Effects of Leptin

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 hum

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, et al., 1997). Tang-Christensen, Havel, Jacobs, Larsen, and Cameron (1999) further studied the effects of central administration of leptin, in the rhesus monkey. They investigated effects on the sympathetic nervous system activity and food intake. Findings showed that peripheral administration (1 and 3 ug/kg, sc), resulting in increments of circulating leptin concentrations, did not inhibit food intake over a three-day period. However, 1 ug/kg leptin, intracerebroventricularly, had no acute effect on food intake but resulted in a significant and sustained suppression (40%- 50%) of food intake for the following day. Circulating norepinephrine levels were also found to increase after intracerebroventricular leptin administration but not after artificial cerebrospinal fluid administration. The authors concluded that these findings imply that leptin signals the central nervous system to decrease food intake in monkeys and it acutely activates the sympathetic nervous system. It was also concluded that leptin did not regulate food intake when peripherally administered. Therefore leptin was found to be more associated with regulation of food intake with sustained changes in circulating leptin concentrations as are found with
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Some common words found in the essay are:
Obese Gene, LH FSH, McCamish O'Rahilly, Clifton Steiner, Western Samoa, Attanasio Blum, Weight Lindpaintner, Strader Davis, Hopkinson Nicolson, Rutanen Andersson, leptin levels, serum leptin, body fat, body mass, serum leptin levels, leptin concentrations, fat mass, food intake, adipose tissue, body mass index, mass index, cord blood, intrauterine growth retardation, clinical endocrinology metabolism, journal clinical endocrinology,
Approximate Word count = 6238
Approximate Pages = 25 (250 words per page)

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