A systematic review of immunosuppressant adherence interventions in transplant recipients: Decoding the streetlight effect

Non-adherence to immunosuppressant medications is an important risk factor for graft dysfunction. To evaluate the effectiveness of adherence-enhancing interventions, we reviewed adherence intervention studies in solid organ transplant recipients (all ages). Using the following databases: PsycINFO, PubMed, Scopus, and ScienceDirect, we identified 41 eligible studies. Only three non-randomized trials showed a possible positive effect on objective indicators of transplant outcomes (such as rejection, liver enzyme levels, kidney function). None of the 21 RCTs showed an improvement in transplant outcomes. Three studies showed a higher rate of adverse events in the intervention group as compared with controls, although this may be related to ascertainment bias. Improvement in adherence as measured indirectly (eg, with electronic monitoring devices) was not aligned with effects on transplant outcomes. We conclude that adherence interventions, to date, have largely been ineffective in improving transplant outcomes. To improve this track record, intervention efforts may wish to concentrate on non-adherent patients (rather than use convenience sampling, which excludes many of the patients who need the intervention), use direct measures of adherence to guide the interventions, and employ strategies that are intensive and yet engaging enough to ensure that non-adherent patients are able to participate.

Improving adherence to medications in pediatric liver transplant recipients

We describe results from a clinical program, which aimed at improving adherence to medications in children who had a liver transplant. We followed the medical outcomes of 23 children and adolescents who participated in a clinical adherence-improvement protocol during the years 2001-2002. The protocol included identification of non-adherent patients by examining tacrolimus blood levels and intervention by increasing the frequency of clinic visits for non-adherent patients. In the two-yr preintervention (1999-2000), there was no improvement in any of the outcomes. After the intervention, the number of patients with high alanine aminotransferase levels (100 and above) decreased significantly, from eight before the intervention to four afterwards. Other outcomes, including the number of rejection episodes (three before, none after) and the degree of adherence to tacrolimus, also improved, but the improvement did not reach statistical significance. Although non-adherent patients were called to clinic more often under the protocol, the intervention did not lead to increased outpatient costs. This adherence--improvement intervention appears to be promising in improving outcomes in pediatric liver transplant recipients. Larger, controlled studies are needed to establish the efficacy of this or other approaches.

Pediatric transplantation in the United States, 1997-2006

This article represents the sixth annual review of the current state of pediatric transplantation in the United States from the Scientific Registry of Transplant Recipients (SRTR). It presents updated trends, discussion of analyses presented during the year by the SRTR to the committees of the Organ Procurement and Transplantation Network (OPTN) and discussion of important issues currently facing pediatric organ transplantation. Unless otherwise stated, the statistics in this article are drawn from the reference tables of the 2007 OPTN/SRTR Annual Report. In this article, pediatric patients are defined as candidates, recipients or donors aged 17 years or less. Data for both graft and patient survival are reported as unadjusted survival, unless otherwise stated (adjusted patient and graft survival are available in the reference tables). Short-term survival (3 month and 1 year) reflects outcomes for transplants performed in 2004 and 2005; 3-year survival reflects transplants from 2002 to 2005; and 5-year survival reports on transplants performed from 2000 to 2005. Details on the methods of analysis employed may be found in the reference tables themselves or in the technical notes of the 2007 OTPN/SRTR Annual Report, both available online at http://www.ustransplant.org.

CMV-IVIG for prevention of Epstein Barr virus disease and posttransplant lymphoproliferative disease in pediatric liver transplant recipients

A randomized controlled trial of CMV-IVIG (cytomegalovirus-intravenous immunoglobulin) for prevention of Epstein Barr virus (EBV) posttransplant lymphoproliferative disease (PTLD) in pediatric liver transplantation (PLTx) recipients was begun in Pittsburgh and subsequently expanded to four additional sites. Protocol EB viral loads were obtained in a blinded fashion; additional loads could be obtained for clinical indications. Patients were followed for 2 years post-LTx. Eighty-two evaluable patients (39 CMV-IVIG, 43 placebo) developed 18 episodes of EBV disease (7 CMV-IVIG, 11 placebo) including nine cases of PTLD (three CMV-IVIG, six placebo). No significant differences were seen in the adjusted 2-year EBV disease-free rate (CMV-IVIG 79%, placebo 71%) and PTLD-free rate (CMV-IVIG 91%, placebo 84%) between treatment and placebo groups at 2 years (p > 0.20). The absence of significant effect of CMV-IVIG may be explained by a lack of efficacy of the drug or limitations of sample size.

Favorable long-term outcome after liver-kidney transplant for recurrent hemolytic uremic syndrome associated with a factor H mutation

A male child initially presented with atypical hemolytic uremic syndrome (HUS) at the age of 4 months and progressed within weeks to end stage renal disease (ESRD). At the age of 2 years he received a live-related kidney transplant from his mother, which, despite initial good function, was lost to recurrent disease after 2 weeks. Complement factor H analysis showed low serum levels and the presence of two mutations on different alleles (c.2918G > A, Cys973Tyr and c.3590T > C, Val1197Ala). His survival on dialysis was at risk because of access failure and recurrent bacteremic episodes. Therefore, at the age of 5 years he received a combined liver-kidney transplant with pre-operative plasma exchange. Initial function of both grafts was excellent and this has been maintained for over 2 years. This report suggests that despite setbacks in previous experience, combined liver-kidney transplantation offers the prospect of a favorable long-term outcome for patients with HUS associated with complement factor H mutations.

Physicochemical and physiological properties of 5alpha-cyprinol sulfate, the toxic bile salt of cyprinid fish

5alpha-Cyprinol sulfate was isolated from bile of the Asiatic carp, Cyprinus carpio. 5alpha-Cyprinol sulfate was surface active and formed micelles; its critical micellization concentration (CMC) in 0.15 M Na+ using the maximum bubble pressure device was 1.5 mM; by dye solubilization, its CMC was approximately 4 mM. At concentrations >1 mM, 5alpha-cyprinol sulfate solubilized monooleylglycerol efficiently (2.1 molecules per mol micellar bile salt). When infused intravenously into the anesthetized rat, 5alpha-cyprinol sulfate was hemolytic, cholestatic, and toxic. In the isolated rat liver, it underwent little biotransformation and was poorly transported (Tmax congruent with 0.5 micromol/min/kg) as compared with taurocholate. 5alpha-Cyprinol, its bile alcohol moiety, was oxidized to its corresponding C27 bile acid and to allocholic acid (the latter was then conjugated with taurine); these metabolites were efficiently transported. 5alpha-Cyprinol sulfate inhibited taurocholate uptake in COS-7 cells transfected with rat asbt, the apical bile salt transporter of the ileal enterocyte. 5alpha-Cyprinol had limited aqueous solubility (0.3 mM) and was poorly absorbed from the perfused rat jejunum or ileum. Sampling of carp intestinal content indicated that 5alpha-cyprinol sulfate was present at micellar concentrations, and that it did not undergo hydrolysis during intestinal transit. These studies indicate that 5alpha-cyprinol sulfate is an excellent digestive detergent and suggest that a micellar phase is present during digestion in cyprinid fish.

The role of magnetic resonance cholangiography in the management of children and young adults after liver transplantation

We reviewed the results of 50 magnetic resonance (MR) cholangiograms to evaluate their usefulness in directing clinical management in young patients after liver transplantation (LTx). Thirty-two patients underwent 50 MR cholangiograms on a 1.5-T unit. Studies were performed from 1 week to 16 yr after LTx. Indications included biochemical abnormalities with (n = 19) or without (n = 16) biopsy evidence for chronic rejection, sepsis (n = 14), and intractable ascites (n = 1). Original interpretations were compared to laboratory and ultrasound findings, and clinical outcome. Of 19 studies performed on 14 patients with biopsy evidence of chronic rejection, 16 were abnormal on MR (but only one was abnormal on ultrasound), resulting in corrective surgery (n = 1), re-Tx (n = 1), and endoscopic dilatation (n = 1). Of 16 studies on 16 patients with biochemical abnormalities without evidence of chronic rejection on biopsy, 14 were abnormal on MR (but only five of 13 on ultrasound), leading to corrective surgery (n = 3) and re-listing for Tx (n = 3). Thirteen of 14 studies on six patients with sepsis were abnormal on MR (five of nine were abnormal on ultrasound), identifying surgically correctable strictures (n = 2), and leading to re-Tx (n = 1) and percutaneous biliary drainage procedures (n = 2). The one patient with ascites had a normal study. We advocate usage of MR cholangiography for the detection of biliary complications after LTx, particularly in those patients who present with biochemical abnormalities that are not easily explained by acute cellular rejection or viral infection and in those with biliary sepsis.

The role of quantitative Epstein-Barr virus polymerase chain reaction and preemptive immunosuppression reduction in pediatric liver transplantation: a preliminary experience

BACKGROUND

Risk factors for the development of posttransplant lymphoproliferative disease (PTLD), a major cause of morbidity and mortality after pediatric liver transplantation, are primary Epstein-Barr virus (EBV) infection and intensity of immunosuppression. The authors assessed monitoring of EBV replication and preemptive immunosuppression reduction in pediatric liver transplant recipients.

METHODS

The authors prospectively followed monthly EBV-quantitative competitive polymerase chain reaction to measure EBV replication in 23 patients who underwent liver transplant between July 1997 and November 1998. Preemptive immunosuppression reduction was instituted for significant EBV replication. Patients were followed up for at least 1 year and divided in two groups for analysis (group 1, pretransplant seronegative for EBV [13 patients]; group 2, seropositive for EBV [10 patients]).

RESULTS

In group 1, 9 of 13 patients had positive polymerase chain reaction results at a mean time of 22.4 weeks after transplantation. All but one of these patients were asymptomatic. In seven of nine patients, preemptive immunosuppression reduction was undertaken without development of PTLD or rejection. In two of nine patients, immunosuppression could not be continuously reduced, and both patients experienced low-grade and medically responsive PTLD. In no patient in group 2 did an EBV-positive viral load or PTLD develop.

CONCLUSIONS

Prospective longitudinal measurement of EBV by quantitative competitive polymerase chain reaction permits early detection of asymptomatic viral replication. Subsequent preemptive reduction of immunosuppression may prevent the progression to PTLD.

Cholecystectomy prevents expansion of the bile acid pool and inhibition of cholesterol 7alpha-hydroxylase in rabbits fed cholesterol

To study the effect of cholecystectomy on the regulation of classic and alternative bile acid syntheses, gallbladder-intact (n = 20) and cholecystectomized (n = 20) New Zealand White rabbits were fed either chow or chow with 2% cholesterol (3 g/day). After 10 days, bile fistulas were constructed in half of each rabbit group to recover and measure the bile acid pool and biliary bile acid flux. After cholesterol feeding, the bile acid pool size increased from 268 +/- 55 to 444 +/- 77 mg (P < 0.01) with a 2-fold rise in the biliary bile acid flux in intact rabbits but did not expand the bile acid pool (270 +/- 77 vs. 276 +/- 62 mg), nor did the biliary bile acid flux increase in cholecystectomized rabbits. Ileal apical sodium-dependent bile acid transporter protein increased 46% from 93 +/- 6 to 136 +/- 23 units/mg (P < 0.01) in the intact rabbits but did not change in cholecystectomized rabbits (104 +/- 14 vs. 99 +/- 19 units/mg) after cholesterol feeding. Cholesterol 7alpha-hydroxylase activity was inhibited 59% (P < 0.001) while cholesterol 27-hydroxylase activity rose 83% (P < 0.05) after cholesterol feeding in the intact rabbits but neither enzyme activity changed significantly in cholesterol-fed cholecystectomized rabbits. Fecal bile acid outputs reflecting bile acid synthesis increased significantly in the intact but not in the cholecystectomized rabbits fed cholesterol. Removal of the gallbladder prevented expansion of the bile acid pool after cholesterol feeding as seen in intact rabbits because ileal bile acid transport did not increase. As a result, cholesterol 7alpha-hydroxylase was not inhibited.

One hundred nine living donor liver transplants in adults and children: a single-center experience

OBJECTIVE

To summarize the evolution of a living donor liver transplant program and the authors' experience with 109 cases.

SUMMARY BACKGROUND DATA

The authors' institution began to offer living donor liver transplants to children in 1993 and to adults in 1998.

METHODS

Donors were healthy, ages 18 to 60 years, related or unrelated, and ABO-compatible (except in one case). Donor evaluation was thorough. Liver biopsy was performed for abnormal lipid profiles or a history of significant alcohol use, a body mass index more than 28, or suspected steatosis. Imaging studies included angiography, computed tomography, endoscopic retrograde cholangiopancreatography, and magnetic resonance imaging. Recipient evaluation and management were the same as for cadaveric transplant.

RESULTS

After ABO screening, 136 potential donors were evaluated for 113 recipients; 23 donors withdrew for medical or personal reasons. Four donor surgeries were aborted; 109 transplants were performed. Fifty children (18 years or younger) received 47 left lateral segments and 3 left lobes; 59 adults received 50 right lobes and 9 left lobes. The average donor hospital stay was 6 days. Two donors each required one unit of banked blood. Right lobe donors had three bile leaks from the cut surface of the liver; all resolved. Another right lobe donor had prolonged hyperbilirubinemia. Three donors had small bowel obstructions; two required operation. All donors are alive and well. The most common indications for transplant were biliary atresia in children (56%) and hepatitis C in adults (40%); 35.6% of adults had hepatocellular carcinoma. Biliary reconstructions in all children and 44 adults were with a Roux-en-Y hepaticojejunostomy; 15 adults had duct-to-duct anastomoses. The incidence of major vascular complications was 12% in children and 11.8% in adult recipients. Children had three bile leaks (6%) and six (12%) biliary strictures. Adult patients had 14 (23.7%) bile leaks and 4 (6.8%) biliary strictures. Patient and graft survival rates were 87.6% and 81%, respectively, at 1 year and 75.1% and 69.6% at 5 years. In children, patient and graft survival rates were 89.9% and 85.8%, respectively, at 1 year and 80.9% and 78% at 5 years. In adults, patient and graft survival rates were 85.6% and 77%, respectively, at 1 year.

CONCLUSION

Living donor liver transplantation has become an important option for our patients and has dramatically changed our approach to patients with liver failure. The donor surgery is safe and can be done with minimal complications. We expect that living donor liver transplants will represent more than 50% of our transplants within 3 years.

Intestinal bile acid transport: biology, physiology, and pathophysiology

Intestinal reabsorption of bile salts plays a crucial role in human health and disease. This process is primarily localized to the terminal ileum and is mediated by a 48-kd sodium-dependent bile acid cotransporter (SLC10A2 = ASBT). ASBT is also expressed in renal tubule cells, cholangiocytes, and the gallbladder. Exon skipping leads to a truncated version of ASBT, which sorts to the basolateral surface and mediates efflux of bile salts. Inherited mutation of ASBT leads to congenital diarrhea secondary to bile acid malabsorption. Partial inhibition of ASBT may be useful in the treatment of hypercholesterolemia and intrahepatic cholestasis. During normal development in the rat ileum, ASBT undergoes a biphasic pattern of expression with a prenatal onset, postnatal repression, and reinduction at the time of weaning. The bile acid responsiveness of the ASBT gene is not clear and may be dependent on both the experimental model used and the species being investigated. Future studies of the transcriptional and posttranscriptional regulation of the ASBT gene and analysis of ASBT knockout mice will provide further insight into the biology, physiology, and pathophysiology of intestinal bile acid transport.

Hepatocyte nuclear factor-1alpha is an essential regulator of bile acid and plasma cholesterol metabolism

Maturity-onset diabetes of the young type 3 (MODY3) is caused by haploinsufficiency of hepatocyte nuclear factor-1alpha (encoded by TCF1). Tcf1-/- mice have type 2 diabetes, dwarfism, renal Fanconi syndrome, hepatic dysfunction and hypercholestrolemia. Here we explore the molecular basis for the hypercholesterolemia using oligonucleotide microchip expression analysis. We demonstrate that Tcf1-/- mice have a defect in bile acid transport, increased bile acid and liver cholesterol synthesis, and impaired HDL metabolism. Tcf1-/- liver has decreased expression of the basolateral membrane bile acid transporters Slc10a1, Slc21a3 and Slc21a5, leading to impaired portal bile acid uptake and elevated plasma bile acid concentrations. In intestine and kidneys, Tcf1-/- mice lack expression of the ileal bile acid transporter (Slc10a2), resulting in increased fecal and urinary bile acid excretion. The Tcf1 protein (also known as HNF-1alpha) also regulates transcription of the gene (Nr1h4) encoding the farnesoid X receptor-1 (Fxr-1), thereby leading to reduced expression of small heterodimer partner-1 (Shp-1) and repression of Cyp7a1, the rate-limiting enzyme in the classic bile acid biosynthesis pathway. In addition, hepatocyte bile acid storage protein is absent from Tcf1-/- mice. Increased plasma cholesterol of Tcf1-/- mice resides predominantly in large, buoyant, high-density lipoprotein (HDL) particles. This is most likely due to reduced activity of the HDL-catabolic enzyme hepatic lipase (Lipc) and increased expression of HDL-cholesterol esterifying enzyme lecithin:cholesterol acyl transferase (Lcat). Our studies demonstrate that Tcf1, in addition to being an important regulator of insulin secretion, is an essential transcriptional regulator of bile acid and HDL-cholesterol metabolism.

Non-adherence in pediatric liver transplant recipients--an assessment of risk factors and natural history

Despite the fact that non-adherence to medical therapy is one of the major causes of late morbidity and mortality in pediatric liver transplant recipients, little is known of the risk factors involved in this behavior. Three cases of fatal non-adherence are reported. Factors associated with non-adherence were investigated by performing a retrospective chart review of a panel of 27 variables in an age-matched cohort of 15 pediatric liver transplant recipients. The most striking differences between the severely non-adherent group and the age-matched cohort included history of substance abuse, child abuse (physical or sexual), not having two parents at home, having received public assistance, having been diagnosed with a psychiatric disorder, and history of school dropout. In addition it appeared that a pretransplant diagnosis of autoimmune hepatitis was associated with more significant medical sequelae related to non-adherence. These findings are preliminary owing to the retrospective design of this study, but could be used as a starting point for a prospective study of this important phenomenon.

Ileal bile acid transport regulates bile acid pool, synthesis, and plasma cholesterol levels differently in cholesterol-fed rats and rabbits

We investigated the effect of ileal bile acid transport on the regulation of classic and alternative bile acid synthesis in cholesterol-fed rats and rabbits. Bile acid pool sizes, fecal bile acid outputs (synthesis rates), and the activities of cholesterol 7alpha-hydroxylase (classic bile acid synthesis) and cholesterol 27-hydroxylase (alternative bile acid synthesis) were related to ileal bile acid transporter expression (ileal apical sodium-dependent bile acid transporter, ASBT). Plasma cholesterol levels rose 2.1-times in rats (98 +/- 19 mg/dl) and 31-times (986 +/- 188 mg/dl) in rabbits. The bile acid pool size remained constant (55 +/- 17 mg vs. 61 +/- 18 mg) in rats but doubled (254 +/- 46 to 533 +/- 53 mg) in rabbits. ASBT protein expression did not change in rats but rose 31% (P < 0.05) in rabbits. Fecal bile acid outputs that reflected bile acid synthesis increased 2- and 2.4-times (P < 0.05) in cholesterol-fed rats and rabbits, respectively. Cholesterol 7alpha-hydroxylase activity rose 33% (24 +/- 2.4 vs. 18 +/- 1.6 pmol/mg/min, P < 0.01) and mRNA levels increased 50% (P < 0.01) in rats but decreased 68% and 79%, respectively, in cholesterol-fed rabbits. Cholesterol 27-hydroxylase activity remained unchanged in rats but rose 62% (P < 0.05) in rabbits. Classic bile acid synthesis (cholesterol 7alpha-hydroxylase) was inhibited in rabbits because an enlarged bile acid pool developed from enhanced ileal bile acid transport. In contrast, in rats, cholesterol 7alpha-hydroxylase was stimulated but the bile acid pool did not enlarge because ASBT did not change. Therefore, although bile acid synthesis was increased via different pathways in rats and rabbits, enhanced ileal bile acid transport was critical for enlarging the bile acid pool size that exerted feedback regulation on cholesterol 7alpha-hydroxylase in rabbits.

A pilot study of posttraumatic stress and nonadherence in pediatric liver transplant recipients

BACKGROUND

Symptoms of posttraumatic stress disorder (PTSD) were described in survivors of life-threatening diseases, the trauma being the experiences associated with the disease or its treatment. Their prevalence in liver transplant recipients is unknown. Based on clinical observations, we hypothesize that a significant proportion of pediatric liver transplant recipients suffers from PTSD symptoms. We further hypothesize that nonadherence (noncompliance) to medical management may, in some cases, be associated with these symptoms. Traumatized patients, according to this hypothesis, will avoid taking their medications, because these serve as painful reminders of the disease.

OBJECTIVES

To determine the prevalence of PTSD symptoms in a sample of pediatric liver transplant recipients. To determine whether symptoms of PTSD are associated with nonadherence in these patients. To describe the clinical presentation of PTSD and the management of severe nonadherence in patients who suffer from this disorder.

METHODS

Nineteen pediatric liver transplant recipients and their caretakers were interviewed, using the UCLA Post Traumatic Stress Disorder Reaction Index (PTSRI). Data were obtained on a few demographic parameters and perception of disease threat. Adherence was evaluated by 2 methods: 1) a clinician panel (taking into account the clinical sequelae of severe nonadherence); and 2) computation of the standard deviations (SDs) of consecutive determinations of blood levels of Tacrolimus (a higher SD means higher variability between individual measures and is therefore an indicator of nonadherence). As an illustration of the general phenomenon, we describe 3 cases of liver transplant recipients who were nonadherent and who suffered from PTSD.

RESULTS

Six of 19 patients had positive scores on all 3 components of the PTSRI (PTSD patients). Three of these, and none of the others, were considered significantly nonadherent by the panel. Therefore, nonadherence was significantly associated with the existence of symptoms from all 3 domains of PTSD (Fisher's exact test) in our sample. In particular, a high avoidance score on the PTSRI was highly correlated with panel-determined nonadherence. Further, SD of medication levels were significantly higher in PTSD patients, compared with the rest of our sample. No significant differences were found in perception of disease threat or demographic variables between PTSD patients and the rest of our sample. The 3 cases that we describe became adherent to their medications when symptoms of PTSD subsided during the course of therapy.

CONCLUSIONS

Clinically significant nonadherence, determined by 2 different methods, was associated with the full spectrum of PTSD symptoms in this sample. It was especially associated with a high avoidance score, which suggests that avoidance of reminders of the disease (eg, medications) may be a mechanism of nonadherence. Screening for and management of these symptoms, therefore, may improve adherence. This novel concept may be applicable to other patient populations. However, more data are needed before any definite conclusions can be drawn.

MR cholangiography in children and young adults with biliary disease

OBJECTIVE

Our objective was to describe the MR cholangiography findings for young patients with suspected biliary disease who underwent half-Fourier acquisition fast spin-echo technique with respiratory triggering.

SUBJECTS AND METHODS

Twenty-eight MR cholangiography studies were performed in 22 patients on a 1.5-T MR unit. Ten of these 22 patients had undergone liver transplantation.

RESULTS

MR cholangiography revealed abnormalities of both the extrahepatic and the intrahepatic major and minor bile duct systems, despite the small diameter of the duct system in this group of patients. Four patterns of biliary disease were shown: global dilatation of extrahepatic or intrahepatic ducts (n = 7); segmental, uniform dilatation of central or peripheral intrahepatic ducts (n = 9); segmental, nonuniform dilatation of central or peripheral intrahepatic ducts (n = 2); and fusiform ectasia with segmental, irregular intrahepatic dilatation and bile lakes (n = 2). The findings of eight studies were interpreted as normal. The four patterns of abnormalities were correlated with the results from percutaneous transhepatic cholangiography, T-tube cholangiography, and liver biopsy and with clinical and surgical information, as available.

CONCLUSION

MR cholangiography is a noninvasive technique for evaluation of biliary disease. The improved resolution afforded by respiratory triggering permits evaluation of both major and minor bile ducts, even in young, uncooperative subjects. Four patterns of abnormalities were prospectively identified, correlated with other information, and used to direct clinical treatment.

Prospective longitudinal analysis of quantitative Epstein-Barr virus polymerase chain reaction in pediatric liver transplant recipients

BACKGROUND

Posttransplant lymphoproliferative disease (PTLD) remains a significant cause of morbidity and mortality in pediatric liver transplant recipients. Epstein-Barr Virus (EBV) mismatch associated with more prevalent use of split-liver, reduced size, and living-related transplants has increased the risk of primary EBV infection and subsequent PTLD. Early identification of EBV viremia may reduce the risk of PTLD, because it allows for early adjustment of immunosuppression and antiviral therapy.

METHODS

EBV viral load was measured monthly by quantitative competitive polymerase chain reactions in three pediatric liver transplant recipients.

RESULTS

Onset of EBV viremia was documented in one recipient. Established EBV viremia was followed in the other two recipients (one with chronic rejection and one with PTLD) who were initially tested once monitoring was initiated in our program.

CONCLUSIONS

EBV quantitative competitive polymerase chain reactions may represent a promising way to follow EBV viral load and potentially prevent the development of PTLD.

Molecular analysis of the adaptive response of intestinal bile acid transport after ileal resection in the rat

BACKGROUND & AIMS

The apical sodium-dependent bile acid transporter is critical for intestinal reclamation of bile salts. Its expression and activity, along with the ileal lipid-binding protein, were studied before and after intestinal resection in the rat.

METHODS

The effects of surgical resection and bile acid feeding on the expression of ileal bile acid transport were assessed by a combination of functional (taurocholate uptake into crude brush border membrane vesicles) and molecular assays (Northern and Western blotting).

RESULTS

Transport, apical sodium-dependent bile acid transporter and ileal lipid-binding protein messenger RNA and protein expression were restricted to the distal 30 cm of ileum. After resection, transport and expression were limited to the remaining portions of this segment. Limited ileal resection increased protein mass and, therefore, transport in the terminal 5 cm of ileum without a specific increase in transporter gene expression. Increased bile acid presentation to the terminal ileum did not induce ileal hyperplasia. Eighty-five percent intestinal resection led to ileal hypertrophy and a specific repression in bile acid transport activity.

CONCLUSIONS

Native and compensatory bile acid transporter gene expression occur predominantly in the terminal 30 cm of ileum. The specific ileal responses to intestinal resection are dependent on the extent of resection.

Sorting of rat liver and ileal sodium-dependent bile acid transporters in polarized epithelial cells

The rat ileal apical Na+-dependent bile acid transporter (ASBT) and the liver Na+-taurocholate cotransporting polypeptide (Ntcp) are members of a new family of anion transporters. These transport proteins share limited sequence homology and almost identical predicted secondary structures but are localized to the apical surface of ileal enterocytes and the sinusoidal surface of hepatocytes, respectively. Stably transfected Madin-Darby canine kidney (MDCK) cells appropriately localized wild-type ASBT and Ntcp apically and basolaterally as assessed by functional activity and immunocytochemical localization studies. Truncated and chimeric transporters were used to determine the functional importance of the cytoplasmic tail in bile acid transport activity and membrane localization. Two cDNAs were created encoding a truncated transporter in which the 56-amino-acid COOH-terminal tail of Ntcp was removed or substituted with an eight-amino-acid epitope FLAG. For both mutants there was some loss of fidelity in basolateral sorting in that approximately 75% of each protein was delivered to the basolateral surface compared with approximately 90% of the wild-type Ntcp protein. In contrast, deletion of the cytoplasmic tail of ASBT led to complete loss of transport activity and sorting to the apical membrane. An Ntcp chimera in which the 56-amino-acid COOH-terminal tail of Ntcp was replaced with the 40-amino-acid cytoplasmic tail of ASBT was largely redirected (82.4 +/- 3.9%) to the apical domain of stably transfected MDCK cells, based on polarity of bile acid transport activity and localization by confocal immunofluorescence microscopy. These results indicate that a predominant signal for sorting of the Ntcp protein to the basolateral domain is located in a region outside of the cytoplasmic tail. These studies have further shown that a novel apical sorting signal is localized to the cytoplasmic tail of ASBT and that it is transferable and capable of redirecting a protein normally sorted to the basolateral surface to the apical domain of MDCK cells.

Neither intestinal sequestration of bile acids nor common bile duct ligation modulate the expression and function of the rat ileal bile acid transporter

The regulatory responses of bile acid (BA) transport in the terminal ileum to perturbations in BA homeostasis are complex, and conflicting results have been reported by different investigators. These studies were designed to examine the response of this system to a reduction in ileal bile salt concentrations at both a functional and molecular level. Common bile duct ligation (BDL) or feeding of a novel bile acid-binding compound, GT31-104HB, for 7 days were used to reduce ileal apical membrane bile salt flux. Apical bile acid transport function was assessed by examining sodium-dependent uptake of [3H]-taurocholate (TC) into brush border membrane vesicles (BBMV). Expression of the apical sodium-dependent bile acid transporter (ASBT) and the ileal lipid-binding protein (ILBP) were assessed by Western blotting with quantitation using [125I]-labeled secondary antibody and a phosphorimager. Neither common BDL nor intestinal sequestration of BA led to a change in ileal bile acid transport function or the expression of the ASBT or the ILBP. These results indicate that a reduction in presentation of bile salts to the apical surface of the terminal ileum does not modulate the expression of the genes involved in their transport.

Cloning and characterization of a novel peptidase from rat and human ileum

A novel 100-kDa ileal brush border membrane protein (I100) has been purified by anionic glycocholate affinity chromatography. Polyclonal antibodies raised against this protein were utilized to clone and characterize I100 in rats. A partial length human I100 cDNA was identified by hybridization screening. In the rat, the I100 protein is a 746-amino acid glycosylated (calculated core molecular mass of 80 kDa) type II integral membrane protein found on the apical surface of ileal villus enterocytes. Its 2.6-kilobase mRNA is expressed in distal small intestine in rats and in humans. The I100 cDNA is homologous to but distinct from human prostate-specific membrane antigen and rat brain N-acetylaspartylglutamate peptidase. It is expressed on both the basolateral and apical surfaces of stably transfected Madin Darby canine kidney cells. Analysis of these stably transfected Madin Darby canine kidney cells and I100 immunoprecipitates of rat ileal brush border membrane vesicles reveals that it has dipeptidyl peptidase IV activity. Future invesitgations will need to determine the exact substrate specificity of this novel peptidase.

Fetal and neonatal expression of the apical sodium-dependent bile acid transporter in the rat ileum and kidney

Previous investigations in rats older than 7 d have shown that apical sodium-dependent bile acid transport in the ileum is abruptly expressed at the time of weaning, whereas it is constitutively expressed in the kidney. The current study was designed to characterize the expression of sodium-dependent bile acid transport in late gestation and in the immediate postnatal period in the rat. Sodium-dependent bile acid transport was measured by rapid filtration using [3H]taurocholate and crude brush border membrane vesicles. Apical sodium-dependent bile acid transporter (ASBT) and ileal lipid binding protein (ILBP) expression were analyzed by Western and Northern blotting. Ileal bile acid content was measured by gas chromatography/mass spectrometry. In the ileum significantly greater sodium-dependent taurocholate uptake was measured in fetal d 22 (E22) membrane vesicles compared with postnatal d 7 (E22 17.0 +/- 5.7. P7 3.9 +/- 2.1 pmol/mg/60 s mean +/- SD, n = 3, p = 0.02). Gas chromatography/mass spectrometry revealed significant quantities of ileal bile acids at E22. Western and northern blotting of fetal ileum revealed ASBT but not ILBP. ASBT expression was suppressed by P7 and then reinduced by P21, whereas ILBP appeared to be first expressed postnatally. In contrast ASBT expression in the kidney was less age-dependent. Therefore, it appears that functional expression of the ASBT gene in the rat ileum is biphasic with a prenatal onset of expression, followed by repression in the early postnatal period and then marked reinduction at weaning.

Glucocorticoids upregulate taurocholate transport by ileal brush-border membrane

The regulation of the enterohepatic circulation of bile acids has not been fully elucidated. Substrate availability has been shown to have a regulatory role on the ileal uptake of taurocholate (TC) by a positive feedback mechanism. Other mechanisms are likely to be involved in regulating ileal bile acid uptake. The present study was designed to test the hypothesis that the ileal bile acid transporter (iBAT) is glucocorticoid sensitive and that changes in expression are mediated by changes in iBAT synthesis. Adult Sprague-Dawley rats (300-400 g) received intraperitoneal injections with either corticosterone (5 mg/ 100 g body weight) or an equivalent vehicle (control) daily for 3 days. On day 4, ileal brush-border membrane vesicles (BBMV) and hepatic basolateral membrane vesicles (BLMV) were prepared, and TC transport was performed using the rapid filtration technique. Initial velocity was measured at selected time points, and kinetics were calculated over a range of TC concentrations. Ileal RNA was isolated, and Northern analysis of steady-state iBAT mRNA levels was determined. Western blot analysis was performed to quantitate the level of the 48-kDa iBAT protein. The initial velocity of Na(+)-dependent TC uptake at 30 s by ileal BBMV was higher in treated animals (264.3 +/- 64.6 pmol/mg protein) compared with control animals (148.3 +/- 41.1 pmol/mg protein; P = 0.07). The maximal velocity of uptake (Vmax) was significantly higher in treated vs. control animals (1,091 +/- 62.7 vs. 689.1 +/- 55.0 pmol.min-1.mg protein-1, respectively; P = 0.002), whereas there was no significant difference in the Michaelis constant (Km) between the control and treated animals (43.3 +/- 7.2 vs. 35.3 +/- 8.7 microM, respectively; P = not significant). Steady-state iBAT mRNA levels were increased twofold in the treated vs. control groups. Western blot analysis showed that the abundance of the 48-kDa iBAT protein was eightfold higher in the treated animals compared with control. Kinetic analysis of hepatic Na(+)-dependent TC uptake revealed nearly identical Vmax and Km between the study and control animals. Therefore, we conclude that TC transport by ileal BBMV is upregulated by administration of glucocorticoids. The increase in BBMV transport Vmax corresponds to an increase in both iBAT transcript and protein.

Hepatic basolateral sodium-dependent-bile acid transporter expression in two unusual cases of hypercholanemia and in extrahepatic biliary atresia

The recent cloning of a human sodium-dependent bile acid transporter (NTCP) permits analysis of its expression in human liver disease and investigation of potential primary defects in its expression. NTCP from normal human liver (NHL) was first characterized in detail. Northern blotting of RNA from NHL revealed a 1.8-kb NTCP transcript. Western blotting of crude NHL plasma membranes using a carboxyterminal antipeptide antibody showed that NTCP is a 39-kd polypeptide that is N-glycosylated to a final molecular weight of 56 kd. Indirect immunofluorescent analysis of NHL sections indicated that the NTCP protein is expressed on the basolateral surface of hepatocytes. We hypothesized that the clinical phenotype of a defect in NTCP might be hypercholanemia in the relative absence of liver disease. Accordingly, the coding region of the NTCP gene of two children with this phenotype was sequenced after reverse transcription/polymerase chain reaction (RT/PCR) amplification. No primary defects in the deduced NTCP amino acid sequence were found. Despite the extremely high serum bile salt levels (235 and 126 micromol/L) in these two patients, NTCP messenger RNA (mRNA) and protein expression were quantitatively normal, in contrast to the published observations in a rat model of cholestasis secondary to common bile duct ligation. Hepatic steady-state NTCP mRNA levels in a group of 23 pre- and postportoenterostomy biliary atresia patients were inversely related to total bilirubin, indicating that extrahepatic bile duct obstruction leads to down-regulation of NTCP mRNA levels, similar to that observed in rat common bile duct ligation. Therefore the lack of down-regulation in the two patients with hypercholanemia indicates that elevated serum bile salts are not sufficient to down-regulate NTCP expression, these two patients have abnormal responses to hypercholanemia, or these two patients have a defect in a gene other than NTCP that influences hepatic clearance of bile salts.

Neonatal liver failure

Neonatal liver failure (NLF) is a distinct and unusual clinical syndrome that requires a specialized approach to its management. This review establishes a definition of NLF and provides a literature-supported differential diagnosis. A specific approach to the diagnostic work-up of an infant with NLF based on this differential diagnosis is outlined. The role of mitochondrial-based diseases in the genesis of NLF is reviewed as well as current advances in the diagnosis and management of neonatal hemochromatosis. The unique range of diseases that cause NLF are associated with specific therapies, which are summarized.

Comparative analysis of the ontogeny of a sodium-dependent bile acid transporter in rat kidney and ileum

An apical sodium-dependent bile acid transporter (ASBT) has recently been cloned and characterized in the rat ileum. Northern and Western blotting revealed both the ASBT mRNA and protein in rat kidney. The coding sequence of the kidney transcript was found to be identical to the previously cloned ileal ASBT. Indirect immunofluorescence studies localized the ASBT protein to the apical membrane of the renal proximal convoluted tubule. Kinetic analysis of sodium-dependent taurocholate uptake using membrane vesicles revealed a similar Michaelis-Menten constant value for taurocholate in the kidney and intestine. ASBT protein and function were present in the kidney but not the ileum from 7-day-old rats. On postnatal day 7, there was a sevenfold increase in ASBT steady-state mRNA levels in the kidney relative to the ileum, yet nuclear run-on assays revealed that the nascent transcription rates at this age were virtually the same. This suggests that the difference in the neonatal expression of the ASBT gene in the kidney and ileum may be in part due to differences in mRNA stability.

Pancreas divisum in a family with hereditary pancreatitis

Hereditary pancreatitis is characterized by an autosomal-dominant mode of inheritance with incomplete penetrance, onset of symptoms in childhood or early adolescence (mean age of onset approximately 13 years), and an approximately equal sex incidence. Pancreas divisum is a congenital variant of pancreatic ductal anatomy in which the ventral and dorsal pancreatic ductal systems fail to fuse, so that two functional papillae drain the exocrine secretions of the pancreas. In recent years, several reports of pancreatitis associated with pancreas divisum in children have appeared. We now report a family in which the mother, son, and daughter all had presented with recurrent pancreatitis from an early age. Both the mother and son have endoscopic retrograde cholangiopancreatography-documented pancreas divisum, whereas the daughter has a stricture in her distal pancreatic duct. To our knowledge, this is the first such report of "familial" pancreas divisum. The implications of these findings in the setting of hereditary pancreatitis highlight the controversial issues of the clinical significance of pancreas divisum and the appropriateness of surgical therapy.

Cloning and molecular characterization of the ontogeny of a rat ileal sodium-dependent bile acid transporter

Sodium-dependent bile acid transport in the rat ileum is abruptly expressed at weaning. Degenerate oligonucleotides, based on amino acid sequence identities between the rat liver and hamster ileal transporters, were used to amplify a rat ileal probe. A 1.2-kb cDNA clone, which contains the full coding region (348 amino acids, 38 kD), was isolated by hybridization screening. In vitro translation yielded a 38-kD protein which glycosylated to 48 kD. Sodium-dependent uptake of taurocholate was observed in oocytes injected with cRNA. Northern blot analysis revealed a 5.0-kb mRNA in ileum, kidney, and cecum. A 48-kD protein was detected in ileal brush border membranes and localized to the apical border of villus ileal enterocytes. mRNA and protein expression, which were negligible before weaning, increased dramatically at weaning. Nuclear transcription rates for the transporter increased 15-fold between postnatal days 7 and 28. The apparent molecular weight of the transporter also increased between days 19 and 28. In summary, the developmental regulation of the rat ileal sodium-dependent bile acid cotransporter is characterized by transcriptionally regulated increases in mRNA and protein levels at the time of weaning with changes in apparent molecular weight of the protein after weaning.

Delta 4-3-oxosteroid 5 beta-reductase deficiency causing neonatal liver failure and hemochromatosis

Neonatal liver failure was evaluated in two infants. Neither infant had evidence of congenital infection, galactosemia, alpha 1-antitrypsin deficiency, tyrosinemia, Zellweger syndrome, or hemophagocytic lymphohistiocytosis. Abnormal levels of iron were detected in the minor salivary glands of the first infant and in the explanted liver of the second. Analyses of urinary bile salts by fast-atom bombardment ionization mass spectrometry and gas chromatography-mass spectrometry revealed a paucity of primary bile acids and a predominance of 7 alpha-hydroxy-3-oxo-4-cholenoic and 7 alpha,12 alpha-dihydroxy-3-oxo-4-cholenoic acids. These findings are consistent with delta 4-3-oxosteroid 5 beta-reductase deficiency, a primary genetic defect in bile acid synthesis. Postmortem evaluation of the first infant revealed significant iron deposition in the liver, pancreas, thyroid, adrenal glands, myocardium, stomach, and submucosal glands of the respiratory tract. In both infants examination of the liver revealed extensive loss of hepatic parenchyma. These cases expand the clinical spectrum of bile acid metabolism defects to include neonatal liver failure with associated hemochromatosis.

Characterization of endogenous carrier-mediated taurocholate efflux from Xenopus laevis oocytes

Taurocholate efflux was studied in Xenopus laevis oocytes and is consistent with a carrier-mediated process. This carrier can be competitively inhibited and trans stimulated by glycocholate. Transport is also trans stimulated by taurochenodeoxycholate and S-hexylglutathione, but not taurolithocholate or daunomycin, reflecting a range of specificity including substrates of both the hepatic canalicular bile acid transporter and the multispecific organic anion transporter. In addition, ATP added to the outside of the oocyte results in an increase in the maximal velocity of this transport process. The physiologic function of this endogenous carrier is not known, but it may act as a generalized system for the efflux of potentially toxic organic anions.

The effects of bile acid feeding on the development of ileal bile acid transport

Sodium-dependent bile acid uptake is developmentally regulated in the rat ileum. Transport activity is abruptly expressed on postnatal d 17, although the mechanisms controlling this expression are poorly understood. Changes in bile salt metabolism and hepatic transport result in a marked increase in bile flow before postnatal d 17, and thus this study examined the effects of bile salt feeding on the development of ileal bile acid transport. Twelve-d-old rat pups were gavage-fed saline, taurocholate, or mannitol on a daily basis for 3 d. Sodium-dependent bile acid transport was studied by rapid filtration using ileal brush-border membrane vesicles prepared from the various experimental groups. Taurocholate feeding resulted in precocious development of sodium-dependent bile acid transport and induction of sucrase activity. Mannitol feeding, used as a control for the effects of diarrhea-induced stress, resulted in similar sucrase activity, yet sodium-dependent bile acid transport was induced to only half the level observed in taurocholate-fed animals (3.2 +/- 1.6 versus 6.9 +/- 2.0 pmol/mg protein/45 s, p < 0.001). Serum corticosterone levels were similar in the mannitol- and taurocholate-fed animals (3.8 +/- 1.3 versus 4.6 +/- 1.8 micrograms/dL). Both feedings lead to histologic maturation of the ileum, with a more pronounced effect in the taurocholate-fed pups. Bile salt feeding induces precocious expression of ileal bile acid transport, apparently by both diarrhea-induced stress and a bile salt-specific effect.

An ontogenically regulated 48-kDa protein is a component of the Na(+)-bile acid cotransporter of rat liver

Recent evidence suggests that the Na(+)-coupled carrier mechanism for bile acids on the hepatocyte basolateral plasma membrane is a polypeptide in the molecular weight range of 48,000-50,000. In this study we used a strategy for the identification and isolation of this transport protein based on the observation that Na(+)-dependent transport activity is abruptly expressed in fetal rat liver just before birth [Suchy et al. Am. J. Physiol. 251 (Gastrointest. Liver Physiol. 14): G665-G673, 1986]. Analysis of basolateral plasma membranes by SDS-PAGE revealed that a protein of apparent molecular weight 48,000 was absent from fetal rat liver on day 19 of gestation, barely detectable on day 20, and thereafter increased progressively with postnatal development. Monospecific, polyclonal antibodies raised against the 48-kDa protein but not preimmune antibodies significantly inhibited the initial rate of Na(+)-dependent taurocholate uptake by isolated rat hepatocytes. In contrast, Na(+)-independent taurocholate transport and uptake of another anion, 35SO4(2-), were not affected by antibody treatment. When an extract containing the total complement of basolateral proteins was incorporated into asolectin liposomes, Na+ gradient-dependent uptake of taurocholate was observed, including a 2- to 2.5-fold accumulation of substrate above its equilibrium concentration (overshoot). However, if the membrane extract was first selectively depleted of the 48-kDa protein by immunoprecipitation with the anti-48-kDa antibody before reconstitution, Na(+)-dependent stimulation of taurocholate transport was completely abolished. These studies indicate that an ontogenically regulated 48-kDa protein is a component of the basolateral Na(+)-dependent transport system for bile acids.