Objectives: The impact of achieving a sustained viral response on extrahepatic manifestations after liver transplant is unclear. In this study, our aim was to evaluate whether sustained viral responses in hepatitis C-positive liver transplant recipients can lead to improved nonhepatic outcomes.

Materials and Methods: We studied 84 consecutive liver transplant recipients who achieved a sustained viral response with direct-acting antiviral agents at the University of California Los Angeles. We collected laboratory data before and after the sustained viral response was achieved. Paired t tests were performed.

Results: The mean age and standard deviation of our cohort was 62.4 ± 7.6 years. The mean time from achieving a sustained viral response to last follow-up in our cohort was 19.5 ± 10.8 months. In the entire cohort, there were no changes in mean fasting blood glucose (123 ± 42 vs 120 ± 35 mg/dL; P = .49). We observed a significant improvement in renal function in recipients with stage 1 and 2 chronic kidney disease (82 ± 15 vs 71.16 ± 16 mL/min/1.73 m²; P < .001) and in those treated within 3 months of liver transplant (75 ± 28 vs 61 ± 16 mL/min/1.73 m²; P = .035). Fasting blood glucose decreased in recipients with a diagnosis of impaired fasting blood glucose (109 ± 16 vs 103 ± 13 mg/dL; P = .001).

Conclusions: The benefits on glucose metabolism and renal function after a sustained viral response in liver transplant recipients appear to be limited to those with early chronic kidney disease and those treated soon after transplant. The potential benefits from direct-acting antiviral agents on these parameters may be overshadowed by the effects of immuno­suppressant therapy.

Key words : Diabetes mellitus, Direct-acting antiviral agent, Fasting blood glucose, Renal insufficiency

Introduction

Chronic hepatitis C virus (HCV) infection can be associated with both hepatic and nonhepatic complications.¹ Infection with HCV remains one of the common causes of cirrhosis and reason for liver transplant in the United States.² Recurrent HCV disease can impact both patient and graft survival due to faster disease progression in liver transplant recipients.^3,4 Recently, the natural history of HCV in liver transplant recipients has been favorably altered with the introduction of direct-acting antiviral agents (DAAs).⁵

Direct-acting antiviral agents have been shown to be safe, effective, and tolerable in liver transplant recipients.⁶ Treatment regimens with DAAs can result in rates of sustained viral responses (SVRs) in liver transplant recipients that are comparable to those described in the general population.⁷ The results of a recent analysis highlighted that HCV may soon be eliminated from liver transplant cohorts by treating both donor candidates and recipients.⁸ Despite the demonstrable improvements in curing HCV in liver transplant recipients with DAAs, their effects on endpoints other than SVR have not been well documented.

Chronic HCV infection has been associated with development of renal insufficiency and insulin resistance/diabetes in the general population.^9,10 Improvements in these extrahepatic manifestations of HCV have been described in patients treated with antiviral therapy.^11-13 The development of HCV-related extrahepatic manifestations such as diabetes and renal disease has also been described after liver transplant.^14-16

Given the association of HCV with both renal insufficiency and diabetes, the hypothesis of our study was that curing HCV in liver transplant recipients with DAAs is associated with improved renal function and glycemic control in the post­transplant setting.

Materials and Methods

Study participants
A chart review was performed on patients who underwent liver transplant procedures and were treated with DAA therapy for HCV at the University of California Los Angeles Medical Center. Our search of an administrative database identified 84 such patients treated between 2012 and 2017. We collected data on the following recipient variables: sex, comorbidities, age at transplant, year of transplant, immunosuppression regimen, duration of treatment, and hematologic, biochemical, and virologic results. We also collected data on treatment type, date of treatment initiation, date of treatment cessation, and dose modifications made during treatment. In addition, information on the immunosuppression regimen was recorded. All data were collected in accordance with institutional review board requirements.

A diagnosis of diabetes mellitus was made if the patient met at least 1 of the following 2 criteria: (1) fasting blood glucose (FBG) greater than or equal to 126 mg/dL on 2 or more occurrences or (2) patient was receiving medications for a prior diagnosis of diabetes mellitus.⁹ An impaired FBG level was defined per the American Diabetes Association criteria as individuals with a FBG greater than or equal to 100 mg/dL.⁹

Chronic kidney disease (CKD) was defined per standard parameters utilizing glomerular filtration rate (GFR) for staging. Stage 1 was defined as kidney damage with normal or increased GFR (> 90 mL/min/1.73 m²), stage 2 was defined as mild reduction in GFR (60-89 mL/min/1.73 m²), stage 3a was defined as moderate reduction in GFR(45-59 mL/min/1.73 m²), stage 3b was defined as moderate reduction in GFR (30-44 mL/min/1.73 m²), stage 4 was defined as severe reduction in GFR (15-29 mL/min/1.73 m²), and stage 5 was defined as kidney failure with GFR < 15 mL/min/1.73 m².¹⁰

The immunosuppression regimens after liver transplant consisted of combinations of cyclosporine, prednisone, tacrolimus, azathioprine, and myco­phenolate mofetil. According to our protocol, patients initially received 1 g of intravenous methylprednisolone on the day of transplant; this was then tapered to 20 mg/day over 1 week. Oral prednisone was subsequently started at 20 mg/day and tapered as tolerated. In general, our protocol for posttransplant target immunosuppression levels for tacrolimus consists of 10 to 12 ng/mL for 1 to 3 months, 8 to 10 ng/mL for 3 to 6 months, 5 to 8 ng/mL for 6 to 12 months, and 2 to 5 ng/mL for greater than 12 months. For cyclosporine, our target values are 250 to 300 ng/mL for 1 to 3 months, 175 to 250 ng/mL for 3 to 6 months, 100 to 175 ng/mL for 6 to 12 months, and 50 to 100 ng/mL for greater than 12 months. Immunosuppression levels were assessed bimonthly to monthly, with changes in doses made to reach target ranges. We collected immuno­suppression values before and during antiviral therapy, as well as at the time of rejection, if applicable.

The indication for performing liver biopsies in all transplant recipients was elevated liver-associated tests found on routine laboratory work. Protocol biopsies are not performed at our institution. Liver biopsies were read by an experienced liver pathologist. The histologic activity index and fibrosis score, as well as the diagnosis of rejection, were determined according to established criteria. Histologic criteria used for the diagnosis of rejection included (1) portal inflammation composed of a mixed infiltrate (lymphocytes, plasma cells, eosinophils, and neutrophils); (2) bile duct inflammation and damage (lymphocytes within bile duct epithelium); and (3) venous endotheliitis demonstrated by lymphocytes infiltrating and lifting the endothelial cells. Rejection severity was based on the number of portal tracts affected by the infiltrate, the degree of damage, and the number of bile ducts damaged. There have been no changes in the histologic diagnostic criteria for rejection over the study period.

Glomerular filtration rate was estimated according to the 2009 Chronic Kidney Disease Epidemiology Collaboration creatinine equation. Fibrosis levels were scored using the Fibrosis-4 (FIB-4) index equation created by Sterling and associates.¹⁷ A FIB-4 score of > 3.25 denotes advance fibrosis, and a FIB-4 of 4 or greater predicts early bridging fibrosis to cirrhosis.¹⁷

Statistical analyses
Categorical variables are expressed as percentages, and continuous variables are presented as mean and standard deviation (SD). All statistical analyses were performed using Microsoft Excel (Microsoft, Seattle, WA, USA).

Results

Baseline characteristics of the recipients who achieved SVR with DAAs are shown in Table 1. The mean ± SD age of our cohort was 62.4 ± 7.6 years, and most recipients were men (73%). The mean time from liver transplant to DAA treatment initiation was 9.7 ± 10 months. The mean time from starting DAAs to last follow-up was 26.78 ± 10.86 months. Most transplant recipients were treated with a sofosbuvir-based regimen, with sofosubvir-ledipasvir used in almost one-half of the liver transplant recipients. Approximately one-third of the recipients (23/84) had advanced fibrosis before DAA therapy. Genotype 1 was noted in almost 80% of the cohort.

Most of the recipients were on a tacrolimus-based immunosuppression regimen. Thirty of our cohort had a diagnosis of diabetes. Twenty of the 30 recipients were on oral diabetic therapy, and 10 patients were not on oral therapy. The treatment regimen for the 5 recipients on hemodialysis included sofosbuvir and ribavirin (2 patients), elbasvir and grazoprevir (2 patients), and sofosbuvir and ledipasvir (1 patient).

Baseline, SVR at 12 weeks posttreatment (SVR12), and last follow-up laboratory values are shown in Table 2. The mean ± SD time between SVR12 and last follow-up was 19.5 ± 10.8 months. We observed a statistically significant improvement in liver-associated tests at the last follow-up relative to baseline values. There was no statistically significant improvement in FBG levels (P = .49).

Subgroup analyses were performed according to the concomitant diagnosis of diabetes and need for hemodialysis (Figure 1). In the 79 recipients not on hemodialysis, SVR was not associated with improve­ment in FBG values (P = .58) and GFR (P = .82). Likewise, there was no improvement in FBG values (P = .32) and GFR (P = .25) in the 30 recipients with a diagnosis of diabetes mellitus.

However, in recipients who met criteria for impaired FBG (n = 28), there was a decrease in FBG with SVR12 (117 ± 13 vs 103 ± 13 mg/dL; P = .001) (Figure 1) without improved changes in GFR (62 ± 24 vs 67 ± 31 mL/min/1.73 m²; P = .40) (Figure 2). In recipients with normal glycemic control (n = 26), there was a statistically significant increase in FBG after SVR12 (90 ± 5 vs 105 ± 15 mg/dL; P = .001) (Figure 1). A new diagnosis of diabetes was not made in recipients whose FBG increased.

Additional subgroup analyses were performed by CKD stage. In patients with CKD stages 1 and 2 (n = 46), there was a statistically significant decrease in GFR (82 ±15 vs 71 ± 16 mL/min/1.73 m²; P < .001). In contrast, liver transplant recipients with CKD stage 3 (n = 31) experienced increased renal function from baseline to last follow-up (49 ± 8 vs 63 ± 27 mL/min/­1.73 m²; P = .008).

Subgroup analyses were also performed based on time between liver transplant and treatment initiation. Impairment in GFR was noted in recipients (n = 18) who were treated within 3 months of liver transplant (77 ±32 vs 61 ± 16 mL/min/1.73 m²; P = .043) (Figure 2). No improvement in GFR was noted in patients treated within 6 months, within 12 months, or after 12 months of transplant.

Discussion

In the general population, the association between extrahepatic manifestations and HCV has been well described.^11-13,18 Two of the better described manifestations are renal disease and diabetes.¹⁶ Moreover, curing HCV has been shown to improve these manifestations.^11-13,18 However, the association between HCV and extrahepatic manifestations after liver transplant has been less clearly described. Although the utilization of DAAs has revolutionized the treatment of HCV in liver transplant recipients and has led to improved patient and graft survival rates, the impact of an SVR on the extrahepatic manifestations of HCV is unknown.

The hypothesis of our study was that curing HCV will lead to improved FBG levels and renal function. The results of our study did not demonstrate any improvement in these outcomes and thus did not support our hypothesis. Subgroup analyses performed across several cohorts in our study demonstrated variable results, with certain cohorts experiencing improvements in the aforementioned parameters, whereas others experiencing an unexpected worsening despite achieving SVR.

Although prior studies have demonstrated a reduction in CKD stage following DAAs and achievement of SVR in nontransplanted patients, we found no significant difference between GFR before treatment and at last follow-up after achieving SVR in our overall analyses.^11,19,20 However, we also noted an improvement in GFR when DAAs were started in recipients within 3 months of liver transplant and before patients developed progressive kidney disease.

There are several factors that may have contributed to these findings, both regarding the posttransplant state and the baseline characteristics of our patient population. It may be that the impact of HCV eradication is best demonstrated by GFR in patients with more relatively intact renal function. In the posttransplant period, calcineurin inhibitor-associated chronic nephrotoxicity is a well-known phenomenon.^21,22 Most of our patients were main­tained on a calcineurin inhibitor-based regimen (Table 1). Therefore, it may be the case that any benefit from eradication of HCV regarding renal function was overshadowed by the renal impairment induced by immunosuppression in the post­transplant period, especially in recipients with already compromised renal function (CKD stage ≥2).

When taken as a whole, our cohort did not demonstrate a significant reduction in FBG. However, in the subset of patients with impaired FBG, a significant reduction in FBG was demonstrated (P = .001). This finding is of particular interest as new-onset diabetes mellitus secondary to immuno­suppressive medications (particularly calcineurin inhibitors and glucocorticoids) is a well-established complication in the period after liver transplant, with a prevalence of 13% to 28% in the first year after transplant.²³ Therefore, the fact that our patients with normal glycemic control did not demonstrate a significant increase in FBG may also point to improved insulin sensitivity in the absence of HCV. This result is also consistent with prior studies that demonstrated a greater decrease in hemoglobin A1c in patients with poorly controlled diabetes mellitus with eradication of HCV compared with patients with hemoglobin A1c measurements closer to goal.¹⁸ Hepatitis C virus cure leads to improved glycemic control by an increase in insulin resistance after SVR, although this effect is less pronounced in patients with severe liver fibrosis.²⁴

The implications for improved glycemic control in liver transplant patients who have obtained SVR with DAAs are important. Poorly controlled diabetes mellitus has been implicated in increased rates of cardiovascular events, graft complications, and even death after transplant.²⁵ It follows that, if cure of HCV reverses the insulin resistance induced by HCV infection in patients after liver transplant, we would hope to see improved glycemic control and in turn improved short- and long-term outcomes for these patients. Unfortunately, in our population, we had insufficient data to determine the impact of SVR on hemoglobin A1c. It is also necessary to consider the potential impact of lifestyle changes, such as dietary modifications and amount of physical activity, after transplant on glycemic control, which would not have been captured in our data set. To fully elucidate the effects of SVR via DAA treatment in these patients, further studies utilizing hemoglobin A1C are needed regarding long-term outcomes.

The possibility of lack of improvement after 3 to 6 months of calcineurin inhibitor treatment regarding renal function and diabetic control may be due to our small cohort size. Additional studies in a larger cohort are warranted to better study the effects of timing of treatment with DAAs. However, given the safety, efficacy, tolerability, and concerns about the impact of delaying DAA therapy, a controlled study assessing timing of posttransplant treatment of HCV may not be feasible.

The results of our study suggest that early DAA treatment after liver transplant can lead to improved maintenance of renal function. Moreover, eradication of HCV improves glycemic control only for those recipients who are prediabetic (ie, with impaired FBG). Many of the benefits of SVR realized in nontransplanted patients may be blunted by the use calcineurin inhibitors in liver transplant recipients.

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