Investigating the potential of dietary iron supplementation to enhance long-chain polyunsaturated fatty acid biosynthesis in Hediste diversicolor

Fatty acyl desaturases are nutritionally regulated and depend on iron (Fe) for optimal activity. We hypothesised that dietary Fe supplementation, under conditions promoting desaturase upregulation, can enhance desaturase activity and improve n-3 LC-PUFA biosynthesis in invertebrates. The present study aimed to evaluate the effects of dietary Fe supplementation on LC-PUFA biosynthesis in H. diversicolor, a commercially important polychaete, using both In vitro and in vivo approaches. The in vitro assays revealed that Fe supplementation, from both inorganic (FeSO₄) and organic (ProPath^® Fe) sources, has potential to increase desaturase activity, particularly on the H. diversicolor methyl-end desaturase ωx2, under high-expression conditions simulated in yeast. In contrast, in vivo feeding trial showed no significant differences in LC-PUFA composition of H. diversicolor fed Fe-supplemented diets compared to controls. This apparent discrepancy may be due to the LC-PUFA-free diet not sufficiently upregulating fatty acyl desaturases, leading to no increased Fe demand for enzyme activity. Alternatively, although the LC-PUFA-free diet may have triggered desaturase upregulation, the expected effects of Fe supplementation on desaturase activity and LC-PUFA content were not observed. This suggests Fe was not a limiting factor, even in the control group.