Lrp6 Genotype affects Individual Susceptibility to Nonalcoholic Fatty Liver Disease and Silibinin Therapeutic Response via Wnt/ß-catenin-Cyp2e1 Signaling.

Background: Nonalcoholic fatty liver disease (NAFLD) is a serious threat to human health worldwide, with a high genetic susceptibility. Rs2302685, a functional germline variant of LRP6, has been recently found to associate with NAFLD risk. This study was aimed to clarify the underlying mechanism associated with rs2302685 risk and its impact on pharmacotherapy in treatment of NAFLD. Methods: Venous blood samples were collected from NAFLD and non-NAFLD patients for SNP genotyping by using mass spectrometry. The Lrp6-floxdel mouse (Lrp6(+/-)) was generated to model the partial function associated with human rs2302685. The liver injury and therapeutic effects of silibinin were compared between Lrp6(+/-) and Lrp6(+/+) mice received a methionine-choline deficient (MCD) diet or normal diet. The effect of Lrp6 functional alteration on Wnt/ß-catenin-Cyp2e1 signaling activities was evaluated by a series of cellular and molecular assays. Results: The T allele of LRP6 rs2302685 was confirmed to associate with a higher risk of NAFLD in human subjects. The carriers of rs2302685 had reduced level of AST and ALT as compared with the noncarriers. The Lrp6(+/-) mice exhibited a less severe liver injury induced by MCD but a reduced response to the treatment of silibinin in comparison to the Lrp6(+/+) mice, suggesting Lrp6 as a target of silibinin. Wnt/ß-catenin-Cyp2e1 signaling together with ROS generation could be exacerbated by the overexpression of Lrp6, while decreased in response to Lrp6 siRNA or silibinin treatment under NAFLD modeling. Conclusions: The Lrp6 function affects individual susceptibility to NAFLD and the therapeutic effect of silibinin through the Wnt/ß-catenin-Cyp2e1 signaling pathway. The present work has provided an underlying mechanism for human individual susceptibility to NAFLD associated with Lrp6 polymorphisms as well as a rationale for the effective use of silibinin in NAFLD patients.

The LRP6 functional mutation rs2302685 contributes to individual susceptibility to alcoholic liver injury related to the Wnt/ß-catenin-TCF1-CYP2E1 signaling pathway.

Low-density lipoprotein receptor-related protein 6 (LRP6) is an important coreceptor in the Wnt/ß-catenin upstream signaling pathway. Rs2302685 is a common functional mutation of LRP6 that has been previously associated with reduced alcoholic liver injury among alcoholic liver disease (ALD) patients, and the present research was designed to study the underlying mechanisms of that finding. A total of 107 ALD patients and 138 non-ALD patients were recruited from hospitalized alcoholics in China. Their venous blood samples were collected for DNA extraction and genotyped using Sequenom MassARRAY. We found that the rs2302685 mutation, which impaired the function of LRP6, was present in higher frequency among alcoholics with ALD than those without ALD. We also conducted a mouse model experiment in which LRP6(+/-) knockdown mice and LRP6(+/+) wild-type mice received daily intragastric doses of ethanol (2.4 g/kg) as well as a larger dose of ethanol (4 g/kg) every 7 days for 28 days. The mouse blood and liver specimens were subsequently collected for laboratory analysis, and cell experiments were performed to compare the inhibition, activation, over-expression, and siRNA of LRP6 in the treatment versus the control HL7702 cells. Expression of the targeted molecules was detected by real-time PCR or western blot analysis. Stably transfected cells with pRL3-CYP2E1 vector were used to further study the underlying mechanisms. The total bile acid (TBA), direct bilirubin, total bilirubin (TBIL), aspartate aminotransferase (AST), mitochondrial aspartate aminotransferase, and AST/ALT values were significantly lower in carriers of the rs2302685 mutation than in the wild-type patients, by 63.4, 60.6, 82.1, 44.8, 45.7, and 21.4%, respectively. Compared to the LRP6(+/+) wild-type mice, the LRP6(+/-) knockdown mice had lower ALT, TBIL, TBA, and ALB/GLO values, as well reduced liver tissue damage, in accordance with their reduced expressions of LRP6, ß-catenin, and CYP2E1. In HL7702 cells exposed to ethanol, AST, ALT, lipid accumulation, and ROS generation decreased in cells that were treated with LRP6 inhibitors or siRNA but increased in cells treated with LRP6 activators or over-expressed LRP6. TCF1 was the transcriptional factor most likely to connect the LRP6-Wnt/ß-catenin signaling pathway to the regulation of CYP2E1. We concluded that the LRP6 functional mutation rs2302685 contributes to individual differences in susceptibility to alcoholic liver injury related to the Wnt/ß-catenin-TCF1-CYP2E1 signaling pathway.

Reversing Epigenetic Alterations Caused by Alcohol: A Promising Therapeutic Direction for Alcoholic Liver Disease.

Alcoholic liver disease (ALD), a liver function disorder caused by excessive alcohol intake, is a serious threat to global public health and social development. Toxic metabolites and reactive oxygen species produced during the metabolism of alcohol can alter the epigenetic state including DNA methylation, histone modifications, and expression of microRNAs. Epigenetic alterations can conversely involve various signaling pathways, which could contribute to the initiation and progression of ALD. To elucidate the relationship between epigenetic alterations and alcohol damage not only reinforces our understanding on pathogenesis of ALD, but also provides novel targets for clinical diagnosis, treatment, and drug research of ALD. In this review, we have summarized the research progress of epigenetic alterations and related mechanisms caused by alcohol in the pathogenesis of ALD. Considering the invertibility of epigenetic alterations, treatment of ALD through epigenetic modification with common less harmful compounds is also related.

The potent mechanism-based inactivation of CYP2D6 and CYP3A4 with fusidic acid in in vivo bioaccumulation.

1. The accumulation of fusidic acid (FA) after multiple doses of FA has been reported on in previous studies but the related mechanisms have not been clarified fully. In the present study, we explain the mechanisms related to the mechanism-based inactivation of CYP2D6 and CYP3A4. 2. The irreversible inhibitory effects of FA on CYP2D6 and CYP3A4 were examined via a series of experiments, including: (a) time-, concentration- and NADPH-dependent inactivation, (b) substrate protection in enzyme inactivation and (c) partition ratio with recombinant human CYP enzymes. Metoprolol α-hydroxylation and midazolam 1'-hydroxylation were used as marker reactions for CYP2D6 and CYP3A4 activities, and HPLC-MS/MS measurement was also utilised. 3. FA caused to the time- and concentration-dependent inactivation of CYP2D6 and CYP3A4. About 55.8% of the activity of CYP2D6 and 75.8% of the activity of CYP3A4 were suppressed after incubation with 10 µM FA for 15 min. KI and kinact were found to be 2.87 µM and 0.033 min-1, respectively, for CYP2D6, while they were 1.95 µM and 0.029 min-1, respectively, for CYP3A4. Inhibition of CYP2D6 and CYP3A4 activity was found to require the presence of NADPH. Substrates of CYP2D6 and CYP3A4 showed that the enzymes were protected against the inactivation induced by FA. The estimated partition ratio for the inactivation was 7 for CYP2D6 and 12 for CYP3A4. 4. FA is a potent mechanism-based inhibitor of CYP2D6 and CYP3A4, which may explain the accumulation of FA in vivo.

Screening of Drug Metabolizing Enzymes for the Ginsenoside Compound K In Vitro: An Efficient Anti-Cancer Substance Originating from Panax Ginseng.

Ginsenoside compound K (CK), a rare ginsenoside originating from Panax Ginseng, has been found to possess unique pharmacological activities specifically as anti-cancers. However, the role of cytochrome P450s (CYPs) in the metabolism of CK is unclear. In this study, we screened the CYPs for the metabolism of CK in vitro using human liver microsomes (HLMs) or human recombinant CYPs. The results showed that CK inhibited the enzyme activities of CYP2C9 and CYP3A4 in the HLMs. The Km and Vmax values of CK were 84.20±21.92 µM and 0.28±0.04 nmol/mg protein/min, respectively, for the HLMs; 34.63±10.48 µM and 0.45±0.05 nmol/nmol P450/min, respectively, for CYP2C9; and 27.03±5.04 µM and 0.68±0.04 nmol/nmol P450/min, respectively, for CYP3A4. The IC50 values were 16.00 µM and 9.83 µM, and Ki values were 14.92 µM and 11.42µM for CYP2C9 and CYP3A4, respectively. Other human CYP isoforms, including CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP2C19, showed minimal or no effect on CK metabolism. The results suggested that CK was a substrate and also inhibitors for both CYP2C9 and CYP3A4. Patients using CK in combination with therapeutic drugs that are substrates of CYP2C9 and CYP3A4 for different reasons should be careful, although the inhibiting potency of CK is much poorer than that of enzyme-specific inhibitors.