Liver X Receptor Agonist 4ß-Hydroxycholesterol as a Prognostic Factor in Coronary Artery Disease.

BACKGROUND: Regardless of progress in treatment of coronary artery disease (CAD), there is still a significant residual risk of death in patients with CAD, highlighting the need for additional risk stratification markers. Our previous study provided evidence for a novel blood pressure-regulating mechanism involving 4ß-hydroxycholesterol (4ßHC), an agonist for liver X receptors, as a hypotensive factor. The aim was to determine the role of 4ßHC as a prognostic factor in CAD. METHODS AND RESULTS: The ARTEMIS (Innovation to Reduce Cardiovascular Complications of Diabetes at the Intersection) cohort consists of 1946 patients with CAD. Men and women were analyzed separately in quartiles according to plasma 4ßHC. Basic characteristics, medications, ECG, and echocardiography parameters as well as mortality rate were analyzed. At baseline, subjects with a beneficial cardiovascular profile, as assessed with traditional markers such as body mass index, exercise capacity, prevalence of diabetes, and use of antihypertensives, had the highest plasma 4ßHC concentrations. However, in men, high plasma 4ßHC was associated with all-cause death, cardiac death, and especially sudden cardiac death (SCD) in a median follow-up of 8.8 years. Univariate and comprehensively adjusted hazard ratios for SCD in the highest quartile were 3.76 (95% CI, 1.6-8.7; P=0.002) and 4.18 (95% CI, 1.5-11.4; P=0.005), respectively. In contrast, the association of cardiac death and SCD in women showed the lowest risk in the highest 4ßHC quartile. CONCLUSIONS: High plasma 4ßHC concentration was associated with death and especially SCD in men, while an inverse association was detected in women. Our results suggest 4ßHC as a novel sex-specific risk marker of cardiac death and especially SCD in chronic CAD. REGISTRATION INFORMATION: clinicaltrials.gov. Identifier NCT01426685.

Short-Term Metabolic Changes and Their Physiological Mediators in the Roux-en-Y Gastric Bypass Bariatric Surgery.

BACKGROUND: The Roux-en-Y gastric bypass (RYGB) is a common bariatric surgery to treat obesity. Its metabolic consequences are favourable and long-term clinical corollaries beneficial. However, detailed assessments of various affected metabolic pathways and their mediating physiological factors are scarce. METHODS: We performed a clinical study with 30 RYGB patients in preoperative and 6-month postoperative visits. NMR metabolomics was applied to profiling of systemic metabolism via 80 molecular traits, representing core cardiometabolic pathways. Glucose, glycated haemoglobin (HbA1c), insulin, and apolipoprotein B-48 were measured with standard assays. Logistic regression models of the surgery effect were used for each metabolic measure and assessed individually for multiple mediating physiological factors. RESULTS: Changes in insulin concentrations reflected those of BMI with robust decreases due to the surgery. Six months after the surgery, triglycerides, remnant cholesterol, and apolipoprotein B-100 were decreased -24%, -18%, and -14%, respectively. Lactate and glycoprotein acetyls, a systemic inflammation biomarker, decreased -16% and -9%, respectively. The concentrations of branched-chain (BCAA; leucine, isoleucine, and valine) and aromatic (phenylalanine and tyrosine) amino acids decreased after the surgery between -17% for tyrosine and -23% for leucine. Except for the most prominent metabolic changes observed for the BCAAs, all changes were almost completely mediated by weight change and insulin. Glucose and type 2 diabetes had clearly weaker effects on the metabolic changes. CONCLUSIONS: The comprehensive metabolic analyses indicate that weight loss and improved insulin sensitivity during the 6 months after the RYGB surgery are the key physiological outcomes mediating the short-term advantageous metabolic effects of RYGB. The clinical study was registered at ClinicalTrials.gov as NCT01330251.

Mobile health behaviour change support system as independent treatment tool for obesity: a randomized controlled trial.

BACKGROUND/OBJECTIVES: Digital health interventions are increasingly utilized as an adjunct to face-to-face counselling in the treatment of obesity. However, previous studies have shown inconsistent efficacy when digital interventions are used as stand-alone treatment. The purpose of this study was to investigate whether a mobile health behaviour change support system (mHBCSS) is effective in weight reduction and weight loss maintenance without additional counselling. Furthermore, changes in cardiometabolic risk factors were investigated. METHODS: In this randomized controlled trial, a mHBCSS intervention was conducted for 200 volunteers with obesity (BMI 30-40 kg/m² and age 18-65 years). The study participants were randomly assigned into two groups: immediate access to mHBCSS intervention or wait-list control with access to mHBCSS after 6 months. Anthropometric and metabolic traits were also measured. The primary outcome was weight loss from the baseline to the 6-month visit. RESULTS: Among 200 participants (88.5% women), mean BMI (SD) was 34.3 kg/m² (2.8) and age 46.5 years (9.5). The retention rate was 98.5% and 89.0% at the 6- and 12-month visits, respectively. At the 6-month visit, those with immediate access to mHBCSS had significantly greater weight loss (-2.5%, 95% CI -3.4 to -1.6, p < 0.001) compared with the wait-list control group (0.2%, 95% CI -0.4 to 0.9, p = 0.466; between groups p < 0.001). Weight loss was maintained until the 12-month time point in the mHBCSS group (-2.1%, 95% CI -3.3 to -0.9, p = 0.001). The usage of mHBCSS had no significant effect on metabolic traits. CONCLUSION: The mHBCSS as a stand-alone treatment of obesity results in weight reduction and weight loss maintenance with remarkable adherence rate. Further studies are needed to establish how to best implement the scalable and resource-efficient mHBCSS into the standard care of obesity to achieve optimal weight loss results.

Impact of RYGB surgery on plasma immunoglobulins: association between blood pressure and glucose levels six months after surgery.

We aimed to study levels of natural antibodies in plasma, and their associations to clinical and fecal biomarkers, before and 6 months after Roux-en-Y gastric bypass (RYGB) surgery. Thirty individuals with obesity [16 type 2 diabetic, 14 non-diabetic (ND)] had RYGB surgery. Total plasma IgA, IgG and IgM antibody levels and specific antibodies to oxidized low-density lipoprotein (oxLDL), malondialdehyde-acetaldehyde adducts, Porphyromonas gingivalis gingipain A hemagglutinin domain (Rgp44), and phosphocholine were measured using chemiluminescence immunoassay. Associations between plasma and fecal antibodies as well as clinical markers were analyzed. RYGB surgery reduced blood pressure, and the glycemic state was improved. A higher level of diastolic blood pressure was associated with lower plasma antibodies to oxLDL after surgery. Also, lower level of glucose markers associated with lower level of plasma antibodies to bacterial virulence factors. Antibodies to oxLDL decreased after surgery, and positive association between active serum lipopolysaccharide and specific oxLDL antibodies was detected. Total IgG levels decreased after surgery, but only in ND individuals. Reduced level of total plasma IgG, improved state of hypertension and hyperglycemia and their associations with decreased levels of specific antibodies in plasma, suggest an improved state of systemic inflammation after RYGB surgery.

Low eating self-efficacy is associated with unfavorable eating behavior tendencies among individuals with overweight and obesity.

Success in long-term weight management depends partly on psychological and behavioral aspects. Understanding the links between psychological factors and eating behavior tendencies is needed to develop more effective weight management methods. This population-based cross-sectional study examined whether eating self-efficacy (ESE) is associated with cognitive restraint (CR), uncontrolled eating (UE), emotional eating (EE), and binge eating (BE). The hypothesis was that individuals with low ESE have more unfavorable eating behavior tendencies than individuals with high ESE. Participants were classified as low ESE and high ESE by the Weight-Related Self-Efficacy questionnaire (WEL) median cut-off point. Eating behavior tendencies were assessed with Three Factor Eating Questionnaire R-18 and Binge Eating Scale, and additionally, by the number of difficulties in weight management. The difficulties were low CR, high UE, high EE, and moderate or severe BE. Five hundred and thirty-two volunteers with overweight and obesity were included in the study. Participants with low ESE had lower CR (p < 0.03) and higher UE, EE, and BE (p < 0.001) than participants with high ESE. Thirty-nine percent of men with low ESE had at least two difficulties in successful weight control while this percentage was only 8% in men with high ESE. In women, the corresponding figures were 56% and 10%. The risk of low ESE was increased by high UE [OR 5.37 (95% CI 1.99-14.51)], high EE [OR 6.05 (95% CI 2.07-17.66)], or moderate or severe BE [OR 12.31 (95% CI 1.52-99.84)] in men, and by low CR [OR 5.19 (95% CI 2.22-12.18)], high UE [OR 7.20 (95% CI 2.41-19.22)], or high EE [OR 23.66 (95% CI 4.79-116.77)] in women. Low ESE was associated with unfavorable eating behavior tendencies and multiple concomitant difficulties in successful weight loss promotion. These eating behavior tendencies should be considered when counseling patients with overweight and obesity.

Pregnane X receptor gene variant rs7643645 and total mortality in subjects with nonalcoholic fatty liver disease.

Pregnane X receptor (PXR) gene variants rs7643645 and rs2461823 are reported to associate with clinically and histologically more severe liver injury in nonalcoholic fatty liver disease (NAFLD). It is known that the more progressive the NAFLD, the higher the hepatic and extra-hepatic mortality and morbidity. Thus, we investigated the total mortality in Finnish middle-aged ultrasonographically verified NAFLD patients with PXR rs7643645 AA/AG ( n = 217) or GG ( n = 27) variants and rs2461823 CC/CT ( n = 215) or TT ( n = 27) variants. In up to 30 years of follow-up, PXR rs7643645 GG subjects were at an increased risk of total mortality compared with AA/AG subjects, 1.676 (1.014-2.772), P = 0.044. The statistically significant difference prevailed after multiple adjustments for potentially confounding factors, RR, 2.024 (1.191-3.440), P = 0.009. In the subjects without NAFLD ( n = 731), the mortality risk was not associated with rs7643645 variants, 1.051 (0.708-1.560; P = 0.804). There was no difference in the total mortality between the PXR rs2461823 variant subgroups, 1.141 (0.663-1.962; P = 0.634). As the rs7643645 G variant disrupts a putative hepatocyte nuclear factor 4α binding site located in the PXR gene promoter and is associated with lower hepatic expression of PXR and its target genes, our result suggests that genetic disruption of xenobiotic metabolism increases mortality in subjects with NAFLD. Further studies are needed to confirm the results of the present study.

Effects of rifampicin on porphyrin metabolism in healthy volunteers.

Pregnane X receptor (PXR) is known to stimulate haem synthesis, but detailed knowledge on the effects of PXR activation on porphyrin metabolism in humans is lacking. We utilized a randomized, crossover, open (blinded laboratory) and placebo-controlled trial with 600-mg rifampicin or placebo dosed for a week to investigate the effects of PXR activation on erythrocyte, plasma, faecal and urine porphyrins. Sixteen healthy volunteers participated on the trial, but the number of volunteers for blood and urine porphyrin analyses was 15 while the number of samples for faecal analyses was 14. Rifampicin increased urine pentaporphyrin concentration 3.7-fold (mean 1.80 ± 0.6 vs. 6.73 ± 4.4 nmol/L, p = 0.003) in comparison with placebo. Urine coproporphyrin I increased 23% (p = 0.036). Faecal protoporphyrin IX decreased (mean 31.6 ± 23.5 vs. 19.2 ± 27.8 nmol/g, p = 0.023). The number of blood erythrocytes was slightly elevated, and plasma bilirubin, catabolic metabolite of haem, was decreased. In conclusion, rifampicin dosing elevated the excretion of certain urinary porphyrin metabolites and decreased faecal protoporphyrin IX excretion. As urine pentaporphyrin and coproporphyrin I are not precursors in haem biosynthesis, increased excretion may serve as a hepatoprotective shunt when haem synthesis or porphyrin levels are increased.

Total fecal IgA levels increase and natural IgM antibodies decrease after gastric bypass surgery.

Obesity is associated with low-grade inflammation and increased systemic oxidative stress. Roux-en-Y gastric bypass (RYGB) surgery is known to ameliorate the obesity-induced metabolic dysfunctions. We aimed to study the levels of natural antibodies in feces, before and 6 months after RYGB surgery in obese individuals with and without type 2 diabetes (T2D). Sixteen individuals with T2D and 14 non-diabetic (ND) individuals were operated. Total IgA, IgG and IgM antibody levels and specific antibodies to oxidized low-density lipoprotein (oxLDL), malondialdehyde-acetaldehyde adducts (MAA adducts), Porphyromonas gingivalis gingipain A hemagglutinin domain (Rgp44) and phosphocholine (PCho) were measured using chemiluminescence immunoassay. Total fecal IgA was elevated, while total IgM and IgG were not affected by the surgery. Fecal natural IgM specific to oxLDL decreased significantly in both T2D and ND individuals, while fecal IgM to Rgp44 and PCho decreased significantly in T2D individuals. A decrease in IgG to MAA-LDL, Rgp44 and PCho was detected. RYGB surgery increases the levels of total fecal IgA and decreases fecal natural IgG and IgM antibodies specific to oxLDL. Natural antibodies and IgA are important in maintaining the normal gut homeostasis and first-line defense against microbes, and their production is markedly altered with RYGB surgery.

Long-term metabolic fate and mortality in obesity without metabolic syndrome.

BACKGROUND: Obesity and metabolic syndrome (MetS) are known to expose to atrial fibrillation (AF), cardiovascular diseases (CVD) and mortality. Metabolically healthy obesity refers to obesity without MetS. This study aimed to investigate how obesity and MetS modify the risk of CVD, AF and mortality in very long-time follow-up. METHODS: Finnish middle-aged subjects (n = 1045) were grouped into four subgroups according to the presence of obesity and MetS. CVD events and AF were followed for 24 years and total mortality for 30 years. Moreover, 600 available patients had a follow-up visit for metabolic examinations after approximately 22 years. RESULTS: One-hundred and sixty-two (30%) subjects without obesity or MetS died during the follow-up. Ninety-two (17%) of the patients in this group had a CVD event and 58 (11%) were diagnosed with AF. As compared to them, obese subjects without MetS had similar metabolic fate and mortality (mortality 26 (38%), p = .143; CVD event 12 (18%), p = .858 and AF 7 (10%), p = .912, respectively), whereas subjects with obesity and MetS had greater mortality (102 (49%), p < .001), more CVD (71 (34%), p < .001) and AF (49 (23%), p < .001). Non-obese individuals with MetS had greater rates of mortality (96 (44%), p < .001) and CVD (80 (37%), p < .001), but not of AF (26 (12%), p = .606). Of the 40 subjects with obesity but without MetS at baseline and available for the follow-up visit, 15 (38%) were metabolically healthy at the follow-up visit. CONCLUSIONS: In the present long-term follow-up study, the presence of MetS, but not obesity only, implies a greater risk of mortality and CVD. The risk of AF is increased only in subjects with both obesity and MetS. However, obesity without MetS tends to progress eventually to obesity with MetS. Key messagesThe presence of metabolic syndrome (MetS), but not obesity only, entails a greater risk of mortality and cardiovascular diseases.The risk of atrial fibrillation is increased only in subjects with both obesity and MetS.Obesity without MetS tends to progress eventually to obesity with MetS.

Pregnane X Receptor‒4ß-Hydroxycholesterol Axis in the Regulation of Overweight- and Obesity-Induced Hypertension.

Background Mechanisms mediating hypertensive effects of overweight and obesity have not been fully elucidated. We showed previously that activation of pregnane X receptor (PXR) by rifampicin elevates 24-hour blood pressure (BP) and plasma 4ß-hydroxycholesterol (4ßHC), agonist for liver X receptor (LXR). Methods and Results In combined "PXR activation data set" (n=62) of 4 clinical trials, 1 week rifampicin dosing increased office systolic BP (SBP) by 3.1 mm Hg, DBP 1.8 mm Hg, and mean arterial pressure 2.2 mm Hg in comparison with placebo (P<0.01). Plasma 4ßHC had negative correlation with SBP both in rifampicin (r=-0.46, P=0.0002) and placebo (r=-0.45, P=0.0003) arms, although 4ßHC was elevated >3-fold by rifampicin. In "non-intervention data set" (n=102) of patients with obesity and healthy volunteers (body mass index, 19.2-55.2 kg/m2), 4ßHC had negative correlations (P<0.00001) with office SBP (r=-0.51), diastolic BP (r=-0.50), and mean arterial pressure (r=-0.54). Lean women had higher 4ßHC than men, with increasing weight repressing 4ßHC (r=-0.62, P<0.00001) in both sexes. In multiple linear regression analysis, the only statistically significant predictor for SBP was 4ßHC. Six-day PXR agonist dosing elevated SBP in rats (n=7-8/group). PXR activation elevated 4ßHC and after PXR agonist was withdrawn and elevated 4ßHC was left to act alone, SBP was reduced on days 7 to 14 in comparison with control rats. Conclusions PXR activation elevates SBP. Elevated circulating 4ßHC lowers SBP in rats, and higher 4ßHC is an independent predictor of lower SBP in humans. PXR-4ßHC-LXR is novel BP-regulating pathway deregulated in overweight and obesity by repressed 4ßHC, with implications for sex-specific BP regulation. Registration URL: https://www.clinicaltrials.gov; Unique identifiers: NCT00985270, NCT01293422, NCT01690104, NCT02329405, and NCT01330251.

Nuclear Receptor PXR in Drug-Induced Hypercholesterolemia.

Atherosclerosis is a major global health concern. The central modifiable risk factors and causative agents of the disease are high total and low-density lipoprotein (LDL) cholesterol. To reduce morbidity and mortality, a thorough understanding of the factors that influence an individual's cholesterol status during the decades when the arteria-narrowing arteriosclerotic plaques are forming is critical. Several drugs are known to increase cholesterol levels; however, the mechanisms are poorly understood. Activation of pregnane X receptor (PXR), the major regulator of drug metabolism and molecular mediator of clinically significant drug-drug interactions, has been shown to induce hypercholesterolemia. As a major sensor of the chemical environment, PXR may in part mediate hypercholesterolemic effects of drug treatment. This review compiles the current knowledge of PXR in cholesterol homeostasis and discusses the role of PXR in drug-induced hypercholesterolemia.

Analysis of the SYSDIET Healthy Nordic Diet randomized trial based on metabolic profiling reveal beneficial effects on glucose metabolism and blood lipids.

BACKGROUND & AIMS: Intake assessment in multicenter trials is challenging, yet important for accurate outcome evaluation. The present study aimed to characterize a multicenter randomized controlled trial with a healthy Nordic diet (HND) compared to a Control diet (CD) by plasma and urine metabolic profiles and to associate them with cardiometabolic markers. METHODS: During 18-24 weeks of intervention, 200 participants with metabolic syndrome were advised at six centres to eat either HND (e.g. whole-grain products, berries, rapeseed oil, fish and low-fat dairy) or CD while being weight stable. Of these 166/159 completers delivered blood/urine samples. Metabolic profiles of fasting plasma and 24 h pooled urine were analysed to identify characteristic diet-related patterns. Principal components analysis (PCA) scores (i.e. PC1 and PC2 scores) were used to test their combined effect on blood glucose response (primary endpoint), serum lipoproteins, triglycerides, and inflammatory markers. RESULTS: The profiles distinguished HND and CD with AUC of 0.96 ± 0.03 and 0.93 ± 0.02 for plasma and urine, respectively, with limited heterogeneity between centers, reflecting markers of key foods. Markers of fish, whole grain and polyunsaturated lipids characterized HND, while CD was reflected by lipids containing palmitoleic acid. The PC1 scores of plasma metabolites characterizing the intervention is associated with HDL (ß = 0.05; 95% CI: 0.02, 0.08; P = 0.001) and triglycerides (ß = -0.06; 95% CI: -0.09, -0.03; P < 0.001). PC2 scores were related with glucose metabolism (2 h Glucose, ß = 0.1; 95% CI: 0.05, 0.15; P < 0.001), LDL (ß = 0.06; 95% CI: 0.01, 0.1; P = 0.02) and triglycerides (ß = 0.11; 95% CI: 0.06, 0.15; P < 0.001). For urine, the scores were related with LDL cholesterol. CONCLUSIONS: Plasma and urine metabolite profiles from SYSDIET reflected good compliance with dietary recommendations across the region. The scores of metabolites characterizing the diets associated with outcomes related with cardio-metabolic risk. Our analysis therefore offers a novel way to approach a per protocol analysis with a balanced compliance assessment in larger multicentre dietary trials. The study was registered at clinicaltrials.gov with NCT00992641.

Rifampicin induces the bone form of alkaline phosphatase in humans.

Pregnane X receptor (PXR) is a xenobiotic-sensing nuclear receptor that regulates drug metabolism in the liver and intestine. In our clinical trials on healthy volunteers to discover novel metabolic functions of PXR activation, we observed that rifampicin, a well-established ligand for human PXR, 600 mg daily for a week, increased the plasma alkaline phosphatase (ALP) significantly compared with the placebo. Further analysis with lectin affinity electrophoresis revealed that especially the bone form of ALP was elevated. To investigate the mechanism(s) of bone ALP induction, we employed osteoblast lineage differentiated from human primary bone marrow-derived mesenchymal stromal cells. Rifampicin treatment increased ALP activity and mRNA level of bone biomarker genes (ALP, MGP, OPN and OPG). PXR expression was detected in the cells, but the expression was very low compared with the human liver. To further investigate the potential role of PXR in the ALP induction, we treated mice and rats with a rodent PXR ligand pregnenolone 16α-carbonitrile (PCN). However, PCN treatment did not increase plasma ALP activity or bone ALP mRNA expression. In conclusion, rifampicin treatment induces the bone form of ALP in the serum of healthy human volunteers. Further studies are required to establish the mechanism of this novel finding.

Serological Biomarker Panel in Diagnosis of Atrophic Gastritis and Helicobacter pylori Infection in Gastroscopy Referral Patients: Clinical Validation of the New-Generation GastroPanel® Test.

BACKGROUND/AIM: Prompted by the increasing demand of non-invasive diagnostic tools for screening of gastric cancer (GC) risk conditions, i.e., atrophic gastritis (AG) and Helicobacter pylori (Hp) infection, the GastroPanel® test (GP: biomarker panel of PGI, PGII, G-17, Hp IgG ELISA) that was developed in the early 2000's, was recently updated to a new-generation (unified GP) test version. This clinical validation study evaluated the diagnostic accuracy of the new-generation GP test in detection of AG and Hp among gastroscopy referral patients in a University Clinic. PATIENTS AND METHODS: Altogether, 522 patients were enrolled among the patients referred for gastroscopy at the Gastro Center, Oulu University Hospital (OUH). All patients underwent gastroscopy with biopsies classified using the Updated Sydney System (USS), and blood sampling for GP testing. RESULTS: Biopsy-confirmed AG was found in 10.2% (53/511) of the patients. The overall agreement between the GP and the USS classification was 92.4% (95%CI=90.0-94.6%), with the weighted kappa (κw) of 0.861 (95%CI=0.834-0.883). In ROC analysis using moderate/severe AG of the corpus (AGC2+) as the endpoint, AUC=0.952 (95%CI=0.891-1.000) and AUC=0.998 (95%CI=0.996-1.000) for PGI and PGI/PGII, respectively. Hp IgG antibody ELISA detected biopsy-confirmed Hp-infection with AUC=0.993 (95%CI=0.987-0.999). CONCLUSION: The new generation GastroPanel® is a precise test for non-invasive diagnosis of atrophic gastritis and Hp-infection in dyspeptic patients referred for diagnostic gastroscopy.

Activation of pregnane X receptor induces atherogenic lipids and PCSK9 by a SREBP2-mediated mechanism.

BACKGROUND AND PURPOSE: Many drugs and environmental contaminants induce hypercholesterolemia and promote the risk of atherosclerotic cardiovascular disease. We tested the hypothesis that pregnane X receptor (PXR), a xenobiotic-sensing nuclear receptor, regulates the level of circulating atherogenic lipids in humans and utilized mouse experiments to identify the mechanisms involved. EXPERIMENTAL APPROACH: We performed serum NMR metabolomics in healthy volunteers administered rifampicin, a prototypical human PXR ligand or placebo in a crossover setting. We used high-fat diet fed wild-type and PXR knockout mice to investigate the mechanisms mediating the PXR-induced alterations in cholesterol homeostasis. KEY RESULTS: Activation of PXR induced cholesterogenesis both in pre-clinical and clinical settings. In human volunteers, rifampicin increased intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and total cholesterol and lathosterol-cholesterol ratio, a marker of cholesterol synthesis, suggesting increased cholesterol synthesis. Experiments in mice indicated that PXR activation causes widespread induction of the cholesterol synthesis genes including the rate-limiting Hmgcr and upregulates the intermediates in the Kandutsch-Russell cholesterol synthesis pathway in the liver. Additionally, PXR activation induced plasma proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of hepatic LDL uptake, in both mice and humans. We propose that these effects were mediated through increased proteolytic activation of sterol regulatory element-binding protein 2 (SREBP2) in response to PXR activation. CONCLUSION AND IMPLICATIONS: PXR activation induces cholesterol synthesis, elevating LDL and total cholesterol in humans. The PXR-SREBP2 pathway is a novel regulator of the cholesterol and PCSK9 synthesis and a molecular mechanism for drug- and chemical-induced hypercholesterolemia.

Gastrointestinal manifestations after Roux-en-Y gastric bypass surgery in individuals with and without type 2 diabetes.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery is an effective treatment for obesity, which improves cardiovascular health and reduces the risk of premature mortality. However, some reports have suggested that RYGB may predispose patients to adverse health outcomes, such as inflammatory bowel disease (IBD) and colorectal cancer. OBJECTIVES: The present prospective study aimed to evaluate the impact of RYGB surgery on cardiovascular risk factors and gastrointestinal inflammation in individuals with and without type 2 diabetes (T2D). SETTING: University hospital setting in Finland. METHODS: Blood and fecal samples were collected at baseline and 6 months after surgery from 30 individuals, of which 16 had T2D and 14 were nondiabetics. There were also single study visits for 6 healthy reference patients. Changes in cardiovascular risk factors, serum cholesterol, and triglycerides were investigated before and after surgery. Fecal samples were analyzed for calprotectin, anti-Saccharomyces cerevisiae immunoglobulin A antibodies (ASCA), active lipopolysaccharide (LPS) concentration, short-chain fatty acids (SCFAs), intestinal alkaline phosphatase activity, and methylglyoxal-hydro-imidazolone (MG-H1) protein adducts formation. RESULTS: After RYGB, weight decreased on average -21.6% (-27.2 ± 7.8 kg), excess weight loss averaged 51%, and there were improvements in cardiovascular risk factors. Fecal calprotectin levels (P < .001), active LPS concentration (P < .002), ASCA (P < .02), and MG-H1 (P < .02) values increased significantly, whereas fecal SCFAs, especially acetate (P < .002) and butyrate (P < .03) levels, were significantly lowered. CONCLUSION: The intestinal homeostasis is altered after RYGB, with several fecal markers suggesting increased inflammation; however, clinical significance of the detected changes is currently uncertain. As chronic inflammation may predispose patients to adverse health effects, our findings may have relevance for the suggested association between RYGB and increased risks of incident IBD and colorectal cancer.

PXR and 4ß-Hydroxycholesterol Axis and the Components of Metabolic Syndrome.

Pregnane X receptor (PXR) activation has been found to regulate glucose and lipid metabolism and affect obesity in response to high-fat diets. PXR also modulates vascular tone. In fact, PXR appears to regulate multiple components of metabolic syndrome. In most cases, the effect of PXR action is harmful to metabolic health, and PXR can be hypothesized to play an important role in metabolic disruption elicited by exposure to endocrine-disrupting chemicals. The majority of the data on the effects of PXR activation on metabolic health come from animal and cell culture experiments. However, randomized, placebo-controlled, human trials indicate that the treatment with PXR ligands impairs glucose tolerance and increases 24-h blood pressure and heart rate. In addition, plasma 4ß-hydroxycholesterol (4ßHC), formed under the control of PXR in the liver, is associated with lower blood pressure in healthy volunteers. Furthermore, 4ßHC regulates cholesterol transporters in peripheral tissues and may activate the beneficial reverse HDL cholesterol transport. In this review, we discuss the current knowledge on the role of PXR and the PXR-4ßHC axis in the regulation of components of metabolic syndrome.

Inhibition and induction of CYP enzymes in humans: an update.

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug-drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug-drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

CYP-associated drug-drug interactions: A mission accomplished?

On the basis of official Finnish Medicines Authority (Fimea)-approved drug monographs, less than half of the approved small-molecule drugs between 2007 and 2016 were substrates, inhibitors or inducers of CYP enzymes, predominantly of CYP3A4. No significant unexpected, life-threatening, CYP-associated drug-drug interactions (CYP-DDIs) of newly approved drug entities have been observed in the last 10-15 years. The present analysis seems to suggest that tools to study and predict potentially significant CYP-DDIs are working and efficient.

4ß-Hydroxycholesterol Signals From the Liver to Regulate Peripheral Cholesterol Transporters.

Activation of pregnane X receptor (PXR) elevates circulating 4ß-hydroxycholesterol (4ßHC), an agonist of liver X receptor (LXR). PXR may also regulate 25-hydroxycholesterol and 27-hydroxycholesterol. Our aim was to elucidate the roles of PXR and oxysterols in the regulation of cholesterol transporters. We measured oxysterols in serum of volunteers dosed with PXR agonist rifampicin 600 mg/day versus placebo for a week and analyzed the expression of cholesterol transporters in mononuclear cells. The effect of 4ßHC on the transport of cholesterol and the expression of cholesterol transporters was studied in human primary monocyte-derived macrophages and foam cells in vitro. The expression of cholesterol transporters was measured also in rat tissues after dosing with a PXR agonist. The levels of 4ßHC were elevated, while 25-hydroxycholesterol and 27-hydroxycholesterol remained unchanged in volunteers dosed with rifampicin. The expression of ATP binding cassette transporter A1 (ABCA1) was induced in human mononuclear cells in vivo. The influx of cholesterol was repressed by 4ßHC, as was the expression of influx transporter lectin-like oxidized LDL receptor-1 in vitro. The cholesterol efflux and the expression of efflux transporters ABCA1 and ABCG1 were induced. The expression of inducible degrader of the LDL receptor was induced. In rats, PXR agonist increased circulating 4ßHC and expression of LXR targets in peripheral tissues, especially ABCA1 and ABCG1 in heart. In conclusion, PXR activation-elevated 4ßHC is a signaling molecule that represses cholesterol influx and induces efflux. The PXR-4ßHC-LXR pathway could link the hepatic xenobiotic exposure and the regulation of cholesterol transport in peripheral tissues.