Leptin and its structural gene, Ob, are exclusively expressed in adipo
se tissue. Leptin is secreted into the blood and is responsible for fa
t mass regulation via leptin receptors in the hypothalamus. This has b
een considered the major role of leptin, but leptin receptor isoforms
are expressed not only in the brain but also in most other tissues in
humans and rodents: heart, placenta, lung, liver, muscle, kidney, panc
reas, spleen, thymus, prostate, testes, ovary, small intestine, and co
lon. This implicates leptin regulation in other systems apart from Cat
mass regulation, and leptin action has been demonstrated in human fet
al development and reproductive development, liver metabolism, hematop
oiesis, and insulin secretion. Four splice variants of the leptin rece
ptor have been identified in humans: the long isoform huOb-R and the s
horter isoforms B219.1 to B219.3. It is known that the long isoform ha
s full intracellular signaling capacity, and is responsible for anorec
tic action in the hypothalamus. The roles of the other isoforms are ye
t to be elucidated. Here, we report the identification by reverse tran
scriptase-polymerase chain reaction (RT-PCR) of three leptin receptor
isoforms coexpressed in human visceral adipose tissue: the long isofor
m huOb-R and the short isoforms huB219.1 and huB219.3. The possible ro
les of these isoforms are discussed. Copyright (C) 1998 by W.B. Saunde
rs Company.