Low bone accrual is associated with osteocyte apoptosis in alcohol-induced osteopenia

1 H-13 C cross-polarization kinetics to probe hydration-dependent organic components of bone extracellular matrix

Bone is a living tissue made up of organic proteins, inorganic minerals, and water. The organic component of bone (mainly made up of Type-I collagen) provides flexibility and tensile strength. Solid-state nuclear magnetic resonance (ssNMR) is one of the few techniques that can provide atomic-level structural insights of such biomaterials in their native state. In the present article, we employed the variable contact time cross-polarization (¹ H-¹³ C CP) kinetics experiments to study the hydration-dependent atomic-level structural changes in the bone extracellular matrix (ECM). The natural abundant ¹³ C CP intensity of the bone ECM is measured by varying CP contact time and best fitted to the nonclassical kinetic model. Different relaxation parameters were measured by the best-fit equation corresponding to the different hydration conditions of the bone ECM. The associated changes in the measured parameters due to varying levels of hydration observed at different sites of collagen protein have provided its structural arrangements and interaction with water molecules in bone ECM. Overall, the present study reveals a better understanding of the kinetics of the organic part inside the bone ECM that will help in comprehending the disease-associated pathways.

Alcohol Consumption and Risk of Fractures: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

Alcohol consumption remains inconsistently correlated with fracture risk, and a dose-response meta-analysis for specific outcomes is lacking. The objective of this study was to quantitatively integrate the data on the relationship between alcohol consumption and fracture risk. Pertinent articles were identified in PubMed, Web of Science, and Embase databases up to 20 February 2022. Combined RRs and 95% CIs were estimated by random- or fixed-effects models. Restricted cubic splines were used to model linear or nonlinear relationships. Forty-four articles covering 6,069,770 participants and 205,284 cases of fracture were included. The combined RRs and 95% CIs for highest compared with lowest alcohol consumption were 1.26 (1.17-1.37), 1.24 (1.13-1.35), and 1.20 (1.03-1.40) for total, osteoporotic, and hip fractures, respectively. A linear positive relationship between alcohol consumption and total fracture risk was detected (Pnonlinearity = 0.057); the risk was correlated with a 6% increase (RR, 1.06; 95% CI: 1.02, 1.10) per 14 g/d increment of alcohol consumption. J-shaped relationships of alcohol consumption with risk of osteoporotic fractures (Pnonlinearity < 0.001) and hip fractures (Pnonlinearity < 0.001) were found. Alcohol consumption of 0 to 22 g/d was linked to a reduced risk of osteoporotic fractures and hip fractures. Our findings show that any level of alcohol consumption is a risk factor for total fractures. Moreover, this dose-response meta-analysis shows that an alcohol consumption level of 0 to 22 g/d is related to a reduction in the risk of osteoporotic and hip fractures. The protocol was registered in the International Prospective Register of Systematic Reviews (CRD42022320623).

Impact of Alcohol on Bone Health in People Living With HIV: Integrating Clinical Data From Serum Bone Markers With Morphometric Analysis in a Non-Human Primate Model

People living with HIV (PLWH) represent a vulnerable population to adverse musculoskeletal outcomes due to HIV infection, antiretroviral therapy (ART), and at-risk alcohol use. Developing measures to prevent skeletal degeneration in this group requires a grasp of the relationship between alcohol use and low bone mass in both the PLWH population and its constituents as defined by sex, age, and race. We examined the association of alcohol use with serum biochemical markers of bone health in a diverse cohort of PLWH enrolled in the New Orleans Alcohol Use in HIV (NOAH) study. To explore the effects of alcohol on bone in the context of HIV and ART and the role of estrogen, we conducted a parallel, translational study using simian immunodeficiency virus (SIV)+/ART+ female rhesus macaques divided into four groups: vehicle (Veh)/Sham; chronic binge alcohol (CBA)/Sham; Veh/ovariectomy (OVX); and CBA/OVX. Clinical data showed that both osteocalcin (Ocn) and procollagen type I N-propeptide (PINP) levels were inversely associated with multiple measures of alcohol consumption. Age (>50 years) significantly increased susceptibility to alcohol-associated suppression of bone formation in both female and male PLWH, with postmenopausal status appearing as an additional risk factor in females. Serum sclerostin (Scl) levels correlated positively with measures of alcohol use and negatively with Ocn. Micro-CT analysis of the macaque tibias revealed that although both CBA and OVX independently decreased trabecular number and bone mineral density, only OVX decreased trabecular bone volume fraction and impacted cortical geometry. The clinical data implicate circulating Scl in the pathogenesis of alcohol-induced osteopenia and suggest that bone morphology can be significantly altered in the absence of net change in osteoblast function as measured by serum markers. Inclusion of sophisticated tools to evaluate skeletal strength in clinical populations will be essential to understand the impact of alcohol-induced changes in bone microarchitecture. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

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.

Secondary Osteoporosis and Metabolic Bone Diseases

Fragility fracture is a worldwide problem and a main cause of disability and impaired quality of life. It is primarily caused by osteoporosis, characterized by impaired bone quantity and or quality. Proper diagnosis of osteoporosis is essential for prevention of fragility fractures. Osteoporosis can be primary in postmenopausal women because of estrogen deficiency. Secondary forms of osteoporosis are not uncommon in both men and women. Most systemic illnesses and organ dysfunction can lead to osteoporosis. The kidney plays a crucial role in maintaining physiological bone homeostasis by controlling minerals, electrolytes, acid-base, vitamin D and parathyroid function. Chronic kidney disease with its uremic milieu disturbs this balance, leading to renal osteodystrophy. Diabetes mellitus represents the most common secondary cause of osteoporosis. Thyroid and parathyroid disorders can dysregulate the osteoblast/osteoclast functions. Gastrointestinal disorders, malnutrition and malabsorption can result in mineral and vitamin D deficiencies and bone loss. Patients with chronic liver disease have a higher risk of fracture due to hepatic osteodystrophy. Proinflammatory cytokines in infectious, autoimmune, and hematological disorders can stimulate osteoclastogenesis, leading to osteoporosis. Moreover, drug-induced osteoporosis is not uncommon. In this review, we focus on causes, pathogenesis, and management of secondary osteoporosis.

Free-fall landing and interval running have different effects on trabecular bone mass and microarchitecture, serum osteocalcin, biomechanical properties, SOST expression and on osteocyte-related characteristics

The effects of treadmill interval training (IT) and free-fall exercise were evaluated on bone parameters including osteocyte related characteristics. Thirty-eight 4-month-old male Wistar rats were randomly divided into a control (C) group and exercise groups: IT, 10 free-fall impacts/day with a 10-s (FF10) or 20-s interval between drops (FF20), 5 days/week, for 9 weeks. We assessed bone mineral density (BMD); microarchitecture by µCT; mechanical strength by a 3-point bending test; density and occupancy of the osteocyte lacunae by toluidine blue staining; osteocalcin and NTx systemic levels by ELISA; and bone tissue Sost messenger RNA (mRNA) expression by RT-PCR. NTx levels were significantly lower in exercise groups as compared with the C group. In exercise groups the Sost mRNA expression was significantly lower than in C. Tb.N was significantly higher for IT and FF20 compared with the C group. Tb.Sp was significantly lower in FF10 compared with the C group. Both IT and FF20 were associated with higher tibial lacunar density as compared with FF10. compared with FF10, IT fat mass was lower, while tibial osteocyte lacunae occupancy and systemic osteocalcin level were higher. All exercise modes were efficient in reducing bone resorption. Both IT and free-fall impact with appropriate recovery periods, which may be beneficial for bone health and osteocyte-related characteristics. Novelty: Interval training is beneficial for bone mineral density. Exercises decreased both bone resorption and inhibition of bone formation (Sost mRNA). Longer interval recovery time favors osteocyte lacunae density.

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.

Cumulative Effects of Strontium Ranelate and Impact Exercise on Bone Mass in Ovariectomized Rats

OBJECTIVE

To explore the effect of physical exercise (EXE), strontium ranelate (SR), or their combination on bone status in ovariectomized (OVX) rats.

DESIGN

Sixty female Wistar rats were randomized to one of five groups: sham (Sh), OVX (O), OVX+EXE (OE), OVX+SR (OSR), and OVX+EXE+SR (OESR). Animals in EXE groups were subjected to 10 drops per day (45 cm in height); rats in SR groups received 625 mg/kg/day of SR, 5 days/week for 8 weeks. Bone mineral density (BMD) and bone mineral content (BMC, dual-energy X-ray absorptiometry (DXA)), mechanical strength of the left femur (three-point bending test), and femur microarchitecture of (micro-computed tomography imaging, microCT) analyses were performed to characterize biomechanical and trabecular/cortical structure. Bone remodeling, osteocyte apoptosis, and lipid content were evaluated by ELISA and immunofluorescence tests.

RESULTS

In OVX rats, whole-body BMD, trabecular parameters, and osteocalcin (OCN) levels decreased, while weight, lean/fat mass, osteocyte apoptosis, and lipid content all increased. EXE after ovariectomy improved BMD and BMC, trabecular parameters, cross-sectional area (CSA), moment of inertia, and OCN levels while decreasing osteocyte apoptosis and lipid content. SR treatment increased BMD and BMC, trabecular parameters, CSA, stiffness, OCN, and alkaline phosphatase (ALP) levels. Furthermore, fat mass, N-telopeptide (NTX) level, osteocyte apoptosis, and lipid content significantly decreased. The combination of both EXE and SR improved bone parameters compared with EXE or SR alone.

CONCLUSION

EXE and SR had positive and synergistic effects on bone formation and resorption.

Effects of Neurological Disorders on Bone Health

Neurological diseases, particularly in the context of aging, have serious impacts on quality of life and can negatively affect bone health. The brain-bone axis is critically important for skeletal metabolism, sensory innervation, and endocrine cross-talk between these organs. This review discusses current evidence for the cellular and molecular mechanisms by which various neurological disease categories, including autoimmune, developmental, dementia-related, movement, neuromuscular, stroke, trauma, and psychological, impart changes in bone homeostasis and mass, as well as fracture risk. Likewise, how bone may affect neurological function is discussed. Gaining a better understanding of brain-bone interactions, particularly in patients with underlying neurological disorders, may lead to development of novel therapies and discovery of shared risk factors, as well as highlight the need for broad, whole-health clinical approaches toward treatment.

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.

Evaluation of the Use of an Inorganic Bone Matrix in the Repair of Bone Defects in Rats Submitted to Experimental Alcoholism

To assess the effects of chronic alcoholism on the repair of bone defects associated with xenograft. Forty male rats were distributed in: control group (CG, n = 20) and experimental group (EG, n = 20), which received 25% ethanol ad libitum after a period of adaptation. After 90 days of liquid diet, the rats were submitted to 5.0-mm bilateral craniotomy on the parietal bones, subdividing into groups: CCG (control group that received only water with liquid diet and the defect was filled with blood clot), BCG (control group that received only water with liquid diet and the defect was filled with biomaterial), CEG (alcoholic group that received only ethanol solution 25% v/v with liquid diet and the defect was filled with blood clot), and BEG (alcoholic group that received only ethanol solution 25% v/v with liquid diet and the defect was filled with biomaterial). In the analysis of body mass, the drunk animals presented the lowest averages in relation to non-drunk animals during the experimental period. Histomorphologically all groups presented bone formation restricted to the defect margins at 60 days, with bone islets adjacent to the BCG biomaterial particles. CEG showed significant difference compared to BEG only at 40 days (17.42 ± 2.78 vs. 9.59 ± 4.59, respectively). In the birefringence analysis, in early periods all groups showed red-orange birefringence turning greenish-yellow at the end of the experiment. The results provided that, regardless of clinical condition, i.e., alcoholic or non-alcoholic, in the final period of the experiment, the process of bone defect recomposition was similar with the use of xenograft or only clot.

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.

Administration of alpha-lipoic acid could maintain bone mass and bone strength in senile female rats with alcohol consumption

Previous studies have demonstrated the damaging effect of alcohol (ALH) consumption on bone tissue and bone metabolism. Alpha-lipoic acid (ALA) promotes osteoblast proliferation and inhibits osteoclast proliferation, and positively affects bone regeneration; however, reports about effects of ALA on bone loss for aged female rats with ALH consumption are limited. This study was designed to investigate the impact of treatment with ALA on bone loss for aged female rats with ALH consumption. In this study 30 female Sprague-Dawley rats (22 months old), weighing approximately 520 g, were incorporated. The animals were randomly divided into three groups: group CON, group ALH and group ALH + ALA and received saline, ALH, ALH plus ALA treatment until death at 16 weeks, respectively. The results of maintaining bone mass and bone strength in senile female rats with ALH consumption were evaluated by histology, microcomputerized tomography, gene expression analysis and biomechanical tests. Results from this study indicated that ALH + ALA had stronger effects on the prevention and treatment of osteoporosis in senile female rats with ALH consumption. The ALH + ALA produced stronger effects on the bone volume ratio (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp), BMD and strength of distal femurs, and regulation of osteogenesis and bone resorption-related gene expression. These results seem to indicate that ALA intervention prevents bone loss in senile female rats with ALH consumption.

Influence of physical training on markers of bone turnover, mechanical properties, morphological alterations, density and mineral contents in the femur of rats exposed to cadmium and/or alcohol

The aim of the study was to investigate the effect of physical training on bone parameters of rats exposed to alcohol (Al) and/or cadmium (Cd). Young female rats were divided into one control group and six groups exposed to Cd and/or Al. Al (36% calories of diet) and Cd (20 mg Cd/kg feed) were administered with liquid diet. Half of the rats from the treated groups were subjected to treadmill training (20 m/min for 0.5 h, 4 days a week). The experiment was carried out for 5 months. Al decreased the concentration of calcium (Ca) and iron (Fe) in the femur, whereas Cd and Cd + Al intake reduced the contents of Ca, Fe and zinc. Al and/or Cd caused an increase in both C-terminal telopeptide of type I collagen (CTX1; bone resorption marker) and osteocalcin (OC; formation indicator) and enhanced the degree of porosity and flexural strength of the femur. Al partially prevented the loss of Fe from the bone caused by Cd, but intensified the inhibition of growth of body weight in comparison with separate exposure to Cd. In rats co-exposed to Cd + Al, the levels of CTX1 were greater compared with those treated with Al or Cd separately, and the density was less than that in rats exposed to Al separately. The training caused increases of magnesium and Ca contents, decreases in CTX1, as well as increases in OC and bone density, decreasing their porosity. The effect of training on the bone status, however, was limited (especially in rats co-exposed to Cd and Al) because of the increase in their mineralization, stimulated by exercises, was insufficient in relation to collagen production intensity. In conclusion, training had favourable effects on some bone parameters, but did not compensate for the negative effects of Al and/or Cd exposure on the poor mineralization and histopathological and morphological changes in the femur.

Resveratrol reverses the negative effect of alcohol on hydroxyapatite-coated implant osseointegration in senile female rats

Previous studies have demonstrated the damaging effect of alcohol (ALH) consumption on bone tissue and bone metabolism. Resveratrol (RES) promotes osteoblast proliferation and inhibits osteoclast proliferation and positively affects bone regeneration; however, reports about effects of RES on osseointegration in aged female rats with ALH consumption are limited. This study was designed to investigate the impact of treatment with RES on osseointegration for aged female rats with ALH consumption. This study included 30 female Sprague-Dawley rats (22 months old), weighing approximately 520 g. All animals were randomly divided into 3 groups of 10: a control group (CON) receiving saline, a group receiving ALH and a group receiving ALH + RES until death after 12 weeks. The results of enhanced osseointegration in senile female rats with RES consumption were evaluated by histology, microcomputerized tomography (micro-CT), gene expression analysis and a biomechanical test. The results of this study indicated that ALH + RES showed stronger effects on the improvement of osseointegration in senile female rats with ALH consumption. The ALH + RES produced stronger effects on bone volume per total volume (BV/TV), mean trabecular thickness (Tb.Th), mean trabecular number (Tb.N) and mean trabecular separation (Tb.Sp), connective tissue density (Conn.D) and maximum push-out force for implants, and regulation of osteogenesis and bone resorption-related gene expression. These results seem to indicate that RES intervention reverses the negative effect of alcohol on hydroxyapatite-coated implant osseointegration in senile female rats with ALH consumption.

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.

Ptychographic X-ray CT characterization of the osteocyte lacuno-canalicular network in a male rat's glucocorticoid induced osteoporosis model

Ptychographic X-ray computed tomography (PXCT) is a quantitative imaging modality that non-destructively maps the 3D electron density inside an object with tens of nanometers spatial resolution. This method provides unique access to the morphology and structure of the osteocyte lacuno-canalicular network (LCN) and nanoscale density of the tissue in the vicinity of an osteocyte lacuna. Herein, we applied PXCT to characterize the lacunae and LCN in a male Wistar rat model of glucocorticoid-induced osteoporosis (GIO). The ptychographic images revealed significant (p < 0.05) differences in the number of canaliculi originating from the lacuna per ellipsoidal surface unit, Ca.Nb (p = 0.0106), and the 3D morphology of the lacuna (p = 0.0064), between GIO and SHAM groups. Moreover, the mean canalicular diameter, Ca.Dm, was slightly statistically un-significantly smaller in GIO (152 ± 6.5) nm than in SHAM group (165 ± 8) nm (p = 0.053). Our findings indicate that PXCT can non-destructively provide detailed, nanoscale information on the 3D organization of the LCN in correlative studies of pathologies, such as osteoporosis, leading to improved diagnosis and therapy.

Association of reduced sclerostin expression with collapse process in patients with osteonecrosis of the femoral head

PURPOSE

Sclerostin is an osteocyte-derived protein that has a potent inhibitory effect on osteoblast activity. The osteocyte apoptosis induced by various causes of osteonecrosis of the femoral head (ONFH) plays a key role in the promotion of femoral head collapse. But the effect of altering sclerostin level on the collapse of ONFH has not been studied. Our aim was to assess the role of sclerostin level in the collapse of ONFH.

METHODS

Between May 2016 and November 2016, 236 subjects were enrolled in the present study. The patients were classified according to the Association Research Circulation Osseous (ARCO) classification. The clinical bone histomorphology, the expression position, and level of sclerostin as well as the plasma sclerostin level were evaluated.

RESULTS

The sclerostin level was significantly lower in the non-traumatic ONFH group than those in the healthy control group (P = 0.002). The sclerostin level was negatively associated with ARCO stages (r = - 0.239, P = 0.009) and significantly lower in the postcollapse group (P = 0.025).

CONCLUSIONS

The reduced expression of sclerostin may play a key role in the collapse process of ONFH and be predictive of the disease progression of ONFH.

Association between alcohol consumption and bone mineral density in elderly Korean men and women

In this cross-sectional study based on Korean elderly men and women, heavy alcohol intake for men was related to low whole-body BMD and light alcohol intake for women was associated with high whole-body, lumbar, and total femur BMD.

PURPOSE

Alcohol is a risk factor of osteoporosis but previous studies on its effect on bone health has been controversial. The aim of this study was to evaluate the association between alcohol intake and bone mineral density in Korean elderly men and women.

METHODS

Based on the Fourth and Fifth Korean National Health and Nutrition Examination Surveys (KNHANES), 2657 men and 2080 women 50 to 79 years of age were included. Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry (DXA). Alcohol consumption was determined by self-administered questionnaires and classified into four groups according to sex: non-drinkers (0 g/day), light drinking (1-19 g/day men, 1-9 g/day women), moderate drinking (20-39 g/day men, 10-29 g/day women), and heavy drinking (≥ 40 g/day men, ≥ 20 g/day women). The adjusted mean values calculated by linear regression analysis for BMD were determined according to the amount of alcohol consumed.

RESULTS

Light drinkers had the highest whole-body BMD for both men (mean 1.164, SD 0.047-1.281) and women (mean 1.046, SD 0.912-1.180). Among men, mean whole-body BMD for heavy drinkers was significantly lower than that among light drinkers (P = 0.031). Among women, BMD for light drinkers was significantly higher in the whole body, lumbar, and total femur than that for non-drinkers (P < 0.001, P = 0.026, P = 0.040, respectively).

CONCLUSIONS

Heavy alcohol intake may be associated with lower BMD in men while light alcohol intake may associate with higher BMD among women. Future longitudinal studies investigating the effect of alcohol consumption on bone mineral density are needed to validate the findings of this study.

The Role of the Osteocyte in Bone and Nonbone Disease

When normal physiologic functions go awry, disorders and disease occur. This is universal; even for the osteocyte, a cell embedded within the mineralized matrix of bone. It was once thought that this cell was simply a placeholder in bone. Within the last decade, the number of studies of osteocytes has increased dramatically, leading to the discovery of novel functions of these cells. With the discovery of novel physiologic functions came the discoveries of how these cells can also be responsible for not only bone diseases and disorders, but also those of the kidney, heart, and potentially muscle.

OPG and RANKL polymorphisms are associated with alcohol-induced osteonecrosis of the femoral head in the north area of China population in men

Alcohol-induced osteonecrosis of the femoral head (ONFH) is an important pathogenesis of nontraumatic ONFH. However, the mechanisms of the pathogenesis are still unknown. Osteoprotegerin (OPG) and receptor activator of nuclear factor-kappa B ligand (RANKL) have been implicated in multiple functions including blocking osteoclast maturation, controlling vascular calcifications, and promoting tumor growth and metastasis. The purpose of this article was to explore the association between OPG and RANKL gene variants and alcohol-induced ONFH. Six hundred seventy male subjects (335 patients and 335 normal individuals) were enrolled in our study. We selected 24 single-nucleotide polymorphisms (SNPs) to evaluate the association between genetic susceptibility variants and alcohol-induced ONFH using the chi-square test and gene model analysis. Overall, the OPG SNPs (rs1032128 and rs11573828) were associated with the strongest increased risk of alcohol-induced ONFH in the recessive model (rs1032128: odds ratio [OR] 1.49, 95% confidence interval [CI] 1.00-2.22, P = 0.04 for G/A; rs11573828: OR 3.32, 95% CI 1.07-10.30, P = 0.03 for T/C). The RANKL SNP rs2200287 was also an increased risk factor (OR 3.65, 95% CI 1.53-8.47, P = 0.003 for T/C) in the recessive model. The rs11573856, rs3134056, and rs1564861 SNPs were considered protective factors for alcohol-induced ONFH. We concluded that OPG and RANKL polymorphisms were associated with the occurrence of alcohol-induced ONFH.

Chronic High Dose Alcohol Induces Osteopenia via Activation of mTOR Signaling in Bone Marrow Mesenchymal Stem Cells

Chronic consumption of excessive alcohol results in reduced bone mass, impaired bone structure, and increased risk of bone fracture. However, the mechanisms underlying alcohol-induced osteoporosis are not fully understood. Here, we show that high dose chronic alcohol consumption reduces osteogenic differentiation and enhances adipogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs), leading to osteopenia in a mouse model. Mechanistically, impaired osteo/adipogenic lineage differentiation of BMMSCs is due to activation of a phosphatidylinositide 3-kinase/AKT/mammalian target of rapamycin (mTOR) signaling cascade, resulting in downregulation of runt-related transcription factor 2 and upregulation of peroxisome proliferator-activated receptor gamma via activation of p70 ribosomal protein S6 kinase. Blockage of the mTOR pathway by rapamycin treatment ameliorates alcohol-induced osteopenia by rescuing impaired osteo/adipogenic lineage differentiation of BMMSCs. In this study, we identify a previously unknown mechanism by which alcohol impairs BMMSC lineage differentiation and reveal a potential rapamycin-based drug therapy for alcohol-induced osteoporosis. Stem Cells 2016;34:2157-2168.

Deficiency of circadian clock protein BMAL1 in mice results in a low bone mass phenotype

The circadian clock is an endogenous time keeping system that controls the physiology and behavior of many organisms. The transcription factor Brain and Muscle ARNT-like Protein 1 (BMAL1) is a component of the circadian clock and necessary for clock function. Bmal1(-/-) mice display accelerated aging and many accompanying age associated pathologies. Here, we report that mice deficient for BMAL1 have a low bone mass phenotype that is absent at birth and progressively worsens over their lifespan. Accelerated aging of these mice is associated with the formation of bony bridges occurring across the metaphysis to the epiphysis, resulting in shorter long bones. Using micro-computed tomography we show that Bmal1(-/-) mice have reductions in cortical and trabecular bone volume and other micro-structural parameters and a lower bone mineral density. Histology shows a deficiency of BMAL1 results in a reduced number of active osteoblasts and osteocytes in vivo. Isolation of bone marrow derived mesenchymal stem cells from Bmal1(-/-) mice demonstrate a reduced ability to differentiate into osteoblasts in vitro, which likely explains the observed reductions in osteoblasts and osteocytes, and may contribute to the observed osteopenia. Our data support the role of the circadian clock in the regulation of bone homeostasis and shows that BMAL1 deficiency results in a low bone mass phenotype.

Sclerostin antibody and interval treadmill training effects in a rodent model of glucocorticoid-induced osteopenia

Glucocorticoids have a beneficial anti-inflammatory and immunosuppressive effect, but their use is associated with decreased bone formation, bone mass and bone quality, resulting in an elevated fracture risk. Exercise and sclerostin antibody (Scl-Ab) administration have both been shown to increase bone formation and bone mass, therefore the ability of these treatments to inhibit glucocorticoid-induced osteopenia alone or in combination were assessed in a rodent model. Adult (4 months-old) male Wistar rats were allocated to a control group (C) or one of 4 groups injected subcutaneously with methylprednisolone (5mg/kg/day, 5 days/week). Methylprednisolone treated rats were injected subcutaneously 2 days/week with vehicle (M) or Scl-Ab-VI (M+S: 25mg/kg/day) and were submitted or not to treadmill interval training exercise (1h/day, 5 days/week) for 9 weeks (M+E, M+E+S). Methylprednisolone treatment increased % fat mass and % apoptotic osteocytes, reduced whole body and femoral bone mineral content (BMC), reduced femoral bone mineral density (BMD) and osteocyte lacunae occupancy. This effect was associated with lower trabecular bone volume (BV/TV) at the distal femur. Exercise increased BV/TV, osteocyte lacunae occupancy, while reducing fat mass, the bone resorption marker NTx, and osteocyte apoptosis. Exercise did not affect BMC or cortical microarchitectural parameters. Scl-Ab increased the bone formation marker osteocalcin and prevented the deleterious effects of M on bone mass, further increasing BMC, BMD and BV/TV to levels above the C group. Scl-Ab increased femoral cortical bone parameters at distal part and midshaft. Scl-Ab prevented the decrease in osteocyte lacunae occupancy and the increase in osteocyte apoptosis induced by M. The addition of exercise to Scl-Ab treatment did not result in additional improvements in bone mass or bone strength parameters. These data suggest that although our exercise regimen did prevent some of the bone deleterious effects of glucocorticoid treatment, particularly in trabecular bone volume and osteocyte apoptosis, Scl-Ab treatment resulted in marked improvements in bone mass across the skeleton and in osteocyte viability, resulting in decreased bone fragility.

Effects of short-term gentle treadmill walking on subchondral bone in a rat model of instability-induced osteoarthritis

OBJECTIVE

Subchondral bone cyst (SBC) growth, caused by osteoclast activity during early knee osteoarthritis (OA) pathogenesis, should be treated to prevent further progressions of OA. In the present study, we evaluated the effects of gentle treadmill walking on subchondral bone and cartilage changes in an experimental rat model of destabilized medial meniscus (DMM).

METHOD

Twelve-week-old Wistar rats underwent DMM surgery in their right knee and sham surgery in their left knee and were assigned to either the sedentary group or walking group (n = 42/group). Animals in the walking group were subjected to treadmill exercise 2 days after surgery, which included walking for 12 m/min, 30 min/day, 5 days/week for 1, 2, and 4 week(s). Subchondral bone and cartilage changes were evaluated by micro-CT analysis, histological analysis, and biomechanical analysis.

RESULTS

Treadmill walking had a tendency to suppress SBC growth, which was confirmed by micro-CT (P = 0.06) and positive staining for tartrate-resistant acid phosphatase (TRAP) activity for the osteoclast number per bone surface (P = 0.09) 4 weeks after surgery. These changes coincide with the prevention of cartilage degeneration as evaluated by the Osteoarthritis Research Society International (OARSI) score (P < 0.05) and biomechanically softening (P < 0.05). Furthermore, treadmill walking could suppressed increasing osteocyte deaths (P < 0.01), which was positively correlated with the OARSI score (r = 0.77; P < 0.01).

CONCLUSION

These results indicate biomechanical and biological links exist between cartilage and subchondral bone; preventive effects of treadmill walking on subchondral bone deterioration might be partly explained by the chondroprotective effects.

Bone quality: the determinants of bone strength and fragility

Bone fragility is a major health concern, as the increased risk of bone fractures has devastating outcomes in terms of mortality, decreased autonomy, and healthcare costs. Efforts made to address this problem have considerably increased our knowledge about the mechanisms that regulate bone formation and resorption. In particular, we now have a much better understanding of the cellular events that are triggered when bones are mechanically stimulated and how these events can lead to improvements in bone mass. Despite these findings at the molecular level, most exercise intervention studies reveal either no effects or only minor benefits of exercise programs in improving bone mineral density (BMD) in osteoporotic patients. Nevertheless, and despite that BMD is the gold standard for diagnosing osteoporosis, this measure is only able to provide insights regarding the quantity of bone tissue. In this article, we review the complex structure of bone tissue and highlight the concept that its mechanical strength stems from the interaction of several different features. We revisited the available data showing that bone mineralization degree, hydroxyapatite crystal size and heterogeneity, collagen properties, osteocyte density, trabecular and cortical microarchitecture, as well as whole bone geometry, are determinants of bone strength and that each one of these properties may independently contribute to the increased or decreased risk of fracture, even without meaningful changes in aBMD. Based on these findings, we emphasize that while osteoporosis (almost) always causes bone fragility, bone fragility is not always caused just by osteoporosis, as other important variables also play a major role in this etiology. Furthermore, the results of several studies showing compelling data that physical exercise has the potential to improve bone quality and to decrease fracture risk by influencing each one of these determinants are also reviewed. These findings have meaningful clinical repercussions as they emphasize the fact that, even without leading to improvements in BMD, exercise interventions in patients with osteoporosis may be beneficial by improving other determinants of bone strength.

EMMPRIN/CD147 deficiency disturbs ameloblast-odontoblast cross-talk and delays enamel mineralization

Tooth development is regulated by a series of reciprocal inductive signaling between the dental epithelium and mesenchyme, which culminates with the formation of dentin and enamel. EMMPRIN/CD147 is an Extracellular Matrix MetalloPRoteinase (MMP) INducer that mediates epithelial-mesenchymal interactions in cancer and other pathological processes and is expressed in developing teeth. Here we used EMMPRIN knockout (KO) mice to determine the functional role of EMMPRIN on dental tissue formation. We report a delay in enamel deposition and formation that is clearly distinguishable in the growing incisor and associated with a significant reduction of MMP-3 and MMP-20 expression in tooth germs of KO mice. Insufficient basement membrane degradation is evidenced by a persistent laminin immunostaining, resulting in a delay of both odontoblast and ameloblast differentiation. Consequently, enamel volume and thickness are decreased in adult mutant teeth but enamel maturation and tooth morphology are normal, as shown by micro-computed tomographic (micro-CT), nanoindentation, and scanning electron microscope analyses. In addition, the dentino-enamel junction appears as a rough calcified layer of approximately 10±5μm thick (mean±SD) in both molars and growing incisors of KO adult mice. These results indicate that EMMPRIN is involved in the epithelial-mesenchymal cross-talk during tooth development by regulating the expression of MMPs. The mild tooth phenotype observed in EMMPRIN KO mice suggests that the direct effect of EMMPRIN may be limited to a short time window, comprised between basement membrane degradation allowing direct cell contact and calcified matrix deposition.

Effect of interval-training exercise on subchondral bone in a chemically-induced osteoarthritis model

OBJECTIVES

The role of subchondral bone in osteoarthritis (OA) development is well admitted. Cross-talk between subchondral bone and cartilage may be disrupted in OA, leading to altered subchondral bone remodeling. Osteocytes are involved in bone remodeling control and could play a key role in OA progression. Our purpose of this study was to evaluate the preventive effect of interval-training exercise on subchondral bone and osteocyte in monosodium iodoacetate (MIA) model of experimental OA.

METHODS

At baseline, 48 male Wistar rats (8 weeks old) were separated into two groups: interval-training exercise or no exercise for 10 weeks. After this training period, each group was divided into two subgroups: MIA-injected knee (1 mg/100 μl saline) and saline-injected knee. Four weeks later, rats were sacrificed and carefully dissected. Evaluated parameters were: cartilage degeneration by OA scoring, bone mineral density (BMD) by Dual energy X-ray Absorptiometry (DXA), trabecular subchondral bone microarchitecture by micro-computed tomography (μCT), cortical subchondral bone lacunar osteocyte occupancy (by Toluidine Blue staining) and cleaved caspase-3 positive apoptosis (by epifluorescence).

RESULTS

Our results showed deleterious effects of MIA on cartilage. OA induced a decrease in proximal tibia (PT) BMD which was prevented by exercise. Exercise induced increase in full osteocyte lacunae surface and osteocyte occupancy (+60%) of cortical subchondral bone independently of OA. Osteocyte apoptosis (<1%) in cortical subchondral bone was not different whatever the group at sacrifice.

CONCLUSION

Our results suggest that preliminary interval-training improved BMD and osteocytes lacunar occupancy in subchondral bone. Our interval-training did not prevent MIA-induced cartilage degeneration.

The thiocarbamate disulphide drug, disulfiram induces osteopenia in rats by inhibition of osteoblast function due to suppression of acetaldehyde dehydrogenase activity

Dithiocarbamates (DTC), a sulfhydryl group containing compounds, are extensively used by humans that include metam and thiram due to their pesticide properties, and disulfiram (DSF) as an alcohol deterrent. We screened these DTC in an osteoblast viability assay. DSF exhibited the highest cytotoxicity (IC50 488nM). Loss in osteoblast viability and proliferation was due to induction of apoptosis via G1 arrest. DSF treatment to osteoblasts reduced glutathione (GSH) levels and exogenous addition of GSH prevented DSF-induced reactive oxygen species generation and osteoblast apoptosis. DSF also inhibited osteoblast differentiation in vitro and in vivo, and the effect was associated with inhibition of aldehyde dehydrogenase (ALDH) activity. Out of various ALDH isozymes, osteoblasts expressed only ALDH2 and DSF downregulated its transcript as well as activity. Alda-1, a specific activator of ALDH2, stimulated osteoblast differentiation. Subcutaneous injection of DSF over the calvarium of new born rats reduced the differentiation phenotype of calvarial osteoblasts but increased the mRNA levels of Runx-2 and osteocalcin. DSF treatment at a human-equivalent dose of 30 mg/kg p.o. to adult Sprague Dawley rats caused trabecular osteopenia and suppressed the formation of mineralized nodule by bone marrow stromal cells. Moreover, DSF diminished bone regeneration at the fracture site. In growing rats, DSF diminished growth plate height, primary and secondary spongiosa, mineralized osteoid and trabecular strength. Substantial decreased bone formation was also observed in the cortical site of these rats. We conclude that DSF has a strong osteopenia inducing effect by impairing osteoblast survival and differentiation due to the inhibition of ALDH2 function.

Alcoholic and isocaloric diet, but not ovariectomy, influence the apoptosis of bone cells within the alveolar bone crest of rats

OBJECTIVE

Studies suggest that chronic alcoholism as well as oestrogen deficiencies may affect bones in general, including alveolar bone and, by doing so, increase individuals' susceptibility to develop progressive periodontal disease. This paper aims to verify the influence of chronic alcoholism and/or oestrogen deficiencies in the apoptosis of bone cells of the alveolar bone crest region in rats.

DESIGN

Initially, 54 rats were divided into ovariectomized (Ovx) and Sham operated (Sham) groups. Thirty days after surgery, these two groups were equally sub-divided, and received, for 56 days, the following dietary intervention: alcoholic diet (with 20% alcohol solution,), isocaloric diet and ad libitum diet (free diet). Analysis was undertaken by immunohistochemistry, using an antibody to detect apoptosis (anti PARP p-85).

RESULTS

When comparing the six experimental groups, no significant differences were observed in the apoptosis of bone cells. Also, there was no significant difference in the quantity of cells undergoing apoptosis when the animals from Ovx groups were compared with those from Sham groups. However, when comparing only different dietary groups, differences were observed between the groups ad libitum and isocaloric, to osteoblasts (p=0.045); and ad libitum and alcohol, to osteocytes (p=0.007).

CONCLUSION

It is concluded that ovariectomy was not able to influence the rate of apoptosis of bone cells of the alveolar bone crest region in rats and that a possible influence of diet on apoptosis of osteoblasts and osteocytes cannot be ruled out.

The osteocyte: an endocrine cell ... and more

Few investigators think of bone as an endocrine gland, even after the discovery that osteocytes produce circulating fibroblast growth factor 23 that targets the kidney and potentially other organs. In fact, until the last few years, osteocytes were perceived by many as passive, metabolically inactive cells. However, exciting recent discoveries have shown that osteocytes encased within mineralized bone matrix are actually multifunctional cells with many key regulatory roles in bone and mineral homeostasis. In addition to serving as endocrine cells and regulators of phosphate homeostasis, these cells control bone remodeling through regulation of both osteoclasts and osteoblasts, are mechanosensory cells that coordinate adaptive responses of the skeleton to mechanical loading, and also serve as a manager of the bone's reservoir of calcium. Osteocytes must survive for decades within the bone matrix, making them one of the longest lived cells in the body. Viability and survival are therefore extremely important to ensure optimal function of the osteocyte network. As we continue to search for new therapeutics, in addition to the osteoclast and the osteoblast, the osteocyte should be considered in new strategies to prevent and treat bone disease.

Effect of the alcohol consumption on osteocyte cell processes: a molecular imaging study

We have previously shown microarchitectural tissue changes with cellular modifications in osteocytes following high chronic alcohol dose. The aim of this study was to assess the dose effect of alcohol consumption on the cytoskeleton activity, the cellular lipid content and modulation of differentiation and apoptosis in osteocyte. Male Wistar rats were divided into three groups: Control (C), Alcohol 25% v/v (A25) or Alcohol 35% v/v (A35) for 17 weeks. Bone mineral density (BMD) was assessed by DXA, osteocyte empty lacunae, lacunae surface, bone marrow fat with bright field microscopy. Osteocyte lipid content was analysed with transmission electron microscopy (TEM) and epifluorescence microscopy. Osteocyte apoptosis was analysed with immunolabelling and TEM. Osteocyte differentiation and cytoskeleton activity were analysed with immunolabelling and real time quantitative PCR. At the end of the protocol, BMD was lower in A25 and A35 compared with C, while the bone marrow lipid content was increased in these groups. More empty osteocyte lacunae and osteocyte containing lipid droplets in A35 were found compared with C and A25. Cleaved caspase-3 staining and chromatin condensation were increased in A25 and A35 versus C. Cleaved caspase-3 was increased in A35 versus A25. CD44 and phosphopaxillin stainings were higher in A35 compared with C and A25. Paxillin mRNA expression was higher in A35 versus A25 and C and sclerostin mRNA expression was higher in A35 versus C. We only observed a dose effect of alcohol consumption on cleaved caspase-3 osteocyte immunostaining levels and on the number of lipid droplets in the bone marrow.

Centrosome fine ultrastructure of the osteocyte mechanosensitive primary cilium

The centrosome is the principal microtubule organization center in cells, giving rise to microtubule-based organelles (e.g., cilia, flagella). The aim was to study the osteocyte centrosome morphology at an ultrastructural level in relation to its mechanosensitive function. Osteocyte centrosomes and cilia in tibial cortical bone were explored by acetylated alpha-tubulin (AαTub) immunostaining under confocal microscopy. For the first time, fine ultrastructure and spatial orientation of the osteocyte centrosome were explored by transmission electron microscopy on serial ultrathin sections. AαTub-positive staining was observed in 94% of the osteocytes examined (222/236). The mother centriole formed a short primary cilium and was longer than the daughter centriole due to an intermediate zone between centriole and cilium. The proximal end of the mother centriole was connected with the surface of daughter centriole by striated rootlets. The mother centriole exhibited distal appendages that interacted with the cell membrane and formed a particular structure called "cilium membrane prolongation." The primary cilium was mainly oriented perpendicular to the long axis of bone. Mother and daughter centrioles change their original mutual orientation during the osteocyte differentiation process. The short primary cilium is hypothesized as a novel type of fluid-sensing organelle in osteocytes.

Vitamin D supplementation protects against bone loss associated with chronic alcohol administration in female mice

Chronic alcohol abuse results in decreased bone mineral density (BMD), which can lead to increased fracture risk. In contrast, low levels of alcohol have been associated with increased BMD in epidemiological studies. Alcohol's toxic skeletal effects have been suggested to involve impaired vitamin D/calcium homeostasis. Therefore, dietary vitamin D supplementation may be beneficial in reducing bone loss associated with chronic alcohol consumption. Six-week-old female C57BL/6J mice were pair-fed ethanol (EtOH)-containing liquid diets (10 or 36% total calories) for 78 days. EtOH exposure at 10% calories had no effects on any measured bone or serum parameter. EtOH consumption at 36% of calories reduced BMD and bone strength (P<0.05), decreased osteoblastogenesis, increased osteoclastogenesis, suppressed 1,25-hydroxyvitamin D3 [1,25(OH)2D3] serum concentrations (P<0.05), and increased apoptosis in bone cells compared with pair-fed controls. In a second study, female mice were pair-fed 30% EtOH diets with or without dietary supplementation with vitamin D3 (cholecalciferol; VitD) for 40 days. VitD supplementation in the EtOH diet protected against cortical bone loss, normalized alcohol-induced hypocalcaemia, and suppressed EtOH-induced expression of receptor of nuclear factor-κB ligand mRNA in bone. In vitro, pretreatment of 1,25(OH)2D3 in osteoblastic cells inhibited EtOH-induced apoptosis. In EtOH/VitD mice circulating 1,25(OH)2D3 was lower compared with mice receiving EtOH alone (P<0.05), suggesting increased sensitivity to feedback control of VitD metabolism in the kidney. These findings suggest dietary VitD supplementation may prevent skeletal toxicity in chronic drinkers by normalizing calcium homeostasis, preventing apoptosis, and suppressing EtOH-induced increases in bone resorption.

Synchrotron ultraviolet microspectroscopy on rat cortical bone: involvement of tyrosine and tryptophan in the osteocyte and its environment

Alcohol induced osteoporosis is characterized by a bone mass decrease and microarchitecture alterations. Having observed an excess in osteocyte apoptosis, we aimed to assess the bone tissue biochemistry, particularly in the osteocyte and its environment. For this purpose, we used a model of alcohol induced osteoporosis in rats. Bone sections of cortical bone were investigated using synchrotron UV-microspectrofluorescence at subcellular resolution. We show that bone present three fluorescence peaks at 305, 333 and 385 nm, respectively corresponding to tyrosine, tryptophan and collagen. We have determined that tyrosine/collagen and tryptophan/collagen ratios were higher in the strong alcohol consumption group. Tryptophan is related to the serotonin metabolism involved in bone formation, while tyrosine is involved in the activity of tyrosine kinases and phosphatases in osteocytes. Our experiment represents the first combined synchrotron UV microspectroscopy analysis of bone tissue with a quantitative biochemical characterization in the osteocyte and surrounding matrix performed separately.

Chronic and intermittent exposure to alcohol vapors: a new model of alcohol-induced osteopenia in the rat

BACKGROUND

Different models are used to study the effects of chronic alcohol consumption on bone tissue in the rat. However, the current models take several months to show indices of osteopenia as observed in chronic drinkers. Numerous studies have supported that chronic and intermittent exposure to ethanol vapors has predictive validity as a model of alcohol dependence in humans. However, this model has never been applied to bone research to study its effects on the parameters that define osteopenia. This was the goal of this study in the rat.

METHODS

Male Wistar rats were exposed to ethanol vapor inhalation (n = 6) or air (controls, n = 6). Animals were exposed to chronic (11 weeks) and intermittent (14 hours a day) ethanol vapor reaching stable blood alcohol levels (BALs; 150 to 250 mg/dl) at the end of the third week of inhalation. After the sacrifice, right and left femur and tibia were dissected free of fat and connective tissue and bone mineral density (BMD) was assessed by dual X-ray absorptiometry. The microarchitecture of the femur was studied using microcomputed tomography.

RESULTS

The BMD of the left and right femurs and the left tibia was lower in the ethanol group compared with the control group. The bone volume fraction (BV/TV) and the bone surface density (BS/TV) were lower in the ethanol group compared with control animals. The trabecular number (Tb.N) was lower in the ethanol group while the trabecular spacing was higher.

CONCLUSIONS

The decrease in the BMD, BV/TV, and Tb.N is in the same range as what is observed in human drinkers and what is reported with other animal alcohol models (Lieber-DeCarli liquid diet, ethanol in the tap water). Therefore, this model could be useful to study the effects of chronic alcohol consumption in the bone research field and has the advantage of controlling easily targeted BALs.

Alcohol and bone: review of dose effects and mechanisms

Alcohol is widely consumed across the world. It is consumed in both social and cultural settings. Until recently, two types of alcohol consumption were recognized: heavy chronic alcohol consumption or light consumption. Today, there is a new pattern of consumption among teenagers and young adults namely: binge drinking. Heavy alcohol consumption is detrimental to many organs and tissues, including bones, and is known to induce secondary osteoporosis. Some studies, however, have reported benefits from light alcohol consumption on bone parameters. To date, little is known regarding the effects of binge drinking on bone health. Here, we review the effects of three different means of alcohol consumption: light, heavy, and binge drinking. We also review the detailed literature on the different mechanisms by which alcohol intake may decrease bone mass and strength. The effects of alcohol on bone are thought to be both direct and indirect. The decrease in bone mass and strength following alcohol consumption is mainly due to a bone remodeling imbalance, with a predominant decrease in bone formation. Recent studies, however, have reported new mechanisms by which alcohol may act on bone remodeling, including osteocyte apoptosis, oxidative stress, and Wnt signalling pathway modulation. The roles of reduced total fat mass, increased lipid content in bone marrow, and a hypoleptinemia are also discussed.