Osteocyte apoptosis and lipid infiltration as mechanisms of alcohol-induced bone loss

The Effects of Acute and Chronic Alcohol Administration and Withdrawal on Bone Microstructure, Mechanical Strength, and Remodeling Protein Expression and Their Relation to an Antioxidant and FGF23 In Vivo

Alcohol's detrimental effects on bone health are well established, yet some literature suggests moderate consumption may offer benefits. With alcohol use on the rise, we investigate the impact of acute and chronic alcohol administration, along with withdrawal, on male Wistar rat femurs. We observed a transient cortical thickness increase with acute alcohol (AA) compared to chronic exposure (CA) but no significant changes in trabecular parameters or mechanical properties. High osteocalcin and osteopontin expression levels were noted in AA, alongside elevated RANKL expression. Conversely, CA showed low TRAP levels. FGF23 expression significantly increased during alcohol withdrawal (AW), while GPX decreased after chronic exposure but rose during withdrawal. Although mechanical strength changes were insignificant, biochemical shifts suggest alcohol exposure promotes bone resorption, reduces antioxidant protection, and potentially hampers active vitamin D and phosphate reabsorption via FGF23 upregulation.

Deleterious effect of chronic high-dose ethanol intake on biomechanical bone properties and periodontal status

To evaluate the effect of high-graduation chronic ethanol (EtOH) intake on bone and periodontal tissues of rats. Male Wistar rats (250 g) were divided into two groups of n = 12 each one. EtOH (5 ml of 3 g/kg) was administered to the experimental group by gastric gavage twice a day for 20 days and the control group received water under the same conditions. The rats were euthanized and used to perform biochemical determination in plasma and gingival tissue, and histological and biomechanical studies in the femur and mandibular tissues. Alcohol increased both TNFα (p < 0.01) and PGE2 (p < 0.05) in plasma and gingiva (p < 0.05) as compared to controls. In addition, EtOH increased the alveolar bone loss as evidenced by the increased distance between the cement enamel junction and the alveolar crest (p < 0.01), the lower % of interradicular bone expressed as bone area/total area (B.Ar/T.Ar, p < 0.05) and the larger periodontal space (p < 0.05), as compared to controls. Likewise, the mandibular microtomographic analysis in alcoholized rats revealed a lower % of interradicular bone volume/total volume (BV/TV, p < 0.05), greater trabecular separation (p < 0.05) and greater % trabecular porosity (p < 0.05) than controls. No biomechanical alteration was observed in lower jaws, while the femur of alcoholized rats presented a decrease in the structural bone properties (p < 0.001), as a systemic consequence of deterioration of the diaphyseal architecture (p < 0.01) without changes in material properties. The consumption of high doses of alcohol produces deleterious effects on periodontal tissues that could be due not only to local but also systemic effects.

Altered Osteoblast Metabolism with Aging Results in Lipid Accumulation and Oxidative Stress Mediated Bone Loss

Cellular aging is associated with dysfunction of numerous tissues affecting multiple organ systems. A striking example of this is related to age-related bone loss, or osteoporosis, increasing fracture incidence. Interestingly, the two compartments of bone, cortical and cancellous or trabecular, rely on different mechanisms for development and maintenance during 'normal' aging. At a cellular level, the aging process disturbs a multitude of intracellular pathways. In particular, alterations in cellular metabolic functions thereby impacting cellular bioenergetics have been implicated in multiple tissues. Therefore, this study aimed to characterize how metabolic processes were altered in bone forming osteoblasts in aged mice compared to young mice. Metabolic flux analyses demonstrated both stromal cells and mature, matrix secreting osteoblasts from aged mice exhibited mitochondrial dysfunction. This was also accompanied by a lack of adaptability or metabolic flexibility to utilize exogenous substrates compared to osteoblasts cultured from young mice. Additionally, lipid droplets accumulated in both early stromal cells and mature osteoblasts from aged mice, which was further depicted as increased lipid content within the bone cortex of aged mice. Global transcriptomic analysis of the bone further supported these metabolic data as enhanced oxidative stress genes were up-regulated in aged mice, while osteoblast-related genes were down-regulated when compared to the young mice. Collectively, these data suggest that aging results in altered osteoblast metabolic handling of both exogenous and endogenous substrates which could contribute to age-related osteoporosis.

A crosstalk between 'osteocyte lacunal-canalicular system' and metabolism

Considering the importance, bone physiology has long been studied to understand what systematic and cellular impact its cells and functions have. Exploring more questions is a substantially solid way to improve the understanding of bone physiological functions in/out sides. In adult bone, osteocytes (Ots) form about 95% of bone cells and live the longest lifespan inside their mineralized surroundings. Ots are the endocrine cells and originate from blood vessel's endothelial cells. In this work, we discussed the vital role of the "Ots". To determine the association between osteocytes' network with metabolic parameters in healthy mice, the experiments were performed on ten (10) adult C57BL6 male mice. Fasting blood and bone samples were collected weekly from mice for measurement of metabolic parameters and bone morphology. Scanning electron microscopy (SEM) revealed a 2D fine morphology of the bone which indicates a strong functional interconnection with bone nano/micro, and macro components of the organs. The long-branched canaliculi look like neurocytes in structure. The morphology and quantitative measurements of the osteocyte lacunal-canalicular system showed its wide spectrum spatial resolution of the positive and negative relationship within this system or metabolite parameters, confirming a strong cross connection between osteocyte lacunal-canalicular system and metabolism. We believe that the findings of this study can deliver a strategy about the potential roles of metabolic relation among osteocytes, insulin, and lipid in management of bone and metabolic diseases.

Alcohol Consumption and Risk of Total Hip Replacement Due to Hip Osteoarthritis in Women

OBJECTIVE

This study was undertaken to examine the relationship between alcohol consumption and hip osteoarthritis in women. Alcohol has been associated with both adverse and beneficial health effects generally; however, the relationship between alcohol consumption and hip osteoarthritis has been minimally studied.

METHODS

Among women in the Nurses' Health Study cohort in the US, alcohol consumption was assessed every 4 years, starting in 1980. Intake was computed as cumulative averages and simple updates with latency periods of 0-4 through 20-24 years. We followed 83,383 women without diagnosed osteoarthritis in 1988 to June 2012. We identified 1,796 cases of total hip replacement due to hip osteoarthritis defined by self-report of osteoarthritis with hip replacement.

RESULTS

Alcohol consumption was positively associated with hip osteoarthritis risk. Compared with nondrinkers, multivariable hazard ratios (HRs) and 95% confidence intervals (95% CIs) were HR 1.04 (95% CI 0.90, 1.19) for drinkers of >0 to <5 grams/day, HR 1.12 (95% CI 0.94, 1.33) for 5 to <10 grams/day, HR 1.31 (95% CI 1.10, 1.56) for 10 to <20 grams/day, and HR 1.34 (95% CI 1.09, 1.64) for ≥20 grams/day (P for trend < 0.0001). This association held in latency analyses of up to 16-20 years, and for alcohol consumption between 35-40 years of age. Independent of other alcoholic beverages, the multivariable HRs (per 10 grams of alcohol) were similar for individual types of alcohol intake (wine, liquor, and beer; P = 0.57 for heterogeneity among alcohol types).

CONCLUSION

Higher alcohol consumption was associated with greater incidence of total hip replacement due to hip osteoarthritis in a dose-dependent manner in women.

Sclerostin in Excessive Drinkers: Relationships with Liver Function and Body Composition

Background: Sclerostin was initially described as an inhibitor of the Wnt-β catenin bone-forming pathway, but it also exerts important effects on intermediate metabolism and body composition. Osteosarcopenia and altered body fat distribution are common findings in excessive drinkers. The role of sclerostin in these patients is uncertain. We aim to analyze the behavior of sclerostin in excessive drinkers and its relationships with body composition (fat mass, lean mass, bone mass), handgrip strength, body mass index (BMI), liver function and ethanol intake. Methods: 107 male active heavy drinkers and 26 age-matched controls were included. Serum sclerostin was determined by ELISA. Body composition analysis was performed by double X-ray absorptiometry. Handgrip strength was recorded using a dynamometer. Liver function was assessed according to Child’s classification. Results: Sclerostin was higher among Child’s C patients, keeping a relationship with deranged liver function. Obesity, defined according to BMI, and body fat were strongly related to sclerostin, being independent of serum creatinine and of liver function. The relationship of sclerostin with total hip bone mineral density was displaced by BMI. Conclusion: Deranged liver function is associated with higher sclerostin levels in alcoholics. Raised sclerostin levels are related to fat deposition and increased BMI.

The altered osteocytic expression of connexin 43 and sclerostin in human cadaveric donors with alcoholic liver cirrhosis: Potential treatment targets

Previous studies suggested that osteocyte lacunar network disruption could play a role in the complex pathophysiology of bone changes in aging and disease. Considering that particular research interest is lacking, we aimed to assess alcoholic liver cirrhosis (ALC)-induced changes in osteocyte lacunar network and bone marrow adiposity. Immunohistochemistry was conducted to assess changes in the micro-morphology of osteocyte lacunar network and bone marrow adiposity, and expression of connexin 43 and sclerostin in vertebral and femoral samples collected from 40 cadaveric men (age range between 44 and 70 years) divided into ALC group (n = 20) and control group (n = 20). Furthermore, the assessment of the potential association between bone changes and the severity of the hepatic disorder (given by Knodell's pathohistologic scoring) was conducted. Our data revealed fewer connexin 43-positive osteocytes per vertebral and femoral bone area (p < 0.01), suggesting defective signal transduction among osteocytes in ALC individuals. Moreover, we found an ALC-induced increase in the number of adipocytes in the vertebral bone marrow (p = 0.038). Considering significant associations between the severity of liver tissue disturbances and impaired functionality of osteocyte lacunar network (Pearson's correlation analyses, p < 0.05), we may assume that timely treatment of the liver disease may delay bone impairment. ALC induced an increase in osteocytic sclerostin expression (p < 0.001), suggesting its role in mediating low bone formation among ALC individuals. Hence, medicaments targeting low bone formation may be beneficial to attenuate the bone changes among ALC patients. However, future clinical studies are required to verify the therapeutic utility of these findings.

Chronic Ethanol Consumption Induces Osteopenia via Activation of Osteoblast Necroptosis

Chronic high-dose alcohol consumption impairs bone remodeling, reduces bone mass, and increases the risk of osteoporosis and bone fracture. However, the mechanisms underlying alcohol-induced osteoporosis are yet to be elucidated. In this study, we showed that excess intake of ethyl alcohol (EtOH) resulted in osteopenia and osteoblast necroptosis in mice that led to necrotic lesions and reduced osteogenic differentiation in bone marrow mesenchymal stem cells (BMMSCs). We found that EtOH treatment led to the activation of the RIPK1/RIPK3/MLKL signaling, resulting in increased osteoblast necroptosis and decreased osteogenic differentiation and bone formation both in vivo and in vitro. We further discovered that excessive EtOH treatment-induced osteoblast necroptosis might partly depend on reactive oxygen species (ROS) generation; concomitantly, ROS contributed to necroptosis of osteoblasts through a positive feedback loop involving RIPK1/RIPK3. In addition, blocking of the RIPK1/RIPK3/MLKL signaling by necrostatin-1 (Nec-1), a key inhibitor of RIPK1 kinase in the necroptosis pathway, or antioxidant N-acetylcysteine (NAC), an inhibitor of ROS, could decrease the activation of osteoblast necroptosis and ameliorate alcohol-induced osteopenia both in vivo and in vitro. Collectively, we demonstrated that chronic high-dose alcohol consumption induced osteopenia via osteoblast necroptosis and revealed that RIPK1 kinase may be a therapeutic target for alcohol-induced osteopenia.

Alcohol consumption induces murine osteoporosis by downregulation of natural killer T-like cell activity

Introduction

Chronic alcohol consumption (CAC) can induce several deleterious effects on the body, including the promotion of osteoporosis; however, the immunological mechanism underlying alcohol‐induced osteoporosis is still unclear.

Methods

We administered alcohol to mice for 4 weeks as the experimental CAC model and analyzed the bone and immune cells that are located in the vicinity of a bone.

Results

IL‐4 is known to be a suppressive factor for osteoclastogenesis, and we found that natural killer T (NKT)‐like cells, which showed NK1.1‐positive, CD3‐positive, and α‐galactosylceramide‐loaded CD1d tetramer‐negative, produced IL‐4 more effectively than CD4⁺ T and natural killer (NK) cells. The alcohol consumption facilitated a significant decrease of bone mineral density with the upregulation of nuclear factor of activated T cells 1 and receptor activator of NF‐κB ligand expression. Meanwhile, we confirmed that alcohol consumption suppressed the activity of antigen‐presenting cells (APCs) and NKT‐like cells, leading to decreased IL‐4 secretion. Moreover, these harmful effects of alcohol consumption were reduced by simultaneous treatment with a glycolipid antigen OCH.

Conclusions

Our results indicate that the inactivation of innate immune cells, APCs, and NKT‐like cells are likely to be crucial for alcohol‐induced osteoporosis and provide a new therapeutic approach for preventing osteoporosis.

Osteoporosis: A role for lipids

An inverse relationship between bone marrow (BM) adiposity and bone mass has been described in different physiological and pathological conditions, including osteoporosis (OP). In osteoporotic patients, lower bone mass density is indeed associated with higher BM fat content, suggesting a potential role for bone lipids in the OP pathogenesis. Nevertheless, some questions remain. Is that BM adiposity a cause or a consequence of the bone loss? What kinds of lipids are involved? Human data are somehow contradictories regarding bone lipid signature related to OP, and animal data are needed to support on one or another way the human observations. Bone lipid signature associated to OP needs to be clarified if we want to understand better their roles in OP. In that context, by using an ovariectomy-induced OP murine model and looking at lipids in two bone compartments: BM and mineralized tissue (MT), our first challenge was to identify local lipid changes in relation to OP, in view to explore later the mechanisms by which those compounds could alter bone quality, particularly during the mineralization process. As the most striking data, long-term OP resulted in an accumulation of triglycerides, reduced levels of arachidonic and docosahexaenoic acids, an increase of stearoyl-CoA desaturase indices and a reduction of sphingomyelin in the MT, and potential consequences on bone properties and cell activities are discussed. The reader will appreciate that we are at an early stage of understanding the roles of lipids in the OP development and more investigations will be necessary.

Low expression of vascular endothelial growth factor and high serum level of cyclic guanine monophosphate as the risk factors of femoral head osteonecrosis in alcohol-exposed Wistar rat

PURPOSE

Severe damage to the femoral head in patients with osteonecrosis has a high impact on morbidity. Despite early diagnosis, the treatment outcome is still unsatisfactory. This study aimed to explore the expression of vascular endothelial growth factor (VEGF) and cyclic guanine monophosphate (cGMP) serum level as the risk factors of femoral head osteonecrosis in alcohol-exposed Wistar rats.

METHODS

This was an experimental study using randomized post-test only control group design, with samples using 10-14 weeks Wistar male rats. Rats were then divided into 6 groups: 3 groups without intervention, and 3 groups with intervention using 40% alcohol given perorally. Each one group from intervention and control group was euthanized by the end of the week for 3 consecutive weeks. Proximal femurs were examined under microscope for osteonecrosis, immunohistochemically for VEGF, and blood serum for cGMP levels.

RESULTS

VEGF expression in the femoral head of alcohol-exposed Wistar rats was lower than those not exposed to alcohol (p < 0.005). Blood serum cGMP levels of alcohol-exposed Wistar rats were higher than those not exposed to alcohol (p < 0.005). The number of necrotic osteocytes in the femoral head of Wistar rats exposed to alcohol was greater than those not exposed to alcohol (p < 0.005). There are significant differences between VEGF, cGMP levels, and number of necrotic osteocytes in the control group and treatment at 1st, 2nd^, and 3rd week (p < 0.005).

CONCLUSIONS

Based on the result of this study, VEGF and cGMP may be considered as diagnostic biomarkers for alcohol-induced femoral head osteonecrosis.

Long Term Ovariectomy-Induced Osteoporosis is Associated with High Stearoyl-CoA Desaturase Indexes in Rat Femur

Osteoporosis is characterized by a bone loss associated to an increased bone marrow adiposity; however, it is still unclear what kind of lipids are involved. Therefore, the main purpose of this study was to see if there is any local bone lipid changes related to osteoporosis, by using the ovariectomy-induced osteoporosis (OVX) rat model. Female SD rats (operated at 6 months of age for skeletal maturity) were divided in control SHAM and OVX groups (n = 6/group) and maintained for 9 month post-surgery. Lipids were analyzed in two compartments of femoral diaphyses: bone marrow (BM) and mineralized tissue (MT), by chromatographic methods. As expected, osteoporotic femurs had a larger BM mass associated with a two-fold increase of lipid content. The MT had a similar lipid enrichment, indicating that adiposity affected the mineral part as well. The main lipids concerned were triglycerides, sphingomyelin, phosphatidylcholine and phosphatidylserine in BM, and triglycerides and cholesterol esters in MT. The increase of both energy-storage and membrane-associated lipids in BM suggested that cell number and/or size was enhanced to allow more triglyceride storage. Interestingly, in MT of osteoporotic femurs, sphingomyelin was decreased, suggesting that its catabolism could be linked to osteoporosis. In both femoral compartments, fatty acid profiles were enriched in 14:0 and 16:1, lowered in 18:0 and 20:4 n-6, and two-fold higher stearoyl-CoA desaturase indexes (16:1/16:0 and 18:1/18:0 ratios), suggesting an increased de novo lipogenesis in osteoporotic femurs. Thus, the present study is first to report local changes of individual lipids in rat osteoporotic femurs and suggests that osteoporosis is a pathologic condition associated with an enhanced de novo lipogenesis. Further studies will be needed to better understand the consequences of these lipid changes in osteoporotic bones.

Lipids in the Bone Marrow: An Evolving Perspective

Because of heavy energy demands to maintain bone homeostasis, the skeletal system is closely tied to whole-body metabolism via neuronal and hormonal mediators. Glucose, amino acids, and fatty acids are the chief fuel sources for bone resident cells during its remodeling. Lipids, which can be mobilized from intracellular depots in the bone marrow, can be a potent source of fatty acids. Thus, while it has been suggested that adipocytes in the bone marrow act as "filler" and are detrimental to skeletal homeostasis, we propose that marrow lipids are, in fact, essential for proper bone functioning. As such, we examine the prevailing evidence regarding the storage, use, and export of lipids within the skeletal niche, including from both in vitro and in vivo model systems. We also highlight the numerous challenges that remain to fully appreciate the relationship of lipid turnover to skeletal homeostasis.

Voluntary Chronic Heavy Alcohol Consumption in Male Rhesus Macaques Suppresses Cancellous Bone Formation and Increases Bone Marrow Adiposity

BACKGROUND

Chronic heavy alcohol consumption is an established risk factor for bone fracture, but comorbidities associated with alcohol intake may contribute to increased fracture rates in alcohol abusers. To address the specific effects of alcohol on bone, we used a nonhuman primate model and evaluated voluntary alcohol consumption on: (i) global markers of bone turnover in blood and (ii) cancellous bone mass, density, microarchitecture, turnover, and microdamage in lumbar vertebra.

METHODS

Following a 4-month induction period, 6-year-old male rhesus macaques (Macaca mulatta, n = 13) voluntarily self-administered water or ethanol (EtOH; 4% w/v) for 22 h/d, 7 d/wk, for a total of 12 months. Control animals (n = 9) consumed an isocaloric maltose-dextrin solution. Tetracycline hydrochloride was administered orally 17 and 3 days prior to sacrifice to label mineralizing bone surfaces. Global skeletal response to EtOH was evaluated by measuring plasma osteocalcin and carboxyterminal collagen cross-links (CTX). Local response was evaluated in lumbar vertebra using dual-energy X-ray absorptiometry, microcomputed tomography, static and dynamic histomorphometry, and histological assessment of microdamage.

RESULTS

Monkeys in the EtOH group consumed an average of 2.8 ± 0.2 (mean ± SE) g/kg/d of EtOH (30 ± 2% of total calories), resulting in an average blood EtOH concentration of 88.3 ± 8.8 mg/dl 7 hours after the session onset. Plasma CTX and osteocalcin tended to be lower in EtOH-consuming monkeys compared to controls. Significant differences in bone mineral density in lumbar vertebrae 1 to 4 were not detected with treatment. However, cancellous bone volume fraction (in cores biopsied from the central region of the third vertebral body) was lower in EtOH-consuming monkeys compared to controls. Furthermore, EtOH-consuming monkeys had lower osteoblast perimeter and mineralizing perimeter, no significant difference in osteoclast perimeter, and higher bone marrow adiposity than controls. No significant differences between groups were detected in microcrack density (2^nd lumbar vertebra).

CONCLUSIONS

Voluntary chronic heavy EtOH consumption reduces cancellous bone formation in lumbar vertebra by decreasing osteoblast-lined bone perimeter, a response associated with an increase in bone marrow adiposity.

Alcohol abuse and disorder of granulopoiesis

Granulocytes are the major type of phagocytes constituting the front line of innate immune defense against bacterial infection. In adults, granulocytes are derived from hematopoietic stem cells in the bone marrow. Alcohol is the most frequently abused substance in human society. Excessive alcohol consumption injures hematopoietic tissue, impairing bone marrow production of granulocytes through disrupting homeostasis of granulopoiesis and the granulopoietic response. Because of the compromised immune defense function, alcohol abusers are susceptible to infectious diseases, particularly septic infection. Alcoholic patients with septic infection and granulocytopenia have an exceedingly high mortality rate. Treatment of serious infection in alcoholic patients with bone marrow inhibition continues to be a major challenge. Excessive alcohol consumption also causes diseases in other organ systems, particularly severe alcoholic hepatitis which is life threatening. Corticosteroids are the only therapeutic option for improving short-term survival in patients with severe alcoholic hepatitis. The existence of advanced alcoholic liver diseases and administration of corticosteroids make it more difficult to treat serious infection in alcoholic patients with the disorder of granulopoieis. This article reviews the recent development in understanding alcohol-induced disruption of marrow granulopoiesis and the granulopoietic response with the focus on progress in delineating cell signaling mechanisms underlying the alcohol-induced injury to hematopoietic tissue. Efforts in exploring effective therapy to improve patient care in this field will also be discussed.

Epidemiology, Cause, and Anatomy of Osteonecrosis of the Foot and Ankle

Osteonecrosis arises throughout the foot and ankle in various forms and due to numerous causes, with a thousand US cases per year estimated for the ankle alone. Although research continues to elucidate specific mechanisms at work, the pathophysiology remains poorly understood. Nevertheless, the various osteonecrosis pathways converge on osteocyte death, and bony lesions follow a pattern of progression. Understanding the specific anatomy and biomechanics associated with common forms of foot and ankle osteonecrosis should help guide diagnosis and interventions, particularly at earlier stages of disease where etiology-specific approaches might become optimal.

Defining osteoblast and adipocyte lineages in the bone marrow

Bone is a complex endocrine organ that facilitates structural support, protection to vital organs, sites for hematopoiesis, and calcium homeostasis. The bone marrow microenvironment is a heterogeneous niche consisting of multipotent musculoskeletal and hematopoietic progenitors and their derivative terminal cell types. Amongst these progenitors, bone marrow mesenchymal stem/stromal cells (BMSCs) may differentiate into osteogenic, adipogenic, myogenic, and chondrogenic lineages to support musculoskeletal development as well as tissue homeostasis, regeneration and repair during adulthood. With age, the commitment of BMSCs to osteogenesis slows, bone formation decreases, fracture risk rises, and marrow adiposity increases. An unresolved question is whether osteogenesis and adipogenesis are co-regulated in the bone marrow. Osteogenesis and adipogenesis are controlled by specific signaling mechanisms, circulating cytokines, and transcription factors such as Runx2 and Pparγ, respectively. One hypothesis is that adipogenesis is the default pathway if osteogenic stimuli are absent. However, recent work revealed that Runx2 and Osx1-expressing preosteoblasts form lipid droplets under pathological and aging conditions. Histone deacetylase 3 (Hdac3) and other epigenetic regulators suppress lipid storage in preosteoblasts and/or control marrow adiposity. Establishing a better understanding of fat storage in bone marrow cells, as well as the osteoblast-adipocyte relationship within the bone marrow niche is necessary to understand the mechanisms underlying disease- and aging-related marrow fat storage and may lead to the development of new therapeutic targets for "fatty bone" and osteoporosis.

A novel method to measure steroid hormone concentrations in walrus bone from archaeological, historical, and modern time periods using liquid chromatography/tandem mass spectrometry

RATIONALE

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was validated and utilized to measure and analyze four steroid hormones related to stress and reproduction in individual samples from a novel tissue, Pacific walrus (Odobenus rosmarus divergens, herein walrus) bone. This method determines steroid hormone concentrations in the remote walrus population over millennia from archaeological (>200 bp), historical (200-20 bp), and modern (2014-2016) time periods.

METHODS

Lipids were extracted from walrus bone collected from these periods using methanol before LC/MS/MS analysis. Isotopically labeled internal standards for each target hormone were added to every sample. Analytical and physiological validations were performed. Additionally, a tissue comparison was done among paired walrus bone, serum, and blubber samples. A rapid resolution liquid chromatography system coupled to a QqQ mass spectrometer was used to analyze all samples after derivatization for progesterone, testosterone, cortisol, and estradiol concentrations. Multiple reaction monitoring was used for MS analysis and data were acquired in positive electrospray ionization mode.

RESULTS

Progesterone, testosterone, cortisol, and estradiol were linear along their respective standard calibration curves based on their R² values (all > 0.99). Accuracy ranged from 93-111% for all hormones. The recovery of extraction, recovery of hormones without matrix effect, was 92-101%. The overall process efficiency of our method for measuring hormones in walrus bone was 93-112%. Progesterone and testosterone concentrations were not affected by reproductive status among adult females and males, respectively. However, estradiol was different among pregnant and non-pregnant adult females. Overall, steroid hormones reflect a long-term reservoir in cortical bone. This method was also successfully applied to walrus bone as old as 3585 bp.

CONCLUSIONS

LC/MS/MS analysis of bone tissue (0.2-0.3 g) provides stress and reproductive data from elusive walruses that were alive thousands of years ago. Based on physiological validations, tissue comparison, and published literature, steroid hormone concentrations measured in walrus cortical bone could represent an accumulated average around a 10-20-year time span. By investigating how stress and reproductive physiology may have changed over the past ~3000 years based on bone steroid hormone concentrations, this method will help answer how physiologically resilient walruses are to climate change in the Arctic.

Intracellular lipid droplets support osteoblast function

Bone formation is an osteoblast-specific process characterized by high energy demands due to the secretion of matrix proteins and mineralization vesicles. While glucose has been reported as the principle fuel source for osteoblasts, recent evidence supports the tenet that osteoblasts can utilize fatty acids as well. Although the ability to accumulate lipid droplets has been demonstrated in many cell types, there has been little evidence that osteoblasts possess this characteristic. The current study provides evidence that osteoblastogenesis is associated with lipid droplet accumulation capable of supplying energy substrates (fatty acids) required for the differentiation process. Understanding the role of fatty acids in metabolic programming of the osteoblast may lead to novel approaches to increase bone formation and ultimately bone mass.

Unfractionated Heparin Promotes Osteoclast Formation in Vitro by Inhibiting Osteoprotegerin Activity

Heparin has been proven to enhance bone resorption and induce bone loss. Since osteoclasts play a pivotal role in bone resorption, the effect of heparin on osteoclastogenesis needs to be clarified. Since osteocytes are the key modulator during osteoclastogenesis, we evaluated heparin’s effect on osteoclastogenesis in vitro by co-culturing an osteocyte cell line (MLO-Y4) and pre-osteoclasts (RAW264.7). In this co-culture system, heparin enhanced osteoclastogenesis and osteoclastic bone resorption while having no influence on the production of RANKL (receptor activator of NFκB ligand), M-CSF (macrophage colony-stimulating factor), and OPG (osteoprotegerin), which are three main regulatory factors derived from osteocytes. According to previous studies, heparin could bind specifically to OPG and inhibit its activity, so we hypothesized that this might be a possible mechanism of heparin activity. To test this hypothesis, osteoclastogenesis was induced using recombinant RANKL or MLO-Y4 supernatant. We found that heparin has no effect on RANKL-induced osteoclastogenesis (contains no OPG). However, after incubation with OPG, the capacity of MLO-Y4 supernatant for supporting osteoclast formation was increased. This effect disappeared after OPG was neutralized and reappeared after OPG was replenished. These results strongly suggest that heparin promotes osteocyte-modulated osteoclastogenesis in vitro, at least partially, through inhibiting OPG activity.

Alcohol: A Simple Nutrient with Complex Actions on Bone in the Adult Skeleton

BACKGROUND

Alcohol is an important nonessential component of diet, but the overall impact of drinking on bone health, especially at moderate levels, is not well understood. Bone health is important because fractures greatly reduce quality of life and are a major cause of morbidity and mortality in the elderly. Regular alcohol consumption is most common following skeletal maturity, emphasizing the importance of understanding the skeletal consequences of drinking in adults.

METHODS

This review focuses on describing the complex effects of alcohol on the adult skeleton. Studies assessing the effects of alcohol on bone in adult humans as well as skeletally mature animal models published since the year 2000 are emphasized.

RESULTS

Light to moderate alcohol consumption is generally reported to be beneficial, resulting in higher bone mineral density (BMD) and reduced age-related bone loss, whereas heavy alcohol consumption is generally associated with decreased BMD, impaired bone quality, and increased fracture risk. Bone remodeling is the principal mechanism for maintaining a healthy skeleton in adults and dysfunction in bone remodeling can lead to bone loss and/or decreased bone quality. Light to moderate alcohol may exert beneficial effects in older individuals by slowing the rate of bone remodeling, but the impact of light to moderate alcohol on bone remodeling in younger individuals is less certain. The specific effects of alcohol on bone remodeling in heavy drinkers are even less certain because the effects are often obscured by unhealthy lifestyle choices, alcohol-associated disease, and altered endocrine signaling.

CONCLUSIONS

Although there have been advances in understanding the complex actions of alcohol on bone, much remains to be determined. Limited evidence implicates age, skeletal site evaluated, duration, and pattern of drinking as important variables. Few studies systematically evaluating the impact of these factors have been conducted and should be made a priority for future research. In addition, studies performed in skeletally mature animals have potential to reveal mechanistic insights into the precise actions of alcohol and associated comorbidity factors on bone remodeling.

Bone changes in alcoholic liver disease

Alcoholism has been associated with growth impairment, osteomalacia, delayed fracture healing, and aseptic necrosis (primarily necrosis of the femoral head), but the main alterations observed in the bones of alcoholic patients are osteoporosis and an increased risk of fractures. Decreased bone mass is a hallmark of osteoporosis, and it may be due either to decreased bone synthesis and/or to increased bone breakdown. Ethanol may affect both mechanisms. It is generally accepted that ethanol decreases bone synthesis, and most authors have reported decreased osteocalcin levels (a “marker” of bone synthesis), but some controversy exists regarding the effect of alcohol on bone breakdown, and, indeed, disparate results have been reported for telopeptide and other biochemical markers of bone resorption. In addition to the direct effect of ethanol, systemic alterations such as malnutrition, malabsorption, liver disease, increased levels of proinflammatory cytokines, alcoholic myopathy and neuropathy, low testosterone levels, and an increased risk of trauma, play contributory roles. The treatment of alcoholic bone disease should be aimed towards increasing bone formation and decreasing bone degradation. In this sense, vitamin D and calcium supplementation, together with biphosphonates are essential, but alcohol abstinence and nutritional improvement are equally important. In this review we study the pathogenesis of bone changes in alcoholic liver disease and discuss potential therapies.

Effects of bioactive lipids and lipoproteins on bone

Although epidemiological studies from the past two decades show a link between atherosclerotic vascular disease and bone loss, that is independent of age, the mechanism is still unclear. This review focuses on evidence that suggests a role for atherogenic lipids and lipoproteins in the pathogenesis of bone loss, including direct effects of these bioactive lipids/lipoproteins on bone cells, inhibiting osteoblastic differentiation and promoting osteoclastic differentiation. It also addresses recent evidence that suggests that bioactive lipids blunt the effects of bone anabolic agents such as teriparatide and bone morphogenetic proteins. Systemic and intracellular oxidant stress and inflammation are implicated in mediating the effects of bioactive lipids/lipoproteins.