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Y Akanuma

Publications and source records attributed to Y Akanuma.

At least 127 records · Page 7Linked to original sources
PubMed1989

Identification of a phosphorylation site of the rat insulin receptor catalyzed by protein kinase C in an intact cell.

In two-dimensional tryptic phosphopeptide mapping, the beta-subunit of the insulin receptor phosphorylated by 12-O-tetradecanoylphorbol-13-acetate in rat hepatoma cells (H-35) was separated into one phosphothreonine-containing peptide and several phosphoserine-containing peptides. The synthetic peptide coding residues 1327-1343 in the C-terminal region of the rat insulin receptor was phosphorylated at the threonine residue by protein kinase C in a phosphatidylserine and oleoylacetylglycerol dependent manner. Tryptic digest of this phosphopeptide migrated to the same position as the phosphothreonine containing peptide obtained from the beta-subunit in two-dimensional phosphopeptide mapping. These data suggested that Thr 1336 of the insulin receptor is the site of phosphorylation by protein kinase C in intact cells.

Animals↗
PubMed1989

Human diabetes associated with a mutation in the tyrosine kinase domain of the insulin receptor.

Insulin receptor complementary DNA has been cloned from an insulin-resistant individual whose receptors have impaired tyrosine protein kinase activity. One of this individual's alleles has a mutation in which valine is substituted for Gly996, the third glycine in the conserved Gly-X-Gly-X-X-Gly motif in the putative binding site fo adenosine triphosphate. Expression of the mutant receptor by transfection into Chinese hamster ovary cells confirmed that the mutation impairs tyrosine kinase activity.

Alleles↗
PubMed1989

Tyrosine phosphorylation of pp185 by insulin receptor kinase in a cell-free system.

Insulin treatment of rat H-35 hepatoma cells causes rapid tyrosine phosphorylation of a high molecular weight protein termed pp185 besides autophosphorylation of the beta-subunit of the insulin receptor (IR) in an intact cell system. To elucidate the molecular basis for tyrosine phosphorylation of pp185, cell-free phosphorylation of pp185 was performed using phosphotyrosine-containing proteins (PYPs) purified from detergent-solubilized cell lysates by immunoprecipitation with anti-phosphotyrosine antibody. After insulin treatment of cells, marked increases of tyrosine phosphorylation of pp185 and IR were observed compared to noninsulin-treated cells. Site-specific antibodies that specifically inactivate IR kinase inhibited tyrosine phosphorylation of pp185 as well as the beta-subunit of IR. PYPs purified from detergent-free cell extracts contained pp185 but little IR; tyrosine phosphorylation of pp185 did not occur. Addition of IR kinase purified from human placenta to these PYPs restored insulin-dependent tyrosine phosphorylation of pp185. These results suggest that tyrosine phosphorylation of pp185 is catalyzed directly by IR kinase in this cell-free system.

Animals↗
PubMed1989

Rabbit brain glucose transporter responds to insulin when expressed in insulin-sensitive Chinese hamster ovary cells.

Transfection of Chinese hamster ovary cells with the expression vector containing rabbit brain HepG2-type glucose transporter cDNA resulted in a dramatic over-expression (approximately 10-fold) of glucose transporter as assessed by either immunoblotting with antipeptide antibody against rabbit brain glucose transporter or photoaffinity labeling with [3H]cytochalasin B. 2-Deoxyglucose uptake was also increased 4-fold in the transfected cells, while no increase in transport activity or transporter amount was observed in cells that were transfected with the expression vector alone without glucose transporter cDNA. Significantly, insulin (10(-7) M) increased 2-deoxyglucose uptake in both control and transfected cells, but the increased amount of the transported 2-deoxyglucose by insulin in the transfected cells was 4.2-fold greater than that in control cells, indicating that the expressed rabbit brain HepG2-type glucose transporter responded to insulin. In addition, we have recently demonstrated that the HepG2-type glucose transporter exists in rat adipocytes and responds to insulin in a fashion similar to a majority of other types of glucose transporters (Oka, Y., Asano, T., Shibasaki, Y., Kasuga, M., Kanazawa, Y., and Takaku, F. (1988) J. Biol. Chem. 263, 13432-13439). In contrast, insulin did not stimulate glucose transport activity in HepG2 cells or IM-9 lymphocytes that have a significant amount of the HepG2-type glucose transporter. Thus, the results in this study further support the notion that insulin regulation of glucose transport activity depends on a tissue-specific signaling mechanism.

Affinity Labels↗
PubMed1989

Plasma insulin levels in Japanese and Japanese-American men with type 2 diabetes may be related to the occurrence of cardiovascular disease.

Sixty-eight second-generation Japanese-American (Nisei) men 45-74 years old and 26 Tokyo Japanese men 40-72 years old with type 2 diabetes were given 75 g glucose by mouth, and their venous blood levels of glucose and insulin were measured at 0, 30, 60, 90, 120, and 180 min. Blood glucose levels were similar for the two groups but the Nisei had higher levels of insulin at all time points (P less than 0.006). The Nisei men had a higher mean body mass index (P less than 0.001) and the Tokyo men had had diabetes for a longer duration (P less than 0.001). Data were also compared following selection of a subgroup of Nisei men (n = 39) with a diabetes duration of 2-25 years, making this group more similar to the Tokyo men with respect to this variable. The Nisei still had significantly higher plasma insulin levels. Because of a significant (P less than 0.01) positive correlation between plasma insulin and body mass index in Nisei, but not in Tokyo men, data comparing the Nisei subgroup and Tokyo men were re-examined by analysis of covariance. With an adjustment for body mass index in the analysis, all differences in plasma insulin, except for the fasting insulin level, were no longer significant between the Nisei and Tokyo men, suggesting that body mass index was responsible for these differences.

Aged↗
PubMed1989

Increased clearance of plasma cholesterol after injection of apolipoprotein E into Watanabe heritable hyperlipidemic rabbits.

Apolipoprotein E (apoE) is known to play an important role in lipoprotein metabolism. We have studied the effect of apoE on the metabolism of plasma cholesterol by injecting apoE intravenously into rabbits deficient in low density lipoprotein receptors [Watanabe heritable hyperlipidemic (WHHL) rabbits]. Approximately 30 mg of apoE was injected per rabbit; a total of five WHHL rabbits were used. One hour later, plasma cholesterol levels fell 8.3% (from 488 +/- 192 to 446 +/- 174 mg/dl). After 3 hr, cholesterol levels had fallen by 19% (to 392 +/- 152 mg/dl). The reduced levels were maintained for at least 8 hr after injection of apoE. Cholesterol in very low density lipoproteins (VLDLs) and intermediate density lipoproteins fell rapidly during the first 2 hr after injection, followed by a reduction in the low density lipoprotein cholesterol level. Changes in apolipoprotein B levels in each lipoprotein fraction were very similar to those of cholesterol. Plasma apoE levels 3 min after injection were elevated 3-fold to 22.8 +/- 6.3 mg/dl and returned to initial levels 8 hr after injection. The rate of removal of intravenously injected 125I-labeled VLDL that had been incubated with apoE was 3-fold higher than that of unmodified VLDL. From these results, we conclude that the injected apoE is incorporated into VLDLs and that VLDL particles carrying more apoE are removed from the blood more rapidly, resulting in reduced formation of low density lipoprotein and lowered cholesterol levels.

Animals↗
PubMed1989

Autoantibodies to the insulin receptor (B-10) can stimulate tyrosine phosphorylation of the beta-subunit of the insulin receptor and a 185,000 molecular weight protein in rat hepatoma cells.

The immunoglobulin G (IgG) fraction obtained from the serum of a patient (B-10) with type B insulin resistance and acanthosis nigricans stimulated both glucose oxidation in rat adipocytes and autophosphorylation of tyrosine residues in the beta-subunit of insulin receptors in H-35 hepatoma cells. Partially purified insulin receptor from H-35 cells, when incubated with B-10 IgG, had increased tyrosine kinase activity for a synthetic peptide sequentially similar to the site of tyrosine phosphorylation in pp60v-arc (the gene product responsible for cellular transformation by the Rous sarcoma virus). In H-35 cells, both B-10 IgG and insulin stimulated tyrosine phosphorylation in an endogenous 185,000 mol wt protein. This phosphoprotein may be similar to the cellular substrate for insulin in hepatoma and other cultured cell lines demonstrated by others. These results suggest that antiinsulin receptor antibodies (B-10) may initiate their insulin-like effects via tyrosine phosphorylation of the insulin receptor, activation of its tyrosine kinase activity, and phosphorylation of a cellular protein substrate of 185,000 mol wt.

Adipose Tissue↗
PubMed1989

Plasma 1,5-anhydro-D-glucitol as new clinical marker of glycemic control in NIDDM patients.

To elucidate the value of using plasma 1,5-anhydro-D-glucitol (AG) as a marker of glycemic control in diabetic patients, the relationship between the plasma concentration of AG and glucosuria was examined in 152 patients with non-insulin-dependent diabetes mellitus (NIDDM). After recovery from the deterioration of glycemic control in NIDDM patients had started, AG began to increase day by day. The recovery of plasma AG showed a constant linear increase curve when excellent glycemic control was attained. The ordinary daily recovery rate of plasma AG was estimated to be 0.3 microgram/ml, which was independent of body weight, sex, age, the difference in treatment, the duration of diabetes, or the level of plasma AG among NIDDM patients. This rate decreased according to the increase in urinary glucose. When we calculated the decrease rate of plasma AG (delta AG), assuming 0.3 microgram/day to be the maximum increase rate in a day, we found a high correlation between delta AG and urinary glucose at almost all AG levels except the normal range and observed that plasma AG (A) times urinary glucose (G) was relatively constant. The formula A x G = 16 is a simple equation for rough estimation of urinary glucose from the plasma AG concentration in a stable glycemic-controlled NIDDM patient, and we call it the A.G index. The plasma AG also correlated significantly with fasting plasma glucose (r = -.810) and glycosylated hemoglobin (r = -.856) in the same stable glycemic-controlled NIDDM patients. Based on these observations, we propose that plasma AG can serve as a new marker that may provide sensitive and analytical information about glycemic control.

Adult↗
PubMed1989

Composition of very-low-density lipoproteins in non-insulin-dependent diabetes mellitus.

We studied the characteristics of very-low-density lipoproteins (VLDLs) composition in patients with non-insulin-dependent diabetes mellitus. VLDLs were isolated from 28 diabetics and 33 nondiabetics with a wide range of plasma lipid concentrations, so we could compare VLDL composition between the two groups at similar lipid concentrations. The mean cholesterol and triglyceride concentrations in plasma of diabetic subjects were 2170 (SD 570) and 2510 (SD 2230) mg/L, respectively, and 2230 (SD 560) and 2210 (SD 1830) mg/L in nondiabetics. Diabetic subjects showed positive correlations between plasma triglyceride concentrations and either preprandial blood glucose or glycated hemoglobin values (P less than 0.02 and less than 0.01, respectively). Concentrations of triglycerides, cholesterol, and apolipoproteins (apo) B, CII, CIII, and E in VLDL were not significantly different between diabetics and nondiabetics. At comparable triglyceride concentrations, the chemical compositions of the VLDL in the two groups were still very similar. Dividing the concentration of each component by the VLDL-apo B concentrations yielded similar contents of each component per unit of VLDL for the two groups. We conclude that the composition of VLDLs in diabetics is much the same as that in nondiabetics at comparable concentrations of triglycerides in plasma.

Adult↗
PubMed1988

Enhanced synthesis and secretion of apolipoprotein E from sciatic nerves of streptozotocin-induced diabetic rats after injury.

To elucidate the pathogenesis of diabetic neuropathy, synthesis and secretion of apolipoprotein E (apo E) from sciatic nerves after injury was studied in normal and streptozotocin-induced diabetic rats. Seven, 14, 28, 45 and 59 days after making crush injury on sciatic nerves with concomitant administration of streptozotocin (50 mg/kg body weight), the nerves were taken out and incubated with [35S]methionine. The [35S]labeled apo E was precipitated with specific antiserum. The amounts of apo E secreted into medium by nerves of diabetic rats were 7 times greater than those of non-diabetic rats 7 days after injury. This enhanced secretion of apo E was relatively selective for this protein, since the ratio of the immunoprecipitable apo E to the TCA preciptitable protein in the medium increased in diabetic rats. Intriguing possibility deduced from these results is that the secretion of apo E is involved in the development of diabetic neuropathy.

Animals↗
PubMed1988

Cloning of a rabbit brain glucose transporter cDNA and alteration of glucose transporter mRNA during tissue development.

A full-length cDNA clone that codes for glucose transporter protein was isolated from a rabbit brain cDNA library by using synthetic oligonucleotide probe derived from the sequence of human glucose transporter cDNA. The coding region shared 93.2% nucleotide and 97.0% amino-acid similarities with those of human glucose transporter and 89.4% nucleotide and 97.4% amino-acid similarities with those of rat transporter. Northern blot analysis revealed that glucose transporter mRNA is most abundant in the placenta and that it is also abundant in the brain. The fat tissue, heart, liver, and skeletal muscle of adult rats contained a very small amount of mRNA, while heart, liver, skeletal muscle and kidney of fetal rats contained a very high amount of glucose transporter mRNA. These results suggest that this type of glucose transporter might be closely related with cell proliferation and tissue development.

Aging↗
PubMed1988

Requirement for receptor-intrinsic tyrosine kinase activities during ligand-induced membrane ruffling of KB cells. Essential sites of src-related growth factor receptor kinases.

We have prepared site-specific antibodies toward human insulin, insulin-like growth factor-I, and epidermal growth factor receptors with chemically synthesized peptides derived from the cDNA-predicted amino acid sequences of these receptors. Two classes of antibodies were produced toward each receptor: one toward the carboxyl termini and the other against the kinase domains containing sequences homologous to the tyrosyl phosphorylation site of the product of src gene (pp60v-src). Both classes of antibodies specifically immunoprecipitated the appropriate 125I-ligand-receptor complexes and [35S]methionine-labeled receptors with almost equal potencies. Antibodies toward the kinase domains inhibited both autophosphorylation and tyrosine kinase activity of the corresponding receptors in a cell-free system, whereas antibodies toward the carboxyl termini did not. Microinjection of the kinase-inhibitory antibodies into the cytoplasm of human epidermoid carcinoma KB cells blocked the ability of the corresponding ligand to induce membrane ruffling. In contrast, these inhibitory antibodies did not block the ability of noncorresponding ligands to induce the same response. Furthermore, control immunoglobulin and antibodies toward the carboxyl termini did not block this biological response. These results support a role for the tyrosine-specific protein kinase activities of these growth factor receptors in mediating their biological effects and suggest that the regions homologous to the tyrosyl phosphorylation site of pp60v-src are important for these kinase activities both in cell-free and intact cell systems.

Amino Acid Sequence↗
PubMed1988

Long-term comparison of oral hypoglycemic agents in diabetic retinopathy. Gliclazide vs. other sulfonylureas.

Gliclazide has been reported to possess the properties of preventing the progression of diabetic retinopathy and of controlling blood glucose levels. This report describes a long-term comparative clinical trial of this agent to assess its efficacy against diabetic retinopathy. One hundred and fifty-nine NIDDM patients with no retinopathy or with simple retinopathy entered this trial. One hundred and nineteen patients receiving other sulfonylurea agents were randomly allocated to two groups (G: gliclazide, SU: other sulfonylureas). Forty patients continued to be treated with diet alone (D group). Finally a total of 60 patients, that is, 21 patients in the G group, 19 patients in the SU group, and 20 patients in the D group, were followed with funduscopic examinations for more than 4 years. The results are summarized as follows. (1) Distribution of background factors between the two drug therapy groups was balanced, but in the D group more male patients and relatively milder cases were involved than in the drug therapy groups. (2) Fasting blood glucose control in the three groups was not significantly different. (3) Funduscopic deterioration was observed less frequently, though not significantly, in the G group than in the other groups. (4) Progression to preproliferative retinopathy was significantly less frequent in the G group than in the SU group. Thus, gliclazide seems to have additional properties compared with other sulfonylurea drugs in preventing deterioration of diabetic retinopathy, and particularly in preventing progression to proliferative retinopathy.

Diabetes Mellitus, Type 2↗
PubMed1988

Hydrogen peroxide stimulates tyrosine phosphorylation of the insulin receptor and its tyrosine kinase activity in intact cells.

H-35 rat hepatoma cells were labelled with [32P]orthophosphate and their insulin receptors isolated on wheat germ agglutinin (WGA)-agarose and anti-(insulin receptor) serum. The incubation of these cells with 10 mM-H2O2 for 10 min increased the phosphorylation of both the serine and tyrosine residues of the beta subunit of the insulin receptor. Next, insulin receptors were purified on WGA-agarose from control and H2O2-treated H-35 cells and the purified fractions incubated with [gamma-32P]ATP and Mn2+. Phosphorylation of the beta subunit of insulin receptors obtained from H2O2-treated cells was 150% of that of control cells. The kinase activity of the WGA-purified receptor preparation obtained from H2O2-treated cells, as measured by phosphorylation of src-related synthetic peptide, was increased about 4-fold over control cells. These data suggest that in intact cell systems, H2O2 may increase the insulin receptor kinase activity by inducing phosphorylation of the beta subunit of insulin receptor.

Amino Acids↗
PubMed1988

Glucocorticoids increase insulin binding and the amount of insulin-receptor mRNA in human cultured lymphocytes.

The effect of steroid hormones on insulin binding and the amount of insulin-receptor mRNA was examined in IM-9 lymphocytes. Cortisol and cortexolone, but not oestrogen, increased both the binding of insulin and the amount of insulin-receptor mRNA in a time- and dose-dependent manner. Cortisol was most potent, and induced a 2-fold increase in insulin binding and a 4-fold increase in mRNA. The elevation in binding was due to an increased number of insulin receptors at the cell surface. The increase in mRNA involved all four of the insulin-receptor mRNAs and could not be inhibited by cycloheximide. The cortisol-induced increase in mRNA was associated with a 3-4-fold increase in the synthesis of pro-receptor. The relative potency of the three steroids indicated that these effects were mediated by an interaction with the glucocorticoid receptor. The results of this study suggest that cortisol can increase the number of insulin receptors at the cell surface by increasing the amounts of insulin-receptor mRNA and the synthesis de novo of insulin receptors.

17-Hydroxycorticosteroids↗