Peptidergic control of food intake and digestion in insects¹This review is part of a virtual symposium on recent advances in understanding a variety of complex regulatory processes in insect physiology and endocrinology, including development, metabolism, cold hardiness, food intake and digestion, and diuresis, through the use of omics technologies in the postgenomic era.

Abstract

Like all heterotrophic organisms, insects require a strict control of food intake and efficient digestion of food into nutrients to maintain homeostasis and to fulfill physiological tasks. Feeding and digestion are steered by both external and internal signals that are transduced by a multitude of regulatory factors, delivered either by neurons innervating the gut or mouthparts, or by midgut endocrine cells. The present review gives an overview of peptide regulators known to control feeding and digestion in insects. We describe the discovery and functional role in these processes for insect allatoregulatory peptides, diuretic hormones, FMRFamide-related peptides, (short) neuropeptide F, proctolin, saliva production stimulating peptides, kinins, and tachykinins. These peptides control either gut myoactivity, food intake, and (or) release of digestive enzymes. Some peptides exert their action at multiple levels, possibly having a biological function that depends on their site of delivery. Many regulatory peptides have been physically extracted from different insect species. However, multiple peptidomics, proteomics, transcriptomics, and genome sequencing projects have led to increased discovery and prediction of peptide (precursor) and receptor sequences. In combination with physiological experiments, these large-scale projects have already led to important steps forward in unraveling the physiology of feeding and digestion in insects.Key words: insect, midgut, digestion, neuropeptides, stomatogastric nervous system. Résumé : Comme tous les organismes hétérotrophes, les insectes requièrent un contrôle strict de leur ingestion de nourriture et la digestion de leur nourriture en nutriments afin de maintenir leur homéostasie et de compléter leurs tâches physiologiques. L'alimentation et la digestion sont gouvernées par des signaux tant externes qu'internes qui sont transmis par un multitude de facteurs régulateurs, livrés ou bien par les neurones qui innervent le tube digestif ou les pièces buccales ou alors par les cellules endocrines du tube digestif moyen. Notre revue fournit une synthèse des régulateurs peptidiques connus pour contrôler l'alimentation et la digestion chez les insectes. Nous décrivons la découverte et le rôle fonctionnel de ces processus dans le cas des peptides allatorégulateurs, des hormones diurétiques, des peptides apparentés aux amides FMRF, du neuropeptide F (court), de la proctoline, des peptides stimulateurs de la production de salive, des kinines et des tachykinines des insectes. Ces peptides contrôlent la myoactivité du tube digestif, l'ingestion de nourriture et(ou) la libération des enzymes digestives. Certains peptides agissent à de multiples niveaux, possédant une fonction biologique qui dépend de leur site d'action. Plusieurs peptides régulateurs ont été extraits physiquement de différentes espèces d'insectes. Cependant, plusieurs projets de peptidomique, de protéomique, de transcriptomique et de génomique ont mené à de nombreuses découvertes supplémentaires et des prédict...

Autumn shifts in cold tolerance metabolites in overwintering adult mountain pine beetles

“…It is a relatively inert compound that can be maintained at high concentration without interfering with other cellular processes or enzymatic reactions [27]. It is also nontoxic, so insects experience few fitness trade-offs when generating this compound, and it can be converted into glycogen when temperatures begin to warm [15,27,28]. Our previous studies have shown that larvae increase their capacity to generate glycerol in correlation to temperature similar to what we have observed here with adults [15,16,22] (Fig 4).…”

Autumn shifts in cold tolerance metabolites in overwintering adult mountain pine beetles

“…It is a relatively inert compound that can be maintained at high concentration without interfering with other cellular processes or enzymatic reactions (Leather et al 1995). It is also nontoxic, so insects experience few fitness trade-offs when generating this compound, and it can be converted into glycogen when temperatures begin to warm (Leather et al 1995; Storey and Storey 2012; Fraser et al 2017). Our previous studies have shown that larvae increase their capacity to generate glycerol in correlation to temperature similar to what we have observed here with adults (Bonnett et al 2012; Robert et al 2016; Fraser et al 2017) (Figure 4a).…”

Peptide Hormones in the Insect Midgut

“…For example, DILP2 is produced by brain nerve cells, DILP3 is produced by gut muscles, DILP5 is produced by ovaries and Malpighian tubules, and DILP6 is mainly produced in the fat body (Nassel and Vanden Broeck, 2016). The expression levels of dilp4 and dilp5 in the gut of Drosophila larvae are high, whereas the expression level of dilp6 in the gut is Diploptera punctate, Aedes aegypti, Anopheles albimanus, Drosophila melanogaster (Reichwald et al, 1994;Hernandez-Martinez et al, 2005;Spit et al, 2012;Vanderveken and O'Donnell, 2014;Nouzova et al, 2015) B: Endocrine cells in the midgut B: Inhibit fore-and hind-gut contractions and food intake. (Brogiolo et al, 2001;Zhang et al, 2009;Gronke et al, 2010) Prothoracicotropic factors (PTTH)…”

“…Nerves are distributed throughout the insect gut, and the central and gastrointestinal nervous systems can affect the insect gut. Peptide hormones control food intake and digestion; therefore, destroying specific nerves can reduce eating behavior (Spit et al, 2012). In addition to regulating the nervous system via the intestinal tract, the peptides produced by various parts of the intestinal tract function to regulate the digestive system itself.…”