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1.
Article in English | MEDLINE | ID: mdl-33160077

ABSTRACT

Rhodnius prolixus, a vector of Chagas disease, is a hematophagous insect that feeds exclusively on blood. Each blood meal is digested within the first fourteen days after feeding, providing substrates for lipid synthesis for storage and egg production. These events are precisely regulated and emerging evidence points to a key function of insulin-like peptides (ILPs) in this control. Here we investigated the role of insulin receptor in the regulation of nutrient metabolism in fed adult females. The expression of insulin receptor (RhoprIR) gene was determined in adult organs, and it was highest in ovaries and previtellogenic follicles. We generated insects with RNAi-mediated knockdown of RhoprIR to address the physiological role of this receptor. RhoprIR deficiency improved longevity and reduced triacylglycerol storage in the fat body, whereas blood digestion remained unchanged for seven days after blood meal. The lower lipid content was attributable to decreased de novo lipogenesis as well as reduced incorporation of hemolymph-derived fatty acids into newly synthesized lipids within this organ. Consistent with that, fat bodies from RhoprIR-deficient insects exhibited decreased gene expression levels of lipophorin receptor (RhoprLpR), glycerol-3-phosphate acyltransferase 1 and 4 (RhoprGpat1 and RhoprGpat4), and carnitine palmitoyltransferase 1 (RhoprCpt1). Although hemolymph lipid profile was not affected by RhoprIR disruption, the concentration of circulating vitellogenin was increased. In line with these changes, RhoprIR-deficient females exhibited smaller ovaries and a marked reduction in oviposition. Taken together, these findings support a key role of insulin receptor in nutrient homeostasis, lipid synthesis and egg production following a blood meal.


Subject(s)
Insect Proteins/deficiency , Insect Vectors/physiology , Oogenesis/genetics , Receptor, Insulin/deficiency , Rhodnius/physiology , Animals , Blood , Chagas Disease/parasitology , Chagas Disease/transmission , Fat Body/metabolism , Feeding Behavior , Female , Gene Expression Regulation, Developmental , Gene Knockdown Techniques , Hemolymph/chemistry , Humans , Insect Proteins/genetics , Insect Vectors/parasitology , Lipid Droplets/metabolism , Lipogenesis/physiology , Models, Animal , Ovary/metabolism , Rabbits , Receptor, Insulin/genetics , Rhodnius/parasitology , Triglycerides/analysis , Triglycerides/metabolism
2.
Insect Biochem Mol Biol ; 69: 51-60, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26163435

ABSTRACT

Adipokinetic hormone (AKH) has been associated with the control of energy metabolism in a large number of arthropod species due to its role on the stimulation of lipid, carbohydrate and amino acid mobilization/release. In the insect Rhodnius prolixus, a vector of Chagas' disease, triacylglycerol (TAG) stores must be mobilized to sustain the metabolic requirements during moments of exercise or starvation. Besides the recent identification of the R. prolixus AKH peptide, other components required for the AKH signaling cascade and its mode of action remain uncharacterized in this insect. In the present study, we identified and investigated the expression profile of the gene encoding the AKH receptor of R. prolixus (RhoprAkhr). This gene is highly conserved in comparison to other sequences already described and its transcript is abundant in the fat body and the flight muscle of the kissing bug. Moreover, RhoprAkhr expression is induced in the fat body at moments of increased TAG mobilization; the knockdown of this gene resulted in TAG accumulation both in fat body and flight muscle after starvation. The inhibition of Rhopr-AKHR transcription as well as the treatment of insects with the peptide Rhopr-AKH in its synthetic form altered the transcript levels of two genes involved in lipid metabolism, the acyl-CoA-binding protein-1 (RhoprAcbp1) and the mitochondrial glycerol-3-phosphate acyltransferase-1 (RhoprGpat1). These results indicate that the AKH receptor is regulated at transcriptional level and is required for TAG mobilization under starvation. In addition to the classical view of AKH as a direct regulator of enzymatic activity, we propose here that AKH signaling may account for the regulation of nutrient metabolism by affecting the expression profile of target genes.


Subject(s)
Insect Hormones/metabolism , Oligopeptides/metabolism , Pyrrolidonecarboxylic Acid/analogs & derivatives , Receptors, Cell Surface/genetics , Rhodnius/genetics , Rhodnius/metabolism , Triglycerides/metabolism , Animals , Fat Body/metabolism , Flight, Animal , Food Deprivation , Gene Expression Regulation , Muscle, Skeletal/metabolism , Pyrrolidonecarboxylic Acid/metabolism , Receptors, Cell Surface/metabolism , Signal Transduction
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