Fibroblast growth factor-21 potentiates the stimulatory effects of 1,25-dihydroxyvitamin D3 on transepithelial calcium transport and TRPV6 Ca2+ channel expression.

Fibroblast growth factor (FGF)-21 is a salient liver-derived endocrine regulator for metabolism of glucose and triglyceride as well as bone remodeling. Previously, certain peptides in the FGF family have been shown to modulate calcium absorption across the intestinal epithelia. Since FGF21 receptor, i.e., FGF receptor-1, is abundantly expressed in the enterocytes, there was a possibility that FGF21 might exert direct actions on the intestine. Herein, a large-scale production of recombinant FGF21 at the multi-gram level was developed in order to minimize variations among various batches. In the oral glucose tolerance test, recombinant FGF21 was found to reduce plasma glucose levels in mice fed high-fat diet. A series of experiments applying radioactive tracer 45Ca in Ussing chamber showed that FGF21 potentiated the stimulatory effect of low-dose 1,25-dihydroxyvitamin D3 [10 nM 1,25(OH)2D3] on the transepithelial calcium transport across intestinal epithelium-like Caco-2 monolayer. FGF21 + 1,25(OH)2D3 also decreased transepithelial resistance, but had no effect on epithelial potential difference or short-circuit current. Furthermore, 1,25(OH)2D3 alone upregulated the Caco-2 mRNA expression of the major apical calcium channels, i.e., transient receptor potential vanilloid subfamily member 6 (TRPV6), which was further elevated by a combination of FGF21 and 1,25(OH)2D3, consistent with the upregulated TRPV6 protein expression in enterocytes of FGF21-treated mice. However, FGF21 was without effects on the mRNA expression of voltage-gated calcium channel 1.3, calbindin-D9k, plasma membrane Ca2+-ATPase 1b, claudin-12 or claudin-15. In conclusion, FGF21 did exert a direct action on the intestinal epithelial cells by potentiating the 1,25(OH)2D3-enhanced calcium transport, presumably through the upregulation of TRPV6 expression.

FGF21 as a mediator of adaptive changes in food intake and macronutrient preference in response to protein restriction.

Free-feeding animals navigate complex nutritional landscapes in which food availability, cost, and nutritional value can vary markedly. Animals have thus developed neural mechanisms that enable the detection of nutrient restriction, and these mechanisms engage adaptive physiological and behavioral responses that limit or reverse this nutrient restriction. This review focuses specifically on dietary protein as an essential and independently defended nutrient. Adequate protein intake is required for life, and ample evidence exists to support an active defense of protein that involves behavioral changes in food intake, food preference, and food motivation, likely mediated by neural changes that increase the reward value of protein foods. Available evidence also suggests that the circulating hormone fibroblast growth factor 21 (FGF21) acts in the brain to coordinate these adaptive changes in food intake, making it a unique endocrine signal that drives changes in macronutrient preference in the context of protein restriction. This article is part of the Special Issue on "Food intake and feeding states".

The role of FGF-21 in promoting diabetic wound healing by modulating high glucose-induced inflammation.

Background: Wound healing is a complex biological process that can be impaired in individuals with diabetes. Diabetic wounds are a serious complication of diabetes that require promoting diagnosis and effective treatment. FGF-21, a member of the endocrine FGF factors family, has caught the spotlight in the treatment of diabetes for its beneficial effects on accelerating human glucose uptake and fat catabolism. However, the therapeutic efficacy of FGF-21 in promoting diabetic wounds remains unknown. This study aims to evaluate the therapeutic potential of FGF-21 in promoting diabetic wound healing. Methods: we investigated the effects of FGF-21 on wound healing related-cells under high-glucose conditions using various assays such as CCK8, scratch assay, flow cytometry analysis, endothelial tube-formation assay, and transmission electron microscopy. Furthermore, we used db/db mice to verify the healing-promoting therapeutic effects of FGF-21 on diabetic wounds. We also conducted qRT-PCR, Western blot, and immunofluorescence staining analyses to elucidate the underlying mechanism. Result: Our results indicate that FGF-21 treatment restored hyperglycemic damage on endothelial cell proliferation, migration, and tube-forming ability. It also reduced endothelial cell death rates under high-glucose conditions. TEM analysis showed that FGF-21 treatment effectively restored mitochondrial damage and morphological changes in endothelial cells caused by glucose. Additionally, qRT-PCR and Western blot analysis indicated that FGF-21 treatment restored inflammatory responses caused by hyperglycemic damage. Animal experiments confirmed these findings, suggesting that FGF-21 may be a promising candidate for the treatment of non-healing diabetic wounds due to its effectiveness in stimulating angiogenesis and anti-inflammatory function. Conclusion: Our study provides evidence that FGF-21 is an essential regulator of wound-related cells under high-glucose conditions and has the potential to be a novel therapeutic target for accelerating diabetic wound healing.

Regeneration of Non-Alcoholic Fatty Liver Cells Using Chimeric FGF21/HGFR: A Novel Therapeutic Approach.

Non-alcoholic fatty liver disease (NAFLD) has emerged as a significant liver ailment attributed to factors like obesity and diabetes. While ongoing research explores treatments for NAFLD, further investigation is imperative to address this escalating health concern. NAFLD manifests as hepatic steatosis, precipitating insulin resistance and metabolic syndrome. This study aims to validate the regenerative potential of chimeric fibroblast growth factor 21 (FGF21) and Hepatocyte Growth Factor Receptor (HGFR) in NAFLD-afflicted liver cells. AML12, a murine hepatocyte cell line, was utilized to gauge the regenerative effects of chimeric FGF21/HGFR expression. Polysaccharide accumulation was affirmed through Periodic acid-Schiff (PAS) staining, while LDL uptake was microscopically observed with labeled LDL. The expression of FGF21/HGFR and NAFLD markers was analyzed by mRNA analysis with RT-PCR, which showed a decreased expression in acetyl-CoA carboxylase 1 (ACC1) and sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP) with increased expression of hepatocellular growth factor (HGF), hepatocellular nuclear factor 4 alpha (HNF4A), and albumin (ALB). These findings affirm the hepato-regenerative properties of chimeric FGF21/HGFR within AML12 cells, opening novel avenues for therapeutic exploration in NAFLD.

Association of hepatokines with markers of endothelial dysfunction and vascular reactivity in obese adolescents.

OBJECTIVES: Obesity-induced insulin resistance (IR) is known to influence hepatic cytokines (hepatokines), including fibroblast growth factor (FGF-21), fetuin-A, and chemerin. This study aimed to investigate the association between hepatokines and markers of endothelial dysfunction and vascular reactivity in obese adolescents. METHODS: A total of 45 obese adolescents were categorized into three groups based on glucose tolerance: normal glucose tolerance (NGT), prediabetes (PD), and type 2 diabetes (T2D). We examined the relationships between FGF-21, fetuin-A, and chemerin with endothelial markers (plasminogen activator inhibitor-1 [PAI-1], intercellular adhesion molecule-1 [ICAM-1], and vascular cell adhesion marker-1 [VCAM-1]) and vascular surrogates (brachial artery reactivity testing [BART] and peak reactive hyperemia [PRH]). RESULTS: Obese adolescents (age 16.2±1.2 years; 62 % female, 65 % Hispanic) with NGT (n=20), PD (n=14), and T2D (n=11) had significant differences between groups in BMI; waist-hip ratio (p=0.05), systolic BP (p=0.008), LDL-C (p=0.02), PAI-1 (p<0.001). FGF-21 pg/mL (mean±SD: NGT vs. PD vs. T2D 54±42; 266±286; 160±126 p=0.006) and fetuin-A ng/mL (266±80; 253±66; 313±50 p=0.018), were significantly different while chemerin ng/mL (26±5; 31±10; 28±2) did not significantly differ between the groups. Positive correlations were found between chemerin and both PAI-1 (r=0.6; p=0.05) and ICAM-1 (r=0.6; p=0.05), FGF-21 and PAI-1 (r=0.6; p<0.001), and fetuin-A with TNFα (r=-0.4; p=0.05). Negative correlations were found between chemerin and PRH (r= -0.5; p=0.017) and fetuin-A and PRH (r=-0.4; p=0.05). CONCLUSIONS: In our cohort, IR predicted higher FGF-21 levels suggesting a linear relationship may exist between the two parameters. Hepatokines can augment alterations in the microvascular milieu in obese adolescents as demonstrated by their associations with the markers PAI-1, ICAM-1, and PRH.

Therapeutic effect of long-acting FGF21 with controlled site-specific modification on nonalcoholic steatohepatitis.

FGF21 plays an active role in the treatment of type 2 diabetes, obesity, nonalcoholic fatty liver disease (NAFLD), and nonalcoholic steatohepatitis (NASH). However, the short half-life and poor stability of wild-type FGF21 limit its clinical application. Previous studies found that PEGylation can significantly increase the stability of FGF21. However, the uneven distribution of PEGylation sites in FGF21 makes it difficult to purify PEG-FGF21, thereby affecting its yield, purity, and activity. To obtain long-acting FGF21 with controlled site-specific modification, we mutated lysine residues in FGF21, resulting in PEGylation only at the N-terminus of FGF21 (mFGF21). In addition, we modified mFGF21 molecules with different PEG molecules and selected the PEG-mFGF21 moiety with the highest activity. The yield of PEG-mFGF21 in this study reached 1 g/L (purity >99 %), and the purification process was simple and efficient with strong quality controllability. The half-life of PEG-mFGF21 in rats reached 40.5-67.4 h. Pharmacodynamic evaluation in mice with high-fat, high-cholesterol- and methionine and choline deficiency-induced NASH illustrated that PEG-mFGF21 exhibited long-term efficacy in improving liver steatosis and reducing liver cell damage, inflammation, and fibrosis. Taken together, PEG-mFGF21 could represent a potential therapeutic drug for the treatment of NASH.

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 ß-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 ß-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 ß-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.

Fibroblast growth factor 21 (FGF21) attenuates tacrolimus-induced hepatic lipid accumulation through transcription factor EB (TFEB)-regulated lipophagy. / æˆçº¤ç»´ç»†èƒžç”Ÿé•¿å› å­21通过TFEBä»‹å¯¼çš„è„‚å™¬ç¼“è§£ä»–å ‹èŽ«å¸å¼•èµ·çš„è‚è„è„‚è´¨ç§¯èš.

Tacrolimus (TAC), also called FK506, is one of the classical immunosuppressants to prevent allograft rejection after liver transplantation. However, it has been proved to be associated with post-transplant hyperlipemia. The mechanism behind this is unknown, and it is urgent to explore preventive strategies for hyperlipemia after transplantation. Therefore, we established a hyperlipemia mouse model to investigate the mechanism, by injecting TAC intraperitoneally for eight weeks. After TAC treatment, the mice developed hyperlipemia (manifested as elevated triglyceride (TG) and low-density lipoprotein cholesterol (LDL-c), as well as decreased high-density lipoprotein cholesterol (HDL-c)). Accumulation of lipid droplets was observed in the liver. In addition to lipid accumulation, TAC induced inhibition of the autophagy-lysosome pathway (microtubule-associated protein 1 light chain 3ß (LC3B) II/I and LC3B II/actin ratios, transcription factor EB (TFEB), protein 62 (P62), and lysosomal-associated membrane protein 1 (LAMP1)) and downregulation of fibroblast growth factor 21 (FGF21) in vivo. Overexpression of FGF21 may reverse TAC-induced TG accumulation. In this mouse model, the recombinant FGF21 protein ameliorated hepatic lipid accumulation and hyperlipemia through repair of the autophagy-lysosome pathway. We conclude that TAC downregulates FGF21 and thus exacerbates lipid accumulation by impairing the autophagy-lysosome pathway. Recombinant FGF21 protein treatment could therefore reverse TAC-caused lipid accumulation and hypertriglyceridemia by enhancing autophagy.

Efruxifermin, an investigational treatment for fibrotic or cirrhotic nonalcoholic steatohepatitis (NASH).

INTRODUCTION: Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and strongly associated with metabolic disorders: obesity, type 2 diabetes (T2D), cardiovascular disease. Persistent metabolic injury results in inflammatory processes leading to nonalcoholic steatohepatitis (NASH), liver fibrosis, and ultimately cirrhosis. To date, no pharmacologic agent is approved for the treatment of NASH. Fibroblast growth factor 21 (FGF21) agonism has been linked to beneficial metabolic effects ameliorating obesity, steatosis, and insulin resistance, supporting its potential as a therapeutic target in NAFLD. AREAS COVERED: Efruxifermin (EFX, also AKR-001 or AMG876) is an engineered Fc-FGF21 fusion protein with an optimized pharmacokinetic and pharmacodynamic profile, which is currently tested in several phase 2 clinical trials for the treatment of NASH, fibrosis and compensated liver cirrhosis. EFX improved metabolic disturbances including glycemic control, showed favorable safety and tolerability, and demonstrated antifibrotic efficacy according to FDA requirements for phase 3 trials. EXPERT OPINION: While some other FGF-21 agonists (e.g. pegbelfermin) are currently not further investigated, available evidence supports the development of EFX as a promising anti-NASH drug in fibrotic and cirrhotic populations. However, antifibrotic efficacy, long-term safety and benefits (i.e. cardiovascular risk, decompensation events, disease progression, liver transplantation, mortality) remain to be determined.

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.

Design and pharmaceutical evaluation of bifunctional fusion protein of FGF21 and GLP-1 in the treatment of nonalcoholic steatohepatitis.

Fibroblast growth factor 21 (FGF21) and glucagon-like peptide-1 (GLP-1) may be useful for the treatment of type 2 diabetes, obesity, and non-alcoholic fatty liver disease (NAFLD). Previous studies have shown that GLP-1 may synergize with FGF21 in the regulation of glucose and lipid metabolism. Currently, no approved drug therapy is available for non-alcoholic steatohepatitis (NASH). Here, we constructed and screened dual-targeting fusion proteins of GLP-1 and FGF21, connected by elastin-like polypeptides (ELPs), to investigate whether a combination of these two hormones would have therapeutic effects in models of NASH. The temperature phase transition and release of the hormones under physiological conditions were studied to identify a bifunctional fusion protein of FGF21 and GLP-1 (GEF) that was highly stable and showed sustained release. We further evaluated the quality and therapeutic efficacy of GEF in three mouse models of NASH. We successfully synthesized a novel recombinant bifunctional fusion protein with high stability and low immunogenicity. The GEF protein synthesized ameliorated hepatic lipid accumulation, hepatocyte damage, and inflammation; prevented the progression of NASH in the three models; reduced glycemia; and caused weight loss. This novel GEF molecule may be suitable for clinical use for the treatment of NAFLD/NASH and related metabolic diseases.

Fibroblast growth factor 21 and bone homeostasis.

Fibroblast growth factor 21 (FGF21), a member of the FGF subfamily, is produced primarily in the liver and adipose tissue. The main function of FGF21 is to regulate energy metabolism of carbohydrates and lipids in the body through endocrine and other means, making FGF21 have potential clinical value in the treatment of metabolic disorders. Although FGF21 and its receptors play a role in the regulation of bone homeostasis through a variety of signaling pathways, a large number of studies have reported that the abuse of FGF21 and its analogues and the abnormal expression of FGF21 in vivo may be associated with bone abnormalities. Due to limited research information on the effect of FGF21 on bone metabolism regulation, the role of FGF21 in the process of bone homeostasis regulation and the mechanism of its occurrence and development have not been fully clarified. Certainly, the various roles played by FGF21 in the regulation of bone homeostasis deserve increasing attention. In this review, we summarize the basic physiological knowledge of FGF21 and the effects of FGF21 on metabolic homeostasis of the skeletal system in animal and human studies. The information provided in this review may prove beneficial for the intervention of bone diseases.

Research Progress of β-Klotho in Energy Metabolism and Tumor Development / 中国生物化学与分子生物学报

β-Klotho (KLB) is a member of the Klotho protein family, which is mainly distributed in organs and tissues such as the liver, fat, pancreas, and brain. KLB is a single-pass transmembrane protein whose structural characteristics determine that KLB acts as a co-receptor for fibroblast growth factor (FGF) 19/21 targeting the activation of fibroblast growth factor receptor (FGFRs). KLB is involved in the regulation of blood glucose, lipids, body weight, bile acid circulation, and hepatocyte proliferation in the FGF21/19-KLB-FGFRs pathway. This paperwill review the structural characteristics and distribution of KLB, as well as the regulatory mechanism of material energy and its role in tumor formation in the FGF19/21-KLB-FGFRs pathways.

Fibroblast growth factor 21 (FGF21) attenuates tacrolimus-induced hepatic lipid accumulation through transcription factor EB (TFEB)-regulated lipophagy / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Tacrolimus (TAC), also called FK506, is one of the classical immunosuppressants to prevent allograft rejection after liver transplantation. However, it has been proved to be associated with post-transplant hyperlipemia. The mechanism behind this is unknown, and it is urgent to explore preventive strategies for hyperlipemia after transplantation. Therefore, we established a hyperlipemia mouse model to investigate the mechanism, by injecting TAC intraperitoneally for eight weeks. After TAC treatment, the mice developed hyperlipemia (manifested as elevated triglyceride (TG) and low-density lipoprotein cholesterol (LDL-c), as well as decreased high-density lipoprotein cholesterol (HDL-c)). Accumulation of lipid droplets was observed in the liver. In addition to lipid accumulation, TAC induced inhibition of the autophagy-lysosome pathway (microtubule-associated protein 1 light chain 3β (LC3B) II/I and LC3B II/actin ratios, transcription factor EB (TFEB), protein 62 (P62), and lysosomal-associated membrane protein 1 (LAMP1)) and downregulation of fibroblast growth factor 21 (FGF21) in vivo. Overexpression of FGF21 may reverse TAC-induced TG accumulation. In this mouse model, the recombinant FGF21 protein ameliorated hepatic lipid accumulation and hyperlipemia through repair of the autophagy-lysosome pathway. We conclude that TAC downregulates FGF21 and thus exacerbates lipid accumulation by impairing the autophagy-lysosome pathway. Recombinant FGF21 protein treatment could therefore reverse TAC-caused lipid accumulation and hypertriglyceridemia by enhancing autophagy.

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 (Aß) generation and clearance are thought to play a pivotal role in the pathogenesis of AD. Historically, strategies targeting Aß clearance have typically focused on central clearance, but with limited clinical success. Recently, the contribution of peripheral systems, particularly the liver, to Aß 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 Aß 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.

Sitagliptin reduces FAP-activity and increases intact FGF21 levels in patients with newly detected glucose abnormalities.

INTRODUCTION: Fibroblast growth factor 21 (FGF21), a hormone with pleiotropic metabolic effects, is inactivated by fibroblast activation protein (FAP), a member of the dipeptidyl peptidase-IV (DPP-IV) family. We investigate if sitagliptin (DPP-IV inhibitor) inhibits FAP-activity and increases intact FGF21. METHODS: Patients with impaired glucose metabolism were randomized to 100 mg sitagliptin (n = 34) or placebo (n = 37) treatment for 12 weeks. Plasma samples obtained at study entry and at 12-weeks were analysed for FAP-activity, FAP, total FGF21 and intact FGF21. RESULTS: Sitagliptin significantly inhibited FAP-activity (497 ± 553 vs. 48 ± 712 RFU/min, p < 0.01) and correspondingly increased intact FGF21 (253 ± 182 vs 141 ± 80 ng/L, p < 0.01) compared to placebo in plasma. Sitagliptin dose-dependently inhibited the FAP-activity in vitro. Intact FGF21 was higher in patients obtaining a normal glucose tolerance regardless of treatment (p = 0.03). CONCLUSION: A sitagliptin-induced increase of intact FGF21 may contribute to an improved metabolic effect in patients with impaired glucose metabolism.