Non-alcoholic steatohepatitis in morbidly obese patients

Roles of innate lymphoid cells in metabolic and alcohol-associated liver diseases

Innate lymphoid cells (ILCs) have been identified as potent regulators of inflammation, cell death and wound healing, which are the main biological processes involved in the progression of chronic liver disease. Obesity and chronic alcohol consumption are the leading contributors to chronic liver diseases in developed countries, due to inappropriate lifestyles. In particular, inflammation is a key factor in these liver abnormalities and promotes the development of more severe lesions such as fibrosis, cirrhosis and hepatocellular carcinoma. Opposite roles of ILC subsets have been described in the development of chronic liver disease, depending on the stage and aetiology of the disease. The heterogeneous family of ILCs encompasses cytotoxic natural killer cells, the cytokine-producing type 1, 2 and 3 ILCs and lymphoid tissue inducer cells. Dysfunction of these immune cells provokes uncontrolled inflammation and tissue damage, which are the basis for tumour development. In this review, we provide an overview of the recent and putative roles of ILC subsets in obesity and alcohol-associated liver diseases, which are currently the major contributors to end-stage liver complications such as fibrosis/cirrhosis and hepatocellular carcinoma.

SYK-3BP2 Pathway Activity in Parenchymal and Myeloid Cells Is a Key Pathogenic Factor in Metabolic Steatohepatitis

BACKGROUND & AIMS

Spleen tyrosine kinase (SYK) signaling pathway regulates critical processes in innate immunity, but its role in parenchymal cells remains elusive in chronic liver diseases. We investigate the relative contribution of SYK and its substrate c-Abl Src homology 3 domain-binding protein-2 (3BP2) in both myeloid cells and hepatocytes in the onset of metabolic steatohepatitis.

METHODS

Hepatic SYK-3BP2 pathway was evaluated in mouse models of metabolic-associated fatty liver diseases (MAFLD) and in obese patients with biopsy-proven MAFLD (n = 33). Its role in liver complications was evaluated in Sh3bp2 KO and myeloid-specific Syk KO mice challenged with methionine and choline deficient diet and in homozygous Sh3bp2^KI/KI mice with and without SYK expression in myeloid cells.

RESULTS

Here we report that hepatic expression of 3BP2 and SYK correlated with metabolic steatohepatitis severity in mice. 3BP2 deficiency and SYK deletion in myeloid cells mediated the same protective effects on liver inflammation, injury, and fibrosis priming upon diet-induced steatohepatitis. In primary hepatocytes, the targeting of 3BP2 or SYK strongly decreased the lipopolysaccharide-mediated inflammatory mediator expression and 3BP2-regulated SYK expression. In homozygous Sh3bp2^KI/KI mice, the chronic inflammation mediated by the proteasome-resistant 3BP2 mutant promoted severe hepatitis and liver fibrosis with augmented liver SYK expression. In these mice, the deletion of SYK in myeloid cells was sufficient to prevent these liver lesions. The hepatic expression of SYK is also up-regulated with metabolic steatohepatitis and correlates with liver macrophages in biopsy-proven MAFLD patients.

CONCLUSIONS

Collectively, these data suggest an important role for the SYK-3BP2 pathway in the pathogenesis of chronic liver inflammatory diseases and highlight its targeting in hepatocytes and myeloid cells as a potential strategy to treat metabolic steatohepatitis.

E-Selectin-Dependent Inflammation and Lipolysis in Adipose Tissue Exacerbate Steatosis-to-NASH Progression via S100A8/9

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, characterized by steatosis and hallmark liver neutrophil infiltration. NASH also is associated with adipose tissue inflammation, but the role of adipose tissue inflammation in NASH pathogenesis remains obscure. The aim of this study was to investigate the interplay between neutrophil recruitment in adipose tissue and the progression of NASH.

METHODS

A mouse model of NASH was obtained by high-fat diet (HFD) feeding plus adenovirus-Cxcl1 overexpression (HFD^+AdCxcl1). Genetic deletion of E-selectin (Sele) and treatment with an S100A9 inhibitor (Paquinimod) were investigated using this model.

RESULTS

By analyzing transcriptomic data sets of adipose tissue from NASH patients, we found that E-selectin, a key adhesion molecule for neutrophils, is the highest up-regulated gene among neutrophil recruitment-related factors in adipose tissue of NASH patients compared with those in patients with simple steatosis. A marked up-regulation of Sele in adipose tissue also was observed in HFD^+AdCxcl1 mice. The HFD^+AdCxcl1-induced NASH phenotype was ameliorated in Sele knockout mice and was accompanied by reduced lipolysis and inflammation in adipose tissue, which resulted in decreased serum free fatty acids and proinflammatory adipokines. S100A8/A9, a major proinflammatory protein secreted by neutrophils, was highly increased in adipose tissue of HFD^+AdCxcl1 mice. This increase was blunted in the Sele knockout mice. Therapeutically, treatment with the S100A9 inhibitor Paquinimod reduced lipolysis, inflammation, and adipokine production, ameliorating the NASH phenotype in mice.

CONCLUSIONS

E-selectin plays an important role in inducing neutrophil recruitment in adipose tissue, which subsequently promotes inflammation and lipolysis via the production of S100A8/A9, thereby exacerbating the steatosis-to-NASH progression. Targeting adipose tissue inflammation therefore may represent a potential novel therapy for treatment of NASH.

Endoplasmic reticulum stress and autophagy dysregulation in alcoholic and non-alcoholic liver diseases

Alcoholic and non-alcoholic liver diseases begin from an imbalance in lipid metabolism in hepatocytes as the earliest response. Both liver diseases share common disease features and stages (i.e., steatosis, hepatitis, cirrhosis, and hepatocellular carcinoma). However, the two diseases have differential pathogenesis and clinical symptoms. Studies have elucidated the molecular basis underlying similarities and differences in the pathogenesis of the diseases; the factors contributing to the progression of liver diseases include depletion of sulfhydryl pools, enhanced levels of reactive oxygen and nitrogen intermediates, increased sensitivity of hepatocytes to toxic cytokines, mitochondrial dysfunction, and insulin resistance. Endoplasmic reticulum (ER) stress, which is caused by the accumulation of misfolded proteins and calcium depletion, contributes to the pathogenesis, often causing catastrophic cell death. Several studies have demonstrated a mechanism by which ER stress triggers liver disease progression. Autophagy is an evolutionarily conserved process that regulates organelle turnover and cellular energy balance through decomposing damaged organelles including mitochondria, misfolded proteins, and lipid droplets. Autophagy dysregulation also exacerbates liver diseases. Thus, autophagy-related molecules can be potential therapeutic targets for liver diseases. Since ER stress and autophagy are closely linked to each other, an understanding of the molecules, gene clusters, and networks engaged in these processes would be of help to find new remedies for alcoholic and non-alcoholic liver diseases. In this review, we summarize the recent findings and perspectives in the context of the molecular pathogenesis of the liver diseases.

Chronic Inflammation in Non-Alcoholic Steatohepatitis: Molecular Mechanisms and Therapeutic Strategies

Non-Alcoholic Steatohepatitis (NASH) is the progressive form of Non-Alcoholic Fatty Liver Disease (NAFLD), the main cause of chronic liver complications. The development of NASH is the consequence of aberrant activation of hepatic conventional immune, parenchymal, and endothelial cells in response to inflammatory mediators from the liver, adipose tissue, and gut. Hepatocytes, Kupffer cells and liver sinusoidal endothelial cells contribute to the significant accumulation of bone-marrow derived-macrophages and neutrophils in the liver, a hallmark of NASH. The aberrant activation of these immune cells elicits harmful inflammation and liver injury, leading to NASH progression. In this review, we highlight the processes triggering the recruitment and/or activation of hepatic innate immune cells, with a focus on macrophages, neutrophils, and innate lymphoid cells as well as the contribution of hepatocytes and endothelial cells in driving liver inflammation/fibrosis. On-going studies and preliminary results from global and specific therapeutic strategies to manage this NASH-related inflammation will also be discussed.

Natural Killer Cells and Type 1 Innate Lymphoid Cells Are New Actors in Non-alcoholic Fatty Liver Disease

Obesity and associated liver diseases (Non Alcoholic Fatty Liver Disease, NAFLD) are a major public health problem with increasing incidence in Western countries (25% of the affected population). These complications develop from a fatty liver (steatosis) to an inflammatory state (steatohepatitis) evolving toward fibrosis and hepatocellular carcinoma. Lipid accumulation in the liver contributes to hepatocyte cell death and promotes liver injury. Local immune cells are activated either by Danger Associated Molecular Patterns (DAMPS) released by dead hepatocytes or by bacterial products (PAMPS) reaching the liver due to increased intestinal permeability. The resulting low-grade inflammatory state promotes the progression of liver complications toward more severe grades. Innate lymphoid cells (ILC) are an heterogeneous family of five subsets including circulating Natural Killer (NK) cells, ILC1, ILC2, ILC3, and lymphocytes tissue-inducer cells (LTi). NK cells and tissue-resident ILCs, mainly located at epithelial surfaces, are prompt to rapidly react to environmental changes to mount appropriate immune responses. Recent works have demonstrated the interplay between ILCs subsets and the environment within metabolic active organs such as liver, adipose tissue and gut during diet-induced obesity leading or not to hepatic abnormalities. Here, we provide an overview of the newly roles of NK cells and ILC1 in metabolism focusing on their contribution to the development of NAFLD. We also discuss recent studies that demonstrate the ability of these two subsets to influence tissue-specific metabolism and how their function and homeostasis are affected during metabolic disorders.

Systems pharmacology-based exploration reveals mechanisms of anti-steatotic effects of Jiang Zhi Granule on non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), which is in parallel with the obesity epidemic, accounts for a large amount of all chronic liver disease. Jiang Zhi Granule (JZG), a clinically used herbal formula, is developed in accordance with traditional Chinese medicine (TCM) pathogenesis for treating patients with NAFLD. In previous studies, the anti-steatotic effects of JZG against NAFLD have been demonstrated, and in this study, a systems pharmacology approach was used to explore the pharmacological mechanisms of JZG by predicting the active compounds within the herbal formula and their corresponding therapeutic targets. Its therapeutic efficacy was confirmed in the beginning of this study, and JZG was shown to significantly improve hepatic dysfunction and lipid droplet accumulation in PA-treated hepatocytes. Systems pharmacology was then performed to identify the active compounds in as well as to predict the therapeutic targets of this Chinese herbal prescription. Enrichment analyses indicated that the mechanisms of the anti-steatotic effects of JZG against NAFLD might be associated with lipid droplet degradation via autophagy, and a series of in vitro and in vivo validation experiments was subsequently performed to confirm that JZG could activate autophagy though the mTOR signalling to improve NAFLD.

Changes in Bile Acid Profile After Laparoscopic Sleeve Gastrectomy are Associated with Improvements in Metabolic Profile and Fatty Liver Disease

BACKGROUND

Bile acids (BA) modulate lipid and glucose metabolism in a feedback loop through production of fibroblast growth factor (FGF) 19 in the terminal ileum. Changes in BA after bariatric surgery may lead to improvements in the metabolic syndrome, including fatty liver disease. This study investigated the relationship between BA and metabolic and inflammatory profiles after laparoscopic sleeve gastrectomy (LSG).

METHODS

Patients undergoing LSG had fasting blood samples taken pre-operatively and 6 months post-surgery. Liver injury was measured using cytokeratin (CK) 18 fragments. BA were measured using liquid chromatography tandem-mass spectrometry. FGF-19 was measured using enzyme-linked immunosorbent assay.

RESULTS

The study included 18 patients (12 females), with mean age 46.3 years (SEM ± 2.9) and BMI 60.1 kg/m(2) (±2.6). After 6 months, patients lost 39.8 kg (±3.1; p < 0.001). Fourteen patients (78 %) had steatosis. FGF-19 increased from median 128.1 (IQR 89.4-210.1) to 177.1 (121.8-288.9, p = 0.045) at 6 months. Although total BA did not change, primary glycine- and taurine-conjugated BA, cholic acid decreased, and secondary BA, glycine-conjugated urodeoxycholic acid increased over the study period. These changes are associated with reduction in insulin resistance, pro-inflammatory cytokines and CK-18 levels.

CONCLUSIONS

The profile of individual BA is altered after LSG. These changes occur in the presence of reductions in inflammatory cytokines and markers of liver injury. This study supports evidence from recent animal models that LSG may have an effect on fatty liver through changes in BA metabolism.

CD44 is a key player in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Cluster of differentiation (CD)44 regulates adipose tissue inflammation in obesity and hepatic leukocyte recruitment in a lithogenic context. However, its role in hepatic inflammation in a mouse model of steatohepatitis and its relevance in humans have not yet been investigated. We aimed to evaluated the contribution of CD44 to non-alcoholic steatohepatitis (NASH) development and liver injury in mouse models and in patients at various stages of non-alcoholic fatty liver disease (NAFLD) progression.

METHODS

The role of CD44 was evaluated in CD44^-/- mice and after injections of an αCD44 antibody in wild-type mice challenged with a methionine- and choline-deficient diet (MCDD). In obese patients, hepatic CD44 (n=30 and 5 NASH patients with a second liver biopsy after bariatric surgery) and serum sCD44 (n=64) were evaluated.

RESULTS

Liver inflammation (including inflammatory foci number, macrophage and neutrophil infiltration and CCL2/CCR2 levels), liver injury and fibrosis strongly decreased in CD44^-/- mice compared to wild-type mice on MCDD. CD44 deficiency enhanced the M2 polarization and strongly decreased the activation of macrophages by lipopolysaccharide (LPS), hepatocyte damage-associated molecular patterns (DAMPs) and saturated fatty acids. Neutralization of CD44 in mice with steatohepatitis strongly decreased the macrophage infiltration and chemokine ligand (CCL)2 expression with a partial correction of liver inflammation and injury. In obese patients, hepatic CD44 was strongly upregulated in NASH patients (p=0.0008) and correlated with NAFLD activity score (NAS) (p=0.001), ballooning (p=0.003), alanine transaminase (p=0.005) and hepatic CCL2 (p<0.001) and macrophage marker CD68 (p<0.001) expression. Correction of NASH was associated with a strong decrease in liver CD44⁺ cells. Finally, the soluble form of CD44 increased with severe steatosis (p=0.0005) and NASH (p=0.007).

CONCLUSION

Human and experimental data suggest that CD44 is a marker and key player of hepatic inflammation and its targeting partially corrects NASH.

LAY SUMMARY

Human and experimental data suggest that CD44, a cellular protein mainly expressed in immune cells, is a marker and key player of non-alcoholic steatohepatitis (NASH). Indeed, CD44 enhances the non-alcoholic fatty liver (NAFL) (hepatic steatosis) to NASH progression by regulating hepatic macrophage polarization (pro-inflammatory phenotype) and infiltration (macrophage motility and the MCP1/CCL2/CCR2 system). Targeting CD44 partially corrects NASH, making it a potential therapeutic strategy.

[Autophagy in chronic liver diseases: a friend rather than a foe?]

Within recycling damaged cell components, autophagy maintains cell homeostasis. Thus, it has been anticipated that autophagy would play an essential role in the pathogenesis of chronic liver diseases. Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the most prevalent chronic liver diseases in Western countries, sharing common histopathologic features and a common disease progression. In this review, we discuss the role of autophagy at different stages of NAFLD and ALD as well as in liver regeneration and hepatocarcinogenesis.

Autophagy in chronic liver diseases: the two faces of Janus

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the leading causes of cirrhosis and increase the risk of hepatocellular carcinoma and liver-related death. ALD and NAFLD share common pathogenic features extending from isolated steatosis to steatohepatitis and steatofibrosis, which can progress to cirrhosis and hepatocellular carcinoma. The pathophysiological mechanisms of the progression of NAFLD and ALD are complex and still unclear. Important links between the regulation of autophagy (macroautophagy and chaperone-mediated autophagy) and chronic liver diseases have been reported. Autophagy may protect against steatosis and progression to steatohepatitis by limiting hepatocyte injury and reducing M1 polarization, as well as promoting liver regeneration. Its role in fibrosis and hepatocarcinogenesis is more complex. It has pro- and antifibrogenic properties depending on the hepatic cell type concerned, and beneficial and deleterious effects on hepatocarcinogenesis at initiating and late phases, respectively. This review summarizes the latest advances on the role of autophagy in different stages of fatty liver disease progression and describes its divergent and cell-specific effects during chronic liver injury.

Non-alcoholic fatty liver disease and flavonoids: Current perspectives

Non-alcoholic fatty liver disease (NAFLD) is an accumulation of fat in the liver despite a low level of alcohol intake, with signs of hepatomegaly. Although in the past, NAFLD was predominantly viewed as an aspect of metabolic syndrome, it is now considered that it should be classified as an independent condition similar to obesity, diabetes, and hypertension. Therefore, new treatment strategies, not based on correcting insulin resistance, are needed for NAFLD. This work analyzes methods of prevention, therapeutic approaches, and mechanisms involved in NAFLD, focusing on the use of flavonoids (epigallocatechin-3-gallate, resveratrol, anthocyanins, and isoflavones) with high antioxidant capacity. In addition, the mechanisms of cholesterol accumulation in the liver are identified as potential avenues for entirely new approaches to NAFLD treatment, contrasting the well-known relation between neutral fat and NAFLD.

Hepatic miR-33a/miR-144 and their target gene ABCA1 are associated with steatohepatitis in morbidly obese subjects

BACKGROUND AND AIM

Abnormal cholesterol metabolism may contribute to the pathogenesis of non-alcoholic steatohepatitis (NASH) and fibrosis. miR-33 and miR-144 regulate adenosine triphosphate binding cassette transporter (ABCA1) and other target genes involved in cholesterol efflux, fatty acid oxidation and inflammation. We explored relationships between non-alcoholic fatty liver disease (NAFLD) and the hepatic expression of ABCA1/ABCG1, as well as other target genes regulated by miR-33 (carnitine O-octanoyltransferase, CROT and hydroxyacyl-CoA-dehydrogenase β-subunit, HADHB) and miR-144 (toll-like receptor-2, TLR2). Moreover, we evaluated whether the expression of these genes is correlated with miR-33a/b and miR-144 expression in Mexican individuals with morbid obesity.

METHODS

Eighty-four morbidly obese subjects undergoing bariatric surgery were included in this study. Liver biopsies were obtained to measure hepatic triglyceride and free cholesterol contents, as well as ABCA1, ABCG1, CROT, HADHB, TLR2, miR-33a/b and miR-144 expression.

RESULTS

Hepatic free cholesterol content was significantly increased in NASH as compared to non-NASH subjects, while ABCA1 and ABCG1 protein levels significantly decreased with NASH and fibrosis progression. The relative expression of miR-33a and miR-144 correlated inversely with ABCA1 but not with ABCG1 protein levels. Moreover, both miRNAs increased significantly in NASH individuals. miR-33 target genes CROT and HADHB correlated inversely with miR-33a. However, the expression of these genes was not associated with NASH.

CONCLUSIONS

miR-33a/144 and their target gene ABCA1 may contribute to the pathogenesis of NASH in morbidly obese subjects.

Roux-En Y Gastric Bypass Results in Long-Term Remission of Hepatocyte Apoptosis and Hepatic Histological Features of Non-alcoholic Steatohepatitis

The long-term effects of bariatric surgery on non-alcoholic steatohepatitis (NASH), focusing on liver injury and hepatocyte apoptosis, are not well-established. We here performed a longitudinal study with paired liver biopsies of nine morbidly obese women (median BMI: 42 [38.7; 45.1] kg/m²) with NASH with a median follow-up of 55 [44; 75] months after laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery. LRYGB surgery was associated with significant weight loss (median BMI loss −13.7 [−16.4; −9.5] kg/m²), improved hepatic steatosis in all patients (55.5% with total resolution), and resolution of hepatic inflammation and hepatocyte ballooning in 100 and 88.8% of cases, respectively. Alanine aminotransferase levels dropped to normal values while hepatic activated cleaved caspase-3 levels strongly decreased after a median follow-up of 55 months. Hepatocyte apoptosis, as evaluated by serum caspase-generated keratin-18 fragment, improved within the first year following LRYGB and these improvements persisted for at least 55 months. LRYGB in morbidly obese patients with NASH is thus associated with a long-lasting beneficial impact on hepatic steatohepatitis and hepatocyte death.

Cross talk of the immune system in the adipose tissue and the liver in non-alcoholic steatohepatitis: Pathology and beyond

Non-alcoholic steatohepatitis (NASH) is considered to be the hepatic manifestation of the metabolic syndrome, thus has a tight correlation with systemic metabolic impairment. The complex mechanisms underlying the pathogenesis of NASH involve different organs and systems that cross talk together contributing to the onset of NASH. A crucial role is played by inflammatory mediators, especially those deriving from the adipose tissue and the liver, which are involved in the cascade of inflammation, fibrosis and eventually tumorigenesis. In this setting cytokines and adipokines as well as immunity are emerging drivers of the key features of NASH. The immune system participates in this process with disturbances of the cells constituting both the innate and the adaptive immune systems that have been reported in different organs, such as in the liver and in the adipose tissue, in clinical and preclinical studies. The role of the immune system in NASH is increasingly studied, not only because of its contribution to the pathogenetic mechanisms of NASH but also because of the new potential therapeutic options it offers in this setting. Indeed, novel treatments acting on the immune system could offer new options in the management of NASH and the correlated clinical consequences.

Jejunal T Cell Inflammation in Human Obesity Correlates with Decreased Enterocyte Insulin Signaling

In obesity, insulin resistance is linked to inflammation in several tissues. Although the gut is a very large lymphoid tissue, inflammation in the absorptive small intestine, the jejunum, where insulin regulates lipid and sugar absorption is unknown. We analyzed jejunal samples of 185 obese subjects stratified in three metabolic groups: without comorbidity, suffering from obesity-related comorbidity, and diabetic, versus 33 lean controls. Obesity increased both mucosa surface due to lower cell apoptosis and innate and adaptive immune cell populations. The preferential CD8αβ T cell location in epithelium over lamina propria appears a hallmark of obesity. Cytokine secretion by T cells from obese, but not lean, subjects blunted insulin signaling in enterocytes relevant to apical GLUT2 mislocation. Statistical links between T cell densities and BMI, NAFLD, or lipid metabolism suggest tissue crosstalk. Obesity triggers T-cell-mediated inflammation and enterocyte insulin resistance in the jejunum with potential broader systemic implications.

Severity of non-alcoholic fatty liver disease is associated with high systemic levels of tumor necrosis factor alpha and low serum interleukin 10 in morbidly obese patients

Morbid obesity has been shown to increase the risk to develop hepatic steatosis, also referred to as non-alcoholic fatty liver disease (NAFLD). Emerging evidence suggests that the severity of NAFLD may associate with increased serum levels of inflammatory markers as well as decreased concentration of mediators with anti-inflammatory actions, such as tumor necrosis factor alpha (TNF-α) and interleukin (IL) 10, respectively. We thus examined the serum levels of TNF-α and IL-10 in 102 morbidly obese women and men (body mass index > 40 kg/m(2)), exhibiting different grades of NAFLD. Blood glucose, glycated hemoglobin, insulin, the homeostatic model assessment of insulin resistance (HOMA-IR), total cholesterol, triglycerides, high- and low-density lipoproteins, parameters of liver function, TNF-α, and IL-10 were measured in each subject. The stage of NAFLD was estimated by abdominal ultrasound imaging. In comparison with morbidly obese subjects without steatosis, morbidly obese patients with NAFLD showed increased age (39.23 ± 9.80 years), HOMA-IR (6.74 ± 1.62), total cholesterol (219.7 ± 9.58 mg/dl), aspartate aminotransferase (36.25 ± 3.24 UI/l), gamma-glutamyl transpeptidase (37.12 ± 3.41 UI/l), and TNF-α (37.41 ± 1.72 pg/ml) as well as decreased serum levels of IL-10 (61.05 ± 2.43 pg/ml). Interestingly, the systemic levels of TNF-α increased, while IL-10 decreased in accordance with the severity of NAFLD, which supports a role for systemic inflammatory mediators in promoting steatosis progression. Further clinical prospective studies need to be addressed to elucidate the role of TNF-α and IL-10 in the development of NAFLD while also establishing their clinical utility in the assessment of morbidly obese patients at higher risk to develop severe steatosis.

Trypanosoma cruzi infection is a potent risk factor for non-alcoholic steatohepatitis enhancing local and systemic inflammation associated with strong oxidative stress and metabolic disorders

BACKGROUND

The immune mechanisms underlying experimental non-alcoholic steatohepatitis (NASH), and more interestingly, the effect of T. cruzi chronic infection on the pathogenesis of this metabolic disorder are not completely understood.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated immunological parameters in male C57BL/6 wild type and TLR4 deficient mice fed with a standard, low fat diet, LFD (3% fat) as control group, or a medium fat diet, MFD (14% fat) in order to induce NASH, or mice infected intraperitoneally with 100 blood-derived trypomastigotes of Tulahuen strain and also fed with LFD (I+LFD) or MFD (I+MFD) for 24 weeks. We demonstrated that MFD by itself was able to induce NASH in WT mice and that parasitic infection induced marked metabolic changes with reduction of body weight and steatosis revealed by histological studies. The I+MFD group also improved insulin resistance, demonstrated by homeostasis model assessment of insulin resistance (HOMA-IR) analysis; although parasitic infection increased the triglycerides and cholesterol plasma levels. In addition, hepatic M1 inflammatory macrophages and cytotoxic T cells showed intracellular inflammatory cytokines which were associated with high levels of IL6, IFNγ and IL17 plasmatic cytokines and CCL2 chemokine. These findings correlated with an increase in hepatic parasite load in I+MFD group demonstrated by qPCR assays. The recruitment of hepatic B lymphocytes, NK and dendritic cells was enhanced by MFD, and it was intensified by parasitic infection. These results were TLR4 signaling dependent. Flow cytometry and confocal microscopy analysis demonstrated that the reactive oxygen species and peroxinitrites produced by liver inflammatory leukocytes of MFD group were also exacerbated by parasitic infection in our NASH model.

CONCLUSIONS

We highlight that a medium fat diet by itself is able to induce steatohepatitis. Our results also suggest a synergic effect between damage associated with molecular patterns generated during NASH and parasitic infection, revealing an intense cross-talk between metabolically active tissues, such as the liver, and the immune system. Thus, T. cruzi infection must be considered as an additional risk factor since exacerbates the inflammation and accelerates the development of hepatic injury.

Autophagy and non-alcoholic fatty liver disease

Autophagy, or cellular self-digestion, is a catabolic process that targets cell constituents including damaged organelles, unfolded proteins, and intracellular pathogens to lysosomes for degradation. Autophagy is crucial for development, differentiation, survival, and homeostasis. Important links between the regulation of autophagy and liver complications associated with obesity, non-alcoholic fatty liver disease (NAFLD), have been reported. The spectrum of these hepatic abnormalities extends from isolated steatosis to non-alcoholic steatohepatitis (NASH), steatofibrosis, which sometimes leads to cirrhosis, and hepatocellular carcinoma. NAFLD is one of the three main causes of cirrhosis and increases the risk of liver-related death and hepatocellular carcinoma. The pathophysiological mechanisms of the progression of a normal liver to steatosis and then more severe disease are complex and still unclear. The regulation of the autophagic flux, a dynamic response, and the knowledge of the role of autophagy in specific cells including hepatocytes, hepatic stellate cells, immune cells, and hepatic cancer cells have been extensively studied these last years. This review will provide insight into the current understanding of autophagy and its role in the evolution of the hepatic complications associated with obesity, from steatosis to hepatocellular carcinoma.

Effects of sleeve gastrectomy in high fat diet-induced obese mice: respective role of reduced caloric intake, white adipose tissue inflammation and changes in adipose tissue and ectopic fat depots

BACKGROUND

Sleeve gastrectomy (SG) has become a popular bariatric procedure. The mechanisms responsible for weight loss and improvement of metabolic disturbances have still not been completely elucidated. We investigated the effect of SG on body weight, adipose tissue depots, glucose tolerance, and liver steatosis independent of reduced caloric intake in high-fat-diet-induced obese mice.

METHODS

C57BI/6 J mice fed a high fat diet (45 %) for 33 weeks were divided into three groups: sleeve gastrectomy (SG, 13 mice), sham-operated ad libitum fed (SALF, 13 mice) and sham-operated pair fed (PFS, 13 mice). The animals were humanely killed 23 days after surgery.

RESULTS

In SG mice, food intake was reduced transiently, but weight loss was significant and persistent compared to controls (SG vs. PFS, P < 0.05; PFS vs. SALF, P < 0.05). SG mice showed improved glucose tolerance and lower levels of liver steatosis compared with controls (area under the curve, SG vs. PFS, P < 0.01; PFS vs. SALF, P < 0.05) (liver steatosis, SG vs. PFS, P < 0.05; PFS vs. SALF, P < 0.01). This was associated with a decrease in the ratios of the weight of pancreas, epididymal and inguinal adipose tissues to body weight, and an increase in the ratio of brown adipose tissue weight to body weight. Epididymal adipose tissue was also infiltrated by fewer activated T cells and by more anti-inflammatory regulatory T cells. Serum levels of fasting acyl ghrelin were still significantly decreased 3 weeks after surgery in SG mice compared to PFS mice (P < 0.05).

CONCLUSIONS

Reduced white adipose tissue inflammation, modification of adipose tissue development (brown vs. white adipose tissue), and ectopic fat are potential mechanisms that may account for the reduced caloric intake independent effects of SG.

Immunological mechanisms in the pathophysiology of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is characterized by the presence of steatosis, inflammation and hepatocyte injury and constitutes hepatic manifestation of the metabolic syndrome. The pathogenesis of NASH is complex and implicates cross-talk between different metabolically active sites, such as liver and adipose tissue. Obesity is considered a chronic low-grade inflammatory state and the liver has been recognized as being an "immunological organ". The complex role of the immune system in the pathogenesis of NASH is currently raising great interest, also in view of the possible therapeutic potential of immunotherapy in NASH. This review focuses on the disturbances of the cells constituting the innate and adaptive immune system in the liver and in adipose tissue.