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Objectives: Hypercholesterolaemia is a major risk factor for developing atherosclerosis. Increased consumption of fruits and vegetables is recommended to hypercholesterolaemic patients. In this study, the hypocholesterolaemic effect of apigenin and luteolin was evaluated in a hamster model., Methods: Hamsters were put on a high-cholesterol diet for 9 weeks, and apigenin or luteolin was administered in the diet at 60 and 300 ppm., Key Findings: Both apigenin and luteolin supplementations could attenuate the aorta plaque formation by 30% and 20%, respectively. Apigenin-fed hamsters at both dosages displayed a 1.5-fold increase in hepatic Ldlr expression and a 40% reduction in non-HDL cholesterol level as compared with those in the control fed a high-cholesterol (HC) diet. Besides, faecal elimination of cholesterol was facilitated by 20% in the hamsters with high apigenin consumption. Suppressing the expression of the cholesterol transporter ncp1l1 in the intestinal mucosa could block the cholesterol absorption and promote its elimination. The differential regulations of ncp1l1 and Ldlr appeared to be the underlying hypocholesterolaemic mechanism of apigenin in this model system. Luteolin supplementation, on the other hand, had no effect on the blood cholesterol., Conclusions: This study illustrated that dietary administration of apigenin attenuated HC feeding-induced hypercholesterolemia in hamsters., (© 2018 Royal Pharmaceutical Society.)

Hypercholesterolemia is a major risk factor in the development of atherosclerosis. High blood cholesterol can be the result of increased biosynthesis or reduced elimination of cholesterol in the system. Increased consumption of fruits and vegetables is recommended for patients suffering from hypercholesterolemia. The plant food flavones apigenin and luteolin have previously been shown to suppress the synthesis of cholesterol in human hepatocytes. The effectiveness of these two flavones in controlling blood cholesterol was examined in a mouse model in the present study. Mice were fed a high-fat diet and apigenin or luteolin at 50 and 250 ppm was mixed in the diet. After 8 weeks of treatment, the administration of 250 ppm apigenin or 250 ppm luteolin could modulate the total and serum non-HDL cholesterol. The expressions of srebf-2 mRNA, Srebp-2 protein and Hmgcr protein were decreased in the livers of apigenin-treated mice; meanwhile, AMPK was activated in this group of mice. In contrast, suppressed ncp1l1 and induced abcg-5/8 mRNA expressions were seen in the intestinal mucosa of luteolin-fed animals. Increased fecal cholesterol content was also observed in the luteolin-treated mice. These results revealed that apigenin suppressed the biosynthesis of cholesterol, whereas luteolin promoted the elimination of cholesterol. In summary, this study illustrated that the two flavones could attenuate high-fat feeding-induced hypercholesterolemia in two different mechanisms., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Consumption of fruits and vegetables is generally regarded as beneficial to plasma lipid profile. The mechanism by which the plant foods induce desirable lipid changes remains unclear. SREBP-2 is crucial in cholesterol metabolism, and it is a major regulator of the cholesterol biosynthesis enzyme HMGCR. Our lab has previously illustrated that apigenin and luteolin could attenuate the nuclear translocation of SREBP-2 through an AMPK-dependent pathway. In the present study, these two flavones were studied for their ability to deter the same in an AMPK-independent signaling route. The processing of SREBP-2 protein was promoted by phorbol 12-myristate 13-acetate (PMA) in the hepatic cells WRL and HepG2, and the increased processing was reversed by apigenin or luteolin co-administration. EMSA results demonstrated that the PMA-induced DNA-binding activity was weakened by the flavones. The increased amount of nuclear SREBP-2 in cells was attenuated by the flavonoid as shown by immunocytochemical imaging. Quantitative reverse transcriptase-polymerase chain reaction assay demonstrated that the transcription of HMGCR under both flavone treatments was reduced. However, apigenin appeared to be stronger than luteolin in restraining PMA-induced HMGCR mRNA expression. Since PMA is a diacylglycerol analog, these findings might have some physiological implications.

Sterol regulatory element-binding protein-2 (SREBP-2) is a pivotal transcriptional factor in cholesterol metabolism. Factors interfering with the proper functioning of SREBP-2 potentially alter plasma lipid concentrations. Consuming fruits and vegetables is associated with beneficial plasma lipid profile. The mechanism by which plant foods induce desirable lipid changes remains unclear. Apigenin, a common plant food flavonoid, was shown to modulate the nuclear translocation of SREBP-2 in the hepatic cells WRL-68 in the present study. The processing of SREBP-2 protein occurred after translation, and apigenin blocked this activation route. Further examination indicated that AMP-activated protein kinase (AMPK) was activated by the flavone, and co-administrating the AMPK-specific inhibitor compound C could release the blockage. Reporter gene assay revealed that the transactivation of sterol responsive element (SRE)-containing 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) promoter was suppressed by the flavone. Similarly, electromobility shift assay result also demonstrated a reduced DNA-binding activity on the SRE domain under the same treatment. The reduced transactivity and DNA-binding activity could be attributed to a decreased amount of SREBP-2 translocating from cytosol to nucleus as depicted by confocal microscopy. Quantitative RT-PCR assay demonstrated that the transcription of HMGCR followed the same pattern of SREBP-2 translocation. In summary, the present study showed that apigenin prevented SREBP-2 translocation and reduced the downstream gene HMGCR transcription. The minimum effective dosage should be achievable in the form of functional food consumption or dietary supplementation.

Aromatase or cytochrome P450 (CYP19) enzyme catalyzes the rate-determining reaction in estrogen synthesis. Inhibiting aromatase is a major strategy in treating breast cancer patients. However, suppression on the transcriptional activity may be equally important in controlling aromatase. Dietary flavones and flavonones have been previously demonstrated to be the most potent aromatase-inhibitory flavonoids. In the present study we examined their effects on the transcription regulation of CYP19 in MCF-7 cells. Real-time PCR results indicated that luteolin suppressed CYP19 mRNA expression while hesperetin increased it. Reporter gene assays were employed to look into the transactivity of CYP19 driven by promoters I.3 and II, and the result was consistent with the observation in mRNA expression. Further investigation using truncation reporter gene and electrophoretic mobility shift assays suggested that luteolin and hesperetin differentially influenced AP-1- and C/EBP-binding on the CYP19 promoter. Western blot analysis indicated that signaling transduction pathways involving JNK and ERK could be the underlying mechanisms for their actions. The present study showed that dietary flavones and flavonones might differentially regulate aromatase transcription in breast cells in addition to the inhibition at the enzyme level., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Cyclooxygenase (COX)-2 is the inducible isozyme catalyzing the conversion of arachidonic acid to prostanoids. Its expression has been linked to the process of carcinogenesis, including tumorigenesis of the breast. Apigenin (APG) is a flavone commonly found in fruit and vegetables, and is shown to be a potential modulator in inflammatory diseases. This study examined the potential suppressive effect of the flavone on phorbol ester-induced COX-2 expression in the breast cell lines MCF-10A and MCF-7. Real-time PCR and/or Western blotting indicated that APG in micromolar range significantly inhibited phorbol 12-myristate 13-acetate (PMA)-induced COX-2 expression in these breast cells. APG treatment reduced the amount of phospho-mitogen-activated protein kinase (MAPK) ERK-1/2, but it did not alter the activity of PKC. Activated ERKs might trigger the transactivation of AP-1 or CRE, which can be located at COX-2 promoter region (-72/-53). Reporter gene assay as well as electrophoretic mobility shift assays (EMSA) illustrated that APG inhibited transcription factor binding at this region in a dose-dependent manner. This study showed that APG down-regulated PMA-induced COX-2 expression in breast cells without affecting PKC activity. These findings could provide a scientific basis for developing APG nutraceutical against breast carcinogenesis., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-methenyltetrahydrofolate (5,10-methenylTHF)) and MeFox (5-methylTHF oxidation product)) by HPLC-MS/MS and RBC total folate by microbiologic assay in US population ≥ 1 year (n approximately 7500) participating in the National Health and Nutrition Examination Survey 2011-2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37.5 nmol/l; 100%), UMFA (1.21 nmol/l; 99.9%), MeFox (1.53 nmol/l; 98.8%), and THF (1.01 nmol/l; 85.2%) were mostly detectable. 5-FormylTHF (3.6%) and 5,10-methenylTHF (4.4%) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86.7%); UMFA (4.0%), non-methyl folate (4.7%) and MeFox (4.5%) contributed smaller amounts. Age was positively related to MeFox, but showed a U-shaped pattern for other folates. We generally noted sex and race/ethnic biomarker differences and weak (Spearman's r< 0.4) but significant (P< 0.05) correlations with physiological and lifestyle variables. Fasting, kidney function, smoking and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiological and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Aromatase is responsible for the rate-determining reaction in estrogen synthesis and is a prime target for treating estrogen-receptor-positive breast cancer. Previous in vitro study has demonstrated that apigenin (APG), naringenin (NGN) and hesperetin (HSP) are three of the most potent natural aromatase inhibitors. Because the enzyme inhibition could potentially block breast cancer development, we employed an established postmenopausal breast cancer model to examine the chemopreventive effect of these flavonoids in vivo. Athymic mice were ovariectomized and transplanted with aromatase-overexpressing MCF-7 cells. Dietary administration of HSP at 1000 ppm and 5000 ppm significantly deterred the xenograft growth, while a null effect was observed in mice treated with APG or NGN. Further study illustrated that plasma estrogen in HSP-treated mice was reduced. Messenger RNA expression of the estrogen-responsive gene pS2 was also decreased in the tumors of mice treated with 1000 and 5000 ppm HSP. On the other hand, western analysis indicated that cyclin D1, CDK4 and Bcl-x(L) were reduced in the tumors. This study suggested that HSP could be a potential chemopreventive agent against breast carcinogenesis through aromatase inhibition. [Copyright &y& Elsevier]