Contrasting effects of puerarin and daidzin on glucose homeostasis in mice

Pueraria lobata antioxidant extract ameliorates non-alcoholic fatty liver by altering hepatic fat accumulation and oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Pueraria lobata is essential medicinal and edible homologous plants widely cultivated in Asian countries. Therefore, P. lobata is widely used in the food, health products and pharmaceutical industries and have significant domestic and international market potential and research value. P. lobata has remarkable biological activities in protecting liver, relieving alcoholism, antioxidation, anti-tumor and anti-inflammation in clinic. However, the potential mechanism of ethyl acetate extract of Pueraria lobata after 70% alcohol extraction (APL) ameliorating nonalcoholic fatty liver disease (NAFLD) has not been clarified.

AIM OF THE STUDY

This study aimed to investigate the ameliorative effect of P. lobata extract on human hepatoma cells and injury in rats, and to evaluate its therapeutic potential for ameliorating NAFLD.

METHODS

Firstly, the effective part of P. lobata extract was determined as APL by measuring its total substances and antioxidant activity. And then the in vitro and in vivo models of NAFLD were adopted., HepG2 cells were incubated with palmitic acid (PA) and hydrogen peroxide (H2O2). In order to evaluate the effect of APL, Simvastatin and Vitamin C (VC) were used as positive control. Various parameters related to lipogenesis and fatty acid β-oxidation were studied, such as intracellular lipid accumulation, reactive oxygen species (ROS), Western Blot, mitochondrial membrane potential, apoptosis, and the mechanism of APL improving NAFLD. The chemical components of APL were further determined by HPLC and UPLC-MS, and molecular docking was carried out with Keap1/Nrf2/HO-1 pathway related proteins.

RESULTS

APL significantly reduced lipid accumulation and levels of oxidative stress-related factors in vitro and in vivo. Immunohistochemical、Western Blot and PCR analysis showed that the expressions of Nrf2 and HO-1 were up-regulated in APL treatment. The Nrf2 inhibitor ML385 can block the rescue by APL of cellular oxidative stress and lipid accumulation induced by H2O2 and PA, demonstrating its dependence on Nrf2. UPLC/MS analysis showed that there were 3'-hydroxyl puerarin, puerarin, 3'-methoxy puerarin, daidzein, genistin, ononin, daidzin and genistein.

CONCLUSION

This study further clarified the mechanism of P. lobata extract in improving NAFLD, which provided a scientific basis for developing new drugs to protect liver injury and laid a solid foundation for developing P. lobata Chinese herbal medicine resources.

Protective effects of puerarin on metabolic diseases: Emphasis on the therapeutical effects and the underlying molecular mechanisms

Metabolic diseases (MetD) such as diabetes mellitus, obesity, and hyperlipidemia have become global health challenges. As a naturally occurring plant component, puerarin has been verified to possess a wide range of pharmacological effects including lowering blood glucose, improving insulin resistance, and regulating lipid metabolism, which has attracted extensive attention in recent years, and its potential in the treatment of MetD has been highly acclaimed. In addition, puerarin has exhibited antioxidant, anti-inflammatory, and cardiovascular protective effects, which are of great significance in the prevention and treatment of MetD. This article comprehensively summarizes the research progress of puerarin in the treatment of MetD and explores its pharmacological mechanisms, clinical applications, and future perspectives. More importantly, this review provided a list of the involved molecular mechanims in treating MetD of puerarin. Taking into account these conclusions, it may provide a strong foundation for the optimized use of puerarin in the treatment of patients suffering from MetD.

Interventional effects of Pueraria oral liquid on T2DM rats and metabolomics analysis

Pueraria lobata, commonly known as kudzu, is a medicinal and food plant widely used in the food, health food, and pharmaceutical industries. It has clinical pharmacological effects, including hypoglycemic, antiinflammatory, and antioxidant effects. However, its mechanism of hypoglycemic effect on type 2 diabetes mellitus (T2DM) has not yet been elucidated. In this study, we prepared a Pueraria lobata oral liquid (POL) and conducted a comparative study in a T2DM rat model to evaluate the hypoglycemic effect of different doses of Pueraria lobata oral liquid. Our objective was to investigate the hypoglycemic effect of Puerarin on T2DM rats and understand its mechanism from the perspective of metabolomics. In this study, we assessed the hypoglycemic effect of POL through measurements of FBG, fasting glucose tolerance test, plasma lipids, and liver injury levels. Furthermore, we examined the mechanism of action of POL using hepatic metabolomics. The study's findings demonstrated that POL intervention led to improvements in weight loss, blood glucose, insulin, and lipid levels in T2DM rats, while also providing a protective effect on the liver. Finally, POL significantly affected the types and amounts of hepatic metabolites enriched in metabolic pathways, providing an important basis for revealing the molecular mechanism of Pueraria lobata intervention in T2DM rats. These findings indicate that POL may regulate insulin levels, reduce liver damage, and improve metabolic uptake in the liver. This provides direction for new applications and research on Pueraria lobata to prevent or improve T2DM.

Comparative analysis of the medicinal and nutritional components of different varieties of Pueraria thomsonii and Pueraria lobata

Pueraria thomsonii and Pueraria lobata are important medicinal plants with unique chemical compositions that are widely used in traditional Chinese medicine. To compare the nutritional and medicinal profiles of these two species, we analyzed the flavonoid, dietary fiber, total starch, and crude protein contents of one P. lobata and three P. thomsonii varieties using ultra-performance liquid chromatography-tandem mass spectrometry, enzyme weight, acid hydrolysis, and Kjeldahl methods. Furthermore, we used principal component analysis and hierarchical clustering heatmap analysis to separate the data obtained from the P. thomsonii and P. lobata samples. We detected 279 flavonoid compounds in the two Pueraria species, including 90 isoflavones and 78 flavonoids. A large proportion of isoflavones and flavonoids were more abundant in P. lobata than in P. thomsonii. The total starch content was significantly higher in P. thomsonii than in P. lobata. By contrast, the soluble dietary fiber, insoluble dietary fiber, and crude protein contents were substantially lower in P. thomsonii than in P. lobata. Taken together, our results demonstrate that P. lobata is better suited for use as a medicine, whereas P. thomsonii is better suited as an edible food, and provide a theoretical foundation for developing P. thomsonii and P. lobata germplasm resources.

Plant Specialised Glycosides (PSGs): their biosynthetic enzymatic machinery, physiological functions and commercial potential

Plants, the primary producers of our planet, have evolved from simple aquatic life to very complex terrestrial habitat. This habitat transition coincides with evolution of enormous chemical diversity, collectively termed as 'Plant Specialised Metabolisms (PSMs)', to cope the environmental challenges. Plant glycosylation is an important process of metabolic diversification of PSMs to govern their in planta stability, solubility and inter/intra-cellular transport. Although, individual category of PSMs (terpenoids, phenylpropanoids, flavonoids, saponins, alkaloids, phytohormones, glucosinolates and cyanogenic glycosides) have been well studied; nevertheless, deeper insights of physiological functioning and genomic aspects of plant glycosylation/deglycosylation processes including enzymatic machinery (CYPs, GTs, and GHs) and regulatory elements are still elusive. Therefore, this review discussed the paradigm shift on genomic background of enzymatic machinery, transporters and regulatory mechanism of 'Plant Specialised Glycosides (PSGs)'. Current efforts also update the fundamental understanding about physiological, evolutionary and adaptive role of glycosylation/deglycosylation processes during the metabolic diversification of PSGs. Additionally, futuristic considerations and recommendations for employing integrated next-generation multi-omics (genomics, transcriptomics, proteomics and metabolomics), including gene/genome editing (CRISPR-Cas) approaches are also proposed to explore commercial potential of PSGs.

Evaluation of pathways to the C-glycosyl isoflavone puerarin in roots of kudzu (Pueraria montana lobata)

Kudzu (Pueraria montana lobata) is used as a traditional medicine in China and Southeast Asia but is a noxious weed in the Southeastern United States. It produces both O- and C-glycosylated isoflavones, with puerarin (C-glucosyl daidzein) as an important bioactive compound. Currently, the stage of the isoflavone pathway at which the C-glycosyl unit is added remains unclear, with a recent report of direct C-glycosylation of daidzein contradicting earlier labeling studies supporting C-glycosylation at the level of chalcone. We have employed comparative mRNA sequencing of the roots from two Pueraria species, one of which produces puerarin (field collected P. montana lobata) and one of which does not (commercial Pueraria phaseoloides), to identify candidate uridine diphosphate glycosyltransferase (UGT) enzymes involved in puerarin biosynthesis. Expression of recombinant UGTs in Escherichia coli and candidate C-glycosyltransferases in Medicago truncatula were used to explore substrate specificities, and gene silencing of UGT and key isoflavone biosynthetic genes in kudzu hairy roots employed to test hypotheses concerning the substrate(s) for C-glycosylation. Our results confirm UGT71T5 as a C-glycosyltransferase of isoflavone biosynthesis in kudzu. Enzymatic, isotope labeling, and genetic analyses suggest that puerarin arises both from the direct action of UGT71T5 on daidzein and via a second route in which the C-glycosidic linkage is introduced to the chalcone isoliquiritigenin.

Food proteins in the regulation of blood glucose control

Food proteins, depending on their origin, possess unique characteristics that regulate blood glucose via multiple physiological mechanisms, including the insulinotropic effects of amino acids, the activation of incretins, and slowing gastric emptying rate. The strategies aimed at curbing high blood glucose are important in preventing impaired blood glucose control, including insulin resistance, prediabetes and diabetes. The effect of proteins on blood glucose control can be achieved with high-protein foods short-term, and high-protein diets long-term using foods that are naturally high in protein, such as dairy, meat, soy and pulses, or by formulating high-protein functional food products using protein concentrates and isolates, or blended mixtures of proteins from different sources. Commercial sources of protein powders are represented by proteins and hydrolysates of caseins, whey proteins and their fractions, egg whites, soy, yellow pea and hemp which will be reviewed in this chapter. The effective doses of food protein that are capable of reducing postprandial glycemia start from 7 to 10g and higher per serving; however, the origin of protein, and macronutrient composition of a meal will determine the magnitude and duration of their effect on glycemia. The theoretical and methodological framework to evaluate the effect of foods, including food proteins, on postprandial glycemia for substantiation of health claims on food has been proposed in Canada and is discussed in the context of global efforts to harmonize the international food regulation and labeling.

Anti-hyperglycemic and anti-hyperlipidemic effects of a methanolic extract of Debregeasia salicifolia in Alloxan-induced diabetic albino mice

Diabetes mellitus (DM), an endocrine syndrome characterized by high blood glucose levels due to abrogated insulin activity. The existing treatments for DM have side effects and varying degrees of efficacy. Therefore, it is paramount that novel approaches be developed to enhance the management of DM. Therapeutic plants have been accredited as having comparatively high efficacy with fewer adverse effects. The current study aims to elucidate the phytochemical profile, anti-hyperlipidemic, and anti-diabetic effects of methanolic extract D. salicifolia (leaves) in Alloxan-induced diabetic mice. Alloxan was injected intraperitoneally (150 mg kg-1, b.w), to induced diabetes in mice. The mice were divided into three groups (n=10). Group 1 (normal control) received normal food and purified water, Group II (diabetic control) received regular feed and clean water and group III (diabetic treated) received a methanolic extract of the plant (300 mg kg-1) for 28 days with a typical diet and clean water throughout the experiment. Blood samples were collected to checked serum glucose and concentration of LDL, TC, TG. The extract demonstrated significant antihyperglycemic activity (P<0.05), whereas improvements in mice's body weight and lipid profiles were observed after treatment with the extract. This study establishes that the extract has high efficacy with comparatively less toxicity that can be used for DM management.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.

Comparative transcriptome analysis of roots, stems, and leaves of Pueraria lobata (Willd.) Ohwi: identification of genes involved in isoflavonoid biosynthesis

BACKGROUND

Pueraria lobata (Willd.) Ohwi is a valuable herb used in traditional Chinese medicine. Isoflavonoids are the major bioactive compounds in P. lobata, namely puerarin, daidzin, glycitin, genistin, daidzein, and glycitein, which have pharmacological properties of anti-cardiovascular, anti-hypertension, anti-inflammatory, and anti-arrhythmic.

METHODS

To characterize the corresponding genes of the compounds in the isoflavonoid pathway, RNA sequencing (RNA-Seq) analyses of roots, stems, and leaves of P. lobata were carried out on the BGISEQ-500 sequencing platform.

RESULTS

We identified 140,905 unigenes in total, of which 109,687 were annotated in public databases, after assembling the transcripts from all three tissues. Multiple genes encoding key enzymes, such as IF7GT and transcription factors, associated with isoflavonoid biosynthesis were identified and then further analyzed. Quantitative real-time PCR (qRT-PCR) results of some genes encoding key enzymes were consistent with our RNA-Seq analysis. Differentially expressed genes (DEGs) were determined by analyzing the expression profiles of roots compared with other tissues (leaves and stems). This analysis revealed numerous DEGs that were either uniquely expressed or up-regulated in the roots. Finally, quantitative analyses of isoflavonoid metabolites occurring in the three P. lobata tissue types were done via high-performance liquid-chromatography and tandem mass spectrometry methodology (HPLC-MS/MS). Our comprehensive transcriptome investigation substantially expands the genomic resources of P. lobata and provides valuable knowledge on both gene expression regulation and promising candidate genes that are involved in plant isoflavonoid pathways.

Puerariae Lobatae radix flavonoids and puerarin alleviate alcoholic liver injury in zebrafish by regulating alcohol and lipid metabolism

Exessive drinking is commonly associated with a wide spectrum of liver injuries. The term alcoholic liver disease (ALD) is generally used to refer to this spectrum of hepatic abnormalities, and the term hepatic steatosis denotes early lesions. Puerariae Lobatae Radix (PLR) is a common traditional Chinese medicine and has been widely used as an efficient treatment for alcohol-induced damage. Flavonoids are the principal components of PLR that could potentially be responsible for the activation of alcohol metabolism and lipid-lowering effects. However, little is known about the mechanisms underlying their activity against alcoholic injury. In this study, PLR flavonoids (PLF) were obtained by microwave extraction. A 2% ethanol solution was used to establish a model of alcoholic fatty liver disease by exposure of zebrafish larvae for 32 h, and then the zebrafish were administered PLF and puerarin. The results showed that PLF and puerarin significantly decreased lipid accumulation and the levels of total cholesterol and triglycerides in zebrafish larvae. Moreover, PLF and puerarin downregulated the expression of genes related to alcohol and lipid metabolism (CYP2y3, CYP3a65, ADH8a, ADH8b, HMGCRB, and FASN), endoplasmic reticulum stress, and DNA damage (CHOP, EDEM1, GADD45αa, and ATF6) and reduced levels of inflammatory factors (IL-1β, TNF-α) in zebrafish larvae. PLF and puerarin increased the phosphorylation of AMP-activated protein kinase-α (AMPKα) and decreased the total protein level of ACC1. The findings suggested that PLF and puerarin alleviated alcohol-induced hepatic steatosis in zebrafish larvae by regulating alcohol and lipid metabolism, which was closely related to the regulation of the AMPKα-ACC signaling pathway. In conclusion, the study provided a possible therapeutic drug for ALD treatment.

Puerarin alleviates osteoporosis in the ovariectomy-induced mice by suppressing osteoclastogenesis via inhibition of TRAF6/ROS-dependent MAPK/NF-κB signaling pathways

In this study, we investigated the mechanisms by which puerarin alleviates osteoclast-related loss of bone mass in ovariectomy (OVX)-induced osteoporosis model mice. Puerarin-treated OVX mice exhibited higher bone density, fewer tartrate-resistant acid phosphatase (TRAcP)-positive osteoclasts, and levels of lower reactive oxygen species (ROS) within bone tissues than vehicle-treated OVX mice. Puerarin suppressed in vitro osteoclast differentiation, hydroxyapatite resorption activity, and expression of osteoclastogenesis-related genes, such as NFATc1, MMP9, CTSK, Acp5 and c-Fos, in RANKL-induced bone marrow macrophages (BMMs) and RAW264.7 cells. It also reduced intracellular ROS levels by suppressing expression of TRAF6 and NADPH oxidase 1 (NOX1) and increasing expression of antioxidant enzymes such as heme oxygenase-1 (HO-1). Puerarin inhibited TRAF6/ROS-dependent activation of the MAPK and NF-κB signaling pathways in RANKL-induced RAW264.7 cells, and these effects were partially reversed by HO-1 silencing or TRAF6 overexpression. These findings suggest puerarin alleviates loss of bone mass in the OVX-model mice by suppressing osteoclastogenesis via inhibition of the TRAF6/ROS-dependent MAPK/NF-κB signaling pathway.

A Rapid High Throughput Vibration and Vortex-Assisted Matrix Solid Phase Dispersion for Simultaneous Extraction of Four Isoflavones for Quality Evaluation of Semen Sojae Praeparatum

Isoflavones (daidzein, daidzin, genistein and genistin) were main chemical components and usually selected as markers for quality control of Traditional Chinese Medicine semen sojae praeparatum (SSP). High throughput vibration and vortex-assisted matrix solid phase dispersion and high performance liquid chromatography with diode array detection were developed to simultaneously extract and quantify four isoflavones in SSP. Some parameters influencing extraction efficiency of isoflavones by vortex-assisted matrix solid phase dispersion such as sorbent type, ratio of sample to sorbent, crushing time, vibration frequency, methanol concentration, eluting solvent volume and vortex time were optimized. It was found that the best extraction yields of four isoflavones were obtained when the sample (20 mg) and SBA-3 (40 mg) was crushed by ball mill machine for 2 min at vibration frequency of 800 times per minute. Methanol/water (1.5 ml, 8:2, v/v) solution was dropped into the treated sample and vortexed for 3 min. The recoveries of the four isoflavones ranged from 86.1 to 94.8% and all relative standard deviations were less than 5%. A good linearity (r > 0.9994) was achieved within the range 0.5-125 μg/ml. It was concluded that the high throughput vibration and vortex-assisted matrix solid-phase dispersion coupled with high performance liquid chromatography was user-friendly extraction and quantification method of multiple isoflavones for quality evaluation of SSP.

Starch and mineral element accumulation during root tuber expansion period of Pueraria thomsonii Benth

Pueraria is a medicine plant with rich starch, and thus can be a potential agricultural and industrial resource. In this study, we evaluated the root tuber yield of a cultivar of starch kudzu (Pueraria thomsonii) and the starch accumulation during expansion period of root tuber. Additionally, mineral elements were quantified in root tuber and starch. The results indicated that the starch kudzu cultivar owned high yield of root tuber (greater than42 tons/hm²), high starch content (greater than17% FW) in root tuber, and rich accumulation of beneficial mineral elements. Interestingly, the root tuber of P. thomsonii contained a high concentration of selenium (70 mg/kg FW) and strontium (40 mg/kg FW), and thus it can be utilized as a Se and Sr rich food. Furthermore, Se and Sr can be well preserved in starch through the optimized starch extraction method.

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.

Management of Diabetes Mellitus with Puerarin, a Natural Isoflavone FromPueraria lobata

Diabetes mellitus (DM) has become one of the most challenging public health problems globally. The increasing prevalence and mortality rates call for more effective therapeutic agents, especially for DM complications. Traditional herbs have a long clinical application history for DM treatment. Puerarin is a natural isoflavone from Pueraria lobata (Wild.) Ohwi which has been consumed both as a functional food and herb in Eastern Asia countries. Documented data has shown that puerarin has cardio-protective, neuroprotective, anti-oxidative, anti-inflammatory and many other effects. In this review, we will summarize the beneficial effects and underlying mechanisms of puerarin on DM and complications. Puerarin may directly benefit DM by decreasing blood glucose levels, improving insulin resistance, protecting islets, inhibiting inflammation, decreasing oxidative stress and inhibiting Maillard reaction and advanced glycation end products (AGEs) formation. Furthermore, puerarin may also benefit DM indirectly by retarding and improving a series of DM complications, such as cardiovascular complications, diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, etc. However, comprehensive studies of its effect and mechanisms are needed. In addition, its efficacy is relatively low, which is partially due to its pharmacokinetics profiles. Though puerarin shows low toxicity to experimental animals, its safety on human remains to be clarified. Collectively, we suggest that puerarin might be a potential adjuvant agent for the treatment of DM and DM complications in future.

Comparing the antidiabetic effects and chemical profiles of raw and fermented Chinese Ge-Gen-Qin-Lian decoction by integrating untargeted metabolomics and targeted analysis

Background

Microbial fermentation has been widely applied in traditional Chinese medicine (TCM) for thousands of years in China. Various beneficial effects of fermentation for applications in TCM or herbals have been reported, such as enhanced anti-ovarian cancer, antioxidative activity, and neuroprotective effects. Ge-Gen-Qin-Lian decoction (GQD), a classic TCM formula, has been used to treat type 2 diabetes mellitus in China. In this study, GQD was fermented with Saccharomyces cerevisiae, and the antidiabetic activities and overall chemical profiles of raw and fermented GQD (FGQD) were systematically compared.

Methods

First, the antidiabetic effects of GQD and FGQD on high-fat diet and streptozotocin (STZ)-induced diabetic rats were compared. Then, high-performance liquid chromatography Q Exactive MS was applied for rapid characterization of the chemical components of GQD. Additionally, we proposed an integrated chromatographic technique based untargeted metabolomics identifying differential chemical markers between GQD and FGQD and targeted analysis determining the fermenting-induced quantitative variation tendencies of chemical marker strategy for overall chemical profiling of raw and fermented GQD.

Results

Both GQD and FGQD displayed effects against HFD and STZ-induced diabetes, and FGQD showed a better recovery trend associated with profound changes in the serum lipoprotein profile and body weight gain. In addition, 133 compounds were characterized from GQD. It was demonstrated that the integrated strategy holistically illuminated 30 chemical markers contributed to the separation of GQD and FGQD, and further elucidated the fermenting-induced chemical transformation mechanisms and inherent chemical connections of secondary metabolites. Although there were no new secondary metabolites in FGQD compared with GQD, the amounts of secondary metabolites, which were mostly deglycosylated, were redistributed in FGQD.

Conclusion

The anti-diabetic activities of GQD could be improved by applying fermentation technology. Moreover, the proposed strategy could serve as a powerful tool for systematically exploring the chemical profiles of raw and fermented formulas.

Electronic supplementary material

The online version of this article (10.1186/s13020-018-0208-7) contains supplementary material, which is available to authorized users.

Daidzein, its effects on impaired glucose and lipid metabolism and vascular inflammation associated with type 2 diabetes

Over the last decades, the incidence of type 2 diabetes (T2D) is increasing substantially. Emerging evidences from epidemiological studies have shown the association between higher intake of soy isoflavones and reduced risk of T2D and its associated health risks. Daidzein, a soy isoflavone, has been found to have a promising therapeutic potential in managing T2D pathophysiology. Fermented soybean is the major source of daidzein; however, it can also be formed via the consumption of its glycosylated moiety, daidzin with subsequent hydrolysis by intestinal bacterial enzyme. Many studies reported the prophylactic effect of daidzein on the improvement of hyperglycemia, insulin resistance, dislipidemia, obesity, inflammation, and other complications associated with T2D. The molecular mechanisms underlying the action of daidzein include diverged pathways where daidzein has been shown to interact with several signaling molecules and receptors to achieve desirable effect. Although the specific molecular mechanism is still elusive, further studies are thus needed to understand it in detail. In this review, we discuss the antidiabetic potential of daidzein with respect to the evidences from various clinical, preclinical, and cell culture studies and the underlying molecular mechanism in a precise way to have a comprehensive account on this isoflavone with promising therapeutic potential. © 2018 BioFactors, 44(5):407-417, 2018.

Puerarin Mitigates Diabetic Hepatic Steatosis and Fibrosis by Inhibiting TGF-β Signaling Pathway Activation in Type 2 Diabetic Rats

Lipid metabolism disorder and inflammation are essential promoters in pathogenesis of liver injury in type 2 diabetes. Puerarin (PUR) has been reported to exert beneficial effects on many diabetic cardiovascular diseases and chemical-induced liver injuries, but its effects on diabetic liver injury and its mechanism are still unclear. The current study was designed to explore the therapeutic effect and mechanism of PUR on liver injury in a type 2 diabetic rat model induced by a high-fat diet combined with low-dose streptozotocin. The diabetic rats were treated with or without PUR (100 mg/kg/day) by gavaging for 8 weeks, and biochemical and histological changes in liver were examined. Results showed that treatment with PUR significantly attenuated hepatic steatosis by regulating blood glucose and ameliorating lipid metabolism disorder. Liver fibrosis was relieved by PUR treatment. PUR inhibited oxidative stress and inflammation which was associated with inactivation of NF-κB signaling, thereby blocking the upregulation of proinflammatory cytokines (IL-1β, TNF-α) and chemokine (MCP-1). This protection of PUR on diabetic liver injury is possibly related with inhibition on TGF-β/Smad signaling. In conclusion, the present study provides evidence that PUR attenuated type 2 diabetic liver injury by inhibiting NF-κB-driven liver inflammation and the TGF-β/Smad signaling pathway.

Effect of cortex mori on pharmacokinetic profiles of main isoflavonoids from pueraria lobata in rat plasma

ETHNOPHARMACOLOGICAL RELEVANCE

Radix pueraria (the root of pueraria lobata (Wild.) Ohwi.), which contains a class of isoflavonoids as the main active components, as well as cortex mori (the root bark of Morus alba L), which contains abundant active alkaloids, have been employed for the treatment of diabetes in traditional Chinese medicine for centuries. In previous studies, pharmacodynamic synergistic reactions have been observed in compatible application of pueraria lobata isoflavonoids extracts (PLF) and cortex mori alkaloids extracts (CME) for inhibiting α-glycosidase activity. It has also been demonstrated that PLF can effectively slow down the absorption of active alkaloid from CME, so as to produce a higher effective concentration in small intestine for depressing the elevation of postprandial blood glucose through inhibiting α-glycosidase activity.

AIM OF THE STUDY

In this study, the hypoglycemic effect of PLF, CME or CME-PLF mixture (the mixture of CME and PLF at a ratio of 1:6.3) was further evaluated through in vivo glucose tolerance studies. And the effect of CME on pharmacokinetic profiles of main isoflavonoids from PLF in rat plasma was investigated to further underlie compatibility mechanism of the two herbs.

MATERIALS AND METHODS

Four groups of rats received an oral dose of starch solution alone or simultaneously with drugs by gavage feeding. The blood samples were collected to determine glucose concentrations by glucose oxidase method. In addition, another two groups of rats were orally administered with PLF or CME-PLF. The plasma samples were collected and assayed using an LC/MS/MS method for comparatively pharmacokinetic studies of five main isoflavonoids.

RESULTS

For starch loading, co-administration of CME-PLF resulted in more potent inhibition effects on glucose responses compared to those by CME or PLF in rat. The isoflavonoids from PLF were rapidly absorbed, presenting similarly low concentrations in plasma. When CME was added, the C_max and AUC of all the five isoflavonoids were increased. A phenomenon of double peaks was found for all analysts. The elimination rates of all the detected isoflavonoids were also slowed down with extension of t_1/2. CONCLUSIONS: CME has been found to increase the absorption and delay the elimination of main isoflavonoids from PLF, which might result in higher concentrations of circulating active compounds for anti diabetes.

Puerarin Suppresses Macrophage Activation via Antioxidant Mechanisms in a CaPO4-Induced Mouse Model of Aneurysm

Aneurysm is characterized by balloon-like expansion of the arterial wall and eventual rupture of the aorta. The pathogenesis of aneurysm is associated with the degradation of matrix proteins by matrix metalloproteinases (MMPs) produced by activated macrophages. Although aneurysm is associated with significant mortality and morbidity, surgical intervention is the only proven treatment strategy. Therefore, development of therapeutic agents for aneurysm is greatly anticipated. Here, we demonstrated the protective effects of the major isoflavone puerarin, which is found in kudzu roots and vines. Aneurysms were surgically induced in ten-wk-old male mice using CaPO₄. Subsequently, animals were intraperitoneally injected daily with puerarin at 2.5 mg/kg body weight or with vehicle alone for 2 wk. CaPO₄-induced aneurysm was significantly suppressed by puerarin administration. In subsequent macrophage activation assays using Tumor necrosis factor (TNFα) and CaPO₄ crystals in vitro, puerarin decreased Mmp9 mRNA expression and secreted protein levels. Moreover, induction of IκB, ERK, and p38 phosphorylation by TNFα and CaPO₄ in macrophages was suppressed by puerarin treatments. Finally, puerarin attenuated reactive oxygen species production, following induction by TNFα and CaPO₄. Taken together, the present data demonstrate that puerarin suppresses macrophage activation by inhibiting IκB, ERK, and p38 activity and reactive oxygen species production in a CaPO₄-induced mouse model of aneurysm.

Anti-Hyperglycemic Effect of a Kudzu (Pueraria lobata) Vine Extract in Ovariectomized Mice

Postmenopausal diabetes is exacerbated by estrogen deficiency. Ovariectomized (OVX) animal models can be used to develop strategies for preventing or treating postmenopausal symptoms. We previously found that a diet containing kudzu (Pueraria lobata) vine ethanol extract (PVEE) suppressed weight gain in OVX mice. Therefore, this study further elucidated how PVEE affected OVX mice. Ten-week-old OVX or sham-operated mice were fed diets containing either no PVEE (control) or 20 mg•kg^-1•d^-1 PVEE for 8 wk, 5 mg•kg^-1•d^-1 PVEE for 24 wk, or 20 mg•kg^-1•d^-1 puerarin (daidzein-8-C-glucoside), a major isoflavone present in PVEE, for 10 wk. The effects of puerarin on glucose tolerance were also tested in OVX mice. The experimental diets were not associated with any abnormalities in any mice tested in the present study. Weight gain and serum glucose levels were increased in OVX mice and these effects were significantly attenuated in OVX mice that consumed PVEE (5 or 20 mg•kg^-1•d^-1) or puerarin. Puerarin-treated OVX mice also showed reduced serum glucose levels following administration of 1,000 mg•kg^-1 glucose. These results suggested that puerarin contributed to PVEE-mediated improvements in glucose metabolism in OVX mice. Although further studies are needed to clarify the molecular mechanism underlying these observations, PVEE and puerarin could provide effective approaches to the amelioration of postmenopausal diabetes.

Molecular characterization of the C-glucosylation for puerarin biosynthesis in Pueraria lobata

C-glycosyltransferases (CGTs) are important enzymes that are responsible for the synthesis of the C-glycosides of flavonoids and isoflavonoids. Flavonoid CGTs have been molecularly characterized from several plant species; however, to date, no gene encoding an isoflavonoid CGT has been reported from any plant species. A significant example of an isoflavonoid C-glycoside is puerarin, a compound that contributes to the major medicinal effects of Pueraria lobata. Little is known about the C-glucosylation that occurs during puerarin biosynthesis. One possible route for puerarin synthesis is via the C-glucosylation of daidzein. This study describes the molecular cloning and functional characterization of a novel glucosyltransferase (PlUGT43) from P. lobata. Biochemical analyses revealed that PlUGT43 possesses an activity for the C-glucosylation of daidzein to puerarin; it shows activity with the isoflavones daidzein and genistein, but displays no activity towards other potential acceptors, including flavonoids. To validate the in vivo function of PlUGT43, the PlUGT43 gene was over-expressed in soybean hairy roots that naturally synthesize daidzein but that do not produce puerarin. The expression of PlUGT43 led to the production of puerarin in the transgenic soybean hairy roots, confirming a role for PlUGT43 in puerarin biosynthesis.

Deglycosylation of isoflavone C-glycosides by newly isolated human intestinal bacteria

BACKGROUND

Plant isoflavones are mostly present in the glycoside form. Isoflavone aglycones produced by intestinal microflora are reported to be more bioactive than the glycoside form. However, the deglycosylation of isoflavone C-glycosides is known to be rare, and is less studied.

RESULTS

Three new bacteria were isolated from human faecal samples, two of which hydrolysed the C-glycosidic bond of puerarin, daidzein-8-C-glucoside. They were identified as two Lactococcus species, herein designated as MRG-IFC-1 and MRG-IFC-3, and an Enterococcus species, herein designated MRG-IFC-2, based on their 16S rDNA sequences. From a reactivity study, it was found that Lactococcus sp. MRG-IFC-1 and Enterococcus sp. MRG-IFC-2 hydrolysed isoflavone C- and O-glycosides, as well as the flavone O-glycoside apigetrin, but could not hydrolyse the flavone C-glycosidic bond of vitexin. The other Lactococcus sp., MRG-IF-3, could not hydrolyse the C-glycosidic linkage of puerarin, while it showed a broad substrate spectrum of O-glycosidase activity similar to the other two bacteria. Puerarin was completely converted to daidzein within 100 min by Lactococcus sp. MRG-IFC-1 and Enterococcus sp. MRG-IFC-2, which is the fastest conversion among the reported human intestinal bacteria.

CONCLUSION

Two new puerarin-metabolising human intestinal bacteria were isolated and identified, and the deglycosylation activity for various flavonoid glycosides was investigated. The results could facilitate the study of C-glycosidase reaction mechanisms, as well as the pharmacokinetics of bioactive C-glycoside natural products.

De novo transcriptome sequencing in Pueraria lobata to identify putative genes involved in isoflavones biosynthesis

Using Illumina sequencing technology, we have generated the large-scale transcriptome sequencing data and indentified many putative genes involved in isoflavones biosynthesis in Pueraria lobata. Pueraria lobata, a member of the Leguminosae family, is a traditional Chinese herb which has been used since ancient times. P. lobata root has extensive clinical usages, because it contains a rich source of isoflavones, including daidzin and puerarin. However, the knowledge of isoflavone metabolism and the characterization of corresponding genes in such a pathway remain largely unknown. In this study, de novo transcriptome of P. lobata root and leaf was sequenced using the Solexa sequencing platform. Over 140 million high-quality reads were assembled into 163,625 unigenes, of which about 43.1% were aligned to the Nr protein database. Using the RPKM (reads per kilo bases per million reads) method, 3,148 unigenes were found to be upregulated, and 2,011 genes were downregulated in the leaf as compared to those in the root. Towards a further understanding of these differentially expressed genes, Gene ontology enrichment and metabolic pathway enrichment analyses were performed. Based on these results, 47 novel structural genes were identified in the biosynthesis of isoflavones. Also, 22 putative UDP glycosyltransferases and 45 O-methyltransferases unigenes were identified as the candidates most likely to be involved in the tailoring processes of isoflavonoid downstream pathway. Moreover, MYB transcription factors were analyzed, and 133 of them were found to have higher expression levels in the roots than in the leaves. In conclusion, the de novo transcriptome investigation of these unique transcripts provided an invaluable resource for the global discovery of functional genes related to isoflavones biosynthesis in P. lobata.

Effects of puerarin on lipid accumulation and metabolism in high-fat diet-fed mice

In order to investigate the mechanisms by which puerarin from kudzu root extract regulates lipid metabolism, fifty mice were randomly assigned to five groups: normal diet, high-fat diet (HFD), and HFD containing 0.2%, 0.4% or 0.8% puerarin for 12 weeks. Body weight, intraperitioneal adipose tissue (IPAT) weight, serum biochemical parameters, and hepatic and feces lipids were measured. Activity and mRNA and protein expressions of hepatic lipid metabolism-related enzymes were analyzed. Compared with HFD, 0.4% and 0.8% puerarin significantly decreased body and IPAT weight. There was a significant decrease in the serum and hepatic concentrations of total cholesterol, triglycerides and leptin in mice fed the 0.4% and 0.8% puerarin diets compared with HFD. Fatty acid synthase activity was suppressed in mice fed the 0.4% and 0.8% puerarin diets, while the activities of AMP-activated protein kinase (AMPK), carnitine acyltransferase (CAT) and hormone-sensitive lipase (HSL) were increased. mRNA expression of peroxisome proliferator-activated receptor γ 2 (PPARγ 2) was down-regulated in liver of mice fed the 0.8% diet compared with HFD, while mRNA expression of CAT and HSL was considerably up-regulated by 0.4% and 0.8% puerarin diets. The protein expression of PPARγ2 in liver was decreased and those of p-AMPK, HSL and p-HSL were increased in mice fed 0.4% and 0.8% puerarin diets. These results suggest that > 0.4% puerarin influenced the activity, mRNA and protein levels of hepatic lipid metabolism-related enzymes, decreasing serum and liver lipids, body weight gain and fat accumulation. Puerarin might be beneficial to prevent lifestyle-related diseases.

Natural Flavonoids as Potential Herbal Medication for the Treatment of Diabetes Mellitus and its Complications

Diabetes mellitus, together with its various complications, is becoming a serious threat to human health. Natural products are secondary metabolites widely distributed in plants, having a broad range of biological activities. The development of antidiabetic medication from natural products, especially those originating from plants with a traceable folk-usage history in treating diabetes, is receiving more attention. Many studies highlighted not only the benefits of natural flavonoids with hypoglycemic effects, but also their importance in the management of diabetic complications. This review describes selected natural flavonoids that have been validated for their hypoglycemic properties, together with their mechanisms of action. Also discussed are their activities in the treatment of diabetic complications demonstrated via laboratory diabetic animal models, in vitro and clinical trials using human subjects. Published papers from 2000 to date on flavonoids and diabetes were covered through accessing Web of Science and multiple databases for biomedical sciences. The major potential benefits of natural flavonoids discussed in this review clearly suggest that these substances are lead compounds with sufficient structural diversity of great importance in the antidiabetic drug developing process.

Anti-obese and anti-diabetic effects of a mixture of daidzin and glycitin on C57BL/6J mice fed with a high-fat diet

We investigated the effects of a mixture of daidzin and glycitin, which are the glycoside-form isoflavones of daidzein and glycitein, respectively, on body weight, lipid levels, diabetic markers, and metabolism in a high-fat diet (HF) fed C57BL/6J mice for 92 days. The mice were divided into basic diet group (CON), HF group, and HF companied with the isoflavone mixture group (HFISO). Results showed that mice in HFISO had a significantly lower body weight and adipose tissue compared to HF group. Blood glucose, serum HbA1c, and serum insulin also showed lower levels in HFISO group. In addition, higher hepatic GSH level and lower serum 8-hydroxy-2'-deoxyguanosine (8-OHdG) level were found in HFISO group mice. This suggests that the regulation of oxidative stress by daidzin and glycitin was closely related to the suppression of adipose tissue and the progression of diabetes.

Acute and Chronic Kudzu Improves Plasma Glucose Tolerance in Non-Diabetic CD-1 Mice

Previous studies demonstrate that kudzu root extract and its major isoflavone (puerarin) improve glucose metabolism in animal models of insulin resistance and type 2 diabetes; however, these beneficial effects have not been investigated in normal glycemic mice. The present study investigates the effect of acute and chronic kudzu root extract supplementation on glucose tolerance in normoglycemic CD-1 mice. Male, adult CD-1 mice were fed a phytoestrogen-free diet containing 0.2% or 0.0% kudzu root extract for 6 weeks. Thereafter, they were acutely administered kudzu root extract (75 mg/kg BW; oral) or vehicle followed by a glucose challenge (2 g/kg BW; oral). In control fed mice, the acute glucose challenge increased blood glucose ~300% after 30 minutes, and acute kudzu root extract administration significantly blunted this response by ~50%. In mice chronically fed a kudzu-supplemented diet, glucose tolerance was improved, and acute treatment caused no additional improvement. Irrespective of treatment, all mice were normoglycemic at the start of each glucose challenge. Administration of insulin resulted in a larger decrease in blood glucose in chronic kudzu-supplemented compared to control mice. Co-administration of phloridzin (a specific inhibitor of SGLT-mediated glucose uptake), improved glucose tolerance in acutely kudzu-treated mice but had no significant effect on glucose tolerance in chronically treated mice. These results indicate that both acute and chronic administration of kudzu root extract improves glucose tolerance in a normal glycemic mouse strain and that the effects of chronic kudzu feeding may be mediated, in part, by enhanced insulin sensitivity (chronic) and inhibition of sodium dependent glucose transport.

A diet formula of Puerariae radix, Lycium barbarum, Crataegus pinnatifida, and Polygonati rhizoma alleviates insulin resistance and hepatic steatosis in CD-1 mice and HepG2 cells

According to the principles of traditional Chinese medicine, medicinal and edible herbs exhibit holistic effects through their actions on multiple target organs.

Molecular cloning and functional characterization of two divergent 4-coumarate : coenzyme A ligases from Kudzu (Pueraria lobata)

As part of the efforts to understand isoflavonoid metabolism in Pueraria lobata at the molecular level, the cDNAs encoding two divergent 4-coumarate : coenzyme A ligases (4CLs, designated Pl4CL1 and Pl4CL2, respectively) were isolated from P. lobata roots. Sequence analysis revealed that Pl4CL1 had an N-terminal extension of twenty-one amino acid residues compared to Pl4CL2. Phylogenetic analysis showed that Pl4CL1 and Pl4CL2 fell into angiosperm Class II and Class I, respectively. Through in vitro biochemical assays, both Pl4CLs were found to have the capacity to utilize 4-coumarate and trans-cinnamate as substrates, while neither of them could convert sinapate. Pl4CL2 had a broader substrate specificity than Pl4CL1. The affinity of Pl4CL1 for 4-coumarate was 2.6-fold higher than that of Pl4CL2 (with the Km values of 3.5 µM and 9.1 µM, respectively). Combining the dataset including gene expression profiles, metabolites measurements, and biochemical properties, our results indicated that Pl4CL1, just as other angiosperm Class II 4CLs, might play a role in isoflavone biosynthesis in P. lobata, while Pl4CL2 belongs to angiosperm Class I, and may function as a housekeeping enzyme concerning lignification.

Clinical Research of Traditional Chinese Medical Intervention on Impaired Glucose Tolerance

To identify a safe and effective Impaired Glucose Tolerance (IGT) intervention program using Traditional Chinese Medicine (TCM) supported by Standard Health Care Advice (SHCA) for the evidence-based TCM intervention in IGT and evidence-based prevention of type 2 diabetes. A total of 510 IGT patients were randomly assigned into either control or TCM intervention group (255 patients for each group). The control group received standard health care according to SHCA. The intervention group also received TCM intervention in addition to standard health care. The study was conducted over a three-year follow-up. At the end of three years follow-up, accumulative incidence and average annual incidence rate of diabetes in the control group was 43.86% and 14.62% respectively. Accumulative incidence and average annual incidence rate of diabetes in the TCM intervention group was 22.17% and 7.39% respectively. Compared with the control treatment, TCM intervention can reduce the relative risk of IGT patients progressing to type 2 diabetes by 49.45% and absolute risk by 21.69%. In the TCM intervention group, oral glucose tolerance test (OGTT), 2 h glucose, glycated hemoglobin, insulin resistance and body mass index were all significantly improved when compared to the control group. No significant side effect was observed during the follow-up in the TCM group. The SHCA-supported TCM intervention can reduce the conversion rate of IGT to diabetes and improve insulin resistance; therefore, it is a safe and effective IGT intervention strategy.

The Chinese Pueraria root extract (Pueraria lobata) ameliorates impaired glucose and lipid metabolism in obese mice

The incidence of type 2 diabetes and metabolic disease is rapidly increasing, but effective therapies for their prevention and treatment have been poorly tolerated or minimally effective. In this study, chronic administration of kudzu root extract (8 months, 0.2%, w/w, in diet) decreased baseline fasting plasma glucose (183±14 vs. 148±11 mg/dl) and improved glucose and insulin tolerance in C57BL/6J ob/ob mice (1.67±0.17 ng/ml [kudzu treated] vs. 2.35±0.63 ng/ml [control]), but such treatment did not alter these parameters in lean control mice. Among the mice on the kudzu supplementation, plasma levels of isoflavone metabolites were significantly higher in ob/ob versus lean control mice, and unmetabolized puerarin (11.50±5.63 ng/g) was found in adipose tissue only in the treated mice. Together, these data demonstrate that a puerarin containing kudzu diet improves glucose and insulin responsiveness in ob/ob mice, suggesting that puerarin may be a beneficial adjuvant for treating metabolic disease.

KIOM-79 protects AGE-induced retinal pericyte apoptosis via inhibition of NF-kappaB activation in vitro and in vivo

KIOM-79 is an herbal mixture of parched Puerariae radix, gingered Magnoliae cortex, Glycyrrhizae radix and Euphorbiae radix. In the present study, we determined the efficacy and possible mechanism of KIOM-79 on the advanced glycation end product (AGE)-modified bovine serum albumin (BSA)-induced apoptosis of cultured bovine retinal pericytes and rat retinal pericytes in Zucker diabetic fatty (ZDF) rats. Seven-week-old male ZDF rats were treated with KIOM-79 (50 mg/kg body weight) once a day orally for 13 weeks. KIOM-79 significantly inhibited pericyte apoptosis which were induced by the AGE-BSA treatment. The KIOM-79 treatment markedly suppressed the activation of nuclear factor-kappaB (NF-κB) through the inhibition of inhibitory κB kinase complex. In addition, the oral administration of KIOM-79 inhibited the changes in retinal vasculature (vascular hyperpermeability, acellular capillary). KIOM-79 strongly inhibited pericyte apoptosis, NF-κB activation and the expression of pro-apoptotic Bax and tumor necrosis factor-α. Our results suggest that KIOM-79 may exert inhibitory effects on AGE-induced pericyte apoptosis by blocking NF-κB activation, thereby ameliorating retinal microvascular dysfunction.

Influence of the traditional Brazilian drink Ilex paraguariensis tea on glucose homeostasis

In this study we examined the acute in vivo effect and short- and long-term in vitro effects of samples from native and commercial Ilex paraguariensis on glucose homeostasis. Also, the potential effect of I. paraguariensis on serum insulin secretion was investigated. The chemical identification and quantification of methyl xanthines and polyphenols in CH₂Cl₂, EtOAc and n-BuOH fractions of native I. paraguariensis as well as infusions of green and roasted I. paraguariensis from a commercial source was verified by high-performance liquid chromatography. The results for the serum glucose-lowering indicated that both fractions and both infusions were able to improve significantly the oral glucose tolerance curve. Additionally, both the EtOAc and n-BuOH fractions induced-insulin secretion, but EtOAc induced an early (at 15 min) and late (at 60 min) biphasic peak of insulin secretion similar to glipizide stimulatory effect. Both fractions increased liver glycogen content compared with fasted normal rats. Also, EtOAc and n-BuOH fractions inhibited in vitro disaccharidases activities after an acute treatment. The maximum inhibitory effect of the EtOAc and n-BuOH fractions on maltase activity (at 5 min) was around 35%. The evident reduction of protein glycation by glucose or fructose with EtOAc and n-BuOH fractions increased from 7 to 28 days of in vitro incubation. Inhibition of bovine serum albumin glycation by glucose and fructose, by around 50% and 90%, respectively, was observed. Additionally, the green and roasted mate infusions reduced the formation of AGEs in a characteristic long-term effect. In conclusion, this study shows that I. paraguariensis has an anti-hyperglycemic potential role able to improve the diabetic status and is probably a source of multiple hypoglycemic compounds.

Glyceollins, soy isoflavone phytoalexins, improve oral glucose disposal by stimulating glucose uptake

Soy glyceollins, induced during stress, have been shown to inhibit cancer cell growth in vitro and in vivo. In the present study, we used prediabetic rats to examine the glyceollins effect on blood glucose. During an oral glucose tolerance test (OGTT), the blood glucose excursion was significantly decreased in the rats treated with oral administration of either 30 or 90 mg/kg glyceollins. Plasma analysis demonstrated that glyceollins are absorbed after oral administration, and duration of exposure extends from 20 min to at least 4 h postadministration. Exposure of 3T3-L1 adipocytes to glyceollins significantly increased both insulin-stimulated and basal glucose uptake. Basal glucose uptake was increased 1.5-fold by exposure to 5 μM glyceollin in a dose-response manner. Coincubation with insulin significantly stimulated maximal glucose uptake above basal uptake levels and tended to increase glucose uptake beyond the levels of either stimulus alone. On a molecular level, polymerase chain reaction showed significantly increased levels of glucose transporter GLUT4 mRNA in 3T3-L1 adipocytes, especially when the cells were exposed to 5 μM glyceollins for 3 h in vitro. It correlated with elevated protein levels of GLUT4 detected in the 5 μM glyceollin-treated cells. Thus, the simulative effect of the glyceollins on adipocyte glucose uptake was attributed to up-regulation of glucose transporters. These findings indicate potential benefits of the glyceollins as an intervention in prediabetic conditions as well as a treatment for type 1 and type 2 diabetes by increasing both the insulin-mediated and the basal, insulin-independent, glucose uptake by adipocytes.

Puerarin activates endothelial nitric oxide synthase through estrogen receptor-dependent PI3-kinase and calcium-dependent AMP-activated protein kinase

The cardioprotective properties of puerarin, a natural product, have been attributed to the endothelial nitric oxide synthase (eNOS)-mediated production of nitric oxide (NO) in EA.hy926 endothelial cells. However, the mechanism by which puerarin activates eNOS remains unclear. In this study, we sought to identify the intracellular pathways underlying eNOS activation by puerarin. Puerarin induced the activating phosphorylation of eNOS on Ser1177 and the production of NO in EA.hy926 cells. Puerarin-induced eNOS phosphorylation required estrogen receptor (ER)-mediated phosphatidylinositol 3-kinase (PI3K)/Akt signaling and was reversed by AMP-activated protein kinase (AMPK) and calcium/calmodulin-dependent kinase II (CaMKII) inhibition. Importantly, puerarin inhibited the adhesion of tumor necrosis factor (TNF)-α-stimulated monocytes to endothelial cells and suppressed the TNF-α induced expression of intercellular cell adhesion molecule-1. Puerarin also inhibited the TNF-α-induced nuclear factor-κB activation, which was attenuated by pretreatment with N(G)-nitro-L-arginine methyl ester, a NOS inhibitor. These results indicate that puerarin stimulates eNOS phosphorylation and NO production via activation of an estrogen receptor-mediated PI3K/Akt- and CaMKII/AMPK-dependent pathway. Puerarin may be useful for the treatment or prevention of endothelial dysfunction associated with diabetes and cardiovascular disease.

Kudzu root: traditional uses and potential medicinal benefits in diabetes and cardiovascular diseases

Kudzu root (Gegen in Chinese) is the dried root of Pueraria lobata (Willd.) Ohwi, a semi-woody, perennial and leguminous vine native to South East Asia. It is often used interchangeably in traditional Chinese medicine with thomson kudzu root (Fengen in Chinese), the dried root of P. thomsonii, although the Chinese Pharmacopoeia has separated them into two monographs since the 2005 edition. For more than 2000 years, kudzu root has been used as a herbal medicine for the treatment of fever, acute dysentery, diarrhoea, diabetes and cardiovascular diseases. Both English and Chinese literatures on the traditional applications, phytochemistry, pharmacological activities, toxicology, quality control and potential interactions with conventional drugs of both species have been included in the present review. Over seventy phytochemicals have been identified in kudzu root, with isoflavonoids and triterpenoids as the major constituents. Isoflavonoids, in particular puerarin, have been used in most of the pharmacological studies. Animal and cellular studies have provided support for the traditional uses of kudzu root on cardiovascular, cerebrovascular and endocrine systems, including diabetes and its complications. Further studies to define the active phytochemical compositions, quality standards and clinical efficacy are warranted. Strong interdisciplinary collaboration to bridge the gap between traditional medicine and modern biomedical medicine is therefore needed for the development of kudzu root as an effective medicine for the management of diabetes and cardiovascular diseases.

A genomic approach to isoflavone biosynthesis in kudzu (Pueraria lobata)

Roots of kudzu (Pueraria lobata) are a rich source of isoflavone O- and C-glycosides. Although O-glycosylation of (iso)flavonoids has been well characterized at the molecular level, no plant isoflavonoid C-glycosyltransferase genes have yet been isolated. To address the biosynthesis of kudzu isoflavonoids, we generated 6,365 high-quality expressed sequence tags (ESTs) from a subtraction cDNA library constructed using RNA from roots that differentially accumulate puerarin. The ESTs were clustered into 722 TCs and 3,913 singletons, from which 15 family I glycosyltransferases (UGTs) were identified. Hierarchical clustering analysis of the expression patterns of these UGTs with isoflavone synthase (IFS) in a range of tissues identified UGTs with potential functions in isoflavone glycosylation. The open reading frames of these UGTs were expressed in E. coli for functional analysis, and one was shown to preferentially glycosylate isoflavones at the 7-O-position. In addition, ESTs corresponding to chalcone synthase, chalcone reductase, chalcone isomerase (CHI) and 2-hydroxyisoflavanone dehydratase were identified. Recombinant CHI proteins had high activities with both 6'-deoxy- and 6'-hydroxy chalcones, typical of Type II CHIs. Establishment of this EST database and identification of genes associated with kudzu isoflavone biosynthesis and glycosylation provide a new resource for metabolic engineering of bioactive kudzu isoflavones.

Inhibition of intestinal glucose absorption by anti-diabetic medicinal plants derived from the James Bay Cree traditional pharmacopeia

BACKGROUND

Type II diabetes and obesity are major health problems worldwide and aboriginal peoples are particularly at risk. To address this problem in Canadian native populations who find modern pharmaceuticals culturally inappropriate, our team is testing the traditional pharmacopeia of the James Bay Cree for anti-diabetic and anti-obesity activities. More specifically, the aim of the present study was to define the effects of traditional plants on intestinal glucose absorption, an under-appreciated anti-hyperglycaemic and anti-obesity activity.

METHODS

Crude ethanol extracts of 17 Boreal forest medicinal plants were tested in vitro using the Caco-2 human enterocytic cell line and in vivo using an oral glucose tolerance test.

RESULTS

Thirteen of seventeen extracts were observed to significantly inhibit uptake when administered simultaneously with (3)H-deoxyglucose. Inhibition was dose-dependent and, in a few cases, even surpassed that induced by a combination of the positive controls. To validate these effects in vivo, four plant extracts were administered by intragastric gavage at 250 mg/kg to normal rats simultaneously with a 3g/kg bolus of glucose. This resulted in a decrease in peak glycaemia by approximately 40% for two of them. Similarly, only 2 extracts reduced glucose transport after long term incubation and this could be related to reductions in the expression of SGLT-1 or GLUT-2 proteins.

CONCLUSIONS

These findings indicate that competitive inhibition of intestinal glucose uptake can be achieved by crude extracts of medicinal plants. Such extracts could be taken with meals to control postprandial glycaemia and reduce caloric intake in high risk populations that are positively inclined towards traditional medicine.

Puerarin enhances adipocyte differentiation, adiponectin expression, and antioxidant response in 3T3-L1 cells

Puerarin, a major isoflavone glycoside from Kudzu root (Pueraria lobata), has been reported to exert antihyperglycemic and antioxidant effects and thus have pharmacological actions in the treatment of diabetes and cardiovascular diseases. We investigated the effects of puerarin on the changes of key gene expression associated with adipocyte differentiation and insulin sensitivity and link to cellular antioxidant response pathways. Puerarin treatment significantly enhanced differentiation of 3T3-L1 preadipocytes accompanying increased lipid accumulation and glucose-6-phosphate dehydrogenase (G6PDH) activity. At a molecular level, puerarin upregulated mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ) and its target genes, an adipocyte-specific fatty acid binding protein (aP2) and GLUT4. Puerarin also caused a significant increase in mRNA level of adiponectin, an important insulin-sensitizing adipocytokine that is downregulated in insulin-resistant and diabetic states. In addition, treatment with puerarin was found to upregulate mRNA levels of G6PDH, glutathione reductase, and catalase, all of which are important for endogenous antioxidant responses. These data suggest that the hypoglycemic effects of puerarin can be attributed to the upregulation of PPARγ and its downstream target genes, GLUT4 and adiponectin expression, leading to increased glucose utilization. Puerarin may also be effective in preventing the rise of oxidative stress during adipocyte differentiation by increasing endogenous antioxidant responses.

Puerarin improves insulin resistance and modulates adipokine expression in rats fed a high-fat diet

The link between obesity and insulin resistance largely accounts for the pathogenesis of metabolic syndrome and diabetes mellitus, in which adipokine expression plays a key role. Puerarin, a major active isoflavone extracted from the traditional Chinese medicine Radix Puerariae, has been studied for its comprehensive biological actions. However, its effect on high-fat diet (HFD)-induced insulin resistance and adipokine expression in rat has not been well investigated. In the present study, male Sprague-Dawley rats were fed on a normal control diet (NCD) or HFD for 6 weeks, followed by administration of puerarin (100 and 200 mg/kg) for up to 8 weeks. Compared to NCD, HFD feeding for 6 weeks led to increased body weight gain and impaired glucose/insulin tolerance manifested by oral glucose/intraperitoneal insulin tolerance tests in rats. These exacerbations prolonged through HFD feeding, but were effectively reversed by puerarin administration. Enzyme-linked immunosorbent assay demonstrated that, serum levels of leptin and resistin, but not that of adiponectin, were markedly augmented by HFD and retarded by puerarin treatment. Real-time reverse transcription polymerase chain reaction results showed that, in agreement with the circulating levels, mRNA expression of leptin and resistin in epididymal white adipose tissue was modified by HFD and improved by puerarin in the same pattern. Collectively, we revealed that puerarin could improve body weight gain, glucose/insulin intolerance and adipokine expression in HFD-induced insulin resistant rats, indicating its potential value for treatment of metabolic syndrome.

KIOM-79 Prevents Lens Epithelial Cell Apoptosis and Lens Opacification in Zucker Diabetic Fatty Rats

Damage of lens epithelial cells (LECs) has been implicated in cataract formation. The aim of this study was to investigate the protective effect of KIOM-79, a combination of four plant extracts, on LECs. We examined the levels of advanced glycation end products (AGEs), nuclear factor-kappaB (NF-κB) activation and inducible nitric oxide synthase (iNOS) expression in LECs during cataract development using the Zucker diabetic fatty (ZDF) rat, an animal model of type 2 diabetes. KIOM-79 was orally administered by gavage to ZDF rats once a day for 13 weeks. Apoptosis was detected by TUNEL assay, and NF-κB activation and iNOS expression were studied by southwestern histochemistry and immunohistochemistry, respectively. In diabetic cataractous lenses, TUNEL-positive LECs were markedly increased 20-fold, and AGEs were highly accumulated (2.7-fold) in LECs. In addition, both NF-κB activation, and iNOS expression were significantly enhanced 3- to 5-fold, respectively, compared to levels found in normal ZL rats. However, the administration of KIOM-79 delayed the development of diabetic cataracts and prevented LEC apoptosis (70%) through the inhibition of AGEs, NF-κB-activation and iNOS expression. These observations suggest that KIOM-79 is useful in inhibiting diabetic cataractogenesis and acts through an antiapoptotic mechanism to protect LECs from injury.