Comp Biochem Physiol Part D Genomics Proteomics 2025 Oct 17;57:101657. doi: 10.1016/j.cbd.2025.101657.

Comprehensive analysis of metabolomic and transcriptomic provides insights on the phospholipid regulating LC-PUFAs accumulation in the gonads of sea urchin Strongylocentrotus intermedius.

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Phospholipids (PLs) are essential for long-chain polyunsaturated fatty acids (LC-PUFAs) accumulation in the gonads of Strongylocentrotus intermedius. However, the mechanism remains to be clarified. Based on previous studies, we hypothesized that S. intermedius might enhance LC-PUFAs accumulation in gonads via PL transport, PL remodeling, or de novo synthesis. Therefore, we formulated three feeds with different PLs and oil sources (palm oil + soybean lecithin (PO + SL), fish oil + soybean lecithin (FO + SL) and palm oil + krill oil (PO + KO)) to test the hypothesis. Each feed was randomly fed three tanks of S. intermedius for 60 days. Then, growth rate, gonad yield and development were monitored and followed by comprehensive analysis of metabolomic and transcriptomic in digestive tract and gonad. The results showed no significant difference in survival, growth rate and gonad yield among the dietary groups. The gonad development among the dietary groups was only significantly observed in male individuals, with the spermatocytes of S. intermedius fed PO + KO and FO + SL thicker and denser than those fed PO + SL. Metabolomic analysis showed that LC-PUFAs were mainly distributed at the sn-2 position of glycerolphospholipid (GP) and glycerolipids (GL), with LC-PUFAs possessing more unsaturated and longer carbon chains in the gonads than those in the digestive tract. The relative contents of LC-PUFAs in GP and GL were highest in the gonads of S. intermedius fed PO + KO and FO + SL, respectively. S. intermedius fed PO + SL showed unpredictable contents of LC-PUFAs at the sn-2 position of GP and GL deposited in their gonads, although no LC-PUFAs were present in this feed. The differential metabolites (DMs) between each comparison group were all enriched in steroid hormone synthesis pathway in digestive tract and gonads of S. intermedius. Transcriptomic analysis showed that the differential expressed genes (DEGs) between each comparison group were enriched in GO terms like phospholipid transport and fatty acid metabolism, and KEGG pathways fatty acid metabolism and linoleic acid metabolism. Notably, DMs in the digestive tract and DEGs in the gonads were all enriched in biosynthesis of unsaturated fatty acids pathway. Based on these results, it suggested that PLs have a direct promoting effect on LC-PUFA synthesis. Furthermore, PLs were hypothesized to facilitate LC-PUFA transport via PL remodeling and cholesterol co-transport mechanisms, thus enhancing LC-PUFAs accumulation in the gonads of S. intermedius. These findings provided insights into the mechanism of PLs regulating the gonad growth and development of S. intermedius.

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