Influence of the PNPLA3 rs738409 Polymorphism on Non-Alcoholic Fatty Liver Disease and Renal Function among Normal Weight Subjects

PNPLA3 variation and kidney disease

Accumulating epidemiological evidence shows that the patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 G allele, which is the most robust genetic variant associated with greater susceptibility to metabolic dysfunction-associated steatotic liver disease (MASLD), is significantly associated with impaired kidney function in both adults and children, regardless of the presence of common renal risk factors, MASLD severity, and other potential confounders. Although some prospective studies have reported a significant association between the PNPLA3 rs738409 G allele and the increased risk of developing chronic kidney disease (CKD), the epidemiological evidence about a possible direct effect of the PNPLA3 rs738409 G allele on the risk of developing CKD is still limited. Experimentally, PNPLA3 is expressed in renal podocytes, pericytes, and proximal tubule cells, thus supporting the notion that the mutant PNPLA3 protein may play a role in developing renal steatosis and fibrosis. However, it cannot be ruled out that a part of the adverse effect of the PNPLA3 rs738409 G allele on kidney function may be driven by a direct impact of this genetic variant on the development and progression of MASLD. It is possible to hypothesize that identifying the PNPLA3 genotype might help identify individuals at higher risk of CKD and those at greater risk of advanced MASLD. In this narrative minireview, we summarize the current epidemiological data about the association between the PNPLA3 rs738409 G allele and the risk of CKD and abnormal albuminuria. We also briefly discuss the putative biological mechanisms underpinning this association and its potential and future clinical implications.

Steatotic liver disease, MASLD and risk of chronic kidney disease

With the rising tide of fatty liver disease related to metabolic dysfunction worldwide, the association of this common liver disease with chronic kidney disease (CKD) has become increasingly evident. In 2020, the more inclusive term metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to replace the old term non-alcoholic fatty liver disease (NAFLD). In 2023, a modified Delphi process was led by three large pan-national liver associations. There was consensus to change the fatty liver disease nomenclature and definition to include the presence of at least one of five common cardiometabolic risk factors as diagnostic criteria. The name chosen to replace NAFLD was metabolic dysfunction-associated steatotic liver disease (MASLD). The change of nomenclature from NAFLD to MAFLD and then MASLD has resulted in a reappraisal of the epidemiological trends and associations with the risk of developing CKD. The observed association between MAFLD/MASLD and CKD and our understanding that CKD can be an epiphenomenon linked to underlying metabolic dysfunction support the notion that individuals with MASLD are at substantially higher risk of incident CKD than those without MASLD. This narrative review provides an overview of the literature on (a) the evolution of criteria for diagnosing this highly prevalent metabolic liver disease, (b) the epidemiological evidence linking MASLD to the risk of CKD, (c) the underlying mechanisms by which MASLD (and factors strongly linked with MASLD) may increase the risk of developing CKD, and (d) the potential drug treatments that may benefit both MASLD and CKD.

Significance of Diabetic Kidney Disease Biomarkers in Predicting Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) and diabetic kidney disease (DKD) share various pathophysiological factors, and epidemiological evidence suggests that these two diseases are associated. Albuminuria and the estimated glomerular filtration rate, which are conventional biomarkers of DKD, are reportedly associated with the risk or severity of MAFLD. Recently, novel DKD biomarkers reflecting renal tubular injury have been introduced to complement conventional DKD markers. In this article, we looked at previous studies that showed an association between MAFLD and DKD, and also reviewed the significance of DKD biomarkers as predictive risk factors for MAFLD.

Nonalcoholic Fatty Liver Disease and Chronic Kidney Disease Cross Talk

Nonalcoholic fatty liver disease is a multisystem condition with effects beyond the liver. The identification of chronic kidney disease as an independent mediator of nonalcoholic fatty liver disease or associated entity with shared cardiometabolic risk factors remains controversial and continues to draw scientific interest. With increasing prevalence of nonalcoholic fatty liver disease and lack of Food and Drug Administration approved therapies, these shared cardiometabolic risk factors have drawn significant attention. In this article, we review shared pathophysiological mechanisms between nonalcoholic fatty liver disease and chronic kidney disease along with current treatment strategies that might be useful for both disease processes.

Survey of Dietary Habits and Physical Activity in Japanese Patients with Non-Obese Non-Alcoholic Fatty Liver Disease

The incidence of non-obese non-alcoholic fatty liver disease (NAFLD), characterized by the presence of a fatty liver in individuals with a normal body mass index, is on the rise globally. Effective management strategies, including lifestyle interventions such as diet and exercise therapy, are urgently needed to address this growing public health concern. The aim of this study was to investigate the association between non-obese NAFLD, dietary habits, and physical activity levels. By elucidating these relationships, this research may contribute to the development of evidence-based recommendations for the management of non-obese NAFLD. The study had a single-center retrospective cross-sectional design and compared clinical data and dietary and physical activity habits between patients with and without non-obese NAFLD. Logistic regression analysis was utilized to investigate the relationship between food intake frequency and the development of NAFLD. Among the 455 patients who visited the clinic during the study period, 169 were selected for analysis, including 74 with non-obese NAFLD and 95 without NAFLD. The non-obese NAFLD group showed a less-frequent consumption of fish and fish products as well as olive oil and canola/rapeseed oil, while they showed more frequent consumption of pastries and cake, snack foods and fried sweets, candy and caramels, salty foods, and pickles compared to the non-NAFLD group. Logistic regression analysis revealed that NAFLD was significantly associated with the consumption of fish, fish products, and pickles at least four times a week. The physical activity level was lower and the exercise frequency was lower in patients with non-obese NAFLD compared to those without NAFLD. The results of this study suggest that a low consumption of fish and fish products and high consumption of pickles may be associated with a higher risk of non-obese NAFLD. Moreover, dietary habits and physical activity status should be taken into consideration for the management of patients with non-obese NAFLD. It is important to develop effective management strategies, such as dietary and exercise interventions, to prevent and treat NAFLD in this patient population.

An international Delphi consensus statement on metabolic dysfunction-associated fatty liver disease and risk of chronic kidney disease

BACKGROUND

With the rising global prevalence of fatty liver disease related to metabolic dysfunction, the association of this common liver condition with chronic kidney disease (CKD) has become increasingly evident. In 2020, the more inclusive term metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to replace the term non-alcoholic fatty liver disease (NAFLD). The observed association between MAFLD and CKD and our understanding that CKD can be a consequence of underlying metabolic dysfunction support the notion that individuals with MAFLD are at higher risk of having and developing CKD compared with those without MAFLD. However, to date, there is no appropriate guidance on CKD in individuals with MAFLD. Furthermore, there has been little attention paid to the link between MAFLD and CKD in the Nephrology community.

METHODS AND RESULTS

Using a Delphi-based approach, a multidisciplinary panel of 50 international experts from 26 countries reached a consensus on some of the open research questions regarding the link between MAFLD and CKD.

CONCLUSIONS

This Delphi-based consensus statement provided guidance on the epidemiology, mechanisms, management and treatment of MAFLD and CKD, as well as the relationship between the severity of MAFLD and risk of CKD, which establish a framework for the early prevention and management of these two common and interconnected diseases.

Association between PNPLA3 rs738409 variant and 5-year estimated glomerular filtration rate decline in post-menopausal women with type 2 diabetes: A panel-data analysis

BACKGROUND AND AIMS

Little is known about the relationship between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 variant and decline in estimated glomerular filtration rate (eGFR) over time in individuals with type 2 diabetes (T2DM).

METHODS AND RESULTS

We enrolled an outpatient sample of 46 post-menopausal women with T2DM and preserved kidney function at baseline (in 2017), who were followed through 2022. eGFR and albuminuria were measured annually. Genotyping of PNPLA3 rs738409 was performed by TaqMan-based RT-PCR system. Overall, 25 (54.3%) patients had PNPLA3 rs738409 CC (homozygous wild-type) genotype and 21 had CG or GG genotypes. During the 5-year follow-up, the presence of rs738409 CG/GG genotypes was associated with faster eGFR decline (coefficient: -6.55; 95% CI -11.0 to -2.08; p = 0.004 by random-effects panel data analysis). This association remained significant even after adjustment for 5-year changes in age, hemoglobin A1c, hypertension status, albuminuria and use of sodium-glucose co-transporter-2 inhibitors or glucagon-like peptide-1 receptor agonists.

CONCLUSIONS

This pilot study suggests that in post-menopausal T2DM women with preserved kidney function at baseline, the risk allele (G) of PNPLA3 rs738409 is associated with a faster eGFR decline during a 5-year follow-up, independent of annual changes in common renal risk factors and use of certain glucose-lowering medications.

Nonalcoholic Fatty Liver Disease in Lean/Nonobese and Obese Individuals: A Comprehensive Review on Prevalence, Pathogenesis, Clinical Outcomes, and Treatment

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, with an estimated prevalence of 25% globally. NAFLD is closely associated with metabolic syndrome, which are both becoming increasingly more common with increasing rates of insulin resistance, dyslipidemia, and hypertension. Although NAFLD is strongly associated with obesity, lean or nonobese NAFLD is a relatively new phenotype and occurs in patients without increased waist circumference and with or without visceral fat. Currently, there is limited literature comparing and illustrating the differences between lean/nonobese and obese NAFLD patients with regard to risk factors, pathophysiology, and clinical outcomes. In this review, we aim to define and further delineate different phenotypes of NAFLD and present a comprehensive review on the prevalence, incidence, risk factors, genetic predisposition, and pathophysiology. Furthermore, we discuss and compare the clinical outcomes, such as insulin resistance, dyslipidemia, hypertension, coronary artery disease, mortality, and progression to nonalcoholic steatohepatitis, among lean/nonobese and obese NAFLD patients. Finally, we summarize the most up to date current management of NAFLD, including lifestyle interventions, pharmacologic therapies, and surgical options.

Adverse effect of PNPLA3 p.I148M genetic variant on kidney function in middle-aged individuals with metabolic dysfunction

BACKGROUND

The PNPLA3 p.I148M variant is the main genetic determinant of nonalcoholic fatty liver disease, and PNPLA3 silencing is being evaluated to treat this liver condition. Data suggest that the p.I148M variant predisposes to kidney damage, but the relative contribution to kidney function, compared to overall genetic susceptibility, is not defined.

AIMS

We aimed to assess the effect of PNPLA3 p.I148M on the estimated glomerular filtration rate (eGFR) in individuals with metabolic dysfunction.

METHODS

We included 1144 middle-aged individuals from the Liver-Bible-2022 cohort. Glomerular filtration rate (eGFR) was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. The effect of PNPLA3 p.I148M on eGFR_CKD-EPI levels was tested under additive genetic models adjusted for clinical predictors, ethnicity and a polygenic risk score of chronic kidney disease (PRS-CKD). In a subset of 144 individuals, we examined the effect of PNPLA3 p.I148M on eGFR_CKD-EPI over a median follow-up of 17 months.

RESULTS

The p.I148M variant was associated with lower eGFR_CKD-EPI levels (-1.24 mL/min/1.73 m² per allele, 95% CI: -2.32 to -0.17; p = 0.023), independent of age, sex, height, waist circumference, systolic blood pressure, LDL-cholesterol, transaminases, fasting insulin, albuminuria, lipid-lowering drugs, ethnicity and PRS-CKD score. In the prospective evaluation, the p.I148M variant was independently associated with faster eGFR_CKD-EPI decline (ΔeGFR_CKD-EPI -3.57 mL/min/1.73 m² per allele, 95% CI: -6.94 to -0.21; p = 0.037).

CONCLUSIONS

We found a detrimental impact of the PNPLA3 p.I148M variant on eGFR_CKD-EPI levels in middle-aged individuals with metabolic dysfunction. This association was independent of established risk factors, ethnicity and genetic predisposition to CKD. PNPLA3 p.I148M silencing may protect against kidney damage progression in carriers.

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.

2019 Global NAFLD Prevalence: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

The increasing rates of obesity and type 2 diabetes mellitus may lead to increased prevalence of nonalcoholic fatty liver disease (NAFLD). We aimed to determine the current and recent trends on the global and regional prevalence of NAFLD.

METHODS

Systematic search from inception to March 26, 2020 was performed without language restrictions. Two authors independently performed screening and data extraction. We performed meta-regression to determine trends in NAFLD prevalence.

RESULTS

We identified 17,244 articles from literature search and included 245 eligible studies involving 5,399,254 individuals. The pooled global prevalence of NAFLD was 29.8% (95% confidence interval [CI], 28.6%-31.1%); of these, 82.5% of included articles used ultrasound to diagnose NAFLD, with prevalence of 30.6% (95% CI, 29.2%-32.0%). South America (3 studies, 5716 individuals) and North America (4 studies, 18,236 individuals) had the highest NAFLD prevalence at 35.7% (95% CI, 34.0%-37.5%) and 35.3% (95% CI, 25.4%-45.9%), respectively. From 1991 to 2019, trend analysis showed NAFLD increased from 21.9% to 37.3% (yearly increase of 0.7%, P < .0001), with South America showing the most rapid change of 2.7% per year, followed by Europe at 1.1%.

CONCLUSIONS

Despite regional variation, the global prevalence of NAFLD is increasing overall. Policy makers must work toward reversing the current trends by increasing awareness of NAFLD and promoting healthy lifestyle environments.

Nonalcoholic Fatty Liver Disease and Chronic Kidney Disease: Epidemiology, Pathogenesis, and Clinical and Research Implications

Nonalcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease worldwide, affecting up to ~30% of adult populations. NAFLD defines a spectrum of progressive liver conditions ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma, which often occur in close and bidirectional associations with metabolic disorders. Chronic kidney disease (CKD) is characterized by anatomic and/or functional renal damage, ultimately resulting in a reduced glomerular filtration rate. The physiological axis linking the liver and kidneys often passes unnoticed until clinically significant portal hypertension, as a major complication of cirrhosis, becomes apparent in the form of ascites, refractory ascites, or hepatorenal syndrome. However, the extensive evidence accumulated since 2008 indicates that noncirrhotic NAFLD is associated with a higher risk of incident CKD, independent of obesity, type 2 diabetes, and other common renal risk factors. In addition, subclinical portal hypertension has been demonstrated to occur in noncirrhotic NAFLD, with a potential adverse impact on renal vasoregulation. However, the mechanisms underlying this association remain unexplored to a substantial extent. With this background, in this review we discuss the current evidence showing a strong association between NAFLD and the risk of CKD, and the putative biological mechanisms underpinning this association. We also discuss in depth the potential pathogenic role of the hepatorenal reflex, which may be triggered by subclinical portal hypertension and is a poorly investigated but promising research topic. Finally, we address emerging pharmacotherapies for NAFLD that may also beneficially affect the risk of developing CKD in individuals with NAFLD.

Triglyceride affects the association between estimated glomerular filtration rate and the onset of non-alcoholic fatty liver disease: A second analysis of a Chinese cohort study

Objective

The role of triglyceride (TG) and estimated glomerular filtration rate (eGFR) effect modifiers on the risk of non-alcoholic fatty liver disease (NAFLD) is unknown. This study examined whether TG modifies the relationship between eGFR and incident NAFLD.

Methods

In a Chinese hospital from January 2010 to December 2014, 15,555 non-obese subjects were collected systematically for this retrospective cohort study. The target-independent and dependent variables were eGFR measured at baseline and NAFLD appearing during follow-up. The modified variable was TG measured at baseline. The multivariate Cox proportional hazards model was used to explore eGFR and TG’s association with NAFLD risk. We explored a priori interaction between eGFR and TG, and performed subgroup analyses to further assess whether the relationship between eGFR and incident NAFLD was modified by TG. We also explored the effect of TG and eGFR interaction on the risk of NAFLD.

Results

The mean age was 43.09 ± 14.92 years, and 8,131 (52.27%) were males. During a median follow-up time of 35.8 months, 2,077 (13.35%) individuals developed NAFLD. In the adjusted model, eGFR was negatively associated with incident NAFLD (HR = 0.984, 95% CI: 0.982, 0.987), while TG was positively related to NAFLD (HR = 1.582, 95% CI: 1.490, 1.681). TG could modify the relationship between eGFR and incident NAFLD. A stronger association between eGFR and NAFLD could be found in the participants without hypertriglyceridemia (HTG) (HR = 0.981, 95% CI: 0.978–0.984, P for interaction = 0.0139). In contrast, the weaker association was probed in the population with HTG (HR = 0.986, 95% CI: 0.983–0.989). At the same time, we also found an interaction between eGFR and TG in influencing NAFLD risk. In participants with decreased eGFR and HTG, the risk of NAFLD was significantly increased. Further, compared to non-HTG subjects with eGFR ≥ 116.56 ml/min/1.73 m², participants with HTG and eGFR < 82.88 ml/min/1.73 m² had about a fourfold increase in the risk (HR = 4.852 95% CI: 3.943–5.970) of NAFLD.

Conclusion

eGFR and TG is independently associated with NAFLD risk. The association of eGFR with incident NAFLD is likely to be modified by TG in the Chinese non-obese population. There was an interactive effect between eGFR and TG in affecting NAFLD risk. In participants with decreased eGFR and hypertriglyceridemia, the risk of NAFLD is significantly increased.

Benefits of Physical Exercise as Approach to Prevention and Reversion of Non-Alcoholic Fatty Liver Disease in Children and Adolescents with Obesity

Non-alcoholic fatty liver disease (NAFLD) is an important health concern during childhood; indeed, it is the most frequent cause of chronic liver diseases in obese children. No valid pharmacological therapies for children affected by this condition are available, and the recommended treatment is lifestyle modification, usually including nutrition and exercise interventions. In this narrative review, we summarized up-to-date information on the benefits of physical exercise on NAFLD in children and adolescents with obesity. The role of exercise as non-pharmacological treatment was emphasized in order to provide recent advances on this topic for clinicians not deeply involved in the field. Several studies on obese children and adults confirm the positive role of physical activity (PA) in the treatment of NAFLD, but to date, there are no pediatric randomized clinical trials on exercise versus usual care. Among the pathogenic mechanisms involved in the PA effects on NAFLD, the main players seem to be insulin resistance and related inflammation, oxidative stress, and gut dysbiosis, but further evaluations are necessary to deeply understand whether these factors are correlated and how they synergistically act. Thus, a deeper research on this theme is needed, and it would be extremely interesting.

Comparative Burden of Metabolic Dysfunction in Lean NAFLD vs Non-lean NAFLD - A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is traditionally associated with obesity. However, there is a subtype of NAFLD, namely NAFLD in lean, that occurs without obesity. However, a recent call to redefine NAFLD to metabolic-associated fatty liver disease focuses on obesity and metabolic dysfunction. Criticism has arisen from the perceived over emphasis on systemic comorbidities, which may disadvantage the lean. The current analysis seeks to quantify the degree of metabolic dysfunction in NAFLD in lean and compare with NAFLD in overweight and obese and non-NAFLD.

METHODS

Medline and Embase databases were searched from inception to March 3, 2022. The inclusion criteria were articles with NAFLD in lean patients presenting with baseline metabolic parameters. Comparisons were conducted with subgroup analysis.

RESULTS

Eighty-five articles were included in the meta-analysis. NAFLD in lean accounted for 13.11% (95% confidence interval [CI], 10.26%-16.62%) of the global population and 14.55% (95% CI, 11.32%-18.51%) in Asia. The degree of metabolic dysfunction was weight dependent with significantly less metabolic dysfunction in NAFLD in lean subjects as compared with NAFLD in overweight counterparts. For NAFLD in lean, only 19.56% (95% CI, 15.28%-24.69%) of the subjects were diabetic, whereas 45.70% (95% CI, 35.01%-56.80%) of obese subjects with NAFLD had diabetes (P < .01). Fasting blood glucose and systolic and diastolic blood pressure values were significantly lower in subjects with NAFLD in lean than in overweight and obese.

CONCLUSION

The current analysis highlights the weight-dependent nature of metabolic dysfunction in NAFLD. Lean subjects with NAFLD were significantly less metabolically unhealthy than were obese and overweight persons with NAFLD. An overreliance on metabolic dysfunction in defining fatty liver will be a flaw in potentially excluding previously characterized NAFLD.

Fatty kidney: A possible future for chronic kidney disease research

BACKGROUND

Metabolic syndrome is a growing twenty-first century pandemic associated with multiple clinical comorbidities ranging from cardiovascular diseases, non-alcoholic fatty liver disease and polycystic ovary syndrome to kidney dysfunction. A novel area of research investigates the concept of fatty kidney in the pathogenesis of chronic kidney disease, especially in patients with diabetes mellitus or metabolic syndrome.

AIM

To review the most updated literature on fatty kidney and provide future research, diagnostic and therapeutic perspectives on a disease increasingly affecting the contemporary world.

MATERIALS AND METHOD

We performed an extensive literature search through three databases including Embase (Elsevier) and the Cochrane Central Register of Controlled Trials (Wiley) and PubMed/Medline Web of Science in November 2021 by using the following terms and their combinations: 'fatty kidney', 'ectopic fat', 'chronic kidney disease', 'cardiovascular event', 'cardio-metabolic risk', 'albuminuria' and 'metabolic syndrome'. Each study has been individually assessed by the authors.

RESULTS

Oxidative stress and inflammation, Klotho deficiency, endoplasmic reticulum stress, mitochondrial dysfunction and disruption of cellular energy balance appear to be the main pathophysiological mechanisms leading to tissue damage following fat accumulation. Despite the lack of large-scale comprehensive studies in this novel field of research, current clinical trials demonstrate fatty kidney as an independent risk factor for the development of chronic kidney disease and cardiovascular events.

CONCLUSION

The requirement for future studies investigating the pathophysiology, clinical outcomes and therapeutics of fatty kidney is clear.

MAFLD: Renovation of clinical practice and disease awareness of fatty liver

Recently, international expert panels have proposed a new definition of fatty liver: metabolic dysfunction-associated fatty liver disease (MAFLD). MAFLD is not just a simple renaming of non-alcoholic fatty liver disease (NAFLD). The unique feature of MAFLD is the inclusion of metabolic dysfunctions, which are high-risk factors for events. In addition, MAFLD is independent of alcohol intake and the co-existing causes of liver disease. This new concept of MAFLD may have a widespread impact on patients, medical doctors, medical staff, and various stakeholders regarding fatty liver. Thus, MAFLD may renovate clinical practice and disease awareness of fatty liver. In this review, we introduce the definition of and rationale for MAFLD. We further describe representative cases showing how the diagnostic processes differ between MAFLD and NAFLD. We also summarize recent studies comparing MAFLD with NAFLD and discuss the impact of MAFLD on clinical trials, Japanese populations, and disease awareness.

Association of metabolic dysfunction-associated fatty liver disease with kidney disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in more than 5% of hepatocytes in the absence of excessive alcohol consumption and other secondary causes of hepatic steatosis. In 2020, the more inclusive term metabolic (dysfunction)-associated fatty liver disease (MAFLD) - defined by broader diagnostic criteria - was proposed to replace the term NAFLD. The new terminology and revised definition better emphasize the pathogenic role of metabolic dysfunction and uses a set of definitive, inclusive criteria for diagnosis. Diagnosis of MAFLD is based on evidence of hepatic steatosis (as assessed by liver biopsy, imaging techniques or blood biomarkers and scores) in persons who are overweight or obese and have type 2 diabetes mellitus or metabolic dysregulation, regardless of the coexistence of other liver diseases or excessive alcohol consumption. The known association between NAFLD and chronic kidney disease (CKD) and our understanding that CKD can occur as a consequence of metabolic dysfunction suggests that individuals with MAFLD - who by definition have fatty liver and metabolic comorbidities - are at increased risk of CKD. In this Perspective article, we discuss the clinical associations between MAFLD and CKD, the pathophysiological mechanisms by which MAFLD may increase the risk of CKD and the potential drug treatments that may benefit both conditions.

Non-Alcoholic Fatty Liver Disease and Risk of Macro- and Microvascular Complications in Patients with Type 2 Diabetes

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome. To date, NAFLD is the most frequent chronic liver disease seen day by day in clinical practice across most high-income countries, affecting nearly 25–30% of adults in the general population and up to 70% of patients with T2DM. Over the last few decades, it clearly emerged that NAFLD is a “multisystemic disease” and that the leading cause of death among patients with NAFLD is cardiovascular disease (CVD). Indeed, several observational studies and some meta-analyses have documented that NAFLD, especially its advanced forms, is strongly associated with fatal and non-fatal cardiovascular events, as well as with specific cardiac complications, including sub-clinical myocardial alteration and dysfunction, heart valve diseases and cardiac arrhythmias. Importantly, across various studies, these associations remained significant after adjustment for established cardiovascular risk factors and other confounders. Additionally, several observational studies and some meta-analyses have also reported that NAFLD is independently associated with specific microvascular conditions, such as chronic kidney disease and distal or autonomic neuropathy. Conversely, data regarding a potential association between NAFLD and retinopathy are scarce and often conflicting. This narrative review will describe the current evidence about the association between NAFLD and the risk of macro- and microvascular manifestations of CVD, especially in patients with T2DM. We will also briefly discuss the biological mechanisms underpinning the association between NAFLD and its advanced forms and macro- and microvascular CVD.

Liver Stiffness, Albuminuria and Chronic Kidney Disease in Patients with NAFLD: A Systematic Review and Meta-Analysis

An association between liver stiffness, a surrogate measure of liver fibrosis, and chronic kidney disease (CKD) in patients with nonalcoholic fatty liver disease (NAFLD) has been proposed. However, most studies were small and had low statistical power. We systematically searched PubMed-MEDLINE and Scopus from inception to August 2021 for cross-sectional or cohort studies reporting the association between liver stiffness diagnosed by vibration controlled transient elastography (VCTE) and renal dysfunction. The primary outcome was CKD, defined as a composite of urinary albumin to creatinine ratio (UACR) ≥ 30 mg/g and estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m². Measures of association from individual studies were meta-analyzed using random effects models. Of the 526 titles initially scrutinized, 7 cross-sectional studies fulfilled the criteria and were included. For CKD, risk was higher in patients with liver fibrosis assessed by VCTE, compared with patients without (n = 5 studies: OR 2.49, 95% CI 1.89–3.29; test for overall effect z = 6.475, p < 0.001). When increased UACR was considered as an outcome, elevated liver stiffness was associated with a significantly increased risk as well (n = 3 studies: OR 1. 98 95% CI 1.29–3.05; test for overall effect z = 3.113, p = 0.002). Neither analysis showed significant heterogeneity (I² = 0% and I² = 46.5%, respectively for the two outcomes). This meta-analysis indicates that elevated liver stiffness is associated with increased odds of kidney outcomes among patients with NAFLD. Wider use of VCTE to screen for advanced fibrosis might help identify patients at risk of end-stage renal disease.

Non-Alcoholic Fatty Liver Disease in Lean and Non-Obese Individuals: Current and Future Challenges

Non-alcoholic fatty liver disease (NAFLD), which approximately affects a quarter of the world’s population, has become a major public health concern. Although usually associated with excess body weight, it may also affect normal-weight individuals, a condition termed as lean/non-obese NAFLD. The prevalence of lean/non-obese NAFLD is around 20% within the NAFLD population, and 5% within the general population. Recent data suggest that individuals with lean NAFLD, despite the absence of obesity, exhibit similar cardiovascular- and cancer-related mortality compared to obese NAFLD individuals and increased all-cause mortality risk. Lean and obese NAFLD individuals share several metabolic abnormalities, but present dissimilarities in genetic predisposition, body composition, gut microbiota, and susceptibility to environmental factors. Current treatment of lean NAFLD is aimed at improving overall fitness and decreasing visceral adiposity, with weight loss strategies being the cornerstone of treatment. Moreover, several drugs including PPAR agonists, SGLT2 inhibitors, or GLP-1 receptor agonists could also be useful in the management of lean NAFLD. Although there has been an increase in research regarding lean NAFLD, there are still more questions than answers. There are several potential drugs for NAFLD therapy, but clinical trials are needed to evaluate their efficacy in lean individuals.

Research progress, challenges and perspectives on PNPLA3 and its variants in Liver Diseases

The human patatin-like phospholipase domain-containing 3 gene (PNPLA3) is highly expressed in liver and adipose tissue and encodes a transmembrane polypeptide chain containing 481 amino acids. The I148M variant of PNPLA3 is a single nucleotide polymorphism, which is related to a variety of liver and cardiovascular diseases and their complications (such as non-alcoholic fatty liver disease, liver fibrosis, coronary artery disease). This review mainly describes the pathophysiological effects of PNPLA3 and its variants, and their roles in the progression of liver disease and its complications.

Liver fibrosis assessed by transient elastography is independently associated with albuminuria in the general United States population

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are frequent and progressive conditions that share traditional risk factors: obesity, type 2 diabetes and hypertension.

AIMS

To evaluate whether an independent relationship exists between liver steatosis and fibrosis and different CKD phenotypes.

METHODS

Cross sectional study based on data from the 2017-18 cycle of the National Health and Nutrition Examination Survey. Vibration controlled transient elastography (VCTE) was performed in a US representative sample allowing the simultaneous assessment of liver steatosis (CAP: controlled attenuation parameter) and fibrosis (LSM: liver stiffness measurement) and their relationships with CKD phenotypes (albuminuria and reduced estimated glomerular filtration rate, eGFR).

RESULTS

4746 adult participants had a complete VCTE exam. Prevalence of liver steatosis and significant fibrosis was 33.7% (95%CI: 30.9-36.6%) and 8.9% (95%CI: 7.5-10.5%), respectively. Logistic regression analysis showed that liver fibrosis, but not steatosis, was associated with albuminuria (OR 2.19, 95%CI: 1.49-3.20) and albuminuria or reduced eGFR (OR 2.18, 95%CI: 1.59-3.00) also when adjusted for age, sex, ethnicity, BMI, diabetes, blood pressure categories, glycated haemoglobin, use of renin-angiotensin-aldosterone system blockers and CAP.

CONCLUSIONS

In the general US population liver fibrosis assessed using VCTE is associated with CKD, and in particular with the albuminuric phenotype, regardless of traditional risk factors.

Association between PNPLA3 rs738409 polymorphism and nonalcoholic fatty liver disease: a systematic review and meta-analysis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a common disorder that is known to be the leading cause of chronic liver disease worldwide. This study aims to systematically review and meta-analyze the association between PNPLA3 rs738409 polymorphism and non-alcoholic fatty liver.

METHODS

Following a systematic review and meta-analysis method, articles without any time limitation, were extracted from SID, MagIran, IranDoc, Scopus, Embase, Web of Science (WoS), PubMed and ScienceDirect international databases. Random effects model was used for analysis, and heterogeneity of studies was investigated considering the I² index and using Comprehensive Meta-Analysis software.

RESULTS

The odds ratio of CC genotype in patients with non-alcoholic fatty liver demonstrates the protective effect of CC genotype with the ratio of 0.52, whereas CG genotype presents an increasing effect of CG genotype with the ratio of 0.19, and GG genotype also showed an increasing effect of GG genotype with the ratio of 1.05. Moreover, CG + GG genotypes as a single group demostrated an odds rartio of 0.88.

CONCLUSION

This meta-analysis highlights that people with CC genotype has 52% lower chance of developing non-alcoholic fatty liver disease, and those with CG genotype had 19% higher risk of developing non-alcoholic fatty liver. Those with GG genotype were 105% more likely to develop non-alcoholic fatty liver than others. Moreover, those present in a population with CG + GG genotypes were 88% more likely to have non-alcoholic fatty liver disease.

A review of non-alcoholic fatty liver disease in non-obese and lean individuals

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of hepatic disorders. It represents a wide range of chronic liver diseases in patients with no history of significant alcohol consumption, starting with simple steatosis and progressing towards non-alcoholic steatohepatitis, cirrhosis, and ultimately hepatocellular carcinoma. NAFLD is usually associated with type 2 diabetes mellitus, dyslipidemia, metabolic syndrome, and obesity. This disease has mostly been studied in obese individuals; however, it has been widely reported and studied among the lean/non-obese population in recent years. The pathogenesis of NAFLD in non-obese patients is associated with various genetic predispositions, particularly a patatin-like phospholipase domain-containing protein 3 G allele polymorphism, which results in the accumulation of triglyceride in the liver and resistance to insulin. Additionally, dietary factors such as high fructose consumption seem to play a substantial role in the pathology of non-obese NAFLD. Although there is not enough evidence on the treatment of NAFLD in non-obese patients, the standard approach is to advise altering one's lifestyle in order to diminish visceral adiposity. Dietary modification, weight loss, and increased physical activity are highly recommended. We aimed to review and summarize the existing information on the prevalence, pathogenesis, genetic predispositions, diagnosis, and treatment of NAFLD in non-obese patients according to the latest literature.

Non-alcoholic fatty liver and chronic kidney disease: Retrospect, introspect, and prospect

With the growing prevalence of obesity and diabetes in the United States and across the world, a rise in the overall incidence and prevalence of non-alcoholic fatty liver disease (NAFLD) is expected. The risk factors for NAFLD are also associated with the development of chronic kidney disease (CKD). We review the epidemiology, risk factors, genetics, implications of gut dysbiosis, and specific pathogenic mechanisms linking NAFLD to CKD. Mechanisms such as ectopic lipid accumulation, cellular signaling abnormalities, and the interplay between fructose consumption and uric acid accumulation have led to the emergence of potential therapeutic implications for this patient population. Transplant evaluation in the setting of both NAFLD and CKD is also reviewed. Potential strategies for surveillance and management include the monitoring of comorbidities, the use of non-invasive fibrosis scoring systems, and the measurement of laboratory markers. Lastly, we discuss the management of patients with NAFLD and CKD, from preventative measures to experimental interventions.

[Chronic kidney injury in patients with liver diseases - Reappraising pathophysiology and treatment options]

Acute and chronic kidney disease concurs commonly with liver disease and is associated with a wide array of complications including dialysis dependency and increased mortality. Patients with liver disease or liver cirrhosis show a higher prevalence of chronic kidney disease. This is attributed to concomitant comorbidities, such as metabolic syndrome, chronic inflammation, hypercoagulability, hyperfibrinolysis, diabetes mellitus and dyslipidaemias. But chronic progressive kidney disease is not always due to hepatorenal syndrome. Beyond that, other diseases or disease entities should be considered. Among them are diabetic nephropathy, secondary IgA nephropathy, hepatitis C -associated membranoproliferative Glomerulonephritis (MPGN) and hepatitis B-associated membranous nephropathy.Coexisting diseases, similar underlying pathophysiologic mechanisms, or simultaneously concurring pathophysiological processes and overlapping clinical manifestations, impede the etiologic diagnosis and corresponding treatment of chronic kidney disease in the setting of chronic liver disease. In this review, we focus on common and rare pathologies, which can lead to chronic kidney disease in this particular patient group and try to summarize the most recent therapeutic modalities.

The epidemiology of NAFLD and lean NAFLD in Japan: a meta-analysis with individual and forecasting analysis, 1995-2040

BACKGROUND

NAFLD is increasing in Asia including Japan, despite its lower obesity rate than the West. However, NAFLD can occur in lean people, but data are limited. We aimed to investigate the epidemiology of NAFLD in Japan with a focus on lean NAFLD.

METHODS

We searched PubMed, Cochrane Library, EMBASE, Web of Science, and the Japan Medical Abstracts Society (inception to 5/15/2019) and included 73 eligible full-text original research studies (n = 258,531). We used random-effects model for pooled estimates, Bayesian modeling for trend and forecasting, contacted authors for individual patient data and analyzed 14,887 (7752 NAFLD; 7135 non-NAFLD-8 studies) patients.

RESULTS

The overall NAFLD prevalence was 25.5%, higher in males (p < 0.001), varied by regions (p < 0.001), and increased over time (p = 0.015), but not by per-person income or gross prefectural productivity, which increased by 0.64% per year (1983-2012) and is forecasted to reach 39.3% in 2030 and 44.8% in 2040. The incidence of NAFLD, HCC, and overall mortality were 23.5, 7.6 and 5.9 per 1000 person-years, respectively. Individual patient-level data showed a lean NAFLD prevalence of 20.7% among the NAFLD population, with lean NAFLD persons being older and with a higher all-cause mortality rate (8.3 vs. 5.6 per 1000 person-years for non-lean NAFLD, p = 0.02). Older age, male sex, diabetes, and FIB-4 were independent predictors of mortality, but not lean NAFLD.

CONCLUSION

NAFLD prevalence has increased in Japan and may affect half of the population by 2040. Lean NAFLD individuals makeup 20% of the NAFLD population, were older, and had higher mortality.

Significance of Simple Steatosis: An Update on the Clinical and Molecular Evidence

Non-alcoholic fatty liver disease (NAFLD) is defined clinicopathologically by the accumulation of lipids in >5% of hepatocytes and the exclusion of secondary causes of fat accumulation. NAFLD encompasses a wide spectrum of liver damage, extending from simple steatosis or non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH)—the latter is characterized by inflammation and hepatocyte ballooning degeneration, in addition to the steatosis, with or without fibrosis. NAFLD is now the most common cause of chronic liver disease in Western countries and affects around one quarter of the general population. It is a multisystem disorder, which is associated with an increased risk of type 2 diabetes mellitus as well as liver- and cardiovascular-related mortality. Although earlier studies had suggested that NAFL is benign (i.e., non-progressive), cumulative evidence challenges this dogma, and recent data suggest that nearly 25% of those with NAFL may develop fibrosis. Importantly, NAFLD patients are more susceptible to the toxic effects of alcohol, drugs, and other insults to the liver. This is likely due to the functional impairment of steatotic hepatocytes, which is virtually undetectable by current clinical tests. This review provides an overview of the current evidence on the clinical significance of NAFL and discusses the molecular basis for NAFL development and progression.

ALT Levels for Asians With Metabolic Diseases: A Meta-analysis of 86 Studies With Individual Patient Data Validation

The current alanine aminotransferase (ALT) upper limit of normal was defined using selected healthy Caucasian blood donors. Given the global rise in obesity and different body habitus in Asians, we aimed to perform a systematic review and meta-analysis combined with bootstrap modeling and individual patient data validation to estimate the ALT upper threshold for Asians, including the overweight and diabetics. We included studies from PubMed, Embase, and Cochrane database searches that identified individuals without known liver diseases (i.e., viral hepatitis, alcohol, and ultrasound-detected nonalcoholic fatty liver disease). The mean ALT (U/L) was estimated using a random-effects mixed model and upper threshold (95th-percentile value, U/L) via a bootstrap model with 10,000 resamples. We screened 4,995 studies and identified 86 studies that reported ALT values for 526,641 individuals without excessive alcohol intake or known liver diseases, yielding a mean ALT of 19 and ALT upper threshold of 32. The ALT upper threshold was 37 in males versus 31 in females, 39 in overweight versus 28 in normal-weight individuals, and 36 for diabetics versus 33 for nondiabetics. We validated our study level data with individual patient level data in 6,058 individuals from five study centers in Japan. Consistent with our study-level data, we found that the ALT upper threshold in our individual patient data analysis was indeed higher in overweight versus normal-weight individuals (39 vs. 32) and in diabetics versus nondiabetics (42 vs. 33). Conclusion: We provide validated reference ranges for ALT upper threshold derived from Asians without known liver disease, including individuals with ultrasound-detected nonalcoholic fatty liver disease who are normal weight, overweight, nondiabetic, and diabetic, to inform practice.

Global prevalence, incidence, and outcomes of non-obese or lean non-alcoholic fatty liver disease: a systematic review and meta-analysis

BACKGROUND

Although non-alcoholic fatty liver disease (NAFLD) is commonly associated with obesity, it is increasingly being identified in non-obese individuals. We aimed to characterise the prevalence, incidence, and long-term outcomes of non-obese or lean NAFLD at a global level.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Embase, Scopus, and the Cochrane Library from inception to May 1, 2019, for relevant original research articles without any language restrictions. The literature search and data extraction were done independently by two investigators. Primary outcomes were the prevalence of non-obese or lean people within the NAFLD group and the prevalence of non-obese or lean NAFLD in the general, non-obese, and lean populations; the incidence of NAFLD among non-obese and lean populations; and long-term outcomes of non-obese people with NAFLD. We also aimed to characterise the demographic, clinical, and histological characteristics of individuals with non-obese NAFLD.

FINDINGS

We identified 93 studies (n=10 576 383) from 24 countries or areas: 84 studies (n=10 530 308) were used for the prevalence analysis, five (n=9121) were used for the incidence analysis, and eight (n=36 954) were used for the outcomes analysis. Within the NAFLD population, 19·2% (95% CI 15·9-23·0) of people were lean and 40·8% (36·6-45·1) were non-obese. The prevalence of non-obese NAFLD in the general population varied from 25% or lower in some countries (eg, Malaysia and Pakistan) to higher than 50% in others (eg, Austria, Mexico, and Sweden). In the general population (comprising individuals with and without NAFLD), 12·1% (95% CI 9·3-15·6) of people had non-obese NAFLD and 5·1% (3·7-7·0) had lean NAFLD. The incidence of NAFLD in the non-obese population (without NAFLD at baseline) was 24·6 (95% CI 13·4-39·2) per 1000 person-years. Among people with non-obese or lean NALFD, 39·0% (95% CI 24·1-56·3) had non-alcoholic steatohepatitis, 29·2% (21·9-37·9) had significant fibrosis (stage ≥2), and 3·2% (1·5-5·7) had cirrhosis. Among the non-obese or lean NAFLD population, the incidence of all-cause mortality was 12·1 (95% CI 0·5-38·8) per 1000 person-years, that for liver-related mortality was 4·1 (1·9-7·1) per 1000 person-years, cardiovascular-related mortality was 4·0 (0·1-14·9) per 1000 person-years, new-onset diabetes was 12·6 (8·0-18·3) per 1000 person-years, new-onset cardiovascular disease was 18·7 (9·2-31·2) per 1000 person-years, and new-onset hypertension was 56·1 (38·5-77·0) per 1000 person-years. Most analyses were characterised by high heterogeneity.

INTERPRETATION

Overall, around 40% of the global NAFLD population was classified as non-obese and almost a fifth was lean. Both non-obese and lean groups had substantial long-term liver and non-liver comorbidities. These findings suggest that obesity should not be the sole criterion for NAFLD screening. Moreover, clinical trials of treatments for NAFLD should include participants across all body-mass index ranges.

FUNDING

None.

Prevalence and Profile of Nonalcoholic Fatty Liver Disease in Lean Adults: Systematic Review and Meta-Analysis

Data on prevalence and profile of nonalcoholic fatty liver disease (NAFLD) among individuals who are lean (normal body mass index) is unclear. Published data from studies comparing lean with obese NAFLD or with healthy subjects on prevalence, comorbidities, liver chemistry and histology, and metabolic/inflammatory markers were analyzed. Data were reported as odds ratio and 95% confidence interval for categorical variables and difference of means for continuous variables. Analysis of 53 studies on 65,029 subjects with NAFLD (38,084 lean) and 249,544 healthy subjects showed a prevalence of lean NAFLD at 11.2% in the general population. Among individuals with NAFLD, the prevalence of lean NAFLD was 25.3%. Lean NAFLD versus healthy subjects had higher odds for abnormalities on metabolic profile, including metabolic syndrome and its components, renal and liver function, and patatin‐like phospholipase domain‐containing protein 3 (PNPLA3) G allele; and inflammatory profile, including uric acid and C‐reactive protein. The abnormalities were less severe among lean versus obese NAFLD on metabolic syndrome with its components, renal and liver chemistry, liver stiffness measurement, PNPLA3 and transmembrane 6 superfamily member 2 polymorphisms, and uric acid levels as markers of inflammation. Lean NAFLD had less severe histologic findings, including hepatocyte ballooning, lobular inflammation, NAFLD activity score, and fibrosis stage. Limited data also showed worse outcomes between obese versus lean NAFLD. Conclusion: Lean NAFLD is a distinct entity with metabolic, biochemical, and inflammatory abnormalities compared to healthy subjects and a more favorable profile, including liver histology of steatohepatitis and fibrosis stage, compared to obese NAFLD. We suggest that prospective multicenter studies examine long‐term hepatic and extrahepatic outcomes in individuals with lean NAFLD.

PNPLA3 I148M gene variant and chronic kidney disease in type 2 diabetic patients with NAFLD: Clinical and experimental findings

BACKGROUND AND AIMS

Emerging evidence suggests an association between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 (I148M protein variant) and risk of chronic kidney disease (CKD), but the mechanisms underpinning this association are poorly understood.

METHODS

We studied 157 patients with type 2 diabetes (T2DM) who underwent ultrasonography and vibration-controlled transient elastography for diagnosing nonalcoholic fatty liver disease (NAFLD). CKD was defined as estimated glomerular filtration rate (e-GFR) <60 mL/min/1.73 m² and/or abnormal albuminuria. We surveyed PNPLA3 mRNA expression in human tissues, using the liver as a positive control, and also measured PNPLA3 mRNA and protein expression levels in human cell lines represented in the kidney and the liver.

RESULTS

In all, 112 patients had NAFLD and 43 had CKD. Patients homozygous for the I148M variant (n = 11) had lower e-GFR levels (60.6 ± 11.7 vs 77.8 ± 15.9 vs 83.5 ± 16.5 mL/min/1.73 m² , P = .0001) and higher prevalence of CKD (63.6% vs 24.2% vs 25.0%, P = .028), compared to those with I/M (n = 66) and I/I (n = 80) PNPLA3 genotype. The association of I148M homozygosity with lower e-GFR levels (P < .0001) and higher risk of CKD (adjusted-odds ratio 6.65; 95% CI 1.65-26.8, P = .008) was independent of liver disease severity (as detected by liver stiffness ≥7kPa) and other risk factors. PNPLA3 mRNA expression was greatest in liver and renal cortex, and podocytes showed high PNPLA3 mRNA and protein levels, comparable to that of hepatocytes and hepatic stellate cells respectively.

CONCLUSIONS

The PNPLA3 I148M variant was associated with CKD, independently of common renal risk factors and severity of NAFLD PNPLA3 expression levels were particularly high in renal podocytes.

Risk of Kidney Dysfunction IN Nafld

Background:

The timely identification of traditional and non-traditional precursors and risk factors for chronic kidney disease (CKD) (a common systemic disease defined as a decreased kidney function documented by reduced glomerular filtration rate, or markers of kidney damage, or both) is relevant in clinical practice, as CKD increases the risk of end-stage renal disease and other serious comorbidities. A possible relationship between non-alcoholic fatty liver disease (NAFLD) (which is to date the most common chronic disease worldwide) and CKD has recently gained significant attention of researchers.

Methods :

A systematic literature search using appropriate keywords was made in order to identify relevant articles that have investigated the association between NAFLD and CKD.

Results:

Several observational studies and meta-analyses have reported the existence of an independent association between NAFLD and risk of CKD in patients with and without diabetes. However, whilst the association between NAFLD and risk of prevalent CKD is strong across various patient populations, whether NAFLD is independently associated with the development and progression of CKD is still debatable. Moreover, emerging evidence now suggests a potential association between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 genotype (the most important genetic variant associated to NAFLD) and decreasing kidney function, independent of NAFLD.

Conclusions :

Convincing evidence now indicates that CKD is increased among patients with NAFLD. For this reason, patients with NAFLD should be regularly monitored for renal function and, on the other hand , NAFLD should be considered in all patients with CKD, especially if they are obese or have type 2 diabetes.

NAFLD as a driver of chronic kidney disease

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are worldwide public health problems, affecting up to 25-30% (NAFLD), and up to 10-15% (CKD) of the general population. Recently, it has also been established that there is a strong association between NAFLD and CKD, regardless of the presence of potential confounding diseases such as obesity, hypertension and type 2 diabetes. Since NAFLD and CKD are both common diseases that often occur alongside other metabolic conditions, such as type 2 diabetes or metabolic syndrome, elucidating the relative impact of NAFLD on the risk of incident CKD presents a substantial challenge for investigators working in this research field. A growing body of epidemiological evidence suggests that NAFLD is an independent risk factor for CKD and recent evidence also suggests that associated factors such as metabolic syndrome, dysbiosis, unhealthy diets, platelet activation and processes associated with ageing could also contribute mechanisms linking NAFLD and CKD. This narrative review provides an overview of the literature on: a) the evidence for an association and causal link between NAFLD and CKD and b) the underlying mechanisms by which NAFLD (and factors strongly linked with NAFLD) may increase the risk of developing CKD.

PNPLA3 gene and kidney disease

Chronic kidney disease (CKD) is a disease regularly seen in clinical practice. At present, CKD is described as a change of kidney structure and/or function and it is classified in relation to cause, values of glomerular filtration rate and albuminuria category. Seeing that CKD is closely linked to the development of end-stage renal disease and other comorbidities, the determination of additional independent predictors for CKD is clinically necessary. At present, there is evidence associating non-alcoholic fatty liver disease (NAFLD) with CKD, thereby suggesting that NAFLD patients may require intensive surveillance to reduce their risk of CKD. In 2008, genome-wide association studies documented an association between the variant rs738409 (C > G p.I148M) in the patatin-like phospholipase domain containing 3 (PNPLA3) gene (mainly implicated in the lipid regulation) and the entire spectrum of NAFLD (i.e., liver steatosis, non-alcoholic steatohepatitis, fibrosis, and hepatocellular carcinoma). In the last years, accumulating epidemiological evidence suggests the existence of a relationship between PNPLA3 rs738409 and risk of CKD, indicating that rs738409 may also contribute to the kidney injury. This is of particular scientific interest, as such association may explain, at least in part, the epidemiological association between liver and kidney disease. In this narrative review, we will discuss the accumulating evidence regarding the association between PNPLA3 rs738409 and risk of CKD, the putative biological mechanisms underpinning such relationship, and the possible future perspective.

Independent and joint correlation of PNPLA3 I148M and TM6SF2 E167K variants with the risk of coronary heart disease in patients with non-alcoholic fatty liver disease

Background

CHD is reported to be the primary cause of death in patients with NAFLD. Genetic susceptibility genes contribute to the developmental risk of NAFLD or CHD. Whether the genetic factors could affect the risk of CHD in NAFLD patients is not clear. The aim of this study was to investigate the association of PNPLA3 I148M and TM6SF2 E167K variants with the risk of CHD in NAFLD patients in Chinese Han population.

Patients and methods

PNPLA3 I148M and TM6SF2 E167K variants were genotyped in a cohort of 189 patients with NAFLD and CHD, as well as 242 patients with NAFLD and 242 healthy controls by gene sequencing. Additionally, serum lipids profiles were determined by standard clinical laboratory methods.

Results

The minor allele frequency of PNPLA3 I148M and TM6SF2 E167K were 0.39 and 0.06 in this cohort, respectively. The distributions of PNPLA3 I148M genotypes and alleles were significant different in NAFLD group vs controls and in NAFLD+CHD group vs NAFLD group (all P <  0.05). NAFLD patients who carry the CG + GG genotype suffered the relative lower risk of CHD than CC genotype carriers (OR = 0.6, 95%CI: 0.40–0.90, P = 0.01). In addition, PNPLA3 I148M and TM6SF2 E167K possess the joint correlation with the decreased risk of CHD in NAFLD patients with the increased number of risk alleles. Besides, PNPLA3 I148M and TM6SF2 E167K variants associated with the decreased serum lipid levels in overall series.

Conclusions

There was a joint protective correlation of PNPLA3 I148M and TM6SF2 E167K variants with the developmental risk of CHD in NAFLD patients. PNPLA3 I148M and TM6SF2 E167K variants might correlated with the decreased risk of CHD in NAFLD patients by associated with the reduced serum lipid levels.

PNPLA3 rs738409 is associated with renal glomerular and tubular injury in NAFLD patients with persistently normal ALT levels

BACKGROUND & AIMS

Patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 polymorphism is associated with NAFLD severity and the PNPLA3 gene is expressed in the kidneys, but whether PNPLA3 rs738409 polymorphism is also associated with renal tubular injury (RTI) is uncertain. We assessed the effect of PNPLA3 genotypes on biomarkers of RTI and glomerular function in subjects with NAFLD who had either normal (nALT) or abnormal (abnALT) alanine aminotransaminase levels.

METHODS

Two hundred and seventeen patients with histologically proven NAFLD of which 75 had persistently nALT (below upper limit of normal for 3 months) were included. Multivariable regression analyses were undertaken to test associations between PNPLA3 genotype and biomarkers of kidney dysfunction.

RESULTS

The nALT patient group had higher urinary neutrophil gelatinase-associated lipocalin levels (u-NGAL, a biomarker of RTI) (P < .001), higher albuminuria (P = .039) and greater prevalence of chronic kidney disease (CKD; P = .046) than the abnALT group. The association between PNPLA3 GG genotype and risk of CKD and abnormal albuminuria remained significant after adjustment for kidney risk factors and severity of NAFLD histology, mostly in the nALT group. Similarly, PNPLA3 GG genotype was associated with higher u-NGAL levels in the nALT group, even after adjustment for the aforementioned risk factors and glomerular filtration-based markers (β-coefficient: 22.29, 95% CI: 0.99-43.60, P = .041).

CONCLUSION

Patients with NAFLD and persistently nALT, who carry the PNPLA3 rs738409 G allele, are at higher risk of early glomerular and tubular damage. We suggest PNPLA3 genotyping may help identify patients with NAFLD at higher risk of RTI.

A Pilot Study Assessing the Possible Combined Effect of Physical Activity and PNPLA3 rs738409 Polymorphism on the Risk for Non-Alcoholic Fatty Liver Disease in the Japanese Elderly General Population

PURPOSE

The patatin-like phospholipase domain containing protein 3 (PNPLA3) rs738409 polymorphism (c.444C>G) is the most well-known genetic risk factor for non-alcoholic fatty liver disease (NAFLD), but whether or not physical activity influences the association between the PNPLA3 genotype and risk of NAFLD is unclear.

PATIENTS AND METHODS

A retrospective longitudinal analysis was conducted among 352 Japanese subjects. Each type of physical activity was assigned a metabolic equivalent (MET), and the subjects were classified into sedentary, low or high groups using the "METS*T" (METs × hours per week) value of 5 or 21 as a threshold.

RESULTS

Among the PNPLA3 G/G genotype carriers, the high and low METS*T groups had a lower risk of NAFLD than the sedentary METS*T group (odds ratio [95% confidence interval]: 0.14 [0.02-0.99] and 0.16 [0.03-1.04], respectively). Furthermore, the PNPLA3 C/C or C/G genotype carriers showed no significant difference in the risk of NAFLD among the three METS*T groups.

CONCLUSION

The PNPLA3 rs738409 genotype may be associated with the beneficial effects of physical activity on the risk of NAFLD among elderly Japanese individuals. Further comprehensive investigations are therefore needed to verify the preliminary results.

Beta-3-adrenergic Receptor rs4994 Polymorphism Is a Potential Biomarker for the Development of Nonalcoholic Fatty Liver Disease in Overweight/Obese Individuals

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. Obesity is the most common and well-established risk factor for NAFLD, but there are large interindividual differences in the relationship between weight status and the development of NAFLD. Beta-3-adrenergic receptor (ADRB3) plays a key role in the development of visceral obesity and insulin resistance; however, the effect of ADRB3 polymorphisms on the risk of NAFLD remains unclear. We investigated whether or not a common rs4994 polymorphism (T190C) in the ADRB3 gene is associated with the risk of NAFLD through an increase in the body mass index (BMI) among the general population. We performed cross-sectional and longitudinal analyses in a total of 591 Japanese health screening program participants. Among the overweight or obese subjects, but not normal-weight subjects, individuals with the C/C genotype had a higher risk of developing NAFLD in comparison to those with other genotypes in the cross-sectional analysis (odds ratio: 4.40, 95% confidence interval (CI): 1.08–17.93). Meanwhile, the receiver operating characteristic curve indicated that the association between an increase in the BMI and the presence of NAFLD in subjects with the C/C genotype (area under the curve: 0.91, 95% CI: 0.78–1.00) was more pronounced in comparison to subjects with other genotypes. These above-described findings were verified by the analyses using a replicated data set consisting of 5,000 random samples from original data sets. Furthermore, among the 291 subjects for whom longitudinal medical information could be collected and who did not have NAFLD at baseline, the Cox proportional hazard model also confirmed that overweight or obese status and the C/C genotype were concertedly related to the increased risk of NAFLD development. These results suggest that genotyping the ADRB3 rs4994 polymorphism may provide useful information supporting the development of personalized BMI-based preventive measures against NAFLD.

Nonalcoholic fatty liver disease and eGFR levels could be linked by the PNPLA3 I148M polymorphism in children with obesity

BACKGROUND

PNPLA3 I148M polymorphism has an effect on modulation of estimated glomerular filtration rate (eGFR) in nonobese nondiabetic adults and in children with histologically confirmed nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

The objective of the study is to explore the impact of PNPLA3 I148M polymorphism on eGFR in children with obesity with and without NAFLD.

METHODS

We genotyped 591 patients with obesity for PNPLA3 I148M polymorphism. Anthropometrical, biochemical, and instrumental data were collected. NAFLD was defined by the presence of ultrasound-detected liver steatosis and/or ALT levels greater than 40 IU/L.

RESULTS

Patients with NAFLD showed significantly lower eGFR levels compared with subjects without NAFLD. Children with PNPLA3 MM genotype showed lower eGFR levels compared with those with either PNPLA3 IM or II genotypes both in the presence and absence of NAFLD. A general linear model for eGFR variance, including gender, duration of obesity, PNPLA3 genotypes, HOMA, BMI-SDS, LDL-C, and triglycerides as covariates, confirmed an inverse association between eGFR and PNPLA3 genotype only in the presence of NAFLD.

CONCLUSIONS

Children with obesity and PNPLA3 MM genotype show lower eGFR levels compared with other genotypes, with a major effect of this polymorphism in the presence of NAFLD.

Nonalcoholic Fatty Liver Disease (NAFLD), But not Its Susceptibility Gene Variants, Influences the Decrease of Kidney Function in Overweight/Obese Children

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of kidney disease in adults and children. However, it is uncertain whether this association is influenced by major NAFLD susceptibility genes. In a sample of 230 overweight/obese children, 105 with NAFLD (hepatic fat fraction ≥5% by magnetic resonance imaging) and 125 without NAFLD, rs738409 in PNPLA3, rs58542926 in TM6SF2, rs1260326 in GCKR, and rs641738 in MBOAT7 were genotyped. Abnormal kidney function was defined as estimated glomerular filtration rate (eGFR) < 90 mL/min/1.73 m² and/or the presence of microalbuminuria (24 h urinary albumin excretion between 30 and 300 mg). In comparison with children without NAFLD, those with NAFLD showed increased prevalence of reduced eGFR (13.3% vs. 1.6%; p < 0.001) and microalbuminuria (8.6% vs. 3.4%, p = 0.025). TM6SF2, GCKR, and MBOAT7 risk alleles did not show any impact on kidney function, while the PNPLA3 G allele was associated with lower eGFR, but only in children with NAFLD (p = 0.003). After adjustment for confounders, NAFLD (OR, 4.7; 95% CI, 1.5–14.8; p_adj = 0.007), but not the PNPLA3 gene variant, emerged as the main independent predictor of renal dysfunction. Overall, our findings suggest that NAFLD remains the main determinant of decline in kidney function in overweight/obese children, while the PNPLA3 rs738409 prosteatogenic variant has a small impact, if any.

The relationship among GNB3 rs5443, PNPLA3 rs738409, GCKR rs780094 gene polymorphisms, type of maternal gestational weight gain and neonatal outcomes (STROBE-compliant article)

The gestational weight gain is determined by food habits, environmental and genetic factors.The aims of this paper were to establish relationships between maternal gene polymorphisms (patatin-like phospholipase domain-containing protein 3 rs738409 [PNPLA3 rs738409], glucokinase regulatory protein rs780094 [GCKR rs780094], and guanine nucleotide-binding protein rs5443 [GNB3 rs5443]) and mothers' gestational weight gain, but also neonatal outcomes (birth weight, length, and ponderal index [PI]).We performed a cross-sectional study in a sample of 158 mothers and their product of conception' in an Obstetrics-Gynecology Clinic from Romania. We divided the pregnant women according to the Institute of Medicine recommendations into 3 subgroups: (1) insufficient gestational weight gain; (2) normal gestational weight gain; and (3) excessive gestational weight gain.The gestational weight gain among pregnant women included in this study was classified as insufficient (10.1%), normal (31%), and excessive (58.9%). We found a tendency towards statistical significance for mothers that were overweight or obese before pregnancy to present an excessive gestational weight gain as compared to the normal weight ones. Similarly, we identified a tendency for statistical significance regarding the association between the variant genotype of GNB3 rs5443 and excessive gestational weight gain. We noticed differences that tended to be statistical significant concerning aspartate aminotransferase values between the 3 subgroups, mothers with excessive gestational weight gain having higher values than mothers with normal gestational weight gain (median, IQR: 22.89[17.53; 31.59] for mothers with excessive gestational weight gain versus 22.71[18.58; 27.37] for mothers with normal gestational weight gain). In mothers with excessive gestational weight gain, we found a significant association between the variant genotype of PNPLA3 rs738409 polymorphism and neonatal PI noticing a decrease of this index in case of newborns from mothers carrying the variant genotype.Excessive gestational weight gain was noticed in pregnant women that were obese and overweight before pregnancy. We found a positive association between the variant genotype of GNB3 rs5443 polymorphism and excessive gestational weight gain. Similarly, the presence of variant genotype of PNPLA3 rs738409 in mothers was associated with a lower PI in their newborns. Our study pointed out the most important factors that influence gestational weight gain and related birth outcomes.

Relationship Between PNPLA3 rs738409 Polymorphism and Decreased Kidney Function in Children With NAFLD

Emerging evidence suggests that patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 genotype (the major genetic variant associated with susceptibility to nonalcoholic fatty liver disease [NAFLD]) is associated with decreased kidney function in adults. Currently, it is uncertain whether this association also occurs in children/adolescents and whether any association is independent of liver disease severity. We enrolled a sample of 142 Caucasian children and adolescents with biopsy-proven NAFLD, presenting to the Liver Unit of the "Bambino Gesù" Children's Hospital. The glomerular filtration rate (e-GFR) was estimated using the Bedside Schwartz equation, whereas 24-hour proteinuria was measured using a radioimmunoassay method. Genotyping for the PNPLA3 rs738409 genotype was undertaken using the single-nucleotide polymorphism genotyping allelic discrimination method. Overall, 45 children had G/G, 56 had G/C, and 41 had C/C PNPLA3 rs738409 genotype, respectively. Children with G/G genotype had significantly lower e-GFR (107.5 ± 20 versus 112.8 ± 18 versus 125.3 ± 23 mL/min/1.73 m² , P = 0.002) and higher 24-hour proteinuria (58.5 ± 21 versus 53.9 ± 22 versus 42.9 ± 20 mg/day, P = 0.012) compared with those with either G/C or C/C genotypes. After adjustment for age, sex, systolic blood pressure, measures of adiposity, homeostasis model assessment-estimated insulin resistance and biopsy-confirmed nonalcoholic steatohepatitis and stage of liver fibrosis, the presence of rs738409 G/G genotype was independently associated with both lower e-GFR (β coefficient: -23.6; 95% confidence interval [CI]: -36.3 to -10.8; P < 0.001) and higher 24-hour proteinuria (β coefficient: 15.3; 95% CI: 1.12 to 30.5; P = 0.046). Conclusion: Regardless of established renal risk factors and the histological severity of NAFLD, the PNPLA3 G/G genotype was strongly associated with decreasing kidney function and increasing 24-hour proteinuria in children/adolescents with histologically confirmed NAFLD.