Moreshwar S. Desai

Atherogenic diet‐induced hepatitis is partially dependent on murine TLR4

Diets high in cholesterol and cholate such as the Paigen diet have been used to study atherogenesis, lithogenesis, and proinflammatory microvascular changes induced by nutritional hypercholesterolemia. Although these diets lead to chronic hepatic inflammation and fibrosis, the early inflammatory changes have been poorly characterized. TLR4, a known receptor for LPS, is also a receptor for a variety of endogenous ligands and has been implicated in atheroma formation. Here, we specifically examined the early inflammatory response of the liver to the atherogenic (ATH) diet and the possible contribution of TLR4. Animals fed the high‐cholesterol/cholate diet for 3 weeks developed a significant, predominantly mononuclear leukocyte infiltration in the liver, hepatic steatosis, elevated hepatic expression of MCP‐1, RANTES, and MIP‐2, and increased serum levels of liver enzymes. In TLR4‐deleted animals, there was a 30% attenuation in the serum alanine transaminase levels and a 50% reduction in the leukocyte infiltration with a fourfold reduction in chemokine expression. In contrast, hepatic steatosis did not differ from wild‐type controls. TLR2 deletion had no effect on diet‐induced hepatitis but increased the amount of steatosis. We conclude that the early inflammatory liver injury but not hepatic lipid loading induced by the ATH diet in mice is mediated in part by TLR4.

Cardiac Structural and Functional Alterations in Infants and Children with Biliary Atresia, Listed for Liver Transplantation

BACKGROUND & AIMS Cirrhotic liver diseases are associated with abnormalities in cardiac geometry and function in adults (cirrhotic cardiomyopathy) but rarely explored in cirrhotic infants or children. We proposed that features of cirrhotic cardiomyopathy are present in infants with cirrhosis due to biliary atresia (BA) as early as the time of evaluation for liver transplant and will correlate with mortality and postoperative morbidity. METHODS Two-dimensional echocardiography (2DE) of infants with BA (n=40; median age, 8 months), listed for transplantation at the Texas Childrens Hospital from 2004 to 2010, were reviewed and compared with age- and sex-matched infants without cardiac or liver disease (controls). Length of stay and correlation with 2DE results were assessed. RESULTS Compared with controls, children with BA had significant increases in multiple 2DE parameters, notably left ventricle wall thickness (23% increase), left ventricular (LV) mass indexed to body surface area (51% increase), and LV shortening fraction (8% increase). Overall, features of cirrhotic cardiomyopathy were observed in most infants (29/40; 72%); 17 had hyperdynamic contractility, and 24 had altered LV geometry. After liver transplantation (33), infants with abnormal 2DE results had longer stays in the intensive care unit (median, 6 vs 4 days) and the hospital (21 vs 11 days) compared with infants who had normal 2DE reports. On univariate analysis, the length of hospital stay correlated with LV mass index. CONCLUSIONS Cardiomyopathy is a prevalent condition in infants with end-stage cirrhotic liver disease due to BA (>70%). This underrecognized condition likely contributes to the prolongation of posttransplant hospitalization.

Hypertrophic cardiomyopathy and dysregulation of cardiac energetics in a mouse model of biliary fibrosis

Cardiac dysfunction is a major cause of morbidity and mortality in patients with end‐stage liver disease; yet the mechanisms remain largely unknown. We hypothesized that the complex interrelated impairments in cardiac structure and function secondary to progression of liver diseases involve alterations in signaling pathways engaged in cardiac energy metabolism and hypertrophy, augmented by direct effects of high circulating levels of bile acids. Biliary fibrosis was induced in male C57BL/6J mice by feeding a 0.1% 3,5‐diethoxycarbonyl‐1,4‐dihydroxychollidine (DDC) supplemented diet. After 3 weeks, mice underwent live imaging (dual energy x‐ray absorptiometry [DEXA] scanning, two‐dimensional echocardiography [2DE], electrocardiography, cardiac magnetic resonance imaging), exercise treadmill testing, and histological and biochemical analyses of livers and hearts. Compared with chow‐fed mice, DDC‐fed mice fatigued earlier on the treadmill, with reduced VO2. Marked changes were identified electrophysiologically (bradycardia and prolonged QT interval) and functionally (hyperdynamic left ventricular [LV] contractility along with increased LV thickness). Hearts of DDC‐fed mice showed hypertrophic signaling (activation of v‐akt murine thymoma viral oncogene/protein kinase B [AKT], inhibition of glycogen synthase kinase‐3β [GSK3β], a 20‐fold up‐regulation of β myosin heavy chain RNA and elevated Gsα/Giα ratio. Genes regulating cardiac fatty acid oxidation pathways were suppressed, along with a threefold increase in myocardial glycogen content. Treatment of mouse cardiomyocytes (which express the membrane bile acid receptor TGR5) with potent natural TGR5 agonists, taurochenodeoxycholic acid and lithocholic acid, activated AKT and inhibited GSK3β, similar to the changes seen in DDC‐fed mouse hearts. This provides support for a novel mechanism whereby circulating natural bile acids can induce signaling pathways in heart associated with hypertrophy. Conclusion: Three weeks of DDC feeding‐induced biliary fibrosis leads to multiple functional, metabolic, electrophysiological, and hypertrophic adaptations in the mouse heart, recapitulating some of the features of human cirrhotic cardiomyopathy. Hepatology 2010;51:2097–2107

Conditional transgenic expression of TIR-domain-containing adaptor-inducing interferon-β (TRIF) in the adult mouse heart is protective in acute viral myocarditis

TIR-domain-containing adaptor-inducing interferon-β (TRIF) plays a major role in Toll-like receptor 3 (TLR3) mediated signaling. Mice deficient in TLR3 and TRIF have been shown to be highly susceptible to enterovirus-induced myocardial injury. These mice have decreased production of antiviral cytokines and increased viral replication in the heart. Therefore, we hypothesized that conditional overexpression of TRIF would change cardiac myocyte susceptibility to virus infection by augmenting the antiviral response. We generated double-transgenic MHC-tTA/MHCtetO-TRIF mice (DT), with conditional cardiac-specific overexpression of TRIF. Naive DT mice had increased cardiac expression of antiviral cytokines and increased cellular infiltration but no alterations in cardiac function. DT mice were less susceptible to encephalomyocarditis virus (EMCV) infection and had a significantly lower viral load in the heart when compared to littermate (LM) and MHCtetO-TRIF (ST) mice. Histopathological examination showed that the severity of myocarditis was also attenuated in DT mice. Furthermore, the decreased virus titers in the DT mouse hearts led to less cardiac damage and better cardiac function when compared to LM and ST mice. Administration of doxycycline to DT mice suppressed the protective effects of TRIF overexpression in the heart. The findings of the present study establish the importance of cardiac-specific TRIF-mediated signaling in the heart in acute viral myocarditis and identify potentially important targets for diagnostic and therapeutic strategies.

Bile acids induce arrhythmias: old metabolite, new tricks

Bile acids (BAs) have traditionally been viewed as mere ‘detergent’ molecules responsible for absorption of dietary fats and lipid-soluble vitamins. However, over the past decade, research in the field of bile acid biology has provided evidence which redefine BAs as potent circulating signalling molecules with the ability to regulate cell biology, metabolism and function of various extrahepatic organs,1 with potential effects on the heart. BAs are secreted in the duodenum and then reabsorbed efficiently from the ileum back to the liver via mesenteric and portal veins. This tightly regulated enterohepatic circulation is disrupted in diseases of the liver such as obstructive jaundice, intrahepatic cholestasis of pregnancy, chronic viral hepatitis and cirrhosis, which leads to spillage of these metabolites into the systemic circulation at pathologically high concentrations (>100–200 µmol/L), resulting in organ dysfunction.2 ,3 It has long been known that high levels of bile acids are toxic to the heart. The cardiotoxicity of bile acids was documented as early as 1863, by Rohrig, who showed that filtered ox bile when injected into the jugular veins of rabbits caused bradycardia, while repeated doses caused cardiac arrest, a phenomenon he described as ‘cardiac paralysis’. At the same time, Landois …

Bile acid excess induces cardiomyopathy and metabolic dysfunctions in the heart

Cardiac dysfunction in patients with liver cirrhosis is strongly associated with increased serum bile acid concentrations. Here we show that excess bile acids decrease fatty acid oxidation in cardiomyocytes and can cause heart dysfunction, a cardiac syndrome that we term cholecardia. Farnesoid X receptor; Small Heterodimer Partner double knockout mice, a model for bile acid overload, display cardiac hypertrophy, bradycardia, and exercise intolerance. In addition, double knockout mice exhibit an impaired cardiac response to catecholamine challenge. Consistent with this decreased cardiac function, we show that elevated serum bile acids reduce cardiac fatty acid oxidation both in vivo and ex vivo. We find that increased bile acid levels suppress expression of proliferator‐activated receptor‐γ coactivator 1α, a key regulator of fatty acid metabolism, and that proliferator‐activated receptor‐γ coactivator 1α overexpression in cardiac cells was able to rescue the bile acid–mediated reduction in fatty acid oxidation genes. Importantly, intestinal bile acid sequestration with cholestyramine was sufficient to reverse the observed heart dysfunction in the double knockout mice. Conclusions: Decreased proliferator‐activated receptor‐γ coactivator 1α expression contributes to the metabolic dysfunction in cholecardia so that reducing serum bile acid concentrations may be beneficial against the metabolic and pathological changes in the heart. (Hepatology 2017;65:189‐201).

Impaired bile acid handling and aggravated liver injury in mice expressing a hepatocyte-specific RXRα variant lacking the DNA-binding domain

BACKGROUND & AIMS Retinoid X Receptor α (RXRα) is the principal heterodimerization partner of class II Nuclear Receptors (NRs), and a major regulator of gene expression of numerous hepatic processes, including bile acid (BA) homeostasis through multiple partners. Specific contributions of hepatic RXRα domains in heterodimer function in response to either BA load or ductular cholestasis are not fully characterized. METHODS Wild-type (WT) mice and mice expressing a hepatocyte-specific RXRα lacking the DNA-Binding-Domain (hs-RxrαΔex4(-/-)), which retains partial ability to heterodimerize with its partners, were fed a 1% cholic acid (CA) diet for 5 days, a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 3 weeks, or control diet. RESULTS Serum ALT (6.5-fold; p<0.05), AST (9.3-fold; p=0.06) and BA (2.8-fold; p<0.05) were increased in CA-fed hs-RxαΔex4(-/-) mice compared to CA-fed WT mice, but were equally induced between genotypes by DDC-feeding. CA-feeding elevated total (4.4-fold; p=0.06) and unconjugated (2.2-fold; p<0.02) bilirubin levels in hs-RxrαΔex4(-/-) mice compared to WT mice, but not in DDC-fed hs-RxrαΔex4(-/-) mice. Increased necrosis and inflammation was observed in CA-fed, but not in DDC-fed hs-RxrαΔex4(-/-) mice. Apoptotic markers DR5, CK8, CK18 RNA were increased in CA- and DDC-fed hs-RxrαΔex4(-/-) mice. Cleaved caspase 3, CK18 and p-JNK protein were elevated in CA-fed but not in DDC-fed hs-RxrαΔex4(-/-) mice. Induction of Ostβ and Cyp2b10 RNA was impaired in CA-fed and DDC-fed hs-RxrαΔex4(-/-) mice. Surprisingly, DDC-fed hs-RxrαΔex4(-/-) mice showed attenuated fibrosis compared to DDC-fed WT mice. CONCLUSIONS These two models of cholestasis identify common and injury-specific roles for RXRα heterodimers and the functional relevance of an intact RXRα-DBD in the hepatocytic adaptive cholestatic response.

Cardiomyopathy reverses with recovery of liver injury, cholestasis and cholanemia in mouse model of biliary fibrosis

Triggers and exacerbants of cirrhotic cardiomyopathy (CC) are poorly understood, limiting treatment options in patients with chronic liver diseases. Liver transplantation alone reverses some features of CC, but the physiology behind this effect has never been studied.

Regional citrate anticoagulation for continuous renal replacement therapy in pediatric patients with liver failure

Pediatric liver failure patients frequently develop multiple organ failure and require continuous renal replacement therapy (CRRT) as part of supportive therapy in the pediatric intensive care unit. While many centers employ no anticoagulation for fear of bleeding complications, balanced coagulation disturbance predisposes these patients to clotting as well as bleeding, making maintenance of longer circuit life to deliver adequate dialysis clearance challenging. Regional citrate anticoagulation (RCA) is an attractive option as it avoids systemic anticoagulation, but since citrate metabolism is impaired in liver failure, concerns about toxicity has limited its use. Pediatric data on RCA with liver failure is very scarce. We aimed to establish safety and efficacy of RCA in pediatric liver failure patients on CRRT. Retrospective review of pediatric patients with liver failure receiving CRRT over 30 months. Demographic data and CRRT related data were collected by chart review. Citrate accumulation (CA) was defined as total calcium (mg/dl) /ionized calcium (mmol/L) ratio >2.5 for > 48 hours. Efficacy was assessed by filter life. Safety was assessed by frequency of adverse events ((AEs) defined as bleeding, hemodynamic instability, arrhythmias). Fifty-one patients (median age 3.5 (IQR 0.75–14.2) years) received 861 CRRT days; 70% experienced at least one episode of CA, only 37% were recorded as such in the medical record. AE rate was 93/1000 CRRT days and did not differ between CA days and others. Median filter life was 66 hours (IQR 29–74); 63% filters lasted longer than 48 hrs. Though common, CA was not associated with increased AEs on in pediatric liver failure patients on CRRT receiving RCA. Filter life was adequate. RCA appears an effective anticoagulation for CRRT in pediatric liver failure. Application of a structured definition would increase recognition of CA to allow timely intervention.

No Child Left Behind: Liver Transplantation in Critically Ill Children

BACKGROUND Advances in critical care prolong survival in children with liver failure, allowing more critically ill children to undergo orthotopic liver transplantation (OLT). In order to justify the use of a scarce donor resource and avoid futile transplants, we sought to determine survival in children who undergo OLT while receiving pre-OLT critical care. STUDY DESIGN We analyzed 13,723 pediatric OLTs using the United Network for Organ Sharing (UNOS) database from 1987 to 2015, including 6,746 recipients in the Model for End-Stage Liver Disease/Pediatric End-Stage Liver Disease (MELD/PELD) era (2002 to 2015). There were 1,816 recipients (26.9%) admitted to the ICU at the time of transplantation. We also analyzed 354 pediatric OLT recipients at our center from 2002 to 2015, one of the largest institutional experiences. Sixty-five recipients (18.3%) were admitted to the ICU at the time of transplantation. Kaplan-Meier, volume threshold, and multivariable analyses were performed. RESULTS Patient survival improved steadily over the study period, (66% 1-year survival in 1987 vs 92% in 2015; p < 0.001). Our institutional experience of ICU recipients in the MELD/PELD era had acceptable outcomes (87% 1-year survival), even among our sickest recipients with vasoactive medications, mechanical ventilation, dialysis, and molecular adsorbent recirculating system requirements. Volume analysis revealed inferior outcomes (hazard ratio [HR] 1.68; 95% CI 1.11 to 2.51) in low-volume centers (<5 annual cases). Identifiable risk factors (previous transplantation, elevated serum sodium, hemodialysis, mechanical ventilation, body weight < 6 kg, and low center volume) increased risk of mortality. CONCLUSIONS This analysis demonstrates that the use of advanced critical care in children and infants with liver failure is justified because OLT can be performed on the sickest children and acceptable outcomes achieved. It is an appropriate use of a scarce donor allograft in a child who would otherwise succumb to a terminal liver disease.