FGF21 as Modulator of Metabolism in Health and Disease

FGF21 affects the glycolysis process via mTOR-HIF1α axis in hepatocellular carcinoma

BACKGROUND

Metabolic reprogramming, particularly glycolysis, is essential in processes like cancer and immune response. While FGF21's role in hepatocyte glucose metabolism has been linked to glucose transporters and its impact on aerobic glycolysis and cellular growth in HCC remain unclear. In this study, we investigated FGF21-mediated modulation of glucose metabolism in HCC through mTOR and HIF1α axis in HCC.

METHODS

The study evaluated the dysregulation of FGF21 and its prognostic impact in HCC using various datasets. The literature review was done to identify glycolysis related genes to find significant interaction with FGF21 using stringdb and their correlation in datasets. The regulation of FGF21 was validated in HepG2 cell lines by transfecting FGF21 and measuring its effects on glycolysis, including glucose uptake, lactate levels, and key glycolytic enzymes using rt-PCR. Additionally, the effect of FGF21 transfection on mTOR and HIF1α was also evaluated using rt-PCR.

RESULTS

The insilico analysis indicates that the FGF21-mTOR-HIF1α signaling axis regulates glucose metabolism, with mTOR as a central integrator of signals from FGF21 and HIF1α. Invitro experiments showed that silencing FGF21 expression via siRNA reduced glycolytic enzyme expression, glucose uptake, lactate levels, and cell proliferation in HepG2 cells. Conversely, recombinant FGF21 treatment has a reverse effect in HepG2 cells. Additionally, FGF21 treatment also affected mTOR and HIF1α expression, highlighting its role in metabolic regulation and disease through the mTOR-HIF1α axis.

CONCLUSION

The regulation of FGF21 influences glycolysis via the mTOR-HIF1α axis, highlighting its critical role in glucose metabolism and metabolic adaptation in response to energy availability.

Hepatic lipogenesis marked by GCKR-modulated triglycerides increases serum FGF21 in children/teens with obesity

AIMS

Fibroblast growth factor 21 (FGF21) decreases hepatic lipogenesis in animal models, and FGF21 analogues decrease serum triglycerides (TG) in adults in phase-2 trials. On the other hand, serum FGF21 is associated with higher TG in observational studies of people with obesity, raising a sort of paradox. We tested the hypothesis that FGF21 is induced by TG in youth with obesity, as a compensatory mechanism.

MATERIALS AND METHODS

We recruited 159 children/adolescents with obesity (80 males, 12.7 ± 2.1 years). Besides serum FGF21 and lipid dosages, we genotyped the Pro446Leu variant at glucokinase regulator (GCKR) as a known marker of genetically increased hepatic de novo lipogenesis, and we used it as an instrumental variable to establish a cause-and-effect relationship between FGF21 and TG, according to a Mendelian randomization analysis.

RESULTS

The Pro446Leu variant increased circulating TG (β = +0.35, p < 0.001), which was positively associated with circulating FGF21 (β = +0.42, p < 0.001). The Pro446Leu variant increased FGF-21 (β = +0.14, p = 0.031) with the expected slope (β-coefficient) in case of association entirely mediated by TG: 0.35 (slope between Pro446Ala and TG) × 0.42 (slope between TG and FGF21) = 0.14.

CONCLUSIONS

Hepatic lipogenesis, marked by GCKR-modulated triglycerides, is significantly associated with increased serum FGF-21 in children/adolescents with obesity.

Human milk feeding practices and serum immune profiles of one-year-old infants in the CHILD birth cohort study

BACKGROUND

Breastfeeding and human milk consumption are associated with immune system development; however, the underlying mechanisms and the impact of different infant feeding practices are unclear.

OBJECTIVES

This study aimed to investigate how current human milk feeding (HMF) status is related to infant immune biomarker profiles, as well as explore relationships with HMF history (i.e., duration, exclusivity, and method: directly from the breast or pumped and bottled).

METHODS

This observational birth cohort study involved 605 infants from the Canadian CHILD Cohort Study. Infant feeding was captured from hospital birth records and parent questionnaires. Ninety-two biomarkers reflecting immune system activity and development were measured in serum collected at 1 y (12.6 ± 1.4 mo) using the Olink Target 96 Inflammation panel. Associations were determined using multivariable regression (adjusted for sex, time until blood sample centrifugation, and study site).

RESULTS

Nearly half (42.6%) of infants were still receiving HMF at the time of blood sampling. Compared with non-HMF infants, HMF infants had higher levels of serum fibroblast growth factor 21 (FGF-21, adjusted standardized β coefficient: 0.56; 95% CI: 0.41, 0.72), cluster of differentiation 244 (CD244, β: 0.35; 95% CI: 0.19, 0.50), chemokine ligand 6 (CXCL6, β: 0.34; 95% CI: 0.18, 0.50), and chemokine ligand 20 (CCL20, β: 0.26; 95% CI: 0.09, 0.42) and lower extracellular newly identified receptor for advanced glycation end-products binding protein (EN-RAGE, β: -0.16; 95% CI: -0.29, -0.03). Among non-HMF infants, serum interleukin 7 (IL-7) had a marginally positive association with past HMF duration (β: 0.05; 95% CI: 0.02, 0.08) that persisted for ≤5 mo post-HMF cessation. Exclusive HMF duration and HMF method (at 3 mo of age) were not associated with any biomarkers.

CONCLUSIONS

Current HMF status and (to a lesser extent) HMF history are associated with several inflammation-associated biomarkers in 1-y-old infants. These results provide new evidence that HMF impacts immune activity and development and suggest hypotheses about the underlying mechanisms. They also highlight the importance of including current HMF status in immune system-focused infant serum proteomic studies.

Sexual dimorphism on the acute effect of exercise in the morning vs. evening: A randomized crossover study

BACKGROUND

Mammalian cells possess molecular clocks, the adequate functioning of which is decisive for metabolic health. Exercise is known to modulate these clocks, potentially having distinct effects on metabolism depending on the time of day. This study aimed to investigate the impact of morning vs. evening moderate-intensity aerobic exercise on glucose regulation and energy metabolism in healthy men and women. It also aimed to elucidate molecular mechanisms within skeletal muscle.

METHODS

Using a randomized crossover design, healthy men (n = 18) and women (n = 17) performed a 60-min bout of moderate-intensity aerobic exercise in the morning and evening. Glucose regulation was continuously monitored starting 24 h prior to the exercise day and continuing until 48 h post-exercise for each experimental condition. Energy expenditure and substrate oxidation were measured by indirect calorimetry during exercise and at rest before and after exercise for 30 min. Skeletal muscle biopsies were collected immediately before and after exercise to assess mitochondrial function, transcriptome, and mitochondrial proteome.

RESULTS

Results indicated similar systemic glucose, energy expenditure, and substrate oxidation during and after exercise in both sexes. Notably, transcriptional analysis, mitochondrial function, and mitochondrial proteomics revealed marked sexual dimorphism and time of day variations.

CONCLUSION

The sexual dimorphism and time of day variations observed in the skeletal muscle in response to exercise may translate into observable systemic effects with higher exercise-intensity or chronic exercise interventions. This study provides a foundational molecular framework for precise exercise prescription in the clinical setting.

Pharmacological PTP1B inhibition rescues motor learning, neuroinflammation, and hyperglycaemia in a mouse model of Alzheimer's disease

BACKGROUND

Patients with Alzheimer's Disease (AD) frequently suffer from comorbidities such as type 2 diabetes mellitus (T2DM), accompanied by shared common pathologies such as increased inflammation and impaired glucose homeostasis. Beta-secretase 1 (BACE1), the rate limiting enzyme in AD associated beta-amyloid (Aβ) production, is also implicated in metabolic dysfunction and can increase central and peripheral protein levels of protein tyrosine phosphatase 1B (PTP1B). PTP1B is a validated target in diabetes and obesity, and is a neuroinflammatory regulator involved in degenerative processes. This study investigated the effects of the PTP1B inhibitor, trodusquemine (MSI-1436) on the cognitive and metabolic phenotypes of the neuronal human BACE1 knock-in (PLB4) mouse, a co-morbidity model of AD and T2DM, and their wild-type (PLBWT) controls.

METHODS

Five-month-old male PLB4 and PLBWT mice received PTP1B inhibitor treatment (1 mg/kg intraperitoneal injection; 5 weeks). Activity and spatial habituation (Phenotyper), motor learning (RotaRod), glucose tolerance, and brain and liver molecular analyses were analysed following treatment.

RESULTS

Inhibition of PTP1B improved motor learning alongside glucose tolerance in PLB4 mice, without affecting body weight/adiposity. MSI-1436 treatment led to lower protein levels of amyloid precursor protein (APP), reduced astrogliosis and restoration of the endoplasmic chaperone immunoglobulin heavy chain binding protein (BIP) in the brain, alongside decreased insulin receptor substrate-1 (IRS1) and dipeptidyl peptidase-4 (DPP4) proteins in the liver.

CONCLUSION

We provide evidence that neuronal BACE1 contributes to neuroinflammation and hyperglycaemia in PLB4 mice, and this can be partially rescued by PTP1B inhibition. Targeting PTP1B may therefore offer an attractive therapeutic approach to ameliorate co-morbidity associated pathologies in AD and T2DM.

Thermogenic adipose tissues: Promising therapeutic targets for metabolic diseases

The ongoing increase in the prevalence of obesity and its comorbidities such as cardiovascular disease, type 2 diabetes (T2D) and dyslipidemia warrants discovery of novel therapeutic options for these metabolic diseases. Obesity is characterized by white adipose tissue expansion due to chronic positive energy balance as a result of excessive energy intake and/or reduced energy expenditure. Despite various efforts to prevent or reduce obesity including lifestyle and behavioral interventions, surgical weight reduction approaches and pharmacological methods, there has been limited success in significantly reducing obesity prevalence. Recent research has shown that thermogenic adipocyte (brown and beige) activation or formation, respectively, could potentially act as a therapeutic strategy to ameliorate obesity and its related disorders. This can be achieved through the ability of these thermogenic cells to enhance energy expenditure and regulate circulating levels of glucose and lipids. Thus, unraveling the molecular mechanisms behind the formation and activation of brown and beige adipocytes holds the potential for probable therapeutic paths to combat obesity. In this review, we provide a comprehensive update on the development and regulation of different adipose tissue types. We also emphasize recent interventions in harnessing therapeutic potential of thermogenic adipocytes by bioactive compounds and new pharmacological anti-obesity agents.

Maternal organokines throughout pregnancy as predictors of neonatal anthropometric characteristics and adiposity

Aims

To evaluate the relation between maternal concentrations of progranulin (PGRN), adipocyte fatty acid-binding protein (AFABP), brain-derived neurotrophic factor (BDNF), and fibroblast growth factor 21 (FGF21) throughout pregnancy with neonatal weight and length at birth and at one month of age, as well as with the percentage of fat mass at one month of age. Besides, we evaluated the association between maternal organokine concentrations with pregestational nutritional status and gestational weight gain (GWG).

Methods

Longitudinal study of 100 healthy pregnant women and their neonates. Conventional biochemical tests were performed and maternal organokine concentrations were measured by ELISA. Neonatal percent fat mass was determined using the PEA POD system, and weight and length were measured using a soft tape measure and a baby scale. Multiple linear regression models were made to predict neonatal anthropometric measurements and adiposity.

Results

In all women, PGRN concentrations significantly increased as pregnancy progressed, while AFABP concentrations increased until the third trimester and the highest BDNF concentrations were observed in the second trimester of pregnancy. In contrast, FGF21 concentrations did not change during pregnancy. Only maternal obesity was associated with some differences in AFABP and FGF21 concentrations. Gestational age at birth, maternal age and third-trimester PGRN concentrations predicted weight (gestational age at birth: β=0.11; maternal age: β=-0.033; PGRN: β=0.003, p<0.001) and, together with first-trimester BDNF concentrations, length (gestational age at birth: β=0.76; maternal age: β=-0.21; PGRN: β=0.24; BDNF: β=0.06, p<0.001) at birth. Maternal age and third-trimester BDNF concentrations predicted one-month-old neonate length (maternal age: β=-1.03; BDNF: β=0.45, p<0.001). Pregestational body mass index (pBMI), GWG, second-trimester FGF21 concentrations, and third-trimester AFABP concentrations predicted neonatal fat mass percentage (pBMI: β=-0.58; GWG: β=-0.32; FGF21: β=-0.004; AFABP: β=-1.27, p<0.001) at one month of age.

Conclusion

Maternal PGRN, AFABP, and BDNF concentrations, but not FGF21, vary throughout pregnancy. These organokines and maternal characteristics can be useful in the prediction of neonatal weight, length, and percentage fat mass.

Mesenchymal Stem Cells Overexpressing FGF21 Preserve Blood-Brain Barrier Integrity in Experimental Ischemic Stroke

Blood-brain barrier (BBB) disruption is a prominent pathophysiological mechanism in stroke. Transplantation of mesenchymal stem cells (MSCs) preserves BBB integrity following ischemic stroke. Fibroblast growth factor 21 (FGF21) has been shown to be a potent neuroprotective agent that reduces neuroinflammation and protects against BBB leakage. In this study, we assessed the effects of transplantation of MSCs overexpressing FGF21 (MSCs-FGF21) on ischemia-induced neurological deficits and BBB breakdown. MSCs-FGF21 was injected into the rat brain via the intracerebroventricular route 24 h after middle cerebral artery occlusion (MCAO) surgery. The behavioral performance was assessed using modified neurological severity scores and Y-maze tests. BBB disruption was measured using Evans blue staining, IgG extravasation, and brain water content. The levels of tight junction proteins, aquaporin 4, and neuroinflammatory markers were analyzed by western blotting and immunohistochemistry. The activity of matrix metalloproteinase-9 (MMP-9) was determined using gelatin zymography. At day-5 after MCAO surgery, intraventricular injection of MSCs-FGF21 was found to significantly mitigate the neurological deficits and BBB disruption. The MCAO-induced loss of tight junction proteins, including ZO-1, occludin, and claudin-5, and upregulation of the edema inducer, aquaporin 4, were also remarkably inhibited. In addition, brain infarct volume, pro-inflammatory protein expression, and MMP-9 activation were effectively suppressed. These MCAO-induced changes were only marginally improved by treatment with MSCs-mCherry, which did not overexpress FGF21. Overexpression of FGF21 dramatically improved the therapeutic efficacy of MSCs in treating ischemic stroke. Given its multiple benefits and long therapeutic window, MSC-FGF21 therapy may be a promising treatment strategy for ischemic stroke.

Gemigliptin mitigates TGF-β-induced renal fibrosis through FGF21-mediated inhibition of the TGF-β/Smad3 signaling pathway

Fibroblast growth factor 21 (FGF21), a well-known regulator of metabolic disorders, exhibits the potential to prevent renal fibrosis by negatively regulating the transforming growth factor β (TGF-β)/Smad3 signaling pathway. Gemigliptin and other dipeptidyl peptidase-4 inhibitors are frequently used for the management of patients with type 2 diabetes. However, the protective effect of gemigliptin against renal fibrosis, particularly its potential to upregulate the expression of FGF21, remains incompletely understood. This study assessed the renoprotective effects of gemigliptin against TGF-β-induced renal fibrosis by enhancing the expression of FGF21 in the cultured human proximal tubular epithelial cell line HK-2. Treatment with FGF21 effectively prevented TGF-β-induced renal fibrosis by attenuating the TGF-β/Smad3 signaling pathway. Similarly, gemigliptin exhibited protective effects against TGF-β-induced renal fibrosis by mitigating TGF-β/Smad3 signaling through the upregulation of FGF21 expression. However, the protective effects of gemigliptin were blocked when FGF21 expression was knocked down in TGF-β-treated HK-2 cells. These results indicate that gemegliptin has the potential to exhibit protective effects against TGF-β-induced renal fibrosis by elevating FGF21 expression levels in cultured human proximal tubular epithelial cells.

Crosstalk between adipogenesis and aging: role of polyphenols in combating adipogenic-associated aging

In the last forty years, the number of people over 60 years of age has increased significantly owing to better nutrition and lower rates of infectious diseases in developing countries. Aging significantly impacts adipose tissue, which plays crucial role in hormone regulation and energy storage. This can lead to imbalances in glucose, and overall energy homeostasis within the body. Aging is irreversible phenomena and potentially causing lipid infiltration in other organs, leading to systemic inflammation, metabolic disorders. This review investigates various pathways contributing to aging-related defects in adipogenesis, such as changes in adipose tissue function and distribution. Polyphenols, a diverse group of natural compounds, can mitigate aging effects via free radicals, oxidative stress, inflammation, senescence, and age-related diseases. Polyphenols like resveratrol, quercetin and EGCG exhibit distinct mechanisms and regulate crucial pathways, such as the TGF-β, AMPK, Wnt, PPAR-γ, and C/EBP transcription factors, and influence epigenetic modifications, such as DNA methylation and histone modification. This review highlights the critical importance of understanding the intricate relationship between aging and adipogenesis for optimizing well-being with increasing age. These findings highlight the therapeutic potential of polyphenols like quercetin and resveratrol in enhancing adipose tissue function and promoting healthy aging.

β-Klotho as novel therapeutic target in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): A narrative review

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) represents the most frequent cause of hepatic disorder, and its progressive form defined as Metabolic Dysfunction-Associated Steatohepatitis (MASH) contributes to the development of fibrosis/cirrhosis and hepatocellular carcinoma (HCC). Today effective therapeutic strategies addressing MASH-related comorbidities, inflammation, and fibrosis are needed. The fibroblast growth factor (FGF) 19 and 21 and their fibroblast growth factor receptor/β-Klotho (KLB) complexes have recently emerged as promising druggable targets for MASLD. However, less is known regarding the causative association between KLB activity and advanced stages of liver disease. In the present narrative review, we aimed to provide an up-to-date picture of the role of the KLB co-receptor in MASLD development and progression. We performed a detailed analysis of recently published preclinical and clinical data to decipher the molecular mechanisms underlying KLB function and to correlate the presence of inherited or acquired KLB aberrancies with the predisposition towards MASLD. Moreover, we described ongoing clinical trials evaluating the therapeutic approaches targeting FGF19-21/FGFR/KLB in patients with MASLD and discussed the challenges related to their use. We furtherly described that KLB exhibits protective effects against metabolic disorders by acting in an FGF-dependent and independent manner thus triggering the hypothesis that KLB soluble forms may play a critical role in preserving liver health. Therefore, targeting KLB may provide promising strategies for treating MASLD, as supported by experimental evidence and ongoing clinical trials.

Therapeutic strategies to modulate gut microbial health: Approaches for sarcopenia management

Sarcopenia is a progressive and generalized loss of skeletal muscle and functions associated with ageing with currently no definitive treatment. Alterations in gut microbial composition have emerged as a significant contributor to the pathophysiology of multiple diseases. Recently, its association with muscle health has pointed to its potential role in mediating sarcopenia. The current review focuses on the association of gut microbiota and mediators of muscle health, connecting the dots between the influence of gut microbiota and their metabolites on biomarkers of sarcopenia. It further delineates the mechanism by which the gut microbiota affects muscle health with progressing age, aiding the formulation of a multi-modal treatment plan involving nutritional supplements and pharmacological interventions along with lifestyle changes compiled in the review. Nutritional supplements containing proteins, vitamin D, omega-3 fatty acids, creatine, curcumin, kefir, and ursolic acid positively impact the gut microbiome. Dietary fibres foster a conducive environment for the growth of beneficial microbes such as Bifidobacterium, Faecalibacterium, Ruminococcus, and Lactobacillus. Probiotics and prebiotics act by protecting against reactive oxygen species (ROS) and inflammatory cytokines. They also increase the production of gut microbiota metabolites like short-chain fatty acids (SCFAs), which aid in improving muscle health. Foods rich in polyphenols are anti-inflammatory and have an antioxidant effect, contributing to a healthier gut. Pharmacological interventions like faecal microbiota transplantation (FMT), non-steroidal anti-inflammatory drugs (NSAIDs), ghrelin mimetics, angiotensin-converting enzyme inhibitors (ACEIs), and butyrate precursors lead to the production of anti-inflammatory fatty acids and regulate appetite, gut motility, and microbial impact on gut health. Further research is warranted to deepen our understanding of the interaction between gut microbiota and muscle health for developing therapeutic strategies for ameliorating sarcopenic muscle loss.

The GPI sidechain of Toxoplasma gondii inhibits parasite pathogenesis

Glycosylphosphatidylinositols (GPIs) are highly conserved anchors for eukaryotic cell surface proteins. The apicomplexan parasite, Toxoplasma gondii, is a widespread intracellular parasite of warm-blooded animals whose plasma membrane is covered with GPI-anchored proteins, and free GPIs called GIPLs. While the glycan portion is conserved, species differ in sidechains added to the triple mannose core. The functional significance of the Glcα1,4GalNAcβ1- sidechain reported in Toxoplasma gondii has remained largely unknown without understanding its biosynthesis. Here we identify and disrupt two glycosyltransferase genes and confirm their respective roles by serology and mass spectrometry. Parasites lacking the sidechain on account of deletion of the first glycosyltransferase, PIGJ, exhibit increased virulence during primary and secondary infections, suggesting it is an important pathogenesis factor. Cytokine responses, antibody recognition of GPI-anchored SAGs, and complement binding to PIGJ mutants are intact. By contrast, the scavenger receptor CD36 shows enhanced binding to PIGJ mutants, potentially explaining a subtle tropism for macrophages detected early in infection. Galectin-3, which binds GIPLs, exhibits an enhancement of binding to PIGJ mutants, and the protection of galectin-3 knockout mice from lethality suggests that Δpigj parasite virulence in this context is sidechain dependent. Parasite numbers are not affected by Δpigj early in the infection in wild-type mice, suggesting a breakdown of tolerance. However, increased tissue cysts in the brains of mice infected with Δpigj parasites indicate an advantage over wild-type strains. Thus, the GPI sidechain of T. gondii plays a crucial and diverse role in regulating disease outcomes in the infected host.IMPORTANCEThe functional significance of sidechain modifications to the glycosylphosphatidylinositol (GPI) anchor in parasites has yet to be determined because the glycosyltransferases responsible for these modifications have not been identified. Here we present identification and characterization of both Toxoplasmsa gondii GPI sidechain-modifying glycosyltransferases. Removal of the glycosyltransferase that adds the first GalNAc to the sidechain results in parasites without a sidechain on the GPI, and increased host susceptibility to infection. Loss of the second glycosyltransferase results in a sidechain with GalNAc alone, and no glucose added, and has negligible effect on disease outcomes. This indicates GPI sidechains are fundamental to host-parasite interactions.

Characterization of FGF21 Sites of Production and Signaling in Mice

Fibroblast growth factor (FGF) 21 is an endocrine hormone that signals to multiple tissues to regulate metabolism. FGF21 and another endocrine FGF, FGF15/19, signal to target tissues by binding to the co-receptor β-klotho (KLB), which then facilitates the interaction of these different FGFs with their preferred FGF receptor. KLB is expressed in multiple metabolic tissues, but the specific cell types and spatial distribution of these cells are not known. Furthermore, while circulating FGF21 is primarily produced by the liver, recent publications have indicated that brain-derived FGF21 impacts memory and learning. Here we use reporter mice to comprehensively assess KLB and FGF21 expression throughout the body. These data provide an important resource for guiding future studies to identify important peripheral and central targets of FGFs and to determine the significance of nonhepatic FGF21 production.

The myokine FGF21 associates with enhanced survival in ALS and mitigates stress-induced cytotoxicity

Amyotrophic lateral sclerosis (ALS) is an age-related and fatal neurodegenerative disease characterized by progressive muscle weakness. There is marked heterogeneity in clinical presentation, progression, and pathophysiology with only modest treatments to slow disease progression. Molecular markers that provide insight into this heterogeneity are crucial for clinical management and identification of new therapeutic targets. In a prior muscle miRNA sequencing investigation, we identified altered FGF pathways in ALS muscle, leading us to investigate FGF21. We analyzed human ALS muscle biopsy samples and found a large increase in FGF21 expression with localization to atrophic myofibers and surrounding endomysium. A concomitant increase in FGF21 was detected in ALS spinal cords which correlated with muscle levels. FGF21 was increased in the SOD1G93A mouse beginning in presymptomatic stages. In parallel, there was dysregulation of the co-receptor, β-Klotho. Plasma FGF21 levels were increased and high levels correlated with slower disease progression, prolonged survival, and increased body mass index. In NSC-34 motor neurons and C2C12 muscle cells expressing SOD1G93A or exposed to oxidative stress, ectopic FGF21 mitigated loss of cell viability. In summary, FGF21 is a novel biomarker in ALS that correlates with slower disease progression and exerts trophic effects under conditions of cellular stress.

Tanshinone IIA Inhibits the Endoplasmic Reticulum Stress-Induced Unfolded Protein Response by Activating the PPARα/FGF21 Axis to Ameliorate Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a critical stage in the progression of nonalcoholic fatty liver disease (NAFLD). Tanshinone IIA (TIIA) is a tanshinone extracted from Salvia miltiorrhiza; due to its powerful anti-inflammatory and antioxidant biological activities, it is commonly used for treating cardiovascular and hepatic diseases. A NASH model was established by feeding mice a methionine and choline-deficient (MCD) diet. Liver surface microblood flow scanning, biochemical examination, histopathological examination, cytokine analysis through ELISA, lipidomic analysis, transcriptomic analysis, and Western blot analysis were used to evaluate the therapeutic effect and mechanism of TIIA on NASH. The results showed that TIIA effectively reduced lipid accumulation, fibrosis, and inflammation and alleviated endoplasmic reticulum (ER) stress. Lipidomic analysis revealed that TIIA normalized liver phospholipid metabolism in NASH mice. A KEGG analysis of the transcriptome revealed that TIIA exerted its effect by regulating the PPAR signalling pathway, protein processing in the ER, and the NOD-like receptor signalling pathway. These results suggest that TIIA alleviates NASH by activating the PPARα/FGF21 axis to negatively regulate the ER stress-induced unfolded protein response (UPR).

Oxidative stress and food as medicine

There has been a sea of change in our understanding of the contribution of food to both our well-being and disease states. When one addresses "food as medicine," the concept of oxidative stress needs to be included. This review interconnects the basic science findings of oxidative stress and redox balance with the medicinal use of food, emphasizing optimization of the redox balance. To better illustrate the impacts of oxidative stress, the concept of the "triple oxidant sink" is introduced as a theoretical gauge of redox balance. Utilizing the concept, the true importance of dietary and lifestyle factors can be emphasized, including the limitations of supplements or a handful of "superfoods," if the remainder of the factors are pro-oxidant. The effects of a whole plant food diet compared with those of dietary supplements, processed foods, animal based nutrients, or additional lifestyle factors can be visually demonstrated with this concept. This paper provides an overview of the process, acknowledging that food is not the only mechanism for balancing the redox status, but one that can be strategically used to dramatically improve the oxidative state, and thus should be used as medicine.

Connecting the Dots: FGF21 as a Potential Link between Obesity and Cardiovascular Health in Acute Coronary Syndrome Patients

Fibroblast growth factor 21 (FGF21) is a hormone involved in regulating the metabolism, energy balance, and glucose homeostasis, with new studies demonstrating its beneficial effects on the heart. This study investigated the relationship between FGF21 levels and clinical, biochemical, and echocardiographic parameters in patients with acute coronary syndromes (ACSs). This study included 80 patients diagnosed with ACS between May and July 2023, categorized into four groups based on body mass index (BMI): Group 1 (BMI 18.5-24.9 kg/m2), Group 2 (BMI 25-29.9 kg/m2), Group 3 (BMI 30-34.9 kg/m2), and Group 4 (BMI ≥ 35 kg/m2). Serum FGF21 levels were measured by ELISA (Abclonal Catalog NO.: RK00084). Serum FGF21 levels were quantifiable in 55 samples (mean ± SD: 342.42 ± 430.17 pg/mL). Group-specific mean FGF21 levels were 238.98 pg/mL ± SD in Group 1 (n = 14), 296.78 pg/mL ± SD in Group 2 (n = 13), 373.77 pg/mL ± SD in Group 3 (n = 12), and 449.94 pg/mL ± SD in Group 4 (n = 16), with no statistically significant differences between groups (p = 0.47). Based on ACS diagnoses, mean FGF21 levels were 245.72 pg/mL for STEMI (n = 21), 257.89 pg/mL for NSTEMI (n = 9), and 456.28 pg/mL for unstable angina (n = 25), with no significant differences observed between these diagnostic categories. Significant correlations were identified between FGF21 levels and BMI, diastolic blood pressure, and serum chloride. Regression analyses revealed correlations with uric acid, chloride, and creatinine kinase MB. This study highlights the complex interplay between FGF21, BMI, and acute coronary syndromes. While no significant differences were found in FGF21 levels between the different BMI and ACS diagnostic groups, correlations with clinical and biochemical parameters suggest a multifaceted role of FGF21 in cardiovascular health. Further research with a larger sample size is warranted to elucidate these relationships.

Beyond reproduction: unraveling the impact of sex hormones on cardiometabolic health

This review thoroughly explores the multifaceted roles of sexual hormones, emphasizing their impact beyond reproductive functions and underscoring their significant influence on cardiometabolic regulation. It analyzes the broader physiological implications of estrogen, testosterone, and progesterone, highlighting their effects on metabolic syndrome, lipid metabolism, glucose homeostasis, and cardiovascular health. Drawing from diverse molecular, clinical, and therapeutic studies, the paper delves into the intricate interplay between these hormones and cardiometabolic processes. By presenting a comprehensive analysis that goes beyond traditional perspectives, and recognizing sexual hormones as more than reproductive agents, the review sheds light on their broader significance in health and disease management, advocating for holistic and personalized medical approaches.

Cold exposure increases circulating fibroblast growth factor 21 in the evening in males and females

Objectives

Cold exposure is linked to cardiometabolic benefits. Cold activates brown adipose tissue (BAT), increases energy expenditure, and induces secretion of the hormones fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15). The cold-induced increase in energy expenditure exhibits a diurnal rhythm in men. Therefore, we aimed to investigate the effect of cold exposure on serum FGF21 and GDF15 levels in humans and whether cold-induced changes in FGF21 and GDF15 levels differ between morning and evening in males and females.

Method

In this randomized cross-over study, serum FGF21 and GDF15 levels were measured in healthy lean males (n = 12) and females (n = 12) before, during, and after 90 min of stable cold exposure in the morning (07:45 h) and evening (19:45 h) with a 1-day washout period in between.

Results

Cold exposure increased FGF21 levels in the evening compared to the morning both in males (+61% vs -13%; P < 0.001) and in females (+58% vs +8%; P < 0.001). In contrast, cold exposure did not significantly modify serum GDF15 levels, and no diurnal variation was found. Changes in FGF21 and GDF15 levels did not correlate with changes in cold-induced energy expenditure in the morning and evening.

Conclusion

Cold exposure increased serum FGF21 levels in the evening, but not in the morning, in both males and females. GDF15 levels were not affected by cold exposure. Thus, this study suggests that the timing of cold exposure may influence cold-induced changes in FGF21 levels but not GDF15 levels and seems to be independent of changes in energy expenditure.

Impact of various dietary lipids on amelioration of biomarkers linked to metabolic syndrome in both healthy and diabetic Wistar rats

BACKGROUND

The present study was designed to investigate the influence of different dietary lipids (sheep's fat, olive oil, coconut oil, and corn oil) on specific biomarkers associated with metabolic syndrome in both healthy and diabetic rats.

METHODS

The study designed for 45 days, utilized a male diabetic wistar rat (body weight, 180-220 g) model induced by streptozotocin (45 mg/kg bw). The rats were divided into two sections: five non-diabetic and five diabetic groups, each containing six rats. The first group in each section serving as the control, received a standard diet. Both non-diabetic or diabetic groups, were provided with a standard diet enriched with 15% sheep fat, 15% coconut oil, 15% olive oil, and 15% corn oil, respectively for a duration of 45 days.

RESULTS

Post-supplementation, both healthy and diabetic control rats exhibited a higher food intake compared to rats supplemented with lipid diet; notably food intake was higher in diabetic control than healthy control. However, rats fed with coconut oil, olive oil and sheep fat showed weight gain at the end of the experiment, in both healthy and diabetic groups. Coconut oil supplementation significantly (p ≤ 0.05) increased HDL-C and total cholesterol level in diabetic groups compared to healthy group, it was confirmed by an increased PPAR-α and ABCA-1 protein level. Olive oil significantly decreased triglyceride, total cholesterol, and LDL-C levels in diabetic rats when compared to sheep fat or coconut oil. Corn oil significantly decreased fasting glucose, total cholesterol and LDL-C levels compared to all other groups. Corn and olive oil supplemented normal groups, found with significant increase in hepatic glucose-lipid oxidative metabolism associated protein, like FGF-21, MSH, ABCA-1, PPAR-γ and decreased lipogenesis proteins like, SREBP and PPAR-α levels. In contrast, sheep grease and coconut oil increased SREBP and PPAR-α expression in both normal and diabetic groups. Most notably, normal and diabetic groups pretreated with sheep grease resulted in increased inflammatory (MCP-1, IL-1β, TLR-4, TNF-α), and oxidative stress markers (LPO, GSH, GPx, SOD and CAT) linked with metabolic complications.

CONCLUSION

The combination or alternative use of olive oil and corn oil in daily diet may play a significant role in preventing proinflammatory condition associated with insulin resistance and cardiovascular diseases.

Growth Differentiation Factor-15 Is Considered a Predictive Biomarker of Long COVID in Non-hospitalized Patients

Mitochondrial dysfunction is associated with various diseases. Mitochondria plays a regulatory role during infection. The association between mitokines and subsequent COVID progression has not been previously studied. The retrospective cohort study aimed to investigate the potential of serum mitokines as long COVID biomarkers in non-hospitalized patients. Patients with confirmed SARS-CoV-2 infection and blood test reports between January 2021 and April 2023 were included. Patients were categorized into two groups, the recovered and long COVID groups, based on fatigue, decline in focus, and pain. Serum levels of growth differentiation factor 15 (GDF-15) and fibroblast growth factor-21 (FGF-21), which are affected by mitochondrial function, along with inflammatory and vascular endothelium markers, were measured using enzyme-linked immunosorbent assays (ELISA). A receiver operating characteristic curve was used to screen the biomarkers. The threshold value of GDF-15 in the acute phase was 965 pg/mL (sensitivity: 71.4%, specificity: 83.3%), indicating that GDF-15 may be associated with the presence of symptoms three months post onset. No association with inflammatory markers and vascular structures was observed. Therefore, elevated GDF-15 levels in the acute phase may act as a predictive biomarker of long COVID.

Effects of SGLT2 Ablation or Inhibition on Corticosterone Secretion in High-Fat-Fed Mice: Exploring a Nexus with Cytokine Levels

Despite recent therapeutic advances, achieving optimal glycaemic control remains a challenge in managing Type 2 Diabetes (T2D). Sodium-glucose co-transporter type 2 (SGLT2) inhibitors have emerged as effective treatments by promoting urinary glucose excretion. However, the full scope of their mechanisms extends beyond glycaemic control. At present, their immunometabolic effects remain elusive. To investigate the effects of SGLT2 inhibition or deletion, we compared the metabolic and immune phenotype between high fat diet-fed control, chronically dapagliflozin-treated mice and total-body SGLT2/Slc5a2 knockout mice. SGLT2 null mice exhibited superior glucose tolerance and insulin sensitivity compared to control or dapagliflozin-treated mice, independent of glycosuria and body weight. Moreover, SGLT2 null mice demonstrated physiological regulation of corticosterone secretion, with lowered morning levels compared to control mice. Systemic cytokine profiling also unveiled significant alterations in inflammatory mediators, particularly interleukin 6 (IL-6). Furthermore, unbiased proteomic analysis demonstrated downregulation of acute-phase proteins and upregulation of glutathione-related proteins, suggesting a role in the modulation of antioxidant responses. Conversely, IL-6 increased SGLT2 expression in kidney HK2 cells suggesting a role for cytokines in the effects of hyperglycemia. Collectively, our study elucidates a potential interplay between SGLT2 activity, immune modulation, and metabolic homeostasis.

Berberine Effects in Pre-Fibrotic Stages of Non-Alcoholic Fatty Liver Disease-Clinical and Pre-Clinical Overview and Systematic Review of the Literature

Non-alcoholic fatty liver disease (NAFLD) is the predominant cause of chronic liver conditions, and its progression is marked by evolution to non-alcoholic steatosis, steatohepatitis, cirrhosis related to non-alcoholic steatohepatitis, and the potential occurrence of hepatocellular carcinoma. In our systematic review, we searched two databases, Medline (via Pubmed Central) and Scopus, from inception to 5 February 2024, and included 73 types of research (nine clinical studies and 64 pre-clinical studies) from 2854 published papers. Our extensive research highlights the impact of Berberine on NAFLD pathophysiology mechanisms, such as Adenosine Monophosphate-Activated Protein Kinase (AMPK), gut dysbiosis, peroxisome proliferator-activated receptor (PPAR), Sirtuins, and inflammasome. Studies involving human subjects showed a measurable reduction of liver fat in addition to improved profiles of serum lipids and hepatic enzymes. While current drugs for NAFLD treatment are either scarce or still in development or launch phases, Berberine presents a promising profile. However, improvements in its formulation are necessary to enhance the bioavailability of this natural substance.

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

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

The role of FGF21 in the interplay between obesity and non-alcoholic fatty liver disease: a narrative review

Obesity poses a significant and escalating challenge in contemporary society, increasing the risk of developing various metabolic disorders such as dyslipidemia, cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), type 2 diabetes, and certain types of cancer. The current array of therapeutic interventions for obesity remains insufficient, prompting a pressing demand for novel and more effective treatments. In response, scientific attention has turned to the fibroblast growth factor 21 (FGF21) due to its remarkable and diverse impacts on lipid, carbohydrate, and energy metabolism. This comprehensive review aims to delve into the multifaceted aspects of FGF21, encompassing its discovery, synthesis, functional roles, and potential as a biomarker and therapeutic agent, with a specific focus on its implications for NAFLD.

Intellectual disability and autism in propionic acidemia: a biomarker-behavioral investigation implicating dysregulated mitochondrial biology

Propionic acidemia (PA) is an autosomal recessive condition (OMIM #606054), wherein pathogenic variants in PCCA and PCCB impair the activity of propionyl-CoA carboxylase. PA is associated with neurodevelopmental disorders, including intellectual disability (ID) and autism spectrum disorder (ASD); however, the correlates and mechanisms of these outcomes remain unknown. Using data from a subset of participants with PA enrolled in a dedicated natural history study (n = 33), we explored associations between neurodevelopmental phenotypes and laboratory parameters. Twenty (61%) participants received an ID diagnosis, and 12 of the 31 (39%) who were fully evaluated received the diagnosis of ASD. A diagnosis of ID, lower full-scale IQ (sample mean = 65 ± 26), and lower adaptive behavior composite scores (sample mean = 67 ± 23) were associated with several biomarkers. Higher concentrations of plasma propionylcarnitine, plasma total 2-methylcitrate, serum erythropoietin, and mitochondrial biomarkers plasma FGF21 and GDF15 were associated with a more severe ID profile. Reduced 1-13C-propionate oxidative capacity and decreased levels of plasma and urinary glutamine were also associated with a more severe ID profile. Only two parameters, increased serum erythropoietin and decreased plasma glutamine, were associated with ASD. Plasma glycine, one of the defining features of PA, was not meaningfully associated with either ID or ASD. Thus, while both ID and ASD were commonly observed in our PA cohort, only ID was robustly associated with metabolic parameters. Our results suggest that disease severity and associated mitochondrial dysfunction may play a role in CNS complications of PA and identify potential biomarkers and candidate surrogate endpoints.

Mind over Microbes: Investigating the Interplay between Lifestyle Factors, Gut Microbiota, and Brain Health

BACKGROUND

The gut microbiota (GM) of the human body comprises several species of microorganisms. This microorganism plays a significant role in the physiological and pathophysiological processes of various human diseases.

METHODS

The literature review includes studies that describe causative factors that influence GM. The GM is sensitive to various factors like circadian rhythms, environmental agents, physical activity, nutrition, and hygiene that together impact the functioning and composition of the gut microbiome. This affects the health of the host, including the psycho-neural aspects, due to the interconnectivity between the brain and the gut. Hence, this paper examines the relationship of GM with neurodegenerative disorders in the context of these aforesaid factors.

CONCLUSION

Future studies that identify the regulatory pathways associated with gut microbes can provide a causal link between brain degeneration and the gut at a molecular level. Together, this review could be helpful in designing preventive and treatment strategies aimed at GM, so that neurodegenerative diseases can be treated.

An organism-wide atlas of hormonal signaling based on the mouse lemur single-cell transcriptome

Hormones mediate long-range cell communication and play vital roles in physiology, metabolism, and health. Traditionally, endocrinologists have focused on one hormone or organ system at a time. Yet, hormone signaling by its very nature connects cells of different organs and involves crosstalk of different hormones. Here, we leverage the organism-wide single cell transcriptional atlas of a non-human primate, the mouse lemur (Microcebus murinus), to systematically map source and target cells for 84 classes of hormones. This work uncovers previously-uncharacterized sites of hormone regulation, and shows that the hormonal signaling network is densely connected, decentralized, and rich in feedback loops. Evolutionary comparisons of hormonal genes and their expression patterns show that mouse lemur better models human hormonal signaling than mouse, at both the genomic and transcriptomic levels, and reveal primate-specific rewiring of hormone-producing/target cells. This work complements the scale and resolution of classical endocrine studies and sheds light on primate hormone regulation.

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.

Phenotyping obesity: A focus on metabolically healthy obesity and metabolically unhealthy normal weight

Over the past 4 decades, research has shown that having a normal body weight does not automatically imply preserved metabolic health and a considerable number of lean individuals harbour metabolic abnormalities typically associated with obesity. Conversely, excess adiposity does not always equate with an abnormal metabolic profile. In fact, evidence exists for the presence of a metabolically unhealthy normal weight (MUHNW) and a metabolically healthy obese (MHO) phenotype. It has become increasingly recognised that different fat depots exert different effects on the metabolic profile of each individual by virtue of their location, structure and function, giving rise to these different body composition phenotypes. Furthermore, other factors have been implicated in the aetiopathogenesis of the body composition phenotypes, including genetics, ethnicity, age and lifestyle/behavioural factors. Even though to date both MHO and MUHNW have been widely investigated and documented in the literature, studies report different outcomes on long-term cardiometabolic morbidity and mortality. Future large-scale, observational and population-based studies are required for better profiling of these phenotypes as well as to further elucidate the pathophysiological role of the adipocyte in the onset of metabolic disorders to allow for better risk stratification and a personalised treatment paradigm.

The effects of 12 weeks of high-intensity interval training and moderate-intensity continuous training on FGF21, irisin, and myostatin in men with type 2 diabetes mellitus

This study investigated the influence of a 12-week high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on irisin, fibroblast growth factor 21 (FGF21), and myostatin (MSTN) among men with type 2 diabetes mellitus (T2DM). Forty-five adult men with T2DM were randomly selected and assigned to receive and perform HIIT (4 × 4 min at 85-95% HRmax with three min of active rest at 50-60% HRmax in between) and MICT (walking/running continuously for 47 min at 60-70% HRmax) three sessions per week for 12 weeks, or to act as a non-exercise control (CON) group. The subjects' blood samples were collected at baseline and 48 hours after the last intervention session. Our research revealed that both interventions resulted in similar decreases in FGF21 and MSTN when compared to the CON (p < .01). However, only the HIIT group showed a significant increase in irisin (p < .01) compared to the CON. Further, improvements in insulin resistance, body composition, and VO2 peak were noted in both intervention groups compared with those of the CON group (p < .01). It seems that while either aerobic exercise strategy could be seen as a therapy for men with T2DM, HIIT had a more advantageous effect on the irisin response.

Metformin Improves the Prerequisites for FGF21 Signaling in Patients With Type 2 Diabetes

CONTEXT

Fibroblast growth factor (FGF) 21 acts as a metabolic regulator and its therapeutic use is under investigation. FGF21 signaling requires binding to surface receptors, FGFR1c and β-klotho. FGF21 resistance is observed in metabolic diseases and FGF21 signaling is regulated by fibroblast activation protein (FAP). Metformin is reported to influence expression and secretion of FGF21 in preclinical models, but the effect of metformin on FGF21 in a clinical trial remains unknown.

OBJECTIVE

To investigate how 12 weeks of treatment with metformin affects the FGF21 signaling pathway in patients with type 2 diabetes (T2D).

METHODS

Randomized, placebo-controlled study in patients with T2D (n = 24) receiving either metformin (1000 mg twice daily) or placebo. A control group of body mass index- and age-matched healthy individuals (n = 12) received a similar dose of metformin. Blood samples and muscle and fat biopsies were collected at study entry and after 12 weeks.

METHODS

Plasma levels of FGF21 (total and intact) and FAP (total and activity) were measured. Muscle and fat biopsies were analyzed for mRNA and protein expression of targets relevant for activation of the FGF21 signaling pathway.

RESULTS

Circulating FAP activity decreased after metformin treatment compared with placebo (P = .006), whereas FGF21 levels were unchanged. Metformin treatment increased gene and protein expression of β-klotho, FGFR1c, and pFGFR1c in adipose tissue. FGF21 mRNA expression increased in muscle tissue after metformin and the FGF21 protein, but not mRNA levels, were observed in adipose tissue.

CONCLUSION

Our findings suggest that metformin suppresses the circulating FAP activity and upregulates the expression of FGFR1c and β-klotho for increased FGF21 signaling in adipose tissue, thus improving peripheral FGF21 sensitivity.

Endocrine FGFs and their signaling in the brain: Relevance for energy homeostasis

Since their discovery in 2000, there has been a continuous expansion of studies investigating the physiology, biochemistry, and pharmacology of endocrine fibroblast growth factors (FGFs). FGF19, FGF21, and FGF23 comprise a subfamily with attributes that distinguish them from typical FGFs, as they can act as hormones and are, therefore, referred to as endocrine FGFs. As they participate in a broad cross-organ endocrine signaling axis, endocrine FGFs are crucial lipidic, glycemic, and energetic metabolism regulators during energy availability fluctuations. They function as powerful metabolic signals in physiological responses induced by metabolic diseases, like type 2 diabetes and obesity. Pharmacologically, FGF19 and FGF21 cause body weight loss and ameliorate glucose homeostasis and energy expenditure in rodents and humans. In contrast, FGF23 expression in mice and humans has been linked with insulin resistance and obesity. Here, we discuss emerging concepts in endocrine FGF signaling in the brain and critically assess their putative role as therapeutic targets for treating metabolic disorders.

Brown adipose tissue CoQ deficiency activates the integrated stress response and FGF21-dependent mitohormesis

Coenzyme Q (CoQ) is essential for mitochondrial respiration and required for thermogenic activity in brown adipose tissues (BAT). CoQ deficiency leads to a wide range of pathological manifestations, but mechanistic consequences of CoQ deficiency in specific tissues, such as BAT, remain poorly understood. Here, we show that pharmacological or genetic CoQ deficiency in BAT leads to stress signals causing accumulation of cytosolic mitochondrial RNAs and activation of the eIF2α kinase PKR, resulting in activation of the integrated stress response (ISR) with suppression of UCP1 but induction of FGF21 expression. Strikingly, despite diminished UCP1 levels, BAT CoQ deficiency displays increased whole-body metabolic rates at room temperature and thermoneutrality resulting in decreased weight gain on high-fat diets (HFD). In line with enhanced metabolic rates, BAT and inguinal white adipose tissue (iWAT) interorgan crosstalk caused increased browning of iWAT in BAT-specific CoQ deficient animals. This mitohormesis-like effect depends on the ATF4-FGF21 axis and BAT-secreted FGF21, revealing an unexpected role for CoQ in the modulation of whole-body energy expenditure with wide-ranging implications for primary and secondary CoQ deficiencies.

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.

Potential role of Akt in the regulation of fibroblast growth factor 21 by berberine

Fibroblast growth factor 21 (FGF21) is expressed in several organs, including the liver, adipose tissue, and cardiovascular system, and plays an important role in cross-talk with other organs by binding to specific FGF receptors and their co-receptors. FGF21 represents a potential target for the treatment of obesity, type 2 diabetes mellitus, and non-alcoholic steatohepatitis (NASH). The production of FGF21 in skeletal muscle was recently suggested to be beneficial for metabolic health through its autocrine and paracrine effects. However, the regulatory mechanisms of FGF21 in skeletal muscle remain unclear. In the present study, we showed that berberine regulated FGF21 production in C2C12 myotubes in a dose-dependent manner. We also examined the effects of A-674563, a selective Akt1 inhibitor, on the berberine-mediated regulation of FGF21 expression in C2C12 myotubes. Berberine significantly increased the secretion of FGF21 in C2C12 myotubes, while A-674563 attenuated this effect. Moreover, a pre-treatment with A-674563 effectively suppressed berberine-induced increases in Bmal1 expression in C2C12 myotubes, indicating that the up-regulation of Bmal1 after the berberine treatment was dependent on Akt1. Additionally, berberine-induced increases in FGF21 secretion were significantly attenuated in C2C12 cells transfected with Bmal1 siRNA, indicating the contribution of the core clock transcription factor BMAL1 to Akt-regulated FGF21 in response to berberine. Collectively, these results indicate that berberine regulates the expression of FGF21 through the Akt1 pathway in C2C12 myotubes. Moreover, the core clock gene Bmal1 may participate in the control of the myokine FGF21. Berberine stimulated Akt1-dependent FGF21 expression in C2C12 myotubes. The up-regulation of FGF21 through the modulation of PI3K/AKT1/BMAL1 in response to berberine may be involved in the regulation of cellular function (such as Glut1 expression) by acting in an autocrine and/or paracrine manner in skeletal muscle.

Mechanosensing in Metabolism

Electrical mechanosensing is a process mediated by specialized ion channels, gated directly or indirectly by mechanical forces, which allows cells to detect and subsequently respond to mechanical stimuli. The activation of mechanosensitive (MS) ion channels, intrinsically gated by mechanical forces, or mechanoresponsive (MR) ion channels, indirectly gated by mechanical forces, results in electrical signaling across lipid bilayers, such as the plasma membrane. While the functions of mechanically gated channels within a sensory context (e.g., proprioception and touch) are well described, there is emerging data demonstrating functions beyond touch and proprioception, including mechanoregulation of intracellular signaling and cellular/systemic metabolism. Both MR and MS ion channel signaling have been shown to contribute to the regulation of metabolic dysfunction, including obesity, insulin resistance, impaired insulin secretion, and inflammation. This review summarizes our current understanding of the contributions of several MS/MR ion channels in cell types implicated in metabolic dysfunction, namely, adipocytes, pancreatic β-cells, hepatocytes, and skeletal muscle cells, and discusses MS/MR ion channels as possible therapeutic targets. © 2024 American Physiological Society. Compr Physiol 14:5269-5290, 2024.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Molecular and Metabolic Analysis of Arsenic-Exposed Humanized AS3MT Mice

BACKGROUND

Chronic exposure to inorganic arsenic (iAs) has been associated with type 2 diabetes (T2D). However, potential sex divergence and the underlying mechanisms remain understudied. iAs is not metabolized uniformly across species, which is a limitation of typical exposure studies in rodent models. The development of a new "humanized" mouse model overcomes this limitation. In this study, we leveraged this model to study sex differences in the context of iAs exposure.

OBJECTIVES

The aim of this study was to determine if males and females exhibit different liver and adipose molecular profiles and metabolic phenotypes in the context of iAs exposure.

METHODS

Our study was performed on wild-type (WT) 129S6/SvEvTac and humanized arsenic + 3 methyl transferase (human AS3MT) 129S6/SvEvTac mice treated with 400   ppb of iAs via drinking water ad libitum. After 1 month, mice were sacrificed and the liver and gonadal adipose depots were harvested for iAs quantification and sequencing-based microRNA and gene expression analysis. Serum blood was collected for fasting blood glucose, fasting plasma insulin, and homeostatic model assessment for insulin resistance (HOMA-IR).

RESULTS

We detected sex divergence in liver and adipose markers of diabetes (e.g., miR-34a, insulin signaling pathways, fasting blood glucose, fasting plasma insulin, and HOMA-IR) only in humanized (not WT) mice. In humanized female mice, numerous genes that promote insulin sensitivity and glucose tolerance in both the liver and adipose are elevated compared to humanized male mice. We also identified Klf11 as a putative master regulator of the sex divergence in gene expression in humanized mice.

DISCUSSION

Our study underscored the importance of future studies leveraging the humanized mouse model to study iAs-associated metabolic disease. The findings suggested that humanized males are at increased risk for metabolic dysfunction relative to humanized females in the context of iAs exposure. Future investigations should focus on the detailed mechanisms that underlie the sex divergence. https://doi.org/10.1289/EHP12785.

Systems levels analysis of lipid metabolism in oxygen-induced retinopathy

Hyperoxia induces glutamine-fueled anaplerosis in the Muller cells, endothelial cells, and retinal explants. Anaplerosis takes away glutamine from the biosynthetic pathway to the energy-producing TCA cycle. This process depletes biosynthetic precursors from newly proliferating endothelial cells. The induction of anaplerosis in the hyperoxic retina is a compensatory response, either to decreased glycolysis or decreased flux from glycolysis to the TCA cycle. We hypothesized that by providing substrates that feed into TCA, we could reverse or prevent glutamine-fueled anaplerosis, thereby abating the glutamine wastage for energy generation. Using an oxygen-induced retinopathy (OIR) mouse model, we first compared the difference in fatty acid metabolism between OIR-resistant BALB/cByJ and OIR susceptible C57BL/6J strains to understand if these strains exhibit metabolic difference that protects BALB/cByJ from the hyperoxic conditions and prevents their vasculature in oxygen-induced retinopathy model. Based on our findings from the metabolic comparison between two mouse strains, we hypothesized that the medium-chain fatty acid, octanoate, can feed into the TCA and serve as an alternative energy source in response to hyperoxia. Our systems levels analysis of OIR model shows that the medium chain fatty acid can serve as an alternative source to feed TCA. We here, for the first time, demonstrate that the retina can use medium-chain fatty acid octanoate to replenish TCA in normoxic and at a higher rate in hyperoxic conditions.

Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism

Fibroblast growth factor 21 (FGF21) plays a vital role in normal eukaryotic organism development and homeostatic metabolism under the influence of internal and external factors such as endogenous hormone changes and exogenous stimuli. Over the last few decades, comprehensive studies have revealed the key role of FGF21 in regulating many fundamental metabolic pathways, including the muscle stress response, insulin signaling transmission, and muscle development. By coordinating these metabolic pathways, FGF21 is thought to contribute to acclimating to a stressful environment and the subsequent recovery of cell and tissue homeostasis. With the emphasis on FGF21, we extensively reviewed the research findings on the production and regulation of FGF21 and its role in muscle metabolism. We also emphasize how the FGF21 metabolic networks mediate mitochondrial dysfunction, glycogen consumption, and myogenic development and investigate prospective directions for the functional exploitation of FGF21 and its downstream effectors, such as the mammalian target of rapamycin (mTOR).

Integrated procedures for accelerating, deepening, and leading genetic inquiry: A first application on human muscle secretome

PURPOSE

Beyond classical procedures, bioinformatic-assisted approaches and computational biology offer unprecedented opportunities for scholars. However, these amazing possibilities still need epistemological criticism, as well as standardized procedures. Especially those topics with a huge body of data may benefit from data science (DS)-assisted methods. Therefore, the current study dealt with the combined expert-assisted and DS-assisted approaches to address the broad field of muscle secretome. We aimed to apply DS tools to fix the literature research, suggest investigation targets with a data-driven approach, predict possible scenarios, and define a workflow.

METHODS

Recognized scholars with expertise on myokines were invited to provide a list of the most important myokines. GeneRecommender, GeneMANIA, HumanNet, and STRING were selected as DS tools. Networks were built on STRING and GeneMANIA. The outcomes of DS tools included the top 5 recommendations. Each expert-led discussion has been then integrated with an DS-led approach to provide further perspectives.

RESULTS

Among the results, 11 molecules had already been described as bona-fide myokines in literature, and 11 molecules were putative myokines. Most of the myokines and the putative myokines recommended by the DS tools were described as present in the cargo of extracellular vesicles.

CONCLUSIONS

Including both supervised and unsupervised learning methods, as well as encompassing algorithms focused on both protein interaction and gene represent a comprehensive approach to tackle complex biomedical topics. DS-assisted methods for reviewing existent evidence, recommending targets of interest, and predicting original scenarios are worth exploring as in silico recommendations to be integrated with experts' ideas for optimizing molecular studies.

Addressing the preventive and therapeutic perspective of berberine against diabetes

Diabetes has emerged as one the leading detrimental factors for human life expectancy worldwide. The disease is mainly considered as outcome of dysregulation in glucose metabolism, resulting in consistent high glucose concentration in blood. At initial stages, the diabetes particularly type 2 diabetes, is manageable by lifestyle interventions such as regular physical activity and diet with less carbohydrates. However, in advance stage, regular intake of external insulin dose and medicines like metformin are recommended. The long-term consumption of metformin is associated with several side effects such as nausea, vomiting, diarrhoea, lectic acidosis etc., In this scenario, several plant-based medicines have shown promising potential for the prevention and treatment of diabetes. Berberine is the bioactive compound present in the different plant parts of berberis family. Biochemical studies have shown that berberine improve insulin sensitivity and insulin secretion. Additionally, berberine induces glucose metabolism by activating AMPK signaling and inhibition of inflammation. A series of studies have demonstrated the antidiabetic potential of berberine at in vitro, pre-clinical and clinical trials. This review provides comprehensive details of preventive and therapeutic potential of berberine against diabetes.

Epigenetic regulation of GABA catabolism in iPSC-derived neurons: The molecular links between FGF21 and histone methylation

OBJECTIVE

Fibroblast growth factor 21 (FGF21) analogs have been tested as potential therapeutics for substance use disorders. Prior research suggests that FGF21 administration might affect alcohol consumption and reward behaviors. Our recent report showed that plasma FGF21 levels were positively correlated with alcohol use in patients with alcohol use disorder (AUD). FGF21 has a short half-life (0.5-2 h) and crosses the blood-brain barrier. Therefore, we set out to identify molecular mechanisms for both the naïve form of FGF21 and a long-acting FGF21 molecule (PF-05231023) in induced pluripotent stem cell (iPSC)-derived forebrain neurons.

METHODS

We performed RNA-seq in iPSC-derived forebrain neurons treated with naïve FGF21 or PF-05231023 at physiologically relevant concentrations. We obtained plasma levels of FGF21 and GABA from our previous AUD clinical trial (n = 442). We performed ELISA for FGF21 in both iPSC-derived forebrain neurons and forebrain organoids. We determined protein interactions using co-immunoprecipitation. Finally, we applied ChIP assays to confirm the occupancy of REST, EZH2 and H3K27me3 by FGF21 using iPSC-derived forebrain neurons with and without drug exposure.

RESULTS

We identified 4701 and 1956 differentially expressed genes in response to naïve FGF21 or PF-05231023, respectively (FDR < 0.05). Notably, 974 differentially expressed genes overlapped between treatment with naïve FGF21 and PF-05231023. REST was the most important upstream regulator of differentially expressed genes. The GABAergic synapse pathway was the most significant pathway identified using the overlapping genes. We also observed a significant positive correlation between plasma FGF21 and GABA concentrations in AUD patients. In parallel, FGF21 and PF-05231023 significantly induced GABA levels in iPSC-derived neurons. Finally, functional genomics studies showed a drug-dependent occupancy of REST, EZH2, and H3K27me3 in the promoter regions of genes involved in GABA catabolism which resulted in transcriptional repression.

CONCLUSIONS

Our results highlight a significant role in the epigenetic regulation of genes involved in GABA catabolism related to FGF21 action. (The ClinicalTrials.gov Identifier: NCT00662571).

The mitochondrial fusion protein OPA1 is dispensable in the liver and its absence induces mitohormesis to protect liver from drug-induced injury

Mitochondria are critical for metabolic homeostasis of the liver, and their dysfunction is a major cause of liver diseases. Optic atrophy 1 (OPA1) is a mitochondrial fusion protein with a role in cristae shaping. Disruption of OPA1 causes mitochondrial dysfunction. However, the role of OPA1 in liver function is poorly understood. In this study, we delete OPA1 in the fully developed liver of male mice. Unexpectedly, OPA1 liver knockout (LKO) mice are healthy with unaffected mitochondrial respiration, despite disrupted cristae morphology. OPA1 LKO induces a stress response that establishes a new homeostatic state for sustained liver function. Our data show that OPA1 is required for proper complex V assembly and that OPA1 LKO protects the liver from drug toxicity. Mechanistically, OPA1 LKO decreases toxic drug metabolism and confers resistance to the mitochondrial permeability transition. This study demonstrates that OPA1 is dispensable in the liver, and that the mitohormesis induced by OPA1 LKO prevents liver injury and contributes to liver resiliency.

Anabolic Resistance in the Pathogenesis of Sarcopenia in the Elderly: Role of Nutrition and Exercise in Young and Old People

The development of sarcopenia in the elderly is associated with many potential factors and/or processes that impair the renovation and maintenance of skeletal muscle mass and strength as ageing progresses. Among them, a defect by skeletal muscle to respond to anabolic stimuli is to be considered. Common anabolic stimuli/signals in skeletal muscle are hormones (insulin, growth hormones, IGF-1, androgens, and β-agonists such epinephrine), substrates (amino acids such as protein precursors on top, but also glucose and fat, as source of energy), metabolites (such as β-agonists and HMB), various biochemical/intracellular mediators), physical exercise, neurogenic and immune-modulating factors, etc. Each of them may exhibit a reduced effect upon skeletal muscle in ageing. In this article, we overview the role of anabolic signals on muscle metabolism, as well as currently available evidence of resistance, at the skeletal muscle level, to anabolic factors, from both in vitro and in vivo studies. Some indications on how to augment the effects of anabolic signals on skeletal muscle are provided.

Development of muscle weakness in a mouse model of critical illness: does fibroblast growth factor 21 play a role?

BACKGROUND

Critical illness is hallmarked by severe stress and organ damage. Fibroblast growth factor 21 (FGF21) has been shown to rise during critical illness. FGF21 is a pleiotropic hormone that mediates adaptive responses to tissue injury and repair in various chronic pathological conditions. Animal studies have suggested that the critical illness-induced rise in FGF21 may to a certain extent protect against acute lung, liver, kidney and brain injury. However, FGF21 has also been shown to mediate fasting-induced loss of muscle mass and force. Such loss of muscle mass and force is a frequent problem of critically ill patients, associated with adverse outcome. In the present study, we therefore investigated whether the critical illness-induced acute rise in FGF21 is muscle-protective or rather contributes to the pathophysiology of critical illness-induced muscle weakness.

METHODS

In a catheterised mouse model of critical illness induced by surgery and sepsis, we first assessed the effects of genetic FGF21 inactivation, and hence the inability to acutely increase FGF21, on survival, body weight, muscle wasting and weakness, and markers of muscle cellular stress and dysfunction in acute (30 h) and prolonged (5 days) critical illness. Secondly, we assessed whether any effects were mirrored by supplementing an FGF21 analogue (LY2405319) in prolonged critical illness.

RESULTS

FGF21 was not required for survival of sepsis. Genetic FGF21 inactivation aggravated the critical illness-induced body weight loss (p = 0.0003), loss of muscle force (p = 0.03) and shift to smaller myofibers. This was accompanied by a more pronounced rise in markers of endoplasmic reticulum stress in muscle, without effects on impairments in mitochondrial respiratory chain enzyme activities or autophagy activation. Supplementing critically ill mice with LY2405319 did not affect survival, muscle force or weight, or markers of muscle cellular stress/dysfunction.

CONCLUSIONS

Endogenous FGF21 is not required for sepsis survival, but may partially protect muscle force and may reduce cellular stress in muscle. Exogenous FGF21 supplementation failed to improve muscle force or cellular stress, not supporting the clinical applicability of FGF21 supplementation to protect against muscle weakness during critical illness.

FGF21 via mitochondrial lipid oxidation promotes physiological vascularization in a mouse model of Phase I ROP

Hyperglycemia in early postnatal life of preterm infants with incompletely vascularized retinas is associated with increased risk of potentially blinding neovascular retinopathy of prematurity (ROP). Neovascular ROP (Phase II ROP) is a compensatory but ultimately pathological response to the suppression of physiological postnatal retinal vascular development (Phase I ROP). Hyperglycemia in neonatal mice which suppresses physiological retinal vascular growth is associated with decreased expression of systemic and retinal fibroblast growth factor 21 (FGF21). FGF21 administration promoted and FGF21 deficiency suppressed the physiological retinal vessel growth. FGF21 increased serum adiponectin (APN) levels and loss of APN abolished FGF21 promotion of physiological retinal vascular development. Blocking mitochondrial fatty acid oxidation also abolished FGF21 protection against delayed physiological retinal vessel growth. Clinically, preterm infants developing severe neovascular ROP (versus non-severe ROP) had a lower total lipid intake with more parenteral and less enteral during the first 4 weeks of life. Our data suggest that increasing FGF21 levels in the presence of adequate enteral lipids may help prevent Phase I retinopathy (and therefore prevent neovascular disease).

TFEB is a central regulator of the aging process and age-related diseases

Old age is associated with a greater burden of disease, including neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, as well as other chronic diseases. Coincidentally, popular lifestyle interventions, such as caloric restriction, intermittent fasting, and regular exercise, in addition to pharmacological interventions intended to protect against age-related diseases, induce transcription factor EB (TFEB) and autophagy. In this review, we summarize emerging discoveries that point to TFEB activity affecting the hallmarks of aging, including inhibiting DNA damage and epigenetic modifications, inducing autophagy and cell clearance to promote proteostasis, regulating mitochondrial quality control, linking nutrient-sensing to energy metabolism, regulating pro- and anti-inflammatory pathways, inhibiting senescence and promoting cell regenerative capacity. Furthermore, the therapeutic impact of TFEB activation on normal aging and tissue-specific disease development is assessed in the contexts of neurodegeneration and neuroplasticity, stem cell differentiation, immune responses, muscle energy adaptation, adipose tissue browning, hepatic functions, bone remodeling, and cancer. Safe and effective strategies of activating TFEB hold promise as a therapeutic strategy for multiple age-associated diseases and for extending lifespan.