Effects of food restriction and lysine supplementation on protein metabolism in the rat
Sika, Mohammed
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Permalink
https://hdl.handle.net/2142/22441
Description
Title
Effects of food restriction and lysine supplementation on protein metabolism in the rat
Author(s)
Sika, Mohammed
Issue Date
1991
Doctoral Committee Chair(s)
Layman, Donald K.
Department of Study
Health Sciences, Nutrition
Discipline
Health Sciences, Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Nutrition
Language
eng
Abstract
These studies examined the effects of prolonged food restriction and lysine supplementation on growth, muscle mass, and protein metabolism in the rat. Two levels of food restriction (40% and 75%) were utilized during an 8-week feeding period to produce moderate or severe undernutrition. Rats restricted to 75% of ad libitum intake lost weight, but reached a stable body weight during the last 4 weeks. The stable body weight was achieved when the animals reached an energy intake/unit body weight comparable to ad libitum fed, age controls.
Lysine supplementation of the wheat gluten diet produced a significant increase in growth of muscle mass in rats fed ad libitum or at the 40% restricted level. Urinary 3-methylhistidine was increased by lysine supplementation in 75% restricted rats suggesting an increase in myofibrillar protein breakdown.
Changes in whole body and muscle protein turnover were investigated in animals after 8 weeks on the respective diets. Measurements were made in both fed (absorptive) and fasted (postabsorptive) states to evaluate the significance of diurnal variations. In the fed state, restricted rats had lower or the same fractional synthesis rates (FSR) of muscle protein as the ad libitum fed rats. However, in the fasted state, restricted rats had a higher skeletal muscle FSR than ad libitum fed rats. Whole body protein turnover, expressed per unit of body weight, was the same in ad libitum and food restricted groups.
In the fed state, lysine supplementation increased FSR for muscles in ad libitum and 40% restricted rats. However, FSR in skeletal muscles decreased in the 75% restricted rats. In the fasted state, lysine supplementation resulted in a decrease in muscle FSR's.
This study demonstrates that rats can reach and maintain a smaller body weight during prolonged undernutrition. This stable body weight is characterized by nitrogen balance and similar rates of whole body protein turnover per unit of body weight as ad libitum fed rats. These studies also showed that the threshold for beneficial effects of lysine supplementation is somewhere between 40% and 75% food restriction.
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