Kimitaka Takitani

Vitamin E decreases bone mass by stimulating osteoclast fusion.

Bone homeostasis is maintained by the balance between osteoblastic bone formation and osteoclastic bone resorption. Osteoclasts are multinucleated cells that are formed by mononuclear preosteoclast fusion. Fat-soluble vitamins such as vitamin D are pivotal in maintaining skeletal integrity. However, the role of vitamin E in bone remodeling is unknown. Here, we show that mice deficient in α-tocopherol transfer protein (Ttpa(-/-) mice), a mouse model of genetic vitamin E deficiency, have high bone mass as a result of a decrease in bone resorption. Cell-based assays indicated that α-tocopherol stimulated osteoclast fusion, independent of its antioxidant capacity, by inducing the expression of dendritic-cell-specific transmembrane protein, an essential molecule for osteoclast fusion, through activation of mitogen-activated protein kinase 14 (p38) and microphthalmia-associated transcription factor, as well as its direct recruitment to the Tm7sf4 (a gene encoding DC-STAMP) promoter. Indeed, the bone abnormality seen in Ttpa(-/-) mice was rescued by a Tm7sf4 transgene. Moreover, wild-type mice or rats fed an α-tocopherol-supplemented diet, which contains a comparable amount of α-tocopherol to supplements consumed by many people, lost bone mass. These results show that serum vitamin E is a determinant of bone mass through its regulation of osteoclast fusion.Bone homeostasis is maintained by the balance between osteoblastic bone formation and osteoclastic bone resorption. Osteoclasts are multinucleated cells that are formed by mononuclear preosteoclast fusion. Fat-soluble vitamins such as vitamin D are pivotal in maintaining skeletal integrity. However, the role of vitamin E in bone remodeling is unknown. Here, we show that mice deficient in α-tocopherol transfer protein (Ttpa−/− mice), a mouse model of genetic vitamin E deficiency, have high bone mass as a result of a decrease in bone resorption. Cell-based assays indicated that α-tocopherol stimulated osteoclast fusion, independent of its antioxidant capacity, by inducing the expression of dendritic-cell–specific transmembrane protein, an essential molecule for osteoclast fusion, through activation of mitogen-activated protein kinase 14 (p38) and microphthalmia-associated transcription factor, as well as its direct recruitment to the Tm7sf4 (a gene encoding DC-STAMP) promoter. Indeed, the bone abnormality seen in Ttpa−/− mice was rescued by a Tm7sf4 transgene. Moreover, wild-type mice or rats fed an α-tocopherol–supplemented diet, which contains a comparable amount of α-tocopherol to supplements consumed by many people, lost bone mass. These results show that serum vitamin E is a determinant of bone mass through its regulation of osteoclast fusion.

α-Tocopherol Transfer Protein Expression in Rat Liver Exposed to Hyperoxia

f -Tochopherol transfer protein ( f TTP), a 32 kDa protein exclusively expressed in liver cytosol, has a high binding affinity for f -tochopherol. The factors that regulate the expression of hepatic f TTP are not clearly understood. In this study, we investigated whether or not exposure to hyperoxia (>95% O 2 for 48 h) could alter the expression of hepatic f TTP. We also examined the association between the expression of antioxidant enzymes (hepatic glutathione peroxidase (GPX) and Mn-superoxide dismutase (Mn-SOD)) and the expression of hepatic f TTP. The levels of thiobarbituric acid-reactive substances (TBARS) in both plasma and liver were significantly higher after rats were exposed to hyperoxia for 48 h when compared with the levels in control rats. Northern blotting showed a decrease in the expression of f TTP messenger RNA (mRNA) after hyperoxia, although the f TTP protein level remained constant. Expression of Mn-SOD mRNA and protein, as well as the expression of GPX mRNA, were stable after hyperoxia. These findings indicate that mRNA for hepatic f TTP, rather than Mn-SOD or GPX, may be highly responsive to oxidative stress.

Severe Vitamin E deficiency exacerbates acute hyperoxic lung injury associated with increased oxidative stress and inflammation

Hyperoxia causes acute lung injury along with an increase of oxidative stress and inflammation. It was hypothesized that vitamin E deficiency might exacerbate acute hyperoxic lung injury. This study used α-tocopherol transfer protein knockout (α-TTP KO) mice fed a vitamin E-deficient diet (KO E(-) mice) as a model of severe vitamin E deficiency. Compared with wild-type (WT) mice, KO E(-) mice showed a significantly lower survival rate during hyperoxia. After 72 h of hyperoxia, KO E(-) mice had more severe histologic lung damage and higher values of the total cell count and the protein content of bronchoalveolar lavage fluid (BALF) than WT mice. IL-6 mRNA expression in lung tissue and the levels of 8-iso-prostaglandin F2α (8-iso-PGF2α) in both lungs and BALF were higher in KO E(-) mice than in WT mice. It was concluded that severe vitamin E deficiency exacerbates acute hyperoxic lung injury associated with increased oxidative stress or inflammation.

Association of Uric Acid with Obesity and Endothelial Dysfunction in Children and Early Adolescents

Background: Hyperuricemia in adults is known to be associated with hypertension, the metabolic syndrome and cardiovascular disease. The purpose of this study was to elucidate the factors associated with hyperuricemia in obese children and early adolescents and to investigate the threshold serum level of uric acid (UA) for the metabolic syndrome in children. Methods: We assessed anthropometric measurements, blood pressure, body composition and biochemical data in 1,559 obese children. To assess endothelial dysfunction, flow-mediated dilatation (FMD) was measured in 92 children. The correlations between serum UA levels and various parameters were examined. The threshold serum UA level for the metabolic syndrome was calculated by receiver-operating characteristic (ROC) curve analysis. Results: Serum UA levels were positively correlated with lipids in both boys and girls, and they were inversely correlated with FMD in the boys but not the girls. The threshold serum UA level for the metabolic syndrome was 5.25 mg/dl in boys and 5.05 mg/dl in girls. However, the specificity and sensitivity of ROC curve analysis are not so striking. Conclusion: The correlation between UA and FMD showed gender differences and might be affected by the hormonal status. The cutoff level of serum UA as a marker of the metabolic syndrome in obese children was affected by both age and gender.

Anorectal and urinary anomalies and aberrant retinoic acid metabolism in cytochrome P450 oxidoreductase deficiency.

CONTEXT Cytochrome P450 oxidoreductase (POR) is an electron donor for all microsomal P450 enzymes including CYP26 involved in inactivation of all-trans retinoic acid (atRA). Although previous studies in Por knockout mice suggest that atRA accumulation is relevant to various posterior organ abnormalities, a systematic analysis has not been performed for anorectal and urinary anomalies in patients with POR deficiency (PORD). OBJECTIVE To report the frequencies of anorectal and urinary anomalies and plasma atRA values in PORD patients. PATIENTS We studied 37 Japanese patients with PORD, consisting of 15 homozygotes for R457H (group A), 15 compound heterozygotes for R457H and one apparently null mutation (group B), and seven patients with other combinations of mutations (group C). Since R457H is a severe hypomorphic mutation, the residual POR function is predicted to be higher in group A than in group B. RESULTS Imperforate anus was observed in four patients (10.8%) and vesicoureteral reflux was found in three patients (8.1%), with no significant difference in the frequencies of such anomalies between groups A and B. In addition, a complex urogenital malformation including penile agenesis was identified in one patient. Plasma atRA values were above the reference range in nine of 12 patients examined, and were similar between groups A and B and between patients with and without anomalies. CONCLUSIONS The results imply that aberrant atRA metabolism due to CYP26 deficiency underlies various anorectal and urinary anomalies in patients with PORD. Clinical phenotypes may be primarily determined by maternal oral retinol intake during pregnancy, and plasma atRA values may be largely influenced by the amount of postnatal oral retinol intake in such patients.

Induction of Apoptosis by γ-Tocotrienol in Human Cancer Cell Lines and Leukemic Blasts From Patients: Dependency on Bid, Cytochrome c, and Caspase Pathway

Tocotrienols (Toc3) have been suggested to possess anticancer effects besides antioxidant and antiinflammatory effects. Previous studies have demonstrated that Toc3 induce apoptosis in epithelial carcinoma. However, the effects of Toc3 on malignant hematopoietic cells have not yet been thoroughly investigated. We investigated Toc3-induced apoptosis in human hematological cancer cell lines. α-, δ-, and γ-Toc3 induced concentration-dependent apoptosis, and γ-Toc3 demonstrated more effective induction than the other Toc3 derivatives in HL-60 cells. γ-Toc3 may have induced apoptosis by activation of the caspase cascade, cytochrome c (Cyt.c) release, Bid cleavage, and mitochondorial membrane depolarization in HL-60, NB-4, Raji, and SY-5Y cells. Furthermore, 10–30 μM γ-Toc3 showed cytotoxicity for leukemic cells from various patients regardless of lymphoblastic, myeloblastic, or relapsed leukemia, but the cytotoxic effect was weak in normal mononuclear cells, interestingly. γ-Toc3 may have a role in cancer prevention and potential for treating hematological malignancies.

Pharmacokinetics of All-trans Retinoic Acid in Pediatric Patients with Leukemia

Since all‐trans retinoic acid (ATRA) induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL), and its effectiveness appears to be related to the plasma or serum level, a pharmacokinetic study of ATRA was undertaken in nine patients with various leukemias. After oral administration at a dose of 30 mg/m2, the time required to reach the peak plasma level of ATRA (20–1198 ng/ml) was between 120 and 240 min and the apparent plasma elimination half life was 21–51 min. In addition, 13‐cis retinoic acid was detected in the plasma of seven patients, indicating the occurrence of ATRA isomerization in vivo. ATRA therapy did not induce complete remission in all patients, even when high plasma levels were achieved. Among the six APL patients given ATRA therapy, one who failed to respond had a very low plasma ATRA level. These findings suggest that it may be useful to monitor plasma levels during oral ATRA therapy in order to achieve an appropriate treatment regimen.

Azacitidine in the treatment of pediatric therapy-related myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation.

We herein present a case of pediatric therapy-related myelodysplastic syndrome (t-MDS) with complex karyotype who was treated with azacitidine (AZA) for AML1-EVI1 fusion transcript as minimal residual disease after allogeneic hematopoietic stem cell transplantation (HSCT). The patient was started on AZA 41 days after the HSCT without having achieved complete remission. After 9 cycles of AZA, the AML1-EVI1 fusion transcript disappeared, and there was no manifestation of graft versus host disease during AZA treatment. Preemptive AZA treatment for minimal residual disease has an acceptable safety profile and appears to be an effective strategy for preventing or substantially delaying hematological relapse in pediatric patients with high-risk myelodysplastic syndrome after HSCT.

The α-tocopherol status and expression of α-tocopherol-related proteins in methionine-choline deficient rats treated with vitamin E

Non-alcoholic fatty liver disease is the most common liver disorder in developed countries, and its incidence is increasing in all population groups. As an antioxidant, vitamin E is effective in the treatment of non-alcoholic fatty liver disease, although the mechanism is still unclear. Methionine-choline deficient Wistar rats (n = 5) used as an experimental model of non-alcoholic fatty liver disease were fed a vitamin E-enriched diet (500 mg/kg) for 4 weeks. The effects were assessed by measuring lipid peroxidation, α-tocopherol levels, and the expression of α-tocopherol-related proteins in the liver. In vitamin E-treated methionine-choline deficient rats, lipid peroxidation was reduced, but liver histopathological changes were not improved. Hepatic α-tocopherol levels in these rats were significantly elevated compared to normal rats treated with vitamin E. Expression of liver α-tocopherol transfer protein in vitamin E-treated methionine-choline deficient rats was significantly repressed compared to methionine-choline deficient rats. The expression of liver cytochrome P450 4F2 and ATP-binding cassette transporter protein 1, involved in metabolism and transport of α-tocopherol, respectively, was significantly repressed in vitamin E-treated methionine-choline deficient rats. In methionine-choline deficient rats, vitamin E treatment altered the hepatic α-tocopherol-related protein expression, which may affect α-tocopherol status in the liver, leading to reduced lipid peroxidation.

Liver X receptor up-regulates α-tocopherol transfer protein expression and α-tocopherol status.

Fat-soluble vitamin E (α-tocopherol) has antioxidant activity. α-Tocopherol transfer protein (α-TTP), a hepatic cytosolic protein, selectively binds α-tocopherol and has an important role regulating circulatory α-tocopherol levels. However, only a few studies have shown the transcriptional regulation of the α-TTP gene. Here, we demonstrate that liver X receptor (LXR) regulates α-TTP expression through direct interaction with the α-TTP gene promoter, and it modulates circulating α-tocopherol levels. LXR belongs to the nuclear receptor superfamily, acts as a ligand-dependent transcription factor for oxysterols and plays an important role in cholesterol metabolism and lipogenesis. We identified an LXR response element (LXRE; DR4, a direct repeat with four-nucleotides spacing) of the human α-TTP gene promoter by using luciferase and electrophoretic mobility shift assays. Mutations in this element abolished activation of this promoter. Moreover, treatment of vitamin E-deficient rats with T0901317, a synthetic LXR ligand, increased α-TTP expression in the liver and cerebrum and increased the plasma α-tocopherol levels. These results indicate that the LXR signaling pathway modulates α-TTP gene expression and plasma α-tocopherol levels. Our observations imply that the LXR signaling pathway might be a useful target for antioxidant properties by controlling the vitamin E status.