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T Kazumi

Publications and source records attributed to T Kazumi.

16 recordsLinked to original sources
PubMed1992

Effect of long-term insulin deficiency and insulin treatment on the composition of triglyceride-rich lipoproteins and triglyceride turnover in rats.

The effect of long-term (4 months) insulin deficiency on triglyceride turnover was examined using Triton WR1339 in rats. Triglyceride secretion rate was estimated in rats 2 weeks and 4 months after induction of diabetes with 40 mg/kg of streptozotocin. By the second week diabetic rats showed prominent hyperglycemia and the plasma insulin level was very low. In spite of a lower triglyceride secretion rate compared to non-diabetic control rats, diabetic rats showed normotriglyceridemia. Thus, the estimated fractional catabolic rate for plasma triglyceride was decreased in the diabetic rats of 2 weeks duration. By the fourth month diabetic rats still showed a suppressed triglyceride secretion rate but plasma triglyceride was markedly higher than in the non-diabetic control rats. Therefore, their estimated fractional catabolic rate for plasma triglyceride was severely suppressed. They also showed hyperglycemia and hypercholesterolemia. The triglyceride-rich lipoprotein particles obtained after Triton injection in long-term diabetic rats were significantly cholesterol-enriched and triglyceride-depleted compared to control rats. These changes were already present in 2-week diabetic rats but the magnitude was significantly smaller that those in long-term diabetic rats. All of these abnormalities (including triglyceride turnover and the particle composition) were almost normalized by 2 weeks of insulin treatment (6 units/day). Thus, it was concluded from the present data that duration of insulin deficiency is an important determinant of triglyceride removal rate from the circulation in rats. Further modification of lipid composition of triglyceride-rich lipoprotein particles by long-term insulin-deficiency could be one of the reasons for this removal defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of mild diabetes and dietary fructose on very-low-density lipoprotein triglyceride turnover in rats.

Very-low-density lipoprotein (VLDL) triglyceride turnover was examined in mildly streptozotocin (25 mg/kg)-diabetic rats, using Triton WR1339. Diabetic rats fed standard rat chow showed mild hyperglycemia and suppressed levels of plasma insulin. Their triglyceride secretion was significantly suppressed despite an elevated level of plasma free fatty acids. However, the plasma triglyceride level of these diabetic rats was significantly elevated compared with nondiabetic controls. This suggested that the removal of triglyceride from the circulation, as well as its entry into the circulation, was impaired in mildly insulin-deficient rats. Glucose or fructose supplementation (10% in drinking water for 14 days) significantly increased the triglyceride secretion rate of diabetic rats. Especially, fructose supplementation increased plasma insulin to normal levels, but resulted in markedly elevated plasma triglyceride levels (three times higher than glucose-supplemented or chow-fed diabetic rats) despite similar triglyceride secretion rates between the two types of sugar-supplemented diabetic rat groups. This suggested an impairment of triglyceride removal by dietary fructose. The result obtained from chow-fed diabetic rats indicates that mild but significant insulin deficiency resulted in mild hypertriglyceridemia, linked to impaired triglyceride removal rather than to an overproduction of VLDL-triglyceride, despite elevated levels of plasma free fatty acids. Furthermore, fructose feeding induced prominent hypertriglyceridemia not only by stimulating triglyceride secretion, but also by suppressing triglyceride removal from the circulation of mildly diabetic rats.

Animals↗
PubMed1992

Effect of probucol on recovery from streptozotocin diabetes in rats.

The present study was conducted to see the effect of probucol on streptozotocin diabetes in rats. After 2 weeks of a 1% probucol diet, 35 or 50 mg/kg of streptozotocin were intravenously injected into male Wistar rats. All the rats became diabetic 2 days after treatment. Thereafter, in order to see the effect of probucol on spontaneous recovery from streptozotocin diabetes, 25 mg/kg of streptozotocin was injected into rats after two weeks of probucol diet and the diet was continued for additional two weeks. All the rats with a standard diet (group CS, n = 13) and 12 of 13 rats with probucol diet (group PS) became diabetic 2 days after streptozotocin injection. One rate from group PS did not develop diabetes. Two weeks after injection, only 4 of 13 rats in groups CS showed recovery, while 11 of 12 rats in group PS showed recovery from streptozotocin diabetes (p less than 0.05). The average blood glucose levels in group PS were significantly lower than group CS (10.5 +/- 4.6 vs 18.5 +/- 0.6 mM, p less than 0.05). In addition, the pancreatic insulin content of group PS was 8 times greater than that of group CS (0.75 +/- 0.24 vs 0.09 +/- 0.03 mmol/pancreas, p less than 0.01). Thus, the in vivo diabetogenic action of streptozotocin could not be reduced by pretreatment with probucol. However, recovery from streptozotocin diabetes was induced by subsequent treatment with probucol. The precise mechanisms for this phenomenon were not known; but the present findings suggest the protective effect of probucol on beta-cell damage induced by small dose of streptozotocin.

Animals↗
PubMed1992

[Insulin receptor Arg1131-->Gln: a novel mutation in the catalytic loop of insulin receptor observed in insulin resistant diabetes].

A novel mutation Arg1131-->Gln in the catalytic loop of insulin receptor (IR) associated with insulin resistant diabetes was detected. A 56-year-old male with hyperinsulinemia (fasting IRI 92 microU/ml) showed moderate impairment in glucose tolerance (HbAlc 7.0%, fructosamine 258 mumol/l, fasting glucose 119 mg/dl, maximum value of blood glucose during 75 g OGTT 220 mg/dl). While insulin binding to erythrocytes IR was normal, the insulin-induced autophosphorylation of the patient's erythrocytes IR in vivo showed marked decrease, suggesting this patient had some defect in the kinase domain (exon 17-21) of IR. PCR-SSCP analysis of kinase domain with a genomic DNA obtained from the patient's leucocytes indicated the presence of some mutations in exon 19. Sequencing analysis in M13 revealed a heterozygous mutation at a position 1131 (CGG-->CAG) substituting Gln for Arg. Four people of patient's family analyzed are revealed to have an identical missense mutation at the same position with the patient.

DNA↗
PubMed1991

Effects of long-term high-fiber diet on macrovascular changes and lipid and glucose levels in STZ-induced diabetic SD rats.

The effects of long-term high-fiber diet on lipid and glucose levels and the histological changes in the coronary arteries and thoracic aorta in STZ-induced diabetic SD rats were investigated. During the first 4 weeks of the study period, all diabetic rats were given regular chow plus water after which, all were grouped according to the following diet regimen: group II, no added cholesterol and glucomannan; group III, no added cholesterol but with glucomannan supplement, group IV, with added cholesterol but no glucomannan supplement; and group V, with both cholesterol and glucomannan supplements. 15% weight of glucomannan and 1.5% weight of cholesterol in regular rat chow were used as supplements when indicated. Non-diabetic rats which received only regular chow served as the control group (group I). In the 18th week all rats were sacrificed and weight gain, glucose, total cholesterol, HDL-cholesterol, triglyceride and lipid peroxidase concentrations were determined. Selected portions of the heart and thoracic aorta were histologically examined. Weight gain was higher in rats supplemented with glucomannan than in those without glucomannan supplements, but the difference is not significant. A lowering tendency in glucose levels was likewise observed. Furthermore, total cholesterol and HDL-cholesterol levels were lower and higher, respectively in diabetic rats receiving glucomannan. Although the triglyceride levels were similar in all rats, lipid peroxidase levels were significantly lower in rats with high-fiber diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Failure of chronic hyperinsulinemia to suppress pancreatic glucagon in vivo in the rat.

To determine the effects of chronic hyperinsulinemia on glucagon release, rats were made hyperinsulinemic for 14 days by supplementation of drinking water with sucrose (10%; sucrose-fed) to increase endogenous release or by implantation of osmotic minipumps (subcutaneous, s.c.; or intraperitoneal, i.p.) to deliver exogenous insulin (6 U/day). Both s.c. and i.p. rats also had sucrose in the drinking water to prevent hypoglycemia. Plasma insulin levels were significantly elevated in sucrose-fed, s.c., and i.p. rats. However, glucose levels were significantly elevated in sucrose-fed rats only. Surprisingly, plasma glucagon concentrations were elevated in i.p. and s.c. rats and were not suppressed in sucrose-fed rats. Inverse relationships were found between the plasma levels of insulin and glucose (n = 65; r = -0.42, p less than 0.0001) and between glucose and glucagon (n = 73; r = -0.46, p less than 0.0001). However, unexpectedly, a positive correlation between insulin and glucagon (n = 65; r = 0.47, p less than 0.0001) was established. As suppression of plasma glucagon levels below basal was not observed in any of the hyperinsulinemic or hyperglycemic rats, we wished to establish further whether pancreatic glucagon release could be suppressed below basal levels in the rat by another means. Thus, high doses of somatostatin (50-100 micrograms.kg-1.min-1) were infused for 45 min into normal rats without or with a concomitant hyperinsulinemic, hyperglycemic glucose clamp. Somatostatin fully suppressed insulin, but although plasma glucagon levels were decreased by somatostatin infusion relative to saline-infused animals, there was still no suppression below basal levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Insulin and glucagon relationships during aging in rats.

Oral glucose tolerance tests were performed under pentobarbital anesthesia in 43 male Wistar rats 2 to 18 months of age in order to determine if insulin and glucagon secretion are altered with aging. Although any linear correlation was not demonstrated between aging and blood glucose, plasma insulin or glucagon levels, post-glucose levels of blood glucose were significantly suppressed and those of plasma glucagon were significantly elevated at 4 to 6 months of age. No significant difference was found between young (2 months of age) and aged rats (12 to 14 and 17 to 18 months of age) in either blood glucose or plasma insulin levels during oral glucose load. On the other hand, post-glucose plasma glucagon levels of the aged rats were significantly higher than those of the young ones. Furthermore, comparisons of various kinds of indices among the different age groups, such as insulinogenic index, insulin/glucagon and so forth during oral glucose tolerance tests also indicate the significant alteration of glucagon secretion during aging process. It is concluded from the present data that glucose tolerance does not apparently deteriorate during aging process in rats but that glucagon responses to oral glucose administration are elevated with aging.

Aging↗
PubMed1979

Glucagon secretion during the development of insulin-secreting tumors induced by streptozotocin and nicotinamide.

Serial oral glucose tolerance tests in rats treated with streptozotocin and nicotinamide showed that blood glucose levels after glucose loading were suppressed significantly 7 months after treatment as compared to those of earlier stages. Post-glucose plasma insulin levels were significantly elevated at the 9th to 12th month and concomitantly fasting plasma glucagon levels rose significantly. At that time pancreatic islet cell tumors were demonstrated in all of the rats in this experiment. Post-glucose plasma glucagon levels, however, did not show remarkable changes throughout the observation. In spite of hyperinsulinemia, post-glucose plasma glucagon levels of tumor-bearing rats were significantly lower than those of body weight adjusted controls. It is inferred from the study that secretory activity of pancreatic A-cells of tumor-bearing rats is restrained by excess insulin released from islet cell tumors.

Adenoma, Islet Cell↗
PubMed1978

Biochemical studies on rats with insulin-secreting islet cell tumors induced by streptozotocin: with special reference to physiological response to oral glucose load in the course of and after tumor induction.

Pancreatic islet cell tumors were induced in 32 of 49 male Wistar rats (73%) surviving 9 months or longer following treatment with streptozotocin alone, with streptozotocin and nicotinamide, or with streptozotocin and picolinamide. Serial oral glucose tolerance tests in rats treated with streptozotocin and nicotinamide showed that the elevation of blood glucose levels after oral glucose load was depressed significantly 7 months after treatment. Plasma insulin responses were distinctly elevated 9 months after treatment. Blood glucose levels remained lower and plasma insulin levels rose markedly after a glucose load in tumor-bearing rats as compared to the response of tumor-free rats. These findings suggest that pancreatic islet cell tumors induced by streptozotocin with and without combined treatment are insulin-secreting, and that streptozotocin itself has oncogenic effects on the rat pancreas. Mean insulin concentration in islet cell tumors amounted to 401 U/g wet wt, whereas the concentration was 14 U/g wet wt in the pancreatic tissue from tumor-free rats.

Adenoma, Islet Cell↗
PubMed1978

Tumorigenic action of streptozotocin on the pancreas and kidney in male Wistar rats.

Pancreatic islet cell tumors were induced in 38 of 44 male Wistar rats (86%), which survived 9 to 14 months following the various treatment schedules. A single i.v. injection of streptozotocin alone, 30, 40, 50, or 65 mg/kg of body weight produced adenomas of pancreatic islet cells in 8 of 9 (89%), 6 of 7 (86%), 2 of 4 (50%), and 1 of 2 rats (50%), respectively. The neoplasms were seen in all of the 8 rats given a single i.p. injection of picolinamide, 250 mg/kg of body weight, 15 min before a single i.v. injection of streptozotocin, 65 mg/kg of body weight. Among the 14 rats given a single i.p. injection of nicotinamide, 500 mg/kg of body weight, 15 min before a single i.v. injection of streptozotocin, 65 mg/kg of body weight, 13 rats (95%) developed pancreatic islet cell tumors. Renal tumors were seen in only 3 rats treated with streptozotocin and nicotinamide. None of rats used in this study developed hepatic tumors. This study demonstrates that steptozotocin, even in a dose of 30 mg/kg of body weight, has an exceedingly marked tumorigenic action on the rat pancreas, while it has little effect on the kidney and no effect on the liver.

Adenoma, Islet Cell↗