Involvement of exercise-induced macrophage migration inhibitory factor in the prevention of fatty liver disease

Unraveling the underlying pathogenic factors driving nonalcoholic steatohepatitis and hepatocellular carcinoma: an in-depth analysis of prognostically relevant gene signatures in hepatocellular carcinoma

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a progressive manifestation of nonalcoholic fatty liver disease (NAFLD) that can lead to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Despite the growing knowledge of NASH and HCC, the association between the two conditions remains to be fully explored. Bioinformatics has emerged as a valuable approach for identifying disease-specific feature genes, enabling advancements in disease prediction, prevention, and personalized treatment strategies.

MATERIALS AND METHODS

In this study, we utilized CellChat, copy number karyotyping of aneuploid tumors (CopyKAT), consensus Non-negative Matrix factorization (cNMF), Gene set enrichment analysis (GSEA), Gene set variation analysis (GSVA), Monocle, spatial co-localization, single sample gene set enrichment analysis (ssGSEA), Slingshot, and the Scissor algorithm to analyze the cellular and immune landscape of NASH and HCC. Through the Scissor algorithm, we identified three cell types correlating with disease phenotypic features and subsequently developed a novel clinical prediction model using univariate, LASSO, and multifactor Cox regression.

RESULTS

Our results revealed that macrophages are a significant pathological factor in the development of NASH and HCC and that the macrophage migration inhibitory factor (MIF) signaling pathway plays a crucial role in cellular crosstalk at the molecular level. We deduced three prognostic genes (YBX1, MED8, and KPNA2), demonstrating a strong diagnostic capability in both NASH and HCC.

CONCLUSION

These findings shed light on the pathological mechanisms shared between NASH and HCC, providing valuable insights for the development of novel clinical strategies.

Exerkines and osteoarthritis

Osteoarthritis (OA) is the most prevalent chronic joint disease, with physical exercise being a widely endorsed strategy in its management guidelines. Exerkines, defined as cytokines secreted in response to acute and chronic exercise, function through endocrine, paracrine, and/or autocrine pathways. Various tissue-specific exerkines, encompassing exercise-induced myokines (muscle), cardiokines (heart), and adipokines (adipose tissue), have been linked to exercise therapy in OA. Exerkines are derived from these kines, but unlike them, only kines regulated by exercise can be called exerkines. Some of these exerkines serve a therapeutic role in OA, such as irisin, metrnl, lactate, secreted frizzled-related protein (SFRP), neuregulin, and adiponectin. While others may exacerbate the condition, such as IL-6, IL-7, IL-15, IL-33, myostatin, fractalkine, follistatin-like 1 (FSTL1), visfatin, activin A, migration inhibitory factor (MIF), apelin and growth differentiation factor (GDF)-15. They exerts anti-/pro-apoptosis/pyroptosis/inflammation, chondrogenic differentiation and cell senescence effect in chondrocyte, synoviocyte and mesenchymal stem cell. The modulation of adipokine effects on diverse cell types within the intra-articular joint emerges as a promising avenue for future OA interventions. This paper reviews recent findings that underscore the significant role of tissue-specific exerkines in OA, delving into the underlying cellular and molecular mechanisms involved.

Intermittent fasting activates macrophage migration inhibitory factor and alleviates high-fat diet-induced nonalcoholic fatty liver disease

Switching to normal diet (ND) is the regular therapy for high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD). Intermittent fasting (IF) is a unique treatment which may exhibits better therapeutic efficacy. Thus, we aim to investigate the therapeutic effects of these treatments and exploring the mechanisms. In the present study, NAFLD mouse model was induced by a 10-week HFD. Thereafter, mice adopted continued HFD, ND, or IF for the next 12 weeks. Finally, the liver was then harvested to assess lipid deposition, lipid metabolism, apoptosis, and autophagy, while blood was collected to determine blood glucose and insulin. The results showed that IF and ND treatment improved lipid deposition and metabolic disorder of NAFLD mice; the increasing body weight, liver weight, and HOMA-IR index of HFD mice were also alleviated by IF and ND. Furthermore, IF and ND treatment activated the macrophage migration inhibitory factor (MIF)/AMPK pathway and regulated its downstream autophagy and apoptosis. However, the efficacy of IF was better than ND. Both IF and ND activates MIF signaling and alleviate the lipotoxicity of NAFLD while IF therapy is more effective than ND. The different MIF up-regulation might be the underlying mechanism of why IF benefits more than ND.

Single-cell dissection of the obesity-exercise axis in adipose-muscle tissues implies a critical role for mesenchymal stem cells

Exercise training is critical for the prevention and treatment of obesity, but its underlying mechanisms remain incompletely understood given the challenge of profiling heterogeneous effects across multiple tissues and cell types. Here, we address this challenge and opposing effects of exercise and high-fat diet (HFD)-induced obesity at single-cell resolution in subcutaneous and visceral white adipose tissue and skeletal muscle in mice with diet and exercise training interventions. We identify a prominent role of mesenchymal stem cells (MSCs) in obesity and exercise-induced tissue adaptation. Among the pathways regulated by exercise and HFD in MSCs across the three tissues, extracellular matrix remodeling and circadian rhythm are the most prominent. Inferred cell-cell interactions implicate within- and multi-tissue crosstalk centered around MSCs. Overall, our work reveals the intricacies and diversity of multi-tissue molecular responses to exercise and obesity and uncovers a previously underappreciated role of MSCs in tissue-specific and multi-tissue beneficial effects of exercise.

Rhodiola activates macrophage migration inhibitory factor to alleviate non-alcoholic fatty liver disease

AIMS

Rhodiola was found to be a potential treatment for nonalcoholic fatty liver disease (NAFLD). The macrophage migration inhibitory factor (MIF)-regulated lipophagy and lipid metabolism might be the therapeutic targets of Rhodiola.

MAIN METHODS

A 16-week high-fat diet (HFD) was used to simulate a NAFLD mouse model. Rhodiola extract or normal saline were administrated to mice. Blood was collected to assess blood glucose and insulin, and livers were harvested to assess lipid accumulation and metabolism. In cell experiments, the active ingredient of Rhodiola, salidroside, and recombinant MIF protein (rMIF) were used to treat palmitate (PA)-incubated HepG2 cells, with MIF-siRNA or NC-siRNA transfection. Then, the level of lipophagy and lipid metabolism was examined.

KEY FINDINGS

Rhodiola improved lipid accumulation and metabolism disorder of HFD mice. The oil red O staining of the liver showed that increased lipid droplets in the NAFLD liver could be relieved by Rhodiola; Rhodiola also alleviated the increasing body weight, liver weight, and HOMA-IR index of HFD mice. Results in cell experiments were consistent: salidroside relieved the lipid droplet accumulation and triglyceride release in PA cells, as well as reduced lipophagosome and lipid metabolism disorder in PA cells. However, all these effects of salidroside were partially blocked by MIF-siRNA transfection.

SIGNIFICANCE

Rhodiola reduces lipid accumulation in the liver of NAFLD by facilitating the MIF pathway and the downstream lipophagy and lipid metabolism. MIF may be an endogenous regulator of liver lipophagy and lipid metabolism and a potential therapeutic target for NAFLD.

The SRPK inhibitor N-(2-(piperidin-1-yl)-5-(trifluoromethyl)phenyl) isonicotinamide (SRPIN340) increases the immune response against metastatic melanoma in mice

Cancers have a strong relationship with immune cells in their microenvironment, which significantly influences tumor proliferation and progression. Thus, pharmacological strategies that stimulate the immune system to combat tumor cells are promising for better therapeutic efficacy. Deregulated expression of the splicing regulatory serine arginine protein kinases (mostly SRPK1 and SRPK2) has been found in different cancer types, leading to the expression of isoforms related to tumor growth and metastasis. The microenvironment of melanoma exhibits a strong presence of immune cells, which significantly influences tumor progression, and around 50% of cutaneous melanoma patients benefit from targeted immunotherapy. Here, we analyzed human malignant melanoma single-cell gene expression data and observed that SRPK1/2 overexpression correlates with immune system pathway alterations. In further analysis, we observed an increased presence of immune cells in biopsies from mice bearing metastatic melanoma treated with SRPIN340, a well-known SRPK1/2 pharmacological inhibitor. Local treatments increased the expression of proinflammatory cytokines at the tumor lesions and the activity of the spleen, accompanied by reduced pulmonary metastasis foci, edema formation, and alveolar congestion. In in vitro assays, SRPIN340 also potentiated immunological susceptibility, by increasing the expression of the antigen presenting MHCI and MHCII molecules and by increasing the ability of B16F10 cells to attract splenic cells in transwell assays. Taken together, these results reveal that the antimetastatic effect of SRPIN340 can also involve an increased immune response, which suggests additional functional clues for SRPKs in tumor biology.

Exercise inhibits JNK pathway activation and lipotoxicity via macrophage migration inhibitory factor in nonalcoholic fatty liver disease

The macrophage migration inhibitory factor (MIF) expressed in hepatocytes can limit steatosis during obesity. Lipotoxicity in nonalcoholic fatty liver disease is mediated in part by the activation of the stress kinase JNK, but whether MIF modulates JNK in lipotoxicity is unknown. In this study, we investigated the role of MIF in regulating JNK activation and high-fat fostered liver lipotoxicity during simultaneous exercise treatment. Fifteen mice were equally divided into three groups: normal diet, high-fat diet, and high-fat and exercise groups. High-fat feeding for extended periods elicited evident hyperlipemia, liver steatosis, and cell apoptosis in mice, with inhibited MIF and activated downstream MAPK kinase 4 phosphorylation and JNK. These effects were then reversed following prescribed swimming exercise, indicating that the advent of exercise could prevent liver lipotoxicity induced by lipid overload and might correlate to the action of modulating MIF and its downstream JNK pathway. Similar detrimental effects of lipotoxicity were observed in in vitro HepG2 cells palmitic acid treatment. Suppressed JNK reduced the hepatocyte lipotoxicity by regulating the BCL family, and the excess JNK activation could also be attenuated through MIF supplementation or exacerbated by MIF siRNA administration. The results found suggest that exercise reduces lipotoxicity and inhibits JNK activation by modulating endogenous hepatic MIF in NAFLD. These findings have clinical implications for the prevention and intervention of patients with immoderate diet evoked NAFLD.

Exercise and Organ Cross Talk

Chronic heart failure, diabetes, depression, and other chronic diseases are associated with high mortality rate and low cure rate. Exercise induces muscle contraction and secretes multiple myokines, which affects the signaling pathways in skeletal muscle tissues and regulate remote organ functions. Exercise is known to be effective in treating a variety of chronic diseases. Here we summarize how exercise influences skeletal muscle, heart, brain, gut, and liver, and prevents heart failure, cognitive dysfunction, obesity, fatty liver, and other diseases. Exercise training may achieve additional benefits as compared to the present medication for these chronic diseases through cross talk among skeletal muscle and other organs.

The Effects of Physical Exercise on Fatty Liver Disease

The increasing prevalence of obesity has made nonalcoholic fatty liver disease (NAFLD) the most common chronic liver disease. As a consequence, NAFLD and especially its inflammatory form nonalcoholic steatohepatitis (NASH) are the fastest increasing etiology of end-stage liver disease and hepatocellular carcinoma. Physical inactivity is related to the severity of fatty liver disease irrespective of body weight, supporting the hypothesis that increasing physical activity through exercise can improve fatty liver disease. This review summarizes the evidence for the effects of physical exercise on NAFLD and NASH. Several clinical trials have shown that both aerobic and resistance exercise reduce the hepatic fat content. From clinical and basic scientific studies, it is evident that exercise affects fatty liver disease through various pathways. Improved peripheral insulin resistance reduces the excess delivery of free fatty acids and glucose for free fatty acid synthesis to the liver. In the liver, exercise increases fatty acid oxidation, decreases fatty acid synthesis, and prevents mitochondrial and hepatocellular damage through a reduction of the release of damage-associated molecular patterns. In conclusion, physical exercise is a proven therapeutic strategy to improve fatty liver disease.

Proinflammatory cytokine MIF plays a role in the pathogenesis of type-2 diabetes mellitus, but does not affect hepatic mitochondrial function

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays an important role in the pathogenesis of type 2 diabetes mellitus (T2DM). Although the effect of high glucose on liver function has been described, the role of MIF in hepatic mitochondrial function during T2DM has not been studied.

OBJECTIVE

We examine the influence of MIF to hepatic mitochondrial function in T2DM mouse model.

METHODS

WT and Mif^-/- BALB/c mice were treated with a single dose of streptozotocin (STZ). After an 8-week follow-up, serum glucose, proinflammatory cytokines, C-reactive protein (CRP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzyme quantification, and liver histological analyses were performed. Liver mitochondria were extracted, and mitochondrial function was evaluated by oximetry, swelling and peroxide production.

RESULTS

Following treatment with STZ, WT mice (WT/STZ) developed significant hyperglycemia and high serum levels of MIF, tumor necrosis factor (TNF)-α, interleukin-β (IL-β), and CRP. Liver damage enzymes ALT and AST were found at high levels. In contrast, Mif^-/-STZ lacked serum MIF levels and showed smaller increases in blood glucose, less TNF-α, IL-1β, CPR, ALT and AST, and failure to develop clinical signs of disease compared to the WT/STZ group. Mitochondria extracted from the Mif^-/-STZ liver showed similar respiratory control (RC) to WT/STZ or healthy mice with glutamate/malate or succinate as substrates. The four respiratory chain complexes also had comparable activities. WT/STZ-isolated mitochondria showed low swelling with calcium compared to mitochondria from Mif^-/-STZ or healthy mice. Peroxide production was comparable in all groups.

CONCLUSION

These results show although high systemic levels of MIF contribute to the development of T2DM pathology, the liver mitochondria remain unaltered. Importantly, the absence of MIF reduced the pathology of T2DM, also without altering liver mitochondrial function. These support MIF as a therapeutic target for the treatment of this disease in humans.

Treatment of nonalcoholic fatty liver disease: role of AMPK

Nonalcoholic fatty liver disease (NAFLD) is a growing worldwide epidemic and an important risk factor for the development of insulin resistance, type 2 diabetes, nonalcoholic steatohepatitis (NASH), and hepatic cellular carcinoma (HCC). Despite the prevalence of NAFLD, lifestyle interventions involving exercise and weight loss are the only accepted treatments for this disease. Over the last decade, numerous experimental compounds have been shown to improve NAFLD in preclinical animal models, and many of these therapeutics have been shown to increase the activity of the cellular energy sensor AMP-activated protein kinase (AMPK). Because AMPK activity is reduced by inflammation, obesity, and diabetes, increasing AMPK activity has been viewed as a viable therapeutic strategy to improve NAFLD. In this review, we propose three primary mechanisms by which AMPK activation may improve NAFLD. In addition, we examine the mechanisms by which AMPK is activated. Finally, we identify 27 studies that have used AMPK activators to reduce NAFLD. Future considerations for studies examining the relationship between AMPK and NAFLD are highlighted.

Role of antigen presenting cell invariant chain in the development of hepatic steatosis in mouse model

The role of Invariant chain (CD74 or Ii) in antigen presentation via Antigen Presenting Cells (APC), macrophage recruitment as well as survival, T cell activation and B cell differentiation has been well recognized. However, the aspect of CD74 which is involved in the development of hepatic steatosis and the pathways through which it acts remain to be studied. In this study, we investigated the role of CD74 in the inflammatory pathway and its contribution to development of hepatic steatosis. For this, wild type C57BL/6J and CD74 deficient mice (Ii(-/-) mice) were fed with high fat high fructose (HFHF) diet for 12 weeks. Chronic consumption of this feed did not develop hepatic steatosis, glucose intolerance or change in the level of immune cells in Ii(-/-) mice. Moreover, there was relatively delayed expression of genes involved in development of non alcoholic fatty liver disease (NAFLD) in HFHF fed Ii(-/-) mice as compared to that of C57BL/6J phenotype. Taken together, the data suggest that HFHF diet fed Ii(-/-) mice fail to develop hepatic steatosis, suggesting that Ii mediated pathways play a vital role in the initiation and propagation of liver inflammation.

Caloric restriction and intermittent fasting alter hepatic lipid droplet proteome and diacylglycerol species and prevent diabetes in NZO mice

Caloric restriction and intermittent fasting are known to improve glucose homeostasis and insulin resistance in several species including humans. The aim of this study was to unravel potential mechanisms by which these interventions improve insulin sensitivity and protect from type 2 diabetes. Diabetes-susceptible New Zealand Obese mice were either 10% calorie restricted (CR) or fasted every other day (IF), and compared to ad libitum (AL) fed control mice. AL mice showed a diabetes prevalence of 43%, whereas mice under CR and IF were completely protected against hyperglycemia. Proteomic analysis of hepatic lipid droplets revealed significantly higher levels of PSMD9 (co-activator Bridge-1), MIF (macrophage migration inhibitor factor), TCEB2 (transcription elongation factor B (SIII), polypeptide 2), ACY1 (aminoacylase 1) and FABP5 (fatty acid binding protein 5), and a marked reduction of GSTA3 (glutathione S-transferase alpha 3) in samples of CR and IF mice. In addition, accumulation of diacylglycerols (DAGs) was significantly reduced in livers of IF mice (P=0.045) while CR mice showed a similar tendency (P=0.062). In particular, 9 DAG species were significantly reduced in response to IF, of which DAG-40:4 and DAG-40:7 also showed significant effects after CR. This was associated with a decreased PKCε activation and might explain the improved insulin sensitivity. In conclusion, our data indicate that protection against diabetes upon caloric restriction and intermittent fasting associates with a modulation of lipid droplet protein composition and reduction of intracellular DAG species.

Relation of physical activity to prevalence of nonalcoholic Fatty liver disease independent of cardiometabolic risk

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance and has been linked with increased cardiovascular risk. Although physical activity (PA) and lifestyle modification are often recommended in patients at cardiovascular risk, the benefit across the cardiometabolic risk spectrum is unclear. We aimed to evaluate the relation of PA and NAFLD independent of metabolic syndrome (MS) or obesity. We evaluated 5,743 healthy Brazilian subjects (43 ± 10 years, 79% men) without clinical coronary heart disease from December 2008 to December 2010. NAFLD was diagnosed using ultrasounds, and self-reported PA was assessed using the International Physical Activity Questionnaire scale. In a multivariate logistic regression adjusted for cardiometabolic risk factors, we evaluated for an independent association of NAFLD and PA. In the total study population, NAFLD prevalence was 36% (n = 2,075), obesity 23% (1,300), and MS 20% (1,152). NAFLD was more prevalent in subjects with MS (74%) than those without (26%) and in those obese (73%) than in those nonobese (25%). Overall, 1,305 (23%) subjects reported low activity, 1,990 (35%) moderate activity, and 2,448 (42%) high activity. NAFLD prevalence was lower at higher levels of reported PA (low 45%, moderate 38%, and high 30%, p <0.001). After adjusting for risk factors, subjects with high activity had lower odds of having NAFLD. The favorable association was independent of obesity or MS. In conclusion, PA presents a dose-response association with NAFLD independent of the MS or obesity. Our results are compatible with the idea that benefits of PA are relevant to everyone regardless of cardiometabolic risk.