| 31. |
- Pacini, Giovanni, et al.
(författare)
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Reappraisal of the intravenous glucose tolerance index for a simple assessment of insulin sensitivity in mice
- 2009
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Ingår i: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 296:5, s. 1316-1324
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Tidskriftsartikel (refereegranskat)abstract
- Pacini G, Ahren M, Ahren B. Reappraisal of the intravenous glucose tolerance index for a simple assessment of insulin sensitivity in mice. Am J Physiol Regul Integr Comp Physiol 296: R1316-R1324, 2009. First published February 11, 2009; doi: 10.1152/ajpregu.90575.2008.- Mice are increasingly used in studies where measuring insulin sensitivity (IS) is a common procedure. The glucose clamp is labor intensive, cannot be used in large numbers of animals, cannot be repeated in the same mouse, and has been questioned as a valid tool for IS in mice; thus, the minimal model with 50-min intravenous glucose tolerance test (IVGTT) data was adapted for studies in mice. However, specific software and particular ability was needed. The aim of this study was to establish a simple procedure for evaluating IS during IVGTT in mice (CSI). IVGTTs (n = 520) were performed in NMRI and C57BL/6J mice (20-25g). After glucose injection (1 g/kg), seven samples were collected for 50 min for glucose and insulin measurements, analyzed with a minimal model that provided the validated reference IS (S-perpendicular to). By using the regression CS perpendicular to = alpha(1) + alpha(2) x K-G/AUC(D), where K-G is intravenous glucose tolerance index and AUC(D) is the dynamic area under the curve, IS was calculated in 134 control animals randomly selected (regression CSI vs. S-I: r = 0.66, P < 0.0001) and yielded alpha(1) = 1.93 and alpha(2) = 0.24. KG is the slope of log (glucose(5-20)) and AUCD is the mean dynamic area under insulin curve in the IVGTT. By keeping fixed alpha(1) and alpha(2), CSI was validated in 143 control mice (4.7 +/- 0.2 min . mu U- . ml(-1), virtually identical to S-I: 4.7 +/- 0.3, r = 0.89, P < 0.0001); and in 123 mice in different conditions: transgenic, addition of neuropeptides, incretins, and insulin (CSI: 6.0 +/- 0.4 vs. SI: 6.1 +/- 0.4, r = 0.94, P < 0.0001). In the other 120 animals, CSI revealed its ability to segregate different categories, as does S-I. This easily usable formula for calculating CSI overcomes many experimental obstacles and may be a simple alternative to more complex procedures when large numbers of mice or repeated experiments in the same animals are required.
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| 32. |
- Pacini, Giovanni, et al.
(författare)
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The dual incretin co-agonist tirzepatide increases both insulin secretion and glucose effectiveness in model experiments in mice
- 2024
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Ingår i: Peptides. - 0196-9781. ; 171
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Tidskriftsartikel (refereegranskat)abstract
- Tirzepatide is a dual GIP and GLP-1 receptor co-agonist which is approved for glucose-lowering therapy in type 2 diabetes. Here, we explored its effects on beta cell function, insulin sensitivity and insulin-independent glucose elimination (glucose effectiveness) in normal mice. Anesthetized female C57/BL/6 J mice were injected intravenously with saline or glucose (0.125, 0.35 or 0.75 g/kg) with or without simultaneous administration of synthetic tirzepatide (3 nmol/kg). Samples were taken at 0, 1, 5, 10, 20 and 50 min. Glucose elimination rate was estimated by the percentage reduction in glucose from min 5 to min 20 (KG). The 50 min areas under the curve (AUC) for insulin and glucose were determined. Beta cell function was assessed as AUCinsulin divided by AUCglucose. Insulin sensitivity (SI) and glucose effectiveness (SG) were determined by minimal model analysis of the insulin and glucose data. Tirzepatide glucose-dependently reduced glucose levels and increased insulin levels. The slope for the regression of AUCinsulin versus AUCglucose was increased 7-fold by tirzepatide from 0.014 ± 0.004 with glucose only to 0.099 ± 0.016 (P < 0.001). SI was not affected by tirzepatide, whereas SG was increased by 78% (P < 0.001). The increase in SG contributed to an increase in KG by 74 ± 4% after glucose alone and by 67 ± 8% after glucose+ tirzepatide, whereas contribution by SI times AUCinsulin insulin (i.e., disposition index) was 26 ± 4% and 33 ± 8%, respectively. In conclusion, tirzepatide stimulates both insulin secretion and glucose effectiveness, with stimulation of glucose effectiveness being the prominent process to reduce glucose.
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| 33. |
- Persson, Kristin, et al.
(författare)
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Islet function phenotype in gastrin-releasing Peptide receptor gene-deficient mice.
- 2002
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 143:10, s. 3717-3726
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Tidskriftsartikel (refereegranskat)abstract
- Gastrin-releasing peptide (GRP) is an islet neuropeptide that stimulates insulin secretion. To explore whether islet GRP contributes to neurally mediated insulin secretion, we studied GRP receptor (GRPR)-deleted mice. By using RT-PCR we showed that GRPR mRNA is expressed in islets of wild-type mice, but is lost in GRPR-deleted mice. Functional studies revealed that GRP potentiates glucose-stimulated insulin secretion in wild-type animals, but not in GRPR-deleted mice. This shows that GRPR is the receptor subtype mediating GRP-induced insulin secretion and that GRPR-deleted mice are tools for studying the physiological role of islet GRP. We found that GRPR-deleted mice display 1) augmentation of the insulin response to glucose by a mechanism inhibited by ganglionic blockade; 2) increased insulin responsiveness also to the cholinergic agonist carbachol, but not to arginine; 3) impaired insulin and glucagon responses to autonomic nerve activation by 2-deoxyglucose; 4) normal islet adaptation to high fat-induced insulin resistance and fasting; and 5) normal islet cytoarchitecture, as revealed by immunocytochemistry of insulin and glucagon. In conclusion, 1) GRPR is the receptor subtype mediating the islet effects of GRP; 2) GRP contributes to insulin secretion induced by activation of the autonomic nerves; and 3) deletion of GRPR is compensated by increased cholinergic sensitivity.
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| 34. |
- Song, Gina, et al.
(författare)
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Glucagon increases insulin levels by stimulating insulin secretion without effect on insulin clearance in mice
- 2017
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781. ; 88, s. 74-79
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Tidskriftsartikel (refereegranskat)abstract
- Circulating insulin is dependent on a balance between insulin appearance through secretion and insulin clearance. However, to what extent changes in insulin clearance contribute to the increased insulin levels after glucagon administration is not known. This study therefore assessed and quantified any potential effect of glucagon on insulin kinetics in mice. Prehepatic insulin secretion in mice was first estimated following glucose (0.35 g/kg i.v.) and following glucose plus glucagon (10 μg/kg i.v.) using deconvolution of plasma C-peptide concentrations. Plasma concentrations of glucose, insulin, and glucagon were then measured simultaneously in individual mice following glucose alone or glucose plus glucagon (pre dose and at 1, 5, 10, 20 min post). Using the previously determined insulin secretion profiles and the insulin concentration-time measurements, a population modeling analysis was applied to estimate the one-compartment kinetics of insulin disposition with and without glucagon. Glucagon with glucose significantly enhanced prehepatic insulin secretion (Cmax and AUC0-20) compared to that with glucose alone (p < 0.0001). From the modeling analysis, the population mean and between-animal SD of insulin clearance was 6.4 ± 0.34 mL/min for glucose alone and 5.8 ± 1.5 mL/min for glucagon plus glucose, with no significant effect of glucagon on mean insulin clearance. Therefore, we conclude that the enhancement of circulating insulin after glucagon administration is solely due to stimulated insulin secretion.
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| 35. |
- Stadler, Marietta, et al.
(författare)
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Effects of smoking cessation on beta cell function, insulin sensitivity, body weight and appetite.
- 2014
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Ingår i: European journal of endocrinology / European Federation of Endocrine Societies. - 1479-683X. ; 170, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- Objective To stop smoking is commonly associated with significant weight gain, but the mechanisms for this are poorly understood. We assessed the effects of smoking cessation on body weight, insulin sensitivity, β-cell function, and appetite. Subjects and methods Twenty-seven long-term smokers (n=27; nine females/18 males, 28±1 years, 22.9±0.6kg/m2) attending an ambulatory smoking cessation program in a community hospital in Vienna, Austria were examined at baseline (Visit A; still smoking) and after a minimum of 3 months of smoking abstinence (Visit B; n=14); relapsed smokers were not followed up. Participants underwent 3-h oral glucose tolerance tests and body composition measurements at each study visit. Fasting (QUICKI) and dynamic (oral glucose insulin sensitivity (OGIS)) insulin sensitivity and β-cell secretion (insulinogenic index 140 (IGI40)) were calculated. Food intake was quantified with a free choice buffet. Fasting plasma concentrations of neuropeptide-Y (NPY), peptide-YY (PYY), glucagon-like peptide 1 (GLP1), leptin, ghrelin, and visfatin were measured. Results After >3 months' smoking abstinence, body weight, and fat mass were increased (+4 and +22% respectively, P<0.05) and fasting insulin sensitivity deteriorated (QUICKI: post, 0.37±0.02 vs baseline, 0.41±0.2; P<0.05), while OGIS remained unchanged throughout. IGI40 increased by 31% after >3 months' smoking abstinence (P<0.01). Carbohydrate ingestion increased after stopping smoking (P<0.05). NPY fasting levels were increased after >3 months (P<0.05), PYY, GLP1, leptin, ghrelin, and visfatin were unchanged. Conclusion Smoking cessation is associated with transient metabolic changes including increased β-cell secretion in response to glucose and fasting insulin resistance. These alterations may be associated with or contribute to the body weight gain after smoking cessation.
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| 36. |
- Sörhede Winzell, Maria, et al.
(författare)
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Beta-Cell-Targeted Expression of a Dominant-Negative Mutant of Hepatocyte Nuclear Factor-1{alpha} in Mice: Diabetes Model with {beta}-Cell Dysfunction Partially Rescued by Nonglucose Secretagogues.
- 2004
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Ingår i: Diabetes. - 1939-327X. ; 53:suppl_3, s. 92-96
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Tidskriftsartikel (refereegranskat)abstract
- We studied islet function in mice with beta-cell-targeted expression of a dominant-negative mutant of hepatocyte nuclear factor (HNF)-1alpha. At age 2-3 months, anesthetized transgenic and wild-type male mice underwent an intravenous glucose (1 g/kg) tolerance test (IVGTT). It was found that transgenic mice had an abolished insulin response in association with severe glucose intolerance. In other tests, the 5-min insulin response to intravenous arginine was impaired by 79% (P=0.032) and the 15-min insulin response to gastric glucose was suppressed by 97% (P=0.006). In islets incubated for 60 min, the insulin response to glucose (3.3-22.2 mmol/l) was impaired by >80% in transgenic mice. In contrast, insulin responses to nonglucose secretagogues were only partially suppressed (to GLP-1 [100 nmol/l] by 40%, to carbachol [1 micromol/l] by 20%, and to palmitate [0.5 mmol/l] by 15%), whereas the response to depolarization by KCl (50 mmol/l) was not reduced. Finally, the IVGTT data insulin sensitivity in transgenic mice was not significantly different from that of wild-type mice. Thus, mice with targeted suppression of beta-cell HNF-1alpha represent a good diabetes model exhibiting severely impaired insulin secretion after glucose with marked glucose intolerance. In contrast, the insulin responses to nonglucose stimuli are not suppressed when the islet insulin content is taken into account.
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| 37. |
- Sörhede Winzell, Maria, et al.
(författare)
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Insulin secretion after dietary supplementation with conjugated linoleic acids and n-3 polyunsaturated fatty acids in normal and insulin-resistant mice.
- 2006
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Ingår i: American Journal of Physiology: Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 290:2, s. 347-354
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Tidskriftsartikel (refereegranskat)abstract
- Insulin secretion after dietary supplementation with conjugated linoleic acids and n-3 polyunsaturated fatty acids in normal and insulin-resistance mice. Am J Physiol Endocrinol Metab 290: E347-E354, 2006. First published September 27, 2005; doi:10.1152/ajpendo.00163.2005.-Conjugated linoleic acids (CLAs) and n-3 polyunsaturated fatty acids (PUFAs) improve insulin sensitivity in insulin-resistant rodents. However, the effects of these fatty acids on insulin secretion are not known but are of importance to completely understand their influence on glucose homeostasis. We therefore examined islet function after dietary supplementation consisting of 1% CLAs in combination with 1% n-3 enriched PUFAs for 12 wk to mice on a normal diet and to insulin-resistant mice fed a high-fat diet (58% fat). In the mice fed a normal diet, CLA/PUFA supplementation resulted in insulin resistance associated with low plasma adiponectin levels and low body fat content. Intravenous and oral glucose tolerance tests revealed a marked increase in insulin secretion, which nevertheless was insufficient to counteract the insulin resistance, resulting in glucose intolerance. In freshly isolated islets from mice fed the normal diet, both basal and glucose-stimulated insulin secretion were adaptively augmented by CLA/PUFA, and at a high glucose concentration this was accompanied by elevated glucose oxidation. In contrast, in high-fat-fed mice, CLA/PUFA did not significantly affect insulin secretion, insulin resistance, or glucose tolerance. It is concluded that dietary supplementation of CLA/PUFA in mice fed the normal diet augments insulin secretion, partly because of increased islet glucose oxidation, but that this augmentation is insufficient to counterbalance the induction of insulin resistance, resulting in glucose intolerance. Furthermore, the high-fat diet partly prevents the deleterious effects of CLA/PUFA, but this dietary supplementation was not able to counteract high-fat-diet-induced insulin resistance.
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| 38. |
- Tura, Andrea, et al.
(författare)
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Four-Point Preprandial Self-Monitoring of Blood Glucose for the Assessment of Glycemic Control and Variability in Patients with Type 2 Diabetes Treated with Insulin and Vildagliptin.
- 2015
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Ingår i: International Journal of Endocrinology. - : Hindawi Limited. - 1687-8337 .- 1687-8345. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- The study explored the utility of four-point preprandial glucose self-monitoring to calculate several indices of glycemic control and variability in a study adding the DPP-4 inhibitor vildagliptin to ongoing insulin therapy. This analysis utilized data from a double-blind, randomized, placebo-controlled crossover study in 29 patients with type 2 diabetes treated with vildagliptin or placebo on top of stable insulin dose. During two 4-week treatment periods, self-monitoring of plasma glucose was undertaken at 4 occasions every day. Glucose values were used to assess several indices of glycemic control quality, such as glucose mean, GRADE, M-VALUE, hypoglycemia and hyperglycemia index, and indices of glycemic variability, such as standard deviation, CONGA, J-INDEX, and MAGE. We found that vildagliptin improved the glycemic condition compared to placebo: mean glycemic levels, and both GRADE and M-VALUE, were reduced by vildagliptin (P < 0.01). Indices also showed that vildagliptin reduced glycemia without increasing the risk for hypoglycemia. Almost all indices of glycemic variability showed an improvement of the glycemic condition with vildagliptin (P < 0.02), though more marked differences were shown by the more complex indices. In conclusion, the study shows that four-sample preprandial glucose self-monitoring is sufficient to yield information on the vildagliptin effects on glycemic control and variability.
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| 39. |
- Tura, Andrea, et al.
(författare)
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Glucagon and insulin secretion, insulin clearance, and fasting glucose in GIP receptor and GLP-1 receptor knockout mice
- 2019
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Ingår i: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 316:1, s. 27-37
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Tidskriftsartikel (refereegranskat)abstract
- It is not known whether GIP receptor and GLP-1 receptor knockout (KO) mice have perturbations in glucagon secretion or insulin clearance, and studies on impact on fasting glycemia have previously been inconsistent in these mice. We therefore studied glucagon secretion after oral whey protein (60 mg) and intravenous arginine (6.25 mg), insulin clearance after intravenous glucose (0.35 g/kg) and fasting glucose, insulin, and glucagon levels after standardized 5-h fasting in female GIP receptor and GLP-1 receptor KO mice and their wild-type (WT) littermates. Compared with WT controls, GIP receptor KO mice had normal glucagon responses to oral protein and intravenous arginine, except for an enhanced 1-min response to arginine, whereas glucagon levels after oral protein and intravenous arginine were enhanced in GLP-1 receptor KO mice. Furthermore, the intravenous glucose test revealed normal insulin clearance in both GIP receptor and GLP-1 receptor KO mice, whereas β-cell glucose sensitivity was enhanced in GIP receptor KO mice and reduced in GLP-1 receptor KO mice. Finally, GIP receptor KO mice had reduced fasting glucose (6.7 ± 0.1, n = 56, vs. 7.4 ± 0.1 mmol/l, n = 59, P = 0.001), whereas GLP-1 receptor KO mice had increased fasting glucose (9.1 ± 0.2, n = 44, vs. 7.7 ± 0.1 mmol/l, n = 41, P < 0.001). We therefore suggest that GIP has a limited role for glucagon secretion in mice, whereas GLP-1 is of importance for glucagon regulation, that GIP and GLP-1 are of importance for the regulation of β-cell function beyond their role as incretin hormones, and that they are both of importance for fasting glucose.
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| 40. |
- Tura, Andrea, et al.
(författare)
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Increased insulin clearance in mice with double deletion of glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptors
- 2018
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Ingår i: American Journal of Physiology - Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 314:5, s. 639-646
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Tidskriftsartikel (refereegranskat)abstract
- To establish whether incretin hormones affect insulin clearance, the aim of this study was to assess insulin clearance in mice with genetic deletion of receptors for both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), so called double incretin receptor knockout mice (DIRKO). DIRKO (n = 31) and wild-type (WT) C57BL6J mice (n = 45) were intravenously injected with D-glucose (0.35 g/kg). Blood was sampled for 50 min and assayed for glucose, insulin, and C-peptide. Data were modeled to calculate insulin clearance; C-peptide kinetics was established after human C-peptide injection. Assessment of C-peptide kinetics revealed that C-peptide clearance was 1.66 ± 0.10 10–31/min. After intravenous glucose administration, insulin clearance during first phase insulin secretion was markedly higher in DIRKO than in WT mice (0.68 ± 0.06 10–3l/min in DIRKO mice vs. 0.54 ± 0.03 10–31/min in WT mice, P = 0.02). In contrast, there was no difference between the two groups in insulin clearance during second phase insulin secretion (P = 0.18). In conclusion, this study evaluated C-peptide kinetics in the mouse and exploited a mathematical model to estimate insulin clearance. Results showed that DIRKO mice have higher insulin clearance than WT mice, following intravenous injection of glucose. This suggests that incretin hormones reduce insulin clearance at physiological, nonstimulated levels.
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