Abstract

Serotonin, a biogenic amine widely found in many organisms, functions as both aneurotransmitter and hormone. Although serotonin is involved in various physiologicalprocesses, this study aimed to review its role in energy metabolism. Given that serotonin cannot cross the blood-brain barrier and is synthesized by two different isoforms of tryptophan hydroxylase in the central nervous system (CNS) and peripheral tissues,it is reasonable to assume that serotonin in the CNS and peripheral tissues functionsindependently. Recent studies have demonstrated how serotonin influences energymetabolism in metabolic target organs such as the intestines, liver, pancreas, andadipose tissue. In summary, serotonin in the CNS induces satiety and appetite suppression, stimulates thermogenesis, and reduces body weight. Conversely, serotonin in the periphery increases intestinal motility, stimulates gluconeogenesis in the liver,suppresses glucose uptake by hepatocytes, promotes fat uptake by liver cells, stimulates insulin secretion while suppressing glucagon secretion in the pancreatic islets, promotes lipogenesis in white adipose tissue, inhibits lipolysis and browning of whiteadipose tissue, and suppresses thermogenesis in brown adipose tissue, thereby storing energy and increasing body weight. However, considering that most experimental results were obtained using mice and conducted under specific nutritional conditions,such as high-fat diets, whether serotonin acts in the same way in humans, whether itwill act similarly in individuals with normal versus obese weights, and whether its effects vary depending on the type of food consumed, remain unknown.