Abstract. The aim was to compare the three molecular forms of plasma immunoreactive gastric inhibitory polypeptide (IR-GIP) i.e. void volume (Vo), 8 and 5 kDa IR-GIP, found in type 1 diabetics with those found in normal subjects. Plasma from 6 non-fasting newly diagnosed ketotic type 1 diabetics obtained before and 1 h after a test meal given at start of insulin treatment, and before and 1 h after a test meal given after one and seven days of insulin treatment, respectively, was gel filtered and so was plasma from 6 normal subjects. The immunoreactivity in the effluents was measured with five different antisera. The elution positions of the three peaks were similar in controls and diabetics. With any given antiserum none of the components differed significantly as to amount of immunoreactivity between diabetics and controls, neither after the meals nor in the fasting state. The amount of Vo did not change in response to the meal, whereas the 8 and 5 kDa forms in the diabetics increased similarly to the increase in normals, also during ketosis. The Vo component did not differ significantly between diabetic and normal subjects, but it decreased significantly after start of insulin treatment. In the non-fasting, ketotic state before start of insulin treatment, no IR-GIP form was elevated significantly above normal postprandial levels. We conclude that the molecular forms of IR-GIP are similar in type 1 diabetics and normal subjects, but the molecular forms measured and their relative amounts vary according to which antiserum is used. The present study does not support that lack of insulin and ketosis markedly influence IR-GIP in plasma.
Thure Krarup, Jens Juul Holst and Sten Madsbad
Steen B Haugaard, Huiling Mu, Allan Vaag and Sten Madsbad
It remains unknown whether sex impacts on intramyocellular triglyceride (IMTG) in obesity, as has been shown in non-obese subjects, and, if so, whether this may have implications on the association between IMTG and insulin sensitivity.
Subject and methods
A muscle biopsy from vastus lateralis was obtained in 27 obese women (body mass index (BMI)=35.5±0.8 kg/m2; mean±s.e.m., percentage of body fat (PBF)=44±1, n=7 impaired fasting glucose, n=7 type 2 diabetes), 20 obese men (BMI=35.8±0.8 kg/m2; PBF=33±1, n=4 impaired-fasting-glucose; n=6 type 2 diabetes) and 12 lean sedentary healthy individuals (controls; n=7 women, BMI=21.8±0.7 kg/m2, PBF=20±2; n=5 men, BMI=23.6±0.5 kg/m2, PBF=13±2). IMTG was determined by chromatography.
IMTG was increased twofold in obese women compared to obese men, lean men and lean women respectively (21.9±2.4 mg/g wet weight, 10.9±1.5, 9.8±2.1 and 10.9±2.4 mg/g, P<0.001). Among obese subjects of either gender IMTG did not increase along with reduced glycaemic control in terms of impaired fasting glucose and diabetes. Plasma insulin levels, which were similar among obese women with different glycaemic control levels, but much lower in lean women, paralleled the changes in IMTG among women. PBF was associated with IMTG in all subjects (P<0.001). In a linear model, sex (P<0.05) and PBF (P<0.05) independently explained variation in IMTG. Plasma free fatty acids (FFA) correlated with IMTG in all subjects (P<0.005).
Obese women display twice as much IMTG as obese men matched for BMI. Increased IMTG could be a pathophysiological element or a mere physiological phenomenon in feminine obesity ensuing prior to impaired glycaemic control, but associated with increased body fat, circulating FFA and insulin.
Christian Gluud, Sten Madsbad, Thure Krarup and Paul Bennett
Ten male patients and 6 female patients with newly diagnosed insulin dependent diabetes mellitus and significant ketosis were studied before and during the first year of insulin treatment. At onset plasma concentrations of testosterone and androstenedione were significantly (P < 0.02) decreased in female patients when compared to healthy sex- and age-matched controls. Plasma concentrations of testosterone and androstenedione increased significantly (P < 0.001 and P < 0.05) in both sexes during insulin therapy. Plasma concentrations of testosterone were not significantly different from controls in both sexes after 4 days of insulin treatment and remained so during the first year of insulin treatment. Plasma concentrations of androstenedione were not significantly different from controls in both sexes after 4 days of insulin treatment, but increased to levels significantly raised in both males (P < 0.001) and females (P < 0.05) after 7 days and during the first year of insulin treatment.
Thure Krarup, Sten Madsbad, Lisbeth Regeur, Ole K. Faber and Bente Tronier
Abstract. The effect of strict glycaemic control on plasma immunoreactive gastric inhibitory polypeptide IR-GIP) concentrations and pancreatic B cell function as estimated by plasma C-peptide was evaluated in 14 Type 1 (insulin-dependent) diabetics. The effect was estimated by giving a test meal before (test 1) and after (test 2) 1 week with near normal blood glucose control (mean blood glucose 6.7 ± 0.2 mmol/l) and again 3 weeks later (test 3) in the outpatient clinic. The glycaemic control was significantly improved at test 2 and test 3 compared with that of test 1. The IR-GIP concentrations before and after the meals were similar at all three tests and not different from those found in 21 normal controls. In 8 patients with a significant B cell response at test 1, B cell function was significantly improved both at test 2 and test 3 but no change in fasting or post-prandial IR-GIP concentrations was found and no correlation between B cell function and IR-GIP existed.
We conclude that strict glycaemic control improves B cell function but does not modulate plasma IR-GIP concentrations. Factors other than GIP seem to be of greater importance in determining the magnitude of B cell function in Type 1 diabetes.
Sten Madsbad, Thure Krarup, Lisbeth Regeur, Ole K. Faber and Christian Binder
Eleven newly diagnosed insulin dependent patients were studied before and during the first 16 h after start of insulin treatment. All the patients were found to have significant amounts of C-peptide in plasma indicating residual insulin secretion. The fall in blood glucose after start of insulin therapy was followed by a parallel decrease in C-peptide (R = 0.99, P < 0.01) suggesting that the beta-cells may respond to variation in blood glucose.
Eight of the patients were studied 1, 4, 7, 14, 90 and 180 days after start of insulin therapy. During the first 90 days of treatment an increasing maximal C-peptide concentration was found after a standard breakfast test meal. Two thirds of this improvement i beta-cell function was found after the initial 14 days with an average increase in maximal C-peptide of 260 per cent. The sensitivity to glucose improved.
Sten Madsbad, Jannik Hilsted, Thure Krarup, Leif Sestoft, Niels Juel Christensen and Bente Tronier
Abstract. After induction of hypoglycaemia in 31 Type 1 (insulin-dependent) patients, the 10 patients with the slowest recovery of blood glucose from hypoglycaemia were arbitrarily compared with the 10 patients with the fastest recovery of blood glucose. No differences were found between the two groups regarding response of glucagon to hypoglycaemia, whereas the epinephrine (2-fold), norepinephrine (2.4-fold) and cortisol responses were significantly greater in the group with the slow recovery.
The plasma free insulin concentrations were higher (2-fold) in the group with slow recovery from 30 min after stop of insulin and throughout the study. This may be explained by a 3-fold greater amount of insulin binding antibodies in this group compared to the group with fast recovery from hypoglycaemia. An inverse significant correlation was demonstrated between the rates of recovery and the amounts of insulin binding antibodies in all the patients (P < 0.02).
This implicates that enhanced counterregulatory hormone responses in the group with the slow recovery from hypoglycaemia could not compensate for the hypoglycaemic effect of a concomitant higher plasma free insulin concentration. Insulin binding antibodies, acting as a depot of circulating insulin, may be a risk factor of prolonged hypoglycaemia in Type 1 diabetics.
Eva W Iepsen, Julie Lundgren, Jens J Holst, Sten Madsbad and Signe S Torekov
The hormones glucagon-like peptide 1 (GLP-1), peptide YY3-36 (PYY3–36), ghrelin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon have all been implicated in the pathogenesis of obesity. However, it is unknown whether they exhibit adaptive changes with respect to postprandial secretion to a sustained weight loss.
The study was designed as a longitudinal prospective intervention study with data obtained at baseline, after 8 weeks of weight loss and 1 year after weight loss.
Twenty healthy obese individuals obtained a 13% weight loss by adhering to an 8-week very low-calorie diet (800kcal/day). After weight loss, participants entered a 52-week weight maintenance protocol. Plasma levels of GLP-1, PYY3–36, ghrelin, GIP and glucagon during a 600-kcal meal were measured before weight loss, after weight loss and after 1 year of weight maintenance. Area under the curve (AUC) was calculated as total AUC (tAUC) and incremental AUC (iAUC).
Weight loss was successfully maintained for 52 weeks. iAUC for GLP-1 increased by 44% after weight loss (P<0.04) and increased to 72% at week 52 (P=0.0001). iAUC for PYY3–36 increased by 74% after weight loss (P<0.0001) and by 36% at week 52 (P=0.02). tAUC for ghrelin increased by 23% after weight loss (P<0.0001), but at week 52, the increase was reduced to 16% compared with before weight loss (P=0.005). iAUC for GIP increased by 36% after weight loss (P=0.001), but returned to before weight loss levels at week 52. Glucagon levels were unaffected by weight loss.
Meal responses of GLP-1 and PYY3–36 remained increased 1 year after weight maintenance, whereas ghrelin and GIP reverted toward before-weight loss values. Thus, an increase in appetite inhibitory mechanisms and a partly decrease in appetite-stimulating mechanisms appear to contribute to successful long-term weight loss maintenance.
Jakob Ryskjær, Carolyn F Deacon, Richard D Carr, Thure Krarup, Sten Madsbad, Jens Holst and Tina Vilsbøll
Objective: Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide are incretin hormones, secreted in response to meal ingestion. The incretin hormones stimulate insulin secretion and are essential for the maintenance of normal plasma glucose concentrations. Both incretin hormones are metabolized quickly by the enzyme dipeptidyl peptidase-IV (DPP-IV). It is well known that type-2 diabetic patients have an impaired incretin effect. Therefore, the aim of the present study was to investigate plasma DPP-IV activity in the fasting and the postprandial state in type-2 diabetic patients and control subjects.
Design: The study included two protocols. Protocol one involved 40 fasting type-2 diabetic patients (28 men); age 61 ± 1.4 (mean ± s.e.m.) years; body mass index (BMI) 31 ± 0.6 kg/m2; HbAlc 7.2 ± 0.2%; and 20 matched control subjects (14 men) were studied. Protocol two involved eight type-2 diabetic patients (six men); age 63 ± 1.2 years; BMI 33 ± 0.5 kg/m2; HbAlc 7.5 ± 0.4%; eight matched control subjects were included.
Methods: In protocol one, fasting values of DPP-IV activity were evaluated and in protocol two, postprandial DPP-IV activity during a standard meal test (566 kcal) was estimated.
Results: Mean fasting plasma DPP-IV activity (expressed as degradation of GLP-1) was significantly higher in this patient group compared with the control subjects (67.5 ± 1.9 vs 56.8 ± 2.2 fmol GLP-1/h (mean ± s.e.m.); P=0.001). In the type-2 diabetic patients, DPP-IV activity was positively correlated to FPG and HbAlc and negatively to the duration of diabetes and age of the patients. No postprandial changes were seen in plasma DPP-IV activity in any of the groups.
Conclusions: Plasma DPP-IVactivity increases in the fasting state and is positively correlated to FPG and HbAlc levels, but plasma DPP-IV activity is not altered following meal ingestion and acute changes in plasma glucose.
Rasmus Rabøl, Pernille F Svendsen, Mette Skovbro, Robert Boushel, Peter Schjerling, Lisbeth Nilas, Sten Madsbad and Flemming Dela
Polycystic ovarian syndrome (PCOS) is associated with skeletal muscle insulin resistance (IR), which has been linked to decreased mitochondrial function. We measured mitochondrial respiration in lean and obese women with and without PCOS using high-resolution respirometry.
Hyperinsulinemic–euglycemic clamps (40 mU/min per m2) and muscle biopsies were performed on 23 women with PCOS (nine lean (body mass index (BMI) <25 kg/m2) and 14 obese (BMI >25 kg/m2)) and 17 age- and weight-matched controls (six lean and 11 obese). Western blotting and high-resolution respirometry was used to determine mitochondrial function.
Insulin sensitivity decreased with PCOS and increasing body weight. Mitochondrial respiration with substrates for complex I and complex I+II were similar in all groups, and PCOS was not associated with a decrease in mitochondrial content as measured by mitochondrial DNA/genomic DNA. We found no correlation between mitochondrial function and indices of insulin sensitivity.
In contrast to previous reports, we found no evidence that skeletal muscle mitochondrial respiration is reduced in skeletal muscle of women with PCOS compared with control subjects. Furthermore, mitochondrial content did not differ between our control and PCOS groups. These results question the causal relationship between reduced mitochondrial function and skeletal muscle IR in PCOS.
Steen B Haugaard, Ove Andersen, Flemming Dela, Jens Juul Holst, Heidi Storgaard, Mogens Fenger, Johan Iversen and Sten Madsbad
Objectives: Lipodystrophy and insulin resistance are prevalent among human immunodeficiency virus (HIV)-infected patients on combined antiretroviral therapy (HAART). Aiming to provide a detailed description of the metabolic adverse effects of HIV-lipodystrophy, we investigated several aspects of glucose metabolism, lipid metabolism and β-cell function in lipodystrophic HIV-infected patients.
Methods: [3-3H]glucose was applied during euglycaemic hyperinsulinaemic clamps in association with indirect calorimetry in 43 normoglycaemic HIV-infected patients (18 lipodystrophic patients on HAART (LIPO), 18 patients without lipodystrophy on HAART (NONLIPO) and seven patients who were naïve to antiretroviral therapy (NAÏVE) respectively). β-cell function was evaluated by an intravenous glucose tolerance test.
Results: Compared with NONLIPO and NAÏVE separately, LIPO displayed markedly reduced ratio of limb to trunk fat (RLF; >34%, P < 0.001), hepatic insulin sensitivity (>40%, P < 0.03), incremental glucose disposal (>50%, P < 0.001) and incremental exogenous glucose storage (>50%, P < 0.05). Furthermore, LIPO displayed reduced incremental glucose oxidation (P < 0.01), increased clamp free fatty acids (P < 0.05) and attenuated insulin-mediated suppression of lipid oxidation (P < 0.05) compared with NONLIPO. In combined study groups, RLF correlated with hepatic insulin sensitivity (r = 0.69), incremental glucose disposal (r = 0.71) and incremental exogenous glucose storage (r = 0.40), all P < 0.01. Disposition index (i.e. first-phase insulin response to intravenous glucose multiplied by incremental glucose disposal) was reduced by 46% (P = 0.05) in LIPO compared with the combined groups of NONLIPO and NAÏVE, indicating an impaired adaptation of β-cell function to insulin resistance in LIPO.
Conclusion: Our data suggest that normoglycaemic lipodystrophic HIV-infected patients display impaired glucose and lipid metabolism in multiple pathways involving liver, muscle tissue and β-cell function.