Update on nonalcoholic fatty liver disease: genes involved in nonalcoholic fatty liver disease and associated inflammation

NAFLD-Related HCC: Focus on the Latest Relevant Preclinical Models

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and one of the deadliest cancers worldwide. Despite extensive research, the biological mechanisms underlying HCC's development and progression remain only partially understood. Chronic overeating and/or sedentary-lifestyle-associated obesity, which promote Non-Alcoholic Fatty Liver Disease (NAFLD), have recently emerged as worrying risk factors for HCC. NAFLD is characterized by excessive hepatocellular lipid accumulation (steatosis) and affects one quarter of the world's population. Steatosis progresses in the more severe inflammatory form, Non-Alcoholic Steatohepatitis (NASH), potentially leading to HCC. The incidence of NASH is expected to increase by up to 56% over the next 10 years. Better diagnoses and the establishment of effective treatments for NAFLD and HCC will require improvements in our understanding of the fundamental mechanisms of the disease's development. This review describes the pathogenesis of NAFLD and the mechanisms underlying the transition from NAFL/NASH to HCC. We also discuss a selection of appropriate preclinical models of NAFLD for research, from cellular models such as liver-on-a-chip models to in vivo models, focusing particularly on mouse models of dietary NAFLD-HCC.

Aberrant FGFR4 signaling worsens nonalcoholic steatohepatitis in FGF21KO mice

Background: Nonalcoholic steatohepatitis (NASH) is the most severe form of non-alcoholic fatty liver disease (NAFLD) and a potential precursor of hepatocellular carcinoma (HCC). In our previous studies, we found that endocrine fibroblast growth factor 21 (FGF21) played a key role in preventing the development of NASH, however, the FGF15/19 mediated-FGFR4 signaling worsened NASH and even contributed to the NASH-HCC transition. The aim of this study is to determine whether FGF15/FGFR4 signaling could alleviate or aggravate NASH in the FGF21KO mice.

Methods: NASH models were established in FGF21KO mice fed with high fat methionine-choline deficient (HFMCD) diet to investigate FGF15/FGFR4 signaling during early stage NASH and advanced stage NASH. Human hepatocytes, HepG2 and Hep3B cells, were cultured with human enterocytes Caco-2 cells to mimic gut-liver circulation to investigate the potential mechanism of NASH development.

Results: Significant increase of FGF15 production was found in the liver of the NASH-FGF21KO mice, however the increased FGF15 protein was unable to alleviate hepatic lipid accumulation. In contrast, up-regulated FGF15/19/FGFR4 signaling was found in the FGF21KO mice with increased NASH severity, as evident by hepatocyte injury/repair, fibrosis and potential malignant events. In in vitro studies, blockage of FGFR4 by BLU9931 treatment attenuated the lipid accumulation, up-regulated cyclin D1, and epithelial-mesenchymal transition (EMT) in the hepatocytes.

Conclusion: The increased FGF15 in NASH-FGF21KO mice could not substitute for FGF21 to compensate its lipid metabolic benefits thereby to prevent NASH development. Up-regulated FGFR4 signaling in NASH-FGF21KO mice coupled to proliferation and EMT events which were widely accepted to be associated with carcinogenic transformation.

Assessment of mitochondrial function in metabolic dysfunction-associated fatty liver disease using obese mouse models

Metabolic dysfunction-associated fatty liver disease (MAFLD) is characterized by deregulated hepatic lipid metabolism; however, the association between MAFLD development and mitochondrial dysfunction has yet to be confirmed. Herein, we employed high-resolution respirometry, blue native polyacrylamide gel electrophoresis-based in-gel activity measurement and immunoblot analysis to assess mitochondrial function in obesity-induced mouse models with varying degrees of MAFLD. Results showed a slight but significant decrease in hepatic mitochondrial respiration in some MAFLD mice compared to mice fed a standard diet. However, the activities and levels of mitochondrial oxidative phosphorylation complexes remained unchanged during obesity-induced MAFLD progression. These results suggest that mitochondrial function, particularly oxidative phosphorylation, was mildly affected during obesity-induced MAFLD development. Moreover, transcriptome profiling of mouse and human liver tissues with varying degrees of MAFLD revealed that the decreased activation of mitochondria-related pathways was only associated with MAFLD of a high histological grade, whereas the major regulators of mitochondrial biogenesis were not altered in mice or humans during MAFLD development. Collectively, our results suggest that impaired hepatic mitochondrial function is not closely associated with obesity-induced MAFLD. Therefore, therapeutic strategies targeting mitochondria for the treatment of MAFLD should be reconsidered.

Antioxidant Versus Pro-Apoptotic Effects of Mushroom-Enriched Diets on Mitochondria in Liver Disease

Mitochondria play a central role in non-alcoholic fatty liver disease (NAFLD) progression and in the control of cell death signalling during the progression to hepatocellular carcinoma (HCC). Associated with the metabolic syndrome, NAFLD is mostly driven by insulin-resistant white adipose tissue lipolysis that results in an increased hepatic fatty acid influx and the ectopic accumulation of fat in the liver. Upregulation of beta-oxidation as one compensatory mechanism leads to an increase in mitochondrial tricarboxylic acid cycle flux and ATP generation. The progression of NAFLD is associated with alterations in the mitochondrial molecular composition and respiratory capacity, which increases their vulnerability to different stressors, including calcium and pro-inflammatory molecules, which result in an increased generation of reactive oxygen species (ROS) that, altogether, may ultimately lead to mitochondrial dysfunction. This may activate further pro-inflammatory pathways involved in the progression from steatosis to steatohepatitis (NASH). Mushroom-enriched diets, or the administration of their isolated bioactive compounds, have been shown to display beneficial effects on insulin resistance, hepatic steatosis, oxidative stress, and inflammation by regulating nutrient uptake and lipid metabolism as well as modulating the antioxidant activity of the cell. In addition, the gut microbiota has also been described to be modulated by mushroom bioactive molecules, with implications in reducing liver inflammation during NAFLD progression. Dietary mushroom extracts have been reported to have anti-tumorigenic properties and to induce cell-death via the mitochondrial apoptosis pathway. This calls for particular attention to the potential therapeutic properties of these natural compounds which may push the development of novel pharmacological options to treat NASH and HCC. We here review the diverse effects of mushroom-enriched diets in liver disease, emphasizing those effects that are dependent on mitochondria.

Insights into the Role and Interdependence of Oxidative Stress and Inflammation in Liver Diseases

The crucial roles of oxidative stress and inflammation in the development of hepatic diseases have been unraveled and emphasized for decades. From steatosis to fibrosis, cirrhosis and liver cancer, hepatic oxidative stress, and inflammation are sustained and participated in this pathological progressive process. Notably, increasing evidences showed that oxidative stress and inflammation are tightly related, which are regarded as essential partners that present simultaneously and interact with each other in various pathological conditions, creating a vicious cycle to aggravate the hepatic diseases. Clarifying the interaction of oxidative stress and inflammation is of great importance to provide new directions and targets for developing therapeutic intervention. Herein, this review is concerned with the regulation and interdependence of oxidative stress and inflammation in a variety of liver diseases. In addition to classical mediators and signaling, particular emphasis is placed upon immune suppression, a potential linkage of oxidative stress and inflammation, to provide new inspiration for the treatment of liver diseases. Furthermore, since antioxidation and anti-inflammation have been extensively attempted as the strategies for treatment of liver diseases, the application of herbal medicines and their derived compounds that protect liver from injury via regulating oxidative stress and inflammation collectively were reviewed and discussed.

Association of patatin-like phospholipase domain-containing protein 3 gene polymorphisms with susceptibility of nonalcoholic fatty liver disease in a Han Chinese population

Gene polymorphisms had been found to be associated with increased risk of nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to assess the association between rs2896019 and rs3810622 in PNPLA3 with the susceptibility to NAFLD in Han Chinese population.A total of 384 NAFLD patients and 384 controls were enrolled in the study. Blood samples collected from each subject were used for biochemical index analysis and DNA extraction. Genotyping analyses of PNPLA3 rs2896019 and rs3810622 were performed by real-time PCR methods.Results showed that patients with genotype GG of rs2896019 had a higher incidence of NAFLD than patients with genotypes GT and TT (62.4% vs 52.0% and 43.3%, respectively, P = 0.002), and a higher risk of moderate to severe NAFLD than patients with genotypes GT and TT (60.3% vs 46.2% and 40.2%, respectively, P = 0.03). Furthermore, patients with genotype GG of rs2896019 had higher levels of low-density lipoprotein (LDL, P < 0.001), ALT (P = 0.003), and AST (P = 0.002). Patients with genotype TT of rs3810622 had a higher incidence of NAFLD than patients with genotypes CT and CC (56.7% vs 48.4% and 41.5%, respectively, P = 0.013). Likewise, patients with genotype TT of rs3810622 had higher levels of ALT (P = 0.021) and blood glucose (GLU) (P = 0.034). Haplotype association analysis showed that GT haplotype conferred a statistically significant increased risk for NAFLD (OR = 1.49; 95% CI = 1.20-1.84, P < 0.01).These results suggest that PNPLA3 rs2896019 and rs3810622 polymorphisms significantly contribute to increased NAFLD risk in Han Chinese population.

Non-alcoholic fatty liver disease and dyslipidemia: An update

Non-alcoholic fatty liver (NAFLD) is the most common liver disease worldwide, progressing from simple steatosis to necroinflammation and fibrosis (leading to non-alcoholic steatohepatitis, NASH), and in some cases to cirrhosis and hepatocellular carcinoma. Inflammation, oxidative stress and insulin resistance are involved in NAFLD development and progression. NAFLD has been associated with several cardiovascular (CV) risk factors including obesity, dyslipidemia, hyperglycemia, hypertension and smoking. NAFLD is also characterized by atherogenic dyslipidemia, postprandial lipemia and high-density lipoprotein (HDL) dysfunction. Most importantly, NAFLD patients have an increased risk for both liver and CV disease (CVD) morbidity and mortality. In this narrative review, the associations between NAFLD, dyslipidemia and vascular disease in NAFLD patients are discussed. NAFLD treatment is also reviewed with a focus on lipid-lowering drugs. Finally, future perspectives in terms of both NAFLD diagnostic biomarkers and therapeutic targets are considered.

A Guide to Non-Alcoholic Fatty Liver Disease in Childhood and Adolescence

Non-Alcoholic Fatty Liver Disease (NAFLD) is now the most prevalent form of chronic liver disease, affecting 10%–20% of the general paediatric population. Within the next 10 years it is expected to become the leading cause of liver pathology, liver failure and indication for liver transplantation in childhood and adolescence in the Western world. While our understanding of the pathophysiological mechanisms underlying this disease remains limited, it is thought to be the hepatic manifestation of more widespread metabolic dysfunction and is strongly associated with a number of metabolic risk factors, including insulin resistance, dyslipidaemia, cardiovascular disease and, most significantly, obesity. Despite this, ”paediatric” NAFLD remains under-studied, under-recognised and, potentially, undermanaged. This article will explore and evaluate our current understanding of NAFLD in childhood and adolescence and how it differs from adult NAFLD, in terms of its epidemiology, pathophysiology, natural history, diagnosis and clinical management. Given the current absence of definitive radiological and histopathological diagnostic tests, maintenance of a high clinical suspicion by all members of the multidisciplinary team in primary and specialist care settings remains the most potent of diagnostic tools, enabling early diagnosis and appropriate therapeutic intervention.

Mechanistic link between nonalcoholic fatty liver disease and cardiometabolic disorders

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition characterized by fat accumulation combined with low-grade inflammation in the liver. A large body of clinical and experimental data shows that increased flux of free fatty acids from increased visceral adipose tissue can lead to NAFLD related with insulin resistance. Thus, individuals with obesity, insulin resistance, and dyslipidemia are at the greatest risk of developing NAFLD. Conversely, NAFLD is one of the phenotypes of insulin resistance or metabolic syndrome. Many researchers have discovered a close association between NAFLD and insulin resistance, and focused on the role of NAFLD in the development of type 2 diabetes. Further, substantial evidence has suggested the association between NAFLD and cardiovascular disease (CVD). In the current review, we provide a plausible mechanistic link between NAFLD and CVD and the potential of the former as a therapeutic target based on pathophysiology. We also discuss in detail about the role of insulin resistance, oxidative stress, low-grade inflammation, abnormal lipid metabolism, gut microbiota, changes of biomarkers, and genetic predisposition in the pathological linking between NAFLD and cardiometabolic disorders.

Gallstone disease does not predict liver histology in nonalcoholic fatty liver disease

Background/Aims

We sought to examine whether the presence of gallstone disease (GD) in patients with biopsy-proven nonalcoholic fatty liver disease (NAFLD) is associated with liver fibrosis and histological nonalcoholic steatohepatitis (NASH) score.

Methods

We included 441 Turkish patients with biopsy-proven NAFLD. GD was diagnosed in the presence of sonographic evidence of gallstones, echogenic material within the gallbladder with constant shadowing and little or no visualization of the gallbladder or absence of gallbladder at ultrasonography, coupled with a history of cholecystectomy.

Results

Fifty-four patients (12.2%) had GD (GD+ subjects). Compared with the GD- subjects, GD+ patients were older, had a higher body mass index and were more likely to be female and have metabolic syndrome. However, GD+ patients did not have a higher risk of advanced fibrosis or definite NASH on histology. After adjustment for potential confounding variables, the prevalence of GD in NAFLD patients was not associated with significant fibrosis (≥2) (odds ratio [OR], 1.06; 95% confidence interval [CI], 0.53 to 2.21; p=0.68) or definite NASH (OR, 1.03; 95% CI, 0.495 to 2.12; p=0.84).

Conclusions

The presence of GD is not independently associated with advanced fibrosis and definite NASH in adult Turkish patients with biopsy-proven NAFLD.

Glucokinase regulatory protein gene polymorphism affects liver fibrosis in non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Variant in glucokinase regulatory protein (GCKR), associated with lipid and glucose traits, has been suggested to affect fatty liver infiltration. We aimed to assess whether GCKR rs780094 C→T SNP influences the expression of steatosis, lobular inflammation and fibrosis in NAFLD patients, after correction for PNPLA3 genotype.

METHODS

In 366 consecutive NAFLD patients (197 from Sicily, and 169 from center/northern Italy), we assessed anthropometric, biochemical and metabolic features; liver biopsy was scored according to Kleiner. PNPLA3 rs738409 C>G and GCKR rs780094 C>T single nucleotide polymorphisms were also assessed.

RESULTS

At multivariate logistic regression analysis in the entire NAFLD cohort, the presence of significant liver fibrosis (>F1) was independently linked to high HOMA (OR 1.12, 95% CI 1.01-1.23, p = 0.02), NAFLD activity score ≥ 5 (OR 4.09, 95% CI 2.45-6.81, p<0.001), and GCKR C>T SNP (OR 2.06, 95% CI 1.43-2.98, p<0.001). Similar results were observed considering separately the two different NAFLD cohorts. GCKR C>T SNP was also associated with higher serum triglycerides (ANOVA, p = 0.02) in the entire cohort.

CONCLUSIONS

In patients with NAFLD, GCKR rs780094 C>T is associated with the severity of liver fibrosis and with higher serum triglyceride levels.

Adherence to the Mediterranean diet is associated with the severity of non-alcoholic fatty liver disease

BACKGROUND & AIMS

Nutrition has been proposed as a potential environmental factor affecting the risk of non-alcoholic fatty liver disease (NAFLD). In the present study, the impact of adherence to the Mediterranean diet (MD) on the presence and severity of NAFLD was explored.

METHODS

Seventy-three consecutive adult patients with recent NAFLD diagnosis were included. Adherence to the MD was estimated with MedDietScore. Demographic and anthropometric data, body composition analysis and several biochemical and inflammatory markers were estimated. Liver stiffness measurements by transient elastography were available in 58 patients and liver biopsies in 34 patients. Fifty-eight patients were matched with 58 healthy controls in terms of age, sex and body mass index.

RESULTS

MedDietScore was negatively correlated to patients' serum alanine aminotransferase (p = 0.03) and insulin levels (p = 0.001), insulin resistance index (p = 0.005) and severity of steatosis (p = 0.006) and positively to serum adiponectin levels (p = 0.04). Patients with non-alcoholic steatohepatitis (NASH) exhibited lower adherence to MD (29.3 ± 3.2 vs. 34.1 ± 4.4, p = 0.004) compared to those with simple fatty liver. Logistic regression analysis revealed that one unit increase in the MedDietScore was associated with 36% lower likelihood of having NASH (odds ratio: 0.64, 95% confidence interval: 0.45-0.92), after adjusting for sex and abdominal fat level. No difference in the MedDietScore was observed between patients and controls.

CONCLUSIONS

Higher adherence to the Mediterranean diet is not associated with lower likelihood of having NAFLD, but it is associated with less degree of insulin resistance and less severe liver disease among patients with NAFLD.

Markers in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD), the most common liver disorder worldwide, encompasses a spectrum of abnormal liver histology ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Population studies show that NAFLD is strongly associated with insulin resistance, obesity, type 2 diabetes mellitus, and lipid abnormalities. In the context of hepatic steatosis, factors that promote cell injury, inflammation, and fibrosis include oxidative stress, early mitochondrial dysfunction, endoplasmic reticulum stress, iron accumulation, apoptosis, adipocytokines, and stellate cell activation. The exact NASH prevalence is unknown because of the absence of simple noninvasive diagnostic tests. Although liver biopsy is the "gold standard" for the diagnosis of NASH, other tests are needed to facilitate the diagnosis and greatly reduce the requirement for invasive liver biopsy. In addition, the development of new fibrosis markers in NASH is needed to facilitate the assessment of its progression and the effectiveness of new therapies. The aim of this chapter, which is overview of biomarkers in NASH, is to establish a systematic approach to laboratory findings of the disease.

Nonalcoholic fatty liver in children and adolescents: an overview

Nonalcoholic fatty liver disease is rapidly becoming one of the most common liver diseases in the pediatric population in industrialized countries because of the growing prevalence of obesity and overweight. For this reason, there is a keen and broad interest among researchers to identify new diagnostic noninvasive tools and novel treatment modalities for this condition. Unfortunately, to date, liver biopsy remains the imperfect gold standard for diagnosis. In addition, available noninvasive markers are not fully satisfactory for the diagnosis of fatty liver. Although in recent years many pharmacological agents, on the basis of pathogenetic mechanism of the disease, have been attempted, to date, the guidelines for the management of fatty liver are still lacking. Establishing effective therapeutic strategies to treat the disease represents the challenge for pediatric hepatologists in the near future. In this article, we briefly review the current knowledge and ideas concerning pediatric nonalcoholic fatty liver disease, and discuss the new perspective therapies.

IL28B and PNPLA3 polymorphisms affect histological liver damage in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Genetic background may affect liver damage in patients with non-alcoholic fatty liver disease (NAFLD). The main outcomes of the study were to assess whether IL28B rs12979860 and rs8099917 polymorphisms, together with PNPLA3 rs738409 C>G polymorphism, are associated with lobular inflammation and fibrosis, in NAFLD patients.

METHODS

One hundred sixty consecutive NAFLD patients were assessed by liver biopsy (Kleiner score); anthropometric, and biochemical and metabolic features were included. IL28B rs12979860 C>T, IL28B rs8099917 G>C, and PNPLA3 rs738409 C>G single nucleotide polymorphisms were tested.

RESULTS

Seventy-four (46.2%) patients had IL28B rs12979860 CC polymorphism, compared with 72 (45%) and 14 (8.8%) with TC and TT variants, respectively. PNPLA3 rs738409 CC polymorphism was present in 47 (29.4%) patients, compared with 79 (49.4%) and 34 (21.3%) with CG and GG variants, respectively. Multivariate logistic regression analysis showed that age (OR 1.043, 95% CI 1.012-1.075, p=0.007), triglycerides (OR 1.005, 95% CI 1.000-1.010, p=0.04), hyperuricemia (OR 5.027, 95% CI 1.839-13.742, p=0.002), IL28B rs12979860 TT/TC (OR 0.219, 95% CI 0.101-0.472, p<0.001), and steatosis grade (OR 1.704, 95% CI 1.048-2.773, p=0.03) were independently linked to moderate-severe lobular inflammation. Finally, IL28B rs12979860 CC was associated with severe fibrosis (F3-F4) on univariate analysis, even if only older age (OR 1.064, 95% CI 1.026-1.104, p=0.001), high HOMA (OR 1.213, 95% CI 1.068-1.377, p=0.003), and lobular inflammation (OR 3.181, 95% CI 1.438-7.036, p=0.004), remained associated in multivariate logistic regression analysis.

CONCLUSIONS

In NAFLD patients, IL28B rs12979860 CC genotype, together with PNPLA3 rs738409 GG, is associated with the severity of liver damage.

Nonalcoholic fatty liver disease: multimodal treatment options for a pathogenetically multiple-hit disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as a significant public health problem. Besides the liver, NAFLD is also associated with increased cardiovascular and overall morbidity and mortality. NAFLD warrants intensive research, because no treatment has been established as yet. This may be partly attributed to the fact that the majority of the relative clinical trials have a monotherapeutic direction. However, the multifactorial pathogenesis of NAFLD may probably direct clinical trials to a combined therapeutic approach. The aim of this review is to provide a description of the multifactorial pathogenesis of NAFLD and type II diabetes mellitus-NAFLD interplay, and to summarize the therapeutic trials focusing on the combined NAFLD treatment, providing a link between the multiple-hit pathogenesis and the multimodal treatment of NAFLD patients. A diabetes-like therapeutic approach for NAFLD is finally proposed.

Non-alcoholic fatty liver disease in children now: lifestyle changes and pharmacologic treatments

Over the past decade, non-alcoholic fatty liver disease (NAFLD) has become one of most common chronic liver diseases in children. A greater understanding about the risk factors and molecular pathogenesis of NAFLD suggests that lifestyle interventions aiming to decrease obesity/body mass index and metabolic derangement are the first line of treatments adopted in children affected by this disease. However, because these therapeutic options are often at the beginning misjudged by the patients and their parents, the use of pharmacologic agents may help to protect the liver and other organs from further irreversible tissue damage. Pharmacologic therapies against one or more specific factors and/or molecules involved in the development of NAFLD (i.e., insulin resistance, free fatty acid lipid toxicity, and oxidative stress) also might slow the progression of this increasingly prevalent pediatric disorder. On this basis, insulin sensitizers, antioxidants, cytoprotective agents, and dietary supplementations have been evaluated in pediatric clinical trials. In this review, we discuss the efficacy of the dietary approaches, possibly coupled with regular exercise, on decreasing the metabolic and histologic damage in pediatric NAFLD. We also emphasize several advantages of the pharmacologic treatments adopted or adoptable in combination with lifestyle interventions in children with NAFLD.

Advances in pediatric nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common cause of pediatric liver disease in the developed world. Children have a form of NAFLD that is pathologically distinct from adults. Although NAFLD remains a pathologic diagnosis, biomarkers and imaging studies hold promise as noninvasive means of both establishing the diagnosis and following the disease course. Significant advancements have recently been made in genetics, pathophysiology, and the treatment of NAFLD. The purpose of this article is to provide a clinically relevant review of pediatric NAFLD with an emphasis on recent developments in the field.

Visceral obesity modulates the impact of apolipoprotein C3 gene variants on liver fat content

OBJECTIVE

It has not been solved whether subjects carrying the minor alleles of the -455T>C or -482C>T single nucleotide polymorphisms (SNPs) in the apolipoprotein-C3-gene (APOC3) have an increased risk for developing fatty liver and insulin resistance. We investigated the relationships of the SNPs with hepatic APOC3 expression and hypothesized that visceral obesity may modulate the effects of these SNPs on liver fat and insulin sensitivity (IS).

METHODS

APOC3 mRNA expression and triglyceride content were determined in liver biopsies from 50 subjects. In a separate group (N=330) liver fat was measured by (1)H-magnetic resonance spectroscopy. IS was estimated during an oral glucose tolerance test (OGTT) and the euglycemic, hyperinsulinemic clamp (N=222).

RESULTS

APOC3 mRNA correlated positively with triglyceride content in liver biopsies (r=0.29, P=0.036). Carriers of the minor alleles (-455C and -482T) tended to have higher hepatic APOC3 mRNA expression (1.80 (0.45-3.56) vs 0.77 (0.40-1.64), P=0.09), but not higher triglyceride content (P=0.76). In 330 subjects the genotype did not correlate with liver fat (P=0.97) or IS (OGTT: P=0.41; clamp: P=0.99). However, a significant interaction of the genotype with waist circumference in determining liver fat was detected (P=0.02) in which minor allele carriers had higher liver fat only in the lowest tertile of waist circumference (P=0.01). In agreement, during a 9-month lifestyle intervention the minor allele carriers of the SNP -482C>T in the lowest tertile also had less decrease in liver fat (P=0.04).

CONCLUSIONS

APOC3 mRNA expression is increased in fatty liver and is regulated by SNPs in APOC3. The impact of the APOC3 SNPs on fatty liver is small and depends on visceral obesity.

Advances in understanding the role of PNPLA3 in the pathogenesis of non-alcoholic fatty liver disease

The incidence of non-alcoholic fatty liver disease (NAFLD) is rising worldwide. Investigation of genes involved in the pathogenesis of NAFLD is significant for replenishing treatment scheme and improving prognosis. Multiple studies have established a correlation between patatin-like phospholipase domain-containing 3 (PNPLA3) gene mutation and the pathogenesis of NAFLD, suggesting that PNPLA3 may affect lipid metabolism. However, the precise mechanism remains to be elucidated. Some researchers believed that PNPLA3 as a patatin-like protein might have triglyceride hydrolysis activity and therefore affect fat metabolism in the liver, while some others thought that PNPLA3 mutation might interfere with the lipid transfer process. In this paper, we give an overview of the PNPLA3 gene and its expression, and explore the correlation between PNPLA3 gene mutation and the pathogenesis of NAFLD.

Liver ATP synthesis is lower and relates to insulin sensitivity in patients with type 2 diabetes

OBJECTIVE

Steatosis associates with insulin resistance and may even predict type 2 diabetes and cardiovascular complications. Because muscular insulin resistance relates to myocellular fat deposition and disturbed energy metabolism, we hypothesized that reduced hepatic ATP turnover (fATP) underlies insulin resistance and elevated hepatocellular lipid (HCL) contents.

RESEARCH DESIGN AND METHODS

We measured hepatic fATP using (31)P magnetic resonance spectroscopy in patients with type 2 diabetes and age- and body mass-matched controls. Peripheral (M and M/I) and hepatic (suppression of endogenous glucose production) insulin sensitivity were assessed with euglycemic-hyperinsulinemic clamps.

RESULTS

Diabetic individuals had 29% and 28% lower peripheral and hepatic insulin sensitivity as well as 42% reduced fATP than controls. After adjusting for HCL, fATP correlated positively with peripheral and hepatic insulin sensitivity but negatively with waist circumference, BMI, and fasting plasma glucose. Multiple regression analysis identified waist circumference as an independent predictor of fATP and inorganic phosphate (P(I)) concentrations, explaining 65% (P = 0.001) and 56% (P = 0.003) of the variations. Hepatocellular P(I) primarily determined the alterations in fATP.

CONCLUSIONS

In patients with type 2 diabetes, insulin resistance relates to perturbed hepatic energy metabolism, which is at least partly accounted for by fat depots.

"The metabolic syndrome... is dead": these reports are an exaggeration

The debates continue over the validity of the metabolic syndrome concept. The continuous increment of the obesity pandemic is almost worldwide paralleled by rising rates of metabolic syndrome prevalence. Then, it seems obvious that these debates drove the need for further investigations as well as a deeper cooperation between relevant national and international organizations regarding the issue. Instead, part of the scientific community elected to totally "dismiss" the concept of the metabolic syndrome. Meanwhile, the best available evidence from three consecutive large meta-analyses has systematically shown that people with metabolic syndrome are at increased risk of cardiovascular events. The most recent and largest of them included near one million patients (total n = 951,083). The investigators concluded that the metabolic syndrome is associated with a 2-fold increase in cardiovascular outcomes and a 1.5-fold increase in all-cause mortality rates. One of the ways to hit the metabolic syndrome is an utterly simplistic view on this concept as a predictive tool only. Of course, the presence of the metabolic syndrome possesses a definite predictive value, but first of all it is a widely accepted concept regarding a biological condition based on the complex and interrelated pathophysiological mechanisms starting from excess central adiposity and insulin resistance. Therefore, it is completely unfair to compare it with statistically constructed predictive tools, including stronger prognostic variables even unrelated to each other from the biological point of view. For example, in the criteria for metabolic syndrome (in contrast to Framingham score) age and cholesterol--presumably low density lipoprotein-cholesterol (LDL-C)--levels are not included, as well as a variety of strong predictors used in other risk-stratification scores: previous myocardial infarction, heart failure, smoking, family history, etc. However, the metabolic syndrome identifies additional important residual vascular risk mainly associated with insulin resistance and atherogenic dyslipidemia (low high density lipoprotein-cholesterol (HDL-C), high triglycerides, small, dense LDL-C). Therefore, the metabolic syndrome could be a useful additional contributor in estimation of global cardiovascular risk beyond age, high LDL-C or other standard risk factors. The components of the metabolic syndrome have partially overlapping mechanisms of pathogenic actions mediated through common metabolic pathways. Therefore their total combined effect could be less than the summed of the individual effects. The concept that the metabolic syndrome is a consequence of obesity and insulin resistance, provides a useful "life-style changes" approach for prevention and treatment: caloric restriction, weight-loss and increased physical activity. The next step could theoretically be pharmacological interventions such as metformin, acarbose, fibrates, weight-loss drugs (currently only orlistat is practically available) and perhaps glucagon-like peptide-1 agonists. A third step should probably be kept for bariatric surgery.