2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone promoted glucose uptake and imposed a paradoxical effect on adipocyte differentiation in 3T3-L1 cells.

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), one of the flavonoids isolated and purified from the dried flower buds of Cleistocalyx operculatus, was explored for its function in glucose uptake/glycogen synthesis in insulin-sensitive tissue cells and its effect and mechanism on 3T3-L1 preadipocyte differentiation. DMC (10 µM) treatment remarkably promoted glucose uptake in differentiated 3T3-L1 adipocytes (P < 0.05 vs control group), whereas the glucose uptake in L6 myoblasts and glycogen synthesis in HepG2 hepatocytes were not affected by the treatment. DMC had paradoxical effects on lipid accumulation in 3T3-L1 cells compared with differentiation control. High concentrations of DMC (10 and 20 µM) markedly diminished lipid accumulation; however, a low concentration of DMC (2.5 µM) enhanced lipid storage in 3T3-L1 cells (P < 0.01 vs differentiation control group), and 5 µM DMC did not impose a significant effect. It was demonstrated that the effect of DMC in lipid accumulation was controlled by the expression of PPAR-γ.

HPLC-FLD determination of NBD-cholesterol, its ester and other metabolites in cellular lipid extracts.

22-[N(-7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-23,24-bisnor-5-cholen-3ß-ol (NBD-cholesterol), a fluorescent cholesterol analog, was an extragenous cholesterol tracer used to study cholesterol absorption and metabolism in cultured cells. In order to measure free intracellular cholesterol and its esters, a precise and sensitive method employing high-performance liquid chromatography/fluorescence detection (HPLC-FLD) was developed for the first time. Method validation showed a limit of detection at 30 ng/mL. The calibration curve was linear within the range of 0.0625-10.0 µg/mL (r(2) = 0.999). Accuracy and precision were highlighted by good recovery and low variations. Apart from NBD-cholesteryl oleate, two additional cellular metabolites of NBD-cholesterol, probably an isomer and an oxidation product, were determined in the lipid extracts of Caco-2 human colon adenocarcinoma cells according to mass spectrometry. In AC29 mouse malignant mesothelioma cells overexpressing acyl-CoA:cholesterol acyltransferase-1 (ACAT1) or ACAT2, only the oxidized metabolite was detected. Using the newly developed method, YIC-C8-434, a known ACAT inhibitor, was shown to inhibit ACAT activity in Caco-2 cells, as well as in AC29/ACAT1 or AC29/ACAT2 cells. In conclusion, the sensitive and specific HPLC-FLD method is a powerful tool for simultaneous quantification of intracellular NBD-cholesterol and its oleoyl-ester.

[Proliferation inhibition of lambda-carrageenan oligosaccharides on HUVEC and expression of apoptotic relevant genes].

To study the anti-proliferation effect of lambda-carrageenan oligosaccharides (lambda-CO) on human umbilical vein endothelial cells (HUVECs) and expression of apoptotic relevant genes, the influence of lambda-CO on HUVECs proliferation was measured by MTT assay; apoptotic rate, cell cycle distribution and the level of active caspase-3 of HUVECs were analyzed using flow cytometry; the mRNA level of apoptosis related genes was determined by RT-PCR. At a high concentration of 1 mg x mL(-1), lambda-CO significantly inhibited the endothelial cell proliferation. Annexin-V FITC/PI double stain assay showed that when treated with 0, 0.8, 1 mg x mL(-1) of lambda-CO for 24 h, cell apoptotic rates were (1.67 +/- 1.6)%, (11.48 +/- 2.4)% and (13.81 +/- 2.2)%, respectively, when treated for 48 h, cell apoptotic rates were (2.02 +/- 2.3)%, (13.84 +/- 1.9)% and (38.72 +/- 2.5)%, respectively, cell cycle assay showed the decrease of cells in G0/G1 phase, and increase in S phase. Furthermore, we observed the level of active caspase-3 increased in a dose-dependent manner at 24 th and 48 th. RT-PCR results indicated that mRNA of TNFalpha, p53, caspase-8 and caspase-3 in cells increased after treated with lambda-CO. lambda-CO induce apoptosis of HUVECs in a dose-dependent way and arrests cells at S phase, which mainly due to the up-regulation of apoptotic genes such as TNFalpha, p53, caspase-8, caspase-3 and increase the level of active caspase-3.