Genistein protects pancreatic beta cells against cytokine-mediated toxicity

Role of polyphenols in the management of diabetic complications

BACKGROUND

Diabetes Mellitus is an endocrine disorder that will affect, about 693 million adults by 2045 worldwide, (>50% increase from 2017). The conventional treatment of the disease, include the oral hypoglycemic drugs which are given in combination with other drugs and are known to possess various adverse effects like gastrointestinal disturbance, nausea, water retention etc. PURPOSE: Due to the urgent need of combating this disorder without side effects, the alternative and complementary therapies should be explored due to their natural origins and comparable safety. Herbal sources serve as new leads, due to the presence of phytoconstituents with potential therapeutic properties, efficacy and safety. In this review, we tried to summarise the polyphenolic phytoconstituents effective in the treatment of diabetic complications.

METHODS

A systematic literature search was conducted using 4 databases (Google scholar, Pubmed, Scopus, Embase) for the identification of relevant data. Search was performed using various key words such as "diabetes", "polyphenols", "marine sources","anti-diabetic polyphenols". The in vitro studies involving the cell lines used in diabetes and animal models were also considered for inclusion. Additional research papers were identified by reviewing abstracts, scrutinizing reference lists, and reviewing previously published review articles.

RESULTS

Polyphenols, a group of phytoconstituents are known worldwide for their tremendous antioxidant potential. So, various research groups have explored their mechanism and therapeutic value in diabetic complications, to improve the insulin sensitivity and glucose metabolism, in controlling the glycemic conditions.

CONCLUSION

Polyphenols exhibit effective therapeutic potential in managing diabetic complications through their multifaceted mechanism of action. They exhibit antioxidative, anti-inflammatory, and anti-glycemic properties, which collectively contribute to their beneficial effects in mitigating diabetic complications. Thus, the inclusion of polyphenols into the diet, may be cosidered as an approach of managing diabetes on long term basis. In this review, we have tried to identify polyphenols effective in diabetes and summarize their mechanism of action along with their potential, for the treatment of diabetic complications.

Cytoprotective effect of genistein against dexamethasone-induced pancreatic β-cell apoptosis

Steroid-induced diabetes is a well-known metabolic side effect of long-term use of glucocorticoid (GC). Our group recently demonstrated dexamethasone-induced pancreatic β-cell apoptosis via upregulation of TRAIL and TRAIL death receptor (DR5). Genistein protects against pancreatic β-cell apoptosis induced by toxic agents. This study aimed to investigate the cytoprotective effect of genistein against dexamethasone-induced pancreatic β-cell apoptosis in cultured rat insulinoma (INS-1) cell line and in isolated mouse islets. In the absence of genistein, dexamethasone-induced pancreatic β-cell apoptosis was associated with upregulation of TRAIL, DR5, and superoxide production, but downregulation of TRAIL decoy receptor (DcR1). Dexamethasone also activated the expression of extrinsic and intrinsic apoptotic proteins, including Bax, NF-κB, caspase-8, and caspase-3, but suppressed the expression of the anti-apoptotic Bcl-2 protein. Combination treatment with dexamethasone and genistein protected against pancreatic β-cell apoptosis, and reduced the effects of dexamethasone on the expressions of TRAIL, DR5, DcR1, superoxide production, Bax, Bcl-2, NF-κB, caspase-8, and caspase-3. Moreover, combination treatment with dexamethasone and genistein reduced the expressions of TRAIL and DR5 in isolated mouse islets. The results of this study demonstrate the cytoprotective effect of genistein against dexamethasone-induced pancreatic β-cell apoptosis in both cell line and islets via reduced TRAIL and DR5 protein expression.

Therapeutic potentials of genistein: New insights and perspectives

Genistein, a polyphenolic isoflavone compound found abundantly in soy or soy-based products, is widely consumed in the Asian population. Genistein has poor bioavailability, to overcome this problem many advanced nano-drug delivery carrier systems are designed to enhance its water solubility and stability. However, further research is required to develop more efficient bioavailability improvement strategies. Genistein is a phytoestrogen which has been associated with reducing the risk of cancer, cardiovascular disorders, and diabetes mellitus. This plant-based bioactive compound possesses numerous biological activities such as anti-oxidant, anti-inflammatory, anti-obesity, anti-cancer, cardioprotective, and anti-diabetic activities to treat various disease states. Genistein has been used as an active therapeutic agent in many medications. Moreover, several clinical trials are in the ongoing stage to develop more efficient treatment therapies, especially for cancer treatment. This article highlights the protective and therapeutic benefits of genistein in the treatment of different ailments, and more specifically elaborates on the anti-cancer potential of genistein regarding various types of cancers. PRACTICAL APPLICATIONS: Genistein possesses versatile biological activities, including anti-diabetic, anti-inflammatory, anti-oxidant, anti-obesity, and anti-angiogenic. The most studied activity is anti-cancer. Currently, a number of pre-clinical and clinical trials are being carried out on anti-neoplastic and cytotoxic activities of genistein to develop novel therapeutic agents with excellent anti-cancer potential for the treatment of various kinds of cancer. Moreover, many bioavailability enhancement strategies have been developed to improve the bioavailability of genistein. Genistein shows significant hypoglycemic effects alone or in combination with other anti-diabetic agents. Genistein in combination with other chemotherapeutic agents is used for the treatment of prostate, bone, colorectal, glioma, breast, and bladder cancer.

Genistein as a regulator of signaling pathways and microRNAs in different types of cancers

Cancers are complex diseases orchestrated by a plethora of extrinsic and intrinsic factors. Research spanning over several decades has provided better understanding of complex molecular interactions responsible for the multifaceted nature of cancer. Recent advances in the field of next generation sequencing and functional genomics have brought us closer towards unravelling the complexities of tumor microenvironment (tumor heterogeneity) and deregulated signaling cascades responsible for proliferation and survival of tumor cells. Phytochemicals have begun to emerge as potent beneficial substances aimed to target deregulated signaling pathways. Isoflavonoid genistein is an essential phytochemical involved in regulation of key biological processes including those in different types of cancer. Emerging preclinical evidence have shown its anti-cancer, anti-inflammatory and anti-oxidant properties. Testing of this substance is in various phases of clinical trials. Comprehensive preclinical and clinical trials data is providing insight on genistein as a modulator of various signaling pathways both at transcription and translation levels. In this review we have explained the mechanistic regulation of several key cellular pathways by genistein. We have also addressed in detail various microRNAs regulated by genistein in different types of cancer. Moreover, application of nano-formulations to increase the efficiency of genistein is also discussed. Understanding the pleiotropic potential of genistein to regulate key cellular pathways and development of efficient drug delivery system will bring us a step towards designing better chemotherapeutics.

Regulation of Intestinal Inflammation by Soybean and Soy-Derived Compounds

Environmental factors, particularly diet, are considered central to the pathogenesis of the inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis. In particular, the Westernization of diet, characterized by high intake of animal protein, saturated fat, and refined carbohydrates, has been shown to contribute to the development and progression of IBD. During the last decade, soybean, as well as soy-derived bioactive compounds (e.g., isoflavones, phytosterols, Bowman-Birk inhibitors) have been increasingly investigated because of their anti-inflammatory properties in animal models of IBD. Herein we provide a scoping review of the most studied disease mechanisms associated with disease induction and progression in IBD rodent models after feeding of either the whole food or a bioactive present in soybean.

The Role of Isoflavones in Type 2 Diabetes Prevention and Treatment-A Narrative Review

Given the growing number of type 2 diabetic individuals and the substantial social and financial costs associated with diabetes management, every effort should be made to improve its prevention and treatment methods. There is an ongoing search for natural dietary compounds that could be used for this purpose. This narrative review focuses on the therapeutic potential of isoflavones in diabetes prevention and treatment. This review summarizes (i) the molecular mechanisms of isoflavones action that are critical to their anti-diabetic properties; (ii) preclinical (in vitro and in vivo) studies evaluating the influence of isoflavones on the function of key organs involved in the pathogenesis of diabetes; and (iii) epidemiological studies and clinical trials that assessed the effectiveness of isoflavones in the prevention and treatment of type 2 diabetes in humans. Apart from discussing the effects of isoflavones on the function of organs “classically” associated with the pathogenesis of diabetes (pancreas, liver, muscles, and adipose tissue), the impact of these compounds on other organs that contribute to the glucose homeostasis (gastrointestinal tract, kidneys, and brain) is also reviewed.

Potentials and Safety of Date Palm Fruit against Diabetes: A Critical Review

Diabetes is a chronic metabolic disorder triggered by disturbances in carbohydrate, protein, and lipid metabolisms, where either reduced secretion or sensitivity of insulin is observed coupled with poor glucose control. Date palm fruits are one of the fruits reported to have good potential in diabetes treatment due to its presence of polyphenols exerting strong antioxidant activities. Other possible mechanisms of action include the polyphenolic compounds, which can inhibit enzymes like α-amylase and α-glucosidase. Flavonoids in dates can stimulate β-cells by increasing the number of islets and β-cells, recovering endocrine pancreatic tissues, reducing β-cell apoptosis, activating insulin receptors following the increase in insulin secretion, in addition to improving diabetes-induced complications. In this review, the in vitro, in vivo, and human study-based evidence of date palm as an anti-diabetic fruit is summarised.

Soy food intake associates with changes in the metabolome and reduced blood pressure in a gut microbiota dependent manner

BACKGROUND AND AIMS

Consumption of soy foods has been associated with protection against cardiometabolic disease, but the mechanisms are incompletely understood. We hypothesized that habitual soy food consumption associates with gut microbiome composition, metabolite production, and the interaction between diet, microbiota and metabolites.

METHODS AND RESULTS

We analyzed dietary soy intake, plasma and stool metabolites, and gut microbiome data from two independent cross-sectional samples of healthy US individuals (N = 75 lean or overweight, and N = 29 obese). Habitual soy intake associated with several circulating metabolites. There was a significant interaction between soy intake and gut microbiome composition, as defined by gut enterotype, on metabolites in plasma and stool. Soy consumption associated with reduced systolic blood pressure, but only in a subset of individuals defined by their gut microbiome enterotype, suggesting that responsiveness to soy may be dependent on microbiome composition. Soy intake was associated with differences in specific microbial taxa, including two taxa mapping to genus Dialister and Prevotella which appeared to be suppressed by high soy intake We identified context-dependent effects of these taxa, where presence of Prevotella was associated with higher blood pressure and a worse cardiometabolic profile, but only in the absence of Dialister.

CONCLUSIONS

The gut microbiome is an important intermediate in the interplay between dietary soy intake and systemic metabolism. Consumption of soy foods may shape the microbiome by suppressing specific taxa, and may protect against hypertension only in individuals with soy-responsive microbiota.

CLINICAL TRIALS REGISTRY

NCT02010359 at clinicaltrials.gov.

Dietary plant flavonoids in prevention of obesity and diabetes

Obesity and diabetes are the most prevailing chronic metabolic diseases worldwide from mainly lipid and glucose metabolic dysfunctions and their incidence is increasing at an alarming high rate. Obesity is characterized by excess fat accumulation in WAT and liver and is the central player of insulin resistance in the peripheral tissues from chronic inflammation, lipotoxicity and gut dysbiosis, and plays a key role for development of type 2 diabetes (T2DM) and vascular diseases. Diabetes mellitus, known as diabetes, is chiefly characterized by hyperglycaemia from impaired insulin secretion and insulin resistance. Several identified mutant genes in insulin secretion and resistance and various environmental factors are considered responsible for the onset of this disease. Currently available oral synthetic drugs, biguanides, incretin mimetic, GLP-1R and PPAR agonists and DPP-4 inhibitors for management of obesity and diabetes have several adverse effects in patients on long-term use. Emerging evidence supports the efficacy of dietary plant flavonoids in prevention and attenuation of obesity and diabetes by the protection and proliferation of pancreatic beta-cells and improvement of their insulin secretory function via activation of cAMP/PKA signaling pathway as well as in the improvement of insulin sensitivity in the peripheral metabolic tisssues for glucose uptake and utilization via inhibition of inflammation, lipotoxicity and oxidative stress. These flavonoids improve GLUT-4 expression and translocation to plasma membrane by activation of insulin-sensitive PI3K/Akt signaling and insulin-independent AMPK, SIRT-1 and MOR activation pathways for regulation of glucose homeostasis, and improve fat oxidation and reduce lipid synthesis by regulation of related genes for lipid homeostasis in the body of obese diabetic animals. In this chapter, we have highlighted all these beneficial anti-obesity and antidiabetic potentials of some dietary plant flavonoids along with their molecular actions, bioavailability and pharmacokinetics. In addition, the present understanding and management of obesity and diabetes are also focused.

Long non-coding RNAs are emerging targets of phytochemicals for cancer and other chronic diseases

The long non-coding RNAs (lncRNAs) are the crucial regulators of human chronic diseases. Therefore, approaches such as antisense oligonucleotides, RNAi technology, and small molecule inhibitors have been used for the therapeutic targeting of lncRNAs. During the last decade, phytochemicals and nutraceuticals have been explored for their potential against lncRNAs. The common lncRNAs known to be modulated by phytochemicals include ROR, PVT1, HOTAIR, MALAT1, H19, MEG3, PCAT29, PANDAR, NEAT1, and GAS5. The phytochemicals such as curcumin, resveratrol, sulforaphane, berberine, EGCG, and gambogic acid have been examined against lncRNAs. In some cases, formulation of phytochemicals has also been used. The disease models where phytochemicals have been demonstrated to modulate lncRNAs expression include cancer, rheumatoid arthritis, osteoarthritis, and nonalcoholic fatty liver disease. The regulation of lncRNAs by phytochemicals can affect multi-steps of tumor development. When administered in combination with the conventional drugs, phytochemicals can also produce synergistic effects on lncRNAs leading to the sensitization of cancer cells. Phytochemicals target lncRNAs either directly or indirectly by affecting a wide variety of upstream molecules. However, the potential of phytochemicals against lncRNAs has been demonstrated mostly by preclinical studies in cancer models. How the modulation of lncRNAs by phytochemicals produce therapeutic effects on cancer and other chronic diseases is discussed in this review.

Mulberry leaf extract displays antidiabetic activity in db/db mice via Akt and AMP-activated protein kinase phosphorylation

Background

Augmenting glucose utilization in skeletal muscle via the phosphatidylinositol-3 kinase (PI3 kinase)/protein kinase B (Akt) pathway or the adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway is necessary to regulate hyperglycemia in patients with type 2 diabetes mellitus.

Objective

We investigated the effect of mulberry leaf extract (MLE) on glucose uptake in skeletal muscle cells and explored its in vivo antidiabetic potential.

Design

Male db/db mice were treated with either MLE (50 mg/kg, 100 mg/kg, and 250 mg/kg) or metformin (100 mg/kg) for 8 weeks.

Results

MLE treatment stimulated glucose uptake, driven by enhanced translocation of glucose transporter 4 to cell membranes in L6 myotubes. These effects of MLE were synergistic with those of insulin and were abolished in the presence of PI3K inhibitor or AMPK inhibitor. In db/db mice, supplementation with MLE decreased fasting blood glucose and insulin levels and enhanced insulin sensitivity, with increases of p-Akt and p-AMPK in skeletal muscle. Moreover, MLE improved blood lipid parameters and attenuated hepatic steatosis in diabetic db/db mice.

Discussion

These findings suggest that MLE exerts antidiabetic activity through stimulating glucose disposal in skeletal muscle cells via the PI3K/Akt and AMPK pathways.

Conclusions

MLE can potentially improve hyperglycemia and hepatic steatosis in patients with type 2 diabetes.

Role of soybean-derived bioactive compounds in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, inflammatory condition of the gastrointestinal tract. Patients with IBD present with debilitating symptoms that alter the quality of life and can develop into severe complications requiring surgery. Epidemiological evidence indicates Westernized societies have an elevated IBD burden when compared with Asian societies. Considering the stark contrast between the typical Western and Eastern dietary patterns, it is postulated that differences in food and lifestyle contribute to lower IBD incidence in Asian countries. Soybeans (Glycine max), which are consumed in high quantities and as various preparations in Eastern societies, contain a wealth of natural, biologically active compounds that include isoflavones, bioactive peptides, protease inhibitors, and phytosterols, among many others. These compounds have been shown to improve human health, and preclinical evidence suggests they have potential to improve the prognosis of IBD. This review summarizes the current state of evidence regarding the effects and the mechanisms of action of these soybean-derived bioactive compounds in experimental models of IBD.

Anti-Diabetic Effects of Acankoreagenin from the Leaves of Acanthopanax Gracilistylus Herb in RIN-m5F Cells via Suppression of NF-κB Activation

Diabetes mellitus is a chronic degenerative disease that causes long-term complications and represents a serious public health problem. In this manuscript, acankoreagenin isolated from the leaves of Acanthopanax gracilistylus (LAG) is thought to possess excellent anti-diabetic properties. In vitro, anti-diabetic activities were assessed based on the inhibitory activities with α-glucosidase (IC₅₀ 13.01 μM), α-amylase (IC₅₀ 30.81 μM), and PTP1B (IC₅₀ 16.39 μM). Acankoreagenin showed better anti-diabetic effects. Then, an investigation was performed to analyze the insulin secretion effects of the insulin-secreting cell line in RIN-m5F cells. It was found that acankoreagenin could increase the insulin release in RIN-m5F cells. It was also found that acankoreagenin reduced NO production, activity of caspase-3, and the reactive oxygen species levels in the cells injured by processing of cytokines. In western blotting, inactivation of NF-κB signaling was confirmed. Acankoreagenin (20 μM) showed a higher I-κBα expression and lower NF-κB expression than the control group and showed a better expression than the positive control L-NAME (1 mM) (p < 0.05). This study demonstrates the anti-diabetic effects of acankoreagenin in vitro and suggests acankoreagenin might offer therapeutic potential for treating diabetes mellitus.

Spirulina Extract Enhanced a Protective Effect in Type 1 Diabetes by Anti-Apoptosis and Anti-ROS Production

Interest in the nutritional value and pharmacological activities of blue-green algae has gradually increased. Spirulina extracts show protective effects against apoptosis and inflammatory damage in various cell types. Here, we investigated the protective effects of extracts from Spirulina maxima in a cytokine-mediated type 1 diabetes model in vitro and in streptozotocin-induced diabetic Wistar rats in vivo. Interleukin-1β and interferon-gamma induced substantial cytotoxicity to RINm5F rat insulinoma cells, increasing nitric oxide (NO) production, nuclear factor-kappa B (NF-κB) activity, the expression of endoplasmic reticulum (ER) stress genes, and activation of mitogen-activated protein kinases and key genes related apoptosis. However, the cytotoxicity of cytokines was significantly attenuated by Spirulina extract, which effectively prevented NO production by inhibiting the synthesis of cytokine-activated NO synthase (iNOS), and apoptosis was suppressed. These results suggest that Spirulina extract might be effective to preserve the viability and function of pancreatic β-cells against cytotoxic conditions. Moreover, diabetic mice orally administered Spirulina extract showed decreased glucose levels, increased insulin, and improvement in liver enzyme markers. The antioxidant effect of Spirulina extract may be helpful in treating type 1 diabetes by enhancing the survival, and reducing or delaying cytokine-mediated β-cells destruction.

STAT3 targeting by polyphenols: Novel therapeutic strategy for melanoma

Melanoma or malignant melanocytes appear with the low incidence rate, but very high mortality rate worldwide. Epidemiological studies suggest that polyphenolic compounds contribute for prevention or treatment of several cancers particularly melanoma. Such findings motivate to dig out novel therapeutic strategies against melanoma, including research toward the development of new chemotherapeutic and biologic agents that can target the tumor cells by different mechanisms. Recently, it has been found that signal transducer and activator of transcription 3 (STAT3) is activated in many cancer cases surprisingly. Different evidences supply the aspect that STAT3 activation plays a vital role in the metastasis, including proliferation of cells, survival, invasion, migration, and angiogenesis. This significant feature plays a vital role in various cellular processes, such as cell proliferation and survival. Here, we reviewed the mechanisms of the STAT3 pathway regulation and their role in promoting melanoma. Also, we have evaluated the emerging data on polyphenols (PPs) specifically their contribution in melanoma therapies with an emphasis on their regulatory/inhibitory actions in relation to STAT3 pathway and current progress in the development of phytochemical therapeutic techniques. An understanding of targeting STAT3 by PPs brings an opportunity to melanoma therapy. © 2016 BioFactors, 43(3):347-370, 2017.

Dietary Supplementation with Isoflavones Prevents Muscle Wasting in Tumor-Bearing Mice

Proinflammatory cytokines contribute to the progression of muscle wasting caused by ubiquitin-proteasome-dependent proteolysis. We have previously demonstrated that isoflavones, such as genistein and daidzein, prevent TNF-α-induced muscle atrophy in C2C12 myotubes. In this study, we examined the effect of dietary flavonoids on the wasting of muscle. Mice were divided into the following four groups: vehicle-injected (control) mice fed the normal diet (CN); tumor-bearing mice fed the normal diet (TN); control mice fed the isoflavone diet (CI); and tumor-bearing mice fed the isoflavone diet (TI). There were no significant differences in the intake of food or body weight gain among these four groups. The wet weight and myofiber size of gastrocnemius muscle in TN significantly decreased, compared with those in CN. Interestingly, the wet weight and myofiber size of gastrocnemius muscle in TI were nearly the same as those in CN and CI, although isoflavone supplementation did not affect the increased tumor mass or concentrations of proinflammatory cytokines, such as TNF-α and IL-6, in the blood. Moreover, increased expression of muscle-specific ubiquitin ligase genes encoding MAFbx/Atrogin-1 and MuRF1 in the skeletal muscle of TN was significantly inhibited by the supplementation of isoflavones. In parallel with the expression of muscle-specific ubiquitin ligases, dietary isoflavones significantly suppressed phosphorylation of ERK in tumor-bearing mice. These results suggest that dietary isoflavones improve muscle wasting in tumor-bearing mice via the ERK signaling pathway mediated-suppression of ubiquitin ligases in muscle cells.

Compound 19e, a Novel Glucokinase Activator, Protects against Cytokine-Induced Beta-Cell Apoptosis in INS-1 Cells

Previously, compound 19e, a novel heteroaryl-containing benzamide derivative, was identified as a potent glucokinase activator (GKA) and showed a glucose-lowering effect in diabetic mice. In this study, the anti-apoptotic actions of 19e were evaluated in INS-1 pancreatic beta-cells co-treated with TNF-α and IL-1β to induce cell death. Compound 19e protected INS-1 cells from cytokine-induced cell death, and the effect was similar to treatment with another GKA or exendin-4. Compound 19e reduced annexin-V stained cells and the expression of cleaved caspase-3 and poly (ADP-ribose) polymerase protein, as well as upregulated the expression of B-cell lymphoma-2 protein. Compound 19e inhibited apoptotic signaling via induction of the ATP content, and the effect was correlated with the downregulation of nuclear factor-κB p65 and inducible nitric oxide synthase. Further, 19e increased NAD-dependent protein deacetylase sirtuin-1 (SIRT1) deacetylase activity, and the anti-apoptotic effect of 19e was attenuated by SIRT1 inhibitor or SIRT1 siRNA treatment. Our results demonstrate that the novel GKA, 19e, prevents cytokine-induced beta-cell apoptosis via SIRT1 activation and has potential as a therapeutic drug for the preservation of pancreatic beta-cells.

Management of diabetic complications through fruit flavonoids as a natural remedy

Diabetes mellitus is a global disorder, and a major issue for health care systems. The current review outlooks the use of fruit flavonoids as natural remedy in the prevention of diabetes mellitus. The onset of diabetes mainly depends upon genetics and lifestyle issues. Currently used therapeutic options for the control of diabetes, like dietary amendments, oral hypoglycemic drugs, and insulin, have their own limitations. Fruit flavonoids possess various antidiabetic, anti-inflammatory, and antioxidant potentials and act on various cellular signaling pathways in pancreas, white adipose tissue, skeletal muscle, and liver function, which in result induces antidiabetic effects. Recently, antidiabetic effect of fruit flavonoids has been studied using various animal models and clinical trials. Research studies revealed a statistically significant potential of fruit flavonoids in managing the altered glucose and oxidative metabolisms in diabetes. Unlike synthetic antidiabetic agents, fruit flavonoids manage diabetes without compromising cellular homeostasis thereby posing no side effects. Further studies are required in purification and characterization of different fruit flavonoids with respect to their beneficial effect for diabetic patients.

Polyphenols in Regulation of Redox Signaling and Inflammation During Cardiovascular Diseases

Cardiovascular diseases remain one of the major health problems worldwide. The worldwide research against cardiovascular diseases as well as genome wide association studies were successful in indentifying the loci associated with this prominent life-threatening disease but still a substantial amount of casualty remains unexplained. Over the last decade, the thorough understanding of molecular and biochemical mechanisms of cardiac disorders lead to the knowledge of various mechanisms of action of polyphenols to target inflammation during cardiac disorders. The present review article summarizes major mechanisms of polyphenols against cardiovascular diseases.

Molecular Mechanisms of the Anti-Obesity and Anti-Diabetic Properties of Flavonoids

Obesity and diabetes are the most prevailing health concerns worldwide and their incidence is increasing at a high rate, resulting in enormous social costs. Obesity is a complex disease commonly accompanied by insulin resistance and increases in oxidative stress and inflammatory marker expression, leading to augmented fat mass in the body. Diabetes mellitus (DM) is a metabolic disorder characterized by the destruction of pancreatic β cells or diminished insulin secretion and action insulin. Obesity causes the development of metabolic disorders such as DM, hypertension, cardiovascular diseases, and inflammation-based pathologies. Flavonoids are the secondary metabolites of plants and have 15-carbon skeleton structures containing two phenyl rings and a heterocyclic ring. More than 5000 naturally occurring flavonoids have been reported from various plants and have been found to possess many beneficial effects with advantages over chemical treatments. A number of studies have demonstrated the potential health benefits of natural flavonoids in treating obesity and DM, and show increased bioavailability and action on multiple molecular targets. This review summarizes the current progress in our understanding of the anti-obesity and anti-diabetic potential of natural flavonoids and their molecular mechanisms for preventing and/or treating obesity and diabetes.

Targeting metabolic disorders by natural products

The most prevalent metabolic disorders are diabetes mellitus, obesity, dyslipidemia, osteoporosis and metabolic syndrome, which are developed when normal metabolic processes are disturbed. The most common pathophysiologies of the above disorders are oxidative stress, Nrf2 pathways, epigenetic, and change in miRNA expression. There is a challenge in the prevention and treatment of metabolic disorders due to severe adverse effects of some synthetic drugs, their high cost, lack of safety and poverty in some conditions, and insufficient accessibility for the general population in the world. With increasing interest in shifting from synthetic drugs to phytotherapy as an alternative treatment, there is still a gap in scientific evidences of plant-derived therapeutic benefits. One reason may be slow rate of translation of animal studies' findings into human clinical trials. Since metabolic disorders are multifactorial, it seems that poly-herbal medications, or drug-herbal combination are needed for their treatment. However, further researches to determine the most effective plant-derived metabolites, and their cellular mechanism in order to set priorities for well-designed animal and clinical trials, and also more studies with strong scientific evidences such as systematic review and meta-analysis of controlled studies are needed.

Polyphenols isolated from Broussonetia kazinoki prevent cytokine-induced β-cell damage and the development of type 1 diabetes

The axis of nuclear factor κB (NF-κB)-inducible NO synthase (iNOS)-nitric oxide plays a key role in cytokine- and streptozotocin-mediated pancreatic β-cell damage. In this study, we investigated the effects of kazinol C and isokazinol D isolated from Broussonetia kazinoki on the β-cell viability and function. RINm5F cells and primary islets were used for in vitro and ex vivo cytokine toxicity experiments, respectively. For type 1 diabetes induction, mice were injected with multiple low-dose streptozotocin (MLDS). Cytokine-induced toxicity was completely abolished in both RINm5F cells and islets that were pretreated with either kazinol C or isokazinol D. Both kazinols inhibited the NF-κB signaling pathway, thereby inhibiting cytokine-mediated iNOS induction, nitric oxide production, apoptotic cell death and defects in insulin secretion. Moreover, the occurrence of diabetes in MLDS-treated mice was efficiently attenuated in kazinol-pretreated mice. Immunohistochemical analysis revealed that the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive apoptotic cells and nuclear p65-positive cells were significantly decreased in kazinol-pretreated mice. Our results suggest that kazinol C and isokazinol D block the NF-κB pathway, thus reducing the extent of β-cell damage. Therefore, kazinol C and isokazinol D may have therapeutic value in delaying pancreatic β-cell damage in type 1 diabetes.

Dietary isoflavone intake is associated with evoked responses to inflammatory cardiometabolic stimuli and improved glucose homeostasis in healthy volunteers

BACKGROUND AND AIMS

Consumption of foods that modulate inflammatory stress in genetically-prone individuals may influence development of cardiometabolic diseases. Isoflavones in soy-derived foods function as phytoestrogens, have antioxidant and anti-inflammatory activity, inhibit protein-tyrosine kinase activity, and may be atheroprotective. We examined the relationship between soy food consumption and inflammatory responses to endotoxemia, postprandial responses to oral lipid tolerance test (OLTT), and insulin sensitivity from frequently sampled intravenous tolerance tests (FSIGTT).

METHODS AND RESULTS

We administered low-dose endotoxin (LPS 1 ng/kg) to induce transient endotoxemia in young, healthy volunteers (N = 215) of African (AA), and European (EA) ancestry as part of the GENE Study. We further supported these findings in two independent samples: the MECHE Study and NHANES. Soy food consumption was a significant predictor of peak cytokine response following LPS. Individuals with moderate-high (>1.48 mg/day, N = 65) vs. low-no (<1.48 mg/day, N = 150) isoflavone consumption had significantly higher tumor necrosis factor alpha (TNFα) post-LPS (AUC, P = 0.009). Further, high-isoflavone consumers were protected against inflammation-induced decline in insulin sensitivity (SI) in GENE. We observed significant differences by soy consumption in the interferon gamma (IFNγ) response to OLTT, and the insulin response to OGTT in MECHE, as well as significantly lower fasting insulin, and 2-hour glucose post-OGTT in EA NHANES subjects.

CONCLUSION

We demonstrate that soy consumption may influence inflammatory and metabolic responses. In research of nutritional exposures, measuring evoked phenotypes may be more informative than describing resting characteristics. The GENE Study was registered under NCT00953667 and the MECHE Study under NCT01172951, both at clinicaltrials.gov.

Genistein-inhibited cancer stem cell-like properties and reduced chemoresistance of gastric cancer

Genistein, the predominant isoflavone found in soy products, has exerted its anticarcinogenic effect in many different tumor types in vitro and in vivo. Accumulating evidence in recent years has strongly indicated the existence of cancer stem cells in gastric cancer. Here, we showed that low doses of genistein (15 µM), extracted from Millettia nitida Benth var hirsutissima Z Wei, inhibit tumor cell self-renewal in two types of gastric cancer cells by colony formation assay and tumor sphere formation assay. Treatment of gastric cancer cells with genistein reduced its chemoresistance to 5-Fu (fluorouracil) and ciplatin. Further results indicated that the reduced chemoresistance may be associated with the inhibition of ABCG2 expression and ERK 1/2 activity. Furthermore, genistein reduced tumor mass in the xenograft model. Together, genistein inhibited gastric cancer stem cell-like properties and reduced its chemoresistance. Our results provide a further rationale and experimental basis for using the genistein to improve treatment of patients with gastric cancer.

St. John's wort extract and hyperforin protect rat and human pancreatic islets against cytokine toxicity

The extract of Hypericum perforatum (St. John's wort, SJW) and its component hyperforin (HPF) were previously shown to inhibit cytokine-induced activation of signal transducer and activator of transcription-1 and nuclear factor κB and prevent apoptosis in a cultured β-cell line. Objective of this study was to assess the protection exerted by SJW and HPF on isolated rat and human islets exposed to cytokines in vitro. Functional, ultrastructural, biomolecular and cell death evaluation studies were performed. In both rat and human islets, SJW and HPF counteracted cytokine-induced functional impairment and down-regulated mRNA expression of pro-inflammatory target genes, such as iNOS, CXCL9, CXCL10, COX2. Cytokine-induced NO production from cultured islets, evaluated by nitrites measurement in the medium, was significantly reduced in the presence of the vegetal compounds. Noteworthy, the increase in apoptosis and necrosis following 48-h exposure to cytokines was fully prevented by SJW and partially by HPF. Ultrastructural morphometric analysis in human islets exposed to cytokines for 20 h showed that SJW or HPF avoided early β-cell damage (e.g., mitochondrial alterations and loss of insulin granules). In conclusion, SJW compounds protect rat and human islets against cytokine effects by counteracting key mechanisms of cytokine-mediated β-cell injury and represent promising pharmacological tools for prevention or limitation of β-cell dysfunction and loss in type 1 diabetes.

The efficacy of SPA0355 in protecting β cells in isolated pancreatic islets and in a murine experimental model of type 1 diabetes

Cytokines activate several inflammatory signals that mediate β-cell destruction. We recently determined that SPA0355 is a strong anti-inflammatory compound, thus reporting its efficacy in protecting β cells from various insults. The effects of SPA0355 on β-cell survival were studied in RINm5F cells and primary islets. The protective effects of this compound on the development of type 1 diabetes were evaluated in non-obese diabetic (NOD) mice. SPA0355 completely prevented cytokine-induced nitric oxide synthase (iNOS) expression and cytotoxicity in RINm5F cells and isolated islets. The molecular mechanism of SPA0355 inhibition of iNOS expression involves the inhibition of nuclear factor κB and Janus kinase signal transducer and activator of transcription pathways. The protective effects of SPA0355 against cytokine toxicity were further demonstrated by normal insulin secretion and absence of apoptosis of cytokine-treated islets. In experiments with NOD mice, the occurrence of diabetes was efficiently reduced when the mice were treated with SPA0355. Therefore, SPA0355 might be a valuable treatment option that delays the destruction of pancreatic β cells in type 1 diabetes.

The small molecule, genistein, increases hepcidin expression in human hepatocytes

Hepcidin, a peptide hormone that decreases intestinal iron absorption and macrophage iron release, is a potential drug target for patients with iron overload syndromes because its levels are inappropriately low in these individuals. Endogenous stimulants of Hepcidin transcription include bone morphogenic protein 6 (BMP6) and interleukin-6 (IL-6) by effects on mothers against decapentaplegic homolog (Smad)4 or signal transducer and activator of transcription (Stat)3, respectively. We conducted a small-scale chemical screen in zebrafish embryos to identify small molecules that modulate hepcidin expression. We found that treatment with the isoflavone, genistein, from 28-52 hours postfertilization in zebrafish embryos enhanced Hepcidin transcript levels, as assessed by whole-mount in situ hybridization and quantitative real-time reverse-transcriptase polymerase chain reaction. Genistein's stimulatory effect was conserved in human hepatocytes: Genistein treatment of HepG2 cells increased both Hepcidin transcript levels and promoter activity. We found that genistein's effect on Hepcidin expression did not depend on estrogen receptor signaling or increased cellular iron uptake, but was impaired by mutation of either BMP response elements or the Stat3-binding site in the Hepcidin promoter. RNA sequencing of transcripts from genistein-treated hepatocytes indicated that genistein up-regulated 68% of the transcripts that were up-regulated by BMP6; however, genistein raised levels of several transcripts involved in Stat3 signaling that were not up-regulated by BMP6. Chromatin immunoprecipitation and ELISA experiments revealed that genistein enhanced Stat3 binding to the Hepcidin promoter and increased phosphorylation of Stat3 in HepG2 cells.

CONCLUSION

Genistein is the first small-molecule experimental drug that stimulates Hepcidin expression in vivo and in vitro. These experiments demonstrate the feasibility of identifying and characterizing small molecules that increase Hepcidin expression. Genistein and other candidate molecules may subsequently be developed into new therapies for iron overload syndromes.

Recent advances in understanding the anti-diabetic actions of dietary flavonoids

Flavonoids are polyphenolic compounds that are abundant in fruits and vegetables, and increasing evidence demonstrates a positive relationship between consumption of flavonoid-rich foods and disease prevention. Epidemiological, in vitro and animal studies support the beneficial effects of dietary flavonoids on glucose and lipid homeostasis. It is encouraging that the beneficial effects of some flavonoids are at physiological concentrations and comparable to clinically-used anti-diabetic drugs; however, clinical research in this field and studies on the anti-diabetic effects of flavonoid metabolites are limited. Flavonoids act on various molecular targets and regulate different signaling pathways in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibers. Flavonoids may exert beneficial effects in diabetes by (i) enhancing insulin secretion and reducing apoptosis and promoting proliferation of pancreatic β-cells; (ii) improving hyperglycemia through regulation of glucose metabolism in hepatocytes; (iii) reducing insulin resistance, inflammation and oxidative stress in muscle and fat and (iv) increasing glucose uptake in skeletal muscle and white adipose tissue. This review highlights recent findings on the anti-diabetic effects of dietary flavonoids, including flavan-3-ols, flavanones, flavonols, anthocyanidins, flavones and isoflavones, with particular emphasis on the studies that investigated the cellular and molecular mechanisms involved in the beneficial effects of the compounds.

Genistein inhibits prostate cancer cell growth by targeting miR-34a and oncogenic HOTAIR

OBJECTIVE

Genistein is a soy isoflavone that has antitumor activity both in vitro and in vivo. It has been shown that genistein inhibits many type of cancers including prostate cancer (PCa) by regulating several cell signaling pathways and microRNAs (miRNAs). Recent studies suggest that the long non-coding RNAs (lncRNAs) are also involved in many cellular processes. At present there are no reports about the relationship between gensitein, miRNAs and lncRNAs. In this study, we focused on miRNAs, lncRNA that are regulated by genistein and investigated their functional role in PCa.

METHOD

Microarray (SurePrint G3 Human GE 8×60K) was used for expression profiling of genistein treated and control PCa cells (PC3 and DU145). Functional assay (cell proliferation, migration, invasion, apoptosis and cell cycle assays) were performed with the PCa cell lines, PC3 and DU145. Both in vitro and in vivo (nude mouse) models were used for growth assays. Luciferase reporter assays were used for binding of miR-34a to HOTAIR.

RESULTS

LncRNA profiling showed that HOTAIR was highly regulated by genistein and its expression was higher in castration-resistant PCa cell lines than in normal prostate cells. Knockdown (siRNA) of HOTAIR decreased PCa cell proliferation, migration and invasion and induced apoptosis and cell cycle arrest. miR-34a was also up-regulated by genistein and may directly target HOTAIR in both PC3 and DU145 PCa cells.

CONCLUSIONS

Our results indicated that genistein inhibited PCa cell growth through down-regulation of oncogenic HOTAIR that is also targeted by tumor suppressor miR-34a. These findings enhance understanding of how genistein regulates lncRNA HOTAIR and miR-34a in PCa.

A systematic review of oxidative stress and safety of antioxidants in diabetes: focus on islets and their defense

A growing body of evidence suggests that hyperglycemia-induced oxidative stress plays an important role in diabetic complications, especially β-cell dysfunction and failure. Under physiological conditions, reactive oxygen species serve as second messengers that facilitate signal transduction and gene expression in pancreatic β-cells. However, under pathological conditions, an imbalance in redox homeostasis leads to aberrant tissue damage and β-cell death due to a lack of antioxidant defense systems. Taking into account the vulnerability of islets to oxidative damage, induction of endogenous antioxidant enzymes or exogenous antioxidant administration has been proposed as a way to protect β-cells against diabetic insults. Here, we consider recent insights into how the redox response becomes deregulated under diabetic conditions, as well as the therapeutic benefits of antioxidants, which may provide clues for developing strategies aimed at the treatment or prevention of diabetes associated with β-cell failure.

Anti-diabetic functions of soy isoflavone genistein: mechanisms underlying its effects on pancreatic β-cell function

Type 2 diabetes is a result of chronic insulin resistance and loss of functional pancreatic β-cell mass. Strategies to preserve β-cell mass and a greater understanding of the mechanisms underlying β-cell turnover are needed to prevent and treat this devastating disease. Genistein, a naturally occurring soy isoflavone, is reported to have numerous health benefits attributed to multiple biological functions. Over the past 10 years, numerous studies have demonstrated that genistein has anti-diabetic effects, in particular, direct effects on β-cell proliferation, glucose-stimulated insulin secretion and protection against apoptosis, independent of its functions as an estrogen receptor agonist, antioxidant, or tyrosine kinase inhibitor. Effects are structure-specific and not common to all flavonoids. While there are limited data on the effects of genistein consumption in humans with diabetes, there are a plethora of animal and cell-culture studies that demonstrate a direct effect of genistein on β-cells at physiologically relevant concentrations (<10 μM). The effects appear to involve cAMP/PKA signaling and there are some studies that suggest an effect on epigenetic regulation of gene expression. This review focuses on the anti-diabetic effects of genistein in both in vitro and in vivo models and potential mechanisms underlying its direct effects on β-cells.

Cytoprotective effect of Coreopsis tinctoria extracts and flavonoids on tBHP and cytokine-induced cell injury in pancreatic MIN6 cells

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Coreopsis tinctoria flowering tops infusion is traditionally used in Portugal for treating the symptoms of diabetes. Recent studies have revealed its antihyperglycemic activity when administered for 3 weeks to a STZ-induced glucose intolerance model in the rat and glucose tolerance regain was even clearer and pancreatic function recovery was achieved when administering Coreopsis tinctoria flavonoid-rich AcOEt fraction. In this study we aimed to evaluate the protective effect of Coreopsis tinctoria flowering tops aqueous extract, AcOEt fraction and the pure compounds marein and flavanomarein, against beta-cell injury, in a mouse insulinoma cell line (MIN6) challenged with pro-oxidant tert-butyl-hydroperoxide (tBHP) or cytokines.

MATERIALS AND METHODS

The protective effects of Coreopsis tinctoria flowering tops extracts and pure compounds were evaluated through pre-incubating MIN6 cells with samples followed by treatment with tBHP (400 μM for 2 h) after which viability was determined through ATP measurements. In order to assess whether plant extracts were involved in decreasing reactive oxygen species, superoxide anion production was determined through a lucigenin-enhanced chemiluminescent method. Lastly, the direct influence of Coreopsis tinctoria extracts and main compounds on cell survival/apoptosis was determined measuring caspase 3 and 7 cleavage induced by cytokines.

RESULTS

Coreopsis tinctoria flowering tops extracts (25-100 μg/mL) and pure compounds (200-400 μM), when pre-incubated with MIN6 cells did not present any cytotoxicity, instead they increased cell viability in a dose dependent manner when challenged with tBHP. Treatment with this pro-oxidant also showed a rise in superoxide radical anion formation in MIN6 cells. This increase was significantly reduced by treatment with superoxide dismutase enzyme (SOD) but not by pre-treatment with Coreopsis tinctoria flowering tops extracts. Caspase 3/7 activation measurements show that Coreopsis tinctoria flowering tops extracts, as well as marein and flavanomarein, significantly inhibit apoptosis.

CONCLUSIONS

Coreopsis tinctoria extracts and pure compounds show cytoprotection that seems to be due to inhibition of the apoptotic pathway, and not through a decrease on superoxide radical production.

Sulfuretin protects against cytokine-induced beta-cell damage and prevents streptozotocin-induced diabetes

NF-kappaB activation has been implicated as a key signaling mechanism for pancreatic beta-cell damage. Sulfuretin is one of the main flavonoids produced by Rhus verniciflua, which is reported to inhibit the inflammatory response by suppressing the NF-kappaB pathway. Therefore, we isolated sulfuretin from Rhus verniciflua and evaluated if sulfuretin could inhibit cytokine- or streptozotocin-induced beta-cell damage. Rat insulinoma RINm5F cells and isolated rat islets were treated with IL-1 beta and IFN-gamma to induce cytotoxicity. Incubation of cells and islets with sulfuretin resulted in a significant reduction of cytokine-induced NF-gamma B activation and its downstream events, iNOS expression, and nitric oxide production. The cytotoxic effects of cytokines were completely abolished when cells or islets were pretreated with sulfuretin. The protective effect of sulfuretin was further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining of islets. However, the diabetogenic effects of streptozotocin were completely prevented when mice were pretreated with sulfuretin. The anti-diabetogenic effects of sulfuretin were also mediated by suppression of NF-kappaB activation. Collectively, these results indicate that sulfuretin may have therapeutic value in preventing beta-cell damage.

Mechanisms of genistein protection on pancreas cell damage in high glucose condition

AIM

An adequate β cell number is important to prevent the onset and development of type 2 diabetes. The aim of this study was to determine if phytoestrogen gesintein has protective effects against high glucose-induced cell apoptosis in human pancreas cells, and to try to determine the possible mechanism for this protection.

METHODS

Human pancreatic β cells were subjected to normal (5 mM) or high glucose (25 mM) with and without the presence of 100 nM genistein, and also in the presence and absence of the pure anti-estrogen ICI-182780 (100 nM). Bcl-2 siRNA transfection was performed to investigate if the effect of genistein was also Bcl-2 dependent. Cell proliferation and apoptosis were determined by Tritiated Thymidine Incorporation Assay and Cell Apoptosis Detection ELISA. Estrogen receptor and Bcl-2 mRNA expression was measured by Real-time Quantitative PCR.

RESULTS

High glucose concentration caused cell proliferation inhibition and apoptosis in cultured human pancreatic β cells, and these effects were significantly reversed by genistein (P<0.01). Estrogen receptor beta was expressed in the cultured cells, and genistein protection was blocked by ICI-182780 administration as well as Bcl-2 siRNA transfection.

CONCLUSION

Phytoestrogen gave protection against high glucose-induced pancreatic cell damage through estrogen receptor beta and Bcl-2 dependent pathways.

Cancer prevention with natural compounds

Botanical and nutritional compounds have been used for the treatment of cancer throughout history. These compounds also may be useful in the prevention of cancer. Population studies suggest that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Thus, the cancer chemopreventive potential of naturally occurring phytochemicals is of great interest. There are numerous reports of cancer chemopreventive activity of dietary botanicals, including cruciferous vegetables such as cabbage and broccoli, Allium vegetables such as garlic and onion, green tea, Citrus fruits, soybeans, tomatoes, berries, and ginger, as well as medicinal plants. Several lead compounds, such as genistein (from soybeans), lycopene (from tomatoes), brassinin (from cruciferous vegetables), sulforaphane (from asparagus), indole-3-carbinol (from broccoli), and resveratrol (from grapes and peanuts) are in preclinical or clinical trials for cancer chemoprevention. Phytochemicals have great potential in cancer prevention because of their safety, low cost, and oral bioavailability. In this review, we discuss potential natural cancer preventive compounds and their mechanisms of action.

Nardostachys jatamansi extract protects against cytokine-induced β-cell damage and streptozotocin-induced diabetes

AIM: To investigate the anti-diabetogenic mechanism of Nardostachys jatamansi extract (NJE).

METHODS: Mice were injected with streptozotocin via a tail vein to induce diabetes. Rat insulinoma RINm5F cells and isolated rat islets were treated with interleukin-1β and interferon-γ to induce cytotoxicity.

RESULTS: Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was confirmed by immunohistochemical staining of the islets. The diabetogenic effects of streptozotocin were completely abolished when mice were pretreated with NJE. Inhibition of streptozotocin-induced hyperglycemia by NJE was mediated by suppression of nuclear factor (NF)-κB activation. In addition, NJE protected against cytokine-mediated cytotoxicity. Incubation of RINm5F cells and islets with NJE resulted in a significant reduction in cytokine-induced NF-κB activation and downstream events, inducible nitric oxide synthase expression and nitric oxide production. The protective effect of NJE was further demonstrated by the normal insulin secretion of cytokine-treated islets in response to glucose.

CONCLUSION: NJE provided resistance to pancreatic β-cell damage from cytokine or streptozotocin treatment. The β-cell protective effect of NJE is mediated by suppressing NF-κB activation.

Curcumin, resveratrol and flavonoids as anti-inflammatory, cyto- and DNA-protective dietary compounds

Numerous dietary compounds, ubiquitous in fruits, vegetables and spices have been isolated and evaluated during recent years for their therapeutic potential. These compounds include flavonoid and non-flavonoid polyphenols, which describe beneficial effects against a variety of ailments. The notion that these plant products have health promoting effects emerged because their intake was related to a reduced incidence of cancer, cardiovascular, neurological, respiratory, and age-related diseases. Exposure of the body to a stressful environment challenges cell survival and increases the risk of chronic disease developing. The polyphenols afford protection against various stress-induced toxicities through modulating intercellular cascades which inhibit inflammatory molecule synthesis, the formation of free radicals, nuclear damage and induce antioxidant enzyme expression. These responses have the potential to increase life expectancy. The present review article focuses on curcumin, resveratrol, and flavonoids and seeks to summarize their anti-inflammatory, cytoprotective and DNA-protective properties.

Neuroprotective effects of genistein and folic acid on apoptosis of rat cultured cortical neurons induced by β-amyloid 31-35

Genistein and folic acid have been reported respectively to protect against the development of cognitive dysfunction; however, the underlying mechanism(s) for this protection remain unknown. In this report, the mechanism(s) contributing to the neuroprotective effects of genistein and folic acid were explored using rat cortical neuron cultures. We found that genistein and folic acid, both separately and collaboratively, increased cell viability and mitochondrial membrane potential in β-amyloid (Aβ) 31-35-treated neurons. Furthermore, reduced percentage of comet cells and shortened tail length were observed in the neurons treated with genistein or folic acid. A more significant reduction in tail length of the comet neurons was observed in the co-administered neurons. RT-PCR analysis of the cultured cortical neurons showed down-regulated expression of p53, bax and caspase-3, but up-regulated expression of bcl-2 in the three neuroprotective treatment groups compared with neurons from the Aβ31-35 solo-treated group. In a nuclear dyeing experiment using Hoechst 33342, we found that both genistein and folic acid prevent neuronal apoptosis. Collectively, these findings suggest that the mechanism underlying the neuroprotection of genistein and folic acid singly or in combination observed in cultured cortical neuron studies might be related to their anti-apoptotic properties.