Enhanced mitigation of diabetic myocardial injury in rats via modulating the adiponectin/IRS-1/PI3K/p-AKT/FOXO-1 signaling by combining methotrexate and insulin.

PURPOSE: The present study aimed to explore the impact of combining methotrexate (MTX) and insulin (INS) to mitigate diabetes-associated myocardial injury and investigate the potential underlying mechanisms. METHOD: Diabetes was induced in rats by a single low-dose streptozotocin (STZ) injection (35 mg/kg, i.p.) after a four-week period of administration of a high-fat diet (HFD) feeding and fructose administration in water. RESULTS: Our data revealed that the diabetic rats had elevated serum cardiac injury biomarkers and a disturbed lipid profile in parallel with marked inflammation and distortion of normal cardiomyocyte architecture. Moreover, diabetes was associated with reduced levels of adiponectin, insulin receptor substrate (IRS)-1, phosphatidylinositol-3-kinase (PI3K), phosphorylated protein kinase B (p-AKT), and phosphorylated glycogen synthase kinase (p-GSK)-3β. Our findings showed that combining low doses of MTX and INS exerted superior ameliorative effects on serum cardiac injury biomarkers and the lipid profile, as well as histopathological abnormalities. Moreover, MTX enhanced the stimulatory effect of INS on adiponectin levels and the IRS-1/PI3K/p-AKT/FOXO-1 signaling pathway in the heart. MTX combined with INS also demonstrated a superior suppressive effect on cardiac FOXO-1 levels and the autophagy-associated biomarkers microtubule-associated protein 1A/1B-light chain (LC3-B) and beclin-1. Interestingly, the enhancement of cardiac INS signaling by MTX was accompanied by the inhibition of biomarkers of oxidative stress and the apoptotic executor caspase-3. CONCLUSION: Low doses of MTX offer added therapeutic value against diabetic cardiac injury when combined with INS. This effect may be attributed, at least in part, to the modulation of the adiponectin/IRS-1/PI3K/p-AKT/FOXO-1 signaling cascade.