Review: Statins and Bone Formation

Abstract

Statins, bone formation and osteoporosis: hope or hype?

Osteoporosis is a major health problem affecting both men and women. Statins, besides their action as lipid-lowering agents, seem to have additional pleiotropic properties, among them a beneficial effect on bone mineral density. The entirety of experimental and the majority of clinical studies as well as the only relevant meta-analysis suggest that statins have an anabolic effect on bone metabolism. Statins, osteoporosis and adipogenesis share the same pathway, RANKL/OPG. It would appear that an imbalance in this pathway could be responsible for the manifestation of some metabolic disorders such as diabetes mellitus, atherogenesis, multiple myeloma, osteoporosis. Possibly in the future, drugs which can intervene in this biochemical and pathophysiological cascade, like statins, in a variety of doses, could be used for the management of ectopic ossification syndromes and other bone disorders, even as an additive treatment. Until then, further large longitudinal randomized controlled studies for each statin separately are required to confirm this hypothesis.

Tsartsalis AN, Dokos C, Kaiafa GD, Tsartsalis DN…
Hormones (Athens)
PMID: 22801558 | Free Full Text

All the available data from the literature, including evidence from experimental studies as well as from the vast majority of observational studies and the results of a single meta-analysis, suggested that there is a positive effect of statins on BMD, although another meta-analysis by Bauer et al72 showed evidence that the beneficial effects on BMD and on fracture risk are observational, while many limitations and the placebo-controlled trials did not demonstrate any clear-cut benefit. However, the in vitro and some clinical studies (Chuengsamarn et al71) suggest that statins inhibit bone resorption and stimulate bone formation, having a dual action on bone metabolism. Therefore, in the future statins might gain a position among drugs used for the prevention and management of osteoporosis, taking into account that clinicians already have a good deal of experience in prescribing statins, for other indications, and feel familiar with this drug family. Their anabolic and anti-resorptive effects on bone make them an ideal candidate for osteoporosis treatment.

Simvastatin Intensifies Bone Formation and Decreases Resorption in Ovariectomized Rats

Abstract

Effects of simvastatin on the development of osteopenia caused by ovariectomy in rats.

Simvastatin is a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-determining enzyme for cholesterol synthesis which is used in the treatment of hypercholesterolemias, particularly in type IIa and IIb hyperlipoproteinemias, frequently in postmenopausal women. Inhibition of cholesterol synthesis by simvastatin may cause disorders of bone remodelling. The aim of the present study was to investigate the effects of simvastatin (3 mg and 6 mg/kg/day per os) administered for 4 weeks on the development of ovariectomy-induced osteopenia in 3-month-old female Wistar rats. The experiments were carried out on six groups of animals: I (C)–sham operated rats, II (S-3)–sham operated rats + simvastatin 3 mg/kg/day p.o., III (S-6)–sham operated rats + simvastatin 6 mg/kg/day p.o., IV (OVX)–ovariectomized rats, V (OVX + S-3)–ovariectomized rats + simvastatin 3 mg/kg/day p.o., VI (OVX + S-6)–ovariectomized rats + simvastatin 6 mg/kg/day p.o. In all the groups, we examined body weight gain, and macrometrical, histomorphometrical and mechanical parameters. Bilateral ovariectomy induced osteopenic skeletal changes in mature female rats. In cortical bone, ovariectomy intensified resorption processes at the marrow cavity, as indicated by a decrease in endosteal transverse growth and an increase in transverse cross-section surface area of the marrow cavity in the tibia. Intensification of resorption processes was observed in cancellous bone (a statistically significant decrease in the width of trabeculae in the epiphysis and metaphysis of the femur). Structural changes in the long bones resulting from bilateral ovariectomy were manifested by deterioration of mechanical properties of the shaft and neck of the femur. The force needed to fracture the neck and shaft of the femur was significantly smaller than that in sham operated rats. Simvastatin (3 and 6 mg/kg/day p.o.) slightly influenced bone remodelling in sham operated rats. Simvastatin (3 and 6 mg/kg p.o. daily) administered to ovariectomized rats intensified bone formation processes and decreased bone resorption processes induced by bilateral ovariectomy, showing stronger activity at 6 mg/kg.

Pytlik M, Janiec W, Misiarz-Myrta M, Gubała I
Pol J Pharmacol
PMID: 12856828 | Free Full Text

Omega-3 Promotes Bone in Young Rats

Abstract

Consumption of different sources of omega-3 polyunsaturated fatty acids by growing female rats affects long bone mass and microarchitecture.

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) consumption has been reported to improve bone health. However, sources of ω-3 PUFAs differ in the type of fatty acids and structural form. The study objective was to determine the effect of various ω-3 PUFAs sources on bone during growth. Young (age 28d) female Sprague-Dawley rats were randomly assigned (n=10/group) to a high fat 12% (wt) diet consisting of either corn oil (CO) or ω-3 PUFA rich, flaxseed (FO), krill (KO), menhaden (MO), salmon (SO) or tuna (TO) for 8 weeks. Bone mass was assessed by dual-energy X-ray absorptiometry (DXA) and bone microarchitecture by micro-computed tomography (μCT). Bone turnover markers were measured by enzyme immunoassay. Lipid peroxidation was measured by calorimetric assays. Results showed that rats fed TO, rich in docosahexaenoic acid (DHA, 22:6ω-3) had higher (P<0.009) tibial bone mineral density (BMD) and bone mineral content (BMC) and lower (P=0.05) lipid peroxidation compared to the CO-fed rats. Reduced lipid peroxidation was associated with increased tibial BMD (r2=0.08, P=0.02) and BMC (r2=0.71, P=0.01). On the other hand, rats fed FO or MO, rich in alpha-linolenic acid (ALA, 18:3ω-3), improved bone microarchitecture compared to rats fed CO or SO. Serum osteocalcin was higher (P=0.03) in rats fed FO compared to rats fed SO. Serum osteocalcin was associated with improved trabecular bone microarchitecture. The animal study results suggest consuming a variety of ω-3 PUFA sources to promote bone health during the growth stage.

Lukas R, Gigliotti JC, Smith BJ, Altman S…
Bone Sep 2011
PMID: 21672645

Omega-3 Inhibits Osteoclasts In Vitro

Abstract

The omega-6 arachidonic fatty acid, but not the omega-3 fatty acids, inhibits osteoblastogenesis and induces adipogenesis of human mesenchymal stem cells: potential implication in osteoporosis.

Arachidonic fatty acid (AA) induces adipogenesis in human mesenchymal stem cells cultures, and high concentrations inhibit osteoblastogenesis; whereas eicosapentaenoic and docosahexaenoic fatty acids do not induce adipogenesis and do not inhibit osteoblastogenesis. In mesenchymal stem cells, omega-6 arachidonic polyunsaturated fatty acid promotes the differentiation of adipocytes and inhibits the osteoblast differentiation. While omega-3 fatty acids do not affect the adipogenic differentiation their effects on osteoblastogenesis are less relevant. An increased ratio of omega-3/omega-6 fatty acid consumption can prevent bone mass loss.
Consumption of omega-3 may protect against osteoporosis since they may inhibit osteoclastogenesis. However, with aging, MSC in bone marrow are increasingly differentiated into adipocytes, reducing the number of osteoblasts. Products derived from omega-6 and omega-3 metabolism may affect MSC differentiation into osteoblasts and adipocytes.
Human MSC have been differentiated into osteoblasts or adipocytes in the presence of omega-6 (AA), or omega-3 (DHA and EPA), and osteoblastic and adipocytic markers have been analyzed.
AA decreases the expression of osteogenic markers and the osteoprotegerin/receptor activator of nuclear factor kappa β ligand gene expression ratio (opg/rankl). High concentrations of AA inhibit the mineralization and cause the appearance of adipocytes in MSC differentiating into osteoblasts to a higher extent than DHA or EPA. In MSC differentiated into adipocytes, AA increases adipogenesis, while DHA and EPA do not affect it. AA caused the appearance of adipocytes in undifferentiated MSC. The lipoxygenase gene (alox15b) is induced by omega-3 in MSC induced to osteoblasts, and by omega-6 in MSC induced to adipocytes.
An increase in the intake of omega-3 respect to omega-6 may provide protection against the loss of bone mass, since omega-6 favors the osteoclastic activity by diminishing the opg/rankl gene expression in osteoblasts and promotes MSC differentiation into adipocytes, thus diminishing the production of osteoblasts.

Casado-Díaz A, Santiago-Mora R, Dorado G, Quesada-Gómez JM
Osteoporos Int May 2013
PMID: 23104199

Alpha Linolenic Acid Increases Bone Strength in Hens

Abstract

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

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.
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.
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.
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.

Tarlton JF, Wilkins LJ, Toscano MJ, Avery NC…
Bone Feb 2013
PMID: 23142806

EPA + DHA: Possible Mechanism

Abstract

PTH1 receptor is involved in mediating cellular response to long-chain polyunsaturated fatty acids.

The molecular pathways by which long chain polyunsaturated fatty acids (LCPUFA) influence skeletal health remain elusive. Both LCPUFA and parathyroid hormone type 1 receptor (PTH1R) are known to be involved in bone metabolism while any direct link between the two is yet to be established. Here we report that LCPUFA are capable of direct, PTH1R dependent activation of extracellular ligand-regulated kinases (ERK). From a wide range of fatty acids studied, varying in chain length, saturation, and position of double bonds, eicosapentaenoic (EPA) and docosahexaenoic fatty acids (DHA) caused the highest ERK phosphorylation. Moreover, EPA potentiated the effect of parathyroid hormone (PTH(1-34)) in a superagonistic manner. EPA or DHA dependent ERK phosphorylation was inhibited by the PTH1R antagonist and by knockdown of PTH1R. Inhibition of PTH1R downstream signaling molecules, protein kinases A (PKA) and C (PKC), reduced EPA and DHA dependent ERK phosphorylation indicating that fatty acids predominantly activate G-protein pathway and not the β-arrestin pathway. Using picosecond time-resolved fluorescence microscopy and a genetically engineered PTH1R sensor (PTH-CC), we detected conformational responses to EPA similar to those caused by PTH(1-34). PTH1R antagonist blocked the EPA induced conformational response of the PTH-CC. Competitive binding studies using fluorescence anisotropy technique showed that EPA and DHA competitively bind to and alter the affinity of PTH1 receptor to PTH(1-34) leading to a superagonistic response. Finally, we showed that EPA stimulates protein kinase B (Akt) phosphorylation in a PTH1R-dependent manner and affects the osteoblast survival pathway, by inhibiting glucocorticoid-induced cell death. Our findings demonstrate for the first time that LCPUFAs, EPA and DHA, can activate PTH1R receptor at nanomolar concentrations and consequently provide a putative molecular mechanism for the action of fatty acids in bone.

Candelario J, Tavakoli H, Chachisvilis M
PLoS ONE 2012
PMID: 23300710 | Free Full Text

In human studies, it has been shown that consuming EPA improved bone quality in elderly female subjects [21]. Consumption of ω-3 fatty acids was also associated with reduced incidence and severity of inflammatory bone/joint diseases in humans [22]. There is evidence of the potential of EPA to counteract bone loss associated with spaceflight; higher consumption of fish (ω-3) was associated with reduced loss of bone mineral density (BMD) after flight [23]. BMD of the total body showed a significant negative correlation with serum concentrations of oleic acids and monounsaturated fatty acids and significant correlations with DHA and ω-3 fatty acids [24]. A higher ratio of ω-6 to ω-3 fatty acids is associated with lower BMD at the hip in both sexes suggesting the relative amounts of dietary PUFA may play a vital role in preserving skeletal integrity in older age [25].

Omega-3 Associated with Lumbar Spine BMD in Postmenopausal Women

Abstract

Association of n-3 polyunsaturated fatty acid intake with bone mineral density in postmenopausal women.

n-3 Polyunsaturated fatty acids (n-3 fatty acids) have been shown to have a beneficial effect on bone in animal studies, although little is known about their role in bone metabolism in humans. We investigated the association between bone mineral density (BMD) and daily n-3 fatty acid intake. This cross-sectional, community-based, epidemiologic study was conducted among 205 healthy postmenopausal women (mean age 63.5 years, range 46-79). We examined BMD, serum N-terminal propeptide of type I collagen (PINP), urinary type-I collagen cross-linked-N-telopeptide (uNTX), total cholesterol, triglycerides, and high-density lipoprotein cholesterol. Nutrient intake was calculated using a food-frequency questionnaire. BMD was measured at the lumbar spine and femoral neck by dual-energy X-ray absorptiometry. Simple regression analysis showed that intake of neither n-3 fatty acid nor n-6 fatty acid was associated with age or lipid metabolism indices. However, simple regression analysis showed that n-3 fatty acid intake was positively associated with both lumbar spine BMD and femoral neck BMD. n-6 fatty acid intake was positively associated with femoral neck BMD but not lumbar spine BMD. Multiple regression analysis showed that n-3 fatty acid intake was positively associated with lumbar spine BMD after adjustment for age, BMI, duration of menopausal state, grip strength, PINP, uNTX, and intakes of calcium, vitamin D, vitamin K, and n-6 fatty acid. In conclusion, n-3 fatty acid intake was positively associated with lumbar spine BMD independent of bone resorption and serum levels of cholesterol and triglycerides in postmenopausal women.

Nawata K, Yamauchi M, Takaoka S, Yamaguchi T…
Calcif. Tissue Int. Aug 2013
PMID: 23708886

Review: Fish Oil Mechanisms of Action on Bone

Abstract

Long-chain polyunsaturated fatty acids: selected mechanisms of action on bone.

Evidence presented over the past 20 years has shown that long-chain polyunsaturated fatty acids (LCPUFAs), especially the n-3 fatty acids such as eicospentaenoic acid (EPA) and docosahexaenoic acid (DHA) are beneficial for bone health. Some studies in humans indicate that LCPUFAs can increase bone formation, affect peak bone mass in adolescents and reduce bone loss as measured using bone mineral densitometry. The cellular mechanisms of action of the LCPUFAs, however, are complex and involve modulation of fatty acid metabolites such as prostaglandins, resolvins and protectins, several signalling pathways, cytokines and growth factors. LCPUFAs affect receptor activator of nuclear factor κβ (RANK), a receptor found on the osteoclast, the cell causing bone resorption, which controls osteoclast formation. Lipoxygenase (LOX) generated lipid mediators (resolvins, lipoxins, protectins and docosanoids) have both anti-inflammatory and pro-resolving activities. Both resolvins and lipoxins inhibit inflammation-induced bone resorption. Arachidonic acid significantly upregulates inducible NO synthase (iNOS) mRNA expression in human osteoblast-like cells, thereby possibly enhancing osteoclastic activity. The protective effect of EPA on osteoblastogenesis could be mediated by the biphasic cross-talk between PGE(2) and NO production involving COX-2 and iNOS pathways. Other mediators of osteoblast maturation include PPARα ligands such as linoleic acid and possibly DHA in association with bone morphogenic proteins. Since DHA is a weaker ligand for PPARγ, more uncommitted mesenchymal stem cells are thought to differentiate into osteoblasts rather than adipocytes. This review addresses selected cellular mechanisms that may explain the beneficial effects of the LCPUFAs on bone.

Kruger MC, Coetzee M, Haag M, Weiler H
Prog. Lipid Res. Oct 2010
PMID: 20600307

EPA and DHA Improve Bone Properties in Mice

Abstract

Effects of long-term supplementation with omega-3 fatty acids on longitudinal changes in bone mass and microstructure in mice.

A diet rich in omega-3s has previously been suggested to prevent bone loss. However, evidence for this has been limited by short exposure to omega-3 fatty acids (FAs). We investigated whether a diet enriched in eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) for the entire adult life of mice could improve bone microstructure and strength. Thirty female mice received a diet enriched in DHA or EPA or an isocaloric control diet from 3 to 17 months of age. Changes in bone microstructure were analyzed longitudinally and biomechanical properties were analysed by a three-point bending test. Bone remodelling was evaluated by markers of bone turnover and histomorphometry. Trabecular bone volume in caudal vertebrae was improved by EPA or DHA at 8 months (+26.6% and +17.2%, respectively, compared to +3.8% in controls, P=.01), but not thereafter. Trabecular bone loss in the tibia was not prevented by omega-3 FAs (BV/TV -94%, -93% and -97% in EPA, DHA and controls, respectively). EPA improved femur cortical bone volume (+8.1%, P<.05) and thickness (+4.4%, P<.05) compared to controls. EPA, but not DHA, reduced age-related decline of osteocalcin (-70% vs. -83% in controls, P<.05). EPA and DHA increased leptin levels (7.3±0.7 and 8.5±0.5 ng ml⁻¹, respectively, compared to 4.5±0.9 ng ml⁻¹ in controls, P=.001); however, only EPA further increased IGF-1 levels (739±108 ng ml⁻¹, compared to 417±58 ng ml⁻¹ in controls, P=.04). These data suggest that long-term intake of omega-3 FA, particularly EPA, may modestly improve the structural and mechanical properties of cortical bone by an increase in leptin and IGF-1 levels, without affecting trabecular bone loss.

Bonnet N, Ferrari SL
J. Nutr. Biochem. Jul 2011
PMID: 21036590

EPA + DHA at 1.48g Shows No Benefit in Humans

Abstract

Supplementation with a low-moderate dose of n-3 long-chain PUFA has no short-term effect on bone resorption in human adults.

Previous research suggests that n-3 PUFA may play a role in bone health. The present analysis aimed to investigate the impact of n-3 PUFA supplementation on bone resorption in adult men and women. Serum samples from 113 mild-moderately depressed individuals (twenty-six males and eighty-seven females, aged 18-67 years) randomised to receive 1.48 g EPA+DHA/d (n 53) or placebo (n 60) for 12 weeks as part of a large recent randomised controlled trial were assayed for n-3 PUFA status and a bone resorption marker, C-terminal cross-linking telopeptide of type 1 collagen (β-CTX). Regression analyses revealed that n-3 PUFA status following supplementation was associated with randomisation (placebo/n-3 PUFA) (B = 3.25, 95 % CI 2.60, 3.91, P < 0.01). However, β-CTX status following supplementation was not associated with randomisation (B = – 0.01, 95 % CI – 0.03, 0.04). Change in β-CTX status was also not associated with change in n-3 PUFA status (B = – 0.002, 95 % CI – 0.01, 0.01). These findings provide no evidence for an association between n-3 PUFA supplementation (1.48 g EPA+DHA/d) for 12 weeks and bone resorption in humans assessed by β-CTX, and suggest that n-3 PUFA supplementation may be unlikely to be of benefit in preventing bone loss.

Appleton KM, Fraser WD, Rogers PJ, Ness AR…
Br. J. Nutr. Apr 2011
PMID: 21129235