Biology Reference
In-Depth Information
sheep suggest that prenatal exposure to testosterone does not alter kisspeptin
content in the ARC of adult females, but blunts the expression of NKB
(
Cheng et al., 2010
).
As final comment in this section, it is stressed that most of the information
regarding the process of sexual differentiation of the hypothalamic Kiss1 sys-
tem has been obtained in rodents, and some of the features described above
might not be shared by other mammalian species. In fact, classical studies
suggested decades ago that the mechanisms of sexual differentiation of
gonadotropin control might be partially different between rodents and pri-
mates, as LH surges could be induced in male monkeys, even not subjected
to hormonal manipulation at early stages of development, if provided with
an appropriate ovarian (estrogen) signal as adults (
Norman & Spies, 1986
).
In this context, additional studies are needed to elucidate the nature and
physiological relevance of the process of sexual differentiation of the hypo-
thalamic kisspeptin system in non-rodent mammalian species, including
humans, and whether this phenomenon plays a significant role in the timing
of puberty in such species.
5. METABOLIC CONTROL OF PUBERTY: LEPTIN,
KISSPEPTINS, AND CELLULAR ENERGY SENSORS
It is well known since Old Ages that the amount of energy reserves of
the organism, and by extension its metabolic status, are important factors in
the modulation of the timing of puberty (
Fernandez-Fernandez et al., 2006;
Martos-Moreno, Chowen, & Argente, 2010
). This is especially evident in
the female, in which acquisition of reproductive capacity implies the need to
face the eventual metabolic drainage of pregnancy and lactation. Hence,
from a teleological perspective, it makes biological sense that puberty is only
achieved when sufficient energy stores and optimal metabolic conditions are
attained. Notwithstanding this, the influence of metabolic cues and energy
homeostasis on puberty and reproductive function is also detected in males
(
Castellano et al., 2009
), in which energy reserves are needed (at least in
wildlife species) to cope with some key aspect of reproduction, such as
territoriality and partner selection (
Elias, 2012; Elias & Purohit, 2013
).
Furthermore, the tight connection between energy balance, puberty, and
reproduction becomes evident not only in conditions of energy deficit,
but also in situations of energy excess that, if of sufficient magnitude and per-
sistent in time (e.g., early-onset morbid obesity), are associated to detectable
alterations of the timing of puberty; for instance, precocious puberty seems
