The Effects of Leptin and Ghrelin Hormones on Metabolism

Leptin was first identified in 1994 by Zhang and colleagues as a signaling factor originating from adipose tissue. Its name is derived from the Greek word “leptos,” meaning “thin” or “slender”. While its primary site of secretion is white adipose tissue, leptin is also secreted in smaller amounts by brown adipose tissue, as well as by the placenta, skeletal muscle, stomach, mammary epithelium, and brain tissue. By acting at the hypothalamic level, leptin reduces appetite. Leptin is a 16-kilodalton, single-chain polypeptide hormone. Initially recognized for its role in satiety and energy balance, leptin was later identified as an anti-obesity factor that exerts feedback effects from adipocytes to the hypothalamus. It has been reported as a key physiological factor in mammals for preventing fat accumulation.Ghrelin, discovered in 1999 by Kojima and colleagues in the stomachs of mice, is a 28-amino acid oligopeptide hormone that stimulates the release of growth hormone. Although primarily secreted by stomach tissue, ghrelin is also produced by the brain, intestines, placenta, kidneys, pituitary gland, and pancreas. The name “ghrelin” is derived from the root “ghre,” meaning “grow,” in Indo-European languages, combined with “relin,” which implies secretion. Ghrelin is also referred to as the "appetite hormone. Isolated from mouse stomach tissue, this 28-amino acid peptide plays crucial physiological roles. Ghrelin has been reported to increase food intake, promote positive energy balance, and influence gastrointestinal motility, cell proliferation, bone metabolism, and reproduction.