De novo nonalcoholic fatty liver disease after liver transplantation
Hepatic steatosis is a recognized problem in patients after orthotopic liver transplant (OLT). However, de novo development of nonalcoholic fatty liver disease (NAFLD) has not been well described. The aim of this study was to determine the prevalence and predictors of de novo NAFLD after OLT. A retrospective analysis was performed on 68 OLT patients with donor liver biopsies and posttransplantation liver biopsies. Individual medical charts were reviewed for demographics, indication for OLT, serial histology reports, genotypes for hepatitis C, comorbid conditions, and medications. Liver biopsies were reviewed blindly and graded according to the Brunt Scoring System. Multivariate logistic regression analysis was used to study the risk factors for developing NAFLD. The interval time from OLT to subsequent follow-up liver biopsy was 28 ± 18 months. A total of 12 patients (18%) developed de novo NAFLD, and 6 (9%) developed de novo NASH. The regression model indicated that the use of angiotensin-converting enzyme inhibitors (ACE-I) was associated with a reduced risk of developing NAFLD after OLT (odds ratio, 0.09; 95% confidence interval, 0.010-0.92; P = 0.042). Increase in body mass index (BMI) of greater than 10% after OLT was associated with a higher risk of developing NAFLD (odds ratio, 19.38; 95% confidence interval, 3.50-107.40; P = 0.001). In conclusion, de novo NAFLD is common in the post-OLT setting, with a significant association with weight gain after transplant. The use of an ACE-I may reduce the risk of developing post-OLT NAFLD. Liver Transpl, 2006. © 2006 AASLD.
It is estimated that nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) affect 3% of the general population, respectively,1–3 but remarkably little is known about de novo development of NAFLD/NASH after orthotopic liver transplant (OLT). This lack of data may partly be attributed to traditional thinking that NAFLD is a diagnosis of exclusion. However, rapid weight gain, diabetes mellitus, hyperlipidemia, hypertension, and consequent metabolic syndrome are more common posttransplantation than in the general population; therefore, the risk of developing NAFLD/NASH in this population may increase.4–6 There are small case reports of NASH developing de novo or recurring in OLT recipients.7, 8 These patients typically exhibit features of the metabolic syndrome, lack of alcohol consumption, and have liver histology consistent with NAFLD/NASH, including a high degree of steatosis, lobular inflammation with neutrophils, ballooning degeneration, Mallory bodies, and fibrosis. The use of immunosuppressive medications could be partially responsible, as both corticosteroids and calcineurin inhibitors promote hypertension and hypercholesterolemia. Prednisone, tacrolimus, and cyclosporine A are diabetogenic, and sirolimus induces hyperlipidemia.9 NAFLD and NASH could also coexist or be superimposed on other liver diseases after OLT such as recurrent hepatitis C virus (HCV) infection.
Recognizing posttransplantation NAFLD/NASH is important because it may significantly affect graft survival by promoting fibrosis and cirrhosis. In addition, data from the pretransplantation population indicate that patients with NAFLD and HCV are much more likely to be nonresponder to antiviral therapy.10–13 The aim of this study was to determine the prevalence of de novo NAFLD post-OLT and attempt to identify risk factors that might lead to the development of future treatment options for NAFLD in the post-OLT setting.
PATIENTS AND METHODS
A retrospective analysis of 68 OLT patients was performed at the University of California Davis Medical Center. All patients had donor liver biopsies. The post-OLT liver biopsies were performed for abnormal liver tests. All study patients were transplanted and followed at University of California Davis Medical Center. We reviewed individual medical charts for demographics, indication for OLT, serial histology reports, specific genotypes for HCV patients, comorbid conditions, and medication profiles (Table 1). All the factors were defined as categorical variables being present or absent during a 6-month period prior to the post-OLT liver biopsy. Significant weight gain was defined as at least a 10% increase in BMI compared to pre-OLT weight. Diagnosis of hypertension was made according to the guideline set by the Joint National Committee.7 Diagnosis of hyperlipidemia was made by the guideline set by the National Cholesterol Education Program III.
Table 1. Univariate Analysis of the Potential Factors Associated With Post-OLT De Novo NAFLD
|Gender|| || |
| Male||55 (81)||0.753|
|Indication(s) for OLT|| || |
| HCV||57 (84)||0.641|
| Genotype 1||38 (67)||0.823|
| Genotype 2||3 (6)||0.331|
| Genotype 3||16 (27)||0.355|
|Increase in BMI ≥ 10% after OLT||24 (35)||0.000|
|Comorbidities|| || |
| Hypertension||47 (69)||0.096|
| Diabetes mellitus||26 (38)||0.514|
| Hyperlipidemia||17 (25)||0.594|
|Medications|| || |
| Tacrolimus||61 (90)||0.693|
| Prednisone||14 (21)||0.910|
| Mycophenolate||12 (18)||0.556|
| Sirolimus||11 (16)||0.453|
| ACE-I||22 (32)||0.014|
| HMG CoA-I||12 (17)||0.386|
| Ursodiol||8 (12)||0.829|
| PPAR-γ receptor agonist||3 (4)||0.497|
This study was approved by the University of California Davis Medical Center Institutional Review Board.
The liver biopsy specimens were reviewed in a blinded fashion by a hepatopathologist for the presence of predominant macrovesicular hepatic steatosis, ballooning degeneration, Mallory's hyaline, perisinusoidal fibrosis, and neutrophilic lobular inflammation. De novo NAFLD was determined in patients who were found to have a greater than 33% increase in steatosis when compared to their donor biopsies. Each specimen with significant steatohepatitis was graded according to the Brunt Scoring System.14 A minimum grade of 2 (moderate) was used to define de novo NASH.
Data were analyzed with SPSS version 13.0 (SPSS, Chicago, IL). To determine the independent predictors of development of NAFLD and NASH, multiple logistic regression analysis was performed for the potential factors shown in Table 1. The backward variable selection procedure based on the likelihood ratio was used to determine the subset of variables in the best regression equation. A P value < 0.05 was considered as statistically significant. Odds ratios were given with the 95% confidence intervals.
Characteristics of the Patient Population
A total of 56 (81%) of the patients were male. The age (± standard deviation) at OLT was 48 ± 8 yr (Table 1). HCV was the most common indication for OLT (84%), with the following genotype distribution: 67% genotype 1; 6% genotype 2; and 27% genotype 3. Our study patients had the following metabolic conditions: 26 patients had type 2 diabetes mellitus; 47 hypertension; and 17 hyperlipidemia. Among the 26 patients noted to have diabetes mellitus post-OLT, 11 patients had preexisting diabetes mellitus before the OLT.
The use of tacrolimus (in 61 patients), sirolimus (11), mycophenolate mofetil (12), prednisone (14), ACE-I (22), peroxisome proliferator-activated receptor-γ receptor agonist (3), HMG-coA reductase inhibitor (12), and ursodiol (8) were also included in the analysis.
A total of 12 patients (18%) developed de novo NAFLD, and 6 (9%) developed de novo NASH, according to our definitions. Median donor age (range) for the study population, the de novo NAFLD subgroup, and the de novo NASH subgroup were comparable: 31 (13-79), 24 (15-55), and 22 (15-55), respectively. The donor biopsies showed 0% steatosis in 43 (63%) patients and 1 to 33% steatosis in 25 (37%). Among those with 0% donor steatosis, 22 (32%) continued to show no steatosis at the post-OLT biopsies, 16 (24%) developed <33% increase in steatosis, and 5 (7%) developed >33% steatosis. Among OLT patients with the presence of minimal donor steatosis, 8 (12%) showed no significant change in steatosis and 17 (25%) showed increased steatosis at the post-OLT biopsies. The median length of time from OLT to the biopsy (range) for the study population, the de novo NAFLD subgroup, and the de novo NASH subgroup were comparable: 23 (9-95), 17 (11-51), and 16 (13-51) months, respectively.
The indication for OLT for all 6 patients with de novo NASH was HCV-related cirrhosis. Among these patients, 3 had genotype 3, 2 had genotype 1, and 1 had genotype 2 infection. All these patients were HCV ribonucleic acid positive. Median HCV ribonucleic acid (range) for de novo NASH vs. non-NASH patients was comparable at 1.6 × 106 (5.7 × 105 to 2.7 × 106) vs. 1.6 × 106 (2.5 × 104 to 3.9 × 107) copies/mL.
Analysis of the Potential Predictors
Table 2 shows the distribution of the study patients with and without the development of de novo NAFLD with respect to their ACE-I use and weight gain after OLT. Among patients who developed de novo NAFLD post-OLT, 83% (10/12) had also gained weight greater than 10% of pretransplantation BMI. Among patients with no significant post-OLT NAFLD, only 25% (14/56) gained significant weight. We found that among patients with NAFLD, only 1 of 12 was receiving ACE-I for at least 6 months prior to biopsy. Among non-NAFLD, 38% (21/56) were receiving ACE-I. The indication for the use of ACE-I was hypertension in all patients in our study group.
Table 2. Distribution of the Patients With and Without the Development of de novo NAFLD With Respect to Their ACE-I Use and Weight Gain After OLT
|de novo NAFLD; n = 12||1 (8)||11 (92)|
|No NAFLD; n = 56||21 (38)||14 (25)|
Table 3 represents the results of multivariate logistic regression analysis performed on potential predictors in Table 1. The best regression equation with significant effects showed that the increase in BMI of greater than 10% post-OLT was associated with increased risk of developing de novo NAFLD (odds ratio, 19.38; 95% confidence interval, 3.50-107.40; P = 0.001). In contrast, the use of ACE-I was associated with a reduced risk of developing de novo NAFLD after OLT (odds ratio, 0.09; 95% confidence interval, 0.01-0.92; P = 0.042).
Table 3. Multivariate Analysis of the Factors Independently Associated With De Novo NAFLD After OLT
|Weight gain (ΔBMI > 10%)||19.38||3.50–107.40||0.001|
In patient with chronic hepatitis C, most investigators require the presence of at least 33% steatosis to warrant a diagnosis of concomitant NAFLD because the significance of minimal steatosis is uncertain.6, 10, 15 Based on this rationale, we have performed the first study that addressed the prevalence of de novo NAFLD in OLT patients.
Our multivariate regression identified an increase in BMI and the use of ACE-I as a positive and a negative risk factor for development of de novo post-OLT NAFLD, respectively. Increase in the BMI is known to be associated with NAFLD in the nontransplantation setting.16 In the first few months after a successful OLT, weight gain can be regarded as one of the positive effects of transplantation. However, within 2 yr of transplantation, excess body weight is recorded in up to 60 to 70% of patients, and 20% of the previously nonobese transplant recipients become obese.4, 5 The exact mechanisms leading to excessive weight gain in such a large proportion of patients are incompletely understood, although a major role is attributed to the development of post-OLT insulin resistance, diabetes mellitus, and the metabolic effects of immunosuppressive medications (corticosteroids, calcineurin inhibitors).
Currently, NAFLD has no known definitive medical therapy, but our finding showed that ACE-I may independently reduce the risk of de novo development of NAFLD in the post-OLT setting. While the true impact of ACE-I on de novo NAFLD must be validated with future studies, experimental data shows that angiotensin receptor inhibition improves insulin sensitivity,17 reduces hepatic triglycerides with a decrease in the macrovesicular steatosis score,18, 19 decreases oxidative stress,20 and attenuates the progression of hepatic fibrosis in rodents.21 In addition, angiotensin receptor inhibition also improved histological scores in patients with NASH.22 While the molecular basis for these observations is not well-described, there is considerable interest in a potential role of angiotensin inhibition on peroxisome proliferator-activated receptor-γ. Peroxisome proliferator-activated receptor-γ has an important role in adipocyte differentiation as well as regulatory function in both hepatic fatty acid synthesis and oxidation, and its activation seems to be beneficial in NAFLD patients.23–27
Commonly used immunosuppressive medications such as prednisone, calcineurin inhibitors, and sirolimus in the OLT setting can increase insulin resistance; but we did not find any statistically significant association between these variables and development of post-OLT NAFLD and NASH. Hyperlipidemia and diabetes are often associated with weight gain and have been implicated in NASH in nontransplantation patients; however, these variables also did not reach statistical significance in our multivariate study. The statistical analysis of these subgroups may be limited by the small sample size, and in the future these findings will have to be verified with larger studies and longer follow-up.
The finding that the use of ACE-I could potentially be beneficial in reducing risk of the post-OLT NAFLD and NASH, is both novel and significant. Larger, prospective trials which include its effect on graft survival are needed to validate the use of ACE-I in the post-OLT population.