HMG CoA reductase inhibitors and the skeleton: a comprehensive review

The Importance of Vitamin K and the Combination of Vitamins K and D for Calcium Metabolism and Bone Health: A Review

The aim of the present review is to discuss the roles of vitamin K (phylloquinone or menaquinones) and vitamin K-dependent proteins, and the combined action of the vitamins K and D, for the maintenance of bone health. The most relevant vitamin K-dependent proteins in this respect are osteocalcin and matrix Gla-protein (MGP). When carboxylated, these proteins appear to have the ability to chelate and import calcium from the blood to the bone, thereby reducing the risk of osteoporosis. Carboxylated osteocalcin appears to contribute directly to bone quality and strength. An adequate vitamin K status is required for the carboxylation of MGP and osteocalcin. In addition, vitamin K acts on bone metabolism by other mechanisms, such as menaquinone 4 acting as a ligand for the nuclear steroid and xenobiotic receptor (SXR). In this narrative review, we examine the evidence for increased bone mineralization through the dietary adequacy of vitamin K. Summarizing the evidence for a synergistic effect of vitamin K and vitamin D3, we find that an adequate supply of vitamin K, on top of an optimal vitamin D status, seems to add to the benefit of maintaining bone health. More research related to synergism and the possible mechanisms of vitamins D3 and K interaction in bone health is needed.

Association between serum lipid profile, body mass index and osteoporosis in postmenopausal Sudanese women

BACKGROUND

Epidemiological observations suggest links between osteoporosis and the risk of acute cardiovascular events. Whether the two clinical conditions are linked by common pathogenic factors or atherosclerosis per se remains incompletely understood. The reduction of bone density and osteoporosis in postmenopausal women contributes to elevated lipid parameters and body mass index (BMI).

OBJECTIVE

To investigate the relationship between serum lipid profile, BMI and osteoporosis in postmenopausal women.

MATERIALS AND METHODS

A prospective analytical case control-study conducted in Khartoum north hospital at Khartoum city, capital of the Sudan from April 2017 to March 2018 after ethical approval obtained from the local Research Ethics Committee of Faculty of Medical Laboratories, Alzaeim Alazhary University on the committee meeting number (109) on Wednesday 15th February 2017. A written informed consent was obtained from all participants to participate in the study.Two hundred postmenopausal women were enrolled in the study. The age was studied in one hundred osteoporosis postmenopausal women as a case group and one hundred non-osteoporosis postmenopausal women as control group. The serum lipid profiles were estimated using spectrophotometers (Mandry) and BMI calculated using Quetelet index formula. The data were analysed using SPSS version 16.

RESULTS

The BMI, serum total cholesterol, triglyceride, HDL and LDL in case group respectively were (24.846±2.1647, 251.190±27.0135 mg/dl, 168.790 ±45.774 mg/dl, 50.620 ± 7.174 mg/dl, 166.868 ±28.978 mg/dl). While the BMI, serum total cholesterol, triglyceride, HDL and LDL in control group respectively were (25.378 ±3.8115, 187.990 ± 26.611 mg/dl, 139.360±20.290 mg/dl, 49.480 ±4.659 mg/dl, 111.667 ±28.0045 mg/dl). All serum lipid profiles significantly increased (p=0.000) in the case group compared to the control group, except serum HDL was insignificant different between the case and control group and also BMI was insignificant different between the case and control group. There was a positive Pearson's correlation between BMD and serum total cholesterol (r= 0.832, P<0.01), serum LDL (r = 0.782, P<0.01) and serum triglyceride (r = 0.72, P<0.01).

CONCLUSIONS

Osteoporotic postmenopausal women had a significant increase in serum lipid profile and BMI. Moreover, we found a positive link between women with cardiovascular diseases and stroke.

Statin use and risk of joint replacement due to osteoarthritis and rheumatoid arthritis: a propensity-score matched longitudinal cohort study

OBJECTIVE

Statins are reported to have a potential benefit on progression of OA and on disease activity in RA, but existing evidence is conflicting. Our objective was to examine whether statins associate with reduction in the risk for joint replacement due to OA and RA.

METHODS

This was a propensity score-matched cohort study. Electronic health records from the UK Clinical Practice Research Datalink were used. We selected people prescribed statins and people never prescribed statins. Each statin user was matched to a non-user by age, gender, practice and propensity score for statin prescription. The main outcome measures were knee or hip joint replacement overall, and specifically because of OA or RA. The association between statins and risk of joint replacement was assessed using Cox proportional hazard regression. Statin exposure was categorized according to the potency of reducing low-density lipoprotein as low (21-28%), medium (32-38%) or high (42-55%) intensity.

RESULTS

A total of 178 467 statin users were matched with 178 467 non-users by age, gender, practice and propensity score. Overall, statin was not associated with reduced risk of knee or hip replacement (hazard ratio 0.99, 95% CI: 0.97, 1.03), unless prescribed at high strength (0.86, 0.75-0.98). The reduced risk was only observed for joint replacement due to RA (0.77, 0.63-0.94) but not OA (0.97, 0.94-1.01).

CONCLUSION

Statins at high intensity may reduce the risk of hip or knee replacement. This effect may be RA specific. Further studies to investigate mechanisms of risk reduction and the impact in people with RA are warranted.

Regulation of Osteoclast Differentiation and Activity by Lipid Metabolism

Bone is a dynamic tissue and is constantly being remodeled by bone cells. Metabolic reprogramming plays a critical role in the activation of these bone cells and skeletal metabolism, which fulfills the energy demand for bone remodeling. Among various metabolic pathways, the importance of lipid metabolism in bone cells has long been appreciated. More recent studies also establish the link between bone loss and lipid-altering conditions—such as atherosclerotic vascular disease, hyperlipidemia, and obesity—and uncover the detrimental effect of fat accumulation on skeletal homeostasis and increased risk of fracture. Targeting lipid metabolism with statin, a lipid-lowering drug, has been shown to improve bone density and quality in metabolic bone diseases. However, the molecular mechanisms of lipid-mediated regulation in osteoclasts are not completely understood. Thus, a better understanding of lipid metabolism in osteoclasts can be used to harness bone cell activity to treat pathological bone disorders. This review summarizes the recent developments of the contribution of lipid metabolism to the function and phenotype of osteoclasts.

Dietary Pattern and Bone Health in Pre and Post-menopausal Obese Women

BACKGROUND AND OBJECTIVE

Obesity and osteoporosis are worldwide health problems that interact with each other. There are also affected by the menopause and dietary pattern. So, this study aimed to find the relation between osteoporosis, body weight and intake of protein, calcium and vitamin D in obese pre and post-menopausal women.

MATERIALS AND METHODS

One hundred and sixteen shared as volunteers in a cross-section study lasted for 2 years. They were divided into 2 groups, pre and post-menopausal women. All women were subjected to, clinical examination, anthropometric measurements and 24 dietary recalls. They were evaluated for bone mass density, biochemical analysis for serum lipids, calcium and vitamin D.

RESULTS

Osteopenia and osteoporosis were higher among normal-weight and overweight (non-obese) women compared to obese as well weakly associated with their serum lipids. The mean daily protein consumption was high as compared to recommended daily allowances (RDAs), especially among osteoporotic women. The mean daily intake of vitamin D and calcium was low as the lower level was noticed among the osteoporotic premenopausal patients. The means serum concentration of calcium and vitamin D were adequate.

CONCLUSION

Data revealed that the prevalence of osteoporosis was lower among obese patients compared to non-obese women. Inadequate daily dietary intake of calcium and vitamin D was reported, however, physiological compensation maintained their optimal normal serum levels.

Adjuvant drug-assisted bone healing: Part III - Further strategies for local and systemic modulation

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is pursued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Association Between Bone Mineral Density, Bone Turnover Markers, and Serum Cholesterol Levels in Type 2 Diabetes

Purpose: The association between bone mineral density (BMD), bone turnover markers, and serum cholesterol in healthy population has already been proved. However, in patients with type 2 diabetes mellitus (T2D), it has not been adequately analyzed. In this study, we investigated the correlation between BMD, bone turnover markers, and serum cholesterol levels in people with T2D. Methods: We enrolled 1,040 men and 735 women with T2D from Zhongshan Hospital between October 2009 and January 2013. Their general condition, history of diseases and medication, serum markers, and BMD data were collected. We used logistic regression analysis to identify the association between serum cholesterol levels and BMD as well as bone turnover markers. Results: In multivariate regression analysis, we observed that in men with T2D, high high-density lipoprotein-cholesterol and total cholesterol levels were significantly associated with low total lumbar, femur neck, and total hip BMD, while low-density lipoprotein-cholesterol level was only inversely associated with total lumbar and femur neck BMD. Total cholesterol and low-density lipoprotein-cholesterol levels were also negatively associated with osteocalcin, procollagen type I N-terminal propeptide, and β-crosslaps. In women with T2D, high-density lipoprotein-cholesterol level was observed to be negatively correlated with total lumbar, femur neck, and total hip BMD, while total cholesterol and low-density lipoprotein-cholesterol levels were only associated with BMD at the total lumbar. Furthermore, total cholesterol was also negatively associated with osteocalcin, procollagen type I N-terminal propeptide, and β-crosslaps; high-density lipoprotein-cholesterol was only related to osteocalcin and parathyroid hormone, while low-density lipoprotein-cholesterol was only related to β-crosslaps in women. Conclusion: Our study suggests a significantly negative correlation between serum cholesterol levels and BMD in both men and women with T2D. The associations between serum cholesterol levels and bone turnover markers were also observed in T2D patients.

Propofol Promotes Ankle Fracture Healing in Children by Inhibiting Inflammatory Response

BACKGROUND The present study aimed to investigate the potential effects of propofol on ankle fracture healing in children and the underlying molecular mechanisms. MATERIAL AND METHODS We first detected the levels of inflammatory cytokines from peripheral blood in children with or without ankle fracture using quantitative real-time polymerase chain reaction (qRT-PCR) and ELISA assay. Then, effects of propofol on inflammatory response in MG-63 cells were investigated. MG-63 cells were pre-treated with or without propofol and then stimulated with 1 μM bradykinin (BK). The productions of cytokines from MG-63 cells were determined by using qRT-PCR and Western blot assay. The expression levels of p-p38, NF-κB p-p65, NLRP3, ASC, caspase-1, and COX-2 were measured by Western blot and/or qRT-PCR. RESULTS The results showed that, compared with the healthy children, the levels of tumor necrosis factor (TNF-α), interleukin (IL)-1β, and IL-6 were significantly up-regulated in children with fractured ankles. No cytotoxicity was observed in MG-63 cells after propofol treatment. BK treatment significantly enhanced TNF-α, IL-1β, and IL-6 expression levels, and these enhancements were reduced by propofol treatment in a dose-dependent manner. Moreover, BK-induced up-regulation of p-p38, NF-κB p-p65, NLRP3, ASC, caspase-1, and COX-2 was dose-dependently down-regulated by propofol treatment. CONCLUSIONS Propofol prevents inflammation in MG-63 cells by regulating p38MAPK-NF-κB pathway, NLRP3 inflammasome, and COX-2 expression. Our findings indicate the benefits of propofol in fracture healing, and provide a more theoretical basis for the clinical treatment of fractures.

N-methyl pyrrolidone promotes ankle fracture healing by inhibiting inflammation via suppression of the mitogen-activated protein kinase signaling pathway

N-methyl pyrrolidone (NMP), a small bioactive molecule, has the potential to stimulate bone formation and inhibit osteoclast differentiation. The aim of the present study was to investigate the effect of NMP on the inflammatory response and underlying molecular mechanisms in MG-63 cells. The mRNA and protein expression of cytokines from peripheral blood in children with or without ankle fracture were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and ELISA, respectively. MG-63 cells were pre-treated with/without NMP and stimulated with 1 µM bradykinin (BK). The production of cytokines from MG-63 cells was assessed by western blotting and RT-qPCR. The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA and protein were measured using western blotting and/or RT-qPCR. Western blotting was used to examine the activation level of mitogen activated protein kinase. Compared with healthy children, levels of tumor necrosis factor (TNF-α), interleukin (IL)-1β and IL-6 mRNA and protein were upregulated in children with ankle fracture. NMP treatment did not induce cytotoxicity in MG-63 cells. The BK-induced upregulation of TNF-α, IL-1β, IL-6, iNOS and COX-2 mRNA and protein was reversed in a dose-dependent manner by NMP. Furthermore, NMP downregulated the activation of c-Jun NH2-terminal kinase and p38 pathways, but not the extracellular signal-related kinase pathway. Therefore, the results of the current study demonstrate that NMP inhibits inflammation dependent on the mitogen-activated protein kinase pathway in MG-63 cells, indicating that it may be beneficial in the healing of fractures.

Effect of simvastatin on osteogenesis of the lumbar vertebrae in ovariectomized rats

The aim of the present study was to assess the role of simvastatin on osteoporosis of the vertebrae by examining the effect of simvastatin on the osteogenesis of the lumbar vertebra in ovariectomized (OVX) rats. A total of 60 6-month-old female Sprague Dawley rats were divided into one sham group and five ovariectomized groups, consisting of four simvastatin groups and one control group. Four dosages of simvastatin (5, 10, 20 and 40 mg/kg/d) were administered by gavage for three months. L4 vertebrae were examined by dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT) to determine the mineral apposition rate (MAR). L5 vertebrae were examined using a compression biomechanical test. Although the measurements from DEXA, pQCT and MAR, and the biomechanical parameters in the OVX + simvastatin rats were higher than those for the OVX + vehicle group, no significant differences were detected. Therefore, simvastatin may not improve osteogenesis of the lumbar vertebra in OVX rats or prevent osteoporosis of the spinal vertebrae.

Associations with fracture in patients with diabetes: a nested case-control study

OBJECTIVES

Diabetes mellitus is associated with an increased risk of fractures, which is not fully explained by bone mineral density and common risk factors. The aim of this study is to investigate the association of medication and biochemical markers on the risk of fracture in a diabetes population.

DESIGN AND SETTING

A nested case-control study was conducted based on Danish diabetes patients from The Danish National Hospital Discharge Registry.

PARTICIPANTS

The cases of the study were diabetes patients with a fracture (n=24,349), and controls were diabetes patients with no fracture (n=132,349). A total of 2627 diabetes patients were available for an analysis of patient characteristics, comorbidities, biochemical parameters and drug usage.

RESULTS

Age (OR=1.02, 95% CI 1.01 to 1.04), diabetes duration (OR=1.06, 95% CI 1.02 to 1.09), a diagnosis of previous fracture (OR=2.20, 95% CI 1.55 to 3.11), an alcohol-related diagnosis (OR=2.94, 95% CI 1.76 to 4.91), total cholesterol level (OR=2.50, 95% CI 1.20 to 5.21) and the usage of antiepileptics (OR=2.12, 95% CI 1.39 to 3.59) all increased the odds of fracture. Low-density lipoprotein cholesterol levels decreased the odds of fracture (OR =0.34, 95% CI 0.16 to 0.74), where the level of 3.04-5.96 mmol/L was optimal with regard to fracture risk.

CONCLUSIONS

Low-density lipoprotein cholesterol may improve our understanding of fractures in diabetes patients, and it may be added to current fracture risk models in diabetes patients.

Risk factors for osteoporosis in Japan: is it associated with Helicobacter pylori?

Background

A number of diseases and drugs may influence bone mineral density; however, there are few reports concerning the relationship between lifestyle-related diseases and osteoporosis in Japan as determined by multivariate analysis. The aim of this study was to investigate the risk factors for osteoporosis and whether infection by or eradication of Helicobacter pylori is associated with osteoporosis.

Methods

Between February 2008 and November 2014, using a cross-sectional study design, we investigated patient profile (age, sex, BMI, alcohol, smoking), H. pylori infection status, comorbidities, internal medicine therapeutic agents (calcium channel blocker, HMG-CoA reductase inhibitors, proton pump inhibitor), serum parameters (Hb, calcium, γGTP), bone turn over markers (bone-specific alkaline phosphatase (BAP) and collagen type I cross-linked N telopeptide (NTX), findings on dual-energy x-ray absorptiometry (DEXA) and upper gastrointestinal endoscopy, and Frequency Scale for the Symptoms of GERD score in consecutive outpatients aged ≥50 years at our hospital. We divided the subjects into an osteoporosis group and a non-osteoporosis group and investigated risk factors for osteoporosis between the two groups by bivariate and multivariate analyses.

Results

Of the 255 eligible study subjects, 43 (16.9%) had osteoporosis. Bivariate analysis showed that advanced age, female sex, lower body mass index, lower cumulative alcohol intake, lower Brinkman index, H. pylori positivity, lower hemoglobin, bone-specific alkaline phosphatase, lower prevalence of hiatal hernia, and endoscopic gastric mucosal atrophy were related to osteoporosis. Multivariate analysis showed that advanced age (odds ratio [OR] 1.13, 95% confidence interval [CI] 1.07–1.19, P<0.001), female sex (OR 6.27, 95% CI 2.26–17.39, P<0.001), low BMI (OR 0.82, 95% CI 0.72–0.94, P=0.005), H. pylori positivity (OR 3.00, 95% CI 1.31–6.88, P=0.009), and BAP (OR 1.07, 95% CI 1.01–1.14, P=0.035) were related to osteoporosis.

Conclusion

Advanced age, low BMI, BAP, and H. pylori positivity were risk factors for osteoporosis; however, the success of H. pylori eradication was not a risk factor for osteoporosis in Japan.

γ-Tocotrienol protects against ovariectomy-induced bone loss via mevalonate pathway as HMG-CoA reductase inhibitor

γ-Tocotrienol (GT3), an analogue of vitamin E, has gained increasing scientific interest recently as it provides significant health benefits. GT3 exerts its biological effects not only by virtue of antioxidant properties but also by inhibiting hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase. Studies have reported that the mevalonate pathway is relevant for bone metabolism and HMG-CoA reductase inhibitors can increase bone mass and are useful in osteoporosis therapy. However, whether it is involved in the bone anabolic activity of GT3 is not clear. This study was conducted to investigate the ability of GT3 to protect against ovariectomy-induced bone loss, as well as the correlation between the protections and mevalonate pathway. Results showed that mice supplemented with 100mg/kg emulsified GT3 via subcutaneous injection once per month for three months were significantly protected from ovariectomy-induced bone loss as evaluated by various bone structural parameters, bone metabolic gene expression levels and serum levels of biochemical markers for bone resorption and bone formation. Importantly, the effect of GT3 on preventing against ovariectomy-induced bone loss could be reversed by daily supplementation with mevalonate, indicating that GT3 may via an HMG-CoA reductase-dependent mechanism to protect against ovariectomy-induced bone loss. Our results suggest that GT3 is suitable as dietary supplement and has potential as an alternative drug to treat or prevent osteoporosis.

A novel anabolic agent: a simvastatin analogue without HMG-CoA reductase inhibitory activity

For the first time, structural information regarding the role of simvastatin in bone anabolism is described, and a bone-specific statin is introduced. Polyaspartate-conjugated simvastatin was synthesized by solid-phase synthesis with the assistance of microwave irradiation. It displays significant bone targeting and bone formation with less toxicity than simvastatin.

Bone mineral density in statin users: a population-based analysis from a Spanish cohort

We studied 2,315 subjects (1,422 women and 893 men) from the Camargo Cohort and analyzed the differences in BMD between statin or non-statin users. We also studied effects of the type of statin, dose, pharmacokinetic properties, and length of treatment on bone mineral density (BMD). Of the subjects, 478 (21 %) were taking statins (256 women and 222 men). Overall, they had higher BMD than non-users (p < 0.0001). In adjusted multivariate models, women taking statins had higher BMD at femoral neck (p = 0.002) and total hip (p = 0.04) than non- users. No differences were found in men. Women taking simvastatin had higher increases in BMD than non-statin users at femoral neck (p = 0.02) and total hip (p = 0.009), those taking fluvastatin had lower BMD values at lumbar spine (p = 0.028), and those receiving lovastatin had higher increases at femoral neck (p = 0.006). In men, only atorvastatin was associated with higher femoral neck BMD than non-statin use (p = 0.029). Comparing with non-statin users, only women receiving lipophilic statins had greater BMD at femoral neck (p = 0.003). According to drug potency, women on high- or lower-potency agents showed higher BMD values at femoral neck than non-users (p = 0.028 and 0.022, respectively). In men, only high-potency statins were associated with higher femoral neck BMD than non-use (p = 0.021). No differences between dose or length of statin therapy were noted regarding BMD in either sex. In summary, in a large population-based cohort, women on statins had higher BMD at the hip than non-users. Overall, this increase in BMD was more evident in subjects on lipophilic or high-potency statins.

Control of cholesterol homeostasis by entero-hepatic bile transport – the role of feedback mechanisms

Cholesterol homeostasis is achieved through a tight regulation between synthesis, dietary absorption, utilization of bile salts, and excretion in the entero-hepatic compartment.

Platelet-rich plasma, plasma rich in growth factors and simvastatin in the regeneration and repair of alveolar bone

Platelet preparations promote bone regeneration by inducing cell migration, proliferation and differentiation in the area of the injury, which are essential processes for regeneration. In addition, several studies have indicated that simvastatin (SIMV), widely used for the treatment of hypercholesterolemia, stimulates osteogenesis. The objective of this study was to evaluate the effects of treatment with either platelet-rich plasma (PRP) or plasma rich in growth factors (PRGF) in combination with SIMV in the regeneration and repair of alveolar bone. The jaws of Sprague Dawley rats (n=18) were subjected to rotary instrument-induced bone damage (BD). Animals were divided into six groups: BD/H₂O (n=3), distilled water without the drug and alveolar bone damage; BD/H₂O/PRP (n=3), BD and PRP; BD/H₂O/PRGF (n=3), BD and PRGF; BD/SIMV (n=3), BD and water with SIMV; BD/SIMV/PRP (n=3), BD, PRP and SIMV; and BD/SIMV/PRGF (n=3), BD, PRGF and SIMV. Conventional histological analysis (hematoxylin and eosin staining) revealed that the BD/SIMV group showed indicators for mature bone tissue, while the BD/SIMV/PRP and BD/SIMV/PRGF groups showed the coexistence of indicators for mature and immature bone tissue, with no statistical differences between the platelet preparations. Simvastatin did not improve the effect of platelet-rich plasma and plasma rich in growth factors. It was not possible to determine which platelet preparation produced superior effects.

Statin use is associated with reduced incidence and progression of knee osteoarthritis in the Rotterdam study

BACKGROUND

Osteoarthritis is the most frequent chronic joint disease causing pain and disability. Besides biomechanical mechanisms, the pathogenesis of osteoarthritis may involve inflammation, vascular alterations and dysregulation of lipid metabolism. As statins are able to modulate many of these processes, this study examines whether statin use is associated with a decreased incidence and/or progression of osteoarthritis.

METHODS

Participants in a prospective population-based cohort study aged 55 years and older (n=2921) were included. x-Rays of the knee/hip were obtained at baseline and after on average 6.5 years, and scored using the Kellgren and Lawrence score for osteoarthritis. Any increase in score was defined as overall progression (incidence and progression). Data on covariables were collected at baseline. Information on statin use during follow-up was obtained from computerised pharmacy databases. The overall progression of osteoarthritis was compared between users and non-users of statins. Using a multivariate logistic regression model with generalised estimating equation, OR and 95% CI were calculated after adjusting for confounding variables.

RESULTS

Overall progression of knee and hip osteoarthritis occurred in 6.9% and 4.7% of cases, respectively. The adjusted OR for overall progression of knee osteoarthritis in statin users was 0.43 (95% CI 0.25 to 0.77, p=0.01). The use of statins was not associated with overall progression of hip osteoarthritis.

CONCLUSIONS

Statin use is associated with more than a 50% reduction in overall progression of osteoarthritis of the knee, but not of the hip.

Role of farnesoid X receptor (FXR) in the process of differentiation of bone marrow stromal cells into osteoblasts

Bone tissue contains bile acids which accumulate from serum and which can be released in large amounts in the bone microenvironment during bone resorption. However, the direct effects of bile acids on bone cells remain largely unexplored. Bile acids have been identified as physiological ligands of the farnesoid X receptor (FXR, NR1H4). In the present study, we have examined the effects of FXR activation/inhibition on the osteoblastic differentiation of human bone marrow stromal cells (BMSC). We first demonstrated the expression of FXR in BMSC and SaOS2 osteoblast-like cells, and observed that FXR activation by chenodeoxycholic acid (CDCA) or by farnesol (FOH) increases the activity of alkaline phosphatase and the calcification of the extracellular matrix. In addition, we observed that FXR agonists are able to stimulate the expression of osteoblast marker genes [bone sialoprotein (BSP), osteocalcin (OC), osteopontin (OPN) and alkaline phosphatase (ALP)] (FXR involvement validated by shRNA-induced gene silencing), as well as the DNA binding activity of the bone transcription factor RUNX2 (EMSA and ChIP assay). Importantly, we observed that nitrogen-containing bisphosphonates (BPs) inhibit the basal osteoblastic differentiation of BMSC, possibly through suppression of endogenous FOH production, independently of their effects on protein prenylation. Likewise, we found that the FXR antagonist guggulsterone (GGS) inhibits ALP activity, calcium deposition, DNA binding of RUNX2, and bone marker expression, indicating that GGS interferes with osteoblastic differentiation. Furthermore, GGS induced the appearance of lipid vesicles in BMSC and stimulated the expression of adipose tissue markers (peroxisome proliferator activated receptor-gamma (PPARγ), adipoQ, leptin and CCAAT/enhancer-binding protein-alpha (C/EBPα)). In conclusion, our data support a new role for FXR in the modulation of osteoblast/adipocyte balance: its activation stimulates RUNX2-mediated osteoblastic differentiation of BMSC, whereas its inhibition leads to an adipocyte-like phenotype.

Fluvastatin increases bone mineral density in postmenopausal women

Although several studies have reported a lower risk of osteoporotic fracture in hypercholesterolemic patients (WHO IIa) treated with statin, longitudinal studies on the effects of statins on bone are lacking. The aim of the present study was to evaluate bone mineral density (BMD) and bone turnover changes induced by 3-year fluvastatin treatment in postmenopausal women. Twenty-eight consecutive postmenopausal non-diabetic, normotensive hypercholesterolemic women (64.0±3.6 years) were treated for 36 months with 30 mg/day fluvastatin and 28 non-diabetic, normotensive normocholesterolemic age- and body mass index-matched postmenopausal women served as the control subjects. The result revealed a significant increase of the BMD as compared with the level at the base line (p< 0.001) in the fluvastairn-treated group, from 6 months on ward after the start treatment. Significant differences of the BMD were found between the controls and fluvastatin-treated group (p< 0.001) were at 6, 12, 24 and 36 months after the start of the study. In conclusion our results, although obtained small sample of postmenopausal hypercholesterolemic women, suggest a probable favorable effect of fluvastatin on bone formation and BMD.

Effects of D-003 (10 mg/day) on bone mineral density of the lumbar spine and femoral neck in postmenopausal women: a randomized, double-blinded study

BACKGROUND/AIMS

Increased osteoclast activity is a pivotal finding in osteoporosis. This increase is mediated via the mevalonate-to-cholesterol pathway, which is involved in producing the intermediates required for osteoclast activity. D-003, a mixture of high molecular weight sugarcane wax acids, has been shown to inhibit cholesterol synthesis prior to mevalonate production, resulting in a reduction of bone loss and resorption in ovariectomized rats. Moreover, previous studies have demonstrated that short-term D-003 treatment reduces urinary excretion of deoxypyridinoline/creatinine in postmenopausal women.

METHODS

We performed a double-blinded, placebo-controlled study to investigate the effects of D-003 (10 mg/day) treatment for 3 years on bone mineral density (BMD) in 83 postmenopausal women with low BMD.

RESULTS

Over 3 years, D-003 treatment increased lumbar spine BMD (5.1%, p < 0.01) and improved osteoporosis-related quality of life scores as compared with placebo-treated controls. D-003 was also well tolerated; the frequency of adverse events in the bone, joints, or muscle with D-003 treatment (p < 0.05) was lower than in the placebo group.

CONCLUSIONS

D-003 treatment (10 mg/day) for 3 years increased lumbar spine BMD and produced clinical improvements in postmenopausal women with low BMD. Further studies, however, will be required to confirm these results.

Pleiotropic effects of the HMG-CoA reductase inhibitors

The HMG-CoA reductase inhibitors (statins) are used extensively in the treatment of hyperlipidemia. They have also demonstrated a benefit in a variety of other disease processes. These secondary actions are known as pleiotropic effects. Our paper serves as a focused and updated discussion on the pleiotropy of statins and emphasizes the importance of randomized placebo-controlled trials to further elucidate this interesting phenomenon.

Use of cyclodextrins as solubilizing agents for simvastatin: effect of hydroxypropyl-β-cyclodextrin on lactone/hydroxyacid aqueous equilibrium

The chemical conversion of simvastatin from the lactone (SVL) to the hydroxyacid (SVA) form is becoming an intriguing issue associated with the pharmacological use of SVL. On this matter, recent findings suggest that SVL complexation with cyclodextrins (CDs) may be a useful strategy to affect its aqueous solubility and chemical stability. In this work, a reverse-phase high-performance liquid chromatography (RP-HPLC) method able to selectively identify and quantify SVL and SVA has been set up, validated and applied to follow SVL hydrolysis in the presence of HPβCD. The combination of stability results with simvastatin/HPβCD stability constants achieved from UV-vis measurements and solubility/dissolution studies allowed to get an insight into SVL/HPβCD, SVA/HPβCD and SVL/SVA equilibria taking place in aqueous solution. Results show that in the presence of HPβCD the aqueous SVL/SVA equilibrium is shifted versus the hydroxyacid form. UV-vis results, showing that the lactone and the open-ring form of simvastatin interact with HPβCD in a similar extent, suggest that hydrolysis occurs also on SVL/HPβCD complex, thus supporting a mode of interaction that does not involve the lactone ring. This hypothesis is strengthened by NMR analysis performed on SVA, HPβCD and their inclusion complex, which indicates that the lactone ring is not included in HPβCD hydrophobic cavity. Finally, results suggest that particular attention must be paid to SVL lactonization in aqueous solution when using CD-based formulations and in demonstrating their effective benefit for a specific therapeutic use.

Farnesyl pyrophosphate inhibits epithelialization and wound healing through the glucocorticoid receptor

Farnesyl pyrophosphate (FPP), a key intermediate in the mevalonate pathway and protein farnesylation, can act as an agonist for several nuclear hormone receptors. Here we show a novel mechanism by which FPP inhibits wound healing acting as an agonist for glucocorticoid receptor (GR). Elevation of endogenous FPP by the squalene synthetase inhibitor zaragozic acid A (ZGA) or addition of FPP to the cell culture medium results in activation and nuclear translocation of the GR, a known wound healing inhibitor. We used functional studies to evaluate the effects of FPP on wound healing. Both FPP and ZGA inhibited keratinocyte migration and epithelialization in vitro and ex vivo. These effects were independent of farnesylation and indicate that modulation of FPP levels in skin may be beneficial for wound healing. FPP inhibition of keratinocyte migration and wound healing proceeds, in part, by repression of the keratin 6 gene. Furthermore, we show that the 3-hydroxy-3-methylglutaryl-CoA-reductase inhibitor mevastatin, which blocks FPP formation, not only promotes epithelialization in acute wounds but also reverses the effect of ZGA on activation of the GR and inhibition of epithelialization. We conclude that FPP inhibits wound healing by acting as a GR agonist. Of special interest is that FPP is naturally present in cells prior to glucocorticoid synthesis and that FPP levels can be further altered by the statins. Therefore, our findings may provide a better understanding of the pleiotropic effects of statins as well as molecular mechanisms by which they may accelerate wound healing.

Analysis of skeletal status by quantitative ultrasonometry in a cohort of postmenopausal women with high blood cholesterol without documented osteoporosis

Osteoporosis and atherosclerosis are leading causes of mortality and morbidity in the Western world. A link between osteoporosis and atherosclerosis was proposed by epidemiologic and laboratory data. In the present study, we investigated skeletal status in postmenopausal women with hypercholesterolemia using quantitative ultrasonometry (QUS). Six hundred healthy postmenopausal subjects were enrolled within a 2-mo period by primary care physicians. Information on lifestyle and calcium intake was collected for each enrolled subject. Subjects (n = 256) were divided into two groups according to lipid profile: normal (n = 180) with serum cholesterol <200 mg/dL and hypercholesterolemic (n = 76) with serum cholesterol >or=200 mg/dL. Hypercholesterolemic subjects were further stratified into two groups, one receiving dietary treatment (n = 34) and the other receiving statin treatment (n = 42). We found a statistically significant reduction in amplitude dependent speed of sound (AD-SoS) in hypercholesterolemic subjects compared with subjects with normal cholesterol (p = 0.006). Calcium intake behaved similarly to AD-SoS (p = 0.0001). No statistical significant difference in AD-SoS were observed between the group on diet treatment versus the group on statin (p = 0.52). Calcium intake was lower in patients on statins treatment compared with subjects on diet treatment only (p < 0.0001). Our data suggest that hypercholesterolemia per se is a risk factor for impaired skeletal status. Our data also call attention to the risk of a poor calcium intake in patient receiving diet to lower plasma cholesterol. Moreover, our data suggest that statins per se may exert a protective effect on bone independently from calcium intake.

Hypertension is a risk factor for fractures

To study the effects of hypertension and other cardiovascular risk factors on risk of fractures, we carried out a case-control study including 124,655 fracture cases and 373,962 age- and gender-matched controls. The main exposure was hypertension, stroke, acute myocardial infarction, ischemic heart disease, atrial fibrillation, peripheral arterial disease, and deep venous thromboembolism, and the main confounders were use of diuretics, antihypertensive drugs, organic nitrates, vitamin K antagonists, and cholesterol lowering drugs along with other confounders. Hypertension and stroke were the only significant risk factors in both the short-term (OR = 1.27, 95% CI = 1.20-1.34 and 1.24, and 95% CI = 1.16-1.31 for < or = 3 years since diagnosis of hypertension and stroke, respectively) and the long-term (OR = 1.11, 95% CI = 1.00-1.23 and 1.09, and 95% CI = 1.02-1.18 for > 6 years since diagnosis of hypertension and stroke, respectively) perspective. Acute myocardial infarction, atrial fibrillation, and deep venous thromboembolism were all associated with a transient increase in the risk of fractures within the first 3 years following diagnosis. Peripheral arterial disease and ischemic heart disease were not associated with an increased risk of fractures. In conclusion, hypertension and stroke seem to be the major cardiovascular risk factors for fractures, whereas acute myocardial infarction, atrial fibrillation, and deep venous thromboembolism seem to be only minor risk factors. The fracture risk in hypertension may explain why antihypertensive drugs as a class effect are associated with a decreased risk of fractures. These drugs may counter some of the deleterious effects of high blood pressure.

Association between lumbar bone mineral density and vascular stiffness as assessed by pulse wave velocity in postmenopausal women

Recent studies have showed a significant correlation between vascular calcification and bone mineral density (BMD). Therefore, an investigation was carried out on the association between arterial stiffness, lumbar BMD and bone metabolic markers in Japanese postmenopausal women. Brachial-ankle PWV (baPWV) and BMD of the lumbar spine and serum bone-specific alkaline phosphatase (BAP) levels in 143 postmenopausal women were measured, where there was a significant negative correlation between baPWV and BMD (r = -0.21; P = 0.0135). An additional analysis included the remaining 75 subjects, but excluded subjects with hypertension and obesity. Here, a more negative correlation between baPWV and BMD (r = -0.315; P = 0.006), and a positive correlation between baPWV and BAP (r = 0.248; P = 0.032) were also significant. A group analysis, where the women were age matched and stratified into three groups of different bone density, i.e., normal BMD, osteopenic and osteoporotic, were further made. This showed lower PWV values in the normal BMD group than in the other two groups. A study also showed that the tertile with the highest BAP was associated with significantly higher PWV values than the other tertiles. However, when the multiple linear regression analysis was carried out, there was no correlation between PWV and BAP values. Low BMD and arterial stiffness show some correlation, suggesting that BAP may reflect the degree of arterial stiffness present.

Inhibition of fracture healing

This paper reviews the current literature concerning the main clinical factors which can impair the healing of fractures and makes recommendations on avoiding or minimising these in order to optimise the outcome for patients. The clinical implications are described.

Increased bone turnover in patients with hypercholesterolemia

Osteoporosis has been linked with arteriosclerotic vascular diseases, suggesting that hypercholesterolemia or dyslipidemia may be a common pathogenetic factor underlying these diseases. However, little is known about the relationship between osteoporosis and hypercholesterolemia. The purpose of this study was, therefore, to investigate the effects of hypercholesterolemia upon bone metabolism, by measuring bone turnover markers in hypercholesterolemic patients. This study included 281 Japanese patients with hypercholesterolemia, and 267 control subjects. Serum bone-specific alkaline phosphatase (BAP) of the patients was significantly higher than that of the controls in women. Serum N-terminal telopeptide of type I collagen (NTx) of the patients was significantly higher than that of the controls in both men and women. In addition, both BAP and NTx in men showed a significantly negative correlation with high density lipoprotein cholesterol (HDL-C). On the other hand, in women, both BAP and NTx showed a significantly positive correlation with total cholesterol and low density lipoprotein cholesterol (LDL-C). These results indicate increased bone turnover in hypercholesterolemic or dyslipidemic patients regardless of gender, and suggest the importance of treating hypercholesterolemia or dyslipidemia in order to prevent not only arteriosclerotic complications but also osteoporotic bone loss and subsequent fractures.

Systems level analysis of osteoclastogenesis reveals intrinsic and extrinsic regulatory interactions

Osteoclasts are bone-resorbing cells derived from the myeloid lineage that play a central role in bone remodeling and inflammatory bone erosion diseases. The receptor activator of NF-kappaB ligand (RANKL) produced by osteoblasts and activated immune cells initiates the development of osteoclasts in the bone marrow. Using time series gene expression data, the intrinsic processes and the extrinsic factors that control osteoclastogenesis were identified. The gene expression profiles display distinct commitment and differentiation phases. Analysis of the time course revealed several mechanistic details, including the complex role of cholesterol in osteoclast development. Epistatic interactions and the coordination between cellular processes that regulate development were inferred from the coexpression network. The coexpression network indicated that osteoclasts induce angiogenesis and recruit T-cells to the site of osteoclastogenesis early in the commitment phase. The resulting model provides an essential framework for a better understanding of the epigenetic program of osteoclastogenesis.

LIF inhibits osteoblast differentiation at least in part by regulation of HAS2 and its product hyaluronan

LIF arrests osteogenesis in fetal rat calvaria cells in a differentiation stage-specific manner. Differential display identified HAS2 as a LIF-induced gene and its product, HA, modulated osteoblast differentiation similarly to LIF. Our data suggest that LIF arrests osteoblast differentiation by altering HA content of the extracellular matrix.

INTRODUCTION

Leukemia inhibitory factor (LIF) elicits both anabolic and catabolic effects on bone. We previously showed in the fetal rat calvaria (RC) cell system that LIF inhibits osteoblast differentiation at the late osteoprogenitor/early osteoblast stage.

MATERIALS AND METHODS

To uncover potential molecular mediators of this inhibitory activity, we used a positive-negative genome-wide differential display screen to identify LIF-induced changes in the developing osteoblast transcriptome.

RESULTS

Although LIF signaling is active throughout the RC cell proliferation-differentiation sequence, only a relatively small number of genes, in several different functional clusters, are modulated by LIF specifically during the LIF-sensitive inhibitory time window. Based on their known and predicted functions, most of the LIF-regulated genes identified are plausible candidates to be involved in the LIF-induced arrest of osteoprogenitor differentiation. To test this hypothesis, we further analyzed the function of one of the genes identified, hyaluronan synthase 2 (HAS2), in the LIF-induced inhibition. Synthesis of hyaluronan (HA), the product of HAS enzymatic activity, was stimulated by LIF and mimicked the HAS2 expression profile, with highest expression in early/proliferative and late/maturing cultures and lowest levels in intermediate/late osteoprogenitor-early osteoblast cultures. Exogenously added high molecular weight HA, the product of HAS2, dose-dependently inhibited osteoblast differentiation, with pulse-treatment effective in the same differentiation stage-specific inhibitory window as seen with LIF. In addition, however, pulse treatment with HA in early cultures slightly increased bone nodule formation. Treatment with hyaluronidase, on the other hand, stimulated bone nodule formation in early cultures but caused a small dose-dependent inhibition of osteoblast differentiation in the LIF- and HA-sensitive late time window.

CONCLUSIONS

Together the data suggest that osteoblast differentiation is acutely sensitive to HA levels and that LIF inhibits osteoblast development at least in part by stimulating high molecular weight HA synthesis through HAS2.

The Interleukin-6 inflammation pathway from cholesterol to aging--role of statins, bisphosphonates and plant polyphenols in aging and age-related diseases

We describe the inflammation pathway from Cholesterol to Aging. Interleukin 6 mediated inflammation is implicated in age-related disorders including Atherosclerosis, Peripheral Vascular Disease, Coronary Artery Disease, Osteoporosis, Type 2 Diabetes, Dementia and Alzheimer's disease and some forms of Arthritis and Cancer. Statins and Bisphosphonates inhibit Interleukin 6 mediated inflammation indirectly through regulation of endogenous cholesterol synthesis and isoprenoid depletion. Polyphenolic compounds found in plants, fruits and vegetables inhibit Interleukin 6 mediated inflammation by direct inhibition of the signal transduction pathway. Therapeutic targets for the control of all the above diseases should include inhibition of Interleukin-6 mediated inflammation.

Farnesol, a mevalonate pathway intermediate, stimulates MCF-7 breast cancer cell growth through farnesoid-X-receptor-mediated estrogen receptor activation

Farnesoid X receptor (FXR) is a metabolic nuclear receptor expressed in the liver and traditionally considered as a bile acid sensor. Yet, FXR has been recently demonstrated in other tissues and cells, such as the kidneys, the adrenals, and arterial smooth muscle cells. Immunohistochemical data reported in this study point to the expression of FXR in human breast cancer. In addition, FXR expression was also found by Western blotting and immunofluorescence microscopy in breast-cancer-derived cell lines MCF-7 (estrogen receptor [ER]-positive) and MDA-MB-231 (ER-negative). The FXR activator farnesol, a mevalonate pathway intermediate, exerts a mitogenic effect on MCF-7 cells. The growth stimulation is completely suppressed by antiestrogens. In contrast, MDA-MB-231 cells appear farnesol-insensitive, suggesting an involvement of ER in farnesol mitogenicity. In accordance with this interpretation, farnesol induces in MCF-7 cells a decrease of ER level, consistent with a phenomenon of receptor downregulation. Farnesol also increases progesterone receptor (PgR) expression in MCF-7 cells and stimulates ER-mediated gene transactivation in MVLN cells (MCF-7 cells stably transfected with an ER reporter gene). Of note, both effects of farnesol on ER expression and activity are completely suppressed by antiestrogens. In addition, farnesol-induced PgR is markedly reduced by FXR gene silencing (siRNA), demonstrating the involvement of FXR in the estrogenic effects of farnesol. Finally, coimmunoprecipitation experiments (FXR immunoprecipitation followed by Western blot analysis of ER in the immunoprecipitate) produced definite evidence that FXR interacts with ER. Altogether, these observations reveal the hitherto unreported presence of FXR in breast cancer and show that the latter receptor functionally interacts with ER. The occurrence of such a crosstalk calls for some caution regarding the pharmacological use of FXR agonists.

Short-term effects of atorvastatin on bone turnover in male patients with hypercholesterolemia

No consensus has been reached on whether the 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, known as statins, have beneficial effects on bone health. The purpose of our study was to evaluate the effects of atorvastatin on bone metabolism by means of measuring bone turnover markers in male patients with hypercholesterolemia both at diagnosis and prospectively after 3 months of treatment. Twenty-two Japanese male patients (mean age 62.36 +/- 10.1 years) with untreated hypercholesterolaemeia were selected for this study. After 3-months treatment of atorvastatin, total cholesterol and low density lipoprotein cholesterol significantly decreased as expected (p<0.001 for both parameters). Bone-specific alkaline phosphatase (BAP) did not change significantly (p = 0.444). However, serum N-terminal telopeptide of type I collagen (NTx) significantly decreased by -19.86 +/- 26.4% (p = 0.020). In addition, delta NTx during the course of this study was negatively correlated with NTx at baseline (r = -0.645, p = 0.0008). Although there was a tendency of positive correlations of delta NTx with delta total cholesterol, delta triglycerides, and delta low density lipoprotein cholesterol, and of negative correlations of delta NTx and delta BAP with delta high density lipoprotein cholesterol, none of them reached statistical significance. Our findings suggest that atorvastatin may have potentially beneficial effects on bone metabolism in patients with hypercholesterolemia mostly by reducing bone resorption rather than by stimulating bone formation. Further studies with more patients and longer duration are warranted to evaluate its effects, if any, on prevention of osteoporosis and subsequent fractures.

Short-term effects of pitavastatin on biochemical markers of bone turnover in patients with hypercholesterolemia

OBJECT

No consensus has been reached whether clinical use of statins has beneficial effects on bone health, partly due to lower statin concentrations because of first-pass metabolism by the liver. We thus evaluated the effects of pitavastatin, which does not undergo first-pass metabolism, on bone metabolism.

METHODS

According to the therapeutic regimen, the subjects were divided into two groups (group A, 66 with pitavastatin; group B, 35 without pitavastatin). Bone-specific alkaline phosphatase (BAP) and serum N-terminal telopeptide of type I collagen (NTx) as bone turnover markers (BTMs) were compared between the two groups and between at baseline and after 3 months of treatment in each group. Correlations between baseline characteristics and deltaBTMs, and between delta lipid profile and deltaBTMs were investigated using both Pearson's correlation analysis and multivariate analysis.

PATIENTS

The subjects were 101 patients with untreated hypercholesterolemia.

RESULTS

After 3 months of treatment, BAP in group A did not change significantly compared with either the baseline value or that in group B. However, NTx in group A significantly decreased compared with both the baseline value and that in group B. In addition, deltaNTx was negatively correlated with NTx at baseline, and the significance of this correlation persisted after multiple regression analysis.

CONCLUSION

Our findings suggest that pitavastatin may have potentially beneficial effects on bone metabolism primarily by reducing bone resorption rather than by stimulating bone formation. Further studies with more patients and longer duration are warranted to evaluate its effects, if any, on prevention of osteoporosis and subsequent fractures.

Anabolic agents and the bone morphogenetic protein pathway

A major unmet need in the medical field today is the availability of suitable treatments for the ever-increasing incidence of osteoporosis and the treatment of bone deficit conditions. Although therapies exist which prevent bone loss, the options are extremely limited for patients once a substantial loss of skeletal bone mass has occurred. Patients who have reduced bone mass are predisposed to fractures and further morbidity. The FDA recently approved PTH (1-34) (Teriparatide) for the treatment of postmenopausal osteoporosis after both preclinical animal and clinical human studies indicated it induces bone formation. This is the only approved bone anabolic agent available but unfortunately it has limited use, it is relatively expensive and difficult to administer. Consequently, the discovery of low cost orally available bone anabolic agents is critical for the future treatment of bone loss conditions. The intricate process of bone formation is co-ordinated by the action of many different bone growth factors, some stored in bone matrix and others released into the bone microenvironment from surrounding cells. Although all these factors play important roles, the bone morphogenetic proteins (BMPs) clearly play a central role in both bone cartilage formation and repair. Recent research into the regulation of the BMP pathway has led to the discovery of a number of small molecular weight compounds as candidate bone anabolic agents. These agents may usher in a new wave of more innovative and versatile treatments for osteoporosis as well as orthopedic and dental indications.

Statins and osteoporosis: new role for old drugs

Osteoporosis is the most common bone disease, affecting millions of people worldwide and leading to significant morbidity and high expenditure. Most of the current therapies available for its treatment are limited to the prevention or slowing down of bone loss rather than enhancing bone formation. Recent discovery of statins (HMG-CoA reductase inhibitors) as bone anabolic agents has spurred a great deal of interest among both basic and clinical bone researchers. In-vitro and some animal studies suggest that statins increase the bone mass by enhancing bone morphogenetic protein-2 (BMP-2)-mediated osteoblast expression. Although a limited number of case-control studies suggest that statins may have the potential to reduce the risk of fractures by increasing bone formation, other studies have failed to show a benefit in fracture reduction. Randomized, controlled clinical trials are needed to resolve this conflict. One possible reason for the discrepancy in the results of preclinical, as well as clinical, studies is the liver-specific nature of statins. Considering their high liver specificity and low oral bioavailability, distribution of statins to the bone microenvironment in optimum concentration is questionable. To unravel their exact mechanism and confirm beneficial action on bone, statins should reach the bone microenvironment in optimum concentration. Dose optimization and use of novel controlled drug delivery systems may help in increasing the bioavailability and distribution of statins to the bone microenvironment. Discovery of bone-specific statins or their bone-targeted delivery offers great potential in the treatment of osteoporosis. In this review, we have summarized various preclinical and clinical studies of statins and their action on bone. We have also discussed the possible mechanism of action of statins on bone. Finally, the role of drug delivery systems in confirming and assessing the actual potential of statins as anti-osteoporotic agents is highlighted.

Statins and bone metabolism

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are potent inhibitors of cholesterol biosynthesis. Cholesterol-lowering therapy using statins significantly reduces the risk of coronary heart disease. However, extensive use of statins leads to increases of other undesirable as well as beneficial effects, so-called pleiotropic effects. With respect to these effects, statins augment the expression of bone morphogenetic protein-2, a potent simulator of osteoblast differentiation and its activity, and promote mineralization by cultured osteoblasts, indicating that statins have an anabolic effect on bone. Chronic administration of statins in ovariectomized (OVX) rats modestly increases bone mineral density (BMD) of cancellous bone but not of compact bone. In clinical studies, there are conflicting results regarding the clinical benefits of this therapy for the treatment of osteoporosis. Observational studies suggest an association between statin use and reduction in fracture risk. Clinical trials reported no effect of statin treatment on BMD in hip and spine, and on bone turnover. Statins also may influence oral osseous tissues. Administration of statins in combination with osteoporosis therapy appears to improve alveolar bone architecture in the mandibles of OVX rats with maxillary molar extraction. Statins continue to be considered as potential therapeutic agents for patients with osteoporosis and possibly with periodontal disease. Development of new statins that are more specific and potent for bone metabolism will greatly increase the usefulness of these drugs for the treatment of bone diseases.

Fluvastatin and lovastatin but not pravastatin induce neuroglial differentiation in human mesenchymal stem cells

Recent studies have shown that statins, the most potent inhibitors of 3-hydroxy-2-methylglutaryl coenzyme A (HMG-CoA) reductase, stimulate bone formation in vitro and in rodents by activating the expression of bone morphogenetic protein-2 (BMP-2), one of the most critical osteoblast differentiation-inducing factors. However, the effect of statins on mesenchymal stem cells (MSCs) is yet to be reported. The purpose of this study is to investigate the influence of fluvastatin, lovastatin, and pravastatin, three commonly prescribed lipid-lowering agents, on the proliferation and differentiation of human MSCs. To our surprise, even though fluvastatin and lovastatin effectively suppressed the growth of human MSCs, a neuroglia rather than osteoblast-like morphology was observed after treatment. Interestingly, such morphological change was inhibited by the co-addition of geranylgeranyl pyrophosphate (GGPP). Immunofluorescence staining with antibodies against neuron-, astrocyte-, as well as oligodendrocyte-specific markers confirmed the neuroglial identity of the differentiated cells. However, BMP-2 is unlikely to play a positive role in neuroglial differentiation of MSCs since its expression was down-regulated in fluvastatin-treated cells. Taken together, our results suggest that fluvastatin and lovastatin induce neuroglial differentiation of human MSCs and that these cholesterol-lowering agents might be used in conjunction with MSC transplantation in the future for treating neurological disorders and injuries.

Hydroxymethylglutaryl-coenzyme A reductase inhibitors and osteoporosis: a meta-analysis

Studies determining the association between hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) and bone metabolism are mixed. We conducted a systematic review to assess the potential impact of statins on fractures, bone mineral density and bone markers. We searched Medline, Embase, the Cochrane Library, and Federal Research in Progress (FEDRIP). Inclusion criteria consisted of human studies with measurable outcomes, which were rated as good or fair according to the United States Preventive Services Task Force (USPSTF) criteria. The effects of statins on bone mineral density (BMD), bone markers and fracture risk were independently extracted by two reviewers and were combined by use of a random-effects model. The 31 analyzed studies included 24 observational studies and seven randomized controlled trials. Overall, statin use was associated with fewer hip fractures (OR 0.60, 95% CI 0.45-0.78) and improved hip BMD (Z score 0.12, 95% CI 0.05-0.19), with a non-significant reduction in vertebral fractures and no effect on vertebral BMD. In subgroup analysis of studies that involved only women there was a reduction in hip fractures (OR 0.75, 95% CI 0.60-0.95) and improvement in hip BMD (Z score 0.11, 95% CI 0.04-0.18). Vertebral BMD was unchanged, and only one study reported on vertebral fractures, finding improvement. Statins had only small effects on bone markers, with a decrease in alkaline phosphatase [standardized mean difference (SMD) -0.18, 95% CI -0.34 to -0.01], an increase in NTX (SMD 0.39, 95% CI 0.07-0.71), with no effect on osteocalcin or CTX. The statistically significant improvement in hip fracture risk was seen only in case-control trials, not in either the eight prospective trials or the two randomized controlled trials (RCTs). Statins may have a beneficial impact on bone metabolism and fracture risk; randomized controlled trials are needed to explore this association.