ORIGINAL CONTRIBUTION

Consumption of wheat bran modified by autoclaving reducesfat mass in hamsters

Scott V. Harding • Harry D. Sapirstein •

Todd C. Rideout • Christopher P. F. Marinangeli •

Arshala K. M. Dona • Peter J. H. Jones

Received: 11 April 2013 / Accepted: 3 September 2013 / Published online: 8 October 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose To investigate the effect that wheat bran modi-

fied by autoclaving (MWB) had on reducing fat accumu-

lation in hamsters fed a hypercholesterolemia- and obesity-

inducing diet.

Methods Male hamsters (n = 45) were randomized into 3

groups and fed a hypercholesterolemia- and obesity-

inducing diet with or without 10 % standard wheat bran or

MWB for 28 days. Our outcome measures included body

composition measured by DXA, oxygen consumption and

plasma lipids and glucose concentrations.

Results Animals fed the MWB diet had lower % fat mass

(49.8 vs. 53.4 %; p = 0.02) and higher % lean body mass

(47.2 vs. 44.1 %; p = 0.02) compared with controls

despite no differences in food intake or weight gain.

Additionally, plasma glucose tended to be lower (6.9 vs.

8.5 mmol/l; p \ 0.08) in the MWB animals compared with

controls.

Conclusions Our data suggest that the compositional

changes in autoclaved wheat bran, specifically solubility of

phenolic antioxidants and fiber, may have contributed to

the lower fat accumulation in our animals. Further study is

needed to determine whether the exact mechanism

involved increased lipolysis and energy utilization from

adipose.

Keywords Adiposity � Wheat bran � Weight

management � Dual-energy X-ray absorptiometry

Abbreviations

WB Wheat bran

MWB Modified wheat bran

DXA Dual-energy X-ray absorptiometry

TPC Total phenolic compounds

RS Resistant starches

DPPH 2,2-Diphenyl-1-picrylhydrazyl

Introduction

With considerable lack of clarity as to the definition of a

‘‘whole-grain’’ food, the messages put forward regarding

the health effects of whole-grain consumption may be

difficult for the average consumer to interpret. Various

jurisdictions have differing definitions of what constitutes a

whole-grain food. For example, the American Association

of Cereal Chemists (AACC) have defined the term ‘‘whole

grain’’ as having the same original composition of endo-

sperm, germ and bran regardless of whether the cereal/

kernel is whole or reconstituted following milling [1].

S. V. Harding � T. C. Rideout � C. P. F. Marinangeli �P. J. H. Jones (&)

Richardson Centre for Functional Foods and Nutraceuticals,

University of Manitoba, Winnipeg, MB R3T 2N2, Canada

e-mail: peter.jones@umanitoba.ca

S. V. Harding

Diabetes and Nutritional Sciences Division, King’s College

London, London SE1 9NH, UK

e-mail: scott.harding@kcl.ac.uk

H. D. Sapirstein (&) � A. K. M. Dona

Department of Food Science, University of Manitoba,

Winnipeg, MB R3T 2N2, Canada

e-mail: harry.sapirstein@umanitoba.ca

T. C. Rideout

Department of Exercise and Nutrition Sciences,

University at Buffalo, Buffalo, NY, USA

123

Eur J Nutr (2014) 53:793–802

DOI 10.1007/s00394-013-0583-x

Recently, the AACC have added the proviso that a ‘‘whole-

grain food’’ must contain at least 8 grams of whole grain

per 30 g serving [2]. The European Food Safety Authority

(EFSA) recognizes that individual countries within the

European Union (EU) define ‘‘whole-grain foods’’ differ-

ently (i.e., UK, whole-grain foods must contain C51 %

whole-grain ingredients by weight; Germany, whole-grain

bread should have at least 90 % whole grain) [3]. The

EFSA scientific opinion regarding whole-grain foods

helping to prevent chronic diseases does not support the

use of such claims since there is not enough data illus-

trating a clear cause and effect relationship [3]. In partic-

ular, the EFSA panel found that defining whole-grain foods

in the studies provided to support the health claims an

ambiguous task. The recent scientific position statement by

the American Society for Nutrition (ASN) regarding the

consumption of cereal fibers (whole grain, fibers and bran)

on obesity and cardiometabolic disease risk reduction

examines these discrepancies in the definition of whole

grains in more depth [4]. Regardless of the lack in clarity of

the whole-grain definition, the number of new whole-grain

food products launched worldwide surged 20-fold between

2000 and 2010 [5].

While the evidence for human health effects is ambiguous

for whole grains in general, increased intakes of foods con-

taining wheat bran are known to associate with positive

health outcomes in humans. In particular, wheat bran is

regularly used as a means to improve stool regularity and

increase fecal bulking [6]. However, the EFSA statement

does not support any claims for the use of wheat bran to aid in

weight loss or weight maintenance [6]. The ASN scientific

statement on cereal fiber or mixtures of whole grains and

bran does support the claim that there is moderate evidence

to suggest that higher consumptions do reduce the risk of

obesity, type 2 diabetes (T2D) and cardiovascular diseases

(CVD) [4]. However, despite epidemiological data sup-

porting these associations, a mechanistic explanation has not

been clearly shown. In fact, it is not clear whether benefits are

tied to consumption of the entire grain or isolated to bioactive

components contained within a specific fraction.

Wheat endosperm, the source of refined wheat flour, is

energy rich and represents [80 % of grain weight but

contains \10 % of the mineral, vitamin and dietary fiber

content of whole grain [7]. The bran fraction of wheat,

generally considered a by-product of wheat milling, con-

tains the majority of the micronutrients, dietary fiber and

potentially bioactive compounds. In fact, wheat bran is a

significant source of dietary fiber, phenolic compounds and

other phytochemicals which may have health benefits [8–

11]. However, despite its compelling nutritive value, wheat

bran is presently predominantly used for animal feed.

What differentiates wheat bran from other cereal brans,

such as oats and barley, is the molecular nature of the fiber

or non-starch polysaccharide (NSP) component. Arabin-

oxylans or pentosans, along with the NSP b-glucan, origi-

nate in cell walls and represent the primary dietary fiber

source of all cereal grains. Unlike b-glucans, which are the

main soluble NSPs of barley and oats, wheat is distin-

guished by a relatively low content of b-glucans and rela-

tively high content of pentosans. The latter are especially

abundant in the bran fraction, comprising about 23–32 %

(wt/wt) [12] depending on the genotype source of bran,

where it derives from the milling operation, and content of

adhering starchy endosperm. These fibers including cellu-

lose and inulin, plus starch and phytic acid make up the

majority of the wheat bran mass, approximately 60 %. The

balance of the wheat bran mass is made up of approximately

15 % protein, 7 % minerals, 5 % lipids and moisture. While

the level of total phenolic compounds (TPC) in wheat bran

is relatively low, as a dietary source, it ranks as major

contributor in the human diet since concentrations range

from 2,800 to 5,600 mg/kg [13]. The TPC in wheat and bran

is dominated by a single-compound ferulic acid, which

comprises 70–95 % (wt/wt) of TPC [13].

In human foods, wheat bran is primarily used to boost

fiber content and has been the food industry standard in that

regard for over a century. This use reflects its high level of

insoluble fiber and associated laxative properties that have

long been known as the major health benefit of bran [14].

Several human studies focusing on the consumption of

mixed fiber sources, including whole wheat, have demon-

strated slight-to-moderate weight reduction [15–17]. Two

of these studies used ready-to-eat breakfast cereals while

another focused on low-glycemic index foods. While these

studies were adequately designed to test the specific pro-

ducts used, the weight reductions observed were mainly

due to suppression of caloric intake or caloric density of the

diet. Similarly, there are weak in vitro and animal data

which suggest that increased consumption of dietary ferulic

acid may affect fat accumulation in such a way to promote

less fat storage [18, 19]. However, there are no human-

feeding studies that confirm this hypothesis. Therefore, no

direct mechanistic inferences can be drawn regarding cer-

eal composition and reduced adiposity.

The primary outcomes of this study were to investigate the

effect of normal (WB) and autoclave-modified wheat bran

(MWB) consumption on (1) adiposity and body composition

and (2) blood lipids in a hamster model of diet-induced

hypercholesterolemia and obesity. A previous study dem-

onstrated that autoclaving significantly increased the water

solubility of fiber and constituent phenolics as well as the

antioxidant activity of extracts [20]. Our two main hypoth-

eses were that autoclave-modified wheat bran would (1)

reduce percentage body fat accumulation and (2) reduce

circulating blood LDL-cholesterol concentrations, com-

pared with controls consuming calorically similar diets.

794 Eur J Nutr (2014) 53:793–802

123

Materials and methods

Wheat bran and modified wheat bran

A representative and commercial sample of milling grade

quality Canada Western Red Spring wheat (*1,000 kg) was

sourced by the Canadian International Grains Institute

(CIGI), Winnipeg, Canada. Wheat was milled on a Buhler

pilot mill to produce bran and flour at an extraction rate of

76 %. Coarse bran was obtained from the unsifted mill-

stream of the final break roll and separated into batches: WB

and MWB (Table 1). MWB was then produced by auto-

claving at 121 �C with 15-min sterilization at 20 psig

(AMSCO 3021, American Sterilizer Co. Pittsburgh, PA).

The total autoclave time was 31 min and included*5 min at

the outset to attain sterilization conditions, and 10 min after

sterilization for drying at approximately 80 �C and -14 psig.

Bran fractionation

For the purpose of compositional analysis, WB and MWB

were fractionated into water-soluble and water-insoluble

components. Typically, 20 g was suspended in deionized

water (1:15 w/v), and the mixture was agitated using a

magnetic stirrer for 18 h at room temperature. Subse-

quently, the suspension was filtered to separate insoluble

hydrated bran from soluble material using fiberglass mesh

with porosity of *1 mm. The filtrate was centrifuged at

4,0009g to obtain a soluble extract. The latter along with

the insoluble residue after filtration were freeze-dried for

subsequent chemical characterization.

Analysis of bran composition

Carbohydrate (Table 2) and amino acid (Table 3) compo-

sition analysis was conducted on the aqueous extract and

the fibrous residue for both the WB and MWB [21, 22].

The moisture and protein (N 9 5.7) contents of wheat bran

were determined using AACC International Approved

Methods 44-15A and 46–30, respectively [23, 24].

Pentosan content of wheat bran and extracts

Pentosan content of wheat bran and freeze-dried water-

soluble extracts was determined in duplicate using a

phloroglucinol colorimetric assay [25]. In this procedure,

bran was subjected to pre-hydrolysis using 0.5 mol/l sul-

furic acid to ensure maximal extraction of pentosans [25].

No pre-hydrolysis was used for aqueous extract samples.

Total phenolic content of wheat bran extracts

Total phenolic content of freeze-dried water-soluble

extracts of wheat bran was determined in duplicate using a

modified version of the Folin–Ciocalteu method [26, 27].

Finely ground sample (30 mg) was extracted with 100 %

methanol (1 ml) in microcentrifuge tubes and vortexed

briefly (5 s) to disperse material. Samples were extracted

for 2 h at room temperature using a RKVSD rotary mixer

(ATR Inc., Laurel, MD) at 20 rpm. Resulting extracts were

centrifuged at 3,1809g for 10 min. In 2-ml microcentri-

fuge tubes, aliquots of the supernatant extract (25 lL) were

oxidized with 0.75 ml of freshly diluted 10 % (v/v) Folin–

Ciocalteu reagent and vortexed briefly. After 5 min, the

mixture was neutralized with 0.75 ml of 6 % (w/v) sodium

carbonate (6 g/100 ml) and subsequently incubated for

90 min at room temperature in the dark. Absorbance was

measured at 725 nm against a methanol blank. Ferulic acid

was used as the standard for calibration (0–3 mM), and

results were expressed as ferulic acid equivalents (FAE

lmol/g sample).

DPPH radical scavenging activity of wheat

bran extracts

DPPH radical scavenging activity was performed in

duplicate according to Cheng et al. [28] with some modi-

fications. Finely ground samples (100 mg) were dispersed

in 50 % v/v acetone (1 ml) in microcentrifuge tubes and

vortexed briefly (5 s) and subsequently extracted for 2 h at

room temperature using a RKVSD rotary mixer (ATR Inc.,

Laurel, MD) at 20 rpm. Extracts were centrifuged at

3,1809g for 10 min. The absorbance at 515 nm of

0.208 mM DPPH solution for each sample was measured

before sample addition to test tubes. After measuring the

initial absorbance, the supernatant (0.1 ml) for each sample

was added to 3.9 ml of 0.208 mM DPPH solution and

vortexed. The solution was then stored at room temperature

for 40 min, and the absorbance at 515 nm was measured

Table 1 Nutrient content of wheat bran prior to production of

modified wheat bran

Nutrient Content (g/100 g)

Fata 5.0

Carbohydrateb 60.8

Starch 5.2

Sugars 2.5

Fiber 53.1

Protein 12.7

Phytic acid 5.0

Moisture 8.7

Ash 7.5

a Estimated from USDA nutrient data file [7]b Further carbohydrate breakdown found in Table 3

Eur J Nutr (2014) 53:793–802 795

123

again. Trolox standards were prepared ranging from 0 to

2 mM. All solutions and incubations were prepared and

conducted in the dark. A standard curve was prepared using

trolox, and results were expressed as trolox equivalents (TE

lmol/g of sample).

Study design and animals

Golden Syrian hamsters (Mesocricetus auratus; n = 15 per

group) were randomized to receive either control diet alone

(Con), formulated in our laboratory (Table 1), or the same

Table 2 Carbohydrate composition (g/100 g) of whole, aqueous extract and residues of untreated wheat bran and modified wheat bran

Whole bran Aqueous extract Extract residue

WB MWB WB MWB WB MWB

Starch 5.2 ± 0.1 4.2 ± 0.2 4.8 ± 0.0 0.4 ± 0.0 – –

Insoluble fibera 49.4 ± 0.07 48.2 ± 0.21 0.4 ± 0.21 1.6 ± 0.14 72.8 ± 0.35 62.5 ± 0.21

Soluble fibera 3.7 ± 0.003 4.4 ± 0.21 3.7 ± 0.78 11.7 ± 0.21 2.0 ± 0.14 3.5 ± 0.21

Resistant oligosaccharidesb 3.8 ± 0.21 3.8 ± 0.07 8.8 ± 0.14 22.7 ± 0.42 0.1 ± 0.0 0.3 ± 0.07

b-Glucan 2.5 ± 0.03 2.6 ± 0.03 ndc 2.5 ± 0.01 2.7 ± 0.007 2.7 ± 0.03

Inulin 1.9 ± 0.13 1.9 ± 0.21 4.6 ± 0.30 13.0 ± 0.28 ndd ndd

Pentosan 25.7 ± 0.16 25.6 ± 0.25 0.08 ± 0.0 4.42 ± 0.01 – –

Total dietary fibere 56.9 56.4 12.9 35.7 74.9 66.3

Values are mean ± SD

WB untreated wheat bran, MWB autoclaved modified wheat brana Insoluble and soluble fiber (AOAC 991.43)b Resistant oligosaccharides (AOAC 2001.03); not measured by AOAC 991.43c Not detected (\0.6 %)d Not detected (\0.5 %)e Sum of insoluble and soluble fiber by AOAC 991.43 plus resistant oligosaccharides. Soluble fiber includes b-glucan and inulin

Table 3 Amino acid composition of whole, aqueous extract and residues of untreated wheat bran and modified wheat bran

Whole bran (%) Aqueous extract (%) Extract residue (%)

WB MWB WB MWB WB MWB

Aspartic acid 1.12 1.11 1.74 0.39 0.96 1.24

Threonine 0.50 0.50 0.57 0.16 0.48 0.60

Serine 0.61 0.61 0.69 0.21 0.56 0.72

Glutamic acid 2.55 2.58 3.10 1.65 2.22 2.76

Proline 0.76 0.78 1.05 0.43 0.66 0.85

Glycine 0.85 0.86 0.95 0.37 0.85 1.01

Alanine 0.76 0.77 0.98 0.27 0.74 0.92

Valine 0.64 0.64 0.75 0.19 0.62 0.78

Methionine 0.20 0.20 0.21 nda 0.19 0.23

Isoleucine 0.45 0.45 0.55 0.14 0.42 0.54

Leucine 0.88 0.88 0.95 0.24 0.84 1.06

Tyrosine 0.43 0.43 0.51 0.15 0.38 0.50

Phenylalanine 0.56 0.56 0.58 0.21 0.54 0.65

Histidine 0.41 0.40 0.43 0.12 0.38 0.48

Lysine 0.59 0.53 0.64 0.16 0.52 0.65

Arginine 1.13 1.12 1.22 0.41 1.11 1.28

Cystine 0.30 0.26 0.55 0.10 0.21 0.31

Total amino acids 12.7 12.7 15.4 5.21 11.7 14.6

WB untreated wheat bran, MWB autoclaved modified wheat brana Not detected; analyte level below detection limit

796 Eur J Nutr (2014) 53:793–802

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diet with added WB or MWB. Both normal and MWB

were then added to the diet in place of cornstarch at 10 %

by weight. The nutrient composition of the wheat bran is

shown in Table 4. This animal/dietary model is commonly

used for cardiometabolic studies in part because of the

similarities in lipid metabolism to that of humans [29, 30].

All animals were then fed the standardized hypercho-

lesterolemia-inducing diets ad libitum for 28 days with

body weight and food consumption measured every three

days [31]. On day 25, oxygen consumption was measured

by indirect calorimetry using a respiratory gas exchange

system for rodents (MM-100 CWE, Inc., Pennsylvania,

USA) and expressed per gram body weight. On day 28,

animals were anesthetized with inhaled isoflurane and

blood sampled by cardiac puncture. Animals were then

killed with an overdose of sodium pentobarbital; body

composition, including total mass, fat mass (FM), lean

body mass (LBM) and bone mineral content (BMC), was

determined immediately by dual-emission X-ray absorpti-

ometry (DXA). The study protocol was approved by the

University of Manitoba Animal Care Committee in

accordance with the Canadian Council on Animal Care

Guidelines.

Blood chemistry

Blood was collected in heparinized tubes and separated

into plasma and packed red blood cells by centrifugation at

3,5009g for 15 min. Plasma glucose, triglycerides, total

cholesterol and HDL cholesterol were measured using the

Vitros Chemistry System 350 (Ortho-Clinical Diagnostics,

Johnson and Johnson, USA).

Statistical analysis

All outcomes were assessed versus control animals by

Student’s t test using SPSS (Version 20, IBM, Inc.,), and

p \ 0.05 was considered significant. Pearson correlations

were performed on all animals (n = 42) for food intake,

final body weight, % body weight increase, % FM and %

LBM with p \ 0.05 considered significant. The variance

was not homogenous for cholesterol and non-HDL cho-

lesterol concentrations; therefore, these variables were log

transformed for statistical testing but reported as arithmetic

means in this manuscript. All data unless otherwise indi-

cated are reported as mean ± SEM.

Results

Physical properties of treatments

Comparing aqueous extracts of MWB and control bran, the

recovery of AOAC 991.43-determined soluble fiber was

3.2-fold higher, resistant oligosaccharides (RO) were 2.6-

fold higher and inulin was 2.8-fold higher (Table 2).

Whereas there was negligible content of pentosans and

b-glucans in water extracts of control bran, corresponding

extracts of MWB contained 4.4 and 2.5 %, respectively

(Table 4). Protein recovery in the aqueous extract was

reduced in the MWB treatment, likely due to thermal

denaturation caused by autoclaving, with the total recovery

of individual amino acids reduced approximately threefold

compared to WB (Table 3). There was an increase in

phenolic content (74.8 ± 2.1 FAE, lmol/g vs. 52.4 ± 1.0

FAE, lmol/g; p \ 0.05) and DPPH radical scavenging

activity (19.8 ± 0.95 TE, lmol/g vs. 3.75 ± 0.18 TE,

lmol/g; p \ 0.05) of MWB compared with WB (Fig. 1).

The increase in phenolic content and antioxidant activity of

aqueous extracts of the MWB treatment is a reflection of

the increase in pentosan content of the same samples

together with ferulic acid (not measured), which is largely

bound to arabinoxylan in wheat bran as noted previously.

Food intake, weight gain and oxygen consumption

No significant differences were observed among groups for

initial and final body weight, % weight gain and food

intake during the 28 days of the experiment (Table 5).

Oxygen consumption, measured during the last week of the

experiment, was higher (2.2 ± 0.2 ml/min g LBM-1 vs.

1.6 ± 0.1 ml/min g LBM-1; p \ 0.05) for the MWB

Table 4 Compositions of control and wheat bran containing

hypercholesterolemia/adiposity-inducing diets

Ingredients Con (g/kg) WB/MWB (g/kg)

Casein 200.0 200.0

Cornstarch 260.0 160.0

Wheat bran/modified wheat brana 0 100.0

Sucrose 330.3 330.3

Lard–sunflower mix (50:50) 50.0 50.0

Cholesterol 2.5 2.5

Cellulose 100.0 100.0

DL-methionine 5.0 5.0

Mineral mixtureb 40.0 40.0

Vitamin mixturec 10.0 10.0

Choline bitartrate 2.0 2.0

BHT 0.2 0.2

WB untreated wheat bran, MWB autoclaved modified wheat bran,

BHT Butylated hydroxytoluenea Nutrient breakdown of WB and MWB is presented in Table 2b Vitamin mix AIN-76A (CA40077; Harlan Teklad, Madison, WI)

[60]c Mineral mix AIN-93 M (TD94047, modified for hamsters; Harlan

Teklad, Madison, WI) [61]

Eur J Nutr (2014) 53:793–802 797

123

group compared with control. There were no differences in

oxygen consumption observed between the WB group and

control or MWB. Food intake (g/day) did not correlate with

final body weight, % weight gain, % FM or % LBM.

Body composition

There were no differences in the body mass, fat mass or

lean mass among the treatment groups, as measured by

DXA. However, percent body fat and the lean/ fat mass

ratio was lower while percent lean body mass was higher in

MWB animals, compared with controls (Table 6). There

were no differences between the WB animals and either

MWB or controls. Food intake did not correlate with final

BW (p = 0.31), % BW increase (p = 0.34), % FM

(p = 0.08) or % LBM (p = 0.11).

Blood biochemistry

Contrary to our hypothesis, no differences were observed

in plasma total cholesterol, non-HDL cholesterol, HDL

cholesterol, triglycerides, glucose, albumin or total protein

between either of the treatment groups or controls

(Table 7). However, there was a trend (p \ 0.08) toward

lower fasting glucose in the MWB compared with both WB

and controls.

Discussion

Our main finding in this study was a reduction in the % FM

in animals consuming the MWB treatment. Despite no

Fig. 1 Total phenolic content and DPPH radical scavenging activity

were determined on aqueous extracts of untreated and modified wheat

bran samples. Both the phenolic content and DPPH scavenging

activity were higher (p \ 0.05) in the modified wheat bran extracts

compared with the unmodified wheat bran extracts

Table 5 Mean body weight, percent body weight gain and daily food intake of male golden Syrian hamsters fed diets with and without untreated

wheat bran and modified wheat bran for 28 days

Parameter Con WB MWB

Initial body weight (g) 122.0 ± 2.8 122.7 ± 2.7 122.8 ± 2.5

Final body weight (g) 130.8 ± 3.8 131.3 ± 3.1 131.8 ± 3.8

Body weight increase (%) 7.3 ± 2.2 7.2 ± 2.0 7.4 ± 2.1

Food consumption (g/day) 9.7 ± 0.3 9.8 ± 0.3 10.0 ± 0.4

Oxygen consumption (ml/min g LBM-1) 1.6 ± 0.1 2.0 ± 0.3 2.2 ± 0.2*

Values are mean ± SEM, n = 13–14

WB untreated wheat bran, MWB autoclaved modified wheat bran

* Different from control, p \ 0.05

Table 6 Mean tissue mass measured by dual-emission X-ray

absorptiometry (DXA) of male golden Syrian hamsters fed diets with

and without normal and modified wheat bran for 28 days

Tissue Mass Con WB MWB

Fat mass (g) 66.4 ± 1.9 63.6 ± 2.4 62.0 ± 2.5

Lean mass (g) 57.8 ± 2.2 60.2 ± 1.6 62.2 ± 2.1

Bone mineral

content (g)

3.1 ± 0.07 3.1 ± 0.07 3.1 ± 0.08

Total mass (g) 127.2 ± 3.7 126.7 ± 3.0 127.3 ± 3.8

Percent fat (%) 52.3 ± 0.8 50.0 ± 1.2 48.6 ± 1.1*

Percent lean (%) 44.1 ± 0.8 46.0 ± 1.2 47.2 ± 1.0*

Lean (g)/fat mass (g) 0.87 ± 0.03 0.97 ± 0.04 1.02 ± 0.05*

Values are mean ± SEM, n = 13–14

WB untreated wheat bran, MWB autoclaved modified wheat bran

* Different from control, p \ 0.05

Table 7 Mean plasma biochemistry of male golden Syrian hamsters

fed diets with and without normal and modified wheat bran for

28 days

Con WB MWB

Glucose 7.83 ± 0.47 8.05 ± 0.54 6.86 ± 0.46

Total cholesterol 7.48 ± 0.44 8.14 ± 0.33 8.49 ± 0.36

HDL cholesterol 3.75 ± 0.10 3.85 ± 0.04 3.86 ± 0.04

Non-HDL cholesterol 3.73 ± 0.37 4.29 ± 0.31 4.63 ± 0.34

Triglycerides 4.10 ± 0.42 3.82 ± 0.32 4.57 ± 0.37

Total protein 64.86 ± 1.66 61.14 ± 1.21 63.43 ± 1.38

Albumin 31.86 ± 0.89 31.43 ± 1.25 32.50 ± 1.17

Values are mean ± SEM, n = 13–14

798 Eur J Nutr (2014) 53:793–802

123

differences in energy intake across treatment groups, fat

accumulation was lower in MWB-treated animals. The

consumption of unmodified WB did not have any effect on

adiposity; neither absolute FM nor % FM was different

from control. It is unlikely that the change in body com-

position was due to the substitution of wheat bran at the

expense of cornstarch in the experimental diet. Replacing

the cornstarch with wheat bran reduced the caloric density

of the diet by only 0.22 kcal/g of diet per day. Therefore,

the daily caloric intakes based on mean daily food con-

sumption of each group would be approximately 35 ± 1.1,

32 ± 1.0 and 33 ± 1.3 kcal/day for the control, WB and

MWB, respectively. As there was no difference in food or

caloric intakes and there was no correlation between food

intakes and body composition, this small variation on mean

daily caloric intake did not account for the differences in

fat accumulation observed. Therefore, we speculate that the

reduced fat accumulation may have been the result of

either the changes in the carbohydrate properties, specifi-

cally the increased bio-accessibility of fiber and/or phen-

olics found in bran.

Modifying the wheat bran in a way that changes the

physical nature of its constituents could possibly modulate

the biological activity of the wheat bran constituents within

the digestive tract. Using autoclave conditions, we have

increased the aqueous recovery of specific NSP (i.e.,

pentosans, inulin and resistant oligosaccharides) and total

dietary fiber in the aqueous extracts by approximately

threefold. This increased aqueous recovery likely increased

the exposure of these polysaccharides to the colonic

microflora and facilitated their fermentation. It has been

suggested that the fermentation of NSP in the colon and the

production of short-chain fatty acids are strongly linked to

the reduction in adiposity observed with NSP consumption

[32, 33]. Furthermore, strong evidence from animal studies

shows inverse associations between dietary RS and inulin,

and reductions in fat mass and body weight. In particular,

consumption of RS, a form of soluble or water-dispersible

fiber, by rats in a diet-induced obesity study reduced both

fat mass and % body fat, with greatest changes in the

mesenteric and subcutaneous adipose tissue [34]. Similarly,

So et al. [35] demonstrated mice consuming high versus

low dietary RS had lower % adiposity despite no differ-

ence in food consumption over 8 weeks. However, dietary

consumption of 25 g NSP and 22 g RS for 4 weeks

increased fecal short-chain fatty acid concentrations in

healthy humans, but was not associated with changes in

adiposity [36]. Comparable results have also been reported

for inulin supplementation. A study in growing female

Sprague–Dawley rats demonstrated reduced fat mass over

8 weeks of supplementation with inulin [37]. Similarly,

Maurer et al. [38] reported reduced body weight and fat

mass in rats supplemented with inulin and oligofructose for

6 weeks had compared with controls and rats fed high

protein diets, although in this work energy consumption

was also reduced. However, in both of these studies, there

was a decrease in either food intake [37] or energy con-

sumed [38], which accounted for the weight loss. Our

study, while having similar dietary fiber contents but dif-

ferent physical properties did not result in different food

intakes across groups.

Animal studies examining biological actions of whole-

grain wheat and various grain fractions do tend to dem-

onstrate reductions in adiposity and body composition. For

example, in the study by Neyrink et al. [33], mice fed 10 %

wheat arabinoxylan for 4 weeks were shown to have

reduced body fat compared with controls [31]. However,

the study by Neyrinck and associates examined prebiotic

effects of arabinoxylan supplementation not specifically

weight change or body composition. Several studies using

specific oligofructose supplements report reduced epidid-

ymal adipose weight in male Wistar rats [39–41]. Again,

the weight changes and adiposity observations were sec-

ondary as these studies were primarily designed to examine

changes in GLP-1 in response to the oligofructose feeding.

In addition to fiber, the phenolic content and antioxidant

activity were substantially increased in aqueous MWB

extracts, which would suggest enhanced bio-accessibility

or bioavailability of phenolic compounds, most notably

ferulic acid, which is the predominant factor in wheat

antioxidant activity [42]. There is increasing evidence that

foods or beverages with high phenolic content can modu-

late physiological and molecular pathways involved in

energy metabolism, adiposity and obesity [43]. Perhaps

most compelling are studies involving phenolic compo-

nents or extracts of green tea which is notable for its high

content of catechins. Rodent studies involving experiments

wherein green tea extract or pure catechins were added to

an atherogenic diet have shown significantly reduced body

weight and/or adipose tissue weight [44, 45]. The generally

favorable effects of consuming green tea catechins on

obesity in mostly small trials in humans have been recently

reviewed [46]. Similar anti-adiposity outcomes in preclin-

ical trials for other types of phenolic compounds have been

observed for curcumin, the principal polyphenol in tur-

meric spice [47] and polyphenol-enriched (mainly antho-

cyanidins) extracts of adzuki beans [48]. As noted, the

major phenolic compound in wheat bran is ferulic acid

[49], but scant animal data exist on the relationship

between ferulic acid intakes and adiposity [50]. In that

study in mice, high-fat diets supplemented with ferulic acid

or a related compound, oryzinol, improved plasma and

hepatic lipid profiles, increased fecal lipid excretion and

lowered final total body mass compared with controls.

However, adiposity was not directly measured. Most of the

proposed mechanisms for phenolic intake and reduced

Eur J Nutr (2014) 53:793–802 799

123

adiposity in this and other studies are still speculative and

require further validation.

We also observed increased oxygen consumption in

hamsters consuming the MWB diet, possibly due to the

increased % LBM of the animals. Alternatively, the

increased oxygen consumption may have been due to direct

effects of the MWB in the gut. The MWB diet treatments

could have affected several gastrointestinal factors directly,

including viscosity and digesta transit time, fecal output

and fecal energy content, and microflora diversity. Each of

these factors may individually or in combination affect

energy balance in these animals. Unfortunately, fecal out-

put, caloric content of the feces and fecal microbial anal-

yses were not conducted in this study. We do not have a

working hypothesis as to how the MWB might have

increased % LBM beyond being the expected artifact of

decreased adiposity. Compositional changes to the protein

(Table 3) of the MWB may have increased the availability

of amino acids and peptides with insulin sensitizing or

mimicking effects in the postprandial period, but our study

was not designed to measure those outcomes.

Epidemiological studies have demonstrated a clear

inverse association between whole-grain consumption and

chronic disease risk [51–53]. However, data from both

population studies and intervention trials have been incon-

clusive with some studies showing whole-grain-induced

reductions in adiposity while other showing no effect [54–

57]. Unfortunately, little in the way of evidence exists for a

specific mechanism by which increased whole grain or grain

fractions would promote reduced adiposity, aside from

reduced total caloric intake. It has been suggested that satiety

can be induced sooner when the bulk of digesta is increased,

which subsequently changes the expression/action of gut

peptides of the gut-brain axis [58]; however, this has not been

demonstrated in intervention trials [59].

A key limitation of our study is the lack of difference

observed in the absolute FM and LBM between the MWB and

the controls. This may be due to high variability in the absolute

changes in body composition between individual hamsters.

While the study was adequately powered for changes in body

weight and blood lipids, there were no available data on

changes in body composition as measured by DXA, which

could have helped in our sample size calculation.

In summary, dietary supplementation for 4 weeks with

wheat bran modified by autoclaving resulted in reduced

adiposity in hamsters consuming a hypercholesterolemic

and obesity-inducing diet. While the exact underlying

mechanisms for these observations is still not clear, there

were significant and compelling compositional changes in

the physicochemical condition of the bran resulting in

increased aqueous recovery of dietary fiber constituents

including phenolic compounds. It seems plausible that the

resulting increase in bio-accessibility or bioavailability of

wheat bran fiber components, including phenolics, may be

involved in the mechanism. Further study is needed to

determine whether the exact mechanism involved cellular

processes such as increased lipolysis and energy utilization

from fat.

Acknowledgments This study was supported by Natural Sciences

and Engineering Research Council of Canada (PJHJ) and Canadian

Wheat Board (HDS).

Conflict of interest All authors have no conflict of interest to report

regarding the work presented in this manuscript.

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