Effects Of Streptozotocin-induced Diabetes Research Articles

Effects of streptozotocin-induced diabetes on strength of the humerus in rats of different ages

Effects of streptozotocin-induced diabetes on strength of the humerus in rats of different ages

The Effects of Streptozotocin-Induced Diabetes and Insulin Treatment on Carnitine Biosynthesis and Renal Excretion.

Carnitine insufficiency is reported in type 1 diabetes mellitus. To determine whether this is accompanied by defects in biosynthesis and/or renal uptake, liver and kidney were obtained from male Sprague-Dawley rats with streptozotocin-induced diabetes. Diabetic rats exhibited the metabolic consequences of type 1 diabetes, including hypoinsulinemia, hyperglycemia, and increased urine output. Systemic hypocarnitinemia, expressed as free carnitine levels, was evident in the plasma, liver, and kidney of diabetic rats. Compared to control rats, the low free carnitine in the plasma of diabetic rats was accompanied by decreased expression of γ-butyrobetaine hydroxylase in liver and kidney, suggesting impaired carnitine biosynthesis. Expression of organic cation transporter-2 in kidney was also reduced, indicating impaired renal reabsorption, and confirmed by the presence of elevated levels of free carnitine in the urine of diabetic rats. Insulin treatment of diabetic rats reversed the plasma hypocarnitinemia, increased the free carnitine content in both kidney and liver, and prevented urinary losses of free carnitine. This was associated with increased expression of γ-butyrobetaine hydroxylase and organic cation transporter-2. The results of our study indicate that type 1 diabetes induced with streptozotocin disrupts carnitine biosynthesis and renal uptake mechanisms, leading to carnitine insufficiency. These aberrations in carnitine homeostasis are prevented with daily insulin treatment.

The effect of streptozotocin-induced diabetes on the copper content in the cells of the immune system of rats

The effect of streptozotocin-induced diabetes on the copper content in the cells of the immune system of rats

329-OR: REDD1 Suppresses the Retinal Antioxidant Response to Diabetes by Destabilizing Nrf2

Oxidative stress is a major contributor to the pathophysiology of diabetes. To combat oxidative stress, the transcription factor nuclear factor erythroid-2-related factor 2 (Nrf2) promotes the expression of an array of antioxidant gene products. However, in both the retina of diabetic patients and in preclinical diabetes models, there is a failure to properly upregulate Nrf2 activity. We previously demonstrated that retinal REDD1 protein expression is enhanced by diabetes-induced hyperglycemia and necessary for both the rise in retinal reactive oxygen species and the development of visual dysfunction in diabetic mice. In the present study, we investigated the hypothesis that signaling events downstream of REDD1 act to limit the retinal Nrf2 antioxidant response to the diabetic metabolic environment. We found that REDD1 ablation not only enhanced retinal Nrf2 activity, but also prevented the suppressive effect of streptozotocin-induced diabetes as compared to wild type mice. Nuclear Nrf2 protein expression and activity were enhanced in REDD1 knockout human MIO-M1 retinal Müller cells in culture, independent of a change in Nrf2 mRNA abundance. REDD1 deletion prevented oxidative stress in response to hyperglycemic conditions, and this protective effect was absent upon Nrf2 knockdown. REDD1 suppressed Nrf2 stability independent of Keap1 by promoting GSK3-mediated nuclear exclusion and proteasomal degradation via the ubiquitin ligase adapter β transducin repeat containing protein (β-TrCP). In the retina of diabetic REDD1-deficient mice, enhanced GSK3 phosphorylation was associated with a decrease in oxidative stress as compared to diabetic wild type mice. Pharmacological inhibition was used to suppress GSK3 activity in both cells in culture and in the retina of diabetic mice. Remarkably, GSK3 inhibition prevented the suppressive effect on Nrf2. Overall these findings support therapeutic approaches targeting REDD1 to prevent diabetes-induced visual dysfunction. Disclosure W.P. Miller: None. A. Toro: None. J. Giordano: None. M.D. Dennis: None. Funding American Diabetes Association/Pathway to Stop Diabetes (1-14-INI-04 to M.D.D.); National Eye Institute (1F31EY031199-01)

Effects of bovine enterovirus and type 1 diabetes on liver and kidney pyruvate kinase activity in an animal model

Type 1 diabetes (T1D) is an autoimmune disease characterized by the selective destruction of pancreatic beta cells. In addition to genetic factors, enteroviruses have been considered the main environmental factor involved in this pathology. Therefore, the objective of this study was to evaluate the effects of streptozotocin-induced diabetes and bovine enterovirus (BEV) on liver and kidney pyruvate kinase activity in rats. Fourteen male Wistar rats were divided in three groups: control, diabetes and a third group, which was fed with water experimentally contaminated by BEV. Increased blood glucose levels were found in both diabetes and enterovirus groups, whereas there were no alterations in the lipid profile. A reduced pyruvate kinase activity was observed in the liver and kidney of animals from diabetes and enterovirus groups. Under our experimental conditions, the ingestion of water experimentally contaminated by BEV induced alterations in glycaemia, and also interfered in the pyruvate kinase activity in liver and kidney of the rats, which might be one of the possible mechanisms involved in the T1D development.

Effects of streptozotocin-induced diabetes on leg muscle contractile properties and motor neuron morphology in rats.

Skeletal muscle fiber subtypes are differentially sensitive to diabetes-related pathology; For example, fast-twitch muscles exhibit severe decreases in contraction force while slow-twitch muscles demonstrate prolonged half-relaxation time. However, such alterations have only been examined after a relatively short period following diabetes onset, with no information available regarding muscle damage caused by longer disease periods (>20weeks). This study examined alterations in the contractile properties of the medial gastrocnemius (fast-twitch) and soleus (slow-twitch) muscles, as well as morphological changes in their motor neurons 12 and 22weeks after diabetes onset. Adult male Wistar rats were divided into diabetic (12- or 22-week post-streptozotocin injection) and age-matched control groups. Electrically evoked maximum twitch and tetanic tension were recorded from leg muscles. Additionally, motor neuron number and cell body size were examined. At 12weeks after diabetes onset, decreases in twitch force were observed predominantly in medial gastrocnemius muscles, while soleus muscles exhibited prolonged half-relaxation time. However, these differences became ambiguous at 22weeks, with decreased twitch force and prolonged half-relaxation time observed in both muscles. On the other hand, reduction in soleus motor neurons was observed 12weeks after diabetes onset, while medial gastrocnemius motor neurons were diminished at 22weeks. These data indicate that experimental diabetes induces differential damage to medial gastrocnemius and soleus muscles as well as motor neurons. These diabetes-induced differences may partly underlie the differential deficits observed in gastrocnemius and soleus.

Effect of streptozotocin-induced diabetes on motor representations in the motor cortex and corticospinal tract in rats

Motor disorders in patients with diabetes are associated with diabetic peripheral neuropathy, which can lead to symptoms such as lower extremity weakness. However, it is unclear whether central motor system disorders can disrupt motor function in patients with diabetes. In a streptozotocin-induced rat model of type 1 diabetes, we used intracortical microstimulation to evaluate motor representations in the motor cortex, recorded antidromic motor cortex responses to spinal cord stimulation to evaluate the function of corticospinal tract (CST) axons, and used retrograde labeling to evaluate morphological alterations of CST neurons. The diabetic rats exhibited size reductions in the hindlimb area at 4 weeks and in trunk and forelimb areas after 13 weeks, with the hindlimb and trunk area reductions being the most severe. Other areas were unaffected. Additionally, we observed reduced antidromic responses in CST neurons with axons projecting to lumbar spinal segments (CST-L) but not in those with axons projecting to cervical segments (CST-C). This was consistent with the observation that retrograde-labeled CST-L neurons were decreased in number following tracer injection into the spinal cord in diabetic animals but that CST-C neurons were preserved. These results show that diabetes disrupts the CST system components controlling hindlimb and trunk movement. This disruption may contribute to lower extremity weakness in patients.

Effect of streptozotocin-induced diabetes on the autonomic ganglia of albino rats

Objectives : One of the common clinical observations regarding long-standing hyperglycemia is autonomic neuropathy, probably due to its unfavorable destructive effects on the neurons of the autonomic ganglia. Accordingly, the current study was aimed to analyze the effect of experimental hyperglycemia on parasympathetic pterygopalatine ganglion (PtG) and sympathetic coeliac ganglion (ClG) of albino rats. Methods: Thirty-six albino rats were divided into six groups (n=6, each) and were designated as control, two weeks, one month, two months, four months and six months groups. Diabetes was induced with a single dose of streptozotocin (STZ, 60 mg/kg, i.p.). Body weight and blood sugar were monitored at biweekly intervals. At the end of each experimental period, animals were euthanized by deep ether anesthesia and blood samples were collected by direct puncture of heart for biochemical analysis. Animals were perfused with Karnovsky fixative. After 48 hours, tissue samples were collected and processed for light microscopy. Results : Biochemical analysis of serum revealed increased serum creatinine and reduced serum total protein. Histopathology and histomorphometry of ganglia revealed that the progressively increasing duration of hyperglycemia was associated with decreased proportion of small-sized neurons, increased proportion of large-sized neurons, dark and dead neurons, and thickening of capsular and endoneurial collagen. Conclusion: The association of the long-standing hyperglycemia with increased neuronal death, altered proportion of neurons and deposition of collagen fibers in autonomic ganglia appear to be important contributing factors likely to be responsible for diabetic autonomic neuropathy.

Effect of streptozotocin-induced diabetes on motoneurons and muscle spindles in rats

This study examined the alterations in the number and size of motoneurons innervating the medial gastrocnemius (MG) and biceps femoris (BF) motor nuclei in diabetic rats (12 or 22 weeks after injection of streptozotocin) and age-matched controls using retrograde labeling technique. Additionally, morphological alterations of muscle spindles in BF and MG muscles were tested. Significantly fewer labeled MG motoneurons were found in 12- and 22-week diabetic rats as compared with age-matched control animals. In contrast, the number of BF motoneurons was preserved in each group. Compared to control animals, the ratio of larger motoneurons of MG and BF muscle were decreased at 12 weeks, and smaller MG motoneurons were drastically decreased at 22 weeks. Moreover, MG muscle spindle showed reduction of its number and increase of intrafusal muscle fibers; however, BF muscle spindles showed little or no difference from control animals. We conclude that there is an early loss of alpha motoneurons for both MG and BF muscles followed by a later loss of gamma motoneurons in MG muscle in diabetic animals. Moreover, loss of gamma motoneuron might induce atrophy of MG muscle spindles.

Effects of Streptozotocin-Induced Diabetes on Proliferation and Differentiation Abilities of Mesenchymal Stem Cells Derived from Subcutaneous and Visceral Adipose Tissues.

Introduction: Accumulated evidence indicates that there are intrinsic differences between adipose tissue-derived stem cells (ASCs) obtained from different body fat depots. Here, we compared the proliferation and multipotency of subcutaneous ASCs (SC-ASCs) and epididymal ASCs (ED-ASCs) before and after induction of diabetes by streptozotocin. Methods: The adipogenic and osteogenic abilities of rat SC-ASCs and ED-ASCs were evaluated using Oil Red O and Alizarin Red staining, respectively. The expression of adipocyte (PPAR-γ, LPL) and osteoblast (ALP, SPP1) specific mRNAs was evaluated by quantitative real-time PCR. MTT test was used for determination of cell proliferation capacity. Results: The proliferation of SC-ASCs was higher than ED-ASCs, both before and after diabetes induction (P<0.05). Diabetes increased the proliferative capability of SC-ASCs (P<0.05) but not ED-ASCs. Before diabetes, both adipogenic and osteogenic differentiation of SC-ASCs were higher than ED-ASCs (P<0.05). After diabetes, both SC-ASCs and ED-ASCs were able to differentiate into adipocyte and osteoblast, but the levels of differentiation were higher in SC-ASCs than in ED-ASCs (P<0.05). Diabetes decreased the expression of PPAR-γ and LPL, but increased the SPP1 and ALP expression in both SC-ASCs and ED-ASCs. Conclusion: Our data suggested that diabetes increases the proliferation of ASCs but decreases their adipogenic differentiation. Also, SC-ASCs have higher proliferation and differentiation abilities than ED-ASCs in normal and diabetic conditions so can be more preferable for cell therapy.

Effect of streptozotocin-induced diabetes on lipids metabolism in the salivary glands

BackgroundDiabetes is one of the most common metabolic diseases. Moreover, previous studies indicate that diabetes may cause changes in the salivary glands phenotype and in the composition of saliva itself. Therefore, the main objective of this study was to determine the effects of streptozotocin induced diabetes on lipid profile of the rat salivary glands. MethodsMale Wistar rats were divided into two groups: control and STZ-induced diabetes. At the end of the experiment all animals were sacrificed and samples of the parotid and submandibular salivary glands were excised. Major lipid fractions concentrations were determined by means of chromatography (TLC and GC). ResultsWe observed a significant increase (∼3.5 fold) in the level of triacylglycerol in both the parotid and submandibular salivary glands of diabetic rats. The abovementioned changes were accompanied by significant, although less dramatic (i.e. from −60% to −90%), decrements in the levels of other lipid classes (phospholipids, free fatty acids and diacylglycerol). ConclusionsIn our study we have showed, presumably for the first time, that streptozotocin induced diabetes causes decrement in PH content with subsequent atrophy and malfunction in both parotid and submandibular salivary glands. Another novel finding of our research is that diabetic rats were characterized by an increased TG accumulation in both parotid and submandibular salivary glands. The later one could be a clinical manifestation of diabetes.

The effects of streptozotocin-induced diabetes on ghrelin expression in rat testis: biochemical and immunohistochemical study.

Ghrelin is a hormone which has effects on the secretion of growth hormone, gastrointestinal system, cardiovascular system, cell proliferation and reproductive system. The present study we focused on the relation between ghrelin and GHS-R1a gene expression and the regulation of their expression in the testes of diabetic rats. 40 male Wistar albino rats were divided into four groups: control, and sampled 4, 8 and 12 weeks after induction of diabetes by streptozotocin (STZ) intraperitoneal injection (40 mg/kg). The rats were decapitated under ketamine anesthesia and their testes were removed. Blood was obtained from heart and serum follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels were measured by ELISA. Tissue ghrelin and GHS-R mRNA levels were determined by qRT-PCR, while ghrelin protein expression was studied by immunohistochemistry. Histopathological damage scores were also assessed. Eight weeks after diabetes induction serum FSH level was increased, whereas LH and testosterone concentrations decreased. The ghrelin and GHS-R1a gene expression and ghrelin immunohistochemistry score first tended to increase after first four weeks of diabetes, and then tended to decrease. Ghrelin-immunopositive cells were detected in Leydig cells in all groups of rats, however, not in the germinal epithelium. Congestion of vessels and hemorrhage, formation of the vacuoles in spermatogonia and spermatocytes, desquamation of spermatids in the lumen and disorganization of seminiferous tubule germinal epithelium were observed in testis of all the diabetic rats. In addition, mean testicular biopsy score and mean seminiferous tubule diameter were getting lower in diabetic animals. Our results suggest that diabetes affects ghrelin expression in rat testis.

Effect of streptozotocin-induced diabetes on performance on a progressive ratio schedule

It has been suggested that streptozotocin (STZ)-induced diabetes causes a motivational deficit in rodents. However, some of the evidence adduced in support of this suggestion may be interpreted in terms of a motor impairment rather than a motivational deficit. This experiment examined the effect of STZ-induced diabetes on performance on a progressive ratio schedule. The data were analysed using a new model derived from Killeen's (Behav Brain Sci 17:105-172, 1994) Mathematical Principles of Reinforcement model which enables the effects of interventions on motivation or incentive value to be separated from effects on motor function. Animals were trained under a progressive ratio schedule using food-pellet reinforcement. Then they received a single intraperitoneal injection of 50mg/kg of STZ or the vehicle. Training continued for 30 sessions after treatment. Running and overall response rates in successive ratios were analysed using the new model, and estimates of the model's parameters were compared between groups. The parameter expressing incentive value was reduced in the group treated with STZ, whereas the parameters expressing motor capacity and post-reinforcement pausing were not affected by the treatment. Blood glucose concentration was significantly elevated in the STZ-treated group compared to the vehicle-treated group. The results are consistent with the suggestion that STZ-induced diabetes is associated with a reduction of the incentive value of food.

Dietary macronutrients modulate the fatty acyl composition of rat liver mitochondrial cardiolipins

The interaction of dietary fats and carbohydrates on liver mitochondria were examined in male FBNF1 rats fed 20 different low-fat isocaloric diets. Animal growth rates and mitochondrial respiratory parameters were essentially unaffected, but mass spectrometry-based mitochondrial lipidomics profiling revealed increased levels of cardiolipins (CLs), a family of phospholipids essential for mitochondrial structure and function, in rats fed saturated or trans fat-based diets with a high glycemic index. These mitochondria showed elevated monolysocardiolipins (a CL precursor/product of CL degradation), elevated ratio of trans-phosphocholine (PC) (18:1/18:1) to cis-PC (18:1/18:1) (a marker of thiyl radical stress), and decreased ubiquinone Q9; the latter two of which imply a low-grade mitochondrial redox abnormality. Extended analysis demonstrated: i) dietary fats and, to a lesser extent, carbohydrates induce changes in the relative abundance of specific CL species; ii) fatty acid (FA) incorporation into mature CLs undergoes both positive (>400-fold) and negative (2.5-fold) regulation; and iii) dietary lipid abundance and incorporation of FAs into both the CL pool and specific mature tetra-acyl CLs are inversely related, suggesting previously unobserved compensatory regulation. This study reveals previously unobserved complexity/regulation of the central lipid in mitochondrial metabolism.

Effect of Streptozotocin-induced Diabetes on Clock Gene Expression in Tissues Inside and Outside the Blood-brain Barrier in Rat

The circadian system allows organisms to remain synchronized with rhythmic environmental changes with a 24-h period. The molecular mechanism of circadian oscillations is based on the rhythmic expression of clock genes organized in feedback loops. Alterations in the circadian system contribute to the development of several pathological conditions including diabetes, but the exact mechanisms responsible for such alterations are not known. Therefore, we employed streptozotocin-induced diabetes to elucidate the influence of metabolic changes on clock gene (clock, npas2, per2) expression in peripheral oscillators in tissues inside (frontal cortex, cerebellum) and outside (heart, kidney) the blood-brain barrier. Diabetes was induced by streptozotocin injection. Seventeen days later, sampling was performed during a 24-h cycle. Gene expression was measured using real-time PCR. We observed a phase advance in rhythmic clock gene expression in the heart and kidney of diabetic rats. The study also focused on the possible role of npas2 in locomotor activity regulation in diabetic animals. The most pronounced changes were observed in the frontal cortex, which displayed up-regulation of npas2 expression. A change in locomotor activity was observed in diabetic rats during the dark phase of the 24-h cycle. We suggest that the altered function of the frontal cortex induced by diabetes might contribute to the modified behavior of diabetic rats.

The expression of growth hormone receptor gene transcript in the prefrontal cortex is affected in male mice with diabetes-induced learning impairments

Previous studies have indicated that both growth hormone (GH) deficiency and diabetes are conditions associated with impairments in learning and memory processes. In this study, we investigated the effect of streptozotocin-induced diabetes on spatial learning in mice using the Barnes maze (BM). The expression of the GH receptor (GHR) gene transcript in areas of the brain associated with learning and memory were examined. The results indicated that the GHR gene transcript is up-regulated in the prefrontal cortex (PFC) of diabetic mice compared to controls. In addition, there was a significant correlation between the expression of GHR mRNA and performance in the BM during the acquisition phase in diabetic but not control mice. These results suggest that diabetes induces an imbalance in the GH/IGF-1 system leading to altered activity in the PFC and associated cognitive deficiencies.

Effect of Streptozotocin-Induced Diabetes and Incomplete Global Cerebral Ischemia on Apoptosis in the Rat Thymus

Effect of Streptozotocin-Induced Diabetes and Incomplete Global Cerebral Ischemia on Apoptosis in the Rat Thymus

Selective responses of myenteric neurons to oxidative stress and diabetic stimuli

Diabetes has a differential effect on different subpopulations of myenteric neurons. Our aim was to investigate an in vitro model to examine the pathways underlying the development of nerve changes in diabetes. The proportions of neuronal cell bodies containing vasoactive intestinal polypeptide (VIP), neuronal nitric oxide synthase (nNOS) and calbindin relative to the pan-neuronal marker HuC/D were quantified in wholemount preparations of the myenteric plexus of adult rat ileum using double labeling immunohistochemistry. Preparations were maintained in culture for 24 h in the presence and absence of stimuli mimicking the diabetic environment including oxidative stress, carbonyl stress, high glucose and advanced glycation end products (AGEs). Data were compared with the effect of streptozotocin-induced diabetes in vivo. KEY RESULTS Only oxidative stress in vitro produced the same pattern as observed in diabetes with an increase in VIP-, decrease in nNOS-, and no change in calbindin-positive neurons. Carbonyl stress and high glucose caused an increase in VIP-containing neurons without affecting nNOS expression. In contrast, exposure to AGEs only caused a decrease in nNOS-positive neurons. Calbindin expression was unaffected by any of the stimuli. The effects of the stimuli were prevented by the antioxidant, α-lipoic acid, or the carbonyl scavenger, aminoguanidine. The results provide evidence that oxidative stress is the common factor in the development of neuronal changes in diabetes; however, the mechanism by which oxidative stress occurs depends on the individual subpopulation of myenteric neurons examined. The presence of calbindin appears to protect myenteric neurons against harmful stimuli.

Effects of streptozotocin-induced diabetes on tau phosphorylation in the rat brain

Brain protein kinase B (Akt) and glycogen synthase kinase-3 (GSK-3) activities are adaptable to changes of peripheral blood glucose level in vivo. GSK-3 phosphorylates microtube-associated protein tau at multiple sites, which can be antagonized by protein phosphatase-2A (PP-2A). The imbalance among these enzymes might have potential connections with diabetes mellitus (DM) and Alzheimer's disease (AD). In this study hyperglycemia rat DM model was achieved by streptozotocin (STZ) treatment. The phosphorylation of tau in the rat hippocampus was detected with specific antibodies. Insulin and Li2CO3 administration were also employed to find out the regulatory efforts of the kinases. We observed that rat hippocampus tau was hyperphosphorylated at Ser396/Ser404 (PHF-1 sites) in STZ-induced DM model, accompanied by lowered phosphorylation levels of Akt, GSK-3 and PP-2A. Lithium, a specific GSK-3 inhibitor, nearly reversed all phosphorylation of tau at above sites in 30days. Insulin administration restored the blood glucose level in DM rats but suppressed PP-2A activity, resulting in the PHF-1 sites of tau not being dephosphorylated. These findings strongly suggest that STZ-induced hyperglycemia may cause disorder of Akt/GSK-3/PP-2A regulations in rat brain and further lead to abnormal phosphorylation of hippocampus tau.

Gender differences in the effects of streptozotocin-induced diabetes on parasympathetic vasodilatation in the rat submandibular gland

Objectives Submandibular vasodilatory responses are impaired in male streptozotocin-diabetic rats. However, the effects of diabetes on submandibular vascular reactivity in female rats have not been examined. The purpose of this study was to determine whether there are gender differences in the effects of diabetes on parasympathetic vasodilatation in the rat submandibular gland. Methods Diabetes was induced using streptozotocin, and vascular responses (calculated as the % increase in submandibular vascular conductance) to parasympathetic stimulation (1–10 Hz) were measured using laser-Doppler flowmetry. To estimate the relative contributions of nitric oxide (NO), prostacyclin (PGI 2) and endothelium-derived hyperpolarizing factor (EDHF), vascular conductance was measured before and after inhibition of cyclooxygenase (COX) and NO synthase (NOS). Results Frequency-dependent increases in blood flow were observed in both male and female rats, but the contribution of EDHF was greater in females than in males. Further, PGI 2 appeared to play a role only in males. Vasodilatory responses were diminished in all diabetic animals, and when compared with their respective controls the degree of impairment was similar in males and females. However, in diabetic males inhibition of COX and NOS had little or no effect, whereas inhibition of NO, but not COX, resulted in a further significant decrease in vascular responses in diabetic females. Conclusions Parasympathetic vasodilatation in the rat submandibular gland is diminished equally in diabetic males and females. However, in males diabetes predominantly impairs PGI 2- and NO-dependent vasodilatation, whereas in females the contribution of EDHF-mediated pathways are affected and NO-dependent vasodilatation is preferentially maintained.