Diet high in fructose leads to an overexpression of lipocalin-2 in rat fatty liver

Manifestations of Liver Impairment and the Effects of MH-76, a Non-Quinazoline α1-Adrenoceptor Antagonist, and Prazosin on Liver Tissue in Fructose-Induced Metabolic Syndrome

Excessive fructose consumption may lead to metabolic syndrome, metabolic dysfunction-associated fatty liver disease (MAFLD) and hypertension. α1-adrenoceptors antagonists are antihypertensive agents that exert mild beneficial effects on the metabolic profile in hypertensive patients. However, they are no longer used as a first-line therapy for hypertension based on Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) outcomes. Later studies have shown that quinazoline-based α1-adrenolytics (prazosin, doxazosin) induce apoptosis; however, this effect was independent of α1-adrenoceptor blockade and was associated with the presence of quinazoline moiety. Recent studies showed that α1-adrenoceptors antagonists may reduce mortality in COVID-19 patients due to anti-inflammatory properties. MH-76 (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride)) is a non-quinazoline α1-adrenoceptor antagonist which, in fructose-fed rats, exerted anti-inflammatory, antihypertensive properties and reduced insulin resistance and visceral adiposity. In this study, we aimed to evaluate the effect of fructose consumption and treatment with α1-adrenoceptor antagonists of different classes (MH-76 and prazosin) on liver tissue of fructose-fed rats. Livers were collected from four groups (Control, Fructose, Fructose + MH-76 and Fructose + Prazosin) and subjected to biochemical and histopathological studies. Both α1-adrenolytics reduced macrovesicular steatosis and triglycerides content of liver tissue and improved its antioxidant capacity. Treatment with MH-76, contrary to prazosin, reduced leucocytes infiltration as well as decreased elevated IL-6 and leptin concentrations. Moreover, the MH-76 hepatotoxicity in hepatoma HepG2 cells was less than that of prazosin. The use of α1-adrenolytics with anti-inflammatory properties may be an interesting option for treatment of hypertension with metabolic complications.

The Role of High-Fructose Diet in Liver Function of Rodent Models: A Systematic Review of Molecular Analysis

The present systematic review of animal studies on long-term fructose intake in rodents revealed a significant decrease in the activities of antioxidant enzymes due to a fructose-rich diet. The reduced activity of these enzymes led to an increase in oxidative stress, which can cause liver damage in rodents. Of eight studies analyzed, 5 (62.5%) and 1 (12.5%) used male and female rats, respectively, while 2 studies (25%) used female mice. Moreover, half of the studies used HFCS, but the other half employed fructose in the diet. Hence, it is essential to monitor dietary habits to ensure public health and nutrition research outcomes.

High concentrations of fructose cause brain damage in mice

Excessive fructose consumption is associated with the incidence of obesity and systemic inflammation, resulting in increased oxidative damage and failure to the function of brain structures. Thus, we hypothesized that fructose consumption will significantly increase inflammation, oxidative damage, and mitochondrial dysfunction in the mouse brain and, consequently, memory damage. The effects of different fructose concentrations on inflammatory and biochemical parameters in the mouse brain were evaluated. Male Swiss mice were randomized into four groups: control, with exclusive water intake, 5%, 10%, and 20% fructose group. The 10% and 20% fructose groups showed an increase in epididymal fat, in addition to higher food consumption. Inflammatory markers were increased in epididymal fat and in some brain structures. In the evaluation of oxidative damage, it was possible to observe significant increases in the hypothalamus, prefrontal cortex, and hippocampus. In the epididymal fat and in the prefrontal cortex, there was a decrease in the activity of the mitochondrial respiratory chain complexes and an increase in the striatum. Furthermore, short memory was impaired in the 10% and 20% groups but not long memory. In conclusion, excess fructose consumption can cause fat accumulation, inflammation, oxidative damage, and mitochondrial dysfunction, which can damage brain structures and consequently memory.

Naringin attenuates fructose-induced NAFLD progression in rats through reducing endogenous triglyceride synthesis and activating the Nrf2/HO-1 pathway

Background: Excessive fructose consumption causes hepatic lipid accumulation via increased triglyceride (TG) synthesis, leading to the development and progression of non-alcoholic fatty liver disease (NALFD). Naringin, a flavanone glycoside found in citrus fruit, has antioxidant and hypolipidemic properties. Therefore, the aim of this study was to investigate the effect of naringin on fructose-induced NAFLD in rats and the possible underlying mechanism. Methods: Male Sprague Dawley rats were given 10% (w/v) fructose in drinking water for 12 weeks. Naringin (100 mg/kg/day) was administered orally to rats for the last 4 weeks of fructose overload. After 12 weeks of treatment, the hepatic lipid content was determined. In addition, the expression of proteins involved in de novo lipogenesis (DNL) and TG synthesis as well as antioxidant and inflammatory mediators in the liver were examined by western blot analysis. Results: Treatment of fructose-fed rats with naringin significantly decreased the hepatic TG and cholesterol content as well as serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. Naringin treatment also decreased the hepatic expression of carbohydrate response element binding protein (ChREBP), sterol regulatory element-binding protein-1c (SREBP-1c) and nuclear SREBP-1c (nSREBP-1c) as well as enzymes involved in DNL (acetyl CoA carboxylase [ACC] and fatty acid synthase [FAS]) and an enzyme involved in TG synthesis (glycerol-3-phosphate acyltransferase 1 [GPAT-1] and diacylglycerol acyltransferase2 [DGAT2]) in fructose-fed rats. In addition, naringin induced a significant decrease in the hepatic expression of nuclear factor kappa B (NF-κB) and tumor necrosis factor α (TNF-α). Furthermore, naringin administration restored the expression of the antioxidant mediators nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1) in the liver of fructose-fed rats. Conclusion: These results demonstrate that oral administration of naringin protects against fructose-induced hepatic steatosis by decreasing DNL and TG synthesis. In addition, naringin could prevent NAFLD progression via targeting the Nrf2/HO-1 and the NF-κB/TNF-α pathways.

NLRP3 activation in neutrophils induces lethal autoinflammation, liver inflammation, and fibrosis

Sterile inflammation is a central element in liver diseases. The immune response following injurious stimuli involves hepatic infiltration of neutrophils and monocytes. Neutrophils are major effectors of liver inflammation, rapidly recruited to sites of inflammation, and can augment the recruitment of other leukocytes. The NLRP3 inflammasome has been increasingly implicated in severe liver inflammation, fibrosis, and cell death. In this study, the role of NLRP3 activation in neutrophils during liver inflammation and fibrosis was investigated. Mouse models with neutrophil-specific expression of mutant NLRP3 were developed. Mutant mice develop severe liver inflammation and lethal autoinflammation phenocopying mice with a systemic expression of mutant NLRP3. NLRP3 activation in neutrophils leads to a pro-inflammatory cytokine and chemokine profile in the liver, infiltration by neutrophils and macrophages, and an increase in cell death. Furthermore, mutant mice develop liver fibrosis associated with increased expression of pro-fibrogenic genes. Taken together, the present work demonstrates how neutrophils, driven by the NLRP3 inflammasome, coordinate other inflammatory myeloid cells in the liver, and propagate the inflammatory response in the context of inflammation-driven fibrosis.

RNA adenosine deaminase (ADAR1) alleviates high-fat diet-induced nonalcoholic fatty liver disease by inhibiting NLRP3 inflammasome

Nonalcoholic fatty liver disease (NAFLD) is a chronic inflammatory disease in which nucleotide-binding domain of leucine-rich repeat protein 3 (NLRP3) inflammasome plays an important role. The present research was aimed to explore the protective function of ADAR1, an RNA editing enzyme, against inflammatory damages in high-fat diet (HFD)-induced NAFLD through inhibiting NLRP3 inflammasome and subsequent inflammation. A total of 30 patients with NAFLD were investigated, and ADAR1 mRNA expression in peripheral blood monocytes surveyed. The in vivo study used lentivirus to explore the function of ADAR1 overexpression in the HFD-induced mouse model of NAFLD. The in vitro study used lentivirus and siRNA to explore the function of ADAR1 on the NLRP3 inflammasome activation in THP-1 cells. Results shown that the ADAR1 expression was upregulated in NAFLD patients in comparison to healthy controls. In vivo, the upregulation of ADAR1 impaired NLRP3 inflammasome activation and alleviated liver disease in HFD mice in comparison to the control group. Moreover, ADAR1 overexpression attenuated NLRP3 inflammasome in lipopolysaccharide (LPS)+ palmitic acid (PA)-induced THP-1 cells, while ADAR1 knockdown increased the NLRP3 inflammasome activation. Furthermore, we speculated that c-Jun may participate in ADAR1's inhibition of NLRP3 inflammasome. Our results suggested that ADAR1 is a potential treatment target for NAFLD via regulating the activation of NLRP3 inflammasome.

Relationship between Leptin and Insulin Resistance among Community-Dwelling Middle-Aged and Elderly Populations in Taiwan

The relationship between leptin and insulin resistance among middle-aged and elderly populations in Asia is seldom reported. Our research included 398 middle-aged and elderly Taiwanese individuals. First, we divided participants into three groups according to the tertiles of the homeostasis model assessment of insulin resistance (HOMA-IR) to analyze the parameters between each group. Pearson’s correlation was then applied to calculate the correlation between HOMA-IR and cardiometabolic risk factors after adjusting for age. A scatter plot indicated a relationship between serum leptin levels and the HOMA-IR index. Finally, the coefficients of the serum leptin level and HOMA-IR were assessed by multivariate linear regression. The participants in the high HOMA-IR index group were more likely to have higher serum leptin levels. Meanwhile, the HOMA-IR index was positively correlated with serum leptin levels, even after adjusting for age. Serum leptin levels were positively correlated with the HOMA-IR index (β = 0.226, p < 0.01) in the multivariate linear regression after adjusting for age, sex, smoking, drinking, BMI, triglycerides, systolic blood pressure, fasting plasma glucose, uric acid, ALT, and creatinine. Furthermore, the leptin−creatinine ratio also showed a significantly positive relationship with HOMA-IR in the same multivariate linear regression model. In conclusion, serum leptin levels showed a positive relationship with insulin resistance in middle-aged and elderly people in Taiwan. Furthermore, serum leptin levels may be an independent risk factor for insulin resistance according to our study.

Excessive intake of sugar: An accomplice of inflammation

High sugar intake has long been recognized as a potential environmental risk factor for increased incidence of many non-communicable diseases, including obesity, cardiovascular disease, metabolic syndrome, and type 2 diabetes (T2D). Dietary sugars are mainly hexoses, including glucose, fructose, sucrose and High Fructose Corn Syrup (HFCS). These sugars are primarily absorbed in the gut as fructose and glucose. The consumption of high sugar beverages and processed foods has increased significantly over the past 30 years. Here, we summarize the effects of consuming high levels of dietary hexose on rheumatoid arthritis (RA), multiple sclerosis (MS), psoriasis, inflammatory bowel disease (IBD) and low-grade chronic inflammation. Based on these reported findings, we emphasize that dietary sugars and mixed processed foods may be a key factor leading to the occurrence and aggravation of inflammation. We concluded that by revealing the roles that excessive intake of hexose has on the regulation of human inflammatory diseases are fundamental questions that need to be solved urgently. Moreover, close attention should also be paid to the combination of high glucose-mediated immune imbalance and tumor development, and strive to make substantial contributions to reverse tumor immune escape.

Lactobacillus plantarum improves lipogenesis and IRS-1/AKT/eNOS signalling pathway in the liver of high-fructose-fed rats

In the present study, we investigated the influence of Lactobacillus plantarum and Lactobacillus helveticus supplementation on lipogenesis, insulin signalling and glucose transporters in liver of high-fructose-fed rats. Fructose was given to the rats as a 20% solution in drinking water for 15 weeks. Lactobacillus plantarum and L. helveticus supplementations were performed by gastric gavage once a day during final 6 weeks. Dietary high-fructose increased hepatic weight, lipid accumulation and FASN expression as well as caused a significant reduction in IRS-1 expression, pAKT/total AKT and peNOS/total eNOS ratios, but an elevation in GLUT2 and GLUT5 mRNAs in the liver. Lactobacillus plantarum supplementation decreased hepatic weight, triglyceride content and FASN expression as well as improved IRS-1/AKT/eNOS pathway and GLUT2 expression in the liver of high-fructose-fed rats. However, L. helveticus supplementation exerted a restoring effect on lipid accumulation by decreasing FASN expression, and regulating effect on IRS-1 and GLUT2 expressions.

The Role of Interferon Regulatory Factors in Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is becoming the most common chronic liver disease with many metabolic comorbidities, such as obesity, diabetes, and cardiovascular diseases. Non-alcoholic steatohepatitis (NASH), an advanced form of NAFLD, accompanies the progression of hepatic steatosis, inflammation, cell death, and varying degree of liver fibrosis. Interferons (IFNs) have been shown to play important roles in the pathogenesis of NAFLD and NASH. Their regulating transcriptional factors such as interferon regulatory factors (IRFs) can regulate IFN expression, as well as genes involved in macrophage polarization, which are implicated in the pathogenesis of NAFLD and advanced liver disease. In this review, the roles of IRF-involved signaling pathways in hepatic inflammation, insulin resistance, and immune cell activation are reviewed. IRFs such as IRF1 and IRF4 are also involved in the polarization of macrophages that contribute to critical roles in NAFLD or NASH pathogenesis. In addition, IRFs have been shown to be regulated by treatments including microRNAs, PPAR modulators, anti-inflammatory agents, and TLR agonists or antagonists. Modulating IRF-mediated factors through these treatments in chronic liver disease can ameliorate the progression of NAFLD to NASH. Furthermore, adenoviruses and CRISPR activation plasmids can also be applied to regulate IRF-mediated effects in chronic liver disease. Pre-clinical and clinical trials for evaluating IRF regulators in NAFLD treatment are essential in the future direction.

Gut and liver metabolic responses to dietary fructose - are they reversible or persistent after switching to a healthy diet?

The link between increased fructose intake and induction of gut and liver dysfunction has been established, while it remains to be understood whether this damage is reversible, particularly in the young population, in which the intake of fructose has reached dramatic levels. To this end, young (30 days old) rats were fed a fructose-rich or control diet for 3 weeks to highlight the early response of the gut and liver to increased fructose intake. After this period, fructose-fed rats were returned to a control diet for 3 weeks and compared to the rats that received the control diet for the entire period to identify whether fructose-induced changes in the gut-liver axis persist or not after switching back to a control diet. Glucose transporter 5 and the tight junction protein occludin were assessed in the ileum and colon. Markers of inflammation and redox homeostasis as well as fructose and uric acid levels were also evaluated in the ileum, colon and liver. From the whole data, it is seen that metabolic derangement elicited by a fructose-rich diet, even after a brief period of intake, is fully reversed in the liver by a period of fructose withdrawal, while the alterations persist in the gut, especially in the ileum. In conclusion, given the increasing consumption of fructose-rich foods in young populations, the present results highlight the risk arising from gut persistent alterations even after the end of a fructose-rich diet. Therefore, dietary recommendations of reducing the intake of this simple sugar is mandatory to avoid not only the related metabolic alterations but also the persistence of these detrimental changes.

Transcriptome analysis reveals the hepatoprotective mechanism of soybean meal peptides against alcohol-induced acute liver injury mice

This study aimed was to explore the hepatoprotective potential of soybean meal peptides (SPs) against alcohol-induced liver injury and investigate the underlying mechanisms through transcriptome analysis. The chemical antioxidant analysis of SPs exhibited potent ABTS radical scavenging capacity (11.94 ± 0.41 mg TE/100 mg peptide), ferric reducing antioxidant power (6.42 ± 0.32 mmol Fe2+/100 mg peptide), and oxygen radical absorption capacity (14.78 ± 0.01 mg TE/100 mg peptide). Moreover, SPs increased cell viability and reduced intracellular reactive oxygen species levels in Caco-2 cells by H2O2-induced, and without cytotoxicity. In the mice model, preintervention with SPs reduced the levels of aspartate transaminase/alanine transaminase, total cholesterol, triglyceride and malondialdehyde by alcohol-induced, meanwhile, increased the levels of total superoxide dismutase, glutathione and catalase by alcohol-induced. Histological analysis showed that SPs alleviated the liver injury by alcohol-induced and no toxic effects on the kidneys. According to transcriptome analysis, 1737 genes were significantly differentially expressed (1076 up-regulated and 661 down-regulated) after SPs pretreatment. The main functions of these genes were related to inflammation, lipid metabolism and oxidation. The findings from the present study suggested that SPs produced positive hepatoprotection and showed potential to be used as a dietary supplement or an ingredient of functional food.

A Highly Sensitive Label-free Aptasensor Based on Gold Nanourchins and Carbon Nanohorns for the Detection of Lipocalin-2 (LCN-2)

A synergistic nanocomposite film composed of gold nanourchins (AuNU), oxidised carbon nanohorns (CNH), and chitosan functioned as an electrode modifier in the fabrication of the sensitive lipocalin-2 (LCN-2) aptasensor. The AuNUs/CNH/CS composite increased the surface area and thereby amplified the signal transduction. The amine-terminated LCN-2 aptamer was immobilised through the amide bond formed between the carboxyl group of polyglutamic acid (PGA) and the amine group of aptamer. Interaction of LCN-2 with the aptamer caused conformational changes in the structure of the aptamer. This generated higher conductivity, resulting in increased DPV peak current. The DPV signal increased with increasing concentration of LCN-2, and the change in signal was used for quantitative detection. The proposed aptasensor was able to detect LCN-2 in the linear range of 0.1 - 100.0 pg mL^-1, with a low detection limit of 10 fg mL^-1. The aptasensor showed high sensitivity, selectivity, reproducibility, and was able to detect LCN-2 in serum samples.

MH-76, a Novel Non-Quinazoline α1-Adrenoceptor Antagonist, but Not Prazosin Reduces Inflammation and Improves Insulin Signaling in Adipose Tissue of Fructose-Fed Rats

Background: Quinazoline α₁-adrenoceptors antagonists have been shown to exert moderately favorable effects on the metabolic profile in hypertensive patients. However, based on AntiHypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) results, they are no longer recommended as a first line therapy of hypertension. Recent studies have shown that quinazoline-based α₁-adrenoceptors antagonists (prazosin, doxazosin) induce the apoptosis and necrosis, which may be responsible for ALLHAT outcomes; however, these effects were proven to be independent of α₁-adrenoceptor blockade and were associated with the presence of quinazoline moiety. MH-76 (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride)) is a non-quinazoline α₁-adrenoceptor antagonist which, in fructose-fed rats, exerted antihypertensive effect, and, contrary to prazosin, reduced insulin resistance and abdominal adiposity. In this study we aimed to further investigate and compare the effects of MH-76 and prazosin on inflammation in adipose tissue of fructose-fed rats. Methods: Abdominal adipose tissue was collected from four groups of fructose-fed rats (Control, Fructose, Fructose + MH-76 and Fructose + Prazosin) and subjected to biochemical, histopathological and immunohistochemical studies. Moreover, selected tissue distribution studies were performed. Results: Treatment with MH-76 but not with prazosin improved endothelial integrity, reduced adipose tissue inflammation and infiltration by immune cells, resulting in lowering leptin, MCP-1, IL-6, TNF-α and PAI-1 levels. In adipose tissue from Fructose + MH-76 animals, a higher amount of eosinophils accompanied with higher IL-4 concentration was observed. Treatment with MH-76 but not with prazosin markedly reduced phosphorylation of IRS-1 at Ser307. Conclusion: MH-76 may improve insulin signaling in adipose tissue by reducing the pro-inflammatory cytokine production and inhibiting the inflammatory cells recruitment. In contrast, in adipose tissue from animals treated with prazosin, the inflammatory effect was clearly enhanced.

Neutrophil: An emerging player in the occurrence and progression of metabolic associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is a common type of chronic liver disease characterized by excessive lipid accumulation in hepatocytes, but the pathogenesis is still unclear. Neutrophils, the most abundant immune cells in the human body, defend against pathogens and regulate the inflammatory response. Recent studies have indicated that excessive liver infiltration of neutrophils is a significant histological hallmark of MAFLD, and neutrophils and their derived granule proteins participate in different stages of MAFLD, including hepatic steatosis, inflammation, fibrosis, cirrhosis and hepatocellular carcinoma. Hence, in this review, we summarize the role of neutrophils in the occurrence and progression of MAFLD and provide a perspective for the clinical application of neutrophils in MAFLD diagnosis and treatment.

Lipocalin 2 mediates appetite suppression during pancreatic cancer cachexia

Lipocalin 2 (LCN2) was recently identified as an endogenous ligand of the type 4 melanocortin receptor (MC4R), a critical regulator of appetite. However, it remains unknown if this molecule influences appetite during cancer cachexia, a devastating clinical entity characterized by decreased nutrition and progressive wasting. We demonstrate that LCN2 is robustly upregulated in murine models of pancreatic cancer, its expression is associated with reduced food consumption, and Lcn2 deletion is protective from cachexia-anorexia. Consistent with LCN2's proposed MC4R-dependent role in cancer-induced anorexia, pharmacologic MC4R antagonism mitigates cachexia-anorexia, while restoration of Lcn2 expression in the bone marrow is sufficient in restoring the anorexia feature of cachexia. Finally, we observe that LCN2 levels correlate with fat and lean mass wasting and is associated with increased mortality in patients with pancreatic cancer. Taken together, these findings implicate LCN2 as a pathologic mediator of appetite suppression during pancreatic cancer cachexia.

A Comparison of Short- and Long-Term Soy Protein Isolate Intake and Its Ability to Reduce Liver Steatosis in Obese Zucker Rats Through Modifications of Genes Involved in Inflammation and Lipid Transport

Obesity can lead to several health disorders including nonalcoholic fatty liver disease (NAFLD), the aggregation of lipids within hepatocytes, and consequent inflammation of the liver tissue. Previously, we reported that feeding obese Zucker rats with soy protein isolate (SPI) can reduce liver steatosis. To understand how SPI reduced liver steatosis, we conducted global gene expression analysis on liver samples obtained from these rats after short- (8 weeks) and long-term SPI feeding (16 weeks). We compared and contrasted these data using Ingenuity Pathway Analysis (IPA) software. This study focused mainly on target molecules that could be participating in inflammation processes and lipid metabolism that are well-known components of NAFLD. Inflammatory response was predicted to be inhibited in animals fed the SPI diet at both 8 and 16 weeks of experiment. This general prediction was based on negative activation z scores obtained through IPA (z score < -2.0, P < .00001) for eight aspects of immune function/inflammatory response. Lipid metabolism was predicted to be strongly enhanced in rats fed the SPI diet for 16 weeks than for 8 weeks. This prediction was based on positive activation z scores (z scores >2.0, P < .00001) of eight functions involved in lipid transport and metabolism. We observed that the longer the rats were fed the SPI diet, the more beneficial it resulted against NAFLD. Based on our findings, the predicted reductions in inflammatory mechanisms while enhancing lipid transport out of the liver could be the reasons behind the reduction of liver steatosis.

A Scoping Review on Lipocalin-2 and Its Role in Non-Alcoholic Steatohepatitis and Hepatocellular Carcinoma

Excess calorie intake and a sedentary lifestyle have made non-alcoholic fatty liver disease (NAFLD) one of the fastest growing forms of liver disease of the modern world. It is characterized by abnormal accumulation of fat in the liver and can range from simple steatosis and non-alcoholic steatohepatitis (NASH) to cirrhosis as well as development of hepatocellular carcinoma (HCC). Biopsy is the golden standard for the diagnosis and differentiation of all NAFLD stages, but its invasiveness poses a risk for patients, which is why new, non-invasive ways of diagnostics ought to be discovered. Lipocalin-2 (LCN2), which is a part of the lipocalin transport protein family, is a protein formally known for its role in iron transport and in inflammatory response. However, in recent years, its implication in the pathogenesis of NAFLD has become apparent. LCN2 shows significant upregulation in several benign and malignant liver diseases, making it a good candidate for the NAFLD biomarker or even a therapeutic target. What makes LCN2 more interesting to study is the fact that it is overexpressed in HCC development induced by chronic NASH, which is one of the primary causes of cancer-related deaths. However, to this day, neither its role as a biomarker for NAFLD nor the molecular mechanisms of its implication in NAFLD pathogenesis have been completely elucidated. This review aims to gather and closely dissect the current knowledge about, sometimes conflicting, evidence on LCN2 as a biomarker for NAFLD, its involvement in NAFLD, and NAFLD-HCC related pathogenesis, while comparing it to the findings in similar pathologies.

Carbohydrates great and small, from dietary fiber to sialic acids: How glycans influence the gut microbiome and affect human health

Gut microbiome composition depends heavily upon diet and has strong ties to human health. Dietary carbohydrates shape the gut microbiome by providing a potent nutrient source for particular microbes. This review explores how dietary carbohydrates in general, including individual monosaccharides and complex polysaccharides, influence the gut microbiome with subsequent effects on host health and disease. In particular, the effects of sialic acids, a prominent and influential class of monosaccharides, are discussed. Complex plant carbohydrates, such as dietary fiber, generally promote microbial production of compounds beneficial to the host while preventing degradation of host carbohydrates from colonic mucus. In contrast, simple and easily digestible sugars such as glucose are often associated with adverse effects on health and the microbiome. The monosaccharide class of sialic acids exerts a powerful but nuanced effect on gut microbiota. Sialic acid consumption (in monosaccharide form, or as part of human milk oligosaccharides or certain animal-based foods) drives the growth of organisms with sialic acid metabolism capabilities. Minor chemical modifications of Neu5Ac, the most common form of sialic acid, can alter these effects. All aspects of carbohydrate composition are therefore relevant to consider when designing dietary therapeutic strategies to alter the gut microbiome.

A high-fructose diet in rats induces systemic iron deficiency and hepatic iron overload by an inflammation mechanism

Nonalcoholic fatty liver disease (NAFLD) correlates with the high intake of fructose-rich soft drinks. Both inflammation and dysregulated iron metabolism are pathogenic factors in the development of NAFLD. The present investigation assessed the effects of a high-fructose diet (HF diet) on inflammation and iron metabolism. In this study, rats were fed a control or HF diet for 4, 8, or 12 weeks, after which insulin resistance, transaminases levels, serum and liver lipid profiles, inflammatory factors, and iron metabolism-related molecules were evaluated. The activities of the hepatic inflammation-associated pathways, IKKβ/NF-κB, and JAK2/STAT3, were detected by western blot. Result showed that the HF diet-fed animals developed a time-dependent serum lipid increase and hepatic lipid accumulation as well as insulin resistance. Serum iron (SI), serum ferritin (SF), and transferrin saturation (TS) decreased while total iron-binding capacity (TIBC) and serum transferrin (s-TF) increased at 8 and 12 weeks in the HF diet group. The HF diet led to increased transaminases levels at 8 and 12 weeks, and iron deposition was observed in the liver, accompanied by an upregulation of ferritin light chain (FTL), hepcidin (HEPC), transferrin (TF), transferrin receptor 1 (TfR1), iron regulatory protein 1 (IRP1), hemojuvelin (HJV), and divalent metal transporter 1 (DMT1). Moreover, ferroportin (FPN1) levels were downregulated, as expected from the increased HEPC. A progressive inflammation phenotype was apparent, with increased inflammatory factors, MDA, IL-1β, IL-6, and TNF-α, in the serum and liver tissue. Concomitantly, the hepatic IKKβ/NF-κB and JAK2/STAT3 pathways were activated. In summary, we verified that HF diet induces systemic iron deficiency and hepatic iron accumulation, likely due to the activation of inflammation via the NF-κB and JAK2/STAT3 pathways. PRACTICAL APPLICATIONS: As increasing numbers of individuals consume HF diets, the health implications of this type of over nutrition become globally relevant. Using a high-fructose diet rat model, our present study reveals inflammation as the link between a HF diet and dysregulated iron metabolism. Importantly, both inflammation and disrupted iron metabolism have been shown to be pathogenic factors in nonalcoholic fatty liver disease (NAFLD). The iron regulatory hormone, HEPC, is a link between the liver, inflammation, and iron metabolism. As fructose-rich foods become increasingly abundant and people's fructose intake increases, the impact of high fructose on health requires increased attention. Little research has been conducted on the effects of fructose on iron metabolism. Our study provides useful insights into the prevention and treatment of iron metabolism disorders arising from metabolic syndrome.

Glucose transporters in adipose tissue, liver, and skeletal muscle in metabolic health and disease

A family of facilitative glucose transporters (GLUTs) is involved in regulating tissue-specific glucose uptake and metabolism in the liver, skeletal muscle, and adipose tissue to ensure homeostatic control of blood glucose levels. Reduced glucose transport activity results in aberrant use of energy substrates and is associated with insulin resistance and type 2 diabetes. It is well established that GLUT2, the main regulator of hepatic hexose flux, and GLUT4, the workhorse in insulin- and contraction-stimulated glucose uptake in skeletal muscle, are critical contributors in the control of whole-body glycemia. However, the molecular mechanism how insulin controls glucose transport across membranes and its relation to impaired glycemic control in type 2 diabetes remains not sufficiently understood. An array of circulating metabolites and hormone-like molecules and potential supplementary glucose transporters play roles in fine-tuning glucose flux between the different organs in response to an altered energy demand.

Automated computerized image analysis for the user-independent evaluation of disease severity in preclinical models of NAFLD/NASH

Pathologists use a semiquantitative scoring system (NAS or SAF score) to facilitate the reporting of disease severity and evolution. Similar scores are applied for the same purposes in rodents. Histological scores have inherent inter- and intra-observer variability and yield discrete and not continuous values. Here we performed an automatic numerical quantification of NASH features on liver sections in common preclinical NAFLD/NASH models. High-fat diet-fed foz/foz mice (Foz HF) or wild-type mice (WT HF) known to develop progressive NASH or an uncomplicated steatosis, respectively, and C57Bl6 mice fed a choline-deficient high-fat diet (CDAA) to induce steatohepatitis were analyzed at various time points. Automated software image analysis of steatosis, inflammation, and fibrosis was performed on digital images from entire liver sections. Data obtained were compared with the NAS score, biochemical quantification, and gene expression. As histologically assessed, WT HF mice had normal liver up to week 34 when they harbor mild steatosis with if any, little inflammation. Foz HF mice exhibited grade 2 steatosis as early as week 4, grade 3 steatosis at week 12 up to week 34; inflammation and ballooning increased gradually with time. Automated measurement of steatosis (macrovesicular steatosis area) revealed a strong correlation with steatosis scores (r = 0.89), micro-CT liver density, liver lipid content (r = 0.89), and gene expression of CD36 (r = 0.87). Automatic assessment of the number of F4/80-immunolabelled crown-like structures strongly correlated with conventional inflammatory scores (r = 0.79). In Foz HF mice, collagen deposition, evident at week 20 and progressing at week 34, was automatically quantified on picrosirius red-stained entire liver sections. The automated procedure also faithfully captured and quantitated macrovesicular steatosis, mixed inflammation, and pericellular fibrosis in CDAA-induced steatohepatitis. In conclusion, the automatic numerical analysis represents a promising quantitative method to rapidly monitor NAFLD activity with high-throughput in large preclinical studies and for accurate monitoring of disease evolution.

The bone hormones and their potential effects on glucose and energy metabolism

The bones form the framework of our body. We know that bones protect our vital organs, regulate calcium and phosphorous homeostasis, and function as a site of erythropoiesis. More recently, however, the identification of bone hormones has allowed us to envision bones as endocrine organs too. Within the last few years, the bone hormones osteocalcin and lipocalin 2 have been implicated with glucose and energy metabolism. We systematically reviewed articles surrounding this subject and found a clear relationship between the osteocalcin levels and glucose tolerance and insulin sensitivity. We also found that many journals have shown the detrimental effects of an absences of lipocalin 2 from adipocytes. As osteocalcin administration to mice showed decreased blood glucose levels and promoted glucose tolerance and insulin sensitivity. Future studies could perhaps explore the use of osteocalcin as a supplement for type 2 diabetes.

Early Hepatic Oxidative Stress and Mitochondrial Changes Following Western Diet in Middle Aged Rats

To assess the effect of 4 weeks of high fat-high fructose feeding on whole body composition, energy balance, specific markers of oxidative stress and inflammation, and insulin sensitivity in the liver of middle-aged rats, rats (1 year) were fed a diet rich in saturated fatty acids and fructose (HFF rats), mimicking the “Western diet”, and compared with rats of the same age that were fed a low fat diet (LF rats). HFF rats exhibited a significant increase in the gain of body weight, energy, and lipids compared to LF rats. HFF rats also showed hepatic insulin resistance, together with an increase in plasma triglycerides, cholesterol, and tumor necrosis factor alpha. Hepatic lipids, triglycerides and cholesterol were higher in HFF rats, while a significant decrease in Stearoyl-CoA desaturase activity was found in this tissue. A marked increase in the protein amount of complex I, concomitant to a decrease in its contribution to mitochondrial respiration, was found in HFF rats. Lipid peroxidation and Nitro-Tyrosine content, taken as markers of oxidative stress, as well as NADPH oxidase activity, were significantly higher in HFF rats, while the antioxidant enzyme catalase decreased in these rats. Myeloperoxidase activity and lipocalin content increased, while peroxisome proliferator activated receptor gamma decreased in HFF rats. The present results provide evidence that middle-aged rats show susceptibility to a short-term “Western diet”, exhibiting altered redox homeostasis, insulin resistance, and early mitochondrial alterations in the liver. Therefore, this type of dietary habits should be drastically limited to pursue a “healthy aging”.

Sex-specific metabolic functions of adipose Lipocalin-2

OBJECTIVE

Lipocalin-2 (LCN2) is a secreted protein involved in innate immunity and has also been associated with several cardiometabolic traits in both mouse and human studies. However, the causal relationship of LCN2 to these traits is unclear, and most studies have examined only males.

METHODS

Using adeno-associated viral vectors we expressed LCN2 in either adipose or liver in a tissue specific manner on the background of a whole-body Lcn2 knockout or wildtype mice. Metabolic phenotypes including body weight, body composition, plasma and liver lipids, glucose homeostasis, insulin resistance, mitochondrial phenotyping, and metabolic cage studies were monitored.

RESULTS

We studied the genetics of LCN2 expression and associated clinical traits in both males and females in a panel of 100 inbred strains of mice (HMDP). The natural variation in Lcn2 expression across the HMDP exhibits high heritability, and genetic mapping suggests that it is regulated in part by Lipin1 gene variation. The correlation analyses revealed striking tissue dependent sex differences in obesity, insulin resistance, hepatic steatosis, and dyslipidemia. To understand the causal relationships, we examined the effects of expression of LCN2 selectively in liver or adipose. On a Lcn2-null background, LCN2 expression in white adipose promoted metabolic disturbances in females but not males. It acted in an autocrine/paracrine manner, resulting in mitochondrial dysfunction and an upregulation of inflammatory and fibrotic genes. On the other hand, on a null background, expression of LCN2 in liver had no discernible impact on the traits examined despite increasing the levels of circulating LCN2 more than adipose LCN2 expression. The mechanisms underlying the sex-specific action of LCN2 are unclear, but our results indicate that adipose LCN2 negatively regulates its receptor, LRP2 (or megalin), and its repressor, ERα, in a female-specific manner and that the effects of LCN2 on metabolic traits are mediated in part by LRP2.

CONCLUSIONS

Following up on our population-based studies, we demonstrate that LCN2 acts in a highly sex- and tissue-specific manner in mice. Our results have important implications for human studies, emphasizing the importance of sex and the tissue source of LCN2.

Paradoxical role of lipocalin-2 in metabolic disorders and neurological complications

Lipocalin-2 (LCN2), also known as 24p3 and neutrophil gelatinase-associated lipocalin (NGAL), is a 25-kDa secreted protein implicated in various metabolic and inflammatory diseases. Early studies suggest the protective function of LCN2 in which it acts as a bacteriostatic agent that competes with bacteria for iron-bound siderophores. However, both detrimental and beneficial roles of LCN2 have recently been documented in metabolic and neuroinflammatory diseases. Metabolic inflammation, as observed in diabetes and obesity, has been closely associated with the upregulation of LCN2 in blood plasma and several tissues in both humans and rodents, suggesting its pro-diabetic and pro-obesogenic role. On the contrary, other studies imply an anti-diabetic and anti-obesogenic role of LCN2 whereby a deficiency in the Lcn2 gene results in the impairment of insulin sensitivity and enhances the high-fat-diet-induced expansion of fat. A similar dual role of LCN2 has also been reported in various animal models for neurological disorders. In the midst of these mixed findings, there is no experimental evidence to explain why LCN2 shows such a contrasting role in the various studies. This debate needs to be resolved (or reconciled) and an integrated view on the topic is desirable. Herein, we attempt to address this issue by reviewing the recent findings on LCN2 in metabolic disorders and assess the potential cellular or molecular mechanisms underlying the dual role of LCN2. We further discuss the possibilities and challenges of targeting LCN2 as a potential therapeutic strategy for metabolic disorders and neurological complications.

Non-Alcoholic Fatty Liver Disease is Associated with Higher Metabolic Expenditure in Overweight and Obese Subjects: A Case-Control Study

Non-alcoholic fatty liver disease (NAFLD) is a common condition in Western countries. However, their metabolic characteristics are poorly known even though they could be important. Therefore, the objective of this study was to measure resting metabolic parameters in overweight/obese adults with hepatic steatosis compared to controls, matched for age, sex, and obesity level. Hepatic steatosis was diagnosed with liver ultrasound. Energy metabolism was measured with indirect calorimetry: energy expenditure (REE), predicted REE, the ratio between REE and the predicted REE, and the respiratory quotient (RQ) were reported. We measured some anthropometric, body composition, and bio-humoral parameters; 301 participants with NAFLD were matched for age, sex, and obesity level with 301 participants without NAFLD. People with NAFLD showed significantly higher REE (1523 ± 238 vs. 1464 ± 212 kcal, p = 0.005), REE/REE predicted ratio (98.2 ± 9.4 vs. 95.7 ± 8.1, p = 0.002), and RQ (0.88 ± 0.08 vs. 0.85 ± 0.07, p = 0.03). Moreover, the NAFLD group had significantly higher inflammatory and insulin-resistance parameters compared to controls. In conclusion, NAFLD is associated with a significantly higher metabolic expenditure, as measured with indirect calorimetry, compared to a similar cohort of individuals without this condition. Higher inflammatory levels in patients with NAFLD can probably explain our findings, even if other research is needed on this issue.

Association between dietary fibre:carbohydrate intake ratio and insulin resistance in Japanese adults without type 2 diabetes

An easily understandable index that measures the quality of carbohydrate may aid people in adopting dietary habits that improve their glucose tolerance. We aimed to evaluate the relationship between a ratio of dietary fibre to carbohydrate intakes (fibre:carbohydrate ratio (F:C-R)) and glucose tolerance cross-sectionally and longitudinally. Subjects were 190 Japanese men and women without type 2 diabetes (mean age 55·4 years) who participated in a 5-month diet and exercise programme. We compared baseline anthropometric, dietary and metabolic profiles between those with higher F:C-R and those with lower ratios. Multivariable regression analyses were performed to examine the associations between the F:C-R and homoeostasis model of assessment for insulin resistance (HOMA-IR) and HbA1c at baseline and between changes in the F:C-R and changes in HOMA-IR and HbA1c over the 5-month period. At baseline, the higher F:C-R group had significantly lower body weight, lean body mass, fasting insulin level and HOMA-IR as compared with the lower F:C-R group. The two groups had similar intakes of carbohydrate and fat, whereas protein intake was greater in the high F:C-R group. Baseline F:C-R was not significantly associated with HOMA-IR or HbA1c at the beginning of the study in multivariable models. Increases in the ratio during the 5-month programme was associated with reductions in HbA1c (P<0·001). These findings highlight the potential utility of the F:C-R in strategies aimed at type 2 diabetes prevention.

The severity of rat liver injury by fructose and high fat depends on the degree of respiratory dysfunction and oxidative stress induced in mitochondria

BACKGROUND

High fat or fructose induces non-alcoholic fatty liver disease (NAFLD) accompanied of mitochondrial dysfunction and oxidative stress. Controversy remains about whether fructose or fat is more deleterious for NAFLD development. To get more insights about this issue and to determine if the severity of liver disease induced by fructose or fat is related to degree of mitochondrial dysfunction, we compared the effects of diets containing high fat (HF), fructose (Fr) or high fat plus fructose (HF + Fr) on NAFLD development, mitochondrial function, ROS production and lipid peroxidation.

METHODS

Wistar rats were assigned to four groups: Control, fed with standard rodent chow; High fat (HF), supplemented with lard and hydrogenated vegetable oil; Fructose (Fr), supplemented with 25% fructose in the drinking water; High fat plus fructose group (HF + Fr), fed with both HF and Fr diets. Rats were sacrificed after 6 weeks of diets consumption and the liver was excised for histopathological analysis by hematoxylin and eosin staining and for mitochondria isolation. Mitochondrial function was evaluated by measuring both mitochondrial respiration and complex I activity. Lipid peroxidation and ROS production were evaluated in mitochondria by the thiobarbituric acid method and with the fluorescent ROS probe 2,4-H₂DCFDA, respectively.

RESULTS

Fr group underwent the lower degree of both liver damage and mitochondrial dysfunction that manifested like less than 20% of hepatocytes with microvesicular steatosis and partial decrease in state 3 respiration, respectively. HF group displayed an intermediate degree of damage as it showed 40% of hepatocytes with microvesicular steatosis and diminution of both state 3 respiration and complex I activity. HF + Fr group displayed more severe damage as showed microvesicular steatosis in 60% of hepatocytes and inflammation, while mitochondria exhibited fully inhibited state 3 respiration, impaired complex I activity and increased ROS generation. Exacerbation of mitochondrial lipid peroxidation was observed in both the Fr and HF + Fr groups.

CONCLUSION

Severity of liver injury induced by fructose or fat was related to the degree of dysfunction and oxidative damage in mitochondria. Attention should be paid on the serious effects observed in the HF + Fr group as the typical Western diet is rich in both fat and carbohydrates.

Comparison of liver gene expression by RNAseq and PCR analysis after 8 weeks of feeding soy protein isolate- or casein-based diets in an obese liver steatosis rat model

Differential expression of genes provides insight into fundamental mechanisms associated with the ability of soy protein isolate to attenuate liver steatosis in genetically obese rats.

The role of gut microbiota in intestinal and liver diseases

The world-wide incidence of many immune-mediated and metabolic diseases, including those of the intestines and liver, is steadily increasing. Gut microbiota plays a central role in the pathogenesis of these diseases as it mediates environmental changes to the intestinal immune system. Various environmental factors including diet, food additives and medication also trigger the compositional and functional alterations of microbiota, that is, dysbiosis, and this dysbiosis is closely associated with many chronic inflammatory diseases. However, the causal relationship remains unclear for the majority of these diseases. In this review, we discuss essential epidemiological data, known pathogenetic factors including those of genetic and environmental nature, while mainly focusing on the role of gut microbiota in the development of selected intestinal and liver diseases. Using specific examples, we also briefly describe some of the most widely-used animal models including gnotobiotic models and their contribution to the research of pathogenetic mechanisms of the host-microbiota relationship.

Early Effects of a Low Fat, Fructose-Rich Diet on Liver Metabolism, Insulin Signaling, and Oxidative Stress in Young and Adult Rats

The increase in the use of refined food, which is rich in fructose, is of particular concern in children and adolescents, since the total caloric intake and the prevalence of metabolic syndrome are increasing continuously in these populations. Nevertheless, the effects of high fructose diet have been mostly investigated in adults, by focusing on the effect of a long-term fructose intake. Notably, some reports evidenced that even short-term fructose intake exerts detrimental effects on metabolism. Therefore, the aim of this study was to compare the metabolic changes induced by the fructose-rich diet in rats of different age, i.e., young (30 days old) and adult (90 days old) rats. The fructose-rich diet increased whole body lipid content in adult, but not in young rats. The analysis of liver markers of inflammation suggests that different mechanisms depending on the age might be activated after the fructose-rich diet. In fact, a pro-inflammatory gene-expression analysis showed just a minor activation of macrophages in young rats compared to adult rats, while other markers of low-grade metabolic inflammation (TNF-alpha, myeloperoxidase, lipocalin, haptoglobin) significantly increased. Inflammation was associated with oxidative damage to hepatic lipids in young and adult rats, while increased levels of hepatic nitrotyrosine and ceramides were detected only in young rats. Interestingly, fructose-induced hepatic insulin resistance was evident in young but not in adult rats, while whole body insulin sensitivity decreased both in fructose-fed young and adult rats. Taken together, the present data indicate that young rats do not increase their body lipids but are exposed to metabolic perturbations, such as hepatic insulin resistance and hepatic oxidative stress, in line with the finding that increased fructose intake may be an important predictor of metabolic risk in young people, independently of weight status. These results indicate the need of corrective nutritional interventions for young people and adults as well for the prevention of fructose-induced metabolic alterations.

Liver cell therapy: is this the end of the beginning?

The prevalence of liver diseases is increasing globally. Orthotopic liver transplantation is widely used to treat liver disease upon organ failure. The complexity of this procedure and finite numbers of healthy organ donors have prompted research into alternative therapeutic options to treat liver disease. This includes the transplantation of liver cells to promote regeneration. While successful, the routine supply of good quality human liver cells is limited. Therefore, renewable and scalable sources of these cells are sought. Liver progenitor and pluripotent stem cells offer potential cell sources that could be used clinically. This review discusses recent approaches in liver cell transplantation and requirements to improve the process, with the ultimate goal being efficient organ regeneration. We also discuss the potential off-target effects of cell-based therapies, and the advantages and drawbacks of current pre-clinical animal models used to study organ senescence, repopulation and regeneration.

Vanadyl Sulfate Effects on Systemic Profiles of Metabolic Syndrome in Old Rats with Fructose-Induced Obesity

BACKGROUND

Currently, energy obtained from hypercaloric diets has been part of the obesity and type 2 diabetes mellitus (T2DM) epidemics from childhood to old age. Treatment alternatives have been sought from plants, minerals, and trace elements with metabolic effects. Vanadyl sulfate (VS) has been investigated as a hypoglycemic compound in animal and human studies showing effective insulin-mimetic properties. This characteristic encompasses several molecules that have beneficial pleiotropic effects. The aim was to determine the antiobesity, hypoglycemic, and hypolipidemic effects of VS on fructose-induced metabolic syndrome in aged rats.

MATERIAL AND METHODS

Five groups of male Wistar rats were made, each with six rats: two groups with normal diet (ND) and three with high-fructose diet (HFD). The first ND group was treated with saline solution (SS), the second with VS; treatment for HFD groups was in the first group with SS, second with VS, and third with metformin. Weight, body mass index (BMI), blood glucose, and lipidic profile were measured; water, food, fructose and energy consumption were also determined. All parameters were compared among groups.

RESULTS AND DISCUSSION

Although obese rats treated with VS presented anorexia, oligodipsia, and a marked weight loss in the first two weeks. They recovered food and water intake in the third week with a slow recovery of some weight weeks later. VS normalized blood glucose level and decreased triglyceride and insulin levels in obese rats. These results suggest that vanadyl sulfate shows antiobesity, hypoglycemic, and hypolipidemic properties in old obese rats and could be useful as an alternative, additional, and potent preventive treatment for obesity and T2DM control in elderly obese and poorly controlled diabetic patients.

CONCLUSION

VS could play an important role in the treatment of metabolic syndrome, contributing to a decrease in obesity and T2DM, through different ways, such as euglycemia, satiety, weight loss, and lipid profile optimization, among others. However, more research is needed to confirm this suggestion.

Lipocalin-2 in Fructose-Induced Fatty Liver Disease

The intake of excess dietary fructose most often leads to non-alcoholic fatty liver disease (NAFLD). Fructose is metabolized mainly in the liver and its chronic consumption results in lipogenic gene expression in this organ. However, precisely how fructose is involved in NAFLD progression is still not fully understood, limiting therapy. Lipocalin-2 (LCN2) is a small secreted transport protein that binds to fatty acids, phospholipids, steroids, retinol, and pheromones. LCN2 regulates lipid and energy metabolism in obesity and is upregulated in response to insulin. We previously discovered that LCN2 has a hepatoprotective effect during hepatic insult, and that its upregulation is a marker of liver damage and inflammation. To investigate if LCN2 has impact on the metabolism of fructose and thereby arising liver damage, we fed wild type and Lcn2^−/− mice for 4 or 8 weeks on diets that were enriched in fructose either by adding this sugar to the drinking water (30% w/v), or by feeding a chow containing 60% (w/w) fructose. Body weight and daily intake of food and water of these mice was then measured. Fat content in liver sections was visualized using Oil Red O stain, and expression levels of genes involved in fat and sugar metabolism were measured by qRT-PCR and Western blot analysis. We found that fructose-induced steatosis and liver damage was more prominent in female than in male mice, but that the most severe hepatic damage occurred in female mice lacking LCN2. Unexpectedly, consumption of elevated fructose did not induce de novo lipogenesis or fat accumulation. We conclude that LCN2 acts in a lipid-independent manner to protect the liver against fructose-induced damage.

Chondroitin Sulfate Inhibits Monocyte Chemoattractant Protein-1 Release From 3T3-L1 Adipocytes: A New Treatment Opportunity for Obesity-Related Inflammation?

Monocyte chemoattractant protein-1 (MCP-1) overproduction from inflamed adipose tissue is a major contributor to obesity-related metabolic syndromes. 3T3-L1 embryonic fibroblasts were cultured and differentiated into adipocytes using an established protocol. Adipocytes were treated with lipopolysaccharide (LPS) to induce inflammation and thus MCP-1 release. At the same time, varying concentrations of chondroitin sulfate (CS) were added in a physiologically relevant range (10-200 µg/mL) to determine its impact on MCP-1 release. Chondroitin sulfate, a natural glycosaminoglycan of connective tissue including the cartilage extracellular matrix, was chosen on the basis of our previous studies demonstrating its anti-inflammatory effect on macrophages. Because the main action of MCP-1 is to induce monocyte migration, cultured THP-1 monocytes were used to test whether CS at the highest physiologically relevant concentration could inhibit cell migration induced by human recombinant MCP-1. Chondroitin sulfate (100-200 µg/mL) inhibited MCP-1 release from inflamed adipocytes in a dose-dependent manner (P < .01, 95% confidence interval [CI]: −5.89 to −3.858 at 100 µg/mL and P < .001, 95% CI: −6.028 to −3.996 at 200 µg/mL) but had no effect on MCP-1–driven chemotaxis of THP-1 monocytes. In summary, CS could be expected to reduce macrophage infiltration into adipose tissue by reduction in adipocyte expression and release of MCP-1 and as such might reduce adipose tissue inflammation in response to pro-inflammatory stimuli such as LPS, now increasingly recognized to be relevant in vivo.

Anti-Obesity Effect of the Above-Ground Part of Valeriana dageletiana Nakai ex F. Maek Extract in High-Fat Diet-Induced Obese C57BL/6N Mice

Valeriana dageletiana Nakai ex F. Maek (VD) has been used as traditional medicine for the treatment of restlessness and sleeping disorders. However, it is still unclear whether obesity in mice can be altered by diet supplementation with VD. In this study, we first investigated the influences of VD on the accumulation of lipid content in 3T3-L1 cells; and the results showed that the above-ground VD extracts (VDAE) suppressed the differentiation of 3T3-L1 preadipocytes in a concentration-dependent manner without cytotoxicity. Thus, the effects of VDAE on preventing obesity were then studied in the C57BL/6N mice for 10 weeks (n = 6): normal-fat diet, high-fat diet (HFD), HFD supplemented with 1% (10 g/kg) Garcinia combogia extract (positive control), and HFD supplemented with 1% (10 g/kg) VDAE. The results showed that VDAE reduced food efficiency ratio, body weight, epididymal adipose and hepatic tissue weight, hepatic lipid metabolites, and triacylglycerol and cholesterol serum levels compared to the high-fat diet group. Moreover, VD significantly inhibited the expression of adipogenic genes, such as PPAR-γ, C/EBP-α, and aP2, and lipogenic genes, such as SREBP-1c, FAS, SCD-1, and CD36, in epididymal adipose tissue and hepatic tissue. These findings indicate anti-adipogenic and anti-lipogenic effects of VDAE and suggest that it could be a potent functional food ingredient for the prevention of high-fat diet-induced obesity.

Toxic AGE (TAGE) Theory for the Pathophysiology of the Onset/Progression of NAFLD and ALD

Non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are among the most common causes of chronic liver diseases in the westernized world. NAFLD and ALD are frequently accompanied by extrahepatic complications, including hepatocellular carcinoma and cardiovascular diseases, which have a negative impact on patient survival. The chronic ingestion of an excessive daily diet containing sugar/high-fructose corn syrup increases the level of the fructose/glucose metabolite, glyceraldehyde (GA), while the chronic consumption of an excessive number of alcoholic beverages increases the level of the alcohol metabolite, acetaldehyde (AA) in the liver. GA and AA are known to react non-enzymatically with the ε- or α-amino groups of proteins, thereby generating advanced glycation end-products (AGEs, GA-AGEs, and AA-AGEs, respectively) in vivo. The interaction between GA-AGEs and the receptor for AGEs (RAGE) alters intracellular signaling, gene expression, and the release of pro-inflammatory molecules and also elicits the production of reactive oxygen species by human hepatocytes and hepatic stellate cells, all of which may contribute to the pathological changes associated with chronic liver diseases. We herein discuss the pathophysiological roles of GA-AGEs and AA-AGEs (toxic AGEs, TAGE) and a related novel theory for preventing the onset/progression of NAFLD and ALD.

Lipocalin-2: A Master Mediator of Intestinal and Metabolic Inflammation

Lipocalin-2 (LCN2), also known as neutrophil gelatinase-associated lipocalin (NGAL), is released by various cell types and is an attractive biomarker of inflammation, ischemia, infection, and kidney damage. Both intestinal and metabolic inflammation, as observed in obesity and related disorders, are associated with increased LCN2 synthesis. While LCN2 in the intestinal tract regulates the composition of the gut microbiota and shows anti-inflammatory activities, it also exhibits proinflammatory activities in other experimental settings. In animal models of metabolic inflammation, type 2 diabetes mellitus (T2DM), or nonalcoholic steatohepatitis (NASH), increased LCN2 expression favors inflammation via the recruitment of inflammatory cells, such as neutrophils, and the induction of proinflammatory cytokines. A better understanding of this crucial marker of innate immunity might pave the way for targeting this pathway in future therapies.

The Protective Effects of p-Coumaric Acid on Acute Liver and Kidney Damages Induced by Cisplatin

In this study, we aimed to investigate the effects of p-Coumaric acid (PCA) on cisplatin (CIS)-induced hepatotoxicity and nephrotoxicity in Wistar adult rats for 24 h compared to untreated control groups. In this experiment, 40 Wistar adult rats were utilized and divided randomly into five groups. After 24 h of CIS administration, liver and kidneys were harvested and assessed by H&amp;E staining. Also, markers for oxidative stress and antioxidants were analyzed in theses tissues. Compared to the control group, accumulation of malondialdehyde was increased in groups treated CIS, whereas superoxide dismutase activities and glutathione levels were distinctly diminished in this group. The study's histopathological findings such as hydropic degeneration, vascular congestion, sinusoidal dilatation in hepatocytes and tubular necrosis in kidneys were in accordance with the results of markers for oxidative stress. PCA may prevent hepatotoxicity and nephrotoxicity by increased antioxidant enzymes and reduced oxidant parameters.

The Metalloproteinase ADAM28 Promotes Metabolic Dysfunction in Mice

Obesity and diabetes are major causes of morbidity and mortality globally. The current study builds upon our previous association studies highlighting that A Disintegrin And Metalloproteinase 28 (ADAM28) appears to be implicated in the pathogenesis of obesity and type 2 diabetes in humans. Our novel study characterised the expression of ADAM28 in mice with the metabolic syndrome and used molecular inhibition approaches to investigate the functional role of ADAM28 in the pathogenesis of high fat diet-induced obesity. We identified that ADAM28 mRNA and protein expression was markedly increased in the livers of mice with the metabolic syndrome. In addition, noradrenaline, the major neurotransmitter of the sympathetic nervous system, results in elevated Adam28 mRNA expression in human monocytes. Downregulation of ADAM28 with siRNA technology resulted in a lack of weight gain, promotion of insulin sensitivity/glucose tolerance and decreased liver tumour necrosis factor-α (TNF-α) levels in our diet-induced obesity mouse model as well as reduced blood urea nitrogen, alkaline phosphatase and aspartate aminotransferase. In addition, we show that ADAM28 knock-out mice also displayed reduced body weight, elevated high density lipoprotein cholesterol levels, and reductions in blood urea nitrogen, alkaline phosphatase, and aspartate aminotransferase. The results of this study provide important insights into the pathogenic role of the metalloproteinase ADAM28 in the metabolic syndrome and suggests that downregulation of ADAM28 may be a potential therapeutic strategy in the metabolic syndrome.

The Angiogenesis Inhibitor ALS-L1023 from Lemon-Balm Leaves Attenuates High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease through Regulating the Visceral Adipose-Tissue Function

Similar to neoplastic tissues, growth and development of adipose tissue are thought to be angiogenesis-dependent. Since visceral adipose tissue (VAT) is associated with development and progression of nonalcoholic fatty liver disease (NAFLD), we hypothesized that angiogenesis inhibition would attenuate obesity-induced NAFLD. We fed C57BL/6J mice a low-fat diet (LFD, chow 10% kcal fat), a high-fat diet (HFD, 45% kcal fat) or HFD supplemented with the lemon-balm extract ALS-L1023 (HFD-ALS) for 15 weeks. ALS-L1023 reduced endothelial cell-tube formation in vitro. HFD increased VAT angiogenesis and induced weight gains including body weight, VAT mass and visceral adipocyte size compared with LFD. However, HFD-ALS led to weight reductions without affecting calorie intake compared with HFD. HFD-ALS also reduced serum ALT and AST levels and improved lipid metabolism. HFD-ALS suppressed steatosis, infiltration of inflammatory cells, and accumulation of collagen in livers. HFD-ALS modulated hepatic expression of genes involved in lipid metabolism, inflammation, fibrosis, antioxidation, and apoptosis. Concomitantly, analysis of VAT function revealed that HFD-ALS led to fewer CD68-positive macrophage numbers and lower expression of inflammatory cytokines compared with HFD. Our findings show that the anti-angiogenic herbal extract ALS-L1023 attenuates NAFLD by targeting VAT during obesity, suggesting that angiogenesis inhibitors could aid in the treatment and prevention of obesity-induced human NAFLD.

Altered mitochondrial and peroxisomal integrity in lipocalin-2-deficient mice with hepatic steatosis

Lipocalin-2 (LCN2) is a secreted adipokine that transports small hydrophobic molecules such as fatty acids and steroids. LCN2 limits bacterial growth by sequestering iron-containing siderophores and in mammalian liver protects against inflammation, infection, injury and other stressors. Because LCN2 modulates hepatic fat metabolism and homeostasis, we performed a comparative profiling of proteins and lipids of wild type (WT) and Lcn2-deficient mice fed either standard chow or a methionine- and choline-deficient (MCD) diet. Label-free proteomics and 2D-DIGE protein expression profiling revealed differential expression of BRIT1/MCPH1, FABP5, HMGB1, HBB2, and L-FABP, results confirmed by Western blotting. Gene ontology enrichment analysis identified enrichment for genes associated with mitochondrial membrane permeabilization and metabolic processes involving carboxylic acid. Measurements of mitochondrial membrane potential, mitochondrial chelatable iron pool, intracellular lipid peroxidation, and peroxisome numbers in primary hepatocytes confirmed that LCN2 regulates mitochondrial and peroxisomal integrity. Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry imaging identified significant changes to sphingomyelins, triglycerides, and glycerophospholipids in livers of mice fed an MCD diet regardless of LCN2 status. However, two arachidonic acid-containing glycerophospholipids were increased in Lcn2-deficient livers. Thus, LCN2 influences peroxisomal and mitochondrial biology in the liver to maintain triglyceride balance, handle oxidative stress, and control apoptosis.

High Dietary Fructose: Direct or Indirect Dangerous Factors Disturbing Tissue and Organ Functions

High dietary fructose is a major contributor to insulin resistance and metabolic syndrome, disturbing tissue and organ functions. Fructose is mainly absorbed into systemic circulation by glucose transporter 2 (GLUT2) and GLUT5, and metabolized in liver to produce glucose, lactate, triglyceride (TG), free fatty acid (FFA), uric acid (UA) and methylglyoxal (MG). Its extrahepatic absorption and metabolism also take place. High levels of these metabolites are the direct dangerous factors. During fructose metabolism, ATP depletion occurs and induces oxidative stress and inflammatory response, disturbing functions of local tissues and organs to overproduce inflammatory cytokine, adiponectin, leptin and endotoxin, which act as indirect dangerous factors. Fructose and its metabolites directly and/or indirectly cause oxidative stress, chronic inflammation, endothelial dysfunction, autophagy and increased intestinal permeability, and then further aggravate the metabolic syndrome with tissue and organ dysfunctions. Therefore, this review addresses fructose-induced metabolic syndrome, and the disturbance effects of direct and/or indirect dangerous factors on the functions of liver, adipose, pancreas islet, skeletal muscle, kidney, heart, brain and small intestine. It is important to find the potential correlations between direct and/or indirect risk factors and healthy problems under excess dietary fructose consumption.

Fructose and NAFLD: The Multifaceted Aspects of Fructose Metabolism

Among various factors, such as an unhealthy diet or a sedentarity lifestyle, excessive fructose consumption is known to favor nonalcoholic fatty liver disease (NAFLD), as fructose is both a substrate and an inducer of hepatic de novo lipogenesis. The present review presents some well-established mechanisms and new clues to better understand the pathophysiology of fructose-induced NAFLD. Beyond its lipogenic effect, fructose intake is also at the onset of hepatic inflammation and cellular stress, such as oxidative and endoplasmic stress, that are key factors contributing to the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Beyond its hepatic effects, this carbohydrate may exert direct and indirect effects at the peripheral level. Excessive fructose consumption is associated, for example, with the release by the liver of several key mediators leading to alterations in the communication between the liver and the gut, muscles, and adipose tissue and to disease aggravation. These multifaceted aspects of fructose properties are in part specific to fructose, but are also shared in part with sucrose and glucose present in energy–dense beverages and foods. All these aspects must be taken into account in the development of new therapeutic strategies and thereby to better prevent NAFLD.

Reduced SHARPIN and LUBAC Formation May Contribute to CCl₄- or Acetaminophen-Induced Liver Cirrhosis in Mice

Linear ubiquitin chain assembly complex (LUBAC), composed of SHARPIN (SHANK-associated RH domain-interacting protein), HOIL-1L (longer isoform of heme-oxidized iron-regulatory protein 2 ubiquitin ligase-1), and HOIP (HOIL-1L interacting protein), forms linear ubiquitin on nuclear factor-κB (NF-κB) essential modulator (NEMO) and induces NF-κB pathway activation. SHARPIN expression and LUBAC formation were significantly reduced in the livers of mice 24 h after the injection of either carbon tetrachloride (CCl₄) or acetaminophen (APAP), both of which produced the fulminant hepatitis phenotype. To elucidate its pathological significance, hepatic SHARPIN expression was suppressed in mice by injecting shRNA adenovirus via the tail vein. Seven days after this transduction, without additional inflammatory stimuli, substantial inflammation and fibrosis with enhanced hepatocyte apoptosis occurred in the livers. A similar but more severe phenotype was observed with suppression of HOIP, which is responsible for the E3 ligase activity of LUBAC. Furthermore, in good agreement with these in vivo results, transduction of Hepa1-6 hepatoma cells with SHARPIN, HOIL-1L, or HOIP shRNA adenovirus induced apoptosis of these cells in response to tumor necrosis factor-α (TNFα) stimulation. Thus, LUBAC is essential for the survival of hepatocytes, and it is likely that reduction of LUBAC is a factor promoting hepatocyte death in addition to the direct effect of drug toxicity.

Effects of Natural Products on Fructose-Induced Nonalcoholic Fatty Liver Disease (NAFLD)

As a sugar additive, fructose is widely used in processed foods and beverages. Excessive fructose consumption can cause hepatic steatosis and dyslipidemia, leading to the development of metabolic syndrome. Recent research revealed that fructose-induced nonalcoholic fatty liver disease (NAFLD) is related to several pathological processes, including: (1) augmenting lipogenesis; (2) leading to mitochondrial dysfunction; (3) stimulating the activation of inflammatory pathways; and (4) causing insulin resistance. Cellular signaling research indicated that partial factors play significant roles in fructose-induced NAFLD, involving liver X receptor (LXR)α, sterol regulatory element binding protein (SREBP)-1/1c, acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD), peroxisome proliferator–activated receptor α (PPARα), leptin nuclear factor-erythroid 2-related factor 2 (Nrf2), nuclear factor kappa B (NF-κB), tumor necrosis factor α (TNF-α), c-Jun amino terminal kinase (JNK), phosphatidylinositol 3-kinase (PI3K) and adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK). Until now, a series of natural products have been reported as regulators of NAFLD in vivo and in vitro. This paper reviews the natural products (e.g., curcumin, resveratrol, and (−)-epicatechin) and their mechanisms of ameliorating fructose-induced NAFLD over the past years. Although, as lead compounds, natural products usually have fewer activities compared with synthesized compounds, it will shed light on studies aiming to discover new drugs for NAFLD.

Insulin Production and Resistance in Different Models of Diet-Induced Obesity and Metabolic Syndrome

The role of the liver and the endocrine pancreas in development of hyperinsulinemia in different types of obesity remains unclear. Sedentary rats (160 g) were fed a low-fat-diet (LFD, chow 13% kcal fat), high-fat-diet (HFD, 35% fat), or HFD+ 30% ethanol+ 30% fructose (HF-EFr, 22% fat). Overnight-fasted rats were culled after one, four or eight weeks. Pancreatic and hepatic mRNAs were isolated for subsequent RT-PCR analysis. After eight weeks, body weights increased three-fold in the LFD group, 2.8-fold in the HFD group, and 2.4-fold in the HF-EFr (p < 0.01). HF-EFr-fed rats had the greatest liver weights and consumed less food during Weeks 4–8 (p < 0.05). Hepatic-triglyceride content increased progressively in all groups. At Week 8, HOMA-IR values, fasting serum glucose, C-peptide, and triglycerides levels were significantly increased in LFD-fed rats compared to that at earlier time points. The greatest plasma levels of glucose, triglycerides and leptin were observed in the HF-EFr at Week 8. Gene expression of pancreatic-insulin was significantly greater in the HFD and HF-EFr groups versus the LFD. Nevertheless, insulin: C-peptide ratios and HOMA-IR values were substantially higher in HF-EFr. Hepatic gene-expression of insulin-receptor-substrate-1/2 was downregulated in the HF-EFr. The expression of phospho-ERK-1/2 and inflammatory-mediators were greatest in the HF-EFr-fed rats. Chronic intake of both LFD and HFD induced obesity, MetS, and intrahepatic-fat accumulation. The hyperinsulinemia is the strongest in rats with the lowest body weights, but having the highest liver weights. This accompanies the strongest increase of pancreatic insulin production and the maximal decrease of hepatic insulin signaling, which is possibly secondary to hepatic fat deposition, inflammation and other factors.

Chronic psychological stress and high-fat high-fructose diet disrupt metabolic and inflammatory gene networks in the brain, liver, and gut and promote behavioral deficits in mice

The mechanisms underlying the association between chronic psychological stress, development of metabolic syndrome (MetS), and behavioral impairment in obesity are poorly understood. The aim of the present study was to assess the effects of mild chronic psychological stress on metabolic, inflammatory, and behavioral profiles in a mouse model of diet-induced obesity. We hypothesized that (1) high-fat high-fructose diet (HFHF) and psychological stress would synergize to mediate the impact of inflammation on the central nervous system in the presence of behavioral dysfunction, and that (2) HFHF and stress interactions would impact insulin and lipid metabolism. C57Bl/6 male mice underwent a combination of HFHF and two weeks of chronic psychological stress. MetS-related conditions were assessed using untargeted plasma metabolomics, and structural and immune changes in the gut and liver were evaluated. Inflammation was measured in plasma, liver, gut, and brain. Our results show a complex interplay of diet and stress on gut alterations, energetic homeostasis, lipid metabolism, and plasma insulin levels. Psychological stress and HFHF diet promoted changes in intestinal tight junctions proteins and increases in insulin resistance and plasma cholesterol, and impacted the RNA expression of inflammatory factors in the hippocampus. Stress promoted an adaptive anti-inflammatory profile in the hippocampus that was abolished by diet treatment. HFHF increased hippocampal and hepatic Lcn2 mRNA expression as well as LCN2 plasma levels. Behavioral changes were associated with HFHF and stress. Collectively, these results suggest that diet and stress as pervasive factors exacerbate MetS-related conditions through an inflammatory mechanism that ultimately can impact behavior. This rodent model may prove useful for identification of possible biomarkers and therapeutic targets to treat metabolic syndrome and mood disorders.