Saul Karpen

Prof. Saul Karpen


Research Focus & Metrics

Academic Career Length

25Years (2002-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 September 2016 in Science Translational Medicine
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ARAnuradha Rao
Anuradha Rao
AKAstrid Kosters
Astrid Kosters
JMJamie E. Mells
Jamie E. Mells
WZWujuan Zhang
Wujuan Zhang
KSKenneth D. R. Setchell
Kenneth D. R. Setchell
SKSaul Karpen
Saul Karpen
Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the Western world, and safe and effective therapies are needed. Bile acids (BAs) and their receptors [including the nuclear receptor for BAs, farnesoid X receptor (FXR)] play integral roles in regulating whole-body metabolism and hepatic lipid homeostasis. We hypothesized that interruption of the enterohepatic BA circulation using a luminally restricted apical sodium-dependent BA transporter (ASBT) inhibitor (ASBTi; SC-435) would modify signaling in the gut-liver axis and reduce steatohepatitis in high-fat diet (HFD)–fed mice. Administration of this ASBTi increased fecal BA excretion and messenger RNA (mRNA) expression of BA synthesis genes in liver and reduced mRNA expression of ileal BA-responsive genes, including the negative feedback regulator of BA synthesis, fibroblast growth factor 15. ASBT inhibition resulted in a marked shift in hepatic BA composition, with a reduction in hydrophilic, FXR antagonistic species and an increase in FXR agonistic BAs. ASBT inhibition restored glucose tolerance, reduced hepatic triglyceride and total cholesterol concentrations, and improved NAFLD activity score in HFD-fed mice. These changes were associated with reduced hepatic expression of lipid synthesis genes (including liver X receptor target genes) and normalized expression of the central lipogenic transcription factor, Srebp1c. Accumulation of hepatic lipids and SREBP1 protein were markedly reduced in HFD-fed Asbt−/− mice, providing genetic evidence for a protective role mediated by interruption of the enterohepatic BA circulation. Together, these studies suggest that blocking ASBT function with a luminally restricted inhibitor can improve both hepatic and whole body aspects of NAFLD.

1 December 2011 in Pediatrics
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SHSanjiv Harpavat
Sanjiv Harpavat
MFMilton J. Finegold
Milton J. Finegold
SKSaul Karpen
Saul Karpen
OBJECTIVES: Healthy infants are thought to acquire biliary atresia (BA) in the first weeks of life. Because those diagnosed earlier have better outcomes, we were interested in determining the earliest time BA could be detected. We started by examining the immediate postnatal period, hypothesizing that newborns would not yet have acquired disease and still have normal direct/conjugated bilirubin (DB/CB) levels. PATIENTS AND METHODS: Newborn DB/CB levels were obtained retrospectively from birth hospitals. Subjects with BA were born between 2007 and 2010 and cared for at Texas Children9s Hospital. Those with BA splenic malformation syndrome or born prematurely were excluded. Control subjects were term newborns who later never developed neonatal liver disease. RESULTS: Of the 61 subjects with BA, 56% had newborn DB/CB levels measured. All DB/CB levels exceeded laboratory norms and rose over time. At 24 to 48 hours of life, subjects with BA had mean DB levels significantly higher than those of controls (1.4 ± 0.43 vs. 0.19 ± 0.075 mg/dL, P < .0001), even while their mean total bilirubin (TB) levels remained below phototherapy limits. Finally, despite the elevated DB/CB levels, the majority of patients (79%) had normal DB:TB ratios ≤0.2. CONCLUSIONS: Patients with BA have elevated DB/CB levels shortly after birth. To detect affected infants earlier and improve outcomes, the results suggest two possibilities: (1) screen all newborns for elevated DB/CB levels, rather than just those who appear jaundiced; and then (2) follow all newborns with elevated DB/CB levels, rather than just those with DB:TB ratios >0.2.

10 August 2012 in Hepatology
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RSRobert H. Squires
Robert H. Squires
ADAnil Dhawan
Anil Dhawan
EAEstella Alonso
Estella Alonso
MNMichael R. Narkewicz
Michael R. Narkewicz
BSBenjamin L. Shneider
Benjamin L. Shneider
FGfor the Pediatric Acute Liver Failure Study Group
for the Pediatric Acute Liver Failure Study Group
N-acetylcysteine (NAC) was found to improve transplantation-free survival in only those adults with nonacetaminophen (non-APAP) acute liver failure (ALF) and grade 1-2 hepatic encephalopathy (HE). Because non-APAP ALF differs significantly between children and adults, the Pediatric Acute Liver Failure (PALF) Study Group evaluated NAC in non-APAP PALF. Children from birth through age 17 years with non-APAP ALF enrolled in the PALF registry were eligible to enter an adaptively allocated, doubly masked, placebo-controlled trial using a continuous intravenous infusion of NAC (150 mg/kg/day in 5% dextrose in water [D5W]) or placebo (D5W) for up to 7 days. The primary outcome was 1-year survival. Secondary outcomes included liver transplantation-free survival, liver transplantation (LTx), length of intensive care unit (ICU) and hospital stays, organ system failure, and maximum HE score. A total of 184 participants were enrolled in the trial with 92 in each arm. The 1-year survival did not differ significantly ( P = 0.19) between the NAC (73%) and placebo (82%) treatment groups. The 1-year LTx-free survival was significantly lower ( P = 0.03) in those who received NAC (35%) than those who received placebo (53%), particularly, but not significantly so, among those less than 2 years old with HE grade 0-1 (NAC 25%; placebo 60%; P = 0.0493). There were no significant differences between treatment arms for hospital or ICU length of stay, organ systems failing, or highest recorded grade of HE. Conclusion : NAC did not improve 1-year survival in non-APAP PALF. One-year LTx-free survival was significantly lower with NAC, particularly among those <2 years old. These results do not support broad use of NAC in non-APAP PALF and emphasizes the importance of conducting controlled pediatric drug trials, regardless of results in adults.

23 May 2013 in Hepatology
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KSKathleen Schwarz
Kathleen Schwarz
BHBarbara H. Haber
Barbara H. Haber
PRPhilip Rosenthal
Philip Rosenthal
CMCara L. Mack
Cara L. Mack
JMJeffrey Moore
Jeffrey Moore
CNChildhood Liver Disease Research and Education Network
Childhood Liver Disease Research and Education Network
The etiology of biliary atresia (BA) is unknown. Given that patterns of anomalies might provide etiopathogenetic clues, we used data from the North American Childhood Liver Disease Research and Education Network to analyze patterns of anomalies in infants with BA. In all, 289 infants who were enrolled in the prospective database prior to surgery at any of 15 participating centers were evaluated. Group 1 was nonsyndromic, isolated BA (without major malformations) (n = 242, 84%), Group 2 was BA and at least one malformation considered major as defined by the National Birth Defects Prevention Study but without laterality defects (n = 17, 6%). Group 3 was syndromic, with laterality defects (n = 30, 10%). In the population as a whole, anomalies (either major or minor) were most prevalent in the cardiovascular (16%) and gastrointestinal (14%) systems. Group 3 patients accounted for the majority of subjects with cardiac, gastrointestinal, and splenic anomalies. Group 2 subjects also frequently displayed cardiovascular (71%) and gastrointestinal (24%) anomalies; interestingly, this group had genitourinary anomalies more frequently (47%) compared to Group 3 subjects (10%). Conclusion: This study identified a group of BA (Group 2) that differed from the classical syndromic and nonsyndromic groups and that was defined by multiple malformations without laterality defects. Careful phenotyping of the patterns of anomalies may be critical to the interpretation of both genetic and environmental risk factors associated with BA, allowing new insight into pathogenesis and/or outcome. (Hepatology 2013;58:1724–1731)

1 October 2011 in Gastroenterology
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Journal Article
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MDMoreshwar S. Desai
Moreshwar S. Desai
SZShabier Zainuer
Shabier Zainuer
CKCurtis Kennedy
Curtis Kennedy
DKDebra Kearney
Debra Kearney
JGJohn Goss
John Goss
SKSaul Karpen
Saul Karpen
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 Children's 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.

21 January 2019 in Hepatology
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Journal Article
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JBJohn‐Paul Berauer
John‐Paul Berauer
AMAnya I. Mezina
Anya I. Mezina
DODavid T. Okou
David T. Okou
ASAniko Sabo
Aniko Sabo
DMDonna M. Muzny
Donna M. Muzny
F(for the Childhood Liver Disease Research Network (ChiLDReN)
for the Childhood Liver Disease Research Network (ChiLDReN)