Hepassocin is required for hepatic outgrowth during zebrafish hepatogenesis

FGL1 and FGL2: emerging regulators of liver health and disease

Liver disease is a complex group of diseases with high morbidity and mortality rates, emerging as a major global health concern. Recent studies have highlighted the involvement of fibrinogen-like proteins, specifically fibrinogen-like protein 1 (FGL1) and fibrinogen-like protein 2 (FGL2), in the regulation of various liver diseases. FGL1 plays a crucial role in promoting hepatocyte growth, regulating lipid metabolism, and influencing the tumor microenvironment (TME), contributing significantly to liver repair, non-alcoholic fatty liver disease (NAFLD), and liver cancer. On the other hand, FGL2 is a multifunctional protein known for its role in modulating prothrombin activity and inducing immune tolerance, impacting viral hepatitis, liver fibrosis, hepatocellular carcinoma (HCC), and liver transplantation. Understanding the functions and mechanisms of fibrinogen-like proteins is essential for the development of effective therapeutic approaches for liver diseases. Additionally, FGL1 has demonstrated potential as a disease biomarker in radiation and drug-induced liver injury as well as HCC, while FGL2 shows promise as a biomarker in viral hepatitis and liver transplantation. The expression levels of these molecules offer exciting prospects for disease assessment. This review provides an overview of the structure and roles of FGL1 and FGL2 in different liver conditions, emphasizing the intricate molecular regulatory processes and advancements in targeted therapies. Furthermore, it explores the potential benefits and challenges of targeting FGL1 and FGL2 for liver disease treatment and the prospects of fibrinogen-like proteins as biomarkers for liver disease, offering insights for future research in this field.

Role of Fibrinogen-like Protein 1 in Tumor Recurrence Following Hepatectomy

Partial hepatectomy is a first-line treatment for hepatocellular carcinoma. Within 2 weeks following partial hepatectomy, specific molecular pathways are activated to promote liver regeneration. Nevertheless, residual microtumors may also exploit these pathways to reappear and metastasize. Therapeutically targeting molecules that are differentially regulated between normal cells and malignancies, such as fibrinogen-like protein 1 (FGL1), appears to be an effective approach. The potential functions of FGL1 in both regenerative and malignant cells are discussed within the ambit of this review. While FGL1 is normally elevated in regenerative hepatocytes, it is normally downregulated in malignant cells. Hepatectomy does indeed upregulate FGL1 by increasing the release of transcription factors that promote FGL1, including HNF-1α and STAT3, and inflammatory effectors, such as TGF-β and IL6. This, in turn, stimulates certain proliferative pathways, including EGFR/Src/ERK. Hepatectomy alters the phase transition of highly differentiated hepatocytes from G0 to G1, thereby transforming susceptible cells into cancerous ones. Activation of the PI3K/Akt/mTOR pathway by FGL1 allele loss on chromosome 8, a tumor suppressor area, may also cause hepatocellular carcinoma. Interestingly, FGL1 is specifically expressed in the liver via HNF-1α histone acetylase activity, which triggers lipid metabolic reprogramming in malignancies. FGL1 might also be involved in other carcinogenesis processes such as hypoxia, epithelial-mesenchymal transition, immunosuppression, and sorafenib-mediated drug resistance. This study highlights a research gap in these disciplines and the necessity for additional research on FGL1 function in the described processes.

Identifying Sex-Specific Serum Patterns of Alzheimer's Mice through Deep TMT Profiling and a Concentration-Dependent Concatenation Strategy

Alzheimer's disease (AD) is the most prevalent form of dementia, disproportionately affecting women in disease prevalence and progression. Comprehensive analysis of the serum proteome in a common AD mouse model offers potential in identifying possible AD pathology- and gender-associated biomarkers. Here, we introduce a multiplexed, nondepleted mouse serum proteome profiling via tandem mass-tag (TMTpro) labeling. The labeled sample was separated into 475 fractions using basic reversed-phase liquid chromatography (RPLC), which were categorized into low-, medium-, and high-concentration fractions for concatenation. This concentration-dependent concatenation strategy resulted in 128 fractions for acidic RPLC-tandem mass spectrometry (MS/MS) analysis, collecting ∼5 million MS/MS scans and identifying 3972 unique proteins (3413 genes) that cover a dynamic range spanning at least 6 orders of magnitude. The differential expression analysis between wild type and the commonly used AD model (5xFAD) mice exhibited minimal significant protein alterations. However, we detected 60 statistically significant (FDR < 0.05), sex-specific proteins, including complement components, serpins, carboxylesterases, major urinary proteins, cysteine-rich secretory protein 1, pregnancy-associated murine protein 1, prolactin, amyloid P component, epidermal growth factor receptor, fibrinogen-like protein 1, and hepcidin. The results suggest that our platform possesses the sensitivity and reproducibility required to detect sex-specific differentially expressed proteins in mouse serum samples.

HPS protects the liver against steatosis, cell death, inflammation, and fibrosis in mice with steatohepatitis

Hepassocin (HPS) is a hepatokine associated with metabolic regulation and development of non-alcoholic steatohepatitis (NASH). However, previous reports on HPS are controversial and its true function is not yet understood. Here, we demonstrated that hepatic HPS expression levels were upregulated in short-term feeding and downregulated in long-term feeding in high-fat diet (HFD)- and methionine- and choline-deficient (MCD) diet-fed mice, as well as in genetically obese (ob/ob) mice. HFD- and MCD-induced hepatic steatosis, inflammation, apoptosis, and fibrosis were more pronounced in HPS knockout mice than in the wild-type mice. Moreover, HPS depletion aggravated HFD-induced insulin resistance. By contrast, HPS administration improved MCD- or HFD-induced liver phenotypes and insulin resistance in HPS knockout and wild-type mice. Mechanistic studies revealed that MCD-induced hepatic oxidative stress was significantly increased by HPS deficiency and could be attenuated by HPS administration. Furthermore, palmitic acid-induced lipid accumulation and oxidative stress were exclusively enhanced in HPS knockout hepatocytes and diminished by HPS cotreatment. These data suggest that HPS ameliorates NASH in mice, at least in part, by inhibiting the oxidative stress. HPS expression levels are downregulated in human fatty liver tissues, suggesting that it may play an important protective role in NASH. Collectively, our findings provide clear genetic evidence that HPS has beneficial effects on the development of steatohepatitis in mice and suggest that upregulating HPS signaling may represent an effective treatment strategy for NASH.

Serum Fibrinogen-Like Protein 1 Levels in Obese Patients Before and After Laparoscopic Sleeve Gastrectomy: A Six-Month Longitudinal Study

PURPOSE

Fibrinogen-like protein (FGL)-1 is an original hepatokine with a critical role in developing hepatic steatosis. This study intends to examine the pre- and postoperative serum FGL-1 levels in bariatric patients and identify its relationship with other clinical indicators.

PATIENTS AND METHODS

Ninety-two individuals (60 bariatric patients and 32 people with normal weight) were enrolled in this research between July 2018 and April 2021. All bariatric patients finished follow-up visits 6 months after laparoscopic sleeve gastrectomy (LSG). Clinical data, anthropometric parameters, biochemical variables, FibroScan, and serum FGL-1 levels were collected at baseline and 6 months after LSG.

RESULTS

FGL-1 levels in patients with obesity (44.66±20.03 ng/mL) were higher than in individuals with normal weight (20.73±9.73 ng/mL, p < 0.001). After LSG, FGL-1 levels were significantly decreased (27.53±11.45 ng/mL, p < 0.001). Besides, body mass index (BMI), liver enzyme levels, glucose metabolism, lipid metabolism, uric acid (UA), controlled attenuation parameter (CAP), and liver stiffness measurement (LSM) were significantly improved. After adjusting possible confounders, FGL-1 levels at baseline were negatively associated with changes in LSM levels; changes in FGL-1 levels showed positive correlations with changes in alanine aminotransferase (ALT), aspartate aminotransferase (AST) and UA levels at 6 months after surgery.

CONCLUSION

Serum FGL-1 levels were significantly decreased following LSG in patients with obesity. The preoperative serum FGL-1 levels could be a predictor of postoperative liver fibrosis improvement. Furthermore, the decreased FGL-1 levels were associated with improved liver enzymes and UA but not with bodyweight or glucolipid metabolism.

Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Immune checkpoint therapy has achieved significant efficacy by blocking inhibitory pathways to release the function of T lymphocytes. In the clinic, anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) have progressed to first-line monotherapies in certain tumor types. However, the efficacy of anti-PD-1/PD-L1 mAbs is still limited due to toxic side effects and de novo or adaptive resistance. Moreover, other immune checkpoint target and biomarkers for therapeutic response prediction are still lacking; as a biomarker, the PD-L1 (CD274, B7-H1) expression level is not as accurate as required. Hence, it is necessary to seek more representative predictive molecules and potential target molecules for immune checkpoint therapy. Fibrinogen-like protein 1 (FGL1) is a proliferation- and metabolism-related protein secreted by the liver. Multiple studies have confirmed that FGL1 is a newly emerging checkpoint ligand of lymphocyte activation gene 3 (LAG3), emphasizing the potential of targeting FGL1/LAG3 as the next generation of immune checkpoint therapy. In this review, we summarize the substantial regulation mechanisms of FGL1 in physiological and pathological conditions, especially tumor epithelial to mesenchymal transition, immune escape and immune checkpoint blockade resistance, to provide insights for targeting FGL1 in cancer treatment.

Role of placental fibrinogen-like protein 1 in gestational diabetes

In view of the increasing prevalence of gestational diabetes mellitus (GDM) and the increased risks of delivering a macrosomic infant, developing preeclampsia, and suffering a perinatal death due to GDM, GDM has emerged as a growing public health problem. Although the placenta was suggested to play a crucial role in the pathology of GDM, the mechanisms that induce the development of GDM are still obscure. Fibrinogen-like protein (FGL)-1 is a hepatokine that plays an important role in hepatogenesis, as well as in nonalcoholic fatty liver disease and diabetes. Although FGL-1 is also expressed by the placenta, the pathophysiological role of FGL-1 in GDM is still unknown. In this study, FGL-1 levels were evaluated in 45 subjects with (n = 16) or without (n = 29) GDM. We found that FGL-1 was mainly expressed by placental trophoblasts, and FGL-1 expression was significantly higher in subjects with GDM. FGL-1 increased trophoblast proliferation through an extracellular signal-regulated kinase 1/2-dependent pathway. In addition, plasma concentrations of FGL-1 were higher in subjects with GDM, and the increased circulating FGL-1 might contribute to systemic insulin resistance. FGL-1 disrupted the gluconeogenic action of insulin in HepG2 cells, and decreased insulin-induced glucose uptake by L6 myotubes. Taken together, placental FGL-1 possibly plays a role in the impairment of insulin function in the development of GDM, and it might be a novel biomarker for diagnosing GDM.

Discovery of a role of the novel hepatokine, hepassocin, in obesity

Obesity is a public health problem that has raised concerns worldwide and is often associated with hepatic steatosis. Hepassocin is a novel hepatokine that causes hepatic steatosis and induces insulin resistance (IR). However, the role of hepassocin in obesity remains obscure. Thus, the aim of this study was to investigate the relationship between hepassocin levels and obesity. In total, 371 subjects who had a normal weight (NW), were overweight, or were obese were enrolled. We found that hepassocin levels in subjects who were overweight (6,705 ± 1,707 pg/ml) or obese (7,335 ± 2,077 pg/ml) were significantly higher than those of subjects with a NW (5,767 ± 1,500 pg/ml) (p < .001, test for trend). A multiple linear regression analysis showed that the body-mass index, waist circumference, nonalcoholic fatty liver disease, and homeostatic model assessment of IR were independently associated with hepassocin after adjusting for age, sex, high-sensitivity C-reactive protein, systolic blood pressure, high-density lipoprotein-cholesterol, log triglycerides, alanine transaminase, and the estimated glomerular filtration rate. This study provides evidence that subjects who were overweight or obese had significantly higher hepassocin levels than those with a NW. Hepassocin may be a useful biomarker in managing obesity and its related metabolic dysregulation.

Targeting fibrinogen-like protein 1 is a novel therapeutic strategy to combat obesity

Fibrinogen-like-protein 1 (FGL1) is a novel hepatokine that plays an important role in hepatic steatosis and insulin resistance. Although FGL1 expression can be detected in adipose tissues, the functions of FGL1 in adipose tissues are still unknown. In this study, 356 participants with (body mass index (BMI) ≥25 kg/m² ; n = 134) or without obesity (BMI <25 kg/m² ; n = 222) were recruited, and we found that the plasma FGL1 concentrations were significantly higher in obese group than those of in the normal weight group, and were positively correlated with age, BMI, waist circumference, fat content, plasma glucose at 2 hours during an oral glucose tolerance test, and the insulin sensitivity index. In univariate analyses, BMI, waist circumference, total fat, visceral fat, and subcutaneous fat areas were positively correlated with FGL1 levels. After adjusting for age and gender, obesity indices, including the BMI and different fat areas, remained significantly associated with FGL1 levels. In order to investigate the causal relationship between FGL1 and obesity, animal and cell models were used. Overexpression of FGL1 in epididymal adipose tissue by lentiviral vector encoding FGL1 increased the fat pad size, whereas FGL1-knockdown by lentiviral vector encoding short-hairpin RNA targeted to FGL1 decreased high-fat diet-induced adiposity. In addition, 3T3-L1 adipocytes were used to clarify the possible mechanism of FGL1-induced adipogenesis. FGL1 induced adipogenesis through an ERK1/2-C/EBPβ-dependent pathway in 3T3-L1 adipocytes. These findings highlight the pathophysiological role of FGL1 in obesity, and FGL1 might be a novel therapeutic target to combat obesity.

Footprint-free human fetal foreskin derived iPSCs: A tool for modeling hepatogenesis associated gene regulatory networks

Induced pluripotent stem cells (iPSCs) are similar to embryonic stem cells and can be generated from somatic cells. We have generated episomal plasmid-based and integration-free iPSCs (E-iPSCs) from human fetal foreskin fibroblast cells (HFF1). We used an E-iPSC-line to model hepatogenesis in vitro. The HLCs were characterized biochemically, i.e. glycogen storage, ICG uptake and release, UREA and bile acid production, as well as CYP3A4 activity. Ultra-structure analysis by electron microscopy revealed the presence of lipid and glycogen storage, tight junctions and bile canaliculi- all typical features of hepatocytes. Furthermore, the transcriptome of undifferentiated E-iPSC, DE, HE and HLCs were compared to that of fetal liver and primary human hepatocytes (PHH). K-means clustering identified 100 clusters which include developmental stage-specific groups of genes, e.g. OCT4 expression at the undifferentiated stage, SOX17 marking the DE stage, DLK and HNF6 the HE stage, HNF4α and Albumin is specific to HLCs, fetal liver and adult liver (PHH) stage. We use E-iPSCs for modeling gene regulatory networks associated with human hepatogenesis and gastrulation in general.