Hyperthyroidism-driven bone loss depends on BMP receptor Bmpr1a expression in osteoblasts.

Hyperthyroidism is a well-known trigger of high bone turnover that can lead to the development of secondary osteoporosis. Previously, we have shown that blocking bone morphogenetic protein (BMP) signaling systemically with BMPR1A-Fc can prevent bone loss in hyperthyroid mice. To distinguish between bone cell type-specific effects, conditional knockout mice lacking Bmpr1a in either osteoclast precursors (LysM-Cre) or osteoprogenitors (Osx-Cre) were rendered hyperthyroid and their bone microarchitecture, strength and turnover were analyzed. While hyperthyroidism in osteoclast precursor-specific Bmpr1a knockout mice accelerated bone resorption leading to bone loss just as in wildtype mice, osteoprogenitor-specific Bmpr1a deletion prevented an increase of bone resorption and thus osteoporosis with hyperthyroidism. In vitro, wildtype but not Bmpr1a-deficient osteoblasts responded to thyroid hormone (TH) treatment with increased differentiation and activity. Furthermore, we found an elevated Rankl/Opg ratio with TH excess in osteoblasts and bone tissue from wildtype mice, but not in Bmpr1a knockouts. In line, expression of osteoclast marker genes increased when osteoclasts were treated with supernatants from TH-stimulated wildtype osteoblasts, in contrast to Bmpr1a-deficient cells. In conclusion, we identified the osteoblastic BMP receptor BMPR1A as a main driver of osteoporosis in hyperthyroid mice promoting TH-induced osteoblast activity and potentially its coupling to high osteoclastic resorption.

Effects of vitamin D3, omega-3 s and a simple strength training exercise program on bone health: the DO-HEALTH randomized controlled trial.

INTRODUCTION: Evidence on the effects of Vitamin D, omega-3 s and exercise on aBMD in healthy older adults is limited. We examined whether vitamin D3, omega-3 s, or a simple home-based exercise program (SHEP), alone or in combination, over three years, improve lumbar spine (LS), femoral neck (FN) or total hip (TH) aBMD assessed by DXA. METHODS: aBMD was a secondary outcome in DO-HEALTH, a 3-year, multicenter, double-blind, randomized 2 × 2 × 2 factorial design trial in generally healthy older adults age ≥ 70 years. The study interventions were vitamin D3 (2000IU/d), omega-3 s (1 g/d), and SHEP (3 × 30 min/wk), applied alone or in combination in 8 treatment arms. Mixed effect models were used adjusting for age, sex, BMI, prior fall, study site and baseline level of the outcome. Main effects were assessed in the absence of an interaction between the interventions. Subgroup analyses by sex, physical activity level, dietary calcium intake, serum 25(OH)D levels, and fracture history were conducted. RESULTS: DXA scans were available for 1493 participants (mean age 75 years; 80.4% were physically active, 44% had 25(OH)D levels <20 ng/ml). At the LS and FN sites, none of the treatments showed a benefit. At the TH, vitamin D vs. no vitamin D treatment showed a significant benefit across 3 years (difference in adjusted means [AM]: 0.0035 [95% CI 0.0011, 0.0059] g/cm2). Furthermore, there was a benefit for vitamin D vs. no vitamin D treatment on LS aBMD in the male subgroup of (interaction P = 0.003; ∆AM: 0.0070 [95% CI 0.0007, 0.0132] g/cm2). CONCLUSIONS: Omega-3 and SHEP had no benefit on aBMD in healthy, active and largely vitamin D replete older adults. Our study suggests a small benefit of 2000 IU vitamin D daily on TH aBMD overall and LS aBMD among men, however, effect sizes were very modest and the clinical impact of these findings is unclear.

Vitamin D, omega-3 fatty acids (omega-3 s) and strength training are simple but promising strategies to improve bone health, however, their effect in healthy older adults over a period of three years was unclear. In this study, we examined whether daily vitamin D supplementation (2000 IU/d), daily omega-3 s supplementation (1 g/d) or a simple strength training program performed three times per week, either applied alone (e.g., only vitamin D supplements) or in combination (e.g., vitamin D and omega-3 s supplements) could improve bone density at the spine, hip or femoral neck. We included 1493 healthy older adults from Switzerland, Germany, France and Portugal who were at least 70 years of age and who had not experienced any major health events in the five years before study start. Taking omega-3 s supplements showed no benefit for bone density. Similarly, the simple strength exercise program showed no benefit. In contrast, participants receiving daily vitamin D supplements experienced a benefit at the hip. However, it should be noted that the effect across three years was very small.

MiR-144-5p and miR-21-5p do not drive bone disease in a mouse model of type 1 diabetes mellitus.

The increased risk of fractures in patients with type 1 diabetes mellitus (T1DM) is nowadays well recognized. However, the exact mechanism of action of diabetic bone disease has not been fully elucidated. MicroRNAs (miRNAs) are gene regulators that operate post-transcriptionally and have been implicated in the development of various metabolic disorders including T1DM. Previous studies have implicated a role for miR-144-5p and miR-21-5p, which are involved in controlling oxidative stress by targeting Nrf2, in T1DM. To date, it is unclear whether miR-144-5p and miR-21-5p affect bone health in T1DM. Thus, this study aimed to investigate the influence of miR-144-5p and miR-21-5p knockdown in the development of bone disease in T1DM male mice. Therefore, T1DM was induced in 10-wk-old male mice using streptozotocin (STZ). One week later, after development of hyperglycemia, antagomir-144-5p and antagomir-21-5p or their non-targeting control were administered at 10 mg/kg BW once a week until the end of the experiment. At 14 wk of age, glucose levels, bone, and fat mass were analyzed. The results revealed that treating T1DM male mice with antagomir-144-5p and antagomir-21-5p did not protect against diabetes development or bone loss, despite the successful downregulation of the miRNAs and the normalization of Nrf2 mRNA levels in bone tissue. Histological and serological parameters of bone formation or resorption were not altered by the antagomir treatment. Finally, we measured the expression of miRNA-144-5p or miRNA-21-5p in the serum of 30 individuals with T1DM and compared them to non-diabetic controls, but did not find an altered expression of either miRNA. In conclusion, the knockdown of miR-144-5p and miR-21-5p does not affect STZ-induced diabetes development or loss of bone mass in male mice. However, it does normalize expression of the anti-oxidant factor Nrf2 in diabetic bone tissue.

Overcoming statin resistance in prostate cancer cells by targeting the 3-hydroxy-3-methylglutaryl-CoA-reductase.

Prostate cancer is the most prevalent malignancy in men. While diagnostic and therapeutic interventions have substantially improved in recent years, disease relapse, treatment resistance, and metastasis remain significant contributors to prostate cancer-related mortality. Therefore, novel therapeutic approaches are needed. Statins are inhibitors of the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme of the mevalonate pathway which plays an essential role in cholesterol homeostasis. Numerous preclinical studies have provided evidence for the pleiotropic antitumor effects of statins. However, results from clinical studies remain controversial and have shown substantial benefits to even no effects on human malignancies including prostate cancer. Potential statin resistance mechanisms of tumor cells may account for such discrepancies. In our study, we treated human prostate cancer cell lines (PC3, C4-2B, DU-145, LNCaP) with simvastatin, atorvastatin, and rosuvastatin. PC3 cells demonstrated high statin sensitivity, resulting in a significant loss of vitality and clonogenic potential (up to - 70%; p < 0.001) along with an activation of caspases (up to 4-fold; p < 0.001). In contrast, C4-2B and DU-145 cells were statin-resistant. Statin treatment induced a restorative feedback in statin-resistant C4-2B and DU-145 cells through upregulation of the HMGCR gene and protein expression (up to 3-folds; p < 0.01) and its transcription factor sterol-regulatory element binding protein 2 (SREBP-2). This feedback was absent in PC3 cells. Blocking the feedback using HMGCR-specific small-interfering (si)RNA, the SREBP-2 activation inhibitor dipyridamole or the HMGCR degrader SR12813 abolished statin resistance in C4-2B and DU-145 and induced significant activation of caspases by statin treatment (up to 10-fold; p < 0.001). Consistently, long-term treatment with sublethal concentrations of simvastatin established a stable statin resistance of a PC3SIM subclone accompanied by a significant upregulation of both baseline as well as post-statin HMGCR protein (gene expression up to 70-fold; p < 0.001). Importantly, the statin-resistant phenotype of PC3SIM cells was reversible by HMGCR-specific siRNA and dipyridamole. Our investigations reveal a key role of a restorative feedback driven by the HMGCR/SREBP-2 axis in statin resistance mechanisms of prostate cancer cells.

Effects of dietary iron deficiency or overload on bone: Dietary details matter.

PURPOSE: Bone is susceptible to fluctuations in iron homeostasis, as both iron deficiency and overload are linked to poor bone strength in humans. In mice, however, inconsistent results have been reported, likely due to different diet setups or genetic backgrounds. Here, we assessed the effect of different high and low iron diets on bone in six inbred mouse strains (C57BL/6J, A/J, BALB/cJ, AKR/J, C3H/HeJ, and DBA/2J). METHODS: Mice received a high (20,000 ppm) or low-iron diet (∼10 ppm) after weaning for 6-8 weeks. For C57BL/6J males, we used two dietary setups with similar amounts of iron, yet different nutritional compositions that were either richer ("TUD study") or poorer ("UCLA study") in minerals and vitamins. After sacrifice, liver, blood and bone parameters as well as bone turnover markers in the serum were analyzed. RESULTS: Almost all mice on the UCLA study high iron diet had a significant decrease of cortical and trabecular bone mass accompanied by high bone resorption. Iron deficiency did not change bone microarchitecture or turnover in C57BL/6J, A/J, and DBA/2J mice, but increased trabecular bone mass in BALB/cJ, C3H/HeJ and AKR/J mice. In contrast to the UCLA study, male C57BL/6J mice in the TUD study did not display any changes in trabecular bone mass or turnover on high or low iron diet. However, cortical bone parameters were also decreased in TUD mice on the high iron diet. CONCLUSION: Thus, these data show that cortical bone is more susceptible to iron overload than trabecular bone and highlight the importance of a nutrient-rich diet to potentially mitigate the negative effects of iron overload on bone.

Clonal hematopoiesis and its impact on the aging osteo-hematopoietic niche.

Clonal hematopoiesis (CH) defines a premalignant state predominantly found in older persons that increases the risk of developing hematologic malignancies and age-related inflammatory diseases. However, the risk for malignant transformation or non-malignant disorders is variable and difficult to predict, and defining the clinical relevance of specific candidate driver mutations in individual carriers has proved to be challenging. In addition to the cell-intrinsic mechanisms, mutant cells rely on and alter cell-extrinsic factors from the bone marrow (BM) niche, which complicates the prediction of a mutant cell's fate in a shifting pre-malignant microenvironment. Therefore, identifying the insidious and potentially broad impact of driver mutations on supportive niches and immune function in CH aims to understand the subtle differences that enable driver mutations to yield different clinical outcomes. Here, we review the changes in the aging BM niche and the emerging evidence supporting the concept that CH can progressively alter components of the local BM microenvironment. These alterations may have profound implications for the functionality of the osteo-hematopoietic niche and overall bone health, consequently fostering a conducive environment for the continued development and progression of CH. We also provide an overview of the latest technology developments to study the spatiotemporal dependencies in the CH BM niche, ideally in the context of longitudinal studies following CH over time. Finally, we discuss aspects of CH carrier management in clinical practice, based on work from our group and others.

Small-molecule CBP/p300 histone acetyltransferase inhibition mobilizes leukocytes from the bone marrow via the endocrine stress response.

Mutations of the CBP/p300 histone acetyltransferase (HAT) domain can be linked to leukemic transformation in humans, suggestive of a checkpoint of leukocyte compartment sizes. Here, we examined the impact of reversible inhibition of this domain by the small-molecule A485. We found that A485 triggered acute and transient mobilization of leukocytes from the bone marrow into the blood. Leukocyte mobilization by A485 was equally potent as, but mechanistically distinct from, granulocyte colony-stimulating factor (G-CSF), which allowed for additive neutrophil mobilization when both compounds were combined. These effects were maintained in models of leukopenia and conferred augmented host defenses. Mechanistically, activation of the hypothalamus-pituitary-adrenal gland (HPA) axis by A485 relayed shifts in leukocyte distribution through corticotropin-releasing hormone receptor 1 (CRHR1) and adrenocorticotropic hormone (ACTH), but independently of glucocorticoids. Our findings identify a strategy for rapid expansion of the blood leukocyte compartment via a neuroendocrine loop, with implications for the treatment of human pathologies.

Comparison of the effects of high dietary iron levels on bone microarchitecture responses in the mouse strains 129/Sv and C57BL/6J.

Iron is an essential nutrient for all living organisms. Both iron deficiency and excess can be harmful. Bone, a highly metabolic active organ, is particularly sensitive to fluctuations in iron levels. In this study, we investigated the effects of dietary iron overload on bone homeostasis with a specific focus on two frequently utilized mouse strains: 129/Sv and C57BL/6J. Our findings revealed that after 6 weeks on an iron-rich diet, 129/Sv mice exhibited a decrease in trabecular and cortical bone density in both vertebral and femoral bones, which was linked to reduced bone turnover. In contrast, there was no evidence of bone changes associated with iron overload in age-matched C57BL/6J mice. Interestingly, 129/Sv mice exposed to an iron-rich diet during their prenatal development were protected from iron-induced bone loss, suggesting the presence of potential adaptive mechanisms. Overall, our study underscores the critical role of genetic background in modulating the effects of iron overload on bone health. This should be considered when studying effects of iron on bone.

High serum levels of leucine-rich α-2 glycoprotein 1 (LRG-1) are associated with poor survival in patients with early breast cancer.

BACKGROUND: Leucine-rich α-2 glycoprotein 1 (LRG-1) is a secreted glycoprotein that is mainly produced in the liver. Elevated levels of LRG-1 are found in a multitude of pathological conditions including eye diseases, diabetes, infections, autoimmune diseases, and cancer. In patients with early breast cancer (BC), high intratumoral LRG-1 protein expression levels are associated with reduced survival. In this study, we assessed serum levels of LRG-1 in patients with early BC and investigated its correlation with the presence of disseminated tumor cells (DTCs) in the bone marrow and survival outcomes. METHODS: Serum LRG-1 levels of 509 BC patients were determined using ELISA and DTCs were assessed by immunocytochemistry using the pan-cytokeratin antibody A45-B/B3. We stratified LRG-1 levels according to selected clinical parameters. Using the log-rank (Mantel-Cox) test and multivariate Cox regression analysis, Kaplan-Meier survival curves and prognostic relevance were assessed. RESULTS: Mean serum levels of LRG-1 were 29.70 ± 8.67 µg/ml. Age was positively correlated with LRG-1 expression (r = 0.19; p < 0.0001) and significantly higher LRG-1 levels were found in patients over 60 years compared to younger ones (30.49 ± 8.63 µg/ml vs. 28.85 ± 8.63 µg/ml; p = 0.011) and in postmenopausal patients compared to premenopausal patients (30.15 ± 8.34 µg/ml vs. 26.936.94 µg/ml; p = 0.002). Patients with no DTCs showed significantly elevated LRG-1 levels compared to the DTC-positive group (30.51 ± 8.69 µg/ml vs. 28.51 ± 8.54 µg/ml; p = 0.004). Overall and BC-specific survival was significantly lower in patients with high serum LRG-1 levels (above a cut-off of 33.63 µg/ml) compared to patients with lower LRG-1 levels during a mean follow-up of 8.5 years (24.8% vs. 11.1% BC-specific death; p = 0.0003; odds ratio 2.63, 95%CI: 1.56-4.36). Multivariate analyses revealed that LRG-1 is an independent prognostic marker for BC-specific survival (p = 0.001; hazard ratio 2.61). CONCLUSIONS: This study highlights the potential of LRG-1 as an independent prognostic biomarker in patients with early BC.

Transferrin receptor 2 mitigates periodontitis-driven alveolar bone loss.

Periodontitis is associated with significant alveolar bone loss. Patients with iron overload suffer more frequently from periodontitis, however, the underlying mechanisms remain largely elusive. Here, we investigated the role of transferrin receptor 2 (Tfr2), one of the main regulators of iron homeostasis, in the pathogenesis of periodontitis and the dental phenotype under basal conditions in mice. As Tfr2 suppresses osteoclastogenesis, we hypothesized that deficiency of Tfr2 may exacerbate periodontitis-induced bone loss. Mice lacking Tfr2 (Tfr2-/- ) and wild-type (Tfr2+/+ ) littermates were challenged with experimental periodontitis. Mandibles and maxillae were collected for microcomputed tomography and histology analyses. Osteoclast cultures from Tfr2+/+ and Tfr2-/- mice were established and analyzed for differentiation efficiency, by performing messenger RNA expression and protein signaling pathways. After 8 days, Tfr2-deficient mice revealed a more severe course of periodontitis paralleled by higher immune cell infiltration and a higher histological inflammation index than Tfr2+/+ mice. Moreover, Tfr2-deficient mice lost more alveolar bone compared to Tfr2+/+ littermates, an effect that was only partially iron-dependent. Histological analysis revealed a higher number of osteoclasts in the alveolar bone of Tfr2-deficient mice. In line, Tfr2-deficient osteoclastic differentiation ex vivo was faster and more efficient as reflected by a higher number of osteoclasts, a higher expression of osteoclast markers, and an increased resorptive activity. Mechanistically, Tfr2-deficient osteoclasts showed a higher p38-MAPK signaling and inhibition of p38-MAPK signaling in Tfr2-deficient cells reverted osteoclast formation to Tfr2+/+ levels. Taken together, our data indicate that Tfr2 modulates the inflammatory response in periodontitis thereby mitigating effects on alveolar bone loss.

Utility and Limitations of TALLYHO/JngJ as a Model for Type 2 Diabetes-Induced Bone Disease.

Type 2 diabetes mellitus (T2DM) increases risk of fractures due to bone microstructural and material deficits, though the mechanisms remain unclear. Preclinical models mimicking diabetic bone disease are required to further understand its pathogenesis. The TALLYHO/JngJ (TH) mouse is a polygenic model recapitulating adolescent-onset T2DM in humans. Due to incomplete penetrance of the phenotype ~25% of male TH mice never develop hyperglycemia, providing a strain-matched nondiabetic control. We performed a comprehensive characterization of the metabolic and skeletal phenotype of diabetic TH mice and compared them to either their nondiabetic TH controls or the recommended SWR/J controls to evaluate their suitability to study diabetic bone disease in humans. Compared to both controls, male TH mice with T2DM exhibited higher blood glucose levels, weight along with impaired glucose tolerance and insulin sensitivity. TH mice with/without T2DM displayed higher cortical bone parameters and lower trabecular bone parameters in the femurs and vertebrae compared to SWR/J. The mechanical properties remained unchanged for all three groups except for a low-energy failure in TH mice with T2DM only compared to SWR/J. Histomorphometry analyses only revealed higher number of osteoclasts and osteocytes for SWR/J compared to both groups of TH. Bone turnover markers procollagen type 1 N-terminal propeptide (P1NP) and tartrate-resistant acid phosphatase (TRAP) were low for both groups of TH mice compared to SWR/J. Silver nitrate staining of the femurs revealed low number of osteocyte lacunar and dendrites in TH mice with T2DM. Three-dimensional assessment showed reduced lacunar parameters in trabecular and cortical bone. Notably, osteocyte morphology changed in TH mice with T2DM compared to SWR/J. In summary, our study highlights the utility of the TH mouse to study T2DM, but not necessarily T2DM-induced bone disease, as there were no differences in bone strength and bone cell parameters between diabetic and non-diabetic TH mice. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reduced Bone Regeneration in Rats With Type 2 Diabetes Mellitus as a Result of Impaired Stromal Cell and Osteoblast Function-A Computer Modeling Study.

Bone has the fascinating ability to self-regenerate. However, under certain conditions, such as type 2 diabetes mellitus (T2DM), this ability is impaired. T2DM is a chronic metabolic disease known by the presence of elevated blood glucose levels that is associated with reduced bone regeneration capability, high fracture risk, and eventual non-union risk after a fracture. Several mechanical and biological factors relevant to bone regeneration have been shown to be affected in a diabetic environment. However, whether impaired bone regeneration in T2DM can be explained due to mechanical or biological alterations remains unknown. To elucidate the relevance of either one, the aim of this study was to investigate the relative contribution of T2DM-related alterations on either cellular activity or mechanical stimuli driving bone regeneration. A previously validated in silico computer modeling approach that was capable of explaining bone regeneration in uneventful conditions of healing was further developed to investigate bone regeneration in T2DM. Aspects analyzed included the presence of mesenchymal stromal cells (MSCs), cellular migration, proliferation, differentiation, apoptosis, and cellular mechanosensitivity. To further verify the computer model findings against in vivo data, an experimental setup was replicated, in which regeneration was compared in healthy and diabetic after a rat femur bone osteotomy stabilized with plate fixation. We found that mechanical alterations had little effect on the reduced bone regeneration in T2DM and that alterations in MSC proliferation, MSC migration, and osteoblast differentiation had the highest effect. In silico predictions of regenerated bone in T2DM matched qualitatively and quantitatively those from ex vivo µCT at 12 weeks post-surgery when reduced cellular activities reported in previous in vitro and in vivo studies were included in the model. The presented findings here could have clinical implications in the treatment of bone fractures in patients with T2DM. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Thyroid hormone receptor Thra and Thrb knockout differentially affects osteoblast biology and thyroid hormone responsiveness in vitro.

Thyroid hormones (TH) are important modulators of bone remodeling and thus, thyroid diseases, in particular hyperthyroidism, are able to compromise bone quality and fracture resistance. TH actions on bone are mediated by the thyroid hormone receptors (TR) TRα1 and TRß1, encoded by Thra and Thrb, respectively. Skeletal phenotypes of mice lacking Thra (Thra0/0 ) and Thrb (Thrb-/- ) are well-described and suggest that TRα1 is the predominant mediator of TH actions in bone. Considering that bone cells might be affected by systemic TH changes seen in these mutant mice, here we investigated the effects of TR knockout on osteoblasts exclusively at the cellular level. Primary osteoblasts obtained from Thra0/0 , Thrb-/- , and respective wildtype (WT) mice were analyzed regarding their differentiation potential, activity and TH responsiveness in vitro. Thra, but not Thrb knockout promoted differentiation and activity of early, mature and late osteoblasts as compared to respective WT cells. Interestingly, while mineralization capacity and expression of osteoblast marker genes and TH target gene Klf9 was increased by TH in WT and Thra-deficient osteoblasts, Thrb knockout mitigated the responsiveness of osteoblasts to short (48 h) and long term (10 d) TH treatment. Further, we found a low ratio of Rankl, a potent osteoclast stimulator, over osteoprotegerin, an osteoclast inhibitor, in Thrb-deficient osteoblasts and in line, supernatants obtained from Thrb-/- osteoblasts reduced numbers of primary osteoclasts in vitro. In accordance to the increased Rankl/Opg ratio in TH-treated WT osteoblasts only, supernatants from these cells, but not from TH-treated Thrb-/- osteoblasts increased the expression of Trap and Ctsk in osteoclasts, suggesting that osteoclasts are indirectly stimulated by TH via TRß1 in osteoblasts. In conclusion, our study shows that both Thra and Thrb differentially affect activity, differentiation and TH response of osteoblasts in vitro and emphasizes the importance of TRß1 to mediate TH actions in bone.

Novel Insights into Osteoclast Energy Metabolism.

PURPOSE OF REVIEW: Osteoclasts are crucial for the dynamic remodeling of bone as they resorb old and damaged bone, making space for new bone. Metabolic reprogramming in these cells not only supports phenotypic changes, but also provides the necessary energy for their highly energy-consuming activity, bone resorption. In this review, we highlight recent developments in our understanding of the metabolic adaptations that influence osteoclast behavior and the overall remodeling of bone tissue. RECENT FINDINGS: Osteoclasts undergo metabolic reprogramming to meet the energy demands during their transition from precursor cells to fully mature bone-resorbing osteoclasts. Recent research has made considerable progress in pinpointing crucial metabolic adaptations and checkpoint proteins in this process. Notably, glucose metabolism, mitochondrial biogenesis, and oxidative respiration were identified as essential pathways involved in osteoclast differentiation, cytoskeletal organization, and resorptive activity. Furthermore, the interaction between these pathways and amino acid and lipid metabolism adds to the complexity of the process. These interconnected processes can function as diverse fuel sources or have independent regulatory effects, significantly influencing osteoclast function. Energy metabolism in osteoclasts involves various substrates and pathways to meet the energetic requirements of osteoclasts throughout their maturation stages. This understanding of osteoclast biology may provide valuable insights for modulating osteoclast activity during the pathogenesis of bone-related disorders and may pave the way for the development of innovative therapeutic strategies.

Lipid Profile after Pharmacologic Discontinuation and Restoration of Menstruation in Women with Endometriosis: A 12-Month Observational Prospective Study.

The lipid profile is affected following menstrual cessation (MC). We aimed to evaluate the effects of goserelin-induced MC and subsequent menstrual restoration (MR) on lipid metabolism. Premenopausal women with histologically verified endometriosis (n = 15) received goserelin monthly for 6 months (6mο), resulting in MC, and were followed-up for another 6 months after MR (12mο). Serum total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), lipoprotein a ([Lp(a)] and lipidomics were measured at baseline, 6mo and 12mo. Shotgun quantitative deep lipidomics were determined at the level of lipid class category, subclass, species, and fatty acyl chain lengths and degree of saturation. TC (p = 0.006), LDL-C (p = 0.028), HDL-C (p = 0.002), and apoA1 (p = 0.013) increased during goserelin-induced MC and remained practically unchanged during MR. TG, apoB, and Lp(a) did not change. From the deep lipidomics analysis, multivariate statistical analysis demonstrated profound alterations in lipid species with MC, whereas no statistically valid models could be fitted for the restoration period. In conclusion, GnRH-analog-induced MC alters lipid profiles at various levels, from standard blood lipid and lipoprotein profiles to several lipid species as detected by lipidomics analysis. Changes largely persist for at least 6 m after MR.

Activation of distinct inflammatory pathways in subgroups of LR-MDS.

Aberrant innate immune signaling has been identified as a potential key driver of the complex pathophysiology of myelodysplastic neoplasms (MDS). This study of a large, clinically and genetically well-characterized cohort of treatment-naïve MDS patients confirms intrinsic activation of inflammatory pathways in general mediated by caspase-1, interleukin (IL)-1ß and IL-18 in low-risk (LR)-MDS bone marrow and reveals a previously unrecognized heterogeneity of inflammation between genetically defined LR-MDS subgroups. Principal component analysis resolved two LR-MDS phenotypes with low (cluster 1) and high (cluster 2) levels of IL1B gene expression, respectively. Cluster 1 contained 14/17 SF3B1-mutated cases, while cluster 2 contained 8/8 del(5q) cases. Targeted gene expression analysis of sorted cell populations showed that the majority of the inflammasome-related genes, including IL1B, were primarily expressed in the monocyte compartment, consistent with a dominant role in determining the inflammatory bone marrow environment. However, the highest levels of IL18 expression were found in hematopoietic stem and progenitor cells (HSPCs). The colony forming activity of healthy donor HSPCs exposed to monocytes from LR-MDS was increased by the IL-1ß-neutralizing antibody canakinumab. This work reveals distinct inflammatory profiles in LR-MDS that are of likely relevance to the personalization of emerging anti-inflammatory therapies.

Activation of ß-adrenergic receptor signaling prevents glucocorticoid-induced obesity and adipose tissue dysfunction in male mice.

Elevated serum concentrations of glucocorticoids (GCs) result in excessive lipid accumulation in white adipose tissue (WAT) as well as dysfunction of thermogenic brown adipose tissue (BAT), ultimately leading to the development of obesity and metabolic disease. Here, we hypothesized that activation of the sympathetic nervous system either via cold exposure or the use of a selective ß3-adrenergic receptor (ß3-AR) agonist alleviates the adverse metabolic effects of chronic GC exposure in rodents. To this end, male 10-wk-old C57BL/6NRj mice were treated with corticosterone via drinking water or placebo for 4 wk while being maintained at 29°C (thermoneutrality), 22°C (room temperature), or 13°C (cold temperature); in a follow-up study mice received a selective ß3-AR agonist or placebo with and without corticosterone while being maintained at room temperature. Body weight and food intake were monitored throughout the study. Histological and molecular analyses were performed on white and brown adipose depots. Cold exposure not only preserved the thermogenic function of brown adipose tissue but also reversed GC-induced lipid accumulation in white adipose tissue and corrected GC-driven obesity, hyperinsulinemia, and hyperglycemia. The metabolic benefits of cold exposure were associated with enhanced sympathetic activity in adipose tissue, thus potentially linking an increase in sympathetic signaling to the observed metabolic benefits. In line with this concept, chronic administration of a selective ß3-AR agonist reproduced the beneficial metabolic effects of cold adaption during exposure to exogenous GCs. This preclinical study demonstrates the potential of ß3-AR as a therapeutic target in the management and prevention of GC-induced metabolic disease.NEW & NOTEWORTHY This preclinical study in mice shows that the ß3-adrenergic receptor can be a potential therapeutic approach to counteracting glucocorticoid (GC)-induced obesity and metabolic dysfunction. Both cold acclimation and ß3-adrenergic receptor stimulation in a mouse model of excess glucocorticoids were adequate in not only preventing obesity, adiposity, and adipose tissue dysfunction but also correcting hyperinsulinemia, hyperleptinemia, and dyslipidemia.

Deconstructing cellular senescence in bone and beyond.

Osteocytes are specialized bone cells that orchestrate skeletal remodeling. Senescent osteocytes are characterized by an activation of cyclin-dependent kinase inhibitor p16Ink4a and have been implicated in the pathogenesis of several bone loss disorders. In this issue of the JCI, Farr et al. have now shown that systemic removal of senescent cells (termed senolysis) prevented age-related bone loss at the spine and femur and mitigated bone marrow adiposity through a robust effect on osteoblasts and osteoclasts, whereas cell-specific senolysis in osteocytes alone was only partially effective. Surprisingly, transplantation of senescent fibroblasts into the peritoneum of young mice caused host osteocyte senescence associated with bone loss. This refined concept of osteocyte senescence and the effects of remote senolysis may help to develop improved senolytic strategies against multisystem aging in bone and beyond.

Rational engineering of glycosaminoglycan-based Dickkopf-1 scavengers to improve bone regeneration.

The WNT signaling pathway is a central regulator of bone development and regeneration. Functional alterations of WNT ligands and inhibitors are associated with a variety of bone diseases that affect bone fragility and result in a high medical and socioeconomic burden. Hence, this cellular pathway has emerged as a novel target for bone-protective therapies, e.g. in osteoporosis. Here, we investigated glycosaminoglycan (GAG) recognition by Dickkopf-1 (DKK1), a potent endogenous WNT inhibitor, and the underlying functional implications in order to develop WNT signaling regulators. In a multidisciplinary approach we applied in silico structure-based de novo design strategies and molecular dynamics simulations combined with synthetic chemistry and surface plasmon resonance spectroscopy to Rationally Engineer oligomeric Glycosaminoglycan derivatives (REGAG) with improved neutralizing properties for DKK1. In vitro and in vivo assays show that the GAG modification to obtain REGAG translated into increased WNT pathway activity and improved bone regeneration in a mouse calvaria defect model with critical size bone lesions. Importantly, the developed REGAG outperformed polymeric high-sulfated hyaluronan (sHA3) in enhancing bone healing up to 50% due to their improved DKK1 binding properties. Thus, rationally engineered GAG variants may represent an innovative strategy to develop novel therapeutic approaches for regenerative medicine.