Data from: How and when do insects rely on endogenous protein and lipid resources during lethal bouts of starvation? a new application for 13C-breath testing

Most of our understanding about the physiology of fasting and starvation
comes from studies of vertebrates; however, for ethical reasons, studies
that monitor vertebrates through the lethal endpoint are scant. Insects
are convenient models to characterize the comparative strategies used to
cope with starvation because they have diverse life histories and have
evolved under the omnipresent challenge of food limitation. Moreover, we
can study the physiology of starvation through its natural endpoint. In
this study we raised populations of five species of insects (adult
grasshoppers, crickets, cockroaches, and larval beetles and moths) on
diets labeled with either 13C-palmitic acid or 13C-leucine to isotopically
enrich the lipids or the proteins in their bodies, respectively. The
insects were allowed to become postabsorptive and then starved. We
periodically measured the δ13C of the exhaled breath to characterize how
each species adjusted their reliance on endogenous lipids and proteins as
energy sources. We found that starving insects employ a wide range of
strategies for regulating lipid and protein oxidation. All of the insects
except for the beetle larvae were capable of sharply reducing reliance on
protein oxidation; however, this protein sparing strategy was usually
unsustainable during the entire starvation period. All insects increased
their reliance on lipid oxidation, but while some species (grasshoppers,
cockroaches, and beetle larvae) were still relying extensively on lipids
at the time of death, other species (crickets and moth larvae) allowed
rates of lipid oxidation to return to prestarvation levels. Although
lipids and proteins are critical metabolic fuels for both vertebrates and
insects, insects apparently exhibit a much wider range of strategies for
rationing these limited resources during starvation.