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Biomedical subjects

T Awata

Publications and source records attributed to T Awata.

At least 37 records · Page 2Linked to original sources
PubMed1999

Troglitazone and metformin, but not glibenclamide, decrease blood pressure in Otsuka Long Evans Tokushima Fatty rats.

To determine whether hypoglycemic agents such as sulfonylureas, biguanides and the newly developed insulin sensitizers such as troglitazone, have hypotensive effects in an animal model of non-insulin-dependent diabetes mellitus associated with insulin resistance, male Otsuka Long Evans Tokushima Fatty (OLETF) rats aged 12 weeks were administered following hypoglycemic agents or vehicle by gavage for 26 weeks; glibenclamide (5 mg/kg/day), metformin (100 mg/kg/day) and troglitazone (70 mg/kg/day). The gain in body weight was similar in the different groups. At 36 weeks of age, troglitazone significantly decreased fasting plasma glucose levels when compared to controls. The area under the curve (AUC) for insulin during glucose loading (2 g/kg, i.p.) was 50% lower in the group treated with troglitazone. Serum triglyceride levels in troglitazone-treated rats were also significantly lower than in the glibenclamide-treated group. Plasma membrane GLUT4 protein content was significantly augmented by a factor of 1.48-fold (p<0.02) in the glibenclamide-treated group and tended to be increased 1.32 times by administration of metformin (p=0.06). The systolic blood pressure increased with age in controls and the glibenclamide-treated group. In contrast, treatment with either metformin or troglitazone significantly decreased systolic blood pressure after the age of 29 weeks. Plasma norepinephrine and epinephrine concentrations did not show a significant decrease in the treated group when compared with the control group. These results suggest that metformin and troglitazone, but not glibenclamide, lower blood pressure in an animal model of insulin resistance, providing further evidence of the beneficial effect of insulin sensitizing hypoglycemic agents on blood pressure.

Animals↗
PubMed1998

Expression of peroxisome proliferator-activated receptor alpha (PPAR alpha) in primary cultures of human vascular endothelial cells.

The peroxisome proliferator-activated receptor (PPAR) is a member of the steroid nuclear receptor superfamily. Three types of PPARs have been described in humans: PPAR alpha, PPAR beta, and PPAR gamma. Here we investigated the levels of PPAR alpha mRNA in primary cultures of human umbilical venous endothelial cells (HUVEC), human umbilical arterial endothelial cells (HUAEC), human coronary arterial endothelial cells (HCAEC), and human aortic endothelial cells (HAEC), using the reverse transcriptase-polymerase chain reaction (RT-PCR). The HUVEC, HAEC, and HCAEC, but not the HUAEC, showed relatively low expression of PPAR alpha in comparison with liver, which was used as a positive control. Moreover, the partial sequences of the PCR-amplified products from HUVEC, HAEC, and HCAEC were similar to that of the PPAR alpha from human liver. The expression of PPAR alpha in cultured HAEC, which were induced by dexamethasone, was inhibited by insulin. In addition, PPAR alpha expression was also increased by benzafibrate or eicosapentaenoic acid with the physiological concentration. These results suggest that the PPAR alpha in endothelial cells may have the same physiological role as the expression of PPAR alpha in the liver.

Aorta↗
PubMed1998

Bezafibrate has an antioxidant effect: peroxisome proliferator-activated receptor alpha is associated with Cu2+, Zn2+-superoxide dismutase in the liver.

Administration of bezafibrate in rats significantly reduced the levels of plasma thiobarbituric acid-reactive substances (TBARS) in comparison with those obtained in rats fed a soy or lard chow. Moreover, an elevation of in vitro conjugated diene production and linoleic acid levels in the high-density lipoproteins and low-density lipoproteins induced by a soy or lard chow, was reduced by bezafibrate administration. In addition, the liver Cu2+, Zn2+-superoxide dismutase (SOD) gene expression showed a significant positive correlation with the liver peroxisome proliferator-activated receptor alpha (PPARalpha) mRNA level (R=0.769, p<0.0001). This unique characteristic of bezafibrate, which possesses both a hypolipidemic effect and antioxidant activity, may be beneficial in preventing vascular complications in hyperlipidemia.

Acyl-CoA Oxidase↗
PubMed1998

Ultrastructural examination of corneal epithelium of spontaneously obese, hyperglycemic rats.

PURPOSE: Otsuka Long-Evans Tokushima fatty (OLETF) rats spontaneously become obese and hyperglycemic with age. We investigated whether the development of hyperglycemia would alter the ultrastructure of the corneal epithelium. METHODS: Scanning and transmission electron microscopy (SEM and TEM) were used to examine the morphology of corneal epithelial cells. Fourteen OLETF rats were evaluated, and 9 Long-Evans Tokushima Otsuka (LETO) rats were used as control. Non-hyperglycemic OLETF rats served as controls. RESULTS: SEM showed exfoliative changes in the surface of the central corneal epithelium of the hyperglycemic OLETF rats. These superficial epithelial cells were irregular in shape as compared to polygonal shapes of those of LETO and non-hyperglycemic OLETF rats. The mean anterior surface area of individual superficial epithelial cells was significantly smaller in the hyperglycemic OLETF than that of the LETO or the non-hyperglycemic OLETF rats. Central protrusion(s) could be found in some of the superficial cells of all rats examined, although this phenomenon was more common in the hyperglycemic rats than in the non-hyperglycemic rats. TEM revealed that there were numerous cytoplasmic vacuoles and wide intercellular spaces in the central corneal epithelium of the hyperglycemic OLETF rats, but not in the non-hyperglycemic rats. CONCLUSIONS: The development of spontaneous hyperglycemia in OLETF rats alters the ultrastructure of the corneal epithelium. The alterations included abnormalities of the corneal epithelial surface observed by SEM and the presence of intracellular vacuoles and enlarged intercellular spaces detected by TEM.

Animals↗
PubMed1998

Effect of the vasodilatory beta-blocker, nipradilol, and Ca-antagonist, barnidipine, on insulin sensitivity in patients with essential hypertension.

OBJECTIVES: To assess the effects of a vasodilatory beta-adrenoceptor blocker, nipradilol, and a long-acting Ca channel blocker, barnidipine, on insulin sensitivity. DESIGN: Insulin sensitivity was determined using a euglycemic hyperinsulinemic clamp technique before and after a 12-week treatment period in eighteen patients with essential hypertension. RESULTS: Both drugs decreased blood pressure without affecting any serum parameters of glucose and lipid metabolism. Nipradilol significantly augmented glucose infusion rate (GIR) from 3.11+/-0.28 to 4.69+/-0.57mg/kg/min (p=0.027). Barnidipine also increased GIR from 3.91+/-0.43 to 5.29+/-0.43 mg/kg/min (p=0.028). Plasma norepinephrine concentrations significantly increased with barnidipine treatment, while nipradilol had no effect on plasma norepinephrine levels. No adverse events were reported during the study. CONCLUSIONS: These results suggest that vasodilatory beta-blockers such as nipradilol and long-acting Ca channel blockers such as barnidipine may be useful in the treatment of insulin resistant hypertensive patients.

Adrenergic beta-Antagonists↗
PubMed1997

Oral administration of lens homogenate suppresses antibody production in mice injected with beta-crystallin emulsified in CFA.

Auto-antibodies (Abs) against lens antigens (Ags) are present in most patients with age-related cataract, and with complement they kill lens epithelial cells (LECs) in vitro. We studied, in an animal model, whether cytotoxic Abs against lens Ags can be suppressed by oral administration of the Ags. Mice were fed calf lens homogenate, 4 mg/mouse, every 4 days for 4-5 weeks, or bovine serum albumin (BSA) before and after immunisation with beta-crystallins emulsified in complete Freund's adjuvant (CFA). Sera from these animals were analysed for Abs to beta-crystallins by enzyme-linked immunosorbent assay (ELISA) and protein blot analysis. In addition, we studied the proliferative response of T-lymphocytes to beta-crystallins. The titer of anti-beta-crystallin Abs in the control animals fed BSA gradually increased to 1.5 x 10(-6) by the 5th week after the first injection. In contrast, the titer of anti-beta-crystallin Abs in animals fed calf lens homogenate was reduced to 30-70% of the control. Feeding lens homogenate prior to or concomitant with beta-crystallins immunization, was more effective than feeding after immunization (65% suppression vs. 30% suppression, respectively). Also the proliferative response of T-lymphocytes to beta-crystallins in mice fed homogenate was suppressed significantly. Thus, oral administration of lens homogenate is a specific and nontoxic method of suppressing anti-beta-crystallin Ab production in mice. We are exploring the therapeutic value of oral administration of lens proteins in age-related cataract.

Animals↗
PubMed1997

Acarbose controls postprandial hyperproinsulinemia in non-insulin dependent diabetes mellitus.

We investigated how fasting or postprandial insulin levels were altered by treatment with acarbose or sulfonylureas. Plasma glucose and serum insulin, C-peptide, and proinsulin levels were measured before as well as 1 and 2 h after breakfast in 23 patients with non-insulin-dependent diabetes mellitus and 17 patients with impaired glucose tolerance. In the diabetic patients, 12 weeks of acarbose therapy decreased the postprandial levels of glucose (1 h: -60.0%; 2 h: -67.6%), insulin (1 h: -67.5%; 2 h: -72.2%) and proinsulin (1 h: -55.2%; 2 h: -46.7%), and proinsulin (1 h: -20.9%; 2 h: -57.5%). In contrast, sulfonylurea treatment increased postprandial insulin and proinsulin levels. Since increased in the serum insulin or proinsulin levels are associated with a higher risk of cardiovascular disease, the present findings suggest that the acarbose-induced reduction of the postprandial serum insulin or proinsulin responses to food intake might be useful for preventing vascular complications in patients with diabetes.

Acarbose↗
PubMed1997

Effects of aldose reductase inhibitor CT-112 on the corneal epithelial barrier of galactose-fed rats.

PURPOSE: To investigate whether the barrier function of the corneal epithelium is disrupted in galactosemic rats, and to assess the effects of the aldose reductase inhibitor CT-112, in the form of eyedrops, on the corneal epithelial barrier in galactosemic rats. METHODS: Forty rats were divided into 3 groups based on their diet: a control group, a galactose group and a CT-112 treated galactose group (CT-112 group). After 3 weeks, 31 rats from the 3 groups were subjected to fluorophotometry, in which fluorescein (F) was instilled into one eye and carboxyfluorescein (CF) was instilled into the other eye in a random fashion. The F and CF uptakes were then measured at the central cornea by a slit-lamp fluorophotometer. Three rats from each group were exposed to a horseradish peroxidase (HRP) solution for one hour, and the HRP-reactive substances within the corneal epithelium were also examined via electron microscopy. RESULTS: There was significantly higher F uptake in the galactose group than in the control (p = 0.003) and CT-112 groups (p = 0.028). There were no significant differences in CF uptake between the 3 groups. Histologically, HRP-reactive substances were found in much greater quantities within the superficial corneal cells of the galactose group than in the control or CT-112 groups. CONCLUSIONS: These results suggest that cell membrane disruption, as detected by F uptake and HRP penetration, was found in the superficial corneal cells of galactose-fed rats, and that intercellular junction integrity can be assayed by CF uptake and histological evaluation. Moreover, CT-112 eyedrops were effective in improving the corneal epithelial barrier dysfunction of galactose-fed rats.

Aldehyde Reductase↗
PubMed1997

Glucose intolerance in spontaneously hypertensive and Wistar-Kyoto rats: enhanced gene expression and synthesis of skeletal muscle glucose transporter 4.

To clarify the relationship between blood pressure and insulin resistance, we studied the role of glucose transporter 4 (GLUT4) in skeletal muscle and the effect of angiotensin-converting enzyme inhibitor on insulin resistance. Blood pressure and plasma glucose and plasma insulin responses to glucose loading (2 g/kg, i.p.) were measured in spontaneously hypertensive rats (SHRs), Wistar-Kyoto rats (WKYs), and Wistar rats at 8, 12, and 20 wk of age. GLUT4 gene expression and plasma membrane protein content were also determined in the gastrocnemius muscle. SHRs and WKYs at the age of 8 wk had significantly higher plasma glucose levels than did age-matched control Wistar rats. Insulin response also tended to be higher. Glucose intolerance was also present in 12-wk-old SHRs, but normalized at the age of 20 wk. In contrast, WKYs were glucose intolerant at 12 and 20 wk. Gene expression and plasma membrane content of GLUT4 were augmented in both 8-wk-old SHRs and WKYs, indicating a compensatory increase in these variables. Effects of captopril (20-30 mg/kg/d from 8 to 20 wk) on GLUT4 were also investigated in these three strains. Captopril improved steady state plasma glucose levels in association with 1.2- to 2.5-fold higher GLUT4 gene expression and a 1.4-fold increase in skeletal muscle GLUT4 protein in SHRs and WKYs. Our results suggest that (1) not only SHRs but also WKYs may have glucose intolerance and hence insulin resistance; (2) gene expression and protein synthesis of skeletal muscle GLUT4 are probably increased compensatorily, indicating that abnormalities in GLUT4 do not have a pivotal role in the development of insulin resistance in SHRs and WKYs; and (3) captopril stimulates skeletal muscle gene expression and synthesis of GLUT4, providing further evidence of its beneficial effect on glucose metabolism.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Evidence for association between the class I subset of the insulin gene minisatellite (IDDM2 locus) and IDDM in the Japanese population.

Although the shortest (class I) minisatellite (i.e., variable number of tandem repeats [VNTR]) alleles in the 5' region of the insulin gene are positively associated with IDDM in Caucasians, the majority of Japanese are homozygous for class I alleles. Here, we determined the exact length, in number of repeat units (RUs), of class I alleles in Japanese subjects. The distribution of class I alleles in Japanese was trimodal, with peaks located at 32/33, 41, and 44 RUs. The shortest component (i.e., 1S [25-38 RUs]) alleles were significantly increased in the IDDM group compared with the control group (54 vs. 46%; P = 0.040). The 1S/1S genotype was significantly increased in the IDDM patients (34 vs. 20%; P = 0.005; relative risk 2.1). Furthermore, the transmission disequilibrium test of Japanese families with 1S/1M or 1S/1L heterozygous parents confirmed the association of 1S alleles; 17 alleles of 1S and 6 alleles of 1M (39-41 RUs) or 1L (42-44 RUs) were transmitted to affected offspring (P = 0.022). In addition, we found tight linkage of 1S with allele 9 of the tyrosine hydroxylase gene microsatellite and allele (-) of the IGF-II gene Apa I polymorphism, but neither 9 nor (-) alleles were significantly associated with IDDM. The present study suggests that a class I subset may have a role in IDDM susceptibility in Japan. It was revealed that the difference between 1S alleles and 1M or 1L alleles is almost consistently characterized by a sequence variation generated by deletion of two copies of an ACAGGGGTCC CGGGG repeat element, implying that sequence variation of class I alleles may influence disease susceptibility.

Adolescent↗
PubMed1996

Effects of topical aldose reductase inhibitor CT-112 on corneal sensitivity of diabetic rats.

PURPOSE: To investigate whether the loss in corneal sensation observed in human diabetics could be duplicated in diabetic rats and if this abnormality could be prevented by topical instillation of an aldose reductase inhibitor (ARI), CT-112. METHODS: Rats were made diabetic by injection of streptozotocin. Some of these rats were treated with eye drops of CT-112 while others were treated with the same vehicle solution without ARI. Normal rats served as controls. Corneal sensitivity was measured by means of a Cochet-Bonnet aesthesiometer, using the blink reflex as an objective sign. Corneal changes in ultrastructure in diabetic rats were also observed. RESULTS: The corneal sensitivity of diabetic rats was significantly decreased and this change was prevented by ARI treatment. Ultrastructurally, degenerations of axons and mitochondria of the corneal nerve were seen in the diabetic rats and the ARI treatment prevented these morphological changes. CONCLUSIONS: It is clear that corneal hypesthesia occurs in diabetic rats as it does in human diabetics, and treatment with an ARI prevents this change. Along with the functional abnormality, the ultrastructural changes of corneal nerve also occur in diabetic rats, and they are prevented by ARI. These results strongly suggest that aldose reductase is involved in corneal hypesthesia and ultrastructural changes of corneal nerve in diabetic rats. These defects are ameliorated by aldose reductase inhibitor.

Administration, Topical↗