Aging: a barrier to renutrition? Nutritional and immunologic evidence in rats.
BACKGROUND
Previous reports suggest that correcting the malnourished state is more difficult in elderly people than in younger ones and that protein requirements may be higher in elderly than in younger adults.


OBJECTIVE
The aim of this study was to establish whether malnourished old rats respond to protein-supplemented nutritional repletion as do young adult rats.


METHODS
Adult (3 mo old) and old (22 mo old) rats were submitted to dietary restriction programs that induced similar metabolic and nutritional alterations. Malnourished adult and old rats were then killed (R groups) or refed for 1 wk with a high-protein diet (HPD; 23% protein) or a very-high-protein diet (VHPD; 27% protein). Control groups at both ages were fed ad libitum throughout the experiment. Effects of food repletion were evaluated in terms of protein metabolism, intestinal histomorphometry, and nonspecific immune status.


RESULTS
In adult rats, HPD sufficed to increase body weight and restore basal values of liver weight and protein content (P: < 0.01 compared with the R adult group), nitrogen balance (P: < 0.01 compared with the R adult group), and hydrogen peroxide production by polymorphonuclear neutrophils and monocytes (P: < 0.01 compared with the R group); VHPD had no supplementary effect except on nitrogen balance. In old rats, HPD was less effective and greater benefit was observed with VHPD in terms of body weight gain (10%; P: < 0.01 compared with the old group fed HPD), albuminemia, muscle weight and protein content, plasma arginine concentration, and hydrogen peroxide production by stimulated polymorphonuclear neutrophils and monocytes compared with the old R group (P: < 0.01).


CONCLUSIONS
Aging is a significant variable affecting the response to nutritional support.
Walrand
S
S
Laboratoire de Biochimie, Biologie Moléculaire et Nutrition, Faculté de Pharmacie, Centre de Recherche en Nutrition Humaine, Clermont-Ferrand, France. s.walrand@netcourrier.com
Chambon-Savanovitch
C
C
Felgines
C
C
Chassagne
J
J
Raul
F
F
Normand
B
B
Farges
M C
MC
Beaufrère
B
B
Vasson
M P
MP
Cynober
L
L
D000375:Aging / Q000502:physiology*; D000596:Amino Acids / Q000097:blood; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004044:Dietary Proteins / Q000008:administration & dosage / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000378:metabolism; D008099:Liver / Q000378:metabolism / Q000473:pathology; D017737:Macrophages, Peritoneal / Q000378:metabolism; D008297:Male; D009000:Monocytes / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D009748:Nutrition Disorders / Q000097:blood / Q000473:pathology / Q000628:therapy*; D009929:Organ Size / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012709:Serum Albumin / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D000596:Amino Acids; D004044:Dietary Proteins; D011506:Proteins; D012709:Serum Albumin; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide