Dietary supplementation with phytosterol and ascorbic acid reduces body mass accumulation and alters food transit time in a diet-induced obesity mouse model

Thornton, Wong, Neumann Rachel, Kozlowski Petri, Wasan

Description

Previous research indicates that animals fed a high fat (HF) diet supplemented with disodium ascorbyl phytostanyl phosphate (DAPP) exhibit reduced mass accumulation when compared to HF control. This compound is a water-soluble phytostanol ester and consists of a hydrophobic plant stanol covalently bonded to ascorbic acid (Vitamin C). To provide insight into the mechanism of this response, we examined the in vivo effects of a high fat diet supplemented with ascorbic acid (AA) in the presence and absence of unesterified phytosterols (PS), and set out to establish whether the supplements have a synergistic effect in a diet-induced obesity mouse model. Our data indicate that HF diet supplementation with a combination of 1% w/w phytosterol and 1% w/w ascorbic acid results in reduced mass accumulation, with mean differences in absolute mass between PSAA and HF control of 10.05%; and differences in mass accumulation of 21.6% (i.e. the PSAA group gained on average 21% less mass each week from weeks 7-12 than the HF control group). In our previous study, the absolute mass difference between the 2% DAPP and HF control was 41%, while the mean difference in mass accumulation between the two groups for weeks 7-12 was 67.9%. Mass loss was not observed in animals supplemented with PS or AA alone. These data suggest that the supplements are synergistic with respect to mass accumulation, and the esterification of the compounds further potentiates the response. Our data also indicate that chronic administration of PS, both in the presence and absence of AA, results in changes to fecal output and food transit time, providing insight into the possibility of long-term changes in intestinal function related to PS supplementation.

Sujets

• Obesity
• Phytosterol
• Ascorbic acid

Informations

• Publié par: biomed
• Publié le: 01 janvier 2011
• Nombre de lectures: 6
• Langue: English

Extrait

Thornton et al. Lipids in Health and Disease 2011, 10:107
http://www.lipidworld.com/content/10/1/107
RESEARCH Open Access
Dietary supplementation with phytosterol and
ascorbic acid reduces body mass accumulation
and alters food transit time in a diet-induced
obesity mouse model
*Sheila J Thornton , Ian TY Wong, Rachel Neumann, Petri Kozlowski and Kishor M Wasan
Abstract
Previous research indicates that animals fed a high fat (HF) diet supplemented with disodium ascorbyl phytostanyl
phosphate (DAPP) exhibit reduced mass accumulation when compared to HF control. This compound is a
watersoluble phytostanol ester and consists of a hydrophobic plant stanol covalently bonded to ascorbic acid (Vitamin
C). To provide insight into the mechanism of this response, we examined the in vivo effects of a high fat diet
supplemented with ascorbic acid (AA) in the presence and absence of unesterified phytosterols (PS), and set out to
establish whether the supplements have a synergistic effect in a diet-induced obesity mouse model. Our data
indicate that HF diet supplementation with a combination of 1% w/w phytosterol and 1% w/w ascorbic acid
results in reduced mass accumulation, with mean differences in absolute mass between PSAA and HF control of
10.05%; and differences in mass accumulation of 21.6% (i.e. the PSAA group gained on average 21% less mass
each week from weeks 7-12 than the HF control group). In our previous study, the absolute mass difference
between the 2% DAPP and HF control was 41%, while the mean difference in mass accumulation between the
two groups for weeks 7-12 was 67.9%. Mass loss was not observed in animals supplemented with PS or AA alone.
These data suggest that the supplements are synergistic with respect to mass accumulation, and the esterification
of the compounds further potentiates the response. Our data also indicate that chronic administration of PS, both
in the presence and absence of AA, results in changes to fecal output and food transit time, providing insight into
the possibility of long-term changes in intestinal function related to PS supplementation.
Keywords: Obesity, phytosterols, phytostanols, ascorbic acid
Introduction induces macrophage production and activates the
Obesity is characterized by an over-accumulation of adi- immune system without a legitimate pathogen [1].
pose tissue that is normally associated with excess calo- Numerous studies indicate that the dysregulation of
ric intake. Over the last few decades, research in the these adipocytokines may directly contribute to
obesityfield of obesity has lead us far from the concept of adi- related diseases [2]. In addition to adipocytokines, the
pose tissue as an energy storage depot. We now under- production of reactive oxygen species (ROS) has also
stand that fat is a secretory tissue, producing a variety been shown to be elevated in obesity and diabetes [3,4].
of bioactive substances collectively referred to as adipo- Hyperglycemia, hyperlipidemia and
hypercholesterolecytokines. A number of these substances, notably tumor mia, key clinical manifestations of obesity and diabetes,
necrosis factor (TNF) alpha and plasminogen activator all promote ROS production through various pathways
inhibitor type 1, suggest that obesity is essentially an [5].
inflammatory disease, where excess adipose tissue Plant sterols (phytosterols) and their saturated
derivatives, phytostanols, are among a growing list of dietary
components that exert a positive effect on hypercholes-* Correspondence: [e-mail]
Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East terolemia. It is well established that certain plant sterols
Mall, Vancouver, BC, Canada
© 2011 Thornton et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.Thornton et al. Lipids in Health and Disease 2011, 10:107 Page 2 of 14
http://www.lipidworld.com/content/10/1/107
and stanols reduce plasma cholesterol levels, ostensibly light/dark cycle and had unrestricted access to food and
by inhibiting enterocytic cholesterol uptake through water throughout the period of the study. Animal mass,
competition with dietary and biliary cholesterol for food mass and water intake were recorded once per
absorption [6-8]. The modification of hydrophobic plant week. Metabolic assessment of all animals was initiated
stanols into a water-soluble phytostanol ester, where the on week 13; therefore only data from the first twelve
phytostanols were covalently bonded to ascorbic acid weeks was used for mass accumulation analysis.
(Vitamin C), was undertaken to combine the hypocho- Following an acclimatization period of eight days on
lesterolemic properties of the phytostanol with the regular mouse chow, C57Bl/6 mice were randomly
potential benefits of an antioxidant [9,10]. The resulting assigned into 4 groups (n = 8) and placed on the diets
chemical, disodium ascorbyl phytostanyl phosphate for 18 weeks. Using Research Diet’s 45 kcal% fat diet
(DAPP) is a phytostanol analogue that exhibits a more D12451 as a high fat control (HF), diet supplements
potent hypocholesterolemic effect than unesterified phy- were milled into the HF control diet using either 1% w/
tosterols and stanols alone [11-14]. w phytosterol/stanol mixture (85451; Sigma Aldrich,
Data from studies examining the hypocholesterolemic Oakville, ON; b-sitosterol ~76%, sitostanol ~13%,
cameffects of DAPP also indicated that animals treated with pesterol ~8%, campestanol ~1%) for the PS diet, 1% w/
the compound experienced a dose-dependent decrease w L-ascorbic acid (A5960; Sigma Aldrich, Oakville, ON)
in body mass accumulation [11,15]. Further analysis of for the AA diet, or a combination of 1%
phytosterol/stathis compound-associated mass loss revealed that adi- nols and 1% L-ascorbic acid for the PSAA diet.
pose tissue stores were reduced with no accompanying
reduction in lean body mass [16,17]. When previously Oxygen Consumption
obese animals were treated with 2% w/w dietary diso- Animals were evaluated for whole animal metabolic
dium ascorbyl phytostanyl phosphate in addition to consumption using indirect flow-through calorimetry
their high fat diet (45% kcal from fat), they immediately during weeks 13-15. Measurement of oxygen
consumpbegan losing adipose tissue and within 8 days, they tion at rest (resting metabolic rate; RMR), and at
maxiachieved a statistically similar body mass to untreated mal swimming rate (VO ); were conducted on each2swim
animals on a low fat diet (10% kcal from fat). After 60 dietary group.
days of compound administration, treated animals Resting metabolic rate is defined as the lowest average
exhibited a 41% decline in total body fat with no adverse oxygen consumption at 21 ± 0.2°C over a 5 min period
effects on organ mass, femur length, muscle mass or during the light phase (between 1000 and 1800 h) using
gross morphology; in addition, a significant increase in an open flow respirometry system. For RMR assessment,
aerobic scope (VO - resting metabolic rate) was animals were placed in a sealed black Plexiglas 1075 ml2swim
observed. In effect, the compound turned previously chamber immersed in a 21 ± 0.2°C water bath as per
obese mice on a high-fat diet into a low-fat diet pheno- methodology outlined in Thornton et al, 2007 [17].
type [17]. Briefly, outside atmospheric air was pushed through the
-1Ingestion of unesterified plant sterols has been chamber at a rate of 800 ml min (0-1.5 l air pump,
reported to result in loss of adipose stores [18]. Research Rena Air 400A; Aalborg Mass Flow controller (0-5 l)). A
also indicates that mice on a high fat diet supplemented subsample of excurrent air was dried and scrubbed of
with high doses of ascorbic acid accumulate significantly CO and passed through an oxygen analyser (Beckman2
less adipose tissue than their non-supplemented coun- OM-11 polarographic oxygen analyzer) at a rate of 300
-1terparts [19-22]. By examining the in vivo effects of diet ml min . Oxygen measurements were recorded each
supplemented with ascorbic acid in the presence and second via a DI-710 A/D converter and the lowest 5
absence of phytosterols, we set out to establish whether min was corrected for pressure and temperature, and
the supplements have a synergistic effect in a diet- then averaged to estimate RMR (Windaq DATAQ
softinduced obesity mouse model, and to investigate possi- ware). Immediately prior to all metabolic measurements,
ble mechanisms for the supplement-induced mass loss. body mass was recorded to ± 0.1 g. Mice were not
denied food or water prior to respirometry
measureMaterials and methods ments; however, as most food intake occurs nocturnally,
Animals and Diets it is an accepted practice to assume the animal is
All animal studies were conducted with approval from approaching a post-prandial state near the end of a
the UBC Animal Care Committee. Male C57BL/6 mice RMR assessment [23,24]. Each animal remained in the
(4 weeks old) were purchased from Charles River chamber for a minimum of 2 hours to ensure that RMR
laboratories (St. Constant, Quebec, Canada) and housed had been achieved.
individually with wood shaving bedding. The mice were To measure VO , a glass funnel was suspend