Insulin-like growth factors: actions on the skeleton

Inflammatory protein levels in asthmatic bronchitis: A study in the Duhok population, Iraq

OBJECTIVES

This study aims to determine the levels of TNF-α, IGF-1, IL-6, and IL-10 protein in blood samples and their potential link to bronchitis-asthma diseases in the Iraq Duhok population, highlighting the prevalence of these long-term inflammatory diseases.

METHODS

Sixty blood samples were used and separated into patients (n = 43) and control (n = 17) groups. Serum samples were separated for each individual. Elisa method was used in terms of 4 different proteins investigated in blood samples with the manufacturer's instruction brand kits.

RESULTS

This study evaluated TNF-α, IGF-1, IL-6, and IL-10 protein levels in blood samples from asthmatic bronchitis patients in Duhok. Although these levels were elevated compared to controls, the differences were not statistically significant.

CONCLUSION

The differences thought to be related to the bronchitis-asthma diseases could not be demonstrated between the patient and control groups in Iraq Duhok population. Future research should explore larger sample sizes and stratified patient groups to identify potential biomarkers.

Association of rs35767 polymorphism in the IGF1 gene with athletic performance in power and endurance sports: A meta-analysis

BACKGROUND

Sport performance is a multifactorial phenotype dependent on the interaction of multiple genetic and non-genetic factors. More than 200 polymorphisms have been associated with athletic performance. The single nucleotide polymorphism (SNP) rs35767, located in the regulatory region of the IGF1 gene, influences its expression and has been associated with sports-related phenotypes. We aimed to perform a meta-analysis to evaluate the association between the rs35767 polymorphism of the IGF1 gene and athletic performance in power and endurance sports.

METHODS

Literature has been retrieved from PubMed, Web of Science, Scopus, Embase, and Sport Discus databases until October 2023. This study was designed according to the PRISMA statement. Different models were tested, and heterogeneity was evaluated.

RESULTS

Three studies were included in this meta-analysis. Statistically significant differences were highlighted for the frequency of the minor allele when comparing all athletes and controls (p < 0.001; OR = 1.74; 95 % CI = 1.26-2.40), endurance athletes and controls (p = 0.016; OR = 1.87; 95 % CI = 1.12-3.1) and power sport athletes and controls (p = 0.007; OR = 1.62; 95 % CI = 1.14-2.31). No statistically significant difference was found between the power and endurance groups. According to data analysis, the recessive model is the most suitable genetic model.

CONCLUSIONS

This metanalysis supports the role of the minor allele of the rs35767 polymorphism of the IGF1 gene as favoring an athlete's performance in endurance and power sports.

Levels of parathyroid hormone and IGF binding protein 1 and associations with mortality and hip fractures in older women

In this study we examined the effect of simultaneously elevated levels of parathyroid hormone (PTH) (≥ 65 ng/mL) and high levels of insulin-like growth factor-binding protein 1 (IGFBP-1) on the 10-year risk of all-cause mortality and hip fractures. Blood tests for levels of PTH and IGFBP-1 was collected at baseline in 338 community-dwelling women in Stockholm aged between 69 and 79 years. Data on hip fractures and all-cause mortality over the next 10 years were retrieved from healthcare registers. The participants were divided into four groups depending on their levels of PTH and IGFBP-1: (A) normal PTH and low IGFBP-1; (B) normal PTH and high IGFBP-1; (C) elevated PTH and low IGFBP-1; (D) elevated PTH and high IGFBP-1. Group D was used as reference. Cox proportional hazard regression (HR) model was used to compare age-adjusted association with hip fractures and all-cause mortality of the four groups. The group with elevated levels of PTH and high IGFBP-1 had a two to three times higher risk of all-cause mortality compared to the other groups but we found no association with hip fractures.

The Crosstalk Between Cartilage and Bone in Skeletal Growth

While the flat bones of the face, most of the cranial bones, and the clavicles are formed directly from sheets of undifferentiated mesenchymal cells, most bones in the human body are first formed as cartilage templates. Cartilage is subsequently replaced by bone via a very tightly regulated process termed endochondral ossification, which is led by chondrocytes of the growth plate (GP). This process requires continuous communication between chondrocytes and invading cell populations, including osteoblasts, osteoclasts, and vascular cells. A deeper understanding of these signaling pathways is crucial not only for normal skeletal growth and maturation but also for their potential relevance to pathophysiological processes in bones and joints. Due to limited information on the communication between chondrocytes and other cell types in developing bones, this review examines the current knowledge of how interactions between chondrocytes and bone-forming cells modulate bone growth.

Meclozine and growth hormone ameliorate bone length and quality in experimental models of achondroplasia

INTRODUCTION

Achondroplasia (ACH) is a common skeletal dysplasia associated with short-limbed short stature caused by gain-of-function mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Meclozine was found to inhibit FGFR3 signaling using a drug repositioning strategy. In some countries, growth hormone (GH) has been employed to ameliorate short stature in children with ACH. This study aims to investigate the effects of meclozine and GH on bone growth and quality using an experimental model of ACH.

MATERIALS AND METHODS

Meclozine (2 mg/kg/day) and/or GH (0.35 mg/kg/day) were administered to a mouse model of ACH from the age of 7 to 56 days. Body length and body weight of each mouse were measured during these treatments. At the end of treatments, these mice were subjected to micro-computed tomography scans to measure the lengths of long bones and bone mineral density (BMD). The width of the growth plate was quantified by histological analysis.

RESULTS

The body and bone length of transgenic mice significantly increased after treatment with meclozine and GH, although there was no additive effect of the combination therapy on promoting bone growth. In contrast, BMD was additively increased by the combination therapy. The width of the growth plate in transgenic mice was significantly increased by both treatments, although the hypertrophic zone was enlarged by meclozine but not by GH.

CONCLUSION

Meclozine or GH may be an option for treating children with ACH to ameliorate bone length and quality, but the additive effect would be limited.

Effects of Growth Hormone on Osteoarthritis Development

Osteoarthritis (OA), a chronic joint disease characterized by primary or secondary degeneration of articular cartilage and bone dysplasia, is associated with various risk factors and is the leading cause of musculoskeletal pain and disability, severely impacting the quality of life. Growth hormone (GH), secreted by the anterior pituitary gland, is essential in mediating the growth and development of bone and cartilage. Reportedly, osteoarthritis increases, and the growth hormone decreases with age. A negative correlation between GH and OA suggests that GH may be related to the occurrence and development of OA. Considering that abnormal growth hormone levels can lead to many diseases related to bone growth, we focus on the relationship between GH and OA. In this review, we will explain the effects of GH on the growth and deficiency of bone and cartilage based on the local pathological changes of osteoarthritis. In addition, the potential feasibility of treating OA with GH will be further explored and summarized.

MR Corge: sensitivity analysis of Mendelian randomization based on the core gene hypothesis for polygenic exposures

SUMMARY

Mendelian randomization is being utilized to assess causal effects of polygenic exposures, where many genetic instruments are subject to horizontal pleiotropy. Existing methods for detecting and correcting for horizontal pleiotropy have important assumptions that may not be fulfilled. Built upon the core gene hypothesis, we developed MR Corge for performing sensitivity analysis of Mendelian randomization. MR Corge identifies a small number of putative core instruments that are more likely to affect genes with a direct biological role in an exposure and obtains causal effect estimates based on these instruments, thereby reducing the risk of horizontal pleiotropy. Using positive and negative controls, we demonstrated that MR Corge estimates aligned with established biomedical knowledge and the results of randomized controlled trials. MR Corge may be widely applied to investigate polygenic exposure-outcome relationships.

AVAILABILITY AND IMPLEMENTATION

An open-sourced R package is available at https://github.com/zhwm/MRCorge.

Association between serum insulin-like growth factor-1 and bone mineral density in patients with type 2 diabetes

Background

Secondary osteoporosis is associated with type 2 diabetes mellitus (T2DM), and there is conflicting evidence regarding the relationship between insulin-like growth factor-1 (IGF-1) and bone mineral density (BMD) in different populations. The objective of this study was to investigate the relationship between serum IGF-1 levels and BMD in patients with T2DM.

Method

A retrospective cross-sectional study was performed on a cohort of 363 patients with T2DM, comprising men aged over 50 and women who are postmenopausal. Those with no significant medical history or medication affecting BMD or IGF-1 were considered. Data analyzed included IGF-1 levels, markers of bone metabolism, and measurements of BMD. To account for age and gender variations, we calculated IGF-1 standard deviation scores (IGF-1 SDS) for further investigation.

Results

A significant increase in BMD at lumbar spine (LS), femoral neck (FN), and total hip (TH) was observed as IGF-1 SDS tertiles rose. We revealed a nonlinear correlation between IGF-1 SDS and BMD at these sites, with a common inflection point identified at an IGF-1 SDS level of -1.68. Additionally, our multivariate piecewise linear regression analysis highlighted a positive association between IGF-1 SDS and BMD at LS, FN, and TH when IGF-1 SDS exceeded the inflection point (β 0.02, 95% CI 0.01, 0.04 for LS; β 0.02, 95% CI 0.01, 0.03 for FN; β 0.02, 95% CI 0.01, 0.03 for TH). Conversely, below the inflection point, this association was not significant (β -0.04, 95% CI -0.10, 0.01 for LS; β -0.04, 95% CI -0.08, 0.01 for FN; β -0.03, 95% CI -0.08, 0.01 for TH).

Conclusion

These findings reveal a nonlinear relationship between IGF-1 SDS and BMD in T2DM patients. Higher serum IGF-1 levels were connected to increased bone density only after surpassing a certain threshold.

IGF signaling pathway in bone and cartilage development, homeostasis, and disease

The skeleton plays a fundamental role in the maintenance of organ function and daily activities. The insulin-like growth factor (IGF) family is a group of polypeptide substances with a pronounced role in osteoblast differentiation, bone development, and metabolism. Disturbance of the IGFs and the IGF signaling pathway is inextricably linked with assorted developmental defects, growth irregularities, and jeopardized skeletal structure. Recent findings have illustrated the significance of the action of the IGF signaling pathway via growth factors and receptors and its interactions with dissimilar signaling pathways (Wnt/β-catenin, BMP, TGF-β, and Hh/PTH signaling pathways) in promoting the growth, survival, and differentiation of osteoblasts. IGF signaling also exhibits profound influences on cartilage and bone development and skeletal homeostasis via versatile cell-cell interactions in an autocrine, paracrine, and endocrine manner systemically and locally. Our review summarizes the role and regulatory function as well as a potentially integrated gene network of the IGF signaling pathway with other signaling pathways in bone and cartilage development and skeletal homeostasis, which in turn provides an enlightening insight into visualizing bright molecular targets to be eligible for designing effective drugs to handle bone diseases and maladies, such as osteoporosis, osteoarthritis, and dwarfism.

Complex ontogeny of sexual size dimorphism in a female-larger gecko: Implications of determinate growth for lizard body size and life-history evolution

Ectothermic vertebrates such as reptiles were assumed to be indeterminate growers, which means that there is no terminal point in time or size for growth in their lifetime. In recent years, evidence for the determinate nature of growth in lizards has accumulated, necessitating a re-examination of models of their ontogeny and evolution of sexual size dimorphism (SSD). In the female-larger gecko Paroedura vazimba, we monitored post-embryonic growth over a period of 15 months. After hatching, females grew faster than males but also reached their final body size, that is, closed growth of their vertebrae, earlier than males. The closure of bone growth in females correlates with the onset of reproductive maturation. We compared this pattern with the previously minutely studied, male-larger species Paroedura picta, where we documented determinate growth as well. We propose a model to explain the evolutionary switches in the direction of SSD in lizards based on bipotential effects of ovarian hormones on growth. In this model, male growth is assumed to require no male-specific growth modifier, such as sex-limited hormonal regulators, while growth is feminized by ovarian hormones in females. Low levels of ovarian hormones can promote bone growth, but high levels associated with maturation of the reproductive organs promote senescence of bone growth plates and thus cessation of bone growth. We suggest that models on growth, life-history and evolution of body size in many lizards should acknowledge their determinate nature of growth.

Animal board invited review: Dietary transition from animal to plant-derived foods: Are there risks to health?

Animal-derived foods (ADFs) are a very varied group of foods, but many are nutrient rich and contain higher quality protein than provided by plant-derived foods such that a simple replacement of ADF protein is likely to lead to a reduction in overall protein quality. In addition, many ADFs are richer in some nutrients than plant-based foods (e.g. Fe, Ca) and these often have a higher bioavailability. ADFs also provide nutrients that plants cannot supply (e.g. vitamin B12) and some provide beneficial health functionality (e.g. hypotensive) which is not explained by traditional nutrition. However, there remains a good health reason to increase the proportion of plant-derived food in many diets to increase the intake of dietary fibre which is often consumed at very sub-optimal levels. It seems logical that the increased plant-derived foods should replace the ADFs that have the least benefit, the greatest risk to health and the highest environmental impact. Processed meat fits these characteristics and should be an initial target for replacement with plant-based based protein-rich foods that additionally provide the necessary nutrients and have high-quality dietary fibre. Processed meat covers a wide range of products including several traditional foods (e.g. sausages) which will make decisions on food replacement challenging. There is therefore an urgent need for research to better define the relative health risks associated with the range of processed meat-based foods. The aim of this review is to examine the evidence on the benefits and risks of this dietary transition including the absolute necessity to consider initial nutrient status before the replacement of ADFs is considered.

Interplay Between Skeletal and Hematopoietic Cells in the Bone Marrow Microenvironment in Homeostasis and Aging

PURPOSE OF THE REVIEW

In this review, we discuss the most recent scientific advances on the reciprocal regulatory interactions between the skeletal and hematopoietic stem cell niche, focusing on immunomodulation and its interplay with the cell's mitochondrial function, and how this impacts osteoimmune health during aging and disease.

RECENT FINDINGS

Osteoimmunology investigates interactions between cells that make up the skeletal stem cell niche and immune system. Much work has investigated the complexity of the bone marrow microenvironment with respect to the skeletal and hematopoietic stem cells that regulate skeletal formation and immune health respectively. It has now become clear that these cellular components cooperate to maintain homeostasis and that dysfunction in their interaction can lead to aging and disease. Having a deeper, mechanistic appreciation for osteoimmune regulation will lead to better research perspective and therapeutics with the potential to improve the aging process, skeletal and hematologic regeneration, and disease targeting.

Skeletal consequences of preterm birth in pigs as a model for preterm infants

Preterm birth affects about 10% of all live births with many resultant health challenges, including metabolic bone disease of prematurity (MBDP), which is characterized by elevated alkaline phosphatase, suppressed phosphate, and deficient skeletal development. Because of the lack of an animal model, very little is known about bone structure, strength, and quality after preterm birth. This study investigated the utility of a pig model to replicate clinical features of preterm birth, including MBDP, and sought to determine if early postnatal administration of IGF-1 was an effective treatment. Preterm pigs, born by caesarean section at 90% gestation, were reared in intensive care facilities (respiratory, thermoregulatory, and nutritional support) and compared with sow-reared term pigs born vaginally. Preterm pigs were systemically treated with vehicle or IGF-1 (recombinant human IGF-1/BP-3, 2.25 mg/kg/d). Tissues were collected at postnatal days 1, 5, and 19 (the normal weaning period in pigs). Most bone-related outcomes were affected by preterm birth throughout the study period, whereas IGF-1 supplementation had almost no effect. By day 19, alkaline phosphatase was elevated, phosphate and calcium were reduced, and the bone resorption marker C-terminal crosslinks of type I collagen was elevated in preterm pigs compared to term pigs. Preterm pigs also had decrements in femoral cortical cross-sectional properties, consistent with reduced whole-bone strength. Thus, the preterm pig model replicates many features of preterm bone development in infants, including features of MBDP, and allows for direct interrogation of skeletal tissues, enhancing the field's ability to examine underlying mechanisms.

Estradiol-17β and bisphenol A affect growth and mineralization in early life stages of seabass

Natural and synthetic estrogens are contaminants present in aquatic ecosystems. They can have significant consequences on the estrogen-sensitive functions of organisms, including skeletal development and growth of vertebrate larvae. Synthetic polyphenols represent a group of environmental xenoestrogens capable of binding the receptors for the natural hormone estradiol-17β (E2). To better understand how (xeno-)estrogens can affect the skeleton in fish species with high ecological and commercial interest, 16 days post-hatch larvae of the seabass were experimentally exposed for 7 days to E2 and Bisphenol A (BPA), both used at the regulatory concentration of surface water quality (E2: 0.4 ng.L-1, BPA: 1.6 μg.L-1) or at a concentration 100 times higher. Skeletal mineralization levels were evaluated using Alizarin red staining, and expression of several genes playing key roles in growth, skeletogenesis and estrogen signaling pathways was assessed by qPCR. Our results show that E2 exerts an overall negative effect on skeletal mineralization at the environmental concentration of 0.4 ng.L-1, correlated with an increase in the expression of genes associated only with osteoblast bone cells. Both BPA exposures inhibited mineralization with less severe effects and modified bone homeostasis by regulating the expression of gene encoding osteoblasts and osteoclasts markers. Our results demonstrate that environmental E2 exposure inhibits larval growth and has an additional inhibitory effect on skeleton mineralization while both BPA exposures have marginal inhibitory effect on skeletal mineralization. All exposures have significant effects on transcriptional levels of genes involved in the skeletal development of seabass larvae.

Bone mineral density in adults growth hormone deficiency with different ages of onset: a real-world retrospective study

PURPOSE

Bone mineral density (BMD) impairment is one of the critical factors for long-term quality of life in adults growth hormone deficiency (AGHD). This study aims to investigate the annual changes in BMD in AGHD patients with different ages of onset and to identify predicting factors that influence BMD.

METHODS

AGHD patients (n = 160) with available data for 4 years follow-up from a major tertiary medical center in China were retrospectively included (110 [68.8%] childhood-onset, 119 [74.4%] male). BMD of the axial bone (including total hip, neck of femur, and L1-4) derived from dual X-ray absorptiometry and final height were investigated at the first visit, 12 months, 24 months, 36 months, and 48 months thereafter. Low BMD was defined as Z-score ≤ -2.

RESULTS

The prevalence of low BMD was 30.0% at baseline and 12.5% at 4 years of follow-up. The CO AGHD group presented a significantly lower BMD than the AO AGHD group at the baseline (P = 0.009). In contrast, the CO AGHD group had significantly greater median annual BMD change than the AO AGHD group (0.044 vs. -0.0003 g/cm2/year in L1-4, P < 0.001), indicating a significant difference in the overall BMD trend between CO and AO groups. Childhood-onset (odds ratio [OR] 0.326, P = 0.012), low serum testosterone (OR 0.847; P = 0.004) and FT4 (OR 0.595; P = 0.039) level were independent risk factors for BMD loss.

CONCLUSION

The annual changes of BMD show a different pattern in AGHD patients with varying ages of onset. Patients with CO AGHD have a lower bone mass, and in general, appropriate replacement therapy is necessary for long-term bone health in AGHD patients.

Comparative Analysis of Myokines and Bone Metabolism Markers in Prepubertal Vegetarian and Omnivorous Children

The role of bone and muscle as endocrine organs may be important contributing factors for children's growth and development. Myokines, secreted by muscle cells, play a role in regulating bone metabolism, either directly or indirectly. Conversely, markers of bone metabolism, reflecting the balance between bone formation and bone resorption, can also influence myokine secretion. This study investigated a panel of serum myokines and their relationships with bone metabolism markers in children following vegetarian and omnivorous diets. A cohort of sixty-eight healthy prepubertal children, comprising 44 vegetarians and 24 omnivores, participated in this study. Anthropometric measurements, dietary assessments, and biochemical analyses were conducted. To evaluate the serum concentrations of bone markers and myokines, an enzyme-linked immunosorbent assay (ELISA) was used. The studied children did not differ regarding their serum myokine levels, except for a higher concentration of decorin in the vegetarian group (p = 0.020). The vegetarians demonstrated distinct pattern of bone metabolism markers compared to the omnivores, with lower levels of N-terminal propeptide of type I procollagen (P1NP) (p = 0.001) and elevated levels of C-terminal telopeptide of type I collagen (CTX-I) (p = 0.018). Consequently, the P1NP/CTX-I ratio was significantly decreased in the vegetarians. The children following a vegetarian diet showed impaired bone metabolism with reduced bone formation and increased bone resorption. Higher levels of decorin, a myokine involved in collagen fibrillogenesis and essential for tissue structure and function, may suggest a potential compensatory mechanism contributing to maintaining bone homeostasis in vegetarians. The observed significant positive correlations between myostatin and bone metabolism markers, including P1NP and soluble receptor activator of nuclear factor kappa-B ligand (sRANKL), suggest an interplay between muscle and bone metabolism, potentially through the RANK/RANKL/OPG signaling pathway.

Growth factors that drive aggrecan synthesis in healthy articular cartilage. Role for transforming growth factor-β?

Introduction

Articular cartilage makes smooth movement possible and destruction of this tissue leads to loss of joint function. An important biomolecule that determines this function is the large aggregating proteoglycan of cartilage, aggrecan. Aggrecan has a relatively short half-life in cartilage and therefore continuous production of this molecule is essential.

Methods

In this narrative review we discuss what is the role of growth factors in driving the synthesis of aggrecan in articular cartilage. A literature search has been done using the search items; cartilage, aggrecan, explant, Transforming Growth factor-β (TGF-β), Insulin-like Growth Factor (IGF), Bone Morphogenetic Protein (BMP) and the generic term "growth factors". Focus has been on studies using healthy cartilage and models of cartilage regeneration have been excluded.

Results

In healthy adult articular cartilage IGF is the main factor that drives aggrecan synthesis and maintains adequate levels of production. BMP's and TGF-β have a very limited role but appear to be more important during chondrogenesis and cartilage development. The major role of TGF-β is not stimulation of aggrecan synthesis but maintenance of the differentiated articular cartilage chondrocyte phenotype.

Conclusion

TGF-β is a factor that is generally considered as an important factor in stimulating aggrecan synthesis in cartilage but its role in this might be very restrained in healthy, adult articular cartilage.

Post-natal muscle growth and protein turnover: a narrative review of current understanding

A model explaining the dietary-protein-driven post-natal skeletal muscle growth and protein turnover in the rat is updated, and the mechanisms involved are described, in this narrative review. Dietary protein controls both bone length and muscle growth, which are interrelated through mechanotransduction mechanisms with muscle growth induced both from stretching subsequent to bone length growth and from internal work against gravity. This induces satellite cell activation, myogenesis and remodelling of the extracellular matrix, establishing a growth capacity for myofibre length and cross-sectional area. Protein deposition within this capacity is enabled by adequate dietary protein and other key nutrients. After briefly reviewing the experimental animal origins of the growth model, key concepts and processes important for growth are reviewed. These include the growth in number and size of the myonuclear domain, satellite cell activity during post-natal development and the autocrine/paracrine action of IGF-1. Regulatory and signalling pathways reviewed include developmental mechanotransduction, signalling through the insulin/IGF-1-PI3K-Akt and the Ras-MAPK pathways in the myofibre and during mechanotransduction of satellite cells. Likely pathways activated by maximal-intensity muscle contractions are highlighted and the regulation of the capacity for protein synthesis in terms of ribosome assembly and the translational regulation of 5-TOPmRNA classes by mTORC1 and LARP1 are discussed. Evidence for and potential mechanisms by which volume limitation of muscle growth can occur which would limit protein deposition within the myofibre are reviewed. An understanding of how muscle growth is achieved allows better nutritional management of its growth in health and disease.

Diagnosis and therapeutic approach to bone health in patients with hypopituitarism

The results of many studies in recent years indicate a significant impact of pituitary function on bone health. The proper function of the pituitary gland has a significant impact on the growth of the skeleton and the appearance of sexual dimorphism. It is also responsible for achieving peak bone mass, which protects against the development of osteoporosis and fractures later in life. It is also liable for the proper remodeling of the skeleton, which is a physiological mechanism managing the proper mechanical resistance of bones and the possibility of its regeneration after injuries. Pituitary diseases causing hypofunction and deficiency of tropic hormones, and thus deficiency of key hormones of effector organs, have a negative impact on the skeleton, resulting in reduced bone mass and susceptibility to pathological fractures. The early appearance of pituitary dysfunction, i.e. in the pre-pubertal period, is responsible for failure to achieve peak bone mass, and thus the risk of developing osteoporosis in later years. This argues for the need for a thorough assessment of patients with hypopituitarism, not only in terms of metabolic disorders, but also in terms of bone disorders. Early and properly performed treatment may prevent patients from developing the bone complications that are so common in this pathology. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary disease.

Gut microbiota in regulation of childhood bone growth

Childhood stunting and wasting, or decreased linear and ponderal growth associated with undernutrition, continue to be a major global public health challenge. Although many of the current therapeutic and dietary interventions have significantly reduced childhood mortality caused by undernutrition, there remain great inefficacies in improving childhood stunting. Longitudinal bone growth in children is governed by different genetic, nutritional and other environmental factors acting systemically on the endocrine system and locally at the growth plate. Recent studies have shown that this intricate interplay between nutritional and hormonal regulation of the growth plate could involve the gut microbiota, highlighting the importance of a holistic approach in tackling childhood undernutrition. In this review, I focus on the mechanistic insights provided by these recent advances in gut microbiota research and discuss ongoing development of microbiota-based therapeutics in humans, which could be the missing link in solving undernutrition and childhood stunting.

Sex-based differences in growth-related IGF1 signaling in response to PAPP-A2 deficiency: comparative effects of rhGH, rhIGF1 and rhPAPP-A2 treatments

BACKGROUND

Children with pregnancy-associated plasma protein-A2 (PAPP-A2) mutations resulting in low levels of bioactive insulin-like growth factor-1 (IGF1) and progressive postnatal growth retardation have improved growth velocity and height following recombinant human (rh)IGF1 treatment. The present study aimed to evaluate whether Pappa2 deficiency and pharmacological manipulation of GH/IGF1 system are associated with sex-specific differences in growth-related signaling pathways.

METHODS

Plasma, hypothalamus, pituitary gland and liver of Pappa2ko/ko mice of both sexes, showing reduced skeletal growth, and liver of these mice treated with rhGH, rhIGF1 and rhPAPP-A2 from postnatal day (PND) 5 to PND35 were analyzed.

RESULTS

Reduced body and femur length of Pappa2ko/ko mice was associated with increases in: (1) components of IGF1 ternary complexes (IGF1, IGFBP5/Igfbp5, Igfbp3, Igfals) in plasma, hypothalamus and/or liver; and (2) key signaling regulators (phosphorylated PI3K, AKT, mTOR, GSK3β, ERK1/2 and AMPKα) in hypothalamus, pituitary gland and/or liver, with Pappa2ko/ko females having a more prominent effect. Compared to rhGH and rhIGF1, rhPAPP-A2 specifically induced: (1) increased body and femur length, and reduced plasma total IGF1 and IGFBP5 concentrations in Pappa2ko/ko females; and (2) increased Igf1 and Igf1r levels and decreased Ghr, Igfbp3 and Igfals levels in the liver of Pappa2ko/ko females. These changes were accompanied by lower phospho-STAT5, phospho-AKT and phospho-ERK2 levels and higher phospho-AMPK levels in the liver of Pappa2ko/ko females.

CONCLUSIONS

Sex-specific differences in IGF1 system and signaling pathways are associated with Pappa2 deficiency, pointing to rhPAPP-A2 as a promising drug to alleviate postnatal growth retardation underlying low IGF1 bioavailability in a female-specific manner.

Genomics comparisons of three chromosome-level mudskipper genome assemblies reveal molecular clues for water-to-land evolution and adaptation

INTRODUCTION

Mudskippers are a large group of amphibious fishes that have developed many morphological and physiological capacities to live on land. Genomics comparisons of chromosome-level genome assemblies of three representative mudskippers, Boleophthalmus pectinirostris (BP), Periophthalmus magnuspinnatus (PM) and P. modestus (PMO), may be able to provide novel insights into the water-to-land evolution and adaptation.

METHODS

Two chromosome-level genome assemblies for BP and PM were respectively sequenced by an integration of PacBio, Nanopore and Hi-C sequencing. A series of standard assembly and annotation pipelines were subsequently performed for both mudskippers. We also re-annotated the PMO genome, downloaded from NCBI, to obtain a redundancy-reduced annotation. Three-way comparative analyses of the three mudskipper genomes in a large scale were carried out to discover detailed genomic differences, such as different gene sizes, and potential chromosomal fission and fusion events. Comparisons of several representative gene families among the three amphibious mudskippers and some other teleosts were also performed to find some molecular clues for terrestrial adaptation.

RESULTS

We obtained two high-quality haplotype genome assemblies with 23 and 25 chromosomes for BP and PM respectively. We also found two specific chromosome fission events in PM. Ancestor chromosome analysis has discovered a common fusion event in mudskipper ancestor. This fusion was then retained in all the three mudskipper species. A loss of some SCPP (secretory calcium-binding phosphoprotein) genes were identified in the three mudskipper genomes, which could lead to reduction of scales for a part-time terrestrial residence. The loss of aanat1a gene, encoding an important enzyme (arylalkylamine N-acetyltransferase 1a, AANAT1a) for dopamine metabolism and melatonin biosynthesis, was confirmed in PM but not in PMO (as previously reported existence in BP), suggesting a better air vision of PM than both PMO and BP. Such a tiny variation within the genus Periophthalmus exemplifies to prove a step-by-step evolution for the mudskippers' water-to-land adaptation.

CONCLUSION

These high-quality mudskipper genome assemblies will become valuable genetic resources for in-depth discovery of genomic evolution for the terrestrial adaptation of amphibious fishes.

Locally Directed Recombinant Adeno- Associated Virus-Mediated IGF-1 Gene Therapy Enhances Osteochondral Repair and Counteracts Early Osteoarthritis In Vivo

BACKGROUND

Restoration of osteochondral defects is critical, because osteoarthritis (OA) can arise.

HYPOTHESIS

Overexpression of insulin-like growth factor 1 (IGF-1) via recombinant adeno-associated viral (rAAV) vectors (rAAV-IGF-1) would improve osteochondral repair and reduce parameters of early perifocal OA in sheep after 6 months in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Osteochondral defects were created in the femoral trochlea of adult sheep and treated with rAAV-IGF-1 or rAAV-lacZ (control) (24 defects in 6 knees per group). After 6 months in vivo, osteochondral repair and perifocal OA were assessed by well-established macroscopic, histological, and immunohistochemical scoring systems as well as biochemical and micro-computed tomography evaluations.

RESULTS

Application of rAAV-IGF-1 led to prolonged (6 months) IGF-1 overexpression without adverse effects, maintaining a significantly superior overall cartilage repair, together with significantly improved defect filling, extracellular matrix staining, cellular morphology, and surface architecture compared with rAAV-lacZ. Expression of type II collagen significantly increased and that of type I collagen significantly decreased. Subchondral bone repair and tidemark formation were significantly improved, and subchondral bone plate thickness and subarticular spongiosa mineral density returned to normal. The OA parameters of perifocal structure, cell cloning, and matrix staining were significantly better preserved upon rAAV-IGF-1 compared with rAAV-lacZ. Novel mechanistic associations between parameters of osteochondral repair and OA were identified.

CONCLUSION

Local rAAV-mediated IGF-1 overexpression enhanced osteochondral repair and ameliorated parameters of perifocal early OA.

CLINICAL RELEVANCE

IGF-1 gene therapy may be beneficial in repair of focal osteochondral defects and prevention of perifocal OA.

The mechanism of lncRNA MALAT1 targeting the miR-124-3p/IGF2BP1 axis to regulate osteogenic differentiation of periodontal ligament stem cells

OBJECTIVES

This study aimed to investigate the regulatory roles of lncRNA MALAT1, miR-124-3p, and IGF2BP1 in osteogenic differentiation of periodontal ligament stem cells (PDLSCs).

MATERIALS AND METHODS

We characterized PDLSCs by employing quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analyses to evaluate the expression of key osteogenic markers including ALPL, SPP1, and RUNX2. Manipulation of lncRNA MALAT1 and miR-124-3p expression levels was achieved through transfection techniques. In addition, early osteogenic differentiation was assessed via Alkaline phosphatase (ALP) staining, and mineral deposition was quantified using Alizarin Red S (ARS) staining. Cellular localization of lncRNA MALAT1 was determined through Fluorescence In Situ Hybridization (FISH). To elucidate the intricate regulatory network, we conducted dual-luciferase reporter assays to decipher the binding interactions between lncRNA MALAT1 and miR-124-3P as well as between miR-124-3P and IGF2BP1.

RESULTS

Overexpression of lncRNA MALAT1 robustly promoted osteogenesis in PDLSCs, while its knockdown significantly inhibited the process. We confirmed the direct interaction between miR-124-3p and lncRNA MALAT1, underscoring its role in impeding osteogenic differentiation. Notably, IGF2BP1 was identified as a direct binding partner of lncRNA MALAT1, highlighting its pivotal role within this intricate network. Moreover, we determined the optimal IGF2BP1 concentration (50 ng/ml) as a potent enhancer of osteogenesis, effectively countering the inhibition induced by si-MALAT1. Furthermore, in vivo experiments utilizing rat calvarial defects provided compelling evidence, solidifying lncRNA MALAT1's crucial role in bone formation.

CONCLUSIONS

Our study reveals the regulatory network involving lncRNA MALAT1, miR-124-3p, and IGF2BP1 in PDLSCs' osteogenic differentiation.

CLINICAL RELEVANCE

These findings enhance our understanding of lncRNA-mediated osteogenesis, offering potential therapeutic implications for periodontal tissue regeneration and the treatment of bone defects.

Developmental morphogens direct human induced pluripotent stem cells toward an annulus fibrosus-like cell phenotype

Introduction

Therapeutic interventions for intervertebral disc herniation remain scarce due to the inability of endogenous annulus fibrosus (AF) cells to respond to injury and drive tissue regeneration. Unlike other orthopedic tissues, such as cartilage, delivery of exogenous cells to the site of annular injury remains underdeveloped, largely due to a lack of an ideal cell source and the invasive nature of cell isolation. Human induced pluripotent stem cells (iPSCs) can be differentiated to specific cell fates using biochemical factors and are, therefore, an invaluable tool for cell therapy approaches. While differentiation protocols have been developed for cartilage and fibrous connective tissues (e.g., tendon), the signals that regulate the induction and differentiation of human iPSCs toward the AF fate remain unknown.

Methods

iPSC-derived sclerotome cells were treated with various combinations of developmental signals including transforming growth factor beta 3 (TGF-β3), connective tissue growth factor (CTGF), platelet derived growth factor BB (PDGF-BB), insulin-like growth factor 1 (IGF-1), or the Hedgehog pathway activator, Purmorphamine, and gene expression changes in major AF-associated ECM genes were assessed. The top performing combination treatments were further validated by using three distinct iPSC lines and by assessing the production of upregulated ECM proteins of interest. To conduct a broader analysis of the transcriptomic shifts elicited by each factor combination, and to compare genetic profiles of treated cells to mature human AF cells, a 96.96 Fluidigm gene expression array was applied, and principal component analysis was employed to identify the transcriptional signatures of each cell population and treatment group in comparison to native AF cells.

Results

TGF-β3, in combination with PDGF-BB, CTGF, or IGF-1, induced an upregulation of key AF ECM genes in iPSC-derived sclerotome cells. In particular, treatment with a combination of TGF-β3 with PDGF-BB for 14 days significantly increased gene expression of collagen II and aggrecan and increased protein deposition of collagen I and elastin compared to other treatment groups. Assessment of genes uniquely highly expressed by AF cells or SCL cells, respectively, revealed a shift toward the genetic profile of AF cells with the addition of TGF-β3 and PDGF-BB for 14 days.

Discussion

These findings represent an initial approach to guide human induced pluripotent stem cells toward an AF-like fate for cellular delivery strategies.

A comprehensive coding and microRNA transcriptome of vertebral bone in postlarvae and juveniles of Senegalese sole (Solea senegalensis)

Understanding vertebral bone development is essential to prevent skeletal malformations in farmed fish related to genetic and environmental factors. This is an important issue in Solea senegalensis, with special impact of spinal anomalies in postlarval and juvenile stages. Vertebral bone transcriptomics in farmed fish mainly comes from coding genes, and barely on miRNA expression. Here, we used RNA-seq of spinal samples to obtain the first comprehensive coding and miRNA transcriptomic repertoire for postlarval and juvenile vertebral bone, covering different vertebral phenotypes and egg-incubation temperatures related to skeleton health in S. senegalensis. Coding genes, miRNA and pathways regulating bone development and growth were identified. Differential transcriptomic profiles and suggestive mRNA-miRNA interactions were found between postlarvae and juveniles. Bone-related genes and functions were associated with the extracellular matrix, development and regulatory processes, calcium binding, retinol and lipid metabolism or response to stimulus, including those revealed by the miRNA targets related to signaling, cellular and metabolic processes, growth, cell proliferation and biological adhesion. Pathway enrichment associated with fish skeleton were identified when comparing postlarvae and juveniles: growth and bone development functions in postlarvae, while actin cytoskeleton, focal adhesion and proteasome related to bone remodeling in juveniles. The transcriptome data disclosed candidate coding and miRNA gene markers related to bone cell processes, references for functional studies of the anosteocytic bone of S. senegalensis. This study establishes a broad transcriptomic foundation to study healthy and anomalous spines under early thermal conditions across life-stages in S. senegalensis, and for comparative analysis of skeleton homeostasis and pathology in fish and vertebrates.

Targeting TRPV1 for Cancer Pain Relief: Can It Work?

Chronic intractable pain affects a large proportion of cancer patients, especially those with metastatic bone disease. Blocking sensory afferents for cancer pain relief represents an attractive alternative to opioids and other drugs acting in the CNS in that sensory nerve blockers are not addictive and do not affect the mental state of the patient. A distinct subpopulation of sensory afferents expresses the capsaicin receptor TRPV1. Intrathecal resiniferatoxin, an ultrapotent capsaicin analog, ablates TRPV1-expressing nerve endings exposed to the cerebrospinal fluid, resulting in permanent analgesia in women with cervical cancer metastasis to the pelvic bone. High-dose capsaicin patches are effective pain killers in patients with chemotherapy-induced peripheral neuropathic pain. However, large gaps remain in our knowledge since the mechanisms by which cancer activates TRPV1 are essentially unknown. Most important, it is not clear whether or not sensory denervation mediated by TRPV1 agonists affects cancer progression. In a murine model of breast cancer, capsaicin desensitization was reported to accelerate progression. By contrast, desensitization mediated by resiniferatoxin was found to block melanoma growth. These observations imply that TRPV1 blockade for pain relief may be indicated for some cancers and contraindicated for others. In this review, we explore the current state of this field and compare the analgesic potential of TRPV1 antagonism and sensory afferent desensitization in cancer patients.

Growth Hormone Treatment for Non-GHD Disorders: Excitement Tempered by Biology

The success of growth hormone (GH) replacement in children with classical GH deficiency has led to excitement that other causes of short stature may benefit similarly. However, clinical experience has shown less consistent and generally less dramatic effects on adult height, perhaps not surprising in light of increased understanding of GH and growth plate biology. Nonetheless, clinical demand for GH treatment continues to grow. Upon the 20th anniversary of the US Food and Drug Administration's approval of GH treatment for idiopathic short stature, this review will consider the factors underlying the expansion of GH treatment, the biological mechanisms of GH action, the non-GH-deficient uses of GH as a height-promoting agent, biological constraints to GH action, and future directions.

Mechanism and physical activities in bone-skeletal muscle crosstalk

Bone and skeletal muscle work in coordination to maintain the function of the musculoskeletal system, in which skeletal muscle contraction drives the movement of the bone lever system while bone provides insert sites for skeletal muscle through the bone-muscle junction. Existing evidence suggests that factors secreted by skeletal muscle and bone mediate the interaction between the two tissues. Herein, we focused on the relationship between skeletal muscle and bone and the underlying mechanism of the interaction. Exercise can promote bone strength and secrete osteocalcin and insulin-like growth factor I into the blood, thus improving muscle quality. In addition, exercise can also promote myostatin, interleukin-6, Irisin, and apelin in muscles to enter the blood so that they can act on bones to maintain the balance between bone absorption and bone formation. There is a special regulatory axis interleukin-6/osteocalcin between myokines and osteokines, which is mainly influenced by exercise. Therefore, we pay attention to the important factors in the bone-muscle intersection that are affected by exercise, which were found or their functions were expanded, which strengthened the connection between organs of the whole body, highlighting the importance of exercise and contributing to the diagnosis, prevention, and treatment of osteoporosis and sarcopenia in the clinic.

Correlation between the middle phalanx of the third finger skeletal maturation staging system and insulin-like growth factor-1 levels among Indian children - A 3-year longitudinal study

INTRODUCTION

Tracking insulin-like growth factor-1 (IGF-1) level alongside the middle phalanx of the third finger (MP3) staging modification could provide valuable insights into the relationship between hormonal factors and skeletal maturation during different stages of growth. Longitudinal studies indeed play a crucial role in understanding these complex relationships over time, allowing for a more comprehensive assessment of how IGF-1 might serve as a marker for pubertal growth stages.

METHODOLOGY

The present longitudinal prospective cohort study was done among 26 boys and 26 girls. For each child, once in every 6 months for 3 years, blood samples (to estimate IGF-1 level) and X-rays of the left hand middle finger were taken. DRG IGF-1 600 Human Enzyme-Linked Immunosorbent Assay kit was used for the quantitative measurement of IGF1 from serum. The MP3 stages of the middle phalanx of the middle finger were evaluated using a modified MP3 system. The collected data were subjected to suitable descriptive and inferential statistics.

RESULTS

The mean IGF1 levels were significantly higher in girls compared to boys across all the stages of MP3 skeletal maturity indicators. However, in both boys and girls, IGF-1 levels showed increasing trends from Stage F to H where it peaked and showed deceleration to Stage I (P < 0.05).

CONCLUSION

The observed increase in serum IGF-1 levels during pubertal stages, followed by a decline in late puberty, aligning with the stages of skeletal maturation, suggests a close relationship between hormonal changes and bone development.

Nutritional strategies to optimise musculoskeletal health for fall and fracture prevention: Looking beyond calcium, vitamin D and protein

Falls and osteoporotic fractures are a major public health problem, particularly among older adults. A third of individuals aged 65 years and over fall at least once each year, with up to 20 % of these resulting in serious injury, including fracture. In conjunction with regular exercise, the importance of diet for musculoskeletal health has largely focused upon calcium, vitamin D, and protein, particularly in the context of preventing falls and fractures. Whilst there is evidence for the benefits of these nutrients for musculoskeletal health, other aspects of the diet remain largely underexplored. For example, vegetables are rich sources of macro- and micronutrients that are essential for muscle function and bone health, which are key factors in the prevention of falls and fractures. Recent work has highlighted the importance of nutrients such as vegetable-derived nitrate and vitamin K1 in optimising muscle strength, physical function, and bone quality. In the context of dietary patterns, vegan/plant-based diets have recently gained popularity due to perceived health benefits, animal welfare, or to tackle climate change. The elimination and/or substitution of animal-based products for plant foods (without careful planning and/or expert dietary guidance) could, however, have long-term negative musculoskeletal consequences; a trend uncovered by recent evidence. Within the overarching theme of nutrition for fall and fracture prevention in older populations, the aim of this review is to (i) summarise the current evidence for calcium, vitamin D and protein; (ii) describe the importance of vegetables and selected nutrients, such as nitrate and vitamin K1, for muscle function and bone structural integrity; and (iii) highlight current evidence around different dietary patterns (e.g., plant-based, diet quality, data driven approaches) and their impact on musculoskeletal health.

Hypertrophic chondrocytes at the junction of musculoskeletal structures

Hypertrophic chondrocytes are found at unique locations at the junction of skeletal tissues, cartilage growth plate, articular cartilage, enthesis and intervertebral discs. Their role in the skeleton is best understood in the process of endochondral ossification in development and bone fracture healing. Chondrocyte hypertrophy occurs in degenerative conditions such as osteoarthritis. Thus, the role of hypertrophic chondrocytes in skeletal biology and pathology is context dependent. This review will focus on hypertrophic chondrocytes in endochondral ossification, in which they exist in a transient state, but acting as a central regulator of differentiation, mineralization, vascularization and conversion to bone. The amazing journey of a chondrocyte from being entrapped in the extracellular matrix environment to becoming proliferative then hypertrophic will be discussed. Recent studies on the dynamic changes and plasticity of hypertrophic chondrocytes have provided new insights into how we view these cells, not as terminally differentiated but as cells that can dedifferentiate to more progenitor-like cells in a transition to osteoblasts and adipocytes, as well as a source of skeletal stem and progenitor cells residing in the bone marrow. This will provide a foundation for studies of hypertrophic chondrocytes at other skeletal sites in development, tissue maintenance, pathology and therapy.

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

Insulin-like growth factors and aging: lessons from Laron syndrome

The growth hormone (GH)-insulin-like growth factor-1 (IGF1) signaling pathway emerged in recent years as a key determinant of aging and longevity. Disruption of this network in different animal species, including flies, nematodes and mouse, was consistently associated with an extended lifespan. Epidemiological analyses have shown that patients with Laron syndrome (LS), the best-characterized disease under the umbrella of the congenital IGF1 deficiencies, seem to be protected from cancer. While aging and cancer, as a rule, are considered diametrically opposite processes, modern lines of evidence reinforce the notion that aging and cancer might, as a matter of fact, be regarded as divergent manifestations of identical biochemical and cellular underlying processes. While the effect of individual mutations on lifespan and health span is very difficult to assess, genome-wide screenings identified a number of differentially represented aging- and longevity-associated genes in patients with LS. The present review summarizes recent data that emerged from comprehensive analyses of LS patients and portrays a number of previously unrecognized targets for GH-IGF1 action. Our article sheds light on complex aging and longevity processes, with a particular emphasis on the role of the GH-IGF1 network in these mechanisms.

Leptin and IGF-1 in Infancy Are Associated With Variants in DHCR7 and CYP2R1 That Relate With Type 1 Diabetes and 25OHD

CONTEXT

Vitamin D has been variably implicated in risk of developing type 1 diabetes based on cohorts of at-risk individuals. Emergent type 1 diabetes in childhood is putatively preceded by altered growth.

OBJECTIVE

We explored whether polymorphisms in vitamin D metabolism genes modify risk of type 1 diabetes via effects on growth in a prospective, population-based cohort of infants.

METHODS

The Cambridge Baby Growth Study enrolled newborns from Cambridgeshire, UK, for follow-up in infancy. In 612 infants, we genotyped single nucleotide polymorphisms in vitamin D metabolism genes that relate with type 1 diabetes: rs10741657 and rs12794714 in CYP2R1, rs12785878 in DHCR7, and rs10877012 in CYP27B1. Multivariate linear regression analyses tested associations between genotypes and anthropometric indices (weight, length, and skinfold thickness) or growth-related hormones (C-peptide, IGF-1, and leptin) in infancy.

RESULTS

Birth weight showed borderline associations with the diabetes risk-increasing alleles in CYP2R1, rs10741657 (β = -.11, P = .02) and rs12794714 (β = -.09, P = .04). The risk-increasing allele rs12794714 was also associated with higher IGF-1 levels at age 24 months (β = .30, P = .01). At age 3 months, the risk-increasing allele rs12785878 in DHCR7, known to negatively associate with 25-hydroxyvitamin D levels, showed a positive association with leptin levels (β = .23, P = .009), which was pronounced in girls (P = .004) vs boys (P = .7).

CONCLUSION

The vitamin D metabolism genes DHCR7 and CYP2R1 might influence infancy leptin and IGF-1 levels respectively. These findings open the possibility for a developmental role of vitamin D that is mediated by growth-related hormones with implications for the onset of type 1 diabetes autoimmunity.

Global and Conditional Disruption of the Igf-I Gene in Osteoblasts and/or Chondrocytes Unveils Epiphyseal and Metaphyseal Bone-Specific Effects of IGF-I in Bone

To evaluate the relative importance of IGF-I expression in various cell types for endochondral ossification, we quantified the trabecular bone at the secondary spongiosa and epiphysis of the distal femur in 8-12-week-old male mice with a global knockout of the Igf-I gene, as well as the conditional deletion of Igf-I in osteoblasts, chondrocytes, and osteoblasts/chondrocytes and their corresponding wild-type control littermates. The osteoblast-, chondrocyte-, and osteoblast/chondrocyte-specific Igf-I conditional knockout mice were generated by crossing Igf-I floxed mice with Cre transgenic mice in which Cre expression is under the control of either the Col1α2 or Col2α1 promoter. We found that the global disruption of Igf-I resulted in 80% and 70% reductions in bone size, defined as total volume, at the secondary spongiosa and epiphysis of the distal femur, respectively. The abrogation of Igf-I in Col1α2-producing osteoblasts but not Col2α1-producing chondrocytes decreased bone size by 25% at both the secondary spongiosa and epiphysis. In comparison, the deletion of the Igf-I globally or specifically in osteoblasts or chondrocytes reduced trabecular bone mass by 25%. In contrast, the universal deletion of Igf-I in all cells, but not the conditional disruption of Igf-I in osteoblasts and/or chondrocytes reduced trabecular bone mass in the epiphysis. The reduced trabecular bone mass at the secondary spongiosa in osteoblast- and/or chondrocyte-specific Igf-I conditional knockout mice is caused by the reduced trabecular number and increased trabecular separation. Immunohistochemistry studies found that the expression levels of chondrocyte (COL10, MMP13) and osteoblast (BSP) markers were less in the secondary spongiosa and the epiphyses in the global Igf-I deletion mice. Our data indicate that local and endocrine Igf-I act pleiotropically and in a cell type- and bone compartment-dependent manner in bone.

Characteristic amino acid residues in the growth hormone receptor gene on Mus minutoides underlying dwarfism

The African pygmy mouse ( Mus minutoides ) displays a dwarfism phenotype distinctive from closely related species. This study aimed to investigate the growth hormone receptor (Ghr) gene sequence in M. minutoides . We identified several amino acid variations, including the P469L mutation. Our findings suggest that this mutation affects Ghr protein functionality, decreasing Igf1 expression and contributing to the dwarfism observed in M. minutoides . Further studies utilizing genome editing technology are necessary to elucidate the mechanisms involved in mammalian body size determination.

The metabolic effects of resumption of a high fat diet after weight loss are sex dependent in mice

Dietary restriction is a frequent strategy for weight loss, but adherence is difficult and returning to poor dietary habits can result in more weight gain than that previously lost. How weight loss due to unrestricted intake of a healthy diet affects the response to resumption of poor dietary habits is less studied. Moreover, whether this response differs between the sexes and if the insulin-like growth factor (IGF) system, sex dependent and involved in metabolic control, participates is unknown. Mice received rodent chow (6% Kcal from fat) or a high-fat diet (HFD, 62% Kcal from fat) for 4 months, chow for 3 months plus 1 month of HFD, or HFD for 2 months, chow for 1 month then HFD for 1 month. Males and females gained weight on HFD and lost weight when returned to chow at different rates (p < 0.001), but weight gain after resumption of HFD intake was not affected by previous weight loss in either sex. Glucose metabolism was more affected by HFD, as well as the re-exposure to HFD after weight loss, in males. This was associated with increases in hypothalamic mRNA levels of IGF2 (p < 0.01) and IGF binding protein (IGFBP) 2 (p < 0.05), factors involved in glucose metabolism, again only in males. Likewise, IGF2 increased IGFBP2 mRNA levels only in hypothalamic astrocytes from males (p < 0.05). In conclusion, the metabolic responses to dietary changes were less severe and more delayed in females and the IGF system might be involved in some of the sex specific observations.

Muscle-Brain crosstalk in cognitive impairment

Sarcopenia is an age-related, involuntary loss of skeletal muscle mass and strength. Alzheimer's disease (AD) is the most common cause of dementia in elderly adults. To date, no effective cures for sarcopenia and AD are available. Physical and cognitive impairments are two major causes of disability in the elderly population, which severely decrease their quality of life and increase their economic burden. Clinically, sarcopenia is strongly associated with AD. However, the underlying factors for this association remain unknown. Mechanistic studies on muscle-brain crosstalk during cognitive impairment might shed light on new insights and novel therapeutic approaches for combating cognitive decline and AD. In this review, we summarize the latest studies emphasizing the association between sarcopenia and cognitive impairment. The underlying mechanisms involved in muscle-brain crosstalk and the potential implications of such crosstalk are discussed. Finally, future directions for drug development to improve age-related cognitive impairment and AD-related cognitive dysfunction are also explored.

Bone-Derived IGF-I Regulates Radial Bone Growth in Adult Male Mice

Insulin-like growth factor-I (IGF-I) levels, which are reduced by age, and cortical bone dimensions are major determinants of fracture risk in elderly subjects. Inactivation of liver-derived circulating IGF-I results in reduced periosteal bone expansion in young and older mice. In mice with lifelong depletion of IGF-I in osteoblast lineage cells, the long bones display reduced cortical bone width. However, it has not previously been investigated whether inducible inactivation of IGF-I locally in bone in adult/old mice affects the bone phenotype. Adult tamoxifen-inducible inactivation of IGF-I using a CAGG-CreER mouse model (inducible IGF-IKO mice) substantially reduced IGF-I expression in bone (-55%) but not in liver. Serum IGF-I and body weight were unchanged. We used this inducible mouse model to assess the effect of local IGF-I on the skeleton in adult male mice, avoiding confounding developmental effects. After tamoxifen-induced inactivation of the IGF-I gene at 9 months of age, the skeletal phenotype was determined at 14 months of age. Computed tomography analyses of tibia revealed that the mid-diaphyseal cortical periosteal and endosteal circumferences and calculated bone strength parameters were decreased in inducible IGF-IKO mice compared with controls. Furthermore, 3-point bending showed reduced tibia cortical bone stiffness in inducible IGF-IKO mice. In contrast, the tibia and vertebral trabecular bone volume fraction was unchanged. In conclusion, inactivation of IGF-I in cortical bone with unchanged liver-derived IGF-I in older male mice resulted in reduced radial growth of cortical bone. This suggests that not only circulating IGF-I but also locally derived IGF-I regulates the cortical bone phenotype in older mice.

Brain-derived extracellular vesicles promote bone-fat imbalance in Alzheimer's disease

Inadequate osteogenesis and excessive adipogenesis of bone marrow mesenchymal stem cells (BMSCs) are key factors in the pathogenesis of osteoporosis. Patients with Alzheimer's disease (AD) have a higher incidence of osteoporosis than healthy adults, but the underlying mechanism is not clear. Here, we show that brain-derived extracellular vesicles (EVs) from adult AD or wild-type mice can cross the blood-brain barrier to reach the distal bone tissue, while only AD brain-derived EVs (AD-B-EVs) significantly promote the shift of the BMSC differentiation fate from osteogenesis to adipogenesis and induce a bone-fat imbalance. MiR-483-5p is highly enriched in AD-B-EVs, brain tissues from AD mice, and plasma-derived EVs from AD patients. This miRNA mediates the anti-osteogenic, pro-adipogenic, and pro-osteoporotic effects of AD-B-EVs by inhibiting Igf2. This study identifies the role of B-EVs as a promoter of osteoporosis in AD by transferring miR-483-5p.

The role of insulin-like growth factor-1 in bone remodeling: A review

Insulin-like growth factor (IGF)-1 is a polypeptide hormone with vital biological functions in bone cells. The abnormal expression of IGF-1 has a serious effect on bone growth, particularly bone remodeling. Evidence from animal models and human disease suggested that both IGF-1 deficiency and excess cause changes in bone remodeling equilibrium, resulting in profound alterations in bone mass and development. Here, we first introduced the functions and mechanisms of the members of IGFs in bone. Subsequently, the critical role of IGF-1 in the process of bone remodeling were emphasized from the aspects of bone resorption and bone formation respectively. This review explains the mechanism of IGF-1 in maintaining bone mass and bone homeostasis to a certain extent and provides a theoretical basis for further research.

Low energy availability reduces bone mass and gonadal function in male mice

INTRODUCTION

In women, the female athlete triad, marked by low energy availability, functional hypothalamic amenorrhea and osteoporosis, is a recognized risk for stress fractures. Stress injuries also occur in men, but by contrast risks and mechanisms underlying them are less characterized.

MATERIALS AND METHODS

5 week-old wild-type male mice were fed ad libitum (ad) or subjected to 60% food restriction (FR) for five weeks. In both groups, some mice were allowed access to an exercise wheel in cages to allow voluntary wheel running (ex) and/or treated with active vitamin D analogues. Mice were sacrificed and analyzed at 10 weeks of age.

RESULT

Male FR mice exhibited significantly reduced testicle weight, serum testosterone levels and bone mass. Such bone losses in FR male mice were enhanced by exercise. Histological analysis revealed that both bone-resorbing and -forming activities were significantly reduced in FR or FR plus exercise (FR + ex) mice, mimicking a state of low bone turnover. Significantly reduced bone mass in FR or FR + ex male mice was significantly rescued by treatment with active vitamin D analogues, with significant restoration of osteoblastic activities. Serum levels of insulin-like growth factor I (IGF-I), which is critical for bone remodeling, were significantly lower in FR versus control male mice.

CONCLUSIONS

Low energy availability puts men at risk for stress injuries as well, and low energy availability is upstream of gonadal dysfunction and osteoporosis in males. Active vitamin D analogues could serve as therapeutic or preventive options for stress injuries in men.

Histologic Severity of Nonalcoholic Fatty Liver Disease Associates with Reduced Bone Mineral Density in Children

BACKGROUND

Lower whole body bone mineral density (BMD) has been reported in children with nonalcoholic fatty liver disease (NAFLD), but potential mediators remain uncertain.

AIMS

To assess BMD at multiple skeletal sites in children with confirmed NAFLD and controls with obesity, adjusting for known determinants of BMD, and examine potential mediators.

METHODS

We assessed age-, sex-, and race-specific, and height-adjusted BMD z-scores of whole body, lumbar spine, hip, femoral neck and forearm by dual-energy-x-ray absorptiometry in 79 children, 8-19 years old: 46 with biopsy-confirmed NAFLD [29 steatohepatitis (NASH)/17 fatty liver (NAFL)] and 33 controls without liver disease. We compared BMD z-scores by multivariable regression, adjusting for known BMD determinants and potential mediators (inflammatory and insulin resistance measures).

RESULTS

Unadjusted mean BMD z-scores in NAFLD were similar to controls, but significantly lower in NASH vs. NAFL at all sites. After covariate adjustment, mean forearm BMD z-score was higher in NAFL (β 0.60 ± SE 0.30, p < 0.05) and lower in NASH (β - 0.49 ± SE 0.26, p = 0.06) vs. controls (p = 0.002 for group), with similar trends at whole body and total hip; hs-CRP negatively associated with whole body and forearm BMD z-scores (p < 0.05), while visceral fat area negatively associated with femoral neck (p < 0.05). Only three children had clinically low whole body BMD z-scores (< - 2), one per group (control, NAFL and NASH).

CONCLUSIONS

NASH, but not NAFL, may be associated with increased risk of reduced BMD in children. Systemic inflammation, independent of body composition and load bearing, may mediate reduction in BMD in NASH.

Evaluating the local expression pattern of IGF-1R in tumor tissues and the circulating levels of IGF-1, IGFBP-1, and IGFBP-3 in the blood of patients with different primary bone tumors

Introduction

The present study tried to provide insights into the expression pattern and diagnostic significance of the IGF-1 axis main mediators in three main primary bone tumor types with different degrees of severity.

Methods

The real-time qRT-PCR (to analyze IGF-1R gene expression), the immunohistochemistry (to measure IGF-1R protein), and the ELISA assay (to assess the circulating level of IGF-1, IGFBP-1, and IGFBP-3) were applied to confirm this hypothesis. A total number of 180 bone tissues (90 tumors and 90 noncancerous adjacent tissues) and 120 blood samples drained from 90 patients with bone tumors and 30 healthy controls were enrolled in the study. The association of insulin-like growth factor (IGF)-1 axis expression pattern with the patient's clinical pathological characteristics and tumor aggressive features, the diagnostic and predictive values were assessed for all tumor groups.

Results

A significantly elevated level of IGF-1R gene and protein was detected in bone tumors compared to the noncancerous bone tissues that were prominent in osteosarcoma and Ewing sarcoma compared to the GCT group. The positive association of the IGF-1R gene and protein level with tumor grade, metastasis, and recurrence was detected in the osteosarcoma and Ewing sarcoma groups. The circulating level of IGF-1, IGFPB-1, and IGFBP-3 were increased in osteosarcoma and Ewing sarcoma and GCT groups that were correlated significantly to the tumor severity. The ability of the IGF-1 axis to discriminate between bone tumors also malignant and benign tumors was considerable.

Discussion

In summary, our data suggested that IGF-1R, IGF-1, IGFBP-1, and IGFBP-3 levels are associated with bone tumor malignancy, metastasis, and recurrence that might serve as biomarkers for osteosarcoma and Ewing sarcoma recurrence.

Bone marrow-derived IGF-1 orchestrates maintenance and regeneration of the adult skeleton

Insulin-like growth factor I (IGF-1) is a key regulator of tissue growth and development in response to growth hormone stimulation. In the skeletal system, IGF-1 derived from osteoblasts and chondrocytes are essential for normal bone development; however, whether bone marrow (BM)-resident cells provide distinct sources of IGF-1 in the adult skeleton remains elusive. Here, we show that BM stromal cells (BMSCs) and megakaryocytes/platelets (MKs/PLTs) express the highest levels of IGF-1 in adult long bones. Deletion of Igf1 from BMSCs by Lepr-Cre leads to decreased bone formation, impaired bone regeneration, and increased BM adipogenesis. Importantly, reduction of BMSC-derived IGF-1 contributes to fasting-induced marrow fat accumulation. In contrast, deletion of Igf1 from MKs/PLTs by Pf4-Cre leads to reduced bone formation and regeneration without affecting BM adipogenesis. To our surprise, MKs/PLTs are also an important source of systemic IGF-1. Platelet-rich plasma (PRP) from Pf4-Cre; Igf1^f/fmice showed compromised osteogenic potential both in vivo and in vitro, suggesting that MK/PLT-derived IGF-1 underlies the therapeutic effects of PRP. Taken together, this study identifies BMSCs and MKs/PLTs as two important sources of IGF-1 that coordinate to maintain and regenerate the adult skeleton, highlighting reciprocal regulation between the hematopoietic and skeletal systems.

A case-control study coupling with meta-analysis elaborates decisive association between IGF-1 rs35767 and osteoporosis in Asian postmenopausal females

BACKGROUND

Osteoporosis (OP) is prevalent in postmenopausal women. Several studies investigated the association between IGF-1 polymorphisms and OP among postmenopausal females with conflicting outcomes.

OBJECTIVE

To investigate whether the IGF-1 (rs35767, rs2288377, rs5742612) were associated with OP in postmenopausal females.

METHODS

In case-control study, 95 OP cases and 222 healthy controls were recruited between March 2015 and July 2019. OP was diagnosed based on WHO criteria for diagnosis of OP as T score of bone mineral density (BMD) ≤-2.5; normal, as T score of BMD ≥-1. IGF-1 SNPs were genotyped by iPLEX Gold SNP genotyping. To be solid, related studies from PubMed, Embase, Cochrane, Web of science, and previous meta-analysis up until November 2020, along with our case-control study, were incorporated into a meta-analysis with criteria of significance using odds ratios (ORs) with corresponding 95% confidence intervals (CI) to evaluate risk factor of SNPs on OP. TSA was used to estimate the sample sizes required to achieve a conclusion.

RESULTS

In dominant model of our case-control study, we found nonsignificant association of rs35767 [Adj-OR: 0.95 (95% CI: 0.56-1.60)], rs2288377 [Adj-OR: 1.15 (95% CI: 0.67-1.97)], and rs5742612 [Adj-OR: 1.07 (95% CI: 0.62-1.83)] with OP in postmenopausal females. However, integration of our case-control study and 3 published studies, rs35767 [OR: 1.24 (95% CI: 1.05-1.47)] showed a conclusively risk association with OP in postmenopausal females judged by TSA with 2267 Asians.

CONCLUSIONS

This study demonstrates a crucial sample to conclude that IGF-1 rs35767 is significantly associated with OP in postmenopausal women.

Factors associated with bone thickness: Comparison of the cranium and humerus

Cortical bone thickness is important for the mechanical function of bone. Ontogeny, aging, sex, body size, hormone levels, diet, behavior, and genetics potentially cause variations in postcranial cortical robusticity. However, the factors associated with cranial cortical robusticity remain poorly understood. Few studies have examined cortical robusticity in both cranial and postcranial bones jointly. In the present study, we used computed tomography (CT) images to measure cortical bone thicknesses in the cranial vault and humeral diaphysis. This study clearly showed that females have a greater cranial vault thickness and greater age-related increase in cranial vault thickness than males. We found an age-related increase in the full thickness of the temporal cranial vault and the width of the humeral diaphysis, as well as an age-related decrease in the cortical thickness of the frontal cranial vault and the cortical thickness of the humeral diaphysis, suggesting that the mechanisms of bone modeling in cranial and long bones are similar. A positive correlation between cortical indices in the cranial vault and humeral diaphysis also suggested that common factors affect cortical robusticity. We also examined the association of polymorphisms in the WNT16 and TNFSF11 genes with bone thickness. However, no significant associations were observed. The present study provides fundamental knowledge about similarities and differences in the mechanisms of bone modeling between cranial and postcranial bones.

Growth hormone treatment improves final height in children with X-linked hypophosphatemia

BACKGROUND/AIM

Despite optimal conventional treatment (oral phosphate supplements and active vitamin D analogs), about 40-50% of children with well-controlled X-linked hypophosphatemia (XLH) show linear growth failure, making them less likely to achieve an acceptable final height. Here, we studied the hypothesis that rhGH treatment improves final height in children with XLH and growth failure.

METHODS

Two cohorts of children with XLH were included in this retrospective longitudinal analysis: (1) a cohort treated with rhGH for short stature (n = 34) and (2) a cohort not treated with rhGH (n = 29). The mean duration of rhGH treatment was 4.4 ± 2.9 years. We collected the auxological parameters at various time points during follow-up until final height.

RESULTS

In rhGH-treated children, 2 years of rhGH therapy was associated with a significant increase in height from - 2.4 ± 0.9 to - 1.5 ± 0.7 SDS (p < 0.001). Their mean height at rhGH discontinuation was - 1.2 ± 0.9 SDS and at final height was - 1.3 ± 0.9 SDS corresponding to 165.5 ± 6.4 cm in boys and 155.5 ± 6.3 cm in girls. Notably, the two groups had similar final heights; i.e., the final height in children not treated with rhGH being - 1.2 ± 1.1 SDS (165.4 ± 6.8 cm in boys and 153.7 ± 7.8 cm in girls), p = 0.7.

CONCLUSION

Treatment with rhGH permits to improve final height in children with XLH and growth failure, despite optimal conventional treatment. We propose therefore that rhGH therapy could be considered as an option for short stature in the context of XLH.