Inborn errors of bile acid biosynthesis and transport. Novel forms of metabolic liver disease

γ-Glutamyl transpeptidase level as a screening marker among diverse etiologies of infantile intrahepatic cholestasis

OBJECTIVES

Low γ-glutamyl transpeptidase (GGT) level is an important marker for progressive familial intrahepatic cholestasis, yet the cutoff level and clinical application is not well defined. This study aimed to evaluate the role of GGT as a screening marker among diverse etiologies of infantile cholestasis.

METHODS

This retrospective study analyzed 256 cholestatic infants admitted to a tertiary referral center between 2000 and 2012. After excluding 121 infants of extrahepatic cholestasis, advanced investigations for 135 infants with intrahepatic cholestasis were performed. The etiologies, outcomes, and correlations with GGT levels were analyzed. Good prognosis was defined as clinical recovery before 1 year of age; poor prognosis as persistent disease, liver transplantation, or death before 1 year.

RESULTS

Among 135 patients of intrahepatic cholestasis, >12 different etiologies were found. Neonatal hepatitis (49.6%), progressive familial intrahepatic cholestasis (21.5%), and neonatal cholestasis caused by citrin deficiency (10.4%) were the leading causes. Patients with initial GGT between 75 and 300 U/L had a higher chance of good prognosis (61/74, 82.4%) than those with GGT <75 U/L or >300 U/L (25/61, 41%, P < 0.0001). In the low-GGT group (≤ 100 U/L), 52.6% (30/57) of the patients have good prognosis; and GGT level ≤ 75 U/L has a sensitivity, specificity, and positive predictive value of 100%, 43.3%, and 61.4% in predicting poor prognosis.

CONCLUSIONS

Patients with GGT levels ≤ 75 or ≥ 300 U/L should receive advanced investigations such as genetic/metabolic assays early; otherwise, the amount of diagnostic workup may be limited if no signs of progressive disease.

Growth and development of a new subspecialty: pediatric hepatology

Several major forces converged to catalyze the formal emergence of a body of knowledge and an organized focus on disorders of the liver in early life. Attendant to the development of a focused clinical subspecialty the pace of patient- and laboratory-based research in the field quickened in parallel to decipher the consequences of genetic or metabolic aberrations on immature liver structure and function. The key research observations that catalyzed the emergence and subsequent rapid growth of Pediatric Hepatology include: (1) an understanding of the dynamic events occurring during hepatobiliary development and the importance of these physiologic variables that occur during liver maturation; (2) the recognition of the unique nature of inherited and acquired liver diseases that affect infants and children-such as biliary atresia and Reye's syndrome; and (3) redefinition of the once obscure inherited intrahepatic cholestatic diseases of the liver, which, in turn, provided insight into normal and abnormal hepatobiliary physiology. The clinical advances were highlighted by the development of specific approaches to the diagnosis and management of liver disease in infants and children, including both liver transplantation and nontransplant treatment options. These seminal events led to the expansion of the workforce, creating a critical mass consisting of individuals with focused, specialized skills and techniques. In-depth expertise allowed more accurate diagnosis and highly effective treatment strategies for advanced hepatobiliary disease in children. The demand for pediatric clinicians with experience in advanced hepatology allowed sub-sub-specialization to flourish. Continued maturation of the field led to definition of hepatology-focused curricular elements and educational content for Pediatric Gastroenterology training programs, and subsequently the development of program requirements for those who wished to acquire additional training in Pediatric Hepatology. A significant rite of passage was marked by the election of pediatric hepatologists to leadership positions in the American Association for the Study of Liver Diseases (AASLD). Further validation of the field occurred with approval of the petition for establishing a Certificate of Added Qualification in Transplant Hepatology by the American Board of Pediatrics. Here I relate my perspective on the history of the advances in our field and the contributions of many of the clinicians and scientists whose efforts led to the development of focused clinical, research, and training programs that improved the care of children with diseases of the liver.

Stoffwechselerkrankungen

Entsprechend ihrer Wanderung bei isoelektrischer Fokussierung werden die allelen Varianten des α1-AT als Proteinaseinhibitorphänotypen (Pi) klassifiziert. Die dominierende Isoform ist der normale Phänotyp M, daneben gibt es die Mangelvarianten S und Z sowie eine 0-Variante.

Living-donor liver transplantation for progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) results in liver cirrhosis during the disease course, although the etiology includes unknown mechanisms. Some PFIC patients require liver transplantation (LT).

METHODS

In this study, 11 patients with PFIC type 1 (PFIC1) and 3 patients with PFIC type 2 (PFIC2) who underwent living-donor LT (LDLT) were evaluated.

RESULTS

Digestive symptoms after LDLT were confirmed in 10 PFIC1 recipients (90.9%); 8 PFIC1 recipients showed steatosis after LDLT (72.7%), which began during the early postoperative period (71.5±55.1 days). Seven of the eight steatosis-positive PFIC1 recipients (87.5%) showed a steatosis degree of ≥80%, which was complicated with steatohepatitis and resulted in fibrosis. Cirrhotic findings persisted in six PFIC1 recipients even after LDLT (54.5%), and three PFIC1 recipients finally died. The survival rates of the PFIC1 recipients at 5, 10, and 15 years were 90.9%, 72.7%, and 54.5%, respectively. In contrast, the PFIC2 recipients showed good courses and outcomes without any steatosis after LDLT.

CONCLUSIONS

The clinical courses and outcomes after LDLT are still not sufficient in PFIC1 recipients owing to steatosis/steatohepatitis and subsequent fibrosis, in contrast to PFIC2 recipients. PFIC2 is good indication for LDLT. PFIC1 patients require LT during the disease course; therefore, we suggest that the therapeutic strategies for PFIC1 patients, including the timing of LDLT, under the donor limitation should be reconsidered. The establishment of more advanced treatments for PFIC1 patients is required to improve the long-term prognosis of these patients.

Inflammatory pseudo-tumor of the liver: a rare pathological entity

Inflammatory pseudo-tumor (IPT) of the liver is a rare benign neoplasm and is often mistaken as a malignant entity. Few cases have been reported in the literature and the precise etiology of inflammatory pseudotumor remains unknown. Patients usually present with fever, abdominal pain and jaundice. The proliferation of spindled myofibroblast cells mixed with variable amounts of reactive inflammatory cells is characteristics of IPT. We reviewed the literature regarding possible etiology for IPT with a possible suggested etiology.

Progressive familial intrahepatic cholestasis: a single-center experience of living-donor liver transplantation during two decades in Japan

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) results in liver cirrhosis. Therefore, some PFIC patients require liver transplantation (LT). Although three types of PFIC have been identified, their etiologies include unknown mechanisms.

PATIENTS

A total of 717 recipients who underwent living-donor LT (LDLT) at <20 yr old were enrolled in this study. Among these recipients, 14 PFIC recipients comprising 11 PFIC type 1 (PFIC1) and three PFIC type 2 (PFIC2) were evaluated.

RESULTS

Three of 11 PFIC1 recipients died, while all three PFIC2 recipients survived. Eight of 11 PFIC1 recipients showed steatosis after LDLT. Among the eight steatosis-positive PFIC1 recipients, seven showed severe steatosis and seven were complicated with steatohepatitis. Nine of 11 PFIC1 recipients showed fibrosis after LDLT, and eight of the nine fibrosis-positive PFIC1 recipients showed severe fibrosis. In contrast to the PFIC1 recipients, the PFIC2 recipients did not show any steatosis or fibrosis after LDLT.

CONCLUSIONS

The clinical courses and outcomes of PFIC1 recipients after LDLT are still not sufficient owing to steatosis/fibrosis, unlike the case for PFIC2 recipients. As PFIC1 patients will require LT during the long-term progression of the disease, further strategy improvements are required for PFIC1 patients.

Variable clinical spectrum of the most common inborn error of bile acid metabolism--3beta-hydroxy-Delta 5-C27-steroid dehydrogenase deficiency

OBJECTIVE

We studied the clinical features of children with 3beta-hydroxy-Delta 5-C27-steroid dehydrogenase (3beta-HSDH) deficiency presenting to King's College and Great Ormond Street hospitals between 1989 and 2005. The diagnosis was made biochemically by detection of sulphated dihydroxycholenoic acids and trihydroxycholenoic acids in urine by fast atom bombardment mass spectrometry or electrospray ionisation tandem mass spectrophotometry and a plasma bile acid profile showing absent or low cholic and chenodeoxycholic acid levels and high concentrations of 3beta-7 alpha-dihydroxy-5-cholenoic acid and 3beta-7 alpha-12 alpha-trihydroxy-5-cholenoic acid.

RESULTS

Eighteen children (12 male) with 3beta-HSDH deficiency were identified and diagnosed at a median age of 1.35 years (range 8 weeks-11 years). The presenting features included neonatal cholestasis (n = 11), rickets (n = 8, 1 of whom also had hypocalcaemic tetany, seizures, and normal liver biochemical markers), hepatomegaly (n = 7), pruritus (n = 3), and steatorrhoea and failure to thrive (n = 3). Ten children had low serum 25-OH vitamin D levels, of whom 8 also had low vitamin E and 6 had low vitamin A serum levels. Liver histology showed giant cell change and hepatocyte disarray in all with added features of cholestasis in 11, bridging fibrosis in 6, micronodular cirrhosis in 1, fatty change in 1, and active lobular and portal inflammation in 1. Five patients were treated with cholic acid and chenodeoxycholic acid (7 mg x kg(-1) x day(-1) of each), 7 with chenodeoxycholic acid only (7-18 mg x kg(-1) x day(-1)), and 1 with cholic acid (8 mg x kg(-1) x day(-1)) only. Repeated liver biopsies performed in 4 patients 6 months after starting replacement therapy showed improved histological changes. Three children died untreated before 5 years of age. After a median follow-up of 5.5 years (range 1-17 years) 12 out of 13 treated children have no clinical signs of liver disease or of fat-soluble vitamin deficiency.

CONCLUSIONS

3beta-HSDH deficiency is a rare inborn error of metabolism with diverse clinical features. Early replacement treatment leads to clinical and biochemical control and prevents chronic liver and bone disease, at least in the medium term.

Progressive familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis (PFIC) refers to heterogeneous group of autosomal recessive disorders of childhood that disrupt bile formation and present with cholestasis of hepatocellular origin. The exact prevalence remains unknown, but the estimated incidence varies between 1/50,000 and 1/100,000 births.

Three types of PFIC have been identified and related to mutations in hepatocellular transport system genes involved in bile formation. PFIC1 and PFIC2 usually appear in the first months of life, whereas onset of PFIC3 may also occur later in infancy, in childhood or even during young adulthood. Main clinical manifestations include cholestasis, pruritus and jaundice. PFIC patients usually develop fibrosis and end-stage liver disease before adulthood. Serum gamma-glutamyltransferase (GGT) activity is normal in PFIC1 and PFIC2 patients, but is elevated in PFIC3 patients. Both PFIC1 and PFIC2 are caused by impaired bile salt secretion due respectively to defects in ATP8B1 encoding the FIC1 protein, and in ABCB11 encoding the bile salt export pump protein (BSEP). Defects in ABCB4, encoding the multi-drug resistant 3 protein (MDR3), impair biliary phospholipid secretion resulting in PFIC3.

Diagnosis is based on clinical manifestations, liver ultrasonography, cholangiography and liver histology, as well as on specific tests for excluding other causes of childhood cholestasis. MDR3 and BSEP liver immunostaining, and analysis of biliary lipid composition should help to select PFIC candidates in whom genotyping could be proposed to confirm the diagnosis. Antenatal diagnosis can be proposed for affected families in which a mutation has been identified. Ursodeoxycholic acid (UDCA) therapy should be initiated in all patients to prevent liver damage. In some PFIC1 or PFIC2 patients, biliary diversion can also relieve pruritus and slow disease progression. However, most PFIC patients are ultimately candidates for liver transplantation. Monitoring of hepatocellular carcinoma, especially in PFIC2 patients, should be offered from the first year of life. Hepatocyte transplantation, gene therapy or specific targeted pharmacotherapy may represent alternative treatments in the future.

Novel resequencing chip customized to diagnose mutations in patients with inherited syndromes of intrahepatic cholestasis

BACKGROUND & AIMS

Inherited syndromes of intrahepatic cholestasis commonly result from mutations in the genes SERPINA1 (alpha(1)-antitrypsin deficiency), JAG1 (Alagille syndrome), ATP8B1 (progressive familial intrahepatic cholestasis type 1 [PFIC1]), ABCB11 (PFIC2), and ABCB4 (PFIC3). However, the large gene sizes and lack of mutational hotspots make it difficult to survey for disease-causing mutations in clinical practice. Here, we aimed to develop a technological tool that reads out the nucleotide sequence of these genes rapidly and accurately.

METHODS

25-mer nucleotide probes were designed to identify each base for all exons, 10 bases of intronic sequence bordering exons, 280-500 bases upstream from the first exon for each gene, and 350 bases of the second intron of the JAG1 gene and tiled using the Affymetrix resequencing platform. We then developed high-fidelity polymerase chain reactions to produce amplicons using 1 mL of blood from each subject; amplicons were hybridized to the chip, and nucleotide calls were validated by standard capillary sequencing methods.

RESULTS

Hybridization of amplicons with the chip produced a high nucleotide sequence readout for all 5 genes in a single assay, with an automated call rate of 93.5% (range, 90.3%-95.7%). The accuracy of nucleotide calls was 99.99% when compared with capillary sequencing. Testing the chip on subjects with cholestatic syndromes identified disease-causing mutations in SERPINA1, JAG1, ATP8B1, ABCB11, or ABCB4.

CONCLUSIONS

The resequencing chip efficiently reads SERPINA1, JAG1, ATP8B1, ABCB11, and ABCB4 with a high call rate and accuracy in one assay and identifies disease-causing mutations.

Molecular mechanisms of cholestasis

Recent progress has enhanced our understanding of the pathogenesis of cholestatic liver diseases. Mutations in genes encoding for hepatobiliary transport systems can cause hereditary cholestatic syndromes and exposure to cholestatic agents (drugs, hormones, inflammatory cytokines) can lead to reduced expression and function of hepatic uptake and excretory systems in acquired forms of cholestasis. In addition to transporter changes which cause or maintain cholestasis, some alterations in transporter gene expression can be viewed as hepatoprotective mechanisms aimed at reducing intrahepatic accumulation of toxic biliary constituents such as bile acids and bilirubin. Alternative excretion of bile acids via the basolateral membrane into the systemic circulation facilitates the renal elimination of bile acids into urine. Moreover, increased bile acid hydroxylation, sulfation and glucuronidation by phase I and II metabolizing enzymes renders bile acids more hydrophilic and less toxic. These molecular changes are mediated by specific nuclear receptors which are regulated by bile acids, proinflammatory cytokines, drugs, and hormones. In addition to transcriptional changes, reduced transporter protein insertion to or increased retrieval from the cell membrane as well as other mechanisms such as altered cell polarity, disruption of cell-to-cell junctions and cytoskeletal changes are involved in the pathogenesis of cholestasis. Understanding the detailed mechanisms regulating expression of transport systems and enzymes is essential for the development of novel therapeutic agents. Such future approaches could specifically target nuclear receptors thus restoring defective transporter expression and supporting hepatic defense mechanisms against toxic bile acids.

Whatever happened to "neonatal hepatitis"?

'Idiopathic neonatal hepatitis' is a term that has traditionally been used to denote a clinical syndrome manifest by prolonged jaundice in the neonate. This description is now used much less frequently because recent studies unite well-defined clinical, biochemical and molecular features of intrahepatic cholestasis into specific syndromes. Advances in the understanding of the molecular basis of cholestatic syndromes now enable the classification of syndromes based on biology and offer an opportunity to develop new diagnostic approaches and treatment strategies that take into account the genetic make-up of the child with cholestasis.

Regulation of bile acid biosynthesis by hepatocyte nuclear factor 4alpha

Hepatocyte nuclear factor 4alpha (HNF4alpha) regulates many genes that are preferentially expressed in liver. Mice lacking hepatic expression of HNF4alpha (HNF4alphaDeltaL) exhibited markedly increased levels of serum bile acids (BAs) compared with HNF4alpha-floxed (HNF4alphaF/F) mice. The expression of genes involved in the hydroxylation and side chain beta-oxidation of cholesterol, including oxysterol 7alpha-hydroxylase, sterol 12alpha-hydroxylase (CYP8B1), and sterol carrier protein x, was markedly decreased in HNF4alphaDeltaL mice. Cholesterol 7alpha-hydroxylase mRNA and protein were diminished only during the dark cycle in HNF4alphaDeltaL mice, whereas expression in the light cycle was not different between HNF4alphaDeltaL and HNF4alphaF/F mice. Because CYP8B1 expression was reduced in HNF4alphaDeltaL mice, it was studied in more detail. In agreement with the mRNA levels, CYP8B1 enzyme activity was absent in HNF4alphaDeltaL mice. An HNF4alpha binding site was found in the mouse Cyp8b1 promoter that was able to direct HNF4alpha-dependent transcription. Surprisingly, cholic acid-derived BAs, produced as a result of CYP8B1 activity, were still observed in the serum and gallbladder of these mice. These studies reveal that HNF4alpha plays a central role in BA homeostasis by regulation of genes involved in BA biosynthesis, including hydroxylation and side chain beta-oxidation of cholesterol in vivo.

Nuclear receptors in cholesterol catabolism: molecular biology of the enterohepatic circulation of bile salts and its role in cholesterol homeostasis

Recent advances in bile-salt research have revolutionized thought pertaining to the regulation of cholesterol homeostasis by highlighting the molecular control of reverse cholesterol transport and cholesterol catabolism to bile acids. The latter involves both feed-forward and feedback regulation of bile-acid synthesis within the territory of the enterohepatic circulation of bile salts. Cholesterol is vital to advanced life forms because it has become essential for membrane structure and function and is a precursor to the synthesis of steroid hormones, vitamins A and D, and bile acids. The liver plays a major part in cholesterol metabolism in that it is capable of de novo cholesterol synthesis and uptake from high-density lipoprotein reverse cholesterol transport, low-density lipoprotein, and chylomicron remnant receptors, so that 50% of total body cholesterol is available to be catabolized to bile acids. Cholesterol catabolism to bile acids allows the eukaryote cell to maintain cholesterol homeostasis because it cannot degrade cholesterol's cyclopentanoperhydrophenanthrene ring. Bile-salt catabolic end products of cholesterol must also be regulated to maintain normal bile-acid pool size, secretion, and elimination to avoid bile-salt hepatocyte toxicity. Nuclear hormone receptors, after sensing inappropriate oxysterol and bile-salt levels, are transcription factors that initiate the genetic transactivation to modulate reverse cholesterol transport, cholesterol catabolism, and bile-acid metabolism contiguous to and within the enterohepatic circulation of bile salts so as to regulate cholesterol and bile-salt homeostasis, respectively. This new knowledge should spawn pharmacologic discoveries that modulate nuclear receptors for the treatment of disorders of cholesterol homeostasis.

Bile acid regulation of gene expression: roles of nuclear hormone receptors

Bile acids derived from cholesterol and oxysterols derived from cholesterol and bile acid synthesis pathways are signaling molecules that regulate cholesterol homeostasis in mammals. Many nuclear receptors play pivotal roles in the regulation of bile acid and cholesterol metabolism. Bile acids activate the farnesoid X receptor (FXR) to inhibit transcription of the gene for cholesterol 7alpha-hydroxylase, and stimulate excretion and transport of bile acids. Therefore, FXR is a bile acid sensor that protects liver from accumulation of toxic bile acids and xenobiotics. Oxysterols activate the liver orphan receptors (LXR) to induce cholesterol 7alpha-hydroxylase and ATP-binding cassette family of transporters and thus promote reverse cholesterol transport from the peripheral tissues to the liver for degradation to bile acids. LXR also induces the sterol response element binding protein-1c that regulates lipogenesis. Therefore, FXR and LXR play critical roles in coordinate control of bile acid, cholesterol, and triglyceride metabolism to maintain lipid homeostasis. Nuclear receptors and bile acid/oxysterol-regulated genes are potential targets for developing drug therapies for lowering serum cholesterol and triglycerides and treating cardiovascular and liver diseases.

Update on the etiologies and management of neonatal cholestasis

The early detection of cholestatic liver disease is one of the major challenges facing pediatricians when evaluating the jaundiced infant. Early recognition of liver disease greatly facilitates the care and outcome of infants, because several serious life-threatening disorders may have cholestasis as a major presenting sign of underlying neonatal liver disease. A key component of the work-up is measurement of serum conjugated bilirubin levels, which if elevated should prompt the clinician to initiate a work-up to determine the cause of neonatal cholestasis. In general, if a patient is developing progressive jaundice soon after birth, is still jaundiced at 2 weeks of life, or develops jaundice within the first month of life, a work-up for neonatal cholestasis should begin. A number of previously undiagnosed causes of neonatal cholestasis are beginning to be assigned genetic and infectious etiologies, with significant implications for the work-up and management of cholestatic infants.

Liver disease caused by disorders of bile acid synthesis

Bile acid synthetic defects are uncommon disorders that cause progressive cholestatic liver disease that is often lethal in infancy or early childhood. Five specific primary defects have been described. Diagnosis is based on mass spectrometry of urine and serum. Pathogenesis of liver injury is related to persistent reduction in levels of normal bile acids and accumulation of abnormal, potentially hepatotoxic, intermediaries. Sites of injury are the liver cell, the bile canaliculus, and the smallest bile ductules. The interlobular bile ducts are normal. The liver lesion is progressive chronic hepatitis with an especially high incidence of GCT in patients who present in infancy. Bile acid replacement therapy is usually effective in arresting the liver injury. Regression of liver damage has been documented during treatment of patients who were diagnosed early in life. Because bile acid synthetic disorders are the only cholestatic diseases of infancy in which GCT of hepatocytes is consistently present, the author suggest that the injury responsible for GCT may be specific for toxic bile acids. Accordingly, immaturity of the bile acid synthetic pathway may render many otherwise normal infants vulnerable to transient "neonatal hepatitis" with GCT in a broad range of cholestatic disorders.

Targeted disruption of the nuclear receptor FXR/BAR impairs bile acid and lipid homeostasis

Mice lacking the nuclear bile acid receptor FXR/BAR developed normally and were outwardly identical to wild-type littermates. FXR/BAR null mice were distinguished from wild-type mice by elevated serum bile acid, cholesterol, and triglycerides, increased hepatic cholesterol and triglycerides, and a proatherogenic serum lipoprotein profile. FXR/BAR null mice also had reduced bile acid pools and reduced fecal bile acid excretion due to decreased expression of the major hepatic canalicular bile acid transport protein. Bile acid repression and induction of cholesterol 7alpha-hydroxylase and the ileal bile acid binding protein, respectively, did not occur in FXR/BAR null mice, establishing the regulatory role of FXR/BAR for the expression of these genes in vivo. These data demonstrate that FXR/BAR is critical for bile acid and lipid homeostasis by virtue of its role as an intracellular bile acid sensor.

Lipid transporters: membrane transport systems for cholesterol and fatty acids

Lipophilic molecules can passively diffuse across cell membranes, a process that is driven by the concentration gradient, by availability of acceptors to facilitate desorption from the bilayer, and by cellular metabolism. However, evidence has accumulated that supports the existence of specialized, protein-facilitated membrane transport systems for many lipophilic molecules. This has generated considerable debate regarding why such systems need to exist. The present review summarizes recent developments related to the membrane transport systems for cholesterol and fatty acids, which have been shown to involve structurally related proteins. General similarities of the cholesterol and fatty acid systems to other lipid transport systems (briefly discussed in the Introduction section) are highlighted in the Conclusion section. The overall aim of the present review is to illustrate why lipid transporters are needed in vivo, and how they accomplish specific functions that can not be met by lipid diffusion alone.

Pediatric hepatology. A half-century of progress

Treating a pediatric patient offers a unique opportunity to develop effective strategies to prevent progressive liver injury and to develop novel therapeutic regimens to reduce the need for OLT. Universal vaccination against hepatitis viruses will prevent cirrhosis and liver cancer. Education and counseling may reduce the incidence of alcoholic liver disease. Precise and early screening for metabolic liver disease and genetic or targeted therapy may prevent disease progression. A retrospective look at the 1983 National Institutes of Health Consensus Conference on Liver Transplantation, after more than 15 years of experience among many centers, indicates that liver transplantation can be effectively used to childhood liver disease. Projections 10 years into the future offer hope that liver transplantation may not be needed in the treatment of certain diseases such as metabolic liver disease and fulminant hepatic failure. Focusing on prevention or treatment of liver disease in early life, thoughtful medical management, precise decision making, and conscientious, creative, and courageous use of nontransplant options, can save both livers and lives.