Liraglutide Enhances Cell Viability and Reduces Oxidative Stress in Hyperglycemic H9c2 Cardiomyocytes

<i>Background and Objectives</i>: Cardiovascular disease remains a leading cause of mortality in Diabetes mellitus (DM), where chronic hyperglycemia induces oxidative stress, mitochondrial dysfunction, and hypoxia in cardiomyocytes. Liraglutide (Lir), a glucagon-like peptide-1 receptor agonist, is widely used for type 2 DM management and has been shown to exert cardioprotective and antioxidant effects. This study aimed to evaluate whether Lir mitigates hyperglycemia-induced oxidative and hypoxic stress in H9c2 cardiomyoblasts while preserving cellular ultrastructure. <i>Materials and Methods</i>: H9c2 cells were cultured under normoglycemic (5.5 mM) or hyperglycemic (30 mM) conditions, with or without Lir. Cell viability was assessed using MTT assay. Ultrastructural changes were examined by transmission electron microscopy (TEM). Hypoxia-inducible factor-1α (HIF-1α), lipid peroxidation markers (LOOH, MDA), advanced oxidation protein products (AOPP), and total antioxidant capacity (TAC) were quantified by spectrophotometric assays. <i>Results</i>: MTT assays revealed that Lir significantly improved cell viability under hyperglycemic conditions and the EC₅₀ was 1.05 ± 0.06 μM after 48 h of treatment. Under HG, HIF-1α, lipid hydroperoxides (LOOH), malondialdehyde (MDA) and advanced oxidation protein products (AOPP) increased and total antioxidant capacity (TAC) decreased (<i>p</i> < 0.001, for all); Lir significantly reversed these changes, restoring values to near-NG levels. Ultrastructural analysis of HG + Lir-treated cells revealed reduced granules, increased vacuolization, and slight rough endoplasmic reticulum dilatation, though mitochondria appeared normal. <i>Conclusions</i>: Lir significantly attenuated oxidative stress and cellular injury in cardiomyocytes under hyperglycemic conditions, improving viability, modulating HIF-1α expression, and restoring antioxidant balance. These findings support a dual role for Lir in diabetic cardiomyopathy: glucose-independent cytoprotection and regulation of mitochondrial and hypoxia pathways, highlighting its therapeutic potential beyond glycemic control.