adenosine-5--(n-ethylcarboxamide) and Diabetes-Mellitus--Type-2

This study aimed to determine the effect and mechanism of action of adenosine 2 receptor (A2R) activation on myocardial ischemia reperfusion injury (MIRI) under diabetic conditions.. MIRI type 2 diabetic rats and H9C2 cardiomyocytes were treated with A2R agonist and then subjected to hypoxia for 6 h and reoxygenation for 18 h. Myocardial damage, and infarct size were determined by cardiac ultrasound. Indicators of cardiomyocyte injury, creatine kinase-MB and cardiac troponin I were detected by Enzyme Linked Immunosorbent Assay. Endoplasmic reticulum stress (ERS) was determined through measuring the expression levels of ERS related genes GRP78, p-IRE1/IRE1, and p-JNKJNK. The mechanism of A2R cardio protection in MIRI through regulating ERS induced autophagy was determined by investigating the ER resident protein IRE-1. The ER-stress inducer Tunicamycin, and the IRE-1 inhibitor STF in combination with the A2R agonist NECA were used, and the cellular responses were assessed through autophagy proteins expression Beclin-1, p62, LC3 and apoptosis.. NECA improved left ventricular function post MIRI, limited myocardial infarct size, reduced myocardial damage, decreased cardiomyocytes apoptosis, and attenuated ERS induced autophagy through regulating the IRE-XBP1s-CHOP pathway. These actions resulted into overall protection of the myocardium against MIRI.. In summary, A2R activation by NECA prior to ischemia attenuates apoptosis, reduces ERS induced autophagy and restores left ventricular function. This protective effect occurs through regulating the IRE1-XBPs-CHOP related mechanisms. NECA is thus a potential target for the treatment of MIRI in patient with type 2 diabetes.

Topics: Adenosine-5'-(N-ethylcarboxamide); Animals; Apoptosis; Autophagy; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Myocardial Reperfusion Injury; Myocytes, Cardiac; Protein Serine-Threonine Kinases; Rats; Rats, Sprague-Dawley

To determine the mechanisms by which blockade of adenosine A(2B) receptors (A(2B)Rs) reduces insulin resistance.. We investigated the effects of deleting or blocking the A(2B)R on insulin sensitivity using glucose tolerance tests (GTTs) and hyperinsulinemic-euglycemic clamps in mouse models of type 2 diabetes. The effects of diabetes on A(2B)R transcription and signaling were measured in human and mouse macrophages and mouse endothelial cells. In addition, tag single nucleotide polymorphisms (SNPs) in ~42 kb encompassing the A(2B)R gene, ADORA2B, were evaluated for associations with markers of diabetes and inflammation.. Treatment of mice with the nonselective adenosine receptor agonist 5'-N-ethylcarboxamidoadensoine (NECA) increased fasting blood glucose and slowed glucose disposal during GTTs. These responses were inhibited by A(2B)R deletion or blockade and minimally affected by deletion of A(1)Rs or A(2A)Rs. During hyperinsulinemic-euglycemic clamp of diabetic KKA(Y) mice, A(2B)R antagonism increased glucose infusion rate, reduced hepatic glucose production, and increased glucose uptake into skeletal muscle and brown adipose tissue. Diabetes caused a four- to sixfold increase in A(2B)R mRNA in endothelial cells and macrophages and resulted in enhanced interleukin (IL)-6 production in response to NECA due to activation of protein kinases A and C. Five consecutive tag SNPs in ADORA2B were highly correlated with IL-6 and C-reactive protein (CRP). Diabetes had a highly significant independent effect on variation in inflammatory markers. The strength of associations between several ADORA2B SNPs and inflammatory markers was increased when accounting for diabetes status.. Diabetes affects the production of adenosine and the expression of A(2B)Rs that stimulate IL-6 and CRP production, insulin resistance, and the association between ADORA2B SNPs and inflammatory markers. We hypothesize that increased A(2B)R signaling in diabetes increases insulin resistance in part by elevating proinflammatory mediators. Selective A(2B)R blockers may be useful to treat insulin resistance.

Topics: Adenosine-5'-(N-ethylcarboxamide); Animals; Biomarkers; Blood Glucose; C-Reactive Protein; Cells, Cultured; Diabetes Mellitus, Type 2; Glucose Clamp Technique; Glucose Tolerance Test; Humans; Inflammation; Insulin; Insulin Resistance; Interleukin-6; Liver; Macrophages; Mice; Mice, Transgenic; Polymorphism, Single Nucleotide; Receptor, Adenosine A2B; Reverse Transcriptase Polymerase Chain Reaction

Adenosine and adenosine receptor antagonists are involved in glucose homoeostasis. The participating receptors are not known, mainly due to a lack of specific agonists and antagonists, but are reasonable targets for anti-diabetic therapy. The stable, albeit nonselective, adenosine analogue NECA (5'-N-ethylcarboxamidoadenosine) (10 microM) reduced glucose-stimulated insulin release from INS-1 cells. This was mimicked by A(1)-(CHA), A(2A)-(CGS-21680) and A(3)-receptor agonists (Cl-IB-MECA). Two newly synthesized A(2B)-receptor antagonists, PSB-53 and PSB-1115, counteracted the inhibitory effect of NECA. These in-vitro effects were mirrored by in-vivo data with respect to CHA, CGS and Cl-IB-MECA. Distinct concentrations of either PSB-53 or PSB-1115 reversed the decrease in plasma insulin induced by NECA. This was not mimicked by a corresponding change in blood glucose. The effect of PSB-1115 was also obvious in diabetic GotoKakizaki rats: plasma insulin was increased whereas blood glucose was unchanged. During most experiments the effects on blood glucose were not impressive probably because of the physiologically necessary homoeostasis. The adenosine levels were not different in normal Wistar rats and in diabetic GotoKakzaki rats. Altogether the A(2B)-receptor antagonists showed an anti-diabetic potential mainly by increasing plasma insulin levels under conditions when the adenosine tonus was elevated in-vivo and increased insulin release in-vitro.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Adenosine A3 Receptor Agonists; Adenosine A3 Receptor Antagonists; Adenosine-5'-(N-ethylcarboxamide); Analysis of Variance; Animals; Antineoplastic Agents; Blood Glucose; Cell Line, Tumor; Diabetes Mellitus, Type 2; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Homeostasis; Insulin; Male; Phenethylamines; Radioimmunoassay; Rats; Rats, Wistar; Receptor, Adenosine A2B; Sulfonic Acids; Xanthines