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J Grizard

Publications and source records attributed to J Grizard.

At least 55 records · Page 3Linked to original sources
PubMed1992

Insulin receptor binding and kinase activity in liver and skeletal muscles of lactating goats.

Lactation in goats has been shown to modify in vivo insulin action. [Debras, E., J. Grizard, E. Aina, S. Tesseraud, C. Champredon, and M. Arnal. Am. J. Physiol. 256 (Endocrinol. Metab. 19): E295-E302, 1989]. To further elucidate the mechanism of insulin action, we studied insulin binding and insulin receptor tyrosine kinase activity in solubilized and partially purified receptor preparations from liver and skeletal muscles (longissimus dorsi, tensor fascia lata, diaphragm, and masseter) from lactating and nonlactating goats. Lactation did not alter insulin receptors in the various skeletal muscles and had a minor influence on liver receptors (where only a 20% increase in receptor number was visible, P less than 0.05). Insulin-stimulated autophosphorylation and the kinase activity against polyglutamyltyrosine (4:1) were not significantly modified in skeletal muscle receptor preparations from lactating goats when compared with nonlactating animals. They tended to decrease in liver preparations, but not significantly. Thus the changes in insulin action in vivo during lactation in goats were not related to modifications in insulin kinase activity but were probably localized at a postreceptor level.

Animals↗
PubMed1992

Regulation of branched chain amino acid metabolism in ruminants.

The regulation of branched-chain amino acid (BCAA) metabolism has been studied in ruminants mainly during the last decade. Evidences support that the rate of BCAA catabolism is lower in ruminants than in monogastrics. This is associated with a low specific BCAA aminotransferase (first catabolic enzyme) activity and a relatively low degree of activation of the second catabolic enzyme in post-natal ruminant tissues. Similarly to monogastrics in vivo BCAA catabolism involves an interorgan cooperation in ruminants. The benefic effect of leucine excess in protein turnover has also been raised. By contrast leucine excess does not stimulate the rate of isoleucine and valine catabolism in ruminants as much as in monogastrics.

Amino Acids, Branched-Chain↗
PubMed1992

[Metabolic adaptation in hyperthyroidism. Implication of insulin].

Hyperthyroidism is associated with intense metabolic disturbances. Thus, an increase of basal metabolism and thermogenesis is noted. Glucose data include increased muscle utilization and hepatic production. Its oxydative catabolism is enhanced, while its use for glycogen synthesis is reduced. Lipid turnover is also increased. In vivo and in vitro improvement of muscle proteolysis in animals induces a reduction of total body protein content; protein synthesis is also paradoxically stimulated. In contrast, this mechanism remains unproved in man. The role of insulin, whose levels usually increase during glucose tolerance tests, is also studied. Glucose tolerance impairment may be related to lower insulin-inhibited glucose production whereas insulin-stimulated glucose peripheral utilization is unmodified. In man, receptor assays demonstrate reduced amount of binding-sites on various cell, while animals studies lead to contradictory results; thus, receptor studies do not demonstrate any clear mechanism for insulin resistance in hyperthyroidism.

Animals↗
PubMed1991

Insulin-like growth factor I (IGF-I) and insulin binding to erythrocytes of normal prepubertal children and adults.

Erythrocyte insulin-like growth factor I (IGF-I) and insulin receptors were characterized in 10 normal prepubertal children (5 girls and 5 boys) aged 4-11 yrs and 10 normal adults (4 women and 6 men) aged 32-47 yrs. erythrocytes were purified from 5 ml of blood by Ficoll-Paque gradient centrifugation. Reticulocytes count in the erythrocyte suspensions were lower than 1%. Insulin and IGF-I binding assays were performed simultaneously. Maximal percent binding of [125I] labelled IGF-I was significantly higher in prepubertal children than in adults (8.7 +/- 0.7% versus 6.2 +/- 0.5% at a concentration of 5 x 10(9) erythrocytes/ml). Scatchard analysis revealed the high affinity constant was better in prepubertal children (Ka = 4.6 +/- 1.3 nM-1 versus 1.8 +/- 0.2 nM-1), whereas the binding capacity was similar (5.8 +/- 1.1 versus 7.7 +/- 0.8 high affinity binding sites/cell). In both groups, unlabelled IGF-I inhibited tracer-binding half maximally at about 1 nM. Insulin was 100-fold less potent. In adults, specific binding of [125I] labelled IGF-I was higher in women (7.6 +/- 0.7%) than in men (5.3 +/- 0.4%). No significant difference was observed in maximal specific binding of [125I] labelled insulin between prepubertal children (8.2 +/- 0.5%) and adults (7.2 +/- 0.7%). In both groups, competition by unlabelled insulin for [125I] labelled insulin binding gave 50% displacement for approximately 0.25 nM and IGF-I was about 80-fold less potent. Both IGF-I and insulin binding parameters were not significantly correlated with plasma hormone levels. In prepubertal children, the high-affinity IGF-I receptors number decreased with increasing high-affinity insulin receptors number.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Influence of low- and high-protein diets on insulin and insulin-like growth factor-1 binding to skeletal muscle and liver in the growing rat.

The influence of protein content of the diet on the plasma concentrations and binding to skeletal muscle and liver of insulin and insulin-like growth factor-1 (IGF-1), was studied in growing rats. Animals with a starting body-weight of 80 g received for an 11 d period isoenergetic diets containing (g/kg dry matter) 155 protein as controls (MP), or 55 (LP) or 300 (HP) protein. Food was offered as six equal meals/d. Daily food intakes provided adequate amounts of energy. Total plasma IGF-1 increased linearly as a function of dietary protein intake. Plasma insulin was lower in the LP than in the MP and HP groups. Hormone binding was studied in wheat-germ agglutinin (WGA) partially purified skeletal muscle receptor preparations. Each 125I-labelled hormone binding was competed for by increasing amounts of homologous and heterologous unlabelled hormone; this displacement needed lower concentrations of homologous than heterologous hormone. When compared with MP-diet feeding, the LP diet resulted in an increased ligand concentration for half-maximal binding. In addition the specific 125I-labelled insulin and 125I-labelled IGF-1 binding increased at all hormone concentrations and, as revealed by Scatchard analysis, the hormone binding capacity also rose (only significant for low-affinity insulin receptors and high-affinity IGF-1 receptors). The HP diet had little effect on hormone binding, except to increase insulin binding at very low insulin concentrations. Hormone binding was further studied in WGA partially purified liver receptor preparations. Those preparations did not exhibit any detectable specific 125I-labelled IGF-1 binding. The specific 125I-labelled insulin binding was not altered by dietary protein level. It is concluded that the increase in skeletal muscle insulin and IGF-1 binding along with a decrease in insulin and IGF-1 in the blood from rats fed on the LP diet, is consistent with the concept of an inverse relationship between plasma hormone and hormone binding. The physiological significance with respect to metabolic adaptation of muscle remains to be established.

Animals↗
PubMed1991

Insulin binding to Leydig cells and insulin levels in testicular interstitial fluid at different stages of development in the rat.

Binding of insulin to purified intact Leydig cells (LC) and LC membranes, and levels of insulin in plasma and testicular interstitial fluid (IF) were quantitatively evaluated in rats at three stages of development. Specific insulin binding to intact LC increased significantly with age. Scatchard analysis of the binding data always gave curvilinear plots; the number of high affinity binding sites/LC were 2590 +/- 514, 3977 +/- 701 and 8342 +/- 2039 at 21, 40 and 70 days respectively. When the results were expressed per micrograms membrane protein, the maximal specific insulin binding also increased between 21 and 40 days but did not significantly change thereafter. With ageing, insulin levels in testicular IF decreased (3.05 +/- 0.30, 2.48 +/- 0.22 and 1.66 +/- 0.13 micrograms/l in 21-, 40- and 70-day-old rats) whereas plasma insulin increased. Taken together, these results suggest (1) that the intratesticular environment in this hormone cannot be evaluated by plasma insulin levels--testicular IF insulin concentration is probably a better index and (2) that insulin may play a role in the development of LC function during sexual maturation.

Animals↗
PubMed1990

Insulin binding and receptor tyrosine kinase activity in rat liver and skeletal muscle: effect of starvation.

Insulin binding and insulin receptor kinase activity were measured in solubilized and partially purified receptor preparations from liver and skeletal muscles of rats that were either fed a standard diet or subjected to a 72-hour fasting period. Insulin binding capacity was increased in both tissues from fasted rats as determined by Scatchard analysis. The affinity of the receptors was not modified by fasting. Affinity labeling of the alpha-subunit of insulin receptors also suggested an increase in the number of insulin receptors in both tissues. The ability of insulin to stimulate the autophosphorylation of the beta-subunit as well as the phosphorylation of the artificial substrate Glu80-Tyr20 was significantly impaired in liver from fasted rats and by contrast unchanged in skeletal muscles. These findings indicate that in rats, fasting produces changes in insulin receptor kinase activity in liver but not in muscle. The physiological significance of this tissue-specific regulation of receptor kinase activity in relation to insulin action during fasting remains to be established.

Affinity Labels↗
PubMed1990

Effect of calorie restriction on skeletal muscle and liver insulin binding in growing rat.

The effect of specific calorie deprivation was studied in meal-fed growing rats. It resulted in a 50% decrease in growth rate. Blood glucose and most non-essential blood free amino acid levels were depressed. Postprandial plasma insulin was decreased. With insulin ranging from 0.01 to 100 nM, insulin binding to crude Triton X-100 solubilized membranes from liver was higher in calorie restricted rats when compared with control rats. Wheat germ agglutinin (WGA) purified receptor preparations also exhibited higher insulin binding in liver from experimental group but the significance (P less than 0.05) was only visible with low insulin levels; both basal and insulin-stimulated tyrosine-kinase activity were left unchanged. In contrast, whatever the skeletal muscle insulin receptor preparation (enriched plasma membranes, crude Triton X-100 solubilized or wheat-germ agglutinin purified extracts) insulin binding was similar in control and calorie-restricted rats.

Amino Acids↗
PubMed1990

[Protein metabolism in the newborn lamb. IV. Consequences of amino acid and lactose ingestion].

A study was made on protein metabolism and hormonal changes following birth in newborn lambs fed amino acids alone or in combination with lactose. Eight newborn lambs taken from their mother immediately after birth were fed hourly for 8 h, either with a solution of peptides and free amino acids obtained by mild hydrolysis of whey proteins (4 lambs; diet AP) or with the same solution + lactose (4 lambs; diet APL). L-[4,5-3H] leucine was continuously perfused into a jugular vein for 6 h when the lambs were 2 h 30 min old. Plasma glucose and insulin levels increased after birth in APL lambs whereas they decreased in the AP; these differences were significantly different. Plasma cortisol levels remained unchanged throughout the experiment. Free essential amino acid levels did not vary when lambs were older than 4.5 h; they depended on the corresponding amino acid intakes. Plasma free threonine, valine, isoleucine, leucine, tyrosine and lysine were lower in APL than in AP lambs. The plasma leucine irreversible loss and leucine oxidation were higher in AP than in APL lambs. The plasma flux of leucine from whole body protein breakdown was lower in APL than in AP lambs inasmuch as the plasma flux of dietary leucine may be estimated by the amounts of leucine ingested in both cases. No significant difference was found for the fractional synthesis rates of tissue proteins such as liver, skin, skeletal muscle, lung, brain and whole body. These rates for skin, muscle and whole body were close to those previously measured in colostrum fed lambs. The increase in whole body protein accretion resulting from lactose feeding in combination with amino acids seemed to result from a decreased protein breakdown that could be mediated by the insulin response.

Amino Acids↗
PubMed1989

Insulin receptor binding and tyrosine kinase activity in liver and skeletal muscle from fasted rats.

Insulin binding and tyrosine kinase activity of the insulin receptor have been measured in the liver and muscles of rats fed or submitted to a 72-h-fasting. In both tissues, insulin binding increased in fasting rats. In liver, the ability of insulin to simulate receptor tyrosine kinase activity greatly unpaired during fasting, but remained unchanged in muscle. The change during fasting of the insulin-stimulated tyrosine kinase activity of the insulin receptor is specific to certain tissue.

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↗
PubMed1988

Chronic intracerebroventricular infusion of insulin failed to alter brain insulin-binding sites, food intake, and body weight.

The present study was performed to explore the role of exogenous insulin in CSF in the control of energy balance in the rat. For this purpose, adult male Sprague-Dawley rats carrying an indwelling cannula in the right lateral cerebral ventricle were infused for a maximum of 10 days with insulin (Actrapid) at various rates (starting at 0, 45, 85, 170, and 600 ng/day) or anti-insulin antibody (IgG fraction; diluted 1:10 wt/vol) with an osmotic minipump. All those treatments did not modify the growing rates; neither total daily food intake nor the circadian rhythm of food intake was further modified. The chronic insulin infusion starting at 600 ng/day resulted in a chronic significant increase in CSF insulin levels without changing the plasma insulin level. It failed to alter specific insulin binding sites to Triton X-100 solubilized microsomal membranes from various brain areas (cerebral cortex, olfactory bulbs, and lateral and medial hypothalami) at the end of the 5- or 10-day period of insulin infusion. Purification of insulin receptors on a wheat germ agglutinin did not reveal any further effect of insulin. From these results, it seems unlikely that the input to the brain insulin-effector systems could arise from CSF insulin.

Animals↗
PubMed1988

[Findings and hormonal coordination of protein metabolism in ruminants].

Protein metabolism roughly exhibits the same characteristics in ruminants and non-ruminant species. Changes in whole-body protein mass are the result of the balance between the simultaneous protein synthesis and breakdown. Essential amino acids are either incorporated into protein or degraded. Insulin, growth hormone and glucagon have been shown to regulate those metabolic pathways in ruminants. Alteration of food intake both decreases protein synthesis and protein breakdown. Protein synthesis is affected to a greater extent than protein breakdown. So protein synthesis is the main factor controlling N balance in response to alteration of food intake. The decrease in protein synthesis may be related to an impairment of plasma insulin. Protein synthesis and breakdown both decrease throughout development. Protein deposition decreases throughout development because protein synthesis declines more rapidly than protein breakdown. The hormonal coordination of those changes depends on the age of the animals. For example the decrease in protein synthesis in the postnatal growth period may be due to either the decrease in plasma growth hormone or to the impairment in cellular insulin receptors. Due to milk protein synthesis in the mammary gland, lactating animals exhibit a large increase in whole-body protein synthesis. Surprisingly, protein synthesis decreases in some non-mammary tissues. This represents a mechanism for a greater partitioning of amino acids towards milk at the expense of body proteins. We recently demonstrated that insulin could be involved in that adaptative process.

Amino Acids↗
PubMed1987

The influence of acute hyperinsulinemia on the insulin-related material in brain, testis, liver, and kidney.

Insulin-related material was measured in acid ethanol extracts of brain, testis, liver, and kidney from adult rats acutely injected with insulin or saline. Insulin injection resulted in a twofold to threefold increase in plasma insulin during a two-hour period after injection. Plasma glucose was greatly depressed. Insulin injection had no effect on the insulin-related material in most areas of brain (cerebral cortex, olfactory bulbs, and medial hypothalamus) and the cerebrospinal fluid; lateral hypothalamus was an exception and paradoxically exhibited a decrease of this material. The testis insulin-related material was unaffected; purification of the testis extracts using the C18 Sep pak method revealed no further difference between the animals. In liver, the insulin-related material was not significantly different in the control and the insulin-injected group; however, we found a significant correlation between this material and plasma insulin within the insulin-injected group. In contrast, insulin injection resulted in an important increase in kidney insulin-related material that paralleled the change in plasma insulin. Thus, like chronic experiments, acute hyperinsulinemia revealed that the insulin-related material was largely independent from blood insulin in tissues that exhibit very different insulin uptake from the blood; kidney appeared to be an exception.

Animals↗
PubMed1986

Binding and degradation of 125I-glucagon by highly purified rat liver plasma membranes.

125I-glucagon binding and degradation were studied in highly purified plasma membranes from rat livers. Specific 125I-glucagon binding increased rapidly with time at 30 degrees C and reached a maximum between 30 and 120 min. At 120 min the labelled material present in the supernatants from incubation mixtures had extensively lost its ability to rebind to fresh membranes whatever the glucagon concentration. This impairment was not due to the release of a degradative activity into the incubation mixture, suggesting a membrane-mediated process. The presence of proteinase inhibitors (bacitracin/aprotinin) resulted both in an increase in specific 125I-glucagon binding to membranes and an improvement in the ability of the labelled material from the supernatant to rebind to fresh membranes. When analysed by Bio-Gel P-10 chromatography the loss in the ability of the labelled material in the supernatants to rebind to fresh membranes correlated with a decrease in the labelled material which eluted as 125I-glucagon from the column. Chromatographic analysis overestimated 125I-glucagon when compared to the radioreceptor assay. The labelled material extracted from membranes by Triton X-100 solubilization or dissociated from membranes after exposure to an excess of unlabelled glucagon mainly eluted as 125I-glucagon. However, a significant amount (20-30%) of the labelled material eluted in the low molecular weight region.

Animals↗