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

Sex-specific effects of Fat-1 transgene on bone material properties, size, and shape in mice

Western diets are becoming increasingly common around the world. Western diets have high omega 6 (ω-6) and omega 3 (ω-3) fatty acids and are linked to bone loss in humans and animals. Dietary fats are not created equal; therefore, it is vital to understand the effects of specific dietary fats on bone. We aimed to determine how altering the endogenous ratios of ω-6:ω-3 fatty acids impacts bone accrual, strength, and fracture toughness. To accomplish this, we used the Fat-1 transgenic mice, which carry a gene responsible for encoding a ω-3 fatty acid desaturase that converts ω-6 to ω-3 fatty acids. Male and female Fat-1 positive mice (Fat-1) and Fat-1 negative littermates (WT) were given either a high-fat diet (HFD) or low-fat diet (LFD) at 4 wk of age for 16 wk. The Fat-1 transgene reduced fracture toughness in males. Additionally, male BMD, measured from DXA, decreased over the diet duration for HFD mice. In males, neither HFD feeding nor the presence of the Fat-1 transgene impacted cortical geometry, trabecular architecture, or whole-bone flexural properties, as detected by main group effects. In females, Fat-1-LFD mice experienced increases in BMD compared to WT-LFD mice; however, cortical area, distal femur trabecular thickness, and cortical stiffness were reduced in Fat-1 mice compared to pooled WT controls. However, reductions in stiffness were caused by a decrease in bone size and were not driven by changes in material properties. Together, these results demonstrate that the endogenous ω-6:ω-3 fatty acid ratio influences bone material properties in a sex-dependent manner. In addition, Fat-1 mediated fatty acid conversion was not able to mitigate the adverse effects of HFD on bone strength and accrual.

Hydroalcoholic extract of Glycyrrhiza glabra root combined with Linum usitatissimum oil as an alternative for hormone replacement therapy in ovariectomized rats

Objective

Plant-derived estrogens (phytoestrogens) with structural similarity to primary female sex hormones could be suitable replacements for sex hormones. Therefore, the effects of the licorice root extract and Linum usitatissimum oil on biochemical and hormonal indices in the serum and uterine stereological changes in ovariectomized rats were evaluated.

Design

In this study, 70 adult female rats were randomly divided into seven groups including 1) control group, 2) sham-operated group, 3) ovariectomized (OVX) group, 4) OVX rats that received 1 mg/kg estradiol for 8 weeks at the day of post-operation, 5) OVX rats which received 2.0 mg/kg body wt Linum usitatissimum oil for 8 weeks at the day of post-operation, 6) OVX rats which received 2.0 mg/kg body wt licorice extract for 8 weeks at the day of post-operation, and 7) OVX rats which received 2.0 mg/kg body wt Linum usitatissimum oil + 2.0 mg/kg body wt licorice extract for 8 weeks at the day of post-operation. After eight weeks, alkaline phosphatase activity, as well as calcium, estradiol, and progesterone concentrations were assessed and tissue samples of the uterus were serologically examined.

Results

The results indicated that after 8 weeks of OVX the alkaline phosphatase activity (Mean = 637.7 IU/L) increased and the calcium (Mean = 7.09 mg/dl), estradiol (5.30 pmol/L), and progesterone (Mean = 3.53 nmol/L) reduced compared to other groups. Moreover, stereological changes in the uterus in ovariectomy groups were seen compared to the other groups. The treatment with Linum usitatissimum oil and licorice extract had a significant therapeutic effect on biochemical factors and stereological changes compared to the ovariectomized group.

Conclusion

The results of this study showed that the combination of Linum usitatissimum oil with licorice extract showed the high potential of hormone replacement therapy in the reduction of OVX complications.

The combination of olive oil and Lepidium sativum improves the deleterious effects resulting from dexamethasone-induced osteoporosis in rats

Introduction

Osteoporosis is characterized by deterioration of bone microarchitecture and reduced bone mass and can increase the risk of fracture. To reduce this risk, the aim of this study was to compare the combination effects of olive oil and Lepidium sativum compared to the conventional drug therapy alendronate.

Methods

Osteoporosed-induced rat model was established by administration of dexamethasone in female adult albino rats. The serum level of Ca2+, P3+, and osteocalcin was assessed. In addition, histopathological changes and immunohistochemical expression of osteopontin within bone specimens were performed.

Results

Our results showed that a combination of olive oil and Lepidium sativum had a beneficial therapeutic effect in the treatment of osteoporosis as compared to alendronate therapy. This was demonstrated by increase of serum Ca2+, P3+, and osteocalcin levels in treated compared to control groups. Intriguingly, the highest effect was noticed in rats that received a combination of olive oil and Lepidium sativum compared to the individual treatment. This was reflected by an increase in the cortical bone thickness and a decrease in immunohistochemical expression of osteopontin compared to individual treated groups.

Conclusion

We concluded that the administration of a combination of olive oil and Lepidium sativum improves bone mineral health and intensity and reduces the risk of osteoporosis in a rat model.

Omega-9 Modifies Viscoelasticity and Augments Bone Strength and Architecture in a High-Fat Diet-Fed Murine Model

The influence of diet on the development of osteoporosis is significant and not fully understood. This study investigated the effect of diets of varying lipid profiles and ω-3, ω-6 and ω-9 composition on the structural and mechanical properties of bone. The hypothesis studied was that a diet high in saturated fat would induce osteoporosis and produce an overall increased detrimental bony response when compared with a diet high in unsaturated ω-6, or ω-9. Male C57BL/6J mice were fed either a control diet, 50:50 mix (saturated:unsaturated) high in ω-9 (HFD50:50), a diet high in saturated fat (HSF) or a polyunsaturated fat diet high in ω-6 (PUFA) over an 8-week duration. Tibiae were retrieved and evaluated using DMA, 3-point-bending, histomorphometry, and microCT. Mice fed a HSF diet displayed key features characteristic of osteoporosis. The loss tangent was significantly increased in the HFD50:50 diet group compared with control (p = 0.016) and PUFA-fed animals (p = 0.049). HFD50:50-fed mice presented with an increased viscous component, longer tibiae, increased loss modulus (p = 0.009), and ultimate stress, smaller microcracks (p < 0.001), and increased trabecular width (p = 0.002) compared with control animals. A diet high in ω-9 resulted in an overall superior bone response and further analysis of its role in bone health is warranted.

An updated review of the effects of eicosapentaenoic acid- and docosahexaenoic acid-derived resolvins on bone preservation

Resolvins are biosynthesized from omega-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in vivo by means of enzymatic activities, and these factors can attenuate inflammation and promote tissue regeneration. Inflammatory bone disorders can lead to bone loss and thereby be harmful to human health. The link between bone preservation and resolvins has been discussed in some experimental studies. Significant evidence has shown that resolvins benefit bone health and bone preservation by promoting the resolution of inflammation and directly regulating osteoclasts and osteoblasts. Therefore, this review highlights the role and beneficial impact of resolvins derived from EPA and DHA on inflammatory bone disorders, such as rheumatoid arthritis and periodontitis. In addition, the mechanisms by which resolvins exert their beneficial effects on bone preservation have also been summarized based on the available literature.

Tilapia nilotica Head Lipids Improved Bone Loss by Regulating Inflammation and Serum Metabolism Through Gut Microbiota in Ovariectomized Rats

Osteoporosis is a global health problem, and it is of great significance to replace the drugs with natural functional factors. In this study, we investigated the antiosteoporotic activity of lipids prepared from Tilapia nilotica fish head lipids (THLs) in the ovariectomized osteoporosis rats. THLs are composed of neutral lipids (NL, 77.84%), phospholipids (PL, 11.86%), and glycolipids (GL, 6.47%). There were apparent differences in the fatty acid composition of disparate components, and PL contains the most abundant Ω-3 polyunsaturated fatty acids. The results proved that THLs could improve bone microstructure, increase bone mineral density, and decrease bone resorption. To illustrate the antiosteoporotic mechanism, we analyzed the changes in gut microbial communities, proinflammation factors, serum metabolites, and metabolic pathways. Further study on gut microbiota showed that THLs significantly decreased the content of Alistipes in the gut and dramatically increased the beneficial bacteria such as Oscillospira, Roseburia, and Dubosiella. Meanwhile, proinflammation factors of serum in OVX rats decreased significantly, and metabolites were changed. Therefore, we speculated that THLs improved bone loss through reducing inflammation and changing the metabolites and metabolic pathways such as arachidonic acid metabolism and primary bile acid metabolism, etc., by altering gut microbiota. The results indicated that THLs could be a functional factor with antiosteoporotic activity.

Effect of flaxseed oil on biochemical parameters, hormonal indexes and stereological changes in ovariectomized rats

The ovariectomized rat is a widely used preclinical model for studying postmenopausal and its complications. In this study, the therapeutic effect of flaxseed oil on the ovariectomized adult rats was investigated. Our results showed that biochemical parameters including calcium, oestrogen and progesterone levels increase 8 weeks after ovariectomy in rats. Also, the amount of alkaline phosphatase decreased significantly after 8 weeks compared with the OVX rat. The healing potential of flaxseed oil was proven by successfully recovering the affected tissue and preventing the unpleasant symptoms of ovariectomized rats. The biological effects of flaxseed oil may be due to high amounts of fatty acids, phytoestrogens and an array of antioxidants. The results suggest that flaxseed oil can mimic the action of oestrogen and can be a potential treatment for hormone replacement therapy (HRT).

Inhibitory effect of omega-3 fatty acids on alveolar bone resorption and osteoclast differentiation

In this study, a Porphyromonas gingivalis (P.g.)-infected mouse periodontitis model was used to investigate the effect of omega-3 fatty acid intake on differentiation and maturation of cultured osteoclast. Four-week-old C57BL/6JJcl mice were divided into four groups according to the diets they were fed from the beginning of the experiment (i.e., food containing omega-3 or omega-6 fatty acids) and whether they were orally administered P.g. Thirty-three days after beginning the experiment, bone marrow cells were sampled from the femoral bone of mice from each group and differentiated into osteoclasts; the effects of the ingestion of different fatty acids were subsequently investigated. There was no statistical interaction between the different fatty acids and P.g. infection on the number of osteoclasts (P = 0.6). However, the fatty acid type affected the number of osteoclasts in mice (P = 0.0013), with the omega-3 groups demonstrating lower osteoclast numbers than the omega-6 groups. Furthermore, the addition of resolvin E1 (RvE1), which is an omega-3 fatty acid-derived lipid mediator, suppressed the differentiation of mouse cultured osteoclasts (P < 0.0001). Therefore, the ingestion of omega-3 fatty acids may suppress osteoclast differentiation while inhibiting bone resorption and tissue destruction due to periodontitis.

Therapeutic potentials and modulatory mechanisms of fatty acids in bone

Bone metabolism is a lifelong process that includes bone formation and resorption. Osteoblasts and osteoclasts are the predominant cell types associated with bone metabolism, which is facilitated by other cells such as bone marrow mesenchymal stem cells (BMMSCs), osteocytes and chondrocytes. As an important component in our daily diet, fatty acids are mainly categorized as long‐chain fatty acids including polyunsaturated fatty acids (LCPUFAs), monounsaturated fatty acids (LCMUFAs), saturated fatty acids (LCSFAs), medium‐/short‐chain fatty acids (MCFAs/SCFAs) as well as their metabolites. Fatty acids are closely associated with bone metabolism and associated bone disorders. In this review, we summarized the important roles and potential therapeutic implications of fatty acids in multiple bone disorders, reviewed the diverse range of critical effects displayed by fatty acids on bone metabolism, and elucidated their modulatory roles and mechanisms on specific bone cell types. The evidence supporting close implications of fatty acids in bone metabolism and disorders suggests fatty acids as potential therapeutic and nutritional agents for the treatment and prevention of metabolic bone diseases.

Free Fatty Acids in Bone Pathophysiology of Rheumatic Diseases

Obesity—in which free fatty acid (FFA) levels are chronically elevated—is a known risk factor for different rheumatic diseases, and obese patients are more likely to develop osteoarthritis (OA) also in non-weight-bearing joints. These findings suggest that FFA may also play a role in inflammation-related joint damage and bone loss in rheumatoid arthritis (RA) and OA. Therefore, the objective of this study was to analyze if and how FFA influence cells of bone metabolism in rheumatic diseases. When stimulated with FFA, osteoblasts from RA and OA patients secreted higher amounts of the proinflammatory cytokine interleukin (IL)-6 and the chemokines IL-8, growth-related oncogene α, and monocyte chemotactic protein 1. Receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin, and osteoblast differentiation markers were not influenced by FFA. Mineralization activity of osteoblasts correlated inversely with the level of FFA-induced IL-6 secretion. Expression of the Wnt signaling molecules, axin-2 and β-catenin, was not changed by palmitic acid (PA) or linoleic acid (LA), suggesting no involvement of the Wnt signaling pathway in FFA signaling for osteoblasts. On the other hand, Toll-like receptor 4 blockade significantly reduced PA-induced IL-8 secretion by osteoblasts, while blocking Toll-like receptor 2 had no effect. In osteoclasts, IL-8 secretion was enhanced by PA and LA particularly at the earliest time point of differentiation. Differences were observed between the responses of RA and OA osteoclasts. FFA might therefore represent a new molecular factor by which adipose tissue contributes to subchondral bone damage in RA and OA. In this context, their mechanisms of action appear to be dependent on inflammation and innate immune system rather than Wnt-RANKL pathways.

Bone Benefits of Fish Oil Supplementation Depend on its EPA and DHA Content

The preventive effect of high-dose (9%) regular-fish oil (FO) against bone loss during aging has been demonstrated, but the effects of a low-dose (1%–4%) of a highly purified concentrated FO (CFO) has not been elucidated. The aim of this study was to determine the dose-dependent effect of a CFO against bone loss in C57BL/6 female mice during aging. Twelve-month old mice were fed with 1% and 4% CFO and 4% safflower oil (SFO) diets, including a group with a 4% regular-FO diet and a group with a lab chow diet for 12 months. Bone mineral density (BMD) was analyzed by dual-energy x-ray absorptiometry (DXA) before and after the dietary intervention. At the end of dietary intervention, bone resorption markers in serum and inflammatory markers in bone marrow and splenocytes and inflammatory signaling pathways in the bone marrow were analyzed. As compared to the 4% SFO control, 4% CFO maintained higher BMD during aging, while 1% CFO offered only a mild benefit. However, the 1% CFO fed group exhibited slightly better BMD than the 4% regular-FO fed group. BMD loss protection by CFO was accompanied by reduced levels of the bone resorption marker, TRAP, and the osteoclast-stimulating-factor, RANKL, without affecting the decoy-receptor of RANKL, osteoprotegerin (OPG). Further, CFO supplementation was associated with an increase in the production of IL-10, IL-12, and IFN-γ and a decrease in the production of TNF-α and IL-6, and the activation of NF-κB, p38 MAPK, and JNK signaling pathways. In conclusion, the supplementation of 4% CFO is very efficient in maintaining BMD during aging, whereas 1% CFO is only mildly beneficial. CFO supplementation starting at middle age may maintain better bone health during aging.

Adverse plasma fatty acid composition in patients with femoral neck fracture1

Our study aimed to examine the status of plasma fatty acids (FAs), inflammatory markers, and lipid peroxidation in patients with femoral neck fractures. The study included 20 patients (64-86 years) with femoral neck fractures indicated for surgery and a control group of 17 elderly subjects without fractures or serious chronic diseases. Plasma was obtained during the first 12 h postfracture and presurgery and 7 days postop. Compared to the control, patients had significantly higher saturated FA (SFA) and monounsaturated FA as well as increased TNF-α and IL-6. Opposite to that, levels of individual and total n-6 polyunsaturated FA (PUFA), individual and total n-3 PUFA, n-6/n-3 ratio, and levels of thiobarbituric acid reactive substances (TBARS) were markedly lower in the patient than in the controls. On the seventh day after the surgery, we showed a further rise in the SFA, oleic acid, and TNF-α and reductions of n-6 PUFA and IL-6. Taken together, our results suggest that altered FA status, especially reduced PUFA, may influence hip fracture repair and even contribute to femoral fracture susceptibility in the elderly. A potential benefit from nutritional intervention with PUFA in prevention and (or) fracture healing should be considered.

Bone Marrow Fat Physiology in Relation to Skeletal Metabolism and Cardiometabolic Disease Risk in Children With Cerebral Palsy

Individuals with cerebral palsy exhibit neuromuscular complications and low physical activity levels. Adults with cerebral palsy exhibit a high prevalence of chronic diseases, which is associated with musculoskeletal deficits. Children with cerebral palsy have poor musculoskeletal accretion accompanied by excess bone marrow fat, which may lead to weaker bones. Mechanistic studies to determine the role of bone marrow fat on skeletal growth and maintenance and how it relates to systemic energy metabolism among individuals with cerebral palsy are lacking. In this review, we highlight the skeletal status in children with cerebral palsy and analyze the existing literature on the interactions among bone marrow fat, skeletal health, and cardiometabolic disease risk in the general population. Clinically vital questions are proposed, including the following: (1) Is the bone marrow fat in children with cerebral palsy metabolically distinct from typically developing children in terms of its lipid and inflammatory composition? (2) Does the bone marrow fat suppress skeletal acquisition? (3) Or, does it accelerate chronic disease development in children with cerebral palsy? (4) If so, what are the mechanisms? In conclusion, although inadequate mechanical loading may initiate poor skeletal development, subsequent expansion of bone marrow fat may further impede skeletal acquisition and increase cardiometabolic disease risk in those with cerebral palsy.

Physiologic and pathologic effects of dietary free fatty acids on cells of the joint

Fatty acids (FAs) are potent organic compounds that not only can be used as an energy source during nutrient deprivation but are also involved in several essential signaling cascades in cells. Therefore, a balanced intake of different dietary FAs is critical for the maintenance of cellular functions and tissue homeostasis. A diet with an imbalanced fat composition creates a risk for developing metabolic syndrome and various musculoskeletal diseases, including osteoarthritis (OA). In this review, we summarize the current state of knowledge and mechanistic insights regarding the role of dietary FAs, such as saturated FAs, omega-6 polyunsaturated FAs (PUFAs), and omega-3 PUFAs on joint inflammation and OA pathogeneses. In particular, we review how different types of dietary FAs and their derivatives distinctly affect a variety of cells within the joint, including chondrocytes, osteoblasts, osteoclasts, and synoviocytes. Understanding the molecular mechanisms underlying the effects of FAs on metabolic behavior, anabolic, and catabolic processes, as well as the inflammatory response of joint cells, may help identify therapeutic targets for the prevention of metabolic joint diseases.

Nox2 Activity Is Required in Obesity-Mediated Alteration of Bone Remodeling

Despite increasing evidence suggesting a role for NADPH oxidases (Nox) in bone pathophysiology, whether Nox enzymes contribute to obesity-mediated bone remodeling remains to be clearly elucidated. Nox2 is one of the predominant Nox enzymes expressed in the bone marrow microenvironment and is a major source of ROS generation during inflammatory processes. It is also well recognized that a high-fat diet (HFD) induces obesity, which negatively impacts bone remodeling. In this work, we investigated the effect of Nox2 loss of function on obesity-mediated alteration of bone remodeling using wild-type (WT) and Nox2-knockout (KO) mice fed with a standard lab chow diet (SD) as a control or a HFD as an obesity model. Bone mineral density (BMD) of mice was assessed at the beginning and after 3 months of feeding with SD or HFD. Our results show that HFD increased bone mineral density to a greater extent in KO mice than in WT mice without affecting the total body weight and fat mass. HFD also significantly increased the number of adipocytes in the bone marrow microenvironment of WT mice as compared to KO mice. The bone levels of proinflammatory cytokines and proosteoclastogenic factors were also significantly elevated in WT-HFD mice as compared to KO-HFD mice. Furthermore, the in vitro differentiation of bone marrow cells into osteoclasts was significantly increased when using bone marrow cells from WT-HFD mice as compared to KO-HFD mice. Our data collectively suggest that Nox2 is implicated in HFD-induced deleterious bone remodeling by enhancing bone marrow adipogenesis and osteoclastogenesis.

Intake of omega-3 fatty acids contributes to bone mineral density at the hip in a younger Japanese female population

This study investigated the relationships between intakes of polyunsaturated fatty acids, omega-3 fatty acids, and omega-6 fatty acids and bone mineral density in Japanese women aged 19 to 25 years. Intakes of omega-3 fatty acids (n-3) were positively associated with peak bone mass at the hip.

INTRODUCTION

Lifestyle factors such as physical activity and nutrition intake are known to optimize the peak bone mass (PBM). Recently, intake of polyunsaturated fatty acids (PUFAs) has been reported to contribute to bone metabolism. In this study, the relationships of intakes of n-3 and omega-6 (n-6) fatty acids with PBM were evaluated in Japanese female subjects.

METHODS

A total of 275 healthy female subjects (19-25 years) having PBM were enrolled, and lumbar and total hip bone mineral density (BMD) and bone metabolic parameters were measured. Dietary intakes of total energy, total n-3 fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total n-6 fatty acids were assessed by a self-administered questionnaire. Physical activity information was also assessed.

RESULTS

The mean ± SD age was 20.6 ± 1.4 years, and BMI was 21.2 ± 2.7 kg/m². BMI and serum bone alkaline phosphatase contributed significantly to lumbar BMD on multiple regression analysis. Intake of n-3 fatty acids and physical activity were also significantly related to total hip BMD. Using EPA or DHA instead of total n-3 fatty acids in the model did not result in a significant result.

CONCLUSION

Adequate total n-3 fatty acid intake may help maximize PBM at the hip.

Quantification of Bone Fatty Acid Metabolism and Its Regulation by Adipocyte Lipoprotein Lipase

Adipocytes are master regulators of energy homeostasis. Although the contributions of classical brown and white adipose tissue (BAT and WAT, respectively) to glucose and fatty acid metabolism are well characterized, the metabolic role of adipocytes in bone marrow remains largely unclear. Here, we quantify bone fatty acid metabolism and its contribution to systemic nutrient handling in mice. Whereas in parts of the skeleton the specific amount of nutrients taken-up from the circulation was lower than in other metabolically active tissues such as BAT or liver, the overall contribution of the skeleton as a whole organ was remarkable, placing it among the top organs involved in systemic glucose as well as fatty acid clearance. We show that there are considerable site-specific variations in bone marrow fatty acid composition throughout the skeleton and that, especially in the tibia, marrow fatty acid profiles resemble classical BAT and WAT. Using a mouse model lacking lipoprotein lipase (LPL), a master regulator of plasma lipid turnover specifically in adipocytes, we show that impaired fatty acid flux leads to reduced amounts of dietary essential fatty acids while there was a profound increase in de novo produced fatty acids in both bone marrow and cortical bone. Notably, these changes in fatty acid profiles were not associated with any gross skeletal phenotype. These results identify LPL as an important regulator of fatty acid transport to skeletal compartments and demonstrate an intricate functional link between systemic and skeletal fatty acid and glucose metabolism.

Synergistic attenuation of ovariectomy-induced bone loss by combined use of fish oil and 17β-oestradiol

Oestrogen and n-3 PUFA, especially EPA and DHA, have been reported to have beneficial effects on bone loss. Thus, the purpose of the present study was to investigate the synergistic bone-protective mechanism of combined treatments of EPA+DHA supplementation and oestrogen injection in ovariectomised rats. Rats were fed a modified American Institute of Nutrition-93G diet with 0 %, 1 % or 2 % n-3 PUFA (EPA+DHA) relative to the total energy intake for 12 weeks. Rats were surgically ovariectomised at week 8, and after a 1-week recovery period rats were injected with either 17β-oestradiol-3-benzoate (E2) or maize oil for the last 3 weeks. Combined use of n-3 PUFA and E2 synergistically increased femoral cortical bone volume, bone mineral content and the bone expression of runt-related transcription factor 2 (RUNX2), but decreased the bone expression of IL-1β. Both n-3 PUFA and E2 decreased the bone expressions of IL-7, TNF-α and PPAR-γ, and increased the bone expression of oestrogen receptor-α. n-3 PUFA in the presence of E2 and E2 alone significantly decreased the bone expressions of IL-1β and IL-6 and increased the bone expression of RUNX2. E2 significantly decreased the serum levels of bone turnover markers and the bone expression of receptor activator of NF-κB ligand, but decreased the bone expression of osteoprotegerin. The combined use of n-3 PUFA and E2 exerted synergistic bone-protective efficacy through up-regulation of RUNX2, an essential transcription factor for bone formation, as well as the suppression of bone-resorbing cytokine IL-1β.

Suppression of NADPH Oxidase Activity May Slow the Expansion of Osteolytic Bone Metastases

Lysophosphatidic acid (LPA), generated in the microenvironment of cancer cells, can drive the proliferation, invasion, and migration of cancer cells by activating G protein-coupled LPA receptors. Moreover, in cancer cells that have metastasized to bone, LPA signaling can promote osteolysis by inducing cancer cell production of cytokines, such as IL-6 and IL-8, which can stimulate osteoblasts to secrete RANKL, a key promoter of osteoclastogenesis. Indeed, in cancers prone to metastasize to bone, LPA appears to be a major driver of the expansion of osteolytic bone metastases. Activation of NADPH oxidase has been shown to play a mediating role in the signaling pathways by which LPA, as well as RANKL, promote osteolysis. In addition, there is reason to suspect that Nox4 activation is a mediator of the feed-forward mechanism whereby release of TGF-beta from bone matrix by osteolysis promotes expression of PTHrP in cancer cells, and thereby induces further osteolysis. Hence, measures which can down-regulate NADPH oxidase activity may have potential for slowing the expansion of osteolytic bone metastases in cancer patients. Phycocyanin and high-dose statins may have utility in this regard, and could be contemplated as complements to bisphosphonates or denosumab for the prevention and control of osteolytic lesions. Ingestion of omega-3-rich flaxseed or fish oil may also have potential for controlling osteolysis in cancer patients.

n-3 polyunsaturated fatty acids stimulate osteoclastogenesis through PPARγ-mediated enhancement of c-Fos expression, and suppress osteoclastogenesis through PPARγ-dependent inhibition of NFkB activation

n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been reported to suppress osteoclastogenesis in vivo. In this study, the effect of PUFAs on receptor for activation of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis was examined using bone marrow-derived monocytes/macrophage precursor cells (BMMs) or bone marrow cells (BMCs) in vitro. EPA and DHA stimulated the osteoclastic differentiation of BMMs, but n-6 PUFAs, linoleic acid and arachidonic acid had no effect. The stimulation of osteoclastogenesis of BMMs by EPA and DHA was associated with enhancement of the gene expressions of c-Fos, tartrate-resistant acid phosphatase, cathepsin K and peroxisome proliferator-activated receptor-γ (PPARγ) and the protein levels of c-Fos, PPARγ and nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent-1 (NFATc1). The PPARγ agonists, rosiglitazone and GW1929, also stimulated the osteoclastogenesis of BMMs. The PPARγ antagonists, T0070907 and GW9662, inhibited the stimulations of osteoclastogenesis and c-Fos expression by EPA or DHA. However, EPA and DHA inhibited the osteoclastogenesis in BMCs including BMMs and mesenchymal stem cells (MSCs). This inhibition was associated with suppression of the expression of RANKL and nuclear factor-κB (NFκB)-regulating genes, cyclooxygenase 2, TNFα and IL-6 in BMCs and MSCs. The agonists and antagonists of PPARγ showed that the inhibitions of NFκB transcriptional activity and osteoclastogenesis by EPA and DHA were PPARγ-dependent. These results suggest that EPA and DHA directly act on BMMs and stimulate osteoclastogenesis through enhancing c-Fos expression mediated by PPARγ but suppress osteoclastogenesis through the PPARγ-dependent inhibition of NFκB activation of MSCs in BMCs.

n-3 Polyunsaturated Fatty Acids and their Role in Cancer Chemoprevention

Polyunsaturated fatty acids (PUFAs), including omega-3 (n-3) and omega-6 (n-6) PUFAs, are essential for human health. Recent research shows n-3 PUFAs and their mediators can inhibit inflammation, angiogenesis and cancer via multiple mechanisms, including reduced release of n-6 fatty acid arachidonic acid from cell membranes, inhibition of enzymatic activities, and direct competition with arachidonic acid for enzymatic conversions. In this review, we discuss inflammation-related cancer, anti-inflammatory effects of n-3 PUFA lipid mediators, antineoplastic activities of n-3 PUFA in vitro and in vivo, and present an update on recent human trials.

Possible antiosteoporotic mechanism of Cicer arietinum extract in ovariectomized rats

OBJECTIVE

The present study aimed to throw the light on the anti-osteoprotic mechanism of Cicer arietinum extract (CAE) seeds against ovariectomized (OVX) rats.

METHODS

Seventy female rats were divided into two groups. The first group (14 rats/group) represented normal rats (Sham operated) while the second group (56 rats/group) underwent bilateral ovariectomy (OVX). After one week of recovery from ovariectomy surgery, the second group was randomly subdivided into 4 subgroups (14 rats/ each subgroup). The rats administered orally; distilled water (vehicle) (1st subgroup), Cicer arietinum extract (CAE) (500 or 1000 mg/kg body weight/day) (2nd and 3rd subgroups), alendronate (6.5 mg/kg mg/kg body weight) as a positive control one time/week (4(rh) subgroup), daily for 10 weeks.

RESULTS

The present study demonstrated that ovariectomy caused significant decrease in bone mineral; density (BMD) and content (BMC), Bone-specific alkaline phosphatase (BALP), calcium (Ca), phosphorus (P), parathyroid hormone (PTH) and calcitonin levels. Furthermore, ovariectomy induced significant elevation of tartrate-resistant acid phosphatase 5b (TRAP 5b) and receptor activator of nuclear factor (NF-kappa β) ligand (RANKL) concentration. Conversely, osteoprotegerin (OPG) and OPG/RANKL ratio were decreased following ovariectomy. The present work suggests that CAE has antiosteoporotic action against ovariectomy effects and its activity may results from its phytochemical and/or phytoestrogen contents.

CONCLUSION

The ongoing study speculates that the CAE exerts its action through regulation of RANK/RANKL/OPG system. As, CAE not only promotes osteoblast differentiation, but also up-regulates OPG and downregulates RANKL secretion in osteoblasts, subsequently prevents bone loss and osteoporosis.

Endogenous conversion of n-6 to n-3 polyunsaturated fatty acids attenuates K/BxN serum-transfer arthritis in fat-1 mice

It is suggested that n-3 polyunsaturated fatty acids (PUFAs) can be used in the preventive or therapeutic management of rheumatoid arthritis (RA); however, controversial results have been reported. Here, we examined the effects of a decrease in the n-6/n-3 PUFA ratio on RA using fat-1 transgenic mice. First, we tested whether fat-1 expression modulated signaling pathways in fibroblast-like synoviocytes (FLSs) stimulated with tumor necrosis factor α (TNF-α). TNF-α activated p38 mitogen-activated protein kinase and increased phosphorylation of the signal transducer and activator of transcription 3 in wild type (WT) FLSs but not in fat-1 FLSs. Arthritis was induced by injection of K/BxN serum. Based on clinical scores, ankle thickness and pathological severity, we showed that WT mice developed clinically overt arthritis, whereas fat-1 mice showed attenuated arthritis. Moreover, fat-1 mice exhibited down-regulated local and systemic levels of inflammatory cytokines. Lastly, bone marrow-derived macrophages (BMMs) of WT mice differentiated into tartrate-resistant acid phosphatase-positive multinucleated osteoclasts, whereas the osteoclastogenenic process was suppressed in BMMs of fat-1 mice. The endogenous conversion of n-6 to n-3 PUFAs via fat-1 plays a key role in attenuation of RA; therefore, dietary supplementation of n-3 PUFAs may have therapeutic potential for the management of RA.

Retinoid X receptors orchestrate osteoclast differentiation and postnatal bone remodeling

Osteoclasts are bone-resorbing cells that are important for maintenance of bone remodeling and mineral homeostasis. Regulation of osteoclast differentiation and activity is important for the pathogenesis and treatment of diseases associated with bone loss. Here, we demonstrate that retinoid X receptors (RXRs) are key elements of the transcriptional program of differentiating osteoclasts. Loss of RXR function in hematopoietic cells resulted in formation of giant, nonresorbing osteoclasts and increased bone mass in male mice and protected female mice from bone loss following ovariectomy, which induces osteoporosis in WT females. The increase in bone mass associated with RXR deficiency was due to lack of expression of the RXR-dependent transcription factor v-maf musculoaponeurotic fibrosarcoma oncogene family, protein B (MAFB) in osteoclast progenitors. Evaluation of osteoclast progenitor cells revealed that RXR homodimers directly target and bind to the Mafb promoter, and this interaction is required for proper osteoclast proliferation, differentiation, and activity. Pharmacological activation of RXRs inhibited osteoclast differentiation due to the formation of RXR/liver X receptor (LXR) heterodimers, which induced expression of sterol regulatory element binding protein-1c (SREBP-1c), resulting in indirect MAFB upregulation. Our study reveals that RXR signaling mediates bone homeostasis and suggests that RXRs have potential as targets for the treatment of bone pathologies such as osteoporosis.

The use of genetic engineering techniques to improve the lipid composition in meat, milk and fish products: a review

The health-promoting properties of dietary long-chain n-3 polyunsaturated fatty acids (n-3 LCPUFAs) for humans are well-known. Products of animal-origin enriched with n-3 LCPUFAs can be a good example of functional food, that is food that besides traditionally understood nutritional value may have a beneficial influence on the metabolism and health of consumers, thus reducing the risk of various lifestyle diseases such as atherosclerosis and coronary artery disease. The traditional method of enriching meat, milk or eggs with n-3 LCPUFA is the manipulation of the composition of animal diets. Huge progress in the development of genetic engineering techniques, for example transgenesis, has enabled the generation of many kinds of genetically modified animals. In recent years, one of the aims of animal transgenesis has been the modification of the lipid composition of meat and milk in order to improve the dietetic value of animal-origin products. This article reviews and discusses the data in the literature concerning studies where techniques of genetic engineering were used to create animal-origin products modified to contain health-promoting lipids. These studies are still at the laboratory stage, but their results have demonstrated that the transgenesis of pigs, cows, goats and fishes can be used in the future as efficient methods of production of healthy animal-origin food of high dietetic value. However, due to high costs and a low level of public acceptance, the introduction of this technology to commercial animal production and markets seems to be a distant prospect.

Effects of ω3- and ω6-polyunsaturated fatty acids on RANKL-induced osteoclast differentiation of RAW264.7 cells: a comparative in vitro study

Polyunsaturated fatty acids (PUFAs) have been reported to have an anabolic effect on bone in vivo, but comparative studies to identify inhibitors of osteoclast formation amongst ω3- and ω6-PUFAs are still lacking. Here we assessed the effects of the ω3-PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the ω6-PUFAs, arachidonic acid (AA) and γ-linolenic acid (GLA) on a RAW264.7 osteoclast differentiation model. The effects of PUFAs on RANKL-induced osteoclast formation were evaluated by counting tartrate resistant acid phosphatase (TRAP)-positive multinucleated cells. PUFAs significantly inhibited RANKL-induced osteoclast formation in a dose-dependent manner with AA- and DHA-mediated inhibition being the strongest. Furthermore, RANKL-induced mRNA- and protein expression of the key osteoclastogenic genes cathepsin K and TRAP were inhibited by AA and more potently by DHA. Owing to the attenuated osteoclastogenesis by DHA and AA, actin ring formation and bone resorptive activity of these cells as evaluated on bone-mimetic plates were severely compromised. Hence, of the tested PUFAs, AA and DHA were found to be the most effective in inhibiting RANKL-induced osteoclast formation with the latter providing the strongest inhibitory effects. Collectively, the data indicates that these PUFAs may play an important role in regulating bone diseases characterized by excessive osteoclast activity.

Endogenous ω-3 polyunsaturated fatty acid production confers resistance to obesity, dyslipidemia, and diabetes in mice

Despite the well-documented health benefits of ω-3 polyunsaturated fatty acids (PUFAs), their use in clinical management of hyperglycemia and obesity has shown little success. To better define the mechanisms of ω-3 PUFAs in regulating energy balance and insulin sensitivity, we deployed a transgenic mouse model capable of endogenously producing ω-3 PUFAs while reducing ω-6 PUFAs owing to the expression of a Caenorhabditis elegans fat-1 gene encoding an ω-3 fatty acid desaturase. When challenged with high-fat diets, fat-1 mice strongly resisted obesity, diabetes, hypercholesterolemia, and hepatic steatosis. Endogenous elevation of ω-3 PUFAs and reduction of ω-6 PUFAs did not alter the amount of food intake but led to increased energy expenditure in the fat-1 mice. The requirements for the levels of ω-3 PUFAs as well as the ω-6/ω-3 ratios in controlling blood glucose and obesity are much more stringent than those in lipid metabolism. These metabolic phenotypes were accompanied by attenuation of the inflammatory state because tissue levels of prostaglandin E2, leukotriene B4, monocyte chemoattractant protein-1, and TNF-α were significantly decreased. TNF-α-induced nuclear factor-κB signaling was almost completely abolished. Consistent with the reduction in chronic inflammation and a significant increase in peroxisome proliferator-activated receptor-γ activity in the fat-1 liver tissue, hepatic insulin signaling was sharply elevated. The activities of prolipogenic regulators, such as liver X receptor, stearoyl-CoA desaturase-1, and sterol regulatory element binding protein-1 were sharply decreased, whereas the activity of peroxisome proliferator-activated receptor-α, a nuclear receptor that facilitates lipid β-oxidation, was markedly increased. Thus, endogenous conversion of ω-6 to ω-3 PUFAs via fat-1 strongly protects against obesity, diabetes, inflammation, and dyslipidemia and may represent a novel therapeutic modality to treat these prevalent disorders.

Exposure to omega-3 fatty acids at early age accelerate bone growth and improve bone quality

Omega-3 fatty acids (FAs) are essential nutritional components that must be obtained from foods. Increasing evidence validate that omega-3 FAs are beneficial for bone health, and several mechanisms have been suggested to mediate their effects on bone, including alterations in calcium absorption and urinary calcium loss, prostaglandin synthesis, lipid oxidation, osteoblast formation and inhibition of osteoclastogenesis. However, to date, there is scant information regarding the effect of omega-3 FAs on the developing skeleton during the rapid growth phase. In this study we aim to evaluate the effect of exposure to high levels of omega-3 FAs on bone development and quality during prenatal and early postnatal period. For this purpose, we used the fat-1 transgenic mice that have the ability to convert omega-6 to omega-3 fatty acids and the ATDC5 chondrogenic cell line as models. We show that exposure to high concentrations of omega-3 FAs at a young age accelerates bone growth through alterations of the growth plate, associated with increased chondrocyte proliferation and differentiation. We further propose that those effects are mediated by the receptors G-protein coupled receptor 120 (GPR120) and hepatic nuclear factor 4α, which are expressed by chondrocytes in culture. Additionally, using a combined study on the structural and mechanical bone parameters, we show that high omega-3 levels contribute to superior trabecular and cortical structure, as well as to stiffer bones and improved bone quality. Most interestingly, the fat-1 model allowed us to demonstrate the role of maternal high omega-3 concentration on bone growth during the gestation and postnatal period.

An investigation of the association between omega 3 FA and bone mineral density among older adults: results from the National Health and Nutrition Examination Survey years 2005–2008

SUMMARY

The relation of omega 3 fatty acids (n-3 FA) with bone mineral density (BMD) was assessed among adults >60 years; NHANES data (2005-2008). The association of dietary n-3 FA with measures of hip BMD was equivocal, but n-3 FA supplement use was significantly associated with higher spine BMD - a finding that deserves further study.

INTRODUCTION

Associations between polyunsaturated fatty acids and bone mineral density are not well understood.

PURPOSE

To evaluate the cross-sectional relation between dietary omega 3 fatty acid intake (specifically docosahexaenoic acid, eicosapentaenoic acid, and octadecatetraenoic) and BMD at the hip and spine among older adults.

METHODS

Omega 3 FA intake (g/day) was assessed from two 24-h recalls using the National Health and Nutrition Examination Survey (NHANES, in 2005-2008); and omega 3 FA supplement use (yes/no) via questionnaire. Multivariable regression models were developed to explain variance in femoral neck, total femur, and lumbar spine BMD among 2,125 men and women over 60 years.

RESULTS

Mean age was 70 years. In adjusted models, dietary omega 3 FA were marginally associated with greater femoral neck BMD (p = 0.0505), but not with total femur BMD (p = 0.95) or lumbar spine BMD (p = 0.74). Omega 3 supplement use was significantly positively associated with lumbar spine BMD (p = 0.005) but not with femoral neck or total femur BMD.

CONCLUSIONS

Dietary intakes of omega 3 FA were marginally associated with femoral neck BMD; however, omega 3 supplement use was significantly associated with higher lumbar spine BMD in older adults. These results emphasize the need for assessment of total omega 3 intakes (diet and supplements) to provide a greater range of intake and a more accurate picture of the relation between omega 3 FA and BMD.

Flaxseed enhances the beneficial effect of low-dose estrogen therapy at reducing bone turnover and preserving bone microarchitecture in ovariectomized rats

Our previous research showed greatest protection to vertebral bone mineral density and strength in ovariectomized (OVX) rats when lignan- and α-linolenic acid-rich flaxseed (FS) is combined with low-dose estrogen therapy (LD) compared with either treatment alone. This study determined the effects of combined FS+LD on serum and tissue markers of bone turnover and microarchitecture to explain our previous findings. Three-month-old OVX rats were randomized to negative control (NEG), FS, LD or FS+LD for 2 or 12 weeks, meaningful time points for determining effects on markers of bone metabolism and bone structure, respectively. Ground FS was added to the AIN-93M diet (100 g/kg diet) and LD (0.42 μg 17β-estradiol/(kg body weight·day)) was delivered by subcutaneous implant. Sham rats were included as positive control. Bone formation (e.g., osteocalcin), bone resorption (e.g., tartrate-resistant acid phosphatase-5β (TRAP-5β)), as well as osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANKL) were analyzed from the 2-week study by commercial assays (serum) and (or) histology (vertebra). Vertebral bone microarchitecture was measured from the 12-week study using microcomputed tomography. In serum, FS+LD and LD induced lower TRAP-5β and osteocalcin, and higher OPG and OPG/RANKL ratio versus NEG and FS (p < 0.05). In vertebrae, FS+LD induced higher OPG and lower osteocalcin versus NEG (p < 0.01) and did not differ from LD and FS. FS+LD improved bone microarchitecture versus NEG, FS, and LD (p < 0.05). In conclusion, FS+LD protects bone tissue because of a reduction in bone turnover. However, elucidating the distinctive action of FS+LD on bone turnover compared with LD requires further investigation.

Effects of arachidonic acid on the concentration of hydroxyeicosatetraenoic acids in culture media of mesenchymal stromal cells differentiating into adipocytes or osteoblasts

Metabolites derived from the polyunsaturated fatty acids (PUFA) may modulate the mesenchymal stromal cell (MSC) differentiation. Such cells can differentiate into different cellular types, including adipocytes and osteoblasts. Aging favors the bone marrow MSC differentiation toward the former, causing a loss of bone density associated with pathologies like osteoporosis. The omega-6 arachidonic acid (AA) favors MSC adipogenesis to a greater extent than omega-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In this work, we study the joint action of both PUFA. Thus, not induced and induced to adipocyte or osteoblast MSC were treated with 20 μM of each PUFA (either AA, AA + DHA or AA + EPA). The expression of osteogenic and adipogenic molecular markers, the alox15b lipoxygenase gene expression and the 5-, 8-, 11-, 12- and 15-hydroxyeicosatetraenoic acids (HETE) derived from the AA metabolism in the culture media were determined. The results show that the adipogenesis induction of AA is not suppressed by the joint presence of EPA and DHA. In fact, both increased the adipogenic effect of AA on MSC differentiated into osteoblasts. The different HETE concentrations increased in cultures supplemented with AA, albeit such concentrations were lower in the cultures induced to differentiate, mainly at day 21 after the induction. Furthermore, the reduction in the HETE concentration was correlated with a higher expression of the alox15b gene. These results highlight the PUFA metabolism differences between uninduced and induced MSC to differentiate into adipocytes and osteoblasts, besides the relevant role of the lipoxygenase gene expression in adipogenesis induction.

Conjugated linoleic Acid prevents ovariectomy-induced bone loss in mice by modulating both osteoclastogenesis and osteoblastogenesis

Postmenopausal osteoporosis due to estrogen deficiency is associated with severe morbidity and mortality. Beneficial effects of conjugated linoleic acid (CLA) on bone mineral density (BMD) have been reported in mice, rats and humans, but the effect of long term CLA supplementation against ovariectomy-induced bone loss in mice and the mechanisms underlying this effect have not been studied yet. Eight-week old ovariectomized (Ovx) and sham operated C57BL/6 mice were fed either a diet containing 0.5 % safflower oil (SFO) or 0.5 % CLA for 24 weeks to examine BMD, bone turn over markers and osteotropic factors. Bone marrow (BM) cells were cultured to determine the effect on inflammation, osteoclastogenesis, and osteoblastogenesis. SFO/Ovx mice had significantly lower femoral, tibial and lumbar BMD compared to SFO/Sham mice; whereas, no difference was found between CLA/Ovx and CLA/Sham mice. CLA inhibited bone resorption markers whereas enhanced bone formation markers in Ovx mice as compared to SFO-fed mice. Reverse transcriptase polymerase chain reaction and fluorescence activated cell sorting analyses of splenocytes revealed that CLA inhibited pro-osteoclastogenic receptor activator of NF-κB (RANKL) and stimulated decoy receptor of RANKL, osteoprotegerin expression. CLA also inhibited pro-inflammatory cytokine and enhanced anti-inflammatory cytokine production of lipopolysaccharide-stimulated splenocytes and BM cells. Furthermore, CLA inhibited osteoclast differentiation in BM and stimulated osteoblast differentiation in BM stromal cells as confirmed by tartrate resistant acid phosphatase and Alizarin Red staining, respectively. In conclusion, CLA may prevent postmenopausal bone loss not only by inhibiting excessive bone resorption due to estrogen deficiency but also by stimulating new bone formation. CLA might be a potential alternative therapy against osteoporotic bone loss.

High-dose eicosapentaenoic acid and docosahexaenoic acid supplementation reduces bone resorption in postmenopausal breast cancer survivors on aromatase inhibitors: a pilot study

Postmenopausal breast cancer survivors are living longer; however, a common class of drugs, aromatase inhibitors (AI), depletes estrogen levels, promotes bone loss, and heightens fracture risk. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may offset AI effects to bone because of the known effects on cellular processes of bone turnover. Therefore, we hypothesized that 4 g of EPA and DHA daily for 3 mo would decrease bone turnover in postmenopausal breast cancer survivors on AI therapy in a randomized, double-blind, placebo controlled pilot study that included 38 women. At baseline and 3 mo, serum fatty acids, bone turnover, and inflammatory markers were analyzed. Serum EPA and DHA, total and long-chain (LC) omega (n)-3 polyunsaturated fatty acids (PUFA) increased, whereas arachidonic acid, total and LC n-6 PUFA, and the LC n-6:n-3 PUFA ratio decreased compared to placebo (all P < .05). Bone resorption was inhibited in the fish oil responders compared to placebo (P < .05). Inflammatory markers were not altered. This short-term, high-dose fish oil supplementation study's findings demonstrate that fish oil can reduce bone resorption; however, longer-term studies are needed to assess bone density preservation and to explore mechanistic pathways in this population at high risk for bone loss.

DHA is a more potent inhibitor of breast cancer metastasis to bone and related osteolysis than EPA

Breast cancer patients often develop bone metastasis evidenced by osteolytic lesions, leading to severe pain and bone fracture. Attenuation of breast cancer metastasis to bone and associated osteolysis by fish oil, rich in EPA and DHA, has been demonstrated previously. However, it was not known whether EPA and DHA differentially or similarly affect breast cancer bone metastasis and associated osteolysis. In vitro culture of parental and luciferase gene encoded MDA-MB-231 human breast cancer cell lines treated with EPA and DHA revealed that DHA inhibits proliferation and invasion of breast cancer cells more potently than EPA. Intra-cardiac injection of parental and luciferase gene encoded MDA-MB-231 cells to athymic NCr nu/nu mice demonstrated that DHA-treated mice had significantly less breast cancer cell burden in bone, and also significantly less osteolytic lesions than EPA-treated mice. In vivo cell migration assay as measured by luciferase intensity revealed that DHA attenuated cell migration specifically to the bone. Moreover, the DHA-treated group showed reduced levels of CD44 and TRAP positive area in bone compared to EPA-treated group. Breast cancer cell burden and osteolytic lesions were also examined in intra-tibially breast cancer cell injected mice and found less breast cancer cell growth and associated osteolysis in DHA-treated mice as compared to EPA-treated mice. Finally, doxorubicin-resistant MCF-7 (MCF-7dox) human breast cancer cell line was used to examine if DHA can improve sensitization of MCF-7dox cells to doxorubicin. DHA improved the inhibitory effect of doxorubicin on proliferation and invasion of MCF-7dox cells. Interestingly, drug resistance gene P-gp was also down-regulated in DHA plus doxorubicin-treated cells. In conclusion, DHA attenuates breast cancer bone metastasis and associated osteolysis more potently than EPA, possibly by inhibiting migration of breast cancer cell to the bone as well as by inhibiting osteoclastic bone resorption.

Polyunsaturated fatty acids and their relation with bone and muscle health in adults

Age-related bone and muscle loss are major public health problems. Investigational therapies to reduce these losses include anti-inflammatory dietary supplementations, such as polyunsaturated fatty acids (PUFA). Surprisingly, this topic has received little attention in the osteoporosis community. Recent research highlights the role of PUFA in inflammatory regulation of bone remodeling via cellular pathways. Emerging research suggests significant roles for PUFA in reducing bone and muscle loss with aging; however, findings are conflicted for PUFA and fracture risk. Limited studies suggest a relation between higher omega-3 FA and better muscle/bone in older adults. This review highlights new research since 2008 and synthesizes our current understanding of PUFA in relation to bone and muscle. Across study designs, evidence indicates that PUFA has positive effects upon bone. As data are sparse, future clinical trials and prospective studies are important to determine the long term benefits of PUFA supplementation upon bone and muscle outcomes.

Enhancement of the synthesis of n-3 PUFAs in fat-1 transgenic mice inhibits mTORC1 signalling and delays surgically induced osteoarthritis in comparison with wild-type mice

BACKGROUND

An exogenous supplement of n-3 polyunsaturated fatty acids (PUFAs) has been reported to prevent osteoarthritis (OA) through undefined mechanisms.

OBJECTIVE

This study investigated the effect of alterations in the composition of endogenous PUFAs on OA, and associations of PUFAs with mammalian target of rapamycin complex 1 (mTORC1) signalling, a critical autophagy pathway in fat-1 transgenic (TG) mice.

METHODS

fat-1 TG and wild-type mice were used to create an OA model by resecting the medial meniscus. The composition of the endogenous PUFAs in mouse tissues was analysed by gas chromatography, and the incidence of OA was evaluated by micro-computed tomography (micro-CT), scanning electron microscopy and histological methods. Additionally, primary chondrocytes were isolated and cultured. The effect of exogenous and endogenous PUFAs on mTORC1 activity and autophagy in chondrocytes was assessed.

RESULTS

The composition of endogenous PUFAs of TG mice was optimised both by increased n-3 PUFAs and decreased n-6 PUFAs, which significantly alleviated the articular cartilage destruction and osteophytosis in the OA model (p<0.01), decreased protein expression of matrix metalloproteinase-13 (MMP-13) and ADAMTS-5 (a disintegrin and metalloproteinase with thrombospondin motifs) in the articular cartilage (p<0.01) and reduced chondrocyte number and loss of cartilage extracellular matrix. Both exogenous and endogenous n-3 PUFAs downregulated mTORC1 activity and promoted autophagy in articular chondrocytes. Conversely, mTORC1 pathway activation suppressed autophagy in articular chondrocytes.

CONCLUSIONS

Enhancement of the synthesis of endogenous n-3 PUFAs from n-6 PUFAs can delay the incidence of OA, probably through inhibition of mTORC1, promotion of autophagy and cell survival in cartilage chondrocytes. Future investigation into the role of the endogenous n-6/n-3 PUFAs composition in OA prevention and treatment is warranted.

Regulation of Cholesterol Metabolism in Liver: Link to NAFLD and Impact of n-3 PUFAs

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease that affects one-third of adults in westernized countries. NAFLD represents a wide spectrum of hepatic alterations, ranging from simple triglyceride accumulation in the liver to steatohepatitis. Several pharmaceutical approaches to NAFLD management have been examined, but no particular treatment has been considered both safe and highly effective. Growing evidence reveal that supplemental fish oil, seal oil and purified n-3 fatty acids can reduce hepatic lipid content in NAFLD through extensive regulation by inhibiting lipogenesis, promoting fatty acid oxidation and suppressing inflammatory responses. Recently, the fat-1 transgenic mice capable of converting n-6 to n-3 polyunsaturated fatty acids (PUFAs) have been used to examine the effects of endogenous n-3 PUFAs on NAFLD. The increased n-3 PUFAs in fat-1 transgenic mice reduced diet-induced hyperlipidemia and fatty liver through induction of CYP7A1 expression and activation of cholesterol catabolism to bile acid. This article introduces the n-3 PUFAs, and addresses the evidence and mechanisms by which endogenously synthesized n-3 PUFAs or increased dietary n-3 PUFAs may ameliorate NAFLD.

Reduced bone breakage and increased bone strength in free range laying hens fed omega-3 polyunsaturated fatty acid supplemented diets

INTRODUCTION

The omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) are the immediate precursors to a number of important mediators of immunity, inflammation and bone function, with products of omega-6 generally thought to promote inflammation and favour bone resorption. Western diets generally provide a 10 to 20-fold deficit in omega-3 PUFAs compared with omega-6, and this is thought to have contributed to the marked rise in incidence of disorders of modern human societies, such as heart disease, colitis and perhaps osteoporosis. Many of our food production animals, fed on grains rich in omega-6, are also exposed to a dietary deficit in omega-3, with perhaps similar health consequences. Bone fragility due to osteoporotic changes in laying hens is a major economic and welfare problem, with our recent estimates of breakage rates indicating up to 95% of free range hens suffer breaks during lay.

METHODS

Free range hens housed in full scale commercial systems were provided diets supplemented with omega-3 alpha linolenic acid, and the skeletal benefits were investigated by comparison to standard diets rich in omega-6.

RESULTS

There was a significant 40-60% reduction in keel bone breakage rate, and a corresponding reduction in breakage severity in the omega-3 supplemented hens. There was significantly greater bone density and bone mineral content, alongside increases in total bone and trabecular volumes. The mechanical properties of the omega-3 supplemented hens were improved, with strength, energy to break and stiffness demonstrating significant increases. Alkaline phosphatase (an osteoblast marker) and tartrate-resistant acid phosphatase (an osteoclast marker) both showed significant increases with the omega-3 diets, indicating enhanced bone turnover. This was corroborated by the significantly lower levels of the mature collagen crosslinks, hydroxylysyl pyridinoline, lysyl pyridinoline and histidinohydroxy-lysinonorleucine, with a corresponding significant shift in the mature:immature crosslink ratio.

CONCLUSIONS

The improved skeletal health in laying hens corresponds to as many as 68million fewer hens suffering keel fractures in the EU each year. The biomechanical and biochemical evidence suggests that increased bone turnover has enhanced the bone mechanical properties, and that this may suggest potential benefits for human osteoporosis.

Oral administration of hyaluronan reduces bone turnover in ovariectomized rats

The effect of oral hyaluronan (HA) on bone loss in ovariectomized (OVX) 3-month-old rats was measured using serum markers of bone turnover and bone mineral density. OVX rats were administered 1 mg/kg HA (OVX + HA) or phosphate-buffered saline (PBS) (OVX + PBS) by oral gavage (5 days/week for 54 days). Additional controls included sham ovariectomy with PBS gavage (Sham + PBS) and no treatment. Oral administration of HA resulted in approximately 50% (p < 0.05) increases in serum HA. Gel filtration analyses showed this was high molecular weight HA (300-500 kDa). Osteopenia was mild due to the young age of the animals. Thus, ovariectomy resulted in a 30% increase in serum collagen N-terminal telopeptides (p < 0.001), a 20% increase in serum nitrate/nitrite levels (p = 0.05), and a 5-6% decrease in femur bone mineral density/content (p < 0.05). HA gavage blunted the development of osteopenia in this model as determined by preventing the 30% increase in serum collagen N-terminal telopeptide levels (p < 0.001) and by reducing bone mineral content loss from 6 to 4%. These results show that oral supplements of HA (gavage solution, 0.12% solution) significantly reduce bone turnover associated with mild osteopenia in rats.

Bivariate genome-wide association study suggests fatty acid desaturase genes and cadherin DCHS2 for variation of both compressive strength index and appendicular lean mass in males

Compressive strength index (CSI) is a newly established index for predicting hip fracture, the most serious consequence of osteoporosis. Appendicular lean mass (ALM), which influences skeletal strength of the lower limbs, is another trait associated with the risk of hip fracture. In this study, we performed a bivariate genome-wide association study (GWAS) to identify new candidate genes responsible for both CSI and ALM. In our discovery sample of 1627 unrelated Chinese subjects (802 males and 825 females), we scanned 909,509 SNPs using the Affymetrix Human Genome SNP 6.0 genotyping array. We successfully replicated our results in a sample of 2286 Caucasian subjects (558 males and 1728 females). The results indicated that five SNPs (rs174583, rs174577, rs174549, rs174548, rs7672337) in the FADS1, FADS2, and DCHS2 genes had significant bivariate associations with CSI and ALM in male subjects for both the GWAS discovery (with P<8.42×10(-6)) and the Caucasian sample (with P<0.07). We performed further replication analysis in a 2nd Caucasian sample with 501 Caucasian male subjects, using Affymetrix 500k arrays, and found that two of the above SNPs (rs174548 and rs174549, P=0.07) had bivariate associations with both CSI and ALM in males; the other 3 SNPs were not typed with the 500k array. The above findings suggest that the 3 genes, FADS1, FADS2, and DCHS2, containing these SNPs might play dual roles influencing both CSI and ALM in males. Our findings provide new insights into our understanding of the genetic basis of bone metabolism and the pathogenesis of osteoporosis.

Intra-articular lentivirus-mediated insertion of the fat-1 gene ameliorates osteoarthritis

Osteoarthritis (OA) is a gradually progressive degenerative disease characterized by gradual inflammatory loss of articular cartilage caused by increased proteolytic catabolism, mediated by interleukin-1 (IL-1), tumor necrosis factor α (TNF-α), matrix metalloproteinase (MMPs), aggrecanases and other proteinases, and reduced anabolism of cartilage components, contributed by interleukin-4 (IL-4), interleukin-10 (IL-10), insulin-like growth factor 1 (IGF-1), transforming growth factor β (TGF-β), and bone morphogenetic proteins (BMPs). Substantial studies showed n-3 polyunsaturated fatty acids (n-3 PUFAs) exhibit a powerful anti-inflammatory effects in and ex vivo through reducing the production of IL-1 and TNF-α and increasing the expression of IL-4, IL-10, TGF-β and IGF-1 in OA. Meanwhile, more convincing results are observed in the fat-1 transgenic mice, which are exogenously inserted in a fat-1 gene from Caenorhabditis elegans, which can endogenously convert n-6 polyunsaturated fatty acids (n-6 PUFAs) to n-3 PUFAs. Taken together, it has long been realized that dietary supplementation with fish oils that are plentiful of n-3 PUFAs can bring benefits in the treatment of osteoarthritis. Previously two phase I human studies based on in vitro transfer of the cDNA via lentivirus to arthritic joints have confirmed its feasibility and safety in human subjects. Consequently, we hypothesis that directly infect the chondrocytes and synoviocytes with lentivirus carrying the fat-1 gene could be a well therapeutic strategy for OA in humans.

HDAC inhibitor trichostatin A suppresses osteoclastogenesis by upregulating the expression of C/EBP-β and MKP-1

Histone deacetylases (HDACs) remove the acetyl groups from the lysine residues of histone tails, leading to the formation of a condensed and transcriptionally silenced chromatin. HDAC inhibitors (HDACi) block this action and can result in hyperacetylation of histones, leading to a less compact and more transcriptionally active chromatin and thereby, gene expression. Previously, we have shown that HDACi inhibit osteoclast differentiation. However, which genes are transcriptionally activated following hyperacetylation of histones, and lead to the suppression of osteoclastogenesis, has yet to be elucidated. In this study, we show that an HDACi, trichostatin A (TSA), inhibits the receptor activator of the nuclear factor-κB (NF-κB) ligand (RANKL)-stimulated TNF-α production, NF-κB activation, and bone resorbing pit formation, and downregulates c-Fos and NFATc1 in RAW 264.7 cells. Interestingly, expression of antiosteoclastogenic factors CCAAT enhancer binding protein (C/EBP)-β and mitogen-activated protein kinase phosphatase (MKP)-1 was significantly upregulated in TSA-treated, RANKL-stimulated RAW 264.7 cells. These findings suggest that TSA upregulates the expression of C/EBP-β and MKP-1, which may downregulate pro-osteoclastogenic factors and signaling molecules, ultimately suppressing osteoclastogenesis.

Dietary intakes of arachidonic acid and alpha-linolenic acid are associated with reduced risk of hip fracture in older adults

PUFA are hypothesized to influence bone health, but longitudinal studies on hip fracture risk are lacking. We examined associations between intakes of PUFA and fish, and hip fracture risk among older adults (n = 904) in the Framingham Osteoporosis Study. Participants (mean age ~75 y at baseline) were followed for incident hip fracture from the time they completed the baseline exam (1988-1989) until December 31, 2005. HR and 95% CI were estimated for energy-adjusted dietary fatty acid exposure variables [(n-3) fatty acids: α-linolenic acid (ALA), EPA, DHA, EPA+DHA; (n-6) fatty acids: linoleic acid, arachidonic acid (AA); and the (n-6):(n-3) ratio] and fish intake categories, adjusting for potential confounders and covariates. Protective associations were observed between intakes of ALA (P-trend = 0.02) and hip fracture risk in a combined sample of women and men and between intakes of AA (P-trend = 0.05) and hip fracture risk in men only. Participants in the highest quartile of ALA intake had a 54% lower risk of hip fracture than those in the lowest quartile (Q4 vs. Q1: HR = 0.46; 95% CI = 0.26-0.83). Men in the highest quartile of AA intake had an 80% lower risk of hip fracture than those in the lowest quartile (Q4 vs. Q1: HR = 0.20; 95% CI = 0.04-0.96). No significant associations were observed among intakes of EPA, DHA, EPA+DHA, or fish. These findings suggest dietary ALA may reduce hip fracture risk in women and men and dietary AA may reduce hip fracture risk in men.

Endogenously produced n-3 fatty acids protect against ovariectomy induced bone loss in fat-1 transgenic mice

Aging is associated with bone loss, leading to increased risk of fractures. Recently, there is growing interest in identifying nutritional supplements that can prevent bone loss with minimum side effects. There is increasing evidence for the beneficial effects of n-3 fatty acids in the prevention of bone loss. A transgenic mouse model (fat-1) that produces n-3 fatty acids endogenously and its wild type counterpart were used in this study to determine the effects of endogenously produced n-3 fatty acids on serum bone turnover markers, long bones, and lumbar vertebrae. Serum alkaline phosphatase and P1NP levels decreased significantly in wild type mice after ovariectomy. No significant changes were seen in osteocalcin. Cancellous and cortical bone mass were higher in the femur of fat-1 mice. In wild type mice, there was significant loss of bone after ovariectomy in the distal femur, femoral neck, proximal tibia, and fourth lumbar vertebra. However, in fat-1 mice, there was no, or significantly less, bone lost after ovariectomy in all the sites studied. We conclude that endogenously produced n-3 fatty acids can attenuate ovariectomy induced bone loss in the different bone sites studied, mainly as a consequence of decreased bone resorption at the endosteal surface.

Apolipoprotein E-dependent inverse regulation of vertebral bone and adipose tissue mass in C57Bl/6 mice: modulation by diet-induced obesity

The long prevailing view that obesity is generally associated with beneficial effects on the skeleton has recently been challenged. Apolipoprotein E (apoE) is known to influence both adipose tissue and bone. The goal of the current study was to examine the impact of apoE on the development of fat mass and bone mass in mice under conditions of diet-induced obesity (DIO). Four week-old male C57BL/6 (WT) and apoE-deficient (apoE(-/-)) mice received a control or a diabetogenic high-fat diet (HFD) for 16 weeks. The control-fed apoE(-/-) animals displayed less total fat mass and higher lumbar trabecular bone volume (BV/TV) than WT controls. When stressed with HFD to induce obesity, apoE(-/-) mice had a lower body weight, lower serum glucose, insulin and leptin levels and accumulated less white adipose tissue mass at all sites including bone marrow. While WT animals showed no significant change in BV/TV and bone formation rate (BFR), apoE deficiency led to a decrease of BV/TV and BFR when stressed with HFD. Bone resorption parameters were not affected by HFD in either genotype. Taken together, under normal dietary conditions, apoE-deficient mice acquire less fat mass and more bone mass than WT littermates. When stressed with HFD to develop DIO, the difference of total body fat mass becomes larger and the difference of bone mass smaller between the genotypes. We conclude that apoE is involved in an inverse regulation of bone mass and fat mass in growing mice and that this effect is modulated by diet-induced obesity.