Effects of insulin on pyruvate dehydrogenase in circulating lymphocytes from normal and diabetic rats (original) (raw)
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The behaviour of pyruvate dehydrogenase in circulating lymphocytes from diabetic children
Diabetologia, 1989
The basal and total pyruvate dehydrogenase activities were assayed in circulating lymphocytes from children with juvenile diabetes at diagnosis and after five days of insulin therapy and from control subjects. In untreated diabetic children, basal and total pyruvate dehydrogenase activities were deeply decreased and both showed very similar values; whereas, in control subjects basal activity was about 30% lower than total activity. In diabetic patients treated with in-sulin (in vivo situation), both basal and total activity levels were equal or even higher than those of the control subjects. The incubation of lymphocytes from diabetic patients with insulin (5 gU/ml) (in vitro situation) stimulates, but less than in vivo, the basal and total pyruvate dehydrogenase activities.
In vitro insulin action on erythrocyte glucose metabolism in normal and diabetic rats
Diabetologia, 1988
Alloxan-induced diabetes in rats significantly impaired the capacity of the erythrocytes to metabolise glucose in vitro to either lactic acid or CO2. Both these metabolic activities were initially insensitive to insulin in normal as well as in diabetic animals; but became responsive when these cells were subjected to insulin and glucose 'starvation' for 1 h through incubation in their absence. This action of insulin in starved cells showed concentration dependence and required preincubation with the hormone prior to addition of glucose.
Low proliferation capacity of lymphocytes from alloxan-diabetic rats
Life Sciences, 2002
The proliferation capacity of lymphocytes obtained from mesenteric lymph nodes of control and alloxandiabetic (40 mg/kg) rats in response to concanavalin A (ConA) and lipopolysaccharide (LPS) stimuli was examined. Proliferation response of lymphocytes from diabetic rats was significantly reduced under Con A (43%) and LPS (46%) stimulation as compared with the control group. Insulin (166 AM) promoted a marked increase of lymphocyte proliferation (7.5-fold) in the control group and this response was much lower (2.6-fold) in lymphocyte from diabetic rats. Cells were also cultured in medium containing glucose at 5, 10 or 20 mM. High glucose concentration (20 mM) caused a marked inhibition of lymphocyte proliferation reaching the values of the diabetic group. In lymphocytes from control rats, the degree of Shc tyrosine phosphorylation was gradually increased, whereas that of cells from diabetic rats was much lower in response to insulin. In lymphocytes obtained from control rats, the tyrosine phosphorylation of IRS-1 was time-dependent on insulin. In cells from diabetic rats, the basal tyrosine phosphorylation of IRS-1 was higher than that of control rats, however, there was no further phosphorylation after insulin addition. We conclude that the response of lymphocyte proliferation from diabetic rats to Con A and LPS stimuli is decreased but insulin was able to promote a significant proliferative effect on these cells. Also, high glycemia in addition to the lack of insulin participates in the reduced proliferation capacity of lymphocytes from diabetic rats.
Possible role of cell surface insulin degrading enzyme in cultured human lymphocytes
Diabetologia, 1987
The kinetic changes of insulin receptors and cell surface insulin degrading enzyme were examined in Bri-7 cultured human lymphocytes after preincubation with or without insulin. The concentration of cell surface insulin degrading enzyme was determined by immunoenzymatic labeling method using a polyclonal antiserum to insulin degrading enzyme. In Bri-7 cells preincubated with 10-1~ to 10-5 mol/1 insulin for 18 h, the surface insulin receptors and insulin degrading enzyme decreased progressively as a function of the concentration of insulin in the preincubation medium. The surface insulin receptors and insulin degrading enzyme of cells preincubated with 10-6 mol/1 insulin were decreased to 25 and 35% of the control respectively. In Bri-7 cells preincubated with 10-6 tool/1 insulin for 30 min to 18 h, the loss of surface insulin degrading enzyme was slightly slower than that of the receptors; however, the curves were essentially parallel to each other. Thus, the treatment of Bri-7 Cells with insulin caused down-regulation of insulin receptors in a dose-and time-dependent manner. Cell surface insulin degrading enzyme also decreased simultaneously. A combination of several insulin degradation assays (trichloroacetic acid precipitation, gel filtration and receptor rebinding) demonstrated that cell surface bound insulin remained intact, and that the degradation in Bri-7 cells seemed to be a limiting proteolysis of insulin. Furthermore, by the receptor rebinding method insulin degrading activity in cells after preincubation with 10-6 mol/1 insulin (19.6+4.6%) was decreased, although not significantly, as compared with cells after preincubation without insulin (24.6 +__ 4.8%). These results suggest a possible hypothesis that cell surface insulin degrading enzyme may be internalized with the insulin-receptor complex, and that it may degrade insulin during the intracellular process.
Diabetes causes marked changes in lymphocyte metabolism
Journal of Endocrinology, 2002
An enhanced susceptibility to infections is well known to occur in a poorly controlled diabetic state. Since glucose and glutamine are essential for lymphocyte function, we investigated whether their metabolism is changed in lymphocytes obtained from mesenteric lymph nodes of alloxan-induced diabetic rats (40 mg/kg body weight). The activities of hexokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase (G6PDH), citrate synthase and phosphate-dependent glutaminase were determined. Decarboxylation of metabolites [U-14C]-, [1-14C]- and [6-14C]-glucose, [1-14C]- and [2-14C]-pyruvic acid, [U-14C]-palmitic acid and [U-14C]-glutamine was evaluated in incubated lymphocytes isolated from mesenteric lymph nodes. The measurements were carried out in cells following three experimental protocols: (1) lymphocytes freshly obtained from control and alloxan-induced diabetic rats, (2) lymphocytes from insulin-treated (2 U/rat per day) diabetic rats and (3) lymphocytes obtained from control ...
Effects of glucose and other modifiers of insulin release on
1971
The oxidation of alanine, arginine, leucine, glucose, and pyruvate was studied in microdissected pancreatic islets of obese-hyperglycaemic mice. The following main observations were made. The oxidation of glucose was enhanced severalfold when its concentration was raised from 3 to 20mm. At the latter concentration the rate was about 65mmol/h per kg dry wt. The oxidation of 17mM-pyruvate amounted to 20mmol/h per kg dry wt. indicating a significant entry of this compound into the f-cells. Leucine oxidation was little affected by concentration changes above 5mM, the rate at 20mM corresponding to about 25% of that obtained with 20mM-glucose. In the absence of glucose, the oxidation of alanine or arginine was barely significant. Glucose stimulated the oxidation of alanine but depressed that of leucine. These effects of glucose were blocked by mannoheptulose or iodoacetamide but were not influenced by adrenaline, diazoxide, dibutyryl 3': 5'cyclic AMP, or glibenclamide. The rate of alanine oxidation was doubled in the presence of 17mM-pyruvate but was unaffected by citrate or succinate. Succinate depressed the oxidation ofleucine. Neither alanine nor leucine significantly affected the oxidation of glucose. It is suggested that the effects of glucose on the oxidation of alanine and leucine were mediated by metabolism of the sugar, and that amino acids do not act as insulin secretagogues by serving as fuels for the f-cells. The results are consistent with the existence of mechanisms auxiliary to glucose metabolism for control of insulin release.
Microvascular Research, 1975
Cutaneous microcirculatory responses to insulin administration (0.5, I .O, and 2.0 IU/kg, iv) were studied in a transparent chamber installed in a rabbit ear under fasting conditions. Vital microscopic observations were made visually with photomicrography and microphotoelectric plethysmography. Following the insulin administration, a marked and persistent vasoconstriction and a low-flow state were developed invariably in connection with insulin hypoglycemia. During the low-flow state, leukocytes became highly adherent especially in venules; in arterioles they obstructed the flow of erythrocytes into the distal vessels, and consequently a profound microcirculatory hypohematocrit-hypoperfusion state occurred. Leukocytes adhering to venules were not easily washed away even by the rapid blood flow, however, they never formed aggregates, thrombi, or coagulates. Administration of glucose (1 .O g/kg, iv) during the insulin-induced low-flow state (1.5 hr after insulin, 2.0 IU/kg iv), which could relieve, if any, insulin convulsions, resulted in a transient complete arrest of the microcirculation followed by a moderated recovery of it. In addition, peripheral circulating leukocytes were counted and a significantly reduced count of lymphocytes was obtained after the insulin administration. Some implications of the findings are discussed from the point of view of hematology as well as physiology.
The International journal of biochemistry, 1987
1. The results of this study indicates that the binding of insulin to brain plasma membranes activates a membrane protease which, by a trypsin like mechanism, produces a soluble factor that modulates the PDH behaviour when added to brain mitochondria. 2. The supernatant from brain plasma membranes incubated with 0.5 mg/ml trypsin added to mitochondria increases PDH activity levels and cancels PDH inhibition by NaF, as has already been seen when the plasma membranes are incubated with 25 microU/ml insulin. No such effects are obtained when the incubation is run out with 0.5 mg/ml chymotrypsin. 3. The supernatants from insulin or trypsin treated plasma membranes retain their activating properties on mitochondrial PDH also after dansylation; from these preparations a dansylated active on PDH material was separated by monodimensional chromatography on HPTLC silica Gel plates, using chloroform/1-butanol (93:7 v/v) as a solvent. 4. Insulin incubation of plasma membranes pretreated with pr...