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J C Cresto

Publications and source records attributed to J C Cresto.

At least 19 recordsLinked to original sources
PubMed2001

ATP inhibits insulin-degrading enzyme activity.

We studied the ability of ATP to inhibit in vitro the degrading activity of insulin-degrading enzyme. The enzyme was purified from rat skeletal muscle by successive chromatographic steps. The last purification step showed two bands at 110 and 60 kDa in polyacrylamide gel. The enzyme was characterized by its insulin degradation activity, the substrate competition of unlabeled to labeled insulin, the profile of enzyme inhibitors, and the recognition by a specific antibody. One to 5 mM ATP induced a dose-dependent inhibition of insulin degradation (determined by trichloroacetic acid precipitation and insulin antibody binding). Inhibition by 3 mM adenosine 5'-diphosphate, adenosine 5'-monophosphate, guanosine 5'-triphosphate, pyrophosphate, beta-gamma-methyleneadenosine 5'-triphosphate, adenosine 5'-O-(3 thiotriphosphate), and dibutiryl cyclic adenosine 5'-monophosphate was 74%, 4%, 38%, 46%, 65%, 36%, and 0%, respectively, of that produced by 3 mM ATP. Kinetic analysis of ATP inhibition suggested an allosteric effect as the plot of 1/v (insulin degradation) versus ATP concentration was not linear and the Hill coefficient was more than 1 (1.51 and 2.44). The binding constant for allosteric inhibition was KiT = 1.5 x 10(-7) M showing a decrease of enzyme affinity induced by ATP. We conclude that ATP has an inhibitory effect on the insulin degradation activity of the enzyme.

Adenosine Triphosphate↗
PubMed2000

Degradation of soluble amyloid beta-peptides 1-40, 1-42, and the Dutch variant 1-40Q by insulin degrading enzyme from Alzheimer disease and control brains.

Insulin degrading enzyme (IDE) is a metalloprotease that has been involved in amyloid beta peptide (A(beta)) degradation in the brain. We analyzed the ability of human brain soluble fraction to degrade A(beta) analogs 1-40, 1-42 and the Dutch variant 1-40Q at physiological concentrations (1 nM). The rate of synthetic 125I-A(beta) degradation was similar among the A(beta) analogs, as demonstrated by trichloroacetic acid precipitation and SDS-PAGE. A 110 kDa protein, corresponding to the molecular mass of IDE, was affinity labeled with either 125I-insulin, 125I-Abeta 1-40 or 125I-A(beta) 1-42 and both A(beta) degradation and cross-linking were specifically inhibited by an excess of each peptide. Sensitivity to inhibitors was consistent with the reported inhibitor profile of IDE. Taken together, these results suggested that the degradation of A(beta) analogs was due to IDE or a closely related protease. The apparent Km, as determined using partially purified IDE from rat liver, were 2.2 +/- 0.4, 2.0 +/- 0.1 and 2.3 +/- 0.3 microM for A(beta) 1-40, A(beta) 1-42 and A(beta) 1-40Q, respectively. Comparison of IDE activity from seven AD brain cytosolic fractions and six age-matched controls revealed a significant decrease in A(beta) degrading activity in the first group, supporting the hypothesis that a reduced IDE activity may contribute to A(beta) accumulation in the brain.

Alzheimer Disease↗
PubMed1998

Long-term follow up of persistent hyperinsulinaemic hypoglycaemia of infancy.

Twenty six children with hypoglycaemia were diagnosed and followed between 1975 and 1995. Diagnosis was confirmed by a high insulin:glucose ratio, and low free fatty acid and 3-hydroxybutyrate on fasting. All patients were treated with diazoxide at a maximum dose of 20 mg/kg/day. Requirement of a higher dose was considered as a failure of medical treatment and an indication for surgery. Sixteen children Responded to diazoxide; 10 failed to respond and underwent pancreatic resection. Six of the latter group started with symptoms in the neonatal period. Eleven of the 26 children have neurological sequelae. Head growth and neurological outcome correlated well. Additionally, non-specific electroencephalogram abnormalities (slow waves) appear to be indicative of subclinical hypoglycaemia during follow up.

Diazoxide↗
PubMed1998

Anti-idiotype guinea pig antibodies as response to insulin immunization.

The study was done using 39 guinea pigs grouped as followed; 18 were injected with 0.5 mg of porcine insulin emulsified in complete Freund's adjuvant; 12 were injected with saline and 9 were used as control of cardiac bleeding during the assay. Intraperitoneal glucose tolerance tests (IGTT) were carried out on days 0, 11, 32 and 38. Seven of the thirteen guinea pigs immunized with insulin which survived after the study, showed glucose intolerance on day 32 at 90 and 120 min (p < 0.01 and p < 0.001) and on day 38 at 120 min (p < 0.05). Anti-idiotypic IgG partially purified from a sera pool from these animals inhibited 125-Insulin binding to rat hepatocytes, immunoprecipitated 125I-rat insulin receptors and recognized the alpha-subunit of insulin receptor in immunoblotting. We conclude that insulin anti-idiotypes in guinea pigs offer a simple way to produce antibodies against insulin receptor binding site. The methodology for anti-idiotype identification can be applied to patients with insulin resistance.

Animals↗
PubMed1997

Patient with an Xp21 contiguous gene deletion syndrome in association with agenesis of the corpus callosum.

The so-called Xp21 contiguous deletion syndrome or complex glycerol kinase deficiency (GKD) usually presents with classical Duchenne muscular dystrophy (DMD) or a milder dystrophic myopathy, adrenal hypoplasia, and GKD. A number of syndromic and nonsyndromic cases of agenesis of the corpus callosum (ACC) also map to that location. To date, none of the cases of complex GKD have been associated with ACC. Here, we report on a patient with a complex phenotype as a result of the Xp21 contiguous deletion syndrome in association with ACC. Biochemical, cytogenetic, and molecular analyses were performed to detect and establish the size of the genomic deletion. It is at least 3 million base pairs in length; however, exact limits could not be determined in the present study. Nevertheless, we suggest the presence of a primary gene involved in the embryogenesis of the corpus callosum between Xp21.1 and Xp22.11.

Agenesis of Corpus Callosum↗
PubMed1996

Non enzymatic liver cells isolation: citrate-perchlorate technique.

In the present study we describe a non-enzymatic technique for the isolation of rat hepatocytes by perfusion of liver through portal vein. The perfusion media consist of 1 mM sodium perchlorate, 5 mM sodium citrate, 10 mM glucose, 129 mM NaCl and 0.1% bovine-serum albumin at pH 7.4. After purification through diatrizoate gradient, electron microscopical studies revealed that most of purified hepatocytes were well preserved and presented a normal ultrastructure, thus correlating with previous biochemical results. The present method enables the recovery of metabolically and morphologically normal hepatocytes.

Animals↗
PubMed1996

[Autoimmune hypoglycemia syndrome with specific anti-human insulin antibodies].

A 33 year old woman with episodes of severe hypoglycemia is presented. The studies showed anti-insulin antibodies and variable C-peptide levels. Circulating insulin measured after acid-ethanol extraction, was of 1,600 uU/ml and shown to be human insulin after characterization by HLPC. Specific anti-human insulin antibodies were of high affinity (Ka1: 6.20 x 10(10) M-1; Ka2: 2.42 x 10(9) M-1). A small cross-reactive porcine and bovine antibody subpopulation was also detected (IgG, light k type chain). Plasmapheresis was undertaken when symptoms were spontaneously declining and turned antibody title negative. Prolonged follow-up showed no relapse of this syndrome.

Adult↗
PubMed1992

The kallikrein-kinin system in early state of diabetes.

The kallikrein-kinin system was studied in 9 normals, healthy subjects (6 men, 3 women, age range 1 to 14 years) and 15 diabetic patients (9 men, 6 women age range 2 to 14 years) with an evolution of the disease between 1 to 14 years. Diabetic patients with low microalbuminuria (6.62 +/- 0.97 mg/24 h) show increased total and pre-kallikrein respect to control (3 and 2 fold respectively). On the other hand patients with high microalbuminuria (44.7 +/- 13.2 mg/24 h) show a total and pre-kallikrein of more than 4 and 8 fold increased respectively, compare with the control. According with these results we can concluded: 1) The total kallikrein and pre-kallikrein is increased in the diabetic state. 2) When microalbuminuria is high, the total and pre-kallikrein correlates with those increasing. 3) These changes could modified the renal hemodynamic in diabetes.

Adolescent↗
PubMed1991

[Insulin/glucagon relationship in spontaneous diabetic remission].

We define diabetic remission as the disappearance of clinical symptoms with normalization of blood glucose for a period over 15 days after withdrawal of insulin therapy. We studied 21 insulin-dependent diabetic children in remission (10 boys and 11 girls) and 29 normal children matched in age and sex as controls. Two tests were performed, intravenous glucose (IVGT) and glucose post-tolbutamide (PTGT). Two remission groups were studied with IVGT. Glucose, insulin, somatotropin and glucagon were determined in one and glucose and C-peptide in the other. Insulin secretion after IVGT was very low in the remission group, not surpassing basal value when stimulated. Only two girls showed normal or high insulin values during the study, and one of them showed the common hypoinsulinism of the remission group in a second study. The kinetics of glucagon and somatotropin secretion in the remission group were normal with low values of glucagon. When the integrated area (0-120 min) of hormone secretion (insulin, somatotropin and glucagon) was determined, the remission group had lower insulin and glucagon values (p less than 0.05) and identical growth hormone as the normal group. The insulin/glucagon ratio in normals and in remission were similar. During IVGT the remission group studied for C-peptide showed lower C-peptide values than normal group, resembling insulin behavior. In both groups, the glucose disappearance rate ("K" value) was higher in normals than in remissions (p less than 0.001). During the PTGT the normal group showed a peak of insulin secretion after tolbutamide and glucose stimulation. In the remission group, glucose was higher and insulin secretion lower than in the normal group, without a peak of insulin, and growth hormone and glucagon secretion were also lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Diabetic nephropathy in children: study using the amount of urinary albumin].

It is well known that 30 to 50% of patients with Type I Diabetes develop nephropathy and that chronic renal failure, it's final pathway, is the main cause of death. Assessment of urinary albumin becomes an essential tool for identifying the population at risk of developing nephropathy, to study its physiopathologic mechanisms and to evaluate the response to therapeutic trials. The present article is a preliminary report on the study of urinary albumin excretion rate (AER) in a pediatric population with Type I Diabetes and its relation to teh duration of the disease. A RIA technique with double antibody was developed for albumin assessment, with a displacement range of 1 to 300 ng/tube. Urine samples were collected during short periods with water load as suggested by Mogensen. Thirty nine children (30 patients and 9 controls) free of renal disease and with normal blood pressure were studied. Patients were divided according to duration of the disease in: Group I: less than 5 years, Group II: 5 to 10 years and Group III: more than 10 years. Results (mean +/- SD) in micrograms/min/1.73 m2 were: Control Group (n = 9) 4.30 +/- 2.53, GI: (n = 12) 10.44 +/- 9.47, GII (n = 10) 8.03 +/- 7.27 and GIII (n = 8) 8.56 +/- 4.26. The mean value of the Control Group (+3 SD) 12 micrograms/min/1.73 m2, was considered as the upper normal limit. Thus, 16.6%, 40%, and 12.5% of children in Groups I, II and III had microalbuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1988

First phase of insulin secretion stimulated by glucose plus theophylline and inhibitory effect of somatostatin in genetically diabetic mice (C57BL/KsJ-mdb).

In a previous study in C57BL/KsJ mdb/mdb mice aged 4 to 12 days we observed a diminished first phase of glucose-induced insulin secretion in vitro, and alterations in the inhibitory effect of somatostatin on insulin secretion. This study explores, using perifused pancreatic slices, whether the reduced B-cell responsiveness to somatostatin in mdb/mdb mice can be overcome upon induction of a biphasic insulin release by using theophylline. Under these conditions our results show: (1) in mdb/mdb mice aged 4 to 6 days, the restoration of the first peak of insulin secretion overcomes the reduced B-cell sensitivity to somatostatin; and (2) in mdb/mdb mice aged 7 to 12 days, the addition of theophylline only causes a partial restoration of B-cell responsiveness to somatostatin, suggesting that other mechanisms could be involved in the progressive impairement of B-cell sensitivity to somatostatin inhibitory effect.

Aging↗
PubMed1987

Increase in insulin secretion induced by plasma from mice injected with allogeneic lymphocytes.

Plasma from BALB/c mice bled 90 minutes after allogeneic lymphocyte injection significantly rises glucose induced insulin secretion. This rise is observed in pancreas either from non-treated or from allogeneized mice. This rise is time and dose-dependent. An 1/40 dilution is enough to bring about a significant increase on insulin secretion. This effect is seen when mice are bled between 60 and 180 minutes after injection with a maximum effect at 90-120 minutes. Plasma from BALB/c mice injected with C57BL/6 J lymphocytes rises insulin secretion from BALB/c, C57BL/6 J, C3h and C57BL/KsJ mice pancreas. Plasma from streptozotocin diabetic BALB/c mice and from genetically diabetic C57BL/KsJ mdb-mdb mice injected with allogeneic lymphocytes stimulates glucose induced insulin secretion but to a lesser extent than plasma from normal non-diabetic mice does.

Animals↗
PubMed1986

Secretion and effect of somatostatin in early stages of the diabetic syndrome in C57BL/KsJ-mdb mice.

In a previous study in C57BL/KsJ (mdb) mice aged 12 to 90 days, we observed alterations in the secretion of insulin and somatostatin and in the inhibitory effect of the latter upon insulin secretion. This study explores whether hormonal alterations are to be found in the very early stages of the diabetic syndrome, i.e. between ages 4 and 12 days. The results demonstrate two distinct phases in the development of the syndrome: up to age 6 days, the perifused slices of pancreata of control animals present biphasic glucose-induced patterns of insulin and somatostatin secretion, whereas the diabetic animals show a diminished first peak of insulin secretion, but a similar pattern of somatostatin secretion, to that of the control animals; between ages 7 and 12 days, the pancreata of diabetic mice exhibit insulin hypersecretion in basal conditions, and an absence of the first secretion peak and insulin hypersecretion in the second phase in response to glucose stimulation. The glucose-induced pattern of somatostatin secretion presents hormonal hypersecretion in both phases. B-cell sensitivity to the inhibitory effect of somatostatin is diminished in mdb mice of the above-mentioned groups, an alteration which becomes more evident as diabetes evolves. The results show that, in very early stages of the evolution of the diabetic syndrome in C57BL/KsJ (mdb) mice, there are already alterations in insulin and somatostatin secretion patterns and in the inhibitory effect of the latter on insulin secretion.

Age Factors↗
PubMed1986

Insulin secretion induced by allogeneic lymphocytes in genetically diabetic mice C57BL/KsJ mdb.

Insulin and somatostatin (SRIF) secretion induced by alloantigen were studied in genetically diabetic mice from the C57BL/KsJ mdb-mdb strain. Diabetic (db) mice injected with allogeneic lymphocytes (A.L.) did not show any increase in their second phase of 27.5 mM glucose stimulated secretion and slightly increased their first phase. Normal A.L. injected mice showed a significant increase in both phases of 27.5 mM glucose stimulated secretion. SRIF secretion of A.L. injected normal and diabetic mice did not significantly differ from that obtained when injected with syngeneic lymphocytes. Lymphocytes from db mice injected into allogeneic mice caused an insulin secretion similar to that produced by allogeneic lymphocytes from non-diabetic mice. Lymphocytes from db mice injected into normal syngeneic mice caused an insulin secretion which was not significantly different from the one caused by syngeneic lymphocytes from non-diabetic mice, and is smaller than the secretion caused by A.L. injection. In summary, db mice showed an impaired hormone response to alloantigenic stimulus, while their lymphocytes maintained their alloantigenic action.

Animals↗
PubMed1984

Insulin binding and degradation in short time incubation at 37 C.

Studies on insulin-receptor binding in a short time incubations at 37 C have shown that neither internalization nor receptor-mediated insulin degradation are demonstrable during the first minutes. In the present study insulin receptor binding at 37 C in short time incubation periods was studied in mouse-hepatocytes, simultaneously determinating the proportion of degradation due to the cell activity. Degradation in the incubation buffer after cell separation was abolished during the experiment (900 sec) by a careful wash of the cells. 7.5 cells/ml were incubated with a tracer concentration (14.17 pM) of 125I-insulin and a pharmacological concentration (16.6 microM) of native insulin plus tracer. In the case of tracer insulin, 50% binding was reached in 55 sec and steady state in 160 sec. Once reached, steady state persisted along the experimental time. Binding follows a second order kinetics with k+1: 5 649 X 10(6) M-1 sec-1. In the presence of pharmacological insulin there is competitive inhibition of the tracer which reduces to zero the percent of binding. Binding increases along the time taking positive values, and the slope of binding versus time intersects the abscissa at 102 sec (r: 0.864). As long as binding of the tracer takes place, no degradation occurs until 635 sec, when a degradation slope abruptly appears (r: 0.722). Dissociation studies were followed previous incubation at 37 C during 200 sec with tracer and pharmacological doses. Specific dissociation follows a monoexponential kinetics with k-1: 3 067 X 10(-3) sec-1 and t 1/2: 226 sec. Eighty percent of bound insulin is dissociated with no changes in the slope (r: 0.820), thus suggesting that insulin-receptor binding in the present experimental conditions is basically a reversible process. No degradation was observed during dissociation, which demonstrates that insulin-receptor binding does not degrade insulin if internalization is not performed. At steady state, competitive inhibition curves showed two components: high and low affinity. Doses of 1.66 microM produce a 98% inhibition in the binding of 125I-insulin. The high affinity slope shows two components in the physiological range of insulin concentrations. The first one of very high affinity has a dissociation constant Ko: 7 075 X 10(-10), and a binding capacity of 1.5 X 10(-10). This study demonstrates that, with physiological concentrations of insulin, internalization is the only mechanism of insulin degradation in mouse-hepatocytes.

Animals↗
PubMed1984

Liver cells binding with high insulin doses at 37 C.

Insulin binding and receptor mediated insulin degradation were studied in isolated rat hepatocytes under physiological conditions (37 C, 100% oxygen, Krebs improved Ringer III with glutamate, pyruvate and fumarate, 150 mg% glucose, 1% bovine albumin). 10(6) rat hepatocytes/tube were incubated with various doses of insulin. Steady state binding with low insulin doses (0.05, 0.5 and 66 ng/tube) was reached in 15 minutes, that state being kept for the rest of the experimental time (75 min). Receptor mediated degradation (Kap) at 15 minutes was 0.0479 min-1, including doses of 5 000 and 50 000 ng/tube. Direct correlation was found between degradation and low doses of insulin, being the slope value equal to Kap. Intracellular accumulation of insulin was found at pharmacological concentrations of insulin (5 000 and 50 000 ng/tube) from the first 15 minutes. That accumulation was dose and time dependent. At 75 minutes, with a 0.2 microM insulin concentration, at least 53% of insulin was estimated as insulin accumulated in the cell, since it was not filtrable with acid medium on Sephadex G 50 superfine. When Triton or dodecyl sulphate were used to solubilize the cells, insulin recovery was complete after binding. Intracellular accumulation, however, was not demonstrated at the first two minutes. Binding studies with 16.67 microM insulin in the presence of degradation inhibitors, such as 2 mM N-ethylmaleimide and 5 mM tetracaine hydrochloride, demonstrated that intracellular accumulation of the hormone occurs when degradation is blocked. On the contrary, after trypsin digestion of receptors, degradation was not observed, while increases in binding were abolished, resembling non-specific binding. Under the experimental conditions reported here, neither intracellular accumulation of insulin nor extracellular release of insulin degradation products can be demonstrated at 2 minutes; insulin accumulation is dose dependent, and it is suggested by the fact that the velocity of insulin internalization exceeds its velocity of degradation.

Animals↗
PubMed1984

Insulin processing. Its correlation with glucose conversion to CO2.

Insulin-receptor binding, insulin degradation and biologic response (14C-glucose conversion into 14CO2) were studied in adipocytes of control (CG), fasted (FG-88 hr) and hyperinsulinic rats (HG-exogenous hyperinsulinism). The number of cells normalized to 3.5 X 10(5) cells/tube in all three groups. Insulin binding and degradation were studied at 5, 15, 30, 60 and 120 minutes of incubation with 3.5 X 10(-11) M, 6.66 X 10(-11) M, 1.0 X 10(-9) M, 6.66 X 10(-9) and 6.66 X 10(-6) M insulin. The net increments of 14CO2 taken into account (delta U-14C-glucose converted into 14CO2) ranged from the basal value to 10(6) microU in each case (30, 60 and 120 minutes). Quantitative analysis of results was performed with the Terris and Steiner degradation equation (formula; see text) (IR). Differences in insulin binding, comparing the three groups, lacked statistical significance, though FG data were systematically plotted above those of CG, occurring the opposite with HG. Degradation studies showed HG to have values statistically higher than the controls, while FG values were lower. HG also showed higher amounts of 14CO2, with basal levels more elevated than CG, while FG showed the inverse behavior. 14CO2 increased in the three groups along the 120-minutes incubation period (30, 60 and 120 minutes). Receptor-mediated degradation at 30 minutes, when binding is in steady state, showed a Kap value very close to that found by linear regression for the 2 and 10 microU doses (Kap min-1 CG: 0.1654, FG: 0.0824, HG: 0.5045; slope values for the 2 and 10 microU doses CG: 0.2181, FG: 0.0824, HG: 0.3718). The degradation velocity, considered as function of IR, was constant in each group at 30, 60 and 120 minutes. Since Kap values in the FG and HG indicate differences in their degradation velocities, this constant can be considered as indicative of the metabolic situations under study. At the same time, the biologic response (14C-glucose conversion into 14CO2) depends as well on the metabolic conditions. Glucose consumption and Kap value were then compared. All the groups showed linear correlation between the binding dependent velocity of degradation (Kap) and the net conversion of U-14C-glucose into 14CO2 at 30, 60 and 120 minutes, with ordinate close to zero (30 min: 0.1539; 60 min: -0.3812; 120 min: 0.1311). The slope increased along the incubation period, indicating that 14CO2 accumulation is time dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗