Suppressive effects of continuous low-dose-rate γ irradiation on diabetic nephropathy in type II diabetes mellitus model mice

It has been proposed that the development of diabetic nephropathy is caused in large part by oxidative stress. We previously showed that continuous exposure of mice to low-dose-rate γ radiation enhances antioxidant activity. Here, we studied the ameliorative effect of continuous whole-body irradiation with low-dose-rate γ rays on diabetic nephropathy. Ten-week-old female db/db mice, an experimental model for type II diabetes, were irradiated with low-dose-rate γ rays from 10?weeks of age throughout their lives. Nephropathy was studied by histological observation and biochemical analysis of serum and urine. Antioxidant activities in kidneys were determined biochemically. Continuous low-dose-rate γ radiation significantly increases life span in db/db mice. Three of 24 irradiated mice were free of glucosuria after 80?weeks of irradiation. Histological studies of kidney suggest that low-dose irradiation increases the number of normal capillaries in glomeruli. Antioxidant activities of superoxide dismutase, catalase and glutathione are significantly increased in kidneys of irradiated db/db mice. Continuous low-dose-rate γ irradiation ameliorates diabetic nephropathy and increases life span in db/db mice through the activation of renal antioxidants. These findings have noteworthy implications for radiation risk estimation of non-cancer diseases as well as for the clinical application of low-dose-rate γ radiation for diabetes treatment.     

Low‐power laser irradiation decreases lipid droplet accumulation in the parotid glands of diabetic rats

Lipid droplet accumulation has been related to salivary gland hypofunction in diabetes. In this study, the effect of laser irradiation on the parotid glands (PGs) of diabetic rats was analyzed with regard to its effect on lipid droplet accumulation, intracellular calcium concentration and calmodulin expression. The animals were distributed into 6 groups: D0, D5, D20 and C0, C5, C20, for diabetic (D) and control animals (C), respectively. Twenty‐nine days following diabetes induction, PGs of groups D5 and C5; D20 and C20 were irradiated with 5 and 20 J/cm² of a red diode laser at 100 mW, respectively. After 24 hours, PGs were removed for histological, biochemical, and western blotting analysis. The diabetic animals showed lipid droplet accumulation, which was decreased after irradiation. Ultrastructurally, the droplets were nonmembrane bound and appeared irregularly located in the cytoplasm. Moreover, diabetic animals showed an increased intracellular calcium concentration. In contrast, after laser irradiation a progressive decrease in the concentration of this ion was observed, which would be in agreement with the results found in the increased expression of calmodulin in D20. These data are promising for using laser to decrease lipid droplet accumulation in PGs, however, more studies are necessary to better understand its mechanisms. Micrographs showing decreased lipid accumulation after laser irradiation in light micrographs (LM), and morphology of lipid droplet in transmission electron microscopic (TEM). LM: (A) PGs from nondiabetic rats that did not receive Laser irradiation (LI), (B) PGs from nondiabetic rats that received a dose of 20 J/cm², (C) lipid accumulation (arrows) in the secretory cells from diabetic rats that did not receive irradiation, (D) reduction of lipid accumulation in the secretory cells from diabetic rats that received a dose of 20 J/cm² and TEM: (E) scale bar = 5 μm, (F) scale bar = 1 μm, and (G) scale bar = 0.5 μm.      

Prevention of type I diabetes by low-dose gamma irradiation in NOD mice

Pretreatment with nonlethal, low-dose irradiation has been shown to have a protective effect against oxidative injury in animal tissues. Since oxidative injury of tissues is known to be a major cause of many human diseases, we examined the effect of low-dose irradiation on the progression of type I diabetes in mice. Nonobese diabetic (NOD) mice were treated with gamma irradiation and the progression of the disease was monitored. An elevated level of glucose in urine was first detected at 15 weeks of age in the control NOD mice, whereas the detection was delayed as long as 7 weeks when the mice received a single dose of 0.5 Gy total-body irradiation between 12 and 14 weeks of age. The greatest effect was observed in the mice irradiated at 13 weeks of age. The increase in blood glucose and decrease in blood insulin were effectively suppressed by irradiation at 13 weeks of age. Both suppression of cell death by apoptosis and an increase in superoxide dismutase (SOD) activity were observed in the pancreas 1 week after irradiation. The results indicate that treatment with 0.5 Gy gamma rays suppresses progression of type I diabetes in NOD mice. This is the first report on the preventive effect of low-dose irradiation on disease progression.     

低强度He-Ne激光血管内照射影响糖尿病兔血液流变性质的可能因素分析

本实验在前工作的基础上,观察对实验性糖尿病兔进行两次低强度He-Ne激光血管内照射后,血中甘油三酯、总胆固醇、红细胞膜总磷脂的动态变化,分析有关参数与红细胞变形能力之间的关系,以期探讨低强度激光血管内照射影响血液流变性质的可能因素。实验结果表明,经两次激光照射后,1．第1天糖尿病兔的红细胞变形能力即见改善,4天-7天后接近注药前水平。2．与其相应,甘油三酯和胆固醇在激光照射后第4天即回复至正常水平。3．红细胞膜总磷脂激光照射后渐升高,至第7天与注药前无明显差异。文章讨论了有关实验指标影响红细胞变形能力的可能性。     

Proton microprobe analysis of 15 elements in pancreatic B cells and exocrine pancreas in diabetic Chinese hamsters

Diabetes mellitus spontaneously develops in certain sublines of non-obese Chinese hamsters, and the diabetic L-subline is known for subnormal pancreatic insulin releasein vitro. The cause of the secretory defect is unknown.Freeze-dried pancreas sections from genetically diabetic Chinese hamsters and normal controls were subjected to proton bombardment and the concentration of 15 elements in B cells and acini was calculated from the X-rays emitted. Diabetic B cells contained significantly less Al (–61%) and significantly more Cu (+92 %), Mg (+6 %) and Rb (+13 %) than their normal counterparts. The diabetic acini showed similar, significant changes. The molar ratio between K and Na was about 10 in endocrine as well as exocrine pancreas from both groups of animals, implying that neither sample preparation nor irradiation had induced significant diffusive changes.In conclusion, the high K/Na ratio suggests that the diabetic B cell has a well-functioning Na⁺/K⁺ pump. However, significant and parallel changes in Al-, Cu-, Mg- and Rb-levels were found in both the B cells and acinar portion of the diabetic pancreas. It is not clear whether these elemental changes cause the islet secretory defect or result from it.     

Photobiomodulation alters matrix protein activity in stressed fibroblast cells in vitro

A balance is maintained between matrix synthesis and degradation, and a prolonged increase in matrix metalloproteinases (MMPs) affects healing. Photobiomodulation (PBM) speeds up healing and alters wound environment. The study aimed to determine changes in protein and gene expression of collagen type 1 (Col‐I), MMP‐3 and ‐9 and TIMP‐1 in fibroblasts irradiated at 660 or 830 nm. Commercially purchased human skin fibroblast cells were modeled into five groups namely, normal, normal wounded, diabetic wounded, hypoxic wounded and diabetic hypoxic wounded. Control cells were sham irradiated. Laser irradiation was conducted at 660 or 830 nm (108/or 94 mW, 9.1 cm², 420/or 483 s) with 5 J/cm². Forty‐eight hours post‐irradiation, protein expression of TIMP‐1, MMP‐3, ?9 and Col‐I was determined by flow cytometry and immunofluorescence, and gene expression by real‐time RT‐PCR. There was an increase in TIMP‐1 and Col‐I, and a decrease in MMP‐3 and ‐9, as well as an alteration in mRNA expression of MMP3, MMP9, TIMP1 and COL1A1 in irradiated cells. Due to the responsiveness of the diabetic hypoxic wounded model, the findings propose this model as appropriate for wound healing studies and suggest that PBM promotes the remodeling phase of wound healing by decreasing matrix degradation and upregulating synthesis.      

Fifteen years of preclinical and clinical experiences about biotherapy treatment of lesions induced by accidental irradiation and radiotherapy

High dose radiation exposures involving medical treatments or accidental irradiation may lead to extended damage to the irradiated tissue. Alleviation or even eradication of irradiation induced adverse events is therefore crucial. Because developments in cell therapy have brought some hope for the treatment of tissues damages induced by irradiation, the Institute for Radiation and Nuclear Safety contributed to establish the clinical guidelines for the management of accidentally irradiated victims and to provide the best supportive care to patients all over the world. In the past 15 years, we contributed to develop and test cell therapy for protection against radiation side effects in several animal models, and we proposed mechanisms to explain the benefit brought by this new therapeutic approach. We established the proof of concept that mesenchymal stem cells (MSCs) migrate to damaged tissues in the nonobese diabetic/severe combined immunodeficiency immunotolerant mice model and in non-human primate after radiation exposure. We showed that the intravenous injection of MSCs sustains hematopoiesis after total body irradiation, improves wound healing after radiodermatitis and protects gut function from irradiation damages. Thanks to a tight collaboration with clinicians from several French hospitals, we report successful treatments of therapeutic/accidental radiation damages in several victims with MSC infusions for hematopoiesis correction, radio-induced burns, gastrointestinal disorders and protection homeostatic functions of gut management after radio-therapy.     

Topical hyperbaric oxygen and low energy laser therapy for chronic diabetic foot ulcers resistant to conventional treatment

Chronic foot ulcers are common in long-standing diabetes, may herald severe complications and are often resistant to therapy. To evaluate the effects of adjunctive topical hyperbaric oxygen treatment (THBO) and low energy laser (LEL) irradiation on ulcer healing, a 100 consecutive patients with chronic diabetic foot ulcers (DFU) refractory to 4.5 +/- 1.2 months of comprehensive treatment, were enrolled in a prospective open study. While conventional treatment was continued as necessary, THBO was administered by pumping 100 percent oxygen into a disposable sealed polythylene hyperbaric chamber (150 min x 2 to 3/wk at up to 1.04 atm). Helium-neon LEL irradiation was given concurrently using a Unilaser Scan Unit at 4 J/cm2 for 20 min. Some patients continued THBO at home or their treatment was confined to THBO at home. Patients were monitored every two weeks revealing 81 percent cure after 25 +/- 13 treatments over 3.2 +/- 1.7 months. On follow-up (median 18 months), only 3/81 (4 percent) had reulceration, which responded to THBO/LEL retreatment. Nonresponders had significantly lower ankle brachial indices (ABI) than patients whose ulcers were healed (0.55 vs. 0.78, p < 0.01) and ultimately required amputation. Patient compliance was full and no adverse events occurred. In conclusion, although the study was open and uncontrolled, an 81 percent healing of DFU in patients who previously did not respond to a comprehensive treatment program, constitutes an intriguing preliminary result. Thus, THBO/LEL therapy may be a safe, simple, and inexpensive early adjunctive treatment for patients with chronic diabetic foot ulcers. Our findings should prompt its evaluation by large randomized controlled trials.     

Low-dose photodynamic therapy effect on closure of scratch wounds of normal and diabetic fibroblast cells: An in vitro study

Chronic wounds such as diabetic ulcers are a serious public health problem. Extensive research is needed to find new alternatives for wound treatment. Photodynamic therapy (PDT) is a non-invasive method, which has been studied for several decades to treat cancer, infections, and other diseases. PDT involves the administration of a photosensitizer compound followed by irradiation with using light at specific wavelength to produce reactive oxygen species (ROS) using molecular oxygen. It is possible that low dose photodynamic therapy (LDPDT) could improve wound healing and stimulates the cell repair process. This study we explored the effect of LDPDT on wound healing in vitro using normal and diabetic cellular wound models. The effects of different concentrations of 5-ALA and different energy densities (dark or light) on the cell viability of human fibroblast cells were studied using the MTT assay. After ascertaining the optimum parameters, a scratch wound assay was performed on both normal and diabetic cells and then cells treated with 1 and 5 μg/mL of 5-ALA at 1 J/cm² energy density. ROS production and morphological alteration of the cells were studied. The mortality of normal fibroblast cells increased with increasing 5-ALA concentration and also increasing energy density (up to 3 J/cm²). However, in diabetic cells, the mortality rate did not decrease. Diabetic cells showed increased migration and closure of the scratch compared to normal cells under similar conditions. A low concentration of 5-ALA (5 μg/mL) and low energy density of 1 J/cm² in both normal and diabetic cells gave a small increase in ROS levels compared to controls. This may explain the positive effects of LDPDT on wound healing. The findings of this study suggest that LDPDT may have a potential effect on the wound healing of diabetic wounds.     

Accelerated Type 1 Diabetes Induction in Mice by Adoptive Transfer of Diabetogenic CD4+ T Cells

The nonobese diabetic (NOD) mouse spontaneously develops autoimmune diabetes after 12 weeks of age and is the most extensively studied animal model of human Type 1 diabetes (T1D). Cell transfer studies in irradiated recipient mice have established that T cells are pivotal in T1D pathogenesis in this model. We describe herein a simple method to rapidly induce T1D by adoptive transfer of purified, primary CD4+ T cells from pre-diabetic NOD mice transgenic for the islet-specific T cell receptor (TCR) BDC2.5 into NOD.SCID recipient mice. The major advantages of this technique are that isolation and adoptive transfer of diabetogenic T cells can be completed within the same day, irradiation of the recipients is not required, and a high incidence of T1D is elicited within 2 weeks after T cell transfer. Thus, studies of pathogenesis and therapeutic interventions in T1D can proceed at a faster rate than with methods that rely on heterogenous T cell populations or clones derived from diabetic NOD mice.     

Chronic alcohol consumption augments loss of sialic acid residues and alters erythrocyte membrane charge in type II diabetic patients

In this study, the effects of alcohol consumption on erythrocyte membrane properties in type 2 diabetic patients were investigated. Therefore, we measured total and lipid-bound sialic acid (LSA) levels, sialidase activities, and erythrocyte membrane negative charge. Three groups, including control group (n = 20), alcohol-consuming diabetic patients group (n = 14), and diabetic patients without alcohol consumption group (n = 42), were created. Plasma total sialic acid (TSA) levels of the alcohol-consuming diabetic group were elevated as compared to the healthy control and diabetic group (p < 0.001 and p < 0.01, respectively). TSA levels of the diabetic group were significantly elevated as compared to the healthy control group (p > 0.001). Plasma LSA levels of the alcohol-consuming diabetic group were higher than that in the healthy control and diabetic group (p < 0.05 and p < 0.05, respectively). LSA levels of the diabetic group were found to be high as compared to the healthy control group (p < 0.05). Plasma sialidase activities of the alcohol-consuming diabetic group and diabetic group were significantly elevated as compared to the healthy control group (p < 0.05 and p < 0.05, respectively). Sialidase activities of the alcohol-consuming diabetic group were elevated as compared to the diabetic group, but this was not statistically significant (p > 0.05). Erythrocyte membrane negativity levels of the alcohol-consuming diabetic group and diabetic group were significantly decreased (p < 0.001 and p < 0.001, respectively) as compared to the healthy control group. Erythrocyte membrane negativity levels of the alcohol-consuming diabetic group were decreased as compared to the diabetic group, but this was not statistically significant (p > 0.05). In conclusion, our results indicate that chronic alcohol consumption may augment membrane alterations in type 2 diabetic patients.     

Metabolism of very-low-density lipoprotein and chylomicrons by streptozotocin-induced diabetic rat heart: effects of diabetes and lipoprotein preference

Very-low-density lipoprotein (VLDL) and chylomicrons (CM) are major sources of fatty acid supply to the heart, but little is known about their metabolism in diabetic myocardium. To investigate this, working hearts isolated from control rats and diabetic rats 2 wk following streptozotocin (STZ) injection were perfused with control and diabetic lipoproteins. Analysis of the diabetic lipoproteins showed that both VLDL and CM were altered compared with control lipoproteins; both were smaller and had different apolipoprotein composition. Heparin-releasable lipoprotein lipase (HR-LPL) activity was increased in STZ-induced diabetic hearts, but tissue residual LPL activity was decreased; moreover, diabetic lipoproteins stimulated HR-LPL activity in both diabetic and control hearts. Diabetic hearts oxidized lipoprotein-triacylglycerol (TAG) to a significantly greater extent than controls (>80% compared with deposition as tissue lipid), and the oxidation rate of exogenous lipoprotein-TAG was increased significantly in diabetic hearts regardless of TAG source. Significantly increased intracardiomyocyte TAG accumulation was found in diabetic hearts, although cardiac mechanical function was not inhibited, suggesting that lipotoxicity precedes impaired cardiac performance. Glucose oxidation was significantly decreased in diabetic hearts; additionally, however, diabetic lipoproteins decreased glucose oxidation in diabetic and control hearts. These results demonstrate increased TAG-rich lipoprotein metabolism concomitant with decreased glucose oxidation in type 1 diabetic hearts, and the alterations in cardiac lipoprotein metabolism may be due to the properties of diabetic TAG-rich lipoproteins as well as the diabetic state of the myocardium. These changes were not related to cardiomyopathy at this early stage of diabetes.     

Protective effects of probucol treatment on pancreatic beta-cell function of SZ-induced diabetic APA hamsters.

To clarify whether oxidative stress is involved in the pathogenesis of islet lesions of diabetic animals, the effects of probucol (PB), an antioxidant and anti-hyperlipidemia agent, on the islets in streptozotocin (SZ)-induced diabetic APA hamsters in the acute and chronic phases of diabetes were examined. The control (CB group) and diabetic (SZ group) hamsters were treated with PB (1% in the diet) for 4 weeks from several days after SZ injection as the acute diabetic group, or 8 weeks from 6 weeks after SZ injection as the chronic diabetic group. Glucose tolerance test revealed that PB treatment decreased the high serum glucose level after glucose injection in the diabetic APA hamsters in the acute diabetic phase. Immunohistochemistry revealed that PB treatment significantly increased the percentage of the insulin positive area in the diabetic hamsters pancreata in both the acute and chronic phases. In addition, 4-hydroxy-2-nonenal (4HNE; an oxidative stress marker) positive cells were slightly reduced by PB treatment in the acute diabetic phase. Double-immunostaining for insulin and PCNA (proliferating cell nuclear antigen) revealed that elevation of the percentage of insulin and PCNA double-positive cells against insulin-positive cells was seen in the islets of PB-treated diabetic hamsters, but the difference was not significant compared with untreated diabetic hamsters (p = 0.07). In semi-quantitative RT-PCR, the expression of two genes, Reg (Regenerating gene) and INGAP (islet neogenesis associated protein), in the diabetic APA hamsters was significantly increased compared to the control groups in both diabetic phases. PB treatment significantly reduced Reg expression in the chronic diabetic phase. These data suggest that PB treatment in SZ-injected diabetic hamsters partially restored beta-cell function through acting as an antioxidant and induced higher expression of Reg and INGAP genes in the pancreas of hamsters.     

Zinc and copper in the serum of diabetic patients

The Zn/Cu ratio was examined in the serum of three groups of persons: healthy volunteers, diabetic patients on diabetic diet (NIDDM), and diabetic patients on diabetic diet and insulin (IDDM). Zinc, copper, the Zn/Cu serum ratio, and the blood glucose level were determined during fasting and 2 h after breakfast. Zn and Cu serum levels in NIDDM and IDDM patients were decreased. The Zn/Cu ratio was higher in both groups of diabetic patients. These changes in the Zn and Cu levels as well as in the Zn/Cu ratio were not related to chronic diabetic complications.     

Radiation Processed Amniotic Membranes in the Treatment of Non-Healing Ulcers of Different Etiologies

The amniotic membranes were collected from the placentae of selected and screened donors. Processing was done by washing the fresh amniotic membrane successively in sterile saline, 0.05% sodium hypochlorite solution and sterile distilled water until it was completely cleared of blood particles. The membranes were sterilized by gamma irradiation at 25 kGy. The processed amniotic membranes were applied to 50 open wounds comprising of 42 full thickness defects and eight partial thickness defects. These included leprotic, diabetic, traumatic, gravitational ulcers and superficial burn in the form of scald and corrosive burn. The radiation processed amniotic membranes favoured healing of unresponsive and non-healing ulcers of different etiologies. Ulcers with duration of minimum 3 weeks to maximum 12 months were found to heal in 2-6 weeks by the application of amniotic membranes.     

Protection by DHA of Early Hippocampal Changes in Diabetes: Possible Role of CREB and NF-κB

The mechanisms underlying diabetic encephalopathy, are only partially understood. In this study, we try to address the mechanisms of diabetes induced damage and whether docosahexaenoic acid (DHA) could attenuate the degenerative changes in diabetic hippocampus in a rodent model of diabetes. Diabetes was induced in rats by an intraperitoneal injection of streptozotocin. Animals were divided into the following experimental groups: control rats; control animals treated with DHA; untreated diabetic rats; diabetic rats treated with insulin; diabetic rats treated with DHA; diabetic rats treated with insulin and DHA. At the end of week 12, rats were killed and one of the hemispheres was cryosectioned and the other was dissected and hippocampi homogenized. The number of bromodeoxyuridine positive cells in the hippocampus of diabetic rats was decreased, and the latency time to find the platform in the Morris Water maze was significantly increased in the diabetic rats when compared to controls. No changes where observed in the expression of p21 in the hippocampus of control and diabetic rats. Biochemical markers of oxidative stress were altered in hippocampus of diabetic rats, and NFκB-positive cells were increased in the hippocampus of diabetic rats when compared to controls. Treatment with DHA, or the combination of DHA with insulin, significantly restored to control levels all the values mentioned above. Our findings confirm a pivotal role for oxidative stress as well as NF-κB, but not p21, in diabetes-induced hippocampal impairments. Administration of DHA as well as insulin prevented the changes induced by diabetes in hippocampus.     

Proteomic alterations of distinct mitochondrial subpopulations in the type 1 diabetic heart: contribution of protein import dysfunction

Diabetic cardiomyopathy is associated with increased risk of heart failure in type 1 diabetic patients. Mitochondrial dysfunction is suggested as an underlying contributor to diabetic cardiomyopathy. Cardiac mitochondria are characterized by subcellular spatial locale, including mitochondria located beneath the sarcolemma, subsarcolemmal mitochondria (SSM), and mitochondria situated between the myofibrils, interfibrillar mitochondria (IFM). The goal of this study was to determine whether type 1 diabetic insult in the heart influences proteomic make-up of spatially distinct mitochondrial subpopulations and to evaluate the role of nuclear encoded mitochondrial protein import. Utilizing multiple proteomic approaches (iTRAQ and two-dimensional-differential in-gel electrophoresis), IFM proteomic make-up was impacted by type 1 diabetes mellitus to a greater extent than SSM, as evidenced by decreased abundance of fatty acid oxidation and electron transport chain proteins. Mitochondrial phosphate carrier and adenine nucleotide translocator, as well as inner membrane translocases, were decreased in the diabetic IFM (P < 0.05 for both). Mitofilin, a protein involved in cristae morphology, was diminished in the diabetic IFM (P < 0.05). Posttranslational modifications, including oxidations and deamidations, were most prevalent in the diabetic IFM. Mitochondrial heat shock protein 70 (mtHsp70) was significantly decreased in diabetic IFM (P < 0.05). Mitochondrial protein import was decreased in the diabetic IFM with no change in the diabetic SSM (P < 0.05). Taken together, these results indicate that mitochondrial proteomic alterations in the type 1 diabetic heart are more pronounced in the IFM. Further, proteomic alterations are associated with nuclear encoded mitochondrial protein import dysfunction and loss of an essential mitochondrial protein import constituent, mtHsp70, implicating this process in the pathogenesis of the diabetic heart.     

Impact of diabetic serum on endothelial cells: an in-vitro-analysis of endothelial dysfunction in diabetes mellitus type 2

Diabetic endothelial dysfunction was characterized by altered levels of adhesion molecules and cytokines. Aim of our study was to evaluate the effects of diabetic serum on cell-growth and proinflammatory markers in human saphenous vein endothelial cells (HSVEC) from diabetic and non-diabetic patients. Diabetic serum showed (1) complementary proliferative activity for non-diabetic and diabetic HSVEC, (2) unchanged surface expression of adhesion molecules, and (3) elevated levels of sICAM-1 in HSVEC of all donors. The concentration of sVCAM-1 was increased only in diabetic cells. The proinflammatory state of diabetic HSVEC characterized by increased levels of cytokines was compensated. We concluded that even under normoglycemic conditions the serum itself contains critical factors leading to abnormal regulation of inflammation in diabetics. We introduced an in vitro model of diabetes representing the endothelial situation at the beginning of diabetes (non-diabetic cells/diabetic serum) as well as the diabetic chronic state (diabetic cells/diabetic serum).     

The quest for the sea urchin egg receptor for sperm

The incretin glucagon-like peptide-1 (GLP-1) and other GLP-1 receptor agonists have been shown to cause both antiapoptotic as well as regenerative effects on beta-cells in different animal models for diabetes. Our aim of this study was to test the hypothesis that spontaneously diabetic non obese diabetic (NOD) mice show an altered expression of GLP-1 compared to normoglycemic age-matched controls as a consequence of a diabetic state. To do this we used an ELISA prototype for mouse GLP-1 to measure plasma total GLP-1 from recently diabetic NOD mice as well as from age-matched normoglycemic NOD mice (controls). We also stained sections of pancreatic glands for GLP-1 from diabetic NOD mice and controls. We found increased levels of plasma total GLP-1 in diabetic NOD mice, when compared to control mice, both from non-fasted mice and from mice fasted for 2h. Furthermore, diabetic NOD mice displayed a higher GLP-1 response to an oral glucose tolerance test, compared to control mice. We also found that sections of pancreatic glands from diabetic NOD mice had an increased GLP-1 positive islet area in regard to relative islet area (i.e. total islet area / total pancreas area of the sections) compared to control mice. To our knowledge, this study is the first to show increased levels of GLP-1 in plasma in spontaneously diabetic NOD mice. We suggest that these results might represent a compensatory mechanism of the diabetic NOD mice to counteract beta-cell loss and hyperglycemia.     

Downregulation of prolactin-releasing peptide gene expression in the hypothalamus and brainstem of diabetic rats

We investigated the prolactin-releasing peptide (PrRP) mRNA levels in the hypothalamus and brainstem of streptozotocin (STZ)-induced diabetic rats and fa/fa Zucker diabetic rats, using in situ hybridization histochemistry. PrRP mRNA levels in the hypothalamus and brainstem of STZ-induced diabetic rats were significantly reduced in comparison with those of control rats. PrRP mRNA levels in the diabetic rats were reversed by both insulin and leptin. PrRP mRNA levels in the fa/fa diabetic rats were significantly reduced in comparison with those of Fa/? rats. PrRP mRNA levels in the fa/fa diabetic rats were significantly increased by insulin-treatment, but did not reach control levels in the Fa/? rats. We also investigated the effect of restraint stress on PrRP mRNA levels in STZ-induced diabetic rats. The PrRP mRNA levels in the control and the STZ-induced diabetic rats increased significantly after restraint stress. The diabetic condition and insulin-treatment may affect the regulation of PrRP gene expression via leptin and other factors, such as plasma glucose level. The diabetic condition may not impair the role of PrRP as a stress mediator.