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-Glucosidase Inhibitory Activity Is Safe and Effective in Humans with Borderline and Mild Type-2 Diabetes
Research and Development Department, Nippon Supplement, Incorporated., Kita-Ku, Osaka, 531-0076, Japan and * Ohshima Clinic, Ibaraki, Osaka, 567-0829, Japan
1To whom correspondence should be addressed. E-mail: ngfh03{at}mail.nichigo.co.jp
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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-glucosidase in
foodstuffs, and Touchi-extract (TE) has been shown to have an
antihyperglycemic effect in rats and humans after a single oral
administration. In the present complementary study, the effects of
powdered Houji-tea with or without (placebo) TE, a formula designed
to enhance good compliance, were monitored in a 3-mo double-blind
randomized group comparison study with placebo controls in humans with
borderline and mild type-2 diabetes (n = 36). All
subjects ingested Houji-tea with or without 0.3 g of TE before
each of three meals per day for 3 mo. In the TE group, initial fasting
blood glucose (6.9 ± 0.1 mmol/L) and glycated hemoglobin
(HbA1c; 6.1 ± 0.1%) levels gradually decreased;
fasting blood glucose decreased significantly after 3 mo (6.4 ± 0.3 mmol/L; P < 0.05) as did HbA1c
(5.6 ± 0.2%; P < 0.01) levels at 2 mo
postingestion of TE and thereafter. In contrast, fasting blood glucose
and HbA1c levels did not change in the placebo group. In
this study, other biochemical variables were not affected in any of the
subjects, and no one complained of any side effects or abdominal
distension. Moreover, there was no deterioration as assessed by fasting
blood glucose and HbA1c levels after withdrawal of TE
ingestion. Thus, the -glucosidase inhibitory TE demonstrated an
antihyperglycemic effect and may prove useful for improving glycemic
control in subjects suffering from borderline and type-2 diabetes mellitus.
KEY WORDS: • Touchi-extract • -glucosidase inhibitor • antiglycemic effect • type-2 noninsulin-dependent diabetes mellitus • humans
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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-glucosidase inhibitory activity have been
useful as oral hypoglycemic agents (1
2
3
4)
. These drugs
inhibit disaccharide hydrolases that convert disaccharides to
monosaccharides, and impede digestion and absorption of glucose to
eventually attenuate increases in postprandial plasma glucose levels.
However, in recent years, the importance of biologically active
substances contained in foods has been recognized, and many physiologic
effects of foods have been reported (5
,6)
. Inhibitors of
-glucosidase or -amylase derived from various sources have also
been isolated (7
8
9
10)
, and their effects have been
investigated in animals and humans (11)
. As such, when
foodstuffs were screened for the presence of -glucosidase
inhibitors, we found that fermented soybean-derived Touchi-extract
(TE) strongly inhibited rat intestinal -glucosidase
(12)
. Touchi, a traditional Chinese food in the form of a
paste, is used mainly for seasoning. Touchi is obtained by first
steaming and then fermenting soybeans with koji (Aspergillus
sp.). TE dose-dependently depresses postprandial rise in blood glucose
levels after oral sucrose loading in rats and humans; the minimum
effective dose is 
0.3 g (12)
. In addition, when four
fully developed diabetics were given 0.3 g of TE before eating
200 g of cooked rice, the postprandial rise in blood glucose was
significantly depressed. In Japan, the Foods for Specified Health Uses,
or the "FOSHU" standard was established in 1992, designating foods
to which a "functional" ingredient has been added for a specific
health effect. This system, approved by the Minister of Health, Labor
and Welfare, encompasses foods that were designed to maintain and
promote good health and that are prepared in a familiar form of
"food," not in formulated form such as pills or capsules. In this
study, we prepared powdered Houji-tea with or without TE for a 3-mo
comparative study involving subjects with borderline and mild type-2
diabetes because Houji-tea is a beverage habitually taken with each
meal in Japan. The antiglycemic effects and safety of long-term
ingestion of TE in subjects with borderline and mild type-2 diabetes
were examined in this study.
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SUBJECTS AND METHODS |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Trypsin (TPCK-treated, bovine pancreas, 10,000 U/mg
protein), chymotrypsin (TLCK-treated, bovine pancreas, 50
U/mg protein), pepsin (porcine stomach mucosa, 3700
U/mg protein), pancreatic lipase (porcine pancreas, 20,000
U/mg protein), rat intestinal acetone powder,
N-benzoyl-L-Arg ethyl ester
(BAEE), N-benzoyl-L-Tyr ethyl ester (BTEE)
and hemoglobin were purchased from Sigma-Aldrich (St. Louis, MO).
Enzyme inhibitory assay.
Trypsin inhibitory activity was measured using BAEE as a substrate and
monitored as increasing absorbance at 253 nm (13)
.
Chymotrypsin inhibition was assayed with BTEE as a substrate and
monitored as increasing absorbance at 253 nm (14)
. The
pepsin inhibitory assay was performed with hemoglobin as a substrate
and measured as trichloroacetic acid–soluble peptides derived from
digestion at 280 nm (15)
. Pancreatic lipase inhibitory
activity was measured using olive oil as a substrate by
titrimetry (16)
. -Glucosidase inhibitory
activity was measured using sucrose as a substrate, and released
glucose was measured with a commercial kit (Wako Pure Chemical, Osaka,
Japan) according to the method described by Miwa et al.
(17)
. -Amylase inhibitory activity was measured with a
commercial kit (Wako Pure Chemical).
TE-supplemented powdered tea.
TE was prepared by a previously reported method (12)
.
Briefly, Touchi (100 g) obtained from commercial sources was milled and
suspended in 900 mL of water before boiling for 60 min. This was
followed by centrifuging at 2050 x g for 30 min at
room temperature and filtering of the supernatant (filter paper No. 5C;
Toyo Roshi, Kawasaki, Japan). The filtrate was electrodialyzed with
microacilizer-G3 (Asahikasei Industry, Tokyo, Japan), and the dialysate
was concentrated before drying under a stream of air. The powder thus
obtained was used as the TE in this study. The 50% inhibitory
concentration (IC50) value of TE in rat intestinal
-glucosidase inhibition using sucrose as a substrate was 0.34 g/L
(17)
. The supplemented powdered Houji tea contained
0.3 g of TE and the IC50 value was 1.03 g/L. The
placebo Houji tea contained steamed soybean powder instead of TE, and
this placebo tea was therefore devoid of any -glucosidase inhibitory
activity (IC50 >10 g/L). Both teas were packed in aluminum
pouches as single servings. All subjects received one package of either
tea, which was dissolved in 100 mL of hot water before drinking with
each meal.
Subjects.
A total of 38 subjects were enrolled for the study; two subjects left the study due to work-site transfer by their companies. Of the 36 subjects who completed the study, 18 (7 men, 11 women) received TE-supplemented tea, whereas the remaining 18 (8 men, 10 women) ingested the placebo Houji-tea. The two groups were comparable with respect to age (63.3 ± 2.4 y), fasting blood glucose level, glycated hemoglobin (HbA1c) level and body mass index (BMI) at the onset of the study.
Human study.
This was a comparative double-blind study conducted between March
and August 2000 at a hospital in Osaka, Japan. Thirty-six
borderline and mildly diabetic subjects (15 men, 21 women) were
enrolled in the study. All subjects gave informed consent for the study
after having being briefed on the nature, purpose and possible side
effects. The investigation was approved by the Institutional Review
Board in February 2000. Their fasting blood glucose concentrations were
5.5–7.4 mmol/L and their HbA1c levels were 5.0–8.0%.
Subjects excluded were those treated with insulin, those with serious
cardiac, renal or hepatic diseases, those with a history of
gastrectomy, enterectomy or other gastrointestinal surgery, those with
a history of hypothyroidism and those judged by the attending physician
to be unsuited for the study for other reasons. Medication with
sulfonylurea was permitted and the dosage remained unchanged throughout
the investigation period. Energy intake of subjects followed the
Standard Food-Body Weight (125.2 kJ/kg) with a Food-Calorie
Conversion Table (18)
, and was 61% of energy as
carbohydrate, 21% as fat and 18% as protein. Compliance and
subjective symptoms were monitored by questionnaire or by questioning
the patients directly. All subjects maintained normal physical
activities and kept a detailed diary of symptoms in addition to
documenting any unexpected deviations in dietary intake and bowel
habits throughout the investigation. After a 12-h fast, blood was
sampled for analysis of hematological and biochemical variables at 0
(before tea ingestion), 1, 2 and 3 mo after 1 mo (withdrawal) tea
ingestion at every meal. In general, the investigation was uneventful.
Blood analysis.
Blood glucose levels were measured by the glucose oxidase method using
a 1140 Glucose Auto and Stat (Kyoto Daiichi Kagaku GA, Kyoto, Japan).
Hematological variables (white blood cell, RBC and hemoglobin) were
measured using an SE-9000 Multi Hematological Analysis System (Sismex,
Kobe Japan); the biochemical parameters (fasting blood glucose,
HbA1c, total cholesterol, HDL cholesterol, triglyceride,
glutamic-oxaloacetic transaminase, glutamic-pyruvic
transaminase, 
-glutamyl transpeptidase and creatinine) were measured
using a 7150 Auto Analysis System (Hitachi, Tokyo, Japan) in a blood
analysis laboratory (BML, Osaka, Japan).
Statistical analysis.
Results are expressed as means ± SEM. The statistical significance of difference before and after ingestion of Houji-tea for each group was assessed using the Wilcoxon signed-rank test. Blood data and characteristics of two the groups were compared with the Mann-Whitney U test (StatView, Abacus Concepts, Berkeley, CA) as well. Differences with P < 0.05 were considered significant.
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RESULTS |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). There was no deterioration as assessed by fasting blood glucose and
HbA1c levels after withdrawal of TE ingestion.
However, in the placebo group, no significant changes in fasting blood
glucose or HbA1c levels were observed. Moreover,
compared with the placebo group, significantly lower fasting blood
glucose and HbA1c levels were observed at 3 mo
post-TE ingestion (Table 1)
. TE effectively attenuated the fasting
blood glucose levels (more than -0.3 mmol/L) in 11 subjects (61.1%)
and HbA1c levels (more than -0.5%) in 8
subjects (44.4%) at 3 mo postingestion. Triglyceride concentrations
tended to be decreased at 2 mo post-TE ingestion (P =
0.08; Table 1
).
|
shows inhibitory activities of TE and Houji tea with or without TE on
gastric proteases and lipase. TE and Houji-tea with TE inhibited
only -glucosidase. Houji-tea itself did not inhibit any of the
activities.
|
.
Other hematological and biochemical data, such as hematocrit, platelet,
total protein, amylase and urea) were also not changed (data not
shown). Furthermore, no deterioration as assessed by the fasting blood
glucose and HbA1c levels occurred after
withdrawal of TE ingestion (Table 1)
. Body weight and BMI were not
affected by TE (Table 1)
. |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. Thus,
suppression of hyperglycemia, especially postprandial increases in
blood glucose, is essential in preventing various microvascular
complications. It has been demonstrated that -glucosidase inhibits
intestinal disaccharidase activity, resulting in delayed absorption of
postprandial blood glucose (20
,21)
and ultimately, an
appropriate time-related distribution of blood glucose
level. Recent reports have supported the effectiveness of an
-glucosidase inhibitor in reducing fasting blood glucose and
HbA1c levels (22
,23)
. However, the
early insulin response after oral glucose loading is decreased in
type-2 diabetic patients (24)
, and disorders of glucose
metabolism can decrease glucose-induced acute insulin secretion in
type-2 diabetic animals (25)
. Thus, -glucosidase
inhibitory substances such as TE may facilitate insulin metabolism
through inhibition of the postprandial rise in blood glucose, although
direct induction of insulin secretion is not the causative factor. Because Houji-tea is a common beverage habitually taken with each meal in Japan, powdered Houji-tea with and without TE was used in this study. During the ingestion period, all subjects maintained regular ingestion of the tea without restriction. Because of excellent compliance by the subjects, the antiglycemic effects of TE-supplemented Houji-tea were evident in the present study.
The major side effects of -glucosidase inhibitory drugs involve the
gastrointestinal system (22)
. In this study, no one
complained of any unwanted gastrointestinal system–related effects,
such as abdominal distension, abdominal pain, retching or flatulence.
This may be due to the lower inhibitory potency of TE on
-glucosidase compared with currently employed therapeutic agents
with similar mechanisms of action, and this may account for the
moderate effects of TE in the small intestine. Because abnormalities in
hematological and relevant biochemical data were not observed, the
safety of long-term TE use is thus reconfirmed. The safety of TE
ingestion is further supported by the fact that Touchi is a traditional
Chinese food derived from fermented soybeans and has long been enjoyed
in the Orient. Soybeans inhibit gastrointestinal proteases, such as
trypsin. Although these inhibitors can induce diarrhea and/or abdominal
pain, TE did not. This finding suggests that TE does not inhibit
gastrointestinal proteases, amylase and lipase (Table 2)
, and is
therefore a safe and useful compound for ingestion.
In this study, 0.9 g TE/d significantly elicited antiglycemic effects after 3 mo of ingestion, i.e., blood glucose levels gradually decreased on TE ingestion to a final fasting blood glucose more than -0.3 mmol/L in 11 subjects (61.1%). In addition, HbA1c levels also gradually decreased with final readings exceeding -0.5% in 8 subjects (44.4%). However, no one became hypoglycemic due to TE ingestion. Thus, TE elicited moderate yet positive effects in diabetic subjects over the ingestion period and may represent a useful means to control blood glucose levels in diabetics.
In a previous study of healthy humans, the main changes in lipid
profile after oral treatment with the -glucosidase inhibitory agent,
acarbose, were reductions in the serum triglyceride and VLDL levels
(26
27
28
29)
. With foodstuffs such as Konjak-Mannnan
(30)
and indigestible dextrin (31)
, reduced
total cholesterol or triglyceride levels have been reported as well.
Moreover, TE tended to exert these effects in this study. These
positive and favorable effects were thought to be due to improvement in
sugar metabolism.
The fact that with TE ingestion, subjects did not show any weight gain
or increases in BMI during the study is consistent with the view that
-glucosidase inhibitory drugs may have potential benefit for the
treatment of obesity. In an animal study, these drugs significantly
reduced body weight and plasma glucose levels in genetically obese
diabetic mice (21)
. It was thought that TE mildly inhibits
-glucosidase in vivo; therefore, ingested carbohydrate or sugars
might have been completely hydrolyzed into monosaccharides in the
intestines.
TE may be a useful antidiabetic food. The mechanism(s) of TE action
involves, at least in part, -glucosidase inhibition. Further
investigations are warranted. In conclusion, TE-supplemented
Houji-tea as a FOSHU product may provide extensive and useful effects
when employed in subjects with borderline and mild diabetes.
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FOOTNOTES |
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-benzoyl-L-Arg ethyl ester; BMI, body mass index; BTEE, N-benzoyl-L-Tyr ethyl ester; HbA1c, glycated hemoglobin; IC50, 50% inhibitory concentration; NIDDM, noninsulin-dependent diabetic mellitus; TE, Touchi extract. 
Manuscript received November 13, 2000. Revision accepted May 22, 2001.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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1.
Toeller M. -Glucosidase inhibitors in diabetes: efficacy in NIDDM subjects. Eur. J. Clin. Investig. 1994;24(suppl. 3):31-35
2. Clissold S. P., Edwards C. Acarbose, a preliminary review of its pharmacodynamic and pharmacokinetics properties, and therapeutic potential. Drugs 1988;35:214-243[Medline]
3.
Saito N., Sakai H., Sekihara H., Yajima Y. Effect of an -glucosidase inhibitor (voglibose), in combination with sulphonilureas, on glycaemic control in type 2 diabetes patients. J. Int. Med. Res. 1998;26:219-232[Medline]
4. Rury R. H., Robert C. T., Carole A. C. A randomized double-blind trial of acarbose in type 2 diabetes shows improved glycaemic control over 3 years (U.K. Prospective Diabetes Study 44). Diabetes Care 1999;22:960-964[Abstract]
5. Fujita H., Yoshikawa M. LKPNM: a prodrug type ACE-inhibitory derived from fish protein. Immunopharmacology 1999;44:123-127[Medline]
6. Fujita H., Yokoyama K., Yoshikawa M. Classification and antihypertensive activity of angiotensin I-converting enzyme derived from food proteins. J. Food Sci. 2000;65:564-569
7.
Maeda K., Kakabayashi S., Matsubara H. Complete amino acid sequence of an -amylase inhibitor in wheat kernel (0.19-inhibitor). Biochem. Biophys. Acta 1985;828:213-221[Medline]
8.
Matsui T., Yoshimoto C., Osajima K., Oki T., Osajima Y. In vitro survey of -glucosidase inhibitory food components. Biosci. Biotechnol. Biochem. 1996;60:2019-2022[Medline]
9.
Watanabe J., Kawabata J., Kurihara H., Niki R. Isolation and identification of -glucosidase inhibitors from Tochu-cha (Encommia ulmoides). Biosci. Biotechnol. Biochem. 1997;61:177-178[Medline]
10.
Hansawasdi H., Kawabata J., Kasai T. -amylase inhibitors from Rosell (Hibiscus sabdariffa Linn.) Tea. Biosci. Biotechnol. Biochem. 2000;64:1041-1043[Medline]
11. Morimoto T., Tanaka S., Miyazaki T., Kodama T., Kitamura I., Inoue S. Effects of long-term ingestion of wheat albumin in mild non-insulin-dependent diabetes mellitus (in Japanese). J. Jpn. Soc. Nutr. Food Sci. 1999;52:293-300
12.
Fujita H., Yamagami T., Ohshima K. Fermented soybean-derived Touchi extract with antiglycemic effect via -glucosidase inhibitory action in rats and humans. J. Nutr. 2001;131:1211-1213
13. Schwert G. W., Takenaka Y. A spectrophotometric determination of trypsin and chymotrypsin. Biochem. Biophys. Acta 1955;16:570-575[Medline]
14. Hummel B.C.W. A modified spectrophotometric determination of chymotrypsin, trypsin, and thrombin. Can. J. Biochem. Physiol. 1959;37:1393-1399
15.
Anson M. L. The estimation of pepsin, trypsin, papain, and cathepsin. J. Gen. Physiol. 1938;22:79-89
16. Marchis M. G., Sarda L., Desnuelle P. Purification of hog pancreatic lipase. Arch. Biochem. Biophys. 1959;83:309-319[Medline]
17.
Miwa I., Okuda J., Horie T., Nakayama M. Inhibition of intestinal -glucosidases and sugar absorption by flavones. Chem. Pharm. Bull. 1986;34:838-844
18. Japan Diabetes Society Food-Calorie Conversion Table 5th ed. (in Japanese) 1993 Bunkodo Tokyo, Japan
19. Unger R. H., Grundy S. Hyperglycaemia as an inducer as well a consequence of impaired islet cell function and insulin resistance: implications for the management of diabetes. Diabetologia 1985;28:12-121[Medline]
20. Okada H., Miki N., Ikeda H. Effect of disaccharidase inhibitor, AO-128, on postprandial hyperglycemia on rats (in Japanese). J. Jpn. Soc. Nutr. Food Sci. 1992;45:27-31
21. Matsuo T., Okada H., Ikeda H. Effect of an intestinal disaccharidase inhibitor (AO-128), on obesity and diabetes. Am. J. Clin. Nutr. 1992;55(suppl. 1):314-317
22. Kamiya F., Hayashi Y., Takeuchi T. Clinical utility of AO-128 long-term treatment in non-insulin dependent diabetes mellitus. J. Adult Dis. 1992;22:573-591
23. Matsuoka A., Takeuchi K., Makimura H. Efficacy and safety of AO-128 long-term treated in non-insulin dependent diabetes mellitus. Med. Consult. New Remed. 1992;29:255-265
24. Porte D. Banting lecture 1990. Beta-cells in type-II diabetes mellitus. Diabetes 1991;40:166-180[Abstract]
25. Tsuura Y., Ishida H., Okamoto Y., Kato S., Horie M., Ikeda H., Seino Y. Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats. Diabetologia 1994;37:1082-1087[Medline]
26.
Hillerbrand I., Boehm K., Frank G., Fink H., Berchtoid P. The effects of the -glucosidase inhibitor BAY g5421 (acarbose) on meal stimulated elevations of circulating glucose, insulin and triglyceride levels in man. Res. Exp. Med. 1979;175:81-86[Medline]
27.
Hillerbrand I., Boehm K., Frank G., Fink H., Berchtoid P. The effects of the -glucosidase inhibitor BAY g5421 (acarbose) on postprandial glucose, serum insulin and triglyceride levels: dose-time-response relationship in man. Res. Exp. Med. 1979;175:87-94[Medline]
28. Homma Y., Irie N., Yano Y., Nakaya N., Goto Y. Changes in plasma lipoprotein levels during medication with a glucosidase-hydrolase inhibitor (acarbose). Tokai J. Exp. Clin. Med. 1982;7:393-396[Medline]
29. Nestel P. J., Bazelmans J., Reardon M. F., Boston R. C. Lower triglyceride production during carbohydrate-rich diet through acarbose, a glucosidase hydrolase inhibitor. Diabetes Metab. 1985;11:316-317
30. Valdimir V., John L. S., Robin O., Renato N. Beneficial effects of viscous dietary fiber from Konjac-Mannan in subjects with the insulin resistance syndrome. Diabetes Care 2000;23:9-14[Abstract]
31. Tokunaga K., Matuoka A. Effect of indigestible dextrin, foods for specified health use, using functional component of on blood glucose and triglyceride levels (in Japanese). Tonyobyo 1999;42:61-65
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