Bile Acids in Neurodegenerative Disorders

The microbiota-gut-brain axis in Huntington's disease: pathogenic mechanisms and therapeutic targets

Huntington's disease (HD) is a currently incurable neurogenerative disorder and is typically characterized by progressive movement disorder (including chorea), cognitive deficits (culminating in dementia), psychiatric abnormalities (the most common of which is depression), and peripheral symptoms (including gastrointestinal dysfunction). There are currently no approved disease-modifying therapies available for HD, with death usually occurring approximately 10-25 years after onset, but some therapies hold promising potential. HD subjects are often burdened by chronic diarrhea, constipation, esophageal and gastric inflammation, and a susceptibility to diabetes. Our understanding of the microbiota-gut-brain axis in HD is in its infancy and growing evidence from preclinical and clinical studies suggests a role of gut microbial population imbalance (gut dysbiosis) in HD pathophysiology. The gut and the brain can communicate through the enteric nervous system, immune system, vagus nerve, and microbiota-derived-metabolites including short-chain fatty acids, bile acids, and branched-chain amino acids. This review summarizes supporting evidence demonstrating the alterations in bacterial and fungal composition that may be associated with HD. We focus on mechanisms through which gut dysbiosis may compromise brain and gut health, thus triggering neuroinflammatory responses, and further highlight outcomes of attempts to modulate the gut microbiota as promising therapeutic strategies for HD. Ultimately, we discuss the dearth of data and the need for more longitudinal and translational studies in this nascent field. We suggest future directions to improve our understanding of the association between gut microbes and the pathogenesis of HD, and other 'brain and body disorders'.

Tauroursodeoxycholic acid: a bile acid that may be used for the prevention and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disease that has become one of the main factors affecting human health. It has serious impacts on individuals, families, and society. With the development of population aging, the incidence of AD will further increase worldwide. Emerging evidence suggests that many physiological metabolic processes, such as lipid metabolism, are implicated in the pathogenesis of AD. Bile acids, as the main undertakers of lipid metabolism, play an important role in the occurrence and development of Alzheimer's disease. Tauroursodeoxycholic acid, an endogenous bile acid, has been proven to possess therapeutic effects in different neurodegenerative diseases, including Alzheimer's disease. This review tries to find the relationship between bile acid metabolism and AD, as well as explore the therapeutic potential of bile acid taurocursodeoxycholic acid for this disease. The potential mechanisms of taurocursodeoxycholic acid may include reducing the deposition of Amyloid-β protein, regulating apoptotic pathways, preventing tau hyperphosphorylation and aggregation, protecting neuronal synapses, exhibiting anti-inflammatory properties, and improving metabolic disorders. The objective of this study is to shed light on the use of tauroursodeoxycholic acid preparations in the prevention and treatment of AD, with the aim of identifying effective treatment targets and clarifying various treatment mechanisms involved in this disease.

Integration of plasma and CSF metabolomics with CSF proteomic reveals novel associations between lipid mediators and central nervous system vascular and energy metabolism

Integration of the omics data, including metabolomics and proteomics, provides a unique opportunity to search for new associations within metabolic disorders, including Alzheimer's disease. Using metabolomics, we have previously profiled oxylipins, endocannabinoids, bile acids, and steroids in 293 CSF and 202 matched plasma samples from AD cases and healthy controls and identified both central and peripheral markers of AD pathology within inflammation-regulating cytochrome p450/soluble epoxide hydrolase pathway. Additionally, using proteomics, we have identified five cerebrospinal fluid protein panels, involved in the regulation of energy metabolism, vasculature, myelin/oligodendrocyte, glia/inflammation, and synapses/neurons, affected in AD, and reflective of AD-related changes in the brain. In the current manuscript, using metabolomics-proteomics data integration, we describe new associations between peripheral and central lipid mediators, with the above-described CSF protein panels. Particularly strong associations were observed between cytochrome p450/soluble epoxide hydrolase metabolites, bile acids, and proteins involved in glycolysis, blood coagulation, and vascular inflammation and the regulators of extracellular matrix. Those metabolic associations were not observed at the gene-co-expression level in the central nervous system. In summary, this manuscript provides new information regarding Alzheimer's disease, linking both central and peripheral metabolism, and illustrates the necessity for the "omics" data integration to uncover associations beyond gene co-expression.

A Low-Protein, High-Carbohydrate Diet Exerts a Neuroprotective Effect on Mice with 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-Induced Parkinson's Disease by Regulating the Microbiota-Metabolite-Brain Axis and Fibroblast Growth Factor 21

Parkinson's disease (PD) is closely linked to lifestyle factors, particularly dietary patterns, which have attracted interest as potential disease-modifying factors. Eating a low-protein, high-carbohydrate (LPHC) diet is a promising dietary intervention against brain aging; however, its protective effect on PD remains elusive. Here, we found that an LPHC diet ameliorated 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced motor deficits, decreased dopaminergic neuronal death, and increased the levels of striatal dopamine, serotonin, and their metabolites in PD mice. Levels of fibroblast growth factor 21 (FGF-21), a member of the fibroblast growth factor family, were elevated in PD mice following LPHC treatment. Furthermore, the administration of FGF-21 exerted a protective effect on MPTP-induced PC12 cells, similar to the effect of an LPHC diet in MPTP-induced mice. Sequencing of the 16S rDNA from fecal microbiota revealed that an LPHC diet normalized the gut bacterial composition imbalance in PD mice, as evidenced by the increased abundance of the genera Bifidobacterium, Ileibacterium, Turicibacter, and Blautia and decreased abundance of Bilophila, Alistipes, and Bacteroides. PICRUSt-predicted fecal microbiome function revealed that an LPHC diet suppressed lipopolysaccharide biosynthesis and the citrate cycle (TCA cycle), biosynthesis of ubiquinone and other terpenoid-quinones, and oxidative phosphorylation pathways caused by MPTP, and enhanced the biosynthesis of amino acids, carbohydrate metabolism, and biosynthesis of other secondary metabolites. A nonmetabolomic analysis of the serum and feces showed that an LPHC diet significantly increased the levels of aromatic amino acids (AAAs), including tryptophan, tyrosine, and phenylalanine. In addition, an LPHC diet elevated the serum concentrations of bile acids (BAs), particularly tauroursodeoxycholic acid (TUDCA) and taurine. Collectively, our current findings point to the potential mechanism of administering an LPHC diet in attenuating movement impairments in MPTP-induced PD mice, with AAAs, microbial metabolites (TUDCA and taurine), and FGF-21 as key mediators along the gut-microbiota-brain axis.

Mechanistic Insight into the Amyloid Fibrillation Inhibition of Hen Egg White Lysozyme by Three Different Bile Acids

Amyloid aggregation of protein is linked to many neurodegenerative diseases. Identification of small molecules capable of targeting amyloidogenic proteins has gained significant importance. Introduction of hydrophobic and hydrogen bonding interactions through site-specific binding of small molecular ligand to protein can effectively modulate the protein aggregation pathway. Here, we investigate the possible roles of three different bile acids, cholic acid (CA), taurocholic acid (TCA), and lithocholic acid (LCA) with varying hydrophobic and hydrogen bonding properties in inhibiting protein fibrillation. Bile acids are an important class of steroid compounds that are synthesized in the liver from cholesterol. Increasing evidence suggests that altered taurine transport, cholesterol metabolism, and bile acid synthesis have strong implications in Alzheimer's disease. We find that the hydrophilic bile acids, CA and TCA (taurine conjugated form of CA), are substantially more efficient inhibitors of lysozyme fibrillation than the most hydrophobic secondary bile acid LCA. Although LCA binds more strongly with the protein and masks the Trp residues more prominently through hydrophobic interactions, the lesser extent of hydrogen bonding interactions at the active site has made LCA a relatively weaker inhibitor of HEWL aggregation than CA and TCA. The introduction of a greater number of hydrogen bonding channels by CA and TCA with several key amino acid residues which are prone to form oligomers and fibrils has weakened the protein's internal hydrogen bonding capabilities for undergoing amyloid aggregation.

Is TGR5 a therapeutic target for the treatment of spinal cord injury?

Bile acids, which are synthesized in liver and colon, facilitate the digestion of dietary lipids. In addition to this metabolic function, they also act as molecular signals with activities in the nervous system. These are mediated primarily by a G-protein-coupled bile acid receptor (known as TGR5). Preceded by a long tradition in Chinese medicine, bile acids are now being investigated as therapeutic options in several neuropathologies. Specifically, one bile acid, tauroursodeoxycholic acid (TUDCA), which passes the blood-brain barrier and shows anti-inflammatory and anti-apoptotic effects, has been tested in animal models of spinal cord injury (SCI). In this review, we discuss the evidence for a therapeutic benefit in these preclinical experiments. At the time of writing, 12 studies with TGR5 agonists have been published that report functional outcomes with rodent models of SCI. Most investigations found cytoprotective effects and benefits regarding the recovery of sensorimotor function in the subacute phase. When TUDCA was applied in a hydrogel into the lesion site, a significant improvement was obtained at 2 weeks after SCI. However, no lasting improvements with TUDCA treatment were found, when animals were assessed in later, chronic stages. A combination of TUDCA with stem cell injection failed to improve the effect of the cellular treatment. We conclude that the evidence does not support the use of TUDCA as a treatment of SCI. Nevertheless, cytoprotective effects suggest that different modes of application or combinatorial therapies might still be explored.

Bile Acids Induce Neurite Outgrowth in Nsc-34 Cells via TGR5 and a Distinct Transcriptional Profile

Increasing evidence supports a neuroprotective role for bile acids in major neurodegenerative disorders. We studied major human bile acids as signaling molecules for their two cellular receptors, farnesoid X receptor (FXR or NR1H4) and G protein-coupled bile acid receptor 1 (GPBAR1 or TGR5), as potential neurotrophic agents. Using quantitative image analysis, we found that 20 μM deoxycholic acid (DCA) could induce neurite outgrowth in NSC-34 cells that was comparable to the neurotrophic effects of the culture control 1 μM retinoic acid (RA), with lesser effects observed for chenodexoycholic acid (CDCA) at 20 μM, and similar though less robust neurite outgrowth in SH-SY5Y cells. Using chemical agonists and antagonists of FXR, LXR, and TGR5, we found that TGR5 agonism was comparable to DCA stimulation and stronger than RA, and that neither FXR nor liver X receptor (LXR) inhibition could block bile acid-induced neurite growth. RNA sequencing identified a core set of genes whose expression was regulated by DCA, CDCA, and RA. Our data suggest that bile acid signaling through TGR5 may be a targetable pathway to stimulate neurite outgrowth.

New insights into the inter-organ crosstalk mediated by ChREBP

Carbohydrate response element binding protein (ChREBP) is a glucose responsive transcription factor recognized by its critical role in the transcriptional control of glycolysis and de novo lipogenesis. Substantial advances in the field have revealed novel ChREBP functions. Indeed, due to its actions in different tissues, ChREBP modulates the inter-organ communication through secretion of peptides and lipid factors, ensuring metabolic homeostasis. Dysregulation of these orchestrated interactions is associated with development of metabolic diseases such as type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). Here, we recapitulate the current knowledge about ChREBP-mediated inter-organ crosstalk through secreted factors and its physiological implications. As the liver is considered a crucial endocrine organ, we will focus in this review on the role of ChREBP-regulated hepatokines. Lastly, we will discuss the involvement of ChREBP in the progression of metabolic pathologies, as well as how the impairment of ChREBP-dependent signaling factors contributes to the onset of such diseases.

Insights by which TUDCA is a potential therapy against adiposity

Adipose tissue is an organ with metabolic and endocrine activity. White, brown and ectopic adipose tissues have different structure, location, and function. Adipose tissue regulates energy homeostasis, providing energy in nutrient-deficient conditions and storing it in high-supply conditions. To attend to the high demand for energy storage during obesity, the adipose tissue undergoes morphological, functional and molecular changes. Endoplasmic reticulum (ER) stress has been evidenced as a molecular hallmark of metabolic disorders. In this sense, the ER stress inhibitor tauroursodeoxycholic acid (TUDCA), a bile acid conjugated to taurine with chemical chaperone activity, has emerged as a therapeutic strategy to minimize adipose tissue dysfunction and metabolic alterations associated with obesity. In this review, we highlight the effects of TUDCA and receptors TGR5 and FXR on adipose tissue in the setting of obesity. TUDCA has been demonstrated to limit metabolic disturbs associated to obesity by inhibiting ER stress, inflammation, and apoptosis in adipocytes. The beneficial effect of TUDCA on perivascular adipose tissue (PVAT) function and adiponectin release may be related to cardiovascular protection in obesity, although more studies are needed to clarify the mechanisms. Therefore, TUDCA has emerged as a potential therapeutic strategy for obesity and comorbidities.

Amyloid Disassembly: What Can We Learn from Chaperones?

Protein aggregation and subsequent accumulation of insoluble amyloid fibrils with cross-β structure is an intrinsic characteristic of amyloid diseases, i.e., amyloidoses. Amyloid formation involves a series of on-pathway and off-pathway protein aggregation events, leading to mature insoluble fibrils that eventually accumulate in multiple tissues. In this cascade of events, soluble oligomeric species are formed, which are among the most cytotoxic molecular entities along the amyloid cascade. The direct or indirect action of these amyloid soluble oligomers and amyloid protofibrils and fibrils in several tissues and organs lead to cell death in some cases and organ disfunction in general. There are dozens of different proteins and peptides causing multiple amyloid pathologies, chief among them Alzheimer's, Parkinson's, Huntington's, and several other neurodegenerative diseases. Amyloid fibril disassembly is among the disease-modifying therapeutic strategies being pursued to overcome amyloid pathologies. The clearance of preformed amyloids and consequently the arresting of the progression of organ deterioration may increase patient survival and quality of life. In this review, we compiled from the literature many examples of chemical and biochemical agents able to disaggregate preformed amyloids, which have been classified as molecular chaperones, chemical chaperones, and pharmacological chaperones. We focused on their mode of action, chemical structure, interactions with the fibrillar structures, morphology and toxicity of the disaggregation products, and the potential use of disaggregation agents as a treatment option in amyloidosis.

Circulating oxylipin and bile acid profiles of dexmedetomidine, propofol, sevoflurane, and S-ketamine: a randomised controlled trial using tandem mass spectrometry

Background

This exploratory study aimed to investigate whether dexmedetomidine, propofol, sevoflurane, and S-ketamine affect oxylipins and bile acids, which are functionally diverse molecules with possible connections to cellular bioenergetics, immune modulation, and organ protection.

Methods

In this randomised, open-label, controlled, parallel group, Phase IV clinical drug trial, healthy male subjects (n=160) received equipotent doses (EC50 for verbal command) of dexmedetomidine (1.5 ng ml-1; n=40), propofol (1.7 μg ml-1; n=40), sevoflurane (0.9% end-tidal; n=40), S-ketamine (0.75 μg ml-1; n=20), or placebo (n=20). Blood samples for tandem mass spectrometry were obtained at baseline, after study drug administration at 60 and 130 min from baseline; 40 metabolites were analysed.

Results

Statistically significant changes vs placebo were observed in 62.5%, 12.5%, 5.0%, and 2.5% of analytes in dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively. Data are presented as standard deviation score, 95% confidence interval, and P-value. Dexmedetomidine induced wide-ranging decreases in oxylipins and bile acids. Amongst others, 9,10-dihydroxyoctadecenoic acid (DiHOME) -1.19 (-1.6; -0.78), P<0.001 and 12,13-DiHOME -1.22 (-1.66; -0.77), P<0.001 were affected. Propofol elevated 9,10-DiHOME 2.29 (1.62; 2.96), P<0.001 and 12,13-DiHOME 2.13 (1.42; 2.84), P<0.001. Analytes were mostly unaffected by S-ketamine. Sevoflurane decreased tauroursodeoxycholic acid (TUDCA) -2.7 (-3.84; -1.55), P=0.015.

Conclusions

Dexmedetomidine-induced oxylipin alterations may be connected to pathways associated with organ protection. In contrast to dexmedetomidine, propofol emulsion elevated DiHOMEs, oxylipins associated with acute respiratory distress syndrome, and mitochondrial dysfunction in high concentrations. Further research is needed to establish the behaviour of DIHOMEs during prolonged propofol/dexmedetomidine infusions and to verify the sevoflurane-induced reduction in TUDCA, a suggested neuroprotective agent.

Clinical trial registration

NCT02624401.

Liver Steatosis and Steatohepatitis Alter Bile Acid Receptors in Brain and Induce Neuroinflammation: A Contribution of Circulating Bile Acids and Blood-Brain Barrier

A tight relationship between gut-liver diseases and brain functions has recently emerged. Bile acid (BA) receptors, bacterial-derived molecules and the blood-brain barrier (BBB) play key roles in this association. This study was aimed to evaluate how non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) impact the BA receptors Farnesoid X receptor (FXR) and Takeda G-protein coupled receptor 5 (TGR5) expression in the brain and to correlate these effects with circulating BAs composition, BBB integrity and neuroinflammation. A mouse model of NAFLD was set up by a high-fat and sugar diet, and NASH was induced with the supplementation of dextran-sulfate-sodium (DSS) in drinking water. FXR, TGR5 and ionized calcium-binding adaptor molecule 1 (Iba-1) expression in the brain was detected by immunohistochemistry, while Zonula occludens (ZO)-1, Occludin and Plasmalemmal Vesicle Associated Protein-1 (PV-1) were analyzed by immunofluorescence. Biochemical analyses investigated serum BA composition, lipopolysaccharide-binding protein (LBP) and S100β protein (S100β) levels. Results showed a down-regulation of FXR in NASH and an up-regulation of TGR5 and Iba-1 in the cortex and hippocampus in both treated groups as compared to the control group. The BA composition was altered in the serum of both treated groups, and LBP and S100β were significantly augmented in NASH. ZO-1 and Occludin were attenuated in the brain capillary endothelial cells of both treated groups versus the control group. We demonstrated that NAFLD and NASH provoke different grades of brain dysfunction, which are characterized by the altered expression of BA receptors, FXR and TGR5, and activation of microglia. These effects are somewhat promoted by a modification of circulating BAs composition and by an increase in LBP that concur to damage BBB, thus favoring neuroinflammation.

Linking Nonalcoholic Fatty Liver Disease and Brain Disease: Focusing on Bile Acid Signaling

A metabolic illness known as non-alcoholic fatty liver disease (NAFLD), affects more than one-quarter of the world's population. Bile acids (BAs), as detergents involved in lipid digestion, show an abnormal metabolism in patients with NAFLD. However, BAs can affect other organs as well, such as the brain, where it has a neuroprotective effect. According to a series of studies, brain disorders may be extrahepatic manifestations of NAFLD, such as depression, changes to the cerebrovascular system, and worsening cognitive ability. Consequently, we propose that NAFLD affects the development of brain disease, through the bile acid signaling pathway. Through direct or indirect channels, BAs can send messages to the brain. Some BAs may operate directly on the central Farnesoid X receptor (FXR) and the G protein bile acid-activated receptor 1 (GPBAR1) by overcoming the blood-brain barrier (BBB). Furthermore, glucagon-like peptide-1 (GLP-1) and the fibroblast growth factor (FGF) 19 are released from the intestine FXR and GPBAR1 receptors, upon activation, both of which send signals to the brain. Inflammatory, systemic metabolic disorders in the liver and brain are regulated by the bile acid-activated receptors FXR and GPBAR1, which are potential therapeutic targets. From a bile acid viewpoint, we examine the bile acid signaling changes in NAFLD and brain disease. We also recommend the development of dual GPBAR1/FXR ligands to reduce side effects and manage NAFLD and brain disease efficiently.

Plasma glycocholic acid and linoleic acid identified as potential mediators of mitochondrial bioenergetics in Alzheimer's dementia

Mitochondrial bioenergetic alterations occur in the brain and peripheral cells of patients with Alzheimer's disease (AD). This study focuses on plasma circulating factors, namely lipids, as mediators of systemic bioenergetic differences in participants with normal cognition (NC), mild cognitive impairment (MCI), and dementia due to probable AD (DEM). We examined bioenergetic differences across cognitive groups by measuring the mitochondrial respiration of peripheral blood mononuclear cells (PBMCs) from 37 participants (12 NC, 12 MCI, 13 DEM). PBMC bioenergetics were lower in the DEM group compared to the NC group. To determine whether circulating factors can mediate bioenergetic differences according to cognitive status, we exposed naïve neuronal Neuro-2a (N2a) cells to plasma from each participant in vitro. N2a bioenergetics were lower following plasma exposure from DEM compared to NC group participants. Notably, PBMC Max and N2a Max positively correlated, suggesting that circulating factors modulate the bioenergetics of naïve N2a cells according to the bioenergetic capacity of donor primary PBMCs. To identify lipid metabolites that may contribute to bioenergetic differences between cognitive groups, we performed liquid chromatography-mass spectrometry to assess the abundance of individual lipid species and correlated PBMC and N2a bioenergetics. Glycocholic acid (GCA) positively correlated with PBMC and N2a bioenergetics, while linoleic acid (LA) was negatively correlated. These data suggest that GCA and LA may contribute to the stimulatory and inhibitory bioenergetics effects related to cognitive status. Post hoc analyses revealed that GCA abundance was lower by 52.9% in the DEM group compared to the NC group and that LA abundance was higher by 55.7% in the DEM group compared to the NC group. To validate these findings, we examined the abundance of GCA and LA in the larger, more diverse, parent cohort (n = 378) and found similar results; GCA abundance was lower by 29.7% in the DEM group compared to the NC group and LA abundance was higher by 17.8% in the DEM group compared to the NC group. These data demonstrate that circulating factors have a direct effect on mitochondrial bioenergetics and that individual circulating factors identified to be associated with mitochondrial function are differentially expressed in patients with dementia.

Implications of glial metabolic dysregulation in the pathophysiology of neurodegenerative diseases

Glial cells are the most abundant cells of the brain, outnumbering neurons. These multifunctional cells are crucial for maintaining brain homeostasis by providing trophic and nutritional support to neurons, sculpting synapses, and providing an immune defense. Glia are highly plastic and undergo both structural and functional alterations in response to changes in the brain microenvironment. Glial phenotypes are intimately regulated by underlying metabolic machinery, which dictates the effector functions of these cells. Altered brain energy metabolism and chronic neuroinflammation are common features of several neurodegenerative diseases. Microglia and astrocytes are the major glial cells fueling the ongoing neuroinflammatory process, exacerbating neurodegeneration. Distinct metabolic perturbations in microglia and astrocytes, including altered carbohydrate, lipid, and amino acid metabolism have been documented in neurodegenerative diseases. These disturbances aggravate the neurodegenerative process by potentiating the inflammatory activation of glial cells. This review covers the recent advances in the molecular aspects of glial metabolic changes in the pathophysiology of neurodegenerative diseases. Finally, we discuss studies exploiting glial metabolism as a potential therapeutic avenue in neurodegenerative diseases.

Gut Microbiome-Linked Metabolites in the Pathobiology of Major Depression With or Without Anxiety—A Role for Bile Acids

Background

The gut microbiome may play a role in the pathogenesis of neuropsychiatric diseases including major depressive disorder (MDD). Bile acids (BAs) are steroid acids that are synthesized in the liver from cholesterol and further processed by gut-bacterial enzymes, thus requiring both human and gut microbiome enzymatic processes in their metabolism. BAs participate in a range of important host functions such as lipid transport and metabolism, cellular signaling and regulation of energy homeostasis. BAs have recently been implicated in the pathophysiology of Alzheimer's and several other neuropsychiatric diseases, but the biochemical underpinnings of these gut microbiome-linked metabolites in the pathophysiology of depression and anxiety remains largely unknown.

Method

Using targeted metabolomics, we profiled primary and secondary BAs in the baseline serum samples of 208 untreated outpatients with MDD. We assessed the relationship of BA concentrations and the severity of depressive and anxiety symptoms as defined by the 17-item Hamilton Depression Rating Scale (HRSD₁₇) and the 14-item Hamilton Anxiety Rating Scale (HRSA-Total), respectively. We also evaluated whether the baseline metabolic profile of BA informs about treatment outcomes.

Results

The concentration of the primary BA chenodeoxycholic acid (CDCA) was significantly lower at baseline in both severely depressed (log₂ fold difference (LFD) = −0.48; p = 0.021) and highly anxious (LFD = −0.43; p = 0.021) participants compared to participants with less severe symptoms. The gut bacteria-derived secondary BAs produced from CDCA such as lithocholic acid (LCA) and several of its metabolites, and their ratios to primary BAs, were significantly higher in the more anxious participants (LFD's range = [0.23, 1.36]; p's range = [6.85E-6, 1.86E-2]). The interaction analysis of HRSD₁₇ and HRSA-Total suggested that the BA concentration differences were more strongly correlated to the symptoms of anxiety than depression. Significant differences in baseline CDCA (LFD = −0.87, p = 0.0009), isoLCA (LFD = −1.08, p = 0.016) and several BA ratios (LFD's range [0.46, 1.66], p's range [0.0003, 0.049]) differentiated treatment failures from remitters.

Conclusion

In patients with MDD, BA profiles representing changes in gut microbiome compositions are associated with higher levels of anxiety and increased probability of first-line treatment failure. If confirmed, these findings suggest the possibility of developing gut microbiome-directed therapies for MDD characterized by gut dysbiosis.

Tauroursodeoxycholic Acid Reduces Neuroinflammation but Does Not Support Long Term Functional Recovery of Rats with Spinal Cord Injury

The bile acid tauroursodeoxycholic acid (TUDCA) reduces cell death under oxidative stress and inflammation. Implants of bone marrow-derived stromal cells (bmSC) are currently under investigation in clinical trials of spinal cord injury (SCI). Since cell death of injected bmSC limits the efficacy of this treatment, the cytoprotective effect of TUDCA may enhance its benefit. We therefore studied the therapeutic effect of TUDCA and its use as a combinatorial treatment with human bmSC in a rat model of SCI. A spinal cord contusion injury was induced at thoracic level T9. Treatment consisted of i.p. injections of TUDCA alone or in combination with one injection of human bmSC into the cisterna magna. The recovery of motor functions was assessed during a surveillance period of six weeks. Biochemical and histological analysis of spinal cord tissue confirmed the anti-inflammatory activity of TUDCA. Treatment improved the recovery of autonomic bladder control and had a positive effect on motor functions in the subacute phase, however, benefits were only transient, such that no significant differences between vehicle and TUDCA-treated animals were observed 1–6 weeks after the lesion. Combinatorial treatment with TUDCA and bmSC failed to have an additional effect compared to treatment with bmSC only. Our data do not support the use of TUDCA as a treatment of SCI.

Poria cocos water-soluble polysaccharide modulates anxiety-like behavior induced by sleep deprivation by regulating the gut dysbiosis, metabolic disorders and TNF-α/NF-κB signaling pathway

Poria cocos (P. cocos) has been traditionally used as folk medicine and functional food in China for more than 2000 years. The water-soluble polysaccharide is the main component of P. cocos decoction. The effects and mechanisms of the water-soluble polysaccharide from P. cocos (PCWP) were investigated in chronic sleep deprivation (CSD)-induced anxiety in rats. CSD induced anxiety, gut dysbiosis, and inflammatory responses, and reduced neurotransmitter levels, whereas PCWP intervention ameliorated anxiety-like behaviors, increased the levels of 5-hydroxytryptamine, dopamine, norepinephrine, and γ-aminobutyric acid in the hypothalamus, regulated gastrointestinal peptide levels, reduced inflammatory factors, and inhibited the tumor necrosis factor (TNF)-α/nuclear factor (NF)-κB signaling pathway in rats with CSD. The changes in the intestinal flora composition were determined using 16S rDNA sequencing, and indicated that PCWP significantly improved species richness and diversity in the intestinal flora of rats with anxiety, and adjusted the abundance of the following dysregulated bacteria closer to that of the normal group: Rikenellaceae_RC9_gut_group, Ruminococcus, Prevotellaceae_UCG-001, Prevotellaceae_NK3B31_group, Fusicatenibacter. Metabolomics was used to analyze fecal samples to identify significantly altered metabolites in the PCWP-treated groups. Thirty-eight PCWP-related metabolites and four metabolic pathways such as sphingolipid metabolism, taurine and hypotaurine metabolism, vitamin B6 metabolism, and glycerophospholipid metabolism were explored. The results of serum metabolomics showed that 26 biomarkers were significantly changed after PCWP intervention compared with the model group. The regulatory effects of metabolic pathway enrichment on sphingolipid, phenylalanine, and taurine and hypotaurine metabolism, and validation results showed that PCWP intervention regulated the activity of enzymes involved in the above metabolic pathways. A strong correlation between intestinal bacteria and potential biomarkers was found. Our findings present new evidence supporting the potential effect of PCWP in preventing the progression of anxiety by inhibiting the TNF-α/NF-κB signaling pathway, alleviating metabolic disorders, and ameliorating the gut microflora imbalance.

The Role of Bile Acids in the Human Body and in the Development of Diseases

Bile acids are specific and quantitatively important organic components of bile, which are synthesized by hepatocytes from cholesterol and are involved in the osmotic process that ensures the outflow of bile. Bile acids include many varieties of amphipathic acid steroids. These are molecules that play a major role in the digestion of fats and the intestinal absorption of hydrophobic compounds and are also involved in the regulation of many functions of the liver, cholangiocytes, and extrahepatic tissues, acting essentially as hormones. The biological effects are realized through variable membrane or nuclear receptors. Hepatic synthesis, intestinal modifications, intestinal peristalsis and permeability, and receptor activity can affect the quantitative and qualitative bile acids composition significantly leading to extrahepatic pathologies. The complexity of bile acids receptors and the effects of cross-activations makes interpretation of the results of the studies rather difficult. In spite, this is a very perspective direction for pharmacology.

Endoplasmic Reticulum Stress and Its Role in Homeostasis and Immunity of Central and Peripheral Neurons

Neuronal cells are specialists for rapid transfer and translation of information. Their electrical properties relay on a precise regulation of ion levels while their communication via neurotransmitters and neuropeptides depends on a high protein and lipid turnover. The endoplasmic Reticulum (ER) is fundamental to provide these necessary requirements for optimal neuronal function. Accumulation of misfolded proteins in the ER lumen, reactive oxygen species and exogenous stimulants like infections, chemical irritants and mechanical harm can induce ER stress, often followed by an ER stress response to reinstate cellular homeostasis. Imbedded between glial-, endothelial-, stromal-, and immune cells neurons are constantly in communication and influenced by their local environment. In this review, we discuss concepts of tissue homeostasis and innate immunity in the central and peripheral nervous system with a focus on its influence on ER stress, the unfolded protein response, and implications for health and disease.

Neuroprotective Effects of Tauroursodeoxicholic Acid Involves Vascular and Glial Changes in Retinitis Pigmentosa Model

Purpose

Retinitis pigmentosa is primarily characterized by a massive photoreceptor loss. But a global retinal remodeling occurs in later stages of the disease. At that phase, glial cells and retinal vasculature are also strongly affected. The main aim of the present work is to assess if the bile acid Tauroursodeoxicholic acid (TUDCA), which has a demonstrated neuroprotective effect in numerous neurodegenerative diseases, is able to prevent glial and vascular degeneration in the P23H rat retina.

Methods

Homozygous P23H (line 3) animals were injected weekly with a TUDCA (500 mg/kg, i.p.) or vehicle solution, from the postnatal day (P) 21 to P120. Sprague-Dawley rats (SD) were used as control. Retinal cross-sections and wholemounts were immunostained using different glial and vascular markers and visualized with confocal microscopy. Retinal blood vessels were stained with nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry and retinal vascular networks were drawn by hand using a camera lucida.

Results

At P120, the photoreceptor degeneration observed in P23H rats was accompanied by a reduction in the vascular network density and complexity at the deep capillary plexus. In addition, astrocytes showed gliotic features and the outer processes of Müller cells displayed an aberrant distribution in ring-shaped structures. When treated with TUDCA, P23H rats displayed better-preserved vessels and capillary loops in the deep capillary plexus which are associated with the partial preservation of photoreceptors. TUDCA treatment also increased the number of astrocytes and reduced the presence of Müller cell process clusters in the outer retina.

Conclusion

This work suggests that, besides its neuroprotective effect on photoreceptor cells, TUDCA treatment also protects from vascular and glial degeneration, a fact that encourages the use of TUDCA as a powerful therapy for neurodegenerative diseases.

Metabolic Rewiring by Human Placenta-Derived Mesenchymal Stem Cell Therapy Promotes Rejuvenation in Aged Female Rats

Aging is a degenerative process involving cell function deterioration, leading to altered metabolic pathways, increased metabolite diversity, and dysregulated metabolism. Previously, we reported that human placenta-derived mesenchymal stem cells (hPD-MSCs) have therapeutic effects on ovarian aging. This study aimed to identify hPD-MSC therapy-induced responses at the metabolite and protein levels and serum biomarker(s) of aging and/or rejuvenation. We observed weight loss after hPD-MSC therapy. Importantly, insulin-like growth factor-I (IGF-I), known prolongs healthy life spans, were markedly elevated in serum. Capillary electrophoresis-time-of-flight mass spectrometry (CE-TOF/MS) analysis identified 176 metabolites, among which the levels of 3-hydroxybutyric acid, glycocholic acid, and taurine, which are associated with health and longevity, were enhanced after hPD-MSC stimulation. Furthermore, after hPD-MSC therapy, the levels of vitamin B6 and its metabolite pyridoxal 5′-phosphate were markedly increased in the serum and liver, respectively. Interestingly, hPD-MSC therapy promoted serotonin production due to increased vitamin B6 metabolism rates. Increased liver serotonin levels after multiple-injection therapy altered the expression of mRNAs and proteins associated with hepatocyte proliferation and mitochondrial biogenesis. Changes in metabolites in circulation after hPD-MSC therapy can be used to identify biomarker(s) of aging and/or rejuvenation. In addition, serotonin is a valuable therapeutic target for reversing aging-associated liver degeneration.

Distinct Bile Acid Signature in Parkinson's Disease With Mild Cognitive Impairment

BACKGROUNDS

Bile acid (BA) plays a crucial role in various neurodegenerative diseases, including Parkinson's disease (PD). However, no clinical evidence supports BA's potential role in patients with PD with mild cognitive impairment (PD-MCI).

OBJECTIVES

This study aimed at investigating the differential BA profile between patients with PD-MCI and those with normal cognitive function (PD-NC).

METHODS

Ultra-high performance liquid chromatography-MS/MS was applied for BA quantitation. After between-group differences of the BA profile were addressed, orthogonal projections to latent structures-discriminant analysis (OPLS-DA) and the area under the receiver-operating-characteristic curve (AUC-ROC) were implemented for further verification.

RESULTS

Lower levels of chenodeoxycholic acid (CDCA), cholic acid (CA), and ursodeoxycholic acid (UDCA) were significantly associated with PD-MCI (p < 0.01 for both; VIP ≈ 2.67, 1.66, and 1.26, respectively). AUC-ROC were 78.1, 74.2, and 74.5% for CDCA, CA, and UDCA, respectively.

CONCLUSION

CA, CDCA, and UDCA might be distinct BA signatures for patients with PD-MCI.

Taurolithocholic acid but not tauroursodeoxycholic acid rescues phagocytosis activity of bone marrow-derived macrophages under inflammatory stress

Spinal cord injury (SCI) causes cell death and consequently the breakdown of axons and myelin. The accumulation of myelin debris at the lesion site induces inflammation and blocks axonal regeneration. Hematogenous macrophages contribute to the removal of myelin debris. In this study, we asked how the inflammatory state of macrophages affects their ability to phagocytose myelin. Bone marrow‐derived macrophages (BMDM) and Raw264.7 cells were stimulated with lipopolysaccharides (LPS) or interferon gamma (IFNγ), which induce inflammatory stress, and the endocytosis of myelin was examined. We found that activation of the TLR4‐NFκB pathway reduced myelin uptake by BMDM, while IFNγ‐Jak/STAT1 signaling did not. Since bile acids regulate lipid metabolism and in some cases reduce inflammation, our second objective was to investigate whether myelin clearance could be improved with taurolithocholic acid (TLCA), tauroursodeoxycholic acid or hyodeoxycholic acid. In BMDM only TLCA rescued myelin phagocytosis, when this activity was suppressed by LPS. Inhibition of protein kinase A blocked the effect of TLCA, while an agonist of the farnesoid X receptor did not rescue phagocytosis, implicating TGR5‐PKA signaling in the effect of TLCA. To shed light on the mechanism, we measured whether TLCA affected the expression of CD36, triggering receptor on myeloid cells‐2 (TREM2), and Gas6, which are known to be involved in phagocytosis and affected by inflammatory stimuli. Concomitant with an increase in expression of tumour necrosis factor alpha, LPS reduced expression of TREM2 and Gas6 in BMDM, and TLCA significantly diminished this downregulation. These findings suggest that activation of bile acid receptors may be used to improve myelin clearance in neuropathologies.

Comprehensive 16S rDNA Sequencing and LC-MS/MS-Based Metabolomics to Investigate Intestinal Flora and Metabolic Profiles of the Serum, Hypothalamus and Hippocampus in p‑Chlorophenylalanine-Induced Insomnia Rats Treated with Lilium brownie

Gut microbiota homeostasis in the organism and insomnia have been reported to influence each other. In the study, a method of 16S rRNA gene sequencing combined with ultra-high performance liquid chromatography-mass/mass spectrometry was adopted to evaluate the effects of Lilium brownie (LB) on intestinal flora and metabolic profiles of serum, hypothalamus and hippocampus in insomnia rat induced by p‑chlorophenylalanine (PCPA). It was observed that the imbalance in the diversity and abundance of gut microbiota induced by PCPA was restored after LB intervention. Among these, the Porphyromonadaceae, Lactobacillus and Escherichia were significantly adjusted at the genus level by PCPA and LB, respectively. It was also found that the most of metabolic phenotypes in serum, hypothalamus and hippocampus perturbed by PCPA were regulated towards normal after LB intervention, especially 5-hydroxy-L-tryptophan of the hypothalamus involving in 5-HT metabolism. Moreover, the arachidonic acid metabolism in serum, hypothalamus and hippocampus, and the serotonergic synapse in hypothalamus and hippocampus were the most fundamentally and significantly affected pathways after LB intervention. The results of correlation analysis showed that several floras including Pseudoruegeria have an outstanding contribution to the change of differential metabolites. In brief, the results confirm that gut microbiota is significantly returned to normal and may interact with the corresponding metabolites to relieve insomnia under LB intervention.

Tauroursodeoxycholic acid alleviates secondary injury in spinal cord injury mice by reducing oxidative stress, apoptosis, and inflammatory response

Background

Tauroursodeoxycholic acid (TUDCA) is a hydrophilic bile acid derivative, which has been demonstrated to have neuroprotective effects in different neurological disease models. However, the effect and underlying mechanism of TUDCA on spinal cord injury (SCI) have not been fully elucidated. This study aims to investigate the protective effects of TUDCA in the SCI mouse model and the related mechanism involved.

Methods

The primary cortical neurons were isolated from E16.5 C57BL/6 mouse embryos. To evaluate the effect of TUDCA on axon degeneration induced by oxidative stress in vitro, the cortical neurons were treated with H₂O₂ with or without TUDCA added and immunostained with Tuj1. Mice were randomly divided into sham, SCI, and SCI+TUDCA groups. SCI model was induced using a pneumatic impact device at T9-T10 level of the vertebra. TUDCA (200 mg/kg) or an equal volume of saline was intragastrically administrated daily post-injury for 14 days.

Results

We found that TUDCA attenuated axon degeneration induced by H₂O₂ treatment and protected primary cortical neurons from oxidative stress in vitro. In vivo, TUDCA treatment significantly reduced tissue injury, oxidative stress, inflammatory response, and apoptosis and promoted axon regeneration and remyelination in the lesion site of the spinal cord of SCI mice. The functional recovery test revealed that TUDCA treatment significantly ameliorated the recovery of limb function.

Conclusions

TUDCA treatment can alleviate secondary injury and promote functional recovery by reducing oxidative stress, inflammatory response, and apoptosis induced by primary injury, and promote axon regeneration and remyelination, which could be used as a potential therapy for human SCI recovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02248-2.

Association of plasma and CSF cytochrome P450, soluble epoxide hydrolase, and ethanolamide metabolism with Alzheimer's disease

BACKGROUND

Alzheimer's disease, cardiovascular disease, and other cardiometabolic disorders may share inflammatory origins. Lipid mediators, including oxylipins, endocannabinoids, bile acids, and steroids, regulate inflammation, energy metabolism, and cell proliferation with well-established involvement in cardiometabolic diseases. However, their role in Alzheimer's disease is poorly understood. Here, we describe the analysis of plasma and cerebrospinal fluid lipid mediators in a case-control comparison of ~150 individuals with Alzheimer's disease and ~135 healthy controls, to investigate this knowledge gap.

METHODS

Lipid mediators were measured using targeted quantitative mass spectrometry. Data were analyzed using the analysis of covariates, adjusting for sex, age, and ethnicity. Partial least square discriminant analysis identified plasma and cerebrospinal fluid lipid mediator discriminates of Alzheimer's disease. Alzheimer's disease predictive models were constructed using machine learning combined with stepwise logistic regression.

RESULTS

In both plasma and cerebrospinal fluid, individuals with Alzheimer's disease had elevated cytochrome P450/soluble epoxide hydrolase pathway components and decreased fatty acid ethanolamides compared to healthy controls. Circulating metabolites of soluble epoxide hydrolase and ethanolamides provide Alzheimer's disease predictors with areas under receiver operator characteristic curves ranging from 0.82 to 0.92 for cerebrospinal fluid and plasma metabolites, respectively.

CONCLUSIONS

Previous studies report Alzheimer's disease-associated soluble epoxide hydrolase upregulation in the brain and that endocannabinoid metabolism provides an adaptive response to neuroinflammation. This study supports the involvement of P450-dependent and endocannabinoid metabolism in Alzheimer's disease. The results further suggest that combined pharmacological intervention targeting both metabolic pathways may have therapeutic benefits for Alzheimer's disease.

Effective sample preparation procedure for the analysis of free neutral steroids, free steroid acids and sterol sulfates in different tissues by GC-MS

Steroids play an important role in cell regulation and homeostasis. Many diseases like Alzheimer's disease or Smith-Lemli-Opitz syndrome are known to be associated with deviations in the steroid profile. Most published methods only allow the analysis of small subgroups of steroids and cannot give an overview of the total steroid profile. We developed and validated a method that allows the analysis of free neutral steroids, including intermediates of cholesterol biosynthesis, free oxysterols, C₁₉ and C₂₁ steroids, free steroid acids, including bile acids, and sterol sulfates using gas chromatography-mass spectrometry. Samples were analyzed in scan mode for screening purposes and in dynamic multiple reaction monitoring mode for highly sensitive quantitative analysis. The method was validated for mouse brain and liver tissue and consists of sample homogenization, lipid extraction, steroid group separation, deconjugation, derivatization and gas chromatography-mass spectrometry analysis. We applied the method on brain and liver samples of mice (10 months and 3 weeks old) and cultured N2a cells and report the endogenous concentrations of 29 physiological steroids.

Neuroactive Type-A γ-Aminobutyric Acid Receptor Allosteric Modulator Steroids from the Hypobranchial Gland of Marine Mollusk, Conus geographus

In a program to identify pain treatments with low addiction potential, we isolated five steroids, conosteroids A-E (1-5), from the hypobranchial gland of the mollusk Conus geographus. Compounds 1-5 were active in a mouse dorsal root ganglion (DRG) assay that suggested that they might be analgesic. A synthetic analogue 6 was used for a detailed pharmacological study. Compound 6 significantly increased the pain threshold in mice in the hot-plate test at 2 and 50 mg/kg. Compound 6 at 500 nM antagonizes type-A γ-aminobutyric acid receptors (GABA_ARs). In a patch-clamp experiment, out of the six subunit combinations tested, 6 exhibited subtype selectivity, most strongly antagonizing α₁β₁γ₂ and α₄β₃γ₂ receptors (IC₅₀ 1.5 and 1.0 μM, respectively). Although the structures of 1-6 differ from those of known neuroactive steroids, they are cell-type-selective modulators of GABA_ARs, expanding the known chemical space of neuroactive steroids.

Pharmacological and Metabolic Significance of Bile Acids in Retinal Diseases

Bile acids (BAs) are amphipathic sterols primarily synthesized from cholesterol in the liver and released in the intestinal lumen upon food intake. BAs play important roles in micellination of dietary lipids, stimulating bile flow, promoting biliary phospholipid secretion, and regulating cholesterol synthesis and elimination. Emerging evidence, however, suggests that, aside from their conventional biological function, BAs are also important signaling molecules and therapeutic tools. In the last decade, the therapeutic applications of BAs in the treatment of ocular diseases have gained great interest. Despite the identification of BA synthesis, metabolism, and recycling in ocular tissues, much remains unknown with regards to their biological significance in the eye. Additionally, as gut microbiota directly affects the quality of circulating BAs, their analysis could derive important information on changes occurring in this microenvironment. This review aims at providing an overview of BA metabolism and biological function with a focus on their potential therapeutic and diagnostic use for retinal diseases.

A combination of three plasma bile acids as a putative biomarker for schizophrenia

The aim of the present study is to determine whether plasma bile acids (BAs) could be used as an auxiliary diagnostic biomarker to distinguish patients with schizophrenia from healthy controls. Seventeen different BAs were quantitatively measured in plasma of 12 healthy participants and 12 patients with schizophrenia. Then, the data were subjected to correlation and linear discriminant analysis (LDA). The concentrations of cholic acid (CA), taurochenodeoxycholic acid (TCDCA) and taurodeoxycholic acid (TDCA) were significantly decreased in plasma of the schizophrenia patients. Correlation analysis showed the concentrations of CA, TCDCA and TDCA were negatively correlated with schizophrenia. In addition, LDA demonstrated that combination of CA, TCDCA and TDCA with a classification formula could predict correctly classified cases and the accuracy of prediction was up to 95.83%. Combination of the three BAs may be useful to diagnose schizophrenia in plasma samples.

Organ-organ communication: The liver's perspective

Communication between organs participates in most physiological and pathological events. Owing to the importance of precise coordination among the liver and virtually all organs in the body for the maintenance of homeostasis, many hepatic disorders originate from impaired organ-organ communication, resulting in concomitant pathological phenotypes of distant organs. Hepatokines are proteins that are predominantly secreted from the liver, and many hepatokines and several signaling proteins have been linked to diseases of other organs, such as the heart, muscle, bone, and eyes. Although liver-centered interorgan communication has been proposed in both basic and clinical studies, to date, the regulatory mechanisms of hepatokine production, secretion, and reciprocation with signaling factors from other organs are obscure. Whether other hormones and cytokines are involved in such communication also warrants investigation. Herein, we summarize the current knowledge of organ-organ communication phenotypes in a variety of diseases and the possible involvement of hepatokines and/or other important signaling factors. This provides novel insight into the underlying roles and mechanisms of liver-originated signal transduction and, more importantly, the understanding of disease in an integrative view.

The contribution of gut bacterial metabolites in the human immune signaling pathway of non-communicable diseases

The interaction disorder between gut microbiota and its host has been documented in different non-communicable diseases (NCDs) such as metabolic syndrome, neurodegenerative disease, and autoimmune disease. The majority of these altered interactions arise through metabolic cross-talk between gut microbiota and host immune system, inducing a low-grade chronic inflammation that characterizes all NCDs. In this review, we discuss the contribution of bacterial metabolites to immune signaling pathways involved in NCDs. We then review recent advances that aid to rationally design microbial therapeutics. A deeper understanding of these intersections between host and gut microbiota metabolism using metabolomics-based system biology platform promises to reveal the fundamental mechanisms that drive metabolic predispositions to disease and suggest new avenues to use microbial therapeutic opportunities for NCDs treatment and prevention. Abbreviations: NCDs: non-communicable disease, IBD: inflammatory bowel disease, IL: interleukin, T2D: type 2 diabetes, SCFAs: short-chain fatty acids, HDAC: histone deacetylases, GPCR: G-protein coupled receptors, 5-HT: 5-hydroxytryptamine receptor signaling, DCs: dendritic cells, IECs: intestinal epithelial cells, T-reg: T regulatory cell, NF-κB: nuclear factor κB, TNF-α: tumor necrosis factor alpha, Th: T helper cell, CNS: central nervous system, ECs: enterochromaffin cells, NSAIDs: non-steroidal anti-inflammatory drugs, AhR: aryl hydrocarbon receptor, IDO: indoleamine 2,3-dioxygenase, QUIN: quinolinic acid, PC: phosphatidylcholine, TMA: trimethylamine, TMAO: trimethylamine N-oxide, CVD: cardiovascular disease, NASH: nonalcoholic steatohepatitis, BAs: bile acids, FXR: farnesoid X receptor, CDCA: chenodeoxycholic acid, DCA: deoxycholic acid, LCA: lithocholic acid, UDCA: ursodeoxycholic acid, CB: cannabinoid receptor, COBRA: constraint-based reconstruction and analysis.

The Potential Mediation of the Effects of Physical Activity on Cognitive Function by the Gut Microbiome

The population of older adults is growing dramatically worldwide. As older adults are at greater risk of developing disorders associated with cognitive dysfunction (i.e., dementia), healthcare costs are expected to double by 2040. Evidence suggests dementia may be slowed or prevented by lifestyle interventions, including physical activity (PA). PA is associated with improved cognitive function and may reduce risk for dementia by mitigating known risk factors (i.e., cardiovascular diseases) and/or by enhancing neurochemical processes. An emerging area of research suggests the gut microbiome may have similar neuroprotective effects. Altering the gut microbiome has been found to target physiological processes associated with dementia risk, and it influences gut-brain-microbiome axis signaling, impacting cognitive functioning. The gut microbiome can be altered by several means (i.e., disease, diet, prebiotics, probiotics), including PA. As PA and the gut microbiome independently influence cognitive function and PA changes the composition of the gut microbiome, cognitive improvement due to PA may be partially mediated by the gut microbiome. The present article provides an overview of the literature regarding the complex associations among PA, cognitive function, and the gut microbiome, as well as their underlying biological mechanisms. A comprehensive, theoretical model integrating evidence for the potential mediation is proposed.

Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson's Disease

Parkinson’s disease (PD) exhibits systemic effects on the human metabolism, with emerging roles for the gut microbiome. Here, we integrate longitudinal metabolome data from 30 drug-naive, de novo PD patients and 30 matched controls with constraint-based modeling of gut microbial communities derived from an independent, drug-naive PD cohort, and prospective data from the general population. Our key results are (1) longitudinal trajectory of metabolites associated with the interconversion of methionine and cysteine via cystathionine differed between PD patients and controls; (2) dopaminergic medication showed strong lipidomic signatures; (3) taurine-conjugated bile acids correlated with the severity of motor symptoms, while low levels of sulfated taurolithocholate were associated with PD incidence in the general population; and (4) computational modeling predicted changes in sulfur metabolism, driven by A. muciniphila and B. wadsworthia, which is consistent with the changed metabolome. The multi-omics integration reveals PD-specific patterns in microbial-host sulfur co-metabolism that may contribute to PD severity.

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Longitudinal metabolomics reveal disturbed transsulfuration in Parkinson’s disease

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Metabolic modeling of gut microbiomes show altered microbial sulfur metabolism

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Changed microbial sulfur metabolism is linked to B. wadsworthia and A. muciniphila

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Taurine-conjugated bile acids are associated with incident Parkinson’s disease

Ursodeoxycholic acid augmentation in treatment-refractory schizophrenia: a case report

Background

Treatment-resistance is recognized as a significant dilemma in schizophrenia, which has been reported to involve approximately one-third of patients with schizophrenia.

Case presentation

This case report described a 12-week treatment course for a 39-year-old Persian man with treatment-refractory schizophrenia, who showed a significant improvement in terms of positive, negative, and cognitive symptoms after taking ursodeoxycholic acid 300 mg capsules twice a day. Also, ursodeoxycholic acid was well tolerated, and he did not exhibit any side effects during treatment, based on interview and physical examination.

Conclusion

Ursodeoxycholic acid augmentation seems to be an effective treatment strategy for patients with treatment-refractory schizophrenia. However, further investigations in this field need to be carried out through randomized controlled trials.

Analyzing the lncRNA, miRNA, and mRNA-associated ceRNA networks to reveal potential prognostic biomarkers for glioblastoma multiforme

Background

Glioblastoma multiforme (GBM) is the most seriously brain tumor with extremely poor prognosis. Recent research has demonstrated that competitive endogenous RNA (ceRNA) network which long noncoding RNAs (lncRNAs) act as microRNA (miRNA) sponges to regulate mRNA expression were closely related to tumor development. However, the regulatory mechanisms and functional roles of ceRNA network in the pathogenesis of GBM are remaining poorly understood.

Methods

In this study, we systematically analyzed the expression profiles of lncRNA and mRNA (GSE51146 dataset) and miRNA (GSE65626 dataset) from GEO database. Then, we constructed a ceRNA network with the dysregulated genes by bioinformatics methods. The TCGA and GSE4290 dataset were used to confirm the expression and prognostic value of candidate mRNAs.

Results

In total, 3413 differentially expressed lncRNAs and mRNAs, 305 differentially expressed miRNAs were indentified in GBM samples. Then a ceRNA network containing 3 lncRNAs, 5 miRNAs, and 60 mRNAs was constructed. The overall survival analysis of TCGA databases indicated that two mRNAs (C1s and HSD3B7) were remarkly related with the prognosis of GBM.

Conclusion

The ceRNA network may increase our understanding to the pathogenesis of GBM. In general, the candidate mRNAs from the ceRNA network can be predicted as new therapeutic targets and prognostic biomarkers for GBM.

Accelerated transsulfuration metabolically defines a discrete subclass of amyotrophic lateral sclerosis patients

Amyotrophic lateral sclerosis is a disease characterized by progressive paralysis and death. Most ALS-cases are sporadic (sALS) and patient heterogeneity poses challenges for effective therapies. Applying metabolite profiling on 77-sALS patient-derived-fibroblasts and 43-controls, we found ~25% of sALS cases (termed sALS-1) are characterized by transsulfuration pathway upregulation, where methionine-derived-homocysteine is channeled into cysteine for glutathione synthesis. sALS-1 fibroblasts selectively exhibited a growth defect under oxidative conditions, fully-rescued by N-acetylcysteine (NAC). [U–¹³C]-glucose tracing showed transsulfuration pathway activation with accelerated glucose flux into the Krebs cycle. We established a four-metabolite support vector machine model predicting sALS-1 metabotype with 97.5% accuracy. Both sALS-1 metabotype and growth phenotype were validated in an independent cohort of sALS cases. Importantly, plasma metabolite profiling identified a system-wide cysteine metabolism perturbation as a hallmark of sALS-1. Findings reveal that sALS patients can be stratified into distinct metabotypes with differential sensitivity to metabolic stress, providing novel insights for personalized therapy.

Structural and biochemical investigation of MARK4 inhibitory potential of cholic acid: Towards therapeutic implications in neurodegenerative diseases

Microtubule affinity regulating kinase (MARK4) is considered as a potential drug target for diabetes, cancer, and neurodegenerative diseases. Since the role of MARK4 in the phosphorylation of tau protein and subsequently Alzheimer's disease has been established, therefore, we have investigated the binding affinity and MARK4 inhibitory potential of cholic acid (CHA) using both computational and spectroscopic methods. Molecular docking suggested a strong binding of CHA to the functionally important residues of MARK4. We further performed 500 ns molecular dynamics simulation which suggested the MARK4-CHA system was quite stable throughout the simulation trajectory. CHA potential binds to the MARK4 with a binding constant (K) of 10⁷ M^-1 at 288 K. Further, MARK4 activity was inhibited by CHA with an IC₅₀ = 5.5 μM. Further insights into the thermodynamic parameters suggested that MARK4-CHA complex formation is driven by both electrostatic and van der Waals interactions. Overall study provides a rationale to use CHA in the drug development via MARK4 inhibition, towards possible therapeutic implications in neurodegenerative diseases.

Farnesoid X receptor knockout protects brain against ischemic injury through reducing neuronal apoptosis in mice

Background

Farnesoid X receptor (FXR) is a nuclear receptor that plays a critical role in controlling cell apoptosis in diverse diseases. Previous studies have shown that knocking out FXR improved cardiac function by reducing cardiomyocyte apoptosis in myocardial ischemic mice. However, the role of FXR after cerebral ischemia remains unknown. In this study, we explored the effects and mechanisms of FXR knockout (KO) on the functional recovery of mice post cerebral ischemia-reperfusion.

Methods

Adult male C57BL/6 wild type and FXR KO mice were subjected to 90-min transient middle cerebral artery occlusion (tMCAO). The mice were divided into five groups: sham, wild-type tMCAO, FXR KO tMCAO, wild-type tMCAO treated with calcium agonist Bayk8644, and FXR KO tMCAO treated with Bayk8644. FXR expression was examined using immunohistochemistry and Western blot. Brain infarct and brain atrophy volume were examined at 3 and 14 days after stroke respectively. Neurobehavioral tests were conducted up to 14 days after stroke. The protein levels of apoptotic factors (Bcl-2, Bax, and Cleaved caspase-3) and mRNA levels of pro-inflammatory factors (TNF-α, IL-6, IL-1β, IL-17, and IL-18) were examined using Western blot and RT-PCR. TUNEL staining and calcium imaging were obtained using confocal and two-photon microscopy.

Results

The expression of FXR was upregulated after ischemic stroke, which is located in the nucleus of the neurons. FXR KO was found to reduce infarct volume and promote neurobehavioral recovery following tMCAO compared to the vehicle. The expression of apoptotic and pro-inflammatory factors decreased in FXR KO mice compared to the control. The number of NeuN⁺/TUNEL⁺ cells declined in the peri-infarct area of FXR KO mice compared to the vehicle. We further demonstrated that inhibition of FXR reduced calcium overload and addition of ionomycin could reverse this neuroprotective effect in vitro. What is more, in vivo results showed that enhancement of intracellular calcium concentrations could aggravate ischemic injury and reverse the neuroprotective effect of FXR KO in mice.

Conclusions

FXR KO can promote neurobehavioral recovery and attenuate ischemic brain injury, inflammatory release, and neuronal apoptosis via reducing calcium influx, suggesting its role as a therapeutic target for stroke treatments.

Mitochondrial Dysfunctions: A Red Thread across Neurodegenerative Diseases

Mitochondria play a central role in a plethora of processes related to the maintenance of cellular homeostasis and genomic integrity. They contribute to preserving the optimal functioning of cells and protecting them from potential DNA damage which could result in mutations and disease. However, perturbations of the system due to senescence or environmental factors induce alterations of the physiological balance and lead to the impairment of mitochondrial functions. After the description of the crucial roles of mitochondria for cell survival and activity, the core of this review focuses on the "mitochondrial switch" which occurs at the onset of neuronal degeneration. We dissect the pathways related to mitochondrial dysfunctions which are shared among the most frequent or disabling neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's, Amyotrophic Lateral Sclerosis, and Spinal Muscular Atrophy. Can mitochondrial dysfunctions (affecting their morphology and activities) represent the early event eliciting the shift towards pathological neurobiological processes? Can mitochondria represent a common target against neurodegeneration? We also review here the drugs that target mitochondria in neurodegenerative diseases.

Serum bile acids profiling by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and its application on pediatric liver and intestinal diseases

Background

A method for bile acid profiling measuring 21 primary and secondary bile acids in serum samples was developed and validated with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sample preparation included spiking with internal standards followed by protein precipitation, centrifugation, drying under nitrogen gas and reconstitution. Extracted samples were injected onto a Phenomenex Kinetex C18 column (150 × 4.60 mm, 2.6 μm).

Methods

Data was collected with LC-MS/MS operated in negative ion mode with multiple reaction monitoring (MRM) and single reaction monitoring (SRM). The analytical run time was 12 min.

Results

The method showed excellent linearity with high regression coefficients (>0.99) over a range of 0.05 and 25 μM for all analytes tested. The method also showed acceptable intra-day and inter-day accuracy and precision. As a proof of concept, the analytical method was applied to patients with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), biliary atresia (BA), and necrotizing enterocolitis (NEC), and distinct bile acids profiles were demonstrated.

Conclusions

The method could be poised to identify possible biomarkers for non-invasive early diagnosis of these disorders.

Born to Protect: Leveraging BDNF Against Cognitive Deficit in Alzheimer's Disease

Alzheimer's disease is a chronic neurodegenerative devastating disorder affecting a high percentage of the population over 65 years of age and causing a relevant emotional, social, and economic burden. Clinically, it is characterized by a prominent cognitive deficit associated with language and behavioral impairments. The molecular pathogenesis of Alzheimer's disease is multifaceted and involves changes in neurotransmitter levels together with alterations of inflammatory, oxidative, hormonal, and synaptic pathways, which may represent a drug target for both prevention and treatment; however, an effective treatment for Alzheimer's disease still represents an unmet goal. As neurotrophic factors participate in the modulation of the above-mentioned pathways, they have been highlighted as critical contributors of Alzheimer's disease etiology, whose modulation might be beneficial for Alzheimer's disease. We focused on the neurotrophin brain-derived neurotrophic factor, providing several lines of evidence pointing to brain-derived neurotrophic factor as a plausible endophenotype of cognitive deficits in Alzheimer's disease, illustrating some of the most recent possibilities to modulate the expression of this neurotrophin in the brain in an attempt to ameliorate cognition and delay the progression of Alzheimer's disease. This review shows that otherwise disparate pharmacologic or non-pharmacologic approaches converge on brain-derived neurotrophic factor, providing a means whereby apparently unrelated medical approaches may nevertheless produce similar synaptic and cognitive outcomes in Alzheimer's disease pathogenesis, suggesting that brain-derived neurotrophic factor-based synaptic repair may represent a modifying strategy to ameliorate cognition in Alzheimer's disease.

Effect of Parkinson's disease and related medications on the composition of the fecal bacterial microbiota

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. PD patients suffer from gastrointestinal dysfunctions and alterations of the autonomous nervous system, especially its part in the gut wall, i.e., the enteric nervous system (ENS). Such alterations and functional gastrointestinal deficits often occur years before the classical clinical symptoms of PD appear. Until now, only little is known about PD-associated changes in gut microbiota composition and their potential implication in PD development. In order to increase knowledge in this field, fecal samples of 34 PD patients and 25 healthy, age-matched control persons were investigated. Here, the V4 and V5 hypervariable region of bacterial 16S rRNA genes was PCR-amplified and sequenced using an Ion Torrent PGM platform. Within the PD group, we observed a relative decrease in bacterial taxa which are linked to health-promoting, anti-inflammatory, neuroprotective or other beneficial effects on the epithelial barrier, such as Faecalibacterium and Fusicatenibacter. Both taxa were lowered in PD patients with elevated levels of the fecal inflammation marker calprotectin. In addition, we observed an increase in shares of the Clostridiales family XI and their affiliated members in these samples. Finally, we found that the relative abundances of the bacterial genera Peptoniphilus, Finegoldia, Faecalibacterium Fusicatenibacter, Anaerococcus, Bifidobacterium, Enterococcus, and Ruminococcus were significantly influenced by medication with L-dopa and entacapone, respectively. Our data confirm previously reported effects of COMT inhibitors on the fecal microbiota of PD patients and suggest a possible effect of L-dopa medication on the relative abundance of several bacterial genera.

Tauroursodeoxycholate-Bile Acid with Chaperoning Activity: Molecular and Cellular Effects and Therapeutic Perspectives

Tauroursodeoxycholic acid (TUDCA) is a naturally occurring hydrophilic bile acid that has been used for centuries in Chinese medicine. Chemically, TUDCA is a taurine conjugate of ursodeoxycholic acid (UDCA), which in contemporary pharmacology is approved by Food and Drug Administration (FDA) for treatment of primary biliary cholangitis. Interestingly, numerous recent studies demonstrate that mechanisms of TUDCA functioning extend beyond hepatobiliary disorders. Thus, TUDCA has been demonstrated to display potential therapeutic benefits in various models of many diseases such as diabetes, obesity, and neurodegenerative diseases, mostly due to its cytoprotective effect. The mechanisms underlying this cytoprotective activity have been mainly attributed to alleviation of endoplasmic reticulum (ER) stress and stabilization of the unfolded protein response (UPR), which contributed to naming TUDCA as a chemical chaperone. Apart from that, TUDCA has also been found to reduce oxidative stress, suppress apoptosis, and decrease inflammation in many in-vitro and in-vivo models of various diseases. The latest research suggests that TUDCA can also play a role as an epigenetic modulator and act as therapeutic agent in certain types of cancer. Nevertheless, despite the massive amount of evidence demonstrating positive effects of TUDCA in pre-clinical studies, there are certain limitations restraining its wide use in patients. Here, molecular and cellular modes of action of TUDCA are described and therapeutic opportunities and limitations of this bile acid are discussed.