Abstract
Leptin, a 16 kDa protein and a product of the ob/ob gene, has a tertiary structure similar to that of a cytokine. It is primarily secreted by white adipose tissue and its levels in the blood correlate positively with percentage body fat. Leptin was first identified in 1994 as a major factor that regulated food intake and energy balance. Leptin in the circulation exists either as a free monomeric hormone or bound to its soluble receptor. Its serum levels usually range from 0.5 to 37.7 ng/ml in males and 2.0 to 45.2 ng/ml in females. The half-life of leptin is between 20 - 30 minutes and it is eliminated mainly by the kidneys. However, research over the last 25 years has revealed numerous other physiological roles for leptin, including roles in inflammation, immune function, neuro-endocrine function, bone metabolism, blood pressure regulation and sexual maturation. Most of these roles have been identified from studies on leptin deficient rodents. Apart from energy balance and sexual maturation, where its role is direct and obvious, its actions on the rest of the other systems are permissive. Actions of leptin are both centrally and peripherally mediated involving receptors that are widely distributed in the body. Six leptin receptor isoforms, belonging to the class 1 cytokine receptor family, have been identified. These receptors are products of the OBR gene. The cellular actions of leptin are mediated through any one of five different signalling pathways that include the JAK-STAT, PI3K, MAPK, AMPK, and the mTOR signalling pathways.
Highlights
Introduction to LeptinLeptin, a 16 k-Da non-glycosylated peptide hormone, consists of 167 amino acids with a tertiary structure that is similar to that of a cytokine
Administration of leptin to normal male adult rats significantly elevated serum levels of FSH and LH [30, 245]. These results demonstrate that leptin stimulates the reproductive endocrine system in both sexes of ob/ob mice, and leptin may serve as a permissive signal to the reproductive system of normal animals
Leptin was initially discovered following a search for an adipocyte factor that regulates appetite and body weight, research over the last 25 years has shown that this adipocyte factor has numerous other far reaching physiological roles in the body
Summary
Introduction to LeptinLeptin, a 16 k-Da non-glycosylated peptide hormone, consists of 167 amino acids with a tertiary structure that is similar to that of a cytokine. Leptin has been reported to stimulate the PI3K pathway in a variety of cells and tissues, including myocytes [115, 116], hepatocytes and hypothalamic tissue [117] and in human adipose. Leptin administration causes an increase in UCP1 mRNA levels in brown adipose tissue and enhances energy expenditure [170].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
