PubMed Health⌕ Search

Biomedical subjects

G Paolisso

Publications and source records attributed to G Paolisso.

At least 181 records · Page 10Linked to original sources
PubMed1987

Greater efficacy of pulsatile insulin in type I diabetics critically depends on plasma glucagon levels.

The aim of this study was to investigate the role of plasma glucagon levels on the blood glucose response to intravenous insulin administered continuously or in a pulsatile manner. Six type I diabetic patients proven to have no residual insulin secretion were investigated. Endogenous glucagon secretion was inhibited by a continuous intravenous infusion of somatostatin (100 micrograms/h) and replaced by exogenous infusions of the hormone at three different rates (7.5, 4.5, and 2.5 micrograms/h), resulting in three different plasma glucagon steady-state levels (i.e., approximately equal to 200, approximately equal to 130, and approximately equal to 75 pg/ml, respectively). Each subject, in random order and on different days, was infused intravenously with regular human insulin either continuously (0.17 mU X kg-1 X min-1) or with the same amount of insulin infused in a pulsatile manner (0.85 mU X kg-1 X min-1 during 2 min followed by 8 min during which no insulin was infused). At plasma glucagon levels approximately equal to 200 pg/ml, blood glucose rose from approximately 10 to approximately 13 mM without any difference between the two modalities of insulin infusion. For plasma glucagon levels approximately equal to 130 pg/ml, plasma glucose remained steady throughout the experiments, but during the last 40 min, plasma glucose levels were significantly lower when insulin was administered intermittently. This greater blood glucose-lowering effect of pulsatile insulin occurred earlier and was more pronounced for plasma glucagon levels averaging 75 pg/ml. We conclude that the greater hypoglycemic effect of insulin administered intravenously in a pulsatile manner in type I diabetics critically depends on plasma glucagon circulating levels.

Adult↗
PubMed1986

Insulin induces opposite changes in plasma and erythrocyte magnesium concentrations in normal man.

Plasma and erythrocyte magnesium levels were measured by atomic absorption spectrophotometry in 10 healthy volunteers during an oral glucose tolerance test and during an euglycaemic hyperinsulinaemic glucose clamp. At min 180 and 210 of the oral glucose tolerance test, a significant decline in plasma magnesium levels (p less than 0.01 and p less than 0.05 respectively) and a significant increase in erythrocyte magnesium levels (p less than 0.01 and p less than 0.05 respectively) were observed. Similar changes were seen during the second hour of the glucose clamp, during which euglycaemia (4.1 +/- 0.4 mmol/l) was maintained despite hyperinsulinaemia (110-130 mU/l). During in vitro incubations, glucose (5 mmol/l) did not modify erythrocyte magnesium levels. In contrast, erythrocyte magnesium levels were significantly increased (p less than 0.01) by insulin (100 mU/l), an effect entirely abolished by ouabain (5 X 10(-4) mol/l). These results suggest that insulin induces a shift of magnesium from the plasma to the erythrocytes both in vivo and in vitro. These data may help to interprete the abnormalities in magnesium circulating levels frequently reported in diabetic patients.

Adult↗
PubMed1986

Effect of sparteine sulfate on insulin secretion in normal men.

This study aimed at evaluating the influence of sparteine sulfate either upon basal plasma glucose and insulin or glucose-induced insulin secretion in normal man. Thirteen overnight fasted volunteers took part in this study; five of them were submitted to sparteine sulfate bolus (15 mg in 10 ml of saline solution) followed by a slow infusion (90 mg/100 ml X 60 min) and eight subjects underwent two different glucose pulses (20 gr. i.v.) in absence or in presence of sparteine, infused as described above. In basal conditions, along with sparteine infusion, plasma glucose showed a progressive and significant decrease (P less than 0.0001) and plasma insulin was significantly higher from min 10 to 120' (P less than 0.0005-0.001). Even during the glucose-induced insulin secretion, in the presence of sparteine infusion, plasma glucose levels were significantly lower while plasma insulin levels were significantly higher when compared to those observed after glucose alone. The acute insulin response (AIR) was 42 +/- 10 microU/ml after glucose alone vs 67 +/- 9 microU/ml after glucose plus sparteine (P less than 0.05). Total insulinemic areas were significantly different being 1410 +/- 190 vs 2250 +/- 310 microU/ml/min (P less than 0.001) during glucose and glucose plus sparteine infusion, respectively. This study thereby, demonstrates that in normal man sparteine sulfate, administrated by intravenous infusion, is able to increase either basal or glucose-induced insulin secretion.

Adult↗
PubMed1986

Insulin oscillations per se do not affect glucose turnover parameters in normal man.

To compare the metabolic effects of pulsatile vs. continuous iv insulin infusion, normal men had two glucose-controlled iv glucose infusions using the Biostator for 260 min, during which endogenous pancreatic hormone secretion was inhibited by a somatostatin infusion and glucagon was replaced by continuous glucagon infusion. The two tests were performed at 1-week intervals, during which human insulin was infused either continuously at a constant rate of 0.2 mU kg-1 min-1 or in a pulsatile manner at a rate of 1.3 mU kg-1 min-1 with a switching on/off length of 2/11 min. Blood glucose levels and glucose infusion rates (GIR) were continuously monitored, and glucose turnover was estimated using a [3H]glucose infusion. In both tests, plasma C-peptide dropped markedly, whereas plasma glucagon levels were about twice basal values. Plasma insulin averaged 7 mU liter-1 during continuous infusion and oscillated between 1.5 and 35 mU liter-1 during pulsatile delivery. During the first 30-60 min of both tests, the glucose appearance rate and endogenous glucose production (EGP) increased, resulting in moderate hyperglycemia, which completely suppressed GIR. During the last 65 min, EGP declined, while the glucose disappearance rate and the glucose MCR increased, so that GIR increased progressively to maintain the blood glucose clamped at about 5 mmol liter-1. During this period, no significant differences were found between the two modes of insulin administration for any of the parameters studied. Thus, continuous and pulsatile insulin iv infusion, resulting in physiological peripheral plasma insulin levels, altered the glucose turnover parameters equally, in particular inhibiting EGP, which was stimulated by glucagon during the first part of the study, and stimulating peripheral glucose uptake at the end of the study period.

Adult↗
PubMed1986

Plasma calcitonin variations in normal women and in women with family history of diabetes during pregnancy.

In eight normal pregnant women and in eighteen women with a family history of diabetes, plasma calcitonin (CT), parathyroid hormone (PTH), insulin and glucagon variations and total plasma calcium levels were investigated. Calcitonin, parathyroid hormone and glucagon were all increased during the 2nd and 3rd trimester of pregnancy in normal women (N.W.) and in women with a family history of diabetes (W.F.H.D.). Plasma calcitonin levels were statistically significantly different between the two groups only in the 3rd trimester (118 +/- 4.9 vs 139 +/- 3.6 pg/ml p less than 0.01 in N.W. and W.F.H.D. respectively). Total plasma calcium levels were decreased significantly in the 3rd trimester in both groups: 3rd vs 1st trimester p less than 0.005 and p less than 0.001 in N.W. and W.F.H.D. respectively. Statistically significant difference between the two groups in total insulinemic area (p less than 0.001), in the rapid phase area (p less than 0.01) and insulinogenic index (p less than 0.05) were observed in the 3rd trimester.

Calcitonin↗
PubMed1985

Sparteine increases insulin release by decreasing the K+ permeability of the B-cell membrane.

The effects of sparteine on the pancreatic B-cell function have been studied with mouse islets. In the presence of a non-stimulatory concentration of glucose (3 mM), sparteine (0.2-1 mM) decreased the rate of 86Rb+ efflux from islet cells, depolarized the B-cell membrane, induced a glucose-like electrical activity and stimulated insulin release. This increase in release was observed over a large range of glucose concentrations (3-20 mM), and was most marked in the presence of 10 mM glucose. At this concentration of glucose, the effect of sparteine was already detected with 0.02 mM and was maximal with 0.5 mM. Higher concentrations of sparteine only had a transient effect on insulin release. In the presence of 10 mM glucose, 0.2 mM sparteine decreased 86Rb+ efflux and increased 45Ca2+ efflux from islet cells. The effect on 86Rb+ efflux was only transient in the presence of extracellular calcium, whereas the effect on 45Ca2+ efflux required the presence of extracellular calcium. The electrical activity induced by glucose in B-cells was augmented by sparteine which, at a concentration of 0.5 mM, produced a persistent depolarization with continuous spike activity. The potentiation of insulin release by sparteine was not reversible, but was inhibited by adrenaline and completely blocked by omission of extracellular calcium. Sparteine reversed the increase in 86Rb+ efflux and the decrease in insulin release caused by diazoxide. These results show that sparteine increases insulin release by reducing the K+-permeability of the B-cell membrane.

Animals↗
PubMed1985

The effects of cesium chloride on insulin release, ionic fluxes and membrane potential in pancreatic B-cells.

Cs+ decreases K+ permeability in nerve and muscle cells. Its effects on the pancreatic B-cell function were studied with mouse islets. In the presence of 3 mM glucose, Cs+ substitution for K+ steadily inhibited 86Rb+ efflux and hyperpolarized the B-cell membrane. Addition of Cs+ to a K+-medium also inhibited 86Rb+ efflux, but depolarized the B-cell membrane. None of these changes altered insulin release. Substitution of Cs+ for K+ in a medium containing 10 mM glucose caused a Ca2+-dependent stimulation of insulin release and 45Ca2+ efflux, produced an initial fall and a secondary rise in 86Rb+ efflux and augmented the electrical activity in B-cells. Reintroduction of K+ to the medium was followed by a marked and transient inhibition of insulin release, that was blocked by ouabain and accompanied by an inhibition of 45Ca2+ and 86Rb+ efflux and by a hyperpolarization of the B-cell membrane. Addition of Cs+ to a K+ medium containing 10 mM glucose stimulated insulin release, 45Ca2+ efflux and 86Rb+ efflux. It also increased the electrical activity in B-cells. In the absence of Ca2+, however, Cs+ addition decreased the rate of 86Rb+ efflux. The effects of Cs+ on the B-cell function may be explained by its ability to decrease K+ permeability of the plasma membrane, by its inability to activate the sodium pump, and by a third unidentified effect likely brought about by the accumulation of intracellular Cs+.

Animals↗
PubMed1985

The effects of lidocaine and procainamide on the sarcolemmal membrane high affinity cyclic AMP phosphodiesterase of rat myocardium.

The incubation of rat myocardial sarcolemmal membranes with 10(-4)M lidocaine or procainamide results in a decreased fluorescence polarization of the extrinsic probes (diphenylhexatriene and 12-anthroylstearate) and in the stimulation of the membrane-bound high affinity cyclic AMP phosphodiesterase activity (PDE). Lidocaine or procainamide do not contrast, but facilitate the aminophylline inhibitory action on the PDE activity, without modifying the basic molecular mechanism of the inhibitory action. The amplitudes of the effects described are inversely correlated to the temperature, being greater at the lower tested temperature (25 degrees greater than 30 degrees greater than 37 degrees C).

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

Effects of salicylate, tolbutamide, and prostaglandin E2 on insulin responses to glucose in noninsulin-dependent diabetes mellitus.

To assess whether the beneficial effects of salicylates compounds and sulfonylureas on insulin secretion in patients with noninsulin-dependent diabetes mellitus could be ascribed to inhibition of prostaglandin E (PGE) synthesis, insulin responses to iv glucose pulses were determined in diabetic patients during infusion of lysine acetylsalicylate (LAS) or tolbutamide, with or without a concurrent infusion of PGE2. In these diabetic patients, the augmenting effects of LAS on glucose-induced insulin secretion were abolished by PGE2 infusion. Partial restoration by tolbutamide infusion of the first and second phases of glucose-induced insulin secretion was not affected by the administration of PGE2. The stimulatory effects of LAS and tolbutamide on insulin secretion were additive, suggesting separate mechanisms of action. Since salicylates and sulfonylureas lower plasma glucose concentrations, we also evaluated whether prevention of the fall in the prestimulus glucose level could result in a further amplification of insulin release. Resetting the prestimulus glucose level to control values by infusing glucose caused a further increase in the second, but not the first, phase of glucose-induced insulin secretion, indicating that the prestimulus glucose level had a role in regulating subsequent insulin release. These results indicate that salicylates, but not sulfonylureas, exert their acute insulinotropic effect in noninsulin-dependent diabetic patients by inhibiting endogenous PGE synthesis and support the idea that endogenous PGE may play a role in the impaired insulin response to glucose in this form of human diabetes.

Adult↗
PubMed1985

Interaction between epinephrine, prostaglandin E, and met-enkephalin in the regulation of insulin release in man.

Prostaglandin E (PGE), epinephrine and metenkephalin are three endogenous substances normally present in the endocrine pancreas which have been reported to inhibit glucose-induced insulin secretion in normal humans. To evaluate possible synergistic interactions between these inhibitory agents upon the regulation of insulin release in man, we examined the effects of PGE, epinephrine and the long-acting met-enkephalin analogue FK 33-824, given alone or in combination, upon glucose-induced insulin secretion in normal man. The infusion of the three agents at doses known to affect insulin secretion (10 micrograms/min, 15 ng/kg/min, 0.5 mg im, respectively) produced the expected inhibitory effects upon insulin responses to an intravenous glucose challenge. The infusion of the three agents at doses which did not produce per se any significant change of insulin responses to glucose (5 micrograms/min, 5 ng/kg/min, 0.2 mg i.m., respectively), caused a significant inhibition of this response when given in combination. In particular, the acute insulin response to glucose decreased from a control value of 50 +/- 9 microU/ml to a value of 21 +/- 6 microU/ml (p less than 0.02). The inhibitory effect of epinephrine (15 ng/kg/min) upon glucose-induced insulin secretion was partially reversed by sodium salicylate, an inhibitor of endogenous prostaglandin synthesis, which increased but not normalized, either the acute insulin response and the glucose disappearance rates. Similarly, the negative effect of FK 33-824 upon glucose-induced insulin secretion was reversed by sodium salicylate. Similar findings were also obtained with indomethacin, another structurally unrelated inhibitor of endogenous prostaglandin synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Low insulin concentrations stimulate in vitro the soluble guanylate cyclase activity of rat liver.

The soluble guanylate cyclase activity of rat liver appears to be stimulated in VITRO by insulin at pMolar concentrations, while proinsulin, denaturated insulin or desoctapeptide insulin, are not able to stimulate the studied enzymic activity. Corresponding concentrations of other peptide hormones such as corticotropin (ACTH) or glucagon, either in the absence or in the presence of bacitracin, do not show any effect on the investigated enzymic system. Insulin stimulation of the soluble guanylate cyclase is characterized by a significant increase in the Vmax together with a decrease of the apparent Km. Insulin at low concentrations doesn't affect the cyclic GMP hydrolyzing activity; conversely higher concentrations of the hormone, while exerting a less marked effect on the guanylate cyclase activity, inhibit the cyclic GMP hydrolyzing activity.

Animals↗
PubMed1983

A stimulating effect of guanyl nucleotides on the rat-liver soluble cyclic GMP high-affinity phosphodiesterase activity.

The high affinity (low Km) cyclic GMP phosphodiesterase (PDE) is activated by GTP, while the cyclic AMP PDE is not. GTP and its hydrolysis-resistant analogue, guanylylimidodiphosphate (GppNHp), display a half-maximal stimulating effect at almost the same concentration (5 X 10(-6) M). The GTP stimulating effect is not observed when the socalled cyclic GMP low affinity (high Km) PDE is operative. GTP cooperates with the increase of the substrate concentration on removing the IBMX inhibitory effect. The isolation through a classical chromatographic procedure on a DEAE-cellulose column, of a PDE fraction specific for cyclic GMP, results in the loss of the GTP stimulating effect.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

Age-related insulin resistance: is it an obligatory finding? The lesson from healthy centenarians.

It is widely known that advancing age is associated with impaired glucose handling. A unifying hypothesis explaining the relationship between aging and insulin resistance might encompass four main pathways, namely: (a) anthropometric changes (relative and absolute increase in body fat combined with a decline in fat free mass) which could be the anatomic substrate for explaining the reduction in active metabolic tissue; (b) environmental causes, mainly diet style and physical activity; (c) neuro-hormonal variations [decline in plasma dehydroepandrosterone sulphate (DHEAS) and IGF-1]; and finally (d) the rise in oxidative stress. Indeed previous studies have also investigated the occurrence and the degree of insulin resistance in healthy centenarians. Such data demonstrated that age-related insulin resistance is not an obligatory finding in the elderly and that healthy centenarians have a preserved insulin action compared to aged subjects. Why insulin action is preserved in centenarians is still not known. Nevertheless, a possible approach to the question is to outline the centenarians' anthropometric, endocrine and metabolic characteristics in order to design a clinical picture of such metabolic "successful aging". According to the remodeling theory of age, the preserved insulin action in centenarians might be the net result of the continuous adaptation of the body to the deleterious changes that occur over time. Nevertheless, only future longitudinal studies specifically designed to investigate the relationship between extreme old age and degree of insulin sensitivity will provide a conclusive answer with regard to the pathophysiology of adaptive metabolic changes occurring in the elderly.

Adipose Tissue↗
PubMedDate not supplied

Effect of human calcitonin (hCT) on glucose- and arginine-stimulated insulin secretion.

Many studies have shown that in normal man salmon and porcine CT administration in bolus inhibits the release of TSH, LH, GH, and glucose- or arginine-induced insulin secretion. In the present study we investigated the effects of human synthetic calcitonin (hCT) on glucose- or arginine-induced insulin secretion in man. Twenty-two subjects were submitted to i.v. administration of hCT during glucose or arginine test. In our opinion, the most interesting results are those observed with arginine plus hCT at two different dosages (25 micrograms and 12.5 micrograms infused in 30 min). In fact arginine plus hCT (25 micrograms in 30 min) administration induced a significant increase of glycemia at 5, 10 and 20 min (p less than 0.01) and at 30 min (p less than 0.05) and a significant decrease of IRI at 5, 10, 20 and 30 min (p less than 0.001) and at 45 min (p less than 0.005). The highest plasma CT levels were observed at 15 and 30 min (490 and 540 pg X ml-1). Arginine plus hCT (12.5 micrograms in 30 min) infusion induced a similar significant increase in plasma glucose at 10, and 20 min (p less than 0.05) and at 30 min (p less than 0.01) and a significant decrease of plasma IRI at 10 min (p less than 0.05) at 20 min and 30 min (p less than 0.005). The highest plasma CT levels were reached at 20 min and 30 min (250 and 270 pg X ml-1, respectively). Our results clearly demonstrate that physiologic doses of hCT are able to inhibit arginine induced insulin secretion in normal man. Since insulin induces hypercalcemia and food ingestion increases both insulin and CT, one could hypothesize that CT inhibits insulin secretion thus controlling post-prandial hypercalcemia by its osteotrophic effect and by its action upon calcium redistributed within the cells.

Arginine↗