Expression of cytochrome P450 2A5 in a C57BL/6J mouse model of nonalcoholic fatty liver disease

Hepatoprotective mechanisms of pomegranate bioactives on a murine models affected by NAFLD as analysed by MS-based proteomics: The mitochondria in the eye of the storm

Deciphering the mechanisms underlying the direct association between fructose consumption and the onset and progression of non-alcoholic fatty liver disease (NAFLD), as well as the high prevalence of metabolic syndrome (MetS), is of great importance for adopting potential nutritional strategies. Thus, an evaluation of the impact of sustained high fructose consumption on the liver physiology of Wistar rats was made. Moreover, the effectiveness of a dietary pomegranate-derived supplement (P) at counteracting fructose-induced liver injury was also assessed. For unveiling the underlying mechanisms, an untargeted proteomic analysis of the livers from nineteen Wistar rats fed on a basal commercial feed and supplemented with either drinking water (C) (n = 6), 30 % (w/v) fructose in drinking water (F) (n = 7) or 30 % (w/v) fructose solution plus 0.2 % (w/v) P (F+P) (n = 6) was assessed. Fructose intake severely increased the abundance of several energy-production related-proteins, such as fructose-bisphosphate aldolase or fatty acid synthase, among others, as well as diminished the amount of another ones, such as carnitine O-palmitoyl transferase or different subunits of acyl-coenzyme A oxidase. These changes could facilitate mitochondrial disturbances and oxidative stress. Regarding the hepatic proteome of F, P extract restored mitochondrial homeostasis and strengthened endogenous antioxidant mechanisms diminishing the amount of proteins involved in process that could increase the oxidative status, as well as increasing both the quantity of several proteins involved in proteasome functionality, as expressing changes in the amount of certain RNA-splicing related-proteins, regarding F proteome.

Western Diet Decreases Hepatic Drug Metabolism in Male LDLr−/−ApoB100/100 Mice

Consumption of a Western diet is an important risk factor for several chronic diseases including nonalcoholic fatty liver disease (NAFLD), but its effect on the xenobiotic metabolizing enzyme activities in the liver has been studied incompletely. In this study, male LDLr−/−ApoB100/100 mice were fed with Western diet (WD) or a standard diet for five months to reveal the effects on drug metabolism such as cytochrome P450 (CYP) oxidation and conjugation activities in the liver. Hepatic steatosis, lobular inflammation, and early fibrosis were observed in WD fed mice, but not in chow diet control mice. When compared to the controls, the WD-fed mice had significantly decreased protein-normalized CYP probe activities of 7-ethoxyresorufinO-deethylation (52%), coumarin 7-hydroxylation (26%), 7-hydroxylation of 3-(3-fluoro-4-hydroxyphenyl)-6-methoxycoumarin (70%), 7-hydroxylation of 3-(4-trifluoromethoxyphenyl)-6-methoxycoumarin (78%), 7-hydroxylation of 3-(3-methoxyphenyl)coumarin (81%), and pentoxyresorufin O-depentylation (66%). Increased activity was seen significantly in sulfonation of 3-(4-methylphenyl)-7-hydroxycoumarin (289%) and cytosol catechol O-methyltranferase (COMT, 148%) in the WD group when compared to the controls. In conclusion, the WD-induced steatosis in male LDLr−/−ApoB100/100 mice was associated with decreased CYP oxidation reactions but had no clear effects on conjugation reactions of glucuronidation, sulfonation, and cytosolic catechol O-methylation. Consequently, the WD may decrease the metabolic elimination of drugs compared to healthier low-fat diets.

Curcumin Successfully Inhibited the Computationally Identified CYP2A6 Enzyme-Mediated Bioactivation of Aflatoxin B1 in Arbor Acres broiler

Cytochrome P450 enzymes are often responsible for the toxic and carcinogenic effects of toxicants, such as aflatoxin B1 (AFB1). The human hepatic CYP2A6 enzyme mediates the oxidative metabolism of several procarcinogens. In this study, we characterized a partial sequence of CYP2A6 gene from Arbor Acres (AA) broiler and studied its role in AFB1 bioactivation. Moreover, the effect of curcumin on CYP2A6 is illustrated. Six groups of AA broiler were treated for 28 days including the control group (fed only basal diet), curcumin alone-treated group (450 mg/kg feed), the group fed AFB1-contaminated feed (5 mg/kg feed) plus the low (150 mg), medium (300 mg) or high (450 mg) of curcumin, and the group fed AFB1-contaminated diet alone (5 mg/kg feed). After the end of treatment period, liver samples were collected for different analyses. The results revealed that the histopathological examination showed clear signs of liver toxicity in AA broliers in AFB1-fed group, but curcumin-supplementation in feed prevented partially AFB1-induced liver toxicity. Liver and body weights were recorded to study the AFB1 harmful effects. We noted an obvious increase in liver weight and decrease in body weight in AFB1-fed group. But, the administration of curcumin partially ameliorated the increase in liver weight and decrease in body weight in a dose-dependent manner. The results (RT-PCR and Elisa) revealed that mRNA and protein expression level enhanced in AFB1-fed group. Consistently, CYP2A6 enzyme activity also increased in AFB1-fed group, suggesting that AA broiler CYP2A6 actively involved in bioactivation of AFB1. However, curcumin treatment inhibited CYP2A6 at mRNA and protein levels in AFB1 treated AA broiler in a dose-dependent manner. Maximum inhibition of liver CYP2A6 enzyme activity in AA broiler has been achieved at a dose of 450 mg/kg curcumin. This is the first study identifying and confirming the role of CYP2A6 enzyme in AFB1 bioactivation in AA broiler liver (in vivo), and the hepatoprotective role of curcumin via inhibiting CYP2A6 expression and enzyme activity. The study contributed to identify an important CYP enzyme involved in AFB1 bioactivation in broilers and thus could pave the way for the prevention of the harmful effects of AFB1 in broilers.

Non-alcoholic fatty liver disease (NAFLD) - pathogenesis, classification, and effect on drug metabolizing enzymes and transporters

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of liver disorders. It is defined by the presence of steatosis in more than 5% of hepatocytes with little or no alcohol consumption. Insulin resistance, the metabolic syndrome or type 2 diabetes and genetic variants of PNPLA3 or TM6SF2 seem to play a role in the pathogenesis of NAFLD. The pathological progression of NAFLD follows tentatively a "three-hit" process namely steatosis, lipotoxicity and inflammation. The presence of steatosis, oxidative stress and inflammatory mediators like TNF-α and IL-6 has been implicated in the alterations of nuclear factors such as CAR, PXR, PPAR-α in NAFLD. These factors may result in altered expression and activity of drug metabolizing enzymes (DMEs) or transporters. Existing evidence suggests that the effect of NAFLD on CYP3A4, CYP2E1 and MRP3 is more consistent across rodent and human studies. CYP3A4 activity is down-regulated in NASH whereas the activity of CYP2E1 and the efflux transporter MRP3 is up-regulated. However, it is not clear how the majority of CYPs, UGTs, SULTs and transporters are influenced by NAFLD either in vivo or in vitro. The alterations associated with NAFLD could be a potential source of drug variability in patients and could have serious implications for the safety and efficacy of xenobiotics. In this review, we summarize the effects of NAFLD on the regulation, expression and activity of major DMEs and transporters. We also discuss the potential mechanisms underlying these alterations.