Ablation of catalase promotes non-alcoholic fatty liver via oxidative stress and mitochondrial dysfunction in diet-induced obese mice

Influence of coffee roasting degree on antioxidant and metabolic parameters: Comprehensive in vitro and in vivo analysis

This study aimed to assess the impact of roasting degree on antioxidant and metabolic parameters in vitro and in vivo. In vitro, we evaluated radical scavenging, lipid peroxidation, and the activity of digestive enzymes (α-glucosidase, α-amylase, and lipase). In vivo, we first examined coffee's effect on carbohydrate and lipid absorption in healthy rats, followed by a chronic evaluation of metabolic disorders and antioxidant markers using a diet-induced obesity model. In vitro results revealed that increased roasting degree reduced the antioxidant capacity of coffee brews. All brews showed lower inhibition of α-glucosidase and α-amylase, and lipase inhibition compared to the positive control (acarbose or orlistat). In vivo, all roasting degrees consistently reduced postprandial glucose levels by 20%. Notably, coffee with a high roasting degree (HRD) decreased serum triglycerides (TG) by ∼44% after a lipid load, while other roasts did not. Chronic administration of unroasted (UN) or HRD coffee significantly reduced weight gain compared to the obese control (∼15% and ∼10%, respectively). Notably, all coffee samples improved lipid metabolism parameters. UN and HRD coffee significantly decreased adipocyte volume by 58% and 48%, respectively, compared to the obese control. Additionally, all groups exhibited less than 30% hepatic lipid droplets independent of roasting degree. HRD treatment notably increased liver catalase (CAT) activity and reduced lipid peroxidation in serum (∼90%), liver (∼59%), and adipose tissue (∼37%) compared to the obese control group. These findings suggest that HRD in coffee may confer certain biological advantages.

Isolation, purification, and structural characterization of polysaccharides from Codonopsis pilosula and its therapeutic effects on non-alcoholic fatty liver disease in vitro and in vivo

Codonopsis pilosula is a famous edible and medicinal plants, in which polysaccharides are recognized as one of the important active ingredients. A neutral polysaccharide (CPP-1) was purified from C. pilosula. The structure was characterized by HPSEC-MALLS-RID, UV, FT-IR, GC-MS, methylation analysis, and NMR. The results showed that CPP-1 was a homogeneous pure polysaccharide, mainly containing fructose and glucose, and a small amount of arabinose. Methylation analysis showed that CPP-1 composed of →1)-Fruf-(2→, Fruf-(1→ and Glcp-(1→ residues. Combined the NMR results the structure of CPP-1 was confirmed as α-D-Glcp-(1 → [2)-β-D-Fruf-(1 → 2)-β-D-Fruf-(1]26 → 2)-β-D-Fruf with the molecular weight of 4.890 × 103 Da. The model of AML12 hepatocyte fat damage was established in vitro. The results showed that CPP-1 could increase the activity of SOD and CAT antioxidant enzymes and reduce the content of MDA, thus protecting cells from oxidative damage. Subsequently, the liver protective effect of CPP-1 was studied in the mouse model of nonalcoholic fatty liver disease (NAFLD) induced by the high-fat diet. The results showed that CPP-1 significantly reduced the body weight, liver index, and body fat index of NAFLD mice, and significantly improved liver function. Therefore, CPP-1 should be a potential candidate for the treatment of NAFLD.

What are the common downstream molecular events between alcoholic and nonalcoholic fatty liver?

Liver fat storage, also called hepatic steatosis, is increasingly common and represents a very frequent diagnosis in the medical field. Excess fat is not without consequences. In fact, hepatic steatosis contributes to the progression toward liver fibrosis. There are two main types of fatty liver disease, alcoholic fatty liver disease (AFLD) and nonalcoholic fatty liver disease (NAFLD). Although AFLD and NAFLD are similar in their initial morphological features, both conditions involve the same evolutive forms. Moreover, there are various common mechanisms underlying both diseases, including alcoholic liver disease and NAFLD, which are commonalities. In this Review, the authors explore similar downstream signaling events involved in the onset and progression of the two entities but not completely different entities, predominantly focusing on the gut microbiome. Downstream molecular events, such as the roles of sirtuins, cytokeratins, adipokines and others, should be considered. Finally, to complete the feature, some new tendencies in the therapeutic approach are presented.

Contributing roles of mitochondrial dysfunction and hepatocyte apoptosis in liver diseases through oxidative stress, post-translational modifications, inflammation, and intestinal barrier dysfunction

This review provides an update on recent findings from basic, translational, and clinical studies on the molecular mechanisms of mitochondrial dysfunction and apoptosis of hepatocytes in multiple liver diseases, including but not limited to alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and drug-induced liver injury (DILI). While the ethanol-inducible cytochrome P450-2E1 (CYP2E1) is mainly responsible for oxidizing binge alcohol via the microsomal ethanol oxidizing system, it is also responsible for metabolizing many xenobiotics, including pollutants, chemicals, drugs, and specific diets abundant in n-6 fatty acids, into toxic metabolites in many organs, including the liver, causing pathological insults through organelles such as mitochondria and endoplasmic reticula. Oxidative imbalances (oxidative stress) in mitochondria promote the covalent modifications of lipids, proteins, and nucleic acids through enzymatic and non-enzymatic mechanisms. Excessive changes stimulate various post-translational modifications (PTMs) of mitochondrial proteins, transcription factors, and histones. Increased PTMs of mitochondrial proteins inactivate many enzymes involved in the reduction of oxidative species, fatty acid metabolism, and mitophagy pathways, leading to mitochondrial dysfunction, energy depletion, and apoptosis. Unique from other organelles, mitochondria control many signaling cascades involved in bioenergetics (fat metabolism), inflammation, and apoptosis/necrosis of hepatocytes. When mitochondrial homeostasis is shifted, these pathways become altered or shut down, likely contributing to the death of hepatocytes with activation of inflammation and hepatic stellate cells, causing liver fibrosis and cirrhosis. This review will encapsulate how mitochondrial dysfunction contributes to hepatocyte apoptosis in several types of liver diseases in order to provide recommendations for targeted therapeutics.

Melatonin Prevents Alcohol- and Metabolic Dysfunction- Associated Steatotic Liver Disease by Mitigating Gut Dysbiosis, Intestinal Barrier Dysfunction, and Endotoxemia

Melatonin (MT) has often been used to support good sleep quality, especially during the COVID-19 pandemic, as many have suffered from stress-related disrupted sleep patterns. It is less known that MT is an antioxidant, anti-inflammatory compound, and modulator of gut barrier dysfunction, which plays a significant role in many disease states. Furthermore, MT is produced at 400-500 times greater concentrations in intestinal enterochromaffin cells, supporting the role of MT in maintaining the functions of the intestines and gut-organ axes. Given this information, the focus of this article is to review the functions of MT and the molecular mechanisms by which it prevents alcohol-associated liver disease (ALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), including its metabolism and interactions with mitochondria to exert its antioxidant and anti-inflammatory activities in the gut-liver axis. We detail various mechanisms by which MT acts as an antioxidant, anti-inflammatory compound, and modulator of intestinal barrier function to prevent the progression of ALD and MASLD via the gut-liver axis, with a focus on how these conditions are modeled in animal studies. Using the mechanisms of MT prevention and animal studies described, we suggest behavioral modifications and several exogenous sources of MT, including food and supplements. Further clinical research should be performed to develop the field of MT in preventing the progression of liver diseases via the gut-liver axis, so we mention a few considerations regarding MT supplementation in the context of clinical trials in order to advance this field of research.

An Innovative Mei-Gin Formula Exerts Anti-Adipogenic and Anti-Obesity Effects in 3T3-L1 Adipocyte and High-Fat Diet-Induced Obese Rats

BACKGROUND

To investigate the potential anti-obesity properties of an innovative functional formula (called the Mei-Gin formula: MGF) consisting of bainiku-ekisu, Prunus mume (70% ethanol extract), black garlic (water extract), and Mesona procumbens Hemsl. (40% ethanol extract) for reducing lipid accumulation in 3T3-L1 adipocytes in vitro and obese rats in vivo.

MATERIAL AND METHODS

The prevention and regression of high-fat diet (HFD)-induced obesity by the intervention of Japan Mei-Gin, MGF-3 and -7, and positive health supplement powder were investigated in male Wistar rats. The anti-obesity effects of MGF-3 and -7 in rats with HFD-induced obesity were examined by analyzing the role of visceral and subcutaneous adipose tissue in the development of obesity.

RESULTS

The results indicated that MGF-1-7 significantly suppressed lipid accumulation and cell differentiation through the down-regulation of GPDH activity, as a key regulator in the synthesis of triglycerides. Additionally, MGF-3 and MGF-7 exhibited a greater inhibitory effect on adipogenesis in 3T3-L1 adipocytes. The high-fat diet increased body weight, liver weight, and total body fat (visceral and subcutaneous fat) in obese rats, while these alterations were effectively improved by the administration of MGF-3 and -7, especially MGF-7.

CONCLUSION

This study highlights the role of the Mei-Gin formula, particularly MGF-7, in anti-obesity action, which has the potential to be used as a therapeutic agent for the prevention or treatment of obesity.

Therapeutic Effects of Heterotrigona itama (Stingless Bee) Bee Bread in Improving Hepatic Lipid Metabolism through theActivation of the Keap1/Nrf2 Signaling Pathway in an Obese Rat Model

Bee bread (BB) has traditionally been used as a dietary supplement to treat liver problems. This study evaluated the therapeutic effects of Heterotrigona itama BB from Malaysia on obesity-induced hepatic lipid metabolism disorder via the regulation of the Keap1/Nrf2 pathway. Male Sprague Dawley rats were fed with either a normal diet or high-fat diet (HFD) for 6 weeks to induce obesity. Following 6 weeks, obese rats were treated either with distilled water (OB group), BB (0.5 g/kg body weight/day) (OB + BB group) or orlistat (10 mg/kg body weight/day) (OB + OR group) concurrent with HFD for another 6 weeks. BB treatment suppressed Keap1 and promoted Nrf2 cytoplasmic and nuclear translocations, leading to a reduction in oxidative stress, and promoted antioxidant enzyme activities in the liver. Furthermore, BB down-regulated lipid synthesis and its regulator levels (SIRT1, AMPK), and up-regulated fatty acid β-oxidation in the liver of obese rats, being consistent with alleviated lipid levels, improved hepatic histopathological changes (steatosis, hepatocellular hypertrophy, inflammation and glycogen expression) and prevented progression to non-alcoholic steatohepatitis. These results showed the therapeutic potentials of H. itama BB against oxidative stress and improved lipid metabolism in the liver of obese rats possibly by targeting the Keap1/Nrf2 pathway, hence proposing its role as a natural supplement capable of treating obesity-induced fatty liver disease.

Peroxisomal Fitness: A Potential Protective Mechanism of Fenofibrate against High Fat Diet-Induced Non-Alcoholic Fatty Liver Disease in Mice

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has been increasing in association with the epidemic of obesity and diabetes. Peroxisomes are single membrane-enclosed organelles that play a role in the metabolism of lipid and reactive oxygen species. The present study examined the role of peroxisomes in high-fat diet (HFD)-induced NAFLD using fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist.

METHODS

Eight-week-old male C57BL/6J mice were fed either a normal diet or HFD for 12 weeks, and fenofibrate (50 mg/kg/day) was orally administered along with the initiation of HFD.

RESULTS

HFD-induced liver injury as measured by increased alanine aminotransferase, inflammation, oxidative stress, and lipid accumulation was effectively prevented by fenofibrate. Fenofibrate significantly increased the expression of peroxisomal genes and proteins involved in peroxisomal biogenesis and function. HFD-induced attenuation of peroxisomal fatty acid oxidation was also significantly restored by fenofibrate, demonstrating the functional significance of peroxisomal fatty acid oxidation. In Ppara deficient mice, fenofibrate failed to maintain peroxisomal biogenesis and function in HFD-induced liver injury.

CONCLUSION

The present data highlight the importance of PPARα-mediated peroxisomal fitness in the protective effect of fenofibrate against NAFLD.

NADPH Oxidases Connecting Fatty Liver Disease, Insulin Resistance and Type 2 Diabetes: Current Knowledge and Therapeutic Outlook

Nonalcoholic fatty liver disease (NAFLD), characterized by ectopic fat accumulation in hepatocytes, is closely linked to insulin resistance and is the most frequent complication of type 2 diabetes mellitus (T2DM). One of the features connecting NAFLD, insulin resistance and T2DM is cellular oxidative stress. Oxidative stress refers to a redox imbalance due to an inequity between the capacity of production and the elimination of reactive oxygen species (ROS). One of the major cellular ROS sources is NADPH oxidase enzymes (NOX-es). In physiological conditions, NOX-es produce ROS purposefully in a timely and spatially regulated manner and are crucial regulators of various cellular events linked to metabolism, receptor signal transmission, proliferation and apoptosis. In contrast, dysregulated NOX-derived ROS production is related to the onset of diverse pathologies. This review provides a synopsis of current knowledge concerning NOX enzymes as connective elements between NAFLD, insulin resistance and T2DM and weighs their potential relevance as pharmacological targets to alleviate fatty liver disease.

Effects of a collagen hyaluronic acid silk-fibroin patch with the electroconductive element polyaniline on left ventricular remodeling in an infarct heart model

Biodegradable cardiac patches have been able to induce improvement in left ventricular (LV) remodeling. A novel scaffold patch made with collagen and silk-fibroin (COL-SF) was further associated to polyaniline (PANi) to increase conductivity. Thus, this study investigated the safety of the association of PANi to a patch, and the improvement in LV remodeling in a myocardial infarct (MI) rat model. Wistar rats underwent MI induction. MI was confirmed with echocardiographic and after 2 weeks, animals (n = 10/group) were randomized into: (a) COL-SF hyaluronic acid patch, (b) PANi hyaluronic acid patch, (c) MI Control (just repeat thoracotomy). Healthy animals were also followed. Echocardiography was performed at pre-treatment, and at 2-, 4-, and 8-weeks post-treatment. Hearts underwent hemodynamic evaluation on Langendorff apparatus and histology for LV thickness and percent of infarct size. Liver, kidneys, and blood samples were evaluated for biochemical, hematological, oxidative stress, and histology. There was a tendency of lower %infarct size in patched animals. LV thickness was higher in the patched animals than controls. Functional echocardiographic indices %Fractional shortening and %LV ejection fraction decreased in the MI control group, but not in the patched animals. PANi presented higher %LVEF versus MI control. PANi presented higher liver transaminases; no morphological changes were observed in histology. Elevation of antioxidant markers was observed. COL-SF and PANi patches were able to induce better remodeling features compared to MI controls on %infarct size and LV thickness and have not presented echocardiographic worsening. Polyaniline may present a slight improvement on LV remodeling, despite associated to signs of hepatotoxicity and pro-oxidant effect.

"Obesity and Insulin Resistance" Is the Component of the Metabolic Syndrome Most Strongly Associated with Oxidative Stress

Metabolic syndrome (MS) is not a homogeneous entity, but this term refers to the coexistence of factors that increase the risk for the development of type 2 diabetes and cardiovascular disease. There are different versions of the criteria for the diagnosis of MS, which makes the population of patients diagnosed with MS heterogeneous. Research to date shows that MS is associated with oxidative stress (OS), but it is unclear which MS component is most strongly associated with OS. The purpose of the study was to investigate the relationship between the parameters of OS and the presence of individual elements of MS in young adults, as well as to identify the components of MS by means of principal components analysis (PCA) and to investigate how the parameters of OS correlate with the presence of individual components. The study included 724 young adults with or without a family history of coronary heart disease (population of the MAGNETIC study). Blood samples were taken from the participants of the study to determine peripheral blood counts, biochemical parameters, and selected parameters of OS. In addition, blood pressure and anthropometric parameters were measured. In subjects with MS, significantly lower activity of superoxide dismutase (SOD), copper- and zinc-containing SOD (CuZnSOD), and manganese-containing SOD (MnSOD) were found, along with significantly higher total antioxidant capacity (TAC) and significantly lower concentration of thiol groups per gram of protein (PSH). We identified three components of MS by means of PCA: "Obesity and insulin resistance", "Dyslipidemia", and "Blood pressure", and showed the component "Obesity and insulin resistance" to have the strongest relationship with OS. In conclusion, we documented significant differences in some parameters of OS between young adults with and without MS. We showed that "Obesity and insulin resistance" is the most important component of MS in terms of relationship with OS.

Activation of PPARα-catalase pathway reverses alcoholic liver injury via upregulating NAD synthesis and accelerating alcohol clearance

Alcohol metabolism in the liver simultaneously generates toxic metabolites and disrupts redox balance, but the regulatory mechanisms have not been fully elucidated. The study aimed to characterize the role of PPARα in alcohol detoxification. Hepatic PPARα and catalase levels were examined in patients with severe alcoholic hepatitis. Mouse studies were conducted to determine the effect of PPARα reactivation by Wy14,643 on alcoholic hepatotoxicity and how catalase is involved in mediating such effects. Cell culture study was conducted to determine the effect of hydrogen peroxide on cellular NAD levels. We found that the protein levels of PPARα and catalase were significantly reduced in the livers of patients with severe alcoholic hepatitis. PPARα reactivation by Wy14,643 effectively reversed alcohol-induced liver damage in mice. Global and targeted metabolites analysis revealed a fundamental role of PPARα in regulating the tryptophan-NAD pathway. Notably, PPARα activation completely switched alcohol metabolism from the CYP2E1 pathway to the catalase pathway along with accelerated alcohol clearance. Catalase knockout mice were incompetent in alcohol metabolism and hydrogen peroxide clearance and were more susceptible to alcohol-induced liver injury. Hydrogen peroxide-treated hepatocytes had a reduced size of cellular NAD pool. These data demonstrate a key role of PPARα in regulating hepatic alcohol detoxification. Catalase-mediated hydrogen peroxide removal represents an underlying mechanism of how PPARα preserves the NAD pool. The study provides a new angle of view about the PPARα-catalase pathway in combating alcohol toxicity.

Simple kinetic method for assessing catalase activity in biological samples

A novel kinetic method for measuring catalase activity in biological samples was evaluated. The principle of the current method is based on the oxidation effect of unreacted hydrogen peroxide (H₂O₂) on pyrogallol red (PGR) using the catalytic effects of molybdenum. The decrease in the absorbance of PGR in the presence of H₂O₂ with time from 0.5 to 4.5 min was directly proportional to the concentration of H₂O₂, and, in turn, directly proportional to catalase activity. Erythrocyte lysate homogenates were used to measure catalase activity and the results of the current method were significantly correlated to those of the ammonium peroxovanadate method. The 3.1% within run and 4.7% between run coefficients of variation indicated the high precision of the present novel method. The validation process confirmed that the diagnostic method is appropriate for different types of biological samples. Here, we describe a rapid, relatively easy, and reliable method for measuring catalase activity. The assay could be applied as a diagnostic tool and is suitable in research contexts.•

A novel kinetic method for measuring catalase activity in biological samples was evaluated.

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The validation process confirmed that the diagnostic method is appropriate for different types of biological samples.

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The assay could be applied as a diagnostic tool and is suitable in research contexts.

Redox Regulation of Lipid Mobilization in Adipose Tissues

Lipid mobilization in adipose tissues, which includes lipogenesis and lipolysis, is a paramount process in regulating systemic energy metabolism. Reactive oxygen and nitrogen species (ROS and RNS) are byproducts of cellular metabolism that exert signaling functions in several cellular processes, including lipolysis and lipogenesis. During lipolysis, the adipose tissue generates ROS and RNS and thus requires a robust antioxidant response to maintain tight regulation of redox signaling. This review will discuss the production of ROS and RNS within the adipose tissue, their role in regulating lipolysis and lipogenesis, and the implications of antioxidants on lipid mobilization.

Mitochondrial Lipid Homeostasis at the Crossroads of Liver and Heart Diseases

The prevalence of NAFLD (non-alcoholic fatty liver disease) is a rapidly increasing problem, affecting a huge population around the globe. However, CVDs (cardiovascular diseases) are the most common cause of mortality in NAFLD patients. Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense LDL (low-density lipoprotein) particles, and decreased HDL-C (high-density lipoprotein cholesterol) levels, is often observed in NAFLD patients. In this review, we summarize recent genetic evidence, proving the diverse nature of metabolic pathways involved in NAFLD pathogenesis. Analysis of available genetic data suggests that the altered operation of fatty-acid β-oxidation in liver mitochondria is the key process, connecting NAFLD-mediated dyslipidemia and elevated CVD risk. In addition, we discuss several NAFLD-associated genes with documented anti-atherosclerotic or cardioprotective effects, and current pharmaceutical strategies focused on both NAFLD treatment and reduction of CVD risk.

Lipoic Acid Exacerbates Oxidative Stress and Lipid Accumulation in the Liver of Wistar Rats Fed a Hypercaloric Choline-Deficient Diet

Non-alcoholic fatty liver disease (NAFLD) is currently estimated as the most prevalent chronic liver disease in all age groups. An increasing body of evidence obtained in experimental and clinical data indicates that oxidative stress is the most important pathogenic factor in the development of NAFLD. The study aimed to investigate the impact of α-lipoic acid (LA), widely used as an antioxidant, on the effects of a hypercaloric choline-deficient diet. Male Wistar rats were divided into three groups: control diet (C); hypercaloric choline-deficient diet (HCCD), and hypercaloric choline-deficient diet with α-lipoic acid (HCCD+LA). Supplementation of HCCD with LA for eight weeks led to a decrease in visceral adipose tissue/body weight ratio, the activity of liver glutathione peroxidase and paraoxonase-1, plasma, and liver total antioxidant activity, as well as an increase in liver/body weight ratio, liver total lipid and triglyceride content, and liver transaminase activities compared to the HCCD group without LA. In conclusion, our study shows that α-lipoic acid detains obesity development but exacerbates the severity of diet-induced oxidative stress and lipid accumulation in the liver of male Wistar rats fed a hypercaloric choline-deficient diet.

Contribution of Adipose Tissue Oxidative Stress to Obesity-Associated Diabetes Risk and Ethnic Differences: Focus on Women of African Ancestry

Adipose tissue (AT) storage capacity is central in the maintenance of whole-body homeostasis, especially in obesity states. However, sustained nutrients overflow may dysregulate this function resulting in adipocytes hypertrophy, AT hypoxia, inflammation and oxidative stress. Systemic inflammation may also contribute to the disruption of AT redox equilibrium. AT and systemic oxidative stress have been involved in the development of obesity-associated insulin resistance (IR) and type 2 diabetes (T2D) through several mechanisms. Interestingly, fat accumulation, body fat distribution and the degree of how adiposity translates into cardio-metabolic diseases differ between ethnicities. Populations of African ancestry have a higher prevalence of obesity and higher T2D risk than populations of European ancestry, mainly driven by higher rates among African women. Considering the reported ethnic-specific differences in AT distribution and function and higher levels of systemic oxidative stress markers, oxidative stress is a potential contributor to the higher susceptibility for metabolic diseases in African women. This review summarizes existing evidence supporting this hypothesis while acknowledging a lack of data on AT oxidative stress in relation to IR in Africans, and the potential influence of other ethnicity-related modulators (e.g., genetic-environment interplay, socioeconomic factors) for consideration in future studies with different ethnicities.

N-Acetyl Cysteine Targets Hepatic Lipid Accumulation to Curb Oxidative Stress and Inflammation in NAFLD: A Comprehensive Analysis of the Literature

Impaired adipose tissue function and insulin resistance remain instrumental in promoting hepatic lipid accumulation in conditions of metabolic syndrome. In fact, enhanced lipid accumulation together with oxidative stress and an abnormal inflammatory response underpin the development and severity of non-alcoholic fatty liver disease (NAFLD). There are currently no specific protective drugs against NAFLD, and effective interventions involving regular exercise and healthy diets have proved difficult to achieve and maintain. Alternatively, due to its antioxidant and anti-inflammatory properties, there has been growing interest in understanding the therapeutic effects of N-acetyl cysteine (NAC) against metabolic complications, including NAFLD. Here, reviewed evidence suggests that NAC blocks hepatic lipid accumulation in preclinical models of NAFLD. This is in part through the effective regulation of a fatty acid scavenger molecule (CD36) and transcriptional factors such as sterol regulatory element-binding protein (SREBP)-1c/-2 and peroxisome proliferator-activated receptor gamma (PPARγ). Importantly, NAC appears effective in improving liver function by reducing pro-inflammatory markers such as interleukin (IL)-6 IL-1β, tumour necrosis factor alpha (TNF-α) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). This was primarily through the attenuation of lipid peroxidation and enhancements in intracellular response antioxidants, particularly glutathione. Very few clinical studies support the beneficial effects of NAC against NAFLD-related complications, thus well-organized randomized clinical trials are still necessary to confirm its therapeutic potential.

New Spectrophotometric Method for the Assessment of Catalase Enzyme Activity in Biological Tissues

Background:

Catalase is a vital antioxidant enzyme that dismutates H2O2 into water and molecular oxygen. Many protocols have been developed to measure catalase enzyme activity. Spectrophotometric methods are the most common assays that used to assess catalase enzyme activity.

Methods:

Because the rate-limiting step during catalase enzyme activity depends upon the dissociation of hydrogen peroxide, the developed assay measures the reaction between a hydroquinone/ anilinium sulfate/ammonium molybdate reagent and Unreacted Hydrogen Peroxide, which results in the production of a purple, disubstituted quinone compound with a maximum absorbance value at 550 nm.

Results:

To clarify the precision of the developed method, the coefficients of variation were determined to be 2.6% and 4.7% within run measurements and between run measurements, respectively. This method returned results that correlated well (r = 0.9982) with the results returned using the peroxovanadate method to assess catalase enzyme activity. Additionally, we examined the use of the newly developed hydroquinone assay to measure catalase enzyme activity in liver and bacterial homogenate samples.

Conclusion:

These results demonstrated that this assay can be used for scientific research and routine health applications because it is inexpensive, simple, accurate, and rapid. This method is suitable for use in clinical pathology laboratories because it is simple and produces precise and reproducible results.

Oxidative stress resulting from the removal of endogenous catalase induces obesity by promoting hyperplasia and hypertrophy of white adipocytes

Obesity is regarded as an abnormal expansion and excessive accumulation of fat mass in white adipose tissue. The involvement of oxidative stress in the development of obesity is still unclear. Although mainly present in peroxisomes, catalase scavenges intracellular H₂O₂ at toxic levels. Therefore, we used catalase-knockout (CKO) mice to elucidate the involvement of excessive H₂O₂ in the development of obesity. CKO mice with C57BL/6J background gained more weight with higher body fat mass with age than age-matched wild-type (WT) mice fed with either chow or high-fat diets. This phenomenon was attenuated by concomitant treatment with the antioxidants, melatonin or N-acetyl cysteine. Moreover, CKO mouse embryonic fibroblasts (MEFs) appeared to differentiate to adipocytes more easily than WT MEFs, showing increased H₂O₂ concentrations. Using 3T3-L1-derived adipocytes transfected with catalase-small interfering RNA, we confirmed that a more prominent lipogenesis occurred in catalase-deficient cells than in WT cells. Catalase-deficient adipocytes presented increased nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) expression but decreased adenosine monophosphate-activated protein kinase (AMPK) expression. Treatment with a NOX4 inhibitor or AMPK activator rescued the propensity for obesity of CKO mice. These findings suggest that excessive H₂O₂ and related oxidative stress increase body fat mass via both adipogenesis and lipogenesis. Manipulating NOX4 and AMPK in white adipocytes may be a therapeutic tool against obesity augmented by oxidative stress.

The impaired redox balance in peroxisomes of catalase knockout mice accelerates nonalcoholic fatty liver disease through endoplasmic reticulum stress

Peroxisomes are essential organelles for maintaining the homeostasis of lipids and reactive oxygen species (ROS). While oxidative stress-induced endoplasmic reticulum (ER) stress plays an important role in nonalcoholic fatty liver disease (NAFLD), the role of peroxisomes in ROS-mediated ER stress in the development of NAFLD remains elusive. We investigated whether an impaired peroxisomal redox state accelerates NAFLD by activating ER stress by inhibiting catalase, an antioxidant expressed exclusively in peroxisomes. Wild-type (WT) and catalase knockout (CKO) mice were fed either a normal diet or a high-fat diet (HFD) for 11 weeks. HFD-induced phenotype changes and liver injury accompanied by ER stress and peroxisomal dysfunction were accelerated in CKO mice compared to WT mice. Interestingly, these changes were also significantly increased in CKO mice fed a normal diet. Inhibition of catalase by 3-aminotriazole in hepatocytes resulted in the following effects: (i) increased peroxisomal H₂O₂ levels as measured by a peroxisome-targeted H₂O₂ probe (HyPer-P); (ii) elevated intracellular ROS; (iii) decreased peroxisomal biogenesis; (iv) activated ER stress; (v) induced lipogenic genes and neutral lipid accumulation; and (vi) suppressed insulin signaling cascade associated with JNK activation. N-acetylcysteine or 4-phenylbutyric acid effectively prevented those alterations. These results suggest that a redox imbalance in peroxisomes perturbs cellular metabolism through the activation of ER stress in the liver.

Corilagin Alleviates Nonalcoholic Fatty Liver Disease in High-Fat Diet-Induced C57BL/6 Mice by Ameliorating Oxidative Stress and Restoring Autophagic Flux

Corilagin (Cori) possesses multiple biological activities. To determine whether Cori can exert protective effects against nonalcoholic fatty liver disease (NAFLD) and its potential mechanisms. C57BL/6 mice were fed with high-fat diet (HFD) alone or in combination with Cori (20 mg/kg, i.p.) and AML12 cells were exposed to 200 μM PA/OA with or without Cori (10 μM or 20 μM). Phenotypes and key indicators relevant to NAFLD were examined both in vivo and in vitro. In this study, Cori significantly ameliorated hepatic steatosis, confirmed by improved serum lipid profiles, and hepatic TC, TG contents, and the gene expression related to lipid metabolism in livers of HFD mice. Moreover, Cori attenuated HFD-mediated autophagy (including mitophagy) blockage by restoring autophagic flux, evidenced by increased number of autophagic double vesicles containing mitochondria, elevated LC3II protein levels, decreased p62 protein levels, as well as enhanced colocalization of autophagy-related protein (LC3, Parkin) and mitochondria. In accordance with this, Cori also reduced the accumulation of ROS and MDA levels, and enhanced the activities of antioxidative enzymes including SOD, GSH-Px, and CAT. In addition, Cori treatment improved mitochondrial dysfunction, evidenced by increased mitochondrial membrane potential (ΔΨm). In parallel with this, Cori decreased mitochondrial DNA oxidative damage, while increased mitochondrial biogenesis related transcription factors expression, mitochondrial DNA content and oxygen consumption rate (OCR). In conclusion, these results demonstrate that Cori is a potential candidate for the treatment of NAFLD via diminishing oxidative stress, restoring autophagic flux, as well as improving mitochondrial functions.

Deficiency of glutathione peroxidase-1 and catalase attenuated diet-induced obesity and associated metabolic disorders

AIMS

Oxidative stress has been considered to contribute to the development of obesity-related metabolic disorders including insulin resistance. To the contrary, deficiency of an anti-oxidizing enzyme, glutathione peroxidase (GPx)-1, was reported to enhance insulin signaling, suggesting that oxidative stress may inhibit the development of type 2 diabetes. However, the beneficial effects of the absence of GPx-1 in metabolic homeostasis, including body weight control, have not yet been clearly manifested. To clarify the relationship between oxidative stress and obesity-related metabolic disorders, we investigated another mouse deficient with both GPx-1 and catalase (Cat).

METHODS

C57BL/6J wild-type and GPx-1^-/- × Cat^-/- mice were fed with a high-fat diet (60% fat) or a normal chow diet for 16 weeks and were investigated for metabolic and histological studies.

RESULTS

Body weight gain was significantly reduced, and glucose metabolism as well as hepatic steatosis was obviously improved in the GPx-1^-/- × Cat^-/- mice. The serum levels of insulin and total cholesterol were also significantly lowered. For the underlying mechanism, inflammation was attenuated and expression of markers for fat browning was enhanced in the visceral white adipose tissues.

CONCLUSIONS

Oxidative stress due to deficiency of GPx-1 and Cat may improve obesity-related metabolic disorders through attenuation of inflammation and fat browning.