Early Stages Of Diabetes Mellitus Research Articles

Dietary Hesperidin Exerts Hypoglycemic and Hypolipidemic Effects in Streptozotocin-Induced Marginal Type 1 Diabetic Rats

Citrus bioflavonoids may offer some protection against the early stage of diabetes mellitus and the development of complications. We investigated the effect of hesperidin on blood glucose levels, hepatic glucose-regulating enzyme activities, serum insulin and adiponectin levels, serum and hepatic lipid levels, and parameters of bone loss in streptozotocin (STZ)-induced marginal type 1 diabetic rats. Weanling male rats were randomly assigned to experimental 3 groups: a control (C) group, a STZ induced marginal type 1 diabetes (S) group, and a diabetes and hesperidin group, and fed their respective diets for 4 weeks. STZ injection increased blood glucose in rats, but the increase was marginal. Serum and hepatic lipids, serum adiponectin and insulin levels were significantly changed by STZ injection. Dietary hesperidin (10 g/kg diet) decreased blood glucose by altering the activity of glucose-regulating enzymes, and normalized the lipids and adiponectin levels, but did not change bone parameters in the marginal type 1 diabetic rats. Hesperidin showed both hypoglycemic and hypolipidemic effects but did not affect bone tissue and bone metabolic makers in STZ-injected marginal diabetic weanling rats without any body weight loss due to STZ injection.

Antioxidant SOD Mimetic Prevents NADPH Oxidase-Induced Oxidative Stress and Renal Damage in the Early Stage of Experimental Diabetes and Hypertension

Aims: The presence of hypertension increases renal oxidative stress by increasing NADPH oxidase-dependent superoxide production and by decreasing antioxidant defense in the early stage of experimental diabetes mellitus (DM). In the present study, we investigated whether the administration of an antioxidant mimetic of the superoxide dismutase (SOD) (tempol) corrects the oxidative imbalance and oxidative stress-induced renal injury in the presence of DM and hypertension. Methods: DM was induced in spontaneously hypertensive rats (SHR) by streptozotocin at 4 weeks of age. The diabetic rats either did or did not receive tempol for 20 days. Oxidative-stress parameters and indices of renal injury were evaluated. Results: Tempol reestablished the imbalance in redox status induced by DM. It elevated the expression of renal antioxidant extracellular SOD, p < 0.0001; decreased (p = 0.049) the production of renal NADPH-dependent superoxide production, and diminished (p = 0.016) a marker of oxidative stress-induced DNA damage, 8-hydroxy-2′-deoxyguanosine. Reduction of oxidative stress markers was associated with reduction in renal damage parameters associated with DN. DM-induced albuminuria and elevation in renal expression of collagen IV were reduced to the level observed in control rats. Conclusion: We conclude that an imbalance in renal redox status is associated with markers of renal injury in the early stage of DM and hypertension. Antioxidant treatment reestablished the redox status and prevented oxidative stress-induced renal damage.

Does ghrelin explain accelerated gastric emptying in the early stages of diabetes mellitus?

During the early stages of diabetes, gastric emptying is often accelerated, rather than delayed. The mechanism of accelerated gastric emptying in diabetes has not been fully studied. A recent study showed that plasma ghrelin levels were elevated in diabetes. As postprandial antropyloric coordination plays an important role in mediating solid gastric emptying, we hypothesize that the elevated plasma ghrelin levels increase postprandial antropyloric coordination to accelerate emptying in the early stages of diabetes. To test this hypothesis, rats were made diabetic by streptozotocin (STZ; 50 mg/kg) injection, and, 2 wk later, pre- and postprandial plasma ghrelin levels, antropyloric coordination, and solid gastric emptying were determined. In control rats, plasma ghrelin levels were immediately reduced after feeding. In contrast, plasma ghrelin levels remained within the fasted levels in STZ rats after feeding. In STZ rats, gastric emptying was significantly accelerated (77.4 +/- 3.2%, n = 6), compared with that of control rats (58.8 +/- 2.5%, n = 6, P < 0.05). Treatments with anti-ghrelin antibodies attenuated accelerated gastric emptying in STZ rats (50.1 +/- 3.5%, n = 6, P < 0.05), while having little effect in vehicle control rats. The incidence of postprandial antropyloric coordination was significantly increased in STZ rats, compared with that of control rats (P < 0.05). Treatments with anti-ghrelin antibodies suppressed this enhanced antropyloric coordination in STZ rats. Our study suggests that elevated endogenous ghrelin enhances antropyloric coordination, which accelerates gastric emptying in the early stages of diabetes.

Cardiac sympathetic denervation imaging in movement disorders and dementias

The sympathetic nervous system greatly influences cardiovascular physiology, and the importance of cardiac innervation abnormalitiesinthephysiopathologyof variouscardiacdiseases has been emphasised. Cardiac neurotransmission imaging with single-photon-emission computed tomography (SPECT) allows in vivo assessment of the myocardial nervous system. At present, the most commonly used SPECT tracer to assess cardiac neurotransmission is metaiodobenzylguanidine labelled with iodine-123 ( 123 I-MIBG). Cardiac 123 I-MIBG scintigraphy allows autonomic neuropathy to be detected in the early stages of diabetes mellitus. In patients with heart failure, the assessment of cardiac sympathetic activity has important prognostic implications. Targeting neuronal dysfunction with 123 I-MIBG scintigraphy in patients with heart transplantation, ischaemic heart disease, hypertension, diabetes mellitus, heart failure, drug-induced cardiotoxicity and dysautonomias can contribute to early diagnosis, prognostic stratification and appropriate treatment [1]. However, this is not all of the uses for 123 I-MIBG, as an emerging application of this tracer is being pursued for studies in movement disorders.

Progress of research on pathogenesis and medical treatment of diabetic retinopathy

Diabetic retinopathy is a common complication of diabetes mellitus. Studies on the pathogenesis of diabetic retinopathy are important for the prevention and treatment of this disease. Neurodegeneration and microvascular dysfunction are the major events of diabetic retinopathy happened in the early stage of diabetes mellitus. The pathologic changes include neuron apoptosis, release of inflammatory mediators and impaired glutamate metabolism. Diabetic retinopathy has many pathological changes with inflammatory characteristics. Because of the adhesion and migration of the leucocyte, increased permeability of blood vessel, haemodynamic change and many inflammatory mediators involved in the process of diabetic retinopathy, more and more researchers believe that diabetic retinopathy is a chronic inflammatory disease. These studies provide new notion of mechanisms of diabetic retinopathy and theoretical foundation for the treatment of this disease. Further studies on the pathogenesis of diabetic retinopathy can provide novel procedures for the prevention and treatment of this disease.

Does alfacalcidol prevent pancreatic beta cells from further destruction in children at the onset of diabetes mellitus type 1?

In recent years studies focused on prevention of type 1 diabetes mellitus (DM) and possibility of beta-cell protection at the clinical diagnosis of DM. Some recent studies have demonstrated beneficial role of vit. D3 analogue in human beta-cell activity maintenance at the early stages of DM.

Targeting neuronal dysfunction and receptor imaging

The sympathetic nervous system has great influence on cardiovascular physiology, and the importance of cardiac innervation abnormalities in the physiopathology of various cardiac diseases has been emphasized. Cardiac neurotransmission imaging with single-photon emission computed tomography (SPECT) allows in vivo assessment of the myocardial nervous system. At present, the most commonly used SPECT tracer to assess cardiac neurotransmission is metaiodobenzylguanidine labelled with iodine-123 ((123)I-MIBG). In patients with heart transplantation, ischemic heart disease, dysautonomias and drug-induced cardiotoxicity, assessment of neuronal function can help characterise the disease and improve the prognostic stratification. Cardiac (123)I-MIBG scintigraphy allows autonomic neuropathy to be detected in the early stages of diabetes mellitus. In patients with heart failure, the assessment of cardiac sympathetic activity has important prognostic implications. Future directions in cardiac sympathetic neurotransmission include the development of new tracers, targeting of second-messenger molecules and early assessment of cardiac neurotransmission in genetically predisposed subjects for prevention of heart failure.

Structural Alterations of the Glomerular Wall and Vessels in Early Stages of Diabetes Mellitus (Light and Transmission Electron Microscopic Study)

Objective: The capillary changes at the initial stage of diabetes may show an angioarchitecture clearly different from those of later stages and/or very severe glomerular change. However, the onset of alterations in the early phases is unclear. This study attempts to determine the structural alterations of the glomerular wall and vessels in the early stage of diabetes. Material and Methods: Twenty-five adult rats were used in this study. They were divided into two groups: the first group of five was used as a control .The second group of 20 (the experimental group) was injected intraperitoneally by a single dose of streptozotocin to induce hyperglycemia. Rats were sacrificed after ten days, two months, and four months. Five rats at two months of age with hyperglycemia were treated with insulin for eight weeks. Renal tissues were prepared by routine technique for light and transmission electron microscopic evaluation. Results: By light microscopy after ten days of induced hyperglycemia, there were no structural modifications detected either in renal glomerular fine vessels or in the glomerular basement membrane of the glomerular capillaries. After two months, there was a moderate glomerular enlargement and dilatation of glomerular capillaries, afferent, and efferent arterioles. After four months, glomerular basement membrane thickening was the only structural alteration observed. Recovery of the glomerular alterations was observed after two months of treatment with insulin. Conclusion: In early stages of diabetes mellitus in rats, there was an increase in the diameter of glomerular vessels. In later stages of the disease, the reverse was seen, but insulin treatment had a positive role in reversing these changes in the study subjects.

Serum TNF-Alpha Level Predicts Nonproliferative Diabetic Retinopathy in Children

The aim of this study was identification of the immunologic markers of the damage to the eye apparatus at early stages of diabetes mellitus (DM) type 1 children. One hundred and eleven children with DM type 1 were divided into two groups: those with nonproliferative diabetic retinopathy (NPDR) and without retinopathy. All the children had their daily urine albumin excretion, HbA1c, C-peptide measured, 24-hour blood pressure monitoring, and ophthalmologic examination. Levels of TNF-α, IL-6, and IL-12 in serum were measured by ELISA tests (Quantikine High Sensitivity Human by R&D Systems, Minneapolis, Minn, USA). The NPDR children demonstrated a significantly longer duration of the disease in addition to higher HbA1c, albumin excretion rate, C-reactive protein, systolic blood pressure, as well as TNF-α and IL-6 levels than those without retinopathy. The logistic regression revealed that the risk of NPDR was strongly dependent on TNF-α [(OR 4.01; 95%CI 2.01−7.96)]. TNF-α appears to be the most significant predictor among the analyzed parameters of damage to the eye apparatus. The early introduction of the TNF-α antagonists to the treatment of young patients with DM type 1 who show high serum activity of the TNF-α may prevent them from development of diabetic retinopathy.

Structural alterations of the glomerular wall and vessels in early stages of diabetes mellitus: (light and transmission electron microscopic study).

ObjectiveThe capillary changes at the initial stage of diabetes may show an angioarchitecture clearly different from those of later stages and/or very severe glomerular change. However, the onset of alterations in the early phases is unclear. This study attempts to determine the structural alterations of the glomerular wall and vessels in the early stage of diabetes.Material and MethodsTwenty-five adult rats were used in this study. They were divided into two groups: the first group of five was used as a control. The second group of 20 (the experimental group) was injected intraperitoneally by a single dose of streptozotocin to induce hyperglycemia. Rats were sacrificed after ten days, two months, and four months. Five rats at two months of age with hyperglycemia were treated with insulin for eight weeks. Renal tissues were prepared by routine technique for light and transmission electron microscopic evaluation.ResultsBy light microscopy after ten days of induced hyperglycemia, there were no structural modifications detected either in renal glomerular fine vessels or in the glomerular basement membrane of the glomerular capillaries. After two months, there was a moderate glomerular enlargement and dilatation of glomerular capillaries, afferent, and efferent arterioles. After four months, glomerular basement membrane thickening was the only structural alteration observed. Recovery of the glomerular alterations was observed after two months of treatment with insulin.ConclusionIn early stages of diabetes mellitus in rats, there was an increase in the diameter of glomerular vessels. In later stages of the disease, the reverse was seen, but insulin treatment had a positive role in reversing these changes in the study subjects.

Hyperglycemia induces protein nonenzymeatic glycosylation in brain neurons of diabetic rats at early stage

Background Protein nonenzymatic glycosylation is supposed to be one of mechanisms for chronic complications development in diabetes mellitus, and therefore, might play an important role in the neuronal degeneration. Objective To study the protein nonenzymatic glycosylation in brain neurons of diabetic rats, and to analyze the pathway of neuronal degeneration at the early stage of hyperglymecia. Design Randomized controlled animal experiment. Setting Department of Endocrinology, First hospital Affiliated to General Hospital of Chinese PLA and Beijing Laboratory for Brain Aging, Xuanwu Hospital Affiliated to Capital Medical University. Materials Thirty-five male Wistar rats (grade II), aged 3 months old, and 11 male purebred Kunming mice (grade III) without special pathogen, aged 3 months old, were provided by the Animal Room of Capital Medical University. Methods This experiment was carried out in the Beijing Laboratory for Brain Aging, Xuanwu Hospital Affiliated to Capital Medical University in 1998. The rats in the diabetic model group were intraperitoneally injected into 10 g/L STZ according to 60 mg/kg to establish rat models of diabetes mellitus. The blood glucose and body mass of rats in each group were determined respectively at 1, 2 and 3 months after modeling. The antibodies of advanced glycosylation end products (AGEs) of bovine serum albumin (anti-BSA) were self-prepared: ▪The antigen of AGEs-BSA was prepared. ▪Eleven male Kuming mice (grade II) of 3 months old without special pathogen were selected to inoculate AGEs-BSA. ▪ The animals were immunized. ▪Primary purification and detection of poly-antibodies of AGEs: the AGEs were performed immunohistochemical examination at 1 month after diabetic modeling by ELISA method. Main outcome measures ▪ Detection results of blood glucose and body mass of rats in two groups at different time points. ▪ Determination of polyclonal antibody titer of AGEs-BSA. ▪ Changes in immunohistochemical image of AGEs in brain tissue of rats in two groups. Results Thirteen rats in the diabetic model group and fifteen rats in the normal model group entered the stage of final analysis. ▪Changes of blood glucose and body mass: At 1, 2 and 3 months after modeling, the blood glucose of rats in the diabetic model group were respectively(28.8±2.8),(23.1±5.5),(25.4±5.1) mmol/L, which were significantly higher than those in the normal control group [(6.2±0.9),(6.1±0.8),(6.1±0.7) mmol/L, P < 0.01]; At 1, 2 and 3 months after modeling, the body mass of rats in the diabetic model group were respectively (250.1±52.2),(263.8±50.0),(261.5±42.6) g, which were significantly lower than those in the normal control group [(422.6±36.2),(462.6±39.0),(485.0±28.8) g, P < 0.01]. ▪Determination of antibody titer of immune serum: The mice were treated by AGEs-BSA of different concentrations twice. After that, the titer of AGEs -BSA was determined, and the results of which indicated that a higher absorbance existed at 1 : 1 000. ▪Determination of antigen concentration: The final titer of antibody in the abdominal dropsy was determined, and the results of which suggested that there was a much higher absorbance in the AGEs-BSA at the concentration of 5–50 mg/L. ▪Determination of antibody titer in abdominal dropsy: The antibody titer in abdominal dropsy was detected by ELISA method with antigen at 20 mg/L, which indicated that the maximum absorbance (1.265±0.039) existed at 1 : 4 000, and very larger absorbance (0.982±0.067) at 1 : 20 000. The polyclonal antibody of AGEs-BSA was successfully prepared. ?Immunohistochemical detection results: The immunohistochemical staining of AGEs showed there were positive neurons in the first month in the diabetic model group, whereas it was not significant in the normal control group. The positive substances were found mainly in the cytoplasm. Conclusion Hyperglycemia at the early stage of diabetes mellitus (1 month after modeling) can lead to protein nonenzymeatic glycosylation in brain neurons, and no obvious reactions mentioned above are found in the normal control group. It suggests that the degenerative changes of tissue structure of central nervous system are related with protein nonenzymeatic glycosylation caused by hyperglycemia.

P10.7 Importance of different electrophysiological findings in early stages of diabetes melitus patients

Background: Diabetic neuropathy is not only the most common cause of neuropathy around the world but also it is the most important cause of morbidity and mortality among these patients. Aims: To clarifying value of different electrophysiological findings for detecting neuropathy in early stages of diabetes mellitus. Patients and method: Thirty patients with early stages of diabetes (duration 126 mg per deciliter) were analyzied with complete neurophysiological tests (motoric and sensory branches of four limbs plus EMG) with Toeenies model during year 2004 in 22 Bahman Mashhad Azad Medical University. Results: Sensory median distal latency was abnormal in 78% of patients whereas NCV of motoric branches of proneal and tibialis nerve was abnormal in 57% of them. Abnormality of sural nerve and EMG findings (positive sharp waves and fibrillation) was detectable in 10%. Radial sensoy nerve was intact in all of the patients. Conclusion: We belive that routine electrophysiological tests is Indicated in all newly diagnosed diabetic patients. The most sensitive test is distal latency of sensory median nerve. EMG had the least value.

Correlation between Adult Diabetic Cataracts and Red Blood Cell Aldose Reductase Levels

To investigate the correlation between adult diabetic cataracts and levels of aldose reductase (AR) in red blood cells (RBCs). The study involved 337 eyes of 337 patients with diabetes. The extent and severity of lens opacity was assessed according to the Lens Opacities Classification System III (LOCS III). The AR levels within RBCs were determined with an ELISA. The relationship between the AR level in RBCs and the prevalence of nuclear cataract, cortical cataract, and posterior subcapsular cataract in patients with diabetes was examined. There were no significant alterations in AR level in RBCs in patients with a diabetes duration of < or = 10 years and patients < 60 years of age. In each subgroup, a higher amount of AR levels in RBCs significantly correlated with the prevalence of posterior subcapsular cataracts. A significant association between cortical cataract and AR level in RBCs was also seen in a subgroup of patients younger than 60 years. AR emerges as an important factor affecting the onset of posterior subcapsular cataracts at the early stages of diabetes mellitus. This raises the possibility that AR inhibitors could play a useful role in treatment of adult diabetic cataract through its inhibition of AR activities.

Real-time measurement of kidney tubule fluid nitric oxide concentrations in early diabetes: Disparate changes in different rodent models

There are several reports indicating that nitric oxide (NO) plays a role in the kidney hyperfiltration seen in the early stages of diabetes mellitus (DM). Whole kidney GFR and single nephron GFR (SNGFR) have been reported to decrease after nitric oxide synthase (NOS) inhibition. To date, no direct, in vivo, quantitative NO measurements have been made within the kidney in any models of early diabetes. To assess the possible association of changes in tubular fluid nitric oxide concentrations (TF [NO]) with early diabetes, a specially modified NO electrode with a tip diameter of about 7 microm was used to measure NO in single tubules in seven rodent groups. In the Sprague-Dawley (SD) rat model, TF [NO] increased by 50% after streptozotocin (STZ) induced DM1. In the B6129G2/J mouse, control TF [NO] was more than twice the rat control value and fell by 50% after STZ treatment. In three other groups of mice-db/db (B6.Cg-m+/+Lepr(db)/J) Type II diabetic (DM2) mouse, db/m (its heterozygote), and the corresponding wild type (WT)-TF [NO] was also much higher than in the rat, and unlike the B6129G2/J STZ diabetic mouse, did not change after the onset of diabetes. Blood glucose concentrations were similar in the three diabetic groups. Accordingly, in different rodent models of diabetes, in vivo TF [NO], measured in real time, varies significantly in control animals and directionally in different models of DM1 and DM2.

Acute and Chronic Regulation of the Renal Na+/H+ Exchanger NHE3 in Rats with STZ-Induced Diabetes mellitus

Background: Early stages of diabetic nephropathy are characterized by alterations of glomerular filtration, increased tubular sodium and water reabsorption, and systemic volume expansion, which may be a major cause for the development of hypertension. As a significant fraction of renal salt and water transport is mediated by the proximal tubular Na⁺/H⁺ exchanger NHE3, we investigated its regulation in rats with STZ-induced diabetes mellitus. Methods: Male Sprague-Dawley rats were injected +/– streptozotocin (STZ, 60 mg/kg), and sacrificed after 2, 7 or 14 days. Renal cortical BBM vesicles were prepared to measure Na⁺/H⁺ exchange (NHE) activity and NHE3 protein abundance. Cortical NHE3 mRNA was extracted to perform Northern blot analysis. Pharmacological inhibitors were used in vivo and in vitro in order to identify isoform specificity conferring changes in NHE activity mediated by the diabetic milieu. Results: Compared to control rats, STZ rats were clearly hyperglycemic at all time points studied. NHE activity was significantly increased by 40 and 37% in diabetic rats after 7 and 14 days, respectively, but not after 2 days. The increase in Na⁺/H⁺ exchange activity was not inhibited by HOE-642 (3 µM). Administration of exogenous insulin to diabetic rats resulted in lower blood sugars, but not NHE activity. Moreover, serum glucose concentration did not correlate with NHE activity in any subgroup nor in all animals analyzed together. However, in STZ rats supplemented with exogenous insulin NHE activity was positively correlated with serum insulin concentrations (r = 0.86, p < 0.01). In vivo, the increase in NHE activity induced by STZ could be completely inhibited when rats were fed 6 ppm of HOE-642 with the diet over 14 days. The changes in Na⁺/H⁺ exchange activity were not paralleled by changes in NHE3 protein or mRNA abundance in diabetic rats at any of the time points investigated. Conclusions: These results suggest that proximal tubular Na/H exchange activity is modified in the early stage of diabetes mellitus.

Reduced urinary excretion of sulfated polysaccharides in diabetic rats

The aim of the present study was to further understand the changes in renal filtration that occur in the early stages of diabetes mellitus. Diabetes was induced in male Wistar rats by a single injection of streptozotocin. Glycemia, body weight, 24-h urine volume and urinary excretion of creatinine, protein and glycosaminoglycans were measured 10 and 30 days after diabetes induction. All the diabetic animals used in the present study were hyperglycemic, did not gain weight, and presented proteinuria and creatinine hyperfiltration. In contrast, the glycosaminoglycan excretion decreased. Dextran sulfates of different molecular weights (6.0 to 11.5 kDa) were administered to the diabetic rats, and to age-matched, sham-treated controls. Most of the dextran sulfate was excreted during the first 24 h, and the amounts excreted in the urine were inversely proportional to the dextran sulfate molecular weight for all groups. Nevertheless, diabetic rats excreted less and accumulated more dextran sulfate in kidney and liver, as compared to controls. These differences, which were observed only for the dextran sulfates of higher molecular weights (>7 kDa), increased with the duration of diabetes. Our findings suggest differential renal processing mechanisms for proteins and sulfated polysaccharides, with the possible involvement of kidney cells.

The Hypoglycemic Effects of Hesperidin and Naringin Are Partly Mediated by Hepatic Glucose-Regulating Enzymes in C57BL/KsJ-db/db Mice

Dietary antioxidant compounds such as bioflavonoids may offer some protection against the early stage of diabetes mellitus and the development of complications. We investigated the effect of citrus bioflavonoids on blood glucose level, hepatic glucose-regulating enzymes activities, hepatic glycogen concentration, and plasma insulin levels, and assessed the relations between plasma leptin and body weight, blood glucose, and plasma insulin. Male C57BL/KsJ-db/db mice (db/db mice, 5 wk old), an animal model for type 2 diabetes, were fed a nonpurified diet for 2 wk and then were fed an AIN-76 control diet or the control diet supplemented with hesperidin (0.2 g/kg diet) or naringin (0.2 g/kg diet). Hesperidin and naringin supplementation significantly reduced blood glucose compared with the control group. Hepatic glucokinase activity and glycogen concentration were both significantly elevated in the hesperidin- and the naringin-supplemented groups compared with the control group. Naringin also markedly lowered the activity of hepatic glucose-6-phosphatase and phosphoenolpyruvate carboxykinase compared with the control group. Plasma insulin, C-peptide, and leptin levels in the db/db mice from the 2 bioflavonoid-supplemented groups were significantly higher than those of the control group. Furthermore, plasma leptin was positively correlated with plasma insulin level (r = 0.578, P < 0.01) and body weight (r = 0.541, P < 0.05), and was inversely correlated with the blood glucose level (r = -0.46, P < 0.05). The current results suggest that hesperidin and naringin both play important roles in preventing the progression of hyperglycemia, partly by increasing hepatic glycolysis and glycogen concentration and/or by lowering hepatic gluconeogenesis.

Mitochondrial reactive oxygen species reduce insulin secretion by pancreatic β-cells

Pancreatic β-cells exposed to hyperglycemia produce reactive oxygen species (ROS). Because β-cells are sensitive to oxidative stress, excessive ROS may cause dysfunction of β-cells. Here we demonstrate that mitochondrial ROS suppress glucose-induced insulin secretion (GIIS) from β-cells. Intracellular ROS increased 15 min after exposure to high glucose and this effect was blunted by inhibitors of the mitochondrial function. GIIS was also suppressed by H 2O 2, a chemical substitute for ROS. Interestingly, the first-phase of GIIS could be suppressed by 50 μM H 2O 2. H 2O 2 or high glucose suppressed the activity of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, and inhibitors of the mitochondrial function abolished the latter effects. Our data suggested that high glucose induced mitochondrial ROS, which suppressed first-phase of GIIS, at least in part, through the suppression of GAPDH activity. We propose that mitochondrial overwork is a potential mechanism causing impaired first-phase of GIIS in the early stages of diabetes mellitus.

Regulation of the apoptosis‐related genes, Bax and Bcl‐2, in the early stage of diabetes mellitus

SUMMARY: Apoptosis is related to a particular phase of the pathogenesis of diabetic nephropathy. the aim of the study is to investigate if (and if so where in the kidney) apoptotic changes occur during the early stage of diabetes mellitus. the incidence of renal cell apoptosis and its related Bcl‐2 proteins was investigated in the early stage of streptozotocin‐induced diabetic rats, using histological sections as well as isolated nephron segments and high glucose treatments in vitro. Modulation of the induced changes with the angiotensin‐converting enzyme (ACE) inhibitor, temocapril, was also analysed. Reverse transcription (RT)‐competitive polymerase chain reaction and western blot analysis were used. Glucose caused an increase of Bax mRNA expression in glomeruli and in the proximal straight tubule (PST), but not in the inner medullary collecting duct (IMCD). Glucose induced a decrease (40%) of Bcl‐2 mRNA expression in PST but not in glomeruli or in IMCD. Western blotting showed an increase of Bax protein expression in PCT, PST, and medullary thick ascending limb (MAL), and a decrease of Bcl‐2 protein expression in PST in diabetic rats. the ratio of Bcl‐2 to Bax decreased in PCT and PST in diabetic rats. the terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end‐labelling (TUNEL) method revealed the presence of apoptotic cells in proximal tubules in diabetic rats. Short‐term administration of temocapril did not affect Bax and Bcl‐2 protein expression in PCT or PST of diabetic rats. In conclusion, high ambient glucose could directly induce apoptotic changes in proximal tubules but not in glomeruli or in distal tubules at the early stage of diabetes mellitus.

Rapid stimulation of L-arginine transport by D-glucose involves p42/44(mapk) and nitric oxide in human umbilical vein endothelium.

D-glucose infusion and gestational diabetes induce vasodilatation in humans and increase L-arginine transport and nitric oxide (NO) synthesis in human umbilical vein endothelial cells. High D-glucose (25 mmol/L, 2 minutes) induced membrane hyperpolarization and an increase of L-arginine transport (V(max) 6.1+/-0.7 versus 4.4+/-0.1 pmol/ microg protein per minute) with no change in transport affinity (K(m) 105+/-9 versus 111+/-16 micromol/L). L-[3H]citrulline formation and intracellular cGMP, but not intracellular Ca2+, were increased by high D-glucose. The effects of D-glucose were mimicked by levcromakalim (ATP-sensitive K+ channel blocker), paralleled by p42/p44(mapk) and Ser(1177)-endothelial NO synthase phosphorylation, inhibited by N(G)-nitro-L-arginine methyl ester (L-NAME; NO synthesis inhibitor), glibenclamide (ATP-sensitive K+ channel blocker), KT-5823 (protein kinase G inhibitor), PD-98059 (mitogen-activated protein kinase kinase 1/2 inhibitor), and wortmannin (phosphatidylinositol 3-kinase inhibitor), but they were unaffected by calphostin C (protein kinase C inhibitor). Elevated D-glucose did not alter superoxide dismutase activity. Our findings demonstrate that the human fetal endothelial L-arginine/NO signaling pathway is rapidly activated by elevated D-glucose via NO and p42/44(mapk). This could be determinant in pathologies in which rapid fluctuations of plasma D-glucose may occur and may underlie the reported vasodilatation in early stages of diabetes mellitus.