Unveiling the lysosomal-cholesterol nexus: NCOA7’s pivotal role in pulmonary artery hypertension pathogenesis and therapy

ABSTRACTDesynchronization between the master clock in the brain, which is entrained by (day) light, and peripheral organ clocks, which are mainly entrained by food intake, may have negative effects on energy metabolism. Bile acid metabolism follows a clear day/night rhythm. We investigated whether in rats on a normal chow diet the daily rhythm of plasma bile acids and hepatic expression of bile acid metabolic genes is controlled by the light/dark cycle or the feeding/fasting rhythm. In addition, we investigated the effects of high caloric diets and time-restricted feeding on daily rhythms of plasma bile acids and hepatic genes involved in bile acid synthesis. In experiment 1 male Wistar rats were fed according to three different feeding paradigms: food was available ad libitum for 24 h (ad lib) or time-restricted for 10 h during the dark period (dark fed) or 10 h during the light period (light fed). To allow further metabolic phenotyping, we manipulated dietary macronutrient intake by providing rats with a chow diet, a free choice high-fat-high-sugar diet or a free choice high-fat (HF) diet. In experiment 2 rats were fed a normal chow diet, but food was either available in a 6-meals-a-day (6M) scheme or ad lib. During both experiments, we measured plasma bile acid levels and hepatic mRNA expression of genes involved in bile acid metabolism at eight different time points during 24 h. Time-restricted feeding enhanced the daily rhythm in plasma bile acid concentrations. Plasma bile acid concentrations are highest during fasting and dropped during the period of food intake with all diets. An HF-containing diet changed bile acid pool composition, but not the daily rhythmicity of plasma bile acid levels. Daily rhythms of hepatic Cyp7a1 and Cyp8b1 mRNA expression followed the hepatic molecular clock, whereas for Shp expression food intake was leading. Combining an HF diet with feeding in the light/inactive period annulled CYp7a1 and Cyp8b1 gene expression rhythms, whilst keeping that of Shp intact. In conclusion, plasma bile acids and key genes in bile acid biosynthesis are entrained by food intake as well as the hepatic molecular clock. Eating during the inactivity period induced changes in the plasma bile acid pool composition similar to those induced by HF feeding.

Circulating bile acids (BA) are signaling molecules that control glucose and lipid metabolism. However, the effects of acute exercise on plasma levels of BA in humans remain poorly understood. Here, we evaluate the effects of a bout of maximal endurance exercise (EE) and resistance exercise (RE) on plasma levels of BA in young, sedentary adults. Concentration of eight plasma BA was measured by liquid chromatography-tandem mass spectrometry before and 3, 30, 60, and 120 min after each exercise bout. Cardiorespiratory fitness (CRF) was assessed in 14 young adults (21.8 ± 2.5 yo, 12 women); muscle strength was assessed in 17 young adults (22.4 ± 2.5 yo, 11 women). EE transiently decreased plasma levels of total, primary, and secondary BA at 3 and 30 min after exercise. RE exerted a prolonged reduction in plasma levels of secondary BA (p < 0.001) that lasted until 120 min. Primary BA levels of cholic acid (CA) and chenodeoxycholic acid (CDCA) were different across individuals with low/high CRF levels after EE (p ≤ 0.044); CA levels were different across individuals with low/high handgrip strength levels. High CRF individuals presented higher levels of CA and CDCA 120 min after exercise vs baseline (+77% and +65%) vs the low CRF group (-5% and -39%). High handgrip strength levels individuals presented higher levels of CA 120 min after exercise versus baseline (+63%) versus the low handgrip strength group (+6%). The study findings indicate that an individual's level of physical fitness can influence how circulating BA respond to both endurance and resistance exercise. Additionally, the study suggests that changes in plasma BA levels after exercising could be related to the control of glucose homeostasis in humans.

BackgroundGut bacteria play a crucial role in the metabolism of bile acids (BA). Whether an association exists between the fecal microbiota composition and circulating BA levels in humans is poorly understood. Here, we investigated the relationship between fecal microbiota diversity and composition with plasma levels of BA in young adults.MethodsFecal microbiota diversity/composition was analyzed with 16S rRNA sequencing in 80 young adults (74% women; 21.9 ± 2.2 years old). Plasma levels of BA were measured using liquid chromatography-tandem mass spectrometry. PERMANOVA and Spearman correlation analyses were used to investigate the association between fecal microbiota parameters and plasma levels of BA.ResultsFecal microbiota beta (P = 0.025) and alpha diversity indexes of evenness (rho = 0.237, P = 0.033), Shannon (rho = 0.313, P = 0.004), and inverse Simpson (rho = 0.283, P = 0.010) were positively associated with plasma levels of the secondary BA glycolithocholic acid (GLCA). The relative abundance of genera belonging to the Firmicutes and Bacteroidetes phyla was positively correlated with plasma levels of GLCA (all rho ≥ 0.225, P ≤ 0.049). However, the relative abundance of species from Firmicutes and Bacteroidetes phyla were negatively correlated with plasma levels of primary and secondary BA (all rho ≤ − 0.220, P ≤ 0.045), except for the relative abundance of Bacteroides vulgatus, Alistipes onderdonkii, and Bacteroides xylanisolvens species (Bacteroidetes phylum) that were positively correlated with the plasma levels of GLCA.ConclusionsThe relative abundance of specific fecal bacteria species is associated with plasma levels of BA in young adults. However, further investigations are required to validate whether the composition of the gut microbiota can regulate the plasma concentrations of BA in humans.

The C57BL/6ByJ (B6By) mouse strain is resistant to diet-induced hypercholesterolemia and atherosclerosis, despite its near genetic identity with the atherosclerosis-susceptible C57BL/6J (B6J) strain. We previously identified a genetic locus, Diet1, which is responsible for the resistant phenotype in B6By mice. To investigate the function of Diet1, we compared mRNA expression profiles in the liver of B6By and B6J mice fed an atherogenic diet using a DNA microarray. These studies revealed elevated expression levels in B6By liver for key bile acid synthesis proteins, including cholesterol 7alpha-hydroxylase and sterol-27-hydroxylase, and the oxysterol nuclear receptor liver X receptor alpha. Expression levels for several other genes involved in bile acid metabolism were subsequently found to differ between B6By and B6J mice, including the bile acid receptor farnesoid X receptor, oxysterol 7alpha-hydroxylase, sterol-12alpha-hydroxylase, and hepatic bile acid transporters on both sinusoidal and canalicular membranes. The overall expression profile of the B6By strain suggests a higher rate of bile acid synthesis and transport in these mice. Consistent with this interpretation, fecal bile acid excretion is increased 2-fold in B6By mice, and bile acid levels in blood and urine are elevated 3- and 18-fold, respectively. Genetic analysis of serum bile acid levels revealed co-segregation with Diet1, indicating that this locus is likely responsible for both increased bile acid excretion and resistance to hypercholesterolemia in B6By mice.

What Can We Learn From Mouse Models About Bile Acid-Mediated Changes After Bariatric Surgery?

The aim of the study was to develop a method for fast and reliable diagnosis of peroxisomal diseases and to facilitate differential diagnosis of cholestatic hepatopathy. For the quantification of bile acids and their conjugates as well as C(27) precursors di- and trihydroxycholestanoic acid (DHCA, THCA), in small pediatric blood samples we combined HPLC separation on a reverse-phase C18 column with ESI-MS/MS analysis in the negative ion mode. Analysis was done with good precision (CV 3,7%-11.1%) and sufficient sensitivity (LOQ: 11-91 nmol/L) without derivatization. Complete analysis of 17 free and conjugated bile acids from dried blood spots and 10 microL serum samples, respectively, was performed within 12 min. Measurement of conjugated primary bile acids plus DHCA and THCA as well as ursodeoxycholic acid was done in 4.5 min. In blood spots of healthy newborns, conjugated primary bile acids were found in the range of 0.01 to 2.01 micromol/L. Concentrations of C(27) precursors were below the detection limit in normal controls. DHCA and THCA were specifically elevated in cases of peroxysomal defects and one Zellweger patient.

This study aimed to characterize plasma bile acid changes from birth to first calving and evaluate the effects of early transition milk (TM) feeding versus milk replacer (MR) during key stages. Fecal bile acids in TM-fed calves were also analyzed, offering insights into bile acid metabolism. Thirty female Holstein calves were fed TM or MR for the first 5 d, followed by 12 L/d MR. From d 14, calves were fed MR and starter with gradual weaning between wk 8 and 14. Blood samples were collected at 7 time points: 30 min and 12 h after birth, preweaning (wk 2, 6), weaning (wk 14), 8 mo, 13 mo, 3 wk before calving, at calving, and 3 wk after calving. Fecal samples were collected from a subset of TM-fed calves (n = 10) at birth, wk 6, wk 14, 8 mo, and calving. Samples were analyzed for bile acids using the Biocrates MxP Quant 500 kit. Cholic acid (CA) in plasma showed significant time-treatment interactions, with higher levels in TM-fed calves at weaning. Taurine- and glycine-conjugated bile acids had no treatment or time-treatment interactions, but all plasma bile acids showed significant time effects. Principal component analysis revealed that bile acid profiles at birth and after colostrum intake were tightly clustered. Plasma bile acid profiles showed greater dispersion during milk feeding and weaning, with tighter clustering observed postweaning, particularly at 13 mo, and in the transition period. Significant effects were observed for CA, deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA), with CA showing a notable interaction and being higher in TM-fed calves at weaning than in MR-fed calves. Bile acid levels increased toward weaning, peaked at wk 14, and decreased after weaning. Glycine-conjugated bile acids changed over time, with glycocholic acid (GCA) and glycodeoxycholic acid (GDCA) peaking at weaning, and glycochenodeoxycholic acid (GCDCA) being elevated before weaning, decreasing thereafter, and increasing again at calving. Taurine-conjugated bile acids also showed temporal changes, peaking at wk 6. The shifts in bile acid composition from birth to postcalving, with taurolithocholic acid (TLCA), GDCA, and taurocholic acid (TCA) initially dominating, CA increasing at weaning, and GDCA and DCA dominating at calving, with CA increasing again postcalving. During the transition to calving, CA decreased whereas glycine-conjugated bile acids increased relative to taurine-conjugated bile acids in plasma, irrespective of treatment. Fecal bile acid profiles in TM-fed calves clustered distinctly at birth, evolving through pre- to postweaning and calving, with increasing profile overlap over time. Most fecal bile acids, except DCA and CA, were abundant at birth but declined over time. Both DCA and CA increased postweaning, mirroring plasma trends. From wk 6 to calving, DCA was the dominant bile acid, accounting for the highest percentage of total bile acids excreted in feces. Spearman's correlation analysis was performed to assess the relationship between plasma and fecal bile acids in TN-fed calves. A significant positive correlation was observed only for GCDCA (Spearman's rank correlation coefficient [rho] = 0.35), whereas all other bile acids were not correlated. These results illustrate the complex dynamics of bile acid profiles during calf development.

Computer simulation of portal venous shunting and other isolated hepatobiliary defects of the enterohepatic circulation of bile acids using a physiological pharmacokinetic model.

pulmonary hypertension (PH), diagnosed when mean pulmonary arterial pressure exceeds the upper limits of normal (i.e., >25 mmHg) at rest (2), occurs in a variety of clinical situations and is associated with a broad spectrum of histological patterns and abnormalities. PH is currently classified into five distinct World Health Organization (WHO) groups, based on common clinical parameters, potential etiological mechanisms, and responses to treatment (22). Although any form of PH can contribute to increased patient morbidity and mortality, pulmonary arterial hypertension (PAH) (WHO group 1) is a particularly severe and progressive form associated with right heart failure and premature death (1). At present, therapeutic approaches to stabilize or reverse this debilitating condition involve treatment with one or a combination of up to three specific classes of agents, including prostacyclin analogs, endothelin-1 receptor antagonists, and/or phosphodiesterase-5 inhibitors. Retrospective (meta)analyses of these therapeutic strategies have demonstrated a reduction in mortality with their use (7, 12); however, many experts believe that current PAH treatment is inadequate given the persistently high mortality rate and functional hemodynamic impairment in many patients. These observations have led to continued intensive investigation into pathogenetic mechanisms and many proposals for additional alternative new therapies (20, 24). Among the potential new therapies, increasing interest in the role of endothelial progenitor cells (EPCs) as a cell-based therapy has emerged. However, issues remain regarding what group of PH patients are most likely to benefit from treatment, at what point in the disease is treatment most likely to be successful, and what types of cells should be utilized for therapy.

Enterohepatic Circulation of Bile Acids Is Activated by Bariatric Surgery before Weight Loss Becomes Apparent

See related article, pages 1109–1114 Idiopathic pulmonary artery hypertension (IPH) is a rare illness with a poor prognosis. Whereas chronic intravenous prostacyclin relieves some of the symptoms of progressive dyspnea and prolongs survival, most patients ultimately require a lung transplant.1 Newer therapies such as nonintravenously administered prostacyclin derivatives,2,3,4 endothelin receptor blockers,5,6 and, to some extent, phosphodiesterase inhibitors,7 hold some promise as alternatives for intravenous prostacyclin, but current expectation is that, like prostacyclin, they will, at best, retard disease progression, serving as a bridge to transplant rather than as an alternative. The pathological features of IPH are loss of small distal precapillary pulmonary arteries, obliterative changes (plexogenic lesions) in more proximal pulmonary arteries associated with migration and proliferation of smooth muscle cells, and increased extracellular matrix deposition. There is also dysregulation of endothelial cells associated with increased proliferation.8 The mechanism underlying the evolution of these changes is unknown, so there was great interest when 2 groups independently identified a mutation in bone morphogenetic protein receptor 11 (BMP-RII) in 60% of families with IPH.9,10 A BMP-RII mutation also occurs in 20% of sporadic cases of IPH,11 but the biological connection between the mutation and the pathobiology of IPH has been relatively elusive. Recent studies using pulmonary artery smooth muscle cells from patients with IPH, including those with and without a BMP-RII mutation, showed similar abnormal proliferation in response to agents such as transforming growth factor-β (TGF-β) or BMP-2.12 In other studies, pulmonary artery smooth muscle cells were transfected with constructs encoding different mutant forms of BMP-RII expressing aberrant kinase or cytoplasmic domains, and impaired signaling was observed related to alterations in the induction of Smads and p38.13 Specifically, suppression of Smad1/5 and activation of p38 were related to smooth muscle cell proliferation. It …

Is CYP2C70 the key to new mouse models to understand bile acids in humans?

e12539 Background: Bile acids are metabolized by the gut microbiome and are involved in fat absorption. Contrary to their carcinogenic role in gastrointestinal cancers, bile acids have been reported to inhibit cancer cell proliferation in breast cancer. We hypothesized that activation of bile acid metabolism is associated with a better prognosis based on previous reports regarding the antitumor effects of bile acids in breast cancer cells. Methods: A total of 6050 patients from three large open primary breast cancer cohorts (GSE96058, METABRIC, and TCGA) were analyzed by bile acid metabolism scores calculated by gene set variation analysis, and the association with the microbiome of the breast cancer tumor microenvironment in TCGA was also investigated. Results: We found that disease free, disease specific and overall survival was significantly improved in the high bile acid metabolism group, which was validated by three large breast cancer cohorts. However, apoptosis, ROS, and unfolded protein response gene sets were not found to be enriched in the high bile acid metabolism group, despite the expectation that oxidative stress-induced apoptosis would lead to improved survival. Several metabolic pathways and pathways associated with bile acid production and regulation were enriched in this group. On the other hand, Ki67 and nuclear grade were higher, and several cell proliferation-related gene sets were upregulated in the low bile acid metabolism group, especially the G2M checkpoint in all cohorts. In association with the higher cell proliferation, the low bile acid metabolism group showed higher mutation load, immune activation, and infiltration of anti-cancer immune cells. We further investigated that the composition of the microbiome in each group and four species that demonstrated significant abundance in the high bile acid metabolism group and three species in the low bile acid metabolism group. Surprisingly, almost all the cell proliferation-related gene sets from Hallmark were enriched in the three microorganisms-rich groups specific for low bile acid metabolism breast cancer. This was not the case for the microorganisms specific to high bile acid metabolism. Conclusions: Clinical relevance of bile acid metabolism in breast cancer is that low bile acid metabolism with abundant Lactobacillus, Ruegeria, and Marichromatium is associated with highly proliferative cancer and worse survival, rather than the growth suppression effect of bile acids.

Glucocorticoid treatment alters systemic bile acid homeostasis by regulating the biosynthesis and transport of bile salts

BackgroundDiabetic kidney disease (DKD) is the major complication of diabetes concomitant with gut dysbiosis and glycometabolic disorder, which are strongly associated with bile acid (BA) metabolism. Yet studies investigating the BA metabolism involving in DKD pathogenesis are limited. This study aimed to explore the metabolomic profiling of BAs in DKD and analyze its association with DKD progression.MethodsAn ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established to quantify BAs in the plasma, fecal and urine samples of patients with DKD or T2DM and healthy individuals (n = 30 for each group). The key BAs associated with DKD were identified by orthogonal partial least-squares discriminant analysis (OPLS-DA) and receiver-operating characteristic (ROC) curve. Polynomial regression and Pearson’s correlation analyses were performed to assess the correlation between the key BAs and the clinical indicators reflecting DKD progression.ResultsMetabolomic profiling of 50 kinds of BAs presented the markedly step-wise alterations of BAs in plasma and feces as well as the little in urine of patients with DKD. Eight kinds of BAs in the plasma, eight kinds in the feces and three kinds in the urine were abnormally expressed, accompanying with the increased conjugated/unconjugated ratios of cholic acid, deoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid and hyocholic acid in the plasma, and of cholic acid, chenodeoxycholic acid and lithocholic acid in the feces. Moreover, the increased plasma level of glycochenodeoxycholic acid, and the increased fecal levels of glycolithocholic acid, 7-ketodeoxycholic acid and chenodeoxycholic acid-3-β-D-glucuronide are strongly correlated with the clinical indicators reflecting DKD progression, including eGFR, 24 h urinary protein and 24 h urinary microalbumin.ConclusionsOur study for the first time disclosed the specific alterations of BA metabolism reflecting the step-wise progression of DKD, providing the basis for early identification and therapeutical strategies for DKD.