Biological role, clinical significance, and therapeutic possibilities of the recently discovered metabolic hormone fibroblastic growth factor 21

Fibroblast Growth Factor 21 Relieves Lipopolysaccharide-Induced Acute Lung Injury by Suppressing JAK2/STAT3 Signaling Pathway

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life-threatening disease without an effective drug at present. Fibroblast growth factor 21 (FGF21) was reported to be protective against inflammation in metabolic disease in recent studies. However, the role of FGF21 in ALI has been rarely investigated. In this study, it was found that the expression of FGF21 was markedly increased in lung tissue under lipopolysaccharide (LPS) stimulation in vivo, whereas it was decreased in lung epithelial cells under LPS stimulation in vitro. Therefore, our research aimed to elucidate the potential role of FGF21 in LPS-induced ALI and to detect possible underlying mechanisms. The results revealed that the deficiency of FGF21 aggravated pathological damage, inflammatory infiltration, and pulmonary function in LPS-induced ALI, while exogenous administration of FGF21 improved these manifestations. Moreover, through RNA sequencing and enrichment analysis, it was unveiled that FGF21 might play a protective role in LPS-induced ALI via JAK2/STAT3 signaling pathway. The therapeutic effect of FGF21 was weakened after additional usage of JAK2 activator in vivo. Further investigation revealed that FGF21 significantly inhibited STAT3 phosphorylation and impaired the nuclear translocation of STAT3 in vitro. In addition, the aggravation of inflammation caused by silencing FGF21 can be alleviated by JAK2 inhibitor in vitro. Collectively, these findings unveil a potent protective effect of FGF21 against LPS-induced ALI by inhibiting the JAK2/STAT3 pathway, implying that FGF21 might be a novel and effective therapy for ALI.

The Role of the FGF19 Family in the Pathogenesis of Gestational Diabetes: A Narrative Review

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. Understanding the pathogenesis and appropriate diagnosis of GDM enables the implementation of early interventions during pregnancy that reduce the risk of maternal and fetal complications. At the same time, it provides opportunities to prevent diabetes, metabolic syndrome, and cardiovascular diseases in women with GDM and their offspring in the future. Fibroblast growth factors (FGFs) represent a heterogeneous family of signaling proteins which play a vital role in cell proliferation and differentiation, repair of damaged tissues, wound healing, angiogenesis, and mitogenesis and also affect the regulation of carbohydrate, lipid, and hormone metabolism. Abnormalities in the signaling function of FGFs may lead to numerous pathological conditions, including metabolic diseases. The FGF19 subfamily, also known as atypical FGFs, which includes FGF19, FGF21, and FGF23, is essential in regulating metabolic homeostasis and acts as a hormone while entering the systemic circulation. Many studies have pointed to the involvement of the FGF19 subfamily in the pathogenesis of metabolic diseases, including GDM, although the results are inconclusive. FGF19 and FGF21 are thought to be associated with insulin resistance, an essential element in the pathogenesis of GDM. FGF21 may influence placental metabolism and thus contribute to fetal growth and metabolism regulation. The observed relationship between FGF21 and increased birth weight could suggest a potential role for FGF21 in predicting future metabolic abnormalities in children born to women with GDM. In this group of patients, different mechanisms may contribute to an increased risk of cardiovascular diseases in women in later life, and FGF23 appears to be their promising early predictor. This study aims to present a comprehensive review of the FGF19 subfamily, emphasizing its role in GDM and predicting its long-term metabolic consequences for mothers and their offspring.

Interplay of skeletal muscle and adipose tissue: sarcopenic obesity

Sarcopenic obesity is becoming a global health concern, owing to the rising older population, causing cardiometabolic morbidity and mortality. Loss of muscle exceeding normal age-related changes has been revealed to be associated with obesity, aggravating each other through complex interactions. Physiological regeneration and proliferation of muscle tissue are achieved through harmonious processes of regulated inflammation, autophagy, muscle satellite cell proliferation, and signaling molecule function. Adipokines and myokines are signaling molecules from adipose tissue and muscle, respectively, that exert autocrine, paracrine, and endocrine effects on fat and muscle tissues. These signaling molecules interact with each other to regulate metabolic homeostasis. However, excessive adiposity creates pro-inflammatory conditions, leading to metabolic disorders and the disorganization of systemic homeostasis. Therefore, obesity impedes muscle tissue regeneration and induces the loss of muscle mass and function. Numerous studies have attempted to demonstrate the pathophysiological interaction between sarcopenia and obesity, but the interwoven matrix of the relationship between myokines and adipokines has made it difficult for researchers to understand them. This review briefly describes updated information about the crosstalk between muscle and adipose tissue.

Role of Thyrotropin-Releasing Hormone in Regulating Fibroblast Growth Factor 21 in Mouse Pancreatic β Cells

Background: Thyrotropin-releasing hormone (TRH) is primarily produced in the hypothalamus and regulates the thyrotropin secretion from the pituitary. TRH is distributed ubiquitously in the extrahypothalamic region, especially in pancreatic islets, while its physiological role remains nebulous. We have previously established a TRH-deficient mouse model, and showed impaired glucose tolerance and downregulated expression of fibroblast growth factor 21 (FGF21) in islets. Recent studies have demonstrated the physiological roles of pancreatic FGF21. Therefore, in this study, we elucidate the direct functions of TRH in pancreatic islets via the regulation of FGF21. Methods: To explore the functions of TRH in pancreatic islets, a microarray analysis using isolated islets from TRH-knockout mice was conducted. The regulatory mechanism of TRH in pancreatic FGF21 was investigated using islet cell lines; reverse transcription-quantitative polymerase chain reaction and Western blotting were used to determine the mRNA and protein expression levels of FGF21 in pancreatic islets and islet cell lines. Induction of FGF21 expression by TRH treatment was examined in vitro. To identify the transcription factors binding to the region responsible for TRH-induced stimulation of the FGF21 promoter, electromobility shift assays were conducted. Results: Among the detected and considerably changed genes in microarray, FGF21 was the most consistently downregulated in TRH-deficient mice islets. FGF21 was strongly co-expressed with insulin in mouse islets, and TRH stimulated endogenous Fgf21 mRNA expression in the islet cell line βHC9. The E-box site in the FGF21 promoter was responsible for TRH-induced stimulation via the extracellular signal-regulated kinase (ERK)1/2 signaling pathway. The transcription factor upstream stimulatory factor 1 (USF1) could specifically bind to the E-box site. Overexpression of USF1 increased FGF21 promoter activity. Conclusion: FGF21 was transcriptionally upregulated by TRH through the ERK1/2 and USF1 pathways in pancreatic β cells.

Adipokines from white adipose tissue in regulation of whole body energy homeostasis

Diseases originating from altered energy homeostasis including obesity, and type 2 diabetes are rapidly increasing worldwide. Research in the last few decades on animal models and humans demonstrates that the white adipose tissue (WAT) is critical for energy balance and more than just an energy storage site. WAT orchestrates the whole-body metabolism through inter-organ crosstalk primarily mediated by cytokines named "Adipokines". The adipokines influence metabolism and fuel selection of the skeletal muscle and liver thereby fine-tuning the load on WAT itself in physiological conditions like starvation, exercise and cold. In addition, adipokine secretion is influenced by various pathological conditions like obesity, inflammation and diabetes. In this review, we have surveyed the current state of knowledge on important adipokines and their significance in regulating energy balance and metabolic diseases. Furthermore, we have summarized the interplay of pro-inflammatory and anti-inflammatory adipokines in the modulation of pathological conditions.

Sexual Dimorphism in Adipose-Hypothalamic Crosstalk and the Contribution of Aryl Hydrocarbon Receptor to Regulate Energy Homeostasis

There are fundamental sex differences in the regulation of energy homeostasis. Better understanding of the underlying mechanisms of energy balance that account for this asymmetry will assist in developing sex-specific therapies for sexually dimorphic diseases such as obesity. Multiple organs, including the hypothalamus and adipose tissue, play vital roles in the regulation of energy homeostasis, which are regulated differently in males and females. Various neuronal populations, particularly within the hypothalamus, such as arcuate nucleus (ARC), can sense nutrient content of the body by the help of peripheral hormones such leptin, derived from adipocytes, to regulate energy homeostasis. This review summarizes how adipose tissue crosstalk with homeostatic network control systems in the brain, which includes energy regulatory regions and the hypothalamic–pituitary axis, contribute to energy regulation in a sex-specific manner. Moreover, development of obesity is contingent upon diet and environmental factors. Substances from diet and environmental contaminants can exert insidious effects on energy metabolism, acting peripherally through the aryl hydrocarbon receptor (AhR). Developmental AhR activation can impart permanent alterations of neuronal development that can manifest a number of sex-specific physiological changes, which sometimes become evident only in adulthood. AhR is currently being investigated as a potential target for treating obesity. The consensus is that impaired function of the receptor protects from obesity in mice. AhR also modulates sex steroid receptors, and hence, one of the objectives of this review is to explain why investigating sex differences while examining this receptor is crucial. Overall, this review summarizes sex differences in the regulation of energy homeostasis imparted by the adipose–hypothalamic axis and examines how this axis can be affected by xenobiotics that signal through AhR.

Multifactorial Mechanism of Sarcopenia and Sarcopenic Obesity. Role of Physical Exercise, Microbiota and Myokines

Obesity and ageing place a tremendous strain on the global healthcare system. Age-related sarcopenia is characterized by decreased muscular strength, decreased muscle quantity, quality, and decreased functional performance. Sarcopenic obesity (SO) is a condition that combines sarcopenia and obesity and has a substantial influence on the older adults’ health. Because of the complicated pathophysiology, there are disagreements and challenges in identifying and diagnosing SO. Recently, it has become clear that dysbiosis may play a role in the onset and progression of sarcopenia and SO. Skeletal muscle secretes myokines during contraction, which play an important role in controlling muscle growth, function, and metabolic balance. Myokine dysfunction can cause and aggravate obesity, sarcopenia, and SO. The only ways to prevent and slow the progression of sarcopenia, particularly sarcopenic obesity, are physical activity and correct nutritional support. While exercise cannot completely prevent sarcopenia and age-related loss in muscular function, it can certainly delay development and slow down the rate of sarcopenia. The purpose of this review was to discuss potential pathways to muscle deterioration in obese individuals. We also want to present the current understanding of the role of various factors, including microbiota and myokines, in the process of sarcopenia and SO.

The Multiple Roles of Fibroblast Growth Factor in Diabetic Nephropathy

Diabetic nephropathy (DN) is a common microvascular complication in the late stages of diabetes. Currently, the etiology and pathogenesis of DN are not well understood. Even so, available evidence shows its development is associated with metabolism, oxidative stress, cytokine interaction, genetic factors, and renal microvascular disease. Diabetic nephropathy can lead to proteinuria, edema and hypertension, among other complications. In severe cases, it can cause life-threatening complications such as renal failure. Patients with type 1 diabetes, hypertension, high protein intake, and smokers have a higher risk of developing DN. Fibroblast growth factor (FGF) regulates several human processes essential for normal development. Even though FGF has been implicated in the pathological development of DN, the underlying mechanisms are not well understood. This review summarizes the role of FGF in the development of DN. Moreover, the association of FGF with metabolism, inflammation, oxidative stress and fibrosis in the context of DN is discussed. Findings of this review are expected to deepen our understanding of DN and generate ideas for developing effective prevention and treatments for the disease.

Development of diabetes mellitus following hormone therapy in prostate cancer patients is associated with early progression to castration resistance

To identify risk factors for the prognosis of prostate cancer (PC), we retrospectively analyzed the impact of lifestyle-related disorders as well as PC characteristics at initial diagnosis on the progression to castration-resistant PC (CRPC) in PC patients undergoing hormone therapy. Of 648 PC patients, 230 who underwent hormone therapy and met inclusion criteria were enrolled in this study. CRPC developed in 48 patients (20.9%). Univariate analysis using Cox proportional hazard model indicated that newly developed diabetes mellitus (DM) following hormone therapy (postDM), but not preexisting DM, as well as PC characteristics at initial diagnosis including prostate-specific antigen (PSA) ≥ 18 were significantly associated with the progression to CRPC. A similar tendency was also observed in the relationship between newly developed hypertension following hormone therapy and CRPC progression. On the other hand, neither dyslipidemia nor hyperuricemia, regardless the onset timing, exhibited any association with CRPC progression. In multivariate analysis, postDM and PSA ≥ 18 were extracted as independent risk factors for CRPC progression (adjusted hazard ratios, 3.38 and 2.34; p values, 0.016 and 0.019, respectively). Kaplan–Meier analysis and log-rank test clearly indicated earlier progression to CRPC in PC patients who developed postDM or had relatively advanced initial PC characteristics including PSA ≥ 18. Together, the development of lifestyle-related disorders, particularly DM, following hormone therapy, as well as advanced PC characteristics at initial diagnosis is considered to predict earlier progression to CRPC and poor prognosis in PC patients undergoing hormone therapy.

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.

FGF21 promotes ischaemic angiogenesis and endothelial progenitor cells function under diabetic conditions in an AMPK/NAD+-dependent manner

Diabetic vascular complications are closely associated with long‐term vascular dysfunction and poor neovascularization. Endothelial progenitor cells (EPCs) play pivotal roles in maintaining vascular homeostasis and triggering angiogenesis, and EPC dysfunction contributes to defective angiogenesis and resultant diabetic vascular complications. Fibroblast growth factor 21 (FGF21) has received substantial attention as a potential therapeutic agent for diabetes via regulating glucose and lipid metabolism. However, the effects of FGF21 on diabetic vascular complications remain unclear. In the present study, the in vivo results showed that FGF21 efficiently improved blood perfusion and ischaemic angiogenesis in both type 1 and type 2 diabetic mice, and these effects were accompanied by enhanced EPC mobilization and infiltration into ischaemic muscle tissues and increases in plasma stromal cell–derived factor‐1 concentration. The in vitro results revealed that FGF21 directly prevented EPC damage induced by high glucose, and the mechanistic studies demonstrated that nicotinamide adenine dinucleotide (NAD⁺) was dramatically decreased in EPCs challenged with high glucose, whereas FGF21 treatment significantly increased NAD⁺ content in an AMPK‐dependent manner, resulting in improved angiogenic capability of EPCs. These results indicate that FGF21 promotes ischaemic angiogenesis and the angiogenic ability of EPCs under diabetic conditions by activating the AMPK/NAD⁺ pathway.

Attenuation of FGF21 signalling might aggravate the impairment of glucose homeostasis during the high sucrose diet induced transition from prediabetes to diabetes in WNIN/GR-Ob rats

Fibroblast growth factor 21 (FGF21) has emerged as a pleiotropic hormone and is known for its beneficiary roles in the management of diabetes and hyperglycaemia. However, the role of FGF21 during the transition from prediabetes to diabetes still remains unclear. Hence, the present study is aimed to understand the regulation of glucose homeostasis by FGF21 during the transition from prediabetes to diabetes in WNIN/GR-Ob rats. A total of 36 WNIN/GR-Ob obese male rats (28 days old) were divided into control and high sucrose (HS) groups and were fed ad libitum with their respective diets. These groups were sacrificed at different time points (week 1, 6, and 12) and various physical, biochemical, and molecular mediators were assessed to address FGF21 mediated glucose homeostasis. The study results revealed that rats developed impaired glucose tolerance and insulin resistance by exhibiting delayed glucose clearance from circulation, elevated fasting insulin, increased AUC glucose and HOMA-IR scores significantly; thereby rats demonstrated prediabetes by week 6 and diabetes complications by week 12. In line with the above, differential expression of genes attributed to FGF21 mediated glucose homeostasis, i.e., PPARα, FGF21, β-klotho, PPARγ, Adiponectin, Akt, and UCP1 suggest that the acute insulin sensitizing effect of FGF21 was significantly impaired during prediabetes to diabetes transition. In addition, increased gene and protein expression of FGF21 during the transition compared to controls could be a compensatory response to possibly counteract the metabolic stress imposed by high sucrose diet in WNIN/GR-Ob rats of the experimental group. Findings from the current study emphasize the potential role of FGF21 in glucose homeostasis and its attenuation might aggravate glucose impairment during the transition from prediabetes to diabetes in high sucrose diet induced WNIN/GR-Ob rats.

Endogenous testosterone reduces hepatic lipid accumulation in protein-restricted male rats

OBJECTIVES

Protein deficiency is known to cause ectopic fat accumulation in the liver. The aim of this study was to analyse the mechanism of suppression of hepatic fat accumulation by testosterone and to clarify the mechanism behind the gender difference in fatty liver formation due to protein deficiency.

METHODS

Hepatic fat accumulation due to protein deficiency was evaluated in male and female rats before and after sexual maturation. Then, the effects of testosterone on liver lipid, muscle protein metabolism and energy expenditure in adipose tissue were investigated in castrated or testosterone-injected male rats fed control or protein-restricted diet.

RESULTS

Hepatic triglyceride accumulation diminished with sex maturation in male but not in female protein-restricted rats. Protein restriction resulted in a significant increase in hepatic triglyceride content in castrated rats but not in sham-operated rats demonstrating that endogenous testosterone reduces hepatic lipid accumulation in male rats. Protein restriction reduced plasma IGF-I and muscle protein synthesis measured using the SUnSET method. Castration increased the plasma corticosterone level and muscle autophagic activity. Muscle weight was reduced and energy expenditure in adipose tissue was increased only when both factors were combined.

CONCLUSIONS

Muscle protein synthesis downregulation owing to protein restriction and activation of autophagy following castration reduced muscle mass thereby releasing surplus energy and promoting steatosis in protein-restricted castrated rats despite increased energy expenditure in adipose tissue. We hypothesize that endogenous testosterone reduces hepatic lipid accumulation in protein-deficient male rats and provide novel findings on the gender-specific differences in hepatic steatosis.

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.

Preparation, characterization, and pharmacological study of a novel long-acting FGF21 with a potential therapeutic effect in obesity

FGF21 (Fibroblast Growth Factor 21), which is expressed in the liver, adipose tissue, and pancreas, has been widely known as a therapeutic candidate for metabolic diseases. Though FGF21 is crucial to glucose, lipid, and energy homeostasis, it is not straightforward to develop a new drug with FGF21 due to its short half-life in serum. Here, we derived a novel long-acting FGF21 (LAPS-FGF21), which is chemically conjugated to the human IgG4 Fc fragment for longer half-life in serum. The recombinant human IgG4 Fc fragment and FGF21 were prepared by the refolding of inclusion body and periplasmic expression in Escherichia coli overexpression systems, respectively. The efficacy study of LAPS-FGF21 in a Diet-Induced Obesity (DIO) mouse model revealed that LAPS-FGF21 reduced body weight effectively accompanied by improved glucose tolerance in a dose-dependent manner. The administration of LAPS-FGF21 also improved the blood profiles with a significant reduction in cholesterol and triglyceride levels. Additionally, the pharmacokinetic (PK) studies of LAPS-FGF21 using normal ICR mice demonstrated that the half-life of LAPS-FGF21 was approximately 64-fold longer than FGF21. Taken together, the LAPS-FGF21 could be a feasible drug candidate with excellent bodyweight loss efficacy and longer dosing interval by half-life increase in serum.

Sarcopenic obesity: Myokines as potential diagnostic biomarkers and therapeutic targets?

Sarcopenic obesity (SO) is a condition characterized by the occurrence of both sarcopenia and obesity and imposes a heavy burden on the health of the elderly. Controversies and challenges regarding the definition, diagnosis and treatment of SO still remain because of its complex pathogenesis and limitations. Over the past few decades, numerous studies have revealed that myokines secreted from skeletal muscle play significant roles in the regulation of muscle mass and function as well as metabolic homeostasis. Abnormalities in myokines may trigger and promote the pathogenesis underlying age-related and metabolic diseases, including obesity, sarcopenia, type 2 diabetes (T2D), and SO. This review mainly focuses on the role of myokines as potential biomarkers for the early diagnosis and therapeutic targets in SO.

Gastrointestinal peptides in children before and after hematopoietic stem cell transplantation

BACKGROUND

Gastrointestinal tract function and it's integrity are controlled by a number of peptides whose secretion is influenced by severe inflammation. In stomach the main regulatory peptide is ghrelin. For upper small intestine cholecystokinin and lower small intestine glucagon-like peptide- 1 are secreted, while fibroblast growth factor-21 is secreted by several organs, including the liver, pancreas, and adipose tissue [12]. Hematopoietic stem cell transplantation causes serious mucosal damage, which can reflect on this peptides.

METHODS

The aim of the study was to determine fasting plasma concentrations of ghrelin, cholecystokinin, glucagon- like peptide-1, and fibroblast growth factor-21, and their gene expressions, before and 6 months after hematopoietic stem cell transplantation.27 children were studied, control group included 26 healthy children.

RESULTS

Acute graft versus host disease was diagnosed in 11 patients (41%, n = 27). Median pre-transplantation concentrations of gastrointestinal peptides, as well as their gene expressions, were significantly lower in studied group compared with the control group. Only median of fibroblast growth factor-21 concentration was near-significantly higher before stem cell transplantation than in the control group. The post-hematopoietic transplant results revealed significantly higher concentrations of the studied peptides (except fibroblast growth factor-21) and respective gene expressions as compare to pre transplant results. Median glucagone like peptide-1 concentrations were significantly decreased in patients with features of acute graft versus host disease. Moreover, negative correlation between glucagone like peptide-1 concentrations and acute graft versus host disease severity was found.

CONCLUSIONS

Increased concentrations and gene expressions of gastrointestinal tract regulation peptides can be caused by stimulation of regeneration in the severe injured organ. Measurement of these parameters may be a useful method of assessment of severity of gastrointestinal tract complications of hematopoietic stem cell transplantation.

Insulin-Independent Reversal of Type-1 Diabetes Following Transplantation of Adult Brown Adipose Tissue Supplemented With IGF-1

As our previous publications show, it is feasible to reverse type 1 diabetes (T1D) without insulin in multiple mouse models, through transplantation of embryonic brown adipose tissue (BAT) in the subcutaneous space. Embryonic BAT transplants result in rapid and long-lasting euglycemia accompanied by decreased inflammation and regenerated healthy white adipose tissue, with no detectable increase in insulin. To translate this approach to human patients, it is necessary to establish practical alternatives for embryonic tissue. Adult adipose tissue transplants or BAT-derived stem cell lines alone fail to reverse T1D. A likely reason is transplant failure resulting from lack of growth factors abundant in embryonic tissue. Adding growth factors may enable transplants to survive and vascularize as well as stimulate adipogenesis and decrease inflammation in the surrounding host tissue. Previous data points to insulin like growth factor 1 (IGF-1) as the most likely candidate. Embryonic BAT abundantly expresses IGF-1, and embryonic BAT transplant recipients exhibit increased plasma levels of IGF-1. Therefore, we tested the ability of temporary administration of exogenous IGF-1 to enable adult BAT transplants to correct T1D.

Methods

Fresh BAT from healthy adult CB7BL/6 donors were transplanted in the subcutaneous space of hyperglycemic nonobese diabetic recipients. Exogenous IGF-1 was administered daily for a week following transplant, at 100 µg/kg SC.

Results

Adult BAT transplants with IGF-1 supplementation produced rapid long-lasting euglycemia at a 57% success rate, in contrast with no recovery in the control groups who received adult BAT alone, IGF-1 alone, or no treatment.

Conclusions

Temporary supplementation with IGF-1 enables adult BAT transplants to correct T1D phenotypes independent of insulin, providing a possible route to translate this treatment to human patients.

Association of the 3'UTR polymorphism (rs11665896) in the FGF21 gene with metabolic status and nutrient intake in children with obesity

Background Fibroblast growth factor 21 (FGF21) is considered an important regulator of lipid and glucose metabolism. However, the role of FGF21 in macronutrient intake and metabolic disease, particularly in pediatric population, still needs further clarification. This study aimed to evaluate the association of rs11665896 in the FGF21 gene with metabolic status and macronutrient intake in a cohort of Mexican children with obesity. Methods Eighty-four lean children and 113 children with obesity, from 8 to 11 years of age, were recruited. FGF21 rs11665896 was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Somatometric evaluations, nutrient intake, glucose, lipids, insulin and FGF21 serum levels were measured in the obesity group. Results The T allele of rs11665896 in the FGF21 gene was associated with obesity (odds ratio [OR] = 1.99, 95% confidence interval [CI] = 1.14-3.46; p = 0.0151). Subjects with obesity carrying the TT genotype consumed less lipids and more carbohydrates compared to other genotypes. Circulating FGF21 levels correlated negatively with carbohydrate intake (r = -0.232, p = 0.022) and positively with body weight (r = 0.269, p = 0.007), waist (r = 0.242, p = 0.016) and hip girth (r = 0.204, p = 0.042). FGF21 levels were lower in carriers of at least one T allele. Conclusions Genetic variants in FGF21 could influence metabolic status, food preferences and qualitative changes in nutritional behavior in children.

Increased levels of circulating fibroblast growth factor 21 in children with Kawasaki disease

The purpose of this study was to examine the serum levels of fibroblast growth factor 21 (FGF21) in children with acute Kawasaki disease (KD) and to investigate its relationship with coronary artery lesions (CALs). Blood samples from 58 children with KD before intravenous immunoglobulin treatment and from 28 healthy children as control group were collected. Serum FGF21 levels in all participants were measured using enzyme-linked immunosorbent assay, and clinical parameters were tested in all KD patients. Serum FGF21 levels were significantly increased in acute KD patients as compared to the control group. Serum levels of FGF21 were substantially higher in the group of KD patients with CALs (KD-CALs) than in KD patients without CALs (KD-NCALs). Positive relationships between serum levels of FGF21 and percentage of leukomonocytes (L %), C-reactive protein, activated partial thromboplastin time and D-dimer were observed in KD patients. Furthermore, serum FGF21 levels were negatively correlated with red blood cell counts, hemoglobin (Hb), percentage of neutrophils (N %) and albumin. Serum level of FGF21 is associated with inflammation and coagulation. The paradoxical increase in serum FGF21 in acute KD patients may indicate a protective compensatory response.

Protection Effect of Exogenous Fibroblast Growth Factor 21 on the Kidney Injury in Vascular Calcification Rats

Background:

Chronic kidney disease (CKD) is closely related to the cardiovascular events in vascular calcification (VC). However, little has known about the characteristics of kidney injury caused by VC. Fibroblast growth factor 21 (FGF21) is an endocrine factor, which takes part in various metabolic actions with the potential to alleviate metabolic disorder diseases. Even FGF21 has been regarded as a biomarker in CKD, the role of FGF21 in CKD remains unclear. Therefore, in this study, we evaluate the FGF21 on the kidney injury in VC rats.

Methods:

The male Sprague-Dawley rats were divided into three groups: (1) control group, (2) Vitamin D3 plus nicotine (VDN)-induced VC group, (3) FGF21-treated VDN group. After 4 weeks, the rats were killed and the blood was collected for serum creatinine, urea nitrogen, calcium, and phosphate measurement. Moreover, the renal tissues were homogenized for alkaline phosphatases (ALPs) activity and calcium content. The levels of FGF21 protein were measured by radioimmunoassay. The levels of β-Klotho and FGF receptor 1 (FGFR1) protein were measured by enzyme-linked immunosorbent assay (ELISA). The structural damage and calcifications in aortas were stained by Alizarin-red S. Moreover, the structure of kidney was observed by hematoxylin and eosin staining.

Results:

The renal function impairment caused by VDN modeling was ameliorated by FGF21 treatment, inhibited the elevated serum creatinine and urea level by 20.5% (34.750 ± 4.334 μmol/L vs. 27.630 ± 2.387 μmol/L) and 4.0% (7.038 ± 0.590 mmol/L vs. 6.763 ± 0.374 mmol/L; P < 0.01), respectively, together with the structural damages of glomerular atrophy and renal interstitial fibrosis. FGF21 treatment downregulated the ALP activity, calcium content in the kidney of VC rats by 42.1% (P < 0.01) and 11.7% (P < 0.05) as well as ameliorated the aortic injury and calcification as compared with VDN treatment alone group, indicating an ameliorative effect on VC. ELISA assays showed that the expression of β-Klotho, a component of FGF21 receptor system, was increased in VDN-treated VC rats by 37.4% (6.588 ± 0.957 pg/mg vs. 9.054 ± 0.963 pg/mg; P < 0.01), indicating an FGF21-resistant state. Moreover, FGF21 treatment downregulated the level of β-Klotho in renal tissue by 16.7% (9.054 ± 0.963 pg/mg vs. 7.544 ± 1.362 pg/mg; P < 0.05). However, the level of FGFR1, the receptor of FGF21, kept unchanged under VDN and VDN plus FGF21 administration (0.191 ± 0.0376 ng/mg vs. 0.189 ± 0.032 ng/mg vs. 0.181 ± 0.034 ng/mg; P > 0.05).

Conclusions:

In the present study, FGF21 was observed to ameliorate the kidney injury in VDN-induced VC rats. FGF21 might be a potential therapeutic factor in CKD by cutting off the vicious circle between VC and kidney injury.

HDAC3 inhibition in diabetic mice may activate Nrf2 preventing diabetes-induced liver damage and FGF21 synthesis and secretion leading to aortic protection

Vascular complications are common pathologies associated with type 1 diabetes. In recent years, histone deacetylation enzyme (HDAC) inhibitors have been shown to be successful in preventing atherosclerosis. To investigate the mechanism for HDAC3 inhibition in preventing diabetic aortic pathologies, male OVE26 type 1 diabetic mice and age-matched wild-type (FVB) mice were given the HDAC3-specific inhibitor RGFP-966 or vehicle for 3 mo. These mice were then euthanized immediately or maintained for an additional 3 mo without treatment. Levels of aortic inflammation and fibrosis and plasma and fibroblast growth factor 21 (FGF21) levels were determined. Because the liver is the major organ for FGF21 synthesis in diabetic animals, the effects of HDAC3 inhibition on hepatic FGF21 synthesis were examined. Additionally, hepatic miR-200a and kelch-like ECH-associated protein 1 (Keap1) expression and nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation were measured. HDAC3 inhibition significantly reduced aortic fibrosis and inflammation in OVE26 mice at both 3 and 6 mo. Plasma FGF21 levels were significantly higher in RGFP-966-treated OVE26 mice compared with vehicle-treated mice at both time points. It also significantly reduced hepatic pathologies associated with diabetes, accompanied by increased FGF21 mRNA and protein expression. HDAC3 inhibition also increased miR-200a expression, reduced Keap1 protein levels, and increased Nrf2 nuclear translocation with an upregulation of antioxidant gene and FGF21 transcription. Our results support a model where HDAC3 inhibition may promote Nrf2 activity by increasing miR-200a expression with a concomitant decrease in Keap1 to preserve hepatic FGF21 synthesis. The preservation of hepatic FGF21 synthesis ultimately leads to a reduction in diabetes-induced aorta pathologies.

The Role of Insulin Resistance on FGF-21 and Inflammatory Markers in Obese Adolescents Undergoing Multicomponent Long-Term Weight Loss Therapy

Objective: The purpose of this study was to investigate the effects of a long-term weight loss therapy in two groups (insulin resistance [IR] and non-insulin resistance [non-IR]) of obese adolescents based on metabolic profile, biomarkers of inflammation, and fibroblast growth factor-21 (FGF-21) concentrations. Methods: Obese adolescents (15–19 years) were randomised into two groups (IR=8 and non-IR=9) and monitored through clinical, exercise training, nutritional, and psychological counselling over 1 year. Measurements of inflammatory biomarkers and FGF-21 were performed. The effects of therapy were verified by two-way ANOVA and post hoc analyses were performed (α ≤5%). Results: A reduction in body mass, visceral fat, and an increase in adiponectin in both groups was found. Only the non-IR group demonstrated improved BMI, body fat mass, lean body mass, and waist circumference. Indeed, in the non-IR group, FGF-21 presence was positively correlated with high-density lipoprotein cholesterol and lean body mass and inversely correlated with plasminogen activator inhibitor-1 and triglycerides. In the IR group, there was a reduction in FGF-21 concentration, adiponectin/leptin ratio, insulin, total cholesterol, low-density lipoprotein cholesterol, and plasminogen activator inhibitor-1. FGF-21 was negatively correlated with delta-triglycerides, waist circumference, and low-density lipoprotein cholesterol. The IR prevalence reduced from 47% to 23.5% in the studied population. Conclusions: Although the multicomponent clinical approach improves, in both analysed groups and in both metabolic and inflammatory states, the presence of IR resulted in a reduction in both FGF-21 concentration and adiponectin/leptin ratio. Additionally, in the IR group, FGF-21 was negatively correlated with proinflammatory markers, and in the non-IR group it was positively associated with high-density lipoprotein, suggesting its role in the control of inflammation counteracting IR. In this way, we suggest that IR can impair the anti-inflammatory effects of FGF-21. It will be helpful if these results can be confirmed in a large cohort, underlying physiological mechanisms to explore how these results can help in setting up more prospective studies.

Fibroblast growth factor 21 in chronic kidney disease

The association between fibroblast growth factor 21 (FGF21) and kidney function has been extensively studied in recent years in both animal and human studies. However, the exact functional role of FGF21 in the kidney remains unclear. Previous animal studies have shown that administration of FGF21 ameliorates kidney function, morphological glomerular abnormalities, dyslipidemia, hyperglycemia, insulin resistance, oxidative stress and obesity. In human studies, FGF21 levels negatively correlated with estimated glomerular filtration rate. FGF21 levels were elevated in patients with end-stage renal disease. The elevation of FGF21 levels in presence of kidney disease has also raised questions as to whether FGF21 is a potential biomarker for detecting a decline in renal function. In recent clinical trials, an FGF21 analogue reduced insulin levels and body weight, and ameliorated dyslipidemia in patients with type 2 diabetes mellitus and obesity, all of which are well-known risk factors for kidney disease. Thus, FGF21 may be a potential therapeutic target for the treatment of kidney disease, although adverse side effects should also be considered when administering FGF21 since FGF21 may affect bone development and reproduction. This review will assess current knowledge on the relationship between FGF21 and kidney function.

Anti-inflammatory effects of exercise training in adipose tissue do not require FGF21

Exercise enhances insulin sensitivity; it also improves adipocyte metabolism and reduces adipose tissue inflammation through poorly defined mechanisms. Fibroblast growth factor 21 (FGF21) is a pleiotropic hormone-like protein whose insulin-sensitizing properties are predominantly mediated via receptor signaling in adipose tissue (AT). Recently, FGF21 has also been demonstrated to have anti-inflammatory properties. Meanwhile, an association between exercise and increased circulating FGF21 levels has been reported in some, but not all studies. Thus, the role that FGF21 plays in mediating the positive metabolic effects of exercise in AT are unclear. In this study, FGF21-knockout (KO) mice were used to directly assess the role of FGF21 in mediating the metabolic and anti-inflammatory effects of exercise on white AT (WAT) and brown AT (BAT). Male FGF21KO and wild-type mice were provided running wheels or remained sedentary for 8 weeks (n = 9-15/group) and compared for adiposity, insulin sensitivity (i.e., HOMA-IR, Adipo-IR) and AT inflammation and metabolic function (e.g., mitochondrial enzyme activity, subunit content). Adiposity and Adipo-IR were increased in FGF21KO mice and decreased by EX. The BAT of FGF21KO animals had reduced mitochondrial content and decreased relative mass, both normalized by EX. WAT and BAT inflammation was elevated in FGF21KO mice, reduced in both genotypes by EX. EX increased WAT Pgc1alpha gene expression, citrate synthase activity, COX I content and total AMPK content in WT but not FGF21KO mice. Collectively, these findings reveal a previously unappreciated anti-inflammatory role for FGF21 in WAT and BAT, but do not support that FGF21 is necessary for EX-mediated anti-inflammatory effects.

FGF21 Attenuates High-Fat Diet-Induced Cognitive Impairment via Metabolic Regulation and Anti-inflammation of Obese Mice

Accumulating studies suggest that overnutrition-associated obesity may lead to development of type 2 diabetes mellitus and metabolic syndromes (MetS). MetS and its components are important risk factors of mild cognitive impairment, age-related cognitive decline, vascular dementia, and Alzheimer's disease. It has been recently proposed that development of a disease-course modification strategy toward early and effective risk factor management would be clinically significant in reducing the risk of metabolic disorder-initiated cognitive decline. In the present study, we propose that fibroblast growth factor 21 (FGF21) is a novel candidate for the disease-course modification approach. Using a high-fat diet (HFD) consumption-induced obese mouse model, we tested our hypothesis that recombinant human FGF21 (rFGF21) administration is effective for improving obesity-induced cognitive dysfunction and anxiety-like behavior, by its multiple metabolic modulation and anti-pro-inflammation actions. Our experimental findings support our hypothesis that rFGF21 is protective to HFD-induced cognitive impairment, at least in part by metabolic regulation in glucose tolerance impairment, insulin resistance, and hyperlipidemia; potent systemic pro-inflammation inhibition; and improvement of hippocampal dysfunction, particularly by inhibiting pro-neuroinflammation and neurogenesis deficit. This study suggests that FGF21 might be a novel molecular target of the disease-course-modifying strategy for early intervention of MstS-associated cognitive decline.

Association between circulating fibroblast growth factor 21 and mortality in end-stage renal disease

Fibroblast growth factor 21 (FGF21) is an endocrine factor that regulates glucose and lipid metabolism. Circulating FGF21 predicts cardiovascular events and mortality in type 2 diabetes mellitus, including early-stage chronic kidney disease, but its impact on clinical outcomes in end-stage renal disease (ESRD) patients remains unclear. This study enrolled 90 ESRD patients receiving chronic hemodialysis who were categorized into low- and high-FGF21 groups by the median value. We investigated the association between circulating FGF21 levels and the cardiovascular event and mortality during a median follow-up period of 64 months. A Kaplan-Meier analysis showed that the mortality rate was significantly higher in the high-FGF21 group than in the low-FGF21 group (28.3% vs. 9.1%, log-rank, P = 0.034), while the rate of cardiovascular events did not significantly differ between the two groups (30.4% vs. 22.7%, log-rank, P = 0.312). In multivariable Cox models adjusted a high FGF21 level was an independent predictor of all-cause mortality (hazard ratio: 3.98; 95% confidence interval: 1.39–14.27, P = 0.009). Higher circulating FGF21 levels were associated with a high mortality rate, but not cardiovascular events in patient with ESRD, suggesting that circulating FGF21 levels serve as a predictive marker for mortality in these subjects.

Fibroblast growth factor 21, assisted by elevated glucose, activates paraventricular nucleus NUCB2/Nesfatin-1 neurons to produce satiety under fed states

Fibroblast growth factor 21 (FGF21), liver-derived hormone, exerts diverse metabolic effects, being considered for clinical application to treat obesity and diabetes. However, its anorexigenic effect is debatable and whether it involves the central mechanism remains unclarified. Moreover, the neuron mediating FGF21’s anorexigenic effect and the systemic energy state supporting it are unclear. We explored the target neuron and fed/fasted state dependence of FGF21’s anorexigenic action. Intracerebroventricular (ICV) injection of FGF21 markedly suppressed food intake in fed mice with elevated blood glucose. FGF21 induced c-Fos expression preferentially in hypothalamic paraventricular nucleus (PVN), and increased mRNA expression selectively for nucleobindin 2/nesfatin-1 (NUCB2/Nesf-1). FGF21 at elevated glucose increased [Ca²⁺]_i in PVN NUCB2/Nesf-1 neurons. FGF21 failed to suppress food intake in PVN-preferential Sim1-Nucb2-KO mice. These findings reveal that FGF21, assisted by elevated glucose, activates PVN NUCB2/Nesf-1 neurons to suppress feeding under fed states, serving as the glycemia-monitoring messenger of liver-hypothalamic network for integrative regulation of energy and glucose metabolism.

Successful Glycemic Control Decreases the Elevated Serum FGF21 Level without Affecting Normal Serum GDF15 Levels in a Patient with Mitochondrial Diabetes

Mitochondrial diabetes mellitus is a subtype of diabetes linked to mutations in mitochondrial DNA. In patients with mitochondrial diabetes mellitus, the effect of glycemic control on the serum concentrations of fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15) has not been evaluated. FGF21 and GDF15 have been reported to be useful biomarkers for the diagnosis and severity assessment of mitochondrial diseases like mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Recent studies have shown FGF21 acts in an endocrine fashion to regulate glucose and lipid metabolism in type 2 diabetes mellitus, while the exact biological functions of GDF15 remain unknown. Although mitochondrial diabetes mellitus is commonly found in cases with mitochondrial diseases, the comparison of FGF21 and GDF15 levels between those with and without diabetes has not been performed. Here, we report a 24-year-old woman with mitochondrial diabetes mellitus, who showed a high level of serum FGF21, but not serum GDF15, at diagnosis. In our case, liraglutide, a glucagon-like peptide-1 receptor agonist, added to insulin glargine was effective for her glycemic control and showed no adverse effects, including gastrointestinal symptoms and hypoglycemia, during a 14-week observation. The successful glycemic control caused a decrease in the FGF21 level, without affecting the GDF15 level. Thus, we should consider patients' glycemic control levels in using FGF21 values for the diagnosis of mitochondrial diseases. In addition, sustained GDF15 levels during glycemic treatment in our case suggest the usefulness of GDF15 as a marker for clinical severity of muscle-manifested mitochondrial diseases.

Pharmacological efficacy of FGF21 analogue, liraglutide and insulin glargine in treatment of type 2 diabetes

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

PPARs and Mitochondrial Metabolism: From NAFLD to HCC

Metabolic related diseases, such as type 2 diabetes, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD), are widespread threats which bring about a significant burden of deaths worldwide, mainly due to cardiovascular events and cancer. The pathogenesis of these diseases is extremely complex, multifactorial, and only partially understood. As the main metabolic organ, the liver is central to maintain whole body energetic homeostasis. At the cellular level, mitochondria are the metabolic hub connecting and integrating all the main biochemical, hormonal, and inflammatory signaling pathways to fulfill the energetic and biosynthetic demand of the cell. In the liver, mitochondria metabolism needs to cope with the energetic regulation of the whole body. The nuclear receptors PPARs orchestrate lipid and glucose metabolism and are involved in a variety of diseases, from metabolic disorders to cancer. In this review, focus is placed on the roles of PPARs in the regulation of liver mitochondrial metabolism in physiology and pathology, from NAFLD to HCC.

The metabolic hormone FGF21 is associated with endothelial dysfunction in hemodialysis patients

PURPOSE

Finding new, reliable biomarkers of cardiovascular risk in hemodialysis (HD) patients is of utmost importance. Fibroblast growth factor 21 (FGF21) has been recently associated with atherosclerosis in the general population. The relationship between markedly elevated FGF21 levels in HD patients and endothelial dysfunction is unknown. The aim of the study was to assess the determinants of FGF21, the correlation between FGF21 and tumor necrosis factor TNF-like weak inducer of apoptosis (sTWEAK) and the correlation between FGF21 and endothelial dysfunction in HD patients.

METHODS

A cross-sectional observational study was conducted in 70 HD patients (mean age 59.9 ± 12.5 years, 14.3% diabetes mellitus, 57.1% male) from Nefromed Dialysis Center Cluj. We registered clinical and biological data, and serum FGF21 levels were measured by ELISA. Endothelial function was evaluated by brachial flow-mediated dilation (FMD). An analysis based on stratification of FGF21 values into quartiles was performed.

RESULTS

FGF21 levels were directly correlated with sTWEAK, tricipital skinfold thickness (TST), systolic blood pressure (SBP), total cholesterol and triglycerides. In multivariate linear analysis, only sTWEAK and SBP remained significantly associated with FGF21. FGF21 values in the inferior quartile were directly correlated with HDL-cholesterol, while FGF21 values in the superior quartile were directly correlated with SBP, pulse pressure and sTWEAK. FMD was significantly higher in the inferior quartile as compared to the superior quartile.

CONCLUSIONS

High FGF21 values in our patients are correlated with atherosclerosis risk factors: hypercholesterolemia, hypertriglyceridemia, hypertension, increased TST and increased levels of sTWEAK. Endothelial dysfunction is associated with high FGF21 in HD patients.

Upregulation of rat liver PPARα-FGF21 signaling by a docosahexaenoic acid and thyroid hormone combined protocol

Prevention of ischemia-reperfusion liver injury is achieved by a combined omega-3 and thyroid hormone (T₃ ) protocol, which may involve peroxisome-proliferator activated receptor-α (PPAR-α)-fibroblast growth factor 21 (FGF21) signaling supporting energy requirements. Combined docosahexaenoic acid (DHA; daily doses of 300 mg/kg for 3 days) plus 0.05 mg T₃ /kg given to fed rats elicited higher hepatic DHA contents and serum T₃ levels, increased PPAR-α mRNA and its DNA binding, with higher mRNA expression of the PPAR-α target genes for carnitine-palmitoyl transferase 1α, acyl-CoA oxidase, and 3-hydroxyl-3-methylglutaryl-CoA synthase 2, effects that were mimicked by 0.1 mg T₃ /kg given alone or by the PPAR-α agonist WY-14632. Under these conditions, the mRNA expression of retinoic X receptor-α (RXR-α) is also increased, with concomitant elevation of the hepatic mRNA and protein FGF21 levels and those of serum FGF21. It is concluded that PPAR-α-FGF21 induction by DHA combined with T₃ may involve ligand activation of PPAR-α by DHA and enhanced expression of PPAR-α by T₃ , with consequent upregulation of the FGF21 that is controlled by PPAR-α. Considering the beneficial effects of PPAR-α-FGF21 signaling on carbohydrate and lipid metabolism, further investigations are required to clarify its potential therapeutic applications in human metabolic disorders. © 2016 BioFactors, 42(6):638-646, 2016.

The regulation of FGF21 gene expression by metabolic factors and nutrients

Fibroblast growth factor 21 (FGF21) gene expression is altered by a wide array of physiological, metabolic, and environmental factors. Among dietary factors, high dextrose, low protein, methionine restriction, short-chain fatty acids (butyric acid and lipoic acid), and all-trans-retinoic acid were repeatedly shown to induce FGF21 expression and circulating levels. These effects are usually more pronounced in liver or isolated hepatocytes than in adipose tissue or isolated fat cells. Although peroxisome proliferator-activated receptor α (PPARα) is a key mediator of hepatic FGF21 expression and function, including the regulation of gluconeogenesis, ketogenesis, torpor, and growth inhibition, there is increasing evidence of PPARα-independent transactivation of the FGF21 gene by dietary molecules. FGF21 expression is believed to follow the circadian rhythm and be placed under the control of first order clock-controlled transcription factors, retinoic acid receptor-related orphan receptors (RORs) and nuclear receptors subfamily 1 group D (REV-ERBs), with FGF21 rhythm being anti-phase to REV-ERBs. Key metabolic hormones such as glucagon, insulin, and thyroid hormone have presumed or clearly demonstrated roles in regulating FGF21 transcription and secretion. The control of the FGF21 gene by glucagon and insulin appears more complex than first anticipated. Some discrepancies are noted and will need continued studies. The complexity in assessing the significance of FGF21 gene expression resides in the difficulty to ascertain (i) when transcription results in local or systemic increase of FGF21 protein; (ii) if FGF21 is among the first or second order genes upregulated by physiological, metabolic, and environmental stimuli, or merely an epiphenomenon; and (iii) whether FGF21 may have some adverse effects alongside beneficial outcomes.

Levothyroxine treatment restored the decreased circulating fibroblast growth factor 21 levels in patients with hypothyroidism

BACKGROUND AND AIMS

Fibroblast growth factor 21 (FGF21) is an important endogenous regulator of energy metabolism. Thyroid hormone has been shown to regulate hepatic FGF21 expression in rodents. The goal of this study was to evaluate the plasma FGF21 levels in participants with normal thyroid function, subclinical hypothyroidism, or overt hypothyroidism and to investigate the change of plasma FGF21 levels in patients with overt hypothyroidism after levothyroxine treatment.

METHODS

A total of 473 drug-naive participants were recruited, including 250 healthy control subjects, 116 patients with subclinical hypothyroidism, and 107 patients with overt hypothyroidism. Thirty-eight patients with overt hypothyroidism were assigned to receive levothyroxine treatment.

RESULTS

The overt hypothyroidism group had decreased FGF21 levels compared with the control and subclinical hypothyroidism groups (P<0.01). Levothyroxine treatment markedly attenuated the increased circulating levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), high-sensitivity C-reactive protein (hsCRP), and homeostasis model assessment index of insulin resistance (HOMA-IR) in patients with overt hypothyroidism. A significant increase in plasma FGF21 levels was observed after levothyroxine treatment (P<0.01). The change in FGF21 levels was correlated with the increase of FT3 and FT4 after levothyroxine treatment (FT3: r=0.44; FT4: r=0.53; all P<0.05).

CONCLUSIONS

Levothyroxine treatment ameliorated metabolic disorders and restored the decreased circulating FGF21 levels in patients with overt hypothyroidism. The increase in FGF21 levels after levothyroxine treatment might be partly associated with the amelioration of metabolic disorders in patients with hypothyroidism.

Insulin sensitizes FGF21 in glucose and lipid metabolisms via activating common AKT pathway

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

NS5ATP6 modulates intracellular triglyceride content through FGF21 and independently of SIRT1 and SREBP1

The prevalence of nonalcoholic fatty liver disease (NAFLD) is rising strikingly in Western countries and China. The molecular biological mechanism of NAFLD remains unclear, with no effective therapies developed so far. Fibroblast growth factor 21 (FGF21) is a recently discovered hormone, with safe lipid lowering effects. FGF21 analogs are being developed for clinical application. Here we demonstrated that a novel gene, NS5ATP6, modulated intracellular triglyceride (TG) content independently of sirtuin1 (SIRT1) and sterol regulatory element binding protein 1 (SREBP1) in HepG2 cells. Interestingly, NS5ATP6 regulated FGF21 expression both at the mRNA and protein levels. The modulatory effects of NS5ATP6 on intracellular TG content depended upon FGF21. Further studies revealed that NS5ATP6 decreased the promoter activity of FGF21. In addition, NS5ATP6 regulated the expression of miR-577, which directly targeted and regulated FGF21. Therefore, miR-577 might be involved in NS5ATP6 regulation of FGF21 at the post-transcriptional level. In conclusion, NS5ATP6 regulates the intracellular TG level via FGF21, and independently of SIRT1 and SREBP1.

Fibroblast Growth Factor 21 (FGF-21) in Peritoneal Dialysis Patients: Natural History and Metabolic Implications

Background

Human fibroblast growth factor 21 (FGF-21) is an endocrine liver hormone that stimulates adipocyte glucose uptake independently of insulin, suppresses hepatic glucose production and is involved in the regulation of body fat. Peritoneal dialysis (PD) patients suffer potential interference with FGF-21 status with as yet unknown repercussions.

Objectives

The aim of this study was to define the natural history of FGF-21 in PD patients, to analyze its relationship with glucose homeostasis parameters and to study the influence of residual renal function and peritoneal functional parameters on FGF-21 levels and their variation over time.

Methods

We studied 48 patients with uremia undergoing PD. Plasma samples were routinely obtained from each patient at baseline and at 1, 2 and 3 years after starting PD therapy.

Results

Plasma FGF-21 levels substantially increased over the first year and were maintained at high levels during the remainder of the study period (253 pg/ml (59; 685) at baseline; 582 pg/ml (60.5–949) at first year and 647 pg/ml (120.5–1116.6) at third year) (p<0.01). We found a positive correlation between time on dialysis and FGF-21 levels (p<0.001), and also, those patients with residual renal function (RRF) had significantly lower levels of FGF-21 than those without RRF (ρ -0.484, p<0.05). Lastly, there was also a significant association between FGF-21 levels and peritoneal protein losses (PPL), independent of the time on dialysis (ρ 0.410, p<0.05).

Conclusion

Our study shows that FGF-21 plasma levels in incident PD patients significantly increase during the first 3 years. This increment is dependent on or is associated with RRF and PPL (higher levels in patients with lower RRF and higher PPL). FGF-21 might be an important endocrine agent in PD patients and could act as hormonal signaling to maintain glucose homeostasis and prevent potential insulin resistance. These preliminary results suggest that FGF-21 might play a protective role as against the development of insulin resistance over time in patients undergoing a continuous glucose load.

Effect of Metformin on Fibroblast Growth Factor-21 Levels in Patients with Newly Diagnosed Type 2 Diabetes

BACKGROUND

Fibroblast growth factor (FGF)-21 is an important regulator of glucose metabolism. In the present study, we investigated whether plasma levels of FGF-21 changed in patients with newly diagnosed type 2 diabetes mellitus (T2DM) and assessed the effects of metformin treatment on plasma FGF-21 levels.

MATERIALS AND METHODS

The plasma FGF-21 levels and the metabolic parameters of 226 patients with newly diagnosed T2DM and 100 sex- and age-matched normal glycemic tolerant (NGT) controls were measured. Seventy-four patients among of the 226 patients with T2DM were treated with metformin throughout the 12-week study period. The fasting plasma FGF-21 and high-sensitivity C-reactive protein (hs-CRP) levels were measured using enzyme-linked immunosorbent assay kits.

RESULTS

The patients with T2DM had significantly higher fasting plasma FGF-21 levels (302.2 pg/mL [range, 201.3-454.4 pg/mL] vs. 104.5 pg/mL [range, 71.6-185.6 pg/mL]; P < 0.00) and hs-CRP levels (2.63 ± 2.81 mg/L vs. 1.58 ± 2.16 mg/L; P < 0.00) than the NGT subjects. The fasting plasma hs-CRP and FGF-21 levels were significantly decreased in the T2DM group after metformin treatment compared with pretreatment (respectively, 2.56 ± 1.75 mg/L vs. 3.28 ± 1.89 mg/L [P < 0.05] and 232.6 pg/mL [range, 154.3-307.8 pg/mL] vs. 313.9 pg/mL [range, 227.7-474.2 pg/mL] [P < 0.01]).

CONCLUSIONS

In patients with T2DM, the plasma FGF-21 levels are increased but are significantly decreased after metformin treatment. Metformin may play a role in reducing the FGF-21 levels in patients with T2DM, likely through the amelioration of glucose-lipid metabolism and inflammation.

Fibroblast Growth Factor 21 (Fgf21) Gene Expression Is Elevated in the Liver of Mice Fed a High-Carbohydrate Liquid Diet and Attenuated by a Lipid Emulsion but Is Not Upregulated in the Liver of Mice Fed a High-Fat Obesogenic Diet

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a regulator of carbohydrate and lipid metabolism; however, the regulation of Fgf21 gene expression by diet remains incompletely understood.

OBJECTIVE

We investigated the effect of a high-carbohydrate (HC) liquid diet, with and without supplementation with a lipid emulsion (LE), and of a high-fat diet (HFD) compared with a low-fat diet (LFD) on the regulation of Fgf21 gene expression in the liver of intact mice.

METHODS

C57BL/6 male mice were fed standard feed pellets (SFPs), a purified HC liquid diet (adequate in calories and protein), or an HC liquid diet containing an LE at either 4% or 13.5% of energy for 5 wk (Expt. 1) or 1 wk (Expt. 2). In Expt. 3, mice were fed a purified LFD (∼10% fat) or HFD (∼60% fat) or were fed an HFD and given access to a running wheel for voluntary exercise for 16 wk.

RESULTS

Fgf21 mRNA in liver and FGF21 protein in plasma were increased by 3.5- to 7-fold in HC mice compared with SFP mice (P < 0.001), whereas the LE dose-dependently attenuated the induction of Fgf21 expression (P < 0.05). After 16 wk, hepatic Fgf21 mRNA did not differ between LFD and HFD mice but was dramatically reduced in the HFD+exercise group to <20% of the level in the HFD group (P < 0.0001).

CONCLUSIONS

In mice, hepatic Fgf21 expression was upregulated by 1 and 5 wk of feeding a lipogenic HC diet but not by 16 wk of feeding an obesogenic HFD, whereas the addition of fat as an LE to the HC formula significantly reduced Fgf21 gene expression and the plasma FGF21 protein concentration. Our results support a strong and reversible response of hepatic Fgf21 expression to shifts in dietary glucose intake.

Circulating CTRP1 Levels in Type 2 Diabetes and Their Association with FGF21

The goal of this study was to investigate whether circulating C1q/TNF-α-related protein 1 (CTRP1) levels are associated with diabetes. In addition, relationships between CTRP1 and other diabetes-related cytokines were elucidated, including adiponectin and fibroblast growth factor 21 (FGF21). A total of 178 subjects (78 men and 100 women) aged 29-70 years (mean age, 46.1 years) were randomly selected. The sera from a normal glucose tolerance group (n = 68) and a prediabetes/type 2 diabetes group (n = 110) were collected; then, circulating levels of CTRP1, adiponectin, and FGF21 were determined via enzyme-linked immunosorbent assay in all sera. Subjects with either prediabetes or diabetes exhibited higher circulating CTRP1 levels than healthy subjects. Sera analysis revealed that CTRP1 was positively correlated with age, body mass index, fasting blood glucose, and circulating FGF21 levels. However, CTRP1 was negatively correlated with total cholesterol and total circulating adiponectin levels in univariate analysis. In addition, multivariate analysis found that CTRP1 was independently associated with age, fasting blood glucose, and circulating FGF21 levels. CTRP1 was correlated with homeostasis model assessment-β (HOMA-β), but no correlation was observed with HOMA-insulin resistance. In conclusion, circulating CTRP1 levels are increased in subjects with type 2 diabetes and are positively associated with circulating FGF21 levels.

Implications of Fibroblast growth factor/Klotho system in glucose metabolism and diabetes

Diabetes mellitus, especially type 2 diabetes, remains the dominant metabolic disease worldwide, with an expected increase in prevalence of over 50% in the next 20 years. Our knowledge about the pathophysiology of type 2 diabetes continues to be incomplete, with unmet medical need for new therapies. The characterization of the fibroblast growth factor (FGF) family and the discovery of endocrine FGFs provided new information on the mechanisms of regulation and homeostasis of carbohydrate metabolism. More specifically, FGF19 and FGF21 signaling pathways have been linked to different glucose metabolic processes, including hepatic glucose synthesis, glycogen synthesis, glucose uptake, and insulin sensitivity, among others, and these molecules have been further related to the pathophysiology of diabetes mellitus. In-depth comprehension of these growth factors may bring to light new potential therapeutic targets for the treatment of diabetes mellitus.

Skeletal muscle mitochondrial uncoupling prevents diabetes but not obesity in NZO mice, a model for polygenic diabesity

Induction of skeletal muscle (SM) mitochondrial stress by expression of uncoupling protein 1 (UCP1) in mice results in a healthy metabolic phenotype associated with increased secretion of FGF21 from SM. Here, we investigated whether SM mitochondrial uncoupling can compensate obesity and insulin resistance in the NZO mouse, a polygenic diabesity model. Male NZO mice were crossed with heterozygous UCP1 transgenic (tg) mice (mixed C57BL/6/CBA background) and further backcrossed to obtain F1 and N2 offspring with 50 and 75 % NZO background, respectively. Male F1 and N2 progeny were fed a high-fat diet ad libitum for 20 weeks from weaning. Blood glucose was reduced, and diabetes (severe hyperglycemia >300 mg/dl) was fully prevented in both F1- and N2-tg progeny compared to a diabetes prevalence of 15 % in F1 and 42 % in N2 wild type. In contrast, relative body fat content and plasma insulin were decreased, and glucose tolerance was improved, in F1-tg only. Both F1 and N2-tg showed decreased lean body mass. Accordingly, induction of SM stress response including FGF21 expression and secretion was similar in both F1 and N2-tg mice. In white adipose tissue, expression of FGF21 target genes was enhanced in F1 and N2-tg mice, whereas lipid metabolism genes were induced in F1-tg only. There was no evidence for induction of browning in either UCP1 backcross. We conclude that SM mitochondrial uncoupling induces FGF21 expression and prevents diabetes in mice with a 50-75 % NZO background independent of its effects on adipose tissue.

Laparoscopic gastric plication and its effect on saccharide and lipid metabolism: a 12-month prospective study

Introduction

Laparoscopic greater curvature plication (LGCP) is a novel restrictive technique that reduces gastric volume by plication of the greater curvature. The advantage of LGCP is its reversibility in comparison to laparoscopic sleeve gastrectomy. Nowadays, the long-term LGCP efficacy, safety and metabolic effect are being investigated.

Aim

To assess body composition, clinical complications and metabolic changes in obese patients 6 and 12 months after laparoscopic greater curvature plication.

Material and methods

A total of 70 subjects underwent LGCP; 52 of them (33 women and 19 men) completed 1-year follow-up study. Anthropometry and biochemical parameters (glucose, glycated haemoglobin, lipids, ghrelin, leptin, adiponectin and fibroblast growth factor 21 [FGF-21]) were assessed before and 3, 6, and 12 months after surgery.

Results

All study participants exhibited statistically significant weight loss at both 6 and 12 months following the LGCP compared to baseline, with significant reductions in body composition – body weight, body mass index, percentage excess weight loss (%EWL), and percentage excess BMI loss (%EBL) (p ≤ 0.001). Moreover, significant lowering of glucose and glycated haemoglobin, triacylglycerols and leptin was observed 12 months after LGCP. On the other hand, plasma concentrations of ghrelin, adiponectin and LDL cholesterol increased significantly. Total cholesterol, LDL cholesterol and FGF-21 levels did not change significantly.

Conclusions

Laparoscopic greater curvature plication appears to be a procedure with good restriction results, which might be mediated through alteration in incretin metabolism. Technical aspects and standardization of the procedure still remain to be worked out.

Rapid increase in fibroblast growth factor 21 in protein malnutrition and its impact on growth and lipid metabolism

Protein malnutrition promotes hepatic steatosis, decreases insulin-like growth factor (IGF)-I production and retards growth. To identify new molecules involved in such changes, we conducted DNA microarray analysis on liver samples from rats fed an isoenergetic low-protein diet for 8 h. We identified the fibroblast growth factor 21 gene (Fgf21) as one of the most strongly up-regulated genes under conditions of acute protein malnutrition (P<0·05, false-discovery rate<0·001). In addition, amino acid deprivation increased Fgf21 mRNA levels in rat liver-derived RL-34 cells (P<0·01). These results suggested that amino acid limitation directly increases Fgf21 expression. FGF21 is a polypeptide hormone that regulates glucose and lipid metabolism. FGF21 also promotes a growth hormone-resistance state and suppresses IGF-I in transgenic mice. Therefore, to determine further whether Fgf21 up-regulation causes hepatic steatosis and growth retardation after IGF-I decrease in protein malnutrition, we fed an isoenergetic low-protein diet to Fgf21-knockout (KO) mice. Fgf21-KO did not rescue growth retardation and reduced plasma IGF-I concentration in these mice. Fgf21-KO mice showed greater epididymal white adipose tissue weight and increased hepatic TAG and cholesterol levels under protein malnutrition conditions (P<0·05). Overall, the results showed that protein deprivation directly increased Fgf21 expression. However, growth retardation and decreased IGF-I were not mediated by increased FGF21 expression in protein malnutrition. Furthermore, FGF21 up-regulation rather appears to have a protective effect against obesity and hepatic steatosis in protein-malnourished animals.

Effects of the intragastric balloon MedSil on weight loss, fat tissue, lipid metabolism, and hormones involved in energy balance

Background

The prevalence of obesity continues to increase worldwide. Because obesity is associated with a number health-related problems as well as a shortened life span, treating obesity is an important clinical concern. Although various treatments are currently available, many are not efficacious in the long term. Therefore, additional medical treatment options for morbidly obese individuals must be explored. In this study, we examined the effects of the intragastric balloon MedSil® on anthropometric measures and hormones associated with lipid and energy metabolism.

Methods

Twenty-two obese patients underwent insertion of the intragastric balloon MedSil® following a clinical exam, body composition scan, and collection of blood samples. Six months following implantation of the balloon, additional anthropometric and serological measures were taken.

Results

Six months following insertion of the MedSil® balloon, we observed significant decreases in body weight, body mass index, and fat mass. Compared with baseline levels, ghrelin serum levels were increased significantly, while leptin, FGF21, and glycated hemoglobin levels significantly decreased, 6 months after balloon insertion.

Conclusions

The MedSil® intragastric balloon is a safe and effective treatment for morbid obesity, with positive effects on anthropometric measures and lipid metabolism.