Identification of UDP-glucuronosyltransferase (UGT) isoforms involved in the metabolism of Chlorophenols (CPs)

Chlorophenols (CPs) are a group of pollutants that pose a great threat to the environment, they are widely used in industrial and agricultural wastes, pesticides, herbicides, textiles, pharmaceuticals and plastics. Among CPs, pentachlorophenol was listed as one of the persistent organic pollutants (POPs) by the Stockholm convention. This study aims to identify the UDP-glucosyltransferase (UGT) isoforms involved in the metabolic elimination of CPs. CPs' mono-glucuronide was detected in the human liver microsomes (HLMs) incubation mixture with co-factor uridine-diphosphate glucuronic acid (UDPGA). HLMs-catalyzed glucuronidation metabolism reaction equations followed Michaelis-Menten or substrate inhibition type. Recombinant enzymes and chemical reagents inhibition experiments were utilized to phenotype the main UGT isoforms involved in the glucuronidation of CPs. UGT1A6 might be the major enzyme in the glucuronidation of mono-chlorophenol isomer. UGT1A1, UGT1A6, UGT1A9, UGT2B4 and UGT2B7 were the most important five UGT isoforms for metabolizing the di-chlorophenol and tri-chlorophenol isomers. UGT1A1 and UGT1A3 were the most important UGT isoforms in the catalysis of tetra-chlorophenol and pentachlorophenol isomers. Species differences were investigated using rat liver microsomes (RLMs), pig liver microsomes (PLMs), dog liver microsomes (DLMs), and monkey liver microsomes (MyLMs). All these results were helpful for elucidating the metabolic elimination and toxicity of CPs.

Explainable Machine Learning-Based Prediction Model for Diabetic Nephropathy

The aim of this study is to analyze the effect of serum metabolites on diabetic nephropathy (DN) and predict the prevalence of DN through a machine learning approach. The dataset consists of 548 patients from April 2018 to April 2019 in the Second Affiliated Hospital of Dalian Medical University (SAHDMU). We select the optimal 38 features through a least absolute shrinkage and selection operator (LASSO) regression model and a 10-fold cross-validation. We compare four machine learning algorithms, including extreme gradient boosting (XGB), random forest, decision tree, and logistic regression, by AUC-ROC curves, decision curves, and calibration curves. We quantify feature importance and interaction effects in the optimal predictive model by Shapley additive explanation (SHAP) method. The XGB model has the best performance to screen for DN with the highest AUC value of 0.966. The XGB model also gains more clinical net benefits than others, and the fitting degree is better. In addition, there are significant interactions between serum metabolites and duration of diabetes. We develop a predictive model by XGB algorithm to screen for DN. C2, C5DC, Tyr, Ser, Met, C24, C4DC, and Cys have great contribution in the model and can possibly be biomarkers for DN.

The association between plasma free amino acids and type 2 diabetes mellitus complicated with infection in Chinese patients

BACKGROUND

Type 2 diabetes mellitus (T2DM), one of the most common public diseases threatening human health, is always accompanied by infection. Though there are still a variety of flaws in the treatment of some infectious diseases, metabolomics provides a fresh perspective to explore the relationship between T2DM and infection. Our research aimed to investigate the association between plasma free amino acids (PFAAs) and T2DM complicated with infection in Chinese patients.

METHODS

A cross-sectional study was conducted from May 2015 to August 2016. We retrieved the medical records of 1032 inpatients with T2DM from Liaoning Medical University First Affiliated Hospital and we used mass spectrometry to quantify 23 PFAAs. Infections contained 15 individual categories that could be retrieved from the database. Principal component analysis was used to extract factors of PFAAs. Multi-variable binary logistic regression was used to obtain odds ratios (OR) and their 95% confidence intervals (CI).

RESULTS

Among 1032 inpatients,109 (10.6%) had infectious diseases. Six factors, accounting for 68.6% of the total variance, were extracted. Factor 4 consisted of Glu, Asp and Orn. Factor 5 consisted of Hcy and Pip. After adjusting for potential confounders, factor 4 was positively correlated with T2DM complicated with infection in Chinese T2DM patients (OR: 1.27, 95%CI: 1.06-1.52). Individual Hcy in factor 5 was positively associated with T2DM complicated with infection (OR: 1.33, 95%CI: 1.08-1.64). Furthermore, factor 4 (OR: 1.44, 95%CI: 1.11-1.87), Orn (OR: 1.01, 95%CI: 1.00-1.02) and Hcy (OR: 1.56, 95%CI: 1.14-3.14) were positively associated with bacterial infection in Chinese T2DM patients, while factor 5 (OR: 0.71, 95%CI: 0.50-1.00) was negatively associated with bacterial infection.

CONCLUSIONS

Urea cycle-related metabolites (Orn, Asp, Glu) and Hcy were positively associated with T2DM complicated with infection in China. Orn and Hcy were positively associated with bacterial infection in T2DM patients in China.

Effect of passive smoking exposure on risk of type 2 diabetes: a systematic review and meta-analysis of prospective cohort studies

Objective

The effect of passive smoking exposure on the risk of type 2 diabetes has not been systematically studied. A meta-analysis was conducted to assess the association between passive smoking exposure and the risk of diabetes.

Methods

We searched three major databases up to 31 October 2022 to identify relevant prospective cohort studies on the association between passive smoking and the risk of type 2 diabetes. The pooled relative risk (RR) and 95% confidence interval (CI) for the association between passive smoking exposure and the risk of type 2 diabetes were analyzed using a fixed-effect model.

Results

Ten prospective cohort studies were included in this meta-analysis, with a total of 251,620 participants involved. The pooled RR showed a significantly positive association between nonsmokers exposed to passive smoking and type 2 diabetes as compared to non-smokers who were not exposed to passive smoking [RR = 1.27; 95% CI (1.19, 1.36); p < 0.001]. Sensitivity analysis indicated that the pooled RR was not substantially affected by any of the individual studies.

Conclusion

Exposure to passive smoking increases the risk of type 2 diabetes. This study may have a positive effect on the prevention of type 2 diabetes.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023372532.

A Metabolism-Based Interpretable Machine Learning Prediction Model for Diabetic Retinopathy Risk: A Cross-Sectional Study in Chinese Patients with Type 2 Diabetes

The burden of diabetic retinopathy (DR) is increasing, and the sensitive biomarkers of the disease were not enough. Studies have found that the metabolic profile, such as amino acid (AA) and acylcarnitine (AcylCN), in the early stages of DR patients might have changed, indicating the potential of metabolites to become new biomarkers. We are amid to construct a metabolite-based prediction model for DR risk. This study was conducted on type 2 diabetes (T2D) patients with or without DR. Logistic regression and extreme gradient boosting (XGBoost) prediction models were constructed using the traditional clinical features and the screening features, respectively. Assessing the predictive power of the models in terms of both discrimination and calibration, the optimal model was interpreted using the Shapley Additive exPlanations (SHAP) to quantify the effect of features on prediction. Finally, the XGBoost model incorporating AA and AcylCN variables had the best comprehensive evaluation (ROCAUC = 0.82, PRAUC = 0.44, Brier score = 0.09). C18 : 1OH lower than 0.04 μmol/L, C18 : 1 lower than 0.70 μmol/L, threonine higher than 27.0 μmol/L, and tyrosine lower than 36.0 μmol/L were associated with an increased risk of developing DR. Phenylalanine higher than 52.0 μmol/L was associated with a decreased risk of developing DR. In conclusion, our study mainly used AAs and AcylCNs to construct an interpretable XGBoost model to predict the risk of developing DR in T2D patients which is beneficial in identifying high-risk groups and preventing or delaying the onset of DR. In addition, our study proposed possible risk cut-off values for DR of C18 : 1OH, C18 : 1, threonine, tyrosine, and phenylalanine.

Inhibition of human sulfotransferases (SULTs) by per- and polyfluoroalkyl substances (PFASs) and structure-activity relationship

Per- and polyfluoroalkyl substances (PFASs) are a family of highly fluorinated aliphatic substances widely used in industrial and commercial applications. This study aims to determine the inhibition of PFASs towards sulfotransferases (SULTs) activity, and trying to explain the toxicity mechanism of PFASs. In vitro recombinant SULTs-catalyzed sulfation of p-nitrophenol (PNP) was utilized as a probe reaction. The incubation system was consisted of PFASs, SULTs, PNP, 3'-phosphoadenosine-5'-phosphosulfate, MgCl₂ and Tris-HCl buffer. Ultra-performance liquid chromatography was employed for analysis of the metabolites. All tested PFASs showed inhibition towards SULTs. The longer the carbon chain length of the PFASs terminated with -COOH, the higher is its capability of inhibiting SULT1A3. PFASs with -SO₃H had a relatively higher ability to inhibit SULT1A3 activity than those with -COOH, -I and -OH. The inhibition kinetic parameter was 2.16 and 1.42 μM for PFOS-SULT1A1, PFTA-SULT1B1. In vitro in vivo extrapolation showed that the concentration of PFOS and PFTA in human matrices might be higher than the threshold for inducing inhibition of SULTs. Therefore, PFASs could interfere with the metabolic pathways catalyzed by SULTs in vivo. All these results will help to understand the toxicity of PFASs from the perspective of metabolism.

Prevalence of Diabetic Retinopathy and Use of Common Oral Hypoglycemic Agents Increase the Risk of Diabetic Nephropathy-A Cross-Sectional Study in Patients with Type 2 Diabetes

OBJECTIVE

This study investigated the effect of amino acid metabolism on the risk of diabetic nephropathy under different conditions of the diabetic retinopathy, and the use of different oral hypoglycemic agents.

METHODS

This study retrieved 1031 patients with type 2 diabetes from the First Affiliated Hospital of Liaoning Medical University in Jinzhou, which is located in Liaoning Province, China. We conducted a spearman correlation study between diabetic retinopathy and amino acids that have an impact on the prevalence of diabetic nephropathy. Logistic regression was used to analyze the changes of amino acid metabolism in different diabetic retinopathy conditions. Finally, the additive interaction between different drugs and diabetic retinopathy was explored.

RESULTS

It is showed that the protective effect of some amino acids on the risk of developing diabetic nephropathy is masked in diabetic retinopathy. Additionally, the additive effect of the combination of different drugs on the risk of diabetic nephropathy was greater than that of any one drug alone.

CONCLUSIONS

We found that diabetic retinopathy patients have a higher risk of developing diabetic nephropathy than the general type 2 diabetes population. Additionally, the use of oral hypoglycemic agents can also increase the risk of diabetic nephropathy.

Relationship between plasma glutamate and cardiovascular disease risk in Chinese patients with type 2 diabetes mellitus by gender

Objectives

This study aimed to assess the association between plasma glutamate (Glu) and the risk of cardiovascular disease (CVD) in patients with type 2 diabetes mellitus (T2DM) and whether this association differs by gender.

Material and methods

We retrieved clinical information on 1032 consecutive patients with T2DM from a same tertiary care center from May 2015 to August 2016. Glu was quantified by liquid chromatography-tandem mass spectrometry analysis. Glu was converted into a categorical variable based on the median concentration in the whole population, while logistic regression was used to obtain the odds ratio (OR) and 95% confidence interval (CI), and the correlation between Glu and various biochemical indices was analyzed.

Results

We found that Glu was positively associated with the risk of CVD in patients with T2DM. This correlation was more significant in women. In T2DM patients, the higher the age, body mass index (BMI), weight and systolic blood pressure (SBP), the lower the glycosylated hemoglobin (HbA1C) concentration and the higher the Glu. In female patients, the correlation between age, weight, BMI, SBP, and plasma Triglycerides (TG), and Glu was also statistically significant.

Conclusion

In conclusion, female T2DM patients with high levels of Glu have a higher risk of developing CVD.

Associations of serum amino acids related to urea cycle with risk of chronic kidney disease in Chinese with type 2 diabetes

OBJECTIVE

Serum levels of amino acids related to urea cycle are associated with risk of type 2 diabetes mellitus (T2DM). Our study aimed to explore whether serum levels of amino acids related to urea cycle, i.e., arginine, citrulline, and ornithine, are also associated with increased risk of chronic kidney disease (CKD) in T2DM.

METHODS

We extracted medical records of 1032 consecutive patients with T2DM from the Electronic Administrative System of Liaoning Medical University First Affiliated Hospital (LMUFAH) system from May 2015 to August 2016. Of them, 855 patients with completed data available were used in the analysis. CKD was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m². Serum amino acids were measured by mass spectrometry (MS) technology. Binary logistic regression was performed to obtain odds ratios (ORs) and their 95% confidence intervals (CIs).

RESULTS

52.3% of the 855 T2DM patients were male, and 143 had CKD. In univariable analysis, high serum citrulline, high ratio of arginine to ornithine, and low ratio of ornithine to citrulline were associated with markedly increased risk of CKD (OR of top vs. bottom tertile: 2.87, 95%CI, 1.79-4.62 & 1.98, 95%CI,1.25-3.14 & 2.56, 95%CI, 1.61-4.07, respectively). In multivariable analysis, the ORs of citrulline and ornithine/citrulline ratio for CKD remained significant (OR of top vs. bottom tertile: 2.22, 95%CI, 1.29-3.82 & 2.24, 1.29-3.87, respectively).

CONCLUSIONS

In Chinese patients with T2DM, high citrulline and low ornithine/citrulline ratio were associated with increased risk of CKD.

Short chain fatty acids for the risk of diabetic nephropathy in type 2 diabetes patients

AIMS

This study aimed to explore relationships short chain fatty acids with diabetic nephropathy (DN) in type 2 diabetes (T2D) patients.

METHODS

We extracted the clinical and omics data of 100 T2D patients and 100 DN patients from April 2018 to April 2019 from a tertiary hospital. Restricted cubic splines were used to examine full-range associations of short chain fatty acids with DN in T2D.Query Logistic regression was used to obtain odds ratio (OR) and confidence interval (CI).

RESULTS

Acetate, butyrate and isovalerate were negatively correlated with DN. Isobutyrate was positively correlated with DN. Propionate ≥ 4.4 μg/mL and isobutyrate ≥ 1.4 μg/mL had threshold effects and their increasing levels above the cutoff points were associated with rapid rises in the risk of DN. The additive interaction between high propionate and high isobutyrate in serum significantly increased the risk of DN (OR34.35; 95%CI 7.11 to 166.08). Presence of hypertension further increased the OR of high propionate for DN to 8.27(95%CI 1.82 to 37.57) with a significant additive interaction. The additive interaction of the high isobutyrate and hypertension was not significant.

CONCLUSIONS

Acetate, butyrate and isovalerate were negatively associated with DN. Isobutyrate was positively associated with DN. Serum high propionate and high isobutyrate worked independently and synergistically to increase the risk of DN in T2D. Presence of hypertension further amplified the effect of copresence of high propionate on DN risk.

The Association of Homocysteine and Diabetic Retinopathy in Homocysteine Cycle in Chinese Patients With Type 2 Diabetes

OBJECTIVE

This study aimed to explore the relationship between homocysteine (Hcy) and diabetic retinopathy (DR) and the impacts of the Hcy pathway on this relationship against this background.

METHODS

This study retrieved 1979 patients with type 2 diabetes (T2D) from the First Affiliated Hospital of Liaoning Medical University in Jinzhou, Liaoning Province, China. Multiple logistic regression was used to analyze the effects of Hcy cycle on the relationship between Hcy and DR. Spearman's rank correlation analysis was used to analyze the correlation between risk factors related to DR progression and Hcy. Finally, the results of logistic regression were supplemented by mediation analysis.

RESULTS

We found there was a negative correlation between low concentration of Hcy and DR (OR : 0.83, 95%CI: 0.69-1). After stratifying all patients by cysteine (Cys) or Methionine (Met), this relationship remained significant only in low concentration of Cys (OR: 0.75, 95%CI: 0.61-0.94). Through the RCS curve, we found that the effect of Hcy on DR presents a U-shaped curve relationship. Mediating effect in Met and Hcy cycles was also significant [Total effect c (OR: 0.968, 95%CI: 0.938-0.998), Direct effect path c' (OR: 0.969, 95%CI: 0.940-0.999), Path a (OR: 1.047, 95%CI: 1.004-1.091), Path b (OR: 0.964, 95%CI: 0.932-0.998)].

CONCLUSIONS

The relationship between Hcy and DR presents a U-shaped curve and the homocysteine cycle pathway has an impact on it. And too low concentration of Hcy indicates a lack of other substances, such as vitamins. It is suggested that the progression of DR is the result of a combination of many risk factors. Further prospective studies are needed to determine the role of Hcy in the pathogenesis of DR.

Relationship Between Acylcarnitine and the Risk of Retinopathy in Type 2 Diabetes Mellitus

OBJECTIVE

Diabetic retinopathy is a common complication of type 2 diabetes mellitus (T2DM). Due to the limited effectiveness of current prevention and treatment methods, new biomarkers are urgently needed for the prevention and diagnosis of DR. This study aimed to explore the relationships between plasma acylcarnitine with DR in T2DM.

METHODS

From May 2015 to August 2016, data of 1032 T2DM patients were extracted from tertiary hospitals. Potential non-linear associations were tested by binary logistic regression models, and ORs and 95% CIs of the research variables were obtained. Correlation heat map was used to analyze the correlation between variables. The change of predictive ability was judged by the area under the receiver operating characteristic curve.

RESULTS

Of the 1032 patients with T2DM, 162 suffered from DR. After adjusting for several confounding variables, C2 (OR:0.55, 95%CI:0.39-0.76), C14DC (OR:0.64, 95%CI:0.49-0.84), C16 (OR:0.64, 95%CI:0.49-0.84), C18:1OH (OR:0.51, 95%CI:0.36-0.71) and C18:1 (OR:0.60, 95%CI:0.44-0.83) were negatively correlated with DR. The area under the curve increased from 0.794 (95% CI 0.745 to 0.842) to 0.840 (95% CI 0.797 to 0.833) when C2, C14DC, C18:1OH and C18:1 added to the traditional risk factor model.

CONCLUSION

There was a negative correlation between C2, C14DC, C16, C18:1OH, and C18:1 and the risk of retinopathy in patients with T2DM. C2, C14DC, C18:1OH, and C18:1 may be new predictors and diagnostic markers of DR.

Inhibition of hydroxylated polychlorinated biphenyls (OH-PCBs) on sulfotransferases (SULTs)

Polychlorinated biphenyls (PCBs) have been demonstrated as a kind of the persistent organic pollutants (POPs) that could exert complicated influences towards metabolism in human bodies. Since hydroxylated polychlorinated biphenyls (OH-PCBs) are important metabolites of PCBs, our study focuses on investigating the potential inhibitory capability of OH-PCBs on four human sulfotransferase (SULT) isoforms. P-nitrophenol (PNP) was utilized as nonselective probe substrate for this study, and recombinant SULT isoforms were utilized as the enzyme resources. Ultra-performance liquid chromatography (UPLC)-UV detecting system was used to analyze PNP and its metabolite PNP-sulfate. As result, 100 μM of most tested OH-PCBs significantly inhibited the activity of four SULT isoforms. Concentration-dependent inhibition of OH-PCBs towards SULTs was found, and half inhibition concentration values (IC₅₀) of some inhibition processes were determined. Inhibition kinetics (inhibition kinetic type and parameters) were determined using 4'-OH-PCB106 as the representative OH-PCB, SULT1B1 and SULT1E1 as representative SULT isoforms. The inhibition kinetic parameters (K_i) were 1.73 μM and 1.81 μM for the inhibition of 4'-OH-PCB106 towards SULT1B1 and SULT1E1, respectively. In silico docking simulation was utilized to analyze the inhibition capability of 2'-OH-PCB5, 4'-OH-PCB9, 2'-OH-PCB12 towards SULT1A3.All these results obtained in this study are helpful for further understanding the toxicity of PCBs.

Genetic variants associated with beta-cell function and insulin sensitivity potentially influence bile acid metabolites and gestational diabetes mellitus in a Chinese population

INTRODUCTION

To investigate associations between genetic variants related to beta-cell (BC) dysfunction or insulin resistance (IR) in type 2 diabetes (T2D) and bile acids (BAs), as well as the risk of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

We organized a case-control study of 230 women with GDM and 217 without GDM nested in a large prospective cohort of 22 302 Chinese women in Tianjin, China. Two weighted genetic risk scores (GRSs), namely BC-GRS and IR-GRS, were established by combining 39 and 23 single nucleotide polymorphisms known to be associated with BC dysfunction and IR, respectively. Regression and mediation analyses were performed to evaluate the relationship of GRSs with BAs and GDM.

RESULTS

We found that the BC-GRS was inversely associated with taurodeoxycholic acid (TDCA) after adjustment for confounders (Beta (SE)=-0.177 (0.048); p=2.66×10^-4). The BC-GRS was also associated with the risk of GDM (OR (95% CI): 1.40 (1.10 to 1.77); p=0.005), but not mediated by TDCA. Compared with individuals in the low tertile of BC-GRS, the OR for GDM was 2.25 (95% CI 1.26 to 4.01) in the high tertile. An interaction effect of IR-GRS with taurochenodeoxycholic acid (TCDCA) on the risk of GDM was evidenced (p=0.005). Women with high IR-GRS and low concentration of TCDCA had a markedly higher OR of 14.39 (95% CI 1.59 to 130.16; p=0.018), compared with those with low IR-GRS and high TCDCA.

CONCLUSIONS

Genetic variants related to BC dysfunction and IR in T2D potentially influence BAs at early pregnancy and the development of GDM. The identification of both modifiable and non-modifiable risk factors may facilitate the identification of high-risk individuals to prevent GDM.

Plasma Amino Acids and Residual Hypertriglyceridemia in Diabetic Patients Under Statins: Two Independent Cross-Sectional Hospital-Based Cohorts

Objective: The objective of the study was to investigate the relationship of amino acid metabolism with hypertriglyceridemia in diabetic patients under statins free of prior cardiovascular diseases.

Methods: Two independent cross-sectional hospital based cohorts, i.e., Liaoning Medical University First Affiliated Hospital (LMUFAH, n = 146) and the Second Affiliated Hospital of Dalian Medical University (SAHDMU, n = 294) were included in the current analysis. Hypertriglyceridemia was defined as triglyceride ≥1.7 mmol/L, and well-controlled LDL-C was defined as <2.6 mmol/L. The adjusted ORs (95% CI) of circulating metabolic measures for hypertriglyceridemia were assessed using logistic regression. Pooled results of metabolites with the same direction of association in both cohorts were combined using inverse variance-weighted fixed-effect meta-analysis. Difference of identified metabolites in patients with and without hypertriglyceridemia were also obtained in the context of LDL-C.

Results: Patients, 86 and 106, were with hypertriglyceridemia in LMUFAH and SAHDMU, respectively. We observed that elevated alanine, asparagine, leucine, and valine were consistently associated with increased hypertriglyceridemia in both cohorts. In fixed-effect pooled analysis, the OR (95% CI) per SD increase was 1.71 (1.32–2.20) for alanine, 1.62 (1.20–2.19) for asparagine, 1.64 (1.22–2.20) for leucine, and 1.62 (1.22–2.13) for valine (all P values ranged from 0.0018 to <0.0001); adjusting for C-peptide attenuated effect sizes of Ala, Leu, and Val for hypertriglyceridemia. The difference were robust in groups with well- or bad-controlled LDL-C.

Conclusion: Among 23 amino acids, alanine, asparagine, leucine, and valine were positively associated with increased residual risk of hypertriglyceridemia in diabetic patients with statin treatment.

Glucagon-like peptide 1 analogue prevents cholesterol gallstone formation by modulating intestinal farnesoid X receptor activity

BACKGROUND & AIMS

Cholesterol gallstone disease (CGD) is a common gastrointestinal disease. Liraglutide, an analogue of glucagon-like peptide 1, has been approved to treat type 2 diabetes. Clinical studies have suggested a potential role of liraglutide in CGD.

METHODS

Mice were subcutaneously injected with liraglutide, then fed a lithogenic diet. Bile duct cannulation was performed to collect bile output in mice. Intestinal-specific ablation or pharmacological inhibition of farnesoid X receptor (FXR) was used to study its functions in CGD.

RESULTS

Liraglutide could protect mice against CGD. Liraglutide treatment increased the biliary concentration of cholesterol, phospholipids and bile acids and thereby decreased the cholesterol saturation index. The resistance to CGD conferred by liraglutide is likely a result of increased bile acid synthesis and efficient bile acid transport. The expression of a key bile acid synthetic enzyme, Cyp7a1, was significantly increased in liraglutide-treated mice. The increased expression of Cyp7a1 resulted from a relieved suppression signal of Fgf15 from the ileum. Mechanistically, liraglutide treatment altered bile acid composition and suppressed FXR activity in the ileum. Genetic ablation or pharmacological inhibition of FXR in the intestine protected mice against CGD. More importantly, intestinal FXR was required for liraglutide-mediated regulation of hepatic expression of Cyp7a1.

CONCLUSION

Liraglutide improved CGD by increasing bile acid secretion and decreasing cholesterol saturation index. Liraglutide attenuates the negative feedback inhibition of bile acids through inhibiting intestinal FXR activity. Our results suggest that liraglutide may represent a novel way for treating or preventing cholesterol gallstones in individuals with high risk of CGD.

Hepatic miR-378 modulates serum cholesterol levels by regulating hepatic bile acid synthesis

Rationale: An improved understanding of thyroid hormone (TH) action on cholesterol metabolism will facilitate the identification of novel therapeutic targets for hypercholesterolemia. TH-regulated microRNAs (miRNAs) have been implicated in TH-controlled biological processes; however, whether and how TH-regulated miRNAs mediate the cholesterol-lowering effect of TH remains unclear. Our aim was to identify TH-regulated microRNAs that have cholesterol-lowering effects and explore the underlying mechanism.

Method: Microarray and RNA-seq were performed to identify TH-regulated microRNAs and the genes regulated by mmu-miR-378-3p (miR-378) in the liver of mice, respectively. Recombinant adenoviruses encoding miR-378, Mafg, and shRNA for Mafg, antagomiR-378, liver-specific miR-378 transgenic mice, and miR-378 knockout mice were employed to investigate the roles of hepatic miR-378 and MAFG in cholesterol and bile acid homeostasis. The levels of bile salt species were determined by using UFLC-Triple-time of flight/MS.

Results: Here, we show that hepatic miR-378 is positively regulated by TH. Transient overexpression of miR-378 in the liver of mice reduces serum cholesterol levels, accompanied with an increase in the expression of key enzymes in primary bile acid synthetic pathways and corresponding increases in biliary and fecal bile acid levels. Consistently, liver-specific miR-378 transgenic mice with moderate overexpression of hepatic miR-378 display decreased serum cholesterol levels and resistance to diet-induced hypercholesterolemia, while mice lacking miR-378 exhibit defects in bile acid and cholesterol homeostasis. Mechanistically, hepatic miR-378 regulates the expression of key enzymes in both classic and alternative bile acid synthetic pathways through MAFG, a transcriptional repressor, thereby modulating bile acid and cholesterol metabolism.

Conclusions: TH-responsive hepatic miR-378 is capable of modulating serum cholesterol levels by regulating both the classic and alternative BA synthetic pathways. Our study not only identifies a previously undescribed role of hepatic miR-378 but also provides new cholesterol-lowering approaches.

Hydroxylated polychlorinated biphenyls (OH-PCBs) exert strong inhibitory effects towards human carboxylesterases (CESs)

Polychlorinated biphenyls (PCBs) have been reported to pose a severe risk towards human health, and hydroxylated polychlorinated biphenyls (OH-PCBs) were potential substances basis for PCBs' toxicity. This study aims to determine the inhibition of OH-PCBs towards human carboxylesterases (CESs), including CES1 and CES2. For phenotypic analysis of CES1 and CES2 activity, we used the hydrolysis metabolism of 2-(2-benzoyl3-methoxyphenyl) benzothiazole (BMBT) and fluorescein diacetate (FD) catalyzed by human liver microsomes (HLMs) as the probe reactions. Preliminary inhibition screening showed that the inhibition potential of OH-PCBs towards CES1 and CES2 increased with the increased numbers of chlorine atoms in OH-PCBs. Both 2'-OH-PCB61 and 2'-OH-PCB65 showed concentration-dependent inhibition towards both CES1 and CES2. Lineweaver-Burk plots showed that 2'-OH-PCB61 and 2'-OH-PCB65 exerted non-competitive inhibition towards CES1 and competitive inhibition towards CES2. The inhibition kinetics parameters (Ki) were 6.8 μM and 7.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES1, respectively. The inhibition kinetics parameters (Ki) were 1.4 μM and 1.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES2, respectively. In silico docking methods elucidate the contribution of hydrogen bonds and hydrophobic contacts towards the binding of 2'-OH-PCB61 and 2'-OH-PCB65 with CES1 and CES2. All these results will provide a new perspective for elucidation of toxicity mechanism of PCBs and OH-PCBs.

Interactive effects of asparagine and aspartate homeostasis with sex and age for the risk of type 2 diabetes risk

BACKGROUND

Asparagine and aspartate homeostasis are linked with type 2 diabetes (T2D). This study aimed to explore whether asparagine and aspartate metabolism interacted with sex and age to increase the risk of T2D.

METHODS

From 27 May 2015 to 3 August 2016, we consecutively retrieved 1032 T2D patients and 1522 subjects without T2D from a tertiary care hospital in Liaoning, China. Restricted cubic spline nested in the logistic regression was used to draw odds ratio curves of plasma asparagine to aspartate ratio for T2D by sex and age. Cut-off point was selected where curves went apart, indicating possible interaction. Addictive interactions of asparagine to aspartate ratio with sex or age and secondary interaction with copresence of unfavorable sex and age were further estimated using relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (S).

RESULTS

Ratio of asparagine to aspartate > 1.5 was associated with elevated risk of T2D (OR 7.99, 95%CI 5.50 to 11.6), which was enhanced by female gender to 13.6, (95%CI 8.10-22.9) and by > 50 years of age to 28.7 (14.6-56.3), with significant additive interactions. There was a significant secondary-interaction of copresence of female sex and > 50 years of age with high asparagine to aspartate ratio for increased T2D risk with the OR being further increased to 34.4 (20.5-57.5).

CONCLUSIONS

High asparagine to aspartate ratio was associated with markedly increased risk of T2D, which was further amplified by either female gender or > 50 years of age, and especially both.

Role of aromatic amino acids in pathogeneses of diabetic nephropathy in Chinese patients with type 2 diabetes

BACKGROUND

We aimed to estimate the associations between aromatic amino acids (AAAs) and diabetic nephropathy (DN) in patients with type 2 diabetes (T2D).

METHODS

We collected clinical and metabolomic data from 132 healthy subjects (HS group), 132 type 2 diabetes patients without diabetic nephropathy (T2D group) and 132 diabetic nephropathy patients (DN group) in tertiary hospital from May 2015 to August 2016. The odds ratio (OR) and 95% confidence interval (CI) were obtained by logistic regression.

RESULTS

The odds ratio of tyrosine for DN increased gradually. High tyrosine was associated with an increased OR of DN (model 3, OR:0.329, 95%CI, 0.144-0.750) when comparing extreme quantiles.

CONCLUSION

In Chinese patients with T2D, elevated tyrosine was associated with increased risk of DN.

Plasma phenylalanine and tyrosine and their interactions with diabetic nephropathy for risk of diabetic retinopathy in type 2 diabetes

OBJECTIVE

Tight control of hyperglycemia reduces risk of diabetic retinopathy (DR), but the residual risk remains high. This study aimed to explore relationships between plasma phenylalanine and tyrosine with DR in type 2 diabetes (T2D) and interactions between the two amino acids, and their secondary interaction with renal dysfunction.

RESEARCH DESIGN AND METHODS

We extracted data of 1032 patients with T2D from tertiary hospital consecutively from May 2015 to August 2016. Binary logistic regression models with restricted cubic spline were used to check potential non-linear associations and to obtain ORs and 95% CIs of variables under study. Addictive interaction was estimated using relative excess risk due to interaction, attributable proportion due to interaction and synergy index. Area under the receiver operating characteristic curve was used to check increased predictive values.

RESULTS

Of 1032 patients, 162 suffered from DR. Copresence of low phenylalanine and low tyrosine increased DR risk (OR 6.01, 95% CI 1.35 to 26.8), while either of them alone did not have a significant effect with significant additive interaction. Presence of diabetic nephropathy further increased the OR of copresence of low phenylalanine and low tyrosine for DR to 25.9 (95% CI 8.71 to 76.9) with a significant additive interaction. Inclusion of phenylalanine and tyrosine in a traditional risk factor model significantly increased area under the curve from 0.81 to 0.83 (95% CI 0.80 to 0.86).

CONCLUSION

Plasma low phenylalanine and low tyrosine worked independently and synergistically to increase the risk of DR in T2D. Presence of renal dysfunction further amplified the effect of copresence of low phenylalanine and low tyrosine on DR risk.

Inhibition of UDP-glucuronosyltransferases (UGTs) by polycyclic aromatic hydrocarbons (PAHs) and hydroxy-PAHs (OH-PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are known as one of the ubiquitous environmental pollutants caused by unavoidable combustion of by-products. Despite decades of research on adverse health effects towards humans, the effects of PAHs and their hydroxylated metabolites (OH-PAHs) on UDP-glucuronosyltransferases (UGTs) remain unclear. This study aimed to investigate inhibitory effects with structure-dependence of 14 PAHs and OH-PAHs towards the activity of 7 isoforms of UGTs using in vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) as the probe reaction. PAHs and OH-PAHs showed inhibitory effects towards different UGT isoforms with different extents. For inhibition kinetics determination, 1-HONAP, 4-HOPHE, 9-HOPHE, and 1-HOPYR were utilized as the representative compounds, and UGT1A6, UGT1A9 and UGT2B7 were chosen as the three representative UGT isoforms. The inhibitory effects of 4-HOPHE, 9-HOPHE and 1-HOPYR on three above UGT isoforms were the same: UGT1A9>UGT1A6>UGT2B; for 1-HONAP, that is UGT1A6>UGT1A9>UGT2B. Molecular docking methods were utilized to find the activity cavity of UGT1A9 and UGT2B7 binding with 1-HONAP and 1-HOPYR. Hydrogen bonds and hydrophobic contacts were mainly contributors to their interactions. In vitro-in vivo extrapolation (IVIVE) showed that high in vivo inhibition possibility exists for the inhibition of OH-PAHs on UGTs. All the results provide a novel viewpoint for an explanation of the toxicity of PAHs and OH-PAHs.

Per- and polyfluoroalkyl substances exert strong inhibition towards human carboxylesterases

PFASs are highly persistent in both natural and living environment, and pose a significant risk for wildlife and human beings. The present study was carried out to determine the inhibitory behaviours of fourteen PFASs on metabolic activity of two major isoforms of carboxylesterases (CES). The probe substrates 2-(2-benzoyl-3-methoxyphenyl) benzothiazole (BMBT) for CES1 and fluorescein diacetate (FD) for CES2 were utilized to determine the inhibitory potentials of PFASs on CES in vitro. The results demonstrated that perfluorododecanoic acid (PFDoA), perfluorotetradecanoic acid (PFTA) and perfluorooctadecanoic acid (PFOcDA) strongly inhibited CES1 and CES2. The half inhibition concentration (IC₅₀) value of PFDoA, PFTA and PFOcDA for CES1 inhibition was 10.6 μM, 13.4 μM and 12.6 μM, respectively. The IC₅₀ for the inhibition of PFDoA, PFTA and PFOcDA towards CES2 were calculated to be 9.56 μM, 17.2 μM and 8.73 μM, respectively. PFDoA, PFTA and PFOcDA exhibited noncompetitive inhibition towards both CES1 and CES2. The inhibition kinetics parameters (K_i) were 27.7 μM, 26.9 μM, 11.9 μM, 4.04 μM, 29.1 μM, 27.4 μM for PFDoA-CES1, PFTA-CES1, PFOcDA-CES1, PFDoA-CES2, PFTA-CES2, PFOcDA-CES2, respectively. In vitro-in vivo extrapolation (IVIVE) predicted that when the plasma concentrations of PFDoA, PFTA and PFOcDA were greater than 2.77 μM, 2.69 μM and 1.19 μM, respectively, it might interfere with the metabolic reaction catalyzed by CES1 in vivo; when the plasma concentrations of PFDoA, PFTA and PFOcDA were greater than 0.40 μM, 2.91 μM, 2.74 μM, it might interfere with the metabolic reaction catalyzed by CES2 in vivo. Molecular docking was used to explore the interactions between PFASs and CES. In conclusion, PFASs were found to cause inhibitory effects on CES in vitro, and this finding would provide an important experimental basis for further in vivo testing of PFASs focused on CES inhibition endpoints.

Evaluation of the inhibition of chlorophenols towards human cytochrome P450 3A4 and differences among various species

Chlorophenols (CPs) are important pollutants detected frequently in the environment. This study intended to detect the inhibitory effects of fourteen CPs (2-CP, 3-CP, 4-CP, 4C2AP, 4C3MP, 2.4-DCP, 2.3.4-TCP, 2.4.5-TCP, 2.4.6-TCP, 3.4.5-TCP, 2.3.4.5-TECP, 2.3.4.6-TECP, 2.3.5.6-TECP and PCP) towards human liver cytochrome P450 3A4 (CYP3A4). Throughout the tests, testosterone was used as the probe substrate and CPs were used as inhibitors. A series of experiments (enzyme activity assays, preliminary screening tests, inhibition kinetics determination) were conducted to determine the inhibition of CPs towards human liver CYP3A4. CPs with the inhibitory effect >80% were selected for the inhibition evaluation in liver microsomes from different animal species (monkey, rat, dog, pig). The results showed that 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP inhibited the activities of CYP3A4 by 80.3%, 93.4%, 91.6%, respectively. Inhibition kinetics type were non-competitive and inhibition kinetics constant (K_i) values were 26.4 μM, 13.5 μM, and 8.8 μM for the inhibition of 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP towards human CYP3A4, respectively. Inhibition kinetics type was competitive and K_i value was 4.9 μM for the inhibition of 2.3.4-TCP towards CYP3A4 in Monkey liver microsomes (MyLMs). Inhibition kinetic types were non-competitive and K_i values were 8.1 μM and 28.7 μM for the inhibition of 3.4.5-TCP and 2.3.4.5-TECP towards CYP3A4 in MyLMs. Inhibition kinetic types were non-competitive and K_i values were 13.8 μM, 0.6 μM, and 6.1 μM for the inhibition of 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP towards CYP3A4 in Dog liver microsomes (DLMs), respectively. By comparing K_i values and inhibition kinetic types, the dog was the most suitable model to assess the inhibition of 2.3.4-TCP and 2.3.4.5-TECP towards CYP3A4, and monkey was the most suitable model to assess the inhibition of 3.4.5-TCP towards CYP3A4. In conclusion, our recent study on the inhibition of CPs towards CYP3A4 and species differences was important for further toxicological studies of CPs in human bodies.

Plasma Free Amino Acids and Risk of Cardiovascular Disease in Chinese Patients With Type 2 Diabetes

OBJECTIVES

This study aimed to explore associations between plasma free amino acids (PFAA) and risk of cardiovascular disease (CVD) in Chinese with Type 2 diabetes (T2D).

METHODS

We retrieved 741 inpatients with T2D consecutively from tertiary hospital. Twenty-three PFAA were measured. CVD was defined as having coronary heart disease (CHD) or stroke. Principal component analysis was used to extract factors of PFAA. Factors and their components were introduced into binary logistic regressions as continuous and tertiles to obtain OR (odds ratio) and 95% confidence interval (CI) for CVD (or its components) risk.

RESULTS

Of 741 inpatients, 282 (38.1%) had CVD (CHD alone: 122, stroke alone: 109, both: 51). Five factors were extracted, accounting for 65% of the total variance. Factor 3 composed of glutamate and tryptophan was associated with increased CVD risk (ORs, 95%CI of top vs. bottom tertiles: 1.60, 1.02-2.50 for CVD; 2.19, 1.17-4.07 for stroke, 1.51, 0.83-2.73 for CHD); the ORs (top vs. bottom tertiles) of glutamate were 2.62 (95%CI, 1.18-5.84) for stroke and 1.44 (0.80-2.61) for CHD; the ORs (top vs. bottom tertiles) of tryptophan were 1.50 (0.81-2.75) for stroke and 1.07 (0.58-1.97) for CHD. Comparable results were observed according to important confounders (all P for interaction >0.05).

CONCLUSIONS

Elevated factor 3 composed of glutamate and tryptophan was associated with increased CVD, especially stroke in T2D in China.

Inhibition of UDP-glucuronosyltransferases (UGTs) by bromophenols (BPs)

Bromophenols (BPs) are important organic compounds which have become dominant pollutants during these years. Our present study investigated the potential inhibition behaviour of BPs on the activity of one of the most important phase II drug-metabolizing enzymes (DMEs), UDP-glucuronosyltransferases (UGTs). Recombinant UDP-glucuronosyltransferases (UGTs)-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was utilized as the probe reaction. 100 μM of BPs was utilized as the inhibition screening concentrations, and the complete inhibition profile of UGT isoforms by BPs was obtained. UGT1A7 was the most vulnerable UGT isoform towards BPs. Some structure-activity relationship for the inhibition of UGTs by BPs was found, and this relationship can be furtherly explained by the hydrophobic contacts of BPs with the activity cavity of UGTs using in silico docking method. The inhibition kinetics determination showed that the inhibition kinetic parameter K_i value was calculated to be 2.85, 3.99 and 31.00 μM for the inhibition of UGT1A3, UGT1A7, and UGT2B7 by representative BPs, 2,4,6-TBP. Combined with in vivo exposure concentration of 2,4,6-TBP, in vitro-in vivo extrapolation (IVIVE) was employed to demonstrate the moderate possibility for the inhibition of UGT1A3 and UGT1A7 by 2,4,6-TBP. In conclusion, our study gave the full description towards the inhibition of BPs towards UGT isoforms, which will provide a new perspective for elucidating the toxicity mechanism of bromophenols (BPs).

The Association Between Leucine and Diabetic Nephropathy in Different Gender: A Cross-Sectional Study in Chinese Patients With Type 2 Diabetes

OBJECTIVE

This study aimed to evaluate how leucine are associated with diabetic nephropathy (DN) in type 2 diabetes (T2D) patients and the gender difference of this association.

METHODS

We retrieved 1,031 consecutive patients with T2D who meet the inclusion and exclusion criteria from the same tertiary care center and extracted clinical information from electronic medical record. Plasma leucine was measured by liquid chromatography-mass spectrometer. Restricted cubic spline (RCS) was conducted to examine potential non-linear relationship between leucine and the risk of DN. Logistic regression was used to obtain odds ratio (OR) and confidence interval (CI). Additive interaction was used to estimate the interaction effect between leucine and gender for DN.

RESULTS

We found there was a negative correlation between leucine and the risk of DN. After stratifying all patients by gender, this relationship only remained significant in women (OR:0.57, CI:0.41-0.79).

CONCLUSIONS

In conclusion, T2D patients with high levels of leucine have a lower risk of developing DN in female.

The Association Between Acylcarnitine Metabolites and Cardiovascular Disease in Chinese Patients With Type 2 Diabetes Mellitus

Objective: The association between acylcarnitine metabolites and cardiovascular disease (CVD) in type 2 diabetes mellitus (T2DM) remains uncertain. This study aimed to investigate associations between acylcarnitines and CVD in Chinese patients with T2DM. Methods: A cross-sectional study was conducted from May 2015 to August 2016. Medical records of 741 patients with T2DM were retrieved from the main electronic database of Liaoning Medical University First Affiliated Hospital. CVD was defined as having either coronary artery disease (CAD) or heart failure (HF) or stroke. Mass Spectrometry was utilized to measure levels of 25 acylcarnitine metabolites in fasting plasma. Factor analysis was used to reduce the dimensions and extracted factors of the 25 acylcarnitine metabolites. Multivariable binary logistic regression was used to obtain odds ratios (OR) of the factors extracted from the 25 acylcarnitine metabolites and their 95% confidence intervals (CI) for CVD. Results: Of the 741 patients with T2DM, 288 had CVD. Five factors were extracted from the 25 acylcarnitines and they accounted for 65.9% of the total variance. Factor 1 consisted of acetylcarnitine, butyrylcarnitine, hydroxylbutyrylcarnitine, glutarylcarnitine, hexanoylcarnitine, octanoylcarnitine, and tetradecanoyldiacylcarnitine. Factor 2 consisted of decanoylcarnitine, lauroylcarnitine, myristoylcarnitine, 3-hydroxyl-tetradecanoylcarnitine, tetradecenoylcarnitine, and 3-hydroxypalmitoylcarnitine. After adjusting for potential confounders, increased factor 1 and 2 were associated with increased risks of CVD in T2DM (OR of factor 1: 1.45, 95% CI: 1.03-2.03; OR of factor 2: 1.23, 95% CI: 1.02-1.50). Conclusions: Elevated plasma levels of some acylcarnitine metabolites, i.e., those extracted into factor 1 and 2, were associated with CVD risk in T2DM.

Trimethylamine N-Oxide Metabolites in Early Pregnancy and Risk of Gestational Diabetes: A Nested Case-Control Study

OBJECTIVES

This study aimed to investigate the associations between trimethylamine N-oxide (TMAO) and related metabolites in early pregnancy and the risk of gestational diabetes mellitus (GDM).

DESIGN

A prospective cohort of 22,302 pregnant women from 2010 to 2012 in Tianjin, China, was used to perform a nested case-control study. A total of 243 women with GDM and 243 women without GDM matched by maternal age (±1 year) were used as cases and controls, respectively. Conditional logistic regression and restricted cubic spline were used to examine the full-range risk associations between individual TMAOs metabolites at the first antenatal care visit with GDM. Trimethylamine conversion ratio (TMAR) was defined as trimethylamine (TMA)/its precursors, and trimethylamine N-oxide conversion ratio (TMAOR) was defined as TMAO/TMA. An additive interaction between high TMAR and low TMAOR indicates a state of TMA accumulation, and a mathematical interaction between high TMAR and high TMAOR indicates accumulation of TMAO.

RESULTS

TMA was linearly associated with GDM, whereas TMA precursors and TMAO were inversely associated with GDM with clear threshold effects, i.e., 16 nmol/mL for TMAO, 200 nmol/mL for betaine, 112 nmol/mL for l-carnitine, and 110 and 270 nmol/mL for cholinechloride (a U-shaped relationship). Copresence of TMAR >0.35 and TMAOR ≤0.15 was associated with a markedly higher OR (11.16; 95% CI, 5.45 to 22.8), compared with TMAR >0.35 only (OR = 1.71; 95% CI, 0.42 to 6.95) or TMAOR ≤0.15 only (OR = 2.06; 95% CI, 1.09 to 3.90), with a significant additive interaction. However, the mathematical interaction was nonsignificant.

CONCLUSIONS

TMAO metabolites in the early pregnancy were associated with the risk of GDM, whereas TMA was more likely to play a causal role in GDM.

Per- and polyfluoroalkyl substances display structure-dependent inhibition towards UDP-glucuronosyltransferases

Per- and polyfluoroalkyl substances (PFASs) are a large group of chemicals and can be detected in environmental and human samples all over the world. Toxicity of existing and emerging PFASs will be a long-term source of concern. This study aimed to investigate structure-dependent inhibitory effects of 14 PFASs towards the activity of 11 UDP-glucuronosyltransferase (UGT) isoforms. In vitro UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was employed to determine the inhibition of PFASs towards different UGT isoforms. All the PFASs showed <75% of inhibition or stimulation effects on UGT1A3, UGT1A7, UGT1A9, UGT2B4, UGT2B7 and UGT2B17. However, PFASs showed broad inhibition on the activity of UGT1A1 and UGT1A8. The activity of UGT1A1 was inhibited by 98.8%, 98%, 79.9%, 77.1%, and 76.9% at 100 μmoL/L of perfluorodecanoic acid (PFDA), perfluorooctanesulfonic acid potassium salt (PFOS), perfluorotetradecanoic acid (PFTA), perfluorooctanoic acid (PFOA) and perfluorododecanoic acid (PFDoA), respectively. UGT1A8 was inhibited by 97.6%, 94.8%, 86.3%, 83.4% and 77.1% by PFDA, PFTA, perfluorooctadecanoic acid (PFOcDA), PFDoA and PFOS, respectively. Additionally, PFDA significantly inhibited UGT1A6 and UGT1A10 by 96.8% and 91.6%, respectively. PFDoA inhibited the activity of UGT2B15 by 88.2%. PFDA and PFOS exhibited competitive inhibition towards UGT1A1, and PFDA and PFTA showed competitive inhibition towards UGT1A8. The inhibition kinetic parameter (K_i) were 3.15, 1.73, 13.15 and 20.21 μmoL/L for PFDA-1A1, PFOS-1A1, PFDA-1A8 and PFTA-1A8, respectively. The values were calculated to be 0.3 μmoL/L and 1.3 μmoL/L for the in vivo inhibition of PFDA towards UGT1A1-and UGT1A8-catalyzed metabolism of substances, and 0.2 μmoL/L and 2.0 μmoL/L for the inhibition of PFOS towards UGT1A1 and the inhibition of PFTA towards UGT1A8, respectively. Molecular docking indicated that hydrogen bonds and hydrophobic interactions contributed to the interaction between PFASs and UGT isoforms. In conclusion, exposure to PFASs might inhibit the activity of UGTs to disturb metabolism of endogenous compounds and xenobiotics. The structure-related effects of PFASs on UGTs would be very important for risk assessment of PFASs.

Plasma Levels of Amino Acids Related to Urea Cycle and Risk of Type 2 Diabetes Mellitus in Chinese Adults

Objective: This study aimed to test associations between type 2 diabetes mellitus (T2DM) and metabolites in urea cycle including arginine, citrulline and ornithine. Methods:This study used a hospital-based cross-sectional study design. We retrieved medical notes of 401 in-patients with onset of T2DM within 2 years and 1,522 healthy subjects who attended annual physical examination. All cases were admitted to a tertiary care center in Jinzhou, China from May 2015 to August 2016. Binary logistic regression analyses were performed to obtain odds ratios (ORs) and 95% confidence intervals (CIs). Results:Patients with T2DM had higher arginine, and lower ornithine than control subjects. Levels of citrulline were similar in two groups. Arginine was positively associated with T2DM (ORs: 1.20, 1.17-1.23) while ornithine was negatively associated with T2DM (OR: 0.89, 0.88-0.91). After adjustment for other amino acids and traditional risk factors, these associations were still significant and persistent for arginine and ornithine. The association between citrulline and T2DM was not significant. Their ratios of pairs of two amino acids were associated with increased risk of T2DM. After adjustment for other ratios of amino acids, effect size for T2DM remained significant. Further adjustment for traditional risk factors did not lead to large changes (ORs: 1.78, 1.20-2.65 for the ratio of arginine to ornithine; ORs: 1.59, 1.37-1.86 for the ratio of citrulline to ornithine, respectively) except the ratio of arginine to citrulline. Conclusions: Plasma levels of amino acids related to urea cycle and their ratios of these amino-acids were associated with T2DM in Chinese adults.

Lipidomics reveal aryl hydrocarbon receptor (Ahr)-regulated lipid metabolic pathway in alpha-naphthyl isothiocyanate (ANIT)-induced intrahepatic cholestasis

1. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole mass spectrometry (UPLC-ESI-QTOF MS)-based lipidomics was employed to elucidate new mechanism of alpha-naphthyl isothiocyanate (ANIT)-induced intrahepatic cholestasis in mice. 2. Multiple lipid components significantly increased in ANIT-induced intrahepatic cholestasis, including PC 16:0, 20:4, PC 16:0, 22:6, PC 16:0, 18:2, LPC 18:2, PC 18:2, LPC 18:1, PC 18:1, 14:0, SM 18:1, 16:0, oleoylcarnitine and palmitoylcarnitine. This alteration of lipid profile was induced by the changed expression of genes choline kinase (Chk) a, sphingomyelin phosphodiesterase (SMPD) and stearoyl-coenzyme A desaturase 1 (SCD1). 3. Knockout of aryl hydrocarbon receptor (Ahr) in mice can significantly reverse ANIT-induced intrahepatic cholestasis, as indicated by lowered ALT, AST and ALP activity, and liver histology. Aryl hydrocarbon receptor knockout significantly reversed ANIT-induced lipid metabolism alteration through regulating the expression of Chka. 4. In conclusion, this study demonstrated ANIT-induced lipid metabolism disruption might be the potential pathogenesis of ANIT-induced intrahepatic cholestasis in mice.

Hydroxy metabolites of polychlorinated biphenyls (OH-PCBs) exhibit inhibitory effects on UDP-glucuronosyltransferases (UGTs)

Hydroxy metabolites of polychlorinated biphenyls (OH-PCBs) are important substance basis for the toxicity of PCBs. This study aims to investigate the inhibition of OH-PCBs on the activity of UDP-glucuronosyltransferases (UGTs), trying to elucidate the toxicity mechanism of PCBs from a new perspective. In vitrohuman recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was used as the probe reaction. The number of chlorine atom can affect the inhibition potential of OH-PCBs towards different isoforms of UGTs, and complex structure-activity relationship was found for the inhibition of OH-PCBs on the activities of UGT isoforms. For the inhibition kinetic determination, 2'OHPCB106 and 4'OHPCB106 were selected as the representative OH-PCBs, and UGT1A1, 1A7, and 2B7 were chosen as the representative UGT isoforms. Competitive inhibition of 2'OHPCB106 and 4'OHPCB106 on the activities of UGT1A1, UGT1A7, and UGT2B7 was found. For 2'OHPCB106, the inhibition kinetic parameters (K_i) were calculated to be 0.4 μM for UGT1A1, 1.3 μM for UGT1A7, and 2.7 μM for UGT2B7, respectively. For 4'OHPCB106, K_i values were calculated to be 0.7 μM for UGT1A1, 6.8 μM for UGT1A7, and 4.8 μM for UGT2B7, respectively. In silico docking method was utilized to elucidate the inhibition difference of UGT1A1 by four OH-PCBs with similar structures (4'OHPCB9, 4'OHPCB26, 4'OHPCB112 and 4'OHPCB165). In conclusion, these data will be helpful for understanding the toxicity mechanisms of PCBs from a view of metabolic interference.

Caffeine Protects Skin from Oxidative Stress-Induced Senescence through the Activation of Autophagy

Skin cells are vulnerable to oxidative stress-induced senescence, which may lead to abnormal aging or aging-related disorders. Therefore, strategies that can ameliorate oxidative stress-induced senescence are expected to protect skin from damage, holding the promise of treating skin diseases in the clinic. This study aims to investigate whether caffeine, a well-known purine alkaloid, is able to prevent skin from oxidative stress-induced senescence, and to explore the underlying molecular mechanisms.

Methods: A free radical inducer 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) was used to induce oxidative stress and cellular senescence in both transformed skin cells and in normal human epidermal keratinocytes (NHEKs). Ultraviolet (UV) irradiation was established as the in vivo oxidative stress model in mouse skin tissues. Cellular senescence was determined by SA β-galactosidase staining, immunofluorescence and western blotting. Activation of autophagy was confirmed by western blotting, immunofluorescence, and transmission electron microscopy. Reactive oxygen species (ROS) detection by commercial kits, gene knockdown by RNA interference (RNAi) and receptor activation/inactivation by agonist/antagonist treatment were applied in mechanistic experiments.

Results: We report that AAPH induced senescence in both transformed skin cells and in NHEKs. Similarly, UV irradiation induced senescence in mouse skin tissues. Remarkably, low dose of caffeine (<10 μM) suppressed cellular senescence and skin damage induced by AAPH or UV. Mechanistically, caffeine facilitated the elimination of ROS by activating autophagy. Using a combination of RNAi and chemical treatment, we demonstrate that caffeine activates autophagy through a series of sequential events, starting from the inhibition of its primary cellular target adenosine A2a receptor (A2AR) to an increase in the protein level of Sirtuin 3 (SIRT3) and to the activation of 5' adenosine monophosphate-activated protein kinase (AMPK). Oral administration of caffeine increased the protein level of SIRT3, induced autophagy, and reduced senescence and tissue damage in UV-irradiated mouse skin. On the other hand, co-administration with autophagy inhibitors attenuated the protective effect of caffeine on UV-induced skin damage in mice.

Conclusion: The results reveal that caffeine protects skin from oxidative stress-induced senescence through activating the A2AR/SIRT3/AMPK-mediated autophagy. Our study not only demonstrated the beneficial effect of caffeine using both in vitro and in vivo models, but also systematically investigated the underlying molecular mechanisms. These discoveries implicate the potential of caffeine in the protection of skin disease.

New insights for risks of chlorophenols (CPs) exposure: Inhibition of UDP-glucuronosyltransferases (UGTs)

Chlorophenols (CPs) are important pollutants extensively utilized in industry, agriculture and forestry. The present study aims to determine the inhibition of CPs on the activity of the important phase II drug-metabolizing enzymes (DMEs) UDP-glucuronosyltransferases (UGTs). 100 μM of fourteen CPs were used for preliminary screening using in vitro incubation. Furthermore, half inhibition concentration (IC₅₀) and inhibition kinetics were determined for CPs with significant inhibition towards UGT isoforms. In silico docking was used to explain the inhibition difference among CPs. Multiple UGT isoforms were inhibited by CPs. In silico docking showed that higher free binding energy due to hydrophobic interactions of 2.4-Dichlorophenol (2.4-DCP) or 4-Chloro-3-methylphenol (4C3MP) with UGT1A9 contributed to stronger inhibition potential of 2.4-Dichlorophenol (2.4-DCP) or 4-Chloro-3-methylphenol (4C3MP) towards UGT1A9 than 4-CP. Pentachlorophenol (PCP) was chosen as the representative CPs to determine the IC₅₀ value towards UGT1A6, UGT1A9 and UGT2B7. IC₅₀ was calculated to be 0.33 μM, 0.24 μM and 31.35 μM for the inhibition of PCP towards UGT1A6, UGT1A9 and UGT2B7. PCP was demonstrated to show competitive inhibition towards UGT1A6, UGT1A9 and UGT2B7, and the inhibition kinetic parameters (Ki) was calculated to be 0.18 μM, 0.01 μM and 5.37 μM for the inhibition of PCP towards UGT1A6, UGT1A9 and UGT2B7. All these information will be beneficial for elucidating the risk of CPs exposure from a new perspective.

Bile acid metabolites in early pregnancy and risk of gestational diabetes in Chinese women: A nested case-control study

Background

Bile acid metabolism plays an important role in metabolism but it is uncertain whether bile acid metabolites in early pregnancy are associated with risk of gestational diabetes mellitus (GDM).

Methods

We organized a 1:1 case-control study nested in a prospective cohort of 22,302 pregnant women recruited from 2010 to 2012 in China: 243 women with GDM were matched with 243 non-GDM controls on age (±1 year). Conditional logistic regression and restricted cubic spline were used to examine full-range associations of bile acid metabolites with GDM.

Findings

All the 9 detectable bile acids were inversely associated with the risk of GDM, among them, 8 in nonlinear and one in largely linear manners in multivariable analysis. Glycoursodeoxycholic acid (GUDCA) at ≤0.07 nmol/mL and deoxycholic acid (DCA) at ≤0.28 nmol/mL had threshold effects and their decreasing levels below the cutoff points were associated with rapid rises in the risk of GDM. In traditional risk factor model, the stepwise procedure identified that GUDCA ≤ 0.07 nmol/mL and DCA ≤ 0.280 nmol/mL were still significant (OR: 6.84, 95%CI: 1.10–42.48 & 2.06, 1.26–3.37), while other bile acids were not. Inclusion of the two bile acids in the model increased the area under operating characteristic's curve from 0.69 to 0.76 (95% CI: 0.71–0.80) (P < .05).

Interpretation

Serum GUDCA ≤ 0.07 nmol/mL and DCA ≤ 0.28 nmol/mL in early pregnancy were independently associated with increased risk of GDM in Chinese pregnant women.

Funding

Talent Recruitment Scheme grant of Tianjin Medical University and National Key Research and Development Program, etc.

Inhibition of UDP-glucuronosyltransferases (UGTs) by phthalate monoesters

Phthalate monoesters are important metabolites of phthalate esters (PAEs) which have been extensively utilized in industry. This study aims to investigate the inhibition of phthalate monoesters on the activity of various isoforms of UDP-glucuronosyltransferases (UGTs), trying to elucidate the toxicity mechanism of environmental endocrine disruptors from the new perspectives. In vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was employed to evaluate 8 kinds of phthalate monoesters on 11 sorts of main human UGT isoforms. 100 μM phthalate monoesters exhibited negligible inhibition towards the activity of UGT1A1, UGT1A3, UGT1A6, UGT1A8, UGT1A10, UGT2B4, UGT2B7, UGT2B15 and UGT2B17. The activity of UGT1A7 was strongly inhibited by monoethylhexyl phthalate (MEHP), but slightly inhibited by all the other phthalate monoesters. UGT1A9 was broadly inhibited by monobenzyl phthalate (MBZP), monocyclohexyl phthalate (MCHP), MEHP, monohexyl phthalate (MHP) and monooctyl phthalate (MOP), respectively. MEHP exhibited competitive inhibition towards UGT1A7, and MBZP, MCHP, MEHP, MHP and MOP showed competitive inhibition towards UGT1A9. The inhibition kinetic parameters (K_i) were calculated to be 11.25 μM for MEHP-UGT1A7, and 2.13, 0.09, 1.17, 7.47, 0.16 μM for MBZP-UGT1A9, MCHP-UGT1A9, MEHP-UGT1A9, MHP-UGT1A9, MOP-UGT1A9, respectively. Molecular docking indicated that both hydrogen bonds formation and hydrophobic interactions significantly contributed to the interaction between phthalate monoesters and UGT isoforms. All these information will be beneficial for understanding the adverse effects of PAEs.

Inhibitory effects of tanshinones towards the catalytic activity of UDP-glucuronosyltransferases (UGTs)

CONTENTS

Danshen is a popular herb employed to treat cardiovascular and cerebrovascular diseases worldwide. Danshen-drug interaction has not been well studied.

OBJECTIVE

The inhibitory effects of four major tanshinones (tanshinone I, tanshinone IIA, cryptotanshinone, and dihydrotanshinone I) on UDP-glucuronosyltransferases (UGTs) isoforms were determined to better understand the mechanism of danshen-prescription drugs interaction.

MATERIALS AND METHODS

In vitro recombinant UGTs-catalyzed 4-methylumbelliferone (4-MU) glucuronidation reaction was employed. Tanshinones (100 μM) was used to perform the initial screening of inhibition capability. High-performance liquid chromatography (HPLC) was used to separate 4-MU and its glucuronide. In vitro-in vivo extrapolation (IV-IVE) was employed to predict in vivo inhibition situation.

RESULTS

Cryptotanshinone inhibited UGT1A7 and UGT1A9 with IC₅₀ values of 1.91 ± 0.27 and 0.27 ± 0.03 μM, respectively. Dihydrotanshinone I inhibited UGT1A9-catalyzed 4-MU glucuronidation reaction with the IC₅₀ value of 0.72 ± 0.04 μM. The inhibition of cryptotanshinone towards UGT1A7 and UGT1A9 was best fit to competitive inhibition type, and UGT1A9 was non-competitively inhibited by dihydrotanshinone I. Using in vitro inhibition kinetic parameters (K_i) and in vivo maximum plasma concentration (C_max) of cryptotanshinone and dihydrotanshinone I, the change of area-under-the-concentration-time curve (AUC) was predicted to be 0.4-4.2%, 3.7-56.3%, and 0.6-6.4% induced by cryptotanshinone and dihydrotanshinone inhibition towards UGT1A7 and UGT1A9, respectively.

DISCUSSION AND CONCLUSION

The inhibitory effects of tanshinones towards important UGT isoforms were evaluated in the present study, which provide helpful information for exploring the mechanism of danshen-clinical drugs interaction.

Inhibitory effects of fifteen phthalate esters in human cDNA-expressed UDP-glucuronosyltransferase supersomes

Phthalate esters (PAEs) have been extensively used in industry as plasticizers and there remains concerns about their safety. The present study aimed to determine the inhibition of phthalate esters (PAEs) on the activity of the phase II drug-metabolizing enzymes UDP-glucuronosyltransferases (UGTs). In vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone was used to investigate the inhibition potentials of PAEs towards various s UGTs. PAEs exhibited no significant inhibition of UGT1A1, UGT1A3, UGT1A8, UGT1A10, UGT2B15, and UGT2B17, and limited inhibition of UGT1A6, UGT1A7 and UGT2B4. However, UGT1A9 was strongly inhibited by PAEs. In silico docking demonstrated a significant contribution of hydrogen bonds and hydrophobic interactions contributing to the inhibition of UGT by PAEs. The K_i values were 15.5, 52.3, 23.6, 12.2, 5.61, 2.79, 1.07, 22.8, 0.84, 73.7, 4.51, 1.74, 0.58, 6.79, 4.93, 6.73, and 7.23 μM for BBOP-UGT1A6, BBZP-UGT1A6, BBOP-UGT1A7, BBZP-UGT1A7, DiPP-UGT1A9, DiBP-UGT1A9, DCHP-UGT1A9, DBP-UGT1A9, BBZP-UGT1A9, BBOP-UGT1A9, DMEP-UGT1A9, DPP-UGT1A9, DHP-UGT1A9, DiBP-UGT2B4, DBP-UGT2B4, DAP-UGT2B4, and BBZP-UGT2B4, respectively. In conclusion, exposure to PAEs might influence the metabolic elimination of endogenous compounds and xenobiotics through inhibiting UGTs.

Growth arrest and DNA damage-inducible 45α protects against nonalcoholic steatohepatitis induced by methionine- and choline-deficient diet

Growth arrest and DNA damage-inducible 45 α (Gadd45α) is a stress-inducible protein that plays an important role in cell survival/death and DNA repair, but its contribution to the development of nonalcoholic steatohepatitis (NASH) has not been investigated. C57BL/6 Gadd45a-null and wild-type (WT) mice were treated with a methionine and choline-deficient diet (MCD) for eight weeks and phenotypic changes examined. Gadd45a-null mice had more severe hepatic inflammation and fibrosis, higher levels of mRNAs encoding pro-inflammatory, pro-fibrotic, and pro-apoptotic proteins, and greater oxidative and endoplasmic reticulum (ER) stress compared with WT mice. Indeed, Gadd45a mRNA was induced in response to ER stress in primary hepatocytes. Lipidomic analysis of NASH livers demonstrated decreased triacylglycerol (TG) in MCD-treated Gadd45a-null mice, which was associated with increased mRNAs encoding phospholipase D (Pld1/2), phosphatidic acid phosphatase type 2A, and choline/ethanolamine phosphotransferase 1 (Cept1), involved in the phosphatidylcholine-phosphatidic acid-diacylglycerol cycle, and decreased mRNAs encoding fatty acid (FA)-binding protein 1 (Fabp1) and FA transport protein 5. Treatment of cultured primary hepatocytes with tumor necrosis factor α, transforming growth factor β, and hydrogen peroxide led to the corresponding induction of Fabp1, Pld1/2, and Cept1 mRNAs. Collectively, Gadd45α plays protective roles against MCD-induced NASH likely due to attenuating cellular stress and ensuing inflammatory signaling. These results also suggest an interconnection between hepatocyte injury, inflammation and disrupted glycerophospholipid/FA metabolism that yields a possible mechanism for decreased TG accumulation with NASH progression (i.e., "burned-out" NASH).

In Vitro Comparative Study of the Inhibitory Effects of Mangiferin and Its Aglycone Norathyriol towards UDP-Glucuronosyl Transferase (UGT) Isoforms

Mangiferin (MGF), the predominant constituent of extracts of the mango plant Mangifera Indica L., has been investigated extensively because of its remarkable pharmacological effects. In vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was used to investigate the inhibition of mangiferin and aglycone norathyriol towards various isoforms of UGTs in our study, which evaluated the inhibitory capacity of MGF and its aglycone norathyriol (NTR) towards UDP-glucuronosyltransferase (UGT) isoforms. Initial screening experiment showed that deglycosylation of MGF into NTR strongly increased the inhibitory effects towards almost all the tested UGT isoforms at a concentration of 100 μM. Kinetic experiments were performed to further characterize the inhibition of UGT1A3, UGT1A7 and UGT1A9 by NTR. NTR competitively inhibited UGT1A3, UGT1A7 and UGT1A9, with an IC₅₀ value of 8.2, 4.4, and 12.3 μM, and a Ki value of 1.6, 2.0, and 2.8 μM, respectively. In silico docking showed that only NTR could dock into the activity cavity of UGT1A3, UGT1A7 and UGT1A9. The binding free energy of NTR to UGT1A3, 1A7, 1A9 were −7.4, −7.9 and −4.0 kcal/mol, respectively. Based on the inhibition evaluation standard ([I]/Ki < 0.1, low possibility; 0.1 < [I]/Ki < 1, medium possibility; [I]/Ki > 1, high possibility), an in vivo herb–drug interaction between MGF/NTR and drugs mainly undergoing UGT1A3-, UGT1A7- or UGT1A9-catalyzed metabolism might occur when the plasma concentration of NTR is above 1.6, 2.0 and 2.8 μM, respectively.

Inhibition of human CYP3A4 and CYP3A5 enzymes by gomisin C and gomisin G, two lignan analogs derived from Schisandra chinensis

Gomisin C (GC) and gomisin G (GG) are two lignan analogs isolated from the Traditional Chinese Medicine Schisandra chinensis which possesses multiple pharmacological activities. However, the potential herb-drug interactions (HDI) between these lignans and other drugs through inhibiting human cytochrome P450 3A4 (CYP3A4) and CYP3A5 remains unclear. In the present study, the inhibitory action of GC and GG on CYP3A4 and CYP3A5 were investigated. The results demonstrated that both GC and GG strongly inhibited CYP3A-mediated midazolam 1'-hydroxylation, nifedipine oxidation and testosterone 6β-hydroxylation. Notably, the inhibitory intensity of GC towards CYP3A4 was stronger than CYP3A5 when using midazolam and nifedipine as substrates. While inhibition of GC towards CYP3A5 was weaker than CYP3A4 when using testosterone as substrate. In contrast, GG showed a stronger inhibitory activity on CYP3A5 than CYP3A4 without substrate-dependent behavior. In addition, docking simulations indicated that the π-π interaction between CYP3A4 and GC, and hydrogen-bond interaction between CYP3A5 and GG might result in their different inhibitory actions. Furthermore, the AUC of drugs metabolized by CYP3A was estimated to increase by 8%-321% and 2%-3190% in the presence of GC and GG, respectively. These findings strongly suggested that GC and GG showed high HDI potentials, and the position of methylenedioxy group determined their different inhibitory effect towards CYP3A4 and CYP3A5, which are of significance for the application of Schisandra chinensis-containing herbs.

Role of the lipid-regulated NF-κB/IL-6/STAT3 axis in alpha-naphthyl isothiocyanate-induced liver injury

Alpha-naphthyl isothiocyanate (ANIT)-induced liver damage is regarded as a useful model to study drug-induced cholestatic hepatitis. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole mass spectrometry (UPLC-ESI-QTOF MS)-based metabolomics revealed clues to the mechanism of ANIT-induced liver injury, which facilitates the elucidation of drug-induced liver toxicity. 1-Stearoyl-2-hydroxy-sn-glycero-3-phosphocholine (LPC 18:0) and 1-oleoyl-2-hydroxy-sn-glycero-3-phosphocholine (LPC 18:1) were significantly increased in serum from ANIT-treated mice, and this increase resulted from altered expression of genes encoding the lipid metabolism enzymes Chka and Scd1. ANIT also increased NF-κB/IL-6/STAT3 signaling, and in vitro luciferase reporter gene assays revealed that LPC 18:0 and LPC 18:1 can activate NF-κB in a concentration-dependent manner. Activation of PPARα through feeding mice a Wy-14,643-containing diet (0.1%) reduced ANIT-induced liver injury, as indicated by lowered ALT and AST levels, and liver histology. In conclusion, the present study demonstrated a role for the lipid-regulated NF-κB/IL-6/STAT3 axis in ANIT-induced hepatotoxicity, and that PPARα may be a potential therapeutic target for the prevention of drug-induced cholestatic liver injury.

The inhibition of UDP-glucuronosyltransferases (UGTs) by vitamin A

1. The exposed level of vitamin A in plasma might be exceeded due to the both inadvertent and clinical utilization. The adverse effects of vitamin A have been frequently reported, however, the mechanism remains unclear. The inhibition of vitamin A on the activity of UDP-glucuronosyltransferases (UGTs) was determined using in vitro incubation system to explain the adverse effects of vitamin A from a new perspective. 2. UGT supersomes catalyzed glucuronidation of 4-methylumbelliferone (4-MU), trifluoperazine (TFP), and cotinine was used as the probe reaction to evaluate the inhibition of vitamin A toward UGT isoforms, and 100 μM of vitamin A significantly inhibited the activity of all the tested UGT isoforms. Vitamin A exerted competitive inhibition on the activity of UGT1A1, 2B4, 2B7, and 2B15, and the inhibition kinetic parameters (K_i) were calculated to be 31.1, 16.8, 2.2, and 11.6 μM for UGT1A1, 2B4, 2B7, and 2B15. In silico docking method was used to try to elucidate the inhibition mechanism of vitamin A toward UGT2B7. The results showed the significant contribution of hydrogen bonds and hydrophobic interaction on the UGT2B7 inhibition by vitamin A. 3. The present study provides a new perspective for the adverse effects of vitamin A through reporting the inhibition of vitamin A on the activity of important phase II drug-metabolizing enzymes UGTs, which benefits our deep understanding of mechanism of vitamin A's adverse effects when high exposure of vitamin A occurs.

Comparison of the inhibitory effects of tolcapone and entacapone against human UDP-glucuronosyltransferases

Tolcapone and entacapone are two potent catechol-O-methyltransferase (COMT) inhibitors with a similar skeleton and displaying similar pharmacological activities. However, entacapone is a very safe drug used widely in the treatment of Parkinson's disease, while tolcapone is only in limited use for Parkinson's patients and needs careful monitoring of hepatic functions due to hepatotoxicity. This study aims to investigate and compare the inhibitory effects of entacapone and tolcapone on human UDP-glucosyltransferases (UGTs), as well as to evaluate the potential risks from the view of drug-drug interactions (DDI). The results demonstrated that both tolcapone and entacapone exhibited inhibitory effects on UGT1A1, UGT1A7, UGT1A9 and UGT1A10. In contrast to entacapone, tolcapone exhibited more potent inhibitory effects on UGT1A1, UGT1A7, and UGT1A10, while their inhibitory potentials against UGT1A9 were comparable. It is noteworthy that the inhibition constants (Ki) of tolcapone and entacapone against bilirubin-O-glucuronidation in human liver microsomes (HLM) are determined as 0.68μM and 30.82μM, respectively, which means that the inhibition potency of tolcapone on UGT1A1 mediated bilirubin-O-glucuronidation in HLM is much higher than that of entacapone. Furthermore, the potential risks of tolcapone or entacapone via inhibition of human UGT1A1 were quantitatively predicted by the ratio of the areas under the plasma drug concentration-time curve (AUC). The results indicate that tolcapone may result in significant increase in AUC of bilirubin or the drugs primarily metabolized by UGT1A1, while entacapone is unlikely to cause a significant DDI through inhibition of UGT1A1.

New insights into the risk of phthalates: Inhibition of UDP-glucuronosyltransferases

Wide utilization of phthalates-containing products results in the significant exposure of humans to these compounds. Many adverse effects of phthalates have been documented in rodent models, but their effects in humans exposed to these chemicals remain unclear until more mechanistic studies on phthalate toxicities can be carried out. To provide new insights to predict the potential adverse effects of phthalates in humans, the recent study investigated the inhibition of representative phthalates di-n-octyl ortho-phthalate (DNOP) and diphenyl phthalate (DPhP) towards the important xenobiotic and endobiotic-metabolizing UDP-glucuronosyltransferases (UGTs). An in vitro UGTs incubation system was employed to study the inhibition of DNOP and DPhP towards UGT isoforms. DPhP and DNOP weakly inhibited the activities of UGT1A1, UGT1A7, and UGT1A8. 100 µM of DNOP inhibited the activities of UGT1A3, UGT1A9, and UGT2B7 by 41.8% (p < 0.01), 45.6% (p < 0.01), and 48.8% (p < 0.01), respectively. 100 µM of DPhP inhibited the activity of UGT1A3, UGT1A6, and UGT1A9 by 81.8 (p < 0.001), 49.1% (p < 0.05), and 76.4% (p < 0.001), respectively. In silico analysis was used to explain the stronger inhibition of DPhP than DNOP towards UGT1A3 activity. Kinetics studies were carried our to determine mechanism of inhibition of UGT1A3 by DPhP. Both Dixon and Lineweaver-Burk plots showed the competitive inhibition of DPhP towards UGT1A3. The inhibition kinetic parameter (Ki) was calculated to be 0.89 µM. Based on the [I]/Ki standard ([I]/Ki < 0.1, low possibility; 1>[I]/Ki > 0.1, medium possibility; [I]/Ki > 1, high possibility), these studies predicted in vivo drug-drug interaction might occur when the plasma concentration of DPhP was above 0.089 µM. Taken together, this study reveales the potential for adverse effects of phthalates DNOP and DPhP as a result of UGT inhibition.