Diabetes aggravates renal ischemia and reperfusion injury in rats by exacerbating oxidative stress, inflammation, and apoptosis
Diabetic patients are more susceptible to renal ischemia/reperfusion (I/R) injury (RI/RI) and have a poor prognosis, but the underlying mechanism remains unclear. The present study aimed to examine whether diabetes could worsen acute kidney injury induced by I/R in rats and clarify its mechanism. Control and streptozotocin-induced diabetic rats were subjected to 45 min renal pedicle occlusion followed by 24 h reperfusion. Tert-butylhydroquinone (TBHQ, 16.7 mg/kg) was administrated intraperitoneally 3 times at intervals of 8 h before ischemia. Serum and kidneys were harvested after reperfusion to evaluate renal function and histological injury. Enzyme-linked immunosorbent assays were used to test pro-inflammatory cytokines. Terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling assays were used to detect apoptotic cells, and western blotting was performed to determine the expression of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and cleaved caspase-3, as well as oxidative stress and inflammation-related proteins, such as nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Toll-like receptor 4 (TLR4), and nuclear factor-κB (NF-κB). Compared with control animals, diabetic rats undergoing I/R exhibited more severe tubular damage and renal dysfunction. Diabetes exacerbated oxidative stress, the inflammatory response, and apoptosis after renal I/R by enhancing TLR4/NF-κB signaling and blocking the Nrf2/HO-1 pathway. RI/RI in diabetic rats was attenuated by pretreatment with TBHQ (a Nrf2 agonist), which exerted anti-inflammatory and anti-apoptotic properties by inhibiting NF-κB signaling. These findings indicate that hyperglycemia exacerbates RI/RI by intensifying oxidative stress, inflammation, and apoptosis. Antioxidant pretreatment may alleviate RI/RI in diabetic patients.
Filtering through the role of NRF2 in kidney disease
Kidney disease affects ~ 10% of the population worldwide, resulting in millions of deaths each year. Mechanistically, oxidative stress is a major driver of various kidney diseases, and promotes the progression from acute to chronic injury, as well as renal cancer development. NRF2, the master regulator of redox balance, has been shown to protect against kidney disease through its negation of reactive oxygen species (ROS). However, many kidney diseases exhibit high levels of ROS as a result of decreased NRF2 protein levels and transcriptional activity. Many studies have tested the strategy of using NRF2 inducing compounds to alleviate ROS to prevent or slow down the progression of kidney diseases. Oppositely, in specific subsets of renal cancer, NRF2 is constitutively activated and contributes to tumor burden and overall poor prognosis; therefore, there has been a recent interest in studies investigating the benefits of NRF2 inhibition. In this review, we summarize recent literature investigating the role of NRF2 and oxidative stress in various kidney diseases, and how pharmacological modification of NRF2 signaling could play a protective role.
Linderane protects pancreatic β cells from streptozotocin (STZ)-induced oxidative damage
Linderane, an important bioactive compound in Linderae, improved glucose and lipid metabolism in ob/ob mice. However, the effect of linderane on streptozotocin (STZ)-induced oxidative damage in INS-1 cells remains unclear.
Conserved roles of glucose in suppressing reactive oxygen species-induced cell death and animal survival
Carbohydrate overconsumption increases blood glucose levels, which contributes to the development of various diseases including obesity and diabetes. It is generally believed that high glucose metabolism increases cellular reactive oxygen species (ROS) levels, damages insulin-secreting cells and leads to age-associated diabetic phenotypes. Here we find that in contrast, high glucose suppresses ROS production induced by paraquat in both mammalian cells and the round worm . The role of glucose in suppressing ROS is further supported by glucose's ability to alleviate paraquat's toxicity on development Consistently, we find that the ROS-regulated transcription factor SKN-1 is inactivated by glucose. As a result, the ROS/SKN-1-dependent lifespan extension observed in paraquat-treated animals, mitochondrial respiration mutant and germline-less mutant are all suppressed by glucose. Our study reveals an unprecedented interaction of glucose with ROS, which could have significant impact on our current understanding of glucose- and ROS-related diseases.
microRNA-155 silencing reduces sciatic nerve injury in diabetic peripheral neuropathy
Neuropathic pain represents one of the most common complications associated with diabetes mellitus (DM) that impacts quality of life. Accumulating studies have highlighted the involvement of microRNAs (miRNAs) in DM. Thus, the current study aimed to investigate the roles of microRNA-155 (miR-155) in diabetic peripheral neuropathy (DPN). In vitro DPN models were established using rat Schwann cells (SCs) by treatment with 5.5 mM glucose. Gain- or loss-of-function studies were conducted to determine the effect of miR-155 on Nrf2, cellular function, reactive oxygen species, and inflammation. Rat DNP models were established by streptozotocin injection and damage of sciatic nerve. Next, miR-155 antagomir or agomir was employed to investigate the effects associated with miR-155 on motor and sciatic nerve conduction velocity (MNCV, SNCV), angiogenesis and inflammatory response in vivo. Nrf2 was identified to be a target of miR-155 by dual-luciferase reporter gene assay. Silencing of miR-155 or restoration of Nrf2 promoted cell proliferation, inhibited apoptosis and alleviated inflammation in vitro. miR-155 antagomir-induced inhibition increased MNCV and SNCV, strengthened angiogenesis and alleviated inflammation in DPN rats. Additionally, the effects exerted by miR-155 were reversed when Nrf2 was restored both in vitro and in vivo. Taken together, the key findings of our study provide evidence indicating that miR-155 targeted and suppressed Nrf2 in DPN. miR-155 silencing was found to alleviate sciatic nerve injury in DPN, highlighting its potential as a therapeutic target for DPN.
Coptisine ameliorates renal injury in diabetic rats through the activation of Nrf2 signaling pathway
The present study has been designed and carried out to evaluate the potential of coptisine on diabetic nephropathy. Diabetes was induced in SD rats through one single intraperitoneal injection of streptozotocin (65 mg/kg) method, and then diabetic rats were orally administered with 25 mg/kg/day coptisine or 50 mg/kg/day coptisine for 8 weeks. Severe impairment of renal function in rats with diabetes was observed as indicated by increased urine protein excretion, kidney hypertrophy index, serum creatinine level, and blood urea nitrogen level. Oxidative stress damage was observed as indicated by increased levels of reactive oxygen species, malondialdehyde, and decreased levels of glutathione, superoxide dismutase, and catalase. However, these alterations in kidneys of rats with diabetes were alleviated by administration of coptisine. Furthermore, the expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2) and its targeted antioxidative genes heme oxygenase 1 and NADPH quinone oxidoreductase 1 in the diabetic kidneys were significantly increased after coptisine treatment. These results suggested that coptisine ameliorated oxidative renal injury in diabetic rats, and the possible mechanisms for the renoprotective effects of coptisine may be related to activation of the Nrf2 signaling pathway.
The anti-nephritic activity of a polysaccharide from okra (Abelmoschus esculentus (L.) Moench) via modulation of AMPK-Sirt1-PGC-1α signaling axis mediated anti-oxidative in type 2 diabetes model mice
Diabetic nephropathy (DN) with high morbidity and mortality is one of the most severe diabetes complications and affects nearly one-third of people with diabetes. Our present experiment was designed to assess the potential therapeutic of a polysaccharide purified from okra (OP) on DN in high-fat diet-fed and streptozotocin (STZ)-induced diabetic mice. We found that an 8-week treatment with OP could significantly decrease the 24-h urine protein (24-h UP), serum creatinine (Scr), serum urea nitrogen (SUN) and glycosylated hemoglobin (HbA1c) levels, which are regard as the biomarkers of renal injury. The results of immunohistochemical analysis and histopathological examination showed that the diabetic-induced microstructural changes and fibrosis in kidney can be alleviated by the administration of OP (400 mg/kg). Our immunofluorescences results demonstrated that OP (400 mg/kg) could greatly reduce the level of reactive oxygen species (ROS) in kidney. In addition, we also studied the level of SOD, GSH, CAT, HO-1, Nrf2, p-AMPK, PGC-1α, Sirt1, Bcl-2, cleaved caspase-3 and Bax in renal tissue by assay kit and western blot. Our results suggested that OP ameliorated DN in diabetic mice, which is possibly related to suppressing apoptosis and oxidative stress through activating AMPK-Sirt1-PGC-1α signaling axis.
Naringenin-induced HO-1 ameliorates high glucose or free fatty acids-associated apoptosis via PI3K and JNK/Nrf2 pathways in human umbilical vein endothelial cells
Naringenin (NG), a flavanone extracted from various plants, has potent vasoprotective effects likely related to the induction of heme oxygenase-1 (HO-1). In the current study, we investigated mechanisms underlying the effect of NG on HO-1 expression and high glucose (HG)- or free fatty acids (FFA)-induced apoptosis in human umbilical vein endothelial cells (HUVECs). First, we found that HUVECs exposed to NG exhibited enhanced HO-1 expression in a concentration- and time-dependent manner. Moreover, HUVECs treated with NG exhibited activation of phosphoinositide 3 kinase (PI3K)/Akt, extracellular-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). LY294002 (a PI3K inhibitor) and SP600125 (a JNK inhibitor) reduced NG-induced HO-1 expression, whereas BIRB796 (a p38 inhibitor) and PD98059 (an ERK inhibitor) had no effect. The cytoprotective effects of NG were correlated with activation of the transcription factor NF-E2-related factor 2 (Nrf2), a critical regulator of HO-1 expression. Indeed, the results of our experiments using LY294002 and SP600125 indicated that NG may stimulate Nrf2 through PI3K/Akt and JNK pathway activation. Moreover, treatment of HUVECs with Nrf2 siRNA decreased NG-induced HO-1 expression. Finally, pretreatment of HUVECs with NG remarkably reduced HG- or FFA-induced cell apoptosis, and this effect was greatly abrogated in the presence of SnPP (an HO-1 inhibitor). Above all, our data show that NG increased HO-1 expression and reduced HG- or FFA-induced cell apoptosis in HUVECs by upregulating PI3K, JNK, and Nrf2 pathways, which may confer an adaptive survival response in diabetes-induced vascular injury.
Ramadan diurnal intermittent fasting modulates SOD2, TFAM, Nrf2, and sirtuins (SIRT1, SIRT3) gene expressions in subjects with overweight and obesity
A growing body of evidence supports the impact of intermittent fasting on normalizing body metabolism and lowering oxidative stress and inflammation. Mounting evidence confirms that oxidative stress and chronic inflammation trigger the way for the development of metabolic diseases, such as diabetes. This research was conducted to evaluate the impact of Ramadan intermittent fasting (RIF) on the expression of cellular metabolism (SIRT1 and SIRT3) and antioxidant genes (TFAM, SOD2, and Nrf2).
Genome-Wide Association Study of Metabolic Syndrome Reveals Primary Genetic Variants at Locus in Indians
Indians, a rapidly growing population, constitute vast genetic heterogeneity to that of Western population; however they have become a sedentary population in past decades due to rapid urbanization ensuing in the amplified prevalence of metabolic syndrome (MetS). We performed a genome-wide association study (GWAS) of MetS in 10,093 Indian individuals (6,617 MetS and 3,476 controls) of Indo-European origin, that belong to our previous biorepository of The Indian Diabetes Consortium (INDICO). The study was conducted in two stages-discovery phase ( = 2,158) and replication phase ( = 7,935). We discovered two variants within/near the gene-rs1800775 and rs3816117-associated with MetS at genome-wide significance level during replication phase in Indians. Additional loci rs7205804, rs1532624, rs3764261, rs247617, and rs173539 also cropped up as modest signals in Indians. Haplotype association analysis revealed GCCCAGC as the strongest haplotype within the locus constituting all seven signals. In combined analysis, we perceived a novel and functionally relevant sub-GWAS significant locus-rs16890462 in the vicinity of gene. Overlaying gene regulatory data from ENCODE database revealed that single nucleotide polymorphism (SNP) rs16890462 resides in repressive chromatin in human subcutaneous adipose tissue as characterized by the enrichment of H3K27me3 and CTCF marks (repressive gene marks) and diminished H3K36me3 marks (activation gene marks). The variant displayed active DNA methylation marks in adipose tissue, suggesting its likely regulatory activity. Further, the variant also disrupts a potential binding site of a key transcription factor, NRF2, which is known for involvement in obesity and metabolic syndrome.
Therapeutic Potential of to Prevent Methylglyoxal-Induced Glucotoxicity in Familiar Diabetic Nephropathy
(LB) is often used in traditional medicine to remove toxins, replenish energy stores, and regulate various symptoms of diabetes. This study aimed to explore the use of LB as a therapeutic to prevent diabetic nephropathy in methylglyoxal (MGO)-treated models in vitro and in vivo. Western blotting, immunostaining, and biochemical assays were used to obtain several experimental readouts in renal epithelial cells (LLC-PK1) and BALB/c mice. These include: production of reactive oxygen species (ROS), formation of advanced glycation end-products (AGEs), expression of receptor for advanced glycation end-products (RAGE), apoptotic cell death, glucose levels, fatty acid and triglyceride levels, expression of pro-inflammatory cytokines IL-1β and TNF-α, glyoxalase 1 (Glo1), and nuclear factor erythroid 2-related factor 2 (Nrf2). Pretreatment with LB significantly reduced MGO-induced cellular apoptosis, intracellular production of ROS, and formation of AGEs to ameliorate renal dysfunction in vitro and in vivo. Interestingly, administering LB in MGO-treated cells and mice upregulated the expression of Nrf2 and Glo1, and downregulated the expression of IL-1β and TNF-α. Moreover, LB reduced MGO-induced AGE accumulation and RAGE expression in the kidneys, which subsequently reduced AGE-RAGE interactions. Overall, LB ameliorates renal cell apoptosis and corrects renal dysfunction in MGO-treated mice. These findings extend our understanding of the pathogenic mechanism of MGO-induced nephrotoxicity and regulation of the AGE/RAGE axis by .
CNTF and Nrf2 Are Coordinately Involved in Regulating Self-Renewal and Differentiation of Neural Stem Cell during Embryonic Development
There is high risk of fetal neurodevelopmental defects in pregestational diabetes mellitus (PGDM). However, the effective mechanism of hyperglycemia-induced neurodevelopmental negative effects, including neural stem cell self-renewal and differentiation, still remains obscure. Neuropoietic cytokines have been shown to play a vital part during nervous system development and in the coordination of neurons and gliocytes. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) dysfunction might be related to a reduction of self-protective response in brain malformation induced by hyperglycemia. We therefore evaluated the role of Nrf2 and neuropoietic cytokines in fetal neurodevelopmental defects induced by PGDM and determined the mechanisms involved. Our data reveal that PGDM dramatically impairs the developmental switch of neural stem cells from neurogenesis to gliogenesis, principally under the cooperative mediation of neuropoietic cytokine CNTF and Nrf2 antioxidative signaling. This indicates that CNTF and Nrf2 could be potentially used in the prevention or therapy of neurodevelopmental defects of PGDM offspring.
Bailcalin Protects against Diabetic Cardiomyopathy through Keap1/Nrf2/AMPK-Mediated Antioxidative and Lipid-Lowering Effects
Previous studies demonstrated that Bailcalin (BAI) prevented cardiac injuries under different disease models. Whether BAI protected against type 2 diabetes mellitus- (T2DM-) associated cardiomyopathy was investigated in this study. T2DM was established by the combination of streptozotocin injection and high-fat diet in mice. BAI was administered daily for 6 months. After evaluating cardiac functions, mice hearts were removed and processed for morphological, biochemical, and molecular mechanism analyses. Neonatal rat cardiomyocytes (NRCM) were isolated and treated with high glucose and palmitate (HG/Pal) for investigation. BAI significantly ameliorated T2DM-induced cardiomyocyte hypertrophy, interstitial fibrosis, and lipid accumulation accompanied by markedly improved cardiac functions in diabetic mice. Mechanically, BAI restored decreased phosphorylation of AMPK and enhanced expression and nuclei translocation of Nrf2. In experiments, BAI also prevented NRCM from HG/Pal-induced apoptosis and oxidative stress injuries by increasing p-AMPK and Nrf2 accumulation. The means by which BAI restored p-AMPK seemed to be related to the antioxidative effects of Nrf2 after silencing AMPK or Nrf2 in NRCM. Furthermore, BAI regulated Nrf2 by inhibiting Nrf2 ubiquitination and consequent degradation mediated by Keap1. This study showed that BAI alleviated diabetes-associated cardiac dysfunction and cardiomyocyte injuries and via Keap1/Nrf2/AMPK-mediated antioxidation and lipid-lowering effects. BAI might be a potential adjuvant drug for diabetes cardiomyopathy treatment.
Ginsenoside Rg1 ameliorates cardiac oxidative stress and inflammation in streptozotocin-induced diabetic rats
Ginsenoside Rg1 (GS Rg1), as an important active substance of Panax ginseng, has been proven to have elaborate cardioprotective effects. The purpose of this study was to detect that GS Rg1 attenuates cardiac oxidative stress and inflammation in streptozotocin (STZ)-induced diabetic rats (DM). Cardiac function was assessed by heart rate and blood pressure. Markers relevant to myocardial oxidative stress and antioxidant capacity, and inflammatory reaction factors were detected. The mRNA and protein expression were detected by RT-qPCR and Western blot, respectively. GS Rg1 treatment signiﬁcantly reduced the symptoms of cardiac hypertrophy and hypertension, and also decreased oxidative stress, inflammation response, NF-κB expression and NLRP3 inflammasome expression. GS Rg1 enhanced mitochondrial biogenesis by increasing PGC-1α, complex III and complex Ⅳ expression. GS Rg1 treatment significantly increased the expression of AMPK, Nrf2 and HO-1 in cardiac tissues. GS Rg1 exhibited protective effect against STZ-induced cardiac dysfunction, which is potentially associated with AMPK/Nrf2/HO-1 signal pathway.
Atorvastatin and Conditioned Media from Atorvastatin-Treated Human Hematopoietic Stem/Progenitor-Derived Cells Show Proangiogenic Activity but Not
Myeloid angiogenic cells (MAC) derive from hematopoietic stem/progenitor cells (HSPCs) that are mobilized from the bone marrow. They home to sites of neovascularization and contribute to angiogenesis by production of paracrine factors. The number and function of proangiogenic cells are impaired in patients with diabetes or cardiovascular diseases. Both conditions can be accompanied by decreased levels of heme oxygenase-1 (HMOX1), cytoprotective, heme-degrading enzyme. Our study is aimed at investigating whether precursors of myeloid angiogenic cells (PACs) treated with known pharmaceuticals would produce media with better proangiogenic activity and if such media can be used to stimulate blood vessel growth . We used G-CSF-mobilized CD34 HSPCs, FACS-sorted from healthy donor peripheral blood mononuclear cells (PBMCs). Sorted cells were predominantly CD133. CD34 cells after six days in culture were stimulated with atorvastatin (AT), acetylsalicylic acid (ASA), sulforaphane (SR), resveratrol (RV), or metformin (Met) for 48 h. Conditioned media from such cells were then used to stimulate human aortic endothelial cells (HAoECs) to enhance tube-like structure formation in a Matrigel assay. The only stimulant that enhanced PAC paracrine angiogenic activity was atorvastatin, which also had ability to stabilize endothelial tubes . On the other hand, the only one that induced heme oxygenase-1 expression was sulforaphane, a known activator of a HMOX1 inducer-NRF2. None of the stimulants changed significantly the levels of 30 cytokines and growth factors tested with the multiplex test. Then, we used atorvastatin-stimulated cells or conditioned media from them in the Matrigel plug angiogenic assay. Neither AT alone in control media nor conditioned media nor AT-stimulated cells affected numbers of endothelial cells in the plug or plug's vascularization. Concluding, high concentrations of atorvastatin stabilize tubes and enhance the paracrine angiogenic activity of human PAC cells . However, the effect was not observed . Therefore, the use of conditioned media from atorvastatin-treated PAC is not a promising therapeutic strategy to enhance angiogenesis.