ERA’S JOURNAL OF MEDICAL RESEARCHVOL.3 NO.1
Short Communication
LEPTIN, THE MEDIATOR OF ENERGY RESERVE HAS ROLE IN FERTILITY:
A REVIEW
Nitin Pandey
Department of Physiology
Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh India– 226003
ABSTRACT
Address for correspondence
Leptin, an adipocytokine was discovered in 1994 as putative hormone
Dr. Nitin Pandey
involved in appetite control acting at hypothalamic level. Since its discovery
Department of Physiology
lot of work has been done over this novel molecule and in variety of
Era's Lucknow Medical College and
physiological domains. Previously it was speculated that fertility, which is the
Hospital, Lucknow–226003, India
basis of species progression has link with total body mass and energy. Leptin
568 Kha/448A Geetapalli,
which is involved both in appetite regulation and reproductive process is
Alambagh,Lucknow (U.P.) PIN–226005
thought to be have role in fertility regulation. Leptin is secreted from adipose
Email: drnitinpandey@gmail.com
tissue, which is marker of energy reserve of the body. In this review the role of
leptin in regulation of fertility has been discussed.
Keyword: Leptin, Adipocytokine, Body Mass and Fertility
reproductive development.
INTRODUCTION
Leptin, the obese (ob) gene product, is synthesized and
LEPTIN AS A SIGNAL OF NUTRITIONAL
secreted exclusively by adipocytes (1). Serum leptin
STATUS LINKED TO THE REPRODUCTIVE
levels correlate with the amount of body fat in rodents and
PROCESS
humans (2, 3) and regulate the amount of food intake by
The amount of body fat stored is known to influence
monitoring energy reserves through interaction with
fertility, indicating a link between adipose tissue and
hypothalamic leptin receptors (4). Leptin binds to its
reproductive system (15). An interesting hypothesis is
receptors on the cell membrane and is involved in the
that leptin is a peripheral signal indicating the adequacy
activation of signal transducer and activator of
of nutritional status for reproductive function (16).
transcription–3 (STAT3), a member of the signal
Therefore it seems possible that low leptin
transducer and activator of transcription family of
concentrations indicate a status of inadequate
proteins (5). In humans at least four types of splice
nutritional stores and could prevent an unwanted
variants of OB–R messenger ribonucleic acid (mrna)
pregnancy which demands additional energy to support
encoding proteins have been identified; they differ in the
a growing fetus.
length of their cytoplasmic domains (6). Although the
It is relatively well documented that leptin's central
long form, referred to as OB–RL, has the full–length
action is mediated via hypothalamic NPY gene
variant, three types of short forms, B219.1 to B219.3, lack
expression (17). In response to energy restriction or
several sequences that are responsible for intracellular
fasting, it is proposed that NPY gene expression
signaling (6). In addition to the action on energy
increases in response to a reduction in circulating leptin
metabolism, leptin appears to influence various
levels. In support of this hypothesis, Ob–Rb is
reproductive functions. Injecting leptin into ob/obmice
coexpressed in NPY neurons in the arcuate nucleus of
that are infertile and with low levels of gonadotropin
the hypothalamus in mice (18). The increase in NPY
increases the weight of the uterus and ovaries and the
production has been postulated to decrease the
number of follicles (7), resulting in restoration of fertility
stimulatory input to downstream neural pathways that
(8). Administering leptin treatment to normal female
ultimately reach the GnRHneurons. The evidence for
mice accelerates puberty (9), and in humans higher leptin
neuroendocrine effects of leptin on GnRHrelease is
levels have been shown to relate to the earlier onset of
EJMR
convincing. Increased gonadotropin secretion
menarche (10). These actions of leptin are considered to
consistently occurs as a result of leptin treatment in
be mediated mainly through brain OB–R. In contrast, the
ob/ob mice and undernourished animals, presumably
m–rnaand protein of leptin and OB–R m–rnaare also
removing the inhibition of GnRH release by NPY
expressed in peripheral reproductive tissue, including
(7, 8). Therefore, leptin communicates the size of the
granulosa cells (11, 12), cumulus cells (6, 11) of human
adipose reserve to the hypothalamus. Leptin is also
preovulatory follicles, oocytes and embryos (11), and
synthesized in the reproductive tissues and it is related
human placental trophoblasts (13, 14). These findings
suggest that leptin plays a physiological role in early
47 Leptin, the mediator of energy reserve has role in fertility: a review
process.
to the hypothalamus–pituitary–ovary axis function.
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