Leptin, ghrelin, and energy metabolism of the spawning burbot (Lota lota, L.)

Abstract

The aim of this study was to investigate the energy metabolism of the burbot (Lota lota, n=38) before, during, and after spawning, which represents the greatest annual metabolic demand for the species. A decrease in body mass, relative weight of the livers, and glycogen concentration of the livers was observed toward the end of spawning. The prespawning period was characterized by high rates of liver glycogenolysis and lipid mobilization. Also, plasma triiodothyronine and sex steroid levels were high before reproduction. During spawning, liver lipolysis was reduced and muscle glycogenolysis stimulated. The levels of triiodothyronine and sex steroids decreased. After reproduction, liver glycogenolysis was suppressed and the rate of gluconeogenesis increased. Thyroid hormone levels were elevated after spawning. Leptin protein and a ghrelin-immunoreactive peptide were detected in burbot plasma. Their concentrations were relatively low before and during reproduction but increased after spawning. The functions of leptin and the ghrelin-immunoreactive peptide in the physiology of the burbot are not consistent with the models of their function in mammals.

Leptin stimulates pituitary prolactin release through an extracellular signal-regulated kinase-dependent pathway

“…The effects of leptin observed in the present study appear physiologically relevant since the effective concentrations fall within circulating values measured in mammals (Accorsi et al 2005) and that of the putative hormone measured in teleosts based on heterologous RIA (Mustonen et al 2002, Nagasaka et al 2006.…”

Leptin‐like immunoreactivity in the muscle of juvenile sea bass (Dicentrarchus labrax)

“…Only recently a fish leptin gene was identified (Kurokawa et al, 2005) and leptin-like immunoreactivity was found in the blood, brain, heart, liver, gut, and plasma of fish (Bosi et al, 2004;Ferrando et al, 2009;Huising et al, 2006;Johnson et al, 2000;Kurokawa et al, 2005;Muruzá bal et al, 2002;Mustonen et al, 2002;Nieminen et al, 2003) and in salmon adipocytes (Vegusdal et al, 2003). Several leptin roles were suggested in fish (Peyon et al, 2001;Volkoff et al, 2003;Weil et al, 2003), but its involvement in food intake and body weight is still controversial due to support by various authors (De Pedro et al, 2006;Ferrando et al, 2009;Volkoff et al, 2003) and denied by others (Baker et al, 2000;Silverstein and Plisetskaya, 2000;Londraville and Duvall, 2002).…”

Molecular cloning and mRNA expression analysis of two GH secretagogue receptor transcripts in orange-spotted grouper (Epinephelus coioides)

“…Physiological roles of ghrelin in teleosts have also been widely studied, including effects on GH secretion (Riley et al 2002, Kaiya et al 2003a,b,c, Ran et al 2004, Shepherd et al 2007, appetite stimulation (Unniappan et al 2002, Matsuda et al 2006a, Jönsson et al 2007, Miura et al 2007, Shepherd et al 2007, water intake (Kozaka & Ando 2003), reproduction (Mustonen et al 2002, Parhar et al 2003, immunity (Yada et al 2006), growth (Riley et al 2005, Fox et al 2007, intestinal motility (Olsson et al 2008), and locomotor behavior (Matsuda et al 2006a,b).…”