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As an endocrine cytokine, fibroblast growth factor 21 (FGF21) exhibits anti-inflammatory properties. With the development of lupus nephritis (LN), which is tightly related to pathogenic factors, including inflammation and immune cell dysregulation, we explored the impact of Fibroblast Growth Factor 21 (FGF21) as well as its underlying mechanism. We induced an in vivo LN model using pristane in both wild-type C57BL/6 and FGF21 knockout (FGF21 -/- ) mice. LN serum obtained from 32-week-old wild-type LN mice was used to stimulate RAW264.7 and human renal tubular epithelial (HK-2) cells to mimic an in vitro LN model. Moreover, our findings revealed that FGF21 -/- mice showed more severe kidney injury compared to wild-type mice, as evidenced by increased levels of renal function markers, inflammatory factors, and fibrosis markers. Notably, exogenous administration of FGF21 to wild-type LN mice markedly mitigated these adverse effects. Additionally, we used tandem mass tag (TMT)-based quantitative proteomics to detect differentially expressed proteins following FGF21 treatment. Results indicated that 121 differentially expressed proteins influenced by FGF21 were involved in biological processes such as immune response and complement activation. Significantly upregulated protein Irgm 1, coupled with modulated inflammatory response, appeared to contribute to the beneficial effects of FGF21. Furthermore, Western blot analysis demonstrated that FGF21 upregulated Irgm 1 while inhibiting nucleotide-binding oligomerization domain-like receptors family pyrin domain including 3 (NLRP3) inflammasome expression. Silencing Irgm 1, in turn, reversed FGF21's inhibitory effect on NLRP3 inflammasome. In summary, FGF21 can potentially alleviate pristane-induced lupus nephritis in mice, possibly through the FGF21/Irgm 1/NLRP3 inflammasome pathway., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Fibroblast growth factor-21 (FGF-21) performs a wide range of biological functions in organisms. Here, we report for the first time that FGF-21 suppresses thrombus formation with no notable risk of bleeding. Prophylactic and therapeutic administration of FGF-21 significantly improved the degree of vascular stenosis and reduced the thrombus area, volume and burden. We determined the antithrombotic mechanism of FGF-21, demonstrating that FGF-21 exhibits an anticoagulant effect by inhibiting the expression and activity of factor VII (FVII). FGF-21 exerts an antiplatelet effect by inhibiting platelet activation. FGF-21 enhances fibrinolysis by promoting tissue plasminogen activator (tPA) expression and activation, while inhibiting plasminogen activator inhibitor 1 (PAI-1) expression and activation. We further found that FGF-21 mediated the expression and activation of tPA and PAI-1 by regulating the ERK1/2 and TGF-β/Smad2 pathways, respectively. In addition, we found that FGF-21 inhibits the expression of inflammatory factors in thrombosis by regulating the NF-κB pathway., (© 2022. The Author(s).)

Although FGF21 ameliorates diabetic nephropathy (DN), the efficacy is not satisfactory. Studies demonstrate that FGF21 combined with Insulin exhibits reciprocal sensitization on glucose and lipid metabolism in mice with type 2 diabetes. However, therapeutic effect of combined use of FGF21 and Insulin on DN has not been reported. Therefore, this study explored therapeutic effect and mechanism of combined use of FGF21 and Insulin on DN. Our results showed that compared with Insulin or FGF21 alone, FGF21 combined with Insulin further ameliorated blood glucose, HbAlc, OGTT, renal function, liver function, blood lipid, histopathological changes, oxidative stress and AGEs in the mice of DN (BKS-Lepr em2Cd479 /Gpt). Moreover, FGF21 combined with Insulin further reduced expressions of IL-1β, IL-6, TNF-α via promoting M1 type macrophage into M2 type macrophage. Results of real-time PCR and Western blot showed that FGF21 combined with Insulin upregulated the expressions of autophagy related genes LC3-Ⅱ and BCL-1. Mesangial cells play an important role in the pathological changes of DN mice. However, the effect of FGF21 on mesangial cells has not been reported. In this study, d-glucose was used in high glucose (HG) model in mesangial cells. The results showed that FGF21 significantly reduced the levels of OS, AGEs and cell overproliferation. Meanwhile, FGF21 significantly ameliorated autophagy level via upregulating the phosphorylation of AMPK and downregulating phosphorylation of mTOR. These effects were reversed in siRNA-β-klotho transfected mesangial cells. In conclusion, our results demonstrate that combination FGF21 with Insulin exhibits a better therapeutic effect on DN compared with FGF21 or Insulin alone. This study provides a theoretical basis for combined used of FGF21 and Insulin as a new treatment for DN and further provides theoretical support for application of FGF21 in treatment of DN., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Previous studies reported that FGF21 prolongs life span and delays the body senescence, but the mechanism is not clear. The present study was designed to investigate the effects of FGF21 on hepatic senescence in aging mice and further research the mechanism. The 14-month-old male mice were administered with PBS, FGF21 or metformin once daily for 6 months. Results showed that FGF21 alleviated liver injury and inhibited accumulation of senescence markers SASP, P53 and P16 in the livers of aging mice. Subsequently we found that the aging mice treated by FGF21 showed transition of type 1 macrophages (M1) to type 2 macrophages (M2) in the livers. Next, we used THP-1 macrophages triggered by LPS to study effects of FGF21 on macrophages. Macrophages triggered by LPS exhibited features of M1, but the addition of FGF21 decreased the expression of M1 markers, and promoted the macrophages to exhibit features of M2. Results showed that the effects of FGF21 on macrophages were associated with the AMPK pathway. After adding AMPK inhibitor, the effects of FGF21 were inhibited, which was associated with the NF-κB signaling pathway. Finally, co-culturing differentiated macrophages and hepatocytes, we found that the large amount of pro-inflammatory factors such as IL-6 promoted hepatocyte senescence, which exhibited enhanced P53, P16 and β-galactosidase. This was contrary to hepatocytes co-cultured with macrophages treated by FGF21. These results indicate that FGF21 alleviates hepatic senescence injury by modulating the polarization of macrophages through the AMPK /NF-κB signaling pathway., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Currently, insulin is commonly used in the clinical management of canine diabetes. However, it must be injected preprandially causing much inconvenience to the owners. Therefore, the development of long-acting hypoglycemic agents has attracted much attention in the scientific community. This study aimed to investigate the long-acting hypoglycemic effect of canine fibroblast growth factor 21 (cFGF-21) in diabetic dogs. Diabetic dogs were administered with cFGF-21, polyethylene glycol-modified cFGF-21 (PEG-cFGF-21), or insulin once a day, once every 2, 3, or 4 days subcutaneously. The results showed that cFGF-21 and PEG-cFGF-21 maintained blood glucose comparable to normal levels for 2 and 3 days respectively while insulin maintained the blood glucose for only 2 h after a single injection. After treatment with cFGF-21, oral glucose tolerance test (OGTT) was significantly improved with glycosylated hemoglobin (HbA1c) close to the normal levels. In addition, cFGF-21 significantly repaired islet β cells, increased insulin content, and protected the pancreas from streptozotocin-induced injury. Furthermore, cFGF-21 exhibited both antioxidant and anti-inflammatory properties in the pancreas. We conclude, therefore, that cFGF-21 and PEG-cFGF-21 can maintain blood glucose comparable to normal levels for 2 and 3 days respectively after a single dose. The long-acting efficacy of cFGF-21 can be attributed to improvement in oxidative stress and the reduction of inflammation in the pancreas.

Previous studies indicate that FGF21 has ability to repair nerve injury, but the specific mechanism is less studied. The present study was designed to investigate the effects of FGF21 on neurodegeneration changes in aging and diabetic mice and its mechanism. The diabetic and aging mice were used to study the effects of FGF21 on neurodegeneration and possible mechanisms. These mice were administrated with PBS, FGF21 or metformin once daily for 4 or 6 months, then the mechanism was studied in SH-SY5Y cells. The relevant gene expression for neurodegeneration was assessed by Quantitative Real Time-PCR, Western blot, H&E staining, immunohistochemistry and ELISA. The Western blot results of NeuN showed that FGF21 inhibited the loss of neurons in diabetic and aging mice. H&E staining results showed that the karyopyknosis and tissue edema around dentate gyrus and Cornu Amonis 3 (CA3) area of hippocampus were also inhibited by FGF21 in aging and diabetes mice. In vivo results revealed that administration of FGF21 suppressed the aggregation of tau and β-amyloid 1-42 in the brains of diabetic and aging mice. The aggregation resulted in apoptosis of neurons. Meanwhile, FGF21 significantly reduced the expression of Iba1, NF-κB, IL6 and IL8 (p < 0.05) and enhanced anti-oxidant enzymes (p < 0.05) in aging and diabetic mice. In addition, the phosphorylation of AKT and AMPKα were increased by FGF21 treatment. In vitro experiment showed that the aggregation of tau and β-amyloid 1-42 wereincreased by LPS in SH-SY5Y cells, and FGF21 inhibited the aggregation through inhibiting the expression of NF-κB and promoting the phosphorylation of AKT and AMPKα. In conclusion, FGF21 attenuates neurodegeneration by reducing neuroinflammation and oxidant stress through regulating the NF-κB pathway and AMPKα/AKT pathway, which enhances the protective effect on mitochondria in neurons., (Copyright © 2020 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Although previous studies have shown the potential of FGF21 to regulate blood glucose in animal and humans, the precise mechanisms of the action have not been well explored. The kidney plays a crucial role for glucose homeostasis. The purpose of this study is to explore the effect of FGF21 on renal glucose reabsorption. Administration of type 2 and type 1 diabetic mice with FGF21 reduced the transport maximum of glucose in the kidney and enhanced urinary glucose excretion in a dose-dependent manner. The inhibition of glucose reabsorption results showed little change in diabetic mice treated with Insulin. In physiological state, both FGF21 and insulin had no effect on glucose reabsorption and urinary glucose excretion. Next, we examined the expression of SGLT2 in the kidney, which is an important molecule for renal glucose reabsorption. SGLT2 was highly expressed in the kidneys of diabetic mice. Administration of FGF21 reduced SGLT2 expression in the kidney of diabetic mice. In contrast, the expression of SGLT2 had little change in diabetic mice treated with Insulin. FGF21 and Insulin did not promote SGLT2 expression in physiological state. To explore the mechanism which drives these changes, we detected the expression of PPARδ in mice and HK-2 cells, which plays a major role in regulating SGLT2 expression. Treatment with FGF21 promoted PPARδ expression in diabetic mice, whereas Insulin had no effect on PPARδ expression. At dose of 2 mg/kg FGF21 treatment promoted PPARδ expression in physiological state, whereas at dose of 1 mg/kg FGF21 did not. In HK-2 cells, treatment with FGF21 enhanced PPARδ expression, whereas Insulin treatment had no effect on PPARδ expression. Importantly, the expression of SGLT2 and PPARδ showed little change in HK-2 cells when β-klotho was knocked down. In conclusion, we discovered for the first time that FGF21 ameliorates hyperglycemia in part via reducing renal glucose reabsorption through PPARδ mediated SGLT2 pathway., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Pulmonary fibrosis (PF) is a chronic, progressive lung disease, characterized by excessive matrix formation, destruction of the normal lung architecture, dysfunction and finally death. Fibroblast growth factor 21 (FGF21) is a promising pleiotropic regulator in glucolipid metabolism. Recently, we reported that FGF21 attenuates hepatic fibrogenesis. However, the role of FGF21 on PF is unknown. In this study, mice endotracheal instilled with bleomycin (BLM) were used to study the effect of FGF21 on PF. Bleomycin-instilled mice were administered with pirfenidone (PFD) or FGF21 daily for 3 weeks from 7 days after instillation of BLM. Results showed FGF21 and PFD attenuated the dense deposition of collagen, intense infiltration of inflammatory cells and destruction of tissue architecture in lungs caused by BLM, and also alleviated the increased expression of TGF-β, Col I and α-SMA and decreased the expression of E-cadherin. At the same time, FGF21 also markedly reversed the activity of SOD and T-AOC, decreased the enhanced content of MDA and increased the expression of Nrf-2 in the lungs of BLM-treated mice. To further explore the mechanisms of FGF21 attenuate PF by amelioration of oxidative stress, we examined the effect of FGF21 in A549 cells treated with paraquat (PQ). A549 cells were incubated with PQ plus FGF21 or PFD for 48 h. The results showed that FGF21 and PFD reduced the expression of TGF-β, Col I and α-SMA and increased the expression of E-cadherin in PQ-treated A549 cells. FGF21 also suppressed oxidative stress in PQ-treated A549 cells, as evidenced by a decrease of the MDA level, a reversed activity of antioxidant enzymes and an increased expression of Nrf-2. We conclude that FGF21 inhibits pulmonary fibrosis through activating Nrf-2 pathway, subsequently suppressing oxidative stress, inhibiting ECM deposition and pulmonary fibrogenesis, suggesting that FGF21 has potential as therapeutic agent for treatment of pulmonary fibrosis., (Copyright © 2018. Published by Elsevier Masson SAS.)

Fibroblast growth factor 21 (FGF21) is a member of the FGF family and acts as a potent regulator of glucose and lipid homeostasis, but its effect on renal fibrosis and the underlying mechanisms are totally unknown. The purpose of this study was designed to investigate whether FGF21 has effect on high glucose-induced fibrogenesis in human mesangial cells (HMCs) and the underlying mechanism. High glucose is well known to stimulate the expression of extracelluar matrix (ECM) in human mesangial cells. In humans, overexpression and deposition of ECM lead to renal fibrosis. Thus, in this study, HMCs were incubated in high glucose with or without various concentrations of FGF21. Results demonstrated that the expression of FN, Col, TGF β1 and α-SMA were significantly up-regulated in HMCs. Whereas, treatment with FGF21 down-regulated the expression of FN, Col, TGF β1 and α-SMA. In addition, growth factors are considered to be an important driving force for the pathogenesis of renal fibrosis. Significantly increased PDGF, VEGF and CTGF expression were found in HMCs induced by high glucose. FGF21 treatments significantly decreased these growth factors expression by down-regulating the phosphorylation level of STAT5. Here, we reported for the first time that FGF21 decreases ECM expression by inhibiting STAT5 signal pathway and consequently decreasing the expression of PDGF, VEGF and CTGF., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Previous studies have reported that Fibroblast growth factor 21 (FGF21) can regulate inflammation and may play an important role in inflammatory and immune-mediated diseases, such as autoimmune diseases. Adalimumab is one of the clinically effective anti-rheumatoid arthritis (RA) drugs. The aim of this study was to compare the therapeutic efficacy of FGF21 and Adalimumab on collagen-induced arthritis (CIA) model mice. Mice with CIA were subcutaneously treated with FGF21 or Adalimumab at dose of 1mgkg -1 d -1 , respectively. Our results showed that FGF21 significantly alleviated the severity of arthritis by reducing cellular immune responses and exerted the similar anti-inflammatory effects with Adalimumab in decreasing the mRNA and protein expression levels of IL-2, IL-6 and IL-17. However, the expression levels of IL-1β, RANKL and IL-10 in the mice treated with FGF21 were decreased 2.2-fold, 2.5-fold and increased 4.3-fold compared with Adalimumab, respectively. However, the levels of TNF-α in the mice treated with Adalimumab were lower than those in the mice treated with FGF21. Western blotting results demonstrated that FGF21 displayed equivalent effects with Adalimumab by inhibiting NF-κB/IκBα signaling pathway. However, FGF21 could also regulate systematic inflammatory response and the mechanism maybe related to other signal pathway. In summary, FGF21 exerts comparable pharmacological efficacy with Adalimumab by regulating systematic inflammatory response, providing that FGF21 may be a promising therapeutic agent for RA patients., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Fibroblast growth factor 21 (FGF21) is a promising regulator of glucose and lipid metabolism with multiple beneficial effects including hypoglycemic and lipid-lowering. Previous studies have reported that FGF21 is expected to become a new drug for treatment of diabetes. Liraglutide and insulin glargine are the two representative anti-diabetic biological drugs. In the current study, we aim to compare the long-term pharmacological efficacy of mFGF21 (an FGF21 analogue), liraglutide and insulin glargine in type 2 diabetic db/db mice. Db/db mice were initially treated with three kinds of proteins (25nmol/kg/day) by subcutaneous injection once a day for 4weeks, then subsequently be treated with once every two days for next 4weeks. After 8weeks of treatments, the blood glucose levels, body weights, glycosylated hemoglobin levels, fasting insulin levels, serum lipid profiles, hepatic biochemical parameters, oral glucose tolerance tests and hepatic mRNA expression levels of several proteins (GK, G6P, GLUT-1 and GLUT-4) associated with glucose metabolism of the experimental mice were detected. Results demonstrated that three proteins could significantly decrease the fed blood glucose levels of db/db mice. After treatment for 1week, the fed blood glucose levels of db/db mice in liraglutide group were significantly lower than those in mFGF21 and insulin glargine groups. However, after 2weeks of administration, the long-lasting hypoglycemic effect of mFGF21 was superior to liraglutide and insulin glargine up to the end of the experiments. Compared with liraglutide and insulin glargine, mFGF21 significantly reduced the glycosylated hemoglobin levels and improved the ability on glycemic control, insulin resistance, serum lipid and liver function states in db/db mice after 8weeks treatments. In addition, mFGF21 regulated glucose metabolism through increasing the mRNA expression levels of GK and GLUT-1, and decreasing the mRNA expression level of G6P. But liraglutide and insulin glargine could only up-regulate the mRNA expression of GLUT-4. In summary, as a hypoglycemic drug for long-term treatment, mFGF21 has the potential to be an ideal drug candidate for the therapy of type 2 diabetes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The aim of this study is to explore a new method-high dose starting and low dose maintaining for PEGylated Fibroblast growth factor 21 (pFGF-21) treatment. Db/db mice were initially treated with pFGF-21 of high dose, then treated with pFGF-21 of low doses. The mice were treated with pFGF-21 at initial dose of 1.0mg/kg for 14days, then treated with pFGF-21 at maintenance doses of 0.125/0.250/0.375/0.500mg/kg for 30days. The hypoglycemic and hypolipidemic effects of pFGF-21 of different maintenance doses were compared. The pharmacological efficacy of the maintenance doses of pFGF-21 was evaluated by blood glucose levels, oral glucose tolerance test, glycosylated hemoglobin levels, insulin levels, body weight, lipid profile parameters, the mRNA expressions of glycolysis-related genes, the mRNA expressions of gluconeogenesis-related genes and the mRNA expressions of lipid metabolism-related genes. Results showed that in comparison to the mice treated only with initial dose, the treatment with pFGF-21 at maintenance doses of 0.125/0.250/0.375/0.500mg/kg exhibited favorable efficacy in lowering blood glucose levels and glycosylated hemoglobin levels, thus alleviating insulin resistance and improving dyslipidemia. However, among all of the maintenance doses, the dose of 0.125mg/kg was less effective than the other maintenance doses. These results suggest that using the treatment method of high dose of PEGylated FGF-21 in the start and low dose maintaining results in favorable control of the glycolipid metabolic balance. This study provides a new method for PEGylated FGF-21 treatment which is beneficial to promote the clinical application of PEGylated FGF-21., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Our previous report has shown that FGF21 has anti-inflammatory properties in a collagen-induced arthritis (CIA) model. In this study, the underlying molecular mechanisms of action were also investigated using RAW 264.7 cells, a murine monocyte-macrophage. RAW 264.7 cells were pre-incubated with various concentrations (2000, 500, 100ng/ml) of FGF21 and stimulated with LPS to induce oxidative stress and inflammation. The result of flow cytometry showed that β-Klotho, FGF21 specific receptor, was expressed in murine splenic macrophages and RAW 264.7. In vitro, FGF21 reduced the expression of TNF-α, IL-1β, IL-6 and IFN-γ and increased the level of IL-10 in a dose-dependent manner in LPS-stimulated RAW 264.7 macrophages. FGF21 also suppressed profound elevation of ROS production and oxidative stress, as evidenced by an increase of the MDA level and depletion of the intracellular GSH level, and restored the activities of antioxidant enzymes SOD and GSH-Px in LPS-stimulated RAW 264.7 macrophages. Moreover, FGF21 inhibited LPS-induced nuclear factor-κB (NF-κB) activation, including degradation of I-κB and nuclear translocation of p65. In addition, the result of Western blot and real-time PCR showed that FGF21 induced heme oxygenase-1 (HO-1) expression and increased the nuclear transcription factor-E2-related factor 2 (Nrf2) levels in a dose-dependent manner in LPS-stimulated RAW 264.7 macrophages. In conclusion, the results suggest that macrophages are the targets for the anti-inflammatory effects of FGF21, and FGF21 exerted an anti-inflammatory effect mainly via enhancing Nrf2-mediated anti-oxidant capacity and suppressing NF-κB signaling pathway., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The aim of this study is to evaluate the role of fibroblast growth factor 21 (FGF21) in nonalcoholic fatty liver disease (NAFLD) and seek to determine if its therapeutic effect is through induction of autophagy. In this research, Monosodium L-glutamate (MSG)-induced obese mice or normal lean mice were treated with vehicle, Fenofibrate, and recombinant murine FGF21, respectively. After 5 weeks of treatment, metabolic parameters including body weight, blood glucose and lipid levels, hepatic and fat gene expression levels were monitored and analyzed. Also, fat-loaded HepG2 cells were treated with vehicle or recombinant murine FGF21. The expression levels of proteins associated with autophagy were detected by western blot, real-time PCR, and transmission electron microscopy (TEM). Autophagic flux was monitored by laser confocal microscopy and western blot. Results showed that FGF21 significantly reduced body weight (P < 0.01) and serum triglyceride, improved insulin sensitivity, and reversed hepatic steatosis in the MSG model mice. In addition, FGF21 significantly increased the expression of several proteins related to autophagy both in MSG mice and fat-loaded HepG2 cells, such as microtubule associated protein 1 light chain 3, Bcl-2-interacting myosin-like coiled-coil protein-1 (Beclin-1), and autophagy-related gene 5. Furthermore, the evidence of TEM revealed an increased number of autophagosomes and lysosomes in the model cells treated with FGF21. In vitro experimental results also showed that FGF21 remarkably increased autophagic flux. Taken together, FGF21 corrects multiple metabolic parameters on NAFLD in vitro and in vivo by inducing autophagy.

FGF-21 has become a potential drug candidate for the treatment of type 2 diabetes. Previous studies have demonstrated that PEGylation of FGF-21 could significantly increase its in vivo half-life and provide its long-lasting blood glucose-lowering effect. To accelerate the development of PEGylated FGF-21 for clinical application as a long-acting antidiabetes drug, we prepared ahmFGF-21 (FGF-21 mutant) and PEGylated ahmFGF-21 in Escherichia coli Rosetta (DE3) by high cell density fermentation at a 50-L scale and pilot-scale purification. The physical and chemical properties of the purified proteins were analyzed in this study, including purity, molecular weight, isoelectric point, bacterial endotoxin, PEGylated site and second structure. As well as the in vitro glucose uptake activity and in vivo anti-diabetic effect were evaluated. Under the optimal fermentation and purification conditions, the average bacterial yield and expression level of target protein of three batches attained 52.2±4.6g/L and 223.92±5.41mg/L, respectively. The purity of pilot product was above 98% by SDS-PAGE (non-reducing or reducing) and HPLC (SEC or RPC) analysis and the final yield of PEGylated ahmFGF-21 was 87.91±1.49mg/L, which indicated that the pilot-scale production process was relatively stable. N-terminal sequencing and circular dichroism (CD) spectroscopy results showed that modification site of PEGylated ahmFGF-21 was alanine at N-terminal and the second structure of ahmFGF-21 had no obvious changes after PEGylation. Compared with ahmFGF-21, the long-acting hypoglycemic effect of PEGylated ahmFGF-21 prepared in the pilot-scale production was significantly improved in type 2 diabetic db/db mice. Our results demonstrated that the pilot-scale production process of PEGylated ahmFGF-21 was successfully established, which was very important for the clinical application., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Previous studies reveal that fibroblast growth factor 21 (FGF21) sensitizes insulin to achieve a synergy in regulating glucose metabolism. Here, we report that insulin sensitizes FGF21 in regulating both glucose and lipid metabolisms. db/db diabetic mice were subcutaneously administrated once a day for 6 weeks. Effective dose of insulin (1 U) could control blood glucose level of the db/db mice for maximum of 2 h, increased the body weight of the db/db mice and did not improve serum lipid parameters. In contrast, effective dose of FGF21 (0.5 mg/kg) could maintain blood glucose of the db/db mice at normal level for at least 24 h, repressed the weight gain of the mice and significantly improved lipid parameters. Ineffective doses of FGF21 (0.125 mg/kg) and insulin had no effect on blood glucose level of the db/db mice after 24 h administration, body weight or lipid parameters. However, combination of the two ineffective doses could maintain blood glucose level of the db/db mice for at least 24 h, suppressed weight gain and significantly improved lipid parameters. These results suggest that insulin sensitizes FGF21 in regulating both glucose and lipid metabolism. The results aimed to study the molecular basis of FGF21 sensitization indicates that combination of the two ineffective doses increased the mRNA expression of glut1, glut4, β-Klotho, sirt1, pgc-1α, ucp-1 and AKT phosphorylation, decreased fasn. The results demonstrate that insulin sensitizes FGF21 through elevating the phosphorylation of common gene Akt and amplifying FGF21 downstream signaling, including increasing expression of glut1 sirt1, pgc-1α, ucp-1, and decreasing fasn expression. In summary, we reports herein for the first time that insulin sensitizes FGF21 to achieve a synergy in regulating glucose and lipid metabolism. Along with previous studies, we conclude that the synergistic effect between FGF21 and insulin is realized through mutual sensitization.

Diabetes mellitus is a common endocrinopathy in dog. Fibroblast growth factor 21 (FGF-21) is a secreted protein, which is involved in glucose homeostasis. We speculate that the recombinant canine FGF-21 (cFGF-21) has the potential to become a powerful therapeutics to treat canine diabetes. The cFGF-21 gene was cloned and expressed in E. coli Rosetta (DE3). After purification, a cFGF-21 protein with the purity exceeding 95% was obtained. Mouse 3T3-L1 adipocytes and type 1 diabetic mice/dogs induced by STZ were used to examine the biological activity of cFGF-21 in vitro and in vivo, respectively. Results showed that cFGF-21 stimulated glucose uptake in adipocytes significantly in a dose-dependent manner, and reduced plasma glucose significantly in diabetic mice/dogs. After treatment with cFGF-21, the serum insulin level, glycosylated hemoglobin (HbA1c) level and the expressions of the hepatic gluconeogenesis genes (glucose-6-phosphatase, G6Pase and phosphoenolpyruvate carboxykinase, PCK) of the diabetic mice/dogs were attenuated significantly. In the mouse experiment, we also found that the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and the expression of suppressor of cytokine signaling 3 (SOCS3) were up-regulated significantly in the livers after treatment. Histopathological and immunohistochemical results showed that treatment with cFGF-21 promoted recovery of pancreatic islets from STZ-induced apoptosis. Besides, we also found that treatment with cFGF-21 protected liver against STZ or hyperglycemia induced damage and the mechanism of this action associated with inhibiting oxidative stress. In conclusion, cFGF-21 represents a promising candidate for canine diabetes therapeutics. The mechanism of cFGF-21 ameliorates hyperglycemia associated with inhibiting hepatic gluconeogenesis by regulation of STAT3 signal pathway and improving pancreatic beta-cell survival.

Fibroblast growth factor 21 (FGF-21) is a secreted protein, which has anti-diabetic and lipocaic effects, but its ability to protect against hepatic fibrosis has not been studied. In this study, we investigated the ability of FGF-21 to attenuate dimethylnitrosamine (DMN)-induced hepatic fibrogenesis in mice and the mechanism of its action. Hepatic fibrosis was induced by injection of DMN, FGF-21 was administered to the mice once daily in association with DMN injection till the end of the experiment. Histopathological examination, tissue 4-hydroxyproline content and expressions of smooth muscle α-actin (α-SMA) and collagen I were measured to assess hepatic fibrosis. Ethanol/PDGF-BB-activated hepatic stellate cells (HSCs) were used to understand the mechanisms of FGF-21 inhibited hepatic fibrogenesis. Results showed that FGF-21 treatment attenuated hepatic fibrogenesis and was associated with a significant decrease in intrahepatic fibrogenesis, 4-hydroxyproline accumulation, α-SMA expression and collagen I deposition. FGF-21 treatment inhibited the activation of HSCs via down-regulating the expression of TGF-β, NF-κB nuclear translocation, phosphorylation levels of smad2/3 and IκBα. Besides, FGF-21 treatment caused activated HSC apoptosis with increasing expression of Caspase-3, and decreased the ratio of Bcl-2 to Bax. In conclusion, FGF-21 attenuates hepatic fibrogenesis and inhibits the activation of HSC warranting the use of FGF-21 as a potential therapeutic agent in the treatment of hepatic fibrosis., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: In this study, we explored whether treatment with FGF-21 could prevent diethylnitrosamine (DEN) induced hepatocarcinogenesis in mice., Methods & Results: Hepatoma was induced by injection of DEN every three days for 18 weeks. For the prophylactic experiment, mice were firstly injected with FGF-21 for 2 weeks, then FGF-21 was administered to the mice once daily in association with DEN injection till the end of the experiment. The hepatoma incidence of mice treated with FGF-21 was 13.3%, while the incidence of mice treated with saline was 61.5%. To understand the mechanisms, we compared the expression of βklotho (KLB) and oxidative stress level in the livers between the mice treated with FGF-21 and saline. We found that FGF-21 could suppress DEN-induced oxidative stress and up-regulate the expression of KLB in the livers. To confirm these results, we compared the expression of KLB in L02 cells stimulated with or without FGF-21. Besides, we established DEN-induced oxidative stress cell model to affirm the relationship between FGF-21 and DEN-induced oxidative stress in vitro. Results showed that FGF-21 increased the expression of KLB and diminished the DEN-induced oxidative stress in vitro in a dose dependent manner., Conclusion: Systemic administration of FGF-21 can prevent DEN-induced hepatocarcinogenesis via suppressing oxidative stress and increasing the expression of KLB.

Fibroblast growth factor-21 (FGF-21) is a new member of the FGF family and potential drug candidate for the treatment of type 2 diabetes mellitus. However, FGF-21 protein has short half-life in vivo, which severely affects its clinical application. In the present study, PEGylated FGF-21 was prepared by modifying the N-terminus of hFGF-21 with 20 kDa mPEG-ALD. The long-acting hypoglycemic effect of PEGylated FGF-21 and liraglutide was compared on type 2 diabetic db/db mice. The pharmacological efficacy of the compounds was evaluated by blood glucose levels, body weight, glycosylated hemoglobin levels, insulin levels, oral glucose tolerance test, lipid levels, and liver function parameters. We noticed that both PEGylated FGF-21 and liraglutide could significantly decrease plasma glucose in db/db mice. However, comparing to liraglutide treatments, PEGylated FGF-21 therapy resulted in more significant effect in lowering blood glucose levels and glycosylated hemoglobin levels, alleviating insulin resistance, improving lipid profile, liver function, and glucose control of the experimental mice. Our results suggest that PEGylated FGF-21 appears more beneficial anti-diabetic effect in type 2 diabetic mice than liraglutide, which holds significant promise as an ideal candidate for the treatment of type 2 diabetic patients.

Fibroblast growth factor 21 (FGF21) is a hormone secreted predominantly in the liver, pancreas and adipose tissue. Recently, it has been reported that FGF21-Transgenic mice can extend their lifespan compared with wild type counterparts. Thus, we hypothesize that FGF21 may play some roles in aging of organisms. In this study d-galactose (d-gal)-induced aging mice were used to study the mechanism that FGF21 protects mice from aging. The three-month-old Kunming mice were subcutaneously injected with d-gal (180mg·kg(-1)·d(-1)) for 8weeks and administered simultaneously with FGF21 (1, 2 or 5mg·kg(-1)·d(-1)). Our results showed that administration of FGF21 significantly improved behavioral performance of d-gal-treated mice in water maze task and step-down test, reduced brain cell damage in the hippocampus, and attenuated the d-gal-induced production of MDA, ROS and advanced glycation end products (AGEs). At the same time, FGF21 also markedly renewed the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and total anti-oxidation capability (T-AOC), and decreased the enhanced total cholinesterase (TChE) activity in the brain of d-gal-treated mice. The expression of aldose reductase (AR), sorbitol dehydrogenase (SDH) and member-anchored receptor for AGEs (RAGE) declined significantly after FGF21 treatment. Furthermore, FGF21 suppressed inflamm-aging by inhibiting IκBα degradation and NF-κB p65 nuclear translocation. The expression levels of pro-inflammatory cytokines, such as TNF-α and IL-6, decreased significantly. In conclusion, these results suggest that FGF21 protects the aging mice brain from d-gal-induced injury by attenuating oxidative stress damage and decreasing AGE formation., (Copyright © 2015 Elsevier Inc. All rights reserved.)

FGF21 is recently discovered with pleiotropic effects on glucose and lipid metabolism. However, the potential protective effect of FGF21 against D-gal-induced injury in the liver has not been demonstrated. The aim of this study is to investigate the pathophysiological role of FGF21 on hepatic oxidative injury and apoptosis in mice induced by D-gal. The 3-month-old Kunming mice were subcutaneously injected with D-gal (180 mg kg(-1) d(-1)) for 8 weeks and administered simultaneously with FGF21 (5 or 1 mg kg(-1) d(-1)). Our results showed that the administration of FGF21 significantly alleviated histological lesion including structure damage, degeneration, and necrosis of hepatocytes induced by D-gal, and attenuated the elevation of liver injury markers, serum AST, and ALP in a dose-dependent manner. FGF21 treatment also suppressed D-gal-induced profound elevation of ROS production and oxidative stress, as evidenced by an increase of the MDA level and depletion of the intracellular GSH level in the liver, and restored the activities of antioxidant enzymes SOD, CAT, GSH-Px, and T-AOC. Moreover, FGF21 treatment increased the nuclear abundance of Nrf2 and subsequent up regulation of several antioxidant genes. Furthermore, a TUNEL assay showed that D-gal-induced apoptosis in the mouse liver was significantly inhibited by FGF21. The expression of caspase-3 was markedly inhibited by the treatment of FGF21 in the liver of D-gal-treated mice. The levels of PI3K and PBK/Akt were also largely enhanced, which in turn inactivated pro-apoptotic signaling events, restoring the balance between pro- and anti-apoptotic Bcl-2 and Bax proteins in the liver of D-gal-treated mice. In conclusion, these results suggest that FGF21 protects the mouse liver against D-gal-induced hepatocyte oxidative stress via enhancing Nrf2-mediated antioxidant capacity and apoptosis via activating PI3K/Akt pathway.

It has been demonstrated that circulating FGF21 levels are elevated in the serum and synovial fluid of patients with rheumatoid arthritis (RA). The aim of this study is to investigate efficacy of FGF21 for treatment of RA and the molecular mechanisms of the therapeutic effect on collagen-induced arthritis (CIA). Mice with CIA were subcutaneously administered with FGF21 (5, 2 or 1mg·kg(-1)·d(-1)), IL-1β antibody (5mg·kg(-1)·d(-1)), IL-17A antibody (5mg·kg(-1)·d(-1)) and dexamethasone (DEX) (1mg·kg(-1)·d(-1)), respectively. The effects of treatment were determined by arthritis severity score, histological damage and cytokine production. The activation of NF-κB was analyzed by Western blotting. We also detected the levels of oxidative stress parameters. Our results showed that FGF21 had beneficial effects on clinical symptom and histological lesion of CIA mice. Similar to antibody and DEX, FGF21 treatment alleviated the severity of arthritis by reducing humoral and cellular immune responses and down-regulating the expression of pro-inflammatory cytokines. FGF21 treatment also reduced the expression of TNF-α, IL-1β, IL-6, IFN-γ and MMP-3 and increased level of IL-10 in the spleen tissue or the plasma of CIA mice in a dose-dependent manner. Furthermore, FGF21 inhibited IκBα degradation and NF-κB p65 nuclear translocation and induced significant changes of oxidative stress parameters (MDA, SOD, CAT, GSH-PX and GSH) in the plasma. FGF21 exerts therapeutic efficacy for RA through antioxidant reaction and inhibiting NF-κB inflammatory pathway. This study provides evidence that FGF21 may be a promising therapeutic agent for RA patients., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Objective: In this study, we compared the long-acting hypoglycemic effect of PEGylated FGF21 (PEG-FGF21) with insulin glargine in mice with STZ-induced type 1 diabetes., Methods: PEG-FGF21 and insulin glargine were administered once daily for two months, and blood glucose was measured prior to the next administration. Real-time PCR was used to measure mRNA expression of glucokinase (GK), glucose 6-phosphatase (G6pase), phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 1 (GLUT1) and glucose transporter 4 (GLUT4)., Results: During long-term treatment, the blood glucose of untreated mice remained at 25.0 to 28.0mmol/L for the whole experiment, and the blood glucose of mice treated with insulin glargine remained at 16.5 to 18.0mmol/L. However, mice treated with PEG-FGF21 had lower blood glucose levels of 8.0 to 9.0mmol/L on day 10 and maintained this level until the end of the experiment. qRT-PCR showed that PEG-FGF21 up-regulated mRNA expression of GK and GLUT1, and down-regulated mRNA expression of G6Pase and PEPCK. Insulin glargine up-regulated mRNA expression of GLUT4, but had no effect on GK, G6Pase, PEPCK or GLUT1., Conclusions: PEG-FGF21 has a better long-acting efficacy than insulin glargine. PEG-FGF21 achieves glucose clearance by accelerating glycolysis by up-regulating expression of GK and GLUT1 and inhibiting gluconeogenesis via down-regulation of G6Pase and PEPCK expression., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Fibroblast growth factor 21 (FGF21), a recently identified member of the FGF superfamily, is mainly secreted from the liver and adipose tissues and plays an important role in improving metabolic syndrome and homeostasis. The aim of this study is to evaluate the role of FGF21 in alcoholic fatty liver disease (AFLD) and to determine if it has a therapeutic effect on AFLD. In this paper, we tested the effect of FGF21 on alcohol-induced liver injury in a murine model of chronic ethanol gavage and alcohol-treated HepG2 cells. Male KM mice received single dose of 5 g/kg ethanol gavage every day for 6 weeks, which induced significant fatty liver and liver injury. The alcohol-induced fatty liver cell model was achieved by adding ethanol into the medium of HepG2 cell cultures at a final concentration of 75 mM for 9 days. Results showed that treatment with recombinant FGF21 ameliorated alcoholic fatty liver and liver injury both in a murine model of chronic ethanol gavage and alcohol-treated HepG2 cells. In addition, FGF21 treatment down-regulated the hepatic expression of fatty acid synthetic key enzyme, activated hepatic AMPK-SIRT1 pathway and significantly down-regulated hepatic oxidative stress protein. Taken together, FGF21 corrects multiple metabolic parameters of AFLD in vitro and in vivo by activation of the AMPK-SIRT1 pathway., (© The Author 2014. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.)

Fibroblast growth factor -21 (FGF-21) is a recently discovered metabolic regulation factor, regulating glucose and lipid metabolism and increasing insulin sensitivity. FGF-21 is expected to be a potential anti-diabetic drug. Expression of FGF-21 as inclusion bodies has advantages for high yield and purity, but the bioactivity of the protein is almost totally lost after denature and renature. That is why FGF-21 is currently expressed in soluble form. As a result, the yield is considerably low. In this study, we used SUMO vector to express SUMO-human FGF-21 (SUMO-hFGF-21) in form of inclusion body. We optimized the culture conditions to increase the yield of the bioactive human fibroblast growth factor-21. We applied the hollow fiber membrane filtration column to enrich the bacteria, wash, denature and renature inclusion bodies. After affinity and gel filtration chromatography, we examined the hypoglycemic activity of FGF-21 by the glucose uptake assay in HepG2 cells. We also detected the blood glucose concentration of type 2 diabetic db/db model mice after short or long-term treatment. The results show that the yield of ihFGF-21 was 4 times higher than that of shFGF-21. The yield was 20 mg/L for ihFGF-21 vs. 6 mg/L for shFGF-21. The purity of ihFGF-21 was above 95%, while shFGF-21 was 90%. Compared with the traditional method of extracting inclusion bodies, the production cycle was about three times shortened by application of hollow fiber membrane filtration column technology, but the bioactivity did not significantly differ. This method provides an efficient and cost-effective strategy to the pilot and industrial production of hFGF-21.

FGF-21 is a potential candidate for the treatment of type 2 diabetes mellitus. However, the clinical application of wild-type human FGF-21 is challenging due to some limitations, such as its poor hypoglycemic potency and short in vivo half-life. In this paper, we have produced an FGF-21 mutant (ahmFGF-21) by exchanging the functional domain of hFGF-21 with that of mFGF-21 to improve the potency of FGF-21. Results showed that the ahmFGF-21 protein was more potent than wild-type hFGF-21 in stimulating glucose uptake in vitro and lowering blood glucose levels of diabetic animals. To decrease its immunogenicity and increase its biostability, the N-terminus of ahmFGF-21 was modified in a sitespecific manner with 20 kDa mPEG-propionaldehyde (mPEG-ALD). We found that the preservation time of ahmFGF-21 in vitro was significantly prolonged after PEGylation. The serum antibody levels against ahmFGF-21 in immunized rabbits with the PEGylated ahmFGF-21 were significantly reduced than those with the unmodified ahmFGF-21, and the target protein concentration in the rabbits administrated with the PEGylated ahmFGF-21 increased 9.5-fold higher than that of the unmodified ahmFGF-21. The animal experimental results showed that PEGylation of ahmFGF-21 enhanced the hypoglycemic effect in diabetic mice. These results suggest that the in vitro and in vivo hypoglycemic effects of FGF-21 are significantly enhanced by genetic modification and the metabolic pharmacology of FGF-21 in type 2 diabetic mice is improved by PEGylation at a specific site.

Fibroblast growth factor (FGF)-21 is a member of the FGF superfamily based on sequence homology. However, unlike most members of this family it does not show any mitogenic activity in all cell types tested. The objective of this study is to identify and characterize receptors for this molecule. Sequencing of the cDNA clones from 3T3-L1 adipocytes indicates that the only isoforms for FGFR-1 and 2 expressed in 3T3-L1 cells are 1IIIc and 2IIIc, respectively, suggesting that FGF-21 regulates glucose metabolism in 3T3-L1 adipocytes through FGFR-1IIIc and FGFR-2IIIc.

The aim of the study is to construct two vectors for efficient expression of soluble recombinant proteins. The first vector was constructed by cloning the HisSUMO fragment into an expression vector pET30a(+) to fuse with the gene of interest (designated as HisSUMO Express). The second vector was constructed in the same way, but with a hydroxylamine cleavage site between HisSUMO and the gene of interest for an economic purpose (designated as HisSUMO Economic). The mouse fibroblast growth factor-21(mFGF-21), which was difficult to express in routine-used expression vectors, was taken as an example to test the vectors. The results showed that the mFGF-21 was expressed at high level in both vectors. The Sumo/mFGF-21 fusion protein accounted for more than 40% of the total bacterial protein. The fusion protein was purified with Ni-TNA column, and the HisSUMO was removed by cleavage of the fusion protein with either hydroxylamine solution or SUMO protease I. The concentration of the purified mFGF-21 mature protein was 54 mg/L and the recovery rate was 6%. The purified proteins derived from either hydroxylamine or SUMO protease I cleavage could stimulate glucose up-take by adipocytes. These results indicated that both HisSUMO Express and HisSUMO Economic were useful expression vectors for efficient expression of soluble recombinant proteins.

Elevated levels of circulating fibroblast growth factor 21 (FGF21) have been reported in patients with hyperuricemia. However, the effect of FGF21 in hyperuricemic nephropathy (HN) remains unexplored. Here, we investigated the effect and mechanism of action of FGF21 on HN. HN model was induced with adenine and potassium oxysalt in wild‐type C57BL/6 mice and FGF21−/− mice. For in vitro studies, human renal tubular epithelial (HK‐2) cells were exposed to uric acid with/without FGF21 or β‐Klotho‐siRNA. Here, we reported aggravated renal dysfunction and structural damage in the FGF21−/− mice compared to the wild‐type mice. These were evident in the upsurge of inflammatory factors IL‐1β, TNF‐α, IL‐6, and IL‐18; fibrotic markers Collagen I and α‐SMA; and oxidation products ROS and MDA. However, exogenous administration of FGF21 to wild‐type HN mice significantly reversed these negative effects. In terms of mechanism, FGF21 significantly inhibited NF‐κB/NLRP3 and TGF‐β1/Smad3 pathways and promoted nuclear translocation of Nrf2 both in vivo and in vitro. Furthermore, the silencing of β‐Klotho was marked by the attenuation of the improved effect of FGF21 on cell damage. In conclusion, our studies revealed that exogenous FGF21 treatment significantly improved HN, which was achieved by the inhibition of inflammation, fibrosis, and oxidative stress. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis, a chronic degenerative autoimmune disease is hallmarked by tenacious inflammation of synovial membranes causing cartilage destruction and bone erosion. The search for effective therapies to mitigate its degenerative conditions remains partly elusive. Fibroblast growth factor 21 (FGF21) is known to modulate inflammation, playing a significant role in immune-mediated diseases such as rheumatoid arthritis. Here, we histopathologically evaluate the therapeutic efficacy of FGF21 in collagen-induced arthritis (CIA) mice. CIA mice were subcutaneously treated with FGF21 (3 mg/kg) for three consecutive weeks. Arthritic severity was scored followed by histopathological evaluation of the joints and immunohistochemistry using rabbit ant-cathepsin K, IL-10, MMP1, and 3 antibodies. Our data revealed that FGF21 significantly mitigated the severity of arthritis. Histopathologically, the articular structure was considerably enhanced by FGF21 through the reduction in the expression of cathepsin K and MMP3 whiles upregulating the expression of IL-10. Taken together, our findings suggest that FGF21 preserves the integrity of the articular structure thereby preventing cartilage and bone destruction in CIA mice. FGF21, therefore, has therapeutic prospects in the treatment of RA. [ABSTRACT FROM AUTHOR]

Fibroblast growth factor-21 (FGF21) is a member of the family of fibroblast growth factors (FGFs). FGF21 (synthesized by many organs) has been studied extensively for its role in the regulation of energy homeostasis. FGF21 came into the spotlight after its beneficial metabolic effects in reducing blood glucose, and weight in obesity were identified. Since then, FGF21 has been extensively exploited for therapeutic purposes and clinical applications with significant achievements. Its therapeutic roles in diabetes, obesity, cardiovascular diseases, fibrosis, cancer and aging among others have been studied over the last decade with significant strides making it a promising candidate for the management of chronic diseases. Here we review the therapeutic prospects of FGF21 with emphasis on the management of chronic diseases, and breakthroughs in its shortfalls. The future of FGF21 as a therapeutic agent is auspicious and will help revolutionize the world of medicine. [ABSTRACT FROM AUTHOR]