Krüppel-like factor 2 promotes liver steatosis through upregulation of CD36

Exploring the Functionality of the Krüppel-like Factors in Kidney Development, Metabolism, and Diseases

The kidneys contribute to the overall health of an organism by maintaining systemic homeostasis. This process involves various biological mechanisms, in which the Krüppel-like factors (KLFs), a family of transcription factors, are essential for regulating development, differentiation, proliferation, and cellular apoptosis. They also play a role in the metabolic regulation of essential nutrients, such as glucose and lipids. The dysregulation of these transcription factors is associated with the development of various pathologies, which can ultimately lead to renal fibrosis, severely compromising kidney function. In this context, the present article provides a comprehensive review of the existing literature, offering an enriching analysis of the findings related to the role of KLFs in nephrology, while also highlighting their potential therapeutic role in the treatment of renal diseases.

Krüppel-like factors family in health and disease

Krüppel-like factors (KLFs) are a family of basic transcription factors with three conserved Cys2/His2 zinc finger domains located in their C-terminal regions. It is acknowledged that KLFs exert complicated effects on cell proliferation, differentiation, survival, and responses to stimuli. Dysregulation of KLFs is associated with a range of diseases including cardiovascular disorders, metabolic diseases, autoimmune conditions, cancer, and neurodegenerative diseases. Their multidimensional roles in modulating critical pathways underscore the significance in both physiological and pathological contexts. Recent research also emphasizes their crucial involvement and complex interplay in the skeletal system. Despite the substantial progress in understanding KLFs and their roles in various cellular processes, several research gaps remain. Here, we elucidated the multifaceted capabilities of KLFs on body health and diseases via various compliable signaling pathways. The associations between KLFs and cellular energy metabolism and epigenetic modification during bone reconstruction have also been summarized. This review helps us better understand the coupling effects and their pivotal functions in multiple systems and detailed mechanisms of bone remodeling and develop potential therapeutic strategies for the clinical treatment of pathological diseases by targeting the KLF family.

KLF4 promotes milk fat synthesis by regulating the PI3K-AKT-mTOR pathway and targeting FASN activation in bovine mammary epithelial cells

Milk fat is an important indicator for evaluating the quality of cow's milk. In this study, we used bovine mammary epithelial cells (BMECs) to investigate the role and molecular mechanism of KLF4 in the regulation of milk fat synthesis. The results showed that KLF4 was more highly expressed in mammary tissues of high-fat cows compared with low-fat cows. KLF4 positively regulated the expression of genes related to milk fat synthesis in BMECs, increasing intracellular triglycerides content, and KLF4 promoted milk fat synthesis by activating the PI3K-AKT-mTOR signaling pathway. Furthermore, the results of animal experiments also confirmed that knockdown of KLF4 inhibited milk fat synthesis. In addition, yeast one-hybrid assays and dual-luciferase reporter gene assays confirmed that KLF4 directly targets and binds to the fatty acid synthase (FASN) promoter region to promote FASN transcription. These results demonstrate that KLF4 is a key transcription factor for milk fat synthesis in BMECs.

Biomechanics-mediated endocytosis in atherosclerosis

Biomechanical forces, including vascular shear stress, cyclic stretching, and extracellular matrix stiffness, which influence mechanosensitive channels in the plasma membrane, determine cell function in atherosclerosis. Being highly associated with the formation of atherosclerotic plaques, endocytosis is the key point in molecule and macromolecule trafficking, which plays an important role in lipid transportation. The process of endocytosis relies on the mobility and tension of the plasma membrane, which is sensitive to biomechanical forces. Several studies have advanced the signal transduction between endocytosis and biomechanics to elaborate the developmental role of atherosclerosis. Meanwhile, increased plaque growth also results in changes in the structure, composition and morphology of the coronary artery that contribute to the alteration of arterial biomechanics. These cross-links of biomechanics and endocytosis in atherosclerotic plaques play an important role in cell function, such as cell phenotype switching, foam cell formation, and lipoprotein transportation. We propose that biomechanical force activates the endocytosis of vascular cells and plays an important role in the development of atherosclerosis.

Transcriptional determinants of lipid mobilization in human adipocytes

Defects in adipocyte lipolysis drive multiple aspects of cardiometabolic disease, but the transcriptional framework controlling this process has not been established. To address this, we performed a targeted perturbation screen in primary human adipocytes. Our analyses identified 37 transcriptional regulators of lipid mobilization, which we classified as (i) transcription factors, (ii) histone chaperones, and (iii) mRNA processing proteins. On the basis of its strong relationship with multiple readouts of lipolysis in patient samples, we performed mechanistic studies on one hit, ZNF189, which encodes the zinc finger protein 189. Using mass spectrometry and chromatin profiling techniques, we show that ZNF189 interacts with the tripartite motif family member TRIM28 and represses the transcription of an adipocyte-specific isoform of phosphodiesterase 1B (PDE1B2). The regulation of lipid mobilization by ZNF189 requires PDE1B2, and the overexpression of PDE1B2 is sufficient to attenuate hormone-stimulated lipolysis. Thus, our work identifies the ZNF189-PDE1B2 axis as a determinant of human adipocyte lipolysis and highlights a link between chromatin architecture and lipid mobilization.

The role of KLF2 in regulating hepatic lipogenesis and blood cholesterol homeostasis via the SCAP/SREBP pathway

Liver steatosis is a common metabolic disorder resulting from imbalanced lipid metabolism, which involves various processes such as de novo lipogenesis, fatty acid uptake, fatty acid oxidation, and VLDL secretion. In this study, we discovered that KLF2, a transcription factor, plays a crucial role in regulating lipid metabolism in the liver. Overexpression of KLF2 in the liver of db/db mice, C57BL/6J mice, and Cd36-/- mice fed on a normal diet resulted in increased lipid content in the liver. Additionally, transgenic mice (ALB-Klf2) that overexpressed Klf2 in the liver developed liver steatosis after being fed a normal diet. We found that KLF2 promotes lipogenesis by increasing the expression of SCAP, a chaperone that facilitates the activation of SREBP, the master transcription factor for lipogenic gene expression. Our mechanism studies revealed that KLF2 enhances lipogenesis in the liver by binding to the promoter of SCAP and increasing the expression of genes involved in fatty acid synthesis. Reduction of KLF2 expression led to a decrease in SCAP expression and a reduction in the expression of SREBP1 target genes involved in lipogenesis. Overexpression of KLF2 also increased the activation of SREBP2 and the mRNA levels of its downstream target SOAT1. In C57BL/6J mice fed a high-fat diet, overexpression of Klf2 increased blood VLDL secretion, while reducing its expression decreased blood cholesterol levels. Our study emphasizes the novelty that hepatic KLF2 plays a critical role in regulating lipid metabolism through the KLF2/SCAP/SREBPs pathway, which is essential for hepatic lipogenesis and maintaining blood cholesterol homeostasis.

Ablation of the deubiquitinase USP15 ameliorates nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) occurs due to the accumulation of fat in the liver, leading to fatal liver diseases such as nonalcoholic steatohepatitis (NASH) and cirrhosis. Elucidation of the molecular mechanisms underlying NAFLD is critical for its prevention and therapy. Here, we observed that deubiquitinase USP15 expression was upregulated in the livers of mice fed a high-fat diet (HFD) and liver biopsies of patients with NAFLD or NASH. USP15 interacts with lipid-accumulating proteins such as FABPs and perilipins to reduce ubiquitination and increase their protein stability. Furthermore, the severity of NAFLD induced by an HFD and NASH induced by a fructose/palmitate/cholesterol/trans-fat (FPC) diet was significantly ameliorated in hepatocyte-specific USP15 knockout mice. Thus, our findings reveal an unrecognized function of USP15 in the lipid accumulation of livers, which exacerbates NAFLD to NASH by overriding nutrients and inducing inflammation. Therefore, targeting USP15 can be used in the prevention and treatment of NAFLD and NASH.

Specificity Proteins (SP) and Krüppel-like Factors (KLF) in Liver Physiology and Pathology

The liver acts as a central hub that controls several essential physiological processes ranging from metabolism to detoxification of xenobiotics. At the cellular level, these pleiotropic functions are facilitated through transcriptional regulation in hepatocytes. Defects in hepatocyte function and its transcriptional regulatory mechanisms have a detrimental influence on liver function leading to the development of hepatic diseases. In recent years, increased intake of alcohol and western diet also resulted in a significantly increasing number of people predisposed to the incidence of hepatic diseases. Liver diseases constitute one of the serious contributors to global deaths, constituting the cause of approximately two million deaths worldwide. Understanding hepatocyte transcriptional mechanisms and gene regulation is essential to delineate pathophysiology during disease progression. The current review summarizes the contribution of a family of zinc finger family transcription factors, named specificity protein (SP) and Krüppel-like factors (KLF), in physiological hepatocyte functions, as well as how they are involved in the onset and development of hepatic diseases.

Exogenous miRNAs from Moringa oleifera Lam. recover a dysregulated lipid metabolism

A balanced diet is critical for human health, and edible plants play an important role in providing essential micronutrients as well as specific microRNAs (miRNAs) that can regulate human gene expression. Here we present the effects of Moringa oleifera (MO) miRNAs (mol-miRs) on lipid metabolism. Through in silico studies we identified the potential genes involved in lipid metabolism targeted by mol-miRs. To this end, we tested the efficacy of an aqueous extract of MO seeds (MOES), as suggested in traditional African ethnomedicine, or its purified miRNAs. The biological properties of MO preparations were investigated using a human derived hepatoma cell line (HepG2) as a model. MOES treatment decreased intracellular lipid accumulation and induced apoptosis in HepG2. In the same cell line, transfection with mol-miRs showed similar effects to MOES. Moreover, the effect of the mol-miR pool was investigated in a pre-obese mouse model, in which treatment with mol-miRs was able to prevent dysregulation of lipid metabolism.

ChemPert: mapping between chemical perturbation and transcriptional response for non-cancer cells

Prior knowledge of perturbation data can significantly assist in inferring the relationship between chemical perturbations and their specific transcriptional response. However, current databases mostly contain cancer cell lines, which are unsuitable for the aforementioned inference in non-cancer cells, such as cells related to non-cancer disease, immunology and aging. Here, we present ChemPert (https://chempert.uni.lu/), a database consisting of 82 270 transcriptional signatures in response to 2566 unique perturbagens (drugs, small molecules and protein ligands) across 167 non-cancer cell types, as well as the protein targets of 57 818 perturbagens. In addition, we develop a computational tool that leverages the non-cancer cell datasets, which enables more accurate predictions of perturbation responses and drugs in non-cancer cells compared to those based onto cancer databases. In particular, ChemPert correctly predicted drug effects for treating hepatitis and novel drugs for osteoarthritis. The ChemPert web interface is user-friendly and allows easy access of the entire datasets and the computational tool, providing valuable resources for both experimental researchers who wish to find datasets relevant to their research and computational researchers who need comprehensive non-cancer perturbation transcriptomics datasets for developing novel algorithms. Overall, ChemPert will facilitate future in silico compound screening for non-cancer cells.

Krüppel-like factors in glycolipid metabolic diseases

Krüppel-like factors (KLFs) are a family of transcription factors characterised by zinc-finger structures at the C-terminal. They play the key roles in cell proliferation, differentiation, and migration, as well as in embryonic development. They have been widely expressed in multiple systems in vivo, and their dysregulation is closely associated with a variety of human diseases. Glycolipid metabolism is a complex physiological process which can be regulated at the transcriptional level. Glycolipid metabolic diseases, such as obesity, non-alcoholic fatty liver disease, diabetes, and their complications, are a serious threat to human health. Recently, increasing studies have shown that KLFs are closely related to glycolipid metabolism and energy balance of the liver, adipose tissue, heart, skeletal muscle, lung, pancreas, and nervous system. In this review, we focused on the correlation between the subtypes of the KLF family and glycolipid metabolic diseases to describe new directions and trends in endocrine and glycolipid metabolic disease treatments.

Role of Krüppel-like factors in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare but deadly disease with a complex pathogenesis. Recent evidence demonstrates that Krüppel-like factors, a diverse family of transcription factors, are involved in several key disease processes such as the phenotypic transition of endothelial cells and smooth muscle cells. Importantly, manipulation of certain Krüppel-like factors enables protection or attenuation against pulmonary arterial hypertension in both animal models and preliminary human studies. In this review, we discuss how Krüppel-like factors, in particular Krüppel-like factors 2, 4 and 5 contribute to the pathological phenomena seen in pulmonary arterial hypertension and how associated signaling and microRNA pathways may be suitable targets for new therapies.

Understanding lipotoxicity in NAFLD pathogenesis: is CD36 a key driver?

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide. NAFLD stages range from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) which can progress to cirrhosis and hepatocellular carcinoma. One of the crucial events clearly involved in NAFLD progression is the lipotoxicity resulting from an excessive fatty acid (FFA) influx to hepatocytes. Hepatic lipotoxicity occurs when the capacity of the hepatocyte to manage and export FFAs as triglycerides (TGs) is overwhelmed. This review provides succinct insights into the molecular mechanisms responsible for lipotoxicity in NAFLD, including ER and oxidative stress, autophagy, lipoapotosis and inflammation. In addition, we highlight the role of CD36/FAT fatty acid translocase in NAFLD pathogenesis. Up-to-date, it is well known that CD36 increases FFA uptake and, in the liver, it drives hepatosteatosis onset and might contribute to its progression to NASH. Clinical studies have reinforced the significance of CD36 by showing increased content in the liver of NAFLD patients. Interestingly, circulating levels of a soluble form of CD36 (sCD36) are abnormally elevated in NAFLD patients and positively correlate with the histological grade of hepatic steatosis. In fact, the induction of CD36 translocation to the plasma membrane of the hepatocytes may be a determining factor in the physiopathology of hepatic steatosis in NAFLD patients. Given all these data, targeting the fatty acid translocase CD36 or some of its functional regulators may be a promising therapeutic approach for the prevention and treatment of NAFLD.

Therapeutic potential of KLF2-induced exosomal microRNAs in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homoeostatic effects of flow-activated transcription factor Krüppel-like factor 2 (KLF2) are compromised in PAH. Here, we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodelling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homoeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice. This study shows that reduced KLF2 signalling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.

High levels of dietary methionine improves sitagliptin-induced hepatotoxicity by attenuating oxidative stress in hypercholesterolemic rats

Background

Both cholesterol (Cho) and methionine (Met, a precursor for homocysteine) are risk factors for fatty liver disease. Since Western diets are rich in Cho and Met, we investigated the hepatic effects of feeding a diet enriched in Met and Cho. Further, based on the reported anti-oxidative and lipid lowering properties of sitagliptin (an antidiabetic drug), we tested whether it could counteract the negative effects of high Cho and Met. We therefore hypothesized that sitagliptin would ameliorate the development of liver pathology that is produced by feeding diets rich in either Cho, Met, or both.

Methods

Male Sprague Dawley rats were fed ad libitum a) control diet, or b) high Met or c) high Cho, or d) high Met + high Cho diets for 35 days. From day 10 to 35, 50% of rats in each dietary group were gavaged with either vehicle or an aqueous suspension of sitagliptin (100 mg/kg/day). Liver samples were harvested for histological, molecular, and biochemical analyses.

Results

The high Cho diet produced significant hepatic steatosis which was unaffected by sitagliptin. Contrary to expectation, sitagliptin exacerbated expression of hepatic markers of oxidative stress and fibrosis in rats fed high Cho. Corresponding increases in 4-hydroxynonenal adducts and collagen deposition were demonstrated by immunohistochemistry and sirius red staining. These hepatic changes were absent in rats on the high Met diet and they were comparable to controls. The inclusion of Met in the high Cho diet resulted in significant reduction of the hepatic steatosis, oxidative stress, and fibrosis produced by high Cho alone.

Conclusion

Sitagliptin exacerbated the effects of high Cho on both oxidative stress and fibrosis, resulting in NASH like symptoms that were significantly reversed by the inclusion of Met.

microRNA-32-5p targets KLF2 to promote gastric cancer by activating PI3K/AKT signaling pathway

Krüppel-like factor 2 (KLF2) is a member of the zinc finger family, which is considered a potential tumor suppressor gene due to its reduced expression in gastric cancer. MicroRNAs (miRNAs) are a class of short non-coding single-stranded RNAs that are closely related to the development of gastric cancer. The purpose of this study was to investigate the miRNAs that regulate KLF2 and explore its specific mechanism in gastric cancer. Bioinformatics software Targetscan identified that microRNA-32-5p (miRNA-32-5p) may bind to KLF2 mRNA to regulate its expression. In order to verify the regulatory effect of miRNA-32-5p on KLF2, the proliferation and migration assays were performed in both KLF2 overexpression and KLF2 knockdown gastric cancer cells. Dual-Luciferase reporter assay proved that KLF2 could bind to the PTEN promoter to induce its expression. Moreover, research on molecular mechanisms indicated that both miRNA-32-5p and shKLF2 downregulated the expression of PTEN and activated the PI3K/AKT signaling to promote the development of gastric cancer. Targeting miRNA-32-5p and KLF2 is expected to provide new sign and target for gastric cancer treatment.

Genome-wide association study for plasma very low-density lipoprotein concentration in chicken

The plasma very low-density lipoprotein (VLDL) concentration is an effective blood biochemical indicator that could be used to select lean chicken lines. In the current study, we used Genome-wide association study (GWAS) method to detect SNPs with significant effects on plasma VLDL concentration. As a result, 38 SNPs significantly associated with plasma VLDL concentration were identified using at least one of the three mixed linear model (MLM) packages, including GRAMMAR, EMMAX and GEMMA. Nearly, all these SNPs with significant effects on plasma VLDL concentration (except Gga_rs16160897) have significantly different allele frequencies between lean and fat lines. The 1-Mb regions surrounding these 38 SNPs were extracted, and twelve important regions were obtained after combining the overlaps. A total of 122 genes in these twelve important regions were detected. Among these genes, LRRK2, ABCD2, TLR4, E2F1, SUGP1, NCAN, KLF2 and RAB8A were identified as important genes for plasma VLDL concentration based on their basic functions. The results of this study may supply useful information to select lean chicken lines.

The Krüppel-Like Factors and Control of Energy Homeostasis

Nutrient handling by higher organisms is a complex process that is regulated at the transcriptional level. Studies over the past 15 years have highlighted the critical importance of a family of transcriptional regulators termed the Krüppel-like factors (KLFs) in metabolism. Within an organ, distinct KLFs direct networks of metabolic gene targets to achieve specialized functions. This regulation is often orchestrated in concert with recruitment of tissue-specific transcriptional regulators, particularly members of the nuclear receptor family. Upon nutrient entry into the intestine, gut, and liver, KLFs control a range of functions from bile synthesis to intestinal stem cell maintenance to effect nutrient acquisition. Subsequently, coordinated KLF activity across multiple organs distributes nutrients to sites of storage or liberates them for use in response to changes in nutrient status. Finally, in energy-consuming organs like cardiac and skeletal muscle, KLFs tune local metabolic programs to precisely match substrate uptake, flux, and use, particularly via mitochondrial function, with energetic demand; this is achieved in part via circulating mediators, including glucocorticoids and insulin. Here, we summarize current understanding of KLFs in regulation of nutrient absorption, interorgan circulation, and tissue-specific use.

Krüppel-Like Factors in Metabolic Homeostasis and Cardiometabolic Disease

Members of the Krüppel-like factor (KLF) family of transcription factors, which are characterized by the presence of three conserved Cys₂/His₂ zinc-fingers in their C-terminal domains, control a wide variety of biological processes. In particular, recent studies have revealed that KLFs play diverse and essential roles in the control of metabolism at the cellular, tissue and systemic levels. In both liver and skeletal muscle, KLFs control glucose, lipid and amino acid metabolism so as to coordinate systemic metabolism in the steady state and in the face of metabolic stresses, such as fasting. The functions of KLFs within metabolic tissues are also important contributors to the responses to injury and inflammation within those tissues. KLFs also control the function of immune cells, such as macrophages, which are involved in the inflammatory processes underlying both cardiovascular and metabolic diseases. This review focuses mainly on the physiological and pathological functions of KLFs in the liver and skeletal muscle. The involvement of KLFs in inflammation in these tissues is also summarized. We then discuss the implications of KLFs' control of metabolism and inflammation in cardiometabolic diseases.

Unexpected metabolic disorders induced by endocrine disruptors in Xenopus tropicalis provide new lead for understanding amphibian decline

Despite numerous studies suggesting that amphibians are highly sensitive to endocrine disruptors (EDs), both their role in the decline of populations and the underlying mechanisms remain unclear. This study showed that frogs exposed throughout their life cycle to ED concentrations low enough to be considered safe for drinking water, developed a prediabetes phenotype and, more commonly, a metabolic syndrome. Female Xenopus tropicalis exposed from tadpole stage to benzo(a)pyrene or triclosan at concentrations of 50 ng⋅L-1 displayed glucose intolerance syndrome, liver steatosis, liver mitochondrial dysfunction, liver transcriptomic signature, and pancreatic insulin hypersecretion, all typical of a prediabetes state. This metabolic syndrome led to progeny whose metamorphosis was delayed and occurred while the individuals were both smaller and lighter, all factors that have been linked to reduced adult recruitment and likelihood of reproduction. We found that F1 animals did indeed have reduced reproductive success, demonstrating a lower fitness in ED-exposed Xenopus Moreover, after 1 year of depuration, Xenopus that had been exposed to benzo(a)pyrene still displayed hepatic disorders and a marked insulin secretory defect resulting in glucose intolerance. Our results demonstrate that amphibians are highly sensitive to EDs at concentrations well below the thresholds reported to induce stress in other vertebrates. This study introduces EDs as a possible key contributing factor to amphibian population decline through metabolism disruption. Overall, our results show that EDs cause metabolic disorders, which is in agreement with epidemiological studies suggesting that environmental EDs might be one of the principal causes of metabolic disease in humans.

Krüppel-like factors: Crippling and un-crippling metabolic pathways

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors that regulate various pathways that control metabolism and other cellular mechanisms. Various KLF isoforms have been associated with cellular, organ or systemic metabolism. Altered expression or activation of KLFs has been linked to metabolic abnormalities, such as obesity and diabetes, as well as with heart failure. In this review article we summarize the metabolic functions of KLFs, as well as the networks of different KLF isoforms that jointly regulate metabolism in health and disease.

The pathogenesis of diclofenac induced immunoallergic hepatitis in a canine model of liver injury

Hypersensitivity to non-steroidal anti-inflammatory drugs is a common adverse drug reaction and may result in serious inflammatory reactions of the liver. To investigate mechanism of immunoallergic hepatitis beagle dogs were given 1 or 3 mg/kg/day (HD) oral diclofenac for 28 days. HD diclofenac treatment caused liver function test abnormalities, reduced haematocrit and haemoglobin but induced reticulocyte, WBC, platelet, neutrophil and eosinophil counts. Histopathology evidenced hepatic steatosis and glycogen depletion, apoptosis, acute lobular hepatitis, granulomas and mastocytosis. Whole genome scans revealed 663 significantly regulated genes of which 82, 47 and 25 code for stress, immune response and inflammation. Immunopathology confirmed strong induction of IgM, the complement factors C3&B, SAA, SERPING1 and others of the classical and alternate pathway. Alike, marked expression of CD205 and CD74 in Kupffer cells and lymphocytes facilitate antigen presentation and B-cell differentiation. The highly induced HIF1A and KLF6 protein expression in mast cells and macrophages sustain inflammation. Furthermore, immunogenomics discovered 24, 17, 6 and 11 significantly regulated marker genes to hallmark M1/M2 polarized macrophages, lymphocytic and granulocytic infiltrates; note, the latter was confirmed by CAE staining. Other highly regulated genes included alpha-2-macroglobulin, CRP, hepcidin, IL1R1, S100A8 and CCL20. Diclofenac treatment caused unprecedented induction of myeloperoxidase in macrophages and oxidative stress as shown by SOD1/SOD2 immunohistochemistry. Lastly, bioinformatics defined molecular circuits of inflammation and consisted of 161 regulated genes.

Altogether, the mechanism of diclofenac induced liver hypersensitivity reactions involved oxidative stress, macrophage polarization, mastocytosis, complement activation and an erroneous programming of the innate and adaptive immune system.

Krüppel-like factor 2 promotes cell proliferation in hepatocellular carcinoma through up-regulation of c-myc

Members of krüppel-like factor family have been shown to play critical roles in the development, metabolism and tumorigenesis. Our previous study demonstrated that up-regulationupregulation of KLF2 in livers from obese mice could promote hepatosteatosis. However, little is known about its effects in hepatocellular carcinogenesis. In the present study, we found that mRNA and protein expression of KLF2 was increased in primary HCC, when compared with that in adjacent normal liver. In vitro studies further showed that enforced overexpression of KLF2 expression enhanced, while its knockdown inhibited cell proliferation and invasion. At the molecular level, c-myc was a direct transcriptional target of KLF2 and a KLF2-binding site in the c-myc promoter bound specifically to KLF2 protein. Indeed, ablation of c-myc largely attenuated the proliferative roles of KLF2 in HCC cells. Therefore, our data highlight an important role for KLF2/c-myc pathway in HCC development and progression.

KLF2 exerts antifibrotic and vasoprotective effects in cirrhotic rat livers: behind the molecular mechanisms of statins

OBJECTIVE

In the liver, the transcription factor, Kruppel-like factor 2 (KLF2), is induced early during progression of cirrhosis to lessen the development of vascular dysfunction; nevertheless, its endogenous expression results insufficient to attenuate establishment of portal hypertension and aggravation of cirrhosis. Herein, we aimed to explore the effects and the underlying mechanisms of hepatic KLF2 overexpression in in vitro and in vivo models of liver cirrhosis.

DESIGN

Activation phenotype was evaluated in human and rat cirrhotic hepatic stellate cells (HSC) treated with the pharmacological inductor of KLF2 simvastatin, with adenovirus codifying for this transcription factor (Ad-KLF2), or vehicle, in presence/absence of inhibitors of KLF2. Possible paracrine interactions between parenchymal and non-parenchymal cells overexpressing KLF2 were studied. Effects of in vivo hepatic KLF2 overexpression on liver fibrosis and systemic and hepatic haemodynamics were assessed in cirrhotic rats.

RESULTS

KLF2 upregulation profoundly ameliorated HSC phenotype (reduced α-smooth muscle actin, procollagen I and oxidative stress) partly via the activation of the nuclear factor (NF)-E2-related factor 2 (Nrf2). Coculture experiments showed that improvement in HSC phenotype paracrinally ameliorated liver sinusoidal endothelial cells probably through a vascular endothelial growth factor-mediated mechanism. No paracrine interactions between hepatocytes and HSC were observed. Cirrhotic rats treated with simvastatin or Ad-KLF2 showed hepatic upregulation in the KLF2-Nrf2 pathway, deactivation of HSC and prominent reduction in liver fibrosis. Hepatic KLF2 overexpression was associated with lower portal pressure (-15%) due to both attenuations in the increased portal blood flow and hepatic vascular resistance, together with a significant improvement in hepatic endothelial dysfunction.

CONCLUSIONS

Exogenous hepatic KLF2 upregulation improves liver fibrosis, endothelial dysfunction and portal hypertension in cirrhosis.

Hyperinsulinemia Enhances Hepatic Expression of the Fatty Acid Transporter Cd36 and Provokes Hepatosteatosis and Hepatic Insulin Resistance

Hepatosteatosis is associated with the development of both hepatic insulin resistance and Type 2 diabetes. Hepatic expression of Cd36, a fatty acid transporter, is enhanced in obese and diabetic murine models and human nonalcoholic fatty liver disease, and thus it correlates with hyperinsulinemia, steatosis, and insulin resistance. Here, we have explored the effect of hyperinsulinemia on hepatic Cd36 expression, development of hepatosteatosis, insulin resistance, and dysglycemia. A 3-week sucrose-enriched diet was sufficient to provoke hyperinsulinemia, hepatosteatosis, hepatic insulin resistance, and dysglycemia in CBA/J mice. The development of hepatic steatosis and insulin resistance in CBA/J mice on a sucrose-enriched diet was paralleled by increased hepatic expression of the transcription factor Pparγ and its target gene Cd36 whereas that of genes implicated in lipogenesis, fatty acid oxidation, and VLDL secretion was unaltered. Additionally, we demonstrate that insulin, in a Pparγ-dependent manner, is sufficient to directly increase Cd36 expression in perfused livers and isolated hepatocytes. Mouse strains that display low insulin levels, i.e. C57BL6/J, and/or lack hepatic Pparγ, i.e. C3H/HeN, do not develop hepatic steatosis, insulin resistance, or dysglycemia on a sucrose-enriched diet, suggesting that elevated insulin levels, via enhanced CD36 expression, provoke fatty liver development that in turn leads to hepatic insulin resistance and dysglycemia. Thus, our data provide evidence for a direct role for hyperinsulinemia in stimulating hepatic Cd36 expression and thus the development of hepatosteatosis, hepatic insulin resistance, and dysglycemia.

Cluster-determinant 36 (CD36) impacts on vitamin E postprandial response

SCOPE

A single nucleotide polymorphism in the cluster determinant 36 (CD36) gene has recently been associated with plasma α-tocopherol concentration, suggesting a possible role of this protein in vitamin E intestinal absorption or tissue uptake.

METHODS AND RESULTS

To investigate the involvement of CD36 in vitamin E transport, we first evaluated the effect of CD36 on α- and γ-tocopherol transmembrane uptake and efflux using transfected HEK cells. γ-Tocopherol postprandial response was then assessed in CD36-deficient mice compared with wild-type mice, after the mice had been fully characterized for their α-tocopherol, vitamin A and lipid plasma, and tissue contents. Both α- and γ-tocopherol uptake was significantly increased in cells overexpressing CD36 compared with control cells. Compared with wild-type mice, CD36-deficient mice displayed a significantly decreased cholesterol hepatic concentration, and males exhibited significantly higher triacylglycerol contents in liver, brain, heart, and muscle. Although tissue α-tocopherol concentration after adjustment for lipid content was not modified, γ-tocopherol postprandial response was significantly increased in CD36-deficient mice compared with controls, likely reflecting the postprandial hypertriglyceridemia observed in these mice.

CONCLUSION

Our findings show for the first time that CD36 participates-directly or indirectly-in vitamin E uptake, and that CD36 effect on postprandial lipid metabolism in turn modifies vitamin E postprandial response.