Aging: a barrier to renutrition? nutritional and immunologic evidence in rats

• Published in: The American journal of clinical nutrition Vol. 72; no. 3; pp. 816 - 824
• Main Authors: WALRAND, Stéphane, CHAMBON-SAVANOVITCH, Chantal, FELGINES, Catherine, CHASSAGNE, Jacques, RAUL, Francis, NORMAND, Bernadette, FARGES, Marie-Chantal, BEAUFRERE, Bernard, VASSON, Marie-Paule, CYNOBER, Luc
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01-09-2000; American Society for Clinical Nutrition, Inc
• Subjects: Aging - physiology; Amino Acids - blood; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Biological and medical sciences; Body Weight - drug effects; Dietary Proteins - administration & dosage; Dietary Proteins - therapeutic use; Dose-Response Relationship, Drug; Hydrogen Peroxide - metabolism; Liver - metabolism; Liver - pathology; Macrophages, Peritoneal - metabolism; Male; Malnutrition; Medical sciences; Metabolic diseases; Monocytes - metabolism; Neutrophils - metabolism; Nutrition Disorders - blood; Nutrition Disorders - pathology; Nutrition Disorders - therapy; Older people; Organ Size - drug effects; Other nutritional diseases (malnutrition, nutritional and vitamin deficiencies...); Proteins; Proteins - metabolism; Rats; Rats, Sprague-Dawley; Serum Albumin - analysis; Tumor Necrosis Factor-alpha - biosynthesis; Senescence; Immune response; Rat; Refeeding; Rodentia; Nutrition disorder; Metabolism; Immunity; Protein; Feeding; Vertebrata; Mammalia; Adult animal; Aged animal; Malnutrition; Restricted diet
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/72.3.816

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.
The aim of this study was to establish whether malnourished old rats respond to protein-supplemented nutritional repletion as do young adult rats.
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.
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).
Aging is a significant variable affecting the response to nutritional support.