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1.7 Tuesday 24th August 1997



J Nutr 1997 Jul;127(7):1382-1387

Total intestinal lactase and sucrase activities are reduced in aged rats.

Lee MF, Russell RM, Montgomery RK, Krasinski SD

Jean Mayer USDA-Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.

Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestinal microvillus membrane hydrolases that play important roles in carbohydrate digestion. Although the expression of these enzymes during postnatal development has been characterized, the effect of old age on disaccharidase activity is poorly understood. In the present investigation, we examined the effect of aging on lactase and sucrase activities and their mRNA levels in the small intestines of 3-, 12- and 24- mo-old rats by sampling from nine equidistant segments of small intestine. Total intestinal disaccharidase activity or mRNA abundance was determined from areas under the proximal-to-distal curves. Rats 24 mo of age had total intestinal lactase and sucrase activities that were 12 and 38% lower, respectively, than the 3-mo-old animals (P < 0.05). In contrast, total LPH and SI mRNA abundance did not change significantly. Thus, total intestinal lactase and sucrase activities decrease with age in a manner that likely involves a posttranscriptional process. The age-related decline in disaccharidase activity, if extrapolated to humans, may have important implications for the digestion of carbohydrate contained in the diet of the elderly.

PMID: 9202095, MUID: 97347456

Cell Immunol 1997 Jun 15;178(2):117-123

Early steps in T cell development are affected by aging.

Thoman ML

Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA.

Involution of the thymus accompanies aging, a process in which the organ diminishes in size and cellularity and becomes disorganized. The rate of T cell emigration from the thymus is markedly reduced with age, and phenotypic analyses have identified alterations in the relative proportions of the major thymocyte subpopulations. The present studies made use of the capacity of the thymus to regenerate following irradiation from an intrathymic radio-resistant precursor population. By analysis of the differentiation of this "wave" of thymocytes, it was determined that aging most severely affects the earliest developmental transitions. While the overall rate of differentiation does not appear to be affected in older mice, fewer thymic progenitors initiate differentiation. The reduced expansion of late pre-T cells in the middle-aged is due to the smaller pool size of these cells.

PMID: 9225002, MUID: 97368388

J Clin Invest 1997 Jun 15;99(12):2883-2889

Glucagon-like peptide-1 can reverse the age-related decline in glucose tolerance in rats.

Wang Y, Perfetti R, Greig NH, Holloway HW, DeOre KA, Montrose-Rafizadeh C, Elahi D, Egan JM

Diabetes Section, Laboratory of Clinical Physiology, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA.

Wistar rats develop glucose intolerance and have a diminished insulin response to glucose with age. The aim of this study was to investigate if these changes were reversible with glucagon-like peptide-1 (GLP-1), a peptide that we have previously shown could increase insulin mRNA and total insulin content in insulinoma cells. We infused 1.5 pmol/ kg-1.min-1 GLP-1 subcutaneously using ALZET microosmotic pumps into 22-mo-old Wistar rats for 48 h. Rat infused with either GLP-1 or saline were then subjected to an intraperitoneal glucose (1 g/kg body weight) tolerance test, 2 h after removing the pump. 15 min after the intraperitoneal glucose, GLP-1-treated animals had lower plasma glucose levels (9.04+/-0.92 mmol/liter, P < 0.01) than saline-treated animals (11.61+/-0.23 mmol/liter). At 30 min the plasma glucose was still lower in the GLP-1-treated animals (8.61+/-0.39 mmol/liter, P < 0.05) than saline-treated animals (10.36+/-0.43 mmol/liter). This decrease in glucose levels was reflected in the higher insulin levels attained in the GLP-1-treated animals (936+/-163 pmol/liter vs. 395+/-51 pmol/liter, GLP-1 vs. saline, respectively, P < 0.01), detected 15 min after glucose injection. GLP-1 treatment also increased pancreatic insulin, GLUT2, and glucokinase mRNA in the old rats. The effects of GLP-1 were abolished by simultaneous infusion of exendin [9-39], a specific antagonist of GLP-1. GLP-1 is therefore able to reverse some of the known defects that arise in the beta cell of the pancreas of Wistar rats, not only by increasing insulin secretion but also by inducing significant changes at the molecular level.

PMID: 9185511, MUID: 97330986

Biologicals 1997 Jun;25(2):205-208

Changes in the Aging Immune System.

Grubeck-Loebenstein B

Institute for Biomecial Aging Research of the Austrian Academy of Sciences, Innsbruck, Austria

The functional capacity of the immune system gradually declines with age. T lymphocytes are more severely affected than B cells or antigen-presenting cells. This is mainly due to the involution of the thymus which is almost complete at the age of 60. The host is then dependent on the T cell pool generated in earlier life. Continuous activation, clonal expansion and elimination of T cells of various specificities eventually lead to changes in the T cell repertoire. CD45RA+ "naive" cells are replaced by CD45RA- "memory" cells and a T cell receptor oligoclonality develops. At the same time, T cells with signal transduction accumulate. Age-related T cell alterations lead to a decreased clonal expansion and a reduced efficiency of T cell effector functions such as cytotoxicity or B cell help. Decreased antibody production and a shortened immunological memory are the consequence. Changes in the aging immune system represent a permissive factor for the frequent occurrence and the severity of disease. Efficient protection of elderly individuals by suitable vaccination strategies is therefore a matter of great importance.

PMID: 9236053

Coll Antropol 1997 Jun;21(1):117-126

The aging process--an analysis of the latent structure of body morphology.

Zivicnjak M, Szirovicza L, Pavicic L, Smolej-Narancic N, Janicijevic B, Milicic J, Rudan P

Institute for Anthropological Research, Zagreb, Croatia.

The morphological characteristics (20 anthropometric variables) of a total of 2,351 examinees (from the age of 18 to 90) were analyzed by a model of the principal components of the factor analysis. Four factors were extracted that explain 71.4% of the total variance. The factors-"general body voluminosity", "subcutaneous fat tissue", "longitudinal body dimensionality" and "upper body voluminosity"-were analyzed within the context of their appearance in different age-determined cohorts. The differences between cohorts (groups per ten years of age) were studied by the canonical discriminant analysis. The first two discriminant functions (describing mostly the variability of cohorts-96.11%) indicate a constant decrease of body and sitting height, and an increase of upper body voluminosity till the fourth age cohort, which is the most crucial one in the change of latent morphological structure. Results of the correct classification of cohort members show that only 48.45% of probands were correctly placed (the best classification determined was in the age between 46 and 55 years) indicating that in males, at least three different groups exist according to the specificity of morphological aging in human organisms.

PMID: 9225505, MUID: 97368908



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