Hormonal and metabolic adaptations to fasting in monosodium glutamate-obese rats

The effect of fasting on hormonal and metabolic variables was evaluated in normal rats and in rats with obesity induced by neonatal treatment with monosodium glutamate (MSG). The hyperinsulinemia of the fed obese rats was reversed by fasting. Plasma corticosterone was also high in the fed obese and...

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Published in:	Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 167; no. 6; pp. 430 - 437
Main Authors:	Ribeiro, E.B, Nascimento, C.M.O. do, Andrade, I.S, Hirata, A.E, Dolnikoff, M.S
Format:	Journal Article
Language:	English
Published:	Germany 01-08-1997
Subjects:	Adaptation, Physiological adipose tissue Adipose Tissue - pathology Animals Animals, Newborn blood lipids blood plasma body fat body protein corticosterone Corticosterone - blood Fasting - physiology Fatty Acids, Nonesterified - blood glycerol Glycerol - metabolism glycogen Hormones - metabolism insulin Insulin - blood lipid metabolism Lipolysis liver Liver Glycogen - metabolism Male monosodium glutamate norepinephrine obesity Obesity - chemically induced Obesity - metabolism Obesity - pathology Proteins - metabolism Rats Rats, Wistar Sodium Glutamate - toxicity starvation thyroid hormones Thyroid Hormones - blood Triglycerides - blood
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Summary:	The effect of fasting on hormonal and metabolic variables was evaluated in normal rats and in rats with obesity induced by neonatal treatment with monosodium glutamate (MSG). The hyperinsulinemia of the fed obese rats was reversed by fasting. Plasma corticosterone was also high in the fed obese and decreased to levels similar to fed controls, while it increased in the latter group during fasting. In contrast, thyroid hormone levels decreased in controls but increased in the obese rats in response to fasting. The fed obese group had lower carcass protein and higher carcass lipid contents than controls. In response to fasting, the decrements of the initial amount of both protein and fat were lower in MSG than in controls. Fasting induced a sustained increase in plasma free fatty acids only in the obese rats, although a single 100 micromoles.l-1 dose of norepinephrine stimulated in vitro glycerol release more pronouncedly in epididymal adipocytes from control than obese rats. The results indicate that MSG-obese rats were able to mobilize fat stores during prolonged fasting. The high availability of lipid fuels and the sharp and sustained decrease in circulating corticosterone in the MSG group were probably important in diminishing body protein consumption during fasting.
ISSN:	0174-1578 1432-136X
DOI:	10.1007/s003600050093