Mechanisms of leptin receptor isoforms expression in heart diseases

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(1)Ischemia/reperfusion in rat heart induces leptin and leptin receptor gene expression.We examined the expression of leptin (ob) and leptin receptor (ob-R) genes in the rat heart following ischemia/reperfusion. Ischemia/reperfusion was induced by coronary artery ligation, and mRNA was obtained from hearts 0.5 to 36 h after initiating reperfusion. Expressions of ob and ob-R mRNA were examined by Real-time quantitative RT-PCR and immunohistochemistry. The ob and ob-Ra mRNAs and proteins significantly exceeded amounts in control hearts after 8 h of reperfusion, and they were present at ischemic wound sites locally. To determine the functional effects of leptin in ischemic heart, rats were treated with anti-leptin antibodies prior to ischemia/reperfusion. This treatment partially prevented elevation of the mRNA expression levels of inflammatory markers such as TNF-α and IL-1β in ischemic hearts.(2)Hypertensive stress directly up-regulates expression of leptin and the long form of the lept … More in receptor (ob-Rb) in rat cardiac myocytesPressure overload was produced by ligation of the abdominal aorta. Using expression of the real-time polymerase chain reaction (PCR), leptin and the long form of the leptin receptor (ob-Rb) gene were significantly increased at 2 and 4 weeks, but expression of the short form of the leptin receptor (ob-Ra) was unchanged after banding. When we examined protein expression of ob-Rb, ob-Rb protein was detected by immunohistochemistry in hypertrophied cardiomyocytes. Plasma leptin concentrations were not different between the control and banding groups. To clarify which hypertension-related stimuli induces ob and ob-Rb expression in the heart, we examined ob and ob-Rb mRNA expression in neonatal rat cardiac myocytes treated with angiotensin II (ANGII), endothelin-1 (ET-1), or cyclic mechanical stretch. ANGII and ET-1 increased only ob mRNA expression. However, mechanical stretch activated both ob and ob-Rb expression in a time-dependent manner, but ob-Ra was unaffected by any stress. Less