Understanding the pathophysiological mechanisms in the pediatric non-alcoholic fatty liver disease: The role of genetics

Metabolic-Associated Fatty Liver Disease in Childhood and Adolescence

Metabolic-associated fatty liver disease (MAFLD) has become the most common cause for chronic liver disease among children and adolescents globally. Although liver biopsy remains the gold standard for diagnosis, emerging technology, like velocity controlled transient elastography, a noninvasive method, is being utilized to evaluate degree of fibrosis in these patients. The discovery of multiple gene polymorphisms has brought new hope for possible treatment targets. However, this research is still ongoing, making lifestyle changes and weight reduction the current mainstay of treatment. This review briefly reviews the most recent data regarding the epidemiology, pathophysiology, diagnostic modalities, and treatment of pediatric MAFLD.

A Comprehensive Review on Liver Targeting: Emphasis on Nanotechnology- based Molecular Targets and Receptors Mediated Approaches

BACKGROUND

The pathogenesis of hepatic diseases involves several cells, which complicates the delivery of pharmaceutical agents. Many severe liver diseases affecting the worldwide population cannot be effectively treated. Major hindrances or challenges are natural physiological barriers and non-specific targeting of drugs administered, leading to inefficient treatment. Hence, there is an earnest need to look for novel therapeutic strategies to overcome these hindrances. A kind of literature has reported that drug safety and efficacy are incredibly raised when a drug is incorporated inside or attached to a polymeric material of either hydrophilic or lipophilic nature. This has driven the dynamic investigation for developing novel biodegradable materials, drug delivery carriers, target-specific drug delivery systems, and many other novel approaches.

OBJECTIVE

Present review is devoted to summarizing receptor-based liver cell targeting using different modified novel synthetic drug delivery carriers. It also highlights recent progress in drug targeting to diseased liver mediated by various receptors, including asialoglycoprotein, mannose and galactose receptor, Fc receptor, low-density lipoprotein, glycyrrhetinic, and bile acid receptor. The essential consideration is given to treating liver cancer targeting using nanoparticulate systems, proteins, viral and non-viral vectors, homing peptides and gene delivery.

CONCLUSION

Receptors based targeting approach is one such approach that was explored by researchers to develop novel formulations which can ensure site-specific drug delivery. Several receptors are on the surfaces of liver cells, which are highly overexpressed in various disease conditions. They all are helpful for the treatment of liver cancer.

Protective effects and mechanisms of Lizhong decoction against non-alcoholic fatty liver disease in a rat model

OBJECTIVE

To investigate the protective effects and molecular mechanisms of Lizhong decoction (, LZD) against non-alcoholic fatty liver disease (NAFLD).

METHODS

Male Wistar rats were fed a high-fat diet for four weeks to induce NAFLD, and were administered LZD by gavage for four weeks. Potential therapeutic targets for NAFLD were analyzed using network pharmacology. Liver pathology was evaluated using Oil Red O and hematoxylin-eosin staining. Furthermore, mitochondrial function, lipid metabolism, oxidative stress, and inflammatory response were examined.

RESULTS

Rats with NAFLD exhibited high levels of hepatic damage and cholesterol deposition. Moreover, apoptosis was increased, superoxide dismutase and glutathione content were reduced, malondialdehyde content was increased, and the protein expression of inflammatory cytokines and p-c-Jun N-terminal kinase was increased. The LZD treatment ameliorated mitochondrial dysfunction, reduced liver damage, inhibited oxidative stress and inflammatory response, upregulated peroxisome proliferator-activated receptor (PPAR)-γ expression, and suppressed dipeptidyl peptidase 4 (DPP4) expression in the liver.

CONCLUSION

It was found that LZD alleviates NAFLD by activating PPAR-γ and inhibiting DPP4.

Advances in pediatric non-alcoholic fatty liver disease: From genetics to lipidomics

As a result of the obesity epidemic, non-alcoholic fatty liver disease (NAFLD) represents a global medical concern in childhood with a closely related increased cardiometabolic risk. Knowledge on NAFLD pathophysiology has been largely expanded over the last decades. Besides the well-known key NAFLD genes (including the I148M variant of the PNPLA3 gene, the E167K allele of the TM6SF2, the GCKR gene, the MBOAT7-TMC4 rs641738 variant, and the rs72613567:TA variant in the HSD17B13 gene), an intriguing pathogenic role has also been demonstrated for the gut microbiota. More interestingly, evidence has added new factors involved in the “multiple hits” theory. In particular, omics determinants have been highlighted as potential innovative markers for NAFLD diagnosis and treatment. In fact, different branches of omics including metabolomics, lipidomics (in particular sphingolipids and ceramides), transcriptomics (including micro RNAs), epigenomics (such as DNA methylation), proteomics, and glycomics represent the most attractive pathogenic elements in NAFLD development, by providing insightful perspectives in this field. In this perspective, we aimed to provide a comprehensive overview of NAFLD pathophysiology in children, from the oldest pathogenic elements (including genetics) to the newest intriguing perspectives (such as omics branches).

Docosahexaenoic Acid Attenuates the Progression of Nonalcoholic Steatohepatitis by Suppressing the Adipocyte Inflammation via the G Protein-Coupled Receptor 120/Free Fatty Acid Receptor 4 Pathway

INTRODUCTION

Our previous study demonstrated that docosahexaenoic acid (DHA), an endogenous G protein-coupled receptor 120 (GPR120)/free fatty acid receptor (FFAR) 4 agonist, attenuated the liver inflammation in nonalcoholic steatohepatitis (NASH), while exacerbated liver inflammation was observed in the GPR120/FFAR4 knockout (GPR120/FFAR4KO) mice. Recently, abdominal adiposity has been reported to correlate with the severity of inflammation and fibrosis in patients with NASH. In this study, we investigated whether the activation of GPR120/FFAR4 suppressed the inflammation of the adipose tissue and whether these suppressive effects attenuated the development of NASH.

METHODS

A choline-deficient and 0.1% methionine-containing high-fat (CDAHF) diet was used to create a mouse model of NASH. DHA was orally administered to the mice for 1 week. Epididymal fat pads which collected from the control-fed wild-type (WT) or GPR120/FFAR4KO mice were used as ex vivo white adipose tissue (WAT) culture systems.

RESULTS

The mice fed a CDAHF diet for 2 weeks showed NASH-like liver diseases. In the WAT of mice fed with the CDAHF diet, inflammation and fibrosis were significantly increased, and the administration of DHA suppressed these phenomena. In an ex vivo adipocyte culture study, DHA dose-dependently suppressed the lipopolysaccharide-induced inflammation in the adipocyte tissue of WT mice, which was reversed by pretreatment with AH7614, a GPR120/FFAR4 antagonist, but not GPR40 or peroxisome proliferator-activated receptor γ antagonist.

CONCLUSIONS

These findings suggest that the activation of GPR120/FFAR4 may suppress the inflammation of adipocytes, which could be a key pathway to prevent the development of NASH.

GPR120 agonist ameliorated insulin resistance and improved ovarian function

GPR120 is implicated in the regulation of glucose and lipid metabolism, and insulin resistance. In the current study, we aimed to investigate the role of GPR120 in polycystic ovary syndrome (PCOS). With the adoption of dehydroepiandrosterone, a rat model was established to simulate PCOS in vitro. mRNA and protein expression levels of GPR120 were measured using RT-qPCR and western blot, respectively. In addition, expression levels of testosterone, estradiol, luteinizing hormone and follicle-stimulating hormone, serum total cholesterol and triglyceride were assessed using the corresponding kits. Moreover, haematoxylin and eosin staining was used to detect pathological changes in ovary or liver and oil red staining was utilized to evaluate lipid accumulation. In the present study, GPR120 was downregulated in plasma, liver and ovary in the PCOS rat model. In addition, the GPR120 agonist regulated lipid metabolism in the liver and weight in the PCOS rat model. Furthermore, the GPR120 agonist decreased insulin resistance in the PCOS rat model but improved the ovarian function. It is suggested that GPR120 plays a vital role in suppressing insulin resistance, regulating ovary function and decreasing lipid accumulation in the liver, demonstrating that targeting GPR120 could be an effective method for the improvement of PCOS.

Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases

Throughout the 20th and 21st centuries, the incidence of non-communicable diseases (NCDs), also known as chronic diseases, has been increasing worldwide. Changes in dietary and physical activity patterns, along with genetic conditions, are the main factors that modulate the metabolism of individuals, leading to the development of NCDs. Obesity, diabetes, metabolic associated fatty liver disease (MAFLD), and cardiovascular diseases (CVDs) are classified in this group of chronic diseases. Therefore, understanding the underlying molecular mechanisms of these diseases leads us to develop more accurate and effective treatments to reduce or mitigate their prevalence in the population. Given the global relevance of NCDs and ongoing research progress, this article reviews the current understanding about NCDs and their related risk factors, with a focus on obesity, diabetes, MAFLD, and CVDs, summarizing the knowledge about their pathophysiology and highlighting the currently available and emerging therapeutic strategies, especially pharmacological interventions. All of these diseases play an important role in the contamination by the SARS-CoV-2 virus, as well as in the progression and severity of the symptoms of the coronavirus disease 2019 (COVID-19). Therefore, we briefly explore the relationship between NCDs and COVID-19.

Pediatric obesity-related non-alcoholic fatty liver disease: waist-to-height ratio best anthropometrical predictor

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder in pediatric obesity. Our study aims to identify a predictive anthropometrical measure for NAFLD in obese children.

METHODS

We retrospectively enrolled children and adolescents with obesity. Physical, biochemical, and ultrasound assessments were available. ROC curve tests were performed to identify the best predictor of NAFLD among waist-to-height ratio (WHR), BMI z-score, and triponderal mass index (TMI, an anthropometric index recently associated with increased adiposity in children). Subsequently, a cut-off value was identified.

RESULTS

In total, 1900 children and adolescents (1011 with NAFLD) were included. WHR (AUC 0.62, 95% CI 0.59-0.64) was the best predictor of NAFLD compared to BMI z-score (AUC 0.58, 95% CI 0.55-0.60) and TMI (AUC 0.58, 95% CI 0.55-0.61). WHR ≥ 0.53 in boys and 0.63 in girls displayed the best sensitivity and specificity for NAFLD presence. In addition, children with high WHR showed a significantly higher risk of NAFLD (boys: OR 2.43, 95% CI 1.61-3.68, p < 0.0001; girls: OR 1.92, 95% CI 1.58-2.34, p < 0.0001) and elevated ALT (OR 5.71, 95% CI 2.09-15.56, p = 0.0007; girls: OR 2.16, 95% CI 1.70-2.74, p < 0.0001) independent of covariates.

CONCLUSIONS

WHR might represent a good anthropometric tool to candidate children and adolescents to NAFLD screening. WHR cut-off differs according to sex, being lower in boys than girls.

IMPACT

Waist-to-height ratio is a better predictor of non-alcoholic fatty liver disease risk compared to other anthropometric measures in obese children and adolescents. The predictive cut-off of waist-to-height ratio differs between boys and girls, being lower in boys than girls. The use of waist-to-height ratio measurement and its cut-off in clinical practice might help clinician in identifying obese children and adolescents at risk of non-alcoholic fatty liver disease.

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.

G protein-coupled receptors: Key molecules in metabolic associated fatty liver disease development

Metabolic associated fatty liver disease (MAFLD) is a range of hepatic disorders with progression to steatohepatitis with risk of development of fibrosis, cirrhosis, and hepatocellular carcinoma. MAFLD is strongly related to metabolic disorders of active fatty acids, which seem to be selective according to their specific ligand of G protein-coupled receptors (GPRs) located in immune response cells. An approach to study the pathophysiological mechanisms of MAFLD could be through the expression of active fatty acids ligands. The expression of GPRs is associated with obesity, microbiota environment, and dietary characteristics in patients with MAFLD. More specifically, GPR41, GPR43, GPR20, and GPR120 have been associated with alteration of lipid metabolism in hepatic and intestinal cells, and consequently they have a key role in metabolic diseases. We observed that GPR120 is not expressed in nonoverweight/obese patients, regardless of the presence of MAFLD; meanwhile the expression of GPR41 is increased in patients with lean MAFLD. GPRs role in liver disease is intriguing and a field of research opportunity. More studies are necessary to define the role of active fatty acids in the development of metabolic diseases.

Transmembrane 6 superfamily member 2 167K allele improves renal function in children with obesity

BACKGROUND

The transmembrane 6 superfamily member 2 (TM6SF2) E167K polymorphism influences estimated glomerular filtration rate (eGFR) in adults without diabetes and without obesity. We aimed exploring the impact of this polymorphism on eGFR in children with obesity with and without non-alcoholic fatty liver disease (NAFLD).

METHODS

We genotyped 531 children with obesity for TM6SF2 E167K polymorphism. NAFLD was defined by ultrasound detected liver steatosis and/or ALT > 40 IU/L.

RESULTS

Patients carrying the TM6SF2 167K allele showed higher eGFR levels compared with E167 homozygous patients both among subjects with and without NAFLD. A general linear model confirmed a direct and significant association of eGFR values with TM6SF2 genotype both in patients with and without NAFLD. This association, however, was stronger in patients with NAFLD.

CONCLUSIONS

Children with obesity carrying the TM6SF2 167K allele show higher eGFR levels compared with E167 allele homozygous subjects, independently of NAFLD. A major effect of this polymorphism in the presence of NAFLD was captured.

Fructose and Uric Acid: Major Mediators of Cardiovascular Disease Risk Starting at Pediatric Age

Recently, there has been a growing interest in epidemiological and clinical studies supporting a pathogenetic role of fructose in cardio-metabolic diseases, especially in children and adolescents. In the present review, we summarize experimental data on the potential biological mechanisms linking fructose and uric acid in the development of insulin resistance, metabolic syndrome, obesity, diabetes, hypertension, non-alcoholic fatty liver disease and chronic renal disease, thereby contributing to an increase in cardiovascular risk at pediatric age.

Contribution of a genetic risk score to clinical prediction of hepatic steatosis in obese children and adolescents

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the commonest liver disease in children and adolescents in Western countries. Complex traits arise from the interplay between environmental and genetic factors in the pathogenesis of NAFLD.

AIMS

We examined the association between NAFLD and eleven single nucleotide polymorphisms (SNPs) at genetic loci potentially associated with liver damage (GCKR, MBOAT7, GPR120), oxidative stress (SOD2), lipid metabolism (PNPLA3, TM6SF2, LPIN1, ELOVL2, FADS2, MTTP) and fibrogenesis (KLF6) in a paediatric population. A genetic risk score (GRS) was performed taking into account both these SNPs and clinical risk factors.

METHODS

We recruited a cohort of 514 obese children and adolescents (mean age [±SD]: 11.2 ± 2.8 years, z-BMI 3.3 ± 0.8). NAFLD was identified by ultrasonography. Genotyping was performed by TaqMan-based RT-PCR system.

RESULTS

The overall prevalence of NAFLD was 67.5% (347 patients). Among the eleven genotyped SNPs, the genetic variants in TM6SF2 rs58542926 (OR = 4.13, p = 0.002), GCKR rs1260326 (OR = 1.53, p = 0.003), PNPLA3 rs738409 (OR = 1.58, p = 0.004) and ELOVL2 rs2236212 (OR = 1.34, p = 0.047) were significantly associated with a higher risk of NAFLD. Addition of a 11-polymorphism GRS to established clinical risk factors significantly (albeit modestly) improved the discriminatory capability of the regression model for predicting the risk of NAFLD (with SNPs C-statistic 0.81 [95%CI 0.75-0.88] vs. 0.77 [0.70-0.84] without SNPs; p = 0.047).

CONCLUSIONS

NAFLD was strongly associated with three genetic variants, TM6SF2 rs58542926, PNPLA3 rs738409 and GCKR rs1260326, and more slightly with ELOVL2 rs2236212, in obese children and adolescents. Addition of a 11-polymorphism GRS to clinical risk factors improved the predictability of 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.

Pediatric non-alcoholic fatty liver disease: current perspectives on diagnosis and management

Non-alcoholic fatty liver disease (NAFLD) represents the most common cause of chronic liver disease in childhood. To date, the “multiple-hit” hypothesis is largely recognized as an explanation of NAFLD pathogenesis and progression. Obesity and features of the metabolic syndrome have been closely linked to NAFLD development. Due to the increased prevalence of obesity worldwide, NAFLD has reached epidemic proportions over time. Given its unfavorable cardiometabolic burden (such as cardiovascular and metabolic consequences), it represents a worrying phenomenon needing a more comprehensive and successful management. Laboratory tests and classical imaging techniques play a pivotal role in NAFLD diagnosis, but novel noninvasive alternative methods to diagnose and monitor NAFLD have been investigated. Currently, lifestyle modifications remain the mainstay treatment, although its efficacy is poor because of the lack of compliance. Pediatric research is focusing on multiple alternative treatments targeting the main pathogenic factors such as insulin-resistance, dyslipidemia, gut-liver axis and microbiota, oxidative stress, and proinflammatory pathways. Results from these studies are promising but larger validation is needed. Innovative therapeutic approaches might add an important piece in the complex knowledge of pediatric NAFLD. We aimed to summarize recent insights into NAFLD diagnosis and treatment in children, with a focus on possible future perspectives in pediatric research.

Diet as moderator in the association of adiposity with inflammatory biomarkers among adolescents in the HELENA study

AIM

Our aim is to demonstrate that a healthy diet might reduce the relation between adiposity and inflammation, whereas an unhealthy diet may increase the effect of adiposity on inflammatory biomarkers.

METHODS

In 618 adolescents (13-17 years) of the European HELENA study, data were available on body composition, a set of inflammation markers, and food intake determined by a self-administered computerized 24-h recall. A 9-point Mediterranean diet score and an antioxidant-rich diet score were used as dietary parameters and tested as moderator. Total body fat was represented by the sum of six skinfold thicknesses and central adiposity by waist circumference. A set of inflammation-related biomarkers was used as outcome: a pro/anti-inflammatory interleukins ratio, TGFβ-1, C-reactive protein, TNF-α, 3 cell adhesion molecules, and 3 types of immune cells; gamma-glutamyltransferase (GGT) and homocysteine were used as cardiovascular disease risk biomarkers, and alanine transaminase (ALT) as liver dysfunction biomarker. Multiple linear regression analyses tested moderation by diet in the adiposity-inflammation association and were adjusted for age, sex, country, puberty, socioeconomic status.

RESULTS

Both the Mediterranean and antioxidant-rich diet, and overall and central adiposity, were important in the moderation. Diet was a significant protective moderator in the effect of adiposity on the pro/anti-inflammatory interleukins ratio, TGFβ-1, GGT, and ALT.

CONCLUSION

In conclusion, in some cases, a diet rich in antioxidants and essential nutrients may attenuate the concentration of inflammatory biomarkers caused by adiposity, whereas a poor diet appears to contribute to the onset of early oxidative stress signs.

Diet as a moderator in the association of sedentary behaviors with inflammatory biomarkers among adolescents in the HELENA study

AIM

To assess if a healthy diet might attenuate the positive sedentary-inflammation relation, whereas an unhealthy diet may increase the effect of sedentary behaviors on inflammatory biomarkers.

METHODS

In 618 adolescents (13-17 years) of the European HELENA study, data were available on body composition, a set of inflammation markers, and food intake assessed by a self-administered computerized 24 h dietary recall for 2 days. A 9-point Mediterranean diet score and an antioxidant-rich diet z-score were used as dietary indices and tested as moderators. A set of low-grade inflammatory characteristics was used as outcome: several cytokines in an inflammatory ratio (IL-6, IL-10, TNF-α, TGFβ-1), C-reactive protein, three cell-adhesion molecules (sVCAM-1, sICAM-1, sE-selectin), three cardiovascular risk markers (GGT, ALT, homocysteine) and three immune cell types (white blood cells, lymphocytes, CD3). Sedentary behaviors were self-reported and analyzed as total screen time. Multiple linear regression analyses tested moderation by diet in the sedentary behaviors-inflammation association adjusted for age, sex, country, adiposity (sum of six skinfolds), parental education, and socio-economic status.

RESULTS

Both diet scores, Mediterranean and antioxidant-rich diet, were significant protective moderators in the effect of sedentary behaviors on alanine-transaminase enzyme (P = 0.014; P = 0.027), and on the pro/anti-inflammatory cytokine ratio (P = 0.001; P = 0.004), but not on other inflammatory parameters.

CONCLUSION

A higher adherence to the Mediterranean diet or an antioxidant-rich diet may attenuate the onset of oxidative stress signs associated by sedentary behaviors, whereas a poor diet seems to increase inflammation.

Pediatric NAFLD: an overview and recent developments in diagnostics and treatment

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children and adults in industrialized countries. Besides liver-related morbidity, NAFLD is also associated with an increased risk of cardiovascular disease, type 2 diabetes and mortality at adult age. However, despite the high prevalence and serious complications, diagnosing and staging of disease remains complicated due to a lack of accurate screening tools and non-invasive methods to detect fibrosis. Areas covered: Recent insights in epidemiology, pathogenesis, diagnostic evaluation and treatment options in pediatric NAFLD are being reviewed, with a particular focus on new developments in diagnostic tools. Expert opinion: Due to their long life span, children with NAFLD are particularly at risk of complications in their lifetime. Therefore, an effective screening strategy for children to identify those with NAFLD at risk of complications is urgently needed. This is further underscored by new pharmacological therapies that are expected to become available in the next 5 years. Momentarily no accurate non-invasive method for diagnosing pediatric NAFLD is available. New promising biomarkers and imaging tools could hopefully provide better screening tools and could contribute to the development of a successful management plan to identify children with NAFLD.

Association between PNPLA3 rs738409 polymorphism and nonalcoholic fatty liver disease (NAFLD) susceptibility and severity: A meta-analysis

OBJECTIVE

This meta-analysis is to investigate the relationship between the patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 polymorphism and the susceptibility and severity of nonalcoholic fatty liver disease (NAFLD).

METHODS

Chinese Journal Full-text Database, Wanfang Database, VIP Database, and PubMed Database were subjected to case-control study retrieving, from January 2008 to December 2014. Following key words were used: fatty liver, PNPLA3, and rs738409 gene or variants or polymorphism or alleles. Meta-analysis was performed based on the retrieved articles.

RESULTS

In total 65 studies were first retrieved according to the key words, and finally 21 studies with 14,266 subjects were included. Meta-analysis showed that PNPLA3 rs738409 polymorphism exerted strong influence not only on fatty liver but also on the histological injury. PNPLA3 rs738409 [G] allele was a risk factor for NAFLD (GG vs CC, OR = 4.01, 95% CI 2.93-5.49; GC vs CC, OR = 1.88, 95% CI 1.58-2.24). PNPLA3 gene variant was significantly associated with the increased serum alanine aminotransferase (ALT) levels (GG vs CC, standardized mean difference  = 0.47, 95% CI 0.14-0.81). In addition, nonalcoholic steatohepatitis (NASH) was more frequently observed in G allele carriers (GG vs CC, OR = 3.24, 95% CI 2.79-3.76; GC vs CC, OR = 2.14, 95% CI 1.43-3.19).

CONCLUSION

PNPLA3 rs738409 polymorphism is not only a factor significantly associated with the susceptibility of NAFLD, but also related to the susceptibility of aggressive diseases.

Association between 14 bp insertion/deletion HLA-G functional polymorphism and insulin resistance in a cohort of Italian children with obesity

BACKGROUND

The non-classical HLA-class I molecule-g (HLA-G) gene shows a deletion/insertion (del/ins) polymorphism of a 14-base-pair sequence (14 bp) in the exon 8 at the 3' untranslated region. The presence of the 14 bp insertion allele has been associated to lower soluble HLA-G protein production, a protein with anti-inflammatory activities. So far, no studies have investigated the relationship between HLA-G 14 bp del/ins polymorphism and metabolic features of obese children and adolescents. We aimed to assess if the HLA-G ins/del polymorphism, and in particular the HLA-G ins/ins genotype determining lower sHLA-G production, is associated to insulin resistance (evaluated by homeostasis model assessment [HOMA]) in a population of obese children.

METHODS

We enrolled 574 obese children and adolescents. Anthropometric and laboratory data were collected. The white blood cell (WBC) count was evaluated as surrogate marker of inflammation. C-reactive protein (CRP) was available in 48 patients. HOMA was calculated. Patients were genotyped for the HLA-G del/ins polymorphism.

RESULTS

Subjects carrying the HLA-G ins/ins genotype, presented with higher HOMA, WBC and CRP values, compared to del/ins and del/del genotypes (P ≤ 0.0009, ≤0.02 and ≤0.0001, respectively). Comparison of the regression line slopes, performed for HOMA and WBC on the basis of HLA-G genotypes, showed that subjects carrying the HLA-G ins/ins genotype presented with a stronger correlation between HOMA and WBC, compared to the other genotypes (Model r² 3.13%, P ≤ 0.006).

CONCLUSIONS

We showed a strong association between HLA-G 14 bp ins/ins genotype and HOMA in obese children and adolescents. This association could be hypothetically modulated by subclinical inflammation.

Current status of imaging in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common diffuse liver disease, with a worldwide prevalence of 20% to 46%. NAFLD can be subdivided into simple steatosis and nonalcoholic steatohepatitis. Most cases of simple steatosis are non-progressive, whereas nonalcoholic steatohepatitis may result in chronic liver injury and progressive fibrosis in a significant minority. Effective risk stratification and management of NAFLD requires evaluation of hepatic parenchymal fat, fibrosis, and inflammation. Liver biopsy remains the current gold standard; however, non-invasive imaging methods are rapidly evolving and may replace biopsy in some circumstances. These methods include well-established techniques, such as conventional ultrasonography, computed tomography, and magnetic resonance imaging and newer imaging technologies, such as ultrasound elastography, quantitative ultrasound techniques, magnetic resonance elastography, and magnetic resonance-based fat quantitation techniques. The aim of this article is to review the current status of imaging methods for NAFLD risk stratification and management, including their diagnostic accuracy, limitations, and practical applicability.

The Membrane-bound O-Acyltransferase7 rs641738 Variant in Pediatric Nonalcoholic Fatty Liver Disease

BACKGROUND

The rs641738 polymorphism in the membrane-bound O-acyltransferase domain containing protein 7 (MBOAT7) gene has been associated with increased risk of nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

To investigate the association between the MBOAT7 rs641738 polymorphism and both hepatic steatosis and biochemical markers of liver damage and to evaluate the potential additive effect of this variant and the I148M patatin-like phospholipase domain-containing 3 (PNPLA3) and the rs58542926 transmembrane 6 superfamily member 2 (TM6SF2) polymorphisms.

METHODS

One thousand and 2 obese children were genotyped for MBOAT7, PNPLA3, and TM6SF2 polymorphisms and underwent anthropometrical, ultrasonographic, and biochemical evaluation. Indirect measurement of liver fibrosis (Pediatric NAFLD Fibrosis Index [PNFI]) and a genetic risk score from these polymorphisms were calculated.

RESULTS

Carriers of the MBOAT7 T allele showed both higher alanine transaminase (ALT) (P = 0.004) and PNFI values (P = 0.04) than noncarriers. These findings were confirmed also for the carriers of the MBOAT7 T allele polymorphism with hepatic steatosis compared with noncarriers. A higher genetic risk score was associated with higher ALT (P = 0.011) and with an odds ratio (OR) to show elevated ALT of 3.4 (95% CI 1.3-5.5, P = 0.003). Patients belonging to genetic risk score 3 group had an OR to present steatosis of 2.6 (95% CI 1.43-4.83, P = 0.0018) compared with those belonging to lower genetic risk score group.

CONCLUSIONS

We first demonstrated in childhood obesity the role of the MBOAT7 rs641738 variant on serum ALT and the combined effect of the MBOAT7, PNPLA3, and TM6SF2 variants on NAFLD risk. We also provided the first pediatric association of the MBOAT7 polymorphism with indirect markers of liver fibrosis.

Lingguizhugan Decoction Protects against High-Fat-Diet-Induced Nonalcoholic Fatty Liver Disease by Alleviating Oxidative Stress and Activating Cholesterol Secretion

Background

Nonalcoholic fatty liver disease (NAFLD) has become a leading cause of liver transplantation. Lingguizhugan decoction (LGZG), a classical Chinese herbal formula, has beneficial effects on NAFLD animal models. Our study examined the impact of LGZG on hepatic global transcriptome of high-fat-diet-induced NAFLD rats.

Methods

Three groups of Wistar rats were included: normal, NAFLD model, and LGZG-treated NAFLD groups. Four weeks for the treatment, liver tissues were harvested for RNA sequencing. Differentially expressed genes (DEGs) and enriched pathways were detected on hepatic global transcriptome profile. Real-time PCR validated the regulatory patterns of LGZG on NAFLD rats.

Results

DEGs between the NAFLD model and normal groups indicated the elevated peroxisome proliferator-activated receptor (PPAR) and hedgehog signaling pathways in NAFLD rats. In bile secretion pathway, genes involved in cholesterol secretion were activated by LGZG treatment. Increased expression of antioxidant OSIGN1 and decreased expression of genes (AHR, IRF2BP2, and RASGEF1B) that induce oxidative stress and inflammation were observed in NAFLD rats treated with LGZG. The regulatory patterns of LGZG treatment on these oxidative stress-related genes were confirmed by real-time PCR.

Conclusion

Our study revealed a “two-hits-targeting” mechanism of LGZG in the treatment for NAFLD: alleviating oxidative stress and activating cholesterol secretion.

Polymorphisms in FFAR4 (GPR120) Gene Modulate Insulin Levels and Sensitivity after Fish Oil Supplementation

The objective was to test whether FFAR4 single nucleotide polymorphisms (SNPs) are associated with glycemic control-related traits in humans following fish oil supplementation. A total of 210 participants were given 3 g/day of omega-3 (n-3) fatty acids (FA) (1.9–2.2 g of eicosapentaenoic acid (EPA) and 1.1 g of docosahexaenoic acid (DHA)) during six weeks. Biochemical parameters were taken before and after the supplementation. Using the HapMap database and the tagger procedure in Haploview, 12 tagging SNPs in FFAR4 were selected and then genotyped using TaqMan technology. Transcript expression levels were measured for 30 participants in peripheral mononuclear blood cells. DNA methylation levels were measured for 35 participants in leukocytes. In silico analyses were also performed. Four gene–diet interactions on fasting insulin levels and homeostatic model assessment of insulin resistance (HOMA-IR) index values were found. rs17108973 explained a significant proportion of the variance of insulin levels (3.0%) and HOMA-IR (2.03%) index values. Splice site prediction was different depending on the allele for rs11187527. rs17108973 and rs17484310 had different affinity for transcription factors depending on the allele. n-3 FAs effectively improve insulin-related traits for major allele homozygotes of four FFAR4 SNPs as opposed to carriers of the minor alleles.

The Association between Non-Alcoholic Fatty Liver Disease and Cardiovascular Risk in Children

The rising prevalence of childhood obesity in the past decades has made Non-Alcoholic Fatty Liver Disease (NAFLD) the most common cause of pediatric chronic liver disease worldwide. Currently, a growing body of evidence links NAFLD with cardiovascular disease (CVD) even at an early age. Data on the pediatric population have shown that NAFLD could represent an independent risk factor not only for cardiovascular events but also for early subclinical abnormalities in myocardial structure and function. Briefly, we review the current knowledge regarding the relationship between pediatric NAFLD and cardiovascular risk in an attempt to clarify our understanding of NAFLD as a possible cardiovascular risk factor in childhood.

Pediatric Non-alcoholic Fatty Liver Disease

Childhood obesity has reached epidemic proportions, and by 2012, more than one third of American children were overweight or obese. As a result, increasingly, children are developing complications of obesity including liver disease. In fact, non-alcoholic fatty liver disease is the most common form of chronic liver disease seen in children today. Recently, there has been a burgeoning literature examining the pathogenesis, genetic markers, and role of the microbiome in this disease. On the clinical front, new modalities of diagnosing hepatic steatosis and hepatic fibrosis are being developed to provide non-invasive methods of surveillance in children. Lastly, the mainstay of treatment of pediatric non-alcoholic fatty liver disease (NAFLD) has been largely through lifestyle interventions, namely, dieting and exercise. Currently, there are a number of clinical trials examining novel lifestyle and drug therapies for NAFLD that are registered with the US National Institutes of Health ClinicalTrials.gov website.

Physical activity and sedentary behavior can modulate the effect of the PNPLA3 variant on childhood NAFLD: a case-control study in a Chinese population

Background

The patatin like phospholipase containing domain 3 gene (PNPLA3) rs738409 C > G polymorphism, one of the most important gene polymorphisms involved in hepatic steatosis, has been reported to interact with different nutrients and dietary patterns on Non-Alcoholic Fatty Liver Disease (NAFLD), but no studies have focused on its interaction with physical activity or sedentary behavior. Therefore, this study aims at determining whether physical activity or sedentary behavior could modulate the effect of the PNPLA3 variant on childhood NAFLD.

Methods

A case-control study was conducted including 1027 Chinese children aged 7–18 years old (162 children with NAFLD and 865 children without). The anthropometric measurements, liver ultrasound examination, questionnaires and genotyping of the PNPLA3 rs738409 polymorphism were performed.

Results

Stratified analyses showed that the proportions of NAFLD increased with the G-allele number only in children who did not have enough physical activity (physical activity < 1 h/d) (OR 3.05, 95% CI 1.82–5.12, P < 0.001), and in children with a sedentary lifestyle (sedentary behavior ≥ 2 h/d) (OR 3.41, 95% CI 1.88–6.18, P < 0.001). Significant interactions on childhood NAFLD were found between the G-allele number in the PNPLA3 rs738409 polymorphism and behaviors, including physical activity (P = 0.001), sedentary behavior (P = 0.010) and the combination of physical activity and sedentary behavior (P < 0.001).

Conclusion

This is the first study to report the interaction between the PNPLA3 rs738409 polymorphism and physical activity or sedentary behavior on NAFLD, providing new clues on the function of the PNPLA3 gene, which will also be useful for future risk assessment and personalized treatment of NAFLD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0352-9) contains supplementary material, which is available to authorized users.

Pediatric liver diseases: current challenges and future perspectives

Chronic liver diseases in children represent a rising problem with significant effects on public health. In fact, several pediatric liver diseases are precursors of adult chronic hepatopathies, cirrhosis and hepatocellular carcinoma. The prevalence of liver diseases in children is unknown. In the USA, every year, 15,000 children are hospitalized for liver diseases, but these disorders continue to be under-recognized or diagnosed late. The main reason is due to the frequent absence of symptoms in the vast majority of liver diseases, especially in the early stages. In the last few decades several advances have been made in understanding the pathogenesis of liver diseases, permitting the discovery of new therapeutic targets to treat liver diseases, thus improving the natural history of these disorders. In this article we discuss the most recent advances in the understanding of the pathogenesis, diagnosis and treatment of the most frequent pediatric liver diseases.

Pediatric non-alcoholic fatty liver disease: Recent solutions, unresolved issues, and future research directions

Non-alcoholic fatty liver disease (NAFLD) in children is becoming a major health concern. A “multiple-hit” pathogenetic model has been suggested to explain the progressive liver damage that occurs among children with NAFLD. In addition to the accumulation of fat in the liver, insulin resistance (IR) and oxidative stress due to genetic/epigenetic background, unfavorable lifestyles, gut microbiota and gut-liver axis dysfunction, and perturbations of trace element homeostasis have been shown to be critical for disease progression and the development of more severe inflammatory and fibrotic stages [non-alcoholic steatohepatitis (NASH)]. Simple clinical and laboratory parameters, such as age, history, anthropometrical data (BMI and waist circumference percentiles), blood pressure, surrogate clinical markers of IR (acanthosis nigricans), abdominal ultrasounds, and serum transaminases, lipids and glucose/insulin profiles, allow a clinician to identify children with obesity and obesity-related conditions, including NAFLD and cardiovascular and metabolic risks. A liver biopsy (the “imperfect” gold standard) is required for a definitive NAFLD/NASH diagnosis, particularly to exclude other treatable conditions or when advanced liver disease is expected on clinical and laboratory grounds and preferably prior to any controlled trial of pharmacological/surgical treatments. However, a biopsy clearly cannot represent a screening procedure. Advancements in diagnostic serum and imaging tools, especially for the non-invasive differentiation between NAFLD and NASH, have shown promising results, e.g., magnetic resonance elastography. Weight loss and physical activity should be the first option of intervention. Effective pharmacological treatments are still under development; however, drugs targeting IR, oxidative stress, proinflammatory pathways, dyslipidemia, gut microbiota and gut liver axis dysfunction are an option for patients who are unable to comply with the recommended lifestyle changes. When morbid obesity prevails, bariatric surgery should be considered.

Reduced lysosomal acid lipase activity - A potential role in the pathogenesis of non alcoholic fatty liver disease in pediatric patients

BACKGROUND

Within the spectrum of nonalcoholic fatty liver disease (NAFLD), recent evidence suggests that adult patients with nonalcoholic steatohepatitis (NASH) have significantly lower blood lysosomal acid lipase (LAL) activity than those with steatosis. This has not been studied in pediatric patients with NAFLD.

AIM

Investigate blood LAL activity in pediatric patients with NAFLD and assess its correlation with histological severity.

METHODS

We collected data on consecutive children with biopsy-proven NAFLD including demographics, anthropometrics, and routine laboratory tests. The histological features were graded according to the NAFLD activity scoring proposed by Kleiner et al. Blood LAL activity was measured prospectively using Lalistat 2.

RESULTS

A total of 168 children were included for analysis. Mean age was 12.6±8.5 years, 60.1% were males and 52.4% had NASH. Children with significant fibrosis (stage 2-3, n=64) had a significantly lower LAL activity compared to those with mild fibrosis (stage 0-1, n=104). There was no significant difference in LAL activity between children with NASH compared to those without NASH.

CONCLUSION

Reduced blood LAL activity correlates with severity of liver fibrosis in children with NAFLD indicating a potential role of reduced LAL activity in the pathogenesis of NAFLD-induced fibrosis.

Fatty liver disease and obesity in youth

PURPOSE OF REVIEW

The purpose of this short review is to summarize recent developments in the understanding of pediatric nonalcoholic fatty liver disease (NAFLD), focusing on novel findings in pathogenetic mechanisms and the therapeutic armamentarium.

RECENT FINDINGS

As a result of the increasing prevalence of pediatric obesity, NAFLD has rapidly become the most common cause of chronic hepatopathies in children. Lifestyle modification and diet remain the mainstay of treatment of pediatric obesity and NAFLD, but with disappointing results because of the difficulty in obtaining sustained long-term results. Considering the risk of progression of liver damage to cirrhosis and end-stage liver disease, in the last decades scientific research in this field has been directed to the identification of pathogenetic mechanisms and possible therapeutic strategies for NAFLD.

SUMMARY

We describe the therapeutic options for the management of pediatric NAFLD, focusing on emerging alternative strategies, including surgical approaches and new drugs directed against novel potential molecular targets.

Free-fatty acid receptor-4 (GPR120): Cellular and molecular function and its role in metabolic disorders

Over the last decade, a subfamily of G protein-coupled receptors that are agonized by endogenous and dietary free-fatty acids (FFA) has been discovered. These free-fatty acid receptors include FFA2 and FFA3, which are agonized by short-chained FFA, as well as FFA1 and FFA4, which are agonized by medium-to-long chained FFA. Ligands for FFA1 and FFA4 comprise the family of long chain polyunsaturated omega-3 fatty acids including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), suggesting that many of the long-known beneficial effects of these fats may be receptor mediated. In this regard, FFA4 has gathered considerable interest due to its role in ameliorating inflammation, promoting insulin sensitization, and regulating energy metabolism in response to FFA ligands. The goal of this review is to summarize the body of evidence in regard to FFA4 signal transduction, its mechanisms of regulation, and its functional role in a variety of tissues. In addition, recent endeavors toward discovery of small molecules that modulate FFA4 activity are also presented.

TM6SF2 E167K Variant, a Novel Genetic Susceptibility Variant, Contributing to Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of liver dysfunction worldwide, and its prevalence is highly associated with genetic susceptibility. The transmembrane 6 superfamily member 2 (TM6SF2) E167K variant represents a general genetic determinant of hepatic triglyceride content and lobular inflammation, and its presence appears to be directly involved in the pathogenesis and development of NAFLD. Although this variant appears to be a novel powerful modifier in the development of NAFLD, whether it is associated with an increased risk of NAFLD-related liver fibrosis and hepatocellular carcinoma (HCC) remains to be determined. The aim of this review is to describe the functions of the TM6SF2 E167K variant and its association with NAFLD, with particular emphasis on the underlying mechanisms of its role in the development and progression of NAFLD. Additionally, the links between the TM6SF2 E167K variant and NAFLD-related liver fibrosis and HCC will be discussed.