HMG-CoA reductase inhibitors prevent bone loss in patients with Type 2 diabetes mellitus

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.

Statins, bone metabolism and treatment of bone catabolic diseases

The discovery that statins had bone anabolic properties initiated many investigations into their use for treatment of bone catabolic diseases, such as osteoporosis. This paper reviews the molecular basis of statin's role in bone metabolism, and animal and human studies on the impact of systemic statins on osteoporosis-induced bone fracture incidence and healing, and on bone density. Limitations of systemic statins are described along with alternative dosing strategies, including local applications and bone-targeting systemic preparations. The principal findings of this review are: (1) traditional oral dosing with statins results in minimal efficacy in the treatment of osteoporosis; (2) local applications of statins show promise in the treatment of accessible bony defects, such as periodontitis; and (3) systemically administered statins which can target bone or inflammation near bone may be the safest and most effective strategy in the treatment of osseous deficiencies.

HMG-CoA reductase inhibitors (statins) and bone mineral density: a meta-analysis

CONTEXT

The association between 3-hydroxy-3methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) and bone mineral density (BMD) is controversial because of conflicting findings from previous studies.

OBJECTIVE AND DESIGN

The purpose of the present study was to evaluate the effect of statins on BMD reported in randomized and non-randomized controlled trials. We searched PubMed and Embase, using text, medical subject headings (MeSH) and keywords "bone mineral density" and "statins" or "HMG-CoA reductase inhibitors". Our last PubMed and Embase queries were updated to August 2012. Data on participants, interventions, and outcomes from each study were abstracted independently by two authors.

RESULTS

Five case-control studies, six cohort studies and four randomized controlled trials (RCTs) met the inclusion criteria. Included studies involved 34,877 subjects (3824 in the intervention group and 31,053 in the control group) in 12 different countries with ages ranging from 44 to 66 years. Statins significantly increased BMD at lumbar spine [standardized mean difference (SMD) 0.15, 95% CI 0.09-0.22], total hip (SMD 0.22, 95% CI 0.17-0.27) and femoral neck (SMD 0.19, 95% CI 0.09-0.29). We carried out subgroup analyses on selected populations of the cohorts. Statistically significant increases were also observed in the lumbar spine (SMD 0.12, 95% CI 0.04-0.21), total hip (SMD 0.23, 95% CI 0.17-0.28) and femoral neck BMD (SMD 0.22, 95% CI 0.08-0.36).

CONCLUSION

The results of this study suggest that statins may help improve and maintain BMD at the lumbar spine, hip and femoral neck, especially in Caucasians and Asians. It also provides justification for prospective RCTs to evaluate the possible role of statins in BMD in different ethnic populations, such as Latin American and Africans.

A systems approach to bone pathophysiology

With evolving interest in multiscalar biological systems one could assume that reductionist approaches may not fully describe biological complexity. Instead, tools such as mathematical modeling, network analysis, and other multiplexed clinical- and research-oriented tests enable rapid analyses of high-throughput data parsed at the genomic, proteomic, metabolomic, and physiomic levels. A physiomic-level approach allows for recursive horizontal and vertical integration of subsystem coupling across and within spatiotemporal scales. Additionally, this methodology recognizes previously ignored subsystems and the strong, nonintuitively obvious and indirect connections among physiological events that potentially account for the uncertainties in medicine. In this review, we flip the reductionist research paradigm and review the concept of systems biology and its applications to bone pathophysiology. Specifically, a bone-centric physiome model is presented that incorporates systemic-level processes with their respective therapeutic implications.

Vascular calcification and bone disease: the calcification paradox

Vascular calcification or ectopic mineralization in blood vessels is an active, cell-regulated process, increasingly recognized as a general cardiovascular risk factor. Remarkably, ectopic artery mineralization is frequently accompanied by decreased bone mineral density or disturbed bone turnover. This contradictory association, observed mainly in osteoporosis and chronic kidney disease, is called the 'calcification paradox'. Here, we review recent advances in our understanding of the calcification paradox, including protein expression patterns governing both normal and ectopic mineralization, the conversion of vascular smooth muscle cells to bone-like cells, and the regulatory pathways involved in both bone and vessel mineralization. Further elucidation of the mechanisms underlying the calcification paradox is crucial in order to develop preventive and therapeutic strategies to deal with vascular calcification and reduce the associated cardiovascular risk.

The relationship among renal injury, changed activity of renal 1-alpha hydroxylase and bone loss in elderly rats with insulin resistance or Type 2 diabetes mellitus

BACKGROUND AND OBJECTIVE

Chronic kidney disease can lead to a decrease in active vitamin D [1,25-(OH)2D], which may be reversed by 1-alpha hydroxyvitamin D [1-alpha(OH)D]. Renal 1-alpha hydroxylase, expressed in renal tubular epithelial cells, is a key enzyme in the synthesis of 1,25-(OH)2D. 1,25- (OH)2D plays an important role in the regulation of calcium and phosphate metabolism, and its deficiency can result in osteoporosis. Type 2 diabetes mellitus (T2DM) and insulin resistance (IR) are associated with renal injury, decrease in 1,25-(OH)2D and bone loss. The study aimed to explore the relationship among renal injury, decrease in 1,25-(OH)2D and bone loss in the presence of IR or T2DM, as well as the role of renal 1-alpha hydroxylase in the process.

MATERIALS AND METHODS

Fifty 18-month-old male Wistar rats were randomized into 5 groups: normal control group (Group N), IR group (Group I), T2DM group (Group D), No.1 treatment group (Group T1), and No.2 treatment group (Group T2), 10 in each group. High-fat diet was administered to induce IR, while high-fat diet and low-dose streptozotocin were jointly applied to induce T2DM. Rats in Groups T1 and T2 were treated with vitamin D and 1-alpha(OH)D, respectively. At week 12, IR was determined by the use of euglycemic insulin clamp technique for rats in each group, and then glucose infusion rate (GIR) was calculated. Meanwhile, urinary albumin (UA), serum 25-(OH)D and 1,25-(OH)2D levels were determined by radioimmunoassay. After the rats were sacrificed, bone mineral density (BMD) in femoral bone and lumbar vertebrae was measured by the use of dual energy X-ray absorption.

RESULTS

The GIR in Group N was significantly higher than that of the other 4 groups (p<0.01). Compared with Groups N (p<0.01) or I (p<0.05), the UA levels in Groups D, T1, and T2 were obviously higher. The UA level in Group I was higher than that of Group N, but the difference was not significant (p>0.05). In Groups D and I, the UA levels showed a negative correlation with GIR. No significant difference was observed in the levels of 25-hydroxyvitamin D [25-(OH)D]. The levels of 1,25-(OH)2D in Groups D and T1 were markedly lower than that of Groups N or T2 (p<0.01). The 1,25-(OH)2D level in Group I was lower than that of Group N (p<0.05), but higher than that of Group D (p<0.01). The 1,25-(OH)2D level in Group T2 was nearly equivalent to that of Group N. In Groups D and I, the levels of 1,25-(OH)2D were negatively correlated with UA, and positively correlated with GIR. The BMD levels in lumbar vertebrae or femoral bone in Groups D and T1 were similar, but both were lower than that of Groups T2 (p<0.05) and N (p<0.01). The BMD levels were lower in Groups I and T2 compared with that of Group N (p<0.05), but higher than that of Groups D and T1 (p<0.05). The BMD levels in lumbar vertebrae or femoral bone in Groups I and D were positively correlated with GIR. The BMD level in lumbar vertebrae or femoral bone in Group D showed negative correlation with UA.

CONCLUSION

In elderly rats with T2DM or IR, renal injury may cause decreased activity of renal 1-alpha hydroxylase, which may result in bone loss and disturbance in VD metabolism, mainly manifesting as a significant reduction in the 1,25-(OH)2D level.

Increased bone mineral density in postmenopausal women with type 2 diabetes mellitus

BACKGROUND AND OBJECTIVES

Studies of bone mineral density (BMD) in women with type 2 diabetes mellitus have shown conflicting results. We conducted this study to determine whether postmenopausal women with diabetes have higher BMD than non-diabetic women of similar age, and to investigate the relationship between BMD and relevant clinical characteristics in these groups of women.

PATIENTS AND METHODS

We retrospectively analyzed lumbar spine, femoral neck, and radius BMD data and other relevant clinical data for 130 postmenopausal women with type 2 diabetes mellitus and 166 non-diabetic women collected during a voluntary screening for osteoporosis in postmenopausal women without a history of low bone mass or osteoporotic fractures.

RESULTS

Women with type 2 diabetes mellitus had significantly higher mean lumbar spine BMD ( 0.903+/-0.165 vs. 0.824+/-0.199, respectively, P<.001) and mean femoral neck BMD (0.870+/-0.132 vs. 0.832+/-0.134, respectively, P<.05) than non-diabetic women. In both groups of women, age correlated negatively with BMD levels at all three anatomical sites. Higher body mass index was associated only with higher lumbar spine BMD in both groups. Alkaline phosphatase levels showed a negative correlation with BMD at all sites in women with type 2 diabetes mellitus.

CONCLUSION

Postmenopausal women with type 2 diabetes mellitus have higher BMD levels than non-diabetic women with similar clinical characteristics, and require a more scrutinized approach in managing low bone mass.

Insufficient renal 1-alpha hydroxylase and bone homeostasis in aged rats with insulin resistance or type 2 diabetes mellitus

This study aimed to explore the relationship between insufficient renal 1-alpha hydroxylase (IRH) and bone homeostasis in type 2 diabetes mellitus (T2DM) or insulin resistance (IR) and to investigate whether IR plays a major role in the pathogenesis of both IRH and bone loss in T2DM. The experimental animal models of T2DM, IR, IR treated with vitamin D (VD), IR treated with 1-alpha hydroxyvitamin D (1alpha(OH) D, the product of renal 1-alpha hydroxylase), T2DM treated with VD, and T2DM treated with 1alpha(OH) D were established on 18-month-old male Wistar rats. For rats in each animal model and normal control rats, IR was detected by euglycemic insulin clamp technique (EICT) and glucose infusion rate (GIR, an index of IR) was calculated. Levels of serum 25-hydroxyvitamin D (25(OH)D) and serum active vitamin D (1,25(OH)(2)D) were determined by radioimmunoassay (RIA), and 1,25(OH)(2)D/25(OH)D ratio (1,25-25-R, an index of renal 1-alpha hydroxylase activity in vivo) was calculated; and bone mineral density (BMD) in femoral bone and lumbar vertebrae was measured by dual-energy X-ray absorption (DEXA). No significant difference was observed among the levels of 25(OH)D in all the rats. In IR rats, 1,25(OH)(2)D level, 1,25-25-R, and BMD level were significantly higher than those in T2DM rats and were lower than those in normal control rats. In the aged rats with T2DM or IR, administration of VD had no effect on 25(OH)D level, 1,25(OH)(2)D level, 1,25-25-R, and BMD level. Administration of 1alpha(OH) D had also no effect on 25(OH)D level but increased 1,25(OH)(2)D level, 1,25-25-R, and BMD level. For the aged rats with T2DM or IR, GIR positively correlated with both levels of 1,25(OH)(2)D and BMD, and 1,25-25-R positively and significantly correlated with levels of BMD. In T2DM or IR, IRH is a precipitating factor for bone loss. IR seems to play a major role in the pathogenesis of both IRH and bone loss in T2DM.

Effects of atorvastatin on bone in postmenopausal women with dyslipidemia: a double-blind, placebo-controlled, dose-ranging trial

CONTEXT

In preclinical models, inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase have been shown to positively affect bone remodeling balance. Observational studies and secondary analyses from lipid-lowering trials have yielded inconsistent results regarding the effect of these agents on bone mineral density and fracture risk.

OBJECTIVE

Our objective was to determine whether clinically significant skeletal benefits result from hydroxymethylglutaryl-coenzyme A reductase inhibition in postmenopausal women.

DESIGN AND SETTING

We conducted a prospective, randomized, double-blind, placebo-controlled, dose-ranging comparative clinical trial at 62 sites in the United States.

PARTICIPANTS

Participants included 626 postmenopausal women with low-density lipoprotein cholesterol levels of at least 130 mg/dl (3.4 mmol/liter) and less than 190 mg/dl (4.9 mmol/liter), and lumbar (L1-L4) spine bone mineral density T-score between 0.0 and -2.5.

INTERVENTION

Once-daily placebo or 10, 20, 40, or 80 mg atorvastatin was administered.

MAIN OUTCOME MEASURES

We assessed percent change from baseline in lumbar (L1-L4) spine bone mineral density with each dose of atorvastatin compared with placebo.

RESULTS

At 52 wk, there was no significant difference between each atorvastatin and placebo group or change from baseline at any tested dose of atorvastatin or placebo in lumbar (L1-L4) spine bone mineral density. Nor did atorvastatin produce a significant change in bone mineral density at any other site. Changes in biochemical markers of bone turnover did not differ significantly between each atorvastatin and placebo group. All doses of atorvastatin were generally well tolerated, with similar incidences of adverse events across all dose groups and placebo.

CONCLUSIONS

Clinically relevant doses of atorvastatin that lower lipid levels had no effect on bone mineral density or biochemical indices of bone metabolism in this study, suggesting that such oral agents are not useful in the prevention or treatment of osteoporosis.

Effects of statins on bone mineral density: a meta-analysis of clinical studies

CONTEXT

Statins inhibit HMG-CoA reductase, preventing synthesis of mevalonate but also of isoprenoids, which affect osteoclast activity. Amino-bisphosphonates share this effect. In vitro and in vivo, statins show convincing anabolic and anti-resorptive bone effects. However, in a clinical meta-analysis (MA), they did not prevent hip fractures.

OBJECTIVE AND DESIGN

Our meta-analysis studied the impact of statins on bone mineral density (BMD) at various sites and compared the effects of lipophilic and more hydrophilic statins.

DATA SOURCES

Our PubMed and Embase queries using two keywords (statins, BMD) were updated to October 2006.

DATA COLLECTION

Two readers independently collected BMDs from studies.

DATA SYNTHESIS

Twenty-one studies, mostly observational (three randomized controlled trials and one pseudo-randomized study), were assessed. Two studies were excluded (no control groups). Three studies could not be analyzed. The sixteen studies analyzed mainly included postmenopausal osteopenic women (2971 patients under statins). Statins significantly increased BMD at total hip (TH) and femoral neck (FN). Effect sizes (ESs) were modest: 0.21 at TH (95% confidence interval [CI]: 0.16-0.25) and 0.20 at FN (CI: 0.08-0.28). Among women, statins acted similarly (ES: 0.20 for TH and 0.18 for FN; CI: 0.14-0.25 and 0.06-0.31 respectively); lipophilic statins (simvastatin, lovastatin) almost entirely caused this effect, at both TH (ES: 0.20; CI: 0.15-0.26) and FN (ES: 0.22; CI: 0.06-0.37).

CONCLUSION

Our findings of modest but statistically significant beneficial effects of statins on hip BMD should promote large double-blind randomized controlled trials on their bone effects, in view of their major beneficial cardiovascular effects with excellent safety profile.

Lovastatin effects on bone mineral density in postmenopausal women with type 2 diabetes mellitus

The objective of this study was to examine the effects of lovastatin on bone mineral density (BMD) of postmenopausal women with type 2 diabetes mellitus (DM). The study was an open-label clinical trial conducted from March 2002 to November 2003. Fifty-five postmenopausal women age 54-67 years with type 2 DM were allocated to lovastatin-treated and control (without lovastatin) groups based on low-density lipoprotein cholesterol (LDL-C) >130 or < or =130 mg/dl. The first group received lovastatin (20 mg daily titrated every 3 months to keep LDL-C less than 130 mg/dl) for a total of 18 months. The second group received their own diabetic regimen without statin. The BMD of the lumbar spine (L1 - L4), femoral neck, Wards triangle, trochanter and total hip was measured by dual-energy X-ray absorptiometry at baseline and after 18 months. In the 28 women treated with lovastatin, the BMD increased in lumbar spine (from 0.946 (0.122) to 0.978 (0.135) g/cm2, p<0.01) and Ward's triangle (from 0.685 (0.123) to 0.780 (0.186) g/cm2, p<0.01). In the 27 women not treated with statin, the changes in BMD at all bone sites were not statistically significant. BMD was higher in femoral neck (1.2% vs. -2.7%, p<0.05), Ward's triangle (13.9% vs. 3.3%, p<0.05), trochanter (-0.1% vs. -2.9%, p<0.05), total hip (1.2% vs. -1.4%, p<0.05) and lumbar spine (3.4% vs. 1.2%, p>0.05) at the end of the study. Treatment with lovastatin may prevent bone loss in postmenopausal women with type 2 DM.

Statins, Fracture Risk, and Bone Remodeling: What Is True?

Besides the action on plasma lipid levels, statins show a series of ancillary effects defined as all of their vascular and nonvascular effects independent from the cholesterol reduction. It has been recently hypothesized that one of these ancillary effects could be the improvement of bone health, due to the interference with bone metabolism. This may potentially represent the rationale for statins' use in the treatment of osteoporosis, the most common disease of the bone. Both experimental observations and clinical studies on this topic generated a number of conflicting results; however, the largest randomized clinical trials, the Scandinavian Simvastatin Survival Study (4S), Long Term Intervention with Pravastatin in Ischemic Disease (LIPID), and Heart Protection Study (HPS), indicate that statins do not prevent or reduce fracture risk.

Influence of simvastatin on bone regeneration of tibial defects and blood cholesterol level in rats

The purpose of this study was to evaluate the effects of simvastatin, by oral or subcutaneous administration, on tibial defects regeneration and blood cholesterol level in rats. A surgical defect was made on the right tibia of 40 male animals assigned to 4 groups (n=10), based on two routes of administration and on the use or not of simvastatin: subcutaneous injection of simvastatin (7 mg/kg) (group AT) or only the vehicle of drug suspension (group AC), above the defect area, for 5 days; and 20 mg/kg of simvastatin macerated on water (group BT) or only water (group BC), orally, daily, during the whole observation period. The animals were sacrificed after 15 or 30 days, when blood samples were analyzed to check plasma cholesterol levels. Tibiae were removed and, after decalcification and routine laboratorial processing, histological and histomorphometrical analyses were carried out. ANOVA was used for statistical analysis at 5% signficance level. The histological and histomorphometrical analyses showed significant differences only between the experimental periods (p<0.05). Animals sacrificed after 30 days showed better bone repair (p<0.05). There was no statistically significant difference (p>0.05) for blood cholesterol levels between the groups. In conclusion, simvastatin administration either orally or subcutaneously did not improve bone repair of experimental tibial defects and did not alter blood cholesterol levels in rats.