Protein storage and reproduction increase in grasshoppers on a diet matched to the amino acids of egg yolk protein

Regulatory mechanisms of nitrogen homeostasis in insect growth and development

Nitrogen is an essential element for the synthesis of proteins, nucleic acids, and various other critical biological molecules in insects. The maintenance of nitrogen homeostasis in insects is achieved through a balance of dietary intake, metabolic conversion, and excretion. Insects primarily acquire nitrogen from their diet, which is subsequently metabolized into amino acids, proteins, and other vital biomolecules following digestion and absorption. Excess nitrogen is excreted in forms such as uric acid, allantoin, allantoic acid, urea, and ammonia. Disruptions in nitrogen regulation can result in ammonia toxicity and abnormal production or excretion of nitrogenous metabolites, including uric acid, ultimately impairing insect development and survival. This review examines the mechanisms underlying nitrogen homeostasis in insects, with a focus on the intricate regulatory roles of carbohydrate metabolism, amino acid metabolism, uric acid metabolism, urea and polyamine metabolism, ammonia transport pathways, and symbiotic interactions. By elucidating these processes, this review aims to enhance our understanding of insect nutritional metabolism and developmental biology, while offering novel perspectives for the development of more effective pest management strategies.

High-quality dietary protein (essential amino acids matched to reproductive needs) partially breaks the lifespan and reproduction trade-off in lubber grasshoppers

Finding interventions to break the trade-off between reproduction and lifespan can provide insight into physiological limitations of animals. Effects of dietary protein quality on the trade-off are currently unclear, but clarity could lead to better designed diets that match animal needs. Dietary amino acid blends matching yolk proteins support reproduction and extend lifespan in fruit flies. To test if this is conserved across species, we matched dietary amino acids to vitellogenin to test reproduction and lifespan in adult females of the lubber grasshopper. Specifically, we compared varying degrees of protein quality by manipulating dietary essential amino acids. We identified a high-quality protein diet (amino acids matched to vitellogenin, or reproductive needs) that increased reproduction and matched lifespan in comparison to diets that differed only in the ratios of essential amino acids (i.e., were isocaloric and isonitrogenous). All these diets had longer lifespan but lower reproductive output than fully fed controls. In a separate experiment, full reproduction was possible on the high-quality artificial diet when offered at a 78% higher protein quantity and with a larger lettuce supplement (~ 17% of ad libitum). Additionally, we observed that as dietary protein quality was decreased (i.e., diets were less matched to vitellogenin), reproduction was reduced, and lifespan was extended in the more extreme scenarios. Taken together, these results indicate that the balance of dietary essential amino acids plays an important role in the lifespan and reproduction trade-off, while more work needs to be conducted to find the optimal diet mix for this species.

How Nutrients Mediate the Impacts of Global Change on Locust Outbreaks

Locusts are grasshoppers that can migrate en masse and devastate food security. Plant nutrient content is a key variable influencing population dynamics, but the relationship is not straightforward. For an herbivore, plant quality depends not only on the balance of nutrients and antinutrients in plant tissues, which is influenced by land use and climate change, but also on the nutritional state and demands of the herbivore, as well as its capacity to extract nutrients from host plants. In contrast to the concept of a positive relationship between nitrogen or protein concentration and herbivore performance, a five-decade review of lab and field studies indicates that equating plant N to plant quality is misleading because grasshoppers respond negatively or neutrally to increasing plant N just as often as they respond positively. For locusts specifically, low-N environments are actually beneficial because they supply high energy rates that support migration. Therefore, intensive land use, such as continuous grazing or cropping, and elevated ambient CO2 levels that decrease the protein:carbohydrate ratios of plants are predicted to broadly promote locust outbreaks.

Exome-informed formulations of food proteins enhance body growth and feed conversion efficiency in ad libitum-fed mice

Meeting requirements for dietary proteins, especially of essential amino acids (EAAs), is critical for the life-long health of living organisms. However, defining EAA targets for preparing biologically-matched nutrition that satisfies metabolic requirements for protein remains challenging. Previous research has shown the advantages of 'exome matching' in representing the specific requirement of dietary AAs, where the target dietary AA profile was derived from in silico translation of the genome of an organism, specifically responsible for protein expression (the 'exome'). However, past studies have assessed these effects in only one sex, for few parameters (body mass and composition), and have used purified diets in which protein is supplied as a mixture of individual AAs. Here, for the first time, we utilise a computational method to guide the formulation of custom protein blends and test if exome matching can be achieved at the intact protein level, through blending standard protein ingredients, ultimately leading to optimal growth, longevity and reproductive function. Mice were provided ad libitum (ad lib) access to one of the four iso-energetic protein-limited diets, two matched and two mis-matched to the mouse exome target, and fed at a fixed protein energy level of 6.2%. During or following 13-weeks of feeding, the food intake, body growth, composition and reproductive functions were measured. Compared to the two mis-matched diets, male and female animals on the exome-matched diet with protein digestibility correction applied, exhibited significantly improved growth rates and final body mass. The feed conversion efficiency in the same diet was also increased by 62% and 40% over the worst diets for males and females, respectively. Male, not female, exhibited higher accretion of lean body mass with the matched, digestibility-corrected diet. All reproductive function measures in both sexes were comparable among diets, with the exception of testicular daily sperm production in males, which was higher in the two matched diets versus the mis-matched diets. The results collectively demonstrate the pronounced advantages of exome-matching in supporting body growth and improving feed conversion efficiency in both sexes. However, the potential impact of this approach in enhancing fertility needs further investigation.

The effects of dietary amino acid balance on post-embryonic development in a lubber grasshopper

Effects of dietary protein quality on insect development (not just growth) are unclear. Dietary amino acid blends matching yolk proteins support reproduction and juvenile development in Drosophila melanogaster. We matched amino acids to vitellogenin and tested development of juvenile male lubber grasshoppers, which do not produce vitellogenin. Last instars were fed classic dry diets with amino acids substituted for proteins. Matching amino acids to vitellogenin allowed molting to adulthood, while an unmatched isonitrogenous diet did not. Health on dry diets was poor, so we developed wet diets with agar, horse feed, and amino acids. Juveniles fed these diets matched to vitellogenin developed comparably to juveniles fed lettuce. However, wet diets with amino acids dissimilar to vitellogenin (low-quality) slowed development but maintained size at adulthood. We observed no compensatory feeding on low-quality diets. Theory suggests accumulation of proteins permits development. To detect a threshold, we started last juvenile instars on high-quality diets, then abruptly switched them to low-qualities diets. When switched to the poor-quality diet at 6d, grasshoppers molted at a similar age (∼17d) to grasshoppers continuously on the high-quality diet. Total hemolymph proteins levels were unaffected by the timing of diet switches. Last, methionine is essential but can be noxious at high levels. Diets with low-quality protein except for methionine slowed growth early but did not alter the time or size at molt. Overall, the feeding threshold is solely due to essential amino acids, and low-quality protein diets slowed development but did not affect adult size.