The effect of 3-month ingestion of Ginkgo biloba extract (EGb 761) on pancreatic beta-cell function in response to glucose loading in individuals with non-insulin-dependent diabetes mellitus

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

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

Traversing through half a century research timeline on Ginkgo biloba, in transforming a botanical rarity into an active functional food ingredient

Neurodegenerative diseases and various other chronic ailments have gradually transformed into public-health issues. Neurodegenerative disorders are a range of progressive neural abnormalities characterized by cellular dysfunctions, neuronal structure, and function loss. Among many chronic disorders, oxidative stress, inflammation, mitochondrial dysregulation, and cellular alterations in the human body are considered the most prevalent diagnostic symptoms. They have a profound impact on patients' health and wellbeing. The disease's poor curability, high healthcare costs, and lethality are the principal reasons for approaching and exploring the conventional treatment's phytotherapeutic alternatives. Ginkgo biloba (Maidenhair tree) is a well-known and widely used herbal plant in the Ginkgoaceae family. Its phytochemical constituents, Flavonoids, and terpenes, have been identified as the primary ingredients of Ginkgo biloba leaf extracts. It has been widely used due to its therapeutic properties, including its neuroprotective, anti-dementia, antioxidant, anti-inflammatory, vasoactive, anti-psychotic, anti-neoplastic, and anti-platelet activity. In recent decades, plenty of Ginkgo-derived substances has been researched and elucidated to have significant therapeutic effects in numerous disease models. This review aims to provide a thorough understanding of the botanical basis for Ginkgo biloba, its usage as herbal medicine, and its pivotal role in functional foods. Additionally, the clinical significance of Ginkgo biloba, as observed in various research works and clinical investigations, is also emphasized, facilitating a better understanding of their molecular basis and application in many chronic diseases.

Antidiabetics Interactions with Herbs: A Compressive Review

Diabetes mellitus is a chronic illness with a variety of causes and pathophysiology. For the management of diabetes, various synthetic antidiabetic drugs are available. Still, people prefer complementary and alternative therapies as well as traditional herbal home remedies because they are perceived to be free of side effects and generally recognized as safe due to their natural origin. Hence, worldwide, the majority of the population is consuming herbs and/or herbal products in their daily routine. It has been observed that individuals with diabetes also consume herbs/herbal products either with or without medical supervision. This co-consumption of antidiabetic medications and herb/herbal products may result in herb-drug interactions, which might be potentially beneficial or harmful or, in some cases, even fatal. Most of the times, these interactions remain unnoticed or undiagnosed due to lack of knowledge and awareness about them. In this review, the authors have summarized some important aspects related to the herb-drug interaction (HDI), which include methods for prediction and mechanism of HDI (pharmacokinetic and pharmacodynamic) and also the clinical and experimental literature on herb-drug interactions (HDI) in the treatment of diabetes. Authors have attempted to categorize the interactions between oral hypoglycemic agents and various herbs as beneficial or harmful based on the results reported in the original research work.

Herb-drug interactions in diabetes mellitus: A review based on pre-clinical and clinical data

Global diabetes epidemic is the major cause of fatality and lethality. As per IDF 2019 report, diabetes caused 4.2 million deaths, approximately 463 million people are living with diabetes and by 2045, this will rise to 700 million. Nowadays, the physicians and common people in both developed and developing countries are using medicinal plants and their formulations to treat diseases with the postulation that organic commodities are safe for consumption. These plants may act as inhibitors or inducers of the Cytochrome P450 or transport and efflux proteins or both and may alter gastrointestinal, renal functions leading to Herb-Drug Interactions. This review intends to focus on the frequently employed medicinal plants, their traditional uses, their Cytochrome P450 inhibition or induction activity, phytochemical, and pharmacological effects, established HDI with the help of in vitro tools, in vivo pharmacokinetics and pharmacodynamics studies to understand the impact of herbs on ADME of the drug and whether it is beneficial, harmful or has no effect respectively. This review will help the physicians and other health care professionals as a reference guide to update their knowledge and expertise about HDI. However, more quality research in this area is needed to evaluate the efficacy of many herbal medicines, thereby reducing side effects and improving the safety of patients.

Effects of Ginkgo biloba intake on cardiometabolic parameters in patients with type 2 diabetes mellitus: A systematic review and meta-analysis of clinical trials

Ginkgo biloba (GKB) may have a beneficial effect on cardiometabolic parameters in type 2 diabetes mellitus (T2DM), but the data is inconsistent. Therefore, the current systematic review and meta-analysis of clinical trials was conducted to assess the influence of GKB on cardiometabolic parameters in T2DM. Several online databases such as PubMed, Embase, Scopus, Web of Sciences, Google Scholar and Cochrane Library were systematically searched from inception up to September 2, 2019. Heterogeneity across included studies was assessed using the Cochran's Q statistic and I2 index. To pool weighted mean differences (WMDs) and the corresponding 95% confidence intervals (CIs) as summary effect size, we selected fixed or random-effects model according to the result of heterogeneity. Seven studies comprising 768 subjects were included in the present meta-analysis which resulted in a significant effect of GKB on hemoglobin A1c (HbA1c) (WMD = 0.26, 95% CI = [0.02, 0.50], p = .034) and serum HDL-cholesterol levels (WMD = 1.99, 95% CI = [0.19, 3.79], p = .030) with no significant publication bias. GKB can significantly modulate HbA1c and HDL-cholesterol levels. However, due to uncertainties related to the limited number of studies, it is too early to conclude whether GKB has any potential effects on the cardiometabolic factors in patients with T2DM or not.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.

Efficacy and safety of Ginkgo biloba extract as an "add-on" treatment to metformin for patients with metabolic syndrome: a pilot clinical study

Background and aim

Ginkgo biloba (GKB) extract has shown to be beneficial in experimental models of metabolic and inflammatory disorders such as diabetes and metabolic syndrome (MTS). The objective of this pilot clinical study was to evaluate the effects of GKB extract as an “add-on” treatment with metformin (Met) in MTS patients.

Patients and methods

We performed a randomized, placebo-controlled, double-blinded clinical study in subjects with MTS. Forty patients completed the 90-day clinical trial and were randomly allocated to administer either GKB extract (120 mg capsule/day) or placebo (120 mg starch/day) as an add-on treatment with their currently used doses of Met for 90 days. During the study, body mass index (BMI), waist circumference (WC), serum leptin, glycated hemoglobin (HbA1c), fasting serum glucose (FSG), insulin, insulin resistance (IR), visceral adiposity index (VAI), lipid profile, and the inflammatory markers high sensitive C-reactive protein (hsCRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were evaluated.

Results

GKB extract significantly decreases HbA1c, FSG and insulin levels, IR, BMI, WC, VAI, serum leptin, and the inflammatory markers compared to baseline values. Simultaneously, GKB did not negatively affect the functions of the liver, kidney, and hematopoietic system.

Conclusion

The use of GKB extract as an adjuvant with Met was effective in improving the outcome of patients with MTS.

Regulation of hepatic energy metabolism by the nuclear receptor PXR

The pregnane X receptor (PXR) is a nuclear receptor that is traditionally thought to be specialized for sensing xenobiotic exposure. In concurrence with this feature PXR was originally identified to regulate drug-metabolizing enzymes and transporters. During the last ten years it has become clear that PXR harbors broader functions. Evidence obtained both in experimental animals and humans indicate that ligand-activated PXR regulates hepatic glucose and lipid metabolism and affects whole body metabolic homeostasis. Currently, the consequences of PXR activation on overall metabolic health are not yet fully understood and varying results on the effect of PXR activation or knockout on metabolic disorders and weight gain have been published in mouse models. Rifampicin and St. John's wort, the prototypical human PXR agonists, impair glucose tolerance in healthy volunteers. Chronic exposure to PXR agonists could potentially represent a risk factor for diabetes and metabolic syndrome. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

The Use of Complementary and Alternative Medicine in Hospitalized Patients with Type 2 Diabetes Mellitus in Israel

INTRODUCTION

The use of complementary and alternative medicine (CAM) has been on the rise in recent years in the general population, as well as among patients with chronic diseases such as diabetes mellitus. The aim of this study was to add information regarding the use of CAM in patients with type 2 diabetes mellitus (DM2) in Israel and explore possible interactions between CAM and prescription medication (PM).

METHODS

This is a cross-sectional study based on questionnaires. The study included type 2 diabetic patients who were hospitalized in an internal medicine department at Assaf Harofeh Medical Center, Zerifin, Israel, between December 2013 and December 2014. Possible interactions between CAM and PM were evaluated by a clinical pharmacist and a clinical pharmacologist.

RESULTS

Out of 111 diabetic patients, 23.4% used CAM. There was no significant difference between the consumers and nonconsumers in terms of age, education, income, smoking, or alcohol habits. Only 11 of the 26 CAM consumers informed their physician regarding the use. We found possible drug-herb interactions in 19 of the 26 CAM consumers. A major interaction was found between omega-3 and antiaggregants and was encountered in 7 (26.9%) of the CAM consumers. Other minor and major interactions were found with vitamin E, ginkgo-biloba, co-enzyme Q10, green tea, fenugreek seeds, pyridoxine, and dandelion.

CONCLUSIONS

Since CAM consumption is on the rise, it is desirable to improve our knowledge concerning their potential effects and adverse effects, especially in conjunction with PM. Given the complexity of pharmaceutics in patients with chronic diseases, among them patients with DM, the use of supplementary medicine cannot be ignored.

The Effect of Ginkgo biloba and Camellia sinensis Extracts on Psychological State and Glycemic Control in Patients with Type 2 Diabetes Mellitus

Interest in finding natural antioxidants for use in food or medical materials to prevent free radical imbalance has increased considerably over the past years. The aim of this research was to evaluate changes in glycemic control and psychological state of patients with type 2 diabetes mellitus (T2DM) after use of antioxidant plant preparations. Fifty-six patients with T2DM were randomly allocated to receive standardized Ginkgo biloba L. leaves dry extract, green tea dry extract, or placebo capsules. Diabetes glycemic control measured as glycated hemoglobin (HbA1c) level, antioxidant state and psychological data were evaluated at baseline, after 9 and 18 months of using either antioxidant preparations or placebo. The level of perceived stress lowered significantly after 9 months ( p=0.038) and 18 months ( p=0.030), and the psychological aspect of quality of life significantly improved after 18 months ( p=0.019) of use of G. biloba extract. No significant differences were detected after using green tea extract. In patients using placebo, significant lowering of HbA1c level was observed after 18 months ( p=0.017). In conclusion, antioxidant G. biloba leaf extract exhibited a mild effect on psychological state and a trend of improving glycemic control in patients with type 2 diabetes mellitus.

Beneficial effects of Ginkgo biloba extract on insulin signaling cascade, dyslipidemia, and body adiposity of diet-induced obese rats

Ginkgo biloba extract (GbE) has been indicated as an efficient medicine for the treatment of diabetes mellitus type 2. It remains unclear if its effects are due to an improvement of the insulin signaling cascade, especially in obese subjects. The aim of the present study was to evaluate the effect of GbE on insulin tolerance, food intake, body adiposity, lipid profile, fasting insulin, and muscle levels of insulin receptor substrate 1 (IRS-1), protein tyrosine phosphatase 1B (PTP-1B), and protein kinase B (Akt), as well as Akt phosphorylation, in diet-induced obese rats. Rats were fed with a high-fat diet (HFD) or a normal fat diet (NFD) for 8 weeks. After that, the HFD group was divided into two groups: rats gavaged with a saline vehicle (HFD+V), and rats gavaged with 500 mg/kg of GbE diluted in the saline vehicle (HFD+Gb). NFD rats were gavaged with the saline vehicle only. At the end of the treatment, the rats were anesthetized, insulin was injected into the portal vein, and after 90s, the gastrocnemius muscle was removed. The quantification of IRS-1, Akt, and Akt phosphorylation was performed using Western blotting. Serum levels of fasting insulin and glucose, triacylglycerols and total cholesterol, and LDL and HDL fractions were measured. An insulin tolerance test was also performed. Ingestion of a hyperlipidic diet promoted loss of insulin sensitivity and also resulted in a significant increase in body adiposity, plasma triacylglycerol, and glucose levels. In addition, GbE treatment significantly reduced food intake and body adiposity while it protected against hyperglycemia and dyslipidemia in diet-induced obesity rats. It also enhanced insulin sensitivity in comparison to HFD+V rats, while it restored insulin-induced Akt phosphorylation, increased IRS-1, and reduced PTP-1B levels in gastrocnemius muscle. The present findings suggest that G. biloba might be efficient in preventing and treating obesity-induced insulin signaling impairment.

Ginkgo biloba Extract for Patients with Early Diabetic Nephropathy: A Systematic Review

Objectives. To evaluate the effectiveness and safety of a Ginkgo biloba extract for patients with early diabetic nephropathy. Methods. Randomised controlled trials (RCTs) conducted on adults with early diabetic nephropathy which used Gingko biloba extract were included. The major databases were searched, and manufacturers of Gingko biloba products were contacted for information on any published or unpublished studies. Two authors independently extracted the data from the included studies. Data analysis was conducted using Review Manager 5.0 software. Results. Sixteen RCTs were included. Ginkgo biloba extract decreased the urinary albumin excretion rate (UAER), fasting blood glucose (FBG), serum creatinine (SCR), and blood urea nitrogen (BUN). The extract also improved hemorheology. The methodological quality in the included studies was low. The explicit generation of the allocation sequence was described in only 6 trials. None of the included trials were confirmed to use blinding. Three studies had observed adverse events. One study using angiotensin-converting enzyme inhibitor (ACEi) reported mild cough in both groups. No serious adverse effects were reported. Conclusions. Gingko biloba extract is a valuable drug which has prospect in treating early diabetic nephropathy, especially with high UAER baseline level. The safety for early diabetic nephropathy is uncertain. Long-term, double-blinded RCTs with large sample sizes are still needed to provide stronger evidence.

Antihyperglycemic effect of Ginkgo biloba extract in streptozotocin-induced diabetes in rats

The Ginkgo biloba extract (GBE) has been reported to have a wide range of health benefits in traditional Chinese medicine. The aim of this study was to evaluate the antihyperglycemic effects of GBE on streptozotocin- (STZ-) induced diabetes in rats. Diabetes was induced in male Wistar rats by the administration of STZ (60 mg/kg b.w.) intraperitoneally. GBE (100, 200, and 300 mg/kg b.w.) was administered orally once a day for a period of 30 days. Body weight and blood glucose levels were determined in different experimental days. Serum lipid profile and antioxidant enzymes in hepatic and pancreatic tissue were measured at the end of the experimental period. Significant decreases in body weight and antioxidant ability and increases in blood glucose, lipid profile, and lipid peroxidation were observed in STZ-induced diabetic rats. The administration of GBE and glibenclamide daily for 30 days in STZ-induced diabetic rats reversed the above parameters significantly. GBE possesses antihyperglycemic, antioxidant, and antihyperlipidemia activities in STZ-induced chronic diabetic rats, which promisingly support the use of GBE as a food supplement or an adjunct treatment for diabetics.

Interaction of herbs and glibenclamide: a review

Herbs and herbal products are considered to be safer and people mix it often with the oral hypoglycemic agent in diabetes therapy. But numerous reports say that every combination of herbs and drugs is not safe. Some combinations may be beneficial and some may be harmful also. So before taking any herbal remedies with oral hypoglycemic agent, patient should consult physician. In this paper we are summarizing the reports available on the interaction of herbal remedies to one of the oral hypoglycemic agents (glibenclamide) and categorizing the effect of the combination is beneficial and harmful.

Herbal remedies, mood, and cognition

Herbal medicines were the "sole" source of medicine for thousands of years, in every culture since the advent of human civilization. Today, patients are increasing the use of these botanicals for numerous conditions, such as mood and cognition. This article will explore commonly used herbal remedies for mood and cognition functioning. It is imperative that nurses and nurse practitioners obtain expertise with these botanicals with regard to efficacy, adverse effects and contraindications, possible drug interactions, and safety considerations.

EGb761, a Ginkgo biloba extract, is effective against atherosclerosis in vitro, and in a rat model of type 2 diabetes

BACKGROUND

EGb761, a standardized Ginkgo biloba extract, has antioxidant and antiplatelet aggregation and thus might protect against atherosclerosis. However, molecular and functional properties of EGb761 and its major subcomponents have not been well characterized. We investigated the effect of EGb761 and its major subcomponents (bilobalide, kaemferol, and quercetin) on preventing atherosclerosis in vitro, and in a rat model of type 2 diabetes.

METHODS AND RESULTS

EGb761 (100 and 200 mg/kg) or normal saline (control) were administered to Otsuka Long-Evans Tokushima Fatty rats, an obese insulin-resistant rat model, for 6 weeks (from 3 weeks before to 3 weeks after carotid artery injury). Immunohistochemical staining was performed to investigate cell proliferation and apoptosis in the injured arteries. Cell migration, caspase-3 activity and DNA fragmentation, monocyte adhesion, and ICAM-1/VCAM-1 levels were explored in vitro. Treatment with EGb761 dose-dependently reduced intima-media ratio, proliferation of vascular smooth muscle cells (VSMCs) and induced greater apoptosis than the controls. Proliferation and migration of VSMCs in vitro were also decreased by the treatment of EGb761. Glucose homeostasis and circulating adiponectin levels were improved, and plasma hsCRP concentrations were decreased in the treatment groups. Caspase-3 activity and DNA fragmentation increased while monocyte adhesion and ICAM-1/VCAM-1 levels decreased significantly. Among subcomponents of EGb761, kaemferol and quercetin reduced VSMC migration and increased caspase activity.

CONCLUSIONS

EGb761 has a protective role in the development of atherosclerosis and is a potential therapeutic agent for preventing atherosclerosis.

Evaluation of alpha-glucosidase, alpha-amylase and protein glycation inhibitory activities of edible plants

The present study was to investigate in vitro alpha-glucosidase, pancreatic alpha-amylase and protein glycation inhibitory activities of nine edible plants. The results indicated that total phenolics, flavonoids, and condensed tannins of nine edible plants showed marked variations, ranging from 12.2 to 80.1 mg gallic acid equivalent/g extract, 2.34 to 13.65 mg quercetin equivalent/g extract, and 97.2 to 460.1 mg catechin equivalent/g extract, respectively. Our findings showed that grape seed, Cat's whiskers and Sweetleaf extract were the most effective pancreatic alpha-amylase, intestinal maltase, and sucrase inhibitor with IC(50) values of 0.29 +/- 0.01 mg/ml, 0.97 +/- 0.10 mg/ml and 0.86 +/- 0.01 mg/ml, respectively. All extracts (1 mg/ml) markedly inhibited the glycation of bovine serum albumin in fructose-mediated non-enzyme glycation by 50-30% at week 1. It was found that Pennywort maintained the high percentage inhibition among those of the extracts during the 4 weeks of experiment. These edible plants may be used for controlling blood glucose level and prevention of the development of type 2 diabetes.

Potential of Ginkgo biloba L. leaves in the management of hyperglycemia and hypertension using in vitro models

Leaves from four different Ginkgo biloba L. trees (1 and 2--females; 3 and 4--males), grown at the same conditions, were collected during a period of 5 months (from June to October, 2007). Water and 12% ethanol extracts were analyzed for total phenolics content, antioxidant activity, phenolic profile, and the potential in vitro inhibitory effects on alpha-amylase, alpha-glucosidase, and Angiotensin I-Converting Enzyme (ACE) enzymes related to the management of diabetes and hypertension. The results indicated a significant difference among the trees in all functional benefits evaluated in the leaf extracts and also found important seasonal variation related to the same functional parameters. In general, the aqueous extracts had higher total phenolic content than the ethanolic extracts. Also, no correlation was found between total phenolics and antioxidant activity. In relation to the ACE inhibition, only ethanolic extracts had inhibitory activity.

Involvement of Ca2+, CaMK II and PKA in EGb 761-induced insulin secretion in INS-1 cells

EGb 761, a standardized form of Ginkgo biloba L. (Ginkgoaceae) leaf extract, was recently reported to increase pancreatic beta-cell function. To determine whether EGb 761 elicits insulin secretion directly, we treated INS-1 rat beta cells with EGb 761 and then measured insulin release. Treatment of EGb 761 (50 microg/ml) significantly stimulated insulin secretion in INS-1 cells, compared with untreated control (p<0.05) and the stimulatory effect of EGb 761 on insulin secretion was dose-dependent. To elucidate the mechanism of EGb 761-induced insulin secretion, we investigated the involvement of calcium. The treatment with nifedipine, an L-type calcium channel blocker, prevented EGb 761-induced insulin secretion and furthermore, EGb 761 itself elevated [Ca(2+)](i), suggesting the involvement of calcium in this process. To identity the protein kinases involved in EGb 761-induced insulin secretion, INS-1 cells were treated with different kinase inhibitors and their effects on EGb 761-induced secretion were investigated. KN62 and H89, calium/calmodulin kinase (CaMK) II and protein kinase A (PKA) inhibitor, respectively, significantly reduced EGb 761-induced insulin secretion. Immunoblotting studies showed an increase in the phosphorylated-forms of CaMK II and of PKA substrates after EGb 761 treatment. Our data suggest that EGb 761-induced insulin secretion is mediated by [Ca(2+)](i) elevation and subsequent activation of CaMK II and PKA.

Effects of Ginkgo biloba extract on pharmacokinetics and pharmacodynamics of tolbutamide and midazolam in healthy volunteers

This study was undertaken to clarify the influence of repeated oral administration of Ginkgo biloba extract (GBE) on CYP2C9 and CYP3A4. CYP2C9 probe (tolbutamide, 125 mg) and CYP3A4 probe (midazolam, 8 mg) were orally administered to 10 male healthy volunteers before and after GBE intake (360 mg/d) for 28 days, and they received 75 g glucose after the dosing of tolbutamide. Plasma drug concentrations and blood glucose levels were measured. The area under concentration versus time curve (AUC0-infinity) for tolbutamide after GBE intake was slightly but significantly (16%) lower than that before GBE intake. Concomitantly, GBE tended to attenuate AUC0-2 of blood glucose-lowering effect of tolbutamide. AUC0-infinity for midazolam was significantly (25%) increased by GBE intake and oral clearance was significantly (26%) decreased. Thus, it is suggested that the combination of GBE and drugs should be cautious in terms of the potential interactions, especially in elderly patients or patients treated with drugs exerting relatively narrow therapeutic windows.

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

BACKGROUND & AIMS

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.

METHOD

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.

RESULTS

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).

CONCLUSION

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.

Short-term oral ingestion of Ginkgo biloba extract (EGb 761) reduces malondialdehyde levels in washed platelets of type 2 diabetic subjects

We have recently reported that ingestion of Ginkgo biloba extract (EGb 761) (a) significantly reduced collagen-induced platelet aggregation and thromboxane B2 (TXB2) production in both non-diabetic individuals as well as those with type 2 diabetes mellitus (T2DM), (b) significantly reduced platelet malondialdehyde (MDA), an index of lipid peroxidation, in non-diabetic subjects. In the present study we report that ingestion of EGb 761 (120 mg daily for 3 months), significantly decreased platelet MDA-thiobarbituric acid reacting substances (TBARS) (41 +/- 9 pmol/10(7) platelets versus 30 +/- 11 pmol/10(7) platelets) (p < 0.005) in T2DM subjects with normal cholesterol levels (total cholesterol, 164 +/- 22 mg/dl; age, 54 +/- 9 years; BMI, 35.0 +/- 8.8 kg/m2, n = 12). In T2DM subjects with high cholesterol (total cholesterol, 218 +/- 15 mg/dl; age, 52 +/- 5 years; BMI, 36.2 +/- 6.6 kg/m2, n = 7), EGb 761 ingestion reduced the platelet TBARS from 29 +/- 9 to 22 +/- 9 pmol/10(7) platelets (p < 0.04). Because ingestion of EGb 761 did not alter platelet counts it is concluded that EGb 761, probably due to the flavonoid fraction, reduced the TBARS by inhibiting cyclooxygenase (COX)-1-mediated arachidonic acid oxygenation or by reducing the arachidonic acid pool. This is likely to lead to a reduction of platelet hyperactivity, a significant contributor to the development of cardiovascular disease in T2DM patients. Because of other reported beneficial properties of EGb 761, such as stimulation of pancreatic beta-cell function in T2DM subjects with pancreatic exhaustion, it appears that T2DM subjects might benefit from ingesting EGb 761 as a dietary supplement.

Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies

For some classes of dietary polyphenols, there are now sufficient intervention studies to indicate the type and magnitude of effects among humans in vivo, on the basis of short-term changes in biomarkers. Isoflavones (genistein and daidzein, found in soy) have significant effects on bone health among postmenopausal women, together with some weak hormonal effects. Monomeric catechins (found at especially high concentrations in tea) have effects on plasma antioxidant biomarkers and energy metabolism. Procyanidins (oligomeric catechins found at high concentrations in red wine, grapes, cocoa, cranberries, apples, and some supplements such as Pycnogenol) have pronounced effects on the vascular system, including but not limited to plasma antioxidant activity. Quercetin (the main representative of the flavonol class, found at high concentrations in onions, apples, red wine, broccoli, tea, and Ginkgo biloba) influences some carcinogenesis markers and has small effects on plasma antioxidant biomarkers in vivo, although some studies failed to find this effect. Compared with the effects of polyphenols in vitro, the effects in vivo, although significant, are more limited. The reasons for this are 1) lack of validated in vivo biomarkers, especially in the area of carcinogenesis; 2) lack of long-term studies; and 3) lack of understanding or consideration of bioavailability in the in vitro studies, which are subsequently used for the design of in vivo experiments. It is time to rethink the design of in vitro and in vivo studies, so that these issues are carefully considered. The length of human intervention studies should be increased, to more closely reflect the long-term dietary consumption of polyphenols.

Ginkgo biloba extract modifies hypoglycemic action of tolbutamide via hepatic cytochrome P450 mediated mechanism in aged rats

We examined hepatic cytochrome P450 (CYP)-mediated interactions between Ginkgo biloba extract (GBE) and tolbutamide, an oral anti-diabetic agent, in aged and young rats. Tolbutamide was orally given to rats with or without GBE treatment, and time-dependent changes in blood glucose were monitored. The basal activity of six CYP subtypes in liver was lower in the aged rats than in the young rats, while the inductions of these enzymes by 5 day pretreatment of 0.1% GBE diet were more in the aged rats. Further, the pretreatment of GBE significantly attenuated the hypoglycemic action of tolbutamide in the aged rats, corresponding well to the enhanced activity of (S)-warfarin 7-hydroxylase, which is responsible for CYP2C9 subtype, a major isoform metabolizing tolbutamide. In contrast, the simultaneous administration of GBE with tolbutamide potentiated the hypoglycemic action of this drug. The in vitro experiments revealed that GBE competitively inhibited the metabolism of tolbutamide by (S)-warfarin 7-hydroxylase in the rat liver microsomes. In the young rats, the 5 day pretreatment with GBE significantly attenuated the hypoglycemic action of tolbutamide, but a simultaneous treatment had little influence on the tolbutamide effect. In conclusion, the present study has shown that the simultaneous and continuous intake of GBE significantly affects the hypoglycemic action of tolbutamide, possibly via a hepatic CYP enzyme-mediated mechanism, particularly in the aged rats. Therefore, it is anticipated that the intake of GBE as a dietary supplement with therapeutic drugs should be cautious, particularly in elderly people.

Systematic review of herbs and dietary supplements for glycemic control in diabetes

OBJECTIVE

To conduct a systematic review of the published literature on the efficacy and safety of herbal therapies and vitamin/mineral supplements for glucose control in patients with diabetes.

RESEARCH DESIGN AND METHODS

We conducted an electronic literature search of MEDLINE, OLDMEDLINE, Cochrane Library Database, and HealthSTAR, from database inception to May 2002, in addition to performing hand searches and consulting with experts in the field. Available clinical studies published in the English language that used human participants and examined glycemic control were included. Data were extracted in a standardized manner, and two independent investigators assessed methodological quality of randomized controlled trials using the Jadad scale.

RESULTS

A total of 108 trials examining 36 herbs (single or in combination) and 9 vitamin/mineral supplements, involving 4,565 patients with diabetes or impaired glucose tolerance, met the inclusion criteria and were analyzed. There were 58 controlled clinical trials involving individuals with diabetes or impaired glucose tolerance (42 randomized and 16 nonrandomized trials). Most studies involved patients with type 2 diabetes. Heterogeneity and the small number of studies per supplement precluded formal meta-analyses. Of these 58 trials, the direction of the evidence for improved glucose control was positive in 76% (44 of 58). Very few adverse effects were reported.

CONCLUSIONS

There is still insufficient evidence to draw definitive conclusions about the efficacy of individual herbs and supplements for diabetes; however, they appear to be generally safe. The available data suggest that several supplements may warrant further study. The best evidence for efficacy from adequately designed randomized controlled trials (RCTs) is available for Coccinia indica and American ginseng. Chromium has been the most widely studied supplement. Other supplements with positive preliminary results include Gymnema sylvestre, Aloe vera, vanadium, Momordica charantia, and nopal.

Effect of the ingestion of Ginkgo biloba extract on platelet aggregation and urinary prostanoid excretion in healthy and Type 2 diabetic subjects

Enhanced platelet function, particularly in response to collagen, is a common occurrence in diabetes that increases the risk of cardiovascular disease. Ginkgo biloba extract is ingested primarily to improve mental focus but it possesses a blood-thinning potential, which has not been well characterized. This study was designed to compare the effect of ingesting G. biloba extract on platelet aggregation in platelet-rich plasma (PRP) and prostanoid urinary excretion in healthy volunteers and subjects with Type 2 diabetes mellitus (T2DM). Before and after ingesting 120 mg of standardized G. biloba extract for 3 months, platelet aggregation was studied in PRP and urinary metabolites of thromboxane B(2) (TXB(2)) and prostacyclin (PGI(2)) were measured. In healthy volunteers (age, 42+/-11 years; BMI, 28.4+/-4.8 kg/m(2); n=28), the ingestion of G. biloba extract significantly increased fasting insulin and C-peptide (10+/-4 vs. 12+/-6 microU/ml, p<0.007 and 1.3+/-0.8 vs. 2.1+/-1.1 ng/ml, p<0.001, respectively) and significantly reduced collagen but not PAF-mediated platelet aggregation, converting 21 of 28 subjects with [COL+/EPI+] platelets to the [COL-/EPI+] phenotype. This was accompanied by a reduction of 11-dehydro-TXB(2) from 12.4+/-6.1 to 10.3+/-6.1 ng/mg Cr (p<0.04) and PGI(2) metabolites (2,3-dinor-6-keto-PGF(1alpha) and 6-keto-PGF(1alpha)) from 2.2+/-0.8 to 1.8+/-0.8 ng/mg Cr (p<0.05). In the T2DM subjects (age, 54+/-8; BMI, 36.6+/-7.9 kg/m(2); n=19), G. biloba ingestion did not affect pancreatic beta-cell function but significantly reduced platelet aggregation, converting 16 of 19 [COL+/EPI+] platelets to the [COL-/EPI+] phenotype. Unlike the healthy volunteers, this was not accompanied by a reduced urinary prostanoid excretion. G. biloba-induced reduction of both classes of prostanoid metabolites in healthy volunteers, but not in T2DM subjects, may suggest a nonselective inhibition of COX-1-mediated TXA(2) in platelets and COX-2-mediated PGI(2) production by the endothelial cells and perhaps platelet-enriched levels of arachidonic acid or COX-1 activity, or both, in T2DM subjects.