# Dietary Supplementation with a 3-Selenoureidoindole Derivative Enhances Thermotolerance and Modifies the Hemolymph Amino Acid Profile in Silkworm (Bombyx mori)

## TL;DR

This study shows that a new selenium compound improves heat tolerance and changes amino acid levels in silkworms.

## Contribution

A novel 3-selenoureidoindole derivative is shown to enhance thermotolerance and alter amino acid profiles in silkworms.

## Key findings

- Selenium supplementation with 3-SeU-Ind increased silkworm survival under high-temperature stress.
- The compound upregulated antioxidant genes like MnSOD, CAT, GPX, and TrxR.
- Methionine and lysine levels in hemolymph were altered in a sex-specific manner.

## Abstract

Organic selenium supplements exhibit enhanced bioactivity and a broader safety dosage range compared to their inorganic counterparts, although their specific effects are contingent upon the compound’s structural composition. This study investigated the biological impacts of a novel organic selenium compound, specifically a 3-selenoureidoindole derivative, as a dietary selenium source in silkworms. The results indicated that selenium was effectively accumulated in the silkworms, leading to improved tolerance to high temperatures and an upregulation of antioxidant gene expression. Furthermore, the compound exerted sex-specific regulatory effects on methionine and lysine concentrations in the hemolymph. These findings contribute valuable insights into the development of organic selenium supplements.

The high bioavailability and low toxicity of organic selenium underscore its potential for nutritional fortification. This study investigated the biological effects of a novel 3-selenoureidoindole derivative (3-SeU-Ind) as a dietary selenium source in the invertebrate model organism silkworm (Bombyx mori). When reared on natural mulberry leaves, supplementation with 3-SeU-Ind (4–400 mg/L) had no significant effect on larval weight, pupal weight, or cocoon production performance. However, under compound diet conditions, the highest concentration (400 mg/L) significantly reduced both larval and pupal weights. Selenium was effectively accumulated in larval tissues and the pupal body. Under high-temperature stress, supplementation with 3-SeU-Ind (100 and 400 mg/L) significantly enhanced silkworm survival, which was associated with the upregulation of key antioxidant genes, including MnSOD, CAT, GPX, and TrxR. Furthermore, the supplementation altered methionine and lysine levels in the hemolymph in a sex-specific manner. Thus, 3-SeU-Ind demonstrated potential as a safe and effective selenium supplement.