Rat heart is a site of leptin production and action

Abstract

Leptin, the 16-kDa peptide hormone product of the ob gene, is produced primarily by adipocytes and was initially thought to exert its effects exclusively through actions on the hypothalamus via distinct leptin receptors termed OB-R. However, recent data show that leptin is produced elsewhere and that receptors are present in many other tissues. Using real-time PCR, we determined whether leptin and its receptors are present in the rat heart and demonstrated regional distribution patterns and gender differences as well as the effect of ischemia and reperfusion. Gene expression of leptin and its receptors (OB-Ra, OB-Rb, and OB-Re) was identified in myocytes and whole heart homogenates from all regions of the heart of male and female rats, with the highest abundance in left and right atria of male and female rats, respectively. No differences in regional distribution of OB-R were evident in male rat hearts. In female rats, expression was highest in right atria for all three isoforms and was significantly greater than in male rats. Ischemia and reperfusion significantly downregulated leptin and OB-R expression, although this was more pronounced in male rat hearts. Leptin release in the coronary effluent was also detected using ELISA, although this was generally unaffected by global ischemia and reperfusion. Our results demonstrate for the first time the presence of the leptin system, including the peptide and its receptors, in all regions of the rat heart. In view of emerging evidence for cardiac effects of leptin, it is proposed that the heart is a target for leptin action and that the peptide modulates function through a paracrine- or autocrine-dependent manner.

Adiponectin and its receptors are expressed in adult ventricular cardiomyocytes and upregulated by activation of peroxisome proliferator-activated receptor γ

“…In this study, we utilized purified primary cardiomyocytes cultures being careful to exclude potential contamination by adipocytes to explore cardiac expression of adiponectin. Recently, a similar cardiac expression of leptin, another protein hormone that is involved in energy metabolic regulation, has been reported [26]. Adiponectin belongs to an adipokine superfamily.…”

Leptin decreases heart rate associated with increased ventricular repolarization via its receptor

“…The transcripts of three isoforms (ObRa, ObRb, and ObRe) of leptin receptor have been identified in the rat heart (26). ObRa is the short form of leptin receptor that lacks the intracellular signaling domain; its function is unclear (23).…”

Role of adipokines in cardiovascular disease

“…The heart produces leptin itself, suggesting that it may act locally to mediate physiological effects (Purdham et al 2004, Karmazyn et al 2008. The primary cardiac physiological response to leptin is a reduction in cardiac output.…”