Biomedical subjects

C Veyrat-Durebex

Publications and source records attributed to C Veyrat-Durebex.

8 recordsLinked to original sources

PubMed2001

Effects of peripheral and central administration of GHRH on feeding in aging LOU rats.

In aging LOU rats, a decreased protein intake is restored by GH administration. To study the contribution of GHRH to macronutrient selection, hGHRH NH(2) was administered sc. (1 mg/kg B.W./day/14 days) or icv. (4 and 40 pmol/rat) to 11-, 19-, 24- and 28-month-old rats. Sc. administration induced a decreased food and lipid intakes from 24 months of age and a transient stimulation of protein intake in 19-month-old and older low protein eaters (<10% protein/total intake). Icv. administration induced decreased food and lipid intakes in all age groups. These results suggest that GHRH may regulate feeding through pituitary and/or hypothalamic GHRH receptor mechanisms.

Animals↗

PubMed2000

Age-related changes in adaptive macronutrient intake in swimming male and female Lou rats.

To evaluate the age-related changes in capacity to adjust the nutrient intake to needs, self-selecting male and female Lou/C/jall rats of 4, 6, 12, 16 and 23 months of age were submitted to a swimming exercise. They were given 6 consecutive days of moderate intensity training (3 x 15 minutes per day). Exercise and postexercise periods were compared with results from the pretraining period. During swimming, a body weight loss and a decrease in both caloric intake and fat selection were observed. This effect was more marked in older groups compared to 4 month-old groups. An increase in protein intake was observed in females, specially in older groups, whereas no effect was seen in males. The ability to increase caloric ingestion and regain weight during the postexercise period decreased with advancing age and was better in females than in males. We also showed an age-related effect on the recovery of initial nutrient intake rate that was more pronounced and more precocious for males. Moreover, males tended to decrease their protein intake, whereas females significantly increased it. The present findings suggest a decrease of capacity of adjusting feeding behavior to metabolic needs in aged rats, may be due to a deterioration of the central control of food intake.

Adaptation, Physiological↗

PubMed2000

Age-related changes in nociception and effect of morphine in the Lou rat.

Little is known about how the ageing process affects pain sensitivity and a relevant animal model is therefore required. The effect of age on pain reactivity in animals has been investigated by several experimenters but the results are conflicting. Four groups of male and female Lou/C/Jall rats (4-29 months old) were used for our study. Four pain tests based on evaluation of reflex or more integrated behaviours after a thermal (tail immersion test) or mechanical (paw pressure test and von Frey test) stimulation were used. With mechanical stimulus, a significant decrease in the pain threshold across age was observed, females were more sensitive than males. This increase in nociceptive sensitivity to mechanical stimulation was more pronounced on integrated behaviours (struggle reaction) than on withdrawal reflex. An age-related increase in sensitivity was found on von Frey test. No effect on the latency of reflex induced by thermal stimulation was observed. In addition, a decrease in the spontaneous motor activity during exploration was observed across ageing; this effect was more marked for the females. The effect of morphine at doses of 1, 3 and 9 mg/kg (s.c.) decreased in intensity across ageing. These data demonstrate the need to use (1) various noxious stimuli because differences were observed in the modification of pain reactivity according to the nature of the stimulus; (2) various pain parameters and particularly integrated behaviours; (3) several age groups. In addition, Lou/C/Jall rat could be a useful model for studying of effect of age on pain.

Aging↗

PubMed1999

Changes in 20S proteasome activity during ageing of the LOU rat.

Muscular functions decline and muscle mass decreases during ageing. In the rat, there is a 27% decrease in muscle protein between 18 and 34 months of age. We examined age-related changes in the proteasome-dependent proteolytic pathway in rats at 4, 18, 24, 29 and 34 months of age. The three best characterised activities of the proteasome (chymotrypsin-like, trypsin-like and peptidylglutamyl peptide hydrolase) increased to 29 months and then decreased in the senescent animal. These variations in activity were accompanied by an identical change in the quantity of 20S proteasome measured by Western blot, whereas the S4 subunit of the 19S regulator and the quantity of ubiquitin-linked proteins remained constant. mRNA of subunits C3, C5, C9, and S4 increased in the senescent animal, but ubiquitin mRNA levels were unchanged. These findings suggest that the 20S proteasome may be partly responsible for the muscular atrophy observed during ageing in the rat.

Aging↗

PubMed1999

Peripheral injection of growth hormone stimulates protein intake in aged male and female Lou rats.

It is well established that growth hormone (GH) induces growth rate and food efficiency and stimulates protein accretion in young mammals. Senescence is characterized by metabolic and hormonal disorders, particularly a decrease in protein turnover, which could be correlated to a decrease in GH and insulin-like growth factor I (IGF-I) secretion. We have shown that body weight, protein intake, and IGF-I plasma levels are greatly decreased with aging in Lou/C rats, particularly in males. In order to specify the GH effect on protein intake during aging, males and females (6, 19, and 24 mo) placed on a self-selection regimen were injected daily with a physiological dose of human GH (0.023 mg/rat sc). No GH effect on caloric intake was observed. Nevertheless, GH treatment stimulated body weight in older rats. It also increased protein intake in females and older males (19-24 mo). This stimulating effect was positively correlated with the degree of weight loss in senescent rats, suggesting that the decrease in protein intake observed with aging could be a marker of senescence.

Aging↗

PubMed1998

Age-related changes in adaptive mechanisms of macronutrient self-selection: evidence for a sexual dimorphism.

The effect of aging on patterns of food intake and nutrient selection was investigated using a longitudinal study. Male (n = 10) and female (n = 10) Wistar-Lou rats from 4 to 28 months of age were repeatedly submitted to a macronutrient self-selection (S-S) regimen while controls were maintained under a standard chow diet (Std). An age-related shift of preferences from CHO to fat diets, and a decrease in protein intake for both males and females were evident. Nevertheless, all these modifications were more pronounced and precocious for males. Physical exercise (45 min/day of swimming, on 6 days) induced a body weight loss and an hypophagia more pronounced for males than for females. S-S regimen results revealed that hypophagia concerned exclusively fat intake and that females significantly increased protein intake during and after the exercise period. Study of longevity curves showed a decrease of the mortality in S-S submitted male rats compared to control rats. This study shows that aging induces a sex-difference in feeding patterns which undoubtedly reveals a sex-difference metabolic requirements. Moreover, these results suggest that allowing rats to select macronutrient intakes could delay the process of senescence.

Adaptation, Physiological↗

PubMed1998

Dietary self-selection can compensate an age-related decrease of rat liver 20 S proteasome activity observed with standard diet.

Aged Lou female rats (33 months) submitted to a self-selection regimen showed a decrease in protein intake (down to 11% of the total intake), whereas mature rats (18 months) selected a high percentage of protein (20% of the total intake) similar to the protein content of the standard diet. To find out if this decrease in protein intake would prevent an observed age-related decrease in proteasome activity, four peptidase activities and oxidized protein degradation were tested with proteasome purified from the liver of 18- and 33-month-old rats. The peptidylglutamyl-peptide hydrolase activity, which is decreased with age for rats fed the standard diet, was restored in the self-selecting old rats to the level observed for the mature rats. Degradation of oxidized glutamine synthetase, which is also decreased with age for rats fed the standard diet, was partly restored. Proteasome from self-selecting old rats showed a slight increase in trypsin-like and chymotrypsin-like activities as compared to proteasome from old rats fed the standard diet. Two-dimensional gel electrophoresis followed by quantitative analysis of the pattern of proteasome subunits revealed an increase in the intensity of two protein spots for proteasome from old rats fed the standard diet as compared with proteasome from either mature rats or self-selecting old rats. These findings may have important implications in aging for proteasome-mediated proteolysis and subsequent accumulation of oxidatively damaged protein.

Aging↗

PubMed1997

Changes in pattern of macronutrient intake during aging in male and female rats.

Transversal and longitudinal studies of the natural patterns of food intake were made in male (n = 65) and female (n = 52) Lou rats, from 4 to 34 months of age. The efficiency of body weight control, especially for females, seems to be a main feature of this strain of rat: these rats are small eaters, have lighter body weight, show no development of obesity with age, and have a longer life expectancy than other common strains of rat. A better adaptation to feeding schedules was shown by female groups throughout the experiments. Moreover, an increased consumption for the oldest animals (from 28 months) enables them to keep their body weight constant up to age 34 months, whereas the male rats gradually lost weight with old age (from 28 months). When male and female rats of different age groups were allowed to choose their diet from pure macronutrient sources (protein, fat, and carbohydrate), an age-related shift of preferences from carbohydrate to fat diets was evidenced during daily energy intake. Protein intake also decreased according to age, earlier for males (around 21 months) than for females (34 months).

Aging↗