Cenicriviroc suppresses and reverses steatohepatitis by regulating macrophage infiltration and M2 polarization in mice.

The inhibition of hepatic macrophage and Kupfer cell recruitment and activation is a potential strategy for treating insulin resistance and nonalcoholic steatohepatitis (NASH). Cenicriviroc (CVC), a dual C-C chemokine receptor 2 (CCR2) and CCR5 antagonist, has shown anti-fibrotic activity in murine models of NASH and has been evaluated in clinical trials on patients with NASH. This study investigated the effects of CVC on macrophage infiltration and polarization in a lipotoxic model of NASH. C57BL/6 mice were fed a high-cholesterol, high-fat (CL) diet or a CL diet containing 0.015% CVC (CL+CVC) for 12 weeks. Macrophage recruitment and activation were assayed by immunohistochemistry and flow cytometry. CVC supplementation attenuated excessive hepatic lipid accumulation and peroxidation and alleviated glucose intolerance and hyperinsulinemia in the mice that were fed the CL diet. Flow cytometry analysis revealed that compared with the CL group, mice fed the CL+CVC diet had fewer M1-like macrophages, more M2-like macrophages, and fewer T cell counts, indicating that CVC caused an M2-dominant shift of macrophages in the liver. Similarly, CVC decreased lipopolysaccharide-stimulated M1-like macrophage activation, whereas it increased interleukin-4-induced M2-type macrophage polarization in vitro. In addition, CVC attenuated hepatic fibrosis by repressing hepatic stellate cell activation. Lastly, CVC reversed insulin resistance as well as steatosis, inflammation, and fibrosis of the liver in mice with pre-existing NASH. In conclusion CVC prevented and reversed hepatic steatosis, insulin resistance, inflammation, and fibrogenesis in the livers of NASH mice via M2 macrophage polarization.

A natural Nrf2 activator glucoraphanin improves hepatic steatosis in high-fat diet-induced obese male mice associated with AMPK activation.

Genetic and pharmacological activation of the transcription factor nuclear factor, erythroid derived 2, like 2 (Nrf2) alleviates high-fat diet (HFD)-induced obesity in mice; however, synthetic Nrf2 activators are not clinically available due to safety concerns. Dietary glucoraphanin (GR), a naturally occurring compound found in cruciferous vegetables that activates Nrf2 and induces its target antioxidant genes. We previously demonstrated that GR increased thermogenesis and mitigated HFD-induced obesity in lean healthy mice. In this study, we investigated the therapeutic effects of GR on pre-existing obesity and associated metabolic disorders, such as hepatic steatosis, with or without low-fat dietary intervention. Eight-week-old male C57BL/6J mice were fed an HFD for 9 weeks to induce obesity. Subsequently, these obese mice were fed either the HFD or a normal chow diet, supplemented with or without GR, for an additional 11 weeks. GR supplementation did not decrease the body weight of HFD-fed mice; however, it significantly reduced plasma alanine aminotransferase and aspartate aminotransferase levels and hepatic triglyceride accumulation. These improvements in liver damage by GR were associated with decreased expression levels of fatty acid synthesis genes and proinflammatory chemokine genes, suppressed c-Jun N-terminal kinase activation, and reduced proinflammatory phenotypes of macrophages in the liver. Moreover, metabolome analysis identified increased hepatic levels of adenosine 5'-monophosphate (AMP) in HFD-GR mice compared with those in HFD mice, which agreed with increased phosphorylation levels of AMP-activated protein kinase. Our results show that GR may have a therapeutic potential for treating obesity-associated hepatic steatosis. Supplementary Information: The online version contains supplementary material available at 10.1007/s13340-023-00658-6.

CX3CL1/CX3CR1 interaction protects against lipotoxicity-induced nonalcoholic steatohepatitis by regulating macrophage migration and M1/M2 status.

BACKGROUND AND OBJECTIVES: Chemokine (C-X3-C motif) ligand 1 (CX3CL1) and its receptor CX3CR1 regulate the migration and activation of immune cells and are involved in the pathogenesis of nonalcoholic steatohepatitis (NASH), but the mechanism remains elusive. Here, the roles of CX3CL1/CX3CR1 in the macrophage migration and polarization in the livers of NASH mice were investigated. METHODS AND RESULTS: The expression of Cx3cl1 and Cx3cr1 was markedly upregulated in the livers of lipotoxicity-induced NASH mice. CX3CR1 was predominantly expressed by F4/80+ macrophages and to a lesser degree by hepatic stellate cells or endothelial cells in the livers of NASH mice. Flow cytometry analysis revealed that, compared with chow-fed mice, NASH mice exhibited a significant increase in CX3CR1+ expression by liver macrophages (LMs), particularly M1 LMs. CX3CR1 deficiency caused a significant increase in inflammatory monocyte/macrophage infiltration and a shift toward M1 dominant macrophages in the liver, thereby exacerbating the progression of NASH. Moreover, transplantation of Cx3cr1-/- bone marrow was sufficient to cause glucose intolerance, inflammation, and fibrosis in the liver. In addition, deletion of CCL2 in Cx3cr1-/- mice alleviated NASH progression by decreasing macrophage infiltration and inducing a shift toward M2 dominant LMs. Importantly, overexpression of CX3CL1 in vivo protected against hepatic fibrosis in NASH. CONCLUSION: Pharmacological therapy targeting liver CX3CL1/CX3CR1 signaling might be a candidate for the treatment of NASH.

CC chemokine ligand 3 deficiency ameliorates diet-induced steatohepatitis by regulating liver macrophage recruitment and M1/M2 status in mice.

BACKGROUND AND AIMS: The global prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing. Chemokines and their receptors have potential as therapeutic targets of NAFLD. We investigated the role of CC chemokine ligand 3 (CCL3) in the development of murine and human NAFLD. METHODS: CCL3-knockout mice (CCL3-/-) and littermate CCL3 wild-type control mice (WT) were fed a high-cholesterol and high-fat (CL) diet for 16 weeks to induce NAFLD. We investigated the impact of CCL3 gene deletion in bone marrow cells and leptin-deficient ob/ob mice on CL diet-induced steatohepatitis. We assayed the serum CCL3 levels in 36 patients with biopsy-proven NAFLD and nine healthy control subjects. RESULTS: Compared with normal chow (NC), the CL diet induced steatohepatitis and hepatic fibrosis and elevated the plasma CCL3 level. In the liver, CCL3 protein colocalized with F4/80+ macrophages, especially CD11c+ M1-like macrophages, rather than other cell types. CCL3-/- attenuated CL diet-induced steatohepatitis and fibrosis associated with M2-dominant liver macrophages compared with the WT. The reconstitution of bone marrow (BM) cells from CCL3-/- attenuated steatohepatitis in WT mice fed a CL diet. Furthermore, crossing CCL3-/- onto the ob/ob background prevented CL diet-induced NAFLD in ob/ob mice, which was associated with a lesser inflammatory phenotype of liver macrophages. Also, the serum and hepatic levels of CCL3 were significantly increased in patients with non-alcoholic steatohepatitis (NASH) compared to those with simple fatty liver (NAFL) and healthy subjects. CONCLUSION: Our data indicate that CCL3 facilitates macrophage infiltration into the liver and M1 polarization in the progression of steatohepatitis and highlight the need for further studies to determine the effect of CCL3-CCR1 and -CCR5 signaling blockade on the treatment of NAFLD.

Effect of Microbiome on Non-Alcoholic Fatty Liver Disease and the Role of Probiotics, Prebiotics, and Biogenics.

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of liver cirrhosis and hepatocellular carcinoma. NAFLD is associated with metabolic disorders such as obesity, insulin resistance, dyslipidemia, steatohepatitis, and liver fibrosis. Liver-resident (Kupffer cells) and recruited macrophages contribute to low-grade chronic inflammation in various tissues by modulating macrophage polarization, which is implicated in the pathogenesis of metabolic diseases. Abnormalities in the intestinal environment, such as the gut microbiota, metabolites, and immune system, are also involved in the pathogenesis and development of NAFLD. Hepatic macrophage activation is induced by the permeation of antigens, endotoxins, and other proinflammatory substances into the bloodstream as a result of increased intestinal permeability. Therefore, it is important to understand the role of the gut-liver axis in influencing macrophage activity, which is central to the pathogenesis of NAFLD and nonalcoholic steatohepatitis (NASH). Not only probiotics but also biogenics (heat-killed lactic acid bacteria) are effective in ameliorating the progression of NASH. Here we review the effect of hepatic macrophages/Kupffer cells, other immune cells, intestinal permeability, and immunity on NAFLD and NASH and the impact of probiotics, prebiotics, and biogenesis on those diseases.

Enhanced enteric neurogenesis by Schwann cell precursors in mouse models of Hirschsprung disease.

Hirschsprung disease (HSCR) is characterized by congenital absence of enteric neurons in distal portions of the gut. Although recent studies identified Schwann cell precursors (SCPs) as a novel cellular source of enteric neurons, it is unknown how SCPs contribute to the disease phenotype of HSCR. Using Schwann cell-specific genetic labeling, we investigated SCP-derived neurogenesis in two mouse models of HSCR; Sox10 haploinsufficient mice exhibiting distal colonic aganglionosis and Ednrb knockout mice showing small intestinal aganglionosis. We also examined Ret dependency in SCP-derived neurogenesis using mice displaying intestinal aganglionosis in which Ret expression was conditionally removed in the Schwann cell lineage. SCP-derived neurons were abundant in the transition zone lying between the ganglionated and aganglionic segments, although SCP-derived neurogenesis was scarce in the aganglionic region. In the transition zone, SCPs mainly gave rise to nitrergic neurons that are rarely observed in the SCP-derived neurons under the normal condition. Enhanced SCP-derived neurogenesis was also detected in the transition zone of mice lacking RET expression in the Schwann cell lineage. Increased SCP-derived neurogenesis in the transition zone suggests that reduction in the vagal neural crest-derived enteric neurons promotes SCP-derived neurogenesis. SCPs may adopt a neuronal subtype by responding to changes in the gut environment. Robust SCP-derived neurogenesis can occur in a Ret-independent manner, which suggests that SCPs are a cellular source to compensate for missing enteric neurons in HSCR.

CX3CL1-CX3CR1 Signaling Deficiency Exacerbates Obesity-induced Inflammation and Insulin Resistance in Male Mice.

The CX3CL1-CX3CR1 system plays an important role in disease progression by regulating inflammation both positively and negatively. We reported previously that C-C chemokine receptors 2 and 5 promote obesity-associated adipose tissue inflammation and insulin resistance. Here, we demonstrate that CX3CL1-CX3CR1 signaling is involved in adipose tissue inflammation and insulin resistance in obese mice via adipose tissue macrophage recruitment and M1/M2 polarization. Cx3cl1 expression was persistently decreased in the epididymal white adipose tissue (eWAT) of high-fat diet-induced obese (DIO) mice, despite increased expression of other chemokines. Interestingly, in Cx3cr1-/- mice, glucose tolerance, insulin resistance, and hepatic steatosis induced by DIO or leptin deficiency were exacerbated. CX3CL1-CX3CR1 signaling deficiency resulted in reduced M2-polarized macrophage migration and an M1-dominant shift of macrophages within eWAT. Furthermore, transplantation of Cx3cr1-/- bone marrow was sufficient to impair glucose tolerance, insulin sensitivity, and regulation of M1/M2 status. Moreover, Cx3cl1 administration in vivo led to the attenuation of glucose intolerance and insulin resistance. Thus, therapy targeting the CX3CL1-CX3CR1 system may be beneficial in the treatment of type 2 diabetes by regulating M1/M2 macrophages.

LECT2 as a hepatokine links liver steatosis to inflammation via activating tissue macrophages in NASH.

It remains unclear how hepatic steatosis links to inflammation. Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine that senses fat in the liver and is upregulated prior to weight gain. The aim of this study was to investigate the significance of LECT2 in the development of nonalcoholic steatohepatitis (NASH). In human liver biopsy samples, elevated LECT2 mRNA levels were positively correlated with body mass index (BMI) and increased in patients who have steatosis and inflammation in the liver. LECT2 mRNA levels were also positively correlated with the mRNA levels of the inflammatory genes CCR2 and TLR4. In C57BL/6J mice fed with a high-fat diet, mRNA levels of the inflammatory cytokines Tnfa and Nos2 were significantly lower in Lect2 KO mice. In flow cytometry analyses, the number of M1-like macrophages and M1/M2 ratio were significantly lower in Lect2 KO mice than in WT mice. In KUP5, mouse kupffer cell line, LECT2 selectively enhanced the LPS-induced phosphorylation of JNK, but not that of ERK and p38. Consistently, LECT2 enhanced the LPS-induced phosphorylation of MKK4 and TAB2, upstream activators of JNK. Hepatic expression of LECT2 is upregulated in association with the inflammatory signature in human liver tissues. The elevation of LECT2 shifts liver residual macrophage to the M1-like phenotype, and contributes to the development of liver inflammation. These findings shed light on the hepatokine LECT2 as a potential therapeutic target that can dissociate liver steatosis from inflammation.

Lactobacillus pentosus strain S-PT84 improves steatohepatitis by maintaining gut permeability.

Intestinal mucosal barrier dysfunction is closely related to the pathogenesis of nonalcoholic steatohepatitis (NASH). Gut immunity has been recently demonstrated to regulate gut barrier function. The Lactobacillus pentosus strain S-PT84 activates helper T cells and natural killer/natural killer T cells. In this study, we examined the effect of S-PT84 on NASH progression induced by high-cholesterol/high-fat diet (CL), focusing on the immune responses involved in gut barrier function. C57BL/6 mice were fed a normal chow or CL diet with or without 1 × 1010 S-PT84 for 22 weeks. S-PT84 administration improved hepatic steatosis by decreasing triglyceride and free fatty acid levels by 34% and 37%, respectively. Furthermore, S-PT84 inhibited the development of hepatic inflammation and fibrosis, suppressed F4/80+ macrophage/Kupffer cell infiltration, and reduced liver hydroxyproline content. Administration of S-PT84 alleviated hyperinsulinemia and enhanced hepatic insulin signalling. Compared with mice fed CL diet, mice fed CL+S-PT84 had 71% more CD11c-CD206+ M2 macrophages, resulting in a significantly decreased M1/M2 macrophage ratio in the liver. Moreover, S-PT84 inhibited the CL diet-mediated increase in intestinal permeability. Additionally, S-PT84 reduced the recruitment of interleukin-17-producing T cells and increased the levels of intestinal tight junction proteins, including zonula occludens-1, occludin, claudin-3, and claudin-7. In conclusion, our findings suggest that S-PT84 attenuates diet-induced insulin resistance and subsequent NASH development by maintaining gut permeability. Thus, S-PT84 represents a feasible approach to prevent the development of NASH.

DPP-4 Inhibition with Anagliptin Reduces Lipotoxicity-Induced Insulin Resistance and Steatohepatitis in Male Mice.

Excessive hepatic lipid accumulation drives the innate immune system and aggravates insulin resistance, hepatic inflammation, and fibrogenesis, leading to nonalcoholic steatohepatitis (NASH). Dipeptidyl peptidase-4 (DPP-4) regulates glucose metabolism and is expressed in many different cell types, including the cells of the immune system. In addition, DPP-4 may be involved in macrophage-mediated inflammation and insulin resistance. This study investigated the effects of anagliptin (Ana), an inhibitor of DPP-4, on macrophage polarity and phenotype in the livers of mice with steatohepatitis. We investigated the effects of Ana on steatohepatitis induced via a high-cholesterol high-fat (CL) diet or a choline-deficient L-amino acid-defined, high-fat (CDAHF) diet. DPP-4 activity, liver histology, and insulin sensitivity were evaluated, and liver DPP-4+ macrophages were quantified using fluorescence-activated cell sorting (FACS). Liver and plasma DPP-4 activity increased significantly in mice on both diets. FACS revealed that, compared with chow-fed mice, the CL-fed mice exhibited a significant increase in the proportion of DPP-4+ liver macrophages, particularly the M1-type macrophages. Ana decreased hepatic lipid and M1 macrophage accumulation and stimulated M2 macrophage accumulation in the liver, thereby attenuating insulin resistance, steatohepatitis, and fibrosis. Importantly, Ana alleviated hepatic fibrosis and steatohepatitis in mice fed CL diet and CDAHF diet. Using Ana to inhibit DPP-4 reduced lipotoxicity-induced hepatic insulin resistance through regulating the M1/M2 macrophage status.

Xanthine oxidase inhibition attenuates insulin resistance and diet-induced steatohepatitis in mice.

Hyperuricemia drives the development of nonalcoholic fatty liver disease (NAFLD). Pharmacological inhibition of xanthine oxidase (XO), a rate-limiting enzyme for uric acid (UA) production, has been demonstrated to improve hepatic steatosis in diet-induced obese mice. However, it remains unclear whether inhibition of XO improves nonalcoholic steatohepatitis (NASH), a more advanced form of NAFLD, in terms of both liver inflammation and fibrosis. Here, we investigated the effects of febuxostat and allopurinol, two XO inhibitors clinically used for gout, on a mouse model of NASH. Furthermore, we conducted a single-arm, open-label intervention study with febuxostat for NAFLD patients with hyperuricemia. Despite a similar hypouricemic effect of the XO inhibitors on blood UA level, febuxostat, but not allopurinol, significantly decreased hepatic XO activity and UA levels in the NASH model mice. These reductions in hepatic XO activity and UA levels were accompanied by attenuation of insulin resistance, lipid peroxidation, and classically activated M1-like macrophage accumulation in the liver. Furthermore, in NAFLD patients with hyperuricemia, treatment with febuxostat for 24 weeks decreased the serum UA level, accompanied by reductions in the serum levels of liver enzymes, alanine aminotransferase and aspartate aminotransferase. XO may represent a promising therapeutic target in NAFLD/NASH, especially in patients with hyperuricemia.

Lycopene prevents the progression of lipotoxicity-induced nonalcoholic steatohepatitis by decreasing oxidative stress in mice.

Excessive fatty acid uptake-induced oxidative stress causes liver injury and the consecutive recruitment of inflammatory immune cells, thereby promoting the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Lycopene, the most effective singlet oxygen scavenger of the antioxidant carotenoids, has anti-inflammatory activity. Here, we investigated the preventive and therapeutic effects of lycopene in a lipotoxic model of NASH: mice fed a high-cholesterol and high-fat diet. Lycopene alleviated excessive hepatic lipid accumulation and enhanced lipolysis, decreased the proportion of M1-type macrophages/Kupffer cells, and activated stellate cells to improve hepatic inflammation and fibrosis, and subsequently reduced the recruitment of CD4+ and CD8+ T cells in the liver. Importantly, lycopene reversed insulin resistance, as well as hepatic inflammation and fibrosis, in pre-existing NASH. In parallel, lycopene decreased LPS-/IFN-γ-/TNFα-induced M1 marker mRNA levels in peritoneal macrophages, as well as TGF-ß1-induced expression of fibrogenic genes in a stellate cell line, in a dose-dependent manner. These results were associated with decreased oxidative stress in cells, which might be mediated by the expression of NADPH oxidase subunits. In summary, lycopene prevented and reversed lipotoxicity-induced inflammation and fibrosis in NASH mice by reducing oxidative stress. Therefore, it might be a novel and promising treatment for NASH.

Empagliflozin reverses obesity and insulin resistance through fat browning and alternative macrophage activation in mice fed a high-fat diet.

Objective: We reported previously that empagliflozin-a sodium-glucose cotransporter (SGLT) 2 inhibitor-exhibited preventive effects against obesity. However, it was difficult to extrapolate these results to human subjects. Here, we performed a therapeutic study, which is more relevant to clinical situations in humans, to investigate antiobesity effects of empagliflozin and illustrate the mechanism underlying empagliflozin-mediated enhanced fat browning in obese mice. Research design and methods: After 8 weeks on a high-fat diet (HFD), C57BL/6J mice exhibited obesity, accompanied by insulin resistance and low-grade chronic inflammation. Cohorts of obese mice were continued on the HFD for an additional 8-week treatment period with or without empagliflozin. Results: Treatment with empagliflozin for 8 weeks markedly increased glucose excretion in urine, and suppressed HFD-induced weight gain, insulin resistance and hepatic steatosis. Notably, empagliflozin enhanced oxygen consumption and carbon dioxide production, leading to increased energy expenditure. Consistently, the level of uncoupling protein 1 expression was increased in both brown and white (WAT) adipose tissues of empagliflozin-treated mice. Furthermore, empagliflozin decreased plasma levels of interleukin (IL)-6 and monocyte chemoattractant protein-1, but increased plasma levels of IL-33 and adiponectin in obese mice. Finally, we found that empagliflozin reduced M1-polarized macrophage accumulation, while inducing the anti-inflammatory M2 phenotype of macrophages in the WAT and liver, thereby attenuating obesity-related chronic inflammation. Conclusions: Treatment with empagliflozin attenuated weight gain by increasing energy expenditure and adipose tissue browning, and alleviated obesity-associated inflammation and insulin resistance by alternative macrophage activation in the WAT and liver of obese mice.

Lycopene Alleviates Obesity-Induced Inflammation and Insulin Resistance by Regulating M1/M2 Status of Macrophages.

SCOPE: Adipose tissue macrophage (ATM) recruitment and polarization are pivotal in the development of insulin resistance. However, treatment modalities targeting ATMs remain limited. The effects of lycopene, an antioxidant carotenoid compound, on adipose tissue inflammation and insulin resistance in high fat (HF)-diet-induced obese mice are examined. METHODS AND RESULTS: C57BL/6J mice are fed an HF diet or an HF diet containing lycopene (HF+LY) for 8 weeks. Lycopene attenuates HF-diet-induced glucose intolerance and hyperinsulinemia. Compared with HF mice, HF+LY mice exhibit attenuated adipocyte hypertrophy and macrophage infiltration in epididymal white adipose tissue (eWAT) and hepatic steatosis and inflammation. Flow cytometry analysis of ATMs demonstrates that lycopene attenuated the increased number of ATMs in HF diet-fed mice. In addition, HF+LY mice have 23% fewer M1-polarized ATMs and 60% more M2-polarized ATMs than HF mice, resulting in the predominance of M2 over M1 in the ATM population. M2-dominant polarization is also seen in hepatic macrophages in HF+LY mice. Moreover, lycopene promotes IL-4-induced M2 polarization by increasing the phosphorylation levels of STAT6 and Akt in Raw 264.7 macrophages. CONCLUSIONS: Lycopene facilitates M2-dominant polarization in ATM, thereby attenuating HF diet-induced inflammation and insulin resistance in eWAT and the liver.

Pirfenidone prevents and reverses hepatic insulin resistance and steatohepatitis by polarizing M2 macrophages.

Nonalcoholic steatohepatitis (NASH) is associated with lipotoxic liver injury, leading to insulin resistance, inflammation, and fibrosis. Despite its increased global incidence, very few promising treatments for NASH are available. Pirfenidone is an antifibrotic agent used to treat pulmonary fibrosis; it suppresses the pulmonary influx of T cells and macrophages. Here, we investigated the effect of pirfenidone in a mouse model of lipotoxicity-induced NASH via a high-cholesterol and high-fat diet. After 12 weeks of feeding, pirfenidone administration attenuated excessive hepatic lipid accumulation and peroxidation by reducing the expression of genes related to lipogenesis and fatty acid synthesis and enhancing the expression of those related to fatty acid oxidation. Flow cytometry indicated that pirfenidone reduced the number of total hepatic macrophages, particularly CD11c+CD206-(M1)-type macrophages, increased the number of CD11c-CD206+(M2)-type macrophages, and subsequently reduced T-cell numbers, which helped improve insulin resistance and steatohepatitis. Moreover, pirfenidone downregulated the lipopolysaccharide (LPS)-induced mRNA expression of M1 marker genes and upregulated IL-4-induced M2 marker genes in a dose-dependent manner in RAW264.7 macrophages. Importantly, pirfenidone reversed insulin resistance, hepatic inflammation, and fibrosis in mice with pre-existing NASH. These findings suggest that pirfenidone is a potential candidate for the treatment of NASH.

Role of vitamin E in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. NAFLD manifests as hepatic lipid accumulation, insulin resistance, and inflammation, and can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis. However, the underlying mechanisms of NAFLD, including those that drive its progression, are unclear. Both liver-resident (Kupffer cells) and recruited macrophages play a crucial role in the development of insulin resistance and NASH. Therefore, NALFD could potentially be ameliorated by modifying the polarization of macrophages/Kupffer cells. Reactive oxygen species induce oxidative stress, which is implicated in the progression of NASH. Micronutrients, including vitamins, are potent antioxidants that exert anti-inflammatory effects, and are used in the treatment of NAFLD. We review here the molecular mechanisms of the pathogenesis of NAFLD and the potential utility of vitamin E in its prevention and/or treatment. © 2018 IUBMB Life, 71(4):516-522, 2019.

TAF7 is a heat-inducible unstable protein and is required for sustained expression of heat shock protein genes.

TATA-binding protein-associated factor 7 (TAF7), a dissociable component of the general transcription factor IID (TFIID), plays a role as a check-point regulator at the step of RNA polymerase II (Pol II) transcription initiation. Here, we focused on the role of TAF7 in heat-shocked cells, where its expression is induced by heat shock factor HSF1. TAF7 is a phosphoprotein, and the phosphorylation status is related to its interaction with TFIID and to its stability controlled by the ubiquitin-proteasome pathway. TAF7 is necessary for the prolonged expression of heat shock protein genes and for efficient recovery of heat-shocked cells. During sustained transcription, TAF7, presumably its TFIID-independent form, binds the promoter and enhances the levels of Pol II at the gene body but not the promoter. These results showed the novel function of TAF7 that is necessary for the transition from initiation to elongation in multiple-round transcription.

A porcine placental extract prevents steatohepatitis by suppressing activation of macrophages and stellate cells in mice.

Nonalcoholic fatty liver disease (NAFLD) is caused by ectopic fat accumulation in the liver. NAFLD is associated with hepatic inflammation and oxidative stress, resulting in nonalcoholic steatohepatitis (NASH) with advanced fibrosis. Placental extracts have been used to treat various chronic diseases due to their antioxidative effect. However, the effects of the extracts on the development of NASH have yet to be elucidated. Here, we demonstrated that supplementation with an oral porcine placental extract (PPE) attenuated lipid accumulation and peroxidation, insulin resistance, inflammatory and stress signaling, and fibrogenesis in the liver of NASH model mice fed a high-cholesterol and high-fat diet. The PPE reduced the number of M1-like liver macrophages, but increased the number of anti-inflammatory M2-like macrophages, resulting in a predominance of M2 over M1 macrophage populations in the liver of NASH mice. Accordingly, the PPE suppressed lipopolysaccharide-induced M1 polarization in isolated murine peritoneal macrophages, whereas it facilitated interleukin 4-induced M2 polarization. Furthermore, the PPE reduced the hepatic stellate cell (HSC) activation associated with the attenuated transforming growth factor-ß/Smad3 signaling, both in the liver of NASH mice and in RI-T cells, a HSC line. The PPE may be a potential approach to prevent NASH by limiting lipid peroxidation, promoting M2 macrophage polarization, and attenuating HSC activation.

SGLT2 Inhibition by Empagliflozin Promotes Fat Utilization and Browning and Attenuates Inflammation and Insulin Resistance by Polarizing M2 Macrophages in Diet-induced Obese Mice.

Sodium-glucose cotransporter (SGLT) 2 inhibitors increase urinary glucose excretion (UGE), leading to blood glucose reductions and weight loss. However, the impacts of SGLT2 inhibition on energy homeostasis and obesity-induced insulin resistance are less well known. Here, we show that empagliflozin, a SGLT2 inhibitor, enhanced energy expenditure and attenuated inflammation and insulin resistance in high-fat-diet-induced obese (DIO) mice. C57BL/6J mice were pair-fed a high-fat diet (HFD) or a HFD with empagliflozin for 16weeks. Empagliflozin administration increased UGE in the DIO mice, whereas it suppressed HFD-induced weight gain, insulin resistance, and hepatic steatosis. Moreover, empagliflozin shifted energy metabolism towards fat utilization, elevated AMP-activated protein kinase and acetyl-CoA carbolxylase phosphorylation in skeletal muscle, and increased hepatic and plasma fibroblast growth factor 21 levels. Importantly, empagliflozin increased energy expenditure, heat production, and the expression of uncoupling protein 1 in brown fat and in inguinal and epididymal white adipose tissue (WAT). Furthermore, empagliflozin reduced M1-polarized macrophage accumulation while inducing the anti-inflammatory M2 phenotype of macrophages within WAT and liver, lowering plasma TNFα levels and attenuating obesity-related chronic inflammation. Thus, empagliflozin suppressed weight gain by enhancing fat utilization and browning and attenuated obesity-induced inflammation and insulin resistance by polarizing M2 macrophages in WAT and liver.

Reply to the Letter to the Editor by Li et al.: Bioinformatics Analysis in Mice with Diet-Induced Nonalcoholic Steatohepatitis Treated with Astaxanthin and Vitamin E.

n/a.