| 1. |
- Ahlkvist, Linda, et al.
(författare)
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Defective insulin secretion by chronic glucagon receptor activation in glucose intolerant mice.
- 2016
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Ingår i: Journal of Endocrinology. - 1479-6805. ; 228, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- Stimulation of insulin secretion by short-term glucagon receptor (GCGR) activation is well characterized, however, the effect of long-term GCGR activation on beta-cell function is not known, but of interest, since hyperglucagonemia occurs early during development of type 2 diabetes. Therefore, we examined whether chronic GCGR activation affects insulin secretion in glucose intolerant mice. To induce chronic GCGR activation, high-fat diet fed mice were continuously (2wk) infused with the stable glucagon analogue ZP-GA-1 and challenged with oral glucose and intravenous glucose +/- GLP-1. Islets were isolated to evaluate the insulin secretory response to glucose +/- GLP-1 and pancreases were collected for immunohistochemical analysis. Two-week ZP-GA-1 infusion reduced insulin secretion both after oral and intravenous glucose challenges in vivo and in isolated islets. These inhibitory effects were corrected for by GLP-1. Also, we observed increased beta-cell area and islet size. We conclude that induction of chronic ZP-GA-1 levels in glucose intolerant mice markedly reduces insulin secretion, and thus, we suggest that chronic activation of the GCGR may contribute to the failure of beta-cell function during development of type 2 diabetes.
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| 2. |
- Ahlkvist, Linda, et al.
(författare)
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Evidence for neural contribution to islet effects of DPP-4 inhibition in mice
- 2016
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 1879-0712 .- 0014-2999. ; 780, s. 46-52
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that neural mechanisms may contribute to effects of the incretin hormones, and, therefore, also to the effects of dipeptidyl peptidase (DPP-4) inhibition. We therefore examined whether muscarinic mechanisms are involved in the stimulation of insulin secretion by DPP-4 inhibition. Fasted, anesthetized mice were given intraperitoneal saline or the muscarinic antagonist atropine (5mg/kg) before duodenal glucose (75mg/mouse), with or without the DPP-4 inhibitor NVPDPP728 (0.095mg/mouse), or before intravenous glucose (0.35g/kg) with or without co-administration with GLP-1 or glucose-dependent insulinotropic polypeptide (GIP) (both 3nmol/kg). Furthermore, isolated islets were incubated (1h) in 2.8 and 11.1mM glucose, with or without GIP or GLP-1 (both 100nM), in the presence or absence of atropine (100µM). Duodenal glucose increased circulating insulin and this effect was potentiated by DPP-4 inhibition. The increase in insulin achieved by DPP-4 inhibition was reduced by atropine by approximately 35%. Duodenal glucose also elicited an increase in circulating intact GLP-1 and GIP and this was augmented by DPP-4 inhibition, but these effects were not affected by atropine. Atropine did also not affect the augmentation by GLP-1 and GIP on glucose-stimulated insulin secretion from isolated islets. Based on these findings, we suggest that muscarinic mechanisms contribute to the stimulation of insulin secretion by DPP-4 inhibition through neural effects induced by GLP-1 and GIP whereas neural effects do not affect the levels of GLP-1 or GIP or the islet effects of the two incretin hormones.
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| 3. |
- Ahlqvist, Emma, et al.
(författare)
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A link between GIP and osteopontin in adipose tissue and insulin resistance.
- 2013
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 62:6, s. 2088-2094
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Tidskriftsartikel (refereegranskat)abstract
- Low grade inflammation in obesity is associated with accumulation of the macrophagederived cytokine osteopontin in adipose tissue and induction of local as well as systemic insulin resistance. Since GIP (glucose-dependent insulinotropic polypeptide) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate osteopontin (OPN) expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13±}0.04 vs 0.04±}0.01, P<0.05) and correlated inversely with measures of insulin sensitivity (r=-0.24, P=0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with lower amount of the exon 9 containing isoform required for transmembrane activity. Carriers of the A-allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone, but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of GIPR rs10423928 A-allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions.
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| 4. |
- Alsalim, Wathik, et al.
(författare)
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Incretin and islet hormone responses to meals of increasing size in healthy subjects.
- 2015
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 100:2, s. 561-568
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Tidskriftsartikel (refereegranskat)abstract
- Context: Postprandial glucose homeostasis is regulated through the secretion of glucagon-like peptide 1 (GLP-1) through stimulation of insulin secretion and inhibition of glucagon secretion. However, how these processes dynamically adapt to demands created by caloric challenges achieved during daily life is not known. Objective: To explore adaptation of incretin and islet hormones after mixed meals of increasing size in healthy subjects. Design: Twenty-four healthy lean subjects ingested a standard breakfast after an overnight fast followed, after four hours, by a lunch of different size (511, 743 and 1034 kcal) but with identical nutrient composition together with 1.5g paracetamol. Glucose, insulin, C-peptide, glucagon, intact glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and paracetamol were measured after the meals. Main outcome measure: Area under the 180 min curve (AUC) for insulin, C-peptide, glucagon, GLP-1 and GIP and model- derived ß-cell function and paracetamol appearance. Results: Glucose profiles were similar after the two larger meals whereas after the smaller meal, there was a post-peak reduction below baseline to nadir of 3.8±0.1mmol/l after 75min (p<0.001). AUC for GLP-1, GIP, insulin and C-peptide were significantly higher by increasing the caloric load as was β-cells sensitivity to glucose. In contrast, AUC glucagon was the same for all three meals, although there was an increase in glucagon after the postpeak glucose reduction in the smaller meal. The 0-20 min paracetamol appearance was increased by increasing meal size. Conclusion: Mixed lunch meals of increasing size elicit a caloric dependent insulin response due to increased β-cell secretion achieved by increased GIP and GLP-1 levels. The adaptation at larger meals results in identical glucose excursions, whereas after a lower caloric lunch the insulin response is high resulting in postpeak suppression of glucose below baseline.
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| 5. |
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| 6. |
- Andersen, Birgitte, et al.
(författare)
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Fibroblast growth factor 21 prevents glycemic deterioration in insulin deficient mouse models of diabetes.
- 2015
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 1879-0712 .- 0014-2999. ; 764, s. 189-194
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Tidskriftsartikel (refereegranskat)abstract
- In type 1 diabetes, there is a rapid loss of glycemic control immediately after onset of the disease. We aimed to determine if the deterioration of glycemic control that occurs early after the onset of insulin-deficient diabetes could be blunted by treatment with recombinant fibroblast growth factor 21 (FGF21). Normal C57BL/6J mice made diabetic by a single high dose injection of streptozotocin (STZ) were randomized to receive twice daily subcutaneous injection of vehicle or recombinant human FGF21 at doses of 0.3 and 1.0mg/kg for 10 days. Body weight was recorded daily and 5h fasted glucose, insulin, glucagon, free fatty acids and ketones were determined at 6 and 10 days post-randomization. The increase in fasting plasma glucose induced by STZ in untreated mice was prevented with FGF21 at 0.3mg/kg BID. In contrast, at 1.0mg/kg BID, FGF21 did not prevent the rise in plasma glucose after STZ. At the end of the study, plasma glucagon was significantly higher in the diabetic group treated with FGF21 1.0mg/kg BID than in the untreated group. This was not seen for the group treated with FGF21 0.3mg/kg BID. There were significant dose dependent reductions in plasma free fatty acids with FGF21 treatment but no significant change in plasma ketones (β-hydroxybutyrate). FGF21 treatment did not have significant effects on body weight in lean insulin deficient mice. In conclusion, FGF21 prevents increases in glycaemia and has lipid lowering properties in mouse models of insulin deficient diabetes, although by increasing the dose increased glucagon levels are seen and hyperglycemia persists.
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| 7. |
- Berggreen, Christine, et al.
(författare)
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Protein kinase B activity is required for the effects of insulin on lipid metabolism in adipocytes.
- 2009
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Ingår i: American Journal of Physiology: Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 296, s. 635-646
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Tidskriftsartikel (refereegranskat)abstract
- Protein kinase B is known to mediate a number of biological responses to insulin and growth factors, its role in glucose uptake being one of the most extensively studied. In this paper, we have employed a recently described allosteric inhibitor of PKB, Akti, to clarify the role of PKB in lipid metabolism in adipocytes - a subject that has received less attention. Pretreatment of primary rat and 3T3L1 adipocytes with Akti resulted in dose-dependent inhibition of PKB phosphorylation and activation in response to insulin, without affecting upstream insulin signaling (IR, IRS) or the insulin-induced PI3-K dependent activation of the ERK/RSK pathway. PKB activity was required for the insulin-induced activation of PDE3B and for the anti-lipolytic action of insulin. Moreover, inhibition of PKB activity resulted in a reduction in de novo lipid synthesis and in the ability of insulin to stimulate this process. The regulation of the rate-limiting lipogenic enzyme ACC by insulin through dephosphorylation of S79, which is a target for AMPK, was dependent on the presence of active PKB. Lastly, AMPK was shown to be phosphorylated by PKB on S485 in response to insulin and this was associated with a reduction in AMPK activity. In summary, we propose that PKB is required for the positive effects of insulin on lipid storage, and that regulation of PDE3B and AMPK by PKB is important for these effects. Key words: Akt, PDE3B, ACC, AMPK, lipogenesis.
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| 8. |
- Bugliani, Marco, et al.
(författare)
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DPP-4 is expressed in human pancreatic beta cells and its direct inhibition improves beta cell function and survival in type 2 diabetes
- 2018
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207. ; 473, s. 186-193
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Tidskriftsartikel (refereegranskat)abstract
- It has been reported that the incretin system, including regulated GLP-1 secretion and locally expressed DPP-4, is present in pancreatic islets. In this study we comprehensively evaluated the expression and role of DPP-4 in islet alpha and beta cells from non-diabetic (ND) and type 2 diabetic (T2D) individuals, including the effects of its inhibition on beta cell function and survival. Isolated islets were prepared from 25 ND and 18 T2D organ donors; studies were also performed with the human insulin-producing EndoC-βH1 cells. Morphological (including confocal microscopy), ultrastructural (electron microscopy, EM), functional (glucose-stimulated insulin secretion), survival (EM and nuclear dyes) and molecular (RNAseq, qPCR and western blot) studies were performed under several different experimental conditions. DPP-4 co-localized with glucagon and was also expressed in human islet insulin-containing cells. Furthermore, DPP-4 was expressed in EndoC-βH1 cells. The proportions of DPP-4 positive alpha and beta cells and DPP-4 gene expression were significantly lower in T2D islets. A DPP-4 inhibitor protected ND human beta cells and EndoC-βH1 cells against cytokine-induced toxicity, which was at least in part independent from GLP1 and associated with reduced NFKB1 expression. Finally, DPP-4 inhibition augmented glucose-stimulated insulin secretion, reduced apoptosis and improved ultrastructure in T2D beta cells. These results demonstrate the presence of DPP-4 in human islet alpha and beta cells, with reduced expression in T2D islets, and show that DPP-4 inhibition has beneficial effects on human ND and T2D beta cells. This suggests that DPP-4, besides playing a role in incretin effects, directly affects beta cell function and survival.
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| 9. |
- Degerman, Eva, et al.
(författare)
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From PDE3B to the regulation of energy homeostasis.
- 2011
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Ingår i: Current Opinion in Pharmacology. - : Elsevier BV. - 1471-4973 .- 1471-4892. ; 11, s. 676-682
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Tidskriftsartikel (refereegranskat)abstract
- The incidence of obesity in the developed world is increasing at an alarming rate. Concurrent with the increase in the incidence of obesity is an increase in the incidence of type 2 diabetes. Cyclic AMP (cAMP) and cGMP are key second messengers in all cells; for example, when it comes to processes of relevance for the regulation of energy metabolism, cAMP is a key mediator in the regulation of lipolysis, glycogenolysis, gluconeogenesis and pancreatic β cell insulin secretion. PDE3B, one of several enzymes which hydrolyze cAMP and cGMP, is expressed in cells of importance for the regulation of energy homeostasis, including adipocytes, hepatocytes, hypothalamic cells and β cells. It has been shown, using PDE3 inhibitors and gene targeting approaches in cells and animals, that altered levels of PDE3B result in a number of changes in the regulation of glucose and lipid metabolism and in overall energy homeostasis. This article highlights the complexity involved in the regulation of PDE3B by hormones, and in the regulation of downstream metabolic effects by PDE3B in several interacting tissues.
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| 10. |
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