HEALTH AND NUTRITION NEWSNo. 13September 15, 2005

Table of Contents
Prefatory Note
Roles of National Institute of Health and Nutrition as a core institute of nutrition research in Japan…………Tsuneyuki Oku

CURRENT RESEARCH PROJECTS
Research on energy metabolism using the human calorimeter.……………..…….……Shigeho Tanaka

THOUGHTS ON HEALTH AND NUTRITION RESEARCH
General term, scientific term and legal term………………...…................................ Mamoru Nishimuta

RESEARCH FINDINGS
Ovariectomy in mice decreases lipid metabolism related gene expression in adipose tissue andskeletal muscle with increased body fat……………………………………………………Yasutomi Kamei
Effects of alcohol consumption on the diabetics among middle-aged Japanese……… Masako Tanaka
Lack of age-related decreases in basal whole-leg blood flow in resistance-trained men………Motohiko Miyachi
Effects of high-intensity exercise on PGC-1α protein expression…………………….……Izumi Tabata© National Institute of Health and Nutrition

Prefatory Note
Roles and expectations for the NIHN as a core instituteof nutrition research in Japan

Professor Tsuneyuki OKU
Graduate School of Human Health Science, The Siebold University of Nagasaki

National Institute of Nutrition (NIN) (later,

the promotion of “recreation and rest” should alsorenamed to National Institute of Health andbe enhanced hereafter.

Nutrition; NIHN) was established in 1920 by

The recommended dietary allowance (RDA)

Dr. Tadasu Saeki, as a standard-bearer ofwas established for the first time in 1947. Since

nutrition improvement. NIN aimed at first tothen, RDA was revised every five year, for which

reduce the undernutrition and to enlighten thethe NIN has played a core role.

public nutrition activities. Since these activities

Now, the Dietary Reference Intakes (DRIs) newly

were implemented under poor social environment

established, which was the first revision of RDA

which was quite different from our current affluent

after NIHN was transformed into an incorporated

society, I am sure that the NIN’s existence andadministrative agency. Great and unconventionalsocial contribution of the institute was highly

efforts were made by the NIHN to establish DRIs,

evaluated.

and I think their contribution for DRIs should

Furthermore, the NIN implemented various

worth of being highly evaluated. Likewise, theactivities and played an important role for the

position of NIHN in the Health Promotion Law

nutrition improvement during the confusing period(enacted in 2002) also clearly shows its roles forwith serious food shortage after the World War II.

the health and nutrition policy.

Along with the rapid economic growth in 1960s,

While we work on the health problems ofthe nutritional status of population was gradually

population, we can not overlook the nutrition

improved.

healthproblems. We, nutrition experts, should be more

problems shifted from acute malnutrition toaware that the term of “nutrition” graduallychronic

lifestyle-related

disappears in the various sections of publicdiseases. And, with an increasing trend of

sectors. For example, there is no longer section

overnutrition, the issue of health promotion beganwith the name of “nutrition” at the Ministry of

to be more seriously discussed, and then, theHealth, Labour and Welfare and the Departments

focus areas of the nutrition research at the NIN

focusing on the nutrition research now hardly

have also been greatly changed. Yet, the NIN’sremain in any national/public/private medical

activities have been consistently concerned with

universities.

Consequently,
diseases,thenamely,main

the public health nutrition for the nutrition

The NINH is now only the research institute in

improvement of population since the foundation

the field of nutrition. I believe that its importanceto date, throughout the periods with differentof existence should be fully acknowledged byhistorical background. Institutional reform and theworking on the health and nutrition problems ofnutrition research, both of which considered the

populations very hard and by contributing thesocial needs in the field of health science, can be

nutrition improvement. I therefore expect that thethe obvious proofs. The current research target

NIHN will continue the efforts for nutrition

on “nutrition”, “exercise” and “dietary supplement”

research aimed at the nutrition improvement ofalso reflects the needs of age. In

population hereafter too.

my opinion,2

Current Research Projects
Research on energy metabolism using the human calorimeter
Shigeho Tanaka
Laboratory of Exercise Physiology
Division of Health Promotion and Exercise
Now, these problems have been sorted out by
the introduction of human calorimeter, as its
measurement error can be kept within ±1%(quite lower than that of earlier methods) for longhours, even for several days, by checking it withregular alcohol combustion test. Furthermore, it isalso possible to estimate the expended energy
sources (e.g. carbohydrate, lipid, protein).
By using this human calorimeter, we are
currently working on the following researches;

In 2000, the first human calorimeter in Japan was
introduced in our Institute (see Photo). Human
Calorimeter enables us to measure accurate 24-henergy expenditure (TEE), as well as energy
expenditure at rest, during sleeping and ofvarious activities, by measuring the changes ofO2 and CO2 concentration while a study subject
stays in the human metabolic chamber.
So far, the following two types of methods weregenerally applied to measure energy expenditure;a) Calculation of energy expenditure from themeasured O2 intake, for which a subject is
asked to wear a face mask etc.
b) Estimation of energy expenditure using therelational formulae with O2 intake, by wearing
heart rate monitor, accelerometer orrecording the activities.
Although the energy expenditure can bemeasured quite accurately by the method a),there are two major limitations; one is thatmeasuring condition greatly differ from the actual
daily life, and the other is that it is impossible tomeasure for long hours. On the other hand, themethod b) is absolutely indirect one and that
there is a limitation with the accuracy for theestimation of low-intensity activities while these
activities take up most of the day.

1) Energy expenditure and physical activity
levels for the specified activities
The energy expenditure for a daily life withtypical physical activity was measured by thehuman calorimeter. As a result, it was exploredthat the prediction by the method described in
the latest 6th Recommended Dietary Allowance(RDA) for Japanese would underestimate theactual energy expenditure and physical activity
levels.
2) Development of methods to assess theenergy expenditure and physical activity level
As is written in the above, it is quite difficult tomeasure the energy expenditure at the daily life,
especially the low-intensity activities (e.g.
activities while sitting). Under this circumstance,in addition to the activity diary method (All theactivities are recorded and predicted energy
expenditure of each activity is applied to
calculate TEE), we are currently working on thedevelopment of a new method to explore thedetails of low-intensity activities.
If this attempt succeeds, the amount andcontents of physical activity in daily life can beassessed more accurately and objectively. We
can also expect that it will be useful todetermine, for example, the effects of physicalactivity on obesity and impact of exercise
prescription.

3

Thoughts on Health and Nutrition Research

General term, scientific term and legal term
Mamoru Nishimuta
Division of Human Nutrition
Topics on nutrition are discussed among not only

each person. So, we can say that the argument

nutrition experts but also general public. The useon “What’s nutrition support food?” actually doesof specific “term”, however, can often be a barrier

not make sense.

in the discussion. For example, when “mineral” is“Health food” is also a general term. Well, what’sused as a general term, the interpretation of

the difference between “food” and “health food”?

“mineral” is not always same between theThis is also a nonsense argument, but why these

speaker and the listener. If somebody asks

foods are named with “health”? Apparently, it is“What’s mineral?”, many of us would get stuck forlikely that sales companies intended to use theanswer. Since there is no strict definition of

positive image on “health” among consumers who“mineral” even as a scientific term, we need tobelieve “health food” is more beneficial thanapply a certain definition when “mineral” is used“food”. Sadly, some of them would even expect

as a scientific term. So, it should be like;the pharmacological effects of “health foods”. In“In this paper, `minerals` is used as a collective

reality, labeling the pharmacological effects onterm of elements except for hydrogen (H),“food” is against the Pharmaceutical Affairs Law.

carbon (C), nitrogen (N) and oxygen (O)”So, generally, no sales company declares theOn the other hand, we normally proceed with thepharmacological effects on foods for marketing.

generalthe

As for “Foods for Specified Health Use”, thedefinition of “term”, which often leads to the above

pharmacological effects of certain components

mentioned confusion. “Mineral water” is also a

are officially acknowledged. Yet, we still need togeneral term, and it is not surprising that somebe careful to declare its effects in the food label.

people may believe it contains relatively lots ofFor example, for “Foods for Specified Health Use”

minerals. In this case, sodium (Na) is notcontaining components with antihypertensive

recognized as a mineral while it is actually aeffects, it is not allowed to put the label like “Thismineral if the above scientific definition is applied

food is effective for the treatment of hypertension”.

here.

Instead, the description on the label should be

So, there may arise a serious argument,

like “This food is recommended for those who areaccusing that “This mineral water has false

concerned about own blood pressure”.

discussion

without

confirming

labeling, because it contains little minerals”.
ミネラル＝minerals

However, in this argument, the discussion ismade on science or law using the undefined term.
It is therefore necessary to confirm the definitionof term first, so as to start scientific discussion.
As for legal term, the definition is clarified by law.
“Foods for Specified Health Use” and “Food withnutrient function claims” are legal terms and thus,
the definition is clearly specified. How about“nutritional supplementary food”, then? Since thisis a general term, the interpretation may vary by4

Latest Research
Ovariectomy in mice decreases lipid metabolism related gene expression in
adipose tissue and skeletal muscle with increased body fat
Yasutomi Kamei (Division of Clinical Nutrition)
When the energy intake from foods exceeds the energy expenditure by exercise, energy is accumulated
as body fat. It has been known that women are likely to be obese after menopause, due to a lack ofestrogen. Ovariectomy in rodents is the most reliable way of expressing menopause in the animalmodel. Since the ovary is the main organ that produces estrogen, the symptoms after ovariectomy could
be similar to those after menopause. Previous studies have shown that bone density decreased in
ovariectomized mice, leading to osteoporosis as in postmenopausal women. In addition, weight gain isalso observed among these mice. Ovariectomy-induced obesity in mice is associated with a decrease inoxygen consumption, indicating repressed energy expenditure. Yet, no study has explored the precise
nature of this decrease in energy expenditure. Skeletal muscle is an important organ for energy
expenditure, and in mice, adipose tissue is also involved. In this study, to elucidate the mechanism ofweight gain after ovariectomy, we examined the expression patterns of genes related to energy
expenditure and lipid metabolism in adipose tissue and skeletal muscle. At 2-4 wk after ovariectomy,
levels of nuclear receptors and cofactors involved in energy expenditure such as ERR1, PPARα andPPARδ, and PGC1α and PGC1β were lower than those in control mice. mRNA levels of their targets,
medium-chain acyl coenzyme A dehydrogenase and acetyl CoA oxidase, enzymes for fatty acid
β-oxidation, also decreased. When fatty acid β-oxidation, a channel to resolve the fatty acid, is activewith high levels of enzymes for fatty acid β-oxidation, body fat is expended as energy. On the contrary,ovariectomized mice had low levels of enzymes for fatty acid β-oxidation, and thus, body fat is not
expended well. Therefore, changes of gene expression observed in this study could explain the obesityin ovariectomized mice. That is, a decrease in the expression of energy expenditure-related genes inadipose tissue and skeletal muscle could be, in part, responsible for obesity after ovariectomy. Further
study should provide more insight into molecular mechanism of OVX-induced obesity,
which could be of medical importance for weight gain among postmenopausal women.
In skeletal muscle and adipose tissue (see Figure), nuclear receptors (e.g. ERR, PPAR) andcofactors (e.g. PGCα, PGCβ) control the expression of genes related to energy expenditureand lipid metabolism. Ovariectomy in mice decreases the expression of these genes: hence,the decrease of energy expenditure, possibly leads to weight gain.

Ovariectomy in mice decreases lipid metabolism-related gene expression in adipose
tissue and skeletal muscle with increased body fat.
Journal of Nutritional Science and Vitaminology. 2005;51(2):110-117.
Kamei Y1)-3), Suzuki M1), Miyazaki H1), Tsuboyama-Kasaoka N1), Wu J1), Ishimi Y1) and Ezaki O1)
1)

National Institute of Health and Nutrition, Shinjuku-ku, Tokyo, Japan.

2)

PRESTO, Japan Science and Technology Agency, Saitama, Japan

3)

Tokyo Medical and Dental University, Tokyo, Japan

Abstract:
Postmenopausal women as well as rodents after ovariectomy, which results in a lack ofestrogen, can become obese. Ovariectomy-induced obesity in mice is associated with a decrease inoxygen consumption, indicating repressed energy expenditure. In this study, to elucidate the mechanism
of weight gain after ovariectomy, we examined the expression patterns of genes related to energy
expenditure and lipid metabolism, in mouse tissues including adipose tissue and skeletal muscle. In
adipose tissue and skeletal muscle, at 2-4 wk after ovariectomy, levels of nuclear receptors andcofactors involved in energy expenditure such as ERR1, PPARα and PPARδ, and PGC1α and
PGC1β were lower than in control mice. mRNA levels of their targets, medium-chain acyl coenzyme A
dehydrogenase and acetyl CoA oxidase, enzymes for fatty acidβ-oxidation, were lower. In addition, theexpression of PPARγ and SREBP1, transcription factors important for lipogenesis, was decreased, as
well as that of acetyl CoA carboxylase and fatty acid synthase, enzymes for fatty acid synthesis, anddiacyl glycerol acetyl transferase 1 and 2, enzymes for triglyceride synthesis. These changes in gene
expression are consistent with the obese phenotype in mice after ovariectomy. Thus a decrease in theexpression of energy expenditure-related genes in adipose tissue and skeletal muscle could, in part, be
responsible for obesity after ovariectomy.
5Latest Research
Effects of alcohol consumption on the diabetics among middle-aged Japanese.
Masako Tanaka (Division of Health Informatics and Education)
Japanese immigrants living in the United States and Brazil have acquired a westernized lifestyle, but theirgeneric background is regarded still same as Japanese. Since the prevalence of type 2 diabetics among theimmigrants is higher than that of Japanese, it is plausible that Type 2 diabetics is associated with a genericpredisposition, but is also strongly influenced by life-style related factors such as diets and/or physical activity.
Over the past decades, however, the prevalence of diabetes has increased dramatically in Asian countries,
including Japan. Prevention of diabetes through improvement of lifestyle is therefore an urgent health issue inthis area. For which, it is important to investigate whether the risk factors identified in western populations could
also apply to Asian ethnic groups. So far, few studies have attempted to answer this question. This study,
therefore, aimed to quantify the risk factors for diabetes in a general Japanese population by a prospective
cohort study (Japan Public Health Center-based prospective study on cancer, cardiovascular diseases: JPHC
study). Total of 28,893 individuals (12,913 men and 15,980 women) without history of diabetes andcardiovascular diseases participated in this study. Following the baseline questionnaire completed in 1990,
follow-up questionnaires were sent to each participant in 1995 and 2000. These self-administeredquestionnaires included the questions on; weight, height, usual physical activity patterns, smoking habits,
alcohol intake (items, frequency per week, amount consumed daily), previously diagnosed medical conditions,family history of diabetes and other lifestyle-related factors. As for alcohol intake, the subjects were classified
into two groups: “non drinkers and infrequent occasional drinkers” and “drinkers”. And, “drinkers” were further
subdivided into three groups by daily ethanol consumption. During the 10-years follow-up, 703 men and 482
women reported newly diagnosed diabetics. Multivariate logistic regression revealed that age, BMI, family
history of diabetes and smoking were significant factors for diabetes in both genders. As for alcohol
2
consumption, whilst no significant association was observed for women and men with BMI > 22kg/m ,moderate/high alcohol consumption showed high risk of developing diabetes for men with BMI ≤ 22kg/m2.
Studies conducted in the United states and Europe showed an inverse correlation between alcohol intake andType 2 diabetes or suggested no significant association. On the other hand, a few study showed an excess
diabetes incidence only in heavy drinkers. Therefore, the association between alcohol intake and diabetes
remains uncertain. Yet, our findings would suggest that alcohol consumption might have more adverse effect on
development diabetes for Japanese, in comparison with western populations. This may be due to the difference
in distribution of polymorphic ethanol-metabolizing enzymes between Japanese and western populations.

Alcohol consumption and other risk factors for self-reported diabetes among middle-aged
Japanese: a population-based prospective study in the JPHC study cohort I.
Diabetic Medicine. 2005;22(3):323-331
Waki K, Noda M, Sasaki S, Matsumura Y, Takahashi Y, Isogawa A, Ohashi Y, Kadowaki T and
Tsugane S for the JPHC study group1) Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
2) Department of Endocrinology and Metabolism, Toranomon Hospital, Tokyo, Japan
3) National Institute of Health and Nutrition, Tokyo, Japan
4) Department of Internal Medicine, Tokyo Hospital of the Printing Bureau, Tokyo, Japan
5) Department of Internal Medicine, Mitsui Memorial Hospital, Tokyo, Japan
6) Department of Biostatistics, Graduate School of Medicine, University of Tokyo, Japan

Abstract:
AIMS: Few prospective studies have examined the relationship between lifestyle characteristics and theincidence of diabetes mellitus in an Asian general population. This study was undertaken to evaluate the risk
factors for Type 2 diabetes in a population-based prospective study of middle-aged Japanese. METHODS: We
investigated 12,913 men and 15,980 women, aged 40-59 years at baseline (year 0), who participated in theJapan Public Health Center-based prospective study on cancer and cardiovascular diseases (JPHC Study)
Cohort I. The participants were followed for up to 10 years. Incident cases of diabetes were identified by
self-reporting of a physician's diagnosis on two questionnaires sent to each participant, one at year 5 and thesecond at year 10. RESULTS: During the 10-year follow-up, 703 men and 482 women reported newly
diagnosed diabetes. Age, body mass index (BMI), family history of diabetes and cigarette smoking were2
independent risk factors in both genders by multivariate analysis. Among men with a BMI ≤ 22 kg/m , asignificant positive association was observed between the diabetes incidence and moderate (23.0 < 46.0 g/day)
to high (> 46.0 g/day) alcohol consumption, odds ratio 1.91 (95% CI, 1.05-3.46) and 2.89 (1.63-5.11),
respectively. Among men with a BMI > 22 kg/m2, a small non-significant increase in odds ratio was observedwith alcohol consumption. CONCLUSIONS: Established risk factors for diabetes in western populations werealso identified as predictors of the disease among Japanese. Moderate to high alcohol consumption was
positively associated with the incidence of diabetes in Japanese lean (BMI ≤ 22 kg/m2) men.
6

Latest Research
Lack of age-related decreases in basal whole-leg blood flow in resistance-trained men.
Motohiko Miyachi (Division of Health Promotion and Exercise)
Reductions in basal leg blood flow, which decrease progressively with advancing age, have been implicated in
the pathogenesis of metabolic syndrome and functional impairment in human. Regular physical activity isimportant for the prevention and treatment of cardiovascular disease and functional ability. Yet, previous studies
show that habitual aerobic exercise does not modulate the age-related reductions in basal leg blood flow in
healthy men. On the other hand, resistance training is known to be effective to prevent the age-related loss inmuscle mass and function (e.g. sarcopenia). This study therefore aimed to determine the relation between
resistance training, leg muscle mass and basal leg blood flow. We hypothesized that resistance training is
associated with elevated leg perfusion in aging humans through its impact on leg skeletal muscle mass. A totalof 104 healthy men aged 20-34 years (young) and 35-65 years (middle-aged) participated in this study. Half ofthem were the resistance-trained men who had been performing vigorous resistance training for > 2 years, andthe other half were sedentary subjects who had not participated in any
regular exercise program for at least the previous 2 years. All the subjects
were normotensive (<140/90mmHg), nonobese and free of overt chronic
diseases as assessed by medical history, physical examination and blood
test. A duplex ultrasound machine equipped with a high resolution
linear-array transducer was used to measure vessel diameter and blood
velocity on the right common femoral artery. This study confirmed that theage-associated reduction in basal whole leg blood flow did not occur inresistance trained men, implicating that daily weight training may prevent
diseases in basal whole blood flow with advancing age. These results
therefore suggest that habitual resistance exercise may favorably
influence leg perfusion and hemodynamics in the aging human. Although
it is well known that abdominal fat accumulation is underlying mechanism
for metabolic syndrome and diabetes, the risk of atrophy in skeletal
muscle (principal organ for energy expenditure) also should not beignored. As is well known, it is essential to increase the physical activity
and exercise, so as to prevent metabolic syndrome and diabetes. While
many people are aware of the effects of aerobic exercise (e.g. walking),
it is important to pay attentions to the effects of resistance training as well.

Lack of age-related decreases in basal whole-leg blood flow in resistance-trained men.
Journal of Applied Physiology. 2005;99(4):1384-90
Miyachi M, Tanaka H, Kawano H, Okajima M and Tabata I.
1) Division of Health Promotion and Exercise, National Institute of Health and Nutrition, Shinjuku, Tokyo, Japan.
2) Department of Kinesiology, University of Wisconsin-Madison, Wisconsin, USA
3) Department of Health and Sports Sciences, Kawasaki University of Medical Welfare, Okayama, Japan
4) Japan Women’s college of Physical Education, Tokyo, Japan

Abstract: Reductions in basal leg blood flow have been implicated in the pathogenesis of metabolic
syndrome and functional impairment in humans. We tested the hypothesis that reductions in basal whole leg
blood flow with age are either absent or attenuated in those who perform regular strength training. A total of 104
normotensive men aged 20-34 yr (young) and 35-65 yr (middle aged), who were either sedentary or resistancetrained, were studied. Mean and diastolic blood pressures were higher (P < 0.05-0.001) in the middle-aged
compared with the young men, but there were no significant differences between the sedentary andresistance-trained groups. In the sedentary group, basal whole leg blood flow (duplex Doppler ultrasound) andvascular conductance were lower (approximately 30 and approximately 38%, respectively; P < 0.01) in the
middle-aged compared with the young men. There were no such age-related differences in theresistance-trained group. In the young men, basal whole leg blood flow and vascular conductance were notdifferent between the two activity groups, but, in the middle-aged men, they were higher (approximately 35 andapproximately 36%, respectively; P < 0.01) in the resistance-trained men than in the sedentary men. Whenblood flow and vascular conductance were expressed relative to the leg muscle mass, the results were
essentially the same. We concluded that the age-related reduction in basal whole leg blood flow is absent inresistance-trained men. These results suggest that resistance training may favorably influence leg perfusion in
aging humans, independent of its impact on leg muscle mass.
7

Latest Research
Effects of high-intensity exercise on PGC-1α protein expression
Izumi Tabata (Division of Health Promotion and Exercise)
It is well known that physical training increases the glucose metabolism and the physical endurance, and also
promotes the energy metabolism. In this way, many adaptive responses to physical training can be observed
concurrently in skeletal muscle. It has been regarded that this phenomena is due that exercise would stimulate agene or more, which develop the expression of several proteins, rather than due that stimulus of exercise would
affect each gene of protein which increased and became bioactive by exercise.
Recent studies have shown that PGC-1α (peroxisome proliferator-activated receptor γ coactivator-1α)
protein is involved in both GLUT-4 expression (which is associated with glucose metabolism in muscle, hence,with diabetes) and mitochondrial proteins (which is associated with endurance and energy metabolism, hence,with obesity). PGC-1α is one of the transcriptional coactivators (which promote the smooth transcription from
DNA to mRNA), and it is said that a person with low expression of PGC-1α is at high risk of developing
diabetes. It is also reported that physical endurance is influenced by the difference in the genetic factor of
PGC-1α. That is, PGC-1α is a possible master key that would influence the transcription of many genes andincrease the expression of many proteins. We therefore hypothesized that PGC-1α might be related to theincrease of protein expression during the exercise, and then confirmed for the first time that PGC-1α would
increase by the exercise/physical training.
This time, in the following article, we explored
Figure. PGC-1α protein content in rat epitrochlearis muscle
that high-intensity intermittent exercise, likeafter high-intensity intermittent swimming exercise
speed skaters would practice, could increase
PGC-1α expression in skeletal muscle to thelevel observed after low-intensity prolonged
exercise. These findings would suggest thathigh-intensity exercise can be as effective as
low-intensity exercise, in terms of the increase of
GLUT-4 and mitochondria. Therefore, thehigh-performance sports with high possibility ofcontinuation can be recommended for theprevention of diabetes and obesity.

Effects of high-intensity intermittent swimming on PGC-1α protein expression in rat
skeletal muscle.
Acta Physiologica Scandinavica, 2005; 184(1):59-65
Terada S1), Kawanaka K1), Goto M2), Shimokawa T2) and Tabata I1)
1) Division of Health Promotion and Exercise, National Institute of Health and Nutrition, Tokyo, Japan
2) School of Sports Sciences, Waseda University, Saitama, Japan
3) Niigata University of Health and Welfare, Niigata, Japan
4) Molecular Medicine Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co. Ltd. Ibaraki, Japan

Abstract:
AIM: The aim of the present investigation was to elucidate the effects of exercise intensity on exercise-induced
expression of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) protein in rat
skeletal muscle. METHODS: We measured PGC-1α content in the skeletal muscles of male Sprague-Dawley
rats (age: 5-6 weeks old; body weight: 150-170 g) after a single session of high-intensity intermittent exercise(HIE) or low-intensity prolonged swimming exercise (LIE). During HIE, the rats swam for fourteen 20-s periods
carrying a weight (14% of body weight), and the periods of swimming were separated by a 10-s pause. LIE rats
swam with no load for 6 h in two 3-h sessions, separated by 45 min of rest. RESULTS: After HIE, the PGC-1α
protein content in rat epitrochlearis muscle had increased by 126, 140 and 126% at 2, 6 and 18 h, respectively,
compared with that of the age-matched sedentary control rats' muscle. Immediately, 6 and 18-h after LIE, thePGC-1α protein content in the muscle was significantly elevated by 84, 95 and 67% respectively. The PGC-1α
protein content observed 6 h after HIE tended to be higher than that observed after LIE. However, there was no
statistically significant difference between the two values (P=0.12). CONCLUSION: The present investigationsuggests that irrespective of the intensity of the exercise, PGC-1α protein content in rat skeletal muscle
increases to a comparable level when stimuli induced by different protocols are saturated. Further, HIE is apotent stimulus for enhancing the expression of PGC-1α protein, which may induce mitochondrial biogenesis in
exercise-activated skeletal muscle.
8