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Biomedical subjects

M Goubern

Publications and source records attributed to M Goubern.

At least 37 records · Page 2Linked to original sources
PubMed1988

Concomitant food intake and adipose tissue responses under chronic insulin infusion in rats.

Body weight (BW), food intake (FI), and activity of white adipose tissue (WAT) and brown adipose tissue (BAT) were studied in adult male rats under chronic insulin infusion. Insulin was infused for 4, 7 or 10 days via implanted minipumps. Insulin-treated rats gained more BW than control rats until 7th day of infusion. At 10 days, the difference in BW decreased. The average cumulative FI was significantly higher after 4, 7 and 10 days of insulin infusion. Feed efficiency (FE) was increased in insulin-treated rats after 4 and 7 days. An increase in WAT weight was observed in insulin-treated rats together with an increased activity of lipogenic enzymes. BAT weight was augmented after 4 days of insulin infusion. This was due mainly to lipid accumulation. Specific mitochondrial guanosine diphosphate (GDP) binding was significantly decreased by 58% in insulin-treated rats after 4 days of infusion. This reduced thermogenic activity, along with the increased FI and FE were responsible for the rapid BW gain observed during the first 7 days of insulin infusion.

Adipose Tissue↗
PubMed1988

Thermogenesis and brown adipose tissue activity in high fat fed Osborne-Mendel rats.

The consequences of hyperlipidic feeding on interscapular brown adipose tissue (IBAT) activity were examined in the cold-acclimated rat. Male Osborne-Mendel rats (7 weeks old) were exposed for 10 weeks at either 28 or 5 degrees C. The rats were fed a semipurified diet (normal fat (NL): 5% lard; high fat (HL): 54% lard) for the last 9 weeks. IBAT weight was greater in HL than in NL rats. This increase was entirely due to accumulation of neutral lipids. Among different IBAT components (proteins, DNA, phospholipids) no variations were observed in HL 28 degrees C rats. HL diet did not modify lipoprotein lipase and cytochrome oxidase activities, but an increase in purine nucleotide binding (taken as an index of thermogenic activity) was observed in HL 28 degrees C rats. Cold acclimation led to comparable stimulation in NL and HL rats. The calorigenic effect of norepinephrine in vivo was not modified by HL diet. Study of arteriovenous differences showed that IBAT fatty acid and glycerol release by norepinephrine was slightly increased in HL 28 degrees C rats. No effect of HL diet was observed at 5 degrees C. These results indicate that HL feeding leads to a moderate increase in the IBAT thermogenic capacity of Osborne-Mendel rats. HL diet does not modify the normal development of nonshivering thermogenesis when rats are kept in a cold environment.

Adaptation, Biological↗
PubMed1988

Effect of environmental temperature on dietary obesity in Osborne-Mendel rats.

The effects of cold acclimation on cellularity, lipoprotein lipase (LPL) activity and lipolysis were studied in white adipose tissue of rats fed a high fat diet. Male Osborne-Mendel rats (7 weeks old) were exposed at either 28 or 5 degrees C for 10 weeks. The rats were fed a semipurified diet (normal fat (NL): 5% lard, high fat (HL): 54% lard) for the last 9 weeks. Caloric intake with NL and HL diets were comparable and cold exposure led to the same increase with both diets. At 28 degrees C, HL diet initiated both hypertrophy and hyperplasia; however, at 5 degrees C only hyperplasia was observed. Total LPL activity showed high stimulation both in 28 and 5 degrees C HL rats. In vitro lipolytic stimulation by norepinephrine was lowered at 5 degrees C and abolished at 28 degrees C in HL-fed rats. HL diet resulted in enhanced lipid deposition without an increase in caloric intake. Even in cold-adapted Osborne-Mendel rats a relative obesity could be produced by a HL diet.

Adaptation, Biological↗
PubMed1986

Modulation of fatty acid synthesis in vivo in brown adipose tissue, liver and white adipose tissue of cold-acclimated rats.

The present experiment was an appraisal of the relative importance of fatty acid synthesis in brown adipose tissue (BAT) in young 28 or 5 degrees C adapted rats (9 weeks old). With a low-fat diet in vivo incorporation of 3H2O into BAT fatty acids was 8 times lower during the day than during the night and was not modified by a 6-hour fast during the day (28 degrees C). Cold acclimation doubled (night) or increased 8 times (day) BAT lipogenesis. Fasting led to a halving of the diurnal rate. A high-fat diet led to large decrease in synthesis rate during the night but had a weak effect on diurnal synthesis. The specific activity of fatty acids was 3 times lower in phospholipids than in neutral lipids. A comparison between 9- and 15-week-old rats indicated that in older warm-adapted rats BAT lipogenesis decreased by half but that cold stimulation was unaltered. These results were compared with hepatic and epididymal white adipose tissue lipogenesis. In conclusion, we showed that BAT of 5 degrees C rats is an important but not the major site for the conversion of carbohydrate to fat and that the proportional involvement of each tissue is age-dependent.

Acclimatization↗
PubMed1985

Effect of temperature on lipoprotein lipase and lipogenic enzyme activities in brown adipose tissue of hypophysectomized rats.

It has been shown that the same modifications on the composition of brown adipose tissue (BAT) which are normally induced following cold stimulation are also observed in hypophysectomized rats acclimated either at 28 degrees C or 15 degrees C. To test the possibility of BAT stimulation in hypophysectomized rats, we have determined some enzymatic activities known to modulate the energy supply to that organ. Seven week old Long-Evans rats were hypophysectomized. Three weeks later, they were exposed to either 28 degrees C or 15 degrees C ambient temperature for five or six weeks. Hypophysectomized rats were compared to age matched or weight matched controls. Total lipoprotein lipase activity (LPL) (triglyceride uptake) was enhanced in BAT of 28 degrees C hypophysectomized rats compared to controls. Cold acclimation led to a large increased activity. Total LPL activity was comparable in BAT of hypophysectomized and control rats. Total malic enzyme and glucose-6-phosphate dehydrogenase activities (in situ lipogenesis) were doubled in BAT of 28 degrees C hypophysectomized compared to controls. A large enhancement was observed in BAT of either 15 degrees C control or 15 degrees C hypophysectomized rats. Among the studied organs (liver, white adipose tissue, heart, BAT) hypophysectomy promotes the three enzyme activities only in BAT. These variations were discussed with relation to the effect of hypophysectomy on brown adipose tissue at 15 degrees C and 28 degrees C.

Adipose Tissue↗
PubMed1983

Ketone bodies in cold-acclimated rats.

Acclimation temperature (28 or 5 degrees C) modifies acetoacetate (AA) and beta-hydroxybutyrate (BOH) levels in blood and liver. In the fed state AA and BOH levels were increased in blood and liver of 5 degrees C adapted rats. In the fasting state (24 or 48 hr) an antiketotic action of cold acclimation was observed. It was found to be more pronounced with high fat diet. These effects were more marked in the blood than in the liver. The variations in ketonemia are discussed with relation to the role of liver in cold adapted rats.

3-Hydroxybutyric Acid↗
PubMed1981

Circadian rhythm and hormonal sensitivity of lipoprotein lipase activity in cold acclimated rats.

To delineate the factors that may affect triglyceride capture in brown adipose tissue, we have determined the lipoprotein lipase activity (LPS) under conditions known to modulate this activity in other tissues. Acclimation temperature (28 degree C or 5 degree C) had no effect on circadian variations of white adipose tissue and heart LPL activity, LPL activity in brown adipose tissue of 28 degree C rats was similar to that in white adipose tissue (peak activity between 21:00 and 07:00 h), whereas LPL activity of the former was four times higher in 5 degree C rats and rhythmicity was altered (peak activity at 17:00 h as for heart). Brown adipose tissue LPL activity was increased in 28 degree C rats but not in 5 degree C rats after a single injection of insulin to fasting animals. A single injection of dexamethasone increased brown adipose tissue LPL activity only in 5 degree C rats, whereas enzyme activity was increased in both 28 degree C and 5 degree C rats by a single injection of norepinephrine to fed animals. These variations were discussed with relation to the role of brown adipose tissue at 5 degrees C and 28 degrees C.

Acclimatization↗
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↗
PubMed1978

Effects of diets and cold acclimation on lipoprotein lipase activity and cyclic nucleotide levels in some tissues of rats.

In view to study a possible regulation of lipoprotein lipase (LPL) activity by tissue cyclic nucleotide levels (cAMP and cGMP), parallel determinations of the three factors were performed on brown adipose tissue (BAT), epidymal fat (WAT) and heart of rats. Opposite variations of cAMP levels and LPL activity were only observed in WAT following high fat diet administration. The enhancement of LPL activity in BAT and in heart by cold acclimation or feeding an hyperlipidic diet was never associated with a decrease in cAMP content. The variations of cAMP and cGMP levels were not dependent. It is concluded that there is no effect of cyclic nucleotide levels in the enhancement of LPL activity in these tissues.

Acclimatization↗
PubMed1976

[Metabolism of nucleic acids in testicles of adult rats deficient in vitamin A].

Avitaminosis A, applied on deficient rats receiving retinoic acid leads to an important decrease of thymidine incorporation in testicular DNA in vivo as well as in vitro. On the contrary uridine incorporation in RNA is considerably increased in vitro as well as in vivo. The function of ribosomes, as measured by the aggregation ability in the polysomes, is not altered by vitamin A deficiency. From these results one can say that the degenerescence of rat testicle is accompagnied by a decrease of DNA anabolism and a stimulation of RNA anabolism due to an increase of its catabolism (compensatory synthesis).

Animals↗
PubMed1976

[Biochemical aspects of testicular degeneration in the vitamin A deficient rat. 4. Permeability of the vascular walls].

Vitamin A deficiency modifies Na and K concentration values in oedematous testes. On one hand there is an increase of Na, on the other hand a decrease of K. Subcellular protein concentrations are impaired. Testicular fluid electrophoresis show it gets from plasma or lymph. No significant influence of ATPase (Na,+ K+) was demonstrable. Stimulation of lysosomal beta-glucuronidase can explain this fluid accumulation.

Adenosine Triphosphatases↗