Non-insulin Dependent Diabetic Rats Research Articles

MON-692 Effect of High Salt Diet on Kidney Weight in Neonatal Streptozotocin Induced Noninsulin Dependent Diabetic Rats

Diabetic kidney hypertrophy may contribute to the development of diabetic kidney disease. Hyperglycemia is recognized as a cause for the kidney endangerment. Salt may accelerate progression of kidney disease in diabetes. To further study the effect of high salt intake on kidney disease we used neonatal streptozotocin induced Noninsulin Dependent Diabetic (NIDD) rats fed ad libitum with regular Purina chow and 2% salt Purina chow. Rats in 5 groups were sacrificed at 6 weeks. Each group had 5–7 rats of diabetics on 2% salt and on regular chow and controls on 2% salt and on regular chow. Blood glucose in diabetics on salt ranged between 185±19–576±20 and in diabetics on regular chow 184±20–458±78 mg/dl. Controls on 2% salt 105±8.6–133±10.3 and controls on regular chow 110±8.9 - 130±3.11. Kidney weights in diabetics on salt was 1.85±0.09–2.0±0.06 gr, diabetics on regular chow 1.6±0.04 - 1.56±0.06 controls on salt 1.19±0.03–1.32±0.05 and controls on regular chow 1.23±0.03. Blood glucose in diabetics on salt and on regular chow was higher than in controls p˂0.05 but did not differ between the diabetic groups. Kidney weight was increased in both diabetic groups compared with controls p˂0.05 and was increased in diabetics on salt compared with diabetics on regular chow p˂0.05 at all glucose levels. Controls on salt and on regular chow had similar kidney weights. Also kidney weight relative to body weight was higher in diabetics than in controls p˂0.05 and was higher in diabetics on salt compared to diabetics on regular chow p˂0.05, but there was no difference between controls on salt and controls on regular diet. Kidney % of water was similar in all four groups but protein to kidney DNA ratio was higher in the diabetic groups p˂0.05 confirming the kidney hypertrophy. Insulin sensitivity measured in controls was not different between groups when glucose transport, glucose oxidation and lipogenesis were measured in fat cells showing no effect of salt on insulin sensitivity. We suggest that high salt intake is an additional risk factor for increased kidney weight in NIDDM that is additive to that of the prevailing glycemia.

Effect of Glycosin alkaloid from Rhizophora apiculata in non-insulin dependent diabetic rats and its mechanism of action: In vivo and in silico studies

Background and aimDiabetes mellitus is a complex multifactorial disorder that remains a great challenging task in the clinical practice. Rhizophora apiculata from Indian medicinal mangrove is widely used to treat inflammation, wound healing and diabetes. Bioassay guided fractionation was followed to isolate Glycosin from the ethanolic extract of R. apiculata. The antidiabetic effect of Glycosin in diabetic rats was investigated and determined their possible mechanism of action. MethodsDiabetes was induced in adult Wistar rats by a single intraperitoneal injection of streptozotocin and nicotinamide. Based on the oral glucose tolerance test, Glycosin (50mg/kg b.wt.) was orally administrated to diabetic rats for a period of 45 days. In different intervals, blood glucose and body weight were recorded. After 45 days, blood samples were collected to determine serum lipid profile, level of plasma insulin, hemoglobin, liver, and kidney functions using the appropriate tests. In addition the levels of carbohydrate metabolic enzymes in the liver homogenate were also measured. To determine the molecular mechanism of action, we followed the molecular docking of Glycosin in its possible targets, dipeptidyl peptidase-IV (DPP-IV), Peroxisome proliferator-activated receptor gamma (PPARγ), phosphorylated insulin receptor, and protein tyrosine phosphatase 1B (PTP-1B). ResultsGlycosin treatment significantly (p<0.01) reduced the blood-glucose level, increased the body weight, increase hemoglobin, high-density lipoprotein and insulin level, protein, in addition the activity of hexokinase when compared to untreated rats. Decreased activities of liver function enzymes as well as level of urea, and creatinine were observed in Glycosin treated rats. Docking simulation confirmed that Glycosin interacted with DPP-IV, Insulin receptor and PTP-1B and PPARγ with more affinity and binding energy. ConclusionGlycosin acts as antihyperglycemic agent, associated with antihyperlipidemic and possibility function as a ligand for proteins that are targets for antidiabetes drugs.

Positive Regulation of Rhizophora mucronata Poir Extracts on Blood Glucose and Lipid Profile in Diabetic Rats

Background: About, five percent of the population in the world has been clinically determined to have diabetes mellitus and considered as one of the principal reasons for death. The present research designed to assess the impact of Rhizophora mucronata leaves ethanolic extract (EtOH-Et) and its dichloromethane (DCM) and aqueous (Aq) fractions in diabetic rats. Methods: Extract and fractions of R. mucronata were determined qualitative and quantitative methods. Different dose (50, 100 and 200 mg/kg of body weight) of extract and fractions were administered intraperitoneally (I.P.) to the normal glycemic rats and their hypoglycemic effect determined for 24 h. Type 1 diabetes mellitus (T1DM) was induced by single injection of streptozotocin (STZ; 60 mg/ kg; I.P.), and type 2 diabetes mellitus (T2DM) was induced by STZ (60 mg/kg; I.P.), after 15 min nicotinamide (120 mg/kg; I.P.). The optimum dose of 100 mg/kg body weight of extract and fractions was administrated to the rats orally for 14 days. The blood glucose level estimated on 0th, 7th, and 14th day. The level of serum cholesterol, triglycerides, and lipoprotein cholesterol were also evaluated on the 14th day. Results: The phytochemical results indicated alkaloids, flavonoids, and terpenoids present in the concentrates of R. mucronata. The content of alkaloids in DCM-F was present in high amount compared with ethanolic extract and an aqueous fraction. All the extract exhibited as non-toxic nature. DCM-F treated rats significantly reduced in blood glucose level (P<0.01), serum cholesterol (P<0.05) and triglycerides (P<0.05) levels whereas HDL-C level was found to be increased (P<0.05) as compared with the diabetic control of T1DM and T2DM. Conclusion: DCM-F of R. mucronata act as effective anti-hyperglycaemic and antihyperlipidemic agent in insulin dependent and non-insulin dependent diabetic rats.

Effect of N-benzoyl-d-phenylalanine on streptozotocin-induced changes in the lipid and lipoprotein profile in rats

The effect of N-benzoyl-D-phenylalanine (NBDP) and metformin combination treatment on circulatory lipids, lipoproteins and lipid peroxidation markers were studied in neonatal streptozotocin (nSTZ) non-insulin dependent diabetic rats. Non-insulin dependent diabetes mellitus (NIDDM) was induced by a single dose injection of streptozotocin (100 mg kg(-1), i. p.) to two-day-old rats. After 10-12 weeks, rats weighing above 150 g were selected for screening for the NIDDM model. The rats were checked for fasting blood glucose levels to confirm the status of NIDDM. NBDP (50,100 or 200 mg kg(-1) ) was administered orally for six weeks to the confirmed diabetic rats (to evaluate the effective dose). The levels of serum lipids and lipid peroxidation markers were significantly increased, whilst the activity of glucose-6-phosphate dehydrogenase was significantly decreased in nSTZ diabetic rats. NBDP and metformin were able to restore the altered serum lipids, lipoproteins, lipid peroxidation marker levels and glucose-6-phosphate dehydrogenase activity to almost control levels. The results showed the antihyperlipidaemic properties of NBDP and metformin in addition to its antidiabetic action. Combination treatment was more effective then either drug alone. The results indicated that the coadministration of NBDP with metformin to nSTZ diabetic rats normalized blood glucose and caused marked improvement in altered serum lipids, lipoproteins and lipid peroxidation markers during diabetes. The data indicated that NBDP represented an effective antihyperglycaemic and antihyperlipidaemic adjunct for the treatment of diabetes, and may be a potential source of new orally active agents for future therapy.

The Significance of Periurethral Fibrosis and the Change of Nitric Oxide Synthase Containing Nerves in the Urethra of Diabetic Rats

We have previously demonstrated that increased urethral resistance was more prominent in diabetic rats than in controls. This may result from a compressive obstruction such as damage of the urethral nerve containing nitric oxide. Another possible cause for urethral obstruction could be a constrictive obstruction such as a periurethral fibrosis. In the present study, we investigated the changes in the expression of nitric oxide synthase(NOS) isoforms(compressive obstruction) and collagen subtypes (constrictive obstruction) in the urethral tissues of non-insulin dependent diabetic rats. Materials and Methods: Thirty-six male Sprague-Dawley rats(18 diabetic rats and 18 control rats), bred from birth, were included in this study. Diabetes mellitus was induced by intraperitoneal administration of streptozotocin(90mg/kg) on the second day after birth. Urethral tissues were harvested at 12, 24 and 36 weeks after induction of diabetes and were stained for neuronal NOS(nNOS) and Masson trichrome. We also performed reverse transcriptase-polymerase chain reaction or Western blot analysis to evaluate mRNA or protein expression of NOS isoforms and collagen subtypes in the urethral tissues. Results: Immunohistochemical staining and Western blot analysis of nNOS revealed that the immunoreactivity and nNOS expression in the urethra was lower in the diabetic rats than in the controls. The Masson trichrome staining showed that there was urethral fibrosis in the diabetic rats. The mRNA or protein expression of collagen subtypes, especially type I collagen, were higher in the diabetic rat urethra than in the controls. Conclusions: These data suggest that the increased urethral resistance in diabetic rats may be attributable to a decrease in the urethral nNOS expression and an increase in collagen content. Urethral dysfunction as well as a cystopathy may play an important role in the pathogenesis of diabetes- induced voiding dysfunction.

Glycoprotein Changes in Non-Insulin Dependent Diabetic Rats: Effect of N-Benzoyl-D-Phenylalanine and Metformin

AbstractThe effect of N-benzoyl-D-phenylalanine (NBDP) and metformin on neonatal streptozotocin (nSTZ) induced diabetes has been studied on plasma and tissue glycoproteins. In some pathological conditions, such as cancer, rheumatoid arthritis and diabetes, there is an abnormal glycosylation of acute phase serum proteins. As most serum proteins are produced in the liver, we have examined glycoprotein metabolism in diabetic condition. To induce non-insulin-dependent diabetes mellitus (NIDDM) a single dose of streptozotocin (100 mg/kg body weight) was injected into two day old rats. After 1012 weeks, rats weighing above 150g were selected for NIDDM model. In these rat, blood glucose and plasma glycoproteins were significantly increased whereas plasma insulin was significantly decreased. There was a significant decrease in the level of sialic acid and elevated levels of hexose, hexosamine and fucose in tissues. Oral administration of NBDP and metformin to diabetic rats decreased blood glucose and plasma glycoproteins. Plasma insulin and tissue sialic acid were increased whereas tissue concentrations of hexose, hexosamine and fucose were near normal. Our study suggests that NBDP and metformin possess a significant beneficial effect on glycoproteins in addition to their antidiabetic effect.

Effect of ascorbic acid treatment on endothelium‐dependent and neurogenic relaxation of corpus cavernosum from middle‐aged non‐insulin dependent diabetic rats

The purpose of the present study was to investigate functional responses and nitric oxide synthase activity in the corpus cavernosum of young control, middle-aged control and middle-aged non-insulin dependent diabetic rats. The animal groups were treated with ascorbic acid. Acetylcholine-mediated endothelium-dependent relaxation of cavernosal tissue was significantly attenuated from a maximum of 58.0 +/- 4.1% (1 mmol, n = 10) in young rats to 44.3 +/- 1.6% in aged-matched controls (P < 0.05) and to 23.3 +/- 2.8% in non-insulin-dependent diabetes mellitus rats (P < 0.01). These deficits in acetylcholine responsiveness were completely prevented by ascorbic acid treatment. Non-adrenergic non-cholinergic relaxations evoked by electrical field stimulation (0.5-64.0 Hz) in the corpus cavernosum of middle-aged control and non-insulin dependent (NID) diabetic rats are blunted and were not restored by ascorbic acid. The histochemical findings demonstrated a decrease of nicotinamide adenine dinucleotide phosphate-diaphorase staining in the cavernosal tissue obtained from middle-aged control rats and middle-aged diabetic rats. Partial correction by ascorbic acid may suggest the importance of reactive oxygen species and a therapeutic approach in impotent NID diabetic men.

4-Hydroxyisoleucine: experimental evidence of its insulinotropic and antidiabetic properties.

We have recently shown in vitro that 4-hydroxyisoleucine (4-OH-Ile), an amino acid extracted from fenugreek seeds, potentiates insulin secretion in a glucose-dependent manner. The present study was designed to investigate whether 4-OH-Ile could exert in vivo insulinotropic and antidiabetic properties. For this purpose, intravenous or oral glucose tolerance tests (IVGTTs and OGTTs, respectively) were performed not only in normal animals but also in a type II diabetes rat model. During IVGTT in normal rats or OGTT in normal dogs, 4-OH-Ile (18 mg/kg) improved glucose tolerance. The lactonic form of 4-OH-Ile was ineffective in normal rats. In non-insulin-dependent diabetic (NIDD) rats, a single intravenous administration of 4-OH-Ile (50 mg/kg) partially restored glucose-induced insulin response without affecting glucose tolerance; a 6-day subchronic administration of 4-OH-Ile (50 mg/kg, daily) reduced basal hyperglycemia, decreased basal insulinemia, and slightly, but significantly, improved glucose tolerance. In vitro, 4-OH-Ile (200 microM) potentiated glucose (16.7 mM)-induced insulin release from NIDD rat-isolated islets. So, the antidiabetic effects of 4-OH-Ile on NIDD rats result, at least in part, from a direct pancreatic B cell stimulation.

Decreased susceptibility to lipid peroxidation of Goto-Kakizaki rats: Relationship to mitochondrial antioxidant capacity

The respiratory function and the antioxidant capacity of liver mitochondrial preparations isolated from Goto-Kakizaki non-insulin dependent diabetic rats and from Wistar control rats, with the age of 6 months, were compared. It was found that Goto-Kakizaki mitochondrial preparations presented a higher coupling between oxidative and phosphorylative systems, compared to non-diabetic preparations. Goto-Kakizaki mitochondria presented a lower susceptibility to lipid peroxidation induced by ADP Fe 2+ , as evaluated by the formation of thiobarbituric acid substances. The decreased susceptibility to peroxidation in diabetic rats was correlated with an increase in mitochondrial vitamin E (α-tocopherol) content and GSH GSSG ratio. Moreover, the glutathione reductase activity was significantly increased, whereas the glutathione peroxidase was decreased. Superoxide dismutase activity was unchanged in diabetic rats. Fatty acid analyses showed that the content in polyunsaturated fatty acids of Goto-Kakizaki mitochondrial membranes was significantly higher compared to controls. These results indicate that the lower susceptibility to lipid peroxidation of mitochondria from diabetic rats was related to their antioxidant defense systems, and may correspond to an adaptative response of the cells against oxidative stress in the early phase of diabetes.

Effects of Adenosine and Isoprenaline in Left Atria from Both Neonatal and Middle-Aged Noninsulin-Dependent Diabetic Rat Models

1. This study examined the ability of atria from neonatal and middle-aged noninsulin-dependent diabetic rat models to respond to both adenosine and isoprenaline. 2. Cumulative additions of adenosine (1–1000 μM) produced concentration-dependent decreases in the force of contraction of rat atria that were unchanged in neonatal diabetic animals. Although direct inotropic responses to adenosine were unchanged, atria from neonatal diabetic animals exhibited an increase in maximum response to adenosine-induced antiadrenergic effect. 3. Atria from middle-aged noninsulin-dependent diabetic rats exhibited a supersensitivity to the direct inotropic effect of adenosine compared with atria from age-matched control rats. The middle-aged, noninsulin-dependent diabetic state did not alter the maximum response of atria to adenosine-induced antiadrenergic effect. 4. A comparison was made between middle-aged (10-month-old) controls and young (4-month-old) controls. Atria from middle-aged control animals exhibited a lower sensitivity and responsiveness to the direct inotropic effect of adenosine compared with those from young controls. 5. Cumulative additions of isoprenaline (10 −9–10 −6 M) produced concentration-dependent increases in inotropy that were unchanged in atria from either neonatal or middle-aged noninsulin-dependent diabetic rats. 6. These results show that neonatal and middle-aged noninsulin-dependent diabetes and age-related factors lead to significant changes in atrial reactivity to the adenosine-induced stimulation in the absence and presence of isoprenaline. However; isoprenaline-induced positive inotropic response cannot change in each diabetic heart to an apparent extent.

Renal function in the noninsulin-dependent diabetic rat: Effects of unilateral nephrectomy

A new model of noninsulin-dependent diabetic (NIDD) is described which exhibits more prominent defects in renal function than does the standard neonatal NIDD model. To produce this model, 2-day-old neonatal male Wistar Kyoto (WKY) rats were injected intraperitoneally with streptozotocin (90 mg/kg; NIDD), while their corresponding nondiabetic controls were administered vehicle (citrate buffer, pH: 4.5; control). At 3 weeks of age, the animals were weaned, and 1 week later, under ether anesthesia, the animals underwent a right nephrectomy or a sham operation. Diabetes was confirmed by intraperitoneal administration of a glucose load (2 g/kg), which resulted in significantly higher blood glucose concentration in the NIDD, compared to the nondiabetic rats. Surgical reduction of renal mass had no effect on the glycemic response to a glucose tolerance test in either group. Intravenous administration of an isotonic saline load resulted in a similar pattern of enhanced sodium and fluid excretion in the two-kidney sham-operated nondiabetic and NIDD rats. These responses were significantly higher than those observed in their counterparts with one remaining kidney. Yet, the natriuretic and diuretic responses to the saline load were significantly lower in the nephrectomized NIDD, compared to the nephrectomized nondiabetic rats. The glomerular filtration rate was similar in the sham-operated (two kidneys) NIDD and nondiabetic rats. In contrast, both the basal and saline-stimulated glomerular filtration rate were lower in the nephrectomized NIDD rats compared to the nephrectomized nondiabetic group. Mean arterial pressure was similar between the two nephrectomized groups, thereby ruling out a significant contribution from the pressure-diuresis-natriuresis mechanism to the reduction in sodium and fluid excretion in the nephrectomized NIDD rats. Thus, unilateral nephrectomy is an effective method of accelerating the manifestation of NIDD-related renal alterations. The mild, but progressive, nature of diabetes in this model should facilitate the investigation of temporal changes in renal function in NIDDM.

Is there a link between impaired glucose metabolism and protein kinase C activity in the diabetic heart?

The activity of the beta isoform of protein kinase C (PKC beta) is reduced in the diabetic heart. Since this isozyme has been implicated in insulin action, we tested the hypothesis that PKC beta contributes to the development of impaired glucose metabolism by the noninsulin-dependent diabetic heart. Exposure of the diabetic heart to buffer containing the protein kinase C activator, phorbol myristate acetate, increased PKC beta activity in the membrane. Associated with the improvement in PKC beta activity was a biphasic change in glucose metabolism. The initial phase was characterized by a breakdown in glycogen stores, a stimulation in glucose oxidation and a decrease in endogenous fatty acid oxidation. This was followed by a second phase in which the uptake of glucose was modestly stimulated. Nonetheless, since the phorbol ester did not overcome the diabetes-linked defect in pyruvate dehydrogenase, the increase in glycolytic flux was not associated with a rise in glucose oxidation. Consequently, nearly 50% of the triose units were diverted into lactate and pyruvate production and the generation of ATP from glucose was restricted. Since insulin promotes not only glucose uptake, but also glycogen synthesis and glucose oxidation, the phorbol ester and insulin effects are very different. Thus, the data do not support a role for PKC beta in the development of glucose metabolic defects in the hearts of noninsulin-dependent diabetic rats.

Altered prostanoid production by cumulus-oocyte complexes in a rat model of non-insulin-dependent diabetes mellitus

Ovulation, oocyte maturation and PGE and PGF 2α production by oocyte-cumulus complexes were evaluated in rats with non-insulin-dependent diabetes induced by neonatal streptozotocin. Diabetic rats had normal estrous cycles, but ovulated a lower number of oocytes at estrus. When oocytes from control and diabetic rats obtained at proestrus were matured “in vitro” during 1, 2 or 4 hours (hr) of culture, differences were not found in the percent of germinal vesicle breakdown between both experimental groups. PGE and PGF 2α accumulation was higher in ovulated oocyte-cumulus complexes when compared to immature or “in vitro”-matured oocyte-cumulus complexes in both normal and diabetic rats. When control and diabetic rats are compared, more PGE and PGF 2α accumulation was observed in immature, “in vitro”-matured and in ovulated oocytecumulus complexes. A lower number of oocytes ovulated and increased oocyte-cumulus complexes prostaglandin production has been observed in this mildly diabetic experimental model. These abnormalities are similar to those previously found when 10 day embryos were evaluated in noninsulin-dependent diabetic rats.

Hypothalamic-pituitary-adrenal axis in WBN/Kob rats with non-insulin dependent diabetes mellitus.

In an attempt to define the hypothalamic-pituitary-adrenal (HPA) axis in non-insulin dependent diabetic rats (WBN/Kob), we measured plasma corticotropin releasing factor (CRF), as well as arginine vasopressin (AVP), ACTH, and corticosterone (B), CRF concentrations in the median eminence (ME), the remainder of the hypothalamus (rHY) and the neurointermediate lobe of the pituitary (NIL). We also measured Iodine-125-labeled ovine CRF ([125I]oCRF) binding in the brain and peripheral tissues. Body and thymus weight in WBN/Kob rats were significantly lower than in control Wistar rats, but adrenal weight was higher in WBN/Kob rats. Plasma ACTH levels were significantly higher in WBN/Kob rats than in the control rats. However, plasma CRF, AVP and B levels in WBN/Kob rats were not different from those in the control rats. The CRF concentration was significantly decreased in the ME of the diabetic rats, compared with control rats, but CRF concentrations in the rHY and NIL were unchanged in the two groups. A significant reduction in [125I]oCRF binding in the anterior pituitary was demonstrated in WBN/Kob rats, but no significant difference between the diabetic and control rats in CRF binding was observed in the frontal cortex, spleen or adrenal gland. These findings suggest that the HPA axis is chronically stimulated in the non-insulin dependent diabetic rats.

Eicosanoid production and phospholipase A 2 activity in uterine tissue from castrated rats with non-insulin dependent diabetes mellitus

In uterine tissue obtained from castrated control and non-insulin dependent diabetic (NIDDM) rats, eicosanoid production and its regulation by glucose levels and by the activity of phospholipase A 2 (PLA 2) was assessed. Basal outputs of prostaglandins (PGs) PGE 2, PGE 1, PGF 2α, 6-keto-PGF 1α (indicating the production of prostacyclin), thromboxane B 2 (TXB 2) (indicating the generation of TXA 2) and leukotriene B 4 (LTB 4) were similar in control and NIDDM uterine preparations as assessed by RIA. When uterine conversion of labelled arachidonate into different prostanoids was evaluated, generation of 6-keto-PGF 1α, PGE 2 and PGF 2α was similar in control and NIDDM uterine tissue, while TXB 2 production was higher in the diabetic group. Moreover, when control tissue was incubated in the presence of elevated concentrations of glucose (22 mM) and compared to control tissue incubated in concentrations of glucose 11 mM, similar generation of 6-keto-PGF 1α, PGE 2 and PGF 2α was observed, and higher concentrations of TXB 2 were found, similar to those observed in diabetic uterine tissue. When NIDDM uterine tissue was incubated in the presence of glucose 22 mM, no difference in any prostanoid evaluated was observed when compared to values obtained in the presence of glucose 11 mM. In this work we have observed in NIDDM uterine tissue a normal TXA 2 production when evaluated by RIA from endogenous arachidonic acid (AA) and a higher TXA 2 generation from exogenous labelled AA. In addition PLA 2 activity was found diminished in the NIDDM uteri in comparison to control uteri. A role of the diminished PLA 2 as a protective mechanism that avoids TXA 2 overproduction in uterine tissue from NIDDM rats is discussed.

Abnormal Ca2+-ATPase Activity in Erythrocytes of Non-Insulin-Dependent Diabetic Rats

Non-insulin-dependent diabetic (NIDD) rats have an increased Ca2(+)-ATPase activity in their kidney basolateral membranes. We find that a similar increased activity occurs in erythrocytes of the NIDD animals. This alteration in membrane ATPase activity appears to be specific for the Ca2(+)-ATPase as (Na(+) + K+) and Mg2(+)-ATPase and Na, K and Mg concentrations in the erythrocyte were not affected by the diabetic condition in these animals. Thus, abnormalities in membrane Ca2(+)-ATPase activity in the NIDD rats are not restricted to one tissue and appear to be a generalized pathology in the NIDD animals.

Effects of food restriction and insulin treatment on (Ca 2+ + Mg 2+)-ATPase response to insulin in kidney basolateral membranes of noninsulin-dependent diabetic rats

Insulin increases (Ca 2+ + Mg 2+)-ATPase activity in cell membranes of normal rats but fails to do so in membranes of non-insulin-dependent diabetic (NIDD) rats. The loss of regulatory effect of the hormone on the enzyme might contribute to the insulin resistance observed in the NIDD animals. To further test this hypothesis, the effects of insulin treatment and acute food restriction on the ability of insulin to regulate the ATPase activity in kidney basolateral membranes (BLM) of NIDD rats were studied. Although insulin levels in NIDD and control rats were similar, plasma glucose was higher in the NIDD rats (18.3 ± 1.5 v 19.3 ± 1.7 μU/mL and 236 ± 32 v 145 ± 3 mg/dL, respectively). Insulin treatment ( 2 U 100 g ), which increased plasma insulin in the NIDD rats (47.8 ± 11.5 μU/mL; P < .05), did not decrease their glucose (221 ± 25 mg/dL). Higher insulin dose ( 4 U 100 g ) decreased glucose level in the NIDD rats (73 ± 3 mg/dL; P < .001) but increased their plasma insulin 10-fold (202.5 ± 52.5 μU/mL). Acute food restriction decreased glucose levels in the NIDD rats to levels seen in controls (135 ± 3 mg/dL), while their insulin decreased by half (8.5 ± 1.0 μU/mL; P < .05). Basal (Ca 2+ + Mg 2+)-ATPase activity in BLM of all diabetic rats was higher than in controls ( P < .05). None of the treatments reversed this defect. Insulin (12.5 to 200 μU/mL) increased the ATPase activity (10% to 40%) in BLM from controls but not from NIDD rats. In BLM from food-restricted diabetic rats, insulin increased the enzyme activity by 16% to 42%, but the dose-response curve was shifted to the right. In BLM from insulin-treated rats, insulin caused a slight (10% to 20%) increase in enzyme activity only at its highest concentration (200 μU/mL). These findings confirm the existence of insulin resistance in the NIDD rats and reveal that acute food restriction ameliorates it. The amelioration of insulin resistance was accompanied by a regained ability of insulin to regulate the membrane (Ca 2+ + Mg 2+)-ATPase. It is suggested that part of the beneficial effect of food restriction on insulin resistance in the NIDD rat is due to a restoration of insulin's ability to regulate cell Ca 2+ homeostasis.

The effects of type-1 and type-2 diabetes on endothelium-dependent relaxation in rat aorta

Diabetes mellitus is know to produce alterations in vascular reactivity. In the present study we have examined the effects of endothelium-dependent and endothelium-independent relaxing substances on thoracic aorta from insulin-dependent (Type-1) and noninsulin-dependent (Type-2) diabetic rats and their appropriate controls. Endothelium-dependent relaxations produced by acetylcholine and histamine in aortic rings precontracted with noradrenaline were significantly increased in insulin-dependent diabetic vessels. In contrast, the relaxations elicited by those agents were significantly attenuated in noninsulin-dependent diabetic aorta preparations. On the other hand, the relaxations induced by sodium nitroprusside (an endothelium-independent relaxant agent) in both types of diabetic preparations were comparable to those in control vessels. The results indicate that insulin-dependent and noninsulin-dependent diabetes lead to specific alterations of the endothelium-dependent relaxation of rat aorta.

Abnormal cell calcium concentrations in cultured bone cells obtained from femurs of obese and noninsulin-dependent diabetic rats

Cytoplasmic free calcium concentration [Ca2+]i was quantified in cultured bone cells with osteoblastic characteristics. The cells were obtained from femurs of obese (fa/fa) Wistar-Kyoto rats, from nonobese, noninsulin-dependent diabetic (NIDD) Sprague Dawley rats, and from their appropriate controls. [Ca2+]i was also determined in bone cells obtained from in vivo insulin-treated NIDD rats. Obese (Wistar Kyoto) rats had increased body weight (313 +/- 13 vs. 249 +/- 4 g; P less than 0.01), decreased femur weights (0.68 +/- 0.05 vs. 0.89 +/- 0.05 g; P less than 0.05), similar glucose levels (148 +/- 5 vs. 139 +/- 3 mg/dl), and higher plasma insulin levels (6.0 +/- 0.5 vs. 0.7 +/- 0.1 ng/ml; P less than 0.01) when compared with their nonobese [(fa/+); (+/+)] littermates. Nonobese, NIDD rats, compared with their appropriate controls (nondiabetic Sprague Dawley rats) had higher plasma glucose levels (235 +/- 32 vs. 145 +/- 3 mg/dl; P less than 0.01) but their plasma insulins, body weights, and femur weights were similar to controls (0.7 +/- 0.1 vs. 0.6 +/- 0.1 ng/ml; 302 +/- 4 vs. 318 +/- 14 g; 0.97 +/- 0.4 vs. 0.98 +/- 0.04 g, respectively). Long-term (4 weeks) daily insulin treatment (2 u/100 g) of the NIDD rats increased their plasma insulin (1.9 ng/ml; P less than 0.05) and body weight (369 +/- 13 g; P less than 0.05) but did not change their plasma glucose levels (225 +/- 5 mg/dl), or femur weights (0.98 +/- 0.4 g).(ABSTRACT TRUNCATED AT 250 WORDS)

NIDDMモデルラットの血漿脂質濃度に及ぼす高コレステロール食の影響

NIDDMモデルラットの血漿脂質濃度に及ぼす高コレステロール食の影響