A Fibroblast Growth Factor 21-Pregnane X Receptor Pathway Downregulates Hepatic CYP3A4 in Nonalcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease changes the expression and activity of hepatic drug-metabolizing enzymes and transporters in rats

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, which can cause serious complications and gradually increase the mortality rate. However, the effects of NAFLD on drug-metabolizing enzymes and transporters remain unclear, which may cause some confusion regarding patient medication. In this study, a NAFLD rat model was constructed by feeding rats with methionine and choline deficiency diets for 6 weeks, and the mRNA and protein levels of drug-metabolizing enzymes and transporter were analyzed by real-time fluorescent quantitative PCR and Western blot, respectively. The activity of drug-metabolizing enzymes was detected by cocktail methods. In the NAFLD rat model, the mRNA expression of phase I enzymes, phase II enzymes, and transporters decreased. At the protein level, only CYP1A1, CYP1B1, CYP2C11, and CYP2J3 presented a decrease. In addition, the activities of CYP1A2, CYP2B1, CYP2C11, CYP2D1, CYP3A2, UGT1A1, UGT1A3, UGT1A6, and UGT1A9 decreased. These changes may be caused by the alteration of FXR, HNF4α, LXRα, LXRβ, PXR, and RXR. In conclusion, NAFLD changes the expression and activity of hepatic drug-metabolizing enzymes and transporters in rats, which may affect drug metabolism and pharmacokinetics. In clinical medication, drug monitoring should be strengthened to avoid potential risks.

Network pharmacology-based analysis of Resinacein S against non-alcoholic fatty liver disease by modulating lipid metabolism

Background

Ganoderma lucidum is reportedly the best source of traditional natural bioactive constituents. Ganoderma triterpenoids (GTs) have been verified as an alternative adjuvant for treating leukemia, cancer, hepatitis and diabetes. One of the major triterpenoids, Resinacein S, has been found to regulate lipid metabolism and mitochondrial biogenesis. Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease that has become a major public health problem. Given the regulatory effects on lipid metabolism of Resinacein S, we sought to explore potential protective effects against NAFLD.

Methods

Resinacein S was extracted and isolated from G. lucidum. And mice were fed with high fat diet with or without Resinacein S to detect hepatic steatosis. According to Network Pharmacology and RNA-seq, we analyzed the hub genes of Resinacein S against NAFLD disease.

Results

Our results can be summarized as follows: (1) The structure of Resinacein S was elucidated using NMR and MS methods. (2) Resinacein S treatment could significantly attenuate high-fat diet (HFD)-induced hepatic steatosis and hepatic lipid accumulation in mouse. (3) GO terms, KEGG pathways and the PPI network of Resinacein S induced Differentially Expressed Genes (DEGs) demonstrated the key target genes of Resinacein S against NAFLD. (4) The hub proteins in PPI network analysis could be used for NAFLD diagnosis and treatment as drug targets.

Conclusion

Resinacein S can significantly change the lipid metabolism in liver cells and yield a protective effect against steatosis and liver injury. Intersected proteins between NAFLD related genes and Resinacein S-induced DEGs, especially the hub protein in PPI network analysis, can be used to characterize targets of Resinacein S against NAFLD.

Salvia miltiorrhiza Bge. (Danshen) in the Treating Non-alcoholic Fatty Liver Disease Based on the Regulator of Metabolic Targets

Non-alcoholic fatty liver disease (NAFLD) is rapidly prevalent due to its strong association with increased metabolic syndrome such as cardio- and cerebrovascular disorders and diabetes. Few drugs can meet the growing disease burden of NAFLD. Salvia miltiorrhiza Bge. (Danshen) have been used for over 2,000 years in clinical trials to treat NAFLD and metabolic syndrome disease without clarified defined mechanisms. Metabolic targets restored metabolic homeostasis in patients with NAFLD and improved steatosis by reducing the delivery of metabolic substrates to liver as a promising way. Here we systematic review evidence showing that Danshen against NAFLD through diverse and crossing mechanisms based on metabolic targets. A synopsis of the phytochemistry and pharmacokinetic of Danshen and the mechanisms of metabolic targets regulating the progression of NAFLD is initially provided, followed by the pharmacological activity of Danshen in the management NAFLD. And then, the possible mechanisms of Danshen in the management of NAFLD based on metabolic targets are elucidated. Specifically, the metabolic targets c-Jun N-terminal kinases (JNK), sterol regulatory element-binding protein-1c (SREBP-1c), nuclear translocation carbohydrate response element–binding protein (ChREBP) related with lipid metabolism pathway, and peroxisome proliferator-activated receptors (PPARs), cytochrome P450 (CYP) and the others associated with pleiotropic metabolism will be discussed. Finally, providing a critical assessment of the preclinic and clinic model and the molecular mechanism in NAFLD.

Hepatocyte-specific fibroblast growth factor 21 overexpression ameliorates high-fat diet-induced obesity and liver steatosis in mice

Fibroblast growth factor (FGF) 21 is an endocrine growth factor mainly secreted by the liver in response to a ketogenic diet and alcohol consumption. FGF21 signaling requires co-receptor β-klotho (KLB) co-acting with FGF receptors, which has pleiotropic metabolic effects, including induced hepatic fatty acid oxidation and ketogenesis, in human and animal models of obesity. We examined the hepatocyte-specific enhancer/promoter of FGF21 expression plasmids in high-fat diet-fed mice for 12 weeks. Hydrodynamic injection for FGF21 delivery every 6 weeks sustained high circulating levels of FGF21, resulting in marked reductions in body weight, epididymal fat mass, insulin resistance, and liver steatosis. FGF21-induced lipolysis in the adipose tissue enabled the liver to be flooded with fat-derived FFAs. The hepatic expression of Glut2 and Bdh1 was upregulated, whereas that of gluconeogenesis-related genes, G6p and Pepck, and lipogenesis-related genes, Srebp-1 and Srebp-2, was significantly suppressed. FGF21 induced the phosphorylation of AMPK at Thr172 and Raptor at ser792 and suppressed that of mTOR at ser2448, which downregulated mTORC1 signaling and reduced IRS-1 phosphorylation at ser1101. Finally, in the skeletal muscle, FGF21 increased Glut4 and Mct2, a membrane protein that acts as a carrier for ketone bodies. Enzymes for ketone body catabolism (Scot) and citrate cycle (Cs, Idh3a), and a marker of regenerating muscle (myogenin) were also upregulated via increased KLB expression. Thus, FGF21-induced lipolysis was continuously induced by a high-fat diet and fat-derived FFAs might cause liver damage. Hepatic fatty acid oxidation and ketone body synthesis may act as hepatic FFAs' disposal mechanisms and contribute to improved liver steatosis. Liver-derived ketone bodies might be used for energy in the skeletal muscle. The potential FGF21-related crosstalk between the liver and extraliver organs is a promising strategy to prevent and treat metabolic syndrome-related nonalcoholic steatohepatitis.

The Nuclear Receptor PXR in Chronic Liver Disease

Pregnane X receptor (PXR), a nuclear receptor known for modulating the transcription of drug metabolizing enzymes and transporters (DMETs), such as cytochrome P450 3A4 and P-glycoprotein, is functionally involved in chronic liver diseases of different etiologies. Furthermore, PXR activity relates to that of other NRs, such as constitutive androstane receptor (CAR), through a crosstalk that in turn orchestrates a complex network of responses. Thus, besides regulating DMETs, PXR signaling is involved in both liver damage progression and repair and in the neoplastic transition to hepatocellular carcinoma. We here summarize the present knowledge about PXR expression and function in chronic liver diseases characterized by different etiologies and clinical outcome, focusing on the molecular pathways involved in PXR activity. Although many molecular details of these finely tuned networks still need to be fully understood, we conclude that PXR and its modulation could represent a promising pharmacological target for the identification of novel therapeutical approaches to chronic liver diseases.

Site-specific protein modification by 3-n-butylphthalide in primary hepatocytes: Covalent protein adducts diminished by glutathione and N-acetylcysteine

AIMS

3-n-Butylphthalide (NBP) is widely used for the treatment of cerebral ischaemic stroke but can causeliver injury in clinical practice. This study aims to elucidate the underlying mechanisms and propose potential preventive strategies.

MAIN METHODS

NBP and its four major metabolites, 3-hydroxy-NBP (3-OH-NBP), 10-hydroxy-NBP, 10-keto-NBP and NBP-11-oic acid, were synthesized and evaluated in primary human or rat hepatocytes (PHHs, PRHs). NBP-related substances or amino acid adducts were identified and semi-quantitated by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The target proteins and binding sites were identified by shotgun proteomics based on peptide mass fingerprinting coupled with tandem mass spectrometry and verified by molecular docking.

KEY FINDINGS

The toxicity of NBP and its four major metabolites were compared in both PHHs and PRHs, and 3-OH-NBP was found to be the most toxic metabolite. 3-OH-NBP induced remarkable cell death and oxidative stresses in hepatocytes, which correlated well with the levels of glutathione and N-acetylcysteine adducts (3-GSH-NBP and 3-NAC-NBP) in cell supernatants. Additionally, 3-OH-NBP covalently conjugated with intracellular Cys, Lys and Ser, with preferable binding to Cys sites at Myh9 Cys1380, Prdx4 Cys53, Vdac2 Cys48 and Vdac3 Cys36. Furthermore, we found that CYP3A4 induction by rifampicin augmented NBP-induced cell toxicity and supplementing with GSH or NAC alleviated the oxidative stresses and reactive metabolites caused by 3-OH-NBP.

SIGNIFICANCE

Our work suggests that glutathione depletion, mitochondrial injury and covalent protein modification are the main causes of NBP-induced hepatotoxicity, which may be prevented by exogenous GSH or NAC supplementation and avoiding concomitant use of CYP3A4 inducers.

Pharmacological Mechanisms Underlying the Hepatoprotective Effects of Ecliptae herba on Hepatocellular Carcinoma

BACKGROUND

The number of hepatocellular carcinoma (HCC) cases worldwide has increased significantly. As a traditional Chinese medicine (TCM) with a long history, Ecliptae herba (EH) has been widely used in HCC patients in China, but its hepatoprotective mechanism is still unclear.

METHODS

In this study, we applied a network pharmacology-based strategy and experimental verification to systematically unravel the underlying mechanisms of EH against HCC. First, six active ingredients of EH were screened from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) by the ADME method. Subsequently, 52 potential targets of 6 active ingredients acting on HCC were screened from various databases, including TCMSP, DGIdb, SwissTargetPrediction, CTD, and GeneCards. Then, by constructing protein-protein interaction (PPI) network from STRING, we displayed the intricate connections among these 52 targets through Cytoscape software. We also applied enrichment analysis, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, to provide an outline and set of concepts for describing gene functions and the advanced functions of biological systems of these 52 targets from genomic and molecular level information. Finally, molecular docking and biological experiments were used to reconfirm these results.

RESULTS

We hypothesized that EH might exert anti-HCC activity by acting on hub genes, including RELA, MMP9, PTGS2, ESR1, EGFR, AR, AKT1, HIF1A, AHR, CYP3A4, ABCG2, and MMP2. Moreover, based on GO and KEGG analysis, we speculated that EH may exert hepatoprotective effects on HCC through the following mechanisms: regulation of the PI3K-AKT signaling pathway to promote apoptosis and inhibit the abnormal proliferation of HCC, downregulation of HIF-1A expression by activating the HIF-1 signaling pathway, prevention of HCC by regulating lipid metabolism, and inhibition of nonalcoholic fatty liver disease (NAFLD) by the cytochrome P450 subfamily. Subsequent biological experiments verified that EH inhibits the PI3K-AKT signaling pathway through its active ingredients, quercetin, and wedelolactone, thereby inhibiting the proliferation of HCC cells and promoting the apoptosis of HCC cells.

CONCLUSIONS

The network pharmacological strategy provides an efficient method to systematically explore the pharmacological mechanism of EH in HCC. Our study demonstrated that the anti-HCC proliferation activity of EH is mainly exerted by two active ingredients (quercetin and wedelolactone), which inhibit the proliferation of HCC cells (HepG2 and Huh-7) by inhibiting PI3K-AKT signaling.

Treatments in Covid-19 patients with pre-existing metabolic dysfunction-associated fatty liver disease: A potential threat for drug-induced liver injury?

Obese patients who often present metabolic dysfunction-associated fatty liver disease (MAFLD) are at risk of severe presentation of coronavirus disease 2019 (COVID-19). These patients are more likely to be hospitalized and receive antiviral agents and other drugs required to treat acute respiratory distress syndrome and systemic inflammation, combat bacterial and fungal superinfections and reverse multi-organ failure. Among these pharmaceuticals, antiretrovirals such as lopinavir/ritonavir and remdesivir, antibiotics and antifungal agents can induce drug-induced liver injury (DILI), whose mechanisms are not always understood. In the present article, we hypothesize that obese COVID-19 patients with MAFLD might be at higher risk for DILI than non-infected healthy individuals or MAFLD patients. These patients present several concomitant factors, which individually can favour DILI: polypharmacy, systemic inflammation at risk of cytokine storm, fatty liver and sometimes nonalcoholic steatohepatitis (NASH) as well as insulin resistance and other diseases linked to obesity. Hence, in obese COVID-19 patients, some drugs might cause more severe (and/or more frequent) DILI, while others might trigger the transition of fatty liver to NASH, or worsen pre-existing steatosis, necroinflammation and fibrosis. We also present the main mechanisms whereby drugs can be more hepatotoxic in MAFLD including impaired activity of xenobiotic-metabolizing enzymes, mitochondrial dysfunction, altered lipid homeostasis and oxidative stress. Although comprehensive investigations are needed to confirm our hypothesis, we believe that the current epidemic of obesity and related metabolic diseases has extensively contributed to increase the number of cases of DILI in COVID-19 patients, which may have participated in presentation severity and death.

Fibroblast growth factor (FGF)-21 based therapies: A magic bullet for nonalcoholic fatty liver disease (NAFLD)?

Introduction: Fibroblast growth factor (FGF) 21 is a member of the FGF19 sub-family of signaling molecules. They have been found to act at the localized paracrine/autocrine and systemic endocrine levels because of their extracellular matrix and co-receptor protein binding characteristics. While the molecule circulates systemically, it has specificity conferred by a co-factor binding protein β-Klotho which is preferentially expressed in hepatic and adipose tissues. This protein, in conjunction with the FGF receptor (FGFR), propagates the downstream effects of the growth factor signaling cascade, which has been linked to fat and glucose metabolism. FGF21 has been recognized as a possible pathway for the treatment of nonalcoholic fatty liver disease (NAFLD). Targeting of the FGF21/FGFR/β-Klotho pathway may halt or reverse hepatic fat infiltration, inflammation, and fibrosis.Areas covered: This article summarizes preclinical and clinical data on the efficacy and safety of two FGF21 agonist therapies in development.Expert opinion: Preclinical and clinical data justify further investigation of FGF21 agonist therapies for the treatment of NAFLD. However, issues including injection site reactions and possible effects on bone homeostasis mean that safety must be evaluated carefully.

Effects of Exenatide and Humalog Mix25 on Fat Distribution, Insulin Sensitivity, and β-Cell Function in Normal BMI Patients with Type 2 Diabetes and Visceral Adiposity

In China, most normal BMI (body mass index of ≥18.5 to <25 kg/m²) adults with type 2 diabetes (T2DM) exhibit visceral adiposity. This study compared the effects of exenatide and humalog Mix25 on normal BMI patients with T2DM and visceral adiposity. A total of 95 patients were randomized to receive either exenatide or humalog Mix25 treatment for 24 weeks. Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were quantified by magnetic resonance imaging (MRI) and liver fat content (LFC) by liver proton magnetic resonance spectroscopy (¹H MRS). Each patient's weight, waist circumference, BMI, blood glucose, insulin sensitivity, pancreatic β-cell function, and fibroblast growth factor 21 (FGF-21) levels were measured. Data from 81 patients who completed the study (40 and 41 in the exenatide and humalog Mix25 groups, respectively) were analysed. The change in 2 h plasma blood glucose was greater in the exenatide group (P = 0.039). HOMA-IR and MBCI improved significantly after exenatide therapy (P < 0.01, P = 0.045). VAT and LFC decreased in both groups (P < 0.01 for all) but to a greater extent in the exenatide group, while SAT only decreased with exenatide therapy (P < 0.01). FGF-21 levels declined more in the exenatide group (P < 0.01), but were positively correlated with VAT in the entire cohort before (r = 0.244, P = 0.043) and after (r = 0.290, P = 0.016) the intervention. The effects of exenatide on glycaemic metabolism, insulin resistance, pancreatic β-cell function, and fat deposition support its administration to normal BMI patients with T2DM and visceral adiposity.

FGF21: An Emerging Therapeutic Target for Non-Alcoholic Steatohepatitis and Related Metabolic Diseases

The rising global prevalence of obesity, metabolic syndrome, and type 2 diabetes has driven a sharp increase in non-alcoholic fatty liver disease (NAFLD), characterized by excessive fat accumulation in the liver. Approximately one-sixth of the NAFLD population progresses to non-alcoholic steatohepatitis (NASH) with liver inflammation, hepatocyte injury and cell death, liver fibrosis and cirrhosis. NASH is one of the leading causes of liver transplant, and an increasingly common cause of hepatocellular carcinoma (HCC), underscoring the need for intervention. The complex pathophysiology of NASH, and a predicted prevalence of 3-5% of the adult population worldwide, has prompted drug development programs aimed at multiple targets across all stages of the disease. Currently, there are no approved therapeutics. Liver-related morbidity and mortality are highest in more advanced fibrotic NASH, which has led to an early focus on anti-fibrotic approaches to prevent progression to cirrhosis and HCC. Due to limited clinical efficacy, anti-fibrotic approaches have been superseded by mechanisms that target the underlying driver of NASH pathogenesis, namely steatosis, which drives hepatocyte injury and downstream inflammation and fibrosis. Among this wave of therapeutic mechanisms targeting the underlying pathogenesis of NASH, the hormone fibroblast growth factor 21 (FGF21) holds considerable promise; it decreases liver fat and hepatocyte injury while suppressing inflammation and fibrosis across multiple preclinical studies. In this review, we summarize preclinical and clinical data from studies with FGF21 and FGF21 analogs, in the context of the pathophysiology of NASH and underlying metabolic diseases.

CYP3A suppression during diet-induced nonalcoholic fatty liver disease is independent of PXR regulation

Cytochrome P450 3A (CYP3A) activity is inhibited, and its expression is suppressed during many diseases, including nonalcoholic fatty liver disease (NAFLD). However, the mechanism is controversial. Here, we report that PXR may not take part in the downregulation of CYP3A during NAFLD. Hepatic CYP3A11 (major subtype of mouse CYP3A) mRNA and protein expression was significantly decreased in both mice fed a high-fat diet (HFD) for 8 weeks and palmitate (PA)-treated mouse primary hepatocytes. Similarly, in HepG2 cells, PA treatment significantly suppressed the CYP3A4 (major subtype of human CYP3A) mRNA level and promoter transcription activity. However, Western blotting analysis found an induction of PXR nuclear translocation during NAFLD in both in vivo and in vitro models. Moreover, immunofluorescence determination also found nuclear translocation effect of PXR by PA stimulation in HepG2 cells. In addition, the siRNA knockdown of PXR did not affect the suppressive effects of PA on the CYP3A4 promoter transcription activity and mRNA levels in HepG2 cells. Similarly, PXR knockdown also did not affect the suppressive effects of PA on CYP3A11 mRNA and protein expression levels in mouse primary hepatoctyes. Taken together, the results showed that the suppressive effect of CYP3A transcription was independent of PXR regulation.

Permethrin and ivermectin modulate lipid metabolism in steatosis-induced HepG2 hepatocyte

Recent studies have reported the positive association between exposure to insecticides and increased risk of obesity and type 2 diabetes, which are closely associated with non-alcoholic fatty liver disease (NAFLD). However, it is not known if insecticide exposure can contribute to NAFLD. Thus, the goal of the current study was to determine if insecticide exposures can exacerbate the physiological conditions of NAFLD by modulating hepatic lipid metabolism. The effects of 12 insecticides on triglycerides (TG) accumulation were tested using palmitic acid (PA)-induced HepG2 hepatoma steatosis model. Results showed that among tested insecticides, permethrin and ivermectin significant interacted with palmitic acid to potentiate (permethrin) or decrease (ivermectin) TG accumulation. Further study showed that permethrin significantly promoted fatty acid synthesis, while suppressed lipid oxidation-related genes only under steatosis conditions. In comparison, ivermectin inhibited lipogenesis-related genes and promoted farnesoid X receptor, which upregulates fatty acid oxidation. Results in this study suggested that hepatic lipid metabolism may be more susceptible to insecticide exposure in the presence of excessive fatty acids, which can be associated with the development of NAFLD.

Suppression of Hepatic CYP3A4 Expression and Activity by 3-Methylcholanthrene in Humanized PXR-CAR-CYP3A4/3A7 Mice

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that activate the aryl hydrocarbon receptor, thereby triggering a range of biologic responses, exemplified by the induction of CYP1A1 PAHs can also regulate the expression of members of the CYP3A subfamily, with reports of mainly suppressive effects on mouse hepatic Cyp3a11 expression, but paradoxically both inductive and suppressive effects on human hepatic CYP3A4 expression. Understanding the regulation of CYP3A4 expression by PAHs is important because of the widespread exposure of humans to these chemicals and the central role of the CYP3A4 enzyme in the metabolism of clinically important drugs and endogenous substances. The present study used 3-methylcholanthrene (MC) as a model PAH to characterize the in vivo regulation of CYP3A4 expression and activity in humanized pregnane X receptor-constitutive androstane receptor-CYP3A4/3A7 mice. Adult mice were treated by intraperitoneal injection with MC (80 mg/kg), or corn oil vehicle, and euthanized 24 or 72 hours later. As a positive control response, pronounced induction of hepatic Cyp1a1 by MC was confirmed at both time points in males and females at the mRNA, protein, and catalytic activity levels. Basal hepatic CYP3A4 expression and activity were significantly higher in female versus male mice. MC treatment suppressed hepatic CYP3A4 in female mice at 72 hours postdosing at the mRNA, protein, and catalytic activity levels. A similar response was observed in male mice, although the suppression of CYP3A4 protein levels did not achieve statistical significance. This mouse model will facilitate further studies of the mechanisms and consequences of CYP3A4 suppression by PAHs.

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view

BACKGROUND

Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

AIMS

To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

METHODS

A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

RESULTS

Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

CONCLUSIONS

The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.

Nonalcoholic Fatty Liver Disease and Diabetes Are Associated with Decreased CYP3A4 Protein Expression and Activity in Human Liver

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease in the Western population. We investigated the association of nonalcoholic fatty liver disease (NAFLD) and diabetes mellitus on CYP3A4 activity in human liver tissue from brain dead donors ( n = 74). Histopathologically graded livers were grouped into normal ( n = 24), nonalcoholic fatty liver (NAFL, n = 26), and nonalcoholic steatohepatitis (NASH, n = 24) categories. The rate of conversion of midazolam to its 1-hydroxy metabolite was used to assess in vitro CYP3A4 activity in human liver microsomes (HLM). A proteomics approach was utilized to quantify the protein expression of CYP3A4 and related enzymes. Moreover, a physiologically based pharmacokinetic (PBPK) model was developed to allow prediction of midazolam concentration in NAFL and NASH livers. CYP3A4 activity in NAFL and NASH was 1.9- and 3.1-fold ( p < 0.05) lower than normal donors, respectively. Intrinsic clearance (CLint) was 2.7- ( p < 0.05) and 4.1-fold ( p < 0.01) lower in donors with NAFL and NASH, respectively. CYP3A4 protein expression was significantly lower in NAFL and NASH donors ( p < 0.05) and accounted for significant midazolam hydroxylation variability in a multiple linear regression analysis (β = 0.869, r² = 0.762, P < 0.01). Diabetes was also associated with decreased CYP3A4 activity and protein expression. Both midazolam CLint and CYP3A4 protein abundance decreased significantly with increase in hepatic fat accumulation. Age and gender did not exhibit any significant association with the observed alterations. Predicted midazolam exposure was 1.7- and 2.3-fold higher for NAFL and NASH, respectively, which may result in a longer period of sedation in these disease-states. Data suggests that NAFLD and diabetes are associated with the decreased hepatic CYP3A4 activity. Thus, further evaluation of clinical consequences of these findings on the efficacy and safety of CYP3A4 substrates is warranted.

Fibroblast Growth Factor 21-Metabolic Role in Mice and Men

Since its identification in 2000, the interest of scientists in the hepatokine fibroblast growth factor (FGF) 21 has tremendously grown, and still remains high, due to a wealth of very robust data documenting this factor's favorable effects on glucose and lipid metabolism in mice. For more than ten years now, intense in vivo and ex vivo experimentation addressed the physiological functions of FGF21 in humans as well as its pathophysiological role and pharmacological effects in human metabolic disease. This work produced a comprehensive collection of data revealing overlaps in FGF21 expression and function but also significant differences between mice and humans that have to be considered before translation from bench to bedside can be successful. This review summarizes what is known about FGF21 in mice and humans with a special focus on this factor's role in glucose and lipid metabolism and in metabolic diseases, such as obesity and type 2 diabetes mellitus. We highlight the discrepancies between mice and humans and try to decipher their underlying reasons.

Fibroblast growth factor 21: a regulator of metabolic disease and health span

Fibroblast growth factor 21 (FGF21) is a potent endocrine regulator with physiological effects on glucose and lipid metabolism and thus garners much attention for its translational potential for the management of obesity and related metabolic syndromes. FGF21 is mainly expressed in several metabolically active tissue organs, such as the liver, adipose tissue, skeletal muscle, and pancreas, with profound effects and therapeutic relevance. Emerging experimental and clinical data point to the demonstrated metabolic benefits of FGF21, which include, but are not limited to, weight loss, glucose and lipid metabolism, and insulin sensitivity. In addition, FGF21 also acts directly through its coreceptor β-klotho in the brain to alter light-dark cycle activity. In this review, we critically appraise current advances in understanding the physiological actions of FGF21 and its role as a biomarker of various metabolic diseases, especially type 2 diabetes mellitus. We also discuss the potentially exciting role of FGF21 in improving our health and prolonging our life span. This information will provide a fuller understanding for further research into FGF21, as well as providing a scientific basis for potentially establishing health care guidelines for this promising molecule.

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.