Id4, a New Candidate Gene for Senile Osteoporosis, Acts as a Molecular Switch Promoting Osteoblast Differentiation

Excessive accumulation of bone marrow adipocytes observed in senile osteoporosis or age-related osteopenia is caused by the unbalanced differentiation of MSCs into bone marrow adipocytes or osteoblasts. Several transcription factors are known to regulate the balance between adipocyte and osteoblast differentiation. However, the molecular mechanisms that regulate the balance between adipocyte and osteoblast differentiation in the bone marrow have yet to be elucidated. To identify candidate genes associated with senile osteoporosis, we performed genome-wide expression analyses of differentiating osteoblasts and adipocytes. Among transcription factors that were enriched in the early phase of differentiation, Id4 was identified as a key molecule affecting the differentiation of both cell types. Experiments using bone marrow-derived stromal cell line ST2 and Id4-deficient mice showed that lack of Id4 drastically reduces osteoblast differentiation and drives differentiation toward adipocytes. On the other hand knockdown of Id4 in adipogenic-induced ST2 cells increased the expression of Pparγ2, a master regulator of adipocyte differentiation. Similar results were observed in bone marrow cells of femur and tibia of Id4-deficient mice. However the effect of Id4 on Pparγ2 and adipocyte differentiation is unlikely to be of direct nature. The mechanism of Id4 promoting osteoblast differentiation is associated with the Id4-mediated release of Hes1 from Hes1-Hey2 complexes. Hes1 increases the stability and transcriptional activity of Runx2, a key molecule of osteoblast differentiation, which results in an enhanced osteoblast-specific gene expression. The new role of Id4 in promoting osteoblast differentiation renders it a target for preventing the onset of senile osteoporosis

Studies on the Glutamic Acid Metabolism of Bacteria II: Glutamic acid metabolism of Staphylococcus albus

As to the physiological or metabolic features of pathogenic staphylococci, there are only a few reports, compared with those of Escherichia coli which was treated in report I. In this report, the author reports about the physiological aspects, particularly about the terminal respiratory system of Staphylococcus albus, entering from the studies of glutamic acid metabolism: 1) Staph. albus has the so-called citric acid cycle as its terminal respiratory ststem. 2) As a result of oxidative deamination, glutamic acid enters into the citric acid cycle and is further oxidized through this cycle. Glutamic acid is, however, best oxidized of all the intermediates of citric acid cycle and the related compounds. 3) Glutamic-aspartic and glutamic-alanic transaminations are carried out by this organism, in which glutamic acid plays the central role. 4) Divalent metal ions (Mg(++), Mn(++) and Fe(++)) show no remarkable effect on the glutamate-respiration of Staph. albus. 5) Of the various inhibitors tested, sodium azide, 2: 4-dinitrophenol, sodium arsenite and 8-hydroxyquinoline inhibit the glutamate-respiration strongly, and the most remarkable is the inhibitive action of 8-hydroxyquinoline. 6) Of the various antibiotics used, the inhibitive action of aureomycin is the most remarkable. Penicillin also shows some inhibitive action at pH 5.4. 7) The inhibition of the glutamate-respiration of this organism by these various inhibitors and antibiotics shows usually the tendency to rise up in the region of lower pH

Studies on the Glutamic Acid Metabolism of Bacteria I: Glutamic acid metabolism of Escherichia coli communis and its application to the analysis of glutamic acid

It is well known that glutamic acid, as well as aspartic acid, plays an important role in the metabolism of microorganisms. The author performed many experiments in order to study the physiological aspects of E. coli communis from the stand point of glutamic acid metabolism, and to apply it to the analysis of glutamic acid. The results were as follows: 1) E. coli can grow at any pH within the range from 5.4 to 8.0, but the growth is the best at pH 6.8 to 7.0. 2) The more remote from the optimum the cultural pH is, the nearer it comes to the optimum after the growth. This phenomenon is particularly remarkable on the acid side. 3) Using glutamic acid as substrate, the decarboxylation is chiefly carried out on the acid side, the deamination on the neutral or slightly alkaline side, and these two reactions are carried out simultaneously at pH 5.5 to 6.5. As for the optimum pH, pH 5.0 for decarboxylation and 7.0 for deamination. 4) The lower the cultural pH is, the higher the glutamic decarboxylase activity of the cultured organism becomes. The optimum reaction pH is, however, never shifted. 5) The E. coli, which was cultured in the pyridoxin-containing semi-synthetic medium, shows a very high activity to glutamic acid, but not to α-ketoglutaric acid, aspartic acid, alanine and pyruvic acid. 6) The aceton powder of the E. coli, which was cultured in the pyridoxin-containing semi-synthetic medium, still has the high glutamic decaboxylase activity. The optimum pH is from 4.4 to 5.1, where carbon dioxide is evolved quantitatively

Studies on the Influence of Buffer on the Bacterial Respiratiration

The preparation of resting cells is one of the most important and most fundamental procedures for the physiological studies on bacteria. In order to know how we should do to get the resting cells suitable to the purposes of experiments, the author studied the influence of washing and suspending on the respiratory activity of bacteria. The results are summarized as follows: 1) For the purpose to obtain the resting cells of high respiratory activity, washing with phosphate buffer is better than that with distilied water or physiological saline solution. 2) When the prepared resting cells are used in a short time after the preparation, the respiratory activity is the same regardless of the sorts of the suspending solutions, distilled water, saline solution and phosphate buffer. 3) Borate and phthalate buffers of high concentration somewhat inhibit the respiration. However, in order to make the shift of pH less, M/15 (final concentration) is good. Phosphate buffer, even of M/15, does not inhibit the respiration. 4) In borate or phthalate buffers, the fall of respiratory activity is diminished by the addition of small amount of phospate

Action of Various Inhibitors and Antibiotics on Glutamate-Respiration of Staphylococcus

The author studied the action of various inhibitors and antibiotics on the glutamaterespiration of staphylococci under the consideration of physiological structure of the cell. Staphylococcus citreus and aureus (Terashima) were used as the test organisms, and L-glutamic acid as the substrate. The results were as follows: 1) Thionine, sodium arsenite and 8-hydroxyquinoline inhibited the respiration of intact cells of staphylococci markedly, but did not inhibit that of cell-free extracts. The inhibitive action of these three sorts of inhibitors was stronger on Staph. aureus (Terashima) than on Staph. citreus. 2) In intact cells, the inhibition of respiration by potassium cyanide and sodium azide was not restored by addition of thionine. In cell-free extracts, however, the inhibition by these two sorts of inhibitors was well restored by thionine. 3) By addition of thionine, the inhibition of the respiration of cell-free extracts by octanole was not so well restored as that by cyanide or azide. 4) 2, 4-Dinitrophenol inhibited the glntamate-respiration of both of the intact cells and cell-free extracts. 5) Of all the antibiotics tested, aureomycin was the only one which noticeably inhibited the glutamate-respiration of staphylococci

Supplement to the Studies on Glutamic Acid Metabolism of Bacillus Coli Communis and Its Application to the Analysis of Glutamic Acid

Akita (1957), one of the present authors, reported on glutamic acid metabolism of Bacillus coli communis and its application to the analysis of glutamic acid. In order to apply the method reported by Akita to a practical use, the authors reinvestigated and somewhat improved the method. The cells of B. coli communis cultured only once in the pyridoxinecontaining semi-synthetic liquid medium showed a high glutamic decarboxylase activity at pH 5.0, and evolved in a very short time carbon dioxide quantitatively from glutamic acid in the presence of cetyltrimethylammonium bromide. The cells, however, showed no activity to pyruvic acid