FGF21 activates AMPK signaling: impact on metabolic regulation and the aging process

NEDD4 enhances bone‑tendon healing in rotator cuff tears by reducing fatty infiltration

Rotator cuff tears (RCT) can cause shoulder pain, weakness and stiffness, significantly affecting daily life. Analysis of the GSE103266 dataset revealed significant changes in the mTOR/PI3K/Akt signaling pathway and lipid metabolism‑related pathways, suggesting that fatty infiltration may affect RCT. The analysis indicated that the ubiquitin ligase NEDD4 plays a critical role in RCT. NEDD4 was found to be highly associated with the mTOR/PI3K/Akt signaling pathway. An RCT model in Sprague‑Dawley (SD) rats was established to study the role of NEDD4 in regulating the mTOR pathway and investigate its effects on fatty infiltration. SD rats were divided into NEDD4 overexpression and knockout groups. Tissue recovery, apoptosis and fat deposition were measured through histological staining, reverse transcription‑quantitative PCR and western blotting. Additionally, cell culture of fibro‑adipogenic progenitors and lentiviral transfection were conducted to investigate the effect of NEDD4 on adipocyte differentiation. NEDD4 overexpression significantly reduced lipid accumulation, whereas NEDD4 knockdown enhanced lipid accumulation. NEDD4 was found to regulate the mTOR pathway and the expression of adipogenesis‑related genes, promoting fat metabolism and inhibiting adipocyte differentiation. Histological analysis indicated that NEDD4 overexpression improved tissue recovery and reduced apoptosis. Targeting NEDD4 offers a potential therapeutic strategy to improve the clinical outcomes of patients with RCT by modulating the mTOR pathway and fat metabolism.

A meta-analysis of genome-wide association studies to identify candidate genes associated with feed efficiency traits in pigs

Pig production is an agricultural sector of great economic and social relevance to Brazil and global markets. Feed efficiency traits directly influence the sustainability of pig production due to the economic impact of feed costs on the production system and the environmental footprint of the industry. Therefore, breeding for improved feed efficiency has been a target of worldwide pig breeding programs. Genome-wide association studies (GWAS) enable the assessment of the genetic background of complex traits, which contributes to a better understanding of the biological mechanisms regulating their phenotypic expression. In this context, the primary objective of this study was to identify and validate genomic regions and candidate genes associated with feed conversion ratio (FCR) and residual feed intake (RFI) in pigs based on a comprehensive systematic review and meta-analysis of GWAS. The METAL software was used to implement the meta-analysis and the Bonferroni multiple testing correction considering a significance threshold 0.05. The significant single nucleotide polymorphisms (SNPs) in the meta-analysis were used to identify candidate genes, followed by a functional genomic enrichment analysis. The systematic review identified 13 studies, of which 7 evaluated FCR, 3 evaluated RFI, and 3 studies investigated both traits, with 160 and 96 SNPs identified for FCR and RFI, respectively. After the meta-analysis, 145 markers were significantly associated with FCR and 90 with RFI. The gene annotation process resulted in 105 and 114 genes for FCR and RFI, respectively. The enrichment analysis for FCR resulted in 16 significant gene ontology (GO) terms, while 6 terms were identified for RFI. The main GO terms were actin cytoskeleton (GO_BP:0030036), membrane (GO_CC:0016020), integral components of the peroxisomal membrane (GO_CC:0005779), and carbohydrate-binding (GO_MF:0030246). The main candidate genes identified were MED18, PHACTR4, ABCC2, TRHDE, FRS2, FAR2 and FIS1 for FCR, and ADGRL2, ASGR1, ASGR2, and MAN2B1 for RFI. These findings contribute to a better understanding of the genetic mechanisms associated with feed efficiency traits in pigs, providing a foundation for future improvements in pig breeding programs.

GLP-1 Receptor Agonists Alleviate Diabetic Kidney Injury via β-Klotho-Mediated Ferroptosis Inhibition

Semaglutide (Smg), a GLP-1 receptor agonist (GLP-1RA), shows renal protective effects in patients with diabetic kidney disease (DKD). However, the exact underlying mechanism remains elusive. This study employs transcriptome sequencing and identifies β-Klotho (KLB) as the critical target responsible for the role of Smg in kidney protection. Smg treatment alleviates diabetic kidney injury by inhibiting ferroptosis in patients, animal models, and HK-2 cells. Notably, Smg treatment significantly increases the mRNA expression of KLB through the activation of the cyclic adenosine monophosphate (cAMP) signaling pathway, specifically through the phosphorylation of protein kinase A (PKA) and cAMP-response element-binding protein (CREB). Subsequently, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway is activated, reprograming the key metabolic processes of ferroptosis such as iron metabolism, fatty acid synthesis, and the antioxidant response against lipid peroxidation. Suppression of ferroptosis by Smg further attenuates renal inflammation and fibrosis. This work highlights the potential of GLP-1RAs and KLB targeting as promising therapeutic approaches for DKD management.

Methionine restriction alleviates diabetes-associated cognitive impairment via activation of FGF21

Glucose metabolism disturbances may result in diabetes-associated cognitive decline (DACI). Methionine restriction (MR) diet has emerged as a potential dietary strategy for managing glucose homeostasis. However, the effects and underlying mechanisms of MR on DACI have not been fully elucidated. Here, we found that a 13-week MR (0.17 % methionine, w/w) intervention starting at 8 weeks of age improved peripheral insulin sensitivity in male db/db mice, a model for type 2 diabetes. Notably, MR significantly improved working as well as long-term memory in db/db mice, accompanied by increased PSD-95 level and reduced neuroinflammatory factors, malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG). We speculate that this effect may be mediated by MR activating hepatic fibroblast growth factor 21 (FGF21) and the brain FGFR1/AMPK/GLUT4 signaling pathway to enhance brain glucose metabolism. To further delineate the mechanism, we used intracerebroventricular injection of adeno-associated virus to specifically knock down FGFR1 in the brain to verify the role of FGFR1 in MR-mediated DACI. It was found that the positive effects of MR on DACI were offset, reflected in decreased cognitive function, impaired synaptic plasticity, upregulated neuroinflammation, and balanced enzymes regulating reactive oxygen species (Sod1, Sod2, Nox4). Of note, the FGFR1/AMPK/GLUT4 signaling pathway and brain glucose metabolism were inhibited. In summary, our study demonstrated that MR increased peripheral insulin sensitivity, activated brain FGFR1/AMPK/GLUT4 signaling through FGF21, maintained normal glucose metabolism and redox balance in the brain, and thereby alleviated DACI. These results provide new insights into the effects of MR diet on cognitive dysfunction caused by impaired brain energy metabolism.

FGF21 inhibits ferroptosis caused by mitochondrial damage to promote the repair of peripheral nerve injury

Introduction

Ferroptosis is a new type of cell death characterized by lipid peroxidation and iron dependency, representing an emerging disease regulation mechanism. The limited understanding of ferroptosis in peripheral nerve injury (PNI) complicates the management of such injuries. Mitochondrial dysfunction, which contributes to ferroptosis, further exacerbates the challenges of peripheral nerve repair.

Methods

In this study, we established an in vitro model of Schwann cells model treated with TBHP and an in vivo sciatic nerve crush injury model in rats. These models were used to investigate the effects of fibroblast growth factor 21 (FGF21) on PNI, both in vitro and in vivo, and to explore the potential mechanisms linking injury-induced ferroptosis and mitochondrial dysfunction.

Results

Our findings reveal that PNI triggers abnormal accumulation of lipid reactive oxygen species (ROS) and inactivates mitochondrial respiratory chain complex III, leading to mitochondrial dysfunction. This dysfunction catalyzes the oxidation of excessive polyunsaturated fatty acids, resulting in antioxidant imbalance and loss of ferroptosis suppressor protein 1 (FSP1), which drives lipid peroxidation. Additionally, irregular iron metabolism, defective mitophagy, and other factors contribute to the induction of ferroptosis. Importantly, we found that FGF21 attenuates the abnormal accumulation of lipid ROS, restores mitochondrial function, and suppresses ferroptosis, thus promoting PNI repair. Notably, glutathione peroxidase 4 (GPX4), a downstream target of nuclear factor E2-related factor 2 (Nrf2), and the ERK/Nrf2 pathway are involved in the regulation of ferroptosis by FGF21.

Conclusion

FGF21 promotes peripheral nerve repair by inhibiting ferroptosis caused by mitochondrial dysfunction. Therefore, targeting mitochondria and ferroptosis represents a promising therapeutic strategy for effective PNI repair.

Gentiopicroside ameliorates glucose and lipid metabolism in T2DM via targeting FGFR1

BACKGROUND

The suppression of the fibroblast growth factor 21/fibroblast growth factor receptor 1 (FGF21/FGFR1) signaling pathway is considered as a vital factor in the type 2 diabetes mellitus (T2DM) progression. Our previous study showed that gentiopicroside (GPS), the main active compound present in Gentiana macrophylla Pall., has the capacity to control disorders related to glucose and lipid metabolism in individuals with T2DM. Nevertheless, the specific mechanism remains unclear.

PURPOSE

In light of the fact that the PharmMapper database suggests FGFR1 as the target of GPS, our investigation aims to determine if GPS can enhance glucose and lipid metabolism issues in T2DM by modulating the FGF21/FGFR1 signaling pathway.

METHODS

In this study, we used palmitic acid (PA)-induced HepG2 cells and db/db mice to investigate the function and mechanism of GPS in the FGF21/FGFR1 signaling pathway. To examine the interaction between GPS and FGFR1, researchers performed Cellular Thermal Shift Assay (CETSA) and Surface Plasmon Resonance (SPR) analysis.

RESULTS

The results suggest that GPS activates the traditional metabolic pathways, including PI3K/AKT and AMPK, which are the subsequent stages of the FGF21/FGFR1 pathway. This activation leads to the enhancement of glucose and lipid metabolism issues in PA-treated HepG2 cells and db/db mice. Furthermore, the depletion of FGFR1 has been noticed to oppose the stimulation of PI3K/AKT and AMPK pathways by GPS in HepG2 cells subjected to PA. Notability, our research affirms that GPS binds directly to FGFR1, hindering the ubiquitinated degradation of FGFR1 by neural precursor cells expressing developmentally decreased protein 4 (NEDD4) and ultimately promoting FGF21 signal transduction.

CONCLUSION

This study demonstrates that GPS targeting FGFR1 activates the PI3K/AKT and AMPK pathways, which is an important mechanism for its treatment of T2DM.

The crosstalk between fibroblast growth factor 21 (FGF21) system and substance use

Existing literature indicates that communication between the central nervous system and the peripheral nervous system is disrupted by substance use disorders (SUDs), including alcohol use disorder (AUD). Fibroblast growth factor 21 (FGF21), a liver-brain axis hormone governing energy homeostasis, has been shown to modulate alcohol intake/preference and other substances. To further elucidate the relationship between FGF21, alcohol use, and other substance use, we conducted a scoping review to explore the association between FGF21 and SUDs. Increases in FGF21 reduce alcohol consumption while suppressing FGF21 increases alcohol consumption, demonstrating an inverse relationship. Alcohol elevates FGF21 levels primarily via the liver, subsequently promoting neuronal signals to curb alcohol intake. FGF21 activation engages molecular pathways that defend against alcohol-induced fat accumulation, oxidative stress, and inflammation. Considering the bidirectional association between FGF21 and alcohol, further studies on the FGF21 system as a potential pharmacotherapy for AUD and alcohol-associated liver disease are warranted.

Sulfur Amino Acid Restriction Enhances Exercise Capacity in Mice by Boosting Fat Oxidation in Muscle

Dietary restriction of the sulfur-containing amino acids methionine and cysteine (SAAR) improves body composition, enhances insulin sensitivity, and extends lifespan; benefits seen also with endurance exercise. Yet, the impact of SAAR on skeletal muscle remains largely unexplored. Here we demonstrate that one week of SAAR in sedentary, young, male mice increases endurance exercise capacity. Indirect calorimetry showed that SAAR increased lipid oxidation at rest and delayed the onset of carbohydrate utilization during exercise. Transcriptomic analysis revealed increased expression of genes involved in fatty acid catabolism especially in glycolytic muscle following SAAR. These findings were functionally supported by increased fatty acid circulatory turnover flux and muscle β-oxidation. Reducing lipid uptake from circulation through endothelial cell (EC)-specific CD36 deletion attenuated the running phenotype. Mechanistically, VEGF-signaling inhibition prevented exercise increases following SAAR, without affecting angiogenesis, implicating noncanonical VEGF signaling and EC CD36-dependent fatty acid transport in regulating exercise capacity by influencing muscle substrate availability.

The effects of exercise on FGF21 in adults: a systematic review and meta-analysis

Background

Fibroblast growth factor 21 (FGF21) is a key hormone factor that regulates glucose and lipid homeostasis. Exercise may regulate its effects and affect disease states. Therefore, we sought to determine how exercise affects FGF21 concentrations in adults.

Methods

The review was registered in the International Prospective Systematic Review (PROSPERO, CRD42023471163). The Cochrane Library, PubMed, and Web of Science databases were searched for studies through July 2023. Studies that assessed the effects of exercise training on FGF21 concentration in adults were included. The random effect model, data with standardized mean difference (SMD), and 95% confidence intervals (CI) were used to evaluate the pooled effect size of exercise training on FGF21. The risk of heterogeneity and bias were evaluated. A total of 12 studies involving 401 participants were included.

Results

The total effect size was 0.3 (95% CI [-0.3-0.89], p = 0.33) when comparing participants who exercised to those who were sedentary. However, subgroup analysis indicated that concurrent exercise and a duration ≥10 weeks significantly decreased FGF21 concentrations with an effect size of -0.38 (95% CI [-0.74--0.01], p < 0.05) and -0.38 (95% CI [-0.63--0.13], p < 0.01), respectively.

Conclusion

Concurrent exercise and longer duration may be more efficient way to decrease FGF21 concentrations in adults with metabolic disorder.

FGF21-mediated autophagy: Remodeling the homeostasis in response to stress in liver diseases

Liver diseases are worldwide problems closely associated with various stresses, such as endoplasmic reticulum stress. The exact interplay between stress and liver diseases remains unclear. Autophagy plays an essential role in maintaining homeostasis, and recent studies indicate tight crosstalk between stress and autophagy in liver diseases. Once the balance between damage and autophagy is broken, autophagy can no longer resist injury or maintain homeostasis. In recent years, FGF21 (fibroblast growth factor 21)-induced autophagy has attracted much attention. FGF21 is regarded as a stress hormone and can be up-regulated by an abundance of signaling pathways in response to stress. Also, increased FGF21 activates autophagy by a complicated signaling network in which mTOR plays a pivotal role. This review summarizes the mechanism of FGF21-mediated autophagy and its derived application in the defense of stress in liver diseases and offers a glimpse into its promising prospect in future clinical practice.

Exploring exercise-driven exerkines: unraveling the regulation of metabolism and inflammation

Exercise has many beneficial effects that provide health and metabolic benefits. Signaling molecules are released from organs and tissues in response to exercise stimuli and are widely termed exerkines, which exert influence on a multitude of intricate multi-tissue processes, such as muscle, adipose tissue, pancreas, liver, cardiovascular tissue, kidney, and bone. For the metabolic effect, exerkines regulate the metabolic homeostasis of organisms by increasing glucose uptake and improving fat synthesis. For the anti-inflammatory effect, exerkines positively influence various chronic inflammation-related diseases, such as type 2 diabetes and atherosclerosis. This review highlights the prospective contribution of exerkines in regulating metabolism, augmenting the anti-inflammatory effects, and providing additional advantages associated with exercise. Moreover, a comprehensive overview and analysis of recent advancements are provided in this review, in addition to predicting future applications used as a potential biomarker or therapeutic target to benefit patients with chronic diseases.

Dapagliflozin promotes browning of white adipose tissue through the FGFR1-LKB1-AMPK signaling pathway

BACKGROUND

Obesity is associated with a wide variety of metabolic disorders that impose significant burdens on patients and society. The "browning" phenomenon in white adipose tissue (WAT) has emerged as a promising therapeutic strategy to combat metabolic disturbances. However, though the anti-diabetic drug dapagliflozin (DAPA) is thought to promote "browning," the specific mechanism of this was previously unclear.

METHODS

In this study, C57BL/6 J male mice were used to establish an obesity model by high-fat diet feeding, and 3T3-L1 cells were used to induce mature adipocytes and to explore the role and mechanism of DAPA in "browning" through a combination of in vitro and in vivo experiments.

RESULTS

The results show that DAPA promotes WAT "browning" and improves metabolic disorders. Furthermore, we discovered that DAPA activated "browning" through the fibroblast growth factor receptors 1-liver kinase B1-adenosine monophosphate-activated protein kinase signaling pathway.

CONCLUSION

These findings provide a rational basis for the use of DAPA in treating obesity by promoting the browning of white adipose tissue.

Neonatal resveratrol administration promotes skeletal muscle growth and insulin sensitivity in intrauterine growth-retarded suckling piglets associated with activation of FGF21-AMPKα pathway

BACKGROUND

Skeletal muscle is a major insulin-sensitive tissue with a pivotal role in modulating glucose homeostasis. This study aimed to investigate the effect of resveratrol (RES) intervention during the suckling period on skeletal muscle growth and insulin sensitivity of neonates with intrauterine growth retardation (IUGR) in a pig model.

RESULTS

Twelve pairs of normal birth weight (NBW) and IUGR neonatal male piglets were selected. The NBW and IUGR piglets were fed basal formula milk diet or identical diet supplemented with 0.1% RES from 7 to 21 days of age. Myofiber growth and differentiation, inflammation and insulin sensitivity in skeletal muscle were assessed. Early RES intervention promoted myofiber growth and maturity in IUGR piglets by ameliorating the myogenesis process and increasing thyroid hormone level. Administering RES also reduced triglyceride concentration in skeletal muscle of IUGR piglets, along with decreased inflammatory response, increased plasma fibroblast growth factor 21 (FGF21) concentration and improved insulin signaling. Meanwhile, the improvement of insulin sensitivity by RES may be partly regulated by activation of the FGF21/AMP-activated protein kinase α/sirtuin 1/peroxisome proliferator activated receptor-γ coactivator-1α pathway.

CONCLUSION

Our results suggest that RES has beneficial effects in promoting myofiber growth and maturity and increasing skeletal muscle insulin sensitivity in IUGR piglets, which open a novel field of application of RES in IUGR infants for improving postnatal metabolic adaptation. © 2023 Society of Chemical Industry.

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.

FGF12 restrains mitochondria-dependent ferroptosis in doxorubicin-induced cardiomyocytes through the activation of FGFR1/AMPK/NRF2 signaling

Fibroblast growth factor-12 (FGF12) has been reported to play important role in regulating heart diseases. We aimed to explore the role of FGF12 in doxorubicin (DOX)-induced myocardial injury. DOX-induced mice and DOX-induced HL-1 cells were used as the myocardial injury in vivo and in vitro. Then, FGF12, Anp, Bnp, and Myh7 expression was detected. The pathological injury in myocardium tissue was observed by H&E staining. The levels of markers related to myocardial damage and oxidative stress were assessed. Then, immunohistochemistry and immunofluorescence staining were used to detect FGF12 and 4-HNE expression. Ferroptosis were detected by Prussian blue staining and western blot. The FGFR1/AMPK/NRF2 signaling was measured by western blot. FGF12 expression was downregulated in DOX-induced mice myocardium tissues. FGF12 overexpression alleviated DOX-induced myocardial tissue pathological injury and reduced Anp, Bnp, and Myh7 expression. Additionally, the levels of CK-MB, LDH and cTnT in serum were decreased after FGF12 upregulation in DOX-induced mice. Moreover, FGF12 overexpression reduced the levels of ROS, MDA, and 4-HNE but increased SOD and GSH-Px activities. Meanwhile, FGF12 led to less deposition of iron ion, decreased ACSL4, PTGS2 and increased GPX4, FTH1 expression. Additionally, FGF12 activated the expressions of FGFR1, p-AMPK, and NRF2. Moreover, FGFR1 silencing reversed the protective effects of FGF12 overexpression on cell viability, oxidative stress, ferroptosis, and FGFR1/AMPK/NRF2 pathway. To sum up, FGF12 inhibited mitochondria-dependent ferroptosis in cardiomyocytes induced by DOX through activation of FGFR1/AMPK/NRF2 signaling. These findings clarify a new mechanism of DOX-induced cardiac injury and provide a promising target to limit the disease development.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Critical role of FGF21 in diabetic kidney disease: from energy metabolism to innate immunity

Diabetic kidney disease (DKD) stands as the predominant cause of chronic kidney disease (CKD) on a global scale, with its incidence witnessing a consistent annual rise, thereby imposing a substantial burden on public health. The pathogenesis of DKD is primarily rooted in metabolic disorders and inflammation. Recent years have seen a surge in studies highlighting the regulatory impact of energy metabolism on innate immunity, forging a significant area of research interest. Within this context, fibroblast growth factor 21 (FGF21), recognized as an energy metabolism regulator, assumes a pivotal role. Beyond its role in maintaining glucose and lipid metabolism homeostasis, FGF21 exerts regulatory influence on innate immunity, concurrently inhibiting inflammation and fibrosis. Serving as a nexus between energy metabolism and innate immunity, FGF21 has evolved into a therapeutic target for diabetes, nonalcoholic steatohepatitis, and cardiovascular diseases. While the relationship between FGF21 and DKD has garnered increased attention in recent studies, a comprehensive exploration of this association has yet to be systematically addressed. This paper seeks to fill this gap by summarizing the mechanisms through which FGF21 operates in DKD, encompassing facets of energy metabolism and innate immunity. Additionally, we aim to assess the diagnostic and prognostic value of FGF21 in DKD and explore its potential role as a treatment modality for the condition.

Mitochondrial Stress and Mitokines: Therapeutic Perspectives for the Treatment of Metabolic Diseases

Mitochondrial stress and the dysregulated mitochondrial unfolded protein response (UPRmt) are linked to various diseases, including metabolic disorders, neurodegenerative diseases, and cancer. Mitokines, signaling molecules released by mitochondrial stress response and UPRmt, are crucial mediators of inter-organ communication and influence systemic metabolic and physiological processes. In this review, we provide a comprehensive overview of mitokines, including their regulation by exercise and lifestyle interventions and their implications for various diseases. The endocrine actions of mitokines related to mitochondrial stress and adaptations are highlighted, specifically the broad functions of fibroblast growth factor 21 and growth differentiation factor 15, as well as their specific actions in regulating inter-tissue communication and metabolic homeostasis. Finally, we discuss the potential of physiological and genetic interventions to reduce the hazards associated with dysregulated mitokine signaling and preserve an equilibrium in mitochondrial stress-induced responses. This review provides valuable insights into the mechanisms underlying mitochondrial regulation of health and disease by exploring mitokine interactions and their regulation, which will facilitate the development of targeted therapies and personalized interventions to improve health outcomes and quality of life.

Liraglutide attenuates type 2 diabetes mellitus-associated non-alcoholic fatty liver disease by activating AMPK/ACC signaling and inhibiting ferroptosis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is one of the most common complications of type 2 diabetes mellitus (T2DM). The pathogenesis of NAFLD involves multiple biological changes, including insulin resistance, oxidative stress, inflammation, as well as genetic and environmental factors. Liraglutide has been used to control blood sugar. But the impact of liraglutide on T2DM-associated NAFLD remains unclear. In this study, we investigated the impact and potential molecular mechanisms of inhibiting ferroptosis for liraglutide improves T2DM-associated NAFLD.

METHODS

Mice were fed on high-fat-diet and injected with streptozotocin to mimic T2DM-associated NAFLD and gene expression in liver was analysed by RNA-seq. The fast blood glucose was measured during the period of liraglutide and ferrostatin-1 administration. Hematoxylin and eosin staining was used to evaluate the pathological changes in the liver. The occurrence of hepatic ferroptosis was measured by lipid peroxidation in vivo. The mechanism of liraglutide inhibition ferroptosis was investigated by in vitro cell culture.

RESULTS

Liraglutide not only improved glucose metabolism, but also ameliorated tissue damage in the livers. Transcriptomic analysis indicated that liraglutide regulates lipid metabolism related signaling including AMPK and ACC. Furthermore, ferroptosis inhibitor rather than other cell death inhibitors rescued liver cell viability in the presence of high glucose. Mechanistically, liraglutide-induced activation of AMPK phosphorylated ACC, while AMPK inhibitor compound C blocked the liraglutide-mediated suppression of ferroptosis. Moreover, ferroptosis inhibitor restored liver function in T2DM mice in vivo.

CONCLUSIONS

These findings indicate that liraglutide ameliorates the T2DM-associated NAFLD, which possibly through the activation of AMPK/ACC pathway and inhibition of ferroptosis.

Fibroblast growth factor 21 and bone homeostasis

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

Lycopene attenuates oxidative stress-induced hepatic dysfunction of insulin signal transduction: involvement of FGF21 and mitochondria

Lycopene (LYC) has been regarded as a nutraceutical that has powerful antioxidant and hepatoprotective bioactivities. In the present study, we aimed to investigate the beneficial effects of LYC on hepatic insulin signal transduction under oxidative stress conditions and the possible involvement of FGF21 and mitochondria pathways. Two-month-old CD-1 mice were treated by intraperitoneal injection of D-galactose (D-gal) 150 mg/kg/day for 8 weeks and received 0.03% LYC (w/w, mixed into diet). The results showed that LYC increased the expression of FGF21, alleviated mitochondrial dysfunction and improved hepatic insulin signal transduction in D-gal-treated mice. Furthermore, knockdown of FGF21 by small interfering RNA notably suppressed mitochondrial function and blunted LYC-stimulated insulin signal transduction in H₂O₂-treated HepG2 cells. Moreover, suppressed mitochondrial function via oligomycin also inhibited insulin signal transduction, indicating that LYC supplementation ameliorated oxidative stress-induced hepatic dysfunction of insulin signal transduction by up-regulating FGF21 and enhancing mitochondrial function.

Respiratory Complex I dysfunction in cancer: from a maze of cellular adaptive responses to potential therapeutic strategies

Mitochondria act as key organelles in cellular bioenergetics and biosynthetic processes producing signals that regulate different molecular networks for proliferation and cell death. This ability is also preserved in pathologic contexts such as tumorigenesis, during which bioenergetic changes and metabolic reprogramming confer flexibility favoring cancer cell survival in a hostile microenvironment. Although different studies epitomize mitochondrial dysfunction as a protumorigenic hit, genetic ablation or pharmacological inhibition of respiratory complex I causing a severe impairment is associated with a low-proliferative phenotype. In this scenario, it must be considered that despite the initial delay in growth, cancer cells may become able to resume proliferation exploiting molecular mechanisms to overcome growth arrest. Here, we highlight the current knowledge on molecular responses activated by complex I-defective cancer cells to bypass physiological control systems and to re-adapt their fitness during microenvironment changes. Such adaptive mechanisms could reveal possible novel molecular players in synthetic lethality with complex I impairment, thus providing new synergistic strategies for mitochondrial-based anticancer therapy.

Second malignant neoplasms in lymphomas, secondary lymphomas and lymphomas in metabolic disorders/diseases

With inconsistent findings, evidence has been obtained in recent years that metabolic disorders are closely associated with the development of lymphomas. Studies and multiple analyses have been published also indicating that some solid tumor survivors develop a secondary lymphoma, whereas some lymphoma survivors subsequently develop a second malignant neoplasm (SMN), particularly solid tumors. An interaction between the multiple etiologic factors such as genetic factors and late effects of cancer therapy may play an important role contributing to the carcinogenesis in patients with metabolic diseases or with a primary cancer. In this review, we summarize the current knowledge of the multiple etiologic factors for lymphomagenesis, focusing on the SMN in lymphoma, secondary lymphomas in primary cancers, and the lymphomas associated to metabolic disorders/diseases, which have been received less attention previously. Further, we also review the data of coexistence of lymphomas and hepatocellular carcinoma (HCC) in patients with infection of hepatitis C virus and hepatitis B virus.

Suppression of obesity by melatonin through increasing energy expenditure and accelerating lipolysis in mice fed a high-fat diet

Backgrounds/objectives

Melatonin promotes brown adipose tissue (BAT) activity, leading to body mass reduction and energy expenditure. However, the mechanisms governing these beneficial effects are not well-established. This study aimed to assess the effects of (1) melatonin on BAT and energy metabolism, and (2) fibroblast growth factor 21 (FGF21) in BAT-mediated thermogenesis.

Methods

Male C57BL/6 J mice received a high-fat diet (HFD) or normal chow, accompanied by intraperitoneal injection of 20 mg/kg melatonin for 12 weeks. FGF21^−/− mice consumed an HFD with or without melatonin for 8 weeks.

Results

Melatonin attenuated weight gain, insulin resistance, adipocyte hypertrophy, inflammation, and hepatic steatosis induced by the HFD and increased energy expenditure. Furthermore, melatonin improved cold tolerance by increasing BAT uncoupling protein 1 (UCP1) expression and producing heat. Notably, melatonin resulted in a shift in energy metabolism favouring the utilization of fat, and it increased FGF21 in circulating and metabolic tissues and skeletal muscle phosphorylation of AMP-activated protein kinase. However, melatonin did not protect against obesity, insulin resistance, and energy expenditure in HFD-fed FGF21^−/− mice.

Conclusions

Melatonin suppressed obesity and insulin resistance resulting from the HFD by enhancing BAT activity and energy expenditure, and these effects were dependent on FGF21.

Regulatory network and interplay of hepatokines, stellakines, myokines and adipokines in nonalcoholic fatty liver diseases and nonalcoholic steatohepatitis

Fatty liver disease is a spectrum of liver pathologies ranging from simple hepatic steatosis to non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and culminating with the development of cirrhosis or hepatocellular carcinoma (HCC). The pathogenesis of NAFLD is complex and diverse, and there is a lack of effective treatment measures. In this review, we address hepatokines identified in the pathogenesis of NAFLD and NASH, including the signaling of FXR/RXR, PPARα/RXRα, adipogenesis, hepatic stellate cell activation/liver fibrosis, AMPK/NF-κB, and type 2 diabetes. We also highlight the interaction between hepatokines, and cytokines or peptides secreted from muscle (myokines), adipose tissue (adipokines), and hepatic stellate cells (stellakines) in response to certain nutritional and physical activity. Cytokines exert autocrine, paracrine, or endocrine effects on the pathogenesis of NAFLD and NASH. Characterizing signaling pathways and crosstalk amongst muscle, adipose tissue, hepatic stellate cells and other liver cells will enhance our understanding of interorgan communication and potentially serve to accelerate the development of treatments for NAFLD and NASH.

Adaptive and Pathological Outcomes of Radiation Stress-Induced Redox Signaling

Significance: Ionizing radiation can damage cells either directly or through oxidative damage caused by ionization. Although radiation exposure from natural sources is very limited, ionizing radiation in nuclear disaster zones and long spaceflights causes inconspicuous, yet measurable physiological effects in men and animals, whose significance remains poorly known. Understanding the physiological impacts of ionizing radiation has a wide importance due to the increased use of medical imaging and radiotherapy. Recent Advances: Radiation exposure has been traditionally investigated from the perspective of DNA damage and its consequences. However, recent studies from Chernobyl as well as spaceflights have provided interesting insights into oxidative stress-induced metabolic alterations and disturbances in the circadian regulation. Critical Issues: In this review, we discuss the physiological consequences of radiation exposure in the light of oxidative stress signaling. Radiation exposure likely triggers many converging or interconnecting signaling pathways, some of which mimic mitochondrial dysfunction and might explain the observed metabolic changes. Future Directions: Better understanding of the different radiation-induced signaling pathways might help to devise strategies for mitigation of the long-term effects of radiation exposure. The utility of fibroblast growth factor 21 (FGF21) as a radiation exposure biomarker and the use of radiation hormesis as a method to protect astronauts on a prolonged spaceflight, such as a mission to Mars, should be investigated. Antioxid. Redox Signal. 37, 336-348.

Lactational delivery of Triclosan promotes non-alcoholic fatty liver disease in newborn mice

Here we show that Triclosan (TCS), a high-volume antimicrobial additive that has been detected in human breastmilk, can be efficiently transferred by lactation to newborn mice, causing significant fatty liver (FL) during the suckling period. These findings are relevant since pediatric non-alcoholic fatty liver disease (NAFLD) is escalating in the United States, with a limited mechanistic understanding. Lactational delivery stimulated hepatosteatosis, triglyceride accumulation, endoplasmic reticulum (ER) stress, signs of inflammation, and liver fibrosis. De novo lipogenesis (DNL) induced by lactational TCS exposure is shown to be mediated in a PERK-eIF2α-ATF4-PPARα cascade. The administration of obeticholic acid (OCA), a potent FXR agonist, as well as activation of intestinal mucosal-regenerative gp130 signaling, led to reduced liver ATF4 expression, PPARα signaling, and DNL when neonates were exposed to TCS. It is yet to be investigated but mother to child transmission of TCS or similar toxicants may underlie the recent increases in pediatric NAFLD.

The Hypoglycemic Effect of JinQi Jiangtang Tablets Is Partially Dependent on the Palmatine-Induced Activation of the Fibroblast Growth Factor Receptor 1 Signaling Pathway

JinQi Jiangtang tablet (JQJTT) is a Chinese patent medicine that has been shown to be beneficial for patients with diabetes both preclinically and clinically; however, the molecular mechanism underlying the effects of JQJTT remains unclear. In this study, surface plasmon resonance fishing was employed to identify JQJTT constituent molecules that can specifically bind to fibroblast growth factor receptor 1 (FGFR1), leading to the retrieval of palmatine (PAL), a key active ingredient of JQJTT. In vivo and in vitro experiments demonstrated that PAL can significantly stimulate FGFR1 phosphorylation and upregulate glucose transporter type 1 (GLUT-1) expression, thereby facilitating glucose uptake in insulin resistance (IR) HepG2 cells as well as alleviating hyperglycemia in diabetic mice. Our results revealed that PAL functions as an FGFR1 activator and that the hypoglycemic effect of JQJTT is partially dependent on the PAL-induced activation of the FGFR1 pathway. In addition, this study contributed to the understanding the pharmacodynamic basis and mechanism of action of JQJTT and provided a novel concept for future research on PAL.

Octanoic Acid-Enrichment Diet Improves Endurance Capacity and Reprograms Mitochondrial Biogenesis in Skeletal Muscle of Mice

Background: Medium Chain Fatty Acids (MCFAs) are a dietary supplement that exhibit interesting properties, due to their smaller molecular size. The acute consumption of MCFAs is expected to enhance exercise performance. However, the short-term effects of MCFAs on endurance performance remains poorly understood. The aim of our study is to evaluate the octanoic acid (C8)-rich diet effect on endurance capacity, and to explore their molecular and cellular effects. Methods: C57BL/6J mice were fed with a chow diet (Control group) or an octanoic acid-rich diet (C8 diet) for 6 weeks. Spontaneous activity, submaximal and maximal exercise tests were carried out to characterize the exercise capacities of the mice. Beta-oxidation and mitochondrial biogenesis pathways were explored in skeletal muscle by RT-qPCR, Western Blot (Quadriceps) and histochemical staining (Gastrocnemius). Results: Mice fed with a C8-rich diet presented a higher spontaneous activity (p < 0.05) and endurance capacities (p < 0.05) than the control, but no effect on maximal effort was observed. They also presented changes in the skeletal muscle metabolic phenotype, with a higher number of the oxidative fibers, rich in mitochondria. At the molecular level, the C8-diet induced an AMPK activation (p < 0.05), associated with a significant increase in PGC1a and CS gene expression and protein levels. Conclusion: Our study provided evidence that C8-enrichment as a food supplementation improves endurance capacities and activates mitochondrial biogenesis pathways leading to higher skeletal muscle oxidative capacities.

Effects of carnosic acid on arsenic-induced liver injury in mice: A comparative transcriptomics analysis

BACKGROUND

Long-term chronic exposure to arsenic can cause different degrees of liver injury. Till date, its molecular mechanism has not meant fully elucidated. Evidence indicates that Carnosic acid (CA) has a protective role in arsenic-induced liver injury. This study aimed to reveal the potential targets and evaluate the potential effect of CA intervention at transcriptional level, and provide reference for the intervention of arsenic-induced liver injury.

METHODS

Arsenic-induced liver injury and CA intervention models were established in C57BL/6 mice. RNA sequencing technique was carried out to obtain the differentially expressed gene (DEG) profiles. The common covariant DEGs between arsenic induction and CA intervention was screened by comparative transcriptomic analysis methods. QRT-PCR was used to verify the covariant DEGs.

RESULTS

Transcriptome results showed that 220 DEGs were identified after arsenic induction. 267 DEGs were identified after CA intervention (|fold change| > 2.0 and adjusted P < 0.05). 42 covariant DEGs were discovered between the comparison of "AS vs Control" and "AS & CA vs AS". In addition, hub gene analysis revealed a total of 8 covariant DEGs (Ehhadh, Fgf21, Cyp2b10, Plin2, Aacs, Cyp7a1, Per2 and Mylip). The mRNA expressions of Fgf21 and Plin2 were significantly increased (P < 0.05) and the mRNA expressions of Cyp2b10, Cyp7a1, Per2 and Mylip were significantly decreased (P < 0.05) after arsenic induction. On the contrary, the changes of these DEGs were reversed after CA intervention.

CONCLUSION

The present study would be helpful to understand the potential health effects of arsenic-induced liver injury and identify new potential targets, and provide a reference for the intervention of CA.

FGF21 Reduces Lipid Accumulation in Bovine Hepatocytes by Enhancing Lipid Oxidation and Reducing Lipogenesis via AMPK Signaling

During the periparturient period, dairy cows suffer drastic metabolic stress because of plasma increased non-esterified fatty acids (NEFAs) that stem from a negative energy balance. Fibroblast growth factor 21 (FGF21) is a hepatokine that activates the AMP-activated protein kinase (AMPK) signaling pathway to maintain intracellular energy balance and tissue integrity via the promotion of catabolism and the inhibition of anabolic regulation. FGF21 treatment caused a 50% reduction in triglyceride (TG) content in liver in dairy cows. However, it is not clear whether FGF21 regulates lipid metabolism in bovine liver. The purpose of this study was to evaluate the influence of FGF21 on lipid metabolism via AMPK signaling in bovine hepatocytes. The hepatocytes isolated from calves were treated with different concentrations of FGF21 or co-treated with AMPK inhibitor (BML-275). Herein, the study showed that FGF21 significantly reduced TG content in a dose–response manner and promoted very-low-density lipoprotein (VLDL) secretion via an up-regulation of the proteins (ApoB 100, ApoE and MTTP) involved in VLDL secretion. Otherwise, the genes associated with lipid transport (LDLR and CD36) and lipid oxidation (PPARGC1A, ACOX1 and CPT1A), were up-regulated following FGF21 treatment. Moreover, FGF21 treatment inhibited lipogenesis via SREBF1, ACACA, FASN and ACLY inhibition. After being co-treated with the AMPK inhibitor, FGF21-induced changes were reversed in some genes. In conclusion, these results indicate that FGF21 adaptively regulates energy metabolism for a negative impact on lipogenesis, strengthens lipid oxidation, and inhibited lipid transportation via AMPK signaling in bovine hepatocytes. The present data suggest the possibility that FGF21 has potential value in alleviating perinatal metabolic diseases in dairy cows, and specific research in vivo should be studied in more detail.

Wheat oligopeptides enhance the intestinal mucosal barrier and alleviate inflammation via the TLR4/Myd88/MAPK signaling pathway in aged mice

Background

Aging can induce oxidative stress, inflammation and mucosal impairment, and few works have been conducted to investigate the protective effects of WP on the natural intestinal aging process.

Objective

The present work aimed to examine the protective effect of wheat oligopeptides (WP) on intestine mucosal impairment in aged mice, and investigate the potential antioxidation, anti-inflammatory effects of WP.

Design

Seventy-two aged mice (24 months old) were randomly divided into six groups, 12 for each group. Twelve young mice (6 months old) were regarded as the young control group. WP (25, 50, 100, 200, or 400 mg/kg) or distilled water were administered daily by gavage for 30 days.

Results

Histological observations showed that intestinal mucosal degeneration was attenuated by WP pretreatment. WP exhibited remarkable antioxidant activity via increasing superoxide dismutase, glutathione peroxidase, total antioxidant capacity and catalase activities, and decreasing the malondialdehyde levels in small intestine mucosa. WP pretreatment significantly suppressed intestinal mucosa inflammation through the reduction of TNF-α, TGF-β, IFN-γ IL-1β and IL-6. WP markedly protect the intestinal mucosal barrier by decreasing the ICAM-1 level, and increasing ZO-1 and JAMA-A levels. WP significantly down-regulated protein expression levels of TLR4, Myd88, and MAPK, suggesting that WP have a potential effect on inhibiting aging-induced inflammatory responses by blocking TLR4/Myd88/MAPK signal transduction.

Conclusion

WP administration effectively alleviated intestinal mucosal impairment in aged mice. The potential mechanism was associated with enhancement of antioxidation and anti-inflammatory action and protection of the intestinal mucosal barrier.

Circulating Fibroblast Growth Factor 21 and Total Testosterone in Type 2 Diabetes Mellitus Men With Coronary Heart Disease

BACKGROUND

Fibroblast growth factor 21 increased in population with type 2 diabetes mellitus (T2DM), while serum total testosterone often decreased in men with T2DM. This study aimed to investigate the relationship between the prevalence of coronary artery disease (CAD) and circulating FGF21 concentrations and serum testosterone in T2DM men.

METHODS

490 men with T2DM from January 2021 to December 2021 were recruited from the Renmin Hospital of Wuhan University, and they were divided into CAD group (n=248) and control group (n=242). FGF21 were determined based on ELISA principle and serum total testosterone was measured in a liquid chromatography mass spectrometer LC/MS-8050 (Shimadzu, Japan). Logistic and restricted cubic spline analyses were performed to examine the association between the prevalence of CAD and circulating FGF21 concentrations and serum testosterone in T2DM men. The receiver operating curve (ROC) analysis was used to explore the predictive performance.

RESULTS

Circulating FGF21 levels were higher in T2DM men with CAD compared with those without CAD [214.63 (121.82, 348.64) pg/ml vs 166.55 (94.81,254.48) pg/ml, p<0.001], while serum total testosterone was lower [3.08 ± 0.07 ng/ml vs 3.76 ± 0.09 ng/ml, p<0.001]. The fully adjusted odds ratio (OR) and 95% confidence intervals (95%CI) was 2.956(1.409,6.201) for those in quartile 4 of FGF21 versus quartile 1 and the fully adjusted OR (95%CI) was 0.346(0.174,0.686) for those in quartile 4 of testosterone versus quartile 1. The receiver operating curve (ROC) analysis showed that the area under the curve (AUC) of combination of FGF21 and testosterone for predicting the occurrence of CAD in men with T2DM was 0.702 (95% CI: 0.667-0.741).

CONCLUSION

Circulating FGF21 levels were positively associated with CAD in men with T2DM, whereas serum total testosterone levels showed an inverse correlation with CAD in diabetic men.

Comprehensive analysis of mRNAs, lncRNAs and circRNAs in the early phase of microglial activation

Sepsis-associated encephalopathy (SAE) is a common complication of sepsis that may seriously affect the prognosis and quality of life of patients with sepsis. Microglial activation is vital to the neuroinflammation and the pathology of SAE. In the present study, in vitro cultured BV-2 microglial cells stimulated with lipopolysaccharide (LPS) were employed as a model of microglia activation. The altered profiles of long noncoding (lnc)RNAs, circular (circ)RNAs and mRNAs in BV-2 cells after 4 h of LPS exposure were arrayed by using the Agilent competing endogenous (ce)RNA Microarray Chip. Using fold change >2 and P<0.05 as the cutoff criteria, 1,135 mRNAs and 2,488 lncRNAs were determined to be upregulated and 630 mRNAs and 744 lncRNAs to be downregulated. The number of differentially expressed circRNAs was lower, with 140 upregulated and 123 downregulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of DE mRNAs suggested that inflammatory responses, as well as lipid metabolism, were involved in microglial activation. Furthermore, analyses of ceRNA networks of the lncRNA-miRNA-mRNA or circRNA-miRNA-mRNA interrelations were performed. The present study revealed a multitude of novel candidate mRNAs, lncRNAs and circRNAs involved in microglial activation, which may improve the current knowledge on neuroinflammation and provide potential therapeutic targets for SAE.

Fibroblast growth factor 21 attenuates iron overload-induced liver injury and fibrosis by inhibiting ferroptosis

Ferroptosis plays a role in several diseases such as iron overload-induced liver diseases. Manipulation of ferroptosis has been explored as a potential therapeutic strategy to treat related diseases. Numerous antioxidants have been identified to control ferroptosis but the cell-autonomous mechanisms responsible for regulating ferroptosis remain elusive. In the present study, we found that iron overload promoted ferroptosis in hepatocytes by excessively inducing HO-1 expression, which contributed to the progression of liver injury and fibrosis, accompanied by the upregulation of the FGF21 protein level in vitro and in vivo. Interestingly, both recombinant FGF21 and Fgf21 overexpression significantly protected against iron overload-induced hepatocytes mitochondria damage, liver injury and fibrosis by inhibiting ferroptosis. In contrast, the loss of FGF21 aggravated iron overload-induced ferroptosis. Notably, FGF21-induced HO-1 inhibition (via the promotion of HO-1 ubiquitination and degradation) and NRF2 activation provide a mechanistic explanation for this phenomenon. Taken together, we identified FGF21 as a novel ferroptosis suppressor. Thus, FGF21 activation may provide an effective strategy for the potential treatment of iron overload-induced ferroptosis-related diseases, such as hereditary haemochromatosis (HH).

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Iron overload robustly induces hepatic FGF21 expression both in vitro and in vivo.

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FGF21 suppresses iron overload-induced hepatocytes ferroptosis.

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Constitutive HO-1 activation contributes to iron overload-induced ferroptosis in hepatocytes.

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FGF21 protects hepatocytes from iron overload-induced ferroptosis by stimulating HO-1 ubiquitination and degradation.

Myokine secretion following moderate-intensity endurance exercise under different environmental temperatures

PURPOSE

In the present study, the effects of endurance exercise under different environmental temperatures on myokine responses were elucidated.

METHODS

Seven healthy males (age: 22.7 ± 0.4 years, height: 173.7 ± 2.7 cm, body weight: 65.2 ± 2.8 kg) performed pedaling at 60% of their maximal oxygen consumption for 60 min under three different environmental temperature conditions, cold (without shivering; 15-19 °C), moderate (24 °C), and hot (34 °C), in a counterbalanced fashion. Exercise intensity (60% maximal oxygen consumption evaluated under each condition) was relatively matched among the conditions. Venous blood samples were collected before, during, immediately after, and at 1, 2, and 3 h after exercise.

RESULTS

Exercise-induced changes in plasma irisin, interleukin-6, insulin or insulin-like growth factor-1 concentrations did not differ significantly among the conditions (P > 0.05). In hot condition, exercise-induced elevation of plasma fibroblast growth factor-21 (FGF21) concentration was significantly enhanced compared with the cold condition, and the myostatin concentration was lowered compared with the moderate condition (P < 0.05). Furthermore, the area under the curve for the myostatin concentration over an exercise session (including during and after exercise) was significantly lower in the hot than moderate condition (P < 0.05). Notably, a positive correlation between the peak plasma FGF21 and myostatin concentrations was observed at the moderate environment, but not at the cold or hot condition (P < 0.05).

CONCLUSION

Irisin and FGF21 concentrations induced by moderate-intensity endurance exercise were not enhanced under the cold environmental temperature without shivering. In contrast, exercise in the hot environmental temperature changed favorably FGF21 and myostatin concentrations compared with thermoneutral environment.

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.

Nuciferine Inhibited the Differentiation and Lipid Accumulation of 3T3-L1 Preadipocytes by Regulating the Expression of Lipogenic Genes and Adipokines

Purposes: Nuciferine, a main aporphine alkaloid component found in lotus leaf (Nelumbo nucifera), has been demonstrated to possess the property of reducing fat mass and alleviating dyslipidemia in vivo. The purpose of this study is to explore the effects of nuciferine on the proliferation and differentiation of 3T3-L1 cells and further investigate the possible underlying molecular mechanisms.

Methods: 3T3-L1 preadipocytes were treated with 0∼20 μM nuciferine for 24∼120 h, the cell viability was assessed using CCK8. 3T3-L1 preadipocytes and human primary preadipocytes were then induced differentiation and the effects of nuciferine on the lipid metabolism in differentiating and fully differentiated adipocytes were observed by the methods of intracellular triglyceride (TG) assay, Oil Red O staining, RT-qPCR and western blot. Transient transfection and dual luciferase reporter gene methods were used to assess the effects of nuciferine on FAS promoter activities.

Results: Nuciferine inhibited the proliferation of 3T3-L1 preadipocytes in a dose- and time-dependent manner. 20 μM nuciferine significantly attenuated lipid accumulation and reduced intracellular TG contents by 47.2, 59.9 and 55.4% on the third, sixth and ninth day of preadipocytes differentiation, respectively (all p < 0.05). Moreover, the mRNA levels of PPARγ, C/EBPα, C/EBPβ, FAS, ACC, HSL and ATGL were notably decreased by 39.2∼92.5% in differentiating preadipocytes when treated with 5∼20 μM nuciferine (all p < 0.05). In fully differentiated adipocytes treated with 20 μM nuciferine for 48 h, the mRNA levels of FAS, ACC and SREBP1 were remarkably downregulated by 22.6∼45.2% compared with the controls (0 μM) (all p < 0.05), whereas the expression of adipokines FGF21 and ZAG were notably promoted by nuciferine. Similarly, in fully differentiated human primary adipocytes, the mRNA levels of FAS, ACC, SREBP1 were decreased and the expression of FGF21 and ZAG were elevated after treated with nuciferine (all p < 0.05). Further mechanism studies showed that 2.5∼20 μM nuciferine significantly decreased FAS promoter activities in 3T3-L1 preadipocytes.

Conclusion: Nuciferine inhibited the proliferation and differentiation of 3T3-L1 preadipocytes. The inhibitory effects of nuciferine on adipogenesis might be due to the downregulation of PPARγ, C/EBPα and C/EBPβ, which led to the reduction of intracellular lipid accumulation in 3T3-L1 cells and by downregulating the expression of critical lipogenic enzymes, especially of FAS, which was achieved by inhibiting the FAS promoter activities. Besides, nuciferine promoted the expression of adipokines in fully differentiated adipocytes.

Key Signaling Pathways in Aging and Potential Interventions for Healthy Aging

Aging is a fundamental biological process accompanied by a general decline in tissue function. Indeed, as the lifespan increases, age-related dysfunction, such as cognitive impairment or dementia, will become a growing public health issue. Aging is also a great risk factor for many age-related diseases. Nowadays, people want not only to live longer but also healthier. Therefore, there is a critical need in understanding the underlying cellular and molecular mechanisms regulating aging that will allow us to modify the aging process for healthy aging and alleviate age-related disease. Here, we reviewed the recent breakthroughs in the mechanistic understanding of biological aging, focusing on the adenosine monophosphate-activated kinase (AMPK), Sirtuin 1 (SIRT1) and mammalian target of rapamycin (mTOR) pathways, which are currently considered critical for aging. We also discussed how these proteins and pathways may potentially interact with each other to regulate aging. We further described how the knowledge of these pathways may lead to new interventions for antiaging and against age-related disease.

Methionine restriction alleviates age-associated cognitive decline via fibroblast growth factor 21

Methionine restriction (MR) extends lifespan and delays the onset of aging-associated pathologies. However, the effect of MR on age-related cognitive decline remains unclear. Here, we find that a 3-month MR ameliorates working memory, short-term memory, and spatial memory in 15-month-old and 18-month-old mice by preserving synaptic ultrastructure, increasing mitochondrial biogenesis, and reducing the brain MDA level in aged mice hippocampi. Transcriptome data suggest that the receptor of fibroblast growth factor 21 (FGF21)-related gene expressions were altered in the hippocampi of MR-treated aged mice. MR increased FGF21 expression in serum, liver, and brain. Integrative modelling reveals strong correlations among behavioral performance, MR altered nervous structure-related genes, and circulating FGF21 levels. Recombinant FGF21 treatment balanced the cellular redox status, prevented mitochondrial structure damages, and upregulated antioxidant enzymes HO-1 and NQO1 expression by transcriptional activation of Nrf2 in SH-SY5Y cells. Moreover, knockdown of Fgf21 by i.v. injection of adeno-associated virus abolished the neuroprotective effects of MR in aged mice. In conclusion, the MR exhibited the protective effects against age-related behavioral disorders, which could be partly explained by activating circulating FGF21 and promoting mitochondrial biogenesis, and consequently suppressing the neuroinflammation and oxidative damages. These results demonstrate that FGF21 can be used as a potential nutritional factor in dietary restriction-based strategies for improving cognition associated with neurodegeneration disorders.

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MR suppresses age-associated cognitive impairment.

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MR improves synapse ultrastructure and mitochondrial biogenesis in the hippocampus.

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FGF21 is required for the beneficial effects of MR.

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FGF21 activates Nrf2 signaling and alleviates neuroinflammation and oxidative stress.

Skeletal Muscle and Bone - Emerging Targets of Fibroblast Growth Factor-21

Fibroblast growth factor 21 (FGF21) is an atypical member of the FGF family, which functions as a powerful endocrine and paracrine regulator of glucose and lipid metabolism. In addition to liver and adipose tissue, recent studies have shown that FGF21 can also be produced in skeletal muscle. As the most abundant tissue in the human body, skeletal muscle has become increasingly recognized as a major site of metabolic activity and an important modulator of systemic metabolic homeostasis. The function and mechanism of action of muscle-derived FGF21 have recently gained attention due to the findings of considerably increased expression and secretion of FGF21 from skeletal muscle under certain pathological conditions. Recent reports regarding the ectopic expression of FGF21 from skeletal muscle and its potential effects on the musculoskeletal system unfolds a new chapter in the story of FGF21. In this review, we summarize the current knowledge base of muscle-derived FGF21 and the possible functions of FGF21 on homeostasis of the musculoskeletal system with a focus on skeletal muscle and bone.

Adipokines and Metabolic Regulators in Human and Experimental Pulmonary Arterial Hypertension

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

Aging and age-related diseases: from mechanisms to therapeutic strategies

Aging is a physiological process mediated by numerous biological and genetic pathways, which are directly linked to lifespan and are a driving force for all age-related diseases. Human life expectancy has greatly increased in the past few decades, but this has not been accompanied by a similar increase in their healthspan. At present, research on aging biology has focused on elucidating the biochemical and genetic pathways that contribute to aging over time. Several aging mechanisms have been identified, primarily including genomic instability, telomere shortening, and cellular senescence. Aging is a driving factor of various age-related diseases, including neurodegenerative diseases, cardiovascular diseases, cancer, immune system disorders, and musculoskeletal disorders. Efforts to find drugs that improve the healthspan by targeting the pathogenesis of aging have now become a hot topic in this field. In the present review, the status of aging research and the development of potential drugs for aging-related diseases, such as metformin, rapamycin, resveratrol, senolytics, as well as caloric restriction, are summarized. The feasibility, side effects, and future potential of these treatments are also discussed, which will provide a basis to develop novel anti-aging therapeutics for improving the healthspan and preventing aging-related diseases.

Advances in Biological Functions and Clinical Studies of FGF21

Fibroblast growth factor 21 (FGF21) regulates many crucial biological processes in human and mammals, particularly metabolic modulation and protective effect after injury. Therefore, determining complex regulatory mechanisms and elucidating the signaling pathway may greatly promote the prevention, diagnosis, and treatment of related injury and metabolic diseases. This review focused on the metabolic modulation and protective effect of FGF21 and summarized the molecular mechanisms and clinical research developments.

Dysregulated Autophagy Mediates Sarcopenic Obesity and Its Complications via AMPK and PGC1α Signaling Pathways: Potential Involvement of Gut Dysbiosis as a Pathological Link

Sarcopenic obesity (SOB), which is closely related to being elderly as a feature of aging, is recently gaining attention because it is associated with many other age-related diseases that present as altered intercellular communication, dysregulated nutrient sensing, and mitochondrial dysfunction. Along with insulin resistance and inflammation as the core pathogenesis of SOB, autophagy has recently gained attention as a significant mechanism of muscle aging in SOB. Known as important cellular metabolic regulators, the AMP-activated protein kinase (AMPK) and the peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) signaling pathways play an important role in autophagy, inflammation, and insulin resistance, as well as mutual communication between skeletal muscle, adipose tissue, and the liver. Furthermore, AMPK and PGC-1α signaling pathways are implicated in the gut microbiome-muscle axis. In this review, we describe the pathological link between SOB and its associated complications such as metabolic, cardiovascular, and liver disease, falls and fractures, osteoarthritis, pulmonary disease, and mental health via dysregulated autophagy controlled by AMPK and/or PGC-1α signaling pathways. Here, we propose potential treatments for SOB by modulating autophagy activity and gut dysbiosis based on plausible pathological links.

Exercise and dietary intervention ameliorate high-fat diet-induced NAFLD and liver aging by inducing lipophagy

Exercise and dietary intervention are currently available strategies to treat nonalcoholic fatty liver disease (NAFLD), while the underlying mechanism remains controversial. Emerging evidence shows that lipophagy is involved in the inhibition of the lipid droplets accumulation. However, it is still unclear if exercise and dietary intervention improve NAFLD through regulating lipophagy, and how exercise of skeletal muscle can modulate lipid metabolism in liver. Moreover, NAFLD is associated with aging, and little is known about the effect of lipid accumulation on aging process. Here in vivo and in vitro models, we found that exercise and dietary intervention reduced lipid droplets formation, decreased hepatic triglyceride in the liver induced by high-fat diet. Exercise and dietary intervention enhanced the lipophagy by activating AMPK/ULK1 and inhibiting Akt/mTOR/ULK1 pathways respectively. Furthermore, exercise stimulated FGF21 production in the muscle, followed by secretion to the circulation to promote the lipophagy in the liver via an AMPK-dependent pathway. Importantly, for the first time, we demonstrated that lipid accumulation exacerbated liver aging, which was ameliorated by exercise and dietary intervention through inducing lipophagy. Our findings suggested a new mechanism of exercise and dietary intervention to improve NAFLD through promoting lipophagy. The study also provided evidence to support that muscle exercise is beneficial to other metabolic organs such as liver. The FGF21-mediated AMPK dependent lipophagy might be a potential drug target for NAFLD and aging caused by lipid metabolic dysfunction.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

Resistance training attenuates circulating FGF-21 and myostatin and improves insulin resistance in elderly men with and without type 2 diabetes mellitus: A randomised controlled clinical trial

Fibroblast growth factor 21 (FGF-21) and myostatin have been proposed to be potential therapeutic target for insulin resistance in age-related metabolic disorders including type 2 diabetes (T2D). Moreover, despite the potential metabolic effect of resistance training on insulin resistance, aging, and T2D; the effect of this type of exercise training on FGF-21 and myostatin in elderly men with and without T2D are unknown. Forty-four elderly men were assigned to either the RT training (RT; without T2D: 12, with TD2 = 10) or the control group (C; without T2D: 12, with TD2 = 10). The RT group performed 12-wk resistance training intervention, 3 days/wk, 10 repetitions with 70% 1RM. At the baseline, the elderly men with T2D had a higher FGF-21 (p = 0.002) and myostatin (p = 0.02) concentrations and lower muscle strength (p = 0.01) than the elderly men without T2D. RT resulted in significant decrease in FGF-21 and myostatin concentration and increase in muscle strength in both elderly men with and without T2D (P = 0.001, for all) as well as decrease in HOMA-IR in only elderly men without T2D (P = 0.001). There was no significant difference in the RT-induced FGF-21 reduction between elderly men with and without T2D (p = 0.77, p = 0.28, respectively), but, RT caused a larger reduction in circulating myostatin in elderly men without T2D than with T2D (P = 0.007). Taken together, our results demonstrated that 12 weeks of RT induced an overall significant reduction of FGF-21 and myostatin in elderly men with and without T2D; with higher reduction of myostatin in elderly men without T2D.

Dipeptidyl peptidase-4 inhibition improves endothelial senescence by activating AMPK/SIRT1/Nrf2 signaling pathway

Dipeptidyl peptidase-4 (DPP4) is elevated in numerous cardiovascular pathological processes and DPP4 inhibition is associated with reduced inflammation and oxidative stress. The aim of this study was to examine the role of DPP4 in endothelial senescence. Sprague-Dawley rats (24 months) were orally administrated saxagliptin (10 mg·kg^-1·d^-1), a DPP4 inhibitor, for 12 weeks in drinking water. Body weight, heart rate, blood glucose, and blood pressure were measured and vascular histological experiments were performed. In vitro studies were performed using H₂O₂-induced senescent human umbilical vein endothelial cells. Both in vivo and in vitro studies confirmed the elevation of DPP4 in senescent vascular endothelium, and inhibition or knockdown of DPP4 ameliorated endothelial senescence. In addition, DPP4 inhibition or silencing reduced endothelial oxidative stress levels in aging vasculature and senescent endothelial cells. Moreover, DPP4 inhibition or knockdown normalized the expression and phosphorylation of AMP-activated protein kinase-α (AMPKα) and sirtuin 1 (SIRT1) expression. Furthermore, the beneficial effects of DPP4 inhibition or knockdown on endothelial cell senescence were at least partly dependent on SIRT1 and Nrf2 activation. In conclusion, our study demonstrated that DPP4 inhibition or silencing ameliorated endothelial senescence both in vivo and in vitro by regulating AMPK/SIRT1/Nrf2. DPP4 may be a new therapeutic target to combat endothelial senescence.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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