Metformin Improves the Prerequisites for FGF21 Signaling in Patients With Type 2 Diabetes

CONTEXT

Fibroblast growth factor (FGF) 21 acts as a metabolic regulator and its therapeutic use is under investigation. FGF21 signaling requires binding to surface receptors, FGFR1c and β-klotho. FGF21 resistance is observed in metabolic diseases and FGF21 signaling is regulated by fibroblast activation protein (FAP). Metformin is reported to influence expression and secretion of FGF21 in preclinical models, but the effect of metformin on FGF21 in a clinical trial remains unknown.

OBJECTIVE

To investigate how 12 weeks of treatment with metformin affects the FGF21 signaling pathway in patients with type 2 diabetes (T2D).

METHODS

Randomized, placebo-controlled study in patients with T2D (n = 24) receiving either metformin (1000 mg twice daily) or placebo. A control group of body mass index- and age-matched healthy individuals (n = 12) received a similar dose of metformin. Blood samples and muscle and fat biopsies were collected at study entry and after 12 weeks.

METHODS

Plasma levels of FGF21 (total and intact) and FAP (total and activity) were measured. Muscle and fat biopsies were analyzed for mRNA and protein expression of targets relevant for activation of the FGF21 signaling pathway.

RESULTS

Circulating FAP activity decreased after metformin treatment compared with placebo (P = .006), whereas FGF21 levels were unchanged. Metformin treatment increased gene and protein expression of β-klotho, FGFR1c, and pFGFR1c in adipose tissue. FGF21 mRNA expression increased in muscle tissue after metformin and the FGF21 protein, but not mRNA levels, were observed in adipose tissue.

CONCLUSION

Our findings suggest that metformin suppresses the circulating FAP activity and upregulates the expression of FGFR1c and β-klotho for increased FGF21 signaling in adipose tissue, thus improving peripheral FGF21 sensitivity.

Mechanism of fibroblast growth factor 21 in cardiac remodeling

Cardiac remodeling is a basic pathological process that enables the progression of multiple cardiac diseases to heart failure. Fibroblast growth factor 21 is considered a regulator in maintaining energy homeostasis and shows a positive role in preventing damage caused by cardiac diseases. This review mainly summarizes the effects and related mechanisms of fibroblast growth factor 21 on pathological processes associated with cardiac remodeling, based on a variety of cells of myocardial tissue. The possibility of Fibroblast growth factor 21 as a promising treatment for the cardiac remodeling process will also be discussed.

Association of NAFLD with FGF21 Polygenic Hazard Score, and Its Interaction with Protein Intake Level in Korean Adults

Fibroblast growth factor 21 (FGF21) is a hormone that participates in the regulation of energy homeostasis and is induced by dietary protein restriction. Preclinical studies have suggested that FGF21 induction exerts a protective effect against non-alcoholic fatty liver disease (NAFLD), while human studies have revealed elevated levels of and potential resistance to FGF21 in patients with NAFLD. However, whether the FGF21 pathway also contributes to NAFLD risk at the genetic level remains uncertain. A few attempts to investigate the impact of individual genetic variants at the loci encoding FGF21 and its receptors on NAFLD risk have failed to establish a clear association due to a limited effect size. Therefore, this study aimed to (1) develop a polygenic hazard score (PHS) for FGF21-related loci that are associated with NAFLD risk and (2) investigate the effect of its interaction with protein intake level on NAFLD risk. Data on 3501 participants of the Korean Genome Epidemiology Study (Ansan-Ansung) were analyzed. Eight single-nucleotide polymorphisms of fibroblast growth factor receptors and beta-klotho were selected for PHS determination using forward stepwise analysis. The association between the PHS and NAFLD was validated (p-trend: 0.0171 for men and <0.0001 for women). Moreover, the association was significantly modulated by the protein intake level in all participants as well as women (p-interaction = 0.0189 and 0.0131, respectively) but not in men. In particular, the women with the lowest PHS values and a protein intake lower than the recommended nutrient intake (RNI) exhibited a greater NAFLD risk (HR = 2.021, p-trend = 0.0016) than those with an intake equal to or greater than the RNI; however, those with higher PHS values had a high risk, regardless of protein intake level. These findings demonstrate the contribution of FGF21-related genetic variants and restricted protein intake to NAFLD incidence.

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.

Targeting Alzheimer's Disease: The Critical Crosstalk between the Liver and Brain

Alzheimer's disease (AD), an age-related neurodegenerative disorder, is currently incurable. Imbalanced amyloid-beta (Aβ) generation and clearance are thought to play a pivotal role in the pathogenesis of AD. Historically, strategies targeting Aβ clearance have typically focused on central clearance, but with limited clinical success. Recently, the contribution of peripheral systems, particularly the liver, to Aβ clearance has sparked an increased interest. In addition, AD presents pathological features similar to those of metabolic syndrome, and the critical involvement of brain energy metabolic disturbances in this disease has been recognized. More importantly, the liver may be a key regulator in these abnormalities, far beyond our past understanding. Here, we review recent animal and clinical findings indicating that liver dysfunction represents an early event in AD pathophysiology. We further propose that compromised peripheral Aβ clearance by the liver and aberrant hepatic physiological processes may contribute to AD neurodegeneration. The role of a hepatic synthesis product, fibroblast growth factor 21 (FGF21), in the management of AD is also discussed. A deeper understanding of the communication between the liver and brain may lead to new opportunities for the early diagnosis and treatment of AD.

[Expression, purification and bioactivity analysis of a recombinant fusion protein rHSA-hFGF21 in Pichia pastoris]

Human fibroblast growth factor 21 (hFGF21) has become a candidate drug for regulating blood glucose and lipid metabolism. The poor stability and short half-life of hFGF21 resulted in low target tissue availability, which hampers its clinical application. In this study, the hFGF21 was fused with a recombinant human serum albumin (HSA), and the resulted fusion protein rHSA-hFGF21 was expressed in Pichia pastoris. After codon optimization, the recombinant gene fragment rHSA-hFGF21 was inserted into two different vectors (pPIC9k and pPICZαA) and transformed into three different strains (X33, GS115 and SMD1168), respectively. We investigated the rHSA-hFGF21 expression levels in three different strains and screened an engineered strain X33-pPIC9K-rHSA-hFGF21 with the highest expression level. To improve the production efficiency of rHSA-hFGF21, we optimized the shake flask fermentation conditions, such as the OD value, methanol concentration and induction time. After purification by hollow fiber membrane separation, Blue affinity chromatography and Q ion exchange chromatography, the purity of the rHSA-hFGF21 protein obtained was 98.18%. Compared to hFGF21, the biostabilities of rHSA-hFGF21, including their resistance to temperature and trypsinization were significantly enhanced, and its plasma half-life was extended by about 27.6 times. Moreover, the fusion protein rHSA-hFGF21 at medium and high concentration showed a better ability to promote glucose uptake after 24 h of stimulation in vitro. In vivo animal studies showed that rHSA-hFGF21 exhibited a better long-term hypoglycemic effect than hFGF21 in type 2 diabetic mice. Our results demonstrated a small-scale production of rHSA-hFGF21, which is important for large-scale production and clinical application in the future.

Retinal degeneration induced in a mouse model of ischemia-reperfusion injury and its management by pemafibrate treatment

Retinal ischemia-reperfusion (I/R) injury is a common cause of visual impairment. To date, no effective treatment is available for retinal I/R injury. In addition, the precise pathological mechanisms still need to be established. Recently, pemafibrate, a peroxisome proliferator-activated receptor α (PPARα) modulator, was shown to be a promising drug for retinal ischemia. However, the role of pemafibrate in preventing retinal I/R injury has not been documented. Here, we investigated how retinal degeneration occurs in a mouse model of retinal I/R injury by elevation of intraocular pressure and examined whether pemafibrate could be beneficial against retinal degeneration. Adult mice were orally administered pemafibrate (0.5 mg/kg/day) for 4 days, followed by retinal I/R injury. The mice were continuously administered pemafibrate once every day until the end of the experiments. Retinal functional changes were measured using electroretinography. Retina, liver, and serum samples were used for western blotting, quantitative PCR, immunohistochemistry, or enzyme linked immunosorbent assay. Retinal degeneration induced by retinal inflammation was prevented by pemafibrate administration. Pemafibrate administration increased the hepatic PPARα target gene expression and serum levels of fibroblast growth factor 21, a neuroprotective molecule in the eye. The expression of hypoxia-response and pro-and anti-apoptotic/inflammatory genes increased in the retina following retinal I/R injury; however, these changes were modulated by pemafibrate administration. In conclusion, pemafibrate is a promising preventive drug for ischemic retinopathies.

CRISPR-Cas9-based genome-wide screening identified novel targets for treating sorafenib-resistant hepatocellular carcinoma: a cross-talk between FGF21 and the NRF2 pathway

The treatment of hepatocellular carcinoma (HCC) has been dominated by multikinase inhibitors for more than a decade. However, drug resistance can severely restrict the efficacy of these drugs. Using CRISPR/CAS9 genome library screening, we evaluated Kelch-like ECH-associated protein 1 (KEAP1) as a key regulator of sorafenib's susceptibility in HCC. We also investigated whether KEAP1's knockdown can stabilize nuclear factor (erythroid-derived 2)-like 2 (NRF2) protein levels that led to sorafenib's resistance, including an NRF2 inhibitor that can synergize with sorafenib to abolish HCC's growth in vitro and in vivo. Furthermore, we clarified that fibroblast growth factor 21 (FGF21) is an important downstream regulator of NRF2 in HCC. Intriguingly, we observed that FGF21 bound to NRF2 through the C-terminus of FGF21, thereby stabilizing NRF2 by reducing its ubiquitination and generating a positive feedback loop in sorafenib-resistant HCC. These findings, therefore, propose that targeting FGF21 is a promising strategy to combat HCC sorafenib's resistance.

LLF580, an FGF21 Analog, Reduces Triglycerides and Hepatic Fat in Obese Adults With Modest Hypertriglyceridemia

PURPOSE

To evaluate the safety and potential efficacy of LLF580, a genetically engineered variant of human fibroblast growth factor-21, for triglyceride lowering, weight loss, and hepatic fat reduction.

METHODS

A multicenter, double-blind, parallel design trial in obese, mildly hypertriglyceridemic adults randomized (1:1) to LLF580 300 mg or placebo subcutaneously every 4 weeks for 3 doses.

RESULTS

Of 64 randomized study participants, 61 (mean ± SD: age 45 ± 11 years, 49% male, 80/15/5% Caucasian/African American/other, body mass index 36.1 ± 3.8 kg/m2) received LLF580 (n = 30) or placebo (n = 31) at 7 research sites in the United States. LLF580 lowered serum triglycerides by 54% (least square mean placebo adjusted change from baseline), total cholesterol 7%, low-density lipoprotein cholesterol 12%, and increased high-density lipoprotein cholesterol 36% compared with placebo (all P < 0.001) over 12 weeks. Substantial reduction of liver fat of 52% over placebo (P < 0.001) was also demonstrated in the setting of improved liver function tests including alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, the composite enhanced liver fibrosis score, and N-terminal type III collagen propeptide (all P < 0.05). Insulin and C-peptide levels and insulin resistance by homeostatic model assessment for insulin resistance were all lower, and adiponectin higher with LLF580 treatment compared with placebo, whereas fasting glucose and glycated hemoglobin were unchanged. Reductions in biomarkers of bone formation without differences in markers of bone resorption were observed. LLF580 was generally safe and well tolerated, except for higher incidence of generally mild to moderate gastrointestinal adverse effects.

CONCLUSIONS

In obese, mildly hypertriglyceridemic adults, LLF580 was generally safe and demonstrated beneficial effects on serum lipids, liver fat, and biomarkers of liver injury, suggesting it may be effective for treatment of select metabolic disorders including hypertriglyceridemia and nonalcoholic fatty liver disease. Assessments of longer term safety and efficacy are warranted.

CLINICALTRIALS.GOV IDENTIFIER

NCT03466203.

Increased Fibroblast Growth Factor 21 (FGF21) Concentration in Early Second Trimester Amniotic Fluid and Its Association with Fetal Growth

Altered fetal growth, either reduced or exacerbated, is associated with adverse perinatal outcomes. The underlying pathogenetic mechanisms of altered growth remain unclear. Fibroblast growth factor 21 (FGF21) and insulin are both considered to be major regulators of tissue growth and metabolism. The aim of our study was to investigate the association of second trimester amniotic fluid FGF21 and insulin concentrations with fetal growth. The amniotic fluid concentrations of FGF21 and insulin were determined in 80 cases of different fetal growth patterns (SGA—small for gestational age, LGA—large for gestational age, and AGA—appropriate for gestational age fetuses). Both peptides were found to be increased in cases of abnormal fetal growth, reduced growth velocity (SGA), or macrosomia (LGA). Specifically, FGF21 was significantly increased, as higher FGF21 levels were observed in the amniotic fluid of SGA and LGA fetuses compared with AGA fetuses (p < 0.05). Furthermore, the more severe the fetal smallness, the higher the FGF21 levels (p < 0.05). Similarly, higher insulin levels were noted in the amniotic fluid of SGA and LGA fetuses compared with those in AGA fetuses, though this was not statistically significant (p > 0.05). Again, the more severe the reduced fetal growth, the higher the insulin levels.

Fibroblast Growth Factor 21 Response in a Preclinical Alcohol Model of Acute-on-Chronic Liver Injury

BACKGROUND AND AIMS

Fibroblast growth factor (FGF) 21 has recently been shown to play a potential role in bile acid metabolism. We aimed to investigate the FGF21 response in an ethanol-induced acute-on-chronic liver injury (ACLI) model in Abcb4-/- mice with deficiency of the hepatobiliary phospholipid transporter.

METHODS

Total RNA was extracted from wild-type (WT, C57BL/6J) and Abcb4-/- (KO) mice, which were either fed a control diet (WT-Cont and KO-Cont groups; n = 28/group) or ethanol diet, followed by an acute ethanol binge (WT-EtOH and KO-EtOH groups; n = 28/group). A total of 58 human subjects were recruited into the study, including patients with alcohol-associated liver disease (AALD; n = 31) and healthy controls (n = 27). The hepatic and ileal expressions of genes involved in bile acid metabolism, plasma FGF levels, and bile acid and its precursors 7α- and 27-hydroxycholesterol (7α- and 27-OHC) concentrations were determined. Primary mouse hepatocytes were isolated for cell culture experiments.

RESULTS

Alcohol feeding significantly induced plasma FGF21 and decreased hepatic Cyp7a1 levels. Hepatic expression levels of Fibroblast growth factor receptor 1 (Fgfr1), Fgfr4, Farnesoid X-activated receptor (Fxr), and Small heterodimer partner (Shp) and plasma FGF15/FGF19 levels did not differ with alcohol challenge. Exogenous FGF21 treatment suppressed Cyp7a1 in a dose-dependent manner in vitro. AALD patients showed markedly higher FGF21 and lower 7α-OHC plasma levels while FGF19 did not differ.

CONCLUSIONS

The simultaneous upregulation of FGF21 and downregulation of Cyp7a1 expressions upon chronic plus binge alcohol feeding together with the invariant plasma FGF15 and hepatic Shp and Fxr levels suggest the presence of a direct regulatory mechanism of FGF21 on bile acid homeostasis through inhibition of CYP7A1 by an FGF15-independent pathway in this ACLI model. Lay Summary: Alcohol challenge results in the upregulation of FGF21 and repression of Cyp7a1 expressions while circulating FGF15 and hepatic Shp and Fxr levels remain constant both in healthy and pre-injured livers, suggesting the presence of an alternative FGF15-independent regulatory mechanism of FGF21 on bile acid homeostasis through the inhibition of Cyp7a1.

PPARα Agonist Oral Therapy in Diabetic Retinopathy

Diabetic retinopathy (DR) is an eye condition that develops after chronically poorly-managed diabetes, and is presently the main cause for blindness on a global scale. Current treatments for DR such as laser photocoagulation, topical injection of corticosteroids, intravitreal injection of anti-vascular endothelial growth factor (VEGF) agents and vitreoretinal surgery are only applicable at the late stages of DR and there are possibilities of significant adverse effects. Moreover, the forms of treatment available for DR are highly invasive to the eyes. Safer and more effective pharmacological treatments are required for DR treatment, in particular at an early stage. In this review, we cover recently investigated promising oral pharmacotherapies, the methods of which are safer, easier to use, patient-friendly and pain-free, in clinical studies. We especially focus on peroxisome proliferator-activator receptor alpha (PPARα) agonists in which experimental evidence suggests PPARα activation may be closely related to the attenuation of vascular damages, including lipid-induced toxicity, inflammation, an excess of free radical generation, endothelial dysfunction and angiogenesis. Furthermore, oral administration of selective peroxisome proliferator-activated receptor alpha modulator (SPPARMα) agonists may induce hepatic fibroblast growth factor 21 expression, indirectly resulting in retinal protection in animal studies. Our review will enable more comprehensive approaches for understanding protective roles of PPARα for the prevention of DR development.

FGF21 regulates hepatic metabolic pathways to improve steatosis and inflammation

The prevalence of non-alcoholic fatty liver disease (NAFLD) has increased dramatically worldwide and, subsequently, also the risk of developing non-alcoholic steatohepatitis (NASH), hepatic fibrosis, cirrhosis and cancer. Today, weight loss is the only available treatment, but administration of fibroblast growth factor 21 (FGF21) analogues have, in addition to weight loss, shown improvements on liver metabolic health but the mechanisms behind are not entirely clear. The aim of this study was to investigate the hepatic metabolic profile in response to FGF21 treatment. Diet-induced obese (DIO) mice were treated with s.c. administration of FGF21 or subjected to caloric restriction by switching from high fat diet (HFD) to chow to induce 20% weight loss and changes were compared to vehicle dosed DIO mice. Cumulative caloric intake was reduced by chow, while no differences were observed between FGF21 and vehicle dosed mice. The body weight loss in both treatment groups was associated with reduced body fat mass and hepatic triglycerides (TG), while hepatic cholesterol was slightly decreased by chow. Liver glycogen was decreased by FGF21 and increased by chow. The hepatic gene expression profiles suggest that FGF21 increased uptake of fatty acids and lipoproteins, channeled TGs toward the production of cholesterol and bile acid, reduced lipogenesis and increased hepatic glucose output. Furthermore, FGF21 appeared to reduce inflammation and regulate hepatic leptin receptor-a expression. In conclusion, FGF21 affected several metabolic pathways to reduce hepatic steatosis and improve hepatic health and markedly more genes than diet restriction (61 vs 16 out of 89 investigated genes).

Alcohol ingestion induces pancreatic islet dysfunction and apoptosis via mediation of FGF21 resistance

Background

Disruption of β-cell insulin secretion and viability caused by excessive ethanol consumption increases type 2 diabetes mellitus (T2DM) pathogenesis risk. Fibroblast growth factor 21 (FGF21) plays a significant role in regulating lipid and glucose homeostasis. Recently, FGF21, best known for its role in lipid and glucose homeostasis regulation, and its obligate co-receptor β-klotho have been shown to inhibit ethanol ingestion and metabolism. It remains unclear whether heavy ethanol intake modulates islet FGF21 expression and function. This study investigated the relationship between ethanol exposure, FGF21, and islet function in vivo/ex vivo islet and in vitro cell models.

Methods

Mice were gavaged with 3.5 g/kg ethanol or saline for 1–3 weeks (long-term exposure). Human MIN6 cells and isolated islets were cultured and treated with 80 mM ethanol for 24 h (short-term exposure) to mimic excessive ethanol consumption. We applied the oral glucose tolerance test (OGTT), blood glucometry, enzyme-linked immunosorbent assay (ELISAs) for insulin and FGF21, glucose stimulated insulin secretion (GSIS) testing, reverse-transcription (RT)-polymerase chain reaction (PCR), and western blot experiments.

Results

Long-term ethanol treatment induced FGF21 resistance in mouse pancreatic islets. Moreover, ethanol exposure damaged insulin secretory ability and glucose homeostasis. In vitro and ex vivo experiments showed that short-term ethanol treatment upregulated the expression of FGF21 signaling pathway-related genes and proteins, without affecting β-cell survival or function.

Conclusions

Long-term ethanol consumption induces FGF21 resistance-mediated pancreatic β-cell dysfunction, and thus diabetes pathogenesis risk.

Fibroblast growth factor 21 prolongs lifespan and improves stress tolerance in the silkworm, Bombyx mori

BACKGROUND

Fibroblast growth factor 21 (FGF21), an FGF family member, is an atypical hormone and pro-longevity factor.

METHODS

To better understand of the effects of exogenous administration of FGF21 on lifespan and stress tolerance, and the underlying molecular basis, we used the silkworm, Bombyx mori, as an experimental animal model to evaluate FGF21's pharmaceutical effects.

RESULTS

Lifespan was significantly prolonged in female silkworms with FGF21 replenishment, whereas no effect was observed in the male silkworms. FGF21 replenishment also significantly improved the activity of antioxidant systems such as glutathione-S-transferase (GST) and superoxide dismutase (SOD) and significantly decreased malondialdehyde (MDA) content. Moreover, FGF21 was found to play a critical role in enhancing stress resistance, including ultraviolet (UV) irradiation tolerance and thermotolerance. Furthermore, AMPK, FoxO, and sirtuins were activated by FGF21 and may be responsible for the prolonged lifespan and enhanced antioxidant activity observed in silkworms.

CONCLUSIONS

Collectively, the results suggest the molecular pathways underlying of FGF21-induced longevity and stress tolerance, and support the use of silkworms as a promising experimental animal model for evaluating the pharmaceutical effects of small molecules.

Long-Acting FGF21 Inhibits Retinal Vascular Leakage in In Vivo and In Vitro Models

The aim of the current study was to investigate the impact of long-acting fibroblast growth factor 21 (FGF21) on retinal vascular leakage utilizing machine learning and to clarify the mechanism underlying the protection. To assess the effect on retinal vascular leakage, C57BL/6J mice were pre-treated with long-acting FGF21 analog or vehicle (Phosphate Buffered Saline; PBS) intraperitoneally (i.p.) before induction of retinal vascular leakage with intravitreal injection of mouse (m) vascular endothelial growth factor 164 (VEGF164) or PBS control. Five hours after mVEGF164 injection, we retro-orbitally injected Fluorescein isothiocyanate (FITC) -dextran and quantified fluorescence intensity as a readout of vascular leakage, using the Image Analysis Module with a machine learning algorithm. In FGF21- or vehicle-treated primary human retinal microvascular endothelial cells (HRMECs), cell permeability was induced with human (h) VEGF165 and evaluated using FITC-dextran and trans-endothelial electrical resistance (TEER). Western blots for tight junction markers were performed. Retinal vascular leakage in vivo was reduced in the FGF21 versus vehicle- treated mice. In HRMECs in vitro, FGF21 versus vehicle prevented hVEGF-induced increase in cell permeability, identified with FITC-dextran. FGF21 significantly preserved TEER compared to hVEGF. Taken together, FGF21 regulates permeability through tight junctions; in particular, FGF21 increases Claudin-1 protein levels in hVEGF-induced HRMECs. Long-acting FGF21 may help reduce retinal vascular leakage in retinal disorders and machine learning assessment can help to standardize vascular leakage quantification.

Pemafibrate Prevents Retinal Pathological Neovascularization by Increasing FGF21 Level in a Murine Oxygen-Induced Retinopathy Model

Large-scale clinical trials, such as the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) and the Action to Control Cardiovascular Risk in Diabetes (ACCORD) studies, have shown that the administration of fenofibrate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist, suppresses the progression of diabetic retinopathy. In this paper, we reveal a therapeutic effect of a selective PPARα modulator (SPPARMα), pemafibrate, against pathological angiogenesis in murine models of retinopathy. Oxygen-induced retinopathy (OIR) was induced in C57BL/6J mice by exposure to 85% oxygen from postnatal day eight (P8) for 72 h. Vehicle, pemafibrate or fenofibrate was administrated by oral gavage from P12 to P16 daily. Administration of pemafibrate, but not fenofibrate, significantly reduced pathological angiogenesis in OIR. After oral pemafibrate administration, expression levels of downstream PPARα targets such as acyl-CoA oxidase 1 (Acox1), fatty acid binding protein 4 (Fabp4), and fibroblast growth factor 21 (Fgf21) were significantly increased in the liver but not in the retina. A significant increase in plasma FGF21 and reduced retinal hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (Vegfa) were also observed after this treatment. In an in vitro HIF-luciferase assay, a long-acting FGF21 analogue, but not pemafibrate, suppressed HIF activity. These data indicate that SPPARMα pemafibrate administration may prevent retinal pathological neovascularization by upregulating FGF21 in the liver.

Fibroblast growth factors 19 and 21 in acute liver damage

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

FAP finds FGF21 easy to digest

Fibroblast growth factor 21 (FGF21) is an endocrine hormone that regulates carbohydrate and lipid metabolism. In humans, circulating FGF21 is inactivated by proteolytic cleavage of its C-terminus, thereby preventing signalling through a receptor complex. The mechanism for this cleavage event and the factors contributing to the post-translational regulation of FGF21 activity has previously been unknown. In a recent issue of the Biochemical Journal, Zhen et al. have identified fibroblast activation protein (FAP) as the endopeptidase responsible for this site-specific cleavage of human FGF21 (hFGF21), and propose that inhibition of FAP may be a therapeutic strategy to increase endogenous levels of active FGF21.

Fibroblast growth factor 21 (FGF21) therapy attenuates left ventricular dysfunction and metabolic disturbance by improving FGF21 sensitivity, cardiac mitochondrial redox homoeostasis and structural changes in pre-diabetic rats

AIMS

Fibroblast growth factor 21 (FGF21) acts as a metabolic regulator and exerts cardioprotective effects. However, the effects of long-term FGF21 administration on the heart under the FGF21-resistant condition in obese, insulin-resistant rats have not been investigated. We hypothesized that long-term FGF21 administration reduces FGF21 resistance and insulin resistance and attenuates cardiac dysfunction in obese, insulin-resistant rats.

METHODS

Eighteen rats were fed on either a normal diet (n = 6) or a high-fat diet (HFD; n = 12) for 12 weeks. Then, rats in the HFD group were divided into two subgroups (n = 6 per subgroup) and received either the vehicle (HFV) or recombinant human FGF21 (rhFGF21, 0.1 mg kg(-1)  day(-1) ; HFF) injected intraperitoneally for 28 days. The metabolic parameters, inflammation, malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial redox homoeostasis, cardiac mitochondrial fatty acid β-oxidation (FAO) and anti-apoptotic signalling pathways were determined.

RESULTS

HFV rats had increased dyslipidaemia, insulin resistance, plasma FGF21 levels, TNF-α, adiponectin and MDA, depressed HRV, and impaired LV and mitochondrial function. HFV rats also had decreased cardiac Bcl-2, cardiac PGC-1α and CPT-1 protein expression. However, FGF21 restored metabolic parameters, decreased TNF-α and MDA, increased serum adiponectin, and improved HRV, cardiac mitochondrial and LV function in HFF rats. Moreover, HFF rats had increased cardiac Bcl-2, cardiac PGC-1α and CPT-1 protein expression.

CONCLUSION

Long-term FGF21 therapy attenuates FGF21 resistance and insulin resistance and exerts cardioprotection by improving cardiometabolic regulation via activating anti-apoptotic and cardiac mitochondrial FAO signalling pathways in obese, insulin-resistant rats.

FGF21 treatment ameliorates alcoholic fatty liver through activation of AMPK-SIRT1 pathway

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.