Nonalcoholic Fatty Liver Disease in Renal Transplant Recipients Proven by Transient Elastography

Correlation Between Serum Transaminase Levels and Estimated Glomerular Filtration Rate After Living-Donor Kidney Transplantation

BACKGROUND

There is a risk of hypoperfusion during kidney transplantation surgery owing to patients' underlying disease and ischemia-reperfusion injury; further, hypoperfusion may cause injury to major organs. We hypothesized that the decrease in blood pressure after ischemia-reperfusion injury during kidney transplantation may be associated with indicators of liver injury and kidney graft function.

METHODS

Data regarding living-donor kidney transplantations performed at our institution between 2018 and 2022 were retrospectively evaluated. Exclusion criteria included pediatric recipients or donors aged <18 years, multiple organ transplantation, and elevated postoperative serum transaminase levels. Correlations among blood pressure, serum transaminase levels on postoperative days 3 to 5, and estimated glomerular filtration rate (eGFR) on postoperative days 7 and 14 were analyzed. Further, a subgroup analysis was performed based on eGFR.

RESULTS

A total of 276 patients were included in the final analysis. Serum transaminase levels were significantly negatively correlated with eGFR (partial correlation coefficient-0.26, P < .001). The postreperfusion decrease in blood pressure was not correlated with serum transaminase levels. However, the postreperfusion decrease in blood pressure and baseline blood pressure correlated with the eGFR (partial correlation coefficient = -0.18, P = .004).

CONCLUSION

These findings indicate a correlation between intraoperative liver injury and kidney graft function, suggesting the importance of intraoperative management of organ perfusion. Since postreperfusion blood pressure changes did not significantly correlate with liver injury indicators, it is important to consider other causative factors for hypoperfusion in major organs during living-donor kidney transplantation, including microcirculatory failure and organ congestion-related ischemia/reperfusion.

Mortality and Cardiovascular Outcomes in Adult Non-Liver Solid Organ Transplant Patients With Nonalcoholic Steatohepatitis

BACKGROUND

The effect of nonalcoholic steatohepatitis (NASH) on mortality or major adverse cardiovascular events (MACE) in non-liver solid organ transplant recipients (NL-SOT) is unknown.

METHODS

Using a retrospective design, adult NL-SOT recipients who had biopsy-proven NASH were compared NL-SOT recipients with normal liver function tests and imaging; propensity matched at a 1:10 ratio on the following: age, sex, race, transplant year, transplant organ, smoking status, and diabetes status. Both deceased and living donor recipients were included; heart and liver transplant patients were excluded. Primary outcome was incidence of all-cause mortality and MACE (a composite outcome of coronary artery disease, ischemic stroke, and peripheral arterial disease).

RESULTS

Seven patients (3 kidney and 4 lung transplants) had biopsy-proven NASH and 70 patients without NASH, both groups were predominantly male (53%-57%), White (86%-91%), and overweight (mean body mass index ∼ 26). The majority of patients were on calcineurin inhibitors (≥85%), antimetabolites (≥97%), and prednisone (≥50%). Survival analysis showed that NASH patients had a higher risk of death (hazard ratio [HR], 3.24; 95% confidence interval [CI], 1.26-8.33, P = 0.02). NASH did not affect the risk of death-censored graft failure (HR, 1.08; 95% CI, 0.14-8.67; P = .94) or the risk of MACE (HR, 1.03; 95% CI, 0.23-4.62; P = .97).

CONCLUSIONS

In NL-SOT recipients, NASH is significantly associated with mortality but not with MACE.

Liver Stiffness is Reduced to Normal After Successful Renal Transplantation: A Prospective Cohort Study

Background

Liver stiffness (LS) may be falsely elevated in patients on maintenance hemodialysis (MHD) due to fluid overload. We measured LS change by transient elastography (TE) in MHD patients before and after successful renal transplantation.

Method

Adults on ≥2 years of MHD, without additional risk factors for liver fibrosis or fluid overload, and planned for renal transplantation were prospectively recruited. LS was measured on two occasions, i.e., within two weeks before transplantation (pre-Tx LS) and after ≥ 3 months after successful transplantation (post-Tx LS). The participants with pre-Tx LS ≤ 7.0 KPa and >7.0 KPa were classified as "Group I" and "Group II," respectively. Categorical and numerical data are expressed as ratio/proportions and mean (SD), respectively.

Results

Paired data from 43 participants (males 42 [97.7%]; age 32 [11] years) were analyzed. The pre-Tx and post-Tx LS of the entire cohort, measured at 307 (198) days of interval, were 8.5 (7.3) KPa and 6.7 (3.1) KPa, respectively. Before transplantation, 21 (49%) participants belonged to Group II and 22 (51%) to Group I. Among the Group II participants, 12 (57%) showed LS normalization after 312 (182) days of transplantation. Of the 22 participants in Group I, three (13.6%) showed LS elevation to >7.0 KPa after 303 (217) days of transplantation. The mean LS changes among the overall cohort, Group II, and Group I were -1.8 KPa, -4.1 KPa, and +0.2 KPa, respectively.

Conclusion

LS in people on MHD may be falsely elevated, which is likely to normalize after successful renal transplantation.

Non-Invasive Assessment of Liver Fibrosis and Steatosis in End-Stage Renal Disease Patients Undergoing Renal Transplant Evaluation

Background

Non-alcoholic fatty liver disease (NAFLD) has an increased prevalence in end-stage renal disease (ESRD) due to similar risk factors. The aim of this study was to assess non-invasive testing including transient elastography (TE) for liver stiffness (LS), controlled attenuated parameter (CAP) for steatosis, Fibrosis-4 (FIB-4) score, aspartate aminotransferase (AST) to platelet ratio index (APRI) and NAFLD fibrosis score (NFS), for evaluation of NAFLD along with advanced fibrosis (AF) in patients with ESRD undergoing renal transplant evaluation.

Methods

Data were retrospectively collected within 12 weeks of TE. Primary outcomes were AF, defined by LS ≥ 9 kPa compared to APRI > 1.5, FIB-4 > 2.67, and NFS of 0.675, and ≥ 5% steatosis by CAP ≥ 263 dB/m compared to liver histology when available.

Results

A total of 171 patients were evaluated: mean age 56, 65% male, 36% obese, 47% had diabetes, 96% hypertension, and 56% dyslipidemia. Mean LS was 6.5 kPa with 21% having AF. Mean CAP was 232 dB/m, with 25% having steatosis. Those with AF were older with higher NFS. Those with steatosis were obese and had diabetes without higher LS or fibrosis scores. Only NFS was associated with LS ≥ 9 kPa. In those with liver histology, AF was associated with LS ≥ 9 kPa but not with APRI, FIB-4, or NFS.

Conclusions

Despite normal liver enzymes, non-invasive assessment via TE in ESRD patients exhibited high prevalence of AF and steatosis not detected by APRI or FIB-4 scores. This high prevalence was secondary to the common risk factors such as obesity and diabetes, among patients with NAFLD and ESRD.

Metabolic Consequences of Solid Organ Transplantation

Metabolic complications affect over 50% of solid organ transplant recipients. These include posttransplant diabetes, nonalcoholic fatty liver disease, dyslipidemia, and obesity. Preexisting metabolic disease is further exacerbated with immunosuppression and posttransplant weight gain. Patients transition from a state of cachexia induced by end-organ disease to a pro-anabolic state after transplant due to weight gain, sedentary lifestyle, and suboptimal dietary habits in the setting of immunosuppression. Specific immunosuppressants have different metabolic effects, although all the foundation/maintenance immunosuppressants (calcineurin inhibitors, mTOR inhibitors) increase the risk of metabolic disease. In this comprehensive review, we summarize the emerging knowledge of the molecular pathogenesis of these different metabolic complications, and the potential genetic contribution (recipient +/- donor) to these conditions. These metabolic complications impact both graft and patient survival, particularly increasing the risk of cardiovascular and cancer-associated mortality. The current evidence for prevention and therapeutic management of posttransplant metabolic conditions is provided while highlighting gaps for future avenues in translational research.

Assessment of Steatosis and Fibrosis in Liver Transplant Recipients Using Controlled Attenuation Parameter and Liver Stiffness Measurements

AIM

The primary objective of this study was to evaluate the prevalence of increased controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) as surrogate markers of liver steatosis and fibrosis in liver transplant recipient (LTR). Secondary objectives were to determine the predictors of increased CAP and LSM in population of LTR.

METHODS

In this prospective, cross-sectional study, we have evaluated 175 LTRs' mean age as 61 (53-65) with a functioning graft for more than one year who came for regular outpatient examinations to the Department of Gastroenterology, University Hospital (UH) Merkur, Zagreb, Croatia.

RESULTS

Of 175 analyzed LTRs, 34.28% had obesity, 64.00% had hypertension, 38.28% had diabetes, and 58.85% had hyperlipidemia. The prevalence of liver steatosis was 68.57%, while the prevalence of severe liver steatosis was 46.85%. On multivariate analysis, independent factors associated with liver steatosis were male gender, total cholesterol as positive predictor, and HDL as negative predictor, and independent factors positively associated with severe liver steatosis were higher body mass index (BMI) and higher triglyceride levels. The prevalence of moderate liver fibrosis was 54.85%, while the prevalence of advanced liver fibrosis was 24%. On multivariate analysis, independent factors positively associated with moderate fibrosis were gamma-glutamyl transferase (GGT) and CAP, while the independent factor positively associated with advanced fibrosis was GGT.

CONCLUSION

Our study showed high prevalence of increased CAP and LSM measurements as surrogate markers of liver steatosis and fibrosis. Metabolic syndrome components were highly present and were associated with CAP and LSM values as well as in the pretransplant setting. Due to high prevalence of metabolic comorbidities and nonalcoholic fatty liver disease in LTRs and the lack of the abnormal liver test in a significant number of these patients, TE with CAP may be a reasonable initial assessment for LTRs with one or more components of the metabolic syndrome.

Activation of Constitutive Androstane Receptor Ameliorates Renal Ischemia-Reperfusion-Induced Kidney and Liver Injury

Acute kidney injury (AKI) is associate with high mortality. Despite evidence of AKI-induced distant organ injury, a relationship between AKI and liver injury has not been clearly established. The goal of this study is to investigate whether renal ischemia-reperfusion (IR) can affect liver pathophysiology. We showed that renal IR in mice induced fatty liver and compromised liver function through the downregulation of constitutive androstane receptor (CAR; -90.4%) and inhibition of hepatic very-low-density lipoprotein triglyceride (VLDL-TG) secretion (-28.4%). Treatment of mice with the CAR agonist 1,4-bis[2-(3,5 dichloropyridyloxy)] benzene (TCPOBOP) prevented the development of AKI-induced fatty liver and liver injury, which was associated with the attenuation of AKI-induced inhibition of VLDL-TG secretion. The hepatoprotective effect of TCPOBOP was abolished in CAR^-/- mice. Interestingly, alleviation of fatty liver by TCPOBOP also improved the kidney function, whereas CAR ablation sensitized mice to AKI-induced kidney injury and lethality. The serum concentrations of interleukin-6 (IL-6) were elevated by 27-fold after renal IR, but were normalized in TCPOBOP-treated AKI mice, suggesting that the increased release of IL-6 from the kidney may have mediated the AKI responsive liver injury. Taken together, our results revealed an interesting kidney-liver organ cross-talk in response to AKI. Given the importance of CAR in the pathogenesis of renal IR-induced fatty liver and impaired kidney function, fatty liver can be considered as an important risk factor for kidney injury, and a timely management of hepatic steatosis by CAR activation may help to restore kidney function in patients with AKI or kidney transplant.

Metabolic syndrome and non-alcoholic fatty liver disease after liver or kidney transplantation

Transplantation is a definitive treatment option for patients with end-stage liver disease, and for some patients with acute liver failure, hepatocellular carcinoma or end-stage renal disease. Long-term post-transplantation complications have become an important medical issue, and cardiovascular diseases (CVD) are now the leading cause of mortality in liver or kidney transplant recipients. The increased prevalence of metabolic syndrome (MS) likely plays a role in the high incidence of post-transplantation CVD. MS and its hepatic manifestation, non-alcoholic fatty liver disease (NAFLD), are prevalent among the general population and in pre- and post-transplantation settings. MS components are associated with recurrent or de novo NAFLD in transplant recipients, potentially influencing post-transplantation survival. Moreover, recent data reveal an important association between NAFLD and risk of incident of chronic kidney disease (CKD). Therefore, NAFLD identification could represent an additional clinical feature for improving the stratification of liver and kidney transplant recipients with regards to risks of CVD, CKD and renal allograft dysfunction. All MS components are potentially modifiable; therefore, it is crucial that hepatologists, nephrologists and primary care physicians become more engaged in managing post-transplantation metabolic complications. The present review discusses the recent clinical evidence regarding the importance of MS and its components after liver and kidney transplantation, as well as the link between MS and NAFLD after liver and kidney transplantation.