Influence of maternal diabetes on fetal rat development: alteration of insulin receptors in fetal liver and lung

The influence of maternal diabetes on fetal development was studied in rats made diabetic by administration of streptozotocin on day 2 of gestation as well as in genetically diabetic BB Wistar rats. A dose of 65 mg streptozotocin/kg produced severe diabetes with plasma glucose levels of approximately 36 mmol/l, this was associated with fetal growth retardation but not fetal hyperinsulinaemia. In contrast, a smaller dose of streptozotocin (45 mg/kg) produced moderate diabetes with plasma glucose levels of approximately 20 mmol/l and was associated with fetal hyperinsulinaemia but only a marginal effect on fetal size. In both groups of diabetic animals, maternal body weight gain was decreased, maternal plasma insulin levels were low and fetal glucose levels were similar. In a small group of genetically diabetic BB rats on insulin therapy the fetuses were macrosomic and hyperinsulinaemic. The specific binding of 125I-labelled insulin to partially purified liver and lung membranes of fetuses of both groups of streptozotocin-induced diabetic rats was significantly lower than the binding to membranes from fetuses of control animals. The specific binding of 125I-labelled insulin to fetal liver and lung membranes from the diabetic BB Wistar rats also appeared to be reduced when compared to tissues from controls. Decreased insulin receptors in fetal lung and liver of diabetic rats suggest a role for insulin in the development of these organs during the fetal and neonatal period.     

In vitro insulin effect on acetylcholine esterase of erythrocyte membranes of normal and diabetic rats

Summary Alloxan induced diabetes in rats was associated with a significant reduction in the acetylcholine esterase activity of the erythrocyte membrane. Preincubation of these membranes with insulin caused a rapid but transient stimulation of this enzyme activity in both normal and diabetic rats, the effect being more marked in the latter group. CDRI Communication No. 3721.     

Effects of nephrectomy and high-protein diets on glomerular hemodynamics and urinary protein excretion in diabetic rats

Renal blood flow, GFR, albumin clearance, and urinary excretion of proteins were assessed in intact control and streptozotocin-diabetic rats (group 1), unilaterally nephrectomized control and diabetic rats (group 2), and nephrectomized control and diabetic rats (divided into high (a) and low (b) glycemia subgroups) fed a 50% protein diet (group 3). After 8 months of diabetes, blood flow did not differ from control rats within each experimental group, although it was increased significantly in both controls and diabetics of groups 2 and 3 versus group 1. GFR in control rats was increased ∼2x by nephrectomy and ∼3x by nephrectomy plus the high protein diet. Diabetes increased GFR ∼50% above control values in group 1; GFR values in diabetic rats of groups 2 and 3a were virtually identical and similar to those of group 2 controls; GFR in group 3b diabetics was increased ∼1.4x versus group 2 diabetics. ¹²⁵I-BSA clearance was increased 3.4x in groups 2 and 3 control rats versus group 1 controls. Both nephrectomy and consumption of the high protein diet caused marked increases in ¹²⁵I-BSA clearance and urinary excretion of albumin in diabetic rats. Urinary excretion of IgG was increased by diabetes in group 1 and remained essentially at this level in groups 2 and 3 diabetic rats. These results demonstrate: 1) additive effects of nephrectomy and increased protein consumption on renal blood flow, GFR, and urinary excretion of albumin and IgG in nondiabetic rats, but only on albumin clearance and excretion in diabetic rats; and 2) consumption of a protein rich diet by nephrectomized diabetic rats was associated with substantial increases in renal blood flow and GFR and with a doubling of albumin clearance and albuminuria despite a substantial amelioration of the diabetic state.     

Effect of physical training on ventricular beta-adrenergic receptor adenylate cyclase system of diabetic rats.

This study was designed to assess the effect of physical training on the ventricular beta-adrenergic receptor adenylate cyclase system of diabetic rats. Mild diabetes mellitus was induced by an intravenous (IV) injection of streptozotocin (45 mg/kg). Rats were randomized into a group submitted to a progressive 10-week running program on a treadmill, while another group was kept sedentary. A group of sedentary nondiabetic rats was used as normal controls. Results showed a similar reduction in the density of beta-adrenergic receptors in sedentary diabetic (P less than .05) and trained diabetic rats (P less than .01) compared with controls, without any significant alteration in the dissociation constant. The basal and the sodium fluoride-stimulated maximal adenylate cyclase activities were similar in the three groups. However, the maximal response of adenylate cyclase to isoproterenol was significantly reduced in the two diabetic groups compared with controls (P less than .01). The decrease in adenylate cyclase response to isoproterenol observed in the diabetic groups appeared to be associated with a reduction in the total number of beta-adrenergic receptors and more specifically in those existing in the high-affinity state. On the other hand, the hyperglycemia and hyperglucagonemia present in sedentary diabetic rats was improved by training. These data suggest that the beneficial effects observed in response to training in experimental diabetes are not associated with changes in beta-adrenergic receptor adenylate cyclase system on membranes from ventricular tissue.     

Diabetes mellitus: changes in the transport properties of isolated intestinal microvillous membranes.

Isolated, small intestinal microvillous membranes from normal and acutely diabetic rats were compared with respect to D-glucose transport. D-Glucose was accumulated to a greater extent by diabetic membrane vesicles when supplied with energy in the form of a NaC1 or a NaSCN gradient across the vesicle membrane. The difference appeared to be caused by an ability of the diabetic membranes to maintain a higher driving force for active D-glucose transport and not by changes in the glucose "carrier." Increasing the glucose-independent Na-+-conductance of the membrane with monactin or gramicidin D reduced the active accumulation of D-glucose by membrane preparations from both control and diabetic groups. Concentrations of monactin and gramicidin D in the incubation medium of membrane vesicles from diabetic animals could be adjusted so that their D-glucose transport became indistinguishable from that of membranes from normal animals not treated with ionophores. These observatins suggest the microvillous membranes as one site where changes occur in acute diabetes. In addition, the change in the transport properties of the isolated membranes offer a rational explanation for the simultaneous elevation of active intestinal sugar, amino acid, and bile salt transport observed for intact intestinal tissue.     

Reduced number of anionic sites is associated with glomerular basement membrane thickening in the diabetic BB-rat

Summary Glomerular basement membranes of diabetic and age- and sex-matched non-diabetic BB rats were studied morphometrically and ultrastructurally using a quantitative histochemical technique employing the cationic dye cuprolinic blue. Six months of diabetes resulted in a significant reduction in the density of anionic sites associated with increased thickness of the glomerular basement membrane. These findings suggest that loss of anionic sites may be an important mechanism in the genesis of glomerular basement membrane dysfunction in diabetes.     

Studies on glomerular basement membrane in experimental diabetes using lectin histochemistry in Wistar rats

Summary This study was designed to establish whether specific early changes in carbohydrate content of proteins in the glomerulus of the diabetic rat could be detected. Lectin staining of kidney sections from streptozotocin-induced diabetic rats were compared with similar sections from healthy and diabetic rats that were treated with insulin. Animal groups were killed 1 month, 3 months and 6 months after induction of diabetes. There were no differences in the staining of the glomerular basement membrane between control, insulin-treated and diabetic rats for the lectins concanavalin A, lotus tetragonolobus, soybean and kidney bean, with and without trypsinisation. Staining of the glomerulur basement membrane with wheat germ agglutinin after trypsinisation was significantly increased in the diabetic group when compared to both healthy and insulin-treated groups (p < 0.01). It was concluded that, in experimental diabetes mellitus in the rat, there is an accumulation of substances in the glomerular basement membrane and mesangium with an affinity for wheat germ agglutinin, most probably N-acetyl glucosamine, and this is partially prevented by insulin treatment.     

Discordant effects of the aldose resuctase inhibitor,sorbinil, on vascular structure and function in chronically diabetic and galactosemic rats

Effects of sorbinil, an aldose reductase inhibitor, were examined on renal glomerular structure, urinary albumin and IgG excretion, and vascular albumin permeation in eyes and aorta of 8-month diabetic, galactose-fed, and age-matched control rats. Sorbinil was added to the diet of one-half of the rats in each group at the time of induction of diabetes and galactosemia. Weight gain was impaired in diabetic and galactose-fed rats versus controls and was improved slightly in corresponding sorbinil-treated groups. Plasma glucose and glycosylated hemoglobin levels, food consumption, and 24-hr urine volume were increased in diabetic rats and were unaffected by sorbinil treatment. Food consumption and glycosylated hemoglobin levels were increased in galactose-fed rats, although the increases were smaller than in diabetic rats; glycosylated hemoglobin levels were decreased by sorbinil. Diabetes- and galactosemia-induced increases in albumin permeation in eyes and aorta were prevented by sorbinil. Urinary excretion of albumin and IgG was increased by diabetes and decreased by sorbinil, although differences between the two diabetic groups were not statistically significant for albumin. Galactosemia was associated with an increase in urinary albumin and IgG excretion that did not reach statistical significance. Glomerular capillary basement membrane width (GBMW) was increased in diabetic versus agematched control rats but was unaffected by galactose feeding. GBMW was increased in controls fed sorbinil and glomerular capillary basement membrane thickening in diabetic rats was not prevented by sorbinil. The fractional volume of the glomerulus occupied by mesangium (V_vmes) was increased in diabetic and galactose fed rats versus agematched controls, and was unaffected by sorbinil. The explanation for the discordant effects of sorbinil on generalized vascular dysfunction versus glomerular structural changes remains unclear.     

Pyridoxine binding to normal and diabetic liver plasma membrane

Pyridoxine binding to liver plasma membrane isolated from livers of normal and streptozotocin-induced diabetic rats was investigated. The effect of increasing concentration of pyridoxine on its binding to the membranes revealed a concentration-dependent and saturable process with a significant decrease in the high affinity receptor sites of the diabetic membrane. Moreover, the incubation of the membranes with procaine, colchicine and vincristine increased significantly pyridoxine binding to normal and diabetic membrane. Treatment of the normal and diabetic membranes with insulin did not affect pyridoxine binding. It could be suggested that streptozotocin-induced diabetes caused an alteration in the pyridoxine binding capacity of the liver plasma membrane which might be due to certain structural changes in the membrane.     

Prevention of glomerular basement membrane thickening by aminoguanidine in experimental diabetes mellitus

The etiology of diabetic glomerulopathy appears to be related, at least in part, to the degree of hyperglycemia, the resultant nonenzymatic glycosylation of proteins, and the eventual formation of advanced glycosylation end products in long-lived structural proteins. To investigate the relationship between the glomerular basement membrane (GBM) changes of diabetic nephropathy and the formation of advanced glycosylation end products, we studied control rats, diabetic rats, and control and diabetic rats who received aminoguanidine, a compound that pharmacologically inhibits formation of advanced glycosylation end products. After 9 months, rat weight was smaller and kidney weight larger in both diabetic groups compared with both control groups. GBM width was increased in the diabetic group compared with the control group. Aminoguanidine administration to diabetic rats ameliorated this increase in GBM. Thus, aminoguanidine administration from the onset of experimental diabetes prevented the widening of the GBM that is typical of diabetes.     

Dicer expression is impaired in diabetic cutaneous wound healing

Diabetes, as a fast growing non-communicable disease, is one of the major health problems of the twenty-first century. Several complications such as cardiovascular disease and renal failure are accompanying diabetes. The chronic cutaneous wound is another diabetes complication, results from the reduced body healing potential. At genome level, diabetic wound environment displays disorganized gene functions emphasizing the critical role of gene regulatory networks in the control of chronic wound repair. MicroRNAs, major regulators of gene activity, have been shown to be impaired in several pathological conditions such as chronic wounds. A reason behind that can be sought in the impaired activity of enzymes involved in the development and production of miRNAs. In current study, streptozocin-induced diabetic rats and non-diabetic controls were used to study the effect of diabetes on Dicer presence in wound environment. Unwounded skin of diabetic animals showed significantly lower level of Dicer expression compared with non-diabetic animal-derived skin. However, at day 7 post-wounding, diabetic animal-derived wounds contained a higher level of Dicer expression compared with non-diabetic ones. Parallel to these findings, the granulation tissue formation and wound closure are impaired in diabetic wounds. This study highlights the dysregulated presence of Dicer at different stages of the diabetic cutaneous wound.     

表皮生长因子纳米微粒对糖尿病大鼠皮肤创面愈合的影响

目的 观察表皮生长因子（EGF）纳米微粒对糖尿病大鼠皮肤创面的愈合作用,探讨EGF纳米微粒促进愈合的机制.方法 制备EGF纳米微粒,测定EGF纳米微粒载药率、包封率和释药行为.用打孔器制备糖尿病大鼠皮肤创面模型.分为4组：EGF纳米组（给予含1μg/d EGF的纳米微粒）,EGF组（给予1μg/d EGF）,空微粒组（给予不含EGF纳米微粒）,磷酸盐缓冲液（PBS）对照组,于3、7、14、21 d照相并取材,计算创面愈合率并比较创面病理学变化及EGF受体阳性细胞面积.结果 EGF纳米微粒平均粒径为193.5 nm,载药率为0.02％,包封率为85％.药物释放达24h.EGF纳米组创面愈合比EGF组快[14 d,（93.8±1.8）％比（89.3±2.3）％,P＜0.05;21 d（96.6±1.6）％比（92.1±4.3）％,P＜0.05].EGF纳米组创面内EGF受体阳性细胞面积高于EGF组[7d,（49.4±6.5）％比（35.1±2.8）％,P ＜0.05;14 d,（80.2±3.8）％比（73.4±1.7）％,P＜0.05].结论 EGF纳米微粒上调创面内细胞EGF受体表达,加速创面的愈合,效果优于EGF.     

Melatonin inhibits lipid peroxidation and stimulates the antioxidant status of diabetic rats

Although melatonin has been established as a free radical scavenger and antioxidant, its effects in diabetes have not been thoroughly investigated. The purpose of this study, therefore, was to investigate the effects of melatonin administration on lipid peroxidation and antioxidant status in streptozotocin (STZ)-induced diabetes in rats. Concentrations of malondialdehyde (MDA) and reduced glutathione (GSH) in erythrocytes and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were compared in 3 groups of 10 rats each [control non-diabetic rats (group I), untreated diabetic rats (group II) and diabetic rats treated with melatonin (group III)]. In the study groups, diabetes developed 3 days after intraperitoneal (i.p.) administration of a single 60-mg/kg dose of STZ. Thereafter, while the rats in group II received no treatment, the rats in group III began to receive a 10-mg/kg i.p. dose of melatonin per day. After 6 wk, the rats in groups II and III had significantly lower body weights and significantly higher blood glucose levels than the rats of group I (P<0.001 and P<0.001, respectively). There were no significant differences in body weight or blood glucose levels between groups II and III. MDA levels in untreated diabetic rats were higher than those in control group rats and in diabetic rats treated with melatonin (P<0.01 and P<0.05, respectively). However, MDA levels in diabetic rats treated with melatonin were not different from those of the control group. The GSH, GSH-Px and SOD levels of untreated diabetic rats were significantly lower than those of the control group (P<0.02, P<0.002 and P<0.05, respectively). In group III, however, melatonin prevented decreases in the thiol antioxidant and the associated enzymes, and so these levels were not significantly different from those in the control group. These results confirm the presence of oxidative stress in STZ-induced experimental diabetes and indicate the beneficial free radical-scavenging and antioxidant properties of melatonin.     

The effect of diabetes and the redox potential on amino acid content and release by isolated rat hemidiaphragms

The free amino acid content of diaphragm muscles of control and diabetic rats was studied 5 days after the injection of streptozotocin. Muscles were prepared for analysis either immediately after sacrifice or following incubation in balanced salt solution containing 5.5 mM glucose, with or without an electron acceptor, 0.02 mM methylene blue. Diaphragms of diabetic rats contained significantly more free taurine, glutamate, and branched chain amino acids than the controls at sacrifice, and significantly less glutamine, serine, asparagine, lysine, arginine, histidine, threonine, citrulline, and carnosine. Alanine decreased in plasma of diabetic rats but not in diaphragms before incubation. Hemidiaphragms of diabetic rats produced less alanine and more glutamate during incubation than controls. After incubation they contained less than half as much alanine and glutamine and twice as much glutamate than the controls, having released approximately 40% less alanine and 25% more glutamate into the medium than the controls. Glutamine release was not significantly different between the two groups. Methylene blue increased the free alanine content in the tissue water as well as alanine release by control and by diabetic muscles; the glutamate content of muscles decreased concomitantly. The effects of methylene blue were greater in the diabetic group. Branched chain amino acid release by diabetic muscles decreased during incubation with methylene blue. Muscles of diabetic rats contained more α-ketoglutarate than the controls after incubation with or without methylene blue. Methylene blue increased the α-ketoglutarate content of muscles and its release into the medium, the effect being greater in diabetics than in controls. Hemidiaphragms from diabetic rats released less pyruvate during incubation than controls, while lactate release by the two groups was not significantly different. Incubation with methylene blue caused a marked increase in pyruvate release by diabetic muscles, and a lesser stimulation in controls; lactate release increased in both groups. After incubation the lactate/pyruvate ratio in muscles was lower in the methylene blue treated group. The in vitro effect of 0.02 mM phenazine methosulfate on alanine production was similar to that of methylene blue. The data is compatible with the hypothesis that the $\text{NADH}\text{NAD}$ ratio may exert a restraining effect on alanine production and release by muscle. The progressive increase in this ratio may play a role in the eventual deceleration of gluconeogenesis during a prolonged fast and may restrain this process in uncompensated diabetes.     

姜黄素促进骨骼肌GLUT4转位改善糖尿病大鼠胰岛素抵抗

目的:研究姜黄素对STZ诱导糖尿病大鼠骨骼肌胰岛素抵抗的影响及其机制。方法:雄性SD大鼠腹腔注射STZ诱导糖尿病大鼠模型。成模大鼠分为糖尿病组(DM),糖尿病＋姜黄素组(DM＋Cur),糖尿病＋缓冲液对照组(DM＋NC)。以正常SD大鼠为正常对照组(NC)。DM＋Cur组予姜黄素灌胃治疗,DM＋NC组给予等体积缓冲液灌...     

Effect of thalidomide and rosiglitazone on the prevention of diabetic retinopathy in streptozotocin-induced diabetic rats

Aims/hypothesis Our aim was to compare the therapeutic effect of thalidomide and rosiglitazone on the prevention of diabetic retinopathy in streptozotocin-induced diabetic rats.Methods Male Holtzman rats of 6 to 8 weeks of age and weighing 170±30 g were randomly divided into four groups: control (n=13), untreated diabetic (n=17) and diabetic rats treated with thalidomide (200 mg kg^–1 day^–1) (n=8) or rosiglitazone (1 mg kg^–1 day^–1) (n=22) for 3 months. Diabetes was induced by streptozotocin with the rats having a body weight of 70 mg/kg. After treatment, vascular endothelial growth factor (VEGF) concentrations in ocular fluid were compared between the different groups, and retinal capillary basement membrane thickness was measured by electron microscopy.Results Higher VEGF concentrations in ocular fluid and thicker basement membranes were observed in untreated diabetic rats compared to the control rats. Similar VEGF concentrations and basement membrane thickness were observed for the thalidomide-treated group compared with the control group, whereas no difference in these parameters was observed between the rosiglitazone-treated rats and the control or untreated diabetic rats.Conclusions/interpretation Our findings confirm the association between VEGF concentrations and diabetic retinopathy as suggested by other investigators. Thalidomide, but not rosiglitazone, was associated with the inhibition of basement membrane thickening and the blockade of the increase of VEGF in ocular fluid, thus representing a potential therapeutic drug for the prevention of diabetic retinopathy.Abbreviations T Thalidomide - R rosiglitazone - VEGF vascular endothelial growth factor - BM basement membrane - BMT basement membrane thickness An erratum to this article can be found at     

Alterations in Ca2+ binding by and composition of the cardiac sarcolemmal membrane in chronic diabetes.

Chronic streptozotocin-induced diabetes in rats was associated with a significant loss in the ability of isolated cardiac sarcolemmal membranes to bind Ca2+. Administration of insulin to the diabetic rats normalized the sarcolemmal Ca2+ binding capacity. The content of sialic acid residues, which are considered to represent a superficial Ca2+ pool in sarcolemma, was decreased in preparations from diabetic rats, and this change also was reversible upon insulin treatment of the diabetic rats. Treatment of sarcolemma with neuraminidase decreased Ca2+ binding by 37% in control preparations but had no effect on diabetic preparations. Diphosphatidylglycerol content was decreased but other acidic phospholipids such as phosphatidylinositol and phosphatidylserine, which also bind Ca2+, were not altered during diabetes. An increase in lysophosphatidylcholine and a decrease in phosphatidylethanolamine contents were observed in membranes isolated from diabetic rats. These results suggest that some alterations occur in Ca2+ binding and composition of heart sarcolemma in chronically diabetic rats and may provide further insight into the pathogenesis of diabetic cardiomyopathy.     

Changes in fluidity and composition of erythrocyte membranes and in composition of plasma lipids in Type I diabetes

Changes in the fluidity and composition of human erythrocyte membranes and in the composition of plasma in Type I (insulin-dependent) diabetes were investigated. The increased microviscosity of diabetic erythrocyte membranes provide unambiguous proof of the structural deterioration of erythrocyte membranes in diabetes. It seems most likely that enhancement of the membrane cholesterol/phospholipid ratio is the main reason for decreased membrane fluidity in diabetes. A distinct correlation between membrane cholesterol/phospholipid ratio, plasma cholesterol content and membrane fluidity was found. Composition and structural changes in erythrocyte membranes and compositional changes in plasma lipids may contribute to the development of diabetic complications in diabetes.     

Collagen ultrastructure and TGF-beta1 expression preserved with aminoguanidine during wound healing in diabetic rats

Advanced glycoxidation end products have been implicated in delayed diabetic wound healing. In this study, we evaluated the effects of aminoguanidine, which is an advanced glycation and nitric oxide (NO) synthase inhibitor, on extracellular matrix protein expression, collagen configuration, and nitrite/nitrate levels in wounds of diabetic rats. Sixteen Wistar male rats were made diabetic by streptozotocin. Of these, eight rats were given AG (aminoguanidine bicarbonate (AG) (group DAG) in their drinking water, and eight rats were followed as diabetic paired controls (group D). Eight healthy rats were followed as the healthy control group (group H). At the eighth week, a 2 x 2 cm area full-thickness skin defect was created. The degree of contraction of the open wounds was evaluated for 2 weeks duration. On the 15th postoperative day, wound surface areas were measured, and wound specimens and blood samples were collected. The shrinking percentage of the wounds was small in both groups H and DAG compared with group D (p < 0.05). Similar to healthy rats, the aminoguanidine-treated diabetic rats had very strong transforming growth factor (TGF)-beta1 expression in granulation tissue and intact skin in comparison with diabetic controls. In the diabetic group, the intact skin demonstrated sparsely distributed regular collagen fibers in the granulation zone, and the regular pattern of collagen fibers was lost. In conclusion, aminoguanidine improves wound healing, restores growth factor TGF-beta1 expression, and preserves collagen ultra structure, whereas it has no prominent effect on NO levels within wound tissue in diabetic rats.     

Modification of the glomerular basement membrane in sucrose-fed and streptozotocin-diabetic rats

Summary Rats were fed on diets containing either sucrose or starch as the carbohydrate component (55%) for eight months. Diabetes was induced in animals of both groups by injecting streptozotocin (50 mg/kg body weight). Diabetic rats failed to gain weight, had enlarged kidneys, polyuria and elevated blood glucose levels. Starch and sucrose fed rats gained weight normally and had normal blood glucose levels. Sucrose fed rats had enlarged kidneys. Regional thickening of the glomerular basement membrane was present in sucrose-fed and diabetic rats but not in starch-fed controls. Glomerular basement membrane isolated from pooled kidney cortices from rats in the different experimental groups were analysed for amino acid, disaccharide and hexosamine content. Hydroxylysine (9 to 20%), hydroxyproline (21 to 24%), disaccharide (27%) and hexosamine (26%) were increased in membranes insolated from the three experimental groups, compared with starch-fed non-diabetic controls. An increase in low molecular weight components of the glomerular basement membrane of sucrose-fed and diabetic rats was observed using electrophoresis in sodium dodecyl sulphate. Significantly higher (p<0.001) glucosyltransferase activity was present in kidney supernatants prepared from sucrose-fed (1050±60 nmol/2 h/kidney) compared to starch-fed rats (510±40 nmol/2 h/kidney). Sucrose feeding induces changes similar to those found in diabetes and the induction of diabetes made little difference over the feeding of sucrose alone.