Acyl Ghrelin and Metabolic Hormones in Pregnant and Lactating Sows N Govoni 1 , A Parmeggiani 1 , G Galeati 1 , P Penazzi 1 , R De Iasio 2 , U Pagotto 2 , R Pasquali 2 , C Tamanini 1 and E Seren 1 1 Department of Veterinary Morphophysiology and Animal Production (DIMORFIPA), University of Bologna, Ozzano Emilia, Bologna; 2 Endocrinology Unit and Center for Applied Biomedical Research (CRBA), S Orsola-Malpighi Hospital, Bologna, Italy Contents Ghrelin, the endogenous ligand of the growth hormone (GH) secretagogue receptor, is considered a pleiotropic regulator involved in a large array of functions, including control of energy balance, regulation of food intake and, more recently, modulation of the reproductive axis. The present study was aimed at determining the changes in plasma concentrations of acyl-ghrelin in pregnant and lactating sows, with special emphasis on the relationship with the levels of GH, leptin, non-esterified fatty acids (NEFA) and insulin-like growth factor (IGF-1). Blood samples were collected via jugular venipuncture from 22 multiparous sow 30, 60 and 90 days after artificial insemination, 7 and 21 days after farrowing and at first oestrus post-weaning. Plasma concentrations of acyl- ghrelin, leptin, GH and IGF-1 were quantified by validated radioimmunoassay; NEFA were determined using a colori- metric procedure. Plasma acyl ghrelin levels were highest at 30 days of pregnancy and decreased thereafter and during lactation. At the beginning of lactation, GH, IGF-1 and NEFA concentrations significantly increased, while a signifi- cant reduction occurred in leptin. In conclusion, ghrelin concentrations in sow maternal circulation does not seem to play an important role in maintaining circulating GH levels during lactation; moreover, ghrelin is not associated with leptin, NEFA and IGF-1 levels. Introduction Pregnancy and lactation are characterized by changes in plasma gonadal steroids, growth hormone (GH) and insulin-like growth factor (IGF-1) concentrations. These conditions promote a mobilization of the animal’s adipose tissue stores, stimulate the gluconeo- genetic process and reduce the assimilation of glucose by non-mammary tissues (Noblet et al. 1990). In ruminants, key adaptations of early lactation include an increased release of GH and a decrease in plasma IGF-1 and leptin concentrations (Schams et al. 1991; Block et al. 2001). These endocrine changes may be beneficial for energy metabolism but also lead to a suppression of non-vital functions such as reproduc- tion. In swine, GH and IGF-I release increases around parturition and high levels of these hormones are maintained throughout lactation (Schams et al. 1994). In contrast to cows, lactating sows are able to take up enough energy from the feed and to mobilize energy from body reserves so as to prevent metabolic disorders (Kraetzl et al. 1998). A recently discovered 28-amino acid peptide, ghrelin, beyond its ability to elicit GH secretion, is also involved in the regulation of energy balance by stimulating food intake and reducing fat utilization (Tschop et al. 2000; Van der Lely et al. 2004) and several research groups sustain the reproductive facets also for this hormone. Ghrelin shows a unique structure with a n-octanoyl ester modification at the third serine residue essential for its biological activity (Kojima et al. 1999). The primary source of this hormone is assumed to be the stomach, but ghrelin and its mRNA have been demonstrated in several other locations, including ovary, testis, intestine, pancreas, kidney, pituitary and hypothalamus (Kojima et al. 1999; Date et al. 2000; Broglio et al. 2003; Gaytan et al. 2003; for a review, see De Ambrogi et al. 2003). In a previous work (Govoni et al. 2005a) we have demon- strated in prepubertal gilts a link between ghrelin and changes of energy balance, in that we have observed a significant increase of the hormone after 72 h of fasting. Several data strongly suggest that systemic ghrelin may also participate in the control of reproduction, as it has been demonstrated to inhibit LH secretion in ovariectomized rats (Furuta et al. 2001), ovariectomized rhesus monkey (Vulliemoz et al. 2004) and sheep (Iqbal et al. 2006) and to reduce prolactin levels in prepubertal rats (Tena-Sempere et al. 2004). Moreover, ghrelin expression has been shown in human and rodent placenta and has been reported to inhibit the develop- ment of mouse pre-implantation embryos in vitro (Gualillo et al. 2001; Kawamura et al. 2003). Recently, Shibata et al. (2004) demonstrated that plasma ghrelin concentrations markedly decrease during pregnancy and lactation in rats and Fuglsang et al. (2005) observed that serum ghrelin levels peak around mid-gestation in pregnant women. Although knowledge of this metabolic hormone is rapidly advancing, its role in different physiological conditions such as pregnancy, lactation and post-weaning resumption of ovarian activity has not yet been evaluated in sows. On the basis of these observations, the present study was undertaken to quantify plasma concentrations of acyl-ghrelin in preg- nant and lactating sows with special emphasis on their relationship with GH, leptin, non-esterified fatty acids (NEFA) and IGF-1. Materials and Methods A total of 25 crossbred (Large-White · Duroc) sows, similar for weight at first month of pregnancy (199.7 ± 4.93 kg, mean ± SEM) and parities (three to four) were used; sows that were diagnosed as non- pregnant by ultrasound scanning 4 weeks after AI, were excluded from the trial (n ¼ 3). During gestation the sows were housed in individual stalls at a temperature of 22 ± 2°C. The ration was fed twice daily at 7.00 AM and at 3.00 PM, whereas water was freely available; the gestation diet contained 12.6 MJ DE/kg, 13.7% crude protein. On day 109 of gestation Reprod Dom Anim 42, 39–43 (2007); doi: 10.1111/j.1439-0531.2006.00722.x ISSN 0936-6768 Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Verlag