Journal of the American College of Nutrition, Vol 16, Issue 2 159-165, Copyright © 1997 by American College of Nutrition

JOURNAL ARTICLE

Evaluation of differential effects of carbohydrate and fat intake on weight gain, serum IGF-1 and erythrocyte Na+K+ATPase activity in suboptimal nutrition in rats

O. Tarim, F. I. Chasalow, J. Murphy, R. Rising, A. Carrillo and F. Lifshitz
Department of Pediatrics, Maimonides Medical Center, Brooklyn, New York, USA.

OBJECTIVE: Suboptimal nutrition leads to growth delay, frequently without over clinical or biochemical signs. We hypothesize that changes in serum IFG-1 and erythrocyte sodium-potassium ATPase activity (ENKA) may be indices of suboptimal nutrition. METHODS: Male Sprague-Dawley rats were pair-fed for 4 weeks with balanced diets of different carbohydrate (CHO) to fat (FAT) ratios (3:1, 2:1, and 1:1) and three levels of energy intake (ad-libitum, 80%, and 60%), corrected for actual body weight). Daily weight gain and weekly tail growth were monitored while ENKA, serum total protein, T3, insulin and IGF-1 were measured after four weeks. Refeeding experiments were also performed with the 3:1 and 1:1 CHO:FAT diets, including 4 weeks of dietary restriction and one week of ad-libitum feeding. RESULTS: Weight gain, tail growth, and IGF-1 decreased (p < 0.05) in all groups after 1 week of dietary restriction. A decrease in ENKA (p < 0.05) was found in rats that consumed 60% of ad-libitum energy intake only after 4 weeks. At the end of dietary treatment, weight gain was higher (p < 0.05) in rats fed the 3:1 CHO:FAT diet. In contrast, when energy was restricted to 80% or 60% of ad-libitum intake, rats fed the 1:1 CHO:FAT diet gained more weight (p < 0.05) compared to the 3:1 and 2:1 CHO:FAT diets. After 1 week of refeeding body weight, tail growth and ENKA returned to control values while serum IGF-1 levels remained depressed. CONCLUSIONS: Acute nutritional changes are clearly detected by a reduction of serum IGF-1 while ENKA may be a useful index for assessing chronic suboptimal nutrition.

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