Effect of fasting and refeeding on duodenal alkaline phosphatase activity in monosodium glutamate obese rats

In the present work the effects of fasting and refeeding on fat pad weight and alkaline phosphatase activity in the brush border of individual duodena l enterocytes have been evaluated in male Wistar rats with obesity induced by monosodium glutamate (MSG) treatment during the early postnatal period. Neonatal rats were treated subcutaneously with MSG (2 mg/g b.w.) or saline (controls) for 4 days after birth. At 4 months of age, two types of experim ents were performed. In the first experiment rats, were submitted to 3 or 6 days lasting food deprivation. In the second experiment the rats were refe d for 3 or 6 days ad libitum or restrictedly (60% of pre-fasting intake) af ter a 6 day-fasting period. Fasting and refeeding influenced the body fat a nd function of the duodenum in MSG-treated rats differently as compared to the controls, However, alkaline phosphatase activity and the weight of epid idymal and retroperitoneal fat depots were significantly increased in MSG o bese rats (P<0.001) during all the periods examined. While 3 days of food d eprivation resulted in both groups in a similar loss of adipose tissue weig ht and alkaline phosphatase activity, the decrements of these parameters af ter 6 days of fasting were lower in obese rats suggesting that their capaci ty to spare body fat stores was enhanced. After 3 days of adlibitum refeedi ng, a more marked adaptational increase of food consumption and also a sign ificantly increased alkaline phosphatase activity above the pre-fasting lev el (P<0.01) was observed in the MSG-treated rats. Consequently, a more rapi d body fat restoration was demonstrated in these animals. Refeeding of rats at 60% of the pre-fasting intake level resulted in a significant increase of alkaline phosphatase activity in both the MSG and control group; moreove r, as food restriction continued, MSG-treated rats tended to further increa se the enzyme activity, Our results revealed that MSG treatment of neonatal rats may significantly change the intestinal functions. Permanently increa sed alkaline phosphatase activity observed in MSG obese rats during all inv estigated periods suggests that this functional alteration is probably not a consequence of actual nutritional variation but could be a component of r egulatory mechanisms maintaining their obesity at critical values.