Systemic bone loss and induction of coronary vessel disease in a rat model of chronic inflammation

Ambient PM2.5 components might exacerbate bone loss among middle-aged and elderly women: evidence from a population-based cross-sectional study

BACKGROUND

Previous studies have primarily focused on the links between fine particulate matter (PM2.5) and bone health among the general population instead of PM2.5 components and the specific population. We aimed to investigate the associations between PM2.5 components and bone health among middle-aged and elderly women.

METHODS

A total of 748 middle-aged and elderly women were randomly sampled from 32 streets/villages in Hubei Province. The concentrations of ambient PM2.5 and its components were extracted across various residential areas from the Tracking Air Pollution in China (TAP) dataset. Bone mineral density measurements were obtained from dual-energy X-ray absorptiometry scans of study participants. Multivariable logistic and linear models were employed to assess the relationship between PM2.5 and its components and bone loss.

RESULTS

Per interquartile range (IQR) increase in nitrate (NO3-) and ammonium (NH4+) concentrations were associated with 1.65 [95% confidence intervals (CI): 1.13, 2.30] and 1.77 (95% CI: 1.26, 2.49) times higher odds of osteoporosis, respectively. Long-term exposure to sulfate (SO42-), NO3-, and NH4+ was negatively associated with T-scores and bone mineral density in L1-L4 lumbar vertebrae. In addition, the elderly, women who have experienced menarche after the age of 14, and postmenopausal women were more susceptible to the water-soluble inorganic salts of PM2.5.

CONCLUSION

The study emphasizes the need for comprehensive policies addressing air quality, with a specific focus on vulnerable populations such as middle-aged and elderly women. Public health interventions aimed at reducing ambient PM2.5 concentrations and minimizing exposure to its harmful components are crucial in mitigating the adverse impact on skeletal health and improving the overall well-being of communities.

PM2.5 exposure inhibits osteoblast differentiation by increasing the ubiquitination and degradation of Smad4

Increasing epidemiological evidence has shown that PM2.5 exposure is significantly associated with the occurrence of osteoporosis. It has been well demonstrated that PM2.5 exposure enhanced the differentiation and function of osteoclasts by indirectly causing chronic inflammation, while the mechanism in osteoblasts remains unclear. In our study, toxic effects were evaluated by direct exposure of 20-80 μg/ml PM2.5 to MC3T3-E1 cells and BMSCs. The results showed that PM2.5 exposure did not affect cell viability via proliferation and apoptosis, but significantly inhibited osteoblast differentiation in a dose-dependent manner. Osteogenic transcription factors Runx2 and Sp7 and other biomarkers Alp and Ocn decreased after PM2.5 exposure. RNA-seq revealed TGF-β signaling was involved in PM2.5 exposure inhibited osteoblast differentiation, which led to P-Smad1/5 and P-Smad2 reduction in the nucleus by increasing the ubiquitination and degradation of Smad4. At last, the inflammation response increased in MC3T3-E1 cells with PM2.5 exposure. Moreover, the mRNA levels of Mmp9 increased in bone marrow-derived macrophage cells treated with the conditional medium collected from MC3T3-E1 cells exposed to PM2.5. Overall, these results indicated that PM2.5 exposure inhibits osteoblast differentiation and concurrently increases the maturation of osteoclasts. Our study provides in-depth mechanistic insights into the direct impact of PM2.5 exposure on osteoblast, which would indicate the unrecognized role of PM2.5 on osteoporosis.

Progress of linking gut microbiota and musculoskeletal health: casualty, mechanisms, and translational values

The musculoskeletal system is important for balancing metabolic activity and maintaining health. Recent studies have shown that distortions in homeostasis of the intestinal microbiota are correlated with or may even contribute to abnormalities in musculoskeletal system function. Research has also shown that the intestinal flora and its secondary metabolites can impact the musculoskeletal system by regulating various phenomena, such as inflammation and immune and metabolic activities. Most of the existing literature supports that reasonable nutritional intervention helps to improve and maintain the homeostasis of intestinal microbiota, and may have a positive impact on musculoskeletal health. The purpose of organizing, summarizing and discussing the existing literature is to explore whether the intervention methods, including nutritional supplement and moderate exercise, can affect the muscle and bone health by regulating the microecology of the intestinal flora. More in-depth efficacy verification experiments will be helpful for clinical applications.

Verbascoside Inhibits/Repairs the Damage of LPS-Induced Inflammation by Regulating Apoptosis, Oxidative Stress, and Bone Remodeling

Osteocytes play an important role as regulators of both osteoclasts and osteoblasts, and some proteins that are secreted from them play a role in bone remodeling and modeling. LPS affects bone structure because it is an inflammatory factor, despite verbascoside's potential for bone preservation and healing. Osteocytes may also be involved in the control of the bone's response to immunological changes in inflammatory situations. MLO-Y4 cells were cultured in either supplemented -MEM alone with a low serum to inhibit cell growth or media with LPS (10 ng/mL) and/or verbascoside (50 g/mL) to show the LPS effect. In our research, LPS treatment increased RANKL levels while decreasing OPG and RUNX2 expression. Treatment with verbascoside reduced RANKL expression. In our work, verbascoside increased the expression of OPG and RUNX2. In MLO-Y4 cells exposed to verbascoside, SOD, CAT, and GSH activities as well as the expression levels of bone mineralization proteins like PHEX, RUNX2, and OPG were all elevated.

Experimental animal models of chronic inflammation

Inflammation is a general term for a wide variety of both physiological and pathophysiological processes in the body which primarily prevents the body from diseases and helps to remove dead tissues. It has a crucial part in the body immune system. Tissue damage can recruit inflammatory cells and cytokines and induce inflammation. Inflammation can be classified as acute, sub-acute, and chronic. If it remained unresolved and lasted for prolonged periods, it would be considered as chronic inflammation (CI), which consequently exacerbates tissue damage in different organs. CI is the main pathophysiological cause of many disorders such as obesity, diabetes, arthritis, myocardial infarction, and cancer. Thus, it is critical to investigate different mechanisms involved in CI to understand its processes and to find proper anti-inflammatory therapeutic approaches for it. Animal models are one of the most useful tools for study about different diseases and mechanisms in the body, and are important in pharmacological studies to find proper treatments. In this study, we discussed the various experimental animal models that have been used to recreate CI which can help us to enhance the understanding of CI mechanisms in human and contribute to the development of potent new therapies.

Air pollution, genetic factors and the risk of osteoporosis: A prospective study in the UK biobank

Purpose

To reveal relationship between air pollution exposure and osteoporosis (OP) risk.

Methods

Based on large-scale data from the UK Biobank, we evaluated the relationship between OP risk and several air pollutants. Then air pollution scores (APS) were constructed to assess the combined effects of multiple air pollutants on OP risk. Finally, we constructed a genetic risk score (GRS) based on a large genome-wide association study of femoral neck bone mineral density and assessed whether single or combined exposure to air pollutants modifies the effect of genetic risk on OP and fracture risk.

Results

PM_2.5, NO₂, NO_x, and APS were significantly associated with an increased risk of OP/fracture. OP and fracture risk raised with increasing concentrations of air pollutants: compared to the lowest APS quintile group, subjects in the highest quintile group had a hazard ratio (HR) (95% CI) estimated at 1.140 (1.072-1.213) for OP and 1.080 (1.026-1.136) for fracture. Moreover, participants with low GRS and the highest air pollutant concentration had the highest risk of OP, the HRs (95% CI) of OP were 1.706 (1.483-1.964), 1.658 (1.434-1.916), 1.696 (1.478-1.947), 1.740 (1.506-2.001) and 1.659 (1.442-1.908), respectively, for PM_2.5, PM₁₀, PM_2.5-10, NO₂, and NO_x. Similar results were also observed for fractures. Finally, we assessed the joint effect of APS and GRS on the risk of OP. Participants with higher APS and lower GRS had a higher risk of developing OP. Similar results were observed in the joint effect of GRS and APS on fracture.

Conclusions

We found that exposure to air pollution, individually or jointly, could improve the risk of developing OP and fractures, and increased the risk by interacting with genetic factors.

Lipopolysaccharide-Induced Bone Loss in Rodent Models: A Systematic Review and Meta-Analysis

Osteoporosis has traditionally been characterized by underlying endocrine mechanisms, though evidence indicates a role of inflammation in its pathophysiology. Lipopolysaccharide (LPS), a component of gram-negative bacteria that reside in the intestines, can be released into circulation and stimulate the immune system, upregulating bone resorption. Exogenous LPS is used in rodent models to study the effect of systemic inflammation on bone, and to date a variety of different doses, routes, and durations of LPS administration have been used. The study objective was to determine whether systemic administration of LPS induced inflammatory bone loss in rodent models. A systematic search of Medline and four other databases resulted in a total of 110 studies that met the inclusion criteria. Pooled standardized mean differences (SMDs) and corresponding 95% confidence intervals (CI) with a random-effects meta-analyses were used for bone volume fraction (BV/TV) and volumetric bone mineral density (vBMD). Heterogeneity was quantified using the I² statistic. Shorter-term (<2 weeks) and longer-term (>2 weeks) LPS interventions were analyzed separately because of intractable study design differences. BV/TV was significantly reduced in both shorter-term (SMD = -3.79%, 95% CI [-4.20, -3.38], I² 62%; p < 0.01) and longer-term (SMD = -1.50%, 95% CI [-2.00, -1.00], I² 78%; p < 0.01) studies. vBMD was also reduced in both shorter-term (SMD = -3.11%, 95% CI [-3.78, -2.44]; I² 72%; p < 0.01) and longer-term (SMD = -3.49%, 95% CI [-4.94, -2.04], I² 82%; p < 0.01) studies. In both groups, regardless of duration, LPS negatively impacted trabecular bone structure but not cortical bone structure, and an upregulation in bone resorption demonstrated by bone cell staining and serum biomarkers was reported. This suggests systemically delivered exogenous LPS in rodents is a viable model for studying inflammatory bone loss, particularly in trabecular bone. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Yangonin treats inflammatory osteoporosis by inhibiting the secretion of inflammatory factors and RANKL expression

OBJECTIVES

As the main cause of osteoporosis, abnormal activity of osteoclasts could disrupt the balance between bone resorption and formation. Moreover, up-regulation of nuclear factor-kappa ligand (RANKL) expression by chronic inflammation-mediated inflammatory factors might contribute to the differentiation of osteoclast precursor cells. Therefore, an anti-inflammatory agent named yangonin was presented for inhibiting osteoclast and relieving inflammatory osteoporosis through down-regulating inflammatory factors.

METHODS

We established a model of macrophage inflammation and then verified the anti-inflammatory effect of yangonin. The inhibitory effect of yangonin on osteoclasts was detected by tartrate-resistant acid phosphatase (TRAP) staining, Western blotting and quantitative real-time PCR (qRT-PCR). Finally, micro-CT, TRAP and hematoxylin-eosin (HE) staining were used to show the effect of yangonin on inflammatory osteoporosis in vivo.

RESULTS

Our results suggested that yangonin was able to reduce the secretion of inflammatory factors, down-regulate osteoclast-related genes such as TRAP, RANKL, cathepsin K (CTSK) and nuclear factor-activated T-cell 1 (NFATc1). Furthermore, it was demonstrated that yangonin could suppress the function of inflammatory cytokines in osteoclast differentiation and reporting, wherein NF-κB, AKT and downstream c-Fos/NFATc1 signaling pathways were involved. In an in vivo study, we implied that yangonin has a relieving effect on inflammatory osteoporosis.

CONCLUSION

Our research shows that yangonin down-regulates inflammatory factors and inhibits the bone-breaking effect of inflammation through NF-κB, AKT and downstream c-Fos/NFATc1 signaling pathways to achieve the purpose of treating inflammatory osteoporosis.

The gut microbiota can be a potential regulator and treatment target of bone metastasis

The gut microbiota, an often forgotten organ, have a tremendous impact on human health. It has long been known that the gut microbiota are implicated in cancer development, and more recently, the gut microbiota have been shown to influence cancer metastasis to distant organs. Although one of the most common sites of distant metastasis is the bone, and the skeletal system has been shown to be a subject of interactions with the gut microbiota to regulate bone homeostasis, little research has been done regarding how the gut microbiota control the development of bone metastasis. This review will discuss the mechanisms through which the gut microbiota and derived microbial compounds (i) regulate gastrointestinal cancer disease progression and metastasis, (ii) influence skeletal remodeling and potentially modulate bone metastasis, and (iii) affect and potentially enhance immunotherapeutic treatments for bone metastasis.

Imbalances in TCA, Short Fatty Acids and One-Carbon Metabolisms as Important Features of Homeostatic Disruption Evidenced by a Multi-Omics Integrative Approach of LPS-Induced Chronic Inflammation in Male Wistar Rats

Chronic inflammation is an important risk factor in a broad variety of physical and mental disorders leading to highly prevalent non-communicable diseases (NCDs). However, there is a need for a deeper understanding of this condition and its progression to the disease state. For this reason, it is important to define metabolic pathways and complementary biomarkers associated with homeostatic disruption in chronic inflammation. To achieve that, male Wistar rats were subjected to intraperitoneal and intermittent injections with saline solution or increasing lipopolysaccharide (LPS) concentrations (0.5, 5 and 7.5 mg/kg) thrice a week for 31 days. Biochemical and inflammatory parameters were measured at the end of the study. To assess the omics profile, GC-qTOF and UHPLC-qTOF were performed to evaluate plasma metabolome; 1H-NMR was used to evaluate urine metabolome; additionally, shotgun metagenomics sequencing was carried out to characterize the cecum microbiome. The chronicity of inflammation in the study was evaluated by the monitoring of monocyte chemoattractant protein-1 (MCP-1) during the different weeks of the experimental process. At the end of the study, together with the increased levels of MCP-1, levels of interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α) and prostaglandin E2 (PGE2) along with 8-isoprostanes (an indicative of oxidative stress) were significantly increased (p-value < 0.05). The leading features implicated in the current model were tricarboxylic acid (TCA) cycle intermediates (i.e., alpha-ketoglutarate, aconitic acid, malic acid, fumaric acid and succinic acid); lipids such as specific cholesterol esters (ChoEs), lysophospholipids (LPCs) and phosphatidylcholines (PCs); and glycine, as well as N, N-dimethylglycine, which are related to one-carbon (1C) metabolism. These metabolites point towards mitochondrial metabolism through TCA cycle, β-oxidation of fatty acids and 1C metabolism as interconnected pathways that could reveal the metabolic effects of chronic inflammation induced by LPS administration. These results provide deeper knowledge concerning the impact of chronic inflammation on the disruption of metabolic homeostasis.

Biomimetic Hydroxyapatite Nanorods Promote Bone Regeneration via Accelerating Osteogenesis of BMSCs through T Cell-Derived IL-22

Manipulations of morphological properties of nanobiomaterials have been demonstrated to modulate the outcome of osteoimmunomodulation and eventually osteogenesis through innate immune response. However, the functions and mechanisms of adaptive immune cells in the process of nanobiomaterials-mediated bone regeneration have remained unknown. Herein, we developed bone-mimicking hydroxyapatite (HAp) nanorods with different aspect ratios as model materials to investigate the impacts of the nanoshape features on osteogenesis and to explore the underlying mechanisms focusing on the functions of T cells and T cell-derived cytokines. HAp nanorods with different aspect ratios (HAp-0, HAp-30, and HAp-100) were implanted into mouse mandibular defect models. Micro-CT and hematoxylin and eosin staining demonstrated that HAp-100 had the best osteogenic effects. Flow cytometry analysis revealed that HAp-100 increased the percentage of T cells in injured mandibles. The osteogenic effects of HAp-100 were significantly blunted in injured mandibles of TCRβ-/- mice. The Luminex xMAP assay and ELISA showed that HAp-100 induced a marked increase of interleukin (IL)-22 in injured mandibles. In cultured T cells, HAp-100 manifested the best capacity to induce the production of IL-22. Conditioned media from HAp-100-primed T cells promoted osteogenesis and JAK1/STAT3 activation in bone marrow stromal cells, all of which were abolished by neutralizing antibodies against IL-22. In summary, bone-mimicking HAp nanorods with different aspect ratios could regulate osteogenesis through modulation of T cells and IL-22 in the bone regeneration process. These findings provided insights for mediation of the immune response of T cells by nanomaterials on osteogenesis and strategies for designing biomaterials with osteoimmunomodulative functions.

Exposure to Air Pollution and Risk of Hip Fracture: A Population-Based Cohort Study With a 6-Year Follow-Up in South Korea

OBJECTIVES

We aimed to investigate whether exposure to air pollutants was associated with the risk of hip fracture.

METHODS

We extracted data on a 2010 cohort of the adult population (more than or equal to 30 years old) from a South Korean database.

RESULTS

A total of 178,147 individuals were included in the analysis, and hip fracture had occurred in 919 individuals (0.5%). In a multivariable logistic regression model, a 1 mcg/m increase in concentrations of particulate matter measuring of less than or equal to 10 μm was associated with 2% increase in hip fracture risk (odds ratio [OR]: 1.02, 95% confidence interval [CI]: 1.01 to 1.03; P = 0.039); there were no significant associations between hip fracture risk and exposure to SO2 (P = 0.076), ozone (P = 0.220), carbon monoxide (P = 0.698), or sulfur dioxide (P = 0.114).

CONCLUSIONS

Particular matter air concentration may be a modifiable risk factor for hip fracture.

Long-term exposure to fine particulate matter and osteoporotic fracture: A case-control study in Taiwan

Few studies have explored the relationship between long-term exposure to particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and osteoporotic fracture, particularly in high PM_2.5 level areas. The aim of this study was to assess the association between long-term exposure to PM_2.5 and osteoporotic fracture. We performed a matched case-control study of 16,175 participants obtained from a hospital registry during 2005-2014 in Taiwan. A major osteoporotic fracture was defined as a fracture of the spine, hip, proximal humerus, and forearm. We applied satellite-based spatiotemporal models with 1-km resolution to individually calculate the 1-year average PM_2.5 concentration before the index date which was defined as the first visit date for the osteoporotic fracture. Logistic regression models with and without potential confounding factors were used to estimate odds ratios (OR) and 95% confidence intervals (CI) between PM_2.5 and osteoporotic fracture, whereas a restricted cubic spline model was used to estimate the dose-response relationship. The sample's median age was 44.7 years (interquartile range: 30.7, 63.1 years). We observed that long-term PM_2.5 exposure was associated with osteoporotic fracture, the OR was 1.12 (95% CI: 1.03, 1.22) per 10-μg/m³ increase in PM_2.5 in women. In the dose-response association, the OR of osteoporotic fracture was significantly increased for PM_2.5 exposures more than 41 μg/m³. We did not find a significant association between PM_2.5 (per 10-μg/m³ increase) and osteoporotic fracture among overall population (adjusted OR, 1.02 [95% CI, 0.97 to 1.08]) and men (adjusted OR, 0.94 [95% CI, 0.86 to 1.02]). The results of the stratified analysis showed that women were more sensitive to the adverse impact of PM2.5 that were men, and evidence was obtained of sex-based effect modification (P for interaction = 0.002). Our findings suggest that long-term exposure to PM_2.5 is associated with osteoporotic fracture, particularly among women.

PERK activator CCT020312 prevents inflammation-mediated osteoporosis in the ovariectomized rats

OBJECTIVE

To investigate the therapeutic effects of PERK activator CCT020312 (CCT) on inflammation-mediated osteoporosis (IMO) in ovariectomized rats.

METHODS

Rats were divided into Sham, IMO, IMO + 1 mg/kg CCT and IMO + 2 mg/kg CCT groups. IMO models were constructed by bilateral ovariectomy (OVX) on 1st day followed by injection with magnesium silicate (Talc) on the 59th day. Sham rats did not undergo OVX surgery and were injected with saline instead of Talc. From 60th to 79th day, rats were treated with DMSO (vehicle control) in the Sham and IMO groups, and 1 or 2 mg/kg CCT020312 in treatment groups. Osteopontin (OPN), osteocalcin (OCN), tartrate-resistant acid phosphatase (TRAP), C-terminal telopeptide of type I collagen (CTX-I), and pro-inflammatory factors were measured on the 80th day. ProdigyDEXA was used to evaluate bone mineral density and content (BMD/BMC). Bone volume/total volume (BV/TV), connectivity density (Conn.D), trabecular number (Tb.N), and trabecular separation (Tb.Sp) was assessed using 3D micro-CT scanner.

RESULTS

CCT up-regulated Conn.D, BV/TV, and Tb.N, but down-regulated Tb.Sp in IMO rats. Besides, the declined femoral BMD and BMC in IMO rats were elevated after CCT treatment. Besides, IMO rats represented declined OPN and OCN, as well as increased TRAP, CTX-I, and pro-inflammatory factors, whereas those in the treatment groups were ameliorated regarding these indexes, with 2 mg/kg CCT showing better effect.

CONCLUSION

PERK activator CCT020312 can be served as a new therapeutic option for the protection against bone loss in the OVX rat model associated with inflammation probably by manipulating inflammatory factors.

The Role of Intestinal Flora in the Regulation of Bone Homeostasis

Intestinal flora located within the intestinal tract comprises a large number of cells, which are referred to as the second gene pool of the human body and form a complex symbiotic relationship with the host. The knowledge of the complex interaction between the intestinal flora and various life activities of the host is a novel and rapidly expanding field. Recently, many studies are being conducted on the relationship between the intestinal flora and bone homeostasis and indicate that the intestinal flora can regulate bone homeostasis via the host immune, metabolic, and endocrine systems. What’s more, based on several clinical and preclinical pieces of evidence, changing the composition and function of the host intestinal flora through the application of probiotics, prebiotics, and fecal microbiota transplantation is being considered to be a potential novel target for the regulation of bone homeostasis. Here, we searched relevant literature and reviewed the role of the intestinal flora in the regulation of bone homeostasis and its modulating interventions.

Trabecular and cortical bone are unaltered in response to chronic lipopolysaccharide exposure via osmotic pumps in male and female CD-1 mice

Chronic low-grade inflammation has been identified as an underlying cause of many diseases including osteoporosis. Lipopolysaccharide (LPS) is a potent inducer of the inflammatory response that can negatively affect bone outcomes by upregulating bone resorption and inhibiting bone formation. The objective of this study was to assess the longitudinal response of trabecular and cortical bone structure and bone mineral density to LPS continuously administered for 12 weeks in male and female CD-1 mice. Mice were assigned to one of four LPS groups at 8-weeks of age: placebo (0.0 μg/d), low (0.9 μg/d), mid (3.6 μg/d) and high (14.4 μg/d) dose. Trabecular and cortical bone outcomes were measured at 8, 12, 16, and 20 weeks of age using in vivo micro-computed tomography. The anticipated serum LPS dose-dependent response was not observed. Therefore, the low, mid, and high LPS groups were combined for analysis. Compared to the placebo group, endpoint serum LPS was elevated in both males (p < 0.05) and females (p < 0.05) when all LPS treatment groups were combined. However, there was no significant change in trabecular or cortical bone outcomes in the combined LPS groups compared to the placebo following the 12-week LPS intervention for either sex. This suggests that although serum LPS was elevated following the 12-week LPS intervention, the dosages administered using the osmotic pumps was not sufficient to negatively impact trabecular or cortical bone outcomes in either male or female CD-1 mice.

Effects of sulfur dioxide, ozone, and ambient air pollution on bone metabolism related biochemical parameters in a rat model

Ambient air pollution (AAP), as an important environmental health problem, affects everyone. A large body of literature links AAP, such as sulfur dioxide (SO2) and ozone (O3), with a wide range of non-communicable diseases. The aim of the present study was to investigate the effects of the pollutants on the bone metabolism biochemical parameters in a rat model. Thirty-two male Wistar rats were divided to four groups: control, SO2 (10 ppm), O3 (0.6 ppm), and AAP groups. After 5 weeks of exposure (3 hours/day, 6 days/week), blood samples were taken, and biochemical parameters were assayed. Vitamin D level of the AAP group was higher than the control and SO2 groups (p=0.004 and 0.003). Parathyroid hormone (PTH) level of the O3 group was significantly higher than the AAP group (p=0.006). Alkaline phosphatase (ALP), phosphorus, magnesium levels of the SO2 group; Vit D, ALP, osteocalcin (OC), and PTH of O3 group; and OC and osteoprotegerin (OPG) of AAP group were higher than those of control group but differences were not significant. Calcium level of the SO2 group; OPG and calcium of O3 group; and PTH of AAP group were less than those of control group but differences were not significant (p>0.05). The results showed significant effect of AAP with natural daylight on vitamin D and also O3 on PTH of the rats. In the concentrations and conditions of the study, we didn't find any significant unwanted effects of AAP, SO2, and O3 on the bone biochemical parameters. More investigations with more concentrations and exposure time are recommended.

Air Pollutants Interaction and Gender Difference on Bone Mineral Density T-Score in Taiwanese Adults

Osteoporosis is defined as a systemic skeletal disease characterized by a reduction in bone mass and microarchitectural deterioration of bone tissue. Previous studies have reported associations between air pollution and lower bone mineral density; however, few studies have investigated the association between air pollution and osteoporosis. In this study, we combined two databases, the first including 5000 individuals registered in the Taiwan Biobank, and the second containing detailed daily data on air pollution. After multivariable adjustments, ozone (O3) (unstandardized coefficient β, 0.015; p = 0.008) was significantly positively associated with T-score, whereas carbon monoxide (CO) (unstandardized coefficient β, -0.809; p < 0.001), sulfur dioxide (SO2) (unstandardized coefficient β, -0.050; p = 0.005), nitric oxide (NO) (unstandardized coefficient β, -0.040; p < 0.001), nitrogen dioxide (NO2) (unstandardized coefficient β, -0.023; p < 0.001), and nitrogen oxide (NOx) (unstandardized coefficient β, -0.017; p < 0.001) were significantly negatively associated with T-score. The interactions between CO and NOx (p = 0.001) and SO2 and NO2 (p = 0.004) on T-score were statistically significant. An increase in exposure to CO, NO and NOx was associated with a faster decline in T-score in the female participants compared to the male participants. In addition, an increase in O3 was associated with a faster increase in T-score in the female participants compared to the male participants. In conclusion, the air pollutants CO, SO2, NO, NO2, and NOx were associated with osteoporosis. In addition, there were interaction and synergetic effects between CO and NOx and SO2 and NO2 on T-score. We also observed differences in the associations between air pollutants and T-score between the female and male participants.

Osteoprotective Roles of Green Tea Catechins

Osteoporosis is the second most common disease only secondary to cardiovascular disease, with the risk of fracture increasing with age. Osteoporosis is caused by an imbalance between osteoblastogenesis and osteoclastogenesis processes. Osteoclastogenesis may be enhanced, osteoblastogenesis may be reduced, or both may be evident. Inflammation and high reactive oxygen enhance osteoclastogenesis while reducing osteoblastogenesis by inducing osteoblast apoptosis and suppressing osteoblastic proliferation and differentiation. Catechins, the main polyphenols found in green tea with potent anti-oxidant and anti-inflammatory properties, can counteract the deleterious effects of the imbalance of osteoblastogenesis and osteoclastogenesis caused by osteoporosis. Green tea catechins can attenuate osteoclastogenesis by enhancing apoptosis of osteoclasts, hampering osteoclastogenesis, and prohibiting bone resorption in vitro. Catechin effects can be directly exerted on pre-osteoclasts/osteoclasts or indirectly exerted via the modulation of mesenchymal stem cells (MSCs)/stromal cell regulation of pre-osteoclasts through activation of the nuclear factor kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system. Catechins also can enhance osteoblastogenesis by enhancing osteogenic differentiation of MSCs and increasing osteoblastic survival, proliferation, differentiation, and mineralization. The in vitro effects of catechins on osteogenesis have been confirmed in several animal models, as well as in epidemiological observational studies on human subjects. Even though randomized control trials have not shown that catechins provide anti-fracture efficacy, safety data in the trials are promising. A large-scale, placebo-controlled, long-term randomized trial with a tea regimen intervention of optimal duration is required to determine anti-fracture efficacy.

Suppression of Inflammation, Osteoclastogenesis and Bone Loss by PZRAS Extract

Panax ginseng has a wide range of activities including a neuroprotective effect, skin protective effects, enhanced DNA repairing, anti-diabetic activity, and protective effects against vascular inflammation. In the present study, we sought to discover the inhibitory effects of a mixture of natural products containing Panax ginseng, Ziziphus jujube, Rubi fructus, Artemisiae asiaticae and Scutellaria baicalensis (PZRAS) on osteoclastogenesis and bone remodeling, as neither the effects of a mixture containing Panax ginseng extract, nor its molecular mechanism on bone inflammation, have been clarified yet. PZRAS upregulated the levels of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GSH-R) and glutathione peroxidase (GSH-Px) and reduced malondialdehyde (MDA) in LPS-treated RAW264.7 cells. Moreover, treatment with PZRAS decreased the production of IL-1β and TNF-α. PZRAS also inhibited osteoclast differentiation through inhibiting osteoclastspecific genes like MMP-2, 9, cathepsin K, and TRAP in RANKL-treated RAW264.7 cells. Additionally, PZRAS has inhibitory functions on the RANKL-stimulated activation of ERK and JNK, which lead to a decrease in the expression of NFATc1 and c-Fos. In an in vivo study, bone resorption induced by LPS was recovered by treatment with PZRAS in bone volume per tissue volume (BV/TV) compared to control. Furthermore, the ratio of eroded bone surface of femurs was significantly increased in LPStreated mice compared to vehicle group, but this ratio was significantly reversed in PZRAS-treated mice. These results suggest that PZRAS could prevent or treat disorders with abnormal bone loss.

Phytochemicals affect T helper 17 and T regulatory cells and gut integrity: implications on the gut-bone axis

The pathology of osteoporosis is multifactorial, but a growing body of evidence supports an important role of the gut-bone axis, especially in bone loss associated with menopause, rheumatoid arthritis, and periodontal disease. Aberrant T cell responses favoring an increase in the ratio of T helper 17 cells to T regulatory cells play a critical role in the underlying etiology of this bone loss. Many of the dietary phytochemicals known to have osteoprotective activity such as flavonoids, organosulfur compounds, phenolic acids, as well as the oligosaccharides also improve gut barrier function and affect T cell differentiation and activation within gut-associated lymphoid tissues and at distal sites. Here, we examine the potential of these phytochemicals to act as prebiotics and immunomodulating agents, in part targeting the gut to mediate their effects on bone.

Poncirin Inhibits Osteoclast Differentiation and Bone Loss through Down-Regulation of NFATc1 In Vitro and In Vivo

Activation of osteoclast and inactivation of osteoblast result in loss of bone mass with bone resorption, leading to the pathological progression of osteoporosis. The receptor activator of NF-κB ligand (RANKL) is a member of the TNF superfamily, and is a key mediator of osteoclast differentiation. A flavanone glycoside isolated from the fruit of Poncirus trifoliata, poncirin has anti-allergic, hypocholesterolemic, anti-inflammatory and anti-platelet activities. The present study investigates the effect of poncirin on osteoclast differentiation of RANKL-stimulated RAW264.7 cells. We observed reduced formation of RANKL-stimulated TRAP-positive multinucleated cells (a morphological feature of osteoclasts) after poncirin exposure. Real-time qPCR analysis showed suppression of the RANKL-mediated induction of key osteoclastogenic molecules such as NFATc1, TRAP, c-Fos, MMP9 and cathepsin K after poncirin treatment. Poncirin also inhibited the RANKL-mediated activation of NF-κB and, notably, JNK, without changes in ERK and p38 expression in RAW264.7 cells. Furthermore, we assessed the in vivo efficacy of poncirin in the lipopolysaccharide (LPS)-induced bone erosion model. Evaluating the micro-CT of femurs revealed that bone erosion in poncirin treated mice was markedly attenuated. Our results indicate that poncirin exerts anti-osteoclastic effects in vitro and in vivo by suppressing osteoclast differentiation. We believe that poncirin is a promising candidate for inflammatory bone loss therapeutics.

Molecular and cellular mechanisms linking air pollution and bone damage

Air pollution is the second most important risk factor associated with noncommunicable diseases after smoking. The effects of pollution on health are commonly attributable to particulate matter (PM), a complex mixture of particles suspended in the air. PM can penetrate the lower respiratory tract and has harmful direct and indirect effects on different organs and tissues. Direct effects are caused by the ability of PM components to cross the respiratory membrane and enter the bloodstream; indirect effects are systemic consequences of the local airway response. Recent work suggests that PM is an independent risk factor for low bone mineral density and osteoporosis-related fractures. Osteoporosis is a common age-related disease closely linked to bone fractures, with severe clinical consequences affecting quality of life, morbidity, and mortality. In this review, we discuss potential mechanisms behind the association between outdoor air pollution, especially PM, and bone damage. The discussion features four main mechanisms: 1) several different atmospheric pollutants can induce low-grade systemic inflammation, which affects bone metabolism through a specific effect of cytokines such as TNFα, IL-1β, IL-6, and IL-17 on osteoblast and osteoclast differentiation and function; 2) some pollutants, particularly certain gas and metal compounds, can cause oxidative damage in the airway and bone cells; 3) different groups of pollutants can act as endocrine disruptors when binding to the receptors in bone cells, changing their functioning; and 4) air pollution can directly and indirectly cause vitamin D deficiency. Characterizing these mechanisms will better define the physiopathology of bone damage, and recognizing air pollution as a modifiable risk factor for osteoporosis will inform environmental policies. Such knowledge will also guide the prevention of fractures due to fragility and help reduce health-related costs.

The Interplay between Immune System and Microbiota in Osteoporosis

Osteoporosis is a disease characterized by low bone mass and alterations of bone microarchitecture, with an increased risk of fractures. It is a multifactorial disorder that is more frequent in postmenopausal women but can be associated to other diseases (inflammatory and metabolic diseases). At present, several options are available to treat osteoporosis trying to block bone reabsorption and reduce the risk of fracture. Anyway, these drugs have safety and tolerance problems in long-term treatment. Recently, gut microbiota has been highlighted to have strong influence on bone metabolism, becoming a potential new target to modify bone mineral density. Such evidences are mainly based on mouse models, showing an involvement in modulating the interaction between the immune system and bone cells. Germ-free mice represent a basic model to understand the interaction between microbiota, immune system, and bone cells, even though data are controversial. Anyway, such models have unequivocally demonstrated a connection between such systems, even if the mechanism is unclear. Gut microbiota is a complex system that influences calcium and vitamin D absorption and modulates gut permeability, hormonal secretion, and immune response. A key role is played by the T helper 17 lymphocytes, TNF, interleukin 17, and RANK ligand system. Other important pathways include NOD1, NOD2, and Toll-like receptor 5. Prebiotics and probiotics are a wide range of substances and germs that can influence and modify microbiota. Several studies demonstrated actions by different prebiotics and probiotics in different animals, differing according to sex, age, and hormonal status. Data on the effects on humans are poor and controversial. Gut microbiota manipulation appears a possible strategy to prevent and treat osteopenia and/or osteoporosis as well as other possible bone alterations, even though further clinical studies are necessary to identify correct procedures in humans.

Association of Ambient and Household Air Pollution With Bone Mineral Content Among Adults in Peri-urban South India

IMPORTANCE

Air pollution is a major threat to global health. Osteoporosis is responsible for a substantial burden of disease globally and is expected to increase in prevalence because of population aging. Few studies have investigated the association between air pollution and bone health, and their findings were inconclusive.

OBJECTIVE

To quantify the association between ambient and household air pollution and bone mass in a sample of the general population in peri-urban India.

DESIGN, SETTING, AND PARTICIPANTS

This was a population-based cross-sectional analysis of the Andhra Pradesh Children and Parents Study cohort, which recruited participants from 28 villages near Hyderabad, South India, during 2009 to 2012. Separate linear mixed models were fitted with nested random intercepts (household within villages) for each exposure-outcome pair and were sequentially adjusted for potential confounders. Data analysis was conducted between April 2019 and July 2019.

EXPOSURES

Annual mean ambient particulate matter air pollution less than 2.5 µm in aerodynamic diameter (PM2.5) and black carbon (BC) levels at the residence estimated by land-use regression and self-reported use of biomass cooking fuel.

MAIN OUTCOMES AND MEASURES

The primary outcome was bone mineral content (BMC) measured in grams, corrected by bone area at the lumbar spine and left hip, as measured by dual-energy x-ray absorptiometry. The secondary outcome was bone mineral density measured in grams per centimeters squared.

RESULTS

A total of 3717 participants were analyzed (mean [SD] age, 35.7 [14.0] years; 1711 [46.0%] women). The annual mean (SD) PM2.5 exposure was 32.8 (2.5) μg/m3, and the annual mean (SD) BC exposure was 2.5 (0.2) μg/m3; 57.8% of participants used biomass cooking fuels. In fully adjusted models, PM2.5 was associated with lower BMC in the spine (mean difference, -0.57 g per 3 μg/m3 increase in PM2.5; 95% CI, -1.06 to -0.07 g per 3 μg/m3 increase in PM2.5) and hip (mean difference, -0.13 g per 3 μg/m3 increase in PM2.5; 95% CI, -0.3 to 0.03 g per 3 μg/m3 increase in PM2.5). After confounder adjustment, exposure to PM2.5 was also associated with lower bone mineral density in the spine (mean difference, -0.011 g/cm2 per 3 μg/m3 increase in PM2.5; 95% CI, -0.021 to 0 g/cm2 per 3 μg/m3 increase in PM2.5) and hip (mean difference, -0.004 g/cm2 per 3 μg/m3 increase in PM2.5; 95% CI, -0.008 to 0.001 g/cm2 per 3 μg/m3 increase in PM2.5). Exposure to BC was associated with lower BMC in the spine (mean difference, -1.13 g per 1 μg/m3 increase in BC; 95% CI, -2.81 to 0.54 g per 1 μg/m3 increase in BC) and hip (mean difference, -0.35 g per 1 μg/m3 increase in BC; 95% CI, -0.96 to 0.25 g per 1 μg/m3 increase in BC), although the confidence intervals were wider. There was no association between biomass fuel use and spine BMC (mean difference, 0.12 g; 95% CI, -0.45 to 0.68 g).

CONCLUSIONS AND RELEVANCE

In a cross-sectional analysis of a population-based cohort, ambient air pollution was associated with lower BMC in a young adult population in a peri-urban area of South India.

Trehalose enhances bone fracture healing in a rat sleep deprivation model

Background

The purpose of this study was to investigate whether sleep deprivation (SD) could delay bone fracture healing and evaluate the therapeutic effect of trehalose.

Methods

Eighteen 300-350 g female Sprague-Dawley rats were created a mid-femoral transverse osteotomy in the right thigh and divided into three groups (i.e., group 1: fracture; group 2: fracture + SD; and group 3: fracture + SD + trehalose). Seven days after surgery, the rats in group 2 and group 3 were started to get sleep-deprived for 18 h per day for 3 weeks. The rats in group 3 were injected with trehalose intraperitoneally at 1 g/kg/d for 3 weeks. Radiological and histological analyses were used to assess fracture healing quality. Circulating cytokines were detected by the end of the study. The expression of M1 and M2 macrophage markers were measured by quantitative real-time polymerase chain reaction (qPCR).

Results

X-rays showed group 2 experienced much poorer fracture healing. Micro CT demonstrated that the bone quality of the fracture callus site in group 2 was much worse than that in groups 1 and 3. Both haematoxylin eosin (H&E) and Masson staining revealed that the bone fracture of the group 2 healed worse. Elisa results demonstrated that the interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) of the rats in group 2 were significantly higher. In vitro study showed that 100 mM trehalose enhanced the expression of M2 macrophage markers (Arg-1 and IL-10), and decreased M1 macrophage polarization through the decreasing expression of IL-6.

Conclusions

The present study showed (SD) could delay bone fracture healing in a rat model. And, trehalose could promote the healing of delayed bone fracture union by down-regulating pro-inflammatory mediators and enhancing M2 polarization.

Microbial osteoporosis: The interplay between the gut microbiota and bones via host metabolism and immunity

The complex relationship between intestinal microbiota and host is a novel field in recent years. A large number of studies are being conducted on the relationship between intestinal microbiota and bone metabolism. Bone metabolism consisted of bone absorption and formation exists in the whole process of human growth and development. The nutrient components, inflammatory factors, and hormone environment play important roles in bone metabolism. Recently, intestinal microbiota has been found to influence bone metabolism via influencing the host metabolism, immune function, and hormone secretion. Here, we searched relevant literature on Pubmed and reviewed the effect of intestinal microbiota on bone metabolism through the three aspects, which may provide new ideas and targets for the clinical treatment of osteoporosis.

Metabolic Syndrome in Arab Adults with Low Bone Mineral Density

There are discrepancies in the reports on the association of metabolic syndrome (MetS) and its components with bone mineral density (BMD) and hence more population-based studies on this subject are needed. In this context, this observational study was aimed to investigate the association between T-scores of BMD at lumbar L1–L4 and full MetS and its individual components. A total of 1587 participants (84.7% females), >35 years and with risk factors associated with bone loss were recruited from February 2013 to August 2016. BMD was done at L1–L4 using dual-energy X-ray absorptiometry (DXA). T-Scores were calculated. Fasting blood samples and anthropometrics were done at recruitment. Fasting lipid profile and glucose were measured. Screening for full MetS and its components was done according to the National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III) criteria. Logistic regression analysis revealed that the odds of having full MetS increased significantly from the lowest T-score tertile to the highest one in both sexes (OR, odd ratio (95% CI, confidence interval) of tertile 2 and 3 at 1.49 (0.8 to 2.8) and 2.46 (1.3 to 4.7), p = 0.02 in males and 1.35 (1.0 to 1.7) and 1.45 (1.1 to1.9), p < 0.01 in females). The odds remained significant even after adjustments with age, body mass index (BMI), and other risk factors associated with bone loss. Among the components of MetS, only central obesity showed a significant positive association with T-score. The study suggests a significant positive association of T-score (spine) with full MetS irrespective of sex, and among the components of MetS this positive association was seen specifically with central obesity.

Crocin attenuates metabolic syndrome-induced osteoporosis in rats

In the current study, anti-osteoporotic activities of crocin were evaluated in a rat model of metabolic syndrome-induced osteoporosis. Metabolic syndrome was confirmed by increased body weight gain, increased fasting blood glucose, hyperinsulinemia, elevated mean arterial blood pressure, and increased serum triglycerides level. Crocin (5 or 10 mg/kg) protected against histological and architectural alteration in bone tissues. Further, it ameliorated the decline in the bone formation markers serum alkaline phosphatase activity and osteocalcin level and inhibited the rise in the bone resorption markers serum tartrate-resistant acid phosphatase and collagen cross-linking carboxyterminal telopeptide, type I. Crocin anti-inflammatory properties were confirmed by a significant decline in serum interleukin-6 and tumor necrosis factor-α. Crocin mitigated oxidative stress in femur distal epiphysis tissues. Mechanically, crocin enhanced both the longitudinal and perpendicular forces of femurs. The current data highlight a protective activity that can be attributed, at least partly, to its anti-inflammatory and antioxidant activities. PRACTICAL APPLICATIONS: Metabolic syndrome is a serious health problem. Its prevalence is present in approximately 25% of all adults. Complications of metabolic syndrome include osteoporosis. This poses high risk of fractures and represents a heavy health, social, and economic burden. The current study highlights the antiosteoporotic activities of crocin in an experimental model of osteoporosis. Thus, crocin and/or other structurally related carotenoids can be lead compounds for synthesizing more potent and bioavailable molecules. These are expected to be devoid of the hazardous adverse effects of the currently available medicaments.

Diallyl disulfide alleviates inflammatory osteolysis by suppressing osteoclastogenesis via NF-κB-NFATc1 signal pathway

Skeletal homeostasis is closely effectuated by the regulation of bone formation and bone resorption. Osteoclasts are multinuclear giant cells responsible for bone resorption. Overactivated osteoclasts and excessive bone resorption result in various lytic bone diseases, such as osteoporosis, osteoarthritis, periprosthetic infection, and inflammatory aseptic loosening of orthopedic implants. In consideration of the severe side effects caused by the currently available drugs, exploitation of novel drugs has gradually attracted attention. Because of its anti-inflammatory, antioxidant, and antitumor capacities, diallyl disulfide (DADS), a major oil-soluble organosulfur ingredient compound derived from garlic, has been widely researched. However, the effects of DADS on osteoclasts and lytic bone diseases are still unknown. In this study, we investigated the effects of DADS on receptor activator of NF-κB ligand (RANKL)- and LPS-mediated osteoclastogenesis, LPS-stimulated proinflammatory cytokines related to osteoclasts, and LPS-induced inflammatory osteolysis. The results showed that DADS significantly inhibited RANKL-mediated osteoclast formation, fusion, and bone resorption in a dose-dependent manner via inhibiting the NF-κB and signal transducer and activator of transcription 3 signaling and restraining the interaction of NF-κB p65 with nuclear factor of activated T cells cytoplasmic 1. Furthermore, DADS also markedly suppressed LPS-induced osteoclastogenesis and reduced the production of proinflammatory cytokines with LPS stimulation to indirectly mediate osteoclast formation. Consistent with the in vitro results, DADS prevented the LPS-induced severe bone loss by blocking the osteoclastogenesis. All of the results indicate that DADS may be a potential and exploitable drug used for preventing and impeding osteolytic lesions.-Yang, J., Tang, R., Yi, J., Chen, Y., Li, X., Yu, T., Fei, J. Diallyl disulfide alleviates inflammatory osteolysis by suppressing osteoclastogenesis via NF-κB-NFATc1 signal pathway.

Colonic Bacteroides are positively associated with trabecular bone structure and programmed by maternal vitamin D in male but not female offspring in an obesogenic environment

BACKGROUND/OBJECTIVES

The gut microbiota is determined early in life, possibly including pregnancy. Pioneering data suggest vitamin D, a nutrient important for bone health, affects this microbiota. We found that high maternal vitamin D lowered circulating lipopolysaccharide (LPS), improved intestinal barrier and bone health in male but not female offspring in an obesogenic environment. This study determined if high maternal dietary vitamin D programs Bacteroides and Prevotella and whether this associates with bone mineral content, density and structure of male and female adult offspring fed an obesogenic diet.

METHODS

C57BL/6J females received an AIN93G diet with high or low vitamin D from before mating until weaning. Post-weaning, male and female offspring remained on their respective vitamin D level or were switched and fed a high fat and sucrose diet until killing (age 7 months). Bacteroides and Prevotella were quantified in dams' feces and offspring colonic contents. LPS concentrations, bone mineral density and content, strength and structure data were integrated from our previous studies in the same mice. Spearman correlations were completed between Bacteroides and LPS, and bone outcomes.

RESULTS

There was a maternal vitamin D effect on colonic Bacteroides but not Prevotella (dam diet: <0.001 and 0.735) in adult male offspring, independent of dams fecal Bacteroides before birth (P=0.998). In males, but not females, Bacteroides correlated with LPS (r=-0.488, P=0.018), trabecular femur peak load (r=0.362, P=0.033), vertebral trabecular separation (r=-0.605, P=0.006), trabecular number (r=0.614, P=0.005) and bone volume fraction (r=0.549, P=0.015).

CONCLUSIONS

Dietary vitamin D programs Bacteroides in male adult offspring only, which correlated negatively with systemic inflammation and positively with bone strength and structure. This may have implications on maternal diet and nutritional guidelines targeting sexes in a different manner.

Nonalcoholic fatty liver disease and osteoporosis: a systematic review and meta-analysis

Several major risk factors for osteoporosis have been identified. One of these risk factors is chronic inflammation. Several recent studies have supported the association between low bone mineral density (BMD) and nonalcoholic fatty liver disease (NAFLD), which comprises a spectrum of disorders involving liver inflammation. However, conflicting evidence regarding this association has been obtained thus far. We, therefore, conducted a meta-analysis of observational studies to show the association between NAFLD and BMD. The Cochrane Central Register of Controlled Trials, Cochrane Library, Medline, and Embase were searched from database inception to November 2014 for all observational studies evaluating the association between NAFLD or nonalcoholic steatohepatitis (NASH) and bone mass, BMD, or osteoporosis. All patients were ≥18 years of age and had no other cause of liver disease, osteoporosis, or pathological bone disease at baseline. Risk factors were NAFLD and NASH; control subjects were individuals without NAFLD. Eleven articles underwent full-length review. Data were extracted from five cross-sectional studies involving 1276 participants; 638 had NAFLD. The main meta-analysis showed no significant difference in BMD between patients with fatty liver disease and controls. Among all variables analyzed, body mass index had the strongest and most significant predictive effect on the difference in BMD. Controversy exists regarding the effect of BMD on NAFLD. Further studies are required to fully show this relationship.

Association of air particulate pollution with bone loss over time and bone fracture risk: analysis of data from two independent studies

BACKGROUND

Air particulate matter (PM) is a ubiquitous environmental exposure associated with oxidation, inflammation, and age-related chronic disease. Whether PM is associated with loss of bone mineral density (BMD) and risk of bone fractures is undetermined.

METHODS

We conducted two complementary studies of: (i) long-term PM <2.5 μm (PM_2.5) levels and osteoporosis-related fracture hospital admissions among 9.2 million Medicare enrollees of the Northeast/Mid-Atlantic United States between 2003-2010; (ii) long-term black carbon [BC] and PM_2.5 levels, serum calcium homeostasis biomarkers (parathyroid hormone, calcium, and 25-hydroxyvitamin D), and annualized BMD reduction over a 8-year follow-up of 692 middle-aged (46.7±12.3 yrs), low-income BACH/Bone cohort participants.

FINDINGS

In the Medicare analysis, risk of bone fracture admissions at osteoporosis-related sites was greater in areas with higher PM_2.5 levels (Risk ratio [RR] 1.041, 95% Confidence Interval [CI], 1.030, 1.051). This risk was particularly high among low-income communities (RR 1.076; 95% CI, 1.052, 1.100). In the longitudinal BACH/Bone study, baseline BC and PM_2.5 levels were associated with lower serum PTH (Estimate for baseline one interquartile increase in 1-year average BC= -1.16, 95% CI -1.93, -0.38; Estimate for baseline one interquartile increase in 1-year average PM_2.5= -7.39; 95%CI -14.17, -0.61). BC level was associated with higher BMD loss over time at multiple anatomical sites, including femoral neck (-0.08%/year per one interquartile increase; 95% CI -0.14, -0.02%/year) and ultradistal radius (-0.06%/year per one interquartile increase; 95% CI -0.12, -0.01%/year).

INTERPRETATION

Our results suggest that poor air quality is a modifiable risk factor for bone fractures and osteoporosis, especially in low-income communities.

Tocotrienols for bone health: a translational approach

Osteoporosis, a degenerative bone disease, is characterized by low bone mass and microstructural deterioration of bone tissue resulting in aggravated bone fragility and susceptibility to fractures. The trend of extended life expectancy is accompanied by a rise in the prevalence of osteoporosis and concomitant complications in the elderly population. Epidemiological evidence has shown an association between vitamin E consumption and the prevention of age-related bone loss in elderly women and men. Animal studies show that ingestion of vitamin E, especially tocotrienols, may benefit bone health in terms of maintaining higher bone mineral density and improving bone microstructure and quality. The beneficial effects of tocotrienols on bone health appear to be mediated via antioxidant/anti-inflammatory pathways and/or 3-hydroxy-3-methylglutaryl coenzyme A mechanisms. We discuss (1) an overview of the prevalence and etiology of osteoporosis, (2) types of vitamin E (tocopherols versus tocotrienols), (3) findings of tocotrienols and bone health from published in vitro and animal studies, (4) possible mechanisms involved in bone protection, and (5) challenges and future direction for research.

A High-Fat Diet Decreases Bone Mass in Growing Mice with Systemic Chronic Inflammation Induced by Low-Dose, Slow-Release Lipopolysaccharide Pellets

Background: Chronic inflammation is associated with increased bone resorption and is linked to osteopenia, or low bone mass. Obesity is also associated with low-grade chronic upregulation of inflammatory cytokines.Objective: This study investigated the effect of high-fat (HF) diet-induced obesity on bone structure changes in growing mice with existing systemic chronic inflammation induced by low-dose, slow-release lipopolysaccharide (LPS).Methods: Forty-eight 6-wk-old female C57BL/6 mice were randomly assigned to 4 treatment groups (n = 12/group) in a 2 × 2 factorial design-control (placebo) or LPS treatment (1.5 μg/d)-and consumed either a normal-fat (NF, 10% of energy as fat) or an HF (45% of energy as fat) diet ad libitum for 13 wk. Bone structure, serum biomarkers of bone turnover, and osteoclast differentiation were measured.Results: No alterations were observed in final body weights, fat mass, or lean mass in response to LPS treatment. LPS treatment increased serum concentration of tartrate-resistant acid phosphatase (TRAP, a bone resorption marker) and bone marrow osteoclast differentiation and decreased femoral and lumbar vertebral bone volume (BV):total volume (TV) by 25% and 24%, respectively, compared with the placebo. Mice fed the HF diet had greater body weight at the end of the study (P < 0.01) due to increased fat mass (P < 0.01) than did mice fed the NF diet. The HF diet increased serum TRAP concentration, bone marrow osteoclast differentiation, and expression of tumor necrosis factor α, interleukin 1β and interleukin 6 in adipose tissue. Compared with the NF diet, the HF diet decreased BV:TV by 10% and 8% at femur and lumbar vertebrae, respectively, and the HF diet was detrimental to femoral and lumbar vertebral bone structure with decreased trabecular number and increased trabecular separation and structure model index.Conclusion: Results suggest that HF diets and systemic chronic inflammation have independent negative effects on bone structure in mice.

Impaired glucose tolerance attenuates bone accrual by promoting the maturation of osteoblasts: Role of Beclin1-mediated autophagy

Patients with type 2 diabetes mellitus (T2DM) experience a 1.5-3.5 fold increase in fracture risk, but the mechanisms responsible for these alterations in bone biomechanical properties remain elusive. Macroautophagy, often referred to as autophagy, is regulated by signaling downstream of the insulin receptor. Metabolic changes associated with the progression of glucose intolerance have been shown to alter autophagy in various tissues, but limited information is available in relation to bone cells. The aim of this study was to (a) investigate whether autophagy is altered in bone tissue during impaired glucose tolerance, and (b) determine how autophagy impacts osteoblast differentiation, activity, and maturation. Four-week-old, male C57BL/6 mice were fed a control (Con) or high fat (HF) diet for 2, 8, or 16 wks. Mice on the HF diet demonstrated elevated fasting blood glucose and impaired glucose tolerance. Reduced trabecular bone in the femoral neck was evident in the mice on the HF diet by 8 wks compared to Con mice. Histological evaluation of the tibia suggested that the high fat diet promoted terminal differentiation of the osteoblast to an osteocyte. This shift of the osteoblasts towards a non-mineralizing, osteocyte phenotype appears to be coordinated by Beclin1-mediated autophagy. Consistent with these changes in the osteoblast in vivo, the induction of autophagy was able to direct MC3T3-E1 cells towards a more mature osteoblast phenotype. Although these data are somewhat observational, further investigation is warranted to determine if Beclin1-mediated autophagy is essential for the terminal differentiation of the osteoblasts and whether autophagy is having a protective or deleterious effect on bone in T2DM.

Effects of a moderately high-protein diet and interval aerobic training combined with strength-endurance exercise on markers of bone metabolism, microarchitecture and turnover in obese Zucker rats

BACKGROUND

Weight loss is a public health concern in obesity-related diseases such as metabolic syndrome, and the protein level of the diets seem to be crucial for the development and maintenance of bone. The nature of exercise and whether exercise in combination with moderately high-protein dietary interventions could protect against potential bone mass deficits remains unclear.

OBJECTIVES

To investigate the effects of a moderately high-protein diet and interval aerobic training combined with strength-endurance exercise (IASE) protocol on bone status, and to assess potential interaction effects (i.e. diet*IASE).

METHODS

Male Zucker fatty rats were randomized distributed into 4 groups (n=8): normoprotein+sedentary; normoprotein+exercise; moderately high-protein+sedentary, and moderately high-protein+exercise. Training groups conducted an IASE program, 5days/week for 2months. Markers of bone metabolism were measured in plasma. Parameters of bone mass and 3D outcomes for trabecular and cortical bone microarchitecture were assessed by micro-computed tomography.

RESULTS

Femur length, plasma osteocalcin, sclerostin, osteoprotegerin, receptor activator of nuclear factor kappa-B ligand, insulin, leptin, PTH, uric acid and urinary phosphorus levels were lower in the moderately high-protein compared to the normoprotein groups (all, p<0.05), whereas plasma alkaline phosphatase, aspartate aminotransferase, alanine transaminase, and urinary uric acid concentrations, and cortical total volume (TV) and bone volume (BV) were higher in the moderately high-protein (all, p<0.01). Final body weight and alkaline phosphatase levels were lower in the exercise compared to the sedentary (both, p<0.05), whereas femur length and weight, aminoterminal propeptides of type I procollagen and C-terminal telopeptides of type I collagen concentrations, and cortical TV and BV were higher in the exercise compared to the sedentary groups (all, p<0.05).

CONCLUSION

The combination of interventions may be effective to enhance trabecular bone microarchitecture and BMD, and has a partial impact on cortical bone in obese rats. Nevertheless, they do not induce any alteration on the bone turnover markers.

Maternal Dietary Vitamin D Does Not Program Systemic Inflammation and Bone Health in Adult Female Mice Fed an Obesogenic Diet

Obesity is associated with systemic inflammation and impaired bone health. Vitamin D regulates bone metabolism, and has anti-inflammatory properties and epigenetic effects. We showed that exposure to high dietary vitamin D during pregnancy and lactation beneficially programs serum concentration of lipopolysaccharide (LPS) and bone structure in male offspring fed an obesogenic diet. Here we assessed if this effect is also apparent in females. C57BL/6J dams were fed AIN93G diet with high (5000 IU/kg diet) or low (25 IU/kg diet) vitamin D during pregnancy and lactation. Post-weaning, female offspring remained on their respective vitamin D level or were switched and fed a high fat and sucrose diet (44.2% fat, 19.8% sucrose) until age seven months when glucose response, adiposity, serum LPS, and bone mineral, trabecular and cortical structure, and biomechanical strength properties of femur and vertebra were assessed. There was no evidence for a programming effect of vitamin D for any outcomes. However, females exposed to a high vitamin D diet post-weaning had higher bone mineral content (p = 0.037) and density (p = 0.015) of lumbar vertebra. This post-weaning benefit suggests that in females, bone mineral accrual but not bone structure is compromised with low vitamin D status in utero until weaning in an obesogenic context.

Maternal vitamin D beneficially programs metabolic, gut and bone health of mouse male offspring in an obesogenic environment

BACKGROUND/OBJECTIVES

Vitamin D is an anti-inflammatory nutrient and a determinant of bone health. Some prospective studies suggest that maternal vitamin D status is positively associated with offspring bone mass. We found that serum concentrations of lipopolysaccharide (LPS), an inflammatory molecule related to adiposity, insulin resistance and bone resorption, is lower in healthy mouse offspring exposed to high dietary vitamin D during pregnancy and lactation. LPS reaches the circulation via the gut. This study investigated whether maternal vitamin D programs metabolic, gut and bone health of male offspring in an obesogenic environment.

METHODS

C57BL/6J dams received an AIN-93G diet with high (H) or low (L) vitamin D during pregnancy and lactation. At weaning, offspring remained on their dam's vitamin D level (LL or HH) or were switched (LH or HL) and fed a high fat (44.2%) and sucrose (19.8%) diet. Glucose response, adiposity, systemic inflammation (LPS, cytokines), intestinal permeability and mass, strength and microarchitecture of trabecular and cortical bone were assessed in 7-month-old male offsprings.

RESULTS

Higher maternal dietary vitamin D resulted in lower intestinal permeability (fecal albumin, P=0.010) and benefited trabecular but not cortical bone structure at the distal femur (higher trabecular number, P=0.022; less trabecular separation, P=0.015) and lumbar vertebra 2 (bone volume/total volume%, P=0.049). Higher maternal and offspring vitamin D resulted in lower fasting glucose (HH versus LL, P=0.039) and serum LPS concentrations (dam diet, P=0.011; pup diet, P=0.002). Higher offspring vitamin D resulted in lower epididymal fat pad relative weight (P=0.006). The serum concentrations of IL-6 and TNF-α did not differ among groups.

CONCLUSIONS

Maternal dietary vitamin D beneficially programs intestinal permeability and systemic LPS concentration, which is accompanied by stronger trabecular bone in an obesogenic environment. Thus, the gut may mediate vitamin D effects. Moreover, optimizing vitamin D in early life may be critical for later health.

Effects of chronic sleep deprivation on bone mass and bone metabolism in rats

BACKGROUND

This study aimed to assess the effects of chronic sleep deprivation (CSD) on bone mass and bone metabolism in rats.

METHODS

Twenty-four rats were randomly divided into CSD and control (CON) groups. Rats were subjected to CSD by using the modified multiple platform method (MMPM) to establish an animal model of CSD. Biochemical parameters such as levels of serum N-terminal propeptide of type I procollagen (PINP), N-terminal cross-linking telopeptide of type I collagen (NTX), growth hormone (GH), estradiol (E2), serum 25(OH)D, and calcium (Ca) were evaluated at 0, 1, 2, and 3 months. After 3 months, each fourth lumbar vertebra and the distal femoral metaphysis of the left extremity of rats were harvested for micro-computed tomography scans and histological analysis, respectively, after the rats were sacrificed under an overdose of pentobarbital sodium.

RESULTS

Compared with rats from the CON group, rats from the CSD group showed significant decreases in bone mineral density (BMD), bone volume over total volume, trabecular bone thickness, and trabecular bone number and significant increases in bone surface area over bone volume and trabecular bone separations (P < 0.05). Bone histomorphology studies showed that rats in the CSD group had decreased osteogenesis, impaired mineralization of newly formed bones, and deteriorative trabecular bone in the secondary spongiosa zone. In addition, they showed significantly decreased levels of serum PINP (1 month later) and NTX (3 months later) (P < 0.05). The serum 25(OH)D level of rats from the CSD group was lower than that of rats from the CON group after 1 month (P < 0.05).

CONCLUSIONS

CSD markedly affects bone health by decreasing BMD and 25(OH)D, deteriorating the bone microarchitecture, and decreasing bone formation and bone resorption markers.

Strain differences in the attenuation of bone accrual in a young growing mouse model of insulin resistance

Skeletal fractures are considered a chronic complication of type 2 diabetes mellitus (T2DM), but the etiology of compromised bone quality that develops over time remains uncertain. This study investigated the concurrent alterations in metabolic and skeletal changes in two mouse strains, a responsive (C57BL/6) and a relatively resistant (C3H/HeJ) strain, to high-fat diet-induced glucose intolerance. Four-week-old male C57BL/6 and C3H/HeJ mice were randomized to a control (Con = 10 % kcal fat) or high-fat (HF = 60 % kcal fat) diet for 2, 8, or 16 weeks. Metabolic changes, including blood glucose, plasma insulin and leptin, and glucose tolerance were monitored over time in conjunction with alterations in bone structure and turn over. Elevated fasting glucose occurred in both the C57BL/6 and C3H/HeJ strains on the HF diet at 2 and 8 weeks, but only in the C57BL/6 strain at 16 weeks. Both strains on the HF diet demonstrated impaired glucose tolerance at each time point. The C57BL/6 mice on the HF diet exhibited lower whole-body bone mineral density (BMD) by 8 and 16 weeks, but the C3H/HeJ strain had no evidence of bone loss until 16 weeks. Analyses of bone microarchitecture revealed that trabecular bone accrual in the distal femur metaphysis was attenuated in the C57BL/6 mice on the HF diet at 8 and 16 weeks. In contrast, the C3H/HeJ mice were protected from the deleterious effects of the HF diet on trabecular bone. Alterations in gene expression from the femur revealed that several toll-like receptor (TLR)-4 targets (Atf4, Socs3, and Tlr4) were regulated by the HF diet in the C57BL/6 strain, but not in the C3H/HeJ strain. Structural changes observed only in the C57BL/6 mice were accompanied with a decrease in osteoblastogenesis after 8 and 16 weeks on the HF diet, suggesting a TLR-4-mediated mechanism in the suppression of bone formation. Both the C57BL/6 and C3H/HeJ mice demonstrated an increase in osteoclastogenesis after 8 weeks on the HF diet; however, bone turnover was decreased in the C57BL/6 with prolonged hyperglycemia. Further investigation is needed to understand how hyperglycemia and hyperinsulinemia suppress bone turnover in the context of T2DM and the role of TLR-4 in this response.

Tea flavonoids for bone health: from animals to humans

Osteoporosis is a skeletal disease characterized by a deterioration of bone mass and bone quality that predisposes an individual to a higher risk of fragility fractures. Emerging evidence has shown that the risk for low bone mass and osteoporosis-related fractures can be reduced by nutritional approaches aiming to improve bone microstructure, bone mineral density, and strength. Tea and its flavonoids, especially those of black tea and green tea, have been suggested to protect against bone loss and to reduce risk of fracture, due to tea's antioxidant and anti-inflammatory properties. Based on the results of animal studies, moderate intake of tea has shown to benefit bone health as shown by mitigation of bone loss and microstructural deterioration as well as improvement of bone strength and quality. Epidemiological studies have reported positive, insignificant, and negative impacts on bone mineral density at multiple skeletal sites and risk of fracture in humans with habitual tea consumption. There are limited human clinical trials that objectively and quantitatively assessed tea consumption and bone efficacy using validated outcome measures in a population at high risk for osteoporosis, along with safety monitoring approach. This review summarizes the current state of knowledge of laboratory animal research, epidemiological observational studies, and clinical trials assessing the skeletal effects of tea and its active flavonoids, along with discussion of relevant future directions in translational research.

Evidence for anti-inflammatory and antioxidative properties of dried plum polyphenols in macrophage RAW 264.7 cells

This study presents the anti-inflammatory and antioxidative properties of dried plum (Prunus domestica L.) polyphenols in macrophage RAW 264.7 cells. We hypothesized that dried plum polyphenols have strong anti-inflammatory and antioxidant properties against lipopolysaccharide (LPS)-induced production of the pro-inflammatory markers, nitric oxide (NO) and cyclooxygenase-2 (COX-2), and the lipid peroxidation product, malondialdehyde, in activated macrophage RAW 264.7 cells. To test this hypothesis, macrophage RAW 264.7 cells were stimulated with either 1 μg ml(-1) (for measurement of NO production) or 1 ng ml(-1) (for measurement of COX-2 expression) of LPS to induce inflammation and were treated with different doses of dried plum polyphenols (0.0, 0.1, 1, 10, 100 and 1000 μg ml(-1)). Dried plum polyphenols at a dose of 1000 μg ml(-1) was able to significantly (P < 0.05) reduce NO production by 43%. Additionally, LPS-induced expression of COX-2 was significantly (P < 0.05) reduced by 100 and 1000 μg ml(-1) dried plum polyphenols. To investigate the antioxidant activity of dried plum polyphenols, macrophage RAW 264.7 cells were stimulated with 100 μg ml(-1) of FeSO4 + 1 mM ml(-1) of H2O2 to induce lipid peroxidation. Dried plum polyphenols at a dose of 1000 μg ml(-1) showed a 32% reduction in malondialdehyde production. These findings indicate that dried plum polyphenols are potent anti-inflammatory and antioxidative agents in vitro.

Chronic exposure to low doses of lipopolysaccharide and high-fat feeding increases body mass without affecting glucose tolerance in female rats

Obesity-related inflammation may have a causal role in the development of diabetes and insulin resistance, and studies using animal models of chronic experimental endotoxemia have shown the link. However, many studies use only males, and much less is known about the role of obesity-related inflammation in females. Therefore, we addressed how experimentally induced chronic inflammation affects body mass, energy intake, and glucose metabolism in female rats. Adult female Sprague Dawley rats were instrumented with slow release pellets that delivered a constant daily dose of 53 or 207 μg of lipopolysaccharide (LPS) per rat for 60 days. Control rats were instrumented with vehicle pellets. Due to inflammatory nature of high-fat diet (HFD) half of the rats received HFD (60% of calories from lard), while the other half remained on control diet to detect possible interactions between two modes of induced inflammation. Our results showed that chronic LPS administration increased female rat body mass and calorie intake in a dose-dependent manner, and that HFD further exacerbated these effects. Despite these effects, no effects of LPS and HFD were evident on female rat glucose metabolism. Only LPS elevated expression of inflammatory markers in the hypothalamus. To conclude, female rats respond to experimentally induced chronic inflammation by increasing body mass, but do not develop glucose intolerance in the given period of time.

Behavioral and systemic consequences of long-term inflammatory challenge

Inflammatory reactions are involved in a diversity of diseases, including major depressive disorder. Cytokines act as intercellular signaling molecules and mediators of inflammation between the periphery and the brain. Within the brain, evidence from animal studies of acute inflammation has shown that elevated cytokine levels are linked to behavioral responses of sickness and depression-like behavior. Although chronic inflammation is more translational to human depression than acute studies, little is known on central cytokine expression and associated behavioral responses following chronic immune challenges. The present study assessed behavioral changes and a selection of cytokines in the brain and in the blood in rats randomized to receive a single or 8week administration with either lipopolysaccharide (LPS, 600μg/kg, i.p.) or saline. Acute and long-term LPS treatments caused similar sickness and depression-like behavior. Chronic LPS administration did not have an effect on blood cytokine levels, indicating endotoxin tolerance, whereas increased fasting blood glucose was observed, indicating insulin resistance, a metabolic consequence of chronic inflammation. While a single LPS injection produced a generalized cytokine response in the brain, long-term LPS administration produced a specific central cytokine response with increased interleukin (IL)-1β and interferon (IFN)-γ. These cytokines can explain the behavioral changes observed, and could indicate microglia activation, although future studies are needed to uncover this assumption. Taken together, although the behavioral outcome was similar between acute and chronic LPS administration, the central cytokine response was distinct. As the long-term LPS paradigm also posed a metabolic demand, this setting may reflect a more translational insight into inflammatory reactions in human depression, and could prove useful for assessing cytokine down-stream effects and experimental antidepressant drug products.

Implications of compromised zinc status on bone loss associated with chronic inflammation in C57BL/6 mice

Compromised zinc status and chronic inflammation are independent factors that can contribute to bone loss. However, zinc’s role in regulating lymphoid and myeloid cell populations, combined with the interplay between the immune and skeletal systems raises the question as to the extent to which a low-grade inflammatory challenge in the context of marginal zinc deficiency would exacerbate bone loss. To address this question, young adult C57BL/6 male mice (n=32) were used in a 2×2 factorial design with dietary zinc (adequate or 35 ppm vs inadequate or −Zn =5 ppm) and lipopolysaccharide (LPS, 0 or 0.1 mg/kg body weight). Mice were fed their respective diets for 10 weeks. On the 6th week, mice had a slow release pellet implanted to induce a low-grade inflammation for the final 4 weeks of the study. −Zn induced a decrease in total white cell counts and peripheral lymphocytes, whereas LPS increased blood monocytes. LPS significantly reduced spine bone mineral density and trabecular bone volume and number of the vertebral body compared with both zinc adequate and inadequate without LPS groups. Likewise, the most pronounced effects on bone strength occurred with LPS, however, −Zn also had negative effects on the bone von Mises stresses. LPS induced an increase in TNF-α and this response was further increased with −Zn. Although the marginal zinc deficiency altered immune function, bone loss was not exacerbated with low-grade chronic inflammation in marginally zinc-deficient young adult mice. These findings demonstrate that in young adult animals an immune challenge modestly increases the inflammatory response and worsens bone biomechanics in the context of a marginal zinc deficiency, but not to the extent that more severe adverse outcomes are observed on bone structural parameters.