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`0022-3565/04/3102-614–619$20.00
`THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
`Copyright © 2004 by The American Society for Pharmacology and Experimental Therapeutics
`JPET 310:614–619, 2004
`
`Vol. 310, No. 2
`64964/1156276
`Printed in U.S.A.
`
`Metformin Causes Reduction of Food Intake and Body Weight
`Gain and Improvement of Glucose Intolerance in Combination
`with Dipeptidyl Peptidase IV Inhibitor in Zucker fa/fa Rats
`
`Nobuyuki Yasuda, Takashi Inoue, Tadashi Nagakura, Kazuto Yamazaki, Kazunobu Kira,
`Takao Saeki, and Isao Tanaka
`Tsukuba Research Laboratories, Eisai Co., Ltd., Tokodai, Tsukuba, Ibaraki, Japan
`Received February 2, 2004; accepted March 23, 2004
`
`ABSTRACT
`An incretin hormone, glucagon-like peptide-1 (GLP-1), has
`been shown to lower plasma glucose via glucose-dependent
`insulin secretion and to reduce appetite. We previously found
`that the biguanide metformin, an antidiabetic agent, causes a
`significant increase of plasma active GLP-1 level in the pres-
`ence of dipeptidyl peptidase IV (DPPIV) inhibitor in normal rats.
`This finding suggested that the combination treatment might
`produce a greater antidiabetic and anorectic effect, based on
`enhanced GLP-1 action. In this study, we assessed the effects
`of subchronic treatment with metformin and a DPPIV inhibitor,
`valine-pyrrolidide (val-pyr), on glycemic control, food intake,
`and weight gain using Zucker fa/fa rats, a model of obesity and
`impaired glucose tolerance. The combination treatment caused
`a significant increase of GLP-1 level in Zucker fa/fa rats. In a
`subchronic study, val-pyr, metformin, or both compounds were
`
`administered orally b.i.d. for 14 days. The combination treat-
`ment significantly decreased food intake and body weight gain,
`although neither metformin nor val-pyr treatment alone had any
`effect. In an oral glucose tolerance test on day 1, the coadmin-
`istration caused a greater improvement of glucose tolerance
`and a prominent increase of plasma active GLP-1 without
`marked insulin secretion. The 14-day combination treatment
`produced a potent reduction of fasting blood glucose and
`plasma insulin levels. These results demonstrate that the com-
`bination therapy of metformin with DPPIV inhibitor leads to
`reduced food intake and body weight gain, most likely through
`the significant increase of plasma GLP-1 level. The combination
`therapy seems to be a good candidate for treatment of type 2
`diabetes with obesity.
`
`Metformin (met) is widely used as an oral antidiabetic
`agent for the treatment of type 2 diabetes. It has multiple
`antidiabetic effects, such as inhibition of gluconeogenesis and
`delay of gastrointestinal absorption of glucose, and it reduces
`food intake or prevents body weight gain in obese patients
`with type 2 diabetes and in animal models of obesity (Bailey,
`1992; Rouru et al., 1992; Bailey and Turner, 1996; Lee and
`Morley, 1998). However, its mechanism of action is not fully
`understood at the molecular level. Recently, it was indicated
`that metformin increases plasma active glucagon-like pep-
`tide-1 (GLP-1) in obese nondiabetic subjects (Mannucci et al.,
`2001).
`GLP-1 is an incretin released from L cells in the intestine
`after oral ingestion of nutrients. This incretin has multiple
`actions, including stimulation of inhibition of glucagon secre-
`tion, increase of glycogen synthase activity, and slowing of
`
`Article, publication date, and citation information can be found at
`http://jpet.aspetjournals.org.
`DOI: 10.1124/jpet.103.064964.
`
`gastric emptying, in addition to promotion of satiety and
`inhibition of food intake (Drucker, 2001, 2002). Mannucci et
`al. (2001) proposed that the reduced food intake and body
`weight gain in subjects treated with metformin might be
`related to GLP-1 increase.
`GLP-1 is rapidly degraded by dipeptidyl peptidase IV (DP-
`PIV or CD26, EC 3.4.14.5), resulting in a circulating half-life
`of only 1 to 2 min. Thus, inhibition of DPPIV activity could be
`a useful strategy to enhance the activity of GLP-1. Many
`studies have confirmed the utility of DPPIV inhibitors not
`only in the treatment of diabetes with obesity in animal
`models (Pederson et al., 1998; Balkan et al., 1999; Pospisilik
`et al., 2002; Reimer et al., 2002; Sudre et al., 2002), but also
`in humans (Ahre´n et al., 2002). These data suggest that
`DPPIV inhibitors would be of value in the treatment of obe-
`sity and diabetes.
`Our previous study demonstrated that acute administra-
`tion of metformin with valine-pyrrolidide, a DPPIV inhibitor
`(Deacon et al., 1998; Ahre´n et al., 2000), synergistically in-
`
`ABBREVIATIONS: met, metformin; GLP-1, glucagon-like peptide-1; DPPIV, dipeptidyl peptidase IV; val-pyr, valine-pyrrolidide; OGTT, oral
`glucose tolerance test.
`
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`Combination of Metformin with DPPIV Inhibitor
`
`615
`
`Food intake was measured every day (5:00 PM), and body weight
`was monitored under fed conditions on days 4, 7, 11, and 14 (5:00
`PM). In addition, the rats were weighed in the fasted state on days
`0 and 15 (10:00 AM).
`Statistical Analysis. Data are expressed as the mean ⫾ S.E.M.
`The statistical significance of differences among the vehicle, val-pyr,
`metformin, and combination groups was determined by one-way
`analysis of variance, followed by the Dunnett type multiple compar-
`ison test. A value of p ⬍ 0.05 (two-sided) was considered statistically
`significant. Statistical analysis was conducted using the software
`package SAS 8.1 (SAS Institute Japan Ltd., Tokyo, Japan).
`
`Results
`Effects of Acute Metformin and/or val-pyr Treatment
`on Plasma Active GLP-1 Levels in Fed Zucker fa/fa
`Rats. Zucker fa/fa rats were given metformin, val-pyr, or a
`mixture of both in the basal fed state. There were no statis-
`tically significant differences in basal plasma active GLP-1
`levels among the four groups: vehicle, 5.5 ⫾ 0.1; val-pyr,
`5.3 ⫾ 0.2; metformin, 5.7 ⫾ 0.3; and combination, 5.4 ⫾ 0.2
`pM. Figure 1 shows that a significant increase of plasma
`active GLP-1 was observed only in the group given the com-
`bination treatment of metformin and val-pyr at 0, 1, 3, 5, and
`7 h after the acute administration. Either metformin or val-
`pyr alone caused a slight elevation of plasma active GLP-1,
`but it was not statistically significant.
`Baseline Body Weight, Food Intake, and Blood Glu-
`cose, Plasma Active GLP-1 and Plasma Insulin Levels
`in Zucker fa/fa Rats. Before the subchronic study, there
`were no significant differences of baseline body weight of the
`rats in the fed state or of food intake during 24 h among the
`
`Fig. 1. Changes of plasma active GLP-1 levels in Zucker fa/fa rats treated
`with met and/or val-pyr, a DPPIV inhibitor. Rats were orally given met
`(300 mg/kg), val-pyr (30 mg/kg), or a mixture of both in the fed state.
`Significant increases of GLP-1 occurred only in rats treated with both met
`and val-pyr. * indicates significant differences versus the vehicle-treated
`group. Data are shown as means ⫾ S.E.M., n ⫽ 7 per group. One and
`three symbols indicate p ⬍ 0.05 and p ⬍ 0.001, respectively.
`
`creases plasma active GLP-1 level in fasted normal rats,
`although neither metformin nor the DPPIV inhibitor alone
`affects the basal GLP-1 level (Yasuda et al., 2002). This
`result showed that DPPIV inhibition is necessary to maxi-
`mize the efficacy of the GLP-1 increase induced by met-
`formin. Consequently, we proposed that the combination
`treatment would be an effective new approach to elevate
`plasma active GLP-1 level.
`Thus, we hypothesized that the combination treatment of
`metformin with a DPPIV inhibitor would provide greater
`benefit for the treatment of type 2 diabetes with obesity than
`treatment with either metformin or DPPIV inhibitor alone.
`The purposes of this study are therefore to evaluate the
`increase of plasma active GLP-1 in response to the combined
`treatment with metformin and DPPIV inhibitor and to inves-
`tigate the effect of subchronic coadministration on glycemic
`control, food intake, and body weight gain in obese Zucker
`fa/fa rats, which display abnormalities characteristic of type
`2 diabetes, including mild hyperglycemia, hyperinsulinemia,
`glucose intolerance, and impaired insulin secretion.
`
`Materials and Methods
`Chemicals. Metformin (1,1-dimethylbiguanide) hydrochloride was
`purchased from Sigma-Aldrich (St. Louis, MO). Valine-pyrrolidide hy-
`drochloride was synthesized in our laboratories. Metformin and val-pyr
`were dissolved in distilled water before administration.
`Animals. Obese male Zucker fa/fa rats (5 weeks old) were pur-
`chased from Charles River Japan (Tokyo, Japan). Zucker fa/fa rats
`were individually housed under conventional conditions with con-
`trolled temperature, humidity, and lighting (22 ⫾ 2°C, 55 ⫾ 5%, and
`a 12-h light/dark cycle with lights on at 7:00 AM), and provided with
`a commercial diet (MF; Oriental Yeast, Tokyo, Japan) and water ad
`libitum. All procedures were conducted according to the Eisai Ani-
`mal Care Committee’s guidelines.
`Biochemistry Determination. Blood glucose was measured
`with Glu CII-test (Wako Pure Chemicals, Osaka, Japan). Plasma
`immunoreactive intact GLP-1 was measured with a glucagon-like
`peptide (active) enzyme-linked immunosorbent assay kit (Linco Re-
`search, St. Charles, MO). Plasma immunoreactive insulin was de-
`termined with an insulin enzyme-linked immunosorbent assay kit
`using rat insulin as a standard (Morinaga, Yokohama, Japan).
`Acute Administration Study. Fifteen-week-old Zucker fa/fa
`rats were used. In the nonfasted state, rats were randomly treated
`orally with metformin (300 mg/kg), val-pyr (30 mg/kg), a mixture of
`both (300 mg/kg metformin and 30 mg/kg val-pyr), or the vehicle
`(distilled water) via a gastric tube at 10:00 AM (n ⫽ 7/group). Blood
`(200 ␮l) was collected from the caudal vein into a heparinized cap-
`illary tube 0, 1, 3, 5, and 7 h after the administration and used for the
`measurement of plasma intact GLP-1 levels.
`Subchronic Administration Study. Zucker fa/fa rats were di-
`vided into the following groups: vehicle (distilled water), val-pyr
`alone (30 mg/kg), metformin alone (300 mg/kg), and both val-pyr (30
`mg/kg) and metformin (300 mg/kg); n ⫽ 10. These agents were
`administered by oral gavage twice daily (10:00 AM and 5:00 PM)
`from 13 weeks of age for 14 days.
`Oral glucose tolerance test (OGTT) was performed on days 1 and
`15 in the repeated administration study. The animals were deprived
`of food for 18 h and then the drugs were administered 0.5 h before
`glucose load (2 g/kg). Blood samples (250 ␮l) were collected 0.5 h
`before the glucose load, and 0, 0.5, 1, and 2 h after the glucose load
`from the caudal vein, using heparinized capillary tubes. They were
`centrifuged to obtain plasma, which was used for the measurement
`of insulin and active GLP-1 levels. Blood samples (10 ␮l) were also
`taken at –0.5, 0, 0.5, 1, 2, and 3 h from the caudal vein for blood
`glucose determination.
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`tration, the subchronic combination treatment showed a
`great reduction of fasting blood glucose and insulin levels
`versus metformin or DPPIV inhibitor treatment alone (Table
`1). No significant difference of basal plasma GLP-1 level was
`found among the four groups after the 14-day administra-
`tion.
`
`Discussion
`Our previous study showed that metformin causes a clear
`elevation of plasma active GLP-1 level in the presence of
`DPPIV inhibitor in normal fasted rats and increases plasma
`active GLP-1 in a dose-dependent manner in DPPIV-nega-
`tive rats (Yasuda et al., 2002). These results suggest that
`metformin increases plasma active GLP-1 in a DPPIV-inde-
`pendent manner possibly through direct GLP-1 secretion.
`In this study, we confirmed that the combination treat-
`ment of metformin with val-pyr led to a marked and lasting
`increase of plasma active GLP-1 level in fed Zucker fa/fa rats,
`an animal model of obesity and mild type 2 diabetes, al-
`though neither metformin nor val-pyr alone caused any sig-
`nificant change of the basal active GLP-1 level. Although the
`detailed mechanism of the enormous impact of the combina-
`tion on active GLP-1 is unclear, we hypothesize that GLP-1
`secretion by metformin plays a major role in the great in-
`crease of GLP-1 as mentioned in our previous report (Yasuda
`et al., 2002). However, possible other factor(s) may contribute
`to the lasting existence of GLP-1 in plasma; for example,
`metformin might inhibit renal GLP-1 excretion or increase
`transcription/translation of the proglucagon gene.
`Furthermore, the present study revealed that the combi-
`nation treatment, but not the metformin or val-pyr treat-
`ment, resulted in a significantly reduced body weight gain
`during 14-day subchronic administration, presumably due to
`the significant decrease of food intake, in Zucker fa/fa rats.
`This phenomenon could be explained by the remarkable in-
`crease of plasma active GLP-1 level in the animals receiving
`the combination treatment, because it is well known that
`GLP-1 enhances satiety and causes inhibition of food intake
`and body weight gain in animal models and type 2 diabetes
`patients (Tang-Christensen et al., 1996; Flint et al., 1998;
`Kalra et al., 1999; Zander et al., 2002).
`We speculate that the alteration of appetite in the combi-
`nation treatment group could have been caused through both
`peripheral and central actions. As a peripheral action, GLP-1
`delays gastric emptying, which would be expected to induce a
`sensation of fullness (Willms et al., 1996; Flint et al., 1998).
`Furthermore, a central effect of GLP-1 on satiety in the
`
`616
`
`Yasuda et al.
`
`four groups: body weight (vehicle, 528.3 ⫾ 5.5; val-pyr,
`528.6 ⫾ 2.2; metformin, 526.0 ⫾ 6.3; and combination,
`527.2 ⫾ 6.9 g) and food intake (vehicle, 31.1 ⫾ 1.1; val-pyr,
`31.4 ⫾ 1.1; metformin, 31.8 ⫾ 1.1; and combination, 32.1 ⫾
`1.2 g). There were also no statistically significant differences
`of basal fasting blood glucose, plasma insulin, or plasma
`active GLP-1 level among the four groups, indicated in Table
`1.
`
`Effects of Subchronic Metformin and/or val-pyr
`Treatment on Food Intake and Body Weight Gain. A
`significant reduction in food consumption had already oc-
`curred on day 1 in the combination treatment group (p ⬍
`0.01), and this reduction continued throughout the experi-
`ment (Fig. 2). In the metformin-treated rats, a significant
`decrease of food intake was observed only on day 1. On day
`14, the values of cumulative food intake were as follows:
`vehicle, 478.1 ⫾ 14.8; val-pyr, 491.8 ⫾ 11.1; metformin,
`484.4 ⫾ 13.3; and metformin plus val-pyr, 417.3 ⫾ 11.1 g.
`Reflecting the continuous reduction in food consumption,
`body weight gain in the combination group was significantly
`smaller than those in the other groups on days 4, 7, 11, and
`14 (p ⬍ 0.05) (Fig. 3). Body weight gains in the fed state on
`day 14 were 66.0 ⫾ 4.2, 60.9 ⫾ 4.4, 62.6 ⫾ 3.7, and 39.5 ⫾
`4.7 g in the vehicle, val-pyr, metformin, and combination
`groups, respectively.
`Effects of Metformin and/or val-pyr on Blood Glu-
`cose, Plasma Insulin, and Plasma Active GLP-1 in
`OGTT. On day 1, metformin did not affect plasma active
`GLP-1 level at any time point after glucose load (Fig. 4C).
`Val-pyr increased plasma active GLP-1 level at 1 h (p ⬍ 0.01),
`compared with the control, but GLP-1 returned to the control
`level at 2 h (Fig. 4C). In the combination group, a marked
`increase of active GLP-1 was observed at 0, 0.5, 1, and 2 h, in
`comparison with the vehicle group (p ⬍ 0.001, p ⬍ 0.001, p ⬍
`0.01, and p ⬍ 0.001, respectively) (Fig. 4C). The combination
`treatment of metformin with val-pyr improved glucose toler-
`ance more effectively than either metformin or val-pyr treat-
`ment alone (Fig. 4A). Insulin secretion in response to the oral
`glucose load was greater in the val-pyr-treated rats at both
`0.5 and 1 h compared with the vehicle-treated rats (p ⬍ 0.05)
`(Fig. 4B). On the other hand, no significant elevation was
`observed in plasma insulin level in either the metformin or
`combination group. After the subchronic treatment, similar
`responses of blood glucose, insulin, and active GLP-1 were
`observed in OGTT (Fig. 4, D–F).
`Effects of Subchronic Treatment with Metformin
`and/or val-pyr on Fasting Blood Glucose, Plasma Insu-
`lin, and Plasma Active GLP-1. After the 14-day adminis-
`
`TABLE 1
`Blood glucose, plasma insulin, and active GLP-1 levels of fasted Zucker fa/fa rats treated with met (300 mg/kg) and/or val-pyr (30 mg/kg), a
`DPPIV inhibitor, b.i.d. for 14 days
`The values are those just before the drug treatment on day 1 and day 15. Data are shown as means ⫾ S.E.M. n ⫽ 10 per group.
`
`Day 1
`
`Day 15
`
`Glucose
`
`Insulin
`
`ng/ml
`mg/dl
`9.8 ⫾ 1.1
`101.4 ⫾ 3.4
`Vehicle
`8.8 ⫾ 1.1
`102.6 ⫾ 3.0
`met (300 mg/kg)
`11.9 ⫾ 1.1
`108.9 ⫾ 5.6
`val-pyr (30 mg/kg)
`9.3 ⫾ 1.3
`99.0 ⫾ 4.6
`val-pyr (30 mg/kg) ⫹ met (300 mg/kg)
`*p ⬍ 0.05 and **p ⬍ 0.01 compared with those of the vehicle group on the same day.
`#p ⬍ 0.05 and ##p ⬍ 0.01 compared with those on day 1.
`
`Active
`GLP-1
`
`pM
`4.8 ⫾ 0.2
`5.4 ⫾ 0.3
`5.1 ⫾ 0.3
`5.1 ⫾ 0.5
`
`Glucose
`
`Insulin
`
`mg/dl
`116.9 ⫾ 4.3#
`107.4 ⫾ 1.9
`105.4 ⫾ 1.7*
`97.3 ⫾ 3.8**
`
`ng/ml
`17.9 ⫾ 1.6##
`10.7 ⫾ 1.1**
`16.0 ⫾ 1.6##
`8.4 ⫾ 0.7**
`
`Active
`GLP-1
`
`pM
`4.7 ⫾ 0.1
`5.8 ⫾ 0.8
`5.0 ⫾ 0.3
`7.4 ⫾ 2.5
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`Combination of Metformin with DPPIV Inhibitor
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`
`Fig. 2. Cumulative food intake in male obese
`fa/fa Zucker rats treated with met (300 mg/kg)
`and/or val-pyr (30 mg/kg), a DPPIV inhibitor,
`b.i.d. (10:00 AM and 5:00 PM) for 14 days. Cu-
`mulative food intake is calculated from the be-
`ginning of the study at 13 weeks of age. Food
`intake was determined by weighing the remain-
`ing food every day before the treatment at 5:00
`PM. # and * indicate significant differences in
`the met- and both val-pyr and met-treated
`groups, respectively, compared with the vehicle-
`treated group. Data are shown as means ⫾
`S.E.M., n ⫽ 10 per group. One, two, and three
`symbols indicate p ⬍ 0.05, p ⬍ 0.01, and p ⬍
`0.001, respectively.
`
`Fig. 3. Changes of body weight gain in male
`obese fa/fa Zucker rats treated with met (300
`mg/kg) and/or val-pyr (30 mg/kg), a DPPIV in-
`hibitor, b.i.d. (10:00 AM and 5:00 PM) for 14
`days. Body weight gain is the change in body
`weight from the beginning of the study at 13
`weeks of age. Body weight was monitored under
`fed conditions on days 4, 7, 11, and 14 before the
`administration at 5:00 PM. There are significant
`differences between the vehicle control and the
`val-pyr and met-group (ⴱⴱ, p ⬍ 0.01). Data are
`shown as means ⫾ S.E.M., n ⫽ 10 per group.
`
`paraventricular nucleus of the hypothalamus has been re-
`ported (Turton et al., 1996; Kalra et al., 1999). However,
`further studies will be needed to clarify the mechanisms
`involved, including the possibility that other factors besides
`GLP-1 play a role.
`To examine the effect of the combination treatment with
`
`metformin and val-pyr on oral glucose tolerance in Zucker
`fa/fa rats, OGTT was conducted before the subchronic ad-
`ministration in Zucker fa/fa rats. This study indicated that a
`marked increase of active GLP-1 level was induced by the
`combination treatment in fasted Zucker fa/fa rats. In addi-
`tion, the improvement of glucose tolerance caused by the
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`Fig. 4. Changes of blood glucose (A and D), plasma insulin (B and E), and plasma active GLP-1 excursion (C and F) in oral glucose tolerance test in
`male obese fa/fa Zucker rats treated with met (300 mg/kg) and/or val-pyr (30 mg/kg), a DPPIV inhibitor, on day 1 (A–C) or 15 (D–F). $, #, and * indicate
`significant differences in the val-pyr-, met-, and both val-pyr and met-treated groups, respectively, compared with the vehicle-treated group. Data are
`shown as means ⫾ S.E.M., n ⫽ 10 per group. One, two, and three symbols indicate p ⬍ 0.05, p ⬍ 0.01, and p ⬍ 0.001, respectively.
`
`combination treatment was greater than that produced by
`monotherapy with metformin or val-pyr in the OGTT. Val-
`pyr increased active GLP-1 level after glucose loading
`through the inhibition of active GLP-1 degradation by DPPIV
`and caused an enhancement of glucose-dependent insulin
`secretion with a consequent attendant improvement in glu-
`cose tolerance. In contrast, metformin improved glucose tol-
`erance, without affecting the peripheral plasma insulin or
`GLP-1 level, suggesting that the antidiabetic effect of met-
`formin may occur through the potentiation of peripheral in-
`sulin action and inhibition of gluconeogenesis (Bailey, 1992;
`Bailey and Turner, 1996). In the combination treatment
`group, no increase of plasma insulin level was seen in re-
`sponse to the oral glucose load, in spite of the greater in-
`crease of plasma active GLP-1 level. The reason for this is not
`clear. As a possible explanation, we speculate that an in-
`crease of portal insulin may be involved in this phenomenon.
`Because plasma active GLP-1 was already sufficiently high
`to enhance glucose-stimulated insulin secretion before the
`glucose load, enhancement of portal insulin level by GLP-1
`could occur immediately after the glucose administration and
`could promote the metformin-induced inhibition of glucose
`production in the liver, leading to the suppression of acute
`elevation of blood glucose. This could explain why no increase
`
`of insulin level was observed in the peripheral caudal region.
`Alternative interpretation is that the enhanced GLP-1 levels
`per se directly contributes to the improvement of glucose
`tolerance, because GLP-1 itself has antidiabetic effects, such
`as inhibition of glucose production from liver (Ikezawa et al.,
`2003) and increase of glycogen synthase activity (Alca´ntara
`et al., 1997).
`On day 15, responses of blood glucose, insulin, and active
`GLP-1 were basically similar to those on day 1 in OGTT. But
`it is noteworthy that the subchronic coadministration of met-
`formin and val-pyr caused significant reductions of fasting
`blood glucose and fasting plasma insulin level (namely, the
`values at ⫺0.5 h in the OGTT), compared with the vehicle
`treatment group. In this study, the changes were not signif-
`icant between the combination group and the metformin or
`val-pyr alone group. Zucker fa/fa rats are obese and insulin
`resistant, with normal or slightly elevated glucose concentra-
`tions in the basal state, reflecting glucose intolerance. To
`demonstrate effects of the combination treatment on the
`improvement of insulin resistance and glycemic control more
`clearly, a further study will be needed using type 2 diabetic
`animal models with hyperglycemia and marked insulin re-
`sistance, such as Zucker diabetic fatty rats and db/db mice.
`Obesity, which leads to hyperlipidemia, hyperinsulinemia,
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`
`Address correspondence to: Dr. Nobuyuki Yasuda, Tsukuba Research Lab-
`oratories, Eisai Co., Ltd., 5-1-3, Tokodai, Tsukuba, Ibaraki 300-2635, Japan.
`E-mail: n-yasuda@hhc.eisai.co.jp
`
`and insulin resistance, has been implicated in the pathogen-
`esis of type 2 diabetes. Hence, dietary and weight control is
`essential in the management of type 2 diabetes with obesity
`(Henry et al., 1986; Blackburn, 1995). However, clinical stud-
`ies have shown that sulfonylurea agents and insulin sensi-
`tizers for the treatment of type 2 diabetic patients lead to
`undesirable weight gain (UKPDS Group, 1998; Khan et al.,
`2002). Together with the results of the present study, we
`expect the combination therapy of metformin with DPPIV
`inhibitors to have a potential therapeutic value in the treat-
`ment of obese patients with type 2 diabetes, also predicted by
`Hinke et al. (2002).
`In conclusion, our results suggest that the marked and
`lasting increase of plasma active GLP-1 level is induced by
`the combination treatment with metformin and DPPIV in-
`hibitor, and this larger GLP-1 elevation may result in signif-
`icant reductions of food intake and body weight gain, contrib-
`uting to the greater improvement of oral glucose tolerance
`compared with monotherapy in type 2 diabetes patients.
`
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