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Abstract Background Bioavailability of omega-3 fatty acids (FA) depends on their chemical form. Superior bioavailability has been suggested for phospholipid (PL) bound omega-3 FA in krill oil, but identical doses of different chemical forms have not been compared. Methods In a double-blinded crossover trial, we compared the uptake of three EPA+DHA formulations derived from fish oil (re-esterified triacylglycerides [rTAG], ethyl-esters [EE]) and krill oil (mainly PL). Changes of the FA compositions in plasma PL were used as a proxy for bioavailability. Twelve healthy young men (mean age 31 y) were randomized to 1680 mg EPA+DHA given either as rTAG, EE or krill oil. FA levels in plasma PL were analyzed pre-dose and 2, 4, 6, 8, 24, 48, and 72 h after capsule ingestion. Additionally, the proportion of free EPA and DHA in the applied supplements was analyzed. Results The highest incorporation of EPA+DHA into plasma PL was provoked by krill oil (mean AUC0-72 h: 80.03 ± 34.71%*h), followed by fish oil rTAG (mean AUC0-72 h: 59.78 ± 36.75%*h) and EE (mean AUC0-72 h: 47.53 ± 38.42%*h). Due to high standard deviation values, there were no significant differences for DHA and the sum of EPA+DHA levels between the three treatments. However, a trend (p = 0.057) was observed for the differences in EPA bioavailability. Statistical pair-wise group comparison's revealed a trend (p = 0.086) between rTAG and krill oil. FA analysis of the supplements showed that the krill oil sample contained 22% of the total EPA amount as free EPA and 21% of the total DHA amount as free DHA, while the two fish oil samples did not contain any free FA. Conclusion Further studies with a larger sample size carried out over a longer period are needed to substantiate our findings and to determine differences in EPA+DHA bioavailability between three common chemical forms of LC n-3 FA (rTAG, EE and krill oil). The unexpected high content of free EPA and DHA in krill oil, which might have a significant influence on the availability of EPA+DHA from krill oil, should be investigated in more depth and taken into consideration in future trials.

Introduction: Ingestion of long-chain n-3 PUFA effectively decreases serum triacylglycerol (TAG) levels and increases the Omega-3 Index, defined as the % of EPA and DHA in erythrocyte fatty acids. However, it remains unclear whether there is a relationship between the Omega-3 Index increase (ΔO3I increase) and the TAG level decrease (ΔTAG). We hypothesized that TAG reduction is strongly depended on Omega-3 Index increase., Subjects and Methods: Secondary analyses of data from a former double-blind placebo-controlled trial in which 150 dyslipidemic statin-treated subjects were randomized to four capsules of fish oil daily either as re-esterified TAG or ethyl esters in identical doses (1.01 g EPA+0.67 g DHA) or corn oil as a placebo for a period of six month., Results: 108 subjects fulfilled the criteria of the current study protocol and were included in the analyses. A weak but significant negative correlation between ΔO3I and ΔTAG was observed (r=-0.211, p<0.05). However, the relation between ΔO3I and serum ΔTAG was not linear (coefficients of determination R(2): 0.044). After sub-grouping the study population into Omega-3 Index response groups, the group with a mean ΔO3I of>4% after six months of n-3 PUFA treatment demonstrated the greatest TAG reduction., Discussion and Conclusions: A weak association between Omega-3 Index increase and TAG level decrease was found. This may be explained by highly fluctuating TAG levels, a large inter-individual difference in response of the Omega-3 Index, a cohort of subjects with only slightly elevated TAG levels and high Omega-3 Index values at baseline, and possibly to insufficient statistical power. Since there was no strong association between Omega-3 Index increase and the TAG level decrease, we conclude that changes in serum TAG levels are not a viable substitute for the Omega-3 Index to monitor treatment with EPA and DHA., (Copyright © 2014. Published by Elsevier Ltd.)

We sought to identify associations of basal metabolic rate (BMR) with morphological traits in laboratory mice. In order to expand the body mass (BM) range at the intra-strain level, and to minimize relevant genetic variation, we used male and female wild type mice (C3HeB/FeJ) and previously unpublished ENU-induced dwarf mutant littermates (David mice), covering a body mass range from 13.5 g through 32.3 g. BMR was measured at 30 degrees C, mice were killed by means of CO(2 )overdose, and body composition (fat mass and lean mass) was subsequently analyzed by dual X-ray absorptiometry (DEXA), after which mice were dissected into 12 (males) and 10 (females) components, respectively. Across the 44 individuals, 43% of the variation in the basal rates of metabolism was associated with BM. The latter explained 47% to 98% of the variability in morphology of the different tissues. Our results demonstrate that sex is a major determinant of body composition and BMR in mice: when adjusted for BM, females contained many larger organs, more fat mass, and less lean mass compared to males. This could be associated with a higher mass adjusted BMR in females. Once the dominant effects of sex and BM on BMR and tissue mass were removed, and after accounting for multiple comparisons, no further significant association between individual variation in BMR and tissue mass emerged.