Synthesis and mobilization of glycogen and trehalose in adult male Rhodnius prolixus

Abstract

The vector of Chagas' disease, Rhodnius prolixus, feeds exclusively on blood. The blood meals are slowly digested, and these insects wait some weeks before the next meal. During the life of an insect, energy-requiring processes such as moulting, adult gonadal and reproductive growth, vitellogenesis, muscular activity, and fasting, lead to increased metabolism. Carbohydrates are a major source of energy and their mobilization is important. We determined the amounts of glycogen, trehalose, and glucose present in the fat body and/or hemolymph of adult males of R. prolixus and recorded the processes of accumulation and mobilization of these carbohydrates. We also tested our hypothesis that these processes are under endocrine control. The amount of glycogen in the fat body progressively increased until the fourth day after feeding (from 9.3+/-2.2 to 77. 3+/-7.5 microg/fat body), then declined to values around 36.3+/-4.9 microg/fat body on the fifteenth day after the blood meal. Glycogen synthesis was eliminated in decapitated insects and head-transplanted insects synthesized glycogen. The amount of trehalose in the fat body increased until the sixth day after feeding (from 16. 6+/-1.7 to 40. 6+/-5.3 nmol/fat body), decreased abruptly, and stabilized between days 7 and 15 at values ranging around 15-19 nmol/fat body. Decapitated insects did not synthesize trehalose after feeding, and this effect was reversed in head-transplanted insects. The concentration of trehalose in the hemolymph increased after the blood meal until the third day (from 0.07+/-0.01 to 0.75+/-0.05 mM) and at the fourth day it decreased until the ninth day (0.21+/-0.01 mM), when it increased again until the fourteenth day (0.79+/-0.06 mM) after the blood meal, and then declined again. In decapitated insects, trehalose concentrations did not increase soon after the blood meal and at the third day it was very low, but on the fourteenth day it was close to the control values. The concentration of glucose in the hemolymph of untreated insects remained low and constant (0.18+/-0.01 mM) during the 15 days after feeding, but in decapitated insects it progressively increased until the fifteenth day (2.00+/-0.10 mM). We recorded the highest trehalase activity in midgut, which was maximal at the eighth day after feeding (2,830+/-320 nmol of glucose/organ/h). We infer that in Rhodnius prolixus, the metabolism of glycogen, glucose, and trehalose are controlled by factors from the brain, according to physiological demands at different days after the blood meal.

Looking for reference genes for real‐time quantitative PCR experiments in Rhodnius prolixus (Hemiptera: Reduviidae)

“…Here, the expression of seven candidate genes was determined in the anterior and posterior midgut, ovary, fat body and flight muscle in adult female insects on the fourth day after a bloodmeal. On this day, R. prolixus metabolism is highly activated, as blood digestion is occurring in the intestinal tract (Grillo et al ., 2007; Ursic‐Bedoya et al ., 2008), nutrients are being accumulated in the fat body (Pontes et al ., 2008; Mariano et al ., 2009) and oocytes are growing at high rates (Atella et al ., 2005; Santos et al ., 2008). After analysis by ge N orm P lus and N orm F inder software, heat shock protein 70 kDa ( RpHSP70 ) and elongation factor 1 ( RpEF‐1 ) were indicated as the best reference genes in this kind of experiment (data not shown).…”

Germ band retraction as a landmark in glucose metabolism during Aedes aegypti embryogenesis

“…It was suggested that glycogen biosynthesis could be supported by concomitant gluconeogenesis [42]. On the other hand, during A. aegypti embryogenesis, PEPCK activity declined between 0 and 24 HAE (Figure 6B), suggesting the availability of other carbohydrates source in insects, such as trehalose [43-46], which should be mobilized and converted into glucose and/or glycogen.…”

cDNA cloning and characterization of two trehalases from Spodoptera litura (Lepidoptera; Noctuidade)

“…Carbohydrates are a primary source of energy for the maintenance of metabolism in insects (Mariano et al, 2009), and trehalose is the main carbohydrate in insects. Trehalose is present in almost all forms of life except mammals (Lee et al, 2001;Elbein et al, 2003;Frison et al, 2007;Silva et al, 2010).…”