Chronic treatment with epigallocatechin gallate reduces motor hyperactivity and affects in vitro
tested intestinal motility of spontaneously hypertensive rats
Sammanfattning
Background: Green tea catechins seem to contribute toward reducing body weight and fat.
Objective: We aimed to investigate whether chronic administration of (–)-epigallocatechin-3-gallate
(EGCG), the most abundant catechin of green tea, reduces weight gain in spontaneously hypertensive
rats (SHR), an animal model of metabolic syndrome, by increasing motor activity and/or by altering
gastrointestinal motility.
Design: Nine-week-old SHR were randomly assigned to two groups and treated by gavage for 3
weeks with vehicle dimethyl sulfoxide or EGCG (200 mg/kg/day). Age-matched Wistar-Kyoto (WKY)
control rats were treated with vehicle alone. The effect of chronic administration of EGCG was
evaluated on open-field motor activity and on ex vivo colonic and duodenal motility. Moreover, in
vitro acute effect of 20-min incubation with EGCG (100 µM) or vehicle was evaluated in colonic and
duodenal specimens from untreated WKY rats and SHR.
Results: Vehicle-treated SHR were normoglycemic and hyperinsulinemic, and showed a reduction of
plasma adiponectin when compared to vehicle-treated WKY rats. In addition, consistent with fasting
glucose and insulin values, vehicle-treated SHR were more insulin resistant than age-matched
vehicle-treated WKY rats. Chronic treatment for 3 weeks with EGCG improved insulin sensitivity,
raised plasma adiponectin levels, and reduced food intake and weight gain in SHR. Vehicle-treated
SHR showed increased open-field motor activity (both crossings and rearings) when tested after each
week of treatment. The overall hyperactivity of vehicle-treated SHR was significantly reduced to the
levels of vehicle-treated WKY rats after 2 and 3 weeks of EGCG treatment. Colonic and duodenal
preparations obtained from SHR chronically treated in vivo with EGCG showed reduced responses to
carbachol (0.05-5 µM) and increased inhibitory response to electrical field stimulation (EFS, 1-10 Hz,
13 V, 1 msec, 10-sec train duration), respectively. In vitro acute EGCG incubation (100 µM, 20 min) of
colonic and duodenum strips obtained from untreated SHR and WKY rats showed a reduced
contractile colonic response to a fixed dose of carbachol (1.5 µM) only in SHR with respect to its own
vehicle, whereas the inhibitory duodenal response to a fixed EFS frequency (5 Hz) was significantly
reduced in both WKY rats and SHR groups with respect to their own vehicle.
Conclusions: These data suggest that EGCG affects body weight gain in rats and this effect seems to
be due to the altered intestinal motility and not to increased motor activity.