Demonstration of the "anti-stress" activity of an extract of Ginkgo biloba (EGb 761) using a discrimination learning task

Preventing dementia? Interventional approaches in mild cognitive impairment

Mild cognitive impairment (MCI) is defined as an intermediate state between normal cognitive aging and dementia. It describes a status of the subjective impression of cognitive decline and objectively detectible memory impairment beyond normal age-related changes. Activities of daily living are not affected. As the population ages, there is a growing need for early, proactive programs that can delay the consequences of dementia and improve the well-being of people with MCI and their caregivers. Various forms and approaches of intervention for older people with MCI have been suggested to delay cognitive decline. Pharmacological as well as non-pharmacological approaches (cognitive, physiological, nutritional supplementation, electric stimulation, psychosocial therapeutic) and multicomponent interventions have been proposed. Interventional approaches in MCI from 2009 to April 2019 concerning the cognitive performance are presented in this review.

Effect of Memo®, a natural formula combination, on Mini-Mental State Examination scores in patients with mild cognitive impairment

Background

Mild cognitive impairment encompasses the clinical continuum between physiologic age-related cognitive changes and dementia. A variety of medications, including herbal preparations (in particular Ginkgo biloba and Panax ginseng), have been advocated as treatments for cognitive impairment in the elderly. In this study, we investigated the effect of an already marketed dietary supplement (Memo®) combining 750 mg of lyophilized royal jelly with standardized extracts of G. biloba 120 mg and P. ginseng 150 mg on Mini-Mental State Examination (MMSE) scores in patients with mild cognitive impairment.

Methods

Sixty-six subjects presenting with forgetfulness and satisfying the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR) clinical criteria for mild cognitive impairment were randomly divided into an experimental group treated with one Memo capsule before breakfast daily for 4 weeks and a control group who took placebo. The mean change in MMSE score from baseline and reported adverse effects were compared between the two groups.

Results

The mean change in MMSE score in the group treated with Memo for 4 weeks was significantly greater than in the control group (+2.07 versus +0.13, respectively) by the Student’s t-test (t = 6.485, P < 0.0001). This was also true after adjusting for age as a covariate and educational level as a factor nested within the treatment groups in a general linear model (analysis of covariance, F = 9.675 [corrected model], P < 0.0001).

Conclusion

This combined triple formula may be beneficial in treating the cognitive decline that occurs during the aging process as well as in the early phases of pathologic cognitive impairment typical of insidious-onset vascular dementia and in the early stages of Alzheimer’s disease. Larger-sized studies with longer treatment durations are needed to confirm this.

Alleviating neuropsychiatric symptoms in dementia: the effects of Ginkgo biloba extract EGb 761. Findings from a randomized controlled trial

PURPOSE

To examine the effects of Ginkgo biloba extract EGb 761(®) on neuropsychiatric symptoms of dementia.

PATIENTS AND METHODS

Randomized, controlled, double-blind, multicenter clinical trial involving 410 outpatients with mild to moderate dementia (Alzheimer's disease with or without cerebrovascular disease, vascular dementia), scoring at least 5 on the Neuropsychiatric Inventory (NPI), with at least one item score of 3 or more. Total scores on the SKT cognitive test battery (Erzigkeit's short syndrome test) were between 9 and 23. After random allocation, the patients took 240 mg of EGb 761(®) or placebo once daily for a period of 24 weeks. Changes from baseline to week 24 in the NPI composite and in the SKT total score were the primary outcomes. The NPI distress score was chosen as a secondary outcome measure to evaluate caregivers' distress.

RESULTS

The NPI composite score improved by -3.2 (95% confidence interval -4.0 to -2.3) in patients taking EGb 761(®) (n = 202), but did not change (-0.9; 0.9) in those receiving placebo (n = 202), which resulted in a statistically significant difference in favor of EGb 761(®) (P < 0.001). Treatment with EGb 761(®) was significantly superior to placebo for the symptoms apathy/indifference, sleep/night-time behavior, irritability/lability, depression/dysphoria, and aberrant motor behavior. Caregivers' distress evaluation revealed similar baseline pattern and improvements.

CONCLUSION

Treatment with EGb 761(®), at a once-daily dose of 240 mg, was safe, effectively alleviated behavioral and neuropsychiatric symptoms in patients with mild to moderate dementia, and improved the wellbeing of their caregivers.

Chemical composition and anti-stress effects of yeast hydrolysate

In the present study, the anti-stress effects of yeast hydrolysate (YH) were investigated. The YH consisted of crude carbohydrate (23.6%) and crude protein (68.3%) with low contents of crude ash (3.1%) and crude fat (0.3%). Also, acidic amino acids (glutamic acid + aspartic acid) were present in large quantities (14.2 and 5.0 mol%, respectively). Pronase digestion had little effect on the affinity of the YH on 5-hydroxytryptamine (serotonin) and norepinephrine transporters, whereas NaIO(4) oxidation of the hydrolysate decreased the affinity by about 10% at 1,000 microg/mL, indicating that the periodate-labile carbohydrate moiety played a leading role in the affinity effects of the carbohydrate in YH. As a result of brain mapping after the administration of the YH for 3 days in human subjects, a symmetrical distribution of theta and alpha waves in the central and parietal lobes was observed. This brain mapping pattern of theta and alpha wave distribution appears in a psychologically stable state. The YH groups showed improvements in Beck Depression Inventory and Beck Anxiety Inventory scores after YH administration for 2 weeks. Treatment also seemed to have a more significant (P < .05) impact on the somatic manifestations of anxiety as indexed by the Beck Anxiety Inventory scores. Food materials used as a source of YH have been found to be associated with increases in alertness and adaptation to stress.

Ginkgo biloba: specificity of neuropsychological improvement--a selective review in search of differential effects

Extracts of Ginkgo biloba are widely used for the treatment of cognitive impairment. Whereas reviews have focused on the question whether ginkgo is effective to enhance cognition in general, little is known about specificity of improvement. This might be crucial for future trials, thus enabling hypotheses about sensitive outcome measures. Therefore, this article summarizes such information, i.e. neuropsychological effects of chronic administration of ginkgo in healthy and cognitively impaired subjects of any age. Objective psychometric test results were considered if they reflected distinct cognitive functions from randomized controlled group-studies (RCT). We reviewed 29 RCTs yielding 209 placebo-drug comparisons of psychometric scores in four different cognitive domains comprising 14 sub-functions. Whereas little specific information can be obtained from trials for treatment of dementia, a pattern of pharmacological actions on cognitive processes emerges here from studies for mild cognitive impairment (MCI), depression, multiple sclerosis and healthy young and elderly subjects. There is consistent evidence that chronic administration improves selective attention, some executive processes and long-term memory for verbal and non-verbal material. Further trials should be more comprehensive as there are few data available on some cognitive functions and psychometric flaws in the selection of tests and the interpretation of their results favouring predominantly beta-errors. Thus, though this pattern is encouraging it also asks for a cautious interpretation to date.

Chronic administration of a Ginkgo biloba leaf extract facilitates acquisition but not performance of a working memory task

RATIONALE

Ginkgo biloba leaf extracts have been shown to improve learning and memory when administered chronically prior to the learning phase. However, the influence of Ginkgo on learning without prior chronic treatment and on memory per se (i.e., post-training administration) is less clear. Thus, experiment 1 investigated the influence of Ginkgo on acquisition, and experiment 2 examined the acute and chronic effects of Ginkgo on memory in rats using a food-reinforced two-component double Y-maze task.

MATERIALS AND METHODS

In experiment 1, 17 rats were treated daily with a standardized G. biloba extract (13.75 mg/kg, i.p.) or vehicle 30 min prior to daily maze training for 14 days. In experiment 2, 12 rats received 24 training trials daily, then received Ginkgo (0, 0.25, 2.5, 13.75, or 25 mg/kg, i.p.) 30 min prior to each test session. Subsequently, the same rats received daily injections of either Ginkgo (13.75 mg/kg, i.p.) or its vehicle. Memory was tested after 10 and 20 days of drug treatment, once under the influence of the drug and once in a drug-free state.

RESULTS

In experiment 1, Ginkgo-treated rats reached the training criteria significantly faster and made fewer errors. In experiment 2, post-training Ginkgo administration did not enhance memory.

DISCUSSION

Taken together, results demonstrate that repeated daily pre-session Ginkgo injection subtly facilitates acquisition of a spatial working memory task, but neither acute nor chronic post-training exposure enhances spatial working memory. We conclude that ongoing Ginkgo administration does not offer any continued beneficial effects in an already-learned working memory task.

Short- and long-term effects of Ginkgo biloba extract on sexual dysfunction in women

Ginkgo biloba extract (GBE) facilitates blood flow, influences nitric oxide systems, and has a relaxant effect on smooth muscle tissue. These processes are important to the sexual response in women and, hence, it is feasible that GBE may have a therapeutic effect. The present study was the first to provide an empirical examination of the effects of both short- and long-term GBE administration on subjective and physiological (vaginal photoplethysmography) measures of sexual function in women with Sexual Arousal Disorder. A single dose of 300 mg GBE had a small but significant facilitatory effect on physiological, but not subjective, sexual arousal compared to placebo in 99 sexually dysfunctional women. The long-term effects of GBE on sexual function were assessed in 68 sexually dysfunctional women who were randomly assigned to 8 weeks treatment of either (1) GBE (300 mg/daily), (2) placebo, (3) sex therapy which focused on training women to attend to genital sensations, or (4) sex therapy plus GBE. When combined with sex therapy, but not alone, long-term GBE treatment significantly increased sexual desire and contentment beyond placebo. Sex therapy alone significantly enhanced orgasm function compared with placebo. Long-term GBE administration did not significantly enhance arousal responses beyond placebo. It was concluded that (1) neither short- or long-term administration of GBE alone substantially impacts sexual function in women, (2) a substantial placebo effect on sexual function exists in women with sexual concerns, and (3) teaching women to focus on genital sensations during sex enhances certain aspects of women's sexual functioning.

The role of functional foods in the psychobiology of health and disease

The effect of psychological stress on health is becoming a serious concern, with figures from the World Health Organization showing that stress-related disorders affect nearly 450 million individuals worldwide. Heightened physiological stress responses and psychosocial factors have been linked to disease pathways such as hypertension and CVD. This has prompted significant interest within the scientific community, public health bodies and industry to employ interventions to control and reduce the impact of stress on health. There is now strong potential for functional foods to offer stress management benefits. Various physiological pathways have been targeted by specific dietary supplements for stress reduction, including the hypothalamic–pituitary–adrenal axis and sympathetic nervous system. Presently there are a number of ingredients, which include vitamin C, milk proteins, a number of herbal extracts (ginkgo biloba, ginseng, kava, valerian and lemon balm), andn-3 fatty acids, that have demonstrated potential stress reactivity-lowering and mood-enhancing effects, although further work is required to substantiate the efficacy in human subjects. Dietary supplements that can alleviate excessive stress responses may play an increasingly important role for the maintenance of health in a stressful environment. However, future research should employ a greater range of measures that will provide stronger evidence to substantiate functional food claims for stress relief.

Effects of Ginkgo biloba extract EGb 761 on neuropsychiatric symptoms of dementia: findings from a randomised controlled trial

In a randomised, double-blind, 22-week trial 400 patients with dementia associated with neuropsychiatric features were treated with Ginkgo biloba extract EGb 761 (240 mg/day) or placebo. Patients with probable Alzheimer's disease, possible Alzheimer's disease with cerebrovascular disease or vascular dementia were eligible if they scored 9 to 23 on the SKT cognitive test battery and at least 5 on the Neuropsychiatric Inventory (NPI). EGb 761 was significantly superior to placebo with respect to the primary (SKT test battery) and all secondary outcome variables. The mean composite score (frequency x severity) and the mean caregiver distress score of the NPI dropped from 21.3 to 14.7 and 13.5 to 8.7, respectively, in the EGb 761-treated patients, but increased from 21.6 to 24.1 and 13.4 to 13.9, respectively, under placebo (p < 0.001). The largest drug-placebo differences in favour of EGb 761 were found for apathy/indifference, anxiety, irritability/lability, depression/dysphoria and sleep/nighttime behaviour.

Ginkgo biloba special extract EGb 761 in generalized anxiety disorder and adjustment disorder with anxious mood: a randomized, double-blind, placebo-controlled trial

Ginkgo biloba special extract EGb 761, an anti-dementia drug, enhances cognitive functioning and stabilizes mood in cognitively impaired elderly subjects. Moreover, EGb 761 had been found to alleviate symptoms of anxiety in people with mental decline, therefore it was now tested for clinical efficacy in younger patients suffering from anxiety. One hundred and seven patients with generalized anxiety disorder (GAD, n=82) or adjustment disorder with anxious mood (ADWAM, n=25) according to the diagnostic and statistical manual of mental disorders, third edition - revised (DSM-III-R) were randomized to daily doses of 480 mg EGb 761, 240 mg EGb 761 or placebo for 4 weeks. Intention-to-treat (ITT) analyses were performed on the primary outcome measure, the Hamilton rating scale for anxiety (HAMA), and the secondary variables, the clinical global impression of change (CGI-C), the Erlangen anxiety tension and aggression scale (EAAS), the list of complaints (B-L'), and the patient's global rating of change. The HAMA total scores decreased by -14.3 (+/-8.1), -12.1 (+/-9.0) and -7.8 (+/-9.2) in the high-dose EGb 761, the low-dose EGb 761 and the placebo group, respectively. Changes were significantly different from placebo for both treatment groups with p=0.0003 (high-dose group) and p=0.01 (low-dose). Regression analyses revealed a dose-response trend (p=0.003). EGb 761 was significantly superior to placebo on all secondary outcome measures. It was safe and well tolerated and may thus be of particular value in elderly patients with anxiety related to cognitive decline.

Ginkgo biloba leave extract: biological, medicinal, and toxicological effects

Ginkgo biloba leave extract is among the most widely sold herbal dietary supplements in the United States. Its purported biological effects include: scavenging free radical; lowering oxidative stress; reducing neural damages, reducing platelets aggregation; anti-inflammation; anti-tumor activities; and anti-aging. Clinically, it has been prescribed to treat CNS disorders such as Alzheimer's disease and cognitive deficits. It exerts allergy and changes in bleeding time. While its mutagenicity or carcinogenic activity has not been reported, its components, quercetin, kaempferol and rutin have been shown to be genotoxic. There are no standards or guidelines regulating the constituent components of Ginkgo biloba leave extract nor are exposure limits imposed. Safety evaluation of Ginkgo biloba leave extract is being conducted by the U.S. National Toxicology Program.

Ginkgo biloba extract improves spatial memory in rats mainly but not exclusively via a histaminergic mechanism

In order to clarify the mechanism of Ginkgo biloba extract (GBE) on learning and memory, we studied the effect of GBE on spatial memory deficits induced by diphenhydramine, pyrilamine and scopolamine using the eight-arm radial maze performance of rats, in comparison with donepezil. Total error (TE), reference memory error (RME) and working memory error (WME) were used as indices of spatial memory deficits. Both GBE and donepezil caused a potent antagonistic effect on the increase in TE, RME and WME induced by diphenhydramine. GBE and donepezil also antagonized scopolamine-induced spatial memory deficits. Although the antagonistic effect of GBE on pyrilamine-induced spatial memory deficits was weak, a significant difference was observed with TE and WME. However, donepezil caused no antagonistic effect on pyrilamine-induced memory deficits. From these findings, we concluded that the effects of GBE are mainly contributable to cholinergic activity and perhaps partly due to a histaminergic mechanism.

Ginkgo biloba leaf extract (EGb 761) enhances catalepsy induced by haloperidol and L-nitroarginine in mice

Ginkgo biloba extract EGb 761 has been reported to have therapeutic effects which have been attributed to anti-oxidant and free radical-scavenging activities, including a direct action on nitric oxide production. L G-nitro-arginine (L-NOARG), a nitric oxide synthase inhibitor, and haloperidol, a drug that blocks dopamine receptors, are both known to induce catalepsy in rodents. Nitric oxide has been shown to influence dopaminergic transmission in the striatum. The purpose of the present study was to evaluate the effect of the extract obtained from leaves of Ginkgo biloba tree EGb 761 on catalepsy induced by haloperidol or by L-NOARG. Albino Swiss mice (35-45 g, N = 8-12) received by gavage a single or repeated oral dose (twice a day for 4 days) of EGb 761 followed by ip injection of haloperidol or L-NOARG. After the treatments, the animals were submitted to behavioral evaluation using the catalepsy test. Acute treatment with 80 mg/kg EGb did not modify the catalepsy induced by L-NOARG but, the dose of 40 mg/kg significantly enhanced haloperidol-induced catalepsy measured at the 10th min of the test. After repeated treatment with 80 mg/kg EGb 761, a significant increase in the cataleptic effect produced by both haloperidol and L-NOARG was observed. These data show that repeated EGb 761 administration increases the effects of drugs that modify motor behavior in mice. Since the catalepsy test has predictive value regarding extrapyramidal effects, the possibility of pharmacological interactions between haloperidol and Ginkgo biloba extracts should be further investigated in clinical studies.

Inhibition of human P450 enzymes by multiple constituents of the Ginkgo biloba extract

The Ginkgo biloba extract EGb761 was tested for its ability to inhibit the major human cytochrome P450 enzymes (CYPs). The full extract was found to strongly inhibit CYP2C9 (Ki = 14+/- 4 microg/mL), and to a lesser extent, CYP1A2 (Ki = 106 +/- 24 microg/mL), CYP2E1 (Ki = 127 +/- 42 microg/mL), and CYP3A4 (Ki = 155 +/- 43 microg/mL). The terpenoidic and flavonoidic fractions of the extract were tested separately against the same P450s to identify the source of inhibition by EGb761. The terpenoidic fraction inhibited only CYP2C9 (Ki = 15 +/-6 microg/mL) whereas the flavonoidic fraction of EGb761 showed high inhibition of CYP2C9, CYP1A2, CYP2E1, and CYP3A4 (Ki's between 4.9 and 55 microg/mL). The flavonoidic fraction was further fractionated using extraction and chromatography. Inhibition studies indicated that the majority of these fractions inhibited P450s at a significant level (IC50 < 40 microg/mL).

Effects of Ginkgo biloba on corticosterone stress responses after inescapable shock exposure in the rat

Extracts from the leaves of the Ginkgo biloba tree (GBE) are found to be clinically effective in neuroprotection, cerebral and cardiovascular function and cognitive processing. Recent animal findings suggest that GBE also may improve stress adaptation and prevent learned helplessness, as evidenced by its reduction of behavioral acquisition deficits of active avoidance after inescapable shock exposure. In the present report, the effects of two doses of GBE were studied on corticosterone stress responses and acquisition of active avoidance after inescapable shock exposure. Forty-eight rats were divided into three groups: either receiving a daily dose of 50 mg/kg or 150 mg/kg of GBE (containing 24% flavonoid and 6% terpenoid) or vehicle for 2 weeks. After 2 weeks of administration, animals were trained for active-avoidance acquisition following inescapable shock exposure (stress induction) or nonshock exposure (nonstress). Administration of 150 mg/kg but not of 50 mg/kg of GBE significantly prevented a corticosterone stress response after inescapable shock exposure (P<.0001) without any beneficial behavioral effect on active avoidance. Repeated administration of GBE particularly improves biological adaptation to noxious stimuli without beneficial behavioral consequences. Present findings do not support previous claims about the benefits of G. biloba on improving behavioral stress adaptation and acquisition of active avoidance and on reducing behavioral deficits indicative of "learned helplessness."

Transcriptional suppression of the adrenal cortical peripheral-type benzodiazepine receptor gene and inhibition of steroid synthesis by ginkgolide B

Treatment of rats and adrenocortical cells with ginkgolide B (GKB), a purified component of Ginkgo biloba leaf extracts, reduces the mRNA, protein, and ligand-binding levels of the adrenal peripheral-type benzodiazepine receptor (PBR), a mitochondrial cholesterol-binding protein, leading to decreased corticosteroid synthesis. In the Y1 adrenocortical cell line, GKB reduced both PBR levels and cyclic AMP-induced steroid formation. In these cells, GKB, but not various steroids and vitamins, reduced the expression of a reporter gene driven by the DNA sequence -624/-513 relative to the transcription start site of the PBR encoding gene. GKB treatment did not affect the SV40 promoter and increased the cytochrome P450 17alpha-hydroxylase gene promoter driven expression of the reporter gene. Electrophoretic mobility shift assays (EMSAs) indicated the presence of a functional transcriptional element bound to the -624/-513 DNA fragment. This GKB-induced inhibition of PBR was mediated by an interaction with a transcription factor that binds to the -636/-616 PBR-promoter region. Deletion or mutation of this sequence eliminated the DNA-protein interaction and the inhibitory effect of GKB on PBR gene transcription. This DNA-binding protein could be detected in nuclear extracts of rat brain, liver, and testis, but not kidney. It is also present in the human adrenal glands. However, the inhibitory effect following GKB treatment could be seen only in the adrenal glands. These results demonstrate that the GKB-activated inhibition of glucocorticoid production is due to a specific transcriptional suppression of the adrenal PBR gene and suggest that GKB might serve as a pharmacological tool to control excess glucocorticoid formation.

Ginkgo biloba extract: cognitive enhancer or antistress buffer

Constituents extracted from the leaves of the Ginkgo biloba tree possess beneficial properties that may buffer the aging nervous system from deterioration due to oxidative stress. In the present investigation, a standardized extract of G. biloba (EGb 761) or an equal volume of the vehicle was administered (100 mg/kg/day) to senescent (20-month) C57BL/6 male mice for up to 82 consecutive days. Animals were tested twice in the Morris water maze (MWM) after 28 and 70 days of treatment. No differences were observed in acquisition or retention of performance on the water maze. Elevated-plus maze (EPM) trials were conducted prior to and subsequent to the chronic treatment regimen. Marked baseline differences in plus-maze performance were present in the first experiment. A second experiment used a matched-pairs design to minimize preexisting differences. Results supported the hypothesis that EGb 761 may serve as an antistress buffer, attenuating the increase in anxiety typically observed in animals after cold water exposure. Tissue samples from the hippocampus and cortex were analyzed by Western blot for the transcription factor cyclic-AMP response element binding (CREB) protein. EGb 761 had no significant effect on immunoreactivity to CREB from either the hippocampus or the cerebral cortex.

Role of the peripheral-type benzodiazepine receptor in adrenal and brain steroidogenesis

The peripheral-type benzodiazepine receptor (PBR) has been demonstrated to be critical for steroidogenesis in all steroid-producing tissues. Here, we review the identification and characterization of the PBR, the evidence pointing to its function as a cholesterol pore involved in transporting cholesterol from the cytoplasm of steroid-producing cells into the inner mitochondrial membrane where it is metabolized, and the known mechanisms regulating its function. We present data on the functions of the PBR in the adrenal gland, a classical steroidogenic tissue, and in the brain, which has only recently been proven to be steroidogenic. Finally, we discuss other potential roles for the PBR in pathological conditions, including cancer, neurodegeneration, and neurotoxicity, and a broader role for the PBR in mediating intracellular cholesterol transport/compartmentalization, which may or may not be linked to steroid biosynthesis.

A possible emerging role of phytochemicals in improving age-related neurological dysfunctions: a multiplicity of effects

It is rare to see a day pass in which we are not told through some popular medium that the population is becoming older. Along with this information comes the "new" revelation that as we enter the next millennium there will be increases in age-associated diseases (e.g., cancer, cardiovascular disease) including the most devastating of these, which involve the nervous system (e.g., Alzheimer's disease [AD] and Parkinson's disease [PD]). It is estimated that within the next 50 years approximately 30% of the population will be aged 65 years or older. Of those between 75 and 84 years of age, 6 million will exhibit some form of AD symptoms, and of those older than 85 years, over 12 million will have some form of dementia associated with AD. What appears more ominous is that many cognitive changes occur even in the absence of specific age-related neurodegenerative diseases. Common components thought to contribute to the manifestation of these disorders and normal age-related declines in brain performance are increased susceptibility to long-term effects of oxidative stress (OS) and inflammatory insults. Unless some means is found to reduce these age-related decrements in neuronal function, health care costs will continue to rise exponentially. Thus, it is extremely important to explore methods to retard or reverse age-related neuronal deficits as well as their subsequent, behavioral manifestations. Fortunately, the growth of knowledge in the biochemistry of cell viability has opened new avenues of research focused at identifying new therapeutic agents that could potentially disrupt the perpetual cycle of events involved in the decrements associated with these detrimental processes. In this regard, a new role in which certain dietary components may play important roles in alleviating certain disorders are beginning to receive increased attention, in particular those involving phytochemicals found in fruits and vegetables.

Effect of the extract of Ginkgo biloba (EGb 761) on the circulating and cellular profiles of polyunsaturated fatty acids: correlation with the anti-oxidant properties of the extract

Ginkgo biloba extract (EGb 761) has beneficial effects on cognitive functions in aging patients, and on various pathologies, including cardiovascular diseases. Although the extract is known to have antioxidant properties and improve membrane fluidity, the cellular mechanisms underlying these effects have not been determined. Here, we examined the in vivo effects of EGb 761 on circulating and cellular lipids. EGb 761 treatment induced significant increases in the levels of circulating polyunsaturated fatty acids (PUFAs), and a decrease in the saturation index SI (saturated/polyunsaturated species). Plasma triglycerides and cholesterol were not affected, while phospholipids were slightly increased at the higher dose of EGb 761. EGb 761 treatment also induced a significant increase in the levels of PUFAs in erythrocyte membranes, especially for the eicosapentaenoic acid (EPA omega 3), and a decrease in the saturation index. Moreover, the response of erythrocytes to oxidative stress was improved in EGb 761-treated animals (H(2)O(2)-induced cell lysis decreased by 50%). Considering that PUFAs are known to improve membrane fluidity and response to oxidative damage, and are precursors of signaling molecules such as prostaglandins, the effects of EGb 761 on circulating and cellular PUFAs may explain some of the pharmacological properties of Ginkgo biloba.

Identification of kaempferol as a monoamine oxidase inhibitor and potential Neuroprotectant in extracts of Ginkgo biloba leaves

The effects of Ginkgo biloba leaf extract on rat brain or livermonoamine oxidase (MAO)-A and -B activity, biogenic amine concentration in nervous tissue, N-methyl-D-aspartate (NMDA)- and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4)-induced neurotoxicity and antioxidant activity was investigated to determine the effects of the extract on monoamine catabolism and neuroprotection. Ginkgo biloba leaf extract was shown to produce in-vitro inhibition of rat brain MAO-A and -B. The Ginkgo biloba extract was chromatographed on a reverse-phase HPLC system and two of the components isolated were shown to be MAO inhibitors (MAOIs). These MAOIs were identified by high-resolution mass spectrometry as kaempferol and isorhamnetin. Pure kaempferol and a number of related flavonoids were examined as MAOIs in-vitro. Kaempferol, apigenin and chrysin proved to be potent MAOIs, but produced more pronounced inhibition of MAO-A than MAO-B. IC50 (50% inhibition concentration) values for the ability of these three flavones to inhibit MAO-A were 7 x 10(-7), 1 x 10(-6) and 2 x 10(-6) M, respectively. Ginkgo biloba leaf extract and kaempferol were found to have no effect ex-vivo on rat or mouse brain MAO or on concentrations of dopamine, noradrenaline, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. Kaempferol was shown to protect against NMDA-induced neuronal toxicity in-vitro in rat cortical cultures, but did not prevent DSP-4-induced noradrenergic neurotoxicity in an in-vivo model. Both Ginkgo biloba extract and kaempferol were demonstrated to be antioxidants in a lipid-peroxidation assay. This data indicates that the MAO-inhibiting activity of Ginkgo biloba extract is primarily due to the presence of kaempferol. Ginkgo biloba extract has properties indicative of potential neuroprotective ability.

Potential role for Ginkgo biloba extract in the treatment of glaucoma

Glaucoma is becoming recognized as a condition for which not only elevated intraocular pressure, but also non-pressure-dependent risk factors are responsible. New avenues of treatment into which investigations are being initiated include agents which could possibly improve blood flow to the eye and neuroprotective drugs. Only calcium channel blockers are presently available for such treatment in glaucoma, and these have not been widely adopted, in contrast to clinical trials involving a number of neuroprotectants in other neurologic disorders. Ginkgo biloba extract is freely available and has several biological actions which combine to make it a potentially important agent in the treatment of glaucoma: improvement of central and peripheral blood flow, reduction of vasospasm, reduction of serum viscosity, antioxidant activity, platelet activating factor inhibitory activity, inhibition of apoptosis, and inhibition of excitotoxicity. The effect of Ginkgo biloba extract as a potential antiglaucoma therapy deserves intensive scrutiny.

Evidence that gingko biloba extract does not inhibit MAO A and B in living human brain

Extracts of Ginkgo biloba have been reported to reversibly inhibit both monoamine oxidase (MAO) A and B in rat brain in vitro leading to speculation that MAO inhibition may contribute to some of its central nervous system effects. Here we have used positron emission tomography (PET) to measure the effects of Ginkgo biloba on human brain MAO A and B in 10 subjects treated for 1 month with 120 mg/day of the Ginkgo biloba extract EGb 761, using [11C]clorgyline and [11C]L-deprenyl-D2 to measure MAO A and B respectively. A three-compartment model was used to calculate the plasma to brain transfer constant K1 which is related to blood flow, and lambdak3, a model term which is a function of the concentration of catalytically active MAO molecules. Ginkgo biloba administration did not produce significant changes in brain MAO A or MAO B suggesting that mechanisms other than MAO inhibition need to be considered as mediating some of its CNS effects.

The effectiveness of popular, non-prescription weight loss supplements

OBJECTIVES

To review the evidence for the effectiveness of popular, non-prescription weight loss supplements.

DATA SOURCES

A detailed literature search including all relevant medical and supplementary medicine databases and evidence submitted from manufacturers.

DATA SYNTHESIS

The theoretical basis and rationale for the use of each substance is considered along with available research in the published literature on effectiveness and potential risks. We classified the level of evidence represented by the main research studies on each substance.

CONCLUSIONS

There is no good evidence for any weight loss benefits from most of the substances reviewed here. There is some support for mild effects of capsaicin, caffeine and fibre, but only in whole foods. In some cases (e.g., chitosan), there is a plausible theoretical basis for the product, but no supporting proof of effect in humans in the absence of a calorie-controlled diet. Possible synergistic effects of different ingredients cannot be dismissed, but cannot be assessed from current data. There is an absence of good quality research on many substances, which means that advertising claims may be misleading.

Effects of single intraperitoneal injections of an extract of Ginkgo biloba (EGb 761) and its terpene trilactone constituents on barbital-induced narcosis in the mouse

A mouse model of barbital-induced narcosis was used to examine the effects of single intraperitoneal injections of an extract of Ginkgo biloba (EGb 761), an extract devoid of terpene trilactones (CP 205), and three terpene trilactone constituents of the extract (ginkgolides A and B, bilobalide). Administration of sodium barbital (180 mg/kg, IP) to the mice caused narcosis, measured as a loss in righting reflex. Single injections of EGb 761 (25 and 50 mg/kg), given 60 min prior to sodium barbital, significantly shortened barbital-induced sleeping time, whereas these same doses of CP 205 were ineffective. Single injections of ginkgolide B (1 mg/kg) and bilobalide (2 and 5 mg/kg) significantly shortened sleeping time, whereas ginkgolide A was ineffective. The effects of ginkgolide B and bilobalide were reflected as increases in latency to onset of sleep and those of EGb 761, ginkgolide B, and bilobalide were correlated with decreases in the number of mice that slept. At the behavioral level, these potent in vivo effects of EGb 761, ginkgolide B, and bilobalide resemble those of certain antidepressants. At the molecular level, it is hypothesized that interactions with the picrotoxinin/TBPT site of GABA-regulated Cl- channels of the CNS may be involved. This information appears useful in explaining the clinically observed "vigilance-enhancing" and "antidepressant-like" actions of EGb 761.

Ginkgo biloba extract EGb761 reduces the development of amphetamine-induced behavioral sensitization: effects on hippocampal type II corticosteroid receptors

Pretreatment of rats with the extract of Ginkgo biloba termed EGb761 reduced the behavioral sensitization induced by successive D-amphetamine administrations (0.5 mg/kg) as estimated by increasing values of locomotor activity. EGb761 pretreatment also prevented the reduced density of [3H]dexamethasone binding sites in the dentate gyrus and the CA1 hippocampal regions of D-amphetamine treated animals. These observations suggest that EGb761, by reducing glucocorticoid levels, could modulate the activity of the neuronal systems involved in the expression of the behavioral sensitization.

In vivo studies on the role of the peripheral benzodiazepine receptor (PBR) in steroidogenesis

In various steroidogenic cell models, mitochondrial preparations and submitochondrial fractions, the expression of the mitochondrial 18 kDa peripheral-type benzodiazepine receptor (PBR) protein confers the ability to take up and release, upon ligand activation, cholesterol. Thus, cholesterol becomes available to P450scc on the inner mitochondrial membrane. These in vitro studies were validated by in vivo experiments. Treatment of rats with ginkgolide B (GKB), specifically reduced the ligand binding capacity, protein, and mRNA expression of the adrenocortical PBR and circulating glucocorticoid levels. Treatment with GKB also resulted in inhibition of PBR protein synthesis and corticosterone production by isolated adrenocortical cells in response to ACTH. The ontogeny of both PBR binding capacity and protein directly paralleled that of ACTH-inducible steroidogenesis in rat adrenal cells and in rats injected with ACTH. In addition, the previously described suppression of luteal progesterone synthesis in the pregnant rat by continuous in vivo administration of a gonadotropin-releasing hormone agonist may be due to decreased luteal PBR ligand binding and mRNA. These results suggest that (i) PBR is an absolute prerequisite for adrenocortical and luteal steroidogenesis, (ii) regulation of adrenal PBR expression may be used as a tool to control circulating glucocorticoid levels and (iii) the stress hypo-responsive period of neonatal rats may result from decreased adrenal cortical PBR expression.

Effect of chronic administration of Ginkgo biloba extract or Ginkgolide on the hypothalamic-pituitary-adrenal axis in the rat

The hypersecretion of glucocorticoids during exposure to various stressors may induce or worsen pathological states in predisposed subjects. Therefore it is of interest to evaluate drugs able to reduce glucocorticoid secretion. It has recently been shown that chronic administration of a Ginkgo biloba extract (EGb 761) inhibits stress-induced corticosterone hypersecretion through a reduction in the number of adrenal peripheral benzodiazepine receptors. The present study was designed to analyze the effect of EGb 761 and one of its components, Ginkgolide B on the biosynthesis and secretion of CRH and AVP, the hypothalamic neurohormones that regulate the pituitary-adrenal axis. Chronic administration of EGb 761 (50 or 100 mg/kg p.o. daily for 14 days) reduced basal corticosterone secretion and the subsequent increase in CRH and AVP gene expression. Under the same conditions, surgically-induced increase in CRH secretion was attenuated while the activation of CRH gene expression, ACTH and corticosterone secretion following insulin-induced hypoglycemia remained unchanged. Chronic i.p. injection of Ginkgolide B reduced basal corticosterone secretion without alteration in the subsequent CRH and AVP increase. However, the stimulation of CRH gene expression by insulin-induced hypoglycemia was attenuated by Ginkgolide B. These data confirm that the administration of EGb 761 and Ginkgolide B reduces corticosterone secretion. In addition, these substances act also at the hypothalamic level and are able to reduce CRH expression and secretion. However the latter effect appears to be complex and may depend upon both the nature of stress and substance (Ginkgolide B or other compounds of EGb 761).

The effects of an extract of Ginkgo biloba, EGb 761, on cognitive behavior and longevity in the rat

Extracts of the leaves of the Ginkgo biloba tree are widely used throughout the world for their purportedly beneficial effects on brain function. In the present investigation, a standardized extract, EGb 761, was self-administered orally by male Fischer 344 rats that were then tested in an eight-arm radial maze. The tasks employed were a) continuous learning and b) delayed nonmatching to position. Chronic postsession administration of EGb 761 at a dose of 50 mg/kg had no effect on continuous learning but the same dose given presession resulted in a trend toward fewer sessions to reach criterion performance as well as fewer errors. In addition, it was observed that rats chronically treated with EGb 761 lived significantly longer than vehicle-treated subjects. In a delayed nonmatching to position task using a 30-min delay in 20-month-old rats. EGb 761 administered presession produced a dose-related decrease in total, retroactive, and proactive errors; a repeated-measures design was used, with subjects serving as their own controls. Following the dose-response determination, the group, now 26 months of age, was divided in two with half receiving EGb 761 at a dose of 200 mg/kg presession and the other half vehicle (sweetened condensed milk). A statistically significant positive effect of treatment with EGb-761 was observed. The present data are consistent with the beneficial effects on cognitive performance which have been widely reported in human subjects. In addition, the data suggest that the methods employed, i.e., continuous learning and delayed nonmatching to position tasks in aged rats, are capable of detecting drugs of possible value in the treatment of human cognitive impairment. Finally, the present results encourage a search for the pharmacologically active principles of EGb 761 and for their mechanisms of action.

Ex vivo regulation of adrenal cortical cell steroid and protein synthesis, in response to adrenocorticotropic hormone stimulation, by the Ginkgo biloba extract EGb 761 and isolated ginkgolide B

We previously demonstrated that repeated treatment of rats with the standardized extract of Ginkgo biloba leaves, EGb 761, and its bioactive component ginkgolide B (GKB), specifically reduces the ligand binding, and protein and messenger RNA expression of the adrenal mitochondrial peripheral benzodiazepine receptor (PBR), a key element in the regulation of cholesterol transport, resulting in decreased circulating corticosterone levels. Adrenocortical cells were isolated from rats treated with EGb 761 or GKB and cultured for 2 and 12 days. The effect of ACTH on normal and metabolically labeled cells was examined. Corticosterone levels were measured by RIA, and protein synthesis was analyzed by two-dimensional gel electrophoresis. Ex vivo treatment with EGb 761 and GKB resulted, respectively, in 50% and 80% reductions of ACTH-stimulated corticosterone production by adrenocortical cells cultured for 2 days compared with that by cells isolated from saline-treated rats. Two-dimensional gel electrophoresis analysis revealed that in cells from both control and drug-treated animals, ACTH induced the synthesis, at the same level, of a 29-kDa and pI 6.4-6.7 protein identified as the adrenal steroidogenic acute regulatory protein (StAR). In addition, treatment with EGb 761 and GKB specifically altered the synthesis of seven proteins, including inhibition of synthesis of a 17-kDa, identified as PBR. After 12 days in culture, ACTH-stimulated adrenocortical cell steroid synthesis was maintained, and it was identical among the cells isolated from animals treated with GKB or saline. Under the same conditions, the expression of PBR was recovered, whereas no effect of ACTH on the 29-kDa and 6.4-6.7 pI protein (StAR) or other protein synthesis could be seen. A comparative analysis of the effects of GKB and EGb 761 on adrenocortical steroidogenesis and protein synthesis identified, in addition to the 17-kDa PBR, target proteins of 32 kDa (pI 6.7) and 40 kDa (pI 5.7-6.0) as potential mediators of the effect of EGb 761 and GKB on ACTH-stimulated glucocorticoid synthesis. In conclusion, these results 1) validate and extend our previous in vivo findings on the effect of EGb 761 and GKB on ACTH-stimulated adrenocortical steroidogenesis, 2) demonstrate the specificity and reversibility of EGb 761 and GKB treatment, 3) question the role of the 29-kDa, 6.4-6.7 pI protein (mature StAR) as the sole mediator of ACTH-stimulated steroid production, and 4) demonstrate the obligatory role of PBR in hormone-regulated steroidogenesis.

Peripheral benzodiazepine receptor in cholesterol transport and steroidogenesis

Steroidogenesis begins with the metabolism of cholesterol to pregnenolone by the inner mitochondrial membrane cytochrome P450 side-chain cleavage (P450scc) enzyme. The rate of steroid formation, however, depends on the rate of cholesterol transport from intracellular stores to the inner mitochondrial membrane and loading of P450scc with cholesterol. In previous in vitro studies, we demonstrated that a key element in the regulation of cholesterol transport is the mitochondrial peripheral-type benzodiazepine receptor (PBR). We also showed that the polypeptide diazepam binding inhibitor (DBI), an endogenous PBR ligand, stimulates cholesterol transport and promotes loading of cholesterol to P450scc in vitro, and that its presence is vital for hCG-induced steroidogenesis by Leydig cells. Based on these data and the observations that i) the mitochondrial PBR binding and topography are regulated by hormones; ii) the 18-kDa PBR protein is functionally coupled to the mitochondrial contact site voltage-dependent anion channel protein; iii) the 18-kDa PBR protein is a channel for cholesterol, as shown by molecular modeling and in vitro reconstitution studies; iv) targeted disruption of the PBR gene in steroidogenic cells dramatically reduces the ability of the cells to transport cholesterol in the mitochondria and produce steroids; v) endocrine disruptors, with known anisteroidogenic effect, inhibit PBR ligand binding; and vi) in vivo reduction of adrenal PBR expression results in reduced circulating glucocorticoid levels, we conclude that PBR is an indispensable element of the steroidogenic machinery.

Extracts of Ginkgo biloba leaves inhibit monoamine oxidase

Extracts of Ginkgo biloba leaves produce reversible inhibition of rat brain monoamine (MAO). Both MAO-A and -B types were inhibited to a similar extent. The MAO inhibitory compound(s) were present in dried or fresh Ginkgo biloba leaves as well as in commercially available capsules of Ginkgo biloba and appear to be heat stable with relatively low molecular weight. MAO inhibition by Ginkgo biloba may be a mechanism underlying reported anti-stress and anxiolytic activities of this natural product.

Stress-induced 5-HT1A receptor desensitization: protective effects of Ginkgo biloba extract (EGb 761)

The effects of sub-chronic cold stress on the functioning of hippocampal 5-HT1A receptors in old isolated rats and the possible protective effects of Ginkgo biloba extract (EGb 761) were investigated. Cold exposure during five days, produced a significant reduction of the inhibitory effect of 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT) on forskolin-stimulated adenylyl cyclase activity. In contrast, neither the affinity nor the density of hippocampal [3H]8-OH-DPAT binding sites were affected indicating that the reduced sensitivity of 5-HT1A receptors induced by stress is probably due to a modification of their coupling mechanisms to adenylyl cyclase. The stress-induced desensitization of 5-HT1A receptors was prevented by the administration of EGb 761 (50 mg/kg per os/14 days). These results clearly indicate that 5-HT1A receptors are desensitized by stress and point out the reduced capacity of old rats to cope with the adverse effects of a chronic stressor. EGb 761 appears to restore the age-related decreased capacity to adapt to a chronic stressor.