Anti-Cholestatic Therapy with Obeticholic Acid Improves Short-Term Memory in Bile Duct-Ligated Mice

Spatial lipidomics reveals sphingolipid metabolism as anti-fibrotic target in the liver

BACKGROUND AND AIMS

Steatotic liver disease (SLD), which encompasses various causes of fat accumulation in the liver, is a major cause of liver fibrosis. Understanding the specific mechanisms of lipotoxicity, dysregulated lipid metabolism, and the role of different hepatic cell types involved in fibrogenesis is crucial for therapy development.

METHODS

We analysed liver tissue from SLD patients and 3 mouse models. We combined bulk/spatial lipidomics, transcriptomics, imaging mass cytometry (IMC) and analysis of published spatial and single-cell RNA sequencing (scRNA-seq) data to explore the metabolic microenvironment in fibrosis. Pharmacological inhibition of sphingolipid metabolism with myriocin, fumonisin B1, miglustat and D-PDMP was carried out in hepatic stellate cells (HSCs) and human precision cut liver slices (hPCLSs).

RESULTS

Bulk lipidomics revealed increased glycosphingolipids, ether lipids and saturated phosphatidylcholines in fibrotic samples. Spatial lipidomics detected >40 lipid species enriched within fibrotic regions, notably sphingomyelin (SM) 34:1. Using bulk transcriptomics (mouse) and analysis of published spatial transcriptomics data (human) we found that sphingolipid metabolism was also dysregulated in fibrosis at transcriptome level, with increased gene expression for ceramide and glycosphingolipid synthesis. Analysis of human scRNA-seq data showed that sphingolipid-related genes were widely expressed in non-parenchymal cells. By integrating spatial lipidomics with IMC of hepatic cell markers, we found excellent spatial correlation between sphingolipids, such as SM(34:1), and myofibroblasts. Inhibiting sphingolipid metabolism resulted in anti-fibrotic effects in HSCs and hPCLSs.

CONCLUSIONS

Our spatial multi-omics approach suggests cell type-specific mechanisms of fibrogenesis involving sphingolipid metabolism. Importantly, sphingolipid metabolic pathways are modifiable targets, which may have potential as an anti-fibrotic therapeutic strategy.

NR1H4 ameliorates Parkinson's disease via inhibiting astrocyte activation and neuroinflammation in a CEBPβ/NF-κB dependent manner

Parkinson's Disease (PD) is a degenerative disease driven by neuroinflammation. Nuclear receptor subfamily 1 group H member 4 (NR1H4), a nuclear receptor involved in metabolic and inflammatory regulation, is found to be widely expressed in central nervous system. Previous studies suggested the protective role of NR1H4 in various diseases related to inflammation, whether NR1H4 participates in PD progression remains unknown. To investigate the role of NR1H4 in neuroinflammation regulation, especially astrocyte activation during PD, siRNA and adenovirus were used to manipulate Nr1h4 expression. RNA-sequencing (RNA-seq), quantitative real-time PCR, enzyme-linked immunosorbent assay, Chromatin immunoprecipitation and western blotting were performed to further study the underlying mechanisms. We identified that NR1H4 was down-regulated during PD progression. In vitro experiments suggested that Nr1h4 knockdown led to inflammatory response, reactive oxygen species generation and astrocytes activation whereasNr1h4 overexpressionhad the opposite effects. The results of RNA-seq on astrocytes revealed that NR1H4 manipulated neuroinflammation in a CEBPβ/NF-κB dependent manner. Additionally, pharmacological activation of NR1H4 via Obeticholic acid ameliorated neuroinflammation and promoted neuronal survival. Our study first proved the neuroprotective effects of NR1H4against PD via inhibiting astrocyte activation and neuroinflammation in a CEBPβ/NF-κB dependent manner.

Age-related decline in the expression of BRG1, ATM and ATR are partially reversed by dietary restriction in the livers of female mice

BRG1 (Brahma-related gene 1) is a member of the SWI/SNF (switch/sucrose nonfermentable) chromatin remodeling complex which utilizes the energy from ATP hydrolysis for its activity. In addition to its role of regulating the expression of a vast array of genes, BRG1 mediates DNA repair upon genotoxic stress and regulates senescence. During organismal ageing, there is accumulation of unrepaired/unrepairable DNA damage due to progressive breakdown of the DNA repair machinery. The present study investigates the expression level of BRG1 as a function of age in the liver of 5- and 21-month-old female mice. It also explores the impact of dietary restriction on BRG1 expression in the old (21-month) mice. Salient findings of the study are: Real-time PCR and Western blot analyses reveal that BRG1 levels are higher in 5-month-old mice but decrease significantly with age. Dietary restriction increases BRG1 expression in the 21-month-old mice, nearly restoring it to the level observed in the younger group. Similar expression patterns are observed for DNA damage response genes ATM (Ataxia Telangiectasia Mutated) and ATR (Ataxia Telangiectasia and Rad3-related) with the advancement in age and which appears to be modulated by dietary restriction. BRG1 transcriptionally regulates ATM as a function of age and dietary restriction. These results suggest that BRG1, ATM and ATR are downregulated as mice age, and dietary restriction can restore their expression. This implies that dietary restriction may play a crucial role in regulating BRG1 and related gene expression, potentially maintaining liver repair and metabolic processes as mice age.

Validation of NBD-coupled taurocholic acid for intravital analysis of bile acid transport in liver and kidney of mice

Fluorophore-coupled bile acids (BA) represent an important tool for intravital analysis of BA flux in animal models of cholestatic diseases. However, addition of a fluorophore to a BA may alter transport properties. We developed and validated a 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole-coupled taurocholic acid (3β-NBD-TCA) as a probe for intravital analysis of BA homeostasis. We compared transport of 3β-NBD-TCA to [3H]-TCA in HEK293 cells stably expressing the mouse hepatic or renal BA carriers mNtcp or mAsbt, respectively. We also studied distribution kinetics intravitally in livers and kidneys of anesthetized wildtype and mOatp1a/1b cluster knockout mice (OatpKO) with and without administration of the Ntcp inhibitor Myrcludex B and the ASBT inhibitor AS0369. In vitro, 3β-NBD-TCA and [3H]-TCA showed comparable concentration- and time-dependent transport via mNtcp and mAsbt as well as similar inhibition kinetics for Myrcludex B and AS0369. Intravital analysis in the livers of wildtype and OatpKO mice revealed contribution of both mNtcp and mOatp1a/1b in the 3β-NBD-TCA uptake from the sinusoidal blood into hepatocytes. Combined deletion of mOatp1a/1b and inhibition of mNtcp by Myrcludex B blocked the uptake of 3β-NBD-TCA from sinusoidal blood into hepatocytes. This led to an increase of 3β-NBD-TCA signal in the systemic circulation including renal capillaries, followed by strong enrichment in a subpopulation of proximal renal tubular epithelial cells (TEC). The enrichment of 3β-NBD-TCA in TEC was strongly reduced by the systemic ASBT inhibitor AS0369. NBD-coupled TCA has similar transport kinetics as [3H]-TCA and can be used as a tool to study hepatorenal BA transport. See also the graphical abstract(Fig. 1).

Regulation of intestinal senescence during cholestatic liver disease modulates barrier function and liver disease progression

Background & Aims

Senescence has been reported to have differential functions in cholangiocytes and hepatic stellate cells (HSCs) during human and murine cholestatic disease, being detrimental in biliary cells and anti-fibrotic in HSCs. Cholestatic liver disease is associated with loss of intestinal barrier function and changes in the microbiome, the mechanistic cause of which is undetermined.

Methods

Intestinal samples were analysed from controls and patients with primary sclerosing cholangitis, as well as wild-type (WT) and p16-3MR transgenic mice. Cholestatic liver disease was induced by bile duct ligation (BDL) and DDC diet feeding. Fexaramine was used as an intestinal-restricted FXR agonist and antibiotics were given to eliminate the intestinal microbiome. Senescent cells were eliminated in p16-3MR mice with ganciclovir and in WT mice with the senolytic drug ABT-263. In vitro studies were done in intestinal CaCo-2 cells and organoids were generated from intestinal crypts isolated from mice.

Results

Herein, we show increased senescence in intestinal epithelial cells (IECs) in patients with primary sclerosing cholangitis and in mice after BDL and DDC diet feeding. Intestinal senescence was increased in response to reduced exposure to bile acids and increased presence of lipopolysaccharide in vitro and in vivo during cholestatic liver disease. Senescence of IECs was associated with lower proliferation but increased intestinal stem cell activation, as supported by increased organoid growth from intestinal stem cells. Elimination of senescent cells with genetic and pharmacological approaches exacerbated liver injury and fibrosis during cholestatic liver disease, which was associated with increased IEC apoptosis and permeability.

Conclusions

Senescence occurs in IECs during cholestatic disease and the elimination of senescent cells has a detrimental impact on the gut-liver axis. Our results point to cell-specific rather than systemic targeting of senescence as a therapeutic approach to treat cholestatic liver disease.

Impact and implications

Cholestatic liver disease associates with the dysregulation of intestinal barrier function, while the mechanisms mediating the disruption of the gut-liver axis remain largely undefined. Here, we demonstrate that senescence, a cellular response to stress, is activated in intestinal cells during cholestatic liver disease in humans and mice. Mechanistically, we demonstrate that the reduction of bile acids and the increased presence of bacterial products mediate the activation of intestinal senescence during cholestatic liver disease. Importantly, the elimination of these senescent cells promotes further damage to the intestine that aggravates liver disease, with increased tissue damage and fibrosis. Our results provide evidence that therapeutic strategies to treat cholestatic liver disease by eliminating senescent cells may have unwanted effects in the intestine and support the need to develop cell/organ-specific approaches.

Golexanolone improves fatigue, motor incoordination and gait and memory in rats with bile duct ligation

BACKGROUND AND AIMS

Many patients with the chronic cholestatic liver disease primary biliary cholangitis (PBC) show fatigue and cognitive impairment that reduces their quality of life. Likewise, rats with bile duct ligation (BDL) are a model of cholestatic liver disease. Current PBC treatments do not improve symptomatic alterations such as fatigue or cognitive impairment and new, more effective treatments are therefore required. Golexanolone reduces the potentiation of GABAA receptors activation by neurosteroids. Golexanolone reduces peripheral inflammation and neuroinflammation and improves cognitive and motor function in rats with chronic hyperammonemia. The aims of the present study were to assess if golexanolone treatment improves fatigue and cognitive and motor function in cholestatic BDL rats and if this is associated with improvement of peripheral inflammation, neuroinflammation, and GABAergic neurotransmission in the cerebellum.

METHODS

Rats were subjected to bile duct ligation. One week after surgery, oral golexanolone was administered daily to BDL and sham-operated controls. Fatigue was analysed in the treadmill, motor coordination in the motorater, locomotor gait in the Catwalk, and short-term memory in the Y-maze. We also analysed peripheral inflammation, neuroinflammation, and GABAergic neurotransmission markers by immunohistochemistry and Western blot.

RESULTS

BDL induces fatigue, impairs memory and motor coordination, and alters locomotor gait in cholestatic rats. Golexanolone improves these alterations, and this was associated with improvement of peripheral inflammation, neuroinflammation, and GABAergic neurotransmission in the cerebellum.

CONCLUSION

Golexanolone may have beneficial effects to treat fatigue, and motor and cognitive impairment in patients with the chronic cholestatic liver disease PBC.

Aging Biomarker Consortium, Jiang M, Zheng Z, Wang X, Chen Y, Qu J, Ding Q, Zhang W, Liu YS, Yang J, Tang W, Hou Y, He J, Wang L, Huang P, Li LC, He Z, Gao Q, Lu Q, Wei L, Wang YJ, Ju Z, Fan JG, Ruan XZ, Guan Y, Liu GH, Pei G, Li J, Wang Y. A biomarker framework for liver aging: the Aging Biomarker Consortium consensus statement

In human aging, liver aging per se not only increases susceptibility to liver diseases but also increases vulnerability of other organs given its central role in regulating metabolism. Total liver function tends to be well maintained in the healthy elderly, so liver aging is generally difficult to identify early. In response to this critical challenge, the Aging Biomarker Consortium of China has formulated an expert consensus on biomarkers of liver aging by synthesizing the latest scientific literature, comprising insights from both scientists and clinicians. This consensus provides a comprehensive assessment of biomarkers associated with liver aging and presents a systematic framework to characterize these into three dimensions: functional, imaging, and humoral. For the functional domain, we highlight biomarkers associated with cholesterol metabolism and liver-related coagulation function. For the imaging domain, we note that hepatic steatosis and liver blood flow can serve as measurable biomarkers for liver aging. Finally, in the humoral domain, we pinpoint hepatokines and enzymatic alterations worthy of attention. The aim of this expert consensus is to establish a foundation for assessing the extent of liver aging and identify early signs of liver aging-related diseases, thereby improving liver health and the healthy life expectancy of the elderly population.

The fibroblast growth factor system in cognitive disorders and dementia

Cognitive impairment is the core precursor to dementia and other cognitive disorders. Current hypotheses suggest that they share a common pathological basis, such as inflammation, restricted neurogenesis, neuroendocrine disorders, and the destruction of neurovascular units. Fibroblast growth factors (FGFs) are cell growth factors that play essential roles in various pathophysiological processes via paracrine or autocrine pathways. This system consists of FGFs and their receptors (FGFRs), which may hold tremendous potential to become a new biological marker in the diagnosis of dementia and other cognitive disorders, and serve as a potential target for drug development against dementia and cognitive function impairment. Here, we review the available evidence detailing the relevant pathways mediated by multiple FGFs and FGFRs, and recent studies examining their role in the pathogenesis and treatment of cognitive disorders and dementia.

Gut microbiota links with cognitive impairment in amyotrophic lateral sclerosis: a multi-omics study

Recently, cognitive impairments (CI) and behavioral abnormalities in patients with amyotrophic lateral sclerosis (ALS) have been reported. However, the underlying mechanisms have been poorly understood. In the current study, we explored the role of gut microbiota in CI of ALS patients. We collected fecal samples from 35 ALS patients and 35 healthy controls. The cognitive function of the ALS patients was evaluated using the Edinburgh Cognitive and Behavioral ALS Screen. We analyzed these samples by using 16S rRNA gene sequencing as well as both untargeted and targeted (bile acids) metabolite mapping between patients with CI and patients with normal cognition (CN). We found altered gut microbial communities and a lower ratio of Firmicutes/ Bacteroidetes in the CI group, compared with the CN group. In addition, the untargeted metabolite mapping revealed that 26 and 17 metabolites significantly increased and decreased, respectively, in the CI group, compared with the CN group. These metabolites were mapped to the metabolic pathways associated with bile acids. We further found that cholic acid and chenodeoxycholic acid were significantly lower in the CI group than in the CN group. In conclusion, we found that the gut microbiota and its metabolome profile differed between ALS patients with and without CI and that the altered bile acid profile in fecal samples was significantly associated with CI in ALS patients. These results need to be replicated in larger studies in the future.

Neurosteroid Activation of GABA-A Receptors: A Potential Treatment Target for Symptoms in Primary Biliary Cholangitis?

BACKGROUND AND AIMS

A third of patients with primary biliary cholangitis (PBC) experience poorly understood cognitive symptoms, with a significant impact on quality of life (QOL), and no effective medical treatment. Allopregnanolone, a neurosteroid, is a positive allosteric modulator of gamma-aminobutyricacid-A (GABA-A) receptors, associated with disordered mood, cognition, and memory. This study explored associations between allopregnanolone and a disease-specific QOL scoring system (PBC-40) in PBC patients.

METHOD

Serum allopregnanolone levels were measured in 120 phenotyped PBC patients and 40 age and gender-matched healthy controls. PBC subjects completed the PBC-40 at recruitment. Serum allopregnanolone levels were compared across PBC-40 domains for those with none/mild symptoms versus severe symptoms.

RESULTS

There were no overall differences in allopregnanolone levels between healthy controls (median = 0.03 ng/ml (IQR = 0.025)) and PBC patients (0.031 (0.42), p = 0.42). Within the PBC cohort, higher allopregnanolone levels were observed in younger patients (r (120) = -0.53, p < 0.001) but not healthy controls (r (39) = -0.21, p = 0.21). Allopregnanolone levels were elevated in the PBC-40 domains, cognition (u = 1034, p = 0.02), emotional (u = 1374, p = 0.004), and itch (u = 795, p = 0.03). Severe cognitive symptoms associated with a younger age: severe (50 (12)) vs. none (60 (13); u = 423 p = 0.001).

CONCLUSION

Elevated serum allopregnanolone is associated with severe cognitive, emotional, and itch symptoms in PBC, in keeping with its known action on GABA-A receptors. Existing novel compounds targeting allopregnanolone could offer new therapies in severely symptomatic PBC, satisfying a significant unmet need.