Study of Synthesis Pathways of the Essential Polyunsaturated Fatty Acid 20:5n-3 in the Diatom Chaetoceros Muelleri Using 13C-Isotope Labeling

The present study sought to characterize the synthesis pathways producing the essential polyunsaturated fatty acid (PUFA) 20:5n-3 (EPA). For this, the incorporation of 13C was experimentally monitored into 10 fatty acids (FA) during the growth of the diatom Chaetoceros muelleri for 24 h. Chaetoceros muelleri preferentially and quickly incorporated 13C into C18 PUFAs such as 18:2n-6 and 18:3n-6 as well as 16:0 and 16:1n-7, which were thus highly 13C-enriched. During the experiment, 20:5n-3 and 16:3n-4 were among the least-enriched fatty acids. The calculation of the enrichment percentage ratio of a fatty acid B over its suspected precursor A allowed us to suggest that the diatom produced 20:5n-3 (EPA) by a combination between the n-3 (via 18:4n-3) and n-6 (via 18:3n-6 and 20:4n-6) synthesis pathways as well as the alternative ω-3 desaturase pathway (via 20:4n-6). In addition, as FA from polar lipids were generally more enriched in 13C than FA from neutral lipids, particularly for 18:1n-9, 18:2n-6 and 18:3n-6, the existence of acyl-editing mechanisms and connectivity between polar and neutral lipid fatty acid pools were also hypothesized. Because 16:3n-4 and 20:5n-3 presented the same concentration and enrichment dynamics, a structural and metabolic link was proposed between these two PUFAs in C. muelleri.

Effect of dietary alpha-linolenic acid and linoleic acid level on growth performance, carcass and meat characteristics of Thai indigenous growing pigs

Presently, indigenous pig farming is relatively growing in Thailand, because Thai consumers increasingly prefer the meat of indigenous pigs. Generally, indigenous pigs tend to store more fat in their carcass than pigs of commercial breeds. The nature of the dietary fat source may have an effect on fat deposition processes in indigenous pigs and subsequently on carcass and meat characteristics. For example, alpha-linolenic acid (ALA, C18:3, n-3) is an essential polyunsaturated fatty acid that is more preferentially oxidized in the body than linoleic acid (LA, C18:2, n-6) and other fatty acids. Therefore, the supplementation of ALA in pig diets should have a more beneficial effect on animal performance than LA supplementation. However, some adverse effects, e.g. meat characteristics, might result from a higher level of ALA supplementation as well. Thus, the aim of this study was to specify the effect of dietary supplementation of ALA versus LA on growth performance, carcass and meat characteristics of pigs.