Fibroblast growth factor 21 and bone homeostasis

Engineered extracellular vesicles with surface FGF21 and enclosed miR-223 for treating metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disorder with a complex pathogenesis that requires combination therapies rather than monotherapies. Extracellular vesicles (EVs) exhibit inherently efficient delivery to the liver and can be engineered to carry various therapeutic substances, making them promising agents. In this study, EVs were engineered to display fibroblast growth factor 21 (FGF21) on their surface and encapsulate miR-223 (223/F-EVs), aiming to improve steatosis and alleviate inflammation and fibrosis, respectively. Introducing the 223/F-EVs into human liver cell lines significantly reduced both basal and induced levels of lipid storage, inflammation, and fibrosis markers. Furthermore, using an FGF21-blocking antibody or miR-223 inhibitor effectively diminished the efficacy of the 223/F-EVs, confirming the essential roles of FGF21 and miR-223 in these processes. In a Choline-Deficient, l-Amino acid-defined, High-Fat Diet (CDAHFD)-fed mouse model, intravenously administered 223/F-EVs demonstrated liver-preferential delivery and a marked reduction in the MASH phenotype without compromising bone density, unlike conventional FGF21 treatment. Collectively, 223/F-EVs convey FGF21 and miR-223 exclusively to the liver, offering strategic advantages by mitigating MASH progression via multiple pathways. This study lays a solid foundation for further investigation of engineered EVs as a transformative therapeutic approach for treating MASH.

Bone Modelling and Remodelling in Cold Environment

People engaged in various activities in cold environments-such as those living in cold climates, polar workers, cold storage workers, and athletes engaged in winter sports-are frequently affected by cold environments. Therefore, it is of great significance to explore the modelling and remodelling of bones in cold environments. Cold environments can shorten the length of bones, thin the thickness of bones, decrease bone mineral density (BMD), change the biomechanical properties of bones, and lead to bone loss. In addition, cold directly affects the bone microenvironment. Exposure to cold causes spindle-like and fibroblast-like changes in bone marrow mesenchymal stem cells (BMSCs) and decreases their proliferation, and cold exposure promotes the osteogenic differentiation of BMSCs partly through the p38 MAPK pathway. Cold also alters the dendritic differentiation of OBs by reducing the transmembrane glycoprotein E11/podoplanin and damages endothelial cells (ECs) by elevating levels of VEGF, resulting in a reduced blood supply and thus fewer OBs. In addition, cold promotes lipolysis of marrow adipose tissue (MAT), but in combination with exercise, it can promote the differentiation of BMSCs into MAT. Cold environments interfere with angiogenesis and inhibit bone growth by affecting factors such as platelet-derived growth factor type BB (PDGF-BB), slit guidance ligand 3 (SLIT3), Notch, and VEGF. In addition, cold environments may promote bone resorption by activating sympathetic nerves to activate β-adrenergic receptors and regulating leptin secretion, and regulate bone metabolism by activating the p38 MAPK signalling pathway and increasing the synthesis of brown fat, which ultimately inhibit bone formation and enhance bone resorption. In this paper, we describe the effects of cold environments on bones in the locomotor system in terms of bone structure, bone mass, biomechanical properties, and various skeletal cells, bone blood vessels, and bone fat systems in the bone microenvironment.

Poor bone health in Duchenne muscular dystrophy: a multifactorial problem beyond corticosteroids and loss of ambulation

Duchenne muscular dystrophy (DMD) is a progressive, fatal muscle wasting disease caused by X-linked mutations in the dystrophin gene. Alongside the characteristic muscle weakness, patients face a myriad of skeletal complications, including osteoporosis/osteopenia, high susceptibility to vertebral and long bone fractures, fat embolism post-fracture, scoliosis, and growth retardation. Those skeletal abnormalities significantly compromise quality of life and are sometimes life-threatening. These issues were traditionally attributed to loss of ambulation and chronic corticosteroid use, but recent investigations have unveiled a more intricate etiology. Factors such as vitamin D deficiency, hormonal imbalances, systemic inflammation, myokine release from dystrophic muscle, and vascular dysfunction are emerging as significant contributors as well. This expanded understanding illuminates the multifaceted pathogenesis underlying skeletal issues in DMD. Present therapeutic options are limited and lack specificity. Advancements in understanding the pathophysiology of bone complications in DMD will offer promising avenues for novel treatment modalities. In this review, we summarize the current understanding of factors contributing to bone problems in DMD and delineate contemporary and prospective multidisciplinary therapeutic approaches.

[Non-classical hormones from the fibroblast growth factor family]

Fibroblast growth factors (FGFs) are a group of signaling molecules named for their ability to promote the growth and proliferation of fibroblasts and various other cell types. Typically, FGFs exert their effects locally by binding to receptors within the tissues where they are synthesized. However, certain members of this family, such as FGF 19, FGF 21, and FGF 23, diverge from this pattern. Following synthesis, these FGFs enter the bloodstream and act on distant organs and tissues by binding to their receptors and associated cofactors, thereby classified as non-classical hormones within the FGF family.The biological functions of FGFs are diverse and contingent upon the specific receptors and cofactors involved in their signaling pathways. For instance, FGF 19 and FGF 21 play crucial roles in regulating glucose and lipid metabolism, whereas FGF 23 primarily influences phosphorus metabolism. Given their varied roles, FGFs present promising targets for therapeutic interventions and drug development.This review aims to consolidate current understanding of FGF family hormones, elucidating their biological impacts and exploring their potential applications as therapeutic targets.

Effect of Fibroblast Growth Factor (FGF) 19 and 21 on Hip Geometry and Strength in Post-menopausal Osteoporosis (PMO)

Fibroblast Growth Factor (FGF) receptor signalling is important for skeletal development. The FGF19 subfamily which includes FGF19 and FGF21 are involved in bone metabolism, although their effects on bone mineral density (BMD) and bone strength remain unclear. To further characterise the influence of these two factors on the skeleton, we studied the association between circulating concentrations of FGF19 and 21 with BMD and parameters of hip geometry and strength in post-menopausal osteoporosis (PMO). The study cohort consisted of 374 women aged (mean [SD]) 68.7[12.3] years with PMO. FGF19 and FGF21 were measured in serum by ELISA. BMD was measured at the lumbar spine (LS), total hip (TH) and femoral neck (FN) (n = 277) by dual energy X-ray absorptiometry (DXA) and hip structural analysis (HSA) parameters (n = 263) at the narrow neck of the femur (NN), Intertrochanter (IT) and Femoral shaft (FS) were derived from DXA scans. FGF19 and 21 were not associated with prevalent fractures or BMD when corrected for covariates; age, BMI, smoking habits and alcohol intake. Log-transformed FGF 21 was negatively associated with HSA parameters including Outer Diameter (OD) (p = 0.019), Cross-sectional area (CSA) (p = 0.01), cross-sectional moment of inertia (CSMI) (p = 0.011), Section modulus (Z) (p = 0.002) and cortical thickness (Co Th) (p = 0.026) at the IT only. CSA, CSMI, Z and Co Th were significantly lower (p < 0.05) in women with FGF21 concentrations greater than the median (> 103.5 pg/ml). Our data suggest that FGF 21 may have potentially adverse effects on the skeleton. Further characterisation is needed, particularly as FGF 21 analogues or agonists may be used to treat obesity-related metabolic disorders.

Aging insights from heterochronic parabiosis models

Heterochronic parabiosis consists of surgically connecting the circulatory systems of a young and an old animal. This technique serves as a model to study circulating factors that accelerate aging in young organisms exposed to old blood or induce rejuvenation in old organisms exposed to young blood. Despite the promising results, the exact cellular and molecular mechanisms remain unclear, so this study aims to explore and elucidate them in more detail.

Meat consumption and the risk of hip fracture in women and men: two prospective Swedish cohort studies

PURPOSE

To study the association between meat intake (predominantly red and processed meats) and the risk of hip fracture, as well as the association between meat intake and biomarkers of inflammation, oxidative stress, bone turnover, body composition, and bone mineral density (BMD).

METHODS

Data from the Swedish Mammography Cohort and the Cohort of Swedish men (n = 83,603, 54% men) with repeated investigations and their respective clinical sub-cohorts was utilised. Incident hip fractures were ascertained through individual linkage to registers. Associations were investigated using multivariable Cox and linear regression analyses.

RESULTS

During up to 23 years of follow-up (mean 18.2 years) and 1,538,627 person-years at risk, 7345 participants (2840 men) experienced a hip fracture. Each daily serving of meat intake conferred a hazard ratio (HR) of 1.03 (95% confidence interval [CI] 1.00; 1.06) for hip fracture. In quintile 5, compared to quintile 2, the HR was 1.11 (95% CI 1.01; 1.21) among all participants. In the sub-cohorts, meat intake was directly associated with circulating levels of interleukin-6, C-reactive protein, leptin, ferritin, parathyroid hormone, and calcium.

CONCLUSION

A modest linear association was found between a higher meat intake and the risk of hip fractures. Our results from the sub-cohorts further suggest that possible mechanisms linking meat intake and hip fracture risk may be related to the regulation of bone turnover, subclinical inflammation, and oxidative stress. Although estimates are modest, limiting red and processed meat intake in a healthy diet is advisable to prevent hip fractures.

Hyperuricemia remodels the serum proteome toward a higher inflammatory state

Gout is an autoinflammatory disease triggered by a complex innate immune response to MSU crystals and inflammatory triggers. While hyperuricemia is an obligatory risk factor for the development of gout, the majority of individuals with hyperuricemia never develop gout but have an increased risk of developing cardiometabolic disorders. Current management of gout aims at MSU crystal dissolution by lowering serum urate. We apply a targeted proteomic analysis, using Olink inflammation panel, to a large group of individuals with gout, asymptomatic hyperuricemia, and normouricemic controls, and we show a urate-driven inflammatory signature. We add in vivo evidence of persistent immune activation linked to urate exposure and describe immune pathways involved in the pathogenesis of gout. Our results support a pro-inflammatory effect of asymptomatic hyperuricemia and pave the way for new research into targetable mechanisms in gout and cardiometabolic complications of asymptomatic hyperuricemia.

Prediabetes and skeletal health

PURPOSE OF REVIEW

Type 2 diabetes mellitus (T2D) confers a greater risk of skeletal fragility and fracture. Whether prediabetes is detrimental to bone health is uncertain.

RECENT FINDINGS

We summarize the current data on the associations of prediabetes with bone turnover, bone mineral density, bone quality, bone material properties and fracture risk.

SUMMARY

In cross-sectional studies, prediabetes was associated with lower bone turnover and worse trabecular bone quality. A longitudinal analysis showed that larger increase in insulin resistance (in the absence of T2D) correlated with faster bone loss. Future research to examine the longitudinal associations of prediabetes with bone health parameters is warranted.

Fibroblast growth factor 21 in metabolic syndrome

Metabolic syndrome is a complex metabolic disorder that often clinically manifests as obesity, insulin resistance/diabetes, hyperlipidemia, and hypertension. With the development of social and economic systems, the incidence of metabolic syndrome is increasing, bringing a heavy medical burden. However, there is still a lack of effective prevention and treatment strategies. Fibroblast growth factor 21 (FGF21) is a member of the human FGF superfamily and is a key protein involved in the maintenance of metabolic homeostasis, including reducing fat mass and lowering hyperglycemia, insulin resistance and dyslipidemia. Here, we review the current regulatory mechanisms of FGF21, summarize its role in obesity, diabetes, hyperlipidemia, and hypertension, and discuss the possibility of FGF21 as a potential target for the treatment of metabolic syndrome.

The roles of hepatokine and osteokine in liver-bone crosstalk: Advance in basic and clinical aspects

Both the liver and bone are important secretory organs in the endocrine system. By secreting organ factors (hepatokines), the liver regulates the activity of other organs. Similarly, bone-derived factors, osteokines, are created during bone metabolism and act in an endocrine manner. Generally, the dysregulation of hepatokines is frequently accompanied by changes in bone mass, and osteokines can also disrupt liver metabolism. The crosstalk between the liver and bone, particularly the function and mechanism of hepatokines and osteokines, has increasingly gained notoriety as a topic of interest in recent years. Here, based on preclinical and clinical evidence, we summarize the potential roles of hepatokines and osteokines in liver-bone interaction, discuss the current shortcomings and contradictions, and make recommendations for future research.