Not all (bile acids) who wander are lost: the first report of a patient with an isolated NTCP defect

Oleanolic acid improved intestinal immune function by activating and potentiating bile acids receptor signaling in E. coli-challenged piglets

BACKGROUND

Infection with pathogenic bacteria during nonantibiotic breeding is one of the main causes of animal intestinal diseases. Oleanolic acid (OA) is a pentacyclic triterpene that is ubiquitous in plants. Our previous work demonstrated the protective effect of OA on intestinal health, but the underlying molecular mechanisms remain unclear. This study investigated whether dietary supplementation with OA can prevent diarrhea and intestinal immune dysregulation caused by enterotoxigenic Escherichia coli (ETEC) in piglets. The key molecular role of bile acid receptor signaling in this process has also been explored.

RESULTS

Our results demonstrated that OA supplementation alleviated the disturbance of bile acid metabolism in ETEC-infected piglets (P < 0.05). OA supplementation stabilized the composition of the bile acid pool in piglets by regulating the enterohepatic circulation of bile acids and significantly increased the contents of UDCA and CDCA in the ileum and cecum (P < 0.05). This may also explain why OA can maintain the stability of the intestinal microbiota structure in ETEC-challenged piglets. In addition, as a natural ligand of bile acid receptors, OA can reduce the severity of intestinal inflammation and enhance the strength of intestinal epithelial cell antimicrobial programs through the bile acid receptors TGR5 and FXR (P < 0.05). Specifically, OA inhibited NF-κB-mediated intestinal inflammation by directly activating TGR5 and its downstream cAMP-PKA-CREB signaling pathway (P < 0.05). Furthermore, OA enhanced CDCA-mediated MEK-ERK signaling in intestinal epithelial cells by upregulating the expression of FXR (P < 0.05), thereby upregulating the expression of endogenous defense molecules in intestinal epithelial cells.

CONCLUSIONS

In conclusion, our findings suggest that OA-mediated regulation of bile acid metabolism plays an important role in the innate immune response, which provides a new diet-based intervention for intestinal diseases caused by pathogenic bacterial infections in piglets.

Bile acids induce Ca2+ signaling and membrane permeabilizations in vagal nodose ganglion neurons

Bile acids (BAs) play an important role in the digestion of dietary fats and act as signaling molecules. However, due to their solubilizing properties, high concentrations in the gut may negatively affect gut epithelium and possibly afferent fibers innervating the gastrointestinal tract (GI). To determine the effect of BAs on intracellular Ca²⁺ and membrane permeabilization we tested a range of concentrations of two BAs on vagal nodose ganglion (NG) neurons, Chinese Hamster Ovary (CHO), and PC12 cell lines. NG explants from mice were drop-transduced with the genetically encoded Ca²⁺ indicator AAV9-Syn-jGCaMP7s and used to measure Ca²⁺ changes upon application of deoxycholic acid (DCA) and taurocholic acid (TCA). We found that both BAs induced a Ca²⁺ increase in NG neurons in a dose-dependent manner. The DCA-induced Ca²⁺ increase was dependent on intracellular Ca²⁺ stores. NG explants, with an intact peripheral part of the vagus nerve, showed excitation of NG neurons in nerve field recordings upon exposure to DCA. The viability of NG neurons at different BA concentrations was determined, and compared to CHO and PC12 cells lines using propidium iodide labeling, showing threshold concentrations of BA-induced cell death at 400–500 μM. These observations suggest that BAs act as Ca²⁺-inducing signaling molecules in vagal sensory neurons at low concentrations, but induce cell death at higher concentrations, which may occur during inflammatory bowel diseases.

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Intracellular Ca²⁺ is measured in hundreds of explant vagal sensory neurons using jGCaMP7s.

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Bile acids deoxycholic acid and taurocholic acid induce a Ca²⁺ increase in vagal sensory neurons.

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Deoxycholic acid -induced Ca²⁺ increase is dependent on intracellular Ca²⁺ stores.

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Bile acid concentrations above 400–500 μM permeabilize the membrane inducing cell death.

Clinical characterization of NTCP deficiency in paediatric patients : A case-control study based on SLC10A1 genotyping analysis

Na⁺ -taurocholate cotransporting polypeptide deficiency (NTCPD) is a newly described disorder arising from biallelic mutations of the SLC10A1 gene. As a result of a lack of compelling evidence from case-control studies, its genotypic and phenotypic features remain open for in-depth investigation. This study aimed to explore the genotypic and clinical phenotypic characteristics of paediatric patients with NTCPD. The SLC10A1 genotypes of all NTCPD patients were confirmed by screening for the prevalent variant c.800C>T and Sanger sequencing when necessary. The clinical presentations and laboratory changes were collected, reviewed and analysed, and then qualitatively and quantitatively compared with the relevant controls. A total of 113 paediatric NTCPD patients were diagnosed while c.374dupG and c.682_683delCT were detected as two novel pathogenic mutations. Hypercholanemia was observed in 99.12% of the patients. Indirect hyperbilirubinemia in affected neonates exhibited higher positive rates in comparison to controls. Moreover, transient cholestatic jaundice, elevated liver enzymes and 25-hydroxyvitamin D (Vit D) deficiency during early infancy were more commonly observed in patients than in controls. All NTCPD patients exhibited favourable clinical outcomes as a result of symptomatic and supportive treatment. The findings enriched the SLC10A1 mutation spectrum and provided comprehensive insights into the phenotypic characteristics of NTCPD. NTCPD should be considered and SLC10A1 gene should be analysed in patients with above age-dependent clinical features. Furthermore, over investigation and intervention should be avoided in the management of NTCPD patients.

Clinical features of sodium-taurocholate cotransporting polypeptide deficiency in pediatric patients: case series and literature review

Sodium-taurocholate cotransporting polypeptide (NTCP) deficiency is a newly reported hereditary bile acid metabolic disease. Here we describe the clinical characteristics of 12 cases of pediatric NTCP deficiency, as well as review 60 previously reported cases in the literature in order to provide better guidance for pediatricians. The clinical records, laboratory and imaging data were collected of 12 cases who were treated at the pediatric infectious disease department of the West China Second University Hospital of Sichuan University, China, from December 2018 to July 2020. PubMed and Wanfang databases were searched and 11 studies including 60 pediatric NTCP deficiency patients from January 2015 to November 2020 were retrieved. In our center, there were 4 girls and 8 boys, with a median age at admission of 9.9 months (range, 2.2 to 70 months). Six patients (50%) had prolonged neonatal jaundice. All of the patients (12/12; 100%) had normal growth and development. The reason for the first visit was prolonged neonatal jaundice (4/12, 33.3%), non-liver related diseases (6/12, 50%) and routine checkup (2/12, 16.7%). Hypercholanemia was documented in 12/12 (100%), elevated aspartate aminotransferase (AST) in 6/12 (50%), and elevated alanine aminotransferase (ALT) in 1/12 (8.3%). All of the patients (12/12; 100%) had homozygous mutations of c.800C>T in SLC10A1. Sixty patients (22 girls and 38 boys) were included in the literature review; 36 (60%) had hyperbilirubinemia after 1 month. The reasons for testing for hypercholanemia were identified in 47/60 cases, and included prolonged neonatal jaundice and neonatal transient cholestasis in 26 (26/47, 55.3%); non-liver related diseases in 14 (14/47, 29.8%); routine medical examination in 3 (3/14, 6.4%); volunteer recruitment in 1 (1/14, 7.1%); dark urine in 1 (1/47, 2.1%). Hypercholanemia was confirmed in 60/60 (100%); 31 (51.7%) had elevated AST, and 10 (16.7%) had elevated ALT. Among 59 Chinese patients, 52 (88.1%) had homozygous mutations of c.800C>T in SLC10A1. The most common symptom of pediatric NTCP deficiency is jaundice. NTCP deficiency can also be detected during routine check-ups. The common biochemical features are hypercholanemia and elevated AST. Screening for c.800C>T mutation in SLC10A1 is useful for primary genetic screening in Chinese infants with persistent hypercholanemia after infectious, structural, and immunological factors are excluded.

Metabolic consequences of ileal interruption of the enterohepatic circulation of bile acids

The enterohepatic circulation of bile acids comprises a tightly regulated process of hepatic bile acid secretion, intestinal reabsorption and transport back to the liver. Disruption of this process has significant consequences for gastrointestinal, liver and whole body homeostasis and therefore offers opportunities for therapeutic intervention. In this review we discuss the effects of (pharmacological) interruption of the enterohepatic circulation at different levels. Recently, several studies have been published on ileal interruption of the enterohepatic circulation of bile acids, targeting the apical-sodium dependent bile acid transporter (ASBT, SLC10A2), as therapy for various diseases. However, ambiguous results have been reported and in-depth mechanistic insights are lacking. Here we discuss these novel studies and review the current knowledge on the consequences of ASBT inhibition and its potential effects on physiology and metabolism.

Sodium Taurocholate Cotransporting Polypeptide (NTCP) Deficiency Hidden Behind Citrin Deficiency in Early Infancy: A Report of Three Cases

Sodium taurocholate cotransporting polypeptide (NTCP), a carrier protein encoded by the gene SLC10A1, is expressed in the basolateral membrane of the hepatocyte to uptake bile acids from plasma. As a new inborn error of bile acid metabolism, NTCP deficiency remains far from being well understood in terms of the clinical and molecular features. Citrin deficiency is a well-known autosomal recessive disease arising from SLC25A13 mutations, and in neonates or infants, this condition presents as transient intrahepatic cholestasis which usually resolves before 1 year of age. All the three patients in this paper exhibited cholestatic jaundice and elevated total bile acids in their early infancy, which were attributed to citrin deficiency by SLC25A13 genetic analysis. In response to feeding with lactose-free and medium-chain triglycerides-enrich formula, their clinical and laboratory presentations disappeared gradually while the hypercholanemia persisted, even beyond 1 year of age. On subsequent SLC10A1 analysis, they were all homozygous for the well-known pathogenic variant c.800C > T (p.Ser267Phe), and NTCP deficiency was thus definitely diagnosed. The findings in this paper indicated that NTCP deficiency could be covered up by citrin deficiency during early infancy; however, in citrin-deficient patients with intractable hypercholanemia following resolved cholestatic jaundice, NTCP deficiency should be taken into consideration.

Organic solute transporter-β (SLC51B) deficiency in two brothers with congenital diarrhea and features of cholestasis

Primary bile acid malabsorption is associated with congenital diarrhea, steatorrhea, and a block in the intestinal return of bile acids in the enterohepatic circulation. Mutations in the ileal apical sodium-dependent bile acid transporter (ASBT; SLC10A2) can cause primary bile acid malabsorption but do not appear to account for most familial cases. Another major transporter involved in the intestinal reclamation of bile acids is the heteromeric organic solute transporter alpha-beta (OSTα-OSTβ; SLC51A-SLC51B), which exports bile acid across the basolateral membrane. Here we report the first patients with OSTβ deficiency, clinically characterized by chronic diarrhea, severe fat soluble vitamin deficiency, and features of cholestatic liver disease including elevated serum gamma-glutamyltransferase activity. Whole exome sequencing revealed a homozygous single nucleotide deletion in codon 27 of SLC51B, resulting in a frameshift and premature termination at codon 50. Functional studies in transfected cells showed that the SLC51B mutation resulted in markedly reduced taurocholic acid uptake activity and reduced expression of the OSTα partner protein.

CONCLUSION

The findings identify OSTβ deficiency as a cause of congenital chronic diarrhea with features of cholestatic liver disease. These studies underscore OSTα-OSTβ's key role in the enterohepatic circulation of bile acids in humans. (Hepatology 2017).

Hypothalamus-Pituitary-Adrenal Dysfunction in Cholestatic Liver Disease

The Hypothalamic-Pituitary-Adrenal (HPA) axis has an important role in maintaining the physiological homeostasis in relation to external and internal stimuli. The HPA axis dysfunctions were extensively studied in neuroendocrine disorders such as depression and chronic fatigue syndrome but less so in hepatic cholestasis, cirrhosis or other liver diseases. The HPA axis controls many functions of the liver through neuroendocrine forward signaling pathways as well as negative feedback mechanisms, in health and disease. This review describes cell and molecular mechanisms of liver and HPA axis physiology and pathology. Evidence is presented from clinical and experimental model studies, demonstrating that dysfunctions of HPA axis are correlated with liver cholestatic disorders. The functional interactions of HPA axis with the liver and immune system in cases of bacterial and viral infections are also discussed. Proinflammatory cytokines stimulate glucocorticoid (GC) release by adrenals but they also inhibit bile acid (BA) efflux from liver. Chronic hepatic inflammation leads to cholestasis and impaired GC metabolism in the liver, so that HPA axis becomes depressed. Recently discovered interactions of GC with self-oscillating transcription factors that generate circadian rhythms of gene expression in brain and liver, in the context of GC replacement therapies, are also outlined.

Monozygotic Twins Suffering From Sodium Taurocholate Cotransporting Polypeptide Deficiency: A Case Report

Sodium taurocholate cotransporting polypeptide (NTCP) is a carrier protein encoded by the human SLC10A1 gene, acting as the principal transporter of conjugated bile salts from the plasma into hepatocytes. Although NTCP was cloned as early as in 1994 and its function has been studied extensively, clinical description of NTCP deficiency remains rather limited thus far. The patients in this paper were 2 female monozygotic twins, who were referred to our hospital at the age 2 years with the complaint of persistently-raised total bile acids (TBA) for 21 months. At age 3 months, they were both diagnosed to have cholestatic liver disease due to raised serum TBA and direct bilirubin (DBIL) with the fraction >20% of the elevated total bilirubin (TBIL). Thereafter, their jaundice subsided and the DBIL levels recovered gradually, while serum TBA remained raised persistently. In view of their refractory hypercholanemia but negative symptoms and signs, SLC10A1 genetic analysis was performed for all family members to evaluate the possibility of NTCP deficiency. As a result, the twins were both homozygotes, while the parents, carriers, of the reportedly pathogenic variant c.800C>T (p.Ser267Phe). These findings suggested that NTCP deficiency may be a unique genetic factor causing transient cholestasis in early infancy, as well as, persistent hypercholanemia in pediatric patients.

Sodium taurocholate cotransporting polypeptide (NTCP) deficiency: Identification of a novel SLC10A1 mutation in two unrelated infants presenting with neonatal indirect hyperbilirubinemia and remarkable hypercholanemia

Sodium taurocholate cotransporting polypeptide (NTCP) is encoded by the gene SLC10A1 and expressed in the basolateral membrane of the hepatocyte, functioning to uptake bile acids from plasma. Although SLC10A1 has been cloned and NTCP function studied intensively for years, clinical description of NTCP deficiency remains rather limited. This study reported the genotypic and phenotypic features of two neonatal patients with NTCP deficiency. They both presented with neonatal indirect hyperbilirubinemia and remarkable hypercholanemia, and harbored the SLC10A1 variants c.800C>T (p.S267F) and c.263T>C (p.I88T). On genetic analysis of the two family trios, the latter missense variant was detected in trans with the former, a reported loss-of-function variant. Having not been reported in any databases, the c.263T>C (p.I88T) variant demonstrated an allele frequency of 0.67% (1/150) in healthy controls. Moreover, this variant involved a relatively conservative amino acid, and was predicted to be pathogenic or deleterious by changing the conformation of the NTCP molecule. In conclusion, the novel variant c.263T>C (p.I88T) in this study enriched the SLC10A1 mutation spectrum; the clinical findings lent support to the primary role of NTCP in hepatic bile acid clearance, and suggested that NTCP deficiency might be a contributing factor for the development of neonatal indirect hyperbilirubinemia.

Homozygous p.Ser267Phe in SLC10A1 is associated with a new type of hypercholanemia and implications for personalized medicine

SLC10A1 codes for the sodium-taurocholate cotransporting polypeptide (NTCP), which is a hepatocellular transporter for bile acids (BAs) and the receptor for hepatitis B and D viruses. NTCP is also a target of multiple drugs. We aimed to evaluate the medical consequences of the loss of function mutation p.Ser267Phe in SLC10A1. We identified eight individuals with homozygous p.Ser267Phe mutation in SLC10A1 and followed up for 8–90 months. We compared their total serum BAs and 6 species of BAs with 170 wild-type and 107 heterozygous healthy individuals. We performed in-depth medical examinations and exome sequencing in the homozygous individuals. All homozygous individuals had persistent hypercholanemia (P = 5.8 × 10^–29). Exome sequencing excluded the involvement of other BA metabolism-associated genes in the hypercholanemia. Although asymptomatic, all individuals had low vitamin D levels. Of six adults that were subjected to bone mineral density analysis, three presented with osteoporosis/osteopenia. Sex hormones and blood lipids were deviated in all subjects. Homozygosity of p.Ser267Phe in SLC10A1 is associated with asymptomatic hypercholanemia. Individuals with homozygous p.Ser267Phe in SLC10A1 are prone to vitamin D deficiency, deviated sex hormones and blood lipids. Surveillance of these parameters may also be needed in patients treated with drugs targeting NTCP.

[Sodium taurocholate cotransporting polypeptide deficiency manifesting as cholestatic jaundice in early infancy: a complicated case study]

Sodium taurocholate cotransporting polypeptide (NTCP) deficiency is caused by SLC10A1 mutations impairing the NTCP function to uptake plasma bile salts into the hepatocyte. Thus far, patients with NTCP deficiency were rarely reported. The patient in this paper was a 5-month-19-day male infant with the complaint of jaundiced skin and sclera for 5.5 months as well as abnormal liver function revealed over 4 months. His jaundice was noticed on the second day after birth, and remained visible till his age of 1 month and 13 days, when a liver function test unveiled markedly elevated total, direct and indirect bilirubin as well as total bile acids (TBA). Cholestatic liver disease was thus diagnosed. Due to unsatisfactory response to medical treatment, the patient underwent exploratory laparotomy, cholecystostomy and cholangiography when aged 2 months. This revealed inspissated bile but unobstructed bile ducts. Thereafter, his jaundice subsided, but the aminotransferases and TBA levels gradually rose. Of note, his mother also had mildly elevated plasma TBA. Since the etiology was unclear, no specific medication was introduced. The infant has been followed up over 2 years. The aminotransferases recovered gradually, but TBA levels fluctuated within 23.3-277.7 μmol/L (reference range: 0-10 μmol/L). On SLC10A1 genetic analysis at 2 years and 9 months, both the infant and his mother proved to be homozygous for a pathogenic variant c.800C>T(p.S267F), and NTCP deficiency was thus definitely diagnosed. The findings suggest that, although only mildly increased plasma TBA is presented in adults with NTCP deficiency, pediatric patients with this disorder exhibit persistent and remarkable hypercholanemia, and some patients might manifest as cholestatic jaundice in early infancy.

Clinical and molecular study of a pediatric patient with sodium taurocholate cotransporting polypeptide deficiency

The human solute carrier family 10 member 1 (SLC10A1) gene encodes sodium taurocholate cotransporting polypeptide (NTCP), the principal transporter of conjugated bile salts from the plasma into hepatocytes. Although the function of NTCP has been studied extensively and a number of SLC10A1 variations have been identified in humans, information regarding NTCP deficiency is limited. To date, only one patient with NTCP deficiency has been described; however, in the present study a pediatric patient who experienced intractable and striking hypercholanemia is presented. Analysis of the SLC10A1 gene in the patient revealed a homozygous p.Ser267Phe (c.800C>T) variation, which proved to be a single-nucleotide polymorphism (SNP) in the allele frequency of 4.7% of healthy controls. This variation involved a conserved amino acid residue on the orthologous alignment that was predicted to be ‘disease-causing’ by functional analysis using a number of bioinformatic tools. Next generation sequencing was performed; however, no other genetic causes were identified that would affect the bile acid homeostasis in the patient. Moreover, an adult, with the same genotype as the pediatric patient, was identified for the first time as experiencing mild hypercholanemia. The molecular and clinical findings in the present study suggest, for the first time, that there is an association between p.Ser267Phe SNP and hypercholanemia, and this information may be used to clinically identify NTCP deficiency worldwide.

Ginseng alleviates cyclophosphamide-induced hepatotoxicity via reversing disordered homeostasis of glutathione and bile acid

Cyclophosphamide (CP), a chemotherapeutic agent, is restricted due to its side effects, especially hepatotoxicity. Ginseng has often been clinically used with CP in China, but whether and how ginseng reduces the hepatotoxicity is unknown. In this study, the hepatoprotective effects and mechanisms under the combined usage were investigated. It was found that ginseng could ameliorate CP-induced elevations of ALP, ALT, ALS, MDA and hepatic deterioration, enhance antioxidant enzymes’ activities and GSH’s level. Metabolomics study revealed that 33 endogenous metabolites were changed by CP, 19 of which were reversed when ginseng was co-administrated via two main pathways, i.e., GSH metabolism and primary bile acids synthesis. Furthermore, ginseng could induce expression of GCLC, GCLM, GS and GST, which associate with the disposition of GSH, and expression of FXR, CYP7A1, NTCP and MRP 3, which play important roles in the synthesis and transport of bile acids. In addition, NRF 2, one of regulatory elements on the expression of GCLC, GCLM, GS, GST, NTCP and MRP3, was up-regulated when ginseng was co-administrated. In conclusion, ginseng could alleviate CP-induced hepatotoxicity via modulating the disordered homeostasis of GSH and bile acid, which might be mediated by inducing the expression of NRF 2 in liver.