The Role of Sphingolipid Metabolism in Bone Remodeling

Combining untargeted and targeted metabolomic profiling reveals principal differences between osteopenia, Osteoporosis and healthy controls

BACKGROUND

Osteopenia (ON) and osteoporosis (OP) are highly prevalent among postmenopausal women and poses a challenge for early diagnosis. Therefore, identifying reliable biomarkers for early prediction using metabolomics is critically important.

METHODS

Initially, non-targeted metabolomics was employed to identify differential metabolites in plasma samples from cohort 1, which included healthy controls (HC, n = 23), osteonecrosis (ON, n = 36), and osteoporosis (OP, n = 37). Subsequently, we performed targeted metabolomic validation of 37 amino acids and their derivatives in plasma samples from cohort 2, consisting of healthy controls (HC, n = 10), osteonecrosis (ON, n = 10), and osteoporosis (OP, n = 10).

RESULTS

The non-targeted metabolomic analysis revealed an increase in differential metabolites with the progression of the disease, showing abnormalities in lipid and organic acid metabolism in ON and OP patients. Several substances were found to correlate positively or negatively with bone mineral density (BMD), for example, N-undecanoylglycine, sphingomyelins, and phosphatidylinositols exhibited positive correlations with BMD, while acetic acid, phenylalanine, taurine, inosine, and pyruvic acid showed negative correlations with BMD. Subsequently, targeted validation of 37 amino acids and their metabolites revealed six amino acids related to ON and OP.

CONCLUSION

Significant metabolomic features were identified between HC and patients with ON/OP, with multiple metabolites correlating positively or negatively with BMD. Integrating both targeted and non-targeted metabolomic results suggests that lipid, organic acid, and amino acid metabolism may represent important metabolomic characteristics of patients with OP, offering new insights into the development of metabolomic applications in OP.

Role of sphingolipid metabolism signaling in a novel mouse model of renal osteodystrophy based on transcriptomic approach

BACKGROUND

Renal osteodystrophy (ROD) is a skeletal pathology associated with chronic kidney disease-mineral and bone disorder (CKD-MBD) that is characterized by aberrant bone mineralization and remodeling. ROD increases the risk of fracture and mortality in CKD patients. The underlying mechanisms of ROD remain elusive, partially due to the absence of an appropriate animal model. To address this gap, we established a stable mouse model of ROD using an optimized adenine-enriched diet and conducted exploratory analyses through ribonucleic acid sequencing (RNA-seq).

METHODS

Eight-week-old male C57BL/6J mice were randomly allocated into three groups: control group ( n = 5), adenine and high-phosphate (HP) diet group ( n = 20), and the optimized adenine-containing diet group ( n = 20) for 12 weeks. We assessed the skeletal characteristics of model mice through blood biochemistry, microcomputed tomography (micro-CT), and bone histomorphometry. RNA-seq was utilized to profile gene expression changes of ROD. We elucidated the functions of differentially expressed genes (DEGs) using gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and gene set enrichment analysis (GSEA). DEGs were validated via quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

By the fifth week, adenine followed by an HP diet induced rapid weight loss and high mortality rates in the mouse group, precluding further model development. Mice with optimized adenine diet-induced ROD displayed significant abnormalities in serum creatinine and blood urea nitrogen levels, accompanied by pronounced hyperparathyroidism and hyperphosphatemia. The femur bone mineral density (BMD) of the model mice was lower than that of control mice, with substantial bone loss and cortical porosity. ROD mice exhibited substantial bone turnover with an increase in osteoblast and osteoclast markers. Transcriptomic profiling revealed 1907 genes with upregulated expression and 723 genes with downregulated expression in the femurs of ROD mice relative to those of control mice. Pathway analyses indicated significant enrichment of upregulated genes in the sphingolipid metabolism pathway. The significant upregulation of alkaline ceramidase 1 ( Acer1 ), alkaline ceramidase 2 ( Acer2 ), prosaposin-like 1 ( Psapl1 ), adenosine A1 receptor ( Adora1 ), and sphingosine-1-phosphate receptor 5 ( S1pr5 ) were successfully validated in mouse femurs by qRT-PCR.

CONCLUSIONS

Optimized adenine diet mouse model may be a valuable proxy for studying ROD. RNA-seq analysis revealed that the sphingolipid metabolism pathway is likely a key player in ROD pathogenesis, thereby providing new avenues for therapeutic intervention.

Identifying Herbal Candidates and Active Ingredients Against Postmenopausal Osteoporosis Using Biased Random Walk on a Multiscale Network

Postmenopausal osteoporosis is a major global health concern, particularly affecting aging women, and necessitates innovative treatment options. Herbal medicine, with its multi-compound, multi-target characteristics, offers a promising approach for complex diseases. In this study, we applied multiscale network and random walk-based analyses to identify candidate herbs and their active ingredients for postmenopausal osteoporosis, focusing on their underlying mechanisms. A dataset of medicinal herbs, their active ingredients, and protein targets was compiled, and diffusion profiles were calculated to assess the propagation effects. Through correlation analysis, we prioritized herbs based on their relevance to osteoporosis, identifying the top candidates like Benincasae Semen, Glehniae Radix, Corydalis Tuber, and Houttuyniae Herba. Gene Set Enrichment Analysis (GSEA) revealed that the 49 core protein targets of these herbs were significantly associated with pathways related to inflammation, osteoclast differentiation, and estrogen metabolism. Notably, compounds such as falcarindiol from Glehniae Radix and tetrahydrocoptisine from Corydalis Tuber-previously unstudied for osteoporosis-were predicted to interact with inflammation-related proteins, including IL6, IL1B, and TNF, affecting key biological processes like apoptosis and cell proliferation. This study advances the understanding of herbal therapies for osteoporosis and offers a framework for discovering novel therapeutic agents.

Impact of ocean warming on early development of the Mediterranean mussel Mytilus galloprovincialis: Effects on larval susceptibility to potential vibrio pathogens

In a global change scenario, ocean warming and pathogen infection can occur simultaneously in coastal areas, threatening marine species. Data are shown on the impact of temperature on early larvae of the Mediterranean mussel Mytilus galloprovincialis. Increasing temperatures (18-20-22 °C) altered larval phenotypes at 48 hpf and affected gene expression from eggs to 24 and 48 hpf, with shell biogenesis related genes among the most affected. The effects of temperature on larval susceptibility to infection were evaluated using Vibrio coralliilyticus, a coral pathogen increasingly associated with bivalve mortalities, whose ecology is affected by global warming. Malformations and mortalities at 48 hpf were observed at higher temperature and vibrio concentrations, with interactive effects. In non-lethal conditions, interactions on gene expression at 24 and 48 hpf were also detected. Although temperature is the main environmental driver affecting M. galloprovincialis early larvae, warming may increase the susceptibility to vibrio infection, with consequences on mussel populations.

New insight into primary hyperparathyroidism using untargeted metabolomics

Primary Hyperparathyroidism (PHPT) is characterized by excessive parathormone (PTH) secretion and disrupted calcium homeostasis. Untargeted metabolomics offers a valuable approach to understanding the complex metabolic alterations associated with different diseases, including PHPT. Plasma untargeted metabolomics was applied to investigate the metabolic profiles of PHPT patients compared to a control group. Two complementary liquid-phase separation techniques were employed to comprehensively explore the metabolic landscape in this retrospective, single-center study. The study comprised 28 female patients diagnosed following the current guidelines of PHPT diagnosis and a group of 30 healthy females as a control group. To evaluate their association with PHPT, we identified changes in plasma metabolic profiles in patients with PHPT compared to the control group. The primary outcome measure included detecting plasma metabolites and discriminating PHPT patients from controls. The study unveiled specific metabolic imbalances that may link L-amino acids with peptic ulcer disease, gamma-glutamyls with oxidative stress, and asymmetric dimethylarginine (ADMA) with cardiovascular complications. Several metabolites, such as gamma-glutamyls, caffeine, sex hormones, carnitine, sphingosine-1-phosphate (S-1-P), and steroids, were connected with reduced bone mineral density (BMD). Metabolic profiling identified distinct metabolic patterns between patients with PHPT and healthy controls. These findings provided valuable insights into the pathophysiology of PHPT.

Sphingolipidomic profiling of human Dental Pulp Stem Cells undergoing osteogenic differentiation

It is now recognized that sphingolipids are involved in the regulation and pathophysiology of several cellular processes such as proliferation, migration, and survival. Growing evidence also implicates them in regulating the behaviour of stem cells, the use of which is increasingly finding application in regenerative medicine. A shotgun lipidomic study was undertaken to determine whether sphingolipid biomarkers exist that can regulate the proliferation and osteogenic differentiation of human Dental Pulp Stem Cells (hDPSCs). Sphingolipids were extracted and identified by direct infusion into an electrospray mass spectrometer. By using cells cultured in osteogenic medium and in medium free of osteogenic stimuli, as a control, we analyzed and compared the SPLs profiles. Both cellular systems were treated at different times (72 hours, 7 days, and 14 days) to highlight any changes in the sphingolipidomic profiles in the subsequent phases of the differentiation process. Signals from sphingolipid species demonstrating clear differences were selected, their relative abundance was determined, and statistical differences were analyzed. Thus, our work suggests a connection between sphingolipid metabolism and hDPSC osteogenic differentiation and provides new biomarkers for improving hDPSC-based orthopaedic regenerative medicine.

Acid sphingomyelinase deficiency and Gaucher disease in adults: Similarities and differences in two macrophage storage disorders

The lysosomal storage diseases chronic visceral acid sphingomyelinase deficiency (ASMD) and Gaucher disease type 1 (GD1) are both macrophage storage disorders with overlapping clinical manifestations. We compared cross-sectional data on visceral, hematological, and biochemical manifestations of untreated adult patients with chronic visceral ASMD (n = 19) and GD1 (n = 85). Spleen volume, liver volume, and bone marrow fat fraction did not significantly differ between the two disease groups (p >0.05 for all). Chitotriosidase activity was higher in GD1 (GD1: median 30 940 nmol/(mL.h), range 513-201 352, ASMD: median 1693 nmol/(mL.h), range 326-6620, p <0.001), whereas platelet levels were lower (GD1: median 102 109/L, range 16-726, ASMD: median 154 109/L, range 86-484, p <0.010), as were hemoglobin levels (GD1: median 7.8 mmol/L, range 5.0-10.4, ASMD: median 9.0 mmol/L, range 7.0-10.4, p <0.001). No bone complications were reported for ASMD, compared to 33% in GD1 (p <0.005). In ASMD pulmonary disease was more severe as evidenced by a median diffusion capacity of the lungs for carbon monoxide of 73% of predicted (range 26-104), compared to 85% (range 53-126) in GD1 (p = 0.029). In conclusion, bone complications, hematological abnormalities, chitotriosidase activity, and CCL18 levels were more prominent in GD1, while pulmonary manifestations were more common in AMSD. Different secondary pathophysiological processes surrounding sphingomyelin and glucosylceramide accumulation might explain these differences.

Lonicera japonica Fermented by Lactobacillus plantarum Improve Multiple Patterns Driven Osteoporosis

Osteoporosis (OP) represents a global health challenge. Certain functional food has the potential to mitigate OP. Honeysuckle (Lonicera japonica) solution has medicinal effects, such as anti-inflammatory and immune enhancement, and can be used in functional foods such as health drinks and functional snacks. The composition of honeysuckle changed significantly after fermentation, and 376 metabolites were enriched. In this study, we used dexamethasone to induce OP in the rat model. Research has confirmed the ability of FS (fermented Lonicera japonica solution) to enhance bone mineral density (BMD), repair bone microarchitectural damage, and increase blood calcium levels. Markers such as tartrate-resistant acid phosphatase-5b (TRACP-5b) and pro-inflammatory cytokines (TNF-α and IL-6) were notably decreased, whereas osteocalcin (OCN) levels increased after FS treatment. FS intervention in OP rats restored the abundance of 6 bacterial genera and the contents of 17 serum metabolites. The results of the Spearman correlation analysis showed that FS may alleviate OP by restoring the abundance of 6 bacterial genera and the contents of 17 serum metabolites, reducing osteoclast differentiation, promoting osteoblast differentiation, and reducing the inflammatory response. This study revealed that Lactobacillus plantarum-fermented honeysuckle alleviated OP through intestinal bacteria and serum metabolites and provided a theoretical basis for the development of related functional foods.

Lipidomics analysis of bone marrow in a mouse model of postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is a major public health problem worldwide, afflicting many postmenopausal women. Although many studies have focused on the biological role of individual lipids in osteoporosis, no studies have systematically elucidated the lipid profile of osteoporosis. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology based on multiple reaction monitoring (MRM) method was used to compare the levels of lipid molecules in bone marrow cells of osteoporotic mice (OVX) group and sham-operation (Sham) group. Principal component analysis (PCA) was used for multivariate statistics. Differential lipids were obtained by bar graph, heatmap and volcano map. A total of 400 lipid molecules were identified. A total of 199 lipid molecules were identified to be associated with PMOP, including 6 phospholipids and 3 sphingolipids. These differential lipid molecules provide a systematic lipid profile for osteoporosis, which helps to discover new candidate osteoporosis biomarkers, and their changes at the molecular level can be used as new targets for diagnosis or prevention.

The bone marrow lipidomics of mice reveal sex-related differences

Osteoporosis is a common skeletal disorder characterized by an imbalance between bone resorption and formation, exhibiting a higher prevalence in women compared with men. While previous studies have primarily focused on genomics and genetics in osteoporosis susceptibility, there is a lack of systematic exploration of sex-specific differences in lipid levels in mouse bone marrow. Multiple reaction monitoring-based liquid chromatography-trandem mass spectrometry (LC-MS/MS) was used to quantify lipidomic profiles in bone marrow samples from three female mice and three male mice. The LC-MS/MS technique based on the multiple reaction monitoring method identified and quantified 184 lipids from 15 lipid classes. The contents of most lipids in the bone marrow cells of female mice were higher than those in male mice, including four polyunsaturated fatty acids, three phospholipids and four sphingolipids. Among all the lipid molecules, lactosylceramide (d18:0/16:0) showed the highest fold change in female mice, while its precursor lipid, glucosylceramide, was the most up-regulated in male mice. This study, focusing on bone marrow lipidomics, elucidates significant sexual dimorphism in lipid levels within bone marrow cells. It provides novel evidence supporting the higher prevalence of osteoporosis in women and enhances our understanding of the connection between sex-specific lipid levels and the risk of osteoporosis.

The Species Effect: Differential Sphingosine-1-Phosphate Responses in the Bone in Human Versus Mouse

The deterioration of osteoblast-led bone formation and the upregulation of osteoclast-regulated bone resorption are the primary causes of bone diseases, including osteoporosis. Numerous circulating factors play a role in bone homeostasis by regulating osteoblast and osteoclast activity, including the sphingolipid-sphingosine-1-phosphate (S1P). However, to date no comprehensive studies have investigated the impact of S1P activity on human and murine osteoblasts and osteoclasts. We observed species-specific responses to S1P in both osteoblasts and osteoclasts, where S1P stimulated human osteoblast mineralisation and reduced human pre-osteoclast differentiation and mineral resorption, thereby favouring bone formation. The opposite was true for murine osteoblasts and osteoclasts, resulting in more mineral resorption and less mineral deposition. Species-specific differences in osteoblast responses to S1P were potentially explained by differential expression of S1P receptor 1. By contrast, human and murine osteoclasts expressed comparable levels of S1P receptors but showed differential expression patterns of the two sphingosine kinase enzymes responsible for S1P production. Ultimately, we reveal that murine models may not accurately represent how human bone cells will respond to S1P, and thus are not a suitable model for exploring S1P physiology or potential therapeutic agents.

Simulated lunar microgravity transiently arrests growth and induces osteocyte-chondrocyte lineage differentiation in human Wharton's jelly stem cells

Human Wharton's jelly stem cells (hWJSCs) are multipotent stem cells that are extensively employed in biotechnology applications. However, the impact of simulated lunar microgravity (sμG) on the growth, differentiation, and viability of this cell population is incompletely characterized. We aimed to determine whether acute (72 h) exposure to sμG elicited changes in growth and lineage differentiation in hWJSCs and if putative changes were maintained once exposure to terrestrial gravity (1.0 G) was restored. hWJSCs were cultured under standard 1.0 G conditions prior to being passaged and cultured under sμG (0.16 G) using a random positioning machine. Relative to control, hWJSCs cultured under sμG exhibited marked reductions in growth but not viability. Cell population expression of characteristic stemness markers (CD 73, 90, 105) was significantly reduced under sμG conditions. hWJSCs had 308 significantly upregulated and 328 significantly downregulated genes when compared to 1.0 G culture conditions. Key markers of cell replication, including MKI67, were inhibited. Significant upregulation of osteocyte-chondrocyte lineage markers, including SERPINI1, MSX2, TFPI2, BMP6, COMP, TMEM119, LUM, HGF, CHI3L1 and SPP1, and downregulation of cell fate regulators, including DNMT1 and EZH2, were detected in sμG-exposed hWJSCs. When returned to 1.0 G for 3 days, sμG-exposed hWJSCs had accelerated growth, and expression of stemness markers increased, approaching normal (i.e. 95%) levels. Our data support earlier findings that acute sμG significantly reduces the cell division potential of hWJSCs and suggest that acute sμG-exposure induces reversible changes in cell growth accompanied by osteocyte-chondrocyte changes in lineage differentiation.

Sphingolipid-Induced Bone Regulation and Its Emerging Role in Dysfunction Due to Disease and Infection

The human skeleton is a metabolically active system that is constantly regenerating via the tightly regulated and highly coordinated processes of bone resorption and formation. Emerging evidence reveals fascinating new insights into the role of sphingolipids, including sphingomyelin, sphingosine, ceramide, and sphingosine-1-phosphate, in bone homeostasis. Sphingolipids are a major class of highly bioactive lipids able to activate distinct protein targets including, lipases, phosphatases, and kinases, thereby conferring distinct cellular functions beyond energy metabolism. Lipids are known to contribute to the progression of chronic inflammation, and notably, an increase in bone marrow adiposity parallel to elevated bone loss is observed in most pathological bone conditions, including aging, rheumatoid arthritis, osteoarthritis, and osteomyelitis. Of the numerous classes of lipids that form, sphingolipids are considered among the most deleterious. This review highlights the important primary role of sphingolipids in bone homeostasis and how dysregulation of these bioactive metabolites appears central to many chronic bone-related diseases. Further, their contribution to the invasion, virulence, and colonization of both viral and bacterial host cell infections is also discussed. Many unmet clinical needs remain, and data to date suggest the future use of sphingolipid-targeted therapy to regulate bone dysfunction due to a variety of diseases or infection are highly promising. However, deciphering the biochemical and molecular mechanisms of this diverse and extremely complex sphingolipidome, both in terms of bone health and disease, is considered the next frontier in the field.

The Interplay of Lipid Signaling in Musculoskeletal Cross Talk: Implications for Health and Disease

The intricate interplay between the muscle and bone tissues is a fundamental aspect of musculoskeletal physiology. Over the past decades, emerging research has highlighted the pivotal role of lipid signaling in mediating communication between these tissues. This chapter delves into the multifaceted mechanisms through which lipids, particularly phospholipids, sphingolipids, and eicosanoids, participate in orchestrating cellular responses and metabolic pathways in both muscle and bone. Additionally, we examine the clinical implications of disrupted lipid signaling in musculoskeletal disorders, offering insights into potential therapeutic avenues. This chapter aims to shed light on the complex lipid-driven interactions between the muscle and bone tissues, paving the way for a deeper understanding of musculoskeletal health and disease.

Evaluation of Current Studies to Elucidate Processes in Dental Follicle Cells Driving Osteogenic Differentiation

When research on osteogenic differentiation in dental follicle cells (DFCs) began, projects focused on bone morphogenetic protein (BMP) signaling. The BMP pathway induces the transcription factor DLX3, whichh in turn induces the BMP signaling pathway via a positive feedback mechanism. However, this BMP2/DLX3 signaling pathway only seems to support the early phase of osteogenic differentiation, since simultaneous induction of BMP2 or DLX3 does not further promote differentiation. Recent data showed that inhibition of classical protein kinase C (PKCs) supports the mineralization of DFCs and that osteogenic differentiation is sensitive to changes in signaling pathways, such as protein kinase B (PKB), also known as AKT. Small changes in the lipidome seem to confirm the participation of AKT and PKC in osteogenic differentiation. In addition, metabolic processes, such as fatty acid biosynthesis, oxidative phosphorylation, or glycolysis, are essential for the osteogenic differentiation of DFCs. This review article attempts not only to bring the various factors into a coherent picture of osteogenic differentiation in DFCs, but also to relate them to recent developments in other types of osteogenic progenitor cells.

Mediating role of host metabolites in strontium's effect on osteoporosis among older individuals: Findings from Wuhan, China

Strontium is receiving widespread attention due to its remarkable biological qualities in preventing bone resorption and fostering osteogenesis. However, the chemical processes behind strontium's dual activities on bone cells are not yet fully understood. This study used the metabolomic technique to identify and examine potential biomarkers between strontium exposure and osteoporosis (OP) risk. A total of 806 participants were recruited for the detection of plasma strontium content via inductively coupled plasma-mass spectrometry. Plasma metabolites were profiled in 254 participants through an untargeted metabolomics technique. Generalized linear models were primarily used to analyze associations among plasma strontium, metabolites, and OP. The mediating effects of metabolites on the strontium-OP association were further investigated. A total of 31 differential metabolites were observed, 10 of which were upregulated and 21 were downregulated in the OP group compared with the non-OP group. Five metabolites (3-phenoxybenzoic acid, Cer (t18:0/16:1), HexCer(t16:1/12:1(2OH)), HexCer(t14:2/18:1(2OH)), and TG(16:0-18:1-24:4)) were selected as potential mediators based on their significant association with OP risk and with femoral neck and lumbar spine bone mineral density (BMD). Moreover, all except TG(16:0-18:1-24:4) were involved in the OP discrimination model with excellent power combined with several traditional variables. 3-Phenoxybenzoic acid and Cer(t18:0/16:1) had significant indirect effects on the strontium-OP association. The five candidate metabolites mediated 83.79 % of the strontium-OP association. Plasma strontium level was associated with reduced OP risk in the Han population in Wuhan. Thus, plasma metabolite profiling revealed five BMD/OP-associated metabolites that acted as mediators in the strontium-OP association. Our findings provided evidence of the mediating role of host plasma metabolites in strontium's effect on OP pathology.

The biocide triclosan as a potential developmental disruptor in Mytilus early larvae

The broadly utilized biocide triclosan (TCS) is continuously discharged in water compartments worldwide, where it is detected at concentrations of ng-µg/L. Given its lipophilicity and bioaccumulation, TCS is considered potentially harmful to human and environmental health and also as a potential endocrine disruptor (ED) in different species. In aquatic organisms, TCS can induce a variety of effects: however, little information is available on its possible impact on invertebrate development. Early larval stages of the marine bivalve Mytilus galloprovincialis have been shown to be sensitive to environmental concentrations of a number of emerging contaminants, including EDs. In this work, the effects of TCS were first evaluated in the 48 h larval assay in a wide concentration range (0.001-1,000 μg/L). TCS significantly affected normal development of D-veligers (LOEC = 0.1 μg/L; EC50 = 236.1 μg/L). At selected concentrations, the mechanism of action of TCS was investigated. TCS modulated transcription of different genes involved in shell mineralization, endocrine signaling, ceramide metabolism, and biotransformation, depending on larval stage (24 and 48 h post-fertilization-hpf) and concentration (1 and 10 μg/L). At 48 hpf and 10 μg/L TCS, calcein staining revealed alterations in CaCO3 deposition, and polarized light microscopy showed the absence of shell birefringence due to the mineralized phase. Observations by scanning electron microscopy highlighted a variety of defects in shell formation from concentrations as low as 0.1 μg/L. The results indicate that TCS, at environmental exposure levels, can act as a developmental disruptor in early mussel larvae mainly by interfering with the processes of biomineralization.

Transcriptome changes during osteogenesis of porcine mesenchymal stem cells derived from different types of synovial membranes and genetic background

Synovial membrane mesenchymal stem cells (SMSCs) often serve as in vitro model for bone disease, but the molecular mechanisms driving osteogenesis in SMSCs from different donor cells of various sources and breeds remain unclear. In this study, porcine SMSCs isolated from adipose synovium (FP) and fibrous synovium (FS) of Angeln Saddleback (AS) and German Landrace (DL) were used to discover the signaling network change after osteogenic induction. During osteogenic differentiation, mineral deposition was first observed at day 14 and further increased until day 21. Transcriptional changes between day 1 and day 21 were enriched in several signaling pathways, including Wnt, PI3K-Akt, and TGF-beta pathway. Certain pathways related to osteogenesis, including osteoblast differentiation, regulation of bone mineralization, and BMP signaling pathway, were enriched at late time points, as confirmed by the osteogenic markers ALPL, COL1A1, and NANOG. A fraction of differentially expressed genes (DEGs) were found between FP and FS, while DEGs between AS and DL increased during the differentiation phase until day 7 and then decreased from day 14 to day 21. These genes are involved in several important signaling pathways, including TGF-beta, Wnt, and lipid-related signaling pathways, suggesting that SMSCs from these two breeds have different osteogenic capabilities.

The Ying and Yang of Sphingosine-1-Phosphate Signalling within the Bone

Bone remodelling is a highly active and dynamic process that involves the tight regulation of osteoblasts, osteoclasts, and their progenitors to allow for a balance of bone resorption and formation to be maintained. Ageing and inflammation are risk factors for the dysregulation of bone remodelling. Once the balance between bone formation and resorption is lost, bone mass becomes compromised, resulting in disorders such as osteoporosis and Paget's disease. Key molecules in the sphingosine-1-phosphate signalling pathway have been identified for their role in regulating bone remodelling, in addition to its more recognised role in inflammatory responses. This review discusses the accumulating evidence for the different, and, in certain circumstances, opposing, roles of S1P in bone homeostasis and disease, including osteoporosis, Paget's disease, and inflammatory bone loss. Specifically, we describe the current, often conflicting, evidence surrounding S1P function in osteoblasts, osteoclasts, and their precursors in health and disease, concluding that S1P may be an effective biomarker of bone disease and also an attractive therapeutic target for disease.

Developmental programming: Preconceptional and gestational exposure of sheep to a real-life environmental chemical mixture alters maternal metabolome in a fetal sex-specific manner

BACKGROUND

Everyday, humans are exposed to a mixture of environmental chemicals some of which have endocrine and/or metabolism disrupting actions which may contribute to non-communicable diseases. The adverse health impacts of real-world chemical exposure, characterized by chronic low doses of a mixture of chemicals, are only recently emerging. Biosolids derived from human waste represent the environmental chemical mixtures humans are exposed to in real life. Prior studies in sheep have shown aberrant reproductive and metabolic phenotypes in offspring after maternal biosolids exposure.

OBJECTIVE

To determine if exposure to biosolids perturbs the maternal metabolic milieu of pregnant ewes, in a fetal sex-specific manner.

METHODS

Ewes were grazed on inorganic fertilizer (Control) or biosolids-treated pastures (BTP) from before mating and throughout gestation. Plasma from pregnant ewes (Control n = 15, BTP n = 15) obtained mid-gestation were analyzed by untargeted metabolomics. Metabolites were identified using Agilent MassHunter. Multivariate analyses were done using MetaboAnalyst 5.0 and confirmed using SIMCA.

RESULTS

Univariate and multivariate analysis of 2301 annotated metabolites identified 193 differentially abundant metabolites (DM) between control and BTP sheep. The DM primarily belonged to the super-class of lipids and organic acids. 15-HeTrE, oleamide, methionine, CAR(3:0(OH)) and pyroglutamic acid were the top DM and have been implicated in the regulation of fetal growth and development. Fetal sex further exacerbated differences in metabolite profiles in the BTP group. The organic acids class of metabolites was abundant in animals with male fetuses. Prenol lipid, sphingolipid, glycerolipid, alkaloid, polyketide and benzenoid classes showed fetal sex-specific responses to biosolids.

DISCUSSION

Our study illustrates that exposure to biosolids significantly alters the maternal metabolome in a fetal sex-specific manner. The altered metabolite profile indicates perturbations to fatty acid, arginine, branched chain amino acid and one‑carbon metabolism. These factors are consistent with, and likely contribute to, the adverse phenotypic outcomes reported in the offspring.

The interaction of CD300lf and ceramide reduces the development of periodontitis by inhibiting osteoclast differentiation

AIM

The regulation of osteoclasts (OCs) by inhibitory immunoreceptors maintains bone homeostasis and is considered an important determinant of the extent of periodontal pathology. The aim of this study was to investigate the role of the inhibitory immunoreceptor CD300lf and its ligand ceramide in osteoclastogenesis in periodontitis.

MATERIALS AND METHODS

The expression of CD300lf was measured in vitro and in a ligature-induced periodontitis model. The effect of CD300lf ablation on osteoclastogenesis was examined in ligature-retained and ligature removal periodontitis models. The effect of ceramide, the ligand of CD300lf, was examined in osteoclastogenesis in vitro and in vivo by smearing 20 μg of ceramide dissolved in carboxymethylcellulose on teeth and gingiva every other day in an experimental periodontitis model and ligature removal model.

RESULTS

CD300lf expression was downregulated during osteoclastogenesis. Ablation of CD300lf in the ligature-induced periodontitis model increased the number of OCs and exacerbated bone damage. Bone resorption caused by CD300lf ablation was reversible following ligature removal. CD300lf-ceramide binding suppressed osteoclastogenesis in vitro and inhibited alveolar bone loss in a mouse periodontitis model.

CONCLUSIONS

Our findings reveal that CD300lf-ceramide binding plays a critical negative role in alveolar bone loss in periodontitis by inhibiting OCs differentiation.

Role of sphingolipid metabolites in the homeostasis of steroid hormones and the maintenance of testicular functions

With the acceleration of life pace and the increase of work pressure, the problem of male infertility has become a social problem of general concern. Sphingolipids are important regulators of many cellular processes like cell differentiation and apoptosis, which are ubiquitously expressed in all mammalian cells. Various sphingolipid catabolic enzymes can generate multiple sphingolipids like sphingosine-1-phosphate and sphingomyelin. Present studies have already demonstrated the role of steroid hormones in the physiological processes of reproduction and development through hypothalamus-pituitary-gonad axis, while recent researches also found not only sphingolipids can modulate steroid hormone secretion, but also steroid hormones can control sphingolipid metabolites, indicating the role of sphingolipid metabolites in the homeostasis of steroid hormones. Furthermore, sphingolipid metabolites not only contribute to the regulation of gametogenesis, but also mediate damage-induced germ apoptosis, implying the role of sphingolipid metabolites in the maintenance of testicular functions. Together, sphingolipid metabolites are involved in impaired gonadal function and infertility in males, and further understanding of these bioactive sphingolipids will help us develop new therapeutics for male infertility in the future.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Influence of sphingomyelin metabolism during epithelial-mesenchymal transition associated with aging in the renal papilla

The renal collecting ducts (CD) are formed by a fully differentiated epithelium, and their tissue organization and function require the presence of mature cell adhesion structures. In certain circumstances, the cells can undergo de-differentiation by a process called epithelial-mesenchymal transition (EMT), in which the cells lose their epithelial phenotype and acquire the characteristics of the mesenchymal cells, which includes loss of cell-cell adhesion. We have previously shown that in renal papillary CD cells, cell adhesion structures are located in sphingomyelin (SM)-enriched plasma membrane microdomains and the inhibition of SM synthase 1 activity induced CD cells to undergo an EMT process. In the present study, we evaluated the influence of SM metabolism during the EMT of the cells that form the CD of the renal papilla during aging. To this end, primary cultures of renal papillary CD cells from young, middle-, and aged-rats were performed. By combining biochemical and immunofluorescence studies, we found experimental evidence that CD cells undergo an increase in spontaneous and reversible EMT during aging and that at least one of the reasons for this phenomenon is the decrease in SM content due to the combination of decreased SM synthase activity and an increase in SM degradation mediated by neutral sphingomyelinase. Age is a risk factor for many diseases, among which renal fibrosis is included. Our findings highlight the importance of sphingolipids and particularly SM as a modulator of the fate of CD cells and probably contribute to the development of treatments to avoid or reverse renal fibrosis during aging.