Korean Society for Exercise Nutrition
[ Review articles ]
Physical Activity and Nutrition - Vol. 24, No. 2, pp.22-29
ISSN: 2733-7545 (Online)
Print publication date 30 Jun 2020
Received 17 Jun 2020 Revised 23 Jun 2020 Accepted 23 Jun 2020
DOI: https://doi.org/10.20463/pan.2020.0011

Suppressing breast cancer by exercise: consideration to animal models and exercise protocols

Jea Jun Lee1 ; Suji Beak2 ; Sang Hyun Ahn3 ; Byung Seok Moon4 ; Jisu Kim5, * ; Kang Pa Lee2, *
1Laboratory Animal Center, Osong Medical Innovation Foundation, Cheongju, Republic of Korea
2Research and Development Center, UMUST R&D Corporation, Seoul, Republic of Korea
3Department of Anatomy, Semyung University, Jecheon, Republic of Korea
4Department of Nuclear Medicine, Ewha Womans University College of Medicine, Seoul, Republic of Korea
5Physical Activity and Performance Institute, Konkuk University, Seoul, Republic of Korea

Correspondence to: *Jisu Kim Ph.D. professor and Kang Pa Lee, Ph.D Jisu Kim Ph.D. professor Physical Activity and Performance Institute, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea Tel: +82-2-2049-6034 / E-mail: kimpro@konkuk.ac.kr Correspondence to: *Kang Pa Lee, Ph.D Research and Development Center, UMUST R&D Corporation, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea / Email: umustrnd@naver.com

©2020 The Korean Society for Exercise Nutrition
©2020 Jea Jun Lee et al.; Licence Physical Activity and Nutrition. This is an open access article distributed under the terms of the creative commons attribution license (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the orginal work is properly cited.

Abstract

[Purpose]

Exercise is thought to have a significant effect on chemotherapy, and previous studies have reported that exercise can increase patient survival. Thus, in this review, we aimed to summarize various animal models to analyze the effects of exercise on breast cancer.

[Methods]

We summarized types of breast cancer animal models from various reports and analyzed the effects of exercise on anti-cancer factors in breast cancer animal models.

[Results]

This review aimed to systematically investigate if exercise could aid in suppressing breast cancer. Our study includes (a) increase in survival rate through exercise; (b) the intensity of exercise should be consistent and increased; (c) a mechanism for inhibiting carcinogenesis through exercise; (d) effects of exercise on anti-cancer function.

[Conclusion]

This review suggested the necessity of a variety of animal models for preclinical studies prior to breast cancer clinical trials. It also provides evidence to support the view that exercise plays an important role in the prevention or treatment of breast cancer by influencing anticancer factors.

Keywords:

Breast cancer, Exercise, Breast cancer mouse models, Exercise protocols, Exercise effects

INTRODUCTION

Non-communicable diseases, as chronic diseases, account for 70% of the mortality rates worldwide, while communicable diseases cause the remaining 30%. Among non-communicable diseases, those with high mortality rates include cancer, diabetes, cardiovascular disease, and lung disease. Cancer is classified as a fatal disease for patients because it is difficult to cure owing to its rapid growth, and is highly likely to spread throughout the body through blood or lymphatic fluid. In particular, reduction of female physical activity due to various social environments is a potential cause of increased breast cancer incidence. In addition, the most frequent characteristic of breast cancer among women is not only high incidence, but also high efficiency of cancer treatment. Although the effectiveness of anti-cancer drugs is very high for breast cancer patients, a lot of pain, caused by chemotherapy, accompanies it. Therefore, there is an urgent need to improve the survival rate of breast cancer patients, and improve the quality of life during chemotherapy treatment. Recently, various preclinical studies have suggested that exercise attenuates tumor growth and tumorigenesis (Table 1). However, molecular mechanisms by which exercise affects cancer progression are not yet clear. In this review, we aimed to summarize studies on exercise methods that could potentially increase the survival rate of breast cancer patients and suppress cancer progression.

Changes in blood variables before exercise and during post-exercise period.

Conventional breast cancer therapy

Modern people often suffer from various diseases, which leads to death. In particular, the four major chronic diseases leading to death have been reported as cancer, diabetes, cardiovascular, and chronic lung diseases. According to the Cancer Society report, the most common cancer among women worldwide is breast cancer1. Furthermore, the most common types of cancer in Korean women were breast cancer (19.9%), thyroid cancer (18.8%), colorectal cancer (10.5%), gastric cancer (9.2%), lung cancer (7.3%), and stomach and liver cancers (3.7%) were investigated according to a survey posted on the National Cancer Information Center (NCIC)2.

Standard treatment methods such as various anti-cancer drugs and surgery are being developed, and alternative medical technologies for incurable diseases are also in development. Currently, there are four main ways of cancer treatments: 1) surgery, 2) chemotherapy, 3) radiation therapy, and 4) hormone therapy.

Prophylactic surgery suppresses the cancer progression by performing a biopsy for the purpose of diagnosis through surgery or removing the benign tumor completely. Surgery also prevents the spread of cancer to other cells in the body and helps relieve symptoms. Chemotherapy refers to the use of therapeutic agents for regulating hyperproliferative cells. Radiation therapy kills cancer cells by directly irradiating them. Hormone therapy that suppresses estrogen action is also used as a cancer treatment method, as breast cancer is affected by estrogen levels, unlike other cancers.

Exercise regulates the breast cancer in animal models by inhibiting carcinogenesis

Disease increase over the last two decades may be due to a more westernized lifestyle, which is accompanied by excessive nutrition and lack of exercise3. Guidelines on cancer prevention are well known, and include recommendations for controlling metabolism, such as a balanced nutrient intake, eating vegetables, regulating vitamin intake, and controlling weight. Furthermore, exercise can prevent and treat various diseases, and in recent years, research on anti-cancer efficacy has been actively conducted.

Physical activities of Korean women are very low compared to women in other countries. Moreover, many women have adopted western food and a sedentary lifestyle, which has led to reduced voluntary exercise. The highest incidence of cancer among Korean women is breast cancer, and it has been suggested that breast cancer may be related to metabolic problems. Therefore, the effectiveness of exercise for the treatment or prevention of breast cancer should be investigated in future clinical studies.

An experimental laboratory animal is defined as an animal developed and improved for use in accordance with the purpose of test, diagnosis, education, research, and biological products in the research process. Among laboratory animals, primates such as Callithrix jacchus and Macaca fascicularis are most similar to humans; however, there exist issues regarding the ethics of conducting research using these animals. Rodents such as Mus muculus, Rattus norvegicus, and Cavia porcellus are the most commonly used experimental animals. In particular, Mus muculus has a genetic similarity with humans (approximately >80%), and a biologically similar body structure, a short pregnancy period (19 - 21 days) is also advantageous for preclinical studies. Therefore, Mus muculus has been used as a knockout mouse, cancer model xenograft, orthotropic model, and chemically induced-disease model. To develop a mouse model of breast cancer, it is necessary to have experimental cells, and patient derived primary cells such as MCF-7 (ER+, PR+, HER2-), MDA-MD-231 (ER+, PR+, HER2-), MC4-L2 (ER+), E0771 (ER+) and 4T1 (ER-) (Fig. 1).

Figure 1.

Breast cancer mouse models

The breast cancer animal model consists of chemically induced models, transgenic mice models, orthotopic mice models, and xenograft models. In the case of chemically induced breast cancer models, 7,12-dimethylbenzanthracene (DMBA; 1 mg/mL weekly, for six weeks) is injected subcutaneously into the side of the abdomen. Poly-aromatic structure of lipophilic molecule, DMBA has high carcinogen activity in the breast. To evaluate tumor progression, mice are established with genetic modifications that target the oncogene, such as simian virus 40 (SV40) T antigens and polymer middle T antigen (PyMT). In the establishment of mice models by injection with breast cancer cells, mice are mainly used in the study of tumor biology and pharmacology, as these models retain the biological properties of cancer. Breast cancer cells are injected into the mammary fat pad of host mice to obtain orthotropic models. In this case, the number of cells used is appropriate (1 x 105 to 1 x 106/mouse), and cancer cells injected into the mouse organs exhibit properties similar to breast cancer generated in the human body over time, and can be correlated to metastatic cancer. To develop a xenograft model, cells (1 x 106 to 1 x 107/mouse) are injected subcutaneously into the dorsal side of the mouse.

Using these various animal models, studies on the beneficial effect of exercise against tumor growth and tumorigenesis of breast cancer have been extensively reported (Fig. 2; Table 1). Tumors are defined as transformed cells that undergo abnormal or rapid proliferation, beyond normal regulatory functions, in the organism. Tumors are divided into two types: benign neoplasms and carcinomas. Benign neoplasms have a relatively slow growth rate, and do not penetrate or spread into other tissues. In contrast, carcinomas rapidly grow, and invade other tissues and metastasize. The process of tumor development by carcinogenesis is a multi-step process. The first stage is initiation, where normal cellular DNA is attacked by carcinogens, leading to genetic modification and irreversible mutations. The second stage is promotion, wherein cell proliferation is actively performed to maintain and promote the population of mutant cells to counter immune response in vivo as it eliminates abnormal cells. The third step is progression, the process of increasing the characteristics of a malignant tumor by converting it from a benign tumor to a malignant tumor. In the process of tumor development, the morphology and function of normal cells are altered by genetic modification through internal or external stimulants. External factors include chemical carcinogens such as smoking, physical stimuli such as radiation, and RNA tumor viruses such as HTLV-1 virus. Internal factors involved in the mutation of the target gene include oncogene and tumor suppressor genes. Tumor suppressor genes include TGF-β, E-Cadherin, NF-1, PTEN, SAMD2, SMAD4, and p53, and regulate cell population through apoptosis and proliferation. Oncogene mutation targets are cell cycle regulatory genes such as cyclin D1, Her2, and K-ras. Many preclinical studies suggest that the beneficial effect of exercise training in cancer progression is brought about by direct regulation of intertumoral factors, i.e., tumor growth rate, metastasis, and tumor immunogenicity (Table 1).

Figure 2.

Exercise regulates carcinogenesis by regulating the microenvironment

Table 1 summarizes the research methods used for controlling the intensity of exercise that underlies the exercise protocols using wheel running, treadmill, and swimming. These preclinical studies clearly demonstrate a decrease in tumor growth rate caused by exercise. Interestingly, Berrueta et al. demonstrated that exercise, such as stretching for 10 minutes once a day over a four-week period, reduced tumor size in a breast cancer model by 50%5. In other studies, voluntary exercise also inhibited tumor size and tumor growth 4,7,9,12,13,15,16-18,27. Moreover, more studies have been conducted on endurance exercise than resistance exercise; endurance exercise has shown anti-tumor effects6,8,10,11,21,22. Taken together, these data suggest that the anti-cancer activity of the exercise protocols is involved in endurance and moderate-intensity exercise.

If so, which mechanism of exercise showed an anti-cancer effect? Results strongly suggest that exercise inhibits epigenetic modification of tumor cells, but enhances apoptosis and immune suppression29. Reactive oxygen species (ROS) perform signal transduction in vivo; however, excessive production can cause oxidative stress, which leads to cancer30. Moderate intensity exercise can regulate ROS and biological signaling in vivo31. It is likely that exercise is related to the regulation of the reactive oxygen species (ROS)-involved microenvironment of cancer32. Therefore, these studies also suggest that controlling ROS a potential mechanism for the treatment of cancer33.

However, this claim raises further questions as to why exercise is closely related to change in the microenvironment of cancer. One possible belief is that exercise can exert anti-cancer effects by solving problems that arise during metabolic processes. During carcinogenesis, most tumor cells exert cell growth signaling pathway via glucose metabolic reprograming34. Recent study suggests that effective anti-cancer effect could be related to the regulation of metabolic syndrome35. The results supporting these claims are as follows: First, exercise can lead to activation of natural killer cell, lymphocyte, consequently resulting in the regulation of the tumor growth and metastasis36. In addition, exercise attenuates tumorigenesis and tumor progression37. Next, the ketone diet (KD) is characterized by high fat, adequate protein, and very low carbohydrate compositions. Some studies have reported that the physiological phenomena caused by exercise or fasting are very similar to physiological conditions observed in the KD38. Various preclinical studies have shown that exercise or the KD displays anti-cancer efficacy39,40. Taken together, a possible hypothesis is that exercise-binding KD modulates metabolic dysfunction and causes internal factors, which involved in the mutation of the target gene such as ROS generation and tumor-suppressor gene mutations, thereby suggesting its potential as a cancer therapeutic.

However, the anti-cancer effects of KD and exercise can be contradictory. Acute exercise did not change tumor formation, but continuous steady aerobic exercise displayed effective anticancer effects. The general view presented in many studies is that exercise exerts an anti-cancer effect by reducing the size of tumors, promoting energy metabolism, and increasing immune activity by constant exercise. Therefore, further studies should investigate that find and apply an appropriate energy source for exercise that show anticancer efficacy.


CONCLUSION

Various preclinical studies have shown that exercise weakens tumor growth and tumor development. Moreover, these studies suggest that mice bearing breast cancer exhibited anti-cancer effects by increasing immune responses and anti-inflammatory factor levels through acclimation of increased exercise intensity every week. Thus, continuous exercise can have potential medical benefits as a prevention or therapeutic method for breast cancer. To facilitate this research, researchers need to study the etiological mechanisms that rely on clinical features with underlying pathological features of the disease, as well as based on mechanisms not necessarily present in patients. For example, using animal models to discover new treatments for a variety of diseases is an essential element in discovering new therapeutic targets and performing drug testing at the preclinical stage.

Acknowledgments

This research was supported by a grant from the Osong Medical Cluster R&D Project funded by the Republic of Korea’s Health and Welfare (grant number HO15C0001). This paper was supported by the KU Research Professor Program of Konkuk University.

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Figure 1.

Figure 1.
Breast cancer mouse models

Figure 2.

Figure 2.
Exercise regulates carcinogenesis by regulating the microenvironment

Table 1.

Changes in blood variables before exercise and during post-exercise period.

Mouse
model
Mouse Induction Exercise Protocols Test Efficacy & Signal pathways Ref
ER: estrogen receptor, PR: progesterone receptor, HER2: receptor tyrosine-protein kinase erbB-2, PTEN: Phosphatase and tensin homolog, APOE: apolipoprotein E, FVB: Friend leukemia virus B, ANKRD1: Ankyrin repeat domain protein, CTGF: connective tissue growth factor, PI3K: phosphoinosidied 3-kinase, AKT: protein kinase B, ERK: extracellular signal regulated kinase, IL: interleukin, TNF-α: tumor necrosis factor – α, CRP : C-eactive protein, VEGF: vascular endothelial growth factor, HIF-1 α: hypoxia-inducible factor 1- α, CCL2: C-C motif chemokine ligand 2, CXCR4: C-XC chemokine receptor type 4, Ldha: lacate dehydrogenase A, HKII: hexokinase II, Glut 1: glucose transporter 1, Mtor : mammalian target of rapamycin, Lats2: large tumor suppressor kinase 2, CD8: cluster of differentiation 8, FoxP3: forkhead box P3, Gata3: GATA binding protein 3, Th : T helper cell, TPM1: tropomyosin alpha-1chain, PDCD4: programmed cell death protein
Xenograft NMRI-Foxn1nu MCF-7 cell
(ER+, PR+, HER2-)
MDA-MB-231 cell

(ER-, PR-, HER2-)
Running Voluntary wheel
running
(4 km per night/cage)
-Tumor growth
- To evaluate the
effect of exercise-conditioned
serum in
cancer cell
- MCF-7 (–36%, P <0.05) and
MDA-MB-231 (–66%, P <
0.01) tumor growth
- Regulating Hippo signaling
(ANKRD1 and CTGF)
4
Orthotopic FVB/NJ p53/PTEN
double-null (−/−)
primary cell
Stretching Treated for 10 minutes
once a day, for four
weeks
Tumor growth 52% reduced tumor size 5
Xenograft Female BALB/c MC4-L2 cell
(ER+, PR+)
Running Using the treadmill;
After acclimation, the
interval exercise training
protocol commenced
at 16–18 m min−1, 0%
gradient, for 10−14 min,
5 days each week for 6
weeks, and the exercise
intensity was gradually
increased each week
- Tumor volume
- mRNA expression &
Protein expression
- Decrease tumor volume and
weight

- Reduced PI3K/AKT and
ERK activation ; Induced
Apoptosis
6
Orthotopic Female
APOE-/-
E0771 cell
(ER+, PR+, HER2+)
Running Voluntary wheel running - Tumor growth &
metastasis

- Property of tumor
- Increasing log phase tumor
growth and inhibiting metastasis

- Reduced tumor hypoxia affect
exponential tumor growth
in APOE-/-mice
7
Orthotopic Female FVB/NJ
Female BALB/c
Female C57/BL6
C3(1)SV40Tag
-p-16-lu cell
(Claudin-low
breast cancer)

E0771 cell

4T07 cell
(ER-, PR-, HER2-)
Running Using the treadmill;
After acclimation, 5 m/
min for 5 min, 10 m/min.
for 5 min, 15 m/min for
5 min., and 20 m/min.
for 45 min., which is
equivalent to 70% VO2
peak.
The exercise intensity
was gradually increased
each week for 2 weeks
-Tumor growth

- Gene expression
- 771 (0.5 folds), C3(1)
SV40Tag-p16-lu cell (2 folds),
4T07 cell ( same size) tumor
size
- Ki67 expressions : E0771
(0.25 folds), C3(1)SV40Tagp16-
lu cell (1.26 folds), 4T07
cell (same expression)
- Hif1-α expressions :E0771
(-5.0 folds), C3(1)SV40Tagp16-
lu cell (11.0 folds), 4T07
cell (same expression)
8
Orthotopic Female
C57/BL6
4T1 cell
(ER-, PR-, HER2-)

E0771 cell
Running Wheels (running group)
vs. without Wheels
(sedentary group)
-Tumor growth, perfusion,
hypoxia, and
components of the
antigenic and apoptotic
cascades
-Statistically significantly reduced
tumor growth and was
associated with a 1.4-fold
increase in apoptosis
9
Xenograft Female
BALB/c
4T1 cell Running Using the treadmill (18
m/min for 30 min once
a day) vs. sedimentary
group for 30 days
-Tumor growth

-Evaluating immune
cell ratio
- Exercise regulates tumor
growth through immune cells
responses

- Exercise with radiotherapy
reduces MDSCs accumulation
and NK cell activation
10
Orthotopic Female
BALB/c
4T1 cell Running Low intensity exercise (6
m/min, 60 min/d) group
(LE),

Medium intensity exercise
(10 m/min, 60 min/
d) group (ME),

High intensity exercise
(15 m/min, 60 min/d)
group (HE) one a day
for 20 days
- Tumor growth

-Evaluating apoptosis
signals
- HE inhibited tumor growth

- HE combined with administration
of didzein induces
apoptosis of breast cancer
11
Orthotopic Female
BALB/c
4T1 cell Running voluntary exercise four
weeks;
170.45±47.5 km and
17.45±1.8 m.min-1,
-Tumor growth - Beneficial effects of voluntary
exercise on breast cancer
progression
12
Orthotopic BALB/cBy 4T1 cell Running Using the wheel running:
The running group
ran an average daily
distance of 4.89 ± 1.73
km over 60 days prior to
4T1 tumor cell injection,
and 2.38 ± 1.51 km over
30 days after tumor cell
injection
-Tumor growth -Running longer distances is
associated with
decreased breast tumor burden
in old mice
13
Xenograft Female
BALB/c
MCF-7 cell
(ER-, PR-, HER2-)
Running Using the wheel
running: 18 m/min for
30 min for days per 12
weeks
-Gene expression -Exercise decrease the IL-
6, IL-18, TNF-a, CRP mRNA
expression
14
Transgenic
mice
FVB/NJ
C3(1)/SV40Tag
Genetically predisposed
to develop
breast cancer
Running Voluntary wheel running
: 1 h/day, 6 days/week
for 20 weeks
-Voluntary physical
activity (Running
distance/ Speed)
Tumor size
-C2(1)/SV40Tag mice < FVB/
N mice
C2(1)/SV40Tag mice > C2(1)/
SV40Tag + exercise
15
Transgenic
mice
p53-deficient
(p53+/−):
MMTV-Wnt-1
Genetically predisposed
to develop
breast cancer
Running 1) voluntary wheel running
Con-WHL, WHL
(exercise)

2) non-Voluntary wheel
running : Untreated
group, 20 m/min
(TREX1), 24 m/min
(TREX2) for 5 days /
weeks
-p53 expression

-Incidence

-Multiplicity & survival
-Con = TREX1 =TREX2 / Con
-WHL = WHL
-Con<TREX1=TREX2 / Con-
WHL < WHL
-Con>TREX1=TREX2 / Con-
WHL < WHL
16
Orthotopic Athymic MDA-MB-231 cell Running Voluntary wheel running
running distance range
~4 to ~6 km/day for 15
weeks
- Survival
-VEGF
-HIF-1alpha expression
-tumor metabolism
- Con = Exercise
- VEGF expression: Con
(48.6 pg/ml > Exercise (47.0
pg/ml)
- HIF-alpha expression: Con
(5.4.%l > Exercise (11.4%)
Con (0.0.34 mmol/g) < Exercise
(0.42 mmol/g)
17
Transgenic
mice
MMTV-PyMT
Tg
Genetically predisposed
to develop
breast cancer
Running Voluntary wheel running -Tumor growth

-Heart mass / Spleen
mass
-cytokine expression
-Con > Exercise

-Con < Exercise
-CCL22 : Con> Exercise
CXCR4: Con <Exercise
18
Orthotopic Female
BALB/c
4T1 cell Running Treadmill running
progressive time (10-15
min) and Speed (8-12
m/min) for 8 weeks
-Carbohydrate oxidation

-Gene expression
-Decrease the carbohydrate
oxidation in Exercise group

-Up-regulated Ldha, HKII, glut
1, HIF-1a, Mtor, p53, Lats2
expression
19
Xenograft Female
BALB/c
MC4-L2 cell
(ER+)
Running 6-18 m/min for 20-30
min for 4 weeks
-Gene expression The lowest level of IL-6,
VEGF
20
Xenograft Female
BALB/c
4T1 cell Running Endurance-trained for
8 weeks;
mice exercised 5 days a
week, for 8 consecutive
weeks
(In the 8th and final
week the mice ran for
26 min a day, spending
1 min at 6 m/min, 1 min
at 8 m/min, 22 min at
10 m/min, and 2 min
12 m/min.)
-Tumor growth



-Gene expression
-Exercise has -17% growth
rate, 24% long survival

- 2- folds CD8+/FoxP3+
(Endurance exercise enhances
antitumor immune efficacy)
21
Xenograft Female
BALB/c
4T1 cell Running Using the treadmill;
After acclimation, 5 m/
min for 5 min., 10 m/
min. for 5 min., 15 m/
min. for 5 min., and
20 m/min. for 45 min.,
which is equivalent to
70% VO2 peak .
The exercise intensity
was gradually increased
each week for 2 weeks

-Gene expression -Anti-inflammation : IL-10/
TNF-α ratio and IL-15 expression
22
Xenograft Female
BALB/c
4T1 cell Swimming Swim training 5 days/
week for 4 weeks
-Gene expression -Th1 systemic response ;
-Gata3 and Foxp3
23
Xenograft Female
BALB/c
4T1 cell Running 4 weeks of high-intensity
interval training (HIIT)
and saffron aqueous
extract (SAE) supplementation
-Tumor growth
-Gene expression
HIIT is associated with a
reduced risk of cancer-related
muscle wasting; SAE enhances
the improvement of muscle
loss and apoptotic indices
24
Xenograft Female
Balb/c
MC4-L2 cell Running Treadmill
16–18 m/min, 0%
grade, 10–14 min, 5
days/week for 5 weeks
-Gene expression -miR-21 pathways; reduced
IL-6 levels, NF-kB and STAT3
expressions & up-regulated
TPM1 and PDCD4 expressions
25
Xenograft Female
C57BL/6
EO771 breast
tumor cell
Running Reached maximum
ethical size in wheel
running (8 km per day)
-Tumor hyposia,
perfusion, vascularity
and proliferation
unknown 26
Xenograft Athymic MDA-MB231 cell Running Voluntary exercise;
The five-week period
ranged from < 1
to 7.9 miles/day
-Tumor growth -Inhibiting the growth of carcinomas 27
Chemical
induced
mouse
model
Female Balb/c 7,12-dimethylbenzanthracene
(1 mg/ml weekly
for 6 weeks)
Swimming physical training of
swimming in
water (30 ± 4°C) for 45
min
(5 times per week for 8
weeks)
-Gene expression -Reduced Th1 cytokine
increasing the Th2 cytokines
and Treg cells
28