84
chapter 5
Thermodynamics, Chemical Kinetics, and Energy Metabolism
births). Deletions in chromosome 15 account for a ma-
jority of cases of Prader-Willi syndrome. In other cases,
a novel genetic mechanism of uniparental disomy is the
cause of this syndrome. Congenital human leptin defi-
ciency is associated with early-onset obesity. Homozygous
mutations in the human leptin receptor gene result in a
truncated leptin receptor lacking both transmembrane and
intracellular domains; such mutations are associated with
early-onset obesity, absence of pubertal development, and
pituitary dysfunction.
In most obese humans, the plasma levels of leptin are
high due to excess adipose tissue. In spite of abundant lep-
tin, there is continued overeating. This puzzling observa-
tion may ultimately be explained by as yet-to-be identified
defects in leptin metabolism.
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