Activation of Liver FGF21 in hepatocarcinogenesis and during hepatic stress

A study of the circulating fibroblast growth factor 21 as a novel noninvasive biomarker of hepatic injury in genotype-4 chronic hepatitis C: Egyptian patients and their response to direct-acting antiviral agents

Background

Fibroblast growth factor (FGF) 21 was reported to be induced by different injurious agents, including chronic hepatitis C (CHC) virus, affecting the liver. The aims of this study were to evaluate the FGF21 levels in CHC patients before and after the treatment with direct-acting antiviral agents (DAAs) in comparison to that in control subjects and to correlate these levels with insulin resistance (IR), lipid profile, and fibrosis stages.

Patients and methods

We studied 75 naive CHC patients and 40 age- and gender-matched healthy control subjects. Patients were divided into five groups based on the severity of fibrosis as detected by Fibroscan as follows: F0, n=2; F1, n=13; F2, n=23; F3, n=16; F4, n=21. We estimated the FGF21 levels at the start of the study for all the participants and for the patients only at the end of treatment with simisipivir (SIM) and sofosbuvir (SOF). These levels were compared between the patients and the control subjects and also for the patients before and after the treatment with DAAs. The FGF21 levels were correlated to IR, lipid profile, and stages of liver fibrosis.

Results

The FGF21, fasting blood sugar (FBS), fasting insulin, and homeostasis model of IR (HOMA-IR) were significantly higher in CHC patients compared to control (5.04±0.75 vs 4.7±0.52, 20.15±5.13 vs 13.15±4.2, 4.49±1.28 vs 2.72±0.87, and 123.7±52.6 vs 21.8±8.8; P≤0.01, P≤0.001, P≤0.001, and P≤0.001, respectively). The posttreatment FGF21 levels were significantly reduced when compared to the pretreatment levels (123.7±52.5 vs 60.5±32.7, P≤0.001). FGF21 levels showed significant negative correlation with FBS and positive correlation with serum albumin (P≤0.05 and P≤0.003, respectively). The multiple linear regression analysis revealed that serum albumin, high-density lipoprotein cholesterol (HDL-c), and the stage of liver fibrosis were independent risk factors for FGF21.

Conclusion

Besides its metabolic modulator role, FGF21 strongly introduced itself as a novel biomarker of hepatic injury in Egyptian, genotype-4, CHC patients.

Increased FGF21 in brown adipose tissue of tyrosine hydroxylase heterozygous mice: implications for cold adaptation

Tyrosine hydroxylase (TH) catalyzes the first step in catecholamines synthesis. We studied the impact of reduced TH in brown adipose tissue (BAT) activation. In adult heterozygous (Th^+/- ) mice, dopamine and noradrenaline (NA) content in BAT decreased after cold exposure. This reduced catecholaminergic response did not impair cold adaptation, because these mice induced uncoupling protein 1 (UCP-1) and maintained BAT temperature to a similar extent than controls (Th^+/+ ). Possible compensatory mechanisms implicated were studied. Prdm16 and Fgf21 expression, key genes in BAT activation, were elevated in Th^+/- mice at thermoneutrality from day 18.5 of embryonic life. Likewise, plasma FGF21 and liver Fgf21 mRNA were increased. Analysis of endoplasmic reticulum (ER) stress, a process that triggers elevations in FGF21, showed higher phospho-IRE1, phospho-JNK, and CHOP in BAT of Th^+/- mice at thermoneutrality. Also, increased lipolysis in BAT of cold-exposure Th^+/- mice was demonstrated by increased phosphorylation of hormone-sensitive lipase (HSL), as well as diacylglycerol (DAG) and FFA content. Overall, these results indicate that the mild effects of Th haploinsufficiency on BAT function are likely due to compensatory mechanisms involving elevations in Fgf21 and Prdm16 and through adaptive changes in the lipid profile.

Prognosis in different subtypes of metaplastic breast cancer: a population-based analysis

BACKGROUND

Metaplastic breast cancer (MpBC) is a rare histological subtype of breast cancer recognized as a unique pathologic entity in 2000. However, the pathogenesis, optimal therapy, and prognosis of MpBC and the potential effect of systemic treatments on different subtypes of MpBC are not well defined.

METHODS

A retrospective population-based study was performed to identify breast cancer patients with MpBC and other triple-negative breast cancers (TNBC) between 2010 and 2014 using the surveillance, Epidemiology, and End Results (SEER) database. Chi-square test was used to analyze characteristics between subgroups. Kaplan-Meier analysis and Multivariate Cox regressions were used to evaluate overall survival (OS) of MpBC, TNBC, and MpBC subgroups. Competing risk analysis and multivariate regression model of competing risk were used to assess breast cancer-specific survival (BCSS) of MpBC and TNBC RESULTS: We identified a study cohort of 22,433 patients (1112 MpBC and 21,321 TNBC). MpBC correlated with older population, larger tumor size and less lymph node involvement, and TNBC phenotype. Patients with MpBC especially with triple-negative subtype (TN-MpBC) had worse survival than the overall TNBC population. However, the prognosis of MpBC without triple-negative subtype (non-TN MpBC) was not different from that of TNBC. In Kaplan-Meier analysis, chemotherapy was not associated with significant difference in OS of TN-MpBC. In non-TN MpBC group, the 3-year OS was 79.8% for patients receiving chemotherapy and 70.5% in patients without chemotherapy, and chemotherapy was associated (P = 0.033) with improved OS. Within the MpBC patients, radiotherapy was significantly (HR 1.544; 95% CI 1.148-2.078; P = 0.004) associated with improved OS and (HR 1.474; 95% CI 1.067-2.040; P = 0.019) BCSS.

CONCLUSIONS

Patients with TN-MpBC had worse prognosis than TNBC and chemotherapy was not associated with improved survival. In contrast, non-TN MpBC may derive survival benefit from chemotherapy and radiotherapy.

A nonalcoholic fatty liver disease model in human induced pluripotent stem cell-derived hepatocytes, created by endoplasmic reticulum stress-induced steatosis

Hepatic steatosis, a reversible state of metabolic dysregulation, can promote the onset of nonalcoholic steatohepatitis (NASH), and its transition is thought to be critical in disease evolution. The association between endoplasmic reticulum (ER) stress response and hepatocyte metabolism disorders prompted us to characterize ER stress-induced hepatic metabolic dysfunction in human induced pluripotent stem cell-derived hepatocytes (hiPSC-Hep), to explore regulatory pathways and validate a phenotypic in vitro model for progression of liver steatosis. We treated hiPSC-Hep with a ratio of unsaturated and saturated fatty acids in the presence of an inducer of ER stress to synergistically promote triglyceride accumulation and dysregulate lipid metabolism. We monitored lipid accumulation by high-content imaging and measured gene regulation by RNA sequencing and reverse transcription quantitative PCR analyses. Our results show that ER stress potentiated intracellular lipid accumulation by 5-fold in hiPSC-Hep in the absence of apoptosis. Transcriptome pathway analysis identified ER stress pathways as the most significantly dysregulated of all pathways affected. Obeticholic acid dose dependently inhibited lipid accumulation and modulated gene expression downstream of the farnesoid X receptor. We were able to identify modulation of hepatic markers and gene pathways known to be involved in steatosis and nonalcoholic fatty liver disease (NAFLD), in support of a hiPSC-Hep disease model that is relevant to clinical data for human NASH. Our results show that the model can serve as a translational discovery platform for the understanding of molecular pathways involved in NAFLD, and can facilitate the identification of novel therapeutic molecules based on high-throughput screening strategies.

Summary: Our study demonstrates expanded use of human induced pluripotent stem cell-derived hepatocytes for molecular studies and drug screening, to evaluate new therapeutics with an antisteatotic mechanism of action for nonalcoholic fatty liver disease.

A PPAR Pan Agonist, MHY2013 Alleviates Age-Related Hepatic Lipid Accumulation by Promoting Fatty Acid Oxidation and Suppressing Inflammation

Nonalcoholic fatty liver disease (NAFLD) is frequently observed in obese and aged individuals. Peroxisome proliferator-activated receptors (PPARs) play a role in regulating hepatic lipid accumulation, a hallmark of NAFLD development. A PPAR pan agonist, 2-(4-(5,6-methylenedioxybenzo[d]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013) has been shown to prevent fatty liver formation and insulin resistance in obese mice (db/db) model. However, the beneficial effects of MHY2013 in aged model remain unknown. In this study, we investigated whether MHY2013 alleviates hepatic lipid accumulation in aged Sprague-Dawley (SD) rats. We confirmed that MHY2013 increased the activities of three PPAR subtypes in HepG2 cells using luciferase assay. When administered orally in aged SD rats, MHY2013 markedly decreased the hepatic triglyceride levels without changes in body weight. Regarding underlying mechanisms, MHY2013 increased the mRNA levels of lipid oxidation-related genes, including carnitine palmitoyltransferase 1 (CPT1) and peroxisomal acyl-CoA oxidase 1 (ACOX1), without apparent change in the mRNA expression of lipogenesis-related genes. Furthermore, MHY2013 significantly increased systemic fibroblast growth factor 21 (FGF21) and adiponectin levels and suppressed inflammatory mRNA expression in the liver. In conclusion, MHY2013 alleviated age-related hepatic lipid accumulation, in part by upregulating β-oxidation signaling and suppressing inflammation in the liver. Therefore, MHY2013 is a potential pharmaceutical agent for treating age-related hepatic lipid accumulation.

Fibroblast growth factors 19 and 21 in acute liver damage

Currently there are very few pharmacological options available to treat acute liver injury. Because its natural exposure to noxious stimuli the liver has developed a strong endogenous hepatoprotective capacity. Indeed, experimental evidence exposed a variety of endogenous hepatic and systemic responses naturally activated to protect the hepatic parenchyma and to foster liver regeneration, therefore preserving individual's survival. The fibroblast growth factor (FGF) family encompasses a range of polypeptides with important effects on cellular differentiation, growth survival and metabolic regulation in adult organisms. Among these FGFs, FGF19 and FGF21 are endocrine hormones that profoundly influence systemic metabolism but also exert important hepatoprotective activities. In this review, we revisit the biology of these factors and highlight their potential application for the clinical management of acute liver injury.

Fibroblast Growth Factor 21 Protects Photoreceptor Function in Type 1 Diabetic Mice

Retinal neuronal abnormalities occur before vascular changes in diabetic retinopathy. Accumulating experimental evidence suggests that neurons control vascular pathology in diabetic and other neovascular retinal diseases. Therefore, normalizing neuronal activity in diabetes may prevent vascular pathology. We investigated whether fibroblast growth factor 21 (FGF21) prevented retinal neuronal dysfunction in insulin-deficient diabetic mice. We found that in diabetic neural retina, photoreceptor rather than inner retinal function was most affected and administration of the long-acting FGF21 analog PF-05231023 restored the retinal neuronal functional deficits detected by electroretinography. PF-05231023 administration protected against diabetes-induced disorganization of photoreceptor segments seen in retinal cross section with immunohistochemistry and attenuated the reduction in the thickness of photoreceptor segments measured by optical coherence tomography. PF-05231023, independent of its downstream metabolic modulator adiponectin, reduced inflammatory marker interleukin-1β (IL-1β) mRNA levels. PF-05231023 activated the AKT-nuclear factor erythroid 2-related factor 2 pathway and reduced IL-1β expression in stressed photoreceptors. PF-05231023 administration did not change retinal expression of vascular endothelial growth factor A, suggesting a novel therapeutic approach for the prevention of early diabetic retinopathy by protecting photoreceptor function in diabetes.

FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury

Cisplatin, a widely used cancer therapy drug, induces nephrotoxicity or acute kidney injury (AKI), but the underlying mechanism remains unclear, and renal protective approaches are not available. Fibroblast growth factor (FGF)21 is an endocrine factor that regulates glucose uptake, metabolism, and energy expenditure. However, recent work has also implicated FGF21 in cellular stress response under pathogenic conditions. The role and regulation of FGF21 in AKI are unclear. Here, we show that FGF21 was dramatically induced during cisplatin treatment of renal tubular cells in vitro and mouse kidneys in vivo. The inductive response was suppressed by pifithrin (a pharmacological inhibitor of P53), suggesting a role of P53 in FGF21 induction. In cultured renal tubular cells, knockdown of FGF21 aggravated cisplatin-induced apoptosis, whereas supplementation of recombinant FGF21 was protective. Consistently, recombinant FGF21 alleviated cisplatin-induced kidney dysfunction, tissue damage, and tubular apoptosis in mice. Mechanistically, FGF21 suppressed P53 induction and activation during cisplatin treatment. Together, these results indicate that FGF21 is induced during cisplatin nephrotoxicity to protect renal tubules, and recombinant FGF21 may have therapeutic potential.-Li, F., Liu, Z., Tang, C., Cai, J., Dong, Z. FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury.

Diverse Changes of Circulating Fibroblast Growth Factor 21 Levels in Hepatitis B Virus-Related Diseases

Fibroblast growth factor 21 (FGF21), a stress-induced hormone in the liver, has been shown the protective functions in pathological conditions. The study investigated the association of circulating FGF21 with hepatitis B virus (HBV) infection and its related diseases. Serum FGF21 levels were measured in 33 acute hepatitis B (AHB), 75 chronic hepatitis B (CHB) and 66 CHB patients with advanced liver diseases including liver cirrhosis, acute-on-chronic liver failure (ALCF) and hepatocellular carcinoma (HCC) together with 200 age- and BMI-matched healthy controls. FGF21 levels were significantly increased in AHB patients and rapidly returned to normal levels after treatment. FGF21 levels reflected the degree of liver injury caused by AHB. However, serum FGF21 levels were decreased in CHB patients especially in those who developed cirrhosis and were associated with hepatic protein synthesis capacity. Serum FGF21 in CHB patients were increased with the occurrence of ACLF. Notably, in CHB patients who developed HCC, serum FGF21 exhibited a dramatic increase, which may provide important information on monitoring tumorigenesis in CHB patients. In conclusion, we revealed the diverse changes of circulating FGF21 in HBV-related diseases. FGF21 may be a useful biomarker in monitoring the tumorigenesis in patients with CHB.

Fibroblast growth factor 21: a regulator of metabolic disease and health span

Fibroblast growth factor 21 (FGF21) is a potent endocrine regulator with physiological effects on glucose and lipid metabolism and thus garners much attention for its translational potential for the management of obesity and related metabolic syndromes. FGF21 is mainly expressed in several metabolically active tissue organs, such as the liver, adipose tissue, skeletal muscle, and pancreas, with profound effects and therapeutic relevance. Emerging experimental and clinical data point to the demonstrated metabolic benefits of FGF21, which include, but are not limited to, weight loss, glucose and lipid metabolism, and insulin sensitivity. In addition, FGF21 also acts directly through its coreceptor β-klotho in the brain to alter light-dark cycle activity. In this review, we critically appraise current advances in understanding the physiological actions of FGF21 and its role as a biomarker of various metabolic diseases, especially type 2 diabetes mellitus. We also discuss the potentially exciting role of FGF21 in improving our health and prolonging our life span. This information will provide a fuller understanding for further research into FGF21, as well as providing a scientific basis for potentially establishing health care guidelines for this promising molecule.

Rush to the fire: FGF21 extinguishes metabolic stress, metaflammation and tissue damage

FGF21 is a master regulator of homeostasis of local and systemic lipid, glucose and energy metabolism. Since its discovery a decade ago, significant progress has been made in understanding the basic molecular, cellular and physiological mechanisms underlying its metabolic roles, and characterizing its beneficial pharmacological activities and possible pathological roles in obesity, diabetes, dyslipidemia, fatty liver disease and their collateral complications and tissue damage. Under basal or normal conditions, FGF21 appears to play a dispensable role in metabolism. However, in response to a variety of cellular and metabolic stress, FGF21 is significantly upregulated to serve as a potent catabolic factor leading to the clearance of excessive lipids and glucose, and therefore, antagonizes metabolic and energy imbalance in a negative fashion. Furthermore, FGF21 treatment ameliorates tissue damage resulted from the harmful effects of metabolic abnormalities, which often ensue an oxidative, pro-inflammatory, inflammatory and/or immune stress state, the so-called metaflammation. Most notably, studies focusing on the liver, pancreas, cardio-vasculature and kidney have revealed its significant protective effects against the structural and functional damages induced by the obese, diabetic or other abnormal metabolic conditions. In this review, we will summarize the current progress on the roles of FGF21 against metaflammation and metabolic tissue damage.

Association between circulating fibroblast growth factor 21 and mortality in end-stage renal disease

Fibroblast growth factor 21 (FGF21) is an endocrine factor that regulates glucose and lipid metabolism. Circulating FGF21 predicts cardiovascular events and mortality in type 2 diabetes mellitus, including early-stage chronic kidney disease, but its impact on clinical outcomes in end-stage renal disease (ESRD) patients remains unclear. This study enrolled 90 ESRD patients receiving chronic hemodialysis who were categorized into low- and high-FGF21 groups by the median value. We investigated the association between circulating FGF21 levels and the cardiovascular event and mortality during a median follow-up period of 64 months. A Kaplan-Meier analysis showed that the mortality rate was significantly higher in the high-FGF21 group than in the low-FGF21 group (28.3% vs. 9.1%, log-rank, P = 0.034), while the rate of cardiovascular events did not significantly differ between the two groups (30.4% vs. 22.7%, log-rank, P = 0.312). In multivariable Cox models adjusted a high FGF21 level was an independent predictor of all-cause mortality (hazard ratio: 3.98; 95% confidence interval: 1.39–14.27, P = 0.009). Higher circulating FGF21 levels were associated with a high mortality rate, but not cardiovascular events in patient with ESRD, suggesting that circulating FGF21 levels serve as a predictive marker for mortality in these subjects.

Identification of Sp1 as a Transcription Activator to Regulate Fibroblast Growth Factor 21 Gene Expression

Fibroblast growth factor 21 (FGF21) is a metabolic hormone with multiple beneficial effects on lipid and glucose homeostasis. Previous study demonstrated that FGF21 might be one of the Sp1 target genes. However, the transcriptional role of Sp1 on FGF21 in adipose tissue and liver has not been reported. In this study, we found that the proximal promoter of mouse FGF21 is located between −63 and −20 containing two putative Sp1-binding sites. Sp1 is a mammalian transcription factor involved in the regulation of many genes during physiological and pathological processes. Our study showed that overexpression of Sp1 or suppressing Sp1 expression resulted in increased or reduced FGF21 promoter activity, respectively. Mutation analysis demonstrated that the Sp1-binding site located between −46 and −38 plays a primary role in transcription of FGF21. Electrophoretic mobility shift assay and chromatin immunoprecipitation analysis indicated that Sp1 specifically bound to this region. Furthermore, the binding activity of Sp1 was significantly increased in adipose tissues of HFD-induced obese mouse and liver of DEN-treated mouse. Thus, our results demonstrate that Sp1 positively regulates the basal transcription of FGF21 in the liver and adipose tissue and contributes to the obesity-induced FGF21 upregulation in mouse adipose tissue and hepatic FGF21 upregulation in hepatocarcinogenesis.

Physiological characterization of a novel PPAR pan agonist, 2-(4-(5,6-methylenedioxybenzo[d]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013)

Recently, agonists targeting multiple peroxisome proliferator-activated receptors (PPARs) have been developed to improve metabolic disorders and minimize the side effects of selective PPAR agonists such as weight gain and dyslipidemia. We newly synthesized six 2-methyl-2-(o-tolyloxy)propanoic acid derivatives based on the structure of a well-known PPAR pan agonist, bezafibrate. Of six compounds, MHY2013 was screened as the strongest activator of three PPAR subtypes based on protein docking simulation and luciferase assays. When treated orally in db/db mice, MHY2013 ameliorated obesity-induced insulin resistance, dyslipidemia, and hepatic steatosis without changes of the body weight and levels of liver and kidney injury markers. MHY2013 decreased the serum triglyceride and fatty acid levels, which is associated with an increase in fatty acid oxidation signaling in the liver and thermogenic signaling on white adipose tissue, respectively. Furthermore, MHY2013 markedly increased serum levels of insulin-sensitizing hormones including fibroblast growth factor 21 (FGF21) and adiponectin. In conclusion, this study suggests that, MHY2013 is a novel PPAR pan agonist that improves obesity-induced insulin resistance, dyslipidemia and hepatic steatosis and elevates insulin-sensitizing hormones in the blood.

FGF21 is a biomarker for mitochondrial translation and mtDNA maintenance disorders

OBJECTIVE

To validate new mitochondrial myopathy serum biomarkers for diagnostic use.

METHODS

We analyzed serum FGF21 (S-FGF21) and GDF15 from patients with (1) mitochondrial diseases and (2) nonmitochondrial disorders partially overlapping with mitochondrial disorder phenotypes. We (3) did a meta-analysis of S-FGF21 in mitochondrial disease and (4) analyzed S-Fgf21 and skeletal muscle Fgf21 expression in 6 mouse models with different muscle-manifesting mitochondrial dysfunctions.

RESULTS

We report that S-FGF21 consistently increases in primary mitochondrial myopathy, especially in patients with mitochondrial translation defects or mitochondrial DNA (mtDNA) deletions (675 and 347 pg/mL, respectively; controls: 66 pg/mL, p < 0.0001 for both). This is corroborated in mice (mtDNA deletions 1,163 vs 379 pg/mL, p < 0.0001). However, patients and mice with structural respiratory chain subunit or assembly factor defects showed low induction (human 335 pg/mL, p < 0.05; mice 335 pg/mL, not significant). Overall specificities of FGF21 and GDF15 to find patients with mitochondrial myopathy were 89.3% vs 86.4%, and sensitivities 67.3% and 76.0%, respectively. However, GDF15 was increased also in a wide range of nonmitochondrial conditions.

CONCLUSIONS

S-FGF21 is a specific biomarker for muscle-manifesting defects of mitochondrial translation, including mitochondrial transfer-RNA mutations and primary and secondary mtDNA deletions, the most common causes of mitochondrial disease. However, normal S-FGF21 does not exclude structural respiratory chain complex or assembly factor defects, important to acknowledge in diagnostics.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that elevated S-FGF21 accurately distinguishes patients with mitochondrial myopathies from patients with other conditions, and FGF21 and GDF15 mitochondrial myopathy from other myopathies.

Nutritional regulation of fibroblast growth factor 21: from macronutrients to bioactive dietary compounds

Obesity is a worldwide health problem mainly due to its associated comorbidities. Fibroblast growth factor 21 (FGF21) is a peptide hormone involved in metabolic homeostasis in healthy individuals and considered a promising therapeutic candidate for the treatment of obesity. FGF21 is predominantly produced by the liver but also by other tissues, such as white adipose tissue (WAT), brown adipose tissue (BAT), skeletal muscle, and pancreas in response to different stimuli such as cold and different nutritional challenges that include fasting, high-fat diets (HFDs), ketogenic diets, some amino acid-deficient diets, low protein diets, high carbohydrate diets or specific dietary bioactive compounds. Its target tissues are essentially WAT, BAT, skeletal muscle, heart and brain. The effects of FGF21 in extra hepatic tissues occur through the fibroblast growth factor receptor (FGFR)-1c together with the co-receptor β-klotho (KLB). Mechanistically, FGF21 interacts directly with the extracellular domain of the membrane bound cofactor KLB in the FGF21- KLB-FGFR complex to activate FGFR substrate 2α and ERK1/2 phosphorylation. Mice lacking KLB are resistant to both acute and chronic effects of FGF21. Moreover, the acute insulin sensitizing effects of FGF21 are also absent in mice with specific deletion of adipose KLB or FGFR1. Most of the data show that pharmacological administration of FGF21 has metabolic beneficial effects. The objective of this review is to compile existing information about the mechanisms that could allow the control of endogenous FGF21 levels in order to obtain the beneficial metabolic effects of FGF21 by inducing its production instead of doing it by pharmacological administration.

Fibroblast growth factor 21 reflects liver fat accumulation and dysregulation of signalling pathways in the liver of C57BL/6J mice

Fibroblast growth factor 21 (Fgf21) has emerged as a potential plasma marker to diagnose non-alcoholic fatty liver disease (NAFLD). To study the molecular processes underlying the association of plasma Fgf21 with NAFLD, we explored the liver transcriptome data of a mild NAFLD model of aging C57BL/6J mice at 12, 24, and 28 months of age. The plasma Fgf21 level significantly correlated with intrahepatic triglyceride content. At the molecular level, elevated plasma Fgf21 levels were associated with dysregulated metabolic and cancer-related pathways. The up-regulated Fgf21 levels in NAFLD were implied to be a protective response against the NAFLD-induced adverse effects, e.g. lipotoxicity, oxidative stress and endoplasmic reticulum stress. An in vivo PPARα challenge demonstrated the dysregulation of PPARα signalling in the presence of NAFLD, which resulted in a stochastically increasing hepatic expression of Fgf21. Notably, elevated plasma Fgf21 was associated with declining expression of Klb, Fgf21’s crucial co-receptor, which suggests a resistance to Fgf21. Therefore, although liver fat accumulation is a benign stage of NAFLD, the elevated plasma Fgf21 likely indicated vulnerability to metabolic stressors that may contribute towards progression to end-stage NAFLD. In conclusion, plasma levels of Fgf21 reflect liver fat accumulation and dysregulation of metabolic pathways in the liver.

Expression of fibroblast growth factor 21 in patients with biliary atresia

Fibroblast growth factor 21 is a critical circulating adipokine involving in metabolic disorders and various liver diseases. This study was performed to investigate whether FGF21 is also associated with the pathophysiology of biliary atresia. Serum FGF21 levels were measured in 57 BA patients and 20 age matched healthy controls. We also examined hepatic FGF21 mRNA expression and FGF21 protein levels in liver tissues obtained from 15 BA patients undergoing liver transplantation and 5 cases of pediatric donation after cardiac death donor without liver diseases by RT-PCR and Western blotting. Patients with BA showed significantly higher serum FGF21 levels than those without BA (554.7pg/mL [83-2300] vs. 124.5pg/mL [66-270], P<0.05). Patients with BA also had significantly higher FGF21 mRNA and protein levels in hepatic tissues than control subjects. Serum FGF21 expression increased corresponding to the severity of liver fibrosis. Furthermore, serum FGF21 levels dropped significantly in BA patients within 6months after liver transplantation and approached baseline in healthy controls (P>0.05). In vivo, FXR knockout could significantly abrogate cholestasis induced FGF21 expression. FGF21 levels in serum and liver tissue increased significantly in BA patients. In vivo, cholestasis could induce FGF21 expression in FXR dependent manner.

Modulation of energy balance by fibroblast growth factor 21

Fibroblast growth factors (FGFs) are a superfamily of 22 proteins related to cell proliferation and tissue repair after injury. A subgroup of three proteins, FGF19, FGF21, and FGF23, are major endocrine mediators. These three FGFs have low affinity to heparin sulfate during receptor binding; in contrast they have a strong interaction with the cofactor Klotho/β-Klotho. FGF21 has received particular attention because of its key role in carbohydrate, lipids, and energy balance regulation. FGF21 improves glucose and lipids metabolism as well as increasing energy expenditure in animal models and humans. Conditions that induce human physical stress such as exercise, lactation, obesity, insulin resistance, and type 2 diabetes influence FGF21 circulating levels. FGF21 also has an anti-oxidant function in human metabolic diseases which contribute to understanding the FGF21 compensatory increment in obesity, the metabolic syndrome, and type 2 diabetes. Interestingly, energy expenditure and weight loss is induced by FGF21. The mechanism involved is through "browning" of white adipose tissue, increasing brown adipose tissue activity and heat production. Therefore, clinical evaluation of therapeutic action of exogenous FGF21 administration is warranted, particularly to treat diabetes and obesity.

Circulating Fibroblast Growth Factor 21 (Fgf21) as Diagnostic and Prognostic Biomarker in Renal Cancer

Background

The finding of new biomarkers is needed to have a better sub-classification of primary renal tumors (RCC) as well as more reliable predictors of outcome and therapy response. In this study, we evaluated the role of circulating FGF21, an endocrine factor, as a diagnostic and prognostic biomarker for ccRCC.

Materials and Methods

Serum samples from healthy controls (HC), clear cell and chromophobe RCC cancer patients were obtained from the serum biobank “Biobanco Público de Muestras Séricas Oncológicas” (BPMSO) of the “Instituto de Oncología “Ángel H. Roffo”. Serum FGF21 and leptin were measured by ELISA while other metabolic markers were measured following routinely clinical procedures.

Results

One of our major findings was that FGF21 levels were significantly increased in ccRCC patients compared with HC. Moreover, we showed an association between the increased serum FGF21 levels and the shorter disease free survival in a cohort of 98 ccRCC patients, after adjustment for other predictors of outcome.

Conclusion

Our results suggest that higher FGF21 serum level is an independent prognostic biomarker, associated with worse free-disease survival.

Metabolic interplay between white, beige, brown adipocytes and the liver

In mammalian evolution, three types of adipocytes have developed, white, brown and beige adipocytes. White adipocytes are the major constituents of white adipose tissue (WAT), the predominant store for energy-dense triglycerides in the body that are released as fatty acids during catabolic conditions. The less abundant brown adipocytes, the defining parenchymal cells of brown adipose tissue (BAT), internalize triglycerides that are stored intracellularly in multilocular lipid droplets. Beige adipocytes (also known as brite or inducible brown adipocytes) are functionally very similar to brown adipocytes and emerge in specific WAT depots in response to various stimuli including sustained cold exposure. The activation of brown and beige adipocytes (together referred to as thermogenic adipocytes) causes both the hydrolysis of stored triglycerides as well as the uptake of lipids and glucose from the circulation. Together, these fuels are combusted for heat production to maintain body temperature in mammals including adult humans. Given that heating by brown and beige adipocytes is a very-well controlled and energy-demanding process which entails pronounced shifts in energy fluxes, it is not surprising that an intensive interplay exists between the various adipocyte types and parenchymal liver cells, and that this influences systemic metabolic fluxes and endocrine networks. In this review we will emphasize the role of hepatic factors that regulate the metabolic activity of white and thermogenic adipocytes. In addition, we will discuss the relevance of lipids and hormones that are secreted by white, brown and beige adipocytes regulating liver metabolism in order to maintain systemic energy metabolism in health and disease.

Lack of fibroblast growth factor 21 accelerates metabolic liver injury characterized by steatohepatities in mice

Fibroblast growth factor 21 (FGF21) concentrations are increased in human subjects who either have type 2 diabetes or nonalcoholic fatty liver disease (NAFLD). While excessive fat in the liver promotes the release of pro-inflammatory cytokines, NAFLD progresses from steatosis to non alcoholic steatohepatitis (NASH), a more aggressive form of hepatic damage, and lastly toward cirrhosis and HCC. In our previous study, loss of FGF21 is associated with hyper-proliferation, aberrant p53, and HCC development in diabetes mice. In this study, we proposed to investigate the liver metabolic disorders by diabetes and the potential roles of FGF21 played in NASH and potential carcinogenetic transformation of HCC. NASH was induced in FGF21 knockout (FGF21KO) mice by streptozotocin administration or fed with high fat diet (HFD). The pathological transformation of steatohepatities as well as parameters of inflammation, lipid metabolism, cellular events, mesenchymal-epithelial transition (MET) and Wnt/β-catenin signaling was determined in the FGF21 KO diabetic mice and HFD fed mice. We found that mice lacking the FGF21 gene are more prone to develop NASH. A compromised microenvironment of NASH, which could facilitate the HCC carcinogenetic transformation, was found in FGF21 KO mice under metabolic disorders by diabetes and HFD feeding. This study provided further evidence that lack of FGF21 worsened the metabolic disorders in NASH and could render a tumor microenvironment for HCC initiation and progression in the liver of diabetes mice.

FGF21 as a mediator of adaptive responses to stress and metabolic benefits of anti-diabetic drugs

Most hormones secreted from specific organs of the body in response to diverse stimuli contribute to the homeostasis of the whole organism. Fibroblast growth factor 21 (FGF21), a hormone induced by a variety of environmental or metabolic stimuli, plays a crucial role in the adaptive response to these stressful conditions. In addition to its role as a stress hormone, FGF21 appears to function as a mediator of the therapeutic effects of currently available drugs and those under development for treatment of metabolic diseases. In this review, we highlight molecular mechanisms and the functional importance of FGF21 induction in response to diverse stress conditions such as changes of nutritional status, cold exposure, and exercise. In addition, we describe recent findings regarding the role of FGF21 in the pathogenesis and treatment of diabetes associated with obesity, liver diseases, pancreatitis, muscle atrophy, atherosclerosis, cardiac hypertrophy, and diabetic nephropathy. Finally, we discuss the current understanding of the actions of FGF21 as a crucial regulator mediating beneficial metabolic effects of therapeutic agents such as metformin, glucagon/glucagon-like peptide 1 analogues, thiazolidinedione, sirtuin 1 activators, and lipoic acid.

Loss of FGF21 in diabetic mouse during hepatocellular carcinogenetic transformation

Diabetes associated metabolic syndrome has been shown to be an independent risk factor for the development of hepatocellular carcinoma (HCC). Cirrhosis, in fact, was not always a prerequisite of HCC development and this might particularly apply to the metabolic abnormality associated HCC. This study was to investigate diabetes associated HCC and the potential role of FGF21 during carcinogenetic transformation of HCC. Dimethylnitrosamine (DEN) was used to induce HCC in the diabetic OVE26 mice. Pronounced damage characterized by steatohepatitis was found in the liver of diabetic mice. Steatohepatitis accompanied by constant cell proliferation and tumor cell growth were also found in the hepatic tissues of diabetic OVE26 mice when DEN being administrated. FGF21 protein level increased in liver tissues at an early stage along with steatohepatitis in diabetic OVE26 mice, but decreased in liver tissues later when HCC was developed. In addition, decreased FGF21 protein level was associated with cancerous hyper-proliferation and aberrant p53 and TGF-β/Smad signaling during HCC development. Loss of FGF21 may play an important role in HCC carcinogenetic transformation during metabolic liver injury in diabetic animals. The present finding calls attention to the need to control metabolic disorders associated with diabetes and may further develop a protective strategy against HCC.

Fibroblast growth factor-21 and the beneficial effects of long-chain n-3 polyunsaturated fatty acids

Long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) in the diet protect against insulin resistance and obesity. Fibroblast growth factor-21 (Fgf21) is a hormonal factor released mainly by the liver that has powerful anti-diabetic effects. Here, we tested whether the beneficial metabolic effects of LC n-3 PUFA involve the induction of Fgf21. C57BL/6 J mice were exposed to an obesogenic, corn-oil-based, high-fat diet (cHF), or a diet in which corn oil was replaced with a fish-derived LC n-3 PUFA concentrate (cHF + F) using two experimental settings: short-term (3 weeks) and long-term treatment (8 weeks). CHF + F reduced body weight gain, insulinemia, and triglyceridemia compared to cHF. cHF increased plasma Fgf21 levels and hepatic Fgf21 gene expression compared with controls, but these effects were less pronounced or absent in cHF + F-fed mice. In contrast, hepatic expression of peroxisome proliferator-activated receptor (PPAR)-α target genes were more strongly induced by cHF + F than cHF, especially in the short-term treatment setting. The expression of genes encoding Fgf21, its receptors, and Fgf21 targets was unaltered by short-term LC n-3 PUFA treatment, with the exception of Ucp1 (uncoupling protein 1) and adiponectin genes, which were specifically up-regulated in white fat. In the long-term treatment setting, the expression of Fgf21 target genes and receptors was not differentially affected by LC n-3 PUFA. Collectively, our findings indicate that increased Fgf21 levels do not appear to be a major mechanism through which LC n-3 PUFA ameliorates high-fat-diet-associated metabolic disorders.

Hepatic mTORC1 controls locomotor activity, body temperature, and lipid metabolism through FGF21

The liver is a key metabolic organ that controls whole-body physiology in response to nutrient availability. Mammalian target of rapamycin (mTOR) is a nutrient-activated kinase and central controller of growth and metabolism that is negatively regulated by the tumor suppressor tuberous sclerosis complex 1 (TSC1). To investigate the role of hepatic mTOR complex 1 (mTORC1) in whole-body physiology, we generated liver-specific Tsc1 (L-Tsc1 KO) knockout mice. L-Tsc1 KO mice displayed reduced locomotor activity, body temperature, and hepatic triglyceride content in a rapamycin-sensitive manner. Ectopic activation of mTORC1 also caused depletion of hepatic and plasma glutamine, leading to peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α)-dependent fibroblast growth factor 21 (FGF21) expression in the liver. Injection of glutamine or knockdown of PGC-1α or FGF21 in the liver suppressed the behavioral and metabolic defects due to mTORC1 activation. Thus, mTORC1 in the liver controls whole-body physiology through PGC-1α and FGF21. Finally, mTORC1 signaling correlated with FGF21 expression in human liver tumors, suggesting that treatment of glutamine-addicted cancers with mTOR inhibitors might have beneficial effects at both the tumor and whole-body level.

The role of fibroblast growth factor 21 in the pathogenesis of liver disease: a novel predictor and therapeutic target

INTRODUCTION

Fibroblast growth factor 21 (FGF21) is one of the FGF family members that is produced mainly by tissues with high metabolic activity such as liver, pancreas, muscle and adipose tissue. The major function of FGF21 is to improve insulin sensitivity, ameliorate hepatic steatosis and enhance energy expenditure. Recently, several studies have reported a correlation between FGF21 and liver disease with numerous cross-sectional studies demonstrating significant correlation. This review will focus on the role of FGF21 in the pathogenesis of liver disease and its potential role as a biomarker and a new target for therapeutic intervention.

AREAS COVERED

This review discusses cross-sectional studies and underlying mechanisms of FGF21 as an endocrine hormone in several liver diseases. Two major theories of 'endoplasmic reticulum stress' and 'FGF21 resistance' in particular are explained. Moreover, early functional detection and pharmacological effect of FGF21 for liver disease are also described.

EXPERT OPINION

FGF21 can be a promising treatment in liver disease. However, still several problems are needed to be answered. The most important are whether different liver disease share common underlying mechanisms and the pharmacological effect in human with limited studies. Further studies are needed to explain the underlying mechanisms and develop potential therapeutic effect for human liver disease.

Changes in FGF21 serum concentrations and liver mRNA expression in an experimental model of complete lipodystrophy and insulin-resistant diabetes

Patients with obesity and type 2 diabetes often display high levels of the anti-diabetic factor fibroblast growth factor-21 (FGF21), suggesting that the overproduction of FGF21 may result from increased adiposity in an attempt by white adipose tissue (WAT) to counteract insulin resistance. However, the production of FGF21 diabetes in the absence of WAT has not been examined. In this study, we investigated the effects of lipodystrophy in A-ZIP F-1 mice on FGF21 production in relation to diabetes. A-ZIP F-1 mice displayed high FGF21 plasma levels resulting from enhanced FGF21 mRNA expression in the liver. Concomitant enhancement of FGF21 receptor (FGFR1) and glucose transporter 1 (GLUT-1) mRNA expression was observed in the muscles of A-ZIP F-1 mice. Furthermore, the activation of hypothalamic NPY and AgRP mRNA expression positively correlated with plasma levels of FGF21 but not active ghrelin. Our study demonstrates that an increased FGF21 plasma level in lipodystrophic A-ZIP F-1 mice results mainly from up-regulated liver production but does not suffice to overcome the lipodystrophy-induced severe type 2-diabetes and insulin resistance in the liver linked to the augmented liver fat deposition.

Molecular characterization and mapping of Fgf21 gene in a foodfish species asian seabass

Fgf21 is a newly discovered fibroblast growth factor. It is typically induced by fasting and plays important roles in the regulation of glucose and lipid metabolisms and energy balance in mammals, whereas potential functions of this gene in teleosts are still unknown. We identified the Fgf21 gene and studied its functions in Asian seabass (Lates calcarifer). The cDNA of the Fgf21 encoded a protein with 206 amino acids. Analysis of DNA and amino acid sequences of Fgf21 genes revealed that the sequences and structure of the Fgf21 genes were highly conserved in vertebrates. Real-time PCR revealed that Fgf21 was exclusively expressed in the intestine and kidney, which was different from the expression profiles of mammals. Fgf21 was down-regulated under fasting, whereas it was significantly increased during the LPS challenge. Exogenous recombinant FGF21 significantly suppressed the appetite of Asian seabass. Our data suggest that Fgf21 plays a role in energy regulation and acute phase response in Asian seabass, and may have different functions in fish and mammals. In addition, we identified one SNP in Fgf21. By using this SNP, the gene was mapped on the linkage group 23, where a suggestive QTL for growth was mapped previously. Association mapping identified significant associations between Fgf21 genotypes at the SNP and growth traits. These results not only provide important information of the functions of Fgf21, but also suggest that the SNP in this gene can be used as a marker in selecting fast-growing individuals of Asian seabass.

Stressed Liver and Muscle Call on Adipocytes with FGF21

Fibroblast growth factor 21 (FGF21) is an emerging regulator of local and systemic metabolic homeostasis. Treatment with pharmacological levels of FGF21 alleviates obesity and associated metabolic diseases including diabetes. However, beyond anti-obesogenic effects, the normal roles and underlying mechanisms of FGF21 as an endocrine hormone remain unclear. A recent wave of studies has revealed that FGF21 is a stress-induced endocrine factor in liver, muscle, and other tissues that targets adipose tissue and adipocytes through the FGFR1-betaKlotho complex. Adipose tissues and adipocytes within diverse tissues respond with metabolites and adipokine signals that affect functions of body tissues systemically and cells within the local microenvironment adjacent to adipocytes. Normally this is to prevent impaired tissue-specific function and damage to diverse tissues secreting FGF21 in response to chronic stress. Therefore, diverse stressed tissues and the adipose tissue and adipocytes constitute a beneficial endocrine and paracrine communication network through FGF21. Here we attempt to unify these developments with beneficial pharmacological effects of FGF21 on obesity in respect to inter-organ stress communication and mechanisms.

Deficiency of metabolic regulator FGFR4 delays breast cancer progression through systemic and microenvironmental metabolic alterations

BACKGROUND

Endocrine FGF21 and FGF19 target adipocytes and hepatocytes through betaKlotho (KLB) and FGFR tyrosine kinases effecting glucose, lipid and energy metabolism. Both factors alleviate obesity and metabolic abnormalities which are contributing factors to breast tumor progression. Genomic manipulation of hepatic FGFR4 has uncovered roles of endocrine FGF signaling in both metabolic and cellular homeostasis. Here we determined whether systemic and microenvironmental metabolic alterations caused by the FGFR4 deficiency affect tumorigenesis in breast where FGFR4 is negligible. Breast tumors were induced in the bigenic mice with ablation of FGFR4 and overexpression of TGFα that activates Her2 in the ductal and lobular epithelium surrounded by adipocytes. Mammary tumorigenesis and alterations in systemic and breast microenvironmental metabolic parameters and regulatory pathways were analyzed.

RESULTS

Ablation of FGFR4 had no effect on cellular homeostasis and Her2 activity of normal breast tissue. However, the absence of FGFR4 reduced TGFα-driven breast tumor incidence and progression and improved host survival. Notable increases in hepatic and serum FGF21, ileal FGF15/19, adiponectin and adipsin, and decreases in systemic Fetuin A, IGF-1, IGFBP-1, RBP4 and TIMP1 were observed. The ablation affected adipogenesis and secretory function of adipocytes as well as lipogenesis, glycolysis and energy homeostasis associated with the functions of mitochondria, ER and peroxisomes in the breast and tumor foci. Treatment with a chemical inhibitor of NAMPT involved in the pathways inhibited the growth and survival of breast tumor cells and tumor-initiating cell-containing spheres. The FGFR4 ablation also caused elevation of inflammatory factors in the breast.

CONCLUSIONS

Although the primary role of FGFR4 in metabolism occurs in hepatocytes, its ablation results in a net inhibitory effect on mammary tumor progression. We suggest that the tumor-delaying effect of FGFR4 deficiency may be in large part due to elevated anti-obesogenic FGF21 that triggers tumor-suppressing signals from both peripheral and breast adipocytes. The predominant changes in metabolic pathways suggested roles of metabolic effects from both peripheral and breast adipocytes on metabolic reprogramming in breast epithelial cells that contribute to the suppression of tumor progression. These results provide new insights into the contribution of systemic and microenvironmental metabolic effects controlled by endocrine FGF signaling to breast carcinogenesis.