Uric acid and anti-TNF antibody improve mitochondrial dysfunction in ob/ob mice

Mitochondrial function and gastrointestinal diseases

Mitochondria are dynamic organelles that function in cellular energy metabolism, intracellular and extracellular signalling, cellular fate and stress responses. Mitochondria of the intestinal epithelium, the cellular interface between self and enteric microbiota, have emerged as crucial in intestinal health. Mitochondrial dysfunction occurs in gastrointestinal diseases, including inflammatory bowel diseases and colorectal cancer. In this Review, we provide an overview of the current understanding of intestinal epithelial cell mitochondrial metabolism, function and signalling to affect tissue homeostasis, including gut microbiota composition. We also discuss mitochondrial-targeted therapeutics for inflammatory bowel diseases and colorectal cancer and the evolving concept of mitochondrial impairment as a consequence versus initiator of the disease.

Hepatic-specific Pgc-1α ablation drives fibrosis in a MASH model

BACKGROUND & AIMS

Metabolic dysfunction-associated steatohepatitis (MASH) is a growing cause of chronic liver disease, characterized by fat accumulation, inflammation and fibrosis, which development depends on mitochondrial dysfunction and oxidative stress. Highly expressed in the liver during fasting, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) regulates mitochondrial and oxidative metabolism. Given the relevant role of mitochondrial function in MASH, we investigated the relationship between PGC-1α and steatohepatitis.

METHODS

We measured the hepatic expression of Pgc-1α in both MASH patients and wild-type mice fed a western diet (WD) inducing steatosis and fibrosis. We then generated a pure C57BL6/J strain loss of function mouse model in which Pgc-1α is selectively deleted in the liver and we fed these mice with a WD supplemented with sugar water that accurately mimics human MASH.

RESULTS

We observed that the hepatic expression of Pgc-1α is strongly reduced in MASH, in both humans and mice. Moreover, the hepatic ablation of Pgc-1α promotes a considerable reduction of the hepatic mitochondrial respiratory capacity, setting up a bioenergetic harmful environment for liver diseases. Indeed, the lack of Pgc-1α decreases mitochondrial function and increases inflammation, fibrosis and oxidative stress in the scenario of MASH. Intriguingly, this profibrotic phenotype is not linked with obesity, insulin resistance and lipid disbalance.

CONCLUSIONS

In a MASH model the hepatic ablation of Pgc-1α drives fibrosis independently from lipid and glucose metabolism. These results add a novel mechanistic piece to the puzzle of the specific and crucial role of mitochondrial function in MASH development.

Kaempferol ameliorates metabolic syndrome by inhibiting inflammation and oxidative stress in high-fat diet-induced obese mice

BACKGROUND/OBJECTIVES

Kaempferol (Ka) is one of the most widely occurring flavonoids found in large amounts in various plants. Ka has anti-obesity, antioxidant, and anti-inflammatory effects. Despite the numerous papers documenting the efficacy of Ka, some controversy remains. Therefore, this study examined the impact of Ka using 3T3-L1 and high-fat diet-induced obese mice.

MATERIALS/METHODS

3T3-L1 cells were treated with 50 μM Ka from the initiation of 3T3-L1 differentiation at D0 until the completion of differentiation on D8. Thirty male mice (C57BL/6J, 4 weeks old) were divided into 3 groups: normal diet (ND), high-fat diet (HFD), and HFD + 0.02% (w/w) Ka (Ka) group. All mice were fed their respective diets ad libitum for 16 weeks. The mice were sacriced, and the plasma and hepatic lipid levels, white adipose tissue weight, hepatic glucose level, lipid level, and antioxidant enzyme activities were analyzed, and immunohistochemistry staining was performed.

RESULTS

Ka suppressed the hypertrophy of 3T3-L1 cells, and the Ka-supplemented mice showed a significant decrease in perirenal, retroperitoneal, mesenteric, and subcutaneous fat compared to the HFD group. Ka supplementation in high-fat diet-induced obese mice also improved the overall blood lipid concentration (total cholesterol, non-high-density lipoprotein-cholesterol, phospholipids, and apolipoprotein B). Ka supplementation in high-fat-induced obesity mice reduced hepatic steatosis and insulin resistance by modulating the hepatic lipid (glucose-6-phosphate dehydrogenase, fatty acid synthase, malic enzyme, phosphatidate phosphohydrolase, and β-oxidation) activities and glucose (glucokinase, phosphoenolpyruvate carboxykinase, and G6pase)-regulating enzymes. Ka supplementation ameliorated the erythrocyte and hepatic mitochondrial H2O2 and inflammation levels (plasma tumor necrosis factor-alpha, monocyte chemoattractant protein-1, interleukin-6, and interferon-gamma and fibrosis of liver and epididymal fat).

CONCLUSION

Ka may be beneficial for preventing diet-induced obesity, inflammation, oxidative stress, and diabetes.

Mitochondria-Derived Vesicles, Sterile Inflammation, and Pyroptosis in Liver Cancer: Partners in Crime or Innocent Bystanders?

Alterations in cellular signaling, chronic inflammation, and tissue remodeling contribute to hepatocellular carcinoma (HCC) development. The release of damage-associated molecular patterns (DAMPs) upon tissue injury and the ensuing sterile inflammation have also been attributed a role in HCC pathogenesis. Cargoes of extracellular vesicles (EVs) and/or EVs themselves have been listed among circulating DAMPs but only partially investigated in HCC. Mitochondria-derived vesicles (MDVs), a subpopulation of EVs, are another missing link in the comprehension of the molecular mechanisms underlying the onset and progression of HCC biology. EVs have been involved in HCC growth, dissemination, angiogenesis, and immunosurveillance escape. The contribution of MDVs to these processes is presently unclear. Pyroptosis triggers systemic inflammation through caspase-dependent apoptotic cell death and is implicated in tumor immunity. The analysis of this process, together with MDV characterization, may help capture the relationship among HCC development, mitochondrial quality control, and inflammation. The combination of immune checkpoint inhibitors (i.e., atezolizumab and bevacizumab) has been approved as a synergistic first-line systemic treatment for unresectable or advanced HCC. The lack of biomarkers that may allow prediction of treatment response and, therefore, patient selection, is a major unmet need. Herein, we overview the molecular mechanisms linking mitochondrial dysfunction, inflammation, and pyroptosis, and discuss how immunotherapy targets, at least partly, these routes.

A potential link between plasma short‑chain fatty acids, TNF‑α level and disease progression in non‑alcoholic fatty liver disease: A retrospective study

The onset and progression of non-alcoholic fatty liver disease (NAFLD) remains unclear, but short-chain fatty acids (SCFAs) in circulation may participate in its pathogenesis by acting as inflammation inhibitors. The aim of this retrospective study was to investigate plasma concentrations of general SCFAs in healthy individuals and in patients with distinct stages of NAFLD. Three main SCFAs (including acetate, propionate and butyrate) were analyzed by gas chromatography. The plasma TNF-α concentration was measured by ELISA. One-way ANOVA, Spearman's correlation and Pearson's correlation analysis were performed to estimate the associations between SCFAs, TNF-α and disease progression. Multiple linear stepwise regression was computed to explore the predictor variables of TNF-α in circulation. A total of 71 patients with NAFLD [including 27 patients with NAFL, 20 patients with non-alcoholic steatohepatitis (NASH) and 24 patients with NAFLD-related cirrhosis (NAFLD-cirrhosis)] and 9 healthy control (HC) subjects were enrolled for analysis. Although not statistically significant, plasma SCFAs were elevated in patients with NAFL compared with HC subjects, whereas the vast majority of SCFAs were statistically reduced in patients with NASH or NAFLD-cirrhosis compared with patients with NAFL. Plasma SCFAs had no significant differences in NASH or NAFLD-cirrhosis patients compared with HC subjects. In addition, significant negative correlations were observed between TNF-α and SCFAs. The progression of NAFLD (β=0.849; P<0.001) and the decline of the total three SCFA concentrations (β=-0.189; P<0.001) were recognized as independent risk variables related to the elevated peripheral TNF-α in the multiple linear stepwise regression model. Plasma SCFA concentrations may alter with the development of NAFLD and may have a potential link to TNF-α and the progression of NAFLD, which may serve a protective role toward disease advancement. Further mechanistic studies, such as analysis of gastrointestinal microecology, signaling pathways and functions involved in TNF-α, need to be performed. Also, therapeutic supplementation of SCFAs for NASH and NAFLD-cirrhosis needs further research and verification.

Mitochondrial Dysfunction Plays Central Role in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a global pandemic that affects one-quarter of the world’s population. NAFLD includes a spectrum of progressive liver disease from steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis and can be complicated by hepatocellular carcinoma. It is strongly associated with metabolic syndromes, obesity, and type 2 diabetes, and it has been shown that metabolic dysregulation is central to its pathogenesis. Recently, it has been suggested that metabolic- (dysfunction) associated fatty liver disease (MAFLD) is a more appropriate term to describe the disease than NAFLD, which puts increased emphasis on the important role of metabolic dysfunction in its pathogenesis. There is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Impaired mitochondrial fatty acid oxidation and, more recently, a reduction in mitochondrial quality, have been suggested to play a major role in NAFLD development and progression. In this review, we provide an overview of our current understanding of NAFLD and highlight how mitochondrial dysfunction contributes to its pathogenesis in both animal models and human subjects. Further we discuss evidence that the modification of mitochondrial function modulates NAFLD and that targeting mitochondria is a promising new avenue for drug development to treat NAFLD/NASH.

Inflammatory Bowel Disease-associated Fatty Liver Disease: the Potential Effect of Biologic Agents

Inflammatory bowel diseases [IBD] exhibit intestinal and systemic manifestations. Nonalcoholic fatty liver disease [NAFLD] is a common co-existing condition, possibly contributing to the cardio-metabolic burden and overall morbidity. Εmerging therapeutic choices of biologic agents have modified the clinical course of IBD; however, their impact on IBD-associated NAFLD has not been extensively evaluated. The prevalence of NAFLD varies among IBD patients, but it appears higher than in the general population in the majority of quality studies. In terms of pathogenetic and risk factors of NAFLD, they may vary with IBD activity. Dysbiosis, mucosal damage, and cytokine release have been implicated in the pathogenesis during the relapses, whereas metabolic risk factors seem to play a dominant role during the remissions of IBD. Considering biologics, although quality data are scarce, agents suppressing tumour necrosis factor may offer potential benefits in IBD-associated NAFLD, whereas anti-integrins do not appear to confer any therapeutic advantage. In conclusion, IBD-associated NAFLD possibly follows two different patterns, one manifested during the relapses and one during the remissions of IBD. Some, but not all, biologics may benefit NAFLD in patients with IBD. Further mechanistic and prospective cohort studies are warranted to illuminate the effects of various biologics on NAFLD.

Aggravation of hepatic lipidosis in red-footed tortoise Chelonoidis carbonaria with age is associated with alterations in liver mitochondria

The occurrence of hepatic lipidosis is commonly reported in different reptilian species, especially in animals under captivity. Liver accumulation of fat is associated with disorders, better described in mammals as non-alcoholic fatty liver diseases (NAFLD), ranging from simple steatosis, to non-alcoholic steatohepatitis (NASH), and to more severe lesions of cirrhosis and hepatocellular carcinoma. Mitochondria play a central role in NAFLD pathogenesis, therefore in this study we characterized livers of ad libitum fed captive red-footed tortoise Chelonoidis carbonaria through histological and mitochondrial function evaluations of juvenile and adult individuals. Livers from adult tortoises exhibited higher levels of lipids, melanomacrophages centers and melanin than juveniles. The observed high score levels of histopathological alterations in adult tortoises, such as microvesicular steatosis, inflammation and fibrosis, indicated the progression to a NASH condition. Mitochondrial oxygen consumption at different respiratory states and with different substrates was 30 to 58% lower in adult when compared to juvenile tortoises. Despite citrate synthase activity was also lower in adults, cardiolipin content was similar to juveniles, indicating that mitochondrial mass was unaffected by age. Mitochondrial Ca²⁺ retention capacity was reduced by 70% in adult tortoises. Overall, we found that aggravation of NAFLD in ad libitum fed captive tortoises is associated with compromised mitochondrial function, indicating a critical role of the organelle in liver disease progression in reptiles.

Lipotoxicity as the Leading Cause of Non-Alcoholic Steatohepatitis

The emerging issues nowadays are non-alcoholic fatty liver disease (NAFLD) and its advanced stage non-alcoholic steatohepatitis (NASH), which further can be a predisposing factor for chronic liver complications, such as cirrhosis and/or development of hepatocellular carcinoma (HCC). Liver lipotoxicity can influence the accumulation of reactive oxygen species (ROS), so oxidative stress is also crucial for the progression of NASH. Moreover, NASH is in strong connection with metabolic disorders, and supporting evidence shows that insulin resistance (IR) is in a close relation to NAFLD, as it is involved in the progression to NASH and further progression to hepatic fibrosis. The major issue is that, at the moment, NASH treatment is based on lifestyle changes only due to the fact that no approved therapeutic options are available. The development of new therapeutic strategies should be conducted towards the potential NAFLD and NASH treatment by the modulation of IR but also by dietary antioxidants. As it seems, NASH is going to be the leading indication for liver transplantation as a consequence of increased disease prevalence and the lack of approved treatment; thus, an effective solution is needed as soon as possible.

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments.

Protective Effects of Almond Oil on Streptozotocin-Induced Diabetic Rats via Regulating Nrf2/HO-1 Pathway and Gut Microbiota

Almond oil has been used as a medicine substitution for its numerous health benefits. This study aimed to evaluate the effect of almond oil on streptozotocin- (STZ-) induced diabetic rats for 4 weeks. The results showed that the administration of almond oil could significantly increase body weight, attenuate abnormally elevated blood glucose, promote insulin secretion, and improve glucose tolerance. Almond oil treatment also suppressed oxidative stress, reduced inflammation reaction, improved liver and kidney function, upregulated the expressions of Nrf2, HO-1, and NQO1, while downregulating the expression of Keap1. Furthermore, almond oil reversed the gut microbiota change by STZ and regulated the gut microbiota associated with glucose metabolism. At the phylum level, the relative abundance of Firmicutes was decreased, while Bacteroidetes was increased by almond oil treatment. More importantly, the ratio of Firmicutes/Bacteroidetes was significantly increased. At the genus level, administration of almond oil increased the abundances of Lactobacillus, Bacteroides, and Lachnospiraceae_NK4A136_group, while decreased the abundances of Ruminococcaceae_UCG-014, Clostridium_sensu_stricto_1, and Fusicatenibacter. These results provided evidence for the regulating effect of almond oil on diabetic rats via the Nrf2/HO-1 pathway and gut microbiota.

The role of uric acid in inflammasome-mediated kidney injury

PURPOSE OF REVIEW

Uric acid is produced after purine nucleotide degradation, upon xanthine oxidase catalytic action. In the evolutionary process, humans lost uricase, an enzyme that converts uric acid into allantoin, resulting in increased serum uric acid levels that may vary according to dietary ingestion, pathological conditions, and other factors. Despite the controversy over the inflammatory role of uric acid in its soluble form, crystals of uric acid are able to activate the NLRP3 inflammasome in different tissues. Uric acid, therefore, triggers hyperuricemic-related disease such as gout, metabolic syndrome, and kidney injuries. The present review provides an overview on the role of uric acid in the inflammasome-mediated kidney damage.

RECENT FINDINGS

Hyperuricemia is present in 20-35% of patients with chronic kidney disease. However, whether this increased circulating uric acid is a risk factor or just a biomarker of renal and cardiovascular injuries has become a topic of intense discussion. Despite these conflicting views, several studies support the idea that hyperuricemia is indeed a cause of progression of kidney disease, with a putative role for soluble uric acid in activating renal NLRP3 inflammasome, in reprograming renal and immune cell metabolism and, therefore, in promoting kidney inflammation/injury.

SUMMARY

Therapies aiming to decrease uric acid levels prevent renal NLRP3 inflammasome activation and exert renoprotective effects in experimental kidney diseases. However, further clinical studies are needed to investigate whether reduced circulating uric acid can also inhibit the inflammasome and be beneficial in human conditions.

A Study on the Therapeutic Efficacy of San Zi Yang Qin Decoction for Non-Alcoholic Fatty Liver Disease and the Underlying Mechanism Based on Network Pharmacology

OBJECTIVE

This study aims to explore the therapeutic efficacy of San Zi Yang Qin Decoction (SZ) and its potential mechanism in the treatment of non-alcoholic fatty liver disease (NAFLD) based on network pharmacology and in vivo experiments.

METHODS

Effective chemicals and targets of SZ were searched in online databases, according to the drug-likeness of compounds and the binomial distribution of targets. A disease-target-chemical network was established using NAFLD-associated genes screened through GeneCards database, Gene Ontology (GO) terms, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Furthermore, animal experiments were conducted to verify the efficacy and mechanism of SZ predicted by network pharmacology. The NAFLD mouse model was established with C57BL/6J mice fed with a high-fat diet for 22 weeks. The mice in the control group were fed with a chow diet. From the 23rd week, the NAFLD mice were treated with intragastric SZ or normal saline for 8 weeks. After the glucose tolerance was measured, the mice were sacrificed, followed by the collection of serum and liver tissues. Pathological changes in liver tissues were examined by H&E staining. Additionally, alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum fast blood glucose, and insulin levels were detected. Expression levels of TNF-α of serum and liver tissues were determined by ELISA and qRT-PCR, respectively. Western blot was used to detect the activation of AKT in liver tissues.

RESULTS

A total of 27 effective compounds and 20 targets of SZ were screened. GO analysis uncovered a significant correlation between the targets of SZ and those of NAFLD. KEGG analysis presented the signaling pathways enriched in SZ and NAFLD, including NAFLD, TNF-α, and apoptosis pathways. The area under the curve of major GO and KEGG pathways indicated the potential role of SZ in improving NAFLD. In vivo experiments demonstrated that SZ significantly alleviated hepatosteatosis and inflammatory cell infiltration in liver tissues, reduced serum transaminases, and improved insulin resistance and glucose tolerance of NAFLD mice. The protein level of phospho-AKT was upregulated by SZ. Additionally, SZ treatment obviously impaired the TNF-α level in the serum and liver tissue of NAFLD mice.

CONCLUSIONS

According to the network pharmacology analysis and in vivo experiments, SZ could have therapeutic efficacy for NALFD. The mechanism mainly involves pathways relative to insulin resistance, TNF-α, and apoptosis. Our results provide a scientific basis for SZ in the clinical treatment of NAFLD.

Immunity as Cornerstone of Non-Alcoholic Fatty Liver Disease: The Contribution of Oxidative Stress in the Disease Progression

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome and has become the major cause of chronic liver disease, especially in western countries. NAFLD encompasses a wide spectrum of hepatic histological alterations, from simple steatosis to steatohepatitis and cirrhosis with a potential development of hepatocellular carcinoma. Non-alcoholic steatohepatitis (NASH) is characterized by lobular inflammation and fibrosis. Several studies reported that insulin resistance, redox unbalance, inflammation, and lipid metabolism dysregulation are involved in NAFLD progression. However, the mechanisms beyond the evolution of simple steatosis to NASH are not clearly understood yet. Recent findings suggest that different oxidized products, such as lipids, cholesterol, aldehydes and other macromolecules could drive the inflammation onset. On the other hand, new evidence indicates innate and adaptive immunity activation as the driving force in establishing liver inflammation and fibrosis. In this review, we discuss how immunity, triggered by oxidative products and promoting in turn oxidative stress in a vicious cycle, fuels NAFLD progression. Furthermore, we explored the emerging importance of immune cell metabolism in determining inflammation, describing the potential application of trained immune discoveries in the NASH pathological context.

Impairment of PGC-1 Alpha Up-Regulation Enhances Nitrosative Stress in the Liver during Acute Pancreatitis in Obese Mice

Acute pancreatitis is an inflammatory process of the pancreatic tissue that often leads to distant organ dysfunction. Although liver injury is uncommon in acute pancreatitis, obesity is a risk factor for the development of hepatic complications. The aim of this work was to evaluate the role of PGC-1α in inflammatory response regulation in the liver and its contribution to the detrimental effect of obesity on the liver during acute pancreatitis. For this purpose, we induced acute pancreatitis by cerulein in not only wild-type (WT) and PGC-1α knockout (KO) mice, but also in lean and obese mice. PGC-1α levels were up-regulated in the mice livers with pancreatitis. The increased PGC-1α levels were bound to p65 to restrain its transcriptional activity toward Nos2. Lack of PGC-1α favored the assembly of the p65/phospho-STAT3 complex, which promoted Nos2 expression during acute pancreatitis. The increased transcript Nos2 levels and the pro-oxidant liver status caused by the down-regulated expression of the PGC-1α-dependent antioxidant genes enhanced nitrosative stress and decreased energy charge in the livers of the PGC-1α KO mice with pancreatitis. It is noteworthy that the PGC-1α levels lowered in the obese mice livers, which increased the Nos2 mRNA expression and protein nitration levels and decreased energy charge during pancreatitis. In conclusion, obesity impairs PGC-1α up-regulation in the liver to cause nitrosative stress during acute pancreatitis.

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.

Mitochondrial oxidative injury: a key player in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. NAFLD is tightly linked to the metabolic syndrome, insulin resistance, and oxidative stress. Globally, its inflammatory form, nonalcoholic steatohepatitis (NASH), has become the main cause of liver-related morbidity and mortality, mainly due to liver cirrhosis and primary liver cancer. One hallmark of NASH is the presence of changes in mitochondrial morphology and function that are accompanied by a blocked flow of electrons in the respiratory chain, which increases formation of mitochondrial reactive oxygen species in a self-perpetuating vicious cycle. Consequences are oxidation of DNA bases and mitochondrial DNA depletion that are coupled with genetic and acquired mitochondrial DNA mutations, all impairing the resynthesis of respiratory chain polypeptides. In general, several maladaptations of pathways that usually maintain energy homeostasis occur with the early and late excess metabolic stress in NAFLD and NASH. We discuss the interplay between hepatocyte mitochondrial stress and inflammatory responses, focusing primarily on events initiated and maintained by mitochondrial free radical-induced damage in NAFLD. Importantly, mitochondrial oxidative stress and dysfunction are modulated by key pharmacological targets that are related to excess production of reactive oxygen species, mitochondrial turnover and the mitochondrial unfolded protein response, mitophagy, and mitochondrial biogenesis. However, the efficacy of such interventions depends on NAFLD/NASH disease stage.

Association between Serum Uric Acid and Nonalcoholic Fatty Liver Disease in Nonobese Postmenopausal Women: A Cross-sectional Study

This study aimed to determine the association between serum uric acid (sUA) and nonalcoholic fatty liver disease (NAFLD) in nonobese postmenopausal women. A total of 4323 female individuals over 18 years of age participated in this cross-sectional study. The subjects were divided into four groups according to menopause status and body mass index. sUA quartiles in this female population were categorized as follows: Q1 ≤ 230 mmol/L, Q2: 231-270 mmol/L, Q3: 271-310 mmol/L and Q4: ≥ 311 mmol/L. The presence or absence of NAFLD was assessed by abdominal ultrasonography. The prevalence of NAFLD was 38.8% in the general population, and the average age was 46.5 ± 11.3 years. Among nonobese and obese subjects, the prevalence of NAFLD was lower in nonmenopausal subjects than in postmenopausal subjects (nonobese: 20.74% vs 45.26%, respectively, P < 0.0001; obese: 70.51% vs 84.35%, respectively, P < 0.0001). After adjusting for age, current smoking status, current alcohol drinking status, diabetes, hypertension disease and triglyceride, the ORs (95% CIs) for NAFLD among individuals in Q2-Q4 were 1.518 (1.062-2.169), 1.431 (1.010-2.027) and 2.054 (1.442-2.927), respectively, P value for trend <0.0001. Higher sUA levels can be used as a predictive biomarker for NAFLD in nonobese postmenopausal women.

Role of oxidative stress in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide and is strongly associated with the presence of oxidative stress. Disturbances in lipid metabolism lead to hepatic lipid accumulation, which affects different reactive oxygen species (ROS) generators, including mitochondria, endoplasmic reticulum, and NADPH oxidase. Mitochondrial function adapts to NAFLD mainly through the downregulation of the electron transport chain (ETC) and the preserved or enhanced capacity of mitochondrial fatty acid oxidation, which stimulates ROS overproduction within different ETC components upstream of cytochrome c oxidase. However, non-ETC sources of ROS, in particular, fatty acid β-oxidation, appear to produce more ROS in hepatic metabolic diseases. Endoplasmic reticulum stress and NADPH oxidase alterations are also associated with NAFLD, but the degree of their contribution to oxidative stress in NAFLD remains unclear. Increased ROS generation induces changes in insulin sensitivity and in the expression and activity of key enzymes involved in lipid metabolism. Moreover, the interaction between redox signaling and innate immune signaling forms a complex network that regulates inflammatory responses. Based on the mechanistic view described above, this review summarizes the mechanisms that may account for the excessive production of ROS, the potential mechanistic roles of ROS that drive NAFLD progression, and therapeutic interventions that are related to oxidative stress.

Interplay between NADH oxidation by complex I, glutathione redox state and sirtuin-3, and its role in the development of insulin resistance

Metabolic diseases are characterized by high NADH/NAD⁺ ratios due to excessive electron supply, causing defective mitochondrial function and impaired sirtuin-3 (SIRT-3) activity, the latter driving to oxidative stress and altered fatty acid β-oxidation. NADH is oxidized by the complex I in the electron transport chain, thereby factors inhibiting complex I like acetylation, cardiolipin peroxidation, and glutathionylation by low GSH/GSSG ratios affects SIRT3 function by increasing the NADH/NAD⁺ ratio. In this review, we summarized the evidence supporting a role of the above events in the development of insulin resistance, which is relevant in the pathogenesis of obesity and diabetes. We propose that maintenance of proper NADH/NAD⁺ and GSH/GSSG ratios are central to ameliorate insulin resistance, as alterations in these redox couples lead to complex I dysfunction, disruption of SIRT-3 activity, ROS production and impaired β-oxidation, the latter two being key effectors of insulin resistance.

Use of a bioengineered antioxidant in mouse models of metabolic syndrome

Background: Oxidative stress has been implicated in metabolic syndrome (MetS); however, antioxidants such as vitamin E have had limited success in the clinic. This prompts the question of what effects amore potent antioxidant might produce. A prime candidate is the recently developed bioengineered antioxidant, poly(ethylene glycol)-functionalizedhydrophilic carbon clusters (PEG-HCCs), which are capable of neutralizing the reactive oxygen species (ROS) superoxide anion and hydroxyl radical at10⁶/molecule of PEG-HCC. In this project, we tested the potential of PEG-HCCs as a possible therapeutic for MetS.Results: PEG-HCC treatment lessened lipid peroxidation, aspartate aminotransferase levels, non-fastingblood glucose levels, and JNK phosphorylation inob/ob mice. PEG-HCC-treated WT mice had an increased response to insulin by insulin tolerance tests and adecrease in blood glucose by glucose tolerance tests. These effects were not observed in HFD-fed mice, regardless of treatment. PEG-HCCs were observed in the interstitial space of liver, spleen, skeletal muscle, and adipose tissue. No significant difference was shown in gluconeogenesis or inflammatory gene expression between treatment and dietary groups.Expert Opinion: PEG-HCCs improved some parameters of disease possibly due to a resulting increase in peripheral insulin sensitivity. However, additional studies are needed to elucidate how PEG-HCCsare producing these effects.

Mitochondrial dysfunction stimulates HBV gene expression through lipogenic transcription factor activation

In previous studies, we showed two consistent findings regarding the functional relationship between hepatitis B virus (HBV) gene expression and hepatic lipid accumulation. One is that HBV X (HBx) protein expression induces hepatic lipid accumulation via specific transcriptional activation. The other is that hepatic rich lipids increase HBV gene expression. A variety of transcription factors, including nuclear receptors have been defined as regulators of HBV promoters and enhancers. However, the association between these metabolic events and HBV gene expression remains to be clearly elucidated. Here, we showed that lipid accumulation due to mitochondrial dysfunction is associated with an increase in HBV gene expression. Saturated fatty acids increase the expression of lipogenic factors cooperated with C/EBPα and LXRα. In addition, activation of PPARγ and SREBP-1 by fatty acids derived from hepatic lipid accumulation was found to increase HBV gene expression through mitochondrial dysfunction. These results provide that metabolic changes in the hepatic cells play a critical role in the HBV gene induction.

Association between Serum Uric Acid and Non-Alcoholic Fatty Liver Disease according to Different Menstrual Status Groups

OBJECTIVE

The present study aimed to explore the association between SUA and NAFLD in women with different menstrual statuses.

METHODS

A total of 6043 women were selected from the Jidong and Kailuan communities for inclusion in the present study. The SUA levels of participants were divided into quartiles. NAFLD was determined by abdominal ultrasonography. Data from laboratory tests and clinical examination were collected, and basic information was obtained from standardized questionnaires. The menstrual status was stratified into menstrual period, menopause transition period, and postmenopause. Multivariate logistic regression models were used to determine the relationship between menstrual status, SUA, and NAFLD.

RESULTS

The levels of SUA in subjects with NAFLD in the menstrual period, menopause transition period, and postmenopause were 268.0 ± 71.1, 265.6 ± 67.8, and 286.7 ± 75.8 (mmol/L), respectively, and were higher than those in subjects without NAFLD. The adjusted odds ratios (ORs) with 95% confidence interval (CI) for NAFLD among participants in the menopause transition period and postmenopausal period were 1.10 (0.89-1.37) and 1.28 (1.04-1.58), respectively, compared with the menstrual period women. Compared to the lowest quartile of SUA, the adjusted ORs with 95% CI of the highest quartile for NAFLD were 2.24 (1.69-2.99) for females in the menstrual period, 1.92 (1.10-3.37) for females in the menopause transition period, and 1.47 (1.06-2.03) for females in postmenopause.

CONCLUSIONS

Menstrual status was significantly correlated with NAFLD. High levels of SUA were associated with NAFLD in females during the three menstrual periods.

miR-873-5p targets mitochondrial GNMT-Complex II interface contributing to non-alcoholic fatty liver disease

Objective

Non-alcoholic fatty liver disease (NAFLD) is a complex pathology in which several dysfunctions, including alterations in metabolic pathways, mitochondrial functionality and unbalanced lipid import/export, lead to lipid accumulation and progression to inflammation and fibrosis. The enzyme glycine N-methyltransferase (GNMT), the most important enzyme implicated in S-adenosylmethionine catabolism in the liver, is downregulated during NAFLD progression. We have studied the mechanism involved in GNMT downregulation by its repressor microRNA miR-873-5p and the metabolic pathways affected in NAFLD as well as the benefit of recovery GNMT expression.

Methods

miR-873-5p and GNMT expression were evaluated in liver biopsies of NAFLD/NASH patients. Different in vitro and in vivo NAFLD murine models were used to assess miR-873-5p/GNMT involvement in fatty liver progression through targeting of the miR-873-5p as NAFLD therapy.

Results

We describe a new function of GNMT as an essential regulator of Complex II activity in the electron transport chain in the mitochondria. In NAFLD, GNMT expression is controlled by miR-873-5p in the hepatocytes, leading to disruptions in mitochondrial functionality in a preclinical murine non-alcoholic steatohepatitis (NASH) model. Upregulation of miR-873-5p is shown in the liver of NAFLD/NASH patients, correlating with hepatic GNMT depletion. Importantly, NASH therapies based on anti-miR-873-5p resolve lipid accumulation, inflammation and fibrosis by enhancing fatty acid β-oxidation in the mitochondria. Therefore, miR-873-5p inhibitor emerges as a potential tool for NASH treatment.

Conclusion

GNMT participates in the regulation of metabolic pathways and mitochondrial functionality through the regulation of Complex II activity in the electron transport chain. In NAFLD, GNMT is repressed by miR-873-5p and its targeting arises as a valuable therapeutic option for treatment.

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The microRNA miR-873-5p is upregulated in human and murine NAFLD/NASH livers.

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miR-873-5p upregulation downregulates GNMT in the liver.

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miR-873-5p inhibition reduces liver steatosis, inflammation and fibrosis in in vivo NAFLD mouse models.

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GNMT is a hepatic metabolic hub with mitochondria activity through the regulation of Complex II of the ETC.

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Mitochondrial GNMT deficiency compromises ETC functionality and metabolism.

Genome-wide association analysis for β-hydroxybutyrate concentration in Milk in Holstein dairy cattle

BACKGROUND

Ketosis in dairy cattle has been shown to cause a high morbidity in the farm and substantial financial losses to dairy farmers. Ketosis symptoms, however, are difficult to identify, therefore, the amount of ketone bodies (mainly β-hydroxybutyric acid, BHB) is used as an indicator of subclinical ketosis in cows. It has also been shown that milk BHB concentrations have a strong correlation with ketosis in dairy cattle. Mid-infrared spectroscopy (MIR) has recently became a fast, cheap and high-throughput method for analyzing milk components. The aim of this study was to perform a genome-wide association study (GWAS) on the MIR-predicted milk BHB to identify genomic regions, genes and pathways potentially affecting subclinical ketosis in North American Holstein dairy cattle.

RESULTS

Several significant regions were identified associated with MIR-predicted milk BHB concentrations (indicator of subclinical ketosis) in the first lactation (SCK1) and second and later lactations (SCK2) in Holstein dairy cows. The strongest association was located on BTA6 for SCK1 and BTA14 on SCK2. Several SNPs on BTA6 were identified in regions and variants reported previously to be associated with susceptibility to ketosis and clinical mastitis in Jersey and Holstein dairy cattle, respectively. One highly significant SNP on BTA14 was found within the DGAT1 gene with known functions on fat metabolism and inflammatory response in dairy cattle. A region on BTA6 and three SNPs on BTA20 were found to overlap between SCK1 and SCK2. However, a novel region on BTA20 (55-63 Mb) for SCK2 was also identified, which was not reported in previous association studies. Enrichment analysis of the list of candidate genes within the identified regions for MIR-predicted milk BHB concentrations yielded molecular functions and biological processes that may be involved in the inflammatory response and lipid metabolism in dairy cattle.

CONCLUSIONS

The results of this study confirmed several SNPs and genes identified in previous studies as associated with ketosis susceptibility and immune response, and also found a novel region that can be used for further analysis to identify causal variations and key regulatory genes that affect clinical/ subclinical ketosis.

Acute fatty liver of pregnancy and concomitant medical conditions: A review of cases at a quaternary obstetric hospital

Acute fatty liver of pregnancy is a rare complication of pregnancy that may result in fulminant hepatic failure. We present a review of all patients presenting to a quaternary obstetric hospital over a 15-year period, with particular regard to biochemical changes, results of gene testing, and pre-existing conditions. Seventeen patients with acute fatty liver of pregnancy were identified. Six patients were documented to have pre-existing gastrointestinal disease; five with inflammatory bowel disease, and one with influenza A hepatitis. Antithrombin III levels were low in this study, consistent with previously published data. There were no recurrences of acute fatty liver of pregnancy in nine subsequent pregnancies to seven mothers. The authors are not aware of any literature addressing pre-existing medical conditions which may predispose to acute fatty liver of pregnancy.

Mitochondrial Oxidative Stress and Antioxidants Balance in Fatty Liver Disease

Fatty liver disease is one of the most prevalent forms of chronic liver disease that encompasses both alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are intermediate stages of ALD and NAFLD, which can progress to more advanced forms, including cirrhosis and hepatocellular carcinoma. Oxidative stress and particularly alterations in mitochondrial function are thought to play a significant role in both ASH and NASH and recognized to contribute to the generation of reactive oxygen species (ROS), as documented in experimental models. Despite the evidence of ROS generation, the therapeutic efficacy of treatment with antioxidants in patients with fatty liver disease has yielded poor results. Although oxidative stress is considered to be the disequilibrium between ROS and antioxidants, there is evidence that a subtle balance among antioxidants, particularly in mitochondria, is necessary to avoid the generation of ROS and hence oxidative stress. Conclusion: As mitochondria are a major source of ROS, the present review summarizes the role of mitochondrial oxidative stress in ASH and NASH and presents emerging data indicating the need to preserve mitochondrial antioxidant balance as a potential approach for the treatment of human fatty liver disease, which may pave the way for the design of future trials to test the therapeutic role of antioxidants in fatty liver disease.

Acute fatty liver of pregnancy in a woman with ulcerative colitis and familial hidradenitis suppurativa

Acute fatty liver of pregnancy is a heterogeneous disorder which may occur in the absence of a detectable gene mutation for the enzyme long-chain L-3-hydroxyacyl-CoA dehydrogenase. Acute fatty liver of pregnancy has been reported to complicate several gastrointestinal disorders including viral hepatitis, chronic active hepatitis and intrahepatic cholestasis of pregnancy. A case of acute fatty liver of pregnancy in a woman with ulcerative colitis and familial hidradenitis suppurativa without a detectable gene mutation is presented. The potential role of inflammatory cytokines in precipitating acute fatty liver of pregnancy is discussed.

Mitochondrial role in the neonatal predisposition to developing nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global epidemic in obese children and adults, and the onset might have fetal origins. A growing body of evidence supports the role of developmental programming, whereby the maternal environment affects fetal and infant development, altering the risk profile for disease later in life. Human and nonhuman primate studies of maternal obesity demonstrate that risk factors for pediatric obesity and NAFLD begin in utero. The pathologic mechanisms for NAFLD are multifactorial but have centered on altered mitochondrial function/dysfunction that might precede insulin resistance. Compared with the adult liver, the fetal liver has fewer mitochondria, low activity of the fatty acid metabolic enzyme carnitine palmitoyl-CoA transferase-1, and little or no gluconeogenesis. Exposure to excess maternal fuels during fetal life uniquely alters hepatic fatty acid oxidation, tricarboxylic acid cycle activity, de novo lipogenesis, and mitochondrial health. These events promote increased oxidative stress and excess triglyceride storage, and, together with altered immune function and epigenetic changes, they prime the fetal liver for NAFLD and might drive the risk for nonalcoholic steatohepatitis in the next generation.

Possible Involvement of Mitochondrial Dysfunction and Oxidative Stress in a Cellular Model of NAFLD Progression Induced by Benzo[a]pyrene/Ethanol CoExposure

Exposure to xenobiotics could favor the transition of nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis in obese patients. Recently, we showed in different models of NAFL that benzo[a]pyrene (B[a]P) and ethanol coexposure induced a steatohepatitis-like state. One model was HepaRG cells incubated with stearate and oleate for 2 weeks. In the present study, we wished to determine in this model whether mitochondrial dysfunction and reactive oxygen species (ROS) overproduction could be involved in the occurrence of this steatohepatitis-like state. CRISPR/Cas9-modified cells were also used to specify the role of aryl hydrocarbon receptor (AhR), which is potently activated by B[a]P. Thus, nonsteatotic and steatotic HepaRG cells were treated with B[a]P, ethanol, or both molecules for 2 weeks. B[a]P/ethanol coexposure reduced mitochondrial respiratory chain activity, mitochondrial respiration, and mitochondrial DNA levels and induced ROS overproduction in steatotic HepaRG cells. These deleterious effects were less marked or absent in steatotic cells treated with B[a]P alone or ethanol alone and in nonsteatotic cells treated with B[a]P/ethanol. Our study also disclosed that B[a]P/ethanol-induced impairment of mitochondrial respiration was dependent on AhR activation. Hence, mitochondrial dysfunction and ROS generation could explain the occurrence of a steatohepatitis-like state in steatotic HepaRG cells exposed to B[a]P and ethanol.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Fructose and sugar: A major mediator of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome; its rising prevalence parallels the rise in obesity and diabetes. Historically thought to result from overnutrition and a sedentary lifestyle, recent evidence suggests that diets high in sugar (from sucrose and/or high-fructose corn syrup [HFCS]) not only increase the risk of NAFLD, but also non-alcoholic steatohepatitis (NASH). Herein, we review the experimental and clinical evidence that fructose precipitates fat accumulation in the liver, due to both increased lipogenesis and impaired fat oxidation. Recent evidence suggests that the predisposition to fatty liver is linked to the metabolism of fructose by fructokinase C, which results in ATP consumption, nucleotide turnover and uric acid generation that mediate fat accumulation. Alterations to gut permeability, the microbiome, and associated endotoxemia contribute to the risk of NAFLD and NASH. Early clinical studies suggest that reducing sugary beverages and total fructose intake, especially from added sugars, may have a significant benefit on reducing hepatic fat accumulation. We suggest larger, more definitive trials to determine if lowering sugar/HFCS intake, and/or blocking uric acid generation, may help reduce NAFLD and its downstream complications of cirrhosis and chronic liver disease.

Sennoside A protects mitochondrial structure and function to improve high-fat diet-induced hepatic steatosis by targeting VDAC1

Mitochondrial dysfunction is mainly associated with high-fat-diet (HFD)-induced hepatic steatosis. Sennoside A (SA), a commonly used clinical stimulant laxative, is reported to improve energy metabolism and insulin resistance. However, the effect and mechanism of SA on HFD-induced hepatic steatosis remain largely unknown. The aim of this study was to determine the effect and mechanism of SA on HFD-induced hepatic steatosis in mice. We examined the liver and body weight of mice to evaluate the physical changes in the liver. Hematoxylin and eosin (H&E) and oil red O staining were used to detect the lipid accumulation. The mitochondrial structure and function were tested by transmission electron microscopy and the Seahorse XF24 Analyzer. Furthermore, mitochondrial complexes I, II, and IV and voltage-dependent anion channel 1 (VDAC1) protein activity were detected to understand the mechanism of the protective effect on mitochondria. As a result, damage to the structure and function in the hepatic mitochondria of HFD-induced hepatic steatosis was observed in mice. The structural damage was in the form of loss of cristae, mitochondrial swelling, vacuolization and even rupturing of the outer mitochondrial membrane (OMM). Functional alterations were found by activation of complex I and deficiency in complexes II and IV. The VDAC1 activity and the total ATP in the liver tissue was increased under hepatic steatosis conditions. The above effects were reversed by SA. These data suggest that inhibition of VDAC1 may be an underlying mechanism of SA for protecting mitochondria in HFD-induced hepatic steatosis in mice. Thus, VDAC1 may be a promising target for treating fatty liver disease.

Associations of hyperuricemia and obesity with remission of nonalcoholic fatty liver disease among Chinese men: A retrospective cohort study

Nonalcoholic fatty liver disease (NAFLD) is a common chronic disease that is associated with high serum uric acid (SUA) levels, although the effects of high SUA levels on NAFLD remission remain unclear. In addition, it is unclear whether obesity and high SUA levels have a combined effect on NAFLD remission. This retrospective cohort study evaluated male employees of seven Chinese companies and investigated the association between high SUA levels and NAFLD remission, as well as the potential combined effect of high SUA levels and obesity on NAFLD remission. The study followed 826 men with NAFLD for 4 years, and the NAFLD remission rate was 23.2% (192/826). Comparing to obese and non-obese individuals with normouricemia, individuals with hyperuricemia had significant higher values for total cholesterol, triglycerides, creatinine, and aspartate transaminase (all P < 0.05). Among non-obese individuals, hyperuricemia was associated with a lower NAFLD remission rate, compared to normouricemia (P < 0.001). However, no significant difference was observed between hyperuricemia and normouricemia among obese subjects (P > 0.05). Similar results were observed in the multivariate cox proportional hazard regression analyses. Compared to the normouricemia subjects, individuals with hyperuricemia had a significant lower likelihood of NAFLD remission (RR = 0.535, 95% CI: 0.312-0.916); and obese subjects had a significant lower likelihood of NAFLD remission than the non-obese individuals (RR = 0.635, 95% CI: 0.439-0.918). In addition, the interaction between hyperuricemia and obesity had a statistically significant effect on NAFLD remission (P = 0.048). In conclusion, hyperuricemia and obesity may be involved in NAFLD development and remission, with similar pathogenic mechanisms. Further studies are needed to confirm our findings and determine how to improve these individuals' conditions.

Resveratrol improves high-fat diet induced fatty liver and insulin resistance by concomitantly inhibiting proteolytic cleavage of sterol regulatory element-binding proteins, free fatty acid oxidation, and intestinal triglyceride absorption

Resveratrol (RES) has the ability to ameliorate nonalcoholic fatty liver disease (NAFLD) and the mechanism remains unclear. Hence, using high-fat diet (HFD) obese rat model, we investigated the effect of a low dose of RES (20 mg/kg) on the hepatic sterol regulatory element-binding protein (SREBPs) – lipogenesis pathway, enzymes involved in β-oxidation and activity of pancreatic lipase. Four groups of rats (n = 8) of control (12% of calories as fat) and HFD (40% of calories as fat) were administered orally with either normal saline as a vehicle or RES as a concomitant treatment for 8 weeks on a daily basis. Then, various biochemical, histological, and molecular experiments were carried out. RES prevented the development and progression of NAFLD and significantly improved insulin sensitivity through (1) inhibiting the proteolytic cleavage of SREBPs-1 and SREBPs-2 without affecting their precursor mRNA or protein levels, (2) inhibiting free fatty acid β-oxidation and generation of reactive oxygen species through significant inhibition of CPT-1 and UCP-2, and (3) decreasing activity of pancreatic lipase in vivo and in vitro. In conclusion, our findings are the first in the literature to show new mechanisms of the hepatoprotective effect of RES against HFD induced NAFLD in rats.

Omentectomy Prevents Metabolic Syndrome By Reducing Appetite and Body Weight In A Diet-Induced Obesity Rat Model

Visceral fat deposition is associated with impairment of glucose and lipid metabolism while leptin levels are frequently related to subcutaneous fat area. At present, there is considerable controversy regarding the role of visceral adipose tissue accumulation in the development of metabolic syndrome (MS). Here we show the effects of omentectomy on the liver and MS in a diet induced obesity rat model. Our results reveal that undergoing omentectomy previously the establishment of the diet-induced-obesity reduced significantly body weight gain and avoid the development of MS, including non-alcoholic fatty liver disease. Intriguingly, the significantly lower body weight gain was due to decreased food intake. Omentum drives obesity progression through leptin resistance mediated by C-reactive protein, Interleucin (IL)-6 and high lipolysis activity. Omentum removal reversed immediately the increased plasma levels of CRP and IL-6 and gradually food intake, weight gain, and features of MS in diet-induced-obesity. Omentectomy caused no changes in normal-weigh-rats. This report displays causal mechanism by which omentum promotes obesity and propose omentectomy as a promising procedure in MS prevention.

Zanthoxylum ailanthoides Suppresses Oleic Acid-Induced Lipid Accumulation through an Activation of LKB1/AMPK Pathway in HepG2 Cells

Zanthoxylum ailanthoides (ZA) has been used as folk medicines in East Asian and recently reported to have several bioactivity; however, the studies of ZA on the regulation of triacylglycerol (TG) biosynthesis have not been elucidated yet. In this study, we examined whether the methanol extract of ZA (ZA-M) could reduce oleic acid- (OA-) induced intracellular lipid accumulation and confirmed its mode of action in HepG2 cells. ZA-M was shown to promote the phosphorylation of AMPK and its upstream LKB1, followed by reduction of lipogenic gene expressions. As a result, treatment of ZA-M blocked de novo TG biosynthesis and subsequently mitigated intracellular neutral lipid accumulation in HepG2 cells. ZA-M also inhibited OA-induced production of reactive oxygen species (ROS) and TNF-α, suggesting that ZA-M possess the anti-inflammatory feature in fatty acid over accumulated condition. Taken together, these results suggest that ZA-M attenuates OA-induced lipid accumulation and inflammation through the activation of LKB1/AMPK signaling pathway in HepG2 cells.

Serum markers for mitochondrial dysfunction and cell death are possible predictive indicators for drug-induced liver injury by direct acting antivirals

AIM

We prospectively screened patients treated with direct-acting antivirals (DAA) in order to detect and analyze serum markers that are present prior to the development of drug-induced liver injury (DILI).

METHODS

The levels of various serum markers among DILI, non-DILI and control groups were compared. The DILI group consisted of eight patients whose alanine aminotransferase (ALT) levels exceeded 32 IU/L during the DAA treatment. Eight patients without DILI were selected for the non-DILI group via a matched-group design based on age, sex and disease severity. Additionally, eight healthy volunteers were employed as the controls. Serum measurements of cytokines/chemokines, cytokeratin-18 fragment (CK-18F) and super oxidase dismutase-2 (SOD2) were evaluated on the date at which hepatitis C virus RNA was absent (baseline). For patients with DILI, serum measurements taken before treatment, 1 week before pronounced transaminase elevation (prominence-1 W) and on the date at which pronounced elevation of transaminase occurred (prominence) were also evaluated.

RESULTS

All patients treated with DAA had normalized transaminase levels at baseline. In patients with DILI, interferon-inducible protein-10 (IP-10) levels were higher at prominence-1 W than at baseline. Those patients also had significantly higher levels of SOD2 and CK-18F at prominence-1 W than at baseline.

CONCLUSION

Elevated IP-10 may be a preconditioning chemokine for DAA-induced liver injury, and damage markers associated with cell death and mitochondrial dysfunction are potential predictive serum markers for DILI.

Do flavanols-rich natural products relieve obesity-related insulin resistance?

Growing evidence support that insulin resistance may occur as a severe problem due to chronic energetic overfeeding and subsequent obesity. When an abundance of glucose and saturated fat enter the cell, impaired blood flow, hypoxia, inflammation and macrophage infiltration in obese adipose tissue may induce oxidative stress and insulin resistance. Excessive circulating saturated fatty acids ectopically accumulate in insulin-sensitive tissues and impair insulin action. In this context, excessive hepatic lipid accumulation may play a central, pathogenic role in insulin resistance. It is thought that dietary polyphenols may ameliorate obesity-related insulin resistance by attenuating inflammatory responses and oxidative stress. The most often occurring natural polyphenolic compounds are flavonoids. In this review, the possible mechanistic effect of flavonoid-rich natural products on insulin resistance-related metabolic pathways is discussed. Polyphenol intake can prevent high-fat-diet-induced insulin resistance via cell surface G protein-coupled estrogen receptors by upregulating the expression of related genes, and their pathways, which are responsible for the insulin sensitivity.

Seabuckthorn Leaves Extract and Flavonoid Glycosides Extract from Seabuckthorn Leaves Ameliorates Adiposity, Hepatic Steatosis, Insulin Resistance, and Inflammation in Diet-Induced Obesity

The aim of the current study was to elucidate the effect of seabuckthorn leaves (SL) extract and flavonoid glycosides extract from seabuckthorn leaves (SLG) on diet-induced obesity and related metabolic disturbances, and additionally, to identify whether flavonoid glycosides and other components in SL can exert a possible interaction for the prevention of metabolic diseases by comparing the effect of SL and SLG. C57BL/6J mice were fed a normal diet (ND, AIN-93G purified diet), high-fat diet (HFD, 60 kcal% fat), HFD + 1.8% (w/w) SL (SL), and HFD + 0.04% (w/w) SLG (SLG) for 12 weeks. In high fat-fed mice, SL and SLG decreased the adiposity by suppressing lipogenesis in adipose tissue, while increasing the energy expenditure. SL and SLG also improved hepatic steatosis by suppressing hepatic lipogenesis and lipid absorption, whilst also enhancing hepatic fatty acid oxidation, which may be linked to the improvement in dyslipidemia. Moreover, SL and SLG improved insulin sensitivity by suppressing the levels of plasma GIP that were modulated by secreted resistin and pro-inflammatory cytokine, and hepatic glucogenic enzyme activities. SL, especially its flavonoid glycosides (SLG), can protect against the deleterious effects of diet-induced obesity (DIO) and its metabolic complications such as adiposity, dyslipidemia, inflammation, hepatic steatosis, and insulin resistance.

Saccharin induced liver inflammation in mice by altering the gut microbiota and its metabolic functions

Maintaining the balance of the gut microbiota and its metabolic functions is vital for human health, however, this balance can be disrupted by various external factors including food additives. A range of food and beverages are sweetened by saccharin, which is generally considered to be safe despite controversial debates. However, recent studies indicated that saccharin perturbed the gut microbiota. Inflammation is frequently associated with disruptions of the gut microbiota. The aim of this study is to investigate the relationship between host inflammation and perturbed gut microbiome by saccharin. C57BL/6J male mice were treated with saccharin in drinking water for six months. Q-PCR was used to detect inflammatory markers in mouse liver, while 16S rRNA gene sequencing and metabolomics were used to reveal changes of the gut microbiota and its metabolomic profiles. Elevated expression of pro-inflammatory iNOS and TNF-α in liver indicated that saccharin induced inflammation in mice. The altered gut bacterial genera, enriched orthologs of pathogen-associated molecular patterns, such as LPS and bacterial toxins, in concert with increased pro-inflammatory metabolites suggested that the saccharin-induced liver inflammation could be associated with the perturbation of the gut microbiota and its metabolic functions.

Associations between Serum Uric Acid and the Remission of Non-Alcoholic Fatty Liver Disease in Chinese Males

Epidemiological studies suggest that higher serum uric acid (sUA) level is significantly associated with nonalcoholic fatty liver disease (NAFLD) development. However, little information is available on the relationships between sUA and NAFLD remission. In the present study, 841 NAFLD males (30-75 years) were recruited from a Chinese prospective cohort study (PMMJS) and followed up for five years. The baseline sUA levels of participants were categorized into four quartiles: 191 μmol/L≤ sUA ≤ 347 μmol/L, 347 μmol/L < sUA ≤ 392 μmol/L, 392 μmol/L < sUA ≤ 441 μmol/L and 441 μmol/L<SUA≤676 μmol/L. As the results show, participants with elevated sUA levels at baseline were significantly associated with the decreased rate of NAFLD remission at the end of study (p<0.0001). After adjustment, RR (95%CI) for remitted NAFLD comparing Q1 to Q3 vs Q4 of sUA were 2.95 (1.49-5.83), 2.40 (1.22-4.73) and 1.39 (0.67-2.86), respectively. Furthermore, the sensitivity analysis showed these significant associations were not affected even after exclusion of participants who had hypertension, diabetes mellitus, MetS and hyperlipidemia. Additionally, the presence of the lowest quartile of sUA levels was still significantly associated with remitted NAFLD when the study population was stratified according to the smoking, and the median values of age, ALT, AST, serum creatinine, HDL-C and LDL-C. Therefore, our present study extended the previous findings and suggested that modulation of sUA levels may attenuate the progression of NAFLD.

Prevalence and Factors Associated with Nonalcoholic Fatty Liver Disease in a Nonobese Korean Population

Background/Aims

Nonalcoholic fatty liver disease (NAFLD) is an emerging problem in Asia, but little is known about the disease in the nonobese population. The aims of this study were to investigate the prevalence of NAFLD and the factors associated with it in a nonobese Korean population and to compare the clinical characteristics of nonobese and obese subjects with NAFLD.

Methods

This cross-sectional study used data from 2,058 subjects who participated in a medical checkup program.

Results

The prevalence of NAFLD was 12.4% (213/1,711) in the nonobese population. A higher body mass index (BMI), higher homeostasis model assessment of insulin resistance (HOMA-IR) values, higher alanine aminotransferase (ALT) levels, triglyceride concentrations 150 mg/dL, and hyperuricemia were independently associated with the presence of NAFLD in the nonobese subjects. Compared with the obese subjects with NAFLD, the nonobese subjects with NAFLD were composed of a higher proportion of females and had lower BMIs, smaller waist circumferences, lower HOMA-IR values, and fewer metabolic irregularities.

Conclusions

Higher BMIs, HOMA-IR values, ALT levels, hypertriglyceridemia, and hyperuricemia were associated with NAFLD in the nonobese subjects. Clinicians should be particularly aware of the possibility of NAFLD in nonobese Asian people.

Preventive effects of dietary walnuts on high-fat-induced hepatic fat accumulation, oxidative stress and apoptosis in mice

We hypothesized that dietary walnut would prevent high-fat-diet (HFD)-induced hepatic apoptosis based on its antioxidant properties. Male C57BL/6J mice were fed a rodent chow or HFD (45% energy-derived)±walnuts (21.5% energy-derived) for 6 weeks. Liver histological and biochemical analyses revealed significantly elevated fat accumulation in mice fed HFD compared to mice fed the chow or HFD±walnuts. Walnut supplementation prevented HFD-mediated alteration of the levels of key proteins in lipid homeostasis such as Sirt1, AMPK and FAS, leading to decreased fat accumulation. In addition, walnut supplementation to HFD significantly decreased the hepatic levels of cytochrome P450-2E1, nitrated proteins and lipid peroxidation. Furthermore, walnut supplementation decreased the activated cell-death-associated p-JNK and p-p38K accompanied with increased hepatocyte apoptosis in HFD group. The beneficial effects of dietary walnut likely result, at least partially, from its antioxidant ingredients and attenuating HFD-induced hepatic steatosis, nitroxidative stress and apoptosis.