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9-Desaturase1 ,2
Valio Limited, FIN-00039, Helsinki, Finland and * Department of Animal Science, Cornell University, Ithaca, NY 14853
5To whom correspondence should be addressed.
 |
ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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9-desaturase and synthesis from
trans-11 18:1, another intermediate in ruminal
biohydrogenation. Our first experiment supplied lactating cows
(n = 3) with trans-11 18:1 by
abomasal infusion and examined the potential for endogenous synthesis
by measuring changes in milk fat CLA. By d 3, infusion of
trans-11 18:1 resulted in a 31% increase in
concentration of cis-9, trans-11 CLA in
milk fat, demonstrating that an active pathway for endogenous synthesis
of CLA exists. Our second experiment examined the quantitative
importance of endogenous synthesis of CLA in lactating cows
(n = 3) by abomasally infusing a putative
stimulator (retinol palmitate) or an inhibitor (sterculic oil) of
9-desaturase. Infusion of retinol palmitate had no
influence on milk fatty acid desaturation, and yield of CLA in milk fat
was not altered. However, sterculic oil infusion decreased the
concentration of CLA in milk fat by 45%. Consistent with
9-desaturase inhibition, the sterculic oil treatment
also altered the milk fat concentration of other
9-desaturase products as indicated by the two- to
threefold increase in the ratios of 14:0 to 14:1, 16:0 to
16:1 and 18:0 to cis-18:1. Using changes in the ratio of
14:0 to 14:1 as an indication of the extent of
9-desaturase inhibition with the sterculic oil
treatment, an estimated 64% of the CLA in milk fat was of endogenous
origin. Overall, results demonstrate that endogenous synthesis of CLA
from trans-11 18:1 represented the primary source of CLA
in milk fat of lactating cows.
KEY WORDS: • conjugated linoleic acid • 9-desaturase • lactation • milk fat • ruminants
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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and Pariza (1999)
]. Many of these may
represent positive health benefits of dietary CLA. Dairy products are
the major dietary source of CLA, and cis-9,
trans-11 octadecadienoic acid is the predominant CLA isomer
in natural lipids (Parodi 1997
). A trivial name, rumenic
acid, was proposed for this isomer on the basis of its ruminant origin
(Kramer et al. 1998
). The sequence of ruminal
biohydrogenation of linoleic acid involves isomerization to form
cis-9, trans-11 CLA followed by successive
reductions to trans-11 octadecenoic acid (vaccenic acid) and
stearic acid (Harfoot and Hazlewood 1988
). On this
basis, the CLA in milk fat and body fat of ruminants has been assumed
to be CLA that has escaped complete biohydrogenation in the rumen
(Chin et al. 1992
, Parodi 1997 and 1999
).
Concentrations of CLA in milk fat can be enhanced by changes in the
diet, especially utilization of diets with greater linoleic acid
content [see review by Griinari and Bauman (1999)
].
However, certain diets that have low levels of linoleic acid, e.g.,
pasture or fish oil feeding, also increase the concentration of CLA in
milk fat. These diets contain high levels of other polyunsaturated
fatty acids (PUFA) that do not yield CLA as an intermediate in rumen
biohydrogenation (Griinari and Bauman 1999
,
Harfoot and Hazelwood 1988
). This raises the possibility
of alternative sources of milk fat CLA. In the ruminal biohydrogenation
of linoleic acid, CLA is a transient intermediate, whereas
trans-11 18:1 accumulates (Harfoot and Hazlewood 1988
). Furthermore, trans-11 18:1 is an intermediate
in the biohydrogenation of several PUFA (Griinari and Bauman 1999
). On this basis, we hypothesized that CLA could be
produced by endogenous synthesis from trans-11 18:1 by
9-desaturase (Griinari et al. 1997
). Consistent with this, mammary gland and adipose tissue
of ruminants have substantial 9-desaturase
activity (Kinsella 1972
, Martin et al. 1999
, St. John et al. 1991
, Ward et al. 1998
).
The objective of this investigation was to examine the endogenous
synthesis of CLA in lactating dairy cows. The first experiment supplied
trans-11 18:1 by abomasal infusion and examined the
potential for endogenous synthesis by measuring changes in milk fat
CLA. In the second experiment, we examined the quantitative importance
of endogenous synthesis of CLA by inhibiting the activity of
9-desaturase with sterculic oil. In this
latter study, we also included a treatment with retinol palmitate, a
compound that has been reported to enhance gene expression of
9-desaturase in mouse liver.
|
MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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) to meet or exceed predicted requirements (NRC 1989
). Ingredients and chemical composition of the diet are
presented in Table 1
. Cows were fed for ad libitum intake with fresh feed being offered
twice daily. The amount of feed consumed was measured daily and water
was available at all times.
|
Treatments were infused into the abomasum. This is a convenient
experimental method to simulate dietary supply of compounds while
avoiding possible alterations by rumen bacteria. The abomasum was
accessed by passing a polyvinyl chloride tube (0.5-cm i.d.) through the
rumen fistula, rumen compartments and sulcus omasi, and into the
abomasum as described previously (Spires et al. 1975
).
Experiment 1.
The three cows averaged 152 ± 25 d postpartum (mean ± SD) at the start of the study. The 11-d experiment
consisted of a pretreatment period (d 1–3), a treatment period (d
4–6), and a post-treatment period (d 7–11). Skim milk (vehicle)
was infused abomasally during the pre- and post-treatment periods.
During the treatment period, a trans fatty acid emulsion
in skim milk was used. A mixture containing equal amounts of
trans-11 and trans-12 octadecenoic acids
(Lot #7363:10; Larodan Fine Chemicals, Malmö, Sweden) was used
due to availability and cost. Company specifications indicated that the
trans-11 and trans-12 18:1 were in equal
ratio and comprised >99% of the fatty acids in the chemical mixture;
this was confirmed by our own analysis. The trans-18:1
mixture was added to heated skim milk and an emulsion prepared using a
microfluidizer as described by Chouinard et al. (1999)
.
The final concentration of the trans-octadecenoic acid
mixture was 0.5% in the skim milk emulsion.
Infusions used a peristaltic pump (Harvard Apparatus, South Natick, MA) calibrated to infuse continuously at a rate of 5 kg/d. This resulted in a delivery rate of 25.0 g/d of the trans-18:1 mixture during the treatment period. Sanitized carboys served as reservoirs for infusates, and were changed every 12 h.
Experiment 2.
Three cows, 144 ± 94 d postpartum, were randomly assigned to a 3 x 3 Latin square design. Treatments were administered by abomasal infusion and included the following: 1) control (200 mL water/d), 2) retinol palmitate (4.8 g/d) and 3) sterculic oil (10 g/d). Equal volumes of the infusates were administered at 6-h intervals for 4 d with a 7-d interval between infusion periods.
For the retinol palmitate treatment, infusions were prepared as a suspension in water. Retinol palmitate (825,000 retinol equivalents/g) was obtained from Sigma-Aldrich (St. Louis, MO), and the final suspensions contained 24 g/L retinol palmitate. Cows were infused 4 times/d with 50 mL/infusion, resulting in a daily dosage of 4.8 g of retinol palmitate.
Sterculic oil was extracted from the seeds of the Sterculia
foetida tree. Seeds were dehulled, crushed and the meats
refluxed in diethyl ether to extract the oil (method 963.15; AOAC 1998
). The yield of extracted oil was 49.6% of the seed meat by
weight. The sterculic oil was prepared for abomasal infusion by making
a 2% emulsion in skim milk as described for Experiment 1. Emulsions
were stored at 4°C until infused, with fresh emulsions prepared for
each treatment period. Cows receiving the sterculic oil treatment were
infused with an equal amount 4 times/d. The daily dose averaged
9.7 g of sterculic oil and 468 mL of emulsion.
Fatty acid analysis.
Lipid extraction of milk fat was performed according to
Hara and Radin (1978)
. Methyl esters of the fatty acids
were prepared by transesterification with sodium methoxide according to
the method of Christie (1982)
as detailed by
Chouinard et al. (1999)
.
Fatty acid methyl esters were quantified by gas chromatography
techniques. Two methods were used to allow complete separation of
trans-11 and trans-12 octadecenoic acids
and their respective desaturase products. One method used a CP-Sil
88 column (cyanopropyl polysiloxane; 100 m x 0.25 mm i.d. with
0.20-µm film thickness; Chrompack, Middlebury, The
Netherlands) with two temperature-programmed gas chromatography
runs. The first involved a temperature gradient program (70–240°C)
and the second was an isothermal run at 160°C as described by
Griinari et al. (1998)
. This method separated
trans-11 and trans-12 octadecenoic acids
into single-component peaks. The second method used a Supelcowax-10
column (fused silica, 60 m x 0.32 mm i.d. with
0.25-µm film thickness; Supelco, Bellefonte, PA) as
described by Chouinard et al. (1999)
. This method
provided data for cis-9, trans-12
octadecadienoic acid concentration, the general fatty acid composition
of milk fat and the fatty acid composition of sterculic oil.
For both gas chromatography methods, fatty acids were identified using pure standards (Nu-Chek-Prep, Elysian, MN). A butter reference standard (CRM 164; Commission of the European Communities, Community Bureau of Reference, Brussels, Belgium) was used to determine recoveries and correction factors for individual fatty acids in milk fat.
Statistical analysis.
Data from Experiment 1 were analyzed using the general linear models
procedure of SAS (1989)
according to the following
model:
 |
where Yij is the observation, µ is the overall mean, Ti is the treatment (i = 1 and 2), Cj is the cow (j = 1, 2 and 3) and Eij is the residual error. Data from d 1 through 3 plus d 9 through 11 of the experimental period constituted the control values and data from d 6 (d 3 of treatment infusion) represented treatment values.
For Experiment 2, data were analyzed as a 3 x 3 Latin square
design using the PROC MIXED procedure of SAS (1989)
according to the following model:
 |
where Yijk is the observation, µ is the overall mean, Ti is the treatment (i = 1, 2 and 3), Pj is the period (j = 1, 2 and 3), Ck is the cow (k = 1, 2 and 3) and Eijk is the residual error. Data from d 3 and 4 from each treatment period were used in the analysis.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Our initial experiment infused trans-11 18:1 abomasally to
examine the potential for endogenous synthesis of CLA by
9-desaturase. Due to availability and cost we
used a 50:50 mixture of trans-11 18:1 and
trans-12 18:1. The 9-desaturase
could catalyze the formation of cis-9, trans-11
CLA and cis-9, trans-12 18:2 from
trans-11 18:1 and trans-12 18:1, respectively.
Cows maintained constant feed intake during the 11 d of the study
(data not presented). The yields of milk and milk fat were also
relatively constant throughout the study (Fig. 1
). However, there were alterations in the pattern of milk fatty acids
over the treatment period. Abomasal infusion of the mixture of
trans-11 and trans-12 octadecenoic acids resulted
in the appearance of these fatty acids in milk fat (Fig. 2
). In addition, the respective cis-9, trans-n
octadecadienoic acids formed from trans-11 and
trans-12 octadecenoic acids by the action of
9-desaturase were increased in milk fat. The
trans-11 18:1 and cis-9, trans-11 18:2
had not reached constant concentrations in milk fat by d 3 of the fatty
acid infusion. In contrast, the increase in trans-12 18:1
and its desaturase product (cis-9, trans-12 18:2)
approached maximum concentrations in milk fat over the first 36 h,
and these were maintained for the remaining 36 h of the abomasal
infusion.
|
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. Using the mean of
the pretreatment period plus the last 3 d of the
post-treatment period for the baseline concentration, we made
comparisons with d 3 of the fatty acid infusion period. Changes in milk
fat yields of trans-11 18:1 and cis-9,
trans-11 CLA accounted for 40 ± 8% (mean ± SEM) of the abomasally infused trans-11 18:1, of
which 31 ± 9% was due to an increase in cis-9,
trans-11 CLA. An average of 64 ± 9% of the abomasally
infused trans-12 18:1 was accounted for by milk fat changes
in yields of trans-12 18:1 and cis-9,
trans-12 18:2, but in this case only 10 ± 2% of the
incorporation was due to the increase in cis-9,
trans-12 18:2 content of milk fat. Thus, slightly more than
one half of the abomasally infused trans 18:1 fatty acids
were accounted for by increases in related fatty acids in milk; in the
case of trans-11 18:1, however, a substantially greater
portion was represented by an increase in the specific fatty acid
formed by the action of 9-desaturase. Experiment 2.
To evaluate the quantitative importance of endogenous synthesis
of CLA, we infused retinol palmitate and sterculic oil abomasally. In
this case, we utilized a diet containing extruded full-fat soybeans
(Table 1)
; this type of diet results in increased milk fat
concentrations of trans-11 18:1 and CLA (Chouinard et al. 1997
, Dhiman et al. 1999
). Dry matter intake
and milk yield were not influenced by treatments (Table 2
). Infusion with retinol palmitate resulted in minor decreases in milk
content and yield of fat and protein (Table 2)
. Retinol palmitate had
minimal effects on fatty acid composition of milk, although
concentrations of CLA and palmitic acid were increased slightly
(Table 3
). However, yield of CLA was not affected, and the activity of
9-desaturase appeared unaltered on the basis
of the constant ratios of relevant saturated fatty acids and their
9-desaturase products (Fig. 3
).
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9-desaturase, the ratios of fatty acid pairs
dependent on this enzyme were altered. Milk fat ratios of 14:0 to 14:1,
16:0 to 16:1 and 18:0 to cis-9 18:1 were increased two- to
threefold by treatment with sterculic oil (Fig. 3)
.
Infusion of sterculic oil also altered the relationship between
trans-11 18:1 and cis-9, trans-11 CLA
as shown by the temporal pattern over the infusion period (Fig. 4
). By d 4 of infusion, the ratio of trans-11 18:1 to CLA was
increased twofold (Fig. 3)
, and the concentration and yield of CLA in
milk fat were reduced 45%. A similar temporal pattern was also
observed for concentration changes of the other desaturase pairs, i.e.,
14:0 vs. 14:1, 16:0 vs. 16:1 and 18:0 vs. cis-9 18:1 (data
not presented).
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|
DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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, Parodi (1997
and 1999)
]. Indeed, CLA is
an intermediate in the biohydrogenation of linoleic acid by rumen
bacteria, and the CLA content of ruminant fats can be increased by
formulating diets that contain more linoleic acid (Dhiman et al. 1999
, Kelly et al. 1998
). However, kinetic
studies of rumen biohydrogenation of linoleic acid to stearic acid have
shown that cis-9, trans-11 CLA is a transient
intermediate, whereas trans-11 18:1 is the intermediate that
accumulates (Harfoot and Hazlewood 1988
, Keeney 1970
). Furthermore, dietary addition of plant oils containing
-linolenic acid also increase the CLA content of ruminant fat, and
intermediates in its pathway of biohydrogenation include
trans-11 18:1 but not CLA [see review by Griinari and Bauman (1999)
]. Accordingly, we hypothesized that the CLA
in ruminant tissues originated in part from endogenous synthesis.
Our initial experiment examined whether lactating cows could produce
CLA from trans-11 18:1. Results clearly demonstrated that
endogenous synthesis occurred. By d 3 of abomasal infusion of
trans-11 18:1 (12.5 g/d), milk fat content of
cis-9, trans-11 CLA had increased by 31%. The
CLA concentration in milk fat had not reached a plateau by d 3 of
infusion, indicating that studies of longer duration will be required
to allow for definitive estimates of transfer efficiency, and these
should also involve a range of trans-11 18:1 doses.
Nevertheless, by d 3 of infusion, the increase in CLA concentration in
milk fat accounted for 12% of the abomasally infused
trans-11 18:1. The infused trans-octadecenoic
acids consisted of a mixture of trans-11 18:1 and
trans-12 18:1. Thus, trans-12 18:1 also provided
a test for endogenous synthesis by
9-desaturase with the product of the reaction
being cis-9, trans-12 18:2. We observed the
appearance of cis-9, trans-12 18:2 in milk fat
during the infusion period, although the amount was substantially less
than observed for conversion of trans-11 18:1 to
cis-9, trans-11 CLA (Fig. 2)
.
The precursor for the endogenous synthesis of CLA in ruminants would be
trans-11 18:1, which originates in the rumen from incomplete
biohydrogenation of PUFA. Several studies have demonstrated that
substantial amounts of trans-18:1 fatty acids (60–300 g/d)
reach the duodenum in lactating cows (Kalscheur et al. 1997a
and 1997b
, Wonsil et al. 1994
). Other investigations
have established that trans fatty acids were absorbed
efficiently from the digestive tract and utilized by different ruminant
tissues, including the mammary gland (Bickerstaffe et al. 1972
, Thompson and Christie 1991
). Methods used
in the above investigations did not allow for separation of specific
trans-18:1 isomers, but trans-11 has been shown
to be the major trans octadecenoic acid isomer produced by
rumen biohydrogenation under typical dietary conditions
(Griinari and Bauman 1999
).
In lactating cows, trans-18:1 fatty acids have been proposed
to cause an inhibition of milk fat synthesis (Davis and Brown 1970
, Erdman, 1996
). Consistent with this, a
decrease in milk fat yield occurs when partially hydrogenated vegetable
oils were infused abomasally (Erdman 1996
) and increases
in milk fat content of trans-18:1 were highly correlated
with reductions in the fat content of milk across a wide range of diets
(Griinari et al. 1998
). However, this effect appears to
be related to specific trans isomers. We observed that
abomasal infusion of 25 g/d of an equal mixture of trans-11
18:1 and trans-12 18:1 had no effect on milk fat yield or
content (Fig. 1)
. Similarly, Rindsig and Schultz (1974)
observed no reduction in milk fat when 25 g/d of trans-9
18:1 was infused abomasally. Other trans-18:1 isomers have
not been examined, but we have shown that dietary-induced
reductions in milk fat yield were closely related to specific increases
in milk fat content of trans-10 18:1 and
trans-10, cis-12 CLA (Griinari et al. 1998
and 1999
). We further demonstrated that a dramatic reduction in
milk fat secretion occurs in dairy cows with abomasal infusion of as
little as 10 g/d of trans-10, cis-12 CLA, whereas
infusion of cis-9, trans-11 CLA had no effect on
milk fat synthesis (Baumgard et al. 2000
).
The oxidative reaction catalyzed by
9-desaturase for endogenous synthesis of CLA
involves cytochrome b5, NADH(P)-cytochrome
b5 reductase and molecular
O2 (Ntambi 1999
).
Palmitoyl-CoA and stearoyl-CoA are the primary substrates for
the microsomal enzyme (Enoch et al. 1976
), but
9-desaturase can also use the CoA esters of
trans fatty acids, including trans-11 18:1
(Mahfouz et al. 1980
, Pollard et al. 1980
). In rodents, the enzyme was located predominantly in the
liver (Ntambi 1995
). In contrast, adipose tissue was the
major site for 9-desaturase in growing
ruminants, and mammary gland the major tissue site in lactating
ruminants (Kinsella 1972
, Martin et al. 1999
, St. John et al. 1991
, Ward et al. 1998
). Studies with rodents have demonstrated that hepatic mRNA
levels and enzyme activity of 9-desaturase are
regulated by many factors, including physiologic state, diet and
hormonal balance (Ntambi 1995
and 1999
, Tocher et al. 1998
). Investigations with ruminants are more limited.
Martin et al. (1999)
characterized the ontogeny of
9-desaturase gene expression in adipose tissue
of growing cattle, and Ward et al. (1998)
demonstrated
that the onset of lactation in sheep resulted in a dramatic increase in
mRNA for 9-desaturase in mammary tissue and a
reciprocal reduction in adipose tissue.
Our second experiment evaluated the quantitative significance of
endogenous synthesis in the production of CLA found in milk fat. For
this objective, treatments were designed to alter tissue activity of
9-desaturase. One treatment involved
administration of retinol palmitate. Administration of retinol
palmitate to mice dramatically increased hepatic expression of
9-desaturase in both vitamin A–deficient and
normal mice. Miller et al. (1997)
demonstrated that
liver desaturase mRNA levels were increased approximately three- and
sevenfold in vitamin A–deficient and normal mice, respectively, when
mice were fed 0.1% vitamin A in the diet. In our study, this treatment
resulted in a significant increase in the concentration of CLA, but had
no effect on the yield of CLA in milk fat. Overall, effects of retinol
palmitate were relatively minor (Tables 2
and 3)
, and this treatment
did not alter the milk fat ratio for any of the fatty acid pairs
related to 9-desaturase activity (Fig. 3)
.
A second treatment involved abomasal infusion of sterculic oil. As in
the work of Kai and Pryde (1982)
, the sterculic oil
contained 55.9% sterculic acid (8-[2-octyl-1-cyclopropenyl] octanoic
acid) and 6.3% malvalic acid (7-[2-octyl-1-cyclopropenyl] heptanoic
acid), fatty acids with a cyclopropene ring at the 9–10 position.
These two cyclopropenoid fatty acids are very specific and highly
potent inhibitors of 9-desaturase
(Jeffcoat and Pollard 1977
). We observed that infusion
with sterculic oil resulted in decreased cis-9,
trans-11 CLA concentration and a reciprocal increase in the
trans-11 18:1 content of milk fat (Fig. 4)
. This clearly
demonstrates the critical role of 9-desaturase
as a source of the CLA in milk fat. Similar dramatic shifts were
observed for the milk fat content of other fatty acid pairs that are
affected by desaturase activity, i.e., 14:0:14:1, 16:0:16:1 and
18:0:cis-9 18:1. Thus, our experiment also confirms the
important role of 9-desaturase in the
production of oleic acid and provides the first evidence that this
enzyme reaction is a major source of the myristoleic acid and
palmitoleic acid found in milk fat.
Sterculic oil has been used previously to inhibit
9-desaturase, generally to study the role of
this enzyme in the conversion of stearic acid to oleic acid. Previous
investigations have included rodents, chickens and other species [see
for example, Fan et al. (1982)
and Phelps et al. (1965)
]. Investigations have also included lactating goats and
cows; these single-animal studies have reported increases in the
18:0:18:1 ratio in milk fat when sterculic oil was given by abomasal
infusion (Bickerstaffe and Johnson 1972
, Porter 1984
) or by dietary addition of a rumen-protected form
(Cook et al. 1976
). Our specific interest was to
evaluate the importance of endogenous synthesis of CLA, and we observed
a 45% reduction in the milk fat content with the sterculic oil
treatment. Thus, under the dietary conditions of the present
experiment, a minimum of one half of the CLA in milk fat was of
endogenous origin involving 9-desaturase.
The above estimate is a minimum based on the assumption that the
sterculic oil dose inhibited 9-desaturase
completely. Complete inhibition is unlikely, but the extent of
9-desaturase inhibition can be evaluated by
comparing results from other fatty acid pairs that represent
substrate:product ratios for the enzyme. A portion of the palmitoleic
acid and oleic acid in milk fat could originate from mammary gland
uptake of these fatty acids. However, comparison of 14:0 with 14:1 is
ideal because 14:0 originates from mammary gland synthesis, and
essentially the only source for myristoleic acid in milk fat is
desaturation by 9-desaturase. During the
sterculic oil treatment, the secretion of 14:1 in milk fat was reduced
to 30% of the control period, indicating that inhibition of
9-desaturase was 
70%. Applying this
adjustment to the relationship between trans-11 18:1 and CLA
gives an estimate that 64% of the CLA in milk fat originated via
9-desaturase. This is a maximum estimate,
which assumes that all of the 14:1 is cis-9 14:1 that
originates from endogenous synthesis. In addition, the kinetics for
sterculic acid and malvalic acid inhibition of
9-desaturase have not been compared for
different substrates, making this a limitation in extending inhibition
estimates across substrates. Nevertheless, it is clear that endogenous
synthesis via 9-desaturase represents the
major source of CLA in milk fat.
A close linear relationship between trans-11 18:1 fatty acid
and CLA has been observed for milk fat in a number of studies and
across a wide range of diets [see review by Griinari and Bauman (1999)
]. This relationship has been generally attributed to a
common source for these two fatty acids as intermediates in ruminal
biohydrogenation. However, our studies demonstrate that the close
relationship between trans-11 18:1 and CLA in milk fat is
related to the formation of cis-9, trans-11 CLA
from trans-11 18:1 via
9-desaturase. This close relationship has also
been observed over a wide range of trans-11 18:1
concentrations (Griinari and Bauman 1999
), suggesting a
high capacity for endogenous synthesis of CLA. This is an important
consideration in developing feeding strategies for the production of
CLA-enriched milk. The focus should be on ruminal formation of
trans-11 18:1 rather than CLA. In practical terms, this
means that the most feasible options to enhance milk fat CLA
concentrations may be to feed supplements containing
trans-11 18:1 or dietary management of rumen
biohydrogenation to increase the formation of trans-11 18:1
(Griinari and Bauman 1999
).
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
9-desaturase and endogenous synthesis of CLA in lactating dairy cows, J. Anim. Sci. 77 (suppl. 1):118 (abs.)]. 
2 Supported in part by National Dairy Council (Rosemont, IL), Valio (Helsinki, Finland), Northeast Dairy Foods Research Center and the Cornell Agricultural Experiment Station.
3 Current address: Department of Animal Science, University of Helsinki, Helsinki, Finland.
4 Current address: Département des sciences animales, Pavillon Paul-Comtois, Université Laval, Québec, Canada G1K 7P4.
Manuscript received January 3, 2000. Initial review completed February 7, 2000. Revision accepted April 12, 2000.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
1. Association of Official Analytical Chemists Official Methods of Analysis of AOAC International 16th ed., 4th rev. 1998 AOAC International Gaithersburg, MD.
2. Banni S., Martin J.-C. Conjugated linoleic acid and metabolites. Sébédio J. J. Christie W. W. eds. Trans Fatty Acids in Human Nutrition 1998:261-302 Oily Press Dundee, Scotland.
3.
Baumgard L. H., Corl B. A., Dwyer D. A., Sæbø A., Bauman D. E. Identification of the conjugated linoleic acid isomer that inhibits milk fat synthesis. Am. J. Physiol. 2000;278:R179-R184
4. Bickerstaffe R., Johnson A. R. The effect of intravenous infusions of sterculic acid on milk fat synthesis. Br. J. Nutr. 1972;27:561-570[Medline]
5. Bickerstaffe R., Noakes D. E., Annison E. F. Quantitative aspects of fatty acid biohydrogenation, absorption and transfer into milk fat in the lactating goat, with special reference to the cis- and trans-isomers of octadecenoate and linoleate. Biochem. J. 1972;130:607-617[Medline]
6. Chin S. F., Liu W., Storkson J. M., Ha Y. L., Pariza M. W. Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens. J. Food Compos. Anal. 1992;5:185-197
7. Chouinard P. Y., Corneau L., Sæbø A., Bauman D. E. Milk yield and composition during abomasal infusion of conjugated linoleic acid. J. Dairy Sci. 1999;82:2737-2745[Abstract]
8. Chouinard P. Y., Lévesque J., Girard V., Brisson G. J. Dietary soybeans extruded at different temperatures: milk composition and in situ fatty acid reactions. J. Dairy Sci. 1997;80:2913-2924[Abstract]
9. Christie W. W. A simple procedure for rapid transmethylation of glycerolipids and cholesteryl esters. J. Lipid Res. 1982;23:1072-1075[Abstract]
10. Cook L. J., Scott T. W., Mills S. C., Fogerty A. C., Johnson A. R. Effects of protected cyclopropene fatty acids on the composition of ruminant milk fat. Lipids 1976;11:705-711[Medline]
11. Davis C. L., Brown R. E. Low-fat milk syndrome. Phillipson A. T. eds. Digestion and Metabolism in the Ruminant 1970:545-565 Oriel Press Newcastle Upon Tyne, UK.
12. Dhiman T. R., Helmink E. D., McMahon D. J., Fife R. L., Pariza M. W. Conjugated linoleic acid content of milk and cheese from cows fed extruded oilseeds. J. Dairy Sci. 1999;82:412-419[Abstract]
13.
Enoch H. G., Catalá A., Strittmatter P. Mechanism of rat liver microsomal stearyl-CoA desaturase. J. Biol. Chem. 1976;251:5095-5103
14. Erdman R. Milk fat depression: some new insights. Proc. Tri-State Dairy Nutr. Conf. 1996:1-16 Fort Wayne, IN.
15. Fan L. L., Hilton B. W., Wohlman A. Effects in rats of cyclopropenoid fatty acids from cottonseed oil. J. Food Prot. 1982;45:48-53
16. Fox D. G., Sniffen C. J., O’Connor J. D., Russell J. B., Van Soest P. J. A net carbohydrate and protein system for evaluating cattle diets: III. Cattle requirements and diet adequacy. J. Anim. Sci. 1992;70:3578-3596[Abstract]
17. Griinari J. M., Bauman D. E. Biosynthesis of conjugated linoleic acid and its incorporation into meat and milk in ruminants. Yurawecz M. P. Mossoba M. M. Kramer J.K.G. Pariza M. W. Nelson G. J. eds. Advances in Conjugated Linoleic Acid Research 1999;1:180-200 AOCS Press Champaign, IL.
18. Griinari J. M., Chouinard P. Y., Bauman D. E. Trans fatty acid hypothesis of milk fat depression revised. Proc. Cornell Nutr. Conf. Feed Manuf. 1997:208-216 Cornell University Ithaca, NY.
19. Griinari J. M., Dwyer D. A., McGuire M. A., Bauman D. E., Palmquist D. L., Nurmela K.V.V. Trans-octadecenoic acids and milk fat depression in lactating dairy cows. J. Dairy Sci. 1998;81:1251-1261[Abstract]
20. Griinari J. M., Nurmela K., Dwyer D. A., Barbano D. M., Bauman D. E. Variation of milk fat concentration of conjugated linoleic acid and milk fat percentage is associated with a change in ruminal biohydrogenation. J. Anim. Sci. 1999;77(suppl. 1):117-118(abs.)
21. Hara A., Radin N. S. Lipid extraction of tissues with a low-toxicity solvent. Anal. Biochem. 1978;90:420-426[Medline]
22. Harfoot C. G., Hazlewood G. P. Lipid metabolism in the rumen. Hobson P. N. eds. The Rumen Microbial Ecosystem 1988:285-322 Elsevier Applied Science Publishers London, UK.
23. Jeffcoat R., Polland M. R. Studies on the inhibition of the desaturases by cyclopropenoid fatty acids. Lipids 1977;12:480-485[Medline]
24. Kai Y., Pryde E. H. Production of branched-chain fatty acids from sterculia oil. J. Am. Oil Chem. Soc. 1982;59:300-305
25. Kalscheur K. F., Teter B. B., Piperova L. S., Erdman R. A. Effect of dietary forage concentration and buffer addition on duodenal flow of trans-C18:1 fatty acids and milk fat production in dairy cows. J. Dairy Sci. 1997a;80:2104-2114[Abstract]
26. Kalscheur K. F., Teter B. B., Piperova L. S., Erdman R. A. Effect of fat source on duodenal flow of trans-C18:1 fatty acids and milk fat production in dairy cows. J. Dairy Sci. 1997b;80:2115-2126[Abstract]
27. Keeney M. Lipid metabolism in the rumen. Phillipson A. T. eds. Physiology of Digestion and Metabolism in the Ruminant 1970:489-503 Oriel Press Newcastle upon Tyne, UK.
28.
Kelly M. L., Berry J. R., Dwyer D. A., Griinari J. M., Chouinard P. Y., Van Amburgh M. E., Bauman D. E. Dietary fatty acid sources affect conjugated linoleic acid concentrations in milk from lactating dairy cows. J. Nutr. 1998;128:881-885
29. Kinsella J. E. Stearyl CoA as a precursor of oleic acid and glycerolipids in mammary microsomes from lactating bovine: possible regulatory step in milk triglyceride synthesis. Lipids 1972;7:349-355[Medline]
30. Kramer J.K.G., Parodi P. W., Jensen R. G., Mossoba M. M., Yurawecz M. P., Adlof R. O. Rumenic acid: a proposed common name for the major conjugated linoleic acid isomer found in natural products [letter]. Lipids 1998;33:835[Medline]
31. Mahfouz M. M., Valicenti A. J., Holman R. T. Desaturation of isomeric trans-octadecenoic acids by rat liver microsomes. Biochim. Biophys. Acta 1980;618:1-12[Medline]
32.
Martin G. S., Lunt D. K., Britain K. G., Smith S. B. Postnatal development of stearoyl coenzyme A desaturase gene expression and adiposity in bovine subcutaneous adipose tissue. J. Anim. Sci. 1999;77:630-636
33. Miller C. W., Waters K. M., Ntambi J. M. Regulation of hepatic stearoyl-CoA desaturase gene 1 by vitamin A. Biochem. Biophys. Res. Commun. 1997;231:206-210[Medline]
34. National Research Council Nutrient Requirements of Dairy Cattle 6th rev. ed. 1989 National Academy of Sciences Washington, DC.
35. Ntambi J. M. The regulation of stearoyl-CoA desaturase (SCD). Prog. Lipid Res. 1995;34:139-150[Medline]
36.
Ntambi J. M. Regulation of stearoyl-CoA desaturase by polyunsaturated fatty acids and cholesterol. J. Lipid Res. 1999;40:1549-1558
37. Pariza M. W. The biological activities of conjugated linoleic acid. Yurawecz M. P. Mossoba M. M. Kramer J.K.G. Pariza M. W. Nelson G. J. eds. Advances in Conjugated Linoleic Acid Research 1999;1:12-20 AOCS Press Champaign, IL.
38.
Parodi P. W. Cow’s milk fat components as potential anticarcinogenic agents. J. Nutr. 1997;127:1055-1060
39. Parodi P. W. Conjugated linoleic acid: the early years. Yurawecz M. P. Mossoba M. M. Kramer J.K.G. Pariza M. W. Nelson G. J. eds. Advances in Conjugated Linoleic Acid Research 1999;1:1-11 AOCS Press Champaign, IL.
40. Phelps R. A., Shenstone F. S., Kemmerer A. R., Evans R. J. A review of cyclopropenoid compounds: biological effects of some derivatives. Poult. Sci. 1965;44:358-394
41. Pollard M. R., Gunstone F. D., James A. T., Morris L. J. Desaturation of positional and geometric isomers of monoenoic fatty acids by microsomal preparations from rat liver. Lipids 1980;15:306-314[Medline]
42. Porter P. A. An Investigation of the Possible Role of trans-Fatty Acids in the Low Milk Fat Syndrome (LMFS) of the Dairy Cow 1984 Cornell University Ithaca, NY. Doctoral thesis
43. Rindsig R. B., Schultz L. H. Effects of abomasal infusions of safflower oil or elaidic acid on blood lipids and milk fat in dairy cows. J. Dairy Sci. 1974;57:1459-1466
44. SAS Institute Inc SAS/STAT User’s Guide, Version 6 4th ed. 1989 SAS Institute Cary, NC.
45. Spires H. R., Clark J. H., Derrig R. G., Davis C. L. Milk production and nitrogen utilization in response to postruminal infusion of sodium caseinate in lactating cows. J. Nutr. 1975;105:1111-1121
46. St. John L. C., Lunt D. K., Smith S. B. Fatty acid elongation and desaturation enzyme activities of bovine liver and subcutaneous adipose tissue microsomes. J. Anim. Sci. 1991;69:1064-1073[Abstract]
47. Thompson G. E., Christie W. W. Extraction of plasma triacylglycerols by the mammary gland of the lactating cow. J. Dairy Res. 1991;58:251-255[Medline]
48. Tocher D. R., Leaver M. J., Hodgson P. A. Recent advances in the biochemistry and molecular biology of fatty acyl desaturases. Prog. Lipid Res. 1998;37:73-117[Medline]
49. Ward R. J., Travers M. T., Richards S. E., Vernon R. G., Salter A. M., Buttery P. J., Barber M. C. Stearoyl-CoA desaturase mRNA is transcribed from a single gene in the ovine genome. Biochim. Biophys. Acta 1998;1391:145-156[Medline]
50. Wonsil B. J., Herbein J. H., Watkins B. A. Dietary and ruminally derived trans-18:1 fatty acids alter bovine milk lipids. J. Nutr. 1994;124:556-565
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