[Preventive and therapeutic management of diabetic patients, a report of failure?].
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Aged↗
Biomedical subjects
J Girard
Publications and source records attributed to J Girard.
Induction of ketogenesis and fatty acid oxidation by glucagon and cyclic AMP in cultured hepatocytes from rabbit fetuses. Evidence for a decreased sensitivity of carnitine palmitoyltransferase I to malonyl-CoA inhibition after glucagon or cyclic AMP treatment.
The effects of pancreatic hormones and cyclic AMP on the induction of ketogenesis and long-chain fatty acid oxidation were studied in primary cultures of hepatocytes from fetal and newborn rabbits. Hepatocytes were cultivated during 4 days in the presence of glucagon (10(-6) M), forskolin (2 x 10(-5) M), dibutyryl cyclic AMP (10(-4) M), 8-bromo cyclic AMP (10(-4) M) or insulin (10(-7) M). Ketogenesis and fatty acid metabolism were measured using [1-14C]oleate (0.5 mM). In hepatocytes from fetuses at term, the rate of ketogenesis remained very low during the 4 days of culture. In hepatocytes from 24-h-old newborn, the rate of ketogenesis was high during the first 48 h of culture and then rapidly decreased to reach a low value similar to that measured in cultured hepatocytes from term fetuses. A 48 h exposure to glucagon, forskolin or cyclic AMP derivatives is necessary to induce ketone body production in cultured fetal hepatocytes at a rate similar to that found in cultured hepatocytes from newborn rabbits. In fetal liver cells, the induction of ketogenesis by glucagon or cyclic AMP results from changes in the partitioning of long-chain fatty acid from esterification towards oxidation. Indeed, glucagon, forskolin and cyclic AMP enhance oleate oxidation (basal, 12.7 +/- 1.6; glucagon, 50.0 +/- 5.5; forskolin, 70.6 +/- 5.4; cyclic AMP, 77.5 +/- 3.4% of oleate metabolized) at the expense of oleate esterification. In cultured fetal hepatocytes, the rate of fatty acid oxidation in the presence of cyclic AMP is similar to the rate of oleate oxidation present at the time of plating (85.1 +/- 2.6% of oleate metabolized) in newborn rabbit hepatocytes. In hepatocytes from term fetuses, the presence of insulin antagonizes in a dose-dependent fashion the glucagon-induced oleate oxidation. Neither glucagon nor cyclic AMP affect the activity of carnitine palmitoyltransferase I (CPT I). The malonyl-CoA concentration inducing 50% inhibition of CPT I (IC50) is 14-fold higher in mitochondria isolated from cultured newborn hepatocytes (0.95 microM) compared with fetal hepatocytes (0.07 microM), indicating that the sensitivity of CPT I decreases markedly in the first 24 h after birth. The addition of glucagon or cyclic AMP into cultured fetal hepatocytes decreased by 80% and 90% respectively the sensitivity of CPT I to malonyl-CoA inhibition. In the presence of cyclic AMP, the sensitivity of CPT I to malonyl-CoA inhibition in cultured fetal hepatocytes is very similar to that measured in cultured hepatocytes from 24-h-old newborns.
Acyl Coenzyme A↗
Development of insulin sensitivity in white adipose tissue during the suckling-weaning transition in the rat. Involvement of glucose transport and lipogenesis.
The changes of insulin responsiveness of white adipose tissue during the suckling-weaning transition in the rat were investigated in vitro on isolated adipocytes. Insulin binding, glucose transport and glucose metabolism in adipocytes from suckling rats and from rats weaned on to a high-carbohydrate (HC) or a high-fat (HF) diet were compared. Despite similar insulin binding, insulin-stimulated glucose transport rate is lower in adipocytes from suckling rats and HF-weaned rats than in adipocytes from HC-weaned rats. Moreover, whereas insulin markedly stimulates glucose metabolism in adipocytes from HC-weaned rats, glucose metabolism is totally unresponsive to insulin in adipocytes from suckling and HF-weaned rats. This insulin resistance is associated with a very low rate of lipogenesis and low activities of acetyl-CoA carboxylase, fatty acid synthase and pyruvate dehydrogenase.
Adipose Tissue↗
Characterization of receptors for alpha-melanocyte-stimulating hormone on human melanoma cells.
Receptors for alpha-melanocyte-stimulating hormone (alpha-MSH) on human malignant melanoma cell lines were investigated with a specific binding assay and characterized with structural analogues of alpha-MSH and adrenocorticotropic hormone and by photoaffinity cross-linking of the hormone-receptor complex. Specific binding of high-performance liquid chromatography-purified, monoiodinated alpha-MSH in the presence of 1 mM 1,10-phenanthroline as protease inhibitor was highest after a 2-h incubation at 37 degrees C. The nonspecific binding was less than 20% and dissociation of the ligand-receptor complex was relatively slow. Ten out of 12 human cell lines showed specific binding sites for alpha-MSH with Kp values ranging from 0.195 to 2.87 nM and the sites/cell being approximately 400 to approximately 1600. Virtually identical results were obtained in an assay where the cells remained attached to the culture dishes during the entire experiment. The study of hormone analogues with the D10 cell line showed that oxidized alpha-MSH had an approximately 40-fold lower affinity than alpha-MSH whereas [Nle4,D-Phe7]-alpha-MSH displayed a threefold and the adrenocorticotropic hormone fragments (1-17) and (1-24) a 20- and 8-fold higher affinity. Cross-linking of the alpha-MSH-receptor complex of three cell lines using monoiodinated [Nle4,D-Phe7,Trp(2-nitro-4-azidophenylsulfenyl)9]-alpha-MSH as photoaffinity label revealed a major Mr 45,000 protein band on sodium dodecyl sulfate-polyacrylamide gels, analogous to the MSH receptor of mouse B16 melanoma cells.
Animals↗
Octanoate metabolism in isolated hepatocytes and mitochondria from fetal, newborn and adult rabbit. Evidence for a high capacity for octanoate esterification in term fetal liver.
Ketogenesis from endogenous fatty acids or from exogenous octanoate has been studied in isolated hepatocytes from fetal. 24-h-old newborn and adult rabbit. In fed adult rabbits, endogenous ketogenesis is low and increases sixfold in the presence of 2 mM octanoate. At birth, endogenous ketogenesis is low and markedly increases 24 h after birth but, in both cases, the addition of 2 mM octanoate does not increase the rates of ketone body production. Hepatocytes isolated from 24-h-old newborn or fed adult rabbits and incubated with [1-14C]octanoate show a preferential channeling of fatty acid into oxidation (84-92% of octanoate metabolized). In contrast, esterification represents 43% of the amount of octanoate metabolized at birth. Chromatographic analysis of labelled triacylglycerols shows that 76 +/- 2% of labelled fatty acids are identified as octanoate and all of the radioactivity in the octanoate peak is due to the carboxyl carbon. In hepatocytes from term fetus, the low capacity for octanoate oxidation is associated with a high capacity for esterification, whatever the octanoate concentration in the medium. Octanoate activated to octanoyl-CoA in the cytosol of fetal hepatocyte is not oxidized in the mitochondria since carnitine acyltransferase I has a low activity at birth in the rabbit. This suggests that only a part of the octanoate pool is activated outside the mitochondria. Factors involved in the direct esterification of octanoate into triacylglycerols in term fetal hepatocytes are discussed.
Animals↗
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↗
The receptor for alpha-melanotropin of mouse and human melanoma cells. Application of a potent alpha-melanotropin photoaffinity label.
The melanotropin (MSH) receptor of mouse B16-F1 melanoma cells was characterized by photoaffinity cross-linking, using a potent alpha-MSH photolabel, [norleucine4, D-phenylalanine7, 1'-(2-nitro-4-azidophenylsulfenyl)-tryptophan9]-alpha-melanotropin (Naps-MSH). Its monoiodinated form, 125I-Naps-MSH, displayed a approximately 6.5-fold higher biological activity than alpha-MSH. Scatchard analysis of the saturation curves with 125I-Naps-MSH revealed approximately 20,000 receptors/B16-F1 cell and an apparent KD of approximately 0.3 nM. Analysis of the cross-linked MSH receptor by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that a photolabeled band of approximately 45 kDa occurs in B16-F1, B16-F10, and Cloudman S91 mouse melanoma, as well as in human D10 and 205 melanoma but not in non-melanoma cells. The labeled 45-kDa protein had an isoelectric point of 4.5-4.9 as determined by two-dimensional gel electrophoresis. Treatment of the labeled 45-kDa protein of B16-F1 cell membranes by neuraminidase shifted the band to approximately 42 kDa. A similar band of about 42 kDa was also observed after receptor labeling of B16-W4 cells, a cell line with a decreased number of terminal N-linked neuraminyl residues. These results indicate that the labeled 45-kDa glycoprotein contains terminal sialic acid residues, explaining the low pI of this protein, and that it is characteristic for melanoma cells and hence part of the MSH receptor.
Affinity Labels↗
Apolipoprotein-E-gene expression in rat liver during development in relation to insulin and glucagon.
An apolipoprotein-E (apo-E) cDNA probe, cloned by immunoscreening of a lambda GT11 rat liver cDNA library, was used to further characterize the expression of the apo-E gene in rat liver during development, in relation to plasma insulin and glucagon levels. The apo-E mRNA level was low in fetus liver, then abruptly increased at birth and rose further during the suckling period. It returned to the level at birth in 10-week-old adults. These variations were paralleled with dramatic changes in plasma glucagon, which rose at birth and remained high during suckling. At the same time, the insulin/glucagon molar ratio fell. Administration of N6,O2-dibutyryl cAMP to 5-day-old rats resulted in a significant induction of liver apo-E mRNA. Moreover, liver apo-E mRNA rose in 10-h-fasted suckling rats as compared to controls, while plasma glucagon increased and the insulin/glucagon ratio decreased. Conversely, glucose feeding of suckling rats did not induce any increase in liver apo-E mRNA, the insulin/glucagon ratio was 10-fold higher than in fasted animals. Our results are consistent with liver apo-E gene expression being under the control of plasma glucagon and of the glucagon/insulin balance.
Animals↗
Normal insulin sensitivity during the phase of glucose intolerance but insulin resistance at the onset of diabetes in the spontaneously diabetic BB rat.
In diabetes-prone BB rats, 30 to 50% of animals undergo autoimmune destruction of the pancreatic B-cells leading to a short period of glucose intolerance, followed by an abrupt onset of diabetes. We have examined whether the glucose intolerance period and the onset of diabetes are associated with changes in insulin sensitivity, using the euglycaemic hyperinsulinaemic clamp coupled with [3-3H] glucose infusion. Glucose intolerant rats were detected by a transient glycosuria one hour after an oral glucose load performed every four days. Insulin sensitivity studied in these rats the day following their detection was normal. Other diabetes-prone BB rats were tested daily and studied on the first day of glycosuria. In the basal state, glucose production was increased in diabetic rats (11.3 +/- 1.1 vs 7.1 +/- 0.8 mg.min-1.kg-1, p less than 0.05). Tissue glucose utilization was similar in diabetic and control rats (8.3 +/- 0.5 vs 7.1 +/- 0.8 mg.min-1.kg-1) despite a three fold higher glycaemia in the diabetic rats. During the hyperinsulinaemic clamps, glycaemia was clamped at 6.1-6.6 mmol/l in diabetic and control rats. A decreased insulin sensitivity was observed in diabetic rats at submaximal (200 microU/ml) and maximal (1500 microU/ml) insulin concentrations for both inhibition of hepatic glucose production and stimulation of glucose utilization. No autoantibodies against insulin could be detected in the plasma of diabetic rats. Plasma concentrations of glucagon, catecholamines, ketone bodies and fatty acids were similar in control and diabetic rats during the clamp studies.(ABSTRACT TRUNCATED AT 250 WORDS)
3-Hydroxybutyric Acid↗
Melanin concentrating hormone. IV. Development of a sensitive solid-phase radioimmunoassay for melanin-concentrating hormone.
A two-step solid-phase radioimmunoassay for melanin-concentrating hormone (MCH) was developed for direct determination of the hormone in plasma samples. To this end, synthetic MCH was coupled to bovine thyreoglobulin and the complex was injected into rabbits. Specific antisera of high titer were obtained which did not crossreact with other hormones. The IgGs were chemically linked to immunobeads, an acrylamide/acrylic acid polymer matrix. In the first step, plasma MCH was immunoextracted by incubation of diluted plasma samples with anti-MCH immunobeads. In the second step, the washed polymer was incubated with radioiodinated MCH tracer for titration of non-occupied sites. This procedure made it possible to determine as little as 4 pg MCH per ml of plasma. Application of the radioimmunoassay to plasma levels of black or white background-adapted trout showed a marked difference in circulating MCH: while trout on a black background contained a mean value of 29 +/- 5.6 pg/ml, animals on a white background had 106 +/- 19 pg/ml. These findings strengthen the hypothesis that MCH is directly involved in the control of color change of teleost fishes. By contrast, there was no detectable salmonid MCH immunoreactivity in rat or human plasma.
Animals↗
Control of fetal and neonatal glucose metabolism by pancreatic hormones.
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Animals↗
Control of acetoacetate production from exogenous palmitoyl-CoA in isolated rat liver mitochondria.
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Acetoacetates↗
Fetal glucose utilization in response to maternal starvation and acute hyperketonemia.
The effects of maternal hypoglycemia and/or hyperketonemia on glucose utilization by individual fetal rat tissues have been studied in vivo. To decrease blood glucose and to raise fetal blood ketone body concentrations, 19-day pregnant rats were submitted to 48 or 96 h of starvation. To differentiate between the effects of decreased blood glucose and increased ketone body concentrations, fed pregnant rats were infused for 2 h with DL-beta-hydroxybutyrate. After 96 h of maternal starvation, fetal 2-deoxy-D-glucose (2DG) uptake decreased from 13.6 +/- 0.5 to 8.6 +/- 1.15 micrograms.min-1.g-1. This was mainly due to a decrease in 2DG uptake by fetal hindlimb muscles and heart. By contrast, 2DG uptake in fetal liver and brain was not affected by maternal starvation. Acute hyperketonemia in fed pregnant rats induced a 23% decrease in 2DG uptake by the whole fetus mainly as the result of a lowered 2DG uptake in fetal hindlimb muscles. These data suggest that fetal 2DG uptake does not simply depend on lowered blood glucose level during maternal starvation but that other hormonal, cardiovascular, or metabolic adaptations are implicated. In the rat, most of the fetal tissues including brain are protected against maternal hypoglycemia.
3-Hydroxybutyric Acid↗
[Regulation of the expression of the hepatic phosphoenolpyruvate carboxykinase gene during development and nutrition transitions].
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Animals↗
[Study of the long-term effects of amiodarone on thyroid function using ultrasensitive TSH measurements. Preliminary report].
The results of a prospective study of basal ultrasensitive TSH concentrations in patients during long-term treatment over 12 months with amiodarone are reported. 2 patients (3%) developed hypothyroidism, whereas no case of hyperthyroidism was observed. A significant increase in FT4 with a simultaneous decrease in T3 was demonstrated at every periodic investigation during amiodarone therapy. In most patients ultrasensitive TSH values stayed within the normal range and showed no significant alteration during treatment. A slow decline in TSH during therapy was observed in a subgroup of patients with completely euthyroid initial TSH concentrations. This TSH decrease reached statistical significance after 12 months' therapy. FT4 showed pathological results in 35% of all determinations at any time during the study, T3 in 27%, and TSH in only 17%. In conclusion, a new steady-state of thyroid tests is attained during treatment with amiodarone and most patients maintain a euthyroid function state. Assessment of ultrasensitive TSH can be recommended as a primary screening test for evaluation of thyroid function in patients under amiodarone therapy.
Amiodarone↗
Regulation by insulin of glucose metabolism in mammary gland of anaesthetized lactating rats. Stimulation of phosphofructokinase-1 by fructose 2,6-bisphosphate and activation of acetyl-CoA carboxylase.
The effect of insulin on glucose metabolism in mammary gland was studied by the euglycaemic/hyperinsulinaemic-clamp technique. Measurement of metabolite concentrations and enzyme activities in the mammary gland suggests two sites of action of insulin: phosphofructokinase-1 and acetyl-coA carboxylase. The increase in phosphofructokinase-1 activity could be linked to the 2-fold increase in fructose 2,6-bisphosphate concentration, since no change in maximal activity and in sensitivity of the enzyme toward fructose 6-phosphate was detected in vitro.
Acetyl-CoA Carboxylase↗
Intramitochondrial factors controlling hepatic fatty acid oxidation at weaning in the rat.
Fatty acid oxidation was studied in isolated liver mitochondria of rats during the suckling-weaning transition. The oxidation rate of oleyl-CoA and palmitoylcarnitine was reduced 2.5-fold in rats weaned on a high-carbohydrate diet compared to suckling rats, when acetyl-CoA produced by beta-oxidation was directed towards ketone-body synthesis. Weaning on a high-fat diet minimized this change. Channeling of acetyl-CoA towards citrate synthesis doubled the oxidation rate of both substrates in HC-weaned rats. Thus, in addition to changes in carnitine palmitoyltransferase I activity, the beta-hydroxymethylglutaryl-CoA synthase pathway is also involved in the decreased fatty acid oxidation at weaning. This was confirmed by measurement of beta-hydroxymethylglutaryl-CoA synthase pathway activity.
Acetyl Coenzyme A↗
Development of insulin-sensitivity at weaning in the rat. Role of the nutritional transition.
This study was undertaken to determine the factors involved in the development of insulin-sensitivity at weaning. Glucose kinetics were studied in suckling rats and in rats weaned on to a high-carbohydrate (HC) or a high-fat (HF) diet, in the basal state and during euglycaemic-hyperinsulinaemic-clamp studies. These studies were coupled with the 2-deoxyglucose technique, allowing a measure of glucose utilization by individual tissues. In the basal state, the glycaemia was higher in HF-weaned rats (124 +/- 4 mg/dl) than in suckling (109 +/- 1 mg/dl) and HC-weaned rats (101 +/- 3 mg/dl). Glucose turnover rates were similar in the three groups of animals (14 mg/min per kg). Nevertheless, basal metabolic glucose clearance rate was 20% lower in HF-weaned rats than in the other groups. During the euglycaemic-hyperinsulinaemic experiments, hepatic glucose production was suppressed by 90% in HC-weaned rats, whereas it remained at 40% of basal value in suckling and HF-weaned rats, indicating an insulin resistance of liver of these animals. Glucose clearance rate during the clamp was 18.3 +/- 0.9 ml/min per kg in suckling rats, whereas it was 35.3 +/- 1.2 ml/min per kg in HC-weaned rats and 27.8 +/- 1.1 ml/min per kg in HF-weaned rats, indicating an insulin resistance of glucose utilization in suckling, and to a lower extent, in HF-weaned rats. The deoxyglucose technique showed that peripheral insulin resistance was localized in muscles and white adipose tissue of suckling and HF-weaned rats. These results indicate that the switch from milk to a HC diet is an important determinant of the development of insulin-sensitivity at weaning in the rat.
Adipose Tissue↗