Activation of triacylglycerol lipase in the fat body of a beetle by adipokinetic hormone

Endocrine control of TAG lipase in the fat body of the migratory locust, Locusta migratoria

“…Previous own research comparing the resting activities of TAG lipase in the fat body of three insects that represent different types of flight metabolism (Auerswald et al 2005), suggested that TAG lipase activity reflects the extent to which lipids contribute to the overall energy supply during flight: the activity in L. migratoria (that uses lipids to power flight) was highest whereas it was about 50% lower in the fruit beetle, which uses carbohydrates and proline equally and about 90% lower in the American cockroach (an exclusive carbohydrate user). In locusts and fruit beetles, TAG lipase is needed to liberate fatty acids from TAG as the first catabolic step to make lipids (or breakdown products thereof) available from the fat body for oxidation by the flight muscles.…”

“…Moreover, activation of lipase by an endogenous AKH peptide was corroborated for the fruit beetle, Pachnoda sinuata (Auerswald et al 2005). This beetle uses carbohydrates and proline as major flight substrates and lipase activation is necessary for the resynthesis of proline (Ga¨de and Auerswald 2002;Auerswald et al 2005). For locusts, only fragments of information on TAG lipase have been published, such as ideal in vitro assay conditions for lipase from the fat body of L. migratoria (Hirayama and Chino 1987) or, differences in lipase activation in gregarious versus solitary phases in the desert locust, Schistocerca gregaria (Ogoyi et al 1998).…”

“…Preparation of extracts, and determination of the activity of TAG lipase were essentially according to Hirayama and Chino (1987) with small modifications as described in Auerswald et al (2005). Activity of TAG lipase is expressed as mU mg À1 protein.…”

“…The most coherent body of information is available for the moth Manduca sexta (see Arrese et al 2001) which has also been shown to use mainly lipids for sustained flight. Moreover, activation of lipase by an endogenous AKH peptide was corroborated for the fruit beetle, Pachnoda sinuata (Auerswald et al 2005). This beetle uses carbohydrates and proline as major flight substrates and lipase activation is necessary for the resynthesis of proline (Ga¨de and Auerswald 2002;Auerswald et al 2005).…”

“…Most of the knowledge on activation of TAG lipase in the fat body of locusts derives from the indirect measurement of its action, via monitoring the concentrations of lipids in the haemolymph. This is a much easier method to perform compared with the laborious procedure of the lipase assay as outlined recently (Auerswald et al 2005).…”