Bilirubin in the Liver-Gut Signaling Axis

Early-life infections in association with development of atopic dermatitis in infancy and early childhood: A nationwide nested case-control study

BACKGROUND

Microbial dysbiosis has been implicated in the development of atopic dermatitis (AD). The risk of development of AD following early-life infections remains unclear.

OBJECTIVE

To investigate the impact of early-life infections on AD development.

METHODS

This population-based nested case-control study was conducted using the Taiwan's National Health Insurance Research Database. A total of 5,454 AD patients and 16,362 control subjects without AD were identified, for the period 1997 to 2013. Demographic characteristics, comorbidities, and maternal factors were compared. Adjusted odds ratio (aOR) was calculated to examine the associations between early-life infections and subsequent AD by conditional stepwise logistic regression analysis.

RESULTS

Mean age was 2.6±2.9 years in both groups. Overall infections (41.8% vs 28.9%) before the diagnosis of AD were more common in AD patients than in control subjects (p<.001). Infectious diseases (aOR, 1.40; 95% confidence interval [CI], 1.29-1.51), skin infections (aOR, 1.55; 95% CI, 1.40-1.71) and systemic antibiotic exposure (aOR 1.67, 95% CI 1.55-1.79) before AD diagnosis were independently associated with AD development on multivariate analyses. These results were consistent across observation periods (0-1, 1-2, and >2 years after birth) and sensitivity analyses after redefining the index date as 3 or 6 months before the date of AD diagnosis. Other independent risk factors included asthma, allergic rhinitis, intussusception, and neonatal hyperbilirubinemia. No association with subsequent AD was found for maternal age at delivery, Cesarean delivery, or prenatal antibiotic exposure.

CONCLUSION

Infections in early life are associated with AD development in infancy and early childhood.

Relationship of circulating total bilirubin, UDP-glucuronosyltransferases 1A1 and the development of non-alcoholic fatty liver disease: a cross-sectional study

Background

This study aimed to investigate the correlation of circulating total bilirubin (TB) and UGT1A1 with NAFLD in Chinese Han population.

Methods

172 adults were enrolled from the Qingdao Municipal Hospital from May 2019 to October 2020. All individuals were examined with MRI-PDFF and divided into no steatosis, mild steatosis, moderate steatosis, and severe steatosis groups according to the MRI-PDFF values. The biochemical indexes and UGT1A1 were measured.

Results

There was no significant difference of circulating TB and UGT1A1 levels between NAFLD group and controls. In the moderate steatosis and severe steatosis groups, the circulating TB levels were higher than that in control group (all P < 0.05). In addition, circulating TB levels were weak positively associated with liver fat fraction in NAFLD patients (ρ = 0.205, P = 0.001). There was no significant correlation between circulating UGT1A1 levels with liver fat fraction in patients with NAFLD (ρ = 0.080, P = 0.179), but positively correlation was found in patients with severe steatosis (ρ = 0.305, P = 0.026).

Conclusions

The circulating TB levels were significant high in patients with moderate and severe steatosis. Circulating TB levels were weakly associated with liver fat fraction in patients with NAFLD, and the circulating UGT1A1 levels were positively correlated with liver fat fraction in NAFLD patients with severe steatosis.

Trial registration: ChiCTR, ChiCTR1900022744. Registered 24 April 2019 – Retrospectively registered, http://www.chictr.org.cn/edit.aspx?pid=38304&htm=4.

Adipose-Specific PPARα Knockout Mice Have Increased Lipogenesis by PASK-SREBP1 Signaling and a Polarity Shift to Inflammatory Macrophages in White Adipose Tissue

The nuclear receptor PPARα is associated with reducing adiposity, especially in the liver, where it transactivates genes for β-oxidation. Contrarily, the function of PPARα in extrahepatic tissues is less known. Therefore, we established the first adipose-specific PPARα knockout (PparaFatKO) mice to determine the signaling position of PPARα in adipose tissue expansion that occurs during the development of obesity. To assess the function of PPARα in adiposity, female and male mice were placed on a high-fat diet (HFD) or normal chow for 30 weeks. Only the male PparaFatKO animals had significantly more adiposity in the inguinal white adipose tissue (iWAT) and brown adipose tissue (BAT) with HFD, compared to control littermates. No changes in adiposity were observed in female mice compared to control littermates. In the males, the loss of PPARα signaling in adipocytes caused significantly higher cholesterol esters, activation of the transcription factor sterol regulatory element-binding protein-1 (SREBP-1), and a shift in macrophage polarity from M2 to M1 macrophages. We found that the loss of adipocyte PPARα caused significantly higher expression of the Per-Arnt-Sim kinase (PASK), a kinase that activates SREBP-1. The hyperactivity of the PASK-SREBP-1 axis significantly increased the lipogenesis proteins fatty acid synthase (FAS) and stearoyl-Coenzyme A desaturase 1 (SCD1) and raised the expression of genes for cholesterol metabolism (Scarb1, Abcg1, and Abca1). The loss of adipocyte PPARα increased Nos2 in the males, an M1 macrophage marker indicating that the population of macrophages had changed to proinflammatory. Our results demonstrate the first adipose-specific actions for PPARα in protecting against lipogenesis, inflammation, and cholesterol ester accumulation that leads to adipocyte tissue expansion in obesity.

Heavy metals exposure is associated with early liver dysfunction among rural residents aged 40-75 years in southwest China

Heavy metals exposure has been associated with liver dysfunction in recent reports, while the hepatoxicity of lead (Pb) and cadmium (Cd) has been well established. However, the combined effects of multi-metal in real-world scenario on liver dysfunction are still unclear. This cross-sectional study examined associations between 10 biomarkers of early liver injury and multiple heavy metals levels. The levels of heavy metals/metalloid (magnesium [Mg], calcium [Ca], iron [Fe], zinc [Zn], arsenic [As], Cd, copper [Cu], and Pb) were measured in blood and urinary sample collected from 725 participants in a Cd-polluted area and an unpolluted area in southwest China. The early liver dysfunction biomarkers included the liver enzymes (ALT, ALP, AST, and GGT), proteins (TP, ALB, and GLO), and bilirubin (TBIL, DBIL, and IBIL). Confounder-adjusted beta coefficients were determined using multiple linear regression model analysis for the group-classified and gender-classified samples. Our results showed that blood Fe, Cd, and Cu levels were found to be positively related to elevated ALT levels and blood Cu was positively associated with AST levels in the Cd-polluted area, while the highest blood Zn quartile in the polluted area and blood Mg quartile in the unpolluted area were associated with lower ALT levels. Our finding implies that industrial pollution results in heavy metals of Cd and Pb exposure and effects of Fe, Cd, Cu, and Pb in the Cd-polluted area may be the main contributors to increase the risk of liver dysfunction while Zn in the Cd-polluted area and Mg in the unpolluted area may be the protective factors.

Serum metabolomics analysis reveals increased lipid catabolism in mildly hyperbilirubinemic Gilbert's syndrome individuals

BACKGROUND

The protective role of mildly elevated bilirubin against CVD and diabetes mellitus type 2 (DMT2) is associated with a favorable lipid phenotype. As the mechanistic understanding of this protection in humans remains elusive, we aimed to assess the metabolomics profile of mildly hyperbilirubinemic (Gilbert's syndrome; GS) individuals especially targeting lipid catabolism.

METHODS AND RESULTS

Using NMR serum metabolomics of 56 GS individuals and 56 age and gender-matched healthy controls, GS individuals demonstrated significantly greater concentrations of acetylcarnitine (+20%, p < 0.001) and the ketone bodies, 3-hydroxybutyric acid (+132%, p < 0.001), acetoacetic acid (+95%, p < 0.001) and acetone (+46%, p < 0.001). Metabolites associated with an increased mitochondrial lipid metabolism such as citrate (+15%, p < 0.001), anaplerotic amino acid intermediates and creatinine were significantly greater and creatine significantly reduced in GS individuals. Stimulators of lipid catabolism including AMPK (+59%, p < 0.001), pPPARα (+24%, p < 0.001) and T3 (+9%, p = 0.009) supported the metabolomics data while concomitantly blood glucose and insulin (-33%, p = 0.002) levels were significantly reduced. We further showed that the increased lipid catabolism partially mediates the favorable lipid phenotype (lower triglycerides) of GS individuals. Increased trimethylamine (+35%, p < 0.001) indicated changes in trimethylamine metabolism, an emerging predictor of metabolic health.

CONCLUSION

We showed an enhanced lipid catabolism in mildly hyperbilirubinemic individuals, novel evidence as to why these individuals are leaner and protected against chronic metabolic diseases emphasizing bilirubin to be a promising future target in obese and dyslipidemia patients.

Long-term environmental cadmium exposure induced serum metabolic changes related to renal and liver dysfunctions in a female cohort from Southwest China

Cadmium (Cd), a toxic heavy mental, has been reported to be correlated with increased incidences of multiple diseases. Only a few studies have paid attention to screen the urine metabolites related to long-term environmental Cd exposure in humans. Research on the Cd exposure-related serum metabolic alternations and biological mechanisms linking Cd exposure to adverse health risks in humans is scanty. In this study, we investigated the serum Cd exposure-related metabolic alternations in a cohort of 101 non-smoking females (two polluted groups and one control group) and 18 Cd exposure-related metabolites were identified. A total of 16 clinical indicators of renal and hepatic functions and bone health were measured. Five health effect biomarkers including serum creatinine, alkaline phosphatase, total bilirubin, direct bilirubin and albumin to globulin ratio that are related to impaired renal and hepatic functions showed significant differences among the three groups and had close correlations with Cd levels. We identified intermediate metabolites that were associated with both Cd exposure and health effect biomarkers using a "meet-in-the-middle" approach. Fourteen Cd exposure-related metabolites in the metabolism of glycerophospholipids, sphingolipids, arachidic acid, linoleic acid and amino acids, were identified to be the intermediates of Cd exposure and the health effect biomarkers. Our findings provided evidence for the linkage of long-term environmental Cd exposure and the renal and hepatic insufficiency.

Lactobacillus lactis and Pediococcus pentosaceus-driven reprogramming of gut microbiome and metabolome ameliorates the progression of non-alcoholic fatty liver disease

BACKGROUND

Although microbioa-based therapies have shown putative effects on the treatment of non-alcoholic fatty liver disease (NAFLD), it is not clear how microbiota-derived metabolites contribute to the prevention of NAFLD. We explored the metabolomic signature of Lactobacillus lactis and Pediococcus pentosaceus in NAFLD mice and its association in NAFLD patients.

METHODS

We used Western diet-induced NAFLD mice, and L. lactis and P. pentosaceus were administered to animals in the drinking water at a concentration of 109 CFU/g for 8 weeks. NAFLD severity was determined based on liver/body weight, pathology and biochemistry markers. Caecal samples were collected for the metagenomics by 16S rRNA sequencing. Metabolite profiles were obtained from caecum, liver and serum. Human stool samples (healthy control [n = 22] and NAFLD patients [n = 23]) were collected to investigate clinical reproducibility for microbiota-derived metabolites signature and metabolomics biomarker.

RESULTS

L. lactis and P. pentosaceus supplementation effectively normalized weight ratio, NAFLD activity score, biochemical markers, cytokines and gut-tight junction. While faecal microbiota varied according to the different treatments, key metabolic features including short chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites were analogously restored by both probiotic supplementations. The protective effects of indole compounds were validated with in vitro and in vivo models, including anti-inflammatory effects. The metabolomic signatures were replicated in NAFLD patients, accompanied by the comparable levels of Firmicutes/Bacteroidetes ratio, which was significantly higher (4.3) compared with control (0.6). Besides, the consequent biomarker panel with six stool metabolites (indole, BAs, and SCFAs) showed 0.922 (area under the curve) in the diagnosis of NAFLD.

CONCLUSIONS

NAFLD progression was robustly associated with metabolic dys-regulations in the SCFAs, bile acid and indole compounds, and NAFLD can be accurately diagnosed using the metabolites. L. lactis and P. pentosaceus ameliorate NAFLD progression by modulating gut metagenomic and metabolic environment, particularly tryptophan pathway, of the gut-liver axis.

Predictive value of different bilirubin subtypes for clinical outcomes in patients with acute ischemic stroke receiving thrombolysis therapy

Aims

To explore the association of total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL) levels with, as well as the incremental predictive value of different bilirubin subtypes for, poor outcomes in acute ischemic stroke patients after thrombolysis.

Methods

We analyzed 588 individuals out of 718 AIS participants, and all patients were followed up at 3 months after thrombolysis. The primary outcome was 3‐month death and major disability (modified Rankin Scale (mRS) score of 3–6). The secondary outcomes were 3‐month mortality (mRS score of 6), moderate‐severe cerebral edema, and symptomatic intracranial hemorrhage (sICH), respectively.

Results

Elevated DBIL pre‐thrombolysis was associated with an increased risk of primary outcome (OR 3.228; 95% CI 1.595–6.535; p for trend = 0.014) after fully adjustment. Elevated TBIL pre‐thrombolysis showed the similar results (OR 2.185; 95% CI 1.111–4.298; p for trend = 0.047), while IBIL pre‐thrombolysis was not significantly associated with primary outcome (OR 1.895; 95% CI 0.974–3.687; p for trend = 0.090). Multivariable‐adjusted spline regression model showed a positive linear dose‐response relationship between DBIL pre‐thrombolysis and risk of primary outcome (p for linearity = 0.004). Adding DBIL pre‐thrombolysis into conventional model had greater incremental predictive value for primary outcome, with net reclassification improvement (NRI) 95% CI = 0.275 (0.084–0.466) and integrated discrimination improvement (IDI) 95% CI = 0.011 (0.001–0.024). Increased DBIL post‐thrombolysis had an association with primary outcome (OR 2.416; 95%CI 1.184–4.930; p for trend = 0.039), and it also elevated the incremental predictive value for primary outcome, with NRI (95% CI) = 0.259 (0.066–0.453) and IDI (95% CI) = 0.025 (0.008–0.043).

Conclusion

Increased DBIL pre‐thrombolysis had a stronger association with, as well as greater incremental predictive value for, poor outcomes than TBIL and IBIL did in AIS patients after thrombolysis, which should be understood in the context of retrospective design. The effect of DBIL on targeted populations should be investigated in further researches.

Intestinal, liver and lipid disorders in genetically obese rats are more efficiently reduced by dietary milk thistle seeds than their oil

We hypothesized that milk thistle seed or seed oil dietary supplementation reduces intestinal, liver and lipid disorders specific to genetic obesity, and the seeds can be more efficient in doing so. Lean and obese male Zucker rats were allocated to 4 groups: the lean (LC) and obese control (OC) groups fed a standard diet and the other 2 obese groups fed a diet supplemented with milk thistle seed oil (O + MTO) or milk thistle seeds (O + MTS). After 5 weeks of feeding, the cecal SCFA pool was slightly and significantly lower in OC and O + MTO compared with LC and O + MTS. The liver fat content was greater in OC, O + MTO and O + MTS compared with LC; however, it was significantly lower in O + MTS than in OC and O + MTO. The plasma cholesterol was greater in OC compared with LC, O + MTO and O + MTS; however, it was significantly greater in O + MTO and O + MTS compared with LC. The plasma bilirubin was detected in OC and O + MTO, whereas it was not present in LC and O + MTS. Milk thistle seeds can improve fermentation events in the distal intestine and reduce other disorders specific to genetically obese rats, and the seed PUFAs are responsible for that to a lesser extent.

Prediction of Moxifloxacin Concentrations in Tuberculosis Patient Populations by Physiologically Based Pharmacokinetic Modeling

Moxifloxacin has an important role in the treatment of tuberculosis (TB). Unfortunately, coadministration with the cornerstone TB drug rifampicin results in suboptimal plasma exposure. We aimed to gain insight into the moxifloxacin pharmacokinetics and the interaction with rifampicin. Moreover, we provided a mechanistic framework to understand moxifloxacin pharmacokinetics. We developed a physiologically based pharmacokinetic model in Simcyp version 19, with available and newly generated in vitro and in vivo data, to estimate pharmacokinetic parameters of moxifloxacin alone and when administered with rifampicin. By combining these strategies, we illustrate that the role of P-glycoprotein in moxifloxacin transport is limited and implicate MRP2 as transporter of moxifloxacin-glucuronide followed by rapid hydrolysis in the gut. Simulations of multiple dose area under the plasma concentration-time curve (AUC) of moxifloxacin (400 mg once daily) with and without rifampicin (600 mg once daily) were in accordance with clinically observed data (predicted/observed [P/O] ratio of 0.87 and 0.80, respectively). Importantly, increasing the moxifloxacin dose to 600 mg restored the plasma exposure both in actual patients with TB as well as in our simulations. Furthermore, we extrapolated the single dose model to pediatric populations (P/O AUC ratios, 1.04-1.52) and the multiple dose model to children with TB (P/O AUC ratio, 1.51). In conclusion, our combined approach resulted in new insights into moxifloxacin pharmacokinetics and accurate simulations of moxifloxacin exposure with and without rifampicin. Finally, various knowledge gaps were identified, which may be considered as avenues for further physiologically based pharmacokinetic refinement.

Gilbert's Syndrome and the Gut Microbiota - Insights From the Case-Control BILIHEALTH Study

The heme catabolite bilirubin has anti-inflammatory, anti-oxidative and anti-mutagenic effects and its relation to colorectal cancer (CRC) risk is currently under evaluation. Although the main metabolic steps of bilirubin metabolism, including the formation of stercobilin and urobilin, take place in the human gastrointestinal tract, potential interactions with the human gut microbiota are unexplored. This study investigated, whether gut microbiota composition is altered in Gilbert's Syndrome (GS), a mild form of chronically elevated serum unconjugated bilirubin (UCB) compared to matched controls. Potential differences in the incidence of CRC-associated bacterial species in GS were also assessed. To this end, a secondary investigation of the BILIHEALTH study was performed, assessing 45 adults with elevated UCB levels (GS) against 45 age- and sex-matched controls (C). Fecal microbiota analysis was performed using 16S rRNA gene sequencing. No association between mildly increased UCB and the composition of the gut microbiota in this healthy cohort was found. The alpha and beta diversity did not differ between C and GS and both groups showed a typical representation of the known dominant phyla. Furthermore, no difference in abundance of Firmicutes and Proteobacteria, which have been associated with the mucosa of CRC patients were observed between the groups. A sequence related to the Christensenella minuta strain YIT 12065 was identified with a weak association value of 0.521 as an indicator species in the GS group. This strain has been previously associated with a lower body mass index, which is typical for the GS phenotype. Overall, sex was the only driver for an identifiable difference in the study groups, as demonstrated by a greater bacterial diversity in women. After adjusting for confounding factors and multiple testing, we can conclude that the GS phenotype does not affect the composition of the human gut microbiota in this generally healthy study group.

Tissue-dependent transcriptional and bacterial associations in primary sclerosing cholangitis-associated inflammatory bowel disease

Background: Primary sclerosing cholangitis (PSC) is a disease of the bile duct and liver. However, patients frequently have co-morbidities including inflammatory bowel disease (IBD) and colorectal cancer. Colorectal cancer risk in patients with PSC-associated ulcerative colitis (PSC/UC) is elevated relative to patients with ulcerative colitis (UC) alone, reasons for which remain obscure. Further, clinical and immunological features, and involved intestinal sites differ between PSC/UC and UC. Understanding the molecular and microbial basis for differences in cancer risk between these two patient groups and how these differ across intestinal sites is important for the development of therapies to prevent colorectal cancer development in at-risk individuals.   Methods: We employed ribonucleic acid sequencing (RNA-seq) analysis of biopsy samples across three intestinal tissue locations (ileum, caecum and rectum) in patients with PSC/UC (n = 8), UC (n = 10) and healthy controls (n = 12) to determine tissue-dependent transcriptional alterations in PSC/UC. We also performed 16S ribosomal RNA (rRNA) amplicon sequencing to determine bacterial associations with PSC/UC and host-microbiome associations. Results: Tissue-defining transcriptional signatures revealed that the ileum was enriched for genes involved in lipid and drug metabolism, the caecum for activated immune cells and the rectum for enteric neurogenesis. Transcriptional alterations relative to healthy control samples were largely shared between patients with PSC/UC or UC although were distinct across tissue locations. Nevertheless, we observed reduced expression of gamma-glutamyl transferase 1 ( GGT1) specifically in the ileum and caecum of patients with PSC/UC. Analysis of the bacterial component of the microbiome revealed high inter-individual variability of microbiome composition and little evidence for tissue-dependency. We observed a reduction in Parabacteroides relative abundance in the rectum of patients with PSC/UC. Conclusions: The role of gamma-glutamyl transferase in maintaining the redox environment through the glutathione salvage pathway makes our observed alterations a potential pathway to PSC-associated colorectal cancer.

Insomnia affects the levels of plasma bilirubin and protein metabolism: an observational study and GWGEIS in UK Biobank cohort

STUDY OBJECTIVES

We aim to explore the mechanism of relationship between insomnia and liver metabolism by examining the gene × insomnia interactions.

METHODS

Individual level genotypic and phenotypic data were obtained from the UK Biobank cohort. Regression analysis was first conducted to test the association of insomnia with plasma total bilirubin (TBil; n = 186,793), direct bilirubin (DBil; n = 159,854) and total protein (TP; n = 171,574) in UK Biobank cohort. Second, genome-wide gene-environment interaction study (GWGEIS) was conducted by PLINK 2.0, and FUMA platform was used to identify enriched pathway terms.

RESULTS

In UK Biobank cohort, we found that TP (P < 2.00 × 10^-16), DBil (P = 1.72 × 10^-3) and TBil (P = 3.38 × 10^-5) were significantly associated with insomnia. GWGEIS of both DBil and TBil observed significant G × INSOMNIA effects between insomnia and UDP Glucuronosyltransferase Family 1 (rs6431558, P = 6.26 × 10^-11) gene. GWGEIS of TP also detected several significant genes interacting with insomnia, such as KLF15, (rs70940816, P = 6.77 × 10^-10) and DOK7, (rs2344205, P = 1.37 × 10^-9). Multiple gene ontology (GO) terms were identified for bilirubin, such as GO_URONIC_ACID_METABOLIC_PROCESS (adjusted P = 4.15 × 10^-26).

CONCLUSION

Our study results suggested negative associations between insomnia and DBil and TBil; and a positive association between insomnia and TP.

Intermittent Hypoxia and Hypercapnia Alter Diurnal Rhythms of Luminal Gut Microbiome and Metabolome

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia and hypercapnia (IHC), affects the composition of the gut microbiome and metabolome. The gut microbiome has diurnal oscillations that play a crucial role in regulating circadian and overall metabolic homeostasis. Thus, we hypothesized that IHC adversely alters the gut luminal dynamics of key microbial families and metabolites. The objective of this study was to determine the diurnal dynamics of the fecal microbiome and metabolome of Apoe-/- mice after a week of IHC exposure. Individually housed, 10-week-old Apoe-/- mice on an atherogenic diet were split into two groups. One group was exposed to daily IHC conditions for 10 h (Zeitgeber time 2 [ZT2] to ZT12), while the other was maintained in room air. Six days after the initiation of the IHC conditions, fecal samples were collected every 4 h for 24 h (6 time points). We performed 16S rRNA gene amplicon sequencing and untargeted liquid chromatography-mass spectrometry (LC-MS) to assess changes in the microbiome and metabolome. IHC induced global changes in the cyclical dynamics of the gut microbiome and metabolome. Ruminococcaceae, Lachnospiraceae, S24-7, and Verrucomicrobiaceae had the greatest shifts in their diurnal oscillations. In the metabolome, bile acids, glycerolipids (phosphocholines and phosphoethanolamines), and acylcarnitines were greatly affected. Multi-omic analysis of these results demonstrated that Ruminococcaceae and tauro-β-muricholic acid (TβMCA) cooccur and are associated with IHC conditions and that Coriobacteriaceae and chenodeoxycholic acid (CDCA) cooccur and are associated with control conditions. IHC significantly change the diurnal dynamics of the fecal microbiome and metabolome, increasing members and metabolites that are proinflammatory and proatherogenic while decreasing protective ones. IMPORTANCE People with obstructive sleep apnea are at a higher risk of high blood pressure, type 2 diabetes, cardiac arrhythmias, stroke, and sudden cardiac death. We wanted to understand whether the gut microbiome changes induced by obstructive sleep apnea could potentially explain some of these medical problems. By collecting stool from a mouse model of this disease at multiple time points during the day, we studied how obstructive sleep apnea changed the day-night patterns of microbes and metabolites of the gut. Since the oscillations of the gut microbiome play a crucial role in regulating metabolism, changes in these oscillations can explain why these patients can develop so many metabolic problems. We found changes in microbial families and metabolites that regulate many metabolic pathways contributing to the increased risk for heart disease seen in patients with obstructive sleep apnea.

Bilirubin Restrains the Anticancer Effect of Vemurafenib on BRAF-Mutant Melanoma Cells Through ERK-MNK1 Signaling

Melanoma, the most threatening cancer in the skin, has been considered to be driven by the carcinogenic RAF-MEK1/2-ERK1/2 signaling pathway. This signaling pathway is usually mainly dysregulated by mutations in BRAF or RAS in skin melanomas. Although inhibitors targeting mutant BRAF, such as vemurafenib, have improved the clinical outcome of melanoma patients with BRAF mutations, the efficiency of vemurafenib is limited in many patients. Here, we show that blood bilirubin in patients with BRAF-mutant melanoma treated with vemurafenib is negatively correlated with clinical outcomes. In vitro and animal experiments show that bilirubin can abrogate vemurafenib-induced growth suppression of BRAF-mutant melanoma cells. Moreover, bilirubin can remarkably rescue vemurafenib-induced apoptosis. Mechanically, the activation of ERK-MNK1 axis is required for bilirubin-induced reversal effects post vemurafenib treatment. Our findings not only demonstrate that bilirubin is an unfavorable for patients with BRAF-mutant melanoma who received vemurafenib treatment, but also uncover the underlying mechanism by which bilirubin restrains the anticancer effect of vemurafenib on BRAF-mutant melanoma cells.

Associations between Prediagnostic Circulating Bilirubin Levels and Risk of Gastrointestinal Cancers in the UK Biobank

We investigated associations between serum levels of bilirubin, an endogenous antioxidant, and gastrointestinal cancer risk. In the UK Biobank, prediagnostic serum levels of total bilirubin were measured in blood samples collected from 440,948 participants. In multivariable-adjusted Cox proportional hazard regression, we estimated hazard ratios (HR) and 95% confidence intervals (CI) for associations between bilirubin levels and gastrointestinal cancer risk (colorectum, esophagus, stomach, mouth, pancreas, and liver). After a median follow-up of 7.1 years (interquartile range: 1.4), 5033 incident gastrointestinal cancer cases were recorded. In multivariable-adjusted models, bilirubin levels were negatively associated with risk of esophageal adenocarcinoma (EAC, HR per 1-SD increment in log-total bilirubin levels 0.72, 95%CI 0.56-0.92, p = 0.01). Weak and less robust negative associations were observed for colorectal cancer (CRC, HR per 1-SD increment in log-total bilirubin levels 0.95, 95%CI 0.88-1.02, p = 0.14). Bilirubin levels were positively associated with risk of hepatocellular carcinoma (HCC, HR per 1-SD increment in log-total bilirubin levels 2.07, 95%CI 1.15-3.73, p = 0.02) and intrahepatic bile duct (IBD) cancer (HR per 1-SD increment 1.67, 95%CI 1.07-2.62, p = 0.03). We found no associations with risks of stomach, oral, and pancreatic cancers. Prediagnostic serum levels of bilirubin were negatively associated with risk of EAC and positively associated with HCC and IBD cancer. Further studies are warranted to replicate our findings for specific GI cancers.

Unconjugated Bilirubin Attenuates DSS-Induced Colitis Potentially via Enhancement of Bilirubin Reabsorption

Studies increasingly show that ulcerative colitis (UC) is a consequence of an imbalance between oxidative stress and antioxidant capacity. Bilirubin exerts an anti-inflammatory effect by scavenging reactive oxygen species (ROS), although the exact mechanism is not completely understood. The aim of this study was to determine the role of serum bilirubin in UC using patient data and a mouse model of dextran sodium sulfate (DSS)-induced colitis. We found that low levels of serum bilirubin correlated to a higher risk of UC in a retrospective case-control population. Pre-treatment with exogenous unconjugated bilirubin (UCB) significantly enhanced colonic bilirubin absorption in mice, and attenuated the DSS-induced body weight loss, colon shortening and histopathological damage. Mechanistically, bilirubin prevented the infiltration of inflammatory cells, and decreased the levels of myeloperoxidase and pro-inflammatory cytokines in the serum and colon. Moreover, bilirubin inhibited ROS and malondialdehyde production, scavenged superoxide anions (O2 ·-) from the colon and enhanced the total antioxidant capacity. In conclusion, exogenous UCB attenuated DSS-induced colitis by directly scavenging O2 ·- and enhancing bilirubin reabsorption in the colon via enterohepatic cycling.

Identification of Binding Regions of Bilirubin in the Ligand-Binding Pocket of the Peroxisome Proliferator-Activated Receptor-A (PPARalpha)

Recent work has shown that bilirubin has a hormonal function by binding to the peroxisome proliferator-activated receptor-α (PPARα), a nuclear receptor that drives the transcription of genes to control adiposity. Our previous in silico work predicted three potential amino acids that bilirubin may interact with by hydrogen bonding in the PPARα ligand-binding domain (LBD), which could be responsible for the ligand-induced function. To further reveal the amino acids that bilirubin interacts with in the PPARα LBD, we harnessed bilirubin’s known fluorescent properties when bound to proteins such as albumin. Our work here revealed that bilirubin interacts with threonine 283 (T283) and alanine 333 (A333) for ligand binding. Mutational analysis of T283 and A333 showed significantly reduced bilirubin binding, reductions of 11.4% and 17.0%, respectively. Fenofibrate competitive binding studies for the PPARα LBD showed that bilirubin and fenofibrate possibly interact with different amino acid residues. Furthermore, bilirubin showed no interaction with PPARγ. This is the first study to reveal the amino acids responsible for bilirubin binding in the ligand-binding pocket of PPARα. Our work offers new insight into the mechanistic actions of a well-known molecule, bilirubin, and new fronts into its mechanisms.

Impact of Nutritional Epigenetics in Essential Hypertension: Targeting microRNAs in the Gut-Liver Axis

PURPOSE OF REVIEW

To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis.

RECENT FINDINGS

There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

Association between per and polyfluoroalkyl substances and markers of inflammation and oxidative stress

OBJECTIVES

This study aimed to examine the association of Per and Polyfluoroalkyl substances (PFAS) and markers of chronic inflammation and oxidative stress.

METHODS

Using data (n = 6652) from the National Health and Nutrition Examination Survey (NHANES) 2005-2012, generalized linear models were used to examine the association between PFAS and inflammatory (ferritin, alkaline phosphatase, C-reactive protein, absolute neutrophil count and lymphocyte count) and oxidative stress (serum bilirubin, albumin and iron) per unit exposure to PFAS while adjusting for covariates. Study participants were those ≥20 years of age. Outcome variables were markers of chronic inflammation and oxidative stress and exposure variables were PFAS.

RESULLTS

Percentage change in Perfluorohexane sulfonic acid (PFHxS), Perfluorononanoic acid (PFNA), Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonic acid (PFOS), and Perfluorodecanoic acid (PFDA) were all significantly associated with percentage increases in lymphocyte counts, beta (95% confidence interval); 0.04(0.02,0.05), 0.04(0.02,0.05), 0.05(0.03, 0.07), 0.04(0.03,0.05), 0.03(0.13,1.23) and with percentage increases in serum iron 0.07(0.05,0.09), 0.04(0.02,0.07), 0.10(0.07,0.12), 0.05(0.03,0.07), 0.04(0.02,0.06) and increased serum albumin 0.02(0.02,0.02), 0.02(0.02,0.03), 0.03(0.03,0.04), 0.02(0.017, 0.025), 0.01 (0.01, 0.05). Only PFHxS, PFNA, PFOA and PFOS were associated with percentage increases in serum total bilirubin 0.04(0.03,0.05), 0.02(0.00,0.03), 0.06(0.04,0.08), 0.03(0.02,0.05). Similar results were obtained for categorical quintile analysis with PFOA showing a significant trend (P < 0.001) with lymphocyte count, serum iron, serum total bilirubin and serum albumin. Trend for neutrophil count was not significant (p = 0.183).

CONCLUSION

Per and Polyfluoroalkyl substances are associated with markers of chronic inflammation and oxidative stress. Increased exposure leads to increase in serum concentration of these markers meaning these chemicals are associated with both chronic inflammation and oxidative stress.

Is a Four-Week Ketogenic Diet an Effective Nutritional Strategy in CrossFit-Trained Female and Male Athletes?

This single-arm interventional study examined the effect of a 4-week ketogenic diet (KD) on aerobic capacity and discipline-specific performance in female (n = 11) and male (n = 11) CrossFit-trained athletes. The participants performed incremental cycling (ICT) and Fight Gone Bad (FGB) tests after consuming a customary diet and a KD. Pre- and post-ICT exercise blood samples were also analysed. Consuming a KD had a slight impact on aerobic capacity and no relevant effect on CrossFit-specific performance. In females, consuming a KD led to an 10.4% decrease in peak oxygen uptake during the ICT (p = 0.027) and resulted in certain alterations in haematological parameters (haemoglobin (HGB), mean corpuscular HGB, and mean corpuscular HGB concentration). Furthermore, in males, alanine aminotransferase activity increased with a simultaneous improvement in the post-ICT blood acid–base balance after consuming a KD. The pre-exercise bilirubin concentration was also elevated in the entire group after consuming a KD. In conclusion, female CrossFit-trained athletes seem to be prone to aerobic performance decrements and increased risk of developing haematological disturbances when consuming a KD. In males who consumed a KD, there was an undesirable alanine aminotransferase elevation and a small tendency towards improved acid–base status. Moreover, consuming a KD had no effect on discipline-specific performance in CrossFit-trained athletes.

Bilirubin as a metabolic hormone: the physiological relevance of low levels

Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.

Baicalin and the liver-gut system: Pharmacological bases explaining its therapeutic effects

With the development of high-throughput screening and bioinformatics technology, natural products with a range of pharmacological targets in multiple diseases have become important sources of new drug discovery. These compounds are derived from various plants, including the dried root of Scutellaria baicalensis Georgi, which is often used as a traditional Chinese herb named Huangqin, a popular medication used for thousands of years in China. Many studies have shown that baicalin, an extract from Scutellaria baicalensis Georgi, exerts various protective effects on liver and gut diseases. Baicalin plays a therapeutic role mainly by mediating downstream apoptosis and immune response pathways induced by upstream oxidative stress and inflammation. During oxidative stress regulation, PI3K/Akt/NRF2, Keap-1, NF-κB and HO-1 are key factors associated with the healing effects of baicalin on NAFLD/NASH, ulcerative colitis and cholestasis. In the inflammatory response, IL-6, IL-1β, TNF-α, MIP-2 and MIP-1α are involved in the alleviation of NAFLD/NASH, cholestasis and liver fibrosis by baicalin, as are TGF-β1/Smads, STAT3 and NF-κB. Regarding the apoptosis pathway, Bax, Bcl-2, Caspase-3 and Caspase-9 are key factors related to the suppression of hepatocellular carcinoma and attenuation of liver injury and colorectal cancer. In addition to immune regulation, PD-1/PDL-1 and TLR4-NF-κB are correlated with the alleviation of hepatocellular carcinoma, ulcerative colitis and colorectal cancer by baicalin. Moreover, baicalin regulates intestinal flora by promoting the production of SCFAs. Furthermore, BA is involved in the interactions of the liver-gut axis by regulating TGR5, FXR, bile acids and the microbiota. In general, a comprehensive analysis of this natural compound was conducted to determine the mechanism by which it regulates bile acid metabolism, the intestinal flora and related signaling pathways, providing new insights into the pharmacological effects of baicalin. The mechanism linking the liver and gut systems needs to be elucidated to draw attention to its great clinical importance.

Natural Product Heme Oxygenase Inducers as Treatment for Nonalcoholic Fatty Liver Disease

Heme oxygenase (HO) is a critical component of the defense mechanism to a wide variety of cellular stressors. HO induction affords cellular protection through the breakdown of toxic heme into metabolites, helping preserve cellular integrity. Nonalcoholic fatty liver disease (NAFLD) is a pathological condition by which the liver accumulates fat. The incidence of NAFLD has reached all-time high levels driven primarily by the obesity epidemic. NALFD can progress to nonalcoholic steatohepatitis (NASH), advancing further to liver cirrhosis or cancer. NAFLD is also a contributing factor to cardiovascular and metabolic diseases. There are currently no drugs to specifically treat NAFLD, with most treatments focused on lifestyle modifications. One emerging area for NAFLD treatment is the use of dietary supplements such as curcumin, pomegranate seed oil, milk thistle oil, cold-pressed Nigella Satvia oil, and resveratrol, among others. Recent studies have demonstrated that several of these natural dietary supplements attenuate hepatic lipid accumulation and fibrosis in NAFLD animal models. The beneficial actions of several of these compounds are associated with the induction of heme oxygenase-1 (HO-1). Thus, targeting HO-1 through dietary-supplements may be a useful therapeutic for NAFLD either alone or with lifestyle modifications.

The role of microbiota in neonatal hyperbilirubinemia

Hyperbilirubinemia accounts for about 60% of full-term and 80% of preterm neonates globally, which is characterized by physiologically elevated unconjugated bilirubin in serum, but abnormally high levels of bilirubin have potential neurotoxic effects. Several factors contribute to the development of neonatal hyperbilirubinemia, including isoimmunization, dysregulated gut flora, genetic alteration and environmental factors. Animal studies have pinpointed the causal roles of several bacteria in bilirubin metabolism. Human studies have revealed microbiota composition in hyperbilirubinemia and found that gut microbiota affect newborns with different severity of hyperbilirubinemia. However, dysbiosis and subsequent changes in microbiota-related metabolic processes are not always considered. This review aims to describe the critical microbiota signatures for neonatal hyperbilirubinemia and focus on the underlying pathogenetic mechanism. These scientific bases give a new and accurate therapeutic strategy for the application of gut microbiota.

Circulating liver function markers and colorectal cancer risk: A prospective cohort study in the UK Biobank

Evidence links the liver to development of colorectal cancer (CRC). However, it remains unknown how liver function may influence CRC risk in the general population. We conducted a prospective cohort study in the UK Biobank of 375 693 participants who provided blood samples in 2006 to 2010. Circulating levels of liver function markers (alanine transaminase [ALT], aspartate transaminase [AST], total bilirubin [TBIL], gamma glutamyltransferase [GGT], alkaline phosphatase [ALP], total protein [TP] and albumin [ALB]) were measured. Incident cancer cases were identified through linkage to the national cancer registry up to 2019. Repeated biomarker measurements were available from a subset of 11 320 participants who were re-assessed in 2012 to 2013. After a median follow-up of 10.0 years, we documented 2662 cases of CRC. Circulating levels of ALT, AST, TBIL, GGT, TP and ALB at baseline were inversely associated with CRC risk (P < .01), with multivariable hazard ratio (95% confidence interval) comparing decile 10 vs 1 of 0.62 (0.51-0.75), 0.63 (0.53-0.75), 0.85 (0.72-1.02), 0.74 (0.61-0.89), 0.70 (0.59-0.84) and 0.66 (0.55-0.79), respectively. Strengthened associations were found after recalibration for repeated measurements. The associations appeared stronger for proximal colon cancer than distal colon cancer and rectal cancer, but consistent for early-, mid- and late-onset CRC. In a large cohort of general population, the UK Biobank, higher circulating levels of ALT, AST, TBIL, GGT, TP and ALB, largely within the normal range, were associated with a lower risk of CRC. The findings support a link between liver function and CRC, and may spur future research on the gut-microbiota-liver axis.

Nonlinear relationship between serum total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation

Objective

This study aimed to examine the relationship between total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation.

Methods

This was a retrospective study. Atrial fibrillation was diagnosed by 24-hour Holter electrocardiography and serum total bilirubin levels were divided into quintiles. Ischemic stroke was diagnosed by symptoms, signs, and a medical image examination. The multivariate Cox proportional hazards model and survival analysis were used to estimate the association of total bilirubin with initial ischemic stroke.

Results

We studied 316 patients with non-valvular atrial fibrillation. During follow-up, there were 42 (13.29%) first ischemic strokes. After multivariate adjustment, for each 1 µmol/L increase in total bilirubin, the risk of first ischemic stroke increased by 4% (95% confidence interval [CI]: 1.01, 1.07). When using the first quintile as the reference, from the second to fifth quintiles, the risks of first ischemic stroke were 0.52 (95% CI: 0.17, 1.65), 0.23 (95% CI: 0.06, 0.87), 0.92 (95% CI: 0.32, 2.67), and 1.33 (95% CI: 1.09, 4.41), respectively. The optimal cut-off point of total bilirubin for the lowest risk of ischemic stroke was 17.0 µmol/L.

Conclusions

Total bilirubin levels are nonlinearly associated with initial ischemic stroke in patients with non-valvular atrial fibrillation.

Rats Genetically Selected for High Aerobic Exercise Capacity Have Elevated Plasma Bilirubin by Upregulation of Hepatic Biliverdin Reductase-A (BVRA) and Suppression of UGT1A1

Exercise in humans and animals increases plasma bilirubin levels, but the mechanism by which this occurs is unknown. In the present study, we utilized rats genetically selected for high capacity running (HCR) and low capacity running (LCR) to determine pathways in the liver that aerobic exercise modifies to control plasma bilirubin. The HCR rats, compared to the LCR, exhibited significantly higher levels of plasma bilirubin and the hepatic enzyme that produces it, biliverdin reductase-A (BVRA). The HCR also had reduced expression of the glucuronyl hepatic enzyme UGT1A1, which lowers plasma bilirubin. Recently, bilirubin has been shown to activate the peroxisome proliferator-activated receptor-α (PPARα), a ligand-induced transcription factor, and the higher bilirubin HCR rats had significantly increased PPARα-target genes Fgf21, Abcd3, and Gys2. These are known to promote liver function and glycogen storage, which we found by Periodic acid–Schiff (PAS) staining that hepatic glycogen content was higher in the HCR versus the LCR. Our results demonstrate that exercise stimulates pathways that raise plasma bilirubin through alterations in hepatic enzymes involved in bilirubin synthesis and metabolism, improving liver function, and glycogen content. These mechanisms may explain the beneficial effects of exercise on plasma bilirubin levels and health in humans.

Predicting Nonalcoholic Fatty Liver Disease through a Panel of Plasma Biomarkers and MicroRNAs in Female West Virginia Population

(1) Background: Nonalcoholic fatty liver disease (NAFLD) is primarily characterized by the presence of fatty liver, hepatic inflammation and fibrogenesis eventually leading to nonalcoholic steatohepatitis (NASH) or cirrhosis. Obesity and diabetes are common risk factors associated with the development and progression of NAFLD, with one of the highest prevalence of these diseased conditions in the West Virginia population. Currently, the diagnosis of NAFLD is limited to radiologic studies and biopsies, which are not cost-effective and highly invasive. Hence, this study aimed to develop a panel and assess the progressive levels of circulatory biomarkers and miRNA expression in patients at risk for progression to NASH to allow early intervention strategies. (2) Methods: In total, 62 female patients were enrolled and blood samples were collected after 8–10 h of fasting. Computed tomography was performed on abdomen/pelvis following IV contrast administration. The patients were divided into the following groups: Healthy subjects with normal BMI and normal fasting blood glucose (Control, n = 20), Obese with high BMI and normal fasting blood glucose (Obese, n = 20) and Obese with high fasting blood glucose (Obese + DM, n = 22). Based on findings from CT, another subset was created from Obese + DM group with patients who showed signs of fatty liver infiltration (Obese + DM(FI), n = 10). ELISA was performed for measurement of plasma biomarkers and RT-PCR was performed for circulating miRNA expression. (3) Results: Our results show significantly increased levels of plasma IL-6, Leptin and FABP-1, while significantly decreased level of adiponectin in Obese, Obese + DM and Obese + DM(FI) group, as compared to healthy controls. The level of CK-18 was significantly increased in Obese + DM(FI) group as compared to control. Subsequently, the expression of miR-122, miR-34a, miR-375, miR-16 and miR-21 was significantly increased in Obese + DM and Obese + DM(FI) group as compared to healthy control. Our results also show distinct correlation of IL-6, FABP-1 and adiponectin levels with the expression of miRNAs in relation to the extent of NAFLD progression. (4) Conclusion: Our results support the clinical application of these biomarkers and miRNAs in monitoring the progression of NAFLD, suggesting a more advanced diagnostic potential of this panel than conventional methods. This panel may provide an appropriate method for early prognosis and management of NAFLD and subsequent adverse hepatic pathophysiology, potentially reducing the disease burden on the West Virginia population.

Antioxidant Effects and Cytoprotective Potentials of Herbal Tea against H2O2-Induced Oxidative Damage by Activating Heme Oxygenase1 Pathway

Herbal tea with antioxidant ingredients has gained increasing attention in the field of functional foods due to their amelioration potential in aging-related diseases. Wanglaoji herbal tea (WHT) is a kind of traditional beverage made from herbal materials. This study was performed to investigate its antioxidant activity and identify its protective effect on a H₂O₂-induced cell damage model. In this study, we identified six kinds of phenolic acids with antioxidant activity in WHT, among which rosmarinic acid had the highest content and the highest contribution ratio to the antioxidant activity of WHT. Moreover, compared with the H₂O₂-induced damage group, the WHT treatment group can significantly increase the viability of cells and decrease the ratio of senescence-associated β-galactosidase-positive cells, intracellular malondialdehyde levels, and the percentage of G1 phase. Furthermore, enrichment analysis of differentially expressed genes revealed that heme oxygenase1 (HMOX1) was a key gene for protective effect of WHT on oxidative stress-induced cell damage. Thus, WHT exerted protective effects not only by scavenging reactive oxygen species but also by inducing the expression of cytoprotective genes by activating the HMOX1 pathway, which showed that WHT had a potential of promoting health by reducing oxidative stress-induced cell damage.

Galectin-3 in Inflammasome Activation and Primary Biliary Cholangitis Development

Primary biliary cholangitis (PBC) is a chronic inflammatory autoimmune liver disease characterized by inflammation and damage of small bile ducts. The NLRP3 inflammasome is a multimeric complex of proteins that after activation with various stimuli initiates an inflammatory process. Increasing data obtained from animal studies implicate the role of NLRP3 inflammasome in the pathogenesis of various diseases. Galectin-3 is a β-galactoside-binding lectin that plays important roles in various biological processes including cell proliferation, differentiation, transformation and apoptosis, pre-mRNA splicing, inflammation, fibrosis and host defense. The multilineage immune response at various stages of PBC development includes the involvement of Gal-3 in the pathogenesis of this disease. The role of Galectin-3 in the specific binding to NLRP3, and inflammasome activation in models of primary biliary cholangitis has been recently described. This review provides a brief pathogenesis of PBC and discusses the current knowledge about the role of Gal-3 in NLRP3 activation and PBC development.

Feasibility of Voltage-Applied SERS Measurement of Bile Juice as an Effective Analytical Scheme to Enhance Discrimination between Gall Bladder (GB) Polyp and GB Cancer

A unique surface-enhanced Raman scattering (SERS) measurement scheme to discriminate gall bladder (GB) polyp and GB cancer by analysis of bile juice is proposed. Along with the high sensitivity of SERS, external voltage application during SERS measurement was incorporated to improve sample discriminability. For this purpose, Au nanodendrites were constructed on a screen-printed electrode (referred to as AuND@SPE), and Raman spectra of extracted aqueous phases from raw bile juice samples were acquired using the AuND@SPE at voltages from -300 to 300 mV. The sample spectra resembled that of bilirubin, possessing an open chain tetrapyrrole, showing that bilirubin derivatives in bile juice were mainly responsible for the observed peaks. Discrimination of GB polyp and GB cancer using just the normal SERS spectra was not achieved but became apparent when the spectra were acquired at a voltage of -100 mV. When voltage-applied SERS spectra of bilirubin and urobilinogen (one of bilirubin's derivatives) were examined, a sudden intensity elevation occurring at -100 mV was observed for urobilinogen but not bilirubin. Based on examination of corresponding cyclic voltammograms, the potential-driven strong adsorption of urobilinogen (no faradaic charge transfer) on AuND occurring at -100 mV induced a substantial increase in SERS intensity. It was presumed that the content of urobilinogen in the bile juice of a GB cancer patient would be higher than that of a GB polyp patient, and the contained urobilinogen was sensitively highlighted by applying -100 mV during SERS measurement, allowing clear discrimination of GB cancer against GB polyp.

Bilirubin remodels murine white adipose tissue by reshaping mitochondrial activity and the coregulator profile of peroxisome proliferator-activated receptor α

Activation of lipid-burning pathways in the fat-storing white adipose tissue (WAT) is a promising strategy to improve metabolic health and reduce obesity, insulin resistance, and type II diabetes. For unknown reasons, bilirubin levels are negatively associated with obesity and diabetes. Here, using mice and an array of approaches, including MRI to assess body composition, biochemical assays to measure bilirubin and fatty acids, MitoTracker-based mitochondrial analysis, immunofluorescence, and high-throughput coregulator analysis, we show that bilirubin functions as a molecular switch for the nuclear receptor transcription factor peroxisome proliferator-activated receptor α (PPARα). Bilirubin exerted its effects by recruiting and dissociating specific coregulators in WAT, driving the expression of PPARα target genes such as uncoupling protein 1 (Ucp1) and adrenoreceptor β 3 (Adrb3). We also found that bilirubin is a selective ligand for PPARα and does not affect the activities of the related proteins PPARγ and PPARδ. We further found that diet-induced obese mice with mild hyperbilirubinemia have reduced WAT size and an increased number of mitochondria, associated with a restructuring of PPARα-binding coregulators. We conclude that bilirubin strongly affects organismal body weight by reshaping the PPARα coregulator profile, remodeling WAT to improve metabolic function, and reducing fat accumulation.

Intestinal microbial metabolite stercobilin involvement in the chronic inflammation of ob/ob mice

It is crucial that the host and intestinal microflora interact and influence each other to maintain homeostasis and trigger pathological processes. Recent studies have shown that transplantation of the murine intestinal content to recipient germ-free mice enables transmission of the donor’s phenotypes, such as low level chronic inflammation associated with lifestyle-related diseases. These findings indicate that intestinal bacteria produce some molecules to trigger pathological signals. However, fecal microbial metabolites that induce obesity and the type II diabetic phenotype have not been fully clarified. Here, we showed that the intestinal bacterial metabolite stercobilin, a pigment of feces, induced proinflammatory activities including TNF-α and IL-1β induction in mouse macrophage RAW264 cells. Proinflammatory stercobilin levels were significantly higher in ob/ob mice feces than in the feces of control C57BL/6 J mice. Moreover, in this study, we detected stercobilin in mice plasma for the first time, and the levels were higher in ob/ob mice than that of C57BL/6 J mice. Therefore, stercobilin is potentially reabsorbed, circulated through the blood system, and contributes to low level chronic inflammation in ob/ob mice. Since, stercobilin is a bioactive metabolite, it could be a potentially promising biomarker for diagnosis. Further analyses to elucidate the metabolic rate and the reabsorption mechanism of stercobilin may provide possible therapeutic and preventive targets.

Toxicity of glyphosate in feed for weanling piglets and the mechanism of glyphosate detoxification by the liver nuclear receptor CAR/PXR pathway

Glyphosate (GLP), the most widely used and productive pesticide worldwide, which safety and reliability gradually become a social concern. It is important to explore the toxic of GLP on the limitation level by governments on piglets and the potential role of hepatic CAR/PXR and Keap1-Nrf2 pathways in low levels of glyphosate detoxification. Compared with the control group, the production performance and organ index of GLP group showed no significant change. However, the liver GLP residue of 40 mg/kg group was significantly higher than the control group. We also found that the activity of ALP increased linearly and DBIL content increased quadratically. Furthermore, GLP could significantly increase SOD and GSH-Px and decrease T-AOC and CAT activities and significantly increase MDA and H2O2 contents (P < 0.05); however, the genes expression of Keap1/Nrf2 pathway was not affected. Gene expression of CAR/PXR pathway showed that GLP could significantly stimulate the expression of CAR, but it could not affect the expression of phase Ⅰ (CYP1A1, CYP1A2, CYP2E1, CYP2A19, CYP3A29), phase Ⅱ (UGT1A6, GSTA1, GSTA2) detoxification enzymes and transporters (MDR1, MRP2, P-gp). Our study showed that although 10-40 mg/kg GLP would inevitably cause some liver damage and dysfunction, it can self-alleviating the toxic effect of GLP.

Obesity and ageing: Two sides of the same coin

Conditions and comorbidities of obesity mirror those of ageing and age-related diseases. Obesity and ageing share a similar spectrum of phenotypes such as compromised genomic integrity, impaired mitochondrial function, accumulation of intracellular macromolecules, weakened immunity, shifts in tissue and body composition, and enhanced systemic inflammation. Moreover, it has been shown that obesity reduces life expectancy by 5.8 years in men and 7.1 years in women after the age of 40. Shorter life expectancy could be because obesity holistically accelerates ageing at multiple levels. Besides jeopardizing nuclear DNA and mitochondrial DNA integrity, obesity modifies the DNA methylation pattern, which is associated with epigenetic ageing in different tissues. Additionally, other signs of ageing are seen in individuals with obesity including telomere shortening, systemic inflammation, and functional declines. This review aims to show how obesity and ageing are "two sides of the same coin" through discussing how obesity predisposes an individual to age-related conditions, illness, and disease. We will further demonstrate how the mechanisms that perpetuate the early-onset of chronic diseases in obesity parallel those of ageing.

Plasma metals and serum bilirubin levels in workers from manganese-exposed workers healthy cohort (MEWHC)

Few studies specifically address the possible associations between multiple-metal exposures and liver damage among the occupational population. This study aimed to explore the cross-sectional relationships of plasma metals with liver function parameters. For 571 on-the-spot workers in the manganese-exposed workers healthy cohort (MEWHC), we determined liver function parameters: total bilirubin (TBILI), direct bilirubin (DBILI), indirect bilirubin (IBILI), alanine transaminase (ALT) and aspartate transaminase (AST). Total concentrations of 22 plasma metals were measured by ICP-MS. The LASSO (least absolute shrinkage and selection operator) penalized regression model was applied for selecting plasma metals independently associated with liver function parameters. Multiple linear regression analyses and restricted cubic spline (RCS) were utilized for identifying the exposure-response relationship of plasma metals with liver function parameters. After adjusting for covariates and selected metals, a 1-SD increase in log-10 transformed levels of iron was associated with increases in the levels of TBILI, DBILI and IBILI by 20.3%, 12.1% and 23.7%, respectively; similar increases in molybdenum for decreases in levels of TBILI, DBILI and IBILI by 6.1%, 2.6% and 8.3%, respectively. The effect of a 1-SD increase in plasma copper corresponded decreases of 3.2%, 3.4% and 5.0% in TBILI, AST and ALT levels, respectively. The spline analyses further clarified the non-linear relationships between plasma iron and bilirubin whilst negative linear relationships for plasma molybdenum and bilirubin. Plasma iron was positively whilst plasma molybdenum was negatively associated with increased serum bilirubin levels. Further studies are needed to validate these associations and uncover the underlying mechanisms.

Primary biliary cholangitis: pathogenesis and therapeutic opportunities

Primary biliary cholangitis is a chronic, seropositive and female-predominant inflammatory and cholestatic liver disease, which has a variable rate of progression towards biliary cirrhosis. Substantial progress has been made in patient risk stratification with the goal of personalized care, including early adoption of next-generation therapy with licensed use of obeticholic acid or off-label fibrate derivatives for those with insufficient benefit from ursodeoxycholic acid, the current first-line drug. The disease biology spans genetic risk, epigenetic changes, dysregulated mucosal immunity and altered biliary epithelial cell function, all of which interact and arise in the context of ill-defined environmental triggers. A current focus of research on nuclear receptor pathway modulation that specifically and potently improves biliary excretion, reduces inflammation and attenuates fibrosis is redefining therapy. Patients are benefiting from pharmacological agonists of farnesoid X receptor and peroxisome proliferator-activated receptors. Immunotherapy remains a challenge, with a lack of target definition, pleiotropic immune pathways and an interplay between hepatic immune responses and cholestasis, wherein bile acid-induced inflammation and fibrosis are dominant clinically. The management of patient symptoms, particularly pruritus, is a notable goal reflected in the development of rational therapy with apical sodium-dependent bile acid transporter inhibitors.

Heme-Derived Metabolic Signals Dictate Immune Responses

Heme is one of the most abundant molecules in the body acting as the functional core of hemoglobin/myoglobin involved in the O2/CO2 carrying in the blood and tissues, redox enzymes and cytochromes in mitochondria. However, free heme is toxic and therefore its removal is a significant priority for the host. Heme is a well-established danger-associated molecular pattern (DAMP), which binds to toll-like receptor 4 (TLR4) to induce immune responses. Heme-derived metabolites including the bile pigments, biliverdin (BV) and bilirubin (BR), were first identified as toxic drivers of neonatal jaundice in 1800 but have only recently been appreciated as endogenous drivers of multiple signaling pathways involved in protection from oxidative stress and regulators of immune responses. The tissue concentration of heme, BV and BR is tightly controlled. Heme oxygenase-1 (HO-1, encoded by HMOX1) produces BV by heme degradation, while biliverdin reductase-A (BLVR-A) generates BR by the subsequent conversion of BV. BLVR-A is a fascinating protein that possesses a classical protein kinase domain, which is activated in response to BV binding to its enzymatic site and initiates the downstream mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways. This links BLVR-A activity to cell growth and survival pathways. BLVR-A also contains a bZip DNA binding domain and a nuclear export sequence (NES) and acts as a transcription factor to regulate the expression of immune modulatory genes. Here we will discuss the role of heme-related immune response and the potential for targeting the heme system for therapies directed toward hepatitis and cancer.

Relationship between Serum Indirect Bilirubin Level and Insulin Sensitivity: Results from Two Independent Cohorts of Obese Patients with Impaired Glucose Regulation and Type 2 Diabetes Mellitus in China

BACKGROUND

Serum bilirubin is an endogenous antioxidant that has protective effects against obesity-related metabolic diseases.

OBJECTIVES

This study aimed to evaluate the characteristics of total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL) and their relationships with insulin sensitivity in obese patients with impaired glucose regulation and type 2 diabetes mellitus (IGR/T2DM) in China. Patients and Methods. Cohort 1 comprised obese patients (n = 71) was divided into the IGR/T2DM group (n = 38, obesity with IGR/T2DM) and control group (n = 33, obesity without IGR/T2DM). Insulin sensitivity was evaluated using the hyperinsulinemic-euglycemic clamp technique (HEC) with glucose disposal rate (GDR, M value). Cohort 2 comprised obese patients with IGR/T2DM who underwent metabolic surgery (n = 109) as complementary to cohort 1. Insulin sensitivity was evaluated with the Matsuda Index and homeostatic model assessment of insulin sensitivity (HOMA-IS).

RESULTS

In cohort 1, TBIL, DBIL, and IBIL were higher within the physiological range in the IGR/T2DM group compared with the control group; IBIL was positively correlated with M value (r = 0.342, p=0.044) in the IGR/T2DM group, and multivariate logistic regression showed that IBIL might be independent protective factors against insulin resistance (odds ratio (OR) = 0.602; 95% confidence interval (CI): 0.413-0.878; p=0.008). In cohort 2, at 1 month after metabolic surgery, serum bilirubin levels (TBIL, DBIL, and IBIL) increased, and the percentage change in IBIL was positively correlated with the change of the Matsuda Index (r = 0.195, p=0.045).

CONCLUSIONS

The relationships between different types of bilirubin and insulin sensitivity varied. Serum indirect bilirubin might be a protective factor that enhances insulin sensitivity.

Albumin-bilirubin score is associated with response to pegylated interferon and nucleos(t)ide analogues in chronic hepatitis B patients

BACKGROUND AND AIM

Recently, the role of albumin-bilirubin (ALBI) score in chronic hepatitis B (CHB) has not been well-understood. We aimed to investigate the association of ALBI score with natural history of chronic HBV infection and treatment response of CHB patients.

METHODS

The ALBI score in a cohort of 849 individuals including 721 chronic HBV-infected patients naïve to anti-HBV treatment in different phases and 128 healthy controls were estimated. Additionally, the dynamic changes of ALBI score of 243 hepatitis B e antigen (HBeAg)-positive CHB patients treated with pegylated interferon-alpha (PEG-IFN-α) or nucleos(t)ide analogues (NAs) were tested for 72 weeks.

RESULTS

ALBI score differed among phases, with the highest score in HBeAg-positive CHB patients, followed by HBeAg-negative CHB patients, HBeAg-positive chronic HBV infection, and HBeAg-negative chronic HBV infection. Besides, CHB patients harbouring high baseline ALBI score exhibited a relatively stronger therapeutic response to PEG-IFN-α or NAs. Moreover, the rate of HBeAg and HBsAg loss in patients with ALBI grade 2 was persistently higher than that in patients with ALBI grade 1 throughout the course of treatment. Furthermore, ALBI score was an independent predictor of sustained response achievement. The combined use of ALBI score, HBeAg and ALT could enhance the predictive value of treatment response.

CONCLUSIONS

ALBI score differed significantly across the natural course of chronic HBV infection and was correlated with PEG-IFN-α and NAs treatment response in HBeAg-positive CHB patients, which suggested that ALBI score could be useful as an auxiliary clinical factor to determine the initiation of therapy and predict stronger antiviral treatment response.

Bilirubin Safeguards Cardiorenal and Metabolic Diseases: a Protective Role in Health

PURPOSE OF REVIEW

To discuss recent advances indicating that bilirubin safeguards against cardiorenal and metabolic diseases.

RECENT FINDINGS

Several investigations from human patient populations and experimental animal models have shown that bilirubin improves cardiorenal and metabolic dysfunction. The latest studies found an entirely new function of bilirubin suggesting that it acts as a hormone signaling molecule capable of activating nuclear receptors for burning fat, which may explain several of its protective actions. This review highlights the current findings (within the last 3 years) regarding cardiorenal and metabolic protective effects of bilirubin and the latest mechanism(s) that may be mediating these effects.

CRISPR Cas9-mediated deletion of biliverdin reductase A (BVRA) in mouse liver cells induces oxidative stress and lipid accumulation

Obesity is the predominant cause of non-alcoholic fatty liver disease (NAFLD), which is associated with insulin resistance and diabetes. NAFLD includes a spectrum of pathologies that starts with simple steatosis, which can progress to non-alcoholic steatohepatitis (NASH) with the commission of other factors such as the enhancement of reactive oxygen species (ROS). Biliverdin reductase A (BVRA) reduces biliverdin to the antioxidant bilirubin, which may serve to prevent NAFLD, and possibly the progression to NASH. To further understand the role of BVRA in hepatic function, we used CRISPR-Cas9 technology to target the Blvra gene in the murine hepa1c1c7 hepatocyte cell line (BVRA KO). BVRA activity and protein levels were significantly lower in BVRA KO vs. wild-type (WT) hepatocytes. Lipid accumulation under basal and serum-starved conditions was significantly (p < 0.05) higher in BVRA KO vs. WT cells. The loss of BVRA resulted in the reduction of mitochondria number, decreased expression of markers of mitochondrial biogenesis, uncoupling, oxidation, and fusion, which paralleled reduced mitochondrial oxygen consumption. BVRA KO cells exhibited increased levels of ROS generation and decreased levels of superoxide dismutase mRNA expression. In conclusion, our data demonstrate a critical role for BVRA in protecting against lipid accumulation and oxidative stress in hepatocytes, which may serve as a future therapeutic target for NAFLD and its progression to NASH.

Roux-Y Gastric Bypass and Sleeve Gastrectomy directly change gut microbiota composition independent of surgery type

Bariatric surgery in morbid obesity, either through sleeve gastrectomy (SG) or Roux-Y gastric bypass (RYGB), leads to sustainable weight loss, improvement of metabolic disorders and changes in intestinal microbiota. Yet, the relationship between changes in gut microbiota, weight loss and surgical procedure remains incompletely understood. We determined temporal changes in microbiota composition in 45 obese patients undergoing crash diet followed by SG (n = 22) or RYGB (n = 23). Intestinal microbiota composition was determined before intervention (baseline, S1), 2 weeks after crash diet (S2), and 1 week (S3), 3 months (S4) and 6 months (S5) after surgery. Relative to S1, the microbial diversity index declined at S2 and S3 (p < 0.05), and gradually returned to baseline levels at S5. Rikenellaceae relative abundance increased and Ruminococcaceae and Streptococcaceae abundance decreased at S2 (p < 0.05). At S3, Bifidobacteriaceae abundance decreased, whereas those of Streptococcaceae and Enterobacteriaceae increased (p < 0.05). Increased weight loss between S3-S5 was not associated with major changes in microbiota composition. No significant differences appeared between both surgical procedures. In conclusion, undergoing a crash diet and bariatric surgery were associated with an immediate but temporary decline in microbial diversity, with immediate and permanent changes in microbiota composition, independent of surgery type.

Circadian Clock Gene Bmal1 Regulates Bilirubin Detoxification: A Potential Mechanism of Feedback Control of Hyperbilirubinemia

Controlling bilirubin to a low level is necessary in physiology because of its severe neurotoxicity. Therefore, it is of great interest to understand the regulatory mechanisms for bilirubin homeostasis. In this study, we uncover a critical role for circadian clock in regulation of bilirubin detoxification and homeostasis. Methods: The mRNA and protein levels of Bmal1 (a core clock gene), metabolic enzymes and transporters were measured by qPCR and Western blotting, respectively. Luciferase reporter, mobility shift and chromatin immunoprecipitation were used to investigate transcriptional gene regulation. Experimental hyperbilirubinemia was induced by injection of bilirubin or phenylhydrazine. Unconjugated bilirubin (UCB) and conjugated bilirubin were assessed by ELISA. Results: We first demonstrated diurnal variations in plasma UCB levels and in main bilirubin-detoxifying genes Ugt1a1 and Mrp2. Of note, the circadian UCB levels were antiphase to the circadian expressions of Ugt1a1 and Mrp2. Bmal1 ablation abrogated the circadian rhythms of UCB and bilirubin-induced hepatotoxicity in mice. Bmal1 ablation also decreased mRNA and protein expressions of both Ugt1a1 and Mrp2 in mouse livers, and blunted their circadian rhythms. A combination of luciferase reporter, mobility shift, and chromatin immunoprecipitation assays revealed that Bmal1 trans-activated Ugt1a1 and Mrp2 through specific binding to the E-boxes in the promoter region. Further, Bmal1 ablation caused a loss of circadian time-dependency in bilirubin clearance and sensitized mice to chemical induced-hyperbilirubinemia. Moreover, bilirubin stimulated Bmal1 expression through antagonism of Rev-erbα, constituting a feedback mechanism in bilirubin detoxification. Conclusion: These data supported a dual role for circadian clock in regulation of bilirubin detoxification, generating circadian variations in bilirubin level via direct transactivation of detoxifying genes Ugt1a1 and Mrp2, and defending the body against hyperbilirubinemia via Rev-erbα antagonism. Thereby, our study provided a potential mechanism for management of bilirubin related diseases.

Role of the intestinal microbiome in liver fibrosis development and new treatment strategies

Liver cirrhosis is a major cause of morbidity and mortality worldwide. The most common chronic liver diseases in western countries are alcohol-associated liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Although these diseases have different causes, liver fibrosis develops via shared mechanisms. The liver and intestinal microbiome are linked by the portal vein and have bidirectional interactions. Changes in the intestinal microbiome contribute to the pathogenesis and progression of liver diseases including ALD, NAFLD, viral hepatitis and cholestatic disorders, based on studies in patients and animal models. Intestinal microbial dysbiosis has been associated with liver cirrhosis and its complications. We review the mechanisms by which alterations in the microbiome contribute to liver fibrosis and discuss microbiome-based treatment approaches.