Background/Aims: Sex hormones may influence the activity of enzymes which are involved in the synthesis of long-chain polyunsaturated fatty acids. The objective of this review was to assess the role of gender in determining the fatty acid composition of human samples, like plasma and erythrocyte membrane lipids, and adipose tissue. Methods: The method included a structured search strategy on MEDLINE, Scopus and the Cochrane databases, with formal inclusion/exclusion criteria, data extraction procedure and meta-analysis. Results: We evaluated 51 publications, dated from 1975 to 2011. Meta-analysis showed significantly lower values of both arachidonic acid (AA) and docosahexaenoic acid (DHA) in total plasma lipids (32 and 33 studies) and in plasma phospholipids (PL; 21 and 23 studies) in men than in women. Primary analysis of the phospholipid fraction showed the mean difference in AA to be 0.42% weight/weight (95% CI: 0.18–0.65, n = 7,769) and in DHA 0.37% weight/weight (95% CI: 0.24–0.51, n = 8,541), while there was no gender difference in the values of linoleic acid and α-linolenic acid. Conclusions: This systematic review based on 51 publications showed significantly lower contribution of AA and DHA to plasma total lipids and plasma PL in men than in women. Gender distribution should be regarded as a significant potential confounding factor in every study assessing data on fatty acid composition.

There appears to be a range of useful biomarkers of DHA status in humans, but further research is needed to characterize which work best in particular population subgroups.

In this study, percentage contributions of arachidonic and docosahexaenoic acids as well as the those of the intermediary metabolites of essential fatty acid metabolism were all significantly higher in early human milk samples of mothers giving birth to very low birth weight preterm as compared with full-term infants.

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Using appropriate statistical methodology, we report null associations. These findings may partly be attributable to several cohort-specific factors associated with breastfeeding and breastmilk collection. Further studies could improve on ours by analyzing samples of breastmilk and formula and by including all children for whom these are exclusively or together the major source of fatty acids in the first months of life.

Background: Fatty acid composition of human milk (HM) is known to change considerably during lactation. However, we were unable to find data on changes of fatty acid composition of HM during the very early phase of lactation, i.e. in the first week of life. Subjects and Methods: HM samples were obtained from 18 healthy lactating women every day during the first week and thereafter on the 14th and 28th days of lactation. Fatty acid composition of colostrum and mature HM samples was determined by high-resolution capillary gas-liquid chromatography. Results: Values of the n-6 essential fatty acid, linoleic acid, in HM did not change significantly during the first month of lactation, whereas values of the n-3 essential fatty acid, α-linolenic acid, showed significant increases during the first 2 weeks of lactation (1st day: 0.49 [0.12], % weight/weight, median [ranges from the 1st to the 3rd quartile], 14th day: 0.69 [0.31], p < 0.05). In contrast, values of the n-6 long-chain metabolites, eicosadienoic-, dihomo-γ-linolenic- and arachidonic acid, as well as the values of the n-3 long-chain metabolites, eicosatrienoic-, and eicosapentaenoic acid exhibited significant decreases during the entire period investigated. The principal n-3 long-chain metabolite, docosahexaenoic acid, showed a significant increase between the 3rd and 14th days, but a significant decrease between the 14th and 28th days (3rd day: 0.15 [0.13], 14th day: 0.28 [0.11], p < 0.05, 28th day: 0.19 [0.12], p < 0.01). There were statistically significant positive correlations between arachidonic and docosahexaenoic acid values on the 1st (r = 0.67, p < 0.01), 5th (r = 0.56, p < 0.05) and the 6th (r = 0.53, p < 0.05) days of lactation. Conclusion: Fatty acid composition of HM changes significantly even during the first week of lactation. The lack of positive correlation between essential fatty acids and their long-chain metabolites suggests that it is not only the availability of essential fatty acids that influences the fatty acid composition of human colostrum.

9 Abstract Nuclear hormone receptors are transcription 10 factors that can be activated by nutrition-derived ligands 11 and alter the expression of various specific target genes. 12 Stearoyl-Coenzyme A desaturase (SCD1) converts palmitic 13 acid (16:0) to palmitoleic acid (16:1n-7) as well as stearic 14 acid (18:0) to oleic acid (18:1n-9). At the same time, 15 elongase 6 (ELOVL6) elongates 16:1n-7 and 18:1n-9 to 16 vaccenic acid (18:1n-7) and eicosenoic acid (20:1n-9). We 17 examined how synthetic selective ligands of nuclear hor-18 mone receptors alter the gene expression of hepatic 19 enzymes in mice. In addition, we examined how the regu-20 lation of these two enzymes influences fatty acid compo-21 sition of phospholipids in liver and plasma. Mice were 22 gavaged daily for 1 week with synthetic ligands of perox-23 isome proliferator-activated receptor (PPAR) a, b/d, c, liver 24 X receptor (LXR), retinoic acid receptor (RAR) and reti-25 noid-X receptor (RXR) for 1 week. Phospholipids from 26 liver and plasma were analysed using ESI-MS/MS and GC 27 after saponification. Hepatic gene expression of SCD1 and 28 ELOVL6 was measured using QRT-PCR. SCD1 and 29 ELOVL6 expression increased after the gavage of LXR and 30 RXR ligands. The analysis of fatty acid composition of total 31 phospholipids in plasma and liver showed increased per-32 centage contributions of the SCD1 and ELOVL6 products 33 18:1n-9, 18:1n-7 and 20:1n-9 after LXR and RXR ligand 34 application. Analysis of total phospholipids from plasma 35 and liver revealed a significant increase in monounsaturated 36 fatty acids bound in phosphatidylcholine (PtdCho)