An extract of Syzygium aromaticum represses genes encoding hepatic gluconeogenic enzymes

Bioactive properties of clove (Syzygium aromaticum) essential oil nanoemulsion: A comprehensive review

Syzygium aromaticum, commonly called clove, is a culinary spice with medical uses. Clove is utilized in cosmetics, medicine, gastronomy, and agriculture due to its abundance of bioactive components such as gallic acid, flavonoids, eugenol acetate, and eugenol. Clove essential oil has been revealed to have antibacterial, antinociceptive, antibacterial activities, antifungal, and anticancerous qualities. Anti-inflammatory chemicals, including eugenol and flavonoids, are found in clove that help decrease inflammation and alleviate pain. The anti-inflammatory and analgesic qualities of clove oil have made it a popular natural cure for toothaches and gum discomfort. Due to its therapeutic potential, it has been used as a bioactive ingredient in coating fresh fruits and vegetables. This review article outlines the potential food processing applications of clove essential oil. The chemical structures of components, bioactive properties, and medicinal potential of clove essential oil, including phytochemical importance in food, have also been thoroughly addressed.

Anti-obesity effects of Camellia (Camellia oleifera Abel) oil treatment on high-fat diet-induced obesity in C57BL/6J mice

PURPOSE

In the current study, we investigated the effects of camellia oil and camellia oil infused with herbs (Camellia oleifera Abel) on obesity in obese mice fed a high-fat diet (HFD).

METHODS

The antioxidant activity of camellia oil in scavenging free radicals was investigated. Additionally, body and organ weight changes, serum and liver marker parameters, antioxidant enzyme activities, liver and epididymal fat histology, protein and gene expression associated with lipogenesis and hyperglycemia effect on adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, were examined in HFD-induced obese mice.

RESULTS

The hepatic steatosis and epididymal fat were significantly reduced by the oral administration of camellia oil and herb-infused camellia oil. Moreover, hepatic and serum marker parameters such as total cholesterol, insulin, triglycerides, tumor necrosis factor-α, adiponectin, thiobarbituric acid reactive substances, aspartate aminotransferase, and alanine transaminase were beneficially impacted. Additionally, the activity of antioxidant enzymes also increased. Camellia oil and herb-infused camellia oil treatments reduced the expression of genes linked to hyperglycemia and lipogenesis via activation of AMPK phosphorylation.

CONCLUSION

For many people, exercise poses an obstacle in the daily routine due to lack of ease, difficulty in maintaining consistency, and hard work. Camellia oil combined with herbs has anti-obesity and antihyperglycemic effects. These findings indicate that treatment with herb-infused camellia oil is most beneficial for elderly individuals who do not prefer frequent exercise.

Exercise and Syzygium aromaticum reverse memory deficits, apoptosis and mitochondrial dysfunction of the hippocampus in Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD), the most common disease in the brain, is associated with cognitive and mitochondrial dysfunction. Emerging evidence suggests that endurance training and Syzygium aromaticum (L.) Merrill and Perry (Myrtaceae) (commonly referred to as clove) are effective interventions to maintain oxidative balance and improve cognitive function.

AIM OF THE STUDY

The present study aimed to investigate the effect of endurance training and clove oil affect spatial memory, apoptosis, mitochondrial homeostasis, and cognitive function in Alzheimer's rats.

MATERIALS AND METHODS

81 rats were randomly assigned to 9 groups: Healthy (H), sham (sh), Healthy-exercise (HE), Healthy-clove (HC), Healthy-exercise-clove (HEC), Alzheimer's (A), Alzheimer's-exercise (AE), Alzheimer's-clove (AC), and Alzheimer's-exercise-clove (AEC). Alzheimer's induction was induced by the injection of 1-42 amyloid into the CA1 region of the hippocampus. The exercise training protocol was performed for 3 weeks, every day for 30 min in swimming training, and clove oil supplementation (0.1 mg/kg) was gavaged daily for 3 weeks in the supplement rat. Shuttle box test was used to measure spatial memory after the last training session, and to determine the mRNAs and protein levels and apoptosis, Real-Time PCR, immunofluorescent, and tunnel methods were used, respectively.

RESULTS

Alzheimer's caused a significant decrease in the PRDX6 and GCN5L1 mRNAs and protein levels and a significant increase in apoptosis in the hippocampus of the Alzheimer's group compared to the control group (P = 0.001). Alzheimer's also reduced the time delay in entering the dark environment and increased the time spent in the dark environment (P = 0.001). Following endurance training and consumption of clove oil, spatial memory (P = 0.001), apoptosis (P = 0.001) and mRNAs and protein levels of PRDX6 (P = 0.001) and GCN5L1 (P = 0.017), were recovered in AE, AC and AEC groups, as compared with A group.

CONCLUSION

Swimming training and consumption of clove can possibly be considered as an effective intervention to maintain oxidative balance and improve mitochondrial homeostasis in Alzheimer's disease.

Function of selected natural antidiabetic compounds with potential against cancer via modulation of the PI3K/AKT/mTOR cascade

Diabetes mellitus (DM) is a metabolic disorder with growing global incidence, as 387 million people were diagnosed in 2014 with an expected projection of 642 million in 2040. Several complications are associated with DM including heart attack, stroke, kidney failure, blindness, and cancer. The latter is the second leading cause of death worldwide accounting for one in every six deaths, with liver, pancreas, and endometrium cancers are the most abundant among patients with diabetes. Phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway plays a vital role in developing a wide array of pathological disorders, among them diabetes and cancer. Natural secondary metabolites that counteract the deleterious effects of reactive oxygen species (ROS) and modulate PI3K/Akt/mTOR pathway could be a promising approach in cancer therapy. Here, 717 medicinal plants with antidiabetic activities were highlighted along with 357 bioactive compounds responsible for the antidiabetic activity. Also, 43 individual plant compounds with potential antidiabetic activities against cancer via the modulation of PI3K/Akt/mTOR cascade were identified. Taken together, the available data give an insight of the potential of repurposing medicinal plants and/or the individual secondary metabolites with antidiabetic activities for cancer therapy.

Histology of hematoxylin–eosin and immunohistochemical diabetes rat pancreas after giving combination of moringa leaves (Moringa oleifera) and clove flower (Syzygium aromaticum) extracts

The purpose of this study was to determine the regeneration activity of pancreatic beta cells by a combination of the ethanol extracts of Moringa leaves and Clove flower. These extracts prepared by maceration with ethanol as solvent . This is an experimental laboratory research by using post test only group design . The subject of this research is 40 white male rats of Wistar strain ( Rattus norvegicus ) and were conditioned DM by streptozotozine-nicotinamide induction . The rats randomly divided into 8 groups , and each group consisted of 5 rats . Combination dose of Moringa leaves and Clove flowers extracts used are  150 : 40 mg / kg body weight of mice , 100 : 80 mg / kg body weight of mice and 50 : 120 mg / kg body weight of mice . The rats were sacrificed and the pancreas taken to be made preparations histopathology , staining and observation tissues with HE and IHC methods. The results showed that the staining and observation tissues of heart with  HE method acquired the positive control group , the single test group and the combination group  were showing the islet on the Langerhans island of the pancreas is bigger than in the negative control group. The morphology of the island of Langerhans increasingly large indicates increasing the regeneration of the cells of the islet beta pancreas; whereas the method of IHC acquired the negative control group seen lack of display intensity of positive reaction Ag  & Ab beta cells with are marked with brown cells . In the positive control group , the single test group and the combination group , seen a positive reaction of Ag & Ab insulin-producing beta cells characterized by brown cells and insulin expression dominating pancreatic island of Langerhans.

Evaluation of the Anti-Diabetic Activity of Some Common Herbs and Spices: Providing New Insights with Inverse Virtual Screening

Culinary herbs and spices are widely used as a traditional medicine in the treatment of diabetes and its complications, and there are several scientific studies in the literature supporting the use of these medicinal plants. However, there is often a lack of knowledge on the bioactive compounds of these herbs and spices and their mechanisms of action. The aim of this study was to use inverse virtual screening to provide insights into the bioactive compounds of common herbs and spices, and their potential molecular mechanisms of action in the treatment of diabetes. In this study, a library of over 2300 compounds derived from 30 common herbs and spices were screened in silico with the DIA-DB web server against 18 known diabetes drug targets. Over 900 compounds from the herbs and spices library were observed to have potential anti-diabetic activity and liquorice, hops, fennel, rosemary, and fenugreek were observed to be particularly enriched with potential anti-diabetic compounds. A large percentage of the compounds were observed to be potential polypharmacological agents regulating three or more anti-diabetic drug targets and included compounds such as achillin B from yarrow, asparasaponin I from fenugreek, bisdemethoxycurcumin from turmeric, carlinoside from lemongrass, cinnamtannin B1 from cinnamon, crocin from saffron and glabridin from liquorice. The major targets identified for the herbs and spices compounds were dipeptidyl peptidase-4 (DPP4), intestinal maltase-glucoamylase (MGAM), liver receptor homolog-1 (NR5A2), pancreatic alpha-amylase (AM2A), peroxisome proliferator-activated receptor alpha (PPARA), protein tyrosine phosphatase non-receptor type 9 (PTPN9), and retinol binding protein-4 (RBP4) with over 250 compounds observed to be potential inhibitors of these particular protein targets. Only bay leaves, liquorice and thyme were found to contain compounds that could potentially regulate all 18 protein targets followed by black pepper, cumin, dill, hops and marjoram with 17 protein targets. In most cases more than one compound within a given plant could potentially regulate a particular protein target. It was observed that through this multi-compound-multi target regulation of these specific protein targets that the major anti-diabetic effects of reduced hyperglycemia and hyperlipidemia of the herbs and spices could be explained. The results of this study, taken together with the known scientific literature, indicated that the anti-diabetic potential of common culinary herbs and spices was the result of the collective action of more than one bioactive compound regulating and restoring several dysregulated and interconnected diabetic biological processes.

(-)-Epicatechin and the Colonic 2,3-Dihydroxybenzoic Acid Metabolite Regulate Glucose Uptake, Glucose Production, and Improve Insulin Signaling in Renal NRK-52E Cells

SCOPE

(-)-Epicatechin (EC) and main colonic phenolic acids derived from flavonoid intake, such as 2,3-dihydroxybenzoic acid (DHBA), 3,4-dihydroxyphenylacetic acid (DHPAA), 3-hydroxyphenylpropionic acid (HPPA), and vanillic acid (VA), have been suggested to exert beneficial effects in diabetes, although the mechanism for their actions remains unknown. In this study, the modulation of glucose homeostasis and insulin signaling by the mentioned compounds on renal proximal tubular NRK-52E cells is investigated.

METHODS AND RESULTS

Levels of the glucose transporters SGLT-2 and GLUT-2, as well as glucose uptake, glucose production, and key proteins of the insulin pathways, namely insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and PI3K/AKT pathway are analyzed. EC (5-20 μm) and DHBA (20 μm) reduced both renal glucose uptake and production. Interestingly, EC and DHBA did not modify the levels of SGLT-2 and GLUT-2, and modulated the expression of phosphoenolpyruvate carboxykinase via AKT leading to a diminished glucose production. EC and DHBA also enhanced the tyrosine phosphorylation and total IR and IRS-1 levels, and activated the PI3K/AKT pathway in NRK-52E cells.

CONCLUSION

EC and DHBA regulate the renal glucose homeostasis by modulating both glucose uptake and production, and strengthen the insulin signaling by activating key proteins of that pathway in NRK-52E cells.

DNA Microarray-Based Screening and Characterization of Traditional Chinese Medicine

The application of DNA microarray assay (DMA) has entered a new era owing to recent innovations in omics technologies. This review summarizes recent applications of DMA-based gene expression profiling by focusing on the screening and characterizationof traditional Chinese medicine. First, herbs, mushrooms, and dietary plants analyzed by DMA along with their effective components and their biological/physiological effects are summarized and discussed by examining their comprehensive list and a list of representative effective chemicals. Second, the mechanisms of action of traditional Chinese medicine are summarized by examining the genes and pathways responsible for the action, the cell functions involved in the action, and the activities found by DMA (silent estrogens). Third, applications of DMA for traditional Chinese medicine are discussed by examining reported examples and new protocols for its use in quality control. Further innovations in the signaling pathway based evaluation of beneficial effects and the assessment of potential risks of traditional Chinese medicine are expected, just as are observed in other closely related fields, such as the therapeutic, environmental, nutritional, and pharmacological fields.

Spices in the management of diabetes mellitus

Diabetes mellitus (DM) remains a major health care problem worldwide both in developing and developed countries. Many factors, including age, obesity, sex, and diet, are involved in the etiology of DM. Nowadays, drug and dietetic therapies are the two major approaches used for prevention and control of DM. Compared to drug therapy, a resurgence of interest in using diet to manage and treat DM has emerged in recent years. Conventional dietary methods to treat DM include the use of culinary herbs and/or spices. Spices have long been known for their antioxidant, anti-inflammatory, and anti-diabetic properties. This review explores the anti-diabetic properties of commonly used spices, such as cinnamon, ginger, turmeric, and cumin, and the use of these spices for prevention and management of diabetes and associated complications.

In vitro inhibition activity of polyphenol-rich extracts from Syzygium aromaticum (L.) Merr. & Perry (Clove) buds against carbohydrate hydrolyzing enzymes linked to type 2 diabetes and Fe(2+)-induced lipid peroxidation in rat pancreas

OBJECTIVE

To investigate and compare the inhibitory properties of free and bound phenolic extracts of clove bud against carbohydrate hydrolyzing enzymes (alpha-amylase & alpha-glucosidase) and Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.

METHODS

The free phenolics were extracted with 80% (v/v) acetone, while bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate. Then, the interaction of the extracts with alpha-amylase and alpha-glucosidase was subsequently assessed. Thereafter, the total phenolic contents and antioxidant activities of the extracts were determined.

RESULTS

The result revealed that both extracts inhibited alpha-amylase and alpha-glucosidase in a dose-dependent manner. However, the alpha-glucosidase inhibitory activity of the extracts were significantly (P<0.05) higher than their alpha-amylase inhibitory activity. The free phenolics (31.67 mg/g) and flavonoid (17.28 mg/g) contents were significantly (P<0.05) higher than bound phenolic (23.52 mg/g) and flavonoid (13.70 mg/g) contents. Both extracts also exhibited high antioxidant activities as typified by their high reducing power, 1,1 diphenyl-2- picrylhydrazyl (DPPH) and 2, 2-azinobis-3-ethylbenzo-thiazoline-6-sulfonate (ABTS) radical scavenging abilities, as well as inhibition of Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.

CONCLUSIONS

This study provides a biochemical rationale by which clove elicits therapeutic effect on type 2 diabetes.

Antihyperglycemic, hypolipidemic, hepatoprotective and antioxidative effects of dietary clove (Szyzgium aromaticum) bud powder in a high-fat diet/streptozotocin-induced diabetes rat model

BACKGROUND

Syzygium aromaticum (L.) Merr. & Perry (clove) bud is an important spice used in the preparation of several delicacies and in folklore for diabetes management. The present study was convened to assess the effects of dietary clove bud powder (CBP) on biochemical parameters in a type 2 diabetes rat model, induced by a combination of high-fat diet and low-dose streptozotocin (35 mg kg⁻¹) for 30 days.

RESULTS

Diabetic rats were placed on dietary regimen containing 20-40 g kg⁻¹ clove bud powder. The results revealed that there was no significant (P > 0.05) difference in the average feed intake and weight changes between the rat groups. Furthermore, supplementation with CBP gradually reduced blood glucose level in diabetic rat compared to control diabetic rats without CBP supplementation (DBC). Moreover, reduced activity of α-glucosidase was observed in CBP and metformin-treated rat groups when compared to that of the DBC rat group. In addition, the DBC group had significantly (P < 0.05) higher lipid concentrations (except for high-density lipoprotein cholesterol) when compared to all other groups. Furthermore, CBP had significantly (P < 0.05) reduced activity of liver enzymes (alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase) and showed elevated levels of antioxidant status (glutathione, ascorbic acid, superoxide dismutase and catalase).

CONCLUSION

The results suggest that the clove bud diet may attenuate hyperglycemia, hyperlipidemia, hepatotoxicity and oxidative stress in the type 2 diabetic condition.

Effects of eugenol-reduced clove extract on glycogen phosphorylase b and the development of diabetes in db/db mice

We found that the 50% aqueous EtOH extract of clove (Syzygium aromaticum) had potent dose-dependent inhibitory activity toward glycogen phosphorylase b and glucagon-stimulated glucose production in primary rat hepatocytes. Among the components, eugeniin inhibited glycogen phosphorylase b and glucagon-stimulated glucose production in primary rat hepatocytes, with IC50 values of 0.14 and 4.7 μM, respectively. In sharp contrast, eugenol showed no significant inhibition toward glycogen phosphorylase b, even at a concentration of 400 μM. Eugenol-reduced clove extracts (erCE) were prepared and when fed to a db/db mouse they clearly suppressed the blood glucose and HbA1c levels. Furthermore, plasma triglyceride and non-esterified fatty acid levels in 5% and 10% erCE-fed db/db mice were significantly lowered, compared with control db/db mice without erCE supplementation. These results suggested that dietary supplementation with the erCE could beneficially modify glucose and lipid metabolism and contribute to the prevention of the progress of hyperglycemia and metabolic syndrome.

Brain-derived neurotrophic factor inhibits glucose intolerance after cerebral ischemia

Brain-derived neurotrophic factor is associated with the insulin signaling pathway and glucose tabolism. We hypothesized that expression of brain-derived neurotrophic factor and its receptor may be involved in glucose intolerance following ischemic stress. To verify this hypothesis, this study aimed to observe the changes in brain-derived neurotrophic factor and tyrosine kinase B receptor expression in glucose metabolism-associated regions following cerebral ischemic stress in mice. At day 1 after middle cerebral artery occlusion, the expression levels of brain-derived neurotrophic factor were significantly decreased in the ischemic cortex, hypothalamus, liver, skeletal muscle, and pancreas. The expression levels of tyrosine kinase B receptor were decreased in the hypothalamus and liver, and increased in the skeletal muscle and pancreas, but remained unchanged in the cortex. Intrahypothalamic administration of brain-derived neurotrophic factor (40 ng) suppressed the decrease in insulin receptor and tyrosine-phosphorylated insulin receptor expression in the liver and skeletal muscle, and inhibited the overexpression of gluconeogenesis-associated phosphoenolpyruvate carboxykinase and glucose-6-phosphatase in the liver of cerebral ischemic mice. However, serum insulin levels remained unchanged. Our experimental findings indicate that brain-derived neurotrophic factor can promote glucose metabolism, reduce gluconeogenesis, and decrease blood glucose levels after cerebral ischemic stress. The low expression of brain-derived neurotrophic factor following cerebral ischemia may be involved in the development of glucose intolerance.

The use of transcriptomics to unveil the role of nutrients in Mammalian liver

Liver is the organ primarily responding to diet, and it is crucial in determining plasma carbohydrate, protein, and lipid levels. In addition, it is mainly responsible for transformation of xenobiotics. For these reasons, it has been a target of transcriptomic analyses. In this review, we have covered the works dealing with the response of mammalian liver to different nutritional stimuli such as fasting/feeding, caloric restriction, dietary carbohydrate, cholesterol, fat, protein, bile acid, salt, vitamin, and oligoelement contents. Quality of fats or proteins has been equally addressed, and has the influence of minor dietary components. Other compounds, not purely nutritional as those represented by alcohol and food additives, have been included due to their relevance in processed food. The influence has been studied not only on mRNA but also on miRNA. The wide scope of the technology clearly reflects that any simple intervention has profound changes in many metabolic parameters and that there is a synergy in response when more compounds are included in the intervention. Standardized arrays to systematically test the same genes in all studies and analyzing data to establish patterns of response are required, particularly for RNA sequencing. Moreover, RNA is a valuable, easy-screening ally but always requires further confirmation.

Cocoa flavonoids improve insulin signalling and modulate glucose production via AKT and AMPK in HepG2 cells

SCOPE

Cocoa and (-)-epicatechin (EC), a main cocoa flavanol, have been suggested to exert beneficial effects in diabetes, but the mechanism for their insulin-like effects remains unknown. In this study, the modulation of insulin signalling by EC and a cocoa phenolic extract (CPE) on hepatic HepG2 cells was investigated by analysing key proteins of the insulin pathways, namely insulin receptor, insulin receptor substrate (IRS) 1 and 2, PI3K/AKT and 5'-AMP-activated protein kinase (AMPK), as well as the levels of the glucose transporter GLUT-2 and the hepatic glucose production.

METHODS AND RESULTS

EC and CPE enhanced the tyrosine phosphorylation and total insulin receptor, IRS-1 and IRS-2 levels and activated the PI3K/AKT pathway and AMPK in HepG2 cells. CPE also enhanced the levels of GLUT-2. Interestingly, EC and CPE modulated the expression of phosphoenolpyruvate carboxykinase, a key protein involved in the gluconeogenesis, leading to a diminished glucose production. In addition, EC- and CPE-regulated hepatic gluconeogenesis was prevented by the blockage of AKT and AMPK.

CONCLUSION

Our data suggest that EC and CPE strengthen the insulin signalling by activating key proteins of that pathway and regulating glucose production through AKT and AMPK modulation in HepG2 cells.

Molecular Mechanism Underlying the Antidiabetic Effects of a Siddha Polyherbal Preparation in the Liver of Type 2 Diabetic Adult Male Rats

A siddha polyherbal preparation consisting of 5 medicinal plants, namely, Asparagus racemosus, Emblica officinalis, Salacia oblonga, Syzygium aromaticum, and Tinospora cordifolia, in equal ratio, was formulated to examine the molecular mechanism by which it exhibits antidiabetic effects in the liver of high-fat and fructose-induced type 2 diabetic rats. The polyherbal preparation treated type 2 diabetic rats showed an increase in insulin receptor, Akt, and glucose transporter2 mRNA levels compared with diabetic rats. Insulin receptor, insulin receptor substrate-2, Akt, phosphorylated Akt substrate of 160kDaThreonine642, α-Actinin-4, β-arrestin-2, and glucose transporter2 proteins were also markedly decreased in diabetic rats, whereas the polyherbal preparation treatment significantly improved the expression of these proteins more than that of metformin-treated diabetic rats. The expression pattern of insulin signaling molecules analyzed in the present study signifies the therapeutic efficacy of the siddha polyherbal preparation.

A brief review on anti diabetic plants: Global distribution, active ingredients, extraction techniques and acting mechanisms

A study has been conducted with the aim to provide researchers with general information on anti diabetic extracts based on relevant research articles collected from 34 reliable medical journals. The study showed that Asian and African continents have 56% and 17% share of the worldwide distribution of therapeutic herbal plants, respectively. In Asia, India and China are the leading countries in herbal plants research, and there has been an increase in medicinal research on plants extract for diabetes treatment since 1995 in these regions. The information collected shows that plant leaves are about 20% more favorable for storing active ingredients, as compared to other parts of herbal plants. A brief review on the extraction techniques for the mentioned parts is also included. Furthermore, the acting mechanisms for the anti diabetic activity were described, and the related active ingredients were identified. The findings reveal that most of the anti diabetic research is focused on the alteration of glucose metabolism to prevent diabetes.

Ameliorating effect of hypothalamic brain-derived neurotrophic factor against impaired glucose metabolism after cerebral ischemic stress in mice

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, has potent neuroprotective effects against brain injury. We recently reported that glucose intolerance/hyperglycemia could be induced by ischemic stress (i.e., post-ischemic glucose intolerance) following ischemic neuronal damage. Therefore, the aim of this study was to determine the effects of BDNF on the development of post-ischemic glucose intolerance and ischemic neuronal damage. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO) for 2 h. On day 1, the expression levels of BDNF were significantly decreased in the cortex, hypothalamus, liver, skeletal muscle, and pancreas. The expression levels of tyrosine kinase B receptor, a BDNF receptor, decreased in the hypothalamus and liver and increased in the skeletal muscle and pancreas, but remained unchanged in the cortex. Intrahypothalamic administration of BDNF (50 ng/mouse) suppressed the development of post-ischemic glucose intolerance on day 1 and neuronal damage on day 3 after MCAO. In the liver and skeletal muscle, the expression levels of insulin receptors decreased, while gluconeogenic enzyme levels increased on day 1 after MCAO. These changes completely recovered to normal levels in the presence of BDNF. These results indicate that regulation of post-ischemic glucose intolerance by BDNF may suppress ischemic neuronal damage.

The effects of Syzygium aromaticum-derived oleanolic acid on glycogenic enzymes in streptozotocin-induced diabetic rats

Studies indicate that the antihyperglycemic effects of Syzygium aromaticum-derived oleanolic acid (OA) are mediated in part through increased hepatic glycogen synthesis. Accordingly, this study assessed the influence of OA on the activity of glucokinase (GK) and hexokinase (HK) of skeletal muscle and liver tissues in streptozotocin (STZ)-induced diabetic rats. After 5 weeks of OA treatment, hepatic and gastrocnemius muscle glycogen concentrations and activities of GK and HK were measured spectrophotometrically in reactions where the oxidation of glucose-6-phosphate (G-6-PDH) formed was coupled to nicotinamide adenine dinucleotide phosphate (NADP+) reduction catalyzed by G-6-PDH dehydrogenase. Rats treated with deionized water or standard hypoglycemic drugs acted as untreated and treated positive controls, respectively. STZ-induced diabetic rats exhibited depleted glycogen levels and low activities of glycogenic enzymes in muscle and hepatic tissues. OA administration restored these biochemical alterations to near normalcy. The combination of OA and insulin did not significantly alter the activities of HK and GK of STZ-induced diabetic rats, suggesting that glycogen synthesis can also occur from precursors such as amino acids or fructose and lactate. The attenuation of the activities of glycogenic enzymes with concomitant increases of hepatic and muscle glycogen concentrations of STZ-induced diabetic rats provides a therapeutic strategy for diabetes treatment.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

Antidiabetic effect of propolis: reduction of expression of glucose-6-phosphatase through inhibition of Y279 and Y216 autophosphorylation of GSK-3α/β in HepG2 cells

Propolis is a sticky, resinous material that honey bees collect from various plants, and mix with wax and other secretions. The aim of this study was to evaluate the antidiabetic effect of propolis through an analysis of the expression and enzyme activity of glucose-6-phosphatase (G6Pase) and to elucidate the mechanism by which propolis inhibits G6Pase gene expression. When HepG2 cells were incubated in high glucose media (25 mm), G6Pase expression was induced. Propolis significantly reduced the expression and enzyme activity of G6Pase; however, the hypoglycemic effect was not abolished by the phosphoinositide 3-kinase inhibitor, LY294002, and by the mitogen-activated protein kinase (MAPK) inhibitor, U0126. Propolis inhibited the activity of GSK3α and β via the inhibition of serine and tyrosine phosphorylation, specifically, Y279 for GSK3α and Y216 for GSK3β. The phosphorylations of Y279 and Y216 occur through autophosphorylation by GSK3α/β and are involved in their own activity. Although propolis showed antioxidant activity, antidiabetic effect of propolis was not influenced by hydrogen peroxide and N-acetylcysteine. These results suggest that propolis inhibits the expression of G6Pase by inhibiting the autophosphorylation of Y279 and Y216 of GSK3α and β, respectively, which are involved in the activation of GSK3. These findings suggest that propolis may be a potential antidiabetic agent for the treatment of insulin-insensitive diabetes.

Synergistic antihyperglycemic effects between plant-derived oleanolic acid and insulin in streptozotocin-induced diabetic rats

Studies from our laboratories indicate that Syzygium cordatum leaf extract contains triterpene mixtures [oleanolic acid (OA) and ursolic acid (UA)] with hypoglycemic properties. The aims of this study were to investigate the hypoglycemic effects of Syzygium aromaticum-derived OA and whether OA influenced the blood glucose lowering effects of insulin in streptozotocin (STZ)-induced diabetic rats. We envisaged that OA may provide a strategy with different mechanism of action for effective diabetic therapy because no single-marketed antidiabetic drug is capable of achieving long-lasting blood glucose control. The effects of various doses of OA and/or standard antidiabetic drugs on blood glucose were monitored in nondiabetic and STZ-induced diabetic rats given a glucose load after an 18-h fast. Rats treated with deionized water and standard antidiabetic drugs acted as untreated and treated positive controls, respectively. Blood glucose concentrations were measured at 15-min intervals for the first hour and hourly thereafter for 3 h. Blood glucose concentrations were also monitored in animals treated with OA and/or standard antidiabetic drugs for 5 weeks. OA like insulin decreased blood glucose concentrations in nondiabetic and STZ-induced diabetic rats. Combined OA and insulin treatment had even greater antihyperglycemic response, suggestive of a synergistic effect of the two. After 5 weeks, STZ-induced diabetic rats exhibited hyperglycemia and depleted hepatic and muscle glycogen concentrations. OA treatment lowered the blood glucose with concomitant restoration of glycogen concentrations to near normalcy. Our results suggest that OA may have a role in improving insulin sensitivity. These findings merit further research in this field.

Mechanisms of blood glucose-lowering effect of aqueous extract from stems of Kothala himbutu (Salacia reticulata) in the mouse

ETHNOPHARMACOLOGICAL RELEVANCE

Kothala himbutu (Salacia reticulata) is a medicinal plant that has been used in Ayurvedic system of Indian and Sri Lankan traditional medicine to treat diabetes.

AIM OF THE STUDY

This study aimed to clarify the mechanism(s) by which aqueous extracts of Kothala himbutu (KTE) stems decreases fasting blood glucose levels.

MATERIALS AND METHODS

Gene expression profiles were assessed by DNA microarray and RT-PCR analyses of RNA from the liver of KK-Ay diabetic mice administered KTE or control distilled water for 4 weeks, and from cultured liver cells treated with freeze-dried KTE (KTED) or selected phenolic compounds.

RESULTS

DNA microarray and RT-PCR analyses revealed that gluconeogenic fructose-1,6-bisphosphatase (FBP) was decreased compared with the control in KTE-treated KK-Ay mice. RT-PCR analysis using cultured liver cells treated with KTED and/or actinomycin D or cycloheximide, revealed that KTED directly decreased FBP mRNA levels via destabilization of the mRNA. One compound in KTE, mangiferin, was demonstrated to dose-dependently down-regulate FBP mRNA.

CONCLUSIONS

These findings suggest that the mangiferin in KTE acts directly on liver cells and down-regulates the gluconeogenic pathway through regulation of FBP expression, thereby decreasing fasting blood glucose levels in mice. Our results demonstrate that gluconeogenic gene regulation is one possible mechanism by which KT exerts its effects in traditional diabetic medicine.

Polyphenolic compounds from Artemisia dracunculus L. inhibit PEPCK gene expression and gluconeogenesis in an H4IIE hepatoma cell line

An ethanolic extract of Russian tarragon, Artemisia dracunculus L., with antihyperglycemic activity in animal models was reported to decrease phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression in STZ-induced diabetic rats. A quantitative polymerase chain reaction (qPCR) assay was developed for the bioactivity-guided purification of the compounds within the extract that decrease PEPCK expression. The assay was based on the inhibition of dexamethasone-stimulated PEPCK upregulation in an H4IIE hepatoma cell line. Two polyphenolic compounds that inhibited PEPCK mRNA levels were isolated and identified as 6-demethoxycapillarisin and 2',4'-dihydroxy-4-methoxydihydrochalcone with IC(50) values of 43 and 61 muM, respectively. The phosphoinositide-3 kinase (PI3K) inhibitor LY-294002 showed that 6-demethoxycapillarisin exerts its effect through the activation of the PI3K pathway, similarly to insulin. The effect of 2',4'-dihydroxy-4-methoxydihydrochalcone is not regulated by PI3K and dependent on activation of AMPK pathway. These results indicate that the isolated compounds may be responsible for much of the glucose-lowering activity of the Artemisia dracunculus extract.

DNA microarrays in herbal drug research

Natural products are gaining increased applications in drug discovery and development. Being chemically diverse they are able to modulate several targets simultaneously in a complex system. Analysis of gene expression becomes necessary for better understanding of molecular mechanisms. Conventional strategies for expression profiling are optimized for single gene analysis. DNA microarrays serve as suitable high throughput tool for simultaneous analysis of multiple genes. Major practical applicability of DNA microarrays remains in DNA mutation and polymorphism analysis. This review highlights applications of DNA microarrays in pharmacodynamics, pharmacogenomics, toxicogenomics and quality control of herbal drugs and extracts.

Some thoughts on the future of ethnopharmacology

A discussion is offered of the future potential role of ethnopharmacology in global health care.

Separation and analysis of the major constituents of cloves by micellar electrokinetic chromatography

A micellar electrokinetic chromatographic method was developed and applied for the first time to the separation and quantification of the main components of cloves, namely eugenol and beta-caryophyllene. The analytes were separated in less than ten minutes in an unmodified fused silica capillary (effective length: 40.0 cm) using a background electrolyte composed of 25 mM carbonate buffer (pH 10.0) and 60 mM sodium dodecylsulfate. Analyte concentrations were determined in clove oil and in methanolic clove extracts after simple sequential dilution with methanol and background electrolyte, and the resulting electropherograms showed no interference due to other components. Precision assays gave satisfactory results, with mean standard deviation of peak areas lower than 4.7% (lower than 1.5% for migration times). The eugenol content of a commercial clove oil was about 70% (RSD% = 3.2), while that of beta-caryophyllene was about 15% (RSD% = 4.2); in clove extracts, on the other hand, eugenol was approximately 15% (RSD% = 4.7) and beta-caryophyllene 4% (RSD% = 5.1). Accuracy was also good (mean recovery >98%).