Biomedical subjects

Naoki Sakane

Publications and source records attributed to Naoki Sakane.

26 records · Page 2Linked to original sources

PubMed2004

Aminopeptidase N/CD13 regulates the fetal liver microenvironment of hematopoiesis.

Fetal liver (FL) hematopoiesis is thought to be important for expanding the cell number during ontogeny. In order to investigate the cellular interaction molecules among FL stromal and hematopoietic cells, we established a monoclonal antibody, Ndk-10, that reacts with FL stromal cells but not with dish non-adherent cells. When Ndk-10 was added to an FL stromal and hematopoietic cell-coculture, it inhibited the survival of c-kit+ cells. The inhibitory activity of Ndk-10 was also observed in the fetal liver organ culture. The Ndk-10 recognized a 150 kD molecule in the adherent cells of FL and kidney, and the N-terminal amino acid sequence was identical to that of mouse aminopeptidase N/CD13. The peptidase activity of CD13 was inhibited by Ndk-10, and addition of its specific inhibitor resulted in the same inhibitory activity as Ndk-10. We propose that aminopeptidase N/CD13 is a critical molecule that regulates the survival of c-kit+ cells in the FL microenvironment.

Animals↗

PubMed2003

The -3826 A-->G variant of the uncoupling protein-1 gene diminishes postprandial thermogenesis after a high fat meal in healthy boys.

This study investigated whether the -3826 A-->G nucleotide variant of the uncoupling protein-1 (UCP1) gene is correlated with postprandial thermogenesis after a high fat meal in children. Healthy boys, aged 8-11 yr, were examined for resting energy expenditure and the thermic effect of a meal (TEM), which were measured by indirect calorimetry for 180 min after a high fat (70% fat, 20% carbohydrate, and 10% protein, providing 30% of the daily energy requirement) and a high carbohydrate meal (20% fat, 70% carbohydrate, and 10% protein). The sympatho-vagal activities were assessed by means of spectral analysis of the heart rate variability during the same period. Children were genotyped for UCP1 polymorphism by applying a PCR-restriction fragment length polymorphism using buccal samples. There was no reaction of sympathetic activity to the high carbohydrate meal in either the GG allele or the AA+AG group and no significant difference in TEM. However, after the high fat meal, sympathetic responses were found in both groups; further, the GG allele group showed significantly lower TEM than the AA+AG group. In conclusion, despite fat-induced sympathetic stimulation, GG allele carriers have a lowered capacity of TEM in response to fat intake, suggesting that such impaired UCP1-linked thermogenesis can have adverse effects on the regulation of body weight.

Adenine↗

PubMed2002

Proinsulin C-peptide activates cAMP response element-binding proteins through the p38 mitogen-activated protein kinase pathway in mouse lung capillary endothelial cells.

Proinsulin C-peptide has been reported to have some biological activities and to be possibly involved in the development of diabetic microangiopathy. In the present study, we examined the effects of C-peptide on the mitogen-activated protein kinase pathway in LEII mouse lung capillary endothelial cells. Stimulation of the cells with C-peptide increased both p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK1/2) activities and activity-related site-specific phosphorylation of the respective kinases in a concentration-dependent manner, but failed to activate c-Jun N-terminal kinase. Stimulation of the cells with C-peptide also induced site-specific phosphorylation of cAMP response element (CRE)-binding protein (CREB)/activating transcription factor 1 (ATF1), and thereby binding of these transcription factors to CRE. Among three CREB kinases tested, phosphorylation of mitogen-activated protein kinase-activated protein kinase 2 (MAPKAP-K2) was induced after stimulation with C-peptide. The phosphorylation of CREB, ATF1 and MAPKAP-K2 were inhibited by SB203580, a p38MAPK inhibitor, but not by PD98059, an ERK kinase inhibitor. These results indicate that C-peptide activates p38MAPK followed by MAPKAP-K2 to enhance DNA-CREB/ATF1 interactions.

Animals↗

PubMed2002

Expression and functional analyses of novel mutations of ATP-binding cassette transporter-1 in Japanese patients with high-density lipoprotein deficiency.

ATP-binding cassette transporter-1 (ABCA1) gene is mutated in patients with familial high-density lipoprotein deficiency (FHD). In order to know the molecular basis for FHD, we characterized three different ABCA1 mutations associated with FHD (G1158A/A255T, C5946T/R1851X, and A5226G/N1611D) with respect to their expression in the passaged fibroblasts from the patients and in the cells transfected with the mutated cDNAs. Fibroblasts from the all patients showed markedly decreased cholesterol efflux to apolipoprotein (apo)-Al. In the fibroblasts homozygous for G1158A/A255T, the immunoreactive mass of ABCA1 could not be detected, even when stimulated by 9-cis-retinoic acid and 22-R-hydroxycholesterol. In the fibroblasts homozygous for C5946T/R1851X, ABCA1 mRNA was comparable. Because the mutant ABCA1 protein (R1851X) was predicted to lack the epitope for the antibody used, we transfected FLAG-tagged truncated mutant (R1851X/ABCA1-FLAG) cDNA into Cos-7 cells, showing that the mutant protein expression was markedly reduced. The expression of N1611D ABCA1 protein was comparable in both fibroblasts and overexpressing cells, although cholesterol efflux from the cells was markedly reduced. These data indicated that, in the three patients investigated, the abnormalities and dysfunction of ABCA1 occurred at the different levels, providing important information about the expression, regulation, and function of ABCA1.

ATP Binding Cassette Transporter 1↗

PubMed2002

(123)I- or (125)I-metaiodobenzylguanidine visualization of brown adipose tissue.

UNLABELLED: (123)I-Metaiodobenzylguanidine (MIBG) accumulations that do not correspond to any tumor are observed occasionally on the medial aspect of the upper back or shoulder of children. The true nature of such accumulations is unknown, and we hypothesized that they represent interscapular brown adipose tissue (IBAT) visualized by scintigraphy. METHODS: Wistar rats (7 wk old) received MIBG labeled with (123)I or (125)I. Autoradiography was performed, and concentrations of the tracer in the interscapular subcutaneous tissue were identified histopathologically. The effects of 6-hydroxydopamine, reserpine, and beta 3-adrenergic receptor agonist (CL316,243) on the accumulation were investigated to elucidate the mechanism of uptake into BAT. RESULTS: Autoradiography showed well-defined distinct accumulation in the subcutaneous tissue on the upper back, and hematoxylin-eosin and anti-uncoupling protein 1 antibody staining confirmed that it was BAT. The percentage injected dose per gram in BAT was as high as that in the heart and was quite different from the concentration in white adipose tissue. Preadministration of 6-hydroxydopamine or reserpine resulted in lower MIBG concentrations in BAT. Activation of the beta 3-adrenergic receptor accelerated the washout of MIBG in BAT and caused an increase in concentration in white adipose tissue. CONCLUSION: MIBG accumulates in the adrenergic nervous system in BAT, and IBAT is distinguished from the surrounding white adipose tissue. To our knowledge, BAT has not been visualized previously. We showed that MIBG scintigraphy might be suitable for the investigation of BAT and treatment of human obesity.

3-Iodobenzylguanidine↗

PubMed2002

Regulation of Lck and Fyn tyrosine kinase activities by transmembrane protein tyrosine phosphatase leukocyte common antigen-related molecule.

Leukocyte common antigen-related molecule (LAR) is a receptor-like protein tyrosine phosphatase (PTPase) with two PTPase domains. In the present study, we detected the expression of LAR in the brain, kidney, and thymus of mice using anti-LAR PTPase domain subunit monoclonal antibody (mAb) YU1. In the thymus, LAR was expressed on CD4(-)CD8(-) and CD4(-)CD8(low) thymocytes. The development of thymocytes in CD45 knockout mice is blocked partially in the maturation of CD4(-)CD8(-) to CD4(+)CD8(+). We postulated that LAR regulates Lck and Fyn in the immature thymocytes. Transfection of wild-type LAR activated extracellular signal-regulated kinase signal transduction pathway in CD45-deficient Jurkat cells stimulated with anti-CD3 mAb. LAR mutants, with Cys to Ser mutation in the catalytic center of PTPase D1, bound to tyrosine-phosphorylated Lck and Fyn, and LAR PTPase domain 2 was tyrosine phosphorylated by Fyn tyrosine kinase. The phosphorylated LAR was associated with Fyn Src homology 2 domain. Moreover, LAR dephosphorylated phosphorylated tyrosine residues in both the COOH terminus and kinase domain of Fyn in vitro. Our results indicate that Lck and Fyn would be substrates of LAR in immature thymocytes and that each LAR PTPase domain plays distinct functional roles in phosphorylation and dephosphorylation.

Amino Acid Motifs↗

PubMedDate not supplied

Risk factors for silent cerebral infarction in the elderly.

BACKGROUND: A silent cerebral infarction (SCI) is often found in the elderly. However, studies on SCIs focusing on an elderly population are sparse. Our objective was to evaluate risk factors of SCIs in healthy elderly individuals. METHODS: One hundred seventy-five neurologically normal community-dwelling Japanese people aged >/=65 years (128 men and 47 women; 77.5 +/- 8.7 years) were studied. Among them we assessed the demographic data and detected SCIs on brain magnetic resonance imaging scans. RESULTS: Eighty four subjects had at least one SCI. Hypertension and low body mass index (BMI) were the significant risks for SCIs in multivariate analysis adjusted for age, sex and other risk factors. Mean BMI in subjects with SCIs was significantly lower than those without SCIs (20.8 +/- 3.2 kg/m(2) vs. 22.1 +/- 3.2 kg/m(2)). In the subgroup analysis by age stratum regarding hypertension and BMI, hypertension was a significant risk factor in subjects aged 65-75 years. Lower BMI had a significant risk in subjects aged >/=81 years. CONCLUSIONS: Hypertension and increasing age have been recognized as risk factors for SCIs, and low BMI might be a significant risk especially in superelderly subjects. Further data with a larger sample size is needed to confirm the relationship between BMI and SCIs among the elderly.

Aged↗

PubMedDate not supplied

Effects of caffeine on the uncoupling protein family in obese yellow KK mice.

1. The hypothesis that caffeine upregulates uncoupling protein (UCP)-1, UCP-2 and UCP-3 expression, which contribute to thermogenesis, was investigated in obese mice. 2. The mRNA levels of UCP-1, -2 and -3 in brown adipose tissue (BAT), UCP-2 in white adipose tissue (WAT), and UCP-2 and -3 in skeletal muscle were measured using real-time quantitative reverse transcription-polymerase chain reaction analysis in obese yellow KK mice 4 h after the subcutaneous administration of either 60 mg/kg caffeine or physiological saline. Plasma free fatty acids, adrenaline, noradrenaline and dopamine levels were also measured. 3. In caffeine-injected obese mice, UCP-1 mRNA levels were significantly increased by 1.5-fold in BAT, UCP-2 mRNA levels were increased by 1.8- and 2.5-fold in BAT and skeletal muscles, respectively, and UCP-3 mRNA levels were increased 1.7- and 3.4-fold in BAT and skeletal muscles, respectively, compared with control mice injected with physiological saline. There was no difference in UCP-2 mRNA levels in WAT between the two groups. 4. Plasma free fatty acids and adrenaline levels were significantly elevated in mice treated with caffeine compared with those injected with physiological saline. 5. It was concluded that caffeine upregulates the expression of UCP-1, UCP-2 and UCP-3 in BAT and UCP-2 and UCP-3 in skeletal muscles, which may contribute to thermogenesis in obese mice.

Adipose Tissue↗