Aqueous extract of Abutilon indicum Sweet inhibits glucose absorption and stimulates insulin secretion in rodents

Toxicological profiling of methanolic seed extract of Abutilon indicum (L.) Sweet: in-vitro and in-vivo analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Abutilon indicum, a shrub of the Malvaceae family, is found abundantly in tropical countries like India. A. indicum is widely used for its high medicinal properties. Traditionally, A. indicum seed powder is consumed to treat piles, constipation, chronic cystitis, gonorrhea, gleet, and pregnancy-related problems. Despite having numerous medicinal properties and widespread traditional use of A. indicum seeds, scientific validation, and toxicity studies have yet to be documented.

AIMS OF THE STUDY

The primary objective of this study is to conduct a comprehensive study on phytochemical profiling, in-vitro cytotoxicity, mutagenicity, and in-vivo acute and sub-acute toxicity, and genotoxicity on animal models of methanolic extract of A. indicum seed (MAS).

MATERIALS AND METHODS

The qualitative analysis of MAS was explored through FTIR and HR LC-MS. For in-vitro cytotoxicity, the HEK-293 cell line was used, and the TA100 (Staphylococcus typhimurium) bacterial strain was used for the Ames mutagenicity test. A single oral dose of 250, 500, 1000, or 2000 mg/kg body weight of MAS was given to each male and female rat for acute toxicity study and observed for 14 days for any toxicity signs. In the sub-acute toxicity study, 250, 500, or 1000 mg/kg body weight of MAS was administered orally to each rat for 28 days. The experimental animals were weighed weekly, and general behavior was monitored regularly. After 28 days of the experiment, the rats were sacrificed, and different serum biochemical, hematological, and histological analyses were performed. The blood samples of different doses of MAS were used for genotoxicity study through comet assay.

RESULTS

FTIR analysis found different functional groups, which indicated the presence of phenolics, flavonoids, and alkaloids. HR LC-MS analysis depicts several components with different biological functions. The cell cytotoxicity and Ames mutagenicity results showed minimal toxicity and mutagenicity up to a certain dose. The acute toxicity study conducted in Wistar albino rats demonstrated zero mortality among the animals, and the LD50 value for seed extract was determined to be 2000 mg/kg body weight. Sub-acute toxicity assessments indicated that the administration of seed extract resulted in no adverse effects at dosages of 250 and 500 mg/kg body weight. However, at higher doses, specifically 1000 mg/kg body weight, the liver of the experimental rats exhibited some toxic effects. In the genotoxicity study, minimal DNA damage was found in 250 and 500 mg/kg doses, respectively, but slightly greater DNA damage was found in 1000 mg/kg doses in both male and female rats.

CONCLUSIONS

The consumption of A. indicum seed powder is deemed safe; however, doses exceeding 500 mg/kg body weight may raise concerns regarding use. These findings pave the path for the creation of innovative medicines with improved efficacy and safety profiles.

Efficacy and safety of dorzagliatin for type 2 diabetes mellitus: A meta-analysis and trial sequential analysis

Objective

To evaluate the efficacy and safety of dorzagliatin in the treatment of type 2 diabetes mellitus (T2DM) by using meta-analysis and trial sequential analysis (TSA).

Method

Search for clinical trials of dorzagliatin for T2DM in eight databases, with a time limit of build to July 2022. The included studies that met the requirements were carried out for meta-analysis and TSA.

Results

In terms of efficacy endpoints, meta-analysis showed that dorzagliatin decreased glycated hemoglobin A1c(HbA1c) [mean difference (MD) -0.65%, 95% confidence interval (CI) -0.76 ~ -0.54, P < 0.00001], fasting plasma glucose (FPG) (MD -9.22 mg/dL, 95% CI -9.99 ~ -8.44, P < 0.00001), 2 h postprandial glucose (2h-PPG) (MD -48.70 mg/dL, 95% CI -55.45 ~ -41.96, P < 0.00001), homeostasis model assessment 2 of insulin resistance (HOMA2-IR) (MD -0.07, 95% CI -0.14 ~ -0.01, P = 0.03) and increased homeostasis model assessment 2 of ß-cells function (HOMA2-β) (MD 2.69, 95% CI 1.06 ~ 4.31, P = 0.001) compared with placebo. And TSA revealed that the benefits observed for the current information set were conclusive, except for HOMA2-IR. In comparison with placebo, dorzagliatin increased triglyceride(TG) (MD 0.43 mmol/L, 95% CI 0.30 ~ 0.56, P < 0.00001), total cholesterol (TC) (MD 0.13 mmol/L, 95% CI 0.05 ~ 0.21, P = 0.001), body weight (MD 0.38 kg, 95% CI 0.12-0.63, P = 0.004) and body mass index (BMI) (MD 0.14 kg/m², 95% CI 0.05-0.24, P = 0.003), while low density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were comparable. And TSA demonstrated that TG, TC, body weight, and BMI were conclusive. In terms of safety endpoints, dorzagliatin increased total adverse events (AEs) [risk ratio (RR) 1.56, 95% CI 1.06 ~ 2.30, P = 0.03], while serious AEs, hyperlipidemia, and hypoglycaemia were all comparable. And TSA indicated that the results need to be confirmed by additional studies. Harbord regression showed no publication bias.

Conclusion

Dorzagliatin was effective in lowering glycemia, reducing insulin resistance and improving islet ß-cells function without affecting blood pressure, LDL-C, and HDL-C. Although dorzagliatin caused a mild increase in TG and TC, it did not increase the incidence of hyperlipidemia, and the small increases in body weight and BMI were not clinically significant enough. In terms of safety, the total AEs caused by dorzagliatin may be a cumulative effect of single AEs, with no drug-related adverse event being reported at a higher incidence than placebo alone. Dorzagliatin's serious AEs, hyperlipidemia, and hypoglycemia are comparable to that of placebo, and dorzagliatin has a good safety profile.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=371802 identifier: CRD42022371802.

Predicting potential medicinal plants with phylogenetic topology: Inspiration from the research of traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are a dominant source of pharmacological drugs for the treatment and cure of different disorders and diseases. However, selecting the most biologically active plant species for further screening is still challenging. Phylogeny has strong explanatory powers and provides predictive perspectives that are not available in traditional plant classifications. China, which is endowed with a diverse set of therapeutic cures from Mother Nature, represents an ideal environment for the phylogenetic analysis of potential medicinal plants.

MATERIALS AND METHODS

Herein, we prepared a database of 7,451 traditional Chinese medicinal (TCM) plants, including species with therapeutic effects grouped in 14 categories. To limit our exploration of novel therapeutic species, we plotted the medicinal effects on the phylogenetic tree of almost 30,000 species of China to find hot nodes of therapeutic effects. We used the net relatedness index (NRI) and the nearest taxon index (NTI) to identify clustering and overdispersion of the phylogenetic distribution of TCM plants.

RESULTS

The NRI and NTI analyses highlighted 3,392 hot node species with single therapeutic effects within 507 genera and 89 families on the phylogenetic tree and about 70% of the 14 medicinal categories clusters identified. The general pattern of the hot nodes on the phylogenetic tree indicates that basal angiosperms and basal eudicots radiated for therapeutic effects.

CONCLUSIONS

Our study may provide a more targeted way to discover phylogeny-guided drugs in the early screening stage, which may lead to a higher discovery efficiency of new drugs with meaningful biological activities. Phylogenetic studies of plants that are richer in bioactive compounds can set the ground for the identification and discovery of alternative drugs.

Medicinal plants utilized in Thai Traditional Medicine for diabetes treatment: Ethnobotanical surveys, scientific evidence and phytochemicals

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus remains the most lethal metabolic disease of contemporaneous times and despite the therapeutic arsenal currently available, research on new antidiabetic agents remains a priority. In recent years, the revitalization of Thai Traditional Medicine (TTM) became a clear priority for the Thai government, and many efforts have been undertaken to accelerate research on herbal medicines and their use in medical services in various hospitals. Additionally, and particularly in rural areas, treatment of diabetes and associated symptomatology frequently relies on herbal preparations recommended by practitioners of TTM. In the current work, medicinal plants used in Thailand for treating diabetes, as well as their hypoglycaemic pharmacological evidences and potential therapeutic use for diabetes-related complications were reviewed.

MATERIALS AND METHODS

Ethnopharmacological information on the plant materials used in TTM for diabetes treatment was collected through literature search in a range of scientific databases using the search terms: diabetes, folk medicine, Thailand medicinal plants, traditional medicine. Information regarding scientific evidence on the antidiabetic effects of surveyed species was obtained considering not only the most common taxonomic designation, but also taxonomic synonyms, and including the keywords 'diabetes' and 'hypoglycaemic effect'.

RESULTS

A total of 183 species known to be used for diabetes management in TTM were reviewed, with 30% of them still lacking experimental evidences to support claims regarding the mechanisms and phytochemicals underlying their antidiabetic properties. Moreover, a total of 46 bioactives displaying effective antidiabetic effects have been isolated from 24 species, their underlying mechanism(s) of action being fully or partially disclosed.

CONCLUSIONS

We deliver the most extensive survey dealing with the ethnomedicinal knowledge of Thai medicinal plants utilized on diabetes management. We are certain that the current review will spark further research on Thai plants for the development of new standardized phytomedicines through drug discovery programmes.

Protective effect of leaf extract of Abutilon indicum on DNA damage and peripheral blood lymphocytes in combating the oxidative stress

The current research explores in vitro antioxidant characteristics, radiation-induced DNA damage protection and quenching effects of the oxidative stress by the ethanolic leaf extract of Abutilon indicum (EEAI) on human peripheral blood lymphocytes (PBLs). PBLs were incubated with various concentrations of EEAI accompanied by pre- and post-treatment with hydrogen peroxide. Cell viability was investigated by MTT assay. In addition, quenching of free radicals were measured in vitro using DPPH, superoxide anion, hydrogen peroxide, reducing power and nitric oxide radical scavenging assays. These activities were compared with ascorbic acid as standard antioxidants. Furthermore, inhibition of UV radiation-induced strand break formation in plasmid pBR322 DNA and anti-Fenton reactions in calf thymus DNA was evaluated. Cytotoxic effects of hydrogen peroxide on PBLs were significantly reduced with EEAI pre-treatment compared to post-treatment in a dose-dependent manner comparable with similar cytoprotective effects of ascorbic acid (p > 0.05). EEAI has shown strong antioxidant effects in the scavenging of DPPH, superoxide anion, hydrogen peroxide, and nitric oxide. EEAI also has a strong protective effect of UV-induced plasmid pBR322 DNA cleavage and Fenton-induced DNA damage. Overall, the results revealed that Abutilon indicum has a cytoprotective, potent antioxidant and DNA protective effect that provide pharmacological credence to justify its overall biological activity. Furthermore, future studies to identifying bioactive molecules and its molecular mechanisms responsible for promising therapeutic applications in the rescue of disease-induced cellular oxidative damage.

A treatment with a boiled aqueous extract of Hancornia speciosa Gomes leaves improves the metabolic status of streptozotocin-induced diabetic rats

Abstract

Background

Hancornia speciosa is usually used in Brazilian folk medicine to treat diabetes. The hypothesis of the present study is that this medicinal plant exerts beneficial effects on hyperglycemia, preventing diabetic complications. Therefore, the aim of this study was to evaluate the treatment effect of the aqueous extract of H. speciosa leaves on metabolic parameters of diabetic rats.

Methods

The H. speciosa extract (400 mg/Kg) was administered to both nondiabetic and severely diabetic female Wistar rats by gavage. The Oral Glucose Tolerance Test was performed and the area under the curve (AUC) was estimated on day 17 of pregnancy. After 21 days of treatment, the animals were anesthetized and killed to obtain organ weights. Blood samples were collected for an analysis of serum biochemical parameters.

Results

After treatment with the H. speciosa extract, the parameters of nondiabetic rats remained unchanged. In treated diabetic rats, glycemia, AUC, dyslipidemia parameters, and relative organ weights were decreased compared with nontreated diabetic rats. Severely diabetic rats showed decompensated hyperglycemia, polydipsia, hyperphagia and dyslipidemia. However, the aqueous extract of H. speciosa leaves decreased diabetes complications (indicating a lack of toxicity), reduced blood glucose levels, and exerced lipid-lowering effects.

Conclusion

Based on or findings, the H. speciosa leaf extract may be a safe and promising candidate treatment for diabetes and other diseases.

Ethnomedicinal, Phytochemical and Ethnopharmacological Aspects of Four Medicinal Plants of Malvaceae Used in Indian Traditional Medicines: A Review

The ethnomedicinal values of plants form the basis of the herbal drug industry. India has contributed its knowledge of traditional system medicines (Ayurveda and Siddha) to develop herbal medicines with negligible side effects. The World Health Organization has also recognized the benefits of drugs developed from natural products. Abutilon indicum, Hibiscus sabdariffa, Sida acuta and Sida rhombifolia are ethnomedicinal plants of Malvaceae, commonly used in Indian traditional system of medicines. Traditionally these plants were used in the form of extracts/powder/paste by tribal populations of India for treating common ailments like cough and cold, fever, stomach, kidney and liver disorders, pains, inflammations, wounds, etc. The present review is an overview of phytochemistry and ethnopharmacological studies that support many of the traditional ethnomedicinal uses of these plants. Many phytoconstituents have been isolated from the four ethnomedicinal plants and some of them have shown pharmacological activities that have been demonstrated by in vivo and/or in vitro experiments. Ethnomedicinal uses, supported by scientific evidences is essential for ensuring safe and effective utilization of herbal medicines.

Hypoglycaemic activity of Mathurameha, a Thai traditional herbal formula aqueous extract, and its effect on biochemical profiles of streptozotocin-nicotinamide-induced diabetic rats

BACKGROUND

The Thai traditional herbal formula-Mathurameha, consisting of 26 medicinal plants, has been used as an alternative and complementary medicine for diabetes treatment in Wangnamyen Hospital, Thailand. To provide scientific evidences on the efficacy and safety of this herbal formula, in vivo hypoglycaemic activity, effect on serum biochemical profiles and acute toxicity were investigated.

METHODS

Experimental type 2 diabetes was induced in male Sprague-Dawley rats by intraperitoneal injection of nicotinamide 15 min prior to intravenous injection of streptozotocin. The most effective extract from the oral glucose tolerant test (OGTT) was administered daily via the oral route to diabetic rats for 2 weeks. Two-hour postprandial plasma glucose (2h-PPG) levels were measured on days 0, 7, and 14. Biochemical data were measured at the end of daily oral administration experiment.

RESULTS

Aqueous extract of the herbal formula was the most potent extract for improving glucose tolerance of streptozotocin-nicotinamide-induced diabetic rats after single oral administration. After 2 weeks of daily oral administration, the aqueous extract showed a dose-dependent glucose lowering effect. At doses of 12.5, 25, and 50 mg/kg, the 2h-PPG level of diabetic rats decreased by 3.32%, 15.78%, and 17.94%, respectively. Most of the biochemical profiles of diabetic rats were improved, including the total cholesterol (TC), alkaline phosphatase (ALP), total protein, albumin, globulin, creatinine, and uric acid levels. The significantly increased triglyceride (TG) level observed in treated diabetic rats indicated a lack of a beneficial effect of the extract on lipid homeostasis. Nevertheless, there were no signs or symptoms of acute toxicity observed after oral administration of aqueous extract (5 g/kg) to both male and female rats.

CONCLUSIONS

The results revealed that the herbal formula aqueous extract has hypoglycaemic activity, beneficial effects on biochemical profiles and a lack of acute toxicity. This study confirms the efficacy and safety of the Mathurameha herbal formula used for treating type 2 diabetes mellitus.

Cucurbitacin E reduces obesity and related metabolic dysfunction in mice by targeting JAK-STAT5 signaling pathway

Several members of cucurbitaceae family have been reported to regulate growth of cancer by interfering with STAT3 signaling. In the present study, we investigated the unique role and molecular mechanism of cucurbitacins (Cucs) in reducing symptoms of metabolic syndrome in mice. Cucurbitacin E (CuE) was found to reduce adipogenesis in murine adipocytes. CuE treatment diminished hypertrophy of adipocytes, visceral obesity and lipogenesis gene expression in diet induced mice model of metabolic syndrome (MetS). CuE also ameliorated adipose tissue dysfunction by reducing hyperleptinemia and TNF-alpha levels and enhancing hypoadiponectinemia. Results show that CuE mediated these effects by attenuating Jenus kinase- Signal transducer and activator of transcription 5 (JAK- STAT5) signaling in visceral fat tissue. As a result, CuE treatment also reduced PPAR gamma expression. Glucose uptake enhanced in adipocytes after stimulation with CuE and insulin resistance diminished in mice treated with CuE, as reflected by reduced glucose intolerance and glucose stimulated insulin secretion. CuE restored insulin sensitivity indirectly by inhibiting JAK phosphorylation and improving AMPK activity. Consequently, insulin signaling was up-regulated in mice muscle. As CuE positively regulated adipose tissue function and suppressed visceral obesity, dyslipedemia, hyperglycemia and insulin resistance in mice model of MetS, we suggest that CuE can be used as novel approach to treat metabolic diseases.

Plants used to treat diabetes in Sri Lankan Siddha Medicine - An ethnopharmacological review of historical and modern sources

INTRODUCTION AND BACKGROUND

In recent decades diabetes mellitus has become a considerable health problem in countries like Sri Lanka and results in an increasing economic burden hampering the social and economic development of these countries. About 60% to 70% of the rural population in Sri Lanka rely on indigenous medicinal systems as their main source for primary health care. Siddha (Tamil) Medicine is one of the four Sri Lankan traditional medicinal systems and it is practised mostly in the eastern and northern provinces of Sri Lanka where the majority of Tamils reside.

AIM

The foundation of this study is a documentation of plant species recorded in historical and modern Sri Lankan Siddha Medical documents used to treat diabetes. Based on the systematic documentation and analysis of Siddha concepts about diabetes and its signs and preparations used to treat diabetes in Sri Lankan Siddha Medicine, the plant species included in these preparations (excluding globally or very widely used, very well studied species) were evaluated in terms of the current state-of-the-art about these species' pharmacology and effectiveness in order to lay a foundation for their further development.

METHOD

Historic and modern Sri Lankan university texts books in Tamil were used as sources for information on diabetes Siddha concepts and antidiabetic Sri Lankan Siddha Medicine preparations. Information on the known antidiabetic effects of extracts and compounds obtained from these species were used in order to assess the current state of the art of these species.

RESULTS AND DISCUSSION

Information of ingredients, preparation methods, amount of ingredients used, and dosages of 60 antidiabetic Sri Lankan Siddha Medicine preparations were obtained. Animal parts including marine organisms, inorganic substances, and plants are the three types of ingredients used. Overall 171 plant species in 73 families were documented. Senna auriculata (L.) Roxb. (Fabaceae) was identified as the most frequently cited species. Globally distributed and very well studied plants were excluded in the pharmacological and clinical literature review which includes 123 plant species. The majority (48%) of the plant species reviewed were studied up to in vivo level as the current maximum level of scientific evidence available. Followed by 41% of species have not been studied for antidiabetic activities or did not show antidiabetic activity. Moreover, 6% and 5% were studied up to in vitro and in clinical levels, respectively. The majority of the species were studied only in the models that represent type 1 diabetes.

CONCLUSION

This is the first study systematically assessing the importance of preparations and plants used in antidiabetic Sri Lankan Siddha Medicine preparations. Antidiabetic plants are a crucial health care resource in Sri Lankan Siddha Medicine. This study also identified a wide range of methodological problems in the studies conducted so far. More and better type 2 diabetes models should be employed in future studies. This comprehensive review creates the basis for a more systematic study of these local resources.

Antioxidant plants and diabetes mellitus

The incidence of diabetes mellitus (DM) is increasing rapidly and it is expected to increase by 2030. Other than currently available therapeutic options, there are a lot of herbal medicines, which have been recommended for its treatment. Herbal medicines have long been used for the treatment of DM because of the advantage usually having no or less side-effects. Most of these plants have antioxidant activities and hence, prevent or treat hard curable diseases, other than having the property of combating the toxicity of toxic or other drugs. In this review other than presenting new findings of DM, the plants, which are used and have been evaluated scientifically for the treatment of DM are introduced.

Cytoprotective and anti-diabetic effects of Derris reticulata aqueous extract

The current study was aimed to investigate pancreatic protective and anti-diabetic activities of the aqueous extract of Derris reticulata stem. First, we evaluated a cytoprotective potential of D. reticulata extract on alloxan-induced damage in vitro. Treatment with D. reticulata extract at the doses of 250 and 500 μg/ml significantly increased cell viability of the pancreatic β-cell line RINm5F after exposure of alloxan. The anti-hyperglycemic activity of D. reticulata extract was further studied in alloxan-induced diabetic rats. A significant reduction in blood glucose level along with an increase in body weight was observed in diabetic rats treated with D. reticulata extract at 250 mg/kg body weight for 15 days. Serum aspartate transaminase and alanine transaminase levels were also significantly decreased compared to diabetic control rats. In accordance with in vitro cytoprotective effect, histopathological examination revealed that pancreatic islet cells of the extract-treated diabetic rat were less damage than those of the untreated diabetic group. In order to find another possible mechanism of action underling hypoglycemic activity, the effect on glucose absorption was examined using everted sac jejunum. The results showed that D. reticulata extract suppressed glucose absorption from small intestine. To corroborate safety use of D. reticulata extract, acute oral toxicity was also conducted in rats. Our results showed that none of the tested doses (250, 500, 1,000, and 2,000 mg/kg) induced signs of toxicity or mortality after administration of the extract. The results suggested that D. reticulata extract possess anti-diabetic activity, which resulting from its pancreatic cytoprotective effect and inhibition of intestinal glucose absorption.

Vietnamese traditional medicine from a pharmacist's perspective

Traditional medicine plays an important role in the healthcare system of Vietnam. Vietnamese traditional medicine (VTM) is underpinned by the oriental philosophy and theory of healing. VTM is largely influenced by traditional Chinese medicine, but differs to a certain extent. VTM is largely not evidence-based from a clinical perspective but subclinical research data from the past decades support the traditional use of many herbal VTM drugs. For safe use, knowledge of the occurrence of adverse reactions and herb-drug interactions is necessary. The Vietnamese government supports further development of VTM in a scientific way and integration of VTM with Western medicine. This article first gives an overview of the general aspects of VTM (historical perspective, regulatory aspects, comparison with traditional Chinese medicine, philosophical background, the Vietnamese market situation, quality assurance and formulations), and subsequently focuses on its safe and effective use in Vietnamese clinical pharmacy and medical practice.

Everted gut sac model as a tool in pharmaceutical research: limitations and applications

OBJECTIVES

This review discusses the limitations and applications of the everted gut sac model in studying drug absorption, metabolism, and interaction.

KEY FINDINGS

The mechanism of drug absorption, interaction and the effect of factors such as age, sex, species, chronic therapy, and disease state on drug absorption have been summarized. The experimental conditions and their effects on the outcomes of trials have been discussed also.

SUMMARY

The everted sac model is an efficient tool for studying in-vitro drug absorption mechanisms, intestinal metabolism of drugs, role of transporter in drug absorption, and for investigating the role of intestinal enzymes during drug transport through the intestine.

Antidiabetic Activities of Abutilon indicum (L.) Sweet Are Mediated by Enhancement of Adipocyte Differentiation and Activation of the GLUT1 Promoter

Abutilon indicum (L.) Sweet is an Asian phytomedicine traditionally used to treat several disorders, including diabetes mellitus. However, molecular mechanisms supporting the antidiabetic effect of A. indicum L. remain unknown. The aim of this study was to evaluate whether extract of A. indicum L. improves insulin sensitivity. First, we observed the antidiabetic activity of aqueous extract of the entire plant (leaves, twigs and roots) of A. indicum L. on postprandial plasma glucose in diabetic rats. The subsequent experiments revealed that butanol fractions of the extract bind to PPARγ and activate 3T3-L1 differentiation. To measure glucose uptake enhanced by insulin-like activity, we used rat diaphragm incubated with various concentrations of the crude extract and found that the extract enhances glucose consumption in the incubated solution. Our data also indicate that the crude extract and the fractions (water and butanol) did not affect the activity of kinases involved in Akt and GSK-3β pathways; however, the reporter assay showed that the crude extract could activate glucose transporter 1 (GLUT1) promoter activity. These results suggest that the extract from A. indicum L. may be beneficial for reducing insulin resistance through its potency in regulating adipocyte differentiation through PPARγ agonist activity, and increasing glucose utilization via GLUT1.

Impact of dietary polyphenols on carbohydrate metabolism

Polyphenols, including flavonoids, phenolic acids, proanthocyanidins and resveratrol, are a large and heterogeneous group of phytochemicals in plant-based foods, such as tea, coffee, wine, cocoa, cereal grains, soy, fruits and berries. Growing evidence indicates that various dietary polyphenols may influence carbohydrate metabolism at many levels. In animal models and a limited number of human studies carried out so far, polyphenols and foods or beverages rich in polyphenols have attenuated postprandial glycemic responses and fasting hyperglycemia, and improved acute insulin secretion and insulin sensitivity. The possible mechanisms include inhibition of carbohydrate digestion and glucose absorption in the intestine, stimulation of insulin secretion from the pancreatic β–cells, modulation of glucose release from the liver, activation of insulin receptors and glucose uptake in the insulin-sensitive tissues, and modulation of intracellular signalling pathways and gene expression. The positive effects of polyphenols on glucose homeostasis observed in a large number of in vitro and animal models are supported by epidemiological evidence on polyphenol-rich diets. To confirm the implications of polyphenol consumption for prevention of insulin resistance, metabolic syndrome and eventually type 2 diabetes, human trials with well-defined diets, controlled study designs and clinically relevant end-points together with holistic approaches e.g., systems biology profiling technologies are needed.