Neuropeptidergic Control of Feeding: Focus on the Galanin Family of Peptides

Abstract

Obesity/overweight are important health problems due to metabolic complications. Dysregulation of peptides exerting orexigenic/anorexigenic effects must be investigated in-depth to understand the mechanisms involved in feeding behaviour. One of the most important and studied orexigenic peptides is galanin (GAL). The aim of this review is to update the mechanisms of action and physiological roles played by the GAL family of peptides (GAL, GAL-like peptide, GAL message-associated peptide, alarin) in the control of food intake and to review the involvement of these peptides in metabolic diseases and food intake disorders in experimental animal models and humans. The interaction between GAL and NPY in feeding and energy metabolism, the relationships between GAL and other substances involved in food intake mechanisms, the potential pharmacological strategies to treat food intake disorders and obesity and the possible clinical applications will be mentioned and discussed. Some research lines are suggested to be developed in the future, such as studies focused on GAL receptor/neuropeptide Y Y1 receptor interactions in hypothalamic and extra-hypothalamic nuclei and sexual differences regarding the expression of GAL in feeding behaviour. It is also important to study the possible GAL resistance in obese individuals to better understand the molecular mechanisms by which GAL regulates insulin/glucose metabolism. GAL does not exert a pivotal role in weight regulation and food intake, but this role is crucial in fat intake and also exerts an important action by regulating the activity of other key compounds under conditions of stress/altered diet.

Leptin—A Potential Bridge between Fat Metabolism and the Brain’s Vulnerability to Neuropsychiatric Disorders: A Systematic Review

“…For instance, leptin suppresses the secretion of cortisol during the stress activation of the adrenal axis, thus contributing to the inhibition of chronic overactivation of the hypothalamic-pituitary-adrenal axis, whereas lowered leptin levels are associated with an increased risk of developing dementia [ 28 ]. Reduction in the energetic reserves and leptin production appear to cause a compensatory change in the reward system and the secretion of orexigenic and anorexigenic neuropeptides [ 99 , 100 ]; meanwhile, negative feedback in the expression of LepR1 as a response to high leptin concentrations has been suggested to occur as a state of leptin resistance and to result in an inability to detect satiety [ 86 ].…”

Involvement of the Orexinergic System in Feeding

“…In humans, feeding behavior is complex since some hypothalamic nuclei are involved in the regulation of food intake, stress response and rewards and, in addition, exert effects on the reward system, cortex or brainstem [4,5,101] (Table 4). Table 4.…”

“…Sci. 2022, 12, x FOR PEER REVIEW 2 of 27 inhibitory for another population of neurons located in the arcuate nucleus that contain pro-opiomelanocortin (POMC) and cocaine-and amphetamine-regulated transcript (CART), are anorexigenic, and inhibit feeding; see [4,5] for review. The interaction of both systems, POMC/CART and NPY/AgRP, is the basis for the regulation of energy homeostasis.…”

“…In this regard, it was reported that orexins A and B, synthesized by neurons of the lateral hypothalamus, activate NPY/AgRP neurons located in the hypothalamic arcuate nucleus and that this projection is reciprocal [3,5]. Simultaneously, orexins inhibit POMC/CART neurons [1].…”

Insects as a New Complex Model in Hormonal Basis of Obesity

“…Galanin is widespread in the vertebrate nervous system, including hypothalamus, which mainly participates in regulation of feeding behavior [ 136 ]. Generally, this hormone regulates many events related to food intake, starting from stimulation of food intake and weight control of animals and ending to regulation of intestinal motility [ 137 ]. All of these prove that between GAL and AST exists a strong functional homology.…”