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E Debras

Publications and source records attributed to E Debras.

13 recordsLinked to original sources
PubMed1998

Acute hyperinsulinemia fails to change GLUT-4 content in crude membranes from goat skeletal muscles and adipose tissue.

The effect of insulin on GLUT-4 protein level in samples of adipose tissue and skeletal muscles from goats was studied in vivo using an euglycemic hyperinsulinemic clamp. The clamp was maintained in conscious goats for 6 h in the presence of amino acids to prevent insulin-induced hypoaminoacidemia. GLUT-4 protein was assessed in crude membrane preparations from adipose tissue and four skeletal muscles (longissimus dorsi, tensor fasciae latae, anconeus and diaphragm) by Western blot analysis. No changes of GLUT-4 protein content were detected after 6 h of hyperinsulinemia in either adipose tissue or skeletal muscles from goats. These results suggest that insulin is not the prime factor involved in the short-term regulation of GLUT-4 protein transporter content in insulin-sensitive tissues from goats.

Acute Disease↗
PubMed1998

Effect of glucocorticoid excess on skeletal muscle and heart protein synthesis in adult and old rats.

This study was carried out to analyse glucocorticoid-induced muscle wasting and subsequent recovery in adult (6-8 months) and old (18-24 months) rats because the increased incidence of various disease states results in hypersecretion of glucocorticoids in ageing. Adult and old rats received dexamethasone in their drinking water for 5 or 6 d and were then allowed to recover for 3 or 7 d. As dexamethasone decreased food intake, all groups were pair-fed to dexamethasone-treated old rats (i.e. the group that had the lowest food intake). At the end of the treatment, adult and old rats showed significant increases in blood glucose and plasma insulin concentrations. This increase disappeared during the recovery period. Protein synthesis of different muscles was assessed in vivo by a flooding dose of [13C]valine injected subcutaneously 50 min before slaughter. Dexamethasone induced a significant decrease in protein synthesis in fast-twitch glycolytic and oxidative glycolytic muscles (gastrocnemius, tibialis anterior, extensor digitorum longus). The treatment affected mostly ribosomal efficiency. Adult dexamethasone-treated rats showed an increase in protein synthesis compared with their pair-fed controls during the recovery period whereas old rats did not. Dexamethasone also significantly decreased protein synthesis in the predominantly oxidative soleus muscle but only in old rats, and increased protein synthesis in the heart of adult but not of old rats. Thus, in skeletal muscle, the catabolic effect of dexamethasone is maintained or amplified during ageing whereas the anabolic effect in heart is depressed. These results are consistent with muscle atrophy occurring with ageing.

Age Factors↗
PubMed1998

Glucocorticoid effects on insulin- and IGF-I-regulated muscle protein metabolism during aging.

This study was performed to assess the effect of glucocorticoids (dexamethasone) on insulin- and IGF-I-regulated muscle protein metabolism in adult and old rats. Muscle atrophy occurred more rapidly in old rats, and recovery of muscle mass was impaired when compared with adults. Muscle wasting resulted mainly from increased protein breakdown in adult rat but from depressed protein synthesis in the aged animal. Glucocorticoid treatment significantly decreased the stimulatory effect of insulin and IGF-I on muscle protein synthesis in adult rats by 25.9 and 58.1% respectively. In old rats, this effect was even greater, being 49.3 and 100% respectively. With regard to muscle proteolysis, glucocorticoids blunted the anti-proteolytic action of insulin and IGF-I in both age groups. During the recovery period, adult rats reversed the glucocorticoid-induced resistance of muscle protein metabolism within 3 days, at which time old rats still exhibited the decrease in insulin-regulated proteolysis. In conclusion, the higher sensitivity of old rat muscle to glucocorticoids may in part result from the greater modification of the effects of insulin and IGF-I on muscle protein metabolism. These responses to glucocorticoids in old rats may be associated with the emergence of muscle atrophy with advancing age.

Aging↗
PubMed1996

Euglycemic hyperinsulinemia and hyperaminoacidemia decrease skeletal muscle ubiquitin mRNA in goats.

Insulin inhibits protein breakdown at the whole body level, but neither the tissues nor the proteolytic pathways on which insulin exerts its antiproteolytic effect are well characterized. We measured the effects of insulin on mRNA levels for cathepsin D and m-calpain (a lysosomal and Ca2(+)-dependent proteinase, respectively) and ubiquitin (a component of ubiquitin-dependent proteolysis) in skeletal muscle, skin, liver, and intestine. We used a 6-h hyperinsulinemic, euglycemic, and hyperaminoacidemic clamp in goats, a species in which insulin markedly inhibited whole body protein breakdown under similar conditions [S. Tesseraud, J. Grizard, E. Debras, I. Papet, Y. Bonnet, G. Bayle, and C. Champredon. Am. J. Physiol. 265 (Endocrinol. Metab. 28): E402-E413, 1993]. Hyperinsulinemia and hyperaminoacidemia had no effect on cathepsin D, m-calpain, and ubiquitin mRNA levels in liver, skin, and jejunum. In contrast, depressed ubiquitin mRNA levels were seen in skeletal muscle without any concomitant reduction in mRNA levels for cathepsin D, m-calpain, and other components of the ubiquitin-dependent proteolytic pathway. The reduced ubiquitin mRNA levels in skeletal muscle may represent a possible mechanism explaining the antiproteolytic effect of insulin in vivo.

Animals↗
PubMed1994

Effect of hyperinsulinemia and hyperaminoacidemia on muscle and liver protein synthesis in lactating goats.

The experiment was carried out to clarify the roles of insulin and amino acids on protein synthesis in fed lactating goats (30 days postpartum). Protein synthesis in the liver and various skeletal muscles was assessed after an intravenous injection of a large dose of unlabeled valine containing a tracer dose of L-[2,3,4-3H]valine. The animals were divided into three groups. Group I was infused with insulin (1.7 mumol/min) for 2.5 h under glucose, potassium, and amino acid replacement. Group A was infused with an amino acid mixture to create stable hyperaminoacidemia for 2.5 h. Group C animals were controls. The fractional synthesis rates (FSR) were 31.5 +/- 2.2, 6.5 +/- 0.4, 4.3 +/- 0.8, 4.0 +/- 1.2, 3.9 +/- 1.2, and 3.6 +/- 0.4%/day (SD) in liver, masseter, diaphragm, anconeus, semitendinosus, and longissimus dorsi, respectively, for group C. Neither hyperinsulinemia in group I nor hyperaminoacidemia in group A had not affected by hyperinsulinemia but was stimulated by hyperaminoacidemia (+30%, P < 0.05). In contrast to previous experiments in which a labeled amino acid was constantly infused, this study revealed a stimulating effect of amino acids on protein synthesis in the liver but not in skeletal muscles. As previously observed in studies with the constant-infusion method, insulin had no effect on protein synthesis.

Amino Acids↗
PubMed1993

Leucine metabolism in lactating and dry goats: effect of insulin and substrate availability.

Early lactating goats show insulin resistance with respect to extramammary glucose utilization. However, much less is known about the two major factors, insulin and plasma amino acid concentration, that regulate protein metabolism in lactating goats. To examine this question, the in vivo effect of acute insulin was studied in goats during early lactation (12-31 days postpartum), midlactation (98-143 days postpartum), and the dry period (approximately 1 yr postpartum). Insulin was infused (at 0.36 or 1.79 nmol/min) under euglycemic and eukaliemic clamps. In addition, appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidemia or to create hyperaminoacidemia and maintain this condition under insulin treatment. Leucine kinetics were assessed using a primed continuous infusion of L-[1-14C]-leucine, which started 2.5 h before insulin. In all animals the insulin treatments failed to stimulate the nonoxidative leucine disposal (an estimate of whole body protein synthesis) under both euaminoacidemic and hyperaminoacidemic conditions. Thus, in goat as well as humans, infusion of insulin fails to stimulate protein synthesis even when combined with a substantially increased provision of amino acids. In contrast, insulin treatments caused a dose-dependent inhibition of the endogenous leucine appearance (an estimate of whole body protein degradation). Under euaminoacidemia the initial slope from the plot of the endogenous leucine appearance as a function of plasma insulin (an insulin sensitivity index) was steeper during early lactation than when compared with the dry period. A similar trend occurred during midlactation but not to any significant degree. These differences were abolished under hyperaminoacidemia. It was concluded that the ability of physiological insulin to inhibit protein degradation was improved during lactation, demonstrating a clear-cut dissociation between the effects of insulin on protein and glucose metabolism. This adaptation no doubt may provide a mechanism to save body protein.

Amino Acids↗
PubMed1992

Effect of insulin in conjunction with glucose, amino acids and potassium on net metabolism of glucose and amino acids in the goat mammary gland.

The hyperinsulinaemic euglycaemic insulin clamp technique was used to study the effect of insulin on the arterio-venous concentration differences of glucose and amino acids across the mammary gland in dairy goats. Insulin was given in conjunction with K to prevent insulin hypokalaemia. Appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidaemia or to create hyperaminoacidaemia and maintain this state under insulin treatment. Hyperaminoacidaemia alone only stimulated mammary leucine uptake but did not significantly modify the net metabolism of other amino acids and glucose. Insulin infusion at physiological level in conjunction with glucose, KCl-NaCl and amino acids failed to alter mammary uptake of glucose and essential amino acids; occasional increase in arginine extraction and decrease in tyrosine extraction were exceptions. Thus these new experimental conditions did not reveal any galactopoietic effect of insulin.

Amino Acids↗
PubMed1990

Methionine flux and tissue protein synthesis in lactating and dry goats.

Whole-body methionine flux (rate of irreversible loss from plasma) and tissue protein synthesis were estimated in dry and early lactating goats (10-14 d postpartum) by intravenous infusion of L-[35S]methionine. Tissue protein mass was significantly (p less than 0.05) higher for mammary gland and liver but lower for carcass in lactating animals. The plasma methionine flux was higher during lactation (8.5 vs. 5.1 g/d). The fractional synthesis rates of tissue proteins (Ksp: %/d) were lower during lactation for some muscles, especially the masseter muscle (1.46 vs. 2.15), and for skin (0.59 vs. 1.22) and the pooled head plus feet fraction (1.64 vs. 2.31), but the rates were greatly increased in mammary gland (42 vs. 3). The non-mammary methionine flux (plasma flux minus the flux corresponding to milk methionine output and methionine utilization for mammary protein synthesis) was significantly (p less than 0.05) lower for the lactating goats than for the dry group (93 vs. 131 mg.d-1.kg empty body weight-1). This is in agreement with the lower rates of protein synthesis in carcass (542 vs. 948 mg.d-1.kg empty body weight-1) and skin (93 vs. 189) for lactating compared to dry goats. It can be inferred from these data that in early lactation, when nutrient requirements of animals are not adequately met, an adaptative mechanism occurs that allows amino acids to be available for the mammary gland by a decrease of their utilization in some extramammary tissues.

Animals↗
PubMed1989

Insulin sensitivity and responsiveness during lactation and dry period in goats.

To investigate the role of insulin in partitioning nutrients between the mammary gland and other tissues during lactation in ruminants, euglycemic-hyperinsulinemic clamps were performed in goats during early lactation (15-26 days postpartum), midlactation (78-91 days postpartum), and dry period (169-194 days postpartum). Insulin was infused at 0.4, 0.7, 1.9, 4.4, and 10 micrograms/min. Basal plasma glucose was constant during all periods despite the fact that basal glucose utilization was approximately 3 times higher during lactation than dry period. Basal plasma insulin was similar during early lactation and dry period but increased during midlactation. Insulin infusion resulted in a dose-dependent stimulation of glucose utilization. The insulin-stimulated glucose utilization above basal was greatly impaired during early lactation when compared with dry period, but this only occurred at very high plasma insulin. Insulin infusion also resulted in a decrease in glucose production; the maximal insulin effect is achieved at the lowest insulin infusion rate. The ability of insulin to decrease glucose production was significantly improved during early lactation when compared with dry period. This phenomenon may provide a mechanism to save gluconeogenic substrates during early lactation. In contrast, midlactation did not result in any significant change in insulin action with both glucose utilization and glucose production.

Animals↗
PubMed1988

Metabolism and action of insulin and glucagon in goat during lactating and dry period.

The metabolism and action of insulin and glucagon were investigated in goats during mid lactating (50 days postpartum) and during the dry period. The animals were fed hay and concentrate during lactation (1:1) and only hay during dry period. Pulse doses of unlabelled insulin and glucagon were injected intravenously. The disappearance of insulin from the circulation was faster during lactation than during dry period; the metabolic clearance rate of insulin was significantly increased during lactation. In contrast, the kinetic parameters of glucagon disappearance were very similar during the two periods. Basal plasma hormones (i.e. before hormone injection) were higher during lactation than during dry period; the molar ratio insulin:glucagon was left unchanged. The increase in plasma insulin following glucagon-stimulated hyperglycaemia was similar during the two periods. The ability of insulin to elicit a decrease in blood glucose was markedly impaired during lactation when compared to dry period. In contrast the ability of glucagon to increase blood glucose was slightly improved during lactation. Those endocrine changes could be related to the effect of both lactation and diet.

Amino Acids↗
PubMed1986

[Effects of lactose ingestion on protein metabolism in the newborn lamb].

Whole body and tissue protein turnovers were measured in 6 newborn lambs taken from their mothers immediately after birth. Three lambs (AJ) were hourly fed 50 ml of saline (NaCl 0.9%), and 3 (AL) were fed, on the same schedule, 50 ml of saline with 2.25 g of lactose added. They were continuously infused L-[4,5(3)H]-leucine for 6 h when they were 2 h 30 min old. Plasma glucose and insulin were higher in AL than in AJ lambs. On the contrary, the lowest plasma levels of free threonine, valine, isoleucine, leucine, phenylalanine, lysine, histidine, serine and alanine occurred in the lactose-fed lambs (table 1). The concentrations of most free amino acids in liver, brain, small intestine and muscle (Longissimus dorsi) were not significantly different (fig. 1). The irreversible loss of plasma leucine did not differ (mean +/- SD : 160 +/- 47 and 156 +/- 11 micro moles/h/kg for AL and AJ lambs, respectively). The leucine catabolic rate was higher in AJ than in AL lambs (22.4 +/- 2.8 vs 17.9 +/- 1.7%). The fractional rates of protein synthesis in the liver, small intestine and brain were not significantly different between AL and AJ lambs; these rates were higher in the muscle, lungs and whole body of the AL lambs (table 2).

Amino Acids↗
PubMed1976

[Influence of microflora on the metabolism of L-threonine at the level of the rat digestive tract].

Intestinal tissues are found to incorporate L threonine 14CU at faster rate in the absence of microflora. Most of the radioactivity of the digestive contents occurs in the TCA soluble compounds, except in the coecum and large intestine of the conventional rats where the microflora synthetized its own proteins from the labelled digestive material. Free threonine is the main labelled soluble compound in the conventional rats digestive contents. In the other hand, in the germfree rats digestive contents, radioactivity of the other compounds is found in higher concentration than free threonine.

Animals↗