Hyperglycemic Animals Research Articles

Chronic Hyperglycemia Modulates Rat Osteoporotic Cortical Bone Microarchitecture into Less Fragile Structures.

There is controversy concerning the diabetes impact on bone quality, notorious in type 2 diabetic postmenopausal women. One pointed cause might be uncontrolled glycemia. In this study, the effect of chronic hyperglycemia in bone turnover, morphology, and biomechanics was evaluated in female Wistar rats in the presence/absence of estrogens (ovariectomy). Animals (n = 28) were divided into sham, ovariectomized (OVX), hyperglycemic (streptozotocin 40 mg/kg, single-dose i.p.-STZ), and hyperglycemic-ovariectomized (STZ + OVX) animals. Blood biomarkers were estimated 60 days postovariectomy. Body weight, vertebral microarchitecture (L4-histomorphometry), femur biomechanical properties (bending tests), tibia ultrastructure (scanning electron microscopy), and femur and urinary calcium (atomic absorption) were also evaluated. The increased PINP/CTX ratio of hyperglycemic animals and the similar ratio between STZ + OVX and healthy animals contrasting with the lower ratio of OVX (in line with its histomorphometric data) suggest a tendency for improved bone formation in hyperglycemic-ovariectomized animals. The increased tibia medullar canal, which contrasts with the unaffected cortical thickness of both hyperglycemic groups while that of OVX decreased, was associated to the increased stiffness and strength of STZ + OVX bones compared to those of OVX, in line with the observed ultrastructure. Concluding, chronic hyperglycemia in ovariectomized female rats causes bone morphological changes that translate positively in the ultrastructure and mechanical properties of cortical bones.

Influence of Varying Dietary Protein Levels on Glycation of Albumin, Tryptophan and Valine in the Plasma of Chickens.

Glycation is a chemical reaction in which reducing sugars bind non-enzymatically to compounds containing amino groups. Avian species like chickens are hyperglycemic animals and have high body temperature compared to mammalian species, which enables avian species to accelerate the glycation of proteins and amino acids with glucose. Although varying dietary crude protein (CP) levels alter plasma concentrations of proteins and amino acids, the influence of varying CP levels on the glycation of plasma proteins and amino acids has not been studied so far. In the present study, therefore, glycation of albumin, tryptophan and valine in the plasma of chickens fed diets with varying CP levels (0, 10, 20, 40 and 60%) was examined. At the end of the experimental period, blood samples were collected and plasma concentrations of glycoalbumin, glycated tryptophan (tryptophan-Amadori product and (1R, 3S) - 1 - (D - gluco - 1, 2, 3, 4, 5 - pentahydroxypentyl) - 1, 2, 3, 4 - tetrahydro - β - carboline - 3 - carboxylic acid (PHP-THβC)), and valine-Amadori product were measured. Although plasma albumin concentration was reduced along with the decrease in dietary CP levels from 20% to 0%, glycoalbumin in the plasma was increased under such dietary conditions. Similar increase in the ratios of tryptophan-Amadori product to tryptophan and valine-Amadori product to valine in the plasma of chickens fed a protein-free diet was observed. These results suggest that dietary protein deficiency might enhance the non-enzymatic glycation of plasma proteins and amino acids in chickens.

Inhibition of mTOR signaling Confers Protection against Cerebral Ischemic Injury in Acute Hyperglycemic Rats.

Hyperglycemia is known to exacerbate neuronal death resulted from cerebral ischemia. The mechanisms are not fully understood. The mammalian target of rapamycin (mTOR) pathway regulates cell growth, division and apoptosis. Recent studies suggest that activation of mTOR may mediate ischemic brain damage. The objective of the present experiment is to explore whether mTOR mediates ischemic brain damage in acute hyperglycemic animals. Rats were subjected to 10 min of forebrain ischemia under euglycemic, hyperglycemic and rapamycin-treated hyperglycemic conditions. The rat brain samples were collected from the cortex and hippocampi after 3h and 16h of reperfusion. The results showed that hyperglycemia significantly increased neuronal death in the cortex and hippocampus and the exacerbation effect of hyperglycemia was associated with further activation of mTOR under control and/or ischemic conditions. Inhibition of mTOR with rapamycin ameliorated the damage and suppressed hyperglycemia-elevated p-MTOR, p-P70S6K and p-S6. In addition, hyperglycemia per se increased the levels of cytosolic cytochrome c and autophagy marker LC3-II, while rapamycin alleviated these alterations. It is concluded that activation of mTOR signaling may play a detrimental role in mediating the aggravating effect of hyperglycemia on cerebral ischemia.

State of hyperglycemic animals during consumption of high-calorie diet with the bionanocomposite supplement

Glucose level and glucose tolerance test in blood of rats under conditions of obesity induced by consumption of high-calorie diet have been determined. It was also researched these indicators in the blood of animals that consumpt high-calorie diet with added bionanocomposite. These data suggest bionanocomposite preventive effect on the development of key indicators prediabetes.

Antidiabetic and Antihyperalgesic Effects of a Decoction and Compounds from Acourtia thurberi.

The purpose of this research was to examine the preclinical efficacy of a decoction from the roots of Acourtia thurberi as a hypoglycemic, antihyperglycemic, and antihyperalgesic agent using well-known experimental models in mice. Acute oral administration of A.thurberi decoction did not produce toxic effects in mice, according to the Lorke procedure. A.thurberi decoction (31.6-316.2 mg/kg, p. o.) decreased blood glucose levels during acute hypoglycemic and the oral glucose tolerance and oral sucrose tolerance tests, both in normoglycemic and hyperglycemic animals. Phytochemical analysis of A.thurberi roots led to the isolation of perezone (1), a mixture of α-pipitzol (2) and β-pipitzol (3), and 8-β-D-glucopyranosyloxy-4-methoxy-5-methyl-coumarin (4). A pharmacological evaluation of compounds 1-4 (3.2-31.6 mg/kg) using the same assays revealed their hypoglycemic and antihyperglycemic actions. Finally, local administration of A.thurberi decoction (31.6-316.2 µg/paw) and compounds 1-4 (3.2-31.6 µg/paw) produced significant inhibition on the licking time during the formalin test in healthy and hyperglycemic mice, demonstrating their antinociceptive and antihyperalgesic potential, respectively. Altogether, these results could be related to the use of A.thurberi for treating diabetes and painful complaints in contemporary Mexican folk medicine. A suitable UPLC-ESI/MS method was developed and successfully applied to quantify simultaneously compounds 1 and 4 in A.thurberi decoction.

PPARG Post-translational Modifications Regulate Bone Formation and Bone Resorption

The peroxisome proliferator-activated receptor gamma (PPARγ) regulates osteoblast and osteoclast differentiation, and is the molecular target of thiazolidinediones (TZDs), insulin sensitizers that enhance glucose utilization and adipocyte differentiation. However, clinical use of TZDs has been limited by side effects including a higher risk of fractures and bone loss. Here we demonstrate that the same post-translational modifications at S112 and S273, which influence PPARγ pro-adipocytic and insulin sensitizing activities, also determine PPARγ osteoblastic (pS112) and osteoclastic (pS273) activities. Treatment of either hyperglycemic or normoglycemic animals with SR10171, an inverse agonist that blocks pS273 but not pS112, increased trabecular and cortical bone while normalizing metabolic parameters. Additionally, SR10171 treatment modulated osteocyte, osteoblast, and osteoclast activities, and decreased marrow adiposity. These data demonstrate that regulation of bone mass and energy metabolism shares similar mechanisms suggesting that one pharmacologic agent could be developed to treat both diabetes and metabolic bone disease.

Increased airway glucose increases airway bacterial load in hyperglycaemia.

Diabetes is associated with increased frequency of hospitalization due to bacterial lung infection. We hypothesize that increased airway glucose caused by hyperglycaemia leads to increased bacterial loads. In critical care patients, we observed that respiratory tract bacterial colonisation is significantly more likely when blood glucose is high. We engineered mutants in genes affecting glucose uptake and metabolism (oprB, gltK, gtrS and glk) in Pseudomonas aeruginosa, strain PAO1. These mutants displayed attenuated growth in minimal medium supplemented with glucose as the sole carbon source. The effect of glucose on growth in vivo was tested using streptozocin-induced, hyperglycaemic mice, which have significantly greater airway glucose. Bacterial burden in hyperglycaemic animals was greater than control animals when infected with wild type but not mutant PAO1. Metformin pre-treatment of hyperglycaemic animals reduced both airway glucose and bacterial load. These data support airway glucose as a critical determinant of increased bacterial load during diabetes.

Progressive Early Breakdown of Retinal Pigment Epithelium Function in Hyperglycemic Rats.

PurposeDiabetic macular edema (DME), an accumulation of fluid in the subretinal space, is a significant cause of vision loss. The impact of diabetes on the breakdown of the inner blood–retina barrier (BRB) is an established event that leads to DME. However, the role of the outer BRB in ocular diabetes has received limited attention. We present evidence that the breakdown of normal RPE function in hyperglycemia facilitates conditions conducive to DME pathogenesis.MethodsBrown Norway rats (130–150 g) were injected intraperitoneally with streptozotocin (STZ; 60 mg/kg) to induce hyperglycemia. After 4 weeks, Evans blue (EB) dye was injected intravenously to determine whether there was leakage of albumin into the retina. Subretinal saline blebs (0.5–1 μL) were placed 4 and 9 weeks after STZ injection, and time-lapse optical coherence tomography tracked the resorption rate. In a subset of rats, intravitreal bevacizumab, a humanized monoclonal antibody targeted to VEGF, was given at 5 weeks and resorption was measured at 9 weeks.ResultsThe ability of the RPE to transport fluid was reduced significantly after 4 and 9 weeks of hyperglycemia with a reduction of over 67% at 9 weeks. No EB dye leakage from inner retinal vessels was measured in hyperglycemic animals compared to control. The intravitreal administration of bevacizumab at week 5 significantly increased the rate of fluid transport in rats subjected to hyperglycemia for 9 weeks.ConclusionsThese results demonstrate that chronic hyperglycemia altered RPE fluid transport, in part dependent on the actions of VEGF. These results support the idea that RPE dysfunction is an early event associated with hyperglycemia that contributes to fluid accumulation in DME.

Suppression of connective tissue growth factor mediates the renoprotective effect of Sitagliptin rather than Pioglitazone in type 2 diabetes mellitus

AimDiabetic nephropathy (DN) is a leading cause of end-stage renal disease, and thus, the ability of antidiabetic drugs to ameliorate renal microvascular disease may be as important as their ability to control blood glucose. Therefore, we investigated the reno-protective effect of the antidiabetic drugs, Sitagliptin and Pioglitazone, versus combined Metformin/Enalapril in a rat model of type 2 diabetes. MethodMale Wistar rats were randomly assigned to be either normal control or diabetic. Induction of type 2 diabetes was done by intraperitoneal injection of\\ low dose streptozotocin (35mg/kg) on top of 2 weeks of high fat diet. Hyperglycemic animals were divided into 4 groups: untreated diabetic, Sitagliptin (10mg/kg), Pioglitazone (10mg/kg) and Metformin/Enalapril (500, 10mg/kg, respectively) treated. After 6 weeks, fasting blood glucose, plasma insulin, β-cell function, insulin resistance, serum lipids, urea & creatinine, albuminurea, kidney weight, renal oxidative stress, plasma connective tissue growth factor (CTGF) and renal histopathology were assessed. Key findingsSitagliptin decreased microalbuminurea, urea & creatinine, renal tropism, oxidative stress and CTGF to levels similar to Metformin/Enalapril group. It also preserved near normal renal histology. Although Pioglitazone treatment reduced urea, creatinine, renal tropism and oxidative stress, it did not improve renal pathological changes or significantly alter CTCF. SignificanceEarly Sitagliptin treatment in type 2 diabetes can equally ameliorate renal functions and structural changes as combined Metformin/Enalapril. Moreover Sitagliptin is a better renoprotective than Pioglitazone, probably due to its suppressor effect on CTGF, a key factor mediating diabetic renal injury.

Vessel Dilation Attenuates Endothelial Dysfunction Following Middle Cerebral Artery Occlusion in Hyperglycemic Rats.

Dynamically observe cerebral vascular changes in hyperglycemic rats in vivo and explore the effect of diabetes on endothelial function after ischemic stroke. Diabetes affects both large and small vessels in the brain, but the dynamic process and mechanism are unclear. We investigated the structural and functional changes of brain vasculature in living hyperglycemic rats and their impact on stroke outcomes via a novel technique: synchrotron radiation angiography. We also examined the effect of prolonged fasudil treatment on arterial reactivity and hemorrhagic transformation. Adult Sprague Dawley rats were treated by streptozotocin to induce type 1 diabetes. These hyperglycemic rats received fasudil pretreatment and then underwent transient middle cerebral artery occlusion. We found that diabetes caused arteries narrowing in the circus Willis as early as 2 weeks after streptozotocin injection (P < 0.05). These vessels were further constricted after middle cerebral artery occlusion. L-NAME could induce regional constrictions and impaired relaxation in hyperglycemic animals. Furthermore, hemorrhagic transformation was also increased in the hyperglycemic rats compared to the control (P < 0.05). In fasudil-treated rats, the internal carotid artery narrowing was ameliorated and L-NAME-induced regional constriction was abolished. Importantly, stroke prognosis was improved in fasudil-treated rats compared to the control (P < 0.05). Our dynamic angiographic data demonstrated that diabetes could impair the cerebral arterial reactivity. Prolonged fasudil treatment could attenuate arterial dysfunction and improve the prognosis of ischemic stroke by affecting both the large and small vasculature.

Acute Hyperglycemia Does Not Affect Brain Swelling or Infarction Volume After Middle Cerebral Artery Occlusion in Rats.

Stroke disproportionally affects diabetic and hyperglycemic patients with increased incidence and is associated with higher morbidity and mortality due to brain swelling. In this study, the intraluminal suture middle cerebral artery occlusion (MCAO) model was used to examine the effects of blood glucose on brain swelling and infarct volume in acutely hyperglycemic rats and normo-glycemic controls. Fifty-four rats were distributed into normo-glycemic sham surgery, hyperglycemic sham surgery, normo-glycemic MCAO, and hyperglycemic MCAO. To induce hyperglycemia, 15 min before MCAO surgery, animals were injected with 50 % dextrose. Animals were subjected to 90 min of MCAO and sacrificed 24 h after reperfusion for hemispheric brain swelling and infarct volume calculations using standard equations. While normo-glycemic and hyperglycemic animals after MCAO presented with significantly higher brain swelling and larger infarcts than their respective controls, no statistical difference was observed for either brain swelling or infarct volume between normo-glycemic shams and hyperglycemic shams or normo-glycemic MCAO animals and hyperglycemic MCAO animals. The findings of this study suggest that blood glucose does not have any significant effect on hemispheric brain swelling or infarct volume after MCAO in rats.

Incorporation of Glycated-Tryptophan and -Valine into Various Cells Derived from Chicken Embryos.

Avian species including chickens are known to be hyperglycemic animals. Hyperglycemia promotes the glycation which at first forms Amadori products undergoing further complex reaction to form advanced glycation end products (AGEs). Our previous study revealed that AGEs derived from glucose and amino acids were predominantly incorporated into spleen, kidney and liver. However, it has not been elucidated whether Amadori products (glycated amino acids) can also be incorporated into cells or not. Therefore, in the present study, radioactive glycated-tryptophan and -valine were prepared and the incorporation of these glycated amino acids into various chicken embryonic cells was studied. Various embryonic cells prepared from muscle, liver, spleen and kidney of chicken embryos were incubated in Medium 199 supplemented with 14C-labeled glycated-tryptophan or -valine. After incubation, embryonic cells were well-rinsed and then the radioactivity incorporated into cells was measured. It was revealed that both glycated amino acids were incorporated into embryonic cells derived from muscle, liver, spleen and kidney. In muscular cells, the incorporation of glycated-tryptophan was higher than that of glycated-valine. On the other hand, in embryonic cells derived from liver and kidney, the amount of glycated-tryptophan incorporated into cells was almost the same to that of glycated-valine. In conclusion, it was supposed that both glycated-tryptophan and -valine could be incorporated into various cells derived from muscle, liver, spleen and kidney of chicken embryos and that the incorporation might have the organ specificity.

The Effects of Ivabradine on Cardiac Function after Myocardial Infarction are Weaker in Diabetic Rats

Background/Aims: Plasma norepinephrine (NE) and brain natriuretic peptide (BNP, termed BNP-45 in rats) are considered as essential neurohormones indicating heart failure progression. The purposes of this study were to examine the effects of ivabradine (IBD) on cardiac function and plasma NE and BNP-45 after chronic ischemic heart failure (CHF) in non-diabetic rats and diabetic rats. We further determined if sympathetic NE uptake-1 (a major pathway to metabolize NE) mechanism is responsible for the role played by IBD. Methods: We ligated rat's coronary artery to induce CHF; and injected streptozotocin (STZ) to induce diabetic hyperglycemia. Echocardiography was employed to determine cardiac function. We used ELISA to examine plasma NE and BNP-45; and Western Blot analysis to examine the protein levels of NE uptake-1 in sympathetic nerves. Results: CHF increased the levels of NE and BNP-45 in non-STZ rats and STZ rats. Systemic injection of IBD significantly attenuated the augmented NE and BNP-45 and impaired left ventricular function induced by CHF in those rats. This effect appeared to be less in STZ rats. A liner relation was observed between the NE/BNP-45 levels and left ventricular function after administration of IBD. Also, IBD was observed to have a recovery effect on the downregulated NE uptake-1 evoked by CHF, but to a smaller degree in STZ rats. Conclusion: Our data revealed specific signaling mechanisms by which IBD improves the cardiac function as IBD alleviates impaired NE uptake-1and thereby decreases heightened NE and BNP-45 induced by CHF. Our data also demonstrated that the effects of IBD are weakened after diabetic hyperglycemia likely due to worsen NE uptake-1 pathway. Thus, targeting sympathetic NE uptake-1 signaling molecules has clinical implications for treatment and management of CHF in diabetes. Our data were also to shed light on strategies for application of this drug because NE and BNP play an important role in regulation of progression and prognosis of CHF, and in particular, because IBD affects NE uptake-1 pathway in hyperglycemic animals to a less degree.

Comparative Evaluation of Diabetogenic Potentials of Alloxan, Streptozotocin and Their Cocktail in Rabbits(Oryctolagus cuniculas)

Comparative diabetogenic potentials of alloxan, streptozotocin (STZ) and alloxan-streptozotocin cocktail in rabbits was investigated. ‘New Zealand White ’rabbits, 1–1.5 kg body weight (b.w.), were administered 100 mg alloxan kg−1 b.w and 65 mg STZ kg−1 b.w, individually and 50 mg alloxan kg−1 b.w. and 35 mg STZ kg−1 b.w. cocktail, as single intravenous dose. Fasting blood glucose levels were monitored on day 0, 3, 5, and 7. Rabbits with fasting blood glucose levels > 200 mg dL−1 were considered diabetic. Alloxan caused early induction of sustained hyperglycaemia while relatively resistant rabbits revealed mild hyperglycaemia on day 3 followed by progressive recovery. In contrast, alloxan-STZ cocktail caused a progressive increase in hyperglycaemic animals upto 7 days. However, the overall diabetogenic efficiency was less than alloxan alone. The hyperglycaemia was mild to moderate when alloxan-STZ cocktail was used as compared to that induced by alloxan alone which resulted in moderate to severe hyperglycaemia. STZ failed to induce significant and sustained hyperglycaemia in rabbits. It may be concluded that low dose alloxan-STZ cocktail is a choice for the induction of diabetic rabbit model whereas rabbits appeared relatively resistant to diabetogenic effects of STZ. Further, spontaneous progressive recovery warrant extra caution in evolving and extrapolating results while using such models.

Activation of Adenosine Triphosphate-regulated Potassium Channels during Reperfusion Restores Isoflurane Postconditioning-induced Cardiac Protection in Acutely Hyperglycemic Rabbits.

Hyperglycemia is known to inhibit myocardial anesthetic postconditioning. The authors tested whether activation of adenosine triphosphate-regulated potassium (KATP) channels would restore anesthetic postconditioning during acute hyperglycemia. Rabbits subjected to 40-min myocardial ischemia and 3-h reperfusion (ischemia-reperfusion [I/R]) were assigned to groups (n = 10 in each group) with or without isoflurane postconditioning (2.1% for 5 min) in the presence or absence of hyperglycemia and/or the KATP channel agonist diazoxide. Creatine kinase MB fraction and infarct size were measured. Phosphorylated protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) were assessed. Oxidative stress was evaluated by measuring malondialdehyde, and apoptosis was assessed by dUTP nick-end labeling and activated caspase-3. Postconditioning significantly reduced myocardial infarct size (26 ± 4% in the isoflurane [ISO] group vs. 53 ± 2% in the I/R group; P = 0.007); whereas, hyperglycemia inhibited this effect (infarct size: 47 ± 2%, P = 0.02 vs. the ISO group). Phosphorylated and eNOS levels increased, whereas malondialdehyde and myocardial apoptosis were significantly lower after isoflurane postconditioning compared with I/R. These effects were inhibited by acute hyperglycemia. Diazoxide restored the protective effect of isoflurane in the hyperglycemic animals (infarct size: 29 ± 2%; P = 0.01 vs. the I/R group), reduced malondialdehyde levels and myocardial apoptosis, but did not affect the expression of phosphorylated Akt or eNOS. KATP channel activation restored anesthetic postconditioning-induced myocardial protection under acute hyperglycemia. This effect occurred without increasing Akt or eNOS phosphorylation, suggesting that KATP channels are located downstream to Akt and eNOS in the pathway of isoflurane-induced myocardial postconditioning.

Insulin therapy normalizes reduced myocardial β-adrenoceptors at both the onset and after sustained hyperglycemia in diabetic rats.

Reduced cardiac β-adrenoceptors (β-AR) and cardiovascular (CV) dysfunction occur in diabetes mellitus (DM) and can be normalized by insulin. It is unclear how the duration of untreated hyperglycemia prior to intervention impacts insulin's effects. This study assesses insulin's effect on reduced myocardial β-AR and CV function, comparing insulin therapy at the onset of hyperglycemia and after a sustained period of hyperglycemia in streptozotocin (STZ) rats. Ex vivo biodistribution experiments with [(3)H]CGP12177 were performed in high-fat fed STZ rats after 8 weeks of hyperglycemia evaluating cardiac β-AR expression. Western blotting of β-AR subtypes was completed in parallel. Serial echocardiography at 0, 6, and 8 weeks post-STZ investigated CV function. Sub-groups of hyperglycemic rats were treated with insulin early, at 1 week post-STZ (InsE) for 7 weeks, or late at 6 weeks post-STZ (InsL) for 2 weeks to observe how the duration of hyperglycemia prior to insulin impacts its effects. Reduced myocardial [(3)H]CGP12177 binding occurred 8 weeks post-STZ in hyperglycemics, but was normal in both insulin treatments. Western blotting supported reduced β1-AR in hyperglycemics, but not in either treatment. InsE and InsL treatments improved prolonged mitral valve deceleration (MVD) observed in hyperglycemic animals, but hyperglycemic and InsL still displayed reduced heart rates (HR). This work supports that glycemic control with insulin normalizes cardiac β-AR effectively regardless of prior hyperglycemia but HR may not recover as readily, indirectly supporting the utility of [(11)C]CGP12177 positron emission tomography (PET) in assessing cardiac β-AR and their modulation with glycemic therapy.

Utilizing a Type 1 Diabetic Nephropathy Model Developed on the Basis of Streptozotocin‐Treated Dahl SS Rats for the Studies of Calcium Handling in the Podocytes

Podocytes play a key role in the development of nephropathy: podocyte depletion results in reduced GFR and progressive glomerulosclerosis. Circulating factors can activate calcium influx in these cells triggering processes that lead to podocyte loss. This study was aimed at developing a proper model of diabetic nephropathy (DN) on the basis of the Dahl Salt‐Sensitive (SS) rat that could be further used for assessing calcium signaling in podocytes. Type I diabetes was induced in 6 week old SS rats by an injection of 75 mg/kg streptozotocin (STZ) which caused an elevation of blood glucose up to 700 mg/dL; this was then decreased to 350 mg/dL by an insulin pellet implant. Rats were monitored throughout the next 6 or 12 weeks; urine analyses revealed progressive proteinuria, whereas sodium and potassium fractional excretion levels were normal in both control and diabetic groups (0.3 and 14 for fractional excretion of Na and K, respectively). However, 6 weeks after the STZ injection was not sufficient to develop histological features characteristic in DN, whereas the 12 week treatment resulted in typical DN kidney damage. Urinary ELISA showed a 50‐fold increase in nephrin excretion in the 12 week hyperglycemic animals, which is indicative of podocyte depletion and foot processes effacement. At the end of the experiment rat glomeruli were isolated and successfully used for ratiometric confocal measurements with fluorescent dyes or patch‐clamp measurements. In conclusion, this rat model shows the features of diabetic kidney injury and is a good basis for the assessment of calcium signaling and glomerular filtration barrier function during type 1 DN.

Abstract W MP96: Low Dose Tissue Plasminogen Activator Amplifies Vascular Injury and Worsens Functional Outcomes in Acute Hyperglycemic Stroke Independent of the Model of Reperfusion

Clinically, hyperglycemia (HG) exacerbates reperfusion injury and aggravates tPA-induced hemorrhagic transformation (HT). Yet, most of the experimental hyperglycemic stroke studies exclusively employed suture occlusion model. Only few studies involved tPA in hyperglycemic setting and employed a 10-fold higher dose of tPA than that is used in patients. Thus, in this translational study using suture and thromboembolic occlusion of middle cerebral artery (MCA), with and without human tPA dose, we tested the hypothesis that even acute mild HG worsens the neurovascular injury and functional outcomes irrespective of the method of reperfusion, and that the use of low dose tPA amplifies this injury. Methods: Control and mildly HG rats (140-200 mg/dl, achieved by 30% glucose ip injection 15 min prior to surgery, n=7-9/group) were subjected to MCA occlusion by either suture (90 min) or humanized clot and 24 h reperfusion. tPA (1mg/kg) was injected IV 2 h after induction of ischemia. At 24 h, neurological deficit, infarct size, edema, HT occurrence rate (HT index) and tissue hemoglobin (Hb) were measured. Results: Cerebral blood flow monitoring indicated that % drop at occlusion were similar across the groups and that low dose tPA effectively resolved the clot in the embolic model. tPA did not increase the infarct size in either control or hyperglycemic animals when compared to no tPA groups (Table). HG increased vascular injury (HT index and Hb content) in both suture and embolic occlusion models. The combination of HG and tPA exacerbated the vascular injury and worsened functional outcomes more than each alone. Conclusion: The interaction between HG and even low dose tPA has a significant deleterious effect on cerebrovasculature and functional outcomes independent of the method of reperfusion.

Estudo da atividade hipoglicemiante do chá do lenho da Quássia-do-Brasil, Picrasma crenata (Vell.) Engl. em camundongos e ratos

The hypoglycemic activity of tea made from the wood of Quassia-do-Brasil [Picrasma crenata (Vell.) Engl.] was studied by assessment of glycemia in normoglycemic animals. The tea was given in concentrations of 5%, 10%, and 20%, with the concentration of 10% proving to be most effective. The 10% concentration promoted a decrease of glycemic levels in diabetic animals who were given streptozotocin (65 mg/kg) and in hyperglycemic animals who received an overloading glucose solution of 25% via intravenous administration Propranolol (10 mg/kg, intraperitoneal), a non-specific adrenergic β-blocker, did not affect the activity of the tea in normal or hyperglycemic animals. The tea of Quassia-do-Brasil was able to inhibit intestinal absorption of glucose as well as its reabsorption from the renal glomerulus. The hypoglycemic mechanism of the tea does not appear to involve enhanced secretion of insulin.

Modest hyperglycemia prevents interstitial dispersion of insulin in skeletal muscle

Insulin injected directly into skeletal muscle diffuses rapidly through the interstitial space to cause glucose uptake, but this is blocked in insulin resistance. As glucotoxicity is associated with endothelial dysfunction, the observed hyperglycemia in diet-induced obese dogs may inhibit insulin access to muscle cells, and exacerbate insulin resistance. Here we asked whether interstitial insulin diffusion is reduced in modest hyperglycemia, similar to that induced by a high fat diet. MethodsDuring normoglycemic (100mg/dl) and moderately hyperglycemic (120mg/dl) clamps in anesthetized canines, sequential doses of insulin were injected into the vastus medialis of one hindlimb; the contra-lateral limb served as a control. Plasma samples were collected and analyzed for insulin content. Lymph vessels of the hind leg were also catheterized, and lymph samples were analyzed as an indicator of interstitial insulin concentration. ResultsInsulin injection increased lymph insulin in normoglycemic animals, but not in hyperglycemic animals. Muscle glucose uptake was elevated in response to hyperglycemia, however the insulin-mediated glucose uptake in normoglycemic controls was not observed in hyperglycemia. Modest hyperglycemia prevented intra-muscularly injected insulin from diffusing through the interstitial space reduced insulin-mediated glucose uptake. ConclusionHyperglycemia prevents the appearance of injected insulin in the interstitial space, thus reducing insulin action on skeletal muscle cells.