Severe dietary restriction initiated in aged rats: evidence for poor adaptation in terms of protein metabolism and intestinal functions

Background Protein energy malnutrition is a common finding in elderly peopl e, increasing morbidity and mortality in aged inpatients. Investigations ne ed to be developed to counteract malnutrition-induced alterations early and to avoid potential irreversible lesions. The aim of this experimental stud y was to evaluate time-response to severe dietary restriction (DR) initiate d in aged rats in terms of protein metabolism and digestive trophicity. Materials and methods After the acclimatization period, 22-month-old male r ats were randomized into six groups: three control groups, fed ad libitum f or 3, 6 or 12 weeks with a standard diet and three corresponding dietary-re stricted groups fed for the same periods with only 50% of the spontaneous i ntake. Intestinal mucosa, liver and skeletal muscles (soleus, extensor digi torum longus and tibialis anterior muscle) were removed when the rats were killed. Results DR induced dramatic body weight loss (up to 50% of initial body wei ght after 12 weeks DR). Protein metabolism was affected in terms of nitroge n balance (P < 0.01) and protein content, in particular at the splanchnic l evel. Morphometrically, the intestine structure was altered after 12 weeks of DR (P < 0.01), and this atrophy was correlated with malabsorption of man nitol (P < 0.01). Ileal hydrolase activities were decreased throughout the 12 weeks of DR. Conclusions Aged rats clearly exhibit a defect of adaptation to long-term D R initiated at an advanced age. Severe DR leads to malnutrition, which beco mes of major importance after 12 weeks, in particular at the intestine leve l. Hence, application of these experimental results to elderly, malnourishe d people may contribute to a better knowledge of denutrition-induced disord ers.