On the importance of albumin binding for the flux of 7α-hydroxy-3-oxo-4-cholestenoic acid in the brain

Exploring the causal association between genetically determined circulating metabolome and hemorrhagic stroke

Background

Hemorrhagic stroke (HS), a leading cause of death and disability worldwide, has not been clarified in terms of the underlying biomolecular mechanisms of its development. Circulating metabolites have been closely associated with HS in recent years. Therefore, we explored the causal association between circulating metabolomes and HS using Mendelian randomization (MR) analysis and identified the molecular mechanisms of effects.

Methods

We assessed the causal relationship between circulating serum metabolites (CSMs) and HS using a bidirectional two-sample MR method supplemented with five ways: weighted median, MR Egger, simple mode, weighted mode, and MR-PRESSO. The Cochran Q-test, MR-Egger intercept test, and MR-PRESSO served for the sensitivity analyses. The Steiger test and reverse MR were used to estimate reverse causality. Metabolic pathway analyses were performed using MetaboAnalyst 5.0, and genetic effects were assessed by linkage disequilibrium score regression. Significant metabolites were further synthesized using meta-analysis, and we used multivariate MR to correct for common confounders.

Results

We finally recognized four metabolites, biliverdin (OR 0.62, 95% CI 0.40-0.96, PMVMR = 0.030), linoleate (18. 2n6) (OR 0.20, 95% CI 0.08-0.54, PMVMR = 0.001),1-eicosadienoylglycerophosphocholine* (OR 2.21, 95% CI 1.02-4.76, PMVMR = 0.044),7-alpha-hydroxy-3 -oxo-4-cholestenoate (7-Hoca) (OR 0.27, 95% CI 0.09-0.77, PMVMR = 0.015) with significant causal relation to HS.

Conclusion

We demonstrated significant causal associations between circulating serum metabolites and hemorrhagic stroke. Monitoring, diagnosis, and treatment of hemorrhagic stroke by serum metabolites might be a valuable approach.

CMS121: a novel approach to mitigate aging-related obesity and metabolic dysfunction

BACKGROUND

Modulated by differences in genetic and environmental factors, laboratory mice often show progressive weight gain, eventually leading to obesity and metabolic dyshomeostasis. Since the geroneuroprotector CMS121 has a positive effect on energy metabolism in a mouse model of type 2 diabetes, we investigated the potential of CMS121 to counteract the metabolic changes observed during the ageing process of wild type mice.

METHODS

Control or CMS121-containing diets were supplied ad libitum for 6 months, and mice were sacrificed at the age of 7 months. Blood, adipose tissue, and liver were analyzed for glucose, lipids, and protein markers of energy metabolism.

RESULTS

The CMS121 diet induced a 40% decrease in body weight gain and improved both glucose and lipid indexes. Lower levels of hepatic caspase 1, caspase 3, and NOX4 were observed with CMS121 indicating a lower liver inflammatory status. Adipose tissue from CMS121-treated mice showed increased levels of the transcription factors Nrf1 and TFAM, as well as markers of mitochondrial electron transport complexes, levels of GLUT4 and a higher resting metabolic rate. Metabolomic analysis revealed elevated plasma concentrations of short chain acylcarnitines and butyrate metabolites in mice treated with CMS121.

CONCLUSIONS

The diminished de novo lipogenesis, which is associated with increased acetyl-CoA, acylcarnitine, and butyrate metabolite levels, could contribute to safeguarding not only the peripheral system but also the aging brain. By mimicking the effects of ketogenic diets, CMS121 holds promise for metabolic diseases such as obesity and diabetes, since these diets are hard to follow over the long term.

Integrated Analysis of Per- and Polyfluoroalkyl Substance Exposure and Metabolic Profiling of Elderly Residents Living near Industrial Plants

Per- and polyfluoroalkyl substances (PFASs) are widely used in industrial production, causing potential health risks to the residents living around chemical industrial plants; however, the lack of data on population exposure and adverse effects impedes our understanding and ability to prevent risks. In this study, we performed screening and association analysis on exogenous PFAS pollutants and endogenous small-molecule metabolites in the serum of elderly residents living near industrial plants. Exposure levels of 11 legacy and novel PFASs were determined. PFOA and PFOS were major contributors, and PFNA, PFHxS, and 6:2 Cl-PFESA also showed high detection frequencies. Association analysis among PFASs and 287 metabolites identified via non-target screening was performed with adjustments of covariates and false discovery rate. Strongly associated metabolites were predominantly lipid and lipid-like molecules. Steroid hormone biosynthesis, primary bile acid biosynthesis, and fatty-acid-related pathways, including biosynthesis of unsaturated fatty acids, linoleic acid metabolism, α-linolenic acid metabolism, and fatty acid biosynthesis, were enriched as the metabolic pathways associated with mixed exposure to multiple PFASs, providing metabolic explanation and evidence for the potential mediating role of adverse health effects as a result of PFAS exposure. Our study achieved a comprehensive screening of PFAS exposure and associated metabolic profiling, demonstrating the promising application for integrated analysis of exposome and metabolome.

Ventriculoperitoneal Shunt Treatment Increases 7 Alpha Hy-Droxy-3-Oxo-4-Cholestenoic Acid and 24-Hydroxycholesterol Concentrations in Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is the most common form of hydrocephalus in the adult population, and is often treated with cerebrospinal fluid (CSF) drainage using a ventriculoperitoneal (VP) shunt. Symptoms of iNPH include gait impairment, cognitive decline, and urinary incontinence. The pathophysiology behind the symptoms of iNPH is still unknown, and no reliable biomarkers have been established to date. The aim of this study was to investigate the possible use of the oxysterols as biomarkers in this disease. CSF levels of the oxysterols 24S- and 27-hydroxycholesterol, as well as the major metabolite of 27-hydroxycholesterol, 7 alpha hydroxy-3-oxo-4-cholestenoic acid (7HOCA), were measured in iNPH-patients before and after treatment with a VP-shunt. Corresponding measurements were also performed in healthy controls. VP-shunt treatment significantly increased the levels of 7HOCA and 24S-hydroxycholesterol in CSF (p = 0.014 and p = 0.037, respectively). The results are discussed in relation to the beneficial effects of VP-shunt treatment. Furthermore, the possibility that CSF drainage may reduce an inhibitory effect of transiently increased pressure on the metabolic capacity of neuronal cells in the brain is discussed. This capacity includes the elimination of cholesterol by the 24S-hydroxylase mechanisms.

Metabolome Genome-Wide Association Study Identifies 74 Novel Genomic Regions Influencing Plasma Metabolites Levels

Metabolites are small products of metabolism that provide a snapshot of the wellbeing of an organism and the mechanisms that control key physiological processes involved in health and disease. Here we report the results of a genome-wide association study of 722 circulating metabolite levels in 8809 subjects of European origin, providing both breadth and depth. These analyses identified 202 unique genomic regions whose variations are associated with the circulating levels of 478 different metabolites. Replication with a subset of 208 metabolites that were available in an independent dataset for a cohort of 1768 European subjects confirmed the robust associations, including 74 novel genomic regions not associated with any metabolites in previous works. This study enhances our knowledge of genetic mechanisms controlling human metabolism. Our findings have major potential for identifying novel targets and developing new therapeutic strategies.

Novel Biomarkers to Distinguish between Type 3c and Type 2 Diabetes Mellitus by Untargeted Metabolomics

Pancreatogenic diabetes mellitus (T3cDM) is a highly frequent complication of pancreatic disease, especially chronic pancreatitis, and it is often misdiagnosed as type 2 diabetes mellitus (T2DM). A correct diagnosis allows the appropriate treatment of these patients, improving their quality of life, and various technologies have been employed over recent years to search for specific biomarkers of each disease. The main aim of this metabolomic project was to find differential metabolites between T3cDM and T2DM. Reverse-phase liquid chromatography coupled to high-resolution mass spectrometry was performed in serum samples from patients with T3cDM and T2DM. Multivariate Principal Component and Partial Least Squares-Discriminant analyses were employed to evaluate between-group variations. Univariate and multivariate analyses were used to identify potential candidates and the area under the receiver-operating characteristic (ROC) curve was calculated to evaluate their diagnostic value. A panel of five differential metabolites obtained an area under the ROC curve of 0.946. In this study, we demonstrate the usefulness of untargeted metabolomics for the differential diagnosis between T3cDM and T2DM and propose a panel of five metabolites that appear altered in the comparison between patients with these diseases.

The Danish Chronic Subdural Hematoma Study-comparison of hematoma age to the radiological appearance at time of diagnosis

INTRODUCTION

Chronic subdural hematomas (CSDH) show different radiological characteristics on CT scans at the time of diagnosis. The reason for this is largely unknown. We hypothesize that the imaging characteristics reflect a time-linked pathophysiological evolution. We therefore conducted a retrospective study to examine a possible relation between the hematoma age and the radiological subtype of a CSDH.

METHODS

Demographic data on patients with CSDH were retrieved from a Danish national cohort from 2010 to 2012. CT scans obtained on admission to a neurosurgical department were categorized as homogenous, separated, mixed, or membranous hematoma subtypes. The time from a known date of head injury to time of diagnostic CT was defined as hematoma age. The hematoma age was correlated to radiological hematoma subtype at the time of diagnosis by analysis of variance testing.

RESULTS

In total, 543 patients were analyzed for hematoma age and classified in the following hematoma subtypes: 231 homogenous, 44 separated, 119 mixed, and 149 membranous. Patients with homogenous, separated, mixed, and membranous hematoma subtypes had a median interval of 37, 36, 40, and 60 days from head injury to diagnostic CT. We found that membranous hematoma is significantly older than other subtypes. Comparison between the other radiological subtypes showed no statistical hematoma age difference. The distribution of radiological subtypes in 590 patients without a known head injury was similar to that of patients with a known head injury. Additionally, we found that hematoma age was significantly younger for patients on antiplatelet medication.

CONCLUSION

In this large national cohort, patients with membranous CSDH had a significantly longer interval between head injury and diagnosis compared to other radiological subtypes. This indicates that the radiological appearance of CSDH evolves over time, causing an alteration from different early radiological subtypes to a radiological subtype with membranes.

CLINICAL TRIAL REGISTRATION NUMBER

The study was approved by the Danish Data Protection Agency (journal no.30-1145).

Further evidence for a continuous flux of bile acids into the brain: trapping of bile acids in subdural hematomas

Bile acids are known to pass the blood-brain barrier and are present at low concentrations in the brain. In a previous work, it was shown that subdural hematomas are enriched with bile acids and that the levels in such hematomas are higher than in the peripheral circulation. The mechanism behind this enrichment was never elucidated. Bile acids have a high affinity to albumin, and subdural hematomas contain almost as high albumin levels as the peripheral circulation. A subdural hematoma is encapsulated by fibrin which may allow passage of small molecules like bile acids. We hypothesized that bile acids originating from the circulation may be 'trapped' in the albumin in subdural hematomas. In the present work, we measured the conjugated and unconjugated primary bile acids cholic acid and chenodeoxycholic acid in subdural hematomas and in peripheral circulation of 24 patients. In most patients, the levels of both conjugated and free bile acids were higher in the hematomas than in the circulation, but the enrichment of unconjugated bile acids was markedly higher than that of conjugated bile acids. In patients with a known time interval between the primary bleeding and the operation, there was a correlation between this time period and the accumulation of bile acids. This relation was most obvious for unconjugated bile acids. The results are consistent with a continuous flux of bile acids, in particular unconjugated bile acids, across the blood-brain barrier. We discuss the possible physiological importance of bile acid accumulation in subdural hematomas.

Formation and metabolism of oxysterols and cholestenoic acids found in the mouse circulation: Lessons learnt from deuterium-enrichment experiments and the CYP46A1 transgenic mouse

While the presence and abundance of the major oxysterols and cholestenoic acids in the circulation is well established, minor cholesterol metabolites may also have biological importance and be of value to investigate. In this study by observing the metabolism of deuterium-labelled cholesterol in the pdgfb^ret/ret mouse, a mouse model with increased vascular permeability in brain, and by studying the sterol content of plasma from the CYP46A1 transgenic mouse overexpressing the human cholesterol 24S-hydroxylase enzyme we have been able to identify a number of minor cholesterol metabolites found in the circulation, make approximate-quantitative measurements and postulate pathways for their formation. These "proof of principle" data may have relevance when using mouse models to mimic human disease and in respect of the increasing possibility of treating human neurodegenerative diseases with pharmaceuticals designed to enhance the activity of CYP46A1 or by adeno-associated virus delivery of CYP46A1.

On the fluxes of side-chain oxidized oxysterols across blood-brain and blood-CSF barriers and origin of these steroids in CSF (Review)

In contrast to cholesterol itself the side-chain oxidized metabolites 24S-hydroxycholesterol (24OH) and 27-hydroxycholesterol (27OH) are able to pass the blood-brain barrier and the blood-CSF barrier. Most 27OH in circulation is formed extracerebrally and according to catheterization experiments about 5 mg of it is taken up by the brain per 24 h. 24OH is almost exclusively produced in the brain and about 6 mg fluxes from the brain into the circulation per 24 h. In addition to these major fluxes a very minor fraction of these two oxysterols flux from the circulation into CSF. Isotope experiments have shown that almost all 27OH in CSF originates from the circulation and evidence has been presented that this is the case also with a substantial part of 24OH. The levels of both 24OH and 27OH in CSF are thus affected by the integrity of the blood-CSF barrier with higher levels when the barrier is defect. Both levels of 24OH and 27OH in CSF are increased in connection with neurodegeneration and in general the increase in 24OH levels is higher than the increase in 27OH levels. A number of observations in different type of patients including measurements of other biochemical markers support that the increase in levels of 24OH due to neurodegeneration is due to a release of this oxysterol or its precursor cholesterol from dying neuronal cells. In contrast the increase in levels of 27OH is likely to be a consequence of reduced metabolism due to loss of the neuronal enzyme CYP7B1. We discuss the driving forces behind the fluxes of oxysterols in the brain, the limitations in the flux across the barriers and the diagnostic potential for side-chain oxidized oxysterols in CSF.

Oxysterol research: a brief review

In the present study, we discuss the recent developments in oxysterol research. Exciting results have been reported relating to the involvement of oxysterols in the fields of neurodegenerative disease, especially in Huntington's disease, Parkinson's disease and Alzheimer's disease; in signalling and development, in particular, in relation to Hedgehog signalling; and in cancer, with a special focus on (25R)26-hydroxycholesterol. Methods for the measurement of oxysterols, essential for understanding their mechanism of action in vivo, and valuable for diagnosing rare diseases of cholesterol biosynthesis and metabolism are briefly considered.

Free oxysterols and bile acids including conjugates - Simultaneous quantification in human plasma and cerebrospinal fluid by liquid chromatography-tandem mass spectrometry

A liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI(+)-MS/MS) assay was developed and qualified for analyzing 35 analytes of the cholesterol metabolism, including free cholesterol, 17 free, non-esterified oxysterols and 17 free and conjugated bile acids in plasma and cerebrospinal fluid. As internal standards, 25 commercially available stable deuterium-labeled analogs of the analytes were used. Pre-analytical investigations included stability tests of analyte concentrations affected by different anticoagulation additives: lithium heparin-, citrate-, EDTA-K₃-stabilized plasma and serum, and the stability in EDTA whole blood at RT. This LC-ESI(+)-MS/MS method was successfully applied for the analysis of paired serum/cerebrospinal fluid samples of patients with and without blood-brain barrier disturbance, as well as of 100 plasma samples of a LIFE-Adult study sub-cohort. A fast and simple sample preparation including protein precipitation and on-line solid-phase extraction was developed. As little as 55 μL of human plasma/serum or cerebrospinal fluid were needed for the analysis. It was possible to separate isomeric oxysterols and bile acids within 23 min using a C18 core-shell column. The assay is capable of quantifying in a linear range of 0.8-250 ng mL^-1 for free hydroxycholesterols, 0.2-10 ng mL^-1 for dihydroxycholesterols, 0.2-500 ng mL^-1 for bile acids and 16-2000 μg mL^-1 for cholesterol with acceptable accuracy and precision. In cerebrospinal fluid one free oxysterols, five free and five conjugated bile acids could be quantified. No significant differences between patients with and without blood-brain barrier disturbance were obtained. In the LIFE-Adult sub-cohort two free oxysterols, four free and seven conjugated bile acids could be quantified in EDTA plasma. Men showed significantly higher concentrations of 26-OHC than women (p = 0.035). Furthermore, in women lower levels of cholic acid, glycocholic acid, glycodeoxycholic acid, chenodeoxycholic acid, glycochenodeoxycholic acid, glycoursodeoxycholic acid, glycolithocholic acid and higher levels of taurocholic acid, taurochenodeoxycholic acid, ursodeoxycholic acid/hyodeoxycholic acid were quantified.