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Dietary glutamine prevents the loss of intestinal barrier function and attenuates the increase in core body temperature induced by acute heat exposure

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Dietary glutamine (Gln) supplementation improves intestinal function in several stressful conditions. Therefore, in the present study, the effects of dietary Gln supplementation on the core body temperature (T core), bacterial translocation (BT) and intestinal permeability of mice subjected to acute heat stress were evaluated. Male Swiss mice (4 weeks old) were implanted with an abdominal temperature sensor and randomly assigned to one of the following groups fed isoenergetic and isoproteic diets for 7 d before the experimental trials: group fed the standard AIN-93G diet and exposed to a high ambient temperature (39°C) for 2 h (H-NS); group fed the AIN-93G diet supplemented with l-Gln and exposed to a high temperature (H-Gln); group fed the standard AIN-93G diet and not exposed to a high temperature (control, C-NS). Mice were orally administered diethylenetriaminepentaacetic acid radiolabelled with technetium (99mTc) for the assessment of intestinal permeability or 99mTc-Escherichia coli for the assessment of BT. Heat exposure increased T core (approximately 41°C during the experimental trial), intestinal permeability and BT to the blood and liver (3 h after the experimental trial) in mice from the H-NS group relative to those from the C-NS group. Dietary Gln supplementation attenuated hyperthermia and prevented the increases in intestinal permeability and BT induced by heat exposure. No correlations were observed between the improvements in gastrointestinal function and the attenuation of hyperthermia by Gln. Our findings indicate that dietary Gln supplementation preserved the integrity of the intestinal barrier and reduced the severity of hyperthermia during heat exposure. The findings also indicate that these Gln-mediated effects occurred through independent mechanisms.
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Dietary glutamine prevents the loss of intestinal barrier function and
attenuates the increase in core body temperature induced by
acute heat exposure
Anne D. N. Soares
1
,Ka
´tia A. Costa
1
, Samuel P. Wanner
2
, Rosana G. C. Santos
1
,
Simone O. A. Fernandes
1
, Flaviano S. Martins
3
, Jacques R. Nicoli
3
,Ca
ˆndido C. Coimbra
4
and Valbert N. Cardoso
1
*
1
Department of Clinical Analysis and Toxicology, School of Pharmacy, Universidade Federal de Minas Gerais, Avenida
Anto
ˆnio Carlos, 6627 Belo Horizonte, MG 31270-901, Brazil
2
Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy,
Universidade Federal de Minas Gerais, Avenida Anto
ˆnio Carlos, 6627 Belo Horizonte, MG 31270-901, Brazil
3
Department of Microbiology, Institute of Biological Sciences, Universidade Federal de Minas Gerais,
Avenida Anto
ˆnio Carlos, 6627 Belo Horizonte, MG 31270-901, Brazil
4
Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais,
Avenida Anto
ˆnio Carlos, 6627 Belo Horizonte, MG 31270-901, Brazil
(Submitted 7 March 2014 – Final revision received 20 July 2014 – Accepted 24 July 2014 – First published online 17 October 2014)
Abstract
Dietary glutamine (Gln) supplementation improves intestinal function in several stressful conditions. Therefore, in the present study, the
effects of dietary Gln supplementation on the core body temperature (T
core
), bacterial translocation (BT) and intestinal permeability of mice
subjected to acute heat stress were evaluated. Male Swiss mice (4 weeks old) were implanted with an abdominal temperature sensor and
randomly assigned to one of the following groups fed isoenergetic and isoproteic diets for 7 d before the experimental trials: group fed the
standard AIN-93G diet and exposed to a high ambient temperature (398C) for 2 h (H-NS); group fed the AIN-93G diet supplemented with
L-Gln and exposed to a high temperature (H-Gln); group fed the standard AIN-93G diet and not exposed to a high temperature (control,
C-NS). Mice were orally administered diethylenetriaminepentaacetic acid radiolabelled with technetium (
99m
Tc) for the assessment of
intestinal permeability or
99m
Tc-Escherichia coli for the assessment of BT. Heat exposure increased T
core
(approximately 418C during
the experimental trial), intestinal permeability and BT to the blood and liver (3 h after the experimental trial) in mice from the H-NS
group relative to those from the C-NS group. Dietary Gln supplementation attenuated hyperthermia and prevented the increases in intes-
tinal permeability and BT induced by heat exposure. No correlations were observed between the improvements in gastrointestinal function
and the attenuation of hyperthermia by Gln. Our findings indicate that dietary Gln supplementation preserved the integrity of the intestinal
barrier and reduced the severity of hyperthermia during heat exposure. The findings also indicate that these Gln-mediated effects occurred
through independent mechanisms.
Key words: Bacterial translocation: Hyperthermia: Immunonutrients: Intestinal permeability
Glutamine (Gln) is an amino acid with many important
metabolic functions. It serves as a fuel for rapidly dividing
cells (particularly lymphocytes and enterocytes)
(1,2)
, induces
the expression of heat shock proteins (HSP)
(3 – 6)
, prevents
apoptosis induced by injury
(7)
, has immunoregulatory func-
tions
(8,9)
, and is a key precursor for the intestinal synthesis
of glutathione, one of the major antioxidants in the
body
(3,10,11)
. Although Gln is the most abundant amino acid
in the bloodstream, under certain conditions of stress, such
as trauma, sepsis, major surgery, bone marrow transplantation,
and intense chemotherapy and radiotherapy, the physiological
requirement for Gln may exceed the capacity for endogenous
synthesis such that Gln becomes a conditionally essential
amino acid
(3)
. Thus, dietary Gln supplementation may be a
useful strategy to improve the body’s response to stressful
conditions.
*Corresponding author: Valbert N. Cardoso, email valbertcardoso@yahoo.com.br
Abbreviations: cpm, counts of radioactivity/min.; C-NS group, non-supplemented mice maintained under temperate conditions; DTPA,
diethylenetriaminepentaacetic acid; Gln, glutamine; H-Gln group, glutamine-supplemented mice subjected to heat stress; H-NS group, non-
supplemented mice subjected to heat stress; HSP, heat shock proteins; sIgA, secretory IgA.
British Journal of Nutrition (2014), 112, 1601–1610 doi:10.1017/S0007114514002608
qThe Authors 2014
British Journal of Nutrition
Recently, our group has reported that Gln therapy is
effective at preserving mucosal integrity and preventing
increases in intestinal permeability and bacterial translocation
(BT) in mice subjected to an experimental model of intestinal
obstruction
(12)
. These positive effects of Gln on the intestinal
barrier function suggest a potential role for Gln in the
prevention of heat stroke, a life-threatening illness character-
ised by elevated core body temperatures (T
core
), generally
above 408C.
Heat stroke events are not rare. According to the US Armed
Forces Health Surveillance Center
(13)
, the incidences of
heat stroke and ‘other heat injury’ events among active-duty
military recruits in 2011 were 0·25 and 1·82 per 1000 person-
years, respectively. A high incidence of heat stroke was also
observed during a heat wave in Europe in the summer of
2003, when tens of thousands of people died from
heat-related injuries
(14)
. The pathogenesis of heat stroke is com-
plex; marked increases in T
core
are associated with blood flow
redistribution, which is characterised by cutaneous vasodilation
that occurs at the expense of decreased intestinal blood
flow
(15 – 18)
. This splanchnic vasoconstriction may cause ischae-
mia and limit local vascular heat exchange, thereby promoting
bowel tissue hyperthermia. Both intestinal ischaemia and
hyperthermia may promote oxidative and nitrosative stresses
that stimulate cytoskeletal relaxation, thus contributing to
the opening of tight junctions and/or injuries to the
epithelium
(16,18 – 21)
. These morphological and functional
changes enhance intestinal permeability
(5,19,20)
, thus facilitating
the translocation of bacteria and endotoxins that are
normally contained in the intestinal lumen
(5,15,19,20,22,23)
and
subsequently increasing the risk of a systemic inflammatory
response syndrome that may culminate in multi-organ system
failure and death
(16,18)
.
A previous investigation has already reported Gln-mediated
beneficial effects in passively heated animals. Singleton &
Wischmeyer
(5)
observed that Gln administration decreased gut
permeability and plasma endotoxin concentrations and also
improved survival following lethal hyperthermia. However,
they conducted their study in rats under anaesthesia with
ketamine and xylazine, which may represent a confounding
factor because deep anaesthesia affects thermoregulation
(24)
.
In addition to this methodological issue, Singleton &
Wischmeyer did not address whether oral Gln supplementation
could change the ability to maintain T
core
during heat exposure.
As Gln modulates the release of inflammatory cytokines
(25,26)
and as systemic inflammation response syndrome is closely
associated with thermoregulatory manifestations
(27)
, Gln
may also exert beneficial effects in passively heated animals
by reducing their thermal strain under extreme environmental
conditions.
Heat stroke is a deadly event that affects not only immuno-
compromised, aged people, but also healthy, young people.
Therefore, the present study aimed to assess T
core
, intestinal
permeability and BT to the blood and extra-intestinal organs
in unanaesthetised and unrestrained mice exposed to a high
ambient temperature. Moreover, because Gln preserves gas-
trointestinal function under several stressful conditions,
another relevant question that was addressed was whether
dietary Gln supplementation can alleviate the functional
changes in the intestine and the increase in T
core
that are
induced by a passive heating protocol.
Experimental methods
Animals and diets
In total, seventy-eight male Swiss mice (4 weeks old) weighing
20·3 (SEM 1·9) g were obtained from the animal care centre
at the Faculty of Pharmacy (Federal University of Minas
Gerais, Brazil) and were used in all the experiments. Mice
were housed in individual cages under controlled light
(05.0019.00 hours) and temperature (24·0 ^2·08C) con-
ditions with water and chow provided ad libitum. The
experiments were approved by the local Ethics Committee
for Animal Experimentation (protocol number: 007/2011)
and carried out in compliance with the Guide for the Care
and Use of Laboratory Animals published by the Institute of
Laboratory Animal Resources.
Mice were surgically implanted with abdominal temperature
sensors, allowed to recover for 5 d, and then randomly allo-
cated to three groups: (1) group fed the standard AIN-93G
diet and maintained at room temperature during the exper-
imental trials (control and non-supplemented group; C-NS);
(2) group fed the standard AIN-93G diet and subjected to
a passive heating protocol (hyperthermic and non-
supplemented group; H-NS); (3) group fed the AIN-93G diet
supplemented with Gln and subjected to a passive heating
protocol (hyperthermic and Gln-supplemented group;
H-Gln). The standard AIN-93G diet was originally formulated
to support the growth, pregnancy and lactation of rodents
by the American Institute of Nutrition
(28)
and has been used
extensively. In the supplemented diet, a portion of casein
(equivalent to 4·375 mg/g) was replaced with L-Gln (Sigma-
Aldrich). Thus, the standard and Gln-supplemented diets
were isoenergetic and isoproteic.
Mice were fed the assigned diets for 7 d
(12,29,30)
. During this
period, water was provided ad libitum and body weight and
food intake were measured once and twice a day, respect-
ively. During the light phase of the day, all mice were given
access to the AIN-93G diet ad libitum. In contrast, during
the dark phase, mice were given access to only 4 g of food,
an amount that they fully consumed on most days. Mice
from the H-Gln group had access to 4 g of the supplemented
diet, which corresponded to a daily intake of 17·5 mg of Gln or
500 mg Gln/kg body weight (i.e. mice had an average body
weight of 35 g on the day of the experimental trials). This
dose of Gln was selected based on previous findings that
showed decreased BT to the liver, lungs and spleen of mice
subjected to intestinal obstruction after the enteral adminis-
tration of 500 mg/kg of Gln once a day for 7 d
(29)
.
After Gln supplementation (or free access to the AIN-93G
diet) for 7 d, mice were subjected to the experimental
trials: a passive heating protocol or resting under temperate
conditions. All experimental trials were performed during
the light phase of the day. To achieve the goals of the
study, three different sets of animals were used, with mice
A. D. N. Soares et al.1602
British Journal of Nutrition
being always allocated to the three groups described earlier
(i.e. C-NS, H-NS and H-Gln). The first set of mice (n12 per
group) was used to measure intestinal permeability, whereas
the second (n8 per group) and third (n6 per group) sets
were used to measure BT and secretory IgA (sIgA) concen-
trations in the intestinal fluid, respectively. The abdominal
temperature of all mice subjected to different protocols was
recorded during the experimental trials.
Implantation of the abdominal temperature sensor
A telemetry transmitter was surgically implanted in each
mouse for recording T
core
(G2 E-Mitter series; Mini Mitter).
Mice were weighed and anaesthetised with ketamine
(60 mg/kg body weight, intraperitoneally) and xylazine
(8 mg/kg body weight, intraperitoneally). During an aseptic
procedure, the device was implanted in the abdominal
cavity via a midline laparotomy and fixed to the lateral
abdominal wall with sutures. Then, the abdominal muscles
and skin were sutured in layers
(31,32)
. To prevent surgical
hypothermia, the surgery was performed by placing the
mice on a pad that was heated to 338C.
Mice were allowed to recover from this surgery for 5d.
This period was sufficiently long for the mice to recover and
overcome their presurgical body weight (26·2 (SEM 0·7) g post-
surgical v. 20·4 (SEM 0·4) g presurgical, P,0·001; the telemetric
probes had an average weight of 1·1 g). During this recovery
period, each mouse was individually housed and maintained
under standard environmental conditions and given access
to the AIN-93G diet (control) and tap water ad libitum.
Experimental trials
Mice were weighed and orally administered diethylenetriami-
nepentaacetic acid (DTPA) radiolabelled with technetium
(
99m
Tc) for the assessment of intestinal permeability or
99m
Tc-Escherichia coli for the assessment of BT. Mice were
then allowed to rest for 30 min in a room with the ambient tem-
perature maintained at 248C. Mice from the H-NS and H-Gln
groups were then transferred from their home cages to an
acrylic chamber (25·5 cm long £14 cm wide £13·5 cm high)
that was preheated to 398C. An electric fan positioned at one
end of the chamber generated an air flow rate of 2·0 –2·5 m/s.
The environment inside the chamber was heated by placing
an electric heater (model AB 1100; Brita
ˆnia) at the same level
20 –30 cm away from the fan and turned on at 1200 W
(33)
.
The ambient temperature was set at 398C based on previous
findings showing that this environment was sufficiently hot to
raise the abdominal temperature of mice above 428C within
4h
(34)
. The ambient temperature was measured using a ther-
mocouple (400A; Yellow Springs Instruments). The heat
exposure protocol lasted 2 h or the time required for an
animal to exhibit the T
core
limit of 428C. This T
core
value was
chosen as a criterion for interrupting the passive heating pro-
tocol because it induces autonomic and behavioural responses
related to heat stroke
(34)
without causing mortality in mice
(35)
.
Rather than being exposed to heat, mice from the C-NS
group were allowed to move freely in their home cages at
an ambient temperature of 248C for 2 h. Food and water
were not provided to the mice while they were resting in
the cage or during the heat exposure protocol. However,
from the end of the heat exposure or control period to the
time of killing, they were given free access to water and
food again.
Measurements
Abdominal temperature. Abdominal temperature was
measured by telemetry at 30 s intervals and was considered
to represent T
core
. The radiowave pulses emitted by the tem-
perature sensors were captured by a receiving plate, which
was positioned next to the chamber (during the experiments
in the hyperthermic groups) or below the home cage of
mice (in the C-NS group). The information received by the
plate was sent to a data acquisition system (Vital View; Mini
Mitter), which converted the frequency values into tempera-
ture values.
Telemetry is a technique that allows the measurement of
temperature in conscious and freely moving animals without
affecting their ability to engage behavioural and autonomic
thermoeffectors to deal with environmental challenges. This
method eliminates the influence of confounders such as
restraint of the animals, stress associated with the insertion
of rectal temperature probes, and anaesthesia on the study
(35)
.
Intestinal permeability. Intestinal permeability was
assessed based on the diffusion of a DTPA solution labelled
with
99m
Tc that was administered orally. The DTPA probe
is large (molecular weight: 500700 Da), allowing for the
evaluation of intestinal permeability through the paracellular
pathway
(36)
.
The experimental trials (i.e. heat exposure protocol or rest-
ing under temperate conditions for 2 h) were carried out
30 min after the administration of 13 MBq of
99m
Tc-DTPA in a
volume of 0·1 ml. At 3, 8 and 18 h after the experimental
trial, groups of six mice were anaesthetised and killed by
decapitation. Trunk blood samples (300 ml) were collected
and placed in appropriate tubes for radioactivity measurement
in an automatic gamma counter (Wallac Wizard model 1480;
Perkin Elmer).
The percentage of the administered dose present in the
blood was calculated using the following equation
(30,37 – 40)
:
%Dose ¼ðcpm in blood=cpm of standardÞ£100;
where cpm represents the counts of radioactivity/min.
Bacterial translocation. BT translocation was measured
in three more groups of mice (n8 each). Mice were orally
administered 0·1 ml of
99m
Tc-E. coli ATCC-10 536 (1·8 MBq)
containing 10
8
colony-forming units. The radiolabelling of
E. coli was performed as described by Diniz et al.
(41)
. The
percentage of
99m
Tc incorporated into the bacterial cells was
determined using the following equation:
%Labeling ¼ðcpm of precipitate=cpm of precipitate
þcpm of supernatant £100Þ:
Mice were subjected to the heat exposure protocol or
allowed to rest under temperate conditions 30 min after the
Dietary glutamine and hyperthermia 1603
British Journal of Nutrition
administration of
99m
Tc-E. coli. BT was evaluated 3 h after the
heat exposure protocol because within the time points studied
this time point corresponded to the period when increased
intestinal permeability was observed. Blood, mesenteric
lymph nodes, liver, spleen, brain and lungs were collected,
weighed and placed into tubes for radioactivity measurement
in an automatic gamma counter (Wallac Wizard model 1480;
Perkin Elmer). The results are expressed as cpm relative to
the mass of tissue analysed
(30,37 – 40)
.
Immunoglobulin analysis. The small intestines of mice
from all groups (C-NS, H-NS and H-Gln; n6 for each group)
were removed after killing the mice. The intestinal contents
(500 mg) were withdrawn, weighed and resuspended in
2 ml of PBS supplemented with an anti-protease cocktail
(1 mM-aprotinin, 25 mM-leupeptin, 1 mM-pepstatin and 1 mM-
phenylmethanesulphonyl fluoride); this anti-protease cocktail
was used by Santos et al.
(30)
. The concentrations of sIgA in
the intestinal fluid were measured by ELISA using a goat
anti-mouse IgA (Sigma Chemical Company) and a horseradish
peroxidase-conjugated goat anti-mouse IgA (Sigma), as
described previously by Martins et al.
(42)
. The measurements
were performed in duplicate. sIgA is an important component
of the intestinal protective immunity and acts by reducing the
number of epithelium-adherent bacteria, thus limiting BT
through the epithelium
(43)
.
Statistical analyses
The variables studied were tested for normality using the
ShapiroWilk test. All the variables, except BT data, were
normally distributed. The BT data are expressed as medians
and analysed using the non-parametric KruskalWallis test.
When significance was detected, Mann Whitney post hoc
tests were conducted to identify differences among the
experimental groups.
Normally distributed data are expressed as means with their
standard errors. The abdominal temperature curves were com-
pared between the experimental groups and time points using
a two-way ANOVA, with repeated measures only for the time
factor. Body weight gain, intestinal permeability, sIgA concen-
trations and food, energy, protein and nitrogen intakes were
compared among the three groups using one-way ANOVA.
Tukey’s test was used as the post hoc test for variables that
had a variation coefficient ,15 % and Duncan’s test for vari-
ables that had a variation coefficient .15 %
(44)
. Differences
in the preoperative and postoperative body weight were
assessed using paired Student’s ttest (data from the three
experimental groups were pooled for this analysis). The role
of Gln supplementation in the prevention of the increase of
T
core
to 428C during the passive heating protocol was assessed
using the log-rank test
(45)
.
The AUC of T
core
across time points was calculated using
trapezoidal integration. The correlation between the thermo-
regulatory parameters (final abdominal temperature, maximal
temperature achieved and area under the temperature curve)
and intestinal permeability or sIgA concentrations was
assessed using Pearson’s coefficient analysis. The correlation
between the thermoregulatory parameters and BT was
assessed using Spearman’s coefficient (non-parametric)
analysis.
All analyses were performed using Sigma Plot version 11.0
(Systat Software, Inc.), and P,0·05 was defined as statistically
significant.
Results
Body weight gain and food intake
There were no significant differences in the nutritional par-
ameters evaluated among the three experimental groups
(P.0·05 for all nutritional parameters; Table 1). The only
exception was the intake of Gln, which was augmented by
approximately 17·5 mg/d in mice from the H-Gln group
when compared with those from the non-supplemented
groups. Mice exhibited an average body weight gain of 7·9
(SEM 0·2) g (pooled data for the three experimental groups)
across the 7 d of treatment with different diets. Their average
daily intakes of food, energy and protein were 5·2 (SEM
0·1) g, 81·3 (SEM 1·5) kJ and 1·03 (SEM 0·02) g, respectively.
Core temperature
Before the experimental trials (at time 0), mice exhibited an
average T
core
that ranged from 37·56 to 37·758C, and no differ-
ences were observed among the three experimental groups
(Fig. 1). At an environmental temperature of 248C, the T
core
of mice from the C-NS group remained stable at
Table 1. Body weight gain and daily chow, energy and protein intakes in the C-NS (non-
supplemented mice maintained under temperate conditions), H-NS (non-supplemented mice
subjected to heat stress) and H-Gln (glutamine-supplemented mice subjected to heat stress)
groups during the 7 d before the experimental trials
(Mean values with their standard errors)
Experimental groups
C-NS H-NS H-Gln
Mean SEM Mean SEM Mean SEM P
Body weight gain (g) 8·6 0·4 7·8 0·4 7·4 0·4 0·124
Chow intake (g/d) 5·3 0·2 5·2 0·2 4·9 0·2 0·286
Energy intake (kJ/d) 83·5 2·6 82·4 2·8 77·8 2·5 0·286
Protein intake (g/d) 1·06 0·03 1·05 0·04 0·99 0·03 0·286
A. D. N. Soares et al.1604
British Journal of Nutrition
approximately 37·58C for 20 min and then gradually decreased
to 37·08C, a value that was sustained until the end of the
recording period. The fact that T
core
decreased in mice from
the C-NS group as the experiments progressed indicates that
the trials were initiated when the mice were still under the
effects of stress hyperthermia induced by the handling and
oral administration procedures.
The heat-exposed mice (i.e. the H-NS and H-Gln groups)
exhibited a steep increase in T
core
because of the exposure
to an uncompensated environmental heat load (Fig. 1).
Exposure to a high ambient temperature (398C) significantly
increased the T
core
of mice from the H-NS group relative to
those from the C-NS group from the 3rd min to the end of
the heat exposure protocol (40·90 (SEM 0·17) v. 37·02 (SEM
0·07)8C at the end; P,0·001). Heat exposure also increased
the T
core
of mice from the H-Gln group relative to those
from the C-NS group; however, Gln-supplemented mice
exhibited attenuation of hyperthermia compared with non-
supplemented mice from the 49th to the 70th min of heating
(39·86 (SEM 0·11) v. 40·33 (SEM 0·15)8C at the 70th min;
P,0·05; Fig. 1).
This Gln-induced protective thermoregulatory effect was
also evident from the analysis of the percentage of mice in
which the T
core
limit of 428C was reached during the passive
heating protocol (P,0·05; log-rank test). Of the twenty-six
mice from the H-NS group, six (23 %) exhibited a T
core
of
428C before the end of the 2 h heat exposure protocol
(Fig. 2). In contrast, this temperature limit was reached in
only one mouse from the H-Gln group (4 %). It is worth
noting that during the passive heating protocol, one mouse
from the H-NS group died with a T
core
value of 41·58C after
being exposed to heat for 100 min (this mouse was excluded
from all analyses). No mice from the H-Gln group died
during the experimental trials.
Intestinal permeability
Mice from the C-NS group exhibited a physiological range of
intestinal permeability values at 3, 6 and 18 h after the exper-
imental trial (Fig. 3). At 3 h after the heat exposure protocol,
mice from the H-NS group exhibited an increased intestinal
permeability that was approximately eleven to twelve times
higher than that of mice from the C-NS group (Fig. 3); how-
ever, this augmented intestinal permeability was transient,
and no differences were observed between these two
groups at 6 and 18 h after the experimental trial. Dietary Gln
supplementation prevented the increase in intestinal per-
meability that was observed in mice from the H-NS group at
3 h after the heat exposure protocol. In fact, the uptake of
99m
Tc-DTPA in the blood samples of mice from the H-Gln
group was similar to that in mice from the C-NS group at
every time point studied.
Bacterial translocation
Mice from the C-NS group exhibited a physiological level of
BT to the blood and all organs at 3 h after the experimental
trial (which corresponded to the time point when increased
intestinal permeability caused by passive heating was
observed; Table 2). Heat exposure increased BT, as demon-
strated by a significantly increased uptake of
99m
Tc-E. coli by
the blood and liver (P,0·05) and a tendency for higher
uptake by the lungs (P¼0·064) in mice from the H-NS group
Time (min)
0 20406080100120
Abdominal temperature (°C)
37
38
39
40
41
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Fig. 1. Abdominal temperature of mice during the experimental trials. C-NS
group, non-supplemented mice maintained under temperate conditions
(–W–); H-NS group, non-supplemented mice subjected to heat stress (X–);
and H-Gln group, glutamine-supplemented mice subjected to heat stress
(). Values are means (n26 per group), with their standard errors rep-
resented by vertical bars. * Mean values for the H-NS and the H-Gln group
were significantly different that of the C-NS group (P,0·001). † Mean value
was significantly different from that of the H-NS group (P,0·05).
Time (min)
0 20406080100120
Percentage of mice that attained
abdominal temperatures <42°C
0
70
80
90
100
*
Fig. 2. Percentage of mice that did not attain the abdominal temperature
limit of 428C at different time points during the passive heating protocol (n26
per group). H-NS group, non-supplemented mice subjected to heat stress
(–X–), and H-Gln group, glutamine-supplemented mice subjected to heat
stress ( ). * Percent age of mice along the whole experimental trial was
significantly different from that of the H-NS group (P,0·05).
Dietary glutamine and hyperthermia 1605
British Journal of Nutrition
compared with those from the C-NS group (Table 2). Dietary
Gln supplementation prevented the hyperthermia-induced BT
to the blood, liver and lungs; the uptake of
99m
Tc-E. coli in
mice from the H-Gln group was lower than that in mice
from the H-NS group (P,0·05) and did not differ from that
in mice from the C-NS group. No differences were observed
in the uptake of
99m
Tc-E. coli by the mesenteric lymph
nodes, spleen and brain among the three experimental
groups.
Secretory IgA concentrations in the intestinal fluid
At 3 h after the experimental trial, no differences were
observed in sIgA concentrations among the three experimen-
tal groups (P¼0·20; Fig. 4).
Correlation analyses
Correlation analyses were performed to determine whether
the beneficial effects of Gln supplementation on intestinal
function were associated with Gln-mediated changes in
thermoregulation. Intestinal permeability, BT and sIgA con-
centrations were found to be not significantly associated
with any of the evaluated thermoregulatory parameters
(i.e. the T
core
after 2 h of heat exposure, the highest T
core
value recorded or the area under the T
core
curve during the
passive heating protocol; Table 3). The only exception was
the positive and significant correlation between sIgA concen-
trations and the highest T
core
attained during heat exposure
(r0·63; P,0·05).
Discussion
The results of the present study demonstrate that the non-
supplemented vigil mice subjected to acute heat stress
attained high T
core
values that were sustained above 408C for
approximately 100 min (Fig. 1). This marked hyperthermia
was associated with increased intestinal permeability (Fig. 3)
and BT to the blood and liver (Table 2). The results also
demonstrate that dietary Gln supplementation improved the
intestinal barrier function, thereby preventing the increase in
intestinal permeability and limiting the BT induced by the pas-
sive heating protocol. Another interesting finding was that
dietary Gln supplementation reduced the magnitude of pas-
sive hyperthermia (Fig. 1) and reduced the risk of reaching
the T
core
limit of 428C (Fig. 2).
All the experimental groups were fed isoenergetic and iso-
nitrogenous diets and exhibited similar food intake and
body weight gain (Table 1). These data indicate that mice tol-
erated the supplemented diet well, despite the possibility that
the addition of Gln, a virtually tasteless powder
(46)
, may have
changed the taste of the diet. This possibility is an important
concern because malnutrition induces BT
(47)
and decreases
T
core(48)
. These data also indicate that the beneficial effects
observed in the supplemented groups can be exclusively
attributed to the actions of Gln.
Increased intestinal permeability was transiently observed
in the passively heated animals; when compared with control
Table 2. Bacterial translocation (counts of radioactivity per minute (cpm)/g) to the blood and extra-intestinal
organs in the C-NS (non-supplemented mice maintained under temperate conditions), H-NS (non-supplemented
mice subjected to heat stress) and H-Gln (glutamine-supplemented mice subjected to heat stress) groups*
(Median and 25th and 75th interquartile ranges (IQR))
C-NS H-NS H-Gln
Organ/blood Median IQR Median IQR Median IQR P
MLN 650 153 1120 733 99–4128 670 528 1346 0·925
Blood 558
a
390–815 1675
b
713–2860 724
a
537– 1009 0·020
Brain 602 261–706 641 115–1563 307 165– 677 0·821
Liver 2584
a
1853–3150 9274
b
4656 –10 897 4158
a
1881– 5733 0·013
Lungs 640 587–902 3868 627 4929 1931 768– 2163 0·064
Spleen 294 191–479 986 110–1858 587 221– 1531 0·471
MLN, mesenteric lymph nodes.
a,b
Median values with unlike superscript letters were significantly different between the experimental groups (P,0·05).
* Simultaneous comparison was performed among the different experimental groups (n8 per group).
Time after the experimental trials (h)
36 1291518
Dose of 99mTc-DTPA in the blood (%)
0·00
0·03
0·06
0·09
**
Fig. 3. Intestinal permeability of mice at 3, 6 and 18 h after the experimental
trials. C-NS group, non-supplemented mice maintained under temperate con-
ditions (–W–); H-NS group, non-supplemented mice subjected to heat stress
(–X–); and H-Gln group, glutamine-supplemented mice subjected to heat
stress ( ). Values are means (n12 per group; four for each time point),
with their standard errors represented by vertical bars. ** Mean value was
significantly different from those of the C-NS and H-Gln groups (P,0·01).
DTPA, diethylenetriaminepentaacetic acid; % dose ¼((cpm in blood £100)/
cpm of administered dose), where cpm ¼counts/min.
A. D. N. Soares et al.1606
British Journal of Nutrition
animals (C-NS), these hyperthermic animals (H-NS) exhibited
higher intestinal permeability at 3 h after the experimental
trial, but not after 6 and 18 h (Fig. 3). This increased intestinal
permeability is in agreement with the results of previous
studies in which anaesthetised animals were subjected
to different passive heating protocols
(5,15,19,21)
and with the
demonstration of rapid repair of the intestinal epithelium
after hyperthermia-induced injury
(49)
. Moreover, as we
measured the radioactivity levels of
99m
Tc-DTPA in the blood
to determine intestinal permeability, we conclude that the
increased permeation observed at 3 h most probably occurred
through the paracellular pathway.
The results of the present study do not exclude the possi-
bility that intestinal permeability may have been even more
pronounced in the period between the end of exposure and
before the 3 h recovery period. This hypothesis is supported
by other studies showing significant increases in intestinal
permeability shortly after passive hyperthermia
(15,19,21)
.
There was no significant difference in sIgA concentrations
in the intestinal fluid among the experimental groups
(Fig. 4), suggesting that the passive heating protocol did not
change the number of immunocompetent cells in the lamina
propria and the local production of cytokines involved in
IgA synthesis
(50,51)
. The concentrations of sIgA were positively
correlated with the highest T
core
attained during the heat
exposure protocol (Table 3) and tended to be higher in
mice from the H-NS group than in those from the C-NS
group (Fig. 4). These observations suggest a physiological
association between the intestinal concentrations of sIgA and
the magnitude of hyperthermia, which should be investigated
further. Nevertheless, the positive correlation between the
concentrations of sIgA and the magnitude of hyperthermia
suggests that the intestinal immune system is acting properly
to restrain BT at physiological levels. Previous evidence
suggests that the increased intestinal permeability caused by
hyperthermia could be attributed to an injury to the epithelial
cell lining and/or opening of epithelial tight junctions
(16,18 – 20)
.
Mice from the C-NS group exhibited a low level of BT to the
blood and all evaluated extra-intestinal organs, confirming
that BT is a physiological process essential for the maturation
and maintenance of a competent gastrointestinal immune
system
(43)
. In contrast, 3 h after exposure to acute heat stress
(exactly at the time when augmented intestinal permeability
was observed), mice from the H-NS group exhibited an
increased uptake of
99m
Tc-E. coli in the blood and liver rela-
tive to those from the C-NS group. This finding is in agreement
with previous reports showing that impaired bowel function
increases intestinal permeability, which may facilitate
BT
(43,52,53)
. It is likely that the bacteria and their products
translocated via the portal circulation to the blood and liver
in the heat-stressed mice, corroborating recent observations
in mice that performed prolonged physical exercise in the
heat and also demonstrated increased bacterial levels in
the blood and liver
(31)
. According to Wiest & Rath
(43)
, bacteria
may translocate from the gastrointestinal tract through differ-
ent routes: (1) via blood vessels to reach the portal system;
(2) by direct transmural migration across the intestinal wall;
(3) by retrograde migration to the lungs; (4) by lymphatic
migration via Peyer’s patches to reach mesenteric lymph
nodes, followed by movement from the thoracic duct into
the left subclavian vein to reach the right side of the heart
and then enter the pulmonary circulation. The preferential
route for BT probably varies according to the magnitude of
the inflammatory insult
(54)
. Our recent findings suggest that
BT associated with hyperthermic states (induced by passive
heating or physical exercise) occurs preferentially through
the portal circulation. In addition, the contribution of a trans-
location pathway that involves the lungs cannot be excluded
C-NS H-NS H-Gln
sIgA concentrations in the intestinal fluid (g/g)
0
350
700
1050
1400
Fig. 4. Secretory IgA (sIgA) concentrations in the intestinal fluid of mice at
3 h after the experimental trials. C-NS group, non-supplemented mice main-
tained under temperate conditions (A); H-NS group, non-supplemented mice
subjected to heat stress (B); and H-Gln group, glutamine-supplemented mice
subjected to heat stress ( ). Values are means (n6 per group), with their
standard errors represented by vertical bars.
Table 3. Correlations between thermoregulatory parameters and
intestinal permeability, bacterial translocation and secretory IgA (sIgA)
concentrations in the H-NS group (non-supplemented mice subjected
to heat stress) and the H-Gln group (glutamine-supplemented mice
subjected to heat stress)
Correlations Coefficient* P
Intestinal permeability
Final core temperature (8C) 0·33 0·422
Maximal core temperature (8C) 0·32 0·434
Area under the temperature curve (8C£min) 0·09 0·830
Bacterial translocation to the blood
Final core temperature (8C) 0·09 0·730
Maximal core temperature (8C) 0·00 0·969
Area under the temperature curve (8C£min) 0·19 0·469
Bacterial translocation to the liver
Final core temperature (8C) 20·02 0·926
Maximal core temperature (8C) 20·05 0·848
Area under the temperature curve (8C£min) 20·26 0·331
Intestinal sIgA
Final core temperature (8C) 0·52 0·082
Maximal core temperature (8C) 0·63 0·028
Area under the temperature curve (8C£min) 0·48 0·115
* Pearson’s coefficient (r) was used for correlations between thermoregulatory par-
ameters and intestinal permeability or sIgA concentrations, whereas Spearman’s
coefficient (r
s
) was used for correlations between thermoregulatory parameters
and bacterial translocation.
Dietary glutamine and hyperthermia 1607
British Journal of Nutrition
because the bacterial content of the lungs of mice from the
H-NS group tended to be higher than that of mice from the
C-NS and H-Gln groups. We also measured the bacterial
content in the brain because hyperthermia may augment the
permeation of the blood brain barrier
(18)
. However, the BT
to the brain was not affected by acute heat stress or dietary
Gln supplementation (Table 2).
Notably, liver failure is frequently associated with heat
stroke
(18)
. In the present study, mice tolerated the heat stress
well, and no deaths were observed in mice in which intestinal
permeability was measured 18 h after the experimental trial. In
fact, the impairment of gastrointestinal function was short-
lived compared with that observed in more severe heat
stress protocols
(5)
, in which anaesthetised rats were heated
until reaching a rectal temperature of 428C (a level of
hyperthermia that was maintained for 30 min) and conse-
quently exhibited increased permeability 6 and 24 h after the
heat exposure protocol had ceased. Therefore, it is likely
that the heat exposure protocol used in the present study
did not cause major dysfunctions in Ku¨pffer cells. This
assumption is supported by the finding that BT to the other
extra-intestinal organs was not increased above the physio-
logical levels, suggesting that the liver efficiently acted as a
scavenger of bacteria and their products
(43)
. Similarly, Hall
et al.
(15)
demonstrated higher concentrations of bacterial
endotoxin in the portal venous blood, but not in the arterial
blood, of anaesthetised rats that were subjected to an increase
in colonic temperature from 37·0 to 41·58C via exposure to an
ambient temperature of 408C, relative to non-stressed animals.
The attenuated increase in T
core
in Gln-supplemented mice
that were passively exposed to heat is a novel finding of the
present study (Fig. 1). Our findings are not corroborated by
previous observations in humans experiencing endotoxaemia,
in whom the magnitude of the febrile response was not influ-
enced by intravascular infusion of Gln
(55)
. Similarly, a recent
investigation subjecting human subjects to treadmill running
under a high ambient temperature did not reveal any
Gln-induced change in T
core
at the end of the exercise
(6)
.We
speculate that this thermoregulatory effect mediated by Gln
may be influenced by the dose, frequency and route of
Gln administration or may be specific to certain stressful
conditions or animal species.
Facilitated heat loss is a physiological response that
could explain the attenuated hyperthermia observed in
supplemented animals. However, an increase in cutaneous
vasodilation mediated by Gln is unlikely to account for the
lower T
core
because the temperature gradient between the
skin and environment is narrow (if not reversed) at an ambient
temperature of 398C; this low gradient hampers dry heat loss
from the body. Whether dietary Gln supplementation facili-
tates evaporative heat loss or behavioural thermoregulation
remains to be determined. Another potential explanation for
the attenuated hyperthermia is the diminished release of
inflammatory cytokines and eicosanoids that provoke fever,
consistent with previous findings showing that Gln decreases
the plasma and tissue concentrations of TNF-a, IL-6 and
PGE
2
( 25,26)
. Finally, the reduced T
core
may be the result of a
Gln-induced reduction in intestinal blood flow, limiting the
delivery of warmed blood from the hot skin to the gastrointes-
tinal system and thereby attenuating the increase in abdominal
temperature. The latter hypothesis is supported by Matheson
et al.
(56)
, who showed that enteral Gln supplementation
impairs nutrient-driven absorptive hyperaemia in the colon,
pancreas, spleen and throughout the small intestine.
The protective effect exerted by Gln on the intestinal barrier
function was independent of the attenuation of hyperthermia
(Table 3). The beneficial effects of dietary Gln enrichment on
gastrointestinal function have already been reported in
rodents subjected to different stressful conditions that are
not necessarily associated with hyperthermia, such as intesti-
nal obstruction
(12,30)
and burns
(9)
. Under these experimental
conditions, Gln exerts beneficial effects through several mech-
anisms, including intestinal tropism
(57)
, inhibition of apopto-
sis
(7)
, stimulation of the Th1 inflammatory response
(8)
,
reinforcement of the immune system against bacteria and
endotoxins
(9)
, preservation of glutathione
(11)
and increased
expression of HSP
(3,5)
. In particular, HSP are involved in
the most basic mechanisms of cellular protection against
stressful conditions
(58)
. Treatment with Gln has been shown
to up-regulate the expression of HSP genes in hyperthermic
animals
(3,5)
, similarly to the HSP expression promoted by a
heat acclimation protocol
(59)
. Moreover, animals that have
undergone genetic knockout of key HSP pathway mediators
are not protected against sepsis and lung injury by Gln admin-
istration
(25)
. Recently, Zuhl et al.
(6)
have shown that in vitro
Gln supplementation increases the concentrations of HSP70
and heat shock factor-1 (the transcription factor that regulates
HSP70) in response to heat stress; moreover, the combined
effect of Gln and heat increased the expression of occludin.
Similarly, Beutheu et al.
(60)
demonstrated that Gln prevented
changes in the concentrations of occludin, claudin-1 and
zonula occludens-1 during chemotherapy-induced mucositis
in rats. Together, these findings suggest that the Gln-mediated
intestinal protection may also be due to the modulation of
the tight-junction proteins.
In conclusion, acute exposure to heat induced marked
hyperthermia, increased intestinal permeability and increased
BT that most probably occurred via the portal circulation.
Dietary Gln supplementation decreased the magnitude of
hyperthermia and prevented the increases in BT and intestinal
permeability caused by the passive heating protocol. Taking
these findings into account, we suggest that Gln supplemen-
tation may be an important nutritional strategy for preventing
severe hyperthermia and heat-related disorders.
Acknowledgements
The authors are grateful to the following sources for providing
financial support: Pro
´-Reitoria de Pesquisa da Universidade
Federal de Minas Gerais (PRPq/UFMG); CNPq (the National
Council of Technological and Scientific Development);
CAPES (the Coordination for the Improvement of Higher
Education Personnel); FAPEMIG (the Minas Gerais State
Foundation for Research Support). The funding agencies
had no role in the design and analysis of the study or in the
writing of this article.
A. D. N. Soares et al.1608
British Journal of Nutrition
The authors’ contributions are as follows: A. D. N. S., K. A.
C., S. P. W., C. C. C. and V. N. C. designed the study; A. D. N.
S., K. A. C., S. P. W., R. G. C. S. and F. S. M. conducted the
study; A. D. N. S., S. P. W., S. O. A. F., J. R. N., C. C. C. and
V. N. C. analysed the data; A. D. N. S., S. P. W. and V. N. C.
wrote the article; V. N. C. had primary responsibility for the
final content. All authors read and approved the final version
of the manuscript.
None of the authors has any conflicts of interest to declare.
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A. D. N. Soares et al.1610
British Journal of Nutrition
... However, digestive enzymes can leak into the central circulation should the intestine's barrier become compromised. Although there may be several effectors in this process, instances of intestinal barrier dysfunction have been linked to high core temperatures [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. In systemic circulation, digestive enzymes generate a pathogenic process that leads to multiorgan dysfunction and/or failure. ...
... A rise in intestinal permeability is caused by dysfunction of the mucosal epithelial barrier, which can occur through multiple mechanisms. A direct mechanism is structural damage of the epithelium and tight junction proteins during elevated core temperatures [22,25,30,32,[36][37][38][39][40]. Colon cell cultures exposed to heat stress (43°C) undergo lysosomal-mitochondrial pathway apoptosis with the release of Cathepsin-B. ...
... The rise of endotoxin concentration in the portal circulation after exposure of rats to 40°C ambient temperature is accompanied by increased levels of the radicals ceruloplasmin, semiquinone, and heme-NO, resulting in an approximate doubling of the endotoxin concentration in the portal circulation [12]. Mice whose core temperatures are raised to 39,40,41, and 42°C showed significant correlations between intestinal levels of the cytokines IL-1β, IL-10, and IL-12p40, as well as intestinal injury scores [22]. Exertional heat stress has shown similar permeability and IL-6 signaling in humans [85]. ...
Article
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Enhanced intestinal permeability is a pervasive issue in modern medicine, with implications demonstrably associated with significant health consequences such as sepsis, multiorgan failure, and death. Key issues involve the trigger mechanisms that could compromise intestinal integrity and increase local permeability allowing the passage of larger, potentially dangerous molecules. Heat stress, whether exertional or environmental, may modulate intestinal permeability and begs interesting questions in the context of global climate change, increasing population vulnerabilities, and public health. Emerging evidence indicates that intestinal leakage of digestive enzymes and associated cell dysfunctions––a process referred to as autodigestion––may play a critical role in systemic physiological damage within the body. This increased permeability is exacerbated in the presence of elevated core temperatures. We employed Latent Dirichlet Allocation (LDA) topic modeling methods to analyze the relationship between heat stress and the nascent theory of autodigestion in a systematic, quantifiable, and unbiased manner. From a corpus of 11,233 scientific articles across four relevant scientific journals (Gut, Shock, Temperature, Gastroenterology), it was found that over 1,000 documents expressed a relationship between intestine, enhanced permeability, core temperature, and heat stress. The association has grown stronger in recent years, as heat stress and potential autodigestion are investigated in tandem, yet still by a limited number of specific research studies. Such findings justify the design of future studies to critically test novel interventions against digestive enzymes permeating the intestinal tract, especially the small intestine.
... Additionally, it was demonstrated that Gln could be utilized at a high rate by rapid dividing cells such as immune cells and was necessary for lymphocyte proliferation and cytokine production [18]. Although Gln has been considered to be the most abundant amino acid in the circulation, the physiological requirement for Gln may exceed the body's synthesis capacity under some catabolic stresses [19,20]. Therefore, exogenous Gln addition maybe an effective method to alleviate immunological stress and improve intestine function in response to stressful conditions. ...
Article
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The present study was conducted to investigate the effects of glutamine (Gln) supplementation on intestinal inflammatory reaction and mucosa barrier of broilers administrated with lipopolysaccharide (LPS) stimuli. A total of 120 1-d-old male broilers were randomly divided into four treatments in a 2 × 2 experimental arrangement, containing immune challenge (injected with LPS in a dose of 0 or 500 μg/kg of body weight) and dietary treatments (supplemented with 1.22% alanine or 1% Gln). The results showed that growth performance of broilers intra-abdominally injected with LPS was impaired, and Gln administration alleviated the adverse effects on growth performance induced by LPS challenge. Furthermore, Gln supplementation reduced the increased concentration of circulating tumor necrosis factor-α, interleukin-6 and interleukin-1β induced by LPS challenge. Meanwhile, D-lactic acid and diamine oxidase concentration in plasma were also decreased by Gln supplementation. In addition, the shorter villus height, deeper crypt depth and the lower ratio of villus height to crypt depth of duodenum, jejunum and ileum induced by LPS stimulation were reversed by Gln supplementation. Gln administration beneficially increased LPS-induced reduction in the expression of intestine tight junction proteins such as zonula occludens protein 1 (ZO-1), claudin-1 and occludin except for the ZO-1 in duodenum and occludin in ileum. Moreover, Gln supplementation downregulated the mRNA expression of toll-like receptor 4, focal adhesion kinase, myeloid differentiation factor 88 and IL-1R-associated kinase 4 in TLR4/FAK/MyD88 signaling pathway. Therefore, it can be concluded that Gln administration could attenuate LPS-induced inflammatory responses and improve intestinal barrier damage of LPS-challenged broilers.
... This may indicate a recognition site specific for taurine, accountable for its effects on thermoregulation (Frosini et al., 2003). Glutamine exhibits the ability to attenuate hyperthermia (Soares et al., 2014). The advantageous effects of glutamine on intestine nutrition and health are related to amino acid metabolism in the intestinal microbiota (Dai et al., 2013;Ren et al., 2014). ...
Article
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Heat stress is a very universal stress event in recent years. Various lines of evidence in the past literatures indicate that gut microbiota composition is susceptible to variable temperature. A varied microbiota is necessary for optimal regulation of host signaling pathways and disrupting microbiota-host homeostasis that induces disease pathology. The microbiota-gut-brain axis involves an interactive mode of communication between the microbes colonizing the gut and brain function. This review summarizes the effects of heat stress on intestinal function and microbiota-gut-brain axis. Heat stress negatively affect intestinal immunity and barrier functions. Microbiota-gut-brain axis is involved in the homeostasis of the gut microbiota, at the same time, heat stress affect the metabolites of microbiota which could alter the function of microbiota-gut-brain axis. We aims to bridge the evidence that the microbiota is adapted to survive and thrive in an extreme environment. Additionally, nutritional strategies for alleviating intestinal heat stress are introduced.
... The addition of alanyl glutamine in nutritional supplements can protect the normal structure and function of intestinal mucosa, and even stimulate the intestinal tract to produce more IgA. [23,24] In addition, alanyl glutamine can also maintain the antioxidant reserves in tissues, which has the effects of anti-lipid peroxidation and protection of superoxide dismutase (SOD) activity. [25] Based on this, in the treatment of critically ill patients such as sepsis, giving alanyl glutamine nutritional support therapy can reduce mortality and shorten Medicine hospitalization time. ...
Article
Background: Sepsis is a systemic inflammatory response caused by infection, which is a common complication after severe infection, trauma, shock, and surgery, and is also an important factor in inducing septic shock and multiple organ dysfunction syndrome (MODS), and has become one of the important causes of death in critically ill patients. Septic patients with gastrointestinal transport function weakened, are prone to malnutrition, resulting in decreased immune function, thereby affecting the therapeutic effect. Clinical practice shows that the nutritional metabolism and immune response of patients with sepsis can be effectively improved by giving alanyl glutamine nutritional support treatment, but there is no evidence of evidence-based medicine. The study carried out in this protocol aims to evaluate the effectiveness of alanyl glutamine in nutritional support therapy for patients with sepsis. Methods: The Cochrane Library, PubMed, Embase, Web of Science, WHO International Clinical Trials Registry Platform, CNKI, CBM, VIP, and Wanfang databases were searched by computer, to retrieve all randomized controlled trials (RCTs) on nutritional support for the treatment of sepsis with alanyl glutamine from the date of database establishment to December 2020. Two researchers independently selected the study, extracted and managed the data. RevMan5.3 software was used to analyze the included literature. Results: This study observed the changes of serum albumin (ALB), prealbumin (PAB), hemoglobin (Hb), C-reactive protein (CRP), immunoglobulin (IgG, IgA, and IgM), APACHE II score before and after treatment to evaluate the efficacy of alanyl glutamine in nutritional support therapy for patients with sepsis. Conclusion: This study will provide reliable evidence for the application of alanyl glutamine in nutritional support therapy for patients with sepsis. Osf registration number: DOI 10.17605/OSF.IO/VRZPJ.
Article
Background Immunonutrition has been shown to reduce hospital stay and postoperative morbidity in patients undergoing gastrointestinal, and head and neck surgery. However, its use has not been demonstrated in patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). This study aims to determine the effectiveness of perioperative immunonutrition on patients undergoing CRS-HIPEC in reducing length of hospitalization and postoperative complications.Patients and Methods From April 2017 to December 2018, patients undergoing CRS-HIPEC for peritoneal metastases in a single center were enrolled in a randomized controlled trial. Patients with evidence of intestinal obstruction or with diabetes mellitus were excluded. Patients were randomly assigned in a 1:1 fashion to receive perioperative oral immunonutrition or standard nutritional feeds. Length of hospital stay and rates of wound infection and complications were recorded and compared between the two groups in an intention-to-treat manner.ResultsA total of 62 patients were recruited and randomized into two groups. Compliance to nutritional feeds in the preoperative period was significantly higher in the standard nutrition group (95.2% versus 75.4%, p = 0.004). There was no difference in postoperative compliance rates. Length of hospital stay and rates of wound infection and postoperative complications were higher in the standard nutrition group when compared with patients on immunonutrition (15.5 versus 11.1 days, p = 0.186; 19% versus 9.7%, p = 0.473; 16% versus 9.7%, p = 0.653; respectively).Conclusions Patients undergoing CRS-HIPEC who received perioperative immunonutrition had shorter hospitalization and less wound infections and postoperative complications, although the differences with the standard nutrition group were not statistically significant. Potential benefits of perioperative immunonutrition need to be further evaluated in larger studies.
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The coronavirus disease 19(COVID-19) is a highly transmittable and pathogenic viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-II), which emerged in Wuhan, China and spread around the world. It is considered a relative of Severe Acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), The cause of COVID-19 is a beta coronavirus named SARS-CoV-2 that affects the lower respiratory tract and manifests as pneumonia in humans. The Asymptomatic carriers have become the current focus of global epidemic prevention and control efforts. These carriers of the virus display no clinical symptoms but are known to be contagious. As "silent spreaders", asymptomatic carriers warrant attention as a part of disease prevention and control. The comparable viral load in a group of asymptomatic carriers of COVID-19 was found to be higher than that of the symptomatic carriers. There are numerous micronutrients which are essential for immunocompetence, particularly Vitamin A, C, D, E, B, iron, selenium, and zinc. Immunonutrition refers to the modulation of the immune system through the modification of dietary nutrients. Vitamins A to E highlighted potentially beneficial roles in the fight against COVID-19 via antioxidant effects, immunomodulation, enhancing natural barriers, and local paracrine signaling. The present review provides a brief information on supplementation of Immunonutrients in form of vitamins which ultimately can act as prophylactic regimen for Asymptomatic carriers of SARS CoV-II virus.
Article
Heat stress can cause tissue damage and metabolic disturbances, including intestinal and liver dysfunction, acid-base imbalance, oxidative damage, inflammatory response, and immune suppression. Serious cases can lead to heatstroke, which can be life-threatening. The body often finds it challenging to counteract these adverse effects, and traditional cooling methods are limited by the inconvenience of tool portability and the difficulty of determining the cooling endpoint. Consequently, more research was conducted to prevent and mitigate the negative effect of heat stress via nutritional intervention. This article reviewed the pathological changes and altered metabolic mechanisms caused by heat stress and discussed the protein (amino acid), vitamin, trace element, and electrolyte action pathways and mechanisms to mitigate heat stress and prevent heat-related disease. The main food sources for these nutrients and the recommended micronutrient supplementation forms were summarized to provide scientific dietary protocols for special populations.
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We here provide an overview of the pathophysiological mechanisms during heat stroke and describe similar mechanisms found in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Both conditions are characterized by disturbed homeostasis in which inflammatory pathways play a central role. Splanchnic vasoconstriction, increased gut permeability, gut-related endotoxemia, systemic inflammatory response, central nervous system dysfunction, blood coagulation disorder, endothelial-cell injury, and mitochondrial dysfunction underlie heat stroke. These mechanisms have also been documented in ME/CFS. Moreover, initial transcriptomic studies suggest that similar gene expressions are altered in both heat stroke and ME/CFS. Finally, some predisposing factors for heat stroke, such as pre-existing inflammation or infection, overlap with those for ME/CFS. Notwithstanding important differences - and despite heat stroke being an acute condition - the overlaps between heat stroke and ME/CFS suggest common pathways in the physiological responses to very different forms of stressors, which are manifested in different clinical outcomes. The human studies and animal models of heat stroke provide an explanation for the self-perpetuation of homeostatic imbalance centered around intestinal wall injury, which could also inform the understanding of ME/CFS. Moreover, the studies of novel therapeutics for heat stroke might provide new avenues for the treatment of ME/CFS. Future research should be conducted to investigate the similarities between heat stroke and ME/CFS to help identify the potential treatments for ME/CFS.
Article
Intestinal barrier integrity and function are compromised during exertional heat stress (EHS) potentially leading to consequences that range from minor gastrointestinal (GI) disturbances to fatal outcomes in exertional heat stroke or septic shock. This mini-review provides a concise discussion of nutritional interventions that may protect against intestinal permeability during EHS and suggests physiological mechanisms responsible for this protection. Although diverse nutritional interventions have been suggested to be protective against EHS-induced GI permeability, the ingestion of certain amino acids, carbohydrates, and fluid per se are potentially effective strategies, whereas evidence for various polyphenols and pre/probiotics is developing. Plausible physiological mechanisms of protection include increased blood flow, epithelial cell proliferation, upregulation of intracellular heat shock proteins, modulation of inflammatory signaling, alteration of the GI microbiota, and increased expression of tight junction (TJ) proteins. Further clinical research is needed to propose specific nutritional candidates and recommendations for their application to prevent intestinal barrier disruption and elucidate mechanisms during EHS.
Article
Intestinal infectious diseases refer to the inflammatory changes in the intestinal tract caused by pathogens (including bacteria, viruses, fungi, protozoa, or parasites) or their toxic products. A large number of microorganisms colonize the intestinal tract of healthy people, which together with the intestinal epithelium constitute the biological barrier of the intestinal tract to resist infectious diseases. As an “invisible organ,” the intestinal flora is closely related to human nutrition metabolism and intestinal infections. A variety of intestinal flora participates in the nutritional metabolism of amino acids, and the small molecular substances produced by the amino acid metabolism through the intestinal flora can enhance intestinal immunity and resist bacterial infections. In turn, amino acids can also regulate the composition of the intestinal flora, maintain the steady-state of the intestinal flora, protect the intestinal barrier, and inhibit colonization by pathogenic bacteria. As a model animal with a clear microbial background, germ-free (GF) animals can clarify the mechanisms of interactions between intestinal microbes and amino acid metabolism in intestinal infections by combining genetic engineering technology and multi-omics studies. This article reviews related researches on the involvement of intestinal microbes in host amino acid metabolism and resistance to intestinal infections and discusses the advantages of GF animal models for studying the underlying mechanisms. The GF animal model is helpful to further study the intervention effects of amino acid metabolism of targeted intestinal flora on intestinal infections.
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The purposes of this study are to assess whether 7 days of oral glutamine supplementation: (1) reduces exercise induced intestinal permeability; (2) prevents the pro-inflammatory response; and (3) to determine whether these changes are associated with the up-regulation of the heat shock response. On separate occasions, eight human subjects participated in baseline testing, glutamine (GLN), and placebo (PLA) trials followed by a 60-min treadmill run. Intestinal permeability was higher in the PLA trial compared to baseline and GLN (0.0604 ± 0.047 vs. 0.0218 ±0.008 and 0.0272 ± 0.007, respectively, p<0.05). PBMC IκBα expression was higher 240-min post-ex in GLN trial compared to PLA (1.411 ± 0.523 vs. 0.9839 ± 0.343, p<0.05). In vitro (Caco-2) we measured effects of glutamine supplementation (0 mM, 4 mM, and 6 mM) on heat-induced (37° or 41.8°C) HSP70, HSF-1, and occludin expression. HSF-1 and HSP70 levels increased in 6 mM 41ºC compared to 0 mM 41ºC (1.785 ± 0.495 vs. 0.6681 ± 0.290, and 1.973 ± 0.325 vs. 1.133 ± 0.129, respectively, p<0.05). Occludin levels increased after 4 mM 41ºC and 6 mM 41ºC compared to 0 mM 41ºC (1.236 ± 0.219 and 1.849 ± 0.564 vs. 0.7434 ± 0.027, p<0.001, respectively). Glutamine supplementation prevented exercise-induced permeability, possibly through HSF-1 activation.
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Increased intestinal permeability occurs during chemotherapy-induced intestinal mucositis. Previous data suggest that glutamine and arginine may have additive or synergic effects to limit intestinal damage. The present study aimed to evaluate the effects of glutamine and arginine, each alone or in combination, on gut barrier function during methotrexate (MTX)-induced mucositis in rats. Eighty Sprague Dawley rats received during 7 days (d) standard chow supplemented with protein powder (PP), glutamine (G, 2%), arginine (A, 1.2%) or glutamine plus arginine (GA). All diets were isonitrogenous. Rats received subcutaneous injections of MTX (2.5 mg/kg) from d0 to d2. The intestinal permeability and tight junction proteins were assessed at d4 and d9 in the jejunum by FITC-dextran and by western blot and immunohistochemistry, respectively. At d4, intestinal permeability was increased in MTX-PP, MTX-A and MTX-GA rats compared with controls but not in MTX-G rats. The expression of claudin-1, occludin and ZO-1 was decreased in MTX-PP group compared with controls but was restored in MTX-G and MTX-A rats. In MTX-GA rats, occludin expression remained decreased. These effects could be explained by an increase of erk phosphorylation and a decrease of IκBα expression in MTX-PP and MTX-GA rats. At d9, Intestinal permeability remained higher only in MTX-GA rats. This was associated with a persistent decrease of occludin expression. Glutamine prevents MTX-induced gut barrier disruption by regulating occludin and claudin-1 probably through erk and NF-κB pathways. In contrast, combined glutamine and arginine has no protective effect in this model.
Conference Paper
Epithelial cell apoptosis is an important regulator of normal gut mucosal turnover; however, excessive apoptosis may inhibit mucosal restitution during pathophysiologic states. Apoptosis is induced by oxidative stress and cytokines, but regulation by specific nutrients has been infrequently studied under these conditions. Glutamine (Gln) is an important metabolic fuel for intestinal epithelial cells and a precursor to the antioxidant glutathione (GSH), which has antiapoptotic effects. In cultured intestinal epithelial cells, Gln depletion increases oxidant-induced apoptosis. This study examined whether Gln protects against apoptosis induced by the cytokine tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL) in the human colon carcinoma cell line, HT-29. TRAIL-induced apoptosis in HT-29 cells was characterized by an increase in the percentage of cells in the sub-G(1) fraction by flow cytometry, nuclear condensation and the activation of caspase-8 and caspase-3. TRAIL-induced apoptosis was completely prevented by Gln, but not inhibited by other amino acids, including the GSH constituents, glutamate, cysteine and glycine. Similar antiapoptotic effects of Gln occurred when apoptosis was induced by a combination of tumor necrosis factor-alpha and interferon-gamma. Cellular GSH was oxidized during TRAIL-induced apoptosis. This effect was completely blocked by Gln, however, inhibition of GSH synthesis with buthionine sulfoximine did not alter Gln antiapoptotic effects. Furthermore, glutamate prevented GSH oxidation in response to TRAIL but did not protect against TRAIL-induced apoptosis. These results show that Gln specifically protects intestinal epithelial cells against cytokine-induced apoptosis, and that this occurs by a mechanism that is distinct from the protection against oxidative stress mediated by cellular GSH.
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• Bacteria have been documented to translocate from the gut to systemic organs, yet the exact route by which they translocate remains unclear. To determine the route of bacterial translocation, different dosages of zymosan were used to activate complement and cause systemic inflammation. At a zymosan dose of 0.1 mg/g, bacteria translocated only to the mesenteric lymph node complex, whereas at a dose of 0.5 mg/g the bacteria translocated systematically. In rats receiving 0.5-mg/g doses of zymosan, the bacteria appeared to reach systemic organs via the portal blood rather than via the mesenteric lymph, as bacteria were present in 87% of portal blood samples but only 25% of lymph samples. The number of bacteria exiting the portal vein was 11 500 times greater than the number exiting via the lymph. Thus, both the route and extent of bacterial translocation varies based on the magnitude of the inflammatory insult, with the portal blood being the major route of bacterial translocation to systemic organs.(Arch Surg. 1991;126:33-37)
Article
Dietary supplementation with l-arginine has been shown to improve the intestinal barrier in many experimental models. This study therefore investigated the effects of arginine supplementation on the intestinal permeability and bacterial translocation (BT) induced by prolonged physical exercise under heat stress. Under anesthesia, male Swiss mice (5 wk old) were implanted with an abdominal sensor to record their core body temperature (Tcore). After recovering from surgery, the mice were divided into 3 groups: a non-supplemented group that was fed the standard diet formulated by the American Institute of Nutrition (AIN-93G; control), a non-supplemented group that was fed the AIN-93G diet and subjected to exertional hyperthermia (H-NS), and a group supplemented with l-arginine at 2% and subjected to exertional hyperthermia (H-Arg). After 7 d of treatment, the H-NS and H-Arg mice were forced to run on a treadmill (60 min, 8 m/min) in a warm environment (34°C). The control mice remained at 24°C. Thirty minutes before the exercise or control trials, the mice received a diethylenetriamine pentaacetic acid (DTPA) solution labeled with technetium-99m ((99m)Tc-DTPA) or (99m)Tc-Escherichia coli by gavage to assess intestinal permeability and BT, respectively. The H-NS mice terminated the exercise with Tcore values of ∼40°C, and, 4 hours later, presented a 12-fold increase in the blood uptake of (99m)Tc-DTPA and higher bacterial contents in the blood and liver than the control mice. Although supplementation with arginine did not change the exercise-induced increase in Tcore, it prevented the increases in intestinal permeability and BT caused by exertional hyperthermia. Our results indicate that dietary l-arginine supplementation preserves the integrity of the intestinal epithelium during exercise under heat stress, acting through mechanisms that are independent of Tcore regulation.