Extended Intake of Mulberry Leaf Extract Delayed Metformin Elimination via Inhibiting the Organic Cation Transporter 2

Diabetes mellitus (DM) has become a major health problem in most countries of the world. DM causes many complications, including hyperglycemia, diabetic ketoacidosis, and death. In Asia, mulberry has been used widely in the treatment of DM. Combination of drugs with herbal medicine may reduce the unwanted side effects caused by drugs. In this study, the influence of extended mulberry leaves extract (MLE) intake on metformin (Met) was evaluated in terms of pharmacokinetics and pharmacodynamics in DM-induced rats. Three week-treatment of MLE alone produced the anti-hyperglycemic effect (around 24%) if compared to the control. Interestingly, Met administration after MLE treatment for 3 weeks enhanced about 49% of the anti-hyperglycemic effect of Met. In addition, the extended intake of MLE potentiated the anti-hyperglycemic effect of Met on various concentrations. This potentiated anti-hyperglycemic effect of Met appears to be due to the pharmacokinetic change of Met. In this study, 3 week-treatment of MLE reduced the elimination of Met in DM-induced rats. In addition, MLE reduced the human organic cation transporter 2 (hOCT2) activity in a concentration-dependent manner. Thus, these findings suggest that MLE lowered the elimination of Met via inhibiting the hOCT2.

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title: Radiochemical assay of glutathione S-epoxide transferase and its enhancement by phenobarbital in rat liver in vivo.
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title: A polysaccharide extract of mulberry leaf ameliorates hepatic glucose metabolism and insulin signaling in rats with type 2 diabetes induced by high fat-diet and streptozotocin.
abstract: Mulberry leaf is a traditional medicine used to treat diabetes in the clinic. The aim of this study was to determine the mechanisms by which mulberry leaf polysaccharide (MLPII), improves hepatic glucose metabolism and insulin resistance in rats with type 2 diabetes induced by high fat and streptozotocin (STZ). MLPII was administered for 6 weeks after establishment of type 2 diabetes in Wistar rats. At the end of the experiment, oral glucose tolerance, liver glycogen content, glucose synthase (GS) activity and insulin resistance were determined. Expression patterns of proteins and genes associated with insulin signaling as well as biomarkers of oxidative stress and antioxidant enzyme activities were assayed. Compared with normal control rats, MLPII treatment significantly improved oral glucose tolerance (P < 0.01) and restored the glycogen level (P < 0.01) and GS activity (P < 0.05) in diabetic rats. Insulin resistance was improved in MLPII-treated diabetic rats (P < 0.01). Furthermore, expression levels of insulin receptor substrate 2 (IRS2), phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB/AKT) involved in insulin signaling were significantly increased (P < 0.01), while protein–tyrosine phosphatase 1B (PTP1B) expression was markedly reduced (P < 0.01). The levels of 8-hydroxy-2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) in livers of the MLPII-treated group were significantly reduced (P < 0.01), while activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), were significantly increased (P < 0.01, P < 0.01, P < 0.01, respectively). The results clearly indicate that MLPII treatment effectively normalizes hepatic glucose metabolism and insulin signaling by inhibiting the expression of PTP1B, activating the PI3K–AKT pathway and mitigating oxidative stress in the livers of rats with type 2 diabetes induced by high fat and STZ.

title: Anti-diabetic effect of mulberry leaf polysaccharide by inhibiting pancreatic islet cell apoptosis and ameliorating insulin secretory capacity in diabetic rats.
abstract: Diabetes mellitus is a clinically complex disease characterized by chronic hyperglycemia with metabolic disturbances. In this study, we investigated the effect of mulberry leaf polysaccharide (MLPII) on pancreatic islet cell apoptosis and insulin secretory function in diabetic rats induced by a high fat diet and streptozotocin. Our results showed that MLPII treatment inhibited pancreatic islet cell apoptosis and ameliorated insulin secretory capacity of pancreatic β-cells in diabetic rats. And further study demonstrated that chronic treatment of diabetic rats with MLPII resulted in up-regulation of anti-apoptotic B-cell leukaemia/lymphoma 2 (Bcl-2) protein and down-regulation of pro-apoptotic Bcl2-associated X (Bax) and caspase-3 protein in pancreatic islet cells. Moreover, MLPII significantly restored pancreatic duodenal homeobox-1 (PDX-1) protein nuclear localization, and increased mRNA and protein expression of PDX-1 and its downstream targets, glucose transporter 2 (GLUT2) and glucokinase (GCK) in pancreatic islet cells of diabetic rats. These findings suggested that MLPII might play a critical role in protecting pancreatic islet cell from apoptosis via elevation of Bcl-2/Bax ratio, and ameliorating insulin secretory capacity of pancreatic β-cells via restoration of PDX-1 nuclear localization and expression levels in diabetic rats. This is the first report to explore the potential molecular mechanism involved in the hypoglycemic activity of the polysaccharide from mulberry leaves.

title: Anti-hyperglycemic Effect of Bilberry, Blackberry and Mulberry Ultrasonic Extracts on Diabetic Rats
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title: Antidiabetic and Antioxidant Effects and Phytochemicals of Mulberry Fruit (Morus alba L.) Polyphenol Enhanced Extract
abstract: The antidiabetic and antioxidant activities of the ethyl acetate-soluble extract (MFE) of mulberry fruit (Morus alba L.) were investigated. In vitro, MFE showed potent α-glucosidase inhibitory activity and radical-scavenging activities against DPPH and superoxide anion radicals. In vivo, MFE could significantly decrease fasting blood glucose (FBG) and glycosylated serum protein (GSP), and increase antioxidant enzymatic activities (SOD, CAT, GSH-Px) in streptozotocin (STZ)-induced diabetic mice. Bioactivity-guided fractionation of the MFE led to the isolation of 25 phenolic compounds, and their structures were identified on the basis of MS and NMR data. All the 25 compounds were isolated from mulberry fruit for the first time. Also, the α-glucosidase inhibitory activity and antioxidant activity of the phenolics were evaluated. Potent α-glucosidase inhibitory and radical-scavenging activities of these phenolics suggested that they may be partially responsible for the antidiabetic and antioxidant activities of mulberry fruit.

title: Mulberry leaf extract intake reduces hyperglycaemia in streptozotocin (STZ)-induced diabetic rats fed high-fat diet
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title: Chlorogenic Acid Stimulates Glucose Transport in Skeletal Muscle via AMPK Activation: A Contributor to the Beneficial Effects of Coffee on Diabetes
abstract: Chlorogenic acid (CGA) has been shown to delay intestinal glucose absorption and inhibit gluconeogenesis. Our aim was to investigate the role of CGA in the regulation of glucose transport in skeletal muscle isolated from db/db mice and L6 skeletal muscle cells. Oral glucose tolerance test was performed on db/db mice treated with CGA and soleus muscle was isolated for 2-deoxyglucose transport study. 2DG transport was also examined in L6 myotubes with or without inhibitors such as wortmannin or compound c. AMPK was knocked down with AMPKα1/2 siRNA to study its effect on CGA-stimulated glucose transport. GLUT 4 translocation, phosphorylation of AMPK and Akt, AMPK activity, and association of IRS-1 and PI3K were investigated in the presence of CGA. In db/db mice, a significant decrease in fasting blood sugar was observed 10 minutes after the intraperitoneal administration of 250 mg/kg CGA and the effect persisted for another 30 minutes after the glucose challenge. Besides, CGA stimulated and enhanced both basal and insulin-mediated 2DG transports in soleus muscle. In L6 myotubes, CGA caused a dose- and time-dependent increase in glucose transport. Compound c and AMPKα1/2 siRNA abrogated the CGA-stimulated glucose transport. Consistent with these results, CGA was found to phosphorylate AMPK and ACC, consistent with the result of increased AMPK activities. CGA did not appear to enhance association of IRS-1 with p85. However, we observed activation of Akt by CGA. These parallel activations in turn increased translocation of GLUT 4 to plasma membrane. At 2 mmol/l, CGA did not cause any significant changes in viability or proliferation of L6 myotubes. Our data demonstrated for the first time that CGA stimulates glucose transport in skeletal muscle via the activation of AMPK. It appears that CGA may contribute to the beneficial effects of coffee on Type 2 diabetes mellitus.

title: Caffeic acid as active principle from the fruit of Xanthium strumarium to lower plasma glucose in diabetic rats.
abstract: The antihyperglycemic effect of caffeic acid, one of the phenolic compounds contained in the fruit of Xanthium strumarium, was investigated. After an intravenous injection of caffeic acid into diabetic rats of both streptozotocin-induced and insulin-resistant models, a dose-dependent decrease of plasma glucose was observed. However, a similar effect was not produced in normal rats. An insulin-independent action of caffeic acid can thus be considered. Otherwise, this compound reduced the elevation of plasma glucose level in insulin-resistant rats receiving a glucose challenge test. Also, glucose uptake into the isolated adipocytes was raised by caffeic acid in a concentration-dependent manner. Increase of glucose utilization by caffeic acid seems to be responsible for the lowering of plasma glucose.

title: Caffeic and chlorogenic acids inhibit key enzymes linked to type 2 diabetes (in vitro): a comparative study
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title: Effects of caffeic acid and cinnamic acid on glucose uptake in insulin-resistant mouse hepatocytes.
abstract: Tumor necrosis factor-alpha was used to induce insulin resistance of mouse liver FL83B cells. Two phenolic acids, caffeic acid and cinnamic acid, were then added separately to investigate their effects on glucose uptake of the insulin-resistant cells. The results suggest that these two phenolic acids may promote insulin receptor tyrosyl phosphorylation, up-regulate the expression of insulin signal associated proteins, including insulin receptor, phosphatidylinositol-3 kinase, glycogen synthase, and glucose transporter-2, increase the uptake of glucose, and alleviate insulin resistance in cells as a consequence.

title: Combination therapy: a new strategy to manage diabetes and its complications.
abstract: Diabetes mellitus is the most common metabolic disorder. The major cause of mortality and morbidity here is due to the complications caused by increased glucose concentrations. All the available commercial antidiabetic drugs are associated with side effects. The combination therapy could be a new and highly effective therapeutic strategy to manage hyperglycemia. Combination of commercial drugs with phytochemicals may reduce the side effects caused by these synthetic drugs. Herbal products have been thought to be inherently safe, because of their natural origin and traditional use rather than based on systemic studies. New formulation and cocrystallisation strategies need to be adopted to match the bioavailability of the drug and the phytochemical. This review describes in detail, the observed synergy and mechanism of action between phytochemicals and synthetic drugs in effectively combating. The mode of action of combination differs significantly than that of the drugs alone; hence isolating a single component may lose its importance thereby simplifying the task of pharma industries.

title: Effect of natural products on commercial oral antidiabetic drugs in enhancing 2-deoxyglucose uptake by 3T3-L1 adipocytes
abstract: The management of diabetes with insulin and synthetic oral hypoglycemic drugs (OHDs) can produce serious side effects and in addition fails to prevent diabetes-related complications in many patients. A new diabetes management strategy is needed that is more effective and has fewer side effects.  This paper analyzes the dose- and time-dependent effect of three phytochemicals: berberine, arecoline and vanillic acid, and two antidiabetic drugs: 2,4-thiazolidinedione (TZD) and metformin, on the uptake of 2-deoxyglucose (2DG) by 3T3-L1 adipocytes. The interactions of the phytochemicals with the OHDs were analyzed with isobolograms and the combination index.  TZD and berberine increased 2DG uptake by 3.3-fold (with respect to control) at 15 µM and 25 µM, respectively. The same concentrations of arecoline and vanillic acid increased 2DG uptake by 3.2-and 2.9-fold, respectively, when compared with the basal level. Berberine and arecoline acted synergistically with both the OHDs, whereas vanillic acid had an additive interaction with TZD and an antagonistic interaction with metformin. Arecoline significantly increased the translocation of GLUT4 via the PPARγ pathway, whereas berberine and vanillic acid did this via the AMPK-dependent pathway.  These phytochemicals significantly reduced the expression of the enzymes involved in fatty acid and cholesterol synthesis, indicating that they might help prevent the secondary complications of diabetes. The current study suggests that berberine and arecoline could allow dosage reduction of OHDs, which could also lead to a reduction in the toxicity and side effects caused by OHDs.

title: Pharmacotherapy of Type 2 Diabetes Mellitus: An Update on Drug–Drug Interactions
abstract: The incidence of type 2 diabetes mellitus is increasing rapidly, as are the associated co-morbidities. Consequently, it has become necessary for a diabetic patient to take multiple medications at the same time to delay progression of the disease. This can put patients at an increased risk of moderate to severe drug interactions, which may threaten patients’ life or may deteriorate the quality of their life. Hence, managing drug–drug interactions is the cornerstone of anti-diabetic therapy. Most of the clinically important drug–drug interactions of anti-diabetic agents are related to their metabolic pathways, but drugs that compete for renal excretion or impair renal status can also play an important role. In this review, we have examined the clinical implications and underlying mechanisms of drugs that are likely to alter the pharmacologic response of or cause adverse events with antidiabetic drugs, and we have outlined safe and efficacious treatment modalities.

title: Clinically and pharmacologically relevant interactions of antidiabetic drugs
abstract: Patients with type 2 diabetes mellitus often require multifactorial pharmacological treatment due to different comorbidities. An increasing number of concomitantly taken medications elevate the risk of the patient experiencing adverse drug effects or drug interactions. Drug interactions can be divided into pharmacokinetic and pharmacodynamic interactions affecting cytochrome (CYP) enzymes, absorption properties, transporter activities and receptor affinities. Furthermore, nutrition, herbal supplements, patient’s age and gender are of clinical importance. Relevant drug interactions are predominantly related to sulfonylureas, thiazolidinediones and glinides. Although metformin has a very low interaction potential, caution is advised when drugs that impair renal function are used concomitantly. With the exception of saxagliptin, dipeptidyl peptidase-4 (DPP-4) inhibitors also show a low interaction potential, but all drugs affecting the drug transporter P-glycoprotein should be used with caution. Incretin mimetics and sodium–glucose cotransporter-2 (SGLT-2) inhibitors comprise a very low interaction potential and are therefore recommended as an ideal combination partner from the clinical–pharmacologic point of view.

title: Natural Products for the Treatment of Type 2 Diabetes Mellitus.
abstract: Type 2 diabetes mellitus is a metabolic disease characterized by persistent hyperglycemia. High blood sugar can produce long-term complications such as cardiovascular and renal disorders, retinopathy, and poor blood flow. Its development can be prevented or delayed in people with impaired glucose tolerance by implementing lifestyle changes or the use of therapeutic agents. Some of these drugs have been obtained from plants or have a microbial origin, such as galegine isolated from Galega officinalis, which has a great similarity to the antidiabetic drug metformin. Picnogenol, acarbose, miglitol, and voglibose are other antidiabetic products of natural origin. This review compiles the principal articles on medicinal plants used for treating diabetes and its comorbidities, as well as mechanisms of natural products as antidiabetic agents. Inhibition of α-glucosidase and α-amylase, effects on glucose uptake and glucose transporters, modification of mechanisms mediated by the peroxisome proliferator-activated receptor, inhibition of protein tyrosine phosphatase 1B activity, modification of gene expression, and activities of hormones involved in glucose homeostasis such as adiponectin, resistin, and incretin, and reduction of oxidative stress are some of the mechanisms in which natural products are involved. We also review the most relevant clinical trials performed with medicinal plants and natural products such as aloe, banaba, bitter melon, caper, cinnamon, cocoa, coffee, fenugreek, garlic, guava, gymnema, nettle, sage, soybean, green and black tea, turmeric, walnut, and yerba mate. Compounds of high interest as potential antidiabetics are: fukugetin, palmatine, berberine, honokiol, amorfrutins, trigonelline, gymnemic acids, gurmarin, and phlorizin.

title: Houttuynia cordata extract increased systemic exposure and liver concentrations of metformin through OCTs and MATEs in rats
abstract: The synergistic activity of Houttuynia cordata ethanol extract (HCT) and metformin combination in diabetic rats has been previously reported, but the fundamental causes remain unsolved. Organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs) transport metformin to the liver and kidneys. Therefore, pharmacological activity and systemic exposure of metformin in HCT–metformin combination were determined from pharmacokinetic change and glucose‐lowering activity using in vitro HEK‐293 cells expressing human OCTs or human MATEs and in vivo rats. HCT inhibited human OCT2 and human MATE1‐mediated metformin transports in vitro. In in vivo rats, treatment with HCT and metformin for 28 days in rats (28MH rats) reduced the rat Oct2‐mediated renal excretion of metformin and thereby the increased systemic exposure of metformin compared with only metformin‐treated rats for 28 days (28M rats). In 28MH rats, rat Oct1‐mediated metformin uptake into the liver was enhanced, leading to an improved glucose‐lowering effect without hypoglycaemia compared with 28M rats. There was no impairment of renal function in HCT and metformin treatments. These results suggest that HCT–metformin combination therapy is applicable in terms of efficacy and safety.

title: Impact of traditional medicinal plant extracts on antiretroviral drug absorption.
abstract: ETHNOPHARMACOLOGICAL RELEVANCE
[corrected] Traditional herbal medicines are often used for the treatment of different diseases in developing countries, especially in the rural areas where a lack of an efficient primary health care system is usually experienced. Many patients infected with the human immunodeficiency virus are taking traditional herbal medicines in conjunction with their modern antiretroviral medication and drug-herb interactions can occur in these cases.



To investigate the effect of water extracts of two traditional medicinal plants, Hypoxis hemerocallidea and Sutherlandia frutescens as well as l-canavanine (a constituent of Sutherlandia frutescens) on the transport of nevirapine across human intestinal epithelial cells.



Nevirapine transport in the apical to basolateral and basolateral to apical directions across Caco-2 cell monolayers was determined alone (normal control) and in the presence of verapamil (positive control), water extracts of Hypoxis hemerocallidea and Sutherlandia frutescens and an aqueous solution of l-canavanine. The cumulative transport and apparent permeability coefficient (P(app)) values were calculated and compared.



Nevirapine alone was substantially effluxed in the basolateral to apical direction across the intestinal epithelial cell monolayers, which was statistically significantly (p < or = 0.05) decreased by addition of verapamil, Hypoxis hemerocallidea extract and the l-canavinine solution. The effect of Sutherlandia frutescens on nevirapine transport was not statistically significantly different from the control.



Hypoxis hemerocallidea and l-canavanine interact with the efflux of nevirapine across intestinal epithelial cells and therefore can potentially increase the bioavailability of this antiretroviral drug when taken concomitantly.

title: Effects of dietary chemopreventive phytochemicals on P-glycoprotein function.
abstract: The effects of dietary phytochemicals on P-glycoprotein function were investigated using human multidrug-resistant carcinoma KB-C2 cells and the fluorescent P-glycoprotein substrates daunorubicin and rhodamine 123. The effects of natural chemopreventive compounds, capsaicin found in chilli peppers, curcumin in turmeric, [6]-gingerol in ginger, resveratrol in grapes, sulforaphane in broccoli, 6-methylsulfinyl hexyl isothiocyanate (6-HITC) in Japanese horseradish wasabi, indole-3-carbinol (I3C) in cabbage, and diallyl sulfide and diallyl trisulfide in garlic, were examined. The accumulation of daunorubicin in KB-C2 cells increased in the presence of capsaicin, curcumin, [6]-gingerol, and resveratrol in a concentration-dependent manner. The accumulation of rhodamine 123 in KB-C2 cells was also increased, and the efflux of rhodamine 123 from KB-C2 cells was decreased by these phytochemicals. Sulforaphane, 6-HITC, I3C, and diallyl sulfide and diallyl trisulfide had no effect. These results suggest that dietary phytochemicals, such as capsaicin, curcumin, [6]-gingerol, and resveratrol, have inhibitory effects on P-glycoprotein and potencies to cause drug-food interactions.

title: Unexpected effect of concomitantly administered curcumin on the pharmacokinetics of talinolol in healthy Chinese volunteers
abstract: ObjectiveTo investigate the effect of concomitantly administered curcumin on the pharmacokinetics of the β1 adrenoceptor blocker talinolol. The study was conducted in a self-controlled, two-period experiment with a randomized, open-labeled design, using 12 healthy volunteers and a wash out period of 1 week between the administration of a single oral dose of 50 mg talinolol and the concomitant administration of curcumin (300 mg day−1 for 6 days) and a single oral dose of 50 mg talinolol on the seventh day. Concentrations of talinolol were measured in plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry. Non-compartmental analysis was used to characterize talinolol plasma concentration-time profiles, all pharmacokinetic parameters were calculated using DAS (ver. 2.0) software, and comparisons of mean values were analyzed by the Wilcoxon signed rank test. Differences were considered to be significant at p < 0.05 (two-sided test).Results The consumption of curcumin for 6 days reduced the area under the curve (AUC) from predose to infinity ($$ {\text{AUC}}_{{{\text{0}} - \infty }} $$) of talinolol from 1860.0 ± 377.9 to 1246.0 ± 328.2 ng.h mL−1, the highest observed concentration values (Cmax) were significantly decreased from 147.8 ± 63.8 to 106.4 ± 39.9 ng mL−1, and the CL/F was increased from 27.9 ± 5.5 to 43.1 ± 13.4 L.h−1 (p < 0.05). There was no significant difference in sampling time for Cmax (tmax) and elimination half-life (t1/2) values between the two periods (p > 0.05). The interindividual variability in AUC0–60 and Cmax of talinolol was comparable in two study periods; the coefficient of variance (CV) of AUC0–60 and Cmax was 26 and 40% after curcumin versus 21 and 43% after talinolol alone, respectively.ConclusionWe suggest that the reduced bioavailability of talinolol is most probably due to the low intraluminal curcumin concentration, or possibly due to the upregulation of further ATP-binding cassette transporters, such as MRP2, in different tissues.

title: Interaction of St John's wort with conventional drugs: systematic review of clinical trials
abstract: To determine the methodological quality of clinical trials that examined possible interactions of St John's wort with conventional drugs, and to examine the results of these trials. Characteristics of methods used in 22 reviewed studies Name and year Study design Herb assayed Control group Blinding  Sample size discussed Mathijssen, 20025 Before and after No No No No No Markowitz, 200016 Before and after Yes No No No No Burstein, 200014 Before and after Yes No No No No Durr, 200020 Before and after No No No No No Piscitelli, 200021 Before and after Yes No No No No Mai, 20037 Before and after Yes No No No Yes Hebert, 200423 Before and after Yes No No No No Bauer, 20036 Before and after Yes No No No Yes Hall, 20038 Before and after Yes No No No Yes Jiang, 200422 Before and after Yes No No Yes Yes Johne, 20024 Before and after Yes No No No Yes Wang, 200110 Before and after Yes No No No Yes Wang, 20029 Before and after Yes No No No No Markowitz, 200324 Before and after No No No No Yes Dresser, 200325 Before and after No No No No No Roby, 200111 Before and after Yes No No No No Wenk, 200412 Before and after No No No No No Sugimoto, 200115 Crossover No Yes (placebo) Yes Yes No Pfrunder, 200317 Crossover Yes Yes No Yes No Wang, 200418 Crossover No Yes (placebo) Yes Yes  No No No No Johne, 199913 Parallel Yes Yes (placebo) Yes No Yes   Electronic databases from inception to April 2004, reference lists from published reports, and experts in the field. Study selection Eligible studies were prospective clinical trials evaluating the pharmacokinetic effect of St John's wort on the metabolism of conventional drugs.  Two reviewers selected studies for inclusion and independently extracted data. Data synthesis 22 pharmacokinetic trials studied an average of 12 (SD 5) participants; 17 trials studied healthy volunteers and five studied patients. Most (17) studies used a “before and after” design; four studies used control groups other than the active group. Three studies randomised the sequence of administration or the participants to study arms or periods; three studies blinded participants or investigators. In 15 trials, investigators independently assayed the herb. Of 19 trials with available plasma data, three found no important interaction (change in area under the curve < 20%) and 17 found a decrease in systemic bioavailability of the conventional drug; in seven studies the 95% confidence interval excluded a decrease of < 20%.  Clinicians and patients should beware of possible decreases in the systemic bioavailability of conventional drugs when taken concomitantly with St John's wort.

title: Interactions between herbs and antidiabetics: an overview of the mechanisms, evidence, importance, and management
abstract: Complementary and alternative therapies are quickly gaining importance because they are perceived to be free of side effects due to their natural origin. However, herbal remedies are complex mixtures of bioactive entities, which may interact with prescription drugs through pharmacokinetic or pharmacodynamic mechanisms and sometimes result in life-threatening consequences. In particular, diabetes patients are often treated with multiple medications due to different comorbidities, and such patients use antidiabetic medications for their entire lives; thus, it is important to make the public aware of herb interactions with antidiabetic drugs. In this paper, we summarize the reports available on the interaction of herbal remedies with oral hypoglycemic agents and describe mechanisms, preclinical or clinical evidence, importance, and management strategies.

title: Formulation and statistical analysis of an herbal medicine tablet containing Morus alba leaf extracts
abstract: It has reported that Morus alba has properties to treat fever, protect liver damage, improve eyesight, strengthen the joint, facilitate discharge of urine, and prevent high blood pressure. Extracts from herbal plants, have hygroscopic and low flowability characteristics. Due to these properties, it is difficult to develop the formulation using herbal extracts in pharmaceutics. In this study, Morus alba leaf extract (MLE) was fermented by Viscozyme® (MLE-V) and Pectinex® (MLE-P) as well as non-fermented MLE (MLE-C). Physicochemical properties of MLEs were evaluated for optimization of formulation. As a result, cell viability was higher MLE-V than MLE-P, although there was no difference in flowability depending on the enzyme type. Based on the pre-formulation study, MLE-V was selected. Wet granulation method was used to overcome the poor flowability of MLE and MLE tablet was developed by statistical-based experimental design method. A Box-Behnken design, one of the models of experimental design, was constructed using lactose content in lactose plus microcrystalline cellulose (X1), disintegration agent (X2), and binding agent (X3). The dependent variables were hardness (Y1), friability (Y2), and disintegration time (Y3). Finally, MLE tablet with hardness (11.83 ± 0.36 Kp), friability (0.26 ± 0.01%) and disintegration time (1395.56 ± 49.84 s) were optimized. This is the first work to report the formulation design using herbal extracts fermented with enzyme through quality by design.

title: Effects of unaltered and bioconverted mulberry leaf extracts on cellular glucose uptake and antidiabetic action in animals
abstract: BackgroundMulberry is a Korean medicinal herb that shows effective prevention and treatment of obesity and diabetes. Bioconversion is the process of producing active ingredients from natural products using microorganisms or enzymes.MethodsIn this study, we prepared bioconverted mulberry leaf extract (BMLE) with Viscozyme L, which we tested in insulin-sensitive cells (i.e., skeletal muscle cells and adipocytes) and insulin-secreting pancreatic β-cells, as well as obese diabetic mice induced by co-administration of streptozotocin (100 mg/kg, IP) and nicotinamide (240 mg/kg, IP) and feeding high-fat diet, as compared to unaltered mulberry leaf extract (MLE).ResultsBMLE increased the glucose uptake in C2C12 myotubes and 3 T3-L1 adipocytes and increased glucose-stimulated insulin secretion in HIT-T15 pancreatic β-cells. The fasting blood glucose levels in diabetic mice treated with BMLE or MLE (300 and 600 mg/kg, PO, 7 weeks) were significantly lower than those of the vehicle-treated group. At the same concentration, BMLE-treated mice showed better glucose tolerance than MLE-treated mice. Moreover, the blood concentration of glycated hemoglobin (HbA1C) in mice treated with BMLE was lower than that in the MLE group at the same concentration. Plasma insulin levels in mice treated with BMLE or MLE tended to increase compared to the vehicle-treated group. Treatment with BMLE yielded significant improvements in insulin resistance and insulin sensitivity.ConclusionThese results indicate that in the management of diabetic condition, BMLE is superior to unaltered MLE due to at least, in part, high concentrations of maker compounds (trans-caffeic acid and syringaldehyde) in BMLE.

title: CYP2C metabolism of oral antidiabetic drugs - impact on pharmacokinetics, drug interactions and pharmacogenetic aspects
abstract: The cytochrome P4502C enzymes account for the metabolism of approximately 20% of therapeutic drugs including certain oral antidiabetic drugs (OADs).  This review focuses on the effect of CYP2C enzymes on metabolism of sulphonylureas (SUs), meglitinides, and thiazolidinediones (TZDs) discussing their impact on pharmacokinetics, drug interactions and toxicological profiles. Pharmacogenetic aspects reflecting individual gene variants and variable drug effects are also considered.  Genetic polymorphisms of CYP2C9 enzymes (*2/*2, *2/*3, *3/*3) influence the glycaemic response to SUs and impair their substrate metabolism. Restricted data from small-sized studies with heterogenous definitions of hypoglycaemia revealed no clear association between CYP2C9 genotypes and the risk of hypoglycaemia. Functional polymorphisms of CYP2C8- and CYP2C9 drug metabolizing genes affect markedly pharmacokinetics of meglitinides. Compared to wild-type carriers, patients treated with TZDs and carrying the common CYP2C8*3 and *4 variants showed a reduced glycaemic control. The strong CYP2C8 and OATP1B1 inhibitor gemfibrozil increases substantially the plasma concentrations of repaglinide and TZDs. Numerous metabolic drug interactions exist between SUs and commonly prescribed drugs, especially anti-infectives. The complex pharmacokinetic and pharmacogenetic properties and the unfavourable short and long term risk profile of glibenclamide and glimepiride raise the question whether their use can be justified any longer.

title: Dose-independent pharmacokinetics of metformin in rats: Hepatic and gastrointestinal first-pass effects.
abstract: Pharmacokinetic parameters of metformin were evaluated after intravenous and oral administration (50, 100, and 200 mg/kg) in rats. The hepatic, gastric, and intestinal first-pass effects were also measured after intravenous, intraportal, intragastric, and intraduodenal administration (100 mg/kg) in rats. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) values were dose-proportional after both intravenous and oral dose ranges studied. After oral administration (100 mg/kg), approximately 4.39% of oral dose was not absorbed and extent of absolute oral bioavailability (F) value was approximately 29.9%. The gastrointestinal first-pass effect of metformin was approximately 53.8% of oral dose in rats (the gastric and intestinal first-pass effects were approximately 23.1 and 30.7%, respectively), and the hepatic first-pass effect was approximately 27.1% after absorption into the portal vein. Since approximately 41.8% of oral metformin was absorbed into the portal vein, the value of 27.1% is equivalent to 11.3% of oral dose. The first-pass effects of metformin in the lung and heart were almost negligible in rats. The low F value of metformin in rats was mainly due to considerable gastrointestinal first-pass effects. The stability of metformin, distribution of metformin between plasma and blood cells, and factors affecting protein binding of metformin to 4% human serum albumin were also discussed.

title: Metformin pathways: pharmacokinetics and pharmacodynamics
abstract: Departments of Genetics, Bioengineering, Stanford University Medical Center, Stanford University, Stanford and Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, USA Correspondence to Teri E. Klein, PhD, Department of Genetics, Stanford University Medical Center, Stanford University, 1501 California Ave, Palo Alto, CA 94304, USA Tel: + 1 650 725 0659; fax: + 1 650 725 3863;

title: Reference Data of the Main Physiological Parameters in Control Sprague-Dawley Rats from Pre-clinical Toxicity Studies
abstract: The purpose of this paper is to provide reference data related to the body weight, food & water consumptions, urinalysis, hematology and serum biochemistry parameters and absolute & relative organ weights obtained from control Sprague-Dawley rats, used in the 4-week and 13-week repeated-dose toxicity studies conducted in our laboratory between 2005 and 2008. The mean, standard deviation, minimum and maximum range values for hematology and serum biochemistry parameters, data of absolute & relative organ weights, and the difference between sexes and study duration of week 4 versus 13 week are presented. The studies were conducted according to “the standards of Toxicity Study for Medicinal Products” (2005) and The KFDA Notification No. 2000-63 ‘Good Laboratory Practice (GLP)’ (2000) issued by KFDA. These data could be used as reference material of Sprague-Dawley rats by conducting the studies to evaluate the toxicological profile of pre-clinical toxicity studies.

title: Effects of dietary mulberry, Korean red ginseng, and banaba on glucose homeostasis in relation to PPAR-α, PPAR-γ, and LPL mRNA expressions
abstract: Despite lack of scientific evidences to support its therapeutic efficacy, the use of herbal supplements has significantly increased. The purpose of this study was to evaluate the effects of traditional anti-diabetic herbs on the progress of diabetes in db/db mice, a typical non-insulin-dependent model. Five different experimental diets were as follows: control diet, 0.5% mulberry leaf water extract diet, 0.5% Korean red ginseng diet, 0.5% banaba leaf water extract diet, and 0.5% combination diet (mulberry leaf water extract/Korean red ginseng/banaba leaf water extract, 1:1:1). Blood levels of glucose, insulin, HbA1c, and triglyceride were measured every 2 weeks. At 12 weeks of age, animals were sacrificed, and tissue mRNA levels of PPAR-alpha, PPAR-gamma, and LPL were determined. Results indicated that mulberry leaf water extract, Korean red ginseng, banaba leaf water extract, and the combination of above herbs effectively reduced blood glucose, insulin, TG, and percent HbA1c in study animals (p<0.05). We also observed that the increased expressions of liver PPAR-alpha mRNA and adipose tissue PPAR-gamma mRNA in animals fed diets supplemented with test herbs. The expression of liver LPL mRNA was also increased with experimental diets containing herbs. The efficacy was highest in animals fed the combination diet for all of the markers used. These results suggest that mulberry leaf water extract, Korean red ginseng, banaba leaf water extract, and the combination of these herbs fed at the level of 0.5% of the diet significantly increase insulin sensitivity, and improve hyperglycemia possibly through regulating PPAR-mediated lipid metabolism.

title: Gluconeogenic substrates and hepatic gluconeogenic enzymes in streptozotocin-diabetic rats: effect of mulberry (Morus indica L.) leaves.
abstract: Mulberry (Morus indica L.) leaves, the sole food of the silk worm, were evaluated for antidiabetic effects in streptozotocin (STZ)-diabetic rats. Treatment with dried mulberry leaf powder at 25% of the diet for a period of 8 weeks was found to be remarkably beneficial to STZ-diabetic rats as evidenced by controlled hyperglycemia and glycosuria. In addition, mulberry leaves countered (reversed) the alterations in gluconeogenic substrates in STZ-diabetic rats as indicated by significant reduction in serum pyruvic and lactic acid levels, a significant increase in proteins and a significant decrease in free amino acid, urea, and creatinine levels in blood, and a decreased urinary excretion of urea and creatinine. Anomalies in the activities of hepatic gluconeogenic enzymes associated with impaired glucose homeostasis in STZ-diabetic rats were ameliorated by feeding the mulberry leaf-supplemented diet, indicating that control over hyperglycemia and associated complications in the diabetic state by mulberry leaves is by way of regulation of gluconeogenesis. With respect to all the parameters, mulberry leaves were more effective than the oral hypoglycemic drug glibenclamide.

title: Inhibitory effects of mulberry leaf extract on postprandial hyperglycemia in normal rats.
abstract: We examined the inhibitory effects of aqueous ethanol extract from mulberry leaves (ME) on postprandial hyperglycemia in normal Wistar rats. ME dose-dependently suppressed the postprandial rise of blood glucose in rats, when ME (0.02-0.5 g/kg) was given 0.5 h before the administration of carbohydrates such as sucrose, maltose and starch. The ME dose showing 50% inhibition of the increment of blood glucose (ED50) was 0.11 g/kg for sucrose, 0.44 g/kg for maltose, and 0.38 g/kg for starch. ME and its basic fraction (MB) containing 1-deoxynojirimycin were assayed for their inhibitory effects (IC50) on disaccharidase derived from the small intestine of rats. The IC50 value of ME was 3.2 microg/mL for sucrase, 10 microg/mL for isomaltase, and 51 microg/mL for maltase. The IC50 value of MB was 0.36 microg/mL for sucrase, 1.1 microg/mL for isomaltase, and 6.2 microg/mL for maltase. The IC50 value of 1-deoxynojirimycin as the principle component in ME was 0.015 microg/mL for sucrase and 0.21 microg/mL for maltase, and this value was comparable to the IC50 of voglibose. The inhibitory activity of ME in a-amylase was weak. These results suggest that ME strongly suppresses postprandial hyperglycemia after carbohydrate loading by inhibiting the activity of disaccharidases in the small intestine of rats.

title: Chlorogenic Acid: Recent Advances on Its Dual Role as a Food Additive and a Nutraceutical against Metabolic Syndrome
abstract: Chlorogenic acid (5-O-caffeoylquinic acid) is a phenolic compound from the hydroxycinnamic acid family. This polyphenol possesses many health-promoting properties, most of them related to the treatment of metabolic syndrome, including anti-oxidant, anti-inflammatory, antilipidemic, antidiabetic, and antihypertensive activities. The first part of this review will discuss the role of chlorogenic acid as a nutraceutical for the prevention and treatment of metabolic syndrome and associated disorders, including in vivo studies, clinical trials, and mechanisms of action. The second part of the review will be dealing with the role of chlorogenic acid as a food additive. Chlorogenic acid has shown antimicrobial activity against a wide range of organisms, including bacteria, yeasts, molds, viruses, and amoebas. These antimicrobial properties can be useful for the food industry in its constant search for new and natural molecules for the preservation of food products. In addition, chlorogenic acid has antioxidant activity, particularly against lipid oxidation; protective properties against degradation of other bioactive compounds present in food, and prebiotic activity. The combination of these properties makes chlorogenic acid an excellent candidate for the formulation of dietary supplements and functional foods.

title: Effects of dosage and dosing frequency on the efficacy and safety of high‐dose metformin in Japanese patients with type 2 diabetes mellitus
abstract: Differences in the efficacy and safety of antidiabetic drugs among different ethnic groups are well documented. Metformin is widely used in the treatment of type 2 diabetes in Western countries, but high doses of metformin have been approved only recently for clinical use in Japan. The aim of the present study was to investigate the effects of dosage and dosing frequency on the efficacy and safety of high‐dose metformin in Japanese patients.

title: Effect of genetic variation in the organic cation transporter 1 (OCT1) on metformin action.
abstract: Metformin is among the most widely prescribed drugs for the treatment of type 2 diabetes. Organic cation transporter 1 (OCT1) plays a role in the hepatic uptake of metformin, but its role in the therapeutic effects of the drug, which involve activation of AMP-activated protein kinase (AMPK), is unknown. Recent studies have shown that human OCT1 is highly polymorphic. We investigated whether OCT1 plays a role in the action of metformin and whether individuals with OCT1 polymorphisms have reduced response to the drug. In mouse hepatocytes, deletion of Oct1 resulted in a reduction in the effects of metformin on AMPK phosphorylation and gluconeogenesis. In Oct1-deficient mice the glucose-lowering effects of metformin were completely abolished. Seven nonsynonymous polymorphisms of OCT1 that exhibited reduced uptake of metformin were identified. Notably, OCT1-420del (allele frequency of about 20% in white Americans), previously shown to have normal activity for model substrates, had reduced activity for metformin. In clinical studies, the effects of metformin in glucose tolerance tests were significantly lower in individuals carrying reduced function polymorphisms of OCT1. Collectively, the data indicate that OCT1 is important for metformin therapeutic action and that genetic variation in OCT1 may contribute to variation in response to the drug.

title: The effect of the ingestion of Ginkgo biloba extract (EGb 761) on the pharmacokinetics of metformin in non-diabetic and type 2 diabetic subjects--a double blind placebo-controlled, crossover study.
abstract: Ginkgo biloba extract (EGb 761) has been shown to ameliorate some defects associated with the insulin resistance syndrome and so patients with Type 2 diabetes mellitus (T2DM) may be inclined to co-ingest the herb with their medications, such as metformin. This study was designed to determine if the co-ingestion of EGb 761 and metformin would alter the pharmacokinetic properties of metformin in T2DM patients and persons without diabetes, who may ingest it for other purposes.



Normal glucose tolerance (NGT) subjects (n=10; age, 39.2+/-14.0 years; fasting plasma glucose (FPG), 90+/-7 mg/dl; body mass index (BMI), 24.1+/-3.7 kg/m(2)) and 10 T2DM patients (n=10; age, 51.7+/-8.9 years; FPG, 150+/-7 mg/dl; BMI, 33.7+/-5.7 kg/m(2)) completed a randomized, double-blind, placebo-controlled crossover study. They ingested either EGb 761 (12 0mg/day as a single dose) or a vegetable-based placebo during each arm for 3 months. At the end of each arm, the NGT subject ingested a single 500 mg dose of metformin (non-diabetics) and the T2DM subject took his/her prescribed metformin dose (250-850 mg) with 120 mg EGb 761. Blood and urine samples were collected over an 8-h period, and in the case of T2DM subjects, additionally over the first 2h of the subsequent 3 days.



Ingestion of EGb 761 produced no significant changes in diagnostic laboratory tests in either group, except reducing glycosylated hemoglobin A(1c) levels (from 7.7+/-1.2 to 7.2+/-0.9%, P<0.05) in T2DM the subjects. The pharmacokinetic parameters of metformin were all significantly different (P<0.05) between the NGT (500 mg) and 8 out of 10 of the T2DM subjects who were prescribed 500 mg of metformin during the placebo cycles. During the EGb 761 cycles, only the elimination half-life in the T2DM subjects was significantly increased (0.117+/-0.085 to 0.141+/-0.100, P<0.05).



The co-ingestion of 120 mg of EGb 761 and 500 mg of metformin did not significantly affect the pharmacokinetic properties of metformin. Further studies are required to verify this observation for smaller and larger dose of metformin with other doses of EGb 761, since T2DM patients on medication constitute a very heterogeneous group.

title: Influences of Re Du Ning Injection, a traditional Chinese medicine injection, on the CYP450 activities in rats using a cocktail method.
abstract: ETHNOPHARMACOLOGICAL RELEVANCE
Re Du Ning Injection (RDN), a traditional Chinese medicine injection, is made from the extracts of Lonicerae japonicae flos (LJF), Artemisiae annuae herba (AAH) and Gardeniae fructus (GF). Since last decade, RDN has been widely used in China for the treatment of fever, inflammation, allergy and viral infection.



To elucidate the potential influences of RDN on the activities of four cytochrome P450 (CYP) isozymes in rats (CYP1A2, CYP2C11, CYP2D1 and CYP3A1/2) by "cocktail method".



A sensitive and specific LC-MS method capable of simultaneous quantification of four substrates and their metabolites in rat plasma was developed and validated. Relative activity estimation of four isozymes was carried out by comparing plasma pharmacokinetics of substrates and their metabolites (phenacetin/ paracetamol for CYP1A2, tolbutamide/4-hydroxytolbutamide for CYP2C11, dextromethorphan/ dextrorphan for CYP2D1 and dapsone/N-acetyl dapsone for CYP3A1/2) between control and RDN treatment groups.



Compared with control group, RDN at different levels could increase the total amount of tolbutamide, dextromethorphan and dapsone absorbed into blood, while decrease the total amount of phenacetin absorbed into blood at low and medium dosage and increase it at high dosage.



RDN could inhibit the activities of CYP2C11, CYP2D1 and CYP3A1/2, induce the activity of CYP1A2 at low and medium dosage but inhibit it at high dosage. The results indicated that drug co-administrated with RDN may need dose adjustment.

title: Inhibition of Re Du Ning Injection on Enzyme Activities of Rat Liver Microsomes Using Cocktail Method
abstract: Re Du Ning Injection (RDN), a Chinese materia medica injection, is made from the extracts of Lonicerae Japonicae Flos, Gardeniae Fructus, and Artemisiae Annuae Herba. Since last decade, RDN has been widely used in China for the treatment of viral infection, fever, and inflammation. To assess the potential interacting of RDN with co-administered drugs, the inhibitory effects of RDN on the enzyme activities (CYP1A1, CYP1A2, CYP2C11, CYP2D1, and CYP3A1/2) of rat liver microsomes were investigated by a cocktail method.  A sensitive and specific LC-MS method capable of simultaneous quantification of five metabolites in rat liver microsomes was developed and validated. Then RDN (0.625%–1.0%) was incubated with rat liver microsomes and specific substrates. The enzyme activities were expressed as the formation rate of the specific metabolites of the substrates (pmol · mg · protein −1 · min −1 ).  RDN competitively inhibited the activities of CYP1A2 and CYP2C11, with inhibition constant ( K i ) values determined to be 0.18% and 0.63%, respectively. RDN exhibited the mixed inhibition on the activity of CYP2D1, with a K i value of 0.15%. The activities of CYP1A1 and CYP3A1/2 were not markedly inhibited even by 1.0% RDN.  RDN could inhibit the rat enzyme activities of CYP1A2, 2C11, and 2D1 in vitro with different inhibition modes, which is worthy of promoting safety and efficacy of RDN.