Effects Of Streptozotocin Diabetes Research Articles

NMDA RECEPTOR SUBUNITS 2A AND 2B DECREASE AND LIPID PEROXIDATION INCREASE IN THE HIPPOCAMPUS OF STREPTOZOTOCIN-DIABETIC RATS: EFFECTS OF INSULIN AND GLICLAZIDE TREATMENTS

Recent studies indicate that diabetes mellitus changes N-methyl-D-aspartate (NMDA) receptor subunit composition and impairs cognitive functions. It also has been known that diabetes mellitus causes lipid peroxidation. This study examined the effects of streptozotocin-diabetes and insulin or gliclazide treatment on the hippocampal NMDA receptor subunit 2A and 2B (NR2A and NR2B) concentrations. In addition, malondial--dehyde (MDA) levels were measured as a marker for lipid peroxidation. Eight weeks after the induction of diabetes MDA, levels were increased, and NR2A and NR2B concentrations were reduced. Insulin and gliclazide treatment partially prevented the reduction of NR2A and NR2B expression and prevented the elevation of MDA levels. There was no significant difference between the effects of insulin and gliclazide. The results suggest that the elevation of lipid peroxidation can be the primary biochemical disturbances in diabetes progression, and that changes in NMDA receptor subunit compositions can be involved in cognitive decline in diabetes

Acrylamide-induced neuropathic changes in rat enteric nerves: Similarities with effects of streptozotocin-diabetes

The effect of acrylamide intoxication (a widely used model for autonomic neuropathy) on the fluorescence intensity and density of catecholamine- and peptide-containing nerve fibres and tissue content of noradrenaline and the peptides vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and neuropeptide Y in the enteric nerves of rat ileum was examined. Histochemical and immunohistochemical techniques were used to localize catecholamine- and peptide-containing nerve fibres. The tissue content of noradrenaline was measured using high-performance liquid chromatography, and an enzyme-linked immunosorbent assay technique was used to determine the tissue content of the peptides investigated. Acrylamide intoxication caused a significant decrease in the density of catecholamine-containing nerve fibres and tissue content of noradrenaline in the myenteric plexus of rat ileum. A decrease in tissue content and immunoreactivity of calcitonin gene-related peptide and an increase in vasoactive intestinal polypeptide was seen in the myenteric plexus of ileum from acrylamide-intoxicated rats. In the submucous plexus, the acrylamide treatment caused a decrease in calcitonin gene-related peptide immunoreactivity and an increase in vasoactive intestinal polypeptide and neuropeptide Y immunoreactivity. There was no change in either tissue content or immunoreactivity of substance P in both myenteric and submucous plexuses of the treated rat ileum. These changes have a striking similarity with those found in the enteric nerves of streptozotocin-diabetic rat ileum, suggesting the possible presence of an underlying common mechanism(s) in the development of neuropathic changes in the autonomic nerves of acrylamide-intoxicated and streptozotocin-diabetic rats.

Effects of streptozotocin-diabetes on sympathetic nerve, endothelial and smooth muscle function in the rat mesenteric arterial bed

Mesenteric arterial function was assessed in constantly perfused preparations isolated from rats 12 weeks after treatment with streptozotocin (65 mg kg −1, i.p.) to induce diabetes. Frequency-dependent vasoconstrictor responses to electrical field stimulation of sympathetic nerves (4–32 Hz, 0.1 ms, 90V, 30 s) were severely attenuated in preparations from streptozotocin-diabetic rats, although dose-dependent vasoconstrictions to the sympathetic cotransmitters noradrenaline and ATP, as well as to potassium chloride, were not significantly changed. Dose-dependent relaxations to the endothelium-dependent vasodilators acetylcholine and ATP were significantly impaired in preparations from streptozotocin-diabetic rats, although endothelium-independent vasodilatation to sodium nitroprusside was unimpaired. These results suggest that 12 weeks after induction of streptozotocin-diabetes in rats there is pre-junctional impairment of sympathetic neurotransmission and impaired endothelial function of the mesenteric arteries. This is in contrast to our previous findings that at 8 weeks after induction of streptozotocin-diabetes sympathetic nerve and endothelial function is normal, although sensory-motor vasodilatation is severely attenuated. It is suggested that selective changes occur in mesenteric arterial function after streptozotocin treatment depending on the duration of diabetes; sensory-motor nerves are affected first, followed by sympathetic nerves and the endothelium, while the smooth muscle is relatively resistant to change.

The effects of streptozotocin diabetes on sodium-glucose transporter (SGLT1) expression and function in rat jejunal and ileal villus-attached enterocytes

Rats treated with streptozotocin for 17 days were used to determine the cellular origin of enhanced brush border glucose transport in the diabetic small intestine. In the jejunum of both normal and diabetic rats, phlorizin-sensitive (SGLT1-mediated) glucose transport was shown, by section autoradiography, to take place in upper villus enterocytes. The distribution of brush border SGLT1 transporters along villi, determined using immunogold cytochemistry, was similar to that found for glucose uptake. Longer villi, supporting a larger number of absorbing enterocytes in the diabetic jejunum, appeared to be responsible for increased glucose uptake in this condition. SGLT1 protein and SGLT1-mediated glucose transport were undetectable in normal distal ileal villi. However, following treatment with streptozotocin, both SGLT1 protein and SGLT1-mediated glucose transport were found to be present in basal ileal villus enterocytes. SGLT1 protein and SGLT1-mediated glucose transport both increased during enterocyte migration to the villus tip. Cellular induction of the SGLT1 transporter, as well as longer villi contribute to enhanced glucose transport in diabetic rat distal ileum. Close correlation between the positional expression of SGLT1 protein and absorptive function suggests that transporter density is an important determinant for up-regulation of sodium-dependent glucose transport in diabetes.

The effects of streptozotocin diabetes on salivary-mediated bacterial aggregation and adherence

Diabetic rats are known to have an increased susceptibility to dental caries and major alterations in parotid salivary composition. Salivary proteins play an important part in oral health maintenance; thus specific changes in salivary protein composition in diabetic animals might alter the ecological balance in favour of cariogenic bacteria, and toward the initiation and progression of the disease process. The ability of whole, parotid and submandibular salivas from control and streptozotocin-diabetic rats to mediate the aggregation and adherence to hydroxyapatite of mutans streptococci was examined. Salivary-mediated bacterial aggregating activity was significantly reduced in whole and parotid salivas from diabetic rats, but bacterial adherence to hydroxyapatite was unaffected. The aggregating and adherence activities of rat whole saliva were derived mainly from parotid saliva, which contains predominantly low molecular-weight proteins and glycoproteins (< 200 kDa), but rat parotid saliva was capable of interacting with the bacterial receptor for the high molecular-weight aggregating factor in human saliva. SDS-PAGE of parotid saliva revealed that a number of proteins, including the basic and acid proline-rich proteins, were altered in the salivas of diabetic animals. After incubation with either Streptococcus mutans or hydroxyapatite several protein bands were depleted, and thus a variety of proteins and glycoproteins may be responsible for the adherence and aggregating activity of rat parotid saliva.

Effects of streptozotocin diabetes on amylase release and cAMP accumulation in rat parotid acinar cells

Rat parotid responses to sympathetic nerve stimulation in vivo are impaired 2–4 weeks after the induction of streptozotocin diabetes. In this study, the effects of experimental diabetes of similar duration and severity on noradrenaline-stimulated amylase release and cAMP accumulation were examined in vitro. Amylase levels were significantly lower in acinar cells isolated from diabetic animals than in controls, and cellular amylase increased after treatment of the diabetic animals with either thyroxine (T 4) or insulin. Diabetes and T 4 had no apparent affect on amylase release measured as a percentage of the total. In contrast, giving insulin resulted in a significant reduction in maximal secretion (20.4 ± 2.4% compared with 43.6 ± 7.6%). Similar results were observed when amylase release was stimulated with forskolin. Basal cAMP levels were unaffected by diabetes or T 4 (7.8 ± 2.3 pmol/mg protein), but stimulated cAMP levels were significantly greater in diabetic acinar cells than in controls. Insulin reversed the effects of diabetes on cAMP accumulation, whereas T 4 had no effect. Thus, diabetes (2–4 weeks) and insulin in vivo appear to have paradoxical effects on parotid amylase release and cAMP accumulation in vitro. Further, the effects of diabetes appear to be unrelated to thyroid status.

Expression of growth hormone, growth hormone releasing hormone, and somatostatin genes is unperturbed in the streptozotocin-induced diabetic rat

The effects of streptozotocin diabetes on the level of growth hormone, growth hormone releasing hormone, and somatostatin mRNA was measured in control rats, in diabetic rats maintained on insulin, and in diabetic rats in which insulin had been withheld for 3 days. Total cytoplasmic RNA samples were prepared from the pituitary and hypothalamic tissues of each animal and analyzed by dot blot or Northern blot hybridization. No significant difference was observed between control and insulin-treated groups with regard to body weight or plasma glucose concentration. The insulin withdrawal group had significantly higher plasma glucose concentrations and lower body weights, confirming diabetic status. There was no significant difference in the level of growth hormone, growth hormone releasing hormone, and somatostatin mRNA among any of the three groups however. We conclude that alterations in the regulation of circulating growth hormone in the streptozotocin-induced diabetic rat, removed from insulin treatment for 3 days, did not occur at the transcriptional or RNA processing level. This conclusion extends to hypothalamic growth hormone releasing hormone, and somatostatin gene expression as well. Regulatory changes in growth hormone level previously noted during insulin withdrawal in the streptozotocin-induced diabetic rat could be the result of post-transcriptional processes operating at the level of hormone synthesis or release.

Effects of diabetes and dietary manipulation on rat parotid gland secretory response to sympathetic nerve stimulation

1. 1. The effects of streptozotocin-diabetes, bulk-diet, low protein diet (8%) and protein-calorie malnutrition on parotid gland response to sympathetic nerve stimulation were studied in male Wistar rats. 2. 2. Mean body weights were considerably less in diabetic and protein-calorie malnourished rats than in the other groups, but parotid gland weight was reduced only in animals placed on a low-protein diet. 3. 3. Salivary flow rate (μ1/min/g tissue) and total protein output (mg secreted/g tissue) were reduced in diabetic rats. 4. 4. Salivary composition was altered in diabetes and protein-calorie restriction, and the specifie changes were unique to each condition. 5. 5. Thus, with the possible exception of gland weight the effects of diabetes on parotid gland structure and function are not related to either hyperphagia or nutritional status.

Glutamate uptake in sinusoidal membrane vesicles isolated from rat liver: effects of streptozotocin diabetes

Glutamate uptake in sinusoidal membrane vesicles isolated from rat liver: effects of streptozotocin diabetes

Effects of Streptozotocin Diabetes in the Rat on Blood Levels of Ten Specific Plasma Proteins and on Their Net Biosynthesis by the Isolated Perfused Liver

Adult male Sprague-Dawley rats with streptozotocin-induced diabetes (6 to 8 wk duration), treated or untreated with insulin, were studied with two aims: (a) to ascertain whether protracted diabetes in the rat is associated with changes in circulating plasma protein levels analogous to those reported in human diabetic patients with clinical evidence of complications; (b) to evaluate the effects of experimental diabetes on the net cumulative biosynthesis of 10 specific plasma proteins by the isolated liver, perfused for 24 hr. Samples of liver donor plasma and samples of perfusate were analyzed by single radial immunodiffusion or by rocket immunoelectrophoresis for albumin, alpha 1-macroglobulin and the acute phase glycoproteins: fibrinogen, alpha 1-acid glycoprotein (Darcy), alpha 1-acid glycoprotein (Kawasaki), haptoglobin, alpha 2-(acute phase) globulin, hemopexin, C3-complement and ceruloplasmin. Diabetes (6 to 8 wk), untreated with insulin, resulted in significantly increased liver donor plasma levels of alpha 1-acid glycoprotein (Darcy) and alpha 1-acid glycoprotein (Kawasaki); plasma levels of hemopexin and of C3 decreased to 75% and 30% of normal, respectively. Insulin treatment of diabetic liver donors for 6 to 8 wk prevented the increase in alpha 1-acid glycoprotein (Darcy) and alpha 1-acid glycoprotein (Kawasaki) and minimized the decrease in C3 to 75% of normal. Perfused livers from untreated diabetic rats (6 to 8 wk) showed slightly decreased cumulative synthesis and secretion of alpha 1-acid glycoprotein (Darcy); however, synthesis of albumin was reduced to 35% of normal and that of eight glycoproteins ranged from 25% of normal (fibrinogen) to 12% of normal (C3). The striking in vitro induction of increased synthesis of acute-phase proteins by cortisol plus insulin in the isolated perfused normal liver was in contrast to the severely attenuated induction in perfused livers of untreated diabetic rats, which ranges from 50% of normal for alpha 1-acid glycoprotein (Darcy) to 5% of normal (C3). Severely negative perfusate nitrogen balance and impaired glucose utilization by perfused untreated diabetic livers contrasted with positive nitrogen balance and good glucose utilization of normal livers in response to insulin plus cortisol. The plasma protein synthetic capacity and the in vitro response to insulin plus cortisol of perfused livers from insulin-treated diabetic rats were normal for seven of the proteins but moderately decreased for albumin, haptoglobin and C3.

糖尿マウスにおける高脂血症

In the present experiment, the effects of streptozotocin diabetes on serum and liver lipid concentrations were investigated in two strains of mice with different responses of serum cholesterol to cholesterol feeding.Serum glucose concentrations were elevated in both strains almost identically by streptozotocin administration. Although serum triglyceride concentrations increased similarly in both strains and had good correlations to serum glucose levels, the elevation of cholesterol was found only in C3H strain, which was a good responder to cholesterol feeding. Consequently, serum cholesterol concentration in the diabetic C3H mouse was higher than that in diabetic DBA. Liver lipid increased on both diabetic mice pallaleled with serum glucose as compared with nondiabetic controls except triglyceride in DBA mouse.It is concluded that the latent metabolic disorder of cholesterol is emphasized in diabetic state, which may be a reason why hypercholesterolemia is not always accompanied with diabetes mellitus.

Enzymes involved in adenosine metabolism in rat white and brown adipocytes. Effects of streptozotocin-diabetes, hypothyroidism, age and sex differences.

1. Adipocytes were isolated from epididymal white fat and interscapular brown fat of male rats, and activities of 5'-nucleotidase, adenosine deaminase and adenosine kinase were measured in cell extracts. 2. 5'-Nucleotidase activity in white adipocytes was increased in streptozotocin-diabetes, decreased in hypothyroidism and increased with age. That activity in brown adipocytes was unchanged in diabetes, decreased in hypothyroidism and increased with age. 5'-Nucleotidase activity was higher in white adipocytes from female rats. 3. Adenosine deaminase activity in white adipocytes was increased in diabetes, decreased in hypothyroidism and increased with age. That activity in brown adipocytes was decreased in diabetes and hypothyroidism. 4. Adenosine kinase activity in both cell types was unchanged in diabetes or hypothyroidism, but increased with age.

Effects of streptozotocin-diabetes, fasting and adrenaline on phosphorylase phosphatase activities of rat skeletal muscle

The distribution of the spontaneous and trypsin-stimulated phosphorylase phosphatase activities between glycogen particles and cytosol was examined in muscle extracts obtained from rats that had been fasted, made diabetic with streptozotocin or injected with adrenaline. In all conditions the particle-bound phosphatase activities decreased, glycogen was degraded and phosphorylase was released from the particles into the cytosol. However, in fasting and diabetes (but not after adrenaline) the combined glycogen particle + cytosolic phosphatase activities decreased, indicating that the activity lost from the particles was not simply shifted to the cytosol. Fasting and diabetes (but not adrenaline) also decreased the phosphatase-activating ability of the muscle extracts, which was, at least in part, attributable to the protein kinase F A. These data indicate the presence of at least two different mechanisms affecting the phosphatase system, one modified by fasting and diabetes, the other by adrenaline.

Carbohydrates, lipids and lipoproteins and islet changes in diabetes with superimposed myocardial infarction

Short-term metabolic and concomitant morphologic effects of streptozotocin diabetes on isoproterenol-induced myocardial infarction was studied in Wistar rats, Of particular significance was the observation that myocardial infarction in concert with diabetes brought about a distinctive exacerbation of the severity and complexity of the histopathological lesions. Of all the biochemical parameters, serum glucose and free fatty acids registered maximum elevation and serum lactate and cardiac glycogen levels a maximum reduction. Among the lipoproteins, an inverse relationship was found between high density lipoproteins and low density and very low density lipoproteins; while high density lipoproteins, ratio of high density lipoprotein to low density lipoprotein and the percentage of high density lipoprotein were decreased, there was a significant increase in low density lipoprotein concentration and percentage values of low density and very low density lipoproteins. In diabetes, the B cell of the endocrine pancreas depicted selective necrosis. Loss of insulin granules and wide-spread necrobiosis of cellular elements of the pancreatic islets were observed, respectively, in myocardial infarction and in diabetes plus myocardial infarction combinations. Pathological evidence of chemical-induced mild toxicity was present in the exocrine parenchyma. Mitotic features and the presence of centroacinar cells in the damaged Langerhans’ islets supposedly formed the basis of regeneration of the tissue in diabetes, with or without vascular complications

The effects of streptozotocin diabetes and of dietary protein content on the composition and metabolism of testicular lipids.

The effect of streptozotocin-induced diabetes on the fatty acid composition and metabolism in testes of rats on diets varying in protein content has been investigated. The protein content of the diet (40, 20, 5%) had little or no effect on essential fatty acid metabolism during the 2 weeks following injection of streptozotocin, but the 5% diet resulted in a high rate of mortality for diabetic rats. Increased amounts of octadeca-9,12-dienoic (linoleic or 18:2) acid and of eicosa-8,11,14-trienoic (dihomo-gamma-linolenic or 20:3) acid and decreased amounts of eicosa-5,8,11,14-tetraenoic (arachidonic or 20:4) acid were observed in testes of some but not all diabetic compared to pair-fed control rats 2 weeks after injection of streptozotocin. Incorporation of 14C from [14C]18:2 into testicular lipids of these rats was determined 26 hr after intratesticular injection. In some rats there was a greater amount of 14C in eicosa-11,14-dienoic acid (dihomolinoleic acid or 20:2) and 20:3 and less 14C in 20:4 of testes of diabetic than in those of control rats. The suggested impairment in conversion of 18:2 to 20:4 was studied further by using [14C]20:3 as the substrate for intratesticular injection. Four hours after administration of the [14C]polyene there was more 14C in 20:3 and less 14C in 20:4 and in docosa-7,10,13,16-tetraenoic (adrenic or 22:4) acid in testes of diabetic than in those of control rats. The results indicate that in diabetic rats at least one enzyme responsible for the decreased conversion of 18:2 to 20:4 is the delta 5-desaturase.

The effects of streptozotocin diabetes on tissue specific lipase activities in the rat.

Fasting in normal rats produced a fall in hepatic triglyceride lipase (H-TGL) activity as well as lipoprotein lipase (LPL) activities of adipose tissue and psoas minor muscle. On the other hand, LPL activities of heart and diaphragm were not decreased by fasting; the former, in fact, was increased significantly. Changes in tissue specific lipase activity caused by withdrawal of insulin from insulin-treated diabetic animals paralleled in direction the changes induced by starvation of normal rats. Furthermore, it was shown in the present paper that the tissue specific lipase activity of diabetic rats became stuck in the starve phase of the starve-feed cycle regardless of dietary intake. The changes of the tissue specific lipase activities, especially of liver, adipose tissue and heart, appeared to coincide with those of plasma insulin levels. These results strongly suggest that the tissue specific lipase system is under hormonal regulation by insulin. Streptozotocin diabetes produced hypertriglyceridemia. The possible mechanism of the hypertriglyceridemia in diabetic animals was discussed in connection with the role of the tissue specific lipase system in the serum triglyceride metabolism.

Effects of streptozotocin diabetes and fasting on intracellular sodium and adenosine triphosphate in rat soleus muscle.

The hypothesis that part of the insulin transduction system consists of a co-ordinated stimulation of the Na pump and of Na-H exchange by the hormone (Moore, 1981) requires that insulin plays a physiological role in the regulation of intracellular Na+. Moreover, this model predicts that in hypoinsulinaemic states, such as diabetes and fasting, intracellular pH and intracellular ATP levels would be depressed. The present study tests the hypothesis that in hypoinsulinaemic states intracellular Na+ is increased and intracellular ATP is decreased by measuring these parameters in soleus muscles removed from both diabetic and fasted rats. When rats were made diabetic by injection of streptozotocin (SZ) plasma insulin significantly decreased by 24 hr and plasma glucose and triglyceride levels increased. Intracellular Na+ was significantly elevated by 48 hr after injection of SZ. The elevation ranged from 18 to 48% and persisted for the duration of the experimental observation (up to 28 days). Intracellular ATP decreased significantly by the seventh day after SZ injection and remained depressed by about 24% for the duration (35 days) of the observation. In one series, a significant negative correlation was seen between plasma insulin levels and intracellular Na+ of both SZ-diabetic animals and their controls. Intracellular Na+ also significantly increased when hypoinsulinaemia was induced by fasting. Again, intracellular ATP did not decrease until after the elevation of intracellular Na+. After 72 hr of fasting, intracellular ATP was still decreased in spite of normal plasma glucose levels. Insulin therapy of SZ diabetic rats restored intracellular ATP and plasma glucose to normal, but did not restore intracellular Na+ to normal levels. The results confirm two predictions of the 'insulin transduction system model (Moore, 1981). Most strongly supported is that part of the model which indicates that the Na pump is regulated by physiological levels of insulin. This is especially convincing since hypoinsulinaemia produced by a non-pharmacological procedure, fasting, was associated with an increase in intracellular Na+.

The effects of streptozotocin diabetes on the activities of rat liver glycosyltransferases.

The effects of streptozotocin diabetes on the activities of rat liver glycosyltransferase enzymes have been investigated. Liver microsomal fractions were prepared from rats that had been injected with streptozotocin (65 mg/kg, i.v.) 3 wk to 2 mo earlier. Preparations from diabetic rats had decreased activities of N-acetylglucosaminyl transferase compared with those of age-matched controls (0.98 +/- 0.11 nmol transferred per mg protein in 30 min versus 3.19 +/- 0.34 for controls, P less than 0.001). Galactosyltransferase activity was also lower in diabetic rat livers (1.48 +/- 0.26 nmol transferred per mg protein in 30 min versus 3.32 +/- 0.56 for controls, P less than 0.025). Sialytransferase activities were not significantly different between diabetic and control rat livers. There were no significant differences between the diabetic and control rat liver microsomes in the activities of UDP N-acetylglucosamine pyrophosphatase, UDP galactose pyrophosphatase, or CMP sialic acid phosphatase. The glycosidases, N-acetylglucosaminidase and galactosidase, had similar activities in the livers of both groups of rats. Sialidase activity could not be detected in microsomal preparations from either diabetic or control rat livers. These results are discussed in relation to our previously reported alterations in glycosyltransferase activities, and plasma membrane glycoprotein composition in the livers of rats made insulin-resistant by a carbohydrate-free, high-fat diet and to the observation of Carter and his colleagues (FEBS Lett. 1979; 104:389-92.) that streptozotocin diabetes alters the glycoprotein composition of rat liver plasma membranes.

The effects of streptozotocin diabetes on the activities of rat liver glycosyltransferases

The effects of streptozotocin diabetes on the activities of rat liver glycosyltransferases

Effects of streptozotocin diabetes and insulin treatment on adipose tissue glucose utilization in the rat.

[U-14C] glucose utilization by pieces of epididymal fat-pad was studied in streptozotocin-diabetic rats, food-restricted animals, and normal controls. Both CO2 and fatty acids formation were greatly reduced in tissues from the diabetic animals treated or not with insulin and this change was milder in tissues from food-restricted rats. A positive correlation was found between [14C] glucose utilization in vitro and plasma RIA-insulin levels when values from all animals were pooled. The percentual response to high doses of insulin was small in adipose tissue from streptozotocin-diabetic animals for CO2 and total lipids formation, but it was high for fatty acids synthesis; the response in food-restricted animals was high and was greatly augmented in tissues from the streptozotocin-diabetic rats treated with insulin. Results indicate that in adipose tissue from streptozotocin-diabetic animals the alteration of insulin responsiveness occurs distal to the receptor events and that impaired basal glucose metabolism is a direct consequence of their hypoinsulinemia.