Hypothalamic neuropeptide expression following chronic food restriction in sedentary and wheel-running rats C E de Rijke, J J G Hillebrand, L A W Verhagen, T A P Roeling and R A H Adan Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands (Requests for offprints should be addressed to R A H Adan; Email: RAHAdan@med.uu.nl) Abstract When rats are given access to a running-wheel in combination with food restriction, they will become hyperactive and decrease their food intake, a paradoxical phenomenon known as activity-based anorexia (ABA). Little is known about the regulation of the hypothalamic neuropeptides that are involved in the regulation of food intake and energy balance during the development of ABA. Therefore, rats were killed during the development of ABA, before they entered a state of severe starvation. Neuropeptide mRNA expression levels were analysed using quantitative real-time PCR on punches of separate hypothalamic nuclei. As is expected in a state of negative energy balance, expression levels of agouti-related protein (AgRP) and neuropeptide Y (NPY) were increased 5-fold in the arcuate nucleus (ARC) of food-restricted running ABA rats vs 2-fold in sedentary food-restricted controls. The co-regulated expression of AgRP and NPY strongly correlated with relative body weight and white adipose tissue mass. Arcuate expression of pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) was reduced 2-fold in the ABA group. In second-order neurons of the lateral hypothalamic area (LHA), melanin-concentrating hormone (MCH) mRNA expression was upregulated 2-fold in food-restricted running rats, but not in food-restricted sedentary controls. Prepro-orexin, CART and corticotropin-releasing hormone expression levels in the LHA and the paraventricular nucleus (PVN) were unchanged in both food-restricted groups. From this study it was concluded that during the development of ABA, neuropeptides in first-order neurons in the ARC and MCH in the LHA are regulated in an adequate response to negative energy balance, whereas expression levels of the other studied neuropeptides in secondary neurons of the LHA and PVN are unchanged and are probably regulated by factors other than energy status alone. Journal of Molecular Endocrinology (2005) 35, 381–390 Introduction The hypothalamus has a major role in the regulation of food intake and energy balance. Several hypothalamic nuclei, including the arcuate nucleus (ARC), para- ventricular nucleus (PVN), lateral hypothalamic area (LHA), ventromedial nucleus (VMH) and dorsomedial nucleus (DMH), express neuropeptides that are involved in the regulation of food intake and energy balance. ARC neurons are first-order neurons in the hypotha- lamic response to the peripheral satiety factors leptin and insulin. First-order ARC neurons project to second-order neurons in the PVN, LHA, VMH and DMH. Second-order neurons subsequently project to various regions including the nucleus of the solitary tract and the dorsomotor nucleus of the vagus in the caudal brainstem as well as to the cortex and the limbic system. The caudal brainstem harbours the basic neural circuitry required for eating reflexes, but needs hypothalamic input for the long-term regulation of energy homeostasis (Schwartz et al. 2000, Hillebrand et al. 2002, Berthoud 2004). There are at least two different populations of first-order neurons in the ARC. One population contains the orexigenic neuropeptides agouti-related protein (AgRP) and neuropeptide Y (NPY). Expression of AgRP and NPY is suppressed in states of positive energy balance when leptin and insulin levels are high. In contrast, leptin and insulin stimulate the expression of pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART), which are co-expressed in the second group of first-order neurons in the ARC. POMC is the precursor of the melanocortin peptide -melanocyte-stimulating hormone (-MSH), which, like CART, has an inhibitory effect on food intake (reviewed in Hillebrand et al. 2002, Leibowitz & Wortley 2004). AgRP and NPY mRNA expression is increased during 1–7 days of fasting and after food restriction in mice (Hahn et al. 1998, Mizuno et al. 1998, Mizuno & Mobbs 1999, Morton et al. 2004) and rats (Brady et al. 1990, Korner et al. 2001, Bertile et al. 2003, Bi et al. 2003, Wolden-Hanson et al. 2004). Both AgRP and NPY are upregulated in the leptin-deficient ob/ob mouse 381 Journal of Molecular Endocrinology (2005) 35, 381–390 0952–5041/05/035–381 © 2005 Society for Endocrinology Printed in Great Britain DOI: 10.1677/jme.1.01808 Online version via http://www.endocrinology-journals.org Downloaded from Bioscientifica.com at 05/26/2020 01:58:12PM via Massachusetts Inst of Technology