Natural antioxidants in the treatment and prevention of diabetic nephropathy; a potential approach that warrants clinical trials

Burdock Fructooligosaccharide Protects Against Diabetic Nephropathy in Mice by Regulating Nrf2 Signaling

Diabetic nephropathy (DN) is a common complication of diabetes mellitus, with oxidative stress playing a critical role in its development. Burdock fructooligosaccharide (BFO), a major compound in Burdock, exhibits antioxidative effects. However, its mechanisms of action and effects on diabetic nephropathy are not clear enough. This study aims to explore the mechanisms of BFO and its impact on streptozotocin-induced diabetic nephropathy in mice. Male C57BL/6J mice were randomly divided into normal control, DN, and BFO groups. Relevant serum biochemical parameters were detected using kits. Renal injury was evaluated through fluorescence microscopy, histopathology, and transmission electron microscopy. Nrf2/HO-1 signaling was analyzed via quantitative real-time PCR, western blotting, and immunohistochemistry. In DN mice, BFO significantly reduced fasting blood glucose, kidney index, urine protein, serum creatinine, blood urea nitrogen, total cholesterol, triglyceride, and low-density lipoprotein cholesterol, while significantly increasing high-density lipoprotein, SOD, and CAT levels. Additionally, BFO protected against streptozotocin-induced renal injury, restored podocyte function, increased both mRNA and protein expression of Nrf2, HO-1, and Bcl-2, and decreased those of Bax. In conclusion, BFO can be used to treat streptozotocin-induced renal injury in mice and is a promising candidate for diabetic nephropathy treatment.

[Inhibition of miR-30d-5p promotes mitochondrial autophagy and alleviates high glucose-induced injury in podocytes]

OBJECTIVES

To study the role of microRNA (miR)-30d-5p in high glucose-induced podocyte injury.

METHODS

Podocytes were hyperglycated with 30 mmol/L glucose, transfected with miR-30d-5p inhibitor and mimic, and then treated with 1 mg/mL 3-methyladenine (3-MA). The transfection efficiency of miR-30d-5p was quantified by reverse transcription PCR. Apoptosis was detected by flow cytometry. The expressions of nephrin, microtubule-associated protein light chain (LC) 3Ⅱ/LC3Ⅰ, P62, autophagy-related gene (ATG) 5, PTEN induced putative kinase (PINK) 1 and Parkin gene (PARK2) were detected by Western blotting. The mito-chondrial membrane potential was detected by JC-1 fluorescent probe, and adenosine triphosphate (ATP) content in cells was detected by relevant kits.

RESULTS

Under high glucose induction, podocyte apoptosis increased, miR-30d-5p and P62 expressions were upregulated, while nephrin, ATG5, PINK1, PARK2 and LC3Ⅱ/LC3Ⅰ expressions decreased (all P<0.01). MiR-30d-5p inhibitor reversed the effect of high glucose on apoptosis, and the expression of ATG5, PINK1, PARK2, nephrin, LC3Ⅱ/LC3Ⅰ and P62 (all P<0.01). High glucose induced loss of mitochondrial membrane potential and ATP content in podocytes, while inhibition of miR-30d-5p increased them. Autophagy inhibitors 3-MA and miR-30d-5p mimics reversed the effects of miR-30d-5p inhibition on apoptosis, autophagy and mitochondrial function of podocytes induced by high glucose (all P<0.05).

CONCLUSIONS

Inhibition of miR-30d-5p may promote mitochondrial autophagy (mitophagy) by promoting the expression of ATG5, PINK1, PARK2 and alleviating high glucose-induced podocyte damage.

β-Arrestin-2 enhances endoplasmic reticulum stress-induced glomerular endothelial cell injury by activating transcription factor 6 in diabetic nephropathy

BACKGROUND

Glomerular endothelial cell (GENC) injury is a characteristic of early-stage diabetic nephropathy (DN), and the investigation of potential therapeutic targets for preventing GENC injury is of clinical importance.

AIM

To investigate the role of β-arrestin-2 in GENCs under DN conditions.

METHODS

Eight-week-old C57BL/6J mice were intraperitoneally injected with streptozotocin to induce DN. GENCs were transfected with plasmids containing siRNA-β-arrestin-2, shRNA-activating transcription factor 6 (ATF6), pCDNA-β-arrestin-2, or pCDNA-ATF6. Additionally, adeno-associated virus (AAV) containing shRNA-β-arrestin-2 was administered via a tail vein injection in DN mice.

RESULTS

The upregulation of β-arrestin-2 was observed in patients with DN as well as in GENCs from DN mice. Knockdown of β-arrestin-2 reduced apoptosis in high glucose-treated GENCs, which was reversed by the overexpression of ATF6. Moreover, overexpression of β-arrestin-2 Led to the activation of endoplasmic reticulum (ER) stress and the apoptosis of GENCs which could be mitigated by silencing of ATF6. Furthermore, knockdown of β-arrestin-2 by the administration of AAV-shRNA-β-arrestin-2 alleviated renal injury in DN mice.

CONCLUSION

Knockdown of β-arrestin-2 prevents GENC apoptosis by inhibiting ATF6-mediated ER stress in vivo and in vitro. Consequently, β-arrestin-2 may represent a promising therapeutic target for the clinical management of patients with DN.

Unlocking the mechanistic potential of Thuja occidentalis for managing diabetic neuropathy and nephropathy

Diabetes mellitus and its debilitating microvascular complications, including diabetic neuropathy and nephropathy, represent a growing global health burden. Despite advances in conventional therapies, their suboptimal efficacy and adverse effects necessitate exploring complementary and alternative medicine approaches. Thuja occidentalis, a coniferous tree species native to eastern North America, has gained significant attention for its potential therapeutic applications in various disorders, attributed to its rich phytochemical composition. The present comprehensive review evaluates the therapeutic potential of Thuja occidentalis in managing diabetic neuropathy and nephropathy, with a particular emphasis on elucidating the underlying cellular and molecular mechanisms. The review delves into the active constituents of Thuja occidentalis, such as essential oils, flavonoids, tannins, and proanthocyanidin compounds, which have demonstrated antioxidant, anti-inflammatory, and other beneficial properties in preclinical studies. Importantly, the review provides an in-depth analysis of the intricate signaling pathways modulated by Thuja occidentalis, including NF-κB, PI3K-Akt, JAK-STAT, JNK, MAPK/ERK, and Nrf2 cascades. These pathways are intricately linked to oxidative stress, inflammation, and apoptosis processes, which play pivotal roles in the pathogenesis of diabetic neuropathy and nephropathy. Furthermore, the review critically evaluates the evidence-based toxicological data of Thuja occidentalis as a more effective and comprehensive therapeutic strategy in diabetes complications. Therefore, the current review aims to provide a comprehensive understanding of the therapeutic potential of Thuja occidentalis as an adjunctive treatment strategy for diabetic neuropathy and nephropathy while highlighting the need for further research to optimize its clinical translation.

Intestinal flora and bile acid interactions impact the progression of diabetic kidney disease

In recent years, with the rapid development of omics technologies, researchers have shown that interactions between the intestinal flora and bile acids are closely related to the progression of diabetic kidney disease (DKD). By regulating bile acid metabolism and receptor expression, the intestinal flora affects host metabolism, impacts the immune system, and exacerbates kidney injury in DKD patients. To explore interactions among the gut flora, bile acids and DKD, as well as the related mechanisms, in depth, in this paper, we review the existing literature on correlations among the gut flora, bile acids and DKD. This review also summarizes the efficacy of bile acids and their receptors as well as traditional Chinese medicines in the treatment of DKD and highlights the unique advantages of bile acid receptors in DKD treatment. This paper is expected to reveal a new and important potential strategy for the clinical treatment of DKD.

Resveratrol delays the progression of diabetic nephropathy through multiple pathways: A dose-response meta-analysis based on animal models

OBJECTIVE

Accumulating experimental evidence has shown that resveratrol supplementation is effective for treating diabetic nephropathy (DN) in animal models. In this systematic review and meta-analysis, we assessed the effects and multiple mechanisms of resveratrol in animal models of DN.

METHODS

Before September 2023, preclinical literature was systematically searched and screened across PubMed, Web of Science, EMBASE, and the Cochrane Library. Forty-two studies were included, and the risk of bias tool from SYRCLE was used to assess the methodological quality. Pooled overall effect sizes of the results were generated by STATA 16.0.

RESULTS

The overall results provide preliminary evidence that the consumption of resveratrol can significantly reduce the mesangial index, glomerular basement membrane thickness, glomerular hypertrophy, serum creatinine, blood urea nitrogen, 24-h urinary protein, blood glucose, kidney index, total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels. In contrast, the levels of albumin and high-density lipoprotein cholesterol are significantly increased. However, resveratrol did not significantly reduce creatinine clearance or glycated hemoglobin levels. Dose-response analysis revealed that resveratrol was most effective at improving kidney function and reducing DN when administered at lower doses of ≤15 mg/kg/day or higher doses of 100-200 mg/kg/day, with significant improvements in biochemical kidney injury markers and a better effect on dysglycemia.

CONCLUSIONS

The benefits of resveratrol in DN are likely due to its anti-inflammatory, antioxidant, metabolic regulatory, and autophagy-promoting effects. To confirm these findings for clinical use, further large-scale, long-term, high-quality preclinical trials are warranted to accurately assess the anti-DN effects and safety of resveratrol.

Management of Microcomplications of Diabetes Mellitus: Challenges, Current Trends, and Future Perspectives in Treatment

Diabetes mellitus is a chronic metabolic disorder characterized by high blood sugar levels, which can lead to severe health issues if not managed effectively. Recent statistics indicate a significant global impact, with 463 million adults diagnosed worldwide and this projected to rise to 700 million by 2045. Type 1 diabetes is an autoimmune disorder where the immune system attacks pancreatic beta cells, reducing insulin production. Type 2 diabetes is primarily due to insulin resistance. Both types of diabetes are linked to severe microvascular and macrovascular complications if unmanaged. Microvascular complications, such as diabetic retinopathy, nephropathy, and neuropathy, result from damage to small blood vessels and can lead to organ and tissue dysfunction. Chronic hyperglycemia plays a central role in the onset of these complications, with prolonged high blood sugar levels causing extensive vascular damage. The emerging treatments and current research focus on various aspects, from insulin resistance to the intricate cellular damage induced by glucose toxicity. Understanding and intervening in these pathways are critical for developing effective treatments and managing diabetes long term. Furthermore, ongoing health initiatives, such as increasing awareness, encouraging early detection, and improving treatments, are in place to manage diabetes globally and mitigate its impact on health and society. These initiatives are a testament to the collective effort to combat this global health challenge.

Effect of a Triterpenoid-Rich Olive Oil on Chronic Kidney Disease in an Experimental Model of Diabetes Mellitus

The aim of this study was to assess the effect of triterpenoids on the development of diabetic nephropathy in an experimental model of diabetes mellitus. For this purpose, a destoned and dehydrated olive oil (DDOO) was used, comparing its effects to a destoned olive oil (DOO). DDOO had a higher triterpenoid content than DOO but an equal content of alcoholic polyphenols. Four study groups (n = 10 animals/group) were formed: healthy rats, diabetic control rats (DRs), and DRs treated orally with 0.5 mL/kg/day of DOO or DDOO for two months. DRs showed impaired renal function (proteinuria, increased serum creatinine, decreased renal creatinine clearance) and morphology (glomerular volume and glomerulosclerosis). These alterations correlated with increased systemic and renal tissue oxidative stress and decreased prostacyclin production. DDOO administration significantly reduced all variables of renal damage, as well as systemic and renal oxidative stress, to a greater extent than the effect produced by DOO. In conclusion, triterpenoid-rich olive oil may prevent kidney damage in experimental diabetes mellitus.

Beneficial Effects of Selenium on Kidney Injury via Nf-Kb and Aquaporin-1 Levels

Systemic inflammation is a serious condition that can affect various tissues and organs, such as the kidneys, and can be life-threatening. Selenium (Se) is an antioxidant and anti-inflammatory trace element. In this study, we aimed to examine the effects of Se, which has antioxidant and anti-inflammatory properties, on lipopolysaccharide (LPS)-induced kidney damage to maintain aquaporin-1 (AQP-1) levels. Four experimental rat groups (n = 8) consisting of the control, LPS alone, LPS + Se, and Se alone were so applied for 7 consecutive days. Upon sacrifice, histopathological results, diagnostic markers of kidney functions, oxidative stress, and inflammation were analyzed. Our results showed that LPS induced mononuclear cell infiltration, cellular residue, and protein deposition in the kidney proximal tubules, and also decreased total antioxidant status levels and increased total antioxidant status and oxidative stress index values. LPS increased the level of creatinine, increased the level of Nuclear Factor kappa B, which has an important role in the inflammation process, and decreased the levels of AQP-1 due to the damage it caused. Se has shown its effect by reversing all these situations. This data suggests that Se can be used as an additive to mitigate LPS-induced toxicity in the kidney.

Alpha-cyperone mitigates renal ischemic injury via modulation of HDAC-2 expression in diabetes: Insights from molecular dynamics simulations and experimental evaluation

Chronic diabetes mellitus is reported to be associated with acute kidney injury. The enzyme histone deacetylase-2 (HDAC-2) was found to be upregulated in diabetes-related kidney damage. Alpha-cyperone (α-CYP) is one of the active ingredients of Cyperus rotundus that possesses antioxidant and anti-inflammatory effects. We evaluated the effect of α-CYP on improving oxidative stress and tissue inflammation following renal ischemia/reperfusion (I/R) injury in diabetic rats. The effect of α-CYP on HDAC-2 expression in renal homogenates and in the NRK-52 E cell line was evaluated following renal I/R injury and high glucose conditions, respectively. Molecular docking was used to investigate the binding of α-CYP with the HDAC-2 active site. Both renal function and oxidative stress were shown to be impaired in diabetic rats due to renal I/R injury. Significant improvements in kidney/body weight ratio, creatinine clearance, serum creatinine, blood urea nitrogen (BUN), and uric acid were observed in diabetic rats treated with α-CYP (50 mg/kg) two weeks prior to renal I/R injury. α-CYP treatment also improved histological alterations in renal tissue and lowered levels of malondialdehyde, myeloperoxidase, and hydroxyproline. Treatment with α-CYP suppressed the increased HDAC-2 expression in the renal tissue of diabetic rats and in the NRK-52 E cell line. The molecular docking reveals that α-CYP binds to HDAC-2 with good affinity, ascertained by molecular dynamics simulations and binding free energy analysis. Overall, our data suggest that α-CYP can effectively prevent renal injury in diabetic rats by regulating oxidative stress, tissue inflammation, fibrosis and inhibiting HDAC-2 activity.

Diabetes and Renal Complications: An Overview on Pathophysiology, Biomarkers and Therapeutic Interventions

Diabetic kidney disease (DKD) is a major microvascular complication of both type 1 and type 2 diabetes. DKD is characterised by injury to both glomerular and tubular compartments, leading to kidney dysfunction over time. It is one of the most common causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Persistent high blood glucose levels can damage the small blood vessels in the kidneys, impairing their ability to filter waste and fluids from the blood effectively. Other factors like high blood pressure (hypertension), genetics, and lifestyle habits can also contribute to the development and progression of DKD. The key features of renal complications of diabetes include morphological and functional alterations to renal glomeruli and tubules leading to mesangial expansion, glomerulosclerosis, homogenous thickening of the glomerular basement membrane (GBM), albuminuria, tubulointerstitial fibrosis and progressive decline in renal function. In advanced stages, DKD may require treatments such as dialysis or kidney transplant to sustain life. Therefore, early detection and proactive management of diabetes and its complications are crucial in preventing DKD and preserving kidney function.

Beneficial effect of honokiol and magnolol on polyol pathway and oxidative stress parameters in the testes of diabetic rats

In diabetes hyperglycemia, excessive production of free radicals and present oxidative stress lead to many complications in the body, including male reproductive system disorders. To prevent the development of diabetic complications in the testes resulting from them, it seems beneficial to include compounds considered as natural antioxidants. Honokiol and magnolol are neolignans obtained from magnolia bark, which possess proven antioxidant properties. The aim of this study was to evaluate the effect of honokiol and magnolol on the parameters of oxidative stress, polyol pathway and glycation products in the testes as well as on selected biochemical parameters in the blood serum of rats with type 2 diabetes. The study was conducted on mature male Wistar rats with high fat diet and streptozotocin-induced type 2 diabetes. Neolignans-treated rats received honokiol or magnolol orally at the doses of 5 or 25 mg/kg, respectively, for 4 weeks. Parameters related to glucose and lipid homeostasis, basic serological parameters and sex hormones level in the serum as well as polyol pathway parameters, antioxidant enzyme activity, endogenous antioxidants level, sumaric parameters for oxidative stress and oxidative damage in the testes were estimated. Oral administration of honokiol and magnolol turned out to be beneficial in combating the effects of oxidative stess in the testes, but showed no favorable effects on serum biochemical parameters. Additionally, magnolol compared to honokiol revealed more advantageous impact indicating the reversal of the effects of diabetic complications in the male reproductive system and counteracted oxidative stress damages and polyol pathway disorders in the testes.

Insights into the Therapeutic uses of Plant Derive Phytocompounds onDiabetic Nephropathy

Diabetic nephropathy (DN) is one of the primary consequences of diabetes mellitus, affecting many people worldwide and is the main cause of death under the age of sixty. Reactive oxygen species (ROS) production rises during hyperglycemia and is crucial to the development of diabetic complications. Advanced glycation end products (AGEs) are produced excessively in a diabetic state and are accumulated in the kidney, where they change renal architecture and impair renal function. Another important targeted pathway for the formation of DN includes nuclear factor kappa-B (NF-kB), Nuclear factor E2-related factor 2 (Nrf2), NLR family pyrin domain containing 3 (NLRP3), protein kinase B/mammalian target of rapamycin (Akt/mTOR), and autophagy. About 40% of individuals with diabetes eventually acquire diabetic kidney disease and end-stage renal disease that needs hemodialysis, peritoneal dialysis, or kidney transplantation to survive. The current state of acceptable therapy for this kidney ailment is limited. The studies revealed that some naturally occurring bioactive substances might shield the kidney by controlling oxidative stress, renal fibrosis, inflammation, and autophagy. In order to provide new potential therapeutic lead bioactive compounds for contemporary drug discovery and clinical management of DN, this review was designed to examine the various mechanistic pathways by which conventional plants derive phytocompounds that are effective for the control and treatment of DN.

The Effects of Apigenin in the Treatment of Diabetic Nephropathy: A Systematic Review of Non-clinical Studies

PURPOSE

Diabetes is one of the important and growing diseases in the world. Among the most common diabetic complications are renal adverse effects. The use of apigenin may prevent the development and progression of diabetes-related injuries. The current study aims to review the effects of apigenin in the treatment of diabetic nephropathy.

METHODS

In this review, a systematic search was performed based on PRISMA guidelines for obtaining all relevant studies on "the effects of apigenin against diabetic nephropathy" in various electronic databases up to September 2022. Ninety-one articles were obtained and screened in accordance with the predefined inclusion and exclusion criteria. Seven eligible articles were finally included in this review.

RESULTS

The experimental findings revealed that hyperglycemia led to the decreased cell viability of kidney cells and body weight loss and an increased kidney weight of rats; however, apigenin administration had a reverse effect on these evaluated parameters. It was also found that hyperglycemia could induce alterations in the biochemical and renal function-related parameters as well as histopathological injuries in kidney cells or tissue; in contrast, the apigenin administration could ameliorate the hyperglycemia-induced renal adverse effects.

CONCLUSION

The results indicated that the use of apigenin could mitigate diabetes-induced renal adverse effects, mainly through its antioxidant, anti-apoptotic, and anti-inflammatory activities. Since the findings of this study are based on experimental studies, suggesting the use of apigenin (as a nephroprotective agent) against diabetic nephropathy requires further clinical studies.

Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia

Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.

Impact of In Vitro Digestion on the Digestibility, Amino Acid Release, and Antioxidant Activity of Amaranth (Amaranthus cruentus L.) and Cañihua (Chenopodium pallidicaule Aellen) Proteins in Caco-2 and HepG2 Cells

This study evaluated the impact of in vitro gastrointestinal digestion on the digestibility, amino acid release, and antioxidant activity of proteins from amaranth (Amarantus cruentus L.) and cañihua (Chenopodium pallidicaule Aellen). Antioxidant activity was assessed using ORAC, ABTS, DPPH, and cellular antioxidant activity (CAA) assays in human intestinal Caco-2 and hepatic Hep-G2 cell lines. The results showed that amaranth had higher protein digestibility (79.19%) than cañihua (71.22%). In addition, intestinal digestion promoted the release of essential amino acids, such as leucine, lysine, and phenylalanine, in both protein concentrates. Concentrations of amaranth and cañihua proteins, ranging from 0.125 to 1.0 mg mL-1, were non-cytotoxic in both cell lines. At a concentration of 0.750 mg mL-1, simulated gastrointestinal digestion enhanced cellular antioxidant activity. Intestinal digest fractions containing peptides >5 kDa were the principal contributors to CAA in both cell lines. Notably, cañihua proteins exhibited high CAA, reaching values of 85.55% and 82.57% in Caco-2 and HepG2 cells, respectively, compared to amaranth proteins, which reached 84.68% in Caco-2 and 81.06% in HepG2 cells. In conclusion, both amaranth and cañihua proteins, after simulated gastrointestinal digestion, showcased high digestibility and released peptides and amino acids with potent antioxidant properties, underscoring their potential health benefits.

Protective effect of eriodictyol against hyperglycemia-induced diabetic nephropathy in rats entails antioxidant and anti-inflammatory effects mediated by activating Nrf2

The pathogenesis of diabetic nephropathy (DN) involves cellular activation of oxidative stress and inflammation. Eriodictyol is a citrus-derived flavonoid with multiple pharmacological and protective effects in various conditions. The protective role of Eriodictyol against diabetes and diabetic nephropathy is less investigated. The current research aimed to explore the role of eriodictyol in protecting against DN prompted by streptozotocin in male rats and investigate some possible mechanisms of action. Diabetes was brought about in rats by an i.p injection of a lone dose (65 mg/kg). Five groups of rats were included (n = 8 each) as control (non-diabetic), eriodictyol (20 mg/kg, orally), STZ-diabetic, STZ + eriodictyol (20 mg/kg, orally), and STZ + eriodictyol (20 mg/kg, orally) + ML385 (30 µg/kg, i.p.). Kidney histology and the levels of some markers of kidney function, renal oxidative stress, and renal inflammation were analyzed in all groups of rats. Treatment with eriodictyol prevented the damage in the renal glomeruli and tubules and reduced renal immune cell infiltration in STZ-treated animals. It also spiked urinary creatinine excretion and reduced urine volume and urinary levels of albumin, monocyte chemoattractant protein 1 (MCP-1), urinary kidney injury molecule-1 (KIM-1), and nephrin in these diabetic rats. In addition, eriodictyol stimulated the nuclear protein accumulation of Nrf2 and boosted the expression of superoxide dismutase (SOD), glutathione (GSH), heme oxygenase-1 (HO-1), and catalase (CAT) in the diabetic rat kidneys. In concomitance, it reduced the nuclear levels of NF-κB and levels of interleukine-6 (IL-6), malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α) and attenuated the reduction in renal ATP levels and the increase in the mitochondria transition pore opening (mtTPT). However, the administration of eriodictyol did not affect rats' body weights and fasting glucose and insulin levels but significantly reduced serum levels of cholesterol, triglycerides, LDL-c, and oxidized LDL-c (ox-LDL-c). In conclusion, eriodictyol prevents STZ-induced nephropathy by a hypolipidemic effect and concomitant antioxidant and anti-inflammatory effects mediated by activating Nrf2/NF-κB/antioxidant axis.

Oxidative stress, free radicals and antioxidants: potential crosstalk in the pathophysiology of human diseases

Introduction: Free radicals are reactive oxygen species that constantly circulate through the body and occur as a side effect of many reactions that take place in the human body. Under normal conditions, they are removed from the body by antioxidant processes. If these natural mechanisms are disrupted, radicals accumulate in excess and contribute to the development of many diseases. Methodology: Relevant recent information on oxidative stress, free radicals, reactive oxidative species, and natural and synthetic antioxidants was collected by researching electronic databases such as PubMed / Medline, Web of Science, and Science Direct. Results: According to the analysed studies, this comprehensive review provided a recent update on oxidative stress, free radicals and antioxidants and their impact on the pathophysiology of human diseases. Discussion: To counteract the condition of oxidative stress, synthetic antioxidants must be provided from external sources to supplement the antioxidant defense mechanism internally. Because of their therapeutic potential and natural origin, medicinal plants have been reported as the main source of natural antioxidants phytocompounds. Some non-enzymatic phytocompounds such as flavonoids, polyphenols, and glutathione, along with some vitamins have been reported to possess strong antioxidant activities in vivo and in vitro studies. Thus, the present review describes, in brief, the overview of oxidative stress-directed cellular damage and the unction of dietary antioxidants in the management of different diseases. The therapeutic limitations in correlating the antioxidant activity of foods to human health were also discussed.

Diosgenin Inhibits ROS Generation by Modulating NOX4 and Mitochondrial Respiratory Chain and Suppresses Apoptosis in Diabetic Nephropathy

Diosgenin (DIO) is a dietary steroid sapogenin possessing multiple biological functions, such as the amelioration of diabetes. However, the remission effect of DIO on diabetic nephropathy (DN) underlying oxidative stress and cell apoptosis remains unclear. Here, the effect of DIO on ROS generation and its induced cell apoptosis was studied in vitro and in vivo. Renal proximal tubular epithelial (HK-2) cells were treated with DIO (1, 2, 4 µM) under high glucose (HG, 30 mM) conditions. DN rats were induced by a high-fat diet combined with streptozotocin, followed by administration of DIO for 8 weeks. Our data suggested that DIO relieved the decline of HK-2 cell viability and renal pathological damage in DN rats. DIO also relieved ROS (O2- and H2O2) production. Mechanistically, DIO inhibited the expression of NOX4 and restored mitochondrial respiratory chain (MRC) complex I-V expressions. Further, DIO inhibited mitochondrial apoptosis by ameliorating mitochondrial membrane potential (MtMP) and down-regulating the expressions of CytC, Apaf-1, caspase 3, and caspase 9, while up-regulating Bcl2 expression. Moreover, the ER stress and its associated cell apoptosis were inhibited through decreasing PERK, p-PERK, ATF4, IRE1, p-CHOP, and caspase 12 expressions. Collectively, DIO inhibited ROS production by modulating NOX4 and MRC complexes, which then suppressed apoptosis regulated by mitochondria and ER stress, thereby attenuating DN.

Effectiveness of analog of Humanin in ameliorating streptozotocin-induced diabetic nephropathy in Sprague Dawley rats

Diabetes mellitus(DM) is associated with numerous complications, including nephropathy, which principally occur due to hyperglycemia-induced oxidative stress and inflammation. Humanin(HN), a novel peptide generated from mitochondria, has anti-oxidant and anti-inflammatory potential as observed in different disease models. However, role of HN in diabetic nephropathy (DN) has not yet been explored. This study aimed to evaluate biochemical and molecular aspects of the effects of HN analog, Humanin-glycine([S14G]-humanin) on streptozotocin (STZ)-induced rat model of DN. Ninety Sprague Dawley (SD) rats were randomly segregated into three groups - A (control), B (disease control) and C (treatment). DM type-I was induced in group B and C via single intra-peritoneal dose of STZ (45mg/Kg). Seven days following STZ injection, rats were deemed diabetic if their blood glucose level was >250mg/dL. Subsequently, diabetic rats in group C were injected with [S14G]-humanin intra-peritoneally (0.4mg/Kg/day) for sixteen weeks. Biochemical analysis revealed that diabetic rats had markedly elevated levels of serum glucose, creatinine, BUN, TNF-α, and kidney tissue SOD. Whereas, significant decline was detected in serum insulin and albumin levels. All these parameters were significantly reversed in group C after administering [S14G]-humanin. Moreover, qRT-PCR analysis displayed up-regulation of pro-inflammatory (IL-18, IL-6, IL-1α, IL-1β, TNF-α) and down-regulation of anti-inflammatory cytokines (IL-10, IL-1RN, IL-4) in diabetic rats (group B). [S14G]-humanin treatment significantly reversed the expression IL-18 and IL-1α, however, change in relative expression of IL-6, IL-1β, TNF-α and anti-inflammatory cytokines was insignificant(group C). Conclusively, the findings of this study depicted potential therapeutic role of [S14G]-humanin in pre-clinical rodent model of DN.

Novel acetic acid derivatives containing quinazolin-4(3H)-one ring: Synthesis, in vitro, and in silico evaluation of potent aldose reductase inhibitors

Aldose reductase (AR) is a crucial enzyme of the polyol pathway through which glucose is metabolized under conditions of hyperglycemia related to diabetes. A series of novel acetic acid derivatives containing quinazolin-4(3H)-one ring (1-22) was synthesized and tested for in vitro AR inhibitory effect. All the target compounds exhibited nanomolar activity against the target enzyme, and all compounds displayed higher activity as compared to the reference drug epalrestat. Among them, Compound 19, named 2-(4-[(2-[(4-methylpiperazin-1-yl)methyl]-4-oxoquinazolin-3(4H)-ylimino)methyl]phenoxy)acetic acid, displayed the strongest inhibitory effect with a KI value of 61.20 ± 10.18 nM. Additionally, these compounds were investigated for activity against L929, nontumoral fibroblast cells, and MCF-7, breast cancer cells using the MTT assay. Compounds 16 and 19 showed lower toxicity against the normal L929 cells. The synthesized compounds' (1-22) absorption, distribution, metabolism, and excretion properties were also evaluated. Molecular docking simulations were used to look into the possible binding mechanisms of these inhibitors against AR.

Nephroprotective Effect of Fennel (Foeniculum vulgare) Seeds and Their Sprouts on CCl4-Induced Nephrotoxicity and Oxidative Stress in Rats

Functional and nutritional characteristics of seed sprouts and their association with oxidative stress-related disorders have recently become a focus of scientific investigations. The biological activities of fennel seeds (FS) and fennel seed sprouts (FSS) were investigated in vitro and in vivo. The total phenolic content (TPC), total flavonoids (TF), total flavonols (TFF), and antioxidant activity (AOA) of FS and FSS were examined. HPLC and GC-MS analyses for FS and FSS were carried out. Consequently, the nephroprotective and antioxidative stress potential of FS and FSS extracts at 300 and 600 mg kg^-1 on CCl₄-induced nephrotoxicity and oxidative stress in rats was investigated. In this context, kidney relative weight, blood glucose level (BGL), lipid profile, kidney function (T. protein, albumin, globulin, creatinine, urea, and blood urea nitrogen (BUN)), and oxidative stress biomarkers (GSH, CAT, MDA, and SOD) in the rat's blood as well as the histopathological alteration in kidney tissues were examined. Results indicated that the sprouting process of FS significantly improved TPC, TF, TFL, and AOA in vitro. HPLC identified nineteen compounds of phenolic acids and their derivatives in FS. Thirteen phenolic compounds in FS and FSS were identified, the highest of which was vanillic acid. Six flavonoids were also identified with a predominance of kaempferol. GC-MS indicated that the trans-anethole (1-methoxy-4-[(E)-prop-1-enyl]benzene) component was predominant in FS and FSS, significantly increasing after sprouting. In in vivo examination, administering FS and FSS extracts ameliorated the BGL, triglycerides (TG), total cholesterol (CHO), and their derivative levels compared to CCl₄-intoxicated rats. A notable improvement in FS and FSS with 600 mg kg^-1 compared to 300 mg kg^-1 was observed. A dose of 600 mg FSS kg^-1 reduced the TG, CHO, and LDL-C and increased HDL-C levels by 32.04, 24.62, 63.00, and 67.17% compared to G2, respectively. The atherogenic index (AI) was significantly improved with 600 mg kg^-1 of FSS extracts. FS and FSS improved kidney function, reduced malondialdehyde (MDA), and restored the activity of reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT). Both FS and FSS extracts attenuated the histopathological alteration in CCl₄-treated rats. Interestingly, FSS extract presented better efficiency as a nephroprotection agent than FS extract. In conclusion, FSS can potentially restore oxidative stability and improve kidney function after acute CCl₄ kidney injury better than FS. Therefore, FS and FSS extracts might be used for their promising nephroprotective potential and to help prevent diseases related to oxidative stress. Further research on their application in humans is highly recommended.

Piceatannol Protects against High Glucose-Induced Injury of Renal Tubular Epithelial Cells via Regulating Carbonic Anhydrase 2

INTRODUCTION

We here evaluated the efficacy of piceatannol (PIC) in high glucose (HG)-induced injury of renal tubular epithelial cells HK-2.

METHODS

After the establishment of an HG-induced cell injury model and the treatment with PIC at both high and low concentrations and/or acetazolamide (ACZ, the inhibitor of carbonic anhydrase 2 [CA2]), MTT and flow cytometry assays were carried out to confirm the viability and apoptosis of HK-2 cells. The levels of oxidative stress markers lactate dehydrogenase (LDH), malondialdehyde (MDA), and reactive oxygen species (ROS), the ratio of glutathione/oxidized glutathione (GSH/GSSG), and the CA2 activity were determined. Both quantitative reverse-transcription polymerase chain reaction and Western blot were used to calculate the expressions of CA2 (the predicted target gene of PIC via intersecting the data from bioinformatic analyses) and AKT pathway-related (phosphatase and tensin homolog [PTEN], phosphorylated [p]-AKT, AKT) and apoptosis-related proteins (Bcl-2 and cleaved caspase-3).

RESULTS

HG suppressed cell viability and the levels of GSH/GSSG ratio, CA2, pThr308-AKT/AKT, pSer473-AKT/AKT, and Bcl-2, while promoting cell apoptosis, the levels of LDH, MDA, and ROS, and the expressions of PTEN and cleaved caspase-3. All effects of HG were reversed by PIC at a high concentration. CA2 was predicted and identified as the target of PIC. In HG-treated HK-2 cells, additionally, ACZ reversed the effects of PIC on the viability, apoptosis, and levels of both oxidative stress markers and AKT pathway- and apoptosis-related factors.

CONCLUSION

PIC protects against HG-induced injury of HK-2 cells via regulating CA2.

The Effect of the Extra Virgin Olive Oil Minor Phenolic Compound 3',4'-Dihydroxyphenylglycol in Experimental Diabetic Kidney Disease

The aim of this study was to analyze the possible nephroprotective effect of 3',4'-dihydroxyphenylglycol (DHPG), a polyphenolic compound of extra virgin olive oil (EVOO), on renal lesions in an experimental model of type 1 diabetes. Rats were distributed as follows: healthy normoglycemic rats (NDR), diabetic rats treated with saline (DR), and DR treated with 0.5 mg/kg/day or 1 mg/kg/day of DHPG. DR showed a significantly higher serum and renal oxidative and nitrosative stress profile than NDR, as well as reduced prostacyclin production and renal damage (defined as urinary protein excretion, reduced creatinine clearance, increased glomerular volume, and increased glomerulosclerosis index). DHPG reduced the oxidative and nitrosative stress and increased prostacyclin production (a 59.2% reduction in DR and 34.7-7.8% reduction in DHPG-treated rats), as well as 38-56% reduction in urinary protein excretion and 22-46% reduction in glomerular morphological parameters (after the treatment with 0.5 or 1 mg/kg/day, respectively). Conclusions: DHPG administration to type 1-like diabetic rats exerts a nephroprotective effect probably due to the sum of its antioxidant (Pearson's coefficient 0.68-0.74), antinitrosative (Pearson's coefficient 0.83), and prostacyclin production regulator (Pearson's coefficient 0.75) effects.

Effects of antioxidants on diabetic kidney diseases: mechanistic interpretations and clinical assessment

Diabetic kidney disease (DKD) is more prevalent with an increase in diabetes mellitus. Oxidative stress is a major factor in the occurrence and progression of DKD. Defending against oxidative stress and restoring antioxidant defense might be key to preventing and treating DKD. The purpose of this article is to provide an explanation of how oxidative stress affects DKD, conduct a systematic review and meta-analysis on DKD, and examine the effect of antioxidants on the disease. An analysis of 19 randomized controlled trials showed that the use of antioxidants could reduce UAE (albumin excretion rate) in patients with DKD (SMD: - 0.31; 95% CI [- 0.47, - 0.14], I² = 0%), UACR (urine albumin/creatinine ratio) (SMD: - 0.60; 95% CI [- 1.15, - 0.06], I² = 89%), glycosylated hemoglobin (hbA1c) (MD: - 0.61; 95% CI [- 1.00, - 0.21], I² = 93%) and MDA (malonaldehyde) (SMD:-1.05; 95% CI [- 1.87, - 0.23], I² = 94%), suggesting that antioxidants seemed to have therapeutic effects in patients with DKD, especially in reducing proteinuria and hbA1c. The purpose of this study is to provide new targets and ideas for drug research and clinical treatment of DKD.

Oxidative Stress and NRF2/KEAP1/ARE Pathway in Diabetic Kidney Disease (DKD): New Perspectives

Diabetes mellitus (DM) is one of the most debilitating chronic diseases worldwide, with increased prevalence and incidence. In addition to its macrovascular damage, through its microvascular complications, such as Diabetic Kidney Disease (DKD), DM further compounds the quality of life of these patients. Considering DKD is the main cause of end-stage renal disease (ESRD) in developed countries, extensive research is currently investigating the matrix of DKD pathophysiology. Hyperglycemia, inflammation and oxidative stress (OS) are the main mechanisms behind this disease. By generating pro-inflammatory factors (e.g., IL-1,6,18, TNF-α, TGF-β, NF-κB, MCP-1, VCAM-1, ICAM-1) and the activation of diverse pathways (e.g., PKC, ROCK, AGE/RAGE, JAK-STAT), they promote a pro-oxidant state with impairment of the antioxidant system (NRF2/KEAP1/ARE pathway) and, finally, alterations in the renal filtration unit. Hitherto, a wide spectrum of pre-clinical and clinical studies shows the beneficial use of NRF2-inducing strategies, such as NRF2 activators (e.g., Bardoxolone methyl, Curcumin, Sulforaphane and their analogues), and other natural compounds with antioxidant properties in DKD treatment. However, limitations regarding the lack of larger clinical trials, solubility or delivery hamper their implementation for clinical use. Therefore, in this review, we will discuss DKD mechanisms, especially oxidative stress (OS) and NRF2/KEAP1/ARE involvement, while highlighting the potential of therapeutic approaches that target DKD via OS.

Ameliorative and Antioxidative Potential of Lactobacillus plantarum-Fermented Oat (Avena sativa) and Fermented Oat Supplemented with Sidr Honey against Streptozotocin-Induced Type 2 Diabetes in Rats

The ameliorative and antioxidative stress effects of probiotic-enriched fermented oat (FOE) or fermented oat with honey (HFOE) extracts on streptozotocin-induced diabetes in rats were examined. The total phenolic content (TPC) and antioxidant activity (AOA) were increased in FOE and HFOE after 72 h of fermentation, and γ-aminobutyric acid (GABA) reached 7.35 mg 100 g-1 in FOE and 8.49 mg 100 g-1 in HFOE. The β-glucan levels were slightly decreased to 2.45 g 100 g-1 DW in FOE and 2.63 g 100 g-1 DW in HFOE. The antidiabetic and hypolipidemic properties of FOE and HFOE were studied in a designed animal model with seven treated groups for 6 weeks. Groups were treated as follows: group 1 (negative group, NR) and group 2 (diabetic rats, DR) were administered 7 mL distilled water orally per day; group 3 (DR + MET) rats were orally administered 50 mg standard drug Metformin kg-1 daily; group 4 (DR + FOE1) diabetic rats were orally administered 3.5 mL FOE daily; group 5 (DR + FOE2) rats were orally administered 7 mL FOE daily; group 6 (DR + HFOE1) rats were orally administered 3.5 mL HFOE daily; and group 7 (DR + HFOE2) rats were orally administered 7 mL HFOE daily. The HFOE at the high dose had a synergistic effect, lowering random blood glucose (RBG) and fasting blood glucose (FBG). The hypolipidemic potential of HFOE at the high dose was indicated by significant reductions in triglycerides (TG), total cholesterol (CHO), high- and low-density lipoproteins (HDL and LDL), and very-low-density lipoproteins (VLDL). In addition, 7 mL of HFOE improved liver and kidney function more effectively than other fermented extracts or Metformin. As well as the antioxidant enzyme activity, reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and malonaldehyde (MDA) were significantly enhanced after the administration of HFOE at 7 mL by 68.6%, 71.5%, 55.69%, and 15.98%, respectively, compared to the DR group. In conclusion, administration of L. plantarum-fermented oats supplemented with honey demonstrated antidiabetic effects and a potential approach for controlling glucose levels and lipid profiles, and protecting against oxidative stress.

Antioxidant Activity of Aqueous Extract of Leaves and Seeds of Datura metel (Solanaceae) in Frog's Heart Failure Model

Objective

The aim of this work was to evaluate the antioxidant potential of Datura metel.

Materials and Methods

Heart failure was induced in the frog's heart by continuous perfusion of hydrogen peroxide. Survival time and some heart tissue parameters of oxidative stress were recorded in the presence of aqueous extracts of the leaves and seeds of Datura metel. Ascorbic acid was used as a reference drug.

Results

H2O2-enriched Ringer's solution inhibited the negative inotropic and chronotropic effects of acetylcholine, indicating the desensibilization of muscarinic receptors due to H2O2-induced oxidative stress. These hearts had a relatively short survival time (14 minutes). In the presence of the aqueous extract of the leaves and seeds of Datura metel (1.5 and 2.5 mg/mL), the time necessary to cause the cardiac arrest was extended to 35 and 37 minutes, respectively, versus 29 minutes for ascorbic acid and 14 minutes for H2O2. Furthermore, antioxidant parameters (MDA, SOD, and CAT) were significantly improved in plant extract-treated hearts, compared to peroxidized hearts.

Conclusion

Aqueous extract of the leaves and seeds of D. metel can extend heart survival time through antioxidant mechanisms.

Salvia spinosa L. Protects against Diabetes-Induced Nephropathy by Attenuation of Mitochondrial Oxidative Damage in Mice

Mitochondrial oxidative damage is a crucial factor in the pathogenesis of diabetic nephropathy (DN), which is among the most prevalent problems of diabetes, and there hasn't been an effective treatment for DN yet. This study planned to investigate the effects of Salvia spinosa L. on mitochondrial function along with its protection against streptozotocin-induced nephropathy in diabetic mice. After the injection of streptozotocin (STZ) and verification of the establishment of diabetes, mice (n = 30) were randomly divided into the following groups: control group, diabetic-control, S. spinosa-treated diabetic (50, 100, and 200 mg/kg), and metformin-treated diabetic group (500 mg/kg). After four weeks of treatment, the mice were weighed. Blood and kidney tissues were examined for biochemical and histological evaluation. Hematoxylin and eosin staining was used for evaluating renal pathologic damage. Oxidative damage in the kidney was assessed by the evaluation of lipid peroxidation and glutathione oxidation. Furthermore, differential centrifugation was used to obtain the isolated mitochondria, and mitochondrial toxicity endpoints (mitochondrial function and mitochondrial oxidative markers) were determined in them. S. spinosa remarkably reduced the blood urea and creatinine concentrations, and also normalized kidney weight/body weight coefficient in the diabetic mice. S. spinosa ameliorated the incidence of glomerular and tubular pathological changes in histological analyses. Moreover, the oxidative and mitochondrial damages were notably attenuated in renal tissues of S. spinosa-treated mice. These results indicate that the methanolic extract of S. spinosa modulates the nephropathy in the diabetic mice by the amelioration of oxidatively induced mitochondrial damage and provides a reliable scientific base, suggesting S. spinosa as a promising alternative remedy against DN.

Therapeutic potential of resveratrol in diabetic nephropathy according to molecular signaling

BACKGROUND

Diabetic nephropathy (DN) as a severe complication of diabetes mellitus (DM), is a crucial menace for human health and survival and remarkably elevates the healthcare systems' costs. Therefore, it is worth noting to identify novel preventive and therapeutic strategies to alleviate the disease conditions. Resveratrol, as a well-defined anti-diabetic/ antioxidant agent has capabilities to counteract diabetic complications. It has been predicted that resveratrol will be a fantastic natural polyphenol for diabetes therapy in the next few years.

OBJECTIVE

Accordingly, the current review aims to depict the role of resveratrol in the regulation of different signaling pathways that are involved in the reactive oxygen species (ROS) production, inflammatory processes, autophagy, and mitochondrial dysfunction, as critical contributors to DN pathophysiology.

RESULTS

The pathogenesis of DN can be multifactorial; hyperglycemia is one of the prominent risk factors of DN development that is closely related to oxidative stress. Resveratrol, as a well-defined polyphenol, has various biological and medicinal properties, including anti-diabetic, anti-inflammatory, and anti-oxidative effects.

CONCLUSION

Resveratrol prevents kidney damages that are caused by oxidative stress, enhances antioxidant capacity, and attenuates the inflammatory and fibrotic responses. For this reason, resveratrol is considered an interesting target in DN research due to its therapeutic possibilities during diabetic disorders and renal protection.

Role of Polyphenol in Regulating Oxidative Stress, Inflammation, Fibrosis, and Apoptosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is known as one of the driving sources of end-stage renal disease (ESRD). DN prevalence continues to increase in every corner of the world andthat has been a major concern to healthcare professionals as DN is the key driver of diabetes mellitus (DM) morbidity and mortality. Hyperglycaemia is closely connected with the production of reactive oxygen species (ROS) that cause oxidative stress response as well as numerous cellular and molecular modifications. Oxidative stress is a significant causative factor to renal damage, as it can activate other immunological pathways, such as inflammatory, fibrosis, and apoptosis pathways. These pathways can lead to cellular impairment and death as well as cellular senescence. Natural substances containing bioactive compounds, such as polyphenols, have been reported to exert valuable effects on various pathological conditions, including DM. The role of polyphenols in alleviating DN conditions has been documented in many studies. In this review, the potential of polyphenols in ameliorating the progression of DN via modulation of oxidative stress, inflammation, fibrosis, and apoptosis, as well as cellular senescence, has been addressed. This information may be used as the strategies for the management of DN and development as nutraceutical products to overcome DN development.

Nephroprotective Effect of the Virgin Olive Oil Polyphenol Hydroxytyrosol in Type 1-like Experimental Diabetes Mellitus: Relationships with Its Antioxidant Effect

The aim of this study was to determine whether hydroxytyrosol administration prevented kidney damage in an experimental model of type 1 diabetes mellitus in rats. Hydroxytyrosol was administered to streptozotocin-diabetic rats: 1 and 5 mg/kg/day p.o. for two months. After hydroxytyrosol administration, proteinuria was significantly reduced (67-73%), calculated creatinine clearance was significantly increased (26-38%), and the glomerular volume and glomerulosclerosis index were decreased (20-30%). Hydroxytyrosol reduced oxidative and nitrosative stress variables and thromboxane metabolite production. Statistical correlations were found between biochemical and kidney function variables. Oral administration of 1 and 5 mg/kg/day of hydroxytyrosol produced an antioxidant and nephroprotective effect in an experimental model of type 1-like diabetes mellitus. The nephroprotective effect was significantly associated with the systemic and renal antioxidant action of hydroxytyrosol, which also influenced eicosanoid production.

Synergistic Anti-inflammatory and Neuroprotective Effects of Cinnamomum cassia and Zingiber officinale Alleviate Diabetes-Induced Hippocampal Changes in Male Albino Rats: Structural and Molecular Evidence

Background: Depression has been reported as a common comorbidity in diabetes mellitus although the underlying mechanism responsible for this is not well known. Although both ginger and cinnamon has anti-diabetic, antioxidant, and neuroprotective properties, their efficacy in inhibiting neuroinflammation, when simultaneously administrated, has not been investigated yet. Objectives: The study was designed to assess the synergistic effect of Cinnamomum cassia and Zingiber officinale on regulating blood glucose, improve hippocampal structural changes and depressive-like alternations in diabetic rats, and try to identify the mechanism behind this effect. Materials and Methods: Thirty male Sprague-Dawley rats were divided into five equal groups (n = 6): the normal control, untreated streptozotocin (STZ)-diabetic, cinnamon-treated diabetic [100 mg/kg of body weight (BW)/day for 6 weeks], ginger-treated diabetic (0.5 g/kg BW/day for 6 weeks), and ginger plus cinnamon-treated diabetic groups. Forced swim test and elevated plus maze behavioral tests were performed at the end of the experiment. HOMA-IR, HOMA β-cells, blood glucose, insulin, corticosterone, pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and IL-6), and total anti-oxidant capacity (TAC) were assessed in the serum. BDNF mRNA level was assessed in hippocampus using qRT-PCR. Hippocampal histopathological changes were also assessed, and immunoexpression of glial fibrillary acidic protein (GFAP), caspase-3, and Ki-67 was measured. Results: Diabetes-induced depressive-like changes in the STZ group were biochemically confirmed by assessing serum corticosterone level, as well as behaviorally using FST and EPM tests. Diabetes also induced degenerative changes in the hippocampus. Treatment of diabetic rats with ginger, cinnamon, or the combination of these alleviated the degenerative structural changes and significantly up-regulated serum insulin, TAC, hippocampal BDNF mRNA, and hippocampal immunoexpression of ki67, while they significantly reduced serum blood glucose, IL-6, TNF-α, IL1β, as well as hippocampal immunoexpression of GFAP and Caspase-3 compared to the untreated diabetic group. Improvement induced by the combination of ginger and cinnamon was superior to the single administration of either of these. Conclusion: Cinnamomum cassia and Zingiber officinale have synergistic anti-diabetic, antioxidant, anti-inflammatory, antidepressant-like, and neuroprotective effects. The use of a combination of these plants could be beneficial as alternative or complementary supplements in managing DM and decreasing its neuronal and psychiatric complications.

Flavonoids on diabetic nephropathy: advances and therapeutic opportunities

With the advances in biomedical technologies, natural products have attracted substantial public attention in the area of drug discovery. Flavonoids are a class of active natural products with a wide range of pharmacological effects that are used for the treatment of several diseases, in particular chronic metabolic diseases. Diabetic nephropathy is a complication of diabetes with a particularly complicated pathological mechanism that affects at least 30% of diabetic patients and represents a great burden on public health. A large number of studies have shown that flavonoids can alleviate diabetic nephropathy. This review systematically summarizes the use of common flavonoids for the treatment of diabetic nephropathy. We found that flavonoids play a therapeutic role in diabetic nephropathy mainly by regulating oxidative stress and inflammation. Nrf-2/GSH, ROS production, HO-1, TGF-β1 and AGEs/RAGE are involved in the process of oxidative stress regulation. Quercetin, apigenin, baicalin, luteolin, hesperidin, genistein, proanthocyanidin and eriodictyol were found to be capable of alleviating oxidative stress related to the aforementioned factors. Regarding inflammatory responses, IL-1, IL-6β, TNF-α, SIRT1, NF-κB, and TGF-β1/smad are thought to be essential. Quercetin, kaempferol, myricetin, rutin, genistein, proanthocyanidin and eriodictyol were confirmed to influence the above targets. As a result, flavonoids promote podocyte autophagy and inhibit the overactivity of RAAS by suppressing the upstream oxidative stress and inflammatory pathways, ultimately alleviating DN. The above results indicate that flavonoids are promising drugs for the treatment of diabetic nephropathy. However, due to deficiencies in the effect of flavonoids on metabolic processes and their lack of structural stability in the body, further research is required to address these issues.

L-ergothioneine and its combination with metformin attenuates renal dysfunction in type-2 diabetic rat model by activating Nrf2 antioxidant pathway

L-ergothioneine (L-egt) is a bioactive compound recently approved by the food and drug administration as a supplement. L-egt exerts potent cyto-protective, antioxidant and anti-inflammatory properties in tissues exposed to injury, while metformin is a first-line prescription in type-2 diabetes. Therefore, the present study investigated the protective effect of L-egt alone, or combined with metformin, on renal damage in a type-2 diabetic (T2D) rat model. T2D was induced in male Sprague-Dawley rats using the fructose-streptozotocin rat model. L-egt administration, alone or combined with metformin, began after confirming diabetes and was administered orally for seven weeks. After the experiment, all animals were euthanized by decapitation, blood samples were collected, and both kidneys were excised. Biochemical analysis, Enzyme-link Immunoassay (ELISA), Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), western blotting, and histological analyses were done to evaluate various biomarkers and structural changes associated with renal damage. Untreated diabetic rats showed loss of kidney functions characterized by increased serum creatinine, blood urea nitrogen, proteinuria, triglycerides, lipid peroxidation, inflammation, and decreased antioxidant enzymes. Histological evaluation showed evidence of fibrosis, mesangial expansion, and damaged basement membrane in the nephrons. However, L-egt alleviates these functional and structural derangements in the kidney, while co-administration with metformin reduced hyperglycemia and improves therapeutic outcomes. Furthermore, L-egt treatment significantly increased the expression of major antioxidant transcription factors, cytoprotective genes and decreased the expression of inflammatory genes in the kidney. Thus, combining L-egt and metformin may improve therapeutic efficacy and be used as an adjuvant therapy to alleviate renal damage in type-2 diabetes.

Flacourtia indica fruit extract modulated antioxidant gene expression, prevented oxidative stress and ameliorated kidney dysfunction in isoprenaline administered rats

This study evaluated the effect of Flacourtia indica fruit extract against isoprenaline (ISO) induced renal damage in rats. This investigation showed that ISO administration in rats increased the level oxidative stress biomarkers such as malondialdehyde (MDA), nitric oxide (NO), advanced protein oxidation product (APOP) in kidneys followed by a decrease in antioxidant enzymes functions. Flacourtia indica fruit extract, which is rich in strong antioxidants, also reduced the MDA, NO and APOP level in kidney of ISO administered rats. Inflammation and necrosis was also visible in kidney section of ISO administered rats which was significantly prevented by atenolol and Flacourtia indica fruit extract. Moreover, atenolol and Flacourtia indica fruit extract also modulated the genes expressions related to inflammation and oxidative stress in kidneys. The beneficial effects could be attributed to the presence of a number of phenolic antioxidants. This study suggests that Flacourtia indica fruit extract may prevent kidney dysfunction in ISO administered rats, probably by preventing oxidative stress and inflammation.

Valeriana rigida Ruiz & Pav. Root Extract: A New Source of Caffeoylquinic Acids with Antioxidant and Aldose Reductase Inhibitory Activities

Valeriana rigida Ruiz & Pav. (V. rigida) has long been used as a herbal medicine in Peru; however, its phytochemicals and pharmacology need to be scientifically explored. In this study, we combined the offline 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)-/ultrafiltration-high-performance liquid chromatography (HPLC) and high-speed counter-current chromatography (HSCCC)/pH-zone-refining counter-current chromatography (pH-zone-refining CCC) to screen and separate the antioxidants and aldose reductase (AR) inhibitors from the 70% MeOH extract of V. rigida, which exhibited remarkable antioxidant and AR inhibitory activities. Seven compounds were initially screened as target compounds exhibiting dual antioxidant and AR inhibitory activities using DPPH-/ultrafiltration-HPLC, which guided the subsequent pH-zone-refining CCC and HSCCC separations of these target compounds, namely 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-di-caffeoylquinic acid, 3,5-O-di-caffeoylquinic acid, 4,5-O-di-caffeoylquinic acid, and 3,4,5-O-tri-caffeoylquinic acid. These compounds are identified for the first time in V. rigida and exhibited remarkable antioxidant and AR inhibitory activities. The results demonstrate that the method established in this study can be used to efficiently screen and separate the antioxidants and AR inhibitors from natural products and, particularly, the root extract of V. rigida is a new source of caffeoylquinic acids with antioxidant and AR inhibitory activities, and it can be used as a potential functional food ingredient for diabetes.

p53 Rather Than β-Catenin Mediated the Combined Hypoglycemic Effect of Cinnamomum cassia (L.) and Zingiber officinale Roscoe in the Streptozotocin-Induced Diabetic Model

Background: The antioxidant, hypoglycemic, and insulin-enhancing effects of ginger and cinnamon were previously confirmed in experimental and human studies, while the combined effect of ginger and cinnamon was not thoroughly investigated until now.

Objectives: This study was designed to assess the antidiabetic effect of combined administration of ginger (Zingiber officinale Roscoe) and cinnamon (Cinnamomum cassia L.) in streptozotocin (STZ)-induced diabetic rats compared to metformin and to explain the mechanism behind this effect.

Materials and methods: STZ was utilized to induce diabetes mellitus in male Sprague–Dawley rats. Assessments of fasting blood glucose level (BGL), the total antioxidant capacity (TAC), serum insulin, HOMA-IR, and HOMA–β cells were performed. Pancreatic gene expression of β-catenin and p53 was assessed using RT-PCR. Assessment of histopathological alterations of pancreatic islet cells was performed using routine and immunohistochemical techniques.

Results: BGL significantly decreased (p = 0.01), while serum insulin and TAC significantly increased (p < 0.001) in both metformin- and ginger plus cinnamon–treated groups compared to the untreated diabetic group. HOMA–β cell index significantly increased (p = 0.001) in ginger plus cinnamon, indicating their enhancing effect on insulin secretion in diabetic conditions. p53 gene expression was significantly upregulated (p < 0.001), while β-catenin was insignificantly downregulated (p = 0.32) in ginger plus cinnamon–treated groups. Insulin immunoexpression in β cells significantly increased (p = 0.001, p = 0.004) in metformin- and ginger plus cinnamon–treated groups, respectively.

Conclusions: The combined administration of ginger and cinnamon has a significant hypoglycemic and antioxidant effect in STZ-induced diabetes mostly through enhancing repair of islet cells mediated via upregulation of pancreatic p53 expression. Therefore, testing this effect in diabetic patients is recommended.

The effect of methylethylpiridinol addition to the therapy on the level of pigment epithelium-derived factor and oxidative status in patients with diabetic nephropathy: randomized controlled open-label clinical study

Purpose

The diabetic nephropathy is associated with oxidative stress and increases in pigment epithelium-derived factor (PEDF) level in the patient's blood. For the first time, authors investigated the effect of methylethylpiridinol addition to the therapy on oxidative status and pigment epithelium-derived factor concentrations, and examined the relationship between these indicators and clinical markers of pathology development.

Methods

Study design: open label randomized controlled trial study. Authors assessed the effect of methylethylpiridinol addition to the therapy vs basic treatment on antioxidant and NADPH-generating enzymes activity, glutathione's concentration and free radical-induced oxidation's intensity using a spectrophotometric method and iron-induced biochemiluminescence. The pigment epithelium-derived factor concentration in the serum was measured by enzyme-linked immunosorbent assay.

Results

Patients receiving combination therapy with methylethylpiridinol showed a more substantial increase in activity of glutathione peroxidase (Δ = 0.04 ± 0.11, p = 0.002), glutathione transferase (Δ = 0.12 ± 0.08, p < 0.001) and the concentration of reduced glutathione (Δ = 0.30 ± 0.17, p = 0.039). In addition, there was a significant decrease in PEDF level (Δ = -6.4 ± 5.4, p = 0.004). Correlation analysis showed a negative link between Δ postprandial glucose and Δ NADP-isocitrate dehydrogenase (-0.39, p = 0.033), Δ reduced glutathione and Δ postprandial glucose (-0.372, p = 0.043), Δ glutathione transferase and Δ PEDF (-0.37, p = 0.044).

Conclusions

The methylethylpiridinol addition to the therapy had a more potent stimulating effect on the patients' oxidative status in comparison with standard treatment, and reliably decreased pigment epithelium-derived factor level in patients' serum. The observed differences seem to be associated with the antioxidant activity of methylethylpiridinol which contributing to the mitigation of oxidative stress reducing at diabetes mellitus.

Modulatory effect of fructooligosaccharide against triphenyltin-induced oxidative stress and immune suppression in goldfish (Carassius auratus)

Triphenyltin (TPT) is a widely used pesticide that is highly toxic to a variety of organisms, including humans, and is a potential contributor to environmental pollution. The present study was conducted to evaluate the oxidative stress and immunotoxicity induced by TPT in goldfish (Carassius auratus) and the protective effects of fructooligosaccharide (FOS). Goldfish (mean weight of 13.3 ± 0.2 g) were randomly divided into six groups with three replicates: (G1) the control group, (G2) the 10 ng/L TPT group, (G3) the 0.4% FOS group, (G4) the 10 ng/L TPT + 0.4% FOS group, (G5) the 0.8% FOS group, and (G6) the 10 ng/L TPT + 0.8% FOS group. The results showed that 10 ng/L TPT induced oxidative stress and significantly decreased the activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), in the liver and the gene expression of SOD, GPx, metallothionein (MT), and peroxiredoxin-4 (Prdx-4). The concentration of malondialdehyde (MDA) and the gene expression of cytochrome P450 (CYP) and glutathione S-transferase (GST) in the liver were significantly increased in the TPT-treated group. Exposure to 10 ng/L TPT in water induced immune suppression and significantly decreased the activities of immune enzymes, such as lysozyme, myeloperoxidase (MPO), alternative complement (ACH50), acid phosphatase (ACP) and alkaline phosphatase (AKP), in the serum. TPT could stimulate the fish to generate large amounts of proinflammatory cytokines, including increased tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and nitric oxide (NO) levels and TNF-α, IL-6, IL-1β, and NF-κB mRNA expression. However, TPT-induced toxicity was significantly ameliorated in the groups treated with FOS, and FOS partly prevented alterations in the activities of antioxidant enzymes and the expression of antioxidant- and ROS scavenger-related genes. In addition, TPT-induced immune toxicity was significantly ameliorated in the groups treated with FOS. FOS markedly suppressed TNF-α, IL-6, IL-1β, and NO production and TNF-α, IL-6, and IL-1β mRNA expression in the TPT-treated groups. The study indicated that TPT-induced oxidative stress may play a critical role in inhibiting immunity. However, FOS administration attenuates TPT-induced oxidative stress and immune suppression in goldfish.

Nrf-2 mediated heme oxygenase-1 activation contributes to the anti-inflammatory and renal protective effects of Ginkgo biloba extract in diabetic nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba extract (GbE) is derived from a medicinal plant and suggested as a treatment for diabetic nephropathy (DN), but the mechanism was not clarified.

AIM OF STUDY

The present study investigated whether GbE prevented DN via activation of heme oxygenase (HO)-1.

MATERIALS AND METHODS

Streptozotocin-induced diabetic mice were fed a high-fat diet to generate DN. Human and murine podocytes were used for the in vitro study.

RESULTS

GbE improved renal function via decreasing glomerular hypertrophy, the kidney/body weight ratio, and albuminuria in DN mice. GbE reversed the reduction of synaptopodin and nephrin and enhanced HO-1 expression in the kidneys of DN mice. GbE decreased the enhancement of TNF-α, IL-6, fibronectin, and lipid accumulation in the glomeruli of DN mice. GbE attenuated the uptake of oxidized low-density lipoprotein and reduced the production of ROS in high glucose-stimulated podocytes, and HO-1 inhibitor treatment abrogated the protective effects of GbE. Nuclear factor erythroid 2-related factor 2 (Nrf-2) siRNA significantly abolished the beneficial effects of GbE via decreased HO-1 expression and enhanced TNF-α and IL-6 levels.

CONCLUSIONS

GbE protected podocytes against hyperglycemia and prevented the development of DN via Nrf-2/HO-1 activation. Our findings provide further mechanistic insight into the potential use of GbE in clinical DN.

Effects of Allicin on Pathophysiological Mechanisms during the Progression of Nephropathy Associated to Diabetes

This study aimed to assess the impact of allicin on the course of diabetic nephropathy. Study groups included control, diabetes, and diabetes-treated rats. Allicin treatment (16 mg/kg day/p.o.) started after 1 month of diabetes onset and was administered for 30 days. In the diabetes group, the systolic blood pressure (SBP) increased, also, the oxidative stress and hypoxia in the kidney cortex were evidenced by alterations in the total antioxidant capacity as well as the expression of nuclear factor (erythroid-derived 2)-like 2/Kelch ECH associating protein 1 (Nrf2/Keap1), hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor (VEGF), erythropoietin (Epo) and its receptor (Epo-R). Moreover, diabetes increased nephrin, and kidney injury molecule-1 (KIM-1) expression that correlated with mesangial matrix, the fibrosis index and with the expression of connective tissue growth factor (CTGF), transforming growth factor-β1 (TGF-β1), and α-smooth muscle actin (α-SMA). The insulin levels and glucose transporter protein type-4 (GLUT4) expression were decreased; otherwise, insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) expression was increased. Allicin increased Nrf2 expression and decreased SBP, Keap1, HIF-1α, and VEGF expression. Concurrently, nephrin, KIM-1, the mesangial matrix, fibrosis index, and the fibrotic proteins were decreased. Additionally, allicin decreased hyperglycemia, improved insulin levels, and prevented changes in (GLUT4) and IRSs expression induced by diabetes. In conclusion, our results demonstrate that allicin has the potential to help in the treatment of diabetic nephropathy. The cellular mechanisms underlying its effects mainly rely on the regulation of antioxidant, antifibrotic, and antidiabetic mechanisms, which can contribute towards delay in the progression of renal disease.

Effects of honey supplementation on renal dysfunction and metabolic acidosis in rats with high-fat diet-induced chronic kidney disease

Background Metabolic diseases are associated with impaired renal function which accelerates chronic kidney disease (CKD) progression. The aim of this study was to investigate the effects of 16-week honey supplementation on renal function, metabolic acidosis and renal abnormalities in Wistar rats fed a high-fat diet (HFD). Methods Wistar rats were fed a HFD and sucrose (30%) solution and randomly grouped and treated. Group 1 was fed rat chow and treated with drinking water while groups 2, 3, 4 and 5 were fed a HFD and treated with drinking water, 1, 2 and 3 g/kg body weight (BW) of honey, respectively, once daily for 16 weeks. After the rats were sacrificed, the serum samples were obtained and used for the analysis of total cholesterol, urea, creatinine, sodium, potassium, calcium, bicarbonates and chloride ions. Histopathological examinations of the kidneys were performed. Results The serum creatinine and anion gap levels were significantly (p < 0.01) higher while the levels of serum total calcium and ionized fraction were significantly (p < 0.01) lower in HFD-fed control rats than in chow-fed rats. The kidney of HFD-fed control rats was characterized by tubular necrosis, glomerular atrophy, hemorrhage and severe focal aggregate inflammatory (FAIC) cells. Honey treatment (1, 2 or 3 g/kg BW) prevented elevations in serum creatinine while it restored serum levels of total calcium and ionized calcium towards those in rats fed chow only. All the three doses of honey also significantly (p < 0.01) reduced anion gap and ameliorated renal lesions. Honey treatment (2 g/kg BW) significantly (p < 0.05) increased bicarbonate and chloride ion in HFD-fed rats compared with HFD-fed control rats. Conclusions Sixteen-week honey supplementation ameliorates renal dysfunction, metabolic acidosis and renal morphological abnormalities in HFD-fed Wistar rats.

Nestin protects podocyte from injury in lupus nephritis by mitophagy and oxidative stress

Podocyte injury is the main cause of proteinuria in lupus nephritis (LN). Nestin, an important cytoskeleton protein, is expressed stably in podocytes and is associated with podocyte injury. However, the role of nestin in the pathogenesis of proteinuria in LN remains unclear. The correlations among nestin, nephrin and proteinuria were analyzed in LN patients and MRL/lpr lupus-prone mice. The expression of nestin in mouse podocyte lines (MPCs) and MRL/lpr mice was knocked down to determine the role of nestin in podocyte injury. Inhibitors and RNAi method were used to explore the role of mitophagy and oxidative stress in nestin protection of podocyte from damage. There was a significantly negative correlation between nestin and proteinuria both in LN patients and MRL/lpr mice, whereas the expression of nephrin was positively correlated with nestin. Knockdown of nestin resulted in not only the decrease of nephrin, p-nephrin (Y1217) and mitophagy-associated proteins in cultured podocytes and the podocytes of MRL/lpr mice, but also mitochondrial dysfunction in podocytes stimulated with LN plasma. The expression and phosphorylation of nephrin was significantly decreased by reducing the level of mitophagy or production of reactive oxygen species (ROS) in cultured podocytes. Our findings suggested that nestin regulated the expression of nephrin through mitophagy and oxidative stress to protect the podocytes from injury in LN.

Potential therapeutic effect of Moroccan propolis in hyperglycemia, dyslipidemia, and hepatorenal dysfunction in diabetic rats

OBJECTIVES

The effect of propolis collected in Morocco on blood glucose, lipid profile, liver enzymes, and kidney function was investigated in control and diabetic rats.

MATERIALS AND METHODS

Antioxidant activity of propolis was evaluated with the use of DPPH, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS•+), ferric reducing power and total antioxidant activity assay. To study its effect in streptozotocin (STZ)-induced diabetes, the rats were divided into eight groups; four control and four diabetics. The animals received distilled water, glibenclamide, or propolis extract, 50 mg/kg/BW) or 100 mg/kg/b.wt, daily for 15 days. Blood glucose, triglyceride, lactic acid dehydrogenase, liver enzymes, creatinine, blood urea, lipid profile, and body weight were measured on day 15 after commencement of the treatment.

RESULTS

Propolis has a strong antioxidant activity and high total flavonoids and polyphenols content. Glibenclamide and propolis have no significant effect on lipid parameters, and renal and hepatic function in non-diabetic rats. However, propolis or glibenclamide caused a significant lowering of blood glucose after a single administration and at day 15 after daily administration in diabetic rats (P<0.05). Both interventions significantly lowered lactic acid dehydrogenase, increased body weight, and ameliorated dyslipidemia and abnormal liver and kidney function caused by diabetes. The effect of propolis was dose-dependent and in a high dose it was more potent than glibenclamide.

CONCLUSION

Propolis exhibited strong antihyperglycemic, antihyperlipidemic, and hepato-renal protective effects in diabetes, and significantly lowered the elevated lactic acid dehydrogenase. The study demonstrated for the first-time the effect of Moroccan propolis in diabetes and it will pave the way for clinical investigations.

Anti-Diabetic Nephropathy Activities of Polysaccharides Obtained from Termitornyces albuminosus via Regulation of NF-κB Signaling in db/db Mice

Termitornyces albuminosus is a kind of traditional Chinese edible fungus rich in nutrients and medicinal ingredients, and it has anti-oxidative, analgesic and anti-inflammatory effects. However, the hypoglycemic and nephroprotective effects of polysaccharides separated from T. albuminosus (PTA) have not been reported. The properties of PTA were analyzed in a BKS.Cg-Dock7^m +/+ Lepr^db/JNju (db/db) mouse model of diabetes. After the administration of PTA for eight weeks, the hypoglycemic and hypolipidemic activities of PTA in the db/db mice were assessed. The results of a cytokine array combined with an enzyme-linked immunosorbent assay confirmed the anti-oxidative and anti-inflammatory activities of PTA. An eight-week administration of PTA caused hypoglycemic and hypolipidemic functioning, as indicated by suppressed plasma glucose levels, as well as the modulation of several cytokines related to glycometabolism, in the sera and kidneys of the mice. PTA treatment also had a protective effect on renal function, restoring renal structures and regulating potential indicators of nephropathy. In the kidneys of the db/db mice, PTA treatment reduced the activation of protein kinase B, the inhibitor of κB kinase alpha and beta, and the inhibitor of κB alpha and nuclear factor-κB (NF-κB). We establish the hypoglycemic, hypolipidemic, and anti-diabetic nephropathy effects of PTA, and we find that the renal protection effects of PTA may be related to anti-inflammatory activity via the regulation of NF-κB signaling.

The Signaling of Cellular Senescence in Diabetic Nephropathy

Diabetic nephropathy is the leading cause of chronic kidney disease (CKD) in western countries. Notably, it has a rapidly rising prevalence in China. The patients, commonly complicated with cardiovascular diseases and neurologic disorders, are at high risk to progress into end-stage renal disease (ESRD) and death. However, the pathogenic mechanisms of diabetic nephropathy have not been determined. Cellular senescence, which recently has gained broad attention, is thought to be an important player in the onset and development of diabetic nephropathy. In this issue, we generally review the mechanisms of cellular senescence in diabetic nephropathy, which involve telomere attrition, DNA damage, epigenetic alterations, mitochondrial dysfunction, loss of Klotho, Wnt/β-catenin signaling activation, persistent inflammation, and accumulation of uremic toxins. Moreover, we highlight the potential therapeutic targets of cellular senescence in diabetic nephropathy and provide important clues for clinical strategies.

Molecular Interactions Between Reactive Oxygen Species and Autophagy in Kidney Disease

Reactive oxygen species (ROS) are highly reactive signaling molecules that maintain redox homeostasis in mammalian cells. Dysregulation of redox homeostasis under pathological conditions results in excessive generation of ROS, culminating in oxidative stress and the associated oxidative damage of cellular components. ROS and oxidative stress play a vital role in the pathogenesis of acute kidney injury and chronic kidney disease, and it is well documented that increased oxidative stress in patients enhances the progression of renal diseases. Oxidative stress activates autophagy, which facilitates cellular adaptation and diminishes oxidative damage by degrading and recycling intracellular oxidized and damaged macromolecules and dysfunctional organelles. In this review, we report the current understanding of the molecular regulation of autophagy in response to oxidative stress in general and in the pathogenesis of kidney diseases. We summarize how the molecular interactions between ROS and autophagy involve ROS-mediated activation of autophagy and autophagy-mediated reduction of oxidative stress. In particular, we describe how ROS impact various signaling pathways of autophagy, including mTORC1-ULK1, AMPK-mTORC1-ULK1, and Keap1-Nrf2-p62, as well as selective autophagy including mitophagy and pexophagy. Precise elucidation of the molecular mechanisms of interactions between ROS and autophagy in the pathogenesis of renal diseases may identify novel targets for development of drugs for preventing renal injury.

Myricetin Attenuated Diabetes-Associated Kidney Injuries and Dysfunction via Regulating Nuclear Factor (Erythroid Derived 2)-Like 2 and Nuclear Factor-κB Signaling

Background/Aims: Previous studies have suggested that myricetin (Myr) could promote the expression and nuclear translocation of nuclear factor (erythroid-derived 2)-like (Nrf2). This study aimed to investigate whether Myr could attenuate diabetes-associated kidney injuries and dysfunction in wild-type (WT) and Nrf2 knockdown (Nrf2-KD) mice.

Methods: Lentivirus-mediated Nrf2-KD and WT mice were used to establish type 1 diabetes mellitus (DM) by streptozotocin (STZ) injection. WT and Nrf2-KD mice were then randomly allocated into four groups: control (CON), Myr, STZ, and STZ + Myr. Myr (100 mg/kg/day) or vehicle was administered for 6 months. Kidneys were harvested and weighed at the end of the experiment. Hematoxylin and eosin staining and Masson’s trichrome staining were used to assess the morphology and fibrosis of the kidneys, respectively. Urinary albumin-to-creatinine ratio was used to test renal function. Western blotting was performed to determine oxidative-stress- or inflammation-associated signaling pathways. Real-time polymerase chain reaction (RT-PCR) was performed to detect the expression of fibrosis or inflammatory cytokines at the message Ribonucleic Acid (mRNA) level.

Results: In WT mice, Myr alleviated DM-induced renal dysfunction, fibrosis, and oxidative damage and enhanced the expression of Nrf2 and its downstream genes. After knockdown of Nrf2, Myr treatment partially but significantly mitigated DM-induced renal dysfunction and fibrosis, which might be associated with inhibition of the I-kappa-B (IκB)/nuclear factor-κB (NF-κB) (P65) signaling pathway.

Conclusions: This study showed that Myr prevented DM-associated decreased expression of Nrf2 and inhibited IκB/NF-κB (P65) signaling pathway. Moreover, inhibition of IκB/NF-κB (P65) signaling pathway is independent of the regulation of Nrf2. Thus, Myr could be a potential treatment for preventing the development and progression of DM-associated kidney injuries and dysfunction.