LEPTIN RELATED TO METABOLISM, WEIGHT, & REPRODUCTIVE FUNCTION
This paper will review previous literature regarding the effects of leptin. Specifically, the effects of leptin on metabolism, body weight, and the reproductive functions will be presented, followed by conclusions.
Leptin is the gene product of the Obese Gene (ob). The ob gene encodes a protein which is preceded by a secretory hydrophobic signal peptide. Leptin is found in high levels in the blood. It tends to be expressed specifically in adipose tissue in humans and many mammalian species, however it is also found in human placentia. Early studies of genetic obesity syndromes included research on two mutant mice, ob/ob (deficient in leptin) and db/db (leptin resistance and elevated leptin levels). These studies began 30 years ago and resulted in over 1000 publications. However it was not until the development of cloning of the ob gene that studies began to describe leptin and the regulation of leptin mRNA and protein. The discovery that leptin mRNA and protein are elevated in rodent obesity models led to the hypothesis that leptin is an adipostat which informs the body regarding energy storage in adipose tissue status, to inform the body regarding needed changes in metabolism, appetite, and nutrient partitioning. Food intake alterations effect leptin levels in mice, with fasting leading to down-regulation and the opposite leading to up-regulation. Studies with humans show that body fat and food intake changes also regulates leptin mRNA levels, although less so than in mice. However, studies with humans do show that protein leptin levels in humans are greatly affected by obesity and fasting; protein leptin is higher in humans with higher body fat levels and weight loss results in down-regulation. It is concluded that leptin therefore mediates responses to starvation in both mice and humans. Research has studied effects on leptin mRNA and protein as a res...