Marine lipids
Total lipids of these tissues, compartments and faeces were extracted
by the procedure of Folch (Folch et al., 1957). Then, a known amount
of internal standard (diheptadecanoyl phosphatidylcholine and dinonadecanoyl triglyceride) was added and lipids were transmethylated
using 10% boron trifluoride in methanol (Fluka, Socolab, Paris, France).
The fatty methyl esters were separated by gas liquid chromatography
using a Carlo Erba 4180 gas chromatograph equipped with a CP wax
52 CB bonded fused-silica capillary column (Chrompack, Les Ulis,
France) as previously described (Guesnet et al., 1997).
For the whole body (n-3) fatty acid balance, the difference between the
intake and the sum of the faecal excretion and accumulation equalled
the apparent β-oxidation (i.e. disappearance). The accumulation of
other (n-3) fatty acids 20:5 (n-3), 22:5 (n-3) which specifically derived from the conversion of β-linolenate or the retroconversion of DHA
was taken into account. The overall accumulation of (n-3) fatty acids
was therefore equal to the rate of accumulation and conversion and/or
retroconversion, excluding losses by |3-oxidation. Whole body iatty
acid content was calculated by totalling the fatty acids of the 6 compartments.
Data is expressed as mean ± SD for n = 6 values. Differences between
the two dietary groups were checked using a one-factor analysis of
variance (ANOVA, StatView SE + Graphics™, Abacus Concepts Inc.,
ASD Meylan, France). Means were compared by Scheffé’s test, the level
of significance being set at p<0.05.
Results
Over the 35-day balance period, the proportional contribution of the
different compartments to the overall weight gain varied from <4.2%
for brain, liver and fat (both internal and subcutaneous), to 8-10% for
viscera and 68-72% for the remaining carcass (data not shown).
Balance analysis showed that a total of 1167.5 ± 47.7 mg of 18:3 (n-3)
were consumed, 5.2 ± 0.8 mg were excreted, 248.1 ±64.5 mg accumulated
as 18:3 (n-3) and 221.6 ± 6.0 mg as (n-3) long-chain fatty acids with
164.6 ± 13.3 mg as 22:6 (n-3) (table 2). In proportion to 18:3 (n-3)
intake, this corresponded to a mean excretion of only 0.5%, an accumulation of 1 8:3 (n-3) of 21.2% , and a net conversion to (n-3) derivatives of 19-0% in a decreasing order as 22:6 (n-3) (14%), 18:4 (n-3)
(1.9% ), 22:5 (n-3) ( 1.6% ) and 20:5 (n-3) (1.4% ). By difference, the rate
of α-linolenate disappearance was 58.0% (± 5.0). Concerning the specific accumulation of 18:3 (n-3), 50% were stored in fat (72.5 ± 25.2 mg
in internal fat and 5 1.5 ± 29-1 mg in subcutaneous fat) and 46% in the
carcass-skin compartment ( 1 13.7 ± 15.6mg). For 22:6 (n-3), the main
deposition was in the remaining carcass (127.5 ± 15.0 mg) and the
lowest in brain (3.2 ± 0.7 mg i.e. 2% of total 22:6 (n-3) (fig. A).
158
Total lipids of these tissues, compartments and faeces were extracted
by the procedure of Folch (Folch et al., 1957). Then, a known amount
of internal standard (diheptadecanoyl phosphatidylcholine and dinonadecanoyl triglyceride) was added and lipids were transmethylated
using 10% boron trifluoride in methanol (Fluka, Socolab, Paris, France).
The fatty methyl esters were separated by gas liquid chromatography
using a Carlo Erba 4180 gas chromatograph equipped with a CP wax
52 CB bonded fused-silica capillary column (Chrompack, Les Ulis,
France) as previously described (Guesnet et al., 1997).
For the whole body (n-3) fatty acid balance, the difference between the
intake and the sum of the faecal excretion and accumulation equalled
the apparent β-oxidation (i.e. disappearance). The accumulation of
other (n-3) fatty acids 20:5 (n-3), 22:5 (n-3) which specifically derived from the conversion of β-linolenate or the retroconversion of DHA
was taken into account. The overall accumulation of (n-3) fatty acids
was therefore equal to the rate of accumulation and conversion and/or
retroconversion, excluding losses by |3-oxidation. Whole body iatty
acid content was calculated by totalling the fatty acids of the 6 compartments.
Data is expressed as mean ± SD for n = 6 values. Differences between
the two dietary groups were checked using a one-factor analysis of
variance (ANOVA, StatView SE + Graphics™, Abacus Concepts Inc.,
ASD Meylan, France). Means were compared by Scheffé’s test, the level
of significance being set at p<0.05.
Results
Over the 35-day balance period, the proportional contribution of the
different compartments to the overall weight gain varied from <4.2%
for brain, liver and fat (both internal and subcutaneous), to 8-10% for
viscera and 68-72% for the remaining carcass (data not shown).
Balance analysis showed that a total of 1167.5 ± 47.7 mg of 18:3 (n-3)
were consumed, 5.2 ± 0.8 mg were excreted, 248.1 ±64.5 mg accumulated
as 18:3 (n-3) and 221.6 ± 6.0 mg as (n-3) long-chain fatty acids with
164.6 ± 13.3 mg as 22:6 (n-3) (table 2). In proportion to 18:3 (n-3)
intake, this corresponded to a mean excretion of only 0.5%, an accumulation of 1 8:3 (n-3) of 21.2% , and a net conversion to (n-3) derivatives of 19-0% in a decreasing order as 22:6 (n-3) (14%), 18:4 (n-3)
(1.9% ), 22:5 (n-3) ( 1.6% ) and 20:5 (n-3) (1.4% ). By difference, the rate
of α-linolenate disappearance was 58.0% (± 5.0). Concerning the specific accumulation of 18:3 (n-3), 50% were stored in fat (72.5 ± 25.2 mg
in internal fat and 5 1.5 ± 29-1 mg in subcutaneous fat) and 46% in the
carcass-skin compartment ( 1 13.7 ± 15.6mg). For 22:6 (n-3), the main
deposition was in the remaining carcass (127.5 ± 15.0 mg) and the
lowest in brain (3.2 ± 0.7 mg i.e. 2% of total 22:6 (n-3) (fig. A).
158