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Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Corresponding authors at: Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Corresponding authors at: Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, AustriaVienna Hepatic Hemodynamic Lab, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
Genetic factors such as the transmembrane 6 superfamily 2 (TM6SF2) rs58542926 single nucleotide variant(SNV) modulate the susceptibility for (advanced) chronic liver disease ([A]CLD). However, the impact of this variant in patients who have already progressed to ACLD is unknown.
Methods
The association between TM6SF2-rs58542926 genotype and liver-related events was evaluated in 938 ACLD patients undergoing hepatic venous pressure gradient (HVPG) measurement.
Results
Mean HVPG was 15±7 mmHg and mean UNOS MELD (2016) 11±5 points. Viral hepatitis (n = 495, 53%) was the most common cause of ACLD, followed by alcohol-related (ARLD; n = 342, 37%) and non-alcoholic fatty liver disease (NAFLD; n = 101, 11%).
While 754 (80%) patients harboured the TM6SF2 wild-type (C/C), 174 (19%) and 10 (1%) patients had one or two T-alleles. At baseline, patients with at least one TM6SF2 T-allele had more pronounced portal hypertension (HVPG: 16±7 vs. 15±7 mmHg; p = 0.031), higher gamma-glutamyl transferase levels (123 [63-229] vs. 97 [55-174] UxL−1; p = 0.002), and more commonly hepatocellular carcinoma (17% vs. 12%; p = 0.049).
Harbouring the TM6SF2 T-allele was associated with the composite endpoint hepatic decompensation/liver transplantation/liver-related death (SHR: 1.44 [95%CI: 1.14-1.83]; p = 0.003). This was confirmed in multivariable competing risk regression analyses that were adjusted for severity of portal hypertension and hepatic dysfunction at baseline.
Conclusion
The TM6SF2 variant modulates liver disease progression beyond the development of ACLD, as it modifies the risks of hepatic decompensation and liver-related death, independently of baseline liver disease severity.
Candidate gene and genome-wide association studies have revealed that genetic variants modulate the susceptibility for and progression of chronic liver diseases. Important examples include detrimental variants in PNPLA3, TM6SF2, MBOAT7, GCKR, and SERPINA1, as well as protective variants in HSD7B13, all of which seemed to be particularly relevant in the context of fatty liver disease [
Systematic evaluation of coding variation identifies a candidate causal variant in TM6SF2 influencing total cholesterol and myocardial infarction risk.
The protein encoded by the transmembrane 6 superfamily member 2 (TM6SF2) gene is located in the endoplasmic reticulum and Golgi apparatus and regulates hepatic lipid metabolism [
. The malfunctioning protein resulting from the loss-of-function rs58542926 C>T/E167K variant leads to impaired very-low-density lipoprotein (VLDL) export, and thus, pathological storage of lipid droplets [
]. Harbouring the TM6SF2 T-allele – which is quite common in Europeans (allelic frequency 0.08) – does not only increase the risk of hepatocellular fat accumulation, but also promotes hepatic inflammation, liver fibrosis [
]. This might be explained by the reduction of circulating lipids (cholesterol and triglycerides) caused by TM6SF2 T-allele, which in turn is associated with reduced cardiovascular events [
In general, most previous studies aiming at elucidating the effects of genetic variants on liver disease were cross-sectional and lacked detailed information on liver disease (especially portal hypertension) severity. Furthermore, there are no longitudinal studies investigating the role of TM6SF2 variants on the course of advanced chronic liver disease (ACLD). Therefore, the aim of our study was to evaluate, if the TM6SF2 rs58542926 C>T/E167K variant impacts the development of liver-related events in a large, thoroughly characterized cohort of patients who have already progressed to ACLD.
2. Methods
2.1 Study design and patients
For this retrospective, single-centre cohort study, we considered ACLD patients undergoing hepatic venous pressure gradient (HVPG) measurement at the Vienna Hepatic Hemodynamic Lab. We only included patients, if the following criteria were fulfilled: (i) evidence of ACLD, as defined by liver stiffness measurement (LSM) ≥10 kPa and/or an HVPG ≥6 mmHg, (ii) viral hepatitis or alcohol-related (ARLD)/NAFLD as underlying aetiology, and (iii) availability of information on TM6SF2 genotype. Exclusion criteria were as follows: History of liver transplantation, active extrahepatic malignancy, vascular liver diseases, or unavailable information on important laboratory parameters and/or clinical follow-up.
2.2 HVPG measurement
HVPG measurements were performed under local anaesthesia, as previously reported [
]. Briefly, a catheter introducer sheath was inserted into the right jugular vein and a large hepatic vein was cannulated via a balloon catheter. To obtain reliable measures, the free and the wedged hepatic venous pressures were measured at least three times and the mean was used for statistical analysis [
DNA was extracted using the QIAamp DNA Blood Mini Kit (QIAGEN) and stored at −20°C until genotyping for TM6SF2 rs58542926 C>T was performed by 7500 Fast Real-Time PCR System and a TaqMan SNP Genotyping Assay (Applied Biosystems, Foster City, CA, USA).
2.4 Reporting of ethnicity
Ethnicity was determine based on geographic origin and reporting adhered to recently published guidelines [
The date of initiation of anti-hepatitis B treatment, sustained virological response in patients with hepatitis C infection, or reported sustained alcohol abstinence in active drinkers defined removal of the primary aetiological factor.
2.6 Definition of hepatic decompensation
Hepatic decompensation was defined by the presence/history of at least one decompensating event, i.e., ascites, variceal bleeding, or hepatic encephalopathy.
2.7 Statistical analysis
Details on statistical analyses can be found in the Supplementary materials.
2.8 Ethics
This study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the local ethics committee (EK1526/2017). The requirement of written informed consent was waived by the ethics committee. However, all patients signed a written informed consent for genetic testing.
3. Results
3.1 Study population
Overall, 2550 patients underwent HVPG measurement within the study period (Fig. 1). After applying in- and exclusion criteria, 938 patients were finally included into our study. Mean age at HVPG measurement was 55±11 years and most patients were male (n = 684, 73%; Table 1). Viral hepatitis was the most common aetiology of liver disease (n = 495, 53%), followed by ARLD (n = 342, 37%) and NAFLD (n = 101, 11%). Regarding portal hypertension severity, mean HVPG was 15±7 mmHg and 62% of patients (n = 482) had varices, of whom 113 (12%) had a history of variceal bleeding. Mean UNOS MELD (2016) was 11±5, and mean CTP score was 6±2 points. Most patients were classified as CTP-A (n = 591, 63%), whereas 29% of patients were classified as CTP-B (n = 269) and 8% as CTP-C (n = 78). Four hundred and two patients (45%) had already experienced hepatic decompensation at study inclusion. Furthermore, 13% (n = 122) of patients had been diagnosed with HCC at baseline.
Seven hundred and fifty-four (80%) patients harboured the TM6SF2 wild-type (C/C), while 174 (19%) and 10 (1%) patients had one and two T-alleles, respectively. Due to the low number of patients homozygous for the T-allele (only 1% of the study population), we decided to merge patients with at least one T-allele for all further analyses (Table 1). Accordingly, 20% of patients harboured at least one T-allele (n = 184).
The vast majority of included patients were of European descent (n = 856, 91%), followed by patients of Arabic (n = 66, 7%), Asian (n = 13, 1.4%), or African descent (n = 3, 0.3%).
3.2 Clinical events during follow-up
Patients were followed for a median of 70.8 (95%CI: 64.3-75.4) months. Fifty-two deaths (6%) were considered non-liver-related, and 310 patients (33%) achieved removal of the primary aetiological factor during follow-up (hepatitis B virus infection: n = 19, median time to date of initiation of antiviral therapy: 10.6 months [95%CI: 0-41.2]; hepatitis C virus infection: n = 251, median time to sustained virological response: 12.0 months [95%CI: 9.6-14.4]; ARLD: n = 40, median time to sustained alcohol abstinence: 5.9 months [95%CI: 4.1-7.7]). Overall, 53 patients (6%) underwent TIPS placement (median time to TIPS placement: 5.1 months [95%CI: 1.0-9.3]) and 69 patients (7%) developed HCC during follow-up (median time to HCC diagnosis: 41.2 months [95%CI: 32.5-49.9]). For the combined endpoint including hepatic decompensation, 252 patients (27%) experienced first/further hepatic decompensation. In total, fifty-eight patients were transplanted (6%) and 190 deaths (20%) were considered liver-related. This resulted in 340 first events for the combined endpoint with 354 competing events [i] and 205 events for the combined endpoint with 430 competing risks [ii].
3.3 Patient characteristics according to TM6SF2 genotypes
Patients harbouring at least one TM6SF2 T-allele were older (57.0±11.8 vs. 54.6±11.1 years; p = 0.010), had more commonly ARLD/NAFLD aetiology (56% vs. 45%; p = 0.040), more pronounced portal hypertension as indicated by higher HVPG (16±7 vs. 15±7 mmHg; p = 0.031), and accordingly, history of variceal bleeding was more common in T-allele carriers (16% vs. 11%; p = 0.084; Table 1). Interestingly, patients harbouring a T-allele had more commonly been diagnosed with HCC (17% vs. 12%; p = 0.049) and presented with higher median gamma-glutamyltransferase levels at study inclusion (123 [IQR: 63-229] vs. 97 [IQR: 55-174] U x L−1; p = 0.002).
While we observed no statistically significant differences in serum lipid profile when comparing patients harbouring at least one TM6SF2 T-allele vs. non-carriers, total cholesterol was significantly lower in those with the TM6SF2 TT genotype (TT: 109±43 vs. CT: 148±49 vs. CC: 148±43 mg x dL−1; p = 0.023).
3.4 Impact of the TM6SF2 T-allele on hepatic decompensation/requirement of liver-transplantation/liver-related death in competing risk analyses
In competing risk analysis, harbouring the TM6SF2 T-allele was associated with hepatic decompensation/requirement of liver transplantation/liver-related death (subdistribution hazard ratio [SHR]: 1.44 [95%CI: 1.14-1.83]; p = 0.003; Fig. 2). After adjusting for age, BMI, HVPG, and CTP stage (model 1) as well as age, BMI, HVPG, UNOS MELD (2016) score, and a history/presence of hepatic decompensation (model 2), associations remained statistically significant for models 1 (adjusted SHR [aSHR]: 1.40 [95%CI: 1.09-1.80]; p = 0.008) and 2 (aSHR: 1.35 [95%CI: 1.05-1.74]; p = 0.019; Table 2).
Fig. 2Cumulative incidence plot of hepatic decompensation/requirement of liver transplantation/liver-related death stratified according to TM6SF2 genotype.
Table 2Multivariable competing risk regression analyses for hepatic decompensation/requirement of liver transplantation/liver-related death including – among other parameters – CTP score (model 1) or history/presence of hepatic decompensation, and UNOS MELD (2016) score (model 2) with removal of the aetiological factor, non-liver-related death, TIPS placement, and HCC development as competing risks.
Patient characteristics
Model 1
Model 2
aSHR (95%CI)
p-value
aSHR (95%CI)
p-value
Age, year
1.02 (1.01-1.03)
<0.001
1.02 (1.01-1.03)
<0.001
BMI, per kg x m−2
1.03 (1.01-1.05)
0.003
1.03 (1.01-1.05)
0.003
HVPG, mmHg
1.04 (1.02-1.06)
<0.001
1.04 (1.03-1.06)
<0.001
CTP stage A
1
-
-
-
CTP stage B
2.63 (2.03-3.42)
<0.001
-
-
CTP stage C
3.29 (2.19-4.96)
<0.001
-
-
UNOS MELD (2016) score, point
-
-
1.06 (1.03-1.09)
<0.001
History/presence of hepatic decompensation
-
-
1.62 (1.24-2.10)
<0.001
TM6SF2 T-allele
1.40 (1.09-1.80)
0.008
1.35 (1.05-1.74)
0.019
Abbreviations: aSHR adjusted subdistribution hazard ratio; BMI body mass index; CTP Child-Turcotte-Pugh score; HCC hepatocellular carcinoma; HVPG hepatic venous pressure gradient; UNOS MELD (2016) United Network for Organ Sharing model for end-stage liver disease (2016) score; TIPS transjugular intrahepatic portosystemic shunt; TM6SF2 transmembrane 6 superfamily 2.
3.5 Impact of the TM6SF2 T-allele on requirement of liver transplantation/liver-related death in competing risk analysis
When combining requirement of liver transplantation/liver-related death into a composite endpoint, harbouring the TM6SF2 T-allele tended to increase the risks of the outcome of interest (SHR: 1.31 [95%CI: 0.96-1.79]; p = 0.090; Fig. 3). After adjusting for relevant covariables, carriage of the TM6SF2 T-allele was associated with an increased risk of liver transplantation/liver-related death on a trend-wise level (model 1: aSHR: 1.27 [95%CI: 0.92-1.75]; p = 0.150; model 2: aSHR: 1.25 [95%CI: 0.90-1.72]; p = 0.180; Table 3). Higher age, BMI, HVPG, CTP stage, and UNOS MELD (2016) score were associated with the endpoint of interest (Table 3).
Fig. 3Cumulative incidence plot of requirement of liver transplantation/liver-related death stratified according to TM6SF2 genotype.
Table 3Multivariable competing risk regression analyses for requirement of liver transplantation/liver-related death including – among other parameters – CTP score (model 1) or history/presence of hepatic decompensation, and UNOS MELD (2016) score (model 2) with removal of the aetiological factor, non-liver-related death, TIPS placement, and HCC development as competing risks.
Patient characteristics
Model 1
Model 2
aSHR (95%CI)
p-value
aSHR (95%CI)
p-value
Age, year
1.03 (1.02-1.05)
<0.001
1.03 (1.02-1.05)
<0.001
BMI, per kg x m−2
1.04 (1.01-1.06)
0.002
1.03 (1.01-1.06)
0.003
HVPG, mmHg
1.01 (0.99-1.04)
0.240
1.02 (0.99-1.04)
0.130
CTP stage A
1
-
-
-
CTP stage B
1.87 (1.32-2.67)
<0.001
-
-
CTP stage C
4.48 (2.81-7.13)
<0.001
-
-
UNOS MELD (2016) score, point
-
-
1.09 (1.05-1.12)
<0.001
History/presence of hepatic decompensation
-
-
1.02 (0.72-1.45)
0.900
TM6SF2 T-allele
1.27 (0.92-1.75)
0.150
1.25 (0.90-1.72)
0.180
Abbreviations: aSHR adjusted subdistribution hazard ratio; BMI body mass index; CTP Child-Turcotte-Pugh score; HCC hepatocellular carcinoma; HVPG hepatic venous pressure gradient; UNOS MELD (2016) United Network for Organ Sharing model for end-stage liver disease (2016) score; TIPS transjugular intrahepatic portosystemic shunt; TM6SF2 transmembrane 6 superfamily 2.
3.6 Impact of the TM6SF2 T-allele in different aetiologies of liver disease
Interestingly, the TM6SF2 T-allele impacted outcomes in patients with viral hepatitis, while no impact in patients with fatty liver was observed (Supplementary materials). Cumulative incidence plots for the different disease aetiology subgroups are provided in the Supplementary materials.
4. Discussion
Longitudinal data evaluating the impact of genetic variants on the outcome of patients who have already progressed to ACLD are scarce. Although several chronic liver disease-modifying alleles have been identified [
, the implications of genetics in patients who have already progressed to ACLD are poorly defined. In the present retrospective longitudinal study, we found that harbouring a TM6SF2 rs58542926 T-allele increases the risk of liver-related events, even after accounting for severity of portal hypertension and hepatic dysfunction at baseline.
Not surprisingly, the TM6SF2 risk variants were overrepresented in our cohort as compared to the general population (T-allele frequency: TM6SF2: 20% vs. 8%). This underlines the importance of this variant in regard to the susceptibility for and progression of chronic liver disease to ACLD in general as well as ARLD/NAFLD in particular, as fatty liver disease was significantly overrepresented among T-allele carriers. Mechanistically, this may be explained by the TM6SF2 loss-of-function mutation and the accumulation of liver fat [
Interestingly, carriage of the TM6SF2 T-allele was associated with more pronounced portal hypertension at baseline, as indicated by higher HVPG. Since no experimental/clinical study so far has investigated the impact of the TM6SF2 T-allele on portal hypertension, we can only speculate about the reason for this association. Most mechanistic considerations are derived from mice models, in which the TM6SF2 protein is expressed 10-fold higher in the small intestine vs. the liver, thereby limiting the translation of findings from mice to humans [
Decompensation in advanced nonalcoholic fatty liver disease may occur at lower hepatic venous pressure gradient levels than in patients with viral disease.
]. As an alternative explanation, higher HVPG in patients harbouring the TM6SF2 T-allele may simply indicate more advanced liver disease. The latter may be attributed to between-genotype differences in aetiology, with a slight overrepresentation of NAFLD but also ARLD patients – who often present late, i.e., after the development of hepatic decompensated – among carriers. Notably, NAFLD also seems to be accompanied by additional presinusoidal increases in intrahepatic resistance [
Decompensation in advanced nonalcoholic fatty liver disease may occur at lower hepatic venous pressure gradient levels than in patients with viral disease.
]. Accordingly, it may be hypothesized that HVPG even underestimates the true increase in portal pressure in TM6SF2 T-allele carriers, which on the hand, would explain an increased risk of clinical events, but may also promote fibrosis progression via mechanosensing pathways, thereby contributing to clinical disease progression [
]. Carriage of the TM6SF2 TT genotype was associated with increased serum cholesterol levels at baseline, which is well in line with the variant's effect on hepatic lipid metabolism and previous data on the serum lipid profile in patients with less advanced disease [
]. Nevertheless, this finding has to be interpreted with caution, as patients harbouring this genotype tended to have more sever liver disease, which may have impacted the circulating lipid profile [
Importantly, our findings remained unaffected when (i) exchanging HVPG with non-invasive prognostic indicators (i.e., von Willebrand factor antigen [VWF], VWF to platelet ratio [VITRO], or liver stiffness measurement [LSM] by vibration-controlled transient elastography) or (ii) combining HVPG and VWF This supports the concept that genetics may extend the prognostic value of biomarkers that reflect the stage of liver disease in patients with ACLD, although findings in the general population suggest that the gain in prognostic information is limited [
], and thus, wide-spread (i.e., including primary prophylaxis for small varices) NSBB treatment was the standard of care at our centre throughout the study period. Accordingly, 552 patients of the whole study population were receiving NSBB therapy, which may be seen as an advantage of our study, as it is reflective of today's (i.e., after Baveno VII [
]) clinical practice, thereby increasing the generalisability of our findings. Importantly, NSBB exposure during follow-up did not differ between TM6SF2 genotypes/risk-allele carriers vs. non-carriers, and thus, is unlikely to have impacted our main finding. Notably, the utilisation of HVPG-response assessment according to [
] and the rates of HVPG-response to NSBB therapy were comparable across carriers and non-carriers (data available in n = 362 patients [39%]; 55% in carriers vs. 56% in non-carriers; p = 0.820). Thus, the latter is unlikely to have affected our findings.
When considering non-liver-related death and aetiological cure as competing events, harbouring the TM6SF2 T-allele significantly increased the risks for developing the two evaluated composite endpoints. In general, these findings were confirmed after adjustment for liver disease and portal hypertension severity at inclusion, although some analyses yielded trends rather than statistically significant results. While harbouring the TM6SF2 T-allele statistically significantly increased the risks (by approximately 30%) for the first composite endpoint including hepatic decompensation, requirement of liver transplantation, and liver-related death in model 1, the effect of the TM6SF2 T-allele only attained borderline significance in the other model. For the composite endpoint comprising liver transplantation and liver-related death, only trends towards an increased risk (by approximately 30%) in TM6SF2 T-allele carriers were observed, which may be explained by limited statistical power, as the aSHR were very similar to the other composite endpoint. To put these findings into perspective, harbouring the less common PNPLA3 rs738409 G/G genotype (prevalence of only 7%, as compared to 20% TM6SF2 T-allele carriers) was associated with a 42%-increased risk for liver-related death in a previous analysis of an overlapping population of patients with ACLD due to viral hepatitis/fatty liver disease [
Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension.
]. Accordingly, the magnitude of the TM6SF2-mediated effect was only slightly lower vs. PNPLA3, while affecting a considerably larger patient population. Importantly, we considered removal of primary etiologic factors (as defined by Baveno VII [
de Franchis R, Bosch J, Garcia-Tsao G, Reiberger T, Ripoll C, Abraldes JG, et al. Baveno VII - renewing consensus in portal hypertension: report of the Baveno VII Consensus Workshop: personalized care in portal hypertension. J Hepatol
]) as competing risks, as it profoundly changes hepatic function and the severity of portal hypertension, and thus, the risk of events, in particular first hepatic decompensation [
]. Accordingly, removal of the primary etiologic factor denotes a paragon of a competing risk that modifies the probability of the event of interest. Moreover, findings in HCV-infected ACLD patients achieving sustained virologic response question the relevance of SNV for disease regression [
Of note, the mean UNOS MELD (2016) of our study population was low (i.e., 12 points) indicating that the vast majority of patients were not on the waiting list for liver transplantation. Thus, the requirement of liver transplantation denotes an adverse liver-related outcome in this patient population, which is why we included the requirement of liver transplantation into the composite endpoints, rather than analysing liver transplantation as a competing event.
Cross-sectional studies indicate that the TM6SF2 T-allele may promote liver fibrosis in patients with hepatitis C. In three studies conducted in Italian chronic hepatitis C cohorts, the TM6SF2 T-allele was an independent risk factor of steatosis [
]. In line, carriage of the TM6SF2 T-allele was linked to significant fibrosis in viral hepatitis patients recruited in Australia and China, with a slightly lower OR (1.39), as compared to NAFLD (OR of 1.62) [
] reporting that the TM6SF2 T-allele was not associated with the severity of hepatic steatosis or liver fibrosis in a large (n = 694) cohort of patients with hepatitis C virus infection [
]. Of note, our study had a very different focus, as all included patients had already developed ACLD. Interestingly, the impact of the TM6SF2 T-allele among patients with viral hepatitis was considerably stronger (SHR of ∼1.8), as compared to the overall study population (SHR of ∼1.3) and the fatty liver disease subgroup, in which no meaningful effect was observed. This contrasts our previous findings on the PNPLA3 rs738409 G/G-genotype, which modified the course of ACLD due to fatty liver disease but did not impact liver-related mortality in NAFLD patients. The previous smaller study [
Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension.
] was performed in a partly overlapping and therefore likely comparable patient cohort. While both polymorphisms impact on hepatic lipid metabolism and show a similar pattern of associations in less advanced patient cohorts, their pathophysiological relevance in patients with ACLD has not been thoroughly investigated. Thus, the available data does not provide a compelling explanation for the etiology-specific differences, which may be an important area for further research. In this regard, we would like to emphasize that observations on indirect endpoints (e.g., liver fibrosis) in less advanced patient cohorts should not be extrapolated to ACLD patients. This is also highlighted by a recent study from our centre evaluating the impact of the presumably protective HSD17B13 rs72613567 TA-allele in patients who had already developed ACLD [
In the light of important advances in the field of gene therapies in other indications as well as promising data on RNA interference-based therapeutics in patients with alpha-1 antitrypsin-related liver disease (SERPINA1 rs28929474, Pi*ZZ) in whom liver fibrosis regression was achieved [
], the drug-ability of further SNV requires evaluation. This is particularly important in ACLD patients, as they are at significant risk for developing hepatic decompensation and death, indicating the urgent need for disease-modifying therapies [
]. However, while the loss-of-function TM6SF2 mutation investigated in our study leads to liver fat accumulation, an upregulation of this gene may cause dyslipidaemia, and thus, increase cardiovascular risk. Moreover, preclinical data suggests that an upregulation of the TM6SF2 wild-type may even lead to a paradoxical worsening of liver disease [
The main limitation of our study is its retrospective design. However, patients were thoroughly characterized at the time of HVPG measurement. Since this was a retrospective data analysis, we cannot exclude that some hepatic decompensation events have been missed. However, we have thoroughly reviewed electronic health records of the Vienna hospital association and nation-wide electronic health records. Moreover, we have also performed searches of the liver transplant database of our institution (i.e., the only transplant centre in eastern Austria) and examined the nation-wide death registry. Since complete information on (reason of) death is guaranteed by the latter measure, we included liver-related death in all composite endpoints to ensure the ascertainment of the most severe disease courses. Of note, lack of adjustment for portal hypertension severity may be an important limitation of previous studies investigating the impact of genetic variants on the course of ACLD, as patients harbouring the respective risk/protective genotypes (i.e., PNPLA3 [
Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension.
Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension.
may have not sufficiently accounted for the baseline condition of the patients, and thus, overestimated the impact of genetic variants on the risk of future events. This is in line with the above-mentioned concept that genetic variants may only offer slight improvements in risk prediction, after accounting for disease stage (i.e., FIB-4). In the context of our study, this potential limitation was overcome by accounting for HVPG, the most accurate surrogate of portal hypertension severity with profound prognostic implications [
]. However, we cannot rule-out selection bias since we included patients at the time of HVPG measurement. Hemodynamic evaluation of our patients are performed on a routinely basis as a standard tool for risk stratification and treatment monitoring purposes, and thus, we are convinced that our study population is not highly selected [
]. Above, we have pointed out the importance of interethnic differences in the interpretation of study results for genetic variants in different patient cohorts and ethnicities. Therefore, we want to emphasize that our study may only be applying for subjects of European descent, as they represent the vast majority of included patients. Finally, we did not include a validation cohort, as we are not aware of another adequately sized cohort connecting data on HVPG and genetics.
In conclusion, ACLD patients harbouring the TM6SF2 T-allele are at higher risk of developing liver-related events, however, this effect seemed to be restricted to those with viral hepatitis. Our findings extend previous knowledge, as they indicate that the TM6SF2 T-allele does not only modulate the risk of ACLD development, but also the further disease course.
CRediT authorship contribution statement
Lorenz Balcar: Conceptualization, Data curation, Methodology, Visualization, Writing – original draft, Writing – review & editing. Bernhard Scheiner: Conceptualization, Data curation, Methodology, Visualization, Writing – original draft, Writing – review & editing. Markus Urheu: Data curation, Writing – review & editing. Patrick Weinberger: Data curation, Writing – review & editing. Rafael Paternostro: Data curation, Writing – review & editing. Benedikt Simbrunner: Writing – review & editing. Georg Semmler: Writing – review & editing. Claudia Willheim: Data curation, Writing – review & editing. Matthias Pinter: Writing – review & editing. Peter Ferenci: Writing – review & editing. Michael Trauner: Writing – review & editing. Thomas Reiberger: Data curation, Writing – review & editing. Albert Friedrich Stättermayer: Data curation, Writing – original draft, Writing – review & editing. Mattias Mandorfer: Conceptualization, Data curation, Methodology, Visualization, Writing – original draft, Writing – review & editing.
Conflict of interest
The authors have nothing to disclose regarding the work under consideration for publication.
Conflicts of interests outside the submitted work:
L.B., M.U., P.W., R.P., G.S., C.W., and A.F.S. have nothing to disclose.
B.Sc. received travel support from AbbVie, Ipsen, and Gilead.
B.Si. received travel support from AbbVie and Gilead.
M.P. served as a speaker and/or consultant and/or advisory board member for Bayer, Bristol-Myers Squibb, Eisai, Ipsen, Lilly, MSD, and Roche, and received travel support from Bayer and Bristol-Myers Squibb.
P.F. served as a speaker and/or consultant and/or advisory board member for AbbVie, Gilead, MYR Pharmaceuticals, and Vivaraxx and received grants/research support from Gilead.
M.T. served as a speaker and/or consultant and/or advisory board member for Albireo, BiomX, Falk, Boehringer Ingelheim, Bristol-Myers Squibb, Falk, Genfit, Gilead, Intercept, Janssen, MSD, Novartis, Phenex, Pliant, Regulus, and Shire, and received travel support from AbbVie, Falk, Gilead, and Intercept as well as grants/research support from Albireo, Alnylam, Cymabay, Falk, Gilead, Intercept, MSD, Takeda, and UltraGenyx. He is also co-inventor of patents on the medical use of 24-norursodeoxycholic acid.
T.R. served as a speaker and/or consultant and/or advisory board member for AbbVie, Bayer, Boehringer Ingelheim, Gilead, Intercept, MSD, Siemens, and W. L. Gore & Associates and received grants/research support from AbbVie, Boehringer Ingelheim, Gilead, Intercept, MSD, Myr Pharmaceuticals, Pliant, Philips, Siemens, and W. L. Gore & Associates as well as travel support from AbbVie, Boehringer Ingelheim, Gilead and Roche.
M.M. served as a speaker and/or consultant and/or advisory board member for AbbVie, Collective Acumen, Gilead, and W. L. Gore & Associates and received travel support from AbbVie, Gilead, and Takeda.
Financial support
No specific financial support was received for this study.
Data statement
The data that support the findings of this study are available from the corresponding authors upon reasonable request.
Systematic evaluation of coding variation identifies a candidate causal variant in TM6SF2 influencing total cholesterol and myocardial infarction risk.
Decompensation in advanced nonalcoholic fatty liver disease may occur at lower hepatic venous pressure gradient levels than in patients with viral disease.
Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension.
de Franchis R, Bosch J, Garcia-Tsao G, Reiberger T, Ripoll C, Abraldes JG, et al. Baveno VII - renewing consensus in portal hypertension: report of the Baveno VII Consensus Workshop: personalized care in portal hypertension. J Hepatol
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