Higher erythrocyte 22:6n-3 and 22:5n-6, and lower 22:5n-3 suggest higher Delta-4-desaturation capacity in women of childbearing age

Sex- and Age-Related Metabolic Characteristics of Serum Free Fatty Acids in Healthy Chinese Adults

Free fatty acids (FFAs), also named nonesterified fatty acids, largely originate from the lipolysis of triacylglycerol stored in adipose tissue. Despite extensive research on sex- and age-dependent effects on lipolysis and lipid mobilization of adipose tissue, the primary differences in the metabolic characteristics of circulating FFAs among normal-weight healthy men and women during aging are still unclear. Here, we measured the concentrations of 45 FFAs in fasting sera of two Chinese community-based studies consisting of 201 metabolically healthy normal-weight adults to ascertain the associations of sex and age with FFA compositions and their upstream and downstream relations. Results showed greater conversions toward n-3 polyunsaturated fatty acids of docosahexaenoic acid and n-6 of docosapentaenoic acid from their precursors in women than in men. Meanwhile, there were significantly positive correlations between the concentrations of a panel of saturated fatty acids with straight chain or branched chain and age in women, whereas no association was found in men. These findings highlight that sex and age should be considered as the potential confounding factors in assessing the risk for metabolic disturbance using FFA biomarkers.

Eicosanoids: Atherosclerosis and cardiometabolic health

Cardiovascular diseases (CVD) have been the leading causes of death in the U.S. for nearly a century. Numerous studies have linked eicosanoids to cardiometabolic disease. Objectives and Methods: This review summaries recent advances and innovative research in eicosanoids and CVD. Numerous review articles and their original human or animal studies were assessed in the relevant and recent studies.

OUTCOME

We identified and discussed recent trends in eicosanoids known for their roles in CVD. Their subsequent relationships were assessed for any possible implications associated with consumption of different dietary lipids, essentially omega fatty acids. Eicosanoids have been heavily sought after over recent decades for their direct role in mediating the enhancement and resolution of acute immune responses. Given the short half-life of these oxidized lipid metabolites, studies on atherosclerosis have had to rely on the metabolites that are actively involved in eicosanoid production, signaling or redox reactions as markers for atherosclerosis-related molecular behaviors.

CONCLUSION

Further investigations expending current knowledge, should be applied to narrow the specific class and species of eicosanoids responsible for inciting inflammation especially in the context of recent clinical studies assessing the role of dietary lipid in cardiovascular diseases.

Kinetics of docosahexaenoic acid ethyl ester accumulation in dog plasma and brain

This study explores dog plasma and brain fatty acid composition achieved after long-term supplementation at high DHA doses. A 90% concentrate of DHA Ethyl Ester (DHA-EE) administered by oral gavage to Beagle dogs at doses of 100, 500, 1000, and 2000mg/kg bw/day for 8 weeks resulted in DHA increases in both plasma and brain. In a subsequent 9-month study, DHA-EE was administered at 150, 1000 and 2000mg/kg bw/day. Plasma DHA increased between 150 and 1000mg/kg bw/day but not between 1000 and 2000mg/kg bw/day and there were increases from Day 1to 92 but not between days 92 and 273. Doses >500mg/kg bw/day in the 8-week and all doses in the 9-month study resulted in DHA increases in the brain. The dose of 150mg/k gbw/day is sufficient to achieve maximal brain concentrations if DHA is administered chronically. For shorter than 6 months of supplementation, higher doses are required.

Differences in long chain polyunsaturates composition and metabolism in male and female rats

Human studies and some animal work have shown more docosahexaenoic acid (DHA) and arachidonic acid (ARA) was accumulated or converted from precursors in females compared to males. This study explored in-depth the effect of gender on fatty acid composition and polyunsaturated fatty acid metabolism in rats fed one of two well-defined diets containing 10% total fat. One diet contained 15% of linoleic acid (LA) and 3% of α-linolenic acid (ALA) of the total fatty acids (LA+ALA diet), while the other diet contained 15% LA and 0.05% ALA (LA diet). At the age of 20 weeks, all animals were orally administered a single dose of a mixture of deuterium-labeled LA and ALA. Caudal venous blood was then drawn at 0, 2, 4, 8, 12, 24, 48, 96 and 168h. The concentrations of the deuterated precursors and their metabolites in plasma total lipids were quantified by GC/MS negative chemical ionization. Endogenous fatty acids were quantified by GC/FID analysis. When expressed as the percentage of oral dosage, female rats accumulated more precursors and more products, deuterated DHA and deuterated n-6 docosapentaenoic acid (²H₅-DPAn-6), in plasma than did male rats in both the LA+ALA diet and the LA diet. For the endogenous non-labeled PUFA, greater concentrations of DHA and DPAn-6 were similarly observed in female rats compared to males within each diet. A lower concentration of non-labeled ARA was observed only in female rats fed the LA+ALA diet. In summary, greater endogenous and exogenous DHA and DPAn-6 was observed in female rat plasma and this was independent of dietary ALA status.

Gender differences in the long-chain polyunsaturated fatty acid status: systematic review of 51 publications

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.

Tissue-specific sex differences in docosahexaenoic acid and Δ6-desaturase in rats fed a standard chow diet

Docosahexaenoic acid (DHA, 22:6n-3) is higher in the blood and tissues of females relative to males, but the underlying mechanism is not clear. The present study examined the expression of enzymes involved in the biosynthesis of DHA from short-chain n-3 polyunsaturated fatty acids in male and female rats (n = 6 for each sex). Rats were maintained on an AIN-93G diet and sacrificed at 14 weeks of age after an overnight fast. Plasma, erythrocytes, liver, heart, and brain were collected for fatty acid composition analysis and the determination of enzyme and transcription factor expression by RT-PCR and immunoblotting. Females had higher DHA concentrations in the total lipids of liver, plasma, erythrocyte, and heart (53%, 75%, 36%, and 25% higher, respectively, compared with males) with no sex differences in brain DHA concentrations. The mRNA content of Δ5-desaturase, Δ6-desaturase, and elongase 2 was 1.0-, 1.4-, and 1.1-fold higher, respectively, in the livers of female rats compared with males, with no differences in the hearts or brains. The protein content of Δ6-desaturase was also higher in females. Higher hepatic mRNA of sterol-regulatory element-binding protein 1-c and estrogen receptor α in the females suggests that lipogenic and estrogen signaling mechanisms are involved. The sex difference in DHA concentration is tissue specific and is associated with higher Δ6-desaturase expression in females relative to males, which appears to be limited to the liver.

Sex-specific differences in essential fatty acid metabolism

Sex hormones may influence the enzymatic synthesis of long-chain polyunsaturated fatty acids (LC-PUFAs), which may lead to sex-specific differences in LC-PUFA status. Isotope studies with U-(13)C α-linolenic acid (ALA) have shown a considerably higher conversion rate of ALA to n-3 (omega-3) LC-PUFAs in women than in men. A review of the literature generally suggested that there was a higher contribution of arachidonic acid (AA) and docosahexaenoic acid (DHA) in blood lipids in women than in men; however, sex-specific differences were not seen in every study. The fatty acid composition of plasma phospholipids was recently reported separately for a large group of women and men (n > 3000) living in 15 regions of Europe. The contributions of saturated and monounsaturated fatty acids were higher, whereas those of AA and DHA were lower in men than in women; however, sex explained only ≈ 2% of the variability of plasma phospholipid DHA values. Results reported from a limited number of randomized controlled trials of perinatal LC-PUFA supplementation have, on occasion, shown sex-specific differences in some outcomes; however, the heterogeneity both in the interventions and outcomes measured made it difficult to draw conclusions on the direction or the extent of the effects. Data summarized in the current review highlight the importance of planning a subgroup analysis by sex in perinatal LC-PUFA supplementation trials.

Influence of gender on DHA synthesis: the response of rat liver to low dietary α-linolenic acid evidences higher ω3 ∆4-desaturation index in females

PURPOSE

The conversion rate of α-linolenic acid (ALA) into docosahexaenoic acid (DHA) is determined by dietary and non-dietary factors. Higher capacity of DHA synthesis has been evidenced in females, indicating that sex factors influence the conversion pathway. To evaluate the extent to which sexual dimorphism of DHA synthesis is subordinated to nutritional handling, we measured the ω3 ∆4-desaturation index in male and female rats receiving adequate or inadequate amounts of ALA. The ω3 ∆4-desaturation index was drawn from the DHA to docosapentaenoic acid (ω3DPA) ratio in liver phospholipids.

METHODS

Male and female rats born to ω3-deficient dams were fed a supplemented diet supplying low, inadequate, intermediate, or adequate ALA (5, 20, 100, or 300 mg ALA/100 g diet, respectively). Control rats from both gender received the adequate diet from fetal life.

RESULTS

Compared with control, low ALA feeding induced the ω3 ∆4-desaturation index to increase by 38 and 70% in the phosphatidylethanolamine fraction of males and females, respectively, and by 67% in phosphatidylcholine in females only. Supplementations with increased doses of ALA progressively smoothed this gender effect. Moreover, the analysis of our data from a previous study shows that ovariectomy decreased, whereas estradiol treatment increased the ω3 index to values comparable with those of diet-matched males and intact females, respectively.

CONCLUSION

Females are more prone than males to increase their index of ω3 ∆4-desaturation, especially in response to low supplies in ALA. Estradiol supports the ω3 index, suggesting that this hormone plays a role in the effect of gender on DHA synthesis.

Alcohol consumption and n-3 polyunsaturated fatty acids in healthy men and women from 3 European populations

BACKGROUND

Because high dietary and blood n-3 (omega-3) fatty acids (FAs) are protective against coronary heart disease and sudden cardiac death, the alcohol-associated increase in blood n-3 FAs could be considered an original mechanism of alcohol's cardioprotective effect.

OBJECTIVE

Our objective was to assess whether alcohol consumption is associated with concentrations of very-long-chain "marine" (eg, fish oil) n-3 FAs both in plasma and in red blood cell membranes.

DESIGN

In the framework of the IMMIDIET (Dietary Habit Profile in European Communities with Different Risk of Myocardial Infarction: the Impact of Migration as a Model of Gene-Environment Interaction) Project, 1604 subjects (802 women-men pairs), aged 26-65 y, were enrolled in Italy, Belgium, and England. A 1-y-recall food-frequency questionnaire was used to evaluate dietary intake.

RESULTS

In fully adjusted multivariate analyses, alcohol intake was positively associated with plasma eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and EPA + DHA concentrations (P < 0.0001, P = 0.036, and P = 0.002, respectively) in women and with EPA and the EPA + DHA index in red blood cells (P < 0.0001 and P = 0.037, respectively). In men, only plasma and red blood cell EPA concentrations were associated with alcohol intake (P = 0.003 and P = 0.004, respectively). Stratified analyses showed an association between alcohol and both plasma and red cell EPA (P = 0.008 and P = 0.002, respectively), DHA (P = 0.014 and P = 0.008, respectively), and the EPA + DHA index (P = 0.010 and P = 0.006, respectively) in wine drinkers, whereas no association was found in those who drink beer and spirits.

CONCLUSIONS

Alcohol intake was associated with higher plasma and red blood cell concentrations of marine n-3 FAs. Components of wine other than alcohol (polyphenols) might exert these effects. Part of the alcohol-induced cardioprotection may be mediated through increased marine n-3 FAs.

n-3 fatty acid enrichment of edible tissue of poultry: a review

There is clear evidence of the nutritional benefits of consuming long-chain n-3 PUFA, which are found predominantly in oily fish. However, oily fish consumption, particularly in the United Kingdom, is declining, as is the consumption of all meats with the exception of poultry, which has increased in consumption by 73% in the last 30 yr. This pattern, if less marked, is reflected throughout Europe, and therefore one means of increasing long-chain n-3 PUFA consumption would be to increase the long-chain n-3 PUFA content in the edible tissues of poultry. This review considers the feasibility of doing this, concentrating particularly on chickens and turkeys. It begins by summarizing the benefits to human health of consuming greater quantities of n-3 FA and the sources of n-3 PUFA in the human diet. The literature on altering the FA composition of poultry meat is then reviewed, and the factors affecting the incorporation of n-3 PUFA into edible tissues of poultry are investigated. The concentration of alpha-linolenic acid (ALA) in the edible tissues of poultry is readily increased by increasing the concentration of ALA in the birds' diet (particularly meat with skin, and dark meat to a greater extent than white meat). The concentration of EPA in both white and dark meat is also increased when the birds' diet is supplemented with EPA, although supplementing the diet with the precursor (ALA) does not result in a noticeable increase in EPA content in the edible tissues. Although supplementing the birds' diets with relatively high concentrations of DHA does result in an increased concentration of DHA in the tissues, the relationship between dietary and tissue concentrations of DHA is much weaker than that observed with ALA and EPA. The impact that altering the FA composition of edible poultry tissue may have on the organoleptic and storage qualities of poultry products is also considered.

Alpha-linolenic acid metabolism in men and women: nutritional and biological implications

PURPOSE OF REVIEW

This review critically evaluates current knowledge of alpha-linolenic acid metabolism in adult humans based on the findings of studies using stable isotope tracers and on increased dietary alpha-linolenic acid intake. The relative roles of alpha-linolenic acid and of longer-chain polyunsaturated fatty acids in cell structure and function are discussed together with an overview of the major metabolic fates of alpha-linolenic acid. The extent of partitioning towards beta-oxidation and carbon recycling in humans is described. The use and limitations of stable isotope tracers to estimate alpha-linolenic acid desaturation and elongation are discussed. A consensus view of the extent of alpha-linolenic acid conversion to longer-chain fatty acids in humans is presented. The extent to which increasing dietary alpha-linolenic acid intake alters the concentrations of longer-chain n-3 fatty acids is described. The biological and nutritional implications of these findings are discussed.

RECENT FINDINGS

Conversion of alpha-linolenic acid to eicosapentaenoic acid is limited in men and further transformation to docosahexaenoic acid is very low. A lower proportion of alpha-linolenic acid is used as a substrate for beta-oxidation in women compared with men, while the fractional conversion to longer-chain fatty acids is greater, possibly due to the regulatory effects of oestrogen.

SUMMARY

Overall, alpha-linolenic acid appears to be a limited source of longer-chain n-3 fatty acids in man and so adequate intakes of preformed n-3 polyunsaturated fatty acids, in particular docosahexaenoic acid, may be important for maintaining optimal tissue function. Capacity to upregulate alpha-linolenic acid transformation in women may be important for meeting the demands of the fetus and neonate for docosahexaenoic acid.