i 2005WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim www.mnf-journal.de
DOI 10.1002/mnfr.200500027Mol. Nutr. Food Res. 2005, 49,772–778
Dietary supplement of isohumulones inhibits the
formation of aberrant cryptfociwith a concomitant
decrease in prostaglandin E2level in ratcolon
Hajime Nozawa1,2, Wakako Nakao2, Feng Zhao2and Keiji Kondo2
1Applied Bioresearch Center, Kirin Brewery Co., Ltd., 3 Mihahara-cho Takasaki-shi Gunma, Japan
2Central Laboratories for Key Technology, Kirin Brewery Co., Ltd., Fukuura, Kanazawa-ku, Yokohama,
Male Fischer 344 rats were subcutaneously injected with azoxymethane (AOM) twice weekly at a
dose of 15 mg/kg and were fed with freeze-dried (FD) samples of beer brewed without hops (non-
hops beer), beer with hops at 4 times the amount of regular lager beer (64-hops beer), and isomer-
ized hop extract (IHE) for the whole experimental period (I/PI) or for the post-initiation period (PI)
only. Feeding FD beer samples at a dose of 1% significantly decreased the number of aberrant cryp
foci (ACF) in the PI protocol over five weeks.64-hops beer showed stronger inhibitory effects on the
development of the numbers of aberrant crypts per focus and large ACF with four or more crypts than
non-hops beer. Feeding IHE to rats at a dose of 0.01% or 0.05% in either the I/PI or PI experiment
significantly reduced the numbers of ACF. Prostaglandin E2 (PGE2) levels in colonic mucosa of
AOM-treated rats were significantly reduced by feeding of IHE. PGE2 production induced by lipopo-
lysaccharide/interferon-c (LPS/IFN-c) in RAW264.7 cells was also reduced by treatment with IHE
and isohumulone in a dose-dependent manner. These observations suggest that isohumulones show
chemopreventive effects on ACF formation in rat colon by inhibiting the production of PGE2.
Keywords:Aberrantcrypt foci/ Chemoprevention/ Hops/ Isohumulones / Prostaglandin E2/
It has been demonstrated by epidemiological and experi-
mental studies that dietary habit may affect the incidence of
colon cancer, one of the most prevalent neoplastic diseases.
The western lifestyle with diets high in fat and low in vege-
table consumption are definitive determinants which may
increase the incidence of colon cancer. It has been reported
that many dietary factors may prevent the incidence of
colon cancer. Such dietary factors, including polyphenols
[1, 2], dietary fiber , polyunsaturated fatty acids [4, 5],
and lactic acidbacteria ,showchemopreventiveeffects.
Our previous study has demonstrated that beer intake inhi-
bits carcinogenesis in rat colon induced by azoxymethane
(AOM), and that the effects are due to ingredients of beer
derived from its raw materials, namely barley malts and
hops . With regard to the association between beer con-
sumption and colorectal cancer risk in an epidemiological
study, some revealed inverse relations , but the others
reported positive relations [9–11]. Beer is the only alco-
of the hop plant (Humulus lupulus L.), and they are used as
an essential raw material for beer brewing toenhance bitter-
ness, aroma, and antimicrobial activity. Many physiological
functions related to chemoprevention have been reported
for the chemical components of hops. For example, the
induction of phase II enzymes by prenylated chalcones [12,
13], inhibition of cyclooxygenase-2 (COX-2) by humulone
, inhibition of angiogenesis by humulone , induc-
tion of apoptosis by humulone [16, 17], anti-inflammatory
effects by prenylated chalcones [18, 19], and agonistic
effects on peroxisome proliferator-activated receptors
Correspondence: Dr. Hajime Nozawa, Applied Bioresearch Center,
Kirin Brewery Co., Ltd., 3 Miyahara-cho Takasaki-shi Gunma
Abbreviations: ACF, aberrant crypt foci; AIN, AIN-76A; AOM,
azoxymethane; COX-2, cyclooxygenase-2; EIA, enzyme immunoas-
say; FD, freeze-dried; IH, isohumulone; IHE, isomerized hops extract;
I/PI, initiation and post-initiation; LPS/IFN-c, lipopolysaccharide/in-
terferon-c; MTT, 3-[4,5-dimethylthyazol-2-yl]-2,5-diphenyltetrazo-
liumbromide; PGE2, prostaglandin E2; PPAR, peroxisome prolifera-
H.Nozawaetal. Mol. Nutr. Food Res. 2005, 49,772–778
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