Fibroblast Growth Factor 21 Receptor Research Articles

Glucosamine Enhancement of Learning and Memory Functions by Promoting Fibroblast Growth Factor 21 Production.

Fibroblast growth factor 21 (FGF21) plays a crucial role in metabolism and brain function. Glucosamine (GLN) has been recognized for its diverse beneficial effects. This study aimed to elucidate the modulation of FGF21 production by GLN and its impact on learning and memory functions. Using both in vivo and in vitro models, we investigated the effects of GLN on mice fed with a normal diet or high-fat diet and on mouse HT22 hippocampal cells, STHdhQ7/Q7 striatal cells, and rat primary cortical neurons challenged with GLN. Our results indicated that GLN promotes learning and memory functions in mice and upregulates FGF21 expression in the hippocampus, cortex, and striatum, as well as in HT22 cells, STHdhQ7/Q7 cells, and cortical neurons. In animals receiving GLN together with an FGF21 receptor FGFR1 inhibitor (PD173074), the GLN-enhanced learning and memory functions and induction of FGF21 production in the hippocampus were significantly attenuated. While exploring the underlying molecular mechanisms, the potential involvement of NF-κB, Akt, p38, JNK, PKA, and PPARα in HT22 and NF-κB, Akt, p38, and PPARα in STHdhQ7/Q7 were noted; GLN was able to mediate the activation of p65, Akt, p38, and CREB in HT22 and p65, Akt, and p38 in STHdhQ7/Q7 cells. Our accumulated findings suggest that GLN may increase learning and memory functions by inducing FGF21 production in the brain. This induction appears to be mediated, at least in part, through GLN's activation of the NF-κB, Akt, p38, and PKA/CREB pathways.

Leucine supplementation in maternal high-fat diet alleviated adiposity and glucose intolerance of adult mice offspring fed a postweaning high-fat diet

BackgroundCombined maternal and postnatal high-fat (HF) diet intake predisposes offspring to metabolic dysregulation during adulthood. As the inhibitory effects of leucine consumption on obesity and metabolic disorders have been reported, the effects of maternal leucine supplementation on metabolic dysregulation in adult offspring were investigated.MethodsFemale mice were exposed to a control (C) or HF diet, with or without leucine (L) supplementation (1.5%, w/v), 3 weeks before mating, during pregnancy, and during lactation (C, CL, HF, and HFL). Male offspring were exposed to an HF diet for 12 weeks after weaning (C/HF, CL/HF, HF/HF, and HFL/HF). Serum biochemical parameters were determined for both the dams and offspring. Oral glucose tolerance test and qRT-PCR analysis were used to investigate metabolic dysregulation in the offspring.ResultsHFL dams exhibited higher relative adipose tissue weights than HF dams. Body weight, relative adipose tissue weight, and serum glucose levels were lower in the HFL/HF offspring than in the HF/HF offspring. Maternal leucine supplementation tended to alleviate glucose intolerance in the offspring of HF diet-fed dams. Additionally, mRNA levels of fibroblast growth factor 21 (FGF21), a hepatokine associated with glucose homeostasis, were higher in HFL/HF offspring than in HF/HF offspring and were negatively correlated with adiposity and serum glucose levels. The mRNA levels of genes encoding a FGF21 receptor complex, Fgf receptor 1 and klotho β, and its downstream targets, proliferator‐activated receptor‐γ co‐activator 1α and sirtuin 1, were higher in adipose tissues of the HFL/HF offspring than in those of the HF/HF offspring. Serum lipid peroxide levels were lower in HFL dams than in HF dams and positively correlated with body and adipose tissue weights of offspring.ConclusionsLeucine supplementation in HF diet-fed dams, but not in control diet-fed dams, resulted in an anti-obesity phenotype accompanied by glucose homeostasis in male offspring challenged with postnatal HF feeding. Activation of FGF21 signaling in the adipose tissue of offspring may be responsible for these beneficial effects of leucine.

The potential function and clinical application of FGF21 in metabolic diseases.

As an endocrine hormone, fibroblast growth factor 21 (FGF21) plays a crucial role in regulating lipid, glucose, and energy metabolism. Endogenous FGF21 is generated by multiple cell types but acts on restricted effector tissues, including the brain, adipose tissue, liver, heart, and skeletal muscle. Intervention with FGF21 in rodents or non-human primates has shown significant pharmacological effects on a range of metabolic dysfunctions, including weight loss and improvement of hyperglycemia, hyperlipidemia, insulin resistance, cardiovascular disease, and non-alcoholic fatty liver disease (NAFLD). Due to the poor pharmacokinetic and biophysical characteristics of native FGF21, long-acting FGF21 analogs and FGF21 receptor agonists have been developed for the treatment of metabolic dysfunction. Clinical trials of several FGF21-based drugs have been performed and shown good safety, tolerance, and efficacy. Here we review the actions of FGF21 and summarize the associated clinical trials in obesity, type 2 diabetes mellitus (T2DM), and NAFLD, to help understand and promote the development of efficient treatment for metabolic diseases via targeting FGF21.

PSUN311 JTV-519 Alleviates the Impairment of FGF21 Axis Signaling after Spinal Cord Contusion in Mice

Abstract Spinal cord injury (SCI) causes adverse changes in body composition and metabolic profile due to dramatic loss of skeletal muscle mass and an extremely sedentary lifestyle. These abrupt and permanent changes increase the risk for cardiovascular disease, liver disorders, and type 2 diabetes compared to the general population. We have reported that metabolic dysregulation following SCI due to transection is associated with impaired fibroblast growth factor 21 (FGF21) and adiponectin (ADPN) signaling [1], two important regulators of metabolism [2, 3]. JTV519, which stabilizes ryanodine receptors and blocks calcium uptake via SERCA [4], has been reported to have a strong cardioprotective effect via stabilization of ryanodine receptor 2. We examined the effects of SCI caused by contusion (a more common cause of SCI), with or without JTV519 administration, on FGF21 and ADPN signaling in tissues collected from mice at 56 days after SCI. SCI reduced serum and hepatic mRNA levels of FGF21 by 75% and 45%, respectively, compared to sham mice. SCI also significantly diminished FGF21 receptor (FGF-R1) and coreceptor (beta-klotho, KLB) mRNA expression in adipose tissue. In addition, SCI decreased serum ADPN levels, particularly its high molecular weight (HMW) isoform which is the most potent form of the protein. These inhibitory effects were associated with decreased hepatic mRNA expression for PPARalpha (55%), type-2 adiponectin receptor (AdipoR2; 70%), and Glut4 (75%). In addition, SCI reduced mRNA expression of leptin (by 85%) and UCP1 (by 95%) in adipose tissue. In skeletal muscle (gastrocnemius), SCI lowered mRNA expression of PGC1alpha (by 38%), ADPN (by 80%), FGF-R1 (by 35%) and AdipoR1 (by 20%) compared to sham mice. Treating sham-mice with JTV519 upregulated FGF21 and ADPN serum and mRNA levels as well as the expression of the associated metabolic genes of interest (mentioned above). Likewise, SCI-mice treated with JTV519 also demonstrated upregulation of serum levels of FGF21, the HMW isoform of ADPN, and hepatic FGF21 mRNA expression compared to vehicle-treated SCI-mice. Decreased hepatic mRNA expression of PPARalpha, AdipoR2, Glut4 and FGF-R1 and KLB mRNA in adipose tissue were also reversed after JTV519 administration, with levels approximately equivalent to those observed in sham-vehicle treated mice but lower than sham-JTV519 treated mice. Moreover, JTV519 treatment protected against SCI-induced decreases of PGC1alpha, ADPN and FGF-R1 mRNA expression in the gastrocnemius. These data imply that JTV-519 is able to alleviate SCI-induced impairments of FGF21/ADPN signaling. Therefore, JTV519 could be a potential pharmacological agent to treat metabolic dysfunction after SCI.

Synbiotics intake improves disturbed metabolism in a rat model of high fat diet-induced obesity; A potential role of adipose tissue browning

Browning of white adipose tissue (WAT) is currently considered a potential therapeutic approach to treat or prevent diet-induced obesity. Synbiotics have protective effects against diet-induced obesity; however, its role in adipose tissue browning has been less investigated. to study the possible effect of synbiotics intake on browning of WAT in obese rats. Twenty-four adult male Wistar rats were randomly divided into four groups; normal diet (ND) control group, high fat diet (HFD) group, ND group receiving synbiotics, and HFD group receiving synbiotics. After eight weeks, all rats were sacrificed; and samples (blood, WAT, brown adipose tissue, and liver) were collected. Lipid profile, liver enzymes, fasting glucose, and fasting insulin levels were measured. The expression of browning-related genes: uncoupler protein-1 (UCP-1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), and peroxisome proliferator-activated receptors gamma (PPARγ) were measured by real-time polymerase chain reaction (PCR) in adipose tissues. Fibroblast growth factor 21 (FGF21) protein level was measured in serum, adipose and liver tissues, and FGF21 receptor expression was performed by real-time PCR in adipose tissues. ynbiotics intake was associated with improvement in lipid profile, liver enzymes, and insulin sensitivity in HFD rats. Moreover, the intake was associated with higher gene expression of brown adipocyte-specific markers. As for the FGF21 and its receptor, intriguing results were obtained that needs further in-depth studies. synbiotics might protect against diet-induced obesity through induction of thermogenic genes resulting in brown-like adipocyte phenotype in WAT.

Fibroblast growth factor-21 improves insulin action in nonlactating ewes.

During metabolically demanding physiological states, ruminants and other mammals coordinate nutrient use among tissues by varying the set point of insulin action. This set point is regulated in part by metabolic hormones with some antagonizing (e.g., growth hormone and TNFα) and others potentiating (e.g., adiponectin) insulin action. Fibroblast growth factor-21 (FGF21) was recently identified as a sensitizing hormone in rodent and primate models of defective insulin action. FGF21 administration, however, failed to improve insulin action in dairy cows during the naturally occurring insulin resistance of lactation, raising the possibility that ruminants as a class of animals or lactation as a physiological state are unresponsive to FGF21. To start addressing this question, we asked whether FGF21 could improve insulin action in nonlactating ewes. Gene expression studies showed that the ovine FGF21 system resembles that of other species, with liver as the major site of FGF21 expression and adipose tissue as a target tissue based on high expression of the FGF21 receptor complex and activation of p44/42 extracellular signal-regulated kinase (ERK1/2) following exogenous FGF21 administration. FGF21 treatment for 13 days reduced plasma glucose and insulin over the entire treatment period and improved glucose disposal during a glucose tolerance test. FGF21 increased plasma adiponectin by day 3 of treatment but had no effect on the plasma concentrations of total, C16:0-, or C18:0-ceramide. Overall, these data confirm that the insulin-sensitizing effects of FGF21 are conserved in ruminants and raise the possibility that lactation is an FGF21-resistant state.

Nicotinamide riboside ameliorates high-fructose-induced lipid metabolism disorder in mice via improving FGF21 resistance in the liver and white adipose tissue.

Fructose has been reported to acutely elevate the circulating fibroblast growth factor 21 (FGF21) levels, which ultimately causes FGF21 resistance. FGF21 resistance is suggested to result in lipid metabolism disorder. Nicotinamide riboside (NR) can alleviate lipid metabolism disorder in mice. It is unknown whether NR supplementation would alleviate lipid metabolism disorder in high-fructose exposed mice via improving FGF21 resistance. In this study, C57BL/6J mice were given 20% fructose solution for free drinking with the supplementation of NR in 400 mg kg-1 day-1. The results showed that NR supplementation decreased the serum and hepatic lipid profile levels. The increase of lipid droplets in the liver and the size of adipose cells in WAT induced by a high-fructose diet were alleviated by the addition of NR. NR supplementation increased the NAD+/NADH ratio and activated the SIRT1/NF-κB pathway. The down-regulation of NF-κB is accompanied by a decrease in inflammation, which may increase the expression of the FGF21 receptor complex, namely KLB and FGFR, then restore its downstream signaling cascade, including ERK phosphorylation and EGR1 and c-FOS expression, and ultimately improve FGF21 resistance. With the FGF21 function recovery, hepatic PGC-1α expression was up-regulated, and hepatic SREBP-1c expression was down-regulated, resulting in decreased lipogenesis. Furthermore, restoration of the FGF21 signaling pathway also led to increased expression of ATGL and HSL in WAT, which promotes lipolysis. In conclusion, we found that NR supplementation could ameliorate high-fructose-induced lipid metabolism disorder by improving FGF21 resistance in the liver and WAT, which may be related to the regulation of inflammation mediated by the SIRT1/NF-κB signaling pathway.

Current status and perspectives of fibroblast growth factor 21 in nonalcoholic fatty liver disease

Fibroblast growth factor 21 (FGF21) is a peptide hormone predominantly secreted by the liver and plays a crucial role in maintaining whole-body energy metabolism and regulating insulin sensitivity. A large number of clinical studies have demonstrated that serum FGF21 levels are increased in obese patients with non-alcoholic fatty liver disease (NAFLD), and high circulating FGF21 is a sensitive biomarker for predicting the onset and progression of NAFLD. Injection of exogenous FGF21 can effectively alleviate pathological process in both animal models and NAFLD patients. This review aims to describe the molecular mechanism underlying the hepatoprotective effects of FGF21; to summarize the current data and challenges of the clinical trials on FGF21 analogs and receptor agonists in the treatment of NAFLD and nonalcoholic steatohepatitis (NASH); and to speculate the future directions of FGF21 as a diagnosis and treatment for NAFLD.

208-LB: Peripheral CB1 Inverse Agonism Improves Metabolism in DIO Mice Independent of Hepatic FGF21

Obesity is associated with an overactive endocannabinoid system, and selective blockade of CB1R in peripheral tissues, including the liver, reverses HFD-induced metabolic abnormalities by restoring normal lipid and glucose homeostasis and avoid unwanted adverse neuropsychiatric effects. The CB1R inverse agonist JD5037 has been shown equal effective with its brain-penetrant compound in reducing appetite, body weight, hepatic steatosis, and insulin resistance. Fibroblast growth factor-21 (FGF21) has emerged as a major endocrine regulator derived from the liver that reduces adiposity and hepatic steatosis and improves glucose tolerance and insulin sensitivity, with changes similar to those induced by CB1R blockade. Here we investigated whether FGF21 mediate the metabolic effects of CB1R blockade by JD5037 in DIO mice. In C57BL/6J wild-type mice, HFD caused a robust increase in hepatic Fgf21 mRNA and serum FGF21 levels, which were reversed by chronic peripheral CB1R antagonist JD5037 treatment to levels observed in STD or vehicle-treated hepatocyte-specific CB1R-/- (hCB1-/-) mice, indicating activation of CB1R in the liver is largely involved in HFD-induced “FGF21-resistant” state. In contrast, the expression of the FGF21 receptor Fgfr1 and co-receptor β-klotho (Klb) were dramatically reduced by HFD in both epididymal fat and brain tissue in wild-type mice, and these effects were reversed by JD5037 treatment. To address whether FGF21 mediated the metabolic effects of CB1R blockade, we repeated JD5037 treatment in liver-specific FGF21-/- (hFGF21-/-) mice. Surprisingly, JD5037 treatment was almost equally effective in both HFD-fed wild-type and in hFGF21-/- mice in reducing body weight and hepatic steatosis, attenuating hyperinsulinemia and hyperleptinemia. The current data suggest that peripheral CB1R blockade by inverse agonist in obese mice improves insulin sensitivity and energy expenditure independently of hepatic FGF21. Disclosure J. Liu: None. Funding National Institutes of Health

The Roles and Pharmacological Effects of FGF21 in Preventing Aging-Associated Metabolic Diseases.

With the continuous improvement of living standards but the lack of exercise, aging-associated metabolic diseases such as obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic fatty liver disease (NAFLD) are becoming a lingering dark cloud over society. Studies have found that metabolic disorders are near related to glucose, lipid metabolism, and cellular aging. Fibroblast growth factor 21 (FGF21), a member of the FGFs family, efficiently regulates the homeostasis of metabolism and cellular aging. By activating autophagy genes and improving inflammation, FGF21 indirectly delays cellular aging and directly exerts anti-aging effects by regulating aging genes. FGF21 can also regulate glucose and lipid metabolism by controlling metabolism-related genes, such as adipose triglyceride lipase (ATGL) and acetyl-CoA carboxylase (ACC1). Because FGF21 can regulate metabolism and cellular aging simultaneously, FGF21 analogs and FGF21 receptor agonists are gradually being valued and could become a treatment approach for aging-associated metabolic diseases. However, the mechanism by which FGF21 achieves curative effects is still not known. This review aims to interpret the interactive influence between FGF21, aging, and metabolic diseases and delineate the pharmacology of FGF21, providing theoretical support for further research on FGF21.

Retinal glial remodeling by FGF21 preserves retinal function during photoreceptor degeneration

SummaryThe group of retinal degenerations, retinitis pigmentosa (RP), comprises more than 150 genetic abnormalities affecting photoreceptors. Finding degenerative pathways common to all genetic abnormalities may allow general treatment such as neuroprotection. Neuroprotection may include enhancing the function of cells that directly support photoreceptors, retinal pigment epithelial cells, and Müller glia. Treatment with fibroblast growth factor 21 (FGF21), a neuroprotectant, from postnatal week 4–10, during rod and cone loss in P23H mice (an RP model) with retinal degeneration, preserved photoreceptor function and normalized Müller glial cell morphology. Single-cell transcriptomics of retinal cells showed that FGF21 receptor Fgfr1 was specifically expressed in Müller glia/astrocytes. Of all retinal cells, FGF21 predominantly affected genes in Müller glia/astrocytes with increased expression of axon development and synapse formation pathway genes. Therefore, enhancing retinal glial axon and synapse formation with neurons may preserve retinal function in RP and may suggest a general therapeutic approach for retinal degenerative diseases.

Epigenetic Regulation of Processes Related to High Level of Fibroblast Growth Factor 21 in Obese Subjects.

We hypothesised that epigenetics may play an important role in mediating fibroblast growth factor 21 (FGF21) resistance in obesity. We aimed to evaluate DNA methylation changes and miRNA pattern in obese subjects associated with high serum FGF21 levels. The study included 136 participants with BMI 27–45 kg/m2. Fasting FGF21, glucose, insulin, GIP, lipids, adipokines, miokines and cytokines were measured and compared in high serum FGF21 (n = 68) group to low FGF21 (n = 68) group. Human DNA Methylation Microarrays were analysed in leukocytes from each group (n = 16). Expression of miRNAs was evaluated using quantitative PCR-TLDA. The study identified differentially methylated genes in pathways related to glucose transport, insulin secretion and signalling, lipid transport and cellular metabolism, response to nutrient levels, thermogenesis, browning of adipose tissue and bone mineralisation. Additionally, it detected transcription factor genes regulating FGF21 and fibroblast growth factor receptor and vascular endothelial growth factor receptor pathways regulation. Increased expression of hsa-miR-875-5p and decreased expression of hsa-miR-133a-3p, hsa-miR-185-5p and hsa-miR-200c-3p were found in the group with high serum FGF21. These changes were associated with high FGF21, VEGF and low adiponectin serum levels. Our results point to a significant role of the epigenetic regulation of genes involved in metabolic pathways related to FGF21 action.

Adipokines and Metabolic Regulators in Human and Experimental Pulmonary Arterial Hypertension

Pulmonary hypertension (PH) is associated with meta-inflammation related to obesity but the role of adipose tissue in PH pathogenesis is unknown. We hypothesized that adipose tissue-derived metabolic regulators are altered in human and experimental PH. We measured circulating levels of fatty acid binding protein 4 (FABP-4), fibroblast growth factor -21 (FGF-21), adiponectin, and the mRNA levels of FABP-4, FGF-21, and peroxisome proliferator-activated receptor γ (PPARγ) in lung tissue of patients with idiopathic PH and healthy controls. We also evaluated lung and adipose tissue expression of these mediators in the three most commonly used experimental rodent models of pulmonary hypertension. Circulating levels of FABP-4, FGF-21, and adiponectin were significantly elevated in PH patients compared to controls and the mRNA levels of these regulators and PPARγ were also significantly increased in human PH lungs and in the lungs of rats with experimental PH compared to controls. These findings were coupled with increased levels of adipose tissue mRNA of genes related to glucose uptake, glycolysis, tricarboxylic acid cycle, and fatty acid oxidation in experimental PH. Our results support that metabolic alterations in human PH are recapitulated in rodent models of the disease and suggest that adipose tissue may contribute to PH pathogenesis.

233-LB: Spinal Cord Injury Inhibited-FGF21 Signaling Is Associated with Dysregulation of Metabolic Gene Expression in Mouse Liver and Adipose Tissue

Spinal cord injury (SCI) causes deleterious changes in the metabolic profile due to muscle atrophy and sedentary lifestyle. SCI is associated with increased risk for cardiovascular disease, liver disorders and type 2 diabetes mellitus (T2DM). Understanding of the mechanisms for these disorders in those with SCI is poor. Fibroblast growth factor 21 (FGF-21), a hepatic hormone, is reported to have beneficial effects on glucose/lipid metabolism in animal models and human subjects with T2DM. However, the expression levels and the potential effect of FGF-21 on SCI related metabolic dysfunction have not been studied. To address this issue, we compared FGF-21 serum and hepatic mRNA levels in sham and SCI mice fed control or high fat diet (HFD) at 84d after SCI. SCI reduced serum FGF-21 levels by 60% and hepatic FGF-21 mRNA levels by 50% compared to sham mice; levels were further suppressed by HFD. These changes were associated with elevated serum levels of alanine aminotransferase, a liver damage marker. In adipose tissue (AT), SCI decreased mRNA expression of FGF-21 receptor (FGFR1), β-Klotho, adiponectin, PPARγ, and leptin. In addition, SCI reduced IRS1 and Glut4 mRNA levels in AT, indicating impaired insulin signaling. Moreover, elevated levels of TNFα in AT and CD11b (a macrophage marker) in the liver were observed, implying a proinflammatory state after SCI. Finally, post-SCI mice fed a HFD had elevated free fatty acid (FFA) levels in serum and liver compared to sham-mice fed a HFD, suggesting defective FFA uptake and metabolism. These data suggest that reduced FGF-21 signaling after SCI may, at least in part, be contributing to the metabolic dysfunction after SCI, and that FGF-21 may be a candidate for the treatment of SCI-related metabolic dysfunction. Disclosure X. Liu: None. L. Harlow: None. Z. Graham: None. J.F. Yarrow: None. K. Cusi: Consultant; Self; Allergan plc., AstraZeneca, Bristol-Myers Squibb, Genentech, Inc., Gilead Sciences, Inc., Merck & Co., Inc. Research Support; Self; Cirius Therapeutics, Echosens, Eli Lilly and Company, Inventiva Pharma, Janssen Pharmaceuticals, Inc., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Poxel SA, Zydus Pharmaceuticals, Inc. W.A. Bauman: None. C.P. Cardozo: None. Funding U.S. Department of Veterans Affairs (B9212C, B2020C)

Fibroblast Growth Factor 21 Signaling Activation by Selected Bioactive Compounds from Cocoa Shell Modulated Metabolism and Mitochondrial Function in Hepatocytes

Abstract Objectives To evaluate the effect of selected bioactive compounds from cocoa shell and its aqueous extract on the activation of fibroblast growth factor 21 (FGF21) signaling in hepatocytes and the resulting modulation of lipid and glucose metabolism, oxidative stress, and mitochondrial function. Methods The bioactive compounds from cocoa shells were extracted using water and characterized by UPLC-MS/MS. An in vitro model of non-alcoholic fatty liver disease was used: HepG2 cells were co-treated with either pure theobromine (TH), protocatechuic acid (PCA), procyanidin B2 (PB2), epicatechin (EPI), catechin (CAT) (10–50 µmol L−1), or the aqueous extract from cocoa shells (CAE, 20–100 µg mL−1) in the presence or absence of palmitic acid (PA, 500 µmol L−1). FGF21 receptor interaction with cocoa shell phytochemical was evaluated in silico. Biomarkers of cell metabolism were assessed 24 h after the co-treatment in cell supernatants and lysates using chemical, biochemical, and immunochemical techniques. Results Phytochemicals from cocoa shell were able to interact in silico with FGF21 receptor (biding energies from −6.0 to −11.0 kcal mol−1) denoting a potential interaction causing FGF21 receptor response. FGF21 hepatic signaling was activated (1.1 to 2.3-fold enhance in ERK1/2 phosphorylation). CAE, TH, PCA, PB2, EPI, and CAT diminished PA-elicited lipid accumulation (5–86%, P < 0.05) by reducing fatty acid synthase expression, and stimulated lipolysis (1–87%, P < 0.05) through the up-regulation of lipoprotein lipase expression. CAE and therein-bioactive compounds, mainly TH and PCA, promoted glucose uptake (4–35%, P < 0.05) via the increase in the phosphorylation of the insulin receptor (2.2-fold, P < 0.05), protein kinase B (2.8-fold, P < 0.05), AMPKα (2.0-fold, P < 0.05), and ERK1/2 (2.8-fold, P < 0.05) phosphorylation. Oxidative stress was prevented (50–100%, P < 0.05), and the loss of mitochondrial content (15–100%, P < 0.05) and function, measured as ATP production, alleviated (28–100%, P < 0.05). Conclusions Results demonstrated that the major bioactive compounds, primarily TH and PCA, found in cocoa shell could activate FGF21 signaling and regulated hepatic lipid and glucose metabolism, preventing insulin resistance, oxidative stress, and mitochondrial dysfunction. Funding Sources USDA-NIFA-HATCH, and the Spanish Ministry of Science and Innovation.

SUN-665 Peripheral CB1R Blocker Improves Metabolism in Diet Induced Obese Mice Independent of Hepatic FGF21

Obesity is associated with an overactive endocannabinoid system, and selective blockade of CB1R in peripheral tissues, including the liver, reverses HFD-induced metabolic abnormalities by restoring normal lipid and glucose homeostasis. Fibroblast growth factor-21 (FGF21) has emerged as a major endocrine regulator derived from the liver that reduces adiposity and hepatic steatosis and improves glucose tolerance and insulin sensitivity, with changes similar to those induced by CB1R blockade. Here we investigated whether FGF21 mediate the metabolic effects of CB1R blockade in DIO mice.In C57BL/6J wild-type mice, HFD caused a robust increase in hepatic Fgf21 mRNA and serum FGF21 levels, which were reversed by chronic CB1R blockade to levels observed in STD or vehicle-treated hepatocyte-specific CB1R-/- (LCB1-/-) mice, indicating activation of CB1R in the liver is largely involved in HFD-induced “FGF21-resistant” state. In contrast, the expression of the FGF21 receptor Fgfr1 and co-receptor β-klotho (Klb) were dramatically reduced by HFD in both epididymal fat and brain tissue in wild-type mice, and these effects were reversed by peripheral CB1R antagonist JD5037 treatment.To address whether FGF21 mediated the metabolic effects of CB1R blockade, we repeated JD5037 treatment in liver-specific FGF21-/- (FGF21-LKO) mice. Surprisingly, JD5037 treatment was almost equally effective in both HFD-fed wild-type and in FGF21-LKO mice in reducing body weight and hepatic steatosis, attenuating hyperinsulinemia and hyperleptinemia. The current data suggest that peripheral CB1R blockade in obese mice improves insulin sensitivity and energy expenditure independently of hepatic FGF21.

Robust RBM3 and β-klotho expression in developing neurons in the human brain

RNA binding motif 3 (RBM3) is a powerful neuroprotectant that inhibits neurodegenerative cell death in vivo and is a promising therapeutic target in brain ischemia. RBM3 is increased by the hormone fibroblast growth factor 21 (FGF21) in an age- and temperature-dependent manner in rat cortical neurons. FGF21 receptor binding is controlled by the transmembrane protein β-klotho, which is mostly absent in the adult brain. We discovered that RBM3/β-klotho is unexpectedly high in the human infant vs. adult brain (hippocampus/prefrontal cortex). The use of tissue homogenates in that study precluded a comparison of RBM3/β-klotho expression among different CNS cell-types, thus, omitted key evidence (i.e. confirmation of neuronal expression) that would otherwise provide a critical link to support their possible direct neuroprotective effects in humans. This report addresses that knowledge gap. High-quality fixed human hippocampus, cortex, and hypothalamic tissues were acquired from the NIH Neurobiobank (<1 yr (premature born) infants, 1 yr, 4 yr, and 34 yr). Dual labeling of cell-type markers vs. RBM3/β-klotho revealed enriched staining of targets in neurons in the developing brain. Identifying that RBM3/β-klotho is abundant in neurons in the immature brain is fundamentally important to guide protocol design and conceptual frameworks germane to future testing of these neuroprotective pathways in humans.

Fibroblast growth factor-21 (FGF21) administration to early-lactating dairy cows. I. Effects on signaling and indices of insulin action

Modern dairy cows rely on hormonally driven mechanisms to coordinate the metabolic adaptations needed to meet the energy and nutrient deficits of early lactation. In the case of glucose, dairy cows cope with its scarcity during early lactation via reduced plasma concentrations of insulin and the insulin sensitizing hormone adiponectin and increased insulin resistance. Reduced insulin action promotes diversion of available glucose to the mammary gland but increases susceptibility to diseases if excessive. In earlier work, we reported that the insulin sensitizing hormone fibroblast growth factor-21 (FGF21) is increased in periparturient dairy cows and identified liver and adipose tissue as possible targets. These observations raised the possibility that FGF21 acts directly on these tissues to limit the insulin resistance of early lactation. To test this hypothesis, dairy cows were randomly assigned on d 12.6 ± 2.2 (± standard error) of lactation to receive either excipient (n = 6) or recombinant human FGF21 (n = 7), first as an FGF21 bolus of 3 mg/kg of body weight, followed 2 d later by a constant i.v. infusion of FGF21 at the rate of 6.3 mg/kg of metabolic body weight for 9 consecutive days. Biopsies of liver and adipose tissue were collected during the bolus phase of the experiment and used to analyze FGF21 signaling by Western blotting and expression of its receptor components by quantitative PCR. Bolus FGF21 administration caused a 4-fold increase in p44/42 MAPK (ERK1/2) activation in adipose tissue but had no effect on AKT and signal transducer and activator of transcription-3 (STAT3) signaling. The liver expressed negligible levels of the preferred FGF21 receptor FGFR1c and failed to mount any FGF21 signaling response. The FGF21 administered as a bolus had no effect on plasma glucose or insulin and did not stimulate an acute release of adiponectin from adipose tissue. Similarly, FGF21 infusion had no effect on plasma levels of glucose or insulin measured over the 9-d infusion or on glucose disposal during an i.v. glucose tolerance test performed on d 8 of infusion. Finally, the chronic FGF21 infusion had no effect on indices of adiponectin production, including plasma adiponectin and adipose tissue mRNA abundance of adiponectin and the endoplasmic reticulum chaperones ERO1A and DSBA-L involved in the assembly of adiponectin into multimeric complexes. These data show that human FGF21 does not act as an insulin sensitizer during the energy and glucose deficit of early lactation but do not rule out such a role in other physiological states.

OR01-3 MicroRNA-34a-Mediated FGF21 Resistance in the Adipose Tissue Contributes to Insulin Resistance and Hypoadiponectinemia in Diet-Induced Obesity

Background and Objective: Fibroblast growth factor 21 (FGF21) is a metabolic hormone with multiple beneficial effects on glucose and lipid homeostasis, in part mediated through its stimulatory effect on adiponectin secretion. However, FGF21 circulating levels are paradoxically elevated in obesity, type 2 diabetes and other obesity-related disorders, suggesting the presence of FGF21 resistance in obesity. MicroRNA-34a (miR-34a) is the most highly elevated microRNA in white adipose tissues of obese mice and a conserved miR-34a seed sequence had been detected within the 3’UTR of FGFR1 and β-klotho. Here we sought to investigate the mediatory role of miR-34a in FGF21resistance. Methods: miR-34a expression and the corresponding changes in the expression of FGFR1 and β-klotho were assessed in visceral adipose tissue from mice with or without diet-induced obesity (DIO). Luciferase assay was used to examine the binding capacity of miR-34a to the FGF21 receptor complex. The ability to reverse FGF21 resistance via inhibiting adipose miR-34a in vivo was evaluated by both lentivirus-mediated miR-34a sponge and adipose tissue specific genetic depletion. Results: A consistent elevation of miR-34a expression in the adipose tissue was observed during the development of DIO, accompanied by a progressive increase in serum FGF21 levels. Following a transient increase at 4 weeks, mRNA levels of FGFR1 and β-klotho markedly decreased with DIO, accompanied by progressive resistance to the actions of exogenous FGF21, in terms of lowering of hyperglycemia and hyperinsulinemia, and adiponectin stimulation. Site-directed mutagenesis and luciferase activity studies showed that miR-34a suppressed the expression of FGFR1 and β-klotho and also adiponectin secretion. Blocking miR-34a actions by in vivo lentivirus-mediated miR-34a sponge or adipose tissue specific gene knock-out counteracted the reduction of FGFR1 and β-klotho expressions in mice with DIO and restored the ability of FGF21 to induce adiponectin secretion in their adipose tissue. Conclusion: During the development of obesity, a progressive increase of miR-34a in visceral adipose tissue is accompanied by a decline in FGF21 sensitivity, leading to hypoadiponectinemia and insulin resistance. The possibility of selective inhibition of miR-34a in the adipose tissue, as a therapeutic approach to obesity-related metabolic disorders, warrants further investigation. Acknowledgement: This work was supported by a grant from the Health & Medical Research Fund (02132836).

Impact of aging and caloric restriction on fibroblast growth factor 21 signaling in rat white adipose tissue

Caloric restriction (CR) suppresses age-related pathophysiology and extends lifespan. We recently reported that metabolic remodeling of white adipose tissue (WAT) plays an important role in the beneficial actions of CR; however, the detailed molecular mechanisms of this remodeling remain to be established. In the present study, we aimed to identify CR-induced alterations in the expression of fibroblast growth factor 21 (FGF21), a regulator of lipid and glucose metabolism, and of its downstream signaling mediators in liver and WAT, across the lifespan of rats. We evaluated groups of rats that had been either fed ad libitum or calorie restricted from 3 months of age and were euthanized at 3.5, 9, or 24 months of age, under fed and fasted conditions. The expression of FGF21 mRNA and/or protein increased with age in liver and WAT. Interestingly, in the WAT of 9-month-old fed rats, CR further upregulated FGF21 expression and eliminated the aging-associated reductions in the expression of FGFR1 and beta-klotho (KLB; FGF21 receptor complex). It also enhanced the expression of FGF21 targets, including glucose transporter 1 and peroxisome proliferator-activated receptor (PPAR)γ coactivator-1α. The analysis of transcriptional regulators of Fgf21 suggested that aging and CR might upregulate Fgf21 expression via different mechanisms. In adipocytes in vitro, constitutive FGF21 overexpression upregulated the FGF21 receptor complex and FGF21 targets at the mRNA or protein level. Thus, both aging and CR induced FGF21 expression in rat WAT; however, only CR activated FGF21 signaling. Our results suggest that FGF21 signaling contributes to the CR-induced metabolic remodeling of WAT, likely activating glucose uptake and mitochondrial biogenesis.