Partial Protection by Dietary Antioxidants Against Ethanol-Induced Osteopenia and Changes in Bone Morphology in Female Mice

Deletion of NADPH oxidase 2 in chondrocytes exacerbates ethanol-mediated growth plate disruption in mice without major effects on bone architecture or gene expression

BACKGROUND

Excess reactive oxygen species generated by NADPH oxidase 2 (Nox2) in response to ethanol exposure mediate aspects of skeletal toxicity including increased osteoclast differentiation and activity. Because perturbation of chondrocyte differentiation in the growth plate by ethanol could be prevented by dietary antioxidants, we hypothesized that Nox2 in the growth plate was involved in ethanol-associated reductions in longitudinal bone growth.

METHODS

Nox2 conditional knockout mice were generated, where the essential catalytic subunit of Nox2, cytochrome B-245 beta chain (Cybb), is deleted in chondrocytes using a Cre-Lox model with Cre expressed from the collagen 2a1 promoter (Col2a1-Cre). Wild-type and Cre-Lox mice were fed an ethanol Lieber-DeCarli-based diet or pair-fed a control diet for 8 weeks.

RESULTS

Ethanol treatment significantly reduced the number of proliferating chondrocytes in the growth plate, enhanced bone marrow adiposity, shortened femurs, reduced body length, reduced cortical bone volume, and decreased mRNA levels of a number of osteoblast and chondrocyte genes. Conditional knockout of Nox2 enzymatic activity in chondrocytes did not consistently prevent any ethanol effects. Rather, knockout mice had fewer proliferating chondrocytes than wild-type mice in both the ethanol- and control-fed animals. Additional analysis of tibia samples from Nox4 knockout mice showed that loss of Nox4 activity also reduced the number of proliferating chondrocytes and altered chondrocyte size in the growth plate.

CONCLUSIONS

Although Nox enzymatic activity regulates growth plate development, ethanol-associated disruption of the growth plate morphology is independent of ethanol-mediated increases in Nox2 activity.

Episodic alcohol exposure attenuates mesenchymal stem cell chondrogenic differentiation during bone fracture callus formation

BACKGROUND

During bone fracture repair, mesenchymal stem cells (MSC) differentiate into chondrocytes and osteoblasts to form a fracture callus. Our laboratory previously reported that alcohol-exposed rodents with a surgically created tibia fracture display deficient fracture callus formation and diminished signs of endochondral ossification characterized by the absence of chondrocytes and mature hypertrophic chondrocytes, suggesting that alcohol may inhibit MSC differentiation. These findings led to our hypothesis that alcohol exposure inhibits mesenchymal stem cell chondrogenic differentiation within the developing fracture callus.

METHODS

In the present study, we utilized a lineage-tracing approach to determine which stage(s) of chondrogenic differentiation are affected by alcohol exposure. We utilized lineage-specific reporter mice to determine the effects of alcohol on MSC and early and late chondrogenic cell frequencies within the fracture callus. In addition, serially sectioned slides were stained immunofluorescently and immunohistochemically and quantified to determine the effect of alcohol on cell proliferation and apoptosis, respectively, within the fracture callus of alcohol-administered rodents.

RESULTS

Alcohol-administered rodents had a reduced fracture callus area at 4, 6, and 9 days postfracture. Alcohol had no effect on apoptosis in the fracture callus at any of the examined timepoints. Alcohol-administered rodents had significantly fewer proliferative cells in the fracture callus at 9 days postfracture, but no effect on cell proliferation was observed at earlier fracture callus timepoints. Alcohol-administered rodents had reduced Collagen2a1- and Collagen10a1-expressing cells in the developing fracture callus, suggesting that alcohol inhibits both early chondrogenic differentiation and later chondrocyte maturation during fracture callus development.

CONCLUSION

The data suggest that alcohol could affect normal fracture healing through the mitigation of MSC chondrogenic differentiation at the callus site.

Leptin and environmental temperature as determinants of bone marrow adiposity in female mice

Bone marrow adipose tissue (BMAT) levels are higher in distal femur metaphysis of female mice housed at thermoneutral (32°C) than in mice housed at 22°C, as are abdominal white adipose tissue (WAT) mass, and serum leptin levels. We performed two experiments to explore the role of increased leptin in temperature-enhanced accrual of BMAT. First, we supplemented 6-week-old female C57BL/6J (B6) mice with leptin for 2 weeks at 10 µg/d using a subcutaneously implanted osmotic pump. Controls consisted of ad libitum (ad lib) fed mice and mice pair fed to match food intake of leptin-supplemented mice. The mice were maintained at 32°C for the duration of treatment. At necropsy, serum leptin in leptin-supplemented mice did not differ from ad lib mice, suggesting suppression of endogenous leptin production. In support, Ucp1 expression in BAT, percent body fat, and abdominal WAT mass were lower in leptin-supplemented mice. Leptin-supplemented mice also had lower BMAT and higher bone formation in distal femur metaphysis compared to the ad lib group, changes not replicated by pair-feeding. In the second experiment, BMAT response was evaluated in 6-week-old female B6 wild type (WT), leptin-deficient ob/ob and leptin-treated (0.3 μg/d) ob/ob mice housed at 32°C for the 2-week duration of the treatment. Compared to mice sacrificed at baseline (22°C), BMAT increased in ob/ob mice as well as WT mice, indicating a leptin independent response to increased temperature. However, infusion of ob/ob mice with leptin, at a dose rate having negligible effects on either energy metabolism or serum leptin levels, attenuated the increase in BMAT. In summary, increased housing temperature and increased leptin have independent but opposing effects on BMAT in mice.

Chronic ethanol consumption does not reduce true bone density in male Wistar rats

Osteoporosis is characterized by reduced bone mineral density (BMD) and increased bone fragility, which may be modified by lifestyle behaviors. In observational studies, chronic moderate ethanol consumption is associated with higher BMD, but results are inconsistent and underlying mechanisms are unknown. To understand the influence of chronic ethanol consumption on true bone density (Archimedes principal), bone mechanical properties (Young's Modulus of bend), and osteogenic gene expression, 12-month-old male Wistar rats were randomly assigned to a control group or ethanol intervention (20% ethanol in drinking water on alternate days) group for 13 weeks and tibiae and femurs were collected. Blood was collected to assess alcohol content and antioxidant enzyme activities. We hypothesized that chronic ethanol consumption would increase true bone density and mechanical properties and increase osteoblastic gene expression and serum antioxidant enzyme activity. Ethanol consumption did not influence femoral or tibial true bone density but did result in lower tibial Young's modulus of bend (p = 0.0002). However, there was no influence of ethanol on other measures of mechanical properties. Femoral pro-osteoclastic gene expression of Dkk1 was lower (p = 0.0006) and pro-osteoblastic gene expression of Ctnnb1 was higher (p = 0.02) with ethanol consumption. We observed no differences in circulating antioxidant activities between groups, other than a tendency for greater (p = 0.08) glutathione peroxidase in the ethanol group. Results showed chronic ethanol consumption did not influence true bone density, only modestly reduced tibial mechanical properties (lower Young's modulus of bend), and moderately impacted expression of genes within the femur known to regulate both osteoblast and osteoclast activities.

Ubiquinol supplementation modulates energy metabolism and bone turnover during high intensity exercise

Bone and energy metabolism are profoundly influenced by exercise. The objective of this study was to determine for the first time whether a short-term supplementation with ubiquinol could have a modulating effect on bone turnover and energy metabolism associated with strenuous exercise. The participants (n = 100 healthy and well-trained firemen) were randomly divided into two groups: ubiquinol group (ubiquinol (200 mg day-1)) and control group (placebo) for two weeks. The protocol consisted of conducting two identical strenuous exercise tests with a rest period between tests of 24 h. Blood samples were collected before supplementation (basal value) (T1), after supplementation (T2), after the first physical exercise test (T3), after 24 h of rest (T4), and after the second physical exercise test (T5). Parathyroid hormone (PTH), osteocalcin (OC), osteoprotegerin (OPG), osteopontin (OPN), sclerotin (SOST), alkaline phosphatase (AP), adrenocorticotropin (ACTH), insulin, leptin, adrenaline, noradrenaline and peroxisome proliferator activated receptor-γ coactivator-1α (PGC-1α) were determined. Our protocol increased ACTH, SOST, PTH and OC levels, while it decreased OPN. This protocol also increased adrenaline, noradrenaline and PCG-1α, and decreased insulin. After ubiquinol supplementation, PTH, OC, OPG, alkaline phosphatase, leptin, insulin, noradrenaline and PGC-1α levels increased in the supplemented group compared to the control group after the exercise protocol. Strenuous exercise has a clear effect on energy metabolism and bone turnover. These effects are modulated by ubiquinol supplementation, which especially increases the biomarkers of bone formation during strenuous exercise. In addition, ubiquinol has a beneficial effect on the mobilization of energy sources, fact that it could represent an ergogenic and physiological advantage for skeletal muscles.

Impact of Alcohol on Bone Health, Homeostasis and Fracture repair

Purpose of review

Alcohol use continues to rise globally. We review the current literature on the effect of alcohol on bone health, homeostasis and fracture repair to highlight what has been learned in people and animal models of alcohol consumption.

Recent findings

Recently, forkhead box O (FoxO) has been found to be upregulated and activated in mesenchymal stem cells (MSC) exposed to alcohol. FoxO has also been found to modulate Wnt/β-catenin signaling, which is necessary for MSC differentiation. Recent evidence suggests alcohol activates FoxO signaling, which may be dysregulating Wnt/β-catenin signaling in MSCs cultured in alcohol.

Summary

This review highlights the negative health effects learned from people and chronic and episodic binge alcohol consumption animal models. Studies using chronic alcohol exposure or alcohol exposure then bone fracture repair model have explored several different cellular and molecular signaling pathways important for bone homeostasis and fracture repair, and offer potential for future experiments to explore additional signaling pathways that may be dysregulated by alcohol exposure.

Chronic Ethanol Feeding in Mice Decreases Expression of Genes for Major Structural Bone Proteins in a Nox4-Independent Manner

Bone loss in response to alcohol intake has previously been hypothesized to be mediated by excessive production of reactive oxygen species via NADPH oxidase (Nox) enzymes. Nox4 is one of several Nox enzymes expressed in bone. We investigated the role of Nox4 in the chondro-osteoblastic lineage of the long bones in mice during normal chow feeding and during chronic ethanol feeding for 90 days. We generated mice with a genotype (PrxCre +/- Nox4 fl/fl) allowing conditional knockout of Nox4 in the limb bud mesenchyme. Adult mice had 95% knockdown of Nox4 expression in the femoral shafts. For mice on regular chow, only whole-body Nox4 knockout mice had clearly increased cortical thickness and bone mineral density in the tibiae. When chronically fed a liquid diet with and without ethanol, conditional Nox4 knockout mice had slightly reduced dimensions of the cortical and trabecular regions of the tibiae (P < 0.1). The ethanol diet caused a significant reduction in cortical bone area and cortical thickness relative to a control diet without ethanol (P < 0.05). The ethanol diet further reduced gene expression of Frizzled related protein (Frzb), myosin heavy chain 3, and several genes encoding collagen and other major structural bone proteins (P < 0.05), whereas the Nox4 genotype had no effects on these genes. In conclusion, Nox4 expression from both mesenchymal and nonmesenchymal cell lineages appears to exert subtle effects on bone. However, chronic ethanol feeding reduces cortical bone mass and cortical gene expression of major structural bone proteins in a Nox4-independent manner. SIGNIFICANCE STATEMENT: Excessive alcohol intake contributes to osteopenia and osteoporosis, with oxidative stress caused by the activity of NADPH oxidases hypothesized to be a mediator. We tested the role of NADPH oxidase (Nox) 4 in osteoblast precursors in the long bones of mice with a conditional Nox4 knockout model. We found that Nox4 exerted effects independent of alcohol intake, and ethanol effects on bone were Nox4-independent.

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.

Reduced Serum Osteocalcin in High-Risk Alcohol Using People Living With HIV Does Not Correlate With Systemic Oxidative Stress or Inflammation: Data From the New Orleans Alcohol Use in HIV Study

BACKGROUND

HIV infection is now largely a chronic condition as a result of the success of antiretroviral therapy. However, several comorbidities have emerged in people living with HIV (PLWH), including alcohol use disorders and musculoskeletal disorders. Alcohol use has been associated with lower bone mineral density, alterations to circulating bone turnover markers, and hypocalcemia. The pathophysiological basis of bone loss in the PLWH population is unclear but has been suggested to be linked to oxidative stress and inflammation. To test the hypothesis that PLWH consuming excessive alcohol have altered markers of bone turnover and/or calcium homeostasis in association with oxidative stress, we correlated measurements of alcohol consumption with markers of oxidative stress and inflammation, serum calcium concentrations, and measurements of bone turnover, including c-terminal telopeptide cross-links (CTX-1) and osteocalcin.

METHODS

Data were drawn from cross-sectional baseline data from the ongoing New Orleans Alcohol Use in HIV (NOAH) study, comprised of 365 in care PLWH. Alcohol consumption measures (Alcohol Use Disorders Test, 30-day timeline follow-back calendar, and phosphatidylethanol [PEth]) were measured in a subcohort of 40 subjects selected based on highest and lowest PEth measurements. Multivariate linear regression was performed to test the relationships between alcohol consumption and systemic oxidative stress (4-hydroxynonenal; 4-HNE) and inflammation (c-reactive protein; CRP).

RESULTS

Serum calcium and CTX-1 did not differ significantly between the high and low-PEth groups. Individuals in the high-PEth group had significantly lower serum osteocalcin (median low-PEth group: 13.42 ng/ml, inter-quartile range [IQR] 9.26 to 14.99 ng/ml; median high-PEth group 7.39 ng/ml, IQR 5.02 to 11.25 ng/ml; p = 0.0005, Wilcoxon rank-sum test). Osteocalcin negatively correlated with PEth (Spearman r = -0.45, p = 0.05) and self-reported measures after adjusting for covariates. Alcohol consumption showed mild, but significant, positive associations with serum 4-HNE, but not with CRP. Osteocalcin did not correlate with either 4-HNE or CRP.

CONCLUSIONS

In this subcohort of PLWH, we detected significant associations between at-risk alcohol use and osteocalcin, and at-risk alcohol use and serum 4-HNE, suggesting suppression of bone formation independent of increased systemic oxidative stress with increasing alcohol consumption.

A Delphinidin-Enriched Maqui Berry Extract Improves Bone Metabolism and Protects against Bone Loss in Osteopenic Mouse Models

In our previous investigation, delphinidin, one of the most abundant anthocyanins found in vegetables and berry fruits, had been shown to inhibit osteoclasts and prevent bone loss in mouse models of osteoporosis. In the present study, we investigated whether a delphinidin glycoside-enriched maqui berry extract (MBE, Delphinol^®) exhibits beneficial effects on bone metabolism both in vitro and in vivo. MBE stimulated the osteoblastic differentiation of MC3T3-E1 cells, as indicated by enhanced mineralized nodule formation, and increased alkaline phosphatase activity, through the upregulation of bone morphogenetic protein 2 (Bmp2), runt-related transcription factor 2 (Runx2), osterix (Osx), osteocalcin (Ocn), and matrix extracellular phosphoglycoprotein (Mepe) mRNA expression. Immunostaining and immunoprecipitation assays demonstrated that MBE suppressed NF-κB transnucleation through acting as a superoxide anion/peroxynitrite scavenger in MC3T3-E1 cells. Simultaneously, MBE inhibited both osteoclastogenesis in primary bone marrow macrophages and pit formation by maturated osteoclasts on dentine slices. Microcomputed tomography (micro-CT) and bone histomorphometry analyses of femurs demonstrated that the daily ingestion of MBE significantly increased BV/TV (ratio of bone volume to tissue volume), Tb.Th (trabecular thickness), Tb.N (trabecular number), N.Nd/N.Tm (node to terminus ratio), OV/TV (ratio of osteoid volume to tissue volume), BFR/TV (bone formation rate per tissue volume), and significantly decreased Tb.Sp (trabecular separation), ES/BS (ratio of eroded surface to bone surface) and N.Oc/BS (number of osteoclast per unit of bone surface), compared to vehicle controls in osteopenic mouse models. These findings suggest that MBE can be a promising natural agent for the prevention of bone loss in osteopenic conditions by not only inhibiting bone resorption, but also stimulating bone formation.

Effects of Acupoint Application Therapy with TianGui Powder on Osteoporosis in Ovariectomized Rats through TGF-β1 and Smad2/3 Signaling Pathway

Objectives

To explore the effects of acupoint application therapy (AAT) with TianGui Powder (TGP) on the expressions of the transforming growth factor β1 (TGF‐β1) and Smad‐2/3 signaling pathway in ovariectomized osteoporosis rats.

Methods

Sixty rats were randomly divided into four groups: normal group (group A), model group (group B), TGP group (group C), and Western medicine group (group D). Group A had only the corresponding amount of adipose tissue around the ovary removed; rats in the other groups had bilateral ovariectomies. After 1 week, groups A and B were given 1 mL/100 mg normal saline solution by gavage, group C was treated with AAT with TGP on ShenQue acupoint (0.2 piece/rat, 6 h/time, 1 time/d) and group D was given calcium carbonate vitamin D3 (36 mg/kg/d) and alfacalcidol (0.05 μg/kg/d) tablet suspension. In this study, the bone mineral density (BMD) , the levels of BALP, TRAP‐5b, and BGP in serum and the changes in bone histomorphology was detected. For acquiring lumbar experimental data, the expression of TGF‐β1, Smad‐2/3 proteins and mRNA of TGF‐β1and Smad‐2/3 were assessed. After 12 weeks, the data were collected for analysis.

Results

Compared with group A, the bone trabecula was thinner and significantly reduced in other groups. The result of BMD improved significantly in both groups C and D compared to group B after intervention (P < 0.05). In contrast, compared to group B, the levels of BALP, TRAP‐5b, and BGP significantly declined in both groups C and D. In group C, the results of protein expressions in TGF‐β1, Smad‐2/3 were 2.870 ± 0.270, 1.552 ± 0.111, and 1.420 ± 0.079, respectively. In groups C and D, those indications significantly declined compared to group B (P < 0.01). In group C, the level of mRNA expressions of TGF‐β1, Smad‐2/3 were 1.872 ± 0.177, 1.672 ± 0.086, and 1.790 ± 0.136, respectively. Compared with group B, those indications had significant difference in groups C and D (P < 0.05).

Conclusion

Acupoint application therapy with TGP could significantly improve the BMD. The TGF‐β1 and Smad‐2/3 signaling pathway could be a therapeutic target of TGP in postmenopausal osteoporosis rats.

Alcoholic liver disease: Utility of animal models

Alcoholic liver disease (ALD) is a major cause of acute and chronic liver injury. Extensive evidence has been accumulated on the pathological process of ALD during the past decades. However, effective treatment options for ALD are very limited due to the lack of suitable in vivo models that recapitulate the full spectrum of ALD. Experimental animal models of ALD, particularly rodents, have been used extensively to mimic human ALD. An ideal animal model should recapitulate all aspects of the ALD process, including significant steatosis, hepatic neutrophil infiltration, and liver injury. A better strategy against ALD depends on clear diagnostic biomarkers, accurate predictor(s) of its progression and new therapeutic approaches to modulate stop or even reverse the disease. Numerous models employing rodent animals have been established in the last decades to investigate the effects of acute and chronic alcohol exposure on the initiation and progression of ALD. Although significant progress has been made in gaining better knowledge on the mechanisms and pathology of ALD, many features of ALD are unknown, and require further investigation, ideally with improved animal models that more effectively mimic human ALD. Although differences in the degree and stages of alcoholic liver injury inevitably exist between animal models and human ALD, the acquisition and translational relevance will be greatly enhanced with the development of new and improved animal models of ALD.

N-Acetyl Cysteine Treatment Restores Early Phase Fracture Healing in Ethanol-Fed Rats

BACKGROUND

Fracture healing in alcoholics is delayed and often associated with infections resulting in prolonged rehabilitation. It has been reported that binge drinking of alcohol increases oxidative stress and delays fracture healing in rats, which is prevented by treatment with the antioxidant n-acetyl cysteine (NAC). Oxidative stress is a significant factor in pathologies of various organs resulting from chronic alcoholism. Therefore, we hypothesize that treatment with NAC reduces oxidative stress and restores fracture healing in chronic alcoholics.

METHODS

Rats (10 months old) were pair-fed the Lieber-DeCarli ethanol (EtOH) diet or control diet for 16 weeks. A closed fracture was performed and rats allowed to recover for 72 hours. Rats were divided into 4 groups-control, control + NAC, EtOH, and EtOH + NAC-and injected intraperitoneally with 200 mg/kg of NAC daily for 3 days. Serum and bone fracture callus homogenates were collected and assayed for traditional markers of inflammation, oxidative stress, and bone regeneration.

RESULTS

The oxidative stress marker malondialdehyde (MDA) was increased in both serum and bone tissue in EtOH-fed animals compared to controls. NAC treatment significantly (p < 0.01) reduced MDA to near normal levels and dramatically increased the index of antioxidant efficacy (catalase/MDA ratio) (p < 0.01). Inflammatory markers tumor necrosis factor-α, interferon-γ, and interleukin-6 were significantly decreased in serum and callus following NAC treatment. NAC treatment reduced EtOH-induced bone resorption as evidenced by significant decreases in C-telopeptide of type-I-collagen levels (p < 0.05) and band-5 tartrate-resistant acid phosphatase levels in the tissue (p < 0.001).

CONCLUSIONS

Oxidative stress and excessive inflammation are involved in the inhibition of fracture healing by EtOH. In this study, early short-term treatment of EtOH-fed animals with the antioxidant NAC reduced oxidative stress and normalized the innate immune response to fracture in the early phase of fracture healing, thereby restoring the normal onset of bone regeneration.

NOX4 Deletion in Male Mice Exacerbates the Effect of Ethanol on Trabecular Bone and Osteoblastogenesis

Chronic alcohol consumption increases bone resorption and decreases bone formation. A major component of ethanol (EtOH) pathology in bone is the generation of excess reactive oxygen species (ROS). The ROS-generating NADPH oxidase-4 (NOX4) is proposed to drive much of the EtOH-induced suppression of bone formation. Here, 13-week-old male wild-type (WT) and NOX4^-/- mice were pair fed (PF) a high-fat (35%), Lieber-DeCarli liquid diet with or without EtOH at 30% of their total calories for 12 weeks. Micro-computed tomography analysis demonstrated significant decreases in trabecular bone volume/total volume (BV/TV) percentage and cortical thickness in WT, EtOH-fed mice compared with PF controls. EtOH-fed NOX4^-/- mice also displayed decreased trabecular BV/TV and trabecular number compared with PF (P < 0.05). However, NOX4^-/- mice were protected against EtOH-induced decreases in cortical thickness (P < 0.05) and decreases in collagen1 and osteocalcin mRNA expression in cortical bone (P < 0.05). In WT and NOX4^-/- vertebral bone, EtOH suppressed expression of Wnt signaling components that promote osteoblast maturation. A role for NOX4 in EtOH inhibition of osteoblast differentiation was further demonstrated by protection against EtOH inhibition of osteoblastogenesis in ex vivo bone marrow cultures from NOX4^-/-, but not p47^phox-/- mice lacking active NADPH oxidase-2. However, bone marrow cultures from NOX4^-/- mice formed fewer osteoblastic colonies compared with WT cultures (P < 0.05), suggesting a role for NOX4 in the maintenance of mesenchymal progenitor cell populations. These data suggest that NOX4 deletion is partially protective against EtOH effects on osteoblast differentiation, but may predispose bone to osteogenic impairments.