Nitric oxide as the mediator of the antiosteoporotic actions of estrogen, statins, and essential fatty acids

Potential Benefits of Statin Therapy in Reducing Osteoarthritis Risk: A Mendelian Randomization Study

OBJECTIVE

The purpose of this study was to determine the causal effect of statins on osteoarthritis (OA) risk using Mendelian randomization (MR).

METHODS

Single nucleotide polymorphism-based genome-wide association analyses of statins were collected from the UK Biobank and FinnGen dataset, and OA data were collected from the UK Biobank and Arthritis Research UK Osteoarthritis Genetics (arcOGEN) study. Two-sample MR analyses were performed using the inverse-variance weighted (IVW) technique. MR-Egger, weighted median, and weighted mode served as supplementary analyses. MR-Egger regression, Cochran's Q test, and Mendelian Randomization Pleiotropy Residual Sum and Outlier analysis were performed as sensitivity analyses. Hydroxymethylglutaryl-coenzyme A reductase (HMGCR) expression and OA risk were evaluated using summary data-based MR (SMR).

RESULTS

MR analyses consistently supported a causal connection between statin use and OA risk. A causal effect was observed for atorvastatin (IVW: β = -2.989, P = 0.003) and rosuvastatin (IVW: β = -14.141, P = 0.006) treatment on hip OA. Meta-analysis showed the association between atorvastatin and knee OA was statistically significant (odds ratio 0.15; P = 0.004). Simvastatin use exhibited a protective effect against knee (IVW: β = -1.056, P = 0.004) and hip OA (IVW: β = -1.405, P = 0.001). Statin medication showed a protective effect on hip OA (IVW: β = -0.054, P = 0.013). HMGCR correlated significantly with a reduced risk of knee OA (β = -0.193, PSMR = 0.017), rather than hip OA (β = 0.067, PSMR = 0.502), which suggested that statins' protective effect on OA may not be related to its lipid-lowering effect.

CONCLUSION

This MR study provides compelling evidence that statin treatment may be a protective factor for OA. Further research is required to clarify its underlying mechanism.

Changes in Bone Marrow Fatty Acids Early after Ovariectomy-Induced Osteoporosis in Rats and Potential Functions

The aim of this study was to investigate the changes in bone marrow fatty acids early after ovariectomy-induced osteoporosis in rats, and explore the potential function of the bone marrow fatty acids. Ninety-six female Sprague Dawley rats (12 weeks) were randomly divided into an ovariectomized (OVX) group and Sham group (N = 48/group) and received ovariectomy or Sham surgery, respectively. After 3, 5, 7,14, 21 and 28 days, eight rats in each group were sacrificed to detect the composition of bone marrow fatty acids by means of gas chromatography-mass spectrometry and evaluate the trabecular bone microarchitecture by means of microCT. Bone marrow rinsing fluid and serum were collected for the detection of nitric oxide synthase/nitric oxide (NOS/NO) and bone metabolism related parameters, respectively. Our results demonstrated that the bone microstructure was damaged significantly from 14 days after OVX surgery onwards. Sample clustering and group separation were observed between the OVX group and Sham group 3 and 14 days after surgery, which suggested the role of bone marrow fatty acids in the early stage of postmenopausal osteoporosis. Palmitoleate, myristate and arachidonate were found to play an important role in classification between the OVX group and Sham group on the 3rd day after surgery (VIP > 1, p < 0.05). Palmitoleate, myristate, alpha linolenate, stearate and eicosenoate were found to play an important role in classification between the OVX group and Sham group on the 14th day after surgery (VIP > 1, p < 0.05). The levels of myristate, palmitoleate, alpha linolenate and eicosenoate were significantly decreased in the OVX group, while the levels of arachidonate and stearate were significantly increased in OVX group (p < 0.05). Additionally, myristate, palmitoleate, alpha linoleate and eicosenoate were negatively correlated with C-terminal telopeptide of type 1 collagen (CTX-1, a bone resorption marker), while arachidonate was negative correlated with osteocalcin (OCN, a bone formation marker) (p < 0.05). A significant correlation was also found between eicosenoate and NOS (p < 0.05). Profound bone marrow fatty acids changes have taken place in the early stage of post-menopausal osteoporosis. They may affect bone formation though affecting the differentiation and function of osteoclasts or osteoblasts, respectively. The NOS/NO system may mediate the influence of eicosenoate on bone formation.

Association between statins and progression of osteoarthritis features on magnetic resonance imaging in a predominantly pre-radiographic cohort: the Vancouver Longitudinal Study of Early Knee Osteoarthritis (VALSEKO): a cohort study

Background

To evaluate the effect of statin use on osteoarthritis (OA) incidence/progression using magnetic resonance imaging (MRI) in a population-based cohort with predominantly pre-radiographic knee OA.

Methods

A cohort aged 40–79 years with knee pain was recruited using random population sampling and followed for 7 years. Baseline exclusions were inflammatory arthritis, recent knee surgery/injury, and inability to undergo MRI. At baseline, current statin use was ascertained. Baseline and follow-up MRIs were read semi-quantitatively for cartilage damage (grade 0–4, 0/1 collapsed, 6 regions), osteophytes (grade 0–3, 8 regions), bone marrow lesions (BML) (grade 0–3, 6 regions) and effusion (grade 0–3). The primary outcome was cartilage damage incidence/progression, while secondary outcomes were incidence/progression of osteophytes, BML, and effusion, each defined as an increase by ≥1 grade at any region. To ensure population representative samples, sample weights were used. Logistic regression was used to assess the association of statin use at baseline with incidence/progression of MRI outcomes. Analyses were adjusted for sex, age, BMI, and multiple comorbidities requiring statin therapy.

Results

Of 255 participants evaluated at baseline, 122 completed the 7-year follow-up. Statin use was not significantly associated with progression of cartilage damage (OR 0.82; 95% CI 0.17, 4.06), osteophytes (OR 3.48; 95% CI 0.40, 30.31), BML (OR 0.61; 95% CI 0.12, 3.02), or effusion (OR 2.38; 95% CI 0.42, 13.63), after adjusting for confounders.

Conclusion

In this population-based cohort of predominantly pre-radiographic knee OA, statins did not affect MRI incidence/progression of cartilage damage, BML, osteophytes or effusion. Therefore, statin use does not appear to affect people with pre-radiographic stages of knee OA.

Fracture risk and impact of osteoporosis in patients with Parkinson's disease: a nationwide database study

INTRODUCTION

Patients with Parkinson's disease (PD) showed an increased risk of fractures in previous studies and a high prevalence of osteoporosis is reportedly a potential contributor. We conducted a nationwide database study on the risk of fractures and the impact of osteoporosis on patients with PD compared to controls.

MATERIALS AND METHODS

Using a nationwide database in South Korea, we identified incident patients with PD in 2004-2006 and selected four age- and sex-matched controls. We checked the occurrence rates of overall and hip fractures and plotted Kaplan-Meier curves and a Cox proportional hazards model to determine risk. We also conducted stratified analyses according to the presence or absence of osteoporosis.

RESULTS

We identified 9126 patients with PD and 35,601 controls. Patients with PD had a greater probability of fractures throughout the study period in Kaplan-Meier curves, and an increased risk of overall (aHR 1.35, 95% CI 1.297-1.405) and hip (aHR 1.814, 95% CI 1.66-1.983) fractures in a Cox proportional hazards model. In the stratified analysis, the increased risk of overall fracture (aHR 1.333, 95% CI 1.273-1.396 and aHR 1.412, 95% CI 1.301-1.532, respectively) and hip fracture (aHR 1.773, 95% CI 1.604-1.96 and aHR 2.008, 95% CI 1.657-2.434, respectively) due to PD was similar between patients with and without osteoporosis.

DISCUSSION

Patients with PD, with or without osteoporosis, are more likely to experience fractures, especially hip fractures. There seems to be no interaction between PD and osteoporosis in regard to the occurrence of fractures, and therefore no effect modification by osteoporosis.

Nigella Sativa-Coated Hydroxyapatite Scaffolds: Synergetic Cues to Stimulate Myoblasts Differentiation and Offset Infections

BACKGROUND

At present osteoporosis has come into view as a major health concern. Skeletal diseases typified by weak and fragile bones have imposed threats of fissure. Hydroxyapatite (HAP) is known to induce osteoblast like differentiation and provide mechanical strength, hence, used in bone tissue engineering; whereas, Nigella sativa has also demonstrated potential to treat bone and muscle diseases. This study was aimed to develop potential orthopedic scaffold exploiting natural resources of Saudi Arabia which can be used as prospective tissue engineering implant.

METHODS

The bone scaffold was developed by grafting biogenic HAP with N. sativa essential oil. N. sativa was applied for boosting osteogenesis and to stimulate antimicrobial potential. Antimicrobial potential was investigated utilizing S. aureus bacteria. Spectroscopic and surface characters of N. sativa grafted HAP scaffolds were analyzed using Fourier-transform infrared spectroscopy, X-ray crystallography and Scanning electron microscopy. To ensure biocompatibility of scaffolds; we selected C2C12 cell-lines; best model to study mechanistic pathways related to osteoblasts and myoblasts differentiation.

RESULTS

Grafting of HAP with N. sativa did not affect typical spherical silhouette of nanoparticles. Characteristically; protein loaded polynucleated myotubes are result of in vitro myogenesis of C2C12 myoblasts in squat serum environment.

CONCLUSION

It is first study of unique combination of N. sativa and HAP scaffold as a possible candidate of implantation for skeletal muscles regeneration. Outcome of this finding revealed N. sativa grafted HAP enhance differentiation significantly over that of HAP. The proposed scaffold will be an economical natural material for hard and soft tissue engineering and will aid in curing skeletal muscle diseases. Our findings have implications for treatment of muscular/bone diseases.

Bioactive Lipids in COVID-19-Further Evidence

Previously, I suggested that arachidonic acid (AA, 20:4 n-6) and similar bioactive lipids (BALs) inactivate SARS-CoV-2 and thus, may be of benefit in the prevention and treatment of COVID-19. This proposal is supported by the observation that (i) macrophages and T cells (including NK cells, cytotoxic killer cells and other immunocytes) release AA and other BALs especially in the lungs to inactivate various microbes; (ii) pro-inflammatory metabolites prostaglandin E2 (PGE2) and leukotrienes (LTs) and anti-inflammatory lipoxin A4 (LXA4) derived from AA (similarly, resolvins, protectins and maresins derived from eicosapentaenoic acid: EPA and docosahexaenoic acid: DHA) facilitate the generation of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages respectively; (iii) AA, PGE2, LXA4 and other BALs inhibit interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) synthesis; (iv) mesenchymal stem cells (MSCs) that are of benefit in COVID-19 elaborate LXA4 to bring about their beneficial actions and (v) subjects with insulin resistance, obesity, type 2 diabetes mellitus, hypertension, coronary heart disease and the elderly have significantly low plasma concentrations of AA and LXA4 that may render them more susceptible to SARS-CoV-2 infection and cytokine storm that is associated with increased mortality seen in COVID-19. Statins, colchicine, and corticosteroids that appear to be of benefit in COVID-19 can influence BALs metabolism. AA, and other BALs influence cell membrane fluidity and thus, regulate ACE-2 (angiotensin converting enzyme-2) receptors (the ligand through which SARS-CoV2 enters the cell) receptors. These observations lend support to the contention that administration of BALs especially, AA could be of significant benefit in prevention and management of COVI-19 and other enveloped viruses.

Vascular dysfunction as a potential culprit of sarcopenia

Aging-related changes to biological structures such as cardiovascular and musculoskeletal systems contribute to the development of comorbid conditions including cardiovascular disease and frailty, and ultimately lead to premature death. Although, frail older adults often demonstrate both cardiovascular and musculoskeletal comorbidities, the etiology of sarcopenia, and especially the contribution of cardiovascular aging is unclear. Aging-related vascular calcification is prevalent in older adults and is a known risk factor for cardiovascular disease and death. The effect vascular calcification has on function during aging is not well understood. Emerging findings suggest vascular calcification can impact skeletal muscle perfusion, negatively affecting nutrient and oxygen delivery to skeletal muscle, ultimately accelerating muscle loss and functional decline. The present review summarizes existing evidence on the biological mechanisms linking vascular calcification with sarcopenia during aging.

Glimepiride promotes osteogenic differentiation in rat osteoblasts via the PI3K/Akt/eNOS pathway in a high glucose microenvironment

Our previous studies demonstrated that glimepiride enhanced the proliferation and differentiation of osteoblasts and led to activation of the PI3K/Akt pathway. Recent genetic evidence shows that endothelial nitric oxide synthase (eNOS) plays an important role in bone homeostasis. In this study, we further elucidated the roles of eNOS, PI3K and Akt in bone formation by osteoblasts induced by glimepiride in a high glucose microenvironment. We demonstrated that high glucose (16.5 mM) inhibits the osteogenic differentiation potential and proliferation of rat osteoblasts. Glimepiride activated eNOS expression in rat osteoblasts cultured with two different concentrations of glucose. High glucose-induced osteogenic differentiation was significantly enhanced by glimepiride. Down-regulation of PI3K P85 levels by treatment with LY294002 (a PI3K inhibitor) led to suppression of P-eNOS and P-AKT expression levels, which in turn resulted in inhibition of RUNX2, OCN and ALP mRNA expression in osteoblasts induced by glimepiride at both glucose concentrations. ALP activity was partially inhibited by 10 µM LY294002. Taken together, our results demonstrate that glimepiride-induced osteogenic differentiation of osteoblasts occurs via eNOS activation and is dependent on the PI3K/Akt signaling pathway in a high glucose microenvironment.

Nigella Sativa reverses osteoporosis in ovariectomized rats

Background

Osteoporosis poses a significant public health issue. It is a skeletal disorder characterized by compromised bone strength that predisposes to increased risk of fracture. There is a direct relationship between the lack of estrogen after menopause and the development of osteoporosis. About 33% of women over 50 will experience bone fractures as a result of osteoporosis. Nigella Sativa (NS) has been shown to have beneficial effects on bone and joint diseases. The present study was conducted to elucidate the protective effect of Nigella Sativa on osteoporosis produced by ovariectomy in rats.

Methods

Female Wistar rats aged 12–14 months were divided into three groups: sham-operated control (SHAM), ovariectomized (OVX), and ovariectomized supplemented with nigella sativa (OVX-NS) orally for 12 weeks; 4 weeks before ovariectomy and 8 weeks after. After 12 weeks, plasma levels of calcium (Ca⁺²), phosphorous (Pi), alkaline phosphatase (ALP), amino terminal collagen type 1 telopeptide, malondialdehyde (MDA), nitrates, nitric oxide surrogate, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured. Histological examination of the liver and the tibia was conducted. Histomorphometric analysis of the tibia was also performed.

Results

OVX rats showed significant decrease in plasma Ca⁺², accompanied by a significant increase in plasma ALP, amino terminal collagen type 1 telopeptide, MDA, nitrates, TNF-α and IL-6. These changes were reversed by NS supplementation in OVX-NS group to be near SHAM levels. Histological examination of the tibias revealed discontinuous eroded bone trabeculae with widened bone marrow spaces in OVX rats accompanied by a significant decrease in both cortical and trabecular bone thickness compared to Sham rats. These parameters were markedly reversed in OVX-NS rats. Histological examination of the liver showed mononuclear cellular infiltration and congestion of blood vessels at the portal area in OVX rats which were not found in OVX-NS rats.

Conclusion

Nigella sativa reverses osteoporosis in ovariectomized rats, which could be attributed to its high content of unsaturated fatty acids as well as its antioxidant and anti-inflammatory properties.

Effects of tocotrienol and lovastatin combination on osteoblast and osteoclast activity in estrogen-deficient osteoporosis

Statins are HMGCoA reductase inhibitors and had been demonstrated to stimulate bone formation in rodents after high oral doses. Observational studies on patients treated with oral statins were varied. Delta-tocotrienol had been found to stimulate the cleavage of HMGCoA reductase and inhibit its activity. Tocotrienols were found to have both catabolic and anabolic effects on bone in different animal models of osteoporosis. The current study aimed to ascertain the effects of delta-tocotrienol and lovastatin combination on biochemical and static bone histomorphometric parameters in a postmenopausal rat model at clinically tolerable doses. 48 Sprague Dawley female rats were randomly divided into 6 groups: (1) baseline control group; (2) sham-operated control group; (3) ovariectomised control group; (4) ovariectomised and 11 mg/kg lovastatin; (5) ovariectomised and 60 mg/kg delta-tocotrienol; (6) ovariectomised and 60 mg/kg delta-tocotrienol + 11 mg/kg lovastatin. These treatments were given daily via oral gavage for 8 weeks. Delta-tocotrienol plus lovastatin treatment significantly increased bone formation and reduced bone resorption compared to the other groups. Therefore, the combined treatment may have synergistic or additive effects and have the potential to be used as an antiosteoporotic agent in patients who are at risk of both osteoporosis and hypercholesterolemia, especially in postmenopausal women.

The mechanism of vascular calcification - a systematic review

Calcification of vessels reduces their elasticity, affecting hemodynamic parameters of the cardiovascular system. The development of arterial hypertension, cardiac hypertrophy, ischemic heart disease or peripheral arterial disease significantly increases mortality in patients over 60 years of age. Stage of advancement and the extent of accumulation of calcium deposits in vessel walls are key risk factors of ischemic events. Vascular calcification is an active and complex process that involves numerous mechanisms responsible for calcium depositions in arterial walls. They lead to increase in arterial stiffness and in pulse wave velocity, which in turn increases cardiovascular disease morbidity and mortality. In-depth study and thorough understanding of vascular calcification mechanisms may be crucial for establishing an effective vasculoprotective therapy. The aim of this study was to present a comprehensive survey of current state-of-the-art research into the impact of metabolic and hormonal disorders on development of vascular calcification. Due to strong resemblance to the processes occurring in bone tissue, drugs used for osteoporosis treatment (calcitriol, estradiol, bisphosphonates) may interfere with the processes occurring in the vessel wall. On the other hand, drugs used to treat cardiovascular problems (statins, angiotensin convertase inhibitors, warfarin, heparins) may have an effect on bone tissue metabolism. Efforts to optimally control calcium and phosphate concentrations are also beneficial for patients with end-stage renal disease, for whom vessel calcification remains a major problem.

Atorvastatin improved scopolamine-induced impairment in memory acquisition in mice: involvement of nitric oxide

Atorvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, widely used in treatment of hypercholesterolemia, slows the progression of mild-to-moderate Alzheimer's disease. In this study, effects of atorvastatin on acquisition of spatial recognition memory and the involvement of nitric oxide (NO) have been determined in a two-trial recognition Y-maze test and passive avoidance. Atorvastatin (1, 5mg/kg, p.o.) was administered prior to acquisition phase, either in presence or in absence of a non-specific NO synthase inhibitor, L-NAME (3, 10mg/kg, i.p.); a specific inducible NO synthase inhibitor, aminoguanidine (100mg/kg); and a NO precursor, l-arginine (750mg/kg).

RESULTS

Atorvastatin significantly improved memory performance in a dose-dependent manner in acquisition of recognition memory, in both Y-maze and passive avoidance tests. 1) Atorvastatin (5mg/kg) significantly increased both exploration time and number of arm entries in scopolamine-treated mice in Y-maze. 2) The beneficial effects of atorvastatin on memory acquisition were significantly reversed by L-NAME (3mg/kg) and aminoguanidine (100mg/kg). 3) The effects of sub-effective dose of atorvastatin (1mg/kg) on memory acquisition were not potentiated by l-arginine (750mg/kg); 4) Administration of atorvastatin (5mg/kg) significantly increased step-through latency in scopolamine-induced memory-impaired mice. 5) Beneficial effect of atorvastatin on passive avoidance was not reversed by L-NAME (up to 10mg/kg). 6) The effects of sub-effective dose of atorvastatin (1mg/kg) on passive avoidance were not potentiated by l-arginine (750mg/kg). The present study demonstrates that atorvastatin improved both short-spatial recognition memory and fear memory. As this effect is reversed by L-NAME and aminoguanidine in short-term memory acquisition, it is concluded that NO might be involved in spatial memory improvement by atorvastatin.

The effect of polyunsaturated fatty acids on bone health

The essential polyunsaturated fatty acids (PUFAs) are divided into two classes, n-3 (ω-3) and n-6 (ω-6) and their dietary precursors are α-linolenic (ALA) and linoleic acid (LA), respectively. PUFAs are precursors of a wide range of metabolites, for example eicosanoids like prostaglandins and leukotrienes, which play critical roles in the regulation of a variety of biological processes, including bone metabolism.

A large body of evidence supports an effect of PUFA on bone metabolism which may be mediated by regulation of osteoblastogenesis and osteoclast activity, change of membrane function, decrease in inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-α), modulation of peroxisome proliferators-activated receptor γ (PPARγ) and influence in NO secretion and NO synthase.

Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. Human studies conducted in elderly subjects suggest that omega-3 instead of omega-6 has a positive effect on bone metabolism. In spite of increasing evidence, studies conducted in humans do not allow us to draw a definitive conclusion on the usefulness of PUFAs in clinical practice.

Olive oil effectively mitigates ovariectomy-induced osteoporosis in rats

BACKGROUND

Osteoporosis, a reduction in bone mineral density, represents the most common metabolic bone disease. Postmenopausal women are particularly susceptible to osteoporosis when their production of estrogen declines. For these women, fracture is a leading cause of morbidity and mortality. This study was conducted to evaluate the protective effects of olive oil supplementation against osteoporosis in ovariectomized (OVX) rats.

METHODS

We studied adult female Wistar rats aged 12-14 months, divided into three groups: sham-operated control (SHAM), ovariectomized (OVX), and ovariectomized rats supplemented with extravirgin olive oil (Olive-OVX) orally for 12 weeks; 4 weeks before ovariectomy and 8 weeks after. At the end of the experiment, blood samples were collected. Plasma levels of calcium, phosphorus, alkaline phosphatase (ALP), malondialdehyde (MDA), and nitrates were assayed. Specimens from both the tibia and the liver were processed for light microscopic examination. Histomorphometric analysis of the tibia was also performed.

RESULTS

The OVX-rats showed a significant decrease in plasma calcium levels, and a significant increase in plasma ALP, MDA, and nitrates levels. These changes were attenuated by olive oil supplementation in the Olive-OVX rats. Light microscopic examination of the tibia of the OVX rats revealed a significant decrease in the cortical bone thickness (CBT) and the trabecular bone thickness (TBT). In addition, there was a significant increase in the osteoclast number denoting bone resorption. In the Olive-OVX rats these parameters were markedly improved as compared to the OVX group. Examination of the liver specimens revealed mononuclear cellular infiltration in the portal areas in the OVX-rats which was not detected in the Olive-OVX rats.

CONCLUSIONS

Olive oil effectively mitigated ovariectomy-induced osteoporosis in rats, and is a promising candidate for the treatment of postmenopausal osteoporosis.

Endogenous n-3 fatty acids protect ovariectomy induced bone loss by attenuating osteoclastogenesis

Beneficial effects of n-3 fatty acids (FA) on bone mineral density (BMD) have been reported in mice, rats and human beings, but the precise mechanisms involved have not been described. This study used the Fat-1 mouse, a transgenic model that synthesizes n-3 FA from n-6 FA to directly determine if outcome of bone health were correlated with n-3 FA. Ovariectomized (Ovx) and sham operated wild-type (WT) and Fat-1 mice were fed an AIN-93M diet containing 10% corn oil for 24 weeks. BMD was analysed by dual energy x-ray absorptiometry. Fat-1 Ovx mice exhibited significantly lower level of osteotropic factors like receptor activator of NF-kappaB ligand and tartrate-resistant acid phosphatase (TRAP)5b in serum and higher BMD in distal femoral metaphysis, proximal tibial metaphysis, femoral diaphysis and lumbar vertebra as compared to WT Ovx mice. LPS-stimulated bone marrow (BM) cells from Fat-1 Ovx mice produced significantly lower level of pro-inflammatory cytokines like tumour necrosis factor-alpha, interleukin (IL)-1-beta, IL-6 and higher level of anti-inflammatory cytokines like IL-10, IFN-gamma and higher level of nitric oxide as compared to BM cells from WT Ovx mice. LPS-stimulated COX-II activity as well as NF-kappaB activation in BM cells from Fat-1 Ovx mice was significantly less as compared to BM cells from WT Ovx mice. Furthermore, Fat-1 BM cells generated significantly less number of TRAP osteoclast-like cells as compared to WT BM cells. In conclusion, we offer further insight into the mechanisms involved in preventing the BMD loss in Ovx mice by n-3 FA using a Fat-1 transgenic mouse model.

Endogenous n-3 fatty acids protect ovariectomy induced bone loss by attenuating osteoclastogenesis

Beneficial effects of n-3 fatty acids (FA) on bone mineral density (BMD) have been reported in mice, rats and human beings, but the precise mechanisms involved have not been described. This study used the Fat-1 mouse, a transgenic model that synthesizes n-3 FA from n-6 FA to directly determine if outcome of bone health were correlated with n-3 FA. Ovariectomized (Ovx) and sham operated wild-type (WT) and Fat-1 mice were fed an AIN-93M diet containing 10% corn oil for 24 weeks. BMD was analysed by dual energy x-ray absorptiometry. Fat-1 Ovx mice exhibited significantly lower level of osteotropic factors like receptor activator of NF-kappaB ligand and tartrate-resistant acid phosphatase (TRAP)5b in serum and higher BMD in distal femoral metaphysis, proximal tibial metaphysis, femoral diaphysis and lumbar vertebra as compared to WT Ovx mice. LPS-stimulated bone marrow (BM) cells from Fat-1 Ovx mice produced significantly lower level of pro-inflammatory cytokines like tumour necrosis factor-alpha, interleukin (IL)-1-beta, IL-6 and higher level of anti-inflammatory cytokines like IL-10, IFN-gamma and higher level of nitric oxide as compared to BM cells from WT Ovx mice. LPS-stimulated COX-II activity as well as NF-kappaB activation in BM cells from Fat-1 Ovx mice was significantly less as compared to BM cells from WT Ovx mice. Furthermore, Fat-1 BM cells generated significantly less number of TRAP osteoclast-like cells as compared to WT BM cells. In conclusion, we offer further insight into the mechanisms involved in preventing the BMD loss in Ovx mice by n-3 FA using a Fat-1 transgenic mouse model.

Icariin isolated from Epimedium pubescens regulates osteoblasts anabolism through BMP-2, SMAD4, and Cbfa1 expression

Epimedii herba is one of the most frequently used herbs in formulas prescribed for the treatment of osteoporosis in China. The main active flavonoid glucoside extracted from Epimedium pubescens is Icariin, which has been reported to enhance bone healing and reduce osteoporosis occurrence. However, the detailed molecular mechanisms remain unclear. In this present study, we examine the molecular mechanisms of icariin by using primary osteoblast cell cultures obtained from adult mice. The osteoblast cells were harvested from 8-month old female Imprinting Control Region (ICR) mice. The effects of icariin stimulation on the proliferation, differentiation and maturation of osteoblasts were examined. The production of nitric oxide (NO) and caspase-3 were analyzed, along with the gene expressions of bone morphogenetic protein-2 (BMP-2), SMAD4, Cbfa1/Runx2, OPG, and RANKL. The viability of the osteoblasts reached its maximum at 10(-8)M icariin. At this concentration, icariin increased the proliferation and matrix mineralization of osteoblasts and promoted NO synthesis. With icariin treatment, the BMP-2, SMAD4, Cbfa1/Runx2, and OPG gene expressions were up-regulated; the RANKL gene expression was however down-regulated. Concurrent treatment involving the BMP antagonist (Noggin) or the NOS inhibitor (L-NAME) diminished the icariin-induced cell proliferation, ALP activity, NO production, as well as the BMP-2, SMAD4, Cbfa1/Runx2, OPG, RANKL gene expressions. In this study, we demonstrate that in vitro icariin is a bone anabolic agent that may exert its osteogenic effects through the induction of BMP-2 and NO synthesis, subsequently regulating Cbfa1/Runx2, OPG, and RANKL gene expressions. This effect may contribute to its action on the induction of osteoblasts proliferation and differentiation, resulting in bone formation.

Evaluation and management of osteoporosis and fragility fractures in the elderly

Osteoporosis is characterized by low bone mass and microarchitectural deterioration that leads to increased bone fragility and fracture. The medical, psychosocial and economic burden that fragility fractures have on individuals and society is staggering. As the geriatric segment of the population continues to expand, so to will the magnitude of this epidemic. There are multiple mechanisms influencing bone quality and bone loss with age. Fragility fracture is a composite of multiple intrinsic and extrinsic factors related to the individual and their environment. Fall prevention remains the cornerstone of management in this problem. The FRAX® fracture risk assessment program, which estimates the 10-year probability of a major osteoporotic fracture, is an exciting new tool in assessing risk. Novel therapeutics, including zoledronic acid, strontium and teriparatide, are now available to complement proven osteoporosis treatments and more effectively decrease fracture risk in vulnerable individuals. Agents in Phase III trials, including denosumab and lasofoxifene, will probably increase the armamentarium of tools clinicians can use to combat the growing problem of osteoporosis and its complications.

Aspects of nitric oxide in health and disease: a focus on hypertension and cardiovascular disease

Nitric oxide (nitrogen monoxide) (NO) plays an important role in a wide range of physiologic processes. A major mediator of endothelial function, NO regulates vasodilatory and antithrombotic actions in the vasculature and plays a role in reproductive functions, bronchodilation, bone formation, memory, insulin sensitivity, and gastrointestinal relaxation. NO is formed from NO synthase. Impaired NO bioactivity is strongly associated with endothelial dysfunction and cardiovascular disease, but is also implicated in a broad range of other disorders, including pulmonary hypertension, insulin resistance, erectile dysfunction, and preeclampsia. Numerous therapies designed to target NO are being investigated and developed, including NO donors and stimulants. The recent African-American Heart Failure Trial (A-HeFT) showed that the NO donor isosorbide dinitrate, combined with the vasodilator hydralazine, significantly reduced morbidity and mortality in black patients with moderate-to-severe heart failure. Antihypertensive drugs, including angiotensin-converting enzyme inhibitors, calcium channel blockers, and third-generation beta-blockers, are NO stimulants that have demonstrated significant improvement of endothelial function and NO bioactivity. Other cardiovascular therapies that may improve NO bioactivity include statins, l-arginine, and nonpharmacologic approaches such as exercise and dietary changes.

Osteoporosis: pathogenesis, new therapies and surgical implications

Many developments occurred in the realm of bone healing in recent years. Genetic discoveries, new proteins affecting bone health, and new treatments have steered our treatment of traumatic and iatrogenic fractures in new directions. Osteoporosis strikes many subsets of the world population, including: women, the elderly, and those suffering from arthritis, autoimmune diseases, HIV, and the immunocompromised. This disease predisposes people to an increased risk of low trauma and fragility fractures. The baby boomer generation and an increasing lifespan may burden the economy by creating such a large group susceptible to such a potentially devastating disease. The novel treatments and coping with the potentially challenging surgical implications will aide the podiatric physician in both medical and surgical management of osteoporosis.

Effects of calcitonin, risedronate, and raloxifene on erythrocyte antioxidant enzyme activity, lipid peroxidation, and nitric oxide in postmenopausal osteoporosis

BACKGROUND

The aims of this study were to compare erythrocyte antioxidant enzyme activities, lipid peroxidation, and nitric oxide levels (NO) in women with postmenopausal osteoporosis (PMO) and non-porotic postmenopausal healthy controls and to assess the relationship between bone mineral density and these oxidant/antioxidant parameters. Additionally, in vivo effects of three different anti-osteoporotic drugs, calcitonin, risedronate and raloxifene, on the erythrocyte oxidant-antioxidant status in women with PMO were also assessed.

METHODS

Postmenopausal women aged 40-65 years and without previous diagnosis or treatment for osteoporosis and independent in activities of daily living were included. Bone mineral density was measured at the lumbar spine and proximal femur using DXA. Erythrocyte enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and lipid peroxidation end-product malondialdehyde (MDA) and nitrite/nitrate levels, by product of NO, were assessed. Fifty-nine women with PMO were included (mean age 56.7 years), 44 completed course of therapy and were analyzed. Twenty-two non-porotic healthy women (mean age 55.8 years) were included as controls.

RESULTS

Patients had significantly lower CAT and GSH-Px enzyme activity and higher levels of MDA and NO than non-porotic healthy controls. Proximal femur BMD measurements significantly correlated with NO levels. QUALEFFO scores improved in different levels with these short-term treatments. In all treatment groups, erythrocyte MDA levels significantly decreased; moreover, risedronate reduced NO levels and raloxifene enhanced CAT enzyme activity.

CONCLUSIONS

Oxidative stress plays an important role in the pathogenesis of PMO. Studied drugs had ultimate effects on reducing lipid peroxidation. Raloxifene also had potent effects in the enhancement of antioxidant defense system.

Organ systems dependent on nitric oxide and the potential for nitric oxide-targeted therapies in related diseases

Nitric oxide (NO) is a universal messenger molecule that plays diverse and essential physiologic roles in multiple organ systems, including the vasculature, bone, muscle, heart, kidney, liver, and central nervous system. NO is produced by 3 known isoforms-endothelial, neuronal, and inducible NO synthase-each of which perform distinct functions. Impairment of NO bioactivity may be an important factor in the pathogenesis of a wide range of conditions, including preeclampsia, osteoporosis, nephropathy, liver disease, and neurodegenerative diseases. Although increased levels of NO synthase or NO bioactivity have been associated with some of these disease states, research increasingly suggests that preservation or promotion of normal NO bioactivity may be beneficial in reducing the risks and perhaps reversing the underlying pathophysiology. Based on this rationale, studies investigating the use of NO-donating or NO-promoting agents in some of these diseases have produced positive results, at least to some degree, in either animal or human studies. Further investigation of NO-targeted therapies in these diverse diseases is clearly mandated.

Design and synthesis of furoxan-based nitric oxide-releasing glucocorticoid derivatives with potent anti-inflammatory activity and improved safety

A series of furoxan-based nitric oxide-releasing glucocorticoid derivatives was synthesized. The pharmacological assays indicated that three compounds, including I(4), I(5), and I(6), had anti-inflammatory activity. Furthermore compared with the leading compound hydrocortisone the safety of I(6) was greatly improved. Due to releasing NO in vivo the side effects of glucocorticoids, including hypertension and osteoporosis, were effectively avoided.

Synthesis of Nitric Oxide in Human Osteoblasts in Response to Physiologic Stimulation of Electrotherapy

Electrotherapy for bone healing, remodeling and wound healing may be mediated by modulation of nitric oxide (NO). Using NO-specific fluorophore (DAF-2), we report here that application of non-invasive, physiologic electrical stimulation induces NO synthesis in human osteoblasts, and that such NO generation is comparable to that induced by estrogen treatment. For example, application of a sinusoidal 1 Hz, 2 V/cm (peak to peak) electrical stimulation (ES) increases NO-bound DAF-2 fluorescence intensity by a 2-fold within 60 min exposure by activating nitric oxide synthase (NOS). Increase in the NO level is found to depend critically on the frequency and strength of ES. While the frequency of 1 Hz ES seems optimal, the ES strength >0.5 V/cm is required to induce significant NO increase, however. Nitric oxide synthesis in response to ES is completely prevented by blocking estrogen receptors using a competitive inhibitor, suggesting that NO generation is likely initiated by activation of estrogen receptors at the cell surface. Based on these findings, physiologic stimulation of electrotherapy appears to represent a potential non-invasive, non-genomic, and novel physical technique that could be used to regulate NO-mediated bone density and facilitate bone remodeling without adverse effects associated with hormone therapy.

Supplemental arginine and high-dose folate may promote bone health by supporting the activity of endothelial-type nitric oxide synthase in bone

The endothelial isoform of NO synthase promotes maintenance of bone density by stimulating osteoblastic activity while inhibiting bone catabolism; it appears to be a key mediator of the anabolic effects of mechanical loading, estrogens, and statin therapy on bone. This enzyme is susceptible to competitive inhibition by elevated systemic levels of asymmetric dimethylarginine (ADMA) encountered in vascular disorders associated with endotheliopathy; it may not be coincidental that reduced bone density has been observed in subjects afflicted with many of these disorders. Supplemental arginine has the potential to offset this adverse effect of ADMA. Superoxide production by osteoclasts may also impair bone NO synthase activity by oxidizing its cofactor tetrahydrobiopterin; high-dose folate has been shown to compensate for endothelial deficiency of this cofactor by effectively "pinch hitting" for it. These considerations suggest that supplementation with arginine as well as high-dose folate might aid maintenance of bone density by helping to preserve optimal NO synthase activity in bone cells.

Different doses of nitric oxide donor prevent osteoporosis in ovariectomized rats

Nitric oxide has important effects on bone cell function. To verify that nitric oxide can protect against bone loss associated with estrogen deficiency, which is dependent on different concentrations of nitric oxide, we applied different doses of nitric oxide to ovariectomized rats. Fifty 12-week-old Sprague-Dawley female rats had ovariectomies, and 10 rats had sham operations. The ovariectomized rats were randomized into five groups: ovariectomized only; 17-beta-estradiol; low-dose nitroglycerin; middle-dose nitroglycerin; and high-dose nitroglycerin. After 12 weeks, the bone mineral density, dry weight, ash weight, calcium content, and nitric oxide concentration were determined. Compared with these same measurements in the sham-operated group, the bone mineral density, dry weight, ash weight, calcium content, and nitric oxide concentration decreased in the control group. Treatment with low-dose nitroglycerin, middle-dose nitroglycerin, and 17-beta-estradiol maintained bone mineral density and reversed the effects of ovariectomy on dry weight, ash weight and calcium content when compared with those in the control group. There were no differences in the bone mineral density, dry weight, ash weight, or calcium concentration between the ovariectomized-only rats and the rats treated with high-dose nitroglycerin. Results of this study suggest that nitric oxide treatment can counteract bone loss in ovariectomized rats. Furthermore, supplementation with a similar or slightly greater than physiologic concentration of nitric oxide has a potentially positive impact on osteoporosis.

A new approach to the treatment of osteoporosis

Osteoporosis remains a significant clinical problem despite the availability of effective therapies. The main therapy still needed is an anabolic agent for the treatment of osteoporosis. This study examined the in vivo effect of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor simvastatin, which controls the first step in the biosynthesis of cholesterol, on bone formation in rats. Histologic specimens were collected 7, 14, and 21 days after administration of 1 mg of simvastatin for 5 days and compared with control specimens for changes in bone tissue. The observed effects on the bone in a healthy animal model included advancement of the blood supply, acceleration of the proliferation and differentiation of osteoprogenitor cells, and formation of osteoid tissue.

Olive oil and its main phenolic micronutrient (oleuropein) prevent inflammation-induced bone loss in the ovariectomised rat

The present study was designed to evaluate the effect of olive oil and its main polyphenol (oleuropein) in ovariectomised rats with or without inflammation. Rats (6 months old) were ovariectomised or sham-operated as control. Ovariectomised rats were separated into three groups receiving different diets for 3 months: a control diet with 25 g peanut oil and 25 g rapeseed oil/kg (OVX), the control diet with 50 g olive oil/kg or the control diet with 0.15 g oleuropein/kg. The sham-operated group was given the same control diet as OVX. Inflammation was induced 3 weeks before the end of the experiment by subcutaneous injections of talc (magnesium silicate) in one-half of each group. The success of ovariectomy was verified at necropsy by the atrophy of uterine horns. Inflammation, oleuropein or olive oil intakes did not have any uterotrophic activity, as they had had no effect on uterus weight. The plasma concentration of alpha-1-acid glycoprotein (an indicator of inflammation) was increased in OVX rats with inflammation. With regard to bone variables, osteopenia in OVX was exacerbated by inflammation, as shown by a decrease in metaphyseal and total femoral mineral density. Both oleuropein and olive oil prevented this bone loss in OVX rats with inflammation. At necropsy, oleuropein and olive oil consumption had had no effect on plasma osteocalcin concentrations (marker of bone formation) or on urinary deoxypyridinoline excretion (marker of bone resorption). In conclusion, oleuropein and olive-oil feeding can prevent inflammation-induced osteopenia in OVX rats.

HMG-CoA reductase inhibitors in osteoporosis: do they reduce the risk of fracture?

Osteoporosis affects a large number of people in industrialised countries. It has clinical and public-health impacts, most importantly due to subsequent fractures. Osteoporotic fractures are one of the most common causes of disability and are associated with enormous healthcare expenditure. The majority of existing treatment options for osteoporosis only inhibit bone resorption and prevent excessive bone loss but are not capable of stimulating bone formation. However, several recent in vitro and in vivo studies in animals demonstrated that HMG-CoA reductase inhibitors stimulate the production of bone morphogenetic protein (BMP-2), which is a potent regulating protein in osteoblast differentiation and activity. This suggests that HMG-CoA reductase inhibitors may have an anabolic effect on bones, making them a potentially interesting treatment option for osteoporosis. Additionally, several studies in humans showed that some HMG-CoA reductase inhibitors may have a beneficial effect on bone turnover and may lead to an increase in bone mineral density. Consequently, several observational studies tried to evaluate whether use of HMG-CoA reductase inhibitors is associated with a decreased risk of fractures. Even though not all results of these epidemiological studies, using different designs in different study populations, were entirely consistent, they provided substantial evidence that HMG-CoA reductase inhibitor use may decrease the bone fracture risk by approximately 50%. On the other hand, reanalysis of two randomised controlled trials of HMG-CoA reductase inhibitor therapy, designed to assess cardiovascular outcomes, could not show that patients treated with HMG-CoA reductase inhibitors had a lower fracture risk in comparison with placebo-treated patients. Therefore, to conclusively assess the potential of HMG-CoA reductase inhibitors in the prevention and treatment of osteoporosis, randomised controlled trials need to be performed to address this conflicting issue. Until the results of such trials are available, practitioners should prescribe the drugs that have been proven to reduce the risk of osteoporotic fractures.

Dietary n-3 fatty acids decrease osteoclastogenesis and loss of bone mass in ovariectomized mice

The mechanisms of action of dietary fish oil (FO) on osteoporosis are not fully understood. This study showed FO decreased bone loss in ovariectomized mice because of inhibition of osteoclastogenesis. This finding supports a beneficial effect of FO on the attenuation of osteoporosis.

INTRODUCTION

Consumption of fish or n-3 fatty acids protects against cardiovascular and autoimmune disorders. Beneficial effects on bone mineral density have also been reported in rats and humans, but the precise mechanisms involved have not been described.

METHODS

Sham and ovariectomized (OVX) mice were fed diets containing either 5% corn oil (CO) or 5% fish oil (FO). Bone mineral density was analyzed by DXA. The serum lipid profile was analyzed by gas chromatography. Receptor activator of NF-kappaB ligand (RANKL) expression and cytokine production in activated T-cells were analyzed by flow cytometry and ELISA, respectively. Osteoclasts were generated by culturing bone marrow (BM) cells with 1,25(OH)2D3. NF-kappaB activation in BM macrophages was measured by an electrophoretic mobility shift assay.

RESULTS AND CONCLUSION

Plasma lipid C16:1n6, C20:5n3, and C22:6n3 were significantly increased and C20:4n6 and C18:2n6 decreased in FO-fed mice. Significantly increased bone mineral density loss (20% in distal left femur and 22.6% in lumbar vertebrae) was observed in OVX mice fed CO, whereas FO-fed mice showed only 10% and no change, respectively. Bone mineral density loss was correlated with increased RANKL expression in activated CD4+ T-cells from CO-fed OVX mice, but there was no change in FO-fed mice. Selected n-3 fatty acids (docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]) added in vitro caused a significant decrease in TRACP activity and TRACP+ multinuclear cell formation from BM cells compared with selected n-6 fatty acids (linoleic acid [LA] and arachidonic acid [AA]). DHA and EPA also inhibited BM macrophage NF-kappaB activation induced by RANKL in vitro. TNF-alpha, interleukin (IL)-2, and interferon (IFN)-gamma concentrations from both sham and OVX FO-fed mice were decreased in the culture medium of splenocytes, and interleukin-6 was decreased in sham-operated FO-fed mice. In conclusion, inhibition of osteoclast generation and activation may be one of the mechanisms by which dietary n-3 fatty acids reduce bone loss in OVX mice.

Modulatory effect of omega-3 polyunsaturated fatty acids on osteoblast function and bone metabolism

Recent investigations indicate that the type and amount of polyunsaturated fatty acids (PUFA) influence bone formation in animal models and osteoblastic cell functions in culture. In growing rats, supplementing the diet with omega-3 PUFA results in greater bone formation rates and moderates ex vivo prostaglandin E(2) production in bone organ cultures. A protective effect of omega-3 PUFA on minimizing bone mineral loss in ovariectomized rats has also been reported. The actions of omega-3 fatty acids on bone formation appear to be linked to altering osteoblast functions. Herein we describe experiments with MC3T3-E1 osteoblast-like cells that support findings in vivo where omega-3 PUFA modulated COX-2 protein expression, reduced prostaglandin E(2) production, and increased alkaline phosphatase activity. Other studies indicate that the dietary source of PUFA may affect protein expression of Cbfa1 and nodule formation in fetal rat calvarial cells.