The role of hepatic macrophages in nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Multicolor Two-Photon Microscopy Imaging of Lipid Droplets and Liver Capsule Macrophages In Vivo

Lipid droplets (LDs) store energy and supply fatty acids and cholesterol. LDs are a hallmark of chronic nonalcoholic fatty liver disease (NAFLD). Recently, studies have focused on the role of hepatic macrophages in NAFLD. Green fluorescent protein (GFP) is used for labeling the characteristic targets in bioimaging analysis. Cx3cr1-GFP mice are widely used in studying the liver macrophages such as the NAFLD model. Here, we have developed a tool for two-photon microscopic observation to study the interactions between LDs labeled with LD2 and liver capsule macrophages labeled with GFP in vivo. LD2, a small-molecule two-photon excitation fluorescent probe for LDs, exhibits deep-red (700 nm) fluorescence upon excitation at 880 nm, high cell staining ability and photostability, and low cytotoxicity. This probe can clearly observe LDs through two-photon microscopy (TPM) and enables the simultaneous imaging of GFP+ liver capsule macrophages (LCMs) in vivo in the liver capsule of Cx3cr1-GFP mice. In the NAFLD mouse model, Cx3cr1+ LCMs and LDs increased with the progress of fatty liver disease, and spatiotemporal changes in LCMs were observed through intravital 3D TPM images. LD2 will aid in studying the interactions and immunological roles of hepatic macrophages and LDs to better understand NAFLD.

Novel insights into macrophage immunometabolism in nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), an inflammatory subtype of nonalcoholic fatty liver disease (NAFLD), is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis, and has been becoming the leading cause of liver-related morbidity and mortality worldwide. Unfortunately, the pathogenesis of NASH has not been completely clarified, and there are no approved therapeutic drugs. Recent accumulated evidences have revealed the involvement of macrophage in the regulation of host liver steatosis, inflammation and fibrosis, and different phenotypes of macrophages have different metabolic characteristics. Therefore, targeted regulation of macrophage immunometabolism may contribute to the treatment and prognosis of NASH. In this review, we summarized the current evidences of the role of macrophage immunometabolism in NASH, especially focused on the related function conversion, as well as the strategies to promote its polarization balance in the liver, and hold promise for macrophage immunometabolism-targeted therapies in the treatment of NASH.

Puerarin Induces Macrophage M2 Polarization to Exert Antinonalcoholic Steatohepatitis Pharmacological Activity via the Activation of Autophagy

To determine the protective mechanism of puerarin against nonalcoholic steatohepatitis (NASH), the pharmacodynamic effects of puerarin on NASH were evaluated by using zebrafish, cells, and mice. Western blotting, flow cytometry, immunofluorescence, and qRT-PCR were used to detect the effects of puerarin on RAW264.7 autophagy and polarization. Key target interactions between autophagy and polarization were detected using immunoprecipitation. Puerarin regulated the M1/M2 ratio of RAW 264.7 cells induced by LPS + INF-γ. Transcriptomics revealed that PAI-1 is a key target of puerarin in regulating macrophage polarization. PAI-1 knockout reduced the number of M1-type macrophages and increased the number of M2-type macrophages. Puerarin regulated PAI-1 and was associated with macrophage autophagy. It increased p-ULK1 expression in macrophages and activated autophagic flux, reducing the level of PAI-1 expression. Stat3/Hif-1α and PI3K/AKT signaling pathways regulated the number of macrophage polarization phenotypes, reducing liver lipid droplet formation, alleviating liver structural abnormalities, decreasing the number of cytoplasmic vacuoles, and decreasing the area of blue collagen in NASH mice. Puerarin is a promising dietary component for NASH alleviation.

Proanthocyanidins-Based Synbiotics as a Novel Strategy for Nonalcoholic Fatty Liver Disease (NAFLD) Risk Reduction

Nonalcoholic fatty liver disease (NAFLD), the most common liver disease worldwide, is a spectrum of liver abnormalities ranging from steatosis to nonalcoholic steatohepatitis (NASH) characterized by excessive lipid accumulation. The prevalence of NAFLD is predicted to increase rapidly, demanding novel approaches to reduce the global NAFLD burden. Flavonoids, the most abundant dietary polyphenols, can reduce the risk of NAFLD. The majority of dietary flavonoids are proanthocyanidins (PACs), which are oligomers and polymers of the flavonoid sub-group flavan-3-ols. The efficacy of PAC in reducing the NAFLD risk can be significantly hindered by low bioavailability. The development of synbiotics by combining PAC with probiotics may increase effectiveness against NAFLD by biotransforming PAC into bioavailable metabolites. PAC and probiotic bacteria are capable of mitigating steatosis primarily through suppressing de novo lipogenesis and promoting fatty acid β-oxidation. PAC and probiotic bacteria can reduce the progression of steatosis to NASH mainly through ameliorating hepatic damage and inflammation induced by hepatic oxidative stress, endoplasmic reticulum stress, and gut microbiota dysbiosis. Synbiotics of PAC are superior in reducing the risk of NAFLD compared to independent administration of PAC and probiotics. The development of PAC-based synbiotics can be a novel strategy to mitigate the increasing incidence of NAFLD.

Lactobacillus helveticus Isolated from Raw Milk Improves Liver Function, Hepatic Steatosis, and Lipid Metabolism in Non-Alcoholic Fatty Liver Disease Mouse Model

Here, we show that Lactiplantibacillus plantarum LP158 (LP158), Lactobacillus helveticus HY7804 (HY7804), and Lacticaseibacillus paracasei LPC226 (LPC226) isolated from raw milk alleviate non-alcoholic fatty acid disease (NAFLD) in a C57BL/6 mouse model. Lactic acid bacteria (LAB) were screened for their ability to inhibit fatty acid accumulation in palmitic acid (PA)-treated HepG2 cells, and three strains were selected based on the results. We also investigated hemolytic activity and antibiotic resistance of the three strains. LP158, HY7804, and LPC226 suppressed expression of mRNA encoding genes related to lipogenesis, and increased expression of genes related to β-oxidation, in a PA-induced HepG2 cell model. Moreover, when LP158, HY7804, and LPC226 were administered at 109 CFU/kg/day for 8 weeks to mice with dietary-induced NAFLD, they all modulated blood biochemistry markers and reduced steatosis in liver tissue. Also, all three strains significantly reduced expression of mRNA encoding lipogenesis genes (Fasn, Acaca, and Srebp-1c) and inflammatory factors (Tnfα and Ccl-2) and fibrosis factors, and increased expression of a β-oxidation gene (Acox1) in the liver. In particular, HY7804 showed the strongest effects both in vitro and in vivo. Therefore, HY7804, LP158, and LPC226 can be proposed as potential supplements that can improve NAFLD through anti-steatosis, anti-inflammatory, and anti-fibrotic effects.

Cellular heterogeneity and plasticity during NAFLD progression

Nonalcoholic fatty liver disease (NAFLD) is a progressive liver disease that can progress to nonalcoholic steatohepatitis (NASH), NASH-related cirrhosis, and hepatocellular carcinoma (HCC). NAFLD ranges from simple steatosis (or nonalcoholic fatty liver [NAFL]) to NASH as a progressive form of NAFL, which is characterized by steatosis, lobular inflammation, and hepatocellular ballooning with or without fibrosis. Because of the complex pathophysiological mechanism and the heterogeneity of NAFLD, including its wide spectrum of clinical and histological characteristics, no specific therapeutic drugs have been approved for NAFLD. The heterogeneity of NAFLD is closely associated with cellular plasticity, which describes the ability of cells to acquire new identities or change their phenotypes in response to environmental stimuli. The liver consists of parenchymal cells including hepatocytes and cholangiocytes and nonparenchymal cells including Kupffer cells, hepatic stellate cells, and endothelial cells, all of which have specialized functions. This heterogeneous cell population has cellular plasticity to adapt to environmental changes. During NAFLD progression, these cells can exert diverse and complex responses at multiple levels following exposure to a variety of stimuli, including fatty acids, inflammation, and oxidative stress. Therefore, this review provides insights into NAFLD heterogeneity by addressing the cellular plasticity and metabolic adaptation of hepatocytes, cholangiocytes, hepatic stellate cells, and Kupffer cells during NAFLD progression.

Filamin A is overexpressed in non-alcoholic steatohepatitis and contributes to the progression of inflammation and fibrosis

Non-alcoholic steatohepatitis (NASH) is a chronic and progressive liver disease characterized by steatosis, inflammation, and fibrosis. Filamin A (FLNA), an actin-binding protein, is involved in various cell functions, including the regulation of immune cells and fibroblasts. However, its role in the development of NASH through inflammation and fibrogenesis is not fully understood. In this study, we found that FLNA expression was increased in liver tissues of patients with cirrhosis and mice with non-alcoholic fatty liver disease (NAFLD)/NASH and fibrosis. Immunofluorescence analysis showed that FLNA was primarily expressed in macrophages and hepatic stellate cells (HSCs). Knocking down of FLNA by specific shRNA in phorbol-12-myristate-13-acetate (PMA)-derived THP-1 macrophages reduced lipopolysaccharide (LPS)-stimulated inflammatory response. The decreased mRNA levels of inflammatory cytokines and chemokines and suppression of the STAT3 signaling were observed in FLNA-downregulated macrophages. In addition, knockdown of FLNA in immortalized human hepatic stellate cells (LX-2 cells) resulted in decreased mRNA levels of fibrotic cytokines and enzymes involved in collagen synthesis, as well as increased levels of metalloproteinases and pro-apoptotic proteins. Overall, these results suggest that FLNA may contribute to the pathogenesis of NASH through its role in the regulation of inflammatory and fibrotic mediators.

Garlic-derived exosomes regulate PFKFB3 expression to relieve liver dysfunction in high-fat diet-fed mice via macrophage-hepatocyte crosstalk

BACKGROUND

Although macrophage-mediated low-grade chronic inflammation and liver dysfunction have been found to be associated with the development of non-alcoholic fatty (NAFLD) and widely reported, but strategies and drugs targeting macrophages for the treatment of NAFLD are limited.

HYPOTHESIS/PURPOSE

Garlic-derived exosomes (GDE) can be useful for NAFLD due to its anti-inflammatory activity. Clarify whether GDE improves liver dysfunction through macrophage-hepatocyte crosstalk.

METHODS

GDE was isolated with PEG precipitation and ultracentrifuge. Inflammatory cytokines were detected by qRT-PCR and ELISA. Expression of 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) was determined using qRT-PCR and western blot. Crosstalk between macrophages and hepatocytes was identified through a co-culture experiment. Small RNA sequencing and bioinformatic analysis were used to identify the key element of GDE regulating the expression of PFKFB3 gene.

RESULTS

GDE regulated the expression of PFKFB3 to reduce the inflammatory response in LPS-treated differentiated THP-1 macrophages. Data from small RNA sequencing and bioinformatics analysis reveal that miR-396e, one of the most abundant miRNAs of GDE, is the key component to regulate PFKFB3 expression. Mechanistically, miR-396e-mediating PFKFB3 expression plays a crucial role in GDE inhibiting inflammatory response and enhancing lipid metabolism in hepatocytes via the macrophage-hepatocyte crosstalk. Notably, GDE supplementation reduced the inflammatory response and improved liver dysfunction in high-fat diet-fed mice.

CONCLUSION

GDE may be useful for improving the symptoms of NAFLD via macrophage-hepatocyte crosstalk and its role in PFKFB3 expression.

S100A6 Activates Kupffer Cells via the p-P38 and p-JNK Pathways to Induce Inflammation, Mononuclear/macrophage Infiltration Sterile Liver Injury in Mice

Noninfectious liver injury, including the effects of chemical material, drugs and diet, is a major cause of liver diseases worldwide. In chemical and drugs-induced liver injury, innate inflammatory responses are mediated by extracellular danger signals. The S100 protein can act as danger signals, which can promote the migration and chemotaxis of immune cells, promote the release of various inflammatory cytokines, and regulate the body's inflammatory and immune responses. However, the role of S100A6 in inflammatory response in chemical and drugs-induced sterile liver injury remains unclear. We constructed the model of sterile liver injury induced by carbon tetrachloride (CCl₄)/Paracetamol (APAP) and performed RNA sequencing (RNA-seq) on the liver tissues after injury (days 2 and 5). We analyzed inflammatory protein secretion in the liver tissue supernatant by enzyme-linked immunosorbent assay (ELISA), determined the inflammation response by bioinformatic analysis during sterile liver injury, and assessed mononuclear/macrophage infiltration by immunohistochemistry and flow cytometry. Immunohistochemistry was used to analyze the location of S100A6. We conducted inflammatory factor expression analysis and molecular mechanistic studies in Kupffer cells (KCs) induced by S100A6 using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), ELISA, and western blot in vitro experiments. We performed chemokine CCL2 expression analysis and molecular mechanism studies using the same method. We used a Transwell assay to show the infiltration of mononuclear/macrophage. We here observed that aggravated inflammatory response was shown in CCl₄ and APAP-administrated mice, as evidenced by enhanced production of inflammatory cytokines (TNF-α, IL-1β), and elevated mononuclear/macrophage infiltration and activation of immunity. The expression of S100A6 was significantly increased on day 2 after sterile liver injury, which is primarily produced by injured liver cells. Mechanistic studies established that S100A6 activates Kupffer cells (KCs) via the p-P38, p-JNK and P65 pathways to induce inflammation in vitro. Furthermore, TNF-α can stimulate liver cells via the p-P38 and p-JNK pathways to produce CCL2 and promote the infiltration of mononuclear/macrophage. In summary, we showed that S100A6 plays an important role in regulating inflammation, thus influencing sterile liver injury. Our findings provide novel evidence that S100A6 can as a danger signal that contributes to pro-inflammatory activation through p-P38 and p-JNK pathways in CCl₄ and APAP-induced sterile liver injury in mice. In addition, the inflammatory factor TNF-α induces a large amount of CCL2 production in normal liver cells surrounding the injured area through a paracrine action, which is chemotactic for blood mononuclear/macrophage infiltration.

Non-Parenchymal Cells and the Extracellular Matrix in Hepatocellular Carcinoma in Non-Alcoholic Fatty Liver Disease

Hepatocellular carcinoma (HCC) in the setting of non-alcoholic fatty liver disease (NAFLD)-related cirrhosis and even in the pre-cirrhotic state is increasing in incidence. NAFLD-related HCC has a poor clinical outcome as it is often advanced at diagnosis due to late diagnosis and systemic treatment response is poor due to reduced immune surveillance. Much of the focus of molecular research has been on the pathological changes in hepatocytes; however, immune cells, hepatic stellate cells, liver sinusoidal endothelial cells and the extracellular matrix may play important roles in the pathogenesis of NAFLD-related HCC as well. Here, we review the role of non-parenchymal cells in the liver in the pathogenesis of HCC in the context of NAFLD-NASH, with a particular focus on the innate and the adaptive immune system, fibrogenesis and angiogenesis. We review the key roles of macrophages, hepatic stellate cells (HSCs), T cells, natural killer (NK) cells, NKT cells and liver sinusoidal endothelial cells (LSECs) and the role of the extracellular matrix in hepatocarcinogenesis within the steatotic milieu.

Vsig4+ resident single-Kupffer cells improve hepatic inflammation and fibrosis in NASH

BACKGROUND

The role of macrophages in the pathogenesis of nonalcoholic steatohepatitis (NASH) is complex and unclear.

METHODS

Single-cell RNA sequencing was performed on nonparenchymal cells isolated from NASH and control mice. The expression of Vsig4⁺ macrophages was verified by qPCR, flow cytometry and immunohistochemistry. Primary hepatic macrophages were cocultured with primary hepatocytes or hepatic stellate cells (LX2) cells by Transwell to detect immunofluorescence and oil red O staining.

RESULTS

Two main single macrophage subsets were identified that exhibited a significant change in cell percentage when NASH occurred: resident Kupffer cells (KCs; Cluster 2) and lipid-associated macrophages (LAMs; Cluster 13). Nearly 82% of resident single KCs in Cluster 2 specifically expressed Cd163, and an inhibited subgroup of Cd163⁺ resident single-KCs was suggested to be protective against NASH. Similar to Cd163, Vsig4 was both enriched in and specific to Cluster 2. The percentage of Vsig4⁺-KCs was significantly decreased in NASH in vivo and in vitro. Hepatocytes and hepatic stellate cells produced less lipid droplet accumulation, proinflammatory protein (TNF-α) and profibrotic protein (α-SMA) in response to coculture with Vsig4⁺-KCs than in those cocultured with lipotoxic KCs.

CONCLUSIONS

A subgroup of Vsig4⁺ resident single-KCs was shown to improve hepatic inflammation and fibrosis in NASH.

Myeloid-specific blockade of Notch signaling ameliorates nonalcoholic fatty liver disease in mice

Rationale: Macrophages play a central role in the development and progression of nonalcoholic fatty liver disease (NAFLD). Studies have shown that Notch signaling mediated by transcription factor recombination signal binding protein for immunoglobulin kappa J region (RBP-J), is implicated in macrophage activation and plasticity. Naturally, we asked whether Notch signaling in macrophages plays a role in NAFLD, whether regulating Notch signaling in macrophages could serve as a therapeutic strategy to treat NAFLD. Methods: Immunofluorescence staining was used to detect the changes of macrophage Notch signaling in the livers of human patients with NAFLD and choline deficient amino acid-defined (CDAA) diet-fed mice. Lyz2-Cre RBP-J^flox or wild-type C57BL/6 male mice were fed with CDAA or high fat diet (HFD) to induce experimental steatohepatitis or steatosis, respectively. Liver histology examinations were performed using hematoxylin-eosin (H&E), Oil Red O staining, Sirius red staining and immunohistochemistry staining for F4/80, Col1α1 and αSMA. The expression of inflammatory factors, fibrosis or lipid metabolism associated genes were evaluated by quantitative reverse transcription (qRT)-PCR, Western blot or enzyme-linked immunosorbent assay (ELISA). The mRNA expression of liver samples was profiled by using RNA-seq. A hairpin-type decoy oligodeoxynucleotides (ODNs) for transcription factor RBP-J was loaded into bEnd.3-derived exosomes by electroporating. Mice with experimental NAFLD were treated with exosomes loading RBP-J decoy ODNs via tail vein injection. In vivo distribution of exosomes was analyzed by fluorescence labeling and imaging. Results: The results showed that Notch signaling was activated in hepatic macrophages in human with NAFLD or in CDAA-fed mice. Myeloid-specific RBP-J deficiency decreased the expression of inflammatory factors interleukin-1 beta (IL1β) and tumor necrosis factor alpha (TNFα), attenuated experimental steatohepatitis in mice. Furthermore, we found that Notch blockade attenuated lipid accumulation in hepatocytes by inhibiting the expression of IL1β and TNFα in macrophages in vitro. Meanwhile, we observed that tail vein-injected exosomes were mainly taken up by hepatic macrophages in mice with steatohepatitis. RBP-J decoy ODNs delivered by exosomes could efficiently inhibit Notch signaling in hepatic macrophages in vivo and ameliorate steatohepatitis or steatosis in CDAA or HFD mice, respectively. Conclusions: Combined, macrophage RBP-J promotes the progression of NAFLD at least partially through regulating the expression of pro-inflammatory cytokines IL1β and TNFα. Infusion of exosomes loaded with RBP-J decoy ODNs might be a promising therapy to treat NAFLD.

Improvement in insulin sensitivity and prevention of high fat diet-induced liver pathology using a CXCR2 antagonist

BACKGROUND

Liver pathology (LP) characteristic of non-alcoholic fatty acid disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is a prevalent co-morbidity of type 2 diabetes (T2D). Accumulating evidence indicates that neutrophils driving insulin resistance (IR), including hepatic IR, precipitate T2D-associated NAFLD/NASH. We hypothesized that targeting neutrophil accumulation into insulin-sensitive tissues in mice using a CXCR2 antagonist under T2D-precipitating high fat diet (HFD) could improve insulin sensitivity and prevent the progression towards liver pathology reminiscent of NAFLD/NASH.

METHODS

Mice were age-matched and on standard rodent chow prior to 1:1 randomization into control and HFD formulated with the CXCR2 antagonist AZD5069 or with biologically inactive substitute. They were monitored for metabolic changes including insulin sensitivity using the hyperinsulinemic-euglycemic clamp and hepatic histopathologic evaluation in H&E-stained sections as well as via immunofluorescence microscopy of liver sections for leukocyte markers, collagen 1A1 formation, α-smooth muscle actin (SMA), and galectin-3 expression, for 16 weeks. Statistical tests used to determine significant differences among study groups and outcomes include Student's t-test, one-way ANOVA, repeated measures two-way ANOVA, and Fisher's exact test, depending on the analytical question.

RESULTS

Compared to mice on HFD, mice in the AZD5069-formulated HFD exhibited improved insulin sensitivity, a modest reduction in weight gain, and a significant improvement in LP and markers related to NAFLD/NASH. Mice in the AZD5069-formulated HFD also exhibited reduced neutrophil accumulation into the liver at the end of the 16 week study period.

CONCLUSIONS

These results show, for the first time, the effectiveness of a selective CXCR2 antagonist to improve insulin sensitivity, concomitantly preventing the progression towards LP characteristic of NAFLD/NASH. This represents a novel approach to target IR and developing LP under T2D-susceptible conditions using a single agent. Furthermore, our data extend the growing evidence in support of neutrophils as a leukocyte population that imprints and maintains a chronic inflammatory state in the progression of dysregulated metabolism in liver-specific co-morbid conditions.

High-fat diet-induced nonalcoholic steatohepatitis is accelerated by low carnitine and impaired glucose tolerance in novel murine models

Carnitine deficiency and impaired glucose tolerance (IGT) exacerbate liver steatosis. Given the current lack of ideal murine nonalcoholic steatohepatitis (NASH) models, we investigated new NASH models using jvs/+ mice with low carnitine and wild-type mice with low-dose alloxan-induced IGT. The jvs/+ and wild-type mice were divided into jvs/+ mice fed a high-fat diet (HFD) from 3 weeks of age (HF hetero group), wild-type mice with low-dose alloxan treatment fed HFD (AL + HF wild group), wild-type mice fed HFD (HF wild group), and two types of mice fed a normal diet-jvs/+ and wild-type (intact group). All mice were sacrificed at 20 or 40 weeks of age. All male HFD-fed mice showed obesity, IGT, high blood insulin levels, homeostatic model assessment of insulin resistance (HOMA-IR), high liver enzyme levels, and high cholesterol levels. The degree of IGT was the worst in the AL + HF wild group, and blood insulin levels and HOMA-IR score were remarkably increased from 20 to 40 weeks of age. Almost all HFD-fed mice showed steatosis, fibrosis, and lobular inflammation in the centrilobular zone. These changes were accompanied by hepatocyte ballooning and were enhanced at 40 weeks of age. Furthermore, the incidence rate of nodular hyperplasia and adenoma in both the HF hetero and AL + HF wild groups was nearly 30%. We successfully established two novel murine models of NASH using male jvs/+ mice with low carnitine and male wild-type mice with IGT that eventually developed obesity, fatty liver, insulin resistance, liver fibrosis, and tumorigenesis. These results suggest that low carnitine levels and early-stage induction of IGT are important factors in the progression of NASH to tumorigenesis, similar to human NASH.

Neutrophil extracellular traps enriched with IL-1β and IL-17A participate in the hepatic inflammatory process of patients with non-alcoholic steatohepatitis

Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of various non-infectious inflammatory and thrombotic diseases. We investigated the presence and possible associations of NETs with various histopathologic parameters in patients with non-alcoholic steatohepatitis (NASH). We retrospectively assessed 20 liver biopsy specimens from patients with non-alcoholic fatty liver disease (NAFLD), including 17 specimens with NASH, and 14 control specimens. NETs were identified with confocal microscopy as extracellular structures with co-localization of neutrophil elastase (NE) and citrullinated histone-3. Interleukin-1β (IL-1β) and IL-17A were assessed with the same methodology. Histologic features of NAFLD were semi-quantitatively evaluated, and correlated with presence of NETs, neutrophil density, and platelet density/aggregates (assessed by immunohistochemistry for NE and CD42b, respectively). NETs were identified in 94.1% (16/17) of the NASH biopsy specimens; they were absent from all other NAFLD and control specimens. The presence of NETs was strongly correlated with steatosis (p = 0.003), ballooning degeneration (p < 0.001), lobular inflammation (p < 0.001), portal inflammation (p < 0.001), NAS score (p = 0.001), stage (p = 0.001), and diagnosis of NASH (p < 0.001). NETs were decorated with IL-1β and IL-17A. Platelet aggregates were much larger in NASH specimens, as compared to controls. In conclusion, NETs are implicated in the pathogenesis of NASH. Their associations with inflammation, ballooning degeneration (a hallmark of NASH), and stage emphasize their role in the disease process. In this setting, NETs provide a vehicle for IL-1β and IL-17A. In addition, platelet aggregation in hepatic sinusoids implies a role for thromboinflammation in NASH, and may explain the low peripheral blood platelet counts reported in patients with NASH.

Mitochondria homeostasis: Biology and involvement in hepatic steatosis to NASH

Mitochondrial biology and behavior are central to the physiology of liver. Multiple mitochondrial quality control mechanisms remodel mitochondrial homeostasis under physiological and pathological conditions. Mitochondrial dysfunction and damage induced by overnutrition lead to oxidative stress, inflammation, liver cell death, and collagen production, which advance hepatic steatosis to nonalcoholic steatohepatitis (NASH). Accumulating evidence suggests that specific interventions that target mitochondrial homeostasis, including energy metabolism, antioxidant effects, and mitochondrial quality control, have emerged as promising strategies for NASH treatment. However, clinical translation of these findings is challenging due to the complex and unclear mechanisms of mitochondrial homeostasis in the pathophysiology of NASH.

The Association of Sarcopenia and Visceral Obesity with Lean Nonalcoholic Fatty Liver Disease in Chinese Patients with Type 2 Diabetes Mellitus

BACKGROUND

Few studies have specifically observed the relationship of sarcopenia, visceral obesity, or their joint effects with lean NAFLD in patients with diabetes. We aimed to investigate the associations of lean NAFLD with sarcopenia, visceral obesity, and sarcopenic visceral obesity (SV) in Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

Altogether, 1,112 T2DM patients with BMI <25 kg/m² were enrolled, and 33.18% of them were diagnosed with lean NAFLD by abdominal ultrasonography. Body composition markers were measured by bioelectrical impedance (BIA). Skeletal muscle mass index (SMI) was calculated as appendicular skeletal muscle mass (ASM) divided by weight, and sarcopenia was defined as SMI < 1 standard deviation (SD) below the sex-specific average for a young reference population. Visceral obesity was defined as visceral fat area (VFA) ≥ 100 cm². Participants were categorized into one of the four body composition groups: nonsarcopenia/nonvisceral obesity (NN), nonsarcopenia/visceral obesity (NV), sarcopenia/nonvisceral obesity (SN), and SV.

RESULTS

Compared to those in the NN group, patients in the NV and SN groups had a higher risk of lean NAFLD after full adjustments (NV: OR = 1.74; 95% CI: 1.09, 2.78; SN: OR =2.07; 95% CI: 1.23, 3.46). Of note, patients in the SV group had the highest odds of lean NAFLD (OR = 3.29; 95% CI: 2.10, 5.17). There were no significant interaction effects between sarcopenia and metabolic risk factors on prevalent lean NAFLD.

CONCLUSIONS

The current study demonstrated that SV was more closely associated with higher prevalent lean NAFLD than sarcopenia or visceral obesity alone in Chinese patients with T2DM. Besides, the harmful effect of sarcopenia on lean NAFLD was not influenced by visceral obesity or other metabolic risk factors. We hypothesize that increasing skeletal muscle mass more than just reducing visceral fat might be more optimal for the prevention and management of lean NAFLD, which needs further investigation in future studies.

Leptin Induces Apoptotic and Pyroptotic Cell Death via NLRP3 Inflammasome Activation in Rat Hepatocytes

Leptin, a hormone that is predominantly produced by adipose tissue, is closely associated with various liver diseases. However, there is a lack of understanding as to whether leptin directly induces cytotoxic effects in hepatocytes as well as the mechanisms that are involved. Inflammasomes, which are critical components in the innate immune system, have been recently shown to modulate cell death. In this study, we examined the effect of leptin on the viability of rat hepatocytes and the underlying mechanisms, with a particular focus on the role of inflammasomes activation. Leptin treatment induced cytotoxicity in rat hepatocytes, as determined by decreased cell viability, increased caspase-3 activity, and the enhanced release of lactate dehydrogenase. NLRP3 inflammasomes were activated by leptin both in vitro and in vivo, as determined by the maturation of interleukin-1β and caspase-1, and the increased expression of inflammasome components, including NLRP3 and ASC. Mechanistically, leptin-induced inflammasome activation is mediated via the axis of ROS production, ER stress, and autophagy. Notably, the inhibition of inflammasomes by treatment with the NLRP3 inhibitor or the IL-1 receptor antagonist protected the hepatocytes from leptin-induced cell death. Together, these results indicate that leptin exerts cytotoxic effects in hepatocytes, at least in part, via the activation of NLRP3 inflammasomes.

Advances in Unhealthy Nutrition and Circadian Dysregulation in Pathophysiology of NAFLD

Unhealthy diets and lifestyle result in various metabolic conditions including metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Much evidence indicates that disruption of circadian rhythms contributes to the development and progression of excessive hepatic fat deposition and inflammation, as well as liver fibrosis, a key characteristic of non-steatohepatitis (NASH) or the advanced form of NAFLD. In this review, we emphasize the importance of nutrition as a critical factor in the regulation of circadian clock in the liver. We also focus on the roles of the rhythms of nutrient intake and the composition of diets in the regulation of circadian clocks in the context of controlling hepatic glucose and fat metabolism. We then summarize the effects of unhealthy nutrition and circadian dysregulation on the development of hepatic steatosis and inflammation. A better understanding of how the interplay among nutrition, circadian rhythms, and dysregulated metabolism result in hepatic steatosis and inflammation can help develop improved preventive and/or therapeutic strategies for managing NAFLD.

Ferulic Acid Ameliorates Hepatic Inflammation and Fibrotic Liver Injury by Inhibiting PTP1B Activity and Subsequent Promoting AMPK Phosphorylation

Chronic inflammation in response to persistent exogenous stimuli or damage results in liver fibrosis, which subsequently progresses into malignant liver diseases with high morbidity and mortality. Ferulic acid (FA) is a phenolic acid widely isolated from abundant plants and exhibits multiple biological activities including anti-oxidant, anti-inflammation and enhancement of immune responses. Adenosine monophosphate-activated protein kinase (AMPK) functions as a critical energy sensor and is regulated through the phosphorylation of liver kinases like LKB1 or dephosphorylation by protein tyrosine phosphatases (PTPs). However, the role of FA in carbon tetrachloride (CCl₄)-induced chronic inflammation and liver fibrosis and AMPK activation has not been elucidated. Here we reported that FA ameliorated CCl₄-induced inflammation and fibrotic liver damage in mice as indicated by reduced levels of serum liver function enzyme activities and decreased expression of genes and proteins associated with fibrogenesis. Additionally, FA inhibited hepatic oxidative stress, macrophage activation and HSC activation via AMPK phosphorylation in different liver cells. Mechanically, without the participation of LKB1, FA-induced anti-inflammatory and anti-fibrotic effects were abrogated by a specific AMPK inhibitor, compound C. Combining with the results of molecular docking, surface plasmon resonance and co-immunoprecipitation assays, we further demonstrated that FA directly bound to and inhibited PTP1B, an enzyme responsible for dephosphorylating key protein kinases, and eventually leading to the phosphorylation of AMPK. In summary, our results indicated that FA alleviated oxidative stress, hepatic inflammation and fibrotic response in livers through PTP1B-AMPK signaling pathways. Taken together, we provide novel insights into the potential of FA as a natural product-derived therapeutic agent for the treatment of fibrotic liver injury.

Non-alcoholic Steatohepatitis Pathogenesis, Diagnosis, and Treatment

There has been a rise in the prevalence of non-alcohol fatty liver disease (NAFLD) due to the popularity of western diets and sedentary lifestyles. One quarter of NAFLD patients is diagnosed with non-alcoholic steatohepatitis (NASH), with histological evidence not only of fat accumulation in hepatocytes but also of liver cell injury and death due to long-term inflammation. Severe NASH patients have increased risks of cirrhosis and liver cancer. In this review, we discuss the pathogenesis and current methods of diagnosis for NASH, and current status of drug development for this life-threatening liver disease.

Visfatin exacerbates hepatic inflammation and fibrosis in a methionine-choline-deficient diet mouse model

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) ranges from simple steatosis to non-alcoholic steatohepatitis, which is characterized by hepatic inflammation that can progress to fibrosis, cirrhosis, and hepatocellular carcinoma. Visfatin, an adipocytokine, was reported to induce pro-inflammatory cytokines and can be associated with liver fibrosis. We investigated the role of visfatin on hepatic inflammation and fibrosis in a methionine-choline-deficient (MCD)-diet-induced steatohepatitis mouse model.

METHODS

Eight-week-old male C57BL/6 J mice were randomly assigned into one of three groups: (1) saline-injected control diet group; (2) saline-injected MCD diet group; and (3) visfatin-injected MCD diet group (n = 8 per group). Mice were administered intravenous saline or 10 μg/kg of recombinant murine visfatin for 2 weeks. Histologic assessment of liver and biochemical and molecular measurements of endoplasmic reticulum (ER) stress, reactive oxidative stress (ROS), inflammation, and fibrosis were performed in livers from these animals.

RESULTS

Visfatin injection aggravated hepatic steatosis and increased plasma alanine aminotransferase and aspartate aminotransferase concentrations. Visfatin increased inflammatory cell infiltration (as indicated by F4/80, CD68, ly6G, and CD3 mRNA expression) and expression of chemokines in the liver. Visfatin also increased the expression of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6) and activated fibrosis markers (CTGF, TIMP1, collagen 1α2, collagen 3α2, αSMA, fibronectin, and vimentin) in liver. Livers of visfatin-injected mice showed upregulation of ER stress and ROS and activation of JNK signaling.

CONCLUSIONS

These results suggest that visfatin aggravates hepatic inflammation together with induction of ER and oxidative stress and exacerbates fibrosis in an MCD-diet-fed mouse model of NAFLD.

Bioengineered Liver Models for Investigating Disease Pathogenesis and Regenerative Medicine

Owing to species-specific differences in liver pathways, in vitro human liver models are utilized for elucidating mechanisms underlying disease pathogenesis, drug development, and regenerative medicine. To mitigate limitations with de-differentiated cultures, bioengineers have developed advanced techniques/platforms, including micropatterned cocultures, spheroids/organoids, bioprinting, and microfluidic devices, for perfusing cell cultures and liver slices. Such techniques improve mature functions and culture lifetime of primary and stem-cell human liver cells. Furthermore, bioengineered liver models display several features of liver diseases including infections with pathogens (e.g., malaria, hepatitis C/B viruses, Zika, dengue, yellow fever), alcoholic/nonalcoholic fatty liver disease, and cancer. Here, we discuss features of bioengineered human liver models, their uses for modeling aforementioned diseases, and how such models are being augmented/adapted for fabricating implantable human liver tissues for clinical therapy. Ultimately, continued advances in bioengineered human liver models have the potential to aid the development of novel, safe, and efficacious therapies for liver disease.

Hepatocyte and immune cell crosstalk in non-alcoholic fatty liver disease

Introduction: Nonalcoholic fatty liver disease (NAFLD) is the most widespread chronic liver disease in the world. It can evolve into nonalcoholic steatohepatitis (NASH) where inflammation and hepatocyte ballooning are key participants in the determination of this steatotic state.Areas covered: To provide a systematic overview and current understanding of the role of inflammation in NAFLD and its progression to NASH, the function of the cells involved, and the activation pathways of the innate immunity and cell death; resulting in inflammation and chronic liver disease. A PubMed search was made with relevant articles together with relevant references were included for the writing of this review.Expert opinion: Innate and adaptive immunity are the key players in the NAFLD progression; some of the markers presented during NAFLD are also known to be immunity biomarkers. All cells involved in NAFLD and NASH are known to have immunoregulatory properties and their imbalance will completely change the cytokine profile and form a pro-inflammatory microenvironment. It is necessary to fully answer the question of what initiators and metabolic imbalances are particularly important, considering sterile inflammation as the architect of the disease. Due to the shortage of elucidation of NASH progression, we discuss in this review, how inflammation is a key part of this development and we presume the targets should lead to inflammation and oxidative stress treatment.

Stress kinases in the development of liver steatosis and hepatocellular carcinoma

Non-alcoholic fatty liver disease (NAFLD) is an important component of metabolic syndrome and one of the most prevalent liver diseases worldwide. This disorder is closely linked to hepatic insulin resistance, lipotoxicity, and inflammation. Although the mechanisms that cause steatosis and chronic liver injury in NAFLD remain unclear, a key component of this process is the activation of stress-activated kinases (SAPKs), including p38 and JNK in the liver and immune system. This review summarizes findings which indicate that the dysregulation of stress kinases plays a fundamental role in the development of steatosis and are important players in inducing liver fibrosis. To avoid the development of steatohepatitis and liver cancer, SAPK activity must be tightly regulated not only in the hepatocytes but also in other tissues, including cells of the immune system. Possible cellular mechanisms of SAPK actions are discussed.

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Hepatic JNK triggers steatosis and insulin resistance, decreasing lipid oxidation and ketogenesis in HFD-fed mice.

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Decreased liver expression of p38α/β in HFD increases lipogenesis.

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Hepatic p38γ/δ drive insulin resistance and inhibit autophagy, which may lead to steatosis.

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Macrophage p38α/β promote cytokine production and M1 polarization, leading to lipid accumulation in hepatocytes.

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Myeloid p38γ/δ contribute to cytokine production and neutrophil migration, protecting against steatosis, diabetes and NAFLD.

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JNK1 and p38γ induce HCC while p38α blocks it. However, deletion of hepatic JNK1/2 induces cholangiocarcinoma.

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SAPK are potential therapeutic target for metabolic disorders, steatohepatitis and liver cancer.

Inflammation/bioenergetics-associated neurodegenerative pathologies and concomitant diseases: a role of mitochondria targeted catalase and xanthophylls

Various inflammatory stimuli are able to modify or even "re-program" the mitochondrial metabolism that results in generation of reactive oxygen species. In noncommunicable chronic diseases such as atherosclerosis and other cardiovascular pathologies, type 2 diabetes and metabolic syndrome, these modifications become systemic and are characterized by chronic inflammation and, in particular, "neuroinflammation" in the central nervous system. The processes associated with chronic inflammation are frequently grouped into "vicious circles" which are able to stimulate each other constantly amplifying the pathological events. These circles are evidently observed in Alzheimer's disease, atherosclerosis, type 2 diabetes, metabolic syndrome and, possibly, other associated pathologies. Furthermore, chronic inflammation in peripheral tissues is frequently concomitant to Alzheimer's disease. This is supposedly associated with some common genetic polymorphisms, for example, Apolipoprotein-E ε4 allele carriers with Alzheimer's disease can also develop atherosclerosis. Notably, in the transgenic mice expressing the recombinant mitochondria targeted catalase, that removes hydrogen peroxide from mitochondria, demonstrates the significant pathology amelioration and health improvements. In addition, the beneficial effects of some natural products from the xanthophyll family, astaxanthin and fucoxanthin, which are able to target the reactive oxygen species at cellular or mitochondrial membranes, have been demonstrated in both animal and human studies. We propose that the normalization of mitochondrial functions could play a key role in the treatment of neurodegenerative disorders and other noncommunicable diseases associated with chronic inflammation in ageing. Furthermore, some prospective drugs based on mitochondria targeted catalase or xanthophylls could be used as an effective treatment of these pathologies, especially at early stages of their development.

Effects of renalase deficiency on liver fibrosis markers in a nonalcoholic steatohepatitis mouse model

Progression of nonalcoholic steatohepatitis (NASH) is attributed to several factors, including inflammation and oxidative stress. In recent years, renalase has been reported to suppress oxidative stress, apoptosis and inflammation. A number of studies have suggested that renalase may be associated with protecting the liver from injury. The present study aimed to clarify the effects of renalase knockout (KO) in mice with NASH that were induced with a choline-deficient high-fat diet (CDAHFD) supplemented with 0.1% methionine. Wild type (WT) and KO mice (6-week-old) were fed a normal diet (ND) or CDAHFD for 6 weeks, followed by analysis of the blood liver function markers and liver tissues. CDAHFD intake was revealed to increase blood hepatic function markers, lipid accumulation and oxidative stress compared with ND, but no significant differences were observed between the WT and KO mice. However, in the KO-CDAHFD group, the Adgre1 and Tgfb1 mRNA levels were significantly higher, and α-SMA expression was significantly lower compared with the WT-CDAHFD group. Furthermore, the Gclc mRNA and phosphorylated protein kinase B (Akt) levels were significantly lower in the KO-ND group compared with the WT-ND group. The results of the current study indicated that as NASH progressed in the absence of renalase, oxidative stress, macrophage infiltration and TGF-β expression were enhanced, while α-SMA expression in NASH may be partly suppressed due to the decreased phosphorylation of Akt level.

miR-21-regulated M2 polarization of macrophage is involved in arsenicosis-induced hepatic fibrosis through the activation of hepatic stellate cells

Arsenicosis induced by chronic exposure to arsenic is recognized as one of the main damaging effects on public health. Exposure to arsenic can cause hepatic fibrosis, but the molecular mechanisms by which this occurs are complex and elusive. It is not known if miRNAs are involved in arsenic-induced liver fibrosis. We found that in the livers of mice exposed to arsenite, there were elevated levels of microRNA-21 (miR-21), phosphorylated mammalian target of rapamycin (p-mTOR), and arginase 1 (Arg1); low levels of phosphatase and tensin homolog (PTEN); and more extensive liver fibrosis. For cultured cells, arsenite-induced miR-21, p-mTOR, and Arg1; decreased PTEN; and promoted M2 polarization of macrophages derived from THP-1 monocytes (THP-M), which caused secretion of fibrogenic cytokines, including transforming growth factor-β1. Coculture of arsenite-treated, THP-M with LX-2 cells induced α-SMA and collagen I in the LX-2 cells and resulted in the activation of these cells. Downregulation of miR-21 in THP-M inhibited arsenite-induced M2 polarization and activation of LX-2 cells, but cotransfection with PTEN siRNA or a miR-21 inhibitor reversed this inhibition. Moreover, knockout of miR-21 in mice attenuated liver fibrosis and M2 polarization compared with WT mice exposed to arsenite. Additionally, LN, PCIII, and HA levels were higher in patients with higher hair arsenic levels, and levels of miR-21 were higher than controls and positively correlated with PCIII, LN, and HA levels. Thus, arsenite induces the M2 polarization of macrophages via miR-21 regulation of PTEN, which is involved in the activation of hepatic stellate cells and hepatic fibrosis. The results establish a previously unknown mechanism for arsenicosis-induced fibrosis.

Astragaloside IV Alleviates Liver Inflammation, Oxidative Stress and Apoptosis to Protect Against Experimental Non-Alcoholic Fatty Liver Disease

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) is the main form of chronic liver disease in the world. Astragaloside IV (ASIV) has been tested in experimental models of different diseases. The purpose of this study was to evaluate the effect and protective mechanism of ASIV on NAFLD.

METHODS

Lipopolysaccharide (LPS)- and palmitate acid (PA)-induced RAW264.7 cells and LO2 cells were used as a NAFLD model. The mice NAFLD model was evaluated by hematoxylin-eosin staining (HE staining), and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Liver lipid metabolism was evaluated by triglyceride (TG) and total cholesterol (TC) kits and oil red O staining. Oxidative stress indicators were examined through biochemical methods. Inflammatory factors were explored through enzyme-linked immuno sorbent assay (ELISA), real-time quantitative PCR and oxidative stress indicator kits. The expression levels of 5-LO (5-lipoxygenase) and leukotriene A4 hydrolase (LTA4H) were checked by real-time quantitative PCR and Western blotting. Apoptosis was detected by Annexin V-FITC/PI cell apoptosis detection kit.

RESULTS

Our results showed that in vivo ASIV significantly reduced liver tissue damage, and serum AST, ALT and serum TG levels in NAFLD mice. In vitro, ASIV reduced cell supernatant TG and TC content increased by PA treatment, and significantly decreased the accumulation of intracellular lipid droplets induced by PA treatment. Additionally, ASIV reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and restored glutathione peroxidase (GSH-Px) levels in PA-treated LO2 cell supernatant. Furthermore, ASIV inhibited the production of proinflammatory cytokines (IL-6 and TNF-α) in RAW264.7 cells induced by LPS. We also found that ASIV downregulated the expression of 5-LO and LTB4 (leukotriene B4) in NAFLD mice. Moreover, ASIV restored apoptotic protein (Bax and Bcl-2) expression in PA-treated LO2 cells.

CONCLUSION

ASIV may reduce liver steatosis, hepatocyte oxidative stress and apoptosis, and decrease liver inflammation, thereby attenuating the progression of NAFLD and thus might be of therapeutic interest.

Deletion of KLF10 Leads to Stress-Induced Liver Fibrosis upon High Sucrose Feeding

Liver fibrosis is a consequence of chronic liver injury associated with chronic viral infection, alcohol abuse, and nonalcoholic fatty liver. The evidence from clinical and animal studies indicates that transforming growth factor-β (TGF-β) signaling is associated with the development of liver fibrosis. Krüppel-like factor 10 (KLF10) is a transcription factor that plays a significant role in TGF-β-mediated cell growth, apoptosis, and differentiation. In recent studies, it has been reported to be associated with glucose homeostasis and insulin resistance. In the present study, we investigated the role of KLF10 in the progression of liver disease upon a high-sucrose diet (HSD) in mice. Wild type (WT) and Klf10 knockout (KO) mice were fed either a control chow diet or HSD (50% sucrose) for eight weeks. Klf10 KO mice exhibited significant hepatic steatosis, inflammation, and liver injury upon HSD feeding, whereas the WT mice exhibited mild hepatic steatosis with no apparent liver injury. The livers of HSD-fed Klf10 KO mice demonstrated significantly increased endoplasmic reticulum stress, oxidative stress, and proinflammatory cytokines. Klf10 deletion led to the development of sucrose-induced hepatocyte cell death both in vivo and in vitro. Moreover, it significantly increased fibrogenic gene expression and collagen accumulation in the liver. Increased liver fibrosis was accompanied by increased phosphorylation and nuclear localization of Smad3. Here, we demonstrate that HSD-fed mice develop a severe liver injury in the absence of KLF10 due to the hyperactivation of the endoplasmic reticulum stress response and CCAAT/enhance-binding protein homologous protein (CHOP)-mediated apoptosis of hepatocytes. The current study suggests that KLF10 plays a protective role against the progression of hepatic steatosis into liver fibrosis in a lipogenic state.

Overall clinical and economic impact of non-alcoholic fatty liver disease

OBJECTIVES

to establish the clinical and economic consequences (resource utilization and healthcare costs) of non-alcoholic fatty liver in the setting of the usual clinical practice in Spain.

PATIENTS AND METHODS

an observational, retrospective study was performed based on a review of the medical records of adult patients ≥ 18 years of age who sought medical care from 2017 to 2018. Patients were categorized into two groups according to fibrosis stage (estimation method: FIB-4): a) F0-F2; and b) F3-F4 (advanced fibrosis). Follow-up lasted one year. Primary endpoints included comorbidity, concomitant medication, resource utilization and costs. Results were analyzed using a multivariate approach with p < 0.05.

RESULTS

a total of 8,151 patients were recruited with a mean age of 61.1 years and 51.5 % were male. By group: a) mild fibrosis n = 7,127, 87.4 %; and b) advanced fibrosis n = 1,024, 12.6 % (6.8 % with liver cirrhosis). The most common comorbidities included 63 % dyslipidemia, 52 % obesity, 52 % hypertension and 35 % diabetes. The average number of drugs used was 2.1 per patient. Patients with advanced fibrosis (F3-F4) had a higher average number of concomitant medications (2.5 vs 2.1; p < 0.001) and a higher AST/ALT ratio (1.1 vs 0.8; p < 0.001). The average cost (patient-year) for subjects with advanced fibrosis, corrected for covariates, was higher (€1,812 vs €1,128, p < 0.001). Age, morbidity, concomitant medication, fibrosis stage and total costs were higher in patients with diabetes.

CONCLUSIONS

patients with advanced fibrosis were associated with more comorbidity and concomitant medications, which resulted in higher healthcare costs for the National Health System.

Co-encapsulation of HNF4α overexpressing UMSCs and human primary hepatocytes ameliorates mouse acute liver failure

BACKGROUND

Acute liver failure (ALF) is a complicated condition that is characterized by global hepatocyte death and often requires immediate liver transplantation. However, this therapy is limited by shortage of donor organs. Mesenchymal stem cells (MSCs) and hepatocytes are two attractive sources of cell-based therapies to treat ALF. The combined transplantation of hepatocytes and MSCs is considered to be more effective for the treatment of ALF than single-cell transplantation. We have previously demonstrated that HNF4α-overexpressing human umbilical cord MSCs (HNF4α-UMSCs) promoted the expression of hepatic-specific genes. In addition, microencapsulation allows exchange of nutrients, forming a protective barrier to the transplanted cells. Moreover, encapsulation of hepatocytes improves the viability and synthetic ability of hepatocytes and circumvents immune rejection. This study aimed to investigate the therapeutic effect of microencapsulation of hepatocytes and HNF4α-UMSCs in ALF mice.

METHODS

Human hepatocytes and UMSCs were obtained separately from liver and umbilical cord, followed by co-encapsulation and transplantation into mice by intraperitoneal injection. LPS/D-gal was used to induce ALF by intraperitoneal injection 24 h after transplantation. In addition, Raw 264.7 cells (a macrophage cell line) were used to elucidate the effect of HNF4α-UMSCs-hepatocyte microcapsules on polarization of macrophages. The protein chip was used to define the important paracrine factors in the conditioned mediums (CMs) of UMSCs and HNF4α-UMSCs and investigate the possible mechanism of HNF4α-UMSCs for the treatment of ALF in mice.

RESULTS

HNF4α-UMSCs can enhance the function of primary hepatocytes in alginate-poly-L-lysine-alginate (APA) microcapsules. The co-encapsulation of both HNF4α-UMSCs and hepatocytes achieved better therapeutic effects in ALF mice by promoting M2 macrophage polarization and reducing inflammatory response mainly mediated by the paracrine factor HB-EGF secreted by HNF4α-UMSCs.

CONCLUSIONS

The present study confirms that the co-encapsulation of HNF4α-UMSC and hepatocytes could exert therapeutic effect on ALF mainly by HB-EGF secreted by HNF4α-UMSCs and provides a novel strategy for the treatment of ALF.

Impact of tissue macrophage proliferation on peripheral and systemic insulin resistance in obese mice with diabetes

INTRODUCTION

Obesity-related insulin resistance is a widely accepted pathophysiological feature in type 2 diabetes. Systemic metabolism and immunity are closely related, and obesity represents impaired immune function that predisposes individuals to systemic chronic inflammation. Increased macrophage infiltration and activation in peripheral insulin target tissues in obese subjects are strongly related to insulin resistance. Using a macrophage-specific proliferation inhibition mouse model (mac-p27Tg), we previously reported that suppressed plaque inflammation reduced atherosclerosis and improved plaque stabilization. However, the direct evidence that proliferating macrophages are responsible for inducing insulin resistance was not provided.

RESEARCH DESIGN AND METHODS

The mac-p27Tg mice were fed a high-fat diet, and glucose metabolism, histological changes, macrophage polarization, and tissue functions were investigated to reveal the significance of tissue macrophage proliferation in insulin resistance and obesity.

RESULTS

The mac-p27Tg mice showed improved glucose tolerance and insulin sensitivity, along with a decrease in the number and ratio of inflammatory macrophages. Obesity-induced inflammation and oxidative stress was attenuated in white adipose tissue, liver, and gastrocnemius. Histological changes related to insulin resistance, such as liver steatosis/fibrosis, adipocyte enlargement, and skeletal muscle fiber transformation to fast type, were ameliorated in mac-p27Tg mice. Serum tumor necrosis factor alpha and free fatty acid were decreased, which might partially impact improved insulin sensitivity and histological changes.

CONCLUSIONS

Macrophage proliferation in adipose tissue, liver, and skeletal muscle was involved in promoting the development of systemic insulin resistance. Controlling the number of tissue macrophages by inhibiting macrophage proliferation could be a therapeutic target for insulin resistance and type 2 diabetes.

Metabolic Profiling Reveals Aggravated Non-Alcoholic Steatohepatitis in High-Fat High-Cholesterol Diet-Fed Apolipoprotein E-Deficient Mice Lacking Ron Receptor Signaling

Non-alcoholic steatohepatitis (NASH) represents the progressive sub-disease of non-alcoholic fatty liver disease that causes chronic liver injury initiated and sustained by steatosis and necroinflammation. The Ron receptor is a tyrosine kinase of the Met proto-oncogene family that potentially has a beneficial role in adipose and liver-specific inflammatory responses, as well as glucose and lipid metabolism. Since its discovery two decades ago, the Ron receptor has been extensively investigated for its differential roles on inflammation and cancer. Previously, we showed that Ron expression on tissue-resident macrophages limits inflammatory macrophage activation and promotes a repair phenotype, which can retard the progression of NASH in a diet-induced mouse model. However, the metabolic consequences of Ron activation have not previously been investigated. Here, we explored the effects of Ron receptor activation on major metabolic pathways that underlie the development and progression of NASH. Mice lacking apolipoprotein E (ApoE KO) and double knockout (DKO) mice that lack ApoE and Ron were maintained on a high-fat high-cholesterol diet for 18 weeks. We observed that, in DKO mice, the loss of ligand-dependent Ron signaling aggravated key pathological features in steatohepatitis, including steatosis, inflammation, oxidation stress, and hepatocyte damage. Transcriptional programs positively regulating fatty acid (FA) synthesis and uptake were upregulated in the absence of Ron receptor signaling, whereas lipid disposal pathways were downregulated. Consistent with the deregulation of lipid metabolism pathways, the DKO animals exhibited increased accumulation of FAs in the liver and decreased level of bile acids. Altogether, ligand-dependent Ron receptor activation provides protection from the deregulation of major metabolic pathways that initiate and aggravate non-alcoholic steatohepatitis.

Immunological distinctions between nonalcoholic steatohepatitis and hepatocellular carcinoma

Nonalcoholic fatty liver disease (NAFLD), the most common cause of chronic liver disease, ranges from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH), which is a more aggressive form characterized by hepatocyte injury, inflammation, and fibrosis. Increasing evidence suggests that NASH is a risk factor for hepatocellular carcinoma (HCC), which is the fifth most common cancer worldwide and the second most common cause of cancer-related death. Recent studies support a strong mechanistic link between the NASH microenvironment and HCC development. The liver has a large capacity to remove circulating pathogens and gut-derived microbial compounds. Thus, the liver is a central player in immunoregulation. Altered immune responses are tightly associated with the development of NASH and HCC. The objective of this study was to differentiate the roles of specific immune cell subsets in NASH and HCC pathogenesis.

Clarifying the role of specific cells in the immune system in the transition from non-alcoholic fatty liver disease (NAFLD) to liver cancer will help to understand disease progression and may open avenues towards new preventive and therapeutic strategies. NAFLD is the most common chronic liver disease. Growing evidence suggests that its most aggressive form, non-alcoholic steatohepatitis (NASH), can promote the development of liver cancer, the second most common cause of cancer deaths worldwide. Chang-Woo Lee and colleagues at Sungkyunkwan University, Suwon, South Korea review the immunological distinction between NASH and liver cancer, focusing on the levels and activities of six key types of immune system cells. Chronic inflammation mediated by the immune system can create conditions for NAFLD, NASH and liver cancer to develop and worsen.

Perforin Acts as an Immune Regulator to Prevent the Progression of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is one of the main causes of cirrhosis and major risk factors for hepatocellular carcinoma and liver-related death. Despite substantial clinical and basic research, the pathogenesis of obesity-related NAFLD remains poorly understood. In this study, we show that perforin can act as an immune regulator to prevent the progression of NAFLD. Aged perforin-deficient (Prf^−/−) mice have increased lipid accumulation in the liver compared to WT mice. With high-fat diet (HFD) challenge, Prf^−/− mice have increased liver weight, more severe liver damage, and increased liver inflammation when compared with WT controls. Mechanistic studies revealed that perforin specifically regulates intrinsic IFN-γ production in CD4 T cells, not CD8 T cells. We found that CD4 T cell depletion reduces liver injury and ameliorates the inflammation and metabolic morbidities in Prf^−/− mice. Furthermore, improved liver characteristics in HFD Prf^−/− and IFN-γR^−/− double knockout mice confirmed that IFN-γ is a key factor for mediating perforin regulation of NAFLD progression. Overall, our findings reveal the important regulatory role perforin plays in the progression of obesity-related NAFLD and highlight novel strategies for treating NAFLD.

A Brazilian regional basic diet-induced chronic malnutrition drives liver inflammation with higher ApoA-I activity in C57BL6J mice

Malnutrition is still considered endemic in many developing countries. Malnutrition-enteric infections may cause lasting deleterious effects on lipid metabolism, especially in children living in poor settings. The regional basic diet (RBD), produced to mimic the Brazilian northeastern dietary characteristics (rich in carbohydrate and low in protein) has been used in experimental malnutrition models, but few studies have explored the effect of chronic RBD on liver function, a central organ involved in cholesterol metabolism. This study aimed to investigate whether RBD leads to liver inflammatory changes and altered reverse cholesterol metabolism in C57BL6/J mice compared to the control group, receiving a standard chow diet. To evaluate liver inflammation, ionized calcium-binding adapter protein-1 (IBA-1) positive cell counting, interleukin (IL)-1β immunohistochemistry, and tumor necrosis factor (TNF)-α and IL-10 transcription levels were analyzed. In addition, we assessed reverse cholesterol transport by measuring liver apolipoprotein (Apo)E, ApoA-I, and lecithin-cholesterol acyltransferase (LCAT) by RT-PCR. Furthermore, serum alanine aminotransferase (ALT) was measured to assess liver function. RBD markedly impaired body weight gain compared with the control group (P<0.05). Higher hepatic TNF-α (P<0.0001) and IL-10 (P=0.001) mRNA levels were found in RBD-challenged mice, although without detectable non-alcoholic fatty liver disease. Marked IBA-1 immunolabeling and increased number of positive-IBA-1 cells were found in the undernourished group. No statistical difference in serum ALT was found. There was also a significant increase in ApoA mRNA expression in the undernourished group, but not ApoE and LCAT, compared with the control. Altogether our findings suggested that chronic RBD-induced malnutrition leads to liver inflammation with increased ApoA-I activity.

The anti-inflammatory, anti-oxidant and protective effects of a probiotic mixture on organ toxicity in a rat model

Aim: The objective of this study was to evaluate the possible protective effects of probiotic bacteria, especially Bifidobacterium and Lactobacillus strains, on 4,4'-dichlorodiphenyltrichloroethane (DDT)-induced toxicity. For this reason, we evaluated the relationship between probiotics and toxicity by checking immunological and immunohistochemical parameters. Materials & methods: Probiotic pretreatment was applied to 36 Wistar albino rats for 12 consecutive days. Serum aspartate aminotransferase and alanine aminotransferase levels were detected. CD3 and NF-κB staining methods were then performed by immunohistochemistry. Finally, pro- and anti-inflammatory cytokines were measured by ELISA. Results: DDT caused a serious increase/decrease in some cytokine parameters. The effective dose was 1 × 10¹¹ colony-forming unit probiotic treatment. CD3 and NF-κB positivity were intense in DDT group whereas the intensity was reduced in probiotic treatment groups. Discussion: The probiotic mixture has a potential to prevent inflammatory and oxidative stress related organ injuries. Further studies should be performed to explain the possible mechanisms.

Chemical hypoxia induces pro-inflammatory signals in fat-laden hepatocytes and contributes to cellular crosstalk with Kupffer cells through extracellular vesicles

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated to intermittent hypoxia (IH) and is an aggravating factor of non-alcoholic fatty liver disease (NAFLD). We investigated the effects of hypoxia in both in vitro and in vivo models of NAFLD.

METHODS

Primary rat hepatocytes treated with free fatty acids (FFA) were subjected to chemically induced hypoxia (CH) using the hypoxia-inducible factor-1 alpha (HIF-1α) stabilizer cobalt chloride (CoCl2). Triglyceride (TG) content, mitochondrial superoxide production, cell death rates, cytokine and inflammasome components gene expression and protein levels of cleaved caspase-1 were assessed. Also, Kupffer cells (KC) were treated with conditioned medium (CM) and extracellular vehicles (EVs) from hypoxic fat-laden hepatic cells. The choline deficient L-amino acid defined (CDAA)-feeding model used to assess the effects of IH on experimental NAFLD in vivo.

RESULTS

Hypoxia induced HIF-1α in cells and animals. Hepatocytes exposed to FFA and CoCl2 exhibited increased TG content and higher cell death rates as well as increased mitochondrial superoxide production and mRNA levels of pro-inflammatory cytokines and of inflammasome-components interleukin-1β, NLRP3 and ASC. Protein levels of cleaved caspase-1 increased in CH-exposed hepatocytes. CM and EVs from hypoxic fat-laden hepatic cells evoked a pro-inflammatory phenotype in KC. Livers from CDAA-fed mice exposed to IH exhibited increased mRNA levels of pro-inflammatory and inflammasome genes and increased levels of cleaved caspase-1.

CONCLUSION

Hypoxia promotes inflammatory signals including inflammasome/caspase-1 activation in fat-laden hepatocytes and contributes to cellular crosstalk with KC by release of EVs. These mechanisms may underlie the aggravating effect of OSAS on NAFLD. [Abstract word count: 257].

Immunometabolism in type 2 diabetes mellitus: tissue-specific interactions

The immune system is frequently described in the context of its protective function against infections and its role in the development of autoimmunity. For more than a decade, the interactions between the immune system and metabolic processes have been reported, in effect creating a new research field, termed immunometabolism. Accumulating evidence supports the hypothesis that the development of metabolic diseases may be linked to inflammation, and reflects, in some cases, the activation of immune responses. As such, immunometabolism is defined by 1) inflammation as a driver of disease development and/or 2) metabolic processes stimulating cellular differentiation of the immune components. In this review, the main factors capable of altering the immuno-metabolic communication leading to the development and establishment of obesity and diabetes are comprehensively presented. Tissue-specific immune responses suggested to impair metabolic processes are described, with an emphasis on the adipose tissue, gut, muscle, liver, and pancreas.

A 3-week nonalcoholic steatohepatitis mouse model shows elafibranor benefits on hepatic inflammation and cell death

The long duration of animal models represents a clear limitation to quickly evaluate the efficacy of drugs targeting nonalcoholic steatohepatitis (NASH). We, therefore, developed a rapid mouse model of liver inflammation (i.e., the mouse fed a high-fat/high-cholesterol diet, where cyclodextrin is co-administered to favor hepatic cholesterol loading, liver inflammation, and NASH within 3 weeks), and evaluated the effects of the dual peroxisome proliferator-activated receptor alpha/delta agonist elafibranor (ELA). C57BL6/J mice were fed a 60% high-fat, 1.25% cholesterol, and 0.5% cholic acid diet with 2% cyclodextrin in drinking water (HFCC/CDX diet) for 3 weeks. After 1 week of the diet, mice were treated orally with vehicle or ELA 20 mg/kg q.d. for 2 weeks. Compared with vehicle, ELA markedly reduced liver lipids and nonalcoholic fatty liver disease activity scoring, through steatosis, inflammation, and fibrosis (all P < 0.01 vs. vehicle). Flow cytometry analysis showed that ELA significantly improved the HFCC/CDX diet-induced liver inflammation by preventing the increase in total number of immune cells (CD45+), Kupffer cells, dendritic cells, and monocytes population, as well as the reduction in natural killer and natural killer T cells, and by blocking conversion of T cells in regulatory T cells. ELA did not alter pyroptosis (Gasdermin D), but significantly reduced necroptosis (cleaved RIP3) and apoptosis (cleaved caspase 3) in the liver. In conclusion, ELA showed strong benefits on NASH, including improvement in hepatic inflammation, necroptosis, and apoptosis in the 3-week NASH mouse. This preclinical model will be useful to rapidly detect the effects of novel drugs targeting NASH.

The Interplay Between Tissue Niche and Macrophage Cellular Metabolism in Obesity

Obesity is associated with the development of metabolic diseases such as type 2 diabetes and non-alcoholic fatty liver disease. The presence of chronic, low-grade inflammation appears to be an important mechanistic link between excess nutrients and clinical disease. The onset of these metabolic disorders coincides with changes in the number and phenotype of macrophages in peripheral organs, particularly in the liver and adipose tissue. Macrophage accumulation in these tissues has been implicated in tissue inflammation and fibrosis, contributing to metabolic disease progression. Recently, the concept has emerged that changes in macrophage metabolism affects their functional phenotype, possibly triggered by distinct environmental metabolic cues. This may be of particular importance in the setting of obesity, where both liver and adipose tissue are faced with a high metabolic burden. In the first part of this review we will discuss current knowledge regarding macrophage dynamics in both adipose tissue and liver in obesity. Then in the second part, we will highlight data linking macrophage metabolism to functional phenotype with an emphasis on macrophage activation in metabolic disease. The importance of understanding how tissue niche influences macrophage function in obesity will be highlighted. In addition, we will identify important knowledge gaps and outstanding questions that are relevant for future research in this area and will facilitate the identification of novel targets for therapeutic intervention in associated metabolic diseases.

Macrophage Function in the Pathogenesis of Non-alcoholic Fatty Liver Disease: The Mac Attack

Obesity is a prevalent predisposing factor to non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the developed world. NAFLD spectrum of disease involves progression from steatosis (NAFL), to steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). Despite clinical and public health significance, current FDA approved therapies for NAFLD are lacking in part due to insufficient understanding of pathogenic mechanisms driving disease progression. The etiology of NAFLD is multifactorial. The induction of both systemic and tissue inflammation consequential of skewed immune cell metabolic state, polarization, tissue recruitment, and activation are central to NAFLD progression. Here, we review the current understanding of the above stated cellular and molecular processes that govern macrophage contribution to NAFLD pathogenesis and how adipose tissue and liver crosstalk modulates macrophage function. Notably, the manipulation of such events may lead to the development of new therapies for NAFLD.

Sarcopenia and fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease which may progress to non-alcoholic steatohepatitis. The prevalence of sarcopenia, which is the loss of muscle mass and strength, is increasing in the aging society. Recent studies reported the relationship between NAFLD and sarcopenia. The skeletal muscle is the primary organ for glucose disposal. Loss of muscle mass can cause insulin resistance, which is an important risk factor for NAFLD. Moreover, obesity, chronic low-grade inflammation, vitamin D deficiency, physical inactivity, hepatokines, and myokines might be involved in the pathophysiologic mechanism of sarcopenia and NAFLD. Although most of the previous studies have demonstrated the positive correlation between sarcopenia and NAFLD, the difference in diagnostic methods of sarcopenia and NAFLD leads to difficulties in interpretation and application. This review discusses the concept and diagnosis of sarcopenia and NAFLD, common pathophysiology, and clinical studies linking sarcopenia to NAFLD. The presentation of the association between sarcopenia and NAFLD may provide an opportunity to prevent the deterioration of fatty liver disease.

Potential Therapeutic Application of Estrogen in Gender Disparity of Nonalcoholic Fatty Liver Disease/Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) caused by fat accumulation in the liver is globally the most common cause of chronic liver disease. Simple steatosis can progress to nonalcoholic steatohepatitis (NASH), a more severe form of NAFLD. The most potent driver for NASH is hepatocyte death induced by lipotoxicity, which triggers inflammation and fibrosis, leading to cirrhosis and/or liver cancer. Despite the significant burden of NAFLD, there is no therapy for NAFLD/NASH. Accumulating evidence indicates gender-related NAFLD progression. A higher incidence of NAFLD is found in men and postmenopausal women than premenopausal women, and the experimental results, showing protective actions of estradiol in liver diseases, suggest that estrogen, as the main female hormone, is associated with the progression of NAFLD/NASH. However, the mechanism explaining the functions of estrogen in NAFLD remains unclear because of the lack of reliable animal models for NASH, the imbalance between the sexes in animal experiments, and subsequent insufficient results. Herein, we reviewed the pathogenesis of NAFLD/NASH focused on gender and proposed a feasible association of estradiol with NAFLD/NASH based on the findings reported thus far. This review would help to expand our knowledge of the gender differences in NAFLD and for developing gender-based treatment strategies for NAFLD/NASH.

Indole-3-Acetic Acid Alleviates Nonalcoholic Fatty Liver Disease in Mice via Attenuation of Hepatic Lipogenesis, and Oxidative and Inflammatory Stress

Recent evidences have linked indole-3-acetic acid (IAA), a gut microbiota-derived metabolite from dietary tryptophan, with the resistance to liver diseases. However, data supporting IAA-mediated protection against nonalcoholic fatty liver disease (NAFLD) from an in vivo study is lacking. In this study, we assessed the role of IAA in attenuating high-fat diet (HFD)-induced NAFLD in male C57BL/6 mice. Administration of IAA (50 mg/kg body weight) by intraperitoneal injection was found to alleviate HFD-induced elevation in fasting blood glucose and homeostasis model assessment of insulin resistance (HOMA-IR) index as well as plasma total cholesterol, low-density lipoprotein cholesterol (LDL-C), and glutamic-pyruvic transaminase (GPT) activity. Histological examination further presented the protective effect of IAA on liver damage induced by HFD feeding. HFD-induced an increase in liver total triglycerides and cholesterol, together with the upregulation of genes related to lipogenesis including sterol regulatory element binding-protein 1 (Srebf1), steraroyl coenzyme decarboxylase 1 (Scd1), peroxisome proliferator-activated receptor gamma (PPARγ), acetyl-CoA carboxylase 1 (Acaca), and glycerol-3-phosphate acyltransferase, mitochondrial (Gpam), which were mitigated by IAA treatment. The results of reactive oxygen species (ROS) and malonaldehyde (MDA) level along with superoxide dismutase (SOD) activity and glutathione (GSH) content in liver tissue evidenced the protection of IAA against HFD-induced oxidative stress. Additionally, IAA attenuated the inflammatory response of liver in mice exposed to HFD as shown by the reduction in the F4/80-positive macrophage infiltration and the expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α). In conclusion, our findings uncover that IAA alleviates HFD-induced hepatotoxicity in mice, which proves to be associated with the amelioration in insulin resistance, lipid metabolism, and oxidative and inflammatory stress.

TRIB1 rs17321515 gene polymorphism increases the risk of coronary heart disease in general population and non-alcoholic fatty liver disease patients in Chinese Han population

Background

Present evidences suggested that TRIB1 rs17321515 polymorphism was tightly associated with the increased risk of NAFLD and CHD. CHD is one of the main complications of NAFLD, whether TRIB1 rs17321515 polymorphism could affect the risk of CHD in general population and NAFLD patients in Chinese Han population was remain unknown. The present study was designed to investigate the association between TRIB1 rs17321515 polymorphism and the risk of CHD in general population and NAFLD patients in Chinese Han population, and investigate the effect of TRIB1 rs17321515 polymorphism on serum lipid levels.

Patients and methods

TRIB1 rs17321515 gene polymorphism was genotyped using the polymerase chain reaction (PCR) in healthy controls (n = 175), CHD patients (n = 155), NAFLD patients (n = 146), and NAFLD+CHD patients (n = 156). Serum lipid profiles were determined using biochemical methods. Statistical analyses were performed using SPSS 24.0 statistical software.

Results

The TRIB1 rs17321515 AA+GA genotypes were the significant risk factors for the CHD in general population (OR = 1.788; 95% CI: 1.104–2.897; P = 0.018) and in the NAFLD patients (OR = 1.760; 95% CI: 1.071–2.891; P = 0.026). After adjusted for age, gender, and body mass index, the risk for CHD in general population (OR = 1.857; 95% CI: 1.116–3.089; P = 0.017) and NAFLD patients was still significant (OR = 1.723; 95% CI: 1.033–2.873; P = 0.037). In addition, TRIB1 rs17321515 A carriers possess the higher lipid profiles in the included subjects.

Conclusions

TRIB1 rs17321515 AA+GA genotypes were significant associated with the risk of CHD in general population and in NAFLD patients in Chinese Han population. The rs17321515 A allele increases the serum lipid profiles in included subjects.

Biocompatibility studies of fluorescent diamond particles-(NV)~800nm (part V): in vitro kinetics and in vivo localization in rat liver following long-term exposure

Background

We recently reported on long-term comprehensive biocompatibility and biodistribution study of fluorescent nanodiamond particles (NV)-Z-average 800nm (FNDP-(NV)) in rats. FNDP-(NV) primary deposition was found in the liver, yet liver function tests remained normal.

Purpose

The present study aimed to gain preliminary insights on discrete localization of FNDP-(NV) in liver cells of the hepatic lobule unit and venous micro-vasculature. Kinetics of FDNP-(NV) uptake into liver cells surrogates in culture was conducted along with cell cytokinesis as markers of cells' viability.

Methods

Preserved liver specimens from a pilot consisting of two animals which were stained for cytoskeletal elements (fluorescein-isothiocyanate-phalloidin) were examined for distribution of FNDP-(NV) by fluorescent microscopy (FM) and Confocal-FM (CFM) using near infra-red fluorescence (NIR). Hepatocellular carcinoma cells (HepG-2) and human umbilical vein endothelial cells (HUVEC) were cultured with FNDP-(NV) and assayed for particle uptake and location using spectrophotometric technology and microscopy.

Results

HepG-2 and HUVEC displayed rapid (<30 mins) onset and concentration-dependent FNDP-(NV) internalization and formation of peri-nuclear corona. FM/CFM of liver sections revealed FNDP-(NV) presence throughout the hepatic lobules structures marked by spatial distribution, venous microvascular spaces and parenchyma and non-parenchyma cells.

Conclusion

The robust presence of FNDP-(NV) throughout the hepatic lobules including those internalized within parenchyma cells and agglomerates in the liver venous micro-circulation were not associated with macro or micro histopathological signs nor vascular lesions. Cells cultures indicated normal cytokinesis in cells containing FNDP-(NV) agglomerates. Liver parenchyma cells and the liver microcirculation remain agnostic to presence of FNDP-(NV) in the sinusoids or internalized in the hepatic cells.