Response of albumin synthesis to oral nutrients in young and elderly subjects.
BACKGROUND
The synthesis of albumin after oral ingestion of nutrients provides a means of storing amino acids, which can be made available during periods of fasting.


OBJECTIVE
This study was undertaken to see whether the response of albumin synthesis to the oral intake of nutrients is compromised in elderly subjects.


METHODS
Albumin synthesis was determined from the incorporation of 43 mg l-[(2)H(5)]phenylalanine/kg body wt. Eight elderly subjects (aged >60 y) and 8 young subjects (aged 21-35 y) were studied on 3 separate occasions: after the intake of water, a liquid meal (with 15% of energy from protein, 30% of energy from fat, and 55% of energy from carbohydrate), or an isonitrogenous but not isocaloric meal containing only protein.


RESULTS
Mean (+/-SEM) albumin synthesis, expressed as an absolute rate (ie, the amount of albumin synthesized per day), was significantly lower in elderly subjects (108 +/- 7 mg . kg body wt(-1) . d(-1)) than in young subjects (141 +/- 7 mg . kg body wt(-1) . d(-1)). In response to the complete meal, albumin synthesis was significantly increased in both the elderly (144 +/- 7 mgkg body wt(-1) . d(-1)) and the young (187 +/- 11 mg . kg body wt(-1) . d(-1)) subjects. The protein component of the meal was sufficient to stimulate albumin synthesis in both the elderly (147 +/- 14 mg . kg body wt(-1) . d(-1)) and the young (182 +/- 6 mg . kg body wt(-1) . d(-1)) subjects.


CONCLUSIONS
Elderly subjects have lower rates of albumin synthesis than do young subjects during fasting, but they stimulate albumin synthesis proportionately in response to the oral ingestion of protein. The intakes of additional fat and carbohydrate do not stimulate albumin synthesis further.
Caso
Giuseppe
G
Departments of Surgery, Stony Brook University, Stony Brook, NY.
Feiner
Joshua
J
Mileva
Izolda
I
Bryan
Leslie J
LJ
Kelly
Patricia
P
Autio
Karen
K
Gelato
Marie C
MC
McNurlan
Margaret A
MA
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000418:Albumins / Q000096:biosynthesis*; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004041:Dietary Fats / Q000008:administration & dosage / Q000494:pharmacology*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004734:Energy Metabolism; D005215:Fasting; D005260:Female; D005502:Food; D006801:Humans; D008297:Male; D014867:Water / Q000008:administration & dosage / Q000494:pharmacology
D000418:Albumins; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D014867:Water