Naringenin ameliorates streptozotocin-induced diabetic rat renal impairment by downregulation of TGF-β1 and IL-1 via modulation of oxidative stress correlates with decreased apoptotic events

Comprehensive review of animal models in diabetes research using chemical agents

Diabetes mellitus, characterized by insufficient insulin secretion and impaired insulin efficacy, disrupts carbohydrate, protein, and lipid metabolism. The global diabetic population is expected to double by 2025, from 380 million, posing a significant health challenge. Most diabetic individuals fall into the type 1 or type 2 categories, and diabetes adversely affects various organs, such as the kidneys, liver, nervous system, reproductive system, and eyes.This review focuses on animal models of diabetes induced by chemical agents, which are essential tools for understanding disease mechanisms, investigating complications, and testing antidiabetic drugs. Models include those caused by streptozotocin (STZ), alloxan, ferric nitrilotriacetate (Fe-NTA), dithizone, and anti-insulin serum.Streptozotocin (STZ)-induced diabetes models create type 1 and 2 diabetes by destroying pancreatic beta cells. The combination of STZ with nicotinamide mimics type 2 diabetes phenotypes. Alloxan induces a hyperglycemic state by causing free radical formation that selectively destroys pancreatic beta cells. Fe-NTA and dithizone also create diabetes models by damaging pancreatic beta cells. Anti-insulin serum models induce insulin resistance and hyperglycemia by generating antibodies against insulin receptors, leading to a condition similar to type 1 diabetes.Each model has unique characteristics that make it suitable for different aspects of diabetes research. These models are used to understand the pathogenesis of diabetes, develop new treatment strategies, and evaluate the efficacy of potential drugs.

Mechanism exploration of Wenshen Jianpi Decoction on renoprotection in diabetic nephropathy via transcriptomics and metabolomics

BACKGROUND

Diabetic nephropathy (DN) is a severe chronic microvascular complications of diabetes mellitus and the leading cause of end-stage renal disease. Although many therapeutic approaches have been developed for treatment of DN, there is still a risk of disease progression. Wenshen Jianpi Decoction (WSJPD), a traditional Chinese medicine, have demonstrated considerable clinical efficacy in treating DN. However, the therapeutic mechanisms of WSJPD remain unclear.

PURPOSE

The study aimed to assess the potential anti-renal injury effects of WSJPD as well as the underlying mechanism.

METHODS

Network pharmacology was performed to predict the potential targets of WSJPD in DN. Subsequently, HE, PAS, Masson staining, TEM and ELISA were used to assess the effects of WSJPD on renal injury in DN rats. Transcriptomics, metabolomics, and qRT-PCR were employed to analyze the potential mechanism.

RESULTS

Network pharmacology analysis revealed that WSJPD might exert a beneficial impact on renal inflammation via the AGE-RAGE signaling pathway. The results of animal experiments indicated that WSJPD had a renoprotective effect by renal dysfunction improvement, inflammation inhibition, glycogen accumulation and podocyte injury suppression.Transcriptomic measures discovered that 212 genes were up-regulated in the DN model group and down-regulated in the WSJPD group. Conversely, 80 genes were down-regulated in the DN model group and up-regulated in the WSJPD group. Moreover, 14 metabolites from rat serum samples were identified as candidate biomarkers. Further analysis demonstrated that WSJPD ameliorated the metabolic disorders and exerted a protective effect by up-regulation of uridine-mediated pyrimidine metabolism, inhibition of inflammation mediated by the NF-κB and TNF signaling pathways, and inhibition of oxidative stress and inflammation mediated by the AGE-RAGE signaling pathway.

CONCLUSION

Our findings showed that WSJPD ameliorated renal damage in DN model rats by regulating kidney pyrimidine metabolism, inflammation-related pathways, and AGE-RAGE signaling pathway. The potential renoprotective effects were verified by histopathology, ELISA, and qRT-PCR. This study not only support a foundation for interpretation of the therapeutic effects of WSJPD on renal lesions, but also provide data support for further explorations of the novel compound preparations to improve renal function in DN.

The potential anti-inflammatory effect of hyaluronic acid gel alone or in combination with grapefruit seed extract on induced periodontitis in mandibular molars of Wistar rats

OBJECTIVES

Antimicrobial agents have been used in conjunction with conventional chemomechanical therapy to improve the treatment outcomes of periodontitis. This study aimed to evaluate the ameliorating effect of topical application of hyaluronic acid (HA) with or without grapefruit seed extract (GFSE) (5, 10, and 15 wt %) in induced periodontitis in rats.

METHODS

Surgical alveolar bone defects were created in 30 adult male Wistar rats, followed by the introduction of a ligature impregnated with Escherichia coli lipopolysaccharide for four weeks to induce periodontitis. Rats were distributed into five groups (n = 6); an untreated periodontitis group and four treated groups in which gel (HA±GFSE) was injected into the sulcus once weekly for two weeks. All rats were euthanized six weeks after starting the experiment, and the mandibles were prepared for histopathological and histomorphometric analyses. Enzyme-linked immunosorbent assay was used for measuring tissue levels of tumor necrosis factor-alpha (TNF-α), transforming growth factor-β1 (TGF-β1), and paraoxonase-1 (PON-1) enzyme.

RESULTS

HA enhanced new bone formation at defect margins, thereby diminishing defect width. This effect significantly increased as HA was combined with GFSE in a dose-dependent manner. Moreover, the HA and GFSE mixture suppressed the tissue levels of TNF-α and TGF-β1, thereby increasing PON-1.

CONCLUSION

The HA and GFSE mixtures exhibited synergistic therapeutic potential for the treatment of chronic periodontitis in a dose-dependent manner.

Chondroitin Sulphate-Chitosan Based Nanogels Loaded with Naringenin-β-Cyclodextrin Complex as Potential Tool for the Treatment of Diabetic Retinopathy: A Formulation Study

Purpose

The main purpose of the study was the formulation development of nanogels (NHs) composed of chondroitin sulfate (CS) and low molecular weight chitosan (lCH), loaded with a naringenin-β-cyclodextrin complex (NAR/β-CD), as a potential treatment for early-stage diabetic retinopathy.

Methods

Different formulations of NHs were prepared by varying polymer concentration, lCH ratio, and pH and, then, characterized for particle size, zeta potential, particle concentration (particles/mL) and morphology. Cytotoxicity and internalization were assessed in vitro using Human Umbilical Vein Endothelial Cells (HUVEC). The NAR/β-CD complex was prepared and evaluated for morphology, complexation efficiency, and solubility. Finally, the most promising NH prototype was loaded with NAR/β-CD (NH@NAR/β-CD) and further characterized for encapsulation efficiency, loading capacity, opacity and cytotoxicity on HUVEC; in vitro release test and DPPH assay were performed to investigate NH capability to sustain NAR release and NH@NAR/β-CD antioxidant properties, respectively.

Results

NH properties were influenced by polymer concentration, lCH ratio, and pH. N3 (0.5 mg/mL; lCH=1.5:1; pH = 5) and N9 (0.5 mg/mL; lCH=1:1; pH = 5) showed optimal characteristics, including small size (<350 nm) and positive zeta potential, facilitating cellular uptake. The NAR/β-CD complex showed 71% complexation efficiency and enhanced NAR solubility. Since characterized by superior properties and better in vitro biocompatibility, N3 was loaded with NAR/β-CD. N3@NAR/β-CD capability to sustain in vitro NAR release, radical scavenging activity and in vitro biocompatibility were finally demonstrated.

Conclusion

The physico-chemical properties of N3@NAR/β-CD were responsible for their cell uptake, suggesting their potential to target retinal endothelial cells. The high NAR/β-CD complexation efficiency and the sustained NAR release over 72 hours could guarantee the maintenance of an effective drug concentration at the damage site while reducing the injection number. Further studies about the safety and the effectiveness of the intravitreal injection of NHs@NAR/β-CD will be performed on a diabetic animal model.

Naringenin improves ovarian health by reducing the serum androgen and eliminating follicular cysts in letrozole-induced polycystic ovary syndrome in the Sprague Dawley rats

Polycystic ovary syndrome (PCOS) is most common in women of reproductive age, giving rise to androgen excess and anovulation, leading to infertility and non-reproductive complications. We explored the ameliorating effect of naringenin in PCOS using the Sprague Dawley (SD) rat model and human granulosa cells. Letrozole-induced PCOS rats were given either naringenin (50 mg/kg/day) alone or in combination with metformin (300 mg/kg/day), followed by the estrous cycle, hormonal analysis, and glucose sensitivity test. To evaluate the effect of naringenin on granulosa cell (hGC) steroidogenesis, we treated cells with naringenin (2.5 μM) alone or in combination with metformin (1 mM) in the presence of forskolin (10 μM). To determine the steroidogenesis of CYP-17A1, -19A1, and 3βHSD2, the protein expression levels were examined. Treatment with naringenin in the PCOS animal groups increased ovulation potential and decreased cystic follicles and levels of androgens. The expression levels of CYP-17A1, -19A1, and 3βHSD2, were seen restored in the ovary of PCOS SD rats' model and in the human ovarian cells in response to the naringenin. We found an increased expression level of phosphorylated-AKT in the ovary and hGCs by naringenin. Naringenin improves ovulation and suppress androgens and cystic follicles, involving AKT activation.

Oxidative stress and inflammation in diabetic nephropathy: role of polyphenols

Diabetic nephropathy (DN) often leads to end-stage renal disease. Oxidative stress demonstrates a crucial act in the onset and progression of DN, which triggers various pathological processes while promoting the activation of inflammation and forming a vicious oxidative stress-inflammation cycle that induces podocyte injury, extracellular matrix accumulation, glomerulosclerosis, epithelial-mesenchymal transition, renal tubular atrophy, and proteinuria. Conventional treatments for DN have limited efficacy. Polyphenols, as antioxidants, are widely used in DN with multiple targets and fewer adverse effects. This review reveals the oxidative stress and oxidative stress-associated inflammation in DN that led to pathological damage to renal cells, including podocytes, endothelial cells, mesangial cells, and renal tubular epithelial cells. It demonstrates the potent antioxidant and anti-inflammatory properties by targeting Nrf2, SIRT1, HMGB1, NF-κB, and NLRP3 of polyphenols, including quercetin, resveratrol, curcumin, and phenolic acid. However, there remains a long way to a comprehensive understanding of molecular mechanisms and applications for the clinical therapy of polyphenols.

The protective roles of citrus flavonoids, naringenin, and naringin on endothelial cell dysfunction in diseases

The endothelial cells (ECs) make up the inner lining of blood vessels, acting as a barrier separating the blood and the tissues in several organs. ECs maintain endothelium integrity by controlling the constriction and relaxation of the vasculature, blood fluidity, adhesion, and migration. These actions of ECs are efficiently coordinated via an intricate signaling network connecting receptors, and a wide range of cellular macromolecules. ECs are naturally quiescent i.e.; they are not stimulated and do not proliferate. Upon infection or disease, ECs become activated, and this alteration is pivotal in the pathogenesis of a spectrum of human neurological, cardiovascular, diabetic, cancerous, and viral diseases. Considering the central position that ECs play in disease pathogenesis, therapeutic options have been targeted at improving ECs integrity, assembly, functioning, and health. The dietary intake of flavonoids present in citrus fruits has been associated with a reduced risk of endothelium dysfunction. Naringenin (NGN) and Naringin (NAR), major flavonoids in grapefruit, tomatoes, and oranges possess anti-inflammatory, antioxidant properties, and cell survival potentials, which improve the health of the vascular endothelium. In this review, we provide a comprehensive summary and present the advances in understanding of the mechanisms through which NGN and NAR modulate the biomarkers of vascular dysfunction and protect the endothelium against unresolved inflammation, oxidative stress, atherosclerosis, and angiogenesis. We also provide perspectives and suggest further studies that will help assess the efficacy of citrus flavonoids in the therapeutics of human vascular diseases.

A natural products solution to diabetic nephropathy therapy

Diabetic nephropathy is one of the most common complications in diabetes. It has been shown to be the leading cause of end-stage renal disease. However, due to their complex pathological mechanisms, effective therapeutic drugs other than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which have been used for 20 years, have not been developed so far. Recent studies have shown that diabetic nephropathy is characterized by multiple signalling pathways and multiple targets, including inflammation, apoptosis, pyroptosis, autophagy, oxidative stress, endoplasmic reticulum stress and their interactions. It definitely exacerbates the difficulty of therapy, but at the same time it also brings out the chance for natural products treatment. In the most recent two decades, a large number of natural products have displayed their potential in preclinical studies and a few compounds are under invetigation in clinical trials. Hence, many compounds targeting these singals have been emerged as a comprehensive blueprint for treating strategy of diabetic nephropathy. This review focuses on the cellular and molecular mechanisms of natural prouducts that alleviate this condition, including preclinical studies and clinical trials, which will provide new insights into the treatment of diabetic nephropathy and suggest novel ideas for new drug development.

Flavonoids in Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is a progressive systemic disease, which changes the function and structure of the kidneys irreversibly over months or years. The final common pathological manifestation of chronic kidney disease is renal fibrosis and is characterized by glomerulosclerosis, tubular atrophy, and interstitial fibrosis. In recent years, numerous studies have reported the therapeutic benefits of natural products against modern diseases. Substantial attention has been focused on the biological role of polyphenols, in particular flavonoids, presenting broadly in plants and diets, referring to thousands of plant compounds with a common basic structure. Evidence-based pharmacological data have shown that flavonoids play an important role in preventing and managing CKD and renal fibrosis. These compounds can prevent renal dysfunction and improve renal function by blocking or suppressing deleterious pathways such as oxidative stress and inflammation. In this review, we summarize the function and beneficial properties of common flavonoids for the treatment of CKD and the relative risk factors of CKD.

Endoplasmic reticulum stress-dependent activation of TRB3-FoxO1 signaling pathway exacerbates hyperglycemic nephrotoxicity: Protection accorded by Naringenin

Endoplasmic reticulum (ER) dysfunction contributes greatly to the pathophysiology of hyperglycemic nephrotoxicity. This study unravels the critical role of Tribbles 3 (TRB3)-Forkhead box O1 (FoxO1) signaling pathway during hyperglycemic renal toxicity. It also uncovers the novel role of Naringenin, a flavanone, in regulating ER stress in proximal tubular cells, NRK 52E, and kidneys of streptozotocin/nicotinamide induced experimental diabetic Wistar rats. Results demonstrate that expression of ER stress marker proteins including phosphorylated protein kinase ER like kinase (p-PERK), phosphorylated eukaryotic Initiation Factor 2α (p-eIF2α), X Box Binding Protein 1 spliced (XBP1s), Activating Transcription Factor 4 (ATF4) and C/EBP Homologous Protein (CHOP) were upregulated in diabetic kidneys indicating the activation of ER stress response due to nephrotoxicity. Treatment with Naringenin reduced the expression of TRB3, an ER stress-inducible pseudokinase, both in vitro and in vivo. Gene silencing of TRB3 enhanced Akt and FoxO1 phosphorylation and alleviated FoxO1 mediated apoptosis during hyperglycemic nephrotoxicity. Notably, TRB3 gene silencing effects were comparable to the response with Naringenin treatment. Prevention of nuclear colocalization of ATF4 and CHOP in Naringenin treated cells was evident. Naringenin also reduced insulin resistance, apoptosis and glycogen accumulation along with enhancement of glucose tolerance in diabetic rats. Prevention of ultrastructural aberrations in the ER of hyperglycemic renal cells by Naringenin confirmed its anti-ER stress effects. These findings affirm that activation of TRB3-FoxO1 signaling is critical in the pathogenesis of hyperglycemia-induced renal toxicity and protective effect of Naringenin via modulation of ER stress may be exploited as a novel approach for its management.

A Systematic Review of Orthosiphon stamineus Benth. in the Treatment of Diabetes and Its Complications

(1) Background: Orthosiphon stamineus Benth. is a traditional medicine used in the treatment of diabetes and chronic renal failure in southern China, Malaysia, and Thailand. Diabetes is a chronic metabolic disease and the number of diabetic patients in the world is increasing. This review aimed to systematically review the effects of O. stamineus in the treatment of diabetes and its complications and the pharmacodynamic material basis. (2) Methods: This systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), using the databases ScienceDirect, PubMed, and Web of Science. (3) Results: Thirty-one articles related to O. stamineus and diabetes were included. The mechanisms of O. stamineus in the treatment of diabetes and its complications mainly included inhibiting α-amylase and α-glucosidase activities, antioxidant and anti-inflammatory activities, regulating lipid metabolism, promoting insulin secretion, ameliorating insulin resistance, increasing glucose uptake, promoting glycolysis, inhibiting gluconeogenesis, promoting glucagon-likepeptide-1 (GLP-1) secretion and antiglycation activity. Phenolic acids, flavonoids and triterpenoids might be the main components for hypoglycemia effects in O. stamineus. (4) Conclusion: O. stamineus could be an antidiabetic agent to treat diabetes and its complications. However, it needs further study on a pharmacodynamic substance basis and the mechanisms of effective constituents.

Quercetin and naringenin abate diethylnitrosamine/acetylaminofluorene-induced hepatocarcinogenesis in Wistar rats: the roles of oxidative stress, inflammation and cell apoptosis

This study was designed to assess the preventive effects and to suggest the probable mechanisms of action of quercetin and naringein in diethylnitrosamine (DEN)/2-acetylaminofluorene (2AAF)-induced hepatocarcinogenesis in Wistar male rats. The chemical-induction of hepatocarcinogenesis was performed by injection of DEN intraperitoneally at 150 mg/kg body weight (b.w.) twice/week for two weeks, followed by oral administration of 2AAF at 20 mg/kg body weight (b.w.) 4 times/week for 3 weeks. The DEN/2AAF-administered rats were co-treated with quercetin and naringenin at dose level of 10 mg/kg b. w. by oral gavage for 20 weeks. The treatment of DEN/2AAF-administered rats with quercetin and naringenin significantly prevented the elevations in serum levels of liver function indicators (ALT, AST, ALP, γ-GT, total bilirubin and albumin) and liver tumor biomarkers including AFP, CEA and CA19.9. The cancerous histological lesions and inflammatory cells infiltration in liver of DEN/2AAF-administered rats were remarkably suppressed by treatments with quercetin and naringenin. The hepatic oxidative stress markers including NO level and lipid peroxidation significantly decreased while the SOD, GPx and CAT activities and GSH content significantly increased in DEN/2AAF-administered rats treated with quercetin and naringenin when compared to DEN/2AFF-administered control rats. Furthermore, the lowered mRNA expression of liver IL-4, P53 and Bcl-2 in of DEN/2AAF-administered rats were significantly counteracted by treatment with quercetin and naringenin. Taken together, our results demonstrate that quercetin and naringenin may abate hepatocarcinogenesis via enhancement of anti-inflammatory, anti-oxidant and apoptotic actions.

Apple polyphenol phloretin complexed with ruthenium is capable of reprogramming the breast cancer microenvironment through modulation of PI3K/Akt/mTOR/VEGF pathways

Our recent investigation directed to synthesize a novel ruthenium-phloretin complex accompanied by the study of antioxidant in addition to DNA binding capabilities, to determine the chemotherapeutic activity against breast carcinoma in vitro and in vivo. Ruthenium-phloretin complex was synthesized and characterized by different spectroscopic methods. The complex was further investigated to determine its efficacy in both MCF-7 and MDA-MB-231 human carcinoma cell lines and finally in an in vivo model of mammary carcinogenesis induced by DMBA in rats. Our studies confirm that the chelation of the metal and ligand was materialize by the 3-OH and 9-OH functional groups of the ligand and the complex is found crystalline and was capable of intercalating with CT-DNA. The complex was capable of reducing cellular propagation and initiate apoptotic events in MCF-7 and MDA-MB-231 breast carcinoma cell lines. Ruthenium-phloretin complex could modulate p53 intervene apoptosis in the breast carcinoma, initiated by the trail of intrinsic apoptosis facilitated through Bcl2 and Bax and at the same time down regulating the PI3K/Akt/mTOR pathway coupled with MMP9 regulated tumor invasive pathways. Ruthenium-phloretin chemotherapy could interrupt, revoke or suspend the succession of breast carcinoma by altering intrinsic apoptosis along with the anti-angiogenic pathway.

Molecular Mechanistic Pathways Targeted by Natural Antioxidants in the Prevention and Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is the progressive loss of renal function and the leading cause of end-stage renal disease (ESRD). Despite optimal therapy, many patients progress to ESRD and require dialysis or transplantation. The pathogenesis of CKD involves inflammation, kidney fibrosis, and blunted renal cellular antioxidant capacity. In this review, we have focused on in vitro and in vivo experimental and clinical studies undertaken to investigate the mechanistic pathways by which these compounds exert their effects against the progression of CKD, particularly diabetic nephropathy and kidney fibrosis. The accumulated and collected data from preclinical and clinical studies revealed that these plants/bioactive compounds could activate autophagy, increase mitochondrial bioenergetics and prevent mitochondrial dysfunction, act as modulators of signaling pathways involved in inflammation, oxidative stress, and renal fibrosis. The main pathways targeted by these compounds include the canonical nuclear factor kappa B (NF-κB), canonical transforming growth factor-beta (TGF-β), autophagy, and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid factor 2-related factor 2 (Nrf2)/antioxidant response element (ARE). This review presented an updated overview of the potential benefits of these antioxidants and new strategies to treat or reduce CKD progression, although the limitations related to the traditional formulation, lack of standardization, side effects, and safety.

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.

Naringenin alleviates myocardial ischemia reperfusion injury by enhancing the myocardial miR-126-PI3K/AKT axis in streptozotocin-induced diabetic rats

Ischemic heart disease (IHD) is a leading cause of death in patients with type 1 diabetes. The key to treating IHD is to restore blood supply to the ischemic myocardium, which inevitably causes myocardial ischemia reperfusion (MI/R) injury. Although naringenin (Nar) prevents MI/R injury, the role of Nar in diabetic MI/R (D-MI/R) injury remains to be elucidated. The PI3K/AKT signaling pathway and microRNA (miR)-126 have previously been shown to serve anti-MI/R injury roles. The present study aimed to investigate the protection of Nar against D-MI/R injury and the role of the miR-126-PI3K/AKT axis. Diabetic rats were treated distilled water or Nar (25 or 50 mg/kg, orally) for 30 days and then exposed to MI/R. The present results revealed that Nar alleviated MI/R injury in streptozotocin (STZ)-induced diabetic rats, as shown below: the reduction myocardial enzymes levels was measured using spectrophotometry, the increase of cardiac viability was detected by MTT assay, the inhibition of myocardial oxidative stress was measured using spectrophotometry and the enhancement of cardiac function were recorded using a hemodynamic monitoring system. Furthermore, Nar upregulated the myocardial miR-126-PI3K/AKT axis in D-MI/R rats. These results indicated that Nar alleviated MI/R injury through upregulating the myocardial miR-126-PI3K/AKT axis in STZ-induced diabetic rats. The current findings revealed that Nar, as an effective agent against D-MI/R injury, may provide an effective approach in the management of diabetic IHD.

Tiliacora triandra extract and its major constituent attenuates diabetic kidney and testicular impairment by modulating redox imbalance and pro-inflammatory responses in rats

BACKGROUND

Literature has demonstrated that diabetes is associated with renal complication and testicular dysfunctions. The current study explored the potential of Tiliacora triandra extract and its major component against diabetic kidney and testicular damages in rats.

METHODS

Diabetes was induced by high fat diet/streptozotocin (HFD/STZ) and treated orally with Tiliacora triandra extract (TTE, 100 and 400 mg kg^-1 body weight) and its major component, 5,7-dihydroxy-6-oxoheptadecanoic acid (DHA, 25 mg kg^-1 body weight) for 30 consecutive days. Testicular activities of testicular enzymes, serum levels of testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), sperm parameters and urinalysis for protein and albumin levels were evaluated. Renal and testicular biomarkers of oxidative stress and pro-inflammation were analysed along with histology.

RESULTS

The experimental diabetes induced significant alterations in the levels and activities of indices evaluated compared to non-diabetic normal rats. The 28-day treatment of diabetic rats with TTE and DHA markedly improved activities of testicular enzymes, restored levels of testosterone, LH and FSH and sperm parameters compared to untreated diabetic rats. TTE and DHA abrogated proteinuria and reversed urine albumin level. Testicular and renal oxidative stress and pro-inflammation were attenuated in diabetic rats treated with TTE and DHA. The diabetes-mediated histopathological damage was alleviated in the kidney and testis.

CONCLUSION

The protective effect of TTE and DHA against diabetes induced kidney and testicular damages may be related to its antioxidant and anti-inflammatory activities. © 2020 Society of Chemical Industry.

A Network Pharmacology-Based Approach for Exploring Key Active Compounds and Pharmacological Mechanisms of Tangshen Formula for Treatment of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the common and severe microvascular complications of diabetes mellitus (DM). The occurrence and development of DN are related to multiple factors in the human body, which makes DN a complex disease, and the pathogeneses of DN have not yet been fully illustrated. Furthermore, DN lacks effective drugs for treatment nowadays. Chinese herbal medicine (CHM) often shows the feature of multicomponents, multitargets, multipathways, and synergistic effects and shows a promising source of new therapeutic drugs for DN. As a CHM, Tangshen Formula (TSF) was used to treat DN patients in China. However, its bioactive compounds and holistic pharmacological mechanisms on DN are both unclear. A network pharmacology approach was firstly applied to explore multiple active compounds and multiple key pharmacological mechanisms for TSF treating DN by drug-targeted interaction databases, herb-compound-target network, protein-protein interaction network, compound-target-pathway network, and analysis methods. And the results showed that TSF have the characteristic of multicomponents, multitargets, multipathways, and synergistic effects for treating DN. The quercetin, naringenin, kaempferol, and isorhamnetin as key active compounds and the PI3K-Akt signaling pathway, TNF signaling pathway, nonalcoholic fatty liver disease (NAFLD), focal adhesion, rap1 signaling pathway, T cell receptor signaling pathway, MAPK signaling pathway, and insulin resistance as the key molecular mechanisms play important roles in TSF treating DN. Moreover, quercetin, naringenin, kaempferol, and isorhamnetin were successfully detected in TSF by the UHPLC-MS/MS analysis method. And their concentrations were 0.224, 8.295, 0.0564, and 0.0879 mg·kg-1, respectively. The present findings not only provide new insights for a deeper understanding of the constituent basis and pharmacology of TSF but also provide guidance for further pharmacological studies on TSF.

Naringenin prevents doxorubicin-induced toxicity in kidney tissues by regulating the oxidative and inflammatory insult in Wistar rats

This study is undertaken to investigate the effects of naringenin on doxorubicin- (Dox) induced nephrotoxicity in Wistar rats. Dox 10 mg/kg body weight was administered intraperitoneally once and naringenin 50 and 100 mg/kg body weight was administered orally daily for 21 d. Dox-induced oxidative stress lead to steep elevation in blood urea nitrogen (BUN), creatinine, lactate dehydrogenase (LDH), and kidney injury molecule-1 (KIM-1), compared to control, treatment with naringenin preserved kidney functions. With Dox treatment significant decrease in antioxidant enzymes with increase in malondialdehyde (MDA) compared to control was observed. Naringenin treatment reversed these values compared to Dox in kidney tissue. Dox treatment showed increased tissue nitric oxide levels naringenin treatment decreased nitric oxide (NO) in kidney tissue. Furthermore, Dox-induced inflammatory burst as indicated by up-regulation of nuclear factor-κB (NF-κB), tumour necrosis factor-α (TNF-α) tissue levels and prostaglandin-E2 (PGE-2). All such events were normalised back to normal by naringenin treatment.

Combination of Naringenin and Lisinopril Ameliorates Nephropathy in Type-1 Diabetic Rats

BACKGROUND

Diabetes is a metabolic disorder affecting a large percentage of the population worldwide. The chronic hyperglycemic condition leads to the generation of advanced glycation end products, reactive oxygen species and inflammatory cytokines, which worsen the functioning of the kidney. Clinical management of diabetic nephropathy is difficult as it requires a multi-focused approach. Hence, a combination of lisinopril a drug used in clinical practice for nephropathy, and naringenin, a flavonoid reported to have a significant effect in nephropathy, may show additive or synergistic effect with less side effects.

OBJECTIVE

The objective of the present study was to evaluate the effect of a combination of lisinopril with naringenin in diabetic nephropathy.

METHODS

Diabetes was induced in male Sprague Dawley rats by streptozotocin (55 mg/kg, i.p.). After four weeks of diabetes induction animals were treated with naringenin alone and a combination of Lisinopril and naringenin for the next four weeks. At the end of the study, various urine and biochemical parameters were evaluated. Oxidative stress parameters like malondialdehyde, reduced glutathione; catalase and superoxide dismutase for kidney tissues were estimated and histopathology studies of kidneys were carried out.

RESULTS

The combination of lisinopril (10 mg/kg) and naringenin (25 and 50 mg/kg) treatment showed significant improvement in the biochemical and urine parameters. Combination treatment also attenuated renal oxidative stress and renal damage as observed in histopathological studies.

CONCLUSION

Treatment with a combination of lisinopril and naringenin showed a promising effect on diabetic nephropathy in rats.

Naringenin improves mitochondrial function and reduces cardiac damage following ischemia-reperfusion injury: the role of the AMPK-SIRT3 signaling pathway

Mitochondrial dysfunction contributed greatly to myocardial ischemia-reperfusion (MI/R)-induced cardiomyocyte apoptosis. Naringenin is a flavonoid exhibiting potential protective effects on myocardial mitochondria under stress conditions. However, the detailed down-stream signaling pathway involved remains uncovered. This study was designed to elucidate naringenin's mitochondrial protective actions during MI/R with a focus on AMPK-SIRT3 signaling. Sprague-Dawley rats were administered with naringenin (50 mg kg-1 d-1) and subjected to MI/R surgery in the presence or absence of compound C (0.25 mg kg-1, Com.C, an AMPK inhibitor) co-treatment. An in vitro study was performed on H9c2 cardiomyoblasts subjected to simulated ischemia-reperfusion treatment. Before the treatment, the cells were administered with naringenin (80 μmol L-1) with or without SIRT3 siRNA/AMPK1α siRNA transfection. Naringenin improved post-reperfusion left ventricular systolic pressure and the instantaneous first derivative of left ventricular pressure, and reduced the infarction size and myocardial apoptosis index by suppressing mitochondrial oxidative stress damage (as evidenced by decreased mitochondrial cytochrome c release and oxidative markers) and enhancing mitochondrial biogenesis [as evidenced by increased NRF1, TFAM and oxidative phosphorylation subunit complexes (II, III and IV)]. These protective actions were abolished by Com.C (in vivo) or SIRT3 siRNA (in vitro) administration. Further investigation revealed that Com.C (in vivo) or AMPK1α siRNA (in vitro) markedly suppressed PGC-1α and SIRT3 levels while SIRT3 siRNA (in vitro) inhibited SIRT3 expression without significantly changing AMPK phosphorylation and PGC-1α levels. Taken together, we found that naringenin directly inhibits mitochondrial oxidative stress damage and preserves mitochondrial biogenesis, thus attenuating MI/R injury. Importantly, AMPK-SIRT3 signaling played a key role in this process.

Naringenin improves insulin sensitivity in gestational diabetes mellitus mice through AMPK

Background

Gestational diabetes mellitus (GDM) is a temporary form of diabetes during pregnancy, which influences the health of maternal-child in clinical practice. It is still urgent to develop new effective treatment for GDM. Naringenin is a bioactive ingredient with multiple activities including anti-diabetic. In current study, the effects of naringenin on GDM symptoms, insulin tolerance, inflammation, and productive outcomes were evaluated and the underlying mechanisms were explored.

Methods

We administrated naringenin to GDM mice and monitored the GDM symptoms, glucose and insulin tolerance, inflammation and productive outcomes. We established tumor necrosis factor alpha (TNF-α)-induced insulin resistance skeletal muscle cell model and evaluated the effects of naringenin on reactive oxygen species (ROS) production, glucose uptake and glucose transporter type 4 (GLUT4) membrane translocation.

Results

We found that naringenin ameliorated GDM symptoms, improved glucose and insulin tolerance, inhibited inflammation, and improved productive outcomes. It was further found that naringenin inhibited TNF-α-induced ROS production, enhanced GLUT4 membrane translocation, and glucose uptake, which were abolished by inhibition of AMP-activated protein kinase (AMPK).

Conclusion

Naringenin improves insulin sensitivity in gestational diabetes mellitus mice in an AMPK-dependent manner.

Anti-Diabetic, Anti-Inflammatory, and Anti-Oxidant Effects of Naringenin in an In Vitro Human Model and an In Vivo Murine Model of Gestational Diabetes Mellitus

SCOPE

Gestational diabetes mellitus (GDM), which affects up to 20% of pregnant women, is associated with maternal peripheral insulin resistance, low-grade inflammation, and oxidative stress. The flavonoid naringenin has potent anti-diabetic, anti-inflammatory, and anti-oxidative properties; however, its effects in GDM remain unknown. The study aimed to determine the effects of naringenin on glucose metabolism, inflammation, and oxidative stress associated with GDM both in vitro and in vivo.

METHODS AND RESULTS

In vitro, human tissue samples obtained at term elective Caesarean section are stimulated with tumour necrosis factor alpha (TNF) to develop a GDM-like environment. Naringenin treatment significantly improves TNF-impaired glucose uptake in skeletal muscle. In placenta and visceral adipose tissue (VAT), naringenin significantly reduces expression of pro-inflammatory cytokines and chemokines and increases antioxidant mRNA expression. Mechanistically, naringenin suppresses nuclear factor κB activation. In vivo, pregnant heterozygous db/+ mice are used to model GDM. Daily intraperitoneal injections of GDM mice with naringenin from gestational day 10-17 significantly improve glucose tolerance, reduces IL1A mRNA expression, and increases antioxidant mRNA expression in placenta, VAT, and subcutaneous adipose tissue.

CONCLUSION

Naringenin is shown to improve insulin sensitivity, inflammation, and oxidative stress associated with GDM and shows promise as a novel preventive therapeutic.

Natural Hydrogen Sulfide Donors from Allium sp. as a Nutraceutical Approach in Type 2 Diabetes Prevention and Therapy

Type 2 diabetes mellitus (DM) is a socially relevant chronic disease with high prevalence worldwide. DM may lead to several vascular, macrovascular, and microvascular complications (cerebrovascular, coronary artery, and peripheral arterial diseases, retinopathy, neuropathy, and nephropathy), often accelerating the progression of atherosclerosis. Dietary therapy is generally considered to be the first step in the treatment of diabetic patients. Among the current therapeutic options, such as insulin therapy and hypoglycemic drugs, in recent years, attention has been shifting to the effects and properties-that are still not completely known-of medicinal plants as valid and inexpensive therapeutic supports with limited side effects. In this review, we report the relevant effects of medicinal plants and nutraceuticals in diabetes. In particular, we paid attention to the organosulfur compounds (OSCs) present in plant extracts that due to their antioxidant, hypoglycemic, anti-inflammatory, and immunomodulatory effects, can contribute as cardioprotective agents in type 2 DM. OSCs derived from garlic (Allium sp.), due to their properties, can represent a valuable support to the diet in type 2 DM, as outlined in this manuscript based on both in vitro and in vivo studies. Moreover, a relevant characteristic of garlic OSCs is their ability to produce the gasotransmitter H₂S, and many of their effects can be explained by this property. Indeed, in recent years, several studies have demonstrated the relevant effects of endogenous and exogenous H₂S in human DM, including by in vitro and in vivo experiments and clinical trials; therefore, here, we summarize the effects and the underlying molecular mechanisms of H₂S and natural H₂S donors.

Activation of 20-HETE/PPARs involved in reno-therapeutic effect of naringenin on diabetic nephropathy

Naringenin is a flavanone compound found in citrus fruits. Recent researches showed that naringenin has many potentially pharmacological effects. However, the therapeutic effect and the potential mechanism of naringenin on diabetic nephropathy (DN) remain to be elucidated. DN model was established by a high-fat diet combined with streptozotocin (STZ), which was confirmed by the levels of fasting blood glucose (FBG, more than 11.1 mmol/L) and urinary albumin (10 times higher than the normal mice). After 5 weeks of STZ injection, the DN was developed in model mice. Then naringenin (25 or 75 mg/kg·d) were supplemented for 4 weeks. At the end of the experiment, the injury of the renal function and structure was deteriorated. Concomitantly, peroxisome proliferators-activated receptors (PPARs) protein expression was down-regulated, and CYP4A expression and 20-hydroxyeicosatetraenoic acid (20-HETE) level were reduced in DN mice. Naringenin administration improved the renal damage of DN mice, and up-regulated PPARs expression, increased CYP4A-20-HETE level. Consistent with the results of in vivo, glucose at 30 mmol/L (high glucose, HG) significantly induced cell proliferation and hypertrophy in NRK-52E cells, following the reductive PPARs protein expression and the downward CYP4A-20-HETE level. Naringenin (0.01, 0.1, 1 μmol/L) reversed these changes induced by HG in a dose-dependent manner. HET0016, a selective inhibitor of 20-HETE synthase, partially blocked the effects of naringenin. In conclusion, naringenin has a therapeutic effect on DN, which may be, at least partly, related to the activation of CYP4A-20-HETE and the up-regulation of PPARs.

Antidiabetic Properties of Naringenin: A Citrus Fruit Polyphenol

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by insulin resistance and hyperglycemia and is associated with personal health and global economic burdens. Current strategies/approaches of insulin resistance and T2DM prevention and treatment are lacking in efficacy resulting in the need for new preventative and targeted therapies. In recent years, epidemiological studies have suggested that diets rich in vegetables and fruits are associated with health benefits including protection against insulin resistance and T2DM. Naringenin, a citrus flavanone, has been reported to have antioxidant, anti-inflammatory, hepatoprotective, nephroprotective, immunomodulatory and antidiabetic properties. The current review summarizes the existing in vitro and in vivo animal studies examining the anti-diabetic effects of naringenin.

Effects and Underlying Mechanisms of Bioactive Compounds on Type 2 Diabetes Mellitus and Alzheimer's Disease

Type 2 diabetes mellitus is a complicated metabolic disorder characterized by hyperglycemia and glucose intolerance. Alzheimer's disease is a progressive brain disorder characterized by a chronic loss of cognitive and behavioral function. Considering the shared characteristics of both diseases, common therapeutic and preventive agents may be effective. Bioactive compounds such as polyphenols, vitamins, and carotenoids found in vegetables and fruits can have antioxidant and anti-inflammatory effects. These effects make them suitable candidates for the prevention or treatment of diabetes and Alzheimer's disease. Increasing evidence from cell or animal models suggest that bioactive compounds may have direct effects on decreasing hyperglycemia, enhancing insulin secretion, and preventing formation of amyloid plaques. The possible underlying molecular mechanisms are described in this review. More studies are needed to establish the clinical effects of bioactive compounds.

The Therapeutic Potential of Naringenin: A Review of Clinical Trials

Naringenin is a flavonoid belonging to flavanones subclass. It is widely distributed in several Citrus fruits, bergamot, tomatoes and other fruits, being also found in its glycosides form (mainly naringin). Several biological activities have been ascribed to this phytochemical, among them antioxidant, antitumor, antiviral, antibacterial, anti-inflammatory, antiadipogenic and cardioprotective effects. Nonetheless, most of the data reported have been obtained from in vitro or in vivo studies. Although some clinical studies have also been performed, the main focus is on naringenin bioavailability and cardioprotective action. In addition, these studies were done in compromised patients (i.e., hypercholesterolemic and overweight), with a dosage ranging between 600 and 800 μM/day, whereas the effect on healthy volunteers is still debatable. In fact, naringenin ability to improve endothelial function has been well-established. Indeed, the currently available data are very promising, but further research on pharmacokinetic and pharmacodynamic aspects is encouraged to improve both available production and delivery methods and to achieve feasible naringenin-based clinical formulations.

Naringenin Attenuates Myocardial Ischemia-Reperfusion Injury via cGMP-PKGIα Signaling and In Vivo and In Vitro Studies

Endoplasmic reticulum (ER) stress and oxidative stress contribute greatly to myocardial ischemia-reperfusion (MI/R) injury. Naringenin, a flavonoid derived from the citrus genus, exerts cardioprotective effects. However, the effects of naringenin on ER stress as well as oxidative stress under MI/R condition and the detailed mechanisms remain poorly defined. This study investigated the protective effect of naringenin on MI/R-injured heart with a focus on cyclic guanosine monophosphate- (cGMP-) dependent protein kinase (PKG) signaling. Sprague-Dawley rats were treated with naringenin (50 mg/kg/d) and subjected to MI/R surgery with or without KT5823 (2 mg/kg, a selective inhibitor of PKG) cotreatment. Cellular experiment was conducted on H9c2 cardiomyoblasts subjected to simulated ischemia-reperfusion treatment. Before the treatment, the cells were incubated with naringenin (80 μmol/L). PKGIα siRNA was employed to inhibit PKG signaling. Our in vivo and in vitro data showed that naringenin effectively improved heart function while it attenuated myocardial apoptosis and infarction. Furthermore, pretreatment with naringenin suppressed MI/R-induced oxidative stress as well as ER stress as evidenced by decreased superoxide generation, myocardial MDA level, gp91^phox expression, and phosphorylation of PERK, IRE1α, and EIF2α as well as reduced ATF6 and CHOP. Importantly, naringenin significantly activated myocardial cGMP-PKGIα signaling while inhibition of PKG signaling with KT5823 (in vivo) or siRNA (in vitro) not only abolished these actions but also blunted naringenin's inhibitory effects against oxidative stress and ER stress. In summary, our study demonstrates that naringenin treatment protects against MI/R injury by reducing oxidative stress and ER stress via cGMP-PKGIα signaling. Its cardioprotective effect deserves further clinical study.

Potential protective effects of naringenin against vancomycin-induced nephrotoxicity via reduction on apoptotic and oxidative stress markers in rats

Vancomycin (VCM), a glycopeptide antibiotic, is a drug widely used in severe infections. However, VCM induce notable nephrotoxic side effects. Naringenin (NAR) is a natural of flavonoid and are known as strongly antioxidant, nefroprotective, antiapoptotic, and anti-inflammatory. The purpose of this study was to determine the potential protective effects of NAR against VCM-induced nephrotoxicity by measuring apoptotic and oxidative stress markers and evaluating histopathological alterations in rats. For this purpose, we used male Wistar albino rats that divided into seven groups: (i) Control [saline, intraperitoneally (i.p.)], (ii) carboxymethyl cellulose (0.5% CMC, orally), (iii) VCM (400 mg/kg, i.p.), (iv) NAR100 (100 mg/kg, orally), (v) VCM + NAR25 (25 mg/kg, orally), (vi) VCM + NAR50 (50 mg/kg, orally), and (vii) VCM + NAR100 (100 mg/kg, orally) groups. VCM administration was started one day after the first treatment of NAR and continued across 7-day. Caspase-3, -8, and-9 activities and malondialdehyde (MDA) and nitric oxide (NO) levels were measured by colorimetric methods in the kidney tissues, creatinine, and blood urea nitrogen (BUN) levels were analyzed based on ELISA in serum. Caspase-3 and -8 activities, NO levels, serum creatinine and BUN levels were significantly higher in VCM group in comparison with VCM + NAR (25, 50, and 100) groups (p < 0.05). Caspase-9 activity and MDA were significantly higher in VCM group compared to VCM + NAR (25 and 50) groups (p < 0.05). Histopathological alterations in VCM group were significantly diminished by administration of NAR, especially NAR 25. In conclusion, NAR 25 and 50 mg have more potent protective effects on VCM-induced nephrotoxicity compared to NAR 100 mg.

Vanadium quercetin complex attenuates mammary cancer by regulating the P53, Akt/mTOR pathway and downregulates cellular proliferation correlated with increased apoptotic events

Flavonoid metal ion complexes have been deliberated in recent years and are considered as a new class of medicinal agents with enhanced therapeutic activity and low toxicity. Our study deals with chemotherapeutic effects of vanadium, when coordinated with the flavonoid quercetin on a defined model of chemically induced rat mammary carcinogenesis in vivo and on human breast cancer cell line MCF-7 in vitro. The characterization of the complex was achieved through UV-Visible, IR, and Mass spectra and antioxidant activity was assessed by DPPH, FRAP and ABTS methods. In vitro studies established that the complex upregulated the expressions of p53, Caspase 3 and 9, whereas down regulating Akt, mTOR and VEGF expressions and also induced apoptosis and DNA fragmentation in a dose dependent manner. Acute and Sub-acute toxicity was performed to determine safe doses. 7,12-Dimethylbenz(α)anthracene (0.5 mg/100 g body weight) was used for induction of breast cancer in female Sprague-Dawley rats via single tail vein injection. The histopathological analysis after 24 weeks of carcinogenesis study depicted substantial repair of hyperplastic lesions. TUNEL assay showed an increase in apoptotic index (0.14 ± 0.03; 0.15 ± 0.01) in vanadium-quercetin treated groups as compared to the carcinogen control (0.02 ± 0.01) along with upregulation of Bcl-2 and downregulation of Bax and p53. Immunohistochemical analysis also exhibited decrease in cell proliferation in the vanadium-quercetin treated groups (11.3 ± 0.12; 11.8 ± 0.10). Thus, results from both in vivo and in vitro studies revealed that vanadium-quercetin complex could be a potential candidate for development of approved drug for breast cancer in the near future.

Flavonoids in Kidney Health and Disease

This review summarizes the latest advances in knowledge on the effects of flavonoids on renal function in health and disease. Flavonoids have antihypertensive, antidiabetic, and antiinflammatory effects, among other therapeutic activities. Many of them also exert renoprotective actions that may be of interest in diseases such as glomerulonephritis, diabetic nephropathy, and chemically-induced kidney insufficiency. They affect several renal factors that promote diuresis and natriuresis, which may contribute to their well-known antihypertensive effect. Flavonoids prevent or attenuate the renal injury associated with arterial hypertension, both by decreasing blood pressure and by acting directly on the renal parenchyma. These outcomes derive from their interference with multiple signaling pathways known to produce renal injury and are independent of their blood pressure-lowering effects. Oral administration of flavonoids prevents or ameliorates adverse effects on the kidney of elevated fructose consumption, high fat diet, and types I and 2 diabetes. These compounds attenuate the hyperglycemia-disrupted renal endothelial barrier function, urinary microalbumin excretion, and glomerular hyperfiltration that results from a reduction of podocyte injury, a determinant factor for albuminuria in diabetic nephropathy. Several flavonoids have shown renal protective effects against many nephrotoxic agents that frequently cause acute kidney injury (AKI) or chronic kidney disease (CKD), such as LPS, gentamycin, alcohol, nicotine, lead or cadmium. Flavonoids also improve cisplatin- or methotrexate-induced renal damage, demonstrating important actions in chemotherapy, anticancer and renoprotective effects. A beneficial prophylactic effect of flavonoids has been also observed against AKI induced by surgical procedures such as ischemia/reperfusion (I/R) or cardiopulmonary bypass. In several murine models of CKD, impaired kidney function was significantly improved by the administration of flavonoids from different sources, alone or in combination with stem cells. In humans, cocoa flavanols were found to have vasculoprotective effects in patients on hemodialysis. Moreover, flavonoids develop antitumor activity against renal carcinoma cells with no toxic effects on normal cells, suggesting a potential therapeutic role in patients with renal carcinoma.

Flavonoid Naringenin Attenuates Oxidative Stress, Apoptosis and Improves Neurotrophic Effects in the Diabetic Rat Retina

Diabetic retinopathy (DR) is one of the leading causes of decreased vision and blindness worldwide. Diabetes-induced oxidative stress is believed to be the key factor that initiates neuronal damage in the diabetic retina leading to DR. Experimental approaches to utilize dietary flavonoids, which possess both antidiabetic and antioxidant activities, might protect the retinal damage in diabetes. The aim of this study was to investigate the potential protective effects of naringenin in the retina of streptozotocin-induced diabetic rats. Diabetic rats were orally treated and untreated with naringenin (50 mg/kg/day) for five weeks and retinas were analyzed for markers of oxidative stress, apoptosis and neurotrophic factors. Systemic effects of naringenin treatments were also analyzed and compared with untreated groups. The results showed that elevated levels of thiobarbituric acid reactive substances (TBARs) and decreased level of glutathione (GSH) in diabetic rats were ameliorated with naringenin treatments. Moreover, decreased levels of neuroprotective factors (Brain derived neurotrophic factor (BDNF)), tropomyosin related kinase B (TrkB) and synaptophysin in diabetic retina were augmented with naringenin treatments. In addition, naringenin treatment ameliorated the levels of apoptosis regulatory proteins; B cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax) and caspase-3 in the diabetic retina. Thus, the study demonstrates the beneficial effects of naringenin that possesses anti-diabetic, antioxidant and antiapoptotic properties, which may limit neurodegeneration by providing neurotrophic support to prevent retinal damage in diabetic retinopathy.

An Overview of Herbal Products and Secondary Metabolites Used for Management of Type Two Diabetes

Diabetes mellitus is a common effect of uncontrolled high blood sugar and it is associated with long-term damage, dysfunction, and failure of various organs. In the adult population, the global prevalence of diabetes has nearly doubled since 1980. Without effective prevention and management programs, the continuing significant rise in diabetes will have grave consequences on the health and lifespan of the world population, and also on the world economy. Supplements can be used to correct nutritional deficiencies or to maintain an adequate intake of certain nutrients. These are often used as treatments for diabetes, sometimes because they have lower costs, or are more accessible or "natural" compared to prescribed medications. Several vitamins, minerals, botanicals, and secondary metabolites have been reported to elicit beneficial effects in hypoglycemic actions in vivo and in vitro; however, the data remain conflicting. Many pharmaceuticals commonly used today are structurally derived from natural compounds from traditional medicinal plants. Botanicals that are most frequently used to help manage blood glucose include: bitter melon (Momordica charantia), fenugreek (Trigonella foenum graecum), gurmar (Gymnema sylvestre), ivy gourd (Coccinia indica), nopal (Opuntia spp.), ginseng, Russian tarragon (Artemisia dracunculus), cinnamon (Cinnamomum cassia), psyllium (Plantago ovata), and garlic (Allium sativum). In majority of the herbal products and secondary metabolites used in treating diabetes, the mechanisms of action involve regulation of insulin signaling pathways, translocation of GLUT-4 receptor and/or activation the PPARγ. Several flavonoids inhibit glucose absorption by inhibiting intestinal α-amylase and α-glucosidase. In-depth studies to validate the efficacies and safeties of extracts of these traditional medicinal plants are needed, and large, well designed, clinical studies need to be carried out before the use of such preparations can be recommended for treatment and/or prevention of diabetes. The main focus of this review is to describe what we know to date of the active compounds in these, along with their glucose-lowering mechanisms, which are either through insulin-mimicking activity or enhanced glucose uptake.

Metformin-like antidiabetic, cardio-protective and non-glycemic effects of naringenin: Molecular and pharmacological insights

Metformin is a widely used drug for the treatment of type 2 diabetes (T2D). Its blood glucose-lowering effects are initially due to inhibition of hepatic glucose production and increased peripheral glucose utilization. Metformin has also been shown to have several beneficial effects on cardiovascular risk factors and it is the only oral antihyperglycaemic agent thus far associated with decreased macrovascular complications in patients with diabetes. Adenosine Monophosphate Activated-Protein Kinase (AMPK) is a major cellular regulator of lipid and glucose metabolism. Recent evidence shows that pharmacological activation of AMPK improves blood glucose homeostasis, lipid profiles, blood pressure and insulin-resistance making it a novel therapeutic target in the treatment of T2D. Naringenin a flavonoid found in high concentrations as its glycone naringin in citrus fruits, has been reported to have antioxidant, antiatherogenic, anti- dyslipidemic and anti-diabetic effects. It has been shown that naringenin exerts its anti-diabetic effects by inhibition of gluconeogenesis through upregulations of AMPK hence metformin-like effects. Naringin has further been shown to have non-glycemic affects like metformin that mitigate inflammation and cell proliferation. This review evaluates the potential of naringenin as anti-diabetic, anti-dyslipidemic anti-inflammatory and antineoplastic agent similar to metformin and proposes its further development for therapeutic use in clinical practice.

Naringenin improves the healing process of thermally-induced skin damage in rats

Objective

To evaluate the effect of the phenolic compound naringenin on thermal burn-induced inflammatory responses and oxidative stress in rats.

Methods

First degree thermal burn injuries were induced in shaved rats by 10 s immersion of the back surface in water at 90℃. Naringenin treatment (25, 50 and 100 mg/kg/day) was initiated 24 h following burn injury, and continued for 7 days. On treatment day 7, serum tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, nitric oxide (NO), prostaglandin (PG)E₂, caspase-3, leukotriene (LT)-B4 and nuclear factor (NF)-κB levels were quantified. Skin sample glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) levels, and catalase, superoxide dismutase (SOD), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities, were also measured.

Results

Serum inflammatory biomarkers were significantly increased in thermal-burn injured rats versus uninjured controls. Naringenin significantly inhibited the increased proinflammatory markers at day 7 of treatment. Increased TBARS levels and decreased GSH levels in wounded skin were significantly restored by naringenin treatment at day 7. SOD, catalase, GPx and GST activities were markedly inhibited in wounded skin tissues, and were significantly increased in naringenin-treated rats.

Conclusion

Naringenin treatment showed anti-inflammatory and antioxidant effects in rats with thermal burn-induced injury.