Abstract
The present study aimed to determine if the long-chain MUFA cetoleic acid (22 : 1n-11) can improve the capacity to synthesise the health-promoting n-3 fatty acids EPA and DHA in human and fish models. Human hepatocytes (HepG2) and salmon primary hepatocytes were first enriched with cetoleic acid, and thereafter their capacities to convert radio-labelled 18 : 3n-3 (α-linolenic acid, ALA) to EPA and DHA were measured. Increased endogenous levels of cetoleic acid led to increased production of radio-labelled EPA + DHA in HepG2 by 40 % and EPA in salmon hepatocytes by 12 %. In order to verify if dietary intake of a fish oil rich in cetoleic acid would have the same beneficial effects on the n-3 fatty acid metabolic pathway in vivo as found in vitro, Atlantic salmon were fed four diets supplemented with either sardine oil low in cetoleic acid or herring oil high in cetoleic acid at two inclusion levels (Low or High). The diets were balanced for EPA + DHA content within the Low and within the High groups. The salmon were fed these diets from 110 to 242 g. The level of EPA + DHA in liver and whole-body retention of docosapentaenoic acid and EPA + DHA relative to what was eaten, increased with increased dietary cetoleic acid levels. Thus, it is concluded that cetoleic acid stimulated the synthesis of EPA and DHA from ALA in human HepG2 and of EPA in salmon hepatocytes in vitro and increased whole-body retention of EPA + DHA in salmon by 15 % points after dietary intake of cetoleic acid.
Highlights
The present study aimed to determine if the long-chain MUFA cetoleic acid (22 : 1n-11) can improve the capacity to synthesise the healthpromoting n-3 fatty acids EPA and DHA in human and fish models
L-15 Glutamax was obtained from Invitrogen, metacain from Norsk Medisinaldepot, laminin and chloroform from Merck Millipore, collagenase from Worthington, 14C-18 : 3n-3 from American Radiolabel Chemicals Inc., RNeasy Plus Mini Kit from Qiagen, Dulbecco's modified Eagle's medium (DMEM), PureLink Pro 96 RNA Purification Kit, PureLink Dnase set and primers from Thermo Fisher Scientific, SYBR Green I Master mix and LightCycler®480 from Roche Applied Science, TaqMan® Reverse Transcription Reagents from Applied Biosystems, cetoleic acid (22 : 1n-11) from BOC Sciences and lactate dehydrogenase assay from Abcam
When both cell types were supplemented with increasing doses from 0 to 80 μM of cetoleic acid to the culture media, the endogenous concentrations of cetoleic acid increased from 0·2 to 18·6 % in HepG2 cells and from 0·5 to 3·7 % in salmon hepatocytes (Fig. 1)
Summary
The present study aimed to determine if the long-chain MUFA cetoleic acid (22 : 1n-11) can improve the capacity to synthesise the healthpromoting n-3 fatty acids EPA and DHA in human and fish models. The efficiency of the conversion of ALA to EPA and DHA is quite low in both species but can be improved by different factors Both diet compositions, life stage, genotype, and growth influence the capacity for EPA and DHA synthesis in salmon[15,16,17,18,19,20]. The DHA status in humans on vegetarian or vegan diets has been shown to be lower than those on omnivore diets (reviewed by Burdge et al[31]), but there appears to be no evidence of increased DHA biosynthesis in these groups[32] This is in contradiction to what is found in Atlantic salmon, where deficiency in EPA and DHA leads to a significant increase in their innate capacities for EPA and DHA production form ALA[3,30]
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