Biomedical subjects

Y Hitier

Publications and source records attributed to Y Hitier.

At least 19 recordsLinked to original sources

PubMed1992

Hypoglycemic effects of a beta-agonist, Ro 16-8714, in streptozotocin-diabetic rats: decreased hepatic glucose production and increased glucose utilization in oxidative muscles.

Streptozotocin (STZ)-induced diabetic rats are glycosuric, hyperglycemic, hyperketonemic, overproduce glucose, and have a decreased glucose utilization in oxidative muscles. Treatment with a beta-agonist, Ro 16-8714, decreases the glycosuria, hyperglycemia, hyperketonemia, and hepatic glucose production. Tissue glucose utilization was unchanged, except in oxidative muscles, where it was increased.

2-Hydroxyphenethylamine↗

PubMed1990

Lipogenic enzyme activities and mRNA in rat adipose tissue at weaning.

The activities and mRNA concentrations of two lipogenic enzymes, fatty acid synthetase and acetyl-CoA carboxylase, and one enzyme involved in glyceroneogenesis, phosphoenolpyruvate carboxykinase (PEPCK), were measured in rat white adipose tissue during the suckling-weaning transition. Activities and mRNA concentrations of lipogenic enzymes were low in suckling rats, whereas activity and mRNA concentration of PEPCK were high. At weaning to a high-carbohydrate diet, the rapid increase in lipogenic enzymes mRNA (10- to 20-fold) and decrease in PEPCK mRNA (10-fold) were followed by parallel changes in enzyme activities. In contrast, weaning to a high-fat diet prevented these modifications. Force feeding suckling rats with carbohydrates induced a rise in blood glucose and plasma insulin concentrations. During these experiments, mRNA concentrations increased 10- to 20-fold for lipogenic enzymes and decreased 5-fold for PEPCK in less than 6 h, whereas all enzyme activities did not vary. This suggests a pretranslational regulation of gene expression. Force feeding suckling rats with a mixture of fat devoid of carbohydrate induced a slight increase in plasma insulin concentration and a fall in PEPCK mRNA but was not accompanied by a rise in lipogenic enzyme mRNAs. This suggested that insulin is a prime regulator of PEPCK gene expression, whereas glucose and insulin act synergistically in the regulation of lipogenic enzyme gene expression.

Acetyl-CoA Carboxylase↗

PubMed1989

Hypoglycaemic effect of metformin in genetically obese (fa/fa) rats results from an increased utilization of blood glucose by intestine.

The insulin-resistant obese fa/fa rat is a convenient model in which to study a potential effect of metformin, a biguanide used in the treatment of non-insulin-dependent diabetes, on insulin-mediated glucose utilization. Female fa/fa rats were given metformin orally for 8 days. Studies were performed on anaesthetized post-absorptive rats 5 h after the last dose of metformin. Glucose production and utilization were enhanced 1.5-fold in metformin-treated rats. The enhanced glucose production was almost entirely due to increased glucose recycling. The digestive tract was the only tissue responsible for the enhanced glucose utilization.

Animals↗

PubMed1987

Lipoprotein lipase activity in skeletal muscle and brown adipose tissue of pregnant and lactating rats.

Changes in lipoprotein lipase (LPL) activity during pregnancy and lactation were followed in skeletal muscles and interscapular brown adipose tissue (BAT) of rats fed two diets differing in energy density (high carbohydrate or high fat). Rats were decapitated after 7, 19 or 21 d of pregnancy or after 3 or 12 d of lactation. Virgin rats and females separated from their litter just after delivery were used as nonpregnant and nonlactating controls, respectively. Blood was collected for determination of plasma glucose, triglycerides (TG) and nonesterified fatty acids (NEFA). Soleus, extensor digitorum longus (EDL), diaphragm and interscapular BAT were rapidly removed and frozen in liquid nitrogen for LPL activity measurement. LPL activity was not significantly higher in muscles and BAT of virgin rats fed the high fat diet than in those of rats fed the high carbohydrate diet. No significant change of skeletal muscle LPL activity was observed during pregnancy, regardless of the diet fed. Although BAT exhibited a transitory hypertrophy during pregnancy, its LPL activity was not significantly altered; during lactation BAT lost weight and its LPL activity dropped sharply when either diet was fed, leaving more TG available for milk production.

Adipose Tissue, Brown↗

PubMed1986

Urea concentration and ornithine decarboxylase in liver of female rats.

In virgin female rats thioacetamide administration (1 mg/100 g body wt) induced a 16-fold increase in liver ornithine decarboxylase (ODC) activity and a significant decrease (19%) in hepatic urea concentration. The ornithine-metabolizing enzymes, ornithine-oxo-acid aminotransferase and ornithine carbamoyltransferase, were not modified by the treatment; only carbamoyltransferase, were not modified by the treatment; only carbamoyl-phosphate synthetase I activity was significantly reduced. In 19-day pregnant rats DL-alpha-difluoromethylornithine treatment inhibited the expression of enhanced ODC activity occurring normally at this stage of pregnancy. Concomitantly an inhibition of the usual decrease in hepatic urea was observed. This increase of ureagenesis occurred without any increase in liver N-acetylglutamate or ornithine concentrations, which remained as low as in normal pregnant rats.

Animals↗

PubMed1985

[Effect of a hyperlipidic diet on lipogenesis, storage and utilization of lipids in the pregnant rat].

The aim of the present investigation was to determine the amount of fat accumulated and mobilized during pregnancy in rats fed either an hyperglucidic or an hyperlipidic diet. The feeding of an hyperlipidic diet increased the liver lipid content and did not modify the composition of the mammary gland. Fat was deposited till day 19 of pregnancy; after that date the fat was mobilized. The increase and decrease of fat stores were independent of the diet consumed. Both were correlated with body changes so that the same linear relationship between the lipid content of the carcass and maternal body weight was observed at all stages of pregnancy.

Animals↗

PubMed1983

Activity of several enzymes of amino acid catabolism in the liver of rats fed protein as a meal.

Rats having a protein-free diet available ad libitum were fed a daily casein meal at the beginning of either the light- or the dark-phase of the day. A control group received a mixed-diet ad libitum. In all three groups, daily food ingestion was the same and casein corresponded to 12% of total intake. Liver activities of alanine, aspartate, ornithine and tyrosine aminotransferase, ornithine decarboxylase and serine dehydratase were assessed. In mixed-fed controls, all activities were low. Tyrosine aminotransferase and ornithine decarboxylase exhibited clear circadian rhythms of low amplitude. Feeding casein as a concentrated meal had no effect on aspartate aminotransferase. It depressed alanine aminotransferase and serine dehydratase activities. Tyrosine aminotransferase and ornithine decarboxylase exhibited rapid and strong stimulatory responses but, within 12 hours, returned to levels similar to those observed in mixed-fed controls. Ornithine aminotransferase was increased in the group receiving the casein meal during the light phase. It is concluded that the capacity for amino acid catabolism remains low in separately-fed animals, and that only tyrosine and especially ornithine, which may become limiting for urea synthesis, are actively metabolized. Thus, when high fluxes of amino acids reach the liver following the absorption of the casein meal, more amino acids are available for incorporation into newly synthesized proteins.

Amino Acids↗

PubMed1983

Liver ornithine decarboxylase in pregnant rats fed two levels of casein.

Liver ornithine decarboxylase (ODC) and tyrosine aminotransferase (TAT) activities were assessed at 2200 h (prandial phase) and at 1000 h (postprandial phase) in virgin and in pregnant (day 13-20) rats fed on different levels of casein and carbohydrate. In virgin rats, ODC levels were higher at 2200 h after resumption of eating than at 1000 hours, the inductive effect being greater with the high-casein than with the low-casein diet. Rapid deinduction followed termination of eating, resulting in equally low enzyme levels at 1000 h with both diets. On the contrary, prandial and postprandial levels of TAT were always greater with the high-protein diet. In pregnant rats, there was a progressive stimulation of ODC that reached a maximum on day 19. However, the inductive capacity of the high-protein diet was lower than that of the low-casein diet. Prandial rest was not followed by enzyme deinduction at 1000 h. In contrast, TAT stimulation remained dependent on overall casein ingestion. At constant casein but restricted carbohydrate intake, pregnant females exhibited a reduction in ODC stimulation. Thus, whereas in virgin females proteins are determinant in the regulation of ODC, during pregnancy there determinant in the regulation of ODC, during pregnancy there is a shift toward modulation by carbohydrates. Levels of liver urea and ornithine were found to vary in inverse proportion with the magnitude of ODC stimulation.

Animals↗

PubMed1982

Circadian feeding pattern in pregnant rats fed three levels of protein.

Food intake was measured at regular intervals over 24 h in pregnant and non-pregnant female rats fed diets of different protein content: 10, 16 and 32%. During the course of pregnancy, a first period of hyperphagia was observed (days 2-12) irrespective of the composition of the diet. A second phase of hyperphagia occurred later (days 16-19) which was more marked with the better balanced diet (16% protein). During the first half of pregnancy, the increase in intake occurred principally at the beginning of the night (compensatory reaction). Later on, the stimulation extended to the last part of the night (anticipatory reaction). The nocturnal predominance of feeding activity was maintained in pregnant females in spite of their increased metabolic requirements.

Animals↗

PubMed1980

Methionine synthesis, aminoimidazole carboxamide excretion and folate levels in pregnant rats.

The capacity for tetrahydrofolate regeneration through folate-linked methionine synthesis and for purine-ring closure through formylation of aminoimidazole carboxamide ribotide was studied in pregnant female rats fed diets containing either methionine or homocystine with or without folic acid. Plasma and liver folates, serine transhydroxymethylase, 5,10-methylene tetrahydrofolate dehydrogenase and glutamate formiminotransferase activities were also assayed. Pregnancy proceeded normally in all groups. Hypotrophic fetuses were observed only with the diet containing homocystine and no folic acid. Plasma folates were severely depleted at the end of pregnancy even when folic acid was present in the diet. Hepatic stores of folate were twice as high in the methionine as in the homocystine-fed pregnant females supplemented with folic acid. This favorable effect of methionine was not observed in folic acid-deficient females. No change in levels of serine transhydroxymethylase, 5,10-methylenetetrahydrofolate dehydrogenase, glutamate formimino-transferase activities was observed. Pregnancy did not stimulate methionine synthetase activity, the level of which was primarily affected by the nutritional conditions. Because of its low output and narrow range of adaptativity, methionine synthetase cannot be the sole regulatory factor of THF regeneration. Urinary excretion of aminoimidazole carboxamide was enhanced in folic acid-deficient pregnant females and was not prevented by supplying methionine.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1980

Possible metabolic implications of pyruvate and lactate accumulation in the liver of pregnant rats.

Experiments were designed to investigate whether the metabolic responses of pregnant females are in keeping with the known state of gestational hyperinsulinemia. Groups of female rats fed a 32% protein diet were killed on days 13, 15, 17, 19 and 21 of pregnancy, during either daytime or during night-time. Liver pyruvate kinase and glucose-6-phosphate dehydrogenase activities were increased over nonpregnant values from day 13 onward in agreement with what can be expected as a result of the gestational hyperinsulinemia. Liver malate dehydrogenase (NADP) activity was increased to lesser extent and later. Pyruvate and lactate accumulated in maternal liver from day 13 onward. The fact that this accumulation could not be related to any further increase of food intake during this time and that it correlated at day 21 with litter size was taken as indication of a probable contribution of the conceptus to maternal pyruvate and lactate accumulation in late pregnancy. Liver alanine amino-transferase activity decreased as pregnancy progressed. No change in serine dehydratase activity was found. Cytosolic aspartate aminotransferase activity remained unchanged. Mitochondrial activity increased as pregnancy progressed.

Alanine Transaminase↗

PubMed1979

[Effects of ingestion of an antioxidant, BHT, on the metabolism of ascorbic acid and vitamin A in rats].

The antioxidant foor additive, BHT, was fed to male rat for 28 days at a 0.5% concentration in a diet containing ascorbic acid or not. BHT intake had no effect on ascorbic and dehydroascorbic acid contents in the adrenals, spleen or liver, whether or not the diet contained ascorbic acid. When the ration included 100 mg/kg of ascorbic acid, BHT intake caused a sharp rise in urinary excretion of this compound. This data confirm the work of other authors studying an ascorbic acid-poor diet. These results indicate that BHT intake leads to increased synthesis of ascorbic acid. This augmentation would be the result of stimulating the biosynthesis pathway of uridyl-di-phospho-glucuronic acid, which is necessary to the elimination of BHT in the form of glucuroconjugate. BHT intake in an ascorbic acid-rich diet reduces hepatic vitamin A concentration by 44 p. 100 and the hepatic reserve of this vitamin by 22 p. 100. BHT detoxication, as that of other exogenous compounds, thus seems to cause increased vitamin A utilization.

Adrenal Glands↗

PubMed1976