Helen A. Bertrand

Inhibition of adenine nucleotide translocator by lipid peroxidation products.

Our previous data showed that aldehydic lipid peroxidation products, interacting with mitochondrial membrane lipids, could alter the physicochemical status of the membrane. This study was initiated to examine the interaction of these aldehydes with a major mitochondrial protein, the adenine nucleotide translocator (ANT). Our findings showed that the transporting activity of ANT in intact mitochondria was inhibited by two unsaturated aldehydes, 4-hydroxynonenal (HNE) and 4-hydroxyhexenal (HHE). To probe further into the underlying mechanism of this inhibition, a reconstituted ANT model was developed by incorporating isolated ANT into liposomes. Pretreatment of ANT with HNE prior to reconstitution resulted in decreased activity in the reconstituted ANT. Further investigation revealed that this decreased activity was probably due to loss of sulfhydryl groups, which are essential for ANT activity. Interestingly, pretreatment of the liposomes with HNE also caused a decrease in the reconstituted ANT activity by indirectly altering the physiochemical status of the lipid environment in which ANT was embedded. These results demonstrate that the reactive aldehydes derived from mitochondrial lipid peroxidation can impair the membrane function by interacting with both the protein and the lipid moieties in the membrane. Thus, the varied damaging effects associated with lipid peroxidation may be mediated by their secondary aldehydic byproducts.

Long-term food restriction depresses serum thyroid hormone concentrations in the rat.

Long-term food restriction exerts an anti-aging action in rodents. The mechanism underlying its modulation of aging processes is unknown but changes in endocrine systems have been postulated as couplers of food restriction to aging. The effects of long-term food restriction on the serum concentrations of thyroid hormones were examined in 6-month-old, male Fischer 344 rats. For 4.5 months a Food Restricted group was fed 60% of the amount consumed by an Ad Libitum group. Food restriction did not alter the 24-h mean T4 concentration but reduced the 24-h mean T3 concentration from 95 +/- 1 to 87 +/- 3 ng/dl. The Ad Libitum group exhibited diurnal rhythms in both serum T4 and T3 concentrations, with peak values for each hormone at 1000 h. Although food restriction eliminated the 1000 h peak for both thyroid hormones, it abolished the diurnal variation only for T3. The dietary-induced changes in serum T4 and T3 are consistent with a role for these hormones in the anti-aging action of food restriction.

Age changes in hepatic metabolic characteristics and their modulation by dietary manipulation

Starting at 6 weeks of age, male Fischer 344 rats were provided five different dietary regimens: group 1, fed ad libitum; group 2, restricted to 60% of the food intake of group 1; group 3, restricted to 60% of the food intake of group 1 until 6 months of age and then fed ad libitum; group 4, fed ad libitum until 6 months of age and then restricted to 60% of the food intake of group 1; group 5, given the same caloric intake as group 1 but 60% of the protein intake. The weight of the liver was maintained at about 2.5% of body weight over the wide range of body weight, age (6 through 30 months of age) and diets of this study. Liver cholesterol concentration increased with age in the rats of group 1 but not in the other groups; the hepatic cholesterol concentration was lower in the rats of groups 2 and 4 than in the others. The liver microsomal 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase activity was higher in 4-month-old rats than in rats 12 months of age and older; also, the microsomal activity from group 2 and group 4 rats was higher than that from rats of the other groups. Liver triglyceride levels increased with age in groups 1, 2, 3 and 5 but not in group 4. At all ages, postabsorptive (15 h without food) hepatic glycogen concentrations were much higher in groups 2 and 4 than in the other groups. Liver phospholipid concentration was not affected by age or diet. Basal adenylate cyclase activity in liver homogenates increased with age in all but group 4, but hormone-stimulated adenylate cyclase activity was little affected by age or diet. The age-related hepatic changes in lipids and in hormone responsiveness noted in the present study were much less marked than those previously found in blood and adipose tissue.

Effects of Aloe vera ingestion in the rat. I. Growth, food and fluid intake and serum chemistry

This study was designed to examine the effects of long‐term (1.5 and 5.5 months) Aloe vera (Aloe barbadensis) ingestion on the growth, food intake and serum chemistry of Fischer 344 male rats. Aloe vera powders, produced by two different methods, were mixed with rat chow at selected concentrations. Process A aloe was prepared from skinned aloe filets by homogenization followed by lyophilization and grinding to a fine powder; Process B aloe was prepared similarly except that the homogenate was charcoal filtered prior to lyophilization. Ingestion of Process A aloe at concentrations greater than 1% was associated with diarrhoea and a decrease in weight gain. Ingestion of 1% Process A and both 1% and 10% Process B aloe had no adverse effect on body weight gain, food intake, gastrointestinal transit time and gross pathology. Serum chemistry was minimally affected. The rats ingesting 10% Process B aloe exhibited a slight, but significant increase in fluid intake. The results indicate that, although high concentrations of aloe should be avoided, ingestion of moderate levels (1%) of aloe from either process causes no apparent adverse effects in the rat.

Effects of dietary restriction and exercise on the age-related pathology of the rat.

Intervention of the aging process is an effective, experimental means of uncovering the bases of aging. The most efficacious and commonly used intervention used to retard the aging processes is dietary restriction (DR). It increases mean and maximum life spans, delays the appearance, frequency, and severity of many age-related diseases, and more importantly, attenuates much of the physiological decline associated with age. Although the subject of intense research, the mechanism by which DR alters the aging processes is still unknown. Physical exercise is another effective intervention shown to affect aging phenomena, especially when applied in combination with DR. Mild exercise in concert with DR is beneficial, but vigorous exercise coupled with DR could be deleterious. With regard to pathology, exercise generally exerts a salutary influence on age-related diseases, both neoplastic and non-neoplastic, and this effect may contribute to the increase in median life span seen with exercised rats. Exercise coupled with 40% DR was found to suppress the incidence of fatal neoplastic disease compared to the sedentary DR group. Exercise with mild DR suppressed the incidence of multiple fatal disease and chronic nephropathy, and also delayed the occurrence of many age-related lesions compared to the ad libitum (AL) control group. However, these effects may have little bearing on the aging process per se, as maximum life span is only minimally affected. Although not as intensively studied as DR, results from studies that utilize exercise as a research probe, either alone or in combination with DR, have helped to assess the validity of proposed mechanisms for DR and aging itself. Neither the retardation of growth rate nor the increase in physical activity, observed with either exercise or DR, appear to contribute to the anti-aging action of DR. Moreover, results from lifelong exercise studies indicate that the effects of DR do not depend upon changes in energy availability or metabolic rate. The mechanisms involving effects on adiposity or immune function are also inadequate explanations for the action of DR on aging. Of the proposed mechanisms, only one, as postulated by the Oxidative Stress Hypothesis of Aging, tenably accounts for the known effects of DR and exercise on aging.

Caloric restriction alters arterial blood pressure and baroreflex responsiveness of the spontaneously hypertensive rat

Aging is associated with an increase in blood pressure and the occurrence of hypertension. Caloric restriction retards the aging process, in general, and is a commonly used therapeutic approach to the control of high blood pressure. The aim of this study was to examine the effects of long term caloric restriction on mean arterial blood pressure, heart rate and the baroreflex responsiveness of spontaneously hypertensive (SH) rats. Male, 3-month-old SH rats were allowed to eat ad libitum or were fed only 60% of the ad libitum amount. After 4 months, cannulas were inserted in the left femoral artery and vein under anesthesia. On the following day the blood pressure and heart rate were measured in the conscious rat. The basal mean arterial pressure of the calorie restricted rats (166±4 mm Hg, N=5) was significantly less than that of the ad libitum fed rats (182±4 mm Hg, N=4). The basal heart rates of the calorie restricted and ad libitum fed rats were 296±12 beats/min and 323±8 beats/min, respectively. The difference between the means was not significant (p>0.1). Nitroprusside and phenylephrine infusions were used to induce hypotensive and hypertensive episodes, respectively. For nitroprusside, the relationship between the change in mean arterial pressure and the reflex heart rate response was significantly steeper in the calorie restricted group (1.90±0.37 beats/min/mm Hg) than in the ad libitum fed group (0.86±0.1 beats/min/mm Hg). For phenylephrine the relationships were 0.98±0.09 and 0.52±0.18 beats/min/mm Hg, respectively. These results demonstrate that chronic caloric restriction reduces mean arterial pressure and enhances baroreflex responsiveness in the SH rat.