Adaptations of intestinal nutrient transport to chronic caloric
restriction in mice.
Casirola, D. M., B. Rifkin, W. Tsai, and R. P. Ferraris.
Department of Physiology, New Jersey Medical School, University of
Medicine and Dentistry of New Jersey, 185 South Orange Ave., Newark,
NJ 07103-2714
APStracts 3:0031G, 1996.
Lifelong caloric restriction increases median and maximum lifespan and
retards the aging process in many organ systems of rodents. Since the
small intestine absorbs a reduced amount of nutrients each day, does
lifelong caloric restriction induce adaptations in intestinal
nutrient transport? We initially compared intestinal transport of
sugars and amino acids between 24 mo old mice allowed free access to
food (ad libitum (AL)) and those provided a calorically-restricted
(40% less than ad libitum (CR)) diet since 3 mo of age. We found that
CR mice had significantly greater transport rates for D-glucose, D
-fructose and several amino acids, and significantly lower villus
heights. Total intestinal absorptive capacity for D-glucose, D
-fructose and L-proline were each 40 - 50% greater in CR mice;
absorptive capacity normalized to metabolic mass (body weight0.75)
were about 80% greater in CR mice. Comparing uptakes in aged AL and
CR mice to previously published results in young AL mice suggests
that caloric restriction delays age-related decreases in nutrient
transport. In contrast to published studies in hibernation and
starvation, chronic caloric restriction enhances not only uptake per
milligram but also uptake per centimeter. We then switched 24 mo-old
AL mice to a calorie restricted diet for one month and found that
short term caloric restriction has no effect on intestinal nutrient
transport, intestinal mass, and total absorptive capacity. Thus,
chronic but not short term caloric restriction increases intestinal
nutrient transport rates in aged mice, and the main mechanism
underlying these increases is enhanced transport rates per unit
intestinal tissue weight.
Received 12 September 1995; accepted in final form 23 January
1996.
APS Manuscript Number G403-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96