Diacylglycerol Oil Reduces Body Fat but Does Overweight, Hypertriglyceridemic Women

Supplemental Material can be found at:
http://jn.nutrition.org/content/suppl/2010/05/20/jn.110.12166
5.DC1.html
The Journal of Nutrition
Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions
Diacylglycerol Oil Reduces Body Fat but Does
Not Alter Energy or Lipid Metabolism in
Overweight, Hypertriglyceridemic Women1–3
Quangeng Yuan,4,5 Vanu R. Ramprasath,4 Scott V. Harding,4 Todd C. Rideout,4 Yen-Ming Chan,4
and Peter J. H. Jones4,5*
4
Richardson Centre for Functional Foods and Nutraceuticals and 5Department of Human Nutritional Sciences, Faculty of Human
Ecology, University of Manitoba, Winnipeg R3T 2N2, Manitoba, Canada
Diacylglycerol (DAG) may undergo differential metabolism compared with triacylglycerol (TAG) in humans, possibly
resulting in decreased serum TAG concentration and TAG synthesis and increased energy expenditure (EE), thus reducing
fat accumulation. Our objective was to examine the efficacy of DAG oil (Enova oil) consumption on serum lipid profiles,
hepatic lipogenesis, EE, and body weight and composition compared with a control oil-blend composed of sunflower,
safflower, and rapeseed oils at a 1:1:1 ratio. Twenty-six overweight (78.3 6 3.6 kg body weight and BMI 30.0 6 0.7 kg/m2)
mildly hypertriglyceridemic (1.81 6 0.66 mmol/L) women underwent 2 treatment phases of 28 d separated by a 4-wk
washout period using a randomized crossover design. They consumed 40 g/d of either DAG or control oil during treatment
phases. The baseline, EE, fat oxidation, body composition, and lipid profiles did not differ between the DAG and control oil
intervention periods. Relative to control oil, DAG oil did not alter endpoint postprandial EE, fat oxidation, serum lipid
profiles, or hepatic lipogenesis. However, DAG oil consumption reduced (P , 0.05) accumulation of body fat within trunk,
android, and gynoid regions at the endpoint compared with control oil, although neither DAG nor control oil altered any of
these variables during the 4-wk intervention period compared with their respective baseline levels. We conclude that
although DAG oil is not effective in lowing serum lipids over a 4-wk intervention, it may be useful for reducing
adiposity. J. Nutr. 140: 1122–1126, 2010.
Introduction
Diacylglycerol (DAG)6 oil naturally occurs in several edible oils
ranging from 0.8% in rapeseed oil to 9.5% in cottonseed oil (1).
DAG, a glycerol derivative, possesses 2 hydroxyl groups
substituted by fatty acids through ester bond formation. DAG
exists either as 1, 2-DAG or 1, 3-DAG and as a digestive
intermediate of lipid digestion where dietary triacylglycerols
(TAG) are broken down by lipase to produce 1, 2-DAG (2). It has
been hypothesized that DAG oil may be metabolized differently
than TAG. Whereas TAG are hydrolyzed, reassembled, and
packaged as chylomicrons in the enterocytes and transported via
the lymphatic system through the peripheral tissues to be
removed from circulation as a chylomicron remnant, DAG may
be absorbed directly into the blood and enter hepatocytes via the
1
Supported by the Heart and Stroke Foundation.
Author disclosures: Q. Yuan, V. R. Ramprasath, S. V. Harding, T. C. Rideout, Y.
M. Chan, and P. J. H. Jones, no conflicts of interest.
3
Supplemental Figure 1 and Tables 1 and 2 are available with the online posting
of this paper at jn.nutrition.org.
6
Abbreviations used: DAG, diacylglycerol; DEXA, dual energy X-ray absorptiometry; EE, energy expenditure; FSR, fraction synthesis rate; RCFFN,
Richardson Centre for Functional Foods and Nutraceuticals; REE, resting energy
expenditure; TAG, triacylglycerol; TAG-FA, triacylglycerol fatty acid.
* To whom correspondence should be addressed. E-mail: peter_jones@
umanitoba.ca.
2
1122
portal vein for rapid oxidation (3–5). Unlike TAG, DAG are not
efficiently hydrolyzed and reassembled as TAG (6); therefore,
high dietary intakes may modify blood lipids (7–15) and possibly
reduce the amount of lipid stored in adipose tissue (16). The
speculation that DAG oil may lower blood lipids and control
body adiposity has lead to it being marketed as a functional food
in the United States and Japan.
Human trials have yet to determine effects of long-term DAG
oil consumption on energy metabolism. Furthermore, the effect of
DAG oil consumption on energy expenditure (EE), body composition, lipid profiles, and hepatic lipogenesis have not been assessed
together in a single study. Therefore, the objective of the present
work was to assess the effects of DAG oil supplementation for
4 wk on resting EE (REE), postprandial EE, fat oxidation, lipid
profiles, hepatic lipogenesis, body weight, and body composition.
We tested the hypothesis that DAG oil consumption would
increase total EE, postprandial EE, fat oxidation, and hepatic
lipogenesis and favorably modify lipid profile, body weight, and
body composition in overweight, hypertriglyceridemic women.
Methods
Participants. Twenty-nine nonsmoking females who did not take lipidlowering medication, aged between 18–65 y, with a BMI 24.5–36 kg/m2,
ã 2010 American Society for Nutrition.
Manuscript received January 25, 2010. Initial review completed February 12, 2010. Revision accepted March 30, 2010.
First published online April 21, 2010; doi:10.3945/jn.110.121665.
Downloaded from jn.nutrition.org at UNIVERSITY OF MANITOBA on November 4, 2011
Abstract
and serum TAG concentrations .1.0 mmol/L (1.81 6 0.66 mm/L) were
recruited by radio advertising. Participants were excluded if they were
diagnosed with diabetes mellitus or kidney or liver disease. Exclusion
criteria also included alcohol consumption .2 drinks/d (34.12 g alcohol)
or use of laxatives, concentrated fiber, fish oil, or plant sterols. Fasting
blood samples were collected to screen for normal biochemical and
hematological characteristics and a physical examination was carried
out by a physician. The study protocol was reviewed and approved by
the Human Ethical Review Committee of the University of Manitoba.
All participants received explanations about the protocol and provided
written consent.
Study design. The study was a randomized, single-blind, crossover
design consisting of 2 independent phases of 4 wk during which
participants consumed either DAG oil or a control oil blend comprised
of sunflower, safflower, and rapeseed oil at a ratio of 1:1:1. A washout
period of at least 4 wk separated the 2 study phases; in our experience,
this period is sufficient. To reduce the error term associated with diet
sequencing, the women were randomly assigned to 1 of 2 predetermined
Latin squares, each of which possessed 2 sequenced phases and 2
subjects. In this manner, we ensured that the crossover design was
balanced. During each intervention, a typical North American breakfast
was provided each day by the metabolic kitchen at the Richardson
Centre for Functional Foods and Nutraceuticals (RCFFN) of the
University of Manitoba. Participants came every day during the
intervention period and consumed the breakfast containing one-half
the portion of the DAG or control oil. A total of 40 g/d of test oil was
consumed by study participants during each intervention. On each day,
20 g of test oil assigned to that phase was incorporated into participants’
breakfasts, which were consumed under supervision, while 20 g was
given to the participants to be consumed with their other meals of the
day. Food energy intake was not controlled during the study period but
was controlled only for breakfast on the day of EE measurement. Basal
energy requirements of the women were estimated using the Mifflin
equation (17). Maintaining a consistent physical activity level during the
2 interventions was strongly recommended.
Energy expenditure. EE was measured using indirect calorimetry
(Viasys Vmax Encore 29N, Summit Technology). Substrate oxidation
was determined from the respiratory quotient on a per-minute basis.
Protein oxidation was calculated and assumed to be constant for each
measurement (18). All lean mass data were obtained from the DEXA
data. The trapezoid method was used to calculate the thermic effect of
food. Metabolic rates were plotted against time under the 6-h curve
minus the REE value obtained at 0 h.
Body composition. Whole-body DEXA scans (GE Lunar BX-1 L8743, GE Healthcare) were performed on participants at the RCFFN at
the beginning and end of each experimental phase. The DEXA unit used
a GE lunar BX-1 L-8743 scanner. Software used to analyze body
composition was Encore 2005, produced by GE Healthcare. Total (fat
and lean) tissue mass and tissue masses at trunk, android, and gynoid
areas were analyzed individually.
Serum analyses. Blood was collected after a 12-h fast on d 1 and 29 of
each phase. Blood samples were centrifuged at 1500 3 g at 48C for
20 min. Serum was immediately separated and stored at 2808C for
future analysis. Total cholesterol, HDL cholesterol, and TAG concen-
Hepatic lipogenesis. Participants received an oral dose of 0.7 g
deuterium oxide/kg estimated body water on d 28 of each study phase.
Blood was collected on d 28 (h 0) and 29 (h 24). Plasma was separated
from RBC and stored at 2808C until further analysis. Human TAG fatty
acid (TAG-FA) synthesis was measured as the rate of incorporation of
deuterium from the plasma water pool into newly synthesized fatty acids
over 24 h. The fraction of newly synthesized TAG-FA was taken as the
enrichment of the baseline (d 28) pool relative to the peak level of
achievable enrichment on d 29. Lipid fractions of plasma were extracted
(20) and samples were analyzed for deuterium enrichment using GC
(Agilent 6890N) isotope ratio MS (Delta V plus, ThermoFinnigan)
(21,22). Separation was achieved using a 6890 N Agilent GC fused
capillary column. Isolated TAG was directed to the pyrolysis reactor to
release hydrogen gas into the MS analyzed for deuterium abundance by
isotope ratio MS. The isotope ratio mass spectrometer was calibrated
each time before use using 3 water standards, including Standard Mean
Ocean Water. Samples for each woman were analyzed using the same set
of standards.
Lean mass was determined from data of DEXA and whole-body
water pool size was estimated by multiplying lean body mass by a factor
of 0.73 (23). Deuterium enrichment of the plasma TAG was estimated by
the following equation:
Fractional synthesis rateðFSRÞð%×d21 Þ ¼ DTGFAðÞ=½DplasmaðÞ×0:477;
where DTGFA is the change in deuterium enrichment over the initial
linear period of incorporation and Dplasma is the mean circulatory pool
deuterium enrichment over the 24 h.
The factor 0.477 was derived from the value given by Jungas of 0.87
g-atom 3H3g-atom carbon21 (24) incorporated into adipose tissue fatty
acids and a correction calculation to account for the glycerol moiety in a
hypothetical TAG containing 3 monounsaturated 17-C fatty acids as
previously described (25).
Statistical analysis. All data were expressed as means and SE. Baseline,
endpoint, and percent change from baseline data were compared using
paired Student’s t tests. Spearman rank correlation was used to test the
association between FSR and serum TAG concentrations. Differences
were considered significant at P , 0.05. JMP statistical software, student
edition (SAS Institute) was utilized to carry out the analyses.
Results
Participants. Twenty-nine predominantly overweight and mild
hypertriglyceridemic females were recruited, of whom 26 (20
premenopausal and 6 postmenopausal; 34.3 6 2.6 y, 78.3 6 3.6 kg
body weight, BMI 30.0 6 0.7 kg/m2) completed the study. Reasons
for dropping out included moving away from the city (n = 1),
failure to commit to daily attendance at the RCFFN for meals (n =
1), and no reason given (n = 1). All participants tolerated the
control and test oils well. Only 1 participant reported a case of flu
during the study, which was not considered to be linked to the test
oils. The sequence of treatments did not affect any of the variables
analyzed.
Energy expenditure. REE was similar at the commencement
and endpoint of each phase (Supplemental Table 1). DAG oil
consumption did not increase EE or fat oxidation during the 6-h
interval after meal consumption compared with baseline or
control oil. Similarly, total EE, fat oxidation, thermic effect of
food, carbohydrate oxidation rates, and percentage changes in
Diacylglycerol and obesity
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Sample size. Group size (n = 26) was calculated to provide an 80%
probability at P , 0.05 of detecting an anticipated difference of 2 kg of
body fat mass as measured by dual energy X-ray absorptiometry
(DEXA). A sample size of 14 was calculated as being sufficient for this 2
treatment crossover study to provide a 20% difference in TAG
concentration with 80% probability at P , 0.05. However, our overall
recruitment goal was initially 33 due to an estimated 20–25% dropout
rate. A post hoc ANCOVA including use of body weight change as a
covariate was used to control for the potential confounder of weight loss.
This approach provided an estimation of the effects of DAG administration, independent of weight loss, on major outcome variables.
trations were measured by automated methods (Ortho-Vitros 350). LDL
cholesterol concentrations were calculated using the Friedewald equation (19), because all participants had TAG concentrations ,4.5 mmol/L.
All samples were analyzed in duplicate and d 1 and 29 samples were used
as initial and endpoint data, respectively.
TABLE 1
Fat
region
Adipose tissue weights in overweight, hypertriglyceridemic women before and after 4-wk
DAG and control oil periods1
DAG oil
Baseline
Control oil
Endpoint
Baseline
P–values
Change during phase
Endpoint
DAG oil
Control oil
Baseline
Endpoint
Change
1.00
0.61
0.66
0.70
0.049
0.030
0.003
0.049
0.13
0.17
0.10
0.07
kg
Total
Trunk
Android
Gynoid
1
35.1 6
17.4 6
3.03 6
6.46 6
1.9
1.1
0.2
0.3
34.8 6
17.3 6
3.05 6
6.46 6
1.6
1.0
0.2
0.3
35.0
16.92
2.96
6.38
6 1.8
6 1.1
6 0.2
6 0.3
35.8
18.01
3.30
6.67
6 1.7
6 1.0
6 0.2
6 0.4
6 0.5
6 0.3
6 0.1
6 0.1
1.78
1.31
0.24
0.32
6 0.9
6 0. 7
6 0.1
6 0.1
Values are means 6 SEM, n = 26.
energy variables did not differ between the study periods. DAG
oil consumption did not result in a different rate of thermogenesis compared with the control oil.
Serum lipids. Serum lipid concentrations did not change after
consumption of DAG or control oil and there were no
differences between the 2 oil interventions (Supplemental Fig.
1; Table 2).
Hepatic lipogenesis. Body water was enriched similarly in
deuterium in both DAG and control phases. TAG FSR did not
differ between the DAG (16.4 6 1.5% d21) and control oil
phases (13.8 6 2.2% d21). Serum TAG was positively correlated
with TAG-FA synthesis after control oil treatment (r2 = 0.50; P ,
0.0001) and tended to be correlated after DAG oil treatment
(r2 = 0.16; P = 0.05).
Discussion
The present results suggest that DAG oil consumption for 4 wk
reduces body fat in the trunk, android, and gynoid areas in
females compared with control oil consumption. The observed
body weight and composition changes in response to DAG oil
consumption appear to be modulated by factors other than
changes in EE, fat oxidation, or lipogenesis. The exact mechanisms of action of DAG oil in modulating body fat were not
identified in the present investigation.
The importance of energy balance to body weight and
composition has been well established. To our knowledge, the
present study is the first to examine the effects of controlled
DAG oil consumption for 4 wk on multiple components of
energy balance, including postprandial EE and fat oxidation, in
women. The absence of change in acute and medium-term
postprandial EE and fat oxidation with the consumption of
DAG oil is consistent with the results reported by Hibi et al. (26).
Other studies have shown that DAG oil consumption increases
short-term total EE (27) and fat oxidation (27–29); in those
trials (28,29), participants maintained an inactive state during
Yuan et al.
the energy measurement interval, as was the case in the present
protocol. Therefore, body weight and composition modifications in our study may have been due to DAG oil consumption
with increased total EE and fat oxidation. More research is
required to reconcile the impact of DAG oil consumption on
total EE and fat oxidation with restricted energy intake and/or
increased physical activity. Hibi et al. (26) suggested that DAG
oil consumption may increase fat oxidation in people who are
overweight or obese. However, this conclusion was based on a
small sample size (n = 11). A growing body of evidence suggests
that hepatic lipid oxidation may influence appetite (3,4,30,31).
Inhibitors of hepatic fat oxidation increase food intake and it is
possible that stimulation of hepatic fat oxidation by DAG might
therefore reduce appetite (3,4). However, DAG oil consumption
did not affect fat oxidation in the present study, even though our
participants had higher BMI values than reported in other
studies (26–28). Therefore, the absence of response of postprandial total EE and fat oxidation in the present work may have
been due to our participants being less sensitive to DAG oil than
were individuals with higher lean mass, as overweight or obese
individuals are more prone to store energy as adipose tissue fat.
We observed that the lower body weight associated with
DAG oil feeding was also associated with lower total body fat as
well as fat in trunk, android, and gynoid areas, consistent with
previous findings (31–35). Contradictory data have shown that
DAG oil exerted no effect on body weight and composition
(7,36). However, these latter studies did not use a crossover
design, so their ability to measure the impact of DAG oil on body
weight/composition may have been compromised by interindividual variation. Nagao et al. (33) demonstrated that DAG
oil consumption reduced body weight by 1.5 kg over 4 mo. Our
results suggest that DAG oil consumption resulted in a 0.3-kg
greater weight reduction than the conventional oil over the 4-wk
period, which is similar to the results of Nagao et al. (33).
Kamphuis et al. (28) suggested that DAG oil consumption causes
4 g/d more fat to be shunted to oxidation than when control oil
with similar side chain fatty acids are consumed, resulting in
TABLE 2
Serum lipids
Percent changes in serum lipid concentrations in
overweight, hypertriglyceridemic women after 4-wk
DAG and control oil periods1
DAG oil
Control oil
P-value
21.8
21.3
2.6
28.7
0.46
0.49
0.63
0.64
% change
Total cholesterol
LDL cholesterol
HDL cholesterol
TAG
1
21.5
2.1
23.2
23.0
6 1.7
6 3.0
6 2.0
6 7.0
Values are means 6 SEM, n = 26.
6 2.0
6 3.0
6 3.0
6 6.0
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Body composition. Baseline body weights did not differ
between DAG (81.2 6 2.5 kg) and control oil (81.9 6 2.5 kg)
phases. Although endpoint body weight was higher after control
oil intake (82.4 6 2.5 kg) compared with DAG oil (81.4 6 2.5 kg)
(P , 0.05), the percent changes in body weight did not differ
between the DAG oil (0.2 6 0.3%) and control oil phases (0.6 6
0.3%). At endpoint, DAG oil reduced total body fat and fat in
trunk, android, and gynoid areas compared with control oil
(Table 1) (P , 0.05) without changing lean mass (Supplemental
Table 2). However, the percent changes in body composition did
not differ between the dietary interventions.
1124
0.16
20.05
0.02
0.02
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Acknowledgments
We thank Khatima Khalloufi for assisting in lipid extraction.
P.J.H.J. and Y-M.C. designed the clinical study; Q.Y. and Y-M.C.
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0.112 kg of fat loss in 4 wk. However, the absence of a detectable
change in EE and lipogenesis data in our study does not support
the weight reduction and body composition modification effect.
Therefore, DAG oil may be acting as an effective appetite
control agent (28). Other factors, including use of a different
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with women, lean compared with overweight, and different
doses of test oils might have contributed to the diversity between
our results and those of previous reports.
In the present study, consumption of DAG oil for a period of
4 wk showed that moderate body weight and composition
changes do not alter fasting lipid concentrations, which was also
suggested by Santosa et al. (37). Our results are consistent with
previous studies examining the effects of DAG on lipid profiles
(7,9,33,35,36,38,39). However, contradictory studies suggest
that DAG oil consumption does modify lipid profiles (6,8,34).
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intake between Japanese and North American populations may
account for the lack of response to the DAG oil consumption in
the latter group. Similarly, a background high-fat diet may be
one of the reasons for the lack of response in serum lipid
concentrations to DAG oil consumption in the present study, in
which lipid concentrations were measured once at baseline and
once at the endpoint of each phase. Failure to measure
concentrations for at least 2 consecutive days and averaging
them could also contribute to biologic variability in the lipid
measurements. However, the sample size used in the current
study was higher than sample size calculated based on previous
studies (7). Tomonobu et al. (42) have suggested that DAG oil
consumption modifies serum TAG in healthy participants with
elevated (.1.13 mmol/L) serum TAG but not in a population
with lower baseline TAG concentrations. Therefore, baseline
fasting TAG (1.81 6 0.66 mmol/L) in the present study may not
be a reason for participants not responding to DAG oil
consumption.
To our knowledge, this is the first study in women examining
the effects of DAG oil consumption on TAG-FA synthesis using
deuterium incorporation. DAG oil consumption for a period of
4 wk did not alter hepatic lipogenesis in the present study. Our
observations are consistent with the results of Saito et al. (38).
However, Taguchi et al. (16) observed a decreased hepatic TAG
concentration with DAG oil consumption, but that study only
assessed short term DAG oil consumption, which may explain
the differences across studies. In addition, we observed a positive
correlation between FSR and fasting serum TAG with control oil
consumption, and a tendency for an association with DAG oil
consumption. However, it is difficult to provide an explanation
for these observations.
In conclusion, although similar EE, fat oxidation, blood lipid
profiles, and hepatic lipogenesis rates occurred after the women
consumed DAG and control oils in the present study, incorporation of DAG oil in daily diets for 4 wk resulted in lower body
weight and adiposity compared with conventional oil consumption. We conclude that DAG oil may be useful for weight loss
among overweight women and further research in other groups
is warranted.
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