| 1. |
- Ahrén, Bo
(författare)
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beta- and alpha-Cell Dysfunction in Subjects Developing Impaired Glucose Tolerance Outcome of a 12-Year Prospective Study in Postmenopausal Caucasian Women
- 2009
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 58:3, s. 726-731
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE-This study assessed insulin and glucagon secretion in relation to insulin sensitivity in Caucasian women who develop impaired glucose tolerance (IGT) versus those who maintain normal glucose tolerance (NGT) over a 12-year period. RESEARCH DESIGN AND METHODS-At baseline and after 3, 8, and 12 years, glucose tolerance (75-g oral glucose tolerance test), insulin sensitivity (euglycemic-hyperinsulinemic clamp), and insulin and glucagon secretion (2- to 5-min responses to 5 g arginine i.v. at fasting, 14 and >25 mmol/l glucose) were determined in 53 healthy Caucasian women (aged 58 years at. baseline) who all had NGT at baseline. RESULTS-During the 12-year period, 26 subjects developed IGT, whereas the remaining 27 subjects maintained NGT throughout the 12-year period. Subjects developing IGT had lower insulin sensitivity than those maintaining NGT in the tests preceding diagnosis of IGT (P <= 0.05). When judged in relation to insulin sensitivity, P-cell glucose sensitivity and maximal insulin secretion were lower in those who later developed IGT than in those maintaining NGT at all tests (P : 0.05). Furthermore, subject's who developed IGT had defective suppression of glucagon secretion by glucose in the test preceding diagnosis of IGT when they still had NGT (P : 0.05). CONCLUSIONS-beta- and alpha-cell dysfunction are evident several years before diagnosis of IGT, and islet dysfunction is manifeste as impaired glucose sensitivity of the beta- and (x-cells and reduced maximal insulin secretion. Diabetes 58:726-731, 2009
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| 2. |
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| 3. |
- Ahrén, Bo, et al.
(författare)
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Neuropeptides and the regulation of islet function.
- 2006
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Ingår i: Diabetes. - 1939-327X. ; 55:Suppl 2, s. 98-107
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Tidskriftsartikel (refereegranskat)abstract
- The pancreatic islets are richly innervated by autonomic nerves. The islet parasympathetic nerves emanate from intrapancreatic ganglia, which are controlled by preganglionic vagal nerves. The islet sympathetic nerves are postganglionic with the nerve cell bodies located in ganglia outside the pancreas. The sensory nerves originate from dorsal root ganglia near the spinal cord. Inside the islets, nerve terminals run close to the endocrine cells. In addition to the classic neurotransmitters acetylcholine and norepinephrine, several neuropeptides exist in the islet nerve terminals. These neuropeptides are vasoactive intestinal polypeptide, pituitary adenylate cyclase-activating polypeptide, gastrin-releasing polypeptide, and cocaine-and amphetamine-regulated transcript in parasympathetic nerves; neuropeptide Y and galanin in the sympathetic nerves; and calcitonin gene-related polypeptide in sensory nerves. Activation of the parasympathetic nerves and administration of their neurotransmitters stimulate insulin and glucagon secretion, whereas activation of the sympathetic nerves and administration of their neurotransmitters inhibit insulin but stimulate glucagon secretion. The autonomic nerves contribute to the cephalic phase of insulin secretion, to glucagon secretion during hypoglycemia, to pancreatic polypeptide secretion, and to the inhibition of insulin secretion, which is seen during stress. In rodent models of diabetes, the number of islet autonomic nerves is upregulated. This review focuses on neural regulation of islet function, with emphasis on the neuropeptides.
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| 4. |
- Ahrén, Bo, et al.
(författare)
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Quantification of insulin secretion in relation to insulin sensitivity in nondiabetic postmenopausal women.
- 2002
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Ingår i: Diabetes. - 1939-327X. ; 51:Suppl 1, s. 202-211
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate mechanisms underlying the close association between insulin secretion and insulin sensitivity, insulin sensitivity was evaluated by the euglycemic-hyperinsulinemic clamp technique (M/I(clamp)) and insulin secretion was determined from the 75-g oral glucose tolerance test (OGTT) and from the glucose-dependent arginine-stimulation test in 81 nondiabetic postmenopausal women, all aged 61 years. M/I(clamp) was normally distributed with mean plus minus SD of 69.9 plus minus 30.5 nmol glucose center dot kg(-1) center dot min(-1)/pmol insulin center dot l(-1). It was found that the several different measures of insulin secretion from the OGTT and the glucose-dependent arginine-stimulation test were all inversely related to M/I(clamp). However, measures determining the direct insulin responses were more markedly potentiated by low M/I(clamp) than were measures determining glucose potentiation of insulin secretion. Moreover, the product of M/I(clamp) times measures of insulin secretion (disposition index [DI]) was inversely related to the 2-h glucose value. Finally, surrogate insulin sensitivity measures quantified from OGTT and the glucose-dependent arginine-stimulation test only weakly correlated to M/I(clamp) (R(2) approximate 0.25). Thus, 1) insulin secretion is adaptively increased when insulin sensitivity is low in nondiabetic postmenopausal women; 2) beta-cell exocytotic ability shows more efficient adaptation than beta-cell glucose recognition to low insulin sensitivity; 3) impaired beta-cell adaptation (i.e., low DI) is associated with higher 2-h glucose values during OGTT, although other regulatory mechanisms also exist; and 4) indirect surrogate measures of insulin sensitivity only weakly correlate to insulin sensitivity as determined by the euglycemic-hyperinsulinemic clamp.
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| 5. |
- Bohlooly-Yeganeh, Mohammad, 1966, et al.
(författare)
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Growth hormone overexpression in the central nervous system results in hyperphagia-induced obesity associated with insulin resistance and dyslipidemia.
- 2005
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Ingår i: Diabetes. - 0012-1797 .- 1939-327X. ; 54:1, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that peripherally administered growth hormone (GH) results in decreased body fat mass. However, GH-deficient patients increase their food intake when substituted with GH, suggesting that GH also has an appetite stimulating effect. Transgenic mice with an overexpression of bovine GH in the central nervous system (CNS) were created to investigate the role of GH in CNS. This study shows that overexpression of GH in the CNS differentiates the effect of GH on body fat mass from that on appetite. The transgenic mice were not GH-deficient but were obese and showed increased food intake as well as increased hypothalamic expression of agouti-related protein and neuropeptide Y. GH also had an acute effect on food intake following intracerebroventricular injection of C57BL/6 mice. The transgenic mice were severely hyperinsulinemic and showed a marked hyperplasia of the islets of Langerhans. In addition, the transgenic mice displayed alterations in serum lipid and lipoprotein levels and hepatic gene expression. In conclusion, GH overexpression in the CNS results in hyperphagia-induced obesity indicating a dual effect of GH with a central stimulation of appetite and a peripheral lipolytic effect.
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| 6. |
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| 7. |
- Færch, Kristine, et al.
(författare)
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Insulin resistance is accompanied by increased fasting glucagon and delayed glucagon suppression in individuals with normal and impaired glucose regulation
- 2016
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 65:11, s. 3473-3481
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Tidskriftsartikel (refereegranskat)abstract
- Hyperinsulinemia is an adaptive mechanism that enables the maintenance of normoglycemia in the presence of insulin resistance. We assessed whether glucagon is also involved in the adaptation to insulin resistance. A total of 1,437 individuals underwent an oral glucose tolerance test with measurements of circulating glucose, insulin, and glucagon concentrations at 0, 30 and 120 min. Early glucagon suppression was defined as suppression in the period from 0 to 30 min, and late glucagon suppression as 30 to 120 min after glucose intake. Insulin sensitivity was estimated by the validated insulin sensitivity index. Individuals with screen-detected diabetes had 30% higher fasting glucagon levels and diminished early glucagon suppression, but greater late glucagon suppression when compared with individuals with normal glucose tolerance (P 0.014). Higher insulin resistance was associated with higher fasting glucagon levels, less early glucagon suppression, and greater late glucagon suppression (P < 0.001). The relationship between insulin sensitivity and fasting glucagon concentrations was nonlinear (P < 0.001). In conclusion, increased fasting glucagon levels and delayed glucagon suppression, together with increased circulating insulin levels, develop in parallel with insulin resistance. Therefore, glucose maintenance during insulin resistance may depend not only on hyperinsulinemia but also on the ability to suppress glucagon early after glucose intake.
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| 8. |
- Fex, Malin, et al.
(författare)
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{beta}-Cell Lipases and Insulin Secretion.
- 2006
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Ingår i: Diabetes. - 1939-327X. ; 55:Suppl 2, s. 24-31
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Tidskriftsartikel (refereegranskat)abstract
- Lipids have been implicated in ß-cell stimulus-secretion coupling. Thus, lipases in ß-cells would be required to generate coupling factors from intracellular lipids. Indeed, we found that glucose stimulates lipolysis in rodent islets and clonal ß-cells. Lipolysis and diglyceride lipase activity in islets are abolished by orlistat, a pan-lipase inhibitor. Moreover, orlistat dose-dependently inhibits glucose- and forskolin-stimulated insulin secretion, while leaving glucose oxidation and the rise in ATP-to-ADP ratio intact. In an effort to identify ß-cell lipase(s), we found that hormone-sensitive lipase (HSL), the rate-limiting enzyme for acylglyceride hydrolysis in adipocytes, is active in rodent ß-cells. To further address the role of HSL, a global and ß-cell–specific inactivation, respectively, of the lipase has been created in mice. Whereas our line of HSL null mice is moderately glucose intolerant due to reduced peripheral insulin sensitivity, it exhibits normal islet metabolism and insulin secretion. Preliminary analysis of the ß-cell–specific HSL knockout has revealed no evidence for disturbed islet function. Thus, studies of ours and others indicate that there is a complex lipid regulatory component in ß-cell stimulus-secretion coupling. The role of HSL and other lipases needs to be further clarified to provide a balanced view of the role of lipids and lipolysis in ß-cells.
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| 9. |
- García, Maria C, et al.
(författare)
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Mature-onset obesity in interleukin-1 receptor I knockout mice.
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:5, s. 1205-13
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Tidskriftsartikel (refereegranskat)abstract
- Interleukin-1 (IL-1) is a major mediator of inflammation that exerts its biological activities through the IL-1 type I receptor (IL-1RI). The body weights of IL-1RI(-/-) mice of both sexes started to deviate from those of wild-type mice at 5-6 months of age and were 20% higher at 9 months of age. Visceral and subcutaneous fat mass, measured by dual-energy X-ray absorptiometry and magnetic resonance imaging, was markedly (1.5- to 2.5-fold) increased. Lean body mass and crown-rump length were also slightly (11 and 5%, respectively) increased, as was serum IGF-I. Obese IL-1RI(-/-) mice were insulin resistant, as evidenced by hyperinsulinemia, decreased glucose tolerance, and insulin sensitivity. To elucidate the mechanisms for the development of obesity, young pre-obese IL-1RI(-/-) mice were investigated. They showed decreased suppression of body weight and food intake in response to systemic leptin treatment. The decreased leptin responsiveness was even more pronounced in older obese animals. Moreover, spontaneous locomotor activity and fat utilization, as measured by respiratory quotient, were decreased in pre-obese IL-1RI(-/-) mice. In conclusion, lack of IL-1RI-mediated biological activity causes mature-onset obesity. This obese phenotype is preceded by decreased leptin sensitivity, fat utilization, and locomotor activity.
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| 10. |
- Henquin, JC, et al.
(författare)
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In vivo and in vitro glucose-induced biphasic insulin secretion in the mouse - Pattern and role of cytoplasmic Ca2+ and amplification signals in beta-cells
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 55:2, s. 441-451
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms underlying biphasic insulin secretion have not been completely elucidated. We compared the pattern of plasma insulin changes during hyperglycemic clamps in mice to that of glucose-induced insulin secretion and cytosolic calcium concentration ([Ca2+](c)) changes in perifused mouse islets. Anesthetized mice were infused with glucose to clamp blood glucose at 8.5 (baseline), 11.1, 16.7, or 30 mmol/l. A first-phase insulin response consistently peaked at 1 min, and a slowly ascending second phase occurred at 16.7 and 30 mmol/l glucose. Glucose-induced insulin secretion in vivo is thus biphasic, with a similarly increasing second phase in the mouse as in humans. In vitro, square-wave stimulation from a baseline of 3 mmol/l glucose induced similar biphasic insulin secretion and [Ca2+](c) increases, with sustained and flat second phases. The glucose dependency (3-30 mmol/l) of both changes was sigmoidal with, however, a shift to the right of the relation for insulin secretion compared with that for [Ca2+](c). The maximum [Ca2+](c), increase was achieved by glucose concentrations, causing half-maximum insulin secretion. Because this was true for both phases, we propose that contrary to current concepts, amplifying signals are also implicated in first-phase glucose-induced insulin secretion. To mimic in vivo conditions, islets were stimulated with high glucose after being initially perifused with 8.5 instead of 3.0 mmol/l glucose. First-phase insulin secretion induced by glucose at 11.1, 16.7, and 30 mmol/l was decreased by similar to 50%, an inhibition that could not be explained by commensurate decreases in [Ca2+](c) or in the pool of readily releasable granules. Also unexpected was the gradually ascending pattern of the second phase, now similar to that in vivo. These observations indicated that variations in prestimulatory glucose can secondarily affect the magnitude and pattern of subsequent glucose-induced insulin secretion.
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