Galanin-like peptide: a key player in the homeostatic regulation of feeding and energy metabolism?

Abstract

The hypothalamus has a critical role in the regulation of feeding behavior, energy metabolism and reproduction. Galanin-like peptide (GALP), a novel 60 amino-acid peptide with a nonamidated C-terminus, was first discovered in porcine hypothalamus. GALP is mainly produced in the hypothalamic arcuate nucleus and is involved in the regulation of feeding behavior and energy metabolism, with GALP-containing neurons forming networks with several feeding-regulating peptide-containing neurons. The effects of GALP on food intake and body weight are complex. In rats, the central effect of GALP is to first stimulate and then reduce food intake, whereas in mice, GALP has an anorectic function. Furthermore, GALP regulates plasma luteinizing hormone levels through activation of gonadotropin-releasing hormone-producing neurons, suggesting that it is also involved in the reproductive system. This review summarizes the research on these topics and discusses current evidence regarding the function of GALP, particularly in relation to feeding and energy metabolism. We also discuss the effects of GALP activity on food intake, body weight and locomotor activity after intranasal infusion, a clinically viable mode of delivery.

Intranasal Delivery of Proteins and Peptides in the Treatment of Neurodegenerative Diseases

“…Galanin and GALP are derived from two separate genes but share a 13-amino-acid sequence. GALP has complex actions on feeding behavior that vary across species (20,21,43). In addition, GALP induces thermogenesis, altering energy balance (44).…”

Insulin resistance, dyslipidemia, and apolipoprotein E interactions as mechanisms in cognitive impairment and Alzheimer's disease

“…Intranasal delivery offers benefits over standard routes of delivery, such as intravenous or oral paths, including allowing direct access to the CNS, decreasing exposure to the periphery to reduce systemic side effects, and negating degradation in the blood. 47,48 Intranasal administration has been used to deliver a variety of peptides to the brain including galanin-like peptide (GALP), 49,50 pituitary adenylate cyclase-activating peptide (PACAP), 51,52 and glucagon-like peptide-1 (GLP-1). 53 When administered to patients with AD, mild cognitive impairment, and even to those who are cognitively intact, intranasal insulin has shown marked improvements in a number of cognitive tests including the delayed story recall and the Dementia Severity Rating Scale.…”

Integrative Control of Energy Balance and Reproduction in Females

“…In rats, the central effect of GALP is to first stimulate and then reduce food intake, whereas in mice, GALP has an anorectic function. Furthermore, GALP shows direct stimulatory action on gonadotropin secretion [147, 148], regulates plasma LH levels through activation of GnRH producing neurons, suggesting that it is also involved in the reproductive system [148, 149]. The presence of galanin within kisspeptin axons innervating GnRH neurones and the oestrogen-dependent regulation of that presence add a new dimension to the roles played by galanin in the central regulation of reproduction [150].…”