Toshitsugu Sugimoto

Randomized Teriparatide [Human Parathyroid Hormone (PTH) 1–34] Once-Weekly Efficacy Research (TOWER) Trial for Examining the Reduction in New Vertebral Fractures in Subjects with Primary Osteoporosis and High Fracture Risk

CONTEXTnWeekly teriparatide injection at a dose of 56.5 μg has been shown to increase bone mineral density.nnnOBJECTIVEnA phase 3 study was conducted to determine the efficacy of once-weekly teriparatide injection for reducing the incidence of vertebral fractures in patients with osteoporosis.nnnDESIGN AND SETTINGnIn this randomized, multicenter, double-blind, placebo-controlled trial conducted in Japan, the incidence of morphological vertebral fractures by radiographs was assessed.nnnPATIENTSnSubjects were 578 Japanese patients between the ages of 65 and 95 yr who had prevalent vertebral fracture.nnnINTERVENTIONnSubjects were randomly assigned to receive once-weekly s.c. injections of teriparatide (56.5 μg) or placebo for 72 wk.nnnMAIN OUTCOME MEASUREnThe primary endpoint was the incidence of new vertebral fracture.nnnRESULTSnOnce-weekly injections of teriparatide reduced the risk of new vertebral fracture with a cumulative incidence of 3.1% in the teriparatide group, compared with 14.5% in the placebo group (P < 0.01), and a relative risk of 0.20 (95% confidence interval, 0.09 to 0.45). At 72 wk, teriparatide administration increased bone mineral density by 6.4, 3.0, and 2.3% at the lumbar spine, the total hip, and the femoral neck, respectively, compared with the placebo (P < 0.01). Adverse events (AE) and the dropout rates by AE were more frequently experienced in the teriparatide group, but AE were generally mild and tolerable.nnnCONCLUSIONnWeekly s.c. administration of teriparatide at a dose of 56.5 μg may provide another option of anabolic treatments in patients with osteoporosis at higher fracture risk.

Role of Osteoglycin in the Linkage between Muscle and Bone

Background: The interaction between muscle tissues and bone metabolism has recently been noted. Results: Osteoglycin is produced in myoblastic cells and enhances bone formation parameters in osteoblasts. Conclusion: Osteoglycin may be a crucial humoral bone anabolic factor that is produced by muscle tissues. Significance: Osteoglycin may be the first potential humoral bone anabolic factor produced from muscle cells. The interaction between muscle tissues and bone metabolism is incompletely understood. We hypothesized that there might be some humoral factors that are produced in muscle tissues and exhibit bone anabolic activity. We, therefore, performed comparative DNA microarray analysis between mouse myoblastic C2C12 cells transfected with either stable empty vector or ALK2 (R206H), the mutation that constitutively activates the bone morphogenetic protein (BMP) receptor, to search for muscle-derived bone anabolic factors. Twenty-five genes whose expression was decreased to <1/4, were identified; these included osteoglycin (OGN). Stable overexpression of OGN significantly decreased the levels of Runx2 and Osterix mRNA compared with those in cells transfected with vector alone in MC3T3-E1 cells. On the other hand, it significantly enhanced the levels of alkaline phosphatase (ALP), type I collagen (Col1), and osteocalcin (OCN) mRNA as well as β-catenin and mineralization. A reduction in endogenous OGN level showed the opposite effects to those of OGN overexpression in MC3T3-E1 and mouse calvarial osteoblastic cells. Transient OGN overexpression significantly suppressed the levels of Runx2, Osterix, ALP, Col1, and OCN mRNA induced by BMP-2 in C2C12 cells. The conditioned medium from OGN-overexpressed and OGN-suppressed myoblastic cells enhanced and decreased, respectively, the levels of ALP, Col1, and β-catenin in MC3T3-E1 cells. Moreover, OGN increased Smad3/4-responsive transcriptional activity as well as Col1 mRNA levels independently of endogenous TGF-β in these cells. In conclusion, this study suggests that OGN may be a crucial humoral bone anabolic factor that is produced by muscle tissues.

Elevated Sclerostin Levels Are Associated With Vertebral Fractures in Patients With Type 2 Diabetes Mellitus

CONTEXTnPatients with type 2 diabetes mellitus (T2DM) patients are at increased risk of vertebral fractures (VFs) compared with non-T2DM individuals, because of poor bone quality. Recent studies in nondiabetic subjects have shown that elevated sclerostin levels are associated with VFs independent of bone mineral density (BMD).nnnOBJECTIVEnWe aimed to investigate the association between sclerostin levels and VFs in T2DM.nnnRESEARCH DESIGN AND METHODSnWe conducted a cross-sectional observational study in 146 postmenopausal women and 175 men over 50 years old. Sclerostin levels were compared in the patients with and without VFs confirmed by spinal radiographs.nnnRESULTSnSclerostin levels were significantly higher in men than in women (P < .01). Stepwise forward multiple regression analyses demonstrated that spine BMD was the strongest and independent positive determinant for sclerostin in both genders. When the participants were divided into 2 subgroups by the T score of spine BMD to eliminate the influence of BMD on sclerostin values, elevated sclerostin levels were associated with an increased risk of VFs in the male patients with BMD T scores ≥-1 (odds ratio = 1.85, 95% confidence interval = 1.12-3.07) and female with T scores <-1 (odds ratio = 3.23, 95% confidence interval = 1.42-7.34) after adjusting for multiple variables including BMD and bone metabolic markers.nnnCONCLUSIONSnElevated sclerostin levels were associated with an increased risk of VFs in T2DM patients independently of BMD and bone turnover in both genders, suggesting that sclerostin levels may reflect bone fragility attributed to the deterioration of bone quality under the gender-specific range of BMD T scores.

The Calcium-sensing Receptor (CaR) is involved in strontium ranelate-induced osteoblast differentiation and mineralization.

Strontium ranelate is known to reduce fracture risk in osteoporotic patients by stimulating bone formation and suppressing bone resorption. However, the mechanism by which strontium exerts this beneficial effect on bone is unclear. We examined whether or not the calcium-sensing receptor (CaR), which is activated by divalent cations including Sr (2+), is involved in this mechanism. Both strontium ranelate and strontium chloride dose-dependently stimulated phosphorylation of extracellular signal-regulated kinase (ERK) in Human Embryonic Kidney 293 cells transiently transfected with the human CaR. Strontium ranelate also dose- and time-dependently stimulated phosphorylation of ERK in mouse osteoblastic MC3T3-E1 cells expressing the CaR endogenously. Strontium ranelate increased mRNA expression of osteocalcin and bone morphogenetic protein-2 in MC3T3-E1 cells as well as mineralization and proliferation of the cells. Pretreatments of NPS2390, a CaR inhibitor, almost totally antagonized strontium ranelate-induced mineralization and proliferation of MC3T3-E1 cells. These findings indicate that strontium ranelate induces not only osteoblast proliferation but also its differentiation and mineralization by activating the CaR, and confirm that the therapeutic efficacy of strontium ranelate for osteoporosis may be partly mediated by the CaR.

FAM5C is a soluble osteoblast differentiation factor linking muscle to bone

Muscle mass is related to higher bone mass and a reduction in fracture risk. However, the interactions between muscle tissues and bone metabolism are incompletely understood and there might be some humoral factors that are produced in muscle tissues and exhibit bone anabolic activity. We therefore investigated the role of FAM5C in osteoblast differentiation and the interactions between muscle and bone. A reduction of endogenous FAM5C by siRNA reduced the levels of osterix, alkaline phosphatase (ALP) and osteocalcin (OCN) mRNA as well as the levels of type 1 collagen and β-catenin in mouse osteoblastic MC3T3-E1 cells and mouse calvarial osteoblasts, although FAM5C overexpression significantly antagonized the levels of osterix, ALP and OCN mRNA induced by bone morphogenetic protein-2 in C2C12 cells. The conditioned medium from FAM5C-overexpressed and -suppressed C2C12 cells increased and decreased the levels of osterix, ALP and OCN mRNA in MC3T3-E1 cells, respectively. In conclusion, the present study is the first to show that FAM5C enhances osteoblast differentiation in differentiated osteoblasts, and that the effects of the conditioned medium from FAM5C-modulated myoblastic cells were positively correlated with the effects of FAM5C on osteoblast phenotype in osteoblasts. FAM5C might be an important humoral bone anabolic factor produced from muscle cells.

Serum osteocalcin levels are inversely associated with abdominal aortic calcification in men with type 2 diabetes mellitus.

SummaryWe found that serum osteocalcin (OC) and undercarboxylated OC (ucOC) levels were negatively associated with abdominal aortic calcification in type 2 diabetes mellitus (T2DM) men. This finding suggests that circulating OC and ucOC are not only related to glucose or fat metabolism but also to arteriosclerosis.IntroductionRecent studies revealed that serum osteocalcin levels were associated with not only bone metabolism but also glucose and fat metabolism. However, the relationship between serum OC levels and arteriosclerosis remains controversial. We examined whether or not bone metabolic markers including OC are associated with abdominal aortic calcification in patients with type 2 diabetes mellitus.MethodsWe recruited 118 men and 100 postmenopausal women with T2DM. We evaluated the abdominal aortic calcification score (ACS) on a lateral lumbar radiograph and examined the association between serum OC or undercarboxylated OC levels and ACS.ResultsThe ACS of 3 and greater, which corresponded well to the highest quartile, was significantly and negatively associated with serum OC and ucOC levels in men by logistic regression analyses after adjusting for age, BMI, serum levels of creatinine and LDL cholesterol, radial bone mineral density, smoking, duration of DM, hemoglobin A1c, and the index of insulin resistance [odds ratio (OR) 0.36, 95xa0% confidence interval (CI) 0.19–0.70, Pu2009<u20090.005, and OR 0.28, 95xa0% CI 0.12–0.69, Pu2009<u20090.01, per standard deviation increase in OC and ucOC, respectively]. These observations were still significant after an additional adjustment for other bone markers. In contrast, there were no significant relationships with serum OC or ucOC levels and ACS in women.ConclusionsThese findings suggest that serum OC and ucOC levels are associated with not only bone metabolism but also arteriosclerosis in men, but not in women with type 2 diabetes mellitus.

Interaction of Tmem119 and the bone morphogenetic protein pathway in the commitment of myoblastic into osteoblastic cells

Bone morphogenetic proteins (BMPs) are critical for bone regeneration and induce ectopic bone formation in vivo. The constitutively activating mutation (R206H) of the BMP type 1 receptor, activin A type 1 receptor/activin-like kinase 2 (ACVR1/ALK2), underlies the molecular pathogenesis of fibrodysplasia ossificans progressiva (FOP) in which heterotopic ossification occurs in muscle tissue. In the present study, we performed a comparative DNA microarray analysis between stable empty vector- and ALK2(R206H)-transfected mouse myoblastic C2C12 cells. Forty genes were identified whose expression was increased >3.5 times in the experimental group versus the control. The bone formation-related factor, Tmem119, was included in this group. Osteoblast differentiation markers and mineralization were enhanced in C2C12 cells stably expressing Tmem119. Differentiation of myoblastic cells into myotubes was suppressed but differentiation into chondrocytes was little affected. Transcriptional activity of the BMP-2 signaling molecules, Smad1/5, was increased even in the absence of exogenous BMP-2. Endogenous BMP-2 levels positively correlated with Tmem119 levels. A BMP-2/4 neutralizing antibody and dorsomorphin, an ALK2 inhibitor, antagonized Tmem119-enhanced alkaline phosphatase (ALP) levels. Tmem119 siRNA antagonized the BMP-2-induced ALP and osteocalcin, but not Runx2 and Osterix, mRNAs, in C2C12 cells. In conclusion, Tmem119 levels were increased by the FOP-associated constitutively activating ALK2 mutation in myoblasts. The data show that Tmem119 promotes the differentiation of myoblasts into osteoblasts and the interaction with the BMP signaling pathway likely occurs downstream of Runx2 and Osterix in myoblasts. Tmem119 may play a critical role in the commitment of myoprogenitor cells to the osteoblast lineage.

Increased low-density lipoprotein cholesterol level is associated with non-vertebral fractures in postmenopausal women

Although a high serum low-density lipoprotein cholesterol (LDL-C) level is an established risk factor for atherosclerosis, it is unclear whether it is associated with osteoporosis. In this study, the associations between the serum LDL-C level and bone mineral density (BMD), bone metabolic markers, and the presence of prevalent vertebral or non-vertebral fractures were examined. A total of 211 healthy postmenopausal women (age range, 46–80xa0years) who visited a community health center were recruited consecutively. Their radiographic and biochemical characteristics were collected. Prevalent vertebral and non-vertebral fractures were found in 49 (23.2xa0%) and 36 (17.1xa0%) subjects, respectively. Simple regression analyses showed that the serum LDL-C level was not significantly correlated with lumbar or femoral BMD or serum levels of total amino-terminal propeptide of type I collagen (PINP) or carboxy-terminal telopeptide of type I collagen (CTX). Logistic regression analyses adjusted for age and BMI showed that the increased serum LDL-C level was selected as an index affecting the presence of prevalent non-vertebral fractures, but not vertebral fractures. This result was still significant after additional adjustments for years since menopause, physical activity, previous cardiovascular events, bone markers, BMD, serum Ca, P, Cr, 25(OH)D, grip strength, tandem gait test, and use of drugs for hyperlipidemia [odds ratio 1.76 (1.13–2.73), pxa0=xa00.012]. These findings suggest that a high serum LDL-C level may be a risk factor for prevalent non-vertebral fragility fractures independent of bone turnover, bone mass, vitamin D insufficiency, or frail status in postmenopausal women, and that it may be detrimental to bone, as well as blood vessels.

Fracture risk is increased by the complication of hypertension and treatment with calcium channel blockers in postmenopausal women with type 2 diabetes

Patients with type 2 diabetes mellitus (T2DM) frequently have other common diseases such as hypertension (HT), dyslipidemia (DL), and cardiovascular disease (CVD). However, it is unknown whether or not the complication of these diseases would affect fracture risk in T2DM patients. We evaluated prevalent morphometric vertebral fractures (VFs) and prior non-VFs in 155 and 195 Japanese T2DM postmenopausal women, respectively, and examined their association with HT, DL, or CVD. VF, non-VF, HT, DL, and CVD were found in 53 (34xa0%), 30 (15xa0%), 136 (70xa0%), 124 (64xa0%), and 45 (23xa0%) women, respectively. Multivariate logistic regression analyses adjusted for age, body mass index (BMI), and serum creatinine showed that the presence of HT significantly increased VF risk [odds ratio (OR) 4.05, Pxa0=xa00.0047], but not non-VF risk. This result was still significant after an additional adjustment for each of blood pressure levels, treatments with anti-hypertensive medications, and a history of falls. In contrast, calcium channel blocker (CCB) treatment significantly increased VF and non-VF risks after adjustments for age, BMI, serum creatinine, and blood pressure levels (OR 2.33, Pxa0=xa00.0320 and OR 2.95, Pxa0=xa00.0150, respectively), while these significances disappeared after an additional adjustment for a history of falls. These findings suggest that the presence of HT increases VF risk independent of blood pressure levels, anti-hypertensive medications, or falls, and that CCB treatment increases both VF and non-VF risks possibly via falls in T2DM postmenopausal women.

Association of n-3 Polyunsaturated Fatty Acid Intake with Bone Mineral Density in Postmenopausal Women

Abstractn-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 63.5xa0years, 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.