Mineko Ichikawa

Retardation of the age-associated decline of immune functions in aging rats under dietary restriction and daily physical exercise

Wistar rats were subjected to dietary restriction and daily physical exercise for 21 months, starting from 2 months of age. At the age of 23 months, the rats were sacrificed and examined for various indices including immunological functions. Body weight was almost the same between rats fed ad libitum (Group A) and those (Group B) fed 80% of the diet consumed by Group A. The body weights of Groups A and B were significantly heavier than that of rats (Group C) fed 60% of the diet consumed by Group A and those (Group D) which were subjected to physical exercise and fed 80% of the diet consumed by Group A. Highly proliferative response of T cells to mitogens was observed in 5 out of 13 rats in group D. Some enhancement of B cell proliferation was also observed in the same rats. Present results suggested that enduring physical exercise together with dietary restriction can retard the age-related decrement of immunological functions.

Physical activity prevented age-related decline in energy metabolism in genetically obese and diabetic rats, but not in control rats.

Laboratory rats are normally confined to cages that markedly restrict their physical activity. In these rats, the resting energy expenditure accounts for 90% of the total daily energy expenditure, while the daily physical activity in humans consumes 30% of the total daily energy expenditure. Otsuka Long Evans Tokushima Fatty (OLETF) rats have been developed as a model of non-insulin-dependent diabetes mellitus (NIDDM) with mild obesity, and obesity is an important factor that induces diabetes in this strain. We implemented a running-wheel exercise regimen that was the equivalent of normal physical activity to provide light exercise for OLETF rats. The purpose of the study was to determine if light exercise improves the age-related decline in energy metabolism and glucose intolerance in OLETF rats. The effects were also compared in control Long Evans Tokushima (LETO) rats. From 12 to 46 weeks of age, the rats performed a running-wheel exercise (3000 m/day). Energy metabolism was determined at 8-week intervals. The typical increase in body weight was significantly decreased in OLETF rats in response to exercise, while no significant effect was observed in LETO rats. Energy expenditure and basal metabolic rate (BMR) per kilogram body weight (not whole-body weight) were increased by exercise in OLETF rats, but not in LETO rats. At 46 weeks of age, after exercise, the blood glucose and hemoglobin (Hb)A1c levels, as well as the plasma levels of insulin, triglyceride, cholesterol, and leptin significantly decreased in OLETF rats, while only the plasma levels of cholesterol and leptin significantly decreased in LETO rats. Light exercise thus appears to be beneficial for preventing age-related decline in energy metabolism and glucose intolerance in OLETF rats.

Effects of long-term, light exercise under restricted feeding on age-related changes in physiological and metabolic variables in male Wistar rats.

The effects of long-term, light exercise under restricted feeding on age-related changes in physiological and metabolic functions were examined in male Wistar rats. Adult (100 days old) rats were divided into sedentary (R10S) and exercise (R11E) groups, and given 10 and 11 g/day, respectively, of a 20% casein diet until they reached 900 days of age. Group R11E simultaneously underwent 3000 m/day of running exercise throughout the test period. As compared with the sedentary group, long-term, light exercise significantly increased body nitrogen retention and serum protein levels, decreased body fat and plasma insulin levels, prevented age-related decline in the basal metabolic rate, and reduced age-associated histopathological changes in the kidney and liver. Long-term, light exercise further enhanced the benefits of restricted feeding on age-related deterioration in physiological and metabolic variables and improved body composition, but did not prolong survival at 900 days of age.

Effect of long-term exercise under restricted-feeding on intestinal content of cholecystokinin and on the pancreas in aging rats

The effects of exercise (5000 m/day running from 100 to 600 days of age) on the cholecystokinin (CCK) content in the proximal intestine, and the enzyme and insulin contents of the pancreas were examined in food-restricted rats. Food restriction decreased the body weight and the wet weights of the pancreas and proximal intestine but not the wet weight of the stomach. Food restriction also decreased the chymotrypsin content of the pancreas but not its amylase content. The contents of enzymes in the pancreas were not affected by exercise. The insulin content of the pancreas was lower in lean rats produced by food restriction and/or exercise than in controls. Exercise increased the wet weight of the proximal intestine and the CCK content of the intestine. The increase in the CCK content may be due to compensational change in the efficiency of digestion of luminal nutrients induced by exercise.

Nutritional status of some Papua New Guinea highlanders as assessed by physical measurements and blood analysis

Nutritional assessment (measurements of height, body weight, skinfold thickness, blood pressure and blood analysis) was performed on 740 residents over 5 years of age in a mountainous village in Papua New Guinea. The subjects live on sweet potato as their staple food and have little salt in their diet. In spite of their low protein intake, they did not suffer from malnutrition. Their total serum protein was high, but the serum albumin level was low. The serum total cholesterol was very low, ranging from 98 to 126 mg/100ml and remained unchanged regardless of age and sex. The same tendency was found with serum high density lipoprotein cholesterol, which ranged from 26 to 33 mg/100ml. Blood pressure did not vary with sex or age.

Disappearance of diurnal rhythm of energy expenditure in genetically diabetic obese rats

The daily profile of energy expenditures was examined in the new animal model of genetically diabetic obese rats. The diurnal rhythm was observed at 8 weeks of age, with highest and lowest values for energy consumption per hour observed in the dark and light periods, respectively. However, at 24 weeks of age after the manifestation of noninsulin-dependent diabetes mellitus, the rhythm completely disappeared, but it did not in the control rats.