Effects of decreased vitamin D and accumulated uremic toxin on human CYP3A4 activity in patients with end-stage renal disease

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

The Impact of Suboptimal 25-Hydroxyvitamin D Levels and Cholecalciferol Replacement on the Pharmacokinetics of Oral Midazolam in Control Subjects and Patients With Chronic Kidney Disease

The aim of this study was to investigate the impact of suboptimal 25-hydroxyvitamin D (25-VitD) and cholecalciferol (VitD3 ) supplementation on the pharmacokinetics of oral midazolam (MDZ) in control subjects and subjects with chronic kidney disease (CKD). Subjects with CKD (n = 14) and controls (n = 5) with suboptimal 25-VitD levels (<30 ng/mL) were enrolled in a 2-phase study. In phase 1 (suboptimal), subjects were administered a single oral dose of VitD3 (5000 IU) and MDZ (2 mg). In phase 2 (replete) subjects who achieved 25-VitD repletion after receiving up to 16 weeks of daily cholecalciferol were given the identical single oral doses of VitD3 and MDZ as in phase 1. Concentrations of MDZ and metabolites, 1'-hydroxymidazolam (1'-OHMDZ), and 1'-OHMDZ glucuronide (1'-OHMDZ-G) were measured by liquid chromatography-tandem mass spectrometry and pharmacokinetic analysis was performed. Under suboptimal 25-VitD, reductions in MDZ clearance and renal clearance of 47% and 87%, respectively, and a 72% reduction in renal clearance of 1'-OHMDZ-G were observed in CKD vs controls. In phase 1 versus phase 2, MDZ clearance increased in all control subjects, with a median (interquartile range) increase of 10.5 (0.62-16.7) L/h. No changes in MDZ pharmacokinetics were observed in subjects with CKD between phases 1 and 2. The effects of 25-VitD repletion on MDZ disposition was largely observed in subjects without kidney disease. Impaired MDZ metabolism and/or excretion alterations due to CKD in a suboptimal 25-VitD state may not be reversed by cholecalciferol therapy. Suboptimal 25-VitD may augment the reductions in MDZ and 1'-OHMDZ-G clearance values observed in patients with CKD.

Development of an in silico prediction system of human renal excretion and clearance from chemical structure information incorporating fraction unbound in plasma as a descriptor

Prediction of pharmacokinetic profiles of new chemical entities is essential in drug development to minimize the risks of potential withdrawals. The excretion of unchanged compounds by the kidney constitutes a major route in drug elimination and plays an important role in pharmacokinetics. Herein, we created in silico prediction models of the fraction of drug excreted unchanged in the urine (f_e) and renal clearance (CL_r), with datasets of 411 and 401 compounds using freely available software; notably, all models require chemical structure information alone. The binary classification model for f_e demonstrated a balanced accuracy of 0.74. The two-step prediction system for CL_r was generated using a combination of the classification model to predict excretion-type compounds and regression models to predict the CL_r value for each excretion type. The accuracies of the regression models increased upon adding a descriptor, which was the observed and predicted fraction unbound in plasma (f_u,p); 78.6% of the samples in the higher range of renal clearance fell within 2-fold error with predicted f_u,p value. Our prediction system for renal excretion is freely available to the public and can be used as a practical tool for prioritization and optimization of compound synthesis in the early stage of drug discovery.

Role of vitamin D receptor in the regulation of CYP3A gene expression

Vitamin D₃ (VD₃) is a multifunctional nutrient which can be either synthesized or absorbed from the diet. It plays a pivotal role in systemic calcium and phosphate homeostasis, as well as in various physiological and pathological processes. VD₃ is converted to the active form, 1α,25-dihydroxyvitamin D₃ (1,25-D3), by cytochrome P450 2R1 (CYP2R1)/CYP27A1 and CYP27B1 sequentially, and deactivated by multiple enzymes including CYP3A4. On the other hand, 1,25-D3 is capable of activating the transcription of CYP3A genes in humans, mice and rats. The vitamin D receptor (VDR)-mediated transactivation of human CYP3A4 and CYP3A5 resembles that known for pregnane X receptor (PXR). Activated VDR forms a heterodimer with retinoid X receptor α (RXRα), recruits co-activators, translocates to the cell nucleus, binds to the specific vitamin D responsive elements (VDRE), and activates the gene transcription. In mice, intestinal Cyp3a11 mRNA levels, but not those of hepatic CYP3As, were induced by in vivo administration of VDR and PXR agonists. In rats, intestinal Cyp3a1 and Cyp3a2 mRNAs were induced by 1,25-D3 or lithocholic acid (LCA), whereas hepatic Cyp3a2, but not Cyp3a1 and Cyp3a9, was modulated to 1,25-D3 treatment. In general, the VDR-mediated regulation of CYP3A presents species and organ specificity.

Hepato-splanchnic circulatory stress: An important effect of hemodialysis

The gastro-intestinal tract is being increasingly recognized as the site of key pathophysiological processes in the hemodialysis patient. Intestinal dysbiosis, increased intraluminal toxin production, and increased intestinal permeability are commonly observed processes which contribute to the pathogenesis of cardiovascular disease and thus elevated mortality. The acute circulatory effects of dialysis itself may contribute significantly to the development of gastrointestinal dysfunction as a result of both local and distant effects. Additionally, the liver, a relatively unknown entity in this process, has a substantial role as a functional barrier between the portal and systemic circulation and in the metabolism of pathogenic gut-derived uremic toxins. Here we summarize the evidence for acute gastro-intestinal and hepatic effects of hemodialysis and identify gaps in knowledge to date which require further study.

Evaluation of Trace Elements in Augmentation of Statin-Induced Cytotoxicity in Uremic Serum-Exposed Human Rhabdomyosarcoma Cells

Patients with end-stage kidney disease (ESKD) are at higher risk for rhabdomyolysis induced by statin than patients with normal kidney function. Previously, we showed that this increase in the severity of statin-induced rhabdomyolysis was partly due to uremic toxins. However, changes in the quantity of various trace elements in ESKD patients likely contribute as well. The purpose of this study is to determine the effect of trace elements on statin-induced toxicity in rhabdomyosarcoma cells exposed to uremic serum (US cells) for a long time. Cell viability, apoptosis, mRNA expression, and intracellular trace elements were assessed by viability assays, flow cytometry, real-time RT-PCR, and ICP-MS, respectively. US cells exhibited greater simvastatin-induced cytotoxicity than cells long-time exposed with normal serum (NS cells) (non-overlapping 95% confidence intervals). Intracellular levels of Mg, Mn, Cu, and Zn were significantly less in US cells compared to that in NS cells (p < 0.05 or 0.01). Pre-treatment with TPEN increased simvastatin-induced cytotoxicity and eliminated the distinction between both cells of simvastatin-induced cytotoxicity. These results suggest that Zn deficiencies may be involved in the increased risk for muscle complaints in ESKD patients. In conclusion, the increased severity of statin-induced rhabdomyolysis in ESKD patients may be partly due to trace elements deficiencies.

Microbiota-derived uremic retention solutes: perpetrators of altered nonrenal drug clearance in kidney disease

INTRODUCTION

Scientific interest in the gut microbiota is increasing due to improved understanding of its implications in human health and disease. In patients with kidney disease, gut microbiota-derived uremic toxins directly contribute to altered nonrenal drug clearance. Microbial imbalances, known as dysbiosis, potentially increase formation of microbiota-derived toxins, and diminished renal clearance leads to toxin accumulation. High concentrations of microbiota-derived toxins such as indoxyl sulfate and p-cresol sulfate perpetrate interactions with drug metabolizing enzymes and transporters, which provides a mechanistic link between increases in drug-related adverse events and dysbiosis in kidney disease. Areas covered: This review summarizes the effects of microbiota-derived uremic toxins on hepatic phase I and phase II drug metabolizing enzymes and drug transporters. Research articles that tested individual toxins were included. Therapeutic strategies to target microbial toxins are also discussed. Expert commentary: Large interindividual variability in toxin concentrations may explain some differences in nonrenal clearance of medications. Advances in human microbiome research provide unique opportunities to systematically evaluate the impact of individual and combined microbial toxins on drug metabolism and transport, and to explore microbiota-derived uremic toxins as potential therapeutic targets.

Identification of potential candidate genes for hypertensive nephropathy based on gene expression profile

Background

This study was aimed to explore the molecular mechanisms of hypertensive nephropathy (HTN).

Methods

Gene expression profile of GSE37460, which based on 27 healthy living donor samples (HTN group) and 15 hypertensive nephropathy samples (control group), were downloaded from Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) between two groups were identified. STRING database was used to reveal protein-protein interaction (PPI) network of DEGs, followed by the functional enrichment analysis of the PPI network. Additionally, miRNA-DEG regulatory network was constructed to reveal the validated miRNAs targeting the DEGs.

Results

In total, 51 up-regulated genes and 140 down-regulated genes were obtained. In the PPI network, cytochrome P450 3A4 (CYP3A4) and angiotensin II receptor type 1 (AGTR1) had a higher degree, and CYP3A4 interacted with CYP4A11. The DEGs in the network were significantly enriched in drug metabolism, focal adhesion and arachidonic acid metabolism. Furthermore, in the miRNA-DEG regulatory network, hsa-miR-335-5p and hsa-miR-26b-5p were the two most outstanding miRNAs. AGTR1, CYP3A4 and CYP4A11 were predicted to be regulated by hsa-miR-26b-5p.

Conclusion

The DEGs, such as AGTR1, CYP3A4 and CYP4A11 may play critical roles in the development of HTN likely via the regulation by hsa-miR-26b-5p and taking part in some pathways.

Metabolomics analysis of serum 25-hydroxy-vitamin D in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study

BACKGROUND

Vitamin D has been discussed in the context of cardiovascular disease, cancer, bone health and other outcomes. Epidemiological studies have reported on the importance of vitamin D in cancer prevention and treatment. The discovery of vitamin D-associated metabolites through agnostic metabolomics analyses offers a new approach for elucidating disease aetiology and health-related pathway identification.

METHODS

Baseline serum 25-hydroxy-vitamin D [25(OH)D] and 940 serum metabolites were measured in 392 men from eight nested cancer case-control studies in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study of Finnish male smokers (aged 50-69 years). The metabolomic profiling was conducted using mass spectrometry. We used linear regression to estimate the standardized beta-coefficient as the effect metric for the associations between metabolites and 25(OH)D levels.

RESULTS

A majority of the metabolites associated with 25(OH)D were of lipid origin, including 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) [beta-estimate 0.38 per 1 standard deviation (SD) increment], stearoyl-arachidonoyl-glycerophosphoethanolamine (GPPE) (-0.38 per SD) and two essential fatty acids: eicosapentaenoate (EPA; 0.17 per SD) and docosahexaenoate (DHA; 0.13 per SD). Each of these lipid metabolites was associated with 25(OH)D at the principal components corrected P-value of 3.09 × 10^-4 CONCLUSIONS: The large number of metabolites, particularly lipid compounds, found to be associated with serum 25(OH)D provide new biological clues relevant to the role of vitamin D status and human health outcomes. The present findings should be re-examined in other metabolomics studies of diverse populations.

The use of vitamin D analogs is independently associated with the favorable renal prognosis in chronic kidney disease stages 4-5: the CKD-ROUTE study

BACKGROUND

Vitamin D analogs have generally been recommended for treatment of mineral bone disease in chronic kidney disease (CKD). However, the association between this treatment and CKD progression has not yet been established.

METHODS

We designed a post hoc propensity score-matched cohort analysis derived from 3-year follow-up data of a prospective cohort. Adult participants with pre-dialysis CKD stages 4-5 who had newly been prescribed active vitamin D analogs during the observation period were eligible as matched cases. Then, matched controls were extracted from participants who had never been prescribed active vitamin D analogs. The primary outcome was a composite of end-stage renal disease or a 50 % reduction in estimated glomerular filtration rate (eGFR). A Cox proportional hazards model evaluated the association between the use of vitamin D analogs and the primary outcome.

RESULTS

We enrolled 240 patients (males, 65 %). The number of matched cases and controls was 30 and 210, respectively. The primary outcome was observed in 94 patients, whereas 25 patients died. The mean ± standard deviation age and eGFR were 69 ± 12 years and 17 ± 5.7 ml/min/1.73 m², respectively. In a Cox proportional hazard model, the use of vitamin D analogs was independently associated with a lower risk of the primary outcome (crude hazard ratio 0.41; 95 % confidence interval 0.19, 0.89; adjusted hazard ratio 0.38; 95 % confidence interval 0.17, 0.88).

CONCLUSION

The use of vitamin D analogs is independently associated with the preservation of renal function in patients with pre-dialysis CKD stages 4-5.

Systematic and quantitative assessment of the effect of chronic kidney disease on CYP2D6 and CYP3A4/5

Recent reviews suggest that chronic kidney disease (CKD) can affect the pharmacokinetics of nonrenally eliminated drugs, but the impact of CKD on individual elimination pathways has not been systematically evaluated. In this study we developed a comprehensive dataset of the effect of CKD on the pharmacokinetics of CYP2D6‐ and CYP3A4/5‐metabolized drugs. Drugs for evaluation were selected based on clinical drug–drug interaction (CYP3A4/5 and CYP2D6) and pharmacogenetic (CYP2D6) studies. Information from dedicated CKD studies was available for 13 and 18 of the CYP2D6 and CYP3A4/5 model drugs, respectively. Analysis of these data suggested that CYP2D6‐mediated clearance is generally decreased in parallel with the severity of CKD. There was no apparent relationship between the severity of CKD and CYP3A4/5‐mediated clearance. The observed elimination‐route dependency in CKD effects between CYP2D6 and CYP3A4/5 may inform the need to conduct clinical CKD studies with nonrenally eliminated drugs for optimal use of drugs in patients with CKD.

Consequences of renal failure on non-renal clearance of drugs

Kidney disease not only alters the renal elimination but also the non-renal disposition of drugs that are metabolized by the liver. Indeed, modifications in the expression and activity of intestinal and hepatic drug metabolism enzymes and uptake and efflux transporters have been reported. Accumulated uremic toxins, inflammatory cytokines, and parathyroid hormones may modulate these proteins either directly or by inhibiting gene expression. This can lead to important unintended variations in exposure and response when drugs are administered without dose adjustment for reduced renal function. This review summarizes our current understanding of non-renal clearance in circumstances of chronic and acute renal failure with experimental but also clinical studies. It also evaluates the clinical impact on drug disposition. Predicting the extent of the drug disposition modification is difficult first because of the complex interplay between metabolic enzymes and transport proteins but also because of the differential effects in the different organs (liver, intestines). Recommendations of the US FDA are presented as they may be potentially helpful tools to predict these modifications when no specific pharmacokinetic studies are available.