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JOURNAL OF MEDICINAL FOOD
J Med Food 11 (3) 2008, 395–404
© Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition
DOI: 10.1089/jmf.2006.0180
Nutrigenomic Studies of Effects of Chlorella on Subjects with High-Risk Factors
for Lifestyle-Related Disease
Toru Mizoguchi,
1
Isao Takehara,
2
Tohru Masuzawa,
2
Toshiro Saito,
3
and Yo Naoki
1
1
Sun Chlorella Corporation, Kyoto;
2
New Drug Development Research Center, Inc., Hokkaido;
and
3
Life Science Group, Hitachi, Ltd., Saitama, Japan
ABSTRACT In order to clarify the physiological effects of Chlorella intake on subjects with high-risk factors for lifestyle-
related diseases, we conducted Chlorella ingestion tests on 17 subjects with high-risk factors for lifestyle-related diseases and
17 healthy subjects over a 16-week period, including a 4-week post-observation period. We conducted blood biochemical tests
and analyzed gene expression profile in whole blood cells in the peripheral blood before and after Chlorella intake. We con-
firmed that in both groups, Chlorella intake resulted in noticeable reductions in body fat percentage, serum total cholesterol,
and fasting blood glucose levels. Through gene expression analysis, we found that gene expression profiles varied with
Chlorella intake and identified many genes that exhibited behavior such that after the completion of the intake period, ex-
pression levels returned to pre-intake expression ones. Among these were genes related to signal transduction molecules, meta-
bolic enzymes, receptors, transporters, and cytokines. A difference in expression level was found between the two groups at
the start of the tests, and we were able to identify genes with noticeable variance in expression level resulting from Chlorella
intake in the high-risk factor group. These included genes involved in fat metabolism and insulin signaling pathways, which
suggests that these pathways could be physiologically affected by Chlorella intake. There were clear variations in the ex-
pression profiles of genes directly related to uptake of glucose resulting from Chlorella intake, indicating that the activation
of insulin signaling pathways could be the reason for the hypoglycemic effects of Chlorella.
KEY WORDS: •hypocholesterolemic effect •hypoglycemic effect •insulin •insulin signaling pathway •gene ex-
pression •microarray •peripheral blood
395
INTRODUCTION
C
LORELLA HAS BEEN CONSUMED
by humans as a food sup-
plement for generations because it is rich in essential
nutrients, including high-quality protein, vitamins, minerals,
and essential amino acids. In recent years, it has gained at-
tention as a health food because it offers an outstanding bal-
ance of nutritional elements. Notably, it has been reported
that Chlorella demonstrates physiological effects such as
immune activation,
1
growth promotion,
2
and improvement
in stress-related ulcers.
3
Most of this prior research, how-
ever, used rats, mice, and other laboratory animals; almost
no large-scale clinical research has been undertaken to eval-
uate its physiological effects in humans.
The physiological effects of specific foods have long been
known empirically, but because foods are composed of di-
verse components, it has been difficult to identify the com-
ponents that are effective in bringing about desirable phys-
iological effects. At the same time, there has been little re-
search conducted on the mechanisms of these physiological
effects, because of the lack of effective testing and analyti-
cal methods that take into account multiple aspects of these
physiological effects. Amid a growing demand for health
foods in recent years, there have been calls for proof of the
effectiveness of these foods in humans, and for clarification
of the mechanisms involved. The term “evidence-based
food” is representative of this trend.
4
Since the announcement in 2004 that the entire human
genome sequence had been decoded, attention has been fo-
cused on a new research field called “nutrigenomics,” which
attempts to examine the utility of food products based on
genomic information.
5
Specifically, a DNA microarray that
can examine expression level of several thousand to several
tens of thousands of genes in a single assay has come to be
used extensively as a new tool for investigating diverse re-
actions in living organisms. This microarray technology is
extremely well suited to comprehensive examinations of
complex reactions in living organisms in which multiple
components bring about complex effects, as in the case when
food is ingested.
Manuscript received 25 September 2006. Revision accepted 6 March 2007.
Address reprint requests to: Toru Mizoguchi, Research and Development Department,
Sun Chlorella Corporation, Karasuma-dori, Gojo, Shimogyo-ku, Kyoto 600-8177, Japan,
E-mail: mizoguchi@sunchlorella.co.jp
In this research, we analyzed the gene expression profiles
in all peripheral blood cells following Chlorella intake in
17 subjects with high risk factors for lifestyle-related dis-
eases (diabetes or hyperlipemia) and 17 healthy subjects. We
also gathered biochemical test data from these subjects.
As a result of these tests, we confirmed that in both
groups, Chlorella intake resulted in noticeable reductions in
body fat percentage, total blood serum cholesterol, and fast-
ing blood glucose levels. Through gene expression analysis,
we found that gene expression varied with Chlorella intake
and identified many genes whose expression returned to pre-
intake expression levels after the completion of the intake
period. In the results for insulin signaling pathways in par-
ticular, variations were observed in the gene clusters directly
related to active uptake of glucose, which provides evidence
for the blood glucose reduction effects of Chlorella.
MATERIALS AND METHODS
Subjects
The subjects were healthy Japanese males 20 years of age
or older. On three occasions—6 weeks, 4 weeks, and 2
weeks—before the start of the ingestion tests, the subjects
were examined by a physician and also received physical
examinations, clinical examinations, and glucose tolerance
tests. Based on the conditions outlined below, 34 subjects
were selected, with 17 assigned to each of two groups: the
high-risk factor (for lifestyle-related diseases) group (re-
ferred to here as the “D Group”) and the normal healthy sub-
ject group (referred to here as the “N Group”).
Healthy subject group (N Group). At all three periods be-
fore beginning the tests, fasting blood glucose, total blood
serum cholesterol, and concentration of triglycerides in the
blood were within normal limits. These subjects were also
judged as having normal glucose tolerance.
High-risk factor group (D Group). Subjects who at all
three periods before beginning the tests (a) exhibited bor-
derline high fasting blood glucose and total blood serum
cholesterol and high triglycerides in blood and who were
also judged as having low glucose tolerance or (b) demon-
strated borderline high fasting blood glucose, were judged
as having low glucose tolerance, and were also judged to
have total blood serum cholesterol and serum triglycerides
that deviated slightly from normal limits. Attributes for sub-
jects in the N Group and D Group are summarized in Table
1. Serum was used for biochemical tests. Body fat percent-
age was evaluated by measuring bioelectrical impedance.
Materials tested
The Chlorella used in these tests was “Sun Chlorella A”
tablets (Sun Chlorella Corp., Kyoto, Japan), which contains
dried Chlorella powder (more than 95.5%) as the active in-
gredient and lecithin (less than 4.5%) as a bulking agent.
The Chlorella powder contained in the tablet was prepared
by crushing the cell wall in a DYNO
®
-Mill (WAB, Inc.,
Basel, Switzerland) and spray-drying. The subjects took 20
tablets each morning and evening (total, 40 tablets/day) af-
ter meals with either cold or hot water.
Test design
This research protocol was approved by the Testing Com-
mittee at Miyawaki Orthopedic Hospital (Hokkaido, Japan).
Before the tests began, the subjects received a written ex-
planation and consent form from the physicians responsible
for the tests. After receiving an explanation of the purpose
and value of the tests as well as the methods, expected ef-
fects, and potential risks, etc., the subjects themselves con-
firmed their understanding of the details explained and then
provided written consent indicating that they were partici-
pating of their own free will.
396 MIZOGUCHI ET AL.
T
ABLE
1. C
HARACTERISTICS OF
H
EALTHY AND
H
IGH
-R
ISK
S
UBJECT
G
ROUPS
Healthy subject group High-risk factor group
Characteristic (NGroup) (DGroup)
Age (years) 34.3 3.2 59.2 1.9
Height (cm) 170.7 1.6 164.5 1.3
Body weight (kg) 64.4 2.2 66.1 1.9
Body fat percentage 19.8 1.5 24.2 1.1
Body mass index (kg/m
2
) 21.8 2.2 24.4 2.1
Cholesterol (mg/dL)
Total 173.8 18.0 218.4 38.7
HDL 59.5 12.0 61.0 11.7
LDL 101.2 18.5 127.4 37.0
Triglycerides (mg/dL) 59.3 21.4 124.4 76.6
Fasting blood sugar (mg/dL) 82.4 7.2 111.4 30.1
Hemoglobin A1c (%) 4.5 0.2 5.3 0.8
Immunoreactive insulin (mU/mL) 5.0 3.1 6.1 4.0
Data are mean SD values.
The tests were conducted in an open test format. The in-
take period lasted for 12 weeks; blood biochemical tests
were conducted every 4 weeks, and again 4 weeks after the
completion of the intake period.
During the test period, one subject from the N Group
dropped out because of stomach pains, but no other subjects
dropped out during the testing period. Data for statistical
analysis were thus gathered for 17 subjects in the D Group
and 16 subjects in the N Group. None of the subjects in ei-
ther group reported any complications that could be con-
sidered to indicate harmful side effects during any of the
four physical examinations conducted during the testing
period.
Gene expression analysis
The blood sampling and RNA extraction for gene ex-
pression analysis was conducted using a PAXgene™ Blood
RNA kit (manufactured by PreAnalytiX GmbH, Hom-
brechtikon, Switzerland), and a model 2100 Bioanalyzer
(manufactured by Agilent Technologies, Palo Alto, CA) was
used to confirm that there was no breakdown in the extracted
RNA (rRNA profile used as a reference). RNA amplifica-
tion reactions were checked based on the in vitro transcrip-
tion method using primers with T7 promoter sequence. At
this time, cRNA was synthesized through the uptake of
dUTP with an aminoallyl group. The cRNA with Cy5 la-
NUTRIGENOMICS OF EFFECTS OF CHLORELLA 397
**
*
*
a
0w
60
N Group
FBS (mg/dL)
4w 8w 12w 16w
**
80 100 120 140 160 180 200
0w
D Group
4w 8w 12w 16w
*
b
0w
15
N Group
Body fat percentage (%)
4w 8w 12w 16w
**
20 25 30 35
0w
D Group
4w 8w 12w 16w
*
c
0w
N Group
T-Cho(mg/dL)
4w 8w 12w 16w
**
150 200 250
0w
D Group
4w 8w 12w 16w
d
0w
30
N Group
HDL-Cho (mg/dL)
4w 8w 12w 16w
**
40 50 60 70 80 90
0w
D Group
4w 8w 12w 16w
*
***
e
0w
50
N Group
LDL-Cho (mg/dL)
4w 8w 12w 16w
*
100 150 200
0w
D Group
4w 8w 12w 16w
*
**
*
FIG. 1. Time profile of (a) fasting blood glucose (FBS), (b) body
fat percentage, (c) total blood serum cholesterol (T-Cho), (d) HDL-
cholesterol (HDL-Cho), and (e) LDL-cholesterol (LDL-Cho) in the
healthy subject group (N Group) and the high-risk factor group (D
Group). The measured values before the start of Chlorella intake (0
weeks) and at each test point were tested for significant difference us-
ing paired ttests.
夹
P5%.
beling was synthesized by applying coupling reactions to
cRNA and Cy5 with a succinimide group (manufactured by
GE Healthcare, Chalfont St. Giles, UK).
As the control sample for expression analysis, we used
total RNA from commercially available human white blood
cells (from Clontech Laboratories, Palo Alto), and Cy3 was
used as a fluorochrome. In addition, we synthesized cRNA
with the same labeling as the above blood-derived sample
and used this cRNA as a common comparative reference
sample for all blood-derived samples.
For the microarray, we used a custom microarray with
additional loading of diabetes-related genes and other
genes on a human drug response DNA chip (manufactured
by Hitachi Ltd., Saitama, Japan) (number of genes loaded,
1,873). After the labeled cRNA is mounted on the mi-
croarray, it is subject to competitive hybridization at 45°C
for 17 hours. Once hybridization is complete, the unit is
washed and dried, and fluorescent images are captured us-
ing a scanner (ScanArray5000, GSI Lumonics, Billerica,
MA). Through numerical processing, we then derived the
variable ratio for expression intensities between the sam-
ples and the reference samples for each of the relevant
genes. The global normalization method was used for nor-
malization of Cy5 and Cy3.
For expression data analysis, we used GeneSpring (Agi-
lent) and the R program package (R project; see http://www.
r-project.org/).
RESULTS
Blood analysis
Figure 1 shows changes over time in fasting blood glu-
cose, body fat percentage, total blood serum cholesterol,
high-density lipoprotein (HDL)-cholesterol, and low-density
lipoprotein (LDL)-cholesterol. Each of the measured values
shows decreasing trends after Chlorella intake and increas-
ing trends after completion of the intake test period (12
weeks). The measured values before the start of intake (0
weeks) and at each test point were tested for significance
using paired ttests. Using a significance level of 5%, both
the N Group and the D Group demonstrated significant dif-
ferences in body fat percentage and total blood serum cho-
lesterol from weeks 4 to 12. Particularly in the case of the
D Group, decreases in HDL-cholesterol and LDL-choles-
terol showed clearly significant differences at all measure-
ment points after the start of Chlorella intake. Blood glu-
cose levels were also significantly decreased in the D Group
after 8 weeks of chlorella consumption. In all of these mea-
sured values, a temporary decreasing trend could be seen af-
ter the start of Chlorella intake; after the completion of the
intake period, these values returned to the levels before in-
take began. This indicates that the variations in blood para-
meters were brought about as a result of Chlorella intake.
On the other hand, no clear variations in volumes of triglyc-
erides in the blood were observed before and after the start
of Chlorella intake in either the healthy subject group or the
high-risk factor group. Furthermore, no trends toward in-
creased concentration of insulin in the blood could be seen
as a result of Chlorella intake.
Based on the above data, we have summarized the effects
of Chlorella intake as follows. With regard to fat metabo-
lism, although no significant changes could be seen in the
concentration of triglycerides in the blood, both body fat
percentage and total serum cholesterol were decreased in
both the N and D Groups. With regard to glucose metabo-
lism, however, Chlorella lowered blood glucose in the D
Group. Since no clear increases in insulin concentrations in
the blood were observed, the decrease in serum glucose con-
centrations may be due to improved insulin sensitivity in-
duced by Chlorella intake.
Gene expression analysis
In both N and D Groups, we identified the genes whose
mRNA expression levels varied owing to Chlorella intake
by comparing expression intensities at 0 weeks (before the
start of intake tests) and 4 weeks and between 0 weeks and
12 weeks. Moreover, the genes whose mRNA expression
levels exhibited behavior consistent with the blood chem-
istry data, namely, gene expression profile varied with
Chlorella intake and then returned nearly to pre-intake ex-
pression levels, were extracted by comparison between ex-
pression change of 4 weeks versus 0 weeks and that of 16
weeks versus 0 weeks based on ttest. For these identifica-
tions, we used ttests with the False Discovery Rate 0.05
as the level of significance.
6
Next, the genes superimposed
in these two kinds of identified genes were extracted in both
the N and D Groups. A total of 129 genes were chosen, 66
of which are associated with canonical pathways in the
Kyoto Encyclopedia of Genes and Genomes (KEGG)
(http://www.genome.jp/kegg) database and are listed in
Table 2. Many kinds of genes involved in signal transduc-
tion, metabolism, receptors, transporters, and cytokines were
included. Moreover, this result suggested that many kinds
of pathways involved in the insulin signaling pathway and
immunological function may be influenced by Chlorella in-
take.
In the D Group, significant differences resulting from
Chlorella intake were observed for fasting blood glucose,
body fat percentage, and total serum cholesterol. In order to
identify the genes associated with these physiological ef-
fects, we extracted genes that demonstrated differences in
expression level between the D Group and the N Group be-
fore the start of the Chlorella intake tests and that also var-
ied as a result of Chlorella intake. Table 3 lists the 18 genes
thus identified. When we referred to the KEGG database to
determine which pathways the identified genes were asso-
ciated with, we found two genes (protein tyrosine phos-
phatase 1B and growth factor receptor-bound protein 2) that
are associated with the insulin signaling pathway. We then
investigated the changes in expressions for the genes among
the loaded genes that were associated with the insulin sig-
naling pathway. The results of this investigation are shown
398 MIZOGUCHI ET AL.
NUTRIGENOMICS OF EFFECTS OF CHLORELLA 399
T
ABLE
2. G
ENES
W
HOSE
E
XPRESSION
L
EVELS
V
ARIED WITH
C
HLORELLA
I
NTAKE AND
R
ETURNED TO
P
RE
-I
NTAKE
E
XPRESSION
V
ALUES
Target
accession Gene
number symbol Gene name Pathway name
NM_000208.1 INSR Insulin receptor Adherens junction, insulin signaling pathway, type 2 diabetes
mellitus, dentatorubropallidoluysian atrophy
Z69881.1 ATP2A3 ATPase, Ca
2
transporting, Calcium signaling pathway
ubiquitous
J03132.1 ICAM1 Intercellular adhesion molecule Cell adhesion molecules
1 (CD54), human rhinovirus
receptor
Y00062.1 PTPRC Protein tyrosine phosphatase, Cell adhesion molecules, T cell receptor signaling pathway
receptor type, C
NM_002592.1 PCNA Proliferating cell nuclear Cell cycle
antigen
M24898.1 NR1D1 Nuclear receptor subfamily 1, Circadian rhythm
group D, member 1
D89479.1 SULT1B1 Sulfotransferase family, Cysteine metabolism
cytosolic, 1B, member 1
D49950.1 IL18 Interleukin 18 (interferon- Cytokine–cytokine receptor interaction
gamma-inducing factor)
U37518.1 TNFSF10 Tumor necrosis factor (ligand) Cytokine–cytokine receptor interaction, apoptosis
superfamily, member 10
U01134.1 FLT1 Fms-related tyrosine kinase 1 Cytokine–cytokine receptor interaction, focal adhesion
(vascular endothelial growth
factor/vascular permeability
factor receptor)
M32977.1 VEGF Vascular endothelial growth Cytokine–cytokine receptor interaction, focal adhesion
factor
M65290.1 IL2B Interleukin 12B (natural killer Cytokine–cytokine receptor interaction, Toll-like receptor signaling
cell stimulatory factor 2, pathway, Jak-STAT signaling pathway
cytotoxic lymphocyte
maturation factor 2, p40)
D29013.1 POLB Polymerase (DNA directed), DNA polymerase
beta
U96132.1 HADH2 Hydroxyacyl-coenzyme A Fatty acid elongation in mitochondria, fatty acid metabolism,
dehydrogenase, type II valine, leucine, and isoleucine degradation, lysine degradation,
tryptophan metabolism, butanoate metabolism, caprolactam
degradation
NM_021187.1 CYP4F11 Cytochrome P450, family 4, Fatty acid metabolism, gamma-hexachlorocyclohexane
subfamily F, polypeptide 11 degradation, tryptophan metabolism
Y12863.1 FIGF c-fos-induced growth factor Focal adhesion
(vascular endothelial growth
factor D)
NM_030773.2 TUBB1 Tubulin, beta 1 Gap junction
J03746.1 MGST1 Microsomal glutathione S- Glutathione metabolism
transferase 1
NM_030821.3 PLA2G12A Phospholipase A2, group XIIA Glycerophospholipid metabolism, prostaglandin and leukotriene
metabolism, MAPK signaling pathway
V00572.1 PGK1 Phosphoglycerate kinase 1 Glycolysis/gluconeogenesis, carbon fixation
U79143.1 PIK3CA Phosphoinositide-3-kinase, Inositol phosphate metabolsim, phosphatidylinositol signaling
catalytic, alpha polypeptide system, apoptosis, focal adhesion, Toll-like receptor signaling
pathway, Jak-STAT signaling pathway, T cell receptor signaling
athway, B cell receptor signaling pathway, regulation of actin
cytoskeleton, insulin signaling pathway, type 2 diabetes mellitus
U92436.1 PTEN Phosphatase and tensin Inositol phosphate metabolism, phosphatidylinositol signaling
homolog (mutated in multiple system, focal adhesion, tight junction
advanced cancers 1)
NM_005399.3 PRKAB2 Protein kinase, AMP-activated, Insulin signaling pathway, adipocytokine signaling pathway
beta 2 noncatalytic subunit
AB003791.1 CHST1 Carbohydrate (keratan sulfate Keratan sulfate biosynthesis
Gal-6) sulfotransferase 1
(continued)
400 MIZOGUCHI ET AL.
U65928.1 COPS5 COP9 constitutive Lysine degradation, biotin metabolism
photomorphogenic homolog
subunit 5 (Arabidopsis)
U28014.1 CASP4 Caspase 4, apoptosis-related MAPK signaling pathway
cysteine protease
X03541.1 NTRK1 Neurotrophic tyrosine kinase, MAPK signaling pathway, apoptosis
receptor, type 1
U24153.1 PAK2 p21 (CDKN1A)-activated MAPK signaling pathway, axon guidance, focal adhesion, T cell
kinase 2 receptor signaling pathway, regulation of actin cytoskeleton
X63717.1 FAS Fas (tumor necrosis factor receptor MAPK signaling pathway, cytokine–cytokine receptor interaction,
superfamily, member 6) apoptosis
L13858.1 SOS2 son of sevenless homolog 2 MAPK signaling pathway, dorsoventral axis formation, focal
(Drosophila) adhesion, gap junction, Jak-STAT signaling pathway, T cell
receptor signaling pathway, regulation of actin cytoskeleton,
insulin signaling pathway
M22995.1 RAP1A RAP1A, member of the RAS MAPK signaling pathway, focal adhesion
oncogene family
X79483.1 MAPK12 MAPK 12 MAPK signaling pathway, Toll-like receptor signaling pathway
AF004709.1 MAPK13 MAPK 13 MAPK signaling pathway, Toll-like receptor signaling pathway
NM_000686.3 AGTR2 Angiotensin II receptor, type 2 Neuroactive ligand–receptor interaction
M18737.1 GZMA Granzyme A (granzyme 1, Neuroactive ligand–receptor interaction
cytotoxic T-lymphocyte-
associated serine esterase 3)
BC007720.1 HTR1D 5-Hydroxytryptamine Neuroactive ligand–receptor interaction
(serotonin) receptor 1D
AF000546.1 P2RY5 Purinergic receptor P2Y, G- Neuroactive ligand–receptor interaction
protein coupled, 5
U13699.1 CASP1 Caspase 1, apoptosis-related Neurodegenerative disorders, MAPK signaling pathway,
cysteine protease (interleukin Huntington’s disease, dentatorubropallidoluysian atrophy
1, beta, convertase)
NM_006312.1 NCOR2 Nuclear receptor co-repressor 2 Notch signaling pathway
NM_004718.2 COX7A2L Cytochrome coxidase subunit Oxidative phosphorylation
VIIa polypeptide 2-like
NM_004374.2 COX6C Cytochrome coxidase subunit Oxidative phosphorylation
VIc
NM_001865.2 COX7A2 Cytochrome coxidase subunit Oxidative phosphorylation
VIIa polypeptide 2 (liver)
L35249.1 ATP6V1B2 ATPase, H
transporting, Oxidative phosphorylation, ATP synthesis
lysosomal 56/58 kDa, V1
subunit B, isoform 2
Y15286.1 ATP6V0E ATPase, H
transporting, Oxidative phosphorylation, ATP synthesis, cholera
lysosomal 9 kDa, V0 subunit e
M62762.1 ATP6V0C ATPase, H
transporting, Oxidative phosphorylation, ATP synthesis, cholera
lysosomal 16 kDa, V0 subunit c
J05682.1 ATP6V1C1 ATPase, H
transporting, Oxidative phosphorylation, ATP synthesis, cholera
lysosomal 42 kDa, V1 subunit
C, isoform 1
NM_024330.1 SLC27A3 Solute carrier family 27 (fatty Propanoate metabolism, ethylbenzene degradation, limonene and
acid transporter), member 3 pinene degradation, caprolactam degradation, alkaloid biosynthesis
II
NM_003739.4 AKR1C3 Aldo-keto reductase family 1, Prostaglandin and leukotriene metabolism
member C3 (3-alpha
hydroxysteroid dehydrogenase,
type II)
NM_000895.1 LTA4H Leukotriene A4 hydrolase Prostaglandin and leuikotriene metabolism
NM_001116.1 ADCY9 Adenylate cyclase 9 Purine metabolism, calcium signaling pathway, gap junction
cholera
AF025840.1 POLE2 Polymerase (DNA directed), Purine metabolism, pyrimidine metabolism, DNA polymerase
epsilon 2 (p59 subunit)
T
ABLE
2. G
ENES
W
HOSE
E
XPRESSION
L
EVELS
V
ARIED WITH
C
HLORELLA
I
NTAKE AND
R
ETURNED TO
P
RE
-I
NTAKE
E
XPRESSION
V
ALUES
(C
ONT
’
D
)
Target
accession Gene
number symbol Gene name Pathway name
in Figure 2, which shows that after Chlorella intake, there
is an increase in expression levels for genes related to the
signal transduction routes linked to translocation of glucose
transporter (GLUT4) below the insulin receptors (produc-
ing insulin receptor substrate, phosphoinositide-3-kinase,
3-phosphoinositide-dependent kinase-1, and v-akt murine
thymoma viral oncogene homolog 3). Protein tyrosine phos-
phate-1B (PTP1B) acts to suppress signal transduction, but
the expression level for PTP1B showed a tendency to de-
crease as a result of Chlorella intake. Based on the changes
in gene expression levels, we can therefore surmise that in-
sulin signaling pathways are activated by the intake of
Chlorella. Recently, Cheng et al.
7
reported that in in vitro
screening systems using monocytes from human peripheral
blood, Chlorella inhibited the activation of PTP1B.
DISCUSSION
Cherng and Shih
8
reported changes in blood glucose con-
centrations resulting from administration of Chlorella in
streptozotocin-induced diabetic mice. In that study, they re-
ported that administration of Chlorella (100 mg/kg) steadily
reduced both glucose concentrations in the blood and in-
creased glucose values during glucose tolerance tests, but
that no increases in insulin concentrations in the blood could
be seen. Their results correspond closely with the results of
the current research on humans. It has also been reported
that in streptozotocin-diabetic mice, Chlorella intake in-
creases glucose uptake in the liver and skeletal muscles.
9
Dimitriadis et al.
10
reported that in monocyte in vitro sys-
tems separated from peripheral blood, insulin exposure
brought about an increase in the uptake of glucose and a
translocation of GLUT4 to the membrane surface. Estrada
et al.
11
reported that exposing peripheral blood monocytes
from healthy subjects and insulin-dependent diabetic pa-
tients to insulin-like growth factor-I immediately causes up-
take of glucose and that although the relationship of insulin-
like growth factor-I concentration and glucose uptake
volumes was similar in both healthy subjects and diabetes
patients, the cells obtained from diabetic patients demon-
strated lower uptake volumes overall. These recent investi-
gations also show that peripheral blood cells are an effec-
NUTRIGENOMICS OF EFFECTS OF CHLORELLA 401
T
ABLE
2. G
ENES
W
HOSE
E
XPRESSION
L
EVELS
V
ARIED WITH
C
HLORELLA
I
NTAKE AND
R
ETURNED TO
P
RE
-I
NTAKE
E
XPRESSION
V
ALUES
(C
ONT
’
D
)
Target
accession Gene
number symbol Gene name Pathway name
Z47727.1 POLR2K Polymerase (RNA) II (DNA Purine metabolism, pyrimidine metabolism, RNA polymerase
directed) polypeptide K, 7.0
kDa
X63563.1 POLR2B Polymerase (RNA) II (DNA Purine metabolism, pyrimidine metabolism, RNA polymerase
directed) polypeptide K, 140
kDa
J04965.1 POLR2E Polymerase (RNA) II (DNA Purine metabolism, pyrimidine metabolism, RNA polymerase
directed) polypeptide K, 25
kDa
U09178.1 DPYD Dihydropyrimidine Pyrimidine metabolism, beta-alanine metabolism, pantothenate and
dehydrogenase coenzyme A biosynthesis
NM_000436.2 OXCT1 3-Oxoacid coenzyme A transferase 1 Synthesis and degradation of ketone bodies, valine, leucine, and
isoleucine degradation, butanoate metabolism
U88878.1 TLR2 Toll-like receptor 2 Toll-like receptor signaling pathway
U88540.1 TLR1 Toll-like receptor 1 Toll-like receptor signaling pathway
NM_001752.2 CAT Catalase Tryptophan metabolism, methane metabolism, amyotrophic lateral
sclerosis
L34587.1 TCEB1 Transcription elongation factor Ubiquitin-mediated roteolysis
B (SIII), polypeptide 1 (15
kDa, elongin C)
NM_005438.2 FOSL1 FOS-like antigen 1 Wnt signaling pathway
NM_030775.2 WNT5B wingless-type mouse Wnt signaling pathway, hedgehog signaling pathway
mammary tumor virus
integration site family, member
5B
L37042.1 CSNK1A1 Casein kinase 1, apha 1 Wnt signaling pathway, hedgehog signaling pathway, gap junction,
circadian rhythm
NM_004422.1 DVL2 dishevelled, dsh homolog 2 Wnt signaling pathway, Notch signaling pathway
(Drosophila)
M74088.1 APC Adenomatosis polyposis coli Wnt signaling pathway, regulation of actin cytoskeleton
A total of 129 genes were extracted (see text) in this study. Among 129 genes, 66 genes that involved in canonical pathways summarized in
KEGG are listed. Jak-STAT, Janus kinase–signal transducers and activators of transduction; MAPK, mitogen-activated protein kinase.
402 MIZOGUCHI ET AL.
tive target for studies of improved glucose uptake and in-
sulin sensitivity. The current research has shown that one of
the mechanisms of reduced blood glucose levels achieved
by Chlorella intake is an activation of insulin signaling path-
ways resulting from changes in gene expression in the pe-
ripheral blood cells. This research also suggests, however,
that changes in gene expression profile in the peripheral
blood can be useful as a surrogate marker when investigat-
ing glucose metabolism. This marker is particularly effec-
tive in research targeting human beings.
The current research also showed that Chlorella intake in
humans is useful in improving fat metabolism. Particularly
in the case of the D Group, significant decreases in total
blood serum cholesterol, HDL-cholesterol, and LDL-cho-
lesterol were observed at all measurement points after the
start of Chlorella intake.
Merchant and Andre
12
used a double blind test to study
the effects of Chlorella intake on symptom improvements
in a total of 55 patients suffering from fibromyalgia syn-
drome, hypertension, and ulcerative colitis. They confirmed
that Chlorella intake lowers cholesterol in the blood, which
is consistent with the outcome of the current research
Shibata et al.
13
reported that in rats raised on feed con-
taining cholesterol, the administration of Chlorella de-
creases cholesterol concentrations in the blood and liver, but
that there were no changes in neutral fat or phospholipid
volumes and that excretion of neutral steroids was increased.
They surmised that the cholesterol-lowering effects of
Chlorella are brought about by increasing neutral steroid
elimination in feces. Sano et al.
14
also reported that in rats
with hyperlipemia created through excess administration of
cholesterol, the administration of Chlorella increased steroid
elimination in the feces. Connor et al.
15
reported that ad-
ministering high-molecular-weight unsaturated fatty acids to
humans increases the neutral steroid content of feces and
also reduces blood cholesterol concentrations. Based on the
fact that about 74% of the fatty acids contained in Chlorella
are unsaturated fatty acids, we can infer that the presence of
a physiological mechanism in which Chlorella intake causes
the reductions in blood cholesterol as follows: Chlorella in-
take may increase neutral steroid elimination in the feces,
causing a concomitant demand for cholesterol in the liver,
which in turn reduces cholesterol concentrations in the
blood.
T
ABLE
3. L
IST OF
G
ENES
T
HAT
S
HOWED
S
IGNIFICANT
D
IFFERENCES IN
E
XPRESSION
L
EVEL
B
ETWEEN THE
D G
ROUP AND THE
N G
ROUP
B
EFORE
THE
S
TART OF THE
C
HLORELLA
I
NTAKE
T
ESTS AND
T
HAT
A
LSO
V
ARIED AS A
R
ESULT OF
C
HLORELLA
I
NTAKE
Target
accession Gene
number symbol Gene name Category
NM_001116.1 ADCY9 Adenylate cyclase 9 Signal
NM_033375.3 MYO1C Myosin IC —
NM_000805.2 GAST Gastrin Receptor
NM_021187.1 CYP4F11 Cytochrome P450, family 4, subfamily F, P450
polypeptide 11
NM_022444.3 SLC13A1 Solute carrier family 13 (sodium/sulfate Transporter
symporters), member 1
NM_004718.2 COX7A2L Cytochrome coxidase subunit VIIa polypeptide Metabolism
2-like
U32519.1 — Ras-GTPase-activating protein SH3-domain- Signal
binding protein
NM_014585.3 SLC40A1 Solute carrier family 40 (iron-regulated Transporter
transporter), member 1
M96995.1 GRB2 Growth factor receptor-bound protein 2 Signal
NM_001114.1 ADCY7 Adenylate cyclase 7 Signal
U48251.1 PRKCBP1 Protein kinase C binding protein 1 Signal
U21858.1 TAF9 TAF9 RNA polymerase II, TATA box binding Repair
protein-associated factor, 32 kDa
U50062.1 RIPK1 Receptor (tumor necrosis factor receptor Apoptosis
superfamily)-interacting serine-threonine
kinase 1
M92287.1 CCND3 Cyclin D3 Cell cycle
NM_014235.2 UBL4 Ubiquitin-like 4 —
AF038950.1 ABCB7 ATP-binding cassette, subfamily B (MDR/TAP), Transporter
member 7
NM_002827.2 PTPN1 Protein tyrosine phosphatase, non-receptor Signal
type 1
L25610.1 CDKN1A Cyclin-dependent kinase inhibitor 1A Cell cycle
(p21, Cip1)
In recent years, the so-called Randle hypothesis
16
was
proposed to describe the inhibition of glucose uptake by
abnormalities in fat metabolism, stating that increases
in fatty acids limit the oxidation and uptake of glucose.
This hypothesis has been explained through extensive
experimental results. Another approach has also been
proposed in skeletal muscle cells whereby the uptake of
free fatty acids is stimulated, deactivating the insulin
signal transduction systems that transduce signals from
insulin receptors to GLUT4.
17
In the current research as
well, we can assume that Chlorella intake first improves
fat metabolism, resulting in improved glucose uptake. Al-
though cholesterol levels in the blood decrease, triglyc-
eride concentrations do not necessarily drop, so the
relationship between the improvement of fat metabolism
and the decrease in blood glucose level is unclear at pre-
sent. It will be necessary to conduct further studies,
including in vitro experiments, to elucidate the mecha-
nisms involved.
CONCLUSIONS
In order to clarify the physiological effects of Chlorella
intake on subjects with high-risk factors for lifestyle-related
diseases, we conducted blood biochemical tests on a high-
risk factor group and a healthy subject group and analyzed
gene expression profiles in peripheral blood cells before and
after Chlorella intake. The results of these tests showed that
Chlorella intake brings about improvements in both fat me-
tabolism and glucose metabolism. The expression of genes
involved in the insulin signaling pathway was also affected
by Chlorella intake, especially those related to glucose up-
take in tissue, providing support for the observation that
Chlorella lower blood glucose levels. These results indicate
that changes in gene expression in the peripheral blood can
be useful as a surrogate marker for investigating the mech-
anisms of modulation of glucose sensitivity in humans. In
the clarification of how functional and health foods can con-
tribute to human health, the combination of the nutrige-
NUTRIGENOMICS OF EFFECTS OF CHLORELLA 403
FIG. 2. Schematic diagram of the insulin signaling pathway based on the KEGG database (see text). The changes of expression level of genes
associated with this pathway resulting from Chlorella intake at 4 weeks, 12 weeks, and 16 weeks compared to 0 week value are mapped in the
heat map format; red and green mean up-regulation and down-regulation, respectively. At each gene six boxes are drawn; the three boxes on the
left display change of expression level measured at 4 weeks, 12 weeks, and 16 weeks (from left to right) in the N Group, and the other three
boxes on the right display the data in the D Group. INS, insulin; INSR, insulin receptor; IRS, insulin receptor substrate 1; PI3K, phosphoinosi-
tide-3-kinase; PTB1B, protein tyrosine phosphatase 1B; Akt, v-akt murine thymoma viral oncogene homolog 3; GYS, glycogen synthase 1; FBP,
fructose-1,6-bisphosphatase 1; SHC, Src homology 2 domain containing transforming protein 2; GRB2, growth factor receptor-bound protein 2;
SOS, son of sevenless homolog 1; Ras, v-Ha-ras Harvey rat sarcoma viral oncogene homolog; Raf, v-raf murine sarcoma 3611 viral oncogene
homolog; Elk1, member of ETS oncogene family. Refer to the following URL for further explanations of other abbreviations:
http://www.genome.ad.jp/dbget-bin/www_bget?pathwayhsa04910.
nomics research methods with conventional blood bio-
chemical tests such as those used in this study is being used
more widely.
AUTHOR DISCLOSURE STATEMENT
No competing financial interests exist.
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