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Biomedical subjects

K Hotta

Publications and source records attributed to K Hotta.

At least 37 records · Page 2Linked to original sources

Cell lineage specificity of newly raised monoclonal antibodies against gastric mucins in normal, metaplastic, and neoplastic human tissues and their application to pathology diagnosis.

The specificity of monoclonal antibodies against gastric mucins (designated as HIK1083, PGM 36, and PGM 37) was studied immunohistochemically in normal, metaplastic, and neoplastic human tissues. These antibodies labeled class III mucin-producing cells identified by paradoxical concanavalin A staining in normal stomach, duodenum (Brunner gland), biliary tract, and main pancreatic duct; in mucinous metaplasia of pancreas and gallbladder; and in adenocarcinomas of stomach (90%), bile duct (80%), gallbladder (100%), pancreas (80%), lung (100% of goblet cell type adenocarcinomas), ovary (67% of mucinous carcinomas), and uterine cervix (100% of adenoma malignum tumors). Normal and neoplastic cells of esophagus, colon, salivary gland, kidney, endometrium, breast, prostate, and liver, as well as normal small intestine, lung, and uterine cervix, were all negative. The antibodies used should be valuable for the detection of class III mucin and class III mucin-producing cells in normal, metaplastic, and neoplastic tissues.

Antibodies, Monoclonal↗

Circulating concentrations of the adipocyte protein adiponectin are decreased in parallel with reduced insulin sensitivity during the progression to type 2 diabetes in rhesus monkeys.

Adiponectin is an adipose-specific plasma protein whose plasma concentrations are decreased in obese subjects and type 2 diabetic patients. This protein possesses putative antiatherogenic and anti-inflammatory properties. In the current study, we have analyzed the relationship between adiponectin and insulin resistance in rhesus monkeys (Macaca mulatta), which spontaneously develop obesity and which subsequently frequently progress to overt type 2 diabetes. The plasma levels of adiponectin were decreased in obese and diabetic monkeys as in humans. Prospective longitudinal studies revealed that the plasma levels of adiponectin declined at an early phase of obesity and remained decreased after the development of type 2 diabetes. Hyperinsulinemic-euglycemic clamp studies revealed that the obese monkeys with lower plasma adiponectin showed significantly lower insulin-stimulated peripheral glucose uptake (M rate). The plasma levels of adiponectin were significantly correlated to M rate (r = 0.66, P < 0.001). Longitudinally, the plasma adiponectin decreased in parallel to the progression of insulin resistance. No clear association was found between the plasma levels of adiponectin and its mRNA levels in adipose tissue. These results suggest that reduction in circulating adiponectin may be related to the development of insulin resistance.

Adiponectin↗

PPARgamma ligands increase expression and plasma concentrations of adiponectin, an adipose-derived protein.

Insulin resistance and its dreaded consequence, type 2 diabetes, are major causes of atherosclerosis. Adiponectin is an adipose-specific plasma protein that possesses anti-atherogenic properties, such as the suppression of adhesion molecule expression in vascular endothelial cells and cytokine production from macrophages. Plasma adiponectin concentrations are decreased in obese and type 2 diabetic subjects with insulin resistance. A regimen that normalizes or increases the plasma adiponectin might prevent atherosclerosis in patients with insulin resistance. In this study, we demonstrate the inducing effects of thiazolidinediones (TZDs), which are synthetic PPARgamma ligands, on the expression and secretion of adiponectin in humans and rodents in vivo and in vitro. The administration of TZDs significantly increased the plasma adiponectin concentrations in insulin resistant humans and rodents without affecting their body weight. Adiponectin mRNA expression was normalized or increased by TZDs in the adipose tissues of obese mice. In cultured 3T3-L1 adipocytes, TZD derivatives enhanced the mRNA expression and secretion of adiponectin in a dose- and time-dependent manner. Furthermore, these effects were mediated through the activation of the promoter by the TZDs. On the other hand, TNF-alpha, which is produced more in an insulin-resistant condition, dose-dependently reduced the expression of adiponectin in adipocytes by suppressing its promoter activity. TZDs restored this inhibitory effect by TNF-alpha. TZDs might prevent atherosclerotic vascular disease in insulin-resistant patients by inducing the production of adiponectin through direct effect on its promoter and antagonizing the effect of TNF-alpha on the adiponectin promoter.

3T3 Cells↗

Visceral fat is a major contributor for multiple risk factor clustering in Japanese men with impaired glucose tolerance.

OBJECTIVE: The significance of abdominal visceral fat accumulation was evaluated in Japanese men with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: The IGT subjects (n = 123) were aged 55 +/- 9 years with a BMI of 24 +/- 3 kg/m(2). The 148 control subjects with normal glucose tolerance (NGT) were matched for age and BMI. IGT and NGT were classified according to the 1985 World Health Organization criteria. Abdominal fat distribution was analyzed by computed tomography at umbilical level. Plasma lipid, glucose, and insulin concentrations and blood pressure (BP) were measured. RESULTS: In subjects with IGT, the average visceral fat area (VFA) was significantly greater than in subjects with NGT. Fasting insulin, the sum of insulin concentrations during an oral glucose tolerance test, insulin resistance according to a homeostasis model assessment for insulin resistance (HOMA-IR), systolic BP, and serum triglyceride were significantly higher, whereas the DeltaI(30-0)/DeltaG(30-0) was significantly lower, in subjects with IGT. Subjects with IGT and NGT were then divided into three subgroups according to the number of risk factors they possessed (dyslipidemia, hypertension, neither, or both). In both IGT and NGT subjects, BMI, VFA, subcutaneous fat area, fasting insulin, HOMA-IR, and insulin secretion of the homeostasis model assessment were significantly higher in the double-risk factor subgroup than in the no-risk factor subgroup, and VFA was a potent and independent variable in association with the presence of a double risk factor. CONCLUSIONS: Visceral fat accumulation is a major contributor for multiple risk factor clustering in Japanese men with IGT and NGT.

Adipose Tissue↗

[Molecular mechanism in the development of the complications associated with obesity--the physiological and pathological role of adipocytokines].

Visceral fat accumulation often accompanies various complications, such as insulin resistance, hypertension, dyslipidemia and atherosclerosis. Adipose tissue has been found to secrete various biologically active adipocytokines including free fatty acids. Accumulation of visceral fat increases the portal free fatty acids concentration to cause insulin resistance and dyslipidemia. Tumor necrosis alpha (TNF alpha) deteriorates insulin resistance in obesity. The levels of plasminogen activator inhibitor(PAI)-1 increase and plasma adiponectin concentration decreases in obesity leading to the development of vascular disease. The finding of genes specifically expressed in visceral fat and new adipocytokines should facilitate clarification of the mechanism for the development and complications of visceral fat accumulation.

Adipocytes↗

Catalysis of decarboxylation by a preorganized heterogeneous microenvironment: crystal structures of abzyme 21D8.

Antibody 21D8 catalyzes the solvent-sensitive decarboxylation of 3-carboxybenzisoxazoles. The crystal structure of chimeric Fab 21D8 with and without hapten at 1.61 A and 2.10 A, respectively, together with computational analysis, shows how a melange of polar and non-polar sites are exploited to achieve both substrate binding and acceleration of a reaction normally facilitated by purely aprotic dipolar media. The striking similarity of the decarboxylase and a series of unrelated esterase antibodies also highlights the chemical versatility of structurally conserved anion binding sites and the relatively subtle changes involved in fine-tuning the immunoglobulin pocket for recognition of different ligands and catalysis of different reactions.

Amino Acid Sequence↗

Adiponectin, an adipocyte-derived plasma protein, inhibits endothelial NF-kappaB signaling through a cAMP-dependent pathway.

BACKGROUND: Among the many adipocyte-derived endocrine factors, we found an adipocyte-derived plasma protein, adiponectin, that was decreased in obesity. We recently demonstrated that adiponectin inhibited tumor necrosis factor-alpha (TNF-alpha)-induced expression of endothelial adhesion molecules and that plasma adiponectin level was reduced in patients with coronary artery disease (CIRCULATION: 1999;100:2473-2476). However, the intracellular signal by which adiponectin suppressed adhesion molecule expression was not elucidated. The present study investigated the mechanism of modulation for endothelial function by adiponectin. METHODS AND RESULTS: The interaction between adiponectin and human aortic endothelial cells (HAECs) was estimated by cell ELISA using biotinylated adiponectin. HAECs were preincubated for 18 hours with 50 microg/mL of adiponectin, then exposed to TNF-alpha (10 U/mL) or vehicle for the times indicated. NF-kappaB-DNA binding activity was determined by electrophoretic mobility shift assays. TNF-alpha-inducible phosphorylation signals were detected by immunoblotting. Adiponectin specifically bound to HAECs in a saturable manner and inhibited TNF-alpha-induced mRNA expression of monocyte adhesion molecules without affecting the interaction between TNF-alpha and its receptors. Adiponectin suppressed TNF-alpha-induced IkappaB-alpha phosphorylation and subsequent NF-kappaB activation without affecting other TNF-alpha-mediated phosphorylation signals, including Jun N-terminal kinase, p38 kinase, and Akt kinase. This inhibitory effect of adiponectin is accompanied by cAMP accumulation and is blocked by either adenylate cyclase inhibitor or protein kinase A (PKA) inhibitor. CONCLUSIONS: These observations raise the possibility that adiponectin, which is naturally present in the blood stream, modulates the inflammatory response of endothelial cells through cross talk between cAMP-PKA and NF-kappaB signaling pathways.

Adenylyl Cyclase Inhibitors↗

Characterization of Brachyury-downstream notochord genes in the Ciona intestinalis embryo.

The notochord has two major roles during chordate embryogenesis, as a source of inductive signals for the patterning of neural tube and paraxial mesoderm and as a supportive organ of the larval tail. Despite the recent identification of mutations that affect the notochord development in vertebrate embryos, little is known about genes that are expressed in the differentiating notochord itself. In the urochordate ascidian Ciona intestinalis, Brachyury (Ci-Bra) plays a key role in notochord differentiation. In a previous study, we isolated cDNA clones for nearly 40 potential Ci-Bra target genes that are expressed in notochord cells (H. Takahashi et al., 1999, Genes Dev. 13, 1519-1523). Here we characterized 20 of them by determining the complete nucleotide sequences of the cDNAs. These genes encode a broad spectrum of divergent proteins associated with notochord formation and function. Two genes encode ascidian homologs of the Drosophila Prickle LIM domain proteins and another encodes the ERM protein, all 3 of which appear to be involved in the control of cytoskeletal architecture. In addition, genes for netrin, leprecan, cdc45, ATP:citrate lyase, ATP sulfurylase/APS kinase, protein tyrosine phosphatase, beta4-galactosyltransferase, fibrinogen-like protein, divergent tropomyosin-like proteins, and Drosophila Pellino-like protein were identified. The observation of the netrin gene expression in the notochord may provide the first molecular evidence that the ascidian notochord is a source of signals as in vertebrates. In addition, the present information should be used to identify nonchordate deuterostome tissues homologous to the notochord as well as genes which are expressed in the notochord cells of vertebrate embryos.

Amino Acid Sequence↗

Aquaporin adipose, a putative glycerol channel in adipocytes.

Adipose tissue is a major site of glycerol production in response to energy balance. However, molecular basis of glycerol release from adipocytes has not yet been elucidated. We recently cloned a novel member of the aquaporin family, aquaporin adipose (AQPap), which has glycerol permeability. The current study was designed to examine the hypothesis that AQPap serves as a glycerol channel in adipocytes. Adipose tissue expressed AQPap mRNA in high abundance, but not the mRNAs for the other aquaglyceroporins, AQP3 and AQP9, indicating that AQPap is the only known aquaglyceroporin expressed in adipose tissue. Glycerol release from 3T3-L1 cells was increased during differentiation in parallel with AQPap mRNA levels and suppressed by mercury ion, which inhibits the function of AQPs, supporting AQPap functions as a glycerol channel in adipocytes. Fasting increased and refeeding suppressed adipose AQPap mRNA levels in accordance with plasma glycerol levels and oppositely to plasma insulin levels in mice. Insulin dose-dependently suppressed AQPap mRNA expression in 3T3-L1 cells. AQPap mRNA levels and adipose glycerol concentrations measured by the microdialysis technique were increased in obese mice with insulin resistance. Accordingly, negative regulation of AQPap expression by insulin was impaired in the insulin-resistant state. Exposure of epinephrine translocated AQPap protein from perinuclear cytoplasm to the plasma membrane in 3T3-L1 adipocytes. These results strongly suggest that AQPap plays an important role in glycerol release from adipocytes.

3T3 Cells↗

Hepatocyte growth factor region specifically activates mucin synthesis in rat stomach.

We investigated the effects of hepatocyte growth factor (HGF) on mucin biosynthesis and the expression of its receptor in distinct sites and layers of rat gastric mucosa. HGF stimulated the mucin biosynthesis in the surface and gland mucus cells of corpus, but not in the antrum, without its trophic effects. The HGF-receptor mRNA expression was high in the surface and deep corpus mucosa, but low in the antrum. These results demonstrate that HGF has distinct effects on mucin biosynthesis in a specific region of rat stomach, suggesting different regulatory mechanisms underlying the mucus metabolism of distinct mucus-producing cells.

Animals↗

Circulating autoantibodies against purified colonic mucin in ulcerative colitis.

To clarify the role of colonic mucin in the autoimmune process of ulcerative colitis, circulating antibodies against human colonic mucin were investigated. Purified colonic mucin, obtained from human colonic mucosa by gel filtration, using a Bio-Gel A-1.5-m column and CsCl equilibrium density gradient, was divided into soluble mucin (S-mucin) secreted extracellularly and membranous mucin (M-mucin) binding to cell membrane. Sodium dodecylsulfate polyacrylamide gel electrophoresis and Western blotting analysis showed that antibodies in the serum samples of some patients with ulcerative colitis recognized purified S- and M-mucin of >180-kD. By enzyme-linked immunosorbent assay (ELISA), anti-mucin antibodies were detected in 11 of 60 patients with ulcerative colitis (18%). In contrast, the antibodies were not detected in 22 patients with Crohn's disease. The titers of antimucin antibodies against S-mucin and M-mucin were not different in each patient. By ELISA using mucin in which the sugar chains were destroyed by neuraminidase or NaIO4 treatment, it was demonstrated that anti-mucin antibodies recognized the epitopes of either the sugar chain or the core protein exposed through destruction of the sugar chains. We then investigated the relationship between anti-mucin antibodies and the patients' clinical features. Anti-mucin antibodies were detected in 6 of 15 patients with chronic continuous type ulcerative colitis (40%) and in 5 of 26 patients with relapsing-remitting type (19%), but there was no antimucin antibody-positive serum in patients who had had only one attack without any relapse. These results suggest that anti-mucin antibodies could be a disease marker for ulcerative colitis and that immunological abnormalities in colonic mucin contribute to the persistence of colonic mucosal inflammation.

Autoantibodies↗

Coexistence of gland mucous cell-type mucin and lysozyme in gastric gland mucous cells.

Class III mucin, identified by paradoxical concanavalin A staining, is confined to gastric gland mucous cells and is an essential component of the gastric surface mucous gel layer. The pretreatment required has hampered the application of this method to electron microscopic studies. Antibody HIK1083 reacts selectively with class III mucins. The present study was undertaken to explore, electron microscopically, the immunoreactivity of the human stomach to HIK1083. We examined normal mucosa from resected human stomachs (five cases; formalin-fixed, paraffin-embedded) and gastric biopsy specimens from patients with early gastric cancer [nine cases; glutaraldehyde- and osmium-fixed, epoxy-embedded (seven cases) and half-strength Karnovsky's solution-fixed, Lowicryl K4M-embedded (two cases)]. Immunostaining with HIK1083 and anti-lysozyme antibody was examined under light and electron microscopes. Gland mucous cells were labeled with HIK1083, and lysozyme was detected in some gland mucous cells and surface mucous cells. Electron microscopically, the secretory granules of gland mucous cells contained a single electron-dense core. HIK1083-positive mucins and lysozyme coexisted in the secretory granules of gastric gland mucous cells. HIK1083-reactive mucins and lysozyme were distributed in the matrix and in the dense core of these secretory granules, respectively. HIK1083 can be used for electron immunohistochemistry.

Antibodies↗

The mucin biosynthesis stimulated by epidermal growth factor occurs in surface mucus cells, but not in gland mucus cells, of rat stomach.

Although epidermal growth factor (EGF) accelerates gastric mucin biosynthesis, information on whether its activation is limited to the specific mucus-producing cells is lacking. In this paper, we investigated the effects of EGF on mucin biosynthesis and the expression of its receptor in distinct layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). EGF enhanced the incorporation of [3H]glucosamine and [14C]threonine into the mucin in the full-thickness tissues of the gastric mucosa. This stimulation disappeared on the removal treatment of the surface mucosal layer chiefly consisting of surface mucus cells. The EGF-induced increase in [3H]-labeled mucin in the full-thickness mucosa was not suppressed by either NG-nitro-L-arginine (10(-5) M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (10(-5) M). The EGF-receptor-mRNA expression was high in the surface mucosal layer but low in the deep and muscle layers of the stomach. These results suggest that EGF-induced stimulation of mucin biosynthesis is limited to the surface mucus cells of the rat gastric mucosa and is independent of the NO pathway.

Animals↗

Effects of rabbit gastrointestinal mucins and dextran on hydrochloride diffusion in vitro.

We compared a viscous fingering formation of hydrochloric acid (HCl) in rabbit corpus, antral and duodenal mucins and with dextran under neutral and acidic conditions with respect to relative viscosity, molecular mass, and carbohydrate composition. The effect of desialyzation of duodenal mucin on the viscous fingering formation of HCl was also examined. HCl (0.1 N) was injected into 1% solutions of mucins and dextran and a subsequent viscous fingering formation was assessed based on an influx volume rate of HCl. A low influx volume rate indicates a high ability of the solutions to produce viscous fingers. The influx volume rate of HCl was lowest in duodenal mucin followed bl corpus mucin, antral mucin, and dextran at pH 7. The influx volume rate of HCl was inversely correlated with the relative viscosity of the solution. Maximum molecular masses were large in the order of corpus, antral, and duodenal mucins, and they were larger than dextran T2000. Rabbit gastrointestinal mucins were very polydisperse system. Duodenal mucin contains more sialic acid than gastric mucins; the influx volume rate of HCl increased in desialylated duodenal mucin. It is suggested that the higher ability of gastric mucins to prevent HCl diffusion than dextran were due to the differences in the molecular mass. The ability of duodenal mucin to prevent HCl diffusion was probably attributed to its high sialic acid content, which may reflect a physiological role of duodenal mucin in the duodenum that has to deal with HCl influx from the stomach.

Animals↗

Colonic mucin-carbohydrate components in colorectal tumors and their possible relationship to MUC2, p53 and DCC immunoreactivities.

To clarify changes in mucus components during colorectal tumorigenesis, we developed novel monoclonal antibodies (Abs) against carbohydrate chains of human colorectal mucin (HCM) obtained from normal sigmoid and rectal mucosae. A hundred and ninety-nine cases of colorectal carcinoma and 67 cases of tubular adenoma, along with 250 normal colonic tissue samples, were investigated immunohistochemically. The results were compared with clinical stage, survival and MUC2 (core protein of the intestinal type mucin) expression, as well as with the status of the p53 and DCC (deleted in colorectal carcinomas) genes. In the normal colonic epithelium, HCM14 Ab reacted with the cytoplasmic regions of the goblet cells and enterocytes, while HCM21 Ab bound to mucous droplets in the former, suggesting a more mature carbohydrate structure. Both HCM14 and 21 scores were significantly decreased in adenomas and carcinomas. This is in line with an altered PAS-Alcian blue staining, indicating accumulation of mucins with incomplete or abnormal glycosylation in tumors. Levels of HCM14 and 21 binding tended to show a positive correlation with expression of MUC2 and DCC, and a negative association with p53 protein accumulation in carcinomas, although there was no apparent link to Duke's stage or the prognostic outcome. These findings suggest a possible involvement of alterations in mucin carbohydrate in colorectal tumor development. The observed changes may be associated with loss of MUC2 and DCC expression, as well as with p53 protein accumulation.

Adenocarcinoma↗

Expression of N-acetylglucosamine residues in developing rat fundic gland cells.

The development of rat fundic gland was studied by immunohistochemistry using a recently developed monoclonal antibody, HIK 1083, at both light and electron microscope levels. Antibody HIK 1083 recognized oligosaccharides with a non-reducing terminal alpha-linked N-acetylglucosamine (GlcNAc) residue. In the developing rat fundic gland, cells expressing alpha-GlcNAc residues were discernible from day 19.5 of gestation and continued to exist till adult. The distribution of the alpha-GlcNAc expressing cells was consistent with that described previously for cells reacting to Griffonia simplicifolia lectin (GSA-II) in all developmental stages. These cells were located at the bottom of the fundic gland when they first appeared. With the elongation and maturation of the gland, these cells moved upwards and were finally restricted in the neck region of the gland. Combining previous reports and the present electron microscopical observations, HIK 1083-positive cells in the adult rat fundic gland are mucous neck cells. The interaction between antibody HIK 1083 and GSA-II lectin was investigated. GSA-II prevented the subsequent binding of HIK 1083, while HIK 1083 did not prevent GSA-II binding to mucous neck cells. Our results suggested that alpha-GlcNAc residues exist in rat fundic gland from day 19.5 of gestation and continue to exist till adult. Cells expressing alpha-GlcNAc residues appeared as typical mucous neck cells from postnatal four weeks.

Acetylglucosamine↗

Effects of ecabet sodium, a novel gastroprotective agent, on mucin metabolism in rat gastric mucosa.

The effects of ecabet sodium (ecabet), 12-sulfodehydroabietic acid monosodium salt, on gastric mucin biosynthesis in rat antrum were compared with those in the corpus. Intragastric administration of ecabet significantly increased [3H]glucosamine incorporation into antral mucin as well as into corpus mucin during five successive hours of organ culture. In contrast, mucin biosynthesis in either antrum or corpus was not susceptible to the addition of ecabet to the culture medium. Ecabet-induced stimulation of prostaglandin E2 production in the antrum was essentially the same as that seen in the corpus. In antrum treated with 100 mg/kg ecabet, immunoreactivity with three distinct anti-mucin monoclonal antibodies was found not only in the specific mucus-producing cells, but also in the secreted mucus present at the surface gel layer. These results suggest that ecabet enhances the mucin metabolism, and this stimulation occurs in both the corpus and antrum, suggesting that ecabet might be a useful tool for the further clarification of the regulatory mechanism of antral mucin synthesis.

Abietanes↗

Genomic structure and mutations in adipose-specific gene, adiponectin.

BACKGROUND: Adiponectin is a collagen-like plasma protein specifically synthesized in adipose tissue. Plasma adiponectin concentrations are decreased in obesity whereas it is adipose-specific. OBJECTIVE: To clarify the significance of the genetic variations in adiponectin gene on its plasma concentrations and obesity. SUBJECTS: Two hundred and nineteen unrelated adult Japanese subjects (123 men and 96 women, age: 20-83 y, BMI: 16-43 kg/m2) including 77 obese subjects (BMI>26.4 kg/m2). MEASUREMENT: Human adiponectin gene was isolated from PAC DNA pools. Mutations in the adiponectin gene were screened by direct sequencing or restriction-fragment polymorphism. The levels of plasma adiponectin were determined by the enzyme-linked immunosorbent assay (ELISA). RESULTS: Adiponectin gene spanned 17 kb on chromosome 3q27, consisting of three exons and two introns. Within 2.1 kb of the 5'-flanking region, there were two octamer elements present in the promoter of adipsin. Two nucleotide changes were identified. One was a polymorphism (G/T) occurring in exon 2, and the other was a missense mutation (R112C) in exon 3. The mean plasma adiponectin levels of the subjects carrying G allele were low (G/G: 4.5 microg/ml; G/T: 5.9 microg/ml; and T/T: 6.3 microg/ml), but were not statistically significant. The allelic frequency between the obese and the non-obese showed no significant difference. The subject carrying R112C mutation showed markedly low concentration of plasma adiponectin. CONCLUSION: Two nucleotide changes have been identified in the adiponectin gene. G/T polymorphism in exon 2 was associated with neither plasma adiponectin concentrations nor the presence of obesity. A subject carrying missense mutation (R112C) showed markedly low plasma adiponectin concentration.

Adipocytes↗