Intermedin1-53 protects against cardiac hypertrophy by inhibiting endoplasmic reticulum stress via activating AMP-activated protein kinase

Objective: Intermedin (IMD), a novel member of the calcitonin/calcitonin gene-related peptide family, is involved in maintaining circulatory homeostasis and is a protective factor of heart and vessel. Here, we investigated the effects of IMD on cardiac hypertrophy in vivo and in vitro and explored the mechanisms involved. Methods and results: IMD1-53 (100 ng/kg/h) was systemically administered to rats with cardiac hypertrophy induced by abdominal aortic constriction (AAC) by a mini-osmotic pump the next day after surgery continuously for 4 weeks. The AAC-treated rats before IMD infusion showed increased IMD content and expression of its receptors in the hearts. In-vivo administration of IMD1-53 greatly attenuated the cardiac hypertrophy as shown by heart weight to body weight ratio (HW/BW), haemodynamics, echocardiography, histological analyses and expression of hypertrophic markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) induced by AAC. IMD1-53 treatment significantly reduced the myocardial protein expression of endoplasmic reticulum stress (ERS) markers such as glucose-regulated protein 78 (GRP78), CCAAT/enhancer binding protein homologous protein (CHOP) and caspase-12, whereas the protein level of phosphorylated AMP-activated protein kinase (p-AMPK) was upregulated with IMD1-53 treatment, which was further confirmed in cultured cardiomyocytes. Concurrently, cardiomyocyte apoptosis in vivo and in vitro was ameliorated by IMD1-53 treatment. The inhibitory effects of IMD1-53 on ERS and apoptosis were eliminated on pretreatment with compound C, an AMPK inhibitor. Conclusion: IMD1-53 could exert its cardioprotective effect on cardiac hypertrophy by inhibiting myocardial ERS and apoptosis, possibly via activation of AMPK signalling.