Fatty allograft and cardiovascular outcomes after liver transplantation

Cardiovascular involvement after liver transplantation: role of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

Patients submitted to liver transplantation (LT) are exposed to high risk of cardiovascular (CV) complications which are the main determinants of both short-term and long-term morbidity and mortality in LT. Non-alcoholic fatty liver disease (NAFLD) is a very frequent condition in general population and is associated with a high risk of cardiovascular disease (CVD) which represents the first cause of death of these patients. NAFLD is predicted to become the first indication to LT and nowadays is also frequently detected in patients submitted to LT for other indications. Thus, the risk of CVD in patients submitted to LT is forecasted to increase in the next years. In this review the extent of CV involvement in patients submitted to LT and the role of NAFLD, either recurring after transplantation or as de novo presentation, in increasing CV risk is analysed. The risk of developing metabolic alterations, including diabetes, hypertension, dyslipidemia and weight gain, all manifestations of metabolic syndrome, occurring in the first months after LT, is depicted. The different presentations of cardiac involvement, represented by early atherosclerosis, coronary artery disease, heart failure and arrhythmias in patients with NAFLD submitted to LT is described. In addition, the tools to detect cardiac alterations either before or after LT is reported providing the possibility for an early diagnosis of CVD and an early therapy able to reduce morbidity and mortality for these diseases. The need for long-term concerted multidisciplinary activity with dietary counseling and exercise combined with drug treatment of all manifestations of metabolic syndrome is emphasized.

Profiling the liver graft

PURPOSE OF REVIEW

Achieving operational tolerance remains a priority in liver transplantation. Although several biomarkers of tolerance and rejection have been identified, few have been reproducible and validated across centers, and therefore have yet to reach clinical practice. Here we summarize findings from prior seminal studies and review current developments in profiling the liver allograft.

RECENT FINDINGS

Substantial efforts and progress have been made in the recent years towards the discovery of reliable biomarkers that can predict and guide successful immunosuppression withdrawal. Recent studies have also investigated the transcriptomic signatures underlying not only acute rejection but also subclinical inflammation and chronic allograft injury.

SUMMARY

As new genomic and sequencing technologies continue to develop, clinical trials are underway to validate biomarkers of tolerance, as well as better understand the mechanisms of both acute and subclinical rejection, with the goal of maximizing allograft survival. Altogether, this will hopefully enable the implementation of immunosuppression withdrawal protocols into clinical practice and make operational tolerance reliably attainable in the near future.

Donor PNPLA3 and TM6SF2 Variant Alleles Confer Additive Risks for Graft Steatosis After Liver Transplantation

BACKGROUND

The rs58542926 polymorphism in transmembrane 6 superfamily member 2 (TM6SF2) is a genetic factor predisposing to nonalcoholic fatty liver disease. We aimed to explore the effect of recipient and donor TM6SF2 rs58542926 genotypes on liver graft fat content after liver transplantation.

METHODS

Steatosis was evaluated in liver biopsies from 268 adult recipients. The influence of recipient and donor TM6SF2 genotypes, patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 genotypes, and nongenetic factors on the steatosis grade assessed 6-30 months after transplantation was analyzed by ordinal logistic regression.

RESULTS

The presence of the TM6SF2 c.499A allele in the donor (P = 0.014), PNPLA3 c.444G allele in the donor (P < 0.001), posttransplant body mass index (P < 0.001), and serum triglycerides (P = 0.047) independently predicted increased liver fat content on multivariable analysis, whereas noncirrhotic liver disease, as an indication for liver transplantation, was associated with lower risk of steatosis (P = 0.003). The effects of the donor TM6SF2 A and PNPLA3 G alleles were additive, with an odds ratio of 4.90 (95% confidence interval, 2.01-13.00; P < 0.001), when both minor alleles were present compared with an odds ratio of 2.22 (95% confidence interval, 1.42-3.61; P = 0.002) when only one of these alleles was present.

CONCLUSIONS

The donor TM6SF2 c.499A allele is an independent risk factor of liver graft steatosis after liver transplantation that is additive to the effects of donor PNPLA3 c.444G allele.

Hepatic Gene Expression Profiles Differentiate Steatotic and Non-steatotic Grafts in Liver Transplant Recipients

Background: Liver transplantation leads to non-alcoholic fatty liver disease or non-alcoholic steatohepatitis in up to 40% of graft recipients. The aim of our study was to assess transcriptomic profiles of liver grafts and to contrast the hepatic gene expression between the patients after transplantation with vs. without graft steatosis. Methods: Total RNA was isolated from liver graft biopsies of 91 recipients. Clinical characteristics were compared between steatotic (n = 48) and control (n = 43) samples. Their transcriptomic profiles were assessed using Affymetrix HuGene 2.1 ST Array Strips processed in Affymetrix GeneAtlas. Data were analyzed using Partek Genomics Suite 6.6 and Ingenuity Pathway Analysis. Results: The individuals with hepatic steatosis showed higher indices of obesity including weight, waist circumference or BMI but the two groups were comparable in measures of insulin sensitivity and cholesterol concentrations. We have identified 747 transcripts (326 upregulated and 421 downregulated in steatotic samples compared to controls) significantly differentially expressed between grafts with vs. those without steatosis. Among the most downregulated genes in steatotic samples were P4HA1, IGF1, or fetuin B while the most upregulated were PLIN1 and ME1. Most influential upstream regulators included HNF1A, RXRA, and FXR. The metabolic pathways dysregulated in steatotic liver grafts comprised blood coagulation, bile acid synthesis and transport, cell redox homeostasis, lipid and cholesterol metabolism, epithelial adherence junction signaling, amino acid metabolism, AMPK and glucagon signaling, transmethylation reactions, and inflammation-related pathways. The derived mechanistic network underlying major transcriptome differences between steatotic samples and controls featured PPARA and SERPINE1 as main nodes. Conclusions: While there is a certain overlap between the results of the current study and published transcriptomic profiles of non-transplanted livers with steatosis, we have identified discrete characteristics of the non-alcoholic fatty liver disease in liver grafts potentially utilizable for the establishment of predictive signature.

Donor PNPLA3 rs738409 genotype is a risk factor for graft steatosis. A post-transplant biopsy-based study

BACKGROUND & AIMS

The rs738409 c.444C > G (p.I148M) polymorphism in PNPLA3 is a major factor predisposing to non-alcoholic fatty liver disease. The aim of the study was to clarify the impact of liver and extrahepatic expression of the PNPLA3 p.148M variant on liver graft steatosis after liver transplantation.

METHODS

Fat content was assessed in liver biopsies from 176 transplant recipients. During a period of 4 ± 1 years after transplantation, 17 patients developed grade 3 steatosis, 14 patients grade 2 steatosis, 56 patients grade 1 steatosis, and 89 patients grade 0 steatosis. The influence of the recipient and donor rs738409 genotype and clinical and laboratory data on liver fat content were analyzed using ordinal logistic regression.

RESULTS

The PNPLA3 rs738409 CC/CG/GG genotype frequencies, respectively, were 0.494/0.449/0.057 in the graft donors and 0.545/0.330/0.125 in the graft recipients. In the multivariate analysis, the presence of the PNPLA3 c.444G allele in donor (OR 1.62; 95%CI 1.12-2.33), post-transplant BMI (OR 1.14; 95%CI 1.07-1.22), diabetes mellitus (OR 1.99; 95%CI 1.22-3.22), and serum triglycerides (OR 1.40; 95%CI 1.11-1.76) were independent risk factors for increased liver graft fat content.

CONCLUSIONS

These data indicate that the liver expression of the PNPLA3 p.148M variant confers a genetic predisposition to liver graft steatosis along with nutritional status and diabetes.