Effects of N-Acetylcysteine and Glycine Administration on Serum Levels of Soluble Suppressor of Tumorigenicity 2 and Cardiac Morphological Characteristics in an Animal Model of Streptozotocin-Induced Diabetes.

Abstract

Background/Objectives: Diabetic cardiomyopathy (DCM) is a major cardiovascular complication of diabetes mellitus characterized by progressive myocardial remodeling driven by oxidative stress, inflammation, and fibrosis. The interleukin-33 (IL-33)/soluble suppression of tumorigenicity 2 (sST2) signaling axis has recently emerged as an important regulator of cardiac remodeling and a potential therapeutic target in DCM. N-acetylcysteine (NAC) and glycine exhibit complementary antioxidant and anti-inflammatory properties; however, their combined effects on circulating IL-33 and sST2 levels and myocardial structural remodeling in experimental diabetes remain insufficiently investigated. This study evaluated the effects of NAC and glycine, administered alone or in combination, on oxidative stress, inflammatory biomarkers, cardiac morphology, and serum sST2 levels in streptozotocin-induced diabetic rats. Methods: Thirty-four adult Wistar rats were randomly assigned to five groups: healthy controls, untreated diabetic animals, diabetic animals treated with NAC (100 mg/kg/day), glycine (250 mg/kg/day), or combined NAC and glycine for 12 weeks. Diabetes was induced by a single intraperitoneal injection of streptozotocin (55 mg/kg). Serum concentrations of sST2, IL-33, malondialdehyde (MDA), and superoxide dismutase (SOD) activity were determined. Cardiac remodeling was evaluated by stereological and histopathological analyses. Results: Experimental diabetes significantly increased serum sST2, IL-33, and MDA concentrations and induced marked myocardial remodeling characterized by expansion of the interstitial and perivascular compartments, increased connective tissue deposition, and reduced cardiomyocyte volume density. Both NAC and glycine significantly attenuated these biochemical and structural abnormalities compared with untreated diabetic animals. Treatment effects varied across outcomes. The combined NAC and glycine regimen was associated with particularly pronounced reductions in sST2 and IL-33 and with preservation of myocardial architecture, whereas the magnitude of improvement in oxidative stress markers differed between treatment groups. Conclusions: NAC and glycine, administered either alone or in combination, attenuated several biochemical and structural alterations associated with streptozotocin-induced diabetes. The magnitude of these effects varied across the assessed outcomes, with the combined regimen showing particularly favorable effects on circulating sST2 and IL-33 levels and myocardial structural remodeling, while some oxidative stress parameters showed greater improvement with NAC monotherapy. These outcome-dependent effects highlight the potential complementary actions of NAC and glycine without implying uniform superiority of the combined regimen. Overall, these findings provide an experimental basis for further investigation of NAC- and glycine-based therapeutic approaches for diabetes-associated myocardial remodeling.