The Role of Leptin in the Brain for Catecholamine (TH) Neurons, Serotonin (5HT) Neurons and Orexin Neurons
CHAPTER II: LITERATURE REVIEW
Leptin is a hormone that plays a crucial role in regulation of food intake and in energy homeostasis (1-3). The hormone was initially identified in mutant mice displaying extreme obesity and feeding excessively. A few decades later, it was revealed that the mutant mice had inadequate proper leptin signalling which were attributed to a mutation in either the hormone (ob/ob) or its analogous receptor. Leptin is synthesised from the adipose tissue in proportion to the quantity of adipose tissue present and it is distributed to its main area of action, the hypothalamus, where it targets anorexigenic and orexigenic neurons to facilitate most of the leptin roles, including regulation of food intake (2, 3).
Since it is produced in proportion to body energy reserves (adipose tissue), leptin levels in the circulation can act an excellent indicator of how much energy the body has on reserve. Leptin has a critical role in glucose homeostasis and the metabolic roles of the hormone are facilitated by the binding of leptin to leptin receptor (the long form) and the activation of Janus Kinase 2 (JAK) transducer and the transcription of three pathways (2,3). Leptin also plays crucial role in growth and development, reproduction, and in the maintenance of the body immunity (4, 5).
2.1.1 The role of leptin in hypothalamic area
Research studies led to the discovery of another mutant mouse, with the mutation being associated with chromosome 4 (the db/db mouse). Consequent empirical research observed that db encoded the long form of the leptin receptor (LepRb) (2). The main action of leptin hormone is vital for energy regulation and is facilitated through populations of LepRb that express neurons all through the entire brain. The neuronal populations of LepRB are plenty within...