTRODUCTION

Recurrent hypoglycemia (RH) impairs secretion of counterregulatory hormones. Whether and how RH affects responses within metabolically important peripheral organs to counterregulatory hormones are poorly understood.

OBJECTIVE

To study the effects of RH on metabolic pathways associated with glucose counterregulation within liver, white adipose tissue and skeletal muscle.

METHODS

Using a widely adopted rodent model of 3-day recurrent hypoglycemia, we first checked expression of counterregulatory hormone G-protein coupled receptors (GPCRs), their inhibitory regulators and downstream enzymes catalyzing glycogen metabolism, gluconeogenesis and lipolysis by qPCR and western blot. Then, we examined epinephrine-induced phosphorylation of PKA substrates to validate adrenergic sensitivity in each organ. Next, we measured hepatic and skeletal glycogen content, degree of breakdown by epinephrine and abundance of phosphorylated glycogen phosphorylase under hypoglycemia and that of phosphorylated glycogen synthase during recovery to evaluate glycogen turnover. Further, we performed pyruvate and lactate tolerance tests to assess gluconeogenesis. Additionally, we measured circulating FFA and glycerol to check lipolysis. The abovementioned studies were repeated in streptozotocin-induced diabetic rat model. Finally, we conducted epinephrine tolerance test to investigate systemic glycemic excursions to counterregulatory hormones. Saline-injected rats served as controls.

RESULTS

RH increased counterregulatory hormone GPCR signaling in liver and epidydimal white adipose tissue (eWAT), but not in skeletal muscle. For glycogen metabolism, RH did not affect total content or epinephrine-stimulated breakdown in liver and skeletal muscle. Although RH decreased expression of phosphorylated glycogen synthase 2, it did not affect hepatic glycogen biosynthesis during recovery from hypoglycemia or after fasting-refeeding. For gluconeogenesis, RH upregulated fructose 1,6-bisphosphatase 1 and monocarboxylic acid transporter 1 that imports lactate as precursor, resulting in a lower blood lactate profile during hypoglycemia. In agreement, RH elevated fasting blood glucose and caused higher glycemic excursions during pyruvate tolerance test. For lipolysis, RH did not affect circulating levels of FFA and glycerol after overnight fasting or upon epinephrine stimulation. Interestingly, RH upregulated the trophic fatty acid transporter FATP1 and glucose transporter GLUT4 to increase lipogenesis in eWAT. These aforementioned changes of gluconeogenesis, lipolysis and lipogenesis were validated in streptozotocin-diabetic rats. Finally, RH increased insulin sensitivity to accelerate glucose disposal, which was attributable to upregulated visceral adipose GLUT4.

CONCLUSIONS

RH caused metabolic adaptations related to counterregulation within peripheral organs. Specifically, adrenergic signaling was enhanced in liver and visceral fat, but not in skeletal muscle. Glycogen metabolism remained unchanged. Hepatic gluconeogenesis was augmented. Systemic lipolysis was unaffected, but visceral lipogenesis was enhanced. Insulin sensitivity was increased. These findings provided insights into mechanisms underlying clinical problems associated with intensive insulin therapy, such as high gluconeogenic flux and body weight gain.

Acrolein plays a culprit role in the pathogenesis of diabetic nephropathy in vitro and in vivo

OBJECTIVE

Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is a major chronic complication of diabetes and is the most frequent cause of kidney failure globally. A better understanding of the pathophysiology of DN would lead to the development of novel therapeutic options. Acrolein, an α,β-unsaturated aldehyde, is a common dietary and environmental pollutant.

DESIGN

The role of acrolein and the potential protective action of acrolein scavengers in DN were investigated using high-fat diet/ streptozotocin-induced DN mice and in vitro DN cellular models.

METHODS

Acrolein-protein conjugates (Acr-PCs) in kidney tissues were examined using immunohistochemistry. Renin-angiotensin system (RAS) and downstream signaling pathways were analyzed using quantitative RT-PCR and Western blot analyses. Acr-PCs in DN patients were analyzed using an established Acr-PC ELISA system.

RESULTS

We found an increase in Acr-PCs in kidney cells using in vivo and in vitro DN models. Hyperglycemia activated the RAS and downstream MAPK pathways, increasing inflammatory cytokines and cellular apoptosis in two human kidney cell lines (HK2 and HEK293). A similar effect was induced by acrolein. Furthermore, acrolein scavengers such as N-acetylcysteine, hydralazine, and carnosine could ameliorate diabetes-induced kidney injury. Clinically, we also found increased Acr-PCs in serum samples or kidney tissues of DKD patients compared to normal volunteers, and the Acr-PCs were negatively correlated with kidney function.

CONCLUSIONS

These results together suggest that acrolein plays a role in the pathogenesis of DN and could be a diagnostic marker and effective therapeutic target to ameliorate the development of DN.

[Effect of electroacupuncture combined with Zhuang-medicine-thread moxibustion on expression of apoptosis-related factors in gastric antrum of diabetic gastroparesis rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA) combined with Zhuang-medicine-thread moxibustion on expression of apoptosis-related factors in gastric antrum of diabetic gastroparesis (DGP) rats, so as to explore its mechanism underlying improvement of DGP.

METHODS

Male SD rats were randomly divided into normal, model, medication, EA, Zhuang-medicine-thread moxibustion (moxibustion) and EA+moxibustion (combination) groups (12 rats in each group). The DGP model was established by intraperitoneal injection of streptozotocin (STZ). Rats of the medication group were treated by gavage of 0.15 mg/mL mosapride citrate suspension （10 mL/kg）. EA (10 Hz/50 Hz, 2 mA, 20 min) or Zhuang-medicine-thread moxibustion (3 cones) was applied to "Zhongwan" (CV12), bilateral "Neiguan" (PC6) and bilateral "Sanyinjiao" (SP6) of the related groups, once a day for 3 weeks. The blood glucose, gastric emptying rate and intestinal propulsion rate of rats were measured. The apoptosis index of gastric antrum cells were observed by TUNEL staining. The protein and mRNA expressions of Caspase-3, B-cell lymphoma/leukemia-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in gastric antrum were detected by Wes-tern blot and real-time quantitative PCR, respectively.

RESULTS

Compared with the normal group, the blood glucose, the apoptosis index, the protein and gene expressions of Caspase-3 and Bax were significantly increased (P<0.01), and the gastric emptying rate, intestinal propulsive rate, the protein and gene expressions of Bcl-2 were considerably decreased (P<0.01) in the model group. In contrast to the model group, the blood glucose in the EA, moxibustion and combination groups, the apoptosis index in the 4 treatment groups, as well as Caspase-3 protein, Bax protein and mRNA expressions in the medication, EA and combination groups, Caspase-3 protein and mRNA, Bax mRNA expressions in the moxibustion group were significantly decreased (P<0.01, P<0.05); while the gastric emptying rate and intestinal propulsive rate in the 4 treatment groups, and Bcl-2 protein and mRNA expressions in the medication and combination groups, Bcl-2 mRNA expressions in the EA and moxibustion groups were obviously increased (P<0.01). The effects of EA+moxibustion were significantly superior to those of simple EA, moxibustion or medication in increasing gastric emptying rate and intestinal propulsive rate, and in lowering blood glucose (P<0.05, P<0.01). And the effects of the combination treatment were better than those of EA in lowering Caspase-3 protein and Bax mRNA expressions (P<0.01), and in increasing Bcl-2 protein and mRNA expressions (P<0.05, P<0.01). Also the effects of the combination treatment were better than those of moxibustion in lowering the apoptosis index, Caspase-3 protein, and Bax protein and mRNA expressions (P<0.01, P<0.05), and in increasing Bcl-2 protein expression (P<0.05).

CONCLUSION

EA combined with Zhuang-medicine-thread moxibustion can reduce blood glucose and improve gastrointestinal motility in DGP rats, which may be related to its effect in regulating of Caspase-3, Bax and Bcl-2 expression.

Intranasal Insulin Attenuates the Long-Term Adverse Effects of Neonatal Hyperglycemia on the Hippocampus in Rats

Hyperglycemia due to relative hypoinsulinism is common in extremely preterm infants and is associated with hippocampus-mediated long-term cognitive impairment. In neonatal rats, hypoinsulinemic hyperglycemia leads to oxidative stress, altered neurochemistry, microgliosis, and abnormal synaptogenesis in the hippocampus. Intranasal insulin (INS) bypasses the blood-brain barrier, targets the brain, and improves synaptogenesis in rodent models, and memory in adult humans with Alzheimer's disease or type 2 diabetes, without altering the blood levels of insulin or glucose. To test whether INS improves hippocampal development in neonatal hyperglycemia, rat pups were subjected to hypoinsulinemic hyperglycemia by injecting streptozotocin (STZ) at a dose of 80 mg/kg i.p. on postnatal day (P) 2 and randomized to INS, 0.3U twice daily from P3-P6 (STZ + INS group), or no treatment (STZ group). The acute effects on hippocampal neurochemical profile and transcript mRNA expression of insulin receptor (Insr), glucose transporters (Glut1, Glut4, and Glut8), and poly(ADP-ribose) polymerase-1 (Parp1, a marker of oxidative stress) were determined on P7 using in vivo 1H MR spectroscopy (MRS) and qPCR. The long-term effects on the neurochemical profile, microgliosis, and synaptogenesis were determined at adulthood using 1H MRS and histochemical analysis. Relative to the control (CONT) group, mean blood glucose concentration was higher from P3 to P6 in the STZ and STZ + INS groups. On P7, MRS showed 10% higher taurine concentration in both STZ groups. qPCR showed 3-folds higher Insr and 5-folds higher Glut8 expression in the two STZ groups. Parp1 expression was 18% higher in the STZ group and normal in the STZ + INS group. At adulthood, blood glucose concentration in the fed state was higher in the STZ and STZ + INS groups. MRS showed 59% higher brain glucose concentration and histochemistry showed microgliosis in the hippocampal subareas in the STZ group. Brain glucose was normal in the STZ + INS group. Compared with the STZ group, phosphocreatine and phosphocreatine/creatine ratio were higher, and microglia in the hippocampal subareas fewer in the STZ + INS group (p < 0.05 for all). Neonatal hyperglycemia was associated with abnormal glucose metabolism and microgliosis in the adult hippocampus. INS administration during hyperglycemia attenuated these adverse effects and improved energy metabolism in the hippocampus.

CaMKIV/CREB/BDNF signaling pathway expression in prefrontal cortex, amygdala, hippocampus and hypothalamus in streptozotocin-induced diabetic mice with anxious-like behavior

Individuals with diabetes mellitus (DM) tend to manifest anxiety and depression, which could be related to changes in the expression of calcium/calmodulin-dependent protein kinase IV (CaMKIV), transcription factor cyclic AMP-responsive element binding protein (CREB), phosphorylated CREB (pCREB) and brain-derived neurotrophic factor (BDNF) in different brain regions. The objective of this study was to determine whether mice with type 1 diabetes (T1DM) induced with streptozotocin show a profile of anxious-type behaviors and alterations in the expression/activity of CaMKIV, CREB, pCREB and BDNF in different regions of the brain (prefrontal cortex, amygdala, hippocampus and hypothalamus) in comparison to non-diabetic mice (NDB). Mice with 3 months of chronic DM showed an anxious-like behavioral profile in two anxiety tests (Open Field and Elevated Plus Maze), when compared to NDB. There were significant differences in the expression of cell signaling proteins: diabetic mice had a lower expression of CaMKIV in the hippocampus, a greater expression of CREB in the amygdala and hypothalamus, as well as a lower pCREB/CREB in hypothalamus than NDB mice (P < 0.05). This is the first study evaluating the expression of CaMKIV in the brain of animals with DM, who presented lower expression of this protein in the hippocampus. In addition, it is the first time that CREB was evaluated in amygdala and hypothalamus of animals with DM, who presented a higher expression. Further research is necessary to determine the possible link between expression of CaMKIV and CREB, and the behavioral profile of anxiety in diabetic animals.

Protective effects of CHIP overexpression and Wharton's jelly mesenchymal-derived stem cell treatment against streptozotocin-induced neurotoxicity in rats

Diabetic neuropathy is a common complication of diabetes mellitus, posing a challenge in treatment. Previous studies have indicated the protective role of mesenchymal stem cells against several disorders. Although they can repair nerve injury, their key limitation is that they reduce viability under stress conditions. We recently observed that overactivation of the carboxyl terminus of heat shock protein 70 (Hsp70) interacting protein (CHIP) considerably rescued cell viability under hyperglycemic stress and played an essential role in promoting the beneficial effects of Wharton's jelly-derived mesenchymal stem cells (WJMSCs). Thus, the present study was designed to unveil the protective effects of CHIP-overexpressing WJMSCs against neurodegeneration using in vivo animal model based study. In this study, western blotting observed that CHIP-overexpressing WJMSCs could rescue nerve damage observed in streptozotocin-induced diabetic rats by activating the AMPKα/AKT and PGC1α/SIRT1 signaling pathway. In contrast, these signaling pathways were downregulated upon silencing CHIP. Furthermore, CHIP-overexpressing WJMSCs inhibited inflammation induced in the brains of diabetic rats by suppressing the NF-κB, its downstream iNOS and cytokines signaling nexus and enhancing the antioxidant enzyme system. Moreover, TUNEL assay demonstrated that CHIP carrying WJMSCs suppressed the apoptotic cell death induced in STZ-induced diabetic group. Collectively, our findings suggests that CHIP-overexpressing WJMSCs might exerts beneficial effects, which may be considered as a therapeutic strategy against diabetic neuropathy complications.

Functional chicken-liver hydrolysates ameliorate insulin resistance and cognitive decline in streptozotocin-induced diabetic mice

As part of the slaughtering processing in Taiwan, approximately 10,000 metric tons of broiler livers are produced yearly. However, these livers are regarded as waste. Our team has successfully developed a functional chicken-liver hydrolysate (CLH) with several useful activities. It has been reported that there is a positive relationship between diabetes mellitus (DM) patients and cognitive decline. To maximize broiler-livers' utilization and add value, we investigated the modulative effects of the CLHs on glucose homeostasis and cognitive decline in streptozotocin (STZ) induced diabetic mice. After a 9-wk experiment, CLH supplementation lowered blood glucose by increasing GLUT4 protein expressions in the brains, livers, and muscles of STZ-induced mice (P < 0.05). CLHs also enhanced antioxidant capacities in the livers and brains of STZ-induced mice. Amended memory and alternation behavior were tested by using water and Y-maze assays (P < 0.05). Besides, STZ-induced mice with CLH supplementation had less contracted neuron bodies in the hippocampus and lower (P < 0.05) Aβ depositions in the dentate gyrus area. Less AGE accumulation and apoptosis-related proteins (RAGE, JNK, and activated Caspase 3) in the brains of STZ-induced mice were also detected by supplementing CLHs (P < 0.05). In conclusion, the results from this study offer not only scientific evidence on the amelioration of insulin resistance and cognitive decline in hyperglycemia but also add value to this byproduct.

Influence of Tangeretin on the Exponential Regression of Inflammation and Oxidative Stress in Streptozotocin-Induced Diabetic Nephropathy

Diabetes is an amalgamation of metabolic disorders marked by hyperglycemia. Over time diabetes brings up several other complications with it like cardiovascular disease, retinopathy, neuropathy, and nephropathy. among which diabetic nephropathy (DN) is the one we are concerned about in the present study. Diabetes management requires following a healthy lifestyle with proper medication. Most of the anti-diabetic drugs available at present come with adverse side effects. Nature has provided us with several components that are anti-diabetic in nature which has fewer or no side effects and tangeretin is one among them. Tangeretin is a natural flavonoid abundantly present in orange peel and tangerines. Our study is designed to evaluate tangeretin, as an anti-diabetic medication especially for patients suffering from diabetic nephropathy. The procured healthy rats were first divided into four groups: the group I was maintained as healthy control and the others were subjected to the induction of diabetes by i.p. injection of streptozotocin (STZ) at the concentration of 55mg/kg b.wt .Then, the diabetic rats were further divided into three groups: group II was used as the diabetic control rats and the group III and group IV were administered with tangeretin (25mg/kg b.wt) and positive control drug metformin (150mg/kg b.wt) for 8 weeks. The body weight, blood glucose, and serum insulin levels were estimated at week 0 and week 8. Reactive oxygen species (ROS) inhibitory effect, antioxidant, antilipidemic, nephroprotective, and anti-inflammatory effects of tangeretin on the diabetic-induced rats were evaluated at the end of week 8 in addition to the histopathological assessment of the sections of the kidneys of the experimental rats. All the test results concluded that tangeretin was able to significantly decelerate the progression of DN in STZ-induced diabetic rats.

[Tetrahydropalmatine alleviated diabetic neuropathic pain by inhibiting activation of microglia via p38 MAPK signaling pathway]

Neuropathic pain is one of the common complications of diabetes. Tetrahydropalmatine(THP) is a main active component of Corydalis Rhizoma with excellent anti-inflammatory and pain-alleviating properties. This study aims to investigate the therapeutic effect of THP on diabetic neuropathic pain(DNP) and the underlying mechanism. High-fat and high-sugar diet(4 weeks) and streptozotocin(STZ, 35 mg·kg~(-1), single intraperitoneal injection) were employed to induce type-2 DNP in rats. Moreover, lipopolysaccharide(LPS) was used to induce the activation of BV2 microglia in vitro to establish an inflammatory cellular model. Fasting blood glucose(FBG) was measured by a blood glucose meter. Mechanical withdrawal threshold(MWT) was assessed with von Frey filaments, and thermal withdrawal latency(TWL) with hot plate apparatus. The protein expression levels of OX42, inducible nitric oxide synthase(iNOS), CD206, p38, and p-p38 were determined by Western blot, the fluorescence expression levels of OX42 and p-p38 in the dorsal horn of the rat spinal cord by immunofluorescence, the mRNA content of p38 and OX42 in rat spinal cord tissue by qRT-PCR, and levels of nitric oxide(NO), interleukin-1β(IL-1β), interleukin-6(IL-6), tumor necrosis factor-α(TNF-α), interleukin-10(IL-10), and serum fasting insulin(FINS) by enzyme-linked immunosorbent assay(ELISA). RESULTS:: showed that the mo-del group demonstrated significant decrease in MWT and TWL, with pain symptoms. THP significantly improved the MWT and TWL of DNP rats, inhibited the activation of microglia and p38 MAPK signaling pathway in rat spinal cord, and ameliorated its inflammatory response. Meanwhile, THP promoted the change of LPS-induced BV2 microglia from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, suppressed the activation of the p38 MAPK signaling pathway, decreased the expression levels of inflammatory factors NO, IL-1β, IL-6, and TNF-α, and increased the expression level of anti-inflammatory factor IL-10. The findings suggested that THP can significantly ameliorate the pain symptoms of DNP rats possibly by inhibiting the inflammatory response caused by M1 polarization of microglia via the p38 MAPK pathway.

Echinops spinosus effect against diabetes and its hepatorenal complications: total extract and flavonoids fraction

The perennial plant Echinops spinosus (ES) grows in the Hail area of Saudi Arabia, and its traditional formulations are often employed in folk medicine. The goal of this study is to identify the active components present in Hail Echinops spinosus and to investigate the anti-diabetic properties of both ES total extract (ESTE) and its high flavonoids fraction (ESHFF) in experimental diabetes induced by streptozotocin (STZ) injection in rats. Forty-two rats were divided into six groups. Diabetes was induced using STZ (55 mg/kg). Seven days after STZ administration, the diabetic animals were treated daily with ESTE, ESHFF, or metformin (MET) as a standard anti-diabetic drug for 28 days. Blood and tissues samples were collected for biochemical, molecular, and histological investigations. Both ESTE and ESHFF demonstrated anti-diabetic properties, as evidenced by lowering glucose levels and increasing the levels of insulin, insulin receptor expression rate, and glycogen synthesis. Additionally, ESTE as well as ESHFF alleviated diabetic complications in the kidneys and liver by decreasing oxidative stress, modulating inflammatory mediators, and suppressing the apoptotic cascade along with correcting diabetic dyslipidemia. It could be deduced that Hail ES extracts could play a role in the treatment of type 2 diabetes and diabetes-related lesions as well as oxidative damage in hepatic and renal tissues.

Loss of urotensin II receptor diminishes hyperglycemia and kidney injury in streptozotocin-treated mice

Beyond the CNS, urotensin II (UII) and its receptor (UT) are functionally expressed in peripheral tissues of the endocrine, cardiovascular, and renal systems. The expression levels of UII and UT in the kidney and circulating UII levels are increased in diabetes. UII also promotes mesangial proliferation and matrix accumulation in vitro. Here, we evaluate the effect of UT deletion on the development of hyperglycemia and diabetic kidney disease (DKD) in streptozotocin (STZ)-treated mice. Ten-week-old WT and UT knockout (KO) mice were injected with STZ for 5 days to induce diabetes. Blood glucose levels were measured weekly, and necropsy was performed 12 weeks after STZ injection. UT ablation slowed hyperglycemia and glucosuria in STZ-treated mice. UT KO also ameliorated STZ-induced increase in HbA1c, but not STZ-induced decrease in plasma insulin levels. However, STZ-induced increases in plasma glucagon concentration and immunohistochemical staining for glucagon in pancreatic islets were lessened in UT KO mice. UT ablation also protected against STZ-induced kidney derangements, including albuminuria, mesangial expansion, glomerular lesions, and glomerular endoplasmic reticulum stress. UT is expressed in a cultured pancreatic alpha cell line, and its activation by UII triggered membrane depolarization, T- and L-type voltage-gated Ca2+channel-dependent Ca2+influx, and glucagon secretion. These findings suggest that apart from direct action on the kidneys to cause injury, UT activation by UII may result in DKD by promoting hyperglycemia via induction of glucagon secretion by pancreatic alpha cells.

Physalis pubescens L. alleviates testicular disruptions associated with streptozotocin-induced diabetes in male Wistar rats, Rattus norvegicus

Testicular impairment is a serious complication of diabetes that is mediated by oxidative stress and inflammation. Physalis has antioxidative and anti-inflammatory actions. Thus, the present study investigated the ameliorative role of Physalis juice (PJ) prepared from the fruits against testicular damages in streptozotocin (STZ)-induced diabetic rats. Adult male Wistar rats were divided randomly into five groups (n=6): control, orally administered 5 mL PJ/kg daily (PJ), injected intraperitoneally with a single dose of 55 mg STZ/kg without treatment (STZ), or treated daily with PJ (STZ+PJ) or with 500 mg metformin/kg (STZ+Met), for 28 days. The STZ group showed a marked elevation in the blood glucose level by 230%, whereas remarkable declines in the serum levels of testosterone (44%), follicle-stimulating hormone (FSH) (48%), and luteinizing hormone (LH) (36%), as compared to controls. In comparison to controls, the testis of the STZ group showed remarkable declines in the testis weight (15%), the glutathione (GSH) content (45%), mRNA and protein levels of B-cell lymphoma-2 (Bcl-2) (48 and 35%), mRNA and activities of superoxide dismutase (SOD) (63 and 40%), catalase (CAT) (56 and 31%), glutathione peroxidase (GPx) (51 and 44%), and glutathione reductase (GR) (62 and 43%), whereas marked elevations in the levels of interleukin-1 beta (IL-1β (169%), tumor necrosis factor-alfa (TNFα) (85%), nitric oxide (NO) (96%), malondialdehyde (MDA) (83%), mRNA and protein levels of Bcl-2-associated X protein (Bax) (400 and 61%), and mRNA level of caspase-3 (Cas-3) (370%). Some histopathological alterations were observed in the testicular tissue of the STZ group. In contrast, PJ markedly alleviated all the abovementioned disturbances. In conclusion, PJ at a dose of 5 mL/kg attenuated the diabetes-associated testicular impairments, which may be due to its antioxidative, anti-inflammatory, and antiapoptotic actions.

Diabetes mellitus causes changes in the activity and expression of brain tryptophan-5-hydroxylases and in the number of serotonergic neurons, which do not return to normal with insulin treatment

INTRODUCTION

Diabetes mellitus (DM) inhibits brain serotonin biosynthesis through changes in tryptophan-5-hydroxylase (TPH) activity and expression.

OBJECTIVES

To determine whether DM-induced changes in brain TPH1 or TPH2 expression and in the number of serotonergic neurons return to normal in diabetic rats treated with insulin.

METHODS

Rats with streptozotocin-induced diabetes were divided in two groups: one treated with insulin and the other without treatment. On day 14, brain stems were obtained in order to quantify L-tryptophan and 5-hydroxytryptamine levels, as well as to determine TPH activity. The expression of TPH1 and TPH2 by West-ern blot, and the number of serotonergic neurons by immunohistochemistry.

RESULTS

In diabetic rats, a decrease in the levels of L-tryptophan, 5-hydroxytryptamine, and TPH activity was confirmed, as well as lower TPH1 and TPH2 expression and lower numbers of serotonergic neurons. When diabetic rats were treated with insulin, L-tryptophan returned to normal, but not 5-hy-droxytryptamine, TPH expression, or the number of serotonergic neurons.

CONCLUSIONS

DM chronically inhibits the synthesis of brain 5-hydroxytryptamine through changes in TPH1 and TPH2 expression and a decrease in the number of serotonergic neurons, which persist despite insulin treatment.

Mitigating effect of single or combined administration of nanoparticles of zinc oxide, chromium oxide, and selenium on genotoxicity and metabolic insult in fructose/streptozotocin diabetic rat model

This research was intended to evaluate the antidiabetic effect of single or combined administration of nanoparticles of zinc oxide nanoparticles (ZnONPs), chromium oxide nanoparticles (Cr₂O₃NPs), and selenium nanoparticles (SeNPs), on genetic and metabolic insult in fructose/streptozotocin diabetic rat model. Type 2 diabetes mellitus was induced by feeding sixty adult male albino rats with a high fructose diet accompanied by a single i.p. injection of streptozotocin (STZ). The rats were divided into 6 groups (10 rats/each) and the doses of nanoparticles were 10 mg/kg b.wt for ZnONPs, 1 mg/kg b.wt for Cr₂O₃, and 0.4 mg/kg b.wt for SeNPs. The results displayed that diabetes significantly decreased bodyweight, serum insulin, C-peptide, adiponectin levels, erythrocyte glutathione peroxidase, serum superoxide dismutase activities, high-density lipoprotein cholesterol (HDL-C), and total antioxidant capacity while causing a substantial increase in serum glucose, C-reactive protein, atherogenic index, HOMA-IR, malondialdehyde, lipid profile, interleukin-6 levels, and liver function and kidney function parameters. Furthermore, the findings showed a decrease in insulin receptor substrate-1 (IRS-1) hepatic mRNA expression level and peroxisome proliferator-activated receptor (PPAR-γ) adipocyte mRNA expression level in type 2 diabetic rats. DNA damage was confirmed by performing the comet assay. Moreover, histological observation of pancreatic and hepatic tissues was performed, which were consistent with the biochemical results. The present study confirmed that oral administration of ZnONPs, Cr₂O₃NPs, SeNPs, and their mixture improved all the biochemical and genetic parameters toward normal levels and ameliorated the diabetic consequences that were manifested by restricting cellular DNA damage which maintaining pancreatic and hepatic tissues from oxidative damage. The best reported antidiabetic effect was observed in the mixture administered group.

Probiotics Fermentation Technology, a Novel Kefir Product, Ameliorates Cognitive Impairment in Streptozotocin-Induced Sporadic Alzheimer's Disease in Mice

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment. Gut microbiota dysfunction (dysbiosis) is implicated in the pathology of AD and is associated with several detrimental consequences, including neurotransmitter depletion, oxidative stress, inflammation, apoptosis, and insulin resistance, which all contribute to the onset of AD. The objective of this study was to assess the effectiveness of Probiotics Fermentation Technology (PFT), a kefir product, in alleviating AD symptoms via regulation of the gut microbiota using a streptozotocin- (STZ-) induced AD mouse model and to compare its activity with simvastatin, which has been proven to effectively treat AD. Mice received one intracerebroventricular injection of STZ (3 mg/kg). PFT (100, 300, 600 mg/kg) and simvastatin (20 mg/kg) were administered orally for 3 weeks. PFT supplementation mitigated STZ-induced neuronal degeneration in the cortex and hippocampus, restored hippocampal acetylcholine levels, and improved cognition in a dose-dependent manner. These effects were accompanied by reductions in oxidative damage, proinflammatory cytokine expression, apoptosis, and tau hyperphosphorylation. Moreover, PFT hindered amyloid plaque accumulation via the enhancement of insulin-degrading enzyme. These beneficial effects were comparable to those produced by simvastatin. The results suggest that PFT can alleviate AD symptoms by regulating the gut microbiota and by inhibiting AD-related pathological events.

Streptozotocin-induced type 1 and 2 diabetes in rodents: a model for studying diabetic cardiac autonomic neuropathy

Background

Several animal models are continually being developed to study diabetic complication. Several conflicting regimen for diabetes induction exist in the literature with varying dose strength and regimen for different study interest in diabetes. This study aims to show the effect of high dose streptozotocin (STZ) on the one hand compared with multiple low doses after high fat diet induction on diabetic cardiac autonomic neuropathy (DCAN).

Methodology

Eighty-four Wistar rats were used to demonstrate DCAN induction using 2 approaches one for T1DM (STZ 50mg/kg) and the other for T2DM (HFD for 8 weeks with STZ 25mg/Kg daily for five days). DCAN features were assessed using invasive biomarkers, histology patterns and cardiac nerve densities.

Results

Diabetes induction rate was 76% and 89% in T1DM and T2DM model respectively. T1DM group had significant weight loss, reduced c-peptide, and insulin level post induction. The T2DM additionally showed significantly higher total cholesterol and Homeostatic model assessment (HOMA) compared with control. Serum levels of catecholamine, choactase, nerve growth factor and cardiac nerve density confirms development of DCAN.

Conclusion

High single dose of STZ and HFD with multiple low doses of STZ may be recommended for DCAN study in T1DM and T2DM rat model respectively.

Minocycline prevents depression-like behavior in streptozotocin-induced diabetic mice

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia. Diabetic patients are known to have a higher prevalence and a higher risk of depression compared with the general population. The pathogenesis of diabetes-related depression is unclear, and the treatment is not well-established. Therefore, the prevention of diabetes-related depression is important for improving the quality of life of diabetic patients. Minocycline, a second-generation tetracycline antibiotic, has recently gained attention as a new agent for depression. In this study, we investigated the effect of minocycline on diabetes-related depression in a streptozotocin-induced mouse model of diabetes. Eight-week-old male C57BL/6 mice were injected with streptozotocin (200 mg/kg, i.p.). Seven days after injection, the mice received minocycline treatment through drinking water. We compared these mice with vehicle-treated control mice and diabetic mice not receiving minocycline treatment. On day 34, depression-like behavior was investigated using the forced swim test. On the following day, brain samples were collected, and formalin-fixed, paraffin-embedded specimens were prepared for immunohistochemistry. Compared with the control group, the diabetic mice not receiving minocycline treatment showed a prolonged duration of immobility in the forced swim test, the observation being interpreted as a depression-like behavior. Immunohistochemistry revealed an increase in microglia with an activated morphology in the diabetic mice without minocycline treatment. The expression of tumor necrosis factor alpha in microglia was increased. In addition, a decrease in the number of doublecortin-positive immature neurons was found in the hippocampus of diabetic mice. Minocycline treatment of diabetic animals prevented the depression-like behavior and microglial activation; however, minocycline did not reverse impaired hippocampal neurogenesis. These results indicate that minocycline has a preventive effect on diabetes-related depression. Inhibition of microglial activation would be a critical target for the antidepressant mechanism of minocycline. Impaired hippocampal neurogenesis was observed in diabetic mice; however, this may not be involved in the pathogenesis of depression.

The renoprotective effects of Heme Oxygenase-1 during contrast-induced acute kidney injury in preclinical diabetic models

OBJECTIVES

Contrast-induced acute kidney injury (CI-AKI) is an important clinical problem that can be aggravated by diabetes mellitus, a major risk factor. However, heme oxygenase-1 (HO-1), a promising therapeutic target, can exert antioxidant effects against CI-AKI. Thus, we investigated the role of HO-1 in CI-AKI in the presence of diabetes mellitus.

METHODS

Twenty-eight male Wistar rats weighing 250-300g were subjected to left uninephrectomy, and concomitantly, diabetes induced by streptozotocin (65 mg/kg). After 12 weeks, iodinated contrast (meglumine ioxithalamate, 6 mL/kg) and hemin (HO-1 inducer-10 mg/k) were administered 60 min before iodinated contrast treatment. The rats were randomly divided into four groups: control, diabetes mellitus (DM), DM iodinated contrast (DMIC), and DMIC hemin (DMICH). Kidney function, albuminuria, oxidative profile, and histology were assessed. All experimental data were subjected to statistical analyses.

RESULTS

CI-AKI in preclinical diabetic models decreased creatinine clearance and increased urinary neutrophil gelatinase-associated lipocalin (NGAL) levels and the degree of albuminuria. Additionally, the levels of oxidative and nitrosative stress metabolites (urinary peroxides, thiobarbituric acid-reactive substances, and NO) were elevated, while thiol levels in kidney tissue were reduced. Kidney histology showed tubular cell vacuolization and edema. HO-1 inducer treatment improved kidney function and reduced urinary the NGAL levels. The oxidative profile showed an increase in the endogenous thiol-based antioxidant levels. Additionally, the tubular injury score was reduced following HO-1 treatment.

CONCLUSIONS

Our findings highlight the renoprotective effects of HO-1 in CI-AKI and preclinical diabetic models. Therefore, HO-1 ameliorates kidney dysfunction, reduces oxidative stress, and prevents cell necrosis.

Intracerebroventricular streptozotocin administration impairs mitochondrial calcium homeostasis and bioenergetics in memory-sensitive rat brain regions

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cardinal manifestation of cognitive dysfunction. The limitation to avail a successful drug candidate encourages researchers to establish an appropriate animal model in the novel anti-AD drug discovery process. In this context, the mechanism of mitochondrial dysfunction in cognitive deficit animals is yet to be established for intracerebroventricular injection of streptozotocin (ICV-STZ). Experimental dementia was induced in male rats by ICV-STZ on day-1 (D-1) of the experimental protocol at a sub-diabetogenic dose (3 mg/kg) twice at an interval of 48 h into both rat lateral ventricles. ICV-STZ caused cognitive decline in terms of increase in the escape latency on D-14 to D-17 and, decrease in the time spent and percentage of distance travelled in the target quadrant during Morris water maze and decrease in the spontaneous alteration behavior during Y-maze tests in rats. Further, ICV-STZ decreased the level of acetylcholine and activity of choline acetyltransferase and increased the activity of acetylcholinesterase in rat hippocampus, pre-frontal cortex and amygdala. Interestingly, ICV-STZ increased the mitochondrial calcium in addition to decrease in the mitochondrial function, integrity and bioenergetics in all rat brain regions. Further, ICV-STZ enhanced the levels of expression of NR1 subunit of N-methyl-D-aspartate receptor, mitochondrial calcium uniporter and sodium-calcium exchanger in these rat brain regions. Thus, NR1-dependent mitochondrial calcium accumulation could be considered as a major attribute to the animal model of ICV-STZ-induced AD-like manifestations. Further, drugs targeting to manage mitochondrial calcium homeostasis could best be studied in this animal model.

Astragalus polysaccharides protect renal function and affect the TGF-/Smad signaling pathway in streptozotocin-induced diabetic rats

OBJECTIVES

The objective was to observe the effects of Astragalus polysaccharides on diabetes and on regulation of the TGF-β/Smad signaling pathway.

METHODS

A type 2 diabetic rat model was established with a high-fat diet in combination with low-dose streptozotocin (35 mg/kg). Astragalus polysaccharides were applied as treatment intervention and changes in blood glucose and kidney morphology and function were assessed.

RESULTS

Eight weeks after model establishment, kidney weight as a proportion of total weight (KW/TW) in the high-, medium-, and low-dose Astragalus polysaccharide groups was significantly lower than that in the model group, and the KW/TW value gradually decreased with increasing dose of polysaccharides in each treatment group. Fasting blood glucose in the low- and medium-dose Astragalus polysaccharide groups was numerically lower than that in the model group and fasting blood glucose in rats in the high-dose group was significantly lower than that in the model group. Levels of 24-hour urinary microalbumin, creatinine, blood urea nitrogen, collagens I, III, and IV, α-smooth muscle actin, transforming growth factor-β1, and Smad3 in Astragalus polysaccharide groups (all doses) were significantly lower than those in the model group.

CONCLUSIONS

Astragalus polysaccharide significantly improved blood glucose and protected kidney function in a rat diabetes model.

Light deprivation reduces the severity of experimental diabetic retinopathy

Illumination of the retina is a major determinant of energy expenditure by its neurons. However, it remains unclear whether light exposure significantly contributes to the pathophysiology of common retinal disease. Driven by the premise that light exposure reduces the metabolic demand of the retina, recent clinical trials failed to demonstrate a benefit for constant illumination in the treatment of diabetic retinopathy. Here, we instead ask whether light deprivation or blockade of visual transduction could modulate the severity of this common cause of blindness. We randomized adult mice with two different models of diabetic retinopathy to 1-3 months of complete dark housing. Unexpectedly, we find that diabetic mice exposed to short or prolonged light deprivation have reduced diabetes-induced retinal pathology, using measures of visual function, compared to control animals in standard lighting conditions. To corroborate these results, we performed assays of retinal vascular health in diabetic Gnat1^-/- and Rpe65^-/- mice, which lack phototransduction. Both mutants displayed less diabetes-associated retinal vascular disease compared to respective wild-type controls. Collectively, these results suggest that light-induced visual transduction promotes the development of diabetic retinopathy and implicate photoreceptors as an early source of visual pathology in diabetes.

Ficus deltoidea extract down-regulates protein tyrosine phosphatase 1B expression in a rat model of type 2 diabetes mellitus: a new insight into its antidiabetic mechanism

Ficus deltoidea var. deltoidea Jack (FD) is a well-known plant used in Malay folklore medicine to lower blood glucose in diabetic patients. For further research of the antihyperglycemic mechanisms, the protein tyrosine phosphatase 1B (PTP1B)-inhibitory effect of FD was analysed both in vitro and in vivo. To optimise a method for FD extraction, water, 50, 70, 80, 90 and 95 % ethanol extracts were prepared and determined for their total phenolic and triterpene contents, and PTP1B-inhibition capacity. Among the tested extracts, 70 % ethanol FD extract showed a significant PTP1B inhibition (92·0 % inhibition at 200 µg/ml) and high phenolic and triterpene contents. A bioassay-guided fractionation of the 70 % ethanol extract led to the isolation of a new triterpene (3β,11β-dihydroxyolean-12-en-23-oic acid; F3) along with six known compounds. In vivo, 4 weeks' administration of 70 % ethanol FD extract (125, 250 and 500 mg/kg/d) to streptozotocin-nicotinamide-induced type 2 diabetic rats reversed the abnormal changes of blood glucose, insulin, total Hb, GLUT2, lipid profile, and oxidative stress in liver and pancreas. Moreover, FD reduced the mRNA expression of the key gluconeogenic enzymes (phosphoenolpyruvate carboxykinase and glucose 6-phosphatase) and restored insulin receptor and GLUT2 encoding gene (Slc2a2) expression. In addition, FD significantly down-regulated the hepatic PTP1B gene expression. These results revealed that FD could potentially improve insulin sensitivity, suppress hepatic glucose output and enhance glucose uptake in type 2 diabetes mellitus through down-regulation of PTP1B. Together, our findings give scientific evidence for the traditional use of FD as an antidiabetic agent.

Intracerebroventricular streptozotocin induces behavioral impairments and increases short‑term C3 gene expression in the hippocampus of Wistar rats

A non‑transgenic rat model based on intracerebroventricular injection of streptozotocin (STZ) has been used as an animal model to investigate mechanisms associated to the late onset of sporadic Alzheimer's disease, such as anatomical and behavioral impairments. However, molecular aspects related to gene expression, mainly in the hippocampus, require more investigation. Thus, this study evaluated the early and late cognitive functions and hippocampal gene expression after STZ administration. Male Wistar rats were divided into 4 groups: STZ (injected bilaterally), control group for the early memory function evaluation (1 month after surgery = phase 1, same volume of vehicle), and the same treatment for the late memory function evaluation (4 months after surgery = phase 2). The animals were observed in the elevated plus maze to assess behaviors related to anxiety, risk‑assessment and fear‑related memories. The behavioral tests were followed by brain removal and hippocampal dissection for RNA extraction and qRT‑PCR to assess the expression levels of 4 Alzheimer's disease related genes: Mapt, Apoe, C3 and Ps‑1. Animals from both phases showed increased time percentage and number of entries into the open arms, indicating risk behavior associated with anxiety, and an increased time percentage in the center square for both exposures (re‑test) when compared to the control group, suggesting working memory impairment related to an aversive event. Statistical analyses indicated that the STZ group presented alterations in anxiety, memory and risk assessment responses. Additionally, one month after STZ administration, C3 gene assays revealed an increased expression. Therefore, current data indicate that neuroinflammatory events linked to the expression of pro inflammatory cytokines such as C3 are related to memory, anxiety and decision-making alterations.

Effects of ghrelin on gastric distention sensitive neurons in the arcuate nucleus of hypothalamus and gastric motility in diabetic rats

This study was performed to observe the effects of ghrelin on the activity of gastric distention (GD) sensitive neurons in the arcuate nucleus of hypothalamus (Arc) and on gastric motility in vivo in streptozocin (STZ) induced diabetes mellitus (DM) rats. Electrophysiological results showed that ghrelin could excite GD-excitatory (GD-E) neurons and inhibit GD-inhibitory (GD-I) neurons in the Arc. However, fewer GD-E neurons were excited by ghrelin and the excitatory effect of ghrelin on GD-E neurons was much weaker in DM rats. Gastric motility research in vivo showed that microinjection of ghrelin into the Arc could significantly promote gastric motility and it showed a dose-dependent manner. The effect of ghrelin promoting gastric motility in DM rats was weaker than that in normal rats. The effects induced by ghrelin could be blocked by growth hormone secretagogue receptor (GHSR) antagonist [d-Lys-3]-GHRP-6 or BIM28163. RIA and real-time PCR data showed that the levels of ghrelin in the plasma, stomach and ghrelin mRNA in the Arc increased at first but decreased later and the expression of GHSR-1a mRNA in the Arc maintained a low level in DM rats. The present findings indicate that ghrelin could regulate the activity of GD sensitive neurons and gastric motility via ghrelin receptors in the Arc. The reduced effects of promoting gastric motility induced by ghrelin could be connected with the decreased expression of ghrelin receptors in the Arc in diabetes. Our data provide new experimental evidence for the role of ghrelin in gastric motility disorder in diabetes.

Insulin-resistant brain state: the culprit in sporadic Alzheimer's disease?

Severe abnormalities in brain glucose/energy metabolism and insulin signaling have been documented to take a pivotal role in early sporadic Alzheimer's disease (sAD) pathology. Indeed, the "insulin-resistant brain state" has been hypothesized to form the core of the neurodegenerative events that occur in sAD. In this vein, intracerebroventricular administration of subdiabetogenic doses of streptozotocin (STZ) in rats can induce an insulin-resistant brain state, which is proposed as a suitable experimental model of sAD. This review highlights the involvement of disturbed brain insulin metabolism in sAD etiopathogenesis. Furthermore, current knowledge demonstrates that central STZ administration produces brain pathology and behavioral changes that resemble changes found in sAD patients. The STZ-intracerebroventricularly treated rat represents a promising experimental tool in this field by providing new insights concerning early brain alterations in sAD, which can be translated in novel etiopathogenic and therapeutic approaches in this disease.

The influence of intracerebral streptozotocin and/or cadmium on memory processes in mice exposed to transient cerebral oligemia

The aim of the study was to examine the effects of simultaneous acute exposure to cadmium (Cd) and in the presence of streptozotozin (STZ) on the central nervous system (CNS) memory processes in mice subjected to transient brain ischemia. In order to obtain transient brain ischemia, operative occlusion of common carotid arteries for 30 min was performed. Cadmium chloride was administered intraperitoneally (ip) after the surgery at a single dose of 0.1 LD(50) (LD(50) = 14 mg/kg). Disturbances in glucose metabolism in the brain tissue were induced by bilateral intracerebral administration of STZ, a drug that inhibits the function of a neuronal insulin receptor. Long-term memory was evaluated by means of a step-through passive avoidance task. Spatial working memory expressed as spontaneous alternations was tested in the Y-maze test. Coexposure to brain oligemia and STZ on the CNS produced significant impairment of long-term memory processes in mice. An additional exposure to Cd exacerbated the deficits of these processes. These results indicate that brain oligemia, Cd, and altered glucose metabolism may aggravate adverse effects on memory.

Mechanisms of nitrosamine-mediated neurodegeneration: potential relevance to sporadic Alzheimer's disease

Streptozotocin (STZ) is a nitrosamine-related compound that causes Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment, brain insulin resistance, and brain insulin deficiency. Nitrosamines and STZ mediate their adverse effects by causing DNA damage, oxidative stress, lipid peroxidation, pro-inflammatory cytokine activation, and cell death, all of which occur in AD. We tested the hypothesis that exposure to N-nitrosodiethylamine (NDEA), which is widely present in processed/preserved foods, causes AD-type molecular and biochemical abnormalities in central nervous system (CNS) neurons. NDEA treatment of cultured post-mitotic rat CNS neurons (48 h) produced dose-dependent impairments in ATP production and mitochondrial function, and increased levels of 8-hydroxy-2'-deoxyguanosine, 4-hydroxy-2-nonenal, phospho-tau, amyloid-beta protein precursor-amyloid-beta (A beta PP-A beta), and ubiquitin immunoreactivity. These effects were associated with decreased expression of insulin, insulin-like growth factor (IGF)-I, and IGF-II receptors, and choline acetyltransferase. Nitrosamine exposure causes neurodegeneration with a number of molecular and biochemical features of AD including impairments in energy metabolism, insulin/IGF signaling mechanisms, and acetylcholine homeostasis, together with increased levels of oxidative stress, DNA damage, and A beta PP-A beta immunoreactivity. These results suggest that environmental exposures and food contaminants may play critical roles in the pathogenesis of sporadic AD.