Oral Administration of Geranylgeraniol Rescues Denervation-induced Muscle Atrophy via Suppression of Atrogin-1.

BACKGROUND/AIM: Geranylgeraniol (GGOH), a C20 isoprenoid naturally occurs in several foods. We previously reported that GGOH treatment reduced the expression levels of Atrogin-1 which is involved in skeletal muscle degradation and stimulates the myogenic differentiation of C2C12 myoblasts. However, the effect of GGOH supplementation on skeletal muscle metabolism in vivo is unknown. MATERIALS AND METHODS: Skeletal muscle atrophy was induced by denervation. The expression levels of Atrogin-1 were assessed by western blotting or real time PCR. RESULTS: Intraoral administration of GGOH reduced the decrease in the cross-sectional area of muscle fibers and also suppressed the expression levels of Atrogin-1 in denervation induced muscle atrophy. Also, GGOH treatment suppressed the expression of Atrogin-1 and the decrease in skeletal muscle fiber size by glucocorticoid in vitro. CONCLUSION: Intraoral administration of GGOH rescues denervation-induced muscle atrophy via suppression of Atrogin-1.

Transducin-like enhancer of split 3 regulates proliferation of melanoma cells via histone deacetylase activity.

Melanoma, one of the most aggressive neoplasms, is characterized by rapid cell proliferation. Transducin-like Enhancer of Split (TLE) is an important regulator of cell proliferation via Histone deacetylase (HDAC) recruitment. Given that HDAC activity is associated with melanoma progression, we examined the relationship between TLE3, a TLE family member, and melanoma. TLE3 expression was increased during the progression of human patient melanoma (p < 0.05). Overexpression of Tle3 in B16 murine melanoma cells led to an increase in cell proliferation (p < 0.01) as well as the number of cyclinD1-positive cells. in vivo injection of mice with B16 cells overexpressing Tle3 resulted in larger tumor formation than in mice injected with control cells (p < 0.05). In contrast, siRNA-mediated knockdown of Tle3 in B16 cells or TLE3 in HMV-II human melanoma cells decreased proliferation (p < 0.01). Treatment of B16 cells with trichostatin A (2.5 µM), a class I and II HDAC inhibitor, prevented the effect s of Tle3 on proliferation. In conclusion, these data indicate that Tle3 is required, at least in part, for proliferation in the B16 mouse melanoma model.

Geranylgeraniol Induces PPARγ Expression and Enhances the Biological Effects of a PPARγ Agonist in Adipocyte Lineage Cells.

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.

Geranylgeraniol-induced Myogenic Differentiation of C2C12 Cells.

BACKGROUND: Geranylgeraniol (GGOH) is a C20 isoprenoid found in fruits, vegetables, and grains, including rice. As a food substance, GGOH is categorized as 'Generally Recognized as Safe'. GGOH is an intermediate product in the mevalonate pathway and acts as a precursor to geranylgeranyl pyrophosphate. MATERIALS AND METHODS: C2C12 mouse myoblasts derived from muscle satellite cells were used. Quantitative reverse-transcriptase polymerase chain reaction, western blotting analysis, and immunocytochemical analysis were performed to respectively assess mRNA expression, protein levels, and the number of myofibers. RESULTS: GGOH reduced the expression levels of skeletal muscle atrophy-related ubiquitin ligases in myofibers derived from C2C12 cells. GGOH induced myogenic differentiation of C2C12 cells via geranylgeranylation. GGOH did not adversely affect the proliferation of C2C12 cells. CONCLUSION: GGOH induces myoblast differentiation in C2C12 cells.

A peptide that blocks the interaction of NF-κB p65 subunit with Smad4 enhances BMP2-induced osteogenesis.

Bone morphogenetic protein (BMP) potentiates bone formation through the Smad signaling pathway in vitro and in vivo. The transcription factor nuclear factor κB (NF-κB) suppresses BMP-induced osteoblast differentiation. Recently, we identified that the transactivation (TA) 2 domain of p65, a main subunit of NF-κB, interacts with the mad homology (MH) 1 domain of Smad4 to inhibit BMP signaling. Therefore, we further attempted to identify the interacting regions of these two molecules at the amino acid level. We identified a region that we term the Smad4-binding domain (SBD), an amino-terminal region of TA2 that associates with the MH1 domain of Smad4. Cell-permeable SBD peptide blocked the association of p65 with Smad4 and enhanced BMP2-induced osteoblast differentiation and mineralization without affecting the phosphorylation of Smad1/5 or the activation of NF-κB signaling. SBD peptide enhanced the binding of the BMP2-inudced phosphorylated Smad1/5 on the promoter region of inhibitor of DNA binding 1 (Id-1) compared with control peptide. Although SBD peptide did not affect BMP2-induced chondrogenesis during ectopic bone formation, the peptide enhanced BMP2-induced ectopic bone formation in subcortical bone. Thus, the SBD peptide is useful for enabling BMP2-induced bone regeneration without inhibiting NF-κB activity.

The transcriptional co-repressor TLE3 regulates myogenic differentiation by repressing the activity of the MyoD transcription factor.

Satellite cells are skeletal muscle stem cells that provide myonuclei for postnatal muscle growth, maintenance, and repair/regeneration in adults. Normally, satellite cells are mitotically quiescent, but they are activated in response to muscle injury, in which case they proliferate extensively and exhibit up-regulated expression of the transcription factor MyoD, a master regulator of myogenesis. MyoD forms a heterodimer with E proteins through their basic helix-loop-helix domain, binds to E boxes in the genome and thereby activates transcription at muscle-specific promoters. The central role of MyoD in muscle differentiation has increased interest in finding potential MyoD regulators. Here we identified transducin-like enhancer of split (TLE3), one of the Groucho/TLE family members, as a regulator of MyoD function during myogenesis. TLE3 was expressed in activated and proliferative satellite cells in which increased TLE3 levels suppressed myogenic differentiation, and, conversely, reduced TLE3 levels promoted myogenesis with a concomitant increase in proliferation. We found that, via its glutamine- and serine/proline-rich domains, TLE3 interferes with MyoD function by disrupting the association between the basic helix-loop-helix domain of MyoD and E proteins. Our findings indicate that TLE3 participates in skeletal muscle homeostasis by dampening satellite cell differentiation via repression of MyoD transcriptional activity.

Two-year clinical comparison of a flowable-type nano-hybrid composite and a paste-type composite in posterior restoration.

AIM: The purpose of the present study was to compare the clinical efficacy between a flowable-type nano-hybrid composite and a paste-type composite for posterior restoration. METHODS: Of 62 posterior teeth in 33 patients (mean age: 34.1 years), 31 were filled with a paste-type composite (Heliomolar [HM] group), and another 31 with a flowable nano-hybrid composite (MI FIL [MI] group). Clinical efficacy was evaluated at 2 years after the restoration. RESULTS: There were no differences for retention, surface texture deterioration, anatomical form change, deterioration of marginal adaptation, and secondary caries, while a statistical difference was found for marginal discoloration, which was significantly greater in the HM group (P < 0.05). Furthermore, color matching in the MI group was superior to that in the HM group immediately after the restoration throughout the study period. CONCLUSIONS: The present 2-year clinical evaluation of different composites showed that the flowable nano-hybrid composite could be an effective esthetic material for posterior restoration.