ABSTRACT
White adipose tissue (WAT) was once regarded as simply a fat depository in animals that released fatty acids and glycerol in times of starvation. However, WAT is now recognized as an active endocrine organ that secretes various hormones and protein factors. Th e name adipokines is given to a group of cytokine proteins, which are produced mainly by the adipocytes of WAT. Adipokines mediate and regulate immunity, infl ammation, and hematopoiesis; thus, they potentially infl uence a variety of physiological processes. Leptin is a small, 166 amino acid peptide hormone primarily secreted by subcutaneous adipose tissue (and somewhat by visceral adipose tissue) crucial to proper energy homeostasis and has a putative signal sequence. Leptin augments the action of insulin on both the inhibition of hepatic glucose production and in stimulating glucose uptake. However, in the obese state, leptin acts to sensitize the eff ect of insulin in target tissues. Studies examining the eff ects of the administration of recombinant leptin to both animals
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and humans have shown a marginal ability to reverse the phenotype associated with leptin defi ciency. Leptin administration has proven to be advantageous in the treatment of hyperphagia (disorder marked by an abnormal appetite and excessive ingestion of food), reducing appetite and normalizing neuroendocrine activity in some leptin-defi cient patients. However, because human obesity is most oft en characterized by elevated serum leptin levels (hyperleptinemia), further study of leptin resistance could be potentially benefi cial in developing a therapeutic treatment. Additionally, further research studies on leptin’s role in cancer development would be needed, as preliminary evidence suggests that leptin may play an important role in the development of various malignancies.
