T1DM Mice Research Articles

Insulin significantly changes the expression of T1DM mice’s circulating microRNA

Insulin significantly changes the expression of T1DM mice’s circulating microRNA

Association of Bactericidal Dysfunction of Paneth Cells in Streptozocin-Induced Diabetic Mice with Insulin Deficiency.

BackgroundType 1 diabetes mellitus (T1DM) is associated with increased risks of enteric infection. Paneth cells constitute the first line of the gut defense. Little is known about the impact of T1DM on the bactericidal function of intestinal Paneth cells.Material/MethodsA T1DM mouse model was induced by intraperitoneal injection of streptozocin. The analysis of intestinal microbiota and the mucosal bactericidal assay were conducted to evaluate intestinal innate defense. Numbers of Paneth cells and their expression of related antimicrobial peptides were analyzed. Expression of total insulin receptor (IR) mRNA and relative levels of IR-A/IR-B were analyzed. The primary mouse small intestinal crypt culture was used to analyze the effect of insulin and glucose on the expression of related antimicrobial peptides of Paneth cells.ResultsIn T1DM mice, bacterial loads were increased and there was an alteration in the composition of the intestinal microflora. Exogenous bacteria had better survival in the small bowel of the T1DM mice. The expression of Paneth cell-derived antimicrobial peptides was significantly decreased in the T1DM mice, although the number of Paneth cells was increased. Relative levels of IR-A/IR-B in Paneth cells of diabetic mice were elevated, but the total IR mRNA did not change. Insulin treatment restored the expression of antimicrobial peptides and normalized the microbiota in the gut of T1DM mice. Subsequently, in vitro culture assay demonstrated that insulin rather than glucose was essential for the optimal expression of Paneth cell-derived antimicrobial peptides.ConclusionsThe bactericidal function of intestinal Paneth cells was impaired in STZ-induced diabetic mice, resulting in the altered intestinal flora, and insulin was essential for the optimal expression of Paneth cell-derived antimicrobial peptides.

Deletion of Protein Tyrosine Phosphatase 1B (PTP1B) Enhances Endothelial Cyclooxygenase 2 Expression and Protects Mice from Type 1 Diabetes-Induced Endothelial Dysfunction.

Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates receptors tyrosine kinase and acts as a molecular brake on insulin signaling pathway. Conditions of metabolic dysfunction increase PTP1B, when deletion of PTP1B protects against metabolic disorders by increasing insulin signaling. Although vascular insulin signaling contributes to the control of glucose disposal, little is known regarding the direct role of PTP1B in the control of endothelial function. We hypothesized that metabolic dysfunctions increase PTP1B expression in endothelial cells and that PTP1B deletion prevents endothelial dysfunction in situation of diminished insulin secretion. Type I diabetes (T1DM) was induced in wild-type (WT) and PTP1B-deficient mice (KO) with streptozotocin (STZ) injection. After 28 days of T1DM, KO mice exhibited a similar reduction in body weight and plasma insulin levels and a comparable increase in glycemia (WT: 384±20 vs. Ko: 432±29 mg/dL), cholesterol and triglycerides, as WT mice. T1DM increased PTP1B expression and impaired endothelial NO-dependent relaxation, in mouse aorta. PTP1B deletion did not affect baseline endothelial function, but preserved endothelium-dependent relaxation, in T1DM mice. NO synthase inhibition with L-NAME abolished endothelial relaxation in control and T1DM WT mice, whereas L-NAME and the cyclooxygenases inhibitor indomethacin were required to abolish endothelium relaxation in T1DM KO mice. PTP1B deletion increased COX-2 expression and PGI2 levels, in mouse aorta and plasma respectively, in T1DM mice. In parallel, simulation of diabetic conditions increased PTP1B expression and knockdown of PTP1B increased COX-2 but not COX-1 expression, in primary human aortic endothelial cells. Taken together these data indicate that deletion of PTP1B protected endothelial function by compensating the reduction in NO bioavailability by increasing COX-2-mediated release of the vasodilator prostanoid PGI2, in T1DM mice.

PTP1B Deletion Enhances Endothelial Cyclooxygenase 2 Expression and Protects Mice from Type 1 Diabetes‐Induced Endothelial Dysfunction

Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates receptors tyrosine kinase and acts as a molecular brake on insulin signaling. Although vascular insulin signaling contributes to the control of glucose disposal, little is known regarding the role of PTP1B in the control of endothelial function. We hypothesized that metabolic dysfunctions increase PTP1B expression in endothelial cells and that PTP1B deletion prevents endothelial dysfunction in situation of diminished insulin secretion. Type I diabetes (T1DM) was induced in wild-type (WT) and PTP1B-deficient mice (KO) with streptozotocin (STZ). After 28 days of T1DM, body weight reduction, decrease in plasma insulin levels and increased in glycemia, cholesterol and triglycerides, were similar in WT and KO mice. T1DM increased PTP1B expression and impaired aortic endothelial NO-dependent relaxation. PTP1B deletion did not affect baseline endothelial NO-dependent relaxation, but preserved endothelium-dependent relaxation, in T1DM mice. NO synthase inhibition with L-NAME abolished endothelial relaxation in control and T1DM WT mice. L-NAME and the cyclooxygenases inhibitor indomethacin were required to abolish endothelium relaxation in T1DM KO mice. PTP1B deletion increased COX-2 expression and PGI2 levels, in mouse aorta and plasma respectively, in T1DM mice. In parallel, simulation of diabetic conditions increased PTP1B expression and knockdown of PTP1B increased COX-2 but not COX-1 expression, in primary human aortic endothelial cells. These data indicate that deletion of PTP1B protected endothelial function by compensating the reduction in NO bioavailability by increasing COX-2-mediated release of the vasodilator prostanoid PGI2, in T1DM mice.

Akt/hypoxia-inducible factor-1α signaling deficiency compromises skin wound healing in a type 1 diabetes mouse model.

The aim of the present study was to investigate the mechanisms for impaired skin wound healing in subjects with diabetes. Type 1 diabetes (T1DM) was induced in BALB/c mice using streptozotocin. One month after the establishment of the T1DM mouse model, a wound was formed on the back of the mice, and tissues from the wounds and the margins were collected on days 0, 3, 7 and 10. Protein levels of cluster of differentiation 31 (CD31) were detected using immunohistochemistry, and the mRNA levels of Akt, hypoxia-inducible factor-1α (Hif-1α), vascular endothelial growth factor (Vegf), VEGF receptor 2 (Vegfr2), stromal cell-derived growth factor-1α (Sdf-1α) and CXC chemokine receptor 4 (Cxcr4) were determined using reverse transcription-quantitative polymerase chain reaction analysis. The corresponding protein levels were determined using western blotting. The skin wound healing rate in the T1DM mice was significantly lower than that in the control mice, and the protein level of CD31 in the wounded skin of the T1DM mice was significantly decreased. Furthermore, the overall mRNA levels of Akt, Hif-1α, Vegf, Vegfr2, Sdf-1α and Cxcr4 in the T1DM mice were significantly lower than those in the control mice, and similar trends were observed in the protein levels. In conclusion, skin wound healing was impaired in the T1DM mice, and this may have been caused by a deficiency of Akt/HIF-1α and downstream signaling, as well as delayed angiogenesis.

Mouse Models of Diabetic Neuropathy

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes and is associated with significant morbidity and mortality. DPN is characterized by progressive, distal-to-proximal degeneration of peripheral nerves that leads to pain, weakness, and eventual loss of sensation. The mechanisms underlying DPN pathogenesis are uncertain, and other than tight glycemic control in type 1 patients, there is no effective treatment. Mouse models of type 1 (T1DM) and type 2 diabetes (T2DM) are critical to improving our understanding of DPN pathophysiology and developing novel treatment strategies. In this review, we discuss the most widely used T1DM and T2DM mouse models for DPN research, with emphasis on the main neurologic phenotype of each model. We also discuss important considerations for selecting appropriate models for T1DM and T2DM DPN studies and describe the promise of novel emerging diabetic mouse models for DPN research. The development, characterization, and comprehensive neurologic phenotyping of clinically relevant mouse models for T1DM and T2DM will provide valuable resources for future studies examining DPN pathogenesis and novel therapeutic strategies.

Hyperglycemia triggers epigenetic machinery to enhance MyD88 expression in macrophages from type 1 diabetes mice (P1350)

Abstract Type I diabetes (T1DM) is characterized by hyperglycemia and insulin deficiency. T1DM is associated with constitutive production of pro-inflammatory cytokine such as the members of IL-1 family. IL-1β binding to its MyD88-associated receptor IL-1R is a major cause of tissue injury in T1DM. We hypothesize that hyperglycemia (HG) enhances MyD88 in macrophages (MA) amplifying IL-1βR responsiveness. We found that both in vitro and in vivo HG increases the expression of MyD88 and its transcription factor STAT-1. Speculating that enhanced MyD88/STAT-1 levels could be due to epigenetic changes, we analyzed the expression of enzymes involved in DNA methylation (DNMT) and Histone deacetylation (HDAC) in MA from T1DM mice. We observed that diabetic mice expressed at least 2 times more HDAC 8, 10 and 11, and DNMT 3b than nondiabetic mice. In vitro inhibition of HDAC (TSA) or DNMT (5-azacyd) in MA impaired HG-enhanced MyD88 and STAT-1 expression. These data suggest a heretofore unrecognized epigenetic changes associated with hyperinflammatory pattern of MA from T1DM, leading to high MyD88 expression and possibly allowing overly IL-1β receptor and other MyD88-dependent receptor activation

Type I diabetes mellitus decreases in vivo macrophage-to-feces reverse cholesterol transport despite increased biliary sterol secretion in mice

Type I diabetes mellitus (T1DM) increases atherosclerotic cardiovascular disease; however, the underlying pathophysiology is still incompletely understood. We investigated whether experimental T1DM impacts HDL-mediated reverse cholesterol transport (RCT). C57BL/6J mice with alloxan-induced T1DM had higher plasma cholesterol levels (P < 0.05), particularly within HDL, and increased hepatic cholesterol content (P < 0.001). T1DM resulted in increased bile flow (2.1-fold; P < 0.05) and biliary secretion of bile acids (BA, 10.5-fold; P < 0.001), phospholipids (4.5-fold; P < 0.001), and cholesterol (5.5-fold; P < 0.05). Hepatic cholesterol synthesis was unaltered, whereas BA synthesis was increased in T1DM (P < 0.001). Mass fecal BA output was significantly higher in T1DM mice (1.5-fold; P < 0.05), fecal neutral sterol excretion did not change due to increased intestinal cholesterol absorption (2.1-fold; P < 0.05). Overall in vivo macrophage-to-feces RCT, using [(3)H]cholesterol-loaded primary mouse macrophage foam cells, was 20% lower in T1DM (P < 0.05), mainly due to reduced tracer excretion within BA (P < 0.05). In vitro experiments revealed unchanged cholesterol efflux toward T1DM HDL, whereas scavenger receptor class BI-mediated selective uptake from T1DM HDL was lower in vitro and in vivo (HDL kinetic experiments) (P < 0.05), conceivably due to increased glycation of HDL-associated proteins (+65%, P < 0.01). In summary, despite higher mass biliary sterol secretion T1DM impairs macrophage-to-feces RCT, mainly by decreasing hepatic selective uptake, a mechanism conceivably contributing to increased cardiovascular disease in T1DM.

β Cell Protecting and Immunomodulatory Activities of Paecilomyces Hepiali Chen Mycelium in STZ Induced T1DM Mice

The anti-hyperglycemic and immunomodulatory activities of the ethanol extract from Paecilomyces Hepiali Chen (PHC), a Chinese medicine, were investigated in streptozotocin-induced type 1 diabetic (T1DM) mice. Male Balb/c mice, which were i.p. injected with streptozotocin (STZ, 50 mg/kg, for 5 consecutive days) on Day 7, were orally administered saline (the normal control and diabetic control group), Metformin (60 mg/kg, b.w., positive group), or the extract (100 mg/kg, b.w., PHC prevention group) from Day 1 to Day 28, Mice i.p. injected with streptozotocin (STZ, 50 mg/kg, b.w.) for 5 consecutive days prior to PHC treatment (100 mg/kg, b.w.) were used as the PHC treatment group. The effects of PHC on postprandial blood glucose concentrations, plasmatic insulin levels, morphology of pancreatic beta cells and CD4(+) T cells proliferation after 28-day treatment were monitored. Results showed that PHC administered 6 days before STZ induction of diabetes in mice significantly decreased blood glucose level (p < 0.01). An increase of insulin level was also observed as compared to those in the diabetic control group (p < 0.01). In addition, fewer inflammatory cells infiltrated the pancreatic islet and fewer beta cells death by apoptosis within the inflamed islets were observed. More importantly, the CD4(+) T cell proliferation was remarkably attenuated ex vivo in mice preventively treated with PHC (p < 0.01). In comparison to the PHC prevention group, no significant hypoglycemia, changes of insulin level and beta cell protection were observed in mice treated with PHC after STZ administration. Our findings demonstrated that preventive administration of PHC protected beta cells from apoptosis in type 1 diabetes induced by STZ, and the underlying mechanism may be involved in suppressing CD4(+) T cells reaction, reducing inflammatory cells infiltration and protecting beta cell apoptosis in pancreatic islet.