What You Eat Matters: Nutrient Inputs Alter the Metabolism and Neuropeptide Expression in Egyptian Cotton Leaf Worm, Spodoptera littoralis (Lepidoptera: Noctuidae).

Cansu Doğan,Umut Toprak,Alp Can,Kardelen K. Güzel,Dwayne D. Hegedus,Gözde Güney

doi:10.3389/fphys.2021.773688

Cansu Doğan, Umut Toprak + Show 4 more

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https://doi.org/10.3389/fphys.2021.773688

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Abstract

Lipids and carbohydrates are the two primary energy sources for both animals and insects. Energy homeostasis is under strict control by the neuroendocrine system, and disruption of energy homeostasis leads to the development of various disorders, such as obesity, diabetes, fatty liver syndrome, and cardiac dysfunction. One critical factor in this respect is feeding habits and diet composition. Insects are good models to study the physiological and biochemical background of the effect of diet on energy homeostasis and related disorders; however, most studies are based on a single model species, Drosophila melanogaster. In the current study, we examined the effects of four different diets, high fat (HFD), high sugar (HSD), calcium-rich (CRD), and a plant-based (PBD) on energy homeostasis in younger (third instar) and older (fifth instar) larvae of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae) in comparison to a regular artificial bean diet. Both HSD and HFD led to weight gain, while CRD had the opposite effect and PBD had no effect in fifth instar larvae and pupae. The pattern was the same for HSD and CRD in third instar larvae while a reduction in weight was detected with HFD and PBD. Larval development was shortest with the HSD, while HFD, CRD, and PBD led to retardation compared to the control. Triglyceride (TG) levels were higher with HFD, HSD, and PBD, with larger lipid droplet sizes, while CRD led to a reduction of TG levels and lipid droplet size. Trehalose levels were highest with HSD, while CRD led to a reduction at third instar larvae, and HFD and PBD had no effect. Fifth instar larvae had similar levels of trehalose with all diets. There was no difference in the expression of the genes encoding neuropeptides SpoliAKH and SpoliILP1-2 with different diets in third instar larvae, while all three genes were expressed primarily with HSD, and SpolisNPF was primarily expressed with HFD in fifth instar larvae. In summary, different diet treatments alter the development of insects, and energy and metabolic pathways through the regulation of peptide hormones.

Highlights

Energy homeostasis is essential to life, and lipids and carbohydrates are the primary energy sources for insects and animals
The highest body weight was detected with high sugar diet (HSD) and high fat diet (HFD), followed by the control diet and plant-based diet (PBD), while the lowest larval body weight was detected with calciumrich diet (CRD) (p < 0.05, Figure 1B), though the difference between PBD-CRD was not significant
The exact role of SpolisNPF needs to be elucidated in caterpillars, including S. littoralis. Both HSD and HFD led to increased weight gain, while CRD led to a reduced weight gain, and PBD did not alter the weight gain

Summary

Introduction

Energy homeostasis is essential to life, and lipids and carbohydrates are the primary energy sources for insects and animals. Drosophila, like many other insects, is easy to produce in large numbers with low cost, suitable for genetic modification and large-scale screens, capable of accumulating fats in a short period of time, allowing rapid observation of metabolic changes over its short lifespan It can be manipulated for different phenotypes (obese, lean, Type I or Type II diabetes, etc.) by artificial diets with different fat or carbohydrate levels (Baker and Thummel, 2007; Buch et al, 2008; Birse et al, 2010; Musselman et al, 2011; Heinrichsen and Haddad, 2012; Na et al, 2013; Liao et al, 2021)

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