Biology Reference
In-Depth Information
expression requires dietary amino acids and fat body TOR activation suggests
that it is not Upd2, but may be the same signal that regulates the insulin pool in
the IPCs in response to dietary proteins. Together, this shows that the fat body
with its nutrient sensing and endocrine functions plays a key role in coordinat-
ing nutrient uptakewith systemic growth required for developmental progres-
sion. Future research should focus on the identification of additional nutrient-
dependent secreted signals from the fat body and investigate their potential
redundancy, interactions, and targets. It is also possible that signals from the
fat body may not only include secreted proteins. A recent study, for example,
indicates that TCA cycle intermediates and upstream metabolites from the fat
body crosstalk with the neuroendocrine system of the brain to control ecdy-
sone release (
Xu, Lu, & Denlinger, 2012
).
3.2. Interactions between the gut microbiota, nutrition,
and developmental progression
Although extensive studies have focused on the fat body, recent reports have
highlighted the important role of intestinal homeostasis in coordinating
nutrient uptake with growth and development timing (
Akman Gunduz &
Douglas, 2009; Ridley, Wong, Westmiller, & Douglas, 2012; Shin et al.,
2011; Storelli et al., 2011
). One of the challenges facing animals in nature
is to find a nutritionally adequate food source. It has been shown that by
engaging in symbiotic relationship with microorganisms some insects can
meet their dietary requirements even on low protein diets (
Akman et al.,
2009
). The host-intestinal microbiota affects the organisms nutritional sup-
ply, and hence, larval growth rate and developmental time (
Ridley et al.,
2012
). Interestingly, two recent reports show that the microenvironment
of the gut seems to have a critical influence on systemic insulin signaling
in
Drosophila
(
Shin et al., 2011; Storelli et al., 2011
). These studies have inves-
tigated the impact of commensal bacteria on
Drosophila
growth and develop-
ment and show that larvae reared under germ-free conditions attenuate
ecdysone release and delay development as nutrients become limited. The
gut bacteria
Acetobacter pomorum
and
Lactobacillus plantarum
modulates insulin
signaling of the host, demonstrating a host-microbe crosstalk that influences
nutrient uptake and developmental progression in
Drosophila
. The role of the
host microbiota in regulating the internal metabolic milieu and insulin
homeostasis has also received increasing attention in mammals (
Boroni
Moreira, Fiche Salles Teixeira, do C Gouveia Peluzio, & de Cassia
Goncalves Alfenas, 2012; De Bandt, Waligora-Dupriet, & Butel, 2011
).
Considering that diet affects the host gut microbiota which modulate the
