6-Hydroxyindole is an endogenous long-lasting OATP1B1 inhibitor elevated in renal failure patients

A high-throughput liquid chromatography-tandem mass spectrometry assay for the simultaneous quantification of p-cresol sulfate, p-cresol glucuronide, indoxyl sulfate, and indoxyl glucuronide in HepaRG culture medium and the demonstration of mefenamic acid as a potent and selective detoxifying agent

BACKGROUND

p-cresol and indole are uremic compounds which undergo sulfonation to generate the highly toxic p-cresol sulfate (pCS) and indoxyl sulfate (IxS). They are also subjected to glucuronidation to produce the less toxic p-cresol glucuronide (pCG) and indoxyl glucuronide (IG). We developed and validated an assay to quantify these metabolites in HepaRG cells. We also tested the effects of mefenamic acid on their in-situ formations in relation to the development of cellular necrosis.

RESEARCH DESIGN AND METHODS

HepaRG cells were exposed to p-cresol or indole (0-1 mM) with mefenamic acid (0-3000 nM) for 24 hours to generate uremic metabolites. Cells were also exposed to 0.5 mM p-cresol or indole with/without 30 nM mefenamic acid to characterize lactate dehydrogenase (LDH) release.

RESULTS

The assay exhibited high sensitivity and wide calibration ranges covering human concentrations. HepaRG cells also generated physiologically-relevant concentrations of each metabolite. Mefenamic acid inhibited pCS formation in a concentration-dependent manner without affecting pCG, IxS, or IG. Mefenamic acid also reduced LDH release from p-cresol (by 50.12±5.86%) or indole (56.26±3.58%).

CONCLUSIONS

This novel assay is capable of quantifying these metabolites in HepaRG cells. Our novel findings suggest that mefenamic acid can be potentially utilized therapeutically to attenuate pCS-associated toxicities.

Emerging Roles of Uremic Toxins and Inflammatory Cytokines in the Alteration of Hepatic Drug Disposition in Patients with Kidney Dysfunction

Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Hence, it is desirable to monitor the drug efficacy and toxicity caused by fluctuations in plasma drug concentrations associated with kidney dysfunction. Recently, pharmacokinetic information of drugs excreted mainly through the urine of patients with kidney dysfunction has been reported via drug-labeling information. Pharmacokinetic changes in drugs mainly eliminated by the liver cannot be overlooked as drug metabolism and/or transport activity in the liver may also be altered in patients with kidney dysfunction; however, the underlying mechanisms remain unclear. To plan an appropriate dosage regimen, it is necessary to clarify the underlying processes of functional changes in pharmacokinetic proteins. In recent years, uremic toxins have been shown to reduce the activity and/or expression of renal and hepatic transporters. This inhibitory effect has been reported to be time-dependent. In addition, inflammatory cytokines, such as interleukin-6, released from immune cells activated by uremic toxins and/or kidney injury can reduce the expression levels of drug-metabolizing enzymes and transporters in human hepatocytes. In this mini-review, we have summarized the renal and hepatic pharmacokinetic changes as well as the potential underlying mechanisms in kidney dysfunction, such as the chronic kidney disease and acute kidney injury. SIGNIFICANCE STATEMENT: Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Increased plasma concentrations of uremic toxins and inflammatory cytokines during kidney disease may potentially affect the activities and/or expression levels of drug-metabolizing enzymes and transporters in the liver and kidneys.

Potential serum metabolites and long-chain noncoding RNA biomarkers for endometrial cancer tissue

BACKGROUND

Endometrial carcinoma (EC) is one of the most common tumors in the female reproductive system. There are nearly 200 000 new cases every year. It is the third most common gynecological malignant tumor leading to female death. The incidence rate is closely related to lifestyle, and the incidence rate varies in different regions. The incidence rate of EC is ranking the first in the female reproductive system cancer just second only to breast, lung, and colorectal cancer in North America and Europe and the incidence rate of EC is only second, followed by breast cancer and cervical cancer in China.

PURPOSE

The potential metabolic markers of endometrial cancer were screened by liquid chromatograph mass spectrometer (LC-MS), and the tissues of patients with hysteromyoma and endometrial cancer were sequenced to explore the relationship between the disease and change in the content of long-chain noncoding RNA (lncRNA).

METHODS

Serum and tissue samples were collected from patients with endometrial dysplasia, endometrial cancer stage I, and endometrial cancer stage III. The metabolites in all serum samples were extracted, and the metabolites in all samples were detected by LC-MS/MS technology. The Pareto-scaling method was used for normalization, and the MetaboAnalyst 4.0 software was used for different analyses. The T test between groups showed that p ≤ 0.05 was regarded as the metabolite with a difference. Further, the function of differential metabolites was determined by metabolite function enrichment and co-expression analysis. Meanwhile, the differentially expressed lncRNA was detected by Illumina second-generation high-throughput sequencing technology, and the expression was analyzed by DEGseq software. Different lncRNA were screened according to p < 0.05. LncRNA with significant differences were screened by p < 0.01, q < 0.001, fold change ≥2, and false discovery rate (FDR) ≤0.001.

RESULTS

Through synthesis of T test, cluster heatmap, and ROC curve analysis, five biomarkers with potential diagnostic ability were obtained, including 2,3-Pyridinedicarboxylic acid (area under the curve (AUC) = 0.69), Hematommic acid, ethyl ester (AUC = 0.69), Maltitol (AUC = 0.69), 13(S)-HODE (AUC = 0.88), and D-Mannitol (AUC = 0.69) had potential diagnostic ability between EC phase I versus EC phase III. At the same time, lncRNA sequencing results showed that when endometrial atypical hyperplasia continued to change, including LINC00511, PVT1, and IQCH-AS1 (downregulated), and only changed significantly in the endometrial dysplasia group, including MALAT1, CARMN (downregulated) and LINC00648, BISPR, LINC01534, and LINC00930 (upregulated). Moreover, both differential metabolites and differential lncRNA were annotated to the lipid metabolism pathway, suggesting that this pathway played an important role in the occurrence and development of endometrial carcinoma.

CONCLUSIONS

It can combine the results of metabolomics and lncRNA sequencing to assist in the early diagnosis of endometrial precancerous lesions and endometrial cancer patients, to enhance the sensitivity and specificity of diagnosis, which has a certain clinical application prospect.

A metabolomic signature of the APOE2 allele

With the goal of identifying metabolites that significantly correlate with the protective e2 allele of the apolipoprotein E (APOE) gene, we established a consortium of five studies of healthy aging and extreme human longevity with 3545 participants. This consortium includes the New England Centenarian Study, the Baltimore Longitudinal Study of Aging, the Arivale study, the Longevity Genes Project/LonGenity studies, and the Long Life Family Study. We analyzed the association between APOE genotype groups E2 (e2e2 and e2e3 genotypes, N = 544), E3 (e3e3 genotypes, N = 2299), and E4 (e3e4 and e4e4 genotypes, N = 702) with metabolite profiles in the five studies and used fixed effect meta-analysis to aggregate the results. Our meta-analysis identified a signature of 19 metabolites that are significantly associated with the E2 genotype group at FDR < 10%. The group includes 10 glycerolipids and 4 glycerophospholipids that were all higher in E2 carriers compared to E3, with fold change ranging from 1.08 to 1.25. The organic acid 6-hydroxyindole sulfate, previously linked to changes in gut microbiome that were reflective of healthy aging and longevity, was also higher in E2 carriers compared to E3 carriers. Three sterol lipids and one sphingolipid species were significantly lower in carriers of the E2 genotype group. For some of these metabolites, the effect of the E2 genotype opposed the age effect. No metabolites reached a statistically significant association with the E4 group. This work confirms and expands previous results connecting the APOE gene to lipid regulation and suggests new links between the e2 allele, lipid metabolism, aging, and the gut-brain axis.