Molecular mechanisms underlying the cholesterol-lowering effect of Ginkgo biloba extract in hepatocytes: a comparative study with lovastatin

The molecular mechanisms of ginkgo (Ginkgo biloba) activity in signaling pathways: A comprehensive review

BACKGROUND

One of the most unique plants that have ever grown on the planet is Ginkgo biloba L., a member of the Ginkgoaceae family with no close living relatives. The existence of several differently structured components of G. biloba has increased the chemical variety of herbal therapy. Numerous studies that investigated the biochemical characteristics of G. biloba suggest this plant as a potential treatment for many illnesses.

PURPOSE

Review the molecular mechanisms involved in the signaling pathways of G. biloba activity in varied circumstances and its potential as a novel treatment for various illnesses.

METHODS

Studies focusing on the molecular processes and signaling pathways of compounds and extracts of G. biloba were found and summarized using the proper keywords and operators from Google Scholar, PubMed, Web of Science, and Scopus without time restrictions.

RESULTS

G. biloba exerts its effects through its anti-inflammatory, anti-apoptotic, anti-cancer, neuroprotective, cardioprotective, hepatoprotective, antiviral, antibacterial, pulmoprotective, renoprotective, anti-osteoporosis, anti-melanogenic, retinoprotective, otoprotective, adipogenic, and anti-adipogenic properties. The most important mechanisms involved in these actions are altering the elevation of ROS formation, inhibiting NADPH oxidases activation, altering the expression of antioxidant enzymes, downregulating MAPKs (p38 MAPK and ERK, and JNK) and AP-1, increasing cAMP, inactivating Stat5, activating the AMPK signaling pathway, affecting Stat3/JAK2, NF-κB, Nrf-2, mTOR, HGF/c-Met, Wnt/β-catenin and BMP signaling pathways, and changing the mitochondrial transmembrane potential, the Bax/Bcl-2 ratio, the release of Cyc from mitochondria to cytosol, the protein cleavage of caspases 3, 7, 8, 9, and 12, poly (ADP-ribose) polymerase, and MMPs levels.

CONCLUSIONS

G. biloba and its components have gained attention in recent years for their therapeutic benefits, such as their anti-inflammatory, antioxidant, anti-apoptotic, and apoptotic effects. By understanding their molecular mechanisms and signaling pathways, potential novel medicines might be developed in response to the rising public desire for new therapies.

Ginkgo biloba attenuated detrimental inflammatory and oxidative events due to Trypanosoma brucei rhodesiense in mice treated with melarsoprol

BACKGROUND

The severe late stage Human African Trypanosomiasis (HAT) caused by Trypanosoma brucei rhodesiense (T.b.r) is characterized by damage to the blood brain barrier, severe brain inflammation, oxidative stress and organ damage. Melarsoprol (MelB) is currently the only treatment available for this disease. MelB use is limited by its lethal neurotoxicity due to post-treatment reactive encephalopathy. This study sought to assess the potential of Ginkgo biloba (GB), a potent anti-inflammatory and antioxidant, to protect the integrity of the blood brain barrier and ameliorate detrimental inflammatory and oxidative events due to T.b.r in mice treated with MelB.

METHODOLOGY

Group one constituted the control; group two was infected with T.b.r; group three was infected with T.b.r and treated with 2.2 mg/kg melarsoprol for 10 days; group four was infected with T.b.r and administered with GB 80 mg/kg for 30 days; group five was given GB 80mg/kg for two weeks before infection with T.b.r, and continued thereafter and group six was infected with T.b.r, administered with GB and treated with MelB.

RESULTS

Co-administration of MelB and GB improved the survival rate of infected mice. When administered separately, MelB and GB protected the integrity of the blood brain barrier and improved neurological function in infected mice. Furthermore, the administration of MelB and GB prevented T.b.r-induced microcytic hypochromic anaemia and thrombocytopenia, as well as T.b.r-driven downregulation of total WBCs. Glutathione analysis showed that co-administration of MelB and GB prevented T.b.r-induced oxidative stress in the brain, spleen, heart and lungs. Notably, GB averted peroxidation and oxidant damage by ameliorating T.b.r and MelB-driven elevation of malondialdehyde (MDA) in the brain, kidney and liver. In fact, the co-administered group for the liver, registered the lowest MDA levels for infected mice. T.b.r-driven elevation of serum TNF-α, IFN-γ, uric acid and urea was abrogated by MelB and GB. Co-administration of MelB and GB was most effective in stabilizing TNFα levels. GB attenuated T.b.r and MelB-driven up-regulation of nitrite.

CONCLUSION

Utilization of GB as an adjuvant therapy may ameliorate detrimental effects caused by T.b.r infection and MelB toxicity during late stage HAT.

Potential dual inhibitors of PCSK-9 and HMG-R from natural sources in cardiovascular risk management

Atherosclerotic cardiovascular disease (ASCVD) stands amongst the leading causes of mortality worldwide and has attracted the attention of world's leading pharmaceutical companies in order to tackle such mortalities. The low-density lipoprotein-cholesterol (LDL-C) is considered the most prominent biomarker for the assessment of ASCVD risk. Distinct inhibitors of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-R), the chief hepatic cholesterogenic enzyme, are being used since last seven decades to manage hypercholesterolemia. On the other hand, discovery and the association of proprotein convertase subtilisin/kexin type-9 (PCSK-9) with increased ASCVD risk have established PCSK-9 as a novel therapeutic target in cardiovascular medicine. PCSK-9 is well reckoned to facilitate the LDL-receptor (LDL-R) degradation and compromised LDL-C clearance leading to the arterial atherosclerotic plaque formation. The currently available HMG-R inhibitors (statins) and PCSK-9 inhibitors (siRNA, anti-sense oligonucleotides, and monoclonal antibodies) have shown great promises in achieving LDL-C lowering goals, however, their life long prescriptions have raised significant concerns. These deficits associated with the synthetic HMG-R and PCSK-9 inhibitors called for the discovery of alternative therapeutic candidates with potential dual HMG-R and PCSK-9 inhibitory activities from natural origins. Therefore, this report firstly describes the mechanistic insights into the cholesterol homeostasis through HMG-R, PCSK-9, and LDL-R functionality and then compiles the pharmacological effects of natural secondary metabolites with special emphasis on their dual HMG-R and PCSK-9 inhibitory action. In conclusion, various natural products exhibit atheroprotective effects via targeting HMG-R and PCSK-9 activities and lipoprotein metabolism, however, further clinical assessments are still warranted prior their approval for ASCVD risk management in hypercholesterolemic patients.

Pharmacokinetic herb-disease-drug interactions: Effect of ginkgo biloba extract on the pharmacokinetics of pitavastatin, a substrate of Oatp1b2, in rats with non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. is a traditional Chinese medicine for hyper lipaemia. Ginkgo flavonols and terpene lactones are responsible for the lipid-lowering effect in non-alcoholic fatty liver disease (NAFLD). However, the pharmacokinetics of ginkgo flavonols and terpene lactones in NAFLD was not clarified.

AIM OF THE STUDY

To investigate the effects of Ginkgo biloba L. leaves extracts (EGB) and NAFLD on hepatocyte organic anion transporting polypeptide (Oatp)1b2, and to assess the pharmacokinetics of EGB active ingredients in NAFLD rats.

MATERIALS AND METHODS

Male rats were fed with a high-fat diet to induce NAFLD models. The pharmacokinetic characteristics of EGB active ingredients were studied in NAFLD rats after two or four weeks of treatment with 3.6, 10.8, and 32.4 mg/kg EGB. The effects of NAFLD and EGB were investigated on the systemic exposure of pitavastatin, a probe substrate of Oatp1b2. The inhibitory effects of ginkgo flavonols and terpene lactones on OATP1B1-mediated uptake of ³H-ES were tested in hOATP1B1-HEK293 cells.

RESULTS

The plasma exposure of ginkgolides and flavonols in NAFLD rats increased in a dose-dependent manner following oral administration of EGB at 3.6-32.4 mg/kg. The half-lives of ginkgolides A, B, C, and bilobalide (2-3 h) were shorter than quercetin, kaempferol, and isorhamnetin (approximately 20 h). NAFLD reduced the plasma pitavastatin exposure by about 50 % due to the increased Oatp1b2 expression in rat liver. Increased EGB (from 3.6 to 32.4 mg/kg) substantially increased the C_max and AUC_0-t of pitavastatin by 1.8-3.2 and 1.3-3.0 folds, respectively. In hOATP1B1-HEK293 cells, kaempferol and isorhamnetin contributed to the inhibition of OATP1B1-mediated uptake of ³H-ES with IC₅₀ values of 3.28 ± 1.08 μM and 46.12 ± 5.25 μM, respectively.

CONCLUSIONS

NAFLD and EGB can alter the activity of hepatic uptake transporter Oatp1b2 individually or in combination. The pharmacokinetic herb-disease-drug interaction found in this research will help inform the clinical administration of EGB or Oatp1b2 substrates.

Beneficial Effects of Plant-Derived Natural Products on Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease is becoming in one of the most prevalent liver diseases that leads to liver transplantation. This health problem is a multisystem disease with a complex pathogenesis that involves liver, adipose tissue, gut, and muscle. Although several pharmacological agents have been investigated to prevent or treat non-alcoholic fatty liver disease, currently there is no effective treatment for the management of this chronic liver disease. Nonetheless, the use of natural products has emerged as a alternative therapeutic for the treatment of hepatic diseases, including non-alcoholic fatty liver disease, due to its anti-inflammatory, antioxidant, antidiabetic, insulin-sensitizing, antiobesity, hypolipidemic, and hepatoprotective properties. In the present review, we have discussed the evidence from experimental and clinical studies regarding the potential beneficial effects of plant-derived natural products (quercetin, resveratrol, berberine, pomegranate, curcumin, cinnamon, green tea, coffee, garlic, ginger, ginseng, and gingko biloba) for the treatment or prevention of non-alcoholic fatty liver disease.

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.

Dietary Ginkgo biloba leaf extract alters immune-related gene expression and disease resistance to Aeromonas hydrophila in common carp Cyprinus carpio

Ginkgo biloba leaf is widely used in traditional medicine in China. The present study aimed to illustrate the effects of dietary Ginkgo biloba leaf extract (GBLE) on growth performance and immune responses in common carp infected by Aeromonas hydrophila. Six different diets either not treated (control) or treated with 0.5, 1, 2, 5 and 10 g/kg of GBLE were designed to feed the fishes for 8 weeks. The results indicated that, compared to the control groups, 10 g/kg dietary GBLE significantly increased body growth and feed utilization. In GBLE dietary groups, red blood cell levels, white blood cells, hematocrit, hemoglobin, total protein, albumin and globulin were significantly increased relative to the control groups. Dietary supplementation with 5 g/kg GBLE increased the phagocytic ratio, and phagocytic indexes increased in the 2, 5 and 10 g/kg groups relative to the control groups. Moreover, 2, 5 and 10 g/kg GBLE diets increased O₂^- production compared to the control groups. Additionally, GBLE diets stimulated lysozyme activity (in 10 g/kg group) and inhibited bactericidal activity (in 0.5, 2, 5 and 10 g/kg group). Quantitative real-time PCR showed that IL1β, IL8, TNF-α, IL10, TGFβ, and inducible enzyme genes were prone to decrease while SAA, hepcidin and GPX1 were increased due to the GBLE diet in the intestine. In the head-kidney, the GBLE treatment decreased IL1β, IL8, TNF-α, IL10, TGFβ, INOS and arginase gene expressions, whereas SOD upregulation was found in the GBLE condition. The mRNA expressions of IL1β, IL8, TNF-α, IL10 and INOS were decreased, but SAA, hepcidin, GPX1 and SOD mRNA levels were increased in the spleen in the GBLE diet compared to the control. Additionally, diet supplemented with GBLE improved the survival rate infected with A. hydrophila. Our observations suggest that GBLE effectively enhanced growth performance, modulated immune-related gene expression. It improved survival rate of common carp after A. hydrophila infection and the optimum concentration we recommend is 10 g/kg of GBLE.

IL-33 promotes IL-10 production in macrophages: a role for IL-33 in macrophage foam cell formation

We evaluated the role of IL-10- in IL-33-mediated cholesterol reduction in macrophage-derived foam cells (MFCs) and the mechanism by which IL-33 upregulates IL-10. Serum IL-33 and IL-10 levels in coronary artery disease patients were measured. The effects of IL-33 on intra-MFC cholesterol level, IL-10, ABCA1 and CD36 expression, ERK 1/2, Sp1, STAT3 and STAT4 activation, and IL-10 promoter activity were determined. Core sequences were identified using bioinformatic analysis and site-specific mutagenesis. The serum IL-33 levels positively correlated with those of IL-10. IL-33 decreased cellular cholesterol level and upregulated IL-10 and ABCA1 but had no effect on CD36 expression. siRNA-IL-10 partially abolished cellular cholesterol reduction and ABCA1 elevation by IL-33 but did not reverse the decreased CD36 levels. IL-33 increased IL-10 mRNA production but had little effect on its stability. IL-33 induced ERK 1/2 phosphorylation and increased the luciferase expression driven by the IL-10 promoter, with the highest extent within the −2000 to −1752 bp segment of the 5′-flank of the transcription start site; these effects were counteracted by U0126. IL-33 activated Sp1, STAT3 and STAT4, but only the STAT3 binding site was predicted in the above segment. Site-directed mutagenesis of the predicted STAT3-binding sites (CTGCTTCCTGGCAGCAGAA→CTGCCTGGCAGCAGAA) reduced luciferase activity, and a STAT3 inhibitor blocked the regulatory effects of IL-33 on IL-10 expression. Chromatin immunoprecipitation (CHIP) confirmed the STAT3-binding sequences within the −1997 to −1700 and −1091 to −811 bp locus regions. IL-33 increased IL-10 expression in MFCs via activating ERK 1/2 and STAT3, which subsequently promoted IL-10 transcription and thus contributed to the beneficial effects of IL-33 on MFCs.

Postprandial hyperglycemia and postprandial hypertriglyceridemia in type 2 diabetes

Postprandial glucose level is an independent risk factor for cardiovascular disease that exerts effects greater than glucose levels at fasting state, whereas increase in serum triglyceride level, under both fasting and postprandial conditions, contributes to the development of arteriosclerosis. Insulin resistance is a prevailing cause of abnormalities in postabsorptive excursion of blood glucose and postprandial lipid profile. Excess fat deposition renders a vicious cycle of hyperglycemia and hypertriglyceridemia in the postprandial state, and both of which are contributors to atherosclerotic change of vessels especially in patients with type 2 diabetes mellitus. Several therapeutic approaches for ameliorating each of these abnormalities have been attempted, including various antidiabetic agents or new compounds targeting lipid metabolism.

Flavonoid ingredients of Ginkgo biloba leaf extract regulate lipid metabolism through Sp1-mediated carnitine palmitoyltranferase 1A up-regulation

BACKGROUND

Lipid accumulation is the primary evidence of non-alcoholic fatty liver disease (NAFLD). Ginkgo biloba extract (GBE) and its flavonoid ingredients (quercetin, kaempferol, and isorhamnetin) could lessen the lipid accumulation associated with up-regulation of the rate-limiting enzyme, carnitine palmitoyltransferase 1A (CPT1A), in the β-oxidation of long-chain fatty acids. In this study, we investigated the mechanisms by which GBE and its flavonoids induced expression of CPT1A.

RESULTS

CPT1A inhibition with RNAi resulted in triglyceride accumulation in HepG2 cells. Through deletion and mutation analysis of CPT1A's promoter combined with electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) experiments, the CPT1A promoter region (-50 to -5 nt) was determined to contain two putative Sp1 binding sites, namely Sp1a and Sp1b, which might act as the GBE regulation response DNA element. Sp1 might be induced to transfer from cytoplasma to nucleus to bind the promoter region of -50 to -5 nt by GBE. The regulatory effects of GBE on CPT1A were also verified on the flavonoid ingredients quercetin, kaempferol, and isorhamnetin.

CONCLUSION

Sp1 was crucial in regulating CPT1A expression with GBE and its flavonoid ingredients, and the -50 to -5 nt region of CPT1A promoter played important roles in Sp1 binding.

Pharmacogenomics in the development and characterization of atheroprotective drugs

Atherosclerosis is the main cause of cardiovascular disease (CVD) and can lead to stroke, myocardial infarction, and death. The clinically available atheroprotective drugs aim mainly at reducing the levels of circulating low-density lipoprotein (LDL), increasing high-density lipoprotein (HDL), and attenuating inflammation. However, the cardiovascular risk remains high, along with morbidity, mortality, and incidence of adverse drug events. Pharmacogenomics is increasingly contributing towards the characterization of existing atheroprotective drugs, the evaluation of novel ones, and the identification of promising, unexplored therapeutic targets, at the global molecular pathway level. This chapter presents highlights of pharmacogenomics investigations and discoveries that have contributed towards the elucidation of pharmacological atheroprotection, while opening the way to new therapeutic approaches.

In Vitro Screening for Antihepatic Steatosis Active Components within Coptidis Rhizoma Alkaloids Extract Using Liver Cell Extraction with HPLC Analysis and a Free Fatty Acid-Induced Hepatic Steatosis HepG2 Cell Assay

A high-throughput method was developed and applied to screen for the active antihepatic steatosis components within Coptidis Rhizoma Alkaloids Extract (CAE). This method was a combination of two previously described assays: HepG2 cell extraction with HPLC analysis and a free fatty acid-induced (FFA) hepatic steatosis HepG2 cell assay. Two alkaloids within CAE, berberine and coptisine, were identified by HepG2 cell extraction with HPLC analysis as high affinity components for HepG2. These alkaloids were also determined to be active and potent compounds capable of lowering triglyceride (TG) accumulation in the FFA-induced hepatic steatosis HepG2 cell assay. This remarkable inhibition of TG accumulation (P < 0.01) by berberine and coptisine occurred at concentrations of 0.2 μg/mL and 5.0 μg/mL, respectively. At these concentrations, the effect seen was similar to that of a CAE at 100.0 μg/mL. Another five alkaloids within CAE, palmatine, epiberberine, jateorhizine, columbamine, and magnoline, were found to have a lower affinity for cellular components from HepG2 cells and a lower inhibition of TG accumulation. The finding of two potent and active compounds within CAE indicates that the screening method we developed is a feasible, rapid, and useful tool for studying traditional Chinese medicines (TCMs) in treating hepatic steatosis.

Inhibitory effect of Ginkgo biloba extract on fatty liver: regulation of carnitine palmitoyltransferase 1a and fatty acid metabolism

OBJECTIVE

To investigate the potential effect of Ginkgo biloba extract (GBE) on the prevention and treatment of nonalcoholic fatty liver disease (NAFLD).

METHODS

Male Wistar rats were divided into 4 groups (the control group, GBE group, high-fat diet [HFD] group and HFD + GBE group). The human hepatocellular carcinoma cell line (HepG2) was treated with GBE and its flavonoid ingredients. The fatty acid composition of the rat liver was analyzed with gas chromatography/time-of-flight mass spectrometry (GC/TOFMS). Triglyceride contents of both the rat liver and HepG2 cells were measured by enzymatic colorimetric method. The expressions of fatty acid metabolism-related genes were analyzed with real-time reverse transcription-polymerase chain reaction (RT-PCR). The protein expression and enzymatic activity were subsequently measured.

RESULTS

In rat livers, GBE reduced the elevations of hepatic triglyceride contents caused by HFD and the increased hepatic fatty acids were differentially affected by GBE. Notably, the expression and total activity of the fatty acid β-oxidation rate-limiting enzyme, carnitine palmitoyltransferase 1a (CPT1A), were also promoted with GBE ingestion. In HepG2 cells, GBE and its ingredients, quercetin, kaempferol and isorhamnetin, could decrease the cellular triglyceride content and upregulate the expression and total activity of CPT1A, respectively.

CONCLUSIONS

The triglyceride-lowering effect of GBE on the HFD rat liver is closely associated with the increased expression and activity of CPT1A, and the flavonoid ingredients are the major contributors of GBE.

Electroacupuncture frequency-related transcriptional response in rat arcuate nucleus revealed region-distinctive changes in response to low- and high-frequency electroacupuncture

Electroacupuncture (EA) has been clinically applied for treating different medical conditions, such as pain, strain, and immune diseases. Low- and high-frequency EAs have distinct therapeutic effects in clinical practice and experimental studies. However, the molecular mechanism of this difference remains obscure. The arcuate nucleus (Arc) is a critical region of the hypothalamus and is responsible for the effect of EA stimulation to remote acupoints. Gene expression profiling provides a powerful tool with which to explore the basis of physiopathological responses to external stimulus. In this study, using cDNA microarray, we investigated gene expressions in the rat Arc region induced by low-frequency (2-Hz) and high-frequency (100-Hz) EAs to two remote acupoints, zusanli (ST36) and sanyinjiao (SP6). We have found that more genes were differentially regulated by 2-Hz EA than 100-Hz EA (154 vs. 66 regulated genes/ESTs) in Arc, especially those related to neurogenesis, which was confirmed by qRT-PCR. These results demonstrate that the expression level of genes in the Arc region could be effectively regulated by low-frequency EA, compared with high-frequency EA, helping to uncover the mechanisms of the therapeutic effects of the low-frequency EA. Our results also indicate different-frequency EAs are spatially specific.

Transcriptome profiling analysis reveals region-distinctive changes of gene expression in the CNS in response to different moderate restraint stress

It is generally believed that temporary moderate stress to a living organism has protective and adaptive effects, but little is known about the responses of CNS to the moderate stresses at molecular level. This study aims to investigate the gene expression changes induced by moderate stress in CNS stress- and nociception-related regions of rats. Moderate restraint was applied to rats for 50 min and cDNA microarrays were used to detect the differential gene expression in different CNS regions. Transcriptome profiling analysis showed that at acute stage stress-related genes were up-regulated in arcuate nucleus; fight-or-flight behavior-related genes were up-regulated in periaqueductal gray, while nitric oxide and GABA signal transmission-related genes were up-regulated in spinal dorsal horn. In addition, immune-related genes were broadly regulated, especially at the late stage. These results suggested that specific genes of certain gene ontology categories were spatiotemporally regulated in specific CNS regions related to relevant functions under moderate external stimuli at acute stage, while immune response was broadly regulated at the late stage. The co-regulated genes among the three different CNS regions may play general roles in CNS when exposed to moderate stress. Furthermore, these results will help to elucidate the physiological processes involved in moderate stress in CNS.