Abstract
Accumulation of methylglyoxal (MG) arising from downregulation of its primary degrading enzyme glyoxalase-1 (Glo1) is an underlying cause of diabetic cardiomyopathy (DC). This study investigated if expressing Glo1 in rat hearts shortly after the onset of Type 1 diabetes mellitus (T1DM) would blunt the development of DC employing the streptozotocin-induced T1DM rat model, an adeno-associated virus containing Glo1 driven by the endothelin-1 promoter (AAV2/9-Endo-Glo1), echocardiography, video edge, confocal imaging, and biochemical/histopathological assays. After eight weeks of T1DM, rats developed DC characterized by a decreased E:A ratio, fractional shortening, and ejection fraction, and increased isovolumetric relaxation time, E: e’ ratio, and circumferential and longitudinal strains. Evoked Ca2+ transients and contractile kinetics were also impaired in ventricular myocytes. Hearts from eight weeks T1DM rats had lower Glo1 and GSH levels, elevated carbonyl/oxidative stress, microvascular leakage, inflammation, and fibrosis. A single injection of AAV2/9 Endo-Glo1 (1.7 × 1012 viron particles/kg) one week after onset of T1DM, potentiated GSH, and blunted MG accumulation, carbonyl/oxidative stress, microvascular leakage, inflammation, fibrosis, and impairments in cardiac and myocyte functions that develop after eight weeks of T1DM. These new data indicate that preventing Glo1 downregulation by administering AAV2/9-Endo-Glo1 to rats one week after the onset of T1DM, blunted the DC that develops after eight weeks of diabetes by attenuating carbonyl/oxidative stresses, microvascular leakage, inflammation, and fibrosis.
Highlights
Heart failure is a major cause of morbidity and mortality in patients with chronic diabetes mellitus [1]
Goat polyclonal anti-TAGLN [SM22α] antibodies were from AbCam Inc. (Cambridge MA, USA); mouse monoclonal, MG-H1, [1H7G5] antibodies were from Hycult Biotech (Wayne PA, USA); rabbit polyclonal Glo1 [FL-184] antibodies, actin [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] antibodies, donkey anti rabbit IgG-HRP, and donkey anti goat IgG-HRP were from Santa Cruz Biotechnology Inc. (Santa Cruz, CA, USA); NF-κB p65 and phosphor-p65 (Ser536, NF-κB) were from Cell Signaling Technologies (Danves MA, USA); chicken anti-rabbit IgG coupled to Alexa Fluor 488, chicken-anti-mouse IgG coupled to Alexa Fluor 488, and donkey anti-goat IgG coupled to Alexa 594 were obtained from Invitrogen Life Technologies (Carlsbad, CA, USA); Fluoroshield with DAP1, bovine serum albumin labeled with fluorescein isothiocyanate (BSA-FITC), and the Trichrome (Masson) staining kit (Cat# HT15-1KT) were from
We showed that daily administration of insulin for two weeks starting six weeks after STZ injection, reversed increases in blood glucose, % glycated hemoglobin and loss in body mass indicating that these changes were not due to STZ toxicity [43,44]
Summary
Heart failure is a major cause of morbidity and mortality in patients with chronic diabetes mellitus [1]. In patients with Type 1 diabetes mellitus (T1DM), diabetic cardiomyopathy (DC) starts with an impairment in diastolic dysfunction and progresses to systolic dysfunction [2,3,4,5]. Inflammation, fibrosis, sympatho-excitation, activation of the renin-angiotensin system, impairment in myocyte intracellular Ca2+ handling, mitochondrial dysfunction, and changes in miRNA composition have been identified as contributing causes of both diastolic and systolic dysfunctions [2,3,4,5,6,7,8,9,10,11,12,13]. Free MG is rapidly degraded by the dual glyoxalase system to minimize cellular toxicity. Glyoxalase-1 (Glo1) is the rate-limiting enzyme and converts a hemiacetal formed between MG and glutathione (GSH)
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