https://doi.org/10.52973/rcfcv-e34434
Received: 03/04/2024 Accepted: 07/05/2024 Published: 21/07/2024
1 of 7
Revista Científica, FCV-LUZ / Vol. XXXIV, rcfcv-e34434
ABSTRACT
The selection of protein sources plays a signicant role in meeting the
dietary requirements of animals and addressing specic nutritional
needs. This study was designed to determine the effects of different
protein sources incorporated into lamb diets on the antioxidant
metabolism of the lung, heart and kidney tissues by means of the
measurement of GSH and LPO levels and SOD, CAT and GPx activities.
For this purpose, 24 male Morkaraman lambs were randomly assigned
to 3 groups, each of 8 animals. The dietary protein sources provided to
the animals were soybean meal + saower meal in the control group
(SSG), wheat gluten in the wheat group (WG), and corn gluten in the
corn group (CG). The diets fed to each group were formulated to be
isonitrogenous (17% crude protein/CP) and isocaloric (2700 kcal·kg
-1
ME). In the lambs fed on the diet supplemented with wheat gluten,
it was determined that SOD activity in the lung (P<0.05) and heart
(P<0.01) tissues, CAT activity in the lung and heart tissues (P<0.01), and
GPx activity in the kidney and heart tissues (P<0.01) had signicantly
increased. In the lambs fed on the diet supplemented with corn gluten,
statistically signicant increases were detected in the SOD activity
of the lung (P<0.05) and heart (P<0.01) tissues, CAT activity of the
lung, heart and kidney tissues (P<0.01, P<0.05), and GPx activity of
the kidney and heart tissues (P<0.01, P<0.05). The lambs fed on the
gluten–supplemented diets presented with statistically signicant
decreases in the LPO levels of the lung tissue (P<0.01, P<0.05), and
the GSH levels of the lung, heart and kidney tissues (P<0.01). In result,
it was ascertained that, when fed on diets supplemented with wheat
gluten and corn gluten, the antioxidant metabolism of the lung, heart
and kidney tissues were signicantly affected in lambs.
Key words: Antioxidant; catalase; glutathione peroxidase; lipid
peroxidation; superoxide dismutase
RESUMEN
La selección de las fuentes de proteínas desempeña un papel
importante a la hora de satisfacer los requisitos dietéticos de los
animales y de atender necesidades nutricionales especícas. Este
estudio se diseñó para determinar los efectos de diferentes fuentes
proteicas incorporadas a las dietas de corderos sobre el metabolismo
antioxidante de los tejidos pulmonar, cardíaco y renal mediante la
medición de los niveles de GSH y LPO y las actividades de SOD, CAT y
GPx. Para ello, se distribuyeron aleatoriamente 24 corderos machos
Morkaraman en 3 grupos de 8 animales cada uno. Las fuentes de
proteínas alimentarias suministradas a los animales fueron harina
de soja + harina de cártamo en el grupo de control (SSG), gluten de
trigo en el grupo de trigo (WG) y gluten de maíz en el grupo de maíz
(CG). Las dietas suministradas a cada grupo se formularon para ser
isonitrogenadas (17 % proteína bruta/CP) e isocalóricas (2700kcal·kg
-1
EM). En los corderos alimentados con la dieta suplementada con
gluten de trigo, se determinó un aumento signicativo de la actividad
SOD en los tejidos pulmonares (P<0,05) y cardíacos (P<0,01), de la
actividad CAT en los tejidos pulmonares y cardíacos (P<0,01) y de
la actividad GPx en los tejidos renales y cardíacos (P<0,01). En los
corderos alimentados con la dieta suplementada con gluten de
maíz, se detectaron aumentos estadísticamente signicativos en la
actividad SOD de los tejidos pulmonares (P<0,05) y cardíacos (P<0,01),
la actividad CAT de los tejidos pulmonares, cardíacos y renales (P<0,01,
P<0,05), y la actividad GPx de los tejidos renales y cardíacos (P<0,01,
P<0,05). Los corderos alimentados con dietas suplementadas con
gluten presentaron descensos estadísticamente signicativos en
los niveles de LPO del tejido pulmonar (P<0,01, P<0,05), y en los
niveles de GSH de los tejidos pulmonar, cardíaco y renal (P<0,01). En
consecuencia, se comprobó que, cuando los corderos se alimentaban
con dietas suplementadas con gluten de trigo y gluten de maíz, el
metabolismo antioxidante de los tejidos pulmonar, cardíaco y renal
se veía signicativamente afectado.
Palabras clave: Antioxidante; catalasa; glutatión peroxidasa;
peroxidación lipídica; superóxido dismutasa
Effect of protein sources on the antioxidant metabolism of visceral organs
of Morkaraman lambs
Efecto de las fuentes de proteicas en el metabolismo antioxidante
de los órganos viscerales de corderos Morkaraman
Mazhar Burak Can
1
* , Aybuke İmik
2
1
Bayburt Provincial Directorate of Agriculture and Forestry, Animal Health Breeding and Aquaculture Branch Directorate. Bayburt, Türkiye.
2
Selcuk University, Faculty of Health Sciences, Department of Nutrition and Dietetics. Konya, Türkiye.
*Corresponding author: drmazharburakcan@gmail.com
Antioxidant parameters in Morkaraman lambs / Can and Imik _______________________________________________________________
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INTRODUCTION
Viability depends on the continuous proceeding of metabolic
activities in the body tissues. On the other hand, health maintenance
depends on the balance of these metabolic activities. Elimination of
free radicals in the body by antioxidants ensures metabolic balance.
Multiple factors, including among others, management conditions
such as heat stress, as well as climatic factors, diseases and nutrition,
are known to affect the generation of free radicals in the body [1].
In the body, there is a balance between free radicals and the
antioxidant system. The disturbance of this balance in favor of free
radicals results in the development of oxidative stress [2]. Cellular
damage resulting from the unavoided increase of free radicals in cells
disrupts the intracellular signaling pathways [3]. The free radicals
generated in cells, referred to as reactive oxygen species (ROS), are
either eliminated or prevented from being generated by antioxidants,
such that cell protection is ensured.
Antioxidants synthesized by tissue cells may fall short or fail in
eliminating free radicals generated in the body. Such cases require
antioxidant supplementation. Antioxidant supplementation can
be provided by incorporating certain feed additives or feedstuffs
into the feed ration. Soybean meal not only contains a high level of
crude protein (40–49% CP) and is rich in certain elements, but also
contains several antioxidant compounds, including phenols, saponins
and avonoids [4, 5, 6]. Corn gluten is the residue of proteinaceous
compounds after the removal of starch and other compounds from
corn grains. Corn gluten, which is composed of nearly 60% of crude
protein, is also a feedstuff rich in hydrophobic amino acids such as
leucine, alanine and phenylalanine. Corn gluten is composed 60–75%
protein, 15–20% residual starch, 1% crude bre and 2% minerals [7].
Previous studies have revealed that protein peptides and hydrolysates
derived from corn protein exhibit potent antioxidant activity in the
elimination of free radicals [8, 9, 10, 11].
Wheat not only feeds most of the human population, but is also
commonly used as a feedstuff in animal nutrition. A wheat kernel
(Triticum) contains nearly 5.4% of gluten. Wheat gluten is composed
of 70–85% of crude protein, 5–15% of carbohydrates, 3–10% of lipids
and 1–2% of crude ash [12]. Recent research has shown that, given
its low production cost, wheat gluten is increasingly used as an
alternative to milk and soybean protein (Glycine max) [8, 13]. The
second most common use of wheat gluten is for animal nutrition,
yet there are no examples of its use for the feeding of ruminants
[14]. Literature reports indicate that both wheat gluten and corn
gluten have limited effect on the immunohistochemical structure of
the liver and intestinal tissues [15, 16]. Nonetheless, to the authors’
knowledge, there is no previous study presenting a comprehensive
investigation of the effects of the use of wheat gluten and corn gluten
as alternative feedstuffs on the antioxidant metabolism of tissues.
Many literature reports have been published on the incorporation
of antioxidant substances into animal feed. The aim of this study was
to determine the effects of different protein sources included in lamb
(Ovis aries) diets on antioxidant metabolism of various internal organs.
MATERIALS AND METHODS
Animal material, experimental groups and nutrition
Twenty–four 9–month–old male Morkaraman lambs, which had
similar body condition scores and live weights, were used in this
study. The lambs were fed on isocaloric (ME: 2700 kcal·kg
-1
) and
isonitrogenous (CP 17%) diets, which were incorporated with 15.93%
of soybean meal and 22% of saower meal in Group SSG, 10.3% of
wheat gluten in Group WG, and 14.78% of corn gluten in Group CG as
different protein sources. After their arrival to the farm, the study
animals were vaccinated against enterotoxaemia, treated for internal
and external parasites, acclimatized for 21 days, and fattened for a
period of 56 days. The composition of the diets provided to the lambs
throughout the study period is presented in TABLE I.
TABLE I
Composition of concentrate feeds containing
dierent protein sources in lambs (%)
Ingredients, %
Groups
SSG WG CG
Wheat gluten (75% CP) – 10.30 –
Corn gluten (61% CP) – – 14.78
Soybean meal (45% CP) 15.93 – –
Saower meal (22% CP) 7.47 – –
Rice bran 10.00 – –
Barley 60.00 52.50 60.00
Wheat – 30.00 –
Corn – – 18.22
Molasses 3.00 3.00 3.00
Marble dust 2.40 1.65 2.35
Dicalcium phosphate – 1.51 0.96
Soy oil 0.60 0.33 –
Salt 0.30 0.31 0.30
Ammonium chloride 0.20 0.30 0.28
Vitamin–Mineral premix 0.10 0.10 0.10
Total 100 100 100
Crude protein, % 17 17 17
Metabolisable energy, (kcal·kg
-1
) 2700 2700 2700
SSG: Soybean meal–Saower meal group. WG: Wheat gluten group. CG: Corn gluten group
Oxidative stress and lipid peroxidation indicators in the lung, kidney
and heart tissues
To obtain tissue homogenates, the lung, kidney and heart tissues
were ground using liquid nitrogen. Tissues were pulverized using
a homogenizer (Tissue Lyser II, Qiagen, Netherlands) with liquid
nitrogen. The powdered tissues were used in all analyses. After this
process, the tissues were homogenized with 1.15 % potassium chloride
diluted 1:10 (w/v). The tissues were then centrifuged at +4°C and
3500rpm for 15 min. The supernatant was analyzed by the method
based on the measurement of the absorbance at 532 nm of the color
formed by the reaction of malondialdehyde (MDA) with thiobarbituric
acid [17]. To determine glutathione peroxidase (GPx) activity and
glutathione (GSH) level in tissues, homogenates were centrifuged
(NUVE NF 800R, Turkey) at 10310 G for 20 min. In the supernatants
obtained, GPx activity and GSH levels in tissues were analyzed by
the method of Lawrence and Burk [18] and Sedlak and Lindsay [19],
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respectively. For superoxide dismutase (SOD) and catalase (CAT)
activity, homogenates were centrifuged (NUVE NF 800R, Turkey)
at 4392 G for 15 min at +4 °C and the supernatants were used for
analysis. The method of Sun et al. [20] and Aebi [21] was used for the
determination of SOD and CAT activities, respectively.
Statistical Analyses
Statistical analysis of the data obtained in the study was performed
using SPSS 20.0 package programme [22]. One–way analysis of
variance (ANOVA) was used for statistical calculations and signicance
control of the difference between the mean values of the groups, and
Duncan multiple comparison test was used for pairwise comparisons
between groups. The results were given as mean ± standard error
of the mean. In TABLE II, feed raw materials were considered as the
independent variable, and tissues as the dependent variable. In Table
III, feed raw materials and tissues were both treated as independent
variables, while antioxidant parameters were regarded as dependent
variables. General Linear Model (GLM) method was used for statistical
analysis of the interaction between diet, organ and diet*organ.
The model used was: Y
ijk
= µ+ a
i
+ b
j
+ (ab)
ij
+ E
ijk
Y
ijk
= Response variable,
µ = Population mean,
a
i
= Diet (soybean meal, wheat gluten and corn gluten),
b
j
= Organ (kidney, lung and heart),
ab
ij
= a × b interaction,
E
ijk
= Experimental error.
RESULTS AND DISCUSSION
Findings of antioxidant parameters in tissues
At the end of the study period, the ameliorative effects of wheat
gluten and corn gluten on oxidative stress–induced damage in
the lung, kidney and heart tissues were assessed by means of the
measurement of the activity of the enzymes superoxide dismutase
(SOD), catalase (CAT) and glutathione peroxidase (GPx), as well as the
levels of glutathione (GSH) and malondialdehyde (MDA), all of which are
part of the antioxidant defense system of the body (TABLE II and III).
When compared to Group SSG, it was found that in Groups WG and
CG, SOD activity in the lung and heart tissues, CAT activity in the lung
and heart tissues, and GPx activity in the kidney and heart tissues
had signicantly increased (P<0.01, P<0.05). In comparison to the
other groups, CAT activity in kidney tissue was signicantly increased
in Group CG (P<0.05). Compared to Group SSG, Groups WG and CG
displayed signicantly decreased LPO levels in the lung tissue (P<0.01).
On the other hand, heart tissue LPO levels were determined to have
signicantly decreased in Group CG, when compared to Groups SSG and
WG (P<0.05). Furthermore, Groups WG and CG displayed a signicant
increase in GSH levels in all tissues compared to Group SSG (P<0.01).
Upon the analysis of Table III, it was observed that SOD and GPx
activities, as well as GSH levels, decreased signicantly in the SSG
group compared to the WG and CG groups (P<0.001). Conversely, the
LPO level exhibited a signicant increase in the SSG group compared
to the WG and CG groups (P<0.001). Meanwhile, CAT enzyme activity
signicantly decreased in the SSG group and increased signicantly
TABLE II
CAT, SOD and GPx activities and GSH and LPO levels
in various tissues in the study groups
Parameters
Groups
P–value
SGG
Mean±SEM
WG
Mean±SEM
CG
Mean±SEM
SOD, mmol·min
-1
·mg tissue
-1
Kidney 35.97 ± 0.60 38.13 ± 0.63 37.84 ± 1.01 NS
Lung 31.00 ± 0.44
b
33.22 ± 0.70
a
34.09 ± 0.93
a
<0.05*
Heart 27.25 ± 0.58
b
30.22 ± 0.65
a
30.47 ± 0.64
a
<0.01**
CAT, mmol·min
-1
·mg tissue
-1
Kidney 52.94 ± 1.03
b
54.92 ± 0.93
ab
56.34 ± 1.23
a
<0.05*
Lung 36.26 ± 0.48
b
38.71 ± 1.15
a
40.73 ± 0.51
a
<0.01**
Heart 41.61 ± 1.02
b
44.52 ± 0.97
a
47.12 ± 0.71
a
<0.01**
GPx, IU·g prot
–1
Kidney 33.31 ± 0.65
b
36.32 ± 0.77
a
36.29 ± 0.75
a
<0.05*
Lung 27.09 ± 0.84 29.17 ± 0.87 29.67 ± 0.93 NS
Heart 22.47 ± 0.63
b
24.78 ± 0.49
a
24.49 ± 0.55
a
<0.05*
LPO, nmol MDA·g tissue
-1
Kidney 21.06 ± 0.48 19.70 ± 0.36 19.66 ± 0.65 NS
Lung 18.64 ± 0.31
a
16.75 ± 0.65
b
15.84 ± 0.63
b
<0.01**
Heart 15.02 ± 0.28
a
13.92 ± 0.42
ab
13.67 ± 0.43
b
<0.05*
GSH, nmol·g tissue
-1
Kidney 4.28 ± 0.060
b
4.68 ± 0.053
a
4.63 ± 0.057
a
<0.01**
Lung 4.07 ± 0.055
b
4.48 ± 0.041
a
4.40 ± 0.081
a
<0.01**
Heart 3.40 ± 0.060
b
3.75 ± 0.043
a
3.80 ± 0.044
a
<0.01**
All values are given as mean ± standard error (n=6) (SEM).
a,b
: The dierence between
means indicated with dierent letters in the same row is signicant (*:
P<0.05; **:
P<0.01). NS: Not signicant, *: Signicant dierences at P<0.05 level, **: Signicant
differences at
P<0.01 level. CAT: Catalase, SOD: Superoxide dismutase, GSH:
Glutathione, GPx: Glutathione peroxidase, LPO: Lipid peroxidation
in the CG group (P<0.001). As for the organs, LPO and GSH levels,
along with GPx and SOD activities, showed a signicant increase in
the SSG group but a signicant decrease in the CG group (P<0.001).
CAT enzyme activity signicantly increased in the SSG group and
signicantly decreased in the WG group (P<0.001). The diet*organ
interaction did not show any statistically signicant differences
between the groups (P>0.05).
Although the impact of diet and organs on tissue antioxidant levels
was signicant, the interaction between diet and organs was found to be
insignicant. These ndings indicate that the antioxidant effect of diet
on tissues remains consistent across all organs examined (TABLE III).
Proteins are known to play a major role in the healthy development
and growth of living beings. The metabolism of proteins in tissue
cells varies with several factors. The primary factors affecting
protein metabolism include species, management conditions,
environmental conditions, feed amino acid prole, feed protein
content and tissue metabolic activity. Liver tissue cells are a primary
site for metabolic activity in the body. The liver tissue plays a critical
role in the metabolism of dietary nutrients. Therefore, the healthy
functioning of the liver tissue is vital for living beings. Although at a
Antioxidant parameters in Morkaraman lambs / Can and Imik _______________________________________________________________
4 of 7
level secondary to that in the liver, metabolic activities also take place
in other visceral organs. The study data provides input on the impact
of nutritional strategy on antioxidant metabolism and should be taken
into consideration in the development of animal nutrition strategies.
Owing to their structural and functional roles, proteins are nutrients
of critical importance for animal nutrition. In particular, amino acids
being the main constituents of the majority of body structures,
including among others the visceral organs, muscles and hormones,
makes the dietary intake of high–quality proteins a basic requirement
for the sustainability of metabolic functions [23].
Free radicals generated in the body may be scavenged either by
means of antioxidant substances ingested in feed, such as vitamins
C and E, or by means of the defense systems of the body tissues. The
enzymes SOD, GPx and CAT, and the antioxidant GSH, are the main
parameters effective in preventing the accumulation of free radicals
and the induction of lipid peroxidation [24, 25]. The measurement of
the level of MDA, the end–product of lipid peroxidation, as well as the
activities of antioxidant enzymes in the blood and tissues enables the
determination of the extent and severity of oxidative damage [26].
In this respect, the present study was designed to measure SOD,
CAT and GPx activities in various visceral organs (lungs, kidneys and
heart), as well as GSH and MDA levels, the last having been selected
for the detection of the severity of lipid peroxidation.
The enzyme SOD is the rst line of defense against reactive oxygen
species in the body [27, 28]. Described as being essential to the
organism, SOD is the enzyme that is rst activated within the antioxidant
system. Acting as a catalyzer, it facilitates the dismutation of the toxic
superoxide anion into hydrogen peroxide (H
2
O
2
) and molecular oxygen
(O
2
). Jiang et al. [29] reported that the incorporation of 5% of fermented
corn gluten into the feed of weaned Holstein calves increased SOD
activity. Fang et al. [30] determined that, the replacement of soybean
meal by 2% of wheat gluten in the diet of broiler chickens did not cause
any difference on day 21 due to the glutamic acid content of the feed,
but reduced oxidative stress by day 42, although insignicantly.
On the contrary to most studies, in research conducted by Han
et al. [31] on weaned piglets, no change having been determined to
occur in SOD activity with the incorporation of 2% of wheat gluten
into the soybean meal–containing basal diet was attributed to the
oxidative stress factors not having been induced. On the other hand,
the group fed on a diet incorporated with enzymatically hydrolyzed
gluten displayed signicantly increased SOD activity on the 28
th
day
of the trial. In the present study, the replacement of the soybean
meal–containing basal diet by diets supplemented with wheat gluten
and corn gluten did not result in any effect on the kidney tissue.
However, dietary supplementation with gluten was associated
with increased SOD activity in the heart and lung tissues, resulting
from cellular damage. Gao et al. [32] reported that extracellular SOD,
synthesized and secreted by broblasts, glial cells and endothelial
cells, occurred at high levels in the pulmonary epithelial cells, as well
as in the smooth muscle cells of the respiratory ducts and blood
vessels. These researchers also described SOD as the only antioxidant
capable of inactivating oxygen at the extracellular level, and highlighted
its important role in protection from several pulmonary disorders,
including among others oxidative damage, inammation and brosis.
In this respect, the present study having demonstrated lung tissue SOD
activity to be signicantly affected by dietary supplementation with
wheat gluten and corn gluten is considered to be an interesting nding.
Catalase is found in various cell organelles, primarily the
mitochondria and endoplasmic reticulum (ER). Despite being found at
low levels in the brain, skeletal muscle and heart, the enzyme catalase
is found at high levels in the bone marrow, blood, kidneys and liver
[33]. CAT is a highly active enzyme, which acts as a catalyzer for the
dismutation of hydrogen peroxide into water (H
2
O) and oxygen (O
2
).
The generation of hydrogen peroxide, in response to the effect of
microbial or pathogenic stimulants, causes either oxidative damage
or oxidative injury [34]. The maintenance of hydrogen peroxide at low
levels by means of catalase activity contributes to the regulation of
various physiological processes such as mitochondrial function, signal
transfer and carbohydrate metabolism [35]. Jiang et al. [29] reported
that the replacement of soybean meal by corn gluten in the basal diet
of Holstein calves increased CAT activity. The present study showed
that while both wheat gluten and corn gluten increased CAT activity in
the lung and heart tissues, corn gluten was more effective than wheat
gluten in inducing the antioxidant defense system in the kidney tissue.
The enzyme GPx, found in the cytoplasm, enables the reduction of
intracellular hydrogen peroxide by means of the glutathione reaction,
prevents hydrogen peroxide–induced oxidative damage, and thereby,
avoids the generation of the hydroxyl radical (OH) [36]. Glutathione
peroxidase is also responsible for the elimination of several peroxides,
including hydrogen peroxide. In their study on weaned piglets, Han
et al. [31] determined that while the incorporation of 2% of wheat
gluten into a basal diet containing soybean meal did not alter serum
GPx activity, dietary supplementation with enzymatically hydrolyzed
wheat gluten (HWG) signicantly increased enzyme activity.
TABLE III
Eects of Diet, Organ and Diet×Organ interaction on antioxidant enzyme activity and ratio
Parameters
Diet Groups Organ Groups
Diet
P–value
Organ
P–value
Diet×Organ
P–value
SGG
Mean±SEM
WG
Mean±SEM
CG
Mean±SEM
SGG
Mean±SEM
WG
Mean±SEM
CG
Mean±SEM
SOD, mmol·min
-1
·mg tissue
-1
31.41 ± 3.93
b
33.87 ± 3.78
a
34.14 ± 3.88
a
37.31 ± 2.30
a
32.77 ± 2.35
b
29.31 ± 2.25
c
0.001 0.001 0.580
CAT, mmol·min
-1
·mg tissue
-1
43.61 ± 7.50
c
46.05 ± 7.39
b
48.07 ± 6.96
a
54.73 ± 3.23
a
38.56 ± 2.81
b
44.41 ± 3.37
c
0.001 0.001 0.801
GPx, IU·g prot
–1
27.63 ± 4.94
b
30.09 ± 5.25
a
30.16 ± 5.35
a
35.30 ± 2.44
a
28.65 ± 2.65
b
23.91 ± 1.84
c
0.001 0.001 0.942
LPO, nmol MDA·g tissue
-1
18.24 ± 2.73
a
16.79 ± 2.76
b
16.39 ± 2.98
b
20.14 ± 1.54
a
17.07 ± 1.92
b
14.20 ± 1.20
c
0.001 0.001 0.837
GSH, nmol·g tissue
-1
3.92 ± 0.41
b
4.31 ± 0.43
a
4.28 ± 0.39
a
4.53 ± 0.23
a
4.32 ± 0.24
b
3.65 ± 0.22
c
0.001 0.001 0.862
All values are given as mean ± standard error (n=3) (SEM).
a,b
: The dierence between means indicated with dierent letters in the same row is signicant. CAT; Catalase,
SOD; Superoxide dismutase, GSH; Glutathione, GPx: Glutathione peroxidase, LPO: Lipid peroxidation
_____________________________________________________________________________Revista Cientifica, FCV-LUZ / Vol. XXXIV, rcfcv-e34434
5 of 7
Furthermore, in a study by Fang et al. [30] on broiler chickens, the
replacement of soybean meal by 2% of wheat gluten was observed
not to cause any change in serum GPx activity on days 21 and 42.
Likewise, in agreement with the previous studies referred to above,
the present study showed that dietary supplementation with wheat
gluten and corn gluten did not affect GPx activity in the lung tissue
[30, 31]. However, GPx activity was increased in kidney and heart
tissues by dietary supplementation of both corn gluten and wheat
gluten. Thus, it was ascertained that the different protein sources
incorporated into the diets of the lambs affected the GPx activity of
the various tissues at different levels.
Lipid peroxidation is dened as the breakdown of free radicals into
by–products by means of their entering into reaction with unsaturated
fatty acids [37]. In such cases, free radicals cause damage to the
proteins found in the structure of the cell membrane, which in return,
leads to decrease in membrane permeability, as well as enzyme and
cell permeability [38]. Malondialdehyde (MDA), which is generated
as a result of the peroxidation of fatty acids and is of toxic nature,
is considered one of the main products of lipid peroxidation (LPO).
The increase of the level of free radicals to a point, which cannot
be compensated by cells, indicates the failure of the antioxidant
defense system in preventing oxidative stress [24]. Differently, Fang
et al. [30] reported that the replacement of soybean meal by 2% of
wheat gluten in broiler chicken feed did not cause any alteration in
serum MDA concentrations on days 21 and 42. Liao et al. [39] reported
that oxidized wheat gluten added to the diet triggers oxidative stress,
which led to an increase in MDA levels in the crop. In our study, MDA
concentrations in the lung and heart tissues having increased in the
lambs fed on the control basal ration containing soybean meal showed
that these animals had developed oxidative stress.
While glutathione (GSH) is mostly found in the cytoplasm, after being
synthesized, part of it may be found in the mitochondria, nucleus,
peroxisomes and ER [40]. Known to be synthesized in many eukaryotic
cells, GSH occurs at abundantly high levels. This antioxidant detoxies
lipid peroxides and hydrogen peroxide, and by means of its catalytic
effect, eliminates singlet oxygen and the hydroxyl anion. GSH is
mainly synthesized in the liver and 40% of it is eliminated from the
body in bile [36]. The non–enzymatic antioxidant GSH is involved
in several cellular and metabolic functions in the body. Although
primarily acting as an antioxidant, it also undertakes different tasks
in detoxication, oxidation–reduction (redox) reactions, the signaling
mechanism, apoptosis and gene expression [41]. GSH also serves in
amino acid transport and the regulation of vitamins E and C as part
of cellular metabolic processes [42]. More than 99% of GSH, which
is described as a major antioxidant, is found in reduced form within
cells [43]. Showing a reductant function, GSH is also involved in the
protection of intracellular molecules, including proteins, cysteine
and coenzyme A, as well as antioxidants such as ascorbate and a–
tocopherol. Research has shown that when ingested, glutathione and
its precursors prevent the development of several pathophysiological
disorders or enable the regression of these disorders to a former
stage [44]. Ölmez et al. [45] reported that when Tuj (Tushin) lambs
were given a SOD–rich dietary antioxidant supplement (30 g/t feed),
their GSH levels increased. In the present study, when compared to
the control group, the groups fed on diets supplemented with wheat
gluten and corn gluten (Groups WG and CG) displaying signicantly
increased GSH levels in the lung, kidney, and heart tissues showed
that these supplements were effective in preventing free radical–
induced oxidative damage.
CONCLUSIONS
Knowledge on the metabolism of feedstuffs used for animal
nutrition is critical to the development of effective nutrition
strategies. This study demonstrated the effects of soybean meal,
wheat gluten and corn gluten, used as different dietary protein
sources, on the antioxidant metabolism of the heart, lung and kidney
tissues. A notable nding was the decrease in MDA levels with wheat
gluten and corn gluten supplementation. Wheat gluten and corn gluten
having been determined to show varying effects on the antioxidant
metabolism of various tissues, and other ndings of this study are
expected to provide a foundation for future research in this area.
Ethical Approval
The study was approved by Ataturk University, Faculty of Veterinary
Medicine Ethics Committee (Decision number: 2024/08).
Conict of Interest
The authors declare there is no conict of interest.
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