Search

Osteoblasts release adenosine triphosphate (ATP) out of the cell following mechanical stress. Although it is well established that extracellular ATP affects bone metabolism via P2 receptors [such as purinergic receptor P2X7 (P2X7R) and purinergic receptor P2Y2 (P2Y2R)], the mechanism of ATP release from osteoblasts remains unknown. Recently, a vesicular nucleotide transporter [VNUT, solute carrier family 17 member 9 (SLC17A9)] that preserves ATP in vesicles has been identified. The purpose of this study was to elucidate the role of VNUT in osteoblast bone metabolism. mRNA and protein expression of VNUT were confirmed in mouse bone and in osteoblasts by quantitative real‐time PCR (qPCR) and immunohistochemistry. Next, when compressive force was applied to MC3T3‐E1 cells by centrifugation, the expression of Slc17a9, P2x7r, and P2y2r was increased concomitant with an increase in extracellular ATP levels. Furthermore, compressive force decreased the osteoblast differentiation capacity of MC3T3‐E1 cells. shRNA knockdown of Slc17a9 in MC3T3‐E1 cells reduced levels of extracellular ATP and also led to increased osteoblast differentiation after the application of compressive force as assessed by qPCR analysis of osteoblast markers such as Runx2, Osterix, and alkaline phosphatase (ALP) as well as ALP activity. Consistent with these observations, knockdown of P2x7r or P2y2r by siRNA partially rescued the downregulation of osteoblast differentiation markers, caused by mechanical loading. In conclusion, our results demonstrate that VNUT is expressed in osteoblasts and that VNUT inhibits osteoblast differentiation in response to compressive force by mechanisms related to ATP release and P2X7R and/or P2Y2R activity., In this study, we show that VNUT (SLC17A9), a vesicular nucleotide transporter, regulates osteoblast differentiation in response to mechanical loading. Mechanical loading promotes adenosine triphosphate (ATP) exocytosis via VNUT. Extracellular ATP subsequently inhibits osteoblast differentiation via activation of P2X7 and/or P2Y2 receptors. Thus, VNUT modulation of purinergic signaling contributes to the regulation of bone metabolism by mechanical loading.

Osteoclasts, which resorb the bone, and osteoblasts, which form the bone, are the key cells regulating bone homeostasis. Osteoporosis and other metabolic bone diseases occur when osteoclast-mediated bone resorption is increased and bone formation by osteoblasts is decreased. Analyses of tyrosine kinase Src-knockout mice revealed that Src is essential for bone resorption by osteoclasts and suppresses bone formation by osteoblasts. Src-knockout mice exhibit osteopetrosis. Therefore, Src is a potential target for osteoporosis therapy. However, Src is ubiquitously expressed in many tissues and is involved in various biological processes, such as cell proliferation, growth, and migration. Thus, it is challenging to develop effective osteoporosis therapies targeting Src. To solve this problem, it is necessary to understand the molecular mechanism of Src function in the bone. Src expression and catalytic activity are maintained at high levels in osteoclasts. The high activity of Src is essential for the attachment of osteoclasts to the bone matrix and to resorb the bone by regulating actin-related molecules. Src also inhibits the activity of Runx2, a master regulator of osteoblast differentiation, suppressing bone formation in osteoblasts. In this paper, we introduce the molecular mechanisms of Src in osteoclasts and osteoblasts to explore its potential for bone metabolic disease therapy.

The transcription factor NFATc1 and its binding partner AP-1 (a complex containing c-fos and c-Jun) play a central role in osteoclast differentiation. NFATc1 and AP-1 promote the expression of target genes such as Acp5, Ctsk and also auto-regulate NFATc1 expression as well. We previously reported that protein phosphatase 1 regulatory subunit 18 (PPP1r18) is a negative regulator of osteoclast bone resorption by inhibiting cell attachment to bone matrix. We also reported that PPP1r18 potentially regulates NFATc1 expression during osteoclast differentiation. To further explore this, in this study we have examined the effect of PPP1r18 on NFATc1 expression and activity by overexpressing PPP1r18 during the early stage of osteoclast differentiation. We found that PPP1r18 suppressed NFATc1 expression through inhibition of the transcriptional activity of NFATc1. Since PPP1r18 does not regulate NFATc1 directly, we next explored the involvement of AP-1. Our data showed that c-fos phosphorylation and nuclear localization were reduced by PPP1r18 overexpression. Further experiments showed that overexpression of c-fos together with PPP1r18 rescued NFATc1 expression and transcriptional activity. Moreover, c-fos activity inhibition by PPP1r18 was canceled by mutation of the phosphatase binding site of PPP1r18. Taken together, PPP1r18-regulated phosphatase activity targets c-fos phosphorylation and suppresses subsequent NFATc1 expression and activity., Highlights • PPP1r18 suppresses osteoclast differentiation. • PPP1r18 suppresses c-fos phosphorylation and nuclear localization. • PPP1r18 suppresses NFAT via c-fos.

Diesel engines exhibit highly efficient, environmentally sound performance under good operational control; however, because of the demand of controlling multiple actuators under various environmental conditions, the conventional experimental method for controlling diesel engines has become increasingly difficult. Therefore, diesel combustion models with less calculation loads were ultimately developed with the aim of implementing such model-based controllers for engine control unit in the future. To achieve the on-board application of the diesel combustion model, the in-cylinder state of a single cycle was discretized into several representative phases such as a valve-opening and valve-closing phase, ignition phase, and maximum pressure phase. Temperature and oxygen quantities in residual gas were considered as the state variables of the system because they have a critical effect on combustion and induce cyclic coupling. The model could take account of the effect of actuators in diesel engines, and the states in each phase were calculated by fundamental thermodynamic equations and some empirical equations. The model was validated against experimental results and had a good agreement with in-cylinder pressures and temperatures at each phase. In addition, the calculation times of the model were confirmed to be capable of on-board application. Furthermore, as a demonstrative example and to show the added value of the model, it was used to synthesize controllers to enable multi-input/multi-output control of a diesel engine in simulation.

Background The global incidence of diabetes mellitus (DM) has risen precipitously, even in middle- and low-income countries. Peroxisome proliferator-activated receptor γ (PPARγ) plays an important role in the control of cellular glucose metabolism. Activation of PPARγ beneficially results in increased insulin sensitivity. However, the expression of PPARγ is reduced by obesity and several nutritional factors. Here we examined the effect of geranylgeraniol (GGOH), a bioactive compound found naturally in fruits, vegetables, and grains, on the expression and activation of PPARγ. Materials and methods C3H10T1/2 mouse embryonic fibroblasts and 3T3-L1 pre-adipocytes were used as in vitro models of adipocyte differentiation and function. Quantitative reverse-transcriptase polymerase chain reaction, western blotting, Oil Red O staining, and luciferase assay were performed to respectively assess mRNA expression, protein levels, lipid droplet formation and transcriptional activity. Results GGOH increased the expression of PPARγ in adipocyte lineage cells. GGOH also enhanced adipogenesis induced by rosiglitazone, a thiazolidinedione class PPARγ agonist. Conclusion GGOH induces PPARγ expression and enhances the biological effects of a PPARγ agonist in adipocyte lineage cells.

When constructing the one-dimensional systemic artery tree, the Windkessel model based on parameters describing the total resistance and compliance is generally applied as outflow boundary conditions. However, the Windkessel model does not include wave propagation effects, and moreover, it is not obvious how the parameters should be estimated. Hence, the main purpose of this study is to develop an outflow boundary condition based on the underlying physiology of the arterioles, enabling the prediction of blood flow and pressure in the systemic arteries including the arterioles. The obtained numerical results show the followings. Firstly, we verified that applying the structured tree model as an outflow boundary condition can reproduce the essential characteristics of the arterial pulse better than applying the Windkessel model. Secondly, by analyzing the pulse wave velocity in aorta, we found a correlation between pulse wave velocity and the degree of arteriosclerosis which correspond to the clinical observation.Copyright © 2012 by ASME

Although the phenomena related to the multiphase flow can be found in many kinds of industrial and engineering applications, the physical mechanism of the multiphase flow has not been investigated in detail. The major reason for the lack of data in the multiphase flow lies in the difficulties in measuring the flow quantities of the multiple phases simultaneously. Presently, the simultaneous visualization and the PIV measurement have been carried out about the both phases of the liquid-liquid two-phase flow. The difference in the refractive indices makes the visualization in the vicinity of the boundary of the multiple phases almost impossible. In this study, the refractive index of the aqueous phase has been equalized to that of the oil phase by adjusting the concentration of aqueous solution. The PIV measurement has been carried out for the flow field around and inside of two falling droplets interacting each other while they travel.

Although the phenomena related to the multiphase flow can be found in many kinds of industrial and engineering applications, the physical mechanism of the multiphase flow has not been investigated in detail. The major reason for the lack of data in the multiphase flow lies in the difficulties in measuring the flow quantities of the multiple phases simultaneously. Presently, the simultaneous visualization and the PIV measurement have been carried out about the both phases of the liquid-liquid two-phase flow. The difference in the refractive indices makes the visualization in the vicinity of the boundary of the multiple phases almost impossible. In this study, the refractive index of the aqueous phase has been equalized to that of the oil phase by adjusting the concentration of aqueous solution. The results show the flow structure both outside and inside of a falling water droplet in the stationary oil simultaneously.