Inventing new medicines: The FGF21 story

Clinical Trial: A Phase 2b Study to Evaluate the Efficacy and Safety of MK-3655 in Individuals With Pre-Cirrhotic MASH

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a metabolic regulator with demonstrated efficacy for the treatment of metabolic dysfunction-associated steatohepatitis (MASH). FGF21 signals through 'c' isoforms of the FGF receptors (FGFR) 1-3 and the co-receptor β-klotho.

AIMS

We report the safety and efficacy of MK-3655, a monoclonal antibody that binds β-klotho and selectively activates the FGFR1c/β-klotho co-receptor complex, in patients with pre-cirrhotic MASH.

METHODS

Phase 2b, randomised, multicenter, double-blind, placebo-controlled, parallel-group study in patients with pre-cirrhotic MASH (NAS ≥ 4 and MASH CRN fibrosis score Stage 2 or 3). Participants were randomised 1:1:1:1 to receive MK-3655 50 mg, 100 mg, 300 mg, or matching placebo subcutaneously every 4 weeks. The primary endpoint was MASH resolution without worsening of fibrosis by histology at Week 52. An interim analysis (IA) of liver fat content (LFC) was planned once ≥ 25 participants per treatment group completed an MRI-PDFF assessment at Week 24.

RESULTS

Among 183 participants, mean BMI was 33.4 kg/m2, mean LFC was 18.1%, and 52.5% had type 2 diabetes. At the IA, the differences from placebo in relative reduction from baseline in LFC were assessed as insufficient for continuation of the trial. Among participants with Week 24 LFC assessment, percent relative reductions from baseline (LS mean difference vs. placebo) for MK-3655 50 mg (N = 33), 100 mg (N = 36), and 300 mg (N = 31), were 19.1%, 19.0%, and 26.1%, respectively. MK-3655 was generally well tolerated.

CONCLUSIONS

In patients with pre-cirrhotic MASH, treatment with MK-3655 resulted in a modest reduction in LFC at 24 weeks.

CLINICAL TRIAL NUMBER

EudraCT: 2019-003048-63; NCT: 04583423.

Enhanced paracrine action of FGF21 in stromal cells delays thymic aging

Age-related thymic involution precedes aging of all other organs in vertebrates and initiates the process of declining T cell diversity, which leads to eventual immune dysfunction. Whether FGF21, a liver-derived pro-longevity hormone that is also produced in thymic stroma, including by adipocytes, controls the mechanism of thymic demise is incompletely understood. Here, we demonstrate that elevation of FGF21 in thymic epithelial cells (TECs) and in adipocytes protects against thymic aging, whereas conditional hepatic overexpression did not impact thymic biology in aged mice. Notably, elevation of thymic FGF21 increased naïve CD8 T cells in aged animals and extended healthspan. Mechanistically, thymic FGF21 overexpression elevated TECs and reduced fibroadipogenic cells. Ablation of β-klotho, the obligatory co-receptor for FGF21 in Foxn1+ TECs, accelerated thymic aging, suggesting regulation of TECs by FGF21 is partially required for thymic lymphopoiesis. These findings establish that paracrine FGF21 improves thymic function and delays immune aging.

Distinct Fgf21 Expression Patterns in Various Tissues in Response to Different Dietary Regimens Using a Reporter Mouse Model

Background: Fibroblast growth factor 21 (FGF21), a secreted protein, plays a crucial role in regulating metabolism and energy homeostasis. Nevertheless, the expression pattern of Fgf21 across diverse tissues and its responsiveness to various dietary regimens remain incompletely understood. Methods: In this study, we developed a Fgf21-enhanced green fluorescent protein (EGFP) reporter mouse model to explore the expression of endogenous Fgf21 in different tissues under four dietary conditions: normal chow, low-protein diet, fasting, and fasting-refeeding. Results: A low-protein diet was found to induce Fgf21 expression in both the liver and skeletal muscle. Notably, Fgf21 was predominantly expressed in the periportal region of the liver. In the pancreas, Fgf21 exhibited a patchy expression pattern in the exocrine portion, but was absent in the endocrine part, regardless of the dietary regimens. Regarding the spleen, fasting triggered the expression of Fgf21, which was mainly localized in the red pulp area. Moreover, under fasting conditions, Fgf21 showed a scattered expression pattern in the small intestine. Conclusions: The Fgf21-EGFP reporter mouse model serves as a valuable tool for dissecting the expression of endogenous Fgf21 in different tissues under various dietary and stress conditions. Further investigations using this model may contribute to uncovering the hitherto unrecognized functions of locally produced FGF21.

The latest reports and treatment methods on polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is an increasingly recognized endocrine disorder. The pathogenesis is not fully known. Polycystic ovary syndrome is still difficult to diagnose correctly, despite simple diagnostic criteria. The aim of the study is to review the current knowledge about PCOS and treatment options for patients with the disease. To explore this topic, publications were reviewed and conclusions drawn from them. The incidence of hyperandrogenism in a patient with PCOS may be as high as 60-80%. Increased androgen levels affect ovulation and menstruation, and also result in hirsutism and acne. Additionally, patients have problems with proper glucose tolerance (insulin resistance), type 2 diabetes, hypertension, cardiovascular diseases and metabolic syndrome. PCOS results in various symptoms in patients.

The latest treatment methods were analysed. A standard review of publications in the field of diagnosis and treatment of PCOS, IR and hyperandrogenism was used.

Lifestyle, especially diet, deserves special attention due to its ease of use. Sleep quality, physical activity and stress reduction are also important. Diet should be the treatment of first choice. Only if dietary intervention does not bring results, the doctor considers pharmacotherapy. Recently, acupuncture and herbal medicine, vagus nerve stimulation have been used in the treatment of PCOS and regulation of hormone levels. Patients are given supplementation to improve the quality of functioning, but it must be remembered that inappropriate doses or too long use may result in a toxic effect opposite to the therapeutic one.

Appropriate diet, physical activity - lifestyle changes are crucial in the treatment of PCOS. Supplementation and pharmaceuticals support treatment. It is mandatory to examine these environmental and lifestyle factors as they not only contribute to the occurrence of the disease but also influence its progression.

Advances in the Treatment of Rare Mutations in Non-Small Cell Lung Cancer

Lung cancer is a malignant tumor with the highest morbidity and mortality rate worldwide, with nearly 2.5 million new cases and more than 1.8 million deaths reported globally in 2022. Lung cancer is broadly categorized into two main types: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), with NSCLC accounting for about 85% of all cases. Early-stage lung cancers often present without obvious symptoms, resulting in most patients being diagnosed at an advanced stage where traditional chemotherapy has limited efficacy. Recent advances in molecular biology have elucidated the pivotal role of gene mutations in tumor development, paving the way for targeted therapies that have markedly benefited patients. Beyond the well-known epidermal growth factor receptor (EGFR) mutation, an increasing number of new molecular targets have been identified, including ROS1 rearrangement, BRAF mutation, NTRK fusion, RET fusion, MET mutation, KRAS G12C mutation, HER2 mutation, ALK rearrangement, and NRG1 fusion. Some of these targeted therapies have already been approved by the Food and Drug Administration (FDA), and many others are currently undergoing clinical trials. This review summarizes recent advances in NSCLC treatment with molecular targets, highlighting progress, challenges, and their impact on patient prognosis.

Comprehensive in silico analysis of prognostic and immune infiltrates for FGFs in human ovarian cancer

BACKGROUND

Fibroblast growth factors (FGFs) are cell signaling proteins that perform multiple biological processes in many biological processes (cell development, repair, and metabolism). The dynamics of tumor cells, such as angiogenesis, transformation, and proliferation, have a significant impact on neoplasia and are modulated by FGFs. FGFs' expression and prognostic significance in ovarian cancer (OC), however, remain unclear.

METHODS

Through a series of in silico analysis, we investigated the transcriptional, survival data, genetic variation, gene-gene interaction network, ferroptosis-related genes, and DNA methylation of FGFs in OC patients.

RESULTS

We discovered that while FGF18 expression levels were higher in OC tissues than in normal OC tissues, FGF2/7/10/17/22 expression levels were lower in the former, and that FGF1/19 expression was related to the tumor stage in OC patients. According to the survival analysis, the clinical prognosis of individuals with OC was associated with the aberrant expression of FGFs. The function of FGFs and their neighboring genes was mainly connected to the cellular response to FGF stimulus. There was a negative correlation between FGF expression and various immune cell infiltration.

CONCLUSIONS

This study clarifies the relationship between FGFs and OC, which might provide new insights into the choice of prognostic biomarkers of OC patients.

Plasma FGF21 Concentration in Kidney Transplant Patients-Results from Prospective and Cross-Sectional Studies

Background/Objectives: Fibroblast growth factor 21 (FGF21) is a protein hormone involved in physiological conditions in the regulation of energy expenditure and several metabolic processes. The aim of this present study was to analyze the effect of successful kidney transplantations on the plasma FGF21 concentration and to study the factors which may influence plasma FGF21 concentration in patients in long time after kidney transplantation. Methods: This study consisted of two independent parts. The first part was a prospective observation of CKD patients in stage 5 before and then on the 14th and 30th day and 6 months after kidney transplantation. The second part of this study was the cross-sectional study completed in patients at least one year after kidney transplantation and the control group. In CKD patients directly before and during the early period after KTx, plasma FGF21 concentrations were measured four times (immediately before and 14 and 30 days and 6 months after KTx). In patients long time after kidney transplantation and in healthy subjects, plasma FGF21 concentration was measured once. Results: Forty patients with chronic kidney disease (CKD) who were either directly before or within the early period after kidney transplantation (KTx), 184 patients longtime after KTx and 50 healthy subjects were enrolled into this study. In CKD patients at the stage directly before receiving a KTx, the mean plasma FGF21 concentration was significantly higher than in the healthy subjects [1013.0 pg/mL versus 239.5 pg/mL, p < 0.001]. At 14, 30 days, and 6 months after the KTx, a significant decrease of plasma FGF21 was observed, with values of 322.5 pg/mL; 355.0 pg/mL; and 344.0 pg/mL (p < 0.001), respectively]. In patients long time after KTx, a negative correlation was found between the plasma FGF21 concentration and the estimated glomerular filtration rate and a positive correlation was found between the plasma FGF21 concentration and the BMI, the serum concentration of triglycerides, insulin, interleukin-6, CRP, and cystatin C. Conclusions: The plasma FGF21 concentration in patients with end-stage renal disease is higher than in healthy subjects and significantly decreases after a successful KTx. The plasma FGF21 concentration measured by ELISA in patients long time after kidney transplantation seems to be related to the degree of kidney function impairment and their metabolic status. The kidneys appear to be one of the main organs involved in the biodegradation and/or elimination of FGF21.

From basic research to clinical application: targeting fibroblast activation protein for cancer diagnosis and treatment

PURPOSE

This study aims to review the multifaceted roles of a membrane protein named Fibroblast Activation Protein (FAP) expressed in tumor tissue, including its molecular functionalities, regulatory mechanisms governing its expression, prognostic significance, and its crucial role in cancer diagnosis and treatment.

METHODS

Articles that have uncovered the regulatory role of FAP in tumor, as well as its potential utility within clinical realms, spanning diagnosis to therapeutic intervention has been screened for a comprehensive review.

RESULTS

Our review reveals that FAP plays a pivotal role in solid tumor progression by undertaking a multitude of enzymatic and nonenzymatic roles within the tumor stroma. The exclusive presence of FAP within tumor tissues highlights its potential as a diagnostic marker and therapeutic target. The review also emphasizes the prognostic significance of FAP in predicting tumor progression and patient outcomes. Furthermore, the emerging strategies involving FAPI inhibitor (FAPI) in cancer research and clinical trials for PET/CT diagnosis are discussed. And targeted therapy utilizing FAP including FAPI, chimeric antigen receptor (CAR) T cell therapy, tumor vaccine, antibody-drug conjugates, bispecific T-cell engagers, FAP cleavable prodrugs, and drug delivery system are also introduced.

CONCLUSION

FAP's intricate interactions with tumor cells and the tumor microenvironment make it a promising target for diagnosis and treatment. Promising strategies such as FAPI offer potential avenues for accurate tumor diagnosis, while multiple therapeutic strategies highlight the prospects of FAP targeting treatments which needs further clinical evaluation.

Long-term effects of a fat-directed FGF21 gene therapy in aged female mice

Fibroblast growth factor 21 (FGF21) has been developed as a potential therapeutic agent for metabolic syndromes. Moreover, FGF21 is considered a pro-longevity hormone because transgenic mice overexpressing FGF21 display extended lifespan, raising the possibility of using FGF21 to promote healthy aging. We recently showed that visceral fat directed FGF21 gene therapy improves metabolic and immune health in insulin resistant BTBR mice. Here, we used a fat directed rAAV-FGF21 vector in 17-month-old female mice to investigate whether long-term FGF21 gene transfer could mitigate aging-related functional decline. Animals with FGF21 treatment displayed a steady, significant lower body weight over 7-month of the study compared to age-matched control mice. FGF21 treatment reduced adiposity and increased relative lean mass and energy expenditure associated with almost 100 folds higher serum level of FGF21. However, those changes were not translated into benefits on muscle function and did not affect metabolic function of liver. Overall, we have demonstrated that a single dose of fat-directed AAV-FGF21 treatment can provide a sustainable, high serum level of FGF21 over long period of time, and mostly influences adipose tissue homeostasis and energy expenditure. High levels of FGF21 alone in aged mice is not sufficient to improve liver or muscle functions.

Comparison of changes in adipokine and inflammatory cytokine levels in patients with newly diagnosed type 2 diabetes treated with exenatide, insulin, or pioglitazone: A post-hoc study of the CONFIDENCE trial

Background

Adipokines and inflammatory cytokines (ADICs) play important roles in type 2 diabetes mellitus (T2DM). This study aimed to compare the changes of ADIC levels (ΔADICs) in patients with newly diagnosed T2DM treated with different antihyperglycemic agents, and further investigate the impact of these changes on metabolic indices, β-cell function and insulin resistance (IR).

Methods

Four hundred and sixteen patients with newly diagnosed T2DM from 25 centers in China randomly received 48-week intervention with exenatide, insulin or pioglitazone. Anthropometric and laboratory data, indices of β-cell function and IR, and levels of AIDCs, including interleukin-1 beta (IL-1β), interferon-gamma (IFN-γ), leptin, and fibroblast growth factor 21 (FGF21) were detected at baseline and the end of the study.

Results

In total, 281 participants (68 % male, age: 50.3 ± 9.4 years) completed the study. After 48- week treatment, IL-1β and IFN-γ were significantly decreased with exenatide treatment (P < 0.001 and P = 0.001, respectively), but increased with insulin (P = 0.009 and P = 0.026, respectively). However, pioglitazone treatment had no impact on ADICs. No significant change in leptin or FGF21 was detected with any of the treatments. After adjustment for baseline values and changes of body weight, waist and HbA1c, the between-group differences were found in ΔIL-1β (exenatide vs. insulin: P = 0.048; and exenatide vs. pioglitazone: P = 0.003, respectively) and ΔIFN-γ (exenatide vs. insulin: P = 0.049; and exenatide vs. pioglitazone: P < 0.001, respectively). Multiple linear regression analysis indicated that Δweight was associated with ΔIL-1β (β = 0.753; 95 % CI, 0.137-1.369; P = 0.017). After adjusting for treatment effects, Δweight was also be correlated with ΔFGF21 (β = 1.097; 95%CI, 0.250-1.944; P = 0.012); furthermore, ΔHOMA-IR was correlated with Δleptin (β = 0.078; 95%CI, 0.008-0.147; P = 0.029) as well. However, ΔHOMA-IR was not significantly associated with ΔIL-1β after adjusting for treatment effects (P = 0.513).

Conclusion

Exenatide treatment led to significant changes of inflammatory cytokines levels (IL-1β and IFN-γ), but not adipokines (leptin and FGF21), in newly diagnosed T2DM patients. The exenatide-mediated improvement in weight and IR may be associated with a decrease in inflammatory cytokine levels.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Studying sex differences in responses to fibroblast growth factor 21 administration in obese mice consuming a sweet-fat diet

In animals, obesity caused by consumption of a sweet-fat diet (SFD) is the most adequate mouse model of human diet-induced obesity. Fibroblast growth factor 21 (FGF21) reduces body weight, beneficially affects taste preferences, and corrects glucose metabolism in obese mice. Sex is known to influence FGF21 effects in different models of diet-induced and hereditary obesity. In mice with SFD-induced obesity, the effects of FGF21 have been studied only in males. The aim of this study was to compare the effects of FGF21 on body weight, food preferences and glucose and lipid metabolism in C57Bl/6J male and female mice with SFD-induced obesity. Mice were fed with a diet consisting of standard chow, lard and cookies for 10 weeks, then they were injected with FGF21 (1 mg per 1 kg) or vehicle for 7 days. Body weight, weights of different types of food, blood parameters, glucose tolerance, gene and protein expression in the liver, gene expression in the white, brown adipose tissues, and the hypothalamus were assessed. FGF21 administration reduced body weight, did not alter total energy consumption, and activated orexigenic pathways of hypothalamus in mice of both sexes. However, sex dimorphism was found in the realization of the orexigenic FGF21 action at the transcriptional level in the hypothalamus. Metabolic effects of FGF21 were also sex-specific. Only in males, FGF21 exerted beneficial antidiabetic action: it reduced fatty acid and leptin plasma levels, improved glucose-tolerance, and upregulated hepatic expression of Ppargc1, Fasn, Accα, involved in lipid turnover, gene Insr and protein glucokinase, involved in insulin action. Only in obese females, FGF21 induced preference of standard diet to sweet food. Thus, in mouse model of obesity induced by consumption of a sweet-fat diet, the catabolic effect of FGF21 was not sex-specific and hormonal, transcriptional and behavioral effects of FGF21 were sex-specific. These data suggest elaboration of different approaches to use FGF21 analogs for correction of metabolic consequences of obesity in different sexes.

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

Background

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

Methods

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

Results

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

Conclusion

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

Biological and pharmacological functions of the FGF19- and FGF21-coreceptor beta klotho

Beta klotho (KLB) is a fundamental component in fibroblast growth factor receptor (FGFR) signaling as it serves as an obligatory coreceptor for the endocrine hormones fibroblast growth factor 19 (FGF19) and fibroblast growth factor 21 (FGF21). Through the development of FGF19- and FGF21 mimetics, KLB has emerged as a promising drug target for treating various metabolic diseases, such as type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease. While rodent studies have significantly increased our understanding of KLB function, current clinical trials that test the safety and efficacy of KLB-targeting drugs raise many new scientific questions about human KLB biology. Although most KLB-targeting drugs can modulate disease activity in humans, individual patient responses differ substantially. In addition, species-specific differences in KLB tissue distribution may explain why the glucose-lowering effects that were observed in preclinical studies are not fully replicated in clinical trials. Besides, the long-term efficacy of KLB-targeting drugs might be limited by various pathophysiological conditions known to reduce the expression of KLB. Moreover, FGF19/FGF21 administration in humans is also associated with gastrointestinal side effects, which are currently unexplained. A better understanding of human KLB biology could help to improve the efficacy and safety of existing or novel KLB/FGFR-targeting drugs. In this review, we provide a comprehensive overview of the current understanding of KLB biology, including genetic variants and their phenotypic associations, transcriptional regulation, protein structure, tissue distribution, subcellular localization, and function. In addition, we will highlight recent developments regarding the safety and efficacy of KLB-targeting drugs in clinical trials. These insights may direct the development and testing of existing and future KLB-targeting drugs.

FGF23 Actions in CKD-MBD and other Organs During CKD

Fibroblast growth factor 23 (FGF23) is a new endocrine product discovered in the past decade. In addition to being related to bone diseases, it has also been found to be related to kidney metabolism and parathyroid metabolism, especially as a biomarker and a key factor to be used in kidney diseases. FGF23 is upregulated as early as the second and third stages of chronic kidney disease (CKD) in response to relative phosphorus overload. The early rise of FGF23 has a protective effect on the body and is essential for maintaining phosphate balance. However, with the decline in renal function, eGFR (estimated glomerular filtration rate) declines, and the phosphorus excretion effect caused by FGF23 is weakened. It eventually leads to a variety of complications, such as bone disease (Chronic Kidney Disease-Mineral and Bone Metabolism Disorder), vascular calcification (VC), and more. Monoclonal antibodies against FGF23 are currently used to treat genetic diseases with increased FGF23. CKD is also a state of increased FGF23. This article reviews the current role of FGF23 in CKD and discusses the crosstalk between various organs under CKD conditions and FGF23. Studying the effect of hyperphosphatemia on different organs of CKD is important. The prospect of FGF23 for therapy is also discussed.

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.

Hepatic Insulin Resistance in Hyperthyroid Rat Liver: Vitamin E Supplementation Highlights a Possible Role of ROS

Thyroid hormones are normally involved in glycaemic control, but their excess can lead to altered glucose metabolism and insulin resistance (IR). Since hyperthyroidism-linked increase in ROS results in tissue oxidative stress that is considered a hallmark of conditions leading to IR, it is conceivable a role of ROS in the onset of IR in hyperthyroidism. To verify this hypothesis, we evaluated the effects of vitamin E on thyroid hormone-induced oxidative damage, insulin resistance, and on gene expression of key molecules involved in IR in the rat liver. The factors involved in oxidative damage, namely the total content of ROS, the mitochondrial production of ROS, the activity of antioxidant enzymes, the in vitro susceptibility to oxidative stress, have been correlated to insulin resistance indices, such as insulin activation of hepatic Akt and plasma level of glucose, insulin and HOMA index. Our results indicate that increased levels of oxidative damage ROS content and production and susceptibility to oxidative damage, parallel increased fasting plasma level of glucose and insulin, reduced activation of Akt and increased activation of JNK. This last result suggests a role for JNK in the insulin resistance induced by hyperthyroidism. Furthermore, the variation of the genes Pparg, Ppara, Cd36 and Slc2a2 could explain, at least in part, the observed metabolic phenotypes.

Deadenylase-dependent mRNA decay of GDF15 and FGF21 orchestrates food intake and energy expenditure

Hepatokines, secretory proteins from the liver, mediate inter-organ communication to maintain a metabolic balance between food intake and energy expenditure. However, molecular mechanisms by which hepatokine levels are rapidly adjusted following stimuli are largely unknown. Here, we unravel how CNOT6L deadenylase switches off hepatokine expression after responding to stimuli (e.g., exercise and food) to orchestrate energy intake and expenditure. Mechanistically, CNOT6L inhibition stabilizes hepatic Gdf15 and Fgf21 mRNAs, increasing corresponding serum protein levels. The resulting upregulation of GDF15 stimulates the hindbrain to suppress appetite, while increased FGF21 affects the liver and adipose tissues to induce energy expenditure and lipid consumption. Despite the potential of hepatokines to treat metabolic disorders, their administration therapies have been challenging. Using small-molecule screening, we identified a CNOT6L inhibitor enhancing GDF15 and FGF21 hepatokine levels, which dramatically improves diet-induced metabolic syndrome. Our discovery, therefore, lays the foundation for an unprecedented strategy to treat metabolic syndrome.

Effects of aerobic exercise on fibroblast growth factor 21 in overweight and obesity. A systematic review

Fibroblast growth factor 21 (FGF21) has been suggested to improve metabolism during aerobic exercise in obesity. However, the variability of exercise interventions gives rise to discrepancies in the field. Therefore, we aimed to systematically review the available literature regarding the effects of aerobic exercise on FGF21 in the context of overweight and obesity. Our search included original articles published between 2009 and November 2021 found in PubMed, Science Direct, and Medline. Clinical and preclinical studies were included. Studies, where subjects or animals presented with other conditions (e.g., cancer, stroke), were excluded. From an initial 43 studies, 19 (clinical studies = 9; preclinical studies = 10) were eligible for inclusion in this review. The main findings were that acute exercise tended to increase circulatory levels of FGF21. In contrast, chronic exercise programs (≥4 weeks) had the opposite effect along with inducing mRNA and protein increases of FGF receptors and β-klotho in adipose tissue, liver, and skeletal muscle. In conclusion, both clinical and preclinical studies showed that aerobic exercise exerts changes in circulatory and tissue FGF21, along with its receptors and co-receptor. Future research is needed to elucidate the mechanisms, along with the physiological and clinical implications of these changes.

The Same Metabolic Response to FGF21 Administration in Male and Female Obese Mice Is Accompanied by Sex-Specific Changes in Adipose Tissue Gene Expression

The preference for high-calorie foods depends on sex and contributes to obesity development. Fibroblast growth factor 21 (FGF21) beneficially affects taste preferences and obesity, but its action has mainly been studied in males. The aim of this study was to compare the effects of FGF21 on food preferences and glucose and lipid metabolism in C57Bl/6J male and female mice with diet-induced obesity. Mice were injected with FGF21 or vehicle for 7 days. Body weight, choice between standard (SD) and high-fat (HFD) diets, blood parameters, and gene expression in white (WAT) and brown (BAT) adipose tissues, liver, muscles, and the hypothalamus were assessed. Compared to males, females had a greater preference for HFD; less WAT; lower levels of cholesterol, glucose, and insulin; and higher expression of Fgf21, Insr, Ppara, Pgc1, Acca and Accb in the liver and Dio2 in BAT. FGF21 administration decreased adiposity; blood levels of cholesterol, glucose, and insulin; hypothalamic Agrp expression, increased SD intake, decreased HFD intake independently of sex, and increased WAT expression of Pparg, Lpl and Lipe only in females. Thus, FGF21 administration beneficially affected mice of both sexes despite obesity-associated sex differences in metabolic characteristics, and it induced female-specific activation of gene expression in WAT.

FGF21 ameliorates hepatic fibrosis by multiple mechanisms

BACKGROUND

Previous study reports that fibroblast growth factor 21 (FGF21) could ameliorate hepatic fibrosis, but its mechanisms have not been fully investigated.

METHODS AND RESULTS

In this study, three models were used to investigate the mechanism by which FGF21 alleviates liver fibrosis. Hepatic fibrosis animal models were respectively induced by CCL₄ and dimethylnitrosamine. Our results demonstrated that liver index and liver function were deteriorated in both models. Hematoxylin and eosin and Masson's staining showed that the damaged tissue architectonics were observed in the mice of both models. Treatment with FGF21 significantly ameliorated these changes. ELISA analysis showed that the serum levels of IL-1β, IL-6 and TNF-α were significantly elevated in both models. However, administration of FGF21 significantly reduced these inflammatory cytokines. Real-time PCR and Western blot analysis showed that treatment with FGF21 significantly decreased mRNA and protein expressions of collagenI, α-SMA and TGF-β. Platelet-derived growth factor-BB (PDGF-BB) stimulant was used to establish the experimental cell model in hepatic stellate cells (HSCs). Real-time PCR and Western blot analysis demonstrated that the expression of collagenI and α-SMA were significantly upregulated by this stimulant in model group. Interestingly, our results showed that mRNA and protein expressions of leptin were also significantly induced in PDGF-BB treated HSCs. Administration of FGF21 significantly reduced leptin expression in a dose dependent manner and these effects were reversed in siRNA (against β-klotho) transfected HSCs. Furthermore, the leptin signaling pathways related protein p-ERK/t-ERK, p-STAT3/STAT3 and TGF-β were significantly downregulated by FGF21 treatment in a dose dependent manner. The expressions of SOCS3 and Nrf-2 were enhanced by treatment with FGF21. The underlying mechanism may be that FGF21 regulates leptin-STAT3 axis via Nrf-2 and SOCS3 pathway in activated HSCs.

CONCLUSIONS

FGF21 ameliorates hepatic fibrosis by multiple mechanisms.

The Saga of Endocrine FGFs

Fibroblast growth factors (FGFs) are cell-signaling proteins with diverse functions in cell development, repair, and metabolism. The human FGF family consists of 22 structurally related members, which can be classified into three separate groups based on their action of mechanisms, namely: intracrine, paracrine/autocrine, and endocrine FGF subfamilies. FGF19, FGF21, and FGF23 belong to the hormone-like/endocrine FGF subfamily. These endocrine FGFs are mainly associated with the regulation of cell metabolic activities such as homeostasis of lipids, glucose, energy, bile acids, and minerals (phosphate/active vitamin D). Endocrine FGFs function through a unique protein family called klotho. Two members of this family, α-klotho, or β-klotho, act as main cofactors which can scaffold to tether FGF19/21/23 to their receptor(s) (FGFRs) to form an active complex. There are ongoing studies pertaining to the structure and mechanism of these individual ternary complexes. These studies aim to provide potential insights into the physiological and pathophysiological roles and therapeutic strategies for metabolic diseases. Herein, we provide a comprehensive review of the history, structure–function relationship(s), downstream signaling, physiological roles, and future perspectives on endocrine FGFs.

[Myokines and adipomyokines: inflammatory mediators or unique molecules of targeted therapy for obesity?]

Skeletal muscles make up about 25% of the total mass in children and more than 40% in adults. Studies of the last twenty years have shown that along with the main functions, muscle tissue has hormonal activity. It was found that myocytes are able to release signaling molecules-myokines. They act auto-and paracrine within the muscle, and at a high level-through the systemic circulation, carrying out interactions between skeletal muscles and various organs and tissues, such as the liver, bone and adipose tissue, the brain. It is proved that the key factor in the expression of myokines is physical activity, and their level largely depends on physical fitness, the amount of skeletal muscle mass and its composition (the ratio of fast and slow fibers), on the intensity and duration of physical activity. Myokines have a wide range of physiological effects: myostatin suppresses the growth and differentiation of muscle tissue, and decorin, acting as its antagonist, promotes muscle hypertrophy. Interleukin 6 provides an energy substrate for contracting muscle fibers, fibroblast growth factor 21 activates the mechanisms of energy production during fasting and improves tissue sensitivity to insulin; irisin stimulates thermogenesis, glucose uptake by myocytes, and also contributes to an increase in bone mineral density. The study of myokines is one of the key links in understanding the mechanisms underlying obesity and metabolic complications, the consequences of a sedentary lifestyle, as well as the implementation of the action of physical activity. Taking into account the physiological effects of myokines in the body, in the future they can become therapeutic targets for the treatment of these conditions.

The role of increased FGF21 in VLDL-TAG secretion and thermogenic gene expression in mice under protein malnutrition

Protein malnutrition promotes hepatic lipid accumulation in growing animals. In these animals, fibroblast growth factor 21 (FGF21) rapidly increases in the liver and circulation and plays a protective role in hepatic lipid accumulation. To investigate the mechanism by which FGF21 protects against liver lipid accumulation under protein malnutrition, we determined whether upregulated FGF21 promotes the thermogenesis or secretion of very-low-density lipoprotein (VLDL)-triacylglycerol (TAG). The results showed that protein malnutrition decreased VLDL-TAG secretion, but the upregulation of FGF21 did not oppose this effect. In addition, protein malnutrition increased expression of the thermogenic gene uncoupling protein 1 in inguinal white adipose and brown adipose tissue in an FGF21-dependent manner. However, surgically removing inguinal white adipose tissue did not affect liver triglyceride levels in protein-malnourished mice. These data suggest that FGF21 stimulates thermogenesis under protein malnutrition, but this is not the causative factor underlying the protective role of FGF21 against liver lipid accumulation.

Contribution of PGC-1α to Obesity- and Caloric Restriction-Related Physiological Changes in White Adipose Tissue

Peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α) regulates mitochondrial DNA replication and mitochondrial gene expression by interacting with several transcription factors. White adipose tissue (WAT) mainly comprises adipocytes that store triglycerides as an energy resource and secrete adipokines. The characteristics of WAT vary in response to systemic and chronic metabolic alterations, including obesity or caloric restriction. Despite a small amount of mitochondria in white adipocytes, accumulated evidence suggests that mitochondria are strongly related to adipocyte-specific functions, such as adipogenesis and lipogenesis, as well as oxidative metabolism for energy supply. Therefore, PGC-1α is expected to play an important role in WAT. In this review, we provide an overview of the involvement of mitochondria and PGC-1α with obesity- and caloric restriction-related physiological changes in adipocytes and WAT.

A Low-Protein High-Fat Diet Leads to Loss of Body Weight and White Adipose Tissue Weight via Enhancing Energy Expenditure in Mice

Obesity has become a worldwide health problem over the past three decades. During obesity, metabolic dysfunction of white adipose tissue (WAT) is a key factor increasing the risk of type 2 diabetes. A variety of diet approaches have been proposed for the prevention and treatment of obesity. The low-protein high-fat diet (LPHF) is a special kind of high-fat diet, characterized by the intake of a low amount of protein, while compared to typical high-fat diet, may induce weight loss and browning of WAT. Physical activity is another effective intervention to treat obesity by reducing WAT mass, inducing browning of WAT. In order to determine whether an LPHF, along with exercise enhanced body weight loss and body fat loss as well as the synergistic effect of an LPHF and exercise on energy expenditure in a mice model, we combined a 10-week LPHF with an 8-week forced treadmill training. Meanwhile, a traditional high-fat diet (HPHF) containing the same fat and relatively more protein was introduced as a comparison. In the current study, we further analyzed energy metabolism-related gene expression, plasma biomarkers, and related physiological changes. When comparing to HPHF, which induced a dramatic increase in body weight and WAT weight, the LPHF led to considerable loss of body weight and WAT, without muscle mass and strength decline, while it exhibited a risk of liver and pancreas damage. The mechanism underlying the LPHF-induced loss of body weight and WAT may be attributed to the synergistically upregulated expression of Ucp1 in WAT and Fgf21 in the liver, which may enhance energy expenditure. The 8-week training did not further enhance weight loss and increased plasma biomarkers of muscle damage when combined with LPHF. Furthermore, LPHF reduced the expression of fatty acid oxidation-related genes in adipose tissues, muscle tissues, and liver. Our results indicated that an LPHF has potential for obesity treatment, while the physiological condition should be monitored during application.

FGF21 and Chronic Kidney Disease

The global nephrology community recognizes the increasing burden of kidney disease and its poor health outcomes in the general population. Given this, strategies to establish early diagnosis, improve understanding of the natural course and develop novel therapeutic interventions to slow progression and reduce complications are encouraged. Fibroblast growth factor 21 (FGF21), a member of the endocrine FGF subfamily, has emerged as a master homeostasis regulator of local and systemic lipid, glucose and energy metabolism. In addition, FGF21 should be considered an autonomic and endocrine regulator of stress responses in general. Promising results has been shown in both dysmetabolic animal models and metabolic disease patients after pharmacological administration of FGF21 analogs. The association of FGF21 with renal function has been studied for more than ten years. However, the functional role of FGF21 in the kidney is still poorly understood. This review summarizes the biological effects of FGF21 and discusses what is currently known about this hormone and chronic kidney disease, highlighting important gaps that warrant further research.

Identification of BR102910 as a selective fibroblast activation protein (FAP) inhibitor

Fibroblast activation protein (FAP) belongs to the family of prolyl-specific serine proteases and displays both exopeptidase and endopeptidase activities. FAP expression is undetectable in most normal adult tissues, but is greatly upregulated in sites of tissue remodeling, which include fibrosis, inflammation and cancer. Due to its restricted expression pattern and dual enzymatic activities, FAP inhibition is investigated as a therapeutic option for several diseases. In the present study, we described the structure-activity relationship of several synthesized compounds against DPPIV and prolyl oligopeptidase (PREP). In particular, BR102910 (compound 24) showed nanomolar potency and high selectivity. Moreover, the in vivo FAP inhibition study of BR102910 (compound 24) using C57BL/6J mice demonstrated exceptional profiles and satisfactory FAP inhibition efficacy. Based on excellent in vitro and in vivo profiles, the potential of BR102910 (compound 24) as a lead candidate for the treatment of type 2 diabetes is considered.

Association between serum FGF21 level and sarcopenia in older adults

BACKGROUND

With emerging basic research evidence suggesting that fibroblast growth factor (FGF) 21 is a catabolic molecule on muscle metabolism, we aimed to analyze the serum FGF21 level in relation to sarcopenia in older adults.

METHODS

Blood samples were collected from 125 participants who underwent evaluation for muscle mass and function in an outpatient geriatric clinic of a teaching hospital. Sarcopenia and related components were determined using cutoff values for the Asian population. The serum FGF21 level was measured using enzyme linked immunosorbent assay.

RESULTS

After controlling for age, sex, and body mass index (BMI), participants with sarcopenia, low muscle mass, and weak muscle strength had 2.3-, 2.0-, and 1.5-fold higher serum FGF21 levels than controls, respectively (p = .033 to <0.001). The serum FGF21 level was positively correlated with sarcopenia phenotype score and inversely correlated with skeletal muscle mass index and grip strength by both crude and multivariate analysis adjusting potential confounders (p = .017 to <0.001). Consistently, higher serum FGF21 level was significantly associated with increased odds for sarcopenia, low muscle mass, and low muscle strength after adjusting for age, sex, and BMI (odds ratio, 1.53-2.61; p = .048 to <0.001).

CONCLUSIONS

Higher circulating FGF21 was associated with the likelihood of sarcopenia, lower muscle mass, and worse grip strength in older adults, supporting a potential catabolic role of FGF21 on human muscle 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.

Visceral adipose tissue-directed FGF21 gene therapy improves metabolic and immune health in BTBR mice

Fibroblast growth factor 21 (FGF21) is a peptide hormone that serves as a potent effector of energy homeostasis. Increasingly, FGF21 is viewed as a promising therapeutic agent for type 2 diabetes, fatty liver disease, and other metabolic complications. Exogenous administration of native FGF21 peptide has proved difficult due to unfavorable pharmacokinetic properties. Here, we utilized an engineered serotype adeno-associated viral (AAV) vector coupled with a dual-cassette design to selectively overexpress FGF21 in visceral adipose tissue of insulin-resistant BTBR T+Itpr3tf/J (BTBR) mice. Under high-fat diet conditions, a single, low-dose intraperitoneal injection of AAV-FGF21 resulted in sustained benefits, including improved insulin sensitivity, glycemic processing, and systemic metabolic function and reduced whole-body adiposity, hepatic steatosis, inflammatory cytokines, and adipose tissue macrophage inflammation. Our study highlights the potential of adipose tissue as a FGF21 gene-therapy target and the promise of minimally invasive AAV vectors as therapeutic agents for metabolic diseases.

Mesenchymal stem cells modified by FGF21 and GLP1 ameliorate lipid metabolism while reducing blood glucose in type 2 diabetic mice

OBJECTIVE

The purpose of this study was to investigate the therapeutic effects of genetically modified mesenchymal stem cells (MSCs) in the treatment of type 2 diabetes mellitus (T2DM) in order to identify a new method for treating diabetes that differs from traditional medicine and to provide a new means by which to fundamentally improve or treat diabetes.

METHODS

MSCs derived from adipose tissue were modified to overexpress FGF21 and GLP1, which was achieved through lentiviral particle transduction. The cells were transplanted into BKS.Cg-Dock7m+/+Leprdb/Nju mice (T2DM mouse model). Injections of physiological saline (0.1 mL) and liraglutide (0.5 mg/kg) were used as negative and positive controls, respectively. ELISA or Western blotting was used for protein analysis, and quantitative real-time PCR was used for gene expression analysis.

RESULTS

Genetic modification had no effects on the morphology, differentiation ability, or immunophenotype of MSCs. Moreover, MSC-FGF21+GLP1 cells exhibited significantly increased secretion of FGF21 and GLP1. In the T2DM mouse model, the transplantation of MSC-FGF21+GLP1 cells ameliorated the changes in blood glucose and weight, promoted the secretion of insulin, enhanced the recovery of liver structures, and improved the profiles of lipids. Moreover, FGF21 and GLP1 exerted synergistic effects in the regulation of glucolipid metabolism by controlling the expression of insulin, srebp1, and srebp2.

CONCLUSION

Stem cell treatment based on MSCs modified to overexpress the FGF21 and GLP1 genes is an effective approach for the treatment of T2DM.

A Low-Carbohydrate Ketogenic Diet and Treadmill Training Enhanced Fatty Acid Oxidation Capacity but Did Not Enhance Maximal Exercise Capacity in Mice

The low-carbohydrate ketogenic diet (LCKD) is a dietary approach characterized by the intake of high amounts of fat, a balanced amount of protein, and low carbohydrates, which is insufficient for metabolic demands. Previous studies have shown that an LCKD alone may contribute to fatty acid oxidation capacity, along with endurance. In the present study, we combined a 10-week LCKD with an 8-week forced treadmill running program to determine whether training in conjunction with LCKD enhanced fatty acid oxidation capacity, as well as whether the maximal exercise capacity would be affected by an LCKD or training in a mice model. We found that the lipid pool and fatty acid oxidation capacity were both enhanced following the 10-week LCKD. Further, key fatty acid oxidation related genes were upregulated. In contrast, the 8-week training regimen had no effect on fatty acid and ketone body oxidation. Key genes involved in carbohydrate utilization were downregulated in the LCKD groups. However, the improved fatty acid oxidation capacity did not translate into an enhanced maximal exercise capacity. In summary, while favoring the fatty acid oxidation system, an LCKD, alone or combined with training, had no beneficial effects in our intensive exercise-evaluation model. Therefore, an LCKD may be promising to improve endurance in low- to moderate-intensity exercise, and may not be an optimal choice for those partaking in high-intensity exercise.

[Relationship between fibroblast growth factor-21, muscle mass, and function outcomes in overweight and obese older adults living in the community. An exploratory study]

BACKGROUND

Age-related decreases in muscle mass and function are associated with the development of metabolic impairments, particularly in the context of obesity. Fibroblast growth factor21 (FGF-21) has been suggested as a common mediator of both processes. No known studies have examined the association between FGF-21 and muscle mass and function in overweight or obese older adults. With this in mind, this study aimed to investigate the association between plasma levels of FGF-21 and muscle mass and function outcomes in overweight or obese older adults.

MATERIALS AND METHODS

Exploratory study, which included 39 adults of 60-70years old with body mass indexes >25kg/m². As study outcomes, measurements were made of appendicular muscle mass (AMM), grip strength, 5 times sit-to-stand test (5xSTT), as well as plasma levels of FGF-21, fasting glucose, and insulin. The homeostatic model assessment index (HOMA-IR) was also calculated to determine the presence of insulin resistance.

RESULTS

Significant relationships were found between plasma levels of FGF-21 vs 5xSTT (rho=0.49; P<.05). Moreover, FGF-21 levels were significantly higher in those with insulin resistance (P<.05), as well as with having lower levels of AMM (P<.05).

CONCLUSION

There is a relationship between the plasma levels of FGF-21 and muscle function outcomes in overweight or obese older adults. Future studies should investigate the potential causalities between these relationships.

A novel GLP-1 and FGF21 dual agonist has therapeutic potential for diabetes and non-alcoholic steatohepatitis

BACKGROUND

Fibroblast growth factor 21 (FGF21) has become a promising therapeutic target for metabolic diseases such as type 2 diabetes (T2D), obesity and non-alcoholic steatohepatitis. However, the clinical application of natural FGF21 molecule is limited because of its instability in vitro and short half-life in vivo. To improve FGF21's therapeutic property, we screened high receptor binding FGF21 analogs and made FGF21-Fc-GLP-1 dual-targeted constructs to investigate their activity in a number of experiments .

METHODS

Utilizing phage display high-throughput screening we identified mutations that could improve β-Klotho binding property of FGF21. IgG4 Fc was fused to FGF21 variants to extend the in vivo half-life. We further explored the potential synergistic actions of FGF21 with the incretin glucagon-like peptide-1 (GLP-1) by generating GLP-1-Fc-FGF21 dual agonists.

FINDINGS

Two Fc-FGF21 variants showed enhanced β-Klotho binding affinity in vitro as well as improved glucose lowering effect in vivo. One of the dual agonists, GLP-1-Fc-FGF21 D1, provided potent and sustained glucose lowering effect in diabetic mice models. It also demonstrated superior weight loss effect to GLP-1 or FGF21 alone. Moreover, GLP-1-Fc-FGF21 D1 exhibited strong anti-NASH effect in the high-fat diet-induced ob/ob model as it improved liver function, serum and hepatic lipid profile and reduced NAFLD activity score with an efficacy superior to either FGF21 or GLP-1 analogs alone.

INTERPRETATION

This novel GLP-1/FGF21 dual agonist is worth clinical development for the treatment of T2D, obesity and NASH.

FUNDING

HEC Pharm R&D Co., Ltd, National natural science fund of China.

Association of serum fibroblast growth factor 21 and urinary glucose excretion in hospitalized patients with type 2 diabetes

AIM

Urinary glucose excretion (UGE) is mainly regulated by the sodium glucose cotransporter (SGLT)-2 in the proximal tubule of kidney. Lower UGE was associated with higher extent of insulin resistance in patients with type 2 diabetes. Animal studies suggested the relation of Fibroblast growth factor 21 (FGF21) and UGE. However, little was known about the association of FGF21 and UGE in human. We conducted a study to investigate the association of serum FGF21 and low UGE in patients with type 2 diabetes.

METHOD

A cohort of 2066 hospitalized patients with type 2 diabetes was screened for the fasting urinary glucose concentration and fasting blood glucose in the medical records. 70 patients with high UGE and 61 patients with Low UGE were analyzed. Frozen serum samples were used for the test of FGF21 levels.

RESULTS

The body mass index (BMI) and serum FGF21 levels were higher in low UGE group. Multivariable logistic regression indicated the association of FGF21 and low UGE after adjusting for age, sex, renal function, fasting plasma glucose, the treatment of insulin, and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index.

CONCLUSION

Higher serum FGF21 levels were independently associated with low UGE in patients with type 2 diabetes.

Discovery of a novel fibroblast activation protein (FAP) inhibitor, BR103354, with anti-diabetic and anti-steatotic effects

Fibroblast growth factor (FGF) 21 is a class of hepatokines that plays a protective role against obesity, insulin resistance, and liver damage. Despite this, protective effects of FGF21 in human appear to be minimal, possibly due to its proteolytic cleavage by the fibroblast activation protein (FAP). Here, we presented a novel FAP inhibitor, BR103354, and described its pharmacological activities as a potential therapeutic agent for the treatment of metabolic disorders. BR103354 inhibited FAP with an IC₅₀ value of 14 nM, showing high selectivity against dipeptidyl peptidase (DPP)-related enzymes and prolyl oligopeptidase (PREP). In differentiated 3T3/L1 adipocytes, the addition of FAP diminished hFGF21-induced Glut1 and phosphorylated levels of ERK, which were restored by BR103354. BR103354 exhibited good pharmacokinetic properties as evidenced by oral bioavailability of 48.4% and minimal hERG inhibition. Single co-administration of BR103354 with hFGF21 reduced nonfasting blood glucose concentrations, in association with increased intact form of hFGF21 in ob/ob mice. Additionally, chronic treatment of BR103354 for 4 weeks reduced nonfasting blood glucose concentrations with improved glucose tolerance and with reduced triglyceride (TG) content in liver of ob/ob mice. Consistently, BR103354 improved hepatic steatosis and fibrosis in a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced non-alcoholic steatohepatitis (NASH) mouse model. FAP inhibitory effects of BR103354 were confirmed in normal cynomolgus monkeys. Together, BR103354 acts as an effective FAP inhibitor in vitro and in vivo, thereby demonstrating its potential application as an anti-diabetic and anti-NASH agent.

Genome-wide association study for circulating fibroblast growth factor 21 and 23

Fibroblast growth factors (FGFs) 21 and 23 are recently identified hormones regulating metabolism of glucose, lipid, phosphate and vitamin D. Here we conducted a genome-wide association study (GWAS) for circulating FGF21 and FGF23 concentrations to identify their genetic determinants. We enrolled 5,000 participants from Taiwan Biobank for this GWAS. After excluding participants with diabetes mellitus and quality control, association of single nucleotide polymorphisms (SNPs) with log-transformed FGF21 and FGF23 serum concentrations adjusted for age, sex and principal components of ancestry were analyzed. A second model additionally adjusted for body mass index (BMI) and a third model additionally adjusted for BMI and estimated glomerular filtration rate (eGFR) were used. A total of 4,201 participants underwent GWAS analysis. rs67327215, located within RGS6 (a gene involved in fatty acid synthesis), and two other SNPs (rs12565114 and rs9520257, located between PHC2-ZSCAN20 and ARGLU1-FAM155A respectively) showed suggestive associations with serum FGF21 level (P = 6.66 × 10^–7, 6.00 × 10^–7 and 6.11 × 10^–7 respectively). The SNPs rs17111495 and rs17843626 were significantly associated with FGF23 level, with the former near PCSK9 gene and the latter near HLA-DQA1 gene (P = 1.04 × 10^–10 and 1.80 × 10^–8 respectively). SNP rs2798631, located within the TGFB2 gene, was suggestively associated with serum FGF23 level (P = 4.97 × 10^–7). Additional adjustment for BMI yielded similar results. For FGF23, further adjustment for eGFR had similar results. We conducted the first GWAS of circulating FGF21 levels to date. Novel candidate genetic loci associated with circulating FGF21 or FGF23 levels were found. Further replication and functional studies are needed to support our findings.

FGF21 Signals Protein Status to the Brain and Adaptively Regulates Food Choice and Metabolism

Reduced dietary protein intake induces adaptive physiological changes in macronutrient preference, energy expenditure, growth, and glucose homeostasis. We demonstrate that deletion of the FGF21 co-receptor βKlotho (Klb) from the brain produces mice that are unable to mount a physiological response to protein restriction, an effect that is replicated by whole-body deletion of FGF21. Mice forced to consume a low-protein diet exhibit reduced growth, increased energy expenditure, and a resistance to diet-induced obesity, but the loss of FGF21 signaling in the brain completely abrogates that response. When given access to a higher protein alternative, protein-restricted mice exhibit a shift toward protein-containing foods, and central FGF21 signaling is essential for that response. FGF21 is an endocrine signal linking the liver and brain, which regulates adaptive, homeostatic changes in metabolism and feeding behavior during protein restriction.

Acute Hyperenergetic, High-Fat Feeding Increases Circulating FGF21, LECT2, and Fetuin-A in Healthy Men

BACKGROUND

Hepatokines such as fibroblast growth factor 21 (FGF21), leukocyte cell-derived chemotaxin 2 (LECT2), fetuin-A, fetuin-B, and selenoprotein P (SeP) are liver-derived proteins that are modulated by chronic energy status and metabolic disease. Emerging data from rodent and cell models indicate that hepatokines may be sensitive to acute nutritional manipulation; however, data in humans are lacking.

OBJECTIVE

The aim was to investigate the influence of hyperenergetic, high-fat feeding on circulating hepatokine concentrations, including the time course of responses.

METHODS

In a randomized, crossover design, 12 healthy men [mean ± SD: age, 24 ± 4 y; BMI (kg/m2), 24.1 ± 1.5] consumed a 7-d hyperenergetic, high-fat diet [HE-HFD; +50% energy, 65% total energy as fat (32% saturated, 26% monounsaturated, 8% polyunsaturated)] and control diet (36% total energy as fat), separated by 3 wk. Whole-body insulin sensitivity was assessed before and after each diet using oral-glucose-tolerance tests. Fasting plasma concentrations of FGF21 (primary outcome), LECT2, fetuin-A, fetuin-B, SeP, and related metabolites were measured after 1, 3, and 7 d of each diet. Hepatokine responses were analyzed using 2-factor repeated-measures ANOVA and subsequent pairwise comparisons.

RESULTS

Compared with the control, the HE-HFD increased circulating FGF21 at 1 d (105%) and 3 d (121%; P ≤ 0.040), LECT2 at 3 d (17%) and 7 d (32%; P ≤ 0.004), and fetuin-A at 7 d (7%; P = 0.028). Plasma fetuin-B and SeP did not respond to the HE-HFD. Whole-body insulin sensitivity was reduced after the HE-HFD by 31% (P = 0.021).

CONCLUSIONS

Acute high-fat overfeeding augments circulating concentrations of FGF21, LECT2, and fetuin-A in healthy men. Notably, the time course of response varies between proteins and is transient for FGF21. These findings provide further insight into the nutritional regulation of hepatokines in humans and their interaction with metabolic homeostasis. This study was registered at clinicaltrials.gov as NCT03369145.

Regulation of Energy Metabolism by Receptor Tyrosine Kinase Ligands

Metabolic diseases, such as diabetes, obesity, and fatty liver disease, have now reached epidemic proportions. Receptor tyrosine kinases (RTKs) are a family of cell surface receptors responding to growth factors, hormones, and cytokines to mediate a diverse set of fundamental cellular and metabolic signaling pathways. These ligands signal by endocrine, paracrine, or autocrine means in peripheral organs and in the central nervous system to control cellular and tissue-specific metabolic processes. Interestingly, the expression of many RTKs and their ligands are controlled by changes in metabolic demand, for example, during starvation, feeding, or obesity. In addition, studies of RTKs and their ligands in regulating energy homeostasis have revealed unexpected diversity in the mechanisms of action and their specific metabolic functions. Our current understanding of the molecular, biochemical and genetic control of energy homeostasis by the endocrine RTK ligands insulin, FGF21 and FGF19 are now relatively well understood. In addition to these classical endocrine signals, non-endocrine ligands can govern local energy regulation, and the intriguing crosstalk between the RTK family and the TGFβ receptor family demonstrates a signaling network that diversifies metabolic process between tissues. Thus, there is a need to increase our molecular and mechanistic understanding of signal diversification of RTK actions in metabolic disease. Here we review the known and emerging molecular mechanisms of RTK signaling that regulate systemic glucose and lipid metabolism, as well as highlighting unexpected roles of non-classical RTK ligands that crosstalk with other receptor pathways.

Possible associations between plasma fibroblast growth factor 21 levels and cognition in bipolar disorder

Bipolar disorder (BD) is a mental disorder characterized by extreme changes in mood polarity. It is also characterized by cognitive and metabolic dysfunctions. Fibroblast growth factor 21 (FGF21) is an endocrine protein that has a multifaceted function such as glucose and lipid regulation in the periphery, and neuroprotection and induction of synaptic plasticity in the central nervous system. Previous studies reported inconsistent results concerning peripheral FGF21 levels in patients with BD. In this study, we compared plasma FGF21 levels between 26 patients with BD and 51 healthy controls using a human FGF21 ELISA Kit. There was no significant difference in plasma FGF21 levels between the patients and controls. We found significant positive correlations between plasma FGF21 levels and some cognitive parameters (word association and motor speed). If our results are replicated that higher peripheral FGF21 may be associated with better cognitive performance in patients with BD.

We compared plasma FGF21 levels between 26 bipolar disorder patients and 51 healthy controls. Although FGF21 concentrations were not different between the patients and controls, we found significant positive correlations between the levels and some cognitive parameters.

Current and new pharmacotherapy options for non-alcoholic steatohepatitis

INTRODUCTION

There is an unmet medical need for an effective anti-fibrotic treatment for NASH with advanced fibrosis.

AREAS COVERED

The authors review the current and novel agents for the treatment of NASH with fibrosis. They also consider the potential future strategies of combination therapies.

EXPERT OPINION

Farnesoid X receptor (FXR) agonist (obeticholic acid [OCA]) significantly ameliorated hepatic fibrosis in NASH stage 2/3 fibrosis in an interim analysis of phase 3 trial. Because OCA has several drawbacks such as itching and elevated low-density lipoprotein-cholesterol (LDL-C), non-bile acid FXR agonists are now under development. Selonsertib (apoptosis signaling kinase 1 inhibitor), emricasan (an irreversible pan-caspase inhibitor), and simtsuzumab (a monoclonal antibody against lysyl oxidase-like 2) were discontinued because of no efficacy over placebo. Peroxisome proliferator-activator receptor α/δ agonists, C-C motif chemokine receptor-2/5 antagonists, and thyroid β receptor agonist are ongoing in phase 3 trials. A variety of agents including fibroblast growth factor (FGF)-21 and FGF-19 agonists, as well as acetyl-CoA carboxylase inhibitors, are also expected. Among antidiabetic agents, semaglutide, a novel GLP-1 RA, is ongoing for NASH stage 1-3 fibrosis in a phase 2 trial. Furthermore, the combination of GLP-RA/glucagon receptor agonist and GLP-RA/gastrointestinal peptide agonist are promising future options.

PPARs as Metabolic Regulators in the Liver: Lessons from Liver-Specific PPAR-Null Mice

Peroxisome proliferator-activated receptor (PPAR) α, β/δ, and γ modulate lipid homeostasis. PPARα regulates lipid metabolism in the liver, the organ that largely controls whole-body nutrient/energy homeostasis, and its abnormalities may lead to hepatic steatosis, steatohepatitis, steatofibrosis, and liver cancer. PPARβ/δ promotes fatty acid β-oxidation largely in extrahepatic organs, and PPARγ stores triacylglycerol in adipocytes. Investigations using liver-specific PPAR-disrupted mice have revealed major but distinct contributions of the three PPARs in the liver. This review summarizes the findings of liver-specific PPAR-null mice and discusses the role of PPARs in the liver.

Antidiabetic Therapy in the Treatment of Nonalcoholic Steatohepatitis

Liver-related diseases are the third-leading causes (9.3%) of mortality in type 2 diabetes (T2D) in Japan. T2D is closely associated with nonalcoholic fatty liver disease (NAFLD), which is the most prevalent chronic liver disease worldwide. Nonalcoholic steatohepatitis (NASH), a severe form of NAFLD, can lead to hepatocellular carcinoma (HCC) and hepatic failure. No pharmacotherapies are established for NASH patients with T2D. Though vitamin E is established as a first-line agent for NASH without T2D, its efficacy for NASH with T2D recently failed to be proven. The effects of pioglitazone on NASH histology with T2D have extensively been established, but several concerns exist, such as body weight gain, fluid retention, cancer incidence, and bone fracture. Glucagon-like peptide 1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors are expected to ameliorate NASH and NAFLD (LEAN study, LEAD trial, and E-LIFT study). Among a variety of SGLT2 inhibitors, dapagliflozin has already entered the phase 3 trial (DEAN study). A key clinical need is to determine the kinds of antidiabetic drugs that are the most appropriate for the treatment of NASH to prevent the progression of hepatic fibrosis, resulting in HCC or liver-related mortality without increasing the risk of cardiovascular or renal events. Combination therapies, such as glucagon receptor agonist/GLP-1 or gastrointestinal peptide/GLP-1, are under development. This review focused on antidiabetic agents and future perspectives on the view of the treatment of NAFLD with T2D.

FGF21 and the Physiological Regulation of Macronutrient Preference

The ability to respond to variations in nutritional status depends on regulatory systems that monitor nutrient intake and adaptively alter metabolism and feeding behavior during nutrient restriction. There is ample evidence that the restriction of water, sodium, or energy intake triggers adaptive responses that conserve existing nutrient stores and promote the ingestion of the missing nutrient, and that these homeostatic responses are mediated, at least in part, by nutritionally regulated hormones acting within the brain. This review highlights recent research that suggests that the metabolic hormone fibroblast growth factor 21 (FGF21) acts on the brain to homeostatically alter macronutrient preference. Circulating FGF21 levels are robustly increased by diets that are high in carbohydrate but low in protein, and exogenous FGF21 treatment reduces the consumption of sweet foods and alcohol while alternatively increasing the consumption of protein. In addition, while control mice adaptively shift macronutrient preference and increase protein intake in response to dietary protein restriction, mice that lack either FGF21 or FGF21 signaling in the brain fail to exhibit this homeostatic response. FGF21 therefore mediates a unique physiological niche, coordinating adaptive shifts in macronutrient preference that serve to maintain protein intake in the face of dietary protein restriction.

Serum Fibroblast Growth Factor 21 in Patients with and without Pterygia

Purpose

Pterygium is a common fibro-vascular-related eye disease. The fibroblast growth factor 21 (FGF21) helps reduce neovascularization. Previous studies have shown that the serum level of FGF21 correlates with vascular eye diseases such as diabetic retinopathy and retinopathy of prematurity. In this study, the serum FGF21 is compared in patients with and without pterygium.

Methods

This descriptive-analytical cross-sectional study examines individuals with pterygium who visited the Ophthalmology Clinic of Khatam-al-Anbia Hospital in Mashhad, Iran, during 2017–2018. Control subjects were selected from healthy people without pterygium disease. Patients with a history of acute illness, chronic liver and kidney disease, diabetes, cancer, malnutrition and drug use, women who were pregnant or breastfeeding, and subjects who were taking anticonvulsants or glucocorticoids were excluded as these may affect insulin and glycosuria levels. Sixty people (30 in each group) were chosen using the convenient sampling method. Intravenous blood samples were taken from all patients. After preparing the patients, the freeze was checked using the enzyme-linked immunosorbent assay (ELISA) method after samples had been taken. Data were analyzed by SPSS using an independent t-test, Mann–Whitney, Chi-square, Kruskal–Wallis, and Kolmogorov–Smirnov tests (α = 0.05).

Results

The serum FGF21 levels were 319.09 ± 246.93 pg/ml and 608.88 ± 449.81 pg/ml (P = 0.005) in the pterygium group and control subjects, respectively. The average serum FGF21 was 281.55 ± 40.74 pg/ml in males and 361.375 ± 10.298 pg/ml in females in the pterygium group. The difference was not statistically significant (P = 0.19)

Conclusion

Our study showed that FGF21 levels were lower in patients with pterygium than the control subjects to a statistically significant level.

miR-22 inhibition reduces hepatic steatosis via FGF21 and FGFR1 induction

Background & Aims

Metabolism supports cell proliferation and growth. Surprisingly, the tumor suppressor miR-22 is induced by metabolic stimulators like bile acids. Thus, this study examines whether miR-22 could be a metabolic silencer.

Methods

The relationship between miR-22 and the expression of fibroblast growth factor 21 (FGF21) and its receptor FGFR1 was studied in cells and fatty livers obtained from patients and mouse models. We evaluated the effect of an miR-22 inhibitor alone and in combination with obeticholic acid (OCA) for the treatment of steatosis.

Results

The levels of miR-22 were inversely correlated with those of FGF21, FGFR1, and PGC1α in human and mouse fatty livers, suggesting that hepatic miR-22 acts as a metabolic silencer. Indeed, miR-22 reduced FGFR1 by direct targeting and decreased FGF21 by reducing the recruitment of PPARα and PGC1α to their binding motifs. In contrast, an miR-22 inhibitor increases hepatic FGF21 and FGFR1, leading to AMPK and ERK1/2 activation, which was effective in treating alcoholic steatosis in mouse models. The farnesoid x receptor-agonist OCA induced FGF21 and FGFR1, as well as their inhibitor miR-22. An miR-22 inhibitor and OCA were effective in treating diet-induced steatosis, both alone and in combination. The combined treatment was the most effective at improving insulin sensitivity, releasing glucagon-like peptide 1, and reducing hepatic triglyceride in obese mice.

Conclusion

The simultaneous induction of miR-22, FGF21 and FGFR1 by metabolic stimulators may maintain FGF21 homeostasis and restrict ERK1/2 activation. Reducing miR-22 enhances hepatic FGF21 and activates AMPK, which could be a novel approach to treat steatosis and insulin resistance.

Lay summary

This study examines the metabolic role of a tumor suppressor, miR-22, that can be induced by metabolic stimulators such as bile acids. Our novel data revealed that the metabolic silencing effect of miR-22 occurs as a result of reductions in metabolic stimulators, which likely contribute to the development of fatty liver. Consistent with this finding, an miR-22 inhibitor effectively reversed both alcohol- and diet-induced fatty liver; miR-22 inhibition is a promising therapeutic option which could be used in combination with obeticholic acid.