Metabolic and genetic determinants for progression to severe liver disease in subjects with obesity from the UK Biobank

Modifiable lifestyle factors, genetic and acquired risk, and the risk of severe liver disease in the UK Biobank cohort: (Lifestyle factors and SLD)

BACKGROUND

Lifestyle intervention is important for the treatment of liver diseases.

AIMS

To clarify the association of healthy lifestyle with severe liver disease (SLD) and assessed whether genetic susceptibility and acquired fibrosis risk can modify the association.

METHODS

We included 417,986 UK Biobank participants who were free of SLD at baseline. Information on seven modifiable lifestyle factors was collected through a baseline questionnaire. SLD was defined as a medical diagnosis of cirrhosis, hepatocellular carcinoma or liver failure. Cox proportional hazards models were used to evaluate the association between healthy lifestyle factors and risk of incident SLD. The polygenic risk score (PRS) and fibrosis-4 index (FIB-4) were calculated and set as an interaction term.

RESULTS

During a median follow-up of 12.6 years, 4542 fatal and non-fatal SLD incidents were identified. A higher overall lifestyle score was associated with a significantly lower SLD risk (Ptrend <0.001). An increment of 1-point lifestyle score combined with a 1-SD increment in FIB-4 or PRS was associated with an additional reduction of 3% or 2% in SLD risk.

CONCLUSIONS

In European individuals, a healthy lifestyle is associated with a lower risk of incident SLD, which is more pronounced among individuals with a higher genetic and fibrosis risk.

Prognostication in NAFLD: physiological bases, clinical indicators, and newer biomarkers

Non-alcoholic fatty liver disease (NAFLD) is becoming an epidemic in Western countries. Notably, while the majority of NAFLD patients will not evolve until advanced liver disease, a minority of them will progress towards liver-related events. Therefore, risk stratification and prognostication are emerging as fundamental in order to optimize human and economic resources for the care of these patients.Liver fibrosis has been clearly recognized as the main predictor of poor hepatic and extrahepatic outcomes. However, a prediction based only on the stage of fibrosis is near-sighted and static, as it does not capture the propensity of disease to further progress, the speed of progression and their changes over time. These determinants, which result from the interaction between genetic predisposition and acquired risk factors (obesity, diabetes, etc.), express themselves in disease activity, and can be synthesized by biomarkers of hepatic inflammation and fibrogenesis.In this review, we present the currently available clinical tools for risk stratification and prognostication in NAFLD specifically with respect to the risk of progression towards hard hepatic outcomes, i.e., liver-related events and death. We also discuss about the genetic and acquired drivers of disease progression, together with the physiopathological bases of their come into action. Finally, we introduce the most promising biomarkers in the direction of repeatedly assessing disease activity over time, mainly in response to future therapeutic interventions.

High-density lipoproteins and non-alcoholic fatty liver disease

Background and aims

Non-alcoholic fatty liver disease (NAFLD), a high incidence liver pathology, is associated with a ∼1.5-fold higher cardiovascular disease risk. This phenomenon is generally attributed to the NAFLD-associated increase in circulating levels of pro-atherogenic apolipoprotein B100-containing small dense low-density lipoprotein and plasma hypertriglyceridemia. However, also a significant reduction in cholesterol transported by anti-atherogenic high-density lipoproteins (HDL) is frequently observed in subjects suffering from NAFLD as compared to unaffected people. In this review, we summarize data regarding the relationship between NAFLD and plasma HDL-cholesterol levels, with a special focus on highlighting potential causality between the NAFLD pathology and changes in HDL metabolism.

Methods and results

Publications in PUBMED describing the relationship between HDL levels and NAFLD susceptibility and/or disease severity, either in human clinical settings or genetically-modified mouse models, were critically reviewed for subsequent inclusion in this manuscript. Furthermore, relevant literature describing effects on lipid loading in cultured hepatocytes of models with genetic alterations related to HDL metabolism have been summarized.

Conclusions

Although in vitro observations suggest causality between HDL formation by hepatocytes and protection against NAFLD-like lipid accumulation, current literature remains inconclusive on whether relative HDL deficiency is actually driving the development of fatty liver disease in humans. In light of the current obesity pandemic and the associated marked rise in NAFLD incidence, it is of clear scientific and societal interest to gain further insight into the relationship between HDL-cholesterol levels and fatty liver development to potentially uncover the therapeutic potential of pharmacological HDL level and/or function modulation.

Alcohol consumption and metabolic syndrome: Clinical and epidemiological impact on liver disease

Alcohol use and metabolic syndrome are highly prevalent in the population and frequently co-exist. Both are implicated in a large range of health problems, including chronic liver disease, hepatocellular carcinoma, and liver-related outcomes (i.e. decompensation or liver transplantation). Studies have yielded mixed results regarding the effects of mild-moderate alcohol consumption on the risk of metabolic syndrome and fatty liver disease, possibly due to methodological differences. The few available prospective studies have indicated that mild-moderate alcohol use is associated with an increase in liver-related outcomes. This conclusion was substantiated by systems biology analyses suggesting that alcohol and metabolic syndrome may play a similar role in fatty liver disease, potentiating an already existing dysregulation of common vital homeostatic pathways. Alcohol and metabolic factors are independently and jointly associated with liver-related outcomes. Indeed, metabolic syndrome increases the risk of liver-related outcomes, regardless of alcohol intake. Moreover, the components of metabolic syndrome appear to have additive effects when it comes to the risk of liver-related outcomes. A number of population studies have implied that measures of central/abdominal obesity, such as the waist-to-hip ratio, can predict liver-related outcomes more accurately than BMI, including in individuals who consume harmful quantities of alcohol. Many studies even point to synergistic interactions between harmful alcohol use and many metabolic components. This accumulating evidence showing independent, combined, and modifying effects of alcohol and metabolic factors on the onset and progression of chronic liver disease highlights the multifactorial background of liver disease in the population. The available evidence suggests that more holistic approaches could be useful for risk prediction, diagnostics and treatment planning.

Biobanking as a Tool for Genomic Research: From Allele Frequencies to Cross-Ancestry Association Studies

In recent years, great advances have been made in the field of collection, storage, and analysis of biological samples. Large collections of samples, biobanks, have been established in many countries. Biobanks typically collect large amounts of biological samples and associated clinical information; the largest collections include over a million samples. In this review, we summarize the main directions in which biobanks aid medical genetics and genomic research, from providing reference allele frequency information to allowing large-scale cross-ancestry meta-analyses. The largest biobanks greatly vary in the size of the collection, and the amount of available phenotype and genotype data. Nevertheless, all of them are extensively used in genomics, providing a rich resource for genome-wide association analysis, genetic epidemiology, and statistical research into the structure, function, and evolution of the human genome. Recently, multiple research efforts were based on trans-biobank data integration, which increases sample size and allows for the identification of robust genetic associations. We provide prominent examples of such data integration and discuss important caveats which have to be taken into account in trans-biobank research.

Effect of common genetic variants on the risk of cirrhosis in non-alcoholic fatty liver disease during 20 years of follow-up

BACKGROUND AND AIMS

Several genotypes associate with a worse histopathological profile in patients with non-alcoholic fatty liver disease (NAFLD). Whether genotypes impact long-term outcomes is unclear. We investigated the importance of PNPLA3, TM6SF2, MBOAT7 and GCKR genotype for the development of severe outcomes in NAFLD.

METHOD

DNA samples were collected from 546 patients with NAFLD. Advanced fibrosis was diagnosed by liver biopsy or elastography. Non-alcoholic steatohepatitis (NASH) was histologically defined. Additionally, 5396 controls matched for age, sex and municipality were identified from population-based registers. Events of severe liver disease and all-cause mortality were collected from national registries. Hazard ratios (HRs) adjusted for age, sex, body mass index and type 2 diabetes were estimated with Cox regression.

RESULTS

In NAFLD, the G/G genotype of PNPLA3 was associated with a higher prevalence of NASH at baseline (odds ratio [OR] 3.67, 95% CI = 1.66-8.08), but not with advanced fibrosis (OR 1.81, 95% CI = 0.79-4.14). After up to 40 years of follow-up, the PNPLA3 G/G genotype was associated with a higher rate of severe liver disease (adjusted hazard ratio [aHR] 2.27, 95% CI = 1.15-4.47) compared with the C/C variant. NAFLD patients developed cirrhosis at a higher rate than controls (aHR 9.00, 95% CI = 6.85-11.83). The PNPLA3 G/G genotype accentuated this rate (aHR 23.32, 95% = CI 9.14-59.47). Overall mortality was not affected by any genetic variant.

CONCLUSION

The PNPLA3 G/G genotype is associated with an increased rate of cirrhosis in NAFLD. Our results suggest that assessment of the PNPLA3 genotype is of clinical relevance in patients with NAFLD to individualize monitoring and therapeutic strategies.

The link between liver fat and cardiometabolic diseases is highlighted by genome-wide association study of MRI-derived measures of body composition

Obesity and associated morbidities, metabolic associated fatty liver disease (MAFLD) included, constitute some of the largest public health threats worldwide. Body composition and related risk factors are known to be heritable and identification of their genetic determinants may aid in the development of better prevention and treatment strategies. Recently, large-scale whole-body MRI data has become available, providing more specific measures of body composition than anthropometrics such as body mass index. Here, we aimed to elucidate the genetic architecture of body composition, by conducting genome-wide association studies (GWAS) of these MRI-derived measures. We ran both univariate and multivariate GWAS on fourteen MRI-derived measurements of adipose and muscle tissue distribution, derived from scans from 33,588 White European UK Biobank participants (mean age of 64.5 years, 51.4% female). Through multivariate analysis, we discovered 100 loci with distributed effects across the body composition measures and 241 significant genes primarily involved in immune system functioning. Liver fat stood out, with a highly discoverable and oligogenic architecture and the strongest genetic associations. Comparison with 21 common cardiometabolic traits revealed both shared and specific genetic influences, with higher mean heritability for the MRI measures (h²= .25 vs. .13, p = 1.8x10^-7). We found substantial genetic correlations between the body composition measures and a range of cardiometabolic diseases, with the strongest correlation between liver fat and type 2 diabetes (r_g= .49, p = 2.7x10^-22). These findings show that MRI-derived body composition measures complement conventional body anthropometrics and other biomarkers of cardiometabolic health, highlighting the central role of liver fat, and improving our knowledge of the genetic architecture of body composition and related diseases.

Attribution of diabetes to the development of severe liver disease in the general population

BACKGROUND AND AIMS

Diabetes is associated with advanced liver disease and predicts mortality regardless of the primary aetiology of the liver disease. Even a family history of diabetes has been linked to advanced liver fibrosis in non-alcoholic fatty liver disease (NAFLD). However, the fraction of liver-related outcomes in the general population that are attributable to diabetes remains unclear.

METHODS

The population attributable fraction (PAF) of diabetes for liver disease as a time-dependent exposure was estimated in the Finnish FINRISK study (n = 28 787) and the British Whitehall II study (n = 7855). We also assessed the predictive ability of a family history of diabetes for liver-related outcomes. Incident diabetes data were from drug purchase/reimbursement and healthcare registries (FINRISK) or follow-up examinations (Whitehall II). Incident severe liver outcomes were identified through linkage with national healthcare registries.

RESULTS

Diabetes was associated with a two-fold risk of liver-related outcomes in both the FINRISK (HR, 1.92; p < .001) and Whitehall II (HR, 2.37; p < .001) cohorts, and this remained significant after adjusting for multiple confounders. PAF analyses demonstrated that diabetes explained 12-14% of the risk for severe liver-related outcomes after 10 and 20 years of follow-up. Also, maternal diabetes increased the risk of liver-related outcomes in the FINRISK (HR, 1.43; p = .044) and Whitehall II (HR, 2.04; p = .051) cohorts.

CONCLUSION

Approximately 12%-14% of severe liver-related outcomes are attributable to diabetes at the population level. The association between maternal diabetes and liver disease might suggest a mitochondrial genetic mechanism.

Body Roundness Index and Waist–Hip Ratio Result in Better Cardiovascular Disease Risk Stratification: Results From a Large Chinese Cross-Sectional Study

Background

The appropriate optimal anthropometric indices and their thresholds within each BMI category for predicting those at a high risk of cardiovascular disease risk factors (CVDRFs) among the Chinese are still under dispute.

Objectives

We aimed to identify the best indicators of CVDRFs and the optimal threshold within each BMI category among the Chinese.

Methods

Between 2012 and 2020, a total of 500,090 participants were surveyed in Hunan, China. Six anthropometric indices including waist circumference (WC), a body shape index (ABSI), body roundness index (BRI), waist–hip ratio (WHR), hip circumference (HC), and waist–height ratio (WHtR) were evaluated in the present study. Considered CVDRFs included dyslipidaemia, hypertension, diabetes mellitus (DM), and chronic kidney disease (CKD). The associations of anthropometrics with CVDRFs within each BMI category were evaluated through logistic regression models. The area under the receiver operating characteristic curve (AUROC) was used to assess the predictive abilities.

Results

For the presence of at least one CVDRFs, the WHR had the highest AUROC in overweight [0.641 (95%CI:0.638, 0.644)] and obese [0.616 (95%CI:0.609, 0.623)] men. BRI had the highest AUROC in underweight [0.649 (95%CI:0.629, 0.670)] and normal weight [0.686 (95%CI:0.683, 0.690)] men. However, the BRI had the highest discrimination ability among women in all the BMI categories, with AUROC ranging from 0.641 to 0.727. In most cases, the discriminatory ability of WHtR was similar to BRI and was easier to calculate; therefore, thresholds of BRI, WHR, and WHtR for CVDRFs identification were all calculated. In men, BRI thresholds of 1.8, 3.0, 3.9, and 5.0, WHtR thresholds of 0.41, 0.48, 0.53, and 0.58, and WHR thresholds of 0.81, 0.88, 0.92, and 0.95 were identified as optimal thresholds across underweight, normal weight, overweight, and obese populations, respectively. The corresponding BRI values in women were 1.9, 2.9, 4.0, and 5.2, respectively, and WHtR were 0.41, 0.48, 0.54, and 0.59, while the WHR values were 0.77, 0.83, 0.88, and 0.90. The recommended BRI, WHtR, or WHR cut-offs could not statistically differentiate high-risk CKD or hypercholesterolemia populations.

Conclusions

We found that BRI and WHR were superior to other indices for predicting CVD risk factors, except CKD or hypercholesterolemia, among the Chinese.