Cholinergic Agonists and Antagonists Have an Effect on the Metabolism of the Beetle Tenebrio Molitor

Abstract

Synthetic insecticides are still widely used in plant protection. The main target for their action is the nervous system, in which the cholinergic system plays a vital role. Currently available insecticides have low selectivity and act on the cholinergic systems of invertebrates and vertebrates. Acetylcholine, a cholinergic system neurotransmitter, acts on cells by two types of receptors: nicotinic and muscarinic. In mammals, the role of muscarinic acetylcholine receptors (mAChRs) is quite well-known but in insects, is still not enough. Based on data indicating that the muscarinic cholinergic system strongly affects mammalian metabolism, we investigated if it similarly occurs in insects. We investigated the influence of agonists (acetylcholine, carbachol, and pilocarpine) and antagonists (tropane alkaloids: atropine and scopolamine) of mAChRs on the level of selected metabolites in Tenebrio molitor beetle trophic tissues. We analyzed the glycogen content in the fat body and midgut, the total free sugar concentration in the hemolymph and the lipid amount in the fat body. Moreover, we analyzed the levels of insulin-like peptides in the hemolymph. The tested compounds significantly influenced the mentioned parameters. They increased the glycogen content in the fat body and midgut but decreased the concentration of free sugars in the hemolymph. The observed effects were tissue-specific, and were also time- and dose-dependent. We used nonligated and neck-ligated larvae (to eliminate the influence of head factors on tissue metabolism) to determine whether the observed changes are the result of direct or indirect impacts on tissues. The obtained data suggest that the cholinergic system affects the fat body and midgut indirectly and directly and a pleiotropic role for mAChRs exists in the regulation of energy metabolism in insects. Moreover, tested compounds significantly affected the level of insulin-like peptides in hemolymph. Our studies for the first time showed that mAChRs are involved in regulation of insect metabolism of trophic tissues, and act on them directly and indirectly. Improved knowledge about insect cholinergic system may help in searching more selective and environment-friendly solutions in pest management.

Expression profiling of winged‐ and wingless‐destined pea aphid embryos implicates insulin/insulin growth factor signaling in morph differences

“…An obvious next step is to explore the functional consequences on wing development of manipulating insulin signaling during aphid embryogenesis. This could be achieved by knockdown of FoxO or InR1 using dsRNA, or by manipulating insulin‐signaling using pharmacological methods (Chowański, Pacholska‐Bogalska, & Rosiński, ). Specifically, if ecdysone injections generate wingless morphs via FoxO, this effect should be reduced in embryos where FoxO expression is also suppressed.…”

Identification of sulfakinin receptors (SKR) in Tenebrio molitor beetle and the influence of sulfakinins on carbohydrates metabolism

“…The level of the insulin-like peptides (ILPs) in insect hemolymph, after injection of SKs, was determined according to the method described by Chowański et al ( 2018 ). Samples of hemolymph were collected from the insects 1 or 2 h after injection of 10 pmol or 20 pmol of sulfakinins.…”

Sulfakinins influence lipid composition and insulin-like peptides level in oenocytes of Zophobas atratus beetles

“…Cat. # EIA2935) as described previously by Chowański et al ( 2018 ) and Słocińska et al ( 2020 ) with some modification. Briefly, for each sample the oenocytes from ten insects were isolated 2 h after hormones or RS injection and collected to 30 μL of ice-cold saline and next, the samples were shaken for 15 min (1400 rpm at 4 °C) on a thermomixer (Eppendorf, Germany) and stored at − 20 °C till measurement.…”