[Frontiers in Bioscience 2, e108-115, November 1, 1997]

	[Frontiers in Bioscience 2, e108-115, November 1, 1997] Reprints PubMed CAVEAT LECTOR
	EFFECT OF AGING AND CALORIC RESTRICTION ON INTESTINAL SUGAR AND AMINO ACID TRANSPORT Ronaldo P. Ferraris Dept of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103 Received 7/17/97 Accepted 10/2/97 8. PERSPECTIVE It is not really known whether age-related changes in transport observed in vitro are physiological, hence, in vivo transport studies are needed. To increase the chance of detecting significant changes, these studies should use animals well past the median lifespan and should also measure age-related changes in intestinal mass. Studies are also needed to identify the mechanisms underlying age-related changes in nutrient absorption. Although Ferraris et al (32) have determined an age-related decrease in the number of specific phlorizin binding sites (glucose transporters) per mg, it is not known whether this decrease is due to fewer functional carriers per cell, or to a decrease in the ratio of absorptive to nonabsorptive cells. The latter is the more probable mechanism, since transport rates of amino acids and fructose tend to decrease with age as well. Nutrition is the most powerful extrinsic factor which influence the aging process. This role has been clarified by such underfeeding paradigms as caloric restriction (66, 67). The effect of caloric restriction on intestinal sugar and amino acid transport has just been studied. Additional studies are required not only to determine the effect of caloric restriction on the transport of other amino acids, but also on transport of micronutrients as well. There is a need to distinguish acute and chronic effects of caloric restriction on intestinal transport of nutrients, as well as to identify hormones that may mediate the effects of caloric restriction on intestinal nutrient transport.

[Frontiers in Bioscience 2, e108-115, November 1, 1997]
Reprints
PubMed
CAVEAT LECTOR

EFFECT OF AGING AND CALORIC RESTRICTION ON INTESTINAL SUGAR AND AMINO ACID TRANSPORT

Ronaldo P. Ferraris

Dept of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103

Received 7/17/97 Accepted 10/2/97

8. PERSPECTIVE

It is not really known whether age-related changes in transport observed in vitro are physiological, hence, in vivo transport studies are needed. To increase the chance of detecting significant changes, these studies should use animals well past the median lifespan and should also measure age-related changes in intestinal mass. Studies are also needed to identify the mechanisms underlying age-related changes in nutrient absorption. Although Ferraris et al (32) have determined an age-related decrease in the number of specific phlorizin binding sites (glucose transporters) per mg, it is not known whether this decrease is due to fewer functional carriers per cell, or to a decrease in the ratio of absorptive to nonabsorptive cells. The latter is the more probable mechanism, since transport rates of amino acids and fructose tend to decrease with age as well.

Nutrition is the most powerful extrinsic factor which influence the aging process. This role has been clarified by such underfeeding paradigms as caloric restriction (66, 67). The effect of caloric restriction on intestinal sugar and amino acid transport has just been studied. Additional studies are required not only to determine the effect of caloric restriction on the transport of other amino acids, but also on transport of micronutrients as well. There is a need to distinguish acute and chronic effects of caloric restriction on intestinal transport of nutrients, as well as to identify hormones that may mediate the effects of caloric restriction on intestinal nutrient transport.