Orexin A but not orexin B regulates lipid metabolism and leptin secretion in isolated porcine adipocytes
Introduction
Neuropeptides orexin A (OxA) and orexin B (OxB), also known as hypocretin 1 and hypocretin 2, respectively, were discovered in 1998 [1], [2]. These 2 isoforms are derived from a common precursor, preproorexin. Biological activity of orexins is regulated by 2 G protein-coupled receptors, namely, orexin receptor 1 (OxR1) and orexin receptor 2 (OxR2).
The knowledge about the role of orexins in regulation of metabolism was focused on human and laboratory animals. However, localization and functions of orexins system in domestic animals have been also investigated. It is known that in different species of livestock (pigs, cattle, horse, and sheep) both orexins and their receptors are expressed in the nervous system and different brain regions including hypothalamus, pituitary gland, preoptic area, stalk median eminence, hippocampus, amygdala, olfactory bulb, and pineal gland [3], [4], [5]. Moreover, the presence of orexins and their receptors has been detected in reproductive system, gastrointestinal tract, pancreas, kidney, and adrenal gland [5], [6].
This widespread distribution of orexins system indicates that OxA and OxB are involved in a number of biological functions in body of farm animals. Literature data show that these peptides regulate food intake [7], [8]. They also influence pancreas and regulate insulin [9] and glucagon secretion [10]. Furthermore, OxA and OxB have been shown to regulate the estrous cycle and gonadal tract by influencing GnRH and LH secretion, and ovarian, uterine, and testis steroidogenesis in pigs [5], [11], [12].
It is well established in rodents that orexins influenced on metabolic processes of adipose tissue [13], [14]. However, there are no data regarding OxA and OxB action in adipose tissue of pigs. Therefore, in this study, we tested the hypothesis that OxA and OxB modulate the metabolism and endocrine functions of isolated porcine adipocytes and adipose tissue explants. Pigs are a very important species of livestock worldwide, and it can be used as an animal model for the study of metabolism of adipose tissue in other species [15]. Specifically, we focused our attention on changes of intensity of lipolysis, glucose uptake, and lipogenesis as well as leptin expression and secretion in isolated porcine adipocytes under the influence of OxA and OxB. We further hypothesized that orexins regulate lipid metabolism in porcine adipose tissue partly via extracellular-signal-regulated kinase 1 and 2 (ERK1/2) pathway.
The results of this study can help to understand the effects of these peptides in domestic animals which may contribute to the development of new strategy of animal nutrition and production programs.
Section snippets
Animals
The study and all trial procedures were approved by the Local Ethical Committee No. 10 of Poznań, Poland (approval number 10/2011).
Six 21-day-old male Złotnicka piglets (average body weight of 6.83 ± 0.79 kg) from an Experimental Station of the Poznan University of Life Sciences, Złotniki, Poland, were sacrificed to obtain adipose tissue. Animals were treated by sedation (using medetomidine hydrochloride and ketamine) and then killed by exsanguination. Experiments were conducted within 30 min
Orexins and OxR expression in porcine-isolated adipocytes and adipose tissue
First, we decided to investigate the mRNA and protein expression level of orexin receptors in visceral and subcutaneous adipose tissue as well as in isolated porcine adipocytes (Fig. 1A–C). We found that there was a higher level of mRNA expression of OxR1 than that of OxR2 in isolated fat cells and examined adipose tissue depots (Fig. 1A; P < 0.01). We also found that OxR1 and OxR2 proteins were expressed in all tested tissues and isolated cells. Despite the use of the same amounts of protein,
Discussion
One of the biggest challenges in porcine nutrition is increasing the productivity and improving the meat quality by regulating fat content in pigs. Despite that the role of orexins in porcine fat metabolism has been elucidated, there is limited information on the regulatory influence of orexins on the metabolism of peripheral tissues in pigs. Hypothalamic expression of orexins and their receptor depends on weaning time and weaning pig weight [21]. Moreover, research has shown that in sheep, the
Acknowledgments
This study was supported by the Ministry of Sciences and Higher Education/National Science Centre, Poland, grant NN311508339.
E. P. O. and P. A. K., designed the study, obtained the data and wrote the manuscript. K. W. N., contributed to the study design, edited, supported and critically revised the manuscript, and contributed to the discussion. M. S., R. M., D. S. Z., and P. K. obtained the data, collected and analyzed the data, and revised the manuscript. All authors have given final approval
References (33)
- et al.
Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior
Cell
(1998) - et al.
Expression of orexin receptors 1 (OX1R) and 2 (OX2R) in the porcine pituitary during the oestrous cycle
Anim Reprod Sci
(2010) - et al.
Adiponectin, orexin A and orexin B concentrations in the serum and uterine luminal fluid during early pregnancy of pigs
Anim Reprod Sci
(2017) - et al.
Localization of orexin A and orexin B in the porcine uterus
Reprod Biol
(2012) - et al.
Cloning of porcine prepro-orexin cDNA and effects of an intramuscular injection of synthetic porcine orexin-B on feed intake in young pigs
Domest Anim Endocrinol
(1999) - et al.
Immunohistochemical evidence of orexin-A in the pancreatic beta cells of domestic animals
Res Vet Sci
(2010) - et al.
Expression of orexins and their precursor in the porcine ovary and the influence of orexins on ovarian steroidogenesis in pigs
Anim Reprod Sci
(2014) - et al.
Changes in plasma orexin A and orexin B concentrations during the estrous cycle of the pig
Peptides
(2013) - et al.
Effects of orexin A on proliferation, survival, apoptosis and differentiation of 3T3-L1 preadipocytes into mature adipocytes
FEBS Lett
(2012) - et al.
Porcine models for the metabolic syndrome, digestive and bone disorders: a general overview
Animal
(2010)
Metabolism of isolated fat cells. 1. Effects of hormones on glucose metabolism and lipolysis
J Biol Chem
The development of porcine models of obesity and the metabolic syndrome
J Nutr
Reduction of blood glucose level by orexins in fasting normal and streptozotocin-diabetic mice
Eur J Pharmacol
Orexins acting at native OX1 receptor in colon cancer and neuroblastoma cells or at recombinant OX1 receptor suppress cell growth by inducing apoptosis
J Biol Chem
The hypocretins: hypothalamus-specific peptides with neuroexcitatory activity
Proc Natl Acad Sci U S A
Expression of orexin receptors 1 (OX1R) and 2 (OX2R) in the porcine hypothalamus during the oestrous cycle
J Physiol Pharmacol
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