Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
Aquatic Ecology, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
Sci Rep. 2023 Jan 19;13(1):1054. doi: 10.1038/s41598-022-24933-9.
Stable isotope analysis of individual compounds is emerging as a powerful tool to study nutrient origin and conversion in host-parasite systems. We measured the carbon isotope composition of amino acids and glucose in the cestode Schistocephalus solidus and in liver and muscle tissues of its second intermediate host, the three-spined stickleback (Gasterosteus aculeatus), over the course of 90 days in a controlled infection experiment. Similar linear regressions of δC values over time and low trophic fractionation of essential amino acids indicate that the parasite assimilates nutrients from sources closely connected to the liver metabolism of its host. Biosynthesis of glucose in the parasite might occur from the glucogenic precursors alanine, asparagine and glutamine and with an isotope fractionation of - 2 to - 3 ‰ from enzymatic reactions, while trophic fractionation of glycine, serine and threonine could be interpreted as extensive nutrient conversion to fuel parasitic growth through one-carbon metabolism. Trophic fractionation of amino acids between sticklebacks and their diets was slightly increased in infected compared to uninfected individuals, which could be caused by increased (immune-) metabolic activities due to parasitic infection. Our results show that compound-specific stable isotope analysis has unique opportunities to study host and parasite physiology.
稳定同位素分析单个化合物正成为研究宿主-寄生虫系统中营养物质来源和转化的有力工具。我们在一项控制感染实验中，测量了绦虫 Schistocephalus solidus 及其第二中间宿主三刺鱼（Gasterosteus aculeatus）肝脏和肌肉组织中氨基酸和葡萄糖的碳同位素组成，历时 90 天。δC 值随时间的相似线性回归和必需氨基酸的低营养分馏表明，寄生虫从与其宿主肝脏代谢密切相关的来源中吸收营养物质。寄生虫中葡萄糖的生物合成可能来自于生糖前体丙氨酸、天冬酰胺和谷氨酰胺，并通过酶促反应产生 -2 到 -3‰的同位素分馏，而甘氨酸、丝氨酸和苏氨酸的营养分馏可解释为通过一碳代谢将大量营养物质转化为寄生虫生长的燃料。与未感染个体相比，感染个体的鱼与其饮食之间的氨基酸营养分馏略有增加，这可能是由于寄生虫感染导致（免疫）代谢活动增加所致。我们的研究结果表明，化合物特异性稳定同位素分析在研究宿主和寄生虫生理学方面具有独特的机会。
