Genistein and quercetin increase connexin43 and suppress growth of breast cancer cells.

Connexin proteins form gap junctions, which permit direct exchange of cytoplasmic contents between neighboring cells. Evidence indicates that gap junctional intercellular communication (GJIC) is important for maintaining homeostasis and preventing cell transformation. Furthermore, connexins may have independent functions including tumor growth suppression. Most tumors express less connexins, have reduced GJIC and have increased growth rates compared with non-tumorigenic cells. The purpose of this study was to determine whether common flavonoids, genistein and quercetin, increase connexin43 (Cx43) levels, improve GJIC and suppress growth of a metastatic human breast tumor cell line (MDA-MB-231). Quercetin (2.5, 5 microg/ml) and genistein (0.5, 2.5, 15 microg/ml) upregulated Cx43 but failed to increase GJIC. Cx43 localized to the plasma membrane following genistein treatment (2.5, 15 mug/ml). In contrast, Cx43 aggregated in the perinuclear region following quercetin treatment (0.5, 2.5, 5, 15 microg/ml). Both genistein (15 microg/ml) and quercetin (2.5, 5, 15 microg/ml) significantly reduced MDA-MB-231 cell proliferation. In summary, genistein and quercetin increase Cx43 and suppress MDA-MB-231 cell proliferation at physiologically relevant concentrations. These results demonstrate that genistein and quercetin are potential anti-breast cancer agents.

In vivo inhibition of growth of human tumor lines by flavonoid fractions from cranberry extract.

Edible fruits and berries may serve as sources for novel anticancer agents, given that extracts of these foods have demonstrated cytotoxic activity against tumor cell lines. Semipurified, flavonoid-rich extracts of cranberry (Vaccinia macrocarpa) were shown previously to arrest proliferation of tumor cells and induce apoptosis. However, the ability of cranberry flavonoids to inhibit tumor growth in vivo has not been reported other than in a preliminary report. As model systems for testing this activity, human tumor cell lines representative of three malignancies were chosen: glioblastoma multiforme (U87), colon carcinoma (HT-29), and androgen-independent prostate carcinoma (DU145). A flavonoid-rich fraction 6 (Fr6) and a more purified proanthocyanidin (PAC)-rich fraction were isolated from cranberry presscake and whole cranberry, respectively, by column chromatography. Fr6 and PAC each significantly slowed the growth of explant tumors of U87 in vivo, and PAC inhibited growth of HT-29 and DU145 explants (P < 0.05), inducing complete regression of two DU145 tumor explants. Flow cytometric analyses of in vitro-treated U87 cells indicated that Fr6 and PAC could arrest cells in G1 phase of the cell cycle (P < 0.05) and also induce cell death within 24 to 48 h of exposure (P < 0.05). These results indicate the presence of a potential anticancer constituent in the flavonoid-containing fractions from cranberry extracts.

Citrus polymethoxylated flavones improve lipid and glucose homeostasis and modulate adipocytokines in fructose-induced insulin resistant hamsters.

The present study was undertaken to determine whether supplementation with polymethoxylated flavones (PMFs) could ameliorate the fructose-induced hypertriglyceridemia and other metabolic abnormalities associated with insulin resistance (IR) in hamsters. Following feeding with the fructose diet, hamsters were supplemented orally with PMF-L or PMF-H (62.5 and 125 mg/kg/day) for 4 weeks. Both PMF-treated groups showed a statistically significant (p<0.05) decrease in serum triglyceride (TG) and cholesterol levels compared to the fructose-fed control group. The fructose control group at the end of the study showed elevated serum insulin and impaired insulin sensitivity (glucose intolerance). On the other hand, PMF-supplemented groups showed a reversal in these metabolic defects, including a decrease in insulin level and an improvement in glucose tolerance. PMF supplementation also reduced TG contents in the liver and heart and was able to regulate adipocytokines by significantly suppressing TNF-alpha, INF-gamma, IL-1beta and IL-6 expression and increasing adiponectin in IR hamsters. The mechanism of PMF on the activation of peroxisome proliferator-activated receptors (PPAR) was also explored. PMF-H supplementation significantly increased PPARalpha and PPARgamma protein expression in the liver. This is the first report of positive effects of PMF on adipocytokine production and on PPAR expression in IR hamsters. This study suggests that PMF can ameliorate hypertriglyceridemia and its anti-diabetic effects may occur as a consequence of adipocytokine regulation and PPARalpha and PPARgamma activation.

Nobiletin, a citrus flavonoid isolated from tangerines, selectively inhibits class A scavenger receptor-mediated metabolism of acetylated LDL by mouse macrophages.

Flavonoids are a class of chemically related polyphenols that are nearly ubiquitous in nature. Of the more-than 4000 flavonoids thus identified, citrus fruit-derived flavonoids are suggested to have an inverse association with the occurrence of coronary heart disease via their ability to reduce plasma cholesterol concentrations. Our current studies examined whether citrus flavonoids possess an additional antiatherogenic effect by modulating macrophage metabolism of the specific class A scavenger receptor (SR-A) ligand, acetylated LDL (acLDL). In this study, both acLDL-metabolism and SR-A expression by cultured murine J774A.1 macrophages was examined following 24 h pretreatment (100 microM) with the flavonoids: naringenin (from grapefruit), hesperetin (from oranges), and tangeretin and nobiletin (from tangerines). Of these flavonoids, only nobiletin inhibited (50-72%) acLDL metabolism as measured by both cellular cholesterol ester mass and [3H]oleate incorporation into cholesterol esters. This nobiletin-mediated effect was specific for SR-A and not a global effect on lipoprotein metabolism by the macrophage, as all four citrus flavonoids significantly reduce the metabolism of beta-VLDL, which is primarily taken up by macrophages via the LDL receptor. Nevertheless, nobiletin did not affect SR-A protein expression, as measured by Western blot analysis, nor was cell surface expression of SR-A affected as measured by 4 degrees C binding studies using [125I]acLDL. In conclusion, our findings suggest that in addition to reducing plasma cholesterol concentrations, nobiletin may prevent atherosclerosis at the level of the vascular wall by inhibiting macrophage foam-cell formation.

Hypolipidemic effects and absorption of citrus polymethoxylated flavones in hamsters with diet-induced hypercholesterolemia.

Formulations containing citrus polymethoxylated flavones (PMFs), mainly tangeretin, or citrus flavanone glucosides, hesperidin and naringin, were evaluated for cholesterol-lowering potential in hamsters with diet-induced hypercholesterolemia. PMF metabolites were also investigated. Diets containing 1% PMFs significantly reduced serum total and very low-density lipoprotein (VLDL) + LDL cholesterol (by 19-27 and 32-40%, respectively) and either reduced or tended to reduce serum triacylglycerols. Comparable reductions were achieved by feeding a 3% mixture of hesperidin and naringin (1:1, w/w), implying lower hypolipidemic potency of the hesperidin/naringin vs PMFs. HPLC-MS analysis identified high serum, liver, and urine concentrations of tangeretin metabolites including dihydroxytrimethoxyflavone and monohydroxytetramethoxyflavone glucuronides and aglycones. Total liver concentrations of tangeretin derivatives corresponded to hypolipidemic concentrations of intact tangeretin in earlier experiments in vitro. This suggests that PMFs are novel flavonoids with cholesterol- and triacylglycerol-lowering potential and that elevated levels of PMF metabolites in the liver might be directly responsible for their hypolipidemic effects in vivo.

Modulation of HepG2 cell net apolipoprotein B secretion by the citrus polymethoxyflavone, tangeretin.

The purpose of the present study was to examine the role of tangeretin, a polymethoxylated flavone from citrus fruits, on the regulation of apolipoprotein B (apoB) and lipid metabolism in the human hepatoma cell-line HepG2. The marked reduction in apoB secretion observed in cells incubated with 72.8 microM tangeretin was rapid, apoB-specific, and partly reversible. The reduction also was observed under lipid-rich conditions and found to be insensitive to proteasomal degradation of nascent apoB. We followed our study by examining lipid synthesis and mass. A 24-h exposure of cells to 72.8 microM tangeretin decreased intracellular synthesis of cholesteryl esters, free cholesterol, and TAG by 82, 45, and 64%, respectively; tangeretin also reduced the mass of cellular TAG by 37%. The tangeretin-induced suppression of TAG synthesis and mass were associated with decreased activities of DAG acyltransferase (up to -39.0 +/- 3.0% vs. control) and microsomal triglyceride transfer protein (up to -35.5 +/- 2.5% vs. control). Tangeretin was also found to activate the peroxisome proliferator-activated receptor, a transcription factor with a positive regulatory impact on FA oxidation and TAG availability (up to 36% increase vs. control). The data suggest that tangeretin modulates apoB-containing lipoprotein metabolism through multiple mechanisms.

Relative bioavailability and antioxidant potential of two coenzyme q10 preparations.

Coenzyme Q10 (CoQ10) is synthesized by the human body and found in certain foods. Daily supplementation of CoQ10 could protect against heart disease but the bioavailability of CoQ10 supplements depends on the formulation taken. We compared the bioavailability and antioxidant properties of two commercial CoQ10 formulations, a commercial grade CoQ10 powder (commercial grade CoQ) and a new BT-CoQ10 BIO-TRANSFORMED (BT-CoQ10) obtained by fermentation of a soy-based, CoQ10-rich media with baker's yeast. Eleven healthy individuals participated in a randomized two-way crossover trial, with a 3-week washout period. Capsules containing 300 mg of either BT-CoQ10 or commercial grade CoQ10 were given daily for 1 week and multiple blood samples were taken for CoQ10, glutathione and glutathione peroxidase (GPx) determination. In 3 subjects, baseline plasma CoQ10 levels were lower prior to BT than prior to commercial grade CoQ treatment. In the remaining participants, ingestion of BT vs. commercial grade CoQ significantly increased maximum plasma CoQ10 concentration (+126%, p = 0.04) and tended to increase CoQ10 area under the curve from 0 to 24 h (+160%, p = 0.07). One week of treatment with each formulation increased plasma CoQ10 but did not alter plasma glutathione or GPx activity. The enhanced bioavailability of the BT product might be due to its predominantly reduced, hydrophilic membrane-complex form.