FGF19 subfamily members: FGF19 and FGF21

Fibroblast growth factor 21

Fibroblast growth factor 21 (FGF21) belongs to the FGF19 subfamily and acts systemically, playing a key role in inter-organ crosstalk. Ranging from metabolism, reproduction, and immunity, FGF21 is a pleiotropic hormone which contributes to various physiological processes. Although most of its production across species stems from hepatic tissues, expression of FGF21 in mice has also been identified in adipose tissue, thymus, heart, pancreas, and skeletal muscle. Elevated FGF21 levels are affiliated with various diseases and conditions, such as obesity, type 2 diabetes, preeclampsia, as well as cancer. Murine knockout models are viable and show modest weight gain, while overexpression and gain-of-function models display resistance to weight gain, altered bone volume, and enhanced immunity. In addition, FGF21-based therapies are at the forefront of biopharmaceutical strategies aimed at treating metabolic dysfunction-associated steatotic liver disease.

A correlation of serum fibroblast growth factor 21 level with inflammatory markers and indicators of nutritional status in patients with inflammatory bowel disease

Background

Fibroblast growth factor 21 (FGF21) is a stress-inducible hormone that regulates nutrient and metabolic homeostasis. Inflammatory state is one of the stimulators of FGF21 secretion. The aim of the study was to assess correlations between serum FGF21 level and inflammatory markers as well as nutritional status indicators in patients with inflammatory bowel disease (IBD).

Methods

Fasting serum FGF21 level was measured using ELISA test in 105 IBD patients and 17 healthy controls. There were 31 subjects with active ulcerative colitis (UC), 16 with inactive UC, 36 with active Crohn's disease (CD), and 22 with inactive CD. Clinical and endoscopic activity of IBD was evaluated based on validated scales and indices. Fecal calprotectin, serum CRP, and selected parameters of nutritional status were tested in all patients.

Results

Serum FGF21 level was characterized by fluctuations depending on the IBD activity. FGF21 level was significantly higher in both active UC and CD compared to inactive phases of the diseases and to the controls. A correlation between FGF21 and fecal calprotectin levels was also found in UC and CD. Additionally, in CD, FGF21 level positively correlated with CRP level. In both UC and CD, a negative correlation was noted between FGF21 level and nutritional status parameters including cholesterol, protein, albumin levels, and BMI.

Conclusion

The intensity of intestinal inflammation is related to FGF21 level, which correlates negatively with nutritional status indicators in IBD. The disturbances in FGF21 secretion may contribute to the multifactorial pathogenesis of malnutrition and weight loss in IBD patients.

Transcriptome analysis of large yellow croaker (Larimichthys crocea) at different growth rates

The unsynchronized growth of the large yellow croaker (Larimichthys crocea), which impacts growth efficiency, poses a challenge for aquaculture practitioners. In our study, juvenile stocks of large yellow croaker were sorted by size after being cultured in offshore cages for 4 months. Subsequently, individuals from both the fast-growing (FG) and slow-growing (SG) groups were sampled for analysis. High-throughput RNA-Seq was employed to identify genes and pathways that are differentially expressed during varying growth rates, which could suggest potential physiological mechanisms that influence growth rate. Our transcriptome analysis identified 382 differentially expressed genes (DEGs), comprising 145 upregulated and 237 downregulated genes in comparison to the SG group. GO and KEGG enrichment analyses indicated that these DEGs are predominantly involved in signal transduction and biochemical metabolic pathways. Quantitative PCR (qPCR) results demonstrated that cat, fasn, idh1, pgd, fgf19, igf2, and fads2 exhibited higher expression levels, whereas gadd45b and gadd45g showed lower expression compared to the slow-growing group. In conclusion, the differential growth rates of large yellow croaker are intricately associated with cellular proliferation, metabolic rates of the organism, and immune regulation. These findings offer novel insights into the molecular mechanisms and regulatory aspects of growth in large yellow croaker and enhance our understanding of growth-related genes.

FGFR inhibition blocks NF-ĸB-dependent glucose metabolism and confers metabolic vulnerabilities in cholangiocarcinoma

Genomic alterations that activate Fibroblast Growth Factor Receptor 2 (FGFR2) are common in intrahepatic cholangiocarcinoma (ICC) and confer sensitivity to FGFR inhibition. However, the depth and duration of response is often limited. Here, we conduct integrative transcriptomics, metabolomics, and phosphoproteomics analysis of patient-derived models to define pathways downstream of oncogenic FGFR2 signaling that fuel ICC growth and to uncover compensatory mechanisms associated with pathway inhibition. We find that FGFR2-mediated activation of Nuclear factor-κB (NF-κB) maintains a highly glycolytic phenotype. Conversely, FGFR inhibition blocks glucose uptake and glycolysis while inciting adaptive changes, including switching fuel source utilization favoring fatty acid oxidation and increasing mitochondrial fusion and autophagy. Accordingly, FGFR inhibitor efficacy is potentiated by combined mitochondrial targeting, an effect enhanced in xenograft models by intermittent fasting. Thus, we show that oncogenic FGFR2 signaling drives NF-κB-dependent glycolysis in ICC and that metabolic reprogramming in response to FGFR inhibition confers new targetable vulnerabilities.

Fibroblast growth factor 21: An emerging pleiotropic regulator of lipid metabolism and the metabolic network

Fibroblast growth factor 21 (FGF21) was originally identified as an important metabolic regulator which plays a crucial physiological role in regulating a variety of metabolic parameters through the metabolic network. As a novel multifunctional endocrine growth factor, the role of FGF21 in the metabolic network warrants extensive exploration. This insight was obtained from the observation that the FGF21-dependent mechanism that regulates lipid metabolism, glycogen transformation, and biological effectiveness occurs through the coordinated participation of the liver, adipose tissue, central nervous system, and sympathetic nerves. This review focuses on the role of FGF21-uncoupling protein 1 (UCP1) signaling in lipid metabolism and how FGF21 alleviates non-alcoholic fatty liver disease (NAFLD). Additionally, this review reveals the mechanism by which FGF21 governs glucolipid metabolism. Recent research on the role of FGF21 in the metabolic network has mostly focused on the crucial pathway of glucolipid metabolism. FGF21 has been shown to have multiple regulatory roles in the metabolic network. Since an adequate understanding of the concrete regulatory pathways of FGF21 in the metabolic network has not been attained, this review sheds new light on the metabolic mechanisms of FGF21, explores how FGF21 engages different tissues and organs, and lays a theoretical foundation for future in-depth research on FGF21-targeted treatment of metabolic diseases.

Role of klotho and fibroblast growth factor 23 in arterial calcification, thickness, and stiffness: a meta-analysis of observational studies

This meta-analysis was conducted to clarify the role of klotho and fibroblast growth factor 23 (FGF-23) in human arterial remodeling across recent studies, in terms of arterial calcification, thickness, and stiffness. A systematic literature search was conducted on five databases for articles up to December 2023. Arterial calcification, thickness, and stiffness were determined using the calcification score and artery affected, carotid intima-media thickness (CIMT), and pulse wave velocity (PWV), respectively. Sixty-two studies with a total of 27,459 individuals were included in this meta-analysis. Most studies involved chronic kidney disease patients. Study designs were mostly cross-sectional with only one case-control and nine cohorts. FGF-23 was positively correlated with arterial calcification (r = 0.446 [0.254-0.611], p < 0.0001 and aOR = 1.36 [1.09-1.69], p = 0.006), CIMT (r = 0.188 [0.02-0.354], p = 0.03), and PWV (r = 0.235 [0.159-0.310], p < 0.00001). By contrast, Klotho was inversely correlated with arterial calcification (r = - 0.388 [- 0.578 to - 0.159], p = 0.001) and CIMT (r = - 0.38 [- 0.53 to - 0.207], p < 0.00001). In conclusion, FGF-23 and Klotho were associated with arterial calcification, thickness, and stiffness, clarifying their role in arterial remodeling processes.

Involvement of the vagus nerve and hepatic gene expression in serum adiponectin concentrations in mice

Several humoral factors, such as adiponectin and urate, have been suggested to affect metabolic syndromes. Previously, we reported a reduction in blood adiponectin concentrations after a high-fructose diet partially via the vagus nerve in rats. Although a lithogenic diet (LD), i.e., supplementation of a normal control diet (CT) with 0.6% cholesterol and 0.2% sodium cholate, reduced blood adiponectin concentrations, the involvement of the vagus nerve in this mechanism remains unclear. To estimate the involvement of the vagus nerve in the regulation of blood adiponectin concentrations using an LD, male imprinting control region mice that had been vagotomized (HVx) or only laparotomized (Sham) were administered a CT or an LD for 10 weeks. Serum adiponectin concentrations in the Sham-LD, HVx-CT, and HVx-LD groups were reduced by half compared with the Sham-CT group. The hepatic mRNA levels of fibroblast growth factor 21 (Fgf21), which reportedly stimulates adiponectin secretion from white adipose tissue, were lower in the LD groups compared with the CT groups. HepG2 hepatoma cells showed that various bile acids reduced the mRNA expression of FGF21. Moreover, the LD increased serum urate concentrations and reduced hepatic expressions of the acyl-CoA oxidase 1 (Acox1) mRNA and glucokinase, suggesting insufficient regeneration of ATP from AMP. In conclusion, serum adiponectin concentration may be regulated via the vagus nerve in normal mice, whereas a reduction of hepatic Fgf21 mRNA by bile acids may also lower serum adiponectin levels. Moreover, the LD may promote hepatic AMP accumulation and subsequently increase the serum urate concentration in mice.

Endocrine FGFs and their signaling in the brain: Relevance for energy homeostasis

Since their discovery in 2000, there has been a continuous expansion of studies investigating the physiology, biochemistry, and pharmacology of endocrine fibroblast growth factors (FGFs). FGF19, FGF21, and FGF23 comprise a subfamily with attributes that distinguish them from typical FGFs, as they can act as hormones and are, therefore, referred to as endocrine FGFs. As they participate in a broad cross-organ endocrine signaling axis, endocrine FGFs are crucial lipidic, glycemic, and energetic metabolism regulators during energy availability fluctuations. They function as powerful metabolic signals in physiological responses induced by metabolic diseases, like type 2 diabetes and obesity. Pharmacologically, FGF19 and FGF21 cause body weight loss and ameliorate glucose homeostasis and energy expenditure in rodents and humans. In contrast, FGF23 expression in mice and humans has been linked with insulin resistance and obesity. Here, we discuss emerging concepts in endocrine FGF signaling in the brain and critically assess their putative role as therapeutic targets for treating metabolic disorders.

Overexpression and Purification of Mitogenic and Metabolic Fibroblast Growth Factors

Fibroblast growth factors (FGFs) are proteins with a vast array of biological activity, such as cell development and repair, glucose and bile acid metabolisms, and wound healing. Due to their critical and diverse physiological functions, FGFs are believed to possess potential as therapeutic agents for many diseases and conditions that warrant further investigations. Thus, a simple, cost-efficient method to purify these biologically active signaling proteins is desirable. Herein, we introduce such techniques to purify FGFs that possess either high heparin-binding affinity or low to no heparin-binding affinity. This method takes advantage of the high affinity toward heparin sulfate from paracrine FGF1 to isolate the targeted protein. It also accounts for FGF members that have low heparin affinity, such as the metabolic FGFs, by introducing poly-histidine tags in the recombinant protein in combination with the immobilized metal affinity chromatography. Subsequently, the purified FGF products are separated from the other small protein by high-speed centrifugation. Products are then subjected to other biophysical experiments like SDS-PAGE, mass spectrometry, circular dichroism, intrinsic fluorescence, isothermal titration calorimetry, differential scanning calorimetry, and biological cell activity assay to confirm that the target proteins are purified with intact native conformation and no significant change in the intrinsic characteristics and biological activities.

Contaminant biomonitoring augmented with a qPCR array indicates hepatic mRNA gene expression effects in wild-collected seabird embryos

Birds can bioaccumulate persistent contaminants, and maternal transfer to eggs may expose embryos to concentrations sufficient to cause adverse effects during sensitive early-life stages. However, using tissue residue concentrations alone to infer whether contaminant effects are occurring suffers from uncertainty, and efficient, sensitive biomarkers remain limited in wildlife. We studied relationships between whole embryo contaminant concentrations (total mercury, organochlorine pesticides, perfluoroalkyl substances, polychlorinated biphenyls, and halogenated flame retardants) together with mRNA expression in embryonic liver tissue from a Pacific Ocean seabird, the rhinoceros auklet (Cerorhinca monocerata). Fresh eggs were collected, incubated under controlled conditions, and from the pre-hatch embryo, hepatic RNA was extracted for qPCR array analysis to measure gene expression (2-∆Cq), while the remaining embryo was analyzed for contaminant residues. Contaminant and gene expression data were assessed with a combination of multivariate approaches and linear models. Results indicated correlations between embryonic total mercury and several genes such as sepp1, which encodes selenoprotein P. Correlation between the biotransformation gene cyp1a4 and the C7 perfluoroalkyl carboxylic acid PFHpA was also evident. This study demonstrates that egg collection from free-living populations for contaminant biomonitoring programs can relate chemical residues to in ovo mRNA gene expression effects in embryo hepatic tissue.

Unveiling the power of microenvironment in liver regeneration: an in-depth overview

The liver serves as a vital regulatory hub for various physiological processes, including sugar, protein, and fat metabolism, coagulation regulation, immune system maintenance, hormone inactivation, urea metabolism, and water-electrolyte acid-base balance control. These functions rely on coordinated communication among different liver cell types, particularly within the liver's fundamental hepatic lobular structure. In the early stages of liver development, diverse liver cells differentiate from stem cells in a carefully orchestrated manner. Despite its susceptibility to damage, the liver possesses a remarkable regenerative capacity, with the hepatic lobule serving as a secure environment for cell division and proliferation during liver regeneration. This regenerative process depends on a complex microenvironment, involving liver resident cells, circulating cells, secreted cytokines, extracellular matrix, and biological forces. While hepatocytes proliferate under varying injury conditions, their sources may vary. It is well-established that hepatocytes with regenerative potential are distributed throughout the hepatic lobules. However, a comprehensive spatiotemporal model of liver regeneration remains elusive, despite recent advancements in genomics, lineage tracing, and microscopic imaging. This review summarizes the spatial distribution of cell gene expression within the regenerative microenvironment and its impact on liver regeneration patterns. It offers valuable insights into understanding the complex process of liver regeneration.

The Role of the FGF19 Family in the Pathogenesis of Gestational Diabetes: A Narrative Review

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. Understanding the pathogenesis and appropriate diagnosis of GDM enables the implementation of early interventions during pregnancy that reduce the risk of maternal and fetal complications. At the same time, it provides opportunities to prevent diabetes, metabolic syndrome, and cardiovascular diseases in women with GDM and their offspring in the future. Fibroblast growth factors (FGFs) represent a heterogeneous family of signaling proteins which play a vital role in cell proliferation and differentiation, repair of damaged tissues, wound healing, angiogenesis, and mitogenesis and also affect the regulation of carbohydrate, lipid, and hormone metabolism. Abnormalities in the signaling function of FGFs may lead to numerous pathological conditions, including metabolic diseases. The FGF19 subfamily, also known as atypical FGFs, which includes FGF19, FGF21, and FGF23, is essential in regulating metabolic homeostasis and acts as a hormone while entering the systemic circulation. Many studies have pointed to the involvement of the FGF19 subfamily in the pathogenesis of metabolic diseases, including GDM, although the results are inconclusive. FGF19 and FGF21 are thought to be associated with insulin resistance, an essential element in the pathogenesis of GDM. FGF21 may influence placental metabolism and thus contribute to fetal growth and metabolism regulation. The observed relationship between FGF21 and increased birth weight could suggest a potential role for FGF21 in predicting future metabolic abnormalities in children born to women with GDM. In this group of patients, different mechanisms may contribute to an increased risk of cardiovascular diseases in women in later life, and FGF23 appears to be their promising early predictor. This study aims to present a comprehensive review of the FGF19 subfamily, emphasizing its role in GDM and predicting its long-term metabolic consequences for mothers and their offspring.

FGF21 alleviates endothelial mitochondrial damage and prevents BBB from disruption after intracranial hemorrhage through a mechanism involving SIRT6

BACKGROUND

Disruption of the BBB is a harmful event after intracranial hemorrhage (ICH), and this disruption contributes to a series of secondary injuries. We hypothesized that FGF21 may have protective effects after intracranial hemorrhage (ICH) and investigated possible underlying molecular mechanisms.

METHODS

Blood samples of ICH patients were collected to determine the relationship between the serum level of FGF21 and the [Formula: see text]GCS%. Wild-type mice, SIRT6flox/flox mice, endothelial-specific SIRT6-homozygous-knockout mice (eSIRT6-/- mice) and cultured human brain microvascular endothelial cells (HCMECs) were used to determine the protective effects of FGF21 on the BBB.

RESULTS

We obtained original clinical evidence from patient data identifying a positive correlation between the serum level of FGF21 and [Formula: see text]GCS%. In mice, we found that FGF21 treatment is capable of alleviating BBB damage, mitigating brain edema, reducing lesion volume and improving neurofunction after ICH. In vitro, after oxyhemoglobin injury, we further explored the protective effects of FGF21 on endothelial cells (ECs), which are a significant component of the BBB. Mitochondria play crucial roles during various types of stress reactions. FGF21 significantly improved mitochondrial biology and function in ECs, as evidenced by alleviated mitochondrial morphology damage, reduced ROS accumulation, and restored ATP production. Moreover, we found that the crucial regulatory mitochondrial factor deacylase sirtuin 6 (SIRT6) played an irreplaceable role in the effects of FGF21. Using endothelial-specific SIRT6-knockout mice, we found that SIRT6 deficiency largely diminished these neuroprotective effects of FGF21. Then, we revealed that FGF21 might promote the expression of SIRT6 via the AMPK-Foxo3a pathway.

CONCLUSIONS

We provide the first evidence that FGF21 is capable of protecting the BBB after ICH by improving SIRT6-mediated mitochondrial homeostasis.

Molecular and Metabolic Analysis of Arsenic-Exposed Humanized AS3MT Mice

BACKGROUND

Chronic exposure to inorganic arsenic (iAs) has been associated with type 2 diabetes (T2D). However, potential sex divergence and the underlying mechanisms remain understudied. iAs is not metabolized uniformly across species, which is a limitation of typical exposure studies in rodent models. The development of a new "humanized" mouse model overcomes this limitation. In this study, we leveraged this model to study sex differences in the context of iAs exposure.

OBJECTIVES

The aim of this study was to determine if males and females exhibit different liver and adipose molecular profiles and metabolic phenotypes in the context of iAs exposure.

METHODS

Our study was performed on wild-type (WT) 129S6/SvEvTac and humanized arsenic + 3 methyl transferase (human AS3MT) 129S6/SvEvTac mice treated with 400   ppb of iAs via drinking water ad libitum. After 1 month, mice were sacrificed and the liver and gonadal adipose depots were harvested for iAs quantification and sequencing-based microRNA and gene expression analysis. Serum blood was collected for fasting blood glucose, fasting plasma insulin, and homeostatic model assessment for insulin resistance (HOMA-IR).

RESULTS

We detected sex divergence in liver and adipose markers of diabetes (e.g., miR-34a, insulin signaling pathways, fasting blood glucose, fasting plasma insulin, and HOMA-IR) only in humanized (not WT) mice. In humanized female mice, numerous genes that promote insulin sensitivity and glucose tolerance in both the liver and adipose are elevated compared to humanized male mice. We also identified Klf11 as a putative master regulator of the sex divergence in gene expression in humanized mice.

DISCUSSION

Our study underscored the importance of future studies leveraging the humanized mouse model to study iAs-associated metabolic disease. The findings suggested that humanized males are at increased risk for metabolic dysfunction relative to humanized females in the context of iAs exposure. Future investigations should focus on the detailed mechanisms that underlie the sex divergence. https://doi.org/10.1289/EHP12785.

Fgf21-Dubosiella axis mediates the protective effects of exercise against NAFLD development

AIM

To explore the mechanism of gut microbiota mediates protective effects of exercise against non-alcoholic fatty liver disease (NAFLD) development.

MAIN METHODS

The male C57BL/6 mice were fed with high fat food (HFD) or normal diet (CON) respectively, and the obese mice were randomly divided into sedentariness (HFD) and exercise groups (HFD + Exe). The total intervention period was 18 weeks. Antibiotic treatment and fecal microbiota transplantation were applied to evaluate gut microbiota mediates the protective effects of exercise against NAFLD development. 16S rDNA profiling of gut microbiota and extracorporeal rehydration of Dubosiella newyorkensis were performed to identify the crucial role of Dubosiella in NAFLD improvement during exercise training. FGF21 knock-out mice were used to reveal the potential mechanism of exercise increased the abundance of Dubosiella. RT-PCR, Western blot, Histopathological examinations and Biochemical testing were performed to evaluate the lipid deposition and function in the liver.

KEY FINDINGS

Treadmill exercise significantly ameliorated hepatic function and mitigated lipid accumulation in NAFLD mice, and these hepatoprotective benefits were mostly mediated by the Dubosiella. In addition, the increased abundance of Dubosiella during exercise training was modulated by FGF21 specifically.

SIGNIFICANCE

In short, Dubosiella, chiefly regulated by FGF21 signaling during exercise training, has been discovered to govern the protective impacts of exercising counter to the development of NAFLD and exhibits a promising treatment target for NAFLD.

Farnesoid X Receptor Agonist GW4064 Protects Lipopolysaccharide-Induced Intestinal Epithelial Barrier Function and Colorectal Tumorigenesis Signaling through the αKlotho/βKlotho/FGFs Pathways in Mice

The farnesoid X receptor (FXR)/βKlotho/fibroblast growth factors (FGFs) pathway is crucial for maintaining the intestinal barrier and preventing colorectal cancer (CRC). We used an FXR agonist, GW4064, and FXR-knockout (FXR-KO) mice to investigate the role of FXR/Klothos/FGFs pathways in lipopolysaccharide (LPS)-induced intestinal barrier dysfunction and colon carcinogenesis. The results showed that upregulation of FXR in enterocytes effectively ameliorated intestinal tight-junction markers (claudin1 and zonula occludens-1), inflammation, and bile acid levels, thereby protecting mice from intestinal barrier dysfunction and colon carcinogenesis. GW4064 treatment increased FXR, αKlotho, βKlotho, FGF19, FGF21, and FGF23 in wild-type mice exposed to LPS, while FXR-KO mice had decreased levels. FXR-KO mice exhibited elevated colon cancer markers (β-catenin, LGR5, CD44, CD34, and cyclin D1) under LPS, underscoring the pivotal role of FXR in inhibiting the development of colon tumorigenesis. The varying gut microbiota responses in FXR-KO mice versus wild-type mice post LPS exposure emphasize the pivotal role of FXR in preserving intestinal microbial health, involving Bacteroides thetaiotaomicron, Bacteroides acidifaciens, and Helicobacter hepaticus. Our study validates the effectiveness of GW4064 in alleviating LPS-induced disruptions to the intestinal barrier and colon carcinogenesis, emphasizing the importance of the FXR/αKlotho/βKlotho/FGFs pathway and the interplay between bile acids and gut microbiota.

Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism

Fibroblast growth factor 21 (FGF21) plays a vital role in normal eukaryotic organism development and homeostatic metabolism under the influence of internal and external factors such as endogenous hormone changes and exogenous stimuli. Over the last few decades, comprehensive studies have revealed the key role of FGF21 in regulating many fundamental metabolic pathways, including the muscle stress response, insulin signaling transmission, and muscle development. By coordinating these metabolic pathways, FGF21 is thought to contribute to acclimating to a stressful environment and the subsequent recovery of cell and tissue homeostasis. With the emphasis on FGF21, we extensively reviewed the research findings on the production and regulation of FGF21 and its role in muscle metabolism. We also emphasize how the FGF21 metabolic networks mediate mitochondrial dysfunction, glycogen consumption, and myogenic development and investigate prospective directions for the functional exploitation of FGF21 and its downstream effectors, such as the mammalian target of rapamycin (mTOR).

The significance of serum Klotho to hearing loss: a potential protector under noise pollution

The issue of hearing protection in the presence of noise pollution is of great importance in the fields of environmental science and clinical medicine. Currently, the clinical significance of Klotho in relation to hearing has not been revealed. The aim of this study was to examine the correlation between serum Klotho levels and Pure Tone Average (PTA) hearing thresholds among individuals in the U.S.. The analysis involved a sample of 1,781 individuals aged 20 to 69, obtained from the 2007-2012 National Health and Nutrition Examination Survey. Various methods were utilized for the analysis, including univariate and multivariate linear regression, stratified analysis, smooth curve fitting, a two-segment linear regression model, and log-likelihood ratio analysis. The results of the univariate analysis indicated that serum Klotho concentration, age, education level, hypertension, diabetes, and smoking all exhibited a significant influence on PTAs. After adjusting for potential confounding factors, it was observed that a decrease in serum Klotho was significantly associated with PTA thresholds at low frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.004), speech frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.007), and high frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.045). Specifically, for every 1 pg/ml decrease in serum Klotho concentration, the PTAs increased by 0.002 dB. Moreover, age and gender-specific analyses revealed significant associations. For individuals aged 59-69, a significant association was found between serum Klotho concentration and high-frequency PTA (β = -4.153; 95% CI: -7.948, -0.358; P = 0.032). Additionally, among females, significant associations were observed between serum Klotho concentration and speech-frequency PTA (β = -1.648, 95% CI: -3.197, -0.099; P = 0.037) as well as high-frequency PTA (β = -3.046; 95% CI: -5.319, -0.772; P = 0.009). Finally, the results of smooth curve fitting and threshold effect analyses indicated a potential negative linear correlation between serum Klotho concentration and PTA thresholds. In conclusion, a lower level of serum Klotho was found to be associated with increased hearing thresholds, particularly among the elderly population. This finding has significant implications for the prevention and treatment of hearing damage.

Insight to the association among fibroblast growth factor 21, non-alcoholic fatty liver disease and cardiovascular outcomes: A population-based study

OBJECTIVE

We aimed to investigate whether there was a joint effect of fibroblast growth factor 21 (FGF21) and non-alcoholic fatty liver disease (NAFLD) or interaction on the incidence of cardiovascular diseases based on a community-dwelling population.

METHODS

Serum FGF21 levels were determined using an enzyme-linked immunosorbent method. NAFLD was diagnosed via ultrasonography. Multivariable-adjusted cox proportional hazards models were used to assess the joint effects of FGF21 and NAFLD on the major adverse cardiovascular events (MACE).

RESULTS

A total of 1194 participants were enrolled in the final analysis. The multivariable-adjusted hazard ratio (HR) of MACE was 1.84 (95% confidence interval (CI) 1.18-2.86) in participants with diagnosed NAFLD at baseline, compared with those without NAFLD at baseline. The multivariable-adjusted HRs of MACE across quintiles of serum FGF21 levels at baseline were 1.00, 1.48 (95%CI 0.68-3.21), 2.01 (95%CI 0.98-4.13), 1.94 (95%CI 0.94-4.02) and 2.14 (95%CI 1.03-4.44) respectively. Participants with high FGF21 levels and NAFLD at baseline showed the highest risk of MACE with a significant interaction between the presence of NAFLD and serum FGF21 levels.

CONCLUSIONS

Both FGF21 and NAFLD were associated with MACE, while the association between FGF21 and MACE may be interacted by the presence of NAFLD at baseline.

Hepatokine Profile in Adolescents with Polycystic Ovary Syndrome: A Case-Control Study

The current guidelines suggest routine screening for non-alcoholic fatty liver disease (NAFLD) in patients with polycystic ovary syndrome (PCOS). Hepatokines seem to be promising surrogate endpoints for the diagnosis and severity of NAFLD. PCOS has its onset in adolescence and its metabolic sequalae begin during the same period. There are scarce data on the hepatokine profile of adolescent PCOS patients. This case-control study examined the serum profile of the hepatokines sex hormone-binding globulin (SHBG), selenoprotein P, fibroblast growth factor 21 (FGF21), and fetuin A in a sample of adolescent PCOS patients, and their association to metabolic and hormonal parameters. The selenoprotein P and SHBG serum concentrations were significantly decreased in PCOS patients vs. the controls (median (IQR), 2.47 (0.40) vs. 2.66 (0.36) μg/mL, p = 0.025; mean ± SD, 41.71 ± 19.41 vs. 54.94 ± 22.12 nmol/L, p = 0.011, respectively), whereas selenoprotein P was significantly and positively associated with testosterone (r = 0.325, p = 0.007) and the free androgen index (r = 0.361, p = 0.002). The SHBG demonstrated multiple significant negative correlations with adverse metabolic parameters. Among the PCOS patients, the FGF21 concentrations were significantly higher in those with NAFLD, whereas a 1 pg/mL increase in the FGF21 concentration increased the odds of NAFLD diagnosis by liver ultrasound by 1%, suggesting FGF21 as a potential biomarker for hepatic disease in females with PCOS in adolescence. Fetuin A was the least differentiated hepatokine between the PCOS patients and controls with the least associations with metabolic and hormonal parameters.

Fibroblast growth factor 21 in metabolic syndrome

Metabolic syndrome is a complex metabolic disorder that often clinically manifests as obesity, insulin resistance/diabetes, hyperlipidemia, and hypertension. With the development of social and economic systems, the incidence of metabolic syndrome is increasing, bringing a heavy medical burden. However, there is still a lack of effective prevention and treatment strategies. Fibroblast growth factor 21 (FGF21) is a member of the human FGF superfamily and is a key protein involved in the maintenance of metabolic homeostasis, including reducing fat mass and lowering hyperglycemia, insulin resistance and dyslipidemia. Here, we review the current regulatory mechanisms of FGF21, summarize its role in obesity, diabetes, hyperlipidemia, and hypertension, and discuss the possibility of FGF21 as a potential target for the treatment of metabolic syndrome.

Chenodeoxycholic acid regulates fibroblast growth factor 23 gene expression via estrogen-related receptor γ in human hepatoma Huh7 cells

Fibroblast growth factor 23 (FGF23) is a glycoprotein that belongs to the FGF19 subfamily and participates in phosphate and vitamin D homeostasis. Chenodeoxycholic acid (CDCA), one of the primary bile acids, is reported to induce the secretion of FGF19 subfamily members, FGF21 and FGF19, in hepatocytes. However, whether and how CDCA influences FGF23 gene expression are largely unknown. Thus, we performed real-time polymerase chain reaction and Western blot analyses to determine the mRNA and protein expression levels of FGF23 in Huh7 cells. CDCA upregulated estrogen-related receptor γ (ERRγ) alongside FGF23 mRNA and protein levels, while, the knockdown of ERRγ ablated the induction effect of CDCA on FGF23 expression. Promoter studies showed that CDCA-induced FGF23 promoter activity occurred partly through ERRγ binding directly to the ERR response element (ERRE) in the human FGF23 gene promoter. Finally, the inverse agonist of ERRγ, GSK5182 inhibited the induction of FGF23 by CDCA. Overall, our results revealed the mechanism of CDCA-mediated FGF23 gene upregulation in the human hepatoma cell line. Moreover, the ability of GSK5182 to reduce CDCA-induced FGF23 gene expression might represent a therapeutic strategy to control abnormal FGF23 induction in conditions that involve elevated levels of bile acids, such as nonalcoholic fatty liver disease and biliary atresia.

Decreased FGF19 and FGF21: possible underlying common pathogenic mechanism of metabolic and cognitive dysregulation in depression

Background

Accumulating studies suggested that major depressive disorder (MDD) was closely related to metabolic syndrome (MetS). Important endogenous regulators fibroblast growth factors (FGFs) 19 and 21 were also reported to participate in psychiatric disorders. This study aimed to investigate the role of FGF19 and FGF21 in MDD and to explore the possible pathogenic mechanism of metabolic and cognitive dysregulation in depression.

Methods

A total of 59 MDD patients and 55 healthy control participants were recruited. The serum levels of FGF19 and FGF21 and lipid profiles were measured by means of enzymatic methods. Cognitive function was measured by repeatable battery for the assessment of neuropsychological status (RBANS) scores. The gene expression of PGC-1α and FNDC5 was determined by quantitative polymerase chain reaction (PCR).

Results

We found that plasma FGF19 and FGF21 levels were significantly decreased in patients with MDD. Meanwhile, triglyceride (TG) was significantly elevated and PGC-1α was significantly downregulated in MDD patients. Correlation analyses showed negative associations between TG and FGF19 levels. As for cognitive performance, both FGF19 and FGF21 levels were positively correlated with immediate memory. However, FGF19 levels were negatively correlated with language, and FGF21 levels were also negatively correlated with attention and delayed memory. Additionally, negative associations were found between FGF19 levels and PGC-1α. FGF21 levels were positively associated with PGC-1α and negatively associated with FNDC5.

Conclusion

This study elucidated the role of FGF19 and FGF21 in MDD. MDD patients were confirmed to have metabolic and cognitive dysregulation, and this abnormality was linked to the decreased concentrations of FGF19 and FGF21 through the PGC-1α/FNDC5 pathway. Our results showed that the alterations of FGF19 and FGF21 levels may be a common pathogenic mechanism of metabolic and cognitive disturbances in patients with MDD.

FGF21-FGFR1 controls mitochondrial homeostasis in cardiomyocytes by modulating the degradation of OPA1

Fibroblast growth factor 21 (FGF21) is a pleiotropic hormone secreted primarily by the liver and is considered a major regulator of energy homeostasis. Recent research has revealed that FGF21 could play an important role in cardiac pathological remodeling effects and prevention of cardiomyopathy; however, the underlying mechanism remains largely unknown. This study aimed to determine the mechanism underlying the cardioprotective effects of FGF21. We engineered FGF21 knock out mice and subsequently elucidated the effects of FGF21 and its downstream mediators using western blotting, qRT-PCR, and mitochondrial morphological and functional analyses. FGF21 knockout mice showed cardiac dysfunction, accompanied by a decline in global longitudinal strain (GLS) and ejection fraction (EF), independent of metabolic disorders. Mitochondrial quality, quantity, and function were abnormal, accompanied by decreased levels of optic atrophy-1 (OPA1) in FGF21 KO mice. In contrast to FGF21 knockout, cardiac-specific overexpression of FGF21 alleviated the cardiac dysfunction caused by FGF21 deficiency. In an in vitro study, FGF21 siRNA deteriorated mitochondrial dynamics and impaired function induced by cobalt chloride (CoCl₂). Both recombinant FGF21 and adenovirus-mediated FGF21 overexpression could alleviate CoCl₂-induced mitochondrial impairment by restoring mitochondrial dynamics. FGF21 was essential for maintaining mitochondrial dynamics and function of the cardiomyocytes. As a regulator of cardiomyocyte mitochondrial homeostasis under oxidative stress, FGF21 could be an important new target for therapeutic options for patients with heart failure.

The fibroblast growth factor system in cognitive disorders and dementia

Cognitive impairment is the core precursor to dementia and other cognitive disorders. Current hypotheses suggest that they share a common pathological basis, such as inflammation, restricted neurogenesis, neuroendocrine disorders, and the destruction of neurovascular units. Fibroblast growth factors (FGFs) are cell growth factors that play essential roles in various pathophysiological processes via paracrine or autocrine pathways. This system consists of FGFs and their receptors (FGFRs), which may hold tremendous potential to become a new biological marker in the diagnosis of dementia and other cognitive disorders, and serve as a potential target for drug development against dementia and cognitive function impairment. Here, we review the available evidence detailing the relevant pathways mediated by multiple FGFs and FGFRs, and recent studies examining their role in the pathogenesis and treatment of cognitive disorders and dementia.

Intestinal BMP-9 locally upregulates FGF19 and is down-regulated in obese patients with diabetes

Bone morphogenetic protein (BMP)-9, a member of the TGFβ-family of cytokines, is believed to be mainly produced in the liver. The serum levels of BMP-9 were reported to be reduced in newly diagnosed diabetic patients and BMP-9 overexpression ameliorated steatosis in the high fat diet-induced obesity mouse model. Furthermore, injection of BMP-9 in mice enhanced expression of fibroblast growth factor (FGF)21. However, whether BMP-9 also regulates the expression of the related FGF19 is not clear. Because both FGF21 and 19 were described to protect the liver from steatosis, we have further investigated the role of BMP-9 in this context. We first analyzed BMP-9 levels in the serum of streptozotocin (STZ)-induced diabetic rats (a model of type I diabetes) and confirmed that BMP-9 serum levels decrease during diabetes. Microarray analyses of RNA samples from hepatic and intestinal tissue from BMP-9 KO- and wild-type mice (C57/Bl6 background) pointed to basal expression of BMP-9 in both organs and revealed a down-regulation of hepatic Fgf21 and intestinal Fgf19 in the KO mice. Next, we analyzed BMP-9 levels in a cohort of obese patients with or without diabetes. Serum BMP-9 levels did not correlate with diabetes, but hepatic BMP-9 mRNA expression negatively correlated with steatosis in those patients that did not yet develop diabetes. Likewise, hepatic BMP-9 expression also negatively correlated with serum LPS levels. In situ hybridization analyses confirmed intestinal BMP-9 expression. Intestinal (but not hepatic) BMP-9 mRNA levels were decreased with diabetes and positively correlated with intestinal E-Cadherin expression. In vitro studies using organoids demonstrated that BMP-9 directly induces FGF19 in gut but not hepatocyte organoids, whereas no evidence of a direct induction of hepatic FGF21 by BMP-9 was found. Consistent with the in vitro data, a correlation between intestinal BMP-9 and FGF19 mRNA expression was seen in the patients' samples. In summary, our data confirm that BMP-9 is involved in diabetes development in humans and in the control of the FGF-axis. More importantly, our data imply that not only hepatic but also intestinal BMP-9 associates with diabetes and steatosis development and controls FGF19 expression. The data support the conclusion that increased levels of BMP-9 would most likely be beneficial under pre-steatotic conditions, making supplementation of BMP-9 an interesting new approach for future therapies aiming at prevention of the development of a metabolic syndrome and liver steatosis.

FGF/FGFR system in the central nervous system demyelinating disease: Recent progress and implications for multiple sclerosis

BACKGROUND

With millions of victims worldwide, multiple sclerosis is the second most common cause of disability among young adults. Although formidable advancements have been made in understanding the disease, the neurodegeneration associated with multiple sclerosis is only partially counteracted by current treatments, and effective therapy for progressive multiple sclerosis remains an unmet need. Therefore, new approaches are required to delay demyelination and the resulting disability and to restore neural function by promoting remyelination and neuronal repair.

AIMS

The article reviews the latest literature in this field.

MATERIALS AND METHODS

The fibroblast growth factor (FGF) signaling pathway is a promising target in progressive multiple sclerosis.

DISCUSSION

FGF signal transduction contributes to establishing the oligodendrocyte lineage, neural stem cell proliferation and differentiation, and myelination of the central nervous system. Furthermore, FGF signaling is implicated in the control of neuroinflammation. In recent years, interventions targeting FGF, and its receptor (FGFR) have been shown to ameliorate autoimmune encephalomyelitis symptoms in multiple sclerosis animal models moderately.

CONCLUSION

Here, we summarize the recent findings and investigate the role of FGF/FGFR signaling in the onset and progression, discuss the potential therapeutic advances, and offer fresh insights into managing multiple sclerosis.

FGF19 increases mitochondrial biogenesis and fusion in chondrocytes via the AMPKα-p38/MAPK pathway

Fibroblast growth factor 19 (FGF19) is recognized to play an essential role in cartilage development and physiology, and has emerged as a potential therapeutic target for skeletal metabolic diseases. However, FGF19-mediated cellular behavior in chondrocytes remains a big challenge. In the current study, we aimed to investigate the role of FGF19 on chondrocytes by characterizing mitochondrial biogenesis and fission-fusion dynamic equilibrium and exploring the underlying mechanism. We first found that FGF19 enhanced mitochondrial biogenesis in chondrocytes with the help of β Klotho (KLB), a vital accessory protein for assisting the binding of FGF19 to its receptor, and the enhanced biogenesis accompanied with a fusion of mitochondria, reflecting in the elongation of individual mitochondria and the up-regulation of mitochondrial fusion proteins. We then revealed that FGF19-mediated mitochondrial biogenesis and fusion required the binding of FGF19 to the membrane receptor, FGFR4, and the activation of AMP-activated protein kinase alpha (AMPKα)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α)/sirtuin 1 (SIRT1) axis. Finally, we demonstrated that FGF19-mediated mitochondrial biogenesis and fusion was mainly dependent on the activation of p-p38 signaling. Inhibition of p38 signaling largely reduced the high expression of AMPKα/PGC-1α/SIRT1 axis, decreased the up-regulation of mitochondrial fusion proteins and impaired the enhancement of mitochondrial network morphology in chondrocytes induced by FGF19. Taking together, our results indicate that FGF19 could increase mitochondrial biogenesis and fusion via AMPKα-p38/MAPK signaling, which enlarge the understanding of FGF19 on chondrocyte metabolism. Video Abstract.

[Adipocytes, adipokines and metabolic alterations in pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is a fatal respiratory disease characterized by severe remodeling of the lung parenchyma, with an accumulation of activated myofibroblasts and extracellular matrix, along with aberrant cellular differentiation. Within the subpleural fibrous zones, ectopic adipocyte deposits often appear. In addition, alterations in lipid homeostasis have been associated with IPF pathophysiology. In this mini-review, we will discuss the potential involvement of the adipocyte secretome and its paracrine or endocrine-based contribution to the pathophysiology of IPF, via protein or lipid mediators in particular.

Fibroblast growth factor-21 (FGF21) analogs as possible treatment options for diabetes mellitus in veterinary patients

Fibroblast growth factors (FGFs) are involved in numerous metabolic processes. The endocrine subfamily of FGFs, consisting of FGF19, FGF21, and FGF23, might have beneficial effects in the treatment of diabetes mellitus (DM) and/or obesity. The analog with the greatest potential, FGF21, lowers blood glucose levels, improves insulin sensitivity, and induces weight loss in several animal models. In this review we summarize recent (pre)clinical findings with FGF21 analogs in animal models and men. Furthermore, possible applications of FGF21 analogs for pets with DM will be discussed. As currently, information about the use of FGF21 analogs in pet animals is scarce.

Fibroblast growth factor 21 and prognosis of patients with cardiovascular disease: A meta-analysis

BACKGROUND

The role of fibroblast growth factor 21 (FGF21) in predicting the long-term prognosis of patients with cardiovascular disease (CVD) remains unknown.

METHODS

A comprehensive search in PubMed, Embase, and the Cochrane Library was performed to identify studies reporting the association between FGF21 and prognosis among patients with CVD. A meta-analysis was performed, with patients stratified by coronary artery disease (CAD) or heart failure (HF). The endpoint of CAD or HF was major adverse cardiovascular events defined by each study and a composite of death or HF readmission, respectively. The I² method and linear regression test of funnel plot asymmetry were used to test heterogeneity (I² > 50% indicates substantial heterogeneity) and publication bias (asymmetry P < 0.05, indicating publication bias).

RESULTS

A total of 807 records were retrieved, and nine studies were finally included. Higher FGF21 levels were significantly associated with the risk of major adverse cardiovascular events in patients with CAD (multivariate hazard ratio [HR]: 1.77, 95% confidence interval [CI]: 1.40-2.23, P < 0.05, I² = 0%, fixed-effect model). Increased FGF21 levels were also associated with the risk of all-cause death among patients with CAD (multivariate HR: 2.67, 95% CI: 1.25-5.72, P < 0.05, I² = 64%, random-effect model). No association was found between FGF21 and the endpoint among patients with HF (HR: 1.57, 95% CI: 0.99-2.48, P > 0.05, random-effect model), but a large heterogeneity (I² = 95%) and potential publication bias (Asymmetry P < 0.05) existed in the analysis.

CONCLUSION

Increased FGF21 levels were independently associated with poor prognosis of CAD, whereas the role of FGF21 in predicting clinical outcomes of HF requires further investigation.

Targeting FGF21 in cardiovascular and metabolic diseases: from mechanism to medicine

Cardiovascular and metabolic disease (CVMD) is becoming increasingly prevalent in developed and developing countries with high morbidity and mortality. In recent years, fibroblast growth factor 21 (FGF21) has attracted intensive research interest due to its purported role as a potential biomarker and critical player in CVMDs, including atherosclerosis, coronary artery disease, myocardial infarction, hypoxia/reoxygenation injury, heart failure, type 2 diabetes, obesity, and nonalcoholic steatohepatitis. This review summarizes the recent developments in investigating the role of FGF21 in CVMDs and explores the mechanism whereby FGF21 regulates the development of CVMDs. Novel molecular targets and related pathways of FGF21 (adenosine 5'-monophosphate-activated protein kinase, silent information regulator 1, autophagy-related molecules, and gut microbiota-related molecules) are highlighted in this review. Considering the poor pharmacokinetics and biophysical properties of native FGF21, the development of new generations of FGF21-based drugs has tremendous therapeutic potential. Related preclinical and clinical studies are also summarized in this review to foster clinical translation. Thus, our review provides a timely and insightful overview of the physiology, biomarker potential, molecular targets, and therapeutic potential of FGF21 in CVMDs.

The role of FGF21 and its analogs on liver associated diseases

Fibroblast growth factor 21 (FGF21), a member of fibroblast growth factor family, is a hormone-like growth factor that is synthesized mainly in the liver and adipose tissue. FGF21 regulates lipid and glucose metabolism and has substantial roles in decreasing lipogenesis and increasing hepatic insulin sensitivity which causing lipid profile improvement. FGF21 genetic variations also affect nutritional and addictive behaviors such as smoking and alcohol consumption and eating sweets. The role of FGF21 in metabolic associated diseases like diabetes mellitus had been confirmed previously. Recently, several studies have demonstrated a correlation between FGF21 and liver diseases. Non-alcoholic fatty liver disease (NAFLD) is the most prevalent type of chronic liver disease worldwide. NAFLD has a wide range from simple steatosis to steatohepatitis with or without fibrosis and cirrhosis. Elevated serum levels of FGF21 associated with NAFLD and its pathogenesis. Alcoholic fatty liver disease (AFLD), another condition that cause liver injury, significantly increased FGF21 levels as a protective factor; FGF21 can reverse the progression of AFLD and can be a potential therapeutic agent for it. Also, NAFLD and AFLD are the most important risk factors for hepatocellular carcinoma (HCC) which is the fourth deadliest cancer in the world. Several studies showed that lack of FGF21 induced oncogenic condition and worsened HCC. In this review article, we intend to discuss different aspects of FGF21 in NAFLD, AFLD and HCC; including the role of FGF21 in pathophysiology of these conditions, the effects of FGF21 mutations, the possible use of the FGF21 as a biomarker in different stages of these diseases, as well as the usage of FGF21 and its analog molecules in the treatment of these diseases.

Increased Circulating Cortisol After Vaginal Birth Is Associated With Increased FGF19 Secretion in Neonatal Pigs

The influence of birth modality (scheduled cesarean or spontaneous vaginal) on the development of the newborn has been a source of controversy in neonatology. The impact of cesarean vs vaginal birth on the development of bile acid and fibroblast growth factor 19 (FGF19) signaling is unknown. Our aim was to determine the effect of birth modality and gestational age (preterm vs term) on plasma hormone levels, bile acid pool distribution, expression of genes in the bile acid-FXR-FGF19 pathway, and plasma levels of FGF19 at birth and on day 3 of life in neonatal pigs. Four sows underwent cesarean delivery on gestation day 105 (n = 2) and 114 (n = 2; term = 115 days), and 2 additional sows were allowed to farrow at term (gestation days 112 and 118). Piglets were euthanized at birth (Term-Vaginal n = 6; Term-Cesarean n = 8; Preterm n = 10) for tissue and blood collection, and the remaining pigs received total parenteral nutrition then were fed enterally on day 3 (Term-Vaginal n = 8; Term-Cesarean n = 10; Preterm n = 8), before blood and tissue were collected. Piglets born vaginally had a markedly (30-fold) higher plasma FGF19 at birth than term pigs born via cesarean delivery, and 70-fold higher than preterm pigs (P < 0.001). However, distal ileum FGF19 gene expression was similar in all groups (P > 0.05). Plasma FGF19 positively correlated with plasma cortisol (r = 0.58; P < 0.05) and dexamethasone treatment increased ileal FGF19 expression in cultured pig tissue explants and human enteroids. Our findings suggest that exposure to maternal or endogenous glucocorticoids in the perinatal period may upregulate the development of the bile acid-FGF19 pathway.

Serum Fibroblast Growth Factor 19 as a Biomarker in Hepatitis B Virus-Related Liver Disease

Background: Past research has found that fibroblast growth factor 19 (FGF19) is associated with several hepatic disorders, such as alcoholic liver disease and primary biliary cirrhosis. However, there is currently a lack of relevant studies on the relationship between FGF19 and hepatitis B virus (HBV)-related liver disease. Objectives: This study aimed to assess the role of serum FGF19 as a new biomarker for HBV-related liver disease and provide scientific data to show the clinical value of this biomarker. Methods: A retrospective study included 37 patients with chronic hepatitis B (CHB), 33 patients with HBV-related cirrhosis (HBV-cirrhosis), and 32 patients with HBV-related hepatocellular carcinoma (HBV-HCC). Furthermore, 33 normal people were randomly selected as healthy controls. The serum levels of FGF19 were measured by ELISA. Results: Serum FGF19 levels were increased sequentially in the CHB group, HBV-cirrhosis group, and HBV-HCC group. Furthermore, serum FGF19 levels positively correlated with alpha-fetoprotein, prothrombin time, international normalized ratio, total bilirubin, direct bilirubin, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl-transferase, alkaline phosphatase, total bile acid, serum markers for liver fibrosis, ascites, cirrhosis, Child-Pugh classification and model for end-stage liver disease sodium (MELD-Na) score, while negatively correlated with platelet count, prothrombin activity, and albumin. The diagnostic threshold of serum FGF19 for HBV-related HCC was 165.32 pg/mL, with a sensitivity of 81.25% and specificity of 58.57%. Conclusions: Serum FGF19 levels are positively associated with cholestasis, hepatocyte damage, and liver fibrosis but negatively correlated with liver synthetic function and liver functional reserve in HBV-related liver disease. Diverse changes in serum FGF19 may be used as a predictive marker for the progression of HBV-related liver disease. In addition, serum FGF19 has a potential role in monitoring carcinogenesis in patients with HBV-related liver disease.

The New Markers of Early Obesity-Related Organ and Metabolic Abnormalities

The objective of our study was to identify new markers related to excessive body adiposity and its early consequences. For this purpose we determined serum FGF-19 and FGF-21 concentrations in obese rats, whose role in the pathogenesis of obesity is not yet established. In addition, a total reflection X-ray fluorescence technique was applied to determine the elemental chemistry of certain tissues affected by obesity. Next, the new biochemical and molecular parameters were correlated with well-known obesity-related markers of metabolic abnormalities. Our obese rats were characterized by increased calorie consumption and body adiposity, hypercholesterolemia, elevated levels of liver enzymes and FGF-21, while the level of FGF-19 was reduced. Strong relationships between new hormones and established metabolic parameters were observed. Furthermore, we demonstrated that obesity had the greatest effect on elemental composition in the adipose tissue and liver and that rubidium (Rb) had the highest importance in distinguishing the studied groups of animals. Tissue Rb strongly correlated with both well-known and new markers of obesity. In conclusion, we confirmed serum FGF-19 and FGF-21 as useful new markers of obesity-related metabolic alternations and we robustly propose Rb as a novel indicator of excessive body adiposity and its early consequences. However, further investigations are encouraged to address this clinical issue.

Hepatic FGF21: Its Emerging Role in Inter-Organ Crosstalk and Cancers

Fibroblast growth factor (FGF) 21 is one of the FGF members with special endocrine properties. In the last twenty years, it has attracted intense research and development for its physiological functions that respond to dietary manipulation, pharmacological benefits of improving the macronutrient metabolism, and clinical values as a biomarker of various human diseases. Generally, FGF21 can be produced by major metabolic organs, but only the subgroup from the liver shows canonical endocrine properties, which emphasizes the special value of delineating the unique secretory and functional characteristics of hepatic FGF21. There has been a growth in literature to address the extra-hepatic activities of FGF21, and many striking findings have therefore been published. Yet, they are fragmented and scattered, and controversies are raised from divergent findings. For this reason, there is a need for a systematic and critical evaluation of current research in this aspect. In this review, we focus on the current knowledge about the molecular biology of endocrine FGF21, especially present details on the regulation of circulating levels of FGF21. We also emphasize its emerging roles in inter-organ crosstalk and cancer development.

Advances in FGFs for diabetes care applications

BACKGROUND

Diabetes mellitus (DM) is an endocrine and metabolic disease caused by a variety of pathogenic factors, including genetic factors, environmental factors and behavior. In recent decades, the number of cases and the prevalence of diabetes have steadily increased, and it has become one of the most threatening diseases to human health in the world. Currently, insulin is the most effective and direct way to control hyperglycemia for diabetes treatment at a low cost. However, hypoglycemia is often a common complication of insulin treatment. Moreover, with the extension of treatment time, insulin resistance, considered the typical adverse symptom, can appear. Therefore, it is urgent to develop new targets and more effective and safer drugs for diabetes treatment to avoid adverse reactions and the insulin tolerance of traditional hypoglycemic drugs.

SCOPE OF REVIEW

In recent years, it has been found that some fibroblast growth factors (FGFs), including FGF1, FGF19 and FGF21, can safely and effectively reduce hyperglycemia and have the potential to be developed as new drugs for the treatment of diabetes. FGF23 is also closely related to diabetes and its complications, which provides a new approach for regulating blood glucose and solving the problem of insulin tolerance.

MAJOR CONCLUSIONS

This article reviews the research progress on the physiology and pharmacology of fibroblast growth factor in the treatment of diabetes. We focus on the application of FGFs in diabetes care and prevention.

Bibliometric analysis of fibroblast growth factor 21 research over the period 2000 to 2021

Background: Fibroblast growth factor 21 (FGF-21) is an evolutionarily conserved protein that plays multiple roles in metabolic regulation. Over the past two decades, numerous studies have deepened our understanding of its various functions and its pharmacological value. Nevertheless, most clinical trials have not achieved the desired results, which raises issues regarding its clinical value. In this bibliometric analysis, we evaluated the state of FGF-21 research over the last 20 years and identified important topics, achievements, and potential future directions.

Methods: Publications related to FGF-21 were collected from the Web of Science Core Collection-Science Citation Index Expanded. HistCite, VOSviewer, and CiteSpace were used for bibliometric analysis and visualization, including the analysis of annual publications, leading countries, active institutions and authors, core journals, co-cited references, and keywords.

Results: Altogether, 2,490 publications related to FGF-21 were obtained. A total of 12,872 authors from 2,628 institutions in 77 countries or regions reported studies on FGF-21. The United States of America was the most influential country in FGF-21 research. Alexei Kharitonenkov, Steven A. Kliewer, and David J. Mangelsdorf were the most influential scholars, and endocrinology journals had a core status in the field. The physiological roles, clinical translation, and FGF-21-based drug development were the main topics of research, and future studies may concentrate on the central effects of FGF-21, FGF-21-based drug development, and the effects of FGF-21 on non-metabolic diseases.

Conclusion: The peripheral metabolic effects of FGF-21, FGF-21-based drug development, and translational research on metabolic diseases are the three major topics in FGF-21 research, whereas the central metabolic effects of FGF-21 and the effects of FGF-21 on metabolic diseases are the emerging trends and may become the following hot topics in FGF-21 research.

Phenotypic spectrum of FGF10-related disorders: a systematic review

FGF10, as an FGFR2b-specific ligand, plays a crucial role during cell proliferation, multi-organ development, and tissue injury repair. The developmental importance of FGF10 has been emphasized by the identification of FGF10 abnormalities in human congenital disorders affecting different organs and systems. Single-nucleotide variants in FGF10 or FGF10-involving copy-number variant deletions have been reported in families with lacrimo-auriculo-dento-digital syndrome, aplasia of the lacrimal and salivary glands, or lethal lung developmental disorders. Abnormalities involving FGF10 have also been implicated in cleft lip and palate, myopia, or congenital heart disease. However, the exact developmental role of FGF10 and large phenotypic heterogeneity associated with FGF10 disruption remain incompletely understood. Here, we review human and animal studies and summarize the data on FGF10 mechanism of action, expression, multi-organ function, as well as its variants and their usefulness for clinicians and researchers.

Investigation of the Characteristics of Crimean Congo Hemorrhagic Fever Cases Reported in Afyonkarahisar Province

OBJECTIVE

Crimean Congo Hemorrhagic Fever (CCHF); fever, widespread pain in the body, deterioration in liver function tests; it is a tick-borne viral infectious disease that can cause bleeding and death in the skin, mucous membranes, and sometimes internal organs. In this study, we retrospectively evaluated the clinical, laboratory, and epidemiological characteristics of CCHF cases diagnosed in Afyonkarahisar.

METHODS

Demographic and clinical characteristics, laboratory findings, treatments, and prognoses of patients diagnosed with CCHF in Afyonkarahisar were retrospectively analyzed.

RESULTS

In Afyonkarahisar, it was determined that 35 case reports were made between 2002 and November 2019, the date when the CCHF was first seen in Turkey. A history of tick attachment was detected in 31 subjects. Tick arrest cases were most common in June (12 cases; 34.3%) and July (9 cases; 2.9%). There was a history of living in rural areas in twenty-seven (77.1%) patients, close contact with animals in 12 patients, and a history of contact with animal blood in 4 patients. All the 35 cases that followed resulted in healing and no mortality was observed.

CONCLUSION

CCHF is an endemic disease that still maintains its importance in our country. The most important factor in the control with the disease is to prevent virus contact to prevent transmission. People living in endemic areas should be informed about the precautions to be taken against tick bites, and awareness should be raised by providing education about the disease.

Association between environmental exposure to perchlorate, nitrate, and thiocyanate and serum α-Klotho levels among adults from the National Health and nutrition examination survey (2007–2014)

Background & aims

Aging is a pathophysiological process driven by a diverse set of complex biological processes, and environmental pollution plays an important role in this process. This study aimed to explore the association between serum α-Klotho levels and urinary perchlorate, nitrate, and thiocyanate levels.

Methods

This secondary dataset analysis included 4875 participants (mean age, 57.69 year; male, 49.58%; non-Hispanic White, 47.67%) from the US National Health and Nutrition Examination Survey (2007–2014). Enzyme-linked immunosorbent assay was used to quantify α-Klotho levels, and ion chromatography coupled with electrospray tandem mass spectrometry was used to quantify thiocyanate, nitrate, and perchlorate levels. Multivariate linear regression models were applied to estimate the association between perchlorate, nitrate, and thiocyanate levels and serum α-Klotho levels.

Results

Urinary thiocyanate levels were negatively associated with α-Klotho levels (β = − 0.006; 95% confidence interval, − 0.010 to − 0.003; P = 0.0004) after adjusting for age, sex, body mass index, race, alcohol consumption, estimated glomerular filtration rate, underlying disease, physical activity, smoking status, usual energy intake, and urinary creatinine and serum cotinine levels and mutual adjustment of urinary perchlorate, urinary nitrate, and urinary thiocyanate levels. The α-Klotho level in participants in the highest quartile was higher by 50.567 ng/mL (β = 50.567; 95% confidence interval, 14.407 to 86.726; P = 0.009) than that in participants in the lowest quartile of urinary perchlorate. A linear relationship was observed between urinary thiocyanate and α-Klotho levels.

Conclusions

Urinary thiocyanate levels were negatively associated with serum α-Klotho levels. Urinary thiocyanate should be further investigated as a potential mediator of aging and age-related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03444-2.

The role of fibroblast growth factor 19 in the pathogenesis of nonalcoholic fatty liver disease

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) has emerged as the predominant cause of chronic liver injury worldwide. Bile acids and their receptors are profoundly implicated in the pathogenesis of NAFLD and its progression to nonalcoholic steatohepatitis and cirrhosis.

AREAS COVERED

We conducted extensive literature search using PubMed database, and we summarized the relevant literature. We provided an overview of the fibroblast growth factor 19 (FGF-19)-farnesoid X receptor (FXR) axis and summarized the latest findings derived from animal and human studies concerning the impact of FGF-19 on NAFLD.

EXPERT OPINION

FGF-19, a nutritionally regulated endocrine post-prandial hormone, governs bile acid metabolism, lipid oxidation, lipogenesis, and energy homeostasis. As no approved medication for NAFLD exists, FGF-19 seems to be a propitious therapeutic opportunity for NAFLD, since its administration was associated with ameliorated results in hepatic steatosis, liver inflammation and fibrosis. Furthermore, promising results have been derived from clinical trials concerning the beneficial efficacy of FGF-19 on histological findings and laboratory parameters of NAFLD. However, we should bear in mind the pleiotropic effects of FGF-19 on various metabolically active tissues along with its potential tumorigenic reservoir. Further clinical research is required to determine the clinical application of FGF-19-based therapies on NAFLD.

Targeted therapeutics and novel signaling pathways in non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH)

Non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH) has become the leading cause of liver disease worldwide. NASH, an advanced form of NAFL, can be progressive and more susceptible to developing cirrhosis and hepatocellular carcinoma. Currently, lifestyle interventions are the most essential and effective strategies for preventing and controlling NAFL without the development of fibrosis. While there are still limited appropriate drugs specifically to treat NAFL/NASH, growing progress is being seen in elucidating the pathogenesis and identifying therapeutic targets. In this review, we discussed recent developments in etiology and prospective therapeutic targets, as well as pharmacological candidates in pre/clinical trials and patents, with a focus on diabetes, hepatic lipid metabolism, inflammation, and fibrosis. Importantly, growing evidence elucidates that the disruption of the gut-liver axis and microbe-derived metabolites drive the pathogenesis of NAFL/NASH. Extracellular vesicles (EVs) act as a signaling mediator, resulting in lipid accumulation, macrophage and hepatic stellate cell activation, further promoting inflammation and liver fibrosis progression during the development of NAFL/NASH. Targeting gut microbiota or EVs may serve as new strategies for the treatment of NAFL/NASH. Finally, other mechanisms, such as cell therapy and genetic approaches, also have enormous therapeutic potential. Incorporating drugs with different mechanisms and personalized medicine may improve the efficacy to better benefit patients with NAFL/NASH.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.

New concepts in regulation and function of the FGF23

In comparison to the regulation of calcium homeostasis, which has been widely studied over the last several decades, phosphate homeostasis is little understood. The parathyroid hormone (PTH)/vitamin D axis has traditionally been used as a conceptual framework for understanding mineral metabolism. Recently, the fundamental regulator of phosphate homeostasis, fibroblast growth factor 23 (FGF23), which is produced by osteocytes and is involved in the hormonal bone-parathyroid-kidney axis, has attracted more attention. The secretion of FGF23 is controlled by diet, serum phosphate levels, PTH, and 1,25(OH)2 vitamin D. FGF-23, the FGF receptors and the obligate co-receptor α-Klotho work in concert to affect FGF-23 actions on targeted organs. Despite all efforts to investigate pleotropic effects of FGF23 in various endocrine organs, many aspects of the regulation and functions of FGF23 and the exact crosstalk among FGF23, serum phosphate, calcium, PTH, and vitamin D in the regulation of mineral homeostasis remain unclear; much efforts need to be established before it can be moved toward therapeutic applications. In this regard, we provide a brief overview of the novel findings in the regulation and function of FGF23 and refer to related questions and hypotheses not answered yet, which can be a window for future projects. We also focus on the current knowledge about the role of FGF23 obtained from our researches in recent years.

Research Progress of Fibroblast Growth Factor 21 in Fibrotic Diseases

Fibrosis is a common pathological outcome of chronic injuries, characterized by excessive deposition of extracellular matrix components in organs, as seen in most chronic inflammatory diseases. At present, there is an increasing tendency of the morbidity and mortality of diseases caused by fibrosis, but the treatment measures for fibrosis are still limited. Fibroblast growth factor 21 (FGF21) belongs to the FGF19 subfamily, which also has the name endocrine FGFs because of their endocrine manner. In recent years, it has been found that plasma FGF21 level is significantly correlated with fibrosis progression. Furthermore, there is evidence that FGF21 has a pronounced antifibrotic effect in a variety of fibrotic diseases. This review summarizes the biological effects of FGF21 and discusses what is currently known about this factor and fibrosis disease, highlighting emerging insights that warrant further research.

Physiological and pathophysiological role of endocrine fibroblast growth factors

The endocrine subfamily of fibroblast growth factors (FGF) includes three factors: FGF19, FGF21, FGF23. They act on distal tissues through FGF receptors (FGFRs). The FGFR activation requires two cofactors: α- and β-Klotho, which are structurally related single-pass transmembrane proteins. The endocrine FGFs regulate various metabolic processes involved in the regulation of glucose and lipid metabolism as well as bile acid circulation, vitamin D modulation, and phosphate homeostasis. The FGF-FGFR dysregulation is widely implicated in the pathogenesis of various disorders. Significant alterations in plasma FGF concentration are associated with the most prevalent chronic diseases, including dyslipidemia, type 2 diabetes, cardiovascular diseases, obesity, non-alcoholic fatty liver disease, diseases of the biliary tract, chronic kidney disease, inflammatory bowel disease, osteomalacia, various malignancies, and depression. Therefore, the endocrine FGFs may serve as disease predictors or biomarkers, as well as potential therapeutic targets. Currently, numerous analogues and inhibitors of endocrine FGFs are under development for treatment of various disorders, and recently, a human monoclonal antibody against FGF23 has been approved for treatment of X-linked hypophosphatemia. The aim of this review is to summarize the current data on physiological and pathophysiological actions of the endocrine FGF subfamily and recent research concerning the therapeutic potential of the endocrine FGF pathways.