Twenty-four hour profiles of plasma C-peptide in Type 1 (insulin-dependent) diabetic children

Summary Twenty-four hour profiles of plasma C-peptide an index of endogenous insulin secretion, were performed in 15 Type 1 (insulin-dependent) diabetic children. Plasma C-peptide was detectable in six children, of whom four (C-peptide producers) had peak values above normal fasting levels. In each of the six children with residual B cell function, there was a close correlation between plasma C-peptide and simultaneous blood glucose (r> 0.50, p< 0.05). Post-breakfast peak blood glucose was 10.2 ± 1.7 mmol/l (mean ±SEM) in the C-peptide producers and 18.7 ± 1.7 mmol/l in the 11 children with low or no detectable C-peptide. Mean M-value, an index of deviation from an ideal blood glucose, was lower in the C-peptide producers (p<0.05). It is concluded that residual functioning B cells in diabetic children behave physiologically in that insulin secretion fluctuates in accordance with the prevailing blood glucose; and that the pattern of action of injected insulin is more critical in non-C-peptide producers who lack the post-prandial dampening effect provided by residual endogenous insulin secretion.     

Influence of insulin on cyclic 3′,5′-AMP phosphodiesterase activity in liver,skeletal muscle,adipose tissue,and kidney

Summary Influence of insulin on liver glycogen metabolism and on lipolysis appears to be mediated by a decreased intracellular 3,5-AMP concentration. Reduced formation of 3,5-AMP had been shown in adipose tissue incubated with insulin. The influence of insulin on 3,5-AMP degradation has been investigated. — 3,5-AMP phosphodiesterase (PDE) activity was reduced in liver, adipose tissue and, insignificantly, in skeletal muscle of insulin deficient, i.e. alloxan diabetic or starved rats. I.V. injection of a low dose of insulin (0.5 U/kg) or stimulation of endogenous insulin secretion by injection of glucose led to a rapid increase of PDE activity in these tissues. 15 min after insulin injection liver PDE activity was increased. The maximal effect occurred after 30–45 min. Renal PDE activity was not decreased in alloxan diabetes, insulin injection has been found ineffective. —In vitro, there was an activating effect of crystalline insulin on PDE purified from beef heart. Insulin concentration required for duplication of enzyme activity was of the order of 2 · 10^–5 M. Treatment with actinomycin D nearly prevented stimulation of liver PDE by insulin. This may indicate that the action of insulin on PDE activity is essentially based on an increased enzyme synthesis. — Owing to the influence of insulin secretion on liver and adipose tissue 3,5-AMP concentration, glycogen metabolism and lipolysis can be quickly adapted to food intake.

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Der Einfluß von Insulin auf die 3,5-AMP-Phosphodiesterase-Aktivität in Leber, Skeletmuskulatur, Fettgewebe und Niere

Zusammenfassung An der Steigerung der Glykogensynthese der Leber und der Verminderung der Lipolyse durch Insulin ist eine Abnahme der 3,5-AMP-Konzentration wesentlich beteiligt. Die 3,5-AMP-Bildung ist in Fettgewebe, das mit Insulin inkubiert wird, vermindert. Insulin beeinflußt jedoch auch den 3,5-AMP-Abbau. -Die 3,5-AMP-Phosphodiesterase (PDE)-Aktivität des Fettgewebes, der Leber und, in geringerem Grade, der Skeletmuskulatur ist im Insulinmangel vermindert, d.h. bei alloxandiabetischen oder hungernden Ratten. I.v. Injektion von 0,5 E/kg Insulin oder eine erhöhte Abgabe von Insulin aus dem Pankreas nach Glucoseinjektion führen in diesen Geweben zu einem raschen Anstieg der PDE-Aktivität. Dieser ist in der Leber schon 15 min nach Insulingabe nachweisbar und erreicht nach 30–45 min sein Maximum. In der Niere ist kein Einfluß von Insulin auf die PDE-Aktivität nachweisbar. — Aus Rinderherz isolierte PDE wirdin vitro durch Insulin aktiviert, jedoch werden2 · 10^–5 M zur Verdopplung der Aktivität benötigt. Actinomycin D verhindert die Steigerung der Leber-PDE-Aktivität nach Insulininjektion. So kann die Wirkung des Hormons im wesentlichen auf eine gesteigerte PDE-Synthese zurückgeführt werden. — Durch diesen Einfluß der Insulininkretion auf die 3,5-AMP-Konzentration in Leber und Fettgewebe können Glykogenstoffwechsel und Lipolyse rasch an die Nahrungsaufnahme angepaßt werden.

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Influence de l'insuline sur l'activité de la 3,5-AMP-phosphodiestérase dans le foie, le muscle strié, le tissu adipeux et le rein

Résumé L'influence de l'insuline sur le métabolisme du glycogène hépatique et sur la lipolyse semble s'exercer par l'intermédiaire d'une diminution de la concentration de 3,5-AMP intracellulaire. Onamontré une diminution de la formation de 35-AMP dans le tissu adipeux incubé avec de l'insuline. L'influence de l'insuline sur la dégradation du 3,5-AMP est étudiée. — L'activité de la 3,5-AMP-phos-phodiestérase (PDE) est diminuée dans le foie, le tissu adipeux et, de façon non-significative, dans le muscle strié des rats qui manquent d'insuline, c-à-d les rats rendus diabétiques par l'alloxane ou les rats privés de nourriture. L'injection intraveineuse d'une faible dose d'insuline (0.5 U/kg) ou la stimulation de la sécrétion d'insuline endogène par une injection de glucose provoquent une augmentation rapide de l'activité de la phosphodiestérase dans ces tissus. 15 min après l'injection d'insuline, l'activité de la phosphodiesterase du foie est augmentée. L'effet maximum est atteint après 30–45 min. L'activité de la phosphodiestérase rénale n'est pas diminuée dans le diabète alloxanique, l'injection d'insuline s'est avérée inefficace.In vitro, l'insuline cristalline a un effet activant sur la phosphodiestérase purifiée du coeur de boeuf. La concentration d'insuline requise pour doubler l'activité de l'enzyme est de l'ordre de 2 · 10^–5 M. Le traitement avec actinomycin D empêche la stimulation par l'insuline de la PDE dans le foie. Ceci peut indiquer que l'action de l'insuline sur l'activité de la phosphodiestérase est essentiellement basée sur une synthèse accrue de l'enzyme. A cause de l'influence de la sécrétion d'insuline sur la concentration en 3,5-AMP du foie et du tissu adipeux, le métabolisme du glycogène et la lipolyse peuvent s'adapter rapidement à la prise de nourriture.

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Non-Standard Abbreviations G 6 P Glucose-6-phosphate - UDPG UDP-glucose - FFA non-esterifled, free fatty acids - 3,5-AMP cyclic adenosine-3,5-monophosphate - PDE 3,5-AMP phosphodiesterase This study was supported by the Deutsche Forschungsgemeinschaft.Deceased October 31, 1967.     

The antigenicity of human hemoglobins

Summary The correlation of the antigenicities among native hemoglobins and their subunit chains were investigated by the absorption of antisera and the combination of urea added immunoelectrophoresis with double diffusion. Alphachain showed identity with Hb-F but partial identity with -chain and Hb-A. Beta-chain showed identity with Hb-A but -chain and Hb-F showed partial identity with this chain. Gamma-chain showed identity only with Hb-F and its antigenicity was considered as being different from those of - or -chains.The lines of -, -and -chains were reconfirmed from the facts that the appearance of them depended always on the existence of anti-Hb-A or anti-Hb-F antibodies in the absorbed antisera and the minor component lines of

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Zusammenfassung Die Zusammenhänge der Antigenität zwischen nativen Hämoglobinen und deren Unterketten wurden mit der Absorption der Antiseren und der Kombination der Harnstoff-Immunelektrophorese und Doppeldiffusion untersucht. Die -Kette zeigte Identität mit Hb-F, aber nur partielle Identität mit der -Kette und Hb-A. Die -Kette war in ihrer Antigenität mit Hb-A identisch, die -Kette und Hb-F waren teilweise identisch mit der -Kette. Die -Kette zeigte die Identität mit Hb-F; es wird angenommen, daß ihre Antigenität verschieden von der -oder -Ketten ist.Für das Auftreten der Linien der -, - und -Ketten müssen Anti-Hb-A-oder Anti-Hb-F-Antikörper in den absorbierten Antiseren vorhanden sein, außerdem fusionieren die schwächeren Linien der Doppeldiffusion nicht mit irgendwelchen Linien der Unterketten. Auch gereinigte - oder -Ketten wurden zur Feststellung ihrer Linien benutzt.

     

Oral glucose tolerance and ambient temperature in non-diabetic subjects

Summary When either a 960-kcal, 140-g carbohydrate meal, or a 75-g glucose load was ingested by non-diabetic Caucasians, the 2-h venous plasma glucose concentration was higher by 0.82 and 1.25 mmol/l, respectively, if the ambient temperature was 33 °C rather than 23 °C. It is likely that this is a result of relative arterialisation of the venous blood. Even at 23 °C room temperature, use of the hot hand technique to obtain arterialised venous blood increases post-load glucose levels in contralateral antecubital veins. If these observations apply to those acclimatised to the heat, they could affect the diagnosis of both diabetes and impaired glucose tolerance in the tropics.     

Glucokinase is not the pancreatic B-cell glucoreceptor

Summary A series of recent experimental findings are reviewed to indicate that glucokinase does not represent the pancreatic B-cell glucoreceptor. (1) Whether in liver, pancreatic islet or insulin-producing tumoral cell homogenates, glucokinase fails to yield a higher reaction velocity with -than -D-glucose. (2) At a high glucose concentration (40 mmol/l), when the phosphorylation of glucose by glucokinase is indeed higher with - than -D-glucose, no preference for -D-glucose is observed in intact islets, as judged from the utilization of D-[5-³H]glucose, production of lactic acid, oxidation of D-[U-¹⁴C] glucose, net uptake of ⁴⁵Ca or release of insulin. (3) The glucose 6-phosphate content of intact islets is higher in the presence of - than -D-glucose. (4) At a low glucose concentration (3.3 mmol/l), when the participation of glucokinase to hexose phosphorylation is minimal, -D-glucose is still better metabolized and stimulates both ⁴⁵Ca net uptake and insulin release more efficiently than -D-glucose, despite the fact that hexokinase yields a higher reaction velocity with - than -D-glucose. (5) In intact islets, -D-glucose is used preferentially to -D-glucose in the pentose cycle pathway as judged from the oxidation of - or -D-[1-¹⁴C]glucose relative to that of - or -D-[6-¹⁴C]glucose. (6) In islets removed from fasted rats, the rate of glycolysis is more severely decreased than expected from the repression of glucokinase. (7) The metabolism of glucose in tumoral insulin-producing cells differs, in several respects, from that in normal pancreatic islets, although the pattern of hexokinase and glucokinase activities is similar in these two types of cells. All these observations point to the participation of regulatory sites distal to glucose phosphorylation in the control of glucose metabolism in islet cells.     

High glucose and hydrogen peroxide increase c-Myc and haeme-oxygenase 1 mRNA levels in rat pancreatic islets without activating NFκB

Aims/hypothesis Hyperglycaemia and the pro-inflammatory cytokine IL-1 induce similar alterations of beta cell gene expression, including up-regulation of c-Myc and haeme-oxygenase 1. These effects of hyperglycaemia may result from nuclear factor-kappa B (NFB) activation by oxidative stress. To test this hypothesis, we compared the effects of IL-1, high glucose, and hydrogen peroxide, on NFB DNA binding activity and target gene mRNA levels in cultured rat islets.Methods Rat islets were pre-cultured for 1 week in serum-free RPMI medium containing 10 mmol/l glucose, and further cultured in glucose concentrations of 5–30 mmol/l plus various test substances. Islet NFB activity was measured by ELISA and gene mRNA expression was measured by RT-PCR.Results IL-1 consistently increased islet NFB activity and c-Myc, haeme-oxygenase 1, inducible nitric oxide synthase (iNOS), Fas, and inhibitor of NFB alpha (IB) mRNA levels. In comparison, 1- to 7-day culture in 30 mmol/l instead of 10 mmol/l glucose stimulated islet c-Myc and haeme-oxygenase 1 expression without affecting NFB activity or iNOS and IB mRNA levels. Fas mRNA levels only increased after 1 week in 30 mmol/l glucose. Overnight exposure to hydrogen peroxide mimicked the effects of 30 mmol/l glucose on haeme-oxygenase 1 and c-Myc mRNA levels without activating NFB. On the other hand, the antioxidant N-acetyl-l-cysteine inhibited the stimulation of haeme-oxygenase 1 and c-Myc expression by 30 mmol/l glucose and/or hydrogen peroxide.Conclusions/interpretation In contrast to IL-1, high glucose and hydrogen peroxide do not activate NFB in cultured rat islets. It is suggested that the stimulation of islet c-Myc and haeme-oxygenase 1 expression by 30 mmol/l glucose results from activation of a distinct, probably oxidative-stress-dependent signalling pathway.     

Glucagon immunoreactivity in plasma from normal and dystrophic mice

Summary The present investigation was undertaken to determine and characterize glucagon immunoreactivity in plasma from normal NMRI mice and from dystrophic mice and their unaffected littermates of the 129/ReJ strain. Very young dystrophic mice (6 weeks old) displayed much higher basal levels of plasma glucagon immunoreactivity than normal mice. In contrast, plasma concentrations of insulin and glucose were lower in these dystrophic mice than in normal NMRI mice. The plasma glucagon levels declined with age in both strains during the time-period studied (1.5–5 months). Gel filtration of plasma from dystrophic as well as normal mice on Sephadex G-200 revealed that a large part of the total glucagon immunoreactivity was eluted in fractions containing the immunoglobulins. The amount of the true glucagon part was lower in plasma from normal mice (about 0.2 g/l) than in plasma from mice of the dystrophic strain (0.4–0.5 g/l)). This finding was indirectly corroborated by the observation that a large intravenous glucose load decreased plasma glucagon by approximately 0.2 g/l in the non-dystrophic NMRI strain and by about 0.4–0.6 g/l in the dystrophic strain. Thus, the ability of glucose to suppress glucagon secretion appeared unaffected in the dystrophic mice. Glucose-induced insulin release, however, was considerably impaired in these animals. It is concluded that mice of the dystrophic 129/ReJ strain have higher plasma levels of true glucagon than mice of the non-dystrophic NMRI strain. Whether the abnormally high plasma glucagon levels in the dystrophic strain, particularly in very young dystrophic mice, might contribute to the development of the muscular dystrophy remains to be elucidated.     

Acute insulin response of donors is correlated with pancreatic islet isolation outcome in the pig

Aims/hypothesis Unpredictability of islet isolation outcome remains a frustrating and costly issue in the clinical implementation of islet transplantation. The aim of this experimental study was to test the hypothesis that the donors insulin secretory reserve, an in vivo surrogate of functional pancreatic mass, is correlated with the outcome of islet isolation.Methods Insulin secretory reserve was evaluated in 28 healthy adult minipigs prior to pancreatectomy and islet isolation. Blood glucose and insulinaemia were measured before and 1, 3, 5, 10, 15, 30, 60 and 90 min after glucose infusion. Following total pancreatectomy, islet isolation was performed according to Ricordis semi-automated method, and the total number of islets obtained was determined. Fasting blood glucose, insulinaemia, acute insulin response (AIR), maximal insulinaemia and the glucose decay constant (K_G) were calculated, and possible associations with the outcome of islet isolation were assessed.Results AIR and maximal insulinaemia after glucose injection were correlated with the outcome of islet isolation (p<0.01). Mean values for AIR and maximal insulinaemia were significantly different between animals in which islet isolation was successful (n=11) vs those in which it was unsuccessful (n=17) (77.6±13.7 U/ml vs 42.3±7.8 U/ml, p<0.05; 144.7±21.6 U/ml vs 71.9±10.4 U/ml, p<0.05, respectively).Conclusions/interpretation This study suggests that the donors pancreatic endocrine mass, as estimated by AIR, is a major determinant of the outcome of islet isolation in large mammals. Our results may explain the frustrating variability of human islet isolation outcome and could lead to a new approach for optimising the selection of brain-dead and/or living pancreas donors.     

Acute insulin response to intravenous glucose,glucagon and arginine in some subjects at risk for Type 1 (insulin-dependent) diabetes mellitus

Summary The relationships between first-phase insulin secretion to i.v. glucagon and i.v. arginine were studied in 19 healthy adult volunteers (Group I) and in 21 subjects at risk for Type 1 (insulin-dependent) diabetes mellitus with either a normal (n=11; Group II a) or a low insulin response to i.v. glucose (n=10; Group II b). Groups I and II a displayed similar insulin responses to the three secretagogues. In contrast, Group II b demonstrated lower insulin responses to both glucagon and arginine than control subjects (p}<0.007 and (p}<0.04 respectively) orthan normo-responders to glucose (#x007D;<0.007 and p<0.04 respectively). In Group II b however, arginine-stimulated insulin release was increased compared to the response to glucose (p}<0.006), while glucagon and glucose led to non-statistically different responses. Five low-responders developed Type 1 diabetes. As a group, they displayed lower responses to glucagon and to arginine than subjects who up to now have not developed the disease (p<0.05 and p<0.0003 respectively). In the subjects who progressed to diabetes, the responses to glucose and glucagon were similarly blunted. In the low-responders who have not developed the disease, no statistical difference could be detected between mean responses to glucagon and glucose, but four out of these five subjects had a glucagon-stimulated response within the control range and higher than their corresponding response to glucose. Arginine led to a higher stimulation than glucose, in subgroups that either progressed to diabetes (p<0.006) or did not (p<0.002). Finally, low-responders who did not develop diabetes displayed similar responses to both glucagon and arginine than normo-responders to glucose. A progressive decrease of arginine-stimulated insulin response may be a later event during pre-Type 1 diabetes than a blunted response to glucose, while a loss of glucagon-stimulated insulin release may be intermediate. Diminished response to all secretagogues may offer better prediction than a low response to glucose alone.     

Islet B-cell dysfunction and the time course of recovery following chronic overinsulinisation of normal rats

Summary Appropriate insulin therapy may preserve or improve islet B-cell function whereas the effects of overinsulinisation are unclear. Pancreatic islet B-cell function was therefore studied after overinsulinisation of normal rats for 4 weeks (fed blood glucose 2.2–4.5 mmol/l, controls 4.1–7.0 mmol/l). Insulin secretion was assessed by a 3-h hyperglycaemic clamp (10.0 mmol/l) performed 1, 48, and 120 h after insulin withdrawal (n=6 in each group). When the clamp was performed 1 h after insulin withdrawal, clamp insulin concentration was 1.6±0.1 g/l, compared to 9.3±1.0 g/l in control rats. The integrated area under the plasma insulin concentration curve was also significantly decreased (4.8±0.4 vs 20.3±2.2 g·l^–1·h^–1, p<0.001), but recovered to 9.4±1.0 g·l^–1·h^–1 after 48 h, and to 17.5±1.4 g·l^–1·h^–1 after 120 h. Pancreatic insulin contents were decreased at 1 h (6±1 g/g wet wt) and 48 h (54±12 g/g wet wt) but not at 120 h (221±30 g/g wet wt) after withdrawal (controls, 303±29 /g wet wt) and there was a strong relationship with pancreatic preproinsulin mRNA and the clamp insulin response. Thus, overinsulinisation with prolonged periods of low blood glucose concentrations impairs islet B-cell function, but is reversible over 5 days.     

Changes in the activity of ‘active’ pyruvate dehydrogenase complex in the newborn of normal and diabetic rats

Summary At birth, hepatic active and dichloracetate-activated pyruvate dehydrogenase complex activities in the newborn of normal, mildly diabetic, and severely diabetic rats were similar. The active and dichloracetate-activated pyruvate dehydrogenase complex activities increased significantly during the first 2 and 6 postnatal h, respectively in the three groups of neonates (p<0.05). The greatest increase in both active and dichloroacetate-activated pyruvate dehydrogenase complex activity was observed in the neonates of mildly diabetic rats. Administration of glucose or insulin at birth to the newborn of normal rats caused a significant increase in the percentage of active pyruvate dehydrogenase complex activity within 1 h (p<0.01). Similar treatment caused no significant increases in the newborn of severely diabetic rats. The transient increases in active pyruvate dehydrogenase complex activity in the neonates of normal and diabetic rats were consistent with rapid disappearance of blood lactate during the first hours of postnatal life.     

Glucose and free fatty acid turnover in normal subjects and in diabetic patients before and after insulin treatment

Summary Turnover rates of glucose and free fatty acids were measured, using³H-glucose and¹⁴C-1-palmitic acid as tracers, in insulin-requiring diabetic patients at presentation and after insulin treatment. Correlations were sought with rates of substrate oxidation, determined independently from respiratory exchange, and with plasma hormone concentrations. The rates of appearance of glucose and of free fatty acids were increased in the diabetics to 17.6 and 10.2 mol min^–1 kg^–1 respectively. Both rates fell to normal (13.3 and 7.1 mol min^–1 kg^–1) after insulin. In the untreated state there was an inverse relationship between the rates of utilisation of glucose and free fatty acids (r=0.61; p<0.05). It is suggested that this relationship represents the impairment of peripheral glucose utilisation by free fatty acids and by ketone bodies in vivo, so far only demonstrated in vitro. The tracer calculated rates of glucose utilisation correlated well over a wide range with the respiratory quotient in untreated diabetics, while respiratory quotient was inversely related to free fatty acid turnover rates. In untreated diabetics plasma cortisol and 3,3, 5-triiodothyronine (rT₃) were increased whereas thyroxine and 3,5,3-triiodothyronine (T₃) were decreased. 3,5,3-Triiodothyronine concentration was closely related to the metabolic clearance rate of glucose (p<0.05), while cortisol concentrations correlated with glucose production (p<0.02) and blood ketone body concentration (p<0.02).It is concluded that glucose overproduction is the major contributor to the hyperglycaemia of untreated diabetes.     

Is a lag-storage curve an early sign of diabetes?

Summary Early insulin responses were measured after a high dose (50 g/1.73 m²) of rapidly injected glucose in 31 subjects who had repeatedly shown lagstorage curves in the OGTT, in 24 controls and in 19 mild maturity-onset diabetics. Division between controls and diabetics was virtually complete, when the insulin responses were expressed as insulindgenic index Twenty out of 31 patients with lag curves showed normal early insulin responses and 11 patients showed diabetic responses. In patients with lag curves, presence of obesity, and absence of family history of diabetes were associated with normal insulin responses. It is concluded that the finding of a lag curve is of little consequence in obese persons but, when in conjunction with a genetic background of diabetes, is suggestive of diabetes.Part of this material was presented at the 8th meeting of the EASD in Madrid, 1972 (24)     

Sertraline Causes Strong Coronary Vasodilation: Possible Relevance for Cardioprotection by Selective Serotonin Reuptake Inhibitors

Summary Objective: Although Selective Serotonin Reuptake Inhibitors (SSRIs) are important antidepressant drugs, knowledge of their vaso active effects is limited. Vaso active effects of the SSRI sertraline were studied in rings of rat aorta, human Internal Mammary Arteries (IMAs) and in Langendorff perfused rat hearts.Methods: The effects of sertraline (0.1 to 300 mol L^{– 1}) on precontracted rat aortic and IMA rings were evaluated in organ bath chambers. Precontraction was elicited by serotonin (5-HT; 10 mol L^{– 1}), phenylephrine (PE; 10 mol L^{– 1}) and potassium chloride (KCl; 50 mmol L^{– 1}). In addition, the effects of sertraline on PE induced contraction curves were established by subjecting vascular rings to increasing doses of PE (1 nmol L^{– 1} to 10 mol L^{– 1}) in the presence of sertraline or vehicle. Finally, the effects of sertraline on ex vivo coronary flow in rat hearts were examined using a retrograde Langendorff perfusion model.Results: Sertraline elicited dose-dependent relaxation, independent of the substance used for precontraction (p < 0.025). Sertraline showed a rightward shift of dose-response curves to PE (p < 0.01). Vasodilatory effects of SSRIs were endothelium independent. In perfused rat hearts, sertraline (0.3 to 10 mol L^{– 1}) showed a concentration-dependent increase in coronary flow that returned to baseline levels after wash-out of the antidepressant (p = 0.005).Conclusions: One of the SSRIs, sertraline, showed marked vasodilatory effects in rat aorta and human IMAs. Sertraline elicited vasodilatation in coronary arteries during perfusion of rat hearts. These hemodynamic effects may explain the observed beneficial effects in myocardial ischemia and infarction.     

Interactive influences of peroxisome proliferator-activated receptor α activation and glucocorticoids on pancreatic beta cell compensation in insulin resistance induced by dietary saturated fat in the rat

Aims/hypothesis We sought to elucidate whether excess glucocorticoids and increased dietary lipids act synergistically to impair glucose tolerance and, if so, whether activation of peroxisome proliferator-activated receptor (PPAR) has an adverse or beneficial effect on glucose tolerance.Methods Dexamethasone (100 g kg^–1 body weight day^–1; 5 days) was administered to insulin-resistant rats fed a high-saturated-fat (HF) diet for 4weeks. The PPAR agonist WY14643 was administered (50 mg kg^–1 body weight intraperitoneally) 24 h before sampling. Glucose-stimulated insulin secretion (GSIS) was assessed in vivo after an acute glucose bolus injection, and in vitro using step-up and step-down islet perifusions.Results Although neither PPAR activation nor dexamethasone alone affected fasting glycaemia in the HF group, dexamethasone in combination with PPAR activation elicited marked postabsorptive hyperglycaemia. Dexamethasone treatment of HF rats had little effect on GSIS after an acute glucose challenge in vivo, but induced glucose intolerance. PPAR activation augmented GSIS in dexamethasone-treated HF rats in vivo, restoring glucose tolerance. Contrasting with data obtained in vivo, greatly enhanced peak rates of GSIS were observed ex vivo in perifusions of islets from dexamethasone-treated HF rats compared with those from untreated HF rats, an effect attenuated by antecedent PPAR activation.Conclusions/interpretation The study demonstrates that glucocorticoid excess precipitates the development of glucose intolerance in rats maintained on a high-saturated-fat diet. It does this by interrupting the negative feedback loop between insulin sensitivity and secretion in vivo, such that further enhancement of compensatory insulin secretion is not possible. PPAR activation restores the coupling between insulin secretion and action.     

Pharmacokinetics,pharmacodynamics and glucose counterregulation following subcutaneous injection of the monomeric insulin analogue [Lys(B28),Pro(B29)] in IDDM

Summary The aim of these studies was to compare the pharmacokinetics, pharmacodynamics, counterregulatory hormone and symptom responses, as well as cognitive function during hypoglycaemia induced by s. c. injection of 0.15 IU/kg of regular human insulin (HI) and the monomeric insulin analogue [Lys(B28),Pro (B29)] (MI) in insulin-dependent-diabetic (IDDM) subjects. In these studies glucose was infused whenever needed to prevent decreases in plasma glucose below 3 mmol/l. After MI, plasma insulin increased earlier to a peak (60 vs 90 min) which was greater than after HI (294±24 vs 255±24 pmol/l), and plasma glucose decreased earlier to a 3 mmol/l plateau (60 vs 120 min) (p<0.05). The amount of glucose infused to prevent plasma glucose falling below 3 mmol/l was three times greater after MI than HI (293±26 vs 90±25 mol · kg^–1 · 60–375 min^–1, p<0.05). After MI, hepatic glucose production was more suppressed (0.7±1 vs 5.9±0.54 mol · kg^–1 · min^–1) and glucose utilization was less suppressed than after HI (11.6±0.65 vs 9.1±0.11mol · kg^–1 · min^–1) (p<0.05). Similarly, plasma NEFA, glycerol, and -OH-butyrate were more suppressed after MI than HI (p<0.05), whereas plasma lactate increased only after MI, but not after HI. Responses of counterregulatory hormones, symptoms and deterioration in cognitive function during plasma glucose plateau of 3 mmol/l were superimposable after MI and HI (p=NS). Post-hypoglycaemia hyperglycaemia was greater after MI than HI (at 480 min 12.1±1 vs 11±1 mmol/l) because of greater hepatic glucose production during insulin waning which occurred at least 135 min earlier with MI as compared to HI (p<0.05). It is concluded that counterregulatory hormones, symptoms and deterioration in cognitive function during hypoglycaemia respond similarly after MI and HI. The biological effect of MI appears greater than that of HI for at least 4 h after the s.c. injection and appears as a good candidate for achieving optimal post-prandial glucose control in IDDM.Abbreviations HI Human insulin - MI monomeric insulin - NEFA non-esterified fatty acid - HGO hepatic glucose production rate - -OH-butyrate -hydroxy-butyrate - IDDM insulin-dependent diabetes mellitus - NIDDM non-insulin-dependent diabetes mellitus     

Beta-cell dysfunction and glucose intolerance: results from the San Antonio metabolism (SAM) study

Aims/hypothesis Both insulin resistance and beta-cell dysfunction play a role in the transition from normal glucose tolerance (NGT) to Type 2 diabetes (T2DM) through impaired glucose tolerance (IGT). The aim of the study was to define the level of glycaemia at which beta-cell dysfunction becomes evident in the context of existing insulin resistance.Methods Insulin response (OGTT) and insulin sensitivity (euglycaemic insulin clamp) were evaluated in 388 subjects in the San Antonio Metabolism (SAM) study (138 NGT, 49 IGT and 201 T2DM). In all subjects the insulin secretion/insulin resistance index (I/G÷IR) was calculated as the ratio of the increment in plasma insulin to the increment in plasma glucose during the OGTT divided by insulin resistance, as measured during the clamp.Results In lean NGTs with a 2-h plasma glucose concentration (2-h PG) between 5.6 and 6.6 and between 6.7 and 7.7 mmol/l, there was a progressive decline in I/G÷IR compared with NGTs with a 2-h PG less than 5.6 mmol/l. There was a further decline in I/G÷IR in IGTs with a 2-h PG between 7.8 and 9.3 and between 9.4 and 11.0 mmol/l, and in Type 2 diabetic patients with a 2-h PG greater than 11.1 mmol/l. Lean and obese subjects showed coincident patterns of relation of 2-h PG to I/G÷IR.Conclusion/interpreation When the plasma insulin response to oral glucose is related to the glycaemic stimulus and severity of insulin resistance, there is a progressive decline in beta-cell function that begins in normal glucose tolerant individuals.Abbreviations T2DM, Type 2 diabetes mellitus - FPG, fasting plasma glucose - 2-h PG, 2-h plasma glucose - EGP, endogenous glucose production - Ra, rate of appearance - TGD, total glucose disposal - IR, insulin resistance     

Growth regulation of rabbit gastric epithelial cells and protooncogene expression

We recently developed a primary culture system for gastric epithelial cells from adult rabbits that allows the investigation of growth regulation at the cellular level. In this study, we demonstrated that epidermal growth factor (EGF), insulin, and dibutyryl adenosine 3,5-cyclic monophosphate (dBcAMP) all stimulated cell proliferation. Insulin and dB-cAMP potentiated the stimulation of cell proliferation by EGF, while transforming growth factor-1 (TGF-1) inhibited it. Expression of c-fos and c-myc was induced in response to the stimulation by these growth regulators, but the degree of expression did not necessarily correlate with the effects of these agents on cell proliferation. In conclusion, EGF, insulin, and dBcAMP were positive growth regulators, while TGF-1 was a negative regulator in gastric epithelial cells. These growth modulators may exert their effects by distinct pathways from a standpoint of the expression of c-fos and c-myc.     

Local and Systemic Liberation of Proinflammatory Cytokines in Ulcerative Colitis

Determination of plasma and tissue cytokinelevels in inflammatory bowel disease have frequentlyresulted in conflicting data. In the present study wedetermined in patients with ulcerative colitis (UC), the levels of the proinflammatory cytokinesinterleukin (IL)-1, IL-6, interferon(IFN)-, and tumor-necrosis factor (TNF)-liberated by peripheral blood mononuclear cells (PBMC)and lamina propria mononuclear cells (LPMC) after 48-hrculture with pokeweed mitogen (PWM). IL-1, IL-6,IFN- and TNF- in the supernatant weredetected by ELISA. Results show low basal levels ofIL-1 secretion by PBMC and LPMC, and a considerableincrease after mitogen stimulation. Basal IL-6production by PBMC was higher in UC patients than incontrols [2029 pg/ml, CI₉ (–165 to4223) vs 572 pg/ml (–383 to 1527) respectively, P = 0.05] and also afterPWM activation [14,995 pg/ml (7759 -22230) vs 6598 pg/ml(3240-9956), respectively, P = 0.05]. In LPMC, nodifferences in IL-6 secretion were observed. TNF- in activated PBMC of patients with UC was notsignificantly increased in relation to control (P =0.09). No constitutive secretion of IFN- wasobserved in mononuclear cells. IFN- levelssecreted by activated LPMC were lower in patients withUC than in controls [1571 pg/ml (–108 to 3251) vs7953 pg/ml (3851-12,055), respectively, P = 0.03]. Theseresults suggest that IL-6, IL-1, and TNF- participate as mediators in the inflammatoryphenomena observed in UC. Further studies are necessaryto evaluate the role of IFN- in thiscondition.     

Differences of cellular composition and adhesion molecule expression in “leukemic” as compared with “normal” human long-term bone marrow cultures

Summary Human long-term bone marrow cultures (HLTBMCs) were established with bone marrow samples collected from 15 patients with acute myeloid leukemia (AML) and compared with HLTBMCs from eight healthy volunteers. During 6 weeks of culture, the cellular composition of HLTBMCs was quantitatively studied. The cells of the HLTBMCs were divided into three main categories: fibroblasts, macrophages, and other cells (endothelial cells, hematopoietic cells and undefined cells). HLTBMCs derived from healthy volunteers demonstrated a very consistent development. The number of fibroblasts increased during culture and the number of macrophages decreased, resulting in a steady state after 3 weeks of culture. In contrast, HLTBMCs derived from patients with AML showed a strikingly different pattern of irregular development and a steady state was not reached under our conditions. The APAAP technique was used to demonstrate expression of adhesion molecules. VLA2, VLA5, VLA6, LFA1, Mac1, p150/95, ₂-chain, HCAM, ICAM1, NCAM, and VCAM1 were more expressed on normal as compared with leukemic bone marrow stromal cells, although this reached significance only for ₂-chain and NCAM. VLA1, 3, and 4 were expressed in a higher percentage on leukemic stroma (not significant). More expression was seen on normal as opposed to leukemic macrophages for the adhesion molecules tested, except for VLA5. The differences reached significance for the majority of molecules tested. It is concluded that striking differences exist in cellular composition and adhesion molecule expression between HLTBMCs from healthy individuals and those from patients with AML. This may have an impact on the pathogenesis of AML.