Effect of Curcuma longa on CYP2D6- and CYP3A4-mediated metabolism of dextromethorphan in human liver microsomes and healthy human subjects

Potential Pharmacological Applications of Nigella Seeds with a Focus on Nigella sativa and Its Constituents against Chronic Inflammatory Diseases: Progress and Future Opportunities

The leading cause of death worldwide has been identified as chronic illnesses, according to the World Health Organization (WHO). Chronic inflammatory conditions such as asthma, cancer, diabetes, heart disease, and obesity account for three out of every five deaths. Although many people benefit from using nonsteroidal anti-inflammatory medicines (NSAIDs) for pain and inflammation relief, there are significant adverse effects to using these medications. Medicinal plants possess anti-inflammatory properties with minimal or no side effects. Nigella sativa (NS), also known as black cumin, is one of the plants used in traditional medicine the most. Many studies on the NS have shown that their therapeutic properties are attributed to the seed, oil, and secondary metabolites. This plant has been studied extensively and has many medical uses, such as anti-inflammatory. NS or its phytochemical compounds, such as thymoquinone, can cause cell apoptosis via oxidative stress, block efflux pumps, enhance membrane permeability, and exert potent biocidal effects. Notwithstanding the extensively documented anti-inflammatory effectiveness observed in the experimental model, the precise mechanisms underlying its anti-inflammatory effects in diverse chronic inflammatory diseases and its multi-targeting characteristics remain largely unexplored. This review examines NS or its secondary metabolites, a valuable source for the therapeutic development of chronic inflammatory diseases. Most clinical studies were done for diabetes and cardiovascular disease; therefore, more studies are required to examine the NS extracts and phytoconstituents to treat cancer, obesity, diabetes, asthma, neurological disorders, and COVID-19. This study will be a significant resource for clinicians and biologists seeking a pharmaceutical solution for inflammatory diseases.

Role of Turmeric and Curcumin in Prevention and Treatment of Chronic Diseases: Lessons Learned from Clinical Trials

Turmeric (Curcuma longa) has been used for thousands of years for the prevention and treatment of various chronic diseases. Curcumin is just one of >200 ingredients in turmeric. Almost 7000 scientific papers on turmeric and almost 20,000 on curcumin have been published in PubMed. Scientific reports based on cell culture or animal studies are often not reproducible in humans. Therefore, human clinical trials are the best indicators for the prevention and treatment of a disease using a given agent/drug. Herein, we conducted an extensive literature survey on PubMed and Scopus following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The keywords "turmeric and clinical trials" and "curcumin and clinical trials" were considered for data mining. A total of 148 references were found to be relevant for the key term "turmeric and clinical trials", of which 70 were common in both PubMed and Scopus, 44 were unique to PubMed, and 34 were unique to Scopus. Similarly, for the search term "curcumin and clinical trials", 440 references were found to be relevant, of which 70 were unique to PubMed, 110 were unique to Scopus, and 260 were common to both databases. These studies show that the golden spice has enormous health and medicinal benefits for humans. This Review will extract and summarize the lessons learned about turmeric and curcumin in the prevention and treatment of chronic diseases based on clinical trials.

Curcuminoids for Metabolic Syndrome: Meta-Analysis Evidences Toward Personalized Prevention and Treatment Management

The metabolic syndrome (MS) is a multifactorial syndrome associated with a significant economic burden and healthcare costs. MS management often requires multiple treatments (polydrug) to ameliorate conditions such as diabetes mellitus, insulin resistance, obesity, cardiovascular diseases, hypertension, and non-alcoholic fatty liver disease (NAFLD). However, various therapeutics and possible drug-drug interactions may also increase the risk of MS by altering lipid and glucose metabolism and promoting weight gain. In addition, the medications cause side effects such as nausea, flatulence, bloating, insomnia, restlessness, asthenia, palpitations, cardiac arrhythmias, dizziness, and blurred vision. Therefore, is important to identify and develop new safe and effective agents based on a multi-target approach to treat and manage MS. Natural products, such as curcumin, have multi-modalities to simultaneously target several factors involved in the development of MS. This review discusses the recent preclinical and clinical findings, and up-to-date meta-analysis from Randomized Controlled Trials regarding the effects of curcumin on MS, as well as the metabonomics and a pharma-metabolomics outlook considering curcumin metabolites, the gut microbiome, and environment for a complementary personalized prevention and treatment for MS management.

HDI Highlighter, The First Intelligent Tool to Screen the Literature on Herb-Drug Interactions

Herbal food supplements are commonly used and can be an important part of patient self-care. Like all other bio-active and therapeutic products, they have a benefit/risk balance. These products are not without adverse effects and potentially interact with other therapies. Educating patients and providing information for health professionals about the risk of herb-drug interactions is key. One of the purposes of the biomedical literature is to inform prescribers. Scientific literature accessible on databases such as PubMed is dense and careful reading is time consuming. We propose a reading aid tool named "HDI highlighter" to help readers to find key information in clinical studies and case reports describing herb-drug interactions. It uses natural language processing algorithms (artificial intelligence) with a pharmaceutical focus. Semantic relation extraction for herb-drug interactions from the biomedical literature are overexpressed using keywords. We have tested it to review 120 published articles over the last 10 years. In these articles, we have shown that case reports often involved long-term or semi-long-term treatments such as cancer or human immunodeficiency virus therapies, antiepileptic drugs, or central nervous system drugs. Similarly, these classes of drugs are more extensively targeted by clinical studies. Herb-drug interactions described in case reports are identified in medicinal, recreational, and alimentary uses. They also usually lack a rigorous description of the herb(s) involved. Typically, clinical studies provide a complete description of protocols and dosages, with a few exceptions explained by patients' needs. Clinical studies on herbs are nevertheless conducted on a limited number of patients. All these limitations make the interpretation of herb-drug interactions complicated, but the HDI highlighter provides a quick overview of the herb-drug interaction literature.

Herb-Drug Interaction in Inflammatory Diseases: Review of Phytomedicine and Herbal Supplements

Many people worldwide use plant preparations for medicinal purposes. Even in industrialized regions, such as Europe, where conventional therapies are accessible for the majority of patients, there is a growing interest in and usage of phytomedicine. Plant preparations are not only used as alternative treatment, but also combined with conventional drugs. These combinations deserve careful contemplation, as the complex mixtures of bioactive substances in plants show a potential for interactions. Induction of CYP enzymes and pGP by St John's wort may be the most famous example, but there is much more to consider. In this review, we shed light on what is known about the interactions between botanicals and drugs, in order to make practitioners aware of potential drug-related problems. The main focus of the article is the treatment of inflammatory diseases, accompanied by plant preparations used in Europe. Several of the drugs we discuss here, as basal medication in chronic inflammatory diseases (e.g., methotrexate, janus kinase inhibitors), are also used as oral tumor therapeutics.

Effect of turmeric supplementation on the pharmacokinetics of paclitaxel in breast cancer patients: A study with population pharmacokinetics approach

Turmeric is one of the most used herbal supplements among cancer patients. It reportedly modulates the function of CYP450 enzymes and drug transporters. This study investigates the effect of turmeric on the pharmacokinetics of paclitaxel in breast cancer patients. This is a prospective longitudinal study with 60 breast cancer patients on treatment with single-agent paclitaxel and turmeric. The patients were followed up for two consecutive chemotherapy cycles, and their blood samples were collected, first without turmeric (first cycle) and the next after a 21-day concomitant administration of 2 g/day turmeric (second cycle). Plasma samples were quantified for paclitaxel concentration using High Performance Liquid Chromatograph with UV detector (HPLC-UV) method. The sparse concentration-time data of paclitaxel were subjected to population pharmacokinetic modeling, and then noncompartmental analysis (NCA) was performed on the simulated data to estimate the pharmacokinetic parameters of paclitaxel, before and after turmeric supplementation, for comparisons. The population pharmacokinetic parameters of paclitaxel differed from before to after turmeric supplementation. NCA of simulated concentration-time profiles showed a statistically significant reduction of 7.7% and 12.1% in AUC_inf and Cmax, respectively. Given the small magnitude of the changes in pharmacokinetic parameters, the observed changes are not clinically relevant. Thereby, turmeric at the recommended dose can be combined safely with paclitaxel.

Herb-Drug Interactions: Worlds Intersect with the Patient at the Center

This review examines three bodies of literature related to herb-drug interactions: case reports, clinical studies, evaluations found in six drug interaction checking resources. The aim of the study is to examine the congruity of resources and to assess the degree to which case reports signal for further study. A qualitative review of case reports seeks to determine needs and perspectives of case report authors. Methods: Systematic search of Medline identified clinical studies and case reports of interacting herb-drug combinations. Interacting herb-drug pairs were searched in six drug interaction resources. Case reports were analyzed qualitatively for completeness and to identify underlying themes. Results: Ninety-nine case-report documents detailed 107 cases. Sixty-five clinical studies evaluated 93 mechanisms of interaction relevant to herbs reported in case studies, involving 30 different herbal products; 52.7% of these investigations offered evidence supporting reported reactions. Cohen's kappa found no agreement between any interaction checker and case report corpus. Case reports often lacked full information. Need for further information, attitudes about herbs and herb use, and strategies to reduce risk from interaction were three primary themes in the case report corpus. Conclusions: Reliable herb-drug information is needed, including open and respectful discussion with patients.

OpenCYP: An open source database exploring human variability in activities and frequencies of polymophisms for major cytochrome P-450 isoforms across world populations

The open source database "OpenCYP database" has been developed based on the results of extensive literature searches from the peer-reviewed literature. OpenCYP provides data on human variability on baseline of activities and polymophism frequencies for selected cytochrome P-450 isoforms (CYP1A2, CYP2A6, CYP2D6, CYP3A4/3A5 and CYP3A7) in healthy adult populations from world populations. CYP enzymatic activities were generally expressed as the metabolic ratio (MR) between an unchanged probe drug and its metabolite(s) in urine or plasma measured in healthy adults. Data on other age groups were very limited and fragmented, constituting an important data gap. Quantitative comparisons were often hampered by the different experimental conditions used. However, variability was quite limited for CYP1A2, using caffeine as a probe substrate, with a symmetrical distribution of metabolic activity values. For CYP3A4, human variability was dependent on the probe substrate itself with low variability when data considering the dextromethorphan/demethilathed metabolite MR were used and large variability when the urinary 6β-hydroxycortisol/cortisol ratio was used. The largest variability in CYP activity was shown for CYP2D6 activity, after oral dosing of dextromethorphan, for which genetic polymorphisms are well characterised and constitute a significant source of variability. It is foreseen that the OpenCYP database can contribute to promising tools to support the further development of QIVIVE and PBK models for human risk assessment of chemicals particularly when combined with information on isoform-specific content in cells using proteomic approaches.

Curcuma longa enhances IFN-γ secretion by natural killer cells through cytokines secreted from macrophages

Interferon-γ (IFN-γ) regulates the human immune system. To study the interaction between macrophages and natural killer (NK) cells, we established a THP-1 macrophage-conditioned media. Among the 58 natural plant extracts tested, Curcuma longa exerted the strongest IFN-γ-enhancing effect in NK-92 cells through THP-1 macrophages. C. longa extract (CLE) enhanced IFN-γ secretion 2.3- and 4.2-fold at 50 and 100 µg/ml, respectively. Therefore, we evaluated its IFN-γ-enhancing effect in vitro. Although NK-92 cells did not produce IFN-γ following treatment with C. longa, enhanced IFN-γ secretion was observed after treatment with THP-1 macrophage-conditioned media. We hypothesized that the cytokines secreted by the CLE-treated THP-1 macrophages are responsible for stimulating NK-92 cells. Cytokine array results show upregulation of cytokines, including MIP-1α, CXCL-1, IL-1β, PAI-1, and TNF-α, in CLE-treated THP-1 macrophages. To determine the cytokines responsible for augmenting IFN-γ secretion, NK-92 cells were stimulated with MIP-1α, CXCL-1, IL-1β, or PAI-1. Enzyme-linked immunosorbent assay results show that all cytokines induced IFN-γ production, although the dose response was somewhat varied. High-performance liquid chromatography analysis of CLE revealed the concentrations of three active curcuminoids, curcumin, demethoxycurcumin, and bisdemethoxycurcumin, as 6.70%, 1.00%, and 0.95%, respectively. Their mixture (with concentrations comparable to their occurrence in CLE) exerted an effect similar to that of the whole CLE. Our findings reveal that CLE indirectly stimulated NK-92 cells to secrete IFN-γ, which is mediated by cytokines produced from THP-1 macrophages. Further, we identified three curcuminoids partly responsible for this IFN-γ-enhancing effect. Therefore, C. longa can be used as a functional food ingredient owing to its immune-boosting ability. PRACTICAL APPLICATION: This study demonstrates that CLE stimulates THP-1 macrophages to secrete cytokines, which can in turn stimulate IFN-γ production by NK-92 cells. A mixture of three curcuminoids present in the extract exerted effects similar to whole CLE, demonstrating that the curcuminoids are partly responsible for the IFN-γ-enhancing effect of C. longa. Since IFN-γ is a key regulator of human immune system, these results suggest the potential use of C. longa as an immune-boosting functional food ingredient.

Complementary and alternative medicine (CAM) supplements in cancer outpatients: analyses of usage and of interaction risks with cancer treatment

Purpose

The aim of our study was to analyze the use of complementary and alternative medicine (CAM) supplements, identify possible predictors, and analyze and compile potential interactions of CAM supplements with conventional cancer therapy.

Methods

We included outpatient cancer patients treated at a German university hospital in March or April 2020. Information was obtained from questionnaires and patient records. CAM–drug interactions were identified based on literature research for each active ingredient of the supplements consumed by the patients.

Results

37.4% of a total of 115 patients consumed CAM supplements. Potential interactions with conventional cancer treatment were identified in 51.2% of these patients. All types of CAM supplements were revealed to be a potential source for interactions: vitamins, minerals, food and plant extracts, and other processed CAM substances. Younger age (< 62 years) (p = 0.020, φc = 0.229) and duration of individual cancer history of more than 1 year (p = 0.006, φc = 0.264) were associated with increased likelihood of CAM supplement use. A wide range of different CAM supplement interactions were reviewed: effects of antioxidants, cytochrome (CYP) interactions, and specific agonistic or antagonistic effects with cancer treatment.

Conclusion

The interaction risks of conventional cancer therapy with over-the-counter CAM supplements seem to be underestimated. Supplements without medical indication, as well as overdoses, should be avoided, especially in cancer patients. To increase patient safety, physicians should address the risks of interactions in physician–patient communication, document the use of CAM supplements in patient records, and check for interactions.

Potential Cytochrome P450-mediated pharmacokinetic interactions between herbs, food, and dietary supplements and cancer treatments

Herbs, food and dietary supplements (HFDS), can interact significantly with anticancer drug treatments via cytochrome p450 isoforms (CYP) CYP3A4, CYP2D6, CYP1A2, and CYP2C8. The objective of this review was to assess the influence of HFDS compounds on these cytochromes. Interactions with CYP activities were searched for 189 herbs and food products, 72 dietary supplements in Web of Knowledge® databases. Analyses were made from 140 of 3,125 clinical trials and 236 of 3,374 in vitro, animal model studies or case reports. 18 trials were found to report direct interactions between 9 HFDS with 8 anticancer drugs. 21 HFDS were found to interact with CYP3A4, a major metabolic pathway for many anticancer drugs. All 261 HFDS were classified for their interaction with the main cytochromes P450 involved in the metabolism of anticancer drugs. We provided an easy-to-use colour-coded table to easily match potential interactions between 261 HFDS and 117 anticancer drugs.

Inhibitory Effects of Schisandra Lignans on Cytochrome P450s and Uridine 5'-Diphospho-Glucuronosyl Transferases in Human Liver Microsomes

Schisandra chinensis has been widely used as a traditional herbal medicine to treat chronic coughs, fatigue, night sweats, and insomnia. Numerous bioactive components including lignans have been identified in this plant. Lignans with a dibenzocyclooctadiene moiety have been known to possess anti-cancer, anti-inflammatory, and hepatoprotective activity. Fragmentary studies have reported the ability of some lignans to modulate some cytochrome P450 (P450) enzymes. Herein, we investigated the drug interaction potential of six dibenzocyclooctadiene lignans (schisandrin, gomisin A, B, C, and N, and wuweizisu C) on nine P450 enzymes (CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A) and six uridine 5'-diphosphoglucuronosyl transferase (UGT) enzymes (UGT1A1, 1A3, 1A4, 1A6, 1A9, and 2B7) using human liver microsomes. We found that lignans with one or two methylenedioxyphenyl groups inhibited CYP2B6, CYP2C8, CYP2C9, CYP2C19, and CYP2E1 activities in a time- and concentration-dependent like their CYP3A inhibition. In comparison, these lignans do not induce time-dependent inhibition of CYP1A2, CYP2A6, and CYP2D6. The time-dependent inhibition of gomisin A against CYP2C8, CYP2C19, and CYP3A4 was also elucidated using glutathione as a trapping reagent of reactive carbene metabolites given that gomisin A strongly inhibits these P450 enzymes in a time-dependent manner. A glutathione conjugate of gomisin A was generated in reactions with human recombinant CYP2C8, CYP2C19, and CYP3A4. This suggests that the time-dependent inhibition of gomisin A against CYP2C8, CYP2C9, and CYP3A4 is due to the production of carbene reactive metabolite. Six of the lignans we tested inhibited the activities of six UGT to a limited extent (IC₅₀ > 15 μM). This information may aid the prediction of possible drug interactions between Schisandra lignans and any co-administered drugs which are mainly metabolized by P450s.

Involvement of GABAergic and nitrergic systems in the anxiolytic and hypnotic effects of Curcuma longa: its interaction with anxiolytic-hypnotics

OBJECTIVES

Concurrent use of herbs with drugs have become a major healthcare problem. Herb-drug interactions could lead to therapeutic failure or toxicity. Hence, this study seeks to evaluate the impact of combining Curcuma longa rhizome (CL) with selected anxiolytic and hypnotic drugs.

METHODS

CL (100, 200 or 400 mg/kg, p.o.) was administered to mice 1 h before subjecting the animals to elevated plus maze (EPM), hole board test (HBT), open field test (OFT) and rotarod test for anxiolytic-like effect as well as hexobarbitone-induced sleeping time (HIST) for hypnotic activity. The involvement of GABAergic and nitrergic systems in CL-induced anxiolytic and hypnotic actions were also evaluated. The effect of concurrent use of CL with midazolam, imipramine, nifedipine, propranolol and carbamazepine were evaluated in anxiolytic-hypnosis models.

RESULTS

The peak anxiolytic-like effect of CL was obtained at 400 mg/kg in the EPM and hole-board test without affecting muscle coordination in the rotarod test while the peak hypnosis-potentiation was observed at 100 mg/kg. CL-induced anxiolytic-hypnotic-like effects were reversed by the pretreatment of mice with flumazenil or NG-nitro-l-arginine.

CONCLUSIONS

Curcuma longa possesses anxiolytic and hypnotic effects through its interaction with GABAergic and nitrergic systems. Conversely, co-administration of C. longa with midazolam potentiate barbiturate-induced hypnosis.

Practical Application of "About Herbs" Website: Herbs and Dietary Supplement Use in Oncology Settings

The Integrative Medicine Service at Memorial Sloan Kettering Cancer Center developed and maintains About Herbs (www.aboutherbs.com), which provides summaries of research data including purported uses, adverse effects, and herb-drug interactions for about 284 dietary supplements. Using Google Analytics, we found the website registered more than 26,317,000 hits since November 2002. The 10 most searched-for herbs/supplements of 2018 are chaga mushroom, turmeric, ashwagandha, reishi mushroom, graviola, Active Hexose-Correlated Compound, boswellia, dandelion, green tea, and Coriolus versicolor. Here we discuss their safety, herb-drug interactions, and appropriate uses in the oncology setting, based on literature searches in PubMed. Over the past 16 years, the evidence for use of these supplements is based mostly on preclinical findings, with few well-designed studies and limited trials conducted in cancer patients. It is important to familiarize health care professionals about popular supplements, so patients can be informed to make decisions that maximize benefits and minimize risks.

Interactions between antiretroviral therapy and complementary and alternative medicine: a narrative review

BACKGROUND

The use of complementary and alternative medicine including herbal medicine (phytotherapy), vitamins, minerals and food supplements is frequent among people living with HIV/AIDS (PLWHAs) who take antiretroviral (ARV) drugs, but is often not known by their prescribing physicians. Some drug-supplement combinations may result in clinically meaningful interactions.

AIMS

In this literature review, we aimed to investigate the evidence for complementary and alternative medicine interactions with ARVs.

SOURCES

A bibliographic search of all in vitro, human studies and case reports of the PubMed database was performed to assess the risk of interactions between complementary and alternative self-medication products and ARVs. The 'HIV drug interaction' (https://www.hiv-druginteractions.org) and 'Natural medicines comprehensive database' (https://naturalmedicines.therapeuticresearch.com) interaction checkers were also analysed.

CONTENT

St John's wort, some forms of garlic, grapefruit and red rice yeast are known to have significant interaction and thus should not be co-administered, or should be used with caution with certain ARV classes. Data on other plant-based supplements come from in vitro studies or very small size in vivo studies and are thus insufficient to conclude the real in vivo impact in case of concomitant administration with ARVs. Some polyvalent minerals such as calcium, magnesium, and iron salts can reduce the absorption of integrase inhibitors by chelation. Potential interactions with vitamin C and quercetin with some ARVs should be noted and efficacy and tolerance of the treatment should be monitored.

IMPLICATIONS

This review shows the importance of screening all PLWHAs for complementary and alternative medicine use to prevent treatment failure or adverse effects related to an interaction with ARVs. Further human studies are warranted to describe the clinical significance of in vitro interactions between numerous complementary and alternative medicine and ARVs.

Hepatotoxicity induced by paclitaxel interaction with turmeric in association with a microcystin from a contaminated dietary supplement

A 67-year-old Caucasian male with lung cancer was presented to the Emergency Department with asthenia, anorexia, jaundice and choluria. The patient's lung cancer was being treated medically by a combination of paclitaxel/carboplatin with bi-monthly frequency. The patient was also self-medicating with several natural products, including Chlorella (520 mg/day), Silybum marianum (total of 13.5 mg silymarin/day), zinc sulphate (5.5 mg), selenium (50 μg) and 15 g/day of Curcuma longa. In first chemotherapy cycle no toxicity was observed even he was taking other medications as budesonide and sitagliptin. The toxic events started only after the introduction of the dietary products. Chlorella had contamination with cyanobacteria (Oscillatoriales) and 1.08 μg of cyanotoxin Microcystin-LR (MC-LR) per gram of biomass was found. Patient was consuming ca 0.01 μg MC-LR/kg/day. This case report describes the first known case of paclitaxel toxicity probably related to pharmacokinetic interaction with Turmeric and a contaminated Chlorella supplement resulting in an acute toxic hepatitis and the impact on oncologic patient health.

Curcumin as a clinically-promising anti-cancer agent: pharmacokinetics and drug interactions

INTRODUCTION

Curcumin has been extensively studied for its anti-cancer properties. While a diverse array of in vitro and preclinical research support the prospect of curcumin use as an anti-cancer therapeutic, most human studies have failed to meet the intended clinical expectation. Poor systemic availability of orally-administered curcumin may account for this disparity. Areas covered: This descriptive review aims to concisely summarise available clinical studies investigating curcumin pharmacokinetics when administered in different formulations. A critical analysis of pharmacokinetic- and pharmacodynamic-based interactions of curcumin with concomitantly administered drugs is also provided. Expert opinion: The encouraging clinical results of curcumin administration are currently limited to people with colorectal cancer, given that sufficient curcumin concentrations persist in colonic mucosa. Higher parent curcumin systemic exposure, which can be achieved by several newer formulations, has important implications for optimal treatment of cancers other than those in gastrointestinal tract. Curcumin-drug pharmacokinetic interactions are also almost exclusively in the enterocytes, owing to extensive first pass metabolism and poor curcumin bioavailability. Greater scope of these interactions, i.e. modulation of the systemic elimination of co-administered drugs, may be expected from more-bioavailable curcumin formulations. Further studies are still warranted, especially with newer formulations to support the inclusion of curcumin in cancer therapy regimens.

miRNA-27b levels are associated with CYP3A activity in vitro and in vivo

Previous in vitro studies have shown that microRNA‐27b (miR‐27b) may regulate mRNA levels of CYP3A4, vitamin D receptor (VDR), and Peroxisome proliferator‐activated receptor α (PPARα) as well as CYP3A4 protein expression and activity. In vitro studies have also shown that vitamin D may affect the expression of CYP3A4. The primary aim of this pilot study was to investigate the association between miR‐27b and CYP3A expression and activity. The secondary aim was to investigate the association between 25‐hydroxy vitamin D in serum and CYP3A activity. Mi‐RNA‐27b was quantified using real‐time PCR in serum samples (n = 28) and 25‐hydroxyvitamin D was measured and correlated with the levels of the endogenous CYP3A activity marker 4β‐hydroxycholesterol. In addition, the correlation between miR‐27b and CYP3A activity, measured by dextromethorphan N‐demethylation and 6β‐hydroxylation of testosterone and the gene expression of CYP3A4, VDR and PPARα were assessed in 20 human liver samples. A significant association between circulatory miR‐27b levels and 4β‐hydroxycholesterol ratio was found; P = 0.04, and between hepatic miR‐27b levels and CYP3A activity, measured by dextromethorphan N‐demethylation in human liver (P = 0.04). There was no association between hepatic miR‐27b and mRNA levels of CYP3A4, VDR or PPARα. There was a significant association between serum 25‐hydroxyvitamin D levels and 4β‐hydroxycholesterol ratio, P = 0.002. In conclusion, this pilot‐study supports the hypothesis that miR‐27b levels as well as 25‐hydroxyvitamin D may affect CYP3A activity in vivo. The results indicate that miR‐27b exerts its inhibitory effect on a translational level rather than affecting mRNA levels.