Ginkgo biloba, inflammation and lipoprotein(a)

Dietary natural products as emerging lipoprotein(a)-lowering agents

Elevated plasma lipoprotein(a) (Lp(a)) levels are associated with an increased risk of cardiovascular disease (CVD). Hitherto, niacin has been the drug of choice to reduce elevated Lp(a) levels in hyperlipidemic patients but its efficacy in reducing CVD outcomes has been seriously questioned by recent clinical trials. Additional drugs may reduce to some extent plasma Lp(a) levels but the lack of a specific therapeutic indication for Lp(a)-lowering limits profoundly reduce their use. An attractive therapeutic option is natural products. In several preclinical and clinical studies as well as meta-analyses, natural products, including l-carnitine, coenzyme Q ₁₀ , and xuezhikang were shown to significantly decrease Lp(a) levels in patients with Lp(a) hyperlipoproteinemia. Other natural products, such as pectin, Ginkgo biloba, flaxseed, red wine, resveratrol and curcuminoids can also reduce elevated Lp(a) concentrations but to a lesser degree. In conclusion, aforementioned natural products may represent promising therapeutic agents for Lp(a) lowering.

Lipoprotein(a) and SYNTAX Score Association with Severity of Coronary Artery Atherosclerosis in North India

OBJECTIVES

This cross-sectional study investigated the association of lipoprotein(a) [Lp(a)] levels as an atherosclerosis predictor and their relationship to the severity of coronary artery disease (CAD).

METHODS

360 consecutive patients at Sanjay Gandhi Postgraduate Institute of Medical Sciences and King George's Medical University hospitals, Lucknow, North India, with chest pains, CAD symptoms and on lipid-lowering therapy were enrolled between June 2009 and October 2011. Before coronary artery angiography (CAG), a fasting blood sample was assessed for lipid and Lp(a) levels. The synergy between percutaneous coronary intervention with taxus and cardiac surgery (SYNTAX) score was calculated according to the CAG results. Patients were divided into 3 groups based on CAD severity and SYNTAX scores.

RESULTS

Angiography revealed CAD in 270 patients. Lp(a) levels were higher in CAD compared to non-CAD patients (48.7 ± 23.8 mg/dl versus 18.9 ± 11.1 mg/dl [P <0.0001]). The levels of Lp(a) were lower in single than in double and triple vessels (39.3 ± 18.4 mg/dl versus 58.0 ± 23.0 mg/dl, and 69.2 ± 24.1 mg/dl, [P <0.05]). Lp(a) levels were significantly higher in severe CAD with SYNTAX score >30 (88.0±24.0 mg/dl). Lp(a) levels correlated significantly with SYNTAX scores (r = 0.70, P <0.0001).

CONCLUSION

In this study, Lp(a) levels were positively associated with a patient's SYNTAX score in diseased vessels. Furthermore, an elevated Lp(a) level was a causal, independent risk factor of CAD. Lowering Lp(a) levels would reduce CAD in primary and secondary prevention settings. There is an urgent need to define more precisely which patients to treat and which to target for earlier interventions.

Ginkgo biloba extract (GbE) enhances the anti-atherogenic effect of cilostazol by inhibiting ROS generation

In this study, the synergistic effect of 6-[4-(1-cyclohexyl- 1H-tetrazol-5-yl) butoxy]-3,4-dihydro-2(1H )-quinolinone (cilostazol) and Ginkgo biloba extract (GbE) was examined in apolipoprotein E (ApoE) null mice. Co-treatment with GbE and cilostazol synergistically decreased reactive oxygen species (ROS) production in ApoE null mice fed a high-fat diet. Co-treatment resulted in a significantly decreased atherosclerotic lesion area compared to untreated ApoE mice. The inflammatory cytokines and adhesion molecules such as monocyte chemoattractant-1 (MCP-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and VCAM-1 which can initiate atherosclerosis were significantly reduced by the co-treatment of cilostazol with GbE. Further, the infiltration of macrophages into the intima was decreased by co-treatment. These results suggest that co-treatment of GbE with cilostazol has a more potent anti-atherosclerotic effect than treatment with cilostazol alone in hyperlipidemic ApoE null mice and could be a valuable therapeutic strategy for the treatment of atherosclerosis.

Optimal therapy for reduction of lipoprotein(a)

WHAT IS KNOWN AND OBJECTIVE

There is a growing body of experimental and clinical evidence for the atherogenic and pro-thrombotic potential of Lipoprotein(a) [Lp(a)], as well as for its causative role in coronary heart disease and stroke. We comment on novel strategies for reducing Lp(a) levels.

COMMENT

Irrespective of the underlying biological mechanisms explaining the athero-thrombotic potential of this lipoprotein, most work has focused on the identification of suitable therapies for hyperlipoproteinemia(a). These include apheresis techniques, nicotinic acid and statins. None of these strategies have been shown to be definitely effective or convenient for the patient and new strategies are being attempted. Promising results are emerging with therapeutic interventions targeting the 'inflammatory pathways' by inhibition of Interleukin-6 (IL-6) signalling with natural compounds (e.g., Ginko biloba) or the IL-6 receptor antibody Tocilizumab. These may both lower Lp(a) and cardiovascular risk of the patients. Besides inhibiting platelet function, antiplatelet therapy with aspirin may also decrease the plasma concentration of Lp(a) and modulate its influence on platelets.

WHAT IS NEW AND CONCLUSION

We highlight the inadequacy of current approaches for lowering Lp(a) and draw attention to novel insights that may lead to better treatment.

Screening and therapeutic management of lipoprotein(a) excess: review of the epidemiological evidence, guidelines and recommendations

Lipoprotein(a) (Lp(a)) is a low density lipoprotein-like particle in which apolipoprotein B100 is covalently linked to the unique apolipoprotein(a). There is a mounting body of evidence suggesting a role of Lp(a) in the development and progression of several vascular diseases, such as coronary heart disease, ischemic stroke, abdominal aortic aneurysm and venous thromboembolism, so that prominent scientific societies have recently endorsed guidelines and recommendations that increasingly encourage the screening and the therapeutic management of Lp(a) excess. In this article, we review the epidemiologic evidence, guidelines and recommendations concerning the relationship between increased plasma Lp(a) levels and risk of cardiovascular disease or venous thromboembolism by systematically retrieving the most relevant articles from electronic databases. Although uncertainty still remains regarding the opportunity to screen for hyperlipoproteinemia(a), it seems inopportune as yet to measure plasma Lp(a) levels in asymptomatic persons, while its measurement might be of clinical significance in selected categories of patients at intermediate or high cardiovascular risk. The measurement of Lp(a) should be performed by using immunometric, harmonized and size-insensitive techniques and results reported in total lipoprotein mass rather than in traditional units. It is uncertain if Lp(a) genotyping or phenotyping add any additional information for the cardiovascular disease risk stratification. Although the optimal therapeutic management of Lp(a) excess is still controversial, a general agreement exists that very high Lp(a) levels should be lowered in patients with multiple cardiovascular risk factors, preferably with nicotinic acid therapy (e.g., 1.0-3.0 g/day).

Application of GC/MS-based metabonomic profiling in studying the lipid-regulating effects of Ginkgo biloba extract on diet-induced hyperlipidemia in rats

AIM

To evaluate the lipid-regulating effects of extract from Ginkgo biloba leaves (EGB) using pharmacological methods and metabonomic profiling in a rat model of diet-induced hyperlipidemia.

METHODS

EGB was orally administered at a dose level of 40 mg/kg in both the EGB-prevention and -treatment groups. All rat samples obtained were examined for known and potential biomarkers and enzyme activity using commercial assay kits and GC/MS-based metabonomic profiling coupled with principal component analysis (PCA).

RESULTS

The data obtained from the assay kits indicated that EGB reduced total cholesterol and low density lipoprotein cholesterol levels and increased high density lipoprotein cholesterol levels in rat plasma obtained from both the EGB-prevention and -treatment groups compared with those of the diet-induced hyperlipidemia group. EGB also increased the activities of lipoprotein lipase and hepatic lipase and excretion of fecal bile acid in rats from the EGB-prevention and-treatment groups. Using GC/MS-based metabonomic analysis, more than 40 endogenous metabolites were identified in rat plasma. PCA of rat plasma samples obtained using GC/MS produced a distinctive separation of the four treatment groups and sampling points within each group. Metabolic changes during hyperlipidemia formation and improvement resulting from EGB treatment were definitively monitored with PCA score plots. Furthermore, elevated levels of sorbitol, tyrosine, glutamine and glucose, and decreased levels of citric acid, galactose, palmitic acid, arachidonic acid, acetic acid, cholesterol, butyrate, creatinine, linoleate, ornithine and proline, were observed in the plasma of rats treated with EGB.

CONCLUSION

EGB exerts multi-directional lipid-lowering effects on the rat metabonome, including limitation of the absorption of cholesterol, inactivation of HMGCoA and favorable regulation of profiles of essential polyunsaturated fatty acid (EFA). Further experiments are warranted to explore the mechanisms of action underlying the lipid-regulating effects of EGB against hyperlipidemia.

Inhibitions of vascular endothelial growth factor expression and foam cell formation by EGb 761, a special extract of Ginkgo biloba, in oxidatively modified low-density lipoprotein-induced human THP-1 monocytes cells

It has been reported that oxidatively modified low-density lipoprotein (Ox-LDL) involvement with vascular endothelial growth factor (VEGF) and foam cell formation play an important role in atherosclerosis (AS). Protective effects of Ginkgo biloba extract (EGb 761) have been identified for some cardiovascular and neurological disorders. The aim of this study was to investigate whether Ox-LDL regulates VEGF expression in human THP-1 monocytes, as well as the effect of EGb 761 on VEGF expression and the formation of foam cells. After exposure to Ox-LDL alone or in combination with EGb 761 for up to 48h, cell viability was measured using the MTT assay. VEGF protein content in the supernatant was analyzed by enzyme-linked immunosorbent assay (ELISA). VEGF mRNA was determined by real-time PCR. To determine the effect of EGb 761 on foam cell formation, an Ox-LDL-induced foam cell model was used. Ox-LDL inhibited the growth of THP-1 cells and EGb 761 increased the cell survival rate. Ox-LDL markedly increased VEGF expression in THP-1 cells in a time- and concentration-dependent manner, which was significantly suppressed by EGb 761. EGb 761 also inhibited monocyte/macrophage-derived foam cell formation. These results suggest that Ox-LDL is involved in the development of human AS through VEGF induction in monocytes, and that EGb 761 prevents in vitro atherogenesis, probably via downregulation of VEGF expression in monocytes and inhibition of monocyte/macrophage-derived foam cell formation. The findings suggest a mechanism for the in vivo anti-AS effect of EGb 761 and support its potential clinical use in AS.

Effect of a short- and long-term treatment with Ginkgo biloba extract on amyloid precursor protein levels in a transgenic mouse model relevant to Alzheimer's disease

Several clinical trials have reported beneficial effects of the Ginkgo biloba extract EGb761 in the prevention and therapy of cognitive disorders including Alzheimer's disease (AD). The aim of the present long-term feeding trial was to study the impact of dietary EGb761 on Amyloid precursor protein (APP) metabolism in mice transgenic for human APP (Tg2576). Tg2576 mice were fed diets with and without EGb761 (300 mg/kg diet) for 1 and 16 months, respectively. Long-term treatment (16 months) with EGb761 significantly lowered human APP protein levels by approximately 50% as compared to controls in the cortex but not in the hippocampus. However, APP levels were not affected by EGb761 in young mice. Current data indicate that APP seems to be an important molecular target of EGb761 in relation to the duration of the Ginkgo biloba treatment and/or the age of the animals. Potential neuroprotective properties of EGb761 may be, at least partly, related to its APP lowering activity.