Manganese superoxide dismutase is reduced in the liver of male but not female humans and rodents with non-alcoholic fatty liver disease

Association between serum trace element, mineral, and amino acid levels with non-alcoholic fatty liver disease (NAFLD) in adult women

The objective of the present study is assessment of serum trace element and amino acid levels in non-alcoholic fatty liver disease (NAFLD) patients with subsequent evaluation of its independent associations with markers of liver injury and metabolic risk.

MATERIALS AND METHODS

140 women aged 20-90 years old with diagnosed NAFLD and 140 healthy women with a respective age range were enrolled in the current study. Analysis of serum and hair levels of trace elements and minerals was performed with inductively-coupled plasma mass-spectrometry (ICP-MS). Serum amino acid concentrations were evaluated by high-pressure liquid chromatography (HPLC) with UV-detection. In addition, routine biochemical parameters including liver damage markers, alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT), were assessed spectrophotometrically.

RESULTS

The findings demonstrated that patients with NAFLD were characterized by higher ALT, GGT, lactate dehydrogenase (LDH) and cholinesterase (CE) activity, as well as increased levels of total cholesterol, low-density lipoprotein cholesterol, triglycerides, and uric acid. NAFLD patients were characterized by reduced serum and hair Co, Se, and Zn levels, as well as hair Cu content and serum Mn concentrations in comparison to controls. Circulating Ala, Cit, Glu, Gly, Ile, Leu, Phe, and Tyr levels in NAFLD patients exceeded those in the control group. Multiple linear regression demonstrated that serum and hair trace element levels were significantly associated with circulating amino acid levels after adjustment for age, BMI, and metabolic parameters including liver damage markers.

CONCLUSION

It is proposed that altered trace element handling may contribute to NAFLD pathogenesis through modulation of amino acid metabolism.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Mitochondrial metabolic dysfunction and non-alcoholic fatty liver disease: new insights from pathogenic mechanisms to clinically targeted therapy

Metabolic dysfunction-associated fatty liver disease (MAFLD) is among the most widespread metabolic disease globally, and its associated complications including insulin resistance and diabetes have become threatening conditions for human health. Previous studies on non-alcoholic fatty liver disease (NAFLD) were focused on the liver's lipid metabolism. However, growing evidence suggests that mitochondrial metabolism is involved in the pathogenesis of NAFLD to varying degrees in several ways, for instance in cellular division, oxidative stress, autophagy, and mitochondrial quality control. Ultimately, liver function gradually declines as a result of mitochondrial dysfunction. The liver is unable to transfer the excess lipid droplets outside the liver. Therefore, how to regulate hepatic mitochondrial function to treat NAFLD has become the focus of current research. This review provides details about the intrinsic link of NAFLD with mitochondrial metabolism and the mechanisms by which mitochondrial dysfunctions contribute to NAFLD progression. Given the crucial role of mitochondrial metabolism in NAFLD progression, the application potential of multiple mitochondrial function improvement modalities (including physical exercise, diabetic medications, small molecule agonists targeting Sirt3, and mitochondria-specific antioxidants) in the treatment of NAFLD was evaluated hoping to provide new insights into NAFLD treatment.

Olanzapine-induced nonalcoholic fatty liver disease: The effects of differential food pattern and the involvement of PGRMC1 signaling

Detrimental dietary habits with high-fat food are common in the psychiatric population, leading to higher obesity rate. Olanzapine (OLZ), as one of the mainstream antipsychotic drugs, shows superior efficacy in treating schizophrenia but limited by adverse effects such as obesity, dyslipidemia and liver injury, which are risk factors for the development of nonalcoholic fatty liver disease (NAFLD). Progesterone receptor component 1 (PGRMC1) is a key regulator associated with antipsychotic drug-induced metabolic disorders. Our study aims to investigate whether high-fat supplementation worsens OLZ-induced NAFLD and to validate the potential role of PGRMC1 pathway. In vivo, eight-week OLZ treatment successfully induced hepatic steatosis in female C57BL/6 mice fed with either a high-fat or normal diet, which is independent of body weight gain. Likewise, in vitro, OLZ markedly led to hepatocyte steatosis along with enhanced oxidative stress, which was aggravated by free fatty acids. Moreover, in vivo and in vitro, high-fat supplementation aggravated OLZ-induced hepatic lipid accumulation and oxidative stress via inhibition of hepatic PGRMC1-AMPK-mTORC1/Nrf2 pathways. Inspiringly, PGRMC1 overexpression effectively reversed OLZ-induced hepatocyte steatosis in vitro. Hence, hepatic PGRMC1 is attributable to OLZ-induced NAFLD especially with high-fat supplementation and potentially serves as a novel therapeutic target.

Hepatocyte expressed chemerin-156 does not protect from experimental non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a rapidly growing liver disease. The chemoattractant chemerin is abundant in hepatocytes, and hepatocyte expressed prochemerin protected from NASH. Prochemerin is inactive and different active isoforms have been described. Here, the effect of hepatocyte expressed muChem-156, a highly active murine chemerin isoform, was studied in the methionine–choline deficient dietary model of NASH. Mice overexpressing muChem-156 had higher hepatic chemerin protein. Serum chemerin levels and the capability of serum to activate the chemerin receptors was unchanged showing that the liver did not release active chemerin. Notably, activation of the chemerin receptors by hepatic vein blood did not increase in parallel to total chemerin protein in patients with liver cirrhosis. In experimental NASH, muChem-156 had no effect on liver lipids. Accordingly, overexpression of active chemerin in hepatocytes or treatment of hepatocytes with recombinant chemerin did not affect cellular triglyceride and cholesterol levels. Importantly, overexpression of muChem-156 in the murine liver did not change the hepatic expression of inflammatory and profibrotic genes. The downstream targets of chemerin such as p38 kinase were neither activated in the liver of muChem-156 producing mice nor in HepG2, Huh7 and Hepa1-6 cells overexpressing this isoform. Recombinant chemerin had no effect on global gene expression of primary human hepatocytes and hepatic stellate cells within 24 h of incubation. Phosphorylation of p38 kinase was, however, increased upon short-time incubation of HepG2 cells with chemerin. These findings show that muChem-156 overexpression in hepatocytes does not protect from liver steatosis and inflammation.

Reactive Oxygen Species Induce Fatty Liver and Ischemia-Reperfusion Injury by Promoting Inflammation and Cell Death

Liver transplantation is the ultimate method for treating end-stage liver disease. With the increasing prevalence of obesity, the number of patients with non-alcoholic fatty liver, a common cause of chronic liver disease, is on the rise and may become the main cause of liver transplantation in the future. With the increasing gap between the number of donor livers and patients waiting for liver transplantation and the increasing prevalence of non-alcoholic fatty liver, the proportion of steatosis livers among non-standard donor organs is also increasing. Ischemia-reperfusion injury has historically been the focus of attention in the liver transplantation process, and severe ischemia-reperfusion injury leads to adverse outcomes of liver transplantation. Studies have shown that the production of reactive oxygen species and subsequent oxidative stress play a key role in the pathogenesis of hepatic ischemia and reperfusion injury and non-alcoholic fatty liver. Furthermore, the sensitivity of fatty liver transplantation to ischemia-reperfusion injury has been suggested to be related to the production of reactive oxygen species (ROS) and oxidative stress. In ischemia-reperfusion injury, Kupffer cell and macrophage activation along with mitochondrial damage and the xanthine/xanthine oxidase system promote marked reactive oxygen species production and the inflammatory response and apoptosis, resulting in liver tissue injury. The increased levels of ROS and lipid peroxidation products, vicious circle of ROS and oxidative stress along with mitochondrial dysfunction promoted the progress of non-alcoholic fatty liver. In contrast to the non-fatty liver, a non-alcoholic fatty liver produces more reactive oxygen species and suffers more serious oxidative stress when subjected to ischemia-reperfusion injury. We herein review the effects of reactive oxygen species on ischemia-reperfusion injury and non-alcoholic fatty liver injury as well as highlight several treatment approaches.

Oxidative stress in obesity and insulin resistance

Since obesity is one of the main factors in the development of insulin resistance (IR) and is also associated with increased oxidative stress (OxS) rate, this study aims to review the published literature to collate and provide a comprehensive summary of the studies related to the status of the OxS in the pathogenesis of obesity and related IR. OxS represents an imbalance between the production of reactive oxygen and nitrogen species (RONS) and the capacity of the antioxidant defense system (AOS) to neutralize RONS. A steady-state of RONS level is maintained through endogenous enzymatic and non-enzymatic AOS components. Three crucial enzymes, which suppress the formation of free radicals, are superoxide dismutases, catalases, and glutathione peroxidases. The second line of AOS includes non-enzymatic components such as vitamins C and E, coenzyme Q, and glutathione which neutralizes free radicals by donating electrons to RONS. Emerging evidence suggests that high RONS levels contribute to the progression of OxS in obesity by activating inflammatory pathways and thus leading to the development of pathological states, including IR. In addition, decreased level of AOS components in obesity increases the susceptibility to oxidative tissue damage and further progression of its comorbidities. Increased OxS in accumulated adipose tissue should be an imperative target for developing new therapies in obesity-related IR.

Blood manganese and nonalcoholic fatty liver disease: A cohort-based case-control study

BACKGROUND & AIMS

As both a toxic and essential trace element in humans, limited research focuses on the association between blood manganese (Mn) and nonalcoholic fatty liver disease (NAFLD). We aimed to assess blood Mn concentration and its relationship with NAFLD among adults in Northern China.

METHODS

We conducted a cohort-based case-control study among 1816 patients with NAFLD (970 males and 846 females) and 1111 healthy controls (598 males and 513 females). We used the restricted cubic splines method to investigate the potential non-linear relationship and logistic regression models to analyze the association between blood Mn and NAFLD.

RESULTS

The median (p₂₅, p₇₅) of blood Mn concentration in males was 10.08 (8.42,11.98) μg/L, higher than that in females [9.79 (8.01,12.04)] μg/L, P = 0.011. Compared with the tertile 1 group of Mn in males, the odds ratio (95 % confidence interval) of NAFLD for tertile 2 and tertile 3 group was 0.82 (0.61,1.10) and 0.64 (0.47,0.87), respectively. The reverse correlation was consistent in patients with different fibrosis severity determined by fibrosis-4 score. The protective association was more evident in those with triglycerides ≥1.7 mmol/L [odds ratio (95 % confidence interval) of tertile 3 vs. tertile 1: 0.40 (0.22,0.75)]. We found a non-significant U-shaped relationship between Mn and NAFLD in women.

CONCLUSION

There may exist sex differences for the association between blood Mn and NAFLD. Higher blood Mn may be a potential protective factor for NAFLD in males. The subjects with TG ≥ 1.7 mmol/L would benefit more from higher blood Mn levels.

Low hepatic manganese concentrations in patients with hepatic steatosis - A cohort study of copper, iron and manganese in liver biopsies

BACKGROUND AND AIMS

Hepatic steatosis is the most common histopathological finding on liver biopsy, with the most prevalent etiology being NAFLD. The pathogenesis of hepatic steatosis and NAFLD is multifactorial, however, studies on the importance of manganese in NAFLD are limited. We aimed to study hepatic manganese content, and other trace elements, in relation to hepatic steatosis in patients with chronic liver diseases of different etiology, mainly NAFLD.

METHODS

Patients with chronically elevated liver function tests underwent a diagnostic work-up, including routine blood tests and two liver biopsies. One of the biopsies was sent for histopathological evaluation, and the other for ultra-trace elemental determinations. Steatosis was graded using conventional histopathological methodology, and fat content was also quantitated in biopsy samples by measuring the steatotic area of the section using stereological point counting (SPC). Ultra-trace elemental analysis was utilized for determining manganese, iron, and copper using inductively coupled plasma sector field mass spectrometry (ICP-SFMS).

RESULTS

76 patients were included in the study. Hepatic manganese concentrations in patients with steatosis were lower than in patients without hepatic steatosis (3.8 ± 1.1 vs. 6.4 ± 1.8, P < 0.001). Similar results were seen for blood manganese levels and hepatic steatosis. We found a strong inverse correlation between steatosis grade and hepatic manganese content (ρ=-0.743, P < 0.001). Also, low levels of manganese independently predicted the presence of steatosis (aOR 0.07 [95%CI: 0.01-0.63]).

CONCLUSION

Patients with NAFLD, or other CLD and concomitant hepatic steatosis, showed lower levels of hepatic manganese content with increasing grade of steatosis.

Remodeling of Mitochondrial Plasticity: The Key Switch from NAFLD/NASH to HCC

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and the third-leading cause of cancer-related mortality. Currently, the global burden of nonalcoholic fatty liver disease (NAFLD) has dramatically overcome both viral and alcohol hepatitis, thus becoming the main cause of HCC incidence. NAFLD pathogenesis is severely influenced by lifestyle and genetic predisposition. Mitochondria are highly dynamic organelles that may adapt in response to environment, genetics and epigenetics in the liver ("mitochondrial plasticity"). Mounting evidence highlights that mitochondrial dysfunction due to loss of mitochondrial flexibility may arise before overt NAFLD, and from the early stages of liver injury. Mitochondrial failure promotes not only hepatocellular damage, but also release signals (mito-DAMPs), which trigger inflammation and fibrosis, generating an adverse microenvironment in which several hepatocytes select anti-apoptotic programs and mutations that may allow survival and proliferation. Furthermore, one of the key events in malignant hepatocytes is represented by the remodeling of glucidic-lipidic metabolism combined with the reprogramming of mitochondrial functions, optimized to deal with energy demand. In sum, this review will discuss how mitochondrial defects may be translated into causative explanations of NAFLD-driven HCC, emphasizing future directions for research and for the development of potential preventive or curative strategies.

Mitochondrial dynamics and nonalcoholic fatty liver disease (NAFLD): new perspectives for a fairy-tale ending?

Nonalcoholic fatty liver disease (NAFLD) includes a broad spectrum of liver dysfunctions and it is predicted to become the primary cause of liver failure and hepatocellular carcinoma. Mitochondria are highly dynamic organelles involved in multiple metabolic/bioenergetic pathways in the liver. Emerging evidence outlined that hepatic mitochondria adapt in number and functionality in response to external cues, as high caloric intake and obesity, by modulating mitochondrial biogenesis, and maladaptive mitochondrial response has been described from the early stages of NAFLD. Indeed, mitochondrial plasticity is lost in progressive NAFLD and these organelles may assume an aberrant phenotype to drive or contribute to hepatocarcinogenesis. Severe alimentary regimen and physical exercise represent the cornerstone for NAFLD care, although the low patients' compliance is urging towards the discovery of novel pharmacological treatments. Mitochondrial-targeted drugs aimed to recover mitochondrial lifecycle and to modulate oxidative stress are becoming attractive molecules to be potentially introduced for NAFLD management. Although the path guiding the switch from bench to bedside remains tortuous, the study of mitochondrial dynamics is providing intriguing perspectives for future NAFLD healthcare.

Short-term high-fat diet intake leads to exacerbation of concanavalin A-induced liver injury through the induction of procoagulation state

Obesity and high-fat diet (HFD) are known to cause proinflammatory and procoagulation states and suggested to become a risk of developing thromboembolic diseases. Non-alcoholic fatty liver disease (NAFLD) is usually associated with obesity and HFD, and a part of NAFLD is known to progress to nonalcoholic steatohepatitis (NASH), the pathogenesis of which has not been fully elucidated. In the current study, we examined the influence of short-term HFD on hepatic expression of the molecules related to inflammation, coagulation, metabolism, and cellular stresses from the perspective that HFD itself can be a risk for the development to NASH. In the analysis in short-term (4 days to 14 days) HFD-fed mice, we found out that HFD increased hepatic expression of IFN-γ, TNF-α, IL-10, monocyte chemotactic protein-1 (MCP-1), tissue factor (TF), plasminogen activator inhibitor-1 (PAI-1) mRNAs, and fibrin/fibrinogen deposition in the liver tissues. And it was suggested that metabolic alterations and endoplasmic reticulum (ER) stresses induced by the HFD intake were associated with this proinflammatory and procoagulation states. When we administered concanavalin A (Con A) to these HFD-fed mice, the extent of liver injury was dramatically exacerbated in HFD-fed mice. Heparin treatment to Con A-administered, HFD-fed mice (for 4 days) profoundly ameliorated the extent of liver injury. These suggest that even short-term of HFD intake induces proinflammatory and procoagulation states in the liver and thereby increases the susceptibility of the liver to circulating inflammatory stimuli. We think that it may explain a part of NASH pathogenesis.

Alpha-syntrophin deficiency protects against non-alcoholic steatohepatitis associated increase of macrophages, CD8+ T-cells and galectin-3 in the liver

Non-alcoholic steatohepatitis (NASH) is characterized by immune cell infiltration. Loss of the scaffold protein alpha-syntrophin (SNTA) protected mice from hepatic inflammation in the methionine-choline-deficient (MCD) diet model. Here, we determined increased numbers of macrophages and CD8⁺ T-cells in MCD diet induced NASH liver of wild type mice. In the mutant animals these NASH associated changes in immune cell composition were less pronounced. Further, there were more γδ T-cells in the NASH liver of the null mice. Galectin-3 protein in the hepatic non-parenchymal cell fraction was strongly induced in MCD diet fed wild type but not mutant mice. Antioxidant enzymes declined in NASH liver with no differences between the genotypes. To identify the target cells responsive to SNTA loss in-vitro experiments were performed. In the human hepatic stellate cell line LX-2, SNTA did not regulate pro-fibrotic or antioxidant proteins like alpha-smooth muscle actin or catalase. Soluble galectin-3 was, however, reduced upon SNTA knock-down and increased upon SNTA overexpression. SNTA deficiency neither affected cell proliferation nor cell death of LX-2 cells. In the macrophage cell line RAW264.7 low SNTA indeed caused higher galectin-3 production whereas release of TNF and cell viability were normal. Moreover, SNTA had no effect on hepatocyte chemerin and CCL2 expression. Overall, SNTA loss improved NASH without causing major effects in macrophage, hepatocyte and hepatic stellate cell lines. SNTA null mice fed the MCD diet had less body weight loss and this seems to contribute to improved liver health of the mutant mice.

Augmented liver inflammation in a microsomal prostaglandin E synthase 1 (mPGES-1)-deficient diet-induced mouse NASH model

In a subset of patients, non-alcoholic fatty liver disease (NAFLD) is complicated by cell death and inflammation resulting in non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and subsequent organ failure. Apart from cytokines, prostaglandins, in particular prostaglandin E₂ (PGE₂), play a pivotal role during inflammatory processes. Expression of the key enzymes of PGE₂ synthesis, cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), was increased in human NASH livers in comparison to controls and correlated with the NASH activity score. Both enzymes were also induced in NASH-diet-fed wild-type mice, resulting in an increase in hepatic PGE₂ concentration that was completely abrogated in mPGES-1-deficient mice. PGE₂ is known to inhibit TNF-α synthesis in macrophages. A strong infiltration of monocyte-derived macrophages was observed in NASH-diet-fed mice, which was accompanied with an increase in hepatic TNF-α expression. Due to the impaired PGE₂ production, TNF-α expression increased much more in livers of mPGES-1-deficient mice or in the peritoneal macrophages of these mice. The increased levels of TNF-α resulted in an enhanced IL-1β production, primarily in hepatocytes, and augmented hepatocyte apoptosis. In conclusion, attenuation of PGE₂ production by mPGES-1 ablation enhanced the TNF-α-triggered inflammatory response and hepatocyte apoptosis in diet-induced NASH.

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.

Attenuated lipotoxicity and apoptosis is linked to exogenous and endogenous augmenter of liver regeneration by different pathways

Nonalcoholic fatty liver disease (NAFLD) covers a spectrum from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Free fatty acids (FFA) induce steatosis and lipo-toxicity and correlate with severity of NAFLD. In this study we aimed to investigate the role of exogenous and endogenous ALR (augmenter of liver regeneration) for FFA induced ER (endoplasmatic reticulum) -stress and lipoapoptosis. Primary human hepatocytes or hepatoma cells either treated with recombinant human ALR (rhALR, 15kDa) or expressing short form ALR (sfALR, 15kDa) were incubated with palmitic acid (PA) and analyzed for lipo-toxicity, -apoptosis, activation of ER-stress response pathways, triacylglycerides (TAG), mRNA and protein expression of lipid metabolizing genes. Both, exogenous rhALR and cytosolic sfALR reduced PA induced caspase 3 activity and Bax protein expression and therefore lipotoxicity. Endogenous sfALR but not rhALR treatment lowered TAG levels, diminished activation of ER-stress mediators C-Jun N-terminal kinase (JNK), X-box binding protein-1 (XBP1) and proapoptotic transcription factor C/EBP-homologous protein (CHOP), and reduced death receptor 5 protein expression. Cellular ALR exerts its lipid lowering and anti-apoptotic actions by enhancing FABP1, which binds toxic FFA, increasing mitochondrial β-oxidation by elevating the mitochondrial FFA transporter CPT1α, and decreasing ELOVL6, which delivers toxic FFA metabolites. We found reduced hepatic mRNA levels of ALR in a high fat diet mouse model, and of ALR and FOXA2, a transcription factor inducing ALR expression, in human steatotic as well as NASH liver samples, which may explain increased lipid deposition and reduced β-oxidation in NASH patients. Present study shows that exogenous and endogenous ALR reduce PA induced lipoapoptosis. Furthermore, cytosolic sfALR changes mRNA and protein expression of genes regulating lipid metabolism, reduces ER-stress finally impeding progression of NASH.

Development of gene polymorphisms in meditators of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease worldwide, the morbidity of which closely correlates with diversity of ethnicity, minority, family and location. Its histology spans from simple steatosis, to nonalcoholic steatohepatitis, which ultimately results in fibrosis, cirrhosis and hepatocellular carcinoma. The accelerating prevalence of NAFLD is due to an incremental incidence of metabolic syndrome that is distinguished by dyslipidemia, glucose impairment, obesity, excessive oxidative stress and adipocytokine impairment. Additionally, the pathogenesis of NAFLD is thought to be a multifactorial and complicated disease associated with lifestyle habits, nutritional factors and genetics. However, the pathogenesis and underlying mechanism in the development of NAFLD caused by genetics remains unclear. People have been increasingly emphasizing on the relationship between NAFLD and gene polymorphisms in recent years, with the aim of having a comprehensive elucidation of associated gene polymorphisms influencing the pathogenesis of the disease. In the current article, the authors attempted to critically summarize the most recently identified gene polymorphisms from the facets of glucose metabolism, fatty acid metabolism, oxidative stress and related cytokines in NAFLD that contribute to promoting the progression of the disease.

Pathogenesis of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common and important chronic liver disease in the world. As the prevalence of obesity increases in adults and children, the incidence of NAFLD has increased rapidly, reaching 17% to 33%. NAFLD is clinically divided into two forms: simple fatty liver (SFL) and non-alcoholic steatohepatitis (NASH), with NASH accounting for 1/3-1/2 of all NAFLD cases. The probability of developing cirrhosis is 0.6%-3.0% in patients with SFL for 10-20 years, and as high as 15%-25% in patients with NASH for 10-15 years. Approximately 1% of cirrhosis cases develop hepatocellular carcinoma each year. The pathogenesis of NAFLD is still not completely clear. It is generally believed that age, sex, obesity, insulin resistance, cytokines, gene polymorphism, and intestinal microflora are involved in the pathogenesis of NAFLD. An in-depth understanding of the pathogenesis of NAFLD can provide a basis for treatment of this disease. In recent years, cytokines or genes have been reported as targets for NAFLD treatment with appreciated effects. Since there is currently no specific treatment for NAFLD, targeted therapy may have a profound impact on the prognosis of the disease.

Dietary supplementation of grape seed and skin flour mitigates brain oxidative damage induced by a high-fat diet in rat: Gender dependency

It is unknown whether gender has an impact on brain injury in obesity, and, if so, whether treatment with grape seed and skin flour could exert a protective effect. Both male and female rats were fed a standard diet (SD) or a high fat diet (HFD) during eight weeks and treated with high dosage grape seed and skin flour (GSSF). Fat-induced oxidative stress was evaluated into the brain with a special emphasis on transition metals determination. HFD induced male-cholesterol overload (+78.12%) and an oxidative stress status characterized by increased lipoperoxidation (+68.97%), carbonylation (+40.28%), decreased antioxidant enzyme activities as glutathione peroxidase (-61.07%) and manganese-superoxide dismutase (-35.47%) but not catalase. Additionally HFD depleted the brain from manganese (-71.31%) and dropped glutamine synthetase activity (-36.16%), without affecting copper nor iron nor their associated enzymes. HFD also altered intracellular mediators as superoxide anion (+36.12%), calcium (+44.41%) and also calpain (+76.54%) a calcium dependent protease. Importantly all these alterations were detected exclusively in male brain and were efficiently corrected upon GSSF treatment. In conclusion, GSSF has the potential to alleviate the deleterious lipotoxic effect of HFD treatment that occurred in male brain and perhaps in post-menauposal female brain.

Evaluation of tissue metal and trace element content in a rat model of non-alcoholic fatty liver disease using ICP-DRC-MS

The primary objective of the study was to assess the level of metals and trace elements in liver, serum, and hair of rats with diet-induced non-alcoholic fatty liver disease (NAFLD) using inductively coupled plasma dynamic reaction cell mass spectrometer (ICP-DRC-MS). 56 female 3-months-old Wistar rats divided into two equal groups were fed either standard (10% calories from fat) or high-fat high-carbohydrate diet (60% calories from fat in chow and 10% sucrose solution) for 6 weeks. Serum was examined for insulin resistance markers, lipid profile, and alanine aminotransferase (ALT) activity. Liver histology was assessed after hematoxylin and eosin staining. Metal and trace element concentrations were assessed by means of ICP-DRC-MS. Overfed animals were characterized by higher values of morphometric parameters. Liver examination revealed large and small droplet steatosis, hepatocyte ballooning and necrosis, being characteristic for NAFLD. Animals with NAFLD were characterized by insulin resistance, atherogenic changes of lipid profile and increased ALT activity. Significantly decreased hepatic Co, Cu, I, Li, Mn, Se, Zn levels were observed in rats with NAFLD. At the same time, only hepatic Mn and Se levels remained decreased after adjustment for total protein. Overfed animals were characterized by significantly lower I, Li, and Mn levels in blood serum, whereas concentration of Co, Se, V, and Sr exceeded the control values. In general, the results of the study demonstrate that NAFLD significantly affects metal and trace element status in experimental animals.

The Serum Oxidative/Anti-oxidative Stress Balance Becomes Dysregulated in Patients with Non-alcoholic Steatohepatitis Associated with Hepatocellular Carcinoma

Objective Oxidative stress is associated with the progression of chronic liver disease. Non-alcoholic fatty liver disease (NAFLD) is also an oxidative stress-related disease. However, the oxidative/anti-oxidative balance has not been fully characterized in NAFLD. The objective of the present study was to investigate the balance between oxidative stress and the anti-oxidative activity in NAFLD, including non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC). Patients We recruited 69 patients with histologically proven NAFLD without HCC (NAFLD; n=58), and with NASH-related HCC (NASH-HCC; n=11). The 58 NAFLD patients included patients with non-alcoholic fatty liver (NAFL; n=14) and NASH (n=44). Methods The serum levels of reactive oxygen metabolites (ROM) and anti-oxidative markers (OXY) were determined and then used to calculate the oxidative index. The correlations among such factors as ROM, OXY, oxidative index, and clinical characteristics were investigated. Results In NAFLD, ROM positively correlated with the body mass index (BMI), hemoglobin A1c (HbA1c), C-reactive protein (CRP), and the histological grade or inflammatory scores, while only high HbA1c and CRP levels were significant factors that correlated with a higher ROM according to a multivariate analysis. OXY positively correlated with the platelet counts, albumin, and creatinine levels, while negatively correlating with age. However, it improved after treatment intervention. The oxidative index positively correlated with BMI, CRP, and HbA1c. The NASH-HCC patients exhibited a lower OXY than the NASH patients, probably due to the effects of aging. Conclusion Oxidative stress correlated with the levels of NASH activity markers, while the anti-oxidative function was preserved in younger patients as well as in patients with a well-preserved liver function. The NASH-HCC patients tended to be older and exhibited a diminished anti-oxidative function.

Annexin A6 protein is downregulated in human hepatocellular carcinoma

Annexin A6 (AnxA6) is a lipid-binding protein highly expressed in the liver, regulating cholesterol homeostasis and signaling pathways with a role in liver physiology. Here, we analyzed whether hepatic AnxA6 levels are affected by pathological conditions that are associated with liver dysfunction and liver injury. AnxA6 levels in the fatty liver of mice fed a high-fat diet, in ob/ob and db/db animals and in human fatty liver are comparable to controls. Similarly, AnxA6 levels appear unaffected in murine nonalcoholic steatohepatitis and human liver fibrosis. Accordingly, adiponectin, lysophosphatidylcholine, palmitate, and TGFbeta, all of which have a role in liver injury, do not affect AnxA6 expression in human hepatocytes. Likewise, adiponectin and IL8 do not alter AnxA6 levels in primary human hepatic stellate cells. However, in hepatic tumors of 18 patients, AnxA6 protein levels are substantially reduced compared to nontumorous tissues. AnxA6 mRNA is even increased in the tumors suggesting that posttranscriptional mechanisms are involved herein. Lipidomic analysis shows trends toward elevated cholesteryl ester and sphingomyelin in the tumor samples, yet the ratio of tumor to nontumorous AnxA6 does not correlate with these lipids. The current study shows that AnxA6 is specifically reduced in human hepatocellular carcinoma suggesting a role of this protein in hepatocarcinogenesis.

(S)YS-51, a novel isoquinoline alkaloid, attenuates obesity-associated non-alcoholic fatty liver disease in mice by suppressing lipogenesis, inflammation and coagulation

Obesity-associated non-alcoholic fatty liver disease (NAFLD) increases coagulation and inflammation. We hypothesized that (S)YS-51, an agent found to be beneficial in animal models of sepsis, may reduce NAFLD in high-fat diet (HFD) mice by reducing coagulation and inflammation. C57BL/6 mice were fed either a chow diet or HFD and each was supplemented with or without (S)YS-51 (10mg/kg, daily, i.p.) for 16 weeks. The results showed that HFD caused significant increases in lipogenesis [CD36, fatty acid synthase (FAS) and sterol response element binding protein (SREBP)-1c mRNA and protein], inflammation [monocyte chemotactic protein (MCP)-1, tumor necrosis factor (TNF)-α, intercellular cell adhesion molecule-1 (ICAM-1), TGF-β, and procollagen type 1 mRNA, macrophage infiltration] and coagulation [tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) mRNA and thrombin antithrombin complex (TAT)] in the liver, adipose tissue and serum, which were significantly reduced by (S)YS-51. These results of (S)YS-51 were accompanied by significant reduction of weight gain, liver size, hepatic steatosis and fibrosis, blood cholesterol, hepatic triglyceride, and macrophage infiltration and inflammatory cytokines in adipose tissue without affecting food intake in HFD mice. Interestingly, (S)YS-51 increased SIRT1 mRNA and protein and AMPK expression in the liver of HFD mice by increasing both NAD(+)/NADH ratio and LKB1 phosphorylation. In HepG2 cells, (S)YS-51 activated SIRT1 followed by AMPK. Finally, (S)YS-51 improved glucose tolerance and insulin resistance in HFD mice. We concluded that (S)YS-51 attenuates NAFLD and insulin resistance in HFD mice by, at least, activation of SIRT1/AMPK signals. Thus, (S)YS-51 may be beneficial in NAFLD treatment.

Mitochondrial Dysfunction Due to Lack of Manganese Superoxide Dismutase Promotes Hepatocarcinogenesis

AIMS

One of the cancer hallmarks is mitochondrial dysfunction associated with oxidative stress. Among the first line of defense against oxidative stress is the dismutation of superoxide radicals, which in the mitochondria is carried out by manganese superoxide dismutase (MnSOD). Accordingly, carcinogenesis would be associated with a dysregulation in MnSOD expression. However, the association studies available so far are conflicting, and no direct proof concerning the role of MnSOD as a tumor promoter or suppressor has been provided. Therefore, we investigated the role of MnSOD in carcinogenesis by studying the effect of MnSOD deficiency in cells and in the livers of mice.

RESULTS

We found that loss of MnSOD in hepatoma cells contributed to their conversion toward a more malignant phenotype, affecting all cellular properties generally associated with metabolic transformation and tumorigenesis. In vivo, hepatocyte-specific MnSOD-deficient mice showed changed organ architecture, increased expression of tumor markers, and a faster response to carcinogenesis. Moreover, deficiency of MnSOD in both the in vitro and in vivo model reduced β-catenin and hypoxia-inducible factor-1α levels.

INNOVATION

The present study shows for the first time the important correlation between MnSOD presence and the regulation of two major pathways involved in carcinogenesis, the Wnt/β-catenin and hypoxia signaling pathway.

CONCLUSION

Our study points toward a tumor suppressive role of MnSOD in liver, where the Wnt/β-catenin and hypoxia pathway may be crucial elements.

Relationship of adiponectin to markers of oxidative stress in type 2 diabetic patients: influence of incipient diabetes-associated kidney disease

PURPOSE

Adiponectin may be beneficial in incipient chronic kidney disease by antagonizing oxidative stress. We evaluated adiponectin, malondialdehyde (MDA), and superoxide dismutase (SOD), in type 2 diabetes mellitus patients (T2DP) with and without incipient nephropathy.

METHODS

T2DP with glomerular filtration rate (GFR) >30 ml/min were compared with 20 healthy controls. Clinical and laboratory evaluations, levels of MDA (fluorimetric thiobarbituric test), SOD (cytochrome reduction method) and adiponectin (ELISA) were obtained.

RESULTS

Sixty-four patients (GFR 91.44 ± 38.50 ml/min, urinary albumin-to-creatinine ratio [UACR] 20.81 [4.64-72.88 mg/g]) were included. MDA was higher in T2DP than in controls: 3.97 (2.43-4.59) versus 1.35 (1.16-1.81) nmol/ml, p < 0.0001. MDA correlated with glycated hemoglobin (r = 0.40, p = 0.001), adiponectin (r = -0.28, p = 0.03), systolic blood pressure (r = -0.28, p = 0.03) and SOD (r = -0.35, p = 0.005); adiponectin (p = 0.01) and glycated hemoglobin (p = 0.02) remained significant predictors of MDA in multiple regression analysis. SOD was negatively correlated with glycemia (r = -0.71, p < 0.0001) and glycated hemoglobin (r = -0.5, p < 0.0001). When patients were divided according to a ROC-derived adiponectin cutoff of 8.9 µg/ml, patients with higher adiponectin had lower MDA, [2.55 (2.35-3.60) vs. 4.10 (2.89-5.31) nmol/ml, p = 0.005] but similar SOD levels. In T2DP with nephropathy (GFR < 60 ml/min or UACR > 30 mg/g), the correlation of adiponectin with MDA was stronger, (r = -0.51, p = 0.004) confirmed in multiple regression analysis (p = 0.03). Adiponectin was not correlated with MDA, and SOD was inversely related to MDA in patients without nephropathy.

CONCLUSION

Adiponectin is a significant predictor of MDA in early diabetic nephropathy, whereas SOD strongly depends only on glycemic control and is not directly related to adiponectin.

Lipid abnormalities in alpha/beta2-syntrophin null mice are independent from ABCA1

The syntrophins alpha (SNTA) and beta 2 (SNTB2) are molecular adaptor proteins shown to stabilize ABCA1, an essential regulator of HDL cholesterol. Furthermore, SNTB2 is involved in glucose stimulated insulin release. Hyperglycemia and dyslipidemia are characteristic features of the metabolic syndrome, a serious public health problem with rising prevalence. Therefore, it is important to understand the role of the syntrophins herein. Mice deficient for both syntrophins (SNTA/B2-/-) have normal insulin and glucose tolerance, hepatic ABCA1 protein and cholesterol. When challenged with a HFD, wild type and SNTA/B2-/- mice have similar weight gain, adiposity, serum and liver triglycerides. Hepatic ABCA1, serum insulin and insulin sensitivity are normal while glucose tolerance is impaired. Liver cholesterol is reduced, and expression of SREBP2 and HMG-CoA-R is increased in the knockout mice. Scavenger receptor-BI (SR-BI) protein is strongly diminished in the liver of SNTA/B2-/- mice while SR-BI binding protein NHERF1 is not changed and PDZK1 is even induced. Knock-down of SNTA, SNTB2 or both has no effect on hepatocyte SR-BI and PDZK1 proteins. Further, SR-BI levels are not reduced in brown adipose tissue of SNTA/B2-/- mice excluding that syntrophins directly stabilize SR-BI. SR-BI stability is regulated by MAPK and phosphorylated ERK2 is induced in the liver of the knock-out mice. Blockage of ERK activity upregulates hepatocyte SR-BI showing that increased MAPK activity contributes to low SR-BI. Sphingomyelin which is well described to regulate cholesterol metabolism is reduced in the liver and serum of the knock-out mice while the size of serum lipoproteins is not affected. Current data exclude a major function of these syntrophins in ABCA1 activity and insulin release but suggest a role in regulating glucose uptake, ERK and SR-BI levels, and sphingomyelin metabolism in obesity.

Oxidative stress contributes to orthopedic trauma-induced acute kidney injury in obese rats

After trauma, obese patients have an increased risk of developing acute kidney injury (AKI). We have demonstrated that obese Zucker (OZ) rats, but not lean Zucker (LZ) rats, develop AKI 24 h after orthopedic trauma. ROS have been implicated in the pathophysiology of AKI in models of critical illness. However, the contribution of ROS to trauma-induced AKI in the setting of obesity has not been determined. We hypothesized that AKI in OZ rats after trauma is mediated by increased oxidative stress. Male LZ and OZ rats were divided into control and trauma groups, with a subset receiving treatment after trauma with the antioxidant apocynin (50 mg/kg ip, 2 mM in drinking water). The day after trauma, glomerular filtration rate, plasma creatinine, urine kidney injury molecule-1, and albumin excretion as well as renal oxidant and antioxidant activity were measured. After trauma, compared with LZ rats, OZ rats exhibited a significant decrease in glomerular filtration rate along with significant increases in plasma creatinine and urine kidney injury molecule-1 and albumin excretion. Additionally, oxidative stress was significantly increased in OZ rats, as evidenced by increased renal NADPH oxidase activity and urine lipid peroxidation products (thiobarbituric acid-reactive substances), and OZ rats also had suppressed renal superoxide dismutase activity. Apocynin treatment significantly decreased oxidative stress and AKI in OZ rats but had minimal effects in LZ rats. These results suggest that ROS play an important role in AKI in OZ rats after traumatic injury and that ROS may be a potential future therapeutic target in the obese after trauma.

Non-alcoholic fatty liver disease: what the clinician needs to know

Non-alcoholic fatty liver disease (NAFLD) is the most frequent cause of liver disease in the Western world. Furthermore, it is increasing worldwide, paralleling the obesity pandemic. Though highly frequent, only about one fifth of affected subjects are at risk of developing the progressive form of the disease, non-alcoholic steatohepatitis with fibrosis. Even in the latter, liver disease is slowly progressive, though, since it is so prevalent, it is already the third cause of liver transplantation in the United States, and it is predicted to get to the top of the ranking in few years. Of relevance, fatty liver is also associated with increased overall mortality and particularly increased cardiovascular mortality. The literature and amount of published papers on NAFLD is increasing as fast as its prevalence, which makes it difficult to keep updated in this topic. This review aims to summarize the latest knowledge on NAFLD, in order to help clinicians understanding its pathogenesis and advances on diagnosis and treatment.