Regulatory mechanism for the stimulatory action of genistein on glucose uptake in vitro and in vivo

Vindoline is a key component of Catharanthus roseus leaf juice extract prepared through an Ayurveda-based method for ameliorating insulin-resistant type 2 diabetes

Catharanthus roseus leaves have been traditionally described to possess potent antidiabetic activity and some leaf-specific alkaloids, including vindoline, have been studied for their antidiabetic potential. The aim of the present study was to validate the antidiabetic property of the plant with special reference to vindoline. An Ayurveda-based method was used to prepare the Swaras [leaf juice extract (LJE)] of three familial C. roseus genotypes differing in their vindoline content [CIM-Sushil (CS) > Dhawal (D) > Nirmal (N)]. In vivo experiments using LJE were performed in Charles Foster rats, whereby metformin (M100, 100 mg/kg BW) and vindoline (V20, 20 mg/kg BW) were used for comparison. OGTT-based screening for LJE doses (N100, N300, N500, D100, D200, D300, CS100, CS200, CS300 mg/kg BW) was carried out. Further analysis of the effective doses (D100, D200, D300, CS100, CS200, CS300) in streptozotocin-induced diabetic rats indicated highest blood glucose depletion in D300 (52.51%) and CS200 (64.55%) together with V20 (56.96%) on the 14th day. CS-LJE was found to be safe up to 2000 mg/kg BW. The role of LJE/vindoline in maintaining glucose homeostasis in liver was found to be mediated through the expression of insulin pathway genes (IRS-1, PI3K, AKT, GLUT2). TNF-α-induced insulin resistance in L6 skeletal muscle cells was used to analyze the effect of LJE/vindoline through glucose uptake assay and expression analysis of insulin pathway genes (IRS-1, PI3K, AKT, GLUT4). The results indicated that the antidiabetic effect of LJE/vindoline is mediated through activation of IRS/PI3K/AKT/GLUT signaling pathway.

Dietary Soy Isoflavones Prevent Metabolic Disturbs Associated with a Deleterious Combination of Obesity and Menopause

This study aimed to evaluate the effects of soy isoflavone supplementation (25 mg/kg) on insulin resistance and inflammation in adipose tissue in an experimental model of menopause-obesity. Twenty-four female Wistar rats were ovariectomized (O) and distributed among the groups: OSD-ovariectomized rats submitted to normocaloric standard diet (n = 6); OHF-ovariectomized rats submitted to high-fat diet (n = 9); and OHFI-ovariectomized rats submitted to high-fat diet with isoflavones (n = 9). Weight gain, body adiposity, food and caloric intake, blood pressure, and glucose tolerance were assessed. After 24 weeks, the rats were euthanized; the thoracic blood collected for serum insulin determination and the homeostatic model assessment-insulin resistance) (HOMA-IR) and homeostatic model assessment-β cell (HOMA-β) indices were calculated. Abdominal adipose tissues were removed, weighed, and fixed for immunohistochemical and morphometric studies. Isoflavones decreased weight gain and blood pressure without changing the food and caloric intake (P < .05). Isoflavones did not affect the weight of the abdominal adipose tissue depots (P < .05). Although they did not alter glucose tolerance, the isoflavones reduced HOMA-IR and HOMA-β, serum insulin levels, in addition to reducing adipocytes' size (P < .05). The number of macrophages, lymphocytes, and crown-like structures in adipose tissue was lower in the group treated with isoflavones (P < .05). In conclusion, our data show that dietary soy isoflavones' supplementation prevents many of well-known deleterious combination of obesity and menopause on metabolism, such as body overweight, adipocyte hypertrophy, and hypertension, as well as insulin resistance and adipose tissue inflammation.

Nutraceuticals as Supportive Therapeutic Agents in Diabetes and Pancreatic Ductal Adenocarcinoma: A Systematic Review

The correlation between pancreatic ductal adenocarcinoma (PDAC) and diabetes-related mechanisms support the hypothesis that early therapeutic strategies targeting diabetes can contribute to PDAC risk reduction and treatment improvement. A systematic review was conducted, using PubMed, Embase and Cochrane Library databases, to evaluate the current evidence from clinical studies qualitatively examining the efficacy of four natural products: Curcumin-Curcuma longa L.; Thymoquinone-Nigella sativa L.; Genistein-Glycine max L.; Ginkgo biloba L.; and a low-carbohydrate ketogenic diet in type 2 diabetes (T2D) and PDAC treatment. A total of 28 clinical studies were included, showing strong evidence of inter-study heterogeneity. Used as a monotherapy or in combination with chemo-radiotherapy, the studied substances did not significantly improve the treatment response of PDAC patients. However, pronounced therapeutic efficacy was confirmed in T2D. The natural products and low-carbohydrate ketogenic diet, combined with the standard drugs, have the potential to improve T2D treatment and thus potentially reduce the risk of cancer development and improve multiple biological parameters in PDAC patients.

Potential roles of genistein in polycystic ovary syndrome: A comprehensive systematic review

Polycystic ovary syndrome (PCOS) is one of the most prevalent polygenic endocrine disorders in reproductive-age women. Genistein is a soy-isolated phytoestrogen and isoflavone with antioxidant, anti-inflammatory, estrogenic, and antineoplastic activity. This systematic review aimed to investigate the therapeutic effects and mechanisms of actions of genistein in PCOS. The present study was conducted according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. We searched PubMed, Scopus, Embase, and Google Scholar databases up to February 2022 using relative keywords. Studies published in English evaluated genistein's effects on PCOS, and its related symptoms were considered. Out of 298 records screened, only 13 articles met the inclusion criteria: Nine animal and 4 human studies. The results of the current study indicated that genistein supplementation may effectively improve PCOS-related symptoms by decreasing insulin resistance and anthropometric indices, improving ovarian morphology and regulating reproductive hormones, and reducing oxidative stress and inflammation by influencing biological pathways. According to the current literature, genistein may diminish the dues of PCOS. Therefore, this study shows that genistein can be considered an effective agent. in reducing the complications of PCOS. However, further studies are recommended for a broad conclusion on the exact mechanism of genistein in PCOS patients.

Synthesis of vildagliptin loaded acrylamide-g-psyllium/alginate-based core-shell nanoparticles for diabetes treatment

Diabetes mellitus has become a major public health concern all over the world. Vildagliptin is one of the antidiabeticdrug that can overcome the existing problem of this prevalent disease. Present study aims to synthesize and investigate the role of vildagliptin-loaded core-shell nanoparticle of grafted psyllium and alginate (VG@P/A-NPs) in anti-diabetes application. FTIR, SEM, XRD, ¹³CNMR and zeta analyzer were used for characterization of the core-shell nanoparticles (VG@P/A-NPs). The synthesized acrylamide-grafted-psyllium was also optimized through varying grafting parameters such as acrylamide and ceric ammonium nitrate (CAN) concentration, time and temperature to obtain the maximum yield of acrylamide-grafted-psyllium. Rheological analysis of pure psyllium, grafted psyllium and alginate were also performed. For biological studies, the first cytotoxicity of grafted psyllium and VG@P/A-NPs were examined on human lung adenocarcinoma cell line A549 in which it was observed that VG@P/A-NPs did not exhibited any toxicity. The antidiabetic potential of VG@P/A-NPs was investigated by glucose uptake assay, using TNF-α induced insulin resistance skeletal cell model using mouse muscle L6 cell line. The insulin signaling impaired cell line displayed a highly significant (p < 0.0001) dose-dependent increase in glucose uptake after treatment with increasing doses of VG@P/A-NPs.The drug release behavior of VG@P/A-NPs was examined at various pH and the highest drug release (98 %) was obtained at pH (7.4). The drug release kinetic data was following the Higuchi (R² = 0.9848) kinetic model, suggesting the release of drug from vildagliptin-loaded grafted psyllium-alginate core-shell nanoparticles (VG@P/A-NPs) as a square root of time-dependent process and diffusion controlled. This study provides an economical and environment-friendly approach towards the synthesis of VG@P/A-NPs with antidiabetes applications.

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.

Antidiabetic Effect of Taxifolin in Cultured L6 Myotubes and Type 2 Diabetic Model KK-Ay/Ta Mice with Hyperglycemia and Hyperuricemia

Muscle is the largest tissue in our body and plays an important role in glucose homeostasis and hence diabetes. In the present study, we examined the effects of taxifolin (TXF) on glucose metabolism in cultured L6 muscle cells (myotubes) and in type 2 diabetic (T2D) model KK-A^y/Ta mice. TXF dose-dependently increased glucose uptake (GU) in L6 myotubes under the condition of insulin absence. This increase in GU was partially, but significantly canceled by TXF treatment in combination with either LY294002, an inhibitor of phosphatidylinositol 3-kinase (PI3K), which phosphorylates protein kinase B (Akt) or Compound C, an inhibitor of 5’-adenosine monophosphate-activated protein kinase (AMPK). Furthermore, TXF was demonstrated to activate (=phosphorylate) both Akt and AMPK, and promote glucose transporter 4 (GLUT4) translocation to the plasma membrane from cytosol of L6 myotubes via both PI3K/Akt and AMPK signaling pathways. Based on these in vitro findings, we conducted an in vivo experiment in KK-A^y/Ta mice with hyperglycemia and hyperuricemia. Fasting plasma glucose, insulin, uric acid levels and an index of insulin resistance (HOMA-IR) increased significantly in the T2D model mice compared with normal ones. Such rises in the T2D state were significantly suppressed by oral administration of TXF for four weeks. These results suggest that TXF is a potent antihyperglycemic and antihyperuricemic phytochemical in the T2D state.

The effect of genistein on insulin resistance, inflammatory factors, lipid profile, and histopathologic indices in rats with polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism, irregular menstruation, ovulatory dysfunction, and insulin resistance. Recent studies have reported the possible role of phytoestrogens in PCOS. This animal study aimed to evaluate the effects of genistein on insulin resistance, inflammatory factors, lipid profile, and histopathologic indices on PCOS.

METHODS

PCOS was induced by 1 mg/kg of letrozole in adult Sprague-Dawley rats. The rats then received normal saline (PCOS group), 150 mg/kg of metformin, or 20 mg/kg of genistein dissolved in 1% methylcellulose solution for 42 days. Body weight, the glycemic and lipid profile, and inflammatory, antioxidative, and histopathological parameters were assessed at the end of the intervention.

RESULTS

Treatment with genistein significantly alleviated the increased level of fasting blood insulin (p=0.16) and the homeostatic model assessment of insulin resistance (p=0.012). In addition, the genistein group had significantly lower levels of serum malondialdehyde (p=0.039) and tumor necrosis factor-alpha (p=0.003), and higher superoxide dismutase enzyme activity (p<0.001). Furthermore, the histopathological analysis indicated that genistein administration led to an increase in luteinization and the development of fewer cysts (p<0.05).

CONCLUSION

Biochemical and histopathological analyses indicated that genistein administration to rats with PCOS induced significant remission in oxidative, inflammatory, and glycemic and histopathologic parameters.

Soy diet for nonalcoholic fatty liver disease: A meta-analysis of randomized controlled trials

INTRODUCTION

The efficacy of soy diet for nonalcoholic fatty liver disease remains controversial. We conduct a systematic review and meta-analysis to explore the influence of soy diet vs placebo on the treatment of non-alcoholic fatty liver disease.

METHODS

We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through October 2020 for randomized controlled trials assessing the efficacy of soy diet vs placebo for nonalcoholic fatty liver disease. This meta-analysis is performed using the random-effect model.

RESULTS

Five randomized controlled trials are included in the meta-analysis. Overall, compared with control group for nonalcoholic fatty liver disease, soy diet is associated with significantly reduced HOMA-IR (standard mean difference [SMD] = -0.42; 95% confidence interval [CI] = -0.76 to -0.08; P = .01), increased insulin (SMD = -0.64; 95% CI = -0.98 to -0.30; P = .0002) and decreased malondialdehyde (SMD = -0.43; 95% CI = -0.74 to -0.13; P = .005), but demonstrated no substantial impact on body mass index (SMD = 0.17; 95% CI = -0.20 to 0.53; P = .37), alanine aminotransferase (SMD = -0.01; 95% CI = -0.61 to 0.60; P = .98), aspartate-aminotransferase (SMD = 0.01; 95% CI = -0.47 to 0.49; P = .97), total cholesterol (SMD = 0.05; 95% CI = -0.25 to 0.35; P = .73) or low density lipoprotein (SMD = 0; 95% CI = -0.30 to 0.30; P = .99).

CONCLUSIONS

Soy diet may benefit to alleviate insulin resistance for nonalcoholic fatty liver disease.

Effects of Soy Isoflavones on Glycemic Control and Lipid Profile in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The aim of the report was to investigate the impact of soy protein and isoflavones on glucose homeostasis and lipid profile in type 2 diabetes. The studies used in this report were identified by searching through the MEDLINE and EMBASE databases (up to 2020). Meta-regression and subgroup analyses were performed to explore the influence of covariates on net glycemic control and lipid changes. Weighted mean differences and 95% confidence intervals (CI) were calculated by using random-effect models. Changes in the lipid profile showed statistically significant decreases in total cholesterol and LDL-C concentrations: ‒0.21 mmol/L; 95% CI, ‒0.33 to ‒0.09; p = 0.0008 and ‒0.20 mmol/L; 95% CI, ‒0.28 to ‒0.12; p < 0.0001, respectively, as well as in HDL-C (−0.02 mmol/L; 95% CI, −0.05 to 0.01; p = 0.2008 and triacylglycerols (−0.19 mmol/L; 95% CI, −0.48 to 0.09; p = 0.1884). At the same time, a meta-analysis of the included studies revealed statistically insignificant reduction in fasting glucose, insulin, HbA1c, and HOMA-IR (changes in glucose metabolism) after consumption of soy isoflavones. The observed ability of both extracted isoflavone and soy protein with isoflavones to modulate the lipid profile suggests benefits in preventing cardiovascular events in diabetic subjects. Further multicenter studies based on larger and longer duration studies are necessary to determine their beneficial effect on glucose and lipid metabolism.

Mormodica charantia L. fruit and Genistein ameliorates type 2 diabetes in rats by preventing lipid accumulation, insulin resistance and enhancing beta cell function

PURPOSE

The present study was aimed at evaluating the role of Momordica charantia L. fruit and Genistein on beta cell, insulin resistance/sensitivity and lipid profile in type 2 diabetic rats.

METHODS

Thirty-five (35) albino rats were divided into seven (7) groups of 5 rats each comprising of five (5) non-diabetic and thirty (30) diabetic rats. Groups 1 and 2 served as the normal control and diabetic control groups respectively and received distill water, groups 3 and 4 received Mormodica charantia L. at 250 mg/kg and 500 mg/kg respectively. Groups 5 and 6 received Genistein at 10 mg/kg and 20 mg/kg respectively while group 7 received Metformin at 500 mg/kg the experiment lasted for four weeks. All the rats were euthanized at the end of the fourth week.

RESULTS

Lipid profile, glucose and insulin levels were determined from the analysis of serum parameters and the histology of the pancreas. A significant reduction (p < 0.05) in blood glucose levels was noticed in rats that received Momordica charantia L. (MC) and genistein when compared with diabetic control rats. A significant decrease (p < 0.05) in cholesterol, triglyceride, low density lipoprotein (LDL) and very low density lipoprotein (VLDL) levels were also noted in rats that received MC and Genistein when compared with the diabetic control rats. MC and Genistein significantly increased (P < 0.05) serum insulin level compared to the diabetic control rats. MC and Genistein significantly decreased (p < 0.05) homeostatic model assessment-insulin resistance (HOMA-IR) level compared with the diabetic control group. Pancreas of rats that received MC and Genistein showed regenerating beta-cells.

CONCLUSION

Momordica charantia L. fruit and Genistein were able to enhance beta cell function and prevent lipid accumulation and insulin resistance in type 2 diabetic rats.

Effectiveness of Genistein Supplementation on Metabolic Factors and Antioxidant Status in Postmenopausal Women With Type 2 Diabetes Mellitus

OBJECTIVES

The risk of type 2 diabetes mellitus (T2DM) increases in women after menopause. Genistein is known to modulate metabolic pathways. The aim of this study was to investigate the effects of genistein supplementation on metabolic parameters, oxidative stress and obesity values in postmenopausal women with T2DM.

METHODS

This randomized, double-blind, placebo-controlled clinical trial was conducted on 54 postmenopausal women 47 to 69 years of age with T2DM. The genistein group (n=28) was given 2 genistein capsules daily for 12 weeks. Each capsule contained 54 mg genistein. The placebo group (n=26) received 2 placebo capsules daily for the same period. Fasting blood samples, anthropometric measurements, dietary intakes and physical activity levels of subjects were collected at baseline and at the end of the trial. Data were analyzed by independent t test, paired t test and analysis of covariance.

RESULTS

Genistein supplementation significantly reduced serum levels of fasting blood glucose (FBS), glycated hemoglobin (A1C), serum triglyceride (TG) and malondialdehyde (MDA) and increased total antioxidant capacity (TAC) compared with the placebo group at the end of the study (p<0.05 for all). Serum high-density lipoprotein cholesterol and quantitative insulin sensitivity check index significantly increased within the genistein group. Changes in anthropometric indexes and other variables were not significant in any of the groups.

CONCLUSIONS

Genistein administration improved FBS, A1C, serum TG, TAC and MDA in postmenopausal women with T2DM and may be useful in the control of metabolic status and oxidative stress in these subjects.

Polyphenols targeting diabetes via the AMP-activated protein kinase pathway; future approach to drug discovery

Regarding the widespread progression of diabetes, its related complications and detrimental effects on human health, investigations on this subject seems compulsory. AMP-activated protein kinase (AMPK) is a serine/threonine kinase and a key player in energy metabolism regulation. AMPK is also considered as a prime target for pharmaceutical and therapeutic studies on disorders such as diabetes, metabolic syndrome and obesity, where the body energy homeostasis is imbalanced. Following the activation of AMPK (physiological or pharmacological), a cascade of metabolic events that improve metabolic health is triggered. While there are several publications on this subject, this is the first report that has focused solely on polyphenols targeting diabetes via AMPK pathway. The multiple characteristics of polyphenolic compounds and their favorable influence on diabetes pathogenesis, as well as their intersections with the AMPK signaling pathway, indicate that these compounds have a beneficial effect on the regulation of glucose homeostasis. PPs could potentially occupy a significant position in the future anti-diabetic drug market.

Protective effect of genistein on nonalcoholic fatty liver disease (NAFLD)

NAFLD is a vital health problem worldwide; however, no effective treatment is currently available for NAFLD. Intensive studies have indicated the efficacy of genistein (GE), a bioactive isoflavone extracted from soy, in treating NAFLD. In addition to its oestrogen-like effects, GE is known to have multiple molecular effects, for instance, lipid and glucose metabolism-promoting effects and activities against lipid peroxidation, inflammation, fibrosis, and NAFLD-related tumours. Here, this review summarizes the potential role of GE in the treatment and prevention of NAFLD and some of the currently known targets and signalling pathways of GE in NAFLD.

Bacterial metabolism as responsible of beneficial effects of phytoestrogens on human health

Phytoestrogens (PE) are compounds found in plants such as soy (isoflavones), flax seeds and cereals (lignans) and pomegranates (ellagitannins). PE have shown estrogenic/antiestrogenic, antioxidant, anti-inflammatory, antineoplastic and apoptotic activities. The human studies are showing promising although inconsistent results about the beneficial effects of PE on ameliorating the menopausal symptoms or reducing the risk of certain cancers, cardiovascular disease or diabetes. The effects of PE on the organism are mediated by the intestinal microbiota, which transforms them into bioactive PE such as genistein, equol, enterolignans and certain urolithins. In this work, we review the most recent findings about the bacteria able to metabolize PE, together with the latest studies on the effects of PE on health. In addition, we describe the possible factors hindering the demonstration of the beneficial effect of PE on health, evincing the importance of measuring the actual circulating PE in order to encompass the variability of PE metabolism due to the intestinal microbiota. With this in mind, we also explore an approach to ensure the access to bioactive PE.

Flavonoids and Insulin-Resistance: From Molecular Evidences to Clinical Trials

Insulin-resistance is one of the main factors responsible for the onset and progression of Metabolic Syndrome (MetS). Among all polyphenols, the effects of flavonoids and their main food sources on insulin sensitivity have been widely evaluated in molecular and clinical studies. The aim of this review is to analyse the data observed in vitro, in vivo and in clinical trials concerning the effects of flavonoids on insulin resistance and to determine the molecular mechanisms with which flavonoids interact with insulin signaling.

Genistein enhances the secretion of glucagon-like peptide-1 (GLP-1) via downregulation of inflammatory responses

Glucagon-like peptide-1 (GLP-1) an incretin hormone, is known to regulate the glucose-mediated insulin secretion. However, reduction in the level of GLP-1 is considered to be a major cause for the reduction of GLP-1-dependent insulin secretory response. Genistein an isoflavone, is an important polyphenol and has wide range of therapeutic potentials, but its therapeutic effects alone and/or in combination with metformin on GLP-1 secretion have not been investigated yet. Hence, we aimed to investigate the stimulatory action of genistein in combination with metformin on GLP-1 via downregulation of inflammatory mediators, hyperlipidemia and hyperglycemia in alloxan-induced diabetic rats. Diabetes was induced in experimental rats by single administration of alloxan intraperitoneally. Metformin (50 mg/kg/day), genistein (20 mg/kg/day) and combination of genistein and metformin was administered in alloxan-induced diabetic rats. We found that genistein alone and/or in combination with metformin significantly increased the serum level (P < 0.01) and tissue content (P < 0.05) of GLP-1 in intestine when compared with that of metformin-treated animals. Similarly, genistein alone and/or in combination with metformin also resulted in normoglycemia (P < 0.001), glucose tolerance (P < 0.01), insulin sensitivity (P < 0.0001), hyperlipidemia (P < 0.01), liver and kidney function biomarkers (P < 0.01) as compared to that of metformin-treated experimental animals. Moreover, genistein alone and/or in combination with metformin also downregulated the inflammatory responses by decreasing the levels of interleuin-6, tumor necrosis factor-α and C-reactive protein in serum (P < 0.05) and intestine (P < 0.001) more efficiently as compared to that of metformin-treated experimental animals. The downregulation of inflammatory responses in intestine, was positively associated with increased secretion of GLP-1 from intestine. Histopathology of pancreas and intestine also showed that genistein significantly improved the deleterious effects of alloxan on pancreas and intestine. Hence, our work provides new insights on the synergistic effects of genistein and metformin on GLP-1 secretion. This may significantly improve the perception for proposing new GLP-1-based synergistic approaches for the treatment of diabetes mellitus.

Nutritional Modulation of AMPK-Impact upon Metabolic-Inflammation

Nutritional status provides metabolic substrates to activate AMP-Activated Protein Kinase (AMPK), the energy sensor that regulates metabolism. Recent evidence has demonstrated that AMPK has wider functions with respect to regulating immune cell metabolism and function. One such example is the regulatory role that AMPK has on NLRP3-inlflammasome and IL-1β biology. This in turn can result in subsequent negative downstream effects on glucose, lipid and insulin metabolism. Nutrient stress in the form of obesity can impact AMPK and whole-body metabolism, leading to complications such as type 2 diabetes and cancer risk. There is a lack of data regarding the nature and extent that nutrient status has on AMPK and metabolic-inflammation. However, emerging work elucidates to a direct role of individual nutrients on AMPK and metabolic-inflammation, as a possible means of modulating AMPK activity. The posit being to use such nutritional agents to re-configure metabolic-inflammation towards more oxidative phosphorylation and promote the resolution of inflammation. The complex paradigm will be discussed within the context of if/how dietary components, nutrients including fatty acids and non-nutrient food components, such as resveratrol, berberine, curcumin and the flavonoid genistein, modulate AMPK dependent processes relating to inflammation and metabolism.

Synthesis, structure, solution behavior, reactivity and biological evaluation of oxidovanadium(iv/v) thiosemicarbazone complexes

The synthesis and characterization of an oxidovanadium(iv) [VIVO(L)(acac)] (1) and of two dioxidovanadium(v) [VVO2(L')] (2) and [VVO2(L)] (2a) complexes of the Schiff base formed from the reaction of 4-(p-fluorophenyl) thiosemicarbazone with pyridine-2-aldehyde (HL) are described. The oxidovanadium(iv) species [VIVO(L)(acac)] (1) was synthesized by the reaction of VIVO(acac)2 with the thiosemicarbazone HL in refluxing ethanol. The recrystallization of [VIVO(L)(acac)] (1) in DMF, CH3CN or EtOH gave the same product i.e. the dioxidovanadium(v) complex [VVO2(L)] (2a); however, upon recrystallization of 1 in DMSO a distinct compound [VVO2(L')] (2) was formed, wherein the original ligand L- is transformed to a rearranged one, L'-. In the presence of DMSO the ligand in complex 1 is found to undergo methylation at the carbon centre attached to imine nitrogen (aldimine) and transformed to the corresponding VVO2-species through in situ reaction. The synthesized HL and the metal complexes were characterized by elemental analysis, IR, UV-Vis, NMR and EPR spectroscopy. The molecular structure of [VVO2(L')] (2) was determined by single crystal X-ray crystallography. The methylation of various other ligands and complexes prepared from different vanadium precursors under similar reaction conditions was also attempted and it was confirmed that the imine methylation observed is both ligand and metal precursor specific. Complexes 1 and 2 show in vitro insulin-like activity against insulin responsive L6 myoblast cells, higher than VIVO(acac)2, with complex 1 being more potent. In addition, the in vitro cytotoxicity studies of HL, and of complexes 1 and 2 against the MCF-7 and Vero cell lines were also done. The ligand is not cytotoxic and complex 2 is significantly more cytotoxic than 1. DAPI staining experiments indicate that an increase in the time of incubation and an increase of concentration of the complexes lead to the increase in cell death.

Egg white hydrolysate and peptide reverse insulin resistance associated with tumor necrosis factor-α (TNF-α) stimulated mitogen-activated protein kinase (MAPK) pathway in skeletal muscle cells

Purpose

Excessive formation of tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, has been implicated in the development of insulin resistance in obesity and type-2 diabetes. In skeletal muscle, chronic exposure to TNF-α impairs insulin-stimulated glucose uptake and insulin signaling. The aim of this study is to investigate the effects of enzymatic egg white hydrolysate (EWH) and its responsible peptide, IRW, on TNF-α-induced insulin resistance and the underlying molecular mechanisms using rat skeletal muscle cells (L6 cells).

Methods

Insulin resistance was induced by treating L6 cells with 5 ng/ml TNF-α for 24 h. Effects of EWH and IRW on glucose uptake were detected by glucose uptake assay, glucose transporter 4 (GLUT4) translocation by immunofluorescence, and western blot, while insulin-signaling pathway and mitogen-activated protein kinase (MAPK) pathway were investigated using western blot.

Results

Adding both EWH and IRW significantly improved glucose uptake in TNF-α-treated cells, increased activation of insulin receptor substrate (IRS-1) tyrosine residue and protein kinase B (Akt), whereas decreased activation of IRS-1 serine residue. In addition, TNF-α-induced activation of p38-mitogen-activated protein kinase (p38) and c-Jun N-terminal kinases (JNK) 1/2 were decreased by either EWH or IRW treatment.

Conclusion

EWH and IRW improve impaired insulin sensitivity by down-regulating the activation of p38 and JNK1/2 in TNF-α-treated skeletal muscle cells.

Egg White Ovotransferrin-Derived ACE Inhibitory Peptide Ameliorates Angiotensin II-Stimulated Insulin Resistance in Skeletal Muscle Cells

SCOPE

The renin-angiotensin system (RAS) is a major contributor to the development of insulin resistance and its related complications. Egg white ovotransferrin-derived tripeptides, IRW (Ile-Arg-Trp), IQW (Ile-Gln-Trp), or LKP (Leu-Lys-Pro) are previously identified as the inhibitors of angiotensin-converting enzyme (ACE), a key enzyme in the RAS. This study aims at determining whether these peptides are effective in improving insulin resistance, and their mechanisms of action, in a rat derived skeletal muscle cell line (L6 cells).

METHODS AND RESULTS

Insulin resistance is induced by treating L6 cells with 1 μm angiotensin II (Ang II) for 24 h. Effects of peptides on glucose uptake are determined using glucose uptake assay, glucose transporter 4 (GLUT4) translocation by immunofluorescence, reactive oxygen species (ROS) by dihydroethidium (DHE) staining, while insulin signaling pathway, Ang II receptor (AT1R or AT2R) levels, and NADPH oxidase activation are measured using Western Blot. Only IRW treatment significantly improves insulin resistance in L6 cells via stimulation of insulin signaling. IRW decreases Ang II-stimulated AT1R expression, ROS formation, and NADPH oxidase activation.

CONCLUSIONS

Of three ACE inhibitory peptides studied, only IRW improves insulin resistance in L6 cells, at least partially via reduced AT1R expression and its anti-oxidative activity.

Hyperuricemia in type 2 diabetic model KK-Ay/Ta mice: a potent animal model with positive correlation between insulin resistance and plasma high uric acid levels

Objective

Hyperuricemia is recognized as a main cause of gout. Accumulating clinical evidence suggests that hyperuricemia is strongly associated with insulin resistance and abnormal glucose metabolism. However, there seem no proper animal models for investigating such associations. Ideal animal model is considered to be hyperuricemic as well as diabetic. Selecting the KK-A^y/Ta mouse model, the relationship between hyperuricemia and insulin resistance has been studied to characterize such an animal model.

Results

Male type 2 diabetic KK-A^y/Ta and age-matched normal C57BL/6J mice were maintained on a basal 20% casein diet for 35 days. Food intake, body weight gain, levels of plasma uric acid, glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and triglyceride in KK-A^y/Ta mice were significantly higher than those in normal mice. Plasma uric acid levels showed significant positive correlations with plasma glucose, insulin, HOMA-IR and triglyceride levels. These results suggest that the KK-A^y/Ta mouse strain is useful for studies on correlation between hyperuricemia and insulin resistance, and for those on effects of foods and their components on the relations.

Genistein supplementation improves insulin resistance and inflammatory state in non-alcoholic fatty liver patients: A randomized, controlled trial

BACKGROUND & AIMS

The beneficial effect of genistein has indicated on metabolic disorders and inflammatory state. The aim of this study was to investigate the effect of genistein supplementation on non-alcoholic fatty liver disease (NAFLD) as the hepatic manifest of metabolic syndrome.

METHODS

In the present randomized double-blind controlled trial, patients with NAFLD were daily supplemented with either 250 mg genistein (n = 41) or placebo (n = 41) for 8-weeks. Both groups were instructed to follow an energy-balanced diet and physical activity recommendations. And their anthropometric and biochemical indices were assessed before and after the intervention.

RESULTS

At the end of the study, the genistein group had lower level of serum insulin (p = 0.001) and homeostasis model assessment for insulin resistance (HOMA-IR) (p = 0.041) compare to the placebo group. In addition serum malondialdehyde (MDA) (p = 0.004), tumor necrosis factor-α (TNF-α) (p = 0.045) and interleukin (IL)-6 (p = 0.018) also were lower in the genistein group. Compare with placebo, genistein supplementation significantly reduced waist to hip ratio (p = 0.021), body fat percentage (p = 0.015) and triglyceride (p = 0.018). However, there were no significant changes in BMI, fasting blood glucose (p = 0.122), alanine aminotransferase (ALT) (p = 0.536), aspartate aminotransferase (AST) (p = 0.265) between the two groups.

CONCLUSIONS

Oral supplementation with 250 mg genistein for 8-weeks can reduce insulin resistance, oxidative and inflammatory indices along with improvement in fat metabolism in patients with NAFLD. Studies with longer duration and larger samples might be needed to reveal other beneficial effects of genistein.

Assessment of Beneficial and Possible Toxic Effects of Two New Alfalfa-Derived Shelf Products

Aerial parts of Medicago sativa L. have been used as food and its consumption has been associated with health benefits, one among the most important being menopausal symptoms control. This work was aimed to explore possible pharmacological effects of two new alfalfa-derived products that have recently emerged as daily beverage preparations. In exploring their potential estrogenic effects, they produced no relevant alteration in the uterus. However, lowering glucose levels until normal values without causing further hypoglycemic effect were observed, when rats were treated with 1.5 g/kg/day samples. In vivo acute toxicity was not found when the alfalfa products were tested up to 3 g/kg rat weight. Furthermore, in vitro studies were conducted to assess their possible toxic effects. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase tests were carried out on the Caco-2 cell model to determine cell viability and membrane integrity. A concentration-dependent effect was observed, with a significant decrease in cell viability after exposure to concentrations of alfalfa product up to 100 mg/mL (after 3 h of incubation) and 50 mg/mL (after 24 h of treatment). Although in vitro level, the decrease in cell viability at these still low doses may underlie some toxicity, making necessary additional studies before any recommendation of a sustained consumption of these products by humans.

Soy isoflavones and glucose metabolism in menopausal women: A systematic review and meta-analysis of randomized controlled trials

SCOPE

The aim of this meta-analysis was to investigate whether soy isoflavones, a type of phytoestrogen, would affect glucose homeostasis in menopausal women.

METHODS AND RESULTS

Studies concerning about the relationship between soy isoflavone treatment and glucose metabolism were searched on MEDLINE and WEB OF SCIENCE (updated through April 2015) and EMBASE (1990-April 2015). Seventeen randomized controlled trials (RCTs) with a total number of 1529 menopausal women were identified for meta-analysis. Soy isoflavones were found to show great significance for the improvement of glucose metabolism, though marked heterogeneity was found between studies. The overall results showed that the average difference in fasting blood glucose values between women assigned to soy isoflavones and women in placebo groups was -0.22 mmol/L (95% CI: -0.38 to -0.07 mmol/L) under a random-effects model. In addition, the effect of soy isoflavones on insulin was also significant: -0.43 μIU/mL (95% CI: -0.71 to -0.14 μIU/mL), as was the effect on homeostasis model assessment insulin resistance (HOMA-IR): -0.52 (95% CI: -0.76 to -0.28).

CONCLUSION

Although the results displayed a significant tendency in favor of soy isoflavones, it appears that genistein alone played an important role in improving glucose metabolism due to its low heterogeneity.

Elucidation of hypoglycemic action and toxicity studies of insulin-like protein from Costus igneus

We have reported earlier, an orally active insulin-like protein (ILP) from Costus igneus having potent hypoglycemic property in STZ-induced diabetic Swiss mice. The blood glucose level was reduced significantly within two hours after feeding ILP orally in an oral glucose tolerance test. The present study elucidates the mechanism underlying the hypoglycemic action of ILP. Mechanism of action of ILP was studied in differentiated L6 myotubes. 2-NBDG uptake stimulated by ILP was studied in differentiated L6 myotubes under normoglycemic, hyperglycemic and induced insulin resistant conditions. ILP treatment significantly increased 2-NBDG uptake in differentiated L6 myotubes. The levels of insulin signaling molecules IRS-1 and GLUT-4 were assessed in ILP treated L6 myotubes by immunoblot analysis of cytoplasmic and plasma membrane fractions respectively. Immunoblot analysis revealed an increase in cytoplasmic IRS-1 with a concomitant increase in GLUT-4 translocation to the plasma membrane in a time dependent manner. Toxicity studies of ILP were performed on normal as well as diabetic Swiss albino mice. ILP did not show any toxicity in the acute and sub-chronic toxicity studies in normal as well as diabetic Swiss albino mice. Mass spectrometry was carried out to identify ILP. MALDI TOF/TOF MS analysis of ILP revealed sequence homology with the predicted protein from Physcomitrella patens. Our study reveals that ILP acts via insulin signaling pathway and can be used as oral insulin mimetic.

Antidiabetic effect of enterolactone in cultured muscle cells and in type 2 diabetic model db/db mice

Enterolactone (ENL) is formed by the conversion of dietary precursors like strawberry lignans via the gut microbiota. Urinary concentrations of lignan metabolites are reported to be significantly associated with a lower risk of Type 2 diabetes (T2D). In the present study, antidiabetic effect of ENL and its modes of action were studied in vitro and in vivo employing a rat skeletal muscle-derived cell line, L6 myocytes in culture, and T2D model db/db mice. ENL dose-dependently increased glucose uptake in L6 myotubes under insulin absent condition. This increase by ENL was canceled by compound C, an inhibitor of 5'-adenosine monophosphate-activated protein kinase (APMK). Activation (=phosphorylation) of AMPK and translocation of glucose transporter 4 (GLUT4) to plasma membrane in L6 myotubes were demonstrated by Western blotting analyses. Promotion by ENL of GLUT4 translocation to plasma membrane was also visually demonstrated by immunocytochemistry in L6 myoblasts that were transfected with glut4 cDNA-coding vector. T2D model db/db mice were fed the basal 20 % casein diet (20C) or 20C supplemented with ENL (0.001 or 0.01 %) for 6 weeks. Fasting blood glucose (FBG) levels were measured every week and intraperitoneal glucose tolerance test (IPGTT) was conducted. ENL at a higher dose (0.01 % in 20C) suppressed the increases in FBG levels. ENL was also demonstrated to improve the index of insulin resistance (HOMA-IR) and glucose intolerance by IPGTT in db/db mice. From these results, ENL is suggested to be an antidiabetic chemical entity converted from dietary lignans by gut microbiota.

A genistein-enriched diet neither improves skeletal muscle oxidative capacity nor prevents the transition towards advanced insulin resistance in ZDF rats

Genistein, a natural food compound mainly present in soybeans, is considered a potent antioxidant and to improve glucose homeostasis. However, its mechanism of action remains poorly understood. Here, we analyzed whether genistein could antagonize the progression of the hyperinsulinemic normoglycemic state (pre-diabetes) toward full-blown T2DM in Zucker Diabetic Fatty (ZDF) rats by decreasing mitochondrial oxidative stress and improving skeletal muscle oxidative capacity. Rats were assigned to three groups: (1) lean control (CNTL), (2) fa/fa CNTL, and (3) fa/fa genistein (GEN). GEN animals were subjected to a 0.02% (w/w) genistein-enriched diet for 8 weeks, whereas CNTL rats received a standard diet. We show that genistein did not affect the overall response to a glucose challenge in ZDF rats. In fact, genistein may exacerbate glucose intolerance as fasting glucose levels were significantly higher in fa/fa GEN (17.6 ± 0.7 mM) compared with fa/fa CNTL animals (14.9 ± 1.4 mM). Oxidative stress, established by electron spin resonance (ESR) spectroscopy, carbonylated protein content and UCP3 levels, remained unchanged upon dietary genistein supplementation. Furthermore, respirometry measurements revealed no effects of genistein on mitochondrial function. In conclusion, dietary genistein supplementation did not improve glucose homeostasis, alleviate oxidative stress, or augment skeletal muscle metabolism in ZDF rats.

1-Deoxynojirimycin Alleviates Insulin Resistance via Activation of Insulin Signaling PI3K/AKT Pathway in Skeletal Muscle of db/db Mice

1-Deoxynojirimycin (DNJ) is widely used for the treatment of diabetes mellitus as an inhibitor of intestinal α-glucosidase. However, there are few reports about its effect on insulin sensitivity improvement. The aim of the present study was to investigate whether DNJ decreased hyperglycemia by improving insulin sensitivity. An economical method was established to prepare large amounts of DNJ. Then, db/db mice were treated with DNJ intravenously (20, 40 and 80 mg·kg(-1)·day(-1)) for four weeks. Blood glucose and biochemical analyses were conducted to evaluate the therapeutic effects on hyperglycemia and the related molecular mechanisms in skeletal muscle were explored. DNJ significantly reduced body weight, blood glucose and serum insulin levels. DNJ treatment also improved glucose tolerance and insulin tolerance. Moreover, although expressions of total protein kinase B (AKT), phosphatidylinositol 3 kinase (PI3K), insulin receptor beta (IR-β), insulin receptor substrate-1 (IRS1) and glucose transporter 4 (GLUT4) in skeletal muscle were not affected, GLUT4 translocation and phosphorylation of Ser473-AKT, p85-PI3K, Tyr1361-IR-β and Tyr612-IRS1 were significantly increased by DNJ treatment. These results indicate that DNJ significantly improved insulin sensitivity via activating insulin signaling PI3K/AKT pathway in skeletal muscle of db/db mice.

Modified Si-Miao-San inhibits inflammation and promotes glucose disposal in adipocytes through regulation of AMP-kinase

Modified Si-Miao-San (mSMS) is composed of Rhizoma Coptidis, Cortex Phellodendri, Rhizoma Coptidis Semen Coicis and Atractylodes Rhizome. The prescription is used for the management of diabetes and insulin resistance in the clinic. This study aims to investigate its regulation of glucose disposal in adipocytes. Differentiated 3T3-L1 adipocytes were stimulated with conditioned medium derived from activated macrophages to induce insulin resistance and observed the effects of Mac-CM on insulin-mediated glucose uptake along the insulin receptor substrate-1/PI3K/Akt signaling pathway. Moreover, its regulation of AMPK phosphorylation was also investigated. mSMS enhanced AMPK phosphorylation and promoted basal glucose uptake in adipocytes; mSMS inhibited NF-κB activation by reducing P65 phosphorylation and improved insulin-stimulated IRS-1 tyrosine and Akt phosphorylation, leading to the restoration of insulin-mediated glucose uptake when cells were exposed to inflammatory stimulation. These beneficial effects were diminished in the presence of the AMPK inhibitor compound C. mSMS positively regulated AMPK activity, and this action contributed to improving insulin PI3K signaling by the beneficial regulation of IRS-1 function through inhibition of inflammation in adipocytes.

Fucosylated chondroitin sulfate from sea cucumber improves insulin sensitivity via activation of PI3K/PKB pathway

This study was to investigate the effects of fucosylated chondroitin sulfate (CHS) from sea cucumber on insulin sensitivity in skeletal muscle of type 2 diabetic mice induced by a high-fat high-sucrose diet (HFSD). CHS supplementation for 19 wk significantly improved insulin sensitivity by 20%, and reduced blood glucose and insulin levels. Western blotting assay showed that CHS significantly increased insulin-stimulated glucose transporter 4 (GLUT4) translocation to 1.7-fold, phosphorylation of phosphoinositide 3-kinase (PI3K) at p85 to 5.0-fold, protein kinase B (PKB) at Ser473 to 1.5-fold, and Thr308 to 1.6-fold in skeletal muscle. However, PI3K, PKB, and GLUT4 total proteins expression were unchangeable. In addition, qRT-PCR analysis proved that the insulin signaling was activated by CHS treatment, showing the increased mRNA expressions of glucose uptake-related key genes. It indicated that CHS improved insulin sensitivity by activation of PI3K/PKB signaling in skeletal muscle of type 2 diabetic mice. Identification of potential mechanism by which CHS increased insulin sensitivity might provide a new functional food or pharmaceutical application of sea cucumber.

Silibinin improves palmitate-induced insulin resistance in C2C12 myotubes by attenuating IRS-1/PI3K/Akt pathway inhibition

The present study investigated the effect of silibinin, the principal potential anti-inflammatory flavonoid contained in silymarin, a mixture of flavonolignans extracted from Silybum marianum seeds, on palmitate-induced insulin resistance in C2C12 myotubes and its potential molecular mechanisms. Silibinin prevented the decrease of insulin-stimulated 2-NBDG (2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose) uptake and the downregulation of glutamate transporter type 4 (GLUT4) translocation in C2C12 myotubes induced by palmitate. Meanwhile, silibinin suppressed the palmitate-induced decrease of insulin-stimulated Akt Ser473 phosphorylation, which was reversed by wortmannin, a specific inhibitor of phosphatidylinositol-3-kinase (PI3K). We also found that palmitate downregulated insulin-stimulated Tyr632 phosphorylation of insulin receptor substrate 1 (IRS-1) and up-regulated IRS-1 Ser307 phosphorylation. These effects were rebalanced by silibinin. Considering several serine/threonine kinases reported to phosphorylate IRS-1 at Ser307, treatment with silibinin downregulated the phosphorylation of both c-Jun N-terminal kinase (JNK) and nuclear factor-κB kinase β (IKKβ), which was increased by palmitate in C2C12 myotubes mediating inflammatory status, whereas the phosphorylation of PKC-θ was not significantly modulated by silibinin. Collectively, the results indicated that silibinin prevented inhibition of the IRS-1/PI3K/Akt pathway, thus ameliorating palmitate-induced insulin resistance in C2C12 myotubes.

RA abrogates hepatic gluconeogenesis and insulin resistance by enhancing IRS-1 and AMPK signalling in experimental type 2 diabetes

RA abrogates hyperglycemia and insulin resistance, the primary features of type 2 diabetes (T2DM).

Genistein improves spatial learning and memory in male rats with elevated glucose level during memory consolidation

Cognitive dysfunction due to higher blood glucose level has been reported previously. Genistein (GEN) is a phytoestrogen that we hypothesized might lead to improved memory, despite elevated blood glucose levels at the time of memory consolidation. To investigate this hypothesis, we compared the effects of orally administered GEN on the central nervous system in normal versus glucose-loaded adult male rats. A battery of behavioral assessments was carried out. In the MAZE test, which measured spatial learning and memory, the time of normal rats was shortened by GEN treatment compared to the vehicle group, but only in the early stages of testing. In the glucose-loaded group, GEN treatment improved performance as mazes were advanced. In the open-field test, GEN treatment delayed habituation to the new environment in normal rats, and increased the exploratory behaviors of glucose-loaded rats. There were no significant differences observed for emotionality or fear-motivated learning and memory. Together, these results indicate that GEN treatment improved spatial learning and memory only in the early stages of testing in the normal state, but improved spatial learning and memory when glucose levels increased during memory consolidation.

Antidiabetic effect of green rooibos (Aspalathus linearis) extract in cultured cells and type 2 diabetic model KK-A(y) mice

Previous studies have demonstrated antidiabetic effects for rooibos (Aspalathus linearis) and aspalathin (ASP), one of its main polyphenols. Rooibos, an endemic plant of South Africa, is well-known for its use as herbal tea. Green ('unfermented') rooibos has been shown to contain more ASP than 'fermented' rooibos tea, currently the major product. In the present study, we investigated the antidiabetic effect of green rooibos extract (GRE) through studies on glucose uptake in L6 myotubes and on pancreatic β-cell protective ability from reactive oxygen species (ROS) in RIN-5F cells. Its in vivo effect was also examined using obese diabetic KK-A(y) mice. GRE increased glucose uptake under insulin absent condition and induced phosphorylation of 5'-adenosine monophosphate-activated protein kinase (AMPK) in L6 myotubes as previously demonstrated for ASP. In addition to AMPK, GRE also promoted phosphorylation of Akt, another promoter of glucose transporter 4 (GLUT4) translocation, in L6 myotubes unlike ASP, suggesting an involvement of GRE component(s) other than ASP in Akt phosphorylation. Promotion of GLUT4 translocation to the plasma membrane by GRE in L6 myotubes was demonstrated by Western blotting analysis. GRE suppressed the advanced glycation end products (AGEs)-induced increase in ROS levels in RIN-5F pancreatic β-cells. Subchronic feeding with GRE suppressed the increase in fasting blood glucose levels in type 2 diabetic model KK-A(y) mice. These in vitro and in vivo results strongly suggest that GRE has antidiabetic potential through multiple modes of action.

Antidiabetic effect of nepodin, a component of Rumex roots, and its modes of action in vitro and in vivo

Many active components derived from edible natural resources such as plant extracts have recently attracted attention for their potential use as functional foods or drugs for preventing and treating metabolic diseases such as diabetes. To obtain a novel modulator of glucose metabolism, we conducted screening of a small compound library in cultured L6 myotubes. We identified nepodin that stimulated glucose uptake dose-dependently in differentiated L6 myotubes. The stimulatory effect of nepodin on glucose uptake was abrogated by a 5'-adenosine monophosphate-activated protein kinase (AMPK) inhibitor. In addition, nepodin stimulated the phosphorylation of AMPK. Nepodin also stimulated the translocation of GLUT4 to the plasma membrane in L6 myoblasts transfected with a Glut4 cDNA-coding vector and in differentiated L6 myotubes. In in vivo study, nepodin suppressed the increases in fasting blood glucose levels and improved the glucose intolerance of C57BL/KsJ-db/db mice, a type 2 diabetic animal model. Nepodin rescued the impaired phosphorylation of AMPK in the skeletal muscle of db/db mice. These results suggest that nepodin has an antidiabetic effect, which is at least partly mediated by stimulation of GLUT4 translocation via AMPK activation by nepodin.

Mechanisms for antidiabetic effect of gingerol in cultured cells and obese diabetic model mice

There have been studies on health beneficial effects of ginger and its components. However, there still remain certain aspects that are not well defined in their anti-hyperglycemic effects. Our aims were to find evidence of possible mechanisms for antidiabetic action of [6]-gingerol, a pungent component of ginger, employing a rat skeletal muscle-derived cell line, a rat-derived pancreatic β-cell line, and type 2 diabetic model animals. The antidiabetic effect of [6]-gingerol was investigated through studies on glucose uptake in L6 myocytes and on pancreatic β-cell protective ability from reactive oxygen species (ROS) in RIN-5F cells. Its in vivo effect was also examined using obese diabetic db/db mice. [6]-Gingerol increased glucose uptake under insulin absent condition and induced 5' adenosine monophosphate-activated protein kinase phosphorylation in L6 myotubes. Promotion by [6]-gingerol of glucose transporter 4 (GLUT4) translocation to plasma membrane was visually demonstrated by immunocytochemistry in L6 myoblasts transfected with glut4 cDNA-coding vector. [6]-Gingerol suppressed advanced glycation end product-induced rise of ROS levels in RIN-5F pancreatic β-cells. [6]-Gingerol feeding suppressed the increases in fasting blood glucose levels and improved glucose intolerance in db/db mice. [6]-Gingerol regulated hepatic gene expression of enzymes related to glucose metabolism toward decreases in gluconeogenesis and glycogenolysis as well as an increase in glycogenesis, thereby contributing to reductions in hepatic glucose production and hence blood glucose concentrations. These in vitro and in vivo results strongly suggest that [6]-gingerol has antidiabetic potential through multiple mechanisms.

Cyclocarya paliurus extract modulates adipokine expression and improves insulin sensitivity by inhibition of inflammation in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cyclocarya paliurus Batal., a Chinese native plant, is the sole species in its genus and its leaves have been widely used as a remedy for diabetes in traditional folk medicine. The study was undertaken to evaluate the effects of Cyclocarya paliurus leaves extracts (CPE) on adipokine expression and insulin sensitivity in mice.

MATERIALS AND METHODS

Mice were stimulated with conditioned medium (prepared from activated macrophages, Mac-CM) to induce adipose dysfunction and insulin resistance. Then mice were treated with CPE (100, 200 and 500 mg/kg, ig.) or metformin (200 mg/kg, ig.), followed by glucose and insulin intolerance, adipokine expression, phosphorylation of insulin receptor substrate (IRS-1) and glucose consumption measurement.

RESULTS

CPE, as well as metformin effectively promoted glucose disposal in oral glucose tolerance test in normal mice. Mac-CM challenge induced glucose and insulin intolerance, but CPE reversed these alternations with increased glycogen content in muscle and liver, well demonstrating its beneficial effects on glucose homeostasis. RT-qPCR analysis showed that CPE inhibited TNF-a, IL-6, MCP-1 and resistin overexpression and effectively enhanced adiponectin expression in adipose tissue when mice were exposed to Mac-CM stimulation. Inflammation impaired insulin signaling in muscle, whereas CPE inhibited inflammation-induced serine phosphorylation of IRS-1 and effectively restored the phosphorylation of both IRS-1 at tyrosine residues and downstream Akt phosphorylation in response to insulin. Moreover, independently of insulin, CPE promoted glucose consumption in adipocytes under normal and inflammatory conditions.

CONCLUSION

Above-mentioned results demonstrated that CPE beneficially regulated adipokines expression and ameliorated insulin resistance through inhibition of inflammation in mice.

Daidzein promotes glucose uptake through glucose transporter 4 translocation to plasma membrane in L6 myocytes and improves glucose homeostasis in Type 2 diabetic model mice

Daidzein shows estrogenic, antioxidant and antiandrogenic properties as well as cell cycle regulatory activity. However, the antihyperglycemic effect of daidzein remains to be elucidated. In this study, we investigated the in vitro effect of daidzein on glucose uptake, AMPK phosphorylation and GLUT4 translocation on plasma membrane in L6 myotubes and its in vivo antihyperglycmic effect in obese-diabetic model db/db mice. Daidzein was found to promote glucose uptake, AMPK phosphorylation and GLUT4 translocation by Western blotting analyses in L6 myotubes under a condition of insulin absence. Promotion by daidzein of glucose uptake as well as GLUT4 translocation to plasma membrane by immunocytochemistry was also demonstrated in L6 myoblasts transfected with a GLUT4 cDNA-coding vector. Daidzein (0.1% in the diet) suppressed the rises in the fasting blood glucose, serum total cholesterol levels and homeostasis model assessment index of db/db mice. In addition, daidzein supplementation markedly improved the AMPK phosphorylation in gastrocnemius muscle of db/db mice. Daidzein also suppressed increases in blood glucose levels and urinary glucose excretion in KK-Ay mice, another Type 2 diabetic animal model. These in vitro and in vivo findings suggest that daidzein is preventive for Type 2 diabetes and an antidiabetic phytochemical.

Genistein protection against acetaminophen-induced liver injury via its potential impact on the activation of UDP-glucuronosyltransferase and antioxidant enzymes

The purpose of this study was to investigate genistein's influence on the relationship between the activation of uridine diphosphate glucuronosyltransferase (UGTs) and the protection against acetaminophen-induced liver toxicity. Animal experimental results revealed that genistein (50, 100 or 200mg/BWkg) significantly ameliorated the biomarkers alanine aminotransferase, alanine aminotransferase, lactate dehydrogenase and malondialdehyde, as indicators of acute liver damage caused by APAP (200mg/BWkg). The level of GSH declined sharply after treatment with APAP within 1h in both the liver and blood with and without genistein. However, after 16h, the levels approached or returned to the original level. Genistein may accelerate and promote APAP glucuronidation as the results showed that APAP-glucuronide increased by 18.44%, 46.79%, and 66.49% for 4h of treatment with genistein dosages of 50, 100 or 200mg/BWkg, respectively, compared with the APAP-only treatment. The activation of UGTs and glutathione peroxidase and the inhibition of CYP2E1 by genistein were observed, and UGTs mRNA expression level with genistein was measured. These findings suggest that genistein can prevent and protect against APAP-induced liver toxicity due to the inhibition of APAP biotransformation and the resistance to oxidative stress via the modulation of the activities of metabolism and the antioxidant enzyme.