Effect of Adrenalectomy on
the Activity of Small Intestine Enzymes in Monosodium Glutamate
Obese Rats
Š. MOZEŠ, Z. ŠEFČÍKOVÁ, Ľ. LENHARDT1, Ľ. RAČEK
Institute of Animal Physiology, Slovak Academy of Sciences and
1Department of Pathology, University of Veterinary Medicine,
Košice, Slovak Republic
Received December 19, 2002
Accepted September 16, 2003
Summary
It is well known that adrenalectomy (ADX) reverses the eating
and energy balance disturbances in a variety of models of
obesity associated with elevated food intake. We have previously
demonstrated enhanced functional activity in the small intestine
of neonatally monosodium glutamate-treated (MSG) obese rats
despite the absence of overeating and we concluded that these
changes might also contribute to the development of MSG obesity.
The objective of the present experiments was to investigate
whether ADX would affect the small intestinal functions and
whether their changes would counteract attenuation or prevention
of obesity development in MSG rats. Therefore the investigation
was carried out in MSG-obese Wistar male rats and untreated
intact rats adrenalectomized on day 40, as well as in lean
littermates of MSG rats and intact rats subjected to Sham-ADX
surgery. All animals had free access to a standard pellet diet
after weaning. At the age of 80 days, body mass, body fat
content and food consumption as well as changes of the
brush-border-bound duodenal and jejunal alkaline phosphatase
(AP), the dipeptidyl(amino)peptidase IV (DPP IV) and maltase
activity were measured. During the postoperative period, ADX
resulted in a significant decrease of mass gain in both MSG and
control rats (P<0.05). ADX fully prevented the development of
obesity in MSG rats (significantly decreased
epididymal+retroperitoneal fat pad mass, P<0.05) and increased
mean daily food intake (P<0.001). These effects were only
minimal in the ADX controls suggesting that enhanced adrenal
secretion is involved in the expression of MSG obesity and its
complications. The AP activity in obese MSG rats was increased
by about 21 % (P<0.01) in both intestinal segments when compared
to the lean controls, whereas no parallel variations in the
activities of DPP IV and maltase were observed in the intestinal
parts mentioned. In MSG rats, ADX significantly reduced the AP
activity in the duodenum and jejunum (P<0.01). A similar
tendency was also seen in the DPP IV activity of
adrenalectomized MSG rats as well as in lean control rats.
Nevertheless, no significant effect of adrenal withdrawal on
maltase activity was found. These results indicate that the
decrease of enzyme activities in the small intestine and the
different effectiveness of nutrient absorption might be a
significant factor preventing the development of excess
adiposity in glutamate-treated rats. This information
contributes to a better understanding of the importance of small
intestinal function for the development of obesity and its
maintenance in later life.
Key words
Neonatal MSG treatment • Adrenalectomy • Small intestine enzymes
• Obesity
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