Long-chain fatty acid activates hepatocytes through CD36 mediated oxidative stress

Investigation of parenteral nutrition-induced hepatotoxicity using human liver spheroid co-cultures

Parenteral nutrition (PN) is typically administered to individuals with gastrointestinal dysfunction, a contraindication for enteral feeding, and a need for nutritional therapy. When PN is the only energy source in patients, it is defined as total parenteral nutrition (TPN). TPN is a life-saving approach for different patient populations, both in infants and adults. However, despite numerous benefits, TPN can cause adverse effects, including metabolic disorders and liver injury. TPN-associated liver injury, known as intestinal failure-associated liver disease (IFALD), represents a significant problem affecting up to 90% of individuals receiving TPN. IFALD pathogenesis is complex, depending on the TPN components as well as on the patient's medical conditions. Despite numerous animal studies and clinical observations, the molecular mechanisms driving IFALD remain largely unknown. The present study was set up to elucidate the mechanisms underlying IFALD. For this purpose, human liver spheroid co-cultures were treated with a TPN mixture, followed by RNA sequencing analysis. Subsequently, following exposure to TPN and its single nutritional components, several key events of liver injury, including mitochondrial dysfunction, endoplasmic reticulum stress, oxidative stress, apoptosis, and lipid accumulation (steatosis), were studied using various techniques. It was found that prolonged exposure to TPN substantially changes the transcriptome profile of liver spheroids and affects multiple metabolic and signaling pathways contributing to liver injury. Moreover, TPN and its main components, especially lipid emulsion, induce changes in all key events measured and trigger steatosis.

Team players in the pathogenesis of metabolic dysfunctions-associated steatotic liver disease: The basis of development of pharmacotherapy

Nutrient metabolism is regulated by several factors. Social determinants of health with or without genetics are the primary regulator of metabolism, and an unhealthy lifestyle affects all modulators and mediators, leading to the adaptation and finally to the exhaustion of cellular functions. Hepatic steatosis is defined by presence of fat in more than 5% of hepatocytes. In hepatocytes, fat is stored as triglycerides in lipid droplet. Hepatic steatosis results from a combination of multiple intracellular processes. In a healthy individual nutrient metabolism is regulated at several steps. It ranges from the selection of nutrients in a grocery store to the last step of consumption of ATP as an energy or as a building block of a cell as structural component. Several hormones, peptides, and genes have been described that participate in nutrient metabolism. Several enzymes participate in each nutrient metabolism as described above from ingestion to generation of ATP. As of now several publications have revealed very intricate regulation of nutrient metabolism, where most of the regulatory factors are tied to each other bidirectionally, making it difficult to comprehend chronological sequence of events. Insulin hormone is the primary regulator of all nutrients' metabolism both in prandial and fasting states. Insulin exerts its effects directly and indirectly on enzymes involved in the three main cellular function processes; metabolic, inflammation and repair, and cell growth and regeneration. Final regulators that control the enzymatic functions through stimulation or suppression of a cell are nuclear receptors in especially farnesoid X receptor and peroxisome proliferator-activated receptor/RXR ligands, adiponectin, leptin, and adiponutrin. Insulin hormone has direct effect on these final modulators. Whereas blood glucose level, serum lipids, incretin hormones, bile acids in conjunction with microbiota are intermediary modulators which are controlled by lifestyle. The purpose of this review is to overview the key players in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) that help us understand the disease natural course, risk stratification, role of lifestyle and pharmacotherapy in each individual patient with MASLD to achieve personalized care and target the practice of precision medicine. PubMed and Google Scholar databases were used to identify publication related to metabolism of carbohydrate and fat in states of health and disease states; MASLD, cardiovascular disease and cancer. More than 1000 publications including original research and review papers were reviewed.

Atf3-mediated metabolic reprogramming in hepatic macrophage orchestrates metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) is regulated by complex interplay between the macrophages and surrounding cells in the liver. Here, we show that Atf3 regulates glucose-fatty acid cycle in macrophages attenuates hepatocyte steatosis, and fibrogenesis in hepatic stellate cells (HSCs). Overexpression of Atf3 in macrophages protects against the development of MASH in Western diet-fed mice, whereas Atf3 ablation has the opposite effect. Mechanistically, Atf3 improves the reduction of fatty acid oxidation induced by glucose via forkhead box O1 (FoxO1) and Cd36. Atf3 inhibits FoxO1 activity via blocking Hdac1-mediated FoxO1 deacetylation at K242, K245, and K262 and increases Zdhhc4/5-mediated CD36 palmitoylation at C3, C7, C464, and C466; furthermore, macrophage Atf3 decreases hepatocytes lipogenesis and HSCs activation via retinol binding protein 4 (Rbp4). Anti-Rbp4 can prevent MASH progression that is induced by Atf3 deficiency in macrophages. This study identifies Atf3 as a regulator of glucose-fatty acid cycle. Targeting macrophage Atf3 or Rbp4 may be a plausible therapeutic strategy for MASH.

Low-Iron Diet-Induced Fatty Liver Development Is Microbiota Dependent and Exacerbated by Loss of the Mitochondrial Iron Importer Mitoferrin2

Iron deficiency is the number one nutritional problem worldwide. Iron uptake is regulated at the intestine and is highly influenced by the gut microbiome. Blood from the intestines drains directly into the liver, informing iron status and gut microbiota status. Changes in either iron or the microbiome are tightly correlated with the development of metabolic dysfunction-associated steatotic liver disease (MASLD). To investigate the underlying mechanisms of the development of MASLD that connect altered iron metabolism and gut microbiota, we compared specific pathogen free (SPF) or germ-free (GF) mice, fed a normal or low-iron diet. SPF mice on a low-iron diet showed reduced serum triglycerides and MASLD. In contrast, GF low-iron diet-fed mice showed increased serum triglycerides and did not develop hepatic steatosis. SPF mice showed significant changes in liver lipid metabolism and increased insulin resistance that was dependent upon the presence of the gut microbiota. We report that total body loss of mitochondrial iron importer Mitoferrin2 (Mfrn2-/-) exacerbated the development of MASLD on a low-iron diet with significant lipid metabolism alterations. Our study demonstrates a clear contribution of the gut microbiome, dietary iron, and Mfrn2 in the development of MASLD and metabolic syndrome.

Interplay of CD36, autophagy, and lipid metabolism: insights into cancer progression

CD36, a scavenger receptor B2 that is dynamically distributed between cell membranes and organelle membranes, plays a crucial role in regulating lipid metabolism. Abnormal CD36 activity has been linked to a range of metabolic disorders, such as obesity, nonalcoholic fatty liver disease, insulin resistance and cardiovascular disease. CD36 undergoes various modifications, including palmitoylation, glycosylation, and ubiquitination, which greatly affect its binding affinity to various ligands, thereby triggering and influencing various biological effects. In the context of tumors, CD36 interacts with autophagy to jointly regulate tumorigenesis, mainly by influencing the tumor microenvironment. The central role of CD36 in cellular lipid homeostasis and recent molecular insights into CD36 in tumor development indicate the applicability of CD36 as a therapeutic target for cancer treatment. Here, we discuss the diverse posttranslational modifications of CD36 and their respective roles in lipid metabolism. Additionally, we delve into recent research findings on CD36 in tumors, outlining ongoing drug development efforts targeting CD36 and potential strategies for future development and highlighting the interplay between CD36 and autophagy in the context of cancer. Our aim is to provide a comprehensive understanding of the function of CD36 in both physiological and pathological processes, facilitating a more in-depth analysis of cancer progression and a better development and application of CD36-targeting drugs for tumor therapy in the near future.

Inhibition of cluster antigen 36 protects against fatty acid-induced lipid accumulation, oxidative stress, and inflammation in bovine hepatocytes

When ketosis occurs, supraphysiological concentrations of nonesterified fatty acids (NEFA) display lipotoxicity and are closely related to the occurrence of hepatic lipid accumulation, oxidative stress, and inflammation, resulting in hepatic damage and exacerbating the progression of ketosis. However, the mechanism of these lipotoxic effects caused by high concentrations of NEFA in ketosis is still unclear. Cluster antigen 36 (CD36), a fatty acid transporter, plays a vital role in the development of hepatic pathological injury in nonruminants. Thus, the aim of this study was to investigate whether CD36 plays a role in NEFA-induced hepatic lipotoxicity in dairy cows with clinical ketosis. Liver tissue and blood samples were collected from healthy (n = 10) and clinically ketotic (n = 10) cows at 3 to 15 d in milk. In addition, hepatocytes isolated from healthy calves were treated with 0, 0.6, 1.2, or 2.4 mM NEFA for 12 h; or infected with CD36 expressing adenovirus or CD36 silencing small interfering RNA for 48 h and then treated with 1.2 mM NEFA for 12 h. Compared with healthy cows, clinically ketotic cows had greater concentrations of serum NEFA and β-hydroxybutyrate and activities of aspartate aminotransferase and alanine aminotransferase but lower serum glucose. In addition, dairy cows with clinical ketosis displayed excessive hepatic lipid accumulation. More importantly, these alterations were accompanied by an increased abundance of hepatic CD36. In the cell culture model, exogenous NEFA (0, 0.6, 1.2, or 2.4 mM) treatment could dose-dependently increase the abundance of CD36. Meanwhile, NEFA (1.2 mM) increased the content of triacylglycerol, reactive oxygen species and malondialdehyde, and decreased the activities of glutathione peroxidase and superoxide dismutase. Moreover, NEFA upregulated phosphorylation levels of nuclear factor κB (NF-κB) and the inhibitor of NF-κB (IκB) α, along with the upregulation of protein abundance of NLR family pyrin domain containing 3 (NLRP3) and caspase-1, and mRNA abundance of IL1B, IL6, and tumor necrosis factor α (TNFA). These alterations induced by NEFA in bovine hepatocytes were associated with increased lipid accumulation, oxidative stress and inflammation, which could be further aggravated by CD36 overexpression. Conversely, silencing CD36 attenuated these NEFA-induced detriments. Overall, these data suggest that CD36 may be a potential therapeutic target for NEFA-induced hepatic lipid accumulation, oxidative stress, and inflammation in dairy cows.

Probiotics attenuate valproate-induced liver steatosis and oxidative stress in mice

Valproate (valproic acid, VPA), a drug for the treatment of epilepsy and bipolar disorder, causes liver steatosis with enhanced oxidative stress. Accumulating evidences exhibite that gut microbiota plays an important role in progression of nonalcoholic fatty liver disease (NAFLD). However, whether gut microbiota contributes to VPA-caused hepatic steatosis needs to be elucidated. A mixture of five probiotics was selected to investigate their effects on liver steatosis and oxidative stress in mice orally administered VPA for 30 days. Probiotics treatment significantly attenuated the hepatic lipid accumulation in VPA-treated mice via inhibiting the expression of cluster of differentiation 36 (CD36) and distinct diacylglycerol acyltransferase 2 (DGAT2). Meanwhile, probiotics exerted a protective effect against VPA-induced oxidative stress by decreasing the pro-oxidant cytochrome P450 2E1 (CYP2E1) level and activating the Nrf2/antioxidant enzyme pathway. Moreover, VPA treatment altered the relative abundance of gut microbiota at the phylum, family and genera levels, while probiotics partially restored these changes. Spearman's correlation analysis showed that several specific genera and family were significantly correlated with liver steatosis and oxidative stress-related indicators. These results suggest that probiotics exert their health benefits in the abrogation of liver steatosis and oxidative stress in VPA-treated mice by manipulating the microbial homeostasis.

Optimization of Statin-Loaded Delivery Nanoparticles for Treating Chronic Liver Diseases by Targeting Liver Sinusoidal Endothelial Cells

In this study, we developed functionalized polymeric micelles (FPMs) loaded with simvastatin (FPM-Sim) as a drug delivery system to target liver sinusoidal endothelial cells (LSECs) for preserving liver function in chronic liver disease (CLD). Polymeric micelles (PMs) were functionalized by coupling peptide ligands of LSEC membrane receptors CD32b, CD36 and ITGB3. Functionalization was confirmed via spectroscopy and electron microscopy. In vitro and in vivo FPM-Sim internalization was assessed by means of flow cytometry in LSECs, hepatocytes, Kupffer and hepatic stellate cells from healthy rats. Maximum tolerated dose assays were performed in healthy mice and efficacy studies of FPM-Sim were carried out in bile duct ligation (BDL) and thioacetamide (TAA) induction rat models of cirrhosis. Functionalization with the three peptide ligands resulted in stable formulations with a greater degree of in vivo internalization in LSECs than non-functionalized PMs. Administration of FPM-Sim in BDL rats reduced toxicity relative to free simvastatin, albeit with a moderate portal-pressure-lowering effect. In a less severe model of TAA-induced cirrhosis, treatment with FPM-CD32b-Sim nanoparticles for two weeks significantly decreased portal pressure, which was associated with a reduction in liver fibrosis, lower collagen expression as well as the stimulation of nitric oxide synthesis. In conclusion, CD32b-FPM stands out as a good nanotransporter for drug delivery, targeting LSECs, key inducers of liver injury.

ATF4-mediated CD36 upregulation contributes to palmitate-induced lipotoxicity in hepatocytes

Hepatic lipotoxicity plays a central role in the pathogenesis of nonalcoholic fatty liver disease; however, the underlying mechanisms remain elusive. Here, using both cultured hepatocytes (AML-12 cells and primary mouse hepatocytes) and the liver-specific gene knockout mice, we investigated the mechanisms underlying palmitate-elicited upregulation of CD36, a class B scavenger receptor mediating long-chain fatty acids uptake, and its role in palmitate-induced hepatolipotoxicity. We found that palmitate upregulates hepatic CD36 expression. Despite being a well-established target gene of PPARγ transactivation, our data demonstrated that the palmitate-induced CD36 upregulation in hepatocytes is in fact PPARγ-independent. We previously reported that the activation of ATF4, one of three canonical pathways activated upon endoplasmic reticulum (ER) stress induction, contributes to palmitate-triggered lipotoxicity in hepatocytes. In this study, our data revealed for the first time that ATF4 plays a critical role in mediating hepatic CD36 expression. Genetic inhibition of ATF4 attenuated CD36 upregulation induced by either palmitate or ER stress inducer tunicamycin in hepatocytes. In mice, tunicamycin upregulates liver CD36 expression, whereas hepatocyte-specific ATF4 knockout mice manifest lower hepatic CD36 expression when compared with control animals. Furthermore, we demonstrated that CD36 upregulation upon palmitate exposure represents a feedforward mechanism in that siRNA knockdown of CD36 in hepatocytes blunted ATF4 activation induced by both palmitate and tunicamycin. Finally, we confirmed that the ATF4-CD36 pathway activation contributes to palmitate-induced hepatolipotoxicity as genetic inhibition of either ATF4 or CD36 alleviated cell death and intracellular triacylglycerol accumulation. Collectively, our data demonstrate that CD36 upregulation by ATF4 activation contributes to palmitate-induced hepatic lipotoxicity.NEW & NOTEWORTHY We provided the initial evidence that ATF4 is a principal transcription factor mediating hepatic CD36 expression in that both palmitate- and ER stress-elicited CD36 upregulation was blunted by ATF4 gene knockdown in hepatocytes, and hepatocyte-specific ATF4 knockout mice manifested lower hepatic CD36 expression. We further confirmed that the ATF4-CD36 pathway activation contributes to palmitate-induced hepatolipotoxicity as genetic inhibition of either ATF4 or CD36 alleviated cell death and intracellular triacylglycerol accumulation in response to exogenous palmitate exposure.

RNA-Seq analysis of obese Pdha1fl/flLyz2-Cre mice induced by a high-fat diet

Pyruvate dehydrogenase complex (PDH) is an important complex of three enzymes that transforms pyruvate into acetyl-CoA, subsequently entering the tricarboxylic acid (TCA) cycle to produce ATP and electron donors. As a key regulator of energy and metabolic homeostasis, PDH is considered a potential therapeutic target of many diseases. On the other hand, the relationship between PDH and obesity is not clear. In this study, peripheral blood of Pdha1^fl/flLyz2-Cre and C57BL/6 mice fed a high-fat diet (HFD) was collected and subjected to extensive transcriptome sequencing. Differentially expressed genes (DEGs) were identified. Enrichment of functions and signaling pathways analyses were performed based on Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the genes selected from RNA sequencing (RNA-seq). Eventually, we found that Pdha1^fl/flLyz2-Cre mice were more susceptible to HFD-induced obesity. A total of 302 up-regulated genes and 30 down-regulated genes were screened that were differentially expressed between Pdha1^fl/flLyz2-Cre mice fed the HFD and the control groups. Furthermore, we verified that significant transcriptional changes in the genes Sgstm1, Ncoa4, Rraga, Slc3a2, Usp15, Gabarapl2, Wipi1, Sh3glb1, Mtmr3, and Cd36 were consistent with the results obtained from RNA-seq analysis. In summary, this study preliminarily established that there is a close relationship between Pdha1 and obesity and revealed the possible downstream pathways and target genes involved, laying a good foundation for the further study of Pdha1 function in the future.

Small-interfering RNA targeting proprotein convertase subtilisin/kexin type 9 might promote fatty liver disease and hepatocellular carcinoma through upregulation of CD36

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low-density lipoprotein (LDL) receptor and fatty acid translocase CD36, inducing lysosomal degradation of these two receptors in the liver cells. Both monoclonal antibody (mAb) and small-interfering RNA (siRNA) targeting PCSK9 have been designed for treatment of familial hypercholesterolemia recently, with elevating LDL receptors on the liver cell surface and increasing LDL uptake as the main beneficial mechanism. However, given that the binding domains of PCSK9 for LDL receptor and CD36 are different, and PCSK9 mAb only attacks the domain for LDL receptor, CD36 expression remains partially controlled under PCSK9 mAb treatment. In contrast, PCSK9 siRNA brings on complete loss of PCSK9, resulting in overexpression of CD36. Based on the fact that CD36 is a key factor in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and subsequent hepatocellular carcinoma (HCC), the risk of developing NAFLD and HCC on long-term use of PCSK9 siRNA is thus raised as a hypothesis. Additionally, because CD36 is also involved in the promotion of malignant diseases other than HCC, such as acute myeloid leukemia, gastric cancer, breast cancer, and colorectal cancer, the speculative danger of flourishing these malignancies by PCSK9 siRNA is discussed as well.

Carotenoids in orange carrots mitigate non-alcoholic fatty liver disease progression

Background

Carotenoids are abundant in colored fruits and vegetables. Non-alcoholic fatty liver disease (NAFLD) is a global burden and risk factor for end-stage hepatic diseases. This study aims to compare the anti-NAFLD efficacy between carotenoid-rich and carotenoid-deficient vegetables.

Materials and methods

Male C57BL/6J mice were randomized to one of four experimental diets for 15 weeks (n = 12 animals/group): Low-fat diet (LFD, 10% calories from fat), high-fat diet (HFD, 60% calories from fat), HFD with 20% white carrot powders (HFD + WC), or with 20% orange carrot powders (HFD + OC).

Results

We observed that carotenoids in the orange carrots reduced HFD-induced weight gain, better than white carrots. Histological and triglyceride (TG) analyses revealed significantly decreased HFD-induced hepatic lipid deposition and TG content in the HFD + WC group, which was further reduced in the HFD + OC group. Western blot analysis demonstrated inconsistent changes of fatty acid synthesis-related proteins but significantly improved ACOX-1 and CPT-II, indicating that orange carrot carotenoids had the potential to inhibit NAFLD by improving β-oxidation. Further investigation showed significantly higher mRNA and protein levels of PPARα and its transcription factor activity.

Conclusion

Carotenoid-rich foods may display more potent efficacy in mitigating NAFLD than those with low carotenoid levels.

Melatonin Alleviates Oxidative Stress Induced by H2O2 in Porcine Trophectodern Cells

Placental oxidative stress has been implicated as a main risk factor for placental dysfunction. Alleviation of oxidative stress and enhancement of antioxidant capacity of porcine trophectoderm (PTr2) cells are effective means to maintaining normal placental function. The present study was conducted to evaluate the protective effect of melatonin (MT) on H₂O₂-induced oxidative damage in PTr2 cells. Our data revealed that pretreatment with MT could significantly improve the decrease in cell viability induced by H₂O₂, and reduce intracellular reactive oxygen species (ROS) levels and the ratio of apoptotic cells. Here, we compared the transcriptomes of untreated versus melatonin-treated PTr2 cells by RNA-seq analysis and found that differentially expressed genes (DEGs) were highly enriched in the Wnt signaling, TGF-beta signaling and mTOR signaling pathways. Moreover, pretreatment with MT upregulated the antioxidant-related genes such as early growth response3 (EGR3), WAP four-disulfide core domain1 (WFDC1), heme oxygenase1 (HMOX1) and vimentin (VIM). These findings reveal that melatonin protects PTr2 cells from H₂O₂-induced oxidative stress damage.

Cytoskeleton alterations in non-alcoholic fatty liver disease

BACKGROUND

Due to its extremely high prevalence and severity, non-alcoholic fatty liver disease (NALFD) is a serious health and economic concern worldwide. Developing effective methods of diagnosis and therapy demands a deeper understanding of its molecular basis. One of the strategies in such an endeavor is the analysis of alterations in the morphology of liver cells. Such alterations, widely reported in NAFLD patients and disease models, are related to the cytoskeleton. Therefore, the fate of the cytoskeleton components is useful to uncover the molecular basis of NAFLD, to further design innovative approaches for its diagnosis and therapy.

MAIN FINDINGS

Several cytoskeleton proteins are up-regulated in liver cells of NAFLD patients. Under pathological conditions, keratin 18 is released from hepatocytes and its detection in the blood emerges as a non-invasive diagnosis tool. α-Smooth muscle actin is up-regulated in hepatic stellate cells and its down-regulation has been widely tested as a potential NALFD therapeutic approach. Other cytoskeleton proteins, such as vimentin, are also up-regulated.

CONCLUSIONS

NAFLD progression involves alterations in expression levels of proteins that build the liver cytoskeleton or associate with it. These findings provide a timely opportunity of developing novel approaches for NAFLD diagnosis and therapy.

Chronic angiotensin receptor activation promotes hepatic triacylglycerol accumulation during an acute glucose challenge in obese-insulin-resistant OLETF rats

PURPOSE

Angiotensin receptor blockers (ARBs) can ameliorate metabolic syndrome (MetS)-associated dyslipidemia, hepatic steatosis, and glucose intolerance, suggesting that angiotensin receptor (AT1) over-activation contributes to impaired lipid and glucose metabolism, which is characteristic of MetS. The aim of this study was to evaluate changes in the lipid profile and proteins of fatty acid uptake, triacylglycerol (TAG) synthesis, and β-oxidation to better understand the links between AT1 overactivation and non-alcoholic fatty liver disease (NAFLD) during MetS.

METHODS

Four groups of 25-week-old-rats were used: (1) untreated LETO, (2) untreated OLETF, (3) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg/d × 8 weeks) and (4) OLETF ± ARB (MINUS; 10 mg olmesartan/kg/d × 4 weeks, then removed until dissection). To investigate the dynamic shifts in metabolism, animals were dissected after an oral glucose challenge (fasting, 3 and 6 h post-glucose).

RESULTS

Compared to OLETF, plasma total cholesterol and TAG remained unchanged in ARB. However, liver TAG was 55% lesser in ARB than OLETF, and remained lower throughout the challenge. Basal CD36 and ApoB were 28% and 29% lesser, respectively, in ARB than OLETF. PRDX6 abundance in ARB was 45% lesser than OLETF, and it negatively correlated with liver TAG in ARB.

CONCLUSIONS

Chronic blockade of AT1 protects the liver from TAG accumulation during glucose overload. This may be achieved by modulating NEFA uptake and increasing TAG export via ApoB. Our study highlights the contributions of AT1 signaling to impaired hepatic substrate metabolism and the detriments of a high-glucose load and its potential contribution to steatosis during MetS.

Overexpression of PDE4D in mouse liver is sufficient to trigger NAFLD and hypertension in a CD36-TGF-β1 pathway: therapeutic role of roflumilast

Emerging evidence has shown that nonalcoholic fatty liver disease (NAFLD) may be both a consequence and a cause of hypertension. Recent studies have demonstrated that phosphodiesterase 4 (PDE4)-cAMP signaling represents a pathway relevant to the pathophysiology of metabolic disorders. This study aims to investigate the impact and the underlying mechanism of PDE4 in the pathogenesis of NAFLD and its associated hypertension. Here we demonstrated that high-fat-diet (HFD) fed mice developed NAFLD and hypertension, with an associated increase in hepatic PDE4D expression, which can be prevented and even reversed by PDE4 inhibitor roflumilast. Furthermore, we demonstrated that hepatic overexpression of PDE4D drove significant hepatic steatosis and elevation of blood pressure. Mechanistically, PDE4D activated fatty acid translocase CD36 signaling which facilitates hepatic lipid deposition, resulting in TGF-β1 production by hepatocytes and excessive TGF-β1 signaling in vessels and consequent hypertension. Specific silencing of TGF-β1 in hepatocytes by siRNA using poly (β-amino ester) nanoparticles significantly normalized hepatic PDE4D overexpression-activated TGF-β1 signaling in vessels and hypertension. Together, the conclusions indicated that PDE4D plays an important role in the pathogenesis of NAFLD and associated hypertension via activation of CD36-TGF-β1 signaling in the liver. PDE4 inhibitor such as roflumilast, which is clinically approved for chronic obstructive pulmonary disease (COPD) treatment, has the potential to be used as a preventive or therapeutic drug against NAFLD and associated hypertension in the future.

The Role and Mechanism of Oxidative Stress and Nuclear Receptors in the Development of NAFLD

The overproduction of reactive oxygen species (ROS) and consequent oxidative stress contribute to the pathogenesis of acute and chronic liver diseases. It is now acknowledged that nonalcoholic fatty liver disease (NAFLD) is characterized as a redox-centered disease due to the role of ROS in hepatic metabolism. However, the underlying mechanisms accounting for these alternations are not completely understood. Several nuclear receptors (NRs) are dysregulated in NAFLD, and have a direct influence on the expression of a set of genes relating to the progress of hepatic lipid homeostasis and ROS generation. Meanwhile, the NRs act as redox sensors in response to metabolic stress. Therefore, targeting NRs may represent a promising strategy for improving oxidation damage and treating NAFLD. This review summarizes the link between impaired lipid metabolism and oxidative stress and highlights some NRs involved in regulating oxidant/antioxidant turnover in the context of NAFLD, shedding light on potential therapies based on NR-mediated modulation of ROS generation and lipid accumulation.

MiR-100 overexpression attenuates high fat diet induced weight gain, liver steatosis, hypertriglyceridemia and development of metabolic syndrome in mice

BACKGROUND

Diet-induced obesity can result in the development of a diverse spectrum of cardiovascular and metabolic diseases, including type 2 diabetes, dyslipidemia, non-alcoholic liver steatosis and atherosclerotic disease. MicroRNAs have been described to be important regulators of metabolism and disease development.

METHODS

In the current study, we investigated the effects of ubiquitous miR-100 overexpression on weight gain and the metabolic phenotype in a newly generated transgenic mouse strain under normal chow and high fat diet and used microarray expression analysis to identify new potential target genes of miR-100.

RESULTS

While transgenic overexpression of miR-100 did not significantly affect weight and metabolism under a normal diet, miR-100 overexpressing mice showed a reduced weight gain under a high fat diet compared to wildtype mice, despite an equal calorie intake. This was accompanied by less visceral and subcutaneous fat development and lover serum LDL cholesterol. In addition, transgenic miR-100 mice were more glucose tolerant and insulin sensitive and demonstrated increased energy expenditure under high fat diet feeding. A comprehensive gene expression profiling revealed the differential expression of several genes involved in lipid storage- and metabolism, among them CD36 and Cyp4A14. Our data showed a direct regulation of CD36 by miR-100, leading to a reduced fatty acid uptake in primary hepatocytes overexpressing miR-100 and the downregulation of several downstream mediators of lipid metabolism such as ACC1, FABP4, FAS and PPARγ in the liver.

CONCLUSIONS

Our findings demonstrate a protective role of miR-100 in high fat diet induced metabolic syndrome and liver steatosis, partially mediated by the direct repression of CD36 and attenuation of hepatic lipid storage, implicating miR-100 as a possible therapeutic target in liver steatosis.

Lipid metabolism and oxidative stress in HPV-related cancers

High-risk human papillomavirus (HR-HPVs) are associated with the development of cervical, anus, vagina, vulva, penis, and oropharynx cancer. HR-HPVs target and modify the function of different cell biomolecules such as glucose, amino acids, lipids, among others. The latter induce cell proliferation, cell death evasion, and genomic instability resulting in cell transformation. Moreover, lipids are essential biomolecules in HR-HPVs infection and cell vesicular trafficking. They are also critical in producing cellular energy, the epithelial-mesenchymal transition (EMT) process, and therapy resistance of HPV-related cancers. HPV proteins induce oxidative stress (OS), which in turn promotes lipid peroxidation and cell damage, resulting in cell death such as apoptosis, autophagy, and ferroptosis. HR-HPV-related cancer cells cope with OS and lipid peroxidation, preventing cell death; however, these cells are sensitized by OS, which could be used as a target for redox therapies to induce their elimination. This review focuses on the role of lipids in HR-HPV infection and HPV-related cancer development, maintenance, resistance to therapy, and the possible treatments associated with lipids. Furthermore, we emphasize the significant role of OS in lipid peroxidation to induce cell death through apoptosis, autophagy, and ferroptosis to eliminate HPV-related cancers.

CD36 and DGAT2 facilitate the lipid-lowering effect of chitooligosaccharides via fatty acid intake and triglyceride synthesis signaling

This study examined the impact of chitobiose (GlcN)2 and chitotriose (GlcN)3 on lipid accumulation modification and their inhibitory functionalities. (GlcN)2 and (GlcN)3 significantly inhibited the total cholesterol (TC), triglyceride (TG), and low-density lipid cholesterol (LDL-c) levels in the liver of the ob/ob-/- mice fed a non-high-fat diet. This phenomenon was associated with a reduction in the mRNA and protein expression of TG synthesis and fatty acid uptake-related signaling, significantly affecting the cluster of differentiation 36 (CD36) and diacylglycerol acyltransferase 2 (DGAT2). Furthermore, the CD36 and DGAT2 genes were overexpressed by constructing a plasmid and transfecting it into HepG2 cells, after which the phenotypic traits of lipid accumulation were assessed in vitro. Consequently, it was evident that (GlcN)2 and (GlcN)3 reduced the overexpression of these proteins and relieved cellular lipid accumulation. In conclusion, these results indicated that (GlcN)2 and (GlcN)3 acted positively against NAFLD while regulating steatosis in the non-high-fat diet NAFLD model. The potential NAFLD treatment strategies, such as targeting CD36 and DGAT2 signaling, could provide scientific insight into further applying food-derived ingredients to reduce the risk of high-fat metabolism.

Lupinus angustifolius Protein Hydrolysates Reduce Abdominal Adiposity and Ameliorate Metabolic Associated Fatty Liver Disease (MAFLD) in Western Diet Fed-ApoE-/- Mice

Metabolic-associated fatty liver disease (MAFLD) is the most important cause of liver disease worldwide. It is characterized by the accumulation of fat in the liver and is closely associated with abdominal obesity. In addition, oxidative stress and inflammation are significant features involved in MAFLD. Recently, our group demonstrated that lupin protein hydrolysates (LPHs) had lipid lowering, antioxidant, and anti-inflammatory effects. Sixty male mice fed with a Western diet were intragastrically treated with LPHs (or vehicle) for 12 weeks. Liver and adipose tissue lipid accumulation and hepatic inflammatory and oxidant status were evaluated. A significant decrease in steatosis was observed in LPHs-treated mice, which presented a decreased gene expression of CD36 and LDL-R, crucial markers in MAFLD. In addition, LPHs increased the hepatic total antioxidant capacity and reduced the hepatic inflammatory status. Moreover, LPHs-treated mice showed a significant reduction in abdominal adiposity. This is the first study to show that the supplementation with LPHs markedly ameliorates the generation of the steatotic liver caused by the intake of a Western diet and reduces abdominal obesity in ApoE^−/− mice. Future clinical trials should shed light on the effects of LPHs on MAFLD.

Metabolic profiling of fatty acids in Tripterygium wilfordii multiglucoside- and triptolide-induced liver-injured rats

Tripterygium wilfordii multiglucoside (TWM) is a fat-soluble extract from a Chinese herb T. wilfordii, that’s used in treating rheumatoid arthritis, nephrotic syndrome and other skin diseases. Triptolide (TP) is a major active component in TWM. However, clinical applications of TWM are limited by its various toxicities especially hepatotoxicity. In recent studies, it has been reported that drug-induced liver injury (DILI) could induce the disorder of lipid metabolism in animals. Hence, this study focuses on the metabolic profile of fatty acids in TWM- and TP-induced liver-injured rats. In serum and liver tissue, 16 free and 16 esterified fatty acids were measured by gas chromatography coupled with mass spectrometry. Metabolic profile of serum fatty acids in rats with liver injury was identified by multivariate statistical analysis. The fatty acid levels in the serum of TWM- and TP-treated rats significantly decreased, whereas those in the liver tissue of TWM- and TP-treated rats obviously increased when compared with the vehicle-treated rats. Four free fatty acids were identified as candidate biomarkers of TWM- and TP-induced liver injury. Therefore, the targeted metabolomic method may be used as a complementary approach for DILI diagnosis in clinic.

Nondestructive molecular imaging by Raman spectroscopy vs. marker detection by MALDI IMS for an early diagnosis of HCC

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide with a steadily increasing mortality rate. Fast diagnosis at early stages of HCC is of key importance for the improvement of patient survival rates. In this regard, we combined two imaging techniques with high potential for HCC diagnosis in order to improve the prediction of liver cancer. In detail, Raman spectroscopic imaging and matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) were applied for the diagnosis of 36 HCC tissue samples. The data were analyzed using multivariate methods, and the results revealed that Raman spectroscopy alone showed a good capability for HCC tumor identification (sensitivity of 88% and specificity of 80%), which could not be improved by combining the Raman data with MALDI IMS. In addition, it could be shown that the two methods in combination can differentiate between well-, moderately- and poorly-differentiated HCC using a linear classification model. MALDI IMS not only classified the HCC grades with a sensitivity of 100% and a specificity of 80%, but also showed significant differences in the expression of glycerophospholipids and fatty acyls during HCC differentiation. Furthermore, important differences in the protein, lipid and collagen compositions of differentiated HCC were detected using the model coefficients of a Raman based classification model. Both Raman and MALDI IMS, as well as their combination showed high potential for resolving concrete questions in liver cancer diagnosis.

Dipeptidyl peptidase-4 inhibitor protects against non-alcoholic steatohepatitis in mice by targeting TRAIL receptor-mediated lipoapoptosis via modulating hepatic dipeptidyl peptidase-4 expression

Dipeptidyl peptidase-4 inhibitors (DPP4i) are antidiabetic medications that prevent cleavage of incretin hormones by dipeptidyl peptidase-4 (DPP4). DPP4 is ubiquitously expressed, and its hepatic DPP4 expression is upregulated under non-alcoholic steatohepatitis (NASH) conditions. We investigated the effect of DPP4i treatment on NASH pathogenesis, as well as its potential underlying molecular mechanisms. Mice were randomly divided into three groups: Group 1, chow-fed mice treated with vehicle for 20 weeks; Group 2, high-fat, high-fructose, and high-cholesterol Amylin liver NASH (AMLN) diet-fed mice treated with vehicle for 20 weeks; Group 3, AMLN diet-fed mice treated with vehicle for the first 10 weeks, followed by the DPP4i teneligliptin (20 mg/kg/day) for additional 10 weeks. DPP4i administration reduced serum liver enzyme and hepatic triglyceride levels and markedly improved hepatic steatosis and fibrosis in the AMLN diet-induced NASH model. In vivo, NASH alleviation significantly correlated with the suppression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor-mediated apoptosis and downregulated hepatic DPP4 expression. In vitro, DPP4i treatment significantly decreased the markers of TRAIL receptor-mediated lipoapoptosis and suppressed DPP4 expression in palmitate-treated hepatocytes. In conclusion, DPP4i may efficiently attenuate the pathogenesis of AMLN diet-induced NASH in mice by suppressing lipotoxicity-induced apoptosis, possibly by modulating hepatic DPP4 expression.

The role of CD36 in cardiovascular disease

CD36, also known as the scavenger receptor B2, is a multifunctional receptor widely expressed in various organs. CD36 plays a crucial role in the uptake of long-chain fatty acids, the main metabolic substrate in myocardial tissue. The maturation and transportation of CD36 is regulated by post-translational modifications, including phosphorylation, ubiquitination, glycosylation, and palmitoylation. CD36 is decreased in pathological cardiac hypertrophy caused by ischaemia-reperfusion and pressure overload, and increased in diabetic cardiomyopathy and atherosclerosis. Deficiency of CD36 alleviates diabetic cardiomyopathy and atherosclerosis, while overexpression of CD36 eliminates ischaemia-reperfusion damage, together suggesting that CD36 is closely associated with the progression of cardiovascular diseases and may be a new therapeutic target. This review summarizes the regulation and post-translational modifications of CD36 and evaluates its role in cardiovascular diseases and its potential as a therapeutic target.

Involvement of CYP2E1-ROS-CD36/DGAT2 axis in the pathogenesis of VPA-induced hepatic steatosis in vivo and in vitro

Valproic acid (VPA) is a widely prescribed antiepileptic drug, which may cause steatosis in the liver. Oxidative stress is associated with the progression of VPA-induced hepatic steatosis. However, the potential mechanisms are not fully understood. In this study, we demonstrated the involvement of CYP2E1-ROS-CD36/DGAT2 axis in the pathogenesis of VPA-induced hepatic steatosis in vitro and in vivo. First, VPA treatment (500 mg/kg in mice, 5 mM in LO₂ cells) induced hepatic steatosis and enhanced reactive oxidative stress (ROS) level, and ROS scavenger, N-acetyl-L-cysteine (NAC, 200 mg/kg in mice, 1 mM in LO₂ cells) reversed the changes. Next, we observed the enhanced expression and enzymatic activity of cytochrome P450 2E1 (CYP2E1) in VPA-treated mice and LO₂ cells. Importantly, VPA-induced ROS accumulation and hepatic steatosis were attenuated when CYP2E1 was inhibited using CYP2E1 inhibitor, diallyl sulfide (DAS, 100 mg/kg in mice, 1 mM in LO₂ cells) or in CYP2E1-knockdown cell line, suggesting that CYP2E1 plays a potential role in ROS production following hepatic steatosis. Furthermore, gene expression analysis showed that the mRNA levels of cluster of differentiation 36 (CD36), a fatty acid translocase protein and distinct diacylglycerol acyltransferase 2 (DGAT2) were significantly upregulated in mice and LO₂ cells after VPA treatment, while the change was alleviated by NAC and DAS. Meanwhile, time course experiments demonstrated that the increase of CYP2E1 level occurred earlier than that of ROS, CD36 and DGAT2, and ROS generation preceded the onset of hepatic steatosis. Taken together, VPA treatment enhances the expression and enzymatic activity of CYP2E1, which promotes ROS production and then causes CD36 and DGAT2 overproduction and hepatic steatosis in mice and LO₂ cells, which provides a novel insight into VPA-induced hepatic steatosis.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

Effects of maternal T-2 toxin exposure on the hepatic glycolipid metabolism in young mice

T-2 toxin is a kind of group A trichothecenes mycotoxins, frequently detected in various foods and feeds, having high toxic effects on both humans and animals. The present study aims to investigate the toxic effects of T-2 toxin exposure to ICR mice during pregnancy and lactation on liver glycolipid metabolism of young mice. The pregnant mice were given 0, 0.005 and 0.05 mg of T-2 toxin/kg bw daily through oral gavage from late gestation (GD 14) to the lactation (LD 21). Liver and serum samples of the young mice were collected on postnatal day 21 (PND 21), PND 28 and PND 56. The results showed that T-2 toxin increased the contents of triglycerides (TG), total cholesterol (T-CHO) and glucose in serum of young mice on PND 21 and PND 28. In addition, obvious lipid droplets of liver in T-2 toxin treatment groups were observed, especially in 0.05 mg group of PND 21and PND 28. Compared with the control group, T-2 treatment also increased the expressions of genes associated with liver glycolipid metabolism, such as PEPCK, Glut2, Fas, Acox1, Hmgcr, PPARα, Srebp1 and CD36. These results demonstrated T-2 toxin exposure to pregnant mice could cause liver glycolipid metabolism disruption in the young mice and the toxic effects weakened on PND 56.

Effects of XIAP on high fat diet-induced hepatic steatosis: a mechanism involving NLRP3 inflammasome and oxidative stress

Increasing evidence indicates that prolonged fat-rich diet (HFD) ingestion is a predisposing factor for metabolic disorder-associated system inflammation and oxidative stress injury, which contributes to the occurrence of non-alcoholic fatty liver disease (NAFLD). NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-mediated inflammatory infiltration was determined to participate in NAFLD. X-linked inhibitor of apoptosis protein (XIAP) was recently confirmed as an essential regulator for apoptosis in cells. However, the role of XIAP in HFD-induced NAFLD is still not understood. Here, XIAP was characterized with respect to HFD-induced NLRP3 inflammasome activation and reactive oxygen species (ROS) generation in vivo and palmitate (PA)-treated cells in vitro. After HFD administration, hepatic injury was confirmed via histological assessment (grading and staging of NAFLD) and biochemical parameters, oxidative stress, and reduced antioxidant activity. Up-regulated hepatic dysfunction were further indicated by elevated dyslipidemia, lipid accumulation, and decreased fatty acid β-oxidation associated gene expression. Moreover, in the absence of XIAP, NLRP3 signaling activated by HFD-triggered oxidative stress was up-regulated, accompanied by reduction in antioxidants including HO-1, NQO-1, GST, SOD and Nrf2 activity. The detrimental effects of XIAP blocking on hepatic steatosis and related pathologies were also confirmed in PA-treated mouse liver cells. In contrast, overexpression of XIAP by transfection in vitro restrained PA-stimulated hepatic steatosis by suppression of oxidative stress, NLRP3 related inflammatory response, and impairment of Nrf2 activity, further alleviating abnormal metabolic disorder associated NAFLD. Taken together, the present study helped to elucidate how HFD-induced hepatic steatosis was regulated by XIAP, possibly via the inhibition of NLRP3 signaling and oxidative stress injury.

Hepatic Forkhead Box Protein A3 Regulates ApoA-I (Apolipoprotein A-I) Expression, Cholesterol Efflux, and Atherogenesis

OBJECTIVE

To determine the role of hepatic FOXA3 (forkhead box A3) in lipid metabolism and atherosclerosis. Approach and Results: Hepatic FOXA3 expression was reduced in diabetic or high fat diet-fed mice or patients with nonalcoholic steatohepatitis. We then used adenoviruses to overexpress or knock down hepatic FOXA3 expression. Overexpression of FOXA3 in the liver increased hepatic ApoA-I (apolipoprotein A-I) expression, plasma HDL-C (high-density lipoprotein cholesterol) level, macrophage cholesterol efflux, and macrophage reverse cholesterol transport. In contrast, knockdown of hepatic FOXA3 expression had opposite effects. We further showed that FOXA3 directly bound to the promoter of the Apoa1 gene to regulate its transcription. Finally, AAV8 (adeno-associated virus serotype 8)-mediated overexpression of human FOXA3 in the hepatocytes of Apoe^-/- (apolipoprotein E-deficient) mice raised plasma HDL-C levels and significantly reduced atherosclerotic lesions.

CONCLUSIONS

Hepatocyte FOXA3 protects against atherosclerosis by inducing ApoA-I and macrophage reverse cholesterol transport.

The fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase can be a source of mitochondrial hydrogen peroxide

Fatty acid oxidation (FAO)-driven H₂O₂ has been shown to be a major source of oxidative stress in several tissues and disease states. Here, we established that the mitochondrial flavoprotein long-chain acyl-CoA dehydrogenase (LCAD), which catalyzes a key step in mitochondrial FAO, directly produces H₂O₂in vitro by leaking electrons to oxygen. Kinetic analysis of recombinant human LCAD showed that it produces H₂O₂ 15-fold faster than the related mitochondrial enzyme very long-chain acyl-CoA dehydrogenase (VLCAD), but 50-fold slower than a bona fide peroxisomal acyl-CoA oxidase. The rate of H₂O₂ formation by human LCAD is slow compared to its activity as a dehydrogenase (about 1%). However, expression of hLCAD in HepG2 cells is sufficient to significantly increase H₂O₂ in the presence of fatty acids. Liver mitochondria from LCAD−/− mice, but not VLCAD−/− mice, produce significantly less H₂O₂ during incubation with fatty acids. Finally, we observe highest LCAD expression in human liver, followed by kidney, lung, and pancreas. Based on our data, we propose that the presence of LCAD drives H₂O₂ formation in response to fatty acids in these tissues.

Bone Morphogenetic Protein-8B Expression is Induced in Steatotic Hepatocytes and Promotes Hepatic Steatosis and Inflammation In Vitro

Non-alcoholic fatty liver disease (NAFLD) is considered to be the hepatic manifestation of the metabolic syndrome. The bone morphogenetic protein-8B (BMP8B) has been shown to be expressed in brown adipose tissues and the hypothalamus and to affect thermogenesis and susceptibility to diet-induced obesity. Here, we aimed to analyze BMP8B expression in NAFLD and to gain insight into BMP8B effects on pathophysiological steps of NAFLD progression. BMP8B mRNA and protein expression were dose-dependently induced in primary human hepatocytes in vitro upon incubation with fatty acids. Furthermore, hepatic BMP8B expression was significantly increased in a murine NAFLD model and in NAFLD patients compared with controls. Incubation with recombinant BMP8B further enhanced the fatty acid-induced cellular lipid accumulation as well as NFκB activation and pro-inflammatory gene expression in hepatocytes, while siRNA-mediated BMP8B depletion ameliorated these fatty acid-induced effects. Analysis of the expression of key factors of hepatocellular lipid transport and metabolisms indicated that BMP8B effects on fatty acid uptake as well as de novo lipogenesis contributed to hepatocellular accumulation of fatty acids leading to increased storage in the form of triglycerides and enhanced combustion by beta oxidation. In conclusion, our data indicate that BMP8B enhances different pathophysiological steps of NAFLD progression and suggest BMP8B as a promising prognostic marker and therapeutic target for NAFLD and, potentially, also for other chronic liver diseases.

Lipid Metabolism Disorder and Renal Fibrosis

Since the lipid nephrotoxicity hypothesis was proposed in 1982, increasing evidence has supported the hypothesis that lipid abnormalities contributed to the progression of glomerulosclerosis. In this chapter, we will discuss the general promises of the original hypothesis, focusing especially on the role of lipids and metabolic inflammation accompanying CKD in renal fibrosis and potential new strategies of prevention.

Vitamin E: Regulatory Role on Signal Transduction

Vitamin E modulates signal transduction pathways by several molecular mechanisms. As a hydrophobic molecule located mainly in membranes it contributes together with other lipids to the physical and structural characteristics such as membrane stability, curvature, fluidity, and the organization into microdomains (lipid rafts). By acting as the main lipid-soluble antioxidant, it protects other lipids such as mono- and poly-unsaturated fatty acids (MUFA and PUFA, respectively) against chemical reactions with reactive oxygen and nitrogen species (ROS and RNS, respectively) and prevents membrane destabilization and cellular dysfunction. In cells, vitamin E affects signaling in redox-dependent and redox-independent molecular mechanisms by influencing the activity of enzymes and receptors involved in modulating specific signal transduction and gene expression pathways. By protecting and preventing depletion of MUFA and PUFA it indirectly enables regulatory effects that are mediated by the numerous lipid mediators derived from these lipids. In recent years, some vitamin E metabolites have been observed to affect signal transduction and gene expression and their relevance for the regulatory function of vitamin E is beginning to be elucidated. In particular, the modulation of the CD36/FAT scavenger receptor/fatty acids transporter by vitamin E may influence many cellular signaling pathways relevant for lipid homeostasis, inflammation, survival/apoptosis, angiogenesis, tumorigenesis, neurodegeneration, and senescence. Thus, vitamin E has an important role in modulating signal transduction and gene expression pathways relevant for its uptake, distribution, metabolism, and molecular action that when impaired affect physiological and patho-physiological cellular functions relevant for the prevention of a number of diseases. © 2018 IUBMB Life, 71(4):456-478, 2019.