Desalted deep-sea water improves cognitive function
in mice by increasing the production of insulin-like
growth factor-I in the hippocampus
NAOAKI HARADA, JUAN ZHAO, HIROKI KURIHARA, NAOMI NAKAGATA, and KENJI OKAJIMA
NAGOYA, TOKYO, AND KUMAMOTO, JAPAN
function by increasing the hippocampal production of insulin-like growth factor-I
(IGF-I) in mice. In the current study, we examined whether oral administration of de-
salted deep-sea water (DSW) increases the hippocampal production of IGF-I by
stimulating sensory neurons in the GI tract, thereby improving cognitive function in
mice. Desalted DSW increased calcitonin gene-related peptide (CGRP) release
from dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice by acti-
vating transient receptor potential vanilloid 1. The plasma levels of IGF-I and tissue
levels of CGRP, IGF-I, and IGF-I mRNA in the hippocampus were increased by oral
administration of desalted DSW in WT mice. In these animals, nociceptive information
originating from the GI tract was transmitted to the hippocampus via the spinothala-
istration of desalted DSW. Distilled DSW showed results similar to those of desalted
DSW in vitro and in vivo. None of the effects of desalted DSW in WT mice were ob-
served after the administration of desalted DSW in CGRP-knockout (CGRP-/-)
mice. No volatile compounds were detected in distilled DSW on GC-MS analysis.
These observations suggest that desalted DSW may increase the hippocampal
IGF-I production via sensory neuron stimulation in the Gl tract, thereby improving
cognitive function in mice. Such effects of desalted DSW might not be dependent
on the minerals but are dependent on the function of the water molecule itself.
(Translational Research 2011;158:106–117)
Abbreviations: BrdU ¼ 5-bromo-2’-deoxyuridine;cDNA ¼ complementary DNA;CGRP¼ calcito-
nin gene-related peptide; CPZ ¼ capsazepine; CT ¼ computed tomography; DG ¼ dentate gy-
rus; DRG ¼ dorsal root ganglion; DSW ¼ deep-sea water; GC-MS ¼ gas chromatography-mass
spectrometry; GFAP ¼ glial fibrillary acidic protein; GH ¼ growth hormone; GI ¼ gastrointestinal;
choleterolemic; LDL ¼ low-density lipoprotein; mRNA ¼ messenger RNA; NTS ¼ solitary tract
potential vanilloid 1; VEGF ¼ vascular endothelial growth factor; WT ¼ wild type
From the Department of Translational Medical Science Research,
Nagoya City University Graduate School of Medical Sciences,
Nagoya, Japan; Department of Physiological Chemistry and
Metabolism, University of Tokyo Graduate School of Medicine,
Tokyo, Japan; Division of Reproductive Engineering, Center for
Submitted for publication August 30, 2010; revision submitted
February 16, 2011; accepted for publication February 16, 2011.
Reprint requests: Kenji Okajima, MD, PhD, Department of Transla-
tional Medical Science Research, Nagoya City University Graduate
School of Medical Sciences, Kawasumi 1, Mizuho-cho, Mizuho-ku,
Nagoya 467-8601, Japan; e-mail: email@example.com.
1931-5244/$ - see front matter
? 2011 Mosby, Inc. All rights reserved.
Deep-sea water (DSW) is water drawn from deep in the
ocean, usually from more than 200 m below the surface.
Water at those depths is free of the contaminants and
pollutants that can taint surface water. Deep-sea water
and minerals such as Mg, Ca, and K.1
The accumulation of lipid and permeation of mac-
for 4 weeks have been shown to be inhibited by the ad-
(LDL) cholesterol levels and cholesterol accumulation
in the arterial wall in rabbits fed 1% cholesterol for 12
weeks were inhibited by administration of desalted
DSW.3Cardiovascular hemodynamics observedin Kur-
osawa and Kusanagi-Hypercholeterolemic (KHC) rab-
bits were improved by drinking of desalted DSW for 6
Although these beneficial effects of desalted DSW
may be related to minerals contained in this water, ther-
apeutic mechanism(s) underlying these beneficial ef-
fects of desalted DSW are not fully understood.4
Insulin-like growth factor-I (IGF-I) is a basic peptide
composed of 70 amino acids with a ubiquitous distribu-
tion in various tissues and cells, which mediates the
growth-promoting actions of growth hormone (GH)
and plays an important role in postnatal and adolescent
Cardiac abnormalities associated with GH deficiency
are corrected by GH therapy, and IGF-I protects against
endothelial dysfunction, atherosclerotic plaque devel-
opment, insulin resistance, and ischemic myocardial
damage.6,7Because IGF-I has vasorelaxant effects8
and blood pressure is increased in mice with severe
IGF-I deficiency,9an increase of IGF-I production
might contribute to the normalization of blood pressure.
Furthermore, IGF-I has been shown to decrease lipid
levels in type 2 diabetic patients.10These observations
suggest that IGF-I may play criticalroles inmaintaining
Because IGF-I has been shown to increase LDL re-
ceptor expression in HepG2 cells in vitro11and it has
tients,11it is possible that improvement of lipid metab-
olism induced by administration of desalted DSW in
rabbits fed 1% cholesterol might be at least in part ex-
plained by the actions of IGF-I. These observations sug-
gest the possibility that drinking desalted DSW might
increase IGF-I production, thereby improving cardio-
vascular abnormalities and hyperlipidema in KHC
Capsaicin-sensitive sensory neurons are nociceptive
neurons thatcanbefoundinmanytissueswithin thelin-
ing epithelia, around blood vessels, and associated with
nonvascular smooth muscle and myocardium of the
atria.12These sensory neurons release calcitonin gene-
related peptide (CGRP) after activation by a wide
variety of noxious physical and chemical stimuli of
the transient receptor potential vanilloid 1 (TRPV1) ex-
pressed on them,13thereby exerting sensory-efferent
functions. CGRP, which is a 37-amino acid neuropep-
tide, is produced by the alternative splicing of the calci-
tonin gene.14It is widely distributed in the central and
peripheral nervous systems15and has been considered
to possess diverse functions.16We reported that CGRP
increases IGF-I production rapidly via increasing its
transcription in various tissues in mice administered
CGRP are also present in the gastrointestinal (GI) tract,
and these neurons are predominantly spinal in origin.18
Furthermore, nociceptive information originating from
the GI tract is transmitted to the brain via the spino-
IGF-I has been shown to enhance excitatory synaptic
transmission in the CA1region of the hippocampus20
and to improve spatial learning by inducing neurogene-
sis in the hippocampus,21,22indicating that IGF-I im-
proves cognitive function by increasing the plasticity
and neurogenesis in the hippocampus. We reported
creased IGF-I production in the hippocampus via in-
creasing in itstranscription,
cognitive function in mice.23
Based on these observations, we hypothesized that
oral administration of desalted DSW might increase
AT A GLANCE COMMENTARY
Harada N, et al.
The stimulation of sensory neurons in the gastroin-
testinal (GI) tract improves the cognitive function
by increasing the hippocampal production of
insulin-like growth factor-I (IGF-I) in mice.
Oral administration of desalted deep-sea water
(DSW) increased tissue levels of IGF-I in the hip-
GI tract, thereby improving the cognitive function
in mice. These observations raised the possibilities
that drinking of desalted DSW might inhibit the
cognitive decline in the elderly and that it might
improve the cognitive function in patients with
the Alzheimer disease.
Volume 158, Number 2Harada et al
corresponding number in WT mice, suggesting that
CGRP and/or IGF-I might be related deeply to neural
stem cell proliferation in the mouse hippocampus.
On the one hand, administration of desalted DSW in-
creased the number of BrdU1 cells and that of both
BrdU1 and calbindin-D28k1 double-positive cells,
but not that of both BrdU1 and GFAP1 double-
positive cells in the DG of WT mice. On the other
hand, administration of desalted DSW had no effect
on the number of these cells in the DG of CGRP-/-
mice. Peripheral infusion of IGF-I was shown to induce
angiogenesis selectively via a vascular endothelial
growth factor (VEGF)-dependent mechanism in the
adult mouse brain41and by neurogenesis in the adult
rat hippocampus.21These observations suggest strongly
that the stimulation of sensory neurons by desalted
DSW may induce angiogenesis and neurogenesis by in-
ducing IGF-I production via an increase of the CGRP
level in the mouse hippocampus. Furthermore, because
angiogenesis has been shown to offer a favorable envi-
ronment for the neuronal stem cell proliferation via ac-
tivation of the VEGF-dependent mechanism,42the
hippocampal neurogenesis induced by desalted DSW
administration in WT mice may be mediated at least
in part by angiogenesis.
IGF-I exerts beneficial effects against the decline of
cognitive function by inducing neurogenesis in the hip-
pocampus,21,43suggesting that administration of de-
salted DSW may improve cognitive function by
increasing IGF-I production through promoting CGRP
release in the mouse hippocampus. Consistent with
this hypothesis, administration of desalted DSW signif-
icantly improved spatial learning function in WT mice
but not in CGRP-/- mice. These observations suggest
that stimulation of sensory neurons with desalted
DSW might increase the release of CGRP, inducing
IGF-I production in the mouse hippocampus and
thereby improving cognitive function.
Because administering distilled DSW produced ef-
fects similar to those induced by desalted DSW, the ma-
jor part of the effects induced by administration of
desalted DSW might not be dependent on the minerals
in the current study.
The precise mechanism(s) by which desalted and dis-
tilled DSW stimulate sensory neurons in vitro is not
known. Mass spectrometric analysis showed that there
were no volatile compounds in distilled DSWas in dis-
tilled water. Water molecules have been shown to play
critical roles in emerging various protein functions in-
cluding electron transport.44,45Thus, it is likely that
for sensory neuron stimulation in vitro. Cryptochromes
are receptors for environmental changes such as those
in blue light and magnetic field,46and they exert the
receptor function via the electron transfer mediated by
the flavin.47Preliminary experiments demonstrated
that distilled DSW did not increase CGRP release
cryptochrome-deficient mice. These observations sug-
gest that the water molecule of distilled DSW may pro-
mote the electron transfer of cryptochromes, thereby
stimulating sensory neurons. Currently, we are investi-
gating the precise mechanism by which distilled DSW
promotes the electron transfer of cryptochromes in sen-
Taken together, observations in the current study sug-
gest strongly that the oral administration of desalted
DSW might increase the tissue levels of CGRP and
IGF-I in the hippocampus via stimulation of sensory
neurons in the GI tract, thereby improving cognitive
function through enhancement of the angiogenesis and
neurogenesis in the mouse hippocampus. Because dis-
tilled DSW showed effects similar to those of desalted
DSW, such beneficial effects of desalted DSW might
not be dependent on the minerals. These observations
suggested the possibility that drinking desalted DSW
might inhibit cognitive decline in the elderly, and it
might also improve cognitive function in patients with
Alzheimer disease. This possibility should be investi-
gated in the clinical setting in the near future.
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