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H Kadowaki

Publications and source records attributed to H Kadowaki.

At least 55 records · Page 3Linked to original sources
PubMed1995

Relationship of membrane phospholipid composition, lactosylceramide molecular species, and the specificity of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase to the molecular species composition of GM3 ganglioside.

The ceramide molecular species specificity of rat brain neuron CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase (LacCer alpha 2,3-ST) was determined using 19 molecular species of lactosylceramide incorporated into liposomes prepared with purified rat brain phospholipids. The neuron enzyme displayed a distinct molecular species specificity (which was different than the specificity of liver LacCer alpha 2,3-ST) based on both the long-chain base and the fatty acid composition of the lactosylceramide. Specifically, compared to the liver enzyme, relatively high activities were obtained with d18:1-16:0, d18:1-22:1, and d18:0-18:0 lactosylceramide molecular species. When the lipid composition of the neuron microsomal membranes was altered to resemble that of rat liver Golgi membrane lipids, the activities towards d18:1-16:0, d18:1-22:1, and d18:0-18:0 lactosylceramide molecular species were significantly (P < 0.01) reduced and the molecular species specificity of the neuron enzyme resembled that of liver LacCer alpha 2,3-ST. In the reciprocal experiment in which the lipid composition of the rat liver Golgi membranes was altered to resemble neuron microsomal membrane lipids, the molecular species specificity of liver LacCer alpha 2,3-ST was virtually identical to the specificity obtained with the native neuron enzyme. Analysis of the molecular species composition of lactosylceramide and GM3 in rat liver Golgi membranes revealed that the molecular species composition of rat liver Golgi membrane GM3 was precisely what would be expected based on the molecular species specificity of LacCer alpha 2,3-ST and the molecular species composition of lactosylceramide in the Golgi membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Molecular scanning of the glycogen synthase and insulin receptor substrate-1 genes in Japanese subjects with non-insulin-dependent diabetes mellitus.

We studied a simple tandem repeat DNA polymorphism in the glycogen synthase gene and polymorphisms at codon 513 (Ala-->Pro) and 972 (Gly-->Arg) in the insulin receptor substrate-1 (IRS-1) gene in 197 non-insulin-dependent diabetes mellitus (NIDDM) and 178 control subjects in Japan. Eight alleles (-3G, -2G, -1G, 0G, 1G, 2G, 3G, and 4G) were identified in the tandem repeat polymorphism in the glycogen synthase gene. No difference in the frequencies of these alleles was found between diabetics and controls. The codon 972 polymorphism of IRS-1 gene was observed in 7 diabetics (3.6%) and 8 controls (4.5%), whereas the codon 513 polymorphism was not found in either of the two groups. We conclude that the tandem repeat polymorphism in the glycogen synthase gene and the polymorphisms at codons 513 and 972 of the IRS-1 gene are not associated with a higher risk for the development of NIDDM in Japanese subjects.

Alanine↗
PubMed1994

Mechanism of GM3 ganglioside synthesis. Kinetic study of rat liver CMP-N-neuraminate:lactosylceramide alpha 2,3-sialyltransferase employing 19 molecular species of lactosylceramide.

The apparent Km and Vmax of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase (LacCer-alpha 2,3-ST) for lactosylceramide and CMP-N-acetylneuraminic acid were determined using 19 molecular species of lactosylceramide. The Km for lactosylceramide varied 6-fold among these molecular species of lactosylceramide, but there was a poor correlation between the Km for a particular molecular species and the activity of Lac-Cer alpha 2,3-ST for that molecular species. The Km for CMP-N-acetylneuraminic acid also varied depending on the molecular species of lactosylceramide used as substrate, and there was a good correlation between the Km of Lac-Cer alpha 2,3-ST for CMP-N-acetylneuraminic acid and the activity of the enzyme. Kinetic studies indicate that the reaction mechanism of LacCer alpha 2,3-ST is a sequential, Ordered Bi Bi system. From considerations of the effects of the structure of the lactosylceramide molecular species on the Vmax and Km for CMP-N-acetylneuraminic acid, it is likely that LacCer alpha 2,3-ST first binds lactosylceramide and then CMP-N-acetylneuraminic acid and that the rate-limiting step in the reaction is the release of the product GM3.

Animals↗
PubMed1994

A subtype of diabetes mellitus associated with a mutation of mitochondrial DNA.

BACKGROUND: Several families have been described in which a mutation of mitochondrial DNA, the substitution of guanine for adenine (A-->G) at position 3243 of leucine transfer RNA, is associated with diabetes mellitus and deafness. The prevalence, clinical features, and pathophysiology of diabetes with this mutation are largely undefined. METHODS: We studied 55 patients with insulin-dependent diabetes mellitus (IDDM) and a family history of diabetes (group 1), 85 patients with IDDM and no family history of diabetes (group 2), 100 patients with non-insulin-dependent diabetes mellitus (NIDDM) and a family history of diabetes (group 3), and 5 patients with diabetes and deafness (group 4) for the mutation. We also studied the prevalence and characteristics of diabetes in 39 patients with a syndrome consisting of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes who were known to have the mutation and 127 of their relatives (group 5). RESULTS: We identified 16 unrelated patients with diabetes associated with the A-->G mutation: 3 patients from group 1 (6 percent), 2 patients from group 3 (2 percent), 3 patients from group 4 (60 percent), and 8 patients from group 5 (21 percent). We also identified 16 additional subjects who had diabetes and the mutation among 42 relatives of the patients with diabetes and the mutation in groups 1, 2, 3, and 4 and 20 affected subjects among the 127 relatives of the patients in group 5. Diabetes cosegregated with the mutation in a fashion consistent with maternal transmission, was frequently (in 61 percent of cases) associated with sensory hearing loss, and was generally accompanied by impaired insulin secretion. CONCLUSIONS: Diabetes mellitus associated with the A-->G mutation at position 3243 of mitochondrial leucine transfer RNA represents a subtype of diabetes found in both patients with IDDM and patients with NIDDM in Japan.

Adolescent↗
PubMed1994

Preparation of defined molecular species of lactosylceramide by chemical deacylation and reacylation with N-succinimidyl fatty acid esters.

A procedure for the preparation of specific molecular species of D-erythro-lactosylceramide involving deacylation and reacylation of lactosylceramide prepared from bovine brain gangliosides is described. Lactosylceramide was N-deacylated by alkaline hydrolysis and the resulting four lysolactosylceramides, which contained d18:1, d20:1, d18:0 and d20:0 long-chain bases, were simultaneously re-N-acylated with the N-succinimidyl ester of either 16:0, 18:0, 20:0, 22:0, 24:0, 20:1, 22:1 or 24:1 fatty acid. The resulting lactosylceramide contained four molecular species of lactosylceramides, i.e., d18:1, d20:1, d18:0 and d20:0 long-chain bases coupled with the fatty acid that was introduced. Lactosylceramides prepared in this manner were separated into four individual molecular species by high-performance liquid chromatography (HPLC). Each of the purified molecular species of lactosylceramide was quantitated by HPLC after derivatization with benzoylchloride and was characterized by mass spectrometry. The yields of reacylated lactosylceramide were 38-58% relative to the starting lactosylceramide; the purity of each of the molecular species of lactosylceramide was greater than 95%.

Acetylation↗
PubMed1994

The high prevalence of the diabetic patients with a mutation in the mitochondrial gene in Japan.

Recently, an A to G transition at position 3243 in transfer ribonucleic acidLeu(UUR) [the 3243 base-pair (bp) mutation] originally found in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes has been identified in patients with diabetes and deafness. To determine the prevalence of the diabetic patients with this mutation in Japan, we screened 550 randomly selected cohorts of diabetic patients without prior information about clinical features such as type of diabetes, family history of diabetes, age of onset, and mode of therapy. We have identified 5 patients with this mutation, suggesting that approximately 0.9% of diabetic patients have the 3243 bp mutation. However, there were no subjects with this mutation in 250 controls with normal glucose tolerance. The percentage of mutant DNA in whole mitochondrial DNA did not correlate to the degree of symptoms. We conclude that the 3243 bp mutation in the mitochondrial gene plays an important part as a cause of diabetes in Japan.

Adolescent↗
PubMed1994

Analysis of the glucokinase gene promoter in Japanese subjects with noninsulin-dependent diabetes mellitus.

Glucokinase plays an important role in glucose metabolism in pancreatic beta-cells and liver. Recently, several mutations responsible for noninsulin-dependent diabetes mellitus (NIDDM) have been identified within the coding regions of the glucokinase gene. We screened the promoter regions using polymerase chain reaction followed by single strand conformation polymorphisms in 240 Japanese NIDDM and 111 control subjects. In the beta-cell promoter, two kinds of sequence variations were detected. One variation, in which 2 nucleotides at position -282 (C-->T) plus -194 (A-->G) were changed simultaneously, was found in 23 NIDDM (9.6%) and 12 control (10.8%) subjects. The other variation [e.g. -30 (G-->A)] was identified in 87 NIDDM (36.3%) and 40 control (36.0%) subjects. In the liver promoter, in addition to the -603 (G-->T) substitution in 1 NIDDM (0.4%) and 2 control (1.8%) subjects, the -120 (G-->T) substitution in 1 control (0.9%) subject was found. However, there were no differences in these allele frequencies between NIDDM and control subjects. We conclude that the prevalence of mutations in the promoter of the glucokinase gene responsible for NIDDM is rare among Japanese patients.

Adolescent↗
PubMed1994

Effect of Golgi membrane phospholipid composition on the molecular species of GM3 gangliosides synthesized by rat liver sialyltransferase.

Previous studies have demonstrated that there is a change in the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase (LacCer alpha 2,3-ST) when the lipid composition of the Golgi membrane is altered (Kadowaki, Grant, and Williams, 1993. J. Lipid Res. 34: 905-914). To understand the basis of this phenomenon, the molecular species specificity of rat liver LacCer alpha 2,3-ST was determined under conditions in which the phospholipid class composition of the Golgi membrane was changed to resemble that of cultured mouse neuroblastoma NB2a cells, a cell line in which LacCer alpha 2,3-ST exhibits no molecular species specificity. The change in the lipid composition of the Golgi membrane was accomplished by incubating the Golgi membrane vesicles with nonspecific lipid transfer protein and a 10-fold excess of liposomes prepared with various proportions of purified rat liver lipids. The molecular species specificity of LacCer alpha 2,3-ST was also determined under conditions where the phospholipid molecular species composition but not the phospholipid class composition of the Golgi membrane was changed, and in which both the phospholipid class and molecular species compositions were changed by using liposomes prepared with lipids purified from a mouse brain tumor (ependymoblastoma). When using liposomes prepared with rat liver lipids, a change in the phospholipid class composition of the Golgi membrane to a composition similar to that of NB2a cells increased rather than decreased the molecular species specificity of rat liver LacCer alpha 2,3-ST.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[HAIR-AN syndrome].

Many clinical observations have suggested that there is a strong relationship between hyperinsulinemia and hyperandrogenism. HAIR-AN syndrome is defined as a constellation of hyperandrogenism (HA), insulin resistance (IR), and acanthosis nigricans (AN). Two major mechanisms could account for this syndrome: (i) hyperinsulinemia induced by insulin resistance causes hyperandrogenism, and (ii) hyperandrogenism causes insulin resistance and hyperinsulinemia. Acanthosis nigricans is considered to be an epiphenomenon caused by hyperinsulinemia. The causes of HAIR-AN syndrome include syndromes of extreme insulin resistance due to mutations in the insulin receptor gene, lipoatrophic diabetes, obesity, some endocrinopathies, and genetic and acquired ovarian hyperandrogenism.

Acanthosis Nigricans↗
PubMed1993

Esophagitis in infants with hypertrophic pyloric stenosis: a source of hematemesis.

This study was undertaken to clarify the source of blood in the vomitus of patients with hypertrophic pyloric stenosis (HPS). Twenty-one infants with HPS were examined. Hematemesis was noted in 14 infants. Esophagogastric endoscopy showed a 100% incidence of esophagitis and in one patient gastric erosion was also observed. Histological study of the esophageal mucosa showed evidence of esophagitis in 18 patients (85.7%). Preoperative pH monitoring showed gastroesophageal reflux (GER) in all infants. Excessive acid exposure (> or = 7%) was significantly correlated with the grade of esophagitis and the incidence of hematemesis, whereas acid exposure time was shorter in the cases without histological esophagitis. These results suggested that the source of bleeding in HPS is the esophageal mucosa affected by esophagitis secondary to excessive acid reflux. Although there is obvious massive gastroesophageal reflux in HPS, it is too difficult to evaluate the lower esophageal sphincter function in HPS.

Esophagitis, Peptic↗
PubMed1993

Sequence variations of the glucokinase gene in Japanese subjects with NIDDM.

Mutations in the glucokinase gene have been identified recently in patients with maturity-onset diabetes of the young, a subtype of NIDDM. The proposed role of glucokinase as a glucose sensor, combined with the low insulin response to glucose found in most Japanese with NIDDM, prompted us to speculate that mutations in the glucokinase gene might be one of the major causes of NIDDM in Japanese subjects. To determine the prevalence of mutations and sequence variations in the glucokinase gene, we screened all 12 exons of the glucokinase gene, including exon/intron junctions, by polymerase chain reaction followed by single-strand conformation polymorphism in 209 Japanese NIDDM subjects. In addition to the mutation in exon 7, which substituted Arg (AGG) for Gly (GGG) at codon 261 (10), a silent mutation of Pro (CCC-->CCG) in exon 4 at codon 145 and several new sequence variations in intervening sequences and the 5'-untranslated region of exon 1 beta (beta-cell-specific exon 1) were identified. Because we identified only one subject who had a structurally abnormal glucokinase molecule, we conclude that the prevalence of structural mutations in the glucokinase gene responsible for NIDDM appears to be rare among Japanese patients. To our knowledge, this is the first thorough study describing the ethnic prevalence of mutations and sequence variations in the glucokinase gene in NIDDM.

Adolescent↗
PubMed1993

Effect of membrane lipids on the lactosylceramide molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide sialyltransferase.

It has previously been shown that when the molecular species specificity of rat liver Golgi CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase was determined, using as the substrate lactosylceramide (LacCer) incorporated into liposomes prepared with rat liver Golgi lipids, the enzyme showed a pronounced variation in activity towards the various molecular species of LacCer (J. Lipid Res. 1989. 30: 1789-1797). In this paper, -the LacCer molecular species specificity of sialyltransferase from neuroblastoma NB2a cells was examined using five naturally occurring and three synthetic molecular species of LacCer. The enzyme activity was determined by following the formation of [14C]GM3 from CMP-[14C]neuraminic acid and individual molecular species of LacCer incorporated into liposomes. Nonspecific lipid transfer protein was included in the enzyme assay to facilitate the transfer of LacCer and other lipids between the liposomes and the membrane where sialyltransferase is located. In these enzyme assays the liposomes contained approximately 10 times more lipid phosphorus than either the microsomal fraction of NB2a cells or the Golgi fraction of rat liver. Thus, in the presence of nonspecific lipid transfer protein, the lipid composition of the membrane where sialyltransferase is located was modified to resemble the lipid composition of the liposomes. When the molecular species specificity of NB2a cell sialyltransferase was determined with LacCer incorporated into liposomes prepared with NB2a cell lipids, the enzyme showed no specificity towards the various molecular species of LacCer. However, when the molecular species specificity of NB2a cell sialyltransferase was determined with LacCer incorporated into liposomes prepared with rat liver Golgi lipids, the enzyme showed a variation in activity towards the various LacCer molecular species similar to that observed with the liver Golgi enzyme using liposomes prepared with liver Golgi lipids. Likewise, when the molecular species specificity of rat liver Golgi sialyltransferase was determined with LacCer incorporated into liposomes prepared with NB2a cell lipids, the liver enzyme then showed no specificity towards the various molecular species of LacCer. These results indicate that the lipid environment of the membrane can alter the molecular species specificity of sialyltransferase towards its lipid substrate, LacCer.

Animals↗
PubMed1993

Effect of phosphatidylcholine molecular species on the uptake of HDL triglycerides and cholesteryl esters by the liver.

It has previously been shown that the hydrolysis of high density lipoprotein (HDL) phospholipids by hepatic lipase promotes the hepatic uptake of triglyceride and cholesteryl ester from HDL. Since the hydrolysis of HDL phospholipids promotes HDL cholesteryl ester uptake, then it is possible that the hepatic metabolism of HDL could be altered by changing the molecular species composition of HDL phosphatidylcholine (PC) (the major phospholipid in HDL). To test this possibility the uptake of [3H]triolein and [14C]cholesteryl oleate by the isolated perfused rat liver was determined in a nonrecirculating perfusion system following a bolus injection of reconstituted HDL (rHDL) prepared with rat serum HDL apolipoproteins, [3H]triolein, [14C]cholesteryl oleate, unesterified cholesterol, and one of five molecular species of phosphatidylcholine (16:0-18:2, 16:1-16:1, 18:0-18:2, 18:1-16:0, or 20:1-20:1), 18:1-16:0 phosphatidylcholine diether, or the total phosphatidylcholine fraction isolated from rat serum HDL. The apolipoprotein profiles and lipid compositions of all the rHDL were similar. The greatest uptake of [3H]triolein was obtained with the rHDL prepared with 16:0-18:2 phosphatidylcholine. The amount of [3H]triolein taken up by the liver when the rHDL were prepared with 16:1-16:1, 18:0-18:2, 18:1-16:0, 20:1-20:1, 18:1-16:0 phosphatidylcholine diether, or rat serum HDL phosphatidylcholine was 56.7%, 51.7, 39.9%, 27.6%, 31.8%, and 84.7%, respectively, of the amount taken up from the rHDL prepared with 16:0-18:2 phosphatidylcholine. Likewise, the greatest amount of [14C]cholesteryl oleate was taken up by the liver when the rHDL was prepared with 16:0-18:2 phosphatidylcholine and the variation in [14C]cholesteryl oleate uptake from the various rHDL displayed a pattern of dependence on the phosphatidylcholine molecular species of rHDL similar to triolein uptake. The variation in the rate of rHDL phosphatidylcholine hydrolysis by hepatic lipase in vitro as a function of the PC molecular species composition of the rHDL also resembled the variation in the hepatic uptake of [14C]cholesteryl oleate and [3H]triolein. Partial substitution of rHDL phosphatidylcholine with the minor phospholipids isolated from rat serum HDL affected neither the hepatic uptake of [3H]triolein or [14C]cholesteryl oleate nor phosphatidylcholine hydrolysis by hepatic lipase in vitro when 16:0-18:2 phosphatidylcholine or rat serum HDL phosphatidylcholine was used to prepare the rHDL. On the other hand, when rHDL was prepared with 20:1-20:1 phosphatidylcholine, the inclusion of the minor phospholipids increased [3H]triolein and [14C]cholesteryl oleate uptake and phosphatidylcholine hydrolysis approximately twofold.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Immunoglobulin heavy chain-binding protein binds to misfolded mutant insulin receptors with mutations in the extracellular domain.

Cell-surface proteins are transported through the endoplasmic reticulum and Golgi apparatus en route to the plasma membrane. Previously, we have identified three point mutations in the insulin receptor gene that impair transport of the mutant receptors to the cell surface: Asn15----Lys, His209----Arg, and Phe382----Val. Furthermore, these mutations impair post-translational processing steps that normally occur as the receptors are transported through the endoplasmic reticulum and Golgi apparatus. In this study, we have demonstrated that the unprocessed Arg209 and Val382 mutant proreceptors are bound to the immunoglobulin heavy chain-binding protein (BiP) in the endoplasmic reticulum. This was demonstrated by the fact that monoclonal anti-BiP antibody coimmunoprecipitated the mutant proreceptors. Moreover, when ATP was added to the immunoprecipitates, the mutant proreceptors were released from BiP. In contrast, neither the normal human insulin receptor nor the Lys15 mutant proreceptor was coimmunoprecipitated by anti-BiP antibody. It seems likely that the Lys15 receptor also binds BiP, but that the affinity was too low to resist dissociation during the stringent washing of the immunoprecipitate. In conclusion, these observation are consistent with the hypothesis that binding to BiP explains the impaired transport of mutant receptors through the endoplasmic reticulum and Golgi apparatus to the plasma membrane.

3T3 Cells↗
PubMed1992

Detection of mutations in the insulin receptor gene in patients with insulin resistance by analysis of single-stranded conformational polymorphisms.

We analyzed single-stranded conformational polymorphisms to screen for mutations and polymorphisms in the insulin receptor gene in subjects with or without insulin resistance. Using this new technique, we demonstrated the existence of mutations in the insulin receptor gene which we had identified previously. In addition, a new mutation was found in exon 20 of the insulin receptor gene in a patient with moderate insulin resistance associated with morbid obesity, acanthosis nigricans, and polycystic ovary syndrome. The patient was heterozygous for a mutation substituting Leu (CTG) for Pro (CCG) at codon 1178. Pro1178 is a part of a characteristic sequence motif (D1150 F1151 G1152---A1177 P1178 E1179) common to many protein kinases. Analysis of single-stranded conformational polymorphisms was also used to estimate the frequency of a polymorphism at codon 1058. The two codons CAC (1058 His) and CAT (1058 His) both had a prevalence of 50% in 30 Japanese subjects. These data demonstrate that analysis of single-stranded conformational polymorphisms is a simple and sensitive screening method for mutations and polymorphisms in the insulin receptor gene in subjects with or without insulin resistance. Identification of a mutation in the insulin receptor gene in a patient with a moderate degree of insulin resistance associated with morbid obesity suggests that insulin receptor mutations may exist in patients with Type 2 (non-insulin-dependent) diabetes mellitus associated with a moderate degree of insulin resistance.

Amino Acid Sequence↗