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Biomedical subjects

S Madsbad

Publications and source records attributed to S Madsbad.

At least 55 records · Page 3Linked to original sources
PubMed2000

Evaluation of beta-cell secretory capacity using glucagon-like peptide 1.

OBJECTIVE: Beta-cell secretory capacity is often evaluated with a glucagon test or a meal test. However, glucagon-like peptide 1 (GLP-1) is the most insulinotropic hormone known, and the effect is preserved in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: We first compared the effects of intravenous bolus injections of 2.5, 5, 15, and 25 nmol GLP-1 with glucagon (1 mg intravenous) and a standard meal (566 kcal) in 6 type 2 diabetic patients and 6 matched control subjects. Next, we studied another 6 patients and 6 control subjects and, in addition to the above procedure, performed a combined glucose plus GLP-1 stimulation, where plasma glucose was increased to 15 mmol/l before injection of 2.5 nmol GLP-1. Finally, we compared the insulin response to glucose plus GLP-1 stimulation with that observed during a hyperglycemic arginine clamp (30 mmol/l) in 8 patients and 8 control subjects. RESULTS: Peak insulin and C-peptide concentrations were similar after the meal, after 2.5 nmol GLP-1, and after glucagon. Side effects were less with GLP-1 than with glucagon. Peak insulin and C-peptide concentrations were as follows (C-peptide concentrations are given in parentheses): for patients (n = 12): meal, 277 +/- 42 pmol/l (2,181 +/- 261 pmol/l); GLP-1 (2.5 nmol), 390 +/- 74 pmol/l (2,144 +/- 254 pmol/l); glucagon, 329 +/- 50 pmol/l (1,780 +/- 160 pmol/l); glucose plus GLP-1, 465 +/- 87 pmol/l (2,384 +/- 299 pmol/l); for control subjects (n = 12): meal, 543 +/- 89 pmol/l (2,873 +/- 210 pmol/l); GLP-1, 356 +/- 51 pmol/l (2,001 +/- 130 pmol/l); glucagon, 420 +/- 61 pmol/l (1,995 +/- 99 pmol/l); glucose plus GLP-1, 1,412 +/- 187 pmol/l (4,391 +/- 416 pmol/l). Peak insulin and C-peptide concentrations during the hyperglycemic arginine clamp and during glucose plus GLP-1 injection were as follows: for patients: 475 +/- 141 pmol/l (2,295 +/- 379 pmol/l) and 816 +/- 268 pmol/l (3,043 +/- 508 pmol/l), respectively; for control subjects: 1,403 +/- 308 pmol/l (4,053 +/- 533 pmol/l) and 2,384 +/- 452 pmol/l (6,047 +/- 652 pmol/l), respectively. CONCLUSIONS: GLP-1 (2.5 nmol = 9 microg) elicits similar secretory responses to 1 mg glucagon (but has fewer side effects) and a standard meal. Additional elevation of plasma glucose to 15 mmol/l did not enhance the response further. The incremental response was similar to that elicited by arginine, but hyperglycemia had an additional effect on the response to arginine.

Aged↗
PubMed1999

The effect of intense exercise on postprandial glucose homeostasis in type II diabetic patients.

AIMS/HYPOTHESIS: The influence of postprandial high intensity exercise on glycaemia was studied in patients with Type II diabetes mellitus. METHODS: Patients who were treated by diet only (n = 8) ate a standardised breakfast and 4 h later a standardised lunch. They were studied in the resting state (control day) and on another day (exercise day) when they did intermittent exercised at high intensity after breakfast) (4 bouts including 3 min at 56.5 +/- 3.9 % V.(O2) (max) (means +/- SEM), 4 min at 98.3 +/- 5.1 % V.(O2) (max) and 6 min of rest). Responses were calculated as areas under the plasma concentration curve (AUC) during 4 h after either breakfast or lunch. RESULTS: Breakfast-AUCs for glucose, insulin and C peptide were lower (p < 0.05) on the exercise day compared with the control day (glucose: 538 +/- 94 vs 733 +/- 64 mmol. l(-1). 240 min; insulin: 16 +/- 4 vs 22 +/- 3 pmol. ml(-1). 240 min; C peptide: 143 +/- 22 vs 203 +/- 29 pmol. ml(-1). 240 min). After breakfast glucose appearance was unaffected by exercise, whereas disappearance and clearance increased (p < 0.05). Muscle glycogen was diminished by exercise (p < 0.05). After lunch no differences were observed between experiments. Exercise-induced reductions in glucose, insulin and C peptide responses were similar (p > 0.05) in this study of intermittent, high intensity exercise and in a previous study of isocaloric but prolonged moderate (45 min at 53 +/- 2 % V.(O2) (max)) postprandial exercise. CONCLUSION/INTERPRETATION: Postprandial high intensity exercise does not deteriorate glucose homeostasis but reduces both glucose concentrations and insulin secretion. The effect of exercise is related to energy expenditure rather than to peak exercise intensity. Finally, postprandial exercise does not influence glucose homeostasis during a subsequent main meal. [Diabetologia (1999) 42: 1282-1292]

Blood Glucose↗
PubMed1999

Metabolic and fibrinolytic response to changed insulin sensitivity in users of oral contraceptives.

The fundamental role of insulin resistance for metabolic changes linked to cardiovascular disease and type 2 diabetes is increasingly recognized. Oral contraceptives (OC) may affect insulin sensitivity, and a detailed characterization hereof, as well as the secondary effects on related metabolic systems, are relevant in the evaluation of the risk of developing vascular disorders or diabetes in OC users. We studied insulin sensitivity index (S(I)), glucose effectiveness (S(g)), and insulin response in young, healthy women by frequently sampled intravenous glucose tolerance tests before and after randomization to 6 months of treatment with ethinyl estradiol in triphasic combination with norgestimate (n = 17) or gestodene (n = 20). Measurements of fasting triglycerides and antigen concentrations of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) were also included. Both compounds increased fasting plasma insulin and reduced S(i) but did not affect S(g). The relationships between S(i) and insulin response were unchanged. No consistent correlation between insulin sensitivity and triglycerides, t-PA, or PAI-1 were demonstrated before or during treatment. We conclude that the treatments were followed by a compensated decrease in insulin sensitivity that was unrelated to changes in triglycerides, t-PA, or PAI-1 antigen.

Adult↗
PubMed1999

The effect of the deterioration of insulin sensitivity on beta-cell function in growth-hormone-deficient adults following 4-month growth hormone replacement therapy.

The purpose of the present study was to evaluate the combined effect of GH treatment on body composition and glucose metabolism, with special focus on beta-cell function in adult GHD patients. In a double-blind placebo-controlled design, 24 GHD adults (18M/6F), were randomized to 4 months treatment with biosynthetic GH 2 IU/m2s.c. daily (n =13) or placebo (n =11). At inclusion and 4 months later an oral glucose tolerance test (OGTT), a frequently sampled intravenous glucose tolerance test (FSIGT) and dual-energy X-ray absorptiometry (DXA) whole-body scanning were performed. During the study period, body weight decreased 1.6 kg from 94.0 +/- 18.7 to 92.4 +/- 19.4 kg (mean +/- SD) (P<0.05) in the GH-treated group, but remained unchanged in the placebo group. Fat mass decreased from 32.4 +/- 9.6 to 28.1 +/- 10.5 kg (P<0.001), whereas lean body mass increased from 58.3 +/- 11.5 to 61.0 +/- 11.7 kg (P<0.01) in the GH-treated group. Treatment with GH for 4 months resulted in a significant increase in fasting blood glucose (before GH 5.0 +/- 0.3 and after 5.4 +/- 0.6 mmol/l, P<0.05), fasting plasma insulin (before GH 38.4 +/- 30.2 and after 55.3 +/- 34.7 pmol/l, P<0.02) and fasting proinsulin (before 8. 1 +/- 6.7 and after 14.6 +/- 16.1 pmol/l, P<0.05). The insulin sensitivity index SI, estimated by Bergmans Minimal Model, decreased significantly [before GH 1.1 +/- 0.7 and after 0.4 +/- 0.2 10(-4)(min x pmol/l), P<0.003]. The non-insulin-dependent glucose uptake (glucose effectiveness SG did not change (before GH 0.017 +/- 0.005 and after 0.015 +/- 0.006 min-1, NS). Insulin secretion was enhanced during GH therapy, but insufficiently to match the changes in SI, resulting in a higher blood glucose level during an OGTT. Blood glucose at 120 min was 5.5 and 6.3 mmol/l before and after GH treatment, respectively (P = 0.07). One patient developed impaired glucose tolerance. Short-term GH replacement therapy in a dose of about 2 IU/m2 daily in GHD adults induces a reduction in insulin sensitivity, despite favourable changes in body composition, and an inadequate enhancement of insulin secretion.

Adenoma↗
PubMed1999

Interaction of sulfonylureas and exercise on glucose homeostasis in type 2 diabetic patients.

OBJECTIVE: To determine whether the plasma glucose-lowering effects of sulfonylureas and acute submaximal exercise are additive and, accordingly, to determine whether they may increase the risk of hypoglycemia when combined in fasting patients. RESEARCH DESIGN AND METHODS: Eight postabsorptive type 2 diabetic patients were examined at three occasions: after oral sulfonylurea (7 mg glibenclamide), during 60 min of ergometer cycle exercise at 57 +/- 3% of VO2max, and during exercise after glibenclamide. RESULTS: Heart rate, VO2, and lactate responses to exercise were comparable (P > 0.05) on days with and without glibenclamide. Plasma insulin concentrations were always increased by glibenclamide, and they were lowered identically by exercise with and without glibenclamide. However, throughout exercise, absolute concentrations of insulin were lower on days without glibenclamide compared with days with glibenclamide (34.5 +/- 4.7 vs. 47.4 +/- 5.5 pmol/l; P < 0.05). At the start of exercise, glucose concentrations were similar between experiments (P > 0.05). The rate of decrease in glucose during exercise was higher (P < 0.05) on days with both glibenclamide and exercise, compared with days with glibenclamide alone and days with exercise alone (-0.035 +/- 0.009 vs. -0.016 +/- 0.002 and -0.022 +/- 0.005 mmol.l-1.min-1, respectively). Consequently, the glucose nadir was lower on days with glibenclamide and exercise than on days with glibenclamide or exercise alone (6.7 +/- 1.1 vs. 8.1 +/- 0.9 and 7.6 +/- 1.0 mmol/l, respectively; P < 0.05). During exercise, the rate of appearance of plasma glucose determined by 3-[3H]glucose infusion was lower on days with glibenclamide than on days without glibenclamide (2.3 +/- 0.1 vs. 2.9 +/- 0.1 mg.min-1.kg-1; P < 0.05). In contrast, glucose clearance was identical (P > 0.05). CONCLUSIONS: In postabsorptive type 2 diabetic patients, the hypoglycemic action of glibenclamide and exercise is enhanced when the treatments are combined. The interaction reflects an increased inhibition by glibenclamide-enhanced insulin levels of hepatic glucose production when hepatic glucose production is accelerated by exercise.

Blood Glucose↗
PubMed1999

Continuous subcutaneous infusion of glucagon-like peptide 1 lowers plasma glucose and reduces appetite in type 2 diabetic patients.

OBJECTIVE: The gut hormone glucagon-like peptide 1 (GLP-1) has insulinotropic and anorectic effects during intravenous infusion and has been proposed as a new treatment for type 2 diabetes and obesity. The effect of a single subcutaneous injection is brief because of rapid degradation. We therefore sought to evaluate the effect of infusion of GLP-1 for 48 h in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We infused GLP-1 (2.4 pmol.kg-1.min-1) or saline subcutaneously for 48 h in randomized order in six patients with type 2 diabetes to evaluate the effect on appetite during fixed energy intake and on plasma glucose, insulin, glucagon, postprandial lipidemia, blood pressure, heart rate, and basal metabolic rate. RESULTS: The infusion resulted in elevations of the plasma concentrations of intact GLP-1 similar to those observed after intravenous infusion of 1.2 pmol.kg-1.min-1, previously shown to lower blood glucose effectively in type 2 diabetic patients. Fasting plasma glucose (day 2) decreased from 14.1 +/- 0.9 (saline) to 12.2 +/- 0.7 mmol/l (GLP-1), P = 0.009, and 24-h mean plasma glucose decreased from 15.4 +/- 1.0 to 13.0 +/- 1.0 mmol/l, P = 0.0009. Fasting and total area under the curve for insulin and C-peptide levels were significantly higher during the GLP-1 administration, whereas glucagon levels were unchanged. Neither triglycerides nor free fatty acids were affected. GLP-1 administration decreased hunger and prospective food intake and increased satiety, whereas fullness was unaffected. No side effects during GLP-1 infusion were recorded except for a brief cutaneous reaction. Basal metabolic rate and heart rate did not change significantly during GLP-1 administration. Both systolic and diastolic blood pressure tended to be lower during the GLP-1 infusion. CONCLUSIONS: We conclude that 48-h continuous subcutaneous infusion of GLP-1 in type 2 diabetic patients 1) lowers fasting as well as meal-related plasma glucose, 2) reduces appetite, 3) has no gastrointestinal side effects, and 4) has no negative effect on blood pressure.

Adult↗
PubMed1999

Effect of a new starch-free bread on metabolic control in NIDDM patients.

BACKGROUND AND AIM: The aim of the study was to evaluate the effect on blood glucose levels in non-insulin-dependent diabetics (NIDDM) of reduction of the carbohydrate content through the use of a new, almost starch-free type of bread (SF-bread). We only substituted the bread in the breakfast meal. METHODS AND RESULTS: The study consisted of two parts: 1) a two-day randomized study of the effect of SF-bread on the morning blood glucose levels of NIDDM patients and 2) an open, crossover trial of three months duration where each patient was given SF- or ordinary bread. Ten patients participated in the first part and eight in the second part of the study. All patients had well established non insulin-dependent diabetes mellitus. In the first part of the study, the area under the curve describing time-dependent changes in blood glucose level after a standard breakfast was significantly lower in patients on SF-bread (182 +/- 154 Units; mean value +/- SD) than in the controls (630 +/- 258 Units; p < 0.00001). Peak blood glucose concentration was 14.8 +/- 2.3 mM on the control day and 11.6 +/- 1.7 mM on the SF-bread day (p < 0.001). In the second part of the study, the diet including SF-bread reduced fasting blood glucose from 13.3 +/- 3.5 mM to 10.2 +/- 2.0 mM (p < 0.006) and the fraction of HbA1c from 0.090 +/- 0.014 to 0.081 +/- 0.015 (p < 0.02). Similar changes were not seen on the ordinary diet. Serum cholesterol levels were significantly reduced by the SF-bread as compared to the ordinary diet (5.8 +/- 0.6 to 5.5 +/- 0.5 mM versus 5.7 +/- 0.8 to 5.8 +/- 0.7 mM; p < 0.05). CONCLUSIONS: Substitution of ordinary bread with starch-free bread at breakfast causes significant improvements in blood glucose levels in NIDDM patients on both a short and long term basis. Possibly secondary to this, a favorable influence on lipid levels was noted.

Aged↗
PubMed1998

Effect of pancreas transplantation and immunosuppression on proinsulin secretion.

Insulin resistance and increased demand for insulin secretion occur after successful pancreas transplantation. To investigate the potential effects of immunosuppression and pancreas transplantation on fasting beta-cell function, we studied fasting proinsulin and 32,33 split proinsulin secretion cross-sectionally and longitudinally in segmental pancreatic graft recipients (SPx, n = 18); in whole-pancreas graft recipients (WPx, n = 13); in nondiabetic kidney transplant recipients (Kx, n = 14) and in normal subjects (Ns, n = 14). Basal insulin secretion rates were significantly increased in SPx 15.8 (1.7), WPx 24.4 (4.5) and Kx 22.1 (2.1) vs Ns 9.7 (1.6) pmol min(-1) l(-1), p < 0.05, mean (SEM). Total proinsulin, intact proinsulin and 32,33 split proinsulin concentrations were significantly higher in all the transplanted groups than in normal subjects (p < 0.05), whereas the total proinsulin to C-peptide ratio and the 32,33 split proinsulin ratio were higher in SPx than in WPx, Kx and Ns (< 0.05). In the longitudinal study, beta-cell function in terms of proinsulin secretion remained stable for 1 year. In conclusion, fasting glucose homeostasis in pancreas-kidney transplant recipients is obtained at the expense of increased proinsulin secretion and increased insulin secretion rates, primarily induced by immunosuppression. In segmental pancreas graft recipients, increased fasting proinsulin and 32,33 split proinsulin relative to the number of beta-cells transplanted indicate more stress on the residual beta-cell and therefore higher secretory demand than in whole pancreas transplant recipients.

Adult↗
PubMed1998

Exaggerated secretion of glucagon-like peptide-1 (GLP-1) could cause reactive hypoglycaemia.

The plasma concentrations of the insulinotropic incretin hormone, glucagon-like peptide-1 (GLP-1) are abnormally high after oral glucose in partially gastrectomised subjects with reactive hypoglycaemia, suggesting a causal relationship. Because of the glucose-dependency of its effects, it is impossible to induce hypoglycaemia in normal subjects in the basal state by exogenous GLP-1, regardless of dose. To further assess the role of the incretin hormones in reactive hypoglycaemia, we reproduced the glucose and hormone profiles of the patients with reactive hypoglycaemia in 8 healthy volunteers in 4 separate protocols: 1) i.v. infusion of glucose (25 g) alone, 2) glucose together with i.v. GLP-1 infusion, and 3) and 4) glucose together with i.v. infusion of the other incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), at two different infusion rates. The plasma glucose, GLP-1 and GIP concentrations (low dose) obtained were comparable with those of the patients. With GLP-1, infusion of a total of 33.4 +/- 1.3 g glucose was required to obtain plasma glucose concentrations similar to those obtained by glucose infusion alone; with low GIP, 28.0 +/- 1.2 g and with high GIP 38.4 +/- 3.5 g. Insulin concentrations increased 10-fold with GLP-1 compared with i.v. glucose alone, but less with high and low GIP. In contrast, C-peptide concentrations were similar after GLP-1 and high GIP. After termination of i.v. glucose the lowest glucose concentrations were 4.5 (3.7-4.9) (median, range) for glucose alone; 2.4 (1.9-2.8) mmol/l with GLP-1; 3.7 (2.6-4.0) with low GIP and 3.3 (2.1-4.2) with high GIP. Thus, the exaggerated GLP-1 response to nutrients in patients with accelerated gastric emptying could be responsible for their high incidence of postprandial reactive hypoglycaemia.

Adult↗
PubMed1998

Insulin secretion rates estimated by two mathematical methods in pancreas-kidney transplant recipients.

After pancreas-kidney transplantation, it is difficult to obtain an accurate estimate of the insulin secretion of the pancreas graft, since several pitfalls are involved using peripheral C-peptide and/or insulin measurements in this determination. In this study, the individual kinetic parameters of C-peptide and then the rates of insulin secretion were estimated by two mathematical methods, the deconvolution method and the "combined model" during slow (oral glucose) and fast (intravenous glucagon) changes in insulin secretion in six successful pancreas-kidney transplant recipients with systemic delivery of insulin (Px), six nondiabetic kidney-transplant recipients with portal insulin secretion (Kx), six nondiabetic controls (NS), and six C-peptide-negative insulin-dependent diabetes mellitus patients (IDDM). Decreased C-peptide clearance and basal and poststimulatory hyperinsulinemia were found in both Px and Kx compared with NS (P < 0.05). Similar glucose responses were observed after intravenous glucagon in all groups, whereas the responses after oral glucose were 30% higher in Px and Kx than in NS (P < 0.05). During oral glucose and after intravenous glucagon, both mathematical methods resulted in significantly lower maximal and incremental insulin secretion rates (ISR) in Px than in Kx (P < 0.05). In contrast, calculations of incremental ISR in NS and Px induced by the two beta-cell stimuli were about the same but significantly higher in Kx than in NS (P < 0.05). These results differed markedly from those obtained using peripheral measurements of insulin and C-peptide alone. In conclusion, when C-peptide clearance and insulin metabolism change, such as in pancreas-kidney transplant recipients, accurate evaluation of insulin secretion from the graft can be obtained only by using individual kinetics of the peptides before calculating the ISR. This study also clearly demonstrates that insulin secretion after pancreas transplantation is still defective.

Adult↗
PubMed1997

Metabolism of oral glucose in pancreas transplant recipients with normal and impaired glucose tolerance.

To gain insight into the pathophysiology of impaired glucose tolerance in pancreas transplantation, glucose kinetics and insulin secretion were assessed after an oral glucose load in four combined pancreas-kidney recipients with impaired glucose tolerance (IPx), in five combined pancreas-kidney recipients with normal glucose tolerance, in six nondiabetic kidney transplant recipients, and in eight normal subjects employing a dual isotope technique, beta-Cell function was evaluated by calculating prehepatic insulin secretion rates, which subsequently were correlated to the ambient glucose concentrations to obtain an index of beta-cell responsiveness. Oxidative and nonoxidative glucose metabolism were assessed by indirect calorimetry. Basal insulin secretion rates, the glucose-stimulated early insulin secretion rates, as well as beta-cell responsiveness were markedly reduced in IPx than in the glucose-tolerant transplant subjects. Total systemic glucose appearance was similar in the groups with apparently comparable inhibition of systemic glucose release and increase in exogenous glucose appearance. The hyperglycemic response in IPx was due to a significant reduction in the glucose disappearance rates during the first 2 h after glucose ingestion. Nonoxidative glucose metabolism increased significantly less in IPx than in glucose-tolerant groups. Glucagon secretion was less suppressed in the early part of the study in IPx, which may have contributed to the excessive hyperglycemia. In conclusion, IPx after pancreas transplantation was characterized by 1) impaired early insulin secretion, 2) reduced beta-cell responsiveness, 3) reduced glucose uptake, 4) impaired nonoxidative glucose metabolism, and 5) impaired early inhibition of glucagon secretion.

Adult↗
PubMed1996

[High triglyceride, low HDL-cholesterol and risk of coronary heart disease].

Hypercholesterolaemia is a strong risk factor of coronary artery disease (CAD). The importance of high triglyceride and low HDL cholesterol in predicting risk of CAD is less well-established. This review presents data showing that high triglyceride and low HDL cholesterol are important risk factors of CAD and suggests that combined lipid profiles of triglyceride, HDL cholesterol, and total cholesterol provide more information about risk of CAD than total cholesterol alone. High triglyceride and low HDL cholesterol is the characteristic dyslipidaemia seen in subjects with insulin resistance, a basic abnormality in glucose- and insulin metabolism. Since insulin resistance and raised triglyceride and decreased HDL cholesterol can be identified in children of patients with NIDDM, essential hypertension, and CAD, we suggest that efforts to prevent CAD should include interventions against all these associated abnormalities in glucose-, insulin-, and lipid metabolism and not only high cholesterol.

Cholesterol, HDL↗
PubMed1996

[Clinical consequences of intranasal insulin therapy in insulin-dependent diabetes mellitus].

Metabolic control, hypoglycaemia frequency and nasal mucosal physiology were evaluated in 31 insulin-dependent diabetics treated with intranasal insulin at mealtimes for one month and with subcutaneous fast-acting insulin for another month in a randomized crossover trial. During both periods the patients were treated with intermediate-acting insulin at bedtime. Six of the patients were withdrawn from the study during intranasal insulin therapy due to metabolic dysregulation. Insulin concentrations increased more rapidly and decreased more quickly during intranasal as compared with subcutaneous insulin administration. Metabolic control, assessed by haemoglobin A1c concentrations, deteriorated after intranasal as compared with subcutaneous insulin therapy. The bioavailability of intranasally applied insulin was low, since intranasal insulin doses were approximately 20 times higher than subcutaneous doses. The frequency of hypoglycemia was similar during intranasal and subcutaneous insulin therapy, and nasal mucosal physiology was unaffected after intranasal insulin. We conclude that due to low bioavailability and to a high rate of therapeutic failure, intranasal insulin treatment is not a realistic alternative to subcutaneous insulin injections at the present time.

Administration, Intranasal↗
PubMed1996

beta-cell function and glucose and lipid oxidation in Graves' disease.

OBJECTIVE: Abnormal glucose metabolism with impaired glucose tolerance has been documented in patients with thyrotoxicosis but the pathogenesis is not fully understood. Therefore, the aim of the present study was to study the beta-cell function and the meal induced oxidative glucose and lipid metabolism in patients with thyrotoxicosis. DESIGN: After an overnight fast the impact of hyperthyroidism on standard mixed meal induced glucose oxidation, lipid oxidation and beta-cell function was studied. PATIENTS: Nine untreated patients with Graves' disease were compared to 9 age and weight matched healthy controls. MEASUREMENTS: Glucose and lipid oxidation were studied by indirect calorimetry before and after the meal. The insulin secretion rate was calculated by the 'combined model' approach, after which the insulin secretion rates and the ambient glucose levels were cross-correlated. The slope of these regression lines was used as a measure of beta-cell sensitivity to glucose and denotes the insulin secretory capacity. beta-Cell function was further evaluated by measurement of proinsulin and its conversion intermediates. Glucoregulatory hormones were also measured. The findings were correlated to the thyroid hormone levels. RESULTS: Fasting blood glucose and post-prandial glucose response were increased in patients (P < 0.01). The hyperthyroid patients displayed a 'dual' beta-cell defect: (a) inability to increase the insulin response appropriately to hyperglycaemia and (b) increased proinsulin levels both in the fasting state and in response to a meal. Indirect calorimetry showed increased lipid oxidation in the fasting state and at the end of the meal (P < 0.01). No difference in glucose oxidation was demonstrated in the fasting state but the post-prandial glucose oxidation was enhanced in the patients (P < 0.01). The adrenaline response was normal, whereas the noradrenaline response was impaired or absent in the patients. The thyroid hormone levels were significantly correlated to fasting levels of blood glucose, insulin, free fatty acids and lipid oxidation, but not to fasting C-peptide, glucose oxidation or catecholamines. CONCLUSIONS: Untreated Graves' disease was associated with glucose intolerance due to quantitative as well as qualitative beta-cell defects. The lipid oxidation was increased in the fasting state and at the end of the meal; after the meal the increase in glucose oxidation was more pronounced in the patients. Thyroid hormones thus increased the oxidation but not by an increase in catecholamines. Indeed, the post-prandial sympathetic response was blunted.

Adult↗
PubMed1996

No differential effects of porcine and human insulin on muscle sympathetic nerve activity during euglycaemia or hypoglycaemia.

On the basis of some clinical studies in diabetic patients, and experimental studies in normal humans, it has been suggested that hypoglycaemic autonomic responses are augmented with porcine (PI) compared to human insulin (HI). A difference in sensory processing has been reported following insulin-induced hypoglycaemia with PI compared to HI, and has been interpreted as different insulin effects on the central nervous system. In a double blind crossover comparison of HI and PI in nine healthy subjects, microneurographic recordings of muscle sympathetic nerve activity (MSNA) were performed, as well as measurements of cardiovascular and hormonal responses during a low dose hyperinsulinaemic euglycaemic glucose clamp (plasma insulin 60.1 +/- 1.9 mU ml-1 (mean +/- SEM)), followed by a period of insulin-induced hypoglycaemia. Plasma insulin and glucose were identical in the two sessions. Plasma glucose nadir during hypoglycaemia was 2.4 +/- 0.2 mmol l-1 for HI and 2.5 +/- 0.1 mmol l-1 for PI. During euglycaemia, MSNA increased from 24 +/- 2 to 34 +/- 3 and 23 +/- 2 to 30 +/- 2 burst/min (P:NS) for HI and PI, respectively, and during hypoglycaemia to 49 +/- 4 and 45 +/- 2 bursts min-1 (P:NS), respectively. The maximal hypoglycaemic increments of MSNA were not different (HI 15 +/- 4; PI 15 +/- 2 bursts min-1 (P:NS)) Responses of plasma noradrenaline and haemodynamic parameters did not differ either. This study does not indicate differing sympathetic responses to PI and HI in healthy humans. Evidence for a modulating effect of insulin on central sympathetic outflow was not found.

Adult↗
PubMed1996

Pancreatic endocrine function in recipients of segmental and whole pancreas transplantation.

To determine potential abnormalities in beta-cell function after pancreas transplantation, the secretory capacity of the pancreatic grafts was assessed by measuring the glucose-potentiating effect on arginine-induced insulin secretion in recipients of cadaveric segmental (SPx; n = 8) and whole organ pancreas grafts (WPx; n = 6) and compared to that in nondiabetic kidney transplant recipients (Kx; n = 6) and normal controls (Ns; n = 7). alpha-Cell adaptation to increasing hyperglycemia and the glucagon response to arginine stimulation were also studied. The secretory capacity of the beta-cell to arginine-induced (5 g L-arginine) insulin secretion was measured at fasting plasma glucose and 15 and 30 mmol/L glucose. Insulin secretion was evaluated by the calculation of insulin secretion rates. Insulin sensitivity was markedly reduced in all three transplanted groups compared to that in normal subjects (P < 0.05). The prestimulation insulin secretion rate and maximal insulin secretion rate in response to hyperglycemia and arginine were significantly lower in SPx than in WPx, Kx, or Ns (P < 0.05). The incremental amount of insulin secreted in response to arginine was reduced by 40-70% in SPx depending on glycemia compared to that in all other groups (P < 0.05), among which there were no statistical differences. Both SPx and WPx demonstrated suppression of glucagon release in response to graded hyperglycemia, but failure to adequately suppress arginine-induced glucagon release. In conclusion, recipients of cadaveric segmental pancreas grafts display a markedly reduced maximal insulin secretory reserve capacity. This impairment was primarily due to an insufficient beta-cell mass. Taking the concomitant insulin resistance into account, recipients of a cadaver whole organ pancreas graft had an impaired insulin secretory reserve capacity as well.

Adult↗
PubMed1996

The effect of glucagon-like peptide I (GLP-I) on glucose elimination in healthy subjects depends on the pancreatic glucoregulatory hormones.

Glucagon-like peptide I (GLP-I) decreases plasma glucose in type II diabetic patients and in healthy subjects indirectly by stimulation of insulin and inhibition of glucagon secretion, whereby the hepatic glucose production decreases. However, recent studies indicate that GLP-I may also directly influence peripheral and hepatic glucose uptake. We infused somatostatin (SS) intravenously (500 or 1,000 microgram/h) in 13 healthy subjects to suppress insulin and glucagon secretion from the endocrine pancreas, together with infusion of either GLP-I (50 pmol / kg / h) or saline intravenously. After 30 min, a 25-g intravenous glucose tolerance test (IVGTT) was carried out, and plasma concentrations of glucose, insulin, glucagon, and GLP-I were measured during the following 2 h. IVGTT together with GLP-I infusion significantly elevated insulin during 500 microgram/h SS but not during 1,000 microgram/h SS. Plasma glucagon was strongly depressed in all experiments. During 500 microgram/h SS, the glucose disappearance constant, Kg, was 0.49 +/- 0.03% per minute with GLP-I and 0.39 +/- 0.04% per minute with saline (n = 8, P = 0.004). With 1,000 microgram/h SS, Kg was 0.42 +/- 0.03% per minute with GLP-I and 0.40 +/- 0.03% per minute without (NS). In conclusion, when endogenous insulin secretion is held at a constant low level, which may be accomplished only with very large doses of SS, GLP-I has no effect on glucose elimination. Thus, an insulin-independent effect of GLP-I on glucose disposal could not be demonstrated.

Adult↗